The near future of rechargeable batteries
In recent years, the issue of improving mobile energy sources has become ever more acute - a question of both global and everyday. The global side is that humanity, in dire need of energy in any of its forms, has chosen electrical energy as freely convertible. 
The reason is a relatively low loss when converting from electric to any other, as well as low transmission losses from the point of output (power plant) to the stationary point of consumption (power outlet). The main source of electricity today is the burning of non-renewable hydrocarbon fuel at TPPs, which is less and less every year, and the price is getting higher. The main harm to the environment is nevertheless caused not by thermal power plants, but by internal combustion engines of automobiles, in view of compactness, not so efficient and equipped with not so good cleaning systems.
Everything says that work cars on electric, our world would become much cleaner, and life even cheaper with time
But it is unlikely that many of us, not counting the fighters for the green world, and even counting them, think about it every day. More often, we remember with an unkind word any icon on the display of our laptop or phone, when we see that they have 20 minutes to use it. And we ask: "Well, when will they make a normal battery, eh?".
Anyway, even 15 years and even 10 years ago this question was not so acute. But the best enemy of the good, and with the increased mobility of the urban dweller, i.e. the transition from a desktop computer to a laptop, from a simple mobile phone to a smartphone, requests for mobile power sources have increased dramatically
With the miniaturization of consumer electronics, its developers must withstand the general direction and reduce the power source, thus sacrificing battery life.
Out of these two problems, two actual requests, two requirements are born that go alongside each other, but which many, and even more, almost all mass information sources fail to distinguish
Unfortunately, high technology is such a thing, where a breakthrough is not always made on request. And so: "bottoms can not, tops do not want." wait for a revolution in battery technology? This article will try to shed light on this article.
the main impetus is the desire to dispel a huge misunderstanding, which was created on the one hand by sensational journalists, on the other, perhaps by scientists whose cross is always to exaggerate their already considerable achievements. Here are just a few examples of news, one of which I heard even in the news of one of the central channels.
New Li-Ion Batteries
Could longer ten times longer
"Found a substitute for rare metals for the production of batteries ... It can be used in smartphones and other devices, the period of autonomous use of which will increase"
"Amprius: More Energy in Batteries, Nanowire Anodes Could Run,"
Nanowire battery lasts 10 times longer
All of them are familiar to most of you about promising batteries, which will be much more capacious.
If the 20th century can be called the century of electricity, then
The last 20 years is the time of mobile electronics and it is to the development of chip technology that the batteries owe their latest achievements. The growth of the portable electronics market over the past 20 years has served as a source of growth for the rechargeable battery market. In 1983, Motorola released the first commercial mobile phone and since the beginning of the 90s it has already become a daily occurrence, and the beginning of the 90s was the birth of an energy-saving laptop on the Intel386 SL. The reverse is also true: new chemical power sources have opened a new era of mobile electronics. So the rapid development of electronics coincides with the commercial introduction of new types of batteries: 1989 - NiMH, 1990 - Li-Ion. At the moment, the market growth is slowing, and this engine is replaced by a new one - the most promising market for hybrid cars.
Today, of course, the most advanced are Lithium-Ion current sources (Li-Ion).
The potential of this technology has not yet been fully disclosed and all short and medium term prospects are connected with them. Please note (Fig. Right) that the variation in performance for various Li-ion designs is much wider than for previous batteries, the fact is that Li-ion is a fundamentally new pattern of battery operation, the representatives of which can vary greatly in layout
To date, the electronic market, apparently, does not have serious growth prospects, because its entire limit has the entire solvent population. And with the advent of smartphones, each representative has 1-2 multimedia devices or batteries. The figure on the left shows that by 2010 the number of cell subscribers. networks have already reached 5.5 billion
')
"Lithium-ion technology,
will dominate
on the market this century. "
Takao Iwasaki - President of Kureha Corp. (Materials and components for Li-ion batteries)
* According to some estimates, by 2020 the market can grow to 5-8 trill. yen (about $ 65-100 billion)
This forecast is based on the invention and introduction of new types of lithium-ion batteries; therefore, from the financial side, all developments in this area enjoy generous support. There have been no shortages of loud statements lately, we will try to figure out what can be expected in the coming years.
1.Very detailed market research: LiB materials industry. Takato Watabe, Masashi Mori January 26, 2011. Deutsche Bank Group.
So, the next decade is the time of lithium-ion batteries, so we will not pay enough attention to the future LiS and Li-air batteries.
Since the design of the battery itself does not undergo revolutionary changes, we can assess the prospects for new developments, pushing off from the existing industrial designs.
To predict the characteristics per gram and liter of battery, remember that it consists of two electrodes, and a separator, as well as current collectors, a steel case. To take into account all the components, we use the model of a cylindrical battery type 18650 and 14430. It is these cylindrical elements that are the filling of the batteries of our laptops.
Consider 2 types of standard cylindrical batteries: 14430 and 18650. Basically they consist of a working part - a roller in an electrolyte twisted from electrodes and a separator, and a steel container as well as a body, as well as covers, clamps, fuses.
To establish the characteristics of the battery, ideally, you need to know the geometry and mass of all the components included in it, but since these data were not found in open sources, we will satisfy curiosity by other means:
To establish the weight and volume of the working and auxiliary parts of the battery, we introduce a model: the battery consists of 3 parts: Steel vertical wall (0.3-0.5 mm) cylindrical working part, as well as lower and upper auxiliary parts (purple) can be taken by cylinders , fixed height, battery radius and unknown density.
To determine the characteristics of comparable batteries of two types, but with the same filling.
And now let's get maximum information out of this: it’s obvious that
V = πr 2 H
M act + M can = M and V act + V can = V
in turn, according to the model
M can = M wall + M add and V can = V wall + V add
wall characteristics are calculated directly
V wall = n (rb) r H
M wall = ρ steel V wall
V add = n (rb) 2 x
V add = n (rb) 2 y ,
where x, y are simply parameters indicating respectively the height and the product of the height and conditional density of the violet cylindrical part.
Now use the fact that the capacity with the same filling is proportional to its quantity
Using the above formulas and data, it is easy to compose and solve the following system of equations
Since matrices underlined in green are already known.
The capacity of the electrodes is equal to each other and equal to the total capacity of the battery . Using this and knowing about the specific capacitances of the electrodes in conventional batteries, you can find the volume allocated for the electrodes in any battery
Calculation of specific capacitances of the electrodes.
The electrode consists of the active substance mixed with the conductive substance and the holder, dried and having a certain porosity. This mixture is attached to the current collector - metal foil (aluminum for the cathode and copper for the anode). The volumetric proportions of the collectors to ordinary electrodes are restored according to [].
Further it is easy to establish the volume occupied by electrolyte.
Model parameters are refined by reducing the mass error
of these two batteries and another modern Sony NexelIon 14430 whose chemistry and characteristics are known
Now, using the model and knowing the mass fractions (wt%), packing density, gravimetric capacity of the active substance, vol% volume fraction and current collector density, it is easy to restore the full consistency of the battery, volume and gravimetric capacities of the electrodes. And make an assessment of the characteristics of the future product. In other words, we can estimate the missing parameters of existing batteries and imagine what characteristics their analogs with new electrodes will have.
In order not to tire with excessive scrupulousness, we will give results
As can be seen from the forecast chart of the capacity of the battery with the LiNi 1-xy Co x Mn y O 2 anodes (for laptops and phones), it can be seen that in the next 10-12 years batteries can become ~ 30-50% more compact, mainly due to the increase in capacity anodes. The question of greater growth rests on the invention of more capacious 
cathodes that are not visible. So far the only consolation is to buy additional batteries for laptops, which simply consist of a larger number of the same cylindrical elements. Regarding smartphones, honestly speaking, I wonder why phone manufacturers ignore the production of batteries of increased capacity, such as they produce for laptops. In principle, I used two Mugen Power and Seido batteries and was very pleased with both of them.
For the car industry is coming really new age:
New cheap cathodes should reduce the total cost of such a battery ~ 50%, compared with similar ones for portable devices. The transition to nanostructured engineering allows us to achieve a significant increase in durability when working at a power of 10 or even 100 times higher than modern. Note that the requirement for promising batteries for cars is a 10-15 fold increase in their service life, and it still remains unfulfilled (~ 5000 cycles)
It is unlikely that any unknown company will be able to intervene in the struggle of such giants as Sony, Panasonic, Sanyo, Samsung, 123systems, etc., except in the form of StartUp, since the main issue in introducing new batteries is their safety, in other words, the company's reputation .
And finally, as a general and optimistic conclusion: It would be better, but not immediately and not so), and in what they do not lie, it’s in the fact that you can go into a conditional coffee shop and charge your batteries in a matter of minutes!
I am well aware that not everyone is interested in such a long post, so a significant part of it can be easily missed by going directly to the results. Below is a fairly detailed overview of the batteries in general and in detail of the lithium ion technology, which should explain from where the legs grow in sensational news, as well as discuss the latest achievements in this field. It is there that the characteristics of the new materials required for the forecast will be given.
Batteries Introduction
Simplest cell
Li-ion battery
Until now, we have talked about batteries exclusively from the consumer side, but all further consideration goes into the details of the operation of devices. At the beginning of the review, calling the batteries mobile sources of energy, the author deliberately avoided concretization: batteries are mobile sources of current, and more specifically Chemical Current Sources (hereinafter HIT). Their purpose is to create an electric current through a connected external network. In other words, to pass through it the flow of electrons (Current) with a certain "force" (voltage)
It should be clarified that although chemistry is primarily associated with various letters and names, it, as a science, is engaged in nothing more than the study of electrical interactions in a substance.
As a musician builds his composition of notes, so the chemist operates with his simple elements - chemical. The chemical element is a stable (and therefore constantly occurring in the same form) structure consisting of a nucleus (a very compact combination of heavy particles — neutrons and positively charged protons), and a shell of light negative electrons corresponding to the charge of this nucleus. Each element differs from the previous one by 1 proton in the nucleus and, accordingly, in the neutral state by one electron in the shell. Electrons are located around the nucleus in the intricate "orbits" - orbitals. These orbitals are due to Coulomb interaction with both the nucleus and neighboring electrons.
It is easy to see that in the periodic table the structure of elements is repeated in columns, changing only in scale, and then the chemical properties of elements are repeated. The outer layer of electrons and is involved in the interaction with other atoms. The force of attraction is proportional to the charge of the nucleus, and inversely proportional to the square of the radius . The rows in the Mendeleev t. Show (from left to right) the filling of the outer shell. When one shell is filled, the radius of its electron orbit is approximately the same, therefore, from left to right, as the charge of the nucleus increases, the attraction increases and the electrons attract closer to the nucleus. While at the beginning of the filling of a new one, all the inner shells push away electrons of the new, thereby reducing the binding force of the electron to the nucleus, and therefore the radius significantly increases when moving to a new row. 
An important consequence of the presence of such complex electrical interactions is that electrons, getting rid of extras or adding additional ones (about how they get rid of or taking players into their cards), tend to form an entirely filled shell, becoming as close as possible to the elements of the last column - self-sufficient inert gases. This pattern is called the octet rule (8 electrons in the outer orbit). Anyway, the main consequence of the above is the fact that different elements have different ability to attract electrons. This is reflected in various numerical indicators ( electronegativity , ionization energy , electron attractiveness ), but the main thing is that a more “strong” element is able to take an electron from a weaker one , and this transfer is an electric current .
In the current classification, HITs are divided into primary (batteries) and secondary (batteries). In this presentation, the author would like to emphasize that these names derive not from the fact that the last ones are able to be recharged, but from the fact that the primary sources of current that are collected in the battery serve as an energy source by themselves, and the secondary ones only transfer the energy received from the charger.
Significantly for the first time the effect that formed the basis of the HIT was discovered by Luigi Galvani, an Italian doctor. In a series of his experiments with a dissected frog, among other things, he was able to observe muscle contraction and record electric current with the help of two different metal blades. But the output of Galvani ”Muscles produce electricity” was incorrect. 
The first correctly interpreted phenomenon and concluded that the electromotive force is born from the contact of two different metals, was the Italian physicist A. Volta. Applying the discovery in practice, Volta created the first chemical cell, which was given the name of Galvani. The figure shows a stack of alternating discs Copper / Paper with H2SO4 / Zinc. In other words, these are series-connected electrochemical cells, i.e. A battery of cells, which you and I used to call simply: Battery.
XIX , : .
() . , — : , «, » . , , , ( ).
Consider the very first current source, invented by Volta and bearing the name of Galvani.
The source of current in any battery can only be a redox reaction. Actually these are two reactions: the atom is oxidized when it loses an electron. Obtaining an electron is called recovery. That is, the redox reaction proceeds at two points: from where and from where the electrons flow.
() . , . , - . Zn – Cu ( ) , , , ( ). . ()(. )
In all HITs preceding Li-ion, the electrolyte is an active participant in the reactions
taking place. See the principle of operation of a lead-acid battery
The electrolyte is also a conductor of current, only of the second kind, in which the ions move the charge. The human body is just such a conductor, and the muscles contract due to the movement of anions and cations.
So L. Galvani accidentally connected two electrodes through a natural electrolyte - a prepared frog.
Capacity - the number of electrons (electric charge) that can be passed through a connected device until the battery is completely discharged [Q] or [Ah = Q / 3600]
The capacity of the entire battery forms the capacity of the cathode and anode: how many electrons the anode is able to give and how many electrons the cathode is able to accept. Naturally, limiting, will be the smaller of the two tanks.
Voltage - potential difference. energy characteristic, showing how much energy a single charge releases when moving from the anode to the cathode [V = J / Q].
Energy is the work that can be done on a given HIT before it is fully discharged. [J] or [Wh = J / 3600]
Power is the rate of energy release or work per unit of time [W = J / sec]
Durability orCoulomb efficiency - what percentage of the capacity is irretrievably lost during the charge-discharge cycle.
All characteristics are predicted theoretically, however, due to a multitude of factors difficult to read, most of the characteristics are determined experimentally. So they can all be predicted for the ideal case, based on chemical composition, but the macrostructure has a huge impact on both capacity and power and durability.
So, the durability and capacity largely depend on both the charge / discharge rate and the macrostructure of the electrode.
Therefore, the battery is characterized not by one parameter, but by a whole set for various modes. For example, the battery voltage (single charge transfer energy **) can be estimated to a first approximation (at the stage of evaluating the prospects of materials) from the ionization energies of the atoms of active substances during oxidation and reduction. But the real value is the difference. potentials, for the measurement of which, as well as for the removal of the charge / discharge curves, a test cell is assembled with a test electrode and a reference one.
For electrolytes based on aqueous solutions, a standard hydrogen electrode is used. For lithium-ion lithium metal.
* The ionization energy is the energy that must be transferred to an electron in order to break the bond between it and the atom. That is, taken with the opposite sign, is the binding energy, and the system always seeks to minimize the binding energy
** The energy of a single transfer is the energy of transfer of one elementary charge 1,6e-19 [Q] * 1 [V] = 1,6e-19 [J] or 1eV (electron volt)
<In the 1980s, lithium was proposed as a promising material for the anode, but due to the high reactivity and uncontrolled conversion of the anode cycle by cycle, for example, leading to an increase in lithium "branches" reaching the cathode directly, which led to a short circuit in the secondary Batteries decided to abandon the use of lithium metal in favor of compounds containing only lithium ions. The properties of lithium in graphite have already been described. And in 1991, Sony released lithium batteries with a graphite anode under the now commonly used name Li-ion.
As already noted, in lithium-ion batteries, the electrolyte is not directly involved in the reaction. Where do the two main reactions occur: oxidation and reduction and how is the charge balance aligned?
Directly, these reactions occur between lithium in the anode and the metal atom in the cathode structure. As noted above, the emergence of lithium-ion batteries is not just the discovery of new connections for electrodes, it is the discovery of a new principle of HIT functioning:
The electron weakly connected with the anode is pulled out along the outer conductor to the cathode.
In the cathode, an electron falling into the metal orbit, compensating for it the 4th electron practically taken away from it by oxygen. Now the electron metal finally joins oxygen, and the resulting lithium ion is drawn into the gap between the oxygen layers by the resulting electric field. Thus, the enormous energy of lithium-ion batteries is achieved by the fact that it deals not with the restoration of external 1.2 electrons, but with the restoration of more “deeper” ones. For example, for kobolt the 4th electron.
Lithium ions are retained in the cathode due to a weak, of the order of 10 kJ / mol, interaction ( Van der Waals ) with the surrounding electron clouds of oxygen atoms (red)
Li - the third element in the periodic table , has a low atomic weight, and small size. Due to the fact that lithium begins and, moreover, only the second row, the size of the neutral atom is rather large, whereas the size of the ion is very small, smaller than the size of the helium and hydrogen atoms, which makes it almost irreplaceable in the LIB scheme. Another consequence of the above: the external electron (2s1) has a minute connection with the nucleus and can easily be lost (this is expressed in the fact that Li has the lowest potential with respect to the hydrogen electrode P = -3.04V).
Unlike traditional batteries, the electrolyte together with the separator does not directly participate in the reaction, but only provides the transport of lithium ions and does not allow the transport of electrons.
Electrolyte requirements:
- good ionic conductivity
- low electronic
- low cost
- low weight
- non-toxicity
- ABILITY TO WORK IN THE SPECIFIED RANGE OF TENSIONS AND TEMPERATURES
- prevent structural changes of the electrodes (to prevent the decrease in capacity)
In this review, I will allow to bypass the topic of electrolytes, technically complex, but not so important for our topic. Basically, LiFP 6 solution is used as an electrolyte.
Although it is believed that the electrolyte with a separator is an absolute insulator, in reality it is not:
In lithium-ion elements there is a self-discharge phenomenon. those. lithium ion with electrons reach the cathode through the electrolyte. Therefore, it is necessary to keep the battery partially charged in case of long-term storage.
At long interruptions in operation, the phenomenon of aging also takes place, when separate groups are separated from uniformly saturated with lithium ions, disturbing the uniformity of concentration and thereby reducing the total capacity. Therefore, when buying a battery, you must check the release date
Anodes are electrodes with a weak bond, both with the “guest” lithium ion, and with the corresponding electron. Currently, there is a boom in the development of a variety of solutions for the anodes of lithium-ion batteries.
Anode requirements
Improvement methods:
In general, anodes for LIB can be divided into 3 groups according to the method of placing lithium in its structure:
Almost all of them remembered from high school that carbon exists in solid form in two main structures - graphite and diamond. The difference in the properties of these two materials is striking: one is transparent - the other is not. One insulator is another conductor, one cuts the glass, the other is rubbed on the paper. The reason is the different nature of interatomic interactions.
A diamond is a crystal structure where interatomic bonds are formed due to sp3 hybridization, that is, all bonds are the same — all three 4 electrons form σ bonds with another atom.
Graphite is formed by sp2 hybridization, which dictates a layered structure, and a weak bond between the layers. The presence of a “floating” covalent π-bond makes carbon graphite an excellent conductor
Graphite is the first and today the main anode material, which has many advantages.
High electronic conductivity
High ionic conductivity
Small volumetric deformation when introducing lithium atoms
Low cost
As the material for the anode, graphite was first proposed as early as 1982 by S.Basu [1] and introduced into the 1985 A. Yoshino lithium-ion cell [2]
At first, graphite was used in the electrode in its natural form and its capacity reached only 200 mAh / g . The main resource for increasing the capacity was improving the quality of graphite (improving the structure and cleaning of impurities). The fact is that the properties of graphite vary considerably depending on its macrostructure, and the presence of a multitude of anisotropic grains in the structure, oriented pink, significantly worsens the diffusion properties of the substance. Engineers tried to increase the degree of graphitization, but its increase led to the decomposition of the electrolyte. The first solution was to use crushed low-graphitized coal mixed with electrolyte, which increased the anode capacity to 280mAh / g (the technology is still widely used) This was overcome in 1998 by introducing special additives into the electrolyte, which create a protective layer in the first cycle (hereinafter SEI solid electrolyte interface) preventing further decomposition of the electrolyte [3] and allowing the use of artificial graphite 320 mAh / g . To date, the capacity of the graphite anode has reached 360 mAh / g [4], and the capacity of the entire electrode 345mAh / g and 476 Ah / l [8]
Reaction: Li 1-x C 6 + Li x ↔ LiC 6
The graphite structure is capable of accepting a maximum of 1 Li atom per 6 C, therefore the maximum achievable capacity is 372 mAh / g (this is not so much theoretical, as is the commonly used figure because here is the rarest case when something real exceeds theoretical, because in practice lithium ions can be placed not only inside the cells, but also on kinks of graphite grains)
Since 1991 The graphite electrode has undergone many changes, and according to some characteristics, it seems, as an independent material, has reached its ceiling . The main field for improvement is power increase, i.e. The discharge / charge rate of the battery. The task of increasing power is at the same time the task of increasing durability, since the rapid discharge / charging of the anode leads to the destruction of the graphite structure, “lithium ions” being pulled through it. In addition to standard techniques for increasing power, which usually boil down to an increase in the surface / volume ratio, it is necessary to note the study of the diffusion properties of graphite single crystal in different directions of the crystal lattice [5] showing that the diffusion rate of lithium can differ by 10 orders of magnitude.
back to conclusions
K.S. Novoselov and A.K. Game - winners of the Nobel Prize in Physics 2010. Discoverers of self-use of graphene
[1] Bell Laboratories US Patent 4,423,125
[2] Asahi Chemical Ind. Japan Patent 1989293
[3] Ube Industries Ltd. US Patent 6,033,809
[4] Masaki Yoshio, Akiya Kozawa, and Ralph J. Brodd. Lithium-Ion Batteries Science and Technologies Springer 2009.
[5] Lithium Diffusion in Graphitic Carbon Kristin Persson at.al. Phis. Chem. Letters 2010 / Lawrence Berkeley National Laboratory. 2010
[6] lithium intercalated graphite LiC6, KR Kganyago, PE Ngoep Phis. Review 2003.
[7] The battery used is a lithium-ion battery and method of manufacturing same. Samsung Display Devices Co., Ltd. (KR) 09 / 923,908 2003
[8] This is an example of graphite anode in lithium ion batteries. Joongpyo Shim and Kathryn A. Striebel
To date, one of the most promising are the anodes from the elements of the 14th group of the periodic table. Thirty years ago, the ability of tin ( Sn ) to form alloys (interstitial solutions) with lithium was well studied [1]. Only in 1995, Fuji announced tin-based anode material (see, for example, [2])
It was logical to expect that the lighter elements of the same group will have the same properties, and indeed Silicon ( Si ) and Germanium ( Ge ) show the identical nature of lithium
Li 22 Sn 5 , Li 22 Ge 5 , Li 15 Si 4
Li x + Sn (Si, Ge) <-> Li x Sn (Si, Ge) (x <= 4.4)
The main and total complexity in the application of this group of materials is huge, from 357% to 400% , volumetric deformations during saturation with lithium (when charging), leading to large losses in capacity due to the loss of a part of the anode material of contact with the current collector.
Perhaps the most developed element of this group is tin:
being the heaviest gives the heavier solutions: the maximum theoretical capacity of such an anode is 960 mAh / g , but compact ( 7000 Ah / l - 1960Ah / l * ) nevertheless surpassing traditional carbon anodes 3 and 8 ( 2.7 * ) times, respectively.
The most promising are silicon-based anodes, which theoretically ( 4200 mAh / g ~ 3590mAh / g [5]) are more than 10 times lighter and 11 ( 3.14 * ) times more compact ( 9340 Ah / l ~ 2440 Ah / l * ) graphite.
Si does not have sufficient electronic and ionic conductivity, which makes it necessary to look for additional means to increase the power of the anode
Ge , germanium is not mentioned as often as Sn and Si, but being intermediate, has a large ( 1600 mAh / g ~ 2200 * Ah / l ) capacity and 400 times higher ionic conductivity than Si, which can outweigh its high cost when creating high-power electrical engineering [4]
Along with large volumetric deformations, there is another problem:
loss of capacity in the first cycle due to the irreversible reaction of lithium with oxides
SnO x + x2Li + -> xLi 2 O + Sn
xLi 2 O + Sn + yLi + <-> xLi 2 O + Li y Sn
which the greater, the greater the contact of the electrode with the air (the larger the surface area, that is, the smaller the structure)
A number of schemes have been developed that allow, in varying degrees, to use the great potential of these compounds, smoothing the weaknesses. However, as well as advantages:
All these materials are currently used in anodes combined with graphite, raising their characteristics by 20-30%
* the values corrected by the author are marked, since common figures do not take into account a significant increase in volume and operate on the density value of the active substance (before saturation with lithium), and therefore do not completely reflect the real state of affairs
[1] MS Foster, CE Crouthamel, SE Wood, J. Phys. Chem., 1966
[2] Jumas, Jean-Claude, Lippens, Pierre-Emmanuel, Olivier-Fourcade, Josette, Robert, Florent Willmann, Patrick 2008
US Patent Application 20080003502.
[3] Sony's Nexelion Chemistry and Structure of
Li-ion Electrode Materials
J. Wolfenstine, JL Allen,
J. Read, and D. Foster
Army Research Laboratory 2006.
[4] High Capacity Li-Ion Battery Anodes Using Ge Nanowires
[5] Electrodes for Li-Ion Batteries — A Old Problem
Journal of The Electrochemical Society, 155 ͑2͒ A158-A163 ͑2008͒.
All existing solutions to the problem of large anode deformations proceed from a single consideration: during expansion, the cause of the mechanical stresses is the solidity of the system: split the monolithic electrode into as many smaller structures as possible, allowing them to expand independently of each other.
The first, most obvious, method is the simple grinding of a substance using a holder to prevent the aggregation of particles into larger ones, as well as the saturation of the resulting mixture with electron-wire agents. A similar solution could be traced in the evolution of graphite electrodes. This method allowed to achieve some progress in increasing the capacity of the anodes, but nevertheless, until the potential of the considered materials is fully revealed, increase the capacity (both volume and mass) of the anode by ~ 10-30% ( 400 - 550 mAh / g ) at low power
A relatively early method of introducing nanosized tin particles (electrolysis) onto the surface of graphite spheres,
The ingenious and simple look at the problem allowed to create an efficient battery using ordinary industrially obtained powder 1668 Ah / l [14]
The next step was the transition from microparticles to nanoparticles: state-of-the-art batteries and their prototypes examine and form the structures of a substance on a nanometer scale, which made it possible to increase the capacity to 500 - 600 mAh / g (~ 600 Ah / l *) with acceptable durability [6]
One of the many promising types of nanostructures in the electrodes is the so-called. the shell – core configuration, where the core is a small-diameter ball of the working substance, and the shell serves as a “membrane” preventing particles from frightening and providing electronic communication with the environment. Impressive results showed the use of copper as a shell for tin nanoparticles [8], showing high capacity ( 800 mAh / g - 540 mAh / g *) for many cycles, as well as at high charge / discharge currents. In comparison with the carbon skin ( 600 mAh / g ) [7] similarly for Si-C [9]. Since Nanoshars are entirely composed of the active substance, its bulk capacity should be recognized as one of the highest ( 1740 Ah / l (*))
As noted, in order to reduce the adverse effects of a dramatic expansion of the working substance, space is required for expansion.
In the past year, researchers have made impressive progress in creating workable nanostructures: nano rods
Jaephil Cho [13] achieved 2800 mAh / g low power per 100 cycles and 2600 → 2400 at higher power using a porous silicon structure
as well as stable Si nanofibres coated with a 40nm graphite film, demonstrating 3400 → 2750 mAh / g (ak. islands) after 200 cycles.
Yan Yao and co-workers [12] suggest using Si in the form of hollow spheres, achieving amazing durability: the initial capacity is 2725 mah / g (and only 336 Ah / l (*)) when the capacity drops after 700 cycles less than 50%
In September 2011, scientists from the Berkley Lab [10] announced the creation of a sustainable electron-conducting gel,
which can revolutionize the use of silica materials. The value of this invention is difficult to overestimate: a new gel can serve as both a holder and a conductor, preventing nanoparticle splicing and loss of contact. Allows the use of cheap industrial powders as an active material and, according to the creators, is comparable in price to traditional holders. Electrode made of industrial materials (nano Si powder) gives a steady 1360 mAh / g and very high 2100 Ah / l (*)
back to conclusions
* - assessment of the actual capacity calculated by the author (see the appendix)
[1] MS Foster, CE Crouthamel, SE Wood, J. Phys. Chem., 1966
[2] Jumas, Jean-Claude, Lippens, Pierre-Emmanuel, Olivier-Fourcade, Josette, Robert, Florent Willmann, Patrick 2008 US Patent Application 20080003502.
[3] Li-ion Electrode Materials Chemistry and Structure of Nexelion J. Wolfenstine, JL Allen, J. Read, and D. Foster Army Research Laboratory 2006.
[4] High Capacity Li-Ion Battery Anodes Using Ge Nanowires
[5] Ball milling Graphite / Tin composite anode materials in liquide medium. Ke Wang 2007.
[6] for the lithium-ion battery Journal of Power Sources 2009.
[7] The Impact of Carbone-Shell on Sn-C composite anode for Lithium-ion Batteries. Kiano Ren et al. Ionics 2010.
[8] Novel Core-Shell Sn-Cu Anodes For Li Rech. Batteries, prepared by redox-transmetallation react. Advanced Materials. 2010
[9] Core double-shell Si @ SiO2 @ C nanocomposites as anode materials for Li-ion batteries Li et al. ChemCom 2010.
[10] Polymers with Tailored Electrodes High Capacity Lithium Battery Electrodes Gao Liu et al. Adv. Mater. 2011, 23, 4679–4683
[12] Interconnected Silicon Hollow Nanospheres for Lithium-Ion Battery Anodes with Long Cycle Life. Yan Yao et al. Nano Letters 2011.
[13] Porous Si anode materials for lithium rechargeable batteries, Jaephil Cho. J. Mater. Chem., 2010, 20, 4009–4014
[14] Electrodes for Li-Ion Batteries — 155 ͑216 A158-A163 ͑2008͒.
[15] ACCUMULATEURS FIXES, US Patent 8,062,556 2006
Special cases of electrode structures :
Estimation of the real capacity of tin nanoparticles with copper coating Cu @ Sn
From the article known volume ratio of particles 1 to 3 m
0.52 is the packing ratio of the powder. Accordingly, the rest of the volume behind the holder 0.48
Nanospheres. Packing Ratio
the low volume capacity given for nanospheres is due to the fact that the spheres inside are hollow, and therefore the packing coefficient of the active material is very low,
even it will be 0.1 , for comparison, for a simple powder - 0.5 ... 07
The group of promising undoubtedly also includes metal oxides, such as Fe 2 O 3 . Possessing high theoretical capacitance, these materials also require solutions to increase the discreteness of the active substance of the electrode. In this context, such an important nanostructure as nanofibers will receive due attention here.
Oxides shows a third way to include and exclude lithium in the structure of the electrode. If in graphite, lithium is predominantly between the layers of graphene, in solutions with silicon, it is embedded in its crystal lattice, then there is more likely a “oxygen exchange” between the “main” metal of the electrode and the guest, Lithium. The electrode array is formed of lithium oxide and basic metal strastaetsya into nanoparticles within the matrix (see, e.g., Figure reacted with molybdenum oxide. MoO 3 + 6Li + + 6e - <-> 3Li 2 O + Mo )
Such a nature of interaction implies the need for easy movement of metal ions in the electrode structure, i.e. High diffusion, which means the transition to fine particles and nanostructures
Speaking about the different anode morphology, ways of providing electronic communication in addition to the traditional (active powder, graphite powder + holder), other forms of graphite can be distinguished as a conductive agent:
A common approach is the combination graphene and the main island, when nanoparticles can be located directly on the “sheet” of graphene, and it, in turn, will serve as a conductor and buffer, when the working substance expands. This structure has been proposed for Co 3 O 4 [1] 778 mAh / gand quite durable. Similarly, 1100 mAh / g for Fe 2 O 3 [2],
but due to the very low density of graphene, it is difficult to even estimate how much similar solutions are applicable.
Another method is the use of graphite nanotubes by
AC Dillon et al. experimenting with MoO 3, they show a high capacity of 800 mAh / g ( 600mAh / g * 1430 Ah / l * ) with 5 wt% holder [3] loss of capacity after 50 cycles while being covered with aluminum oxide as well as with Fe 3 O 4 , without using holder resistant 1000 mAh / g ( 770 - 1000 Ah / l *) Figure right: SEM image of anode / Fe 2 O 3 nanofibers with 5 wt% graphite fine tubes (white) [3]
M x O y + 2yLi + + 2ye - <-> yLi 2 O + xM
back to conclusions
Recently, nanofibers are one of the hottest topics for materials science publications, in particular those devoted to promising batteries, since they provide a large active surface with good communication between particles.
Initially, nanofibers were used as a kind of nanoparticles of active material, which, in a homogeneous mixture with a holder and conductive agents, form an electrode.
The question of the packing density of nanofibers is very complicated, since it depends on many factors. And, apparently, consciously almost not illuminated (specifically in relation to the electrodes). This already makes it difficult to analyze the real indicators of the entire anode. For compiling an evaluative opinion, the author took the risk of using the work of RE Muck [4], devoted to the analysis of hay density in bunkers. Judging by the SEM images of nanofibers, an optimistic analysis of the density of the package will be 30-40%
In the last 5 years, more attention has been focused on the synthesis of nanofibers directly on the current receiver, which has several serious advantages:
Direct contact of the working material with the current collector is provided, contact with the electrolyte is improved, the need for graphite additives is eliminated. several stages of production are passed, the packing density of the working substance increases significantly.
K. Chan and colleagues tested Ge nanofibers obtained 1000mAh / g ( 800Ah / l ) for low power and 800 → 550 ( 650 → 450 Ah / l *) at 2C after 50 cycles [5]. At the same time, Yanguang Li and colleagues showed a high capacity and enormous power. Co 3 O 4 : 1100 → 800 mAh / g ( 880 →640Ah / l *) after 20 cycles and 600 mAh / g ( 480 Ah / l *) at a 20-fold increase in current [6]
Separately, it should be noted and recommended to everyone to familiarize the inspiring works of A. Belcher **,
which are the first steps to a new the era of biotechnology.
By modifying the bacteriophage virus, A. Belcher succeeded in building a nanofiber on its basis at room temperature, due to the natural biological process. Given the high structural definition of such fibers, the resulting electrodes are not only environmentally friendly, but also show both compaction of the fiber package and much more durable work [7] [8] [9]
back to conclusions
* - assessment of the actual capacity calculated by the author (see the appendix)
**
Angela Belcher is an outstanding scientist (chemist, electrochemist, microbiologist). Inventor of the synthesis of nanofibers and their ordering into electrodes by means of specially derived cultures of viruses
( see interview )
As was said, the charge of the anode occurs through the reaction.
I did not find in the literature indications of the actual expansion rates of the electrode during charging, so I suggest evaluating them by the smallest possible changes. That is, by the ratio of the molar volumes of the reactants and the reaction products ( V Lihitated is the volume of the charged anode, V UnLihitated is the volume of the discharged anode). The densities of metals and their oxides can be easily found in open sources.
It should be borne in mind that the resulting volume capacity is the capacity of a continuous active substance, therefore, depending on the type of structure, the active substance occupies a different share of the volume of the whole material, this will be taken into account by entering the packing coefficient k p . For example, for the powder it is 50-70%
[1] Highly reversible Co3O4 / graphene hybrid anode for lithium rechargeable batteries. H. Kim et al. CARBON 49 (2011) 326 –332
[2] Nanostructured Reduced Grain Phenoxy Oxide / Fe2O3 Compound As Metallic Lithium Ion Batteries. ACSNANO VOL. 4 ▪ NO. 6 ▪ 3187–3194 ▪ 2010
[3] Nanostructured Metal Oxide Anodes. AC Dillon. 2010
[4] A New Way Of Looking At Bunker Silage Density. RE Muck. Dairy Forage Research US Center Madison, Madison WI
[5] High Capacity Li Ion Battery Anodes Using Ge Nanowires K. Chan et. al. NANO LETTERS 2008 Vol. 8, No.1 307-309
[6] Meshorous Co3O4 Nanowire Arrays for Lithium Ion Batteries with High Capacity and Rate Capability. Yanguang Li et. al. NANO LETTERS 2008 Vol. 8, No.1 265-270
[7] Virus-Enabled Synthesis and Assembly of Nanowires Ion Battery Electrodes Ki Tae Nam, Angela M. Belcher et al. www.sciencexpress.org / 06 April 2006 / Page 1 / 10.1126 / science.112271
[8] Virus-Enabled Silicon Anode for Lithium-Ion Batteries. Xilin Chen et al. ACS Nano, 2010, 4 (9), pp 5366–5372.
[9] VIRUS SCAFFOLD FOR SELF-ASSEMBLED, FLEXIBLE AND LIGHT LITHIUM BATTERY MIT, Belcher A. US 006121346 (A1) WO 2008124440 (A1)
The cathodes of lithium-ion batteries should mainly be able to accept lithium ions, and to provide high voltage, which means that along with the capacitance more energy.
An interesting situation has arisen in the design and manufacture of cathodes for Li-Ion batteries. In 1979, John Goodenough and Mizuchima Koichi patented cathodes for Li-Ion batteries with a layered structure of the LiMO2 type , which almost all existing cathodes of lithium-ion batteries fall under. [1] [2] The
key elements of the cathode are
oxygen, as a connecting link, a bridge, as well as a “catching” lithium with its electron clouds.
Transition metal (i.e., a metal having valence d-orbitals), since it can form structures with a different number of bonds. The first cathodes used sulfur TiS 2 [5] [6],
but then they switched to oxygen, a more compact, and most importantly more electronegative element, giving an almost completely ionic bond with metals. The layered structure of LiMO 2 (*) is the most common, and all developments roll around the three candidates M = Co, Ni, Mn and constantly look at very cheap Fe .
Cobalt , in spite of many things, captured Olympus immediately and hardens it so far (90% of the cathodes), but due to the high stability and correctness of the layered structure with 140 mAh / g, the capacity of LiCoO 2 increased to 160-170mAh / g due to the expansion of the voltage range.
But because of the rarity for the Earth, Co is too expensive, and its use in its pure form can be justified only in small batteries, for example, for telephones. 90% of the market is occupied by the very first, and at the moment, still the most compact cathode.
Nickel has been and remains a promising material, showing a high 190mA / g , but it is much less stable and such a layered structure in its pure form for Nidoes not exist [5]. Extraction of Li from LiNiO 2 produces almost 2 times more heat than from LiCoO 2 [3], which makes its use in this area unacceptable.
Manganese . Another well-studied structure is invented in 1992. Jean-Marie Tarasco [4], a cathode of the Spinel type of manganese oxide LiMn 2 O 4 : with a slightly lower capacity, this material is much cheaper than LiCoO 2 and LiNiO 2and much safer. Today it is a good variant for hybrid vehicles. Recent developments are associated with the doping of nickel with cobalt, which significantly improves its structural properties. A significant improvement in the stability when Ni is doped with electrochemically inactive Mg is also noted: LiNi 1-y Mg y O 2 . There are many alloys LiMn x O 2x , for Li-ion cathodes.
The fundamental problem is how to increase capacity. We have already seen with the example of tin and silicon that the most obvious way to increase capacity is to travel up the periodic table, but to
universally regret, there is nothing above the currently used transition metals (fig. right). Therefore, the entire progress of recent years associated with cathodes is generally associated with the elimination of the shortcomings of the already existing ones: an increase in durability, an improvement in quality, the study of their combinations (the left above) .
Iron . From the very beginning of the lithium ion era, many attempts were made to use iron in the cathodes, but all without success. Although LiFeO 2 would be an ideal cheap and powerful cathode, it was shown [7] that Li could not be extracted from the structure in the normal voltage range [8]. This situation changed dramatically in 1997, with the cis-adherence to e / x properties of olivine LiFePO 4 . High capacity ( 170 mAh / g) approximately 3.4V with a lithium anode and the lack of a serious drop in capacity even after several hundred cycles. The main disadvantage of olivine for a long time was poor conductivity, which
significantly limited power. To remedy the situation, classical moves (grinding with graphite coating) were used, using a gel with graphite, it was possible to achieve high power at 120 mAh / g for 800 cycles. Indeed, enormous progress was achieved by meager doping of Nb, increasing the conductivity by 8 orders of magnitude.
Everything suggests that Olivine will become the most popular material for electric vehicles. For exclusive ownership of LiFePO 4 rightsA123 Systems Inc. has been suing for years. and Black & Decker Corp, not without reason believing that the future of electric vehicles. Do not be surprised, but the patents are issued on the same captain of cathodes - John Gudenaf.
Olivine proved the possibility of using cheap materials and struck a kind of platinum. Inzheneraya thought immediately rushed into the resulting space. For example, the replacement of sulfates by fluorophosphates is now being actively discussed, which will increase the voltage by 0.8 V, i.e. Increase energy and power by 22% [9].
Funny: while there is a dispute about the rights to use olivine, I came across a lot of noname manufacturers offering items on a new cathode,
back to the conclusions
* All these compounds are stable only with Lithium. And, accordingly, they are already made saturated. Therefore, when buying batteries based on them, you must first charge the battery, overtaking part of the lithium to the anode.
** Understanding the development of the cathodes of lithium-ion batteries, you involuntarily begin to perceive it as a duel between two giants: John Goudanaf and Jean-Marie Tarasco. If Goudanaf patented his first fundamentally successful cathode of 1980 ( LiCoO 2 ) a year, then Dr. Trasko responded twelve years later ( Mn 2 O 4 ). The second principal achievement of the American took place in 1997 ( LiFePO 4), and in the middle of the past decade, the Frenchman is engaged in expanding the idea, introducing LiFeSO 4 F , and is working on the use of fully organic electrodes
[1] Goodenough, JB; Mizuchima, KUS Patent 4,302,518, 1980.
[2] Goodenough, JB; Mizushima, KUS Patent 4,357,215, 1981.
[3] Lithium-Ion Batteries Science and Technologies. Masaki Yoshio, Ralph J. Brodd, Akiya Kozawa
[4] Method for preparation of LiMn2 O4 intercalation and secondary lithium batteries. Barboux; Philippe Shokoohi; Frough K., Tarascon; Jean-Marie. Bell Communications Research, Inc. 1992 US Patent 5,135,732.
[5] Lithium Batteries and Cathode Materials. M. Stanley Whittingham Chem. Rev.2004, 104, 4271−4301
[6] Rechargeable electrochemical cell with cathode stoichiometric titanium disulfide Whittingham; M. Stanley. US Patent 4,084,046 1976
[7] Kanno, R .; Shirane, T .; Inaba, Y .; Kawamoto, YJ Power Sources 1997, 68, 145.
[8] Lithium Batteries and Cathode Materials. M. Stanley Whittingham Chem. Rev.2004, 104, 4271−4301
[9] A 3.6 V lithium-based fluorosulphate insertion positive electrode for lithium-ion batteries. N. Recham1, JN. Chotard1, L. Dupont1, C. Delacourt1, W. Walker1,2, M. Armand1 and JM. Tarascon. NATURE MATERIAL November 2009.
The capacity of the cathodes is determined again as the maximum extracted charge per weight of the substance, for example, the group
Li 1-x MO 2 + Li + + e - ---> Li x MO 2
For example, for Co
with extraction degree Li x = 0.5, the capacity of the substance will be
At the moment, an improvement in the technical process has allowed to increase the degree of extraction and reach 160mAh / g.
But, of course, most of the powders on the market do not achieve these indicators.
.
. , , : , , , 1 kWh 387 kWh . , , (70-100 kg CO 2at 1 kWh). Moreover, in a modern consumer society, goods are not used until their resources are exhausted. That is, the period for “discouraging” this energy loan is small, and the utilization of modern batteries is expensive, and not everywhere available. Thus, the energy efficiency of modern batteries is still in question [1].
Recently, there have been several encouraging biotechnologies that allow synthesizing electrodes at room temperature. A. Belcher (viruses), J.M. Tarasco (use of bacteria).
An excellent example of such a promising biomaterial is lithiated oxocarbon - Li 2 C 6 O 6(Lithium Radisonate) [2], which, having the ability to reversibly place up to four Li per formula, showed a large gravimetric capacity, but since the recovery is associated with pi bonds, a somewhat lower potential (2.4 V). Similarly, other aromatic rings are considered as the basis for a positive electrode [2], also reporting a significant battery relief.
The main "disadvantage" of any organic compounds is their low density, since all organic chemistry deals with light elements C , H , O and N. To understand how promising this direction is, it is enough to say that these substances can be obtained from apples and corn, as well as are easily recyclable and recyclable.
Lithium radionate would already be considered the most promising cathode for the automotive industry, if not for the limited current density (power) and the most promising for portable electronics, if it were not for the low density of the material (low volume capacity) (left). In the meantime, this is just one of the most promising fronts of work.
back to conclusions
[1] for example, see Hybrid vs disel
[2] Yasushi Morita et al. Nature Mat. 10,947–951 (2011)
Of course, something is described very superficially, it may not even be entirely correct, but it is enough to outline the perspectives of
ALL YOU.
The reason is a relatively low loss when converting from electric to any other, as well as low transmission losses from the point of output (power plant) to the stationary point of consumption (power outlet). The main source of electricity today is the burning of non-renewable hydrocarbon fuel at TPPs, which is less and less every year, and the price is getting higher. The main harm to the environment is nevertheless caused not by thermal power plants, but by internal combustion engines of automobiles, in view of compactness, not so efficient and equipped with not so good cleaning systems.Everything says that work cars on electric, our world would become much cleaner, and life even cheaper with time
But it is unlikely that many of us, not counting the fighters for the green world, and even counting them, think about it every day. More often, we remember with an unkind word any icon on the display of our laptop or phone, when we see that they have 20 minutes to use it. And we ask: "Well, when will they make a normal battery, eh?".
Anyway, even 15 years and even 10 years ago this question was not so acute. But the best enemy of the good, and with the increased mobility of the urban dweller, i.e. the transition from a desktop computer to a laptop, from a simple mobile phone to a smartphone, requests for mobile power sources have increased dramatically
With the miniaturization of consumer electronics, its developers must withstand the general direction and reduce the power source, thus sacrificing battery life.
Out of these two problems, two actual requests, two requirements are born that go alongside each other, but which many, and even more, almost all mass information sources fail to distinguish
- Hybrid and electric vehicles need light batteries
- Portable Electronics - Compact
Unfortunately, high technology is such a thing, where a breakthrough is not always made on request. And so: "bottoms can not, tops do not want." wait for a revolution in battery technology? This article will try to shed light on this article.
the main impetus is the desire to dispel a huge misunderstanding, which was created on the one hand by sensational journalists, on the other, perhaps by scientists whose cross is always to exaggerate their already considerable achievements. Here are just a few examples of news, one of which I heard even in the news of one of the central channels.
New Li-Ion Batteries
Could longer ten times longer
"Found a substitute for rare metals for the production of batteries ... It can be used in smartphones and other devices, the period of autonomous use of which will increase"
"Amprius: More Energy in Batteries, Nanowire Anodes Could Run,"
Nanowire battery lasts 10 times longer
All of them are familiar to most of you about promising batteries, which will be much more capacious.
Market condition
If the 20th century can be called the century of electricity, then
The last 20 years is the time of mobile electronics and it is to the development of chip technology that the batteries owe their latest achievements. The growth of the portable electronics market over the past 20 years has served as a source of growth for the rechargeable battery market. In 1983, Motorola released the first commercial mobile phone and since the beginning of the 90s it has already become a daily occurrence, and the beginning of the 90s was the birth of an energy-saving laptop on the Intel386 SL. The reverse is also true: new chemical power sources have opened a new era of mobile electronics. So the rapid development of electronics coincides with the commercial introduction of new types of batteries: 1989 - NiMH, 1990 - Li-Ion. At the moment, the market growth is slowing, and this engine is replaced by a new one - the most promising market for hybrid cars.Today, of course, the most advanced are Lithium-Ion current sources (Li-Ion).
The potential of this technology has not yet been fully disclosed and all short and medium term prospects are connected with them. Please note (Fig. Right) that the variation in performance for various Li-ion designs is much wider than for previous batteries, the fact is that Li-ion is a fundamentally new pattern of battery operation, the representatives of which can vary greatly in layoutTo date, the electronic market, apparently, does not have serious growth prospects, because its entire limit has the entire solvent population. And with the advent of smartphones, each representative has 1-2 multimedia devices or batteries. The figure on the left shows that by 2010 the number of cell subscribers. networks have already reached 5.5 billion
| portable electronics (~ 10-12 billion $ / g) | electric car market (potentially ~ 60-100 billion $ / g.) |
 |  |
| At the moment, mobile electronics need more compact current sources, and for them the critical characteristic is specific volume capacity [Ah / l] and energy [Wh / l] | The competitiveness of hybrid and electric vehicles with classic ones requires a significant battery relief: an increase in their capacity [Ah / g], power [W / g], energy per gram of battery [Wh / g]. Also a significant increase in durability and reliability, while reducing the cost [Wh / $] |
')
"Lithium-ion technology, will dominate
on the market this century. "
Takao Iwasaki - President of Kureha Corp. (Materials and components for Li-ion batteries)
* According to some estimates, by 2020 the market can grow to 5-8 trill. yen (about $ 65-100 billion)
This forecast is based on the invention and introduction of new types of lithium-ion batteries; therefore, from the financial side, all developments in this area enjoy generous support. There have been no shortages of loud statements lately, we will try to figure out what can be expected in the coming years.
Read
1.Very detailed market research: LiB materials industry. Takato Watabe, Masashi Mori January 26, 2011. Deutsche Bank Group.
Battery design
So, the next decade is the time of lithium-ion batteries, so we will not pay enough attention to the future LiS and Li-air batteries.
Since the design of the battery itself does not undergo revolutionary changes, we can assess the prospects for new developments, pushing off from the existing industrial designs.
To predict the characteristics per gram and liter of battery, remember that it consists of two electrodes, and a separator, as well as current collectors, a steel case. To take into account all the components, we use the model of a cylindrical battery type 18650 and 14430. It is these cylindrical elements that are the filling of the batteries of our laptops.Method of assessment. Determination of battery design parameters
Consider 2 types of standard cylindrical batteries: 14430 and 18650. Basically they consist of a working part - a roller in an electrolyte twisted from electrodes and a separator, and a steel container as well as a body, as well as covers, clamps, fuses.
To establish the characteristics of the battery, ideally, you need to know the geometry and mass of all the components included in it, but since these data were not found in open sources, we will satisfy curiosity by other means:
To establish the weight and volume of the working and auxiliary parts of the battery, we introduce a model: the battery consists of 3 parts: Steel vertical wall (0.3-0.5 mm) cylindrical working part, as well as lower and upper auxiliary parts (purple) can be taken by cylinders , fixed height, battery radius and unknown density.
| Basically, the battery consists of 3 parts: the working (active) part - the roller twisted from the electrodes and the separator in the electrolyte, and the body - the steel container, as well as covers, cleats, fuses. To establish the weight and volume of the working and auxiliary parts of the battery, we introduce a model: |  |
| The active part is a cylinder (orange), and the body ( can ) is a steel vertical wall ( wall ) is a tube with thickness b = 0.3-0.5 mm,. The lower and upper auxiliary parts (purple ( add )) can be taken by cylinders (generally one cylinder), and a radius equal to the inner radius of the tube of the walls of the battery, a certain fixed height and unknown density. |  |
To determine the characteristics of comparable batteries of two types, but with the same filling.
| Diameter D [mm] | Height H [mm] | Weight M [g] | Capacity C [Ah] | |
|---|---|---|---|---|
| NoName14430 | 14 | 43 | 17 | 0.65 |
| NoName18650 | 18 | 65 | 46 | 2.2 |
And now let's get maximum information out of this: it’s obvious that
V = πr 2 H
M act + M can = M and V act + V can = V
in turn, according to the model
M can = M wall + M add and V can = V wall + V add
wall characteristics are calculated directly
V wall = n (rb) r H
M wall = ρ steel V wall
V add = n (rb) 2 x
V add = n (rb) 2 y ,
where x, y are simply parameters indicating respectively the height and the product of the height and conditional density of the violet cylindrical part.
Now use the fact that the capacity with the same filling is proportional to its quantity
Using the above formulas and data, it is easy to compose and solve the following system of equations
Since matrices underlined in green are already known.Calculation of the volume and mass of the electrodes
The capacity of the electrodes is equal to each other and equal to the total capacity of the battery . Using this and knowing about the specific capacitances of the electrodes in conventional batteries, you can find the volume allocated for the electrodes in any battery
Calculation of specific capacitances of the electrodes.
The electrode consists of the active substance mixed with the conductive substance and the holder, dried and having a certain porosity. This mixture is attached to the current collector - metal foil (aluminum for the cathode and copper for the anode). The volumetric proportions of the collectors to ordinary electrodes are restored according to [].
Further it is easy to establish the volume occupied by electrolyte.
Model parameters are refined by reducing the mass error
of these two batteries and another modern Sony NexelIon 14430 whose chemistry and characteristics are known
| Diameter D [mm] | Height H [mm] | Weight M [g] | Capacity C [Ah] | |
|---|---|---|---|---|
| NexelIon14430 | 14 | 43 | 20 | 0.91 |
Forecast
Now, using the model and knowing the mass fractions (wt%), packing density, gravimetric capacity of the active substance, vol% volume fraction and current collector density, it is easy to restore the full consistency of the battery, volume and gravimetric capacities of the electrodes. And make an assessment of the characteristics of the future product. In other words, we can estimate the missing parameters of existing batteries and imagine what characteristics their analogs with new electrodes will have.
In order not to tire with excessive scrupulousness, we will give results
As can be seen from the forecast chart of the capacity of the battery with the LiNi 1-xy Co x Mn y O 2 anodes (for laptops and phones), it can be seen that in the next 10-12 years batteries can become ~ 30-50% more compact, mainly due to the increase in capacity anodes. The question of greater growth rests on the invention of more capacious cathodes that are not visible. So far the only consolation is to buy additional batteries for laptops, which simply consist of a larger number of the same cylindrical elements. Regarding smartphones, honestly speaking, I wonder why phone manufacturers ignore the production of batteries of increased capacity, such as they produce for laptops. In principle, I used two Mugen Power and Seido batteries and was very pleased with both of them.For the car industry is coming really new age:
New cheap cathodes should reduce the total cost of such a battery ~ 50%, compared with similar ones for portable devices. The transition to nanostructured engineering allows us to achieve a significant increase in durability when working at a power of 10 or even 100 times higher than modern. Note that the requirement for promising batteries for cars is a 10-15 fold increase in their service life, and it still remains unfulfilled (~ 5000 cycles)
It is unlikely that any unknown company will be able to intervene in the struggle of such giants as Sony, Panasonic, Sanyo, Samsung, 123systems, etc., except in the form of StartUp, since the main issue in introducing new batteries is their safety, in other words, the company's reputation .
And finally, as a general and optimistic conclusion: It would be better, but not immediately and not so), and in what they do not lie, it’s in the fact that you can go into a conditional coffee shop and charge your batteries in a matter of minutes!
I am well aware that not everyone is interested in such a long post, so a significant part of it can be easily missed by going directly to the results. Below is a fairly detailed overview of the batteries in general and in detail of the lithium ion technology, which should explain from where the legs grow in sensational news, as well as discuss the latest achievements in this field. It is there that the characteristics of the new materials required for the forecast will be given.
Part II. Content
Batteries Introduction
Simplest cell
Li-ion battery
- History and Principle of Action
- The main components of the LIB
Chemical current source. Battery. Introduction
Until now, we have talked about batteries exclusively from the consumer side, but all further consideration goes into the details of the operation of devices. At the beginning of the review, calling the batteries mobile sources of energy, the author deliberately avoided concretization: batteries are mobile sources of current, and more specifically Chemical Current Sources (hereinafter HIT). Their purpose is to create an electric current through a connected external network. In other words, to pass through it the flow of electrons (Current) with a certain "force" (voltage)
Chemistry and Electricity
It should be clarified that although chemistry is primarily associated with various letters and names, it, as a science, is engaged in nothing more than the study of electrical interactions in a substance.
As a musician builds his composition of notes, so the chemist operates with his simple elements - chemical. The chemical element is a stable (and therefore constantly occurring in the same form) structure consisting of a nucleus (a very compact combination of heavy particles — neutrons and positively charged protons), and a shell of light negative electrons corresponding to the charge of this nucleus. Each element differs from the previous one by 1 proton in the nucleus and, accordingly, in the neutral state by one electron in the shell. Electrons are located around the nucleus in the intricate "orbits" - orbitals. These orbitals are due to Coulomb interaction with both the nucleus and neighboring electrons.
It is easy to see that in the periodic table the structure of elements is repeated in columns, changing only in scale, and then the chemical properties of elements are repeated. The outer layer of electrons and is involved in the interaction with other atoms. The force of attraction is proportional to the charge of the nucleus, and inversely proportional to the square of the radius . The rows in the Mendeleev t. Show (from left to right) the filling of the outer shell. When one shell is filled, the radius of its electron orbit is approximately the same, therefore, from left to right, as the charge of the nucleus increases, the attraction increases and the electrons attract closer to the nucleus. While at the beginning of the filling of a new one, all the inner shells push away electrons of the new, thereby reducing the binding force of the electron to the nucleus, and therefore the radius significantly increases when moving to a new row. An important consequence of the presence of such complex electrical interactions is that electrons, getting rid of extras or adding additional ones (about how they get rid of or taking players into their cards), tend to form an entirely filled shell, becoming as close as possible to the elements of the last column - self-sufficient inert gases. This pattern is called the octet rule (8 electrons in the outer orbit). Anyway, the main consequence of the above is the fact that different elements have different ability to attract electrons. This is reflected in various numerical indicators ( electronegativity , ionization energy , electron attractiveness ), but the main thing is that a more “strong” element is able to take an electron from a weaker one , and this transfer is an electric current .
In the current classification, HITs are divided into primary (batteries) and secondary (batteries). In this presentation, the author would like to emphasize that these names derive not from the fact that the last ones are able to be recharged, but from the fact that the primary sources of current that are collected in the battery serve as an energy source by themselves, and the secondary ones only transfer the energy received from the charger.
Galvani effect and Frankenstein
Significantly for the first time the effect that formed the basis of the HIT was discovered by Luigi Galvani, an Italian doctor. In a series of his experiments with a dissected frog, among other things, he was able to observe muscle contraction and record electric current with the help of two different metal blades. But the output of Galvani ”Muscles produce electricity” was incorrect. The first correctly interpreted phenomenon and concluded that the electromotive force is born from the contact of two different metals, was the Italian physicist A. Volta. Applying the discovery in practice, Volta created the first chemical cell, which was given the name of Galvani. The figure shows a stack of alternating discs Copper / Paper with H2SO4 / Zinc. In other words, these are series-connected electrochemical cells, i.e. A battery of cells, which you and I used to call simply: Battery.XIX , : .
() . , — : , «, » . , , , ( ).
.
Consider the very first current source, invented by Volta and bearing the name of Galvani.
The source of current in any battery can only be a redox reaction. Actually these are two reactions: the atom is oxidized when it loses an electron. Obtaining an electron is called recovery. That is, the redox reaction proceeds at two points: from where and from where the electrons flow.
() . , . , - . Zn – Cu ( ) , , , ( ). . ()(. )
In all HITs preceding Li-ion, the electrolyte is an active participant in the reactions
taking place. See the principle of operation of a lead-acid battery
Galvani error
The electrolyte is also a conductor of current, only of the second kind, in which the ions move the charge. The human body is just such a conductor, and the muscles contract due to the movement of anions and cations.
So L. Galvani accidentally connected two electrodes through a natural electrolyte - a prepared frog.
HIT characteristics
Capacity - the number of electrons (electric charge) that can be passed through a connected device until the battery is completely discharged [Q] or [Ah = Q / 3600]
The capacity of the entire battery forms the capacity of the cathode and anode: how many electrons the anode is able to give and how many electrons the cathode is able to accept. Naturally, limiting, will be the smaller of the two tanks.
Voltage - potential difference. energy characteristic, showing how much energy a single charge releases when moving from the anode to the cathode [V = J / Q].
Energy is the work that can be done on a given HIT before it is fully discharged. [J] or [Wh = J / 3600]
Power is the rate of energy release or work per unit of time [W = J / sec]
Durability orCoulomb efficiency - what percentage of the capacity is irretrievably lost during the charge-discharge cycle.
All characteristics are predicted theoretically, however, due to a multitude of factors difficult to read, most of the characteristics are determined experimentally. So they can all be predicted for the ideal case, based on chemical composition, but the macrostructure has a huge impact on both capacity and power and durability.
So, the durability and capacity largely depend on both the charge / discharge rate and the macrostructure of the electrode.
Therefore, the battery is characterized not by one parameter, but by a whole set for various modes. For example, the battery voltage (single charge transfer energy **) can be estimated to a first approximation (at the stage of evaluating the prospects of materials) from the ionization energies of the atoms of active substances during oxidation and reduction. But the real value is the difference. potentials, for the measurement of which, as well as for the removal of the charge / discharge curves, a test cell is assembled with a test electrode and a reference one.
For electrolytes based on aqueous solutions, a standard hydrogen electrode is used. For lithium-ion lithium metal.
* The ionization energy is the energy that must be transferred to an electron in order to break the bond between it and the atom. That is, taken with the opposite sign, is the binding energy, and the system always seeks to minimize the binding energy
** The energy of a single transfer is the energy of transfer of one elementary charge 1,6e-19 [Q] * 1 [V] = 1,6e-19 [J] or 1eV (electron volt)
Lithium ion batteries
<In the 1980s, lithium was proposed as a promising material for the anode, but due to the high reactivity and uncontrolled conversion of the anode cycle by cycle, for example, leading to an increase in lithium "branches" reaching the cathode directly, which led to a short circuit in the secondary Batteries decided to abandon the use of lithium metal in favor of compounds containing only lithium ions. The properties of lithium in graphite have already been described. And in 1991, Sony released lithium batteries with a graphite anode under the now commonly used name Li-ion.
As already noted, in lithium-ion batteries, the electrolyte is not directly involved in the reaction. Where do the two main reactions occur: oxidation and reduction and how is the charge balance aligned?
Directly, these reactions occur between lithium in the anode and the metal atom in the cathode structure. As noted above, the emergence of lithium-ion batteries is not just the discovery of new connections for electrodes, it is the discovery of a new principle of HIT functioning:
The electron weakly connected with the anode is pulled out along the outer conductor to the cathode.In the cathode, an electron falling into the metal orbit, compensating for it the 4th electron practically taken away from it by oxygen. Now the electron metal finally joins oxygen, and the resulting lithium ion is drawn into the gap between the oxygen layers by the resulting electric field. Thus, the enormous energy of lithium-ion batteries is achieved by the fact that it deals not with the restoration of external 1.2 electrons, but with the restoration of more “deeper” ones. For example, for kobolt the 4th electron.
Lithium ions are retained in the cathode due to a weak, of the order of 10 kJ / mol, interaction ( Van der Waals ) with the surrounding electron clouds of oxygen atoms (red)
Li - the third element in the periodic table , has a low atomic weight, and small size. Due to the fact that lithium begins and, moreover, only the second row, the size of the neutral atom is rather large, whereas the size of the ion is very small, smaller than the size of the helium and hydrogen atoms, which makes it almost irreplaceable in the LIB scheme. Another consequence of the above: the external electron (2s1) has a minute connection with the nucleus and can easily be lost (this is expressed in the fact that Li has the lowest potential with respect to the hydrogen electrode P = -3.04V).
The main components of the LIB
Electrolyte
Unlike traditional batteries, the electrolyte together with the separator does not directly participate in the reaction, but only provides the transport of lithium ions and does not allow the transport of electrons.
Electrolyte requirements:
- good ionic conductivity
- low electronic
- low cost
- low weight
- non-toxicity
- ABILITY TO WORK IN THE SPECIFIED RANGE OF TENSIONS AND TEMPERATURES
- prevent structural changes of the electrodes (to prevent the decrease in capacity)
In this review, I will allow to bypass the topic of electrolytes, technically complex, but not so important for our topic. Basically, LiFP 6 solution is used as an electrolyte.
Although it is believed that the electrolyte with a separator is an absolute insulator, in reality it is not:
In lithium-ion elements there is a self-discharge phenomenon. those. lithium ion with electrons reach the cathode through the electrolyte. Therefore, it is necessary to keep the battery partially charged in case of long-term storage.
At long interruptions in operation, the phenomenon of aging also takes place, when separate groups are separated from uniformly saturated with lithium ions, disturbing the uniformity of concentration and thereby reducing the total capacity. Therefore, when buying a battery, you must check the release date
Anodes
Anodes are electrodes with a weak bond, both with the “guest” lithium ion, and with the corresponding electron. Currently, there is a boom in the development of a variety of solutions for the anodes of lithium-ion batteries.
Anode requirements
- High electronic and ionic conductivity (Fast lithium injection / extraction process)
- Low voltage with test electrode (Li)
- High specific capacity
- High stability of the anode structure during the introduction and extraction of lithium, which is responsible for the Coulomb
Improvement methods:
- Change the macrostructure structure of the anode substance
- Reduce the porosity of the substance
- Choose a new material.
- Use combined materials
- To improve the properties of the border with the electrolyte phase.
In general, anodes for LIB can be divided into 3 groups according to the method of placing lithium in its structure:
- Placement in the “grooves” of the anode structure , for example, between graphene layers in graphites, in spines, and also in layered 3d-metal nitrides.
Advantages : high structural stability, durability.
cons : low capacity - dissolution in the crystal of another substance, the formation of alloys - alloys with silicon, tin, germanium.
pluses : the greatest capacity
Minuses : The greatest structural changes: ~ 3-4 times volume change - Aubin reactions - interaction with metal oxides, consisting in the replacement of the main metal oxide, lithium oxide and back
pluses : large capacity
cons : major structural changes: ~ 2 times volume change
Anodes - hosts. Graphite
Almost all of them remembered from high school that carbon exists in solid form in two main structures - graphite and diamond. The difference in the properties of these two materials is striking: one is transparent - the other is not. One insulator is another conductor, one cuts the glass, the other is rubbed on the paper. The reason is the different nature of interatomic interactions.
A diamond is a crystal structure where interatomic bonds are formed due to sp3 hybridization, that is, all bonds are the same — all three 4 electrons form σ bonds with another atom.
Graphite is formed by sp2 hybridization, which dictates a layered structure, and a weak bond between the layers. The presence of a “floating” covalent π-bond makes carbon graphite an excellent conductor
Graphite is the first and today the main anode material, which has many advantages.
High electronic conductivity
High ionic conductivity
Small volumetric deformation when introducing lithium atoms
Low cost
As the material for the anode, graphite was first proposed as early as 1982 by S.Basu [1] and introduced into the 1985 A. Yoshino lithium-ion cell [2]
At first, graphite was used in the electrode in its natural form and its capacity reached only 200 mAh / g . The main resource for increasing the capacity was improving the quality of graphite (improving the structure and cleaning of impurities). The fact is that the properties of graphite vary considerably depending on its macrostructure, and the presence of a multitude of anisotropic grains in the structure, oriented pink, significantly worsens the diffusion properties of the substance. Engineers tried to increase the degree of graphitization, but its increase led to the decomposition of the electrolyte. The first solution was to use crushed low-graphitized coal mixed with electrolyte, which increased the anode capacity to 280mAh / g (the technology is still widely used) This was overcome in 1998 by introducing special additives into the electrolyte, which create a protective layer in the first cycle (hereinafter SEI solid electrolyte interface) preventing further decomposition of the electrolyte [3] and allowing the use of artificial graphite 320 mAh / g . To date, the capacity of the graphite anode has reached 360 mAh / g [4], and the capacity of the entire electrode 345mAh / g and 476 Ah / l [8]Reaction: Li 1-x C 6 + Li x ↔ LiC 6
The graphite structure is capable of accepting a maximum of 1 Li atom per 6 C, therefore the maximum achievable capacity is 372 mAh / g (this is not so much theoretical, as is the commonly used figure because here is the rarest case when something real exceeds theoretical, because in practice lithium ions can be placed not only inside the cells, but also on kinks of graphite grains)
Since 1991 The graphite electrode has undergone many changes, and according to some characteristics, it seems, as an independent material, has reached its ceiling . The main field for improvement is power increase, i.e. The discharge / charge rate of the battery. The task of increasing power is at the same time the task of increasing durability, since the rapid discharge / charging of the anode leads to the destruction of the graphite structure, “lithium ions” being pulled through it. In addition to standard techniques for increasing power, which usually boil down to an increase in the surface / volume ratio, it is necessary to note the study of the diffusion properties of graphite single crystal in different directions of the crystal lattice [5] showing that the diffusion rate of lithium can differ by 10 orders of magnitude.
back to conclusions
K.S. Novoselov and A.K. Game - winners of the Nobel Prize in Physics 2010. Discoverers of self-use of graphene[1] Bell Laboratories US Patent 4,423,125
[2] Asahi Chemical Ind. Japan Patent 1989293
[3] Ube Industries Ltd. US Patent 6,033,809
[4] Masaki Yoshio, Akiya Kozawa, and Ralph J. Brodd. Lithium-Ion Batteries Science and Technologies Springer 2009.
[5] Lithium Diffusion in Graphitic Carbon Kristin Persson at.al. Phis. Chem. Letters 2010 / Lawrence Berkeley National Laboratory. 2010
[6] lithium intercalated graphite LiC6, KR Kganyago, PE Ngoep Phis. Review 2003.
[7] The battery used is a lithium-ion battery and method of manufacturing same. Samsung Display Devices Co., Ltd. (KR) 09 / 923,908 2003
[8] This is an example of graphite anode in lithium ion batteries. Joongpyo Shim and Kathryn A. Striebel
Tin anodes and co. Alloys
To date, one of the most promising are the anodes from the elements of the 14th group of the periodic table. Thirty years ago, the ability of tin ( Sn ) to form alloys (interstitial solutions) with lithium was well studied [1]. Only in 1995, Fuji announced tin-based anode material (see, for example, [2])It was logical to expect that the lighter elements of the same group will have the same properties, and indeed Silicon ( Si ) and Germanium ( Ge ) show the identical nature of lithium
Li 22 Sn 5 , Li 22 Ge 5 , Li 15 Si 4
Li x + Sn (Si, Ge) <-> Li x Sn (Si, Ge) (x <= 4.4)
The main and total complexity in the application of this group of materials is huge, from 357% to 400% , volumetric deformations during saturation with lithium (when charging), leading to large losses in capacity due to the loss of a part of the anode material of contact with the current collector.
Perhaps the most developed element of this group is tin:
being the heaviest gives the heavier solutions: the maximum theoretical capacity of such an anode is 960 mAh / g , but compact ( 7000 Ah / l - 1960Ah / l * ) nevertheless surpassing traditional carbon anodes 3 and 8 ( 2.7 * ) times, respectively.
The most promising are silicon-based anodes, which theoretically ( 4200 mAh / g ~ 3590mAh / g [5]) are more than 10 times lighter and 11 ( 3.14 * ) times more compact ( 9340 Ah / l ~ 2440 Ah / l * ) graphite.
Si does not have sufficient electronic and ionic conductivity, which makes it necessary to look for additional means to increase the power of the anode
Ge , germanium is not mentioned as often as Sn and Si, but being intermediate, has a large ( 1600 mAh / g ~ 2200 * Ah / l ) capacity and 400 times higher ionic conductivity than Si, which can outweigh its high cost when creating high-power electrical engineering [4]
Along with large volumetric deformations, there is another problem:
loss of capacity in the first cycle due to the irreversible reaction of lithium with oxides
SnO x + x2Li + -> xLi 2 O + Sn
xLi 2 O + Sn + yLi + <-> xLi 2 O + Li y Sn
which the greater, the greater the contact of the electrode with the air (the larger the surface area, that is, the smaller the structure)
A number of schemes have been developed that allow, in varying degrees, to use the great potential of these compounds, smoothing the weaknesses. However, as well as advantages:
All these materials are currently used in anodes combined with graphite, raising their characteristics by 20-30%
* the values corrected by the author are marked, since common figures do not take into account a significant increase in volume and operate on the density value of the active substance (before saturation with lithium), and therefore do not completely reflect the real state of affairs
[1] MS Foster, CE Crouthamel, SE Wood, J. Phys. Chem., 1966
[2] Jumas, Jean-Claude, Lippens, Pierre-Emmanuel, Olivier-Fourcade, Josette, Robert, Florent Willmann, Patrick 2008
US Patent Application 20080003502.
[3] Sony's Nexelion Chemistry and Structure of
Li-ion Electrode Materials
J. Wolfenstine, JL Allen,
J. Read, and D. Foster
Army Research Laboratory 2006.
[4] High Capacity Li-Ion Battery Anodes Using Ge Nanowires
[5] Electrodes for Li-Ion Batteries — A Old Problem
Journal of The Electrochemical Society, 155 ͑2͒ A158-A163 ͑2008͒.
Existing Development
All existing solutions to the problem of large anode deformations proceed from a single consideration: during expansion, the cause of the mechanical stresses is the solidity of the system: split the monolithic electrode into as many smaller structures as possible, allowing them to expand independently of each other.The first, most obvious, method is the simple grinding of a substance using a holder to prevent the aggregation of particles into larger ones, as well as the saturation of the resulting mixture with electron-wire agents. A similar solution could be traced in the evolution of graphite electrodes. This method allowed to achieve some progress in increasing the capacity of the anodes, but nevertheless, until the potential of the considered materials is fully revealed, increase the capacity (both volume and mass) of the anode by ~ 10-30% ( 400 - 550 mAh / g ) at low power
A relatively early method of introducing nanosized tin particles (electrolysis) onto the surface of graphite spheres,
The ingenious and simple look at the problem allowed to create an efficient battery using ordinary industrially obtained powder 1668 Ah / l [14]
The next step was the transition from microparticles to nanoparticles: state-of-the-art batteries and their prototypes examine and form the structures of a substance on a nanometer scale, which made it possible to increase the capacity to 500 - 600 mAh / g (~ 600 Ah / l *) with acceptable durability [6]
One of the many promising types of nanostructures in the electrodes is the so-called. the shell – core configuration, where the core is a small-diameter ball of the working substance, and the shell serves as a “membrane” preventing particles from frightening and providing electronic communication with the environment. Impressive results showed the use of copper as a shell for tin nanoparticles [8], showing high capacity ( 800 mAh / g - 540 mAh / g *) for many cycles, as well as at high charge / discharge currents. In comparison with the carbon skin ( 600 mAh / g ) [7] similarly for Si-C [9]. Since Nanoshars are entirely composed of the active substance, its bulk capacity should be recognized as one of the highest ( 1740 Ah / l (*)) As noted, in order to reduce the adverse effects of a dramatic expansion of the working substance, space is required for expansion.In the past year, researchers have made impressive progress in creating workable nanostructures: nano rods
Jaephil Cho [13] achieved 2800 mAh / g low power per 100 cycles and 2600 → 2400 at higher power using a porous silicon structure
as well as stable Si nanofibres coated with a 40nm graphite film, demonstrating 3400 → 2750 mAh / g (ak. islands) after 200 cycles.
Yan Yao and co-workers [12] suggest using Si in the form of hollow spheres, achieving amazing durability: the initial capacity is 2725 mah / g (and only 336 Ah / l (*)) when the capacity drops after 700 cycles less than 50%
In September 2011, scientists from the Berkley Lab [10] announced the creation of a sustainable electron-conducting gel,which can revolutionize the use of silica materials. The value of this invention is difficult to overestimate: a new gel can serve as both a holder and a conductor, preventing nanoparticle splicing and loss of contact. Allows the use of cheap industrial powders as an active material and, according to the creators, is comparable in price to traditional holders. Electrode made of industrial materials (nano Si powder) gives a steady 1360 mAh / g and very high 2100 Ah / l (*)
back to conclusions
* - assessment of the actual capacity calculated by the author (see the appendix)
[1] MS Foster, CE Crouthamel, SE Wood, J. Phys. Chem., 1966
[2] Jumas, Jean-Claude, Lippens, Pierre-Emmanuel, Olivier-Fourcade, Josette, Robert, Florent Willmann, Patrick 2008 US Patent Application 20080003502.
[3] Li-ion Electrode Materials Chemistry and Structure of Nexelion J. Wolfenstine, JL Allen, J. Read, and D. Foster Army Research Laboratory 2006.
[4] High Capacity Li-Ion Battery Anodes Using Ge Nanowires
[5] Ball milling Graphite / Tin composite anode materials in liquide medium. Ke Wang 2007.
[6] for the lithium-ion battery Journal of Power Sources 2009.
[7] The Impact of Carbone-Shell on Sn-C composite anode for Lithium-ion Batteries. Kiano Ren et al. Ionics 2010.
[8] Novel Core-Shell Sn-Cu Anodes For Li Rech. Batteries, prepared by redox-transmetallation react. Advanced Materials. 2010
[9] Core double-shell Si @ SiO2 @ C nanocomposites as anode materials for Li-ion batteries Li et al. ChemCom 2010.
[10] Polymers with Tailored Electrodes High Capacity Lithium Battery Electrodes Gao Liu et al. Adv. Mater. 2011, 23, 4679–4683
[12] Interconnected Silicon Hollow Nanospheres for Lithium-Ion Battery Anodes with Long Cycle Life. Yan Yao et al. Nano Letters 2011.
[13] Porous Si anode materials for lithium rechargeable batteries, Jaephil Cho. J. Mater. Chem., 2010, 20, 4009–4014
[14] Electrodes for Li-Ion Batteries — 155 ͑216 A158-A163 ͑2008͒.
[15] ACCUMULATEURS FIXES, US Patent 8,062,556 2006
application
Special cases of electrode structures :
Estimation of the real capacity of tin nanoparticles with copper coating Cu @ Sn
From the article known volume ratio of particles 1 to 3 m
0.52 is the packing ratio of the powder. Accordingly, the rest of the volume behind the holder 0.48
Nanospheres. Packing Ratio
the low volume capacity given for nanospheres is due to the fact that the spheres inside are hollow, and therefore the packing coefficient of the active material is very low,
even it will be 0.1 , for comparison, for a simple powder - 0.5 ... 07
Anodes of exchange reactions. Metal oxides.
The group of promising undoubtedly also includes metal oxides, such as Fe 2 O 3 . Possessing high theoretical capacitance, these materials also require solutions to increase the discreteness of the active substance of the electrode. In this context, such an important nanostructure as nanofibers will receive due attention here.
Oxides shows a third way to include and exclude lithium in the structure of the electrode. If in graphite, lithium is predominantly between the layers of graphene, in solutions with silicon, it is embedded in its crystal lattice, then there is more likely a “oxygen exchange” between the “main” metal of the electrode and the guest, Lithium. The electrode array is formed of lithium oxide and basic metal strastaetsya into nanoparticles within the matrix (see, e.g., Figure reacted with molybdenum oxide. MoO 3 + 6Li + + 6e - <-> 3Li 2 O + Mo )Such a nature of interaction implies the need for easy movement of metal ions in the electrode structure, i.e. High diffusion, which means the transition to fine particles and nanostructures
Speaking about the different anode morphology, ways of providing electronic communication in addition to the traditional (active powder, graphite powder + holder), other forms of graphite can be distinguished as a conductive agent:
A common approach is the combination graphene and the main island, when nanoparticles can be located directly on the “sheet” of graphene, and it, in turn, will serve as a conductor and buffer, when the working substance expands. This structure has been proposed for Co 3 O 4 [1] 778 mAh / gand quite durable. Similarly, 1100 mAh / g for Fe 2 O 3 [2],
but due to the very low density of graphene, it is difficult to even estimate how much similar solutions are applicable.
Another method is the use of graphite nanotubes by
AC Dillon et al. experimenting with MoO 3, they show a high capacity of 800 mAh / g ( 600mAh / g * 1430 Ah / l * ) with 5 wt% holder [3] loss of capacity after 50 cycles while being covered with aluminum oxide as well as with Fe 3 O 4 , without using holder resistant 1000 mAh / g ( 770 - 1000 Ah / l *) Figure right: SEM image of anode / Fe 2 O 3 nanofibers with 5 wt% graphite fine tubes (white) [3]M x O y + 2yLi + + 2ye - <-> yLi 2 O + xM
back to conclusions
A few words about nanofibres
Recently, nanofibers are one of the hottest topics for materials science publications, in particular those devoted to promising batteries, since they provide a large active surface with good communication between particles.Initially, nanofibers were used as a kind of nanoparticles of active material, which, in a homogeneous mixture with a holder and conductive agents, form an electrode.
The question of the packing density of nanofibers is very complicated, since it depends on many factors. And, apparently, consciously almost not illuminated (specifically in relation to the electrodes). This already makes it difficult to analyze the real indicators of the entire anode. For compiling an evaluative opinion, the author took the risk of using the work of RE Muck [4], devoted to the analysis of hay density in bunkers. Judging by the SEM images of nanofibers, an optimistic analysis of the density of the package will be 30-40% In the last 5 years, more attention has been focused on the synthesis of nanofibers directly on the current receiver, which has several serious advantages:Direct contact of the working material with the current collector is provided, contact with the electrolyte is improved, the need for graphite additives is eliminated. several stages of production are passed, the packing density of the working substance increases significantly.
K. Chan and colleagues tested Ge nanofibers obtained 1000mAh / g ( 800Ah / l ) for low power and 800 → 550 ( 650 → 450 Ah / l *) at 2C after 50 cycles [5]. At the same time, Yanguang Li and colleagues showed a high capacity and enormous power. Co 3 O 4 : 1100 → 800 mAh / g ( 880 →640Ah / l *) after 20 cycles and 600 mAh / g ( 480 Ah / l *) at a 20-fold increase in current [6]
Separately, it should be noted and recommended to everyone to familiarize the inspiring works of A. Belcher **,
which are the first steps to a new the era of biotechnology.By modifying the bacteriophage virus, A. Belcher succeeded in building a nanofiber on its basis at room temperature, due to the natural biological process. Given the high structural definition of such fibers, the resulting electrodes are not only environmentally friendly, but also show both compaction of the fiber package and much more durable work [7] [8] [9]
back to conclusions
* - assessment of the actual capacity calculated by the author (see the appendix)
**
Angela Belcher is an outstanding scientist (chemist, electrochemist, microbiologist). Inventor of the synthesis of nanofibers and their ordering into electrodes by means of specially derived cultures of viruses( see interview )
application
As was said, the charge of the anode occurs through the reaction.
I did not find in the literature indications of the actual expansion rates of the electrode during charging, so I suggest evaluating them by the smallest possible changes. That is, by the ratio of the molar volumes of the reactants and the reaction products ( V Lihitated is the volume of the charged anode, V UnLihitated is the volume of the discharged anode). The densities of metals and their oxides can be easily found in open sources.
| Calculation forums | Calculation Example for MoO 3 |
|---|---|
    |      |
It should be borne in mind that the resulting volume capacity is the capacity of a continuous active substance, therefore, depending on the type of structure, the active substance occupies a different share of the volume of the whole material, this will be taken into account by entering the packing coefficient k p . For example, for the powder it is 50-70%
[1] Highly reversible Co3O4 / graphene hybrid anode for lithium rechargeable batteries. H. Kim et al. CARBON 49 (2011) 326 –332
[2] Nanostructured Reduced Grain Phenoxy Oxide / Fe2O3 Compound As Metallic Lithium Ion Batteries. ACSNANO VOL. 4 ▪ NO. 6 ▪ 3187–3194 ▪ 2010
[3] Nanostructured Metal Oxide Anodes. AC Dillon. 2010
[4] A New Way Of Looking At Bunker Silage Density. RE Muck. Dairy Forage Research US Center Madison, Madison WI
[5] High Capacity Li Ion Battery Anodes Using Ge Nanowires K. Chan et. al. NANO LETTERS 2008 Vol. 8, No.1 307-309
[6] Meshorous Co3O4 Nanowire Arrays for Lithium Ion Batteries with High Capacity and Rate Capability. Yanguang Li et. al. NANO LETTERS 2008 Vol. 8, No.1 265-270
[7] Virus-Enabled Synthesis and Assembly of Nanowires Ion Battery Electrodes Ki Tae Nam, Angela M. Belcher et al. www.sciencexpress.org / 06 April 2006 / Page 1 / 10.1126 / science.112271
[8] Virus-Enabled Silicon Anode for Lithium-Ion Batteries. Xilin Chen et al. ACS Nano, 2010, 4 (9), pp 5366–5372.
[9] VIRUS SCAFFOLD FOR SELF-ASSEMBLED, FLEXIBLE AND LIGHT LITHIUM BATTERY MIT, Belcher A. US 006121346 (A1) WO 2008124440 (A1)
Lithium Ion HIT. Cathodes
The cathodes of lithium-ion batteries should mainly be able to accept lithium ions, and to provide high voltage, which means that along with the capacitance more energy.
An interesting situation has arisen in the design and manufacture of cathodes for Li-Ion batteries. In 1979, John Goodenough and Mizuchima Koichi patented cathodes for Li-Ion batteries with a layered structure of the LiMO2 type , which almost all existing cathodes of lithium-ion batteries fall under. [1] [2] Thekey elements of the cathode are
oxygen, as a connecting link, a bridge, as well as a “catching” lithium with its electron clouds.Transition metal (i.e., a metal having valence d-orbitals), since it can form structures with a different number of bonds. The first cathodes used sulfur TiS 2 [5] [6],
but then they switched to oxygen, a more compact, and most importantly more electronegative element, giving an almost completely ionic bond with metals. The layered structure of LiMO 2 (*) is the most common, and all developments roll around the three candidates M = Co, Ni, Mn and constantly look at very cheap Fe .| Fe | Mn | Ni | Co | |
|---|---|---|---|---|
| content in the crust (ppm) | 50,000 | 950 | 75 | 25 |
| Market value ($ / kg) | 0.23 | 0.5 | 13 | 25 |
| MPC in air (mg / m 3 ) | ten | five | one | 0.1 |
| MPC in water (mg / l) | 300 | 200 | 13.4 | 0.7 |
Cobalt , in spite of many things, captured Olympus immediately and hardens it so far (90% of the cathodes), but due to the high stability and correctness of the layered structure with 140 mAh / g, the capacity of LiCoO 2 increased to 160-170mAh / g due to the expansion of the voltage range.
But because of the rarity for the Earth, Co is too expensive, and its use in its pure form can be justified only in small batteries, for example, for telephones. 90% of the market is occupied by the very first, and at the moment, still the most compact cathode.Nickel has been and remains a promising material, showing a high 190mA / g , but it is much less stable and such a layered structure in its pure form for Nidoes not exist [5]. Extraction of Li from LiNiO 2 produces almost 2 times more heat than from LiCoO 2 [3], which makes its use in this area unacceptable.
Manganese . Another well-studied structure is invented in 1992. Jean-Marie Tarasco [4], a cathode of the Spinel type of manganese oxide LiMn 2 O 4 : with a slightly lower capacity, this material is much cheaper than LiCoO 2 and LiNiO 2and much safer. Today it is a good variant for hybrid vehicles. Recent developments are associated with the doping of nickel with cobalt, which significantly improves its structural properties. A significant improvement in the stability when Ni is doped with electrochemically inactive Mg is also noted: LiNi 1-y Mg y O 2 . There are many alloys LiMn x O 2x , for Li-ion cathodes.
The fundamental problem is how to increase capacity. We have already seen with the example of tin and silicon that the most obvious way to increase capacity is to travel up the periodic table, but to
universally regret, there is nothing above the currently used transition metals (fig. right). Therefore, the entire progress of recent years associated with cathodes is generally associated with the elimination of the shortcomings of the already existing ones: an increase in durability, an improvement in quality, the study of their combinations (the left above) .Iron . From the very beginning of the lithium ion era, many attempts were made to use iron in the cathodes, but all without success. Although LiFeO 2 would be an ideal cheap and powerful cathode, it was shown [7] that Li could not be extracted from the structure in the normal voltage range [8]. This situation changed dramatically in 1997, with the cis-adherence to e / x properties of olivine LiFePO 4 . High capacity ( 170 mAh / g) approximately 3.4V with a lithium anode and the lack of a serious drop in capacity even after several hundred cycles. The main disadvantage of olivine for a long time was poor conductivity, which
significantly limited power. To remedy the situation, classical moves (grinding with graphite coating) were used, using a gel with graphite, it was possible to achieve high power at 120 mAh / g for 800 cycles. Indeed, enormous progress was achieved by meager doping of Nb, increasing the conductivity by 8 orders of magnitude.Everything suggests that Olivine will become the most popular material for electric vehicles. For exclusive ownership of LiFePO 4 rightsA123 Systems Inc. has been suing for years. and Black & Decker Corp, not without reason believing that the future of electric vehicles. Do not be surprised, but the patents are issued on the same captain of cathodes - John Gudenaf.
Olivine proved the possibility of using cheap materials and struck a kind of platinum. Inzheneraya thought immediately rushed into the resulting space. For example, the replacement of sulfates by fluorophosphates is now being actively discussed, which will increase the voltage by 0.8 V, i.e. Increase energy and power by 22% [9].
Funny: while there is a dispute about the rights to use olivine, I came across a lot of noname manufacturers offering items on a new cathode,
back to the conclusions
* All these compounds are stable only with Lithium. And, accordingly, they are already made saturated. Therefore, when buying batteries based on them, you must first charge the battery, overtaking part of the lithium to the anode.
** Understanding the development of the cathodes of lithium-ion batteries, you involuntarily begin to perceive it as a duel between two giants: John Goudanaf and Jean-Marie Tarasco. If Goudanaf patented his first fundamentally successful cathode of 1980 ( LiCoO 2 ) a year, then Dr. Trasko responded twelve years later ( Mn 2 O 4 ). The second principal achievement of the American took place in 1997 ( LiFePO 4), and in the middle of the past decade, the Frenchman is engaged in expanding the idea, introducing LiFeSO 4 F , and is working on the use of fully organic electrodes[1] Goodenough, JB; Mizuchima, KUS Patent 4,302,518, 1980.
[2] Goodenough, JB; Mizushima, KUS Patent 4,357,215, 1981.
[3] Lithium-Ion Batteries Science and Technologies. Masaki Yoshio, Ralph J. Brodd, Akiya Kozawa
[4] Method for preparation of LiMn2 O4 intercalation and secondary lithium batteries. Barboux; Philippe Shokoohi; Frough K., Tarascon; Jean-Marie. Bell Communications Research, Inc. 1992 US Patent 5,135,732.
[5] Lithium Batteries and Cathode Materials. M. Stanley Whittingham Chem. Rev.2004, 104, 4271−4301
[6] Rechargeable electrochemical cell with cathode stoichiometric titanium disulfide Whittingham; M. Stanley. US Patent 4,084,046 1976
[7] Kanno, R .; Shirane, T .; Inaba, Y .; Kawamoto, YJ Power Sources 1997, 68, 145.
[8] Lithium Batteries and Cathode Materials. M. Stanley Whittingham Chem. Rev.2004, 104, 4271−4301
[9] A 3.6 V lithium-based fluorosulphate insertion positive electrode for lithium-ion batteries. N. Recham1, JN. Chotard1, L. Dupont1, C. Delacourt1, W. Walker1,2, M. Armand1 and JM. Tarascon. NATURE MATERIAL November 2009.
application
The capacity of the cathodes is determined again as the maximum extracted charge per weight of the substance, for example, the group
Li 1-x MO 2 + Li + + e - ---> Li x MO 2
For example, for Co
with extraction degree Li x = 0.5, the capacity of the substance will be
At the moment, an improvement in the technical process has allowed to increase the degree of extraction and reach 160mAh / g.
But, of course, most of the powders on the market do not achieve these indicators.
.
. , , : , , , 1 kWh 387 kWh . , , (70-100 kg CO 2at 1 kWh). Moreover, in a modern consumer society, goods are not used until their resources are exhausted. That is, the period for “discouraging” this energy loan is small, and the utilization of modern batteries is expensive, and not everywhere available. Thus, the energy efficiency of modern batteries is still in question [1].
Recently, there have been several encouraging biotechnologies that allow synthesizing electrodes at room temperature. A. Belcher (viruses), J.M. Tarasco (use of bacteria).
An excellent example of such a promising biomaterial is lithiated oxocarbon - Li 2 C 6 O 6(Lithium Radisonate) [2], which, having the ability to reversibly place up to four Li per formula, showed a large gravimetric capacity, but since the recovery is associated with pi bonds, a somewhat lower potential (2.4 V). Similarly, other aromatic rings are considered as the basis for a positive electrode [2], also reporting a significant battery relief.The main "disadvantage" of any organic compounds is their low density, since all organic chemistry deals with light elements C , H , O and N. To understand how promising this direction is, it is enough to say that these substances can be obtained from apples and corn, as well as are easily recyclable and recyclable.
Lithium radionate would already be considered the most promising cathode for the automotive industry, if not for the limited current density (power) and the most promising for portable electronics, if it were not for the low density of the material (low volume capacity) (left). In the meantime, this is just one of the most promising fronts of work.
back to conclusions
[1] for example, see Hybrid vs disel
[2] Yasushi Morita et al. Nature Mat. 10,947–951 (2011)
Of course, something is described very superficially, it may not even be entirely correct, but it is enough to outline the perspectives of
ALL YOU.
Source: https://habr.com/ru/post/137276/
All Articles