Where did the sub tag go?

Recently published a topic How to extend the life (resource) of a lithium-ion battery , but for chemical formulas there was no sub ... / sub tag.



At the moment, the list of allowed tags includes sup ... / sup; however, for some reason, the developers of the habr have forgotten about the support of indices.



Please support the sub tag, as it is very difficult to use pictures to represent simple chemical and other formulas.