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Discussions about batteries often revolve around energy density. What we want is a battery that stores a whole lot of energy in a very tiny volume, preferably in a manner that doesn’t involve explosions or fire. At the cutting edge of research, what we get are batteries that are a mix of amazing and amazingly bad.
Modern batteries are, quite frankly, a miracle compared to ye olde lead acid battery. Yet they still contain less energy per unit mass than the equivalent mass of wood. Essentially, we simply don’t pack enough atoms into a small enough volume to compete with hydrocarbons. But, now it seems that graphene—it’s always graphene—might help pack lithium in.
The invisible metal
Although there are many ways to make a lithium-ion battery, the chemistry boils down to the following: lithium is stored in some form at one electrode. The lithium is released as an ion, where it travels to another electrode and reacts. At the same time, the electrons that complete the reaction travel out into the world via one electrode, do some work, and end up at the other electrode, where they complete the reaction.