Re: I dont get it.
I'll just give another plug to a "forgotten" battery technology: NiFe
On the minus side it has a low energy/weight ratio (worse than lead-acid). It also has a high self-discharge rate, so it's not useful for storing energy for more than a few days. Pretty useless even as a starter battery for a conventional auto.
On the plus side this battery is made of Iron, Nickel, and Potassium Hydroxide. Things that you can go out and purchase by the megatonne, that aren't in any sense hard to obtain or in danger of running out of. The battery also has a longer service life, and a greater tolerance of abuse, than any other battery technology I've ever read about. They are virtually indestructible. I read about somebody finding one made in the 1930s that had been sitting in a scrapyard for decades, and putting it back into service.
Ideal for storing solar energy, once solar becomes cheap and plentiful enough that there's an economic justification to store electricity by day and sell it (at a higher price) by night.