Lithium Iron Phosphate is an already-viable chemistry that has a lot of upsides and only a few downsides compared to Lithium Cobalt.

https://en.wikipedia.org/wiki/Lithium_iron_phosphate_battery

The tl;dr is slightly lower energy density (~14%) in exchange for non-toxicity, extremely low self-discharge rates, not prone to runaway thermalling, and great cycle life.

It also has the advantage of being able to be essentially a drop-in replacement for many lead-acid uses.