One drawback of using lots of lithium batteries in your home is that they might experience thermal runaway and burn your house down. Not having to worry about that should have some additional value.
Most new solar installations now use LiFePO4 which apparently is much safer on that runaway side...
That's good, but is that what's used in "used car-batteries with degraded capacity"?
Used car batteries are conventional unsealed, lead-acid batteries. Lithium-iron-phosphate (aka LiFePO4, LFP) batteries is a different battery chemistry altogether. It is touted as the answer to a deep-cycle, lithium-based electrical storage that the traditional lead acid batteries occupy.
I think they mean used EV batteries - EV batteries that are at the end of their useful life in cars.
That makes more sense.
Also way better cycle life, but the density is slightly lower.