Lithium Titanate (LTO) is the only lithium based home battery I would feel comfortable with but same sentiment on safety. The chance of thermal runaway is low but results are catastrophic.
It's basically LiFePO4 but even more so: really high charge (10C! and it doesn't even get warm to the touch) and discharge rates, even harder to damage to the point of failure, and really long lifetime (many, many full charge/discharge cycles). Slightly worse energy density. Main downside is it's pretty expensive and niche still. I wouldn't necessarily consider it optimal for solar power storage, where it really shines is high duty cycle high power operation like electric busses, because you can fast-charge it multiple times a day for years.
Spot on. The cost is definitely the main issue IMO. I think they make for great option for home backup/offgrid use mainly due to their crazy high cycles like you pointed out. An Australian company (Zenaji) sells a solution with a warranty on 22,000 cycles. Again, super expensive (~$3k AUD per 1.95kWh) but IMO a superior tech other than density (not a huge difference but definitely not as good as LiFePO4/NMC), which doesn't matter as much in home/commercial stationary backup scenarios.
