https://www.youtube.com/watch?v=7G4ipM2qjfw
OP is… trying his best, I guess. For now lipo is the best solution. Actually multiple things are the solution. Pumped water has a delay that needs to be covered by something else. Flywheels have mechanical chalenges. Molten salt also has problems. Etc. They all compliment each other. IMO best single solution would be nuclear. Salt will be better then lithium, but in some years.
When batteries (ahcually accumulators, but whatever) are done properly, the fires should not go beyond one cell, if at all.
PS Gravity, except pumped water, is hilariously bad.
Electrolisis is relatively inefficient and wears down the electrodes. While not as bad on an industrial scale, those are still problems. And then you have to convert it back, that is even less efficient.
Good in theory, barely passable in practice. Growing sugar cane and making ethanol would be better, like brazil does it.