Precisely. Any attempt to "optimise" the specific energy of a storage approach will inevitably bring it closer to closer to the point where it explosively disintegrates.

This is why it's a bit hilarious to see how upset people are about lithium batteries occasionally exploding. That's... sort of the point! They've been optimised until the safety margin (=weight) is a low as possible. You want safe batteries? Carry around something the size and weight of a brick!

Ditto with all possible kinetic energy recovery system (KERS) designs. You can have weight-efficient or safe, but not both.

Lithium batteries typically explode because the electrolytes we use are highly flammable. It's actually entirely incidental to the amount of energy stored in the battery. A Li-ion battery with a different electrolyte material could have the same energy density, but a greatly reduced risk of fires and explosion.

Only somewhat - batteries tend to explode when damaged (punctured, squished, etc) when they short internally, or when they get a thermal runaway.

Putting armor, heat sinks, etc. on them does make them safer. Adding battery safety circuitry (charge control, overcurrent protection) also helps. It also adds weight. Unarmored lipo batteries are notoriously dangerous for a reason, and it’s not the electrolyte.