[Pashute]'s linked idea gave me another one.
I haven't got all the details on this so this may change. It's allegedly inadvisable to recharge a non-rechargeable battery because they can explode in the process. I say "allegedly" because really, things should explode on a regular basis, although it
might be nice sometimes if they exploded safely.
An exploded battery is currently a wasted one because the energy of the explosion is allowed to dissipate into the surroundings in a shocking display of entropy compliance. This is not necessary. There are such things as bomb calorimeters which measure the chemical energy content of substances by combustion. Explosion is not combustion, of course, but rapid expansion. Why not harness the heat and kinetic energy of the battery explosion and use that to recharge another battery in a manner akin to a bomb calorimeter?
Firstly, an exploding battery involves a difference in temperature. That can be exploited using thermoelectric effects to generate voltage.
Secondly, an exploding battery involves movement. Use this movement by sealing the battery in an armoured piston and use linear induction at the end to use the energy.
Feed both effects into a normal battery and you have saved the energy.
This is one of those HB ideas which imagines huge amounts of energy can be generated from tiny effects. Even still.
(A work in progress).