Almost any combination of reagents can work as primary cell - even a literal potato! But designing a secondary (rechargeable) cell is a different story... Ever

Almost any combination of reagents can work as primary cell - even a literal potato! But designing a secondary (rechargeable) cell is a different story... Every promising chemistry has been investigated for many decades and yet the successes are few. Magnesium, sodium or aluminium-based rechargeable battery can in theory be just as capable as lithium-based one, but we can't just get them to work.