[xenadu02]

It's not just about the discovery - though that won the Nobel Prize. You have to be able to reliably lay down sub-100nm thick layers of material. A tall order pre-1960s.

You also need to develop separator films with the correctly sized pores with very few defects or the battery eats itself. Pores big enough for lithium to pass but nothing else. And a stable non-liquid electrolyte.

No one could even conceive of such ideas in 1900 let alone attempt to make such things. They didn't even know where to start looking to grasp the problem, let alone any solutions to try.