Korean designers have proposed a rechargeable 1.5V battery in a memory foam case that could squeeze down from D to AAA-sized. People think deeply about everything, even batteries.

The first batteries were made in the 1800s and have changed a lot since then. The reason batteries come in so many types has as much to do with history as innovation.

Batteries are made in certain sizes and shapes for reasons of cost and manufacturability, but in other cases because of legacy manufacturing processes. Market demand also plays a role.