China is hoping to become the Detroit of the battery-powered electric vehicle industry. Sales of EVs are expected to reach 1 million this year alone, and the government has big plans for expansion. But this welcome trend comes with a perplexing side effect: China is now using up more lithium-ion batteries than anywhere else in the world. What to do with them?

Throwing those batteries away could be environmentally hazardous. Recycling them, meanwhile, turns out not to be very profitable. The solution China has hit on is simple — but may have profound consequences for the environment.

Since the 1990s, rechargeable lithium-ion batteries have proved to be a useful way to store lots of energy in small spaces. This makes them ideal not only for cars but for consumer electronics, such as power tools and iPhones. It's only natural that China, the world's leading manufacturer and consumer of such gadgets, is also now the top maker of lithium-ion batteries.