It's great that manufacturers recover lead from discarded car batteries to use in new ones, since lead production from ores yields toxic residues. The problem is, when we shift from lead-acid to lithium-ion and other types of batteries (and we're starting to), over 200 million old batteries could be retired in the US and cause serious environmental issues. Thankfully, a team of MIT researchers has discovered one way to recycle lead from car batteries, and the end product is something very, very useful: long-lasting solar cells. We're talking about a new breed of solar cells in particular, one that uses a compound called perovskite, which needs lead to be manufactured.