"These rechargeable batteries are more sustainable and safer than lithium—and half the cost. The battery is water-based and uses other cheap, readily available materials like manganese and metal oxide.
Since lithium-ion batteries were first sold 30 years ago, they’ve dropped in cost by 97%. But they’re still too expensive for making electric cars that can compete in cost with fossil-fueled cars without subsidies, or to economically store wind and solar power on the grid. That’s why one Boston-area startup is developing a different type of rechargeable battery that it says can cut costs in half—while avoiding some of the other flaws of current batteries, from the environmental impact of mining to the fact that lithium-ion batteries can catch on fire."