An unexpected discovery has led to a rechargeable battery that's as inexpensive as conventional car batteries, but has a much higher energy density. The new battery could become a cost-effective, environmentally friendly alternative for storing renewable energy and supporting the power grid. The Department of Energy's Pacific Northwest National Laboratory (PNNL) identified this energy storage gem after realizing the new battery works in a different way than they had assumed.

Lithium-ion batteries store and release energy by lithium ions entering and exiting microscopic spaces in between the atoms of a battery's two electrodes. When PNNL scientists started considering a low-cost, safe alternative to lithium-ion batteries − a rechargeable zinc-manganese oxide battery − they assumed zinc would similarly move in and out of that battery's electrodes. The team was surprised to realize their device was undergoing an entirely different process.