If necessity is the mother of invention, potential profit has to be the father. Both incentives are driving an effort to transform zinc batteries from small, throwaway cells often used in hearing aids into rechargeable behemoths that could be attached to the power grid, storing solar or wind power for nighttime, or when the wind is calm. Zinc batteries promise to be cheaper and safer than conventional lithium-ion batteries, today’s battery leader. But turning zinc cells into long-lived rechargeables faces several challenges. Now, advances in critical zinc battery components are injecting renewed optimism that rechargeable zinc batteries face a bright future.