Rechargeable lithium-ion batteries suitable for the mass consumer market require robust safety and tolerance to repeated overdischarge and overcharge to avoid costly charge control circuitry and to allow simple replacement of individual cells by consumers. A chemical redox shuttle additive to the electrolyte is shown to provide this protection. The molecule, 2,5 ditertbutyl-1,4-dimethoxybenzene, provides overcharge and overdischarge protection for hundreds of charge-discharge cycles in both single cells and series-connected batteries. (C) 2004 The Electrochemical Society.