Operational strategy to stabilize lithium metal anodes by applied thermal gradient

External thermal gradients have a profound impact on lithium metal battery plating and stripping stability, potentially providing a path to safe, rechargeable, lithium metal batteries. The direction of the thermal gradient for the first Li plating determines whether the cell is stable and capable of high-rate, high-capacity plating/stripping or is instead unstable and vulnerable to internal shorting. Symmetric lithium metal batteries with a negative thermal gradient (0 degrees C negative electrode, 40 degrees C positive electrode) reproduce conditions known to result in high-aspect ratio plating deposits and high surface non-uniformity for the first Li plating. Non-uniform deposition increases unfavorable side reactions between freshly plated Li and the electrolyte that increases interfacial resistance, reduces ionic conductivity due to electrolyte consumption, and forms a mass transport-limiting layer of electrochemically inactive lithium at the electrode surface-similar to observations for isothermal 0 degrees C and 20 degrees C control cases. Alternatively, a positive thermal gradient (40 degrees C negative electrode, 0 degrees C positive electrode) forms a uniform initial electrodeposit that predisposes the cell to stable, long-term cycling. A positive thermal gradient reduces detrimental electrode-electrolyte reactions, reduces electrochemically inactive lithium formation, and maintains a low tortuosity diffusion pathway for higher effective ionic conductivity and lower interfacial resistances. A positive thermal gradient reduces cell voltage hysteresis by up to 39% compared to isothermal 20 degrees C control at a broad range of current densities and capacities (up to 5.0 mA cm(-2) and 10 mAh cm(-2)), dramatically enhancing high-rate cycling and demonstrating promise for a positive thermal gradient as an operational strategy to enable faster charging for batteries with lithium metal anodes.