Lithium metal batteries hold promise for pushing cell-level energy densities beyond 300 Wh kg⁻¹ while operating at ultra-low temperatures (below −30 °C). Batteries capable of both charging and discharging at these temperature extremes are highly desirable due to their inherent reduction in the need for external warming. Here we demonstrate that the local solvation structure of the electrolyte defines the charge-transfer behaviour at ultra-low temperature, which is crucial for achieving high Li metal Coulombic efficiency and avoiding dendritic growth. These insights were applied to Li metal full-cells, where a high-loading 3.5 mAh cm⁻² sulfurized polyacrylonitrile (SPAN) cathode was paired with a onefold excess Li metal anode. The cell retained 84% and 76% of its room temperature capacity when cycled at −40 and −60 °C, respectively, which presented stable performance over 50 cycles. This work provides design criteria for ultra-low-temperature lithium metal battery electrolytes, and represents a defining step for the performance of low-temperature batteries.

锂金属电池有望在超低温（低于-30°C）下运行时将电池级能量密度提高到300 Wh kg ^-1以上。能够在这些极端温度下充电和放电的电池非常受欢迎，因为它们固有地减少了外部变暖的需要。在这里，我们证明电解质的局部溶剂化结构决定了超低温下的电荷转移行为，这对于实现高锂金属库仑效率和避免枝晶生长至关重要。这些见解被应用于锂金属全电池，其中高负载3.5 mAh cm ^-2硫化聚丙烯腈（SPAN）阴极与单倍过量的锂金属阳极配对。该电池在-40°C和-60°C循环时分别保留了84%和76%的室温容量，在50次循环后表现出稳定的性能。这项工作为超低温锂金属电池电解质提供了设计标准，并代表了低温电池性能的决定性一步。