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是非常需要的，因为它们固有地减少了对外部加热的需求。在这里，我们证明了电解质的局部溶剂化结构定义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。这些见解应用于锂金属全电池，其中高负载的 3.5 mAh cm ^-2硫化聚丙烯腈（SPAN）正极与单倍过量的锂金属负极配对。当循环在-40和-60°C时，电池分别保持了84%和76%的室温容量，在50个循环中表现出稳定的性能。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步骤。