Carbonate Ester‐Based Sodium Metal Battery with High‐Capacity Retention at −50 °C Enabled by Weak Solvents and Electrodeposited Anode.

Sodium metal batteries (SMBs) have received increasing attention due to the abundant sodium resources and high energy density, but suffered from the sluggish interfacial kinetic and unstable plating/stripping of sodium anode at low temperature, especially when matched with ester electrolytes. Here, we develop a stable ultra‐low‐temperature SMBs with high‐capacity retention at −50 °C in a weak solvated carbonate ester‐based electrolyte, combined with an electrodeposited Na (Cu/Na) anode. The Cu/Na anode with electrochemically activated "deposited sodium" and stable inorganic‐rich solid electrolyte interphase (SEI) is favor for the fast Na+ migration, therefore accelerating the interfacial kinetic process. As a result, the Cu/Na||NaCrO2 battery exhibited the highest capacity retention (compared to room‐temperature capacity) in carbonate ester‐based SMBs (98.05 % at −25 °C, 91.3 % at −40 °C, 87.9 % at −50 °C, respectively). The cyclic stability of 350 cycles at −25 °C with a high energy efficiency of 96.15 % and 70 cycles at −50 °C can be achieved. Even in chill atmospheric environment with the fluctuant temperature, the battery can still operate over one month. This work provides a new opportunity for the development of low‐temperature carbonate ester‐based SMBs. [ABSTRACT FROM AUTHOR]