Abstract

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) was 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.