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

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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.