Air-exposed lithium metal as a highly stable anode for low-temperature energy storage applications

The demand for cryogenic applications has resulted in higher requirements for the low-temperature performance of energy storage systems. Lithium-metal batteries are the most promising energy storage systems. Lithium-metal anodes have the merits of high capacity and low potential. However, at low temperatures, especially sub-zero, the formation of lithium dendrites seriously hinders their applications. Herein, distinct from the traditional strategies of separating lithium metal from oxygen substances, we propose a new strategy to suppress dendrites by exposing lithium metal to air for short periods to generate a controlled oxidative protective layer in situ that is compact, homogeneous and mainly composed of Li3N, Li2O, LiOH and Li2CO3. Symmetrical and full cells are assembled. The air-pretreated Li metal symmetrical cell exhibits an excellent lifespan of up to 4500 h (1 mA cm-2) at 30 °C and also shows a smaller voltage polarization of 20 mV at 1.0 mA cm-2 at -20 °C. Importantly, the full cell using the air-pretreated Li metal as an anode and NCM811 as a cathode can charge-discharge normally at -20 and -40 °C. This work provides an efficient and facile approach for developing superior lithium-metal batteries for future utilization at a wide range of temperatures.