A competitive coordination effect to simultaneously achieve high-energy and stable cycles in a Li-metal pouch cell at −40 °C

Abstract

Lithium metal batteries (LMBs) are expected to have significant advantages under extremely low-temperature conditions (i.e., −40 °C), mainly due to the much shorter ion transport pathway and the deposition/stripping mechanism of the Li metal anode. However, high-energy-density Li-metal pouch cells capable of stable operation at −40 °C have rarely been reported due to the harsh conditions of extremely low temperature. Herein, a Li-metal pouch cell suitable for use at −40 °C is designed, and coupled with a newly developed electrolyte, to simultaneously achieve high energy and stable cycling performance. The low-temperature capability of the LMBs is activated by a competitive coordination effect in the first solvation sheaths. The competitive coordination between Li⁺ and dimethyl carbonate (DMC) and 1,2-dimethoxyethane (DME) weakens the interaction between Li⁺ and the solvent, widens the voltage window, and facilitates the formation of robust inorganic-rich interfaces under low-temperature conditions. Notably, a low-temperature Li-metal pouch cell was designed and assembled with an energy of 300 Wh kg⁻¹. When tested at an extremely low temperature of −40 °C, the Li-metal pouch cell could retain 77% of its energy output, with 93% capacity retention after 70 cycles. This work paves the way for low-temperature LMBs with competitive energy density and stable cycle life.