Loosely coordinating diluted highly concentrated electrolyte toward −60 °C Li metal batteries

Lithium metal batteries (LMBs) promise energy density over 400 Wh kg−1. However, they suffer severe electrochemical performance deterioration at sub-zero temperatures. Such failure behavior highly correlates to inferior lithium metal anode (LMA) compatibility and sluggish Li+ desolvation. Here, we demonstrate that cyclopentylmethyl ether (CPME) based diluted high-concentration electrolyte (DHCE) enables −60 °C LMBs operation. By leveraging the loose coordination between Li+ and CPME, such developed electrolyte boosts the formation of ion clusters to derive anion-dominant interfacial chemistry for enhancing LMA compatibility and greatly accelerates Li+ desolvation kinetics. The resulting electrolyte demonstrates high Coulombic efficiencies (CE), providing over 99.5%, 99.1%, 98.5% and 95% at 25, −20, −40, and −60 °C, respectively. The assembled Li-S battery exhibits remarkable cyclic stability in −20, and −40 °C at 0.2 C charging and 0.5 C discharging. Even at −60 °C, Li-S cell with this designed electrolyte retains > 70% of the initial capacity over 170 cycles. Besides, lithium metal coin cell and pouch cell with 10 mg cm−2 high S cathode loading exhibit cycling stability at −20 °C. This work offers an opportunity for rational designing electrolytes toward low temperature LMBs.