Solvent-derived organic-rich SEI enables capacity enhancement for low-temperature lithium metal batteries

Abstract

Anion-derived inorganic-rich solid electrolyte interface (SEI) is generally considered beneficial for lithium metal batteries (LMBs). Surprisingly, an anomaly was observed in this study that the inorganic-rich SEI can cause severe capacity degradation in low-temperature (LT) LMBs due to sluggish interfacial transport kinetics. Herein, the solvent-derived organic-rich SEI was demonstrated to exhibit lower interfacial impedance due to weak interfacial force and rapid pore diffusion mechanism. As a proof of concept, an organosilicon electrolyte, combined with LT formation cycling, successfully constructed solvent-derived SEI with a 16.51-fold increase in organic components, ultimately resulting in a 22.5% capacity enhancement of LMBs at −40°C. Consequently, Li||NCM811 cells miraculously maintained discharge functionality even at −114.05°C, and 1.2 Ah pouch cells maintained 92.1% capacity retention over 50 cycles at −20°C with the lean electrolyte (2.5 mL Ah⁻¹). This strategy of increasing battery capacity through organic-rich SEI opens up a new era of research on LT batteries.