Electrolyte strategy toward the low-temperature Li-metal secondary battery

Abstract

Lithium metal battery (LMB) always faces a huge challenge at low temperature due to the sluggish reaction kinetics. An effective electrolyte could well tackle the issues as it much determines the Li+ de-solvation behavior and solid electrolyte interface (SEI) formation, and further greatly influenced the Li deposition. A practicable and cost-effective electrolyte was proposed in this work which sophisticatedly handled the balance between the ion-transfer character, Li solvation and SEI requirement. Highly fluent methyl acetate (MA) and SEI-beneficial fluoroethylene carbonate (FEC) together with Li salt constituted an anti-freezing electrolyte with sufficient ion-conductivity. More importantly, appropriate coordination between salt and solvent facilitated the de-solvation stage in Li+-reduction, additionally, the dual salt of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium difluoro(oxalate)borate (LiODFB) combining with LiNO3 additive endowed the electrolyte with wide electrochemical window and Al compatibility. With them, repetitive Li striping/plating was achieved at −40 °C, and Li/LiNi0.5Co0.2Mn0.3O2 (NCM) full cell could be stably cycled for more than 150 times.