High-concentration electrolytes for lithium-metal batteries operating at high temperatures

Commercialized electrolytes for lithium-metal batteries have a maximum temperature restriction of 60 °C, which significantly restricts the use of these batteries in situations with greater temperatures. In this paper, we study the construction of a high-temperature electrolyte system for lithium-metal batteries, using 0.5 M LiODFB-EC/EMC (3:7) as the basic electrolyte system, and 1, 2, and 3 M LiTFSI were added to form electrolytes with different concentrations, to investigate the effect of LiTFSI concentration on lithium-metal batteries. The mixed lithium salts used in this system are lithium bis(trifluorosulfonyl) imide (LiTFSI) and lithium difluoro-oxalate-borate (LiODFB), with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) as the mixed solvent systems. Additionally, we study the electrochemical performance at 45 °C and 70 °C. The best battery performance was achieved with batteries built with the 3.0 M LiTFSI/0.5 M LiODFB electrolyte. In the LiCoO₂/Li discharge performance after 500 cycles, the battery’s discharge-specific capacity was 117.8 mAh/g, and its capacity retention rate was 82.8%. Better than previous concentration electrolyte systems, the battery constructed with this electrolyte has a greater discharge-specific capacity and cycle stability at 70 °C.