Unlocking superior safety, rate capability, and low-temperature performances in LiFePO4 power batteries

Abstract

The safety concerns associated with lithium-ion batteries (LIBs) have sparked renewed interest in lithium iron phosphate (LiFePO4) batteries. It is noteworthy that commercially used ester-based electrolytes, although widely adopted, are flammable and fail to fully exploit the high safety potential of LiFePO4. Additionally, the slow Li+ ion diffusion and low electronic conductivity of LiFePO4 batteries limit their utility in high-power applications. Despite the crucial role played by liquid electrolytes in LIBs, achieving simultaneous improvements in safety, rate capability, and low-temperature performance remains a formidable challenge. In this study, we addressed these challenges by innovatively applying a single solvent ethyl vinyl sulfone (EVS) electrolyte to graphite/LiFePO4 batteries. While renowned for its broad electrochemical window, low freezing point and superior safety performance, the EVS electrolyte exhibited compatibility issues with the graphite anode. To overcome this hurdle effectively, we utilized vinylene carbonate as an additive with lower reductive reactivity than EVS to modify the interphase formed by EVS successfully. Simultaneously, the EVS-based electrolyte was found to create a sulfone-rich interphase on the LiFePO4 cathode surface, significantly enhancing Li+ ion diffusion both across the interphase and within the material. These modifications culminated in a conspicuous improvement in the performance of graphite/LiFePO4 batteries. Our study illuminates the potential of EVS-based electrolytes in boosting the rate capability, low-temperature performance, and safety of LiFePO4 power lithium-ion batteries. It yields valuable insights for the design of safer, high-output, and durable LiFePO4 power batteries, marking an important stride in battery technology research.