Regeneration of Slightly Deteriorated LiPF 6 -Based Electrolyte by Dual Additive Engineering to Achieve High-Safety and High-Electrochemical Performance Batteries

LiPF6-based electrolyte is widely used in lithium-ion batteries (LIBs) due to its excellent electrochemical performance. However, in improper operation (such as exposure to high-temperature environments), deterioration is inevitable, leading to a deterioration of the battery performance and posing safety hazards. Herein, 5 wt % ethoxy(pentafluorocyclotriphosphazene) (PFPN) and 1 wt % tris(trimethylsilyl)borate (TMSB) are introduced as dual additives to achieve the regeneration of the slightly deteriorated LiPF6-based electrolyte. Both of them demonstrate excellent capture capabilities for HF and H2O, reducing the contents of HF and H2O in the deteriorated electrolyte to meet the basic requirements of LIBs. After employing it to Li-rich layered oxide (LRLO)/Li cells with high energy density, the regenerated electrolyte shows excellent compatibility with the LRLO cathode, which is mainly attributed to three aspects. (1) TMSB additives help construct a stable and conductive cathode electrolyte interface (CEI) film rich in inorganic components via the in situ formation of lithium difluorophosphate (LiDFP) additives, thereby improving the cycling stability and tolerance to high temperature. (2) PFPN additives terminate the chain reaction triggered by the combustion radicals at high temperatures, enhancing the flame retardancy of electrolytes. (3) Dual additives significantly suppress the gas production of the battery, enhancing the safety of LIBs. As a result, the regenerated electrolyte demonstrate superior electrochemical performances compared to fresh electrolytes reported in the literature, especially at a high temperature of 55 °C (0.2 C, 67.2% capacity retention after 200 cycles). This work not only proposes a simple and easy-to-implement electrolyte regeneration strategy but also proposes an effective strategy for the development of electrolyte systems demonstrating high compatibility with lithium-rich layered oxide (LRLO) cathodes, a factor that is critically important for advancing lithium-ion batteries with enhanced energy density.