Electrically Coupled Electrolyte Engineering Enables High Interfacial Stability for High-Voltage Sodium-Ion Batteries

摘要

Sodium-ion batteries (SIBs) suffer from severe capacity decay as the harmfulsubstances caused by the violent decomposition of electrolyte under highvoltages continue to erode the cathodes. Therefore, the design of high-voltageelectrolyte and construction of robust cathode-electrolyte interface (CEI) arecritical for long-life SIBs. Herein, an electrically coupled composite electrolytethat takes the merits of cross-linked gel polymers and s well-tuned antioxidantadditive (4-trifluoromethylphenylboronic acid, TFPBA) is proposed. Throughan electrical coupling effect, TFPBA can be anchored by the cross-linkedpolymer framework to immobilize the PF_6~? anion and adsorb onto cathodesurface spontaneously, both of which promote the formation of a robust CEIlayer to facilitate Na~+ transportation and suppress subsequent side reactionsand corrosive cracking. As a result, the cells integrating high-voltage P2/O3cathode and well-tailored gel polymer electrolyte achieve stable cycling over550 cycles within 1.8-4.2 V with a capacity retention of 71.0 and a high-ratedischarge capacity of 77.4 mAh g~(?1) at 5 C. The work paves the way for thedevelopment of functionalized quasi-solid electrolyte for practical nextgeneration high-voltage SIBs.