Preactivation Strategy for a Wide Temperature Range In Situ Gel Electrolyte-Based LiNi_0.5Co_0.2Mn_0.3O₂∥Si-Graphite...

The silicon-based anode has been regarded as the most competitive anode candidate for next-generation lithium-ion batteries based on its high theoretical specific capacity. However, the severe volume expansion of the anode leads to undesirable cycling performance, hindering its further application in full cells. In this work, a preactivation method is carried out in a LiNi_0.5Co_0.2Mn_0.3O₂∥Si-graphite battery with an in situ gel electrolyte composed of carbonate solvents, lithium hexafluorophosphate (LiPF₆), β-cyanoethyl ether of poly(vinyl alcohol) (PVA-CN), and additive lithium difluoro(oxalato)borate (LiDFOB). After the charge-discharge test at ambient temperature (300 cycles), the capacity retention of the battery with the in situ gel electrolyte (75.4%) is impressively promoted compared with that with a base liquid electrolyte (45.7%). The in situ gelation and the strong solid electrolyte interphase (SEI) film effectively suppress the volume expansion of the anode, and the detected cathode transition metal elements on cycled anodes sharply decline. At an elevated temperature (55 °C), the cycle stability and Coulombic efficiency of the battery are also effectively improved. Meanwhile, the battery owns good rate capability and low-temperature performances similar to that with the liquid electrolyte. These results would provide a feasible solution for applying in situ gel electrolytes in wide temperature range batteries with Si-based anodes in practical applications.