Rational design of an in-build quasi-solid-state electrolyte for high-performance lithium-ion batteries with the silicon-based anode

Design and optimization of the electrolyte are essential for improving electrochemical performances of high-energy–density lithium-ion batteries (LIBs) with silicon-based anodes. However, the dramatic volume change of silicon and the repeated destruction of the solid electrolyte interphase (SEI) film bring formidable challenges for electrolyte exploitation. Herein, a quasi-solid-state electrolyte is proposed via in situ polymerization with 1,3,5-trioxane (TXE) as the monomer, lithium bistrifluoromethanesulfonimide (LiTFSI) and lithium difluoro(oxalato) borate (LiDFOB) as lithium salts, which delivers excellent ionic conductivity and sufficient anion transference number. By half-cell evaluation with the quasi-solid-state electrolyte, the in situ generated polymer skeleton and modified SEI film effectively suppressed the volume expansion of silicon-graphite (Si-Gr) anode to 26.7% after 300 cycles, significantly lower than 60.7% for conventional liquid electrolytes. Furthermore, the LiNi0.6Co0.2Mn0.2O2||Si-Gr full-cell test demonstrates that the quasi-solid-state electrolyte can also protect the cathode structure and inhibit the dissolution and shuttling of transition metals. Ultimately, capacity retention of the full cell is up to 86.0% after 200 cycles with high average coulombic efficiency (99.79%) at 25 °C, and the electrolyte further enhances its cycling stability at high temperature (60 °C). This work proposes a straightforward strategy for the comprehensive enhancement of battery safety and electrochemical performance with Si-based anodes.