Covalent Organic Framework Mediated Solvation in Quasi-Solid-State Polymer Electrolyte for High-Performance Silicon-Based Lithium-Ion Batteries

The practical application of solid polymer electrolytes (SPEs) is limited by their low ionic conductivity and poor interfacial compatibility with silicon (Si) anodes in high-energy-density, safe lithium-ion batteries (LIBs). Here, we introduce a lithiated covalent organic framework (COF) into a poly(vinylidene fluoride-cohexafluoropropylene) (PVDF-HFP)-based quasi-solid polymer electrolyte (QSPE) containing plasticizers to increase its electrochemical performance. The resulting COF-based QSPE has a high ionic conductivity of 2.99 mS cm⁻¹ and enables Si anodes to deliver a remarkable specific capacity of 1722 mAh g⁻¹ after 500 cycles, along with an excellent rate capability of up to 10 A g⁻¹. Furthermore, we provide new insights into the role of lithiated COFs in modulating the Li⁺ solvation structure, facilitating ionic migration and promoting desolvation in plasticizer-containing solid electrolytes at the molecular scale. These findings offer valuable guidelines for the rational design of stable Si anodes in solid-state batteries.