Covalent Organic Framework Mediated Solvation Regulation Reinforces Anion‐Derived Interface in Quasi‐Solid‐State Electrolytes for High‐Performance Silicon‐Based Lithium‐Ion Batteries

The pursuit of high‐energy‐density and intrinsically safe lithium‐ion batteries (LIBs) has intensified interest in quasi‐solid‐state electrolytes (QSSEs) coupled with silicon (Si) anodes. However, most in situ‐formed polymer electrolytes suffer from low ionic conductivity and limited Li + transference numbers, primarily arising from high polymer crystallinity and sluggish segmental dynamics. Herein, a 1,3,5‐trioxane (TXE)‐derived QSSE is engineered by incorporating fluoroethylene carbonate (FEC) and methyl propionate (MP) as plasticizers, together with a lithiated covalent organic framework (COFLi) as a functional filler to suppress crystallization, enhance Li + transport, and improve interfacial stability. Consequently, the optimized COFLi‐modified TXE‐based electrolyte enables the Si anode to deliver a high reversible capacity of 1814.6 mAh g −1 at 2 A g −1 after 200 cycles and to retain 1530 mAh g −1 at 0.5 A g −1 even at −20°C. Moreover, a molecular‐level interfacial model is proposed to elucidate the role of COFLi in regulating the Li + solvation structure, reducing desolvation energy, and promoting the formation of a LiF‐rich inorganic solid–electrolyte interphase), thereby suppressing electrolyte decomposition and mitigating Si pulverization. This work provides fundamental insights into solvation chemistry and interfacial evolution in TXE‐based QSSEs and offers a rational design strategy for high‐performance, Si‐compatible quasi‐solid‐state LIBs.