Interfacial Chemistry of Plasticizer to Invoke High‐Performance Silicon Anodes for Quasi‐Solid Lithium‐Ion Batteries

Quasi‐esolid lithium‐ion batteries, integrating quasi‐solid polymer electrolytes (QSPEs) and high‐capacity silicon (Si) anodes, exhibit great promise for next‐generation energy storage due to their high energy density and improved safety. However, their practical application is significantly hindered by poor electrolyte‐electrode interface compatibility associated with plasticizers in QSPEs. Herein, a novel QSPE based on poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) is developed by introducing diethylene glycol dimethyl ether (DEGDME) and fluoroethylene carbonate (FEC) as plasticizers. These plasticizers synergistically promote the formation of favorable interfacial clusters on the Si anode, enabling rapid de‐solvation and high reduction stability, which effectively mitigates electrolyte decomposition and enhances the stability of the electrolyte–electrode interface. Consequently, the designed QSPE delivers excellent ionic conductivity of 2.14 mS cm −1 and enables the Si anode to maintain a specific capacity of 1843.6 mAh g −1 after 200 cycles at 2 A g −1 and demonstrates excellent rate performance over 10 A g −1 . Moreover, this work sheds new light on the molecular‐level evolution of plasticizers at the solid‐state electrolyte–electrode interface and elucidates their significant synergistic effect on electrode performance, providing a guideline for designing QSPEs that stabilize Si anodes by prioritizing interfacial compatibility alongside ionic conductivity.