Anion‐Modulated Solvated Structure for All‐Solid‐State Lithium Metal Batteries with Inorganic‐Rich SEI

Abstract The limited salt dissociation efficiency and unstable (Li(DMF)x) ⁺ solvation structures in poly(vinylidene fluoride) (PVDF)‐based solid‐state electrolytes (SSEs) significantly impede both high‐rate ion transport and electrode‐electrolyte interfacial stability. However, developing SSEs that combine high ionic conductivity (>1 mS cm ⁻¹ ) with stable electrode‐electrolyte interfaces remains a major scientific challenge. Here, a high‐voltage solid‐state lithium‐metal battery is presented employing a PVDF‐SCS (PVDF modified with benzenesulfonylated chitosan) electrolyte. The nitrogen‐based anionic receptors in sulfonamide chitosan (SCS) facilitated lithium salt dissociation through preferential anion‐cation pair disruption, thereby enhancing the free Li⁺ concentration. Crucially, the electron‐deficient nitrogen centers exhibit strong coordination with lithium salt anions, promoting their electrochemical reduction and forming a stable, anion‐derived solid electrolyte interphase (SEI). Consequently, the PVDF‐SCS electrolyte demonstrates an elevated Li⁺ conductivity of 1.35 mS cm ⁻ ¹ and effectively mitigates dendritic growth, enabling a stable operation of Li|PVDF‐SCS|NCM523 full batteries for 400 cycles at a high voltage of 4.3 V. This work demonstrates the anion engineering can simultaneously enhance Li ⁺ transport and interfacial stability, paving the way for high‐performance solid‐state batteries.