Constructing Continuously‐Distributed and Crystalline‐NaF‐Rich SEI on Hard Carbon Anode Through Binder Chemistry for High‐Performance Sodium‐Ion Batteries

Abstract

Abstract Constructing the continuously‐distributed and crystalline‐NaF‐rich solid electrolyte interface (CC‐NaF‐SEI) is expected to greatly promote the sodium storage performance of hard carbon (HC) anodes. However, such an impressive concept remains extremely intractable to achieve and lacks an efficiently cost‐less strategy. Herein, the application of the commercially available LA133 binder is pioneered to engineer such a CC‐NaF‐SEI. Through comparative analysis of representative binders with distinct functional groups, reveals the critical role of binder chemistry on SEI regulation. Specifically, the LA133 binder demonstrates a dual‐regulation mechanism for CC‐NaF‐SEI formation. The anion‐coordination preferred ─CN bonds induce an anion‐enriched interfacial solvation structure, and the ─CONH/─CN groups catalytically cleave P─F bond dissociation in PF 6 − , synergistically promoting anion decomposition kinetics to form crystalline NaF. Furthermore, robust hydrogen bonds between multiple polar groups in LA133 and HC surface create the spatially anion‐confined microenvironments to guide orderly anion decomposition and facilitate continuous NaF growth into a mechanically integrated SEI. The optimized CC‐NaF‐SEI endows HC anodes with exceptional sodium storage performance: an ultrahigh initial Coulombic efficiency (95.9%), remarkable reversible capacity (356.6 mAh g −1 ), and stable cycling under extreme conditions (−20–60 °C). This work provides fundamental insights into binder‐SEI correlations, establishing a novel paradigm for interfacial optimization in sodium‐ion batteries.