Selective Adsorption of Electrolyte Anions with Chitosan Skin Producing LiF‐Enriched Solid Electrolyte Interphase for Si‐Based Lithium‐Ion Batteries

Abstract Silicon (Si) is a promising anode material for high‐energy‐density lithium‐ion batteries. To achieve wide practical applications, it is highly desirable to build effective solidelectrolyte interphase (SEI) with high stability and high Li⁺ conductivity. Herein, a novel interface engineering strategy is demonstrated with the assistance of a surfactant and the self‐assembly of chitosan (CS) skin on Si surface. A high coating integrity of the Si particle is obtained compared to that without surfactants. Unlike traditional surface coatings, the positive charge of the applied CS layer enables it to selectively absorb PF₆⁻ anions in the electrolyte. The PF₆⁻ aggregates in Helmholtz layer lead to the formation of anion‐derived SEI enriched in LiF species. As the result, the prepared CS‐decorated Si anode exhibits a high initial coulombic efficiency of 92.2% and a high rate capability of 2200 mAh g⁻¹ capacity at 10 C rate. After 500 charge–discharge cycles, it is still able to retain a reversible capacity 1621.3 mAh g⁻¹. Furthermore, the excellent electrochemical property is demonstrated in full cells against NCM811 cathode. The novel interface engineering strategy provides a new SEI mechanism and demonstrates a feasible and effective way to develop high‐performance Si‐based lithium‐ion batteries.