Trifluoropropylene Carbonate‐Driven Interface Regulation Enabling Greatly Enhanced Lithium Storage Durability of Silicon‐Based Anodes

Abstract The extremely high specific capacity of Si anodes is a double‐edged sword, bringing both high energy density and poor lifespan to Li‐ion batteries (LIBs). Despite recent advances in constructing nanostructured/composite‐Si anodes with an alleviated volume change and improved cycle life, daunting challenges still remain for Si anodes to suppress the irreversible capacity loss associated with the repeated rupture/reconstruction of the solid electrolyte interphase (SEI) layer. Herein, an electrolyte‐based optimization strategy is devised to in situ construct a thin, continuous, and mechanically stable SEI film on Si surface by using a trifluoropropylene carbonate (TFPC) cosolvent, targeting highly stable Si‐based anodes for LIBs. TFPC is featured with its low unoccupied molecular orbital energy, high reduction potential and outstanding film‐forming capability, outperforming those of the state‐of‐the‐art fluoroethylene carbonate additive. More importantly, TFPC plays a key role in regulating the structure and component of SEI layer. As such, 10 wt% TFPC addition promotes the formation of an optimal SEI film with appropriate amounts of polyolefins and LiF, endowing the SEI layer with enhanced rigidity and toughness as well as high ionic conductivity. Both the Si nanoparticle‐based and Si/C composite electrodes deliver a greatly enhanced cycling stability, rate capability, and overall structural integrity in such optimized electrolyte.