Zwitterion‐Induced Interfacial‐Potential Regulation Stabilizes Micron‐Sized Silicon Anodes in Quasi‐Solid‐State Lithium‐Ion Batteries

Abstract Micron‐sized silicon (μ‐Si) is an attractive anode material for high‐energy lithium‐ion batteries owing to its high tap density, large specific capacity, and compatibility with scalable manufacturing. Its practical deployment, however, is impeded by an uncontrolled interfacial‐potential landscape that drives heterogeneous Li + transport, spatially non‐uniform reduction and recurrent solid‐electrolyte interphase (SEI) rupture, thereby accelerating capacity fade. Here, we report a zwitterion‐modified quasi‐solid‐state electrolyte that regulates the interfacial‐potential distribution at the μ‐Si/electrolyte interface. In situ polymerization of 3‐(1‐vinyl‐3‐imidazolyl)propanesulfonate (VIPS) within a conventional carbonate electrolyte yields PVIPSE, whose spatially proximate imidazolium and sulfonate groups stabilize μ‐Si anodes through synergistic effects: (i) electrostatic screening that equalizes potential across the inner/outer Helmholtz planes and homogenizes Li + flux; (ii) Li + –sulfonate coordination that restructures the solvation environment and biases reduction pathways toward an inorganic‐rich, electronically insulating SEI; and (iii) selective partitioning of fluoroethylene carbonate at the interface to promote uniform LiF‐rich passivation. Scanning electrochemical microscopy directly visualizes the reduced interfacial‐potential heterogeneity and improved SEI uniformity. As a result, the quasi‐solid‐state PVIPSE enables stable long‐term cycling of μ‐Si anodes, establishing interfacial‐potential regulation as a distinct and effective design principle, orthogonal to solvation engineering and mechanical reinforcement, for stabilizing high‐capacity alloying anodes.