Homogeneous solid electrolyte interphase network confines electrochemical sintering toward ultra-stable micro-silicon sulfide solid-state anodes

Abstract

Micro-silicon (μSi) is a promising high-capacity anode material for sulfide solid-state lithium batteries; however, repeated lithiation/delithiation induces severe chemo-mechanical degradation, accompanied by electrode-scale full electrochemical sintering, localized stress concentration, crack propagation, and interfacial contact loss. Herein, we construct a homogeneous organic-inorganic hybrid solid electrolyte interphase (H-SEI) network throughout the μSi electrode to enable confined electrochemical sintering via interphase engineering. Unlike conventional gradient SEI architectures, the interconnected H-SEI network simultaneously integrates high mechanical modulus and is proposed to promote interfacial interactions with both silicon and sulfide solid electrolyte. The homogeneous interphase reduces the formation of high-volume-expansion crystalline Li₁₅Si₄, redistributes lithiation-induced stress, and confines electrochemical sintering at the microparticle scale, preventing its propagation across the electrode. Meanwhile, the uniformly distributed organic components maintain intimate and stable Si/LPSCl contact during long-term electrochemical cycling. Benefiting from the synergistic regulation of electrochemical sintering and interfacial stability, the H-SEI-modified μSi electrode delivers a high areal capacity of 2.15 mAh cm^-2, ultralong cycling stability over 1400 cycles with an ultralow average capacity decay rate of 0.032% per cycle, and excellent rate capability of 958 mAh g^-1 at 8.75 A g^-1. This work provides an effective interphase engineering strategy for regulating electrochemical sintering and chemo-mechanical evolution in micro-silicon anodes, offering new insights into the development of durable sulfide solid-state lithium batteries.