Surface reconstruction of metal halides for S-site shielding toward long-cycle all-solid-state lithium batteries

Despite their high ionic conductivity and mechanical processability, sulfide electrolytes suffer from severe interfacial reactivity and structural incompatibility with Ni-rich layered oxide cathodes, causing rapid capacity fading that limits their practical viability in all-solid-state lithium batteries. Conventional coatings provide primarily physical isolation without fully eliminating reactive surface sulfur sites, rendering the interface vulnerable to gradual deterioration over prolonged cycling. Here, we propose a coordination-driven interfacial reconstruction strategy that exploits the volatility and strong Lewis acidity of ZrCl₄ to enable its interaction with electron-rich sulfur species on the Li₆PS₅Cl surface, thereby inducing the in situ formation of a Li-Zr-Cl-S (LZCS) passivation interphase. The resulting protective interphase exhibits favorable chemical compatibility with the sulfide host and effectively passivates highly reactive surface sulfur sites, thereby substantially suppressing parasitic interfacial reactions. As a result, the cell pairing the modified electrolyte with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathode retains 91.4% capacity after 1400 cycles at 1C, highlighting exceptional long-cycle stability under practical conditions. Even at a high cutoff voltage of 4.5 V, the cell still exhibits 94.5% capacity retention after 600 cycles (1C). This work establishes a strategy for constructing functional halide interphases on sulfide electrolytes, thereby enabling stable integration with Ni-rich layered cathodes.