High‐Humidity‐Tolerant Chloride Solid‐State Electrolyte for All‐Solid‐State Lithium Batteries

Abstract Halide solid‐state electrolytes (SSEs) hold promise for the commercialization of all‐solid‐state lithium batteries (ASSLBs); however, the currently cost‐effective zirconium‐based chloride SSEs suffer from hygroscopic irreversibility, low ionic conductivity, and inadequate thermal stability. Herein, a novel indium‐doped zirconium‐based chloride is fabricated to satisfy the abovementioned requirements, achieving outstanding‐performance ASSLBs at room temperature. Compared to the conventional Li2ZrCl6 and Li3InCl6 SSEs, the hc‐Li2+xZr1‐xInxCl6 (0.3 ≤ x ≤ 1) possesses higher ionic conductivity (up to 1.4 mS cm−1), and thermal stability (350 °C). At the same time, the hc‐Li2.8Zr0.2In0.8Cl6 also shows obvious hygroscopic reversibility, where its recovery rate of the ionic conductivity is up to 82.5% after 24‐h exposure in the 5% relative humidity followed by heat treatment. Theoretical calculation and experimental results reveal that those advantages are derived from the lattice expansion and the formation of Li3InCl6 ·2H2O hydrates, which can effectively reduce the migration energy barrier of Li ions and offer reversible hydration/dehydration pathway. Finally, an ASSLB, assembled with reheated‐Li2.8Zr0.2In0.8Cl6 after humidity exposure, single‐crystal LiNi0.8Mn0.1Co0.1O2 and Li‐In alloy, exhibits capacity retention of 71% after 500 cycles under 1 C at 25 °C. This novel high‐humidity‐tolerant chloride electrolyte is expected to greatly carry forward the ASSLBs industrialization.