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 Li 2 ZrCl 6 and Li 3 InCl 6 SSEs, the hc‐Li 2+x Zr 1‐x In x Cl 6 (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‐Li 2.8 Zr 0.2 In 0.8 Cl 6 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 Li 3 InCl 6 ·2H 2 O hydrates, which can effectively reduce the migration energy barrier of Li ions and offer reversible hydration/dehydration pathway. Finally, an ASSLB, assembled with reheated‐Li 2.8 Zr 0.2 In 0.8 Cl 6 after humidity exposure, single‐crystal LiNi 0.8 Mn 0.1 Co 0.1 O 2 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.