Solution-derived Nb-doped Li3InCl6 halide electrolytes for fast Li+ conduction and stable all-solid-state lithium batteries

Halide solid electrolytes hold great promise for all-solid-state lithium batteries (ASSLBs), yet achieving fast Li + transport and high electrochemical stability through scalable synthesis remains challenging. Herein, we report a facile wet-chemical route to synthesize Nb-doped Li 3 InCl 6 solid electrolytes, where a stepwise slow drying and thermal treatment protocol is adopted to regulate crystallization kinetics. By optimizing the solvent and dopant concentration, the 10% Nb-substituted sample (LIC Nb 1 ) prepared in ethanol shows optimal performance. Structural refinement and spectroscopic analysis reveal that aliovalent Nb 5+ creates Li vacancies and optimizes local lattice environments, promoting fast Li + conduction. Accordingly, LIC-Nb 1 exhibits a room-temperature ionic conductivity of 0.95 mS cm −1 , more than twice that of pristine LIC(Et) (0.44 mS cm −1 ), with a lower activation energy of 0.31 eV and enhanced electrochemical stability. ASSLBs based on LIC-Nb 1 delivers substantially improved rate capability and cycling stability relative to pristine LIC-based cells. At 30 °C, the LIC-Nb 1 -based cell shows stable charge/discharge behavior over 2–4.4 V (vs. Li/Li + ), affording an initial discharge capacity of 182.4 mAh g −1 , and an initial Coulombic efficiency of 91.02%. Under the more demanding rate and prolonged cycling evaluations conducted at 60 °C, the capacity retention of LIC-Nb 1 -based cell after 30 cycles at 0.1C under 100% depth of discharge reaches 83.5%, compared with 66.8% for the LIC(Et)-based counterpart. This work systematically clarifies the solvent effect on the crystal structure and ionic conductivity of LIC electrolytes, proposes a crystallization kinetics modulation strategy to eliminate structural defects, and validates the practical application potential of Nb-doped LIC electrolytes in high-voltage ASSLBs. These findings highlight the integrated strategy of kinetic regulation and heteroatom doping as an effective strategy for engineering high-performance halide solid electrolytes toward advanced all-solid-state lithium batteries.