Enhancement of ion transport in Li3InCl6 solid electrolyte by in-rich strategy

Solid electrolytes, as the core components of all-solid-state batteries, are a prominent research focus due to its lithium-ion rapid diffusion capability. The halide solid electrolyte Li 3 InCl 6 , distinguished by its high ionic conductivity and remarkable moisture reversibility, has garnered considerable attention in the realm of electrochemistry. This study systematically investigates the influence of Li + vacancy defect concentration on lattice configuration and ionic transport properties through In-rich compositional modulation in Li 3 InCl 6 electrolytes with varying Li/In cation ratios. Experimental results reveal that, under an invariant primary lattice framework, increasing In 3+ content induces preferential occupation of the 4 g Wyckoff sites by In 3+ , generating lattice distortion that deforms the cation layer in the (001) crystallographic plane. Concurrently, substantial tetrahedral vacancy defects emerge within the Li + layer of the (002) plane. This synergistic structural evolution markedly enhances lithium-ion transport kinetics by weakening anion framework constraints on Li + migration. Correspondingly, electrochemical characterization demonstrates that the optimized Li 2.55 In 1.15 Cl 6 electrolyte achieves a threefold increase in ionic conductivity compared to the pristine sample. The performance enhancement originates from distorted non-migrating ion sites and generated vacancy defects within the crystal lattice. Consequently, all-solid-state lithium batteries incorporating this optimized electrolyte exhibit significantly improved cycling stability and rate capability. This study prepares Li 3-3x In 1+x Cl 6 via ball milling and investigates the structure-performance relationships through vacancy regulation, demonstrating a viable strategy for solid-state electrolyte design. In this work, the In-rich strategy is employed to induce lattice distortion in the Li 3 InCl 6 electrolyte while generating Li + vacancy defects. This synergistic structural evolution significantly enhances the ionic transport performance. • In-rich Li 3 InCl 6 exhibits lattice distortion and Li + vacancies, weakening anion confinement and enhancing Li + transport. • Combined XRD, XPS, and DFT reveal defect engineering mechanisms for improved solid-state electrolytes. • In-rich strategy boosts humidity stability of Li 3 InCl 6 by lowering H 2 O adsorption and suppressing hydrolysis. • Optimized Li 2.55 In 1.15 Cl 6 shows a threefold increase in ionic conductivity and better cycling stability and rate performance.