Enhanced ion conductivity and stability against Li metal in Dy3+-doped Li2ZrCl6 electrolytes for high-performance all-solid-state batteries

The development of chloride-based solid-state electrolytes faces significant challenges in achieving an optimal balance among ionic conductivity, compatibility with Li metal, and cost-effectiveness. Herein, a novel Dy 3+ -doped Li 2 ZrCl 6 (Li 2+ x Zr 1− x Dy x Cl 6 ) halide electrolyte is rationally designed via mechanochemical synthesis. By partially substituting Zr 4+ with larger Dy 3+ ions, the optimized Li 2.25 Zr 0.75 Dy 0.25 Cl 6 exhibits: (1) superior ionic conductivity of 1.54 mS/cm (a 4.4-fold increase over pristine Li 2 ZrCl 6 ) after low-temperature annealing, (2) 3D Li + transport pathways confirmed by DFT calculations, and (3) suppressed reduction of Zr 4+ at the Li metal interface, extending symmetric cell cycling to 500 h (0.2 mA/cm 2 ). Synchrotron XAFS and XPS/TOF-SIMS analyses reveal that Dy 3+ doping broadens Li + migration channels and inhibits elemental Zr formation. The LiCoO 2 -based all-solid-state lithium batteries exhibit superior cycling stability (81.4% capacity retention at 1000 cycles) and outstanding rate performance (82.9 mA·h·g −1 at 3 C). This work presents a paradigm for designing efficient and economical halide solid-state electrolytes.