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 Dy³⁺-doped Li₂ZrCl₆ (Li_2+xZr_1−xDy_xCl₆) halide electrolyte is rationally designed via mechanochemical synthesis. By partially substituting Zr⁴⁺ with larger Dy³⁺, the optimized Li_2.25Zr_0.75Dy_0.25Cl₆ exhibits: (1) Superior ionic conductivity of 1.54 mS/cm (a 4.4-fold increase over pristine Li₂ZrCl₆) after low-temperature annealing, (2) 3D Li⁺ transport pathways confirmed by DFT calculations, and (3) suppressed reduction of Zr⁴⁺ at the Li metal interface, extending symmetric cell cycling to 500 h (0.2 mA/cm²). Synchrotron XAFS and XPS/TOF-SIMS analyses reveal that Dy³⁺ doping broadens Li⁺ migration channels and inhibits elemental Zr formation. The LiCoO₂-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.