Multi-Ion Doped Zr-Based Halide Solid Electrolytes for High-Performance All-Solid-State Batteries

Zr-based halide solid-state electrolytes (SSEs) hold significant commercial potential owing to their cost-effectiveness, excellent mechanical deformability, and superior oxidative stability. However, their practical applications are still hindered by limited room-temperature ionic conductivity and insufficient compatibility with high-voltage oxide cathodes. Here, a oxygen-doped high-entropy SSE (HESSEO, Li_2.89Zr_0.72Nb_0.07Mo_0.07Ta_0.07Hf_0.07Cl_4.9O_1.1) was synthesized by introducing M (M = Nb, Mo, Ta, and Hf) and O ions into Li₂ZrCl₆ (LZC), achieving a high ionic conductivity of 2.13 mS cm^-1 at room temperature. Density functional theory (DFT) calculations confirmed that HESSEO exhibits higher Li⁺ diffusion coefficients and lower diffusion barriers compared with those of LZC. All-solid-state batteries (ASSBs) with HESSEO demonstrated excellent long-term cycling stability, delivering an initial discharge capacity of 187.2 mAh g^-1 and retaining 78.8% of the capacity after 1000 cycles at 2 C with the cutoff voltage of 4.3 V (vs. Li⁺/Li). Moreover, the batteries maintained stable operation for over 300 cycles even at 1 C with a higher cutoff voltage of 4.5 V. This multi-ion synergistic design provides a viable strategy to simultaneously enhance the ionic conductivity and high-voltage stability of halide SSEs, offering a practical approach for the development of commercially relevant ASSBs.