A Zr–O co-doping strategy for halide solid electrolytes toward high-performance all-solid-state batteries

Abstract

All-solid-state batteries (ASSBs) are regarded as a pivotal direction for next-generation energy storage due to their high energy density and superior safety. As the core component of ASSBs, solid-state electrolytes (SEs) critically determine cell performance. Halide-based SEs have attracted significant attention owing to their wide electrochemical windows and favorable compatibility with high-voltage cathodes. However, their practical application is hindered by insufficient ionic conductivity and poor interfacial stability. To address these challenges, this study proposes a synergistic Zr–O co-doping strategy to enhance the performance of Li₃InCl₆ (LIC) solid electrolyte. Specifically, oxygen doping enhances the structural robustness by forming strong ionic bonds, albeit at the expense of reduced ionic conductivity. In contrast, substituting In³⁺ with Zr⁴⁺ induces local lattice distortion within the [In/ZrCl₆] octahedra and generates lithium vacancies, which significantly lower the Li⁺ migration barrier, as confirmed by CI-NEB calculations. The synergistic effect of Zr and O co-doping enables the development of Li₃In_0.75Zr_0.25Cl_5.75O_0.25 (LIZCO) electrolyte with: (1) a high ionic conductivity of 1.12 mS cm⁻¹ at room temperature; (2) an oxidative stability exceeding 4 V vs. Li⁺/Li; and (3) significantly improved chemical compatibility with sulfide-based solid electrolytes. When paired with a bare LiNi_0.9Co_0.05Mn_0.05O₂ (NCM955) cathode, the ASSBs deliver excellent electrochemical performance, achieving a discharge capacity of 110 mA h g⁻¹ at 5C and retaining 71% of its initial capacity after 1000 cycles at 3C. This work provides a viable design strategy and theoretical foundation for the development of halide-based solid electrolytes with simultaneously high ionic conductivity and interfacial stability.