A novel LaCl3-based oxychloride solid-state electrolyte enables fast Li-ion transport and is compatible with lithium metal

Abstract

Solid electrolytes are pivotal in ushering in the new era of energy technology, offering fresh prospects for its advancement. Recently, halide solid electrolytes have garnered significant attention due to their wide electrochemical window, high lithium ion conductivity at room temperature (RT), and high stability to the positive electrode. In particular, a promising LaCl₃-based solid-state electrolyte (SSE) with a non-close-packed structure could provide abundant one-dimensional (1D) channels for lithium ions, and it is compatible with lithium metal. However, the 1D channels are easily blocked by defects, and doping with several high-cost elements on the La site has been reported to optimize the migration path. Therefore, there is an imperative need to devise innovative strategies to further enhance the properties of LaCl₃-based SSEs and to expand the LaCl₃-based material family. Here, we report a cost-effective Zr⁴⁺ and O²⁻ co-doping LaCl₃-based oxychloride Li⁺ superionic conductor (Li_0.5+xZr_0.25La_0.5Cl_3−xO_x). The sample with the optimized composition, Li_0.8Zr_0.25La_0.5Cl_2.7O_0.3, exhibits a high ionic conductivity of 0.75 mS cm⁻¹ at room temperature, a low activation energy of 0.23 eV, and remarkable compatibility with Li metal. The critical current density attains a high value of 7 mA cm⁻², and the long-term cycling of Li–Li symmetric cells experiences the stable plating/striping process under 0.1 mA cm⁻² and 3 mA cm⁻². Furthermore, the all-solid-state battery with the LiCoO₂ composite cathode delivers commendable cycling performance at 0.2C and 0.5C.