Cation-Anion-Engineering Modified Oxychloride Zr-Based Lithium Superionic Conductors for All-Solid-State Lithium Batteries

Abstract

Within the family of halide solid electrolytes (SEs), Li₂ZrCl₆ demonstrates high oxidative stability, cost-effectiveness, and mechanical deformability, positioning it as a promising candidate for SEs. However, the application of Li₂ZrCl₆ as a SEs was hindered by its low ionic conductivity at room temperature. Current strategies to enhance the ionic conductivity of Li₂ZrCl₆ primarily are focused on single cation or anion sublattice-engineering, each with distinct advantages and limitations. Here, we propose a novel cation and anion-sublattice-engineering strategy, termed CASE, to increase the amorphous content and thus enhance ionic conductivity. The incorporation of Cu²⁺ and O²⁻ induces distinctive structural modifications within Li₂ZrCl₆. This structure corroborated through analytic data of X-ray absorption spectroscopy, the neutron diffraction, and ab initio molecular dynamics. Consequently, the amorphous Li_2.1Zr_0.95Cu_0.05Cl_4.4O_0.8 achieves an enhanced ionic conductivity of 2.05 mS cm⁻¹ at 25 °C. Furthermore, all-solid-state lithium batteries utilizing the amorphous Li_2.1Zr_0.95Cu_0.05Cl_4.4O_0.8 as an electrolyte and LiNi_0.83Co_0.11Mn_0.06O₂ as a cathode exhibit a superior long-term cycling stability retaining 90.3% of capacity after 1000 cycles at 2 C under room temperature, which are much higher than those of Zr-based halide electrolytes in publications. Such a result might stimulate the development of more amorphous structures with high ionic conductivity in the CASE strategy.