Multi-Anion/Cation Engineering Enables Fast Ion Transport and Stable Interfaces in Zr-Based Halide Electrolytes for All-Solid-State Batteries

Abstract

The Zr-based halide solid-state electrolyte (SE) Li₂ZrCl₆ (LZC) has emerged as a promising candidate for all-solid-state lithium metal batteries (ASSLBs) due to the natural abundance and low cost of zirconium. However, its relatively low ionic conductivity and insufficient interfacial stability severely limit its practical application. Herein, we propose a synergistic multi-anion and cation co-doping strategy to construct a highly amorphous halide electrolyte, Li2.25Zr0.75Al0.25Cl4.2O0.8F0.2. The incorporation of O2- induces substantial amorphization, facilitating Li⁺ transport and improving mechanical deformability. Meanwhile, Al³⁺ substitution increases Li⁺ concentration via charge compensation, further promoting ion transport. In addition, F⁻ incorporation enhances oxidative stability and enables the formation of a robust F-rich cathode–electrolyte interphase (CEI), effectively suppressing interfacial side reactions. As a result, the optimized electrolyte exhibits a high ionic conductivity of 1.12 × 10⁻³ S cm⁻¹ with reduced activation energy. When paired with a LiNi0.90Co0.05Mn0.05O2 cathode, the assembled ASSLB delivers excellent rate capability and long-term stability, retaining ~70% of its initial capacity after 500 cycles at 0.5 C. This work demonstrates that synergistic multi-anion and cation engineering enables amorphization that effectively couples fast ion transport with stable interfaces in halide solid electrolytes.