Cu+ doping in Li3InCl6 for enhanced ionic conductivity and air stability

Halide solid electrolytes have emerged as highly attractive electrolyte materials owing to their excellent ionic conductivity and high oxidation potential. In this work, low-cost CuCl is employed as a dopant, and Cu⁺-doped Li₃InCl₆ is prepared via ball milling, yielding a series of novel Li₃₋ ₓ Cu ₓ InCl₆ (0 ≤  x  ≤ 0.4) electrolytes. Cu⁺ doping modifies the crystal structure and regulates the ionic conductivity of the material. Among them, Li₂.₉Cu₀.₁InCl₆ exhibits a lower activation energy and achieves a room-temperature ionic conductivity of 1.04 mS cm⁻¹. Cu⁺ doping enhances the air stability of Li₃InCl₆ and mitigates the degradation of ionic conductivity after air exposure. Furthermore, Cu⁺ doping reduces surface cracks, improves the deformability of the material, and lowers interfacial resistance. All-solid-state batteries using Li₂.₉Cu₀.₁InCl₆ as the electrolyte display superior capacity and cycling performance compared to those with pristine Li₃InCl₆. This work demonstrates that Cu⁺ doping is an effective strategy to boost ionic conductivity, improve air stability, and enhance the electrochemical performance of Li₃InCl₆.