Synthesis and interfacial engineering of nitride–halide electrolytes in all-solid-state Li batteries

Abstract

Halide solid-state electrolytes have attracted significant interest due to their high room-temperature ionic conductivity and electrochemical oxidation stability. However, their reliance on rare-earth metal-centered frameworks (e.g., Y, In, Sc, and La) results in high costs and susceptibility to reduction. As a cost-effective alternative, Li₂ZrCl₆ leverages the earth abundance of zirconium but suffers from relatively low ionic conductivity (∼10⁻⁴ S cm⁻¹), limiting its performance. Here, we report the synthesis of an amorphous nitride–halide electrolyte, Li_2+2xZrCl_6−xN_x (LZC-Nx, 0 ≤ x ≤ 0.25), which simultaneously enhances ionic transport and anodic interfacial stability. The optimized LZC-N0.15 exhibits a twofold increase in room-temperature ionic conductivity (1.5 mS cm⁻¹) compared to LZC. The in situ formed N-rich interfacial layer enables a Li/Li symmetric battery to achieve stable cycling for over 3000 hours with a critical current density of 2.8 mA cm⁻². Notably, LZC-N0.15 maintains compatibility with high-voltage cathodes while improving anodic stability. The all-solid-state battery employing an LZC-N0.15 electrolyte and a LiCoO₂ cathode delivers a high discharge capacity of 218.4 mAh g⁻¹ at 4.62 V.