Promoting Ion Conduction and Li Metal Compatibility Through Nb5+-Substituted Zirconium-Based Chlorides for All-Solid-State Batteries

Zirconium-based halide electrolytes were created as prospective candidates for all-solid-state lithium batteries (ASSLBs) because of their low cost, wide electrochemical window, and superior compatibility with oxide cathodes. However, practical implementation is hindered by limitations such as suboptimal room-temperature (RT) ionic conductivity (< 1 mS cm −1 ) and poor interfacial compatibility with lithium metal. Herein, we report a new class of zirconium-based chlorides, Li 2− x Zr 1− x Nb x Cl 6 , synthesized by a high-valent Nb 5+ doping method. The introduction of Nb 5+ induces local lattice decrease, which simultaneously weakens the binding intensity of Li─Zr and optimizes ion migration pathways and defect concentrations. Therefore, the optimal composition, Li 1.75 Zr 0.75 Nb 0.25 Cl 6 (denoted as LZC-Nb), achieves a high RT ionic conductivity of 1.82 mS cm −1 and exceptional moisture resistance. Furthermore, the dynamic interfacial modulation of LZC-Nb forms a low-impedance passivation layer, enhancing Li + transport kinetics. This improvement in interfacial stability enables symmetric batteries to exceed a critical current density of 1.3 mA cm −2 . Combined with a LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode, the resultant ASSLB retains 81.8% of its initial capacity (157.5 mAh g −1 ) after 600 cycles at 0.3 C. This study provides a proven strategy for developing inorganic ionic conductors with superior ionic transport and interfacial compatibility, offering a viable pathway toward high-performance ASSLBs.