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

Abstract

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−xZr_1−xNb_xCl₆, synthesized by a high-valent Nb⁵⁺ doping method. The introduction of Nb⁵⁺ 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_1.75Zr_0.75Nb_0.25Cl₆ (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_0.8Mn_0.1Co_0.1O₂ 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.

Keywords

all-solid-state lithium metal batteries / halide solid electrolytes / ion conduction / Li metal compatibility / moisture stability

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