Dual Zr–N co-doping endowing 3D Li-ion transport and enhanced Li-ion concentration in UCl3-type chloride electrolytes

Abstract

Halide solid electrolytes are attractive candidates for all-solid-state batteries owing to their favorable ionic conductivity, high oxidation stability, and superior mechanical deformability. However, limited Li+ concentration and intrinsically one-dimensional diffusion pathways impede their performance. Herein, dual anion–cation co-doping strategy is involved in UCl3-type electrolytes, yielding a series of nitride-chloride compounds of Li0.5 + 2zZrxLayCl3−zNz. The ionic conductivities are systematically studied through modulating elementary composition and ball-milling time, revealing the correlation among defect chemistry, processing conditions, and Li+ transport behavior. Zr4+ substitution generates cation vacancies that enable one-dimensional channels into three-dimensional networks for Li+ migration, while partial N3− substitution increases the Li+ carrier concentration. Consequently, the optimized Li0.6Zr0.357La0.357Cl2.95N0.05 electrolyte achieves an ionic conductivity of 0.66 mS cm−1 at 25 °C and a low activation energy of 0.285 eV, achieving an enhancement of three orders of magnitude compared with pristine Li0.5La0.833Cl3. This electrolyte remains electrochemically stable up to approximately 4.00 V vs Li+/Li. All-solid-state batteries employing the LiCoO2 as cathode and Li-In as anode deliver an initial discharge capacity of 129.3 mAh g−1 at 0.1 C and retain 77.4% capacity over 100 cycles at 0.33 C. This study highlights coordinated defect engineering and processing optimization for overcoming intrinsic transport limitations in halide solid electrolytes, thereby supporting the development toward high-performance all-solid-state batteries.