High-Conductivity Li<sub>2</sub>ZrCl<sub>6</sub> Electrolytes via an Optimized Two-Step Ball-Milling Method for All-Solid-State Lithium–Metal Batteries
Juntao Shi, Zhujun Yao, Jiayuan Xiang, Chen Cai, Fangfang Tu, Yongqi Zhang, Weilin Yao, Qixiang Jia, Yan Zhou, Shenghui Shen, Yefeng Yang
Abstract
The combined advantages of good mechanical deformability, high Li + conductivity, and strong compatibility with 4 V-class cathodes make halide solid-state electrolytes promising candidates for high-energy all-solid-state lithium–metal batteries (ASSLMBs). Among these, the cost-effective Li 2 ZrCl 6 has garnered significant attention due to the non-inclusion of rare-earth metals. However, the conventional one-step ball-milling synthesized Li 2 ZrCl 6 always exhibits an ionic conductivity lower than 5 × 10 –4 S cm –1 in most literature. Here, a simple optimized two-step ball-milling strategy is adopted to achieve a high Li + conductivity of nearly 1 × 10 –3 S cm –1 at 30 °C for Li 2 ZrCl 6 . Simultaneously, the effects of rotational speed and ball-to-powder mass ratio on the structure and ionic conductivity of Li 2 ZrCl 6 are investigated. The Li + migration pathways in electrolytes are also studied by bond valence site energy (BVSE) calculations. Moreover, the application potential of the modified Li 2 ZrCl 6 electrolyte in ASSLMBs assembled with the LiCoO 2 cathode and the lithium–indium alloy anode has been studied. The ASSLMBs exhibit an initial discharge capacity of 123.4 mA h g –1 at room temperature (0.1 C) and a capacity retention of 71% after 50 cycles. Therefore, this study introduces an effective strategy for synthesizing high-performance halide electrolytes, thus facilitating the practical implementation of halide-based ASSLMBs.