Degradation Evolution for Li<sub>2</sub>ZrCl<sub>6</sub> Electrolytes in Humid Air and Enhanced Air Stability via Effective Indium Substitution
Xuming Luo, Xiaoyu Hu, Yu Zhong, Xiuli Wang, Jiangping Tu
Abstract
Abstract Superionic halides have aroused interests in field of solid electrolytes such as Li 2 ZrCl 6 . However, they are still facing challenges including poor air stability which lacks in‐depth investigation. Here, moisture instability of Li 2 ZrCl 6 is demonstrated and decomposition mechanism in air is clearly revealed. Li 2 ZrCl 6 decomposes into Li 2 ZrO 3 , ZrOCl 2 · x H 2 O and LiCl during initial stage as halides upon moisture exposure. Later, these side products evolve into LiCl(H 2 O) and Li 6 Zr 2 O 7 after longer time exposure. More importantly, structure of destroyed halides cannot be recovered after postheating. Later, Indium is doped into Li 2 ZrCl 6 (9.7 × 10 −5 S cm −1 ) to explore its effect on structure and properties. Crystal structure of ball‐milled In‐doped Li 2 ZrCl 6 electrolytes is converted from the Li 3 YCl 6 ‐like to Li 3 InCl 6 ‐like with increasing In content and ionic conductivity can also be enhanced (0.768–1.13) × 10 −3 S cm −1 ). More importantly, good air stability of optimal Li 2.8 Zr 0.2 In 0.8 Cl 6 is achieved since halide hydrates are formed after air exposure instead of total decomposition and the hydrates can be restored to Li 2.8 Zr 0.2 In 0.8 Cl 6 after postheating. Moreover, reheated Li 2.8 Zr 0.2 In 0.8 Cl 6 after air exposure is successfully applied in solid‐state LiNi 0.8 Co 0.1 Mn 0.1 O 2 /halides/Li 6 PS 5 Cl/Li–In battery. The results in this work can provide insights into air instability of Li 2 ZrCl 6 and effective strategy to regulate air stability of halides.