Solid-state electrolytes can improve the stability and safety of lithium-ion batteries. Inorganic materials with high lithium-ion conductivity are promising as solid-state electrolytes. In particular, layered materials with two-dimensional ion channels can achieve fast ionic transport. However, examples of this type of material with sufficient room-temperature lithium-ion conductivity are rare.
Changzheng Wu, University of Science & Technology of China, Hefei, and Hefei Comprehensive National Science Center, and colleagues have synthesized a layered material of the type LixAg1–xCrS2 (0 < x < 0.4), in which the silver ions acts as “pillars” between the layers to facilitate the transport of lithium ions. The team first prepared AgCrS2 single crystals using chemical vapor transport (CVT). The AgCrS2 was mixed with n-BuLi in hexane under an argon atmosphere and heated to 90 °C to obtain LixAg1–xCrS2.
The researchers built an all-solid-state cell using a mixture of TiS2 and LixAg1–xCrS2 as the cathode, metallic lithium foil as the anode, and LixAg1–xCrS2 in pellet form as the separator. The room-temperature ionic conductivity for the system with x = 0.31 reaches values up to 19.6 mS·cm–1, which is comparable to that of currently best lithium-ion conductors. This good conductivity can be attributed to the pillar effect of the silver ions, which increases interlayer spacing and allows for fast diffusion of lithium ions.
- Fast Lithium Ion Conductivity in Layered (Li–Ag)CrS2,
Jing Peng, Yuhua Liu, Yu Pan, Jiajing Wu, Yueqi Su, Yuqiao Guo, Xiaojun Wu, Changzheng Wu, Yi Xie,
J. Am. Chem. Soc. 2020.