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 Li_xAg_1–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 Li_xAg_1–xCrS₂.

The researchers built an all-solid-state cell using a mixture of TiS₂ and Li_xAg_1–xCrS₂ as the cathode, metallic lithium foil as the anode, and Li_xAg_1–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.
  https://doi.org/10.1021/jacs.0c08448