期刊
ACS APPLIED ENERGY MATERIALS
卷 4, 期 8, 页码 7930-7941出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsaem.1c01262
关键词
solid-state battery; solid electrolyte; density functional theory; lithium halide; superionic conductor
资金
- Hong Kong Innovation and Technology Fund [UIM/369]
- Research Grants Council of Hong Kong [16201820, 16206019]
The research found that in the Li3YX6 series, trigonal Li3YCl6 has the lowest activation energy and highest ionic conductivity, attributed to a fast Li diffusion pathway and weaker Coulombic attraction between Li and Cl ions. Additionally, partially substituting Y with transition metals like La and Zr effectively reduces activation energy or increases vacancy concentration, consequently improving Li ion conductivity.
The lithium halide Li3YX6 (X = F, Cl, Br, and I) is a promising solid electrolyte candidate because of its outstanding electrochemical stability and superior ionic conductivity. In this work, we apply density functional theory (DFT) to investigate the impact of halide ions and the partial substitution of Y with transition metals (e.g., Sr, Sc, La, and Zr) on the transportation, electrochemical stability, and defect chemistry of Li3YX6. Our result shows that trigonal Li3YCl6 has the lowest activation energy and the highest ionic conductivity in the Li3YX6 series. Such outstanding performance is attributed to the existence of a fast octahedral-to-octahedral Li diffusion pathway and the relatively weaker Coulombic attraction between Li ions and Cl ions. Moreover, we discuss the impact of partially substituting Y with a transition metal (e.g., Sr, Sc, La, and Zr) on the electrochemical stability and transport performance of Li3YCl6. The partial substitution of Y with a larger transition metal such as La reduces the activation energy by increasing the diffusion channel size. Furthermore, partially substituting Y with higher valence transition metal ions such as Zr effectively increases the concentration of vacancies by charge compensation, potentially improving Li conductivity.
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