Nucleation and Conversion Transformations of the Transition Metal Polysulfide VS 4 in Lithium-Ion Batteries.
ACS applied materials & interfaces(2019)
摘要
Transition metal polysulfides with high S content, such as VS, TiS, and MoS, have high specific Li capacities, but their reaction mechanisms for lithium-ion batteries remain unclear due to unknown intermediate products. In this work, first-principles calculations based on the density functional theory were performed to reveal the electrochemical properties of VS for lithium-ion batteries. The results demonstrated multiple phase transformations during Li insertion, starting with nucleation transformation from VS to LiVS and followed by gradual decomposition reactions. Enthalpy-driven long-range migration of LiS molecules resulted in crystalline to amorphous transformation during decomposition. S and V successively behaved as redox centers for Li VS before and after x = 3. Moreover, low activation energy and high Li diffusivity were observed at room temperature, revealing superior rate capability of the material.
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关键词
conversion reaction,structure prediction,structure transformation,transition metal polysulfide,vanadium tetra-sulfide
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