Improvement of electrochemical property of VS4electrode material by amorphization via mechanical milling process

Abstract

Amorphous VS4(a-VS4) electrode material was synthesized by mechanical milling of crystalline VS4(c-VS4). The columbic efficiency of the a- VS4cell was significantly improved (ca. 86 %) at the first cycle as compared with the c-VS4cell (ca. 77 %), resulting in the improved capacity retention for prolonged cycling. Pair distribution function (PDF) analysis obtained from X-ray total scattering data, revealed that the radial atomic distribution of a-VS4at initial stage was similar to that of the low-crystalline VS4appeared after the first cycle of c-VS4. This is suggestive that the amorphization via mechanical milling process gave rise to the preparation of "first cycled VS4" which would contribute to the improved columbic efficiency at the first cycle and the resulting improved capacity retention for prolonged cycling. The structure of a-VS4could be visualized by first-principles molecular dynamic calculation of "first-cycled VS4".