Improvement of Electrochemical Property of VS₄ Electrode 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-VS₄ cell was significantly improved (ca. 86 %) at the first cycle as compared with the c-VS₄ cell (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-VS₄ at initial stage was similar to that of the low-crystalline VS₄ appeared 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-VS₄ could be visualized by first-principles molecular dynamic calculation of “first-cycled VS₄”.