Preparation of -LiVO from polyoxovanadate cluster Li[VO(CO)] as a high-performance cathode material and its reaction mechanism revealed by XAFS

Wang, H.*; Idobe, Jin*; Shimizu, Takeshi*; Matsumura, Daiju   ; Ina, Toshiaki*; Yoshikawa, Hirofumi*

-phase LiVO, which shows superior electrochemical performance as cathode material in Li-ion batteries, was prepared by annealing the polyoxovanadate cluster Li[VO(CO)]. The reaction mechanism was studied using X-ray absorption fine structure (XAFS), powder X-ray diffraction (PXRD), and X-ray photoelectron spectroscopy (XPS) analyses. The X-ray absorption near edge structure (XANES) and XPS results reveal that -LiVO undergoes two-electron redox reaction per VO pyramid unit, resulting in a large reversible capacity of 260 Ah/kg. The extended X-ray absorption fine structure (EXAFS) and PXRD analyses also suggest that the V-V distance slightly increases, due to the reduction of V to V during Li ion intercalation as the material structure is maintained. As a result, -LiVO shows highly reversible electrochemical reaction with x = 0.1-1.9.