Crystal structure and spin dynamics for the Li9V3P8−δO29−δ′ insertion electrode system with a multiple-electron reaction

Abstract

The crystal structure, the electron configurations of V ions and the spin dynamics for the Li9V3P8−δO29−δ′ insertion electrode system that exhibits a multiple-electron reaction are explored through measurements of x-ray four-circle diffraction, magnetization and nuclear magnetic resonance. The structure for the stoichiometric composition with δ = δ′ = 0 is refined precisely and the effective valences of all ions are determined. The electron configurations of V ions for the system annealed at various temperatures are considered in the framework of intermediate crystal field approach. For the system that often exhibits the charge–discharge performance better than the double-electron reaction, the spin dynamics mainly for the tetrahedral Li3 ions is understood on the basis of the relaxation mechanisms of quadrupole coupling and resonance shift anisotropy caused by the dipolar field of V ions. The correlation time of fluctuating fields is proportional to the temperature above 30 K, below which it follows the fractional Debye–Stokes–Einstein relation.