Li+Ionic Diffusion in LiCuO2Exposed to Heating-Cooling Cycles

Abstract

The temperature dependence of 7 Li NMR line widths and electrical conductivity of LiCuO 2 have been measured to elucidate the Li + ionic diffusion in disordered layer structure. The line widths were constant below around 380 K, while the narrowing of line widths attributed to the Li + ionic diffusion was observed above 380 K in a heating-cooling cycle. The temperature dependence of conductivity shows hysteresis in the first heating-cooling cycle. It is strongly affected by the extrinsic conduction induced by the CuO phase produced at high temperatures. Therefore, it is difficult to extract the intrinsic ionic conduction from the electrical conductivity. However, the motional narrowing of 7 Li line widths is explained with a thermal activation model for Li + ion hopping, which yields the activation energy of around 0.22 eV through the heating-cooling cycle. It indicates that the Li + ionic diffusion occurs even in LiCuO 2 which has undergone the local change in structure produced by exposure to the heating...