EPR STUDIES ON THE MICROSTRUCTURE OF LiNi_(1-y)Co_yO_2 ELECTRODE MATERIALS FOR LITHIUM-ION BATTERIES

摘要

The launch of the first commercial lithium-ion battery by Sony at 1990 has promoted intense research interest in layered LiNi_(1-y)Co_yO_2 solid solutions. The interest in these oxides is not only practical, but also theoretical, aimed at understanding the electronic structure of oxo-bridged mixed valence Ni~(2+)-Ni~(3+) pairs. The availability of diamagnetic Co~(3+) and paramagnetic Ni~(3+) in Ni/CoO_2-layers provides an opportunity to use electron paramagnetic resonance spectroscopy (EPR) of Ni~(3+) for studying in details the order phenomena in LiCo_(1-y)Ni_yO_2. In this paper we demonstrate the power of the EPR of Ni~(3+) as an experimental tool to assess the local coordination of Ni~(3+) in LiNi_(1-y)Co_yO_2 used as cathode materials in lithium-ion cells.