Cation order/disorder in lithium transition-metal oxides as insertion electrodes for lithium-ion batteries

Abstract

Results on the local cation ordering in layered lithium-nickel/cobalt oxides and metal-substituted lithium-manganese spinels are presented. It is shown that electron spin resonance of Ni3+ and Mn4+ and magnetic susceptibility measurements are powerful tools to monitor the short-range cation ordering in these compounds, which is not accessible by diffraction techniques. Thus, owing to the different strength of the 90° and 180° Ni3+-O-Ni3+/2+ exchange interactions, the distribution of Ni3+/Ni2+ between the lithium and nickel layers in Li1-xNi1+xO2 with 0 < x < 0.4 can be determined. For layered LiNi1-yCoyO2 and spinel LiMn2-xCOxO4 solid solutions, analysis of the temperature-independent EPR line width in terms of dipole-dipole and exchange interactions has been used to examine the local Ni3+/Co3++ and Mn4+/Co3+ ordering. The results obtained are correlated with the electrochemical intercalation of lithium in these compounds.