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

摘要

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 Ni~(3+) and Mn~(4+) 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 deg and 180 deg Ni~(3+)-O-Ni~(3+/2+) exchange interactions, the distribution of Ni~(3+)/Ni~(2+) between the lithium and nickel layers in Li_(1-x)Ni_(1+x)O_2 with 0 < x < 0.4 can be determined. For layered LiNi_(1-y)Co_yO_2 and spinel LiMn~_(2-)Co_xO_4 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 Ni~(3+)/Co~(3+) and Mn~(4+)/Co~(3+) ordering. The results obtained are correlated with the electrochemical intercalation of lithium in these compounds.