Application of the Low-heating Solid-state Reaction Method in Preparation of Multi-metal Oxides Composite -Synthesis, Structure and Electrochemical Properties of Rhombohedral LiMnO_2 Cathode Material for Lithium-ion Batteries

LiMn02 compounds with rhombohedral structure were prepared by the low-heating solid-state reaction method at the temperature range of 350-700℃. The powder X-ray diffraction technique was applied to investigate the structures of the obtained samples. XRD result shows that the structures of these samples are the same as that of LiCoO2- Compared with LiCoO2 and LiCo0.8Ni0.2O2 prepared by the same method, the lattice parameter of r-LiMnO2, c/α, is relatively smaller due to the Jahn-Teller deformation. Selected-area electron diffraction and XRD results indicate the existence of the cubic spinel impurities in the r-LiMnO2 samples sintered at 600℃ and 700℃. The tests of charge/discharge show that the samples prepared above 600℃ have two voltage plateaus of 3V and 4V, of which the plateau at 4V is related to the cubic spinel impurities. Whereas, the samples obtained below 500℃ present only one plateau of 3V. Especially, the sample obtained at 500c℃ exhibits good structural stability in lithium-ion intercalation/deintercalation processes.