Preparation And Modification Of Spinel LiMn₂O₄ Cathode Materials For Lithium Ion Battery

In this paper, the spinel LiMn2O4 cathode material for lithium-ion battery was synthesized by sol-gel method, and the effects of precursor preparation methods, sintering temperature, additives on structure, morphology and electrochemical performance of LiMn2O4 were investigated. The results showed that the spinel LiMn2O4 cathode materials prepared by microwave drying and then sintering had a higher degree of crystallinity, finer particles and more evenly distribution, thus the stable deintercalation/intercalation of Li+ was obtained and the capacity retention rate of the spinel LiMn2O4 was 86.09% after 30 charging/discharging cycles; With the increasing of sintering temperature, the particles of spinel LiMn2O4 was larger, but the particle size distribution is not uniform anymore. The spinel LiMn2O4 had a high first discharge capacity when T=800℃and a high capacity retention 94.85% after 30 charging/discharging cycles when T=700℃; Smallest particle size and most regular morphology were obtained with the use of PEG additives. The capacity retention of PEG2K and PEG2W were 80.51% and 79.00% after 100 charging/discharging cycles respectively.To resolve the problem of Capacity loss in spinel LiMn2O4, the modification of LiMn2O4 by one or two metal ions doping was investigated and the doping effect of different amount of metal ions on the electrochemical performance of cathode materials was studied. For LiNixMn2-xO4, the capacity retention maintained above 95% because of its enhancement of structure stability when 0.1<x<0.5; different micro-crystal defects in LiNixMn2-xO4 appeared when 0.01<x<0.1, and the smaller of micro-crystal defects in LiNixMn2-xO4, the higher first discharge capacity and capacity retention of it. For LiNi0.03-xMxMn1.97O4 (M=Cr/Mg), the intensity ratio of (311)/(400) peaks can be important parameters which had an effect on the electrochemical performance of the spinel LiMn2O4 doped. The electrochemical behaviour was excellent when the small intensity ratio of (311)/(400) peaks was obtained, such as LiNi0.028Cr0.002Mn1.97O4 and LiNi0.027Mg0.003Mn1.97O4.