The Property Research Of Spinel Limn₂O₄ Cathode Materials

The material of spinel lithium manganese is the most essential anode material of the secondary lithium ion batteries because of its high discharge voltage, low toxicity, abundant resources in the earth. In recent years, it is believed that spinel lithium manganese has become the most important dynamical energy for vehicles in our daily life. An amount of researches shows, the electrochemical properties of the material are affected by such factors as, synthesis process, the surface morphology and the spinel structure. In our studies, much work were developed in changing the morphology and modifying the material to optimize the compositive performance of the spinel lithium manganese.Calcining temperature and calcining periods have influence on the morphology, the structure and the electrochemical performance, which was the important studies, using glycine- cellulose-fiber combustion. Datas shows the conditions of temperature, time and milling impact greatly on the spinel structure, micro-morpology and the properties. The sample synthesized in 750℃for 6h delivers a discharge capacity of 112.9 mAh/g and remains 90 mAh/g after 30 cycles. The characterization of SEM and XRD pictures shows uniform particles, slippy surface and net state with all particles with pure phase. To improve cycleability of LiMn₂O₄ material, Cr-doped LiMn₂O₄ was attempted by glycine- cellulose-fiber combustion. The amounts of dopant were investigated in these studies. The result reveals that the amount of dopant x = 0.08 is the optional one.The sol was heated in a proper microwave, and then the precursor was annealed in a high temperature using the Net of Macromolecule PAM Sol assisted with microwave. It is thought that the sample prepared in 800℃for 6h is the optional one. The results suggest the properties are infleunced by annealed temperature and AM concentration. Besides it was also determined by dispersant and polymerization initiator. Researching the structure and morphology via XRD and SEM shows spherical balls of 3-5μm diameters are pure spinel LiMn₂O₄. The sample prepared in the condition of heating 800℃remained for 6h with microwave is the optional one for the method. The initial discharge specific capacity of the sample is 129.5 mAh/g and remains 103 mAh/g after 50 cycles. In our studies, Cr-doped LiMn₂O₄ was also tried by the Net of Macromolecule PAM Sol assisted with microwave. The initial discharge specific capacities of Cr-doped LiMn₂O₄ was 94.4mAh/g and remains 85.8 mAh/g after 38 cycles. Li deintercalation/intercalation process from spinel LiMn₂O₄ was studied by AC impedance measurement. It was found that the cycleability was enhanced obviously.