| Lithium-ion batteries have a good prospect in application for its favorable advantages of high voltage, big specific capacity, long cycling life and non-pollution. Cathode is the key of the development of lithium-ion batteries. LiMn2O4 spinel is believed to be the most promising cathode material for lithium-ion batteries because of its abundant resources, low cost, simple synthesis processing environmental friendly nature. However, the low initial capacity and poor cyclability prevent LiMn2O4 spinel from wide application. Several mechanism about the attenuation of LiMn2O4 spinel and some way to improve the performance of this cathode material had been illuminated in the paper.In the present work, LiMn2O4 spinel compound was synthesized by means of the so called sol-gel process. The effects of the mole ratio of citric acid to metallic ions, the mole ratio of glycol to citric acid, pH value, and calcination process on the structure and properties of the LiMn2O4 spinel materials were discussed. The experimental results show that pure spinel phase of LiMn2O4 cathode was obtained under the experimental conditions of the mole ratio of citric acid to metallic ions being 0.5:1, the mole ratio of glycol to citric acid 3:1, pH value 7~8, when heating process was divided into 3 stages, i.e. 500℃6h→ 650℃12h→750℃ 12h. Based on the conventional solid phase synthesis, we studied the improvement function of dispersant and mechanical ballmilling to the properties of materials. Instead of using dehydrated alcohol as dispersant, distilled water was employed as dispersant in the experiments. The experiments revealed that distilled water can replace the dehydrated alcohol as dispersant without destroying the properties of materials. The advantages and disadvantages of the sol-gel method and solid phase synthesis were compared. The author believed that the sol-gel is far from being used in practical production at present duo to high running cost and environmental unfriendly. Optimized solid phase synthesis method, however, was believed as one of the promising technologies which is supposed to avoid the problems in traditional solid phase method.One of the important investigation points in the present thesis was modification of LiMn2O4 by ions-doping. Cr3+, Al3+, Co3+ and Ni2+-doping spinels were prepared. Their structure and electrochemical properties were characterized by means of XRD.SEM-EDS, TG-DTA, ICP techniques. The results shown that the cycle performance of the spinels were improved by doping all over the four kind of ions, but the specific capacities decreased. It was found that the amount of Cr3+and Al3+- doping were in the range of 0.05-0.08 and 0.02-0.04 respectively can clearly improve the performance of the materials. In addition, Al3+- doping process need the experimental conditions being well-controlled. Otherwise, it is difficult to prepared high pure phase spinel LiMn2O4-F"-doping was proved to be favorable to form full crystal and increase the specific capacity of the materials. But the amount of F"-doping is had better being controlled below 0.05.Generally speaking, the cycle performance of spinel LiMn2O4 was evidently improved through cation doping even though the specific capacity of materials were reduced to some extent. The effect mechanism of F"-doping on the properties of materials maybe complicated, and need to be investigated.
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