| Lithium ion battery, as a high performance rechargeable battery, has been widely used in many ways, like the laptop, electric car or bike, for its high capacity, high working voltage, good safety performance and long cycle life. As one of the most promising cathode materials, the spinel LiMn2O4 has been studied extensively by many researchers in the world. Compared with other batteries, it has many advantages, high energy density, simple synthesis method, low cost,low toxicity and so on. But it has a fatal disadvantage the capacity fading too fast, especially in high temperature(55℃), because of manganese dissolution, Jahn-Teller effect and electrolyte oxidation during the charge and discharge cycle process. In this paper, the spinel LiMn2O4 was prepared by Sol-Gel method, and doping it with Cr and Al was introduced to improve the performance of cathode material.The effect of sintering temperature, proportion of ion doping, crystal structure and performance of the material was investigated by XRD, SEM and electrochemical method. The result is that the pure LiMn2O4 has high capacity, but poor cycle performance, and the performance at 750℃after 12 hours is the best. At the same time, the cycle performance is improved greatly after doping, though the first discharge capacity decreases at different levels. Through the investigation, the best proportion of the doping ion is obtained, when x=0.05, LiMn1.95Cr0.05O4 and LiAl0.05Mn1.95O4 both have the best performance. The first discharge capacity of pure LiMn2O4 is 128.3mAh/g while LiMn1.95Cr0.05O4 and LiAl0.05Mn1.95O4 are respectively 112.05mAh/g and 114.45mAh/g. In respect of cycle performance, the capacity of pure LiMn2O4, LiMn1.95Cr0.05O4 and LiAl0.05Mn1.95O4 after 30 cycles are respectively 89.5mAh/g,106.6mAh/g,110.32mAh/g, so the capacity fading rate of LiMn2O4 is 30.24%, its capacity loss is the most; the second is LiMn1.95Cr0.05O4, it decreases 14.7%; LiAl0.05Mn1.95O is the best, its capacity fading rate is only 3.61%. |
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