Preparation And Modification Of Spinel LiMn₂O₄

With the rapid development of electronic equipment, the problem of energy sources and environmental issues are outstanding important. People put forward higher requirements to the chemical power. The spinel lithium manganese oxide (LiMn2O4) has advantages like rich resources, low cost, no pollution and so on. It is recognized as a most promising cathode material for rechargeable lithium-ion batteries. But due to the dissolution of manganese, decomposition of electrolyte and Jahn Teller effect, the performance of lithium manganese oxide (LiMn2O4) is still not very well, so it becomes a research hotspot to improve its performance.The cathode material for pure spinel lithium manganese oxide (LiMn2O4) were prepared by the combination of high temperature and section sintering method with the low-cost Li2CO3 and MnO2 as main raw material. Determine the sintering temperature of product based on the differential thermal analyzer and thermal gravimetric (DTA-TG); characterize the structure of the product and the microstructure based on the X-ray diffraction (XRD) and scanning electron microscopy (SEM) and study the comprehensive electrochemical properties of the material based on charge and discharge measurement test.The spinel lithium manganese oxide (LiMn2O4) of the cathode material for rechargeable lithium-ion batteries was synthesized by improving the method of synthesis, modification by doping the phase and modification of Material surface coating respectively.Study the effect of technological condition in changing the ball-milling method of raw material and the ball-milling to LiMn2O4 (111) crystal plane firstly in the research direction of improving the method of synthesis. The performance of the spinel lithium manganese oxide (LiMn2O4) synthesized after ball-milling is more outstanding. The optimum value of ball-milling time is at 6 hours (Charge and discharge for the first time in 0.5 C ratio is 129.3 mAh/g and keep rate of capacity after 30 cycling is 94.95%) Studies shows that ball-milling can change the size of the LiMn2O4 (111) crystal plane which can affect the electrochemical performance of lithium manganese oxide (LiMn2O4).Study the effect of electrochemical performance of the rechargeable lithium-ion batteries by doping of zwitterions of Ni, Co, Al and F respectively and doping of zwitterions of Al and F compositely. in the research direction of modification by doping the phase. Studies show that the charge and discharge is reduced for the first time, but circulating rate has improved significantly while doping of zwitterions of Ni, Co and Al respectively. The charge and discharge is increased for the first time and circulating rate has improved significantly while doping of zwitterions of F. The charge and discharge is stable for the first time and circulating rate has improved significantly while doping of zwitterions of Al and F compositely.Study the effect of electrochemical performance of the rechargeable lithium-ion batteries by modifying silica sol coating in the research direction of modification of Material surface coating. Studies show that the surface of lithium manganese oxide form a layer of wrapped phase after packing modified lithium manganese oxide. With the increase of the amount of silica sol, the discharge specific capacity of the sample is reduced but the rate of capacity retention is increases first then decreases. When it is less than 2.0 wt% for the amount of silica sol added, the rate of capacity retention increase from 92.241% to 94.068% but when the content of silicon sol added is greater than 2.0 wt%, rate of capacity retention begin to decrease.