The Synthesis And Modification Of Li-Mn Spinel Cathode Materials For Li-ion Battery

Spinel LiMn₂O₄ is one of the most promising cathode materials for lithium-ion batteries due to its advantages, such as high working voltage, high safety, low toxcity, low cost, abundant in resources. But its capacity is low in comparison with other cathode materials. And the problem of rapid capacity reduction during cycling should be solved before it can replace the current widely used LiCoO₂ cathode material. In this dissertation, spinel LiMn2O4 were synthesized by the method of traditional high temperature solid-state reaction. Different cation-doping and co-doping methods were used to improve the cycling performance in the optimal conditions. And coating methods were also explored. The coating investigation is worth for supplying data for industrial applications.Firstly, Spinel LiMn2O4 materials were prepared using traditional high temperature solid-state reaction method. Effects of different sintering time, sintering temperatures and different Li/Mn values on the electrochemical properties of synthesized LiMn2O4 were taken into account in this paper. Samples synthesized at 800℃,with sintering time of 12h and the Li/Mn value of 1.08:2 showed the best cycling performance.Studies of doping modification of spinel LiMn2O4 was conducted using different cation-doping and anion-cation co-doping methods. In all of the Mg-doped materials, LiMg0.06Mn1.94O4 showed the best cycling performance, and so did the material LiCe0.02Mn1.98O4 in all of the Ce-doped LiMn2O4 materials. Studies on anion-cation co-doping materials showed that LiMn1.95Al0.05F0.05O3.95 had good cycling performance, which manifested that it's an effective method to solve the problem of capacity reduction during cycling.Experiments on coating modification were conducted using Li₂CO₃ and Al₂O₃ as the coating materials. Spinel LiMn₂O₄ coated by Li₂CO₃ showed that the material with a coating amount of 0.5% had the best cycling performance. Of all the materials coated by different methods using Al2O3, the material synthesized by CMC polymerization method showed better cycling performance than that of other methods.