Research On Preparation And Modification Of High Voltage Type（4.35V） LiNi_0.5Co_0.2Mn_0.3O₂ For Lithium-ion Batteries

Ternary cathode material is by far the most promising, and it is most likely to be the production of materials for power lithium-ion battery. Various reaction conditions on the performance of the high voltage type Li Ni0.5Co0.2Mn0.3O2 preparation process and modification research in this article, to make it have higher capacity and better cycle stability.This article adopted co-precipitation to prepared ternary precursor, then ternary precursor mixed with the lithium salt with a high temperature solid the synthesis Li Ni0.5Co0.2Mn0.3O2 material. At the precursor stage, studied the impact of reaction system p H value on the material surface morphology, microstructure, tap density and electrochemical cycling performance. Comprehensive analysis of the above test results concluded that: the p H=11, ternary precursor have good physical and chemical properties. Corresponding synthesized under the condition of the precursor and the ternary material resulting from the lithium salt through the performance test, the test results show that the material performance of the optimal reaction conditions.Performance will be the best precursor mixed with lithium salt by using solid state reaction method, after high temperature sintering to get Li Ni0.5Co0.2Mn0.3O2 material. This part studied the sintering temperature, sintering time and the ratio of lithium effect on the properties of material. Test of the ternary matrial sintered at different conditions of the physical and chemical properties, including: morphology, microstructure and electrochemical cycling performance. After analysis and comparisons, the best performance of the sintering conditions is: the radio of lithium is 1.06, sintering temperature is 900℃ and sintering time is 12 hours. Materials were synthesized under these conditions and tested at 25℃, 0.5C rate current between 2.75 and 4.35 V, the results show that the first discharge was 173.6m Ah/g, the discharge capacity after 100 times cycles was 154.2m Ah/g. The cycling retention capacity after 172 times cycles was more than 80%.The 3%Al3+ doped sample was tested at 25℃, 0.5C rate current between 2.75 and 4.35 V, the results show that the first discharge was 171.9m Ah/g, the discharge capacity after 100 times cycles was 166.7m Ah/g. The cycling retention capacity after 223 times cycles was more than 80%.The 1%Ti4+ doped sample was tested at 25℃, 0.5C rate current between 2.75 and 4.35 V, the results show that the first discharge was 170.2m Ah/g, the discharge capacity after 100 times cycles was 159.5m Ah/g. The cycling retention capacity after 248 times cycles was more than 80%.The 0.5%Al2O3 coated sample was tested at 25℃, 0.5C rate current between 2.75 and 4.35 V, the results show that the first discharge was 174.9m Ah/g, the discharge capacity after 100 times cycles was 169.9m Ah/g. The cycling retention capacity after 256 times cycles was more than 80%, and the performance of ratio and high temperature storage is also good.Comprehensive modification experiment results,Al3+ doping can better improve the cycle performance of ternary material, Ti4+ doping in the view of improving the performance of material circulation will not reduce the capacity at the same time, Al2O3 coating is good to prevent the corrosion of electrolyte to positive active material,stabile material structure.