Study On The Synthesis And Doping Of LiNi_0.5Mn_1.5O₄ Cathode Material For High Voltage Lithium-ion Battery

With the development of electric vehicles,hybrid electric vehicles,people have higher requirements on the performance of lithium ion batteries,especially on their energy density and power density.High voltage cathode material LiNi_0.5Mn_1.5O₄ is considered as one of the most promising power battery cathode materials due to its high discharge plateau 4.7V,large capacity and low cost.But due to the decomposition of electrolyte under high potential and dissolution of Mn,the battery's cycling performance and rate performance are poor,especially at elevated temperatures,which limited the application of LiNi_0.5Mn_1.5O₄ material.In this paper,in order to improve the cycle performance of LiNi_0.5Mn_1.5O₄,the strategy of dop:ing elements such as Fe and Al was carried out.The effects of low-temperature annealing treatment in air on the structure,morphology and electrochemical performance of LiNi_0.5Mn_1.5O)4 were investigated respectively.The structure and morphology of the prepared samples were characterized by X-ray diffraction?XRD?,fourier transform infrared spectroscopy?FTIR?and scanning electron microscope?SEM?,and the charge-discharge performance of materials was tested at both room temperature and elevated temperature of 55?.?1?The effect of low-temperature annealing hours on the structure and electrochemical performance of LiNi_0.5Mn_1.5O₄ cathode material was studied,the material was synthesized by a wet chemical method combining a solid state reaction process.The results indicated that the content of Mn3+ in the materials was decreased and the space group of the LiNi_0.5Mn_1.5O₄ transformed from Fd3m to P4332 after annealing treatment.The electrochemical performance of LiNi_0.5Mn_1.5O₄ was improved by annealing in air at 650 ?.The material which was annealed for 6h could reach a discharge capacity of 116.6mAh/g with the capacity retention of 76.6%after 100 cycles at 55? and 0.5C rate.?2?The A1 doped material LiNi_0.45Al_0.1Mn_1.45O₄ was prepared by different annealing hours.Al doping stabilized the structure of spinel material and ameliorated the cycle performance of the material.The LiNi_0.45Al_0.1Mn_1.45O₄ material annealed for 20h in air at 650 ? displayed the best electrochemical performance.The material which was annealed for 20h could reserve 87.3%of the highest dicharge capacity after 100 cycles at 55 ? and 0.5C rate.?3?The Fe doped LiNi_0.45Fe_0.1Mn_1.45O₄ material by different annealing hours were prepared.The LiNi_0.45Fe_0.1Mn_1.45O₄ material annealed for 20h in air at 650 ? exhibited the best electrochemical performance.The LiNi_0.45Fe_0.1Mn_1.45O₄ material which was annealed for 20h could reach a discharge capacity of 118.4mAh/g with the capacity retention of 70.9%after 100 cycles at 55 ? and 0.5C rate.