Preparation And Modification Of Ternary Cathode Materials For Lithium Ion Batteries

The global energy problem is increasingly serious,and environmental issues are becoming increasingly prominent.The development of new and efficient energy technologies and new energy materials has become an important way to solve social energy and environmental problems.Lithium-ion batteries,a clean and efficient energy device,have received widespread attention.As an important part of the lithium ion battery,major scientific research institutes and enterprises are committed to developing cathode materials with high capacity and long cycle life.After analyzing the current situation of lithium-ion battery cathode materials,this paper selects ternary cathode materials Li Ni0.6Co0.2Mn0.2O2(NCM622)with high specific capacity for research.The following remarkable results have been achieved by exploring the synthetic process of materials and subsequent modification studies.First,we synthesized a lithium ion battery ternary cathode material NCM622 by a high-temperature solid-phase method assisted by nano-ball milling,and optimized process parameters such as ball milling parameters and synthesis temperature.After the electrochemical performance test,the material has a discharge specific capacity of 181.9m Ah / g at a rate of 0.1C,and a discharge specific capacity of 125.4 m Ah / g after 100 cycles at a rate of 1C,and the cycle retention rate is 82.0%.In order to further improve the electrochemical performance of the material,we have synthesized the ternary cathode material NCM622 modified with rubidium ion.The best electrochemical properties are obtained when the doping amount of rubidium ions is 1%.After the modification,the lithium layer space is expanded,and the coefficient of lithium-ion lithium-ion diffusion is increased to 4.64×10-13 cm2/s.After the modification of rubidium,the space of the lithium layer is enlarged,and the lithium ion diffusion coefficient is increased.The modified material has a specific discharge capacity of 188.9m Ah / g at 0.1C and a retention rate of 89.4% after 100 cycles(1C).Finally,in order to improve the cycle performance of the material,yttrium ions were used to replace part of the transition metal layer ions.The ion radius of yttrium ions(0.960?)is much larger than the ion radius of the transition metal layer(Ni2+(0.69 ?)、Co3+(0.545 ?)、Mn4+(0.530 ?)).After doping,the intermetallic layer spacing is enlarged,which greatly improves the deintercalation of lithium ions;At the same time,the Y-O bond has a stronger binding ability,which provides a basis for stabilizing the structure of the material.The cycle performance after yttrium doping was significantly improved,the initial capacity(1C)was 159.2 m Ah / g,and the cycle retention rate reached 92.2% after 100 cycles at 1C,the material cycle performance was significantly improved.