Synthesis And Modification Of LiNi_0.85Co_0.1Al_0.05O₂ Ternary Cathode Materials For Lithium Ion Battery

The high nickel ternary material is a lithium-ion battery cathode material that have a high discharge specific capacity and environmentally friendly,but the cycle performance and rate performance of material is poor,especially under high voltage.In this paper,the high nickel ternary cathode material LiNi_0.85Co_0.10Al_0.05O₂（N85CA）is selected as the research object,to explore the materials of synthesis process and modification,and the following results have been obtained.The LiNi_0.85Co_0.10Al_0.05O₂（N85CA）cathode material was synthesized by solid-phase method,and the preferred synthesis process parameters were listed as follows:the best ball milling time is 1h,the best calcination temperature is 750℃,and the best treatment pressure is3.5MPa.In addition,the influence of various synthesis parameters on the material structure and electrochemical performance was also conducted.The results showed that the cathode material N85CA synthesized under the optimized process offers a first discharge specific capacity of195 m Ah/g at a rate of 0.1C,and a discharge specific capacity of 123 m Ah/g at a higher rate of5C.All the results indicate high potential of the approach in practical application.In order to improve the stability of the N85CA cathode material during cycling,the cathode material N85CA was modified with niobium doping method based on the fact that Nb-O bond has a strong bond energy,which inhibits the phase change during the cycle,improves the stability of the material structure,and thereby increases the capacity retention.Meanwhile,when niobium is doped into the cathode material,the lattice parameters and the thickness of the lithium layer will be increased,thereby improving the rate performance of the material.At a doping amount of 0.5%,the material has excellent electrochemical performance.After 100cycles,a capacity retention of 94.19%was observed,and the discharge specific capacity at 5C is 156.2m Ah/g.Compared with that of the pristine sample,the values are increased by 24.73%,33.2 mAh/g respectively.Further,in view of the problem that the initial capacity is reduced due to the doping of a single element into the transition layer,the co-doping approach using sodium and niobium to synergistically modify the material was attempted.The study found that the synergistic effect of Na and Nb reduces the mixing of ions,improves the ordering of the crystal lattice,suppresses the phase transition,inhibits structural instability,and therefore improves the electrochemical performance of the material.The test results show that the initial discharge capacity of the sample CO-NCA at 0.1C is 212.5m Ah/g,and the capacity retention after 100 cycles at 0.5C is93.31%.At a rate of 5C,the specific capacity of the sample CO-NCA is kept as 152.2m Ah/g.Compared to the values of Nb doped sample,the increase in electrochemical performance is significant,showing high potential for Liion battery.