Preparation And Modification Of Ternary Cathode Material LiNi_0.8Co_0.1Mn_0.1O₂

The positive electrode material is a key component in lithium ion batteries?LIBs?.The high nickel ternary layered material LiNi_0.8Co_0.1Mn_0.1O₂ which has the advantages of high density,good cycle performance,low cost,low environmental pollution?less cobalt content?and so on is considered to be a positive application of LIBs positive electrode.However,this material is prone to structural instability under high pressure conditions,resulting in a rapid decline in battery capacity.Therefore,it is imperative to find a suitable method to modify the ternary material to make its structure stable,so as to improve the cycle stability of assembled batteries.In this paper,co-precipitation method is used to prepare LiNi_0.8Co_0.1Mn_0.1O₂ precursor,which is prepared with lithium and then calcined at high temperature.The optimal synthesis conditions are explored by controlling the reaction parameters;The influence of different coating amounts on material stability and battery performance is explored by coating different materials such as Li₂TiO₃ and CaF₂ on the surface of the material.The main experiments and conclusions are as follows:1.Preparation of precursor LiNi_0.8Co_0.1Mn_0.1?OH?₂ using co-precipitation method.The effects of solution p H,ammonia concentration of complexing agent and calcination temperature on the structure,morphology and electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ material were studied to determine the best synthesis conditions.The XRD and SEM results show that the sample prepared at pH value 11,ammonia concentration of 1.0 mol/L,lithium excess of 5%,and calcination temperature of 800 ? has the best ?-NaFeO₂ layered structure and spherical or quasi-spherical shape The electrochemical performance tests showed that the samples under the above comprehensive conditions had the best electrochemical performance.At 0.1 C rate?room temperature 25 ??,the first discharge capacity of the samples reached 0.19.9 m Ah/g,and the capacity retention rate after 100 cycles was 75.6%.2.Using ethanol ultrasonic dispersion and wet grinding to successfully attach TiO₂ and Li₂CO₃ on the surface of LiNi_0.8Co_0.1Mn_0.1O₂ material,and then calcined at high temperature to synthesize LiNi_0.8Co_0.1Mn_0.1O₂ sample(denoted as Li₂TiO₃@ LiNi_0.8Co_0.1Mn_0.1O₂).XRD results show that different Li₂TiO₃ coatings have no effect on the microstructure of LiNi_0.8Co_0.1Mn_0.1O₂ material.The TEM image shows that the pure phase material particles have a relatively transparent coating layer on the surface.By the electrochemical performance test,it can be found that 0.5 % Li₂TiO₃@ LiNi_0.8Co_0.1Mn_0.1O₂ has a high first discharge capacity?185.9 m Ah/g,0.1 C?,a high first coulombic efficiency?84.1 %?,a good cycle Performance?85.3%,100 cycles?and a good rate performance.The analysis of the results of CV and EIS tests further shows that the coating improves the electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ during charge and discharge.Li₂TiO₃ can not only improve the conductivity of lithium ions,but also improve the stability of the material structure,which is conducive to improving the electrochemical performance of the material.It effectively reduces the corrosion of the electrode material by the electrolyte,suppresses the occurrence of adverse reactions on the surface of the positive electrode material.Because of this,the material has higher ion migration ability and electron transfer ability,which can improve the cycle performance of the high nickel ternary material.3.The liquid phase method is used to dissolve calcium nitrate and ammonium fluoride in the ethanol solution,and generate calcium fluoride?CaF₂?through continuous stirring.After high temperature calcination,the LiNi_0.8Co_0.1Mn_0.1O₂ sample coated with CaF₂(denoted as CaF₂@ LiNi_0.8Co_0.1Mn_0.1O₂)can be synthesized.here,ethanol is used to replace the aqueous solution to avoid introducing new impurities to the material.XRD results show that different CaF₂ coatings have no effect on the crystal structure of LiNi_0.8Co_0.1Mn_0.1O₂ material.By electrochemical performance test,it can be found that 2.0 % CaF₂@LiNi_0.8Co_0.1Mn_0.1O₂ has a higher first discharge capacity?195.5 m Ah/g,0.1 C?,a higher first-time Coulomb efficiency?85.7 %?,a better Cycle performance?75.3 %,100 cycles?and rate performance...