Preparation And Modification Of Nickel-rich Ternary Cathode Materials For Lithium Ion Batteries

Nickel-rich ternary cathode material LiNixCoyMn1-x-yO2(x?0.6)can be applied to electric vehicles,electric two-wheelers,logistics vehicles and energy storage base stations due to its high volumetric energy density and high voltage.With the deepening of petroleum energy consumption and environmental pollution,people prefer to use electric vehicles instead of traditional vehicles,and nickel-rich ternary cathode materials have become a research hotspot as well.At present,the nickel-rich ternary cathode material have poor cycle performances and rate performances.This directly leads to the poor battery life and poor charging ability of the electric vehicle after the battery is loaded,and even threatens the safety performance of the electric vehicle.Therefore,there is a need to find a method for improving the cycle rate performance of a high nickel ternary positive electrode material.This study presents coprecipitation doping,solid phase doping,core-shell structure,mechanical mixing and other modification methods to improve the cycle rate performance of nickel-rich ternary cathode materials.Therefore,exploring the preparation process of nickel-rich ternary material modification method and the selection of modified materials have important scientific research significance and practical application value.In this study,the NixCoyMn1-x-y(OH)2 precursor of nickel-rich ternary cathode material was prepared by co-precipitation method.The synthesis of nickel-rich ternary cathode material precursor was explored by laser particle size analysis,tap density analysis and XRD analysis.The effects of different preparation parameters on the morphology and cycle rate performance of the precursors were investigated by SEM and electrochemical analysis methods.Then Ti4+doped Li(Ni0.8Co0.1Mn0.1)O2 material was prepared by solid phase sintering method.The dual core-shell structure cathode material 0.5LiNi0.8Co0.1Mn0.1O2-0.5LiNi0.6Co0.2Mn0.2O2 and Mg2+doped into the nichel-rich cathode material Li(Ni0.8Co0.1Mn0.1)xMg1-xO2 was prepared by coprecipitation method.LiNio.6Co0.2Mn0.2O2-Li3/8Sr7/16Hf1/4Ta3/4O3 were prepared by mechanical mixing method.The synthesis process of nickel-rich ternary positive electrode modified materials was investigated by means of laser particle size analysis,XRD,SEM,etc.Electrochemical analysis methods such as EIS,CV,charge and discharge analysis were used to explore the modification process for nickel-rich ternary materials.The effect of electrochemical performance,and getting the following results:(1)The precursor of nickel-rich ternary cathode material was prepared by coprecipitation method.According to the thermodynamic analysis and control variable analysis of precursor reaction,the preparation of nickel-rich ternary cathode material Ni0.8Co0.1Mn0.1(OH)2 was determined.The optimum ammonia concentration is 1.0 mol/L,the optimum pH is 11.1,and the optimum stirring speed in the 20L reactor is 900rpm.According to the influence of various parameters in the reaction process on the tap density of the precursor,a model is established to predict the tap density of the ternary precursor Ni0.8C.00.1Mn0.1(OH)2 prepared by the current reaction parameters,or the effect of the change of the middle parameter on the tap density of the ternary precursor Ni0.8Co0.1Mn0.1(OH)2 in the reaction process.(2)Double nickel-rich core-shell structure cathode material 0.5LiNi0.8Co0.1Mn0.1O20.5LiNi0.6Co0.2Mn0.2O2 were prepared by coprecipitation method.The optimal parameters of preparation are 830? of sintering temperature and 1.05 times stoichiometric of lithium doping amount.The initial 1C discharge specific capacity can reach 172.15mAh/g,and the capacity retention rate can reach 82.9%after 150 cycles at 1 C rate.(3)In experiment,the solid phase sintering method was used to dope the titanium ions in 3wt.%nano-titanium dioxide into LiNi0.8Co0.1Mn0.1O2 material.When the doping amount was 3wt.%,the battery was cycled 125 times at 5C rate.The capacity retention rate can still be maintained at around 75.0%.(4)In the experiment,Mg2+was doped into the Ni0.8Co0.1Mn0.1(OH)2 precursor by coprecipitation method.When the Mg2+doping amount is 2mol%,the first charge and discharge efficiency from 80.6%to 82.9%;in the rate test analysis,the ratio of 5C/0.1C increased from 65.9%to 70.0%;the capacity retention rate of 100 cycles under 1C rate increased from 80.8%to 91.9%when compared with the undoped material.(5)The composite was prepared by mixing solid electrolyte Li3/8Sr7/16Hf1/4Ta3/4O3 with LiNi0.6Co0.2Mn0.2O2.When LiNi0.6Co0.2Mn0.2O2 was mixed 3wt.%of Li3/8Sr7/16Hfi/4Ta3/4O3,the redox peak voltage difference decreased from 0.211V to 0.160V compared with the unmixed cathode material,and the polarization was alleviated;the capacity retention rate after 100 cycles at 1C rate is 86.1%,around 13.6%higher than the ternary material without electrolyte.The ratio of 3C/0.1C of mixed materials in the rate performance test increased from 73.2%to 79.6%.