Synthesis And Modification Of Single Crystal LiNi_0.6Co_0.2Mn_0.2O₂ Cathode Material

Adjusting the chemical metering ratio of excessive metals,NCM622 cathode materials possess the advantages of high energy density,low cost and excellent safety performance.Meanwhile,the mutual influence between transition metals solves some defects of Li₂CoO₃,LiNiO₂ and LiMnO₂ when they act alone,and has become one of the most promising cathode materials for power batteries in EV.The routine conventional materials use a secondary particle polymer-type NCM622 which will cause a series of problems in the circulation process due to the difference of stress inside the aggregates.In this paper,we improved the material microform that the cathode materials exist in the form of monocrystalline particles to solve the above problems.The synthesis and modification of the material were also studied.The factors affecting the electrochemical properties of single crystal NCM622 and its modification effects were discussed.The research content of this paper is as follows:L16?4⁵?orthogonal test table was used and the third platform temperature T?°C?platform,final temperature holding time T?h?,lithium Li elements in the source and precursor ratio m[Li/?Ni+Mn+Co?mole ratio]was set as the controlling factors.Analysis of the 16group of orthogonal experiment datadetermined the optimum sintering process:the sintering temperature of 930°C,sintering time of 12 h,the ratio of lithium was 1.06.The initial discharge specific capacity was 173.2 mAh/g at 3.0-4.3 V and 0.1 C,with the highest capacity retention of 90.5%after 50 cycles in 1 C rate.Single-crystal LiNi_0.6Co_0.2Mn_0.2-2xTi_xZr_xO₂?x=0.0,0.001,0.002,0.003?has been successfully synthesized by co-precipitation and high-temperature solid-state method.The effects of partial substitution of Ti and Zr for Mn on its structure,electrochemical properties and Li⁺diffusion coefficient have been extensively studied.The results showed that the modified LiNi_0.6Co_0.2Mn_0.2-2xTi_xZr_xO₂ had better electrochemical properties than the pristine cathode material.As the increasing of doped elements,the discharge capacity,coulomb efficiency and diffusion coefficient of lithium ions increased.In the voltage range of 3.0-4.3V,the initial discharge capacity of LiNi_0.6Co_0.2Mn_0.196Ti_0.002Zr_0.002O₂ at 1 C rate is 163.2mAh/g,and the corresponding retention ratios is 93.2%after 50 cycles,which is higher than that of un-doped samples?92.1%?.Cu?Ac?₂·H₂O?AR?was used as the coating material,pure phase single crystal NCM622 anode materials as the substrate,coating amount for variables?0.0,1.0,2.0,1.0wt.%?.The surface of substrate was modified by wet coating method and its electrochemical performance were tested and analyzed.The results showed that:CuO=2.0wt.%of the coated samples were recycled for 50 cycles at 1C magnification,and the discharge capacity decreased from 155.1mAh/g to 146.7mAh/g,with a retention rate of 94.6%.In the multiplier performance test,the discharge specific capacity of 5C rate was 124.3 mAh/g,higher than that of the pure phase sample 113.9 mAh/g.