Preparation And Electrochemical Properties Of LiNi_1/3Co_1/3Mn_1/3O₂ Cathode

With the continuous popularization of electric products,LiNi_1/3Co_1/3Mn_1/3O₂ cathode has widen prospects due to its good thermal stability,long cycle life and high safety.However,the high rate capability of LiNi_1/3Co_1/3Mn_1/3O₂ cathode was in need of improvement,which could enable electronic products to achieve fast charging and improve the utilization efficiency of electronic products.In the paper,LiNi_1/3Co_1/3Mn_1/3O₂was used as the research object,the author prepared LiNi_1/3Co_1/3Mn_1/3O₂ cathode with excellent high rate capability,and explored the relationship of the structure,morphology and electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂,the main contents and conclusions of the paper are as follows:Firstly,LiNi_1/3Co_1/3Mn_1/3O₂ cathodes from disc-shaped to spherical were prepared by solvothermal method within using ethanol/water as a mixed solvent and regulating the amount of urea added in the solvothermal process.The electrochemical test results of above-mentioned LiNi_1/3Co_1/3Mn_1/3O₂ cathodes with different morphologies showed that the semi-closed LiNi_1/3Co_1/3Mn_1/3O₂ cathode had the highest discharge capacity of 167 mAh g^-1and the spherical LiNi_1/3Co_1/3Mn_1/3O₂ cathode with the smallest specific surface area had the lowest capacity of 145 mAh g^-1at 1 C.Besides,the discharge capacity of the semi-closed LiNi_1/3Co_1/3Mn_1/3O₂ cathode was 157.7,140.9 and 114.3 mAh g^-1at 2,5 and 10 C respectively,indicated the excellent rate capability.Then,the D_Li⁺values of above-mentioned LiNi_1/3Co_1/3Mn_1/3O₂ cathodes with the disc to spherical morphologies were 1.81×10^-8,2.77×10^-8,2.03×10^-8,1.79×10^-8 cm² s^-1 respectively and semi-closed LiNi_1/3Co_1/3Mn_1/3O₂ cathode with highest D_Li⁺,combined with the characterization results of XRD,SEM,EDS,BET techonologies to analyzed that the excellent high-rate performance of the semi-closed LiNi_1/3Co_1/3Mn_1/3O₂ cathode may caused by its semi-closed structure that could facilitated the permeation of electrolyte inside LiNi_1/3Co_1/3Mn_1/3O₂,constructed a wide ion-electron transport network and shorten the transport path of Li⁺,thereby improved LiNi_1/3Co_1/3Mn_1/3O₂high rate capability.Finally,LiNi_1/3Co_1/3Mn_1/3O₂?R-NCM?with rice cake morphology was prepared by using the template method combined with co-precipitation method.The characterization results of XRD,SEM,EDS,BET techonologies demonstrated the R-NCM with rice cake shape,high crystallinity,low cation mixing and good layered structure.R-NCM cathode showed a discharge capacities of 165.4,158.0,153.2,146.0,135.8,112.6 mAh g^-1at 0.2,0.5,1,2,3 and 5 C respectively,and still had 115.2 mAh g^-1after 250 cycles at 1 C,reflected the upgraded cycle performance and rate capability.The AC impedance and D_Li⁺curves of LiNi_1/3Co_1/3Mn_1/3O₂ cathode showed the R_ct is about 130?and the D_Li⁺ value is 1.35×10^-8cm²s^-1,which indicated that the rice cake structure could also improved R-NCM cathode electrical conductivity and lithium ion diffusion speed.