Modification And Electrochemical Performance Of High Nickel Cathode Material Of Lithium Cobalt Aluminum Oxide For Lithium-ion Power Batterie

In recent years,high-nickel cathode materials（Ni>80 mol%）have attracted much attention due to their high reversible capacity and low cost.The ternary cathode material Li Ni_xCo_yAl_1-x-yO₂（NCA）combines the advantages of high capacity,low toxicity and low cost.The capacity of the layered high-nickel cathode material will increase with the increase of elemental Ni content,but it will also intensify the degree of Li/Ni mixing and increase the residual lithium compound,resulting in more serious capacity decay during the cycle of the cathode material.This paper mainly focuses on the cycle stability of current high-nickel cathode materials,especially the interfacial side reactions caused by excessive residual lithium,and studies them in detail from three aspects:process control,surface coating and element doping.（1）Select different material-liquid ratios to wash water to remove residual lithium compounds on the surface of the material,and adjust the material structure through different backburning temperatures.The research shows that the Li Ni_0.88Co_0.07Al_0.05O₂cathode material prepared by using the ratio of solid to liquid 1:25,washed with water for 3 times,and calcined at 600°C for 2 h,the first discharge specific capacity at 0.2C is 207.6 m Ah·g^-1,and the 1 C cycle After 100 cycles,the discharge specific capacity of this material of 148.0 m Ah·g^-1 is much higher than that of the unmodified material of 129.8 m Ah·g^-1.（2）Combined with the treatment methods of water washing and backburning,the high nickel cathode material was modified by V₂O₅ coating by spray drying method.The modified cathode material synthesized by the coating amount of 2 wt%and oxidative sintering at 600°C for 5 h has excellent comprehensive electrochemical performance.There is still 163.8 m Ah·g^-1,and the capacity retention rate is effectively improved（71.4%to 83.4%）.（3）By adjusting the oxidation sintering time,the electrochemical performance of the 2wt%MoO₃ cathode material before and after washing was studied.The research shows that the MoO₃-coated cathode material obtained by water washing-coating-oxidative sintering for 9 h has excellent electrochemical performance,the first discharge specific capacity at 0.2 C is 195.9 m Ah·g^-1,and after 100 cycles of 1 C charge-discharge cycle,the capacity is still 153.6 m Ah·g^-1,and the capacity retention rate is 82.5%.（4）A series of high-nickel cathode materials Li(Ni_0.88Co_0.07Al_0.051-x)Zr_xO₂（x=0.01,0.015,0.02,0.025 and 0.03）were synthesized by adjusting the addition of Zr source.The Ni_0.928Co_0.072（OH）₂ powder and C₁₅H₃₆O₅Zr solution were added in sequence after C₉H₂₁Al O₃ was dissolved.When x=0.02,the first discharge specific capacity of the material at 0.2 C was 198.7 m Ah·g^-1,and the capacity was maintained for 100 cycles at 1 C.The rate was 86.0%.（5）Synthesis of Li(Ni_0.88Co_0.07Al_0.05)_1-xSn_xO₂（x=0.01,0.015,0.02,0.025 and 0.03）high nickel cathode materials by adjusting the amount of Sn source added,when x=0.02,at 4.5 V At the high cut-off voltage of 0.2 C,the first discharge specific capacity was206.0 m Ah·g^-1.After 100 cycles at 1 C,the discharge specific capacity was still 170.3m Ah·g-1,and the capacity retention rate was 88.8%.