Study On Surface Modification Of Nickel-rich Layered Cathode Material LiNi_0.8Co_0.1Mn_0.1O₂ Using Simple Metal Oxides

Nickel-rich cathode material LiNi_0.8Co_0.1Mn_0.1O₂ with layered structure is considered to be one of the most promising cathode materials for lithium-ion batteries,due to its high theoretical specific capacity,low cost and environmental friendliness.However,owing to the structural characteristics,LiNi_0.8Co_0.1Mn_0.1O₂ has disadvantages such as rapid capacity decay,poor high-rate performance,and poor high-temperature stability,which limits its commercial application.In view of the above problems,a variety of oxides were selected as coating materials,and LiNi_0.8Co_0.1Mn_0.1O₂ was modified by a wet chemical method to improve the surface stability of the material and improve its electrochemical performance,thereby promoting the practical application of LiNi_0.8Co_0.1Mn_0.1O₂.Firstly,LiNi_0.8Co_0.1Mn_0.1O₂ was coated with four oxides of TiO₂,Pr₆O₁₁,MoO₃and Co₃O₄,and the presence of cladding layers was determined by means of XRD,TEM and EDS.The galvanostatic charge-discharge test results show that the four coating materials improve the cycle stability of the host material to varying degrees.The effect of different Co₃O₄ coating ratios on the modification of LiNi_0.8Co_0.1Mn_0.1O₂ was further studied.Among them,0.5 wt.%Co₃O₄ coated samples showed the best electrical performance.And its discharge capacity still has130.8mAh g^-1,corresponding capacity retention is 74.9%at 5C after 200 cycles.At the same time,the results of CV and EIS tests show that the Co₃O₄ coated material exhibits lower polarization,and smaller charge transfer resistance.The effects of different coating amount of CeO₂ coating on the electrical properties of LiNi_0.8Co_0.1Mn_0.1O₂ material were studied.The 1.0 wt.%CeO₂-coated LiNi_0.8Co_0.1Mn_0.1O₂ samples exhibited the best charge-discharge performance and high-temperature cycling stability.After 200 cycles at 55°C,the discharge capacity is still 159.8 mAh g^-1,and the corresponding capacity retention is 80.9%,which is significantly higher than that of LiNi_0.8Co_0.1Mn_0.1O₂?72.2%?,and its average Coulombic efficiency is as high as 98.84%.The analysis of XPS,CV,and EIS shows that because of the good ionic conductivity and high temperature stability of CeO₂and the good binding force with the host material,a certain thickness of CeO₂ coating layer can improve the surface stability of the material and effectively block the direct contact between the host material and the electrolyte isolate the host material.Therefore,the occurrence of parasitic reactions and the accumulation of by-products can be suppressed,and excessive consumption of the electrolyte can be reduced at the same time.The EIS test revealed that CeO₂ can significantly reduce the charge transfer resistance and accelerate the reaction kinetics,thus making the electrochemical reaction more reversible and exhibiting better cycle stability performance.