MgO/Y2O3复合包覆对LiNi0.9Mn0.1O2结构及性能的影响OA

LiNi0.9Mn0.1O2(NM91)is one of the most promising cathode materials for lithium-ion batteries owing to its high energy density,favorable cost-effectiveness,and environmental friendliness.However,its practical application is hindered by poor rate performance and cycling performance.In this study,MgO and Y2O3 were used as raw materials,and single MgO and MgO/Y2O3 composite were coated on NM91 via a high-temperature solid-state method,yielding the corresponding samples designated as NM91-M and NM91-MY.Effects of these coatings and their underlying mechanisms were systematically investigated.Research results indicate that surface coatings do not change the crystal form of NM91,but both can make the material's surface rougher,inhibit the lattice shrinkage and expansion of the material during the cycling process,and mitigate the erosion of electrolytes on the electrode surface,leading to overall performance enhancement.The composite coating,owing to the introduction of Y2O3,removes surface residual lithium while generating the fast ion conductor LiYO2 thus drastically reducing the material's interfacial impedance,enhancing its ionic diffusion capability,and showing the best modification effect.After composite coating,the discharge specific capacity of the material at 5C(1C=180 mA·g-1)increased from 90.7 mAh·g-1 to 129.7 mAh·g-1.After 150 cycles at 1C,the specific capacity retention rate of the material increased from 73.3%to 87.9%.Even at a high cut-off voltage of 4.5 V,after 100 cycles(1C),the composite-coated material still maintained a specific capacity retention rate of 85.8%,which was much higher than that of NM91(70.5%).In addition,the thermal decomposition temperature of the material after 150 cycles increased from 223.5℃to 230.5℃.This study demonstrates that MgO/Y2O3 composite coating is an effective strategy to improve the electrochemical performance and thermal stability of NM91 materials.