Study On Doping Modification Of Elements In Lithium-Rich Manganese Based Layered Cathode

Li-rich manganese-based layered material xLi2MnO3·(1-x)LiMO2(M=Mn,Co,Ni)has high energy density,and it is promising as the next generation of high energy density lithium ion battery cathode material,but for this cathode material,there are problems such as poor rate performance,poor cycle performance,and rapid attenuation of capacity and discharge platform,which limits its application in the commercial field.Based on the above problems,Lii.2Mn0.56Ni0.i6Co0.08O2 lithium-rich material was used as the research system,and the doping modification of Li1.2Mn0.56Ni0.16Co0.08O2 with F,A1 and Mo elements was researched by sol-gel method.The main research contents are as followsTo overcome poor stability of the lithium-rich and manganese-based layered material xLi2MnO3·(1-x)LiMO2(M=Mn,Co,Ni)during charge-discharge long-cycles,we prepared the fluorine-doped Li1.2Mn0.56Ni0.16Co0.08O2-xFx by sol-gel method.Our results show that the crystal structure of the fluorine doped materials is similar to that of the undoped material,but the fluorine doping significantly improves the long-cycling stability of the materials during charge-discharge process.After cycling 500 times at a current density of 125 mA/g,the Li1.2Mn0.56Ni0.16Co0.08O1.95F0.05 doped with 5%exhibits 79.2%of its initial specific capacity,and the loss of the discharge platform potential was greatly decreased.However,the undoped Lii.2Mn0.56Ni0.16Co0.08O2 material exhibits only 16%of its initial capacity,and its discharge platform potential has completely disappeared.These results indicate that fluorine doping can effectively decrease the loss of specific capacity and discharge platform of lithium-rich manganese-based layered cathode materials during charge and discharge processThe cycle stability and discharge platform stability of the Al-doped Lii.2Mn0.56-xAlxNi0.16 Co0.08O2 materials are improved.The Al-doped materials still have a higher discharge specific capacity at 1250 mA/g and 2500 mA/g current density,and the Li1.2Mn0.51Al0.05Ni0.i6Co0.0sO2 material is cycled 300 times at a current density of 125 mA/g,and the capacity retention rate is as high as 94%,and the material still has a higher discharge platform potential.In contrast,the capacity retention rate of the Li1.2Mn0.56Ni0.16Co0.08O2 material is only 50%,and its discharge platform potential is sharply attenuated,and it has disappeared after 300 cycles These indicate that Al ion doping can effectively improve the electrochemical performance of the lithium-rich manganese-based layered material.The Mo-doped Li1.2Mn0.56-xMoxNi0.16Co0.0sO2 lithium-rich manganese-based layered materials were synthesized by sol-gel method.Mo ion doping can reduce the charge transfer resistance of lithium-rich materials,which can improve rate performance of the materials.The Li1.2Mn0.53Mo0.03Ni0.16Co0.08O2 material doped with 3%Mo has a specific discharge capacity of 92 mAh/g at 10 C rate.In addition,the Li1.2Mn0.53Mo0.03Ni0.16Co0.08O2 material was cycled 300 times at a current density of 125 mA/g,and the capacity retention rate of the material was 67%,which was higher than that of the undoped Li1.2Mn0.56Ni0.16Co0.08O2 material,and the capacity retention rate of the Li1.2Mn0.56Ni0.16Co0.08O2 material is only 50%.These are shown that doping Mo ions can improve the cycle stability of lithium-rich manganese-based layered materials.