Prepare And Study Of The Performance Of LiNi_1/3Co_1/3Mn_1/3O₂ Of Power Battery Positive Electrode Materials

The LiNi_l/3Co_l/3Mn_l/3O₂ ternary cathode material of lithium-ion battery combines the advantages of LiCoO₂,LiNiO₂ and LiMnO₂.What's more,it has the superiority of high energy density,good safety and no memory effect.Lithium-ion battery is widely used in portable electronic devices and electric vehicles,and being the most promising material for all batteries.In this thesis,LiNi_l/3Co_l/3Mn_l/3O₂ material was synthesized by a stepwise co-precipitation method.The electrochemical properties of LiNi_l/3Co_l/3Mn_l/3O₂ was improved by doping(Mg²⁺,Zr⁴⁺),surface coating?TiO₂?and surfactant?CTAB?controlling.The conclusions are as follows:1.The LiNi_l/3Co_l/3Mn_l/3O₂ cathode material was synthesized by a stepwise co-precipitation-based method.The effects of calcination temperature,calcination time,and different lithium sources on the electrochemical properties were studied.The results showed that the material exhibited the best electrochemical performance,when calcined at 850?for 20h with lithium acetate.The initial discharge capacity of LiNi_l/3Co_l/3Mn_l/3O₂ cathode material was 160.4 mAh g^-11 at a voltage range of 2.5⁴.3V and at 0.2C.After 20 cycles,the capacity retention rate was 93.5%.2.The LiNi_1/3Co_1/3Mn_1/3-xMg_xO₂?x=0,0.01,0.02,0.03,0.04?material was synthesized by a stepwise co-precipitation-based method,which delivered the best electrochemical performance,when its doping amount was x=0.02.The initial discharge capacity of LiNi_l/3Co_l/3Mn_l/3-0.02Mg_0.02O₂ cathode was 180.02 mAh g^-11 at0.1C between 2.5⁴.3V,which was 4.54 mAh g^-11 higher than the pure phase.The initial discharge capacity of LiNi_l/3Co_l/3Mn_l/3-0.02Mg_0.02O₂ cathode material was 169.5mAh g^-11 and the capacity retention was 86.3%after 50 cycles at 0.2C.After being coated by TiO₂,the initial discharge capacity of LiNi_l/3Co_l/3Mn_l/3-0.02Mg_0.02O₂/TiO₂material was 176.8 mAh g^-1at 0.2C and the capacity retention was 88.7%after 50cycles.3.The LiNi_1/3Co_1/3Mn_1/3-xZr_xO₂?x=0,0.02,0.04,0.06,0.08,0.10?material was synthesized by a stepwise co-precipitation-based method,which exhibited the best electrochemical performance,when its doping amount was x=0.04.The initial discharge capacity of LiNi_1/3Co_1/3Mn_1/3-0.04Zr_0.04O₂ was 165.3 mAh g^-11 at 0.5C and the capacity retention was 91.5%after 30 cycles.4.The electrochemical performance was investigated by adding the surfactant of CTAB?0 mmol,3 mmol,6 mmol,9 mmol?.The results showed that LiNi_l/3Co_l/3Mn_l/3O₂ material exhibited the best electrochemical performance with the content of 3 mmol CTAB.The initial discharge capacity of LiNi_l/3Co_l/3Mn_l/3O₂ was162.7 mAh g^-11 at 1C and the capacity retention was 89.9%during 30 cycles.