Long Life Cathode Material LiNi 1/3 Co 1/3Synthesis And Electrochemical Properties Of Mn 1/3 O 2

In this paper,the precursor Ni_1/3Co_1/3Mn_1/3（OH）₂ was prepared by coprecipitation method and decomposed by high temperature（sintering additive）to obtain the composite metal oxide Ni_1/3Co_1/3Mn₍1/30O2.The positive electrode material Li Ni_1/3Co_1/3Mn₍1/30O2 was further synthesized from this material.By optimizing the synthesis process and sintering system,the cathode material with stable cycle performance was obtained.Based on this,the materials were modified by doping Cr and coated with Al₂O₃.X-ray diffraction（XRD）Electron microscopy（SEM）,energy dispersive spectroscopy（EDS）and electrochemical impedance spectroscopy（EIS）were used to characterize the samples.Concluded as follow:（1）In the process of synthesis of LiNi_1/3Co_1/3Mn_1/3O₂.The influence factors of the structure,surface morphology and electrochemical properties of the cathode materials were discussed to determine the best process conditions.The p H value of the precursor system was 11.0,and 0.5 wt% LiF sintering additive was added to the hydroxide precursor.The mixture was incubated at 800 ℃ for 6 h,mixed with lithium source,and then held at 950 ℃ sintering temperature for 15 h.The materials showed better degree of layered structure and lower degree of cationic mixing,clear surface morphology,good sphericity and dispersion.The capacity retention rate is 82.14 % in the voltage range of 2.75⁴.2 V.The first discharge specific capacity of 145.7 mAh/g with 43.6 % capacity retention rate after 1000 cycles times with a current of 1C current between 2.75 and 4.35 V.While the cut-off voltage was 4.35 V,the capacity retention rate was 43.6 % at 1 C after 1000 cycles.The high voltage performance of material still needs to be improved.（2）LiNi_1/3Co_1/3-xMn_1/3Cr_xO₂ was prepared by different doping ratios and methods.The results show that when the doping amount is x = 0.01,the materials showed good layered structure,lower degree of cationic mixing,clear surface morphology,good sphericity and dispersion.The charge capacity is 109.9 mAh/g with 87 % capacity retention rate after 500 cycle times with 1C current between 2.75 and 4.2 V.The charge capacity is 109.9 mAh/g and the capacity retention rate is 87 % after 500 cycle times of charge and discharge with a current of 1 C between 2.75 and 4.35 V.In the adiabatic environment,the overall battery temperature was increased 7.34 ℃,compared to undoped battery increased 7.78 ℃ at a cycle of charge and discharge at 0.5C current.The battery safety is further improved.（3）The positive electrode material Li Ni_1/3Co_1/3Mn₍1/30O2 was synthesized by different coating ratio of Al₂O₃.The results show that when the coating amount was 1wt%,the layered structure of the material would more stable,the degree of cationic mixing would lower.The first discharge capacity was 122.9 mAh/g at 0.5 C,and the capacity retention rate was 95.1 % after 50 cycles.After coating,the coating could effectively reduce the side reaction between the electrolyte and material and improve the cycle stability of the battery.