Preparation And Modification Of Li_1.167Ni_0.4Mn_0.383Co_0.05O₂ As Cathode Moterial Of Lithium-ion Batteries

In this study,Li_1.167Ni_0.4Mn_0.383Co_0.05O₂ cathode material for lithium ion batteries was synthesized by the method of co-precipitation.The effects of reaction temperature,pH,calcining temperature and calcining time on electrochemical properties of Li_1.167Ni_0.4Mn_0.383Co_0.05O₂ were discussed.Then the materials were modified by doping metal elements and coating metal oxide.The crystal structure features and electrochemical properties of the powders were studied in detail by XRD,SEM,EIS,CV and electrochemical performance tests.Through the investigation of reaction temperature of the precursor?25?,50?and75??,50?was identified as the best reaction temperature;Through the investigation of pH value?10.5,11.0,11.5 and 12.0?,the pH of 11.5 was the best choice in the experiment.Through the investigation of calcination temperature?750,800,850 and 900??and calcination time?12,14,16 and 18h?,the optimum conditions were that the calcination temperature was at 850?a nd the calcination time was 16 h.Under the optimal conditions,it delivered an initial discharge capacity of 187.8 mAh/g and had a capacity retention of91.43%after 10 cycles at 0.1 C.With Ti,Al and Mg as doping element,Li_1.167Ni_0.4-xMn_0.383Co_0.05M_xO₂?M=Ti,Al and Mg,x=0,0.02,0.04,0.06 and 0.08?was synthesized.And the effects of different doping amount on the crystal structure features and electrochemical properties was studied.The results show that the discharge specific capacity for the first time was reduce after doping these metal elements.Li_1.167Ni_0.36Mn_0.383Co_0.05Ti_0.04O₂ showed the best electrochemical performanceafterTidoping.Theinitialdischargecapacitiesof Li_1.167Ni_0.36Mn_0.383Co_0.05Ti_0.04O₂ at 0.1,0.2,0.5 and 1.0 C were 185.5,163.0,140.0 and118.0 mAh/g and had a capacity retention of 99.41%?98.59%?97.22%and 99.07%after10 cycles,respectively.The best Al-doped material was Li_1.167Ni_0.36Mn_0.383Co_0.05Al_0.04O₂,and the initial discharge capacities of Li_1.167Ni_0.36Mn_0.383Co_0.05Mg_0.02O₂ at 0.1,0.2,0.5 and1.0 C were 186.6,165,143 and 123 mAh/g,having a capacity retention of 94.05%,93.76%,93.78%and 90.17%after 10 cycles,respectively.The cycle stability of the material can be improved after Mg doping.Li_1.167Ni_0.38Mn_0.383Co_0.05Mg_0.02O₂ showed the bestelectrochemicalperformance.Theinitialdischargecapacitiesof Li_1.167Ni_0.36Mn_0.383Co_0.05Mg_0.04O₂ at 0.1C,0.2,0.5 and 1.0 C were 185.4?150.3?144.3 and112.1 mAh/g,having a capacity retention of 94.97%,96.01%,95.80%and 94.30%after10 cycles,respectively.In addition,Na-substituted Li_1.167-xNa_xNi_0.4Mn_0.383Co_0.05O₂?x=0,0.02,0.04,0.06 and0.08?materials were also studied in the paper.Li_1.127Na_0.04Ni_0.4Mn_0.383Co_0.05O₂ delivered an initial discharge capacity of 190.4 mAh/g and had a capacity retention of 94.02%after 10cycles at 0.1 C.The Li_1.167Ni_0.4Mn_0.383Co_0.05O₂ material was coated by MgO and Al₂O₃ with the amount of 1wt.%,2wt.%,3wt.%and 4wt.%,respectively.The cycle performance was improved.2wt.%MgO-coted Li_1.167Ni_0.4Mn_0.383Co_0.05O₂ material delivered an initial discharge capacity of 179.6 mAh/g and had a capacity retention of 98.58%after 10 cycles at 0.1 C.1wt.%Al₂O₃-coted Li_1.167Ni_0.4Mn_0.383Co_0.05O₂ material delivered an initial discharge capacity of 186.7 mAh/g and had a capacity retention of 96.64%after 10 cycles at 0.1 C.