Synthesis And Electrochemical Properties Of LiNi_0.8Co_0.15Al_0.05O₂ Cathode Material For Lithium-ion Batteries

LiNi_0.8Co_0.15Al_0.05O₂（NCA）is a very important cathode material for lithium-ion batteries.NCA has attracted widespread attention because of its high energy density,stable cycling performance,and environmental friendliness.The structure and electrochemical characteristics of cathode materials are significantly influenced by the chemical preparation process.Therefore,it is necessary to investigate the preparation process of NCA cathode materials.In this work,nano-sized Al（OH）₃was prepared firstly by homogeneous precipitation method with Al₂（SO₄）₃and Al（NO₃）₃as Al sources,and the molar ratio of SO₄^2-and NO^3-is 1:9.Then Al（OH）₃was ultrasonically mixed with binary hydroxide Ni_0.8Co_0.15（OH）_1.9to prepare the NCA cathode material precursor.The precursors were then calcined at different calcination temperatures（750,800,850℃）and calcination times（16,20,24 h）,and the NCA cathode materials were prepared finally.XRD data shows that the NCA cathode material hasα-Na Fe O₂layered structure and the cell volume increases with the increase of calcination temperature and time.When calcined at 800℃for 20 h,XRD data shows the value of I_（003）/I_（104）is 2.13.The SEM and Mapping results show that the primary particles of the material are tightly agglomerated into secondary particles with a size of about 10μm.The Ni,Co,and Al elements are uniformly distributed.The electrochemical data shows the capacity retention rate is 85.18%after 120 cycles at a current density of 0.2 C.The morphology and particle size of Al（OH）₃may also influence the electrochemical properties of the final prepared NCA cathode materials.Therefore,Al（OH）₃with flocculent and spherical particles of about 44 nm in size was prepared by adjusting the molar ratio of SO₄^2-and NO^3-to 0:10 and 5:5,then ultrasonically mixed with Ni_0.8Co_0.15（OH）_1.9.XRD data show that both cathode materials haveα-Na Fe O₂type layered structures.The electrochemical data shows that when the molar ratio of SO₄^2-and NO^3-is smaller,the initial discharge-specific capacity of NCA cathode material is higher.When the SO₄^2-and NO^3-molar ratio is 1:9,the NCA cathode material has the highest capacity retention rate.