Synthesis And Modification Research Of Ni-rich Ternary Cathode Materials

LiNi_xCo_yM_1-x-yO₂?M=Mn,Al?,a three-component cathode material with a layered structure of?-NaFeO₂,is considered to be one of the most promising cathode materials for lithium batteries due to its numerous advantages,such as high energy density,excellent cycling performance and low costs.However,there are still many technical problems in the preparation and use of the materials,such as cumbersome preparation process,reduced thermal stability and cycling stability.In this paper,the cathode material LiNi_0.815Co_0.15Al_0.035O₂ was taken as the research object,and it was prepared by using the spray drying method with soluble metal salts as raw material.The process parameters,such as calcining temperature,calcining time and optimal lithium content,were systematically investigated.The physicochemical and electrochemical properties of the cathode material were studied by a series of characterization tests,such as XRD,SEM,TEM,CV,Constant current charging-discharging and so on.Secondly,the LiNi_0.8Co_0.1Mn_0.1O₂ cathode material was taken as the research object and it was prepared by a high temperature solid phase method with LiNi_0.8Co_0.1Mn_0.1?OH?₂ precursor and lithium hydroxide as the raw materials.Meanwhile,the influence of Zr⁴⁺ion doping and Co₃O₄ surface coating on the physical-chemical properties and electrochemical property of the material were systematically investigated.The optimal ion doping amount and the coating amount of LiNi_0.8Co_0.1Mn_0.1O₂ were explored.The specific research content is as follows:?1?The preparation of high nickel ternary cathode material LiNi_0.815Co_0.15Al_0.035O₂ by spray drying method.The LiNi_0.815Co_0.15Al_0.035O₂ precursors were prepared by spray drying technology,and then it was calcined at high temperature after calcining at low temperature in oxygen atmosphere.And then the target product LiNi_0.815Co_0.15Al_0.035O₂ was obtained after cooling to room temperature and grinding sufficiently.Then,the effects of calcining temperature,calcining time and lithium content on the physicochemical and electrochemical properties of the materials were systematically studied.The corresponding results show that the materials possess a better performance after calcinating at 500?for 4 h and 750?for 18 h with lithium amount of 1.05.The first specific discharge capacity of the as prepared LiNi_0.815Co_0.15Al_0.035O₂ at 0.1C was197.1 mAh g^-1.Meanwhile,the discharge specific capacity was 151.4 mAh g^-1 and the corresponding capacity retention rate was 95%after 100 cycles at 0.5C.Even,the discharge specific capacity could reach up to 160.3 mAh g^-1 after circulating for 100cycles at 1C.Next,Integrating the LiNi_0.815Co_0.15Al_0.035O₂ cathode and the graphite anode in a full cell configuration,the full cell generates a high reversible discharge specific capacity and excellent cycling performance.?2?The modification research of high nickel ternary cathode material LiNi_0.8Co_0.1Mn_0.1O₂ by Zr⁴⁺ion doping.The LiNi_0.8Co_0.1Mn_0.1O₂ cathode material was prepared by a high-temperature solid-phase sintering peocess with LiNi_0.8Co_0.1Mn_0.1?OH?₂ precursor and lithium hydroxide as raw materials.The effect of Zr⁴⁺ion doping on the physical-chemical properties and electrochemical properties of cathode material LiNi_0.8Co_0.1Mn_0.1O₂was studied.And the corresponding results show that 0.05wt%Zr⁴⁺ion doping can significantly improve the cyclic stability of the material.The first discharge specific capacity is 191 mAh g^-1 of 0.05 wt%Zr⁴⁺doped material under the current density of0.1C,lower than that of the pure LiNi_0.8Co_0.1Mn_0.1O₂(195 mAh g^-1)under the same condition.However,the discharge specific capacity of modified materials is still 176mAh g^-1 after 150 cycles under the current density of 1C and the capacity retention are 98.92%.Meanwhile,the capacity retention rate of the pure LiNi_0.8Co_0.1Mn_0.1O₂ is only 92.87%under the same condition.?3?The modification research of high nickel ternary cathode materials LiNi_0.8Co_0.1Mn_0.1O₂ by surface Co₃O₄ coating.The LiNi_0.8Co_0.1Mn_0.1O₂ cathode material was prepared by a high-temperature solid-phase sintering peocess with LiNi_0.8Co_0.1Mn_0.1?OH?₂ precursors and lithium hydroxide as raw materials.The effect of Co₃O₄ coating on the physical-chemical properties and electrochemical properties of the cathode material LiNi_0.8Co_0.1Mn_0.1O₂was studied.And the corresponding results show that 1wt%Co3O4 coating layer could significantly improve the cyclic stability of the material.The first discharge specific capacity is 196 mAh g^-1 under 0.1C.It is positioned at the same level as the pure LiNi_0.8Co_0.1Mn_0.1O₂(195 mAh g^-1)under the same condition.However,the discharge specific capacity of modified material was still 176 mAh g^-1 after 150cycles under the current density of 1C and the capacity retention was 95.8%.However,the capacity retention rate of the pure LiNi_0.8Co_0.1Mn_0.1O₂ was only 92.8%under the same condition.