Modification Of Li-rich Mn-based Cathode Materials And Their Electrochemical Properties At Different Temperatures

The lithium-rich manganese-based cathode material has the characteristics of abundant reserves,good self-circulation performance,low application research and development cost,and has broad application prospects.At present,relevant researches mainly focus on the microstructure control of high-quality cathode materials and the electrochemical performance testing and evaluation of room temperature.However,the temperature dependence of the microstructure and electrochemical properties of lithium-rich manganese-based cathode materials has not been studied in depth.In this paper,the transition metal salt was prepared as a precursor by chemical co-precipitation method.The precursor was mixed with lithium carbonate to prepare lithium-rich manganese-based oxide materials by high-temperature calcination synthesis,and Zr and Ti ion doping were modified respectively.AlPO₄ coating modification study.XRD and SEM,laser Raman and X-ray photoelectron spectroscopy?XPS?were used to analyze the microstructure,composition and morphology of the materials prepared by electrochemical workstation and blue light.The battery test system tests the cycle performance and charge-discharge ratio of the material at different temperatures.In this paper,the lithium-rich manganese-based oxide was prepared by chemical co-precipitation method,and the precursor was synthesized by using transition metal salt.After mixing with lithium carbonate,it was calcined?firstly kept at 500^? for 5h,then kept at 900^? for 12h?to obtain the required The positive electrode material,electrochemical test showed that its specific room temperature capacity was 163mAh/g,the specific capacity at 45^? was 202mAh/g,and the specific capacity decreased to37mAh/g at-25^?.The surface treatment of the lithium-rich manganese-based oxide material was carried out by dilute nitric acid solution with a concentration of 0.2M.It was found that the spinel phase increased with acid etching time after acid treatment.The lithium-rich manganese-based oxide powder after acid treatment for 2 hours was electrochemically tested and found to have a specific capacity value of 210mAh/g at room temperature,but the specific capacity decreased under different temperature conditions,and the specific capacity at 45^? and-25^? were 169mAh/g and 6mAh/g.ZrO₂ and TiO₂ are mixed with the precursor and lithium carbonate powder respectively,and calcined to obtain Zr or Ti ion doped modified lithium-rich manganese-based oxide material.When the Zr doping amount is x=0.025,the first coulombic efficiency of the battery at room temperature is 68.59%,which is higher than the first coulombic efficiency of undoped material of 41.67%.Under different test temperature conditions,Zr-doped lithium-rich manganese-based oxidation The electrochemical properties of the material are better than those of the undoped material,indicating that the doping of Zr element has a good effect on the electrochemical performance improvement,especially the Zr doping amount x=0.025.The highest specific capacities of Li_1.1Zr_0.025Ni_0.13Co_0.13Mn_0.54O₂ lithium-rich manganese-based oxide materials at different temperatures?–25^?,0^?,25^? and 45^??are 70mAh/g,103mAh/g,168mAh/g and227mAh/g.When the Ti doping amount is x=0.075,the first Coulomb efficiency of the material at room temperature is 62.99%.The effect of temperature on the first coulombic efficiency is not obvious,and the effect of Ti doping on the specific capacity of discharge is not obvious at different temperatures.The AlPO₄ coating modification treatment of Li_1.1Zr_0.025Ni_0.13Co_0.13Mn_0.54O₂ by hydrothermal method was found to increase with the coating amount of AlPO₄?2wt.%,5wt.%,7wt.%and 10wt.%?.The powder particles showed a certain degree of agglomeration,and the spinel phase content of the powder material first decreased and then increased;compared with the uncoated Li_1.1Zr_0.025Ni_0.13Co_0.13Mn_0.54O₂ material,The first coulombic efficiency of the material after AlPO₄ coating treatment at room temperature increased significantly from 68.59%to 83.22%.However,the charge and discharge tests under different temperature conditions showed that the specific capacity of AlPO₄ coated materials decreased at 45^? and–25^?.