Preparation And Modification Of LiNi_0.5Mn_1.5O₄ Lithium-ion Cathode Material By Co-precipitation Method

Lithium-ion battery has become the most widely used battery due to its excellent performance,but it still cannot meet the strict demand of people.Lithium nickel manganate（Li Ni0.5Mn1.5O4）is one of the lithium-ion batteries with a better future development direction,and its characteristics such as high discharge platform,low preparation cost and low toxicity are the features that society is eager to have for lithium batteries.Firstly,the high voltage of lithium nickel manganate,up to 4.9V or more,ensures that lithium nickel manganate can carry out high quality electrical output;secondly,low cost and low toxicity,the low price of manganese source ensures its low production cost,while low nickel and no cobalt ensure its environmental friendliness.In this paper,in addition to the conventional analyses such as electrochemistry and scanning electron microscopy,thermodynamic analyses were performed to further understand the reaction history and influencing factors in the preparation of lithium nickel manganate to achieve lithium nickel manganate with high cycle performance.In this paper,different lithium nickel-manganate precursors were prepared by co-precipitation method using nickel sulfate and manganese sulfate as nickel and manganese sources,and sodium hydroxide,sodium carbonate and sodium oxalate as precipitating agents,respectively.Then,differential thermal-thermogravimetric and X-ray diffraction analyses were performed on the lithium-free Ni and Mn precursors and the precursors with lithium carbonate added,respectively.The change process of the material during calcination and the activation energy of the reaction were obtained.The results indicate that pre-sintering before 700°C and subsequent calcination with long holding time after700°C is necessary.In this paper,the study of different precipitants and surfactants on the preparation of lithium nickel manganate was also carried out,and the results showed that the lithium nickel manganate prepared with surfactants showed spherical morphology,and the first charge/discharge and cycling performance were better than the unused case and among the three different surfactants,polyethylene glycol was the most effective surfactant,which indicated that the use of surfactants could enhance the electrochemical performance of lithium nickel manganate.This indicates that the use of surfactants can improve the electrochemical performance of Li Ni_0.5Mn_1.5O₄,and the degree of improvement varies among surfactants.