Preparation And Electrochemical Properties Of Manganese Based Oxide Electrode Materials

Lithium-ion batteries have been widely used in portable electronic devices.With the development of new energy industry in the world,electric vehicles will become the largest demand area for lithium-ion batteries.Therefore,power lithium batteries with higher energy density are the mainstream of lithium battery industry development.Manganese-based oxide has the advantages of high theoretical capacity and low discharge platform,and is a promising lithium battery anode material.However,manganese-based oxides have problems of low conductivity and volume change of lithium deintercalation process.It has become a research hotspot to modify manganese-based oxide materials and develop electrode materials with superior performance.In this paper,different preparation methods were used to prepare manganese-based oxide materials with different structures and special morphologies through optimization of process parameters,and the electrochemical properties of the materials were further improved by ion doping and carbon coating.The main work includes the following Four aspects:(1)Micro/nano hierarchical structure of manganese dioxide materials.Manganese dioxide materials with different structures and morphologies were prepared by hydrothermal method using potassium permanganate and hydrochloric acid as raw materials.The results show that when the reaction temperature is?150? or the reaction time is<6 h,the globular 8-MnO2 is obtained.As the reaction temperature increases and the reaction time increases,sea urchin-like/thorn-like a-MnO2 is obtained.The urchin-like manganese dioxide showed better electrochemical performance with an initial discharge capacity of 1501 mAh/g and a discharge capacity of 651 mAh/g after 100 cycles.(2)Element doping of La,MnO2(x=0,05,0.1,0.15).As the element La is doped,when x?0.15,the material is pure phase ?-MnO2.The prepared La0.05MnO2,La0.1MnO2,and La0.15MnO2 were petal,spherical and spheroidal,respectively.The petal-like La0.05MnO2 showed the best electrochemical performance,the first discharge capacity was 1455 mAh/g,the discharge specific capacity was 997 mAh/g after 100 cycles,the capacity retention rate was about 69%,and at current density of 1600 mA/g(about 1.3 C),the discharge capacity was 304 mAh/g.(3)Research on solid and hollow spherical a-Mn02 materials.First,spherical ammonium carbonate material was prepared by liquid phase precipitation method using ammonium hydrogencarbonate and manganese sulfate as raw materials.Then,a solid spherical manganese dioxide material is obtained by calcination at 150?,respectively,and treated by potassium permanganate and hydrochloric acid to obtain a hollow spherical manganese dioxide material.The spherical material has a diameter of about 2 um,a uniform size,and good dispersibility.The hollow spherical manganese dioxide material has a specific surface area of 105 m2/g,showing superior electrochemical performance.The initial discharge capacity is 1508 mAh/g,and the discharge capacity is 802 mAh/g after 160 cycles,at current density of 1600 mA/g.The discharge capacity at high current density is 432 mAh/g,and the results show that the material has good cycle stability and rate performance.(4)Research on carbon-coated spherical tetramanganese oxide materials.The core-shell structure of Mn3O4@C was prepared by solid spherical manganese dioxide as the matrix and formaldehyde and resorcinol as carbon sources by hydrothermal method and nitrogen atmosphere calcination.The particle size is uniformly dispersed,and a carbon coating layer is present on the surface of the trimanganese tetraoxide.The initial discharge capacity of the material was 1414 mAh/g,and the specific capacity of discharge was 973 mAh/g after 800 cycles,and the capacity retention rate was 69%.The discharge capacity is 382 mAh/g at a high current density of 3200 mA/g.The above results show that the core-shell structure Mn3O4@C material has excellent cycle stability.