Preparation And Electrical Performance Of The Mn-based Aerogel And Graphene-Mn-based Aerogel

Recently,the energy shortage and environmental problems caused by the fossil energy consumption have stimulated the urge to develop the new energy storage devices to instead of the traditional devices.Then the supercapacitors and Li-iron batteries arise at the historic moment.As we all know,the properties and structure of the electrode materials have important influence on the electrical performance.The advantages of oxides of manganese,such as various oxidation states,high capacity,environmental friendly,make them of first selection as the electrode materials.Besides,the porous structure providing large surface area can facilitate fast transportation of the electric and alleviate the volume effect.So,the specific capacitance will be improved.Aerogels with high porosity and large surface area,have been widely used in many fields,such as adsorption,catalysis and energy storage.Therefore,if we prepare the oxides of manganese in the form of aerogel,it will have both high capacitance and porous structure.The main research contents as follows:In this research,we synthesized porous Mn-based aerogel,using Mn（NO₃）₂（50wt%）as manganese resource,the citric acid as plate,epoxide as the gelation accelerator and incorporation with the supercritical drying with ethanol.The influence of the plate materials,the consumption of epoxide and citric acid on the sol-gel process and structure properties were discussed.The optimize plate and reaction ratio were determined as citric acid and n（Mn₂）:n（C₆H₈O₇）:n（C₃H₆O）= 1:1.25:1.Then the effect of temperature under air atmosphere on the capacitance characteristic was studied.The porous Mn₃O₄ material was obtained when the Mn-based aerogel was treated at 350℃.These porous Mn₃O₄ material displayed high capacity of 347 F g^-1 at 100 mA g^-1 and good cycle ability at 5 A g^-1 with 83.6%capacitance retention after 5000 cycles when used as supercapacitor.Besides,the impact of temperature under N₂ atmosphere on the Li-iron batteries was studied.The MnO nanoparticles encapsulated in the 3D conductive carbon networks was synthesized when the Mn-based aerogel was treated at 550℃.When evaluated as electrode material for Li-iron batteries,the synthesized 3D carbon coated MnO composites displayed high capacity of～910 mA h g^-1 with columbic efficiency of～100%at the current density of 200 mA g^-1 over 100 cycles.In this paper,we also use the sample method prepare the porous graphene-manganese-based aerogel composite.The influence of the graphene ratio on the sol-gel process and capacitance were discussed.These material displayed good cycle ability at 1 A g^-1 with 95.1%capacitance retention after 1000 cycles when used as supercapacitor.When evaluated as electrode material for Li-iron batteries,the sample with ratio of 0.1 wt%treated at 550℃ under N₂ atmosphere have the best electrical performance.