Preparation Of Manganese Oxide Based Electrode Materials And Their Application For Supercapacitors

In recent years,the gradual depletion of fossil fuels has led to an increasingly serious energy crisis.At the same time,environmental pollution is essential in the use of fossil fuels.As a result,energy and the environment are the primary problems that must be addressed in the process of sustainable human development.Searching renewable clean energy and developing clean energy conversion devices is an important way to reduce environmental pollution and take a sustainable path today.People are eager to find and develop green and efficient energy storage and the corresponding conversion equipments.Among them,the supercapacitor as an energy storage device gradually become a research hotspot,because of its high power density,long cycle stability,fast charge and discharge and better temperature characteristics.It has a huge application value in the consumer electronics,storage backup systems,hybrid cars,industrial power equipment and aerospace and other fields.Manganese oxide as a supercapacitor electrode material has been extensively studied,which has the advantages of low cost,high theoretical capacitance,abundant reserves,and environmental friendliness.In this paper,manganese oxide with unique structural morphology was obtained by low cost chemical preparation.The influence of morphology and specific surface area on the electrochemical properties of manganese oxide was discussed.The main contents are as follows:1)Using uniform polyaniline nanospheres as sacrificial templates and potassium permanganate as an oxidizing agent,hollow manganese oxide nanospheres are prepared by rapid oxidation at room temperature.The synthesis route is simple,the sample product can be expanded for mass production.The unique structure of manganese oxide is obtained by equilibrating the diffusion rate of potassium permanganate and polyaniline.The hollow structure of the manganese oxide shows a high specific surface area of 284.5 m2/g,and as a supercapacitor electrode material,the specific capacitance reaches 308 F/g at a current density of 0.2 A/g.In the current density of 2 A/g for charge/discharge cycle test for 3000 times,the specific capacity retention rate is about 91%.With the activated carbon material for the electrode composition of asymmetric capacitors,it can reach avoltage window with 1.8 V.When the power density is 180 W/kg,the energy density can reach 20.93 Wh/kg;while the power density is 9000 W/kg,the energy density can reach 7.23 Wh/kg.After the two-electrode system is charged for 2000 times,the capacitance retention rate of 76 % is retained.2)Based on the formation of hollow manganese oxide by in situ reaction of polyaniline and potassium permanganate,homogeneous polyaniline-coated gold nanoparticles?Au@PANI?are used as sacrificial templates.Under 40 oC reaction conditions,potassium permanganate solution with a certain concentration is added into Au@PANI dispersion for redox reaction,and a yolk-shell nanostructured Au@MnO₂ is obtained.The yolk-shell nanostructured Au@MnO₂ materials exhibit high specific surface area of 358 m2/g,and as a supercapacitor electrode material,the specific capacitance reaches 320 F/g at a current density of 0.2 A/g.In the current density of 2 A/g for charge/discharge cycle test for 3000 times,the specific capacity retention rate is about 90%.When the asymmetric capacitor is made up with the activated carbon material as the counter electrode,the voltage window can reach 1.8 V.When the power density is 180 W/kg,the energy density can reach 21.6 Wh/kg;while power density is 9000 W/kg,the energy density can reach 7.69 Wh/kg.During the two-electrode cycle charge test for 2000 times,the specific capacity retention rate of 78 % is observed.This indicates that the electrochemical properties of the hollow manganese oxide nanomaterials with a movable Au core are improved owing to improved conductivity.