Research On The Structure Of Super Capacitor Electrode Materials MnO₂and Its Electrochemical Performance

Super capacitor with no pollution,fast charge,large capacitance and can be recycled etc,is widely used,it causes great concern,but its specific capacitance is so small and the stability is not good enough,theses defects limit super capacitor applications,in which the electrode material is one of the most elements of its Electrochemical Performance,and therefore the research of super capacitor electrode material has been become an important thing.a-MnO2is a good super capacitor electrode material and it is a semiconductor material itself.But after being repeatedly used, its resistivity becomes high,its electrochemical performance and its applications have been affected.In this paper,the crystal structure of α-MnO2is prepared by the liquid-phase co-precipitation,and make a research on the its preparation conditions and electrochemical performance.To improve the crystal structure of α-MnO2and the electric capacity of α-MnO2and improve circulation stability,what we make a further study of is how the electrode material of Ni or Fe-doped α-MnO2impact on its electrochemical properties,the main work and results are as follows:(1)With Manganese sulfate and potassium permanganate as raw materials,the nano-powders of α-MnO2is prepared in the liquid precipitation/Tested by XRD、SEM、TG-DSC、cyclic voltammetry、 charge-discharge and AC impedance,the results showed that:the α-MnO2with rod diameter about10～20nm was generated in the reaction with potassium permanganate and manganese sulfate at80℃in four hours,when the electrolyte solution is in the1mol/L Na2SO4,at75mV/s scan voltage condition,it exhibits good cycle characteristics,when the constant current is300mA/g,its specific capacitor is112.6F/g,its loop stability is preferable,the impedance is approximately0.75Ω.(2) Study on the morphology structure and electrochemical properties of the manganese dioxide which is being adding different anion,the result shows that the anion in the reaction solution makes a effect on the morphology structure of manganese dioxide.when the reducing agent is manganese sulfate,the reaction solution contains SO42-,the manganese dioxide is the crystal structure α-MnO2,which is a rod morphology,its impedance is about0.2Ω,with scanning speed of5mV/s,the specific capacitance is about127.4F/g;when manganese chloride is as a reducing agent,the reaction solution contains Cl-,the manganese dioxide is the crystal structure of the mixture α-MnO2and γ-MnO2with shape spherical appearance,its impedance is about1.2Ω,the specific capacitance is smaller,When the oxidizing agent is ammonium persulfate, the reaction solution contains SO42-,the scanning speed is50mv/s,the maximum specific capacitance ratio is as132.5F/g.(3)Study on the morphology structure and electrochemical properties of the manganese dioxide which is being doped with different cations.when the nickel is doped manganese dioxide,the crystal structure of manganese dioxide is transformed from α-MnO2structure gradually into the type structure of γ-MnO2,the morphology is changed from rod into a spherical shape, the doping amount was found at around10%,its impedance is about0.2Ω,the specific capacitance is133F/g larger than that of the α-MnO2,as the amount of doping increases,the impedance decreases. When manganese sulfate,ferrous sulfate and ammonium persulfate as raw materials,the iron-doped α-MnO2is prepared.After being doped,the crystal structure of manganese dioxide is transferred from the two-dimensional tunnel α-MnO2into three-dimensional structure of γ-MnO2,after being doped the wispy manganese dioxide is bonded into cellular material,cellular substance adhesions,unevenly distributed,shape nor rule;when the scanning speed is25mv/s,its electric capacity is for156.1F/g at least,its impedance is small.