Preparation Of High Capacity Carbon Manganese Dioxide Composite Electrode And Study Of Its Electrochemical Proprties

Electrochemical capacitors,also known as supercapacitors,which not only has the characteristics of physical capacitors with high power,but also has high energy density resulted from traditional batteries.Based on the above advantages,it has broad application prospects in electronic devices and hybrid electric vehicle for supercapacitors,and they cause the attention of various countries.In recent years,the research on supercapacitors is mainly focus on the preparation of high performance electrode materials.Reference a large number of literature investigation,this paper firmly grasp the latest development of international in this area.Taking carbon and manganese dioxide composite materials as a starting point,through the optimization of material preparation method,the high performance of carbon/manganese dioxide thin film electrode has been developed.Both the two electrodes and three electrodes system were used as the test unit,respectively.It has been used SEM,TEM,nitrogen adsorption/desorption and XRD methods for structure characterization of materials,respectively.We use cyclic voltammograms,constant current charge-discharge and ac impedance for supercapacitor performance testing.Combined with characterization and testing,the research will provide experimental basis and theoretical reference for the development of new electrode materials.In this paper,the research content is as follows:A new type of core-shell structured material consisting of multi-walled carbon nanotubes(MWCNTs)and manganese dioxide(Mn02)nanoflake is synthesized using an in-situ co-precipitation method.That core-shell structured material electrode presents excellent electrochemical capacitance properties with the specific capacitance reaching 380 F g-1 at the current density of 5 A g-1 in 0.5 M Na2SO4 electrolyte.In addition,the electrode also exhibits good performance(the power density:11.28 kW kg-1 at 5 A g-1)and long-term cycling stability(retaining 82.7%of its initial capacitance after 3500 cycles at 5 A g-1).It mainly attributes to MWCNTs not only providing considerable specific surface area for high mass loading of MnO2 nanoflakes to ensure effective utilization of MnO2 nanoflake,but also offering an electron pathway to improve electrical conductivity of the electrode materials.It is clearly indicated that such core-shell structured materials including MWCNTs and MnO2 nanoflake may find important applications for supercapacitors.Sandwiched films of reduced graphene oxide(RGO)and manganese oxide(MnO2)are assembled on glassy carbon electrode(GCE)substrates by a layer-by-layer electro-deposition technique in two different electrolytes.Using scanning electron microscopy,we demonstrate that the framework is composed of crumpled RGO and porous MnO2 nanoneedles to give the interconnected network structure.The GCE/(RGO/MnO2)3 electrode exhibits remarkable enhancement of combined performance both with respect to discharge capacitance(up to 55 mF cm-2 at 0.05 mA cm-2)and cycling stability(retaining 95.9%of its initial capacitance after 3000 cycles at 0.68 mA cm-2).This special technique which holds great promise for patterning RGO films in device and composite applications could facilitate electrochemical energy storage.