Preparation Of Manganese Dioxide And Its Composite Materials And Study On Properties Of Supercapacitors

As a widely used energy storage device,supercapacitors are featured by rapid charging and discharging,high power density and good cycling performance,which play an increasingly important role in the field of energy storage.As a common electrode material for supercapacitors,manganese dioxide has the characteristics of abundant sources,environmental friendliness and high theoretical specific capacity,but its application in supercapacitors is still limited due to its complex preparation process and low energy density.Therefore,in this experiment,MnSO4,MnCl2 and KMnO4 and Mn(NO3)2 were used as the source of manganese,through hydrothermal method in the preparation of the manganese dioxide nanorods(MnO2 NRs),manganese dioxide nanoflowers(MnO2 NFs)and manganese dioxide nano wires(?-MnO2 NWs)powders.At the same time,using the MnO2 NWs and graphene oxide dispersion(GO)as raw material,?-MnO2 NWs/rGO aerogel composites were synthesized through the hydrothermal method.Then the above materials were used as active materials to make the working electrode of supercapacitor and tested the electrochemical performance,respectively.Among them,with 1 mol L-1 Na2SO4 electrolyte,the specific capacitance of MnO2 NFs reached 207.5 F g-1,and the ?-MnO2 NWs/rGO aerogel composites was self-supporting The specific volume of the electrode reached 203.7 F g-1 at 1 A g-1,and the latter had a capacitor retention rate of 86%after 8000 charge and discharge cycles,showing good cycle stability.Here are the results.Using a three-electrode test system,the specific capacitance of MnO2 NRs is 70 F g-1 at a current density of 1 A g-1,while the specific capacitance of MnO2 NFs is 207.5 F g-1.Obviously,the latter has a significant specific capacitance improve.The difference of specific capacitance performance lies in the morphologies of the corresponding active materials.It is obvious that the latter has larger specific surface area and richer pore structure,providing more redox active sites and electrolyte ion transport channels,leading to a significant increase in specific capacitance.?-MnO2 NWs were compounded with conductive reduced graphene oxide(rGO)to obtain ?-MnO2 NWs/rGO aerogel composites.The(3-MnO2 NWs/rGO aerogel composites with a specific surface area of 120.02 m2 g-1 and a total pore volume of 0.098 cm3 g-1 were prepared,in which ?-MnO2 NWs grew vertically on the surface of rGO.Next,the effect of the mass ratio of ?-MnO2 NWs to rGO on the electrochemical performance was studied.When the mass ratio of ?-MnO2 NWs to rGO was 1:1(?-MnO2 NWs/rGO-1),the specific capacitance of ?-MnO2 NW/rGO aerogel composites is 203.7 F g-1,which is much higher than the specific capacitance of ?-MnO2 NWs and rGO.At the same time,the composites has good cycle stability.The excellent performance of ?-MnO2 NWs/rGO aerogel composites was further analyzed.This is mainly due to the synergy between ?-MnO2 NWs and rGO.On the one hand,?-MnO2 NWs are fixed between rGO nanosheets as spacers,which can effectively suppress the stacking of rGO.On the other hand,the combination between ?-MnO2 NWs and rGO can enhance the interface charge transfer and improve the conductivity of ?-MnO2 NWs.Through the above synergistic effect,the electron conduction rate of the electrode material and the transmission efficiency of electrolyte ions are improved,thereby effectively improving the electrochemical performance.