Preparation And Capacitance Properties Of Sugarcane Bagasse-Based Biomass Carbon/MnO₂ Composites

As a new type of energy storage device,supercapacitor has attracted extensive attention because of its fast charge-discharge and good cycle stability.The main factor affecting the performance of supercapacitors is the electrode materials.Therefore,the search for high specific capacitance electrode materials has become one of the focuses of supercapacitors research.In this paper,the composite electrode materials with high specific capacitance were prepared by using the prepared sugarcane biomass carbon material as matrix material and MnO2 with different morphologies under hydrothermal conditions.The structure and morphology of the materials were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction,nitrogen adsorption and desorption and Raman spectrometer,and the electrical properties of the materials were tested.The final results are as follows:(1)A graded porous bagasse-based biomass carbon material is prepared by changing the amount of KOH,the time of bagasse immersion in a KOH solution and the activation temperature using bagasse as carbon source.It was found by scanning electron microscopy that the carbon material prepared was rich inpores and the pore structure was intact.The carbon material obtained by Raman spectroscopy showed an ID/IG value of 0,9.The specific surface area of the prepared porous carbon material is 956 m2/g by nitrogen adsorption desorption test.The electrochemical test showed that the specific capacitance is 398 F/g at a current density of 1 A/g,and the capacitance retention reaches 92%after 2000 charge and discharge cycles at a current density of 5 A/g.(2)MnO2 electrode materials with different morphologies were prepared by hydrothermal method.The prepared MnO2 nanospheres were obtained by scanning electron microscopy and transmission electron microscopy.The prepared MnO2 nanotubes were partially hollow.It was found by XRD that the crystallinity of MnO2 nanospheres was the lowest,indicating that the structure was loose and favorable for electron transport.The electrochemical properties of three different morphologies of MnO2 were tested in 6 M KOH and 1 M Na2SO4 electrolytes.It is found that the electrochemical performance of MnO2 is excellent in the Na2SO4 electrolyte.The specific capacitance of the MnO2 nanospheres can reach 325 F/g at a current density of 1 A/g and the current retention rate is 75%after 1000 charge and discharge cycles.(3)The MnO2 nanospheres were synthesized by hydrothermal method using bagasse-based biomass carbon as the matrix material and different morphology MnO2 at different ratios.After scanning electron microscopy,it was found that MnO2 mainly grows in the pores of carbon materials,which is beneficial to the synergistic effect of the electric double layer and tantalum capacitor.It is found that the diameter of MnO2 nanorods and MnO2 nanospheres is greatly reduced after compounding,but MnO2 nanotubes are greatly reduced.After the compounding,the morphology changed greatly and the size increased.It was found by XRD test that the crystallinity of MnO2 nanorods and MnO2 nanospheres was reduced after compounding with carbon materials.It was found by Raman spectroscopy that the amount of MnO2 in the composite after MnO2 nanotubes were combined with carbon materials was limited,which limited the storage effect of tantalum capacitors.The specific capacitance of the composite materials in KOH electrolyte and Na2SO4 electrolyte was calculated.The material carbon has the highest specific capacitance of the 1:1 composite electrode material,reaching 747 F/g at a current density of 1 A/g,and the capacitance retention rate can still reach 77%after 1000 charge and discharge cycles.