Preparation And Supercapacitor Property Of Flexible Graphene Based Hybrid Films

Flexible supercapacitor electrode material, which has a better cycle life thansecondary battery, has a wide application range, especially in flexible devices. However,how to further improve the rate performance and specific capacitance remains achallenge. In this paper, graphene based flexible films were prepared by vacuumfiltration with different contents of carbon black dispersions. The relationship betweenstructure and electrical performance was studied to optimize the carbon content ofgraphene/carbon black hybrid films. Electric deposition method was used to depositMnO2on as prepared graphene/carbon black hybrid film. The influence of depositiontime on microstructure and electrical performance was performed. Asymmetrysupercapacitor device was assembled based on as prepared graphene/carbon blackbinary films and graphene/carbon black/MnO2ternary hybrid film.The results indicate that the content of carbon black has a great influence on theperformance of graphene/carbon black hybrid film. In1M of H2SO4electrolyte, thegraphene/carbon black hybrid film with graphene oxide/carbon black proportion of5:1.5(RGO/CB-1.5) showed superior rate capability with a specific capacitance r83F/g.The graphene/carbon black hybrid films with graphene oxide/carbon black proportion of5:0.5(RGO/CB-0.5) have the best performance in0.5M of Na2SO4electrolyte. Thedifferent behavior in1M of H2SO4and0.5M of Na2SO4depends on the coordinationbetween the pore sizes and electrolyte ions. The hydrate hydrogen ion has a smaller ionradius than hydrate sodium, which means hydrate hydrogen ion has a better motivationcapability in micropores. Therefore the RGO/CB-1.5shows better performance in1Mof H2SO4electrolyte, while the RGO/CB-0.5shows better performance in0.5M ofNa2SO4electrolyte.The higher carbon black content in the hybrid film, the more micropores will beclogged by carbon black as well as the more obvious it shrinks after drying. In addition,with carbon black added in the hybrid film, the capacitance decreases and the ratecapability performed not as good as expected.The graphene/carbon black/MnO2hybrid films were prepared by electricdeposition in0.1M manganese acetate electrolyte based on graphene/carbon black. Inthree-electrode system, the ternary hybrid film with depositing MnO2for10min,showed the best specific capacitance of108F/g. However, with depositing time beyond15min, the specific capacitance decreased to102F/g, and the rate capabilitydeteriorated dramatically. In two-electrode system, the ternary hybrid film of depositingMnO2for10min also showed the best performance with specific capacitance141F/g at the scan rate of5mV/s, which is significantly higher than that of the binary films. Inaddition, increasing the scan rate from5mV/s to500mVs, the ternary hybrid films withdepositing MnO2for10min showed superior capacitance property thangraphene/carbon black hybrid.The asymmetry supercapacitor was fabricated using graphene/carbon black binaryfilms as negative electrode and graphene/carbon black/MnO2ternary hybrid film aspositive electrode. The working voltage was successfully increased to1.6V, while theenergy density and power density were5.98Wh/kg and1183W/kg, respectively. ALED bulb (3.2V) was lightened by two asymmetry supercapacitor devices in series.