Abstract
High theoretical capacitance of MnO2 nanoparticles were successfully electrodeposited on the conductive graphene/activated carbon (GN/AC) composite film, and the urchin type MnO2 microspheres were controlled by adjusting the electro-deposition reaction times. The GN/AC/MnO2-1200s composite electrodes exhibited a maximum specific capacitance of 1231 mF/cm2 (MnO2 loading mass of 7.65 mg/cm2 and the mass specific capacitance of 123 F/g) at a current density of 0.5 mA/cm2. The assembled flexible solid-state symmetric supercapacitor had a good mechanical flexibility (about 88.6% of its original capacitance after 500 bending times) and prominent cycling stability (about 82.8% retention in capacitance over 10000 cycles). More importantly, the device could possess a maximum energy density of 0.27 mW h/cm3 and a maximum power density of 0.02 W/cm3. These results well demonstrate a great potential for applications of GN/AC/MnO2 composite electrodes in flexible energy storage devices.
Highlights
Graphene (GN), an atom-thick, honeycomb two-dimensional structure, has the characteristics of higher specific surface area, excellent conductivity or mechanical flexibility[1,2,3]
graphene/activated carbon (GN/Activated Carbon (AC))/MnO2 composite electrodes were prepared by two steps (Fig. 1): firstly, AC particles were bonded together with two-dimensional GN sheets using self-assembly method by a facile vacuum filtration process, which expanded the layer spacing and increased the specific surface area of GN
We reported a two-step process for constructing a 3D GN/AC/MnO2 flexible electrode using vacuum filtration and electro-deposition methods
Summary
GN/AC/MnO2 composite electrodes were prepared by two steps (Fig. 1): firstly, AC particles were bonded together with two-dimensional GN sheets using self-assembly method by a facile vacuum filtration process, which expanded the layer spacing and increased the specific surface area of GN. The area specific capacitances of GN/AC/MnO2-1200s electrodes (520 mF/cm[2] at a scan rate of 10 mV/s) were much larger than others, and it decreased slightly when the deposition time increased to. As the amount of MnO2 deposition increases, the mass specific capacitances of the composite electrodes are going to decrease For applications such as flexible and small energy storage devices, the amount of energy stored per area is more important than energy per mass[38]. Upon increasing the current density up to 5 mA/cm[2], the specific capacitance of GN/AC/MnO2-1200s composite electrodes (740 mF/cm2) could retain about 60% of its original values, and more than 3.98 times higher than GN/AC flexible films (186 mF/cm[2]). We can determine that the flexible GN/AC/MnO2 SCs, with a good mechanical flexibility and superior electrochemical performance, are promising candidates for assembling flexible, environment friendly, low price and ultrathin SCs
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