Preparation Of Carbon-based Composite Electrode Material And Assembly Of Flexible Supercapacitors

Carbon materials have been widely used as electrode materials for supercapacitors due to their excellent electrical conductivity,excellent mechanical properties,flexibility and light weight.However,supercapacitors assembled from carbon materials have the disadvantage of low energy density.According to the formula E=CV²/2,increasing the specific capacity of electrode materials and expanding the working potential window of supercapacitors are the inevitable choices to improve the energy density of supercapacitors.The neutral potential electrolyte can be used to expand the working potential window of the electrode material.In the first part of this paper,reduced graphene oxide/polymer quantum dots?rGO/PDs?composites were prepared and their electrochemical properties were evaluated using 1 mol L^–11 Na₂SO₄ as electrolyte.A symmetrical supercapacitor with an output potential of 1.7 V was obtained by controllable electrochemical charge injection technique.The results show that:?1?The presence of PDs had alleviated the overlapping phenomenon of rGO,the overlap of rGO layers,and provided pseudocapacitance and improved the specific surface area of composites.?2?The weight ratio of GO/PDs plays an important role in the electrochemical performance of rGO/PDs nanocomposites.The target product rGO/PDs-1 prepared at the mass ratio of GO to PDs of 1:1 had better electrochemical properties.?3?The assembled flexible supercapacitor can be circulated for 5,000 cycles under0.5A g_¹,with a capacity retention rate of 90.6%,an energy density of 7.1 W h kg^-1,a corresponding power density of 85 W kg^-1,and an output working potential of 1.7 V.Assembling asymmetric supercapacitors was another effective way to expand the working potential window of devices.In the second part of this paper,NTP/C?RCP asymmetric flexible supercapacitors were assembled using waste zn-mn dry battery recycled carbon package?RCP?as positive electrode material and nitrogen-doped carbon-coated NaTi₂?PO₄?₃?NTP/C?as negative electrode material,and their electrochemical properties were evaluated.The results show that:?1?with 1 mol L^-1 Na₂SO₄ as electrolyte,RCP can provide 100 F g^-1 mass specific capacity at 1 A g^-1 in the three-electrode system.The specific capacity was maintained at 86 F g^-1,and the coulomb efficiency was close to 100%.?2?With 1 mol L^-1 Na₂SO₄ as the electrolyte,the specific capacities of NTP/C were 320 and 273 F g^-1at 1 and 10 A g^-1,respectively.The excellent rate performance of NTP/C was attributed to its nitrogen-doped carbon layer and high specific surface area.?3?NTP/C?RCP asymmetric flexible supercapacitor assembled with 1 mol L^-1Na₂SO₄ as electrolyte.At 0.5 A g^-1,the energy density reached 17.8 W h kg^-1,and the corresponding power density was 503 W kg^-1.After 2000 cycles,the energy density remained at 15 W h kg^-1.