Preparation Of Waste Compound Resin-based Activated Carbon And Its Application In Supercapacitors

In recent years,the increasing amount of waste from carbon fibre composites has seriously polluted the human living environment.Therefore,it is crucial to make effective use of the waste resin in carbon fibre composites.Supercapacitors are already widely used for new energy automobiles,high-tech electronic devices and other fields due to their fast charging and discharging speed,high cycle rate and high power sensitivity and have become the ideal choice for a new generation of energy storage devices.Currently,carbon materials prepared from resin as precursors are ideal electrode materials for supercapacitors and have received increasing attention.In this paper,recycled waste composite resin was used as the carbon source precursor,and carbon based materials were prepared by using different carbonization temperatures and chemical activator phosphoric acid（H₃PO₄）to obtain porous carbon and activated carbon materials with different pore characteristics such as specific surface area,porosity and pore size distribution,and the composite materials were prepared by hydrothermal method with manganese dioxide（MnO₂）using activated carbon as the carrier.The prepared carbon materials were tested and analysed by scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）and nitrogen adsorption-desorption characterisation methods.The electrochemical properties of porous carbon,activated carbon and activated carbon/manganese dioxide composites as electrode materials for electric supercapacitors were also investigated.The main findings are as follows.（1）Carbon materials with graded porous structures were obtained by one-step carbonisation using waste composite resin as the carbon source,and the effects of different carbonisation temperatures on the structure and properties of porous carbon were investigated.The effect of different carbonisation temperatures on the structure and properties of porous carbon was investigated.It was shown that when the carbonisation temperature was 800℃,the specific surface area of the prepared porous carbon could reach 986 m²/g,the total pore volume reached 0.72 cm³/g and the microporous content was as high as 79%.When applied to supercapacitor electrodes,the specific capacitance was as high as 299 F/g at a current density of 1 A/g,and had good cycling stability.After 10,000cycles of the constant current charge and discharge.,the specific capacitance was maintained at nearly 100%,showing excellent electrochemical properties,indicating the high value of the waste composite resin.（2）The activated carbon was prepared by phosphoric acid activation using the waste composite resin as the carbon source,and the effects of different activation temperatures on the structure and properties of the activated carbon materials were investigated.The study showed that the best performance of the prepared activated carbon was achieved when the activation temperature was 500℃,the impregnation ratio was 1:10 and the activation time was 2 h.The specific surface area was as high as 1481m²/g.Under the three-electrode test system,the specific capacitance was as high as 537 F/g at a current density of 1 A/g,and the capacitance retention rate was still as high as 105%after 10,000 cycles of charging and discharging at a high current density of 20 A/g,showing excellent cycling stability.The activated carbon prepared by the phosphoric acid activation method exhibited more excellent pore structure and electrochemical properties.（3）Manganese dioxide/activated carbon composites were prepared by hydrothermal synthesis using the activated carbon prepared by the phosphoric acid activation method as a carrier.It was shown that the prepared composites have unique structure,excellent stability and good electrochemical properties.In the three-electrode system,the specific capacitance was as high as 673 F/g at a current density of 1 A/g,much higher than the 537 F/g of the activated carbon electrode,and still had a good cycle life（92.3%capacitance retention after 10,000 cycles）,indicating a good synergy between manganese dioxide and activated carbon.Assembled MnO₂@PAC//PAC asymmetric supercapacitor with high operating voltage（1.6 V）,the device has a specific capacitance of107.96 F/g at a current density of 0.5 A/g,an energy density of 53 Wh/kg at a power density of 400 W/kg,and an excellent cycling stability with a capacitance retention rate of 83.9%after 10,000 cycles.