Fabrication Of Koh-activated Or Nitrogen And Phosphorus Co-doped Benzoxazines-based Carbons And Their Applications In Supercapacitors

Carbon materials have been promising electrode materials for supercapacitors(SCs)due to their good rate capability and cycling stability,but the specific capacitance of carbon materials is limited.The KOH-activation process and the nitrogen and phosphorus(N/P)co-doping method are effective ways to improve the specific capacitance of carbon materials.Therefore,we did the following research about benzoxazines-based carbons:(1)Benzoxazines-based porous carbons were fabricated by a KOH-activation process.The BET specific surface area of benzoxazines-based porous carbons is 1433.2 m2/g.The benzoxazines-based porous carbons electrode displays a high specific capacitance of 203 F/g at 0.5 A/g.Even when the current density was increased to 15 A/g,the specific capacitance of the electrode could still maintain 168.9 F/g.Moreover,the electrode displays a superior cycling stability,maintaining a high specific capacitance of 175.7 F/g with a capacitance retention of 97.0%after 5000 cycles at 5 A/g.The micropores and mesopores formed by KOH activation can increase the specific capacitance and rate performance of the benzoxazines-based porous carbons electrode,respectively.(2)Benzoxazines-based N/P co-doped carbons were fabricated by a N/P co-doping method,which have high nitrogen and phosphorus contents(N:7.5wt%,P:13.6wt%).The benzoxazines-based N/P co-doped carbons electrodes displays a high specific capacitance of 203.0 F/g at 0.5 A/g.Even when the current density was increased to 20 A/g,the specific capacitance of the electrode could still maintain 173.2 F/g.Moreover,the electrode displays a superior cycling stability,maintaining a high specific capacitance of 175.0 F/g with a capacitance retention of 90.1%after 5000cycles at 5 A/g.The SC fabricated using the benzoxazines-based N/P co-doped carbons electrodes displays a high energy density of 11.45 Wh/kg at a power density of 50 W/kg and even maintains 5.55 Wh/kg at a high power density of 25 kW/kg.Moreover,the SCs displays a superior cycling stability,maintaining a high capacitance retention of 79.9%after 10000 cycles at 5 A/g.The superior electrochemical performance can be contributed to the synergistic effect of N/P co-doping.