Modification Of Carbon-based Supercapacitor Electrode Materials And Their Electrochemical Properties

In this study,mesoporous carbon and hierarchical porous carbon were successfully synthesized by three different methods:sol-gel,hydrothermal carbonization and chemical activation,and the samples were doped with various elements to improve their electrochemical performances.SEM,TEM,XRD,Raman,and N2 adsorption/desorption were used to characterize channel structures,XPS was used to characterize elemental compositions and chemical status,and electrochemical workstation was applied to investigate electrochemical performances.Synthetic mechanisms and the important role of functional resorcinarene were analyzed on details.?1?We developed a novel sol-gel method based on EISA technology to prepare high-performance N/P co-doped ordered mesoporous carbon,using resin as C source,C2H5OH and H2O simultaneously as solvent,cyanide diamine and phytic acid as N and P sources respectively.The method simplifies synthetic steps and saves a lot of time.The sample shows regular pore structure,high specific surface area and abundant heteroatomic functional groups.Electrochemical tests show that when the mass ratio of the P source to the N source is 1:3,the sample NP-OMC-3 has the highest capacitance.Specific capacitance reaches 320 F g^-1 at 1 A g^-1.Even at 20 A g^-1,the capacitance retention can still maintain 70%,showing an excellent rate ability.In addition,the specific capacitance of the sample remains 97.2%of original capacitance after 6,000cycles,showing outstanding cyclic stability.Such excellent electrochemical properties make it competitive in the field of supercapacitors.?2?N/P/B co-doped hierarchical porous carbon was successfully prepared by a two-step post-treatment method with chitosan simultaneously as C and N sources,H3PO4 as P source,and H3BO3 simultaneously as B source and pore-forming agent.The sample shows a three-dimensional interconnected pore structure of micro/mesopores.The material exhibits a high surface area of 2435 m² g^-1 and a large pore volume of 1.97 cm³g^-1.Also,it possesses abundant heteroatomic functional groups,and the synergistic effect of N/P/B greatly improves electrochemical performances.The NPB-HPC-800demonstrates a high specific capacitance of 413 F g^-1 at 1 A g^-1and the capacitance remains 298 F g^-1at 20 A g^-1,exhibiting excellent rate ability.After 6,000 cycles,it still remains 95.6%of the initial capacitance,showing excellent chemical stability.The symmetrical supercapacitor assembled based on NPB-HPC-800 also shows excellent electrochemical performance.The energy density can reach 18.75 Wh kg^-1 at a power density of 225 W kg^-1.Even at 9000 W kg^-1,the energy density is still as high as 11 W h kg^-1.After 10,000 charge/discharge tests,the device maintains 95.4%of the initial capacitance,showing outstanding cyclic stability.?3?A facile and cost-effective strategy was explored to synthesize N,P-codoped hierarchical porous carbons via hydrothermal carbonization coupled with chemical activation using chitosan as C source.We innovatively introduced phosphoric acid during the hydrothermal process to achieve in-situ P doping as well as develop abundant pores.Employment of NaNH2 is of vital importance,which serves as an activating agent and N-source simultaneously,thus achieving a high-level N doping.The obtained samples exhibit a unique three-dimensional hierarchical structure with an ultra-high specific surface area(3646 m² g^-1)and ultra-high N-doping level?9.81 at%?.Benefiting by a series of outstanding physicochemical properties and synergistic effects of N and P,the samples exhibit superior electrochemical properties:an ultra-high capacitance of 586F g^-1 at 1 A g^-1,superior rate capability of 409 F g^-1 at 20 A g^-1 and excellent long-term stability of 97%capacitance retention after more than 10,000 cycles.Moreover,an assembled symmetric supercapacitor delivers a high energy density of 28.1 Wh kg^-1 at a power density of 450 W kg^-1 in 1 M Na2SO4,demonstrating a great potential for the application of supercapacitors.