Biochar Was Modified To Prepare Electrode Materials And Its Electrochemical Properties Were Studied

Supercapacitor is a promising energy storage device with the advantages of fast charge and discharge rate,high power density and long cycle life.The development of cheap and efficient electrode materials is the key to improve the performance of supercapacitor.Biomass is greenrenewable resource with abundant sources and low price.Therefore,it is of great significance to develop biomass-based electrode materials.The porous carbon materials prepared from biomass have the advantages of good conductivity,easy size regulation,high specific surface area and excellent electrochemical stability.Based on the above analysis,this paper uses biomass as raw material to design and synthesize a low-cost,excellent performance of high-efficiency supercapacitor electrode material through the optimization of preparation process and heteroatom doping.The specific research contents are as follows:（1）Coconut shell-based hierarchical porous carbon material CSCK-T-x was prepared by a simple one-step KOH activation method using coconut shell carbon as precursor.The effects of KOH/C ratio（x）and carbonation temperature（T,^oC）on its structure and electrochemistry were studied.The results show that CSCK-800-2 has a specific surface area of 2143.6 m²·g^-1with a hierarchical porous structure.The specific capacitance reaches 317 F·g^-1at the current density of 0.5 A·g^-1.In the CSCK-800-2 symmetric supercapacitor test,the energy density can reach 13.5 Wh·kg^-1when the power density is 250 W·kg^-1.After 5000 charge-discharge cycles at a current density of 5 A·g^-1,there is no loss of capacitance,indicating good stability.（2）On the basis of the study of coconut shell based hierarchical porous carbon materials,the coconut shellcarbon derived N-doped porous carbon material NCSCK-y was prepared by KOH activation coupled with urea nitrogen doping modification（y=0.5,1and 2,representing the mass ratio of urea to coconut shell carbon）.The doping amount of urea was adjusted,and the effect of urea modification on the structure and electrochemical properties of NCSCK-y was investigated.The results show that among NCSCK-y,NCSCK-1 has the highest specific surface area(1964.4 m²·g^-1),and the highest content of pyridine nitrogen and pyrrole nitrogen（1.42%）,which is conducive to the improvement of electrochemical performance.The specific capacitance of NCSCK-1 is 394 F·g^-1at 0.5 A·g^-1.The symmetric supercapacitor based on NCSCK-1 can provide an energy density of 14.9 Wh·kg^-1when the power density is258.6 W·kg^-1.After 5000 charge-discharge cycles at 5 A·g^-1,the capacitance retention rate is99.7%.（3）Nitrogen and sulfur co-doped porous carbon materials（NSHPC-T）with excellent performance were successfully prepared by hydrothermal polymerization and chemical activation using sodium lignosulfonate as carbon source and sulfur source,1,6 hexanediamine as nitrogen source and crosslinking agent.The effect of activation temperature T（^oC）on its structure and electrochemical performance was investigated.The results show that NSHPC-800 has a surface area of 1959.9 m²·g^-1with an interconnected pore structure.The specific capacitance of NSHPC-800 is up to 445.5F·g^-1at 0.5A·g^-1.The symmetric supercapacitor based on NSHPC-800 can achieve an energy density of 16.5 Wh·kg^-1when the power density is 250 W·kg^-1.The capacitance retention is 98.0%after 5000 cycles at 5 A·g^-1.