Preparation Of Lignin-based Porous Carbon Materials And Study On Their Performance In Supercapacitor

Supercapacitor,which is a type of energy-storage devices bridging the power/energy gap between batteries and traditional dielectric capacitors,has aroused wide public attention.Porous carbon materials are the most important electrode materials in supercapacitor for their distinctive properties,including high specific surface area,good stability,excellent electronic conductivity and low cost.The utilization of biomass to prepare carbon materials as supercapacitor electrode material is of significant importance to resource and environment.This paper used lignin and sodium lignosulfonate as carbon source,which were activated by chemical activator to prepare porous carbon materials.Scanning electron microscope,N₂adsorption-desorption analyzer,X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy were used to characterize surface morphology,microstructure,specific surface area and pore structure characteristics and elements content of these carbon materials.The as-prepared porous carbons were then used as supercapacitor electrode materials in different electrolyte.The main contents are as follows:?1?Hierarchical porous carbons were prepared by phosphoric acid-assisted pre-carbonization and followed KOH activation with corn cob lignin as precursor.Considering the pore collapse caused by thermoplasticity of lignin during annealing,a small amount of phosphoric acid was added during pre-carbonization to prepare intermediate char with high specific surface area and hierarchical porous structure,which is beneficial for the following KOH activation.Hierarchical porous carbons?HPC?were obtained after KOH activation at different temperature.Among them,HPC-700 prepared at 700? exhibited a large specific surface area,favorable pore size distribution.Thus it exhibited excellent electrochemical performance in both three-electrode and two-electrode systems?the electrolyte was 6 M?2?KOH?.In the two-electrode system,HPC-700 exhibited a specific capacitance of 250 F g^-1at 0.5 A g^-1,and a good rate performance with a capacity retention of 79.6%at 50 A g^-1.After 10,000 cycles at 2A g^-1,the capacity still remains 97.5%.?3?Porous carbons with high mesopore ratio were prepared with sodium lignosulfonate and gelatin as the precursors and sodium nitrate as activator.The effects of activator dosage and activation temperature on the porous carbon structure,element content and pore structure were investigated.The porous carbon?PC-0.5-900?prepared under optimal condition showed a high carbon content of 96.3at%,high graphitization,and specific surface area of 2453.3 m²g^-1.The ratios of specific surface area and pore volume of mesopore were 79.7%and 89.7%,respectively.When PC-0.5-900 was used in ionic liquid electrolyte capacitors,it showed excellent electrochemical performance.At the current density of0.5 A g^-1,the specific capacitance reached 166 F g^-1.At 50 A g^-1,the specific capacitance still remained137 F g^-1.The material also exhibited excellent cyclic stability,with a capacitance retention rate of93.1%after 10,000 cycles at a current density of 2 A g^-1.