Biomass Derived Carbon As Electrode Materials And Its Electrochemical Performance

In recent years,abundant low-cost renewable biomass has received more and more attention due to the intensification of environmental and resource issues.However,the utilization rate of biomass resources is very low.Therefore,exploration of advanced environmental energy storage and conversion technologies has been a key to improve the utilization of biomass resources.Supercapacitors have attracted widespread attention as a type of energy storage device,because they possess both high energy density of the battery and high power density of the conventional capacitor.The electrode material is the core of the supercapacitor,doping with heteroatom is a common method for increasing the specific capacitance of a carbon-based supercapacitor.As a kind of natural macromolecule,biomass materials are excellent carbon precursors in terms of sustainability,cost,and performance.In this paper,low-cost lignin sodium sulfonate and sodium carboxymethyl cellulose were used as raw materials,porous carbon materials with excellent electrochemical performances could be obtained by one-step high-temperature carbonization,and their properties as electrode materials were systematically studied.The main contents of the research are as follows:(1)Nitrogen-doped porous carbons with good electrochemical performance have been prepared by one-step carbonization of carboxymethyl cellulose sodium at temperature between 600°C and 900°C.Obtained NCS material integrates several advantages,with abundant nitrogen and oxygen functional groups(up to 32.60%?42.24%),high specific surface area and pore volume.As electrode materials in 6 M KOH electrolyte,the prepared carbon materials showed a high specific capacitance of 264 F g-1 at a current density of 0.1 A g-1 in a three-electrode system.Morever,the carbon material exhibited an excellent cycling stability of 98.8%retention after 10000 consecutive charge/discharge cycles.In the two-electrode system,the carbonized samples at 700 °C exhibited good cycle stability of 98.4%retention after 10000 long-cycle life.(2)Nitrogen-doped porous carbon material was successfully prepared by one-step pyrolysis with sodium lignosulfonate and melamine as raw materials.The effects of nitrogen doping,melamine addition,carbonization time,and heating rate on the structure and electrochemical properties of carbon materials were investigated.In the three-electrode system,the specific capacitance of the nitrogen-doped porous carbon material can reach 229 F g-1 at a current density of 0.1 A g-1 in 6 M KOH,and good stability of 99%capacitance retention after 10,000 long charge/discharge cycles.In the two-electrode system,the assembled devices exhibited good rate performance(retention of 65%from 0.1 to 20 A g-1)and excellent electrochemical stability of 99.7%retention after10,000 cycles.(3)A hierarchical porous carbon material was prepared via the self-activation effect with sodium ligninsulfonate as carbon precursor under different carbonization temperature.The effect of carbonization temperature on its self-activation effect and the surface structure and electrochemical performance of carbon materials was investigated systematically.In a three-electrode system,6 M KOH,the specific capacitance is 300 F g-1 at a current density of 0.1 A g-1,and 192 A g-1 at high current density of 20 A g-1.Besides,the carbon material shows excellent cycle stability with only 1%capacitance loss after 10,000 cycles of charge and discharge.In the two-electrode system,the carbonized samples at 700 °C exhibited good rate performance(1 M KOH,71%capacitance retention;1 M Na2SO4,44%capacitance retention from 0.1 to 20 A g-1)and excellent cycle stability.Morever,a superior energy density of 7.9 W h kg-1 and a power density of 7905 W kg-1(3.51 W h kg-1)in 6 M KOH,and energy density of 22.7 W h kg-1 and a power density of 10890 W kg-1(3.63 W h kg-1)in 1 M Na2SO4.