Preparation,Characterization And Charge Storage Performance Of Porous Carbon Materials From Biomass And Its Derivatives

The super capacitor realizes energy storage and output through the physical adsorption and desorption of the electrolyte ions on the inner and outer surfaces of the electrode material or the Faraday tantalum capacitor reaction,so the charging and discharging speed is very fast,and the large current discharge characteristics are excellent,and the power density is achieved 5-10 times the battery.At present,improving energy density and reducing costs are still the main theme of the development of supercapacitors.Activated carbon is currently the most widely used electrode material,so finding a high-quality carbon source and an efficient activator is crucial for the preparation of porous carbon materials with excellent electrochemical properties.In this paper,the easily available green mushroom and soluble starch were used as the carbon source,and porous carbon materials with high specific capacitance,good charge and discharge cycle stability,and high energy density were prepared through activation treatment of different activators.1.Using KOH and FeCl₃ as activators,carbonized shiitake mushrooms were used to prepare carbon materials,and the activation mechanism of FeCl₃ was preliminarily explored.FeCl₃ is green and environmentally friendly,and its price is low,and its activated carbon material has more carbon material than that activated by KOH.High degree of graphitization,better wettability and a higher proportion of mesopores?66.5%?.Therefore,it exhibits higher mass specific capacitance?247.8 F/g?in 6 mol/L KOH electrolyte.In addition,because of the additional pseudo capacitance contribution of the N,O functional group,it can obtain a specific capacitance of 307.4F/g and a specific energy of 5.28 Wh/kg in a 1 mol/L H₂SO₄ electrolyte and the capacitance does not exceed 87 000 charge and discharge cycles.?104.3%?.The stable working voltage of FeCl₃activated carbon material can reach 3.0 V in 1 mol/L TEABF₄/PC organic electrolyte.Therefore,it has high specific energy?62.6 Wh/kg?,and the capacitance retention rate after 10 000 charge and discharge cycles.There is still 89.3%.In addition,the negative electrode material of sodium ion battery exhibited good stability and rate performance,and the reversible capacity was maintained at¹38.6 mAh/g,5 A/g,at a current density of 0.2 A/g through 1 000 charge and discharge cycles.At high currents there is⁷3.5 mAh/g.2.The microstructure and electrochemical properties of lentinan derived porous carbons treated with different activators?NaOH,NaHCO₃,ZnCl₂ and KHCO₃?were studied.Among them,KHCO₃ activated porous carbon has the best wettability,moderate specific surface area and rich micro/mesoporous and N,O functional groups.Its mass/volume capacitance in 6 mol/L KOH electrolyte is 333.8 F/g and 207.0 F/cm³.Some N,O functional groups have a pseudo-capacitance in the acidic electrolyte.Therefore,the mass/volume specific capacitance and specific energy in the 1 mol/L H₂SO₄ electrolyte reach 387.2 F/g,240.1 F/cm³ and 6.94 Wh/kg,respectively,and Capacitance can experience 165 000 charge and discharge without derogation?103.6%?.In addition,in the 1 mol/L TEABF₄/PC electrolyte,it also has a high electrochemical stability?after10 000 charge and discharge cycles at a voltage window of 2.5 V,a capacitance retention rate of92.6%?and a higher specific energy?55.2 Wh/kg?.In addition,its sodium electric performance is also very good.Under 0.2 A/g current density,the reversible capacity is maintained at¹41.0mAh/g and the current density at 10 A/g is⁶7.2 mAh/g.Importantly,KHCO₃ is universally suitable for most biomass?such as rice husk,peach blossom,sweet-scented osmanthus,parsley,banana peel,and toon leaf?.3.Using soluble starch as a carbon source,monodisperse carbon microspheres were prepared by hydrothermal reaction and KHCO₃ activation.The physical properties indicated that it had a high specific surface area?1972.8 m²/g?and rich micropores?88.8%?.The mass/volume capacitance in the 6 mol/L KOH electrolyte was 331.4 F/g and 238.6 F/cm³,respectively.The contribution of some pseudo-capacitors containing O-functional groups resulted in higher mass/volume capacitance in 1 mol/L H₂SO₄ electrolytes,which were 474.6 F/g and 341.7 F/cm³,respectively,and the capacitance did not decay after 70 000 charge/discharge cycles?100.8%?.High specific energy?50.4 Wh/kg?can be obtained in TEABF₄/PC electrolyte.The spherical carbon density is high and the voids formed by stacking can buffer the electrolyte ions.Therefore,it can maintain the reversible capacity?0.1 A/g?of¹70mAh/g in the sodium ion battery for 2000 times of charge and discharge,and 5 A/g.There is also⁷8 mAh/g.