| Supercapacitors,which have higher power density than batteries and higher energy density than traditional capacitors,can fill the gap between the batteries and traditional capacitors.The electrode materials are the core part of the supercapacitors,and determine the performance of the supercapacitors.Considering that carbon materials usually have large surface area,proper pore size,good electrical conductivity and low cost,carbon are widely used as electrode materials for supercapacitor.In this study,we prepared a series of potato-based porous activated carbons through a simple chemical activation method using dry potato chips as carbon source and KOH as activating agent under different processing conditions.The morphologies,specific surface area,pore structure and electrochemical properties of the samples were characterized by Scanning Electro Microscope,Transmission Electron Microscope,X-ray diffractometer,Raman Spectra,Nitrogen adsorption-desorption,Elemental analyzer and electrochemical workstation.The main studies are as follows:1.A series of porous activated carbon were prepared by using potato and KOH under different processing conditions that different carbonization temperature,activation temperature and the mass ratio of the activating agent to potato.The experimental results show that the optimal carbonization temperature,activation energy and mass ratio of KOH to carbon are 600?,800 ?,and 5:1,respectively.The total yield of whole process is around 10%.Under these conditions,the carbon?C600-800-5?with the largest micropores?0.70 and 1.55 nm?was obtained.Moreover,the specific surface area can be as high as 2392m2·g-1,while the total pore volume of activated carbon material can reach 1.00 cm3·g-1.The electrochemical results indicate that the highest specific capacitance achieved in this research is 337 F·g-1 at a current density of 1 A·g-1 in the 6 mol·L-1 KOH electrolyte.The carbon material C600-800-5 prepared under optimal conditions was assembled into a symmetrical supercapacitor to investigate its electrochemical performance in 6 mol·L-1 KOH electrolyte.The electrochemical results indicated that the cyclic voltammetric curves still maintains a good rectangular shape even at a high scanning rate of 100 mv·s-1 in 6 mol·L-1 KOH aqueous electrolyte;When the current density is 10 A·g-1,the constant current charge-discharge curve shows a more symmetrical triangle;The symmetric supercapacitor has a high energy density of 13.6 Wh·kg-1 at a power density of 500 W·kg-1,it maintains a high energy density up to 10.9 Wh·kg-1 even at a high power density of 10 kW·kg-1.The cyclic stability of C600-800-5 was also tested,after 3000 cycles,the capacitance could still maintain 95.6%at a 5 A·g-1 current density,suggesting the excellent long-term stability.2.Nitrogen-doped activated carbons with microporous structure and high surface areas were prepared by using potato as carbon source and ethylenediamine as nitrogen source and KOH as activated agent.The results indicate that when the mass ratio of KOH to carbon is 5:1?NC600-800-5?,the specific surface area of activated carbon material can be as high as 2440m2g-1,the total pore volume can reach 1.07 cm3·g-1 and the pore sizes can be the largest?0.82 nm and 1.80 nm?.The specific capacitance can be as high as 370 F·g-1 at a current density of 1 A-g'1 in the 6mol·L-1 KOH electrolyte.The electrochemical performance of the NC600-800-5 carbon material was tested in a two-electrode system.When the power density was 500 W·kg-1,the corresponding energy density was 14.6 Wh·kg-1,It maintains a high energy density up to 10.8 Wh·kg-1 even at a high power density of 10 kW·kg-1.After 3000 cycles,the capacitance could still maintain 95.2%at a current density of 5 A·g-1. |
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