Research On Modification And Electrochemical Performance Of Hypercoals-based Activated Carbon

Supercapacitor is a new energy device in the contemporary era,which has the advantages of high power density,long service life,good safety and more suitable for high-power applications.However,it still exists the problem of low energy density.The key to prepare electrode materials is to improve the energy density.Hypercoals is used as carbon electrode.It can eliminate the effect of ash content on the properties of capacitors.In addition,the modification of hypercoals-based activated carbon can increase the surface functional groups,the specific capacitance of material and the energy density.At the same time,it can improve the electrochemical performance.Using three kinds of modifying agents to modify activated carbon,such as HNO₃,melamine and ammonia,then determining the best type of modifying agents.The effects of modification conditions on the pore structure,surface functional groups and electrochemical properties of hypercoals-based activated carbon are investigated by adjusting the concentration of the best modifying agent,refluxing time and refluxing temperature.The relationship between specific surface areas,pore size distributions,surface functional groups and the specific capacitance of activated carbon are discussed.The results show that HNO₃ is more suitable for hypercoals-based activated carbon compared with melamine and ammonia.The pore size of hypercoals-based activated carbon is in 0.4⁰.55 nm and 0.6⁰.8 nm is achieved with the concentration of 1%,the refluxing time of 2 h and refluxing temperature of 60?.Surface functional groups are mostly in C-O-H,-COO^-and N-5,which can enhances the wettability of materials,electrical conductivity and reduced resistance;it shows the good energy density and power density,and the specific capacitance and the energy density reach to 309 F/g at 50 mA/g and 27.91 Wh/kg,respectively.Compared with the unmodified activated carbon electrode,it increased by 38.6%.