Preparation, Characterization And Electrochemical Performance Of Anode Material For Aqueous Electrochemical Capacitors

At present,wind,hydropower and solar energy are the new types of renewable energy sources.Compared with the traditional energy,new energy has the characteristics of less pollution,large reserves.It is of great significance to solve the serious problems of environmental pollution and the depletion of fossil.However,the energy application is limited by natural and geographical conditions,besides,it can't satisfy people's demand for energy in our daily life.Thus,there is an urgent need for an energy storage system in which energy can be stored for a long time and released when needed.The research focus of this paper is to prepare suitable cathode material for the aqueous supercapacitor with improvement of the specific capacity and the cycle performance of the electrode material.The contents and results of this work have the following three parts:?1?The electrochemical properties of h-BN and h-BN/C electrode prepared by solid phase method were tested in 2 mol L-1 KOH aqueous solution.h-BN electrode presents a specific capacitance of 54.8 F g-1 at the current density of 0.5 A g-1.At the same current density,the specific capacitance of h-BN/C nanocomposite is 250 F g-1,which is about 4.56 times as long as that of virginal h-BN.Moreover,the h-BN/C electrode still has more than 88.9% after 1000 charge-discharge cycles.The two materials are respectively assembled with the activated carbon electrode in aqueous asymmetric capacitor,at voltage window 0¹.45 V?The AC/h-BN/C capacitor has an energy density of 16.4 Wh kg-1 at a power density of 511 W kg-1.When the power density of AC//h-BN is 511 W kg-1,the energy density is only 5.1 Wh kg-1.Besides,AC//h-BN/C presents excellent cycling behavior after 1000 charge-discharge cycles.?2?These porous carbons of different aperture are prepared via solid phase method and their electrochemical performances as electrode in 0.5 mol?L-1 H2SO4 +0.5 mol?L-1 Li Br aqueous solution were investigated.At the current density of 30 A g-1,MgC-900 has the highest capacity of 1100 mAh g-1 among the three kinds of porous carbons.Because the average pore diameter of porous carbon of MgC-900 is biggest,which calcination temperature is 900 ?.It can provide more reactive sites for electrochemical reaction,so pseudocapacitor of the system can be increased.?3?By the simple hydrothermal method to prepare Zn-Ni MOFs,Then the ZnO-NiO composite material(Zn_0.8Ni_0.2O)is prepared by calcination.The Zn_0.8Ni_0.2O electrode material shows a good electrochemical performance in 2 mol L-1 KOH electrolyte.The specific capacity of Zn_0.8Ni_0.2O electrode material is 175 F g-1 when the current density is 1 A g-1,which is larger than specific capacity of Zn O material?20 F g-1?.Besides,it has good rate performance.The material presents excellent cycling behavior after charging and discharging cycle of 900 times,which capacitance attenuation rate is 19.5%.