The Study Of Electrochemical Performance Of Magnesium Type LDH Electrode Materials For Supercapacitors

Due to layered double hydroxides(LDHs)with the hydrotalcite structure has some drawbacks as electrode material in supercapacitors,such as poor electronic conductivity,slow reaction rate and inferior cycling stability at high current density,and frequent agglomeration in the electrolyte during cycling,which hinder its practical applications in supercapacitors.Therefore,it has very important theoretical and practical significance to overcome these disadvantages of LDHs electrode material and realize its commercial applications by researching the structure and performance of Mg-Co-Al-LDH in this study.In this article,Mg-Co-Al-LDH electrode materials was obtained through coprecipitation method with NaOH being ueded to adjust pH of reaction,Mg(NO3)2·6H2O and Al(NO3)3·9H2O as raw materials,Co(NO3)2·6H2O as doping materials.The optimum process conditions were determined by single-factor experiment and orthogonal test as below: for nMg:nAl = 3:1(mol: mol),reaction time t= 2h,coprecipitation reaction pH=12.0,coprecipitation reaction medium 5% ethanol,the doping ratio of Cobalt element: nCo:nMg=2:3,n(Mg+Co):nAl=2:1.The structure and composition of Mg-Co-Al-LDH are characterized by using Fourier transform infraredspectroscopy(FT-IR),X-Ray diffraction spectroscopy(XRD),scan-ning electron microscope(SEM)and transmission electron microscope(TEM),for further characterization and analysis.SEM and TEM characterization testing results show that the particle size of materials is about 350-450 nm.The layered structure of the material is obviously presented and the distribution is relatively uniform.FT-IR and XRD tests show that the Co element is doped into Mg-Al-LDH crystal lattice indeed,which has no obvious effect on crystal shape of the materials.The electrochemical performances of Mg-Al-LDH and Mg-Co-Al-LDH electrode was evaluated and compared by galvanostatic charge-discharge test,cyclic voltammogram(CV)and electrochemical impedance spectroscopy(EIS).Test shows that the specific capacity of Mg-Al-LDH and Mg-Co-Al-LDH electrode are up to114.2 F/g and 381.3 F/g at high current density of 1A/g.And after 10000 cycles,the capacity retention rate remains 83.32% and 86.23%.Cyclic voltammograms tests have shown that Mg-Co-Al-LDH electrode has the better capacitance performance,and the electrochemical polarization effect is smaller.The results of Ac impedance test and equivalent circuit fitting show that the resistance of Mg-Co-Al-LDH issignificantly lower than Mg-Al-LDH electrode.The results of research show that Mg-Co-Al-LDH can be used as electrode material for supercapacitor at the high power condition with better specific capacity and cycling stability.