Synthesis Of Fe_xSn_yMn_1-x-yO₂ Deposited On MCM-41 And Electrochemical Performance For Supercapacitors

Manganese dioxide?MnO₂? is widely used as electrode material in supercapacitors due to its superior characteristics such as large theoretical specificcapacitance, environmentally benign nature, naturalabundance and low cost. Despite all of the superiority, some drawbacks still exist such as low surface area, poor electronic conductivity and partial dissolution in the electrolyte during cycling, which hinder its practical applications in supercapacitors. Therefore, it is an important task to overcome these disadvantages of MnO₂ electrode material and realize its commercial applications.In this article, mesoporous silica MCM-41 was firstly synthesized by hydrolysis method, and then deposed MnCO3 on MCM-41 with SnCl₄ and FeCl₃ as doping materials through coprecipitation method, followed by annealing at certain conditions, and Fe_xSn_yMn_1-x-yO₂@MCM-41 electrode materials?FS-MnO₂@M?was obtained. The optimum process conditions were determined by single-factor experiment and orthogonal test as below: for MnO₂, MCM-41 = 3:6?mol: mol?; Sn: Mn = 4:100?mol: mol?; Fe, Mn = 5:100?mol: mol?, coprecipitation reaction temperature T = 40?, 450? calcination temperature.The electrochemical performances of FS-MnO₂@M was evaluated and compared by galvanostatic charge-discharge test, cyclic voltammogram?CV? and electrochemical impedance spectroscopy?EIS?. Test shows that the specific capacity of FS-MnO₂@M electrode is up to 319F/g at high current density of 2A/g. And after 10000 cycles, the capacity retention rate remains 88.37%. Cyclic voltammograms tests have shown that FS-MnO₂@M electrode has the best capacitance performance, and the electrochemical polarization effect is small. The results of Ac impedance test and equivalent circuit fitting show that the resistance of FS-MnO₂@M is significantly lower than pure MnO₂ electrode.The structure and composition of FS-MnO₂@M are characterized by using scan-ning electron microscope?SEM?, transmission electron microscope?TEM?, nitrogen adsorption?BET?, Fourier transform infraredspectroscopy?FT-IR? and X-Ray diffraction spectroscopy?XRD? for further characterization and analysis. SEM and TEM characterization testing results show that the particle size of materials is about 500-600 nm with the sedimentary thickness of 50 nm. The porous structure of the material is obviously presented and the sediment is relatively uniform. BET test results show that the average pore diameter of FS-MnO₂@M electrode material is 2.7 nm, and the specific surface area reaches up to 528 m²/ g, which is much higher than that of pure MnO₂. FT-IR and XRD tests show that the Fe, Sn elements are doped into MnO₂ crystal lattice indeed, and repeatedly circulation of charge and discharge tests has no obvious effect on crystal shape of the materials.