Effect of vacancy defects and co-doping on the quantum capacitance of silicene-based electrode materials

The design of electrode materials with high energy storage properties plays a key role in developing electric double-layer supercapacitor technology. In recent years, silicene has aroused great interest in the field of energy storage. In this paper, the electronic structure and quantum capacitance of single vacancy defects, topological defects and four kinds of double vacancy defects were systematically investigated, based on density functional theory. It is found that silicene with the topological defect is the most stable defect structure, with the formation energy of 2.067 eV. In the systems of Ag, Au, Cu, Ti, Mn and N co-doping on silicene, the structural stability enhances with the increase of N atoms. CuN2-o-Si structure shows the highest quantum capacitance of 145.499 μF/cm2, which could be an ideal anode material for supercapacitors. The increased quantum capacitance is due to the introduction of localized states near the Fermi level. Both defects and doping can enhance the quantum capacitance of silicene-based electrode materials, and then improve the total interfacial capacitance.