A Novel DFT Study of Quantum Capacity and Electronic Structure of 2D Materials for Li-ion Batteries

Abstract

2D materials have a wide surface and unique electronic properties as compared to bulk materials. Due to the high stability, high abundance, and the existence of an excellent compatible oxide, Si and Si-based layered materials are the leading ones for microelectronic devices and may be the most promising materials for realistic applications. Lithium-ion batteries (LIBs) have become the most successful type of energy-storage device for applications ranging from portable electronic devices to modes of transport such as electric vehicles, due to their lightweight, environmental friendliness, and high energy density. Si-based 2D materials, unlike metals, do not have a good screening. Therefore, it is expected that their intrinsic capacitance has a prominent influence on the performance of devices when these materials are used in electrodes. We performed DFT calculations of Liq adsorption (q = -1, 0 or +1) on a silicene single layer. Pristine and defective silicene configurations with and without Li doping were studied: single vacancy (SV), double vacancy (DV) and Stone-Wales (STW). Quantum capacity (QC) and charge density studies were performed on Li adsorbed in various sites of the substrate. Moreover, structural studies, adsorption energies, electronic structure and charge density difference analysis were performed before and after adsorption at the most stables sites, which showed the presence of a magnetic moment in the undoped SV system, the displacement of the Fermi level produced by Li doping and a charge transfer from Li to the surface. The QC analysis showed that the generation of defects and doping improves the QC of silicene in positive bias, because of the existence of 3p orbital in the zone of the defect. Consequently, the innovative calculations performed in this work of charged lithium doping on silicene can be used for future comparison with experimental studies of this Li-ion battery anode material candidate.