silicon phosphide is a layered semiconductor crystallizing in C2/m two-dimensional anisotropic / orthorhombic crystal phase. It has been shown to undergo indirect (bulk) to direct (monolayer) gap transition from 1.69 eV to 2.5 eV, and to host anisotropic excitons, thermal conduction, optical absorption, and electronic mobility.
SiP has attracted a lot of attention in the field of energy storage due to its stable semiconducting 2D structure and promising theoretical specific capacity of 3120 mA h g-1 for lithium ion batteries (LIBs) anodes. However, bulk SiP is too thick for effective lithiation of Li ions in anodes of a typical LIB cell and requires reversible synthesis of nano-sized SiP nanoflakes.
Few-layer SiP nanoflakes with a successful mechanical exfoliation exhibit better electrical conductivity, faster charge transfer kinetics, and lower resistance than bulk SiP. This results in enhanced fast chargeability and long cycleability of the anodes, a process that may be used to develop next-generation anodes in LIBs.
A novel phosphorus compound called SixPy was discovered by combining global structural prediction and first-principles calculations, showing that it could be formed stably at the stoichiometries of y/x > 1. These compounds have comparable formation enthalpies to allotropes, and can be tuned in an extremely wide range with an appropriate band gap.
In order to explore the potential of these materials for use in Li ion batteries, we synthesized and evaluated binary (semi)metal-phosphorus compounds by vapour-transport reaction in a cotton wool-like product. A layered 2D crystalline microribbon-like space group Cmc21 morphology was obtained which facilitates a rapid Li ion intercalation/diffusion kinetics and opens up new perspectives for ultra-thin optoelectronics or flexible photovoltaics.