Haeckelite phosphorus: an emerging 2D allotrope of phosphorus for potential use in LIBs/SIBs

A large surface-to-volume ratio is an essential feature of 2D materials used in many potential electronic applications. This work proposed that the haeckelite-structured phosphorus can be another promising alternative to the known phosphorus allotropes by DFT calculations. This allotrope can be considered a suitable anode material that may provide outstanding performance in LIBs and SIBs. Our simulations confirm that the haeckelite-structured P, composed of alternate square and octagonal rings, is thermally and mechanically stable. The phosphorus haeckelite exhibits a semiconductor with a bandgap of 2 eV and converts to a metallic phase after Li/Na adsorption, which is profoundly the basis for ideal performance of a battery. It provides a high specific capacity and a small OCV with a minimal volume expansion during lithiation/sodiation. The haeckelite-structured P exhibits much higher Li/Na adsorption properties with a small Li/Na migration barrier, which are highly essential in the charge-discharge performance of LIBs/SIBs. Based on the details mentioned above, our study would supply supportive guidelines to advance better opportunities to design and develop flexible Li/Na-ion batteries for future energy conversion and storage applications.