First-Principles Study of Black Phosphorus as Anode Material for Rechargeable Potassium-Ion Batteries

In two-dimensional materials, black phosphorus has shown excellent performance as electrode materials for lithium- and sodium-ion batteries, due to its thermodynamic stability, layered anisotropic structure, and electrical conductivity. Recently, high capacity anodes based on black phosphorus as an active component for potassium-ion batteries (PIBs) have also been reported. However, in-depth studies are required to clarify the adsorption and diffusion of K ions on black phosphorus and the K-P reaction mechanism. In this work, the surface adsorption, bulk diffusion, and K-P binary phase formation were firstly investigated in detail using first-principle calculations. We found that compared with Li and Na, K has the lowest diffusion energy barrier in the bulk phase (0.182 eV for zigzag type and 2.013 eV for armchair type). Black phosphorus structure irreversibly collapses when the K ion concentration is up to 0.625, and no K3P phase is formed through the electrochemical profiles obtained by calculation of the binary phase alloy structures. Furthermore, the maximum capacitance of black phosphorous for PIBs is calculated to be 864.8 mAh.g(-1). This work will help in understanding the mechanism and further improving the performance of K-ion batteries. Graphic