Metallic two-dimentional penta-PC2 structure with excellent electrical conductivity as superior anode material for both Li and Na ion batteries

Two-dimentional (2D) structures have been known as the potential candidates of electrode materials in lithium (Li) and sodium (Na) ion batteries. Recently, as a unique family of 2D structures, 2D penta structures have received increasing attention for the application of electrode materials. Note that, most proposed 2D penta electrode structures are semiconducting. In this work, via density functional theory (DFT) calculations, we uncovered that metallic penta-PC2 can be promising electrode material. We found that the charge density of metallic state, which comes from C-2pz orbital, is equably and unitedly spreading in whole penta-PC2, resulting in the excellent current conducting ability of penta-PC2. Apart from the dynamical stability, we found Penta-PC2 also can possess the thermal and mechanical stabilities. Particularly, it can withstand the temperature as high as 1500 K. Interestingly, it has ultrahigh theoretical storage capacity with 1462/1949 mAh·g−1 for Li/Na absorption, which is about 3/4 times larger than that of graphite. More importantly, penta-PC2 also can exhibit rather negative absorption energies, small variations of lattice constants, low and isotropic migration barriers and appropriate average open-circuit voltages (OCV). All of these results highlight the potential of penta-PC2 structure as an ideal 2D electrode material of Li and Na ion batteries.