A comparative first-principles study of the lithiation, sodiation, and magnesiation of black phosphorus for Li-, Na-, and Mg-ion batteries

Abstract

Using first-principles calculations, we describe and compare atomistic lithiation, sodiation, and magnesiation processes in black phosphorous with a layered structure similar to graphite for Li-, Na-, and Mg-ion batteries because graphite is not considered to be an electrode material for Na- and Mg-ion batteries. The three processes are similar in that an intercalation mechanism occurs at low Li/Na/Mg concentrations, and then further insertion of Li/Na/Mg leads to a change from the intercalation mechanism to an alloying process. Li and Mg show a columnar intercalation mechanism and prefer to locate in different phosphorene layers, while Na shows a planar intercalation mechanism and preferentially localizes in the same layer. In addition, we compare the mechanical properties of black phosphorous during lithiation, sodiation, and magnesiation. Interestingly, lithiation and sodiation at high concentrations (Li2P and Na2P) lead to the softening of black phosphorous, whereas magnesiation shows a hardening phenomenon. In addition, the diffusion of Li/Na/Mg in black phosphorus during the intercalation process is an easy process along one-dimensional channels in black phosphorus with marginal energy barriers. The diffusion of Li has a lower energy barrier in black phosphorus than in graphite.

Intercalant-independent transition temperature in superconducting black phosphorus

“…The above compositions are stoichiometric (or stage I, ref. 29), in agreement with the first-principles calculations for Li, Na and Mg intercalation132526, which predicted that the metal atoms should occupy certain positions between the puckered hexagonal layers, as shown in Fig. 1b.…”

“…1a,b (refs 13, 25, 26, 27). BP consists of weakly bonded phosphorene layers, within which covalently bonded P atoms form a honeycomb network, similar to graphene, but each layer is puckered with a zigzag-shaped edge along the x axis and an armchair-shaped edge along the y axis27.…”

“…At the same time, one can see a clear shift of all three modes to lower frequencies, corresponding to phonon softening within phosphorene layers. Such softening is expected as a result of the doping of phosphorene, which according to the first-principle calculations1325 should result in charge transfer of 0.8e − per P atom for monovalent and 1.5e − for divalent donors.…”

“…This is also in agreement with theory. The first-principle calculations25 found an optimum charge transfer for monovalent alkali atoms (Li and Na) of 0.8e − per P atom and for divalent Mg of 1.5 e − . It is reasonable to expect the same electron doping for K, Rb and Cs that were not covered in the calculations and a close doping for divalent Ca that is chemically similar to Mg and intercalates in twice smaller concentrations than alkali metals.…”

2D Black Phosphorus: from Preparation to Applications for Electrochemical Energy Storage

“…Theoretical studies to date have indicated that 2D BP is a promising anode material for SIBs 185, 217, 218. BP has a layered structure similar to that of graphite, but BP has a greater interlayer channel size (3.08 vs 1.86 Å in graphite), which implies that sodium can be stored between the 2D BP layers 105.…”