Mechanism of Efficient Adsorption of Na Atoms on Electron-Deficient Doped MoS2 for Battery Electrodes

Due to the similarities in electrochemical and physicochemical properties of sodium and lithium, sodium-ion batteries are an attractive substitute for lithium-ion batteries. The selection of appropriate electrode materials for $\mathrm{Na}$-ion batteries is an important step to achieve high stability and theoretical capacity. Here, the effects of heteroatom doping and charge variation on the ability of the ${\mathrm{Mo}\mathrm{S}}_{2}$ substrate to capture $\mathrm{Na}$ ions are studied using first-principles calculations. The results show that the interaction between $\mathrm{Na}$ ions and the ${\mathrm{Mo}\mathrm{S}}_{2}$ substrate is enhanced by electron deficiency or substituting a $\mathrm{S}$ atom with a dopant atom (X) with fewer valence electrons (X = $\mathrm{B}$, $\mathrm{Al}$, $\mathrm{Ga}$, $\mathrm{In}$, $\mathrm{C}$, $\mathrm{Si}$, $\mathrm{Ge}$, $\mathrm{Sn}$, $\mathrm{N}$, $\mathrm{P}$, $\mathrm{As}$, $\mathrm{Sb}$). In contrast, adding electrons to the ${\mathrm{Mo}\mathrm{S}}_{2}$ substrate weakens its interaction with $\mathrm{Na}$. We further analyze the diffusion barrier, open-circuit voltage, and theoretical capacity of hypothetical $\mathrm{Na}$-ion batteries using doped $X\text{\ensuremath{-}}{\mathrm{Mo}\mathrm{S}}_{2}$ (X = heteroatom) as electrode materials. We find that $\mathrm{Al}\text{\ensuremath{-}}$ or $\mathrm{Si}$-doped ${\mathrm{Mo}\mathrm{S}}_{2}$ can serve as good electrode materials for $\mathrm{Na}$-ion batteries, with a high theoretical capacity that exceeds 700 mAh/g. This work provides practical guidance for the development of electrode materials of $\mathrm{Na}$-ion batteries using two-dimensional materials.