High Ion Mobility and Capacity of Monolayer GaS as a Promising Anode Battery Material
Layered gallium sulphide (GaS) with hexagonal symmetry is a typical metal mono-chalcogenide and is mechanically stable under tension. In this work, we used the first-principles density functional theory to study the performance of monolayer (ML) GaS as anode material for Li, Na, K, Mg, and Al-ion batteries. The most stable binding sites for the metal atoms on ML GaS are all in the hollow sites, and the Fermi level of ML GaS moves upward into the conduction band after adsorption of Li, Na, K, and Al atoms, showing a semiconductor-to-metal transition of ML GaS, with exception of Mg atom. The binding energies of the metal atoms with ML GaS are all negative at all the studied densities, indicating a steady adsorbing process. The Li, Na, K, and Al ions prefer to move along the zigzag direction on ML GaS, with relatively low diffusion barrier heights of 0.110, 0.078, 0.037, and 0.034 eV, respectively. Such low diffusion barriers make ML GaS have a high rate capacity. The maximum theoretical specific capacities for Li, Na, K, and Al-ion batteries are 526.74, 32.92, 32.92, and 98.76 mAh/g, respectively. Noticeably, the theoretical specific capacity of ML GaS for Li-ion batteries (LIBs) is even higher than the theoretical one (372 mAh/g) of commercially used graphite. Besides, an appropriate average open circuit voltage of 0.53 V is generated for ML GaS based LIBs. Our study suggests that ML GaS is a suitable anode material for LIBs.