Ion incorporation on the Zr₂CS₂ MXene monolayer towards better-performing rechargeable ion batteries

We study Li and, for the first time, K, Mg and Zn ion intercalation on the surface of the Zr₂CS₂ MXene monolayer, taking advantage of the fact that the S terminations lower the diffusion barrier of the ions. We find that the Zr₂CS₂-Li, Zr₂CS₂-K and Zr₂CS₂-Mg structures are identical, with only Zr₂CS₂-Zn differing as to the position of the ion and Zn detaching from the MXene's surface during migration. Regarding the use of Zr₂CS₂ as anode material in ion batteries, we examine as criteria the adsorption energy, diffusion barrier energy and open-circuit voltage for each of the ions considered. We show that the K ion has higher mobility, as well as lower open-circuit voltage. These results lead to the fact that KIB have fastest charge/discharge rates and higher energy density than LIB, MIB, and ZIB when it comes to the use of S-terminated, Zr-based materials as negative (anode) electrodes. KIB, therefore, seem the best alternative to LIB, especially after taking under consideration K's low cost and abundance of resources.