NiX₂ (X = S, Se, and Te) Monolayers: Promising Anodes in Li/Na-Ion Batteries and Superconductors

Abstract

Based on the density functional theory calculations, we report the stability, electron structure, and potential applications in single-layer (SL) NiX2 (X = S, Se, and Te) that show high thermal, dynamical, and mechanical stability and possess ultralow isotropic Young’s modulus. Moreover, these NiS2, NiSe2, and NiTe2 monolayers have high energy storage capacities of 874, 496, and 342 mA h g–1 and low diffusion energy barriers of 0.23/0.24/0.27 and 0.12/0.13/0.12 eV when used as anodes in lithium-ion batteries and sodium-ion batteries, respectively. SL NiS2 and NiSe2 show semiconducting traits in their freestanding crystals. Specifically, the 2D NiTe2 monolayer is determined to be an intrinsic superconductor with a transition temperature (Tc) of ∼2.24 K. The Tc can be improved to 5.48 K when subjected to an in-plane compressive strain of 6%. These results enrich the family of transition metal-based 2D materials with multifunctionality and facilitate further experimental efforts toward next-generation nanodevices.