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

Based on the density functional theory calculations, we report the stability, electron structure, and potential applications in single-layer (SL) NiX 2 (X = S, Se, and Te) that show high thermal, dynamical, and mechanical stability and possess ultralow isotropic Young’s modulus. Moreover, these NiS 2, NiSe 2, and NiTe 2 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 NiS 2 and NiSe 2 show semiconducting traits in their freestanding crystals. Specifically, the 2D NiTe 2 monolayer is determined to be an intrinsic superconductor with a transition temperature ( T c ) of ∼2.24 K. The T c 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.