Two-dimensional (2D) transition metal di-nitrides (TMN2) have been arousing great interest for their unique mechanic, electronic, optoelectronic, and magnetic properties. The recent successful growth of monolayer MSi2N4 (M = Mo...

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.

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