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 potentialapplications in single-layer (SL) NiX2(X = S, Se, and Te) thatshow high thermal, dynamical, and mechanical stability andpossess ultralow isotropic Young's modulus. Moreover, these NiS2,NiSe2, and NiTe2monolayers have high energy storage capacitiesof 874, 496, and 342 mA h g-1and low diffusion energy barriers of0.23/0.24/0.27 and 0.12/0.13/0.12 eV when used as anodes inlithium-ion batteries and sodium-ion batteries, respectively. SLNiS2and NiSe2show semiconducting traits in their freestandingcrystals. Specifically, the 2D NiTe2monolayer is determined to bean intrinsic superconductor with a transition temperature (Tc)of similar to 2.24 K. TheTccan be improved to 5.48 K when subjected to anin-plane compressive strain of 6%. These results enrich the family of transition metal-based 2D materials with multifunctionality andfacilitate further experimental efforts toward next-generation nanodevices