The electronic structure of nickel iodide monolayer in NiI2/ScX2 (X = S, Se and Te) and NiI2/NiTe2 heterostructures was investigated by density functional theory (DFT). The spin-asymmetric semiconducting behavior of NiI2 monolayer in these interfaces was observed. The width of the band gap of the NiI2 monolayer practically does not change in heterostructures and remains at the level of 1.7 and 3.0 eV for minor and major spin channels, respectively. The NiI2 layer can be p-doped by stacking with ScX2 dichalcogenides. On the contrary, charge transfer (~0.01 |e| per f.u.) from NiTe2 leads to n-doping of NiI2. As a result, the Fermi level shifts up to the area of NiI2 conduction band with spin down carriers only, which gives prospects of using this material in spin filter applications. The electronic structure of NiI2/ScTe2 under isotropic deformation in the plane remains the same under tension and compression within 5%, except for a small change in the band gap in the composite layers of NiI2 within 25%. This allows one to conclude about the stability of the electronic properties under deformations, which gives possibility to use the heterostructures in flexible electronics devices.