A theoretical study of the optical properties of new NiO-Ni nanoshells (NSs) with different radii and shell thicknesses dispersed in silica was carried out in a wide range of ultraviolet, visible and infrared optical spectra from 200 nm to 5000 nm. The established remarkable tunability of absorption (extinction) spectrum and the high absorption properties of NiO-Ni NSs in the presented spectral ranges are very interesting for use in various photothermal and laser high-temperature technologies, including applications in light-to-heat conversion, solar thermal energy, laser nanomedicine and others.