Experimental study and simulation of electrochromic properties of TiO2-doped NiO films

TiO2-doped NiO films were prepared via magnetron sputtering in this paper. The experimental results suggest that the doping of TiO2 increases the size of NiO particles, then makes NiO particles grow along the (111) plane, and subsequently increases the surface roughness of the film. It finally decreases the film's impedance of charge transfer and ion diffusion. The NiO film doped with TiO2 at a power of 20 W has the most developed micromorphology and the most significant particle gaps, benefiting ion transfer and diffusion in the electrochromic process. At the 10th cycle, the optical contrast of TiO2-doped NiO film at a power of 20 W is 64.91 % (@ 550 nm), the coloration efficiency is 29.65 cm2/C, the coloring time and bleaching time are τc = 6.77 s, τb = 2.94 s, respectively. After the 1000 cycles, its charge capacity decreased by −0.958 % compared with the charge capacity at the 10th cycle, expressing excellent cycle stability. The first-principle calculation results suggested that the Ti doping could change the NiO lattice structure, and the doping of the Ti element could reduce the migration barrier of Li+ in NiO film, and facilitate the migration of Li+ in NiO film, conforming with the experimental results.