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Nickel oxide (NiO) has great application prospects as a counter electrode in electrochromic devices, such as smart windows and displays. However, the cycle stability and electrochromic properties of pure NiO films are rather poor in lithium ion based non-aqueous electrolyte. To improve these properties, Li–Ti co-doped NiO films were prepared by sol–gel spin coating technique. Compared with undoped NiO films, Li and Ti doping deteriorate the symmetry of NiO cubic phase, increase lattice disorder and change the valence state of nickel in the films. The investigations of NiO-based films in LiClO 4 /PC electrolyte reveal enhancement of electrochromic properties and cycle stability with Li–Ti co-doping. Finally, electrochromic devices assembled with poly(3,4-(2,2-dimethylpropylenedioxy)thiophene) and Li–Ti–NiO films exhibit rapid color change within 1 s, excellent optical variation for about 56% at 580 nm and high stability up to 1,000,000 cycles. [ABSTRACT FROM AUTHOR]

Vanadium pentoxide (V 2 O 5 ) is a promising material for constructing electrochromic devices, due to its outstanding properties of lithium ion intercalation/deintercalation. However, its poor cyclic stability limits practical applications. We report here that V 2 O 5 films gain significantly improved cyclic stability by doping with titanium (Ti) and perform well in WO 3 -based electrochromic devices. V 2 O 5 films were fabricated by spin coating with a vanadium triisopropoxy oxide solution followed by heat treatment. X-ray diffraction studies reveal that introducing the Ti element reduces the crystallinity of a V 2 O 5 film and distorts its layer structure. The cyclic stability of the V 2 O 5 films increases as the doped Ti content increases. The electrochromic device assembled with an optimized V 2 O 5 electrode (V:Ti = 2:1) has lasted 200,000 cyclic switching times between the lowest (2%) and highest (62%) transmittance with no significant degradation of performance. [ABSTRACT FROM AUTHOR]