NiO　films　are　prepared　by　sol-　gel　method.　With　the　increasing　of　annealing　temperature,　the　change　from　the　amorphous　to　the　crystalline　nature　of　the　NiO　films　is　observed.　Amorphous　NiO　films　have　higher　electrochromic　activity　as　well　as　poor　reversibility.　However,　higher　crystalline　film　annealed　at　400　degrees　C　leads　to　better　reversibility　with　lower　optical　modulation.　The　NiO　film　annealed　at　350　degrees　C　exhibits　noticeable　electrochromic　performance,　such　as　the　highest　observed　optical　modulation　of　50.7%　at　550　nm,　long-term　durability,　high　coloration　efficiency　(71.4　cm(2)　C-1)　and　excellent　reversibility　(Q(ex)/Q(in)　=　92.3%).　(C)　2016　Elsevier　B.V.　All　rights　reserved.