High Li+-Ion Storage Capacity and Double-Electrochromic Behavior of Sol−Gel-Derived Iron Oxide Thin Films with Sulfate Residues

FeSO4·7H2O was precipitated with ammonia solution in the presence of H2O2 as an oxidant. The precipitate was washed slightly with deionized water and then peptized with acetic acid (ca. 60 mol %) t...