The application provides an
anode foil and a preparation method thereof. The preparation method comprises the following steps: providing an unformed foil, wherein the unformed foil comprises an
aluminum foil base material and an aluminum
powder sintering layer arranged on the surface of the
aluminum foil base material; and sequentially performing the following processes on the unformed foil: water boiling, first-stage
chemical conversion, second-stage
chemical conversion, third-stage
chemical conversion, power feeding treatment, fourth-stage chemical conversion, fifth-stage chemical conversion, first-stage heat treatment, first chemical conversion repair, first
phosphoric acid treatment, second chemical conversion repair, second-stage heat treatment, third chemical conversion repair and second
phosphoric acid treatment. The solutes of the
electrolyte of the first-stage chemical conversion, the second-stage chemical conversion and the third-stage chemical conversion comprise
citric acid, triammonium citrate,
adipic acid,
ammonium adipate,
salicylic acid,
hypophosphite,
boric acid and
ammonium salt, and the
solvent is water. The solutes of the
electrolyte of the fourth-stage chemical conversion and the fifth-stage chemical conversion comprise
citric acid, triammonium citrate,
sebacic acid,
ammonium sebacate,
salicylic acid,
sodium hypophosphite,
boric acid and ammonium salt, and the
solvent is water. An
anode foil prepared by the preparation method has a high specific capacity and a small hydration leakage current.