Aqueous secondary battery

Abstract

The aqueous secondary battery of the present disclosure comprises: a positive electrode active material layer, an aqueous electrolyte, and a negative electrode active material layer, wherein the aqueous electrolyte contains an aqueous solvent and potassium polyphosphate which has two or more elemental phosphorus, and any one of potassium ion, proton, hydroxide ion, and polyphosphoric anion is a carrier ion, a positive electrode active material contained in the positive electrode active material layer has a monoclinic crystal structure represented by space group C2/m, is represented by composition formula MnO2·AxBy(H2O)z, and the A, B, and H2O are present in a space interposed between layers composed of Mn—O octahedrons, A is an alkali metal or alkali rare earth metal, B is an anion, 0<x<1, 0<y<1, and 0<z<2.

Dependencies are inferred from the claim text.