Provided is a lithium ion secondary battery that has superior battery performance and that is a battery provided with a positive electrode formed using a composition comprising an aqueous solvent. The battery is provided with a positive electrode and a negative electrode, and the positive electrode is provided with a positive electrode collector and a positive electrode mixed layer formed on the collector and containing at least a binding material and a positive electrode active material. The surface of the positive electrode active material is covered by a hydrophobic coating film, and the binding material dissolves or disperses in the aqueous solvent.