A battery is composed of a positive electrode in which a positive electrode active material layer including a positive electrode active material is formed on a positive electrode collector, a negative electrode in which a negative electrode active material layer including a negative electrode active material is formed on a negative electrode collector, a separator provided between the positive electrode and the negative electrode, and an electrolyte impregnated in the separator. The battery further includes at least one of a heteropoly acid and a heteropoly acid compound as an additive at least in one of the positive electrode, the negative electrode, the separator, and the electrolyte.