METAL-ION SECONDARY BATTERY

An object of the present disclosure is to provide a secondary battery having excellent cyclability by using a sulfur-based active material as a negative-electrode active material while preventing a reaction between an eluted polysulfide and a positive electrode. The metal-ion secondary battery comprises a negative electrode comprising a sulfur-containing compound as a negative-electrode active material, a positive electrode and an electrolyte, and has a polymer gel layer on a surface of the positive electrode.