FLUORIDE ION SECONDARY BATTERY

A fluoride ion secondary battery, comprising: a positive electrode layer, a solid electrolyte layer, and a negative electrode layer, wherein the positive electrode layer comprises a positive electrode active material; the positive electrode active material comprises a composite fluoride comprising copper and a fluoride; the solid electrolyte comprises BaCaF; the negative electrode layer comprises a negative electrode active material, a conductive aid, and a solid electrolyte; the negative electrode active material comprises a lanthanoid fluoride doped with the alkaline earth metal fluoride; the conductive aid comprises a carbon material, the solid electrolyte contained in the negative electrode layer comprises at least one of BaCaFand SrCaF; and the lanthanoid fluoride doped with the alkaline earth metal fluoride forms a composite with the carbon material.