ACTIVE MATERIAL INCLUDING METAL COMPOSITE FLUOEIDE FOR FLUORIDE ION SECONDARY BATTERY, AND FLUORIDE ION SECONDARY BATTERY USING THE SAME

An active material for a fluoride ion secondary battery includes a metal composite fluoride. The metal composite fluoride contains at least one metal selected from the group consisting of an alkali metal, an alkaline earth metal, scandium, yttrium, and a lanthanoid; a first transition metal; a second transition metal different from the first transition metal; and fluorine.