A composite body includes a positive electrode active material composed of a lithium composite metal oxide containing Li and at least one type of transition metal, and an electrolyte, wherein the positive electrode active material is present on one surface of the composite body, the one type of transition metal is Co, and the molar ratio of Co (cobalt) in the positive electrode active material (lithium cobalt oxide) present on the one surface is equal to or more than the molar ratio of O (oxygen).