A battery includes a unit cell including an electrode layer and a counter electrode layer; a first current collector disposed on a side of the electrode layer opposite to the counter electrode layer and electrically connected to the electrode layer; a first solid electrolyte layer disposed in contact with a lateral side of the unit cell; and a first copper sulfide layer containing copper sulfide. The first current collector contains copper. The first copper sulfide layer is disposed between the first current collector and the first solid electrolyte layer and in contact with the first current collector and the first solid electrolyte layer.