A first separator (130) covers a first surface of a cathode electrode (110). The first separator (130) has a melting point of a first temperature. A second separator (140) covers a second surface of the cathode electrode (110). The second separator (140) has a melting point of a second temperature higher than the first temperature. An adhesive layer (132) is formed by melting a portion of the first separator (130). The adhesive layer (132) pastes the first separator (130) and the second separator (140) to each other.