A battery module includes: a plurality of rechargeable batteries; and a connector for connecting a first terminal of one of the plurality of rechargeable batteries and including a first material, to a second terminal of another one of the plurality of rechargeable batteries and including a second material, wherein welded portions connect the connector to the first terminal and the second terminal, respectively, at least one of the welded portions including a nugget zone including a mixture of the respective materials of the connector and a corresponding one of the first terminal or the second terminal.