A secondary battery of a secondary battery module includes an electrode assembly including a first electrode plate, a second electrode plate, and a separator between the first and second electrode plates, a case accommodating the electrode assembly, a cap plate coupled to the case, and first and second terminals each having a flat shape and each coupled to the cap plate. The first terminal may include a first terminal plate electrically coupled to the first electrode plate and formed of a first material. The second terminal may include a second terminal plate electrically coupled to the second electrode plate and further including a first part formed of a second material different from the first material, and a second part formed integrally with the first part and formed of the first material.