SECONDARY BATTERY

A secondary battery includes: a case accommodating an electrode assembly; a cap plate sealing the case; a negative electrode terminal and a positive electrode terminal on the cap plate; a first negative-electrode-current-collector plate extending along a lower side of the cap plate between the electrode assembly and the cap plate and having a first end electrically connected to the negative electrode plate and a second end electrically connected to the negative electrode terminal; and a first positive-electrode-current-collector plate extending along the lower side of the cap plate between the electrode assembly and the cap plate and having a first end electrically connected to the positive electrode plate and a second end electrically connected to the positive electrode terminal. The first positive-electrode-current-collector plate has a greater thickness than the first negative-electrode-current-collector plate, and the first negative-electrode-current-collector plate has a first protrusion that locally protrudes toward the electrode assembly.