A rechargeable battery according to an exemplary embodiment may include: an electrode assembly including an electrode provided with a coated region and an uncoated region tab at opposite sides of a separator and configured to be spirally wound; an insulating case to accommodate and electrically insulate the electrode assembly; a case to accommodate the insulating case; and a cap plate including an electrolyte injection opening for injecting an electrolyte solution and combined with an opening of the case, wherein the insulating case may include: an internal electrolyte injection opening corresponding to the electrolyte injection opening; a pillar around the internal electrolyte injection opening protruding toward an inner side of the cap plate; and a valve flap that rotates via a hinge, induces injection of the electrolyte solution, and prevents backflow of the electrolyte solution.