A battery includes a casing having two first peripheral portions and two second peripheral portions, a cell disposed within the casing, two conductive tabs electrically connected to the cell and exposed from at least one of the first peripheral portions, and an absorbent. Each of the second peripheral portions has a sealed region that has a sealed edge adjacent to the cell. The sealed region of at least one of the second peripheral portions has an inner sealed section disposed adjacent to the sealed edge, an outer sealed section, and an isolating section disposed between the inner sealed section and the outer sealed section. The absorbent is received in the isolating section for absorbing moisture or gas.