Battery pack exhibiting enhances structural strength

A battery pack comprising:

• a bare cell having a can that receives an electrode assembly, wherein the can of the bare cell also has a pair of first side portions opposite to each other, a pair of second side portions opposite to each other, and a pair of plane portions opposite to each other, the second side portions and the plane portions being connected to ends of the first side portions;
• a protection circuit module electrically connected to the bare cell;
• an inner frame provided between the bare cell and the protection circuit module, the inner frame having at least a pair of ribs opposite to each other while extending over a part of the plane portions of the can of the bare cell wherein the inner frame covers at least a portion of one of the first side portions of the can of the bare cell and at least a portion of the second side portions of the can of the bare cell and wherein the ribs extend over the part of the plane portions of the can of the bare cell adjacent the one of the first side portions so as to directly contact the plane portions of the can and the second side portions of the can of the bare cell;
• and
• an outer frame for accommodating the bare cell, the protection circuit module and the inner frame, the outer frame being formed so that the pair of plane portions of the bare cell are exposed and so that the outer frame overlies the inner frame over at least a portion of the second side portions of the bare cell wherein at least one of the pair of ribs of the inner frame extending over the part of the plane portion defines at least one protrusion that extends outward from the plane of the plane portion of the cells and wherein the outer frame defines an edge with at least one opening formed so as to extend from the edge and so as to be parallel to the plane of the plane portions of the bare cell and wherein the at least one protrusion is positioned within the at least one opening in the outer frame.