Prismatic secondary battery having improved stability

A prismatic secondary battery, comprising:

• a housing in which at least one side forms an opening;
• an electrode assembly comprising a plurality of unit cells, each unit cell comprising a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode, and the plurality of unit cells being stored inside the housing;
• a cap plate comprising a positive electrode terminal and a negative electrode terminal electrically connected to a positive electrode tab and a negative electrode tab of the electrode assembly, and is joined to seal the opening of the housing;
• and
• an electrolyte,
• wherein the electrode assembly further comprises a protective stack layer on an outermost part of the electrode assembly, comprising a positive electrode foil, a negative electrode foil, and a separator between the positive electrode foil and the negative electrode foil;
• and on outer surfaces of the positive electrode foil and the negative electrode foil, respectively,
• wherein the positive electrode foil and the negative electrode foil comprise a positive electrode foil tab and a negative electrode foil tab, respectively,
• wherein the electrode assembly further comprises a positive electrode tab and a negative electrode tab, and
• wherein the positive electrode foil tab is electrically connected to the positive electrode tab of the electrode assembly, and the negative electrode foil tab is electrically connected to the negative electrode tab of the electrode assembly.