Secondary battery including plurality of electrode assemblies

A secondary battery comprising:

• a first electrode assembly comprising a first cathode, a first separator and a first anode;
• and
• a second electrode assembly comprising a second cathode, a second separator and a second anode,
• wherein the second electrode assembly is stacked on the first electrode assembly,
• wherein an electrode plate area of the second electrode assembly is smaller than an electrode plate area of the first electrode assembly,
• wherein a cross-sectional thickness of the second electrode assembly is larger than a cross-sectional thickness of the first electrode assembly,
• wherein the electrode plate area of the first electrode assembly and the electrode plate area of the second electrode assembly are expressed by the following Equation:
• 0.5≦S2/S1≦0.98
• where S1 is the electrode plate area of the first electrode assembly, and S2 is the electrode plate area of the second electrode assembly,
• wherein the cross-sectional thickness of the first electrode assembly and the cross-sectional thickness of the second electrode assembly are expressed by the following Equation:
• 0≦I1/I2≦0.2
• where I1 is the cross-sectional thickness of the first electrode assembly, and I2 is the cross-sectional thickness of the second electrode assembly, and
• wherein the electrode material used for the second electrode assembly has a higher efficiency than that used for the first electrode assembly.