An electrode group stack comprising a stacked structure of electrode groups, each comprising a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, in which the electrode groups are stacked in a height direction on the basis of a plane such that the positive electrode and the negative electrode face each other in a state in which the separator is disposed between the positive electrode and the negative electrode, wherein the stacked structure of the electrode groups comprises a first electrode group and a second electrode group having different areas at an interface between the first electrode group and second electrode group, the second electrode group having a larger area than the first electrode group, and a ratio of capacity to area of the positive electrode and the negative electrode at the interface between the first electrode group and the second electrode group (N/P ratio) is equal to or greater than a ratio of capacity to area of a positive electrode and a negative electrode constituting the second electrode group (N/P ratio), wherein a loading level of a negative electrode constituting the first electrode group is equal to or greater than a loading level of the negative electrode constituting the second electrode group, wherein each of the electrode groups is a stacked type electrode group (300, 400) comprising a positive electrode plate, a negative electrode plate, and a plate-shaped one-unit separation sheet disposed between the positive electrode plate and the negative electrode plate, which is configured to have a structure in which the positive electrode plate and the negative electrode plate are stacked in the height direction on the basis of the plane in a state in which the separator is disposed between the positive electrode plate and the negative electrode plate, or wherein each of the electrode groups is a stacked and folded type electrode group comprising a positive electrode plate, a negative electrode plate, and a one-unit separation sheet disposed between the positive electrode plate and the negative electrode plate, which is configured to have a structure in which the positive electrode plate and the negative electrode plate are stacked in the height direction on the basis of the plane in a state in which the separation sheet is disposed between the positive electrode plate and the negative electrode plate, characterized in that the separation sheet covers sides of the electrode plates at which no electrode terminals are formed. the stacked structure of the electrode groups comprises a first electrode group and a second electrode group having different areas at an interface between the first electrode group and second electrode group, the second electrode group having a larger area than the first electrode group, and a ratio of capacity to area of the positive electrode and the negative electrode at the interface between the first electrode group and the second electrode group (N/P ratio) is equal to or greater than a ratio of capacity to area of a positive electrode and a negative electrode constituting the second electrode group (N/P ratio), wherein a loading level of a negative electrode constituting the first electrode group is equal to or greater than a loading level of the negative electrode constituting the second electrode group, wherein each of the electrode groups is a stacked type electrode group (300, 400) comprising a positive electrode plate, a negative electrode plate, and a plate-shaped one-unit separation sheet disposed between the positive electrode plate and the negative electrode plate, which is configured to have a structure in which the positive electrode plate and the negative electrode plate are stacked in the height direction on the basis of the plane in a state in which the separator is disposed between the positive electrode plate and the negative electrode plate, or wherein each of the electrode groups is a stacked and folded type electrode group comprising a positive electrode plate, a negative electrode plate, and a one-unit separation sheet disposed between the positive electrode plate and the negative electrode plate, which is configured to have a structure in which the positive electrode plate and the negative electrode plate are stacked in the height direction on the basis of the plane in a state in which the separation sheet is disposed between the positive electrode plate and the negative electrode plate, characterized in that the separation sheet covers sides of the electrode plates at which no electrode terminals are formed.