CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of the priority of Korean Patent Application No. 10-2018-0046762, filed on Apr. 23, 2018, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an electrode assembly and a method for manufacturing the same, and more particularly, to an electrode assembly having a curved surface and a method for manufacturing the same.

BACKGROUND ART

As the demands for electronic devices and the consumer's demands for electronic devices become increasingly diverse, specifications required for secondary batteries that are mounted on the electronic devices and repeatedly chargeable and dischargeable are also diversified. For example, recently, to improve the grip feeling when the user for utilizing the electronic device holds the electronic device by using his/her hand, the electronic device may be required to have a curved shape deviating from the existing angular shape. For this, the secondary battery may also be required to have a curved shape deviating the existing shape. Alternatively, to maximize the utilization of the internal space of the electronic device, it is required that the shape of the secondary battery has an irregular shape such as the curved shape or the like deviating the existing regular shape.

To manufacture the secondary battery having the curved shape, it is generally necessary to press an outer surface of an electrode assembly by using a pressing press having a curved surface. However, according to the related art, there have been various problems in the process of pressing the outer surface of the electrode assembly by using the pressing press to form the curved surface.

For example, an electrode and a separator are in a state of being bonded to each other within the electrode assembly before being pressed by the pressing press. Thus, even if the electrode assembly is pressed by the pressing press to form the curved shape, the curved surface may not be maintained due to the bonding force between the electrode and the separator before being pressed by the pressing press, and thus, the curved surface may return to the state before being pressed. This problem tends to become worse as a radius of curvature of the curved surface formed by the pressing press decreases (i.e., as the electrode assembly is more bent by the pressing press).

Also, when a curved surface is formed by pressing the stacked type electrode assembly in which the electrode and the separator are alternately stacked, since a constituent for supporting the electrode assembly to maintain the curved shape of the stacked type electrode assembly is not provided, the electrode and the separator within the electrode assembly may be delaminated. This problem also tends to become worse as the radius of curvature of the curved surface formed by the pressing press decreases.

The above problems have been obstacles to manufacture an electrode assembly, on which a curved surface having a relatively small curvature radius is formed, and a secondary battery.

DISCLOSURE OF THE INVENTION

Technical Problem

Therefore, an object to be solved by the present invention is to manufacture an electrode assembly on which a curved surface having a curvature radius that is relatively less than that of an electrode assembly according to the related art.

Technical Solution

To achieve the above object, according to an aspect of the present invention, an electrode assembly may include an electrode stack including a plurality of radical units, each radical unit including at least one electrode and at least one separator, wherein the plurality of radical units are sequentially stacked, wherein at least a portion of a circumference of the electrode stack is surrounded by a wound separator, wherein a curved surface having a curvature radius is formed on a top or bottom surface of the electrode stack, and wherein the separator surrounding at least the portion of the circumference of the electrode stack surrounds the curved surface formed on the electrode stack to maintain a relative distance between the radical units adjacent to each other.

The curvature radius may range between 70 mm to 110 mm.

The plurality of radical units may include a first bi-cell of which a positive electrode of the at least one electrode is disposed on outermost ends thereof, and a second bi-cell of which a negative electrode of the at least one electrode is disposed on opposite outermost ends thereof, wherein the electrode stack has a structure in which the first bi-cell and the second bi-cell are alternately stacked, and wherein a separate separator is disposed between the first bi-cell and the second bi-cell.

The wound separator surrounding at least the portion of the circumference of the electrode stack may be separated from the at least one separator of each radical unit and the separate separator disposed between the first bi-cell and the second bi-cell.

The wound separator surrounding at least the portion of the circumference of the electrode stack may surround the entire circumference of the electrode stack.

To achieve the above object, according to another aspect of the present invention, a method for manufacturing an electrode assembly may include a step of preparing a plurality of first bi-cells of which a positive electrode is disposed on opposite outermost ends of each first bi-cell and a plurality of second bi-cells on which a negative electrode is disposed on opposite outermost ends of each second bi-cell; a stacking step of alternately stacking each of the first bi-cells, a separate separator, and each of the second bi-cells to manufacture an electrode stack; a separator winding step of providing a wound separator to surround at least a portion of a circumference of the electrode stack; and a curved surface formation step of pressing the electrode stack by using a pressing press having a curved surface to form a curved surface on a top or bottom surface of the electrode stack, wherein, after the curved surface formation step, the wound separator surrounding at least the portion of the circumference of the electrode stack surrounds the curved surface formed on the electrode stack to maintain a relative distance between the first and second bi-cells adjacent to each other.

In the curved surface formation step, the curved surface formed on the top or bottom surface of the electrode stack may have a curvature radius of 70 mm to 110 mm.

In the stacking step, the first bi-cell may be disposed on opposite outermost ends of the electrode stack, and a single-sided positive electrode on which a positive electrode active material is applied to only one surface of a collector is provided as one of the positive electrodes disposed on one of the outermost ends of the first bi-cell, which is disposed on outermost ends of the electrode stack.

The first bi-cell may have a structure in which one of the positive electrodes, a separator, a negative electrode, a separator, and an other of the positive electrodes are disposed, and the second bi-cell may have a structure in which one of the negative electrodes, a separator, a positive electrode, a separator, and an other of the negative electrodes are disposed.

In the stacking step, eight first bi-cells and seven second bi-cells may be provided in the electrode stack.

In the separator winding step, the wound separator surrounding at least the portion of the circumference of the electrode stack may be a separator that is separated from the separators of the first and second bi-cells and the separate separator disposed between the first bi-cell and the second bi-cell.

In the separator winding step, the wound separator surrounding at least the portion of the circumference of the electrode stack may surround the entire circumference of the electrode stack.

In the curved surface formation step, the pressing press may press the electrode stack at a temperature of 60° C. to 100° C.

In the curved surface formation step, the pressing press may press the electrode stack at a pressure of 400 kgf to 800 kgf.

In the curved surface formation step, the pressing press may press the electrode stack for a time period of 40 seconds to 70 seconds.

Advantageous Effects

According to the present invention, the electrode assembly on which the curved surface having the curvature radius that is relatively less than that of the electrode assembly according to the related art, may be manufactured.

