CN117501491A - Electrode assembly and secondary battery including the same - Google Patents

Abstract

An electrode assembly according to an embodiment of the present invention may include: a cell stack part including a plurality of unit cells stacked on each other, the unit cells having electrodes and separators alternately stacked and integrally coupled; and a sub-unit cell stacked on the cell stack portion, including a polymer film at an outermost portion thereof, and having electrodes and separators alternately stacked and integrally coupled with the polymer film. The polymer film may be flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in the lateral direction and the central portion is less than 1mm. The thickness of the polymer film may be greater than or equal to the thickness of the separator.

Description

Electrode assembly and secondary battery including the same

Technical Field

Cross Reference to Related Applications

The present application claims the priority of korean patent application No. 10-2021-0109087 filed on month 8 of 2021 and korean patent application No. 10-2022-0102965 filed on month 17 of 2022, the contents of which are incorporated herein by reference in their entirety.

The present invention relates to an electrode assembly and a secondary battery including the same, and more particularly, to a stacked electrode assembly and a secondary battery including the same.

Background

In general, secondary batteries are chargeable and dischargeable, unlike primary batteries, which are not chargeable and are widely used in electronic devices such as mobile phones, notebook computers, camcorders, etc., electric vehicles, etc. In particular, since lithium secondary batteries have a larger capacity than nickel-cadmium batteries or nickel-hydrogen batteries and have a high energy density per unit weight, the degree of utilization thereof is rapidly increasing.

Lithium secondary batteries are classified according to the structure of an electrode assembly of a cathode/separator/anode structure. Typically, the electrode assembly includes: a rolled core type electrode structure having a structure in which a long sheet-like positive electrode and a negative electrode are wound with a separator interposed therebetween; a simple stacked electrode assembly in which a plurality of positive and negative electrodes (each of which is cut into units having a predetermined size) are sequentially stacked with a separator interposed therebetween; a laminated and stacked electrode assembly in which a plurality of unit cells manufactured through a lamination process are stacked; and a stacked/folded electrode having a structure in which a plurality of unit cells (each of the positive and negative electrodes is cut into units having a predetermined size) stacked with a separator interposed therebetween are wound.

In particular, in the case of the laminated and stacked electrode assembly, since the electrodes and the separators are not stacked one by one, the manufacturing time is shortened, the productivity is high, and the plurality of electrodes are precisely aligned, thus having the advantage of high efficiency and being widely used.

However, in the conventional laminated and stacked electrode assembly, a separator is generally disposed on the outermost layer. However, in this case, bending occurs in the electrode assembly, which may cause internal short circuits.

Disclosure of Invention

Technical problem

An object of the present invention is to provide an electrode assembly with minimized bending and a secondary battery including the same.

Technical proposal

The electrode assembly according to an embodiment of the present invention may include: a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators; and a sub-unit cell stacked on the cell stack portion and provided with a polymer film at an outermost side thereof, and in which electrodes and separators alternately stacked are integrally coupled together. The polymer film may be flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm. The thickness of the polymer film may be equal to or greater than the thickness of the separator.

The polymer film may have a stronger adhesion within the subunit cell than between the subunit cell and the cell stack.

The thickness of the polymer film may be less than three times the thickness of the separator

The polymer film may be stacked on the electrode.

The polymer film may include at least one of polyethylene terephthalate, polyvinyl chloride, polyamide, polyimide, polyaramid, or polypropylene.

The number of electrodes disposed in the subunit cells may be less than the number of electrodes disposed in the unit cells.

The polymer film may be disposed at one side of the outermost side of the electrode assembly, and the outermost separator of the cell stack may be disposed at the other side of the outermost side of the electrode assembly.

The electrode assembly according to an embodiment of the present invention may include: a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators; a first sub-unit cell stacked on one side of the cell stack portion and provided with a first polymer film at an outermost side thereof, and electrodes and separators alternately stacked in the first sub-unit cell are integrally coupled together with the first polymer film; and a second sub-unit cell stacked on the other side of the cell stack portion and provided with a second polymer film at the outermost side thereof, and electrodes and separators alternately stacked in the second sub-unit cell are integrally coupled together with the second polymer film. The first polymer film may be flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm. The thickness of each of the first and second polymer films may be equal to or greater than the thickness of the separator.

The second polymer film may be flat, or a central portion of the second polymer film in the width direction is convexly curved toward opposite sides of the cell stack portion instead of both edges of the second polymer film.

The secondary battery according to an embodiment of the present invention may include: a pouch-type battery case; and an electrode assembly accommodated in the battery case. The electrode assembly may include: a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators; and a sub-unit cell stacked on the cell stack portion and provided with a polymer film at an outermost side thereof, and in which electrodes and separators alternately stacked are integrally coupled together. The polymer film may be flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm. The thickness of the polymer film may be equal to or greater than the thickness of the separator.

The polymer film may face an inner surface of one side of the battery case, and an outermost separator of the cell stack may face an inner surface of an opposite side of the battery case.

The secondary battery according to an embodiment of the present invention may include: a pouch-type battery case; and an electrode assembly accommodated in the battery case. The electrode assembly may include: a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators; a first sub-unit cell stacked on one side of the cell stack portion and provided with a first polymer film at an outermost side thereof, and electrodes and separators alternately stacked in the first sub-unit cell are integrally coupled together with the first polymer film; and a second sub-unit cell stacked on the other side of the cell stack portion and provided with a second polymer film at the outermost side thereof, and electrodes and separators alternately stacked in the second sub-unit cell are integrally coupled together with the second polymer film. The first polymer film may be flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm. And each of the first and second polymer films may have a thickness equal to or greater than a thickness of the separator.

The first polymer film may face an inner surface of one side of the battery case, and the second polymer film may face an inner surface of an opposite side of the battery case.

Advantageous effects

According to the preferred embodiment, since the polymer film has a sufficiently high rigidity, bending of the electrode assembly can be effectively prevented or minimized.

Further, in the case where the polymer film is disposed only at the outermost sides of the electrode assembly, the polymer film may be disposed at one side concavely curved on both the outermost sides of the electrode assembly. As a result, adhesion between the polymer film and the electrode can be stably maintained, and a bent state of the electrode assembly can be minimized.

In addition, in the case of an embodiment in which the polymer film is disposed only at one side of the outermost side of the electrode assembly, there may be an advantage in that the reduction of the energy density of the electrode assembly is minimized, and the electrode assembly is manufactured using a single type of sub-unit cell.

In addition, in the case of the embodiment in which the polymer films are disposed at the two outermost sides of the electrode assembly, bending of the electrode assembly can be more effectively prevented or minimized.

Further, effects obvious to those skilled in the art can be predicted from the configuration according to the embodiment of the present invention.

Drawings

Fig. 1 is a plan view of a secondary battery according to an embodiment of the present invention.

Fig. 2 is an exploded perspective view illustrating a secondary battery according to an embodiment of the present invention;

fig. 3 is a sectional view illustrating a stacked structure of an electrode assembly according to an embodiment of the present invention.

Fig. 4 is a sectional view illustrating a modification of the electrode assembly shown in fig. 3.

Fig. 5 is an enlarged side view illustrating a polymer film of an electrode assembly according to an embodiment of the present invention.

Fig. 6 is a sectional view illustrating a stacked structure of an electrode assembly according to another embodiment of the present invention.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily perform the present invention. The invention may, however, be embodied in several different forms and is not limited or restricted by the examples below.

For the purpose of clearly explaining the present invention, detailed descriptions of related known techniques, which are not related to the description or may unnecessarily obscure the gist of the present invention, are omitted, and in the present specification, reference numerals are added to the parts in each drawing. In this case, the same or similar reference numerals are assigned to the same or similar elements throughout the specification.

Furthermore, the terms or words used in the present specification and claims should not be construed restrictively as ordinary meanings or dictionary-based meanings, but should be construed as meanings and concepts conforming to the scope of the present invention based on the concept that the inventors can properly define terms in order to describe and explain their inventive principles in the best way.

Fig. 1 is a plan view of a secondary battery according to an embodiment of the present invention, and fig. 2 is an exploded perspective view illustrating the secondary battery according to the embodiment of the present invention.

The secondary battery 1 according to the present invention may include an electrode assembly 100 and a pouch-type battery case 200 accommodating the electrode assembly 100.

The electrode assembly 100 may include a plurality of electrodes 130 and a plurality of separators 140 alternately stacked, and a polymer film 150 disposed at the outermost side. The plurality of electrodes 130 may include first electrodes 131 and second electrodes 132, and the first electrodes 131 and the second electrodes 132 are alternately stacked with the separator 140 interposed therebetween and have polarities opposite to each other. For example, the first electrode 131 may be a positive electrode, and the second electrode 132 may be a negative electrode.

Further, the polymer film 150 may be disposed at least one of the two outermost sides of the electrode assembly 100, and may be stacked on the electrode 130.

The detailed construction of the electrode assembly 100 will be described later in detail.

The electrode assembly 100 may include a plurality of electrode tabs 160 welded to each other. The plurality of electrode tabs 160 may be connected to the plurality of electrodes 130 and protrude from the electrode assembly 100 to the outside to serve as a passage through which electrons move between the inside and the outside of the electrode assembly 100.

The electrode tab 160 connected to the first electrode 131 and the electrode tab 160 connected to the second electrode 132 may protrude in different directions with respect to the electrode assembly 10. For example, the electrode tab 160 connected to the first electrode 131 and the electrode tab 160 connected to the second electrode 132 may protrude in opposite directions with respect to the overall length direction of the electrode assembly 100. However, the present invention is not limited thereto, and the electrode tab 160 connected to the first electrode 131 and the electrode tab 160 connected to the second electrode 132 may protrude in parallel with each other.

The lead 170 supplying power to the outside of the secondary battery 1 may be connected to the plurality of electrode tabs 160 by spot welding or the like. The lead 170 may have one end connected to the plurality of electrode tabs 160 and the other end protruding to the outside of the battery case 200.

A portion of the electrode lead 170 may be surrounded by the insulating member 180. For example, the insulating member 180 may include an insulating tape. Insulating member 180 may be disposed between a pair of steps 240 of battery case 200 to be described later, and in this state, the pair of steps 240 may be thermally fused with each other. In this case, a portion of a pair of terraces 240 may be thermally fused to insulating member 180. Accordingly, the insulating member 180 may prevent the power generated from the electrode assembly 100 from flowing to the battery case 200 through the lead 170 and may maintain the sealing of the battery case 200.

The battery case 200 may be provided by sealing a pair of cases 210 and 22 connected to each other by a fold 220. However, the present invention is not limited thereto, and the pair of cases 210 may be sealed in a state of being separated from each other to provide the battery case 200.

Further, at least one of the pair of housings 210 may be provided with a receiving portion 230 having a concave shape. Receptacle 230 may be recessed a predetermined depth from landing 240 to define recessed space S1. Next, a case where the accommodating portion 230 is defined in each of the pair of housings 210 will be described as an example.

The receiving parts 230 of the pair of housings 21 and 210 may be connected to each other by the folding part 220. That is, the folded portion 220 may be disposed between the pair of receiving portions 230, and in the unfolded state of the pouch 20, the folded portion 220 may be referred to as a bridge. The folded portion 220 may be elongated in the entire length direction of the battery case 200.

In a state in which the electrode assembly 100 is received in the recess space S1 of any one of the receiving parts 230, the folded part 220 may be folded such that the pair of receiving parts 230 face each other. Accordingly, the other receiving part 230 may cover the electrode assembly 100 from above. That is, the recess spaces S1 of the receiving part 230 may communicate with each other, and the electrode assembly 100 may be received in the recess spaces S1.

Each housing 210 may include a landing 240 disposed about receptacle 230. In more detail, a landing 240 may be coupled to an upper end of an outer circumferential surface of the receiving part 230. Landing 240 of each housing 210 may have an approximationIs a shape of (c).

In a state in which the electrode assembly 100 is disposed between the pair of receiving parts 230 of the battery case 200, the folding part 220 may be folded, and the pair of stages 240 may be fused with each other to provide a sealing part, thereby providing the secondary battery 1 in which the pair of cases 210 are sealed with each other.

Fig. 3 is a sectional view illustrating a stacked structure of an electrode assembly according to an embodiment of the present invention, and fig. 4 is a sectional view illustrating a modification of the electrode assembly shown in fig. 3.

The electrode assembly 100 according to an embodiment of the present invention may include a cell stack 101 and a sub-unit cell 120 stacked on the cell stack 101, the cell stack 101 including a plurality of unit cells 110 stacked on each other.

The cell stack 101 may have a structure in which a plurality of unit cells 110 are stacked such that a plurality of electrodes 130 and a plurality of separators 140 are alternately stacked.

The cell stack part 101 may have a structure in which one type of unit cells 110 are repeatedly stacked as shown in fig. 3, or a structure in which two types of unit cells 110 are stacked in a predetermined order as shown in fig. 4.

Each unit cell 110 may be provided by integrally coupling the electrodes 130 and the separators 140, which are alternately stacked, with each other. That is, the electrode 130 and the separator 140 of each unit cell 110 may be adhered to each other through a lamination process or a rolling process.

Further, the plurality of unit cells 110 disposed in the cell stack 101 may not adhere to each other or adhere to each other with less adhesion force than between the electrode 130 and the separator 140 in each unit cell 110. Here, the adhesion force may mean a peeling force. Therefore, the cell stack 101 can be easily separated in units of the unit cells 110.

The number of electrodes 130 and the number of separators 140 disposed in each unit cell 110 may be the same. For example, as shown in fig. 3, the unit cell 110 may be provided by stacking two electrodes 130 and two separators 140. As another example, as shown in fig. 4, the unit cell 110 may be provided by stacking three electrodes 130 and three separators 140.

An electrode 130 may be disposed at one end of each unit cell 110, and a separator 140 may be disposed at the other end of each unit cell 110. Accordingly, the electrode 130 may be disposed at one side of the outermost side of the cell stack 101 provided by stacking the plurality of unit cells 110, and the separator 140 may be disposed at the other side of the outermost side.

As shown in fig. 3, when the cell stack part 101 is formed by repeatedly stacking one type of unit cells 110, each unit cell 110 may have a four-layer structure in which the first electrode 131, the separator 140, the second electrode 132, and the separator 140 are sequentially stacked, or a four-layer structure repeatedly arranged structure (e.g., an eight-layer structure or a twelve-layer structure).

On the other hand, as shown in fig. 4, when the cell stack part 101 is provided by stacking two or more types of unit cells 110 in a predetermined order, a four-layer structure or a structure in which four-layer structures are repeatedly disposed may be provided by a combination of the two or more types of unit cells 110.

Hereinafter, a case in which the plurality of unit cells 110 includes the first unit cells 110a and the second unit cells 110b alternately stacked will be described as an example.

The first electrode 131 may be disposed at one end of the first unit cell 110a, and the separator 140 may be disposed at the other end of the first unit cell 110 a. The second electrode 132 may be disposed at one end of the second unit cell 110b, and the separator 140 may be disposed at the other end of the second unit cell 110 b. Accordingly, a four-layer structure or a structure in which the four-layer structure is repeatedly disposed may be provided by a combination of the first unit cells 110a and the second unit cells 110b adjacent to each other.

For example, the first unit cell 110a may have a six-layer structure in which the first electrode 131, the separator 140, the second electrode 132, the separator 140, the first electrode 131, and the separator 140 are sequentially stacked, and the second unit cell 110b may have a six-layer structure in which the second electrode 132, the separator 140, the first electrode 131, the separator 140, the second electrode 132, and the separator 140 are sequentially stacked. In this case, the six-layer structure of the first unit cell 110a and the six-layer structure of the second unit cell 110b are stacked to provide a twelve-layer structure in which four-layer structures are repeatedly arranged.

The sub-unit cells 120 are provided at the outermost sides with polymer films 150, and the electrodes 130 and the separators 140 alternately stacked may be integrally coupled with the polymer films 150. That is, the electrode 130, the separator 140, and the polymer film 150 of the subunit cell 120 may be in a state of being adhered to each other through a lamination process or a rolling process.

The polymer film 150 will be described in detail later.

The subunit cells 120 may not adhere to the cell stack 101, or may adhere to the cell stack 101 with less adhesion than between the electrodes 130, the separator 140, and the polymer film 150 in the subunit cells 120. Here, the adhesion force may mean a peeling force. Thus, the subunit cells 120 can be easily separated from the cell stack 101.

The number of electrodes 130 disposed in the sub-unit cells 120 may be smaller than the number of electrodes 130 disposed in each unit cell 110 of the cell stack 101. For example, as shown in fig. 3, each unit cell 110 may include two electrodes 130, and the subunit cell 120 may include one electrode 130. As another example, as shown in fig. 4, each unit cell 110 may include three electrodes, and the sub-unit cell 120 may include one electrode 130.

The polymer film 150 may be disposed at one side of the outermost side of the subunit cells 120, and the separator 140 may be disposed at the other side of the outermost side of the subunit cells 120. Accordingly, the polymer film 150 disposed at the outermost side of the sub-unit cell 120 may be disposed at the outermost side of the electrode assembly 100, and the separator 140 disposed at the other side of the outermost side of the sub-unit cell 120 may be stacked on the electrode 130 disposed at the one side of the outermost side of the cell stack 101. In addition, the separator 140 disposed at the other side of the outermost side of the cell stack 101 may be disposed at the outermost side of the electrode assembly 100.

That is, the polymer film 150 may be disposed at one side of the outermost side of the electrode assembly 100, and the outermost separator 140 of the cell stack 101 may be disposed at the other side of the outermost side of the electrode assembly 100. Accordingly, in a state in which the electrode assembly 100 is received in the battery case 200 (see fig. 2), the polymer film 150 may face the inner surface of one side of the battery case 200, and the outermost separator 140 of the cell stack 101 may face the inner surface of the opposite side of the battery case 200.

As described above, since the polymer films 150 are disposed only at either side of the two outermost sides of the electrode assembly 100, the electrode assembly 100 may be manufactured using a single type, i.e., one sub-unit cell 120. Further, as will be described later, since the thickness t2 of the polymer film 150 is equal to or greater than the thickness t1 of the separator 140, a decrease in energy density of the electrode assembly 100 can be minimized.

In addition, the polymer film 150 may be stacked on the electrode 130. The polarity of the electrode 130 adjacent to the polymer film 150 in the subunit cell 120 may be the same as the polarity of the electrode 130 adjacent to the outermost separator 140 of the cell stack 101. For example, in the subunit cells 120, the polymer film 150 may be adjacent to the second electrode 132, and the outermost separator 140 of the cell stack 101 may also be adjacent to the second electrode 132.

The polymer film 150 may have insulating properties that are not conductive. In more detail, the polymer film 150 may include at least one of polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyamide (PA), polyimide (PI), polyaramid, or polypropylene (PP).

The polymer film 150 has a stiffness greater than that of the diaphragm 140 and can withstand bending stresses greater than that of the diaphragm 140.

In more detail, since the separator 140 includes a large number of fine pores and is sufficiently impregnated with an electrolyte, rigidity may be slightly lowered. On the other hand, since the polymer film 150 does not include pores and the degree of impregnation in the electrolyte is significantly reduced, the rigidity of the polymer film 150 may be significantly greater than that of the separator 140. Accordingly, since the polymer film 150 is disposed at the outermost portion of the electrode assembly 100, bending of the electrode assembly 100 can be minimized.

Further, in order to ensure that the polymer film 150 has a sufficiently high rigidity, the thickness t2 of the polymer film 150 may be greater than or equal to the thickness t1 of the separator 140, or may preferably be greater than the thickness t1 of the separator 140. However, when the thickness t2 of the polymer film 150 is too thick, the thickness t2 of the polymer film 150 may be less than three times the thickness t1 of the separator 140 since the energy density of the electrode assembly 100 is reduced.

However, the present invention is not limited thereto, and if the rigidity of the polymer film 150 is sufficiently high, the thickness t2 of the polymer film 150 may be smaller than the thickness t1 of the separator 140. For example, the thickness t2 of the polymer film 150 may be about 10 μm.

Fig. 5 is an enlarged side view illustrating a polymer film of an electrode assembly according to an embodiment of the present invention.

The polymer film 150 disposed at the outermost side of the electrode assembly 100 may be flat or finely curved.

When fine bending occurs in the electrode assembly 100, the central portion 151 of the polymer film 150 in the width direction may be bent to be recessed toward the cell stack portion 101 instead of the two edges 152.

That is, the polymer film 150 may be disposed at one side of the concave curve among the two outermost sides of the electrode assembly 100. Therefore, both the edge of the polymer film 150 and the central portion of the adjacent electrode 130 can be more firmly adhered to the polymer film 150 in the width direction. That is, the edge of the polymer film 150 may be prevented from gradually peeling from the electrode 130.

Accordingly, the adhesion between the polymer film 150 and the electrode 130 can be stably maintained, and the bending of the electrode assembly 100 can be more effectively reduced due to the high rigidity of the polymer film 150.

In more detail, a distance between a reference plane P passing through both edges 152 in a width direction of the polymer film 150 and one outer surface (e.g., a top surface) of the polymer film 150 may gradually increase toward the central portion 151. The reference plane P may be a virtual plane, and one outer surface of the polymer film 150 may be a surface opposite to the surface adhered to the electrode 130.

Furthermore, the maximum distance d between the reference plane P and one outer surface of the polymer film 150 may be less than 1mm. That is, the distance d between the reference plane P and the central portion 151 may be less than 1mm.

That is, the polymer film 150 may be flat, or a distance d between the reference plane P connecting the two edges 152 in the width direction and the central portion 151 may be less than 1mm so as to be concavely curved toward the cell stack portion 101.

Hereinafter, experimental examples showing the bending resistance effect of the polymer film 150 will be described.

As experimental example 1, a stack having a seven-layer structure in which four separators (each having a width of 2cm, a length of 9cm, and a thickness of 15 μm) and three cathodes (each having a width of 2cm and a length of 9 cm) were alternately stacked between a pair of protective sheets by a press. Here, the separator is disposed at the uppermost and lowermost ends of the stack, and each of the protective sheets includes a polyethylene terephthalate (PET) film having a width of 7cm and a length of 10cm in contact with the stack, and paper having a width of 7cm and a length of 10cm and covering the PET film. The press was then heated to a temperature of 60 degrees celsius and pressed at a pressure of 5.2 MPa. Thereafter, a flat object is placed on both edges of the uppermost diaphragm of the integrally bonded stack in the width direction, and then the distance between the bottom surface of the object and the central portion of the top surface of the uppermost diaphragm is measured. Distance refers to the degree of bending of the stack.

As experimental example 2, the same separator was additionally stacked on the uppermost end of the stack of experimental example 1, and other conditions were also maintained. That is, two diaphragms are disposed at the uppermost end of the stack of experimental example 2.

As experimental example 3, the separator provided at the uppermost end of the stack of experimental example 1 was replaced with a polymer film having a width of 2cm, a length of 9cm, a thickness of 35 μm and made of a polyethylene terephthalate (PET) material, and other conditions were maintained as well. That is, the polymer film was disposed at the uppermost end of the stack of experimental example 3. Then, a flat object was placed on both edges in the width direction of the polymer film, and then the distance between the bottom surface of the object and the central portion of the top surface of the uppermost membrane was measured.

As a result, the degree of bending of the stack according to each experimental example was measured to be 2.5mm in experimental example 1, 2.0mm in experimental example 2, and 0.3mm in experimental example 3.

That is, it was confirmed that when a polymer film was placed on the outermost side of the stack instead of the separator, the degree of bending of the stack was significantly reduced as compared with the use of a plurality of overlapping separators on the outermost surface.

Fig. 6 is a sectional view illustrating a stacked structure of an electrode assembly according to another embodiment of the present invention.

Hereinafter, contents repeated from those described previously will be referred to, and differences will be described with emphasis.

In the electrode assembly 100' according to this embodiment, the polymer films 150a and 150b may be disposed on the two outermost sides, respectively. Accordingly, bending of the electrode assembly 100' according to the embodiment may be further minimized as compared to the electrode assembly 100 according to the foregoing embodiment.

In more detail, the electrode assembly 100' may include a cell stack 101, a first sub-unit cell 121 stacked on one side of the cell stack 101 and provided with a first polymer film 150a at the outermost side, and a second sub-unit cell 122 stacked on the other side of the cell stack 101 and provided with a second polymer film 150b at the outermost side.

The first subunit cell 121 and the second subunit cell 122 may include different numbers of electrodes 13. In more detail, the number of the electrodes 130 disposed in the first subunit cell 121 may be smaller than the number of the electrodes 130 disposed in the second subunit cell 122. Further, the number of the electrodes 130 disposed in the second sub-unit cells 122 may be the same as the number of the electrodes 130 disposed in each unit cell 110 of the cell stack 101. For example, each of the unit cell 110 and the second subunit cell 122 may include two electrodes 130, and the first subunit cell 121 may include one electrode 130.

The first polymer film 150a may be disposed at one side of the outermost side of the first subcell cell 121, and the separator 140 may be disposed at the other side of the outermost side of the first subcell cell 121. The electrode 130 may be disposed at one side of the outermost side of the second subcell cell 122, and the second polymer film 150b may be disposed at the other side of the outermost side of the second subcell cell 122.

Accordingly, the first polymer film 150 disposed at the outermost side of the first sub-unit cell 121 may be disposed at the outermost side of the electrode assembly 100', and the separator 140 disposed at the other side of the outermost side of the first sub-unit cell 121 may be stacked on the electrode 130 disposed at the one side of the outermost side of the cell stack 101. In addition, the electrode 130 disposed at one outermost side of the second sub-unit cell 122 may be stacked on the separator 140 disposed at the other outermost side of the cell stack 101, and the second polymer film 150b disposed at the other outermost side of the second sub-unit cell 122 may be disposed at the outermost side of the electrode assembly 100'.

That is, the first polymer film 150a may be disposed at one side of the outermost side of the electrode assembly 100', and the second polymer film 150b may be disposed at the other side of the outermost side of the electrode assembly 100'. Accordingly, in a state in which the electrode assembly 100' is received in the battery case 200 (see fig. 2), the first polymer film 150a may face the inner surface of one side of the battery case 200, and the second polymer film 150b may face the inner surface of the opposite side of the battery case 200.

The first polymer film 121 and the second polymer film 122 may be stacked on the electrode 130.

The electrode 130 adjacent to the first polymer film 150a in the first subunit cell 121 may have the same polarity as the electrode 130 adjacent to the second polymer film 150b in the second subunit cell 122. For example, in the first subunit cell 121, the first polymer film 150a may be adjacent to the second electrode 132, and in the second subunit cell 122, the second polymer film 150b may also be adjacent to the second electrode 132.

The thickness of each of the first and second polymer films 150a and 150b may be greater than the thickness of the separator 140. The first polymer film 150a and the second polymer film 150b may have the same thickness, but are not limited thereto. In addition, the first and second polymer films 150a and 150b may be made of the same material, but are not limited thereto.

The first and second polymer films 150a and 150b may be flat or finely curved.

When the electrode assembly 100' is finely bent, the first polymer film 150a and the second polymer film 150a may be bent in the same direction.

For example, the central portion of the first polymer film 150a in the width direction may be concavely bent toward the cell stack 101 instead of both edges of the first polymer film 150a, and the central portion of the second polymer film 150b in the width direction may be convexly bent toward the opposite side of the cell stack 101 instead of both edges of the second polymer film 150 b.

In this case, as in the above-described embodiment, the first polymer film 150a may be flat, or a distance d between the central portion 151 and the reference plane P connecting the edges 152 (see fig. 5) in the width direction may be less than 1mm so as to be concavely curved toward the cell stack portion 101. In addition, the second polymer film 150b may also be flat or may be slightly curved with the same or similar curvature as that of the first polymer film 150 a.

In this embodiment, the energy density of the electrode assembly 100' may be slightly increased, but the pair of polymer films 150a and 150b having high rigidity may more effectively prevent the electrode assembly 100 from being bent.

The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present disclosure.

Accordingly, the embodiments of the present invention should be regarded as illustrative rather than restrictive, and the technical spirit of the present invention is not limited to the foregoing embodiments.

Accordingly, the scope of the present disclosure is defined not by the detailed description of the invention but by the appended claims, and all differences within the scope will be construed as being included in the present disclosure.

[ description of the symbols ]

1: secondary battery 1 00: electrode assembly

101: cell stack 1 10: unit cell

120: subunit cells 130: electrode

131: first electrode 132: second electrode

140: diaphragm 150: polymer film

200: and a battery case.

Claims (13)

1. An electrode assembly, the electrode assembly comprising:

a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators; and

a sub-unit cell stacked on the cell stack portion and provided at an outermost side thereof with a polymer film, and in which alternately stacked electrodes and separators are integrally coupled together with the polymer film,

wherein the polymer film is flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm, and

the thickness of the polymer film is equal to or greater than the thickness of the separator.

2. The electrode assembly of claim 1, wherein the polymer film has a stronger adhesion within the subunit cell than between the subunit cell and the cell stack.

3. The electrode assembly of claim 2, wherein the thickness of the polymer film is less than three times the thickness of the separator.

4. The electrode assembly of claim 1, wherein the polymer film is stacked on the electrode.

5. The electrode assembly of claim 1, wherein the polymer film comprises at least one of polyethylene terephthalate, polyvinyl chloride, polyamide, polyimide, polyaramid, or polypropylene.

6. The electrode assembly of claim 1, wherein the number of electrodes disposed in the subunit cells is less than the number of electrodes disposed in the unit cells.

7. The electrode assembly according to claim 1, wherein the polymer film is disposed at an outermost side of the electrode assembly, and

the outermost separator of the cell stack is disposed at the other side of the outermost side of the electrode assembly.

8. An electrode assembly, the electrode assembly comprising:

a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators;

a first sub-unit cell stacked on one side of the cell stack portion and provided with a first polymer film at an outermost side thereof, and electrodes and separators alternately stacked in the first sub-unit cell are integrally coupled together with the first polymer film; and

a second sub-unit cell stacked on the other side of the cell stack portion and provided at the outermost side thereof with a second polymer film, and electrodes and separators alternately stacked in the second sub-unit cell are integrally coupled together with the second polymer film,

wherein the first polymer film is flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm, and

the thickness of each of the first and second polymer films is equal to or greater than the thickness of the separator.

9. The electrode assembly according to claim 8, wherein the second polymer film is flat or a central portion of the second polymer film in a width direction is convexly curved toward opposite sides of the cell stack portion instead of both edges of the second polymer film.

10. A secondary battery, the secondary battery comprising:

a pouch-type battery case; and

an electrode assembly received in the battery case,

wherein the electrode assembly includes:

a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators; and

a sub-unit cell stacked on the cell stack portion and provided at an outermost side thereof with a polymer film, and in which alternately stacked electrodes and separators are integrally coupled together with the polymer film,

wherein the polymer film is flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm, and

the thickness of the polymer film is greater than or equal to the thickness of the separator.

11. The secondary battery according to claim 10, wherein the polymer film faces an inner surface of one side of the battery case, and

the outermost separator of the cell stack faces the inner surface of the opposite side of the battery case.

12. A secondary battery, the secondary battery comprising:

a pouch-type battery case; and

an electrode assembly received in the battery case,

wherein the electrode assembly includes:

a cell stack part including a plurality of unit cells stacked one on another, the unit cells being provided by integrally coupling alternately stacked electrodes and separators;

a first sub-unit cell stacked on one side of the cell stack portion and provided with a first polymer film at an outermost side thereof, and electrodes and separators alternately stacked in the first sub-unit cell are integrally coupled together with the first polymer film; and

a second sub-unit cell stacked on the other side of the cell stack portion and provided at the outermost side thereof with a second polymer film, and electrodes and separators alternately stacked in the second sub-unit cell are integrally coupled together with the second polymer film,

wherein the first polymer film is flat or concavely curved toward the cell stack portion such that a distance between a reference plane connecting both edges in a width direction and a central portion is less than 1mm, and

the thickness of each of the first and second polymer films is equal to or greater than the thickness of the separator.

13. The secondary battery according to claim 12, wherein the first polymer film faces an inner surface of one side of the battery case, and

the second polymer film faces an inner surface of an opposite side of the battery case.