KR20150038945A - Battery Cell Having Separation Film of Suppressed Thermal Shrinkage - Google Patents

Abstract

The present invention provides a battery cell where an electrode assembly including unit cells in a stacked structure of an anode, a cathode, and a separator provided therebetween, and a separation layer consecutively reeling the unit cells are installed in a storage unit of a battery case; a positive tab or a negative tap protrudes from at least one side of the outer surface of the anode and the cathode of the unit cells; two or more separation layers among the separation layers in the unit cells lie between the anode and the cathode and protrude longer than the anode and the cathode to form separation a layer extension part; and at least portions of the separation layer extension parts are connected to each other on the outer surface of the unit cells, and a portion of the separation film corresponding to the interconnected separation layer extension parts is exposed to the outside to allow an electrolyte to enter.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery cell having suppressed thermal contraction of a separator,

The present invention provides an electrode assembly including a positive electrode, a negative electrode, a unit cell having a laminated structure composed of a separator interposed between the positive and negative electrodes, and a separation film for continuously winding the unit cells, Have; A positive electrode tab and a negative electrode tab protruding from at least one side of an outer peripheral surface of the positive electrode and the negative electrode in the unit cells; At least two separators of the separators in the unit cells protrude longer than the positive and negative electrodes in a state interposed between the positive and negative electrodes to form a separator extension part; Wherein at least a part of the separation membrane elongation parts are coupled to each other at an outer circumferential surface of the unit cells and a part of the separation film corresponding to the mutually coupled separation membrane elongation parts is opened to the outside for the inflow of the electrolyte solution. .

In recent years, the demand for environmentally friendly alternative energy sources has become an indispensable factor for the future, as the increase in the price of energy sources due to depletion of fossil fuels and the interest in environmental pollution are amplified. Various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continuing, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.

Particularly, as technology development and demand for mobile devices are increasing, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries that can meet various demands have been conducted.

Typically, in terms of the shape of a battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery which can be applied to products such as mobile phones with a small thickness, and has advantages such as high energy density, discharge voltage, There is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries.

The secondary battery includes a cylindrical battery and a prismatic battery in which the electrode assembly is housed in a cylindrical or rectangular metal can according to the shape of the battery case, and a pouch type battery in which the electrode assembly is housed in a pouch-shaped case of an aluminum laminate sheet .

In particular, in recent years, a pouch-shaped battery having a structure in which a stacked or stacked / folded electrode assembly is embedded in a pouch-shaped battery case of an aluminum laminate sheet has attracted much attention due to low manufacturing cost, small weight, And its usage is gradually increasing.

Also, the secondary battery is classified according to the structure of the electrode assembly having the structure in which the anode, the cathode, and the separator interposed between the anode and the cathode are laminated. Typically, the long battery- A stacked (stacked) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a predetermined size unit are sequentially stacked with a separator interposed therebetween, the jelly-roll type (wound type) electrode assembly having a structure in which a separator is interposed; In recent years, in order to solve the problems of the jelly-roll type electrode assembly and the stack type electrode assembly, an electrode assembly having an advanced structure, which is a combination of the jelly-roll type and the stack type, Bi-cells or full cells, which are stacked with a separator interposed between an anode and a cathode, are sequentially wound on a separator film Stacked / folded electrode assemblies have been developed.

One of the major research tasks in such secondary batteries is to improve safety. For example, a secondary battery can have a high temperature and / or high temperature inside the battery that can be caused by an abnormal operating condition of the battery, such as an internal short circuit, an overcharged condition exceeding an allowable current and voltage, exposure to a high temperature, The explosion of the battery may be caused by high pressure.

One of the problems of safety is that the internal short circuit due to shrinkage or breakage of the separator which occurs when the battery is exposed to high temperature is very serious.

In general, a porous polymer film such as polyethylene or polypropylene is used as a separator. Such a separator is advantageous in that it is inexpensive and has excellent chemical resistance and is suitable for operation of a battery, but is liable to shrink in a high temperature environment.

FIG. 1 schematically illustrates a typical structure of a conventional stack / folding type electrode assembly.

1, the electrode assembly 100 includes first unit cells 102 and 104 having a structure in which a cathode is disposed between positive electrodes and a separator is disposed between the positive and negative electrodes, and an anode is disposed between the cathodes , And a combination of second unit cells (101, 103, 105) having a structure in which a separation membrane is interposed between the anode and the cathode.

The separation film 106 interposed between the first unit cells 102 and 104 and the second unit cells 101 and 103 and 105 of the electrode assembly 100 is a first The electrode assembly includes the first unit cells 102 and 104 and the second unit cells 102 and 104 on the separation film 106. The first unit cells 102 and 104 and the second unit cells 101 and 103 and 105, Two unit cells 101, 103, and 105 are arranged and the separation film 106 is wound.

Generally, in the case of such a stack / folding type electrode assembly, the separator interposed between the anode and the cathode of the unit cell and the separator film interposed between the unit cells are made of the same material. However, The separation membrane that is interposed between the anode and the cathode in the unit cells shrinks at the both ends of the separator between the interfaces of the electrodes in a high temperature environment, .

Therefore, there is a high need for a technique capable of fundamentally solving such problems.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior art and the technical problems required from the past, and it is an object of the present invention to at least partially solve the problems in the prior art, And an object of the present invention is to provide a battery cell in which shrinkability is suppressed, internal short circuit is prevented, and safety can be improved.

It is still another object of the present invention to provide a battery having a structure capable of preventing deterioration of the impregnability of the electrolyte in the manufacturing process of the battery cell by opening the part of the separation film corresponding to the separation film extension parts, Cell.

According to an aspect of the present invention, there is provided a battery cell comprising:

An electrode assembly including a positive electrode, a negative electrode, a unit cell having a laminated structure composed of a separator interposed between the positive electrode and the negative electrode, and a separator film for continuously winding the unit cells are mounted on a receiving portion of the battery case;

A positive electrode tab and a negative electrode tab protruding from at least one side of an outer peripheral surface of the positive electrode and the negative electrode in the unit cells;

At least two separators of the separators in the unit cells protrude longer than the positive and negative electrodes in a state interposed between the positive and negative electrodes to form a separator extension part;

The separation membrane elongation parts are at least partially connected to each other at the outer circumferential surfaces of the unit cells and the separation membrane part corresponding to the mutually coupled separation membrane elongation parts is opened to the outside for the inflow of the electrolytic solution.

As described above, the battery cell according to the present invention is configured such that the separation membrane elongation portions of the electrode assembly are at least partially connected to each other at the outer circumferential surfaces of the unit cells, so that the heat shrinkability of the separation membrane is suppressed to prevent internal short- .

In addition, since the portion of the separation film corresponding to the mutually coupled separation film extension portions is opened to the outside, the impregnation property of the electrolyte solution can be prevented from deteriorating in the manufacturing process of the battery cell.

In one specific example, the electrode assembly may have a structure in which the unit cells are sequentially wound with the unit cells positioned on a long length of the separation film.

In other words, the electrode assembly of the battery cell according to the present invention includes unit cells of a laminated structure composed of an anode, a cathode, and a separator interposed between the anode and the cathode, Wherein the width of the separation film is the size of the outer circumferential surface of the separation film in the direction parallel to the electrode tab projecting direction of the unit cells positioned on the separation film, Is the size of the outer circumferential surface of the separation film in the direction perpendicular to the width.

Therefore, the electrode assembly of the battery cell according to the present invention is an advanced electrode assembly in which the jelly-roll type electrode assembly and the stacked electrode assembly are mixed, and the problems of the conventional jelly- Can be solved.

In this case, the unit cells of the electrode assembly may have a structure in which the outermost electrodes have the same polarity, or a structure in which the outermost electrodes have different polarities from each other.

Specifically, the unit cell has a structure in which an anode, a separator, a cathode, a separator, and a cathode are stacked in this order. Thus, a cathode having the same polarity may be positioned on both sides of the unit cell, or a cathode, a separator, A structure in which a cathode having the same polarity is located on both sides of the unit cell may be used.

On the other hand, the unit cell may have a structure in which an anode, a separator, and a cathode are stacked in this order, and the anode and the cathode having different polarities may be positioned on both sides of the unit cell.

However, the structure of the unit cell is not limited to this, and may be a structure in which a plurality of positive electrodes, a separator, and a negative electrode are laminated, and the outermost electrodes have the same polarity or different lamination structures, It is not.

In another specific example, the unit cells may have a structure in which the positive electrode tab and the negative electrode tab are protruded on the same surface on the outer circumferential surface of the unit cells, but the present invention is not limited thereto, And may protrude on one surface and the other surface facing each other on the outer peripheral surface of the cells.

In other words, the unit cells may have a structure in which the positive electrode tab and the negative electrode tab protrude in the same direction or protrude in directions opposite to each other, The outer surface of the assembly, and the opposite surface of the outer circumferential surface, except for the protruding portions of the positive electrode tab and the negative electrode tab.

In one specific example, the size of the separator extension may be between 5 and 30% of the width or length of the anode or cathode.

The term of the width indicates the size of the outer circumferential surface of the positive electrode, the negative electrode, the separator, the separator film and the unit cell perpendicular to the protruding direction of the positive electrode tab and the negative electrode tab in the battery cell, , The size of the outer circumferential surface of the anode, the cathode, the separator, the separator film, and the unit cell parallel to the protruding direction of the positive electrode tab and the negative electrode tab.

The separator extension portions may be connected to each other at an outer circumferential surface of the electrode assembly protruding from the positive electrode tab and the negative electrode tab and at an opposite surface of the separator extension portion or at outer peripheral surfaces adjacent to the outer circumferential surface of the unit cell, They may be mutually coupled structures.

Specifically, the separation membrane elongation regions may be bonded to the outer circumferential surfaces of the unit cells, and in this case, the bonding may be performed on the outer circumferences facing each other.

Therefore, with respect to the positive electrode tab and the negative electrode tab of the unit cell, the separator extension portions are connected to each other at the outer peripheral surface of the unit cell protruded from the positive electrode tab and the negative electrode tab and at the opposite surface thereof, or the positive electrode tab and the negative electrode tab protrude Side outer circumferential surfaces adjacent to the outer circumferential surface of the unit cell, and may be mutually coupled on the outer circumferential surfaces of the unit cells facing each other.

In this case, the size of the portion where the separator extension portions are coupled to each other may be 30% or more to 100% or less of the width or length of the unit cells.

In other words, the separator extension portions may be structured such that they are mutually coupled at outer circumferential surfaces opposed to each other in the outer circumferential surfaces of the unit cells, and in this case, they may be mutually coupled at some or all of the outer circumferential surfaces opposed to each other. The size of the portion where the separator extension portions are coupled to each other may be 30% or more to 100% or less based on the width or length of the unit cells.

In another specific example, the method of joining the separation membrane elongation parts is not particularly limited as long as they are firmly coupled to each other and can suppress the contraction of the separation membrane under high temperature conditions. Preferably, Structure.

In this case, the thermal fusing may be performed for 1 to 10 seconds at a temperature of 50 to 120 degrees Celsius, preferably for 2 to 4 seconds at a temperature of 50 to 60 degrees Celsius.

If the thermal bonding temperature is less than 50 degrees Celsius or the thermal bonding time is less than 1 second, the desired bonding force of the separation membrane can not be exhibited. If the thermal bonding temperature exceeds 120 degrees Celsius or the thermal bonding time is 10 seconds Excessive amounts can lead to excessive shrinkage and damage to the separator membrane, which possesses weaker properties at high temperatures.

In addition, the thermal fusion may be performed before inserting the electrode assembly into the battery case. Specifically, before the unit cells are placed on the separation film during the manufacture of the electrode assembly, And then inserted into the battery case in a wound state.

The separating film of the battery cell according to the present invention may be in a structure in which the uncoated state is maintained at mutually coupled separator extension portions.

Therefore, by providing a sufficient space for the electrolyte solution to flow into the electrode assembly during the manufacture of the battery cell, impairment of impregnability of the electrolyte solution can be prevented.

Meanwhile, the battery case of the battery cell according to the present invention may be formed of a laminate sheet including a resin layer and a metal layer.

The battery cell according to the present invention is not particularly limited as long as it has the above-described structure. Specific examples thereof include a lithium ion battery having advantages such as high energy density, discharge voltage, and output stability, a lithium ion polymer battery And the like.

The configuration, structure, and manufacturing method of the battery cell including the lithium secondary battery are well known in the art, and a detailed description thereof will be omitted in this specification.

The present invention provides a device comprising the battery cell, the device comprising a cell phone, a tablet computer, a notebook computer, a power tool, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, Lt; / RTI >

Such devices or devices are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the battery cell according to the present invention is configured such that the separation membrane extension portions of the electrode assembly are at least partially connected to each other on the outer peripheral surface of the unit cells, so that the heat shrinkability of the separation membrane is suppressed under high temperature conditions, And the part of the separation film corresponding to the mutually coupled separation film extensions is opened to the outside, whereby the impregnability of the electrolyte solution in the process of manufacturing the battery cell can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view schematically showing a general structure of a conventional stack / folding type electrode assembly; FIG.
2 is a schematic view showing a structure of unit cells constituting an electrode assembly of a battery cell according to an embodiment of the present invention;
3 is a plan view showing a structure of unit cells constituting an electrode assembly of a battery cell according to an embodiment of the present invention;
FIGS. 4 to 5 are plan views schematically showing heat-sealed portions of unit cells constituting an electrode assembly of a battery cell according to an embodiment of the present invention; FIG.
FIG. 6 is a schematic view showing a structure of a separator of an electrode assembly constituting a battery cell according to an embodiment of the present invention, after performing heat fusion; FIG.
FIG. 7 is a schematic view illustrating a method of constructing an electrode assembly of a battery cell according to an embodiment of the present invention; FIG.
FIG. 8 is a schematic view illustrating a structure of one surface of the electrode assembly of the battery assembly according to an embodiment of the present invention, in which electrode tabs protrude; FIG.
FIG. 9 is a schematic view illustrating a structure of an opposite surface of one side of an electrode assembly of a battery cell according to an embodiment of the present invention, in which electrode tabs protrude; FIG.
10 is a partially enlarged partial schematic view of a laminated structure of an electrode assembly constituting a battery cell according to still another embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings according to the embodiments of the present invention, but the scope of the present invention is not limited thereto.

FIG. 2 is a schematic view showing a structure of unit cells constituting an electrode assembly of a battery cell according to an embodiment of the present invention.

Referring to FIG. 2, the electrode assembly of the battery cell according to the present invention includes a plurality of unit cells 210, 220, and 230, and each of the unit cells 210, 220, And the polarities of the outermost electrodes may be different from each other.

That is, the unit cells may have the structure 210 in which the cathode 202 is disposed between the anode 201 and the separator 203 is interposed between the anode 201 and the cathode 202, The outermost electrodes may have a laminated structure having the same polarity as each other like the structure 220 located between the cathodes 202 and the separator 203 interposed between the cathodes 202 and the anodes, The outermost electrodes may have a laminated structure in which the polarities of the outermost electrodes are different from each other, such as the structures 230 and 240 in which a separation membrane is interposed between the cathode and the cathode.

The unit cells 210, 220 and 230 include at least two separation membranes 203 and the separator 203 interposed between the anode 201 and the cathode 202 is connected to the anode 201, And the extending portion 206 of the separating film 203 protrudes from the length 205 of the anode 201 or the cathode 202 to a length of 5 To 30%.

3 is a plan view showing a structure of unit cells constituting an electrode assembly of a battery cell according to an embodiment of the present invention.

3, the unit cells 310 and 320 have positive electrode tabs 311 and 321 and negative electrode tabs 312 and 322 protruding from at least one surface of the outer surface of the positive electrode and the negative electrode, The anode tabs 312 and 322 and the anode tabs 312 and 322 protrude on the same surface on the outer circumferential surface of the unit cells 310 and 320 or on the outer surface of the unit cells 310 and 320, And may be a structure 320 protruding on one surface and the other surface.

FIGS. 4 to 5 are top views schematically showing heat-welded portions of unit cells constituting an electrode assembly of a battery cell according to an embodiment of the present invention.

4, the unit cell 400 includes a positive electrode tab 401 and a negative electrode tab 402 protruding on the same surface on the outer peripheral surfaces of the positive electrode and the negative electrode, And a separation membrane 403.

The separator 403 has a separation membrane extension part 405 protruding in a length greater than the length of the anode and the cathode. The separator extension part 405 is formed in the outer peripheral surface of the unit cell 400, A portion 404 where the separation membrane elongation portions 405 are mutually coupled is formed in a portion of the outer circumferential surface of the unit cell 400 except for a portion where the positive electrode tab 401 and the negative electrode tab 402 protrude .

In this case, the size W2, W3 of the portion 404 where the separation membrane elongation portions 405 are mutually coupled may be 30% or more and 100% or less with respect to the width W1 of the unit cell 400.

5, the separation membrane elongation portions 505 of the unit cell 500 are formed by thermal fusion bonding at the outer circumferential surfaces adjacent to the outer circumferential surface of the unit cell 500 where the positive electrode tab 501 and the negative electrode tab 502 protrude The sizes S2 and S3 of the portion 504 where the separation membrane elongation portions 505 are coupled to each other are not less than 30% and not more than 30% with respect to the length S1 of the unit cell 500. In this case, May be less than 100%.

That is, the separation membrane extension portions 405 and 505 of the unit cells 400 and 500 are at least partially coupled to each other on the outer peripheral surface of the unit cells 400 and 500, The widths W2 and W4 of the portions 404 and 504 to which the separation membrane elongation portions 405 and 505 are coupled may be mutually coupled to each other at a portion or all of the outer circumferential surfaces opposed to each other among the outer circumferential surfaces of the cells 400 and 500, W3, S2 and S3 may be 30% or more and 100% or less based on the width W1 or the length S1 of the unit cells 400 and 500.

FIG. 6 is a schematic view schematically showing a structure of a separator of an electrode assembly constituting a battery cell according to an embodiment of the present invention after thermal fusion is performed.

6, a unit cell 600 includes one anode 602 between two cathodes 601 and 603, and a separation membrane 604 is formed between the anode 602 and the cathodes 601 and 603. In this case, The separation membrane 604 protrudes to a length longer than the length of the anode 602 and the cathodes 601 and 603 to form a separation membrane extension part 606. The separation membrane extension parts 606 are heat- Respectively.

Therefore, the battery cell according to the present invention can suppress heat shrinkability of the separator 604 under high temperature conditions, prevent internal short-circuit, and improve safety.

FIG. 7 is a schematic view illustrating a method of constructing an electrode assembly of a battery cell according to an embodiment of the present invention.

7, the electrode assembly 700 includes a unit cell 701 having a structure in which a cathode 701 is disposed between the anodes 702 and a separation membrane 709 is disposed between the anodes 702 and the cathode 701, The unit cells 720 having a structure in which the separators 709 are interposed between the cathodes 701 and the anodes 702 are separated from the separators 701 and 730 and the anodes 702 are disposed between the cathodes 701, The positive electrode tab 704 protruded from the anode 702 and the negative electrode tab 703 protruding from the negative electrode 701 are arranged so as to face the same direction at the same position .

The electrode assembly 700 is manufactured by sequentially winding the unit cells 710, 720, and 730 located on the separation film 740.

FIG. 8 is a schematic view showing a structure of one surface of the electrode assembly of the battery assembly according to an embodiment of the present invention, in which electrode tabs protrude.

8, the electrode assembly 800 includes first unit cells 820 and 840 having a structure in which a cathode is disposed between the anodes and a separator is interposed between the anodes and the anode, and an anode is disposed between the cathodes And a second unit cell (810, 830, 850) having a structure in which a separator is interposed between the anode and the cathode.

The separation films 890 interposed between the first unit cells 820 and 840 of the electrode assembly 800 and the second unit cells 810 and 830 and 850 are formed in a first The first unit cells 820 and 840 and the second unit cells 810 and 830 are formed on the separation film 890 so as to surround the respective side surfaces of the unit cells 820 and 840 and the second unit cells 810, (810, 830, 850) and winding the separation film (890).

The positive electrode tab 870 and the negative electrode tab 860 of the unit cells 810, 820, 830, 840 and 850 are formed on the same outer surface of the unit cells 810, 820, 830, 840, And a portion 880 where the separator extension portions are mutually coupled by thermal welding is formed on the outer peripheral surface of one surface of the electrode assembly except for the portion where the positive electrode tab 870 and the negative electrode tab 860 protrude .

FIG. 9 is a schematic view schematically showing a structure of an opposite surface of one side of an electrode assembly of a battery cell according to an embodiment of the present invention, in which electrode tabs protrude.

Referring to FIG. 9, extending portions of the separator are thermally fused to the opposite surfaces of the electrode assembly in which the positive and negative electrode tabs protrude from the unit cells 810, 820, 830, 840, And a portion 880 that is mutually coupled by a pair of electrodes is formed.

The size of the portion 880 where the separation membrane elongation portions are mutually coupled is such that the separation membrane elongation portions can be stably fixed so that contraction of the separation membrane elongation portions can be suppressed under high temperature conditions, To 100%.

As described above, the electrode assembly constituting the battery cell according to the present invention may have a structure in which the separator extension portions are coupled to each other at an outer circumferential surface where the positive electrode tab and the negative electrode tab protrude from the electrode assembly and at the opposite surface, May be mutually coupled at lateral outer circumferential surfaces adjacent to the protruding outer circumferential surfaces.

That is, the separation membrane elongation regions may be bonded to the outer peripheral surfaces of the unit cells, and in this case, the bonding may be performed on the outer peripheral surfaces opposed to each other.

Therefore, the electrode assembly constituting the battery cell according to the present invention can suppress the heat shrinkability of the separator under high temperature conditions, prevent internal short-circuiting, improve safety, and prevent deterioration of impregnability of the electrolyte in the process of manufacturing the battery cell The effect can be achieved.

FIG. 10 is a partial schematic view showing a partially enlarged laminated structure of an electrode assembly constituting a battery cell according to still another embodiment of the present invention.

10, the electrode assembly 800 includes a plurality of unit cells 810 and 820 including at least two separators, and the separators include an anode 812, a cathode 821, and a cathode 823, 821 and 823 and the cathodes 811 and 813 and 822 in a state of being interposed between the unit cells 810 and 813 and 822, 820, the separation film 890 is interposed.

In addition, the separation membrane elongation regions are at least partially mutually coupled (880) on the outer circumferential surfaces of the unit cells, and a portion of the separation film 890 corresponding to the mutually coupled separation membrane elongation regions is opened to the outside .

Therefore, the separation film 890 maintains the non-bonded state at the separation membrane elongation parts 880 bonded to each other, thereby preventing impregnability of the electrolyte from being deteriorated in the manufacturing process of the battery cell.

The structure of the battery cell according to the present invention is not limited to this. The unit cell having the laminated structure in which the outermost electrodes have different polarities can be included in the electrode assembly of the battery cell, and the positive electrode tab and the negative electrode tab, And a unit cell protruding on one surface and the other surface may be included.

Also, the electrode assembly of the battery cell according to the present invention may be manufactured by folding unit cells with a structure in which the separation film is wrapped in a Z-shape from the lowermost unit cell to the uppermost unit cell.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (18)

An electrode assembly including a positive electrode, a negative electrode, a unit cell having a laminated structure composed of a separator interposed between the positive electrode and the negative electrode, and a separation film for continuously winding the unit cells are mounted on a receiving portion of the battery case;
A positive electrode tab and a negative electrode tab protruding from at least one side of an outer peripheral surface of the positive electrode and the negative electrode in the unit cells;
At least two separators of the separators in the unit cells protrude longer than the positive and negative electrodes in a state interposed between the positive and negative electrodes to form a separator extension part;
Wherein at least a part of the separation membrane elongation parts are coupled to each other at an outer circumferential surface of the unit cells and a part of the separation film corresponding to the mutually coupled separation membrane elongation parts is opened to the outside for the inflow of the electrolyte solution. . The battery cell according to claim 1, wherein the electrode assembly has a structure in which the unit cells are sequentially wound while being positioned on a long length of a separation film. The battery cell according to claim 2, wherein the unit cells have a laminate structure in which outermost electrodes have the same polarity. The battery cell according to claim 2, wherein the unit cells have a laminated structure in which outermost electrodes have different polarities from each other. The battery cell according to claim 1, wherein the unit cells have a positive electrode tab and a negative electrode tab protruding from the same outer surface of the unit cells. The battery cell according to claim 1, wherein the unit cells are protruded on one surface and the other surface of the unit cells facing each other on the outer circumferential surface of the unit cells. The battery cell according to claim 1, wherein a size of the separation membrane elongation portion is 5 to 30% of a width or a length of the anode or the cathode. The battery cell according to claim 1, wherein the separator extension portions are coupled to each other at an outer circumferential surface of the unit cell where the positive electrode tab and the negative electrode tab protrude and an opposite surface thereof. The battery cell according to claim 1, wherein the separator extension portions are coupled to each other at lateral outer circumferential surfaces adjacent to an outer circumferential surface where the positive electrode tab and the negative electrode tab protrude from the unit cell. The battery cell according to claim 8 or 9, wherein a size of a region where the separator extension portions are coupled to each other is 30% or more to 100% or less with respect to a width or a length of the unit cells. The battery cell according to claim 1, wherein the separator extension portions are coupled to each other by thermal fusion. The battery cell according to claim 11, wherein the thermal fusion is performed for 1 to 10 seconds at a temperature in the range of 50 to 120 degrees Celsius. The battery cell according to claim 12, wherein the thermal fusion is performed before inserting the electrode assembly into the battery case. The battery cell according to claim 1, wherein the separator film is kept in a non-coupled state with the separator extension parts coupled to each other. The battery cell according to claim 1, wherein the battery case comprises a laminate sheet including a resin layer and a metal layer. The battery cell according to claim 1, wherein the battery cell is a lithium secondary battery. A device comprising at least one battery cell according to claim 1. 18. The device of claim 17, wherein the device is any one selected from a cell phone, a tablet computer, a notebook computer, a power tool, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device.

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