KR20170014246A - Cell pouch with excellent flexibility and secondary battery comprising the same - Google Patents

Abstract

Disclosed are a cell pouch having excellent bending resistance and a secondary battery including the same. The cell pouch includes a metal layer having an uneven surface and a barrier layer including a buffer reinforcing layer to coat the uneven surface. The present invention has an effect of providing the cell pouch having excellent bending resistance and the secondary battery including the same, capable of predicting a problem of the barrier degradation of the barrier layer and pin hole generation.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a cell pouch having excellent bendability and a secondary battery including the cell pouch.

Disclosed herein is a cell pouch having excellent bendability and a secondary battery including the cell pouch, more particularly, a cell pouch including a metal layer on which an uneven surface is formed and a buffer strengthening layer for applying the uneven surface, and a secondary battery comprising the same.

In general, a cell such as a secondary battery is embedded in a metal can. The metal can is mainly made of aluminum (Al), and is formed into a cylindrical shape or a square shape (such as a rectangular parallelepiped) through press working.

However, the metal can has a limit that the outer wall is rigid and the shape of the cell itself is determined by the shape of the metal can. In order to overcome such a limitation, a flexible cell pouch has been developed and used. In general, a flexible cell pouch is manufactured in a multi-layer structure in consideration of gas barrier property, electrolyte resistance and heat adhesion property. Fig. 1 shows a cross-sectional structural view (laminated structure) of a flexible cell pouch according to the prior art.

1, the cell pouch generally comprises a sealant layer, a barrier layer (e.g., an aluminum metal layer) for gas barrier, and an outer layer (e.g., a nylon resin layer) as an outermost layer do.

The sealant layer is located innermost in the flexible cell pouch and contacts the contents, i.e., the cell. The sealant layer mainly comprises a polypropylene resin in order to stabilize the heat resistance and cold resistance of the battery. The barrier layer is intended to block gas entry along with mechanical strength, and this is mainly an aluminum foil. The outer layer is for protecting the barrier layer, and polyethylene terephthalate (PET) resin and / or nylon resin is mainly used in consideration of heat resistance, pinhole resistance and abrasion resistance.

On the other hand, in recent years, attention has been focused on a flexible cell pouch excellent in miniaturization trend of a product and bending property, so that an ultra-thin flexible cell pouch is required. In particular, ultra-thin flexible cellular pouches are required for wearable IT equipment. In order to form a thin flexible flexible cell pouch, the thickness of the aluminum metal layer, that is, the barrier layer is reduced. When the thickness of the barrier layer is small, the barrier property is deteriorated. When the external force is continuously applied to the cell pouch, Holes are formed in the cell pouch, and even cell pouches are torn.

Korean Patent Publication No. 10-2008-0058823

In one aspect, the present invention aims to provide a cell pouch which is excellent in bendability that can reduce the barrier property of the barrier layer and the problem of pinholes in the flexible cell pouch.

In another aspect, the present invention aims to provide a secondary battery including a cell pouch excellent in bendability.

In one aspect, the presently disclosed technology relates to a flexible cell pouch comprising: a sealant layer; A barrier layer formed on the sealant layer; And an outer layer formed on the barrier layer, wherein the barrier layer comprises: a) a metal layer on which an uneven surface is formed; and b) a buffer reinforcing layer on which the uneven surface is coated.

According to one exemplary embodiment, the metal layer may be composed of aluminum or an aluminum alloy.

According to an exemplary embodiment, the uneven surface may be formed to a thickness corresponding to 5 to 35% of the entire thickness of the metal layer.

According to one exemplary embodiment, the buffer reinforcing layer may comprise a urethane-based resin.

According to an exemplary embodiment, the cushioning reinforcing layer is formed by filling the gap between the concavities and convexities so as to have a thickness of 3 占 퐉 or more in the outward direction of the concavo-convex surface with reference to a convex top point of the convexo-concaves can do.

According to one exemplary embodiment, the cell pouch may be durable to a number of bending repetitions of less than 15,000 times in a bend test at 25R angular conditions.

In another aspect, the techniques disclosed herein provide a secondary cell comprising the cell pouch.

In one aspect, the technique disclosed in this specification includes a barrier layer including a metal layer on which an irregular surface is formed and a buffer reinforcing layer on which the irregular surface is coated, so that a bending property This provides an excellent cell pouch, for example, a wearable cell pouch.

In another aspect, the technique disclosed in this specification has an effect of providing a secondary battery, for example, a lithium polymer secondary battery including a cell pouch excellent in bending.

1 is a sectional view of a cell pouch according to the prior art.
2 is a cross-sectional view of a cell pouch according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

As used herein, the term "cell " refers to a battery, and includes all kinds of batteries such as a secondary battery such as a lithium ion battery, a lithium polymer battery, and a portable battery.

In the present specification, the term "cell pouch" refers to a structure in which a cell component such as an anode, a cathode, and a separator is impregnated with an electrolyte solution. The cell pouch includes gas barrier properties, Thermal adhesiveness and the like are processed in the form of a bag or a box.

In this specification, "flexibility" means a degree of warpage of a cell and / or a cell pouch, and the cell and / or the flexible cell pouch can be easily bent as the bendability is better.

In the present specification, the "buffering and reinforcing layer" is a layer laminated on the uneven surface formed in the metal layer. The layer is formed to have a constant thickness filling the gap between the unevenness, thereby alleviating damage to the barrier layer, reinforcing the bending property of the uneven surface, Thereby further enhancing the durability of the bending of the bobbin.

In the present specification, the term "top point" means the uppermost point of the unevenness having convexity in the unevenness provided on the uneven surface.

The cell pouch according to one embodiment of the present disclosure includes a sequentially stacked sealant layer; Barrier layer; And at least three layers including an outer layer. At this time, a layer structure, components, and the like that are commonly used for adhesion, heat resistance, cold resistance, corrosion resistance, insulation, and / or moldability between the sealant layer and the barrier layer and between the barrier layer and the outer layer are appropriately employed can do.

A cell pouch according to an embodiment herein includes a sealant layer; A barrier layer formed on the sealant layer; And an outer layer formed on the barrier layer, wherein the barrier layer includes: a) a metal layer on which an uneven surface is formed; and b) a buffer strengthening layer on which the uneven surface is coated.

The sealant layer may include a sealing resin for heat bonding, which is formed by holding (embedding) a cell and then being adhered (heat-sealed) by heat to give sealing property. Since the sealant layer is in contact with the cell component, the sealant layer can be constructed by suitably employing a layer structure commonly used for imparting insulating properties, electrolyte resistance, and / or high heat bonding strength (sealability).

The sealing resin is not limited as long as it can be fused (thermally adhered) by heat, and it may preferably be a resin having heat resistance, insulation property, electrolyte resistance and / or cold resistance.

The sealing resin may preferably be selected from a low-melting-point resin which can be thermally fused at a low temperature.

In one exemplary embodiment, the sealing resin is not limited thereto. For example, a polyolefin series such as a polypropylene (PP) series or a polyethylene (PE) series, a copolymer or a derivative thereof, and an ethylene vinyl acetate May be used. The sealing resin may also be selected from co-polymers or ter-polymers, such as ethylene / propylene copolymers or terpolymers of ethylene / propylene / butadiene (terpolymers) have. In general, polypropylene (PP) based resins are excellent in thermal adhesiveness (sealability) and insulation, and are excellent in mechanical properties such as tensile strength, rigidity and surface hardness, and chemical resistance such as electrolyte resistance, Lt; / RTI >

In an exemplary embodiment, the thickness of the sealant layer is not particularly limited, but may have a thickness of, for example, 10 탆 to 80 탆. The sealant layer may preferably have a thickness of 20 占 퐉 or more, specifically 20 占 퐉 to 70 占 퐉, and more preferably 30 占 퐉 to 60 占 퐉, for good heat-seal strength (sealability).

The barrier layer includes a) a metal layer on which an uneven surface is formed, and b) a buffer layer on which the uneven surface is coated. The barrier layer can block moisture from outside, air, and gas generated from the inside.

The metal layer is not limited as long as it is a metal having a gas barrier property. The metal layer may include at least one selected from a metal thin film and a metal deposition layer. The metal thin film may be a metal foil or the like and the metal vapor deposition layer may be a separate plastic film such as a film made of polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP) For example, by vacuum evaporation.

The metal constituting the metal layer, specifically, the metal constituting the metal thin film or the metal deposition layer may be, for example, aluminum (Al), iron (Fe), copper (Cu), nickel (A single metal or a mixture of single metals) selected from the group consisting of tin (Sn), zinc (Zn), indium (In) and tungsten (W), or alloys of two or more selected therefrom . The metal may preferably be selected from aluminum (Al) or an aluminum alloy (Al alloy).

The metal layer has an irregular surface by molding the surface structure of one surface thereof into a specific pattern, so that the bending property of the cell pouch is further improved.

Unevenness means having concave and / or convex structures, and there is no limitation on the specific shape or number of the concave and / or convex structures. In addition, the height of the irregularities may be the same or different.

Specifically, the uneven surface is preferably 5 to 35%, preferably 7 to 30%, more preferably 10 to 30%, preferably 15 to 27%, more preferably 20 To 25% by weight.

The cushioning reinforcing layer may include a urethane-based resin, specifically, polyurethane. The cushioning reinforcing layer has a synergistic effect that the durability against bending of the cell pouch is further improved by applying a buffering reinforcing layer that acts as a buffer to a portion molded in a specific pattern. That is, it is possible to alleviate damage to any specific portion of the barrier layer.

The cushioning reinforcing layer is formed by filling the gap between the concavities and convexities so as to have a thickness of 3 占 퐉 or more, specifically, 3 to 5 占 퐉 in the outward direction of the concavo-convex surface based on the convex top point of any one of the concavities and convexities can do. Referring to FIG. 2, "H " in the outward direction of the irregular surface with reference to the convex top point of any of the concavities and convexities. For example, the cushioning reinforcing layer can be coated with a concavo-convex surface so as to have a thickness of 3 占 퐉 or more in the outward direction of the concavo-convex surface based on the concave top point of the lowest unevenness or the convex top point of the highest unevenness.

In an exemplary embodiment, the barrier layer may have a thickness of 20 탆 or less, preferably 9 to 20 탆, for facilitating the cell pouch of the secondary battery and improving the bendability of the flexible cell pouch.

The outer layer can protect the barrier layer. The outer layer is preferably made of a material having excellent abrasion resistance as well as heat resistance, cold resistance, pinhole resistance, insulation, solvent resistance and / or moldability (shape retention when a flexible cell pouch is processed into a predetermined shape Lt; RTI ID = 0.0 > and / or < / RTI >

Specifically, the outer layer may include one or more resins selected from nylon resin, polyethylene terephthalate (PET) resin, polyolefin resin, and the like. Here, the polyolefin-based resin may be exemplified by polyethylene (PE) and polypropylene (PP).

In an exemplary embodiment, the outer layer may preferably comprise a nylon resin.

In an exemplary embodiment, the thickness of the outer layer is not particularly limited, but may be, for example, 10 占 퐉 to 50 占 퐉, preferably 5 占 퐉 to 30 占 퐉, more preferably 10 占 퐉 to 25 占 퐉 Lt; / RTI >

The cell pouch can have a durability against bending repetition times of less than 15,000 times in the bending test at 25R angle condition. The durability refers to a performance that is maintained without tearing against the number of bending cycles. The bending property of the flexible cell pouch finished article can be improved by including the metal layer on which the uneven surface is formed and the buffer reinforcing layer for applying the uneven surface. In addition, when the bendability of the flexible cell pouch finished product is improved, the problem of pinholes or the like due to insufficient bending of the cell can be improved. Therefore, the cell pouch is very useful in a secondary battery field used in a flexible device requiring high bendability, which is repeatedly bent and extended.

A method of manufacturing a cell pouch excellent in bendability according to an embodiment of the present invention includes: forming a barrier layer; Forming an outer layer; And forming a sealant layer. The detailed constituent components of each layer are the same as those of the above-described cell pouches, and thus a detailed description thereof will be omitted.

First, a barrier layer is formed.

Specifically, a metal layer is formed using aluminum (Al) metal, and a surface of a push roll used in rolling is formed by etching a surface of the metal layer to form a specific pattern on one surface of the metal layer.

The metal layer may be formed to include at least one selected from a metal thin film and a metal deposition layer. The metal layer may be formed of a plastic film such as polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP) or the like.

Thereafter, thermoplastic polyurethane (TPU), which is an elastomer, is added to an epoxy resin (adhesive), and an uneven surface formed on the metal layer is coated to form a buffer reinforcing layer.

Next, an outer layer is formed on the buffer reinforcing layer.

Specifically, a polymer material such as nylon, polyethylene terephthalate (PET) or the like may be used to laminate the outer layer and the barrier layer by, for example, a lamination process. An example of the lamination process is a dry lamination process.

The outer layer may be formed by coating or co-extruding a composition containing a resin such as nylon resin or the like on the barrier layer, or may be formed by laminating a film made of resin such as nylon resin. The film may include a stretched film such as OPP (Oriented PP).

Then, a sealant layer is formed under the barrier layer.

Specifically, the sealant layer may be formed by performing a dry lamination process, a sandwich lamination process, and / or an extrusion coating process using a material including a sealing resin.

In an exemplary embodiment, the sealing resin may be, for example, a polypropylene-based resin.

In an exemplary embodiment, the temperature of the lamination process can be from about 50 to 250 캜, and preferably from about 150 to 200 캜.

The cell pouch is fabricated by processing a film of the above laminated structure into a bag shape, a box shape, or the like. In the cell pouch, cell components such as an anode, a cathode, and a separator are impregnated with an electrolytic solution and then stored. After housing the cell components, the cell pouch inlet is thermally bonded (heat sealed) to maintain airtightness.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

Example .

A metal layer having a thickness of about 20 μm was formed using aluminum (Al) metal, and the surface of the pressing roll used for rolling was formed by etching the surface of the metal layer to form an uneven surface on one surface of the metal layer. Thereafter, 5% by weight of a thermoplastic polyurethane (TPU), which is an elastomer, was added to an epoxy resin (adhesive) and the uneven surface was coated to form a buffer reinforcing layer. Thereafter, a sealant layer was coated on one side of the barrier layer including the metal layer on which the uneven surface was formed and the full-layer reinforcing layer to have a thickness of about 50 탆 at 180 캜. Then, an outer layer of nylon resin was coated on the other surface of the barrier layer to a thickness of about 12 μm.

Thereby, as shown in FIG. 2, a flat shape in which the sealant layer 10, the metal layer 20, the buffer reinforcing layer 30, and the outer layer 40 are sequentially laminated, Cell pouches were prepared.

Comparative Example .

In the above example, a cell pouch was manufactured under the same conditions as those of the above example except that the barrier layer was formed of an aluminum thin film having a thickness of about 20 mu m. That is, the barrier layer of the comparative example has no uneven surface on one surface of the metal layer and does not have a buffer reinforcing layer.

Test Example  One.

The cell pouches prepared according to the above Examples and Comparative Examples were each fixed to a bending test machine, bent at an angle of 25R, and then bending was repeatedly performed to perform a bending test. Here, 25R means the radius of curvature of a sphere having a radius of 2.5 cm. In addition, the result is shown as "OK" when the shape is maintained without tearing at a specific site according to the number of times of bending, and "NG (no good)" when a tear occurs at a specific site. On the other hand, if the result is "NG", it is meaningless to apply additional bending afterwards.

Table 1. Bending test results of the cell pouch according to Examples and Comparative Examples

As a result, as shown in Table 1, in the case of the cell pouch manufactured according to the comparative example not including the metal layer on which the uneven surface was formed and the buffer layer for applying the uneven surface, Tearing occurred at specific sites when repeatedly applied. As described above, in the conventional flexible cell pouch structure, when the surface of the aluminum metal layer is smooth and bending, there is a problem that a specific portion is damaged.

On the other hand, in the case of the cell pouch fabricated according to the embodiment including the metal layer on which the uneven surface is formed and the buffer reinforcing layer on which the uneven surface is coated, it was confirmed that the outer shape was maintained without being broken by the bending test of less than 15,000 times. Thus, it can be seen that the buffer layer that fills the gap between the metal layer on which the uneven surface is formed and the unevenness and damages that may occur when the buffering and reinforcing layer that applies the uneven surface is bent, provides buffering action and gives excellent bendability to the cell pouch there was.

Test Example  2.

The cell pouches were manufactured in the same manner as in the above example except that the cell pouches including the metal layer having the irregularities formed in the thicknesses of 0, 5, 10, 15, 20, 25 and 30% A bendability test was conducted in the same manner as in Test Example 1 above.

Table 2. Bending test results according to the height of concave and convex in the cell pouch according to the embodiment

As a result, as shown in Table 2, when the thickness of the uneven surface is 0%, the bending characteristics are insufficient, but when the thickness of the uneven surface is increased up to 25%, the bending durability is increased in proportion thereto. On the other hand, when the thickness of the uneven surface was 25%, the best bendability was exhibited.

Test Example  3.

The cell pouches were prepared in the same manner as in the above example except that the cushioning reinforcing layer was applied to the height of the concave and convex portions, 3 to 5 占 퐉 was applied to the concave and convex portions, and 5 占 퐉 or more was applied to the concave and convex portions to prepare cell pouches , A bendability test was conducted in the same manner as in Test Example 1 above.

Table 3. Bending test results according to the height of the cushioning reinforcing layer in the cell pouch according to the embodiment

As a result, as shown in Table 3, when the cushioning reinforcing layer was applied by the height of the unevenness, the bending property was insufficient and the adhesion with the film to be cemented was not secured. However, when the cushioning reinforcing layer was applied over 3 μm, the bending durability It was found to be improved. On the other hand, bending durability did not change even when the buffer reinforcing layer was formed to a thickness of 5 탆 or more.

Having described specific portions of the present invention in detail, it will be apparent to those skilled in the art that this specific description is only a preferred embodiment and that the scope of the present invention is not limited thereby. It will be obvious. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (7)

A sealant layer;
A barrier layer formed on the sealant layer; And
And an outer layer formed on the barrier layer,
Wherein the barrier layer comprises: a) a metal layer on which an uneven surface is formed; and b) a buffer reinforcing layer for applying the uneven surface.
The method according to claim 1,
Wherein the metal layer is made of aluminum or an aluminum alloy.
The method according to claim 1,
Wherein the uneven surface is formed to a thickness corresponding to 5 to 35% of the entire thickness of the metal layer.
The method according to claim 1,
Wherein the buffer reinforcing layer comprises a urethane-based resin.
The method according to claim 1,
Characterized in that the cushioning reinforcing layer is formed by filling the gap between the concavities and convexities and applying the concavo-convex surface so as to have a thickness of 3 占 퐉 or more in the outward direction of the concavo-convex surface on the basis of the convex top point of any one of the concavities and convexities This excellent cell pouch.
The method according to claim 1,
Wherein the cell pouch has durability against a number of bending repetitions of less than 15,000 times in a bending test at an angle condition of 25R.
A secondary battery comprising the cell pouch of any one of claims 1 to 6.

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