KR102036586B1 - Pouch-type Secondary Battery Having Gas Adsorbent Polymer Layer - Google Patents

Abstract

The present invention relates to a secondary battery in which an electrode assembly is sealed in an inside of a pouch-type battery case together with an electrolyte solution, wherein the battery case is formed of a laminate sheet including an outer coating layer and a metal layer, and the laminate sheet is a gas generated inside the battery. It provides a secondary battery comprising a gas-adsorbable polymer layer for adsorbing.

Description

Pouch-type Secondary Battery Having Gas Adsorbent Polymer Layer

The present invention relates to a pouch type secondary battery comprising a gas adsorptive polymer layer.

As technology development and demand for mobile devices increase, the demand for batteries as energy sources is rapidly increasing, and accordingly, many studies on batteries that can meet various demands have been conducted.

Representatively, there is a high demand for square and pouch type secondary batteries that can be applied to products such as mobile phones with a thin thickness in terms of shape of batteries, and high energy density, discharge voltage, and output stability in terms of materials. Demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries is high.

In addition, a pouch-type battery having a structure in which a stack type or a stack / fold type electrode assembly is incorporated in a pouch type battery case of an aluminum laminate sheet has attracted much attention due to its low manufacturing cost, small weight, and easy shape deformation. Its usage is gradually increasing.

However, conventional lithium secondary batteries have a risk of ignition / explosion when exposed to high temperatures. Specifically, when the temperature of the battery rises, the reaction between the electrolyte and the electrode is promoted, and as a result, heat of reaction is generated to further increase the temperature of the battery, which in turn accelerates the reaction between the electrolyte and the electrode. Therefore, due to the vicious cycle of rapid increase of the battery temperature and the acceleration of the reaction between the electrolyte and the electrode, a thermal runaway phenomenon in which the temperature of the battery rises rapidly may occur, and the battery may ignite when the temperature rises above a certain level. .

In addition, when the lithium secondary battery is used and stored for a long time or at a high temperature, the electrolyte is decomposed or a reaction between the electrolyte and the electrode, gas such as carbon dioxide is generated, and the internal pressure of the battery is increased, resulting in a swelling phenomenon. Lithium secondary batteries will explode. The risk of ignition / explosion can be said to be the most fatal drawback of lithium secondary batteries.

Therefore, essential considerations for the development of a lithium secondary battery are to ensure safety.

Thus, one of the methods using the material inside the cell is a method of adding an additive that improves safety to the electrolyte or the electrode. Such a chemical safety device does not require additional processes and spaces and has the advantage of being applicable to all kinds of batteries, but has a problem that the performance of the battery is degraded due to the addition of materials.

Therefore, there is a high demand for the development of new safety means for preventing fire / explosion without degrading overall performance of the battery.

The present invention aims to solve the problems of the prior art as described above and the technical problems that have been requested from the past.

The inventors of the present application, after repeated studies and various experiments, as described later, when manufacturing a pouch-type battery cell using a laminate sheet containing a polymer layer containing a gas-adsorbable polymer, the gas adsorption Due to the structural characteristics of the polymer, the adsorption of gas generated inside the battery cell may be increased.

In addition, in terms of preventing the overall thickness increase of the laminate sheet, not only the gas adsorbent polymer layer can be used as a structure to replace the internal adhesive layer of the conventional laminate sheet, but also can be used together with the internal adhesive layer, increasing the gas inside the battery cell. It is possible to improve the safety of the battery by suppressing explosion and fire.

In order to achieve the above object, a secondary battery according to the present invention is a secondary battery in which an electrode assembly is sealed in an inside of a pouch-type battery case together with an electrolyte, and the battery case is formed of a laminate sheet including an outer coating layer and a metal layer. The laminate sheet has a structure including a gas adsorbent polymer layer for adsorbing gas generated in the battery.

As described above, the secondary battery according to the present invention has a structure including a gas adsorptive polymer layer capable of absorbing gas such as carbon dioxide generated in a battery cell during a normal use process, and has a hollow fiber form in the gas adsorptive polymer layer. By incorporating a polymer of, the gas inside the battery cell can be adsorbed. Therefore, in the related art, the swelling phenomenon due to the gas generation inside the battery cell, and the explosion and ignition phenomena caused by the battery can be improved, thereby greatly improving the safety of the battery.

In addition, when oxides or hydroxides are used as gas adsorbents in the related art, there is a problem that side reactions with electrolytes occur. When gas adsorbent polymers are used, there is no reactivity with membranes or electrodes, thereby preventing side reactions with electrolytes. Not only can it solve the problem of poor cell performance.

In one specific example, the gas adsorptive polymer layer is located inside the opposite side of the metal layer facing the outer coating layer. As such, since the gas-adsorbable polymer layer is positioned to be adjacent to the electrode assembly housed in the battery case, the gas can be adsorbed quickly and easily.

The laminate sheet used in the secondary battery does not include a separate adhesive layer, unlike an adhesive layer for sealing a battery case in a conventional general laminate sheet, and the gas absorbent polymer layer includes a matrix binder in addition to a gas absorbent polymer. It may be a configuration.

Herein, the matrix binder refers to a polymer present in the polymer matrix forming the gas adsorptive polymer layer, and the gas adsorbent polymer layer existing on the innermost side of the laminate sheet has a matrix binder in addition to the polymer for gas adsorption for sealing the battery case sealing part. It contains more.

Therefore, the matrix binder may be included in an appropriate range in consideration of the ratio of the gas-adsorbable polymer within the range of not lowering the sealing force of the battery case sealing portion.

The gas-adsorbable polymer may be polybenzimidazole (PBI), and the PBI is formed in the shape of a hollow fiber having a porous structure. As such, due to the large surface area and hollow structure of the PBI, not only a large amount of carbon dioxide can be adsorbed, but also a stable polymer structure does not cause chemical side reactions with the compounds in the battery cell, thereby degrading performance. Does not occur.

The material of the matrix binder is not particularly limited as long as it does not lower the adhesive strength of the sealing portion. For example, in the group consisting of epoxy, phenol, melamine, polyester, urethane, polyethylene terephthalate and polyetherurethane, It may be made of one or more selected.

In one specific example, the gas-adsorbing polymer may be included in 40% by weight to 90% by weight based on the total weight of the gas absorbent polymer layer, in detail, may be included in 50% by weight to 90% by weight, more Specifically, it may be included in 50% by weight to 80% by weight.

When the gas-adsorbing polymer contains less than 40% by weight based on the total weight of the gas-adsorbing polymer layer, since the amount of gas that can be adsorbed is reduced, the amount of gas that can be stored is small and swelling phenomenon occurs in a short time. It may occur, if it is included in more than 90% by weight, it is not preferable because the content of the matrix binder is relatively reduced, there is a fear that the adhesive strength of the sealing portion is lowered.

On the other hand, the thickness of the gas-adsorbable polymer layer may be formed in the range of 10 micrometers to 30 micrometers, in detail, may be formed in the range of 15 micrometers to 30 micrometers.

If the thickness of the gas-adsorbable polymer layer is thinner than 10 micrometers, there is a problem that the amount of gas that can be adsorbed is reduced because the amount of the gas-adsorbing polymer contained is reduced, and if the thickness of the gas-adsorbable polymer layer is thicker than 30 micrometers, the overall laminate sheet Increasing the thickness of the battery cell can not provide a compact structure is not preferable.

In one specific example, in order to improve the sealing force of the battery case sealing portion, an inner adhesive layer may be formed, the laminate sheet is a metal layer is located on one side of the gas-adsorbing polymer layer, at least of the other surface of the gas-adsorbing polymer layer An internal adhesive layer may be located in some.

For example, the inner adhesive layer may be located at a portion where the sealing portion of the battery case is formed. As such, since the inner adhesive layer is formed only at the portion where the sealing portion is formed, an additional inner adhesive layer is not formed around the accommodating portion. It is possible to prevent the thickness of the cell from increasing.

In this case, the thickness of the gas-adsorbable polymer layer is required to be formed thinner than when not including a separate inner adhesive layer, considering that the inner adhesive layer is further included, it may be 5 micrometers to 20 micrometers And in detail, may be 8 micrometers to 15 micrometers.

If the thickness of the gas-adsorbing polymer layer is thinner than 5 micrometers, it is difficult to expect to exhibit a desired degree of gas adsorption, and if it is thicker than 20 micrometers, the thickness of the entire laminate sheet may be thick, which is not preferable. .

In one specific example, the gas-adsorbing polymer layer may be formed only in the accommodating part as an inner side of the metal layer facing the outer coating layer, and an inner adhesive layer may be formed in the inner side of the metal layer corresponding to the sealing part except the accommodating part.

In the case of using a laminate sheet having such a structure, since the internal adhesive layer is not additionally interposed, there is no problem of increasing the thickness of the overall laminate sheet, and the gas adsorptive power is also prevented from being lowered because the gas adsorbent polymer layer is not formed thin. can do.

On the other hand, when the thickness of the gas-adsorbing polymer layer and the thickness of the inner adhesive layer is formed to be the same, the thickness in the entire area of the laminate sheet may be formed uniformly.

On the other hand, the thickness of the gas-adsorbable polymer layer may be formed relatively larger than the thickness of the inner adhesive layer, so that when the size of the electrode assembly accommodated in the battery cell is increased, the amount of gas generated is increased. Therefore, since the thickness of the gas-adsorbable polymer layer is required to increase, it is preferable to use a laminate sheet having such a structure.

In another specific example, the laminate sheet constituting the secondary battery according to the present invention may have a structure further comprising an inner adhesive layer between the metal layer and the gas-adsorbable polymer layer.

As such, when the internal adhesive layer is interposed between the metal layer and the gas-adsorbable polymer layer, the thickness of the metal layer or the gas-adsorbable polymer layer may be thin in order to prevent an increase in the thickness of the laminate sheet. In the case where the strength of the cell is weakened, and the thickness of the gas-adsorbable polymer layer becomes thin, the swelling phenomenon can be easily taken into consideration, and can be set within an appropriate range.

In another specific example, the gas adsorptive polymer layer may be formed on at least a portion of an outer surface of the inner adhesive layer. For example, the gas absorbent polymer layer may be formed of an inner adhesive layer contacted with an electrolyte except for a sealing part of a battery case. It may be formed on the outer surface. As such, even when the internal adhesive layer is interposed, when the gas-adsorbable polymer layer is formed only at the portion except the sealing part of the battery case, there is no problem of increasing the thickness of the laminate sheet and an advantage of increasing the carbon dioxide adsorption power. There is this.

The present invention also provides a battery pack including the lithium secondary battery as a unit cell and a device including the battery pack as a power source.

Specifically, the battery pack may be used as a power source for devices requiring high temperature safety, long cycle characteristics, and high rate characteristics. Detailed examples of such a device include a power tool that is driven by a mobile electronic device and a battery-based motor. power tool; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric motorcycles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf carts; Power storage systems and the like, but is not limited thereto.

Since the structure of these devices and their fabrication methods are known in the art, detailed description thereof is omitted herein.

As described above, the secondary battery according to the present invention includes a polymer layer containing a gas-adsorbable polymer in the laminate sheet constituting the pouch-type battery cell, thereby adsorbing the gas generated in the normal use process of the battery and swelling phenomenon. It is possible to prevent, and to suppress the explosion or ignition of the battery due to the increase in the internal pressure of the battery, as a result can significantly improve the safety of the battery.

In addition, since the gas-adsorbable polymer layer can be used as a structure to replace the adhesive layer of the conventional laminate sheet, or can be formed only on a part of the laminate sheet, it is possible to prevent the reduction of the battery capacity by preventing the thickness of the entire laminate sheet from increasing. have.

1 is a vertical sectional view of a laminate sheet on which a gas-adsorbable polymer layer is formed according to one embodiment of the present invention;
2 is a perspective view of a pouch type secondary battery according to the present invention;
3 is a cross-sectional view taken along the line AA ′ of FIG. 2;
4 is a vertical sectional view of a laminate sheet on which a gas adsorptive polymer layer is formed, according to another embodiment of the present invention; And
5 is a vertical cross-sectional view of a laminate sheet on which a gas adsorptive polymer layer is formed according to another embodiment of the present invention.

Hereinafter, although described with reference to the drawings according to an embodiment of the present invention, this is for easier understanding of the present invention, the scope of the present invention is not limited thereto.

1 schematically shows a cross section of a laminate sheet on which a gas-adsorbable polymer layer is formed according to one embodiment of the present invention.

Referring to FIG. 1, in the laminate sheet 100, an outer coating layer 110, a metal layer 120, and a gas adsorbent polymer layer 130 are sequentially stacked from the outside. In the laminate sheet of such a structure, the thickness in the entire area of the laminate sheet can be formed uniformly.

Since the outer coating layer 110 forms the outer surface of the battery case, high tensile strength and weather resistance are required to stably protect the electrode assembly against the external environment, and made of polyethylene terephthalate (PET) or stretched nylon (Ony). The outer cladding layer 110 may satisfy such requirements.

The metal layer 120 is a layer for blocking gas, moisture, and the like including air. The metal layer 120 is excellent in formability, can be given a predetermined strength, and can block moisture or air, and is preferably aluminum, aluminum alloy, or copper. Etc. can be used.

The gas adsorbent polymer layer 130 includes a gas adsorbent polymer 131 as a main component, and the gas adsorbent polymer 131 is 40 wt% to 90 wt% based on the total weight of the polymer layer 130. Included. Meanwhile, the thickness D1 of the gas absorbent polymer layer 130 may be set within a range of 10 micrometers to 30 micrometers.

FIG. 2 schematically illustrates a perspective view of a pouch type secondary battery according to the present invention, and FIG. 3 schematically illustrates a cross-sectional view of a cut part of the battery case cut along the line AA ′ of FIG. 2.

2 and 3, in the pouch type secondary battery of FIG. 2, the lower case 220 including the electrode assembly accommodating part 203 and the lower case 220 and the sealing are formed on the upper surface of the accommodating part 203. Is composed of an upper case 210, the upper case 210 and the lower case 220 is made of a structure connected to each other on the outer peripheral surface. The upper case 210 and the lower case 220 are sealed by heat fusion, and the sealing part is formed on the outer periphery 211 of the upper case 210 and the outer periphery 221 of the lower case 220. do.

In the laminate sheet 300 of FIG. 3, the outer coating layer 310, the metal layer 320, and the gas-adsorbing polymer layer 330 are sequentially stacked from the outside, and the sealing portion of the battery case is formed at the portion forming the sealing portion 301. An inner adhesive layer 340 is formed to improve the force. In the laminate sheet 300, the thickness D2 of the gas adsorptive polymer layer 330 may be 5 micrometers to 20 micrometers.

Figure 4 schematically shows a vertical cross-sectional view of the laminate sheet constituting the pouch-type battery case according to the present invention, showing another embodiment cut at the same portion as AA 'of FIG.

Referring to FIG. 4, in the laminate sheet 400, an outer coating layer 410, a metal layer 420, and a gas adsorbent polymer layer 430 are sequentially stacked from the outside, and the gas adsorbent polymer layer 430 is formed in the metal layer. It is formed only on a part of the side. Specifically, the gas adsorbent polymer layer 430 is not formed on the inner side of the metal layer corresponding to the sealing part 401, and the inner adhesive layer 440 is formed, and the gas adsorbent polymer layer 430 is the sealing part. It is formed on the inner surface of the remaining metal layer except for 401. Therefore, eliminating unnecessary formation of the gas-adsorbing polymer layer in the sealing portion, and solve the problem that the sealing force may be reduced due to the formation of the gas-adsorbing polymer layer.

On the other hand, the thickness (D4) of the gas-adsorbing polymer layer including the gas-adsorbing polymer 430 may be formed to be the same as the thickness (D3) of the internal adhesive layer, the thickness (D4) of the gas-adsorbing polymer layer to increase the gas adsorption force Of course it can be formed thicker than the thickness (D3) of the inner adhesive layer.

Figure 5 schematically shows a vertical cross-sectional view of the laminate sheet constituting the pouch-type battery case according to the present invention, showing another embodiment cut in the same portion as A-A 'of FIG.

Referring to FIG. 5, in the laminate sheet 500, an outer coating layer 510, a metal layer 520, an inner adhesive layer 540, and a gas adsorbent polymer layer 530 are sequentially stacked from the outside, and the inner adhesive layer 540 is laminated. It is interposed in the whole inner surface of the silver metal layer, and the gas adsorption polymer layer 530 is formed in a part of the inner surface of an inner adhesion layer.

Specifically, since the gas-adsorbing polymer layer 530 is formed only in the remaining portion of the inner adhesive layer 540 except for the portion corresponding to the sealing portion 501, the gas-adsorbing polymer layer 530 does not reduce the adsorption force of the gas generated inside the battery cell. It can prevent that a sealing force falls.

Those skilled in the art will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Claims (19)

A secondary battery in which an electrode assembly is sealed in an inside of a pouch-type battery case together with an electrolyte solution, wherein the battery case is formed of a laminate sheet including an outer coating layer and a metal layer, and the laminate sheet adsorbs gas generated in the battery. Including a gas-adsorbable polymer layer,
The gas adsorptive polymer layer is formed only in the housing part in close contact with the inner side of the metal layer facing the outer coating layer, and an inner adhesive layer thinner than the thickness of the gas adsorption polymer layer is formed in the sealing part except the housing part.
The gas adsorbent polymer layer is a secondary battery comprising an adsorbent polymer of polybenzimidazole (PBI) having a hollow fiber shape having a porous structure, and a matrix binder. delete delete delete delete The secondary battery of claim 1, wherein the matrix binder comprises at least one selected from the group consisting of epoxy, phenol, melamine, polyester, urethane, polyethylene terephthalate and polyetherurethane. . The secondary battery of claim 1, wherein the gas adsorbent polymer is included in an amount of 40 wt% to 90 wt% based on the total weight of the gas adsorbent polymer layer. The secondary battery of claim 1, wherein a thickness of the gas adsorptive polymer layer is 10 micrometers to 30 micrometers. delete delete delete delete delete delete delete delete delete A battery pack comprising the secondary battery according to any one of claims 1 and 6 to 8 as a unit cell. A device comprising the battery pack according to claim 18 as a power source.

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