KR20170064796A - 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 inside a pouch-shaped battery case together with an electrolyte solution, the battery case is composed of a laminate sheet including an outer coating layer and a metal layer, The present invention also provides a secondary battery comprising the gas-absorbing polymer layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pouch-type secondary battery including a gas-absorbing polymer layer,

The present invention relates to a pouch-type secondary battery including a gas-absorbing polymer layer.

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 capable of meeting 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.

Further, 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 is attracting much attention due to low manufacturing cost, small weight, Its usage is gradually increasing.

However, the conventional lithium secondary battery has a risk of ignition / explosion when exposed at a high temperature. Specifically, when the temperature of the battery rises, the reaction between the electrolyte and the electrode is promoted. As a result, a reaction heat is generated, and the temperature of the battery further rises, which accelerates the reaction between the electrolyte and the electrode again. Therefore, a thermal runaway phenomenon occurs in which the temperature of the battery rises sharply due to a vicious cycle of rapid increase of the battery temperature and acceleration of the reaction between the electrolyte and the electrode, and when the temperature rises to a certain level or more, the battery may ignite .

Further, when the lithium secondary battery is used and stored for a long time or at a high temperature, the electrolytic solution is decomposed or a gas such as carbon dioxide is generated as a result of the reaction between the electrolytic solution and the electrode, The lithium secondary battery explodes. Such a risk of ignition / explosion is the most fatal disadvantage of the lithium secondary battery.

Therefore, it is necessary to secure safety for the development of lithium secondary batteries.

As a method of using the material inside the cell, there is a method of adding an additive for improving the safety to the electrolytic solution or the electrode. Such a chemical safety device does not require additional process and space, and has the advantage that it can be applied to all kinds of batteries. However, the performance of the battery deteriorates due to the addition of materials.

Therefore, there is a high need for the development of new safety measures for preventing ignition / explosion without deteriorating the overall performance of the battery.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that when a pouch-shaped battery cell is manufactured using a laminate sheet having a polymer layer including a gas-absorbing polymer as described later, Due to the structural characteristics of the polymer, adsorption of gas generated inside the battery cell can be increased.

In addition, from the viewpoint of preventing an increase in the overall thickness of the laminate sheet, the gas-absorbing polymer layer can be used together with the inner adhesive layer as well as the structure replacing the inner adhesive layer of the conventional laminate sheet, So that the safety of the battery can be improved.

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 inside a pouch-shaped battery case together with an electrolyte solution, and the battery case is composed of a laminate sheet including an outer coating layer and a metal layer The laminate sheet has a structure including a gas-absorbing polymer layer that absorbs gas generated in the battery.

As described above, the secondary battery according to the present invention includes a gas-absorbing polymer layer capable of absorbing a gas such as carbon dioxide generated in the battery cell during normal use, wherein the gas-absorbing polymer layer has a hollow fiber shape The gas inside the battery cell can be adsorbed. Accordingly, the swelling phenomenon due to the generation of gas in the battery cell and the explosion and ignition phenomenon of the battery due to the generation of gas inside the battery cell can be improved, and thus the safety of the battery can be greatly improved.

In the case of using an oxide or a hydroxide as a gas adsorbing material in the past, there has been a problem of side reaction with an electrolyte. In the case of using a gas adsorbing polymer, there is no reactivity with a separator or an electrode, The problem of deteriorating cell performance can be solved.

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

The laminate sheet used for the secondary battery does not include a separate adhesive layer unlike the conventional laminate sheet in which an adhesive layer for sealing the battery case is formed. The gas-absorbent polymer layer includes a matrix binder in addition to the gas- Lt; / RTI >

Here, the matrix binder means a polymer existing in the polymer matrix forming the gas-absorbing polymer layer. In the gas-adsorbing polymer layer located on the innermost side of the laminate sheet, a matrix binder .

Therefore, the matrix binder can be included within an appropriate range in consideration of the ratio of the gas-adsorbing polymer within a range not lowering the sealing ability of the battery case sealing portion.

The gas-absorbing polymer may be a polybenzimidazole (PBI), and the PBI may be in the form of a hollow fiber having a porous structure. As described above, the large surface area and the hollow structure of the PBI can not only absorb a large amount of carbon dioxide, but also cause a chemical side reaction with the compounds in the battery cell due to the stable polymer structure, .

The material of the matrix binder is not particularly limited as long as it does not lower the adhesive force of the sealing portion. For example, it is preferable that the matrix binder is composed of an epoxy-based, phenol- And can be made of at least one kind selected.

In one specific example, the gas-absorbing polymer may be contained in an amount of 40% by weight to 90% by weight, more specifically 50% by weight to 90% by weight, based on the total weight of the gas- And more specifically 50% to 80% by weight.

When the gas-absorbing polymer is contained in an amount of less than 40% by weight based on the total weight of the gas-absorbing polymer layer, the amount of gas that can be adsorbed is reduced, If it is contained in an amount of more than 90% by weight, the content of the matrix binder may be relatively decreased, and the adhesive strength of the sealing portion may be lowered.

The thickness of the gas-absorbing polymer layer may be in the range of 10 micrometers to 30 micrometers, and more specifically in the range of 15 micrometers to 30 micrometers.

When the thickness of the gas-absorbing polymer layer is thinner than 10 micrometers, the amount of the gas-adsorbing polymer contained therein is reduced, thereby reducing the amount of adsorbable gas. When the thickness is greater than 30 micrometers, The battery cell of a compact structure can not be provided.

In one specific example, an inner adhesive layer may be formed in order to improve the sealing performance of the battery case sealing portion. The laminate sheet may include a metal layer on one surface of the gas-absorbing polymer layer, An internal adhesive layer may be located on some.

For example, the inner adhesive layer may be located at a portion where the sealing portion of the battery case is formed. Since the inner adhesive layer is formed only in the portion where the sealing portion is formed, no additional inner adhesive layer is formed around the receiving portion. It is possible to prevent the thickness of the cell from increasing.

The thickness of the gas-absorbing polymer layer is required to be thinner than that of the gas-absorbing polymer layer not including the separate internal adhesive layer, considering that the internal adhesive layer is further included, And more specifically from 8 micrometers to 15 micrometers.

When the thickness of the gas-absorbing polymer layer is less than 5 micrometers, it is difficult to expect a desired degree of gas adsorption, and when the thickness is more than 20 micrometers, the overall thickness of the laminate sheet may become too thick .

In one specific example, the gas-absorbing polymer layer is formed only on the accommodating portion as an inner side opposite to the metal layer facing the outer covering layer, and an inner adhesive layer may be formed on the inner side of the metal layer corresponding to the sealing portion excluding the accommodating portion.

When a laminate sheet having such a structure is used, there is no problem of an increase in the thickness of the entire laminate sheet because no internal adhesive layer is additionally provided, and the gas adsorption polymer layer is not required to be formed thin, can do.

On the other hand, when the thickness of the gas-absorbing polymer layer and the thickness of the inner adhesive layer are the same, the thickness of the entire laminate sheet can be uniformly formed.

On the other hand, since the thickness of the gas-absorbing polymer layer can be relatively larger than the thickness of the internal adhesive layer, when the size of the electrode assembly housed in the battery cell becomes large as a high capacity battery cell, The thickness of the gas-absorbing polymer layer is required to be increased. It is therefore 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 including an inner adhesive layer between the metal layer and the gas-absorbing polymer layer.

When the internal adhesive layer is interposed between the metal layer and the gas-absorbing polymer layer, the thickness of the metal layer or the gas-absorbing polymer layer may be thinned to prevent the thickness of the laminate sheet from being increased. There is a problem that the strength of the cell is weakened, and when the thickness of the gas-absorbing polymer layer is thin, the swelling phenomenon can easily occur.

In another specific example, the gas-absorbing polymer layer may be formed on at least a part of the outer surface of the inner adhesive layer. For example, the gas-absorbing polymer layer may include an inner adhesive layer May be formed on the outer surface. Thus, even when the internal adhesive layer is interposed, in the case where the gas-absorbing polymer layer is formed only in the portion excluding the sealed portion of the battery case, there is no problem of an increase in the thickness of the substantially laminated sheet and an advantage .

The present invention also provides a battery pack including the lithium secondary battery as a unit battery 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. Examples of such devices include mobile electronic devices, power tools that are powered by a battery- a power tool; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; And a power storage system, but the present invention is not limited thereto.

The structure of these devices and their fabrication methods are well known in the art, and a detailed description thereof will be omitted herein.

As described above, the secondary battery according to the present invention includes a polymer layer including a gas-absorbing polymer in a laminate sheet constituting a pouch-shaped battery cell, thereby adsorbing gas generated during normal use of the battery, And the explosion or ignition of the battery due to an increase in the internal pressure of the battery is suppressed. As a result, the safety of the battery can be greatly improved.

Further, since the gas-absorbing polymer layer can be used as a substitute for the adhesive layer of the conventional laminate sheet or can be formed only in a part of the laminate sheet, the thickness of the entire laminate sheet is not increased, have.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical cross-sectional view of a laminate sheet having a gas-absorbing polymer layer 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 line A-A 'of FIG. 2;
4 is a vertical sectional view of a laminate sheet having a gas-absorbing polymer layer formed according to another embodiment of the present invention; And
5 is a vertical sectional view of a laminated sheet having a gas-absorbing polymer layer according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a cross-section of a laminate sheet having a gas-absorbing polymer layer according to an embodiment of the present invention.

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

Since the outer coating layer 110 forms the outer surface of the battery case, it is required to have high tensile strength and weather resistance in order to protect the electrode assembly stably against the external environment, and is made of polyethylene terephthalate (PET) or stretched nylon The outer coating layer 110 can satisfy the above-described requirements.

The metal layer 120 is a layer that blocks gas, moisture, etc., including air, and is excellent in moldability, can be given a predetermined strength, and is capable of blocking moisture and air, and aluminum, aluminum alloy, copper Etc. may be used.

The gas-adsorbing polymer layer 130 includes the gas-adsorbing polymer 131 as a main constituent. The gas-absorbing polymer layer 131 is contained in an amount of 40 to 90% by weight based on the total weight of the polymer layer 130 . On the other hand, the thickness D1 of the gas-absorbing polymer layer 130 may be set within a range of 10 micrometers to 30 micrometers.

FIG. 2 schematically shows a perspective view of a pouch type secondary battery according to the present invention, and FIG. 3 schematically shows a cross-sectional view of a cut-away portion of a battery case cut along a line A-A 'in FIG.

2 and 3, the pouch type secondary battery of FIG. 2 includes a lower case 220 including an electrode assembly receiving portion 203 and a sealing portion formed on an upper surface of the receiving portion 203 with the lower case 220 The upper case 210 and the lower case 220 are connected to each other at a part of the outer circumferential surface. The upper case 210 and the lower case 220 are sealed by thermal fusion so that a sealing portion is formed on the outer periphery 211 of the upper case 210 and the outer periphery 221 of the lower case 220 do.

3, the outer covering layer 310, the metal layer 320 and the gas-absorbing polymer layer 330 are sequentially laminated from the outer side. In the portion where the sealing portion 301 is formed, An internal adhesive layer 340 is formed to improve the strength. The thickness D2 of the gas-absorbing polymer layer 330 in the laminate sheet 300 may be 5 to 20 micrometers.

FIG. 4 schematically shows a vertical cross-sectional view of a laminated sheet constituting a pouch-shaped battery case according to the present invention, and shows another embodiment cut at the same portion as A-A 'in FIG.

4, the laminate sheet 400 is sequentially laminated with an outer coating layer 410, a metal layer 420 and a gas-absorbing polymer layer 430 from the outside, and the gas-absorbing polymer layer 430 is laminated on the inner side of the metal layer And is formed only on a part of the side surface. Specifically, the gas-absorbing polymer layer 430 is not formed on the inner surface of the metal layer corresponding to the sealing portion 401, but an internal adhesive layer 440 is formed. The gas- (Not shown). Therefore, the formation of an unnecessary gas-absorbing polymer layer is eliminated in the sealed portion, and the sealing ability can be lowered due to the formation of the gas-absorbing polymer layer.

The thickness D4 of the gas-absorbing polymer layer including the gas-absorbing polymer 430 may be the same as the thickness D3 of the inner adhesive layer. However, the thickness D4 of the gas- May be formed to be thicker than the thickness D3 of the inner adhesive layer.

Fig. 5 schematically shows a vertical cross-sectional view of a laminated sheet constituting a pouch-shaped battery case according to the present invention, and shows another embodiment in which the laminate sheet is cut at the same portion as A-A 'in Fig.

5, the laminate sheet 500 includes an outer coating layer 510, a metal layer 520, an inner adhesive layer 540, and a gas-absorbing polymer layer 530 sequentially stacked from the outside, and the inner adhesive layer 540, And the gas-absorbing polymer layer 530 is formed on a part of the inner surface of the inner adhesive layer.

Specifically, since the gas-absorbing polymer layer 530 is formed only in the remaining portion of the internal adhesive layer 540 excluding the portion corresponding to the sealing portion 501, the gas- It is possible to prevent the sealing force from being lowered.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (19)

A secondary battery in which an electrode assembly is sealed in an interior of a pouch-shaped battery case together with an electrolyte, wherein the battery case is composed of a laminate sheet including an outer coating layer and a metal layer, and the laminate sheet adsorbs And a gas-absorbing polymer layer. The secondary battery according to claim 1, wherein the gas-absorbing polymer layer is located on the opposite side of the metal layer facing the outer coating layer. The secondary battery according to claim 1, wherein the gas-absorbing polymer layer comprises a gas-absorbing polymer and a matrix binder. The secondary battery according to claim 3, wherein the gas-absorbing polymer is polybenzimidazole (PBI). 5. The secondary battery according to claim 4, wherein the PBI is in the form of a hollow fiber having a porous structure. The secondary battery according to claim 3, wherein the matrix binder is at least one selected from the group consisting of epoxy, phenol, melamine, polyester, urethane, polyethylene terephthalate and polyether urethane. . The secondary battery according to claim 3, wherein the gas-absorbing polymer is contained in an amount of 40% by weight to 90% by weight based on the total weight of the gas-absorbing polymer layer. The secondary battery according to claim 1, wherein the thickness of the gas-absorbing polymer layer is 10 micrometers to 30 micrometers. The secondary battery according to claim 1, wherein the laminate sheet has a metal layer on one surface of the gas-absorbing polymer layer and an inner adhesive layer on at least a part of the other surface of the gas-absorbing polymer layer. The secondary battery according to claim 9, wherein the inner adhesive layer is located at a portion where a sealing portion of the battery case is formed. The secondary battery according to claim 9, wherein the thickness of the gas-absorbing polymer layer is 5 micrometers to 20 micrometers. The secondary battery according to claim 1, wherein the gas-absorbing polymer layer is formed only in the accommodating portion as an inner side opposite to the metal layer facing the outer covering layer, and an inner adhesive layer is formed in the sealing portion excluding the accommodating portion. The secondary battery according to claim 12, wherein a thickness of the gas-absorbing polymer layer is equal to a thickness of the internal adhesive layer. The secondary battery according to claim 12, wherein a thickness of the gas-absorbing polymer layer is larger than a thickness of the inner adhesive layer. The secondary battery according to claim 1, wherein the laminate sheet further comprises an internal adhesive layer between the metal layer and the gas-absorbing polymer layer. 16. The secondary battery according to claim 15, wherein the gas-absorbing polymer layer is formed on at least a part of the outer surface of the inner adhesive layer. 17. The secondary battery according to claim 16, wherein the gas-absorbing polymer layer is formed on the outer surface of the inner adhesive layer where the electrolyte comes in contact with the outer surface of the battery case except for the sealing portion. 18. A battery pack comprising a secondary battery according to any one of claims 1 to 17 as a unit cell. A device comprising the battery pack according to claim 18 as a power source.

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