CN111095594A

CN111095594A - Pouch case and secondary battery including the same

Info

Publication number: CN111095594A
Application number: CN201880056402.XA
Authority: CN
Inventors: 金龙; 金像熏; 崔龙洙; 庾亨均; 黄隨枝; 金奈润; 姜旻亨
Original assignee: LG Chem Ltd
Current assignee: LG Energy Solution Ltd
Priority date: 2017-10-25
Filing date: 2018-10-24
Publication date: 2020-05-01
Also published as: WO2019083279A2; KR102328646B1; KR20190046172A; WO2019083279A3

Abstract

Provided is a secondary battery including: an electrode assembly; an electrode lead connected to the electrode assembly; a pouch case receiving the electrode assembly and sealing the electrode assembly in a state in which the electrode leads are drawn out of the outside; and a sealant layer located at least one of an edge of the pouch case and a portion between the pouch case and the electrode lead, wherein the sealant layer includes a polymer-matrix composite.

Description

Pouch case and secondary battery including the same

Technical Field

Cross Reference to Related Applications

This application claims priority and benefit to korean patent application No. 10-2017-.

The present invention relates to a pouch case and a secondary battery including the same. More particularly, the present invention relates to a pouch case and a pouch type secondary battery having high tensile strength.

Background

With the development of technology and the increase in demand for mobile devices, the demand for secondary batteries as an energy source has rapidly increased. Accordingly, various studies have been made on secondary batteries capable of satisfying various demands.

Secondary batteries have attracted considerable attention as energy sources for power-driven devices such as electric bicycles, electric vehicles, and hybrid vehicles, and for mobile devices such as cellular phones, digital cameras, and portable computers.

Small-sized battery packs mounted with battery cells are used for small-sized devices such as cellular phones and digital cameras. On the other hand, a middle-or large-sized battery pack mounted with a battery pack including two or more battery cells connected in parallel and/or series with each other is used for middle-or large-sized devices such as portable computers and electric vehicles.

In terms of the shape of the secondary battery, the demand for prismatic secondary batteries and pouch-type secondary batteries, which have a relatively small thickness and are thus suitable for articles such as cellular phones, is high. In the case of a prismatic lithium secondary battery, it is advantageous to protect the electrode assembly from external impact and to facilitate the liquid injection process. However, since the shape of the prismatic lithium secondary battery is fixed, it is difficult to reduce the volume thereof. On the other hand, in the case of a pouch type lithium secondary battery, there are advantages in that it is suitable for the production of a thin battery because there is no limitation in shape and size, and it is easy to thermally fuse assembly, and it has high safety because it helps to discharge gas or liquid when abnormal behavior occurs. However, since the pouch-type secondary battery uses a thin soft laminate sheet as a case, its stability against external impact and the like may be low due to weak physical and mechanical strength and low sealing reliability, as compared to the prismatic secondary battery.

Disclosure of Invention

Technical problem

The present invention has been made in an effort to provide a pouch case having high tensile strength to improve stability of a pouch type secondary battery, and a secondary battery including the same.

However, the problems to be solved by the exemplary embodiments of the present invention are not limited to the above-described problems, but various extensions may be made within the technical spirit of the present invention.

Technical scheme

An exemplary embodiment of the present invention provides a pouch case, which includes: an upper case and a lower case, wherein one of an edge of the upper case and an edge of the lower case includes a base layer, a metal layer, and a sealant layer, which are sequentially laminated, and the sealant layer includes a polymer-matrix composite.

The thermoplastic resin layer of the sealant layer may have a plurality of fiber-type or web-type matrices dispersed therein.

The matrix may include at least one of glass fibers, carbon fibers, and aramid fibers.

The carbon fibers may include graphite nanoplatelets.

The thermoplastic resin layer may include a polypropylene resin, a polyester resin, or an epoxy resin.

Another exemplary embodiment of the present invention provides a secondary battery including: an electrode assembly; an electrode lead connected to the electrode assembly; a pouch case receiving the electrode assembly and sealing the electrode assembly in a state in which the electrode leads are drawn out of the outside; and a sealant layer located at least one of an edge of the pouch case and a portion between the pouch case and the electrode lead, wherein the sealant layer includes a polymer-matrix composite.

The carbon fibers may include graphite nanoplatelets.

The sealant layers located at the edges of the pouch case may include first and second sealant layers located between upper and lower cases constituting the pouch case, and the sealant layers located at the portions between the pouch case and the electrode leads include third and fourth sealant layers formed on both surfaces of the electrode leads, respectively.

The first, second, third, and fourth sealant layers may be located between the pouch case and the electrode leads, and the first sealant layer may be located between the upper case and the third sealant layer, the second sealant layer may be located between the lower case and the fourth sealant layer, the third sealant layer may be located between the first sealant layer and the electrode leads, and the fourth sealant layer may be located between the electrode leads and the second sealant layer.

The pouch case may include the upper case and the lower case, the upper case may include a first base layer, a first metal layer, and a first sealant layer sequentially positioned from an outside of the upper case toward an inside thereof, and the lower case may include a second base layer, a second metal layer, and a second sealant layer sequentially positioned from an outside of the lower case toward an inside thereof.

The first and second substrate layers may each comprise nylon or polyethylene terephthalate.

The secondary battery may further include: adhesive layers between the first base layer and the first metal layer, between the first metal layer and the first sealant layer, between the second base layer and the second metal layer, and between the second metal layer and the second sealant layer, respectively.

The first sealant layer and the second sealant layer may contact each other at the edge of the pouch case.

The pouch case may include an upper case and a lower case, and the sealant layers may be respectively located between the upper case and the electrode leads and between the lower case and the electrode leads.

Advantageous effects

According to the exemplary embodiments of the present invention, the polymer-matrix composite is used as at least one of the sealing material of the pouch case and the sealing material of the electrode lead, thereby being capable of providing a secondary battery having improved tensile strength without an additional reinforcing layer.

Drawings

Fig. 1 is an enlarged perspective view illustrating a pouch-shaped case and a secondary battery including the same according to an exemplary embodiment of the present invention.

Fig. 2 is a view illustrating a pouch-type secondary battery including the pouch case of fig. 1.

Fig. 3 is an enlarged sectional view of the area a shown in fig. 2.

Fig. 4 is a sectional view of the region B shown in fig. 2.

Fig. 5 is a detailed sectional view of the region S shown in fig. 4.

Fig. 6 is a sectional view showing a modification of the secondary battery described in fig. 5.

Fig. 7 is a graph showing tensile strength depending on volume fraction of glass fiber in the case where a polypropylene thermoplastic resin layer is mixed with glass fiber to be used as a polymer-matrix composite according to an exemplary embodiment of the present invention.

Fig. 8 is a graph showing tensile strength depending on a weight ratio of graphite nanoplatelets in the case where a polypropylene thermoplastic resin layer is mixed with graphite nanoplatelets to be used as a polymer-matrix composite according to an exemplary embodiment of the present invention.

Detailed Description

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily practice the invention. However, the present invention may be embodied in various different forms and is not limited to the exemplary embodiments described herein.

The description is to be regarded as illustrative in nature, and not as restrictive. Throughout the specification, the same reference numerals denote the same or similar elements.

In addition, the size and thickness of each component shown in the drawings are randomly expressed for convenience of explanation, but the present invention is not limited to the shown size and thickness of the component. In the following drawings, thicknesses are exaggerated to clearly illustrate several layers and regions. In addition, in the drawings, the thickness of some layers and regions are exaggerated for clarity.

It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being on or over another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being directly on another element, there are no intervening elements present. Further, the words "on … …" or "above … …" refer to being located above or below the subject portion, and do not necessarily mean being located on the upper side of the subject portion based on the direction of gravity.

In addition, throughout this specification, unless explicitly described to the contrary, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of other elements but not the exclusion of any other elements.

Further, throughout the specification, the term "on a plane" refers to a case where the object is viewed from the top, and the term "on a cross section" refers to a case where a cross section of the object taken in a vertical direction is viewed from the side.

Fig. 1 is an enlarged perspective view illustrating a pouch-shaped case and a secondary battery including the same according to an exemplary embodiment of the present invention. Fig. 2 is a view illustrating a pouch-type secondary battery including the pouch case of fig. 1.

Referring to fig. 1 and 2, a secondary battery according to an exemplary embodiment of the present invention includes a pouch case 100 and an electrode assembly 200. The pouch case 100 includes an upper case 110 and a lower case 120. The case where the upper case 110 and the lower case 120 are coupled to each other to be integrally formed is shown in fig. 1, but the upper case 110 and the lower case 120 may be separated from each other. The shape of the pouch case 100 is not limited to the shape shown in fig. 1, and may have any shape capable of receiving and sealing the electrode assembly 200. The upper case 110 and the lower case 120 of fig. 1 each include a receiving part having a concave shape. The receiving part may receive the electrode assembly 200 and the electrolyte.

The electrode assembly 200 may be configured to have a cathode plate, an anode plate, and a separator interposed between the cathode plate and the anode plate. In this case, the electrode assembly 200 may have a structure in which one cathode plate and one anode plate are wound with a separator interposed therebetween, or a structure in which a plurality of cathode plates and a plurality of anode plates are stacked with a separator interposed therebetween. Each of the cathode plate and the anode plate may have an electrode current collector coated with an active material slurry. Generally, the slurry can be obtained by adding a solvent to an active material, a conductive material, a binder, a plasticizer, and the like and stirring the mixture thereof.

In the electrode assembly 200, the electrode plates may have uncoated portions that are not coated with the slurry. Each of the uncoated portions may have an electrode tab corresponding to each of the electrode plates. In detail, as shown in fig. 1, the cathode tab 310 may be attached to a cathode plate of the electrode assembly 200, and the anode tab 410 may be attached to an anode plate of the electrode assembly 200. The cathode tabs 310 and the anode tabs 410 are electrically connected to the cathode lead 320 and the anode lead 420, respectively, to form the

electrode terminals

300 and 400, respectively. In this case, as shown in fig. 2, the cathode lead 320 and the anode lead 420 may be drawn out to the outside of the pouch case 100.

The pouch-type secondary battery of fig. 2 is an example of a pouch-type secondary battery in which an upper case 110 and a lower case 120 shown in fig. 1 are bonded and sealed to each other.

Fig. 3 is an enlarged sectional view of the area a shown in fig. 2.

Referring to fig. 3, each of the upper case 110 and the lower case 120 constituting the pouch case according to the exemplary embodiment of the present invention includes a sealing part formed at an edge of the pouch case 100 around a receiving part receiving the electrode assembly 200 of fig. 1. The sealing part is formed along the edge of the pouch case 100, and the sealing part may be all or part of a coupling area where the upper case 110 and the lower case 120 are coupled to each other. The upper case 110 and the lower case 120 may be thermally fused to seal the pouch case 100.

A sectional structure of the pouch case 100 located in the bonding area will be described. The upper case 110 and the lower case 120, each including a base layer, a metal layer, and a sealant layer, are in contact with each other. The lamination direction of the base layer, the metal layer, and the sealant layer included in the upper case 110 is opposite to the lamination direction of the base layer, the metal layer, and the sealant layer included in the lower case 120. Specifically, as shown in fig. 3, the upper case 110 includes a first base layer 112, a first metal layer 114, and a first sealant layer 116 sequentially positioned from the outside of the upper case 110 toward the inside thereof. The lower case 120 includes a second base layer 122, a second metal layer 124, and a second sealant layer 126, which are sequentially positioned from the outside of the lower case 120 toward the inside thereof. In this case, the first sealant layer 116 and the second sealant layer 126 may be in contact with each other.

Adhesive layers

113, 115, 123, and 125 may be located between the first base layer 112 and the first metal layer 114, between the first metal layer 114 and the first sealant layer 116, between the second base layer 122 and the second metal layer 124, and between the second metal layer 124 and the second sealant layer 126, respectively.

The first and second substrate layers 112 and 122 may be formed of an insulating material such as polyethylene terephthalate (PFT) resin, nylon resin, or the like, to ensure insulation of the secondary battery from the outside and moldability of the secondary battery.

The first and

second metal layers

114 and 124 may include any one selected from the group consisting of copper, aluminum, nickel, iron, carbon, chromium, manganese, and alloys thereof.

The first sealant layer 116 and the second sealant layer 126 according to exemplary embodiments may be formed of a polymer-matrix composite. In detail, the polymer-based composite included in the first sealant layer 116 and the second sealant layer 126 may have a structure in which a plurality of fiber-type or mesh-type matrixes are dispersed in the

thermoplastic resins

106 and 206, respectively. As an example, a structure in which a plurality of fiber-

type matrices

105 and 205 are dispersed in

thermoplastic resins

106 and 206, respectively, is shown in fig. 3. The

fibrous substrates

105 and 205 according to example embodiments may include at least one of glass fibers, carbon fibers, and aramid fibers. Here, the carbon fiber may include graphite nanoplatelets, and the

thermoplastic resins

106 and 206 may include polypropylene resin, polyester resin, or epoxy resin.

Fig. 4 is a sectional view of the region B shown in fig. 2.

Referring to fig. 4, the electrode assembly 200 includes a cathode plate 211, an anode plate 213, a separator 212, and an electrode tab 410. In fig. 4, the electrode assembly 200 in which the separator 212 is interposed between the cathode plate 211 and the anode plate 213 is illustrated as a laminate type electrode assembly, but the electrode assembly 200 may be a jelly-roll type electrode assembly.

The cathode plate 211 may have an aluminum electrode collector coated with a cathode active material, and the anode plate 213 may have a copper electrode collector coated with an anode active material. The electrode tabs 410 may be integrally formed with the

electrode plates

211 and 213, and correspond to uncoated portions of the

electrode plates

211 and 213, which are not coated with the electrode active material.

The electrode lead 420 is connected to the electrode tap 410, and may be drawn out to the outside of the upper and

lower cases

110 and 120. The electrode lead 420 may be formed of an aluminum or copper material. The third sealant layer 133 and the fourth sealant layer 134 are located on both surfaces, respectively. The third sealant layer 133 is located between the distal end surface of the upper case 110 and the electrode leads 420, and the fourth sealant layer 134 is located between the distal end surface of the lower case 120 and the electrode leads 420. Hereinafter, an exterior material of the pouch type secondary battery according to an exemplary embodiment of the present invention will be described in detail with reference to fig. 5.

Fig. 5 is a detailed sectional view of the region S shown in fig. 4.

Referring to fig. 5, the upper case 110 and the lower case 120 are positioned based on the electrode leads 420. The electrode lead 420 and the upper case 110 may be bonded to each other by thermal fusion, and the electrode lead 420 and the lower case 120 may be bonded to each other by thermal fusion. Since the components of the upper case 110 and the lower case 120 are the same as those described in fig. 3, detailed descriptions thereof will be omitted. The third encapsulant layer 133 is located between the first encapsulant layer 116 of the upper case 110 and the electrode leads 420. The fourth encapsulant layer 134 is located between the second encapsulant layer 126 of the lower case 120 and the electrode leads 420.

The third and fourth sealant layers 133 and 134 according to exemplary embodiments may be formed of a polymer-matrix composite, similar to the first and second sealant layers 116 and 126. The detailed description of the polymer-matrix composite is the same as that of the first sealant layer 116 and the second sealant layer 126 with reference to fig. 1, and the description will apply to the third sealant layer 133 and the fourth sealant layer 134.

In the exemplary embodiment of fig. 5, the case is depicted where the first sealant layer 116, the second sealant layer 126, the third sealant layer 133, and the fourth sealant layer 134 are all formed of a polymer-matrix composite. However, as a modification of the exemplary embodiment depicted in fig. 5, at least one of the first, second, third, and fourth sealant layers may be formed of a polypropylene resin, a polyester resin, or an epoxy resin.

The exemplary embodiment depicted in fig. 6 is largely identical to the exemplary embodiment depicted in fig. 5. Therefore, only different components will be described, and the contents described in the exemplary embodiment of fig. 5 may be applied to other components.

Referring to fig. 6, the first sealant layer 116 included in the upper case 110 shown in fig. 5 and the third sealant layer 133 located on one end surface of the electrode lead 420 are combined to form one sealant layer 137 in the exemplary embodiment of fig. 6. The second sealant layer 126 included in the lower case 120 shown in fig. 5 and the fourth sealant layer 134 located on one end surface of the electrode lead 420 are combined to form one sealant layer 138 in the exemplary embodiment of fig. 6.

The pouch case according to the exemplary embodiments of the present invention and the secondary battery including the same as described above may improve the tensile strength of the pouch case or the electrode lead itself by using a polymer-matrix composite instead of the existing polypropylene as an exterior material of the pouch case or the electrode lead. Therefore, the tensile strength of the pouch case and the electrode lead after the thermal fusion process may be improved.

Referring to fig. 7, it can be confirmed that, by using the polymer-matrix composite of polypropylene and glass fiber at room temperature, the tensile strength is improved when the volume fraction of the glass fiber is changed to 0%, 20%, or 30%.

Referring to fig. 8, it can be confirmed that, by using the polymer-matrix composite of maleic anhydride-grafted polypropylene and graphite nanoplatelets, the tensile strength increases up to 15 wt% as the weight ratio of the graphite nanoplatelets increases, while the tensile strength slightly decreases at 20 wt%.

While the invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Reference numerals

110: bag-shaped shell

105. 205: substrate

116: first sealant layer

126: second sealant layer

133: third sealant layer

134: a fourth sealant layer

200: electrode assembly

420: electrode lead

Claims

1. A pouch case, comprising:

an upper shell and a lower shell, wherein,

wherein one of the edge of the upper case and the edge of the lower case includes a base layer, a metal layer, and a sealant layer, which are sequentially laminated, and

the sealant layer includes a polymer-matrix composite.

2. The pouch case of claim 1, wherein:

the sealant layer has a thermoplastic resin layer in which a plurality of fiber-type or web-type matrixes are dispersed.

3. The pouch case of claim 2, wherein:

the matrix includes at least one of glass fibers, carbon fibers, and aramid fibers.

4. The pouch case of claim 3, wherein:

the carbon fibers include graphite nanoplatelets.

5. The pouch case of claim 2, wherein:

the thermoplastic resin layer includes a polypropylene resin, a polyester resin, or an epoxy resin.

6. The pouch case of claim 1, further comprising:

an adhesive layer between the base layer and the metal layer and between the metal layer and the sealant layer, respectively.

7. A secondary battery, comprising:

an electrode assembly;

an electrode lead connected to the electrode assembly;

a pouch case receiving the electrode assembly and sealing the electrode assembly in a state in which the electrode leads are drawn out of the outside; and

a sealant layer located at least one of an edge of the pouch case and a portion between the pouch case and the electrode lead,

wherein the sealant layer comprises a polymer-matrix composite.

8. The secondary battery according to claim 7, wherein:

9. The secondary battery according to claim 8, wherein:

10. The secondary battery according to claim 9, wherein:

the carbon fibers include graphite nanoplatelets.

11. The secondary battery according to claim 8, wherein:

12. The secondary battery according to claim 7, wherein:

the sealant layer at the edge of the pouch case includes a first sealant layer and a second sealant layer between upper and lower cases constituting the pouch case, and

the sealant layers located at the portion between the pouch case and the electrode lead include third and fourth sealant layers formed on both surfaces of the electrode lead, respectively.

13. The secondary battery according to claim 12, wherein:

the first, second, third, and fourth sealant layers are located between the pouch case and the electrode leads, and

the first sealant layer is located between the upper case and the third sealant layer, the second sealant layer is located between the lower case and the fourth sealant layer, the third sealant layer is located between the first sealant layer and the electrode leads, and the fourth sealant layer is located between the electrode leads and the second sealant layer.

14. The secondary battery according to claim 12, wherein:

the pouch case includes the upper case and the lower case,

the upper case includes a first base layer, a first metal layer, and a first sealant layer, which are sequentially positioned from an outside of the upper case toward an inside thereof, and

the lower case includes a second base layer, a second metal layer, and a second sealant layer, which are sequentially positioned from an outside of the lower case toward an inside thereof.

15. The secondary battery according to claim 14, wherein:

the first and second substrate layers each comprise nylon or polyethylene terephthalate.

16. The secondary battery according to claim 14, further comprising:

adhesive layers between the first base layer and the first metal layer, between the first metal layer and the first sealant layer, between the second base layer and the second metal layer, and between the second metal layer and the second sealant layer, respectively.

17. The secondary battery according to claim 14, wherein:

the first sealant layer and the second sealant layer are in contact with each other at the edge of the pouch case.

18. The secondary battery according to claim 7, wherein:

the pouch case includes an upper case and a lower case, and

the sealant layers are respectively located between the upper case and the electrode leads and between the lower case and the electrode leads.