US-20260128427-A1 - Pouch Film Stack and Secondary Battery

US20260128427A1US 20260128427 A1US20260128427 A1US 20260128427A1US-20260128427-A1

Abstract

A pouch film stack according to the present invention includes a base layer, a gas barrier layer, and a sealant layer stacked in that order. The sealant layer includes a first sealant layer located adjacent to the gas barrier layer and a second sealant layer stacked on the first sealant layer. A percentage difference in yield strength between the first and second sealant layers (ΔY) is 66% to 120%, where ΔY is defined as: {(Yield strength of second sealant layer−Yield strength of first sealant layer)/Yield strength of first sealant layer}×100.

Inventors

Soo Ji HWANG
Sang Hun Kim
Hyung Kyun YU
Min Hyeong KANG
Dae Woong Song
Hun Hee Lim

Assignees

LG ENERGY SOLUTION, LTD.

Dates

Publication Date: 20260507
Application Date: 20251231
Priority Date: 20211001

Claims (11)

1 . A pouch film stack, comprising: a base layer, a gas barrier layer, and a sealant layer, wherein the gas barrier layer is stacked on the base layer, and the sealant layer is stacked on the gas barrier layer; wherein the sealant layer includes: a first sealant layer located adjacent to the gas barrier layer; and a second sealant layer stacked on the first sealant layer, wherein the yield strength of the first sealant layer is less than the yield strength of the second sealant layer, and a difference between the yield strength of the first sealant layer and the yield strength of the second sealant layer is less than or equal to 8 N/15 mm.
2 . The pouch film stack of claim 1 , wherein the yield strength of the first sealant layer is in a range from 7 N/15 mm to 15 N/15 mm.
3 . The pouch film stack of claim 1 , wherein the yield strength of the second sealant layer is in a range from 10 N/15 mm to 30 N/15 mm.
4 . The pouch film stack of claim 1 , wherein a thickness ratio between the first sealant layer and the second sealant layer is in a range from 1:0.3 to 1:3.
5 . The pouch film stack of claim 1 , wherein a thickness of the first sealant layer is in a range from 10 μm to 60 μm.
6 . The pouch film stack of claim 1 , wherein a thickness of the second sealant layer is in a range from 20 μm to 70 μm.
7 . The pouch film stack of claim 1 , wherein the first sealant layer and the second sealant layer comprise polypropylene.
8 . The pouch film stack of claim 1 , wherein the gas barrier layer comprises aluminum.
9 . The pouch film stack of claim 1 , wherein peel strength between the gas barrier layer and the first sealant layer is greater than 23 N/15 mm.
10 . The pouch film stack of claim 1 , wherein an additive is added to at least one of the first sealant layer and the second sealant layer.
11 . The pouch film stack of claim 17 , wherein the additive comprises at least one of carbon fiber, glass fiber and aramid fiber.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a continuation under 35 U.S.C. § 120 of U.S. application Ser. No. 18/573,259, filed Dec. 21, 2023, which is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2022/014552 filed Sep. 28, 2022, which claims priority from Korean Patent Application No. 10-2021-0131121, filed on Oct. 1, 2021, which are hereby incorporated by reference in their entirety. TECHNICAL FIELD The present invention relates to a pouch film stack and a secondary battery manufactured by forming same and, more specifically, to a pouch film stack, which enhances seal strength of a pouch, and a secondary battery manufactured by forming same. BACKGROUND ART In general, there are several types of secondary batteries, such as nickel cadmium batteries, nickel hydrogen batteries, lithium ion batteries, and lithium ion polymer batteries. These secondary batteries have been applied in and used for not only small products, such as digital cameras, P-DVDs, MP3Ps, cellular phones, PDAs, portable game devices, power tools, and E-bikes, but also large products requiring high power, such as electric vehicles and hybrid vehicles, as well as power storage devices or backup-power storage devices for storing surplus generated power and new renewable energy. In order to manufacture the secondary batteries, first of all, electrode active material slurry is applied to a positive electrode collector and a negative electrode collector to manufacture a positive electrode and a negative electrode, and the positive electrode and the negative electrode are stacked on both sides of a separator to form an electrode assembly having a predetermined shape. Subsequently, the electrode assembly is accommodated in a battery case, and the battery case is sealed after an electrolyte is injected therein. Secondary batteries are classified into a pouch type, a can type, or the like, according to a material of a case that accommodates the electrode assembly. In the pouch type, the electrode assembly is accommodated in a pouch made of a flexible polymer material. In the can type, the electrode assembly is accommodated in a case made of a metal, a plastic material, or the like. The pouch of a pouch-type secondary battery is manufactured by forming a cup portion through press processing on a flexible pouch film stack. When the cup portion is formed, the electrode assembly is accommodated in an inner accommodation space of the cup portion and the sealing portion is sealed. Accordingly, the secondary battery may be manufactured. In general, the pouch film stack includes a plurality of layers in which a polymer film such as polyethylene terephthalate is stacked on one surface of a metal gas barrier layer and a sealant layer is stacked on the other surface thereof. However, regarding the pouch film stack according to the related art, when the pouch-type secondary battery is in harsh environmental conditions, the sealing portion of the pouch may become vented. Accordingly, the electrode assembly accommodated inside the pouch may be contaminated or functionally disordered. DISCLOSURE OF THE INVENTION Technical Problem The present invention provides a pouch film stack that improves seal strength of a pouch by optimizing yield strength of a sealant layer. The objects of the present invention are not limited to the aforementioned objects, but other objects not described herein will be clearly understood by those skilled in the art from descriptions below. Technical Solution In a pouch film stack according to an embodiment of the present invention, a base layer, a gas barrier layer, and a sealant layer are stacked in that order. The sealant layer includes a first sealant layer located adjacent to the gas barrier layer and a second sealant layer stacked on the first sealant layer, wherein ΔY according to Equation (1) is 66% to 120%. ΔY={(Yield strength of second sealant layer−Yield strength of first sealant layer)/Yield strength of first sealant layer}×100 [Equation 1] In the pouch film stack according to the present invention, a difference between the yield strength of the first sealant layer and the yield strength of the second sealant layer may be less than or equal to 8 N/15 mm. In the pouch film stack according to the present invention, the yield strength of the first sealant layer may be less than the yield strength of the second sealant layer. In the pouch film stack according to the present invention, the yield strength of the first sealant layer may be 7 N/15 mm to 15 N/15 mm. In the pouch film stack according to the present invention, the yield strength of the second sealant layer may be 10 N/15 mm to 30 N/15 mm. In the pouch film stack according to the present invention, a thickness ratio between the first sealant layer and the second sealant layer may be 1:0.3 to 1:3. In the pouch film stack according to the present invention, a thickness of the first sealant layer may be 10 μm to 60