Pouch secondary battery and battery module including the same

Abstract

A pouch-type secondary battery according to an embodiment of the present invention is a pouch-type secondary battery in which a cell assembly is accommodated in a pouch case, the cell assembly including: a stacked positive electrode and negative electrode, a separator interposed between the positive electrode and the negative electrode, at least one electrode tab protruding from the electrode assembly, and an electrode lead connected to the at least one electrode tab. The pouch-type secondary battery includes a lead film disposed between the pouch case and the electrode lead, and wherein the lead film includes a first sealing portion in a region away from the electrode assembly and a second sealing portion in a region close to the electrode assembly, and the thickness of the second sealing portion is greater than the thickness of the first sealing portion.

Description

Technical Field

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10 - 2020 - 0134562, filed on Oct. 16, 2020, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

[0003] The present disclosure relates to a pouch - type secondary battery and a battery module including the same, and more particularly, to a pouch - type secondary battery with improved sealing quality and a battery module including the pouch - type secondary battery. Background Art

[0004] As energy prices continue to rise due to the depletion of fossil fuels and environmental pollution is increasingly concerned, the demand for environmentally friendly alternative energy has become an important factor in future life. Therefore, research on various power generation technologies such as nuclear energy, solar energy, wind energy, and tidal energy is underway, and energy storage devices for more efficient use of the generated energy have also attracted much attention.

[0005] In particular, with the technological development and increasing demand for mobile devices and electric vehicles, the demand for batteries as an energy source is rapidly increasing.

[0006] Typically, high demand is shown for lithium secondary batteries such as lithium - ion batteries and lithium - ion polymer batteries, which have advantages such as high energy density, discharge voltage, and output stability.

[0007] Based on the shape of the battery case, secondary batteries are classified into cylindrical batteries in which the electrode assembly is installed in a cylindrical metal can, prismatic batteries in which the electrode assembly is installed in a prismatic metal can, and pouch - type batteries in which the electrode assembly is installed in a pouch - type case formed of an aluminum laminate.

[0008] In pouch - type secondary batteries, a large amount of gas generated during high - temperature environments and long - term cycling tests may cause ventilation in the sealing part of the pouch case and the electrode lead. For this reason, safety problems are occurring in secondary batteries. To reduce this safety problem, it is necessary to improve the sealing quality of the pouch case and the electrode lead. Summary of the Invention

[0009] Technical Problem

[0010] An object of the present disclosure is to provide a pouch - type battery cell with improved sealing quality and a secondary battery including the same.

[0011] However, the problems to be solved by the embodiments of the present disclosure are not limited to the above problems, and various extensions can be made within the scope of the technical concept included in the present disclosure.

[0012] Technical solution

[0013] According to an embodiment of the present disclosure, a pouch-type secondary battery is provided. In the pouch-type secondary battery, a battery cell assembly is accommodated in a pouch case. The battery cell assembly includes an electrode assembly in which a positive electrode and a negative electrode are stacked and a separator is interposed between the positive electrode and the negative electrode, at least one electrode terminal protruding from the electrode assembly, and an electrode lead connected to the electrode terminal. Wherein, the secondary battery includes a lead film disposed between the pouch case and the electrode lead, and wherein the lead film includes a first sealing portion in a region away from the electrode assembly and a second sealing portion in a region close to the electrode assembly, and the thickness of the second sealing portion is greater than the thickness of the first sealing portion.

[0014] A portion of the pouch case corresponding to the second sealing portion of the lead film may have a bent portion, and the bent portion is bent due to accommodating the electrode assembly having a thickness greater than a portion sealing the lead film and the pouch case.

[0015] A portion of the pouch case corresponding to the second sealing portion of the lead film may be joined to the second sealing portion of the lead film.

[0016] More specifically, both the first sealing portion and the second sealing portion may be joined to the pouch case.

[0017] The first sealing portion may be formed by pressing with a sealing tool.

[0018] The pouch case includes a resin layer and a metal layer. The lead film has a structure in which a first layer, a second layer, and a third layer are sequentially stacked. Among the first layer, the second layer, and the third layer, the third layer is disposed closest to the pouch case, and the third layer may be formed of the same material as the resin layer of the pouch case.

[0019] The third layer has a first end close to the electrode assembly and a second end disposed on the opposite side of the first end, and the thickness of the first end may be greater than the thickness of the second end.

[0020] The first end of the third layer and the pouch case may be sealed to each other to form a sealing portion.

[0021] The third layer may contain polypropylene.

[0022] According to another embodiment of the present disclosure, a battery module including the above-mentioned pouch-type secondary battery is provided. Brief description of the drawings

[0023] Figure 1is an exploded perspective view of a pouch-type secondary battery according to an embodiment of the present disclosure;

[0024] Figure 2 illustrates Figure 1 a perspective view of the assembled state of the pouch-type secondary battery;

[0025] Figure 3 is a cross-sectional view taken along the Figure 2 cutting line A-A';

[0026] Figure 4 is a view showing a sealing region according to a comparative example of the present disclosure;

[0027] Figure 5 is Figure 3 an enlarged cross-sectional view of the region P; and

[0028] Figure 6 specifically illustrates Figure 5 a detailed view of the pouch-type secondary battery forming the sealing region. Detailed Embodiments

[0029] Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. The present disclosure can be modified in various different ways and is not limited to the embodiments described herein.

[0030] For clarity, descriptions of parts not relevant to the description will be omitted herein, and throughout the description, the same reference numerals denote the same elements.

[0031] In addition, in the drawings, for convenience of description, the size and thickness of each element are arbitrarily illustrated, and the present disclosure is not necessarily limited to those illustrated in the drawings. In the drawings, for clarity, the thickness of layers, regions, etc. is exaggerated. In the drawings, for convenience of description, the thickness of some layers and regions is exaggerated.

[0032] In addition, it will be understood that when an element such as a layer, film, region, or plate is referred to as being "on" or "above" another element, it can be directly on the other element or there can also be an intermediate element. In contrast, when an element is referred to as being "directly on" another element, this means that there are no other intermediate elements. In addition, the terms "on" or "above" mean being disposed above or below the reference part, and do not necessarily mean being disposed at the upper end of the reference part in the direction opposite to gravity.

[0033] In addition, throughout the description, when a part is referred to as "including" a certain component, this means that the part may also include other components without excluding other components, unless otherwise specified.

[0034] In addition, throughout the description, when referred to as a "plane", it means observing the target part from the upper side, and when referred to as a "section", it means observing the target part from one side of a vertically cut section.

[0035] Figure 1 is an exploded perspective view illustrating a pouch-type secondary battery according to an embodiment of the present disclosure. Figure 2 illustrates Figure 1 The perspective view of the assembled state of the pouch-type secondary battery. Figure 3 is a cross-sectional view taken along the Figure 2 Cutting line A-A' of.

[0036] Referring to Figures 1 to 3 , the pouch-type secondary battery 100 according to the present embodiment can be manufactured by accommodating the electrode assembly 200 inside the pouch case 300 and then sealing the case. The electrode assembly 200 may include a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The electrode assembly 200 may be a stacked electrode assembly, a jelly roll electrode assembly, or a stacked / folded electrode assembly.

[0037] Each of the positive electrode and the negative electrode includes an electrode tab 210t, and the electrode leads 210 and 220, which are both connected to the electrode tab 210t, may be exposed to the outside of the pouch case 300. In addition, the electrode leads 210 and 220 may be respectively disposed in the sealing portion 300S in a state covered by the lead film 600, thereby ensuring sealing properties and insulating properties.

[0038] The pouch case 300 is made of a laminate and may include a resin layer for thermal melting and a metal layer for preventing material penetration.

[0039] Specifically, referring to Figure 6 , each of the upper case 310 and the lower case 320 may include an inner resin layer 310a for sealing and a metal layer 310b for preventing material penetration. If necessary, each of the upper case 310 and the lower case 320 may further include an outermost external resin layer (not shown).

[0040] Compared with its thickness, the external resin layer may have excellent tensile strength and weather resistance and have electrical insulation properties in order to protect the pouch-type secondary battery 100 from external influences. The external resin layer may contain polyethylene terephthalate (PET) resin or nylon resin. The metal layers 310b and 320b can prevent air, moisture, etc. from flowing into the pouch-type secondary battery 100. The metal layers 310b and 320b may contain aluminum (Al). The inner resin layers 310a and 320a may be thermally melted with each other due to the heat and pressure applied in the state where the electrode assembly 200 is built in. The inner resin layer may contain cast polypropylene (CPP) or polypropylene (PP).

[0041] Return reference Figures 1 to 3 A recessed receiving portion 300ST in which the electrode assembly 200 can be disposed may be formed in each of the upper case 310 and the lower case 320. Sealing portions 300S1 and 300S2 may be provided along the outer peripheral edge of the recessed receiving portion 300ST for each of the upper case 310 and the lower case 320. The sealing portion 300S1 of the upper case 310 and the sealing portion 300S2 of the lower case 320 may be thermally melted with each other to form a sealing portion 300S and seal the pouch case 300.

[0042] In another embodiment of the present invention, one side of the upper case and one side of the lower case may be integrally connected to each other, and the remaining three sides may be thermally melted.

[0043] On the other hand, each of the plurality of positive electrodes and the plurality of negative electrodes included in the electrode assembly 200 may include a positive electrode terminal and a negative electrode terminal, and the electrode leads 210 and 220 are connected to the positive electrode terminal and the negative electrode terminal. Specifically, one of the electrode leads 210 and 220 may be a positive electrode lead, and the other may be a negative electrode lead. As described above, the electrode leads 210 and 220 connected to the electrode assembly 200 protrude from one end of the pouch case 300 and are exposed to the outside of the pouch case 300.

[0044] Figure 4 is a view showing a sealing region according to a comparative example of the present disclosure.

[0045] Reference Figure 4 , the lead film 60 included in the pouch-type secondary battery 10 according to the comparative example includes a double resin layer. At this time, the lead film 60 may include an adhesive resin layer 60a and a heat-resistant resin layer 60b. By forming a structure in which the pouch case 30 floats on one end of the lead film 60 located inside the battery cell (in the direction adjacent to the electrode assembly), an unsealed region that is not sealed can be formed between the lead film 60 and the pouch case 30.

[0046] Figure 5 is Figure 3 an enlarged cross-sectional view of the region P. Figure 6 is a detailed view of a pouch-type secondary battery specifically illustrating the sealing region formed Figure 5 thereof.

[0047] Reference Figure 3 , Figure 5 and Figure 6, the pouch-type secondary battery 100 according to the present embodiment has a structure in which a cell assembly is accommodated in a pouch case 300. The cell assembly includes an electrode assembly 200, at least one electrode tab 210t protruding from the electrode assembly 200, and an electrode lead 210 connected to the at least one electrode tab 210t. At this time, a lead film 600 is formed between the pouch case 300 and the electrode lead 210, and the thickness of a second sealing portion SR2 of the lead film 600 in a region close to the electrode assembly 200 is greater than the thickness of a first sealing portion SR1 of the lead film 600 in a region away from the electrode assembly.

[0048] As Figure 5 shown, a part of the pouch case 300 corresponding to the second sealing portion of the lead film 600 has a bent portion that is bent due to the accommodation of the electrode assembly 200, and the thickness of the electrode assembly 200 is greater than the thickness of the portion that seals the lead film 600 and the pouch case 300. Different from the above comparative example, according to the present embodiment, the thickness of the second sealing portion SR2 of the lead film 600 corresponding to the floating pouch case 300 is formed thick, so that an additional sealing region can be formed. At this time, a part of the pouch case 300 corresponding to the second sealing portion SR2 of the lead film 600 can be joined to the second sealing portion SR2 of the lead film 600. Therefore, the thickness of the second sealing portion SR2 can also be configured to gradually increase in the direction of the electrode assembly 200 according to the shape of the bent portion of the pouch case 300.

[0049] Referring to Figure 6 , the sealing region SR that seals the lead film 600 and the pouch case 300 corresponds to the entirety of the second sealing portion SR2 and the first sealing portion SR1 provided closer to the Figure 3 electrode assembly 200 than the first sealing portion SR1. Therefore, the pouch case 300 can be joined to both the first sealing portion SR1 and the second sealing portion SR2. At this time, the first sealing portion SR1 can be formed by pressing with a sealing tool, and when the first sealing portion SR1 is formed, the outermost layer 600c of the lead film 600 melted by heat can be pushed by pressure to form the second sealing portion SR2.

[0050] The lead film 600 according to the present embodiment may have a structure in which a first layer 600a, a second layer 600b, and a third layer 600c are stacked in sequence. Among the first layer 600a, the second layer 600b, and the third layer 600c, the third layer 600c is disposed closest to the pouch case 300, and the third layer 600c may be formed of the same material (for example, polypropylene) as the inner resin layer 310a of the pouch case 300. The third layer 600c serves as an adhesion assisting layer, and in this way, the third layer 600c of the lead film 600 and the inner resin layer 310a of the pouch case 300 that are in contact with each other are formed of the same material, thereby improving the sealing quality.

[0051] The third layer 600c has a first end close to Figure 2 a first end of the electrode assembly 200 and a second end disposed on the opposite side of the first end, and the thickness of the first end may be greater than the thickness of the second end. The first end of the third layer 600c and the bag housing 300 may be sealed to each other to form a second sealing portion SR2.

[0052] On the other hand, pouch secondary batteries according to embodiments of the present invention are aggregated in plurality to constitute a battery module, and one or more of these battery modules may be encapsulated in a battery pack housing to form a battery pack.

[0053] The above-mentioned battery module and the battery pack including the battery module can be applied to various devices. Such devices can be applied to vehicle devices such as electric bicycles, electric vehicles, or hybrid vehicles, but the present disclosure is not limited thereto and is applicable to various devices capable of using the battery module, which also falls within the scope of the present disclosure.

[0054] Although the present invention has been shown and described above with reference to preferred embodiments, the scope of the present disclosure is not limited thereto, and numerous other modifications and improvements designed by those skilled in the art using the basic principles of the present invention described in the appended claims will fall within the spirit and scope of the present disclosure.

[0055] [Description of Reference Numerals]

[0056] 100: Pouch secondary battery

[0057] 300: Bag housing

[0058] 310a, 320a: Inner resin layer

[0059] 600: Lead film

[0060] Industrial Applicability

[0061] According to an embodiment of the present disclosure, the thickness of the lead film facing the battery cell inside increases to increase the sealing area between the bag housing and the electrode lead, thereby improving the sealing quality.

[0062] In addition, an adhesion assisting layer in contact with the bag housing may be formed on the double layer of the lead film, thereby improving the sealing quality.

[0063] The effects of the present disclosure are not limited to the above-mentioned effects, and those skilled in the art will clearly understand additional other effects not described above according to the description of the appended claims.

Claims

1. A pouch-type secondary battery, in which a cell assembly is accommodated in a pouch case, the cell assembly including an electrode assembly in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween, at least one electrode tab protruding from the electrode assembly, and an electrode lead wire connected to the electrode tab. Wherein, The secondary battery includes a lead film disposed between the pouch case and the electrode lead, wherein the lead film includes a first sealing portion in a region away from the electrode assembly and a second sealing portion in a region close to the electrode assembly, and the thickness of the second sealing portion is increased such that the thickness of the second sealing portion is greater than the thickness of the first sealing portion, wherein the distance from the upper surface of the second sealing portion to the center of the electrode lead in the vertical direction is greater than the distance from the upper surface of the first sealing portion to the center of the electrode lead in the vertical direction, wherein the pouch case includes a resin layer and a metal layer, the lead film has a structure in which a first layer, a second layer, and a third layer are sequentially stacked, among the first layer, the second layer, and the third layer, the third layer is disposed closest to the pouch case, and the third layer is formed of the same material as the resin layer of the pouch case, wherein the third layer has a first end close to the electrode assembly and a second end disposed on the opposite side of the first end, and the thickness of the first end is greater than the thickness of the second end, and wherein the first end of the third layer and the pouch case are sealed to each other to form a sealing portion.

2. The pouch-type secondary battery according to claim 1, Wherein, A portion of the pouch case corresponding to the second sealing portion of the lead film has a bent portion that is bent due to accommodating the electrode assembly, and the thickness of the electrode assembly is greater than the thickness of the portion sealing the lead film and the pouch case.

3. The pouch-type secondary battery according to claim 1, Wherein, A portion of the pouch case corresponding to the second sealing portion of the lead film is joined to the second sealing portion of the lead film.

4. The pouch-type secondary battery according to claim 1, Wherein, Both the first sealing portion and the second sealing portion are joined to the pouch case.

5. The pouch-type secondary battery according to claim 1, Wherein, The first sealing portion is formed by applying pressure with a sealing tool.

6. The pouch-type secondary battery according to claim 1, Wherein, The third layer includes polypropylene.

7. The pouch-type secondary battery according to claim 1, Wherein, The third layer includes cast polypropylene.

8. The pouch-type secondary battery according to claim 2, Wherein, The thickness of the second sealing portion is configured to gradually increase in the direction of the electrode assembly according to the shape of the bent portion of the pouch case.

9. A battery module including the pouch-type secondary battery according to any one of claims 1-8.

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