Battery cells and battery modules containing them

Abstract

To provide: a battery cell with improved external emission of gas generated inside the battery cell; and a battery module including the same.SOLUTION: A battery cell includes: a battery case which has an accommodation portion receiving a battery assembly and includes a sealing portion structured with an outer periphery sealed by heat fusion; an electrode lead electrically connected to an electrode tab included in the battery assembly, the electrode lead protruding toward outside the battery case through the sealing portion; and a lead film positioned at a portion corresponding to the sealing portion on at least one of upper and lower sides of the electrode lead. The lead film includes a gas discharge portion formed to extend from inside the battery case toward outside the battery case, and the gas discharge portion is opened toward inside the battery case.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Mutual citation with related applications The present application claims the benefit of priority based on Korean Patent Application No. 10-2020-0147669 filed on November 6, 2020 and Korean Patent Application No. 10-2021-0142441 filed on October 25, 2021, and all contents disclosed in the documents of said Korean patent application are incorporated as a part of the present specification.

[0002] The present invention relates to a battery cell and a battery module including the same, and more specifically, to a battery cell with improved external discharge of gas generated inside the battery cell and a battery module including the same.

Background Art

[0003] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. In particular, secondary batteries have attracted much attention not only as an energy source for mobile devices such as mobile phones, digital cameras, notebook computers and wearable devices, but also for power devices such as electric bicycles, electric vehicles and hybrid electric vehicles.

[0004] Such secondary batteries are classified according to the shape of the battery case into cylindrical batteries and prismatic batteries in which an electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries in which an electrode assembly is housed in a pouch-type case made of an aluminum laminate sheet. Here, the electrode assembly housed in the battery case is a chargeable / dischargeable power generating element comprising a positive electrode, a negative electrode, and a separation membrane structure interposed between the positive electrode and the negative electrode. It is classified into a jelly-roll type in which a separation membrane is interposed between long sheet-type positive and negative electrodes coated with an active material and then wound, and a stacked type in which a plurality of positive electrodes and negative electrodes are sequentially stacked with a separation membrane interposed between them.

[0005] Among these, pouch-type batteries, in particular, which have a structure in which stacked or stacked / folding electrode assemblies are housed in a pouch-type battery case made of aluminum laminate sheet, are seeing a gradual increase in usage due to their low manufacturing cost, small weight, and easy deformation.

[0006] Figure 1 is a top view of a conventional battery cell. Figure 2 is a cross-sectional view taken along the a-a' axis in Figure 1. Referring to Figures 1 and 2, the electrode assembly 11 of the conventional battery cell 10 is mounted in a housing 21 and includes a battery case 20 that includes a sealing portion 25 whose outer periphery is sealed by heat fusion. Here, electrode leads 30 protrude outward from the battery case 20 via the sealing portion 25, and a lead film 40 is located between the upper and lower parts of the electrode leads 30 and the sealing portion 25.

[0007] However, recently, as the energy density of battery cells increases, a problem has arisen: the amount of gas generated inside the battery cell also increases. In the case of conventional battery cells 10, there are no components to vent the gas generated inside the battery cell, and the battery cell can experience venting due to gas generation. Similarly, battery cells damaged by venting can allow moisture to enter, causing side reactions, which leads to a decrease in battery performance and additional gas generation. This has increased the need to develop battery cells with improved external gas emission capabilities. [Overview of the project] [Problems that the invention aims to solve]

[0008] The problem that this invention aims to solve is to provide a battery cell and a battery module including the same, in which the external discharge of gas generated inside the battery cell is improved.

[0009] The problems that this invention aims to solve are not limited to those described above, and any problems not mentioned will be clearly understood by those skilled in the art from this specification and the accompanying drawings. [Means for solving the problem]

[0010] A battery cell according to one embodiment of the present invention includes a battery case having a sealing portion in which an electrode assembly is mounted and the outer periphery is sealed by heat fusion; electrode leads electrically connected to electrode tabs included in the electrode assembly and protruding outward from the battery case via the sealing portion; and a lead film located at least one of the upper and lower parts of the electrode lead in a portion corresponding to the sealing portion, wherein the lead film has a gas discharge portion formed therein extending from the inside of the battery case outward from the battery case, and the gas discharge portion is open toward the inside of the battery case.

[0011] The front and both sides of the gas discharge section are closed with respect to the direction in which the electrode lead protrudes.

[0012] The present invention may further include an internal layer that covers at least a portion of the surface of the gas discharge section.

[0013] The material forming the inner layer has a higher melting point and does not react with the electrolyte compared to the material forming the lead film.

[0014] The lead film comprises a polyolefin-based material, and the inner layer may comprise at least one material selected from polyolefin-based, fluorine-based, and porous ceramic-based materials.

[0015] The lead film may have a wider width than the electrode lead.

[0016] The lead film may have a length greater than the length of the sealing portion and a length less than the length of the electrode lead.

[0017] The gas discharge section may have a width wider than the electrode lead.

[0018] The lead film includes a first lead film and a second lead film, the first lead film may be located above the electrode lead, and the second lead film may be located below the electrode lead.

[0019] The electrode lead is located between the first lead film and the second lead film, and the first lead film and the second lead film are connected to each other.

[0020] An end portion of the gas discharge portion formed in the lead film may be located outside an outer surface of the battery case.

[0021] An end portion of the gas discharge portion open toward the inside of the battery case may be located inside an inner surface of the battery case.

[0022] A battery module according to another embodiment of the present invention may include the battery cell described above. Effects of the Invention

[0023] According to embodiments, the present invention provides a battery cell including an electrode lead to which a lead film with a maximized permeable area is attached, and a battery module including the same, thereby improving the amount of gas generated inside the battery cell discharged to the outside.

[0024] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and the accompanying drawings. Brief Description of the Drawings

[0025] [Figure 1] It is a top view of a conventional battery cell. [Figure 2] It is a cross-sectional view taken along line a-a' in FIG. 1. [Figure 3] It is a top view of the battery cell according to the present embodiment. [Figure 4] It is a perspective view of an electrode lead included in the battery cell of FIG. 3. [Figure 5] Figure 4 is a cross-sectional view taken along the c-c' axis. [Figure 6] Figure 4 is a cross-sectional view taken along the d-d' axis. [Figure 7] Figure 3 is a cross-sectional view taken along the b-b' axis. [Figure 8] Figure 7 is a diagram showing the flow of gas generated inside the battery cell and discharged to the outside. [Figure 9] This is a diagram showing a cross-section of a battery cell according to Experimental Example 1. [Figure 10] This diagram shows the results of measuring the gas pressure inside a battery cell using Experimental Example 2. [Modes for carrying out the invention]

[0026] The present invention will be described in detail below with reference to the attached drawings, so that various embodiments may be easily implemented by those skilled in the art. The present invention can be embodied in a variety of different forms and is not limited to the embodiments described herein.

[0027] To clearly illustrate the present invention, irrelevant parts have been omitted, and the same or similar reference numerals have been used throughout the specification for identical or similar components.

[0028] Furthermore, the dimensions and thicknesses of each component shown in the drawings are arbitrary for the sake of explanation, and therefore the present invention is not necessarily limited to those shown. The thicknesses are shown enlarged in the drawings to clearly represent the various layers and regions. Additionally, the thicknesses of some layers and regions are exaggerated in the drawings for the sake of explanation.

[0029] Furthermore, when a part of the specification "includes" a certain component, unless otherwise stated, this does not exclude other components, but rather means that other components may be included.

[0030] Furthermore, throughout the specification, "on a plane" refers to a top view of the part in question, and "on a cross-section" refers to a side view of a cross-section of the part in question cut perpendicularly.

[0031] The following describes a pouch battery cell 100 according to an embodiment of the present invention. However, although the description here is based on one of the two sides of the pouch battery cell 100, it is not necessarily limited to this side, and the same or similar content will be used when describing the other side.

[0032] Figure 3 is a top view of the battery cell according to this embodiment.

[0033] Referring to Figure 3, the battery cell 100 according to this embodiment includes a battery case 200, electrode leads 300, and lead film 400.

[0034] The battery case 200 includes a sealing section 250 in which the electrode assembly 110 is mounted in a storage section 210 and the outer periphery is sealed by heat fusion. The battery case 200 is a laminate sheet including a resin layer and a metal layer. More specifically, the battery case 200 is made of a laminate sheet and can consist of an outer resin layer forming the outermost casing, a barrier metal layer to prevent penetration of materials, and an inner resin layer for sealing.

[0035] Furthermore, the electrode assembly 110 may consist of a jelly roll type (winding type), a stack type (layered type), or a composite type (stack / folding type). More specifically, the electrode assembly 110 may consist of a positive electrode, a negative electrode, and a separation membrane placed between them.

[0036] The following explanation will focus on the electrode lead 300 and the lead film 400.

[0037] Figure 4 is a perspective view of the electrode leads included in the battery cell shown in Figure 3.

[0038] Referring to Figures 3 and 4, the electrode lead 300 is electrically connected to an electrode tab (not shown) included in the electrode assembly 110 and protrudes outward from the battery case 200 via the sealing portion 250. The lead film 400 is located on at least one of the upper and lower parts of the electrode lead 300, corresponding to the sealing portion 250. This allows the lead film 400 to improve the sealing between the sealing portion 250 and the electrode lead 300 while preventing short circuits in the electrode lead 300 during heat fusion.

[0039] Furthermore, the lead film 400 may have a wider width than the electrode lead 300. The lead film may have a length greater than the length of the sealing portion and a length less than the length of the electrode lead. This allows the lead film 400 to prevent the sides of the electrode lead 300 from being exposed to the outside without interfering with the electrical connection of the electrode lead 300.

[0040] Furthermore, the lead film 400 includes a first lead film and a second lead film, the first lead film being located above the electrode lead 300 and the second lead film being located below the electrode lead 300. In this case, the electrode lead 300 is heat-fused together with the sealing portion 250 while positioned between the first lead film and the second lead film, so that the first lead film and the second lead film are connected to each other.

[0041] This allows the lead film 400 to prevent the sides of the electrode lead 300 from being exposed to the outside while improving the sealing between the sealing portion 250 and the electrode lead 300.

[0042] Figure 5 is a cross-sectional view taken along the c-c' axis in Figure 4. Figure 6 is a cross-sectional view taken along the d-d' axis in Figure 4. Figure 7 is a cross-sectional view taken along the b-b' axis in Figure 3.

[0043] Referring to Figures 5 to 7, the lead film 400 has a gas discharge section 450 that extends from inside the battery case 200 toward the outside of the battery case 200, and the gas discharge section 450 is open toward the inside of the battery case 200. Furthermore, the front and both sides of the gas discharge section 450 are closed with respect to the protruding direction of the electrode lead 300. Here, the gas discharge section 450 refers to the portion of the lead film 400 where the remaining surfaces, excluding the surface open toward the inside of the battery case 200, are not adhered to each other. Also, the gas discharge section 450 may have a wider width than the electrode lead 300.

[0044] As a result, the lead film 400 allows gas generated from inside the battery case 200 to flow within the gas discharge section 450. Furthermore, when the pressure of the lead film 400 exceeds a predetermined level, the gas generated from inside the battery case 200 passes through the gas discharge section 450 and is discharged to the outside. In addition, the gas discharge section 450 maximizes the gas permeability area of ​​the lead film 400, allowing a large amount of gas to be discharged.

[0045] The lead film 400 may further include an inner layer 410 that covers at least a portion of the surface of the gas exhaust section 450. More preferably, the inner layer 410 covers the entire surface of the gas exhaust section 450. Here, the inner layer 410 is either coated onto the gas exhaust section 450 or manufactured as a separate film and attached to the gas exhaust section 450.

[0046] As a result, even if the lead film 400 is heat-sealed together with the sealing portion 250 while positioned at least one of the upper or lower parts of the electrode lead 300, the gas exhaust portion 450 is preserved in a state where it is not heat-sealed by the inner layer 410.

[0047] More specifically, the inner layer 410 may be made of a material with a higher melting point than the material making up the lead film 400. Furthermore, the inner layer 410 may be made of a material that does not react with the electrolyte contained in the battery case 200. For example, the lead film 400 may contain a polyolefin-based substance, while the inner layer 410 may contain at least one substance from among polyolefin-based, fluorine-based, and porous ceramic-based materials. Additionally, the inner layer 410 may contain a getter substance, which increases gas permeability while minimizing moisture penetration. Examples of getter substances include calcium oxide (CaO), barium oxide (BaO), lithium chloride (LiCl), and silica (SiO2), but are not limited to these; any substance that reacts with water (H2O) can be used.

[0048] As a result, the inner layer 410, being made of the aforementioned material, does not react separately with the electrolyte, and no thermal fusion or thermal deformation occurs during the high-temperature thermal fusion process, allowing the gas exhaust section 450 to maintain its void. In other words, the inner surface of the gas exhaust section 450 is kept in a non-adherent state. Furthermore, when gas generated in the battery case 200 flows into the gas exhaust section 450, the inner surfaces of the gas exhaust section 450 separate from each other, allowing the gas that has flowed into the gas exhaust section 450 to be easily discharged to the outside. In addition, the lead film 400, being made of the aforementioned material, can maintain the airtightness of the battery cell 100 and prevent leakage of the internal electrolyte.

[0049] Referring to Figure 7, the end of the gas discharge section 450 formed within the lead film 400 may be located outside the outer surface of the battery case 200. Also, the end of the gas discharge section 450 that is open toward the inside of the battery case 200 may be located inside the inner surface of the battery case 200.

[0050] As a result, the lead film 400 can maximize the area of ​​the gas discharge section 450 and the area of ​​the inner layer 410 to which the gas generated from inside the battery case 200 is exposed. In addition, the permeable area of ​​the gas generated from inside the battery case 200 is maximized, allowing a large amount of gas to be discharged.

[0051] Figure 8 is a diagram showing the flow of gas generated inside the battery cell in Figure 7 and discharged to the outside.

[0052] Referring to Figures 5 to 8, the gas generated from inside the battery cell 100 in Figure 7 flows toward the gas discharge section 450 of the lead film 400. At this time, the gas discharge section 450 expands upward and downward compared to Figure 7 due to the gas inside the battery cell 100. Also, as shown in Figure 8A, if the gas inside the battery cell 100 exceeds a predetermined pressure, the gas inside the battery cell 100 is discharged to the outside through the gas discharge section 450.

[0053] As a result, compared to Figure 2, the gas discharge section 450 is located on the lead film 400, maximizing the gas permeability area inside the battery cell 100, and thereby maximizing the amount of gas generated from inside the battery cell 100 that is discharged to the outside.

[0054] Another embodiment of the present invention includes the aforementioned battery cells. Alternatively, one or more of the battery modules according to this embodiment may be packaged in a pack case to form a battery pack.

[0055] The aforementioned battery modules and battery packs containing them are applicable to a variety of devices. Such devices include means of transport such as electric bicycles, electric vehicles, and hybrid vehicles, but the present invention is not limited thereto and is applicable to a variety of devices in which battery modules and battery packs containing them can be used, and this also falls within the scope of the present invention.

[0056] The present invention will be explained below through more specific examples, but these examples are for illustrative purposes only and the scope of the present invention is not limited thereto.

[0057] <Examples> A battery cell was manufactured in which an electrode assembly is housed within a battery case, and a sealing section is included in the structure where the outer periphery of the battery case is sealed by heat fusion. In this cell, the electrode tabs included in the electrode assembly are electrically connected to the electrode leads, which protrude outward from the battery case via the sealing section. At this time, a lead film is attached to the upper part of the electrode lead at a position corresponding to the sealing section, and a gas exhaust section is formed within the lead film, extending from the inside of the battery case outward from the battery case.

[0058] <Comparative Example> The battery cell was manufactured in the same manner as in the embodiment, except that a separate gas exhaust section was not formed within the lead film.

[0059] <Experimental Example 1 - CT Image> For the battery cell of the embodiment, CT imaging was performed focusing on the sealing area where the lead film and electrode leads are located, and a CT image of that area was obtained as shown in Figure 9.

[0060] Figure 9 is a diagram showing a cross-section of a battery cell according to Experimental Example 1. In the example battery cell, Figure 9(a) is a CT scan image of the cross-section of the lead film and electrode lead before the internal pressure of the example battery cell increased, and Figure 9(b) is a CT scan image of the cross-section of the lead film and electrode lead after gas was injected into the example battery cell and the internal pressure of the example battery cell increased.

[0061] Referring to Figure 9(a), it can be seen that before the internal pressure of the battery cell in the embodiment increases, there is no change around the gas vent portion formed in the lead film. However, as the internal pressure of the battery cell in the embodiment increases, it can be seen that the gas vent portion formed in the lead film separates vertically (in the direction of the arrow), as shown in Figure 9(b).

[0062] As a result, in this embodiment, when a gas vent is formed within the lead film of the battery cell, when the internal pressure of the battery cell increases, the gas vent separates vertically, allowing gas from inside the battery cell to flow into the gas vent. In other words, it can be confirmed that the gas vent included in the battery cell of this embodiment plays the role of a gas vent path for the battery cell.

[0063] <Experimental Example 2 - Measurement of Gas Pressure in a Battery Cell> The internal gas pressure of the battery cells in the examples and comparative examples was measured over time, and the results are shown in Figure 10. In the battery cells of the examples, the initial internal pressure of the battery cell was 1 atmosphere.

[0064] Figure 10 is a diagram showing the results of measuring the gas pressure inside the battery cell in Experimental Example 2.

[0065] Referring to Figure 10, it can be confirmed that in the comparative example, the internal pressure of the battery cell decreases relatively little over time, starting from an initial internal pressure of 1 atmosphere. In contrast, in the battery cell according to this embodiment, it can be confirmed that the internal pressure decreases relatively significantly over time, starting from an initial internal pressure of 1 atmosphere. That is, it can be confirmed that in the battery cell according to this embodiment, the internal gas is effectively discharged to the outside through the gas discharge section formed in the lead film over time.

[0066] Thus, in this embodiment, a gas discharge section is formed within the lead film of the battery cell, and it can be confirmed that when the internal pressure of the battery cell increases, gas is easily discharged to the outside through the gas discharge section.

[0067] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art, utilizing the basic concepts of the present invention as defined in the claims, also fall within the scope of the present invention. [Explanation of Symbols]

[0068] 100: Battery cell 110: Electrode assembly 200: Battery case 210: Storage compartment 250: Sealing section 300: Electrode Leads 400: Lead film 410:Inner layer 450: Gas exhaust section

Claims

1. A battery case including a sealing section in which an electrode assembly is mounted in a storage section and the outer periphery is sealed by heat fusion, An electrode lead is electrically connected to an electrode tab included in the electrode assembly and protrudes outward from the battery case via the sealing portion, The electrode lead includes, at least one of the upper and lower parts, a lead film located in the portion corresponding to the sealing portion, The lead film has a gas discharge portion formed therein that extends from the inside of the battery case toward the outside of the battery case. The gas discharge section is formed from the lead film, A battery cell further comprising an internal layer that covers at least a portion of the surface of the gas discharge section.

2. The battery cell according to claim 1, wherein the gas discharge section is open toward the inside of the battery case, and the front and both sides of the gas discharge section are closed with respect to the direction in which the electrode leads protrude.

3. The battery cell according to claim 1 or 2, wherein the material forming the inner layer has a higher melting point and does not react with the electrolyte compared to the material forming the lead film.

4. The battery cell according to any one of claims 1 to 3, wherein the internal layer is coated on the gas outlet portion or manufactured from a separate film and attached to the gas outlet portion.

5. The aforementioned inner layer is made of water (H ２ A battery cell according to any one of claims 1 to 4, comprising a getter substance that reacts with O).

6. The battery cell according to any one of claims 1 to 5, wherein when gas generated inside the battery case flows into the gas discharge section, the inner surfaces of the gas discharge sections separate from each other.

7. The battery cell according to claim 5, wherein the gas discharge section has a width wider than the electrode lead.

8. The lead film includes a first lead film and a second lead film. The first lead film is located on the upper part of the electrode lead, The second lead film is located below the electrode lead, The battery cell according to any one of claims 1 to 7, wherein the gas discharge portion is formed in the first lead film and the second lead film, respectively.

9. The battery cell according to claim 8, wherein the electrode lead is located between the first lead film and the second lead film, and the first lead film and the second lead film are connected to each other.

10. The battery cell according to any one of claims 1 to 9, wherein the end of the gas discharge portion formed within the lead film is located outside the outer surface of the battery case.

11. The battery cell according to any one of claims 1 to 10, wherein the end of the gas discharge portion, which is open toward the inside of the battery case, is located inward from the inner surface of the battery case.

12. The battery cell according to claim 1, wherein the lead film is heat-sealed together with the sealing portion, and the gas discharge portion is stored in an unheat-sealed state and kept as a blank space.

13. A battery module comprising a battery cell according to any one of claims 1 to 12.

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