Pouch-type battery cell with a safety element between the electrode lead and the lead film

Abstract

The present invention relates to a pouch-type battery cell including an electrode assembly to which electrode leads are joined, a pouch case that houses the electrode assembly and has a sealing portion formed therein for sealing it from the outside, and a lead film that is interposed between the electrode leads and the sealing portion of the pouch case, wherein the pouch-type battery cell further includes a safety element between the electrode leads and the lead film that absorbs energy inside the battery cell and discharges the battery cell when the battery cell is overheated above a certain temperature.

Description

[Technical field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2021-0121677 filed on September 13, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a pouch-type battery cell that is equipped with a safety element between an electrode lead and a lead film, thereby preventing the risk of fire or explosion due to an abnormality in the battery cell. [Background technology]

[0003] As technological development and demand for mobile devices such as smartphones, notebook PCs, and digital cameras increases, research into rechargeable secondary battery technology is being actively conducted. Secondary batteries are an alternative energy source to fossil fuels that generate air pollutants, and are used in electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and energy storage devices (ESSs).

[0004] Currently, the types of secondary batteries that are widely used include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel metal hydride batteries, and nickel zinc batteries. The operating voltage of such unit secondary battery cells, i.e., unit battery cells, is about 2.0V to 5.0V. Therefore, if a higher output voltage is required, a cell module assembly can be constructed by connecting a plurality of battery cells in series, or a battery module can be constructed by connecting cell module assemblies in series or parallel depending on the required output voltage or charge / discharge capacity. In this way, it is common to manufacture a battery pack by adding additional components using at least one battery module.

[0005] Such battery cells can be roughly classified into rectangular, cylindrical and pouch types depending on the shape of the case.

[0006] Among these, the pouch-type battery cell is usually manufactured from a pouch case having an inner layer / metal layer / outer layer laminate sheet structure.

[0007] 1 is a schematic diagram of a conventional pouch-type battery cell. A conventional pouch-type battery cell is manufactured by accommodating an electrode assembly 10 together with an electrolyte inside a pouch case 20, and sealing the outer shell by a method such as heat fusion to form a sealing part 21.

[0008] In addition, a portion of the electrode lead 11 connected to the electrode assembly 10 protrudes outside the pouch case 20 to be electrically connected to a bus bar, etc. It is common to interpose a lead film 30 between the electrode lead 11 and the pouch case 20 for the purposes of improving electrical insulation and adhesion between them.

[0009] Such pouch-type battery cells have the advantages of being able to be formed in a desired shape and size and of being able to increase the volume ratio, but have the disadvantage of being relatively vulnerable to fire, explosion, and the like.

[0010] Therefore, various methods are applied to improve safety when manufacturing pouch-type battery cells.

[0011] One of the most widely used methods is to use an element such as a fuse to cut off the current flow of a battery cell when an abnormality such as overheating due to an overcurrent occurs.

[0012] However, this method has problems such as increased manufacturing costs and reduced volume ratio of the battery cells due to the need to provide each battery cell with an element to cut off overcurrent. Also, even if an overcurrent is detected and cut off, the battery cell in question is already in a high energy state due to the overcurrent, which poses a further risk of fire or explosion. Summary of the Invention [Problem to be solved by the invention]

[0013] In order to solve the above-mentioned problems, an object of the present invention is to provide a pouch-type battery cell that is equipped with a safety element between the electrode lead and the lead film, thereby preventing the risk of fire or explosion due to an abnormality in the battery cell. [Means for solving the problem]

[0014] In order to achieve the above-mentioned objects, a pouch-type battery cell according to the present invention is a pouch-type battery cell including: an electrode assembly to which an electrode lead is joined; a pouch case having a sealing portion formed therein for accommodating the electrode assembly and sealing it from the outside; and a lead film interposed between the electrode lead and the sealing portion of the pouch case, wherein a safety element is included between the electrode lead and the lead film for absorbing energy inside the battery cell and discharging the battery cell when the battery cell is overheated above a certain temperature.

[0015] In the pouch-type battery cell according to the present invention, a portion of the lead film is exposed to the outside through the sealing portion, and the lead film is provided on both sides of the electrode lead.

[0016] In the pouch-type battery cell according to the present invention, the safety element is a thin plate-like element made of a semiconductor material.

[0017] In the pouch-type battery cell according to the present invention, the thickness of the safety element is thinner than the thickness of the lead film.

[0018] In the pouch-type battery cell according to the present invention, the safety elements are provided on both sides of the electrode leads.

[0019] In the pouch-type battery cell according to the present invention, a portion of the safety element is exposed to the outside from the lead film.

[0020] In the pouch-type battery cell according to the present invention, the safety element is located within the lead film.

[0021] In addition, in the pouch-type battery cell according to the present invention, a portion of the lead film is exposed to the outside from the sealing portion, and the lead film includes a first lead film covering the safety element, and a second lead film connected to the first lead film and positioned within the sealing portion.

[0022] In the pouch-type battery cell according to the present invention, the first lead film is made of a material having a lower melting point than the second lead film.

[0023] In addition, in the pouch-type battery cell according to the present invention, the first lead film is a film made of polyethylene (PE), and the second lead film is a film made of polypropylene (PP).

[0024] A battery module according to the present invention is characterized by including the pouch-type battery cell of the present invention.

[0025] A device according to the present invention is also characterized in that it includes the battery module of the present invention. Effect of the Invention

[0026] The pouch-type battery cell of the present invention has the advantage that, by providing a safety element between the electrode lead and the lead film, the internal current can be discharged in the event of an abnormality in the battery cell, preventing fire or explosion of the battery cell.

[0027] Furthermore, the pouch-type battery cell of the present invention has the advantage that, by providing a safety element, the safety of the battery cell can be improved without requiring complicated processes or design changes. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic diagram of a conventional pouch-type battery cell. [Diagram 2] 1 is a schematic diagram of a pouch-type battery cell including a safety element according to an embodiment of the present invention; [Diagram 3] 2 is an enlarged view of a portion of a pouch-type battery cell including a safety element according to an embodiment of the present invention, in which the safety element is located. [Figure 4] 13 is an enlarged view of a portion of a pouch-type battery cell including a safety element according to another embodiment of the present invention, in which the safety element is located. FIG. [Diagram 5] 13 is an enlarged view of a portion where a safety element is located in a pouch-type battery cell having a first lead film and a second lead film according to yet another embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In this application, the terms "including," "having," or "comprising" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but should be understood as not precluding the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0030] In addition, the same reference numerals are used throughout the drawings for parts having similar functions and actions. Throughout the specification, when a part is said to be connected to another part, this includes not only the case where the part is directly connected to another part, but also the case where the part is indirectly connected via another element between the two parts. In addition, unless otherwise specified, the term "including a certain component" does not mean to exclude other components, but means that the part may further include other components.

[0031] Hereinafter, a pouch-type battery cell according to the present invention will be described with reference to the accompanying drawings.

[0032] FIG. 2 is a schematic diagram of a pouch-type battery cell including a safety element according to an embodiment of the present invention.

[0033] The pouch-type battery cell 100 of the present invention will be described with reference to FIG. 2. The pouch-type battery cell 100 includes an electrode assembly 110, a pouch case 120, a lead film 130, and a safety element 140.

[0034] First, the electrode assembly 110 may be, but is not limited to, a jelly roll type assembly having a structure in which long sheet-like positive and negative electrodes are wound with a separator interposed between them, a stack type assembly having a structure in which rectangular positive and negative electrodes are stacked with a separator interposed between them, a stack folding type assembly in which unit cells are wound with a long separator film, or a lamination stack type assembly in which battery cells are stacked with a separator interposed between them and attached to each other.

[0035] In the electrode assembly 110, positive and negative electrode tabs are formed, and positive and negative electrode leads 111 are generally connected to the positive and negative electrode tabs, respectively.

[0036] The positive and negative electrode leads 111 may be formed to protrude in opposite directions as shown in FIG. 2, but are not limited thereto, and various other shapes are possible, such as the positive and negative electrode leads 111 protruding in the same direction.

[0037] The pouch case 120 accommodates the electrode assembly 110 and an electrolyte therein, and includes a sealing portion 121 that seals the outer shell accommodating the electrode assembly 110 by a method such as heat sealing.

[0038] Such a pouch case 120 generally has an inner layer / metal layer / outer layer laminate sheet structure. The inner layer must have insulating properties and electrolyte resistance since it is in direct contact with the electrode assembly 110, and must have excellent sealing properties, i.e., excellent thermal adhesive strength at the sealing portion where the inner layers are thermally bonded to each other, in order to seal against the outside.

[0039] The material for such an inner layer may be selected from polyolefin resins such as polypropylene, polyethylene, polyethylene acrylic acid, and polybutylene, polyurethane resins, and polyimide resins, which have excellent chemical resistance and sealing properties.

[0040] The metal layer in contact with the internal layer corresponds to a barrier layer that prevents moisture and various gases from penetrating into the interior of the battery from the outside. A preferred material for such a metal layer is a thin aluminum film, which is lightweight yet has excellent formability.

[0041] An outer layer is provided on the other side of the metal layer. The outer layer may be made of a heat-resistant polymer having excellent tensile strength, moisture permeability, and air permeability so as to protect the electrode assembly 110 and ensure heat resistance and chemical resistance. Examples of the outer layer include, but are not limited to, nylon or polyethylene terephthalate.

[0042] Meanwhile, the lead film 130 is positioned between the electrode lead 111 and the sealing portion 121 of the pouch case 120 to prevent a short circuit from occurring between the electrode lead 111 and the metal layer of the pouch case 120, and to improve the sealing force and prevent leakage of the electrolyte.

[0043] The lead film 130 may include at least one material selected from the group consisting of polyimide (PI), polyprophylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and epoxy resin, each of which has insulating and heat-sealing properties.

[0044] Moreover, the lead film 130 can generally be configured to surround the electrode lead 111 by disposing a pair of films on both sides of the electrode lead 111 and then bonding the portions not in contact with the electrode lead 111 by a method such as heat fusion. From the viewpoint of preventing short circuits, it is preferable to form the lead film 130 so that a portion of the film protrudes outside the pouch case 120 after the pouch case 120 is sealed.

[0045] Meanwhile, the pouch-type battery cell 100 of the present invention further includes a safety element 140 between the electrode lead 111 and the lead film 130, which serves to absorb internal energy, i.e., current, and discharge the pouch-type battery cell 100 when the pouch-type battery cell 100 is overheated above a certain temperature due to an overcurrent or the like.

[0046] The safety element 140 preferably has a thin plate shape made of a semiconductor material that has low electrical conductivity at room temperature and increases electrical conductivity as the temperature rises.

[0047] When the pouch-type battery cell 100 is operating normally, the safety element 140 made of such a semiconductor material has a relatively small current flow therethrough compared to the electrode lead 111 due to its low electrical conductivity.

[0048] However, if the pouch-type battery cell 100 is overheated due to an overcurrent or the like, the temperature of the safety element 140 also rises, causing the amount of current flowing through the safety element 140 to increase rapidly.

[0049] As a result, the current inside the pouch-type battery cell 100 is forcibly discharged, thereby preventing additional risks such as fire and explosion.

[0050] Additionally, if an excessive amount of current flows through the safety element 140, the temperature of the safety element 140 will rise due to heat generation caused by internal resistance, and such an increase in temperature may deteriorate the lead film 130 and the inner layer of the pouch case 120, which act as insulation between the electrode lead 111 and the pouch case 120.

[0051] That is, a short circuit occurs between the electrode lead 111 and the metal layer of the pouch case 120, and the discharge of the pouch-type battery cell 100 can be accelerated.

[0052] FIG. 3 is an enlarged view of a portion where a safety element is located in a pouch-type battery cell including a safety element according to one embodiment of the present invention, and FIG. 4 is an enlarged view of a portion where the safety element is located in a pouch-type battery cell including a safety element according to another embodiment of the present invention.

[0053] Considering the positions at which the electrode lead 111 and the safety element 140 are provided with reference to Figures 3 and 4, the safety element 140 may protrude partially outside the lead film 130 as shown in Figure 3, or may be completely inserted inside the lead film 130 as shown in Figure 4.

[0054] Since the degree to which the lead film 130 deteriorates due to heat generation from the safety element 140 can differ depending on the contact area between the safety element 140 and the lead film 130, it is also possible to adjust the degree to which the lead film 130 deteriorates to some extent by appropriately adjusting the contact area.

[0055] Of course, the degree of deterioration can also vary depending on the material of the lead film 130.

[0056] Since the safety element 140 is positioned to overlap the sealing portion 121 and / or the lead film 130 of the pouch-type battery cell 100 partially or entirely, it is preferable that the safety element 140 has a thickness as small as possible.

[0057] Specifically, it is preferable that the thickness of the lead film 130 covering the safety element 140 is the same as or smaller than that of the lead film 130 .

[0058] Also, although FIGS. 2 to 4 show the case where safety element 140 is located on one surface of electrode lead 111, the pouch-type battery cell 100 of the present invention can also be provided with multiple safety elements 140 on both surfaces of electrode lead 111.

[0059] Meanwhile, although Figures 2 to 4 of the present invention illustrate an example in which the lead film 130 is formed from a uniform material throughout the entire lead film 130, the lead film 130 of the present invention may be formed from different materials depending on the region.

[0060] FIG. 5 is an enlarged view of a portion where a safety element is located in a pouch-type battery cell having a first lead film and a second lead film according to still another embodiment of the present invention.

[0061] Referring to FIG. 5, considering another example of the lead film 130 of the present invention, the lead film 130 having two regions includes a first lead film 131, a portion of which is exposed outside the sealing portion 121 and covers the safety element 140, and a second lead film 132, which is connected to the first lead film and is positioned within the sealing portion 121.

[0062] Here, the first lead film 131 is made of a material having a lower melting point than the second lead film 132 .

[0063] For example, the first lead film 131 may be made of polyethylene (PE), and the second lead film 132 may be made of polypropylene (PP).

[0064] In this manner, when a lead film 130 having two regions is applied, the first lead film 131 deteriorates at a lower temperature due to heat generation from the safety element 140, and as a result, a short circuit occurs between the electrode lead 111 and the metal layer of the pouch case 120 more quickly, thereby further promoting discharge inside the pouch-type battery cell 100.

[0065] To briefly explain the manufacturing method of the pouch-type battery cell 100 of the present invention described above, it first includes the steps of forming an electrode assembly 110 and joining an electrode lead 111 to the electrode tab of the formed electrode assembly 110.

[0066] Here, the electrode tab and the electrode lead 111 can be joined by various known welding methods such as resistance welding, ultrasonic welding, laser welding, etc.

[0067] Next, a safety element 140 is positioned on the electrode lead 111, and then a lead film 130 is interposed between the electrode assembly 110 and the electrode assembly 110 is housed in a pouch case 120 so that a portion of the electrode lead 111 is exposed. An electrolyte is then injected, and a sealing portion 121 is formed for sealing, thereby forming a pouch-type battery cell 100.

[0068] In other words, except for the inclusion of the safety element 140, the manufacturing process can be similar to that of existing pouch-type battery cells, which has the advantage that no significant additional production costs are incurred and a pouch-type battery cell 100 with improved safety can be manufactured.

[0069] In addition, a battery module or a battery pack can be manufactured by incorporating the pouch-type battery cell 100 including the safety element 140 of the present invention, and the battery module or battery pack manufactured in this manner can be used as a power supply source for various devices such as various electronic devices, electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (P-HEVs).

[0070] Although certain parts of the contents of the present invention have been described in detail above, it will be apparent to a person having ordinary knowledge in the field that such specific techniques are merely preferred embodiments and do not limit the scope of the present invention. It will be apparent to a person skilled in the art that various changes and modifications are possible within the scope and technical ideas of the present invention, and it goes without saying that such changes and modifications also fall within the scope of the attached claims. [Explanation of symbols]

[0071] 100 pouch type battery cells 110 Electrode assembly 111 Electrode lead 120 Pouch Case 121 Sealing part 130 Lead Film 131 First Lead Film 132 2nd Lead Film 140 Safety Elements

Claims

1. an electrode assembly to which an electrode lead is joined; a pouch case having a sealing portion for receiving the electrode assembly and sealing it against the outside; A pouch-type battery cell including: a lead film interposed between the electrode lead and the sealing portion of the pouch case, a safety element is provided between the electrode lead and the lead film, the safety element absorbing energy within the pouch-type battery cell to discharge the pouch-type battery cell when the pouch-type battery cell is overheated above a certain temperature; A pouch-type battery cell, wherein the safety element is a thin plate-like element made of a semiconductor material that has low electrical conductivity at room temperature and whose electrical conductivity increases as the temperature rises.

2. The pouch-type battery cell according to claim 1 , wherein a portion of the lead film is exposed to the outside from the sealing portion, and the lead film is provided on both sides of the electrode lead.

3. The pouch-type battery cell according to claim 1 , wherein the thickness of the safety element is less than the thickness of the lead film.

4. The pouch-type battery cell according to claim 1 , wherein the safety elements are provided on both sides of the electrode lead.

5. The pouch-type battery cell according to claim 1 , wherein a portion of the safety element is exposed to the outside from the lead film.

6. The pouch-type battery cell according to claim 1 , wherein the safety element is located within the lead film.

7. 2. The pouch-type battery cell according to claim 1, wherein the safety element is configured to degrade the lead film and the inner layer of the pouch case when the temperature increases, causing a short circuit between the electrode lead and the metal layer of the pouch case.

8. 2. The pouch-type battery cell of claim 1, wherein a portion of the lead film is exposed to the outside from the sealing portion, and the lead film includes a first lead film covering the safety element, and a second lead film connected to the first lead film and positioned within the sealing portion.

9. The pouch-type battery cell according to claim 8 , wherein the first lead film is formed from a material having a lower melting point than the second lead film.

10. 10. The pouch type battery cell according to claim 9, wherein the first lead film is a film made of polyethylene (PE), and the second lead film is a film made of polypropylene (PP).

11. A battery module comprising the pouch-type battery cell according to any one of claims 1 to 10.

12. A device comprising the battery module of claim 11.

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