Pouch-type battery cell with improved safety

Abstract

The present invention relates to a pouch-type battery cell with improved safety, and more particularly, to a pouch-type battery cell including an electrode assembly including a negative electrode, a separator, and a positive electrode, and a cell case including a lower case and an upper case that form a space to accommodate the electrode assembly, the space being provided with a rupture induction part that induces rupture of the cell case when the internal pressure of the cell case increases.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2021-0148144 filed on November 1, 2021, and all contents disclosed in the literature of the Korean patent application are included as part of this specification.

[0002] The present invention relates to a pouch-type battery cell with improved safety. More specifically, by providing a rupture-inducing part inside the case, the pressure during swelling is used to induce the rupture of the case, and further, it relates to a pouch-type battery cell with improved safety that can easily identify the front and back surfaces of the battery cell.

Background Art

[0003] With the increasing development and demand for mobile devices such as smartphones, notebook PCs, and digital cameras, technologies related to rechargeable secondary batteries have been actively studied. In addition, secondary batteries are alternative energy sources for fossil fuels that generate air pollutants and are applied to electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (P-HEVs), and energy storage devices (ESSs).

[0004] Currently widely used types of secondary batteries include lithium-ion batteries, lithium polymer batteries, nickel-cadmium batteries, nickel-metal hydride batteries, nickel-zinc batteries, etc.

[0005] Such secondary batteries are generally formed by accommodating an electrode assembly, an electrolyte, etc. inside a battery case. Depending on the type of battery case, the electrode assembly is built into a cylindrical or rectangular metal can, including cylindrical batteries and rectangular batteries, and pouch-type batteries in which the electrode assembly is built into a cell case of an aluminum laminate sheet.

[0006] On the one hand, secondary batteries involve repeated charge and discharge processes. During this time, heat is inevitably generated, and in some cases, thermal runaway may occur due to short circuits, thermal shocks, insulation breakdowns, etc., leading to major accidents such as fires and explosions.

[0007] That is, during the charge and discharge process, the space inside the negative electrode where lithium ions detached from the positive electrode can be inserted becomes insufficient, and lithium ions precipitate as metallic lithium on the surface of the negative electrode, or metallic component impurities mixed in during the battery manufacturing process recrystallize and contact the positive electrode through the separator.

[0008] In particular, pouch-type battery cells, different from cylindrical batteries and prismatic batteries, require more attention because the thickness of the case surrounding the electrode assembly is thin and flexible. However, since pouch-type battery cells have a structure that simply seals the electrode assembly, there is no reliable safety means to ensure safety.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] In order to solve the above problems, the present invention aims to provide a pouch-type battery cell with improved safety that can prevent secondary disasters such as fires and explosions by rupturing the case prior to the occurrence of thermal runaway in the pouch-type battery cell.

[0011] Also, the present invention aims to provide a pouch-type battery cell with improved safety that can easily identify the front and back of the battery cell during the manufacture of battery modules and battery packs, thereby enhancing the speed and accuracy of manufacturing.

Means for Solving the Problems

[0012] The pouch-type battery cell according to the present invention for achieving the above object includes an electrode assembly (100) including a negative electrode (110), a separator (120), and a positive electrode (130), and a cell case (200) composed of a lower case (210) and an upper case (220) for forming a space portion (S) so as to accommodate the electrode assembly (100). A rupture induction portion (300) for inducing rupture of the cell case (200) when the internal pressure of the cell case (200) increases is provided in the space portion (S) of the cell case (200).

[0013] Also, in the pouch-type battery cell according to the present invention, the rupture induction portion (300) has a three-dimensional shape having a predetermined volume.

[0014] Also, in the pouch-type battery cell according to the present invention, the rupture induction portion (300) includes a core portion (311) and a coating portion (312) surrounding the core portion (311). The core portion (311) is made of a metal material, and the coating portion (312) is made of a resin of a non-conductive material.

[0015] Also, in the pouch-type battery cell according to the present invention, the rupture induction portion (300) is made of a resin of a non-conductive material.

[0016] Also, in the pouch-type battery cell according to the present invention, one or more rupture induction portions (300) are provided between the electrode assembly (100) and the inner surface of the lower case (210) and / or between the electrode assembly (100) and the inner surface of the upper case (220).

[0017] Further, in the pouch-type battery cell according to the present invention, when a plurality of the rupture-inducing portions (300) are provided between the electrode assembly (100) and the inner surface of the lower case (210) and between the electrode assembly (100) and the inner surface of the upper case (220), the arrangement structures of the rupture-inducing portions 300 provided on the inner surfaces of the lower case (210) and the upper case (220) are different from each other.

[0018] Further, in the pouch-type battery cell according to the present invention, the portion where the rupture-inducing portion (300) of the lower case (210) and / or the upper case (220) is disposed protrudes in a swollen state.

[0019] Further, in the pouch-type battery cell according to the present invention, when the electrode assembly (100) is configured in the order of the separator (120), the negative electrode (110), the separator (120), and the positive electrode (130) from the outermost shell toward the inner side, the rupture-inducing portion (300) is located between the separator (120) located on the outermost contour of the electrode assembly (100) and the inner surface of the cell case (200).

[0020] Further, in the pouch-type battery cell according to the present invention, the rupture-inducing portion (300) is fixed to the separator (120) located on the outermost contour and / or the inner surface of the cell case (200).

[0021] Further, in the pouch-type battery cell according to the present invention, when the electrode assembly (100) is configured in the order of the separator (120), the negative electrode (110), the separator (120), and the positive electrode (130) from the outermost shell toward the inner side, the rupture-inducing portion (300) is located between the separator (120) located on the outermost contour of the electrode assembly (100) and the negative electrode (110) adjacent to the separator (120) located on the outermost contour.

[0022] In the pouch-type battery cell according to the present invention, when the electrode assembly (100) is configured in the order of an auxiliary separator (120’), a separator (120), a negative electrode (110), a separator (120), and a positive electrode (130) from the outermost shell toward the inner side, the rupture induction part (300) is located between the auxiliary separator (120’) of the electrode assembly (100) and the separator (120) located adjacent to the auxiliary separator (120’).

[0023] The present invention also provides a battery pack including the above-described pouch-type battery cell.

Advantages of the Invention

[0024] According to the pouch-type battery cell with improved safety of the present invention, by providing a rupture induction part inside the cell case, when a swelling phenomenon occurs inside the case, it is possible to induce a rapid rupture of the case and prevent fires and explosions in advance.

[0025] Also, according to the pouch-type battery cell with improved safety of the present invention, by making the arrangement structures of the rupture induction parts provided inside the upper case and the lower case different, it becomes easy to distinguish the front and rear surfaces of the battery cell, and it can contribute to improving the speed and accuracy of the manufacturing process during the assembly of the battery module and the battery pack.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0027] In this application, terms such as "including", "having", or "comprising" are intended to specify the presence of features, numbers, steps, components, parts, or combinations thereof described in the specification, and it should be understood that they do not preclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0028] Also, the same reference numerals are used for parts having similar functions and actions throughout the drawings. Throughout the specification, when it is said that a part is connected to another part, this includes not only the case where they are directly connected, but also the case where they are indirectly connected with other elements interposed therebetween. Also, including a certain component means, unless otherwise specified to the contrary, it does not exclude other components and can further include other components.

[0029] Hereinafter, a pouch-type battery cell with improved safety according to the present invention will be described with reference to the accompanying drawings.

[0030] FIG. 1 is an exploded perspective view of a pouch-type battery cell according to the first embodiment of the present invention, FIG. 2 is a plan view of the pouch-type battery cell shown in FIG. 1, and FIG. 3 is a cross-sectional view of a part of the pouch-type battery cell shown in FIG. 1 cut along the line A-A'.

[0031] The pouch-type battery cell with improved safety according to the present invention includes an electrode assembly 100, a cell case 200 for housing the electrode assembly 100, and a rupture induction part 300.

[0032] First, the electrode assembly 100 housed in the cell case 200 can be a jelly-roll type electrode assembly having a structure in which a separator 120 is interposed between a long sheet-like negative electrode 110 and a positive electrode 130 and then wound, a stack type electrode assembly composed of unit cells having a structure in which rectangular positive and negative electrodes are laminated with a separator interposed therebetween, a stack-folding type electrode assembly in which unit cells are wound by a long separation film, or a lamination-stack type electrode assembly in which unit cells are laminated with a separator interposed therebetween and adhered to each other, etc., but is not limited thereto.

[0033] Specifically, the negative electrode 110 is manufactured by applying a slurry in which a negative electrode active material and a binder are mixed to a negative electrode current collector.

[0034] Here, as the negative electrode active material, for example, carbon such as graphitizable carbon and graphite-based carbon; Li x Fe2O3 (0 ≦ x ≦ 1), Li x WO2 (0 ≦ x ≦ 1), Sn x Me 1-x Me’ y O z (Me: Mn, Fe, Pb, Ge; Me’: Al, B, P, Si, Group 1, 2, 3 elements of the periodic table, halogen; 0 < x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8), etc. metal composite oxides; lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; metal oxides such as SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5; conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Si-based materials that are Si, SiO, SiO2 alone or mixtures thereof, etc. can be used, but are not limited only thereto.

[0035] The positive electrode 130 is manufactured by applying a slurry in which a positive electrode active material and a binder are mixed to a positive electrode current collector.

[0036] Here, as the positive electrode active material, there are layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; chemical formula LiNi 1-x MxO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga and x = 0.01 to 0.3), Ni-site type lithium nickel oxides represented by this formula; chemical formula LiMn 2-x M x O2 (where M = Co, Ni, Fe, Cr, Zn, or Ta and x = 0.01 to 0.1) or lithium manganese composite oxides represented by Li2Mn3MO8 (where M = Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which a part of the Li in the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, etc. can be mentioned, but it is not limited only to these.

[0037] On the other hand, the negative electrode current collector and the positive electrode current collector are composed of a portion where a slurry mixed with the active material is applied and a plain portion where the slurry is not applied, and the plain portion is cut to form or a separate conductive member is connected to the plain portion by ultrasonic welding or the like to form an electrode tab.

[0038] An electrode lead 140 is connected to such an electrode tab by spot welding or the like, and an insulating film 150 is located around the electrode lead 140.

[0039] Here, the insulating film 150 is located at the sealing portion where the lower case 210 and the upper case 220 are heat-sealed, and fixes the electrode lead 140 to the cell case 200.

[0040] Therefore, it is possible to prevent the electricity generated in the electrode assembly 100 from flowing into the cell case 200 via the electrode lead 140 and maintain the sealing of the cell case 200. On the other hand, such an insulating film 150 is preferably made of a non-conductive material with poor electrical conductivity. Generally, an insulating tape that easily adheres to the electrode lead 140 and has a relatively small thickness is often used, but it is not limited thereto.

[0041] Next, the cell case 200 will be described.

[0042] The cell case 200 is composed of a lower case 210 and an upper case 220, and is provided with a pocket-shaped space portion S so that the electrode assembly 100 can be accommodated.

[0043] Such a cell case 200 uses a laminate sheet composed of an outer coating layer, a metal layer, and an inner coating layer to form a space portion capable of accommodating the electrode assembly 100.

[0044] Since the inner coating layer is in direct contact with the electrode assembly 100, it must have insulation and electrolyte resistance. Also, for sealing against the outside, the sealing property, that is, the sealing portion where the inner layers are thermally adhered to each other, must have excellent thermal adhesion strength.

[0045] As materials for such an inner coating layer, polyolefin resins such as polypropylene, polyethylene, polyethylene acrylic acid, and polybutylene, which are excellent in chemical resistance and have good sealing properties, polyurethane resins, and polyimide resins can be selected, but are not limited thereto. Polypropylene, which is excellent in mechanical physical properties such as tensile strength, rigidity, surface hardness, and impact resistance, and chemical resistance, is most preferred.

[0046] The metal layer in contact with the inner coating layer corresponds to a barrier layer that prevents moisture and various gases from penetrating from the outside into the inside of the battery. As a suitable material for such a metal layer, an aluminum thin film that is light and has excellent formability can be used.

[0047] On the other side of the metal layer, an external coating layer is provided. As such an external coating layer, a heat-resistant polymer excellent in tensile strength, moisture vapor barrier property, and air permeation prevention property can be used so as to protect the electrode assembly and ensure heat resistance and chemical resistance. As an example, nylon or polyethylene terephthalate can be used, but it is not limited thereto.

[0048] In the drawings, the lower case 210 and the upper case 220 are shown in a completely separated shape, but the lower case 210 and the upper case 220 can be connected at one side edge, and either one of the lower case 210 and the upper case 220 can have a plate-like flat plate structure without a separate space portion.

[0049] Next, the rupture induction part 300 housed in the space part S of the cell case 200 will be described.

[0050] When the internal pressure of the cell case 200 increases due to swelling or the like, the rupture induction part 300 guides the cell case 200 to swell more and ruptures the cell case 200. Thus, prior to the occurrence of thermal runaway, by cutting off the connection with the lead, it is a configuration for minimizing secondary damage such as fire and explosion.

[0051] FIG. 4 is a perspective view illustrating a rupture induction part according to the first embodiment of the present invention. Referring to FIGS. 1 to 4 together, the rupture induction part 300 can have a three-dimensional shape having a predetermined volume.

[0052] For example, a round spherical shape, a polygonal columnar shape formed of four or more planes, a conical shape, a frustum of a cone shape, a frustum of a pyramid shape, a shape composed of a plane and a curved surface, etc., as long as it has a volume by itself, the shape is not particularly limited.

[0053] Here, the size is not particularly limited, but since it must be located between the electrode assembly 100 and the inner surface of the cell case 200, the maximum inner diameter is preferably 6 mm or less.

[0054] The rupture induction part 300 as described above is preferably provided between the electrode assembly 100 and the inner surface of the lower case 210, between the electrode assembly 100 and the inner surface of the upper case 220, or both between the electrode assembly 100 and the inner surface of the lower case 210 and between the electrode assembly 100 and the inner surface of the upper case 220, and more preferably provided in plurality.

[0055] In particular, when provided both between the electrode assembly 100 and the inner surface of the lower case 210 and between the electrode assembly 100 and the inner surface of the upper case 220, and in plurality, it is more preferable that the arrangement structures of the first rupture induction part 310 located between the inner surface of the lower case 210 and the electrode assembly 100 and the second rupture induction part 320 located between the inner surface of the upper case 220 and the electrode assembly 100 are different from each other.

[0056] Generally, a battery module is obtained by stacking a large number of battery cells. Here, the battery cells must be sequentially stacked along a predetermined direction. However, in the case of a pouch-type battery cell provided with space parts in both the upper case and the lower case, since the outer shapes of the upper case and the lower case are similar, it cannot be easily confirmed.

[0057] However, when the rupture induction part 300 is provided on the inner surfaces of the upper case 220 and the lower case 210, the outer surfaces of the lower case 210 and the upper case 220 can protrude so as to bulge slightly due to the volume of the rupture induction part 300 itself. Furthermore, since the arrangement structures of the rupture induction parts 300 provided on the inner surfaces of each case are different from each other, the upper case 220 and the lower case 210 can be easily confirmed with the naked eye, not only is the stacking process easy, but also the accuracy of the process can be improved.

[0058] In FIGS. 1 and 2, on the one hand, six (2×3) first rupture-inducing portions 310, two in the lateral direction and three in the longitudinal direction, are provided on the inner surface of the lower case 210 at predetermined intervals. On the other hand, six (3×2) second rupture-inducing portions 320, three in the lateral direction and two in the longitudinal direction, are provided on the inner surface of the upper case 220. However, this is merely an example, and it is obvious that the number and arrangement structure of the rupture-inducing portions can be variously changed.

[0059] On the one hand, FIG. 3 shows a case where the electrode assembly 100 configured in the order of the separator 120, the negative electrode 110, the separator 120, and the positive electrode 130 from the outermost shell toward the inner side is accommodated. Here, the rupture-inducing portion 300 can be located between the separator 120 located at the outermost contour of the electrode assembly 100 and the inner surface of the cell case 200.

[0060] For the purpose of increasing the energy density, there is almost no gap between the electrode assembly 100 and the inner surface of the cell case 200, so the rupture-inducing portion 300 can be maintained in a fixed state without separate fixing means. However, it is also possible to fix it using an adhesive made of a known non-conductive material so that it can be securely fixed at a desired position. Of course, it is obvious that the rupture-inducing portion 300 can be formed together during the forming process of the cell case 200.

[0061] Here, since the rupture-inducing portion 300 must be in direct contact with the electrode assembly 100, it is preferably made of polypropylene, polyethylene, or polyimide resin, which has no chemical reaction with the electrolytic solution and is a non-conductive material.

[0062] FIG. 5 is a cross-sectional view of the rupture-inducing portion according to the first embodiment of the present invention.

[0063] When the rupture-inducing portion 300 is strongly adhered to the inner surface of the cell case 200 by the internal pressure of the cell case 200, the first rupture-inducing portion 310 can be composed of a core portion 311 and a coating portion 312 surrounding the core portion 311 so as to minimize the volume reduction.

[0064] Here, the core part 311 can be made of aluminum or a metal material, and the coating part 312 is preferably made of a non-conductive material such as polypropylene, polyethylene, or polyimide resin so that the core part 311 and the electrode assembly 100 cannot be energized.

[0065] Of course, it is obvious that the second rupture-inducing part 320 can also be composed of a core part and a coating part, similar to the first rupture-inducing part 310.

[0066] FIG. 6 is a cross-sectional view of a part of a secondary battery according to the second embodiment of the present invention, in which a part is cut.

[0067] The remaining configuration is the same as that of the first embodiment described with reference to FIGS. 1 to 5, except that only the position of the rupture-inducing part 300 is different. Therefore, only the different configuration will be described below.

[0068] The second embodiment is a case where the electrode assembly 100 configured in the order of the separator 120, the negative electrode 110, the separator 120, and the positive electrode 130 from the outermost periphery toward the inner side is housed. Here, the first rupture-inducing part 310 and the second rupture-inducing part 320 can be located between the separator 120 located at the outermost periphery of the electrode assembly 100 and the negative electrode 110 located adjacent to the separator 120 located at the outermost periphery.

[0069] Such first rupture-inducing part 310 and second rupture-inducing part 320 are in a state inserted during the manufacturing process of the electrode assembly 100. In this case, they can be fixed together without separate fixing means.

[0070] In FIG. 6, the vicinity of the first rupture-inducing part 310 and the second rupture-inducing part 320 is shown as having a gap, but this is for more detailed explanation of the location where these rupture-inducing parts are located, and the negative electrode 110 and the separator 120 maintain a close contact state.

[0071] FIG. 7 is a cross-sectional view of a secondary battery according to the third embodiment of the present invention, with a part thereof cut away.

[0072] The remaining configuration is the same as that of the first embodiment described with reference to FIGS. 1 to 5, except that only the position of the rupture-inducing portion 300 is different. Therefore, only the different configuration will be described below.

[0073] The third embodiment is a case where an electrode assembly 100 configured in the order of an auxiliary separator 120', a separator 120, a negative electrode 110, a separator 120, and a positive electrode 130 from the outside shell inward is housed. Here, the first rupture-inducing portion 310 and the second rupture-inducing portion 320 can be located between the auxiliary separator 120' of the electrode assembly 100 and the separator 120 adjacent to the auxiliary separator 120'.

[0074] The auxiliary separator 120' is for surrounding the separator 120 located on the outermost periphery again for the purpose of improving insulation. Similar to the second embodiment, the first rupture-inducing portion 310 and the second rupture-inducing portion 320 can be inserted during the manufacturing process of the electrode assembly 100 and can be fixed together without separate fixing means.

[0075] Also, in FIG. 7, the vicinity of the first rupture-inducing portion 310 and the second rupture-inducing portion 320 is shown as having a gap, but this is for more detailed explanation of the location where these rupture-inducing portions are located, and the separator 120 and the auxiliary separator 120' are in close contact.

[0076] Such a pouch-type battery cell can be stacked in a plurality to form a single battery module or battery pack, and these can be used as a power supply for various devices such as electric vehicles and energy storage devices.

[0077] Although the specific parts of the content of the present invention have been described in detail above, such specific technologies are merely preferred embodiments for those with ordinary knowledge in the art, and thus the scope of the present invention is not limited thereby. It is obvious to those skilled in the art that various changes and modifications are possible within the scope of the category and technical idea of the present invention, and it goes without saying that such variations and modifications are also included in the appended claims.

Explanation of Reference Numerals

[0078] 100 Electrode Assembly 110 Negative Electrode 120 Separator 120’ Auxiliary Separator 130 Positive Electrode 140 Electrode Lead 150 Insulating Film 200 Cell Case 210 Lower Case 220 Upper Case 300 Rupture Inducing Portion 310 First Rupture Inducing Portion 311 Core Portion 312 Coating Portion 320 Second Rupture Inducing Portion

Claims

1. An electrode assembly including a negative electrode, a separator, and a positive electrode, and a cell case composed of a lower case and an upper case for forming a space portion so as to accommodate the electrode assembly. In the space portion of the cell case, a rupture induction portion for inducing rupture of the cell case when the internal pressure of the cell case increases is provided. The rupture induction portion has a three-dimensional shape having a predetermined volume. In the stacking direction of the negative electrode, the separator, and the positive electrode, one or more rupture induction portions are provided between the electrode assembly and the inner surface of the lower case and between the electrode assembly and the inner surface of the upper case. The arrangement structures of the rupture induction portions provided on the inner surface of the lower case and the inner surface of the upper case are different from each other. A pouch-type battery cell in which the portions where the rupture induction portions of the lower case and the upper case are arranged protrude in a swollen state.

2. The rupture induction portion includes a core portion and a coating portion surrounding the core portion. The core portion is made of a metal material, and the coating portion is made of a resin of a non-conductive material. The pouch-type battery cell according to claim 1.

3. The rupture induction portion is made of a resin of a non-conductive material. The pouch-type battery cell according to claim 1.

4. When the electrode assembly is configured in the order of a separator, a negative electrode, a separator, and a positive electrode from the outermost shell toward the inner side, the rupture induction portion is located between the separator located at the outermost contour of the electrode assembly and the inner surface of the cell case. The pouch-type battery cell according to claim 1.

5. The rupture induction portion is fixed to the separator located at the outermost contour and / or the inner surface of the cell case. The pouch-type battery cell according to claim 4.

6. When the electrode assembly is composed in the order of a separator, a negative electrode, a separator, and a positive electrode from the outermost shell toward the inner side, the rupture-inducing portion is located between the separator positioned at the outermost contour of the electrode assembly and the negative electrode positioned adjacent to the separator positioned at the outermost contour. The pouch-type battery cell according to claim 1.

7. When the electrode assembly is composed in the order of an auxiliary separator, a separator, a negative electrode, a separator, and a positive electrode from the outermost shell toward the inner side, the rupture-inducing portion is located between the auxiliary separator of the electrode assembly and the separator positioned adjacent to the auxiliary separator. The pouch-type battery cell according to claim 1.

8. A battery pack including the pouch-type battery cell according to any one of claims 1 to 7.

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