Pouch-type battery cell with venting and its manufacturing method

Abstract

To provide a pouch type battery case that opens and quickly releases gas when internal pressure of the pouch type battery case increases, and can reversibly shut off the inside and outside of the battery case, and to which a venting portion that can be opened and closed is attached, and a manufacturing method thereof.SOLUTION: A pouch type battery case 110 consists of a laminated sheet, and includes a venting portion 130 for exhausting internal gas, an opening is formed, the opening is opened and closed by the venting portion attached to the inside of the opening. The venting portion has a structure in which a first layer with pores and a second layer without pores are laminated.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 2019-0166594, filed on December 13, 2019, 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 having a vent attached thereto and a manufacturing method thereof, and more particularly to a pouch-type battery cell having an openable vent attached to the outer surface of a pouch-type battery case so that gas can be smoothly released when the internal pressure of the pouch-type battery cell increases, and a manufacturing method thereof. [Background technology]

[0003] Reusable and high-energy-density lithium secondary batteries are attracting attention as a new energy source with environmentally friendly properties, as they can dramatically reduce the use of fossil fuels and do not produce by-products due to energy consumption.

[0004] The lithium secondary battery can be classified into a pouch-type battery cell made of a laminate sheet and a cylindrical or prismatic battery cell made of a metal can depending on the type and shape of the exterior material, and the electrode assembly can be classified into a jelly-roll type electrode assembly, a stack type electrode assembly, a stack / folding type electrode assembly, and a lamination / stack type electrode assembly depending on the shape.

[0005] The pouch-type lithium secondary battery can be easily manufactured in various sizes, and is lightweight and has high energy density, so it is used as a power source for electric vehicles or hybrid vehicles that require a high-output, large-capacity energy source.

[0006] The pouch-type lithium secondary battery is manufactured by placing an electrode assembly and an electrolyte in a pouch-type battery case made of a laminate sheet, and then sealing the outer periphery of the battery case by applying heat and pressure.

[0007] Lithium secondary batteries generate gas due to the decomposition reaction of the electrolyte during the activation process during the manufacturing process, and also increase their internal pressure due to the gas generated inside the battery cell during charging and discharging and in abnormal usage environments.

[0008] Such an increase in internal pressure can cause the battery cell to explode, so research is being conducted to ensure safety by venting the gas to the outside before the battery explodes.

[0009] In this regard, Patent Document 1 relates to a battery module to which a valve member including a breathable film made of Teflon (registered trademark) resin is added, and the valve member is made of a breathable film made of PTFE material, and the breathable film has a structure in which it is fixed by a support member below a vent hole formed in a housing cover.

[0010] That is, Patent Document 1 only discloses a valve member that is applied to a battery module housing, but does not disclose a venting member that is applicable to a pouch-type battery cell.

[0011] Patent Document 2 relates to a secondary battery having a structure in which gas inside the case is discharged through a communication passage inside a protrusion formed integrally with the case, and the protrusion and communication passage have a structure in which they protrude from one side of the outer periphery of the battery case.

[0012] As such, there is a strong need for a pouch-type battery cell and a manufacturing method thereof that has a structure that does not increase the external size of the battery case, smoothly releases gas when the internal pressure of the pouch-type battery cell increases, and allows the battery to be used continuously after the gas is released. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Korean Patent Publication No. 2012-0009592 [Patent Document 2] Korean Patent Publication No. 2018-0038880 Summary of the Invention [Problem to be solved by the invention]

[0014] The present invention has been made to solve the above problems, and an object of the present invention is to provide a pouch-type battery cell in which an openable and closable vent is attached to the inside of an opening formed in a pouch-type battery case, and a manufacturing method thereof. [Means for solving the problem]

[0015] To achieve this object, a pouch-type battery cell with a vent attached according to the present invention includes a pouch-type battery case made of a laminate sheet, an electrode assembly housed inside the pouch-type battery case, and a vent for discharging internal gas from the pouch-type battery case, wherein the pouch-type battery case has an opening formed therein that is opened and closed by a vent attached to the inside of the opening.

[0016] The venting part may have a structure in which a first layer having pores and a second layer having no pores are stacked.

[0017] The first layer and the second layer may be made of the same material.

[0018] The material may be polytetrafluoroethylene (PTFE).

[0019] The pouch-type battery case may include an outer resin layer, a metal layer, and an inner resin layer, and the venting part may be attached so that the first layer and the inner resin layer are in contact with each other.

[0020] The inner resin layer may be hardened in a state where a portion of the inner resin layer is melted into the pores of the first layer, thereby bonding the inner resin layer to the first layer.

[0021] The venting portion may be attached to a portion adjacent to a sealing portion of the pouch-type battery case.

[0022] The pouch-type battery case may include a first battery case having an electrode assembly receiving portion formed therein, and a second battery case coupled to the first battery case to seal the pouch-type battery case, and the venting portion may be attached to at least one of a center of the first battery case and a center of the second battery case.

[0023] Meanwhile, the present invention provides a method for manufacturing a pouch-type battery cell, which includes the steps of (a) preparing a laminate sheet having an opening, (b) attaching a vent to the opening, (c) forming the laminate sheet to manufacture a pouch-type battery case, and (d) housing an electrode assembly in the pouch-type battery case and sealing it.

[0024] The venting part may have a structure in which a first layer having pores and a second layer having no pores are stacked.

[0025] The first layer and the second layer may be made of the same material.

[0026] The material may be polytetrafluoroethylene (PTFE).

[0027] The present invention also provides a battery pack including the pouch-type battery cell. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a perspective view of a pouch-type battery cell having a vent formed therein according to a first embodiment. FIG. [Figure 2] FIG. 10 is a perspective view of a pouch-type battery cell having a vent according to a second embodiment. [Figure 3] FIG. 2 is a partially enlarged vertical cross-sectional view taken along line AA' in FIG. [Figure 4] This is an SEM photograph of the first layer of the venting section. [Figure 5] This is an SEM photograph of the second layer of the venting section. [Figure 6] FIG. 4 is a diagram showing another embodiment of FIG. 3. [Figure 7] This is an SEM photograph of the part where the pouch-type battery case and the venting part are overlapped and joined. DETAILED DESCRIPTION OF THE INVENTION

[0029] Hereinafter, a detailed description will be given of embodiments of the present invention that will enable those skilled in the art to easily carry out the present invention with reference to the accompanying drawings. However, in describing the operation principle of the preferred embodiments of the present invention in detail, detailed descriptions of related well-known functions or configurations will be omitted if it is determined that such detailed descriptions may unnecessarily obscure the gist of the present invention.

[0030] Furthermore, 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 a direct connection but also an indirect connection via another element therebetween. Furthermore, unless otherwise specified, "including a certain element" does not mean that other elements are excluded, but that other elements may also be included.

[0031] Descriptions that limit or specify additional elements are applicable to all inventions unless otherwise limited, and are not limited to a particular invention.

[0032] The invention will now be described on the basis of detailed embodiments with reference to the drawings.

[0033] FIG. 1 is a perspective view of a pouch-type battery cell having a vent according to a first embodiment.

[0034] Referring to FIG. 1, a pouch-type battery cell 100 has an electrode assembly and an electrolyte housed inside a pouch-type battery case made of a laminate sheet, and has a sealed outer periphery.

[0035] The electrode assembly may be a unidirectional electrode assembly in which the positive electrode lead 101 and the negative electrode lead 102 protrude in one direction, or a bidirectional electrode assembly in which the positive electrode lead and the negative electrode lead protrude in different directions, unlike that shown in FIG. 1.

[0036] The pouch-type battery case 110 includes a first battery case 111 in which an electrode assembly receiving portion 113 is formed, and a second battery case 112 that is combined with the first battery case 111 to seal the pouch-type battery case 110. An opening is formed in the center of the second battery case 112, and a venting portion 130 is attached to the inside of the opening.

[0037] The venting portion 130 has a circular shape in a plan view and is larger in diameter than the opening formed in the pouch-type battery case 110, so that it has a shape that closes the opening of the pouch-type battery case from the inside.

[0038] Although not shown in FIG. 1, a venting portion may be formed in the center of the first battery case 111 in addition to the center of the second battery case 112, or a venting portion may be formed only in the center of the first battery case.

[0039] When the pouch-type battery case 110 expands due to gas generated by a side reaction inside the pouch-type battery cell 100, the centers of the first and second battery cases expand the most, causing pressure to concentrate in the bulging state. In this case, the difference between the gas pressure in the vent and the external pressure of the pouch-type battery cell becomes large, allowing the gas to be discharged through the pores in the vent.

[0040] That is, when there is little or no difference between the internal and external pressures of the pouch-type battery cell, the vent according to the present invention does not discharge gas and blocks the inflow of external substances into the battery cell, but when the pressure difference between the inside and outside of the pouch-type battery cell is 0.1 atm or more, the internal gas is discharged through the first and second layers of the vent due to the pressure difference. After that, as the gas is discharged to a certain extent, when the pressure difference between the inside and outside of the pouch-type battery cell becomes 0.1 atm or less, this process of blocking gas discharge again can occur reversibly.

[0041] FIG. 2 is a perspective view of a pouch-type battery cell having a vent according to a second embodiment.

[0042] Referring to FIG. 2, the pouch-type battery cell 200 has the same configuration as that described in FIG. 1, except that the position of the venting portion 230 is different from the position of the venting portion 130 formed in the pouch-type battery cell of FIG. 1.

[0043] The venting portion 230 of FIG. 2 has a structure in which three spaced apart venting portions 230 are attached to adjacent portions of the sealing portion 215 .

[0044] The radius of the vent 230 shown in FIG. 2 is the same as that of the vent 230 shown in FIG. 130 The number, size and position of the vents can be selectively determined in consideration of the attachment position of the vents, the size of the battery case and the amount of gas generated.

[0045] FIG. 3 is a partially enlarged vertical cross-sectional view taken along line AA' of FIG. 1, specifically illustrating the structure of a pouch-type battery case having a vent according to the present invention.

[0046] Referring to FIG. 3, the pouch-type battery case 110 includes an outer resin layer 110a, a metal layer 110b, and an inner resin layer 110c.

[0047] The outer resin layer protects the battery cell from the outside and must therefore have excellent resistance to the external environment, and is required to have excellent tensile strength and weather resistance relative to its thickness. For example, polyester-based resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyolefin-based resins such as polyethylene (PE) and polypropylene (PP), polystyrene-based resins such as polystyrene, polyvinyl chloride-based resins, and polyvinylidene chloride-based resins can be used. These materials can be used alone or in combination, and ONy (oriented nylon film) can also be used.

[0048] The metal layer can be made of aluminum (Al) or an aluminum alloy to prevent the intrusion of foreign substances such as gas and moisture, or the leakage of electrolyte, as well as to improve the strength of the battery case. Examples of aluminum alloys include alloy numbers 8079, 1N30, 8021, 3003, 3004, 3005, 3104, and 3105, which can be used alone or in combination.

[0049] The inner resin layer may be made of a polymer resin that has heat fusion (thermal adhesiveness), has low hygroscopicity to the electrolyte to prevent the electrolyte from penetrating, and is not swollen or eroded by the electrolyte, and is preferably made of polypropylene, acid-modified polypropylene, or a combination thereof.

[0050] As a preferred example, the pouch-type battery case according to the present invention may have a structure in which the thickness of the outer coating layer is 5 μm to 40 μm, the thickness of the metal layer is 20 μm to 150 μm, and the thickness of the inner resin layer is 10 μm to 50 μm. If the thickness of each layer of the laminate sheet is too thin, it is difficult to expect improved barrier function and strength against substances, while if it is too thick, it is undesirable because it reduces processability and increases the sheet thickness.

[0051] The venting portion 130 according to the present invention has a structure in which a first layer 131 having pores and a second layer 132 having no pores are laminated together, and the first layer 131 and the second layer 132 are made of the same material, that is, polytetrafluoroethylene (PTFE).

[0052] PTFE has excellent electrolyte resistance, heat resistance, and hydrophobicity, and can be used as a material for the venting portion attached to the inside of a pouch-type battery case.

[0053] The venting portion 130 is different in shape in that the first layer 131 has a structure in which pores are formed, whereas the second layer 132 has a structure in which pores are not formed.

[0054] In this regard, FIG. 4 shows an SEM photograph of the first layer of the venting section, and FIG. 5 shows an SEM photograph of the second layer of the venting section.

[0055] 4 and 5, it can be seen that the first layer in Fig. 4 has a structure in which open pores are formed, connecting the inside and outside, while the second layer in Fig. 5 has a morphology in which folds are formed on the surface but no pores are formed. However, because the second layer is made of a PTFE material, gas can be discharged through the fine gaps formed between the polymers.

[0056] That is, the internal resin layer of the pouch-type battery case dissolves into the pores of the first layer of the venting portion, allowing the venting portion to be stably attached to the inner surface of the pouch-type battery case, and gas formed inside the pouch-type battery case can be discharged to the outside through the first and second layers of the venting portion.

[0057] On the other hand, the melting point of PTFE is 327°C, but the melting point of polypropylene (PP), which is mainly used as the inner resin layer of pouch-type battery cases, is about 160°C, so there is a big difference. Therefore, when applying heat and pressure to attach the PTFE venting part to the PP inner resin layer, the PP may be damaged if the heating temperature is at the melting point of PTFE.On the other hand, if the PP is heated to a temperature at which it melts but not damaged, the PTFE does not melt, making it difficult for them to bond together.

[0058] Therefore, in the present invention, a structure is used in which the venting portion is attached to the pouch-type battery case so that the first layer 131 having pores contacts the internal resin layer 110c of the pouch-type battery case. When the overlapping portion of the pouch-type battery case and the venting portion are heated and pressurized at high temperature to attach the venting portion to the pouch-type battery case, a portion of the internal resin layer 110c hardens while melting into the pores of the first layer 131, thereby anchoring the internal resin layer 110c to the first layer 131.

[0059] FIG. 6 shows another embodiment of FIG. 3, specifically illustrating the structure of a pouch-type battery case having a venting portion according to the present invention.

[0060] 6, pouch-type battery case 310 has a structure in which, from top to bottom, outer resin layer 310a, adhesive layer 310d, metal layer 310b, adhesive layer 310d, and inner resin layer 310c are layered in this order, and differs from the pouch-type battery case shown in FIG. 3 in that adhesive layers are further added between the outer resin layer and the metal layer, and between the metal layer and the inner resin layer. That is, the addition of the adhesive layers allows the pouch-type battery case of FIG. 6 to have stronger adhesion between the layers than the pouch-type battery case of FIG. 3.

[0061] The venting portion 330 includes a first layer 331 having pores and a second layer 332 having no pores, and the first layer 331 is attached to the inner resin layer 310c.

[0062] Therefore, when the overlapping portion between the venting portion and the pouch-type battery case 310 is heated and pressurized to join them, the inner resin layer 310c melts and moves into the pores of the first layer 331, thereby forming an anchoring bond.

[0063] On the other hand, even if the venting part is attached to the outside of the opening of the pouch-type battery case, the gas discharge effect can be achieved when the internal gas pressure increases. However, in this case, the metal layer of the pouch-type battery case is exposed at the opening, and hydrofluoric acid generated by a side reaction of the electrolyte may corrode the metal layer made of aluminum, which is not preferable.

[0064] FIG. 7 shows an SEM photograph of the portion where the pouch-type battery case and the venting part are overlapped and joined.

[0065] 7, the pouch-type battery case is made up of an outer resin layer 410a, a metal layer 410b, and an inner resin layer 410c. The venting portion 430 has a structure in which a first layer 431 and a second layer 432 are laminated.

[0066] The outer resin layer 410a has a structure in which a PET layer, an adhesive layer, a nylon layer, and an adhesive layer are laminated in this order from the outside to the inside, the metal layer 410b is a layer made of aluminum, and the inner resin layer 410c has a form in which polypropylene and acid-modified polypropylene are combined, or can be made of a non-stretched polypropylene film.

[0067] Venting portion 430 is made of a PTFE material and is composed of a first layer 431 having pores formed therein, and a second layer 432 also made of a PTFE material and having no pores formed therein.

[0068] Before the pouch-type battery case and the venting portion are joined together, the total thickness of the outer resin layer may be 33.1 μm, the thickness of the metal layer may be 41.4 μm, and the thickness of the inner resin layer may be 80 μm.

[0069] The inner resin layer may be manufactured by extruding polypropylene and acid-modified polypropylene onto a metal layer, and the inner resin layer may be laminated with the metal layer and the outer resin layer to manufacture a pouch-type battery case. The polypropylene may have a thickness of 40 μm, and the acid-modified polypropylene may have a thickness of 40 μm.

[0070] Alternatively, the inner resin layer may be in the form of a 80 μm thick unstretched polypropylene (CPP) film, and the unstretched polypropylene film may be attached to a metal layer with an adhesive and laminated together with the outer resin layer to produce a pouch-type battery case.

[0071] When the pouch-type battery case and the venting portion are joined by heating and pressure, the polypropylene in the inner resin layer melts and enters the pores of the first layer, reducing the thickness of the inner resin layer to 12.2 μm as shown in FIG. 7, and the pores in the first layer 431 become invisible.

[0072] In other words, the inner resin layer is introduced into the pores of the first layer and anchored, ensuring uniform adhesion throughout the entire area, and the venting part is stably attached to the inside of the pouch-type battery case.

[0073] The temperature for bonding the first layer and the inner resin layer can be selected from the ranges of 180° C. to 220° C., pressure from 0.05 MPa to 0.5 MPa, and pressure time from 1 second to 5 seconds.

[0074] In one specific example, when gas is generated due to a side reaction of the electrolyte occurring inside the pouch-type battery cell, the internal pressure of the pouch-type battery cell becomes higher than the external pressure, and the gas can be discharged through the opening and the first and second layers of the venting portion formed in the pouch-type battery case.

[0075] Therefore, the pouch-type battery cell according to the present invention can reversibly perform the process of discharging internal gas through the vent when the internal pressure of the battery cell increases, and blocking gas discharge and preventing external moisture from entering when the internal pressure becomes the same as the external pressure of the battery cell.

[0076] Meanwhile, a method for manufacturing a pouch-type battery cell according to the present invention may include the steps of: (a) preparing a laminate sheet having an opening; (b) attaching a vent to the opening; (c) forming the laminate sheet to manufacture a pouch-type battery case; and (d) housing an electrode assembly in the pouch-type battery case and sealing it.

[0077] That is, it is preferable from the viewpoint of process convenience that the opening is formed in the pouch-type battery cell before molding, and the electrode assembly receiving portion is molded with the vent portion attached to the opening.

[0078] However, if necessary, step (b) may be performed between steps (c) and (d), or a step of forming an opening in the laminate sheet and attaching a venting portion may be performed between steps (c) and (d).

[0079] The venting part may have a structure in which a first layer having pores and a second layer having no pores are laminated, and the first and second layers may be made of PTFE.

[0080] Those skilled in the art will appreciate that the above content will enable various applications and modifications within the scope of the present invention. [Industrial Applicability]

[0081] As described above, the pouch-type battery cell according to the present invention has a structure in which a vent is attached to the inside of a battery case, so that an increase in the size of the battery cell due to the addition of the vent can be minimized.

[0082] Furthermore, when the internal pressure of the battery cell increases, the gas can be immediately discharged, so that the internal pressure of the battery cell can be maintained at a constant level.

[0083] In addition, the venting portion according to the present invention is not broken when opened, but can be opened and closed for reversible use, allowing the battery cell to be used continuously after exhausting. The following items are also disclosed: [Item 1] a pouch-shaped battery case made of a laminate sheet; an electrode assembly housed inside the pouch-type battery case; a venting portion for discharging internal gas from the pouch-type battery case; Including, The pouch-type battery case has an opening formed therein, and the opening is opened and closed by the venting portion attached to the inside of the opening. [Item 2] Item 1. The pouch-type battery cell according to item 1, wherein the venting portion has a structure in which a first layer having pores formed therein and a second layer having no pores formed therein are stacked. [Item 3] Item 3. The pouch-type battery cell according to item 2, wherein the first layer and the second layer are made of the same material. [Item 4] Item 4. The pouch-type battery cell according to item 3, wherein the material is polytetrafluoroethylene (PTFE). [Item 5] the pouch-type battery case includes an outer resin layer, a metal layer, and an inner resin layer; 5. The pouch-type battery cell according to any one of items 2 to 4, wherein the venting portion is attached so that the first layer and the inner resin layer are in contact with each other. [Item 6] Item 6. The pouch-type battery cell according to item 5, wherein the internal resin layer and the first layer are bonded together by hardening a portion of the internal resin layer in a state where the internal resin layer is melted into the pores of the first layer. [Item 7] 7. The pouch-type battery cell according to any one of items 1 to 6, wherein the venting portion is attached to an adjacent portion of the sealing portion of the pouch-type battery case. [Item 8] the pouch-type battery case includes a first battery case in which an electrode assembly receiving portion is formed, and a second battery case that is coupled to the first battery case to seal the pouch-type battery case, 8. The pouch-type battery cell according to any one of items 1 to 7, wherein the venting portion is attached to at least one of the center of the first battery case and the center of the second battery case. [Item 9] (a) attaching a venting portion to an opening formed in a laminate sheet; (b) forming the laminate sheet into a pouch-shaped battery case; (c) housing an electrode assembly in the pouch-type battery case and sealing it; A method for manufacturing a pouch-type battery cell, comprising: [Item 10] Item 10. The method for manufacturing a pouch-type battery cell according to item 9, wherein the venting portion has a structure in which a first layer having pores formed therein and a second layer having no pores formed therein are stacked. [Item 11] Item 11. The method for manufacturing a pouch-type battery cell according to item 10, wherein the first layer and the second layer are made of the same material. [Item 12] Item 12. The method for manufacturing a pouch-type battery cell according to Item 11, wherein the material is polytetrafluoroethylene (PTFE). [Item 13] A battery pack including the pouch-type battery cell according to any one of items 1 to 8. [Explanation of symbols]

[0084] 100, 200 pouch type battery cells 101 Positive lead 102 Negative lead 110, 310 Pouch-type battery case 110a, 310a, 410a outer resin layer 110b, 310b, 410b metal layer 110c, 310c, 410c internal resin layer 111 First battery case 112 Second battery case 113 Electrode assembly storage section 130, 230, 330, 430 Venting section 131, 331, 431 1st layer 132, 332, 432 2nd layer 215 Sealing section 310d adhesive layer

Claims

1. It consists of a laminated sheet, a venting section for discharging internal gas; an opening is formed, and the opening is opened and closed by the venting portion attached to the inside of the opening; the venting portion has a structure in which a first layer having pores and a second layer having no pores are laminated together, An outer resin layer, a metal layer, and an inner resin layer, the venting portion is attached so that the first layer and the inner resin layer are in contact with each other; The pouch-type battery case is such that the internal resin layer and the first layer are bonded together by hardening a portion of the internal resin layer in a state where the portion of the internal resin layer is melted into the pores of the first layer.

2. 2. The pouch-type battery case according to claim 1, wherein the first layer and the second layer are made of the same material.

3. 3. The pouch-type battery case according to claim 2, wherein the material is polytetrafluoroethylene (PTFE).

4. The pouch-type battery case according to claim 1 , wherein the venting portion is attached to a portion adjacent to the sealing portion.

5. a first battery case having an electrode assembly receiving portion formed therein; and a second battery case coupled to the first battery case to seal the pouch-type battery case, The pouch-type battery case according to claim 1 , wherein the venting portion is attached to at least one of a center portion of the first battery case and a center portion of the second battery case.

6. (a) attaching a venting portion to an opening formed in a laminate sheet; (b) forming the laminate sheet; A method for producing the pouch-type battery case according to claim 1 , comprising:

7. The method for manufacturing a pouch-type battery case according to claim 6 , wherein the venting portion has a structure in which a first layer having pores and a second layer having no pores are laminated together.

8. The method for manufacturing a pouch-type battery case according to claim 7 , wherein the first layer and the second layer are made of the same material.

9. The method for manufacturing a pouch-type battery case according to claim 8, wherein the material is polytetrafluoroethylene (PTFE).

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