Battery cell assembly and manufacturing method thereof

Abstract

The present invention discloses a battery cell assembly and a manufacturing method thereof. The battery cell assembly of the present invention includes a battery cell formed by stacking a plurality of unit cells each including a cathode, a separator, and an anode; and a heat insulating cover that surrounds the outer periphery of the battery cell one or more times.

Description

[Technical field]

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2021-0187982 filed on December 27, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a battery cell assembly and a manufacturing method thereof, and more particularly to a battery cell assembly and a manufacturing method thereof that can block heat transfer between adjacent battery cells, delay ignition time, and ensure evacuation time for users. [Background technology]

[0003] Typically, as the development and demand for mobile devices and electric vehicles increases, the demand for secondary batteries as energy sources increases exponentially, which has led to a great deal of research being conducted on secondary batteries to meet various demands.

[0004] Typically, in terms of the shape of the secondary battery, there is a high demand for square-type secondary batteries and pouch-type secondary batteries which are thin and applicable to products such as mobile phones, and in terms of materials, there is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries which have high energy density, discharge voltage, and stable output.

[0005] FIG. 1 is a plan view illustrating a conventional battery cell assembly, and FIG. 2 is a plan view illustrating a state in which a separator contracts when the battery cell assembly of FIG. 1 is heated to about 100 to 120° C.

[0006] 1 and 2, the secondary battery is formed by stacking a plurality of battery cells 10. The battery cell 10 is formed by stacking a cathode 11, a separator 13, and an anode 15.

[0007] The battery cell 10 can be manufactured by a lamination and stacking process, in which a separator 13, a cathode 11, a separator 13, and an anode 15 are laminated, and then cut to manufacture a mono-cell, and a plurality of mono-cells are laminated.

[0008] Although these battery cells 10 have a simple structure and a high degree of electrolyte impregnation, they have problems in that the production speed is slow and the degree of alignment is low. In these battery cells 10, a taping process is performed to ensure the degree of alignment of the stacked cathode 11, separator 13, and anode 15. In this taping process, a plurality of tapes 17 are attached to both side surfaces and parts of the top and bottom surfaces of the battery cell 10.

[0009] However, when a conventional battery cell 10 is heated to about 100 to 120°C as shown in Fig. 2, the separator 13 shrinks and the separator 13 and the cathode 11 are deformed into a round shape. In particular, around the separator 13, the portion of the separator 13 to which the tape 17 is attached does not shrink, but the portion to which the tape 17 is not attached shrinks. As a result, the portion to which the tape 17 is not attached shrinks, exposing the cathode 11 and the anode 15 to each other, which causes a problem of short circuit between the cathode 11 and the anode 15 and ignition.

[0010] In addition, since the battery cells 10 are built in a battery module, when a particular battery cell 10 overheats or ignites, thermal propagation is likely to occur to the adjacent battery cells 10. Therefore, there is a demand for development of a technology that can block the transfer of heat from the battery cell 10 and delay the propagation of the ignition in the adjacent battery cells 10.

[0011] The background technology of the present invention is disclosed in Korean Patent Publication No. 2021-0053570 (published on May 12, 2021). Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been devised to solve the above-mentioned problems, and an object of the present invention is to provide a battery cell assembly and a manufacturing method thereof that can block heat transfer between adjacent battery cells, delay the ignition time, and ensure evacuation time for passengers. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention may include a battery cell including a plurality of unit cells stacked together, each unit cell including a cathode, a separator, and an anode; and a heat insulating cover surrounding the outer periphery of the battery cell at least once.

[0014] The thickness of the insulating cover may be 10 μm or more and 20 μm or less.

[0015] The insulating cover may be made of a heat-resistant film.

[0016] The heat insulating cover may be a polyimide film (PI film).

[0017] The polyimide film may have a thickness of 5 μm or more and 10 μm or less.

[0018] The insulating cover can be wound up in close contact with the battery cell.

[0019] The battery cell may include a structure in which a plurality of unit cells of a cathode-separator-anode-separator type or an anode-separator-cathode-separator type are stacked.

[0020] The battery cell may have a structure in which a cathode-separator-anode-separator-cathode type or an anode-separator-cathode-separator-anode type unit cell is attached to a long separator and then folded and stacked.

[0021] The method for manufacturing the battery cell assembly may include the steps of stacking a plurality of unit cells to fabricate a battery cell; and winding the unit cells one or more times around the battery cell to form an insulating cover around the battery cell.

[0022] The insulating cover may be a polyimide film.

[0023] The thickness of the insulating cover can be determined by the number of times the polyimide film is wound. Effect of the Invention

[0024] According to the present invention, the insulating cover is installed so as to surround the battery cell, so that even if the battery cell is heated by a flame from an adjacent cell, the heat propagation time and the ignition time can be delayed.

[0025] According to the present invention, when the thickness of the insulating cover is 5 to 10 μm, it is possible to maximize the heat propagation retardation performance while minimizing the increase in thickness and volume of the battery cell assembly.

[0026] According to the present invention, the thickness of the insulating cover can be determined by adjusting the number of times the polyimide film is wound.

[0027] The above-mentioned effects and specific effects of the present invention will be described in conjunction with the following description of the preferred embodiment of the invention. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a plan view illustrating a schematic configuration of a conventional battery cell assembly. [Diagram 2] 2 is a plan view showing a state in which a separator contracts when the battery cell assembly of FIG. 1 is heated to about 100 to 120° C. FIG. [Diagram 3] 1 is a plan view illustrating a battery cell assembly according to the present invention; [Figure 4]FIG. 4 is a cross-sectional view illustrating the battery cell assembly of FIG. 3. [Diagram 5] 4 is a diagram illustrating a state in which a polyimide film in the battery cell assembly of FIG. 3 is wound once to form a heat insulating cover. [Figure 6] 4 is a schematic diagram showing a state in which a polyimide film in the battery cell assembly of FIG. 3 is wound twice to form a heat insulating cover. [Figure 7] 1 is a schematic diagram illustrating an experimental device for heat propagation in a cell assembly according to the present invention; [Figure 8] 4 is a diagram showing a schematic direction in which an insulating cover contracts when a cell assembly according to the present invention is heated to about 110° C.; [Figure 9] 8 is a graph showing a heat propagation delay time and a voltage drop time versus a thickness of a polyimide film in the heat propagation experimental apparatus of FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0030] The present invention is not limited to the embodiments disclosed below, and may be embodied in various different forms and may be modified in various ways. However, the present embodiments are provided to complete the disclosure of the present invention and to fully inform those skilled in the art of the scope of the invention. Therefore, the present invention is not limited to the embodiments disclosed below, and should be understood to include all modifications, equivalents, and alternatives within the technical spirit and scope of the present invention, as well as the substitution or addition of the configuration of any embodiment with the configuration of another embodiment.

[0031] The accompanying drawings are provided to facilitate understanding of the embodiments disclosed in this specification, and the accompanying drawings are not intended to limit the technical ideas disclosed in this specification, and should be understood to include any modifications, equivalents, or alternatives included in the ideas and technical scope of the present invention. Although the components in the drawings may be exaggerated in size or thickness to make them larger or smaller for ease of understanding, the scope of protection of the present invention should not be interpreted as being limited thereby.

[0032] The terms used in this specification are merely used to describe specific examples and embodiments, and are not intended to limit the present invention. Furthermore, singular expressions include plural expressions unless the context clearly indicates otherwise. Terms such as "includes", "comprises", and the like in the specification are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification. In other words, terms such as "includes", "comprises", and the like in the specification should not be understood to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0033] Although terms including ordinal numbers such as first, second, etc. may be used to describe various components, the components are not limited by the terms, and the terms are used only to distinguish one component from another.

[0034] When an element is referred to as being "coupled" or "connected" to another element, it should be understood that it may be directly coupled or connected to the other element, but that there may be additional elements between them. On the other hand, when an element is referred to as being "directly coupled" or "directly connected" to another element, it should be understood that there are no additional elements between them.

[0035] When a component is referred to as being "on top of" or "on bottom of" another component, it should be understood that there may be other components in between, not just directly on top of the other component.

[0036] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention pertains. Terms commonly used and similar to those defined in dictionaries should be interpreted to have a meaning consistent with the meaning they have in the context of the relevant art, and should not be interpreted in an idealized or overly formal sense in this application unless expressly defined.

[0037] Hereinafter, a battery cell assembly according to an embodiment of the present invention will be described.

[0038] FIG. 3 is a plan view illustrating a battery cell assembly according to the present invention, FIG. 4 is a cross-sectional view illustrating the battery cell assembly of FIG. 3, FIG. 5 is a diagram illustrating a state in which the polyimide film in the battery cell assembly of FIG. 3 is wound once to form an insulating cover, and FIG. 6 is a diagram illustrating a state in which the polyimide film in the battery cell assembly of FIG. 3 is wound twice to form an insulating cover.

[0039] 3 to 6, a battery cell assembly 100 according to an embodiment of the present invention includes a battery cell 110 and a thermal insulation cover 120. As shown in FIG.

[0040] The battery cell 110 is formed by stacking a plurality of unit cells 110a, each of which includes a cathode 111, a separator 113, and an anode 115. A cathode lead 112 is connected to the cathode 111, and an anode lead 116 is connected to the anode 115. A separator 113 is interposed between the cathode 111 and the anode 115.

[0041] The battery cell 110 according to the present invention can be manufactured by stacking mono-cells or bi-cells and stacking a half-cell 118 on the top end. The half-cell 118 has a structure in which only the cathode 111 or the anode 115 is stacked on the separator 113.

[0042] The mono-cell refers to a unit cell 110a in which the electrode disposed at the top end and the electrode disposed at the bottom end have opposite polarities. For example, a unit cell 110a in which a cathode 111-separator 113-anode 115-separator 113 are sequentially stacked is called a C-type mono-cell, and a unit cell 110a in which an anode 115-separator 113-cathode 111-separator 113 are sequentially stacked is called an A-type mono-cell.

[0043] A bi-cell has a structure in which electrodes of the same polarity are arranged on both outermost surfaces of a unit cell 110a. For example, a unit cell 110a in which a cathode 111-separation membrane 113-anode 115-separation membrane 113-cathode 111 are sequentially stacked is called a C-type bi-cell, and a unit cell 110a in which an anode 115-separation membrane 113-cathode 111-separation membrane 113-anode 115 are sequentially stacked is called an A-type bi-cell.

[0044] First, the process of manufacturing the battery cell 110 by stacking mono-cells will be described.

[0045] The anode 115, separation membrane 113, cathode 111, and separation membrane 113 are continuously fed while being wound into a roll, and the anode 115 and cathode 111 are cut and loaded onto the separation membrane 113. The separation membrane 113 with the anode 115 and cathode 111 loaded is fed to a laminating device, and the anode 115, separation membrane 113, cathode 111, and separation membrane 113 are bonded together by heat and pressure while passing through the laminating device. While the bonded anode 115, separation membrane 113, cathode 111, and separation membrane 113 are being transported, a cut is made between adjacent anodes 115 and anodes 115 (adjacent cathodes 111 and cathodes 111), and monocells are continuously manufactured. A plurality of unit cells 110a (mono cells) manufactured in this manner are stacked in a cathode 111-separator 113-anode 115-separator 113 type or an anode 115-separator 113-cathode 111-separator 113 type in a stacking process, and a half-cell 118 is stacked on the uppermost unit cell 110a to manufacture a battery cell 110. This method of manufacturing the battery cell 110 is called a lamination and stacking method.

[0046] Next, a process for stacking bi-cells to manufacture a battery cell will be described.

[0047] The unit cells 110a of the cathode 111-separator 113-anode 115-separator 113-cathode 111 type or the anode 115-separator 113-cathode 111-separator 113-anode 115 type are continuously attached to a long separator 113. The separator 113 stack is rotated in one direction and folded and stacked. Then, a half cell 118 is stacked on the uppermost unit cell 110a. This manufacturing method of the battery cells 110 is called a stacking and folding method.

[0048] The cathode 111, the separator 113, and the anode 115 in the battery cell 110 may be stacked in various configurations. In addition, a plurality of tapes (not shown) may be attached to the periphery of the stacked battery cells 110 as shown in FIG.

[0049] The heat insulating cover 120 is installed so as to surround the outer periphery of the battery cell 110 with a heat resistant film at least once. The heat insulating cover 120 can be manufactured with a film made of a material having excellent heat insulating properties and heat resistance. For example, the heat insulating cover 120 can be made of various types of films such as a polyimide film 121.

[0050] The thickness of the insulating cover 120 may be 10 μm or more and 20 μm or less. If the thickness of the insulating cover 120 is less than 10 μm, the insulating performance and heat resistance of the insulating cover 120 may decrease, making it difficult to sufficiently delay the ignition propagation. In addition, if the thickness of the insulating cover 120 is more than 20 μm, it has been confirmed that the ignition delay time does not increase substantially even if the thickness is increased further. This will be described in detail below.

[0051] The thickness of the polyimide film 121 may be 5 μm or more and 10 μm or less. If the thickness of the polyimide film 121 is less than 5 μm, the number of times the polyimide film 121 is wound around the battery cell 110 increases, which may reduce the productivity of the cell assembly. If the thickness of the polyimide film 121 exceeds 10 μm, the polyimide film 121 may be difficult to wind up due to its close contact with the battery cell 110. If a polyimide film 121 having a thickness of 5 μm or more and 10 μm or less is used, the thickness of the insulating cover 120 can be easily adjusted to multiples of 5 μm depending on the number of times the polyimide film 121 is wound.

[0052] As described above, since the insulating cover 120 is installed to surround the battery cell 110, even if the battery cell 110 is heated by the flame of an adjacent cell, the insulating cover 120, the anode 115, the cathode 111, and the separator 113 can shrink in all directions during the heat propagation delay time to form a polyimide barrier (PI barrier). In addition, since the anode 115, the cathode 111, and the separator 113 shrink in the same direction, the time when the cathode 111 and the anode 115 short out and ignition occurs can be delayed.

[0053] A method for manufacturing the battery cell assembly according to the present invention configured as above will now be described.

[0054] A plurality of unit cells 110a are stacked to manufacture the battery cell 110. At this time, the battery cell 110 may be manufactured by stacking a plurality of mono-cells or a plurality of bi-cells. The battery cell 110 may be manufactured by a lamination and stacking method or a stacking and folding method.

[0055] The insulating cover 120 is formed around the battery cell 110 by winding it around the battery cell 110 one or more times. The insulating cover 120 may be a polyimide film 121. In this case, the thickness of the insulating cover 120 is determined by the number of times the polyimide film 121 is wound. For example, the 5 μm polyimide film 121 may be wound once around the battery cell 110 to form a 5 μm insulating cover 120, the 5 μm polyimide film 121 may be wound twice around the battery cell 110, or the 10 μm polyimide film 121 may be wound once to form a 10 μm insulating cover 120.

[0056] A thermal propagation test of the above-mentioned battery cell assembly will now be described.

[0057] FIG. 7 is a diagram showing an outline of a heat propagation test apparatus for a cell assembly according to the present invention, FIG. 8 is a diagram showing an outline of the direction in which the insulating cover contracts when the cell assembly according to the present invention is heated to about 110° C., and FIG. 9 is a graph showing an outline of the heat propagation delay time and voltage drop time versus the thickness of the polyimide film in the heat propagation test apparatus of FIG. 7.

[0058] 7 to 9, a trigger cell 210 with no heat insulating cover 120 wound around it and a battery cell 110 with the heat insulating cover 120 wound around it are prepared. The trigger cell 210 and the battery cell 110 are disposed between a pair of aluminum plates 221 and 222, and a heat pad 230 is interposed between the trigger cell 210 and one of the aluminum plates 221. A first temperature sensor 241 is interposed between the trigger cell 210 and the heat pad 230, a second temperature sensor 242 is interposed between the trigger cell 210 and the battery cell 110, and a third temperature sensor 243 is interposed between the battery cell 110 and the other aluminum plate 222. When power is supplied to the heat pad 230, the heat pad 230 heats the trigger cell 210.

[0059] It was confirmed that the heat propagation time (TP Time) from the reference trigger cell 210 without the insulating cover 120 to the battery cell 110 without the insulating cover 120 took about 5 seconds (L1, L11), the heat propagation time (TP Time) from the trigger cell 210 to the battery cell 110 with the insulating cover 120 having a thickness of 5 μm increased by about 40% (L2, L12), and the heat propagation time from the trigger cell 210 to the battery cell 110 with the insulating cover 120 having a thickness of 10 μm increased by about 110% (L3, L13). However, it was found that the heat propagation time (TP Time) to the battery cell 110 with the insulating cover 120 having a thickness of 15 μm decreased to about 100% (L4, L14).

[0060] In addition, in the case of the battery cell 110 without the insulating cover 120, the voltage drop time from 4V to 0V takes about 2 seconds (L1, L11), the voltage drop time of the battery cell 110 with the insulating cover 120 having a thickness of 5 μm increases by about 100% (L2, L12), and the voltage drop time of the battery cell 110 with the insulating cover 120 having a thickness of 10 μm increases by about 150% (L3, L13). However, it was found that the voltage drop time of the battery cell 110 with the insulating cover 120 having a thickness of 15 μm decreases by about 50% (L4, L14).

[0061] As described above, in the range where the thickness of the insulation cover 120 is 5 to 10 μm, the heat propagation delay time and the voltage drop time increase rapidly as the thickness of the insulation cover 120 increases, but in the range where the thickness of the insulation cover 120 is 10 to 15 μm, the heat propagation delay time and the voltage drop time decrease even if the thickness of the insulation cover 120 increases. Therefore, it was confirmed through this experiment that the range where the thickness of the insulation cover 120 is 5 to 10 μm is the range where the thickness of the insulation cover 120 is maximized while minimizing the increase in thickness and volume of the battery cell assembly 100.

[0062] As described above, the present invention has been described with reference to the illustrative drawings, but the present invention is not limited to the embodiments and drawings disclosed in this specification, and it is obvious that a person skilled in the art can make various modifications within the scope of the technical concept of the present invention. Even if the effects of the configuration of the present invention are not explicitly described and explained while describing the embodiments of the present invention, it is natural that the effects that can be predicted by the configuration should also be recognized. [Explanation of symbols]

[0063] 10 Battery Cells 11 Cathode 13 Separation membrane 15 Anode 17 Tape 100 Battery cell assembly 110 Battery Cell 110a unit cell 111 Cathode 112 Cathode lead 113 Separation membrane 115 Anode 116 Anode lead 118 Half Cell 120 Insulation Cover 121 Polyimide film 210 Trigger Cell 221,222 Aluminum plate 230 Heat Pad 241 First temperature sensor 242 Second temperature sensor 243 3rd Temperature Sensor

Claims

1. A battery cell including a plurality of unit cells each including a cathode, a separator, and an anode; and a thermal insulating cover surrounding the outer periphery of the battery cell one or more times; Battery cell assembly.

2. The thickness of the insulating cover is 10 μm or more and 20 μm or less. The battery cell assembly of claim 1 .

3. The insulating cover is made of a heat-resistant film. The battery cell assembly of claim 1 .

4. The insulating cover is a polyimide film (PI film). The battery cell assembly of claim 3 .

5. The thickness of the polyimide film is 5 μm or more and 10 μm or less. The battery cell assembly of claim 4.

6. The heat insulating cover is wound up in close contact with the battery cell. The battery cell assembly of claim 1 .

7. The battery cell includes a structure in which a plurality of unit cells of a cathode-separator-anode-separator type or an anode-separator-cathode-separator type are stacked; The battery cell assembly of claim 1 .

8. The battery cell includes a structure in which a cathode-separator-anode-separator-cathode type or anode-separator-cathode-separator-anode type unit cell is attached to a long separator and then folded and stacked; The battery cell assembly of claim 1 .

9. A method for manufacturing a battery cell assembly according to any one of claims 1 to 8, comprising the steps of: A step of stacking a plurality of unit cells to form a battery cell; and wrapping the insulating material around the battery cell one or more times to form an insulating cover around the battery cell. A method for manufacturing a battery cell assembly.

10. The insulating cover is a polyimide film. The method for manufacturing the battery cell assembly of claim 9.

11. The thickness of the insulating cover is determined by the number of times the polyimide film is wound. The method of manufacturing the battery cell assembly of claim 10.

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