Battery cell assembly and method for manufacturing the same

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 based on Korean Patent Application No. 10-2021-0187982, filed on December 27, 2021, and all the contents disclosed in the Korean Patent Application are incorporated herein by reference.

[0002] The present invention relates to a battery cell assembly and a method for manufacturing the same, and more particularly, to a battery cell assembly and a method for manufacturing the same, which can block heat transfer between adjacent battery cells, delay the ignition time, and secure an evacuation time for a user.

Background Art

[0003] Generally, as the development and demand for technologies related to mobile devices and electric vehicles increase, the demand for secondary batteries as an energy source increases rapidly. Accordingly, numerous studies on secondary batteries that can meet various requirements have been conducted.

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

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

[0006] Referring to FIGS. 1 and 2, a secondary battery includes a plurality of battery cells 10 stacked thereon. Each battery cell 10 includes a cathode 11, a separator 13, and an anode 15 stacked thereon.

[0007] The battery cell 10 can be manufactured by a lamination and stacking process. In this process, a separation membrane 13, a cathode 11, another separation membrane 13, and an anode 15 are laminated together, then cut to produce a monocell, and multiple monocells are then laminated together.

[0008] These battery cells 10 have a simple structure and a high degree of electrolyte impregnation, but they suffer from slow production speeds and a decrease in alignment. In these battery cells 10, a taping process is performed to ensure the alignment of the stacked cathode 11, separation membrane 13, and anode 15. In this taping process, multiple tapes 17 are attached to both sides and parts of the top and bottom surfaces of the battery cell 10.

[0009] However, in conventional battery cells 10, as shown in Figure 2, when heated to approximately 100-120°C, the separator membrane 13 shrinks and the separator membrane 13 and cathode 11 deform into a round shape. In particular, the portion of the separator membrane 13 to which the tape 17 is attached does not shrink, while 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 anode 15 to each other, which can cause a short circuit and ignition.

[0010] Furthermore, since multiple battery cells 10 are housed within a battery module, when a particular battery cell 10 overheats or catches fire, it is prone to theremal propagation of the fire to adjacent battery cells 10. Therefore, there is a need to develop a technology that can block the transmission of heat from one battery cell 10 and delay the propagation of fire to adjacent battery cells 10.

[0011] The background art of this invention is disclosed in Korean Published Patent Publication No. 2021-0053570 (published on May 12, 2021). [Overview of the project] [Problems that the invention aims to solve]

[0012] The present invention was devised to solve the above-mentioned problems, and aims to provide a battery cell assembly and a method for manufacturing the same that can block heat transfer between adjacent battery cells, delay ignition time, and secure time for passengers to evacuate. [Means for solving the problem]

[0013] To solve the above-mentioned problems, the present invention may include a battery cell comprising a plurality of unit cells, each consisting of a cathode, a separator membrane, and an anode, stacked together; and a heat insulating cover that surrounds the outer periphery of the battery cell one or more times.

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

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

[0016] The aforementioned heat insulating cover may be made of polyimide film (PI film).

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

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

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

[0020] The battery cell may include a structure in which unit cells of the cathode-separator-anode-separator-cathode type, or anode-separator-cathode-separator-anode type, are attached to a long separator membrane and then folded and stacked.

[0021] The manufacturing method of the battery cell assembly may include the steps of fabricating a battery cell by stacking a plurality of unit cells; and winding around the battery cell one or more times to form a heat insulation cover around the battery cell.

[0022] The heat insulation cover may be a polyimide film.

[0023] The thickness of the heat insulation cover can be determined by the number of times the polyimide film is wound.

Advantages of the Invention

[0024] According to the present invention, since the heat insulation cover is installed so as to surround the battery cell, even if the battery cell is heated by the flame of 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 heat insulation cover is 5 to 10 μm, it is possible to minimize an increase in the thickness and volume of the battery cell assembly while maximizing the heat propagation delay performance.

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

[0027] The above-described advantages and the specific advantages of the present invention will be described and described while explaining the embodiments for carrying out the following invention.

Brief Description of the Drawings

[0028] [Figure 1] It is a plan view schematically showing a conventional battery cell assembly. [Figure 2] It is a plan view schematically showing a state in which a separation membrane shrinks when the battery cell assembly of FIG. 1 is heated to about 100 to 120°C. [Figure 3] It is a plan view schematically showing a battery cell assembly according to the present invention. [Figure 4]Figure 3 is a schematic cross-sectional view of the battery cell assembly. [Figure 5] Figure 3 is a schematic diagram showing the state in which the polyimide film in the battery cell assembly has been wound once to form an insulating cover. [Figure 6] Figure 3 is a schematic diagram showing the state in which the polyimide film in the battery cell assembly has been wound twice to form an insulating cover. [Figure 7] This is a schematic diagram showing a heat transfer experimental apparatus for a cell assembly according to the present invention. [Figure 8] This diagram schematically shows the direction in which the insulating cover shrinks when the cell assembly according to the present invention is heated to approximately 110°C. [Figure 9] Figure 7 is a schematic graph showing the heat propagation delay time and voltage drop time as a function of the thickness of the polyimide film in the heat propagation experimental apparatus. [Modes for carrying out the invention]

[0029] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] The present invention is not limited to the embodiments disclosed below, and can be modified in various ways and embodied in various different forms. However, these embodiments are provided to complete the disclosure of the present invention and to fully inform those in the ordinary skill of the scope of the invention. Therefore, the present invention is not limited to the embodiments disclosed below, and should be understood to include any modifications, equivalents, or substitutions that fall within the technical spirit and scope of the present invention, as well as the substitution or addition of any configuration of one embodiment to that of another embodiment.

[0031] The accompanying drawings are provided to facilitate understanding of the embodiments disclosed herein and should not be understood as limiting the technical concept disclosed herein, but rather as including any modifications, equivalents, or substitutions that fall within the concept and technical scope of the present invention. Components in the drawings may be exaggerated in size or thickness to appear larger or smaller for ease of understanding, but this should not be interpreted as restricting the scope of protection of the present invention.

[0032] The terms used herein are used solely to describe specific examples or embodiments and are not intended to limit the invention. Furthermore, singular expressions include plural expressions unless otherwise clearly indicated in the context. Terms such as "includes" and "constitutes" in the specification are intended to indicate the existence of features, figures, stages, operations, components, parts, or combinations thereof described in the specification. That is, terms such as "includes" and "constitutes" in the specification should not be understood as preemptively excluding the existence or possibility of adding one or more other features, figures, stages, operations, components, parts, or combinations thereof.

[0033] Terms including ordinal numbers, such as "First," "Second," etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely for the purpose of distinguishing one component from others.

[0034] When it is mentioned that one component is “linked” or “connected” to another component, it must be understood that it is directly linked to or may be connected to the other component, but that there may be other components in between. On the other hand, when it is mentioned that one component is “directly linked” or “directly connected” to another component, it must be understood that there are no other components in between.

[0035] When one component is described as being "above" or "below" another component, it must be understood that this means not only is it positioned directly above the other component, but that other components may exist between them.

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

[0037] The following describes a battery cell assembly according to an embodiment of the present invention.

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

[0039] Referring to Figures 3 to 6, the battery cell assembly 100 according to an embodiment of the present invention includes a battery cell 110 and an insulating cover 120.

[0040] The battery cell 110 is made up of multiple unit cells 110a stacked together, each unit cell 110a consisting of a cathode 111, a separator membrane 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. The separator membrane 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 at the uppermost end. The half-cell 118 has a structure in which only either a cathode 111 or an anode 115 is stacked on a separation membrane 113.

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

[0043] A bicell 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 cathode 111-separation membrane 113-anode 115-separation membrane 113-cathode 111 is sequentially stacked is called a C-type bicell, and a unit cell 110a in which anode 115-separation membrane 113-cathode 111-separation membrane 113-anode 115 is sequentially stacked is called an A-type bicell.

[0044] First, we will explain the process of manufacturing battery cell 110 by stacking monocells.

[0045] The anode 115, separation membrane 113, cathode 111, and separation membrane 113 are supplied in a rolled state, continuously unwound, 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 supplied to a laminating device, and as it passes through the laminating device, the anode 115, separation membrane 113, cathode 111, and separation membrane 113 are bonded together by heat and pressure. As the bonded anode 115, separation membrane 113, cathode 111, and separation membrane 113 are transported, the space between adjacent anodes 115 and anodes 115 (adjacent cathodes 111 and cathodes 111) is cut to continuously produce monocells. Multiple unit cells 110a (monocells) manufactured in this manner are stacked in a stacking process in the form of cathode 111-separation membrane 113-anode 115-separation membrane 113 type, or anode 115-separation membrane 113-cathode 111-separation membrane 113 type, and a half-cell 118 is stacked on top of the uppermost unit cell 110a to manufacture a battery cell 110. This manufacturing method for battery cells 110 is called the lamination and stacking method.

[0046] Next, we will explain the process of manufacturing battery cells by stacking bicells.

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

[0048] The cathode 111, separator membrane 113, and anode 115 in the battery cell 110 described above can be stacked in various configurations. Furthermore, multiple tapes (not shown) may be attached around the stacked battery cell 110, as shown in Figure 1.

[0049] The heat-insulating cover 120 is installed so as to surround the outer perimeter of the battery cell 110 with a heat-resistant film one or more times. The heat-insulating cover 120 can be manufactured from a film material that has excellent heat insulation and heat resistance. For example, various types of films, such as polyimide film 121, can be used as the heat-insulating cover 120.

[0050] The thickness of the insulation cover 120 may be between 10 μm and 20 μm. If the thickness of the insulation cover 120 is less than 10 μm, the insulation performance and heat resistance performance of the insulation cover 120 may decrease, making it difficult to sufficiently delay ignition propagation. Furthermore, if the thickness of the insulation cover 120 exceeds 20 μm, it has been confirmed that the ignition delay time does not increase significantly even if the thickness is increased further. This will be explained in detail below.

[0051] The thickness of the polyimide film 121 may be between 5 μm and 10 μm. If the thickness of the polyimide film 121 is less than 5 μm, the number of times the polyimide film 121 is wound onto the battery cell 110 increases, which may reduce the productivity of the cell assembly. Also, if the thickness of the polyimide film 121 is greater than 10 μm, it may be difficult to wind the polyimide film 121 tightly onto the battery cell 110. Furthermore, by using a polyimide film 121 with a thickness of between 5 μm and 10 μm, the thickness of the heat-insulating cover 120 can be easily adjusted in multiples of 5 μm depending on the number of times the polyimide film 121 is wound.

[0052] As described above, since the heat 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 heat insulating cover 120, anode 115, cathode 111, and separator membrane 113 can contract in all directions during the heat propagation delay time, thereby generating a polyimide barrier (PI barrier). Furthermore, since the anode 115, cathode 111, and separator membrane 113 contract in the same direction, the time it takes for the cathode 111 and anode 115 to short-circuit and ignite can be delayed.

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

[0054] Multiple unit cells 110a are stacked to produce a battery cell 110. In this process, the battery cell 110 can be produced by stacking multiple monocells or by stacking multiple bicells. These battery cells 110 can be produced using either a lamination and stacking method or a stacking and folding method.

[0055] The polyimide film 121 is wound around the battery cell 110 at least once to form an insulating cover 120 around the battery cell 110. The insulating cover 120 may be made of polyimide film 121. The thickness of the insulating cover 120 is determined by the number of times the polyimide film 121 is wound. For example, a 5μm polyimide film 121 can be wound around the battery cell 110 once to form a 5μm insulating cover 120, or a 5μm polyimide film 121 can be wound around the battery cell 110 twice, or a 10μm polyimide film 121 can be wound once to form a 10μm insulating cover 120.

[0056] The following describes the thermal propagation test of the battery cell assembly mentioned above.

[0057] Figure 7 is a schematic diagram of a heat transfer experimental apparatus for a cell assembly according to the present invention, Figure 8 is a schematic diagram showing the direction in which the insulating cover shrinks when the cell assembly according to the present invention is heated to approximately 110°C, and Figure 9 is a schematic graph showing the heat transfer delay time and voltage drop time with respect to the thickness of the polyimide film in the heat transfer experimental apparatus of Figure 7.

[0058] Referring to Figures 7 to 9, a trigger cell 210 with the insulation cover 120 unwound and an adjacent battery cell 110 with the insulation cover 120 wound on are prepared. The trigger cell 210 and the battery cell 110 are placed 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. In addition, 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] The heat transfer time (TP Time) from the reference trigger cell 210 without the heat insulation cover 120 to the battery cell 110 without the heat insulation cover 120 was approximately 5 seconds (L1, L11). The heat transfer time (TP Time) from the trigger cell 210 to the battery cell 110 with a heat insulation cover 120 thickness of 5 μm increased by approximately 40% (L2, L12). The heat transfer time from the trigger cell 210 to the battery cell 110 with a heat insulation cover 120 thickness of 10 μm increased by approximately 110% (L3, L13). However, the heat transfer time (TP Time) to the battery cell 110 with a heat insulation cover 120 thickness of 15 μm actually decreased to approximately 100% (L4, L14).

[0060] Furthermore, in the case of a battery cell 110 without an insulating cover 120, the voltage drop time from 4V to 0V was approximately 2 seconds (L1, L11). The voltage drop time (Cell Voltage Drop Time) of a battery cell 110 with an insulating cover 120 thickness of 5 μm increased by approximately 100% (L2, L12), and the voltage drop time of a battery cell 110 with an insulating cover 120 thickness of 10 μm increased by approximately 150% (L3, L13). However, it was found that the voltage drop time of a battery cell 110 with an insulating cover 120 thickness of 15 μm actually decreased to approximately 50% (L4, L14).

[0061] As described above, in the range where the thickness of the insulating cover 120 is 5 to 10 μm, the heat propagation delay time and voltage drop time increase sharply as the thickness of the insulating cover 120 increases. However, in the range where the thickness of the insulating cover 120 is 10 to 15 μm, the heat propagation delay time and voltage drop time actually decrease even as the thickness of the insulating cover 120 increases. Therefore, this experiment confirmed that the range where the thickness of the insulating cover 120 is 5 to 10 μm is the range that maximizes the heat propagation delay performance while minimizing the increase in thickness and volume of the battery cell assembly 100.

[0062] As described above, the present invention has been explained with reference to the illustrative drawings. However, the present invention is not limited by the embodiments and drawings disclosed herein, and it is obvious to a person of the skill of the art within the scope of the present invention that various modifications can be made. Furthermore, even if the effects of the configuration of the present invention are not explicitly described while embodiments of the present invention have been described above, it is natural to acknowledge that the effects that can be predicted by such configuration should also be acknowledged. [Explanation of Symbols]

[0063] 10 battery cells 11 Cathode 13 Separation membrane 15 Anodes 17 Tapes 100 Battery Cell Assembly 110 battery cells 110a unit cell 111 Cathode 112 Cathode Lead 113 Separation membrane 115 Anodes 116 Anode Leads 118 Half Cell 120 Insulation Cover 121 Polyimide film 210 Trigger Cells 221,222 Aluminum Plates 230 Heat Pads 241 First temperature sensor 242 Second temperature sensor 243 Third temperature sensor

Claims

1. A battery cell comprising multiple stacked unit cells each having a cathode, a separator membrane, and an anode; and An insulating cover is formed of a heat-resistant insulating film that is tightly wound around the outer circumference of the battery cell one or more times so as to generate an insulating barrier; The aforementioned heat-insulating film is a polyimide film (PI film), The thickness of the aforementioned heat-insulating film is 5 μm or more and 10 μm or less. The thickness of the aforementioned heat insulating cover is 5 μm or more and 10 μm or less. Battery cell assembly.

2. The battery cell includes a structure in which multiple unit cells of the cathode-separator-anode-separator type, or anode-separator-cathode-separator type, are stacked. The battery cell assembly according to claim 1.

3. 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 membrane and then folded and stacked. The battery cell assembly according to claim 1.

4. A method for manufacturing a battery cell assembly according to any one of claims 1 to 3, The steps include:

1. Manufacturing a battery cell by stacking multiple unit cells; The process includes the step of tightly wrapping the heat insulating film around the battery cell one or more times to form a heat insulating cover around the battery cell. A method for manufacturing a battery cell assembly.

5. The thickness of the heat-insulating cover is determined by the number of times the heat-insulating film is wound. A method for manufacturing a battery cell assembly according to claim 4.

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