Secondary battery and cell stack containing the same

Abstract

This invention relates to a secondary battery that offers fewer restrictions on shape, improved battery capacity, and prevents problems caused by gases generated during charging and discharging. A secondary battery according to an embodiment of the present invention includes an electrode assembly comprising a plurality of electrodes and a separator membrane stacked side by side, a sheet-type exterior material having an internal space for housing the electrode assembly and an exterior material opening that communicates the internal space with the outside, and a cap that covers the exterior material opening of the sheet-type exterior material, wherein the height of the cap with respect to the stacking direction of the electrodes and separator membrane may be formed to be greater than the height of the electrode assembly.

Description

Technical Field

[0001] [Cross - reference to Related Applications] This application claims the benefit of priority based on Korean Patent Application No. 10 - 2023 - 0159301 filed on November 16, 2023 and Korean Patent Application No. 10 - 2024 - 0162452 filed on November 14, 2024, and all the contents disclosed in the documents of the Korean patent applications are incorporated herein by reference as part of this specification.

[0002] The present invention relates to a secondary battery and a cell stack including the same, and more particularly, to a secondary battery capable of charging and discharging and a cell stack including the same.

Background Art

[0003] Recently, due to the depletion of fossil fuels, the price of energy sources has increased, and concerns about environmental pollution have been amplified. The demand for environmentally friendly alternative energy sources has become an essential and indispensable factor for future life. Therefore, research on various power generation technologies such as solar power, wind power, and tidal power has continued, and power storage devices such as batteries for more efficiently using the electrical energy produced in this way have also received great attention.

[0004] Furthermore, as the technological development and demand for electronic mobile devices and battery - powered vehicles using batteries increase, the demand for batteries as an energy source has rapidly increased, and accordingly, many studies have been conducted on batteries that can meet various requirements.

[0005] Batteries for storing electrical energy can generally be classified into primary batteries and secondary batteries. A primary battery is a disposable and consumable battery, while a secondary battery is a rechargeable battery manufactured using a material in which the oxidation and reduction processes between current and substances can be repeated. That is, when a reduction reaction with respect to the material is performed by current, the power source is charged, and when an oxidation reaction with respect to the material is performed, the power source is discharged, and electricity is generated while such charging - discharging is repeated.

[0006] Secondary batteries can be classified into cylindrical cells, pouch cells, prismatic cells, etc., depending on their form. Among these, pouch cells may be manufactured in which an electrode assembly, in which a positive electrode, negative electrode, separator membrane, etc. are stacked inside a pouch, is housed, and the outside of the pouch is sealed.

[0007] Secondary batteries can be classified into cylindrical cells, pouch cells, prismatic cells, etc., depending on their form. Among these, pouch cells may be manufactured in which an electrode assembly, in which a positive electrode, negative electrode, separator membrane, etc. are stacked inside a pouch, is housed, and the outside of the pouch is sealed.

[0008] Conventional pouch cells have a problem where cracks occur in the pouch film during the molding process, resulting in a large amount of pouch film being discarded after the degassing process. In addition, the material properties of the pouch film limit the depth to which molding is possible, which also limits the increase in battery capacity.

[0009] Therefore, there is a need for a form of secondary battery that offers relatively few restrictions on shape while still being able to improve battery capacity. [Overview of the project] [Problems that the invention aims to solve]

[0010] The objective of this invention is to provide a secondary battery that offers fewer restrictions on shape, improved battery capacity, and prevents problems caused by gases generated during charging and discharging. [Means for solving the problem]

[0011] A secondary battery according to an embodiment of the present invention includes an electrode assembly comprising a plurality of electrodes and a separator membrane stacked side by side, a sheet-type exterior material having an internal space for housing the electrode assembly and an exterior material opening that communicates the internal space with the outside, and a cap that covers the exterior material opening of the sheet-type exterior material, wherein the height of the cap in the stacking direction of the electrodes and separator membrane may be formed to be greater than the height of the electrode assembly.

[0012] The sheet-type exterior material may include a connecting portion that is coupled to the cap, a cover portion that is positioned adjacent to the electrode assembly from the connecting portion and has one side facing the electrode assembly, and a connecting portion that is positioned between the connecting portion and the cover portion and has a distance from the electrode assembly in the stacking direction that gradually increases as it approaches the connecting portion.

[0013] The sheet-type exterior material may be provided such that the height of the connecting portion in the stacking direction increases as it approaches the cap.

[0014] The sheet-type exterior material may be bonded to the outer or inner surface of the cap.

[0015] The cap may be coupled with terminals that are electrically connected to the electrode assembly.

[0016] The cap may include a metal material, and the sheet-type exterior material may be provided with a barrier layer containing metal for welding to the cap.

[0017] The cap may include a metal material, and the sheet-type outer material may be provided with a resin layer that is bonded to the cap by heat and pressure.

[0018] The sheet-type exterior material may be provided with a barrier layer containing aluminum (Al) or stainless steel (STS) to prevent moisture from penetrating toward the electrode assembly.

[0019] The sheet-shaped exterior material may be joined to the cap by an adhesive applied between the sheet-shaped exterior material and the cap.

[0020] When the height of the cap in the stacking direction of the electrode and the separator is L, the thickness of the sheet-shaped exterior material is t, and the height of the electrode assembly in the stacking direction is h, the secondary battery can satisfy the following formula (1).

Equation

[0021] The cell stack according to an embodiment of the present invention includes a plurality of secondary batteries arranged side by side, and pads arranged between the secondary batteries so that the heat transfer rate between the plurality of secondary batteries is reduced. The secondary battery includes an electrode assembly including a plurality of electrodes and separators stacked together, an internal space for housing the electrode assembly, a sheet-shaped exterior material having an exterior material opening for communicating the internal space with the outside, and a cap for covering the exterior material opening of the sheet-shaped exterior material. The height of the cap in the stacking direction of the electrode and the separator may be formed to be larger than the height of the electrode assembly.

[0022] When the height of the cap in the stacking direction of the electrode and the separator is L, the thickness of the sheet-shaped exterior material is t, and the height of the electrode assembly in the stacking direction is h, the cell stack can satisfy the following formula (1).

Equation

Equation

[0023] The heat transfer rate of the pad may be lower than the heat transfer rate of the sheet-shaped exterior material.

[0024] The pad may be formed such that its length is shorter than the length of the secondary battery with reference to the length direction.

[0025] The sheet-like exterior material includes a coupling portion coupled to the cap and a cover portion disposed adjacent to the electrode assembly from the coupling portion and provided such that one surface faces the electrode assembly, and the pad may be disposed so as to contact the cover portion.

Advantages of the Invention

[0026] The secondary battery according to a preferred embodiment of the present invention does not have a process of forming a sheet-like exterior material, so there are few restrictions on the form in which the sheet-like exterior material accommodates the electrode assembly, the possibility of defects such as cracks occurring in the sheet-like exterior material is reduced, and the battery capacity can be improved.

[0027] Also, even if gas is generated inside due to charging and discharging, the change in the outer shape can be minimized by the internal free space.

[0028] Also, the structural stability of the secondary battery can be improved by the coupling relationship and arrangement form of the sheet-like exterior material and the cap.

[0029] At the same time, the secondary battery may be efficiently electrically connected to the outside by the terminal coupled to the cap.

[0030] The cell laminate according to a preferred embodiment of the present invention can minimize heat transfer between adjacent secondary batteries by the pad disposed in the free space between the plurality of secondary batteries.

[0031] Also, the change in the outer shape of the cell laminate due to swelling of the secondary battery can be minimized. [

[0032] [[ID=3 &]]The effects according to the present invention are not limited to the contents exemplified above, and more various effects are included in this specification.

Brief Description of the Drawings

[0033] [Figure 1] This is a schematic perspective view illustrating a secondary battery according to Example 1 of the present invention. [Figure 2] This is an exploded perspective view illustrating a secondary battery according to Example 1 of the present invention. [Figure 3] This is a schematic cross-sectional view showing a section cut along line A-A' in Figure 1. [Figure 4] This is a schematic side view illustrating a conventional cell laminate. [Figure 5] This is a schematic side view illustrating a cross-section of a cell laminate according to Embodiment 2 of the present invention. [Modes for carrying out the invention]

[0034] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that they can be easily implemented by a person with ordinary skill in the art to which the present invention pertains. However, the present invention may be embodied in a variety of different forms and is not limited to or restricted by the following embodiments.

[0035] In order to clearly explain the present invention, detailed descriptions of relevant prior art that are irrelevant to the description or that could unnecessarily obscure the gist of the invention have been omitted. In this specification, when assigning reference numerals to components in each figure, the same or similar reference numerals are assigned to components that are the same or similar throughout the specification.

[0036] Furthermore, the terms and words used in this specification and the claims shall not be interpreted to be limited to their ordinary or dictionary meanings, but rather to be interpreted in a way that is consistent with the technical idea of ​​the present invention, in accordance with the principle that inventors may define the concepts of terms as appropriate to best describe their invention.

[0037] Example 1 Figure 1 is a schematic perspective view illustrating a secondary battery 10 according to Embodiment 1 of the present invention. Figure 2 is a schematic exploded perspective view illustrating a secondary battery 10 according to Embodiment 1 of the present invention, and Figure 3 is a schematic cross-sectional view illustrating a cross section cut along line A-A' in Figure 1.

[0038] The secondary battery 10 according to Embodiment 1 of the present invention may include an electrode assembly 100, a sheet-type outer casing material 200, and a cap 300. Each component of the secondary battery 10 will be described in more detail below. For reference, the contents of Embodiment 1 may also be applied to the embodiments described later, provided they do not conflict with each other.

[0039] electrode assembly The electrode assembly 100 of the secondary battery 10 may include a positive electrode, a negative electrode, and a separator membrane. Here, the separator membrane is placed between the positive electrode and the negative electrode to physically separate them. The electrode assembly 100 may be in a form in which the positive electrode, negative electrode, and separator membrane are stacked, or in a jelly roll form in which the positive electrode, negative electrode, and separator membrane are wound.

[0040] On the other hand, the electrode assembly 100 may include electrode tabs 110 connected to the electrodes. The electrode tabs 110 may be provided separately or as part of the current collector constituting the electrodes. For reference, if the electrode assembly 100 is an all-solid-state battery, a solid electrolyte may be provided instead of a separator membrane.

[0041] The electrode assembly 100 may be electrically connected to a terminal 320, which will be described later. The terminal 320 is connected to the electrode tab 110 and can be exposed to the outside of the cap 300, which will be described later. In other words, the electrode assembly 100 of the secondary battery 10 may be electrically connected to the outside by the terminal 320.

[0042] Sheet-type exterior materials Referring to Figure 1, the secondary battery 10 according to Embodiment 1 of the present invention may include a sheet-type casing material 200. The sheet-type casing material 200 of the secondary battery 10 may be provided so as to enclose a part of the electrode assembly 100. Specifically, the sheet-type casing material 200 may be provided so as to enclose the cap 300 and the electrode assembly 100, which will be described later. More specifically, the sheet-type casing material 200 can be coupled with the cap 300 to form an internal space, and the electrode assembly 100 may be housed in the internal space.

[0043] On the other hand, in Embodiment 1 of the present invention, the case in which the sheet-type exterior material 200 is bonded to the outer circumferential surface of the cap 300 will be described as an example. However, this is merely one example, and the sheet-type exterior material 200 may also be bonded to the inner circumferential surface of the cap 300.

[0044] The sheet-type casing material 200 of the secondary battery 10 may have a shape in which a sheet or film is wound along the side surface of the electrode assembly 100. That is, the sheet-type casing material 200 may be arranged in a manner that encloses the side of the electrode assembly 100. In this case, the sheet-type casing material 200 may be arranged in a manner that encloses the electrode assembly 100 while one end and the other end are in contact with each other. Regarding the manner in which one end and the other end of the sheet-type casing material 200 are in contact with each other, they may be joined so that one surface of one end and multiple surfaces of the other end are in contact with each other (see Figure 1). This is merely an example, and there may be various ways in which one end and the other end are joined in order for the sheet-type casing material 200 to form a space for housing the electrode assembly 100.

[0045] Regarding the method by which one end of the sheet-type exterior material 200 is joined to the other end, the two ends of the sheet-type exterior material 200 may be joined to each other by heat sealing or by heat and pressure sealing. That is, the sheet-type exterior material 200 may contain a material that has heat sealing properties.

[0046] As an example of the structure of the sheet-type exterior material 200, the sheet-type exterior material 200 may be formed in the form of a film. Specifically, the sheet-type exterior material 200 may consist of multiple layers, including a sealant layer, a barrier layer, and an insulating layer. More specifically, the sheet-type exterior material 200 may be arranged in the order of sealant layer, barrier layer, and insulating layer from the inside closest to the electrode assembly 100.

[0047] The sealant layer may contain a material that has thermal sealing properties so as to bond one end to the other end of the sheet-type exterior material 200. For example, the sealant layer of the sheet-type exterior material 200 may contain one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polypolyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyarylate, Teflon®, and glass fibers. Polyolefin resins such as polypropylene (PP) or polyethylene (PE) may be mainly used. In particular, polypropylene (PP) can be excellent in mechanical properties such as tensile strength, rigidity, surface hardness, abrasion resistance, and heat resistance, as well as chemical properties such as corrosion resistance.

[0048] The barrier layer may contain a metal. For example, the metal in the barrier layer may be one or more substances selected from the group consisting of iron (Fe), carbon (C), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al). As an example, the barrier layer may also contain stainless steel (STS). Alternatively, the barrier layer may be made of an alloy such as an aluminum alloy.

[0049] The insulating layer may contain various materials. That is, the electrode assembly 100 can be insulated from the outside by the insulating layer. Therefore, the insulating layer can prevent short circuits in the sheet-type exterior material 200. For example, the insulating layer may contain one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polypolyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, poly(p-phenylenebenzobisoxazole), polyarylate, Teflon®, and glass fibers. Polymers such as nylon resin or polyethylene terephthalate (PET), which have abrasion resistance and heat resistance, may be mainly used.

[0050] On the other hand, the secondary battery 10 may be arranged such that the sheet-type exterior material 200 covers a part of the electrode assembly 100, and the cap 300 encloses the rest of the electrode assembly 100. Specifically, if the sheet-type exterior material 200 is arranged to enclose the electrode assembly 100 along its sides, exterior material openings may be formed at both ends of the electrode assembly 100. The cap 300 of the secondary battery 10 may be connected to the sheet-type exterior material 200 in a manner that covers the exterior material openings at both ends of the electrode assembly 100, and the electrode assembly 100 may be housed in the internal space formed by the sheet-type exterior material 200 and the cap 300.

[0051] The sheet-type exterior material 200 may be joined to the cap 300. As an example of how the cap 300 and the sheet-type exterior material 200 can be joined, they can be welded together. Specifically, the cap 300 may contain a metal material, and the sheet-type exterior material 200 may include a barrier layer in the portion facing the cap 300 that can be welded to the cap 300. Here, the barrier layer may contain metal, as described above.

[0052] Another example of a method of joining the cap 300 and the sheet-type exterior material 200 is that the cap 300 and the sheet-type exterior material 200 may be joined by sealing. Specifically, the sheet-type exterior material 200 may include a resin layer in the portion facing the cap 300 that can bond to the cap 300 with heat and pressure. Alternatively, the cap 300 may include a resin material that is heat-adherent. Here, the resin layer may include a substance that has the heat-sealing properties described above.

[0053] Another example of a method of joining the cap 300 and the sheet-type exterior material 200 is that the cap 300 and the sheet-type exterior material 200 can be joined via an adhesive. In this case, the adhesive can be applied between the cap 300 and the sheet-type exterior material 200. Here, the type and application method of the adhesive for joining may vary.

[0054] Conventional pouch cells were constructed by molding a sheet or film to form a cup portion for housing the electrode assembly 100. During the molding process of the cup portion, the depth to which molding could be performed was limited by the material properties of the sheet or film, and the capacity to house the electrode assembly 100 was also limited. Furthermore, when molding a sheet or film, the thickness was thinnest at the corners, which frequently resulted in defects such as cracks. At the same time, conventional pouch cells required a gas collection section to collect gas during the degassing process to remove gas accumulated inside the pouch, and a large portion of the gas collection section was removed and discarded after the degassing process.

[0055] On the other hand, in the secondary battery 10 according to Embodiment 1 of the present invention, the sheet-type outer casing material 200 is used so as to match the volume of the electrode assembly 100, so there is no limitation on the capacity that can accommodate the electrode assembly 100. Furthermore, since molding of the cup portion is not required, defects such as cracks in the sheet-type outer casing material 200 can be prevented, and the material and thickness of the sheet-type outer casing material 200 can be selected relatively freely. At the same time, since the electrolyte injection and degassing processes can be carried out through the cap 300, no sheet-type outer casing material 200 is discarded, so the economic efficiency of the process can be improved.

[0056] On the other hand, the secondary battery 10 may contain an electrolyte along with the electrode assembly 100. In this case, residual water in the electrolyte and water that has penetrated from the outside react with the lithium salt inside the secondary battery 10 to generate HF (hydrogen phosphate), and gases such as carbon dioxide, carbon monoxide, ethylene, and methane may be generated due to the decomposition of the electrolyte. In addition, hydrogen and HF may be generated depending on the material of the positive electrode contained in the electrode assembly, and overheating may occur due to overcharging and internal short circuits during the charging and discharging process. As a result, a large amount of gas may be generated inside the secondary battery 10. Such gases can increase the pressure inside the secondary battery 10, and the increased pressure may cause a swelling phenomenon in which the sheet-type outer material 200 expands, or a venting phenomenon in which part of the sheet-type outer material 200 or cap 300 ruptures.

[0057] As an example of a configuration to minimize shape changes due to internal gas, the sheet-type outer material 200 of the secondary battery 10 according to Embodiment 1 of the present invention may include a joint portion 210, a connecting portion 220, and a cover portion 230.

[0058] Referring to Figures 1 to 3, the joint portion 210 of the sheet-type exterior material 200 may be joined to the cap 300. As explained earlier, the sheet-type exterior material 200 can be joined to the cap 300 to form an internal space that can accommodate the electrode assembly 100. In this case, the joint portion 210 of the sheet-type exterior material 200 may be the part that is joined to the cap 300.

[0059] The cover portion 230 of the sheet-type exterior material 200 is positioned adjacent to the electrode assembly 100 from the joint portion 210, and one side may be positioned facing the electrode assembly 100. The manufacturing process of the secondary battery 10 may include an activation process that imparts electrical characteristics to the secondary battery 10 through charging and discharging. Through the activation process, gas is generated in the secondary battery 10, and gas may accumulate inside the secondary battery 10. Therefore, the manufacturing process of the secondary battery 10 may further include a degassing process to remove the gas accumulated inside the secondary battery 10. Through the degassing process, the inside of the secondary battery 10 can be made to a near-vacuum state. That is, through the degassing process, the cover portion 230 of the sheet-type exterior material 200 may be positioned in close contact with the electrode assembly 100. Preferably, the cover portion 230 may be positioned so that one side is in contact with the electrode assembly 100.

[0060] The connecting portion 220 of the sheet-type exterior material 200 may be positioned between the connecting portion 210 and the cover portion 230. That is, the connecting portion 210 and the cover portion 230 may be connected to each other by the connecting portion 220. The form of the connecting portion 220, along with the shape of the cap 300, will be described in detail below.

[0061] cap The cap 300 of the secondary battery 10 can be coupled with the sheet-type outer casing material 200 to cover the electrode assembly 100. Specifically, the cap 300 may be positioned to close the outer casing opening formed by the sheet-type outer casing material 200.

[0062] As an example of a configuration to minimize shape changes due to internal gas, the cap 300 of the secondary battery 10 according to Embodiment 1 of the present invention may be formed to have a height greater than the height of the electrode assembly 100. Here, the height of the cap 300 may refer to the length of the electrodes and separation membrane of the electrode assembly 100 in the stacking direction (for example, the vertical direction based on Figure 3). In this regard, the connecting portion 220 of the sheet-type exterior material 200 may be provided such that the distance from the electrode assembly 100 in the stacking direction gradually increases as it approaches the connecting portion 210. Specifically, the sheet-type exterior material 200 may be provided such that the height of the connecting portion 220 in the stacking direction increases as it approaches the cap 300.

[0063] Referring to Figure 3, due to the height difference between the electrode assembly 100 and the cap 300, the connecting portion 220 may be arranged in such a way that its height increases as it approaches the cap 300. Also, due to the height difference between the cap 300 and the electrode assembly 100, a height difference may occur between the connecting portion 210 and the cover portion 230 of the sheet-type exterior material 200.

[0064] Preferably, the secondary battery 10 according to Embodiment 1 of the present invention can satisfy the following equation (1) when the height of the cap 300 in the stacking direction of the electrodes and separation membrane is L, the thickness of the sheet-type outer material 200 is t, and the height of the electrode assembly 100 in the stacking direction is h.

number

[0065] Figure 4 is a schematic side view illustrating a conventional cell laminate S.

[0066] Referring to Figure 4, conventional rechargeable batteries quickly expand on their surfaces due to gas. Therefore, in conventional cell stacks S containing multiple rechargeable batteries, the arrangement of the batteries can be altered by swelling. As illustrated in Figure 4, when the surface of the rechargeable batteries expands due to swelling, the cell stack S can become structurally unstable. In other words, conventional battery modules containing cell stacks S have the problem of reduced structural stability with use.

[0067] On the other hand, the secondary battery 10 according to Embodiment 1 of the present invention may exhibit a reduced phenomenon of surface expansion. Therefore, the structural stability of the secondary battery 10 may be improved. Furthermore, the amount of space between the caps 300 can be reduced by the available space. This may improve the structural stability of a battery module containing multiple secondary batteries 10.

[0068] On the other hand, a coupling hole 310 may be formed in the cap 300. A terminal 320 may be coupled to the coupling hole 310. An electrode tab 110 of the electrode assembly 100 may be coupled to one side of the terminal 320. These may be welded to each other, but the coupling structure between the terminal 320 and the electrode tab 110 is not particularly limited.

[0069] The coupling hole 310 may have a shape that penetrates from one side of the cap 300 to the other. A terminal 320 may be provided so as to penetrate the coupling hole 310 for connection between the electrode assembly 100 and the outside. That is, the terminal 320 may extend from one side of the cap 300 to the other.

[0070] The terminal 320 may have a rivet shape to prevent it from falling off the cap 300. However, the structure and shape of the terminal 320 are not particularly limited as long as the electrode assembly 100 can be energized with the outside.

[0071] Example 2 Figure 5 is a schematic cross-sectional view illustrating a side view of the cell laminate 1 according to Embodiment 2 of the present invention.

[0072] In the following, a detailed explanation of a configuration identical to that of the secondary battery 10 according to Embodiment 1 of the present invention will be omitted.

[0073] The cell stack 1 according to Embodiment 2 of the present invention may include a plurality of secondary batteries 10 and pads 20. The secondary batteries 10 may be arranged side by side, and the pads 20 may be arranged between the secondary batteries 10. Specifically, the pads 20 may be arranged between adjacent secondary batteries 10.

[0074] The secondary battery 10 of the cell stack 1 may include an electrode assembly 100, a sheet-type outer casing 200, and a cap 300. Here, the height of the cap 300 in the direction in which the electrodes and separation membrane of the electrode assembly 100 are stacked may be greater than the height of the electrode assembly 100. Specifically, the secondary battery 10 can satisfy the following equation (1) when the height of the cap 300 in the direction in which the electrodes and separation membrane are stacked is L, the thickness of the sheet-type outer casing 200 is t, and the height of the electrode assembly 100 in the direction in which the electrodes and separation membrane are stacked is h.

number

[0075] The cell stack 1 may have the pad 20 placed in the space formed between the secondary battery 10 and the electrode assembly 100 due to the difference in height between the cap 300 and the electrode assembly 100 of the secondary battery 10.

[0076] The pads 20 of the cell stack 1 can reduce the heat transfer coefficient between the secondary batteries 10. That is, the heat transfer coefficient of the pads 20 may be lower than the heat transfer coefficient of the secondary batteries 10. Specifically, the heat transfer coefficient of the pads 20 may be lower than the heat transfer coefficient of the sheet-type outer casing material 200 of the secondary batteries 10. More specifically, the pads 20 may be made of a material with a lower heat transfer coefficient than the material of the sheet-type outer casing material 200.

[0077] The cell stack 1 according to Embodiment 2 of the present invention can reduce the heat transferred between the secondary batteries 10, including the pads 20. Therefore, if a flame occurs in a particular secondary battery 10, it is possible to prevent the flame from spreading to other secondary batteries 10. This can prevent thermal runaway in the module including the cell stack 1, and the stability of the module can be improved.

[0078] The following provides a more detailed explanation of the arrangement of pad 20.

[0079] With respect to the height direction (for example, the up and down direction in Figure 5), the pad 20 of the cell stack 1 according to Embodiment 2 of the present invention may be positioned in the space formed by the height difference between the cap 300 of the secondary battery 10 and the electrode assembly 100. Specifically, when the pad 20 has a thickness of p, the following equation (2) can be satisfied.

number

[0080] With respect to the length direction (for example, the left-right direction in Figure 5), the pad 20 of the cell stack 1 according to Embodiment 2 of the present invention may be formed to be shorter in length than the length of the secondary battery 10. Specifically, the length of the pad 20 may be formed to be smaller than the length of the secondary battery 10 minus the length of the cap 300. Therefore, the pad 20 may be positioned to be in contact with the cover portion 230 of the sheet-type exterior material 200.

[0081] On the other hand, the pad 20 may be deformed by pressure. Specifically, the pad 20 may be designed so that its shape is deformed by the pressure caused by the volume expansion of the secondary battery 10. Therefore, if the cover portion 230 of the sheet-type exterior material 200 or the like pressurizes the pad 20 due to the gas inside the secondary battery 10, the pad 20 may be compressed.

[0082] The cell stack 1 may have pressure absorbed by the pads 20 that can be transmitted to other secondary batteries 10 by the gas inside the secondary batteries 10. Therefore, the structural stability of the cell stack 1 can be improved.

[0083] In the cell stack 1 according to Embodiment 2 of the present invention, a space may be formed between adjacent secondary batteries 10 depending on the shape of the secondary batteries 10. Pads 20 can be placed in such a space to reduce the heat and pressure transmitted between adjacent secondary batteries 10. Therefore, the stability of the cell stack 1 is improved, which can lead to improved stability of the battery module including the cell stack 1.

[0084] Although the present invention has been described above, even with limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible by persons with ordinary skill in the art to which the present invention pertains, within the equivalent scope of the technical concept of the present invention and the claims described below. [Explanation of symbols]

[0085] 1: Cell laminate 10: Secondary battery 20: Pad 100: Electrode assembly 110: Electrode Tab 200: Sheet-type exterior material 210:Joining part 220: Connection part 230: Cover section 300: Cap 310: Joint Hole 320: Terminal S: Conventional cell laminate

Claims

1. An electrode assembly comprising multiple electrodes and a separator membrane stacked side by side; A sheet-type exterior material having an internal space for housing the electrode assembly and an exterior material opening that connects the internal space to the outside; and Includes a cap that covers the opening of the exterior material of the sheet-type exterior material, A secondary battery in which the height of the cap in the stacking direction of the electrodes and the separation membrane is greater than the height of the electrode assembly.

2. The aforementioned sheet-type exterior material is The connecting portion that connects to the aforementioned cap; A cover portion provided that is positioned closer to the electrode assembly than the aforementioned coupling portion, with one side facing the electrode assembly; and The secondary battery according to claim 1, comprising a connecting portion disposed between the connecting portion and the cover portion, wherein the distance between the connecting portion and the electrode assembly in the stacking direction gradually increases as it approaches the connecting portion.

3. The aforementioned sheet-type exterior material is The secondary battery according to claim 2, wherein the height of the connecting portion in the stacking direction increases as it approaches the cap.

4. The aforementioned sheet-type exterior material is The secondary battery according to claim 1, which is coupled to the outer or inner surface of the cap.

5. The secondary battery according to claim 1, wherein the cap is coupled to a terminal that is electrically connected to the electrode assembly.

6. The aforementioned cap includes a metal material, The secondary battery according to claim 1, wherein the sheet-type exterior material is provided with a barrier layer containing metal for welding to the cap.

7. The aforementioned cap includes a metal material, The secondary battery according to claim 1, wherein the sheet-type exterior material is provided with a resin layer that is bonded to the cap.

8. The aforementioned sheet-type exterior material is The secondary battery according to claim 7, wherein a barrier layer containing aluminum (Al) or stainless steel (STS) is provided to prevent moisture from penetrating toward the electrode assembly.

9. The secondary battery according to claim 1, wherein the sheet-type exterior material is bonded to the cap by an adhesive applied between the sheet-type exterior material and the cap.

10. The secondary battery according to claim 1, wherein when the height of the cap in the stacking direction of the electrodes and the separation membrane is L, the thickness of the sheet-type outer material is t, and the height of the electrode assembly in the stacking direction is h, the following equation (1) is satisfied. [Math 1]

11. Multiple secondary batteries arranged side by side; and The pads are placed between the secondary batteries such that the heat transfer coefficient between the plurality of secondary batteries is reduced, The aforementioned secondary battery is An electrode assembly comprising multiple electrodes and a separator membrane stacked side by side; A sheet-type exterior material having an internal space for housing the electrode assembly and an exterior material opening that connects the internal space to the outside; and Includes a cap that covers the opening of the exterior material of the sheet-type exterior material, A cell stack in which the height of the cap in the electrode and separation membrane stacking direction is greater than the height of the electrode assembly.

12. The cell laminate according to claim 11, wherein when the height of the cap in the stacking direction of the electrodes and the separation membrane is L, the thickness of the sheet-type outer material is t, and the height of the electrode assembly in the stacking direction is h, the following equation (1) is satisfied. [Math 2]

13. The cell laminate according to claim 12, wherein when the thickness of the pad is p, the following equation (2) is satisfied. [Math 3]

14. The aforementioned pad is The cell laminate according to claim 11, which is provided so as to deform in shape due to the pressure caused by the volume expansion of the secondary battery.

15. The aforementioned pad is The cell laminate according to claim 11, wherein the heat transfer coefficient is lower than that of the sheet-type exterior material.

16. The aforementioned pad is The cell laminate according to claim 11, wherein the length is formed such that the length is shorter than the length of the secondary battery, with respect to the length direction.

17. The aforementioned sheet-type exterior material is The coupling portion that connects to the cap; and It includes a cover portion which is positioned closer to the electrode assembly than the aforementioned coupling portion and is provided such that one side faces the electrode assembly, The cell laminate according to claim 11, wherein the pad is arranged to be in contact with the cover portion.

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