Secondary battery and cell stack comprising same

Abstract

The present invention relates to a secondary battery which has improved battery capacity while having few limitations with respect to shape, and which can prevent problems caused by gas being generated due to charging and discharging. The secondary battery according to an embodiment of the present invention comprises: an electrode assembly including a plurality of electrodes and separators stacked in parallel; a sheet-like exterior material having an inner space for accommodating the electrode assembly, and an exterior material opening by which the inner space and the outside communicate; and a cap for covering the exterior material opening of the sheet-like exterior material, wherein the height of the cap with respect to the stacking direction of the electrodes and the separators can be higher than the height of the electrode assembly.

Description

Secondary battery and cell stack including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0159301, filed November 16, 2023, and Korean Patent Application No. 10-2024-0162452, filed November 14, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to a secondary battery and a cell stack including the same, and more specifically, to a secondary battery capable of being charged and discharged and a cell stack including the same.

[0005] In recent years, rising energy prices due to the depletion of fossil fuels and growing concerns about environmental pollution have made the demand for eco-friendly alternative energy sources essential for future living. Research is continuing into various power generation technologies, such as solar, wind, and tidal power. Furthermore, significant interest is being focused on power storage devices, such as batteries, to more efficiently utilize the generated electricity.

[0006] Moreover, with the technological development and increasing demand for battery-powered electronic mobile devices and electric vehicles, the demand for batteries as an energy source is rapidly increasing, and accordingly, much research is being conducted on batteries that can meet various needs.

[0007] Batteries that store electrical energy can generally be divided into primary and secondary batteries. Primary batteries are disposable, consumable batteries, whereas secondary batteries are rechargeable batteries manufactured using materials capable of repeatable oxidation and reduction processes between current and a substance. In other words, when current causes a reduction reaction in a material, the battery is charged, and when an oxidation reaction occurs in the material, the battery is discharged. This repeated charging and discharging process generates electricity.

[0008] Secondary batteries can be classified into cylindrical cells, pouch cells, and prismatic cells based on their shape. Among them, pouch cells can be manufactured in a form in which an electrode assembly in which a positive electrode, a negative electrode, and a separator are laminated is accommodated inside a pouch, and the outer part of the pouch is sealed.

[0009] Secondary batteries can be classified into cylindrical cells, pouch cells, and prismatic cells based on their shape. Among them, pouch cells can be manufactured in a form in which an electrode assembly in which a positive electrode, a negative electrode, and a separator are laminated is accommodated inside a pouch, and the outer part of the pouch is sealed.

[0010] Conventional pouch cells suffer from cracks in the pouch film during the forming process, resulting in significant waste after the degassing process. Furthermore, the material properties of the pouch film limit the depth at which it can be formed, limiting any increase in battery capacity.

[0011] Therefore, there is a need for a secondary battery that has relatively few restrictions on shape while allowing for increased battery capacity.

[0012] The object of the present invention is to provide a secondary battery that has fewer restrictions on shape, has improved battery capacity, and can prevent problems caused by gas generated during charging and discharging.

[0013] A secondary battery according to an embodiment of the present invention comprises an electrode assembly including a plurality of electrodes and a separator that are stacked in parallel, a sheet-shaped outer material having an internal space that accommodates the electrode assembly and an outer material opening that communicates the internal space with the outside, and a cap that covers the outer material opening of the sheet-shaped outer material, wherein the height of the cap with respect to the stacking direction of the electrodes and the separator can be formed to be greater than the height of the electrode assembly.

[0014] The sheet-shaped outer material may include a joining portion that is joined to the cap, a cover portion that is positioned closer to the electrode assembly than the joining portion and has one side facing the electrode assembly, and a connecting portion that is positioned between the joining portion and the cover portion and is positioned such that the gap with respect to the electrode assembly in the stacking direction gradually increases as it gets closer to the joining portion.

[0015] The above sheet-shaped exterior material may be arranged so that the height of the connecting portion with respect to the stacking direction increases as it gets closer to the cap.

[0016] The above sheet-shaped outer material can be combined with the outer circumferential surface or the inner circumferential surface of the cap.

[0017] The above cap may be coupled with a terminal electrically connected to the electrode assembly.

[0018] The cap may include a metal material, and the sheet-shaped outer material may be provided with a barrier layer including a metal so as to be welded to the cap.

[0019] The cap may include a metal material, and the sheet-shaped outer material may be provided with a resin layer that is bonded to the cap by heat and pressure.

[0020] The above sheet-shaped outer material may be provided with a barrier layer including aluminum (Al) or stainless steel (STS) to prevent moisture penetration toward the electrode assembly.

[0021] The above sheet-shaped exterior material can be combined with the cap by an adhesive applied between the sheet-shaped exterior material and the cap.

[0022] A secondary battery can satisfy the following equation (1) when the height of the cap with respect to the stacking direction of the electrode and separator is L, the thickness of the sheet-shaped outer material is t, and the height of the electrode assembly with respect to the stacking direction is h.

[0023] … (1)

[0024] A cell stack according to an embodiment of the present invention includes a plurality of secondary batteries arranged in parallel with each other, and a pad arranged between the secondary batteries so as to reduce a heat transfer rate between the plurality of secondary batteries, wherein the secondary battery includes an electrode assembly including a plurality of electrodes and separators stacked in parallel, a sheet-shaped outer material having an internal space accommodating the electrode assembly, and an outer material opening communicating the internal space with the outside, and a cap covering the outer material opening of the sheet-shaped outer material, wherein a height of the cap with respect to the electrode and separator stacking direction may be formed to be greater than a height of the electrode assembly.

[0025] The cell stack can satisfy the following equation (1) when the height of the cap with respect to the stacking direction of the electrode and separator is L, the thickness of the sheet-shaped outer material is t, and the height of the electrode assembly with respect to the stacking direction is h.

[0026] … (1)

[0027] The cell stack can satisfy the following equation (2) when the thickness of the pad is p.

[0028] … (2)

[0029] The above pad may be configured to change shape due to pressure caused by volume expansion of the secondary battery.

[0030] The above pad may have a heat transfer rate lower than that of the sheet-shaped outer material.

[0031] The above pad may be formed to have a length shorter than the length of the secondary battery, based on the longitudinal direction.

[0032] The sheet-shaped outer material includes a connecting portion that is connected to the cap, and a cover portion that is positioned closer to the electrode assembly than the connecting portion and has one surface facing the electrode assembly, and the pad can be positioned to be in contact with the cover portion.

[0033] Since the secondary battery according to a preferred embodiment of the present invention does not have a process for forming a sheet-shaped outer material, there are fewer restrictions on the shape in which the sheet-shaped outer material accommodates the electrode assembly, the possibility of defects such as cracks occurring in the sheet-shaped outer material is reduced, and the battery capacity can be improved.

[0034] Additionally, even if gas is generated inside due to charging and discharging, changes in appearance can be minimized due to the free space inside.

[0035] In addition, the structural stability of the secondary battery can be improved by the bonding relationship and arrangement form of the sheet-shaped outer material and the cap.

[0036] Additionally, the secondary battery can be efficiently electrically connected to the outside by the terminal coupled to the cap.

[0037] A cell stack according to a preferred embodiment of the present invention can minimize heat transfer between adjacent secondary batteries by means of pads arranged in free spaces between a plurality of secondary batteries.

[0038] In addition, changes in the external shape of the cell stack due to swelling of the secondary battery can be minimized.

[0039] The effects according to the present invention are not limited to the contents exemplified above, and more diverse effects are included in this specification.

[0040] FIG. 1 is a perspective view schematically illustrating a secondary battery according to Example 1 of the present invention.

[0041] Figure 2 is an exploded perspective view schematically illustrating a secondary battery according to Example 1 of the present invention.

[0042] Figure 3 is a cross-sectional view schematically illustrating a cross-section taken along line A-A' of Figure 1.

[0043] Figure 4 is a side view schematically illustrating a conventional cell stack.

[0044] FIG. 5 is a side view schematically illustrating a cross-section of a cell stack according to Example 2 of the present invention.

[0045] Hereinafter, with reference to the attached drawings, preferred embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. However, the present invention may be implemented in various different forms and is not limited or restricted by the following examples.

[0046] In order to clearly explain the present invention, a detailed description of a part that is irrelevant to the description or a related known technology that may unnecessarily obscure the gist of the present invention has been omitted, and when adding reference signs to components of each drawing in this specification, the same or similar reference signs are attached to the same or similar components throughout the specification.

[0047] In addition, terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0048] Example 1

[0049] Fig. 1 is a perspective view schematically illustrating a secondary battery (10) according to Embodiment 1 of the present invention. In addition, Fig. 2 is an exploded perspective view schematically illustrating a secondary battery (10) according to Embodiment 1 of the present invention, and Fig. 3 is a cross-sectional view schematically illustrating a cross-section taken along line A-A' of Fig. 1.

[0050] A secondary battery (10) according to Example 1 of the present invention may include an electrode assembly (100), a sheet-shaped outer material (200), and a cap (300). Hereinafter, each component of the secondary battery (10) will be described in more detail. For reference, the contents of Example 1 may be equally applied to the embodiments described later, as long as they do not conflict with each other.

[0051] electrode assembly

[0052] The electrode assembly (100) of the secondary battery (10) may include a positive electrode, a negative electrode, and a separator. Here, the separator may be placed between the positive electrode and the negative electrode to physically separate the positive electrode and the negative electrode. The electrode assembly (100) may be in the form of a stacked positive electrode, a negative electrode, and a separator, or in the form of a jelly-roll in which the positive electrode, the negative electrode, and the separator are rolled up.

[0053] Meanwhile, the electrode assembly (100) may be provided with an electrode tab (110) connected to the electrode. The electrode tab (110) may be provided separately or as part of a current collector constituting the electrode. For reference, if the electrode assembly (100) is an all-solid-state battery, a solid electrolyte may be provided instead of a separator.

[0054] The electrode assembly (100) can be electrically connected to a terminal (320) described later. The terminal (320) can be connected to the electrode tab (110) and exposed to the outside of the cap (300) described later. That is, the electrode assembly (100) of the secondary battery (10) can be electrically connected to the outside by the terminal (320).

[0055] Sheet-type exterior material

[0056] Referring to FIG. 1, a secondary battery (10) according to Embodiment 1 of the present invention may include a sheet-shaped outer material (200). The sheet-shaped outer material (200) of the secondary battery (10) may be provided to wrap a portion of an electrode assembly (100). Specifically, the sheet-shaped outer material (200) may be provided to wrap a cap (300) to be described later and the electrode assembly (100). More specifically, the sheet-shaped outer material (200) may be combined with the cap (300) to form an internal space, and the electrode assembly (100) may be accommodated in the internal space.

[0057] Meanwhile, in Example 1 of the present invention, an example is given in which a sheet-shaped outer material (200) is bonded to the outer circumferential surface of a cap (300). However, this is merely an example, and the sheet-shaped outer material (200) may also be bonded to the inner circumferential surface of a cap (300).

[0058] The sheet-shaped outer covering (200) of the secondary battery (10) may have a shape in which the sheet or film is rolled along the side of the electrode assembly (100). That is, the sheet-shaped outer covering (200) may be arranged in a shape that wraps around the side of the electrode assembly (100). At this time, one end and the other end of the sheet-shaped outer covering (200) may be arranged in a shape in which they meet each other and wrap around the electrode assembly (100). With regard to the shape in which one end and the other end of the sheet-shaped outer covering (200) meet each other, one side of one end and the other side of the other end may be joined so as to be in contact with each other (see FIG. 1). This is merely an example, and the shape in which one end and the other end of the sheet-shaped outer covering (200) are joined to form a space that accommodates the electrode assembly (100) may vary.

[0059] With regard to the method by which one end and the other end of the sheet-shaped exterior material (200) are joined, one end and the other end of the sheet-shaped exterior material (200) may be joined to each other by heat sealing or heat and pressure sealing. That is, the sheet-shaped exterior material (200) may include a material having heat sealing properties.

[0060] As an example of the structure of the sheet-shaped exterior material (200), the sheet-shaped exterior material (200) may be formed in a film form. Specifically, the sheet-shaped exterior material (200) may be provided with a plurality of layers including a sealant layer, a barrier layer, and an insulating layer. More specifically, the sheet-shaped exterior material (200) may be arranged in the order of the sealant layer, the barrier layer, and the insulating layer from the inside closer to the electrode assembly (100).

[0061] The sealant layer may include a material having heat-sealing properties so that one end and the other end of the sheet-shaped exterior material (200) can be joined. For example, the sealant layer of the sheet-shaped exterior material (200) may include one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Mainly, a polyolefin resin such as polypropylene (PP) or polyethylene (PE) may be used. In particular, polypropylene (PP) may have excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance.

[0062] The barrier layer may include a metal. For example, the metal of the barrier layer may be one or more materials selected from the group consisting of iron (Fe), carbon (C), chromium (Cr), manganese (Mn), nickel (Ni), and aluminum (Al). For example, the barrier layer may include stainless steel (STS). Additionally, the barrier layer may be formed of an alloy, such as an aluminum alloy.

[0063] The insulating layer may include an insulating material. That is, the electrode assembly (100) may be insulated from the outside by the insulating layer. Therefore, the insulating layer may prevent short circuits, etc., of the sheet-shaped outer shell (200). For example, the insulating layer may include one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Mainly, a polymer such as nylon resin or polyethylene terephthalate (PET) having wear resistance and heat resistance may be used.

[0064] Meanwhile, the secondary battery (10) may be arranged in a form in which the sheet-shaped outer covering (200) wraps around a portion of the electrode assembly (100) and the cap (300) wraps around the remainder of the electrode assembly (100). Specifically, when the sheet-shaped outer covering (200) is arranged in a form in which the electrode assembly (100) wraps around the electrode assembly (100) along the side of the electrode assembly (100), outer covering openings may be formed at both ends of the electrode assembly (100). The cap (300) of the secondary battery (10) is combined with the sheet-shaped outer covering (200) in a form in which the outer covering openings at both ends of the electrode assembly (100) are covered, and the electrode assembly (100) may be accommodated in the internal space formed by the sheet-shaped outer covering (200) and the cap (300).

[0065] The sheet-shaped exterior material (200) can be combined with the cap (300). As an example of a method of combining the cap (300) and the sheet-shaped exterior material (200), the cap (300) and the sheet-shaped exterior material (200) can be combined by welding. Specifically, the cap (300) may include a metal material, and the sheet-shaped exterior material (200) may include a barrier layer that can be combined with the cap (300) by welding at a portion facing the cap (300). Here, the barrier layer may include a metal, as described above.

[0066] As another example of a method of joining the cap (300) and the sheet-shaped exterior material (200), the cap (300) and the sheet-shaped exterior material (200) may be joined by sealing. Specifically, the sheet-shaped exterior material (200) may include a resin layer that can be joined to the cap (300) by heat and pressure at a portion facing the cap (300). In addition, the cap (300) may include a resin material that has adhesiveness due to heat. Here, the resin layer may include a material that has sealing properties due to heat as described above.

[0067] As another example of a method of joining a cap (300) and a sheet-shaped exterior material (200), the cap (300) and the sheet-shaped exterior material (200) may be joined using an adhesive. At this time, the adhesive may be applied between the cap (300) and the sheet-shaped exterior material (200). Here, the type and application form of the adhesive for joining may vary.

[0068] Conventional pouch cells were formed by forming a cup portion to accommodate an electrode assembly (100) by forming a sheet or film. During the forming process of the cup portion, the depth that can be formed was limited depending on the material properties of the sheet or film, and the capacity that could accommodate the electrode assembly (100) was also limited. In addition, when forming a sheet or film, the thickness at the corners was the thinnest, so defects such as cracks frequently occurred. In addition, conventional pouch cells required a gas collection portion to collect gas in the degassing process to remove gas accumulated inside the pouch, and there were many cases where the gas collection portion was removed and discarded after the degassing process.

[0069] On the other hand, in the secondary battery (10) according to Example 1 of the present invention, since the sheet-shaped outer packaging material (200) can be used according to the volume of the electrode assembly (100), there may be no limitation on the capacity that can accommodate the electrode assembly (100). In addition, since molding of the cup portion is not required, the occurrence of defects such as cracks in the sheet-shaped outer packaging material (200) can be prevented, and the material and thickness of the sheet-shaped outer packaging material (200) can be selected relatively freely. In addition, since the electrolyte injection and degassing processes can be performed through the cap (300), the sheet-shaped outer packaging material (200) is not discarded, so the economic feasibility of the process can be improved.

[0070] Meanwhile, an electrolyte may be accommodated inside the secondary battery (10) together with an electrode assembly (100). At this time, residual moisture in the electrolyte inside the secondary battery (10) or moisture that has penetrated from the outside may react with a lithium salt to generate HF (hydrogen fluoride), and gases such as carbon dioxide, carbon monoxide, ethylene, and methane may be generated due to decomposition of the electrolyte. In addition, depending on the material of the positive electrode included in the electrode assembly, hydrogen and HF may be additionally generated, which may cause overheating due to overcharging and internal short circuit during the charging and discharging process. Accordingly, a large amount of gas may be generated inside the secondary battery (10). The pressure inside the secondary battery (10) may increase due to such gas, and the increased pressure may cause a swelling phenomenon in which the sheet-shaped outer material (200) swells or a venting phenomenon in which a part of the sheet-shaped outer material (200) or the cap (300) bursts.

[0071] As an example of a configuration for minimizing shape change due to internal gas, the sheet-shaped outer shell (200) of the secondary battery (10) according to Example 1 of the present invention may include a joining portion (210), a connecting portion (220), and a cover portion (230).

[0072] Referring to FIGS. 1 to 3, the joining portion (210) of the sheet-shaped outer material (200) can be joined to the cap (300). As described above, the sheet-shaped outer material (200) can be joined to the cap (300) to form an internal space capable of accommodating the electrode assembly (100). At this time, the joining portion (210) of the sheet-shaped outer material (200) can be a portion joined to the cap (300).

[0073] The cover portion (230) of the sheet-shaped exterior material (200) may be arranged closer to the electrode assembly (100) than the joining portion (210), and may be provided so that one surface faces 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 from the secondary battery (10) is generated, and the gas may accumulate inside the secondary battery (10). Therefore, the manufacturing process of the secondary battery (10) may further include a degassing process that removes the gas accumulated inside the secondary battery (10). Through the degassing process, the inside of the secondary battery (10) may be made into an approximately vacuum state. That is, through the degassing process, the cover portion (230) of the sheet-shaped exterior material (200) may be arranged in a form that is in close contact with the electrode assembly (100). Preferably, the cover portion (230) can be positioned so that one side is in contact with the electrode assembly (100).

[0074] The connecting portion (220) of the sheet-shaped exterior material (200) may be positioned between the joining portion (210) and the cover portion (230). That is, the joining portion (210) and the cover portion (230) may be connected to each other by the joining portion (220). The shape of the joining portion (220) will be described in detail later along with the shape of the cap (300).

[0075] cap

[0076] The cap (300) of the secondary battery (10) can be combined with the sheet-shaped outer material (200) to cover the electrode assembly (100). Specifically, the cap (300) can be positioned to block the outer material opening formed by the sheet-shaped outer material (200).

[0077] As an example of a configuration for minimizing shape change 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 with respect to the stacking direction of the electrode and separator of the electrode assembly (100) (for example, the up-down direction with reference to FIG. 3). In this regard, the connecting portion (220) of the sheet-shaped outer material (200) may be provided so that the gap with respect to the electrode assembly (100) with respect to the stacking direction gradually increases as it gets closer to the joining portion (210). Specifically, the sheet-shaped outer material (200) may be provided so that the height of the connecting portion (220) with respect to the stacking direction increases as it gets closer to the cap (300).

[0078] Referring to FIG. 3, due to the height difference between the electrode assembly (100) and the cap (300), the connecting portion (220) may be arranged in a form in which the height increases as it approaches the cap (300). In addition, due to the height difference between the cap (300) and the electrode assembly (100), a height difference may occur between the connecting portion (210) of the sheet-shaped outer material (200) and the cover portion (230).

[0079] Preferably, the secondary battery (10) according to Example 1 of the present invention can satisfy the following equation (1) when the height of the cap (300) with respect to the stacking direction of the electrode and the separator is L, the thickness of the sheet-shaped outer material (200) is t, and the height of the electrode assembly (100) with respect to the stacking direction is h.

[0080] … (1)

[0081] Accordingly, the secondary battery (10) can have a free height of L - (2t + h). That is, even if internal gas is generated by charging and discharging in the secondary battery (10), the gas can accumulate in the free space due to the free height.

[0082] Fig. 4 is a side view schematically illustrating a conventional cell stack (S).

[0083] Referring to Fig. 4, the surface of a conventional secondary battery is immediately swollen by gas. Therefore, a conventional cell stack (S) including a plurality of secondary batteries may change the arrangement of the secondary batteries due to swelling. As illustrated in Fig. 4, if the surface of the secondary battery swells due to swelling, the cell stack (S) may become structurally unstable. In other words, a conventional battery module including a cell stack (S) has a problem in that its structural stability decreases with use.

[0084] On the other hand, the secondary battery (10) according to Example 1 of the present invention can reduce the phenomenon of surface swelling. Therefore, the structural stability of the secondary battery (10) can be improved. Furthermore, the degree of gap between the caps (300) due to the free space can be reduced. Accordingly, the structural stability of a battery module including a plurality of secondary batteries (10) can be improved.

[0085] Meanwhile, 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 an 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.

[0086] The coupling hole (310) may have a shape that penetrates from one side of the cap (300) to the other side. A terminal (320) may be provided 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 side.

[0087] The terminal (320) may have a rivet shape so as not to be detached from the cap (300). However, the structure or shape of the terminal (320) is not particularly limited as long as it can conduct current through the electrode assembly (100) to the outside.

[0088] Example 2

[0089] Figure 5 is a cross-sectional view schematically illustrating a side surface of a cell stack (1) according to Example 2 of the present invention.

[0090] Below, a detailed description of the same configuration as that of the secondary battery (10) according to Example 1 of the present invention is omitted.

[0091] A 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 in parallel with each other, and the pads (20) may be arranged between the secondary batteries (10). Specifically, the pads (20) may be arranged between adjacent secondary batteries (10).

[0092] A secondary battery (10) of a cell stack (1) may include an electrode assembly (100), a sheet-shaped outer covering (200), and a cap (300). Here, the height of the cap (300) with respect to the direction in which the electrodes and separators of the electrode assembly (100) are stacked may be formed to be greater than the height of the electrode assembly (100). Specifically, the secondary battery (10) may satisfy the following equation (1) when the height of the cap (300) with respect to the stacking direction of the electrodes and separators is L, the thickness of the sheet-shaped outer covering (200) is t, and the height of the electrode assembly (100) with respect to the stacking direction of the electrodes and separators is h.

[0093] … (1)

[0094] Meanwhile, the sheet-shaped outer covering (200) of the secondary battery (10) may include a joining portion (210), a connecting portion (220), and a cover portion (230). Since each configuration of the sheet-shaped outer covering (200) may be the same as that of Example 1 of the present invention, a detailed description thereof will be omitted.

[0095] The cell stack (1) can have a pad (20) placed in the space formed between the secondary battery (10) due to the height difference between the cap (300) of the secondary battery (10) and the electrode assembly (100).

[0096] The pad (20) of the cell stack (1) can reduce the heat transfer rate between the secondary batteries (10). That is, the heat transfer rate of the pad (20) can be lower than the heat transfer rate of the secondary battery (10). Specifically, the heat transfer rate of the pad (20) can be lower than the heat transfer rate of the sheet-shaped outer material (200) of the secondary battery (10). More specifically, the pad (20) can be made of a material having a lower heat transfer rate than the material of the sheet-shaped outer material (200).

[0097] The cell stack (1) according to Embodiment 2 of the present invention can reduce heat transferred between secondary batteries (10) by including pads (20). Therefore, when a flame occurs in a specific secondary battery (10), the flame can be prevented from being transferred to other secondary batteries (10). Accordingly, a thermal runaway phenomenon of a module including the cell stack (1) can be prevented, and the stability of the module can be improved.

[0098] Below, the arrangement of the pad (20) will be described in more detail.

[0099] With respect to the height direction (e.g., the up-down direction of FIG. 5), the pad (20) of the cell stack (1) according to Example 2 of the present invention can be placed in a 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, it can satisfy the following equation (2).

[0100] … (2)

[0101] Therefore, the pad (20) can be more efficiently placed between the secondary batteries (10).

[0102] With respect to the longitudinal direction (e.g., the left-right direction in FIG. 5), the pad (20) of the cell stack (1) according to Example 2 of the present invention may be formed to have a length shorter 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). Accordingly, the pad (20) may be arranged to be in contact with the cover portion (230) of the sheet-shaped outer material (200).

[0103] Meanwhile, the pad (20) may be shaped and deformed by pressure. Specifically, the pad (20) may be designed to be shaped and deformed by pressure due to volume expansion of the secondary battery (10). Accordingly, when the cover portion (230) of the sheet-shaped outer material (200) or the like presses the pad (20) by gas inside the secondary battery (10), the pad (20) may be compressed.

[0104] The cell stack (1) can absorb pressure that can be transmitted to another secondary battery (10) by the gas inside the secondary battery (10) to the pad (20). Therefore, the structural stability of the cell stack (1) can be improved.

[0105] The cell stack (1) according to Example 2 of the present invention can form a space between adjacent secondary batteries (10) due to the shape of the secondary batteries (10). A pad (20) is arranged in this space to reduce heat and pressure transferred between adjacent secondary batteries (10). Accordingly, the stability of the cell stack (1) is improved, which can lead to improved stability of a battery module including the cell stack (1).

[0106] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and various embodiments are possible within the scope equivalent to the technical idea of ​​the present invention and the claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

[0107] [Explanation of symbols]

[0108] 1: Cell stack

[0109] 10: Secondary battery

[0110] 20: Pad

[0111] 100: Electrode assembly

[0112] 110: Electrode tab

[0113] 200: Sheet-type exterior material

[0114] 210: Joint

[0115] 220: Connection

[0116] 230: Cover

[0117] 300: Cap

[0118] 310: Combination hole

[0119] 320: Terminal

[0120] S: Conventional cell stack

Claims

1. An electrode assembly comprising a plurality of electrodes and a separator stacked in parallel; A sheet-shaped outer material having an internal space for accommodating the electrode assembly and an outer material opening for communicating the internal space with the outside; and Including a cap covering the opening of the above sheet-shaped exterior material, A secondary battery, wherein the height of the cap with respect to the stacking direction of the electrode and separator is formed to be greater than the height of the electrode assembly.

2. In paragraph 1, The above sheet-shaped exterior material is, A joint coupled with the above cap; A cover part arranged adjacent to the electrode assembly rather than the above-mentioned joint part and having one side facing the electrode assembly; and A secondary battery including a connecting portion arranged between the connecting portion and the cover portion, the gap between the electrode assembly and the stacking direction gradually increasing as it gets closer to the connecting portion.

3. In paragraph 2, The above sheet-shaped exterior material is, A secondary battery, wherein the height of the connecting portion with respect to the stacking direction is arranged to increase as it gets closer to the cap.

4. In paragraph 1, The above sheet-shaped exterior material is, A secondary battery coupled to the outer circumferential surface or inner circumferential surface of the above cap.

5. In paragraph 1, A secondary battery, wherein the cap is coupled with a terminal electrically connected to the electrode assembly.

6. In paragraph 1, The above cap comprises a metal material, A secondary battery, wherein the sheet-shaped outer shell is provided with a barrier layer including metal so as to be welded to the cap.

7. In paragraph 1, The above cap comprises a metal material, A secondary battery, wherein the above sheet-shaped outer material is provided with a resin layer that is bonded to the cap by heat and pressure.

8. In paragraph 7, The above sheet-shaped exterior material is, A secondary battery having a barrier layer including aluminum (Al) or stainless steel (STS) to prevent moisture penetration toward the electrode assembly.

9. In paragraph 1, A secondary battery, wherein the sheet-shaped outer covering is joined to the cap by an adhesive applied between the sheet-shaped outer covering and the cap.

10. In paragraph 1, A secondary battery, wherein the height of the cap with respect to the stacking direction of the electrode and separator is L, the thickness of the sheet-shaped outer material is t, and the height of the electrode assembly with respect to the stacking direction is h, satisfies the following equation (1). … (1) 11. A plurality of secondary batteries arranged in parallel; and Including a pad arranged between the secondary batteries so as to reduce the heat transfer rate between the plurality of secondary batteries, The above secondary battery, An electrode assembly comprising a plurality of electrodes and a separator stacked in parallel; A sheet-shaped outer material having an internal space for accommodating the electrode assembly and an outer material opening for communicating the internal space with the outside; and Including a cap covering the opening of the above sheet-shaped exterior material, A cell stack, wherein the height of the cap with respect to the electrode and separator stacking direction is formed to be greater than the height of the electrode assembly.

12. In paragraph 11, A cell laminate satisfying the following equation (1), when the height of the cap with respect to the stacking direction of the electrode and separator is L, the thickness of the sheet-shaped outer material is t, and the height of the electrode assembly with respect to the stacking direction is h. … (1) 13. In paragraph 12, A cell laminate satisfying the following equation (2) when the thickness of the above pad is p. … (2) 14. In paragraph 11, The above pad, A cell stack which is arranged to have a shape deformed by pressure caused by volume expansion of the secondary battery.

15. In paragraph 11, The above pad, A cell laminate having a heat transfer rate lower than that of the sheet-shaped exterior material.

16. In paragraph 11, The above pad, A cell stack formed so that its length is shorter than that of the secondary battery, based on the longitudinal direction.

17. In paragraph 11, The above sheet-shaped exterior material is, a joint coupled with the above cap; and It includes a cover part which is positioned adjacent to the electrode assembly rather than the above-mentioned connecting part and has one side facing the electrode assembly, A cell laminate, wherein the above pads are arranged to contact the above cover portion.

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