Pouch-type battery case and lithium secondary battery comprising same

Abstract

A pouch-type battery case according to the present invention comprises a base layer, a gas barrier layer, and a sealant layer, which are sequentially deposited, wherein the sealant layer comprises a particulate fire extinguishing agent, and the particulate fire extinguishing agent comprises at least one selected from the group consisting of a first fire extinguishing component containing sodium hydrogen carbonate, a second fire extinguishing component containing calcium hydrogen carbonate, a third fire extinguishing component containing ammonium phosphate, and a fourth fire extinguishing component containing urea, so that a pouch-type battery case with improved safety can be provided.

Description

Pouch-type battery case and lithium secondary battery including the same

[0001] The present invention relates to a pouch-type battery case and a lithium secondary battery including the same, and more particularly, to a pouch-type battery case with improved safety and a lithium secondary battery including the same.

[0002]

[0003] Common types of secondary batteries include nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, and lithium-ion polymer batteries. These batteries are used not only in small products such as digital cameras, DVDs, MP3 players, mobile phones, PDAs, portable game devices, power tools, and e-bikes, but also in larger products requiring high output, such as electric and hybrid vehicles, as well as in power storage devices that store surplus power or renewable energy, and as backup power storage devices.

[0004] To manufacture these secondary batteries, first, an electrode active material slurry is applied to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and these are laminated on both sides of a separator to form an electrode assembly of a predetermined shape. Then, the electrode assembly is housed in a battery case, filled with electrolyte, and sealed.

[0005] Secondary batteries are classified into pouch type and can type, depending on the material of the case that houses the electrode assembly. Pouch type batteries house the electrode assembly in a pouch made of a flexible polymer material. Can type batteries house the electrode assembly in a case made of materials such as metal or plastic.

[0006] The pouch, which is the case of a pouch-type secondary battery, is manufactured by performing press processing on a flexible pouch film laminate to form a cup portion. Once the cup portion is formed, an electrode assembly can be accommodated in the inner receiving space of the cup portion and the sealing portion can be sealed to manufacture a secondary battery.

[0007] Typically, pouch-type battery cases are formed by laminating a polymer film, such as polyethylene terephthalate, on one side of a metal gas barrier layer, and a sealant layer on the other side, forming multiple layers. However, in the case of such conventional pouch-type battery cases, as the size needs to increase due to the high density and large capacity of batteries, there is a problem that as the molding depth increases, tensile stress due to swelling occurs significantly, and the risk of explosion increases accordingly.

[0008]

[0009] The present invention is intended to solve the above problems, and to provide a pouch-type battery case that improves safety by additionally including a solid particle-type pyrophoric agent in the film-laminated structure of the pouch-type battery case to counteract the risk of explosion, thereby preventing thermal runaway and explosion by causing an early extinguishing effect in the event of abnormal behavior of the battery.

[0010] The tasks of the present invention are not limited to the tasks mentioned above, and other tasks not mentioned will be clearly understood by those skilled in the art from the description below.

[0011]

[0012] [1] According to one embodiment of the present invention, a pouch-type battery case comprises a substrate layer, a gas barrier layer, and a sealant layer sequentially laminated, wherein the sealant layer comprises a particulate fire extinguishing agent, and the particulate fire extinguishing agent comprises at least one selected from the group consisting of a first fire extinguishing agent containing sodium bicarbonate, a second fire extinguishing agent containing calcium bicarbonate, a third fire extinguishing agent containing ammonium phosphate, and a fourth fire extinguishing agent containing urea.

[0013] [2] In the above [1], the particle-type fire extinguishing agent may be included in an amount of 10 wt% to 90 wt% based on the total weight of the sealant layer.

[0014] [3] In the above [1] and / or [2], the particulate fire extinguishing agent is included in the form of a filler in the sealant layer as a particulate fire extinguishing agent, and the particulate fire extinguishing agent has an average particle diameter D 50 This may be less than 1 ㎛.

[0015] [4] In any one or more of the above [1] to [3], the sealant layer may include a first sealant layer arranged to be in contact with the gas barrier layer, a fire extinguishing agent layer including the particulate fire extinguishing agent and arranged to be in contact with the first sealant layer, and a second sealant layer arranged to be in contact with the fire extinguishing agent layer.

[0016] [5] In any one or more of the above [1] to [4], the pouch-type battery case comprises a cup portion having a recessed shape so that an electrode assembly can be accommodated; and a sealing portion formed along the periphery of the cup portion; and the particulate fire extinguishing agent may be included in an area excluding the sealing portion.

[0017] [6] In any one or more of the above [1] to [5], the particulate fire extinguishing agent may be included in a cup portion spaced apart from the sealing portion by a width greater than that of the sealing portion.

[0018] [7] In any one or more of the above [1] to [6], the substrate layer is a multilayer structure including two or more layers made of different polymers, and the particulate fire extinguishing agent may be further included in one or more layers selected from the multilayers.

[0019] [8] A lithium secondary battery according to another embodiment of the present invention includes the above-described pouch-type battery case; and an electrode assembly housed inside the pouch-type battery case.

[0020]

[0021] According to one embodiment of the present invention, a pouch-type battery case can improve safety by preventing thermal runaway and explosion by additionally including a solid fire extinguishing component in the film laminated structure of the pouch-type battery case to cause an early fire extinguishing effect in the event of abnormal behavior of the battery in order to respond to the risk of explosion.

[0022] Specifically, the pouch-type battery case includes a solid particle-type fire extinguishing agent, and particularly, by including it in an inner layer of the pouch film laminate rather than the gas barrier layer, it causes an early fire extinguishing effect in the event of an abnormal behavior of the battery, and by applying a solid, it is possible to prevent problems such as the fire extinguishing agent in the lower case not being able to perform the fire extinguishing effect and leaking to the outside or side reactions with the electrolyte or a decrease in concentration due to penetration into the interior of the pouch, as in the case of a liquid fire extinguishing agent that is more fluid than a solid, in the event of an abnormal behavior.

[0023]

[0024] Figure 1 is a cross-sectional view of a pouch-type battery case containing a particulate fire extinguishing agent as a filler according to the present invention.

[0025] Figure 2 is a plan view of a lithium secondary battery including a pouch-type battery case according to the present invention.

[0026] Figure 3 is an exploded assembly diagram of a lithium secondary battery according to Figure 2.

[0027] Figure 4 is a plan view of a lithium secondary battery including a pouch-type battery case according to the present invention.

[0028] Fig. 5 is a vertical cross-sectional view showing a pouch-type battery case when cut along the line S-S' in Fig. 4.

[0029]

[0030] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0031] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0032] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0033]

[0034] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0035] In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0036] In this specification, the upper portion of a drawing may be referred to as the "upper portion" or "upper side" of the configuration depicted in the drawing, and the lower portion thereof may be referred to as the "lower portion" or "lower side." Furthermore, the portion between the upper and lower portions of the configuration depicted in the drawing, or the portion excluding the upper and lower portions, may be referred to as the "side portion" or "side." Relative terms such as "upper portion" and "upper side" may be used to describe the relationship between the configurations depicted in the drawing, and the present disclosure is not limited by such terms.

[0037] In this specification, the direction toward the interior space of a structure may be referred to as "inside," and the direction protruding into the open exterior space may be referred to as "outside." Relative terms such as "inside," "outside," etc. may be used to describe the relationship between components depicted in the drawings, and the present disclosure is not limited by such terms.

[0038] In this specification, the description of “A and / or B” means A, or B, or A and B.

[0039] In this specification, when it is said that a part is connected to another part, this includes not only cases where they are directly connected, but also cases where they are connected with another structure in between.

[0040] In this specification, "average particle size" means the particle size corresponding to the average value of weight percentages in a particle size distribution curve, and unless otherwise explicitly indicated, means weight %. The above average particle size can be measured using an electron microscope or optical microscope after cutting a sample of a pouch-type battery case.

[0041] In this specification, each of the pouch-type battery case and the lithium secondary battery includes at least one of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways.

[0042]

[0043] pouch-type battery case

[0044] According to one embodiment of the present invention, a pouch-type battery case comprises a substrate layer, a gas barrier layer, and a sealant layer sequentially laminated, wherein the sealant layer includes a particulate fire extinguishing agent, and the particulate fire extinguishing agent includes at least one selected from the group consisting of a first fire extinguishing agent containing sodium bicarbonate, a second fire extinguishing agent containing calcium bicarbonate, a third fire extinguishing agent containing ammonium phosphate, and a fourth fire extinguishing agent containing urea.

[0045]

[0046] Hereinafter, with reference to FIG. 1, a pouch-type battery case according to the present invention and each layer included in the pouch-type battery case will be described in detail.

[0047]

[0048] Figure 1 is a cross-sectional view of a pouch-type battery case (100) containing a fire extinguishing agent in a sealant layer, and illustrates a case in which a particle-type fire extinguishing agent is included as a filler.

[0049] As illustrated in FIG. 1, the pouch-type battery case (100) includes a substrate layer (110), a gas barrier layer (120), and a sealant layer (130).

[0050]

[0051] (1) Sealant layer containing digestive components

[0052] The sealant layer (130) is bonded through heat compression to seal the battery case, and is located on the innermost layer of the pouch-type battery case (100).

[0053] The sealant layer (130) must have insulating and corrosion resistance properties because it is the surface that comes into contact with the electrolyte and electrode assembly after being formed into a battery case, and must completely seal the inside to block material movement between the inside and the outside, so it must have high sealing properties.

[0054] The above sealant layer (130) may be made of a polymer material, and may be made of at least one selected from the group consisting of, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, and Teflon. Among these, it is particularly preferable to include polypropylene (PP), which has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance.

[0055] The above sealant layer (130) may include polypropylene, cast polypropylene (CPP), acid modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof.

[0056] The above sealant layer (130) may have a single-layer structure or may have a multi-layer structure including two or more layers made of different polymer materials.

[0057] The sealant layer may have a total thickness of 60 ㎛ to 100 ㎛, preferably 60 ㎛ to 90 ㎛, and more preferably 60 ㎛ to 80 ㎛. If the thickness of the sealant layer is too thin, the sealing durability and insulation may be reduced, and if it is too thick, the flexibility may be reduced and the total thickness of the pouch film laminate may increase, which may lower the energy density per volume.

[0058] The sealant layer (130) includes a particulate fire extinguishing agent, and the particulate fire extinguishing agent includes at least one selected from the group consisting of a first fire extinguishing agent containing sodium bicarbonate, a second fire extinguishing agent containing calcium bicarbonate, a third fire extinguishing agent containing ammonium phosphate, and a fourth fire extinguishing agent containing urea. Specifically, the particulate fire extinguishing agent may include at least one selected from the group consisting of NaHCO3, KHCO3, NH4H2PO4, and KC2N2H3O3. Preferably, the particulate fire extinguishing agent may include NaHCO3 and / or KHCO3. When a fire occurs, the particulate fire extinguishing agent may react with high heat and prevent the spread of a fire that has occurred inside and outside the electrode assembly.

[0059] The content of the particulate fire extinguishing agent may be 10 wt% to 90 wt%, preferably 15 wt% to 75 wt%, and more preferably 25 wt% to 65 wt%, based on the total weight of the sealant layer.

[0060] If the content of the above-mentioned particle-type extinguishing agent is too low, the extinguishing effect may be reduced, and if the content is too high, the total thickness of the pouch-type battery case may increase, thereby increasing the overall thickness of the cell, which may lower the energy density, and the formability may be poor when forming a pouch film laminate.

[0061] The above particle-type fire extinguishing agent (140) may have a spherical, rod-shaped, or irregular shape, and the shape is not particularly limited, and the particle-type fire extinguishing agent (140) may be dispersed in the form of a filler in the sealant layer (130).

[0062] The above particle-type fire extinguishing agent (140) has an average particle diameter D 50This may be 1.0 ㎛ or less, preferably 0.1 ㎛ to 0.8 ㎛, more preferably 0.2 ㎛ to 0.6 ㎛. The size of the particulate fire extinguishing agent (140) may be applied to be 1.0 ㎛ or less in order to prevent the overall thickness of the cell from increasing excessively. The particulate fire extinguishing agent may be manufactured by injecting it into a molten polymer when extruding the polymer forming the sealant layer, and the method is not particularly limited.

[0063] A method may be considered in which a fire extinguishing agent layer is formed by including a fire extinguishing agent in a pouch film laminate and placed at an arbitrary position between the laminates, or a method may be considered in which a fire extinguishing agent is injected into a capsule and formed into a separate layer and placed at an arbitrary position between the laminates. However, in the case of forming a separate layer with a fire extinguishing agent, an increase in the overall thickness of the pouch film laminate inevitably occurs, and this may be a factor in worsening the formability, such as causing cracks to occur at the corners when drawing and forming the pouch film laminate into a case.

[0064] Increasing the thickness of the pouch film laminate may prevent the battery from swelling due to gas generated inside, but in reality, prevention of swelling must be controlled by the electrode assembly or electrolyte included inside the pouch. Therefore, if swelling is suppressed by increasing the thickness of the pouch film laminate, the stress on the electrode assembly inside the pouch-shaped case will only increase. Therefore, the pouch film laminate needs to be designed to allow swelling at the same level as the gap between battery cells in the battery pack. Therefore, additional layers other than those for functioning as the pouch film laminate are not desirable in terms of battery performance.

[0065] When forming a capsule, the overall thickness of the pouch film inevitably increases by more than 50%, which can cause a problem in which the pouch formability is greatly deteriorated. For example, during drawing forming, problems such as capsule bursting may occur because excessive tension is applied to the corners. On the other hand, a pouch-type battery case according to an embodiment of the present invention includes a particle-type fire extinguishing agent in the sealant layer, and is characterized by including the fire extinguishing agent in a solid state. Unlike when the fire extinguishing agent is liquid, when the solid fire extinguishing agent is liquid, there is no possibility of a problem occurring due to the liquid penetrating from the sealant layer into the pouch and mixing with the electrolyte, and there is an advantage that when the lower case is damaged due to abnormal behavior of the battery, the fire extinguishing agent cannot perform the fire extinguishing effect and does not leak to the outside.

[0066] The pouch-type battery case can immediately extinguish a fire when the battery exhibits abnormal behavior by including a particulate fire extinguishing agent in the sealant layer, thereby extinguishing the heat generated early and thereby preventing an explosion due to thermal runaway, thereby greatly contributing to improving safety. In other words, if the case is not positioned inside the pouch based on the gas barrier layer, for example, if the sealant layer does not include the fire extinguishing agent and is included in the external substrate layer, the fire extinguishing agent can only occur after sufficient heat has accumulated by the gas barrier layer. In this case, it is highly likely that the energy has already increased to a level that is difficult to extinguish with the fire extinguishing agent, making it difficult to prevent an explosion due to thermal runaway in advance. Therefore, in order to suppress abnormal behavior of the battery before thermal runaway occurs, it is preferable to include a particulate fire extinguishing agent in the sealant layer located inside the gas barrier layer rather than in the gas barrier layer.

[0067]

[0068] (2) Gas barrier layer

[0069] The gas barrier layer (120) is laminated between the substrate layer (110) and the sealant layer (130) to secure the mechanical strength of the pouch, block the ingress of gas or moisture from the outside of the pouch-type battery case, and prevent electrolyte leakage from the inside of the pouch-type battery case.

[0070] The gas barrier layer (120) may be formed of a metal, and specifically, may be formed of an aluminum alloy thin film. When the gas barrier layer is formed using an aluminum alloy thin film, a mechanical strength higher than a predetermined level can be secured, while being light in weight, and the electrochemical properties of the electrode assembly and the electrolyte can be supplemented and heat dissipation properties can be secured. The aluminum alloy thin film may include one or two or more metal elements other than aluminum, for example, one or more metal elements selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0071] The thickness of the gas barrier layer (120) may be 40 µm to 100 µm, specifically 50 µm to 90 µm, and more specifically 55 µm to 85 µm. When the thickness of the gas barrier layer (120) satisfies the above range, the formability and gas barrier performance are excellent when forming the cup portion.

[0072]

[0073] (3) Substrate layer

[0074] The substrate layer (110) is formed on the outermost layer of the pouch film laminate (100) to protect the secondary battery from friction and collision with the outside. The substrate layer (110) is made of a polymer and can electrically insulate the electrode assembly from the outside. The substrate layer (110) may be made of one or more materials selected from the group consisting of, for example, polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Among them, it is particularly preferable that the substrate layer (110) be made of polyethylene terephthalate (PET), nylon, or a combination thereof, which have wear resistance and heat resistance.

[0075] The substrate layer (110) may have a single-layer structure made of a single material. Alternatively, the substrate layer (110) may have a multi-layer structure formed by forming two or more materials in layers.

[0076] The thickness of the substrate layer (110) may be 5 ㎛ to 50 ㎛, specifically 7 ㎛ to 50 ㎛, and more specifically 7 ㎛ to 40 ㎛. When the thickness of the substrate layer (110) satisfies the above range, the pouch film laminate may have excellent external insulation, and since the thickness of the entire pouch is not thick, the energy density per volume of the secondary battery may be excellent.

[0077] The above-mentioned base layer (110) may include a fire extinguishing component, and when the above-mentioned base layer (110) has a multi-layer structure, the fire extinguishing component may be included in one or more layers selected from these layers, and the fire extinguishing component may be included in the same form as that included in the sealant layer described above. In this case, in addition to the phenomenon of heat running wild due to abnormal behavior of the battery inside the pouch, there is an advantage in that the fire extinguishing action can be more reliably performed when the battery case is damaged by an impact applied from the outside.

[0078]

[0079] The pouch-type battery case (100) as described above can be manufactured through a method for manufacturing a pouch-type battery case known in the art. For example, the pouch-type battery case of the present invention can be manufactured through a method of attaching a substrate layer (110) to the upper surface of a gas barrier layer (120) using an adhesive, and forming a sealant layer (130) on the lower surface of the gas barrier layer (120) using co-extrusion or an adhesive layer, and the pouch film manufactured in this way can be manufactured into a pouch-type battery case through cup molding, but is not limited thereto, and the method for including a particulate fire extinguishing agent is as described above.

[0080] The above pouch-shaped battery case may have a total thickness of 160 μm to 200 μm, preferably 180 μm to 200 μm. When the thickness of the pouch-shaped battery case satisfies the above range, the molding depth can be increased while minimizing a decrease in battery accommodation space and a decrease in sealing durability due to an increase in the thickness of the battery case.

[0081]

[0082] lithium secondary battery

[0083] According to another embodiment of the present invention, a lithium secondary battery is provided, including the aforementioned pouch-shaped battery case; and an electrode assembly housed inside the pouch-shaped battery case.

[0084]

[0085] Figure 2 is a plan view of an example of a lithium secondary battery (200) including a pouch-type battery case (210).

[0086] The above pouch-type battery case (210) may be provided with a cup portion (240) having a recessed shape so that an electrode assembly (260) can be accommodated therein; and a sealing portion (251) formed along the circumference of the cup portion (240). The sealing portion (251) is an area indicated by a hatched pattern in FIG. 3, is located on the terrace portion (250), and may be formed by sealing all or part of the terrace portion (250). In addition, the cup portion (240) may have a recessed shape by molding so that an electrode assembly (260) can be accommodated therein, and the electrode assembly may be electrically connected to an electrode tab, and the electrode tab may be electrically connected to an electrode lead (280) extended outward.

[0087]

[0088] FIG. 3 is an exploded assembly drawing of a lithium secondary battery (200) including an electrode assembly (260) according to FIG. 2 and a pouch-type battery case (210) in which the electrode assembly is housed.

[0089] As illustrated in FIG. 3, a lithium secondary battery (200) according to the present invention may include a pouch-type battery case (210) and an electrode assembly (260) housed in the pouch-type battery case (210). The electrode assembly (260) may be formed by stacking a positive electrode, a separator, and an anode, and may include an electrode tab (270), an electrode lead (280), and a lead film (290). The lithium secondary battery (200) may be manufactured by injecting an electrolyte into the inside of the pouch-type battery case (210) with the electrode assembly (260) housed therein, and then sealing the terrace portion (250).

[0090]

[0091] The pouch-shaped battery case (210) can house an electrode assembly (260) inside. The pouch-shaped battery case (210) can be manufactured by molding a pouch film laminate. Since the detailed configuration and properties of the pouch film laminate are the same as those described above, a detailed description thereof will be omitted.

[0092] In order to manufacture a pouch-type battery case (210), a pouch film laminate may be formed by drawing and stretching using a punch or the like, thereby forming a cup portion (240) including a pocket-shaped receiving space (241) to receive an electrode assembly (260).

[0093] As illustrated in FIG. 3, the pouch-type battery case (210) may include an upper case and a lower case. In one embodiment, the lower case may include a lower cup portion (240) formed therein to include a receiving space (241) capable of receiving an electrode assembly (260), and the upper case may cover the receiving space (241) from above to prevent the electrode assembly (260) from being separated from the outside of the battery case (210). The upper and lower cases may be manufactured such that one side thereof is connected to the other, but the present invention is not limited thereto and may be manufactured in various ways, such as being manufactured separately and separated from the other. Accordingly, the sealing portion may be formed on three sides, may be formed on all four sides, and may also be formed such that the cup portion exists only on the lower case.

[0094] The pouch-type battery case (210) can be sealed while housing the electrode assembly (260) so that a portion of the electrode lead (280), i.e., the terminal portion, is exposed. Specifically, when the electrode lead (280) is connected to the electrode tab (270) of the electrode assembly (260) and a lead film (290) is formed on a portion of the electrode lead (280), the electrode assembly (260) can be housed in the housing space (241) provided in the cup portion (240) of the lower case, and the upper case can cover the housing space (241) from above. Subsequently, an electrolyte can be injected into the interior of the housing space (241), and the terrace portions (250) formed on the edges of the upper and lower cases can be sealed. The electrolyte is intended to move lithium ions generated by an electrochemical reaction of an electrode during charging / discharging of a lithium secondary battery (200), and may include a non-aqueous organic electrolyte that is a mixture of a lithium salt and an organic solvent, or a polymer using a polymer electrolyte. Furthermore, the electrolyte may include a solid electrolyte of a sulfide type, oxide type, or polymer type, and such a solid electrolyte may have flexibility that allows it to be easily deformed by an external force.

[0095]

[0096] A pouch-type battery case comprises a cup portion having a recessed shape to accommodate an electrode assembly; and a sealing portion formed along the circumference of the cup portion; wherein the solid extinguishing agent may be included in an area excluding the sealing portion. That is, the sealing portion may be characterized in that no extinguishing agent is included.

[0097]

[0098] FIG. 4 is a plan view of a lithium secondary battery (200) including a pouch-type battery case (210) according to one embodiment of the present invention.

[0099] Referring to Fig. 4, the particle-type fire extinguishing agent (shaded portion) within the sealant layer may be formed in an area excluding the sealing portion (251), i.e., a portion of the cup portion (240) and the terrace portion (250), and the sealing portion (251) may not include the particle-type fire extinguishing agent. If the fire extinguishing agent within the sealant layer is also included in the area to be sealed, the fire extinguishing effect may occur due to the sealing temperature during sealing, increasing the sealing time and thus deteriorating the processability or sealing performance.

[0100] The above particle-type fire extinguishing agent may be included in a sealant layer corresponding to a cup portion spaced apart from the sealing portion by a width (AA") or more of the sealing portion, and may be included starting from a portion spaced apart by the distance A-A' shown in FIG. 4. That is, the distance A-A' may be greater than or equal to the distance AA", and in this case, a pouch-type battery case that can maximize the effect of the fire extinguishing action without affecting the sealing property can be provided.

[0101]

[0102] FIG. 5 is a cross-sectional view showing a pouch-type battery case when cut along the line S-S' of FIG. 4. The cup portion (240) is provided with a flat portion (242) where the electrode assembly is accommodated, and an inclined portion (243) that is connected from the flat portion (242) to a terrace portion (250) and formed by molding, and a part or all of the terrace portion (250) may have a sealing portion (251) formed by sealing. The particulate fire extinguishing agent may be included from the right side of line A of FIG. 5, and it may be preferable to include it from a portion spaced apart at least by the distance between A and A". Accordingly, the solid fire extinguishing agent may be provided in the terrace portion (250), the inclined portion (243), and the flat portion (242), and it is preferable to include it at least in the flat portion (242).

[0103]

[0104] Hereinafter, a lithium secondary battery (200) will be further described with reference to FIG. 3.

[0105] The electrode assembly (260) can be formed by alternately stacking electrodes and separators. Specifically, the electrode assembly (260) can be formed into a predetermined shape by applying a slurry containing an electrode active material, a binder, and / or a conductive material to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, and stacking the slurry on both sides of a separator. The electrode assembly (260) can be inserted into a pouch-type battery case (210) and sealed by the pouch-type battery case (210) after electrolyte injection. In one embodiment, the types of the electrode assembly (260) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc.

[0106] The electrode assembly (260) may include two types of electrodes, a positive electrode and a negative electrode, and a separator interposed between the electrodes to mutually insulate the electrodes. The positive electrode and the negative electrode may each have a structure in which an active material slurry is applied to an electrode current collector in the form of a metal foil or metal mesh containing aluminum and copper, respectively. The slurry may typically be formed by stirring a granular active material, an auxiliary conductor, a binder, and a conductive agent with a solvent added thereto. The solvent may be removed in a subsequent process.

[0107]

[0108] The electrode tabs (270) are respectively connected to the positive and negative electrodes of the electrode assembly (260), and may protrude outward from the electrode assembly (260) to serve as a path for electrons to move between the inside and the outside of the electrode assembly (260). The electrode current collector of the electrode assembly (260) may be composed of a portion where an electrode active material is applied and an end portion where the electrode active material is not applied, i.e., a non-coated portion. The electrode tabs (270) may be formed by cutting the non-coated portion or by connecting a separate conductive member to the non-coated portion by ultrasonic welding, etc. As illustrated in FIG. 3, the electrode tabs (270) may protrude in different directions of the electrode assembly (260), but are not limited thereto, and may be formed to protrude in various directions, such as protruding in parallel in the same direction from one side.

[0109]

[0110] An electrode lead (280) can supply electricity to the outside of a secondary battery (200). The electrode lead (280) can be connected to an electrode tab (270) of an electrode assembly (260) by spot welding, etc. At least a portion of the electrode lead (280) can be surrounded by an insulating member (290). In one embodiment, the electrode lead (280) may have one end connected to the electrode tab (270) and the other end protruding outward from the battery case (210). The electrode lead (280) may include a positive lead (282) having one end connected to a positive tab (272) and extending in a direction in which the positive tab (272) protrudes, and a negative lead (284) having one end connected to a negative tab (274) and extending in a direction in which the negative tab (374) protrudes.

[0111] Both the positive electrode lead (282) and the negative electrode lead (284) may have their other ends protruded to the outside of the pouch-type battery case (210). Therefore, electricity generated inside the electrode assembly (260) may be supplied to the outside. In addition, since the positive electrode tab (272) and the negative electrode tab (274) are formed to protrude in various directions, the positive electrode lead (282) and the negative electrode lead (284) may also extend in various directions. In one embodiment, the positive electrode lead (282) and the negative electrode lead (284) may be made of different materials. That is, the positive electrode lead (282) may be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead (284) may be made of the same copper (Cu) material as the negative electrode current collector or a nickel (Ni)-coated copper material. A portion of the electrode lead (280) protruding to the outside of the battery case (210) may serve as a terminal portion and be electrically connected to an external terminal.

[0112]

[0113] Examples and Comparative Examples

[0114] Hereinafter, the present invention will be described in more detail through specific examples. However, the following examples are merely illustrative and serve to aid understanding of the present invention and do not limit its scope. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope and technical spirit of this disclosure, and such modifications and variations are naturally within the scope of the appended claims.

[0115]

[0116] Example 1

[0117] A polyethylene terephthalate film measuring 266 mm wide, 50 m long, and 12 μm thick and a nylon film measuring 266 mm wide, 50 m long, and 25 μm thick were laminated on one side of an aluminum alloy film measuring 266 mm wide, 50 m long, and 60 μm thick, and a non-stretched polypropylene (CPP) film measuring 266 mm wide, 50 m long, and 50 μm thick was laminated to manufacture a pouch film laminate having a polyethylene terephthalate / nylon / aluminum alloy film / non-stretched polypropylene structure.

[0118] At this time, the above non-stretched polypropylene has an average particle size (D) corresponding to 30 wt% of the total weight thereof 50 ) was injected during extrusion to include the digestive component by adding NaHCO3 of approximately 0.7㎛.

[0119] Here, polyethylene terephthalate and nylon are the substrate layer, aluminum alloy film is the gas barrier layer, and non-stretched polypropylene is the sealant layer.

[0120] The manufactured pouch-shaped film laminate was mounted on a two-cup molding device equipped with a die and a punch, and drawing molding was performed by lowering the punch at a pressure of 0.5 MPa and a speed of 20 mm / min to obtain a molding depth of 9.6 mm, thereby manufacturing a pouch-shaped battery case.

[0121]

[0122] Example 2

[0123] In the above non-stretched polypropylene, an average particle size (D) corresponding to 30 wt% of the total weight thereof 50 ) A pouch-type battery case was manufactured in the same manner as in Example 1, except that KHCO3 having a particle size of approximately 0.7 μm was injected during extrusion.

[0124]

[0125] Example 3

[0126] In addition to the above non-stretched polypropylene, polyethylene terephthalate also contains an average particle size (D) corresponding to 30 wt% of the total weight thereof. 50 ) was injected during extrusion so that the digesting component was included in the polyethylene terephthalate layer and the non-stretched polypropylene layer, and a pouch-type battery case was manufactured in the same manner as in Example 1.

[0127]

[0128] Comparative Example 1

[0129] A pouch-type battery case was manufactured in the same manner as in Example 1, except that no extinguishing agent was included in the non-woven polypropylene.

[0130]

[0131] Comparative Example 2

[0132] A pouch-type battery case was manufactured in the same manner as in Example 1, except that the fire extinguishing agent was not included in the non-flexible polypropylene and only the polyethylene terephthalate was included.

[0133]

[0134] Comparative Example 3

[0135] A pouch-type battery case was manufactured in the same manner as in Example 1, except that NaHCO3 was injected into a capsule having a diameter of about 10 μm, and a pouch film laminate was manufactured by placing a digestive agent layer having a thickness of about 50 μm between nylon and aluminum alloy thin films using the capsule.

[0136]

[0137] Comparative Example 4

[0138] A pouch-type battery case was manufactured in the same manner as in Example 1, except that NaHCO3 was injected into a capsule having a diameter of about 10 μm, and a pouch film laminate was manufactured by placing a digestive agent layer having a thickness of about 50 μm between an aluminum alloy thin film and non-stretched polypropylene using the capsule.

[0139]

[0140] Experimental Example 1

[0141] The pouch-type battery cases manufactured in the above examples and comparative examples were applied to the lithium secondary batteries described below and evaluated as follows, and the results are shown in Table 1. The experimental results are shown in Table 1 below. In this case, in Table 1, the "◎" mark means very good, the "○" mark means good, the "△" mark means average, and the "X" mark means poor.

[0142]

[0143] Manufacturing of lithium secondary batteries

[0144] A positive electrode slurry was prepared by mixing a positive electrode active material (NCM65 1520), a conductive agent (Li-435), and a PVDF binder (KF9700, AD-c01) in a weight ratio of 96.5:1.5:2.0 in N-methylpyrrolidone, and the positive electrode slurry was applied to one surface of an aluminum current collector, dried at 140°C, and then rolled to prepare a positive electrode.

[0145] In the case of the negative electrode, a slurry was prepared by mixing the negative electrode active material, conductive agent, and binder in a 5:5 ratio of natural graphite and artificial graphite in a weight ratio of 95.6:0.9:3.4, and then applying it on a copper current collector, followed by drying and rolling to prepare the negative electrode.

[0146] An electrode assembly was manufactured by interposing a separator between the positive and negative electrodes manufactured by the above-described method, and then placed inside the battery case of the above-described examples and comparative examples, and an electrolyte was injected into the case to manufacture a battery cell. The electrolyte was manufactured by dissolving 0.7 M LiPF6 in a mixed organic solvent mixed in a volume ratio of ethylene carbonate (EC): propylene carbonate (PC): ethyl methyl carbonate (EMC) = 2:1:7.

[0147]

[0148] 1) Fire occurrence test: Five of the manufactured battery cells were assembled into a module, and a heating pad was attached to one of the battery cells, applying heat at a rate of 0.5°C / sec. The battery cell to which the heating pad was attached was observed for ignition. At this time, the longer the time it took for ignition (fire or smoke) to first occur, the better it was, and the results were evaluated in four stages.

[0149] 2) Heat Propagation Delay Test: Five of the manufactured battery cells are assembled into a module, and heat is applied to one battery cell at a rate of 0.5°C / sec using a heating pad. The heat to adjacent cells is measured using a thermocouple to determine whether there is a time delay in heat propagation. The results are evaluated in four stages.

[0150] 3) Penetration test: A nail penetration test was performed by penetrating the manufactured battery cell at a speed of 0.1 mm / s using a sharp nail type, and the test was divided into four stages and evaluated based on the time of initial ignition occurrence, the size of the flame at ignition, and the amount of smoke.

[0151] 4) Formability: When performing drawing forming to achieve a forming depth of 9.6 mm during the manufacture of a pouch-type battery case, it was checked whether cracks occurred in the pouch film. Specifically, a case in which no cracks occurred at all was evaluated as ○, a case in which cracks occurred in the surface substrate layer was evaluated as △, and a case in which the gas barrier layer was exposed or cut due to cracks was evaluated as X.

[0152] 5) Swelling stability: After operating the lithium secondary battery for 200 cycles, the change in thickness of the lithium secondary battery was measured, and if the thickness change rate exceeded 5%, it was evaluated as ○, and if it was 5% or less, it was evaluated as X.

[0153]

[0154] Fire occurrence testHeat propagation delay testPenetration testFormabilitySwellingStabilityExample 1○○○○○Example 2○○○○○Example 3○◎○○○Comparative example 1△X△○○Comparative example 2△△○○○Comparative example 3△△○△XComparative example 4○○○△X

[0155] Referring to Table 1 above, it can be confirmed that the Examples exhibit superior safety in terms of fire occurrence and heat transfer due to energy accumulation compared to the Comparative Examples, and that it does not affect not only the formability but also the performance of the battery. On the other hand, Comparative Example 1 does not include a fire extinguishing agent, so it exhibits a considerably unstable aspect in terms of fire or explosion safety, and in particular, it can be confirmed that heat transfer occurs quickly, which increases the risk of explosion. In addition, when the fire extinguishing agent is positioned outside the pouch rather than on the gas barrier layer as in Comparative Example 2, the same results were obtained in the nail penetration test, which is an abnormal phenomenon due to external impact, but the effect in terms of fire occurrence and heat transfer was confirmed to be less. In addition, Comparative Examples 3 and 4, which formed a separate fire extinguishing agent layer through capsule formation, cracks occurred at the corners of the cup portion during forming due to the increase in the pouch thickness. Furthermore, when gas is generated inside the pouch, swelling must be allowed to a certain extent up to a certain thickness allowed by the gap between cells in the battery pack to reduce the stress on the electrode assembly and prevent the resulting performance degradation. However, in the case of Comparative Examples 3 and 4, swelling is not allowed due to the increase in the pouch thickness, and thus the problem of the stress on the electrode assembly inside the pouch being large can be confirmed.

[0156]

[0157] [Explanation of symbols]

[0158] 100, 210: Pouch-type battery case

[0159] 110: Base layer 120: Gas barrier layer

[0160] 130: Sealant layer 131: First sealant layer

[0161] 132: Second sealant layer 140: Particulate fire extinguishing agent

[0162] 200: Lithium secondary battery

[0163] 240: Cup section 241: Reception space

[0164] 242: Flat area 243: Sloping area

[0165] 250: Terrace section 251: Ceiling section

[0166] 260: Electrode assembly 270: Electrode tab

[0167] 280: Electrode lead 290: Lead film

Claims

1. The substrate layer, gas barrier layer, and sealant layer are sequentially laminated. The above sealant layer contains a particulate fire extinguishing agent, A pouch-type battery case, wherein the particle-type fire extinguishing agent comprises at least one selected from the group consisting of a first fire extinguishing agent containing sodium bicarbonate, a second fire extinguishing agent containing calcium bicarbonate, a third fire extinguishing agent containing ammonium phosphate, and a fourth fire extinguishing agent containing urea.

2. In paragraph 1, A pouch-type battery case, wherein the particle-type fire extinguishing agent is contained in an amount of 10% to 90% by weight based on the total weight of the sealant layer.

3. In paragraph 1, The above particle type fire extinguishing agent has an average particle diameter D 50 A pouch-type battery case with a size of 1 μm or less.

4. In paragraph 1, The above pouch-type battery case, A cup portion having a recessed shape to accommodate an electrode assembly; and a sealing portion formed along the circumference of the cup portion; A pouch-type battery case in which the above particle-type fire extinguishing agent is included in an area excluding the above sealing portion.

5. In paragraph 4, A pouch-type battery case, wherein the above particle-type fire extinguishing agent is contained in a cup portion spaced apart from the sealing portion by a width greater than that of the sealing portion.

6. In paragraph 1, A pouch-type battery case, wherein the above-mentioned substrate layer is a multilayer structure including two or more layers made of different polymers, and the particulate fire extinguishing agent is further included in one or more layers selected from the multilayers.

7. A pouch-type battery case according to any one of clauses 1 to 6; and A lithium secondary battery comprising an electrode assembly housed inside the pouch-shaped battery case.

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