Secondary battery
Patent Information
- Application Number
- VN1202601299
- Authority / Receiving Office
- VN · VN
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-08-18
- Filing Date
- 2024-08-13
- Publication Date
- 2026-08-03
Smart Images
Figure VN1202601299_0
Abstract
Description
secondary batteries The present invention relates to a secondary battery, and more particularly, to a secondary battery with improved energy density and safety. 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. 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. 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. Fig. 1 is a perspective view of a case of a conventional pouch-type secondary battery. The pouch, which is the case of the pouch-type secondary battery, is manufactured by performing press processing on a flexible pouch film laminate to form cup portions (12, 13) on the upper and lower portions or on one side. Once the cup portions (12, 13) are formed, an electrode assembly is accommodated in the inner receiving space (14) of the cup portion, and a portion or all of a terrace portion (15) surrounding the receiving space (14) is sealed to manufacture a secondary battery. Pouch-type secondary batteries of this structure have a problem in that the presence of the terrace portion (15) causes a spatial disadvantage in the production of battery modules or packs, which in turn reduces energy density. To utilize space, the terrace portion (15) is folded and finished, but in this case, there is a problem in that the additional process for this increases the cost, and the durability of the pouch in the folded portion may decrease, resulting in problems such as a decrease in insulation performance. In addition, there is also a problem in that it is difficult to maintain the sealing properties of the sealing portion where the electrode lead is drawn out. In addition, the molding depth of the cup portion formed on the pouch film is limited due to the material properties of the pouch film. Accordingly, it is difficult to mold the cup portion deep enough to increase battery capacity, and the material and thickness of the pouch film must also be selected within restrictions. As the thickness of the pouch film decreases during the molding of the cup portion, defects such as cracks are likely to occur in the outer material. In addition, pouch-type cases typically include a pocket portion to capture gas generated during activation, but the pocket portion is removed after the gas from the pocket portion is discharged through the degassing process. This causes the problem that some of the cases are always discarded. The present invention is intended to solve the above-mentioned problems and to provide a secondary battery that can solve various problems that occur in the process of forming a cup portion for accommodating an electrode assembly. In addition, it is to provide a secondary battery that can prevent the disposal of external materials that occur after the degassing process. In addition, it is intended to provide a secondary battery that can improve safety by maintaining excellent sealing properties and sealing durability of the sealing portion where the outer film covering the electrode assembly comes into contact, as well as the sealing properties of the cover member portion. 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. [1] A secondary battery according to one embodiment of the present invention includes: an electrode assembly; an outer film having an internal space for accommodating the electrode assembly, and an outer opening for communicating the internal space with the outside; and a cover member for covering the outer opening of the outer film; wherein the outer film has a sealing surface in which an inner surface and an outer surface of the outer film meet in a direction perpendicular to the outer opening and are joined by an adhesive film, and the adhesive film is characterized in that a sealing index (SI) defined by the following Equation 1 is 1.00 to 6.00. [Formula 1] SI = PS / CA In the above equation 1, SI of the adhesive film is a sealing index, CA is a unitless number of the contact angle of the adhesive surface of the adhesive film, and PS is an electrolyte-based peel strength, which is obtained from a T-peel peel test at a speed of 300 mm / sec after the sealed pouch-type case is immersed in an electrolyte for 24 hours, and is a unitless number when the unit is gf / 25 mm. [2] In the above [1], the contact angle (CA) may be 80° or more. [3] In the above [1] and / or [2], the electrolyte peel strength (PS) may be 100 gf / 25 mm or more. [4] In at least one of the above [1] to [3], the sealing index may be 1.30 to 5.50. [5] In at least one of the above [1] to [4], the secondary battery may further include a gasket member disposed between the cover member and the outer film. [6] In at least one of the above [1] to [5], the adhesive film includes a rubber-based adhesive resin, and the rubber-based adhesive resin may include at least one selected from the group consisting of natural rubber, epoxidized natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isobutylene rubber, epoxidized styrene-butadiene-styrene rubber, styrene-isobutylene-styrene rubber, epoxidized styrene-isobutylene-styrene rubber, styrene-ethylene-alphaolefin-styrene rubber, and ethylene-propylene-diene rubber. [7] In at least one of the above [1] to [6], the adhesive film may have a single-layer structure comprising an adhesive layer; a two-layer structure comprising a base film and an adhesive layer disposed on the base film; or a three-layer structure comprising a base film and adhesive layers disposed on both sides of the base film; and the adhesive layer may include a rubber-based adhesive resin. [8] In at least one of the above [1] to [7], the base film may include at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyimide, non-stretched polypropylene, high-density polyethylene, and low-density polyethylene. [9] In at least one of the above [1] to [8], the outer film may include a sealant layer on the inner surface and an outer insulating layer on the outer surface, and the sealant layer may include at least one selected from the group consisting of polypropylene, non-stretched polypropylene, acid-modified polypropylene, and polypropylene-butylene-ethylene copolymer.
[0010] In at least one of the above [1] to [9], the outer film may include a sealant layer on the inner surface and an outer insulating layer on the outer surface, and the outer insulating layer may include at least one selected from the group consisting of polyethylene terephthalate and nylon.
[0011] In at least one of the above [1] to
[0010] , the outer film may have a structure in which a sealant layer, a gas barrier layer, and an outer insulation layer are sequentially laminated from the inner side.
[0012] A battery module according to another embodiment of the present invention includes a plurality of the aforementioned pouch-type secondary batteries. In a secondary battery according to one embodiment of the present invention, since an outer material can be prepared without forming a cup portion for accommodating an electrode assembly, the battery capacity can be easily increased by increasing the size of the outer material, the material and thickness of the sheet for manufacturing the outer material can be selected relatively freely, and defects such as cracks can be less likely to occur. In addition, the secondary battery according to one embodiment of the present invention can prevent unnecessary disposal of the outer material since electrolyte injection and degassing can be performed through the electrolyte injection hole of the cover member. Furthermore, a secondary battery according to one embodiment of the present invention can improve sealing processability and safety by improving sealing performance and sealing durability in a sealing portion formed by contacting external films in a more simplified manner. Figure 1 is a perspective view of a pouch-type case of a conventional structure. Figure 2 is an exploded assembly diagram of a secondary battery according to one embodiment of the present invention. Figure 3 is a perspective view of a secondary battery according to one embodiment of the present invention. Figure 4 is a cross-sectional view along line AA of the secondary battery of Figure 3. Fig. 5 is a cross-sectional view illustrating another example of a gasket member in the secondary battery of Fig. 3. Fig. 6 is an enlarged cross-sectional view of part B of Fig. 3, which is an enlarged cross-sectional view when a single-layer adhesive film is applied. Fig. 7 is an enlarged cross-sectional view of part B of Fig. 3, which is an enlarged cross-sectional view when a two-layer adhesive film is applied. Fig. 8 is an enlarged cross-sectional view of part B of Fig. 3, which is an enlarged cross-sectional view when a two-layer adhesive film is applied. Fig. 9 is an enlarged cross-sectional view of part B of Fig. 3, which is an enlarged cross-sectional view when a three-layer adhesive film is applied. 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. 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. 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. Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The secondary battery described in this specification includes at least one of the technical configurations described below, and may include any combination between technically possible configurations among the technical configurations below. 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. 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. 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. In this specification, the description of “A and / or B” means A, or B, or A and B. 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. secondary batteries According to one embodiment of the present invention, a secondary battery includes: an electrode assembly; an outer film having an internal space for accommodating the electrode assembly and an outer opening for communicating the internal space with the outside; and a cover member covering the outer opening of the outer film; wherein the outer film has a sealing surface in which an inner surface and an outer surface meet in a direction perpendicular to the outer opening and are joined by an adhesive film, and the adhesive film is characterized in that a sealing index (SI) defined by the following Equation 1 is 1.00 to 6.00. [Formula 1] SI = PS / CA In the above equation 1, SI of the adhesive film is a sealing index, CA is a unitless number of the contact angle of the adhesive surface of the adhesive film, and PS is an electrolyte-based peel strength, which is obtained from a T-peel peel test at a speed of 300 mm / sec after the sealed pouch-type case is immersed in an electrolyte for 24 hours, and is a unitless number when the unit is gf / 25 mm. 1) Adhesive film and sealing index According to one embodiment of the present invention, the secondary battery has a sealing surface in which the inner and outer surfaces of the outer film meet in a direction perpendicular to the outer opening of the outer material and are joined by an adhesive film, and the adhesive film is characterized in that it has a sealing index (SI) of 1.00 to 6.00. The conventional pouch-type case (10) according to Fig. 1 has a problem in process and energy density due to the presence of the terrace portion (15), and the pouch-type case with a new structure to improve this has a problem in sealing durability. To address these issues, a method can be adopted in which the electrode assembly is wrapped widthwise using a predetermined sheet, such as a pouch film, and the openings at both ends are covered with caps to seal them. A pouch-type battery case having this structure can be sealed by wrapping the electrode assembly widthwise with a pouch film and then sealing the sheet on one side. One of the sealing methods is to seal by bringing the innermost layers of the pouch film into contact with each other. This method reduces the number of terrace sections that need to be folded compared to the conventional structure, but it cannot solve the problems of the conventional process as long as the folding process of the terrace sections exists, and the advantage of changing the mass production process compared to utilizing the existing process is very minimal. Another method is to prevent the formation of a terrace by bringing the innermost and outermost layers of the pouch film into contact. However, in this case, since the properties of the polymers forming the innermost and outermost layers are different, there is a problem with sealing even if heat-sealing is performed. In addition, heat-sealing is a method of bonding two surfaces by applying heat and pressure, but due to its structure, it is difficult to apply pressure, so there is also a problem that it is difficult to apply the heat-sealing process. In the case of a secondary battery according to one embodiment of the present invention, even if the sealant layer of the outer film and the outer insulating layer are sealed, since sealing is performed using an adhesive film, pressurization is unnecessary during sealing, and thus difficulties in the sealing process due to structural problems that make it difficult to pressurize can be resolved, and while a secondary battery without a terrace portion can be implemented, the problem of sealing durability can be resolved. However, even when using adhesive film for sealing, sealing durability may be compromised depending on the adhesive film's properties. Due to its properties, adhesive film may exhibit different peel strengths on the two surfaces when bonded to the sealant layer and external insulating layer of the outer film. Furthermore, compared to sealing with heat sealing, peel strength may be weakened when exposed to electrolyte. Accordingly, the present invention aims to solve the problems of weakened adhesiveness and peel strength upon exposure to electrolyte, as well as electrolyte leakage, by introducing a sealing index (SI). The sealing index is characterized by being 1.00 to 6.00, and is defined by the following equation 1. [Formula 1] SI = PS / CA In the above equation 1, SI of the adhesive film is a sealing index, CA is a contact angle of the adhesive surface of the adhesive film, a unitless number with a unit of °, and PS is an electrolyte-based peel strength, which is obtained from a T-peel peel test at a speed of 300 mm / sec after the sealed pouch-type case is immersed in an electrolyte for 24 hours, and is a unitless number when the unit is gf / 25 mm. The contact angle of the adhesive surface of the adhesive film may be at least greater than the surface contact angle of the sealant layer or the outer insulating layer of the outer film, which is the adherend surface, and preferably greater than the surface contact angle of the sealant layer and the outer insulating layer of the outer film. Specifically, the contact angle may be 80° or greater, and the contact angle may be obtained by dropping a drop of distilled water on the surface to be measured and then measuring the angle formed by the surface and the water droplet within 5 seconds. The contact angle may preferably be 90° or greater, 95° or greater, 100° or greater, or 105° or greater. In addition, the contact angle may be at most 150°, and may be 140° or less, 130° or less, or 125° or less. The contact angle of the adhesive surface of the adhesive film can be determined by various factors, such as the material applied as the adhesive layer of the adhesive film and the degree of surface treatment, and can be a measure of the degree of hydrophobicity. Therefore, considering the possibility of electrolyte leakage from the inside and the possibility of moisture penetration from the outside, it is desirable to have a contact angle at the same level as described above. The above electrolyte-substrate peel strength may be 100 gf / 25 mm or more. The above electrolyte-substrate peel strength may be obtained by impregnating the adhesive film in an electrolyte (an organic solvent in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethylene carbonate (DMC) are mixed in a volume ratio of 3:3:4 and a lithium salt of 1.0 M LiPF6) for 24 hours while the adhesive film is adhered between the sealant layer and the outer insulating layer of the pouch cover, and then performing a T-peel peel test at a speed of 300 mm / sec. The above electrolyte peel strength may be 100 gf / 25mm or more, 120 gf / 25mm or more, 150 gf / 25mm or more, 180 gf / 25mm or more, or 200 gf / 25mm or more, more preferably 230 gf / 25mm or more, and may have an upper limit of 600 gf / 25mm or less. However, in reality, when the peel strength is 600 gf / 25mm or more, it may be difficult to implement with an adhesive film, and even if it is implemented, in order to have such a peel strength, a material having properties opposite to those of the electrolyte must be applied, and therefore, the material cannot help but have a high affinity for moisture, and accordingly, a problem of vulnerability to moisture penetration from the outside may occur. The sealing index is characterized by being 1.00 to 6.00. The sealing index is a ratio of the contact angle (unit: °) to the electrolyte sub-peel strength (unit: gf / 25mm). In order to achieve the desired level of sealing durability, the sealing index must be 1.00 to 6.00 before the range of the peel strength and contact angle described above. The sealing durability of secondary batteries can be affected by various factors. For example, external moisture ingress can be a problem, and internal electrolyte leakage and gas generation can increase internal pressure. To reduce the possibility of moisture ingress, the bonding surface must be as hydrophobic as possible, and the material applied to the adhesive film must also be hydrophobic. This can be expressed through the contact angle of the bonding surface of the adhesive film. Furthermore, to eliminate the possibility of electrolyte leakage, excellent adhesion and high peel strength under the electrolyte must be achieved. To achieve high peel strength under the electrolyte, the adhesive must have high peel strength under normal conditions and possess electrolyte-resistant properties with low affinity for the electrolyte. To achieve the sealing durability of a secondary battery according to one embodiment of the present invention, all of the aforementioned characteristics must be considered, which can be expressed by the sealing index described above. Through this, a sealing portion with excellent sealing durability can be realized that prevents moisture infiltration while reducing the possibility of electrolyte leakage and maintaining a certain level of adhesive strength, based on the ratio of the electrolyte peel strength and contact angle. The secondary battery needs to apply an adhesive film so that the sealing index is 1.00 to 6.00, and preferably, the sealing index may be 1.10 or more, 1.20 or more, 1.25 or more, 1.30 or more, or 1.33 or more, and preferably, the sealing index may be 6.00 or less, 5.80 or less, 5.70 or less, 5.60 or less, 5.50 or less, or 5.45 or less. The above adhesive film may include a rubber-based adhesive resin, and the rubber-based adhesive resin may include at least one selected from the group consisting of natural rubber, epoxidized natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isobutylene rubber, epoxidized styrene-butadiene-styrene rubber, styrene-isobutylene-styrene rubber, epoxidized styrene-isobutylene-styrene rubber, styrene-ethylene-alphaolefin-styrene rubber, and ethylene-propylene-diene rubber. In the case of the rubber-based adhesive resin as described above, it may be a material that has the basic conditions for satisfying the sealing index described above, and post-processing may be performed on the material as described above through additional surface treatment, etc., so as to satisfy the sealing index described above. In the case where an acrylic adhesive resin is applied instead of the rubber-based adhesive resin, even if post-processing is performed, the peel strength under the electrolyte is significantly low, making it difficult to satisfy the sealing index, and therefore it may be desirable to utilize a rubber-based adhesive resin as the material for the adhesive film. 2) Structure of secondary batteries Hereinafter, a secondary battery according to the present invention will be described with reference to the attached drawings. A secondary battery according to one embodiment of the present invention comprises: an electrode assembly; an outer film having an internal space for accommodating the electrode assembly and an outer opening for communicating the internal space with the outside; and a cover member for covering the outer opening of the outer film; wherein the outer film is characterized in that it has a sealing surface in which an inner surface and an outer surface of the outer film meet in a direction perpendicular to the outer opening and are joined by an adhesive film. Electrode assembly, etc. According to one embodiment, the electrode assembly (160) may be formed by alternately stacking electrodes and separators. The electrode assembly (160) illustrated in FIG. 2 may 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 (160) may be surrounded by an outer film (110) and sealed by an adhesive film (114). In one embodiment, the types of the electrode assembly (160) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc. In one embodiment, the electrode assembly (160) 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 the addition of a solvent. The solvent may be removed in a subsequent process. The electrode tabs (170) are respectively connected to the positive and negative electrodes of the electrode assembly (160), and may protrude outward from the electrode assembly (160) to serve as a path for electrons to move between the inside and the outside of the electrode assembly (160). The electrode current collector of the electrode assembly (160) 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 (170) 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. The electrode tabs (170) may protrude in different directions of the electrode assembly (160), 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. The electrode lead (not shown) can supply electricity to the outside of the secondary battery (100), and this role can be replaced by the electrode terminal (134) included in the cover member (130). However, as a different example, a through hole can be formed in the cover member (130) so that the electrode lead can be pulled out to the outside instead of the electrode terminal (134). In this case, the electrode lead (180) can have one end connected to the electrode tab (170) of the electrode assembly (160) by spot welding or the like, and the other end can protrude to the outside through the through hole formed in the cover member (130). The electrode lead can include a positive lead having one end connected to the positive tab and extending in the direction in which the positive tab protrudes, and a negative lead having one end connected to the negative tab and extending in the direction in which the negative tab protrudes. Both the positive electrode lead and the negative electrode lead may have their other ends protrude outward through the through-hole of the cover member (130). Therefore, electricity generated inside the electrode assembly (160) may be supplied to the outside. In addition, since the electrode tabs (170) are formed such that the positive electrode tabs and the negative electrode tabs protrude in various directions, the positive electrode lead and the negative electrode lead may also extend in various directions. In one embodiment, the positive electrode lead and the negative electrode lead may be made of different materials. That is, the positive electrode lead may be made of the same aluminum (Al) material as the positive electrode collector, and the negative electrode lead may be made of the same copper (Cu) material as the negative electrode collector or a nickel (Ni)-coated copper material. A portion of the electrode lead protruding outward may serve as a terminal portion and be electrically connected to an external terminal. The electrolyte is intended to move lithium ions generated by an electrochemical reaction of the electrode during charging / discharging of a pouch-type secondary battery (100), 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. exterior film The outer film (110) may be an outer material that accommodates the electrode assembly (160). The outer film (110) may include an internal space (115) that accommodates the electrode assembly (160). The outer film (110) may include an outer material opening (116) that connects the internal space (115) to the outside of the outer film (110). The outer material opening (116) may be provided at each of the longitudinal ends of the outer film (110). The outer material opening (116) may be sealed by a cover member (130) and a gasket member (140) that will be described later. The outer film (110) can be obtained from a predetermined sheet (110a). The predetermined sheet (110a) may be a sheet having a first end (110b) and a second end (110c) spaced apart from the first end (110b) in a predetermined direction. When such a sheet (110a) is rolled or folded so that the first end (110b) and the second end (110c) meet, the outer film (110) can be obtained. The first end (110b) and the second end (110c) can be joined to each other, and at this time, the inner surface of the first end (110b) can be joined to the outer surface of the second end (110c) as illustrated in FIG. 3. An adhesive film can be attached to this portion to form a sealing portion. Since the sealing using the adhesive film of the first end (110b), for example, the outer insulating layer (111), and the second end (110c), for example, the sealant layer (113), has been described above, a detailed description thereof will be omitted. The sheet (130a; see FIG. 3), for example, the pouch film, may be a sheet including a metal layer such as aluminum or stainless steel. The sheet (130a) may also be a laminate sheet further including a resin layer laminated on the metal layer. The resin layer may include a first resin layer disposed on the inner surface of the metal layer. The first resin layer may be a layer formed of polypropylene (PP) or polyphthalamide (PPA). Since the first resin layer may require high insulation and corrosion resistance, the first resin layer may be formed of another resin that satisfies such requirements. The resin layer may include a second resin layer disposed on the outer surface of the metal layer. The second resin layer may be a layer formed of polyethylene terephthalate (PET). Since the second resin layer may require protection and insulation of the secondary battery (100), the second resin layer may be formed of another resin that satisfies such requirements. As another example, the sheet (130a) forming the outer film (110) may have a structure in which a sealant layer (113), a gas barrier layer (112), and an outer insulating layer (111) are sequentially laminated from the innermost side. The above outer insulating layer (111) is formed on the outer surface of the outer film to protect the secondary battery from friction and collision with the outside. The outer insulating layer (111) is made of a polymer and can electrically insulate the electrode assembly from the outside. The outer insulating layer (111) 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 outer insulating layer (111) is made of polyethylene terephthalate (PET), nylon, or a combination thereof, which have wear resistance and heat resistance. The outer insulating layer (111) may have a single film structure made of a single material. Alternatively, the outer insulating layer (111) may have a composite film structure formed by forming layers of two or more materials. The thickness of the outer insulating layer (111) may be 5 ㎛ to 50 ㎛, specifically 7 ㎛ to 50 ㎛, and more specifically 7 ㎛ to 40 ㎛. When the thickness of the outer insulating layer (111) 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. The above gas barrier layer (112) is laminated between the external insulating layer (111) and the sealant layer (113) 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. The gas barrier layer (112) 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). Meanwhile, the thickness of the gas barrier layer (112) 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 (112) satisfies the above range, the formability and gas barrier performance are excellent when forming the cup portion. The above sealant layer (113) may be a layer located on the innermost side of the outer film (110). The sealant layer (113) comes into contact with the electrolyte and electrode assembly and must completely seal the inside to block material movement between the inside and the outside, so it must have insulating properties and corrosion resistance, and must have high sealing properties for sealing with the upper and lower caps. The above sealant layer (113) 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. More specifically, the sealant layer (113) may include polypropylene, cast polypropylene (CPP), acid modified polypropylene, polypropylene-butylene-ethylene copolymer, or a combination thereof. The above sealant layer (113) may have a single-layer structure or may have a multi-layer structure including two or more layers made of different polymer materials. 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. Sealing part The above sealing surface is characterized in that the outer insulating layer (111) is sealed with the first end (110b) of the outer film (110) and the sealant layer (113) with the second end (110c) by the adhesive film (114). The adhesive film (114) can be attached to the sealant layer (113) so as to be bonded to the outer insulating layer (111) after surrounding the electrode assembly (160), and conversely, can be attached to the outer insulating layer (111) so as to be bonded to the sealant layer (113) after surrounding the electrode assembly (160). As described above, the secondary battery (100) according to one embodiment of the present invention can improve the energy density because the sealing surface is formed without a terrace portion, and can have excellent sealing durability because the adhesive film (114) is designed to satisfy the sealing index as described above. Figures 6 to 9 illustrate enlarged cross-sectional views of portion B of Figure 3. According to one embodiment of the present invention, the adhesive film (114) may have a single-layer structure of an adhesive layer (1141) as in Figure 6, or a two-layer structure including a base film (1142) and an adhesive layer (1141) disposed on the base film as in Figures 7 and 8, or a three-layer structure including a base film (1142) and adhesive layers (1141, 1143) disposed on both sides of the base film as in Figure 9, and the adhesive layer may include a rubber-based adhesive resin. Since the rubber-based adhesive resin has been described above, its description is omitted. In the case of the above Fig. 5, a single-layer adhesive film (114) is shown. After being attached to the sealant layer (113) or the external insulating layer (111) of the pouch cover (110), a release film (not shown) that may be present on the adhesive layer (1141) is removed, and then the electrode assembly (160) is wrapped with the pouch cover (110), and then the external insulating layer (111) or the sealant layer (113) can be adhered. The two-layer adhesive film (114) illustrated in FIGS. 7 and 8 may include a base film (1142) and an adhesive layer (1141). At this time, the base film (1142) may be formed by pre-attaching the adhesive film (114) to the sealant layer (113) or the outer insulating layer (111) by heat fusion, and then surrounding the electrode assembly (160). Accordingly, the base film (1142) may include, for example, at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyimide, non-stretched polypropylene, high-density polyethylene, and low-density polyethylene. Preferably, when the base film (1142) is attached to the sealant layer (113) or the outer insulating layer (111) by heat fusion, the same material as the material of the surface to which it is attached may be applied, and in this case, excellent adhesive strength may be maintained. In addition, the adhesive film (114) of the three-layer structure illustrated in FIG. 9 may have a base film (1142) positioned between adhesive layers (1141), and in this case, the rigidity of the adhesive film is secured, so there is an advantage of no risk of damage during the process. Cover absence The cover member (130) may be a member that covers the outer material opening (115) of the outer film (110), as illustrated in FIGS. 2 and 3. In order to prevent leakage of the electrolyte filling the internal space (131) of the outer film (110), the cover member (130) may seal the outer material opening (115) of the outer film (110) together with a gasket member (140) to be described later. The cover member (130) may include a first member (131) that blocks the outer opening (115) as illustrated in FIG. 2. FIG. 4 is a cross-sectional view taken along line AA of the secondary battery of FIG. 3. The first member (131) may be formed to correspond to the shape of the outer opening (115) in order to block the outer opening (115). FIG. 2 illustrates a first member (131) formed in a square shape (the shape of the outer opening). The first member (131) may be obtained from a material that is not easily permeable to moisture in order to seal the internal space (131) of the outer film (110). For example, the first member (131) may be obtained from metal or resin, or from a laminate sheet including a metal layer. The same may be true for the second member (132) described below. The cover member (130) may include a second member (132) extending from the first member (131), as illustrated in FIG. 4. The second member (132) may be formed integrally with the first member (131), or may be formed as a separate body and then joined to the first member (131). The second member (132) may be positioned facing the inner surface of the outer film (110). Conventionally, a pouch-shaped outer packaging material was manufactured by forming a cup portion on a pouch film and sealing the cup portion with another pouch film. However, the molding depth of the cup portion was limited by the material properties of the pouch film, making it difficult to form the cup portion deeply enough to increase battery capacity. Furthermore, the material and thickness of the pouch film had to be selected within certain limits. Furthermore, as the thickness of the pouch film decreased during the molding process, defects such as cracks were likely to occur in the pouch-shaped outer packaging material. In contrast, in the case of the secondary battery (100) of the present embodiment, since the outer film (110) is prepared without forming the cup portion, and the electrode assembly (160) can be inserted into the outer film (110) through the outer material opening (115), the above limitations or defects do not occur, so the battery capacity can be easily increased by increasing the size of the outer film (110), the material and thickness of the sheet (110a) can be selected relatively freely, and defects such as cracks can not easily occur. For reference, in the case where the outer film (110) is prepared by rolling or folding the sheet (110a), the sheet (110a) can be rolled or folded while the electrode assembly (160) is positioned on the upper surface of the sheet (110a) in the unfolded state, and even in this case, the outer film (110) can be prepared without forming the cup portion. In addition, the secondary battery (100) is superior not only to conventional pouch-type batteries but also to square batteries. In the case of square batteries, if the volume expansion of the electrode assembly occurs during charging and discharging, the electrode assembly may be damaged due to the square metal can that hardly experiences shape change. In contrast, in the case of the secondary battery of the present embodiment, if the volume expansion of the electrode assembly occurs during charging and discharging, the shape of the outer film may change in response, that is, the outer film may be stretched, so that damage to the electrode assembly may not occur. Absence of gasket The gasket member (140) may be a member disposed between the cover member (130) and the outer film (110), as illustrated in FIGS. 2 and 3. The gasket member (140) may be disposed between the second member (132) of the cover member (130) and the inner surface of the outer film (110), as illustrated in FIG. 4. The gasket member (140) may be formed to entirely surround the cover member (130), as illustrated in FIGS. 2 and 3. For example, the gasket member (140) may be formed in a frame shape to surround the second member (132) of the cover member (130). Alternatively, the gasket member (140) may be formed to entirely surround not only the second member (132), but also the inner sides of the first member (131) and the second member (132), i.e., the inner side of the cover member (130), as illustrated in FIG. 5. FIG. 5 is a cross-sectional view illustrating a first modified example of the gasket member (140) of the secondary battery of FIG. 3. The gasket member (140) can prevent the internal electrolyte from leaking through the space between the cover member (130) and the outer film (110). Specific structure of the cover member The cover member (130) may include an electrode terminal (134) as illustrated in FIG. 4. The electrode terminal (134) may be an electrically conductive member provided on the first member (131). The electrode terminal (134) may be a member that is exposed to the inner space (115) of the outer film (110) to be electrically connected to the electrode tabs (111) of the electrode assembly (110) and also exposed to the outside of the first member (131). An electrode terminal having an I-shaped cross-sectional shape is illustrated in FIG. 4. For example, by welding the electrode tabs (170) of the electrode assembly (160) to the inner surface of the electrode terminal (134) and electrically connecting another device (not shown) to the outer surface of the electrode terminal (134), the other device and the electrode assembly (160) may be electrically connected. The first member (131) may include an electrolyte injection hole (not shown) for injecting an electrolyte into the internal space (115) of the outer film (110). Through this, an electrolyte injection process and a post-activation degassing process can be performed. For example, when the secondary battery (100) is placed so that the first member (131) in which the electrolyte injection hole is provided faces upward, the electrolyte can be injected into the internal space (115) of the outer film (110) through the electrolyte injection hole. In the degassing process, the internal gas can be discharged through the open electrolyte injection hole. After the electrolyte injection and degassing, the electrolyte injection hole can be closed by sealing or welding. Alternatively, a valve that can be opened and closed can be installed in the electrolyte injection hole so that the electrolyte injection hole is opened only when necessary. In the past, a pouch-type outer packaging material had a storage portion for accommodating an electrode assembly and a pocket portion for accommodating gases generated during activation. After the gas in the pocket portion was discharged through a degassing process, the pocket portion was removed. This resulted in a problem in that some of the pouch-type outer packaging material was always discarded. However, the secondary battery (100) of the present embodiment can perform electrolyte injection and degassing through an electrolyte injection hole, so that such discarding of the outer packaging material may not occur. Among the cover members (130), the second member (132) may be formed along the edge of the first member (131) as illustrated in FIG. 5. In order to be firmly bonded to the outer film (110), the second member (132) may be formed along the entire edge of the first member (131), but it may also be considered to be formed along a portion of the edge. FIG. 3 illustrates an example of the second member (132) formed along the entire edge of the first member (131). The second member (132) may extend from the first member (131) in a direction facing the internal space (131) (right direction in FIG. 5). The second member (132) may be set to a length that contacts the electrode assembly (160). This may prevent the electrode assembly (160) from moving within the outer film (110). battery module According to another embodiment of the present invention, a battery module including a plurality of pouch-type secondary batteries is provided. The above battery module refers to a battery assembly (assembly) in which a certain number of pouch-type secondary batteries are bundled and placed in a frame to protect them from external shock, heat, vibration, etc. In addition, according to another embodiment of the present invention, a battery pack including a plurality of battery modules is provided, and the battery pack means a final form of a battery system mounted on an electric vehicle or the like. The above battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as power tools; electric vehicles including electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs); or power storage systems. Examples and Comparative Examples 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. Example 1 Manufacturing of exterior films 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 on the other side, thereby manufacturing an outer film having a polyethylene terephthalate / nylon / aluminum alloy film / non-stretched polypropylene structure. Here, polyethylene terephthalate and nylon are the outer insulating layer, aluminum alloy film is the gas barrier layer, and non-stretched polypropylene is the sealant layer. Manufacturing of electrode assemblies An electrode assembly was manufactured by stacking and laminating a positive electrode, a negative electrode, and a porous polyethylene separator. An electrode lead was then attached to the electrode assembly. Electrolyte injection and sealing Afterwards, the electrode assembly was wrapped with an outer film, and a polyisoprene rubber-based adhesive resin was applied to the adhesive layer of the adhesive film having a single-layer structure, and a resin having a contact angle and an electrolyte peel strength as shown in Table 1 below was applied, and the sealant layer of the outer film and the outer insulating layer were sealed using this. Then, after attaching and sealing the lower cap, an electrolyte in which LiPF6 was dissolved in a solvent (EC:EMC:DMC = 3:3:4 volume ratio) to a concentration of 1.0 M was injected, and the upper cap was attached and sealed to manufacture a secondary battery. Example 2 A pouch-type secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using a styrene-isobutylene-styrene copolymer (SIBS) as a rubber-based adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was applied. Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using polyisobutylene as a rubber-based adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was applied. Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using ethylene-propylene-diene copolymer (EPDM) as a rubber-based adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was applied. Comparative Example 1 A secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using polyacrylate as an adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was used. Comparative Example 2 A secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using polyvinyl acetate as an adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was used. Comparative Example 3 A secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using polydimethylsiloxane (PDMS) as an adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was used. Comparative Example 4 A secondary battery was manufactured in the same manner as in Example 1, except that an adhesive film using polytetrafluoroethylene (PTFE) as an adhesive resin having a contact angle and an electrolyte peel strength as described in Table 1 below was used. In Table 1 below, the contact angle and electrolyte peel strength were measured using the following method. 1) Contact angle: Using SEO's Phoenix mt, a drop of distilled water was dropped on the adhesive surface of the adhesive film at room temperature (25℃), and the angle formed by the surface and the water droplet was measured within 5 seconds. 2) Peel strength under electrolyte: For the outer films of the above examples and comparative examples, the sealant layer and the outer insulation layer were bonded with an adhesive film without an electrode assembly, and then impregnated in an electrolyte containing an organic solvent mixed with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethylene carbonate (DMC) in a volume ratio of 3:3:4 and a lithium salt of 1.0 M LiPF6 at 60°C for 24 hours, and then a T-peel peel test was performed at a speed of 300 mm / sec. Sealing index Contact angle (˚) Electrolyte peel strength (gf / 25mm) Example 13.83120460 Example 21.3390120 Example 35.45110600 Example 42.40100240 Comparative example 10.297020 Comparative example 20.08605 Comparative example 30.93107100 Comparative example 40.0091101 Experimental Example 1 The secondary batteries manufactured in the above examples and comparative examples were evaluated as follows, and the results are shown in Table 2. 1) Moisture penetration test: For the secondary batteries of the above examples and comparative examples, the moisture content was measured by measuring the HF concentration in the electrolyte inside the outer film after storing them in a chamber at a temperature of 60°C and a relative humidity of 90% for 16 weeks. 2) Electrolyte leakage test: The amount of electrolyte leakage was measured by injecting 20 g of electrolyte into the case using INFICON's ELT3000 and then measuring the amount of liquid and / or gaseous electrolyte leaking from the inside of the outer film to the outside when a vacuum atmosphere was created outside. Moisture penetration (ppm) Electrolyte leakage (g) Example 1800<0.1 Example 21,200<0.1 Example 31,000<0.1 Example 41,100<0.1 Comparative Example 12,0003 Comparative Example 24,0005 Comparative Example 33,000<1 Comparative Example 410,00018 Referring to Table 2 above, it can be confirmed that in the cases of Examples 1 to 4, the amount of moisture penetration is significantly less than that of the Comparative Examples, and there is almost no leakage of electrolyte. However, it can be confirmed that the contact angle is low and the peel strength under the electrolyte is very small, so not only the amount of moisture penetration but also the amount of electrolyte leakage is considerably large. In other words, when the sealing index is less than 1.00, even if the contact angle is large and the peel strength under the electrolyte satisfies a certain level, the amount of moisture penetration may be high, as in Comparative Example 3, and in Comparative Examples 1, 2, and 4, which are cases where it is significantly less than 1.00, it can be confirmed that not only the amount of moisture penetration but also the amount of electrolyte leakage is considerably poor. In particular, in the case of Comparative Example 4, it can be seen that the amount of moisture penetration and the amount of electrolyte leakage are considerable because the peel strength is very weak, so the sealing is not performed normally. [Explanation of symbols] 11: Pouch-type battery case 12, 13: Cup 14: Accommodation space 15: Terrace 100: Pouch-type secondary battery 110: Exterior film 110a: sheet, 110b: first end, 110c: second end 111: outer insulation layer, 112: gas barrier layer, 113: sealant layer 114: adhesive film, 1141: adhesive layer, 1142: base film 130: Cover member 131: First Absence 132: Second Absence 134: Electrode terminal 140: Gasket absence 160: Electrode assembly 170: Electrode tab
Claims
1. Electrode assembly; An outer film having an inner space for accommodating the electrode assembly and an outer material opening for communicating the inner space with the outside; and A cover member covering the outer material opening of the outer film; The above outer film has a sealing surface where the inner and outer surfaces of the outer film meet in a direction perpendicular to the opening of the outer material and are joined by an adhesive film. The above adhesive film has a sealing index (SI) of 1.00 to 6.00, as defined by the following formula 1, a secondary battery: [Formula 1] SI = PS / CA In the above formula 1, SI of the adhesive film is the sealing index, CA is a unitless number with a contact angle of the adhesive surface of the adhesive film and a unit of °, and PS is an electrolyte-based peel strength, which is obtained from a T-peel peel test at a speed of 300 mm / sec after the sealed pouch-type case is immersed in an electrolyte for 24 hours, and is a unitless number with a unit of gf / 25 mm.
2. In paragraph 1, A secondary battery having a contact angle (CA) of 80˚ or more.
3. In paragraph 1, A secondary battery having an electrolyte peel strength (PS) of 100 gf / 25 mm or more.
4. In paragraph 1, A secondary battery having a sealing index of 1.30 to 5.
50.
5. In paragraph 1, A secondary battery further comprising a gasket member disposed between the cover member and the outer film.
6. In paragraph 1, The above adhesive film contains a rubber-based adhesive resin, A secondary battery, wherein the above rubber-based adhesive resin comprises at least one selected from the group consisting of natural rubber, epoxidized natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isobutylene rubber, epoxidized styrene-butadiene-styrene rubber, styrene-isobutylene-styrene rubber, epoxidized styrene-isobutylene-styrene rubber, styrene-ethylene-alphaolefin-styrene rubber, and ethylene-propylene-diene rubber.
7. In paragraph 1, The above adhesive film, A single-layer structure with an adhesive layer; A two-layer structure comprising a substrate film and an adhesive layer disposed on the substrate film; or A three-layer structure comprising a base film and an adhesive layer disposed on both sides of the base film; A pouch-type secondary battery, wherein the adhesive layer comprises a rubber-based adhesive resin.
8. In paragraph 7, A pouch-type secondary battery, wherein the above-mentioned base film comprises at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyimide, non-stretched polypropylene, high-density polyethylene, and low-density polyethylene.
9. In paragraph 1, A pouch-type secondary battery, wherein the outer film includes a sealant layer on the inner surface and an outer insulating layer on the outer surface, and the sealant layer includes at least one selected from the group consisting of polypropylene, non-stretched polypropylene, acid-modified polypropylene, and polypropylene-butylene-ethylene copolymer.
10. In paragraph 1, A pouch-type secondary battery, wherein the outer film includes an inner sealant layer and an outer insulating layer, and the outer insulating layer includes at least one selected from the group consisting of polyethylene terephthalate and nylon.
11. In paragraph 1, The above outer film is a secondary battery having a structure in which a sealant layer, a gas barrier layer, and an outer insulating layer are sequentially laminated from the inner side.
12. A battery module comprising a plurality of secondary batteries of the first paragraph.