Pouch film laminate, pouch-type battery case, and pouch-type secondary battery

Abstract

The present invention relates to a pouch film laminate comprising a base layer, a gas barrier layer, and a sealant layer laminated in this order, in which the value of fT represented by the following [Equation 1] of the sealant layer is 0.32 to 3.1, and the surface roughness (Ra) of the sealant layer is 0.11 [mu] m to 0.75 [mu] m. [Equation 1] fT = fT2 / fT1. In [Equation 1], fT1 is the coefficient of friction of the sealant layer at T1, fT2 is the coefficient of friction of the sealant layer at T2, and T1 and T2 are different temperatures.

Description

TECHNICAL FIELD

[0001] Cross Reference to Related Applications

[0002] This application claims the benefit of Korean Patent Application No. 10-2023-0120750, filed September 11, 2023, the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0004] The present application relates to a pouch film laminate, a pouch-type battery case, and a pouch-type secondary battery. More particularly, the present application relates to a pouch film laminate, a pouch-type battery case, and a pouch-type secondary battery that have improved formability by having a coefficient of friction within a certain range regardless of temperature. BACKGROUND

[0005] Secondary batteries are used for small products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, electric bicycles, large products requiring high output such as electric vehicles or hybrid vehicles, and power storage devices for storing surplus generated power or renewable energy and backup power storage devices.

[0006] Generally, a secondary battery is manufactured by applying an electrode active material slurry to a positive electrode current collector and a negative electrode current collector to manufacture a positive electrode and a negative electrode, stacking the electrodes on both sides of a separator to form an electrode assembly having a predetermined shape, and then housing the electrode assembly in a battery case, injecting an electrolyte, and sealing.

[0007] Secondary batteries are classified into pouch and can types according to the material of the case in which the electrode assembly is housed. The pouch type houses the electrode assembly in a pouch made of a flexible polymer material. The can type houses the electrode assembly in a case made of a material such as metal or plastic.

[0008] The pouch-type battery case is manufactured by performing a press process on a flexible pouch film laminate to form a cup-shaped portion. Then, if the cup-shaped portion is formed, an electrode assembly is housed in a receiving space of the cup-shaped portion and a sealing portion is sealed to manufacture a secondary battery.

[0009] In the press process, drawing forming is performed by inserting the pouch film into a press device and applying pressure to the pouch film laminate using a punch to elongate the pouch film laminate. The pouch film laminate is generally formed as a plurality of layers in which a polymer film such as polyethylene terephthalate is laminated on one side of a gas barrier layer of a metal material and a sealant layer is laminated on the other side.

[0010] Recently, as the demand for high-capacity batteries such as electric vehicle batteries and ESS batteries increases, the demand for battery cases that can accommodate more electrode assemblies is also increasing. Accordingly, the depth of the cup portion for forming a pouch-type battery case is increasing, or a double cup forming method that increases the volume of the cup portion by forming a cup portion on each of the upper case and the lower case is being attempted.

[0011] In the manufacture of a conventional pouch film laminate, a slip agent is included in the sealant layer of the innermost layer of the pouch film or is applied to the surface of the sealant layer in order to prevent adhesion between the pouch films and to facilitate post-processing. However, there is a problem in that the slip agent penetrates into the sealant layer and disappears at high temperatures.

[0012] Accordingly, there is a need to develop a pouch film laminate that can prevent adhesion between pouch film laminates regardless of temperature and facilitate post-processing, while also preventing cracks from occurring even in the case of an increase in the depth for forming a cup portion. SUMMARY

[0013] TECHNICAL PROBLEM

[0014] The present application aims to solve the above problems and provides a pouch film laminate, a pouch-type battery case, and a pouch-type secondary battery that have excellent formability while preventing adhesion between pouch film laminates regardless of temperature and in which the coefficient of friction does not significantly change according to temperature.

[0015] The tasks of the present application are not limited to the above tasks, and other tasks not mentioned can be clearly understood by those skilled in the art from the following description.

[0016] TECHNICAL SOLUTION

[0017] [1] The present application provides a pouch film laminate including a base layer, a gas barrier layer, and a sealant layer laminated in order, wherein the sealant layer has a value of f T of 0.32 to 3.1, and a surface roughness (Ra) of the sealant layer is 0.11 μm to 0.75 μm.

[0018] [Equation 1]

[0019] f T = f T2 / f T1

[0020] In [Equation 1], f T1 is the coefficient of friction of the sealant layer at T1, f T2 is the coefficient of friction of the sealant layer at T2, and T1 and T2 are different temperatures.

[0021] [2] In the present invention according to [1], f T may be 0.33 to 3.0.

[0022] [3] In the present invention according to [1] or [2], T1may be 25°C, and T2may be any temperature between 0°C and 125°C except 25°C.

[0023] [4] In the present invention according to any one of [1] to [3], T1may be 25°C, and T2may be 60°C.

[0024] [5] In the present invention according to any one of [1] to [4], the surface roughness (Ra) of the sealant layer can be 0.16 μm to 0.55 μm.

[0025] [6] In the present invention according to any one of [1] to [5], the sealant layer can include positive projections.

[0026] [7] In the present invention according to any one of [1] to [6], the coefficient of friction of the sealant layer at 60°C can be less than or equal to 0.38.

[0027] [8] In the present invention according to any one of [1] to [7], the value of DTof the pouch film laminate represented by the following [Equation 2] can be 0.82 to 1.22.

[0028] [Equation 2]

[0029] D T = D T2,a / D T1,a

[0030] In [Equation 2], D T1,a is a forming depth in which a crack occurs when the pouch film laminate is cut into a size of 300 mm x 400 mm at T1,a and then formed to have two cup-shaped portions each having a measured width and length of 90 mm x 160 mm, D T2,a is a forming depth in which a crack occurs when the pouch film laminate is cut into a size of 300 mm x 400 mm at T2,a and then formed to have two cup-shaped portions each having a measured width and length of 90 mm x 160 mm, and T1,a and T2,a are different temperatures.

[0031] [9] In the present invention according to any one of [1] to [8], the base layer can be a laminate structure of a polyethylene terephthalate film and a nylon film.

[0032]

[10] In the present invention according to any one of [1] to [9], the thickness of the gas barrier layer can be 20 to 100 μm.

[0033]

[11] In the present invention according to any one of [1] to

[10] , the thickness of the sealant layer can be 30 to 130 μm.

[0034]

[12] The present invention provides a pouch cell case manufactured by drawing and forming the pouch film laminate according to [1].

[0035]

[13] The present invention provides a pouch-type secondary battery including the cell case according to

[12] .

[0036] Advantageous Effects

[0037] The sealant layer included in the pouch film laminate according to the present invention has a coefficient of friction within a certain range regardless of temperature, and also has a surface roughness (Ra) within a certain range, so that even in the case where a slip agent on the surface of the sealant layer penetrates into the sealant layer at high temperature, blocking in which the pouch film laminates adhere to each other is prevented, and at the same time, excellent formability is achieved. In addition, in the case of using the pouch film laminate of the present invention, the rate of poor formation caused by the storage temperature and the aging period of the pouch film laminate can be reduced, the pouch film laminate can be transported without aging after production, and since temperature control is not required, workability can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0038] The accompanying drawings attached to the present specification illustrate preferred embodiments of the present invention and together with the content of the present specification, serve to provide further understanding of the technical concept of the present invention, thus the present invention is not limited to the features described in the drawings. At the same time, the shape, size, ratio, or proportion of the elements in the drawings included in the specification can be exaggerated to emphasize a clearer explanation.

[0039] Figure 1 is a cross-sectional view of a pouch film laminate according to an embodiment of the present invention.

[0040] Figure 2 is an exploded assembly view of a secondary battery according to an embodiment of the present invention.

[0041] Figure 3 is a view showing that no pouch rupture occurred when forming a pouch after storing the pouch film laminate manufactured according to Example 1 at 60°C.

[0042] Figure 4This is a diagram showing the bag rupture that occurs during bag formation after the bag film laminate manufactured according to Comparative Example 3 is stored at 60°C. Detailed Implementation

[0043] The invention will be described in more detail below.

[0044] The words or terms used in this specification and claims should not be construed as having the meanings defined in common dictionaries. Based on the principle that the inventors may appropriately define the meanings of words or terms to best illustrate the invention, these words or terms should be interpreted as having meanings consistent with the technical concept of the invention.

[0045] In this invention, the MD direction (machine direction) refers to the length direction of the bag film laminate, and the TD direction (transverse direction) refers to the width direction of the bag film laminate.

[0046] In this invention, surface roughness (Ra) is measured using an optical measurement device (NV-2700, an optical profilometer from Nano System Co.), with a lens of type i20X and an FOV of 1.0X (FOV - 316 μm × 237 μm), and measured using WSI envelope mode. Specifically, the scanning range is 10 μm above and below, and the surface roughness is measured at 7 points in each 2D topological image (316 μm × 237 μm) measured at any point on the sample, and the average and standard deviation of the values ​​at the 5 points other than the maximum and minimum values ​​are calculated.

[0047] The inventors have conducted repeated research to solve problems arising from the penetration of slip agents into the sealant layer at high temperatures, as well as problems encountered during the manufacturing and storage of bag film laminates via a roll-to-roll process. Therefore, the inventors have discovered that excellent formability can be achieved regardless of temperature by controlling the ratio of the coefficient of friction of the sealant layer in the bag film laminate within a certain range, and simultaneously controlling the surface roughness of the sealant layer within a certain range, thus completing this invention.

[0048] The present invention will be described in detail below.

[0049] The pouch film laminate, pouch battery housing, and pouch secondary battery according to the present invention include at least one of the configurations disclosed below, and may include any combination of technically possible configurations among the following configurations.

[0050] Bag film laminate

[0051] Figure 1An embodiment of the bag film laminate according to the present invention is illustrated. In the following text, reference will be made to... Figure 1 The bag film laminate according to the present invention will be described.

[0052] Reference Figure 1 The bag film laminate 1 according to the present invention comprises a base layer 10, a gas barrier layer 20 and a sealant layer 30 laminated in sequence, wherein the sealant layer 30 is represented by the following [Equation 1] f T The value is 0.32 to 3.1, and the surface roughness (Ra) of the sealant layer 30 is 0.11 μm to 0.75 μm.

[0053] [Equation 1]

[0054] f T = f T2 / f T1

[0055] In [Equation 1], f T1 It is the coefficient of friction of the sealant layer at T1, f T2 It is the coefficient of friction of the sealant layer at T2, and T1 and T2 are different temperatures.

[0056] In the conventional manufacturing of pouch film laminates, to prevent adhesion between the film layers and facilitate post-processing, a slip agent is included in the innermost sealant layer of the film, or the slip agent is applied to the surface of the sealant layer to control the coefficient of friction. However, at high temperatures, the slip agent penetrates into the sealant layer and disappears, and the coefficient of friction of the sealant layer increases rapidly. In this case, if the coefficient of friction increases, cracks may appear in the pouch during the molding of the cup-shaped portion of the pouch battery casing, potentially preventing the increase of the molding depth of the cup-shaped portion. Furthermore, if the slip agent disappears, there is a problem of blockage caused by the pouch film laminates adhering to each other during storage.

[0057] Therefore, the inventors of this invention have repeatedly developed a bag film laminate that prevents adhesion between bag film laminates even at high temperatures, facilitates post-processing, and does not produce cracks even when the forming depth of the cup-shaped portion increases. Thus, the inventors have discovered that if the coefficient of friction of the sealant layer at different temperatures is controlled within a certain range, and the surface roughness of the sealant layer is controlled within a certain range, excellent formability can be achieved regardless of temperature, and more specifically, excellent formability can be achieved even at high temperatures.

[0058] f as expressed by the above [Equation 1] TThe value can specifically represent values ​​greater than or equal to 0.32, 0.322, 0.324, 0.326, 0.328, or 0.33, and can also represent values ​​less than or equal to 3.1, 3.09, 3.08, 3.07, 3.06, 3.05, 3.04, 3.03, 3.02, 3.01, or 3.0.

[0059] Additionally, in [Equation 1], T1 and T2 are different temperatures. Preferably, T1 can be 25°C, and T2 can be any temperature between 0°C and 125°C except 25°C. More preferably, T1 can be 25°C, and T2 can be any temperature between 40°C and 125°C. Even more preferably, T1 can be 25°C, and T2 can be any temperature between 50°C and 125°C. And even more preferably, T1 can be 25°C, and T2 can be 60°C.

[0060] If f T If the value is less than 0.32 or greater than 3.1, the following problems exist: the coefficient of friction of the sealant layer varies greatly at different temperatures, causing the formability to deteriorate with temperature, and blockage occurs due to adhesion between the bag film laminates, resulting in problems with processability. Therefore, if f T If the value meets the above range, the coefficient of friction of the sealant layer at different temperatures can be appropriately controlled, so that the formability can be excellent regardless of the temperature, and the processability can be excellent since there is no need to control the temperature.

[0061] Preferably, the sealant layer 30 is represented by the following [Equation 1-1] f 60,25 The value can be from 1.00 to 3.15, specifically from 1.5 to 3.1, more specifically from 1.80 to 3.05, and more specifically from 2.0 to 3.0.

[0062] [Equation 1-1]

[0063] f 60,25 = f 60°C / f 25°C

[0064] In [Equation 1-1], f 60°C Let f be the coefficient of friction of the sealant layer at 60°C, and f 25°C The coefficient of friction of the sealant layer at 25°C.

[0065] f TIt can be controlled in various ways, such as by controlling the amount of slip agent contained in the sealant layer, the melting point of the slip agent, the mixing ratio of the slip agent, or the surface roughness (Ra) of the sealant layer. Preferably, f T The value can be controlled within an appropriate range by controlling the surface roughness (Ra) of the sealant layer.

[0066] In addition, the surface roughness (Ra) of the sealant layer 30 is 0.11 μm to 0.75 μm, preferably 0.12 μm to 0.72 μm, more preferably 0.13 μm to 0.70 μm, even more preferably 0.14 μm to 0.65 μm, even more preferably 0.15 μm to 0.60 μm, and even more preferably 0.16 μm to 0.55 μm.

[0067] When the roll-to-roll process is applied to the mass production and high-speed manufacturing of bag film laminates, the bag film laminates are stored in a roll shape in which a cuboid is wound in one direction during the stage after the bag film laminates are produced and before the bag-shaped shell is formed. In this case, the sealant layer 30 located at the bottom part of the bag film laminate is in a roll shape that contacts the base layer 10 due to the winding shape.

[0068] In this case, if the surface roughness (Ra) of the sealant layer 30 is less than 0.11 μm, the contact area with the substrate layer may increase due to the lower surface roughness. Consequently, the slip agent on the surface of the sealant layer 30 may transfer to the surface of the substrate layer, further reducing the amount of slip agent on the surface of the sealant layer 30. Furthermore, if stored at high temperatures and at room temperature, the solubility of the slip agent on the surface of the sealant layer 30 may increase, causing a significant amount of slip agent to transfer to the surface of the substrate layer. This increases the coefficient of friction at room temperature, and this coefficient of friction may vary considerably with temperature, resulting in increased fluctuations in the coefficient of friction with temperature changes. In this case, the maximum forming depth may decrease with temperature changes, and the maximum forming depth may also decrease depending on the storage and / or transportation method of the bag film laminate.

[0069] Furthermore, if the surface roughness (Ra) of the sealant layer 30 is greater than 0.75 μm, the contact area with the base layer may be reduced due to the higher surface roughness, and therefore, the amount of lubricant transferred from the surface of the sealant layer 30 to the surface of the base layer 10 may be reduced. Simultaneously, if a bag-shaped shell is formed, the sealant layer 30 may contact one end of the jig, and the base layer 10 may contact the portion opposite to said one end. However, as mentioned above, the reduced amount of lubricant transferred to the surface of the base layer 10 may increase the coefficient of friction of the base layer 10, and therefore, may result in a reduction in the maximum forming depth. Additionally, if the surface roughness is too high, the coefficient of friction may increase due to the anchoring effect, potentially reducing formability. In this case, the maximum forming depth may decrease with temperature variations, and there is a disadvantage that the maximum forming depth may decrease depending on the storage and / or transportation method of the bag film laminate.

[0070] Therefore, if the above range is met, the two surfaces will not adhere, and the adhesion points will not repeatedly form and break during the sliding process. This ensures a suitable coefficient of friction, thereby achieving excellent formability and preventing excessive unevenness, thus maintaining formability regardless of temperature. If a roll-to-roll process is performed, the amount of slip agent present on the surfaces of the sealant layer 30 and the base layer 10 can be appropriately controlled to achieve excellent formability while also providing excellent insulation and sealing properties.

[0071] The sealant layer 30 may include positive or negative protrusions, and preferably, it may be a positive protrusion. In the case of a positive protrusion, particles with different average particle diameters may be added to the surface layer of the sealant layer to form the positive protrusion, so that the processability can be excellent because the surface roughness can be easily controlled.

[0072] The coefficient of friction of the sealant layer 30 at 25°C can be less than or equal to 0.20, preferably 0.01 to 0.15, more preferably 0.01 to 0.13, even more preferably 0.01 to 0.12, and even more preferably 0.02 to 0.11. If this range is met, the coefficient of friction of the sealant layer is low enough even at room temperature to ensure excellent formability and prevent clogging caused by adhesion between the bag film laminates. Furthermore, the coefficient of friction of the sealant layer does not change significantly with temperature, resulting in excellent formability and processability.

[0073] The coefficient of friction of the sealant layer 30 at 60°C can be less than or equal to 0.38, preferably 0.01 to 0.35, more preferably 0.05 to 0.33, and even more preferably 0.05 to 0.30. If this range is met, the coefficient of friction of the sealant layer is sufficiently low even at high temperatures, thus ensuring excellent formability and preventing clogging caused by adhesion between the bag film laminates. Furthermore, the coefficient of friction of the sealant layer does not change significantly with temperature, resulting in excellent formability and processability.

[0074] The sealant layer 30 may contain a slip agent. The slip agent can be any substance that imparts smoothness and is not particularly limited, but may be, for example, erucamide. The presence of a slip agent can prevent whitening in the sealant layer and can prevent contamination during the molding process.

[0075] The sealant layer 30 may not include a slip agent layer formed by applying a slip agent. Typically, a slip agent application process can be added to improve formability or maintain smoothness; however, since the sealant layer according to the invention exhibits excellent smoothness and formability even without a slip agent layer, it may not be necessary. Because there is no additional slip agent application process, processability is improved and contamination during the molding process can be prevented.

[0076] Meanwhile, the D of the bag film laminate is represented by the following [Equation 2]. T The value can be from 0.82 to 1.22, preferably from 0.85 to 1.2, more preferably from 0.9 to 1.1, and even more preferably from 0.94 to 1.06.

[0077] [Equation 2]

[0078] D T = D T2,a / D T1,a

[0079] In [Equation 2], D T1,a The forming depth D is the depth at which cracks occur when the bag film laminate is cut into 300 mm × 400 mm dimensions under T1,a and then formed into two cup-shaped portions, each measuring 90 mm × 160 mm in width and length. T2,a The forming depth of the crack occurs when the bag film laminate is cut into 300 mm × 400 mm dimensions at T2,a and then formed into two cup-shaped portions with a width and length of 90 mm × 160 mm, respectively, and T1,a and T2,a are different temperatures.

[0080] In this case, T1,a can be 25°C, and T2,a can be any temperature between 0°C and 125°C except 25°C. More preferably, T1,a can be 25°C, and T2,a can be any temperature between 40°C and 125°C. Even more preferably, T1,a can be 25°C, and T2,a can be any temperature between 50°C and 125°C. And even more preferably, T1,a can be 25°C, and T2,a can be 60°C.

[0081] In the following text, each layer of the bag film laminate according to the present invention will be described in detail.

[0082] (Basal layer)

[0083] The base layer 10 is disposed on the outermost layer of the battery casing to protect the electrode assembly from external impacts and to electrically insulate it.

[0084] According to an embodiment, the substrate layer 10 may have a laminated structure of a polyethylene terephthalate (PET) film and a nylon film. In this case, it is preferable that the nylon film is disposed on the side of the gas barrier layer 20, i.e., the inner side, and the polyethylene terephthalate film is disposed on the surface side of the battery casing.

[0085] Polyethylene terephthalate (PET) possesses excellent durability and electrical insulation properties; therefore, placing a PET film on the surface side results in superior durability and insulation. However, in the case of PET film, due to its weak adhesion to the aluminum alloy film constituting the gas barrier layer 20 and its different tensile characteristics, placing the PET film on the gas barrier layer side may cause the substrate layer and gas barrier layer to separate during the molding process, and the gas barrier layer may not be stretched uniformly, potentially leading to deterioration in formability. Conversely, since nylon film has similar tensile characteristics to the aluminum alloy film constituting the gas barrier layer 20, placing the nylon film between the polyethylene terephthalate and the gas barrier layer can improve formability.

[0086] The thickness of the polyethylene terephthalate (PET) film can be from 5 μm to 20 μm, preferably from 5 μm to 15 μm, more preferably from 7 μm to 15 μm, and the thickness of the nylon film can be from 20 μm to 40 μm, preferably from 20 μm to 35 μm, more preferably from 25 μm to 35 μm. If the thicknesses of the PET film and the nylon film meet the above ranges, the formability and rigidity after forming are excellent.

[0087] (Gas barrier layer)

[0088] The gas barrier layer 20 is laminated between the base layer 10 and the sealant layer 30 to ensure the mechanical strength of the bag, prevent gas or moisture from entering or leaving the secondary battery from the outside, and prevent electrolyte from leaking from the inside of the bag-type battery casing.

[0089] The gas barrier layer 20 can be formed of a metal. For example, the gas barrier layer can be a thin film of one or more metals selected from the group consisting of aluminum (Al), copper (Cu), stainless steel (SUS), nickel (Ni), titanium (Ti), and Invar, but is not limited thereto.

[0090] According to an embodiment of the present invention, the gas barrier layer 20 can be formed of an aluminum alloy thin film. Using an aluminum alloy thin film to form the gas barrier layer 20 ensures a higher-than-predetermined mechanical strength while maintaining a lighter weight, and also ensures complementary properties to the electrochemical characteristics of the electrode assembly and electrolyte, as well as heat dissipation. The aluminum alloy thin film can contain elements other than aluminum (Al). For example, the aluminum alloy thin film can contain one or more elements selected from the group consisting of iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0091] In another embodiment, the gas barrier layer 20 may be formed of a stainless steel film. Specifically, the gas barrier layer 20 may be manufactured by shaping and / or processing the stainless steel film. The gas barrier layer 20 formed of stainless steel has a relatively low thermal conductivity, thereby effectively preventing or delaying heat diffusion to other cells during thermal runaway, and the gas barrier layer 20 has relatively high toughness, thereby suppressing pouch rupture during use of the pouch cell. Stainless steel may contain one or more elements other than iron (Fe), such as copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0092] The thickness of the gas barrier layer 20 can be from 20 μm to 100 μm, preferably from 30 μm to 90 μm, and more preferably from 40 μm to 85 μm. Even if the sealing temperature increases and heat may be transferred to the sealant layer, the present invention will not cause the problem of substrate deformation, so that when forming the cup-shaped portion, the formability and gas shielding performance can be improved by using a gas barrier layer that is thicker than a conventional gas barrier layer.

[0093] (Sealant layer)

[0094] The sealant layer 30 is used to completely seal the interior of the pouch cell housing by thermal bonding at the sealing portions during the sealing of the pouch cell housing containing the electrode assemblies. For this purpose, the sealant layer 30 can be formed of a material with excellent thermal bonding strength.

[0095] The sealant layer 30 can be formed of a material with insulating, corrosion-resistant, and sealing properties. Specifically, since the sealant layer 30 is in direct contact with the electrode components and / or electrolyte inside the pouch cell housing, it can be formed of a material with insulating and corrosion-resistant properties. Furthermore, since the sealant layer 30 needs to completely isolate the interior of the pouch cell housing and prevent material movement between the interior and exterior, it can be formed of a material with high sealing properties (e.g., excellent thermal bonding strength). To ensure such insulating, corrosion-resistant, and sealing properties, the sealant layer 30 can be formed of a polymer material.

[0096] The sealant layer 30 may be made of one or more materials selected from the group consisting of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, nylon, polyester, poly(terephthalamide), polyarylate, and polytetrafluoroethylene, and preferably may be formed from polyolefin resins, such as polypropylene (PP) and / or polyethylene (PE). In this case, polypropylene may include cast polypropylene (CPP), acid-modified polypropylene (PPa), polypropylene-ethylene copolymer, and / or polypropylene-butene-ethylene terpolymer.

[0097] The thickness of the sealant layer 30 can be from 30 μm to 130 μm, preferably from 40 μm to 120 μm, and more preferably from 60 μm to 100 μm. If the thickness of the sealant layer meets the above range, it has the effect of ensuring the formability of the bag film laminate while ensuring the sealing strength of the sealed portion.

[0098] Meanwhile, the sealant layer 30 according to the present invention can have a composite film structure in which two or more materials are respectively formed in each layer. For example, the sealant layer 30 can have a multilayer structure. An adhesive layer and / or a surface layer can be provided between the layers of the sealant layer 30 having a composite film structure. The adhesive layer and / or the surface layer can be thermally adhesive and thus can play a role in facilitating the adhesion between the layers of the sealant layer 30. For example, the adhesive layer and / or the surface layer can contain a polypropylene-based resin, but is not limited thereto. In addition, the adhesive layer and / or the surface layer can be provided between the sealant layer 30 and the gas barrier layer 20.

[0099] As described above, the bag film laminate of the present invention can be manufactured using methods known in the art for manufacturing bag film laminates. For example, the bag film laminate of the present invention can be manufactured by attaching the base layer 10 to the upper surface of the gas barrier layer 20 by means of an adhesive and forming the sealant layer 30 on the lower surface of the gas barrier layer 20 by means of co-extrusion or an adhesive layer, and can be manufactured by methods such as dry lamination and sandwich lamination. However, the manufacturing method of the bag film laminate is not limited to these methods.

[0100] The total thickness of the pouch film laminate according to the present invention can be from 120 μm to 300 μm, specifically from 130 μm to 280 μm, and more preferably from 140 μm to 250 μm. If the thickness of the pouch film laminate meets the above range, the forming depth can be increased, while minimizing the reduction in battery housing space and the deterioration of sealing durability caused by the increase in the thickness of the pouch laminate.

[0101] pouch-type secondary batteries

[0102] Next, the pouch-type secondary battery according to the present invention will be described.

[0103] Figure 2 This is an exploded assembly diagram of the pouch-type secondary battery 200 according to the present invention.

[0104] like Figure 2 As shown, the pouch-type secondary battery 200 according to the present invention may include a pouch-type battery housing 210 manufactured by forming the aforementioned pouch film laminate, and an electrode assembly 260 housed in the pouch-type battery housing 210. Specifically, the pouch-type secondary battery 200 of the present invention may include a pouch-type battery housing 210, an electrode assembly 260, electrode leads 280, an insulating portion 290, and an electrolyte (not shown).

[0105] In the following text, reference will be made to Figure 2 The various configurations of the pouch-type secondary battery of the present invention will be described in more detail.

[0106] (Pouch-type battery casing)

[0107] The pouch-type battery housing 210 can be manufactured by forming the pouch film laminate of the present invention mentioned above. The pouch-type battery housing 210 can internally house the electrode assembly 260. Since the detailed configuration and characteristics of the pouch film laminate are the same as those described above, a detailed description thereof will be omitted.

[0108] The pouch film laminate can be formed by drawing and stretching using a punch or the like to manufacture the pouch-type battery housing 210. Therefore, the pouch-type battery housing 210 may include a cup-shaped portion 222 and a receiving portion 224. The receiving portion 224 is a place for accommodating electrode components and may refer to a receiving space formed in the form of a recess inside the cup-shaped portion 222 when the cup-shaped portion 222 is formed.

[0109] According to embodiments of the present invention, such as Figure 3 As shown, the pouch-type battery housing 210 may include a first housing 220 and a second housing 230. The first housing 220 includes a receiving portion 224 for receiving an electrode assembly 260, and the second housing 230 can cover the receiving portion 224 from above, preventing the electrode assembly 260 from falling out of the battery housing 210. Figure 3 As shown, the first housing 220 and the second housing 230 can be manufactured in a manner that connects them to each other with one side, but are not limited thereto, and the first housing 220 and the second housing 230 can be manufactured in various ways, such as by manufacturing them separately from each other.

[0110] According to another embodiment of the invention, if cup-shaped portions are formed in the bag film laminate, two symmetrical cup-shaped portions 222 and 232 can be drawn and formed adjacent to each other in one bag film laminate. In this case, as Figure 3 As shown, cup-shaped portions 222 and 232 can be formed in each of the first housing 220 and the second housing 230. After the electrode assembly 260 is accommodated in the receiving portion 224 provided in the cup-shaped portion 222 of the first housing 220, the bridging portion 240 formed between the two cup-shaped portions 222 and 232 can be folded so that the two cup-shaped portions 222 and 232 face each other. In this case, the cup-shaped portion 232 of the second housing 230 can accommodate the electrode assembly 260 from above. Therefore, since the two cup-shaped portions 222 and 232 accommodate one electrode assembly 260, an electrode assembly 260 with a greater thickness can be accommodated compared to the case where only one cup-shaped portion 222 is provided. In addition, since one corner of the secondary battery 200 is formed by folding the pouch-type battery housing 210, the number of corners to be sealed during the subsequent sealing process can be reduced. Therefore, the processing speed of the pouch-type secondary battery 200 can be improved, and the number of sealing processes can be reduced.

[0111] The pouch-type battery housing 210 can be sealed with the electrode assembly 260 housed such that a portion of the electrode leads 280, i.e., the terminal portion, described later, is exposed. Specifically, if the electrode leads 280 are connected to the electrode tabs 270 of the electrode assembly 260 and an insulating portion 290 is formed on a portion of the electrode leads 280, the electrode assembly 260 is housed in a receiving portion 224 provided in the cup-shaped portion 222 of the first housing 220, and the second housing 230 can cover the receiving portion 224 from above. Electrolyte is then injected into the interior of the receiving portion 224, and the sealing portions 250 formed on the edges of the first housing 220 and the second housing 230 can be sealed.

[0112] The sealing portion 250 serves to seal the receiving portion 224. Specifically, the sealing portion 250 can seal the receiving portion 224 while being formed along its edge. The temperature for sealing the sealing portion 250 can be from 180°C to 250°C, specifically from 200°C to 250°C, and more specifically from 210°C to 240°C. If the sealing temperature meets the above-mentioned range, the pouch-type battery housing 210 can ensure sufficient sealing strength through thermal bonding.

[0113] (Electrode assembly)

[0114] The electrode assembly 260 can be inserted into the pouch battery housing 210 and sealed through the pouch battery housing 210 after electrolyte is injected.

[0115] Electrode assembly 260 can be formed by sequentially stacking a positive electrode, a spacer, and a negative electrode. Specifically, electrode assembly 260 may include two types of electrodes—a positive electrode and a negative electrode—and spacers inserted between the electrodes to insulate them from each other.

[0116] The positive and negative electrodes can 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 mesh containing aluminum and copper. The slurry can be formed by stirring the granular active material, auxiliary conductor, binder, and conductive material while adding a solvent. The solvent can be removed in a subsequent process.

[0117] An electrode assembly 260 of a predetermined shape can be manufactured by applying a slurry containing electrode active materials, binders, and / or conductive materials to a positive electrode current collector and a negative electrode current collector to manufacture positive and negative electrodes, and then laminating them onto two sides of a separator. The type of electrode assembly 260 may include, but is not limited to, stacked, wound, stacked, and folded types.

[0118] Electrode assembly 260 may include electrode tabs 270.

[0119] Electrode contacts 270 are respectively connected to the positive and negative electrodes of the electrode assembly 260, and protrude outward from the electrode assembly 260 to serve as a path for electrons to move between the interior and exterior of the electrode assembly 260. The electrode current collector included in the electrode assembly 260 can be composed of a portion coated with an electrode active material and a terminal portion without an electrode active material, i.e., an uncoated portion. Electrode contacts 270 can be formed by cutting the uncoated portion or by connecting individual conductive members to the uncoated portion using methods such as ultrasonic welding. Figure 2 As shown, electrode tab 270 can protrude from electrode assembly 260 in different directions, but is not limited thereto, and electrode tab 270 can be formed to protrude in different directions, such as protruding parallel to each other from one side in the same direction.

[0120] (Electrode leads)

[0121] Electrode lead 280 can supply power to the external environment of secondary battery 200. Electrode lead 280 can be connected to electrode contacts 270 of electrode assembly 260 by spot welding or the like.

[0122] Electrode leads 280 can be connected to electrode assemblies 260 and can protrude to the outside of pouch cell housing 210 via sealing portions 250. Specifically, one end of electrode lead 280 is connected to electrode assembly 260, particularly to electrode tabs 270, and the other end of electrode lead 280 can protrude to the outside of pouch cell housing 210.

[0123] Electrode leads 280 may include a positive lead 282 and a negative lead 284. One end of the positive lead 282 is connected to the positive terminal 272 and extends in the direction in which the positive terminal 272 protrudes, and one end of the negative lead 284 is connected to the negative terminal 274 and extends in the direction in which the negative terminal 274 protrudes. The other ends of both the positive lead 282 and the negative lead 284 may protrude to the outside of the battery housing 210. Therefore, the power generated inside the electrode assembly 260 can be supplied to the outside. Furthermore, since the positive terminal 272 and the negative terminal 274 are formed to protrude in different directions, the positive lead 282 and the negative lead 284 may also extend in different directions respectively. The positive lead 282 and the negative lead 284 may be made of different materials. In other words, the positive electrode lead 282 can be made of the same aluminum (Al) material as the positive electrode current collector, and the negative electrode lead 284 can be made of the same copper (Cu) material as the negative electrode current collector, or of copper material coated with nickel (Ni). The portion of the electrode lead 280 protruding outside the battery casing 210 can be a terminal portion and can be electrically connected to an external terminal.

[0124] (Insulation part)

[0125] The insulating portion 290 prevents the electricity generated from the electrode assembly 260 from flowing through the electrode lead 280 to the battery housing 210 and maintains the seal of the battery housing 210. For this purpose, the insulating portion 290 can be formed of a non-conductive material that does not conduct electricity well. Typically, the insulating portion 290 is made of an insulating tape or film that is easy to attach to the electrode lead 280 and has a relatively small thickness, but is not limited thereto, and any material that can insulate the electrode lead 280 can be used.

[0126] The insulating portion 290 can be positioned to surround the outer surface of the electrode lead 280. Specifically, at least a portion of the electrode lead 280 can be surrounded by the insulating portion 290. In this case, the insulating portion 290 can be positioned between the electrode lead 280 and the pouch battery housing 210. The insulating portion 290 can be positioned within a sealing portion 250 formed by the thermal fusion of the first housing 220 and the second housing 230 of the pouch battery housing 210, and the electrode lead 280 can be attached to the battery housing 210.

[0127] (electrolytes)

[0128] The pouch-type secondary battery 200 according to the invention may further include an electrolyte (not shown) injected inside the pouch-type battery casing 210. The electrolyte is used to move lithium ions generated by the electrochemical reaction of the electrodes during charging / discharging of the secondary battery 200, and may include a non-aqueous organic electrolyte as a mixture of lithium salt and organic solvent, or a polymer electrolyte. Furthermore, the electrolyte may include a sulfide-type, oxide-type, or polymer-type solid electrolyte, and such solid electrolyte may have flexibility that is easily deformed by external force.

[0129] The invention will be described in more detail below with reference to specific examples. However, these examples are merely illustrative and are not intended to limit the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope and concept of this disclosure, and such changes and modifications naturally fall within the scope of the appended claims.

[0130] Examples and Comparison Examples

[0131] Example 1: Manufacturing of bag film laminates

[0132] A sealant layer is manufactured by adding polypropylene (PP) particles with a diameter of 10 μm to the surface of a polypropylene (PP) film with a width of 400 mm, a length of 50 m, and a thickness of 80 μm to create surface roughness.

[0133] Subsequently, a second adhesive film, a 15 μm thick nylon film, a first adhesive film, and a 12 μm thick polyethylene terephthalate (PET) film are sequentially laminated onto one side of a 40 μm thick aluminum alloy film, and a manufactured sealant layer is sequentially laminated onto the other side of the aluminum alloy film. Thus, a bag film laminate with the structure of sequentially laminated sealant layer / aluminum alloy film / second adhesive film / nylon film / first adhesive film / PET film is manufactured.

[0134] Example 2: Manufacturing of bag film laminates

[0135] Except that the sealant layer is manufactured by adding polypropylene (PP) particles with a particle diameter of 15 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0136] Example 3: Manufacturing of bag film laminates

[0137] Except that the sealant layer is manufactured by adding polypropylene (PP) particles with a particle diameter of 20 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0138] Example 4: Manufacturing of bag film laminates

[0139] Except that the sealant layer is manufactured by adding polypropylene (PP) particles with a particle diameter of 25 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0140] Comparative Example 1: Manufacturing of Bag Film Laminates

[0141] Except that the sealant layer is manufactured by adding Si particles with a diameter of 1 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0142] Comparative Example 2: Manufacturing of Bag Film Laminates

[0143] Except that the sealant layer is manufactured by adding Si particles with a diameter of 3 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0144] Comparative Example 3: Manufacturing of Bag Film Laminates

[0145] Except that the sealant layer is manufactured by adding Si particles with a diameter of 5 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0146] Comparative Example 4: Manufacturing of Bag Film Laminates

[0147] Except that the sealant layer is manufactured by adding Si particles with a diameter of 50 μm to the surface layer to form a surface roughness, the bag film laminate is manufactured in the same manner as in Example 1.

[0148] Experimental Example 1: Measurement of Surface Roughness

[0149] The surface roughness of the sealant layer in each of the bag film laminates manufactured according to Examples 1 to 4 and Comparative Examples 1 to 4 was measured using an optical measuring device (NV-2700, optical profilometer, Nano System Co.).

[0150] The measured surface roughness (Ra) is listed in Table 1 below.

[0151] [Table 1]

[0152]

[0153] Experimental Example 2: Measurement of the coefficient of friction based on temperature

[0154] Each of the bag film laminates manufactured according to Examples 1 to 4 and Comparative Examples 1 to 4 was stored at 25°C and 60°C for 6 hours, respectively, and the coefficient of friction was subsequently measured.

[0155] As a method for measuring the coefficient of friction, a sled metal with dimensions of 130 mm (MD direction) × 65 mm (TD direction) and a weight of 200 g is brought into contact with the sealant layer of a bag film laminate with dimensions of 500 mm (MD direction) × 400 mm (TD direction) and the measurement is performed.

[0156] In detail, the slider metal was moved 100 mm over the sealant layer at a speed of 100 mm / min, and the coefficient of friction was measured by averaging the kinetic friction coefficients obtained from five measurements over a section of 20 mm to 80 mm.

[0157] The coefficients of friction measured for bag film laminates stored at 25°C and 60°C for 6 hours are shown in Table 2 below.

[0158] [Table 2]

[0159]

[0160] As described in [Table 2] above, it can be seen that the ratio of the coefficient of friction at 60°C to the coefficient of friction at 25°C in Comparative Examples 1 to 4, where the surface roughness of the sealant layer is formed to be too low or too high, is higher than that in Examples 1 to 4.

[0161] Experimental Example 3: Evaluation of the formability of bag film laminates based on temperature

[0162] Each of the bag film laminates manufactured according to Examples 1 to 4 and Comparative Examples 1 to 4 was stored at 25°C and 60°C for 6 hours, respectively, and the formability of the bag film laminates was subsequently evaluated.

[0163] As a method for evaluating the formability of the bag film laminate, each bag film laminate is cut into identical dimensions of 300 mm (MD direction) × 400 mm (TD direction). The forming depth in a battery casing forming apparatus having two forming portions with dimensions of 90 mm (MD direction) × 160 mm (TD direction) is then varied, and the forming depth at which cracks occur is recorded. Here, the punch and forming portion of the battery casing forming apparatus are chamfered at corners and edges. The punch has a curvature of 2 mm at the corners and 0.5 mm at the edges, while the forming portion has a curvature of 2.0 mm at the corners and 1 mm at the edges. Furthermore, the gap between the punch and the forming portion is 0.5 mm.

[0164] The measured forming depths of the bag film laminates stored at 25°C and 60°C for 6 hours are shown in Table 3 below.

[0165] [Table 3]

[0166]

[0167] As described in [Table 3] above, in the cases of Examples 1 to 4, unlike Comparative Examples 1 to 4, the forming depth of the cup portion did not change significantly with temperature, and it can be found that even when using bag film laminates stored at high temperatures, excellent forming depth is exhibited.

[0168] Explanation of reference numerals in the attached figures

[0169] 1: Bag film laminate

[0170] 10: Grassroots

[0171] 20: Gas barrier layer

[0172] 30: Sealant layer

[0173] 200: Pouch-type secondary battery

[0174] 210: Bag-shaped shell

[0175] 220: First shell

[0176] 222: Cup-shaped part

[0177] 224: Acceptance Section

[0178] 230: Second shell

[0179] 232: Cup-shaped part

[0180] 240: Bridging section

[0181] 250: Sealing part

[0182] 260: Electrode assembly

[0183] 270: Electrode contacts

[0184] 272: Positive electrode connector

[0185] 274: Negative electrode connector

[0186] 280: Electrode lead

[0187] 282: Positive lead

[0188] 284: Negative lead

[0189] 290: Insulation part

Claims

1. A bag film laminate, the bag film laminate comprising a base layer, a gas barrier layer, and a sealant layer laminated in sequence. in, The sealant layer is represented by the following [Equation 1] f T The value ranges from 0.32 to 3.1, and The surface roughness (Ra) of the sealant layer is from 0.11 μm to 0.75 μm. [Equation 1] f T = f T2 / f T1 In [Equation 1], f T1 f is the coefficient of friction of the sealant layer at T1. T2 The coefficient of friction of the sealant layer at T2, where T1 and T2 are different temperatures.

2. The bag film laminate according to claim 1, wherein, f T The value ranges from 0.33 to 3.

0.

3. The bag film laminate according to claim 1, wherein, T1 is 25°C, and T2 is any temperature between 0°C and 125°C except 25°C.

4. The bag film laminate according to claim 1, wherein, T1 is 25°C and T2 is 60°C.

5. The bag film laminate according to claim 1, wherein, The surface roughness (Ra) of the sealant layer is from 0.16 μm to 0.55 μm.

6. The bag film laminate according to claim 1, wherein, The sealant layer includes positive protrusions.

7. The bag film laminate according to claim 1, wherein, The coefficient of friction of the sealant layer at 60°C is less than or equal to 0.

38.

8. The bag film laminate according to claim 1, wherein, The D of the bag film laminate is represented by the following [Equation 2]. T Values ​​range from 0.82 to 1.22: [Equation 2] D T = D T2,a / D T1,a In [Equation 2], D T1,a The forming depth of the crack is determined when the bag film laminate is cut into 300 mm × 400 mm dimensions under T1,a, and then the bag film laminate is formed into two cup-shaped portions, each with a measured width and length of 90 mm × 160 mm. T2,a The forming depth at which cracks occur is determined when the bag film laminate is cut into 300 mm × 400 mm dimensions at T2,a and then the bag film laminate is formed into two cup-shaped portions each having a measured width and length of 90 mm × 160 mm, and T1,a and T2,a are different temperatures.

9. The bag film laminate according to claim 1, wherein, The base layer is a laminated structure of polyethylene terephthalate film and nylon film.

10. The bag film laminate according to claim 1, wherein, The thickness of the gas barrier layer is 20 µm to 100 µm.

11. The bag film laminate according to claim 1, wherein, The thickness of the sealant layer is 30 µm to 130 µm.

12. A pouch-shaped battery housing, said pouch-shaped battery housing being manufactured by stretching and forming the pouch film laminate according to claim 1.

13. A pouch-type secondary battery, the pouch-type secondary battery comprising the battery casing according to claim 12.

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