Adhesive film and pouch-type secondary battery comprising same

Abstract

The present invention relates to an adhesive film comprising: an external insulating layer; and a pressure-sensitive adhesive layer disposed on one surface of the external insulating layer, wherein the pressure-sensitive adhesive layer includes a thermosetting resin, the adhesive film satisfies at least one of an adhesive force of 100 gf / 25 mm or more with respect to a stainless steel substrate and an adhesive force of 200 gf / 25 mm or more with respect to a polyester-based resin substrate, and the adhesive force is measured by pressing a surface of the pressure-sensitive adhesive layer opposite to the surface in contact with the external insulating layer onto the stainless steel substrate or the polyester-based resin substrate using a 2 kg roller, and then peeling the adhesive film at 140°C, at a peeling speed of 300 mm / min and a peeling angle of 180°.

Description

Adhesive film and pouch-type secondary battery containing the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0068918, filed May 27, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to an adhesive film and a pouch-type secondary battery including the same, and more particularly, to an adhesive film that ensures heat resistance during the folding process of a battery case of a pouch-type secondary battery, and a pouch-type secondary battery including the same.

[0005]

[0006] With the recent rapid expansion of electric vehicles (EVs), demand for high-energy-density lithium secondary batteries is increasing. Consequently, development of pouch-type battery cases that are lightweight and space-efficient is actively underway.

[0007] Pouch-type battery cases are manufactured by forming a cup portion through press processing on a flexible pouch film, housing an electrode assembly within the cup portion, and sealing the perimeter of the cup portion. However, the sealing portion, which is the perimeter of the sealed cup portion, protrudes more than other parts of the case, which can reduce energy density. In addition, the sealing at the ends of the seal portion may weaken, or the metal barrier layer within the pouch film may be exposed, resulting in reduced insulation. To address these issues, a folding method is applied to the seal portion.

[0008] Methods for folding the sealing portion include single-side folding (SSF), in which the end of the sealing portion is folded 90° toward the cup portion; wing folding (WF), in which the end of the sealing portion is folded 180° toward the cup portion; and double-side folding (DSF), in which the end of the sealing portion is folded 270° toward the cup portion. Among these, single-side folding and double-side folding have been mainly used in the past, and by wrapping the sealing portion and cup portion that are in close contact with each other using the above methods, the folding is fixed and the end of the sealing portion is protected.

[0009] However, in the case of single-side folding and double-side folding, the sealing part can be relatively more damaged than the wing folding, so there are increasing attempts to apply wing folding rather than the existing single-side folding and double-side folding. However, unlike single-side folding and double-side folding, one side of the sealing part of wing folding does not come into close contact with the cup part, so it is impossible to fix it with an adhesive film after folding. Therefore, in the case of wing folding, a method is used in which an adhesive film is attached to the end of the sealing part before folding, then folded 180°, and heat is applied to the area to fix the folding.

[0010] However, in the case of conventional single-side folding and double-side folding, the process of applying heat to the adhesive film during fixing is unnecessary, so the adhesive film previously applied to single-side folding and double-side folding has low durability against high-temperature environments, making it difficult to apply it as is to the wing folding method.

[0011]

[0012] The present invention is intended to solve the above problems, and to provide an adhesive film having excellent heat resistance in a high-temperature environment and preventing detachment, and a pouch-type secondary battery including the same.

[0013]

[0014] [1] The present invention provides an adhesive film comprising an outer insulating layer; and an adhesive layer disposed on one surface of the outer insulating layer; wherein the adhesive layer comprises a thermosetting resin, and the adhesive film satisfies at least one of an adhesive strength of 100 gf / 25 mm or more to a stainless steel substrate and an adhesive strength of 200 gf / 25 mm or more to a polyester resin substrate, and the adhesive strength is an adhesive strength obtained when the opposite surface of the adhesive layer in contact with the outer insulating layer is pressed against a stainless steel substrate or a polyester resin substrate using a 2 kg roller, and then the adhesive film is peeled at a peeling speed of 300 mm / min and a peeling angle of 180° at 140°C.

[0015] [2] The present invention provides an adhesive film in the above [1], wherein the stainless steel substrate is a SUS304 substrate.

[0016] [3] The present invention provides an adhesive film according to [1] or [2], wherein the thermosetting resin is a silicone resin, an epoxy resin, or a combination thereof.

[0017] [4] The present invention provides an adhesive film, wherein the adhesive layer includes a curing agent in at least one of the above [1] to [3].

[0018] [5] The present invention provides an adhesive film in the above [4], wherein the thermosetting resin is a silicone resin and the curing agent includes a silicone-hydride group (Si-H group).

[0019] [6] The present invention provides an adhesive film according to the above [4], wherein the thermosetting resin is an epoxy resin and the curing agent is an amine-based curing agent.

[0020] [7] The present invention provides an adhesive film, wherein in at least one of the above [1] to [6], the adhesive layer includes an adhesive-providing resin.

[0021] [8] The present invention provides an adhesive film, wherein, in the above [7], the adhesive-imparting resin includes at least one selected from the group consisting of a rosin-based resin, a terpene-based resin, a hydrocarbon-based resin, a hydrogenated hydrocarbon-based resin, a styrene-based resin, a phenol-based resin, and a xylene-based resin.

[0022] [9] The present invention provides an adhesive film, wherein in at least one of the above [1] to [8], the stainless steel substrate is a SUS304 substrate.

[0023]

[0010] The present invention provides an adhesive film in which, in at least one of the above [1] to [9], the polyester resin substrate is a polyethylene terephthalate (PET) substrate.

[0024]

[0011] The present invention provides an adhesive film, wherein, in at least one of the above [1] to

[0010] , the thermosetting resin is included in an amount of 10% by weight to 99% by weight based on the total weight of the adhesive layer.

[0025]

[0012] The present invention provides an adhesive film, wherein in at least one of the above [1] to

[0011] , the adhesive strength of the adhesive film to the stainless steel substrate and the polyester resin substrate is 500 gf / 25 mm or less.

[0026]

[0013] The present invention, in at least one of the above [1] to

[0012] , the storage elastic modulus (G') of the adhesive layer at 140°C is 1×10 4 Pa to 1×10 6 Pain provides adhesive films.

[0027]

[0014] The present invention, in at least one of the above [1] to

[0013] , the loss elastic modulus (G'') of the adhesive layer at 140°C is 2×10 3 Pa to 1×10 5 Pain provides adhesive films.

[0028]

[0015] The present invention provides an adhesive film in which, in at least one of the above [1] to

[0014] , the adhesive layer has a tanδ (G'' / G') of 0.01 to 0.45 at 140°C.

[0029]

[0016] The present invention provides an adhesive film, wherein in at least one of the above [1] to

[0015] , the adhesive film has a thickness of 30 µm to 150 µm.

[0030]

[0017] The present invention provides a pouch-type secondary battery comprising: an electrode assembly including a positive electrode, a negative electrode, and a separator; a pouch-type case including a receiving portion for receiving the electrode assembly, a terrace portion formed along the periphery of the receiving portion, and a sealing portion; electrode tabs protruding from each of the positive electrode and the negative electrode of the electrode assembly; electrode leads connected to the electrode tabs and protruding outward via the terrace portion; and an adhesive film according to any one of [1] to

[0016] positioned to wrap a cross-section exposed at an end of the sealing portion.

[0031]

[0032] The adhesive film according to the present invention can improve the heat resistance of the adhesive film by including a thermosetting resin in the adhesive layer and ensuring that the adhesive strength measured at a high temperature (140°C) satisfies a specific range. Accordingly, in the manufacturing process of a lithium secondary battery, even if the adhesive film located at the sealing portion of the battery case is pressed at a high temperature, the adhesive film may not be detached from the outer surface of the battery case. In particular, when the sealing portion is folded using a wing folding method, if the adhesive film according to the present invention is used, the adhesive film does not detach even when pressed at a high temperature, so that the folding can be effectively fixed, and the end of the sealing portion is effectively protected, which is advantageous in securing insulation. In addition, in the process of pressing the adhesive film at a high temperature, the problem of the components of the adhesive layer of the adhesive film leaking and transferring to the next working battery can be prevented, and the processability and the appearance of the battery can be improved.

[0033]

[0034] Fig. 1 is a cross-sectional view showing a laminated state of an adhesive film according to one embodiment of the present invention.

[0035] Figure 2 is an exploded assembly diagram of a pouch-type secondary battery before sealing.

[0036] Figure 3 is a cross-sectional view of a sealed pouch-type secondary battery.

[0037] Figure 4 is a cross-sectional view of a pouch-type secondary battery with the sealing portion folded.

[0038]

[0039] Hereinafter, the present invention will be described in more detail.

[0040] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0041] In the present invention, “storage modulus (G')” refers to the amount of elastic energy stored in a vibrating material. The storage modulus (G') was measured using a rotational rheometer (product name: TA DHR-20) in oscillation-frequency sweep mode, under conditions of a strain of 5% and a frequency range of 0.1 Hz to 100 Hz, at a frequency of 1 Hz and 140°C.

[0042] In the present invention, “loss modulus (G”)” refers to the amount of elastic energy lost in a vibrating material. The loss modulus (G”) was measured at a frequency of 1 Hz and 140°C under conditions of a strain of 5% and a frequency range of 0.1 Hz to 100 Hz using a rotational rheometer (product name: TA DHR-20) in oscillation-frequency sweep mode.

[0043] In the present invention, “tanδ(G” / G')” means the ratio of the storage elastic modulus and the loss elastic modulus, and after measuring the storage elastic modulus and the loss elastic modulus by the above method, it can be calculated by the formula G” / G'.

[0044]

[0045] adhesive film

[0046] An adhesive film according to the present invention comprises an outer insulating layer; and an adhesive layer disposed on one surface of the outer insulating layer. The adhesive layer comprises a thermosetting resin.

[0047]

[0048] The above adhesive film satisfies at least one of an adhesive strength of 100 gf / 25 mm or more to a stainless steel substrate and an adhesive strength of 200 gf / 25 mm or more to a polyester resin substrate, and preferably, an adhesive strength of 100 gf / 25 mm or more to a stainless steel substrate and an adhesive strength of 200 gf / 25 mm or more to a polyester resin substrate. When the above ranges are satisfied, even if a sealing portion to which the adhesive film is attached is pressed at a high temperature during a folding process of a battery case in a manufacturing process of a lithium secondary battery, the adhesive film does not detach, and the problem of a component of the adhesive layer melting and leaking to the outside of the adhesive film can be prevented.

[0049] Here, the adhesive strength is the adhesive strength when the surface opposite to the surface of the adhesive layer in contact with the outer insulating layer is pressed against a stainless steel substrate or a polyester resin substrate using a 2 kg roller, and then the adhesive film is peeled at a peeling speed of 300 mm / min and a peeling angle of 180° at 140°C.

[0050]

[0051] Pouch-type battery cases are manufactured by forming a cup portion through press processing on a flexible pouch film, housing an electrode assembly in the cup portion, and sealing the perimeter of the cup portion. However, the sealing portion, which is the perimeter of the sealed cup portion, protrudes more than other parts of the case, which can reduce energy density. In addition, the sealing at the ends of the sealing portion may weaken, or the metal barrier layer within the pouch film may be exposed, resulting in reduced insulation. To address these issues, a folding method is applied to the sealing portion.

[0052] In the past, single-side folding, in which the end of the sealing part is folded 90° toward the cup part, and double-side folding, in which the end of the sealing part is folded 270° toward the cup part, were mainly used as a method of folding the sealing part. However, there was a problem that it caused more damage to the sealing part, so recently, attempts to apply wing folding, in which the end of the sealing part is folded 180° toward the cup part, are increasing.

[0053] However, since the existing single-side folding and double-side folding have one side of the sealing portion and the cup portion in close contact when folding, the folding can be fixed and the end of the sealing portion can be protected by attaching an adhesive film to wrap around the closed portion. However, in the case of wing folding, the sealing portion does not come into close contact with the cup portion when folding, so it is impossible to fix the folding with an adhesive film after folding. Therefore, in the case of wing folding, a method is used in which an adhesive film is attached to the end of the sealing portion before folding, then folded 180°, and heat is applied to the area to fix the folding.

[0054] However, in the case of conventional single-side folding and double-side folding, the process of applying heat to the adhesive film during fixing is unnecessary, so the adhesive film previously applied to single-side folding and double-side folding has low durability in high-temperature environments, making it difficult to apply it as is to the wing folding method. Specifically, when the adhesive film previously applied to single-side folding and double-side folding was applied to wing folding, problems such as the adhesive film being detached during the high-temperature pressurization process or the components of the adhesive layer melting and leaking to the outside of the adhesive film occurred.

[0055] Accordingly, the inventors of the present invention have conducted repeated research to develop an adhesive film with improved durability against high-temperature environments, and as a result, have found that when the adhesive strength of the adhesive layer at high temperatures (e.g., 140°C) is controlled within a specific range, not only can the problem of the adhesive film detaching during the high-temperature pressurization process after folding be prevented, but also the problem of the adhesive layer component melting can be solved, thereby completing the present invention.

[0056] The above adhesive strength can be controlled by the type and content of the thermosetting resin, the adhesive-providing resin and the curing agent, the surface treatment and surface roughness of the adhesive layer, and the thickness and components of the combined external insulating layer. For example, when silicone is used as the thermosetting resin, the adhesive strength can be appropriately controlled by hydrosilylation by using PDMS (Polydimethylsiloxane) having a vinyl terminal group as the silicone, or by using together a curing agent having a silicon-hydride group (Si-H group). In addition, when an epoxy resin is used as the thermosetting resin, the adhesive strength can be appropriately controlled by including an -OH group in the epoxy resin or by using together an amine-based curing agent.

[0057] Specifically, the adhesive film may have an adhesive strength to a stainless steel substrate of 100 gf / 25 mm or more, 102 gf / 25 mm or more, 104 gf / 25 mm or more, 106 gf / 25 mm or more, 108 gf / 25 mm or more, 110 gf / 25 mm or more, 500 gf / 25 mm or less, 450 gf / 25 mm or less, 400 gf / 25 mm or less, 350 gf / 25 mm or less, 300 gf / 25 mm or less, 250 gf / 25 mm or less, 200 gf / 25 mm or less, 160 gf / 25 mm or less, and the above numerical ranges may be combined without limitation. For example, the adhesive film may have an adhesive strength to a stainless steel substrate of 100 gf / 25 mm or more, 100 gf / 25 mm to 500 gf / 25 mm, 104 gf / 25 mm to 300 gf / 25 mm, or 110 gf / 25 mm to 160 gf / 25 mm. The adhesive strength to the stainless steel substrate is an adhesive strength when the opposite side of the adhesive layer in contact with the outer insulating layer is pressed against the stainless steel substrate using a 2 kg roller, and then the adhesive film is peeled at a peeling speed of 300 mm / min and a peeling angle of 180° at 140°C. If the adhesive film has an adhesive strength to the stainless steel substrate lower than the above range, when pressurized at a high temperature during wing folding, the adhesive layer component may melt and flow out, and the adhesive film may be detached, making folding fixation impossible. Accordingly, when the adhesive film has an adhesive strength to a stainless steel substrate that satisfies the above range, even when the adhesive film is pressed at a high temperature (e.g., 140°C or higher) during wing folding, the components of the adhesive film do not melt, thereby improving processability and appearance defects of the battery. In addition, since the adhesive film does not detach from the sealing portion to which it is attached, the folding is effectively fixed, while protecting the end of the sealing portion to maintain insulation.

[0058] The adhesive film may have an adhesive strength to a polyester resin substrate of 200 gf / 25 mm or more, 202 gf / 25 mm or more, 204 gf / 25 mm or more, 206 gf / 25 mm or more, 208 gf / 25 mm or more, 210 gf / 25 mm or more, and may have an adhesive strength of 500 gf / 25 mm or less, 450 gf / 25 mm or less, 400 gf / 25 mm or less, 350 gf / 25 mm or less, 300 gf / 25 mm or less, 270 gf / 25 mm or less. For example, the adhesive film may have an adhesive strength to a polyester resin substrate of 200 gf / 25 mm or more, 200 gf / 25 mm to 500 gf / 25 mm, 204 gf / 25 mm to 350 gf / 25 mm, or 210 gf / 25 mm to 270 gf / 25 mm. The adhesive strength to the polyester resin substrate is the adhesive strength when the surface opposite to the surface of the adhesive layer in contact with the outer insulating layer is pressed against a polyester resin steel substrate using a 2 kg roller, and then the adhesive film is peeled at a peeling speed of 300 mm / min and a peeling angle of 180° at 140°C. If the adhesive film has a viscosity lower than the above range for a polyester resin substrate, the adhesive layer components may melt and flow out when pressurized at a high temperature during wing folding, and the adhesive film may detach, making folding fixation impossible. Therefore, if the adhesive film has a viscosity lower than the above range for a polyester resin substrate, even if the adhesive film is pressed at a high temperature (e.g., 140°C or higher) during wing folding, the components of the adhesive film do not melt, thereby improving processability and appearance defects of the battery. In addition, since the adhesive film does not detach from the attached sealing portion, the folding is effectively fixed while protecting the end of the sealing portion to maintain insulation.

[0059] The above stainless steel substrate may be a SUS304 substrate.

[0060] The above polyester resin substrate may be a polyethylene terephthalate (PET) substrate.

[0061] Meanwhile, the storage elastic modulus (G') of the adhesive layer at 140°C is 1×10 4 Pa to 1×10 6 Pa, 1.5×10 4 Pa to 5×10 5 Pa, 2×10 4 Pa to 2×10 5 Pa, or 3.5×10 4 Pa to 7×10 4 It can be Pa. If the above range is satisfied, the cohesive force of the adhesive layer is sufficient, so the adhesive force can be excellent.

[0062] The loss modulus (G'') of the above adhesive layer at 140°C is 2×10 3 Pa to 1×10 5 Pa, 2.5×10 3 Pa to 5×10 4 Pa, 4×10 3 Pa to 3×10 4 Pa, or 8×10 3 Pa to 2×10 4 It can be Pa. If the above range is satisfied, the adhesive strength of the adhesive layer to the adherend can be excellent.

[0063] The tanδ(G'' / G') of the adhesive layer at 140°C may be 0.01 to 0.45, 0.05 to 0.40, 0.1 to 0.3, or 0.2 to 0.3. When the above range is satisfied, the adhesive strength of the adhesive layer is excellent, so that the problem of detachment occurring in a high-temperature process can be solved.

[0064] The adhesive film may have a thickness of 20 µm to 150 µm, 30 µm to 120 µm, 35 µm to 100 µm, 40 µm to 80 µm, or 50 µm to 70 µm. When the above ranges are satisfied, the adhesive film can have sufficient adhesive strength, durability, heat resistance, and insulation while minimizing the space it occupies within a lithium secondary battery.

[0065]

[0066] Fig. 1 is a cross-sectional view showing the laminated state of an adhesive film (10) according to one embodiment of the present invention.

[0067] Referring to FIG. 1, an adhesive film (10) according to one embodiment of the present invention includes an outer insulating layer (11) and an adhesive layer (12) disposed on one surface of the outer insulating layer (11).

[0068]

[0069] The shape of the adhesive film (10) may vary without limitation depending on the intended use. For example, the adhesive film (10) used to fix the shape of the electrode assembly may be in the form of a rectangular flat plate, but is not limited thereto and may be used in various shapes such as a circular, triangular, or amorphous flat plate.

[0070]

[0071] (1) Outer insulation layer

[0072] The external insulating layer according to the present invention can serve to provide the mechanical rigidity necessary to implement the adhesive force of the adhesive film (10), and can be manufactured from an insulating material to insulate the adhesive film (10) from the outside, and can serve to protect the adhesive layer from friction and collision with the outside. At this time, the external insulating layer (11) is a film or sheet-shaped layer, and can have a shape such as a circle, a triangle, or an amorphous shape in addition to a square shape.

[0073] The above outer insulating layer (11) can be used without any particular limitation as long as it can provide mechanical rigidity to the adhesive film (10) and protect the adhesive layer. For example, the above outer insulating layer (11) may include one or more selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), polyimide (PI), cast polypropylene (CPP), high density polyethylene (HDPE), and low density polyethylene (LDPE).

[0074] Preferably, the outer insulating layer (11) may include at least one selected from the group consisting of polyethylene terephthalate and polyimide, and more preferably, may include polyimide. In this case, when combined with the adhesive layer according to the present invention, the adhesive strength to a stainless steel substrate and the adhesive strength to a polyester resin substrate are further improved, thereby improving the heat resistance of the adhesive film.

[0075] The thickness of the outer insulating layer (11) may be 10 µm to 60 µm, 15 µm to 50 µm, 20 µm to 45 µm, or 20 µm to 30 µm. When the thickness of the outer insulating layer (11) satisfies the above range, the adhesive strength of the adhesive film (10) can be improved, and the tensile strength of the outer insulating layer (11) is sufficiently secured, so that the tape does not break easily during the roll process of attaching the adhesive film (10) to the secondary battery, and the attachment process can be facilitated.

[0076]

[0077] (2) Adhesive layer

[0078] The adhesive layer (12) according to the present invention can serve to attach the adhesive film (10) to an adherend, and specifically, can serve to attach the adhesive film (10) to the sealing portion by contacting the outer surface of the sealing portion of the battery case included in the lithium secondary battery.

[0079] The above adhesive layer (12) contains a thermosetting resin.

[0080] The thermosetting resin above refers to a resin that has the property of being hardened when heat is applied, and the thermosetting resin can play a role in preventing detachment of the adhesive film (10) when heat is applied and pressurized at a high temperature during the folding process of the sealing portion after sealing the battery case, by reinforcing the heat resistance of the adhesive film. Specifically, when manufacturing a lithium secondary battery, in order to prevent detachment of the adhesive film during the process of attaching the adhesive film to a portion of the end of the sealing portion where the electrode lead is not located and then folding the sealing portion and pressing the sealing portion to which the adhesive film is attached at a high temperature, it is important to maintain the heat resistance at a certain level or higher at high temperatures. Accordingly, the adhesive film according to the present invention can strengthen the heat resistance of the adhesive layer by including the thermosetting resin in the adhesive layer, so that the adhesive layer can implement an adhesive force above a certain level even at high temperatures, thereby preventing detachment of the adhesive film during the high-temperature pressurization process.

[0081]

[0082] The thermosetting resin may be a silicone resin, an epoxy resin, or a combination thereof. In this case, since the structural stability is excellent even when heated at a high temperature for a long time, the adhesive layer can have sufficient heat resistance even when pressurized at a high temperature (e.g., 140°C), thereby preventing the problem of the adhesive film (10) being detached during the wing folding process and preventing the problem of the components of the adhesive layer from leaking. Specifically, when the thermosetting resin is a silicone resin, the silicone resin has high heat resistance and electrical insulation properties, so that the adhesive force can be sufficiently maintained even at high temperatures. In addition, when the thermosetting resin is an epoxy resin, the resin has excellent durability and impact resistance, and when exposed to heat, polymer cross-linking is formed, so that it can have high strength, so that the resin has excellent stability even at high temperatures and can sufficiently maintain the adhesive force even at high temperatures.

[0083]

[0084] The above silicone resin refers to a resin having a skeleton that includes bonds formed by alternating oxygen bonds to silicone having an organic group. The silicone resin may include at least one selected from the group consisting of polydimethylsiloxane (PDMS), polydiphenylsiloxane, and polyfluorosiloxane, and preferably includes polydimethylsiloxane. In this case, the adhesive strength to a polyester-based resin substrate and the adhesive strength to a stainless steel substrate can be further improved, thereby increasing the heat resistance of the adhesive film.

[0085] Additionally, the silicone resin may include a vinyl terminal group. In this case, the adhesive strength of the adhesive layer at high temperatures can be controlled within a desired range, thereby preventing the problem of the adhesive film detaching during the pressurization process after folding.

[0086]

[0087] The above epoxy resin may refer to a resin containing two or more epoxy bonds in a molecule. For example, the epoxy resin may include at least one selected from the group consisting of cresol novolac epoxy resin, bisphenol F-type epoxy resin, bisphenol F-type novolac epoxy resin, bisphenol A-type epoxy resin, bisphenol A-type novolac epoxy resin, phenol novolac epoxy resin, tetrafunctional epoxy resin, biphenyl-type epoxy resin, biphenyl-type novolac epoxy resin, triphenol methane-type epoxy resin, alkyl-modified triphenol methane epoxy resin, naphthalene-type epoxy resin, dicyclopentadiene-type epoxy resin, dicyclopentadiene-modified phenol-type epoxy resin, glycidyl ester-type epoxy resin, glycidylamine-type epoxy resin, and aliphatic cyclic epoxy resin. In this case, the adhesion to a polyester resin substrate and the adhesion to a stainless steel substrate can be further improved, thereby increasing the heat resistance of the adhesive film.

[0088] Additionally, the epoxy resin may contain a hydroxyl group (OH group). In this case, the adhesive strength of the adhesive layer at high temperatures can be controlled within a desired range, thereby preventing problems of adhesive film detachment and deterioration of insulation during the pressurization process after folding.

[0089] The thermosetting resin may have a weight average molecular weight of 10,000 g / mol to 1,000,000 g / mol, 30,000 g / mol to 700,000 g / mol, or 40,000 g / mol to 600,000 g / mol. When the above range is satisfied, excellent durability of the adhesive layer can be realized.

[0090]

[0091] The thermosetting resin may be included in an amount of 10 wt% to 99 wt% based on the total weight of the adhesive layer (12). Specifically, the thermosetting resin may be included in an amount of 10 wt% or more, 20 wt% or more, 30 wt% or more, 40 wt% or more, 50 wt% or more, 60 wt% or more, 70 wt% or more, or 80 wt% or more, based on the total weight of the adhesive layer (12), and may be included in an amount of 99 wt% or less, 95 wt% or less, 90 wt% or less, 85 wt% or less, 80 wt% or less, 75 wt% or less, 70 wt% or less, 65 wt% or less, or 60 wt% or less. The above numerical ranges may be combined without limitation. For example, the thermosetting resin may be included in an amount of 10 wt% to 99 wt%, 50 wt% to 90 wt%, or 60 wt% to 90 wt% based on the total weight of the adhesive layer (12). When the above range is satisfied, excellent durability and heat resistance of the adhesive layer can be secured.

[0092]

[0093] The above adhesive layer may include a curing agent. The curing agent may chemically crosslink the thermosetting resin to improve the cohesiveness of the adhesive layer and to improve the adhesiveness of the adhesive layer at high temperatures.

[0094] When the thermosetting resin is a silicone resin, the curing agent may be a curing agent containing a silicone-hydride group (Si-H group), and specifically, may contain a dimethylsiloxane-methylhydrogen siloxane copolymer. In this case, the adhesive strength can be appropriately controlled by a hydrosilylation reaction between the silicone resin and the curing agent.

[0095] Additionally, when using epoxy resin as a thermosetting resin, the curing agent may be an amine-based curing agent, specifically an imidazole curing agent. In this case, the curing reaction with the epoxy resin can be sufficiently promoted to strengthen the cohesive strength of the adhesive layer and appropriately control the adhesive strength.

[0096] The above curing agent may be included in an amount of 0.1 wt% to 30 wt%, 0.5 wt% to 20 wt%, or 1 wt% to 10 wt% based on the total weight of the adhesive layer. When the above range is satisfied, tack properties and cohesiveness are appropriately provided to the adhesive layer, thereby improving the adhesiveness to a desired range.

[0097] The thermosetting resin and the curing agent may be included in a weight ratio of 50:50 to 99.3:0.7, 70:30 to 99:1, 90:10 to 98.7:1.3, or 95:5 to 98.5:1.5. When the above range is satisfied, the thermosetting resin and the curing agent are sufficiently crosslinked, so that excellent adhesiveness can be achieved at high temperatures.

[0098] The thermosetting resin and the curing agent may be included in a weight ratio of 0.1:1 to 5:1, 0.5:1 to 2:1, or 0.8:1 to 1.5:1 based on the functional groups that cross-link with each other. When the above range is satisfied, both the thermosetting resin and the curing agent may react to increase the cross-linking density, thereby providing excellent adhesive strength.

[0099]

[0100] Meanwhile, the adhesive layer may include an adhesive-providing resin. The adhesive-providing resin may serve to increase the adhesiveness of the surface of the adhesive layer (12) that adheres to the adherend.

[0101] When the adhesive layer contains only a thermosetting resin, the initial tack of the adhesive film may be insufficient. Therefore, when the adhesive layer additionally contains a tackifying resin, sufficient initial tack can be secured, resulting in excellent initial adhesion performance. Accordingly, detachment of the adhesive film can be further prevented not only at high temperatures but also at room temperature.

[0102]

[0103] The above-mentioned adhesive-imparting resin may include at least one selected from the group consisting of a rosin-based resin, a terpene-based resin, a hydrocarbon-based resin, a hydrogenated hydrocarbon-based resin, a styrene-based resin, a phenol-based resin, and a xylene-based resin, and preferably may include at least one selected from the group consisting of a hydrogenated hydrocarbon-based resin and a rosin-based resin. For example, when the thermosetting resin is a silicone resin, the adhesive-imparting resin may include a hydrogenated hydrocarbon-based resin, and when the thermosetting resin is an epoxy resin, the adhesive-imparting resin may include a rosin-based resin. In this case, the adhesive strength of the adhesive layer can be sufficiently strengthened to strongly adhere the adhesive film (10) to the outer surface of the battery case.

[0104] Specifically, the rosin-based resin may be a concept encompassing both rosins and rosin derivative resins. For example, the rosins include unmodified rosins (raw rosins) such as gum rosin, tall oil rosin, and wood rosin; modified rosins such as hydrogenated rosin, disproportionated rosin, and polymerized rosin, which are obtained by modifying the unmodified rosin through hydrogenation, disproportionation, polymerization, etc.; or combinations thereof. The rosin derivative resin is a derivative of the rosins, and includes derivatives of unmodified rosin, derivatives of modified rosin, or combinations thereof. The rosin derivative resin includes rosin esters such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, or modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid-modified rosins, which are rosins modified with unsaturated fatty acids; It may include unsaturated fatty acid-modified rosin esters in which rosin esters are modified with unsaturated fatty acids; rosin alcohols in which the carboxyl group of rosin or the various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosin and unsaturated fatty acid-modified rosin esters) is reduced; metal salts of rosin or the various rosin derivatives; or combinations thereof.

[0105] The above terpene resin may include at least one selected from the group consisting of polymers of terpenes (e.g., monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene, aromatic modified terpene resins, styrene modified terpene resins, hydrogenated terpene resins, and terpene phenol resins. The above terpene polymer may be a homopolymer of one type of terpene or a copolymer of two or more types of terpenes. The above terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, and may include a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin); a homopolymer or copolymer of terpenes modified with phenol (phenol modified terpene resin); or a combination thereof.

[0106] The hydrocarbon resin may include at least one selected from the group consisting of aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic petroleum resins, aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, coumarone resins, and coumarone-indene resins. For example, the aliphatic petroleum resin may be a C5 type petroleum resin, and the aromatic petroleum resin may be a C9 type petroleum resin.

[0107] The above hydrogenated hydrocarbon resin refers to a resin having a structure in which the above hydrocarbon resin is hydrogenated.

[0108] The above styrenic resin may include at least one selected from the group consisting of poly-α-methylstyrene, α-methylstyrene / styrene copolymer, styrenic monomer / aliphatic monomer copolymer, styrenic monomer / α-methylstyrene / aliphatic monomer copolymer, styrenic monomer copolymer, and styrenic monomer / aromatic monomer copolymer.

[0109] The above phenolic resin may be at least one selected from the group consisting of terpene phenol resin, hydrogenated terpene phenol resin, alkylphenol resin, and rosin phenol resin. The terpene phenol resin is the same as described above, and the hydrogenated terpene phenol resin means a resin having a structure obtained by hydrogenating the above-described terpene phenol resin. The rosin phenol resin means a phenol-modified product of a rosin derivative resin such as rosin or rosin ester, unsaturated fatty acid-modified rosin, and unsaturated fatty acid-modified rosin ester, and for example, the rosin phenol resin can be obtained by a method of adding phenol to the rosin or the rosin derivative resin using an acid catalyst and thermally polymerizing it.

[0110] The above xylene-based resin may include at least one selected from the group consisting of xylene resin, alkyl phenol-based xylene resin, novolac phenol resin, resol-type phenol-based xylene resin, polyol-modified xylene resin, and ethylene oxide-modified xylene resin.

[0111] The tackifying resin may be present in an amount of 5 wt% or more, 10 wt% or more, 15 wt% or more, 20 wt% or more, 25 wt% or more, 30 wt% or more, 35 wt% or more, 40 wt% or more, or 45 wt% or more, based on the total weight of the adhesive layer (12), and may be present in an amount of 50 wt% or less, 45 wt% or less, 40 wt% or less, 35 wt% or less, 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, or 10 wt% or less. The above numerical ranges may be combined without limitation. For example, the tackifying resin may be present in an amount of 5 wt% to 50 wt%, 5 wt% to 30 wt%, 5 wt% to 20 wt%, or 5 wt% to 15 wt% based on the total weight of the adhesive layer (12). When the above range is satisfied, the adhesive layer can have excellent initial adhesion performance, thereby securing the adhesive strength of the adhesive layer above a certain level, and the adhesive strength can be maintained sufficiently well in various temperature ranges from high temperature to room temperature, thereby preventing detachment of the adhesive film.

[0112] The thermosetting resin and the adhesive-providing resin may be included in the adhesive layer (12) in a weight ratio of 1:99 to 99:1, 30:70 to 99:1, 50:50 to 95:5, 60:40 to 95:5, or 70:30 to 90:10. When the weight ratio is satisfied, the adhesiveness and heat resistance can be appropriately controlled to ensure excellent adhesiveness in a variety of temperature ranges from high temperature to room temperature.

[0113]

[0114] The above adhesive layer (12) may have a thickness of 10 µm to 100 µm, 12 µm to 80 µm, 20 µm to 50 µm, or 30 µm to 50 µm. When the above range is satisfied, the adhesive layer has sufficient strength, and in this case, the adhesive strength to a polyester resin substrate and the adhesive strength to a stainless steel substrate can be further improved, thereby increasing the heat resistance of the adhesive film.

[0115]

[0116] pouch-type secondary battery

[0117] An electrode assembly comprising a pouch-shaped secondary positive electrode, negative electrode, and separator according to one embodiment of the present invention; a pouch-shaped case including a receiving portion for receiving the electrode assembly, a terrace portion formed along a periphery of the receiving portion, and a sealing portion; electrode tabs protruding from each of the positive and negative electrodes of the electrode assembly; electrode leads connected to the electrode tabs and protruding outward via the terrace portions; and an adhesive film according to claim 1 positioned to wrap a cross-section exposed at an end of the sealing portion.

[0118]

[0119] Figure 2 is an exploded assembly diagram of a pouch-type secondary battery (100) according to the present invention, and Figure 3 is a cross-sectional view of a sealed pouch-type secondary battery (100).

[0120]

[0121] Hereinafter, with reference to FIGS. 2 and 3, each component of the pouch-type secondary battery according to the present invention will be described in more detail.

[0122]

[0123] (1) Electrode assembly

[0124] The above electrode assembly includes an anode, a cathode, and a separator.

[0125] According to one embodiment of the present invention, the electrode assembly (160) may be inserted into a pouch-shaped case (110) and sealed by the pouch-shaped case (110) after electrolyte injection.

[0126] The electrode assembly (160) may be formed by sequentially stacking an anode, a separator, and a cathode. Specifically, the electrode assembly (160) may include two types of electrodes, an anode and a cathode, and a separator interposed between the electrodes to mutually insulate the electrodes.

[0127] The positive and negative electrodes 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 is typically formed by stirring granular active materials, auxiliary conductors, binders, and conductive agents with the addition of a solvent. The solvent can be removed in a subsequent process.

[0128] A slurry containing an electrode active material, a binder, and / or a conductive material 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, thereby manufacturing an electrode assembly (160) in a predetermined shape. The types of electrode assembly (160) may include, but are not limited to, a stack type, a jelly roll type, a stack and folding type, etc.

[0129]

[0130] (2) Pouch-type case

[0131] The above pouch-shaped case includes a receiving portion for storing the electrode assembly, a terrace portion formed along the periphery of the receiving portion, and a sealing portion.

[0132] According to one embodiment of the present invention, the pouch-shaped case (110) can accommodate an electrode assembly (160) inside. The pouch-shaped case (110) can be manufactured by molding a pouch film laminate. In this case, the pouch film laminate can include a substrate layer, a gas barrier layer, and a sealant layer. In the pouch film laminate, the substrate layer, the gas barrier layer, and the sealant layer can be sequentially laminated.

[0133] The substrate layer is formed on the outermost layer of the pouch film laminate to protect the secondary battery from friction and collision with the outside world. The substrate layer is made of polymer and can electrically insulate the electrode assembly from the outside world.

[0134] The substrate layer 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, aramid, nylon, polyester, polyparaphenylene benzobisoxazole, polyarylate, Teflon, and glass fiber. Preferably, the substrate layer may be made of polyethylene terephthalate (PET), nylon, or a combination thereof, which have wear resistance and heat resistance.

[0135] The substrate layer may have a single-layer structure composed of a single material. Alternatively, the substrate layer may have a composite-layer structure composed of two or more materials, each formed as a layer.

[0136] The thickness of the substrate layer may be 5 ㎛ to 50 ㎛, specifically 7 ㎛ to 40 ㎛, and more specifically 25 ㎛ to 38 ㎛. When the thickness of the substrate layer satisfies the above range, the external insulation is excellent, and the thickness of the entire pouch is not thick, so the energy density per volume of the secondary battery can be excellent.

[0137] The gas barrier layer is laminated between the substrate layer and the sealant layer to secure the mechanical strength of the pouch, block the ingress of gas or moisture from outside the secondary battery, and prevent electrolyte leakage from inside the pouch-type case.

[0138] The gas barrier layer 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 ensuring complementary electrochemical properties and heat dissipation properties due to the electrode assembly and electrolyte. The aluminum alloy thin film may include at least one selected from the group consisting of metal elements other than aluminum (Al), for example, iron (Fe), copper (Cu), chromium (Cr), manganese (Mn), nickel (Ni), magnesium (Mg), silicon (Si), and zinc (Zn).

[0139] The thickness of the gas barrier layer may be 40 ㎛ to 100 ㎛, specifically 50 ㎛ to 90 ㎛, and more specifically 55 ㎛ to 85 ㎛. When the thickness of the gas barrier layer satisfies the above range, the formability and gas barrier performance are excellent when forming the cup portion.

[0140] The sealant layer is intended to completely seal the interior of the pouch-shaped case, which houses the electrode assembly inside, by mutually thermally bonding at the sealing portion when the pouch-shaped case is sealed. To this end, the sealant layer may be formed of a material having excellent thermal bonding strength.

[0141] The sealant layer may be formed of a material having insulating, corrosion-resistant, and sealing properties. Specifically, since the sealant layer is in direct contact with the electrode assembly and / or electrolyte inside the pouch-shaped case, it may be formed of a material having insulating and corrosion-resistant properties. In addition, since the sealant layer must completely seal the inside of the pouch-shaped case to prevent material movement between the inside and the outside, it may be formed of a material having high sealing properties (e.g., excellent thermal bonding strength). To secure such insulating, corrosion-resistant, and sealing properties, the sealant layer may be formed of a polymer material.

[0142] The sealant layer 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, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, Teflon, and glass fiber, and preferably may be made of a polyolefin resin such as polypropylene (PP) and / or polyethylene (PE). In this case, the polypropylene may be composed of cast polypropylene (CPP), acid modified polypropylene (Acid Modified Polypropylene, PPa), polypropylene-ethylene copolymer, and / or polypropylene-butylene-ethylene terpolymer.

[0143] The thickness of the sealant layer may be 30 ㎛ to 130 ㎛, specifically 50 ㎛ to 120 ㎛, and more specifically 70 ㎛ to 100 ㎛. When the thickness of the sealant layer satisfies the above range, there is an effect of securing the sealing strength of the sealing portion while also securing the formability of the pouch film laminate.

[0144]

[0145] Meanwhile, the pouch film laminate may be drawn and stretched by a punch or the like to manufacture a pouch-shaped case (110). As a result, the pouch-shaped case (110) may include a cup portion (122) and a receiving portion (124). The receiving portion (124) is a place for receiving the electrode assembly, and may refer to a receiving space formed in the shape of a pocket on the inside of the cup portion (122) as the cup portion (122) is formed.

[0146] According to one embodiment of the present invention, the pouch-type case (110) may include a first case (120) and a second case (130) as illustrated in FIG. 1. The first case (120) includes a receiving portion (124) capable of receiving an electrode assembly (160), and the second case (130) may cover the receiving portion (124) from above to prevent the electrode assembly (160) from being separated from the outside of the battery case (110). The first case (120) and the second case (130) may be manufactured such that one side thereof is connected to each other as illustrated in FIG. 1, but are not limited thereto and may be manufactured in various ways, such as being manufactured separately and separated from each other.

[0147] According to another embodiment of the present invention, when forming a cup portion on a pouch film laminate, two symmetrical cup portions (122, 132) can be drawn and formed adjacent to each other on one pouch film laminate. In this case, cup portions (122, 132) can be formed on the first case (120) and the second case (130) respectively, as shown in FIG. 1. After the electrode assembly (160) is accommodated in the receiving portion (124) provided in the cup portion (122) of the first case (120), the bridge portion (140) formed between the two cup portions (122, 132) can be folded so that the two cup portions (122, 132) face each other. In this case, the cup portion (132) of the second case (130) can accommodate the electrode assembly (160) from above. Accordingly, since two cup portions (122, 132) accommodate one electrode assembly (160), an electrode assembly (160) having a thicker thickness can be accommodated than when there is only one cup portion (122). In addition, since one corner of the secondary battery (100) is formed by folding the pouch-type case (110), the number of corners to be sealed can be reduced when performing the sealing process later. Accordingly, the process speed of the pouch-type secondary battery (100) can be improved, and the number of sealing processes can be reduced.

[0148] The pouch-type case (110) can be sealed while housing the electrode assembly (160) so that a portion of the electrode lead (180) described later, i.e., a terminal portion, is exposed. Specifically, when the electrode lead (180) is connected to the electrode tab (170) of the electrode assembly (160) and a lead film (190) is formed on a portion of the electrode lead (180), the electrode assembly (160) can be housed in a receiving portion (124) provided in a cup portion (122) of the first case (120), and the second case (130) can cover the receiving portion (124) from above. Subsequently, an electrolyte can be injected into the interior of the receiving portion (124), and a portion of the peripheral portion (150) formed along the perimeter of the first case (120) and the second case (130) can be sealed to form a sealing portion (300) and a terrace portion (400).

[0149] Accordingly, the pouch-shaped case includes a receiving portion for receiving the electrode assembly, a terrace portion formed along the periphery of the receiving portion, and a sealing portion.

[0150] The above sealing portion (300) refers to an area of ​​the sealed circumference (150) from which the electrode lead does not protrude.

[0151] The above terrace portion (400) refers to an area in the sealed peripheral portion (150) where the electrode lead protrudes, and the electrode lead protrudes to the outside via the terrace portion.

[0152] The sealing portion (300) and the terrace portion (400) can serve to seal the receiving portion (124). Specifically, the sealing portion (300) and the terrace portion (400) can seal the receiving portion (124) while being formed on the perimeter portion (150) formed along the perimeter of the receiving portion (124).

[0153] The temperature for sealing the above-mentioned sealing portion (300) and the above-mentioned terrace portion (400) may be 180°C to 250°C, 200°C to 250°C, or 210°C to 240°C. When the sealing temperature satisfies the above numerical range, the pouch-type case (110) can secure sufficient sealing strength through thermal bonding.

[0154] The sealing portion (300) may be folded so that the end (302) of the sealing portion faces the receiving portion (124), and specifically, 30% to 70%, 35% to 65%, or 40% to 60% of the width of the sealing portion (300) may be folded. In this case, the width of the sealing portion (300) may mean the length from the boundary between the receiving portion (124) and the sealing portion (300) to the end (302) of the sealing portion. In this case, the energy density of the lithium secondary battery may be improved, and the vent pressure may be improved.

[0155] The above sealing portion (300) can be folded 180° (with a margin of error of ±10%) so that the end portion (302) of the sealing portion faces the receiving portion (124). In this case, the end portion (302) of the sealing portion is protected by an adhesive film so that the metal barrier layer is not exposed, thereby providing the advantage of more effective insulation and less damage to the sealing portion.

[0156]

[0157] (3) Electrode tab

[0158] Electrode tabs (170) protrude from each positive and negative electrode of the electrode assembly (160).

[0159] Specifically, the electrode tabs (170) are respectively connected to the positive and negative electrodes of the electrode assembly (160), and protrude outward from the electrode assembly (160) to serve as a path through which electrons can move between the inside and the outside of the electrode assembly (160). The electrode current collector included in the electrode assembly (160) may be composed of a portion where an electrode active material is applied and a terminal 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. As illustrated in FIG. 1, 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.

[0160]

[0161] (4) Electrode leads

[0162] The electrode lead is connected to the electrode tab and protrudes outwardly from the pouch-shaped case, specifically, can protrude outwardly via the terrace portion of the pouch-shaped case.

[0163] Specifically, the electrode lead (180) can supply electricity to the outside of the pouch-type secondary battery (100). The electrode lead (180) can be connected to the electrode tab (170) of the electrode assembly (160) by spot welding, etc.

[0164] The electrode lead (180) may be connected to the electrode assembly (160) and may protrude to the outside of the pouch-type case (110) via the terrace portion (400). Specifically, one end of the electrode lead (180) may be connected to the electrode assembly (160), particularly to the electrode tab (170), and the other end of the electrode lead (180) may protrude to the outside of the pouch-type case (110) via the terrace portion (400).

[0165] The electrode lead (180) may include a positive lead (182) having one end connected to the positive tab (172) and extending in the direction in which the positive tab (172) protrudes, and a negative lead (184) having one end connected to the negative tab (174) and extending in the direction in which the negative tab (174) protrudes. Both the positive lead (182) and the negative lead (184) may have other ends protruding outward from the battery case (110). Accordingly, electricity generated inside the electrode assembly (160) may be supplied to the outside. In addition, since the positive tab (172) and the negative tab (174) are formed to protrude in various directions, the positive lead (182) and the negative lead (184) may also extend in various directions, respectively. The positive lead (182) and the negative lead (184) may be made of different materials. That is, the positive electrode lead (182) may be made of the same aluminum (Al) material as the positive electrode collector, and the negative electrode lead (184) 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 (180) protruding outside the pouch-shaped case (110) may serve as a terminal portion and be electrically connected to an external terminal.

[0166] A film layer (200) including at least one selected from the group consisting of chromium (Cr), nickel (Ni), aluminum oxide (Al2O3), zirconium (Zr)-based anhydride salts, and titanium (Ti)-based anhydride salts may be formed on one surface of the electrode lead (180) that is in direct contact with the lead film (190) and / or the gas discharge portion (not shown). In this case, corrosion resistance against the electrolyte and adhesion to the lead film (190) and / or the gas discharge portion can be secured.

[0167] The electrode lead (180) may include a lead film (190).

[0168] The lead film (190) prevents electricity generated from the electrode assembly (160) from flowing to the pouch-shaped case (110) through the electrode lead (180) and can maintain the sealing of the pouch-shaped case (110). To this end, the lead film (190) may be formed of a non-conductive material that does not conduct electricity well. In general, the lead film (190) is often made of an insulating tape or film that is easy to attach to the electrode lead (180) and has a relatively thin thickness, but is not limited thereto, and any material capable of insulating the electrode lead (180) may be used.

[0169] The lead film (190) may be arranged to surround the outer circumference of the electrode lead (180). Specifically, at least a portion of the electrode lead (180) may be surrounded by the lead film (190). In this case, the lead film (190) may be arranged between the electrode lead (180) and the pouch-shaped case (110). The lead film (190) may be positioned limited to the sealing portion (300) where the first case (120) and the second case (130) of the pouch-shaped case (110) are heat-sealed, and may adhere the electrode lead (180) to the pouch-shaped case (110).

[0170]

[0171] (5) Adhesive film

[0172] Since the structure and components of the above adhesive film (10) are the same as described above, a detailed description is omitted.

[0173] The adhesive film (10) according to the present invention is positioned to wrap the cross-section exposed at the end (302) of the sealing portion (300).

[0174] Specifically, the adhesive film (10) may be positioned to cover both surfaces of the sealing portion (300) while wrapping around the cross-section exposed to the end (302) of the sealing portion (300) where the electrode lead (180) does not protrude, or the adhesive film (10) may be positioned to cover both surfaces of the sealing portion (300) with the same area while wrapping around the cross-section exposed to the end (302) of the sealing portion (300) where the electrode lead (180) does not protrude. In this case, the gas barrier layer included in the pouch film laminate can be prevented from being exposed at the end of the sealing portion, thereby preventing a short circuit of the battery and maintaining the insulation of the pouch-type case can be obtained.

[0175] At this time, when the adhesive film (10) is positioned to cover both surfaces of the sealing portion (300), the adhesive film (10) can cover 20% to 80%, 30% to 70%, or 40% to 60% of the surface area of ​​the sealing portion (300). In addition, the adhesive film (10) can cover 50% or more, 60% or more, 70% or more, or 80% or more of the circumference of the sealing portion (300).

[0176]

[0177] Figure 4 is a cross-sectional view of a pouch-type secondary battery (100) with the sealing portion (300) folded.

[0178] Referring to FIG. 4, in a state where the adhesive film (10) is positioned to wrap the cross-section exposed to the end (302) of the sealing portion (300) where the electrode lead (180) does not protrude, the sealing portion (300) can be folded so that the end (302) of the sealing portion faces the receiving portion (124), and specifically, the sealing portion (300) can be folded 180° so that the end (302) of the sealing portion faces the receiving portion (124). When the sealing portion (300) is folded, the adhesive film (10) can be positioned on the folded sealing portion.

[0179] After folding the sealing portion (300), the folded sealing portion (300) can be pressurized at high temperature. Accordingly, by allowing the sealing portion to be fixed in a folded state, the energy density of the lithium secondary battery can be improved. In addition, when the pressurization is performed, the adhesive film positioned on the outer surface of the sealing portion is also pressurized at high temperature. In the past, when the adhesive film applied to single-side folding or double-side folding was pressurized at high temperature, there was a problem that the adhesive film was detached or the components of the adhesive layer melted and leaked. In contrast, the lithium secondary battery according to the present invention can solve the problem that the adhesive film was detached and the components of the adhesive layer were leaked during the wing folding process, which requires a high-temperature pressurization process, by positioning an adhesive film having an adhesive strength at high temperatures of a certain level or higher on the cross-section exposed to the end of the sealing portion.

[0180] Specifically, the sealing portion (300) in a folded state can be pressurized by a heating press device. In this case, the sealing portion (300) in the folded state can be pressurized by 0.01 to 1 MPa, 0.05 to 0.7 MPa, or 0.1 to 0.5 MPa by the heating press device. In this case, by fixing the sealing portion in a folded state, the energy density of the battery can be improved, and the adhesive film located at the end of the sealing portion can be prevented from being excessively heated and detached, thereby preventing the end of the folded sealing portion from being exposed, and accordingly, the gas barrier layer of the pouch film laminate can be prevented from being exposed to the outside, thereby obtaining the effect of maintaining the insulation and the safety of the battery case.

[0181]

[0182] (6) Electrolyte

[0183] The pouch-type secondary battery (100) according to the present invention may further include an electrolyte (not shown) injected into the pouch-type case (110).

[0184] As the above electrolyte, various electrolytes that can be used in lithium secondary batteries, such as organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes, can be used, and the types thereof are not particularly limited.

[0185] Specifically, the electrolyte may include an organic solvent and a lithium salt.

[0186] The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (wherein R is a C2 to C20 linear, branched, or cyclic hydrocarbon group, and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0187] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of 0.1 to 5.0 M, and preferably 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0188] In addition to the electrolyte components, the electrolyte may further include additives for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. For example, the additives may include haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexamethylphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, which may be used alone or in combination, but are not limited thereto. The additives may be included in an amount of 0.1 to 10 wt%, preferably 0.1 to 5 wt%, based on the total weight of the electrolyte.

[0189]

[0190]

[0191] Examples and Comparative Examples

[0192] Example 1

[0193] A composition for forming an adhesive layer was prepared by mixing polydimethylsiloxane (PDMS) having a vinyl terminal as a thermosetting resin and a dimethylsiloxane-methylhydrogensiloxane copolymer as a curing agent in a weight ratio of 98:2.

[0194] An adhesive film was manufactured by preparing a polyethylene terephthalate (PET) film as an outer insulating layer, coating the composition for forming an adhesive layer manufactured above on one side of the polyethylene terephthalate film, and then drying at a temperature of 140°C for 3 minutes to form an adhesive layer. In the manufactured adhesive film, the outer insulating layer had a thickness of 25 μm, and the adhesive layer had a thickness of 40 μm.

[0195]

[0196] Example 2

[0197] In the manufactured adhesive film, an adhesive film was manufactured in the same manner as in Example 1, except that the thickness of the adhesive layer was 20 μm.

[0198]

[0199] Example 3

[0200] An adhesive film was manufactured in the same manner as in Example 1, except that a polyimide (PI) film with a thickness of 25 μm was used as the outer insulating layer.

[0201]

[0202] Example 4

[0203] An adhesive film was manufactured in the same manner as in Example 1, except that an epoxy resin having an OH group was used instead of polydimethylsiloxane as a thermosetting resin, and an imidazole curing agent (C11Z-A) was used as a curing agent.

[0204]

[0205] Comparative Example 1

[0206] An adhesive layer forming composition was prepared by mixing an acrylic copolymer containing acrylic acid (AA), butyl acrylate (BA), and ethylhexyl acrylate (EHA) as an acrylic resin and a rosin ester adhesive-providing resin at a weight ratio of 90:10.

[0207] An adhesive film was manufactured by preparing a polyethylene terephthalate (PET) film as an outer insulating layer, coating the composition for forming an adhesive layer manufactured above on one side of the polyethylene terephthalate film, and then drying at a temperature of 140°C for 3 minutes to form an adhesive layer. In the manufactured adhesive film, the outer insulating layer had a thickness of 25 μm, and the adhesive layer had a thickness of 40 μm.

[0208]

[0209] Comparative Example 2

[0210] An adhesive film was manufactured using the same method as Comparative Example 1, except that the thickness of the outer insulating layer was 40 μm and the thickness of the adhesive layer was 7 μm.

[0211]

[0212] Comparative Example 3

[0213] An adhesive film was manufactured in the same manner as in Comparative Example 1, except that a polyimide (PI) film with a thickness of 25 μm was used as the outer insulating layer.

[0214]

[0215] Comparative Example 4

[0216] An adhesive film was manufactured in the same manner as in Example 1, except that the thermosetting resin and the curing agent were mixed in a weight ratio of 99.5:0.5.

[0217]

[0218] Experimental Example 1: Adhesion Measurement Test

[0219] 1) Adhesion measurement on stainless steel substrate

[0220] Each adhesive film manufactured in Examples 1 to 4 and Comparative Examples 1 to 4 was cut to a size of 25 mm × 150 mm. The opposite side of the adhesive layer of the cut adhesive film was pressed onto a SUS304 stainless steel substrate using a 2 kg roller. Thereafter, the adhesive film was peeled at 140°C at a peel speed of 300 mm / min and a peel angle of 180°. The adhesive strength at this time was measured using ASTM D 3330. The measurement results are shown in Table 1 below.

[0221]

[0222] 2) Measurement of adhesion to polyester resin substrate

[0223] Each adhesive film manufactured in Examples 1 to 4 and Comparative Examples 1 to 4 was cut to a size of 25 mm × 150 mm. The opposite side of the adhesive layer of the cut adhesive film was pressed onto a polyethylene terephthalate (PET) substrate, which is a polyester resin substrate, using a 2 kg roller. Thereafter, the adhesive film was peeled at 140°C at a peel speed of 300 mm / min and a peel angle of 180°. The adhesive strength at this time was measured using ASTM D 3330. The measurement results are shown in Table 1 below.

[0224]

[0225] SUS304 substrate adhesion [gf / 25mm]PET substrate adhesion [gf / 25mm]Example 1140240Example 2110210Example 3160270Example 4400300Comparative example 12449Comparative example 24075Comparative example 35090Comparative example 42030

[0226] Experimental Example 2: Measurement of storage modulus and loss modulus

[0227] The adhesive layers included in the adhesive films manufactured according to Examples 1 to 4 and Comparative Examples 1 to 4 were laminated to a thickness of 800 to 1000 μm on parallel plates having a diameter of 8 mm, and then cut by punching holes with a diameter of 8 mm. Thereafter, the storage modulus (G') and loss modulus (G'') of the adhesive films were measured using each DHR-20 rotational rheometer (manufactured by TA). All measurements were performed under the conditions of an axial force of 100 gf, a strain of 5%, and a frequency range of 0.1 to 100 Hz, at a frequency of 1 Hz and 140°C in an oscillation-frequency sweep mode.

[0228] The measurement results are shown in Table 2 below.

[0229]

[0230] Storage modulus (G') [Pa] Loss modulus (G'') [Pa] tanδ (G'' / G') Example 1 35,000 8,000 0.23 Example 2 35,000 8,000 0.23 Example 3 35,000 8,000 0.23 Example 4 70,000 20,000 0.29 Comparative Example 1 2,000 1,000 0.5 Comparative Example 2 2,000 1,000 0.5 Comparative Example 3 2,000 1,000 0.5 Comparative Example 4 1,500 8,000 0.53

[0231] Experimental Example 3: Adhesive Film Detachment Test

[0232] A lithium secondary battery was manufactured using the adhesive films manufactured in Examples 1 to 4 and Comparative Examples 1 to 4. Specifically, after the electrode assembly was accommodated in the receiving portion of a pouch-type battery case, the upper portion of the receiving portion was covered, and the peripheral portion formed along the periphery of the receiving portion was sealed. Thereafter, each adhesive film was positioned so that the end portion of the sealing portion, which is the portion where the electrode lead does not protrude, was in contact with the adhesive layer of each adhesive film manufactured in Examples 1 to 4 and Comparative Examples 1 to 4, and the adhesive film was adhered in a manner that wrapped the end portion of the sealing portion, and then folded 180° so that the end portion of the sealing portion faced the receiving portion, thereby manufacturing a lithium secondary battery.

[0233] In the lithium secondary batteries manufactured above, the sealing portions in which the adhesive films manufactured in Examples 1 to 4 and Comparative Examples 1 to 4 were adhered and folded were pressurized at a temperature of 140°C. At this time, it was visually confirmed whether the adhesive films manufactured in Examples 1 to 4 and Comparative Examples 1 to 4 were detached from the outer surface of the pouch-type battery case of each lithium secondary battery, and the results are shown in Table 3 below.

[0234] - O: The adhesive film is detached from the outer surface of the pouch-type battery case.

[0235] - X: The adhesive film does not detach from the outer surface of the pouch-type battery case.

[0236]

[0237] Whether the adhesive film detaches or notExample 1XExample 2XExample 3XExample 4XComparative Example 10Comparative Example 20Comparative Example 30Comparative Example 40

[0238] Referring to Table 3 above, it can be confirmed that the adhesive films manufactured in Examples 1 to 4 did not detach when pressurized at 140°C, but the adhesive films manufactured in Comparative Examples 1 to 4 detached when pressurized at 140°C.

[0239] (Explanation of symbols)

[0240] 10: Adhesive film

[0241] 11: Outer insulation layer

[0242] 12: Adhesive layer

[0243] 100: Pouch-type secondary battery

[0244] 110: Pouch-type case

[0245] 120: Case 1

[0246] 122: Cup

[0247] 124: Reception area

[0248] 130: Case 2

[0249] 132: Cup

[0250] 140: Bridge section

[0251] 150: Circumference

[0252] 160: Electrode assembly

[0253] 170: Electrode tab

[0254] 172: Positive tab

[0255] 174: Negative tab

[0256] 180: Electrode lead

[0257] 182: Positive lead

[0258] 184: Negative lead

[0259] 190: Lead Film

[0260] 200: Film layer

[0261] 300: Sealing part

[0262] 302: End of the sealing section

[0263] 400: Terrace

Claims

1. Outer insulation layer; and In an adhesive film including an adhesive layer disposed on one surface of the outer insulating layer, The above adhesive layer includes a thermosetting resin, The above adhesive film satisfies at least one of an adhesive strength of 100 gf / 25 mm or more to a stainless steel substrate and an adhesive strength of 200 gf / 25 mm or more to a polyester resin substrate. The adhesive film, wherein the adhesive strength is the adhesive strength when the surface opposite to the surface of the adhesive layer in contact with the outer insulating layer is pressed against a stainless steel substrate or a polyester resin substrate using a 2 kg roller, and then the adhesive film is peeled at a peeling speed of 300 mm / min and a peeling angle of 180° at 140°C.

2. In claim 1, An adhesive film, wherein the outer insulating layer comprises at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyimide, non-stretched polypropylene, high-density polyethylene, and low-density polyethylene.

3. In claim 1, The above thermosetting resin is an adhesive film, which is a silicone resin, an epoxy resin or a combination thereof.

4. In claim 1, The adhesive film, wherein the adhesive layer contains a curing agent.

5. In claim 4, The above thermosetting resin is a silicone resin, An adhesive film, wherein the curing agent comprises a silicon-hydride group (Si-H group).

6. In claim 4, The above thermosetting resin is an epoxy resin, An adhesive film wherein the above curing agent is an amine curing agent.

7. In claim 1, An adhesive film, wherein the adhesive layer comprises an adhesive-providing resin.

8. In claim 7, An adhesive film, wherein the adhesive-imparting resin comprises at least one selected from the group consisting of a rosin-based resin, a terpene-based resin, a hydrocarbon-based resin, a hydrogenated hydrocarbon-based resin, a styrene-based resin, a phenol-based resin, and a xylene-based resin.

9. In claim 1, The above stainless steel substrate is a SUS304 substrate, adhesive film.

10. In claim 1, The above polyester resin substrate is an adhesive film that is a polyethylene terephthalate (PET) substrate.

11. In claim 1, An adhesive film in which the thermosetting resin is contained in an amount of 10% to 99% by weight based on the total weight of the adhesive layer.

12. In claim 1, An adhesive film having an adhesive strength of 500 gf / 25 mm or less to the stainless steel substrate and polyester resin substrate.

13. In claim 1, The storage elastic modulus (G') of the above adhesive layer at 140°C is 1×10 4 Pa to 1×10 6 Pain, adhesive film.

14. In claim 1, The loss modulus (G'') of the above adhesive layer at 140°C is 2×10 3 Pa to 1×10 5 Pain, adhesive film.

15. In claim 1, An adhesive film, wherein the tanδ(G'' / G') of the adhesive layer at 140°C is 0.01 to 0.

45.

16. In claim 1, The above adhesive film is an adhesive film having a thickness of 30 ㎛ to 150 ㎛.

17. Electrode assembly including anode, cathode and separator; A pouch-shaped case including a receiving portion for storing the electrode assembly, a terrace portion formed along the periphery of the receiving portion, and a sealing portion; Electrode tabs protruding from each positive and negative electrode of the electrode assembly; An electrode lead connected to the electrode tab and protruding outward via the terrace portion; and A pouch-type secondary battery comprising an adhesive film according to claim 1 positioned to wrap a cross-section exposed at an end of the sealing portion.

Images