Secondary battery cell pouch having excellent chemical resistance

Abstract

Disclosed is a cell pouch for a secondary battery, the cell pouch using a coating layer that contains a melamine resin, and having excellent moldability and excellent chemical resistance in terms of electrolyte resistance, solvent resistance, and scratch resistance. The cell pouch according to the present invention is characterized by comprising: a coating layer containing a melamine resin; an outer resin layer disposed on one surface of the coating layer; a metal layer disposed on one surface of the substrate layer; and an inner resin layer disposed on one surface of the metal layer.

Description

Cell pouch for secondary batteries with excellent chemical resistance

[0001] The present invention relates to a cell pouch for a secondary battery having excellent chemical resistance using a coating layer containing a melamine resin.

[0002] Secondary batteries are classified into pouch-type secondary batteries, cylindrical secondary batteries, and prismatic secondary batteries depending on the material of the case that accommodates the electrode assembly. Pouch-type secondary batteries are mainly used in terms of capacity and safety.

[0003] Pouch-type secondary batteries have a structure in which an electrode assembly is housed in a pouch formed from a flexible polymer material pouch film. This pouch film is used in a structure including an innermost layer, an intermediate layer, a barrier layer, a resin layer, and an outermost layer.

[0004] Meanwhile, pouches of medium to large sizes are currently widely used in energy storage systems (ESS) and electric vehicles (EVs), requiring high capacity and output. In this regard, pouches used in high-capacity, high-output ESS and EVs are facing stability issues.

[0005] However, in the case of small pouches, the outermost layer is composed of nylon, and cracks can occur in that area due to small scratches or foreign matter on the surface. Consequently, small pouches pose a greater risk of fire and explosion.

[0006] For pouches of medium to large sizes and larger, a PET film, resistant to scratches, abrasion, and solvents, is laminated onto a nylon layer to address issues such as cracking. However, laminating the PET film onto the nylon layer results in lower formability compared to pouch films with a nylon layer as the outermost layer, making it insufficient to meet the required physical properties.

[0007] Therefore, there is a need for research on materials that have excellent formability, satisfy the physical properties of pouches, and can replace existing PET films.

[0008]

[0009] The purpose of the present invention is to provide a cell pouch for a secondary battery having excellent formability, electrolyte resistance, solvent resistance, and scratch resistance by using a coating layer containing a melamine resin that can replace an existing PET film.

[0010] In addition, an object of the present invention is to provide a cell pouch for a secondary battery having improved slipperiness by adding wax to a coating layer.

[0011] In addition, the purpose of the present invention is to provide a cell pouch for a secondary battery that can implement physical properties using only a melamine resin-containing coating layer instead of a conventional PET film and is economical in terms of manufacturing cost.

[0012]

[0013] The objectives of the present invention are not limited to those mentioned above. Other objectives and advantages of the present invention not mentioned above can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objectives and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0014] A cell pouch according to the present invention is characterized by including a coating layer comprising a melamine resin; an outer resin layer disposed on one surface of the coating layer; a metal layer disposed on one surface of the base layer; and an inner resin layer disposed on one surface of the metal layer.

[0015] The above coating layer includes a subject and a hardener, and the subject may include 70 to 100 parts by weight of urethane resin, 15 to 30 parts by weight of silica powder, 2 to 15 parts by weight of wax, and 2 to 10 parts by weight of polyester polyol, relative to 100 parts by weight of melamine resin.

[0016] The above coating layer may contain the subject:curing agent in a weight ratio of 14 to 16:1.

[0017] The viscosity of the above melamine resin may be 90 to 150 cps at 25°C.

[0018] The diameter of the above silica powder may be 1 to 20 μm.

[0019] The diameter of the above wax may be 1 to 20 μm.

[0020] Under conditions of 23℃ and 50% humidity, the tensile strength in each of the MD and TD directions can be 10 to 30 kg / 15 mm.

[0021] Under conditions of 23℃ and 50% humidity, the elongation in each of the MD and TD directions can be 80 to 100%.

[0022] Regarding formability, when a mold machine having a forming groove depth of 4 to 7.5 mm is used, a hydraulic cylinder is lowered into the forming groove to form a cell pouch, and when observed with the naked eye, the depth until no cracks occur on the surface of the cell pouch can be 7.0 to 7.5 mm.

[0023] (The above crack means a crack with a length of 0.1 mm or more.)

[0024] Regarding the electrolyte, when one drop of the electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M) is dropped on the surface of the coating layer of a cell pouch having a size of 100 x 100 mm in width and height using a dropper, and after 60 seconds, the dropped electrolyte is wiped off. When the surface condition of the coating layer is observed with the naked eye, the same surface condition as before dropping the electrolyte using the dropper can be maintained.

[0025] Regarding the content resistance, when a cotton swab soaked in any one of electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M), ethyl alcohol, methyl ethyl ketone, and toluene) is rubbed on the surface of the coating layer of a cell pouch having a size of 100 x 100 mm in width and height, 1 cm on each side of the point of contact, and the number of times the coating layer surface is peeled off is measured, it may be 30 times or more.

[0026] Regarding scratch resistance, when a steel brush is placed on the surface of a cell pouch measuring 80 x 150 mm in width and height using a KP-M4250 device, a 400 g weight is pressed down, and the degree of scratch is measured after performing a reciprocating motion 2 or 6 times, there may be no scratches. (The above scratch means a scratch of 0.1 μm or more in the depth direction or / and length direction of the surface of the cell pouch.)

[0027] According to another embodiment, a cell pouch according to the present invention comprises a coating layer comprising a melamine resin, wherein the coating layer comprises a subject and a curing agent, and the subject comprises 70 to 100 parts by weight of a urethane resin, 15 to 30 parts by weight of silica powder, 2 to 15 parts by weight of wax, and 2 to 10 parts by weight of polyester polyol, based on 100 parts by weight of the melamine resin.

[0028] According to another embodiment, a cell pouch according to the present invention comprises a coating layer comprising a melamine resin, wherein the coating layer comprises a subject and a curing agent, and wherein the subject comprises a melamine resin, a urethane resin, silica powder, wax, and polyester polyol.

[0029] According to another embodiment, a cell pouch according to the present invention comprises a coating layer comprising a melamine resin, wherein the coating layer comprises a subject and a curing agent, wherein the subject comprises a melamine resin, a urethane resin, silica powder, wax, and polyester polyol, and is characterized in that it satisfies at least one of a viscosity of 90 to 150 cps at 25°C and a specific gravity of 0.93 to 1.03 at 25°C.

[0030] According to another embodiment, a cell pouch according to the present invention comprises a coating layer comprising a melamine resin, wherein the coating layer comprises a subject and a curing agent, wherein the subject comprises a melamine resin, a urethane resin, silica powder, wax, and polyester polyol, and is characterized in that the polyester polyol satisfies at least one of a hydroxyl value (OH Value) of 48 to 55 mgKOH / g, a weight average molecular weight of 2000 to 2500 g / mol, and a viscosity at 25°C of 3000 to 4000 cP.

[0031] According to another embodiment, a cell pouch according to the present invention comprises a coating layer comprising a melamine resin, wherein the coating layer comprises a subject and a curing agent, and wherein the coating layer comprises the subject: curing agent in a weight ratio of 14 to 16:1.

[0032] According to another embodiment, the cell pouch according to the present invention comprises a coating layer comprising a melamine resin, wherein the viscosity of the melamine resin is 90 to 150 cps at 25°C.

[0033] According to another embodiment, the cell pouch according to the present invention is characterized in that the tensile strength in each of the MD direction and the TD direction is 10 to 30 kg / 15 mm under conditions of 23°C and 50% humidity.

[0034] According to another embodiment, the cell pouch according to the present invention is characterized in that the elongation in each of the MD direction and the TD direction is 80 to 100% under conditions of 23°C and 50% humidity.

[0035] According to another embodiment, the cell pouch according to the present invention is characterized in that, when a hydraulic cylinder is lowered into the forming groove to form the cell pouch using a molding machine having a forming groove depth of 4 to 7.5 mm, and when observed with the naked eye, the depth until no cracks occur on the surface of the cell pouch is 7.0 to 7.5 mm.

[0036] According to another embodiment, the cell pouch according to the present invention is characterized in that when one drop of an electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M) is dropped on the surface of a coating layer of a cell pouch having a size of 100 mm in width and 100 mm in length using a dropper, and after 60 seconds, the dropped electrolyte is wiped off, and the surface state of the coating layer is observed with the naked eye, the surface state is maintained the same as before the dropper electrolyte was dropped.

[0037] According to another embodiment, a cell pouch according to the present invention is characterized in that when a cotton swab soaked in any one of an electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M), ethyl alcohol, methyl ethyl ketone, and toluene) is rubbed on the surface of a coating layer of a cell pouch having a size of 100 mm in width and 100 mm in length, 1 cm on each side of the point of contact, and the number of times the coating layer surface is peeled off is measured, the number of times is 30 or more.

[0038] According to another embodiment, the cell pouch according to the present invention is characterized in that when a steel brush is placed on the surface of a cell pouch having a size of 80 x 150 mm in width and height, a 400 g weight is pressed, and the degree of scratches is measured after performing a reciprocating motion 2 or 6 times using a KP-M4250 device, there are no scratches.

[0039] (The above scratch means a scratch of 0.1㎛ or more in the depth direction or / and length direction of the cell pouch surface.)

[0040] The cell pouch for a secondary battery according to the present invention has excellent moldability, electrolyte resistance, solvent resistance, and scratch resistance by using a coating layer containing a melamine resin, and can replace existing PET films.

[0041] In addition, by adding wax to the coating layer, slipperiness was improved, and the physical properties can be realized with only a melamine resin-containing coating layer instead of the existing PET film, and it has an excellent economical effect in terms of manufacturing cost.

[0042] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0043] Figure 1 is a cross-sectional view of a cell pouch for a secondary battery according to the present invention.

[0044] Figure 2 shows the results of an electrolyte resistance test of a cell pouch for a secondary battery according to Example 1 of the present invention.

[0045] Figure 3 shows the results of a content resistance test of a cell pouch for a secondary battery according to Example 1 of the present invention.

[0046] Figure 4 shows the results of a scratch resistance test of a cell pouch for a secondary battery according to Example 1 of the present invention.

[0047] [Explanation of symbols]

[0048] 10: Coating layer

[0049] 20: Outer resin layer

[0050] 30: Metal layer

[0051] 40: Inner resin layer

[0052] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0053] Hereinafter, the phrase "any configuration is placed on (or below)" a component or "on (or below)" a component may mean that any configuration is placed in contact with the upper surface (or lower surface) of said component, and that other configurations may be interposed between said component and any configuration placed on (or below) said component.

[0054] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component.

[0055] Hereinafter, a cell pouch for a secondary battery having excellent chemical resistance according to some embodiments of the present invention will be described.

[0056]

[0057] The outermost layer of the cell pouch is made of PET film to protect the nylon layer and prevent scratches and foreign matter. However, the low elongation of PET film has resulted in poor formability.

[0058] Accordingly, the inventors of the present invention confirmed that by using a melamine resin-containing coating layer on the outermost layer of a cell pouch for a secondary battery, the formability, electrolyte resistance, solvent resistance, and scratch resistance are excellent, and that it can replace the existing PET film.

[0059] Furthermore, the inventors of the present invention improved the formability and slipperiness of cell pouches by adding wax to the coating layer. Furthermore, the inventors confirmed that the physical properties of cell pouches can be achieved using only a melamine resin-containing coating layer, instead of the conventional PET film, and that this also has a beneficial effect in terms of unit price competitiveness.

[0060] Figure 1 is a cross-sectional view of a cell pouch for a secondary battery according to the present invention.

[0061] As illustrated in FIG. 1, the cell pouch for a secondary battery according to the present invention is characterized by including a coating layer (10), an outer resin layer (20), a metal layer (30), and an inner resin layer (40).

[0062] The coating layer (10) becomes the outermost layer, and the internal resin layer (40) becomes the innermost layer. When assembling a secondary battery, the internal resin layers located around the secondary battery are thermally fused together to seal the secondary battery, thereby sealing the secondary battery.

[0063] Coating layer (10)

[0064] The coating layer is a cured product of a composition containing a subject, a curing agent, and a solvent. The solvent evaporates from the coating layer, leaving only the subject and the curing agent.

[0065] The subject matter imparts properties to the coating layer and is an important factor in securing the formability, electrolyte resistance, solvent resistance, and scratch resistance of the cell pouch.

[0066] In the past, PET material was mainly used for the coating layer, but due to the low elongation of PET, the formability was reduced, and accordingly, there was a problem that it was difficult to implement the physical properties that the cell pouch should have.

[0067] To improve these problems, the subject matter of the present invention may include melamine resin, urethane resin, silica powder, wax, and polyester polyol. Preferably, the subject matter may include 70 to 100 parts by weight of urethane resin, 15 to 30 parts by weight of silica powder, 2 to 15 parts by weight of wax, and 2 to 10 parts by weight of polyester polyol, per 100 parts by weight of melamine resin.

[0068] In other words, the coating layer may be a cured product of a composition comprising a subject matter including melamine resin, urethane resin, silica powder, wax and polyester polyol, and a curing agent and a solvent.

[0069] Melamine resin is a thermosetting resin made by reacting melamine with formaldehyde. It belongs to the amino resin family. Melamine resin can enhance the solvent resistance, electrolyte resistance, adhesion, durability, and strength of the coating layer, while also providing a surface strengthening effect.

[0070] A composition containing melamine resin can coat the surface of the outer resin layer while simultaneously providing adhesiveness to the outer resin layer. Upon curing, the composition containing melamine resin forms a colorless, transparent film. The film or coating layer formed by curing the composition containing melamine resin is water-resistant, heat-resistant, and chemical-resistant, and is colorless, transparent, glossy, and scratch-resistant.

[0071] From this point of view, the viscosity of the melamine resin can be 90 to 150 cps at 25°C, preferably 100 to 140 cps, using a Brookfield viscometer RV1, 50 RPM. Since the viscosity of the melamine resin satisfies 90 to 150 cps at 25°C, it has the effect of excellent workability for coating.

[0072] In addition, the specific gravity of the melamine resin can be 0.93 to 1.03 at 25℃, and the curing temperature can satisfy 170 to 190℃ and the curing time can satisfy 5 to 20 seconds.

[0073] Urethane resin is flexible, contributes to adhesion with the outer resin layer, and exhibits excellent moldability. As a result, it is beneficial in minimizing cracking at the corners when molding cell pouches.

[0074] Such urethane resins may include curable urethane resins that are reaction products of polyols and isocyanates.

[0075] Polyol is a compound having two or more hydroxyl functional groups, and may include one or more of polyester polyol, polyether polyol, polycarbonate polyol, acrylic polyol, and polycaprolactone polyol.

[0076] Isocyanates include aromatic diisocyanates (e.g., 2,6-toluene diisocyanate; 2,5-toluene diisocyanate; 2,4-toluene diisocyanate; m-phenylene diisocyanate; p-phenylene diisocyanate; methylene bis(o-chlorophenyl diisocyanate); methylenediphenylene-4,4'-diisocyanate; polycarbodiimide-modified methylenediphenylene diisocyanate; (4,4'-diisocyanato-3,3',5,5'-tetraethyl) diphenylmethane; 4,4'-diisocyanato-3,3'-dimethoxybiphenyl (o-dianisidine diisocyanate); 5-chloro-2,4-toluene diisocyanate; and 1-chloromethyl-2,4-diisocyanatobenzene), aromatic-aliphatic diisocyanates (e.g., m-xylylene diisocyanate and tetramethyl-m-xylylene diisocyanate); aliphatic diisocyanates (e.g., 1,4-diisocyanatobutane; 1,6-diisocyanatohexane; 1,12-diisocyanatododecane; and 2-methyl-1,5-diisocyanatopentane); Alicyclic diisocyanates (e.g., methylenedicyclohexylene-4,4'-diisocyanate; 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate); 2,2,4-trimethylhexyl diisocyanate; and cyclohexylene-1,4-diisocyanate), polymeric or oligomeric compounds terminated by two isocyanate functionalities (e.g., polyoxyalkylenes, polyesters, polybutadienyls, etc.) (e.g., toluene-2,4-diisocyanate-terminated diurethanes of polypropylene oxide glycol); It may include one or more of the polyisocyanates available from Bayer Corporation (Pittsburgh, PA, USA) under the trade names MONDUR and DESMODUR (e.g., DESMODUR XP7100 and DESMODUR 3300).Preferably, the isocyanate may include at least one of TDI (tlylene diisocyanate), HDI (hexamethylene diisocyanate) and MDI (methylenebis(4,1-phenylene)diisocyanate).

[0077] The subject may include 70 to 100 parts by weight of urethane resin, and preferably 80 to 100 parts by weight, per 100 parts by weight of melamine resin.

[0078] By satisfying the content of urethane resin of 70 to 100 parts by weight, excellent flexibility and moldability of the cell pouch can be secured.

[0079] Silica powder is added to the coating layer to impart a matte or glossy finish. By incorporating silica powder into the coating, the degree of matteness can be controlled, thereby suppressing glossiness, thereby ensuring a stable appearance. Furthermore, the inclusion of silica powder in the coating layer improves slipperiness and formability. Consequently, this has the beneficial effect of minimizing the adhesion of cell pouch layers.

[0080] From this perspective, the diameter of the silica powder may be 1 to 20 μm, and preferably 1 to 15 μm. By satisfying the diameter of the silica powder of 1 to 20 μm, it is advantageous for controlling mattness and has the effect of excellent dispersibility within the subject.

[0081] It is preferable to use silica powder with a low specific surface area rather than high porous silica powder with a high specific surface area for the silica powder included in the coating layer to improve not only the matte effect but also the reactivity with melamine resin, urethane resin and wax.

[0082] If porous silica is used, the porous silica powder may absorb solvent and moisture, which may cause dullness and staining due to changes in the surface area of ​​the silica powder.

[0083] In addition, although the surface coating of the cell pouch may be good during printing, it may be difficult to use the cell pouch because the area after printing may become stained due to moisture absorption.

[0084] The subject matter may include 15 to 30 parts by weight of silica powder, preferably 20 to 25 parts by weight, per 100 parts by weight of melamine resin.

[0085] By satisfying the content of silica powder of 15 to 30 parts by weight, an excellent appearance of the cell pouch can be secured.

[0086] Silica powder may cause unevenness on the surface of the coating layer. To alleviate and improve the unevenness, wax may be included in the coating layer.

[0087] The coating layer contains a small amount of wax, which can provide a matte effect and enhanced scratch resistance. In particular, the wax minimizes friction between the coating layer and metal parts during molding, thereby improving the slipperiness of the coating layer and, consequently, enhancing formability.

[0088] Good slip properties mean that the coating layer has very little residual stress, so there is almost no flaking or lifting. However, if the slip properties are too good, misalignment may occur during molding, resulting in insufficient molding.

[0089] This slipperiness can be quantified as surface slip strength (N / mm), which is the force (N) per movement distance (mm). A high surface slip strength value indicates high adhesion to the coating layer, which may lead to staining or lifting. A low surface slip strength value means the coating layer easily slips even with a small force.

[0090] From this perspective, the wax may include one or more of carnauba wax, paraffin wax, polyethylene wax, silicone wax, polyethylene wax, and polypropylene wax.

[0091] The wax is in powder form, and the diameter of the wax may be 1 to 20 μm, preferably 2 to 15 μm. By satisfying the diameter of the wax of 1 to 20 μm, there is an advantage in securing slipperiness and a matte effect.

[0092] It may contain larger diameter wax to enhance the matte effect.

[0093] However, if the wax diameter exceeds 20㎛, there is a high possibility of printing defects.

[0094] Therefore, in order to secure easy dispersibility, a matte effect, and slipperiness, it is desirable that the wax diameter be 1 to 20㎛.

[0095] Meanwhile, as the silica powder and wax are dispersed during the process of manufacturing the subject composition, the silica powder and wax may be split into smaller pieces and have a finer size.

[0096] The subject matter may contain 2 to 15 parts by weight of wax, preferably 2 to 10 parts by weight, per 100 parts by weight of melamine resin.

[0097] By satisfying the wax content of 2 to 15 parts by weight, the slipperiness, moldability, and excellent physical properties of the cell pouch can be secured.

[0098] Polyester polyol may be added to react with moisture in the air during a 1:1 ratio reaction with an isocyanate curing agent and then subsequently react with the curing agent contained in the ink.

[0099] From this point of view, the hydroxyl value (OH Value) of the polyester polyol can be 45 to 62 mgKOH / g, the weight average molecular weight can be 1800 to 3000 g / mol, and the viscosity at 25°C can be 1000 to 5000 cP.

[0100] Specifically, the hydroxyl value (OH Value) of the polyester polyol may be 48 to 55 mgKOH / g, the weight average molecular weight may be 2000 to 2500 g / mol, and the viscosity at 25°C may be 3000 to 4000 cP.

[0101] As the polyester polyol, a material obtained by reacting at least one polybasic acid and at least one diol can be used. Examples of the polybasic acid include aliphatic dibasic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and brassylic acid; and aromatic dibasic acids such as isophthalic acid, terephthalic acid, and naphthalene dicarboxylic acid. Examples of the diol include aliphatic diols such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, methyl pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, and dodecanediol; alicyclic diols such as cyclohexanediol and hydrogenated xylylene glycol; and aromatic diols such as xylylene glycol.

[0102] The subject may include 2 to 10 parts by weight of polyester polyol, preferably 2 to 5 parts by weight, per 100 parts by weight of melamine resin.

[0103] When the content of polyester polyol satisfies 2 to 10 parts by weight, the polyester polyol and the isocyanate curing agent react at a ratio of 1:1, and the curing reaction progresses as the OH content decreases, thereby obtaining the desired physical properties.

[0104] However, if the content of polyester polyol exceeds 10 parts by weight, the drying time becomes long as the OH that does not participate in the reaction increases, and blacking may occur, resulting in insufficient formation of a coating layer.

[0105] In this way, the coating layer includes a subject matter including 70 to 100 parts by weight of urethane resin, 15 to 30 parts by weight of silica powder, 2 to 15 parts by weight of wax, and 2 to 10 parts by weight of polyester polyol, relative to 100 parts by weight of melamine resin, and may also include a curing agent.

[0106] The curing agent exhibits a curing reaction by combining with the hydroxyl group of the polyester polyol included in the subject at a ratio of 1:1, and may include an isocyanate curing agent.

[0107] Polyester polyol and isocyanate curing agent react in a 1:1 ratio. If the content of the isocyanate curing agent is greater than that of the polyester polyol, the isocyanate will first combine with OH in the air, and then the remaining isocyanate will combine with the polyester polyol. Accordingly, it is preferable that the content of the isocyanate curing agent in the coating layer be greater than that of the polyester polyol.

[0108] For 100 parts by weight of the subject matter, the content of the polyol is 2 to 10 parts by weight, and considering that the ratio of the subject matter and the curing agent is 14 to 16:1, the content of the isocyanate curing agent may be 6 to 7 parts by weight. That is, the content of the polyol may be 2 to 10 parts by weight, the content of the curing agent may be 6 to 7 parts by weight, and the content of the curing agent may be greater than the content of the polyol.

[0109] The isocyanate curing agent may include at least one of 2,4- or 2,6-tolylene diisocyanate, xylylene isocyanate, 4,4'-diphenylmethane diisocyanate, methylene diisocyanate, isopropylene diisocyanate, lysine diisocyanate, 2,2,4- or 2,4,4-trimethylhexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and isopropylidene dicyclohexyl-4,4'-diisocyanate.

[0110] The coating layer may include an organic solvent together with the subject and the curing agent to increase the viscosity of the composition and the dispersibility of the components.

[0111] The organic solvent may include at least one of toluene, methyl ethyl ketone (MEK), n-hexane, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N-methyl-2-pyrrolidinone (NMP), 2-butanone, 4-methyl-2-pentanone, methyl alcohol, ethyl alcohol (EA), isopropyl alcohol, isobutyl alcohol, t-butyl alcohol, benzyl alcohol, and ethylene glycol.

[0112] Preferably, the organic solvent may include at least one of methyl ethyl ketone (MEK) and ethyl alcohol.

[0113] When the organic solvent includes at least one of methyl ethyl ketone (MEK) and ethyl alcohol, it has the advantage of excellent compatibility with the melamine resin, so that no particles are generated and no gelation phenomenon occurs.

[0114] The thickness of the coating layer may be 0.5 to 10 μm, preferably 1 to 5 μm.

[0115] The coating layer may contain the subject: curing agent in a weight ratio of 14 to 16:1, and the subject: curing agent: solvent in a weight ratio of 14 to 16:1:1 to 3.

[0116] By ensuring that the ratio of the subject matter, hardener, and solvent satisfies the above range, workability is improved through the curing and coating properties of the coating layer. Furthermore, it has the advantage of exhibiting the desired surface properties and physical properties of the coating layer.

[0117] The coating layer is a cured product of a composition containing a subject, a hardener, and a solvent, and the solvent has evaporated from the coating layer, leaving only the subject and the hardener.

[0118] Outer resin layer (20)

[0119] The outer resin layer is placed on one side of the coating layer. The outer resin layer protects the secondary battery from friction and collision with the outside world, while electrically insulating the electrode assembly from the outside world.

[0120] For example, such an outer resin layer may include one or more of polyethylene, polypropylene, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymer, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, and Teflon.

[0121] In particular, the outer resin layer may include a stretched film of a heat-resistant resin in terms of formability and heat resistance. The heat-resistant resin may include at least one of nylon and polyethylene terephthalate (PET), and preferably at least one of nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, and polymethaxylylene adipamide (MXD6).

[0122] The outer resin layer may have a single film structure or a composite film structure formed by forming layers.

[0123] When the outer resin layer has a composite membrane structure, each membrane may be bonded using an adhesive composition, or may be performed by a dry lamination method or a coextrusion method, but is not limited thereto.

[0124] The thickness of the outer resin layer is not particularly limited, but is preferably 10 to 40 μm, and more preferably 15 to 25 μm. If the thickness of the outer resin layer is less than 10 μm, raw material costs may increase. Conversely, if the thickness of the outer resin layer exceeds 40 μm, the elongation of the cell pouch may decrease and formability may be degraded.

[0125] Adhesive layer (not shown)

[0126] In order to firmly bond the outer resin layer (20) and the metal layer (30), an adhesive layer is formed between the outer resin layer and the metal layer. The adhesive used to form the adhesive layer may be a two-component curing adhesive or a one-component curing adhesive.

[0127] In addition, there is no particular limitation on the bonding mechanism of the adhesive used to form the adhesive layer, and any of a chemical reaction type, a solvent volatile type, a heat melting type, a heat pressure type, etc. can be used.

[0128] Specifically, the resin component of the adhesive layer (2) may include at least one of polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polyethylene isophthalate, polycarbonate, and copolymerized polyester; polyether adhesive; polyurethane adhesive; epoxy resin; phenol resin; polyamide resins such as nylon 6, nylon 66, nylon 12, and copolymerized polyamide; polyolefin resins such as polyolefin, acid-modified polyolefin, and metal-modified polyolefin; polyvinyl acetate resin; cellulose adhesive; (meth)acrylic resin; polyimide resin; amino resins such as urea resin and melamine resin; rubbers such as chloroprene rubber, nitrile rubber, and styrene-butadiene rubber; silicone resin; and fluorinated ethylene propylene copolymer.

[0129] Preferably, the adhesive component may include at least one of a blend resin of polyamide and acid-modified polyolefin, a blend resin of polyamide and metal-modified polyolefin, a blend resin of polyamide and polyester, a blend resin of polyester and acid-modified polyolefin, and a blend resin of polyester and metal-modified polyolefin. Among these, from the viewpoint of being excellent in durability or suppression of response under high-humidity conditions, suppression of thermal deterioration during heat sealing, etc., and suppressing a decrease in lamination strength between the outer resin layer and the metal layer, thereby effectively suppressing the occurrence of delamination, a polyurethane-based two-component curing adhesive; may include at least one of a blend resin of polyamide, polyester, or these and a modified polyolefin.

[0130] The thickness of the adhesive layer may be, but is not limited to, 2 to 50 μm.

[0131] Metal layer (30)

[0132] The metal layer is placed on one side of the substrate layer. In addition to enhancing the strength of the cell pouch, the metal layer also prevents water vapor, oxygen, and light from entering the battery.

[0133] Examples of the metal constituting the metal layer include aluminum, stainless steel, titanium, etc., and aluminum is preferred. Specifically, the metal layer may utilize metal foil or metal deposition, and aluminum foil is preferred.

[0134] When manufacturing a cell pouch, from the viewpoint of preventing wrinkles or pinholes from forming in the metal layer, soft aluminum foil such as annealed aluminum (JIS A8021P-O, JIS A8079P-O) can be used.

[0135] The thickness of the metal layer may be 10 to 200 μm, preferably 20 to 100 μm.

[0136] Inner resin layer (40)

[0137] The inner resin layer is positioned on one side of the metal layer. The inner resin layer is located on the electrode assembly side and seals the electrode assembly by heat-sealing during secondary battery assembly. Since the inner resin layer comes into direct contact with the electrode assembly, it must have insulating properties, and since it also comes into contact with the electrolyte, it must be corrosion-resistant.

[0138] Such an inner resin layer may comprise an elongated film of a thermoplastic resin.

[0139] The thermoplastic resin may include at least one of polyethylene, polypropylene, olefin copolymers such as polypropylene-butylene-ethylene terpolymers, polycarbonate, polyethylene terephthalate, polyvinyl chloride, acrylic polymers, polyacrylonitrile, polyimide, polyamide, cellulose, aramid, nylon, polyester, polyparaphenylenebenzobisoxazole, polyarylate, and Teflon, and preferably may include a polyolefin resin such as polypropylene (PP) or polyethylene (PE).

[0140] Since polypropylene (PP) has excellent mechanical properties such as tensile strength, rigidity, surface hardness, wear resistance, and heat resistance, and chemical properties such as corrosion resistance, it has an advantage in implementing the properties of cell pouches when manufacturing the inner resin layer.

[0141] In the present invention, by using a stretched thermoplastic resin film in the inner resin layer, formability can be improved compared to when using a non-stretched thermoplastic resin film. For example, by using a stretched polypropylene film in the inner resin layer, formability can be improved compared to when using a non-stretched polypropylene (Casted Polypropylene, CPP) film.

[0142] Stretched polypropylene film is a polypropylene film that is forcibly stretched due to a speed difference in equipment. Stretched polypropylene film can be manufactured by increasing the process speed in at least one section of the casting roll, corona roll, guide roll, and winder after the polypropylene resin melt is discharged through the T die in the T die method for manufacturing non-stretched polypropylene film. For example, stretched polypropylene film can be manufactured by increasing the process speed by 1% or more, preferably 1.2 to 3%, compared to when manufacturing non-stretched polypropylene film. Alternatively, the stretched polypropylene film can be manufactured by obtaining and using a commercially available product having the above-mentioned tensile properties.

[0143] The thickness of the inner resin layer may be 20 to 100 μm, preferably 40 to 80 μm. If the thickness of the inner resin layer is less than 20 μm, the electrolytic resistance may not be satisfied. Conversely, if the thickness of the inner resin layer exceeds 100 μm, the formability may not be satisfied.

[0144] The overall thickness of the cell pouch for secondary batteries may range from 50 to 500 μm, and preferably from 80 to 300 μm. If the overall thickness of the cell pouch for secondary batteries is less than 50 μm, molding maintenance may be insufficient. Conversely, if the overall thickness of the cell pouch exceeds 500 μm, processing costs increase.

[0145] A cell pouch for a secondary battery can be manufactured by applying an adhesive layer to one surface of an outer resin layer using one of the following methods: extrusion, gravure coating, or roll coating, and then attaching a metal layer and an inner resin layer thereto using a co-extrusion method, a lamination method using thermal lamination, or the like. The coating layer located on the outermost layer can be manufactured by applying it to the other surface of the outer resin layer and curing it.

[0146] A secondary battery has a structure in which an electrode assembly and an electrolyte are contained in a cell pouch. The cell pouch may be composed of upper and lower films based on the position of the electrode assembly.

[0147] Secondary batteries may include, but are not limited to, nickel cadmium batteries, nickel hydrogen batteries, lithium ion batteries, and lithium ion polymer batteries.

[0148] Secondary batteries can be used in small products such as digital cameras, mobile phones, and portable computers; large products requiring high output such as electric or hybrid vehicles; power storage devices that store surplus generated power or renewable energy; and backup power storage devices.

[0149] The cell pouch of the present invention can exhibit the following physical properties.

[0150] Under conditions of 23℃ and 50% humidity, the tensile strength in each of the MD and TD directions may be 10 to 30 kg / 15 mm, and preferably 12.0 to 20.0 kg / 15 mm.

[0151] Under conditions of 23℃ and 50% humidity, the elongation in each of the MD and TD directions can be 80 to 100%, and preferably 90.0 to 100%.

[0152] Regarding formability, when a mold machine having a forming groove depth of 4 to 7.5 mm is used, a hydraulic cylinder is lowered into the forming groove to form a cell pouch, and when visually observed, the depth until no cracks occur on the surface of the cell pouch may be 7.0 to 7.5 mm. Here, the crack means a length of 0.1 mm or more.

[0153] Regarding the electrolyte, when one drop of the electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M) is dropped on the surface of the coating layer of a cell pouch having a size of 100 x 100 mm in width and height using a dropper, and after 60 seconds, the dropped electrolyte is wiped off. When the surface condition of the coating layer is observed with the naked eye, the same surface condition as before dropping the electrolyte using the dropper can be maintained.

[0154] Regarding the content resistance, a cotton swab soaked in any one of electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M), ethyl alcohol, methyl ethyl ketone, and toluene) is rubbed 1 cm on each side based on the point of contact on the coating layer surface of a cell pouch having a size of 100 x 100 mm in width and height. Afterwards, when the number of times the coating layer surface is peeled off is measured, it may be 30 times or more.

[0155] Rubbing 1cm above means rubbing an area corresponding to 1cm.

[0156] Regarding scratch resistance, when a steel brush is placed on the surface of a cell pouch measuring 80 x 150 mm in width and height using a KP-M4250 device, a 400 g weight is pressed down, and the degree of scratch is measured after performing a reciprocating motion 2 or 6 times, there may be no scratches. (The above scratch means a scratch of 0.1 μm or more in the depth direction or / and length direction of the surface of the cell pouch.)

[0157] Specific examples of cell pouches for secondary batteries with excellent chemical resistance are as follows.

[0158] 1. Manufacturing of cell pouches for secondary batteries with excellent chemical resistance

[0159] Example 1

[0160] 1) Coating layer:

[0161] Subject: A coating layer having a thickness of 3 μm was prepared from a composition in which a curing agent and a solvent were mixed in a weight ratio of 15:1:2.

[0162] As a subject, it contains 70 parts by weight of urethane resin, 15 parts by weight of silica powder (diameter 5 to 15㎛), 2 parts by weight of carnauba wax (diameter 10 to 15㎛), and 2 parts by weight of polyester polyol for 100 parts by weight of melamine resin (25℃@100cps, specific gravity 1.00).

[0163] The curing agent included isocyanate, and the solvent included EA and MEK. The hydroxyl value (OH Value) of the polyester polyol was 50 mgKOH / g, the weight average molecular weight was 2000 g / mol, and the viscosity at 25°C was 4000 cP.

[0164] 2) Outer resin layer: Nylon resin was used and the thickness is 25㎛.

[0165] 3) Metal layer: Aluminum was used and the thickness is 40㎛.

[0166] 4) Inner resin layer: Non-stretched polypropylene (CPP) was used, and the thickness is 80㎛.

[0167] A 153㎛ pouch film was manufactured including the above 1) to 4) and an adhesive layer.

[0168] Example 2

[0169] In the coating layer, a pouch film was manufactured under the same conditions as Example 1, except that 90 parts by weight of urethane resin and 20 parts by weight of silica powder (diameter 5 to 15 ㎛) were used for 100 parts by weight of melamine resin (25℃@140cps, specific gravity 1.00).

[0170] Example 3

[0171] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer contained 10 parts by weight of carnauba wax (diameter 10 to 15 μm) as the subject.

[0172] Example 4

[0173] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer contained 10 parts by weight of polyester polyol as the subject, the hydroxyl value (OH Value) of the polyester polyol was 60 mgKOH / g, the weight average molecular weight was 2500 g / mol, and the viscosity at 25°C was 3000 cP.

[0174] Example 5

[0175] In the coating layer, a pouch film was manufactured under the same conditions as Example 1, except that 60 parts by weight of urethane resin was used for 100 parts by weight of melamine resin (25℃@160cps, specific gravity 1.50).

[0176] Example 6

[0177] In the coating layer, a pouch film was manufactured under the same conditions as Example 1, except that 110 parts by weight of urethane resin was used for 100 parts by weight of melamine resin (25℃@160cps, specific gravity 1.50).

[0178] Example 7

[0179] A pouch film was manufactured under the same conditions as Example 1, except that in the coating layer, 10 parts by weight of silica powder (diameter 30 to 45 ㎛) was used as the subject.

[0180] Example 8

[0181] A pouch film was manufactured under the same conditions as Example 1, except that 40 parts by weight of silica powder (diameter 30 to 45 ㎛) was used as the subject in the coating layer.

[0182] Example 9

[0183] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer contained 1 part by weight of carnauba wax (diameter 25 to 40 μm) as the subject.

[0184] Example 10

[0185] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer contained 20 parts by weight of carnauba wax (diameter 25 to 40 μm) as the subject.

[0186] Example 11

[0187] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer contained 1 part by weight of polyester polyol as the subject, the hydroxyl value (OH Value) of the polyester polyol was 70 mgKOH / g, and the weight average molecular weight was 3200 g / mol.

[0188] Example 12

[0189] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer contained 15 parts by weight of polyester polyol as the subject, the hydroxyl value (OH Value) of the polyester polyol was 65 mgKOH / g, and the weight average molecular weight was 1700 g / mol.

[0190] Example 13

[0191] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer was a composition in which the subject: curing agent: solvent was mixed in a weight ratio of 13:1:2.

[0192] Example 14

[0193] A pouch film was manufactured under the same conditions as Example 1, except that the coating layer was a composition in which the subject: curing agent: solvent was mixed in a weight ratio of 17:1:2.

[0194] Comparative Example 1

[0195] A pouch film was manufactured under the same conditions as Example 1 except that there was no coating layer.

[0196] 2. Physical property evaluation method and results

[0197] For the pouch films manufactured in Examples 1 to 14 and Comparative Example 1, the physical properties were measured and listed in Tables 1 to 3 below.

[0198] Tensile strength in the MD and TD directions was measured under conditions of 23℃ and 50% humidity.

[0199] The elongation was measured in the MD and TD directions under conditions of 23℃ and 50% humidity.

[0200] [Table 1]

[0201]

[0202] [Table 2]

[0203]

[0204] [Table 3]

[0205]

[0206] Figure 2 shows the results of an electrolyte resistance test of a cell pouch for a secondary battery according to Example 1 of the present invention. The electrolyte resistance test was measured using the method described in this specification.

[0207] From the results in Fig. 2, it can be confirmed that the cell pouch according to Example 1 has considerably excellent electrolyte resistance. On the other hand, Comparative Example 1 exhibited a surface condition as if a foreign substance was present on the PET layer even after only 5 seconds.

[0208] As a result of measuring Examples 2 to 4, similar physical property results were shown as in Example 1.

[0209] On the other hand, the results of measuring Examples 5 to 14 showed a surface condition similar to Comparative Example 1, as if a foreign substance was present.

[0210] Figure 3 shows the results of a content resistance test of a cell pouch for a secondary battery according to Example 1 of the present invention. The content resistance test was measured using the method described in this specification.

[0211] From the results in Fig. 3, it can be confirmed that the cell pouch according to Example 1 has considerably excellent solvent resistance. On the other hand, Comparative Example 1 was confirmed to have weak resistance to each solvent.

[0212] As a result of measuring Examples 2 to 4, similar physical property results were shown as in Example 1.

[0213] On the other hand, Examples 5 to 14 were confirmed to have weak solvent resistance, similar to Comparative Example 1.

[0214] Figure 4 shows the results of a scratch resistance test of a cell pouch for a secondary battery according to Example 1 of the present invention. The scratch resistance test was measured using the method described in this specification.

[0215] From the results in Fig. 4, it can be confirmed that the cell pouch according to Example 1 exhibits scratch resistance in which white lines do not appear after two and six tests, respectively. On the other hand, Comparative Example 1 exhibited white lines (inside the red dotted line) on the surface after six tests.

[0216] Examples 2 to 4 showed similar physical property results to Example 1.

[0217] On the other hand, Examples 5 to 14 showed white lines on the surface similar to Comparative Example 1.

[0218] Although the present invention has been described with reference to the drawings exemplified above, it is to be understood that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications may be made by those skilled in the art within the scope of the technical idea of ​​the present invention. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

Claims

1. Coating layer containing melamine resin; An outer resin layer disposed on one surface of the above coating layer; A metal layer disposed on one side of the above substrate layer; and A cell pouch comprising an inner resin layer disposed on one surface of the metal layer.

2. In paragraph 1, The above coating layer comprises a subject and a hardener, The above subject matter is a cell pouch comprising 70 to 100 parts by weight of urethane resin, 15 to 30 parts by weight of silica powder, 2 to 15 parts by weight of wax, and 2 to 10 parts by weight of polyester polyol, per 100 parts by weight of melamine resin.

3. In paragraph 2, The above coating layer is a cell pouch containing the subject: curing agent in a weight ratio of 14 to 16:

1.

4. In paragraph 1, Cell pouch having the viscosity of the above melamine resin of 90 to 150 cps at 25°C.

5. In paragraph 2, A cell pouch having a diameter of the above silica powder of 1 to 20 μm.

6. In paragraph 2, A cell pouch having a diameter of 1 to 20 μm of the above wax.

7. In paragraph 1, Cell pouch with a tensile strength of 10 to 30 kg / 15 mm in each of the MD and TD directions under conditions of 23℃ and 50% humidity.

8. In paragraph 1, Cell pouch having an elongation of 80 to 100% in each of the MD and TD directions under conditions of 23°C and 50% humidity.

9. In paragraph 1, A cell pouch having a depth of 7.0 to 7.5 mm when a hydraulic cylinder is lowered into the forming groove to form a cell pouch using a molding machine having a forming groove depth of 4 to 7.5 mm and when observed with the naked eye, the depth until no cracks occur on the surface of the cell pouch is 7.0 to 7.5 mm. (The above crack means a crack with a length of 0.1 mm or more.) 10. In paragraph 1, A cell pouch having a size of 100 mm wide x 100 mm long, in which one drop of electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M) is dropped using a dropper on the surface of the coating layer of the cell pouch, and after 60 seconds, the dropped electrolyte is wiped off. When the surface condition of the coating layer is observed with the naked eye, the cell pouch maintains the same surface condition as before dropping the electrolyte using the dropper.

11. In paragraph 1, A cell pouch having a size of 100 x 100 mm in width and height, when a cotton swab soaked in any one of electrolyte (ethylene carbonate (EC): diethyl carbonate (DEC): ethyl methyl carbonate (EMC) = 1:1:1, LiPF61M), ethyl alcohol, methyl ethyl ketone, and toluene) is rubbed 1 cm on each side based on the point of contact, and the number of times the coating layer surface is peeled off is measured, is 30 or more times.

12. In paragraph 1, Using the KP-M4250 equipment, a steel brush was placed on the surface of a cell pouch measuring 80 x 150 mm in width and height, and a 400g weight was pressed down. After performing a reciprocating motion 2 or 6 times, the degree of scratches was measured. A cell pouch without scratches. (The above scratch means a scratch of 0.1㎛ or more in the depth direction or / and length direction of the cell pouch surface.)

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