Manufacturing apparatus for separators for secondary batteries, method for manufacturing separators for secondary batteries, and secondary battery

Abstract

The present invention provides a manufacturing apparatus and method for secondary battery separators that can produce separators for secondary batteries having a low thermal shrinkage rate and a low shutdown temperature. [Solution] In a manufacturing apparatus for a secondary battery separator, the secondary battery separator includes a porous substrate and a coating layer, the manufacturing apparatus includes a drying section for the coating layer, the drying section includes a drying oven that provides a drying space for the coating layer, and an injector located inside the drying oven and having an injection plate with a plurality of discharge holes that inject hot air toward the coating layer, the injection plate having an opening ratio of 10 to 65% in Equation 1, where d is 5 to 20 mm and p is 10 to 15 mm: [Equation 1] Opening ratio = (90.5 × d 2 ) / p 2 (d is the average diameter of the discharge holes, and p is the average distance between the centers of multiple discharge holes).

Description

Technical Field

[0001] This application claims the benefit of priority based on Republic of Korea Patent Application No. 10-2025-0026703 filed on February 28, 2025, and all contents disclosed in the documents of the corresponding Republic of Korea patent application are incorporated as a part of the present specification.

[0002] The present invention relates to an apparatus for manufacturing a separator for a secondary battery, a method for manufacturing a separator for a secondary battery, and a secondary battery.

Background Art

[0003] Recently, with the rapid spread of battery-powered electronic devices such as mobile phones, laptop computers, and electric vehicles, demand for high-energy-density, high-capacity secondary batteries has been increasing rapidly. Accordingly, research and development for improving the performance of lithium secondary batteries are being actively promoted.

[0004] A lithium secondary battery is a battery comprising a positive electrode and a negative electrode containing an active material capable of intercalation and deintercalation of lithium ions, and an electrolyte, and generates electrical energy through oxidation and reduction reactions that occur when lithium ions are intercalated into and deintercalated from the positive electrode and the negative electrode.

[0005] A lithium secondary battery may include a separator between a positive electrode and a negative electrode. The separator may consist only of a porous base material, but the performance of the separator can be further improved by forming a coating layer on at least one surface of the porous base material. The coating layer can be formed by coating a coating layer composition onto at least one surface of the porous base material to form a coating film for the coating layer, and drying the coating film for the coating layer.

Prior Art Literature

Patent Literature

[0006]

Patent Literature 1

[0007] As one embodiment, there is provided an apparatus and a method for manufacturing a separator for a secondary battery, which can manufacture a separator for a secondary battery having a low thermal shrinkage rate and a low shutdown temperature.

[0008] As another embodiment, there is provided an apparatus and a method for manufacturing a separator for a secondary battery, which can manufacture a separator for a secondary battery having uniform thermal shrinkage rate and uniform shutdown temperature. Means for Solving the Problem

[0009] According to one embodiment, an apparatus for manufacturing a separator for a secondary battery is provided.

[0010] In the apparatus for manufacturing a separator for a secondary battery, the separator for a secondary battery includes a porous substrate and a coating layer formed on at least one surface of the porous substrate, the manufacturing apparatus includes a drying section for a coating film for the coating layer of the separator for a secondary battery, and the drying section includes a drying oven that provides a drying space for the coating film for the coating layer, and an injector positioned in the drying oven and having an injection plate provided with a plurality of injection holes for injecting hot air toward the coating film for the coating layer, the injection plate has an opening porosity of 10 to 65% according to the following Formula 1, in the following Formula 1, d is 5 to 20 mm, and p is 10 to 15 mm:

[0011] [Formula 1] Opening porosity = (90.5 × d 2 ) / p 2 (In Formula 1 above, d is the average diameter of the injection holes, p is the average value of the separation distances between the centers of the injection holes among the plurality of injection holes).

[0012] In another embodiment, a method for manufacturing a separator for a secondary battery is provided.

[0013] The method for manufacturing the secondary battery separator includes the steps of: manufacturing a laminate of a porous substrate and a coating film formed on at least one surface of the porous substrate; and transferring the laminate into a drying section of a secondary battery manufacturing apparatus to dry the coating film, wherein the drying section includes a drying oven that provides a drying space for the coating film, and an injector located inside the drying oven and having an injection plate with a plurality of discharge holes for injecting hot air toward the coating film, wherein the injection plate has an opening ratio of 10 to 65% in the following formula 1, where d is 5 to 20 mm and p is 10 to 15 mm:

[0014] [Formula 1] Open area ratio =(90.5 × d 2 ) / p 2 (In formula 1 above, d is the average diameter of the discharge hole. p is the average value of the distance between the centers of the multiple discharge holes.

[0015] In another embodiment, a secondary battery is provided.

[0016] The secondary battery includes a positive electrode, a negative electrode, and a separator for a secondary battery located between the positive electrode and the negative electrode, which is manufactured by the manufacturing apparatus or manufacturing method. [Effects of the Invention]

[0017] A manufacturing apparatus and method for a secondary battery separator according to one embodiment has a low thermal shrinkage rate and a low shutdown temperature, and by manufacturing a secondary battery separator with a uniform thermal shrinkage rate and shutdown temperature, the reliability of the secondary battery can be improved. [Brief explanation of the drawing]

[0018] [Figure 1]Figure 1 illustrates a secondary battery manufacturing apparatus according to one embodiment. [Figure 2] Figure 2 illustrates the drying section of the secondary battery manufacturing apparatus shown in Figure 1. [Figure 3] Figure 3 is a magnified plan view of a portion of the spray plate within the drying section shown in Figure 2. [Figure 4] Figure 4 is an enlarged plan view of a portion of the injection plate according to another embodiment. [Figure 5] Figure 5 is a plan view of an injection plate according to another embodiment. [Figure 6] Figure 6 illustrates a secondary battery according to one embodiment. [Figure 7] Figure 7 illustrates a secondary battery according to one embodiment. [Figure 8] Figure 8 illustrates a secondary battery according to one embodiment. [Figure 9] Figure 9 illustrates a secondary battery according to one embodiment. [Modes for carrying out the invention]

[0019] The following describes in detail embodiments of the present invention. However, these are presented as examples only and do not limit the present invention, which is defined solely by the scope of the claims described below.

[0020] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is described as being "on top of" another part, this includes not only the case where it is "directly on top of" the other part, but also the case where there is yet another part in between.

[0021] Unless otherwise specified herein, singular nouns may also include plural nouns. Furthermore, unless otherwise specified, "A or B" may mean "containing A, containing B, or containing both A and B."

[0022] In this specification, “these combinations” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the constituents.

[0023] In this specification, “particle size D50” means particle size, which refers to the diameter of a particle whose cumulative volume in the particle size distribution is 50% by volume. The particle size distribution can be measured by methods widely known to those skilled in the art. For example, the particle size distribution may be measured with a particle size analyzer, or by transmission electron microscope or scanning electron microscope images. Alternatively, it may be measured using a measuring device that utilizes dynamic light scattering, and after performing data analysis to count the number of particles for each particle size range, the D50 value can be calculated from there. Or, it can be measured using the laser diffraction method. More specifically when measuring by laser diffraction, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (e.g., Microtrac's MT 3000), and after irradiating with ultrasound at approximately 28 kHz at an output of 60 W, the D50 based on the 50% particle size distribution in the measuring device can be calculated.

[0024] In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0025] In this specification, when a numerical range is described, "X to Y" means "X or greater and Y or less (X ≤ and ≤ Y)."

[0026] A manufacturing apparatus for a secondary battery separator according to one embodiment can produce a secondary battery separator having a low thermal shrinkage rate and a low shutdown temperature, and in which the thermal shrinkage rate and shutdown temperature are uniform throughout the separator. The manufacturing apparatus can provide the aforementioned low thermal shrinkage rate, low shutdown temperature, uniform thermal shrinkage rate, and uniform shutdown temperature by controlling the drying of the coating film for the coating layer during the manufacturing of the secondary battery separator.

[0027] The secondary battery separator includes a porous substrate and a coating layer formed on at least one surface of the porous substrate. The coating layer can be formed by coating at least one surface of the porous substrate with a coating layer composition to form a coating film, and then drying the coating film through a drying section as described below.

[0028] The apparatus for manufacturing the secondary battery separator includes a drying section for the coating film of the secondary battery separator.

[0029] The manufacturing apparatus for separators for secondary batteries will be explained with reference to Figures 1 to 3.

[0030] Figure 1 illustrates a secondary battery manufacturing apparatus according to one embodiment. Figure 2 illustrates the drying section of the secondary battery manufacturing apparatus shown in Figure 1. Figure 3 is an enlarged plan view of a portion of the spray plate in the drying section shown in Figure 2.

[0031] The manufacturing apparatus for separators for secondary batteries includes a coating section 200 and a drying section 300.

[0032] The coating section 200 coats at least one surface of the porous substrate 1 with the coating layer composition. The coating section 200 forms a laminate of the porous substrate 1 and the coating layer film 2 formed on one surface of the porous substrate 1.

[0033] The coating unit 200 may include a coating die 210 for coating one surface of the porous substrate 1 with a coating layer composition 220. The coating unit 200 may further include a coating layer composition supplier for supplying the coating layer composition 220 to the coating die 210. The coating unit 200 may further include a transfer roll 4 for transporting the porous substrate 1.

[0034] The coating die 210, the coating layer composition feeder, and the transfer rolls are all commonly used in typical secondary battery separator manufacturing equipment known to those skilled in the art, and therefore, a detailed explanation is omitted.

[0035] The drying unit 300 can dry the laminate of the porous substrate 1 and the coating film 2 transferred from the coating unit 200 to form a porous substrate 1 and a separator having a coating layer (3) formed on one surface of the porous substrate 1. In one embodiment, the drying unit 300 can dry the coating film 2.

[0036] The drying section 300 may include a drying oven 310 and an injector 320 located inside the drying oven 310.

[0037] The drying unit 300 can dry the coating film 2 while transferring the porous substrate 1 and the coating film 2 in the mechanical direction MD of the porous substrate 1.

[0038] The drying oven 310 can provide a drying space for the coating film 2 for the coating layer. The shape and size of the drying oven can be adjusted by the size of the spray plate, etc. Although not shown in Figure 2, the drying oven 310 may further include a controller that can maintain a predetermined temperature and humidity at a constant level.

[0039] The sprayer 320 can dry the coating film 2 of the laminate that has been transferred into the drying oven 310 to form a coating layer.

[0040] The injector 320 may include an injector body 321, a blower fan 322, and an injection plate 323.

[0041] The sprayer body 321 can support the blower fan 322 and the spray plate 323. Figure 2 shows a case where one sprayer 320 is included in the drying oven 310, but the drying oven may contain multiple sprayers 320 along the transport direction of the porous substrate 1 and the coating film 2 for the coating layer.

[0042] The blower fan 322 may be located inside the sprayer body 321 or above the spray plate 323. The blower fan 322 can generate hot air through rotation and transfer the hot air to the spray plate.

[0043] The spray plate 323 may have a plurality of discharge holes 324 formed therein for spraying hot air toward the coating film 2 for the coating layer.

[0044] The discharge hole 324 is a hole that penetrates the injection plate 323. The discharge hole 324 can transfer hot air produced by the blower fan 322 located above the injection plate 323 to the coating layer film 2. The discharge hole 324 may be formed by punching the injection plate 323, but is not limited thereto. The injection plate 323 may be made of a metal with excellent heat resistance, but is not limited thereto.

[0045] The injection plate 323 has an opening ratio of 10-65% in the following formula 1, where d is 5-20 mm and p is 10-15 mm.

[0046] [Formula 1] Open area ratio =(90.5 × d 2 ) / p 2 (In formula 1 above, d is the average diameter of the discharge hole. p is the average value of the distance between the centers of the multiple discharge holes.

[0047] The drying section of the manufacturing apparatus is equipped with an injection plate having a plurality of discharge holes, and by controlling the average diameter of the plurality of discharge holes, the distance between the centers of the discharge holes, and the porosity of the openings in formula 1, it is possible to provide a low thermal shrinkage rate and a low shutdown temperature, thereby producing a secondary battery separator with uniform thermal shrinkage rate and shutdown temperature.

[0048] In the above formula 1, the average diameter d of the discharge holes may be the average value of the combined diameters of the discharge holes formed in the injection plate.

[0049] Here, "discharge hole diameter" can refer to the normal diameter if the discharge hole is circular. If the discharge hole is not circular, the discharge hole diameter can refer to the longest length within the discharge hole.

[0050] In the above formula 1, the separation distance between the centers of the discharge holes may be the average value of the measured separation distances, obtained by defining an arbitrary discharge hole formed in the injection plate and a discharge hole formed immediately adjacent to the arbitrary discharge hole, and measuring the separation distance between the centers 324a of the two discharge holes.

[0051] Here, the center of the discharge hole can mean the center of a circle if the discharge hole is circular. If the discharge hole is not circular, it is defined as the point where lines drawn from any point on the surface forming the discharge hole to any opposite point intersect.

[0052] The porosity of 10-65% in Formula 1 provides a separator that offers a low thermal shrinkage rate, a low shutdown temperature, and a uniform thermal shrinkage rate when a coating film for a coating layer is dried using a spray plate formed with discharge holes having the d and p values ​​in Formula 1.

[0053] If the porosity in formula 1 is less than 10%, the coating film for the coating layer may not dry sufficiently with hot air, resulting in insufficient formation of the coating layer. In such cases, only a portion of the coating film for the coating layer may dry, leading to uneven thermal shrinkage and shutdown temperature.

[0054] If the porosity in formula 1 exceeds 65%, the coating film for the coating layer and the porous substrate may become excessively dry, which could actually increase the thermal shrinkage rate.

[0055] The porosity in formula 1 may be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, or 65%.

[0056] In the above formula 1, d may be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 mm, and p may be 10, 11, 12, 13, 14, or 15 mm.

[0057] For example, in formula 1, d may be 5 to 10 mm and p may be 10 to 15 mm. For example, in formula 1, the porosity may be 10 to 45%, 10 to 41%, or, for example, 20 to 25%. Within this range, it may be easy to manufacture an injection plate having the porosity of formula 1.

[0058] For example, in formula 1, d may be 5 to 8 mm, p may be 10 to 15 mm, and the porosity may be 10 to 25%. Within this range, the thermal shrinkage rate may be lower and the air permeability may be improved.

[0059] For example, in formula 1, d may be 5 to 8 mm, p may be 10 to 15 mm, and the porosity may be 20 to 25%. Within this range, the thermal shrinkage rate becomes significantly lower, and the air permeability can be improved.

[0060] The discharge hole 324 may be circular. However, the discharge hole is not limited to being circular and may be elliptical or amorphous. Preferably, the discharge hole 324 may be circular.

[0061] The minimum distance m between discharge holes may be 5 to 15 mm, for example, 5 to 10 mm. Within this range, it may be easy to manufacture separators having a uniform thermal shrinkage rate and a uniform shutdown temperature.

[0062] Here, "minimum distance between discharge holes" can mean the minimum distance between any discharge hole formed in the injection plate and a discharge hole formed immediately adjacent to that discharge hole.

[0063] In the injection plate, the discharge holes may be formed spaced apart from each other along the machine direction (MD) of the porous substrate.

[0064] In this specification, a "row of discharge holes" is defined as a series of discharge holes formed along the median diameter (MD) of a porous substrate, spaced apart from one another and arranged in a single row.

[0065] In a spray plate, only one row of discharge holes may be formed along the transverse direction (TD) of the porous substrate. However, forming multiple rows of discharge holes along the transverse direction of the porous substrate in a spray plate may be advantageous in providing a more uniform thermal shrinkage rate and shutdown temperature, as it allows for more uniform distribution of hot air to a coating film of the same area.

[0066] Figure 3 illustrates an injection plate in which three rows of discharge holes are formed along the width direction of a porous substrate. However, the present invention is not limited to this, and rows of three or more discharge holes may be formed.

[0067] The injection plate 323 may have a first row of discharge holes L1 and a second row of discharge holes L2 that are sequentially formed along the width direction TD of the porous substrate.

[0068] The first row of discharge holes L1 may include a plurality of discharge holes 324 formed spaced apart from each other along the mechanical direction MD of the porous substrate. The second row of discharge holes L2 may include a plurality of discharge holes 324 formed spaced apart from each other along the mechanical direction MD of the porous substrate.

[0069] The centers 324a of the discharge holes in the second row of discharge holes L2 may be positioned between the centers 324a of the discharge holes in the first row of discharge holes L1. In this case, hot air can be more uniformly transferred from the spray plate to the coating layer, thereby further improving the uniformity of the thermal shrinkage rate and shutdown temperature. The centers of the discharge holes are the same as those described above.

[0070] According to one embodiment, a line T1 connecting the center 324a of a discharge hole in a first row of discharge holes and the center 324a of a discharge hole in a second row of discharge holes can form an angle (θ) of 55 to 65° with respect to the mechanical direction MD of the porous substrate. The angle indicates the position between a discharge hole in the first row of discharge holes and a discharge hole in the second row of discharge holes. Within this angle range, separators with low thermal shrinkage and shutdown temperature can be manufactured with high efficiency using an injection plate of the same area. For example, the angle can be 60°.

[0071] The line T2 connecting the centers of the discharge holes in the first row of discharge holes and the line T3 connecting the centers of the second row of discharge holes may be parallel to each other. In this case, since the discharge holes are uniformly formed not only in the mechanical direction of the porous substrate but also in the width direction of the porous substrate, it may be easy to manufacture a separator with a uniform thermal shrinkage rate and shutdown temperature.

[0072] According to one embodiment, the spacing between discharge holes 324 in the first row of discharge holes L1 may be the same as that between them. According to one embodiment, the spacing between discharge holes 324 in the second row of discharge holes L2 may be the same as that between them. According to one embodiment, the spacing between discharge holes in the first row of discharge holes may be the same as the spacing between discharge holes in the second row of discharge holes.

[0073] The spacing distance n between the first row of discharge holes and the second row of discharge holes may be smaller than the average diameter d of the discharge holes in Equation 1. In such a case, since the distance between the first row of discharge holes and the second row of discharge holes is not excessively large, the opening ratio of 10-45% in Equation 1 can be easily achieved. For example, the spacing distance between the first row of discharge holes and the second row of discharge holes may be 10-20 mm, for example, 10-15 mm.

[0074] Here, "the distance between the first row of discharge holes and the second row of discharge holes" may mean the minimum distance in the width direction of the porous substrate between the discharge holes contained in the first row of discharge holes and the discharge holes contained in the second row of discharge holes.

[0075] Although not shown in Figures 2 and 3, the manufacturing apparatus may further include a transfer roll located inside a drying oven for transferring the porous substrate and the coating film for the coating layer within the drying oven.

[0076] The transfer roll allows for continuous drying of the coating film by transferring the porous substrate and the coating film within the drying oven.

[0077] The following describes a manufacturing apparatus for a secondary battery separator according to another embodiment.

[0078] The aforementioned secondary battery separator manufacturing apparatus is substantially identical to the secondary battery separator manufacturing apparatus shown in Figures 1 to 3, except that it includes an injection plate as described in Figure 4.

[0079] Figure 4 is an enlarged plan view of a portion of the injection plate according to another embodiment.

[0080] Referring to Figure 4, the injection plate 323 has additional discharge holes 325 formed between the first row of discharge holes L1 and the second row of discharge holes L2, with smaller discharge hole diameters. The discharge holes 325 allow for easy adjustment of the discharge hole diameter in at least one of the first row of discharge holes L1 or the second row of discharge holes L2, assuming an injection plate with the same opening ratio.

[0081] The following describes a manufacturing apparatus for a secondary battery separator according to another embodiment.

[0082] The aforementioned secondary battery separator manufacturing apparatus is substantially identical to the secondary battery separator manufacturing apparatus shown in Figures 1 to 3, except that it includes an injection plate as described in Figure 5.

[0083] Figure 5 is a plan view of an injection plate according to another embodiment.

[0084] Referring to Figure 5, the injection plate 323 has regions along the width direction TD of the porous substrate where the porosity ratio of Equation 1 differs from region to region. The injection plate 323 includes a central region A and peripheral regions B and C adjacent to the central region A. The porosity ratio of Equation 1 in the central region A may be higher than that of the peripheral regions B and C. In such a case, a uniform air permeability distribution effect may be further possible.

[0085] <Manufacturing method for separators for secondary batteries> The following describes a method for manufacturing a separator for secondary batteries according to one embodiment.

[0086] The method for manufacturing the secondary battery separator includes the steps of: manufacturing a laminate of a porous substrate and a coating film formed on at least one surface of the porous substrate; and transferring the laminate to a drying section of a secondary battery separator manufacturing apparatus to dry the coating film, wherein the drying section includes a drying oven that provides a drying space for the coating film, and a spray plate located inside the drying oven that has a plurality of discharge holes for spraying hot air toward the coating film, wherein the spray plate has an opening ratio of 10 to 65% in formula 1, where d is 5 to 20 mm and p is 10 to 15 mm.

[0087] In the above manufacturing method, by drying the coating film for the coating layer in the drying section, it is possible to manufacture a secondary battery separator having a low thermal shrinkage rate and a low shutdown temperature, and having a uniform thermal shrinkage rate and shutdown temperature.

[0088] In one embodiment, the above-described manufacturing apparatus for secondary battery separators can be used in the manufacturing method.

[0089] In the above manufacturing method, the manufacturing apparatus and drying section for the secondary battery separator are substantially the same as those described above. Therefore, only the remaining parts will be described below.

[0090] The porous substrate may have numerous pores and may be a substrate commonly used in electrochemical elements. The porous substrate may be a polymer film formed from any one polymer selected from the group consisting of polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon®, or polytetrafluoroethylene, or from a copolymer or mixture of two or more of these polymers.

[0091] The porous substrate may, for example, be a polyolefin-based substrate containing polyolefin. The polyolefin-based substrate has excellent shutdown functionality and can contribute to improving battery safety. The polyolefin-based substrate can be selected from, for example, a single polyethylene film, a single polypropylene film, a polyethylene / polypropylene double film, a polypropylene / polyethylene / polypropylene triple film, or a polyethylene / polypropylene / polyethylene triple film. In addition, the polyolefin-based substrate may contain a non-olefin resin in addition to the olefin resin, or a copolymer of an olefin and a non-olefin monomer.

[0092] The porous substrate can have a thickness of 1 μm to 40 μm. For example, the porous substrate may have a thickness of 1 to 10 μm.

[0093] The coating film for the coating layer may be a coating film of a composition containing a filler and a (meth)acrylic binder.

[0094] The filler may be, for example, an inorganic filler, an organic filler, a composite filler containing inorganic substances, or a combination thereof. The inorganic filler may be a ceramic material that can improve heat resistance. The inorganic filler may include, for example, a metal oxide, a quasi-metallic oxide, a metal fluoride, a metal hydroxide, or a combination thereof. The inorganic filler may include, but is not limited to, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof. The organic filler may include, but is not limited to, an acrylic compound, an imide compound, an amide compound, or a combination thereof. The organic filler may have, but is not limited to, a core-shell structure. Preferably, the filler may be boehmite. The filler may have a particle size D50 of 0.4 μm or less, for example, 0.3 μm or less, for example, 0.1 μm to 0.3 μm. Within this range, an effect of improving the heat resistance of the separator may be obtained. The filler may be included in a binder:filler mass ratio of 1:10 to 1:50, for example, 1:20 to 1:30. Within this range, the separator may be easily manufactured using the separator manufacturing apparatus.

[0095] The (meth)acrylic binder may contain sulfonic acid group-containing structural units. The (meth)acrylic binder may further contain one or more structural units derived from (meth)acrylate or (meth)acrylic acid, cyano group-containing structural units, or (meth)acrylamide.

[0096] The sulfonic acid group-containing structural units may be present in the (meth)acrylic binder in amounts of 0.1 to 60 mol%, for example, 0.1 to 20 mol%, 0.1 to 10 mol%, 1 to 20 mol%, for example, 1 to 10 mol%, for example, 20 to 65 mol%, or 30 to 65 mol%. When the sulfonic acid group-containing structural units are present within these ranges, the separator can exhibit excellent adhesion, heat resistance, and air permeability.

[0097] The structural units derived from (meth)acrylate or (meth)acrylic acid may be present in the (meth)acrylic binder in amounts of 0 mol% to 70 mol%, for example, 10 mol% to 70 mol%, 10 to 60 mol%, 20 to 60 mol%, 10 to 50 mol%, 30 to 60 mol%, 10 to 40 mol%, or 40 to 55 mol%. Within this range, the separator can exhibit excellent adhesion, heat resistance, air permeability, and oxidation resistance.

[0098] The cyano group-containing structural units may be present in the (meth)acrylic binder in amounts of 0 to 85 mol%, for example, 30 to 85 mol%, 30 to 70 mol%, 30 to 60 mol%, 35 to 60 mol%, or 35 to 55 mol%. Within this range, the separator can ensure excellent oxidation resistance and exhibit adhesive strength, heat resistance, and air permeability.

[0099] The structural units derived from (meth)acrylamide may be present in the (meth)acrylic binder in amounts of 0 mol% to 95 mol%, for example, 40 to 85 mol%, 50 to 85 mol%, 55 to 95 mol%, 60 to 85 mol%, 75 to 95 mol%, and 80 to 95 mol%. Within this range, the separator can ensure excellent oxidation resistance and exhibit adhesive strength, heat resistance, and air permeability.

[0100] According to one embodiment, the (meth)acrylic binder may have sulfonic acid group-containing structural units, structural units derived from (meth)acrylate or (meth)acrylic acid, and cyano group-containing structural units. In one embodiment, the sum of the sulfonic acid group-containing structural units, structural units derived from (meth)acrylate or (meth)acrylic acid, and cyano group-containing structural units may be 95 mol% or more, for example, 95-100 mol% or 100 mol%, of 100 mol% of the (meth)acrylic binder.

[0101] According to other embodiments, the (meth)acrylic binder may have sulfonic acid group-containing structural units and structural units derived from (meth)acrylamide. In one embodiment, the sum of the sulfonic acid group-containing structural units and structural units derived from (meth)acrylamide may be 95 mol% or more, for example, 95-100 mol% or 100 mol%, of 100 mol% of the (meth)acrylic binder.

[0102] In other embodiments, the (meth)acrylic binder may have sulfonic acid group-containing structural units, structural units derived from (meth)acrylate or (meth)acrylic acid, and structural units derived from (meth)acrylamide. In one embodiment, the sum of the sulfonic acid group-containing structural units, structural units derived from (meth)acrylate or (meth)acrylic acid, and structural units derived from (meth)acrylamide may be present in 95 mol% or more of 100 mol% of the (meth)acrylic binder, for example, 95-100 mol% or 100 mol%.

[0103] The structural units derived from (meth)acrylate or (meth)acrylic acid may be represented, for example, by the following chemical formulas 1, 2, 3, or combinations thereof:

[0104] [ka]

[0105] [ka]

[0106] [ka]

[0107] (In the above chemical formulas 1 to 3, R 1 ~R 6each independently represent hydrogen or a methyl group, and in Chemical Formula 2, M is an alkali metal.). The alkali metal may be, for example, lithium, sodium, potassium, rubidium or cesium.

[0108] The cyano group-containing structural unit may be represented by, for example, the following Chemical Formula 4.

[0109]

Chemical Formula

[0110] (In Chemical Formula 4, R 7 and R 8 each independently represent hydrogen or a C1~C3 alkyl group, L 1 represents -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, x is an integer of 0 to 2, L 2 is a substituted or unsubstituted C1~C10 alkylene group, a substituted or unsubstituted C3~C20 cycloalkylene group, a substituted or unsubstituted C6~C20 arylene group, or a substituted or unsubstituted C3~C20 heterocyclic group, and y is an integer of 0 to 2.)

[0111] The sulfonic acid group-containing structural unit may be a structural unit containing a conjugate base of sulfonic acid, a sulfonate, sulfonic acid or a derivative thereof. For example, the sulfonic acid group-containing structural unit may be represented by the following Chemical Formula 5, Chemical Formula 6, Chemical Formula 7 or a combination thereof.

[0112]

Chemical Formula

[0113]

Chemical Formula

[0114]

Chemical Formula

[0115] (In the above chemical formulas 5 to 7, R 9 ~R 14 Each is independently either hydrogen or a C1-C3 alkyl group, L 3 , L 5 and L 7 These are independently -C(=O)-, -C(=O)O-, -OC(=O)-, -O-, or -C(=O)NH-, and L 4 , L 6 and L 8 Each of these is independently a substituted or unsubstituted C1-C10 alkylene group, a substituted or unsubstituted C3-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or unsubstituted C3-C20 heterocyclic group; a, b, c, d, e, and f are independently integers from 0 to 2; and in the above chemical formula 6, M is an alkali metal.

[0116] The structural unit derived from (meth)acrylamide can be represented by the following chemical formula 8.

[0117] [ka]

[0118] (In chemical formula 8, R 15 and R 16 These are, independently, hydrogen or a methyl group.

[0119] The (meth)acrylic binder may be in various forms, such as an alternating polymer in which the structural units are alternately distributed, a random polymer in which they are arbitrarily distributed, or a graft polymer in which some of the structural units are grafted. The weight-average molecular weight (Mw) of the (meth)acrylic binder may be 200,000 g / mol to 700,000 g / mol, for example, 200,000 g / mol to 600,000 g / mol or 300,000 g / mol to 600,000 g / mol. Within this range, the separator can exhibit excellent adhesion, heat resistance, air permeability, and oxidation resistance. The weight-average molecular weight may also be the average molecular weight on a polystyrene basis measured using gel permeation chromatography. The glass transition temperature of the (meth)acrylic binder may be 200°C to 280°C, for example, 210°C to 270°C or 210°C to 260°C. Within the aforementioned range, the separator can exhibit excellent adhesive strength, heat resistance, air permeability, and oxidation resistance. The glass transition temperature may be a value measured by differential scanning calorimetry. The (meth)acrylic binder may have a melting point (Tm) of 160°C or higher.

[0120] The coating film for the coating layer can be formed by applying the coating composition for the coating layer to at least one surface of the porous substrate to a predetermined thickness.

[0121] The thickness of the coating film for the coating layer may be 0.1 to 10 μm, for example, 0.1 to 5 μm or 0.5 to 5 μm. Within this range, the separator can be easily manufactured by the manufacturing apparatus.

[0122] <Separator for secondary batteries> A separator for a secondary battery according to one embodiment can be manufactured using the manufacturing apparatus for secondary battery separators described above.

[0123] The aforementioned separator for secondary batteries can exhibit excellent air permeability. For example, the separator may have an air permeability of less than 125 sec / 100 cc, for example, 122 sec / 100 cc or less.

[0124] The aforementioned separator for secondary batteries may have a thermal shrinkage rate of 3.0% or less in both the mechanical and width directions, for example, 2.8% or less. Within this range, the reliability of the battery can be improved.

[0125] The lithium secondary battery separator may have a shutdown temperature of less than 145°C, for example, 143°C or lower. Within this range, the reliability of the battery can be improved by quickly shutting down the battery in the event of thermal runaway.

[0126] <Lithium-ion secondary battery> Another embodiment provides a lithium secondary battery comprising a separator membrane for a lithium secondary battery according to one embodiment, a positive electrode, and a negative electrode.

[0127] The separator membrane for lithium secondary batteries is as described above. The separator membrane for lithium secondary batteries may be located between the positive and negative electrodes.

[0128] <Positive electrode> A positive electrode for a lithium secondary battery may include a current collector and a positive electrode active material layer formed on the current collector. The positive electrode active material layer may include a positive electrode active material and further include a binder and / or a conductive material. As an example, the positive electrode may further include an additive that can act as a sacrificial positive electrode.

[0129] <Cathode active material> As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithium-intercalated intercalation compound) can be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, or combinations thereof can be used.

[0130] The aforementioned composite oxide may be a lithium transition metal composite oxide, and specific examples include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free nickel-manganese oxides, or combinations thereof.

[0131] As an example, a compound represented by any one of the following chemical formulas can be used: Li a A 1-b X b O 2-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);Li a Mn 2-b X b O 4-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);Li a Ni 1-b-c Co b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0≦e≦0.1);Li a NiG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-b G b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn2Gb O4(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-g G g PO4(0.90≦a≦1.8, 0≦g≦0.5);Li (3-f) Fe2(PO4)3(0≦f≦2);Li a FePO4 (0.90 ≤ a ≤ 1.8).

[0132] In the above chemical formula, A is Ni, Co, Mn or a combination thereof, X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof, D is O, F, S, P or a combination thereof, G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof, L 1 These are Mn, Al, or a combination thereof.

[0133] As an example, the positive electrode active material may be a high-nickel positive electrode active material in which the nickel content relative to 100 mol% of the metal excluding lithium is 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, and 99 mol% or less. High-nickel positive electrode active materials can realize high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0134] The content of the positive electrode active material is 90% to 99.5% by weight of 100% by weight of the positive electrode active material layer, and the content of the binder and conductive material may be 0.5% to 5% by weight, respectively, based on 100% by weight of the positive electrode active material layer.

[0135] The binder plays a role in ensuring good adhesion between positive electrode active material particles and good adhesion of the positive electrode active material to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0136] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes in the battery can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0137] Al can be used as the current collector, but is not limited to it.

[0138] <Negative electrode> A negative electrode for a lithium secondary battery includes a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer contains a negative electrode active material and may further contain a binder and / or a conductive material.

[0139] For example, the negative electrode active material layer may contain 90% to 99% by weight of negative electrode active material, 0.5% to 5% by weight of binder, and 0% to 5% by weight of conductive material.

[0140] <Negative electrode active material> The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of being doped and undoped with lithium, or a transition metal oxide.

[0141] The material capable of reversibly intercalating / deintercalating lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, platy, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0142] As the alloy of lithium metal, an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0143] As the material capable of being doped and undoped with lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0<x<2), a Si-Q alloy (wherein Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination of the foregoing. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination of the foregoing.

[0144] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (core) formed by granulating primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0145] The silicon-carbon composite may further contain crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of the core.

[0146] The Si-based or Sn-based anode active material can be used in combination with a carbon-based anode active material.

[0147] The binder plays a role in ensuring good adhesion between the negative electrode active material particles and good adhesion between the negative electrode active material and the current collector. The binder can be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0148] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0149] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0150] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0151] The dryer is a polymer material that can be formed into fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0152] The conductive material is used to impart conductivity to the electrodes, and any electronically conductive material that does not cause chemical changes can be used in the battery that is constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0153] As the negative electrode current collector, copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof can be used.

[0154] Lithium secondary batteries may also contain an electrolyte.

[0155] <Electrolyte> The electrolyte for lithium secondary batteries may also contain a non-aqueous organic solvent and a lithium salt.

[0156] The aforementioned non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0157] The non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0158] Examples of carbonate-based solvents that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0159] Suitable ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0160] As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. can be used. As ketone-based solvents, cyclohexanone, etc. can be used. As alcohol-based solvents, ethyl alcohol, isopropyl alcohol, etc. can be used, and as aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include a double bond, aromatic ring, or ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; sulfolanes, etc. can be used.

[0161] The aforementioned non-aqueous organic solvents can be used alone or in combination of two or more.

[0162] Furthermore, when using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and these can be mixed in a volume ratio of 1:1 to 1:9.

[0163] The aforementioned lithium salts dissolve in organic solvents and act as a source of lithium ions within the battery, enabling the operation of basic lithium secondary batteries and promoting the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N(lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (where x and y are integers from 1 to 20), may contain one or more selected from lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0164] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, etc., depending on their form. Figures 6 to 9 are schematic diagrams showing a lithium secondary battery according to one embodiment. Figure 6 shows a cylindrical type, Figure 7 shows a prismatic type, and Figures 8 and 9 show a pouch-type battery form. Referring to Figures 6 to 9, the lithium secondary battery 100 may include an electrode assembly 40 with a separator membrane 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, negative electrode 20, and separator membrane 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in Figure 6. Also, in Figure 7, the lithium secondary battery 100 may include a positive electrode lead tap 11 and a positive electrode terminal 12, and a negative electrode lead tap 21 and a negative electrode terminal 22. As shown in Figures 8 and 9, the lithium secondary battery 100 may include electrode taps 70, namely a positive electrode tap 71 and a negative electrode tap 72, which serve as electrical pathways for inducing the current formed in the electrode assembly 40 to the outside.

[0165] A lithium secondary battery according to one embodiment of the present invention can be applied to automobiles, mobile phones, and / or various forms of electrical devices, but the present invention is not limited to these.

[0166] Examples and comparative examples of the present invention are described below. However, the following examples are merely one embodiment of the present invention, and the present invention is not limited to the following examples.

[0167] (Manufacturing example) In a 10 L four-necked flask equipped with a stirrer, thermometer, and condenser, 6361 g of distilled water, 1.0 mol of acrylic acid, 8.5 mol of acrylamide, 0.01 mol of potassium persulfate, 0.5 mol of 2-acrylamido-2-methylpropanesulfonic acid, and 1.05 equivalents of 5N lithium hydroxide aqueous solution (relative to the total amount of 2-acrylamido-2-methylpropanesulfonic acid) were added. The internal pressure was then reduced to 10 mmHg using a diaphragm pump, and the internal pressure was returned to atmospheric pressure with nitrogen. This process was repeated three times. The reaction was allowed to proceed for 12 hours while controlling the temperature of the reaction solution to stabilize between 65°C and 70°C. After cooling to room temperature, the pH of the reaction solution was adjusted to 7-8 using a 25% aqueous ammonia solution. Poly(acrylic acid-co-lithium acrylate-co-acrylamido-co-2-acrylamido-2-methylpropanesulfonic acid lithium salt) was produced in this manner. The molar ratio of acrylic acid + lithium acrylate salt, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid is 10:85:5. Approximately 10 mL of the reaction solution (reaction product) was taken out, and the non-volatile components were measured to be 9.5% (theoretical value: 10%).

[0168] (Example 1) An acrylic binder (10% by weight in distilled water) produced in Production Example 1 and boehmite (particle size D50: 200 nm, plate-shaped) as a filler were mixed, added to water as a solvent, and then milled and dispersed using a bead mill at 25°C for 30 minutes to produce a coating layer composition. The weight ratio of the acrylic binder to the filler in the coating layer composition is 1:20.

[0169] As a porous substrate, a polyethylene film (thickness: 5.5 μm, manufactured by SK Corporation, air permeability: 120 sec / 100 cc, puncture strength: 480 kgf) is coated with the aforementioned coating layer composition to a thickness of 1.8 μm using a coating method, thereby forming a coating film on one surface of the porous substrate.

[0170] A laminate of a porous substrate and a coating film for the coating layer was placed in a drying oven with the spray plate shown in Figure 3 and dried to produce a separator having a porous substrate and a coating layer formed on one surface of the porous substrate. The temperature inside the drying oven was 70°C and the drying time inside the drying oven was maintained at 5 minutes. The detailed configuration of the spray plate inside the drying oven is shown in Table 1 below, and the discharge holes are circular and have the same diameter.

[0171] (Examples 2 and 3) The separator was manufactured using the same method as in Example 1, except that the spray plate in the drying oven was modified as shown in Table 1 below.

[0172] (Example 4) The separator was manufactured using the same method as in Example 1, except that the spray plate in the drying oven was modified as shown in Table 1 below.

[0173] (Comparative Example 1) The separator was manufactured in the same manner as in Example 1, except that an injection plate with slot-shaped discharge holes was used instead of multiple discharge holes as in Example 1.

[0174] (Comparative Example 2 and Comparative Example 3) The separator was manufactured using the same method as in Example 1, except that the spray plate in the drying oven was modified as shown in Table 1 below.

[0175] The following physical properties were evaluated using the separators manufactured in the examples and comparative examples.

[0176] <Air permeability and standard deviation (unit: sec / 100cc)> Air permeability was measured by measuring the time (in seconds) it took for 100cc of air to pass through the separator using a measuring device (EG01-55-1MR, manufactured by Asahi Seiko).

[0177] A separator (200 mm wide) was divided into five equal sections, and the air permeability was measured for each section. The average value and standard deviation were then calculated.

[0178] <Dry heat shrinkage rate and standard deviation (unit: %)> The separators of the examples and comparative examples are cut to a size of 5 cm × 5 cm to prepare samples. After leaving the samples in a convection oven at 130°C for 1 hour, the thermal shrinkage rates in the mechanical direction (MD) and the perpendicular direction (TD) are calculated. The shrinkage rates are calculated using the following formula 1.

[0179] [Mathematics 1] Thermal shrinkage rate = (L0 - L1) / L0 × 100 (L0 is the initial length of the separator, and L1 is the length of the separator after being left at 130°C for 1 hour.)

[0180] A separator (200 mm wide) was divided into five equal parts, and the thermal shrinkage rate was measured for each part. The average value and standard deviation were then calculated.

[0181] <Shutdown temperature and standard deviation (unit: °C)> Samples were prepared by cutting the lithium secondary battery separators of the examples and comparative examples to a size of 5 cm × 5 cm. A positive electrode slurry was prepared by mixing 97 wt% lithium cobalt nickel aluminum oxide as the positive electrode active material, 1.5 wt% carbon nanotubes as the conductive material, and 1.5 wt% polyvinylidene fluoride as the binder, and adding N-methyl-2-pyrrolidone. The prepared positive electrode slurry was applied to aluminum foil, dried, and rolled to produce a positive electrode. A negative electrode slurry was prepared by mixing 97.4 wt% artificial graphite, 1.0 wt% carboxymethylcellulose as the negative electrode active material, 1.5 wt% styrene-butadiene rubber as the binder, and 0.1 wt% carbon nanotubes as the conductive material, and adding distilled water. The prepared negative electrode slurry was applied to copper foil, dried, and rolled to produce a negative electrode. One sample was placed between the positive and negative electrodes to create three sets of positive-sample-negative electrode stacks, which were then placed in pouches. 2 g of electrolyte (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in which 1.5 M LiPF6 was dissolved (30:50:20 volume ratio based on a total volume of 100)) was injected to completely impregnate the stacks in the electrolyte. After sealing, the stacks were left at 25°C for 12 hours to manufacture a lithium secondary battery. While the lithium secondary battery was running, the impedance of the battery was measured using an EIS (electrochemical impedance spectroscopy) device while the temperature was increased at a heating rate of 10°C / min. The temperature at which the impedance became 100 times the initial value was defined as the shutdown temperature.

[0182] A separator (200 mm wide) was divided into five equal parts, and the shutdown temperature was measured for each part. The average value and standard deviation were then calculated.

[0183] [Table 1]

[0184] *A coated separator (200mm wide) was divided into five equal parts, and measurements were taken for each part. The average value and standard deviation were then calculated.

[0185] As shown in Table 1 above, the separator manufacturing apparatus of the embodiment has a low thermal shrinkage rate and a low shutdown temperature, and by manufacturing a separator for secondary batteries with a uniform thermal shrinkage rate and shutdown temperature, the reliability of secondary batteries can be improved.

[0186] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and can be implemented in various ways within the scope of the claims, the detailed description of the invention, and the attached drawings, and these also naturally fall within the scope of the present invention. [Explanation of symbols]

[0187] 1: Porous base material 2: Coating film for the coating layer 3: Coating layer 4: Transfer Roll 10: Positive electrode 11: Positive lead tap 12: Positive terminal 20: Negative electrode 21: Negative lead tap 22: Negative terminal 30: Separation membrane 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode Tap 71: Positive Tap 72: Negative electrode tap 200: Coating part 210: Coating Die 220: Composition for coating layer 300:Drying section 310: Drying oven 320: Injector 321: Injector body 322: Blower fan 323: Injection Plate 324, 325, 326: Discharge holes 324a: Center of the discharge hole A: Central area B, C: Peripheral area d: Average diameter of the discharge hole L1: Row of the first discharge holes L2: Row of the second discharge holes m: Minimum distance between discharge holes MD: Mechanical direction n: Distance between the first row of discharge holes and the second row of discharge holes. p: Average distance between the centers of multiple discharge holes. T1: A line connecting the center 324a of the discharge holes in the first row of discharge holes and the center 324a of the discharge holes in the second row of discharge holes. T2: A line connecting the centers of the discharge holes in the first row of discharge holes. T3: A line connecting the centers of the rows of the second discharge holes. TD: Width direction θ: Angle of T1 relative to MD (mechanical direction)

Claims

1. A manufacturing apparatus for separators for secondary batteries, The separator for the secondary battery includes a porous substrate and a coating layer formed on at least one surface of the porous substrate. The aforementioned manufacturing apparatus, Including the dried portion of the coating film for the coating layer of the separator for the secondary battery, The drying section includes a drying oven that provides a drying space for the coating layer film, and a sprayer located inside the drying oven and having a spray plate with a plurality of discharge holes for spraying hot air toward the coating layer film. The injection plate has an opening ratio of 10 to 65% according to the following formula 1. A manufacturing apparatus for a secondary battery separator, characterized in that, in the following formula 1, d is 5 to 20 mm and p is 10 to 15 mm: [Formula 1] Open area ratio = (90.5 × d) 2 ) / p 2 (In the above formula 1, d is the average diameter of the discharge hole. p is the average value of the distance between the centers of the multiple discharge holes.

2. The apparatus for manufacturing a separator for a secondary battery according to claim 1, characterized in that the minimum distance between the discharge hole and a discharge hole adjacent to the discharge hole is 5 to 15 mm.

3. The apparatus for manufacturing a separator for a secondary battery according to claim 1, characterized in that the discharge holes are each circular or elliptical in shape.

4. The injection plate has a row of discharge holes formed therein. The apparatus for manufacturing a separator for a secondary battery according to claim 1, characterized in that the row of discharge holes is formed such that the plurality of discharge holes are spaced apart from each other along the mechanical direction of the porous substrate.

5. The apparatus for manufacturing a separator for a secondary battery according to claim 4, characterized in that a plurality of rows of discharge holes are formed along the width direction (transverse direction) of the porous substrate.

6. The injection plate has rows of discharge holes, including a first row of discharge holes and a second row of discharge holes, which are sequentially formed along the width direction of the porous substrate. The apparatus for manufacturing a separator for a secondary battery according to claim 5, characterized in that the center of the discharge holes in the second row of discharge holes is located between the centers of the discharge holes in the first row of discharge holes.

7. The apparatus for manufacturing a separator for a secondary battery according to claim 6, characterized in that the line connecting the center of the discharge holes in the first row of discharge holes and the center of the discharge holes in the second row of discharge holes forms an angle of 55 to 65° with respect to the mechanical direction of the porous substrate.

8. The apparatus for manufacturing a separator for a secondary battery according to claim 6, characterized in that the line connecting the centers of the discharge holes in the first row of discharge holes and the line connecting the centers of the discharge holes in the second row of discharge holes are parallel to each other.

9. The apparatus for manufacturing a secondary battery separator according to claim 6, characterized in that the distances between discharge holes in the first row of discharge holes are the same, and the distances between discharge holes in the second row of discharge holes are the same.

10. The apparatus for manufacturing a separator for a secondary battery according to claim 6, characterized in that the separation distance between the first row of discharge holes and the second row of discharge holes is smaller than the average diameter d of the discharge holes in formula 1.

11. The manufacturing apparatus for a secondary battery separator according to claim 1, further comprising a transfer roll located inside the drying oven for transferring the porous substrate and the coating film for the coating layer inside the drying oven.

12. The apparatus for manufacturing a separator for a secondary battery according to claim 11, characterized in that a plurality of transfer rolls are arranged along the mechanical direction of the porous substrate.

13. In the above formula 1, d is 5 to 8 mm, p is 10 to 15 mm, and the aperture ratio is 20 to 25%. The injection plate has rows of discharge holes including a first row of discharge holes and a second row of discharge holes formed sequentially along the width direction of the porous substrate, and the line connecting the center of the discharge holes in the first row of discharge holes and the center of the discharge holes in the second row of discharge holes forms an angle of 55 to 65° with respect to the mechanical direction of the porous substrate, as described in claim 1, for manufacturing a separator for a secondary battery.

14. A step of manufacturing a laminate of a porous substrate and a coating film for a coating layer formed on at least one surface of the porous substrate, The step includes transferring the laminate to the drying section of a secondary battery manufacturing apparatus to dry the coating film for the coating layer, The drying section includes a drying oven that provides a drying space for the coating film for the coating layer, and The sprayer includes a spray plate located inside the drying oven and having multiple discharge holes for spraying hot air toward the coating layer film, A method for manufacturing a separator for secondary batteries, characterized in that the injection plate has an opening ratio of 10 to 65% in the following formula 1, where d is 5 to 20 mm and p is 10 to 15 mm: [Formula 1] Open area ratio = (90.5 × d) 2 ) / p 2 (In the above formula 1, d is the average diameter of the discharge hole. p is the average value of the distance between the centers of the multiple discharge holes.

15. The porous substrate has a thickness of 1 to 10 μm. The method for manufacturing a separator for a secondary battery according to claim 14, characterized in that the coating film for the coating layer has a thickness of 0.5 to 5 μm.

16. The method for manufacturing a separator for a secondary battery according to claim 14, characterized in that the coating film for the coating layer is a coating film of a coating layer composition in which the mass ratio of (meth)acrylic binder to filler is 1:10 to 1:

50.

17. The method for producing a separator for a secondary battery according to claim 16, characterized in that the (meth)acrylic binder contains one or more of the following: a sulfonic acid group-containing structural unit, a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing structural unit, or a structural unit derived from (meth)acrylamide.

18. A secondary battery comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, manufactured by a manufacturing apparatus according to any one of claims 1 to 13.

19. A secondary battery comprising a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode, manufactured by the manufacturing method described in any one of claims 14 to 17.

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