Apparatus for preparing separator for rechargeable battery, method for preparing separator for rechargeable battery and rechargeable battery

Abstract

An apparatus for manufacturing a separator for a secondary battery, a method for manufacturing a separator for a secondary battery, and a secondary battery are provided.

Description

Technology Field

[0001] The 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 Technology

[0003] Recently, accompanied by the rapid proliferation of battery-powered electronic devices such as mobile phones, laptop computers, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries is rapidly increasing. Accordingly, research and development to improve the performance of lithium-ion batteries is actively underway.

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

[0005] A lithium secondary battery may include a separator between the positive electrode and the negative electrode. The separator may consist solely of a porous substrate, but the performance of the separator can be further enhanced by forming a coating layer on at least one surface of the porous substrate. The coating layer may be formed by coating a coating layer composition on at least one surface of the porous substrate to form a coating film, and then drying the coating film. The problem to be solved

[0007] One embodiment provides an apparatus and method for manufacturing a separator for a secondary battery that can manufacture a separator for a secondary battery having a low thermal shrinkage rate and a low shutdown temperature.

[0008] Another embodiment provides an apparatus and method for manufacturing a separator for a secondary battery that can manufacture a separator for a secondary battery with uniform thermal shrinkage rate and shutdown temperature. means of solving the problem

[0010] According to one embodiment, a manufacturing apparatus for a separator for a secondary battery is provided.

[0011] In the above-described manufacturing apparatus for a separator for a secondary battery, the separator for a secondary battery comprises a porous substrate and a coating layer formed on at least one surface of the porous substrate, and the manufacturing apparatus comprises a drying section for a coating film for the coating layer of the separator for a secondary battery, wherein the drying section comprises a drying oven providing a drying space for the coating film for the coating layer, and a sprayer having a spray plate having a plurality of discharge holes located within the drying oven and spraying hot air toward the coating film for the coating layer, wherein the spray plate has an opening ratio of 10 to 65% according to Equation 1 below, where d is 5 to 20 mm and p is 10 to 15 mm:

[0012] [Equation 1]

[0013] Opening rate = (90.5 xd 2 ) / p 2

[0014] (In the above Equation 1,

[0015] d is the average diameter of the discharge hole,

[0016] p is the average value of the distance between the centers of the discharge holes among the plurality of discharge holes mentioned above).

[0017] Another embodiment provides a method for manufacturing a separator for a secondary battery.

[0018] The above method for manufacturing a separator for a secondary battery comprises 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 device to dry the coating film, wherein the drying section comprises a drying oven providing a drying space for the coating film, and a sprayer having a spray plate having a plurality of discharge holes located within the drying oven and spraying hot air toward the coating film, wherein the spray plate has an opening ratio of 10 to 65% according to Equation 1 below, where d is 5 to 20 mm and p is 10 to 15 mm:

[0019] [Equation 1]

[0020] Opening rate = (90.5 xd 2 ) / p 2

[0021] (In the above Equation 1,

[0022] d is the average diameter of the discharge hole,

[0023] p is the average value of the distance between the centers of the discharge holes among the plurality of discharge holes mentioned above).

[0024] Another embodiment is provided with a secondary battery.

[0025] The above-described arch battery includes a positive electrode, a negative electrode, and a separator for a secondary battery located between the positive electrode and the negative electrode and manufactured by the above-described manufacturing device or the above-described manufacturing method. Effects of the invention

[0027] The apparatus and method for manufacturing a separator for a secondary battery according to one embodiment can increase the reliability of a secondary battery by manufacturing a separator for a secondary battery that has a low thermal shrinkage rate and a low shutdown temperature, and has a uniform thermal shrinkage rate and shutdown temperature. Brief explanation of the drawing

[0029] FIG. 1 illustrates a secondary battery manufacturing apparatus according to one embodiment. Figure 2 illustrates the drying section of the secondary battery manufacturing apparatus of Figure 1. Figure 3 is an enlarged plan view of a portion of the spray plate in the drying section of Figure 2. FIG. 4 is an enlarged plan view of a portion of a spray plate according to another embodiment. FIG. 5 is a plan view of a spray plate according to another embodiment. FIGS. 6 to 9 illustrate a secondary battery according to one embodiment. Specific details for implementing the invention

[0030] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0031] Unless otherwise specifically stated in this specification, when a part such as a layer, film, region, plate, etc. is described as being "on" another part, this includes not only cases where it is "immediately on" another part, but also cases where there is another part in between.

[0032] Unless otherwise specified in this specification, a singular form may also include a plural form. Additionally, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0033] In this specification, "combination of these" may mean a mixture of components, a laminate, a composite, a copolymer, an alloy, a blend, and a reaction product, etc.

[0034] In this specification, 'particle size D50' refers to a particle size that represents 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 using a particle size analyzer, or by using a transmission electron microscope (TEM) image or a scanning electron microscope (SEM) image. Alternatively, the D50 value may be obtained by measuring using a measuring device utilizing dynamic light scattering, performing data analysis to count the number of particles for each particle size range, and then calculating from this. Or, it may be measured using a laser diffraction method. When measuring by laser diffraction, more specifically, after dispersing the particles to be measured in a dispersion medium, they are introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000) and irradiated with ultrasound of about 28 kHz at an output of 60 W, and then D50 can be calculated based on 50% of the particle size distribution in the measuring device.

[0035] In this specification, '(meth)acrylic' means acrylic and / or methacrylic.

[0036] In this specification, when describing a numerical range, 'X to Y' means 'X or greater and Y or less (X ≤ and ≤ Y).'

[0037] A manufacturing apparatus for a separator for a secondary battery according to one embodiment can manufacture a separator for a secondary battery having a low thermal shrinkage rate and a low shutdown temperature, and having a uniform thermal shrinkage rate and shutdown temperature 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 separator for the secondary battery.

[0038] The above-described separator for a secondary battery comprises a porous substrate and a coating layer formed on at least one surface of the porous substrate. The coating layer may be formed by coating a coating layer composition on at least one surface of the porous substrate to form a coating film, and drying the coating film through a drying unit described below.

[0039] The above-mentioned manufacturing apparatus for a secondary battery separator includes a drying section for a coating film for a coating layer of a secondary battery separator.

[0040] Referring to FIGS. 1 to 3, an apparatus for manufacturing a separator for a secondary battery will be described.

[0041] FIG. 1 illustrates a secondary battery manufacturing apparatus according to one embodiment. FIG. 2 illustrates a drying section of the secondary battery manufacturing apparatus of FIG. 1. FIG. 3 is an enlarged plan view of a portion of the spray plate of the drying section of FIG. 2.

[0042] The manufacturing device for a separator for a secondary battery includes a coating section (200) and a drying section (300).

[0043] The coating portion (200) coats a composition for a coating layer on at least one surface of the porous substrate (1). The coating portion (200) forms a laminate of the porous substrate (1) and a coating film (2) formed on one surface of the porous substrate (1).

[0044] The coating section (200) may include a coating die (210) for coating a coating layer composition (220) on one surface of a porous substrate (1). The coating section (200) may further include a coating layer composition feeder for supplying the coating layer composition (220) to the coating die (210). The coating section (200) may further include a transfer roller for transporting the porous substrate (1).

[0045] The coating die (210), the composition feeder for the coating layer, and the transfer roll are each typically applied in a conventional secondary battery separator manufacturing device known to those skilled in the art, so a detailed description is omitted.

[0046] 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 separation membrane having the porous substrate (1) and the 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).

[0047] The drying unit (300) may include a drying oven (310); and a sprayer (320) located inside the drying oven (310).

[0048] The drying unit (300) can dry the coating film (2) while transporting the porous substrate (1) and the coating film (2) in the mechanical direction (MD) of the porous substrate (1).

[0049] 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 according to the size of the spray plate, etc. Although not shown in FIG. 2, the drying oven (310) may further include a controller capable of maintaining a constant temperature and humidity.

[0050] The sprayer (320) can dry the coating film (2) for the coating layer among the laminates transferred into the drying oven (310) to form a coating layer.

[0051] The sprayer (320) may include a sprayer body (321), a blower fan (321), and a spray plate (323).

[0052] The sprayer body (321) can support the blower fan (322) and the spray plate (323). FIG. 2 illustrates a case where one sprayer (320) is included in the drying oven (310), but multiple sprayers (320) may be included in the drying oven along the conveying direction of the porous substrate (1) and the coating film (2) for the coating layer.

[0053] The blower fan (322) may be located within the sprayer body (321) and on the upper part of the spray plate (323). The blower fan (323) can generate hot air through rotation and transfer the hot air to the spray plate.

[0054] The spray plate (323) may have a plurality of discharge holes (324) formed therein for spraying hot air toward the coating film (2).

[0055] The discharge hole (324) is a hole that penetrates the spray plate (323). The discharge hole (324) can transmit hot air generated from a blower fan (322) located on the upper part of the spray plate (323) to the coating film (2) for the coating layer. The discharge hole (324) may be formed by punching the spray plate (323), but is not limited thereto. The spray plate (323) may be formed of a metal with excellent heat resistance, but is not limited thereto.

[0056] The injection plate (323) has an opening rate of 10 to 65% according to Equation 1 below, where d is 5 to 20 mm and p is 10 to 15 mm.

[0057] [Equation 1]

[0058] Opening rate = (90.5 xd 2 ) / p 2

[0059] (In the above Equation 1,

[0060] d is the average diameter of the discharge hole,

[0061] p is the average value of the distance between the centers of the discharge holes among the plurality of discharge holes mentioned above).

[0062] The drying unit of the above-described manufacturing device is equipped with a spray plate having a plurality of discharge holes formed therein, and by controlling the average diameter of the plurality of discharge holes, the distance between the centers of the discharge holes, and the opening rate of Equation 1, it is possible to provide a low thermal shrinkage rate and a low shutdown temperature, and to manufacture a separator for a secondary battery in which both the thermal shrinkage rate and the shutdown temperature are uniform.

[0063] In the above Equation 1, the average diameter d of the discharge holes may be the average value of the sum of the diameters of the discharge holes formed in the injection plate.

[0064] Here, 'diameter of the discharge hole' may refer to the standard diameter if the discharge hole is circular. If the discharge hole is not circular, the diameter of the discharge hole may refer to the longest length within the discharge hole.

[0065] In the above Equation 1, the distance between the centers of the discharge holes may be the average value of the measured distances, by determining an arbitrary discharge hole formed in the injection plate and a discharge hole formed immediately adjacent to the arbitrary discharge hole, and measuring the distance between the centers (324a) of the two discharge holes.

[0066] Here, the center of the discharge hole may refer to the center of a normal circle when the discharge hole is circular. When the discharge hole is not circular, it is defined as the point where lines meet when lines are drawn from any point on the surface forming the discharge hole to any point opposite it.

[0067] The opening rate of 10 to 65% in the above Equation 1 can provide a separator that provides a low thermal shrinkage rate, a low shutdown temperature, a uniform thermal shrinkage rate, and a uniform shutdown temperature when a coating film for a coating layer is dried using a spray plate having discharge holes formed with the d and p values ​​in the above Equation 1.

[0068] If the perforation rate in Equation 1 above is less than 10%, the coating film for the coating layer may not be properly dried by hot air, and the coating layer may not be properly formed, and drying may occur only in some areas of the coating film for the coating layer, resulting in uneven heat shrinkage rate and shutdown temperature.

[0069] If the porosity in Equation 1 above exceeds 65%, the thermal shrinkage rate may actually increase as the coating film and porous substrate become excessively dry.

[0070] For example, in the above formula 1, d may be 5 to 10 mm and p may be 10 to 15 mm. For example, in the above formula 1, the opening rate may be 10 to 45%, 10 to 41%, for example, 20 to 25%. Within the above range, it may be easy to manufacture a spray plate having the opening rate of the above formula 1.

[0071] For example, in the above formula 1, d may be 5 to 8 mm, p may be 10 to 15 mm, and the opening rate may be 10 to 25%. Within the above range, the heat shrinkage rate may be lowered and air permeability may be improved.

[0072] For example, in the above formula 1, d may be 5 to 8 mm, p may be 10 to 15 mm, and the opening rate may be 20 to 25%. Within the above range, the thermal shrinkage rate may be significantly reduced and air permeability may be improved.

[0073] The discharge hole (324) may be circular. However, the discharge hole is not limited to a circular shape and may be elliptical or amorphous. Preferably, the discharge hole (324) may be circular.

[0074] The minimum distance (m) between discharge holes can be 5 to 15 mm, for example, 5 to 10 mm. Within the above range, it is easy to manufacture a separator having a uniform thermal shrinkage rate and a uniform shutdown temperature.

[0075] Here, 'minimum distance between discharge holes' may refer to the minimum distance between two discharge holes formed immediately adjacent to an arbitrary discharge hole formed in a spray plate.

[0076] In the injection plate, discharge holes may be formed spaced apart from each other along the machine direction (MD) of the porous substrate.

[0077] In this specification, a plurality of discharge holes formed spaced apart from each other along the MD of a porous substrate and arranged in a single row is defined as a 'row of discharge holes'.

[0078] In the spray plate, only one row of discharge holes may be formed along the transverse direction (TD) of the porous substrate. However, since multiple rows of discharge holes may be formed along the transverse direction of the porous substrate in the spray plate, hot air can be delivered more uniformly to the coating film of the same area, which may be advantageous for providing a more uniform thermal shrinkage rate and shutdown temperature.

[0079] FIG. 3 illustrates a spray 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 thereto, and three or more rows of discharge holes may be formed.

[0080] The injection plate (323) may have a row (L1) of first discharge holes and a row (L2) of second discharge holes formed sequentially along the width direction (TD) of the porous substrate.

[0081] 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.

[0082] The center of the discharge hole (324a) of the second discharge hole row (L2) may be located between the center of the discharge hole (324a) of the first discharge hole row (L1). In this case, hot air from the injection plate can be delivered more uniformly to the coating film for the coating layer, thereby increasing the uniformity of the thermal shrinkage rate and shutdown temperature. The center of the discharge hole is the same as described above.

[0083] According to one embodiment, a line (T1) connecting the center (324a) of the first discharge hole row and the center (324a) of the second discharge hole row may 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 the discharge hole in the first discharge hole row and the discharge hole in the second discharge hole row. Within the angle range, a separator with low thermal shrinkage rate and shutdown temperature can be manufactured with high efficiency on a spray plate of the same area. For example, the angle may be 60°.

[0084] The line (T2) connecting the centers of the first discharge holes and the line (T3) connecting the centers of the second discharge holes may be parallel to each other. In this case, 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, making it easier to manufacture a separator with uniform thermal shrinkage rate and shutdown temperature.

[0085] According to one embodiment, the spacing between discharge holes (324) in the row (L1) of the first discharge holes may be equal to each other. According to one embodiment, the spacing between discharge holes (324) in the row (L1) of the second discharge holes may be equal to each other. According to one embodiment, the spacing between discharge holes in the row of the first discharge holes may be equal to the spacing between discharge holes in the row of the second discharge holes.

[0086] The spacing distance (n) between the row of the first discharge holes and the row of the second discharge holes may be smaller than the average diameter d of the discharge holes in Equation 1 above. In this case, the distance between the row of the first discharge holes and the row of the second discharge holes is not excessively large, so that the opening rate of 10 to 65% in Equation 1 above can be easily reached. For example, the spacing distance between the row of the first discharge holes and the row of the second discharge holes may be 10 to 20 mm, for example, 10 to 15 mm.

[0087] Here, 'separation distance between the row of the first discharge hole and the row of the second discharge hole' may mean the minimum distance in the width direction of the porous substrate between the discharge hole included in the row of the first discharge hole and the discharge hole included in the row of the second discharge hole.

[0088] Although not shown in FIGS. 2 and 3, the manufacturing device may further include a transfer roller located inside a drying oven and transferring the porous substrate and the film for the coating layer inside the drying oven.

[0089] The transfer roll can continuously dry the coating film by transferring the porous substrate and the coating film within the drying oven.

[0090] Hereinafter, a separator manufacturing apparatus for a secondary battery according to another embodiment is described.

[0091] The above-mentioned manufacturing apparatus for a secondary battery separator is substantially the same as the manufacturing apparatus for a secondary battery separator of FIG. 1 to FIG. 3, except that it is equipped with a spray plate described in FIG. 4.

[0092] FIG. 4 is an enlarged plan view of a portion of a spray plate according to another embodiment.

[0093] Referring to FIG. 4, the injection plate (323) has additionally formed discharge holes (325) with a smaller diameter between the first discharge hole row (L1) and the second discharge hole row (L2). The discharge holes (325) can be made easy to adjust the diameter of the discharge holes in at least one of the first discharge hole row (L1) and the second discharge hole row (L2) when assuming an injection plate with the same opening rate.

[0094] Hereinafter, a separator manufacturing apparatus for a secondary battery according to another embodiment is described.

[0095] The above-mentioned manufacturing apparatus for a secondary battery separator is substantially the same as the manufacturing apparatus for a secondary battery separator of FIG. 1 to FIG. 3, except that it is equipped with a spray plate described in FIG. 5.

[0096] FIG. 5 is a plan view of a spray plate according to another embodiment.

[0097] Referring to FIG. 5, the injection plate (323) has regions with different opening rates of Equation 1 along the width direction (TD) of the porous substrate. The injection plate (323) includes a central region (A) of the injection plate (323) and peripheral regions (B, C) adjacent to the central region (A). The opening rate of Equation 1 of the central region (A) may be higher than the opening rate of the peripheral regions (B, C). In this case, there may be a more uniform air permeability distribution effect.

[0098] Method for manufacturing a separator for a secondary battery

[0099] Hereinafter, a method for manufacturing a separator for a secondary battery according to one embodiment is described.

[0100] The above method for manufacturing a separator for a secondary battery comprises 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 manufacturing device for a separator for a secondary battery to dry the coating film, wherein the drying section comprises a drying oven providing a drying space for the coating film, and a spray plate having a plurality of discharge holes located within the drying oven and spraying hot air toward the coating film, wherein the spray plate has an opening ratio of 10 to 65% in Equation 1, and in Equation 1, d is 5 to 20 mm and p is 10 to 15 mm.

[0101] In the above manufacturing method, by drying the coating film for the coating layer with the above drying unit, a separator for a secondary battery can be manufactured having a low thermal shrinkage rate and a low shutdown temperature, and having a uniform thermal shrinkage rate and shutdown temperature.

[0102] In one embodiment, the above-described manufacturing apparatus for a secondary battery separator may be used in the manufacturing method.

[0103] In the above manufacturing method, the apparatus for manufacturing the separator for the secondary battery and the drying unit are substantially the same as those described above. Therefore, only the remaining parts will be described below.

[0104] The porous substrate may have a plurality of pores and may be a substrate typically used in electrochemical devices. The porous substrate may be, but is not limited to, any one polymer selected from the group consisting of polyolefins such as polyethylene and 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, and polytetrafluoroethylene, or a polymer membrane formed from a copolymer or mixture of two or more of these.

[0105] The porous substrate may be a polyolefin-based substrate including, for example, a polyolefin, and the polyolefin-based substrate may contribute to improving the safety of the battery by having an excellent shutdown function. The polyolefin-based substrate may be selected from, for example, a polyethylene single membrane, a polypropylene single membrane, a polyethylene / polypropylene double membrane, a polypropylene / polyethylene / polypropylene triple membrane, and a polyethylene / polypropylene / polyethylene triple membrane. In addition, the polyolefin-based resin may include a non-olefin resin in addition to an olefin resin, or may include a copolymer of an olefin and a non-olefin monomer.

[0106] The porous substrate may have a thickness of 1 μm to 40 μm. For example, the porous substrate may have a thickness of 1 to 10 μm.

[0107] The film for the above coating layer may be a film of a composition comprising a filler and a (met)acrylic binder.

[0108] The above filler may be, for example, an inorganic filler, an organic filler, an organic-inorganic composite filler, or a combination thereof. The above inorganic filler may be a ceramic material capable of improving heat resistance. The above inorganic filler may include, for example, a metal oxide, a metal metal oxide, a metal fluoride, a metal hydroxide, or a combination thereof. The above inorganic filler may include, for example, Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or a combination thereof, but is not limited thereto. The above organic filler may include an acrylic compound, an imide compound, an amide compound, or a combination thereof, but is not limited thereto. The above organic filler may have a core-shell structure, but is not limited thereto. Preferably, the filler may be boehmite. The above 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, there may be an effect of improving the heat resistance of the separation membrane. The above filler may be included in a mass ratio of the binder to the above filler of 1:10 to 1:50, for example, 1:20 to 1:30. Within this range, the separation membrane may be easy to manufacture using the separation membrane manufacturing apparatus.

[0109] The above (meth)acrylic binder may include a sulfonate group-containing structural unit. The above (meth)acrylic binder may further include one or more of a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing structural unit, and a structural unit derived from (meth)acrylamide.

[0110] The above sulfonate group-containing structural unit may be included in the above (meth)acrylic binder in an amount 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 above sulfonate group-containing structural unit is included in the above range, the separator may exhibit excellent adhesion, heat resistance, and air permeability.

[0111] The structural unit derived from the above (meth)acrylate or (meth)acrylic acid may be included in the above (meth)acrylic binder in an amount 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 the above range, the separator may exhibit excellent adhesion, heat resistance, air permeability, and oxidation resistance.

[0112] The above cyano group-containing structural unit may be included in the above (meth)acrylic binder in an amount 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 the above range, the separator can secure excellent oxidation resistance and exhibit adhesion, heat resistance, and air permeability.

[0113] The structural unit derived from the above (meth)acrylamide may be included in the above (meth)acrylic binder in an amount 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%, or 80 to 95 mol%. Within the above range, the separator can secure excellent oxidation resistance and exhibit adhesion, heat resistance, and air permeability.

[0114] According to one embodiment, the (meth)acrylic binder may have a sulfonate group-containing structural unit, a structural unit derived from (meth)acrylate or (meth)acrylic acid, and a cyano group-containing structural unit. In one embodiment, the total sum of the sulfonate group-containing structural unit, the structural unit derived from (meth)acrylate or (meth)acrylic acid, and the cyano group-containing structural unit may be 95 mol% or more of the 100 mol% of the (meth)acrylic binder, for example, 95 to 100 mol%, or 100 mol%.

[0115] According to another embodiment, the (meth)acrylic binder may have a structural unit containing a sulfonate group and a structural unit derived from (meth)acrylamide. In one embodiment, the total sum of the structural unit containing the sulfonate group and the structural unit derived from (meth)acrylamide may be 95 mol% or more of the 100 mol% of the (meth)acrylic binder, for example, 95 to 100 mol%, or 100 mol%.

[0116] According to another embodiment, the (meth)acrylic binder may have a sulfonate group-containing structural unit, a structural unit derived from (meth)acrylate or (meth)acrylic acid, and a structural unit derived from (meth)acrylamide. In one embodiment, the total sum of the sulfonate group-containing structural unit, the structural unit derived from (meth)acrylate or (meth)acrylic acid, and the structural unit derived from (meth)acrylamide may be 95 mol% or more of the 100 mol% of the (meth)acrylic binder, for example, 95 to 100 mol%, or 100 mol%.

[0117] The structural unit derived from the above (meth)acrylate or (meth)acrylic acid may be represented, for example, by the following Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or a combination thereof:

[0118] [Chemical Formula 1]

[0119]

[0120] [Chemical Formula 2]

[0121]

[0122] [Chemical Formula 3]

[0123]

[0124] (In the above Chemical Formulas 1 to 3, R 1 to R 6 Each is independently hydrogen or a methyl group, and in the above formula 2, M is an alkali metal). The alkali metal may be, for example, lithium, sodium, potassium, rubidium, or cesium.

[0125] The above cyano group-containing structural unit can be represented, for example, by the following chemical formula 4.

[0126] [Chemical Formula 4]

[0127]

[0128] (In the above chemical formula 4, R 7 and R 8 Each is independently hydrogen or a C1 to C3 alkyl group, and L 1 is -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, x is an integer from 0 to 2, and L 2 is a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, and y is an integer from 0 to 2).

[0129] The above sulfonate 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 above sulfonate group-containing structural unit may be represented by the following chemical formulas 5, 6, 7, or a combination thereof.

[0130] [Chemical Formula 5]

[0131]

[0132] [Chemical Formula 6]

[0133]

[0134] [Chemical Formula 7]

[0135]

[0136] (In the above chemical formulas 5 to 7, R 9 to R 14 Each is independently hydrogen or a C1 to C3 alkyl group, and L 3 , L 5 and L 7 Each is independently -C(=O)-, -C(=O)O-, -OC(=O)-, -O- or -C(=O)NH-, and L 4 , L 6 and L 8 Each is independently a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, and a, b, c, d, e, and f are each independently integers from 0 to 2, and in the above formula 6, M is an alkali metal).

[0137] The structural unit derived from the above (meth)acrylamide can be represented by the following chemical formula 8.

[0138] [Chemical Formula 8]

[0139]

[0140] (In the above chemical formula 8, R 15 and R 16 Each is independently a hydrogen or methyl group).

[0141] The above (meth)acrylic binder may be in various forms, such as an alternating polymer in which the structural units are alternately distributed, a randomly distributed polymer, or a graft polymer in which some structural units are grafted. The weight-average molecular weight (Mw) of the above (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 the above range, the separator may exhibit excellent adhesion, heat resistance, air permeability, and oxidation resistance. The above weight-average molecular weight may be the polystyrene-equivalent average molecular weight measured using gel permeation chromatography. The glass transition temperature of the above (meth)acrylic binder may be 200°C to 280°C, for example, 210°C to 270°C, or 210°C to 260°C. Within this range, the separator may exhibit excellent adhesion, heat resistance, air permeability, and oxidation resistance. The glass transition temperature may be a value measured by differential scanning calorimetry. The above (meth)acrylic binder may have a melting point (Tm) of 160°C or higher.

[0142] The coating film for the above coating layer can be formed by applying the composition for the coating layer to at least one surface of the porous substrate to a predetermined thickness.

[0143] The thickness of the film for the coating layer above may be 0.1 to 10 μm, for example, 0.1 to 5 μm, or 0.5 to 5 μm. Within the above range, the manufacturing of the separation membrane by the manufacturing device may be easy.

[0144] Separator for secondary batteries

[0145] A separator for a secondary battery according to one embodiment can be manufactured using a manufacturing apparatus for the separator for a secondary battery.

[0146] The above-described separator for a secondary battery may 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.

[0147] The above-mentioned separator for a secondary battery may have a thermal shrinkage rate of 3.0% or less in the mechanical direction and 2.8% or less in the width direction, respectively. Within this range, the reliability of the battery can be increased.

[0148] The above separator for the secondary battery may have a shutdown temperature of less than 145°C, for example, 143°C or lower. Within this range, the battery can be quickly shut down in the event of a thermal runaway, thereby increasing the reliability of the battery.

[0149] lithium secondary battery

[0150] Another embodiment provides a lithium secondary battery comprising a separator for a lithium secondary battery according to one embodiment; a positive electrode; and a negative electrode. The separator for the lithium secondary battery is described above. The separator for the lithium secondary battery may be positioned between the positive electrode and the negative electrode.

[0151] anode

[0152] 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 may further include a binder and / or a conductive material. As an example, the positive electrode may further include an additive capable of acting as a sacrificial electrode.

[0153] positive electrode active material

[0154] As a positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (a lithated intercalation compound) may be used. Specifically, one or more composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof may be used.

[0155] The above composite oxide may be a lithium transition metal composite oxide, and specific examples include a lithium nickel-based oxide, a lithium cobalt-based oxide, a lithium manganese-based oxide, a lithium iron phosphate-based compound, a cobalt-free nickel-manganese-based oxide, or a combination thereof.

[0156] As an example, a compound represented by any one of the following chemical formulas may 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 bO2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b 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).

[0157] 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, a rare earth element, 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 is Mn, Al, or a combination thereof.

[0158] For example, the above-mentioned 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 in the lithium transition metal composite oxide 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. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity, high-density lithium secondary batteries.

[0159] The content of the above positive active material is 90% to 99.5% by weight of 100% by weight of the positive active material layer, and the content of the binder and the conductive material may each be 0.5% to 5% by weight with respect to 100% by weight of the positive active material layer.

[0160] The above binder serves to adhere the positive active material particles well to each other and also to adhere the positive active material well to the current collector. Representative 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)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0161] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0162] Al may be used as the current collector mentioned above, but is not limited thereto.

[0163] cathode

[0164] A negative electrode for a lithium secondary battery comprises a current collector and a negative electrode active material layer located on the current collector. The negative electrode active material layer comprises a negative electrode active material and may further comprise a binder and / or a conductive material.

[0165] For example, the negative electrode active material layer may comprise 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.

[0166] cathode active material

[0167] 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 doping and dedoping lithium, or a transition metal oxide.

[0168] A material capable of reversibly intercalating / deintercalating the above lithium ions may be a carbon-based negative electrode active material, such as crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0169] As the above lithium metal alloy, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0170] As a material capable of doping and undoping the above lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may 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 thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn-based alloy, or a combination thereof.

[0171] 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 a secondary particle (core) assembled from silicon primary particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particle. The amorphous carbon may also be located between the silicon primary particles, so that, for example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0172] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core comprising crystalline carbon and silicon particles and an amorphous carbon coating layer located on the surface of the core.

[0173] The above Si-based or Sn-based negative electrode active material can be used in combination with a carbon-based negative electrode active material.

[0174] The above binder serves to effectively bond the negative electrode active material particles to each other and also to effectively bond the negative electrode active material to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof may be used.

[0175] Examples of the above-mentioned non-aqueous binders include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0176] The above-mentioned water-based binder may be selected from styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylenepropylenediene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0177] When a water-based binder is used as the above-mentioned cathode binder, a cellulose-based compound capable of imparting viscosity may be further included. As this cellulose-based compound, one or more types such as carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used. Na, K, or Li may be used as the alkali metal.

[0178] The above dry binder is a polymer material capable of fiberization, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0179] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes can be used in the battery being constructed. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fiber, carbon nanofiber, carbon nanotube; metal-based materials in the form of metal powder or metal fibers including copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0180] As the above-mentioned cathode current collector, a material selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof may be used.

[0181] Lithium secondary batteries may contain additional electrolyte.

[0182] electrolyte

[0183] The electrolyte for a lithium secondary battery may include a non-aqueous organic solvent and a lithium salt.

[0184] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0185] The above-mentioned non-aqueous organic solvent may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, a non-protic solvent, or a combination thereof.

[0186] The above carbonate-based solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0187] Ester-based solvents such as methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, decanolide, mevalonolactone, valerolactone, and caprolactone may be used.

[0188] As ether-based solvents, dibutyl ether, tetraglame, diglame, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. may be used. Additionally, as ketone-based solvents, cyclohexanone, etc. may be used. As alcohol-based solvents, ethyl alcohol, isopropyl alcohol, etc. may be used, and as aprotic solvents, nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane, 1,4-dioxolane; sulfolanes, etc. may be used.

[0189] The above-mentioned non-aqueous organic solvent can be used alone or in a mixture of two or more types.

[0190] In addition, when using a carbonate-based solvent, a mixture of cyclic carbonates and chain carbonates can be used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0191] The above lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and facilitating the movement of lithium ions between the anode and cathode. Representative 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, LiN(C x F 2x+1 SO2)(C y F 2y+1It may include one or more selected from SO2)(x and y are integers from 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0192] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, coin, etc., depending on their shape. FIGS. 6 to 9 are schematic diagrams illustrating a lithium secondary battery according to one embodiment. FIG. 6 can be described as a cylindrical battery, FIG. 7 as a prismatic battery, and FIGS. 8 and 9 as a pouch battery. Referring to FIGS. 6 to 9, the lithium secondary battery 100 may include an electrode assembly 40 having a separator 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, the negative electrode 20, and the separator 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 in FIG. 6. In addition, in FIG. 7, the lithium secondary battery 100 may include a positive lead tab 11 and a positive terminal 12, a negative lead tab 21 and a negative terminal 22. As shown in FIG. 8 and FIG. 9, the lithium secondary battery 100 may include an electrode tab 70, namely a positive tab 71 and a negative tab 72, which serve as an electrical path to induce current formed in the electrode assembly 40 to the outside.

[0193] A lithium secondary battery according to one embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electric devices, etc., but the present invention is not limited thereto.

[0195] Examples and comparative examples of the present invention are described below. However, the following examples are merely one example of the present invention, and the present invention is not limited to the following examples.

[0197] Preparation Example

[0198] Distilled water (6361 g), acrylic acid (1.0 mol), acrylamide (8.5 mol), potassium persulfate (0.01 mol), 2-acrylamido-2-methylpropanesulfonic acid (0.5 mol), and 5N aqueous lithium hydroxide solution (1.05 equivalents relative to the total amount of 2-acrylamido-2-methylpropanesulfonic acid) were added to a 10 L four-necked flask equipped with a stirrer, thermometer, and condenser. Then, the internal pressure was reduced to 10 mmHg using a diaphragm pump, and the internal pressure was returned to atmospheric pressure using nitrogen, a process that was repeated three times. The reaction was carried out for 12 hours while controlling the temperature of the reaction mixture to stabilize between 65°C and 70°C. After cooling to room temperature, the pH of the reaction mixture was adjusted to 7 to 8 using a 25% aqueous ammonia solution. Poly(acrylic acid-co-lithium acrylate-co-acrylamide-co-2-acrylamido-2-methylpropanesulfonic acid) was prepared using this method. The molar ratio of acrylic acid + lithium acrylate, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid was 10:85:5. About 10 mL of the reaction solution (reaction product) was taken and the non-volatile component was measured, resulting in 9.5% (theoretical value: 10%).

[0199] Example 1

[0200] An acrylic binder (10 wt%) prepared in Preparation Example 1 and boehmite (particle size D50: 200 nm, plate-like) as a filler were mixed, added to water as a solvent, milled using a bead mill at 25°C for 30 minutes, and dispersed to prepare a coating layer composition. The weight ratio of the acrylic binder to the filler in the coating layer composition is 1:20.

[0201] A coating layer composition is coated to a thickness of 1.8 μm on one side of a porous polyethylene film (thickness: 5.5 μm, SK Co., air permeability: 120 sec / 100 cc, puncture strength: 480 kgf) as a porous substrate using a coating method to form a coating film on one side of the porous substrate.

[0202] A laminate of a porous substrate and a coating film for a coating layer was placed into a drying oven formed with the spray plate of Fig. 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 as shown in Table 1 below, and the discharge holes are circular and have the same diameter.

[0203] Examples 2 to 3

[0204] A separator was prepared in the same manner as in Example 1, except that the spray plate used in the drying oven in Example 1 was changed as shown in Table 1 below.

[0205] Example 4

[0206] A separator was prepared in the same manner as in Example 1, except that the spray plate used in the drying oven in Example 1 was changed as shown in Table 1 below.

[0207] Comparative Example 1

[0208] A separator was manufactured in the same manner as in Example 1, except that a spray plate having a straight discharge hole was used without multiple discharge holes.

[0209] Comparative Examples 2 to 3

[0210] A separator was prepared in the same manner as in Example 1, except that the spray plate used in the drying oven in Example 1 was changed as shown in Table 1 below.

[0211] The following properties were evaluated using the separation membranes prepared in the examples and comparative examples.

[0212] Air Permeability and Standard Deviation (Unit: sec / 100cc)

[0213] Air permeability was measured by measuring the time (in seconds) it takes for 100cc of air to pass through the membrane using a measuring device (EG01-55-1MR, Asahi Seiko).

[0214] The width of the membrane, 200 mm, was divided into 5 sections for measurement, and the average and standard deviation were presented.

[0215] Dry heat shrinkage rate and standard deviation (Unit: %)

[0216] Samples are prepared by cutting the separator membranes of the examples and comparative examples into pieces measuring 5 cm × 5 cm. After leaving the samples in a convection oven at 130°C for 1 hour, the shrinkage rates in the mechanical direction (MD) and the perpendicular direction (TD), respectively, are calculated. The shrinkage rates are calculated according to the following mathematical formula 1.

[0217] [Mathematical Formula 1]

[0218] Shrinkage rate = (L0 - L1) / L0 x 100

[0219] (L0 is the initial length of the membrane, L1 is the length of the membrane after standing at 130°C for 1 hour).

[0220] The width of the membrane, 200 mm, was divided into 5 sections for measurement, and the average and standard deviation were presented.

[0221] Shutdown temperature and standard deviation (Unit: ℃)

[0222] A sample was prepared by cutting the separator for a lithium secondary battery of the example and comparative example into a size of 5 cm x 5 cm. An anode slurry was prepared by mixing 97 wt% of lithium cobalt-nickel-aluminum-based oxide as an anode active material, 1.5 wt% of carbon nanotubes as a conductive material, and 1.5 wt% of polyvinylidene fluoride as a binder, and adding N-methyl-2-pyrrolidone. An anode was prepared by coating the prepared anode slurry onto aluminum foil, drying it, and rolling it. An anode was prepared by mixing 97.4 wt% of artificial graphite as an anode active material, 1.0 wt% of carboxymethylcellulose, 1.5 wt% of styrene-butadiene-based rubber as a binder, and 0.1 wt% of carbon nanotubes as a conductive material, and adding distilled water. An anode was prepared by coating the prepared anode slurry onto copper foil, drying it, and rolling it. One of the above samples was placed between the anode and the cathode to create three sets of anode-sample-cathode stacks, which were then placed in a pouch. 2g of electrolyte (ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate dissolved in 1.5M LiPF6 (volume ratio of 30:50:20 based on total volume of 100)) was injected to completely immerse the stacks in the electrolyte, and the mixture was sealed and left at 25°C for 12 hours to manufacture a lithium secondary battery. While operating the lithium secondary battery, the impedance of the battery was measured using an electrochemical impedance spectroscopy (EIS) device while increasing the temperature at a rate of 10°C / min. The temperature at which the impedance reached 100 times the initial value was set as the shutdown temperature.

[0223] The width of the membrane, 200 mm, was divided into 5 sections for measurement, and the average and standard deviation were presented.

[0224] Examples Comparative example 1 2 3 4 1 2 3 discharge hole form porous porous porous porous Straight type porous porous Diameter d(mm) 5 5 10 10 - 5 5 Separation distance p(mm) 15 10 15 12 - 17 7 Opening Rate (%) 10.1 22.7 40.3 62.8 - 8 48 airway 122 119 121 120 125 131 127 Standard deviation of air permeability 1.14 2.07 2.41 2.39 4.95 5.12 6.80 Thermal shrinkage rate 2.6 2.3 2.8 3.1 3.2 3.9 3.7 Standard deviation of heat shrinkage rate 0.17 0.11 0.24 0.36 0.78 0.79 0.76 Shutdown temperature 143 143 142 141 145 144 143.5 Shutdown temperature standard deviation 0.53 0.18 0.46 0.26 1.70 1.16 1.23

[0225] As shown in Table 1 above, the manufacturing apparatus of the separator of the example has a low thermal shrinkage rate and a low shutdown temperature, and by manufacturing a separator for a secondary battery that has a uniform thermal shrinkage rate and shutdown temperature, the reliability of the secondary battery can be increased.

[0227] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

Claims

Claim 1 An apparatus for manufacturing a separator for a secondary battery, wherein the separator for the secondary battery comprises a porous substrate and a coating layer formed on at least one surface of the porous substrate, and the apparatus comprises a drying section for a coating film of the coating layer of the separator for the secondary battery, wherein the drying section comprises a drying oven providing a drying space for the coating film of the coating layer, and a sprayer having a spray plate having a plurality of discharge holes located within the drying oven and spraying hot air toward the coating film of the coating layer, wherein the spray plate has an opening ratio of 10 to 65% according to Equation 1 below, wherein d is 5 to 20 mm and p is 10 to 15 mm, an apparatus for manufacturing a separator for a secondary battery: [Equation 1] Opening ratio = (90.5 x d 2 ) / p 2 (In the above Equation 1, d is the average diameter of the discharge hole, and p is the distance between the centers of the discharge holes among the plurality of discharge holes). Claim 2 An apparatus for manufacturing a secondary battery separator according to claim 1, wherein the minimum distance between the discharge hole and the discharge hole adjacent to the discharge hole is 5 to 15 mm. Claim 3 A manufacturing apparatus for a secondary battery separator according to claim 1, wherein the discharge holes are each circular, elliptical, or amorphous. Claim 4 A manufacturing apparatus for a secondary battery separator according to claim 1, wherein the injection plate has a row of discharge holes formed therein, and the row of discharge holes is formed such that the plurality of discharge holes are spaced apart from each other along the machine direction of the porous substrate. Claim 5 A manufacturing apparatus for a secondary battery separator according to claim 4, wherein the rows of discharge holes are formed in plurality along the transverse direction of the porous substrate. Claim 6 A manufacturing apparatus for a secondary battery separator according to claim 5, wherein the injection plate has a row of discharge holes including a row of first discharge holes and a row of second discharge holes formed sequentially along the width direction of the porous substrate, and the center of the discharge hole in the row of second discharge holes is located between the centers of the discharge holes in the row of first discharge holes. Claim 7 An apparatus for manufacturing a secondary battery separator according to claim 6, wherein the line connecting the center of the discharge hole in the row of the first discharge hole and the center of the discharge hole in the row of the second discharge hole forms an angle of 55 to 65° with respect to the mechanical direction of the porous substrate. Claim 8 A manufacturing apparatus for a secondary battery separator according to claim 6, wherein the line connecting the centers of the discharge holes in the row of the first discharge holes and the line connecting the centers of the discharge holes in the row of the second discharge holes are parallel to each other. Claim 9 An apparatus for manufacturing a secondary battery separator according to claim 6, wherein the spacing between discharge holes in the row of the first discharge holes is the same as each other, and the spacing between discharge holes in the row of the second discharge holes is the same as each other. Claim 10 An apparatus for manufacturing a secondary battery separator according to claim 6, wherein the distance between the row of the first discharge holes and the row of the second discharge holes is smaller than the average diameter d of the discharge holes in Equation 1. Claim 11 A manufacturing apparatus for a secondary battery separator according to claim 1, wherein the manufacturing apparatus is located within the drying oven and further comprises a transfer roller for transferring the porous substrate and the coating film for the coating layer within the drying oven. Claim 12 In claim 11, the above transfer rolls are arranged in plurality along the mechanical direction of the porous substrate, in a manufacturing apparatus for a secondary battery separator. Claim 13 An apparatus for manufacturing a separator for a secondary battery according to claim 1, wherein in the above formula 1, d is 5 to 8 mm, p is 10 to 15 mm, and the opening ratio is 20 to 25%, and the injection plate has a row of discharge holes including a row of first discharge holes and a row of second discharge holes formed sequentially along the width direction of the porous substrate, and the line connecting the center of the discharge hole in the row of first discharge holes and the center of the discharge hole in the row of second discharge holes forms an angle of 55 to 65° with respect to the mechanical direction of the porous substrate. Claim 14 A method for manufacturing a separator for a secondary battery, comprising the steps of: manufacturing a laminate of a porous substrate and a film for a coating layer formed on at least one surface of the porous substrate; and transferring the laminate into a drying section of a secondary battery manufacturing device to dry the film for the coating layer, wherein the drying section comprises a drying oven providing a drying space for the film for the coating layer, and a spray plate having a plurality of discharge holes located within the drying oven and spraying hot air toward the film for the coating layer, wherein the spray plate has an opening ratio of 10 to 65% as in Equation 1 below, wherein d is 5 to 20 mm and p is 10 to 15 mm: [Equation 1] Opening ratio = (90.5 x d 2 ) / p 2 (In the above Equation 1, d is the average diameter of the discharge hole, and p is the distance between the centers of the discharge holes among the plurality of discharge holes). Claim 15 A method for manufacturing a separator for a secondary battery according to claim 14, wherein the porous substrate has a thickness of 1 to 10 μm and the coating film for the coating layer has a thickness of 0.5 to 5 μm. Claim 16 A method for manufacturing a separator for a secondary battery according to claim 14, wherein the film for the coating layer is a film of a coating layer composition having a mass ratio of (meth)acrylic binder to filler of 1:10 to 1:

50. Claim 17 A method for manufacturing a separator for a secondary battery according to claim 16, wherein the (meth)acrylic binder comprises a sulfonate group-containing structural unit; and one or more of a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing structural unit, and a structural unit derived from (meth)acrylamide. Claim 18 A secondary battery comprising: an anode; a cathode; and a separator located between the anode and the cathode and manufactured by the manufacturing apparatus of any one of claims 1 to 13 or the manufacturing method of any one of claims 14 to 17.

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