Separator for secondary batteries

Abstract

This invention relates to a separator comprising a separator substrate made of a porous material and an inorganic layer formed on at least one surface of the separator substrate by coating, wherein the separator substrate and the inorganic layer each have a porosity that satisfies the following relationship with the permeability of the separator: (10 × porosity of the separator substrate) - (4 × porosity of the inorganic layer) ≤ permeability of the separator.

Description

Technical Field

[0001] This application claims priority to Korean Patent Application No. 2021-0083162, filed on June 25, 2021, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This invention relates to a separator for a secondary battery. More specifically, this invention relates to a separator for a secondary battery configured such that the porosity of the separator substrate and the inorganic layer constituting the separator are adjusted, thereby adjusting the impregnationability of the separator. Background Technology

[0003] Lithium-ion batteries can be manufactured by housing an electrode assembly configured such that a separator is inserted between the positive and negative electrodes in a battery casing, injecting electrolyte into the battery casing, and heat-sealing the battery casing.

[0004] To prevent electrical connection between the positive and negative electrodes and ensure insulation, a separator can be configured with a structure in which a coating comprising inorganic materials and adhesives is formed on a polyolefin-based substrate made of a porous material, thereby enabling lithium-ion mobility. Polyolefin-based materials have low heat resistance. For this reason, a coating can be added, thereby improving the high-temperature safety and mechanical properties of the separator.

[0005] The coating, which includes inorganic materials and adhesives, is configured to have a porous structure that increases the space for introducing liquid electrolyte therein, thereby improving impregnation with electrolyte and lithium-ion conductivity.

[0006] In lithium-ion batteries, the electrolyte is the pathway for lithium ions to move, and therefore improving the impregnationability of the separator with the electrolyte to reduce separator resistance is very important.

[0007] In particular, as the application of lithium-ion batteries expands to devices requiring high voltage and high capacity, the size of battery cells tends to increase. Therefore, there is a need to develop a separator with improved electrolyte impregnation properties that can be used as a separator in battery cells with increased volume.

[0008] In this regard, Patent Document 1 relates to an inorganic oxide powder for forming an inorganic oxide porous membrane that has excellent heat resistance, insulation and membrane strength even at a small apparent weight and has the porosity required to impart sufficient ion permeability, wherein the inorganic oxide powder is added to the surface of at least one of a positive electrode, a negative electrode and a separator.

[0009] That is, in Patent Document 1, an inorganic oxide powder with properties that can improve ion permeability was used, thereby improving the physical properties of the separator.

[0010] Patent Document 2 relates to a separator comprising a porous polymer membrane and a porous coating formed on the porous polymer membrane, wherein the surface filaments of the porous polymer membrane and the particles included in the porous coating are entangled at the interface between the porous polymer membrane and the porous coating. As described above, the bonding force between the porous polymer membrane and the porous coating is further increased because the particles included in the porous coating are entangled between the filaments formed on the surface of the porous polymer membrane prior to bonding.

[0011] In Patent Document 2, the porous polyolefin membrane is coated with a slurry and the temperature at which the slurry is heat-fixed is higher than the conventional heat-fixing temperature, thereby providing a separator with reduced heat shrinkage and improved permeability.

[0012] Generally speaking, for a separator comprising a porous substrate and a porous coating, the porosity of the substrate and the coating are related to the impregnation of the separator.

[0013] In order to improve the physical properties of the partition, a specific inorganic oxide powder was added in Patent Document 1, and heat fixation was performed at high temperature in Patent Document 2.

[0014] However, no method has yet been proposed that can ensure the impregnation of the partition to a predetermined or higher level using conventional partition manufacturing methods without performing additional processes or introducing additional materials, or a method that can indirectly check whether the impregnation of the partition is poor.

[0015] (Existing technical literature)

[0016] (Patent Document 1) Korean Patent Registration No. 1913990 (October 31, 2018)

[0017] (Patent Document 2) Korean Patent Registration No. 1666045 (October 13, 2016) Summary of the Invention

[0018] Technical issues

[0019] The present invention addresses the above-mentioned problems, and the object of the present invention is to provide a separator for a secondary battery configured to adjust the porosity of the separator substrate and the porosity of the inorganic layer, thereby adjusting the impregnation of the separator.

[0020] Technical solution

[0021] The separator according to the invention, which achieves the above objectives, comprises a separator substrate made of a porous material and an inorganic layer formed on at least one surface of the separator substrate by coating, wherein the separator substrate and the inorganic layer each have a porosity that satisfies the following relationship with the permeability of the separator.

[0022] (10 × porosity of the partition substrate) - (4 × porosity of the inorganic layer) ≤ permeability of the partition

[0023] The porosity of the inorganic layer can be 55% or greater.

[0024] The permeability of the partition can be 200 sec / 100 cc or less.

[0025] The inorganic layer may have a thickness equivalent to 30% or more of the total thickness of the partition.

[0026] The inorganic material constituting the inorganic layer may be composed of materials with a molecular weight of 3.0 μm. 2 Made from BET particles of 1 g or larger.

[0027] The inorganic material may have a dielectric constant of 1 or greater, piezoelectricity, or lithium-ion transport capability.

[0028] The diffusion distance in the MD direction and the diffusion distance in the TD direction of the partition can each be 2.0 mm or greater.

[0029] The present invention provides a cylindrical secondary battery having an electrode assembly including the separator housed in a cylindrical battery casing.

[0030] In addition, the present invention provides a battery pack comprising the cylindrical secondary battery as a unit battery, wherein the battery pack is used as an energy source for an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or an energy storage device.

[0031] In addition, the present invention can provide various combinations of the above-mentioned solutions.

[0032] Beneficial effects

[0033] It is evident from the above description that, in the separator according to the present invention, the porosity of the separator substrate and the porosity of the inorganic layer can be adjusted, thereby adjusting the impregnationability of the separator with the electrolyte.

[0034] In addition, the permeability of the separator can be measured, which can indirectly check whether the separator has poor impregnation with the electrolyte.

[0035] In addition, separators with improved impregnation properties can be provided using conventional separator manufacturing methods without performing additional processes or introducing additional materials, and these separators can be applied to large-volume cylindrical secondary batteries for use in devices requiring high capacity and fast charging, such as electric vehicles. Attached Figure Description

[0036] Figure 1 These are drop test photos of the partition according to Example 1.

[0037] Figure 2 These are photos of a drip test of the partition according to Example 2.

[0038] Figure 3 These are photos of a drip test of the partition according to Example 3.

[0039] Figure 4 These are drop test photos of the partition according to Example 4.

[0040] Figure 5 These are photos of a drip test of the partition according to Example 5.

[0041] Figure 6 These are photos of a drip test of the partition according to Example 6.

[0042] Figure 7 These are drop test photos of the partition according to Example 7.

[0043] Figure 8 These are photographs of the drip test of the partition in Comparative Example 1.

[0044] Figure 9 These are photographs of the drip test of the partition in Comparative Example 2.

[0045] Figure 10 These are photographs of the drip test of the partition in Comparative Example 3.

[0046] Figure 11 These are photographs of the drip test of the partition in Comparative Example 4.

[0047] Figure 12 These are photographs of the drip test of the partition in Comparative Example 5.

[0048] Figure 13 These are photographs of the drip test of the partition in Comparative Example 6.

[0049] Figure 14 These are photographs of the drip test of the partition in Comparative Example 7. Detailed Implementation

[0050] Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily implement these preferred embodiments. While the operational principles of the preferred embodiments are described in detail, detailed descriptions of known functions and configurations incorporated herein will be omitted where they might obscure the subject matter of the invention.

[0051] In addition, the same reference numerals will be used throughout the accompanying drawings to refer to parts that perform similar functions or operations. Where a part is referred to as "connected to another part" throughout the specification, this means not only that the one part is directly connected to the other part, but also that the one part is indirectly connected to the other part via yet another part. Furthermore, including a particular element does not imply the exclusion of other elements, but rather means that these elements may be further included unless otherwise specified.

[0052] In addition, descriptions of elements by limiting or adding are applicable to all inventions unless otherwise specified, and do not limit any particular invention.

[0053] Furthermore, in the description of the invention and the claims of this application, the singular form is intended to include the plural form, unless otherwise stated.

[0054] Furthermore, in the description of the invention and the claims of this application, "or" includes "and" unless otherwise mentioned. Therefore, "including A or B" means three cases: including A, including B, and including both A and B.

[0055] In addition, all numerical ranges include the minimum value, the maximum value, and all intermediate values ​​in between, unless the context clearly indicates otherwise.

[0056] The separator according to the present invention may include a separator substrate made of a porous material and an inorganic layer formed on at least one surface of the separator substrate by coating, wherein the porosity of the separator substrate and the porosity of the inorganic layer may satisfy the following relationship with the permeability of the separator.

[0057] (10 × porosity of the partition substrate) - (4 × porosity of the inorganic layer) ≤ permeability of the partition

[0058] The partition substrate may comprise a polyolefin-based polymer resin commonly used in the art to which this invention pertains, and may be made from, for example, at least one selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-high molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, polyethylene naphthalate, and mixtures thereof.

[0059] Generally, when only a separator substrate comprising a polyolefin-based polymer resin is used as a separator, the separator not only has low heat resistance but also low mechanical strength. To address these issues, an inorganic layer comprising inorganic materials and adhesives is disposed on one or opposite surfaces of the separator substrate.

[0060] Materials with a dielectric constant of 1 or greater, piezoelectricity, or lithium-ion transport capability can be used as inorganic materials to form inorganic layers.

[0061] Specifically, non-limiting examples of inorganic materials having a dielectric constant of 1 or greater are SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, boehmite, alumina trihydrate (ATH), or mixtures thereof.

[0062] Piezoelectric inorganic materials are materials configured such that a potential difference is formed between the positive and negative charges generated between the opposing surfaces of the particles when a predetermined pressure is applied thereto, and non-limiting examples may be selected from BaTiO3, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), Pb(Mg) 1 / 3 Nb 2 / 3 At least one of the group consisting of O3-PbTiO3 (PMN-PT), hafnium oxide (HfO2), and mixtures thereof.

[0063] Inorganic materials containing lithium but capable of transporting lithium ions without storing lithium can be selected from lithium phosphate (Li3PO4) and lithium titanium phosphate (Li... x Ti y (PO4)3, 0 < x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), such as 14Li2O-9Al2O3-38TiO2-39P2O5 (LiAlTiP). x O y Base glass (1 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), such as Li 3.25 Ge 0.25 P 0.75 Lithium germanium thiophosphate (Li) such as S4 x GeyP z S w 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as lithium nitrides (Li3N) x N y (0 < x < 4, 0 < y < 2), such as SiS2-based glasses (Li3PO4-Li2S-SiS2, etc.) x Si y S z 0 < x < 3, 0 < y < 2, 0 < z < 4), such as P2S5-based glasses (LiI-Li2S-P2S5), etc. x P y S z At least one of the groups consisting of , 0 < x < 3, 0 < y < 3, 0 < z < 7, and mixtures thereof.

[0064] The inorganic material constituting the inorganic layer can be composed of materials with a molecular weight of 3.0 μm. 2 Made from BET particles of 1 g or larger.

[0065] If the BET of inorganic particles is less than 3.0m 2 If the impregnation rate is reduced to / g, then the impregnation property will decrease, which is undesirable.

[0066] There are no particular restrictions on the type of adhesive, as long as it does not chemically alter the inorganic layer of the separator. For example, the adhesive can be made from: polyolefins, such as polyethylene or polypropylene; fluorinated resins, such as polyvinylidene fluoride or polytetrafluoroethylene; fluorinated copolymers, such as vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers or ethylene-tetrafluoroethylene copolymers; styrene-butadiene copolymers or their cyanides; (meth)acrylate copolymers, such as methacrylate copolymers, acrylonitrile acrylate copolymers, or styrene acrylate copolymers; rubbers, such as ethylene propylene rubber; polyvinyl acetate; and materials with a melting point of 180°C or higher. Resins with a glass transition temperature, such as polyphenylene ether, polysulfone, polyethersulfone, polyphenylene sulfide, polyetherimide, polyamide, polyimide, polyamideimide, polyetheramide, polyester, aromatic polyester, or polyetheretherketone; polycarbonate; polyacetal; water-soluble resins, such as carboxyalkyl cellulose, alkyl cellulose, hydroxyalkyl cellulose, starch, polyvinyl alcohol, sodium alginate, polyethylene glycol, cellulose ester, polyacrylic acid, polyacrylamide, or polymethacrylic acid; (meth)acrylic resins; or copolymers comprising two or more of these.

[0067] The inorganic layer may further include a dispersant. For example, the dispersant may be an acrylic copolymer, cyanoethyl polyvinyl alcohol, polyvinylpyrrolidone, baicalin, luteolin, taurine, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, leucine, phenolic compounds including tannins, pyrogallol, amylose, amylopectin, xanthan gum, fatty acid compounds, or polymeric compounds of two or more of these.

[0068] Generally speaking, when comparing the impregnation of the separator substrate with that of the inorganic layer, the porosity of the separator substrate tends to be less than that of the inorganic layer, taking into account the fact that the impregnation of the inorganic layer is higher than that of the separator substrate.

[0069] In addition, when the porosity of the separator substrate and the porosity of the inorganic layer are each equal to or greater than a certain level, the impregnationability of the separator substrate can be increased. In the separator according to the present invention, when the porosity of the separator substrate and the porosity of the inorganic layer have the above relationship, if the permeation time of the separator meets the condition of 200 sec / 100 cc or less, it can be determined that the impregnationability of the separator substrate is excellent.

[0070] That is, when simply comparing the results calculated by applying the porosity values ​​of the separator substrate and the inorganic layer according to the above relationship with the permeability value of the separator without considering the units of porosity and permeability, if the above relationship is satisfied, it can be determined that the impregnationability of the separator substrate is excellent.

[0071] In a specific example, the porosity of the inorganic layer can be 55% or greater, while the porosity of the separator substrate can be adjusted so that the permeability of the separator is 200 sec / 100 cc or less while satisfying the porosity of the inorganic layer.

[0072] The porosity of the inorganic layer can be adjusted depending on the ratio of inorganic material to binder, wherein the ratio of inorganic material to binder can be from 10% to 90% by weight based on 100% by weight of a mixture including inorganic particles and binder.

[0073] Meanwhile, the thickness of the inorganic layer can be 30% or more of the total thickness of the separator. For example, when the inorganic layer is formed only on one surface of the separator substrate, the thickness of the inorganic layer formed only on one surface of the separator substrate can be 30% or more of the total thickness of the separator. Alternatively, when the inorganic layer is formed on opposite surfaces of the separator substrate, the sum of the thicknesses of the inorganic layers formed on opposite surfaces of the separator substrate can be 30% or more of the total thickness of the separator. Specifically, the thickness of the inorganic layer formed only on one surface of the separator substrate or the sum of the thicknesses of the inorganic layers formed on opposite surfaces of the separator substrate can be 50% or more, more specifically 70% or more of the total thickness of the separator.

[0074] For a separator that satisfies the above relationship, the diffusion distance in the MD direction and the diffusion distance in the TD direction can each be 2.0 mm or greater. Specifically, the diffusion distance in the MD direction can be 3.0 mm or greater, more specifically 3.5 mm or greater. For a separator that does not satisfy the above relationship, the diffusion distance in the MD direction and the diffusion distance in the TD direction are each less than 2.0 mm. That is, it can be seen that the impregnationability of the separator according to the present invention is significantly improved.

[0075] The MD direction corresponds to the direction in which the partition sheet moves forward during partition manufacturing, while the TD direction is perpendicular to the MD direction.

[0076] The present invention provides a cylindrical secondary battery having an electrode assembly including the separator housed in a cylindrical battery casing.

[0077] The electrode assembly can be a jelly roll type electrode assembly, which is configured to have a structure in which a positive electrode sheet and a negative electrode sheet are wound in a state in which a long separator sheet is disposed between the positive electrode sheet and the negative electrode sheet and added to the outer surface of either the positive electrode sheet or the negative electrode sheet.

[0078] Alternatively, when manufacturing electrode assemblies for cylindrical secondary batteries, a separator with a single-sided coating having an inorganic layer formed only on one surface of the separator substrate can be used, thereby increasing the battery's capacity and energy density, since safety assurance requirements are relatively low due to the characteristics of cylindrical secondary batteries.

[0079] Conventional products may be used without restriction as the respective electrode sheets, positive electrode mixtures, and negative electrode mixtures constituting the positive electrode sheet and the negative electrode sheet, and their detailed descriptions will be omitted from this specification.

[0080] In addition, the present invention may provide a battery pack comprising a cylindrical secondary battery as a unit battery, wherein the battery pack may be used as an energy source for devices such as electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, power storage devices, or energy storage systems.

[0081] The structure of the battery pack and the structure of the device are well known in the art to which this invention pertains, and therefore their detailed description will be omitted from this specification.

[0082] The invention will be described below with reference to embodiments. These embodiments are provided merely to facilitate a better understanding of the invention and should not be construed as limiting the scope of the invention.

[0083] <Example 1>

[0084] A separator substrate having a porosity of 34% as measured using a porosimeter was prepared as a porous separator substrate comprising a polyolefin-based polymer material, and comprising 100 parts by weight of a material having a porosity of 3m 2 The solid content of / g BET alumina (Al2O3), 1 part by weight of acrylic binder, and 1 part by weight of dispersant was prepared into inorganic particles.

[0085] 30% by weight of solids content is dissolved in 70% by weight of water to produce an inorganic slurry.

[0086] One surface of a porous separator substrate is coated with an inorganic slurry to a thickness of 5 μm to manufacture a water-based separator with a single-sided coating of an inorganic layer formed on one surface.

[0087] The porosity of the inorganic layer, calculated according to the following equation, is 56%.

[0088] (1 - (density of inorganic layer / density of solid content)) × 100

[0089] In the above equation, the density of the solid content can be calculated from the sum of the densities of the individual components constituting the solid content, with the content ratio reflected therein.

[0090] <Example 2>

[0091] The single-sided coated waterborne separator was manufactured using the same method as in Example 1, except that, unlike Example 1, it has a 6m... 2 / g of BET alumina was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 2 parts by weight of binder has a porosity of 58%.

[0092] <Example 3>

[0093] The single-sided coated waterborne separator was manufactured using the same method as in Example 1, except that, unlike Example 1, it has a 9m... 2 / g of BET alumina was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 3 parts by weight of binder has a porosity of 57%.

[0094] <Example 4>

[0095] The single-sided coated waterborne separator was manufactured using the same method as in Example 1, except that, unlike Example 1, it has a 5m... 2 / g of BET boehmite was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 2 parts by weight of binder has a porosity of 60%.

[0096] <Example 5>

[0097] The single-sided coated waterborne separator was manufactured using the same method as in Example 1, except that, unlike Example 1, it has a 15m... 2 / g of BET boehmite was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 6 parts by weight of binder has a porosity of 58%.

[0098] <Example 6>

[0099] The single-sided coated waterborne separator was manufactured using the same method as in Example 1, except that, unlike Example 1, it has a 10m... 2 / g of BET's ATH was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 5 parts by weight of binder has a porosity of 56%.

[0100] <Example 7>

[0101] The single-sided coated waterborne separator was manufactured using the same method as in Example 1, except that, unlike Example 1, it has a 15m... 2 / g of BET's ATH was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 6 parts by weight of binder has a porosity of 55%.

[0102] <Comparative Example 1>

[0103] A separator substrate having a porosity of 40% as measured using a porosimeter was prepared as a porous separator substrate comprising a polyolefin-based polymer material, and comprising 100 parts by weight of a material having a porosity of 3m 2 The solid content of / g BET alumina (Al2O3), 1 part by weight of acrylic binder, and 1 part by weight of dispersant was prepared into inorganic particles.

[0104] 19% by weight of solids were dissolved in 81% by weight of water to produce an inorganic slurry.

[0105] One surface of a porous separator substrate is coated with an inorganic slurry to a thickness of 5 μm to manufacture a water-based separator with a single-sided coating of an inorganic layer formed on one surface.

[0106] The porosity of the inorganic layer, calculated according to the following equation, is 47%.

[0107] (1 - (density of inorganic layer / density of solid content)) × 100

[0108] In the above equation, the density of the solid content can be calculated from the sum of the densities of the individual components constituting the solid content, with the content ratio reflected therein.

[0109] <Comparative Example 2>

[0110] A single-sided coated waterborne separator was manufactured using the same method as in Comparative Example 1, except that, unlike Comparative Example 1, it has a 6m... 2 / g of BET alumina was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 2 parts by weight of binder has a porosity of 47%.

[0111] <Comparative Example 3>

[0112] A single-sided coated waterborne separator was manufactured using the same method as in Comparative Example 1, except that, unlike Comparative Example 1, it has a 9m... 2 / g of BET alumina was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 5 parts by weight of binder has a porosity of 48%.

[0113] <Comparative Example 4>

[0114] A single-sided coated waterborne separator was manufactured using the same method as in Comparative Example 1, except that, unlike Comparative Example 1, it has a 5m... 2 / g of BET boehmite was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 2 parts by weight of binder has a porosity of 51%.

[0115] <Comparative Example 5>

[0116] A single-sided coated waterborne separator was manufactured using the same method as in Comparative Example 1, except that, unlike Comparative Example 1, it has a 15m... 2 / g of BET boehmite was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 6 parts by weight of binder has a porosity of 49%.

[0117] <Comparative Example 6>

[0118] A single-sided coated waterborne separator was manufactured using the same method as in Comparative Example 1, except that, unlike Comparative Example 1, it has a 10m... 2 / g of BET's ATH was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 5 parts by weight of binder has a porosity of 47%.

[0119] <Comparative Example 7>

[0120] A single-sided coated waterborne separator was manufactured using the same method as in Comparative Example 1, except that, unlike Comparative Example 1, it has a 15m... 2 / g of BET's ATH was used as inorganic particles to replace those with 3m 2 / g of BET alumina, and the inorganic layer made with an inorganic slurry comprising 100 parts by weight of inorganic particles and 6 parts by weight of binder has a porosity of 46%.

[0121] Permeability measurement

[0122] Permeability refers to the time it takes for 100cc of air to travel through the target being measured, and is measured in sec / 100cc.

[0123] In addition, permeability can be expressed as a Gurley value. In this specification, the permeability of the entire partition, including the inorganic layer, is measured according to JIS P8117.

[0124] The Seiko R150-02 from Asahi Company was used as a permeability measuring instrument.

[0125] The permeability measurement results of the partitions of Examples 1 to 7 and Comparative Examples 1 to 7, and the values ​​calculated according to the above relationships, are shown in Tables 1 and 2 below.

[0126] [Table 1]

[0127]

[0128] [Table 2]

[0129]

[0130]

[0131] Referring to Tables 1 and 2 above, it can be seen that for the partition according to the embodiment, the left-hand side value of the relationship is less than the permeability, while for the partition according to the comparative example, the left-hand side value of the relationship is greater than the permeability.

[0132] To check the impregnation of the separator according to the embodiment that satisfies the above relationship, and the impregnation of the separator according to the comparative example that does not satisfy the above relationship, an electrolyte drip test was performed as follows.

[0133] <Electrolyte dripping test>

[0134] Prepare a digital optical microscope (AD7013MZT(R4) from AnMo Electronics Corporation) and a steel ruler. Adjust the height of the digital optical microscope while simultaneously focusing it so that the scale of the digital optical microscope matches the measurement on the steel ruler.

[0135] Each partition manufactured according to the embodiments and comparative examples was cut to a size of 50 mm in length and 50 mm in width. The cut partitions were placed on a glass slide, and adhesive tape was attached to each vertex to secure the partitions to the glass slide.

[0136] A microsyringe with a capacity of 10 μl was filled with 2 μl of propylene carbonate, and the propylene carbonate was dripped onto a fixed septum in the form of water droplets.

[0137] Press the Capture button immediately after the drop falls to check the shape of the droplet, and capture the shape of the droplet again after 5 minutes.

[0138] The diffusion distance of water droplets falling onto the partition was measured in the MD and TD directions.

[0139] The diffusion distance of the partition according to Examples 1 to 7 is shown in Figures 1 to 7 The diffusion distances of the partitions in Comparative Examples 1 to 7 are shown in the photographs and Table 3 below. Figures 8 to 14 The photos and Table 4 below.

[0140] [Table 3]

[0141]

[0142] [Table 4]

[0143]

[0144] Referring to Tables 3 and 4 above, the diffusion distance of the partition according to the embodiment is 3.5 mm or more in the MD direction and 2.0 mm or more in the TD direction, while the diffusion distance of the partition according to the comparative example is 1.4 mm or less in the MD direction and 1.1 mm or less in the TD direction.

[0145] As a result, it can be seen that the impregnationability of the partition according to the embodiment, which satisfies this relationship, is significantly improved. Consequently, it can be indirectly seen that when the permeability of the partition is constant and the porosity of the partition substrate and the inorganic layer are set to satisfy the above relationship, the permeability of the partition is significantly improved.

[0146] Those skilled in the art will understand that, based on the above description, various applications and modifications are possible within the scope of this invention.

Claims

1. A partition, comprising: The partition substrate is made of porous material; and An inorganic layer is formed on at least one surface of the partition substrate by coating, wherein The partition substrate and the inorganic layer each have a porosity that satisfies the following relationship with the permeability of the partition: (10 × porosity of the partition substrate) - (4 × porosity of the inorganic layer) ≤ permeability of the partition. The permeability of the partition is 200 sec / 100 cc or less.

2. The partition according to claim 1, wherein the porosity of the inorganic layer is 55% or greater.

3. The partition according to claim 1, wherein the inorganic layer has a thickness equivalent to 30% or more of the total thickness of the partition.

4. The partition according to claim 1, wherein the inorganic material constituting the inorganic layer is composed of materials having a molecular weight of 3.0 μm. 2 Made from BET particles of / g or larger.

5. The separator according to claim 4, wherein the inorganic material has a dielectric constant, piezoelectricity, or lithium-ion transport capability of 1 or greater.

6. The partition according to claim 1, wherein the diffusion distance in the MD direction and the diffusion distance in the TD direction of the partition are each 2.0 mm or greater.

7. A cylindrical secondary battery having an electrode assembly comprising a separator according to any one of claims 1 to 6, housed in a cylindrical battery casing.

8. A battery pack comprising a cylindrical secondary battery as a unit cell according to claim 7.

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