Battery separator and battery

Abstract

The present invention relates to a battery separator and a battery. A battery separator and a battery of the present invention comprise: a base layer; an outer layer positioned on one surface or both surfaces of the base layer and comprising a first binder, which is a fluorine-based binder, and a second binder, which is a vinyl-based binder; and an inner layer positioned between the base layer and an organic layer and comprising inorganic particles, wherein the ratio (P1:P2) of the content (P1) of the first binder of the separator to the content (P2) of the second binder of the separator can be adjusted.

Description

Battery separator and battery

[0001] This application claims the benefit of the priority date of Application No. 10-2024-0087481, filed with the Korean Intellectual Property Office on July 3, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a battery separator.

[0003] The present invention relates to a battery.

[0004] A separator can be positioned between the anode and cathode in a battery. Charge carriers, such as lithium ions, can move through the separator. The separator can prevent physical contact between the anode and cathode. During the battery manufacturing process, an adhesive layer can attach the separator to the electrodes.

[0005] A non-aqueous composition containing a binder and an organic solvent can be used to produce an adhesive layer by coating and drying. Technological trends are shifting towards replacing organic solvents with aqueous solvents for environmental reasons.

[0006] The battery assembly process requires adhesion of the separator to the electrode (electrode adhesion) at an appropriate level of adhesive layer and adhesion between the layers that make up the separator (peel strength).

[0007] It is difficult to improve electrode adhesion and peel strength along with other performances of the battery separator based on an aqueous composition.

[0008] Accordingly, it is difficult to improve or maintain the performance of the battery, such as durability and electrical properties.

[0009] One embodiment of the present invention is a battery separator comprising: a substrate layer; an outer layer positioned on one or both sides of the substrate layer and including a first binder that is a fluorine-based binder and a second binder that is a vinyl-based binder; and an inner layer positioned between the substrate layer and the outer layer and including inorganic particles; wherein a ratio (P1:P2) of the first binder content (P1) of the battery separator and the second binder content (P2) of the battery separator is in a range of 0.5:1 to 5:1.

[0010] The above outer layer may include a sea-island structure.

[0011] The first binder can form a diagram of the sea-island structure, and the second binder can form a solution of the sea-island structure.

[0012] The peel strength of the above inner layer to the above substrate layer may be 125 gf / 25 mm or more.

[0013] The above first binder may include a PVDF-based binder.

[0014] The above first binder may include PVDF-HFP.

[0015] The above first binder may include PVDF-HFP having an HFP substitution ratio of 10 wt% or less.

[0016] The above first binder may be a particulate binder.

[0017] The average size of the first binder may be in the range of 100 nm to 800 nm.

[0018] The above second binder may be a non-particulate binder.

[0019] The above second binder may be a particulate binder.

[0020] The average size of the second binder may be in the range of 0.1 um to 2.0 um.

[0021] The second binder may comprise a single polymer comprising polymerized units derived from a vinyl monomer.

[0022] The above vinyl monomer may include at least one selected from the group consisting of vinyl alcohol, vinyl butyral, vinyl pyrrolidone, and vinyl acetate.

[0023] The above vinyl monomer may include at least one selected from the group consisting of vinyl butyral and vinyl acetate.

[0024] The above vinyl monomer may include at least one selected from the group consisting of vinyl alcohol and vinyl pyrrolidone.

[0025] The second binder may be positioned closer to the inner layer than the first binder.

[0026] The above outer layer may not contain inorganic particles.

[0027] The inorganic particle content of the inner layer may be 80 wt% or more.

[0028] Another specific embodiment of the present invention is a battery comprising: a positive electrode; a negative electrode; and a separator positioned between the positive electrode and the negative electrode; wherein the separator comprises: a substrate layer; an outer layer positioned on one or both sides of the substrate layer and including a first binder that is a fluorine-based binder and a second binder that is a vinyl-based binder; and an inner layer positioned between the substrate layer and the organic layer and including inorganic particles; wherein a ratio (P1:P2) of the first binder content (P1) of the separator and the second binder content (P2) of the separator is in a range of 0.5:1 to 5:1.

[0029] The battery separator of the present invention can simultaneously exhibit high electrode adhesion, high peel strength, excellent electrolyte impregnation, and appropriate air permeability.

[0030] The battery of the present invention can exhibit excellent durability and electrical performance.

[0031] Fig. 1 is a surface SEM photograph of Example 1. Fig. 2 is an enlarged view of Fig. 1.

[0032] Fig. 3 is a surface SEM photograph of Example 2. Fig. 4 is an enlarged view of Fig. 3.

[0033] Fig. 5 is a surface SEM photograph of Example 3. Fig. 6 is an enlarged view of Fig. 5.

[0034] Fig. 7 is a surface SEM photograph of Example 4. Fig. 8 is an enlarged view of Fig. 7.

[0035] Fig. 9 is a surface SEM photograph of Comparative Example 1. Fig. 10 is an enlarged view of Fig. 9.

[0036] This document may use ordinal numbers, such as “first” and “second,” to refer to multiple components. There is no order of precedence between the components.

[0037] In this document, the numerical range of “A to B” may mean “A or more and B or less.”

[0038] In this document, the unit "um" means "micrometer".

[0039] The following document describes the present invention in more detail.

[0040] When a specific commercial product is used as an ingredient in this document, the properties of that ingredient may refer to the properties described in the technical data sheet (TDS) or certification of analysis of that product.

[0041] One specific embodiment of the present invention is a battery separator.

[0042] A separator may be positioned between the electrodes in the separator. The separator may be positioned between the positive and negative electrodes in the battery. The separator may prevent physical contact between the positive and negative electrodes in the battery. Charge carriers (e.g., metal ions such as lithium ions) may move between the electrodes through the separator.

[0043] The above battery may include any element that performs an electrochemical reaction.

[0044] The above battery may refer to any type of primary battery, secondary battery, fuel cell, solar battery, or capacitor. In particular, the battery may refer to a lithium secondary battery. The lithium secondary battery may include a lithium metal secondary battery, a lithium polymer secondary battery, a lithium ion polymer secondary battery, or a lithium ion secondary battery.

[0045] Among these, the lithium ion secondary battery may include an electrode assembly composed of a plurality of unit cells including a basic battery unit and a battery case that accommodates the electrode assembly. The secondary battery may be classified into pouch-shaped, square-shaped, cylindrical, or coin-shaped types depending on the shape of the battery case.

[0046] The battery separator of the present invention can increase interlayer peeling strength and adhesion to electrodes by including an adhesive layer, as described later. Such a battery separator can be suitable for pouch-type secondary batteries or square secondary batteries.

[0047] The electrode assembly for pouch-type secondary batteries can typically be manufactured using a lamination-stacking process. If the battery separator's peel strength and adhesion to the electrodes are adequately maintained, defects such as delamination during assembly or post-production operation can be reduced.

[0048] The above battery separator comprises at least three different layers. The battery separator may include a substrate layer; an outer layer positioned on one or both sides of the substrate layer; and an inner layer positioned between the substrate layer and the outer layer.

[0049] The above substrate layer can support the separator and provide structural stability to the separator. The substrate layer may be a porous substrate. The substrate layer may include a polyolefin-based polymer.

[0050] The outer layer can attach the separator and electrode. The outer layer can be located on one side of the substrate layer and another side facing the one side. The outer layer can include specific polymers to improve electrode adhesion and peel strength.

[0051] The above outer layer may be positioned on both sides of the substrate layer. The composition of the outer layers positioned on each side of the substrate layer may be the same or different.

[0052] The outer layer may include two or more types of binders of different series. The outer layer may include a first binder and a second binder. The first binder and the second binder may be binders of different series. The first binder may be a fluorine-based binder. The second binder may be a vinyl-based binder.

[0053] The component that mainly exerts the adhesive force of the above-mentioned separator may be the first binder. The second binder may mainly further increase the adhesive force exerted by the first binder.

[0054] The above fluorine-based binder may contain a polymerization unit derived from a fluorine-containing monomer as a main component.

[0055] The above vinyl binder may contain a polymerization unit derived from a vinyl monomer as a main component.

[0056] Including a component as a main component may mean that the place containing said component contains said component in a content of 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more or 99% or more of the total weight.

[0057] The above inner layer may contain inorganic particles to perform a specific function.

[0058] The battery separator of the present invention may have a structure in which the base layer, the outer layer, and the inner layer are laminated in the above order, and the type of binder(s) included in the outer layer and the mixing ratio therebetween may be controlled. The ratio (P1:P2) of the first binder content (P1) of the battery separator and the second binder content (P2) of the battery separator may be within a range of 0.5:1 to 5:1.

[0059] The ratio of P2 based on the above P1 may be higher than that of the conventional separator. This is different from the conventional separator that uses a vinyl-based binder as an additive component such as a dispersant. This is because the present invention includes the second binder as a binder in the outer layer. The separator can simultaneously exhibit high electrode adhesion, high peel strength, excellent electrolyte impregnation property, and appropriate air permeability by combining the first binder and the second binder.

[0060] The above P1:P2 may be in the range of 1:1 to 4:1, 1:1 to 4.5:1, 1:1 to 5:1, 2:1 to 4:1, 2:1 to 4.5:1, 2:1 to 5:1, 3:1 to 4:1, 3:1 to 4.5:1, 3:1 to 5:1, 4:1 to 4:1, 4:1 to 4.5:1, or 4:1 to 5:1.

[0061] An outer layer coating liquid of a specific composition can form the outer layer.

[0062] The outer layer coating solution may be an aqueous coating solution. The outer layer coating solution may include an aqueous solvent, the first binder, and the second binder. The P1:P2 value of the outer layer coating solution may control the P1:P2 value of the separator.

[0063] The aqueous solvent may be composed of water or may be a mixture containing water and other components. If the aqueous solvent is a mixture containing water and other components, the aqueous solvent may contain water as a main component.

[0064] If the outer coating solution contains an aqueous solvent, it may be difficult to ensure sufficient electrode adhesion of the separator or to reduce the electrical resistance of the separator. However, the outer coating solution used in the present invention contains a combination of specific binders, and by adjusting the content ratio of these binders, the electrode adhesion of the separator can be increased and the electrical resistance of the separator can be reduced.

[0065] The outer layer coating liquid of the above-described composition forms the outer layer, and the inner layer between the base layer and the outer layer includes inorganic particles, so that the outer layer can exhibit a specific aspect in the separator.

[0066] The above outer layer may include a sea-island structure. The sea-island structure may refer to a structure in which the island of the dispersive phase is dispersed in the sea, which is a continuous phase.

[0067] When observed from the surface of the above battery separator, the above diagram can form a closed curve, and the above solution can surround the above diagram.

[0068] When observed from the side of the above battery separator, the sea may be adjacent to the inner layer and the island may be located on the sea in the outer layer.

[0069] The surface image of the above-mentioned battery separator, specifically the surface image of the outer layer, and more specifically the surface SEM image of the outer layer, can show the above-mentioned sea-island structure. The examples below describe in more detail a method for confirming the above-mentioned sea-island structure.

[0070] When the outer layer includes a sea-island structure, the outer layer surface can form a porous structure suitable for the movement of electrolyte and charge carriers. In addition, when the outer layer includes a sea-island structure, the sea can bind to the inner layer, thereby increasing the adhesive strength between the outer layer and the inner layer. In addition, when the outer layer includes a sea-island structure, the island containing a component suitable for improving the properties of the separator is exposed to the outer layer surface, thereby increasing the adhesive strength of the outer layer surface to the electrode. The sea-island structure of the outer layer can improve the electrode adhesive strength, peel strength, air permeability, and electrical resistance of the battery separator, and thus the performance of the battery.

[0071] Since the solubility of the binders included in the outer layer in a specific solvent (specifically, an aqueous solvent) differs, the outer layer may include a sea-island structure. Specifically, if the second binder included in the outer layer is closer to hydrophobic than hydrophilic, the outer layer may include a sea-island structure.

[0072] In the outer layer, the first binder can form a sea-island structure. This may be because, when the outer layer includes the sea-island structure, the outer layer coating liquid disperses the first binder in an aqueous solvent.

[0073] In the outer layer, the second binder can form a solution of the sea-island structure. This may be because, when the outer layer includes the sea-island structure, the outer layer coating liquid dissolves the second binder in an aqueous solvent.

[0074] The battery assembly process can apply external forces to the separator in various directions, which can affect the bonding between the layers that make up the battery separator. Improving the peel strength of the battery separator is crucial for ensuring a smooth battery assembly process and preventing assembly defects between battery components.

[0075] The above battery separator can further improve peel strength by including a specific component as a second binder in the outer layer. Specifically, the battery separator can improve the peel strength of the inner layer with respect to the base layer to 125 gf / 25 mm or more.

[0076] The peel strength [gf / 25mm] of the above battery separator may be 250 or less, 200 or less, 190 or less, or 180 or less.

[0077] This may be because the second binder included in the outer layer includes a polar functional group, specifically a hydrophilic functional group, and more specifically a hydrophilic functional group including an oxygen atom.

[0078] The present invention can also specifically control the composition of the first binder and the second binder.

[0079] The above first binder may include a PVDF-based binder. The PVDF-based binder can increase electrode adhesion and peel strength while maintaining the performance of the battery in the battery separator.

[0080] The PVDF-based binder may include at least one selected from the group consisting of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyvinylidene fluoride-co-trichloroethylene (PVDF-TCE), poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE), poly(vinylidene fluoride-co-tetrafluoroethylene) (PVDF-TFE), and poly(vinylidene fluoride-co-trifluoroethylene (PVDF-TrFE). Preferably, the first binder may include poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). More preferably, the HFP substitution rate of the PVDF-HFP included in the first binder may be 10 wt% or less.

[0081] The HFP substitution rate [weight %] of PVDF-HFP included in the above first binder may be within a range of 0.1 to 10, 0.1 to 9, 0.1 to 8, 0.1 to 7, 0.5 to 9, 0.5 to 8, 0.5 to 7, 1 to 9, 1 to 8, 1 to 7, 2 to 8, 2 to 7, 3 to 7, 4 to 7, 5 to 7, or 6 to 7.

[0082] The first binder may form an emulsion in the outer layer coating liquid. The first binder may form an emulsion in an aqueous solvent. The first binder may be a particulate binder. A particulate binder may refer to a binder having a particle structure in which its components are aggregated into a predetermined shape.

[0083] The present invention can improve electrode adhesion and peel strength of the battery separator and exhibit appropriate performance by controlling the average size of the first binder. The average size of the first binder can be in the range of 100 nm to 800 nm.

[0084] In this document, the average particle size may mean the sum of the longest lengths of each particle identified in an image showing the particles divided by the number of particles.

[0085] The average size [nm] of the first binder is 150 to 700, 150 to 600, 150 to 500, 150 to 450, 150 to 400, 150 to 350, 150 to 300, 200 to 600, 200 to 500, 200 to 450, 200 to 400, 200 to 350, 200 to 300, 250 to 500, 250 to 450, 250 to 400, 250 to 350, 250 to 300, 290 to 500, 290 to 450, 290 to 400, 290 to 350, or 290 to It can be within the range of 300.

[0086] The above outer coating solution can dissolve the second binder. The aqueous solvent can dissolve the second binder. The second binder may be a non-particulate binder. Unlike the particulate binder, the non-particulate binder may refer to a binder whose components do not readily coagulate with each other but rather have a structure in which they spread out in a network or net shape.

[0087] The above second binder may be a non-particulate binder.

[0088] The outer layer coating solution may not dissolve the second binder. That is, the second binder may form an emulsion in the outer layer coating solution. The second binder may form an emulsion in an aqueous solvent. The second binder may be a particulate binder.

[0089] The present invention can further improve the electrode adhesion and peel strength of the battery separator by controlling the average size of the second binder. The average size of the second binder can be in the range of 0.1 um to 2.0 um.

[0090] The average size [um] of the second binder is 0.11 to 1.9, 0.11 to 1.7, 0.11 to 1.5, 0.11 to 1.3, 0.11 to 1.1, 0.11 to 1.0, 0.11 to 0.9, 0.11 to 0.7, 0.11 to 0.5, 0.13 to 1.7, 0.13 to 1.5, 0.13 to 1.3, 0.13 to 1.1, 0.13 to 1.0, 0.13 to 0.9, 0.13 to 0.7, 0.13 to 0.5, 0.15 to 1.5, 0.15 to 1.3, 0.15 to 1.1, 0.15 to It may be in the range of 1.0, 0.15 to 0.9, 0.15 to 0.7, 0.15 to 0.5, 0.17 to 1.3, 0.17 to 1.1, 0.17 to 1.0, 0.17 to 0.9, 0.17 to 0.7, 0.17 to 0.5, 0.19 to 1.1, 0.19 to 1.0, 0.19 to 0.9, 0.19 to 0.7, 0.19 to 0.5, 0.2 to 1.0, 0.2 to 0.9, 0.2 to 0.7, or 0.2 to 0.5.

[0091] The glass transition temperature of the second binder may be 90°C or lower. This may be lower than the drying temperature of the coating solution used in manufacturing the battery separator. The second binder may exhibit a rubbery state in the separator. The glass transition temperature [°C] of the second binder may be in the range of 15 to 90, or 20 to 90, or 20 to 80.

[0092] In this paper, the method for measuring the glass transition temperature of a polymer may be differential scanning calorimetry (DSC) with a specified measurement temperature range and heating and cooling rates.

[0093] As described above, the second binder may contain as a main component a polymerization unit derived from a vinyl monomer. In addition, the polymer contained in the second binder may be a homopolymer of the vinyl monomer. In other words, the second binder may contain a homopolymer containing a polymerization unit derived from a vinyl monomer.

[0094] The above-described outer layer properties (sea-island structure and / or improved peel strength) can be achieved when the vinyl monomer contains a specific component.

[0095] The above vinyl monomer may include at least one selected from the group consisting of vinyl alcohol, vinyl butyral, vinyl pyrrolidone, and vinyl acetate.

[0096] The above vinyl monomer may include at least one selected from the group consisting of vinyl butyral and vinyl acetate. In this case, the outer layer may include a sea-island structure.

[0097] The above vinyl monomer may include at least one selected from the group consisting of vinyl alcohol and vinyl pyrrolidone. In this case, the peel strength of the battery separator including the outer layer may be 125 gf / 25 mm or more.

[0098] Vinyl alcohol contains a hydroxyl group (-OH) within the polymerization unit. This hydroxyl group can increase the bonding strength between the outer layer and the inner layer.

[0099] If the second binder comprises a single polymer containing polymerized units derived from vinyl alcohol, the second binder may be an aqueous solution. In this case, the second binder may be a non-particulate binder in the outer layer.

[0100] When the second binder comprises a single polymer including a polymerization unit derived from vinyl alcohol, the weight average molecular weight of the second binder may be in the range of 100,000 g / mol to 300,000 g / mol. The weight average molecular weight [*10000 g / mol] of the second binder may be in the range of 11 to 19, 11 to 18, 11 to 17, 11 to 16, 11 to 15, 12 to 18, 12 to 17, 12 to 16, 12 to 15, 13 to 17, 13 to 16, 13 to 15, 14 to 16, 14 to 15.

[0101] In this document, the method for measuring the weight average molecular weight of a polymer may be standard polystyrene-based gel permeation chromatography.

[0102] When the second binder comprises a single polymer including a polymerization unit derived from vinyl alcohol, the glass transition temperature of the second binder may be within a range of 50° C. to 85° C. In this case, the glass transition temperature [° C.] of the second binder may be within a range of 55 to 85, 55 to 80, 55 to 75, 55 to 70, 55 to 65, 55 to 60, 60 to 80, 60 to 75, 60 to 70, or 60 to 65.

[0103] Vinyl butyral can form a sea-island structure in the outer layer, thereby improving the air permeability and electrical resistance of the battery separator.

[0104] If the second binder comprises a single polymer containing polymerized units derived from vinyl butyral, the outer layer coating liquid may comprise the second binder as a powdered binder. The second binder may be a particulate binder in the outer layer.

[0105] When the second binder comprises a single polymer including a polymerization unit derived from vinyl butyral, the weight average molecular weight of the second binder may be in the range of 10,000 g / mol to 100,000 g / mol. The weight average molecular weight [*10000 g / mol] of the second binder may be in the range of 2 to 9, 2 to 8, 2 to 7, 2 to 6, 3 to 8, 3 to 7, 3 to 6, 4 to 7, 4 to 6, or 5 to 6.

[0106] When the second binder comprises a single polymer including a polymerization unit derived from vinyl butyral, the glass transition temperature of the second binder may be within a range of 50°C to 85°C. In this case, the glass transition temperature [°C] of the second binder may be within a range of 5 to 80, 55 to 75, 55 to 70, 55 to 65, 55 to 60, 60 to 75, 60 to 70, or 60 to 65.

[0107] Vinyl pyrrolidone can make polymers containing it amphoteric. Furthermore, because vinyl pyrrolidone contains oxygen in its molecule, it can further increase the bonding strength between the outer layer and the inner layer.

[0108] If the second binder comprises a single polymer containing a polymerization unit derived from vinyl pyrrolidone, the outer layer coating solution may comprise the second binder as a powder binder. The second binder may be a particulate binder in the outer layer.

[0109] When the second binder comprises a single polymer comprising a polymerization unit derived from vinyl pyrrolidone, the degree of polymerization of the second binder may be in the range of 100 to 1000. The degree of polymerization of the second binder may be in the range of 200 to 900, 200 to 800, 200 to 700, 200 to 600, 300 to 800, 300 to 700, 300 to 600, 400 to 700, 400 to 600, or 500 to 600.

[0110] In this document, the degree of polymerization of a polymer means the weight average molecular weight of the polymer divided by the molecular weight of the polymerization unit.

[0111] When the second binder comprises a single polymer including a polymerization unit derived from vinyl pyrrolidone, the glass transition temperature of the second binder may be within a range of 50°C to 85°C. In this case, the glass transition temperature [°C] of the second binder may be within a range of 5 to 80, 55 to 75, 55 to 70, 55 to 65, 55 to 60, 60 to 75, 60 to 70, or 60 to 65.

[0112] Vinyl acetate can form a sea-island structure in the outer layer, thereby improving the air permeability and electrical resistance of the battery separator.

[0113] If the second binder comprises a single polymer comprising polymerized units derived from vinyl acetate, the second binder may be an aqueous emulsion. In this case, the second binder may be a particulate binder in the outer layer.

[0114] When the second binder comprises a single polymer including polymerized units derived from vinyl acetate, the average size of the second binder may be in the range of 0.1 um to 2.0 um. The average size [um] of the second binder may be in the range of 0.15 to 1.5, 0.15 to 1.0, 0.15 to 0.5, 0.2 to 1.0, or 0.2 to 0.5.

[0115] When the second binder comprises a single polymer including a polymerization unit derived from vinyl acetate, the weight average molecular weight of the second binder may be in the range of 10,000 g / mol to 30 g / mol. The weight average molecular weight [*10,000 g / mol] of the second binder may be in the range of 5 to 25, 5 to 20, 5 to 15, 10 to 20, or 10 to 15.

[0116] When the second binder comprises a single polymer including a polymerization unit derived from vinyl acetate, the glass transition temperature of the second binder may be in a range of 15° C. to 60° C. The glass transition temperature [° C.] of the second binder may be in a range of 20 to 55, 20 to 50, 20 to 45, 20 to 40, 25 to 50, 25 to 45, 25 to 40, 30 to 45, 30 to 40, or 35 to 40.

[0117] The inner layer may also be formed of an aqueous inner layer coating solution like the outer layer. The inorganic particles included as a main component of the inner layer may also generally exhibit hydrophilicity. Therefore, in the outer layer, the second binder, which is generally hydrophilic, may be positioned more toward the inner layer, and the first binder, which is less hydrophilic, may be positioned more toward the outer surface of the outer layer. In other words, the second binder may be positioned closer to the inner layer than the first binder. This may mean that the second binder is positioned in greater quantity than the first binder in a portion of the outer layer closer to the inner layer, and the first binder is positioned in greater quantity than the second binder in a portion closer to the outer surface of the outer layer.

[0118] As described above, the substrate layer may contain a polyolefin polymer as a main component.

[0119] The above polyolefin-based film may contain the polyolefin-based polymer in an amount of 50% by volume or more, 90% by volume or more, or 95% by volume or more of the total material constituting the polyolefin-based film.

[0120] The weight average molecular weight of the component contained in the above polyolefin polymer is 3×10 5 25×10 6 It can be. When the weight average molecular weight of the component included in the polyolefin polymer is 1 million or more, the strength of the separator including the polyolefin porous film can be improved.

[0121] The polyolefin polymer may include a thermoplastic polymer. The thermoplastic polymer may include a homopolymer (e.g., polyethylene, polypropylene, polybutene) or a copolymer (e.g., ethylene-propylene copolymer) formed by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene.

[0122] The above polyolefin film may be a layer containing only one of these polyolefin polymers, or a layer containing two or more of these polyolefin polymers. Among these, polyethylene and high molecular weight polyethylene with ethylene as the main skeleton can block (shut down) excessive current flow at lower temperatures. In addition, the polyolefin film may additionally contain components other than the polyolefin polymer that do not impair the function of the film.

[0123] As described above, the inner layer may include inorganic particles to impart functions such as heat resistance to the separator.

[0124] The above inorganic particles may have one or more of the following properties: lithium ion transport capability, piezoelectricity, and flame retardancy.

[0125] Lithium ion-conducting inorganic particles can function to transport lithium ions without storing lithium, although they contain lithium. The lithium ion-conducting inorganic particles may have a defect within them. Charge carriers, such as lithium ions, can utilize this defect to transport. Therefore, the lithium ion-conducting inorganic particles can enhance lithium ion conductivity within a battery. As a result, battery performance can also be enhanced.

[0126] The above lithium ion conductive inorganic particles are Li x Ti y (PO4)3(0 <x<2, 0<y<3), Li x Al y Ti z (PO4)3(0 <x<2, 0<y<1, 0<z<3), Li x La y TiO3(0 <x<2, 0<y<3) 및 Li7La3Zr2O 12 It may include one or more selected from the group consisting of .

[0127] Piezoelectric inorganic particles are materials that exhibit different electrical conductivity depending on the applied pressure. Specifically, piezoelectric inorganic particles are insulators at normal pressure, but become electrical conductors when a certain pressure is applied. The permittivity of the piezoelectric inorganic particles is relatively high. The permittivity constant of the piezoelectric inorganic particles may be 100 or more. When the piezoelectric inorganic particles are stretched or compressed under a certain pressure, an electric charge may be generated. One side of the piezoelectric inorganic particles is positively charged and the other side is negatively charged, so that a potential difference may be generated in the piezoelectric inorganic particles. When a short circuit occurs inside the positive and negative electrodes due to an external impact, the piezoelectric inorganic particles arranged in the separator can prevent physical contact between the positive and negative electrodes. This potential difference can apply a microcurrent between the positive and negative electrodes. This microcurrent can gradually decrease the voltage of the battery when a short circuit occurs, thereby improving the safety of the battery.

[0128] The above piezoelectric inorganic particles are BaTiO3, BaSO4, Pb(Zr,Ti)O3(PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT)(0 <x<1, 0<y<1), Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3(PMN-PT) and HfO2(Hafnia) may be included.

[0129] The above flame-retardant inorganic particles can impart flame-retardant properties to the separator and prevent a rapid rise in the temperature inside the battery.

[0130] The above flame retardant inorganic particles may include at least one selected from the group consisting of SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, Al2O3, AlOOH, Al(OH)3, and TiO2.

[0131] The inorganic particle content of the inner layer may be 80 wt% or more. The inorganic particle content [wt%] of the inner layer may be in the range of 85 to 99, 85 to 98, 85 to 97, 85 to 96, 85 to 95, 90 to 98, 90 to 97, 90 to 96, or 90 to 95.

[0132] The inorganic particles may form an interstitial volume in the inner layer. The interstitial volume may refer to a void created by the shape of the inorganic particles when the inorganic particles are densely positioned in the inner layer. The interstitial volume may provide a path for metal ions (e.g., lithium ions) that operate the battery to move.

[0133] If the inner layer of the above battery separator includes inorganic particles, the outer layer may not include inorganic particles. The inorganic particle content of the outer layer may be, for example, 1 wt% or less, 0.5 wt% or less, 0.1 wt% or less, 0.01 wt% or less, or 0.001 wt% or less.

[0134] The inner layer may further comprise a binder. The inner layer may comprise a third binder, and the third binder may bind the inorganic particle(s) and bind the inner layer to the substrate layer or the outer layer.

[0135] The third binder may take on a specific form in the inner layer or the inner layer coating solution. The third binder may be dispersed in the inner layer coating solution to form a particulate binder. Alternatively, the third binder may be dissolved in the inner layer coating solution to form a non-particulate binder.

[0136] The above third binder may be an acrylic binder.

[0137] In this document, the acrylic binder may include a polymer containing as a main component a polymerization unit derived from a (meth)acryloyl group-containing compound such as (meth)acrylate and (meth)acrylamide.

[0138] The above acrylic binder may include a polymerization unit derived from a monomer including at least one selected from the group consisting of (meth)acrylamide, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, n-oxyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and tetradecyl (meth)acrylate.

[0139] The inner layer may further include a dispersant. The dispersant may improve the dispersibility of the inorganic particles in the inner layer.

[0140] The first dispersant may include at least one selected from the group consisting of an acrylic copolymer; cyanoethyl polyvinyl alcohol; a phenolic compound including baicalin, luteolin, taxifolin, myricetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, piceatenol, and tannic acid; and a fatty acid compound including pyrogallic acid, amylose, amylopectin, and xanthan gum.

[0141] The acrylic copolymer included in the above dispersant may include at least one functional group selected from the group consisting of an OH group, a COOH group, a CN group, an amine group, and an amide group.

[0142] The acrylic copolymer included in the above dispersant may include at least one selected from the group consisting of an ethyl acrylate-acrylic acid-N,N-dimethylacrylamide copolymer, an ethyl acrylate-acrylic acid-2-(dimethylamino)ethyl acrylate copolymer, an ethyl acrylate-acrylic acid-N,N-diethylacrylamide copolymer, and an ethyl acrylate-acrylic acid-2-(diethylamino)ethyl acrylate copolymer.

[0143] The thickness of the inner layer may be in the range of 1 μm to 5 μm. The thickness of the inner layer may be 1.5 μm or more or 2 μm or more. The thickness of the inner layer may be 4.5 μm or less, 4.0 μm or less, 3.5 μm or less, 3.0 μm or less or 2.5 μm or less.

[0144] Another specific example of the present invention is a battery.

[0145] The battery includes a positive electrode; a negative electrode; and a separator positioned between the positive electrode and the negative electrode.

[0146] The above separator may be a battery separator of the present invention. Therefore, the description of the battery separator of the present invention can be applied as is to the description of the battery of the present invention.

[0147] As a result, the battery of the present invention can exhibit excellent durability and electrical performance.

[0148] The electrode of the above battery may include an electrode active material attached to an electrode current collector.

[0149] Among the above electrode active materials, the positive electrode active material may include a lithium intercalation material. The lithium intercalation material may include a lithium transition metal oxide. The lithium intercalation material may include at least one selected from the group consisting of lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, and lithium iron oxide, lithium nickel-manganese oxide, lithium nickel-cobalt oxide, and lithium nickel-manganese-cobalt oxide.

[0150] Among the above electrode active materials, the negative electrode active material may include a lithium adsorption material. The lithium adsorption material may include at least one selected from the group consisting of lithium-based metals including lithium metal and lithium alloys; carbon-based compounds including carbon, petroleum coke, activated carbon, and graphite; and silicon-based compounds such as silicon carbide, silicon oxide, silicon-carbon composites, and silicon nanoparticles.

[0151] The above positive electrode current collector may be a metal foil including at least one selected from the group consisting of aluminum and nickel.

[0152] The above negative electrode current collector may be a metal foil including at least one selected from the group consisting of copper, gold, and nickel.

[0153] The above battery may further include an electrolyte.

[0154] The above electrolyte may include a non-aqueous solvent and a lithium salt. The lithium salt may be dissolved in the non-aqueous solvent.

[0155] The non-aqueous solvent may refer to an organic solvent that does not contain water or contains trace amounts of water. The non-aqueous solvent may include a carbonate solvent, an ether solvent, an ester solvent, a polar functional group-containing solvent, or a mixture thereof.

[0156] The above carbonate solvent may include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), and ethyl methyl carbonate (EMC).

[0157] The above ether solvent may include at least one selected from the group consisting of dimethoxyethane, diethoxyethane, and tetrahydrofuran.

[0158] The above ester solvent may include at least one selected from the group consisting of N-methyl-2-pyrrolidone (NMP) and gamma butyrolactone (γ-butyrolactone).

[0159] The above polar functional group-containing solvent may include at least one selected from the group consisting of dimethyl sulfoxide and acetonitrile.

[0160] The above ionic salt is A + B - It can have the structure of . In the above structure, A + is Li + , Na + , and K + It may include alkali metal cations such as B. In the above structure, B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , and C(CF2SO2)3 - It may contain anions such as:

[0161] The present disclosure is described in more detail below with examples and comparative examples. However, the present disclosure is not limited to the examples.

[0162] Example 1. Battery separator

[0163] The battery separator was manufactured according to the following sequence.

[0164] (1) The substrate layer is a polyethylene film (Toray's B09PJ1) with a thickness of 9.0 um.

[0165] (2) The inner coating liquid is composed of inorganic particles (Al2O3) in a weight ratio of 96:2:2; It is a water-based coating solution containing: Sumitomo's AES-11): binder (acrylic binder; Toyo's CSB-130): dispersant (Daicel's 1220).

[0166] (3) The outer coating solution is a mixture of a first binder and a second binder in a weight ratio of 4:1. The first binder is Solef 2042 from Solvay, which has a melting point of 140°C, a particle size (D50) of approximately 290 nm, a pH of approximately 7.5, and an aqueous emulsion containing PVDF-HFP in a VDF:HFP weight ratio of 93.3:6.7. The second binder is SNB-007 from Eco Chemical, which is a polyvinyl acetate aqueous emulsion with a weight average molecular weight of 100,000 to 150,000, a particle size (D50) of 200 to 500 nm, and a glass transition temperature of 38°C.

[0167] (4) The inner layer coating solution is applied and dried on both sides of the substrate layer. An inner layer with a thickness of 2 ㎛ per layer is positioned on the substrate layer.

[0168] (5) The above outer layer coating solution is applied and dried on the inner layer. An outer layer having a thickness of 1 μm per layer is positioned on the inner layer. A battery separator is obtained.

[0169] Example 2. Battery separator

[0170] The same process as Example 1 is repeated, except that BH-S from Sekisui, a polyvinyl butyral (PVB) powder having a weight average molecular weight of about 50,000 and a glass transition temperature of 60°C, is used instead of SNB-007 from Ecochemical as the second binder in (3). A battery separator is obtained.

[0171] Example 3. Battery separator

[0172] The same process as Example 1 is repeated, except that BD60 from Sannopco, which is a polyvinyl alcohol aqueous solution having a weight average molecular weight of 150,000 g / mol and a glass transition temperature of 60°C, is used instead of SNB-007 from Ecochemical as the second binder in (3). A battery separator is obtained.

[0173] Example 4. Battery separator

[0174] The same process as Example 1 is repeated, except that Sekisui's KX-1, a polyvinyl pyrrolidone powder with a polymerization degree of about 600 and a glass transition temperature of 60°C, is used instead of Ecochemical's SNB-007 as the second binder in (3). A battery separator is obtained.

[0175] Comparative example. Battery separator

[0176] The same process as Example 1 is repeated, except that the outer layer coating liquid is formed solely by the first binder in (3). A battery separator is obtained.

[0177] [Evaluation Method]

[0178] 1. Outer layer application amount

[0179] The amount of outer layer applied is the weight per unit area (g / m) of the final manufactured membrane. 2 ) Weight per unit area of ​​the laminate (laminated material and inner layer) before forming the outer layer (g / m) 2 ) was calculated as the value minus the difference.

[0180] 2. Membrane permeability

[0181] The standard for measuring the air permeability of membranes is JIS P-8117. The air permeability measuring device is a Gurley-type air permeability meter. The air permeability is measured by measuring the air permeability of 100 cc of air through a 28.6 mm diameter and 645 mm 2 It is measured as the time it takes to pass through a membrane having an area of ​​.

[0182] 3. Peel strength

[0183] The peel strength of the membranes manufactured in the examples and comparative examples was measured according to the following process.

[0184] (1) A sample is prepared in which the membrane is cut to a size of 25 mm * 100 mm.

[0185] (2) A specimen is prepared in which a glass substrate and the above sample are attached with double-sided adhesive tape (3M's Scotch 665). In this specimen, the outer layer is attached to the glass substrate with adhesive tape.

[0186] (3) This specimen was mounted on a UTM device (Instron). A bidirectional force was applied to the specimen at a rate of 300 mm / min, and the peel strength was measured as the force [gf / 25 mm] required to separate the bonded specimen from the glass substrate at a peel angle of 180 degrees. The peel strength was measured three times, and the results were summarized as a mean value based on the number of measurements.

[0187] 4. Negative dry adhesion of the separator

[0188] (1) A slurry containing natural graphite and an aqueous binder mixed in a weight ratio of 92:8 is coated and rolled onto a copper foil (current collector) to prepare an electrode (cathode). The area of ​​the cathode is 100 mm * 25 mm.

[0189] (2) The separator of the examples and comparative examples is cut to a size of 150 mm x 25 mm and then placed on the electrode. Then, a pressure of 6.5 MPa is applied to the separator for 1 second under temperature conditions of 60°C. A specimen in which the separator is laminated on the electrode is obtained.

[0190] (3) This specimen was mounted on a UTM device (Instron). A bidirectional force was applied to the specimen at a rate of 300 mm / min, and the force required to separate the separator from the electrode at a 180-degree peel angle was measured as the negative electrode adhesion. The negative electrode adhesion was measured three times, and the results were averaged based on the number of measurements.

[0191] 5. Resistance of the membrane

[0192] The resistance of the membrane was measured according to the following process.

[0193] (1) The battery separator is punched out to fit the size of the coin cell case.

[0194] (2) The punched battery separator is stored in a coin cell case.

[0195] (3) An electrolyte is injected into the coin cell case. The electrolyte is a 1.2 M concentration of LiPF6 dissolved in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7.

[0196] (4) The coin cell case is completely sealed with a compressor. It is then aged at room temperature for 3 hours. Electrical resistance measurement specimens are produced.

[0197] (5) The frequency-dependent impedance of the specimen is plotted using electrochemical impedance spectroscopy (EIS). Impedance spectroscopy is performed using Solaton's 1470E cell test system and frequency response analyzer 1255B at a temperature of 25°C and a frequency of 100,000 Hz to 10,000 Hz.

[0198] (6) The resistance of the membrane was determined by the real part (x-intercept) of the impedance.

[0199] 6. SEM photography

[0200] Surface SEM images of the battery separator were taken using a Hitachi SU3900 equipment. The photographed specimens were pretreated by platinum sputtering for 30 seconds.

[0201] [Results and Discussion]

[0202] The evaluation results for the examples and comparative examples are shown in Table 1 below.

[0203] Unit comparison example Example 1234 Thickness um 12.0 13.0 12.2 12.0 12.1 Outer layer application amount g / m 2 0.50.50.40.50.5 Air permeability sec / 100cc 85727810085 Peel strength gf / 15mm 10090121180127 Cathode adhesion gf / 25mm 540332443 Resistance ohm 0.540.480.510.530.51

[0204] Referring to Table 1, only the membranes of Examples 1 to 4 had a low coating amount (0.5 g / m 2 ) can be confirmed to have excellent air permeability, peel strength, cathode adhesion and resistance.

[0205] Figures 1 to 10 are surface SEM photographs of battery separators of examples and comparative examples.

[0206] Referring to FIGS. 1 to 10 and Table 1, it can be seen that, particularly in the outer layers of Examples 1 and 2, the second binder is positioned closer to the inner layer than the first binder, and the first binder protrudes outward. This indicates that the outer layers of Examples 1 and 2 include a sea-island structure, which can improve the air permeability and electrical resistance of the battery separator and, thus, the performance of the battery.

[0207] Also, referring to FIGS. 1 to 10 and Table 1, it can be seen that although there is no difference in the appearance of the outer layers between Examples 3 and 4 and the comparative example, the combination of binders included in the outer layers of Examples 3 and 4 can significantly improve the peel strength of Examples 3 and 4.

Claims

1. Base layer; An outer layer positioned on one or both sides of the substrate layer and including a first binder which is a fluorine-based binder and a second binder which is a vinyl-based binder; and An inner layer located between the substrate layer and the outer layer and containing inorganic particles; A battery separator including A battery separator, wherein the ratio (P1:P2) of the first binder content (P1) of the battery separator and the second binder content (P2) of the battery separator is within a range of 0.5:1 to 5:

1.

2. A battery separator according to claim 1, wherein the outer layer comprises a sea-island structure.

3. A battery separator in the second paragraph, wherein the first binder forms a sea-island structure, and the second binder forms a sea of ​​the sea-island structure.

4. A battery separator in accordance with claim 1, wherein the peel strength of the inner layer with respect to the substrate layer is 125 gf / 25 mm or more.

5. A battery separator according to claim 1, wherein the first binder comprises a PVDF-based binder.

6. In the first paragraph, the first binder is a battery separator comprising PVDF-HFP.

7. A battery separator according to claim 1, wherein the first binder comprises PVDF-HFP having an HFP substitution rate of 10 wt% or less.

8. A battery separator according to claim 1, wherein the first binder is a particle-type binder.

9. A battery separator according to claim 1, wherein the average size of the first binder is in the range of 100 nm to 800 nm.

10. A battery separator according to claim 1, wherein the second binder is a non-particulate binder.

11. A battery separator according to claim 1, wherein the second binder is a particle-type binder.

12. A battery separator according to claim 11, wherein the average size of the second binder is in the range of 0.1 um to 2.0 um.

13. A battery separator according to claim 1, wherein the second binder comprises a single polymer including a polymerization unit derived from a vinyl monomer.

14. A battery separator according to claim 13, wherein the vinyl monomer comprises at least one selected from the group consisting of vinyl alcohol, vinyl butyral, vinyl pyrrolidone, and vinyl acetate.

15. A battery separator according to claim 13, wherein the vinyl monomer comprises at least one selected from the group consisting of vinyl butyral and vinyl acetate.

16. A battery separator according to claim 13, wherein the vinyl monomer comprises at least one selected from the group consisting of vinyl alcohol and vinyl pyrrolidone.

17. A battery separator according to claim 1, wherein the second binder is positioned closer to the inner layer than the first binder.

18. A battery separator according to claim 1, wherein the outer layer does not contain inorganic particles.

19. A battery separator according to claim 1, wherein the content of inorganic particles in the inner layer is 80 wt% or more.

20. Including an anode; a cathode; and a separator positioned between the anode and the cathode; The separator comprises a substrate layer; an outer layer positioned on one or both sides of the substrate layer and including a first binder that is a fluorine-based binder and a second binder that is a vinyl-based binder; and an inner layer positioned between the substrate layer and the organic layer and including inorganic particles. A battery in which the ratio (P1:P2) of the first binder content (P1) of the separator and the second binder content (P2) of the separator is within a range of 0.5:1 to 5:1.

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