Polymer composition, polymer paste, separator for battery, and battery

Abstract

The present invention relates to a polymer composition, which can include a polymer component including a first polymerized unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymerized unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; a third polymerized unit derived from a monomer containing a lactam group having 6 or more nuclear atoms; and a fourth polymerized unit derived from a monomer containing a photoreactive functional group; a polymer slurry, a separator for a battery, and a battery.

Description

Technical Field

[0001] This document claims priority to application No. 10-2024-0114939 filed with the Korean Intellectual Property Office on August 27, 2024, and the entire contents of the application are incorporated herein by reference.

[0002] This invention relates to polymer compositions.

[0003] This invention relates to polymer slurries.

[0004] This invention relates to separators for batteries.

[0005] This invention relates to batteries. Background Technology

[0006] Polymer compositions, or polymer slurries as mixtures of such polymer compositions, can be used in a variety of ways in secondary batteries, such as electrodes, separators, etc. Conventional polymer compositions or slurries used in separators are based on organic solvents.

[0007] Recently, there has been a trend towards converting polymer compositions or slurries used in battery separators to those based on aqueous solvents. However, aqueous solvents are a major contributor to side reactions in the electrolyte solution of secondary batteries.

[0008] During battery assembly or operation, separators may be easily exposed to heat. Heat-exposed separators are prone to shrinkage. Shrinking separators can adversely affect battery stability.

[0009] Therefore, there is a need to develop water-based polymer compositions or slurries that can reduce the moisture content and thermal shrinkage rate of separators used in batteries. Summary of the Invention

[0010] Technical issues

[0011] The present invention aims to provide a polymer composition capable of reducing the moisture content and thermal shrinkage rate of battery separators.

[0012] The present invention aims to provide a polymer slurry capable of reducing the moisture content and thermal shrinkage rate of separators for batteries.

[0013] The present invention aims to provide a separator for batteries with reduced moisture content and thermal shrinkage rate.

[0014] The present invention aims to provide a battery capable of suppressing side reactions in the electrolyte solution and having improved stability.

[0015] Technical solution

[0016] One embodiment of the present invention is a polymer composition comprising a polymer component comprising: a first polymeric unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymeric unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; a third polymeric unit derived from a monomer containing a lactam group having six or more nuclear atoms; and a fourth polymeric unit derived from a monomer containing a photoreactive functional group.

[0017] The content of the first polymerization unit of the polymer component can be 50% by weight or more.

[0018] The content of the second polymer unit in the polymer component can be in the range of 5 to 20 parts by weight relative to 100 parts by weight of the first polymer unit.

[0019] The content of the third polymer unit in the polymer component can be in the range of 10 parts by weight to 50 parts by weight relative to 100 parts by weight of the first polymer unit.

[0020] The content of the fourth polymer unit in the polymer component can be in the range of 0.1 parts by weight to 5 parts by weight relative to 100 parts by weight of the first polymer unit.

[0021] The first polymerization unit may include polymerization units derived from (meth)acrylamide.

[0022] The second polymerization unit may include a polymerization unit derived from dimethyl (meth)acrylamide.

[0023] The third polymerization unit may include a polymerization unit derived from a monomer containing an N-substituted lactam group having six or more nuclear atoms.

[0024] The third polymerization unit can be derived from monomers whose lower critical solution temperature (LCST) is in the range of 25°C to 50°C.

[0025] The third polymerization unit may include polymerization units derived from N-vinylcaprolactam.

[0026] The fourth polymerization unit may include a polymerization unit derived from a monomer containing benzoylphenyl.

[0027] The fourth polymerization unit may include a polymerization unit derived from a (meth)acrylate monomer containing benzoylphenyl.

[0028] The weight-average molecular weight of the polymer components can range from 200,000 to 500,000.

[0029] The polydispersity index of polymer components can be in the range of 2 to 3.

[0030] The solid content of the polymer composition can range from 1% by weight to 10% by weight.

[0031] The polymer composition may also contain an aqueous solvent.

[0032] Another embodiment of the present invention is a polymer slurry comprising: a first polymer composition; inorganic particles; and a second polymer composition, wherein the first polymer composition comprises a first polymer component comprising: a first polymer unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymer unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; a third polymer unit derived from a monomer containing a lactam group having six or more nuclear atoms; and a fourth polymer unit derived from a monomer containing a photoreactive functional group.

[0033] The second polymer composition may contain a copolymer based on (meth)acrylate.

[0034] The content of the first polymer composition in the polymer slurry can be in the range of 1 to 5 parts by weight relative to 100 parts by weight of inorganic particles.

[0035] The content of the second polymer composition in the polymer slurry can be in the range of 1 to 5 parts by weight relative to 100 parts by weight of inorganic particles.

[0036] The solids content of polymer slurry can range from 30% to 70% by weight.

[0037] Polymer slurries may also contain aqueous solvents.

[0038] Another embodiment of the present invention is a separator for a battery, comprising: a porous substrate layer; and a polymer layer disposed on one or both surfaces of the porous substrate layer, wherein the polymer layer comprises a first polymer composition; inorganic particles; and a second polymer composition, and the first polymer composition comprises a first polymer component comprising: a first polymer unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymer unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; a third polymer unit derived from a monomer containing a lactam group having six or more nuclear atoms; and a fourth polymer unit derived from a monomer containing a photoreactive functional group.

[0039] The thickness of each polymer layer can range from 1 μm to 1.5 μm.

[0040] Another embodiment of the present invention is a battery comprising: a positive electrode; a negative electrode; a separator disposed between the positive and negative electrodes; and an electrolyte solution, wherein the separator comprises a porous substrate layer; and a polymer layer disposed on one or both surfaces of the porous substrate layer, the polymer layer comprising a first polymer composition; inorganic particles; and a second polymer composition, wherein the first polymer composition comprises a first polymer component comprising: a first polymer unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymer unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; a third polymer unit derived from a monomer containing a lactam group having six or more nuclear atoms; and a fourth polymer unit derived from a monomer containing a photoreactive functional group.

[0041] Electrolyte solutions may contain carbonate-based solvents.

[0042] The polymer layer can adhere to the positive electrode and the substrate, the negative electrode and the substrate, or both the positive electrode and the substrate and the negative electrode and the substrate.

[0043] Beneficial effects

[0044] The polymer composition of the present invention can reduce the moisture content and heat shrinkage rate of battery separators.

[0045] The polymer slurry of the present invention can reduce the moisture content and thermal shrinkage rate of battery separators.

[0046] The battery separator of the present invention can reduce moisture content and thermal shrinkage rate.

[0047] The battery of the present invention can suppress side reactions of the electrolyte solution and has improved stability. Detailed Implementation

[0048] When referring to multiple components, this document may use ordinal numbers, such as "first" and "second". There is no priority among the components.

[0049] In this document, when a specific commercially available product is used as a component, the characteristics of that component may refer to the characteristics described in the product's technical data sheet (TDS) or certificate of analysis (COA).

[0050] In this document, when the physical properties of a particular material vary with temperature and pressure, the measurement standard for such physical properties can be 25°C and 101.325 kPa.

[0051] In this document, the numerical range “A to B” means “A or greater and B or less”.

[0052] The values ​​mentioned in this document are rounded. For example, 1.5 is a number in the range of 1.45 to 1.54.

[0053] The invention is described in more detail below.

[0054] One embodiment of the present invention is a polymer composition.

[0055] Polymer compositions may contain polymer components with specific compositions.

[0056] The polymer component may contain at least three different polymeric units. The common feature of the three polymeric units is that they all contain at least an amide group.

[0057] The polymer component may comprise: a first polymeric unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymeric unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; and a third polymeric unit derived from a monomer containing a lactam group having six or more nuclear atoms.

[0058] In addition, the polymer component may contain specific monomers for additional curing under specific conditions, thereby further reducing the moisture content and heat shrinkage of the separator.

[0059] The polymer component may also contain a fourth polymeric unit derived from a monomer containing a photoreactive functional group. The photoreactive functional group may be a photocurable functional group. When light irradiates the polymer component, the photoreactive functional group can form a cured structure of the polymer component.

[0060] The polymer component may also contain a fifth polymeric unit derived from a monomer containing an N-monosubstituted (meth)acrylamide group.

[0061] In this document, a polymer unit may refer to the main chain that makes up the polymer.

[0062] In this document, a monomer containing an N-unsubstituted (meth)acrylamide group can refer to a monomer in which neither of the two hydrogen atoms on the nitrogen of the (meth)acrylamide group is replaced by a functional group other than hydrogen.

[0063] In this document, a monomer containing an N-monosubstituted (meth)acrylamide group can refer to a monomer in which one of the two hydrogen atoms on the nitrogen of the (meth)acrylamide group is replaced by a functional group other than hydrogen.

[0064] In this document, a monomer containing an N-disubstituted (meth)acrylamide group can refer to a monomer in which both hydrogen atoms on the nitrogen of the (meth)acrylamide group are replaced by functional groups other than hydrogen.

[0065] In this document, a monomer containing a lactam group having 6 or more nuclear atoms can refer to a monomer containing a cyclic amide group having 6 or more nuclear atoms.

[0066] In this document, monomers containing photoreactive functional groups may refer to monomers containing derivatives of photoreactive functional groups.

[0067] The minimum critical eutectic temperature (LCST) of the homopolymers of each of the first to third polymerization units can be different. By appropriately combining polymerization units derived from nitrogen-containing monomers with different homopolymer LCSTs, the moisture content and thermal shrinkage rate of battery separators made from this polymer composition can be reduced.

[0068] While not limited to theory, moisture in battery separators can react with electrolyte salts (such as LiPF6) to form unstable byproducts such as HF. This can accelerate the degradation of electrode interfaces (SEI and CEI) and corrode electrode active materials, thereby reducing lifespan and stability. Excessive moisture content in battery separators can also degrade the ionic conductivity of the electrolyte. A certain amount of moisture in battery separators can improve wettability and facilitate electrolyte impregnation. However, this is limited to improving initial performance, and in the long term, it may lead to a decline in battery life and safety.

[0069] Furthermore, the thermal shrinkage rate of the battery separator can be determined by the balance between the thermal shrinkage tendency of the porous substrate layer and the bonding force of the polymer layer, as described later, wherein the thermal shrinkage rate of the battery separator can vary according to the homopolymer LCST of the monomers constituting the polymer components contained in the polymer layer.

[0070] Monomers with low LCST in homopolymers can undergo phase separation at relatively low temperatures to induce thermal shrinkage of the separator, while monomers with high LCST in homopolymers can increase the bonding force between the polymer layer and the porous substrate layer at relatively high temperatures, thereby suppressing the thermal shrinkage rate. The polymer composition of the present invention can simultaneously reduce both the moisture content and thermal shrinkage rate of the separator for batteries by adjusting the balance between the two.

[0071] In this document, the LCST of a polymer can refer to the temperature at which the polymer and solvent separate into different phases. The LCST can be determined by differential scanning calorimetry (DSC) or turbidity measurement. Therefore, the polymer may exist as a homogeneous phase in the solvent at temperatures below the LCST, while it may undergo phase separation from the solvent at temperatures above the LCST. The solvent may include aqueous solvents.

[0072] In particular, the third polymer unit, due to its cyclic structure and number of nuclear atoms, can further reduce the moisture content of the battery separator prepared using this polymer component. Specifically, the monomer component derived from this third polymer unit can exhibit relative nonpolarity compared to monomers containing lactam groups with fewer nuclear atoms. This relative nonpolarity can further reduce the moisture content of the separator prepared using the polymer composition containing this third polymer unit.

[0073] In polymer compositions, it is important not only that the polymer components undergo phase separation at specific temperatures above room temperature to reduce the moisture content of the separators prepared therefrom, but also that the polymer composition is successfully coated. Therefore, it is preferable that the polymer components comprise, in appropriate amounts, polymeric units having relatively low homopolymer LCST and polymeric units having relatively high homopolymer LCST.

[0074] The fourth polymerization unit can further cure the polymer component under specific conditions. The cured product formed from this polymer component may not be easily soluble in water, and its structure may not easily change even when exposed to high temperatures. As a result, the moisture content and thermal shrinkage rate of the separator made from this polymer composition can be further reduced.

[0075] In the polymer composition, the content of the first to fourth polymerization units can be appropriately adjusted to prepare battery separators with low moisture content and low thermal shrinkage.

[0076] In the polymer composition, the polymer component may contain a first polymeric unit in a specific ratio. Specifically, the content of the first polymeric unit in the polymer component may be 50% by weight or more. The lower limit of the content (in weight%) of the first polymeric unit in the polymer component may be 55, 60, or 65. The upper limit of the content of the first polymeric unit in the polymer component may not be particularly limited.

[0077] The content of the second polymer unit in the polymer component can range from 5 parts by weight to 20 parts by weight relative to 100 parts by weight of the first polymer unit. The lower limit of the content (in parts by weight) of the second polymer unit in the polymer component can be 6, 7, 8, 9, 10, 11, 12, 13, or 14. The upper limit of the content (in parts by weight) of the second polymer unit in the polymer component can be 19, 18, 17, 16, or 15.

[0078] The content of the third polymer unit in the polymer component can range from 10 parts by weight to 50 parts by weight relative to 100 parts by weight of the first polymer unit. The lower limit of the content of the third polymer unit in the polymer component (in parts by weight) can be 15, 20, or 25. The upper limit of the content of the third polymer unit in the polymer component (in parts by weight) can be 45, 40, 35, or 30.

[0079] The content of the fourth polymer unit in the polymer component can range from 0.1 parts by weight to 5 parts by weight relative to 100 parts by weight of the first polymer unit. The lower limit of the content (in parts by weight) of the fourth polymer unit in the polymer component can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1. The upper limit of the content (in parts by weight) of the fourth polymer unit in the polymer component can be 4.5, 4, 3.5, 3, 2.5, 2, or 1.5.

[0080] Monomers containing an N-unsubstituted (meth)acrylamide group may include one or more selected from (meth)acrylamide and maleic amide. Preferably, monomers containing an N-unsubstituted (meth)acrylamide group may include (meth)acrylamide. More preferably, monomers containing an N-unsubstituted (meth)acrylamide group may include acrylamide.

[0081] Monomers containing an N-monosubstituted (meth)acrylamide group may include one or more of the following: N-isopropyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, diacetone (meth)acrylamide, (meth)acrylamide tert-butylsulfonic acid, hydroxyethyl (meth)acrylamide, N-n-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N,N-methylenebis(meth)acrylamide, and N-tert-butyl (meth)acrylamide sulfonic acid. Preferably, monomers containing an N-monosubstituted (meth)acrylamide group may include diacetone (meth)acrylamide. More preferably, monomers containing an N-monosubstituted (meth)acrylamide group may include diacetone acrylamide.

[0082] Monomers containing an N-disubstituted (meth)acrylamide group may include one or more selected from: N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, and (meth)acryloylmorpholine. Preferably, monomers containing an N-disubstituted (meth)acrylamide group may include N,N-dimethyl (meth)acrylamide. More preferably, monomers containing an N-disubstituted (meth)acrylamide group may include N,N-dimethylacrylamide.

[0083] In monomers containing lactam groups with six or more nuclear atoms, one of the hydrogen atoms on the nitrogen atom of the central ring of the lactam may be substituted with a functional group other than hydrogen or may remain unsubstituted. Preferably, monomers containing lactam groups with six or more nuclear atoms may include monomers containing N-substituted lactam groups with six or more nuclear atoms. A monomer containing N-substituted lactam groups with six or more nuclear atoms may refer to a monomer in which one of the hydrogen atoms on the nitrogen atom of the central ring of the lactam is substituted with a functional group other than hydrogen. More preferably, monomers containing lactam groups with six or more nuclear atoms may be N-vinylcaprolactam.

[0084] Monomers containing lactam groups with six or more nuclear atoms can exhibit specific thermal behaviors. Specifically, monomers containing lactam groups with six or more nuclear atoms can satisfy specific homopolymer properties.

[0085] The lowest critical cosolubility temperature (LCST) of homopolymers containing monomers with lactam groups having six or more nuclear atoms can be within a specific range. That is, the LCST of solutions of water and homopolymers composed of a third polymerization unit can be within a specific range. Specifically, the LCST of homopolymers containing monomers with lactam groups having six or more nuclear atoms can be in the range of 25°C to 50°C. The water solubility of homopolymers composed of a third polymerization unit may change abruptly at the LCST. This temperature range can be lower than the battery temperature during the battery manufacturing process or during battery operation.

[0086] As described above, compared with the moisture content and heat shrinkage rate of separators prepared by conventional polymer compositions, polymer compositions containing a third polymerization unit of homopolymer LCST below the battery temperature during battery manufacturing or battery operation can further reduce the moisture content and heat shrinkage rate of separators prepared therefrom.

[0087] The photoreactive functional group can be benzoylphenyl. That is, the fourth polymerization unit can include polymerization units derived from monomers containing benzoylphenyl.

[0088] The monomer containing the photoreactive functional group can be a (meth)acrylate monomer containing benzoylphenyl. The fourth polymerization unit can include a polymerization unit derived from a (meth)acrylate monomer containing benzoylphenyl. Preferably, the fourth polymerization unit can include a polymerization unit derived from a methacrylate monomer containing benzoylphenyl.

[0089] The properties of the polymer components can also be adjusted appropriately.

[0090] The weight-average molecular weight of the polymer component can range from 200,000 to 500,000. The lower limit of the weight-average molecular weight of the polymer component can be 250,000, 300,000, 350,000, 400,000, or 450,000. The upper limit of the weight-average molecular weight of the polymer component can be 490,000, 470,000, 460,000, or 450,000. When the weight-average molecular weight of the polymer component is within the stated range, the shear stress between the molecules constituting the polymer component can be adjusted. Therefore, the polymer composition can exhibit a low rate of thermal shrinkage.

[0091] The polydispersity index of the polymer component can range from 2.5 to 3. The lower limit of the polydispersity index can be 2.55, 2.6, 2.65, 2.7, or 2.75. The upper limit of the polydispersity index can be 2.95, 2.9, 2.85, or 2.8. When the polydispersity index of the polymer component is within the range described, the polymer component can be stacked efficiently. Therefore, the polymer composition can exhibit low thermal shrinkage.

[0092] The polymer composition may also contain a solvent. The polymer composition may also contain an aqueous solvent. That is, the polymer composition may be based on an aqueous solvent. Even if the polymer composition is based on an aqueous solvent, it can be manufactured as a separator with a low moisture content.

[0093] The polymer component can be water-soluble. Therefore, the polymer component can be dissolved in an aqueous solvent in the polymer composition.

[0094] The proportion of polymer components in the polymer composition, i.e., the solids content of the polymer composition, can also be adjusted. That is, the content of components other than the solvent in the polymer composition can be adjusted. The solids content of the polymer composition can range from 1% by weight to 10% by weight. The lower limit of the solids content (unit: weight%) can be 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, or 8.0. The upper limit of the solids content (unit: weight%) can be 9.5, 9.0, 8.5, or 8.0. When the solids content of the polymer composition is within the stated range, separators containing the composition can be smoothly manufactured without gelling.

[0095] Another embodiment of the present invention is a polymer slurry.

[0096] Polymer slurries can contain a plurality of different polymer compositions.

[0097] In this document, a plurality of different polymer compositions may mean that the types, contents, characteristics and / or functions of the polymer components constituting each of them are different from each other.

[0098] The polymer slurry may comprise at least a first polymer composition and a second polymer composition. Herein, the first polymer composition may be the polymer composition of the present invention as described above.

[0099] Therefore, in the description of the polymer slurry, the description of the first polymer composition may be the same as the description of the polymer composition of the present invention as described above.

[0100] The polymer slurry may further comprise inorganic particles. The polymer slurry may comprise inorganic particles to impart functions such as heat resistance to a battery separator.

[0101] The inorganic particles may have one or more properties selected from the group consisting of lithium ion conductivity, piezoelectricity and flame retardancy.

[0102] Lithium ion conductive inorganic particles may contain lithium but do not store lithium, and can perform the function of transporting lithium ions. The interior of the lithium ion conductive inorganic particles may have certain defects. Charge carriers such as lithium ions can move via said defects. Therefore, the lithium ion conductive inorganic particles can improve the lithium ion conductivity in a battery. Accordingly, the performance of the battery can also be improved.

[0103] The lithium ion conductive inorganic particles may include one or more selected from the group consisting of 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) and Li7La3Zr2O 12 .

[0104] Piezoelectric inorganic particles are materials that exhibit different electrical conductivity depending on the applied pressure. Specifically, piezoelectric inorganic particles are insulators under normal pressure, but become electrical conductors when a certain pressure is applied. Piezoelectric inorganic particles have a relatively high dielectric constant, which can be 100 or greater. When piezoelectric inorganic particles are stretched or compressed under certain pressure, they can generate an electric charge. One side of the piezoelectric inorganic particle can be positively charged, and the other side can be negatively charged, thus creating a potential difference within the particle. When an external impact causes a short circuit between the positive and negative electrodes, the piezoelectric inorganic particles placed in the separator can prevent physical contact between the positive and negative electrodes. This potential difference can apply a weak current between the positive and negative electrodes. When a short circuit occurs in the battery, this weak current can gradually reduce the battery voltage, thereby improving battery safety.

[0105] Piezoelectric inorganic particles may include one or more of the following: 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 (hafnium dioxide).

[0106] Flame-retardant inorganic particles can add flame-retardant properties to the separator and prevent rapid temperature rise inside the battery.

[0107] Flame-retardant inorganic particles may include one or more of the following: SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, Al2O3, AlOOH, Al(OH)3, and TiO2.

[0108] In the polymer slurry, the first polymer composition and the second polymer composition can exhibit at least different functions from each other. The first polymer composition can serve to adhere the separator made from the polymer slurry to the electrode. The second polymer composition can serve to bind the inorganic particles contained in the polymer slurry.

[0109] In the polymer slurry, the first polymer composition and the second polymer composition can have different compositions from each other. Since the first polymer composition can be the same as the polymer composition of the present invention, it can be a (meth)acrylamide-based polymer composition. The second polymer composition can have a different composition from the first polymer composition. For example, the second polymer composition can contain a (meth)acrylate-based copolymer. Thus, the second polymer composition can exhibit the aforementioned adhesive properties.

[0110] In the polymer slurry, the content of each of the first polymer composition and the second polymer composition can also be adjusted appropriately.

[0111] The content of the first polymer composition relative to 100 parts by weight of inorganic particles can range from 1 part by weight to 5 parts by weight. The lower limit of the content (in parts by weight) of the first polymer composition relative to 100 parts by weight of inorganic particles can be 1.5, 2.0, 2.5, or 3.0. The upper limit of the content (in parts by weight) of the first polymer composition relative to 100 parts by weight of inorganic particles can be 4.5, 4.0, 3.5, or 3.0.

[0112] The content of the second polymer composition relative to 100 parts by weight of inorganic particles can range from 1 part by weight to 5 parts by weight. The lower limit of the content (in parts by weight) of the second polymer composition relative to 100 parts by weight of inorganic particles can be 1.1, 1.2, 1.3, 1.4, or 1.5. The upper limit of the content (in parts by weight) of the first polymer composition relative to 100 parts by weight of inorganic particles can be 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, or 1.5.

[0113] In addition to the components mentioned above, the polymer slurry may also contain other components. Specifically, the polymer slurry may also contain a dispersant to disperse the polymer composition within the slurry. Furthermore, the polymer slurry may contain a surfactant to give the polymer composition a particulate form within the slurry. Known components or products can be used as dispersants and surfactants. The types of dispersants and surfactants are not particularly limited.

[0114] Like the polymer compositions of the present invention, the polymer slurry can also be based on an aqueous solvent. Therefore, the polymer slurry can also contain an aqueous solvent. Even if the polymer slurry is based on an aqueous solvent, it can simultaneously reduce the moisture content and thermal shrinkage rate of the battery separator.

[0115] Another embodiment of the present invention is a separator. Specifically, the separator can be a battery separator.

[0116] In this document, a battery can refer to a device that can convert electrical energy into chemical energy or chemical energy into electrical energy through an oxidation-reduction reaction.

[0117] Battery separators may include a porous substrate layer and a polymer layer.

[0118] Porous substrates can support separators and provide structural stability to them. Porous substrates can include polyolefin-based membranes.

[0119] Here, polyolefin-based membranes refer to membranes that contain polyolefin-based polymers as the main component.

[0120] Polyolefin-based membranes may contain polyolefin-based polymers in amounts of 50% or more, 90% or more, or 95% or more of the total material constituting the polyolefin-based membrane.

[0121] Polyolefin-based polymers can contain components with a weight-average molecular weight of 3 × 10⁻⁶. 5 Up to 25×10 6 When the weight-average molecular weight of the components contained in a polyolefin-based polymer is 1,000,000 or greater, the strength of the separator, including a polyolefin porous membrane, can be improved.

[0122] Polyolefin-based polymers may include thermoplastic polymers. Thermoplastic polymers may include homopolymers (e.g., polyethylene, polypropylene, polybutene) or copolymers (e.g., ethylene-propylene copolymers) formed by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene.

[0123] Polyolefin-based membranes can be layers comprising a single polyolefin-based polymer, or layers comprising two or more of these polyolefin-based polymers. Polyethylene (especially high molecular weight polyethylene) with ethylene as the main chain can block (shut off) excessive current flow at lower temperatures. Furthermore, polyolefin-based membranes can also contain components other than polyolefin-based polymers that do not impair the membrane's function.

[0124] The polymer layer can be disposed on one or both surfaces of the porous substrate. Preferably, the polymer layer can be disposed on both surfaces of the porous substrate.

[0125] In the separator, the polymer layer can be prepared from the aforementioned polymer slurry. Specifically, the polymer layer can be formed by coating the aforementioned polymer slurry onto one or both surfaces of the porous substrate and then drying it. Therefore, the polymer layer can contain most of the components contained in the aforementioned polymer slurry.

[0126] The polymer layer may comprise a first polymer composition; inorganic particles; and a second polymer composition.

[0127] The first polymer composition contained in the polymer layer may be a polymer composition as disclosed herein.

[0128] The inorganic particles and the second polymer composition contained in the polymer layer may be the same as those described in the polymer slurry of this disclosure.

[0129] As described above, the separator of the polymer slurry using the present invention can reduce moisture content and thermal shrinkage. When this separator is applied to a battery, side reactions of the electrolyte solution are reduced, thereby improving performance.

[0130] The polymer layer exhibits sufficient performance even when formed by applying a small amount of polymer slurry. Furthermore, applying a relatively small amount of polymer slurry can help reduce the moisture content of the separator. Therefore, the polymer layer formed in the separator can be relatively thin. For example, the thickness of the polymer layer can range from 1 μm to 1.5 μm. The thickness of the polymer layer can refer to the thickness per layer.

[0131] Another embodiment of the present invention is a battery. The battery may include the battery separator of the present invention.

[0132] A battery may include at least a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. A battery may also include an electrolyte solution.

[0133] The separator can be the battery separator of the present invention. Therefore, the description of the separator in the battery description can be applied as described above. The battery can minimize side reactions caused by the electrolyte solution and can have improved thermal durability. This is because the electrolyte solution usually undergoes side reactions with water, but the separator has reduced its water content, and the separator usually shrinks due to heat, but the separator has reduced its shrinkage rate.

[0134] The battery can be a lithium-ion battery. The electrolyte solution of a lithium-ion battery can typically contain a carbonate-based solvent. Water undergoes side reactions with the carbonate-based solvent and degrades the battery's performance, but because the battery of this invention has a low water content, its performance degradation can be minimized.

[0135] Furthermore, the polymer layer included in the separator can be a layer possessing both heat resistance and adhesiveness. Therefore, the polymer layer can impart heat resistance to the separator or battery. Additionally, the polymer layer can adhere the porous substrate layer of the separator to the electrodes (positive and / or negative electrodes). Separators exhibiting heat resistance and adhesiveness as separate layers can also be included within the scope of this invention. Such separators can also include an inorganic layer disposed between the polymer layer and the porous substrate layer and containing inorganic particles. In this case, the inorganic particles may be contained solely in the inorganic layer.

[0136] In the battery, the positive electrode and the substrate, the negative electrode and the substrate, or the positive electrode and the substrate and the negative electrode and the substrate can be adhered via a polymer layer. Preferably, the positive electrode and the substrate and the negative electrode and the substrate can be adhered via a polymer layer.

[0137] Invention Embodiments

[0138] In the following document, the invention is described in more detail with reference to examples and comparative examples. However, this document is not intended to limit the invention to the examples.

[0139] [Preparation of Experimental Samples]

[0140] Preparation Example 1. Polymer Composition

[0141] (1) 69 parts by weight of acrylamide, 10 parts by weight of dimethylacrylamide, 20 parts by weight of N-vinylcaprolactam and 1 part by weight of benzoylphenyl methacrylate were loaded into a reaction vessel.

[0142] (2) Then, 300 ppm of 3-mercaptopropionic acid was added to the reaction vessel as a molecular weight regulator.

[0143] (3) Then, distilled water is added to the reaction vessel as a reaction solvent, so that the solid content of the reaction solution is 8% by weight.

[0144] (4) After that, the interior of the reaction vessel was replaced with nitrogen and the temperature was raised to 70°C.

[0145] (5) Next, 5,000 ppm of potassium persulfate (KPS) was added to the reaction vessel as a polymerization initiator and polymerization was carried out for 8 hours.

[0146] Preparation Example 2. Polymer Composition

[0147] Repeat the same steps as in Preparation Example 1, except that in step (1), 70 parts by weight of acrylamide, 10 parts by weight of dimethylacrylamide and 20 parts by weight of N-vinylcaprolactam are loaded into the reaction vessel; in step (2), 5,000 ppm of 3-mercaptopropionic acid is loaded; and in step (3), distilled water is loaded as the reaction solvent, so that the solid content is 8 by weight.

[0148] Example. Polymer slurry

[0149] 100 parts by weight of inorganic particles (boehmite), 3 parts by weight of a first polymer composition, 1 part by weight of a dispersant (BYK-154), 1.5 parts by weight of a second polymer composition (binder, CSB-400), and 0.5 parts by weight of a surfactant (WE-3475) were mixed in distilled water to obtain a polymer slurry. The polymer composition of Preparation Example 1 was used as the first polymer composition.

[0150] Comparative example: Polymer slurry

[0151] Repeat the same steps as in the examples, except that the polymer composition of Preparation Example 2 is used as the first polymer composition.

[0152] [Evaluation Methodology]

[0153] The weight-average molecular weight and polydispersity index of the polymer components of the polymer compositions of Preparation Example 1 and Preparation Example 2 were measured by gel permeation chromatography performed under the following conditions.

[0154] (1) Column (manufacturer, model): 2×TSKgel SupermultiporeHZ-M + TSKgel SuperHZ-2500

[0155] (2) Eluent: THF

[0156] (3) Temperature: 40℃

[0157] (4) Flow rate: 1.0 mL / min

[0158] (5) Injection volume, sample concentration: 30 μL, 1 mg / mL to 10 mg / mL

[0159] (6) Standard material: polystyrene

[0160] (7) Detector: RI

[0161] (8) Device: PL GPC220 (Agilent Technologies) or GPC-900 (JASCO)

[0162] 2. Moisture content

[0163] The moisture content of the separators made from the polymer slurry obtained in the examples and comparative examples was measured according to the following procedure.

[0164] (1) The polymer slurry obtained in the examples and comparative examples was coated onto the polyethylene substrate using a Mayer rod.

[0165] (2-1) The coating slurry of the comparative example was dried in a Mathis oven to prepare a separator.

[0166] (2-2) The coating slurry of the example was dried in a Mathis oven and irradiated with UV-A (1160 mJ) using a Miltec H-type lamp to prepare the separator.

[0167] (3) Cut a separator of about 0.2 g to obtain a measurement sample.

[0168] (4) Place the sample into a vial and measure the moisture content according to the Karl-Fischer measurement. The measuring device is a Metrohm 899 coulometer, and the moisture content can be calculated from the amount of Karl-Fischer reagent consumed.

[0169] (5) The moisture content of the separator was determined to be the average of the three measurements in (4) above.

[0170] 3. Thermal shrinkage rate

[0171] The thermal shrinkage rate of the separators made from the polymer slurry obtained in the examples and comparative examples was measured according to the following procedure.

[0172] (1) The polymer slurry obtained in the examples and comparative examples was coated onto a polyethylene substrate with a thickness of 11 μm using a Mayer rod.

[0173] (2-1) The coating slurry of the comparative example was dried in a Mathis oven to prepare a separator.

[0174] (2-2) The coating slurry of the example was dried in a Mathis oven and irradiated with UV-A (1160 mJ) using a Miltec H-type lamp to prepare the separator.

[0175] (3) Cut the divider into pieces with an area of ​​5×5 cm. 2 A square shape is used to obtain the measurement sample.

[0176] (4) Mark four points spaced 1.5 cm apart on the test specimen with an oil-based marker.

[0177] (5) Heat-treat the separator sample in a Mathis oven at 150°C for about 30 minutes.

[0178] (6) Remove the separator sample from the Mathis oven and measure the distance between the four marked points on the sample with a ruler. Since the distance variation was observed at three points, the average value at the three points was used as the distance between the points after heat treatment.

[0179] (7) The rate of change of the distance between the four points before and after heat treatment is evaluated as the thermal shrinkage rate.

[0180] [Results and discussion]

[0181] Tables 1 and 2 below summarize the evaluation results of the polymer compositions of the preparation examples and the polymer slurries of the examples and comparative examples.

[0182] [Table 1]

[0183]

[0184] [Table 2]

[0185]

[0186] Referring to Tables 1 and 2, it can be determined that, compared with the separator of the comparative example, the separator of the embodiment reduces the moisture content by approximately 167 ppm and the heat shrinkage rate by approximately 4%. Considering that even trace amounts of moisture degrade battery performance, it can be seen that the difference in moisture content and heat shrinkage rate between the separators of the embodiment and the comparative example can impart a significant difference in battery performance.

[0187] The separators of the embodiments were manufactured by using the polymer composition of Preparation Example 1 as the first polymer composition and curing it under ultraviolet light. The separators of the comparative examples were manufactured by using the polymer composition of Preparation Example 2 as the first polymer composition and subjecting it to heat drying. This confirms that polymers containing polymeric units derived from photoreactive functional groups further reduce the moisture content and thermal shrinkage rate of the separators for batteries.

Claims

1. A polymer composition comprising a polymer component, said polymer component comprising: The first polymerization unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; The second polymerization unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; A third polymeric unit derived from a monomer containing a lactam group having six or more nuclear atoms; and The fourth polymer unit derived from a monomer containing a photoreactive functional group.

2. The polymer composition according to claim 1, The content of the first polymer unit in the polymer component is 50% by weight or more.

3. The polymer composition according to claim 1, The content of the second polymer unit in the polymer component is in the range of 5 to 20 parts by weight relative to 100 parts by weight of the first polymer unit.

4. The polymer composition according to claim 1, The content of the third polymer unit in the polymer component is in the range of 10 parts by weight to 50 parts by weight relative to 100 parts by weight of the first polymer unit.

5. The polymer composition according to claim 1, The content of the fourth polymer unit in the polymer component is in the range of 0.1 parts by weight to 5 parts by weight relative to 100 parts by weight of the first polymer unit.

6. The polymer composition according to claim 1, The first polymerization unit includes a polymerization unit derived from (meth)acrylamide.

7. The polymer composition according to claim 1, The second polymerization unit includes a polymerization unit derived from dimethyl (meth)acrylamide.

8. The polymer composition according to claim 1, The third polymerization unit comprises a polymerization unit derived from a monomer containing an N-substituted lactam group having 6 or more nuclear atoms.

9. The polymer composition according to claim 1, The third polymerization unit is derived from monomers whose lowest critical cosolubility temperature (LCST) is in the range of 25°C to 50°C.

10. The polymer composition according to claim 1, The third polymerization unit includes a polymerization unit derived from N-vinylcaprolactam.

11. The polymer composition according to claim 1, The fourth polymerization unit comprises a polymerization unit derived from a monomer containing benzoylphenyl.

12. The polymer composition according to claim 1, The fourth polymerization unit comprises a polymerization unit derived from a (meth)acrylate monomer containing benzoylphenyl.

13. The polymer composition according to claim 1, The weight-average molecular weight of the polymer component is in the range of 200,000 to 500,000.

14. The polymer composition according to claim 1, The polydispersity index of the polymer component is in the range of 2 to 3.

15. The polymer composition according to claim 1, The solid content of the polymer composition is in the range of 1% to 10% by weight.

16. The polymer composition according to claim 1, further comprising: Aqueous solvent.

17. A polymer slurry comprising: First polymer composition; Inorganic particles; and Second polymer composition; The first polymer composition comprises a first polymer component, the first polymer component comprising a first polymer unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymer unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; and a third polymer unit derived from a monomer containing a lactam group having 6 or more nuclear atoms. And the fourth polymer unit derived from monomers containing photoreactive functional groups.

18. The polymer slurry according to claim 17, The second polymer composition comprises a copolymer based on (meth)acrylate.

19. The polymer slurry according to claim 17, The content of the first polymer composition in the polymer slurry is in the range of 1 to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

20. The polymer slurry according to claim 17, The content of the second polymer composition in the polymer slurry is in the range of 1 to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

21. The polymer slurry according to claim 17, The solids content of the polymer slurry is in the range of 30% to 70% by weight.

22. The polymer slurry according to claim 17, further comprising: Aqueous solvent.

23. A battery separator, comprising: Porous substrate layer; and A polymer layer disposed on one or both surfaces of the porous substrate; The polymer layer comprises a first polymer composition; inorganic particles; The second polymer composition, The first polymer composition comprises a first polymer component, the first polymer component comprising a first polymer unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymer unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; and a third polymer unit derived from a monomer containing a lactam group having 6 or more nuclear atoms. And the fourth polymer unit derived from monomers containing photoreactive functional groups.

24. The battery separator according to claim 23, The thickness of each polymer layer is in the range of 1 μm to 1.5 μm.

25. A battery, comprising: Positive electrode; negative electrode; a separator disposed between the positive electrode and the negative electrode; and electrolyte solution, The separator comprises a porous substrate layer; and a polymer layer disposed on one or both surfaces of the porous substrate layer. The polymer layer comprises a first polymer composition; inorganic particles; and a second polymer composition. The first polymer composition comprises a first polymer component, the first polymer component comprising a first polymer unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; a second polymer unit derived from a monomer containing an N-disubstituted (meth)acrylamide group; and a third polymer unit derived from a monomer containing a lactam group having 6 or more nuclear atoms. And the fourth polymer unit derived from monomers containing photoreactive functional groups.

26. The battery according to claim 25, The electrolyte solution contains a carbonate-based solvent.

27. The battery according to claim 25, The polymer layer adheres to the positive electrode and the substrate layer, the negative electrode and the substrate layer, or the positive electrode and the substrate layer and the negative electrode and the substrate layer.

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