Polymer composition, polymer slurry, battery separator and battery

Abstract

The present invention relates to a polymer composition, a polymer slurry, a battery separator and a battery, and may comprise a polymer component comprising: a first polymerization unit derived from an N-unsubstituted (meth) acrylamide group-containing monomer; a second polymerization unit derived from an N-2 substituted (meth) acrylamide group-containing monomer; a third polymerization unit derived from a lactam group-containing monomer having 6 or more ring atoms; and a fourth polymerization unit derived from a photoreactive functional group-containing monomer.

Description

Polymer composition, polymer slurry, battery separator and battery

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

[0002] The present invention relates to a polymer composition.

[0003] The present invention relates to a polymer slurry.

[0004] The present invention relates to a separator for a battery.

[0005] The present invention relates to a battery.

[0006] Polymer compositions or polymer slurries, which are mixtures of these polymer compositions, can be used in various ways, such as electrodes and separators in secondary batteries. Existing polymer compositions or slurries used in separators were organic solvent-based.

[0007] A recent technological trend is to convert polymer compositions or slurries used in battery separators to aqueous solvents. However, aqueous solvents are a major cause of side reactions in the electrolyte in secondary batteries.

[0008] The separator can be easily exposed to heat during battery assembly and operation. Separators exposed to heat are prone to shrinkage. Shrinking separators can adversely affect the stability of the battery.

[0009] Therefore, there is a need for the development of a polymer composition or slurry based on an aqueous solvent that can reduce the moisture content and thermal shrinkage rate of a battery separator.

[0010] The present invention seeks to provide a polymer composition capable of reducing the moisture content and thermal shrinkage rate of a battery separator.

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

[0012] The present invention aims to provide a battery separator having reduced moisture content and thermal shrinkage.

[0013] The present invention aims to provide a battery capable of suppressing electrolyte side reactions and having improved stability.

[0014] One embodiment of the present invention is a polymer composition comprising a polymer component comprising a first polymerization unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymerization unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymerization unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymerization unit derived from a photoreactive functional group-containing monomer.

[0015] The first polymerization unit content of the above polymer component may be 50 wt% or more.

[0016] The content of the second polymerization unit of the above polymer component may be in the range of 5 to 20 parts by weight relative to 100 parts by weight of the first polymerization unit.

[0017] The content of the third polymerization unit of the above polymer component may be in the range of 10 parts by weight to 50 parts by weight relative to 100 parts by weight of the first polymerization unit.

[0018] The content of the fourth polymerization unit of the above polymer component may be in the range of 0.1 to 5 parts by weight relative to 100 parts by weight of the first polymerization unit.

[0019] The above first polymerization unit may include a (meth)acrylamide-derived polymerization unit.

[0020] The second polymerization unit may include a polymerization unit derived from dimethyl (meth)acrylamide.

[0021] The third polymerization unit may include a polymerization unit derived from a monomer containing an N-substituted lactam group having a number of nuclear atoms of 6 or more.

[0022] The third polymerization unit may be derived from a monomer having a lower critical solution temperature (LCST) of the single polymer within a range of 25°C to 50°C.

[0023] The third polymerization unit may include a polymerization unit derived from N-vinyl caprolactam.

[0024] The fourth polymerization unit may include a polymerization unit derived from a benzoylphenyl group-containing monomer.

[0025] The fourth polymerization unit may include a polymerization unit derived from a benzoylphenyl group-containing (meth)acrylate monomer.

[0026] The weight average molecular weight of the above polymer component may be in the range of 200,000 to 500,000.

[0027] The polydispersity index of the above polymer component may be in the range of 2 to 3.

[0028] The solids content of the polymer composition may be in the range of 1 wt% to 10 wt%.

[0029] The polymer composition may further include an aqueous solvent.

[0030] 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 an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymer unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymer unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymer unit derived from a photoreactive functional group-containing monomer.

[0031] The second polymer composition may include a (meth)acrylate copolymer.

[0032] The content of the first polymer composition of the polymer slurry may be in the range of 1 part by weight to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

[0033] The content of the second polymer composition of the polymer slurry may be in the range of 1 part by weight to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

[0034] The solids content of the polymer slurry may be in the range of 30 wt% to 70 wt%.

[0035] The above polymer slurry may further include an aqueous solvent.

[0036] Another specific embodiment of the present invention is a battery separator 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; wherein the first polymer composition comprises a first polymer component including: a first polymer unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymer unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymer unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymer unit derived from a photoreactive functional group-containing monomer.

[0037] The thickness per layer of the polymer layer may be in the range of 1 μm to 1.5 μm.

[0038] Another specific embodiment of the present invention is a battery comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte; wherein the separator comprises 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; wherein the first polymer composition comprises a first polymer component comprising a first polymer unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymer unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymer unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymer unit derived from a photoreactive functional group-containing monomer.

[0039] The above electrolyte may include a carbonate solvent.

[0040] The polymer layer can attach 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.

[0041] The polymer composition of the present invention can reduce the moisture content and thermal shrinkage rate of a battery separator.

[0042] The polymer slurry of the present invention can reduce the moisture content and thermal shrinkage rate of a battery separator.

[0043] The battery separator of the present invention can reduce moisture content and thermal shrinkage.

[0044] The battery of the present invention can suppress electrolyte side reactions and have improved stability.

[0045] 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.

[0046] When a specific commercial product is used as an ingredient in this document, the properties of that ingredient may refer to the properties listed on the product's Technical Data Sheet (TDS) or Certification of Analysis (COA).

[0047] In this document, if the properties of a specific material vary depending on temperature and pressure, the measurement standards for the properties may be 25 ℃ and 101.325 kPa.

[0048] In this document, the numerical range of “A to B” means “A or more and B or less.”

[0049] The numbers mentioned in this document are rounded values. For example, 1.5 is a number within the range of 1.45 to 1.54.

[0050] The following document describes the present invention in more detail.

[0051] One specific example of the present invention is a polymer composition.

[0052] The polymer composition may include a polymer component of a specific composition.

[0053] The polymer component may include at least three different polymerization units. The three polymerization units may have in common at least an amide group.

[0054] The polymer component may include a first polymerization unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymerization unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; and a third polymerization unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more.

[0055] Additionally, the polymer component can further be cured under specific conditions by further including specific monomers, thereby further reducing the moisture content and thermal shrinkage of the separator.

[0056] The polymer component may further comprise a fourth polymerization unit derived from a monomer containing a photoreactive functional group. The photoreactive functional group may be a photocurable functional group. When the polymer component is irradiated with light, the photoreactive functional group can form a cured structure of the polymer component.

[0057] The above polymer component may further include a fifth polymerization unit derived from an N-1 substituted (meth)acrylamide group-containing monomer.

[0058] In this document, a polymerization unit may mean a backbone forming a polymer.

[0059] In this document, an N-unsubstituted (meth)acrylamide group-containing monomer may mean a monomer in which two hydrogens on the nitrogen of the (meth)acrylamide group are not substituted with a functional group other than hydrogen.

[0060] In this document, an N-1 substituted (meth)acrylamide group-containing monomer may mean a monomer in which one hydrogen on the nitrogen of the (meth)acrylamide group is replaced with a functional group other than hydrogen.

[0061] In this document, an N-2 substituted (meth)acrylamide group-containing monomer may mean a monomer in which both hydrogens on the nitrogen of the (meth)acrylamide group are replaced with a functional group other than hydrogen.

[0062] In this document, a lactam group-containing monomer having a nuclear atom number of 6 or more may mean a monomer containing a cyclic amide group, the nuclear atom number of which is 6 or more.

[0063] In this document, a photoreactive functional group-containing monomer may mean a monomer containing a derivative of a photoreactive functional group.

[0064] The lower critical solution temperature (LCST) of each of the first to third polymerization units may be different from that of the homopolymer. By appropriately combining polymerization units derived from nitrogen-containing monomers having different homopolymer LCSTs, the moisture content and thermal shrinkage of a battery separator made from the polymer composition can be reduced.

[0065] Although not limited by theory, moisture in battery separators can react with electrolyte salts (such as LiPF6) to form unstable byproducts such as HF. This can accelerate the deterioration of the electrode interface (SEI and CEI) and corrode the electrode active material, reducing its lifespan and stability. Excessive moisture in battery separators can also reduce the ionic conductivity of the electrolyte. In battery separators, a certain amount of moisture improves the membrane's wettability, facilitating electrolyte impregnation. However, this only improves initial performance and can ultimately lead to deterioration of battery life and safety in the long term.

[0066] In addition, the thermal shrinkage rate of the battery separator can be determined according to the balance between the thermal shrinkage tendency of the porous substrate layer described below and the bonding force of the polymer layer, and here, the thermal shrinkage rate of the battery separator can vary according to the homopolymer LCST of the monomer constituting the polymer component included in the polymer layer.

[0067] A monomer with a low homopolymer LCST can induce thermal shrinkage of a separator by phase separation at a relatively low temperature, and a monomer with a high homopolymer LCST can suppress thermal shrinkage by increasing the bonding strength between the polymer layer and the porous substrate layer at a relatively high temperature. The polymer composition of the present invention can simultaneously reduce the moisture content and thermal shrinkage of a battery separator by controlling the balance between these.

[0068] In this document, the LCST of a polymer may refer to the temperature at which the polymer and the solvent separate into different phases. The LCST may be determined by differential scanning calorimetry (DSC) or turbidity measurement. Accordingly, a polymer may exist as a homogeneous phase in a solvent at a temperature below the LCST, and may phase separate from the solvent at a temperature above the LCST. The solvent may include an aqueous solvent.

[0069] In particular, the third polymerization unit can further reduce the moisture content of a battery separator manufactured from the polymer component due to its cyclic structure and number of nuclear atoms. Specifically, the monomer component derived from the third polymerization unit can exhibit relatively non-polarity compared to a lactam group-containing monomer having a smaller number of nuclear atoms. This relative non-polarity can further reduce the moisture content of a separator manufactured from a polymer composition including the third polymerization unit.

[0070] In the polymer composition, it is important that the polymer component undergoes phase separation at a specific temperature above room temperature, thereby reducing the moisture content of the membrane produced therefrom, and also that the polymer composition be smoothly applied. Therefore, it is preferable that the polymer component include an appropriate amount of each of a polymer unit having a relatively low single polymer LCST and a polymer unit having a relatively high single polymer LCST.

[0071] The fourth polymerization unit can further cure the polymer component under specific conditions. The cured product formed from the polymer component may not dissolve well in water and may not be easily deformed even when exposed to high temperatures. As a result, the moisture content and thermal shrinkage of the separator made from the polymer composition may be further reduced.

[0072] By appropriately controlling the content of the first polymerization unit to the fourth polymerization unit in the above polymer component, a battery separator having a low moisture content and thermal shrinkage rate can be manufactured.

[0073] In the polymer composition, the polymer component may contain the first polymerization unit in a specific ratio. Specifically, the first polymerization unit content of the polymer component may be 50 wt% or more. The lower limit (unit: wt%) of the first polymerization unit content of the polymer component may be 55, 60, or 65. The upper limit of the first polymerization unit content of the polymer component may not be particularly limited.

[0074] The second polymerization unit content of the polymer component may be in the range of 5 to 20 parts by weight based on 100 parts by weight of the first polymerization unit. The lower limit (unit: parts by weight) of the second polymerization unit content of the polymer component may be 6, 7, 8, 9, 10, 11, 12, 13, or 14. The upper limit (unit: parts by weight) of the second polymerization unit content of the polymer component may be 19, 18, 17, 16, or 15.

[0075] The third polymerization unit content of the polymer component may be in the range of 10 to 50 parts by weight relative to 100 parts by weight of the first polymerization unit. The lower limit (unit: parts by weight) of the third polymerization unit content of the polymer component may be 15, 20, or 25. The upper limit (unit: parts by weight) of the third polymerization unit content of the polymer component may be 45, 40, 35, or 30.

[0076] The fourth polymerization unit content of the polymer component may be in the range of 0.1 to 5 parts by weight relative to 100 parts by weight of the first polymerization unit. The lower limit (unit: parts by weight) of the fourth polymerization unit content of the polymer component may be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1. The upper limit (unit: parts by weight) of the fourth polymerization unit content of the polymer component may be 4.5, 4, 3.5, 3, 2.5, 2, or 1.5.

[0077] The above N-unsubstituted (meth)acrylamide group-containing monomer may include at least one selected from the group consisting of (meth)acrylamide and maleic acid amide. Preferably, the N-unsubstituted (meth)acrylamide group-containing monomer may include (meth)acrylamide. More preferably, the N-unsubstituted (meth)acrylamide group-containing monomer may include acrylamide.

[0078] The above N-1 substituted (meth)acrylamide group-containing monomer may include at least one selected from the group consisting of N-isopropyl (meth)acrylamide, N-methylol (meth)acrylamide, diacetone (meth)acrylamide, (meth)acrylamide t-butylsulfonic acid, hydroxyethyl (meth)acrylamide, Nn-butoxymethyl (meth)acrylamide, N-isobutoxymethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, Nt-butyl (meth)acrylamide, N,N-methylenebis (meth)acrylamide, and Nt-butyl (meth)acrylamide sulfonic acid. Preferably, the N-1-substituted (meth)acrylamide group-containing monomer may include diacetone (meth)acrylamide. More preferably, the N-1-substituted (meth)acrylamide group-containing monomer may include diacetone acrylamide.

[0079] The above N-2-substituted (meth)acrylamide group-containing monomer may include at least one selected from the group consisting of N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and (meth)acryloylmorpholine. Preferably, the N-2-substituted (meth)acrylamide group-containing monomer may include N,N-dimethyl(meth)acrylamide. More preferably, the N-2-substituted (meth)acrylamide group-containing monomer may include N,N-dimethylacrylamide.

[0080] The lactam group-containing monomer having a number of nuclear atoms of 6 or more may be one in which one hydrogen atom on the nitrogen atom of the central ring of the lactam is substituted or unsubstituted with a functional group other than hydrogen. Preferably, the lactam group-containing monomer having a number of nuclear atoms of 6 or more may include an N-substituted lactam group-containing monomer having a number of nuclear atoms of 6 or more. The N-substituted lactam group-containing monomer having a number of nuclear atoms of 6 or more may mean one in which one hydrogen atom on the nitrogen atom of the central ring of the lactam is substituted with a functional group other than hydrogen. More preferably, the lactam group-containing monomer having a number of nuclear atoms of 6 or more may be N-vinyl caprolactam.

[0081] The lactam group-containing monomer having a number of nuclear atoms of 6 or more can exhibit specific thermal behavior. Specifically, the lactam group-containing monomer having a number of nuclear atoms of 6 or more can satisfy certain single polymer properties.

[0082] The lactam group-containing monomer having a number of nuclear atoms of 6 or more may have a homopolymer lower critical solution temperature (LCST) within a specific range. That is, a solution of the homopolymer composed of the third polymerization unit and water may have an LCST within a specific range. Specifically, the lactam group-containing monomer having a number of nuclear atoms of 6 or more may have a homopolymer lower critical solution temperature within a range of 25°C to 50°C. The water solubility of the homopolymer composed of the third polymerization unit may change rapidly at the LCST. The temperature range may be lower than the temperature of the battery during the battery manufacturing process or the battery operation process.

[0083] In this way, the polymer composition including the third polymer unit having a single polymer LCST lower than the temperature of the battery during the battery manufacturing process or the battery operating process can further reduce the moisture content and thermal shrinkage of the separator manufactured using the same compared to the conventional one.

[0084] The photoreactive functional group may be a benzoylphenyl group. That is, the fourth polymerization unit may include a polymerization unit derived from a benzoylphenyl group-containing monomer.

[0085] The above photoreactive functional group-containing monomer may be a benzoylphenyl group-containing (meth)acrylate monomer. The fourth polymerization unit may include a polymerization unit derived from a benzoylphenyl group-containing (meth)acrylate monomer. Preferably, the fourth polymerization unit may include a polymerization unit derived from a benzoylphenyl group-containing methacrylate monomer.

[0086] The properties of the above polymer component can also be appropriately controlled.

[0087] The weight average molecular weight of the polymer component may be within a range of 200,000 to 500,000. The lower limit of the weight average molecular weight of the polymer component may 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 may be 490,000, 470,000, 460,000, or 450,000. When the weight average molecular weight of the polymer component is within the above range, the shear stress between molecules constituting the polymer component can be controlled. Accordingly, the polymer composition can exhibit low heat shrinkage.

[0088] The polydispersity index of the polymer component may be within the range of 2.5 to 3. The lower limit of the polydispersity index of the polymer component may be 2.55, 2.6, 2.65, 2.7, or 2.75. The upper limit of the polydispersity index of the polymer component may be 2.95, 2.9, 2.85, or 2.8. When the polydispersity index of the polymer component is within the above range, packing of the polymer component may proceed efficiently. Accordingly, the polymer composition may exhibit low heat shrinkage.

[0089] The polymer composition may further comprise a solvent. The polymer composition may further comprise an aqueous solvent. That is, the polymer composition may be aqueous solvent-based. Even if the polymer composition is aqueous solvent-based, it can be manufactured into a separator having a low moisture content.

[0090] The polymer component may be water-soluble. Accordingly, the polymer component may be dissolved in the aqueous solvent in the polymer composition.

[0091] The ratio of the polymer component in the polymer composition, i.e., the solid content of the polymer composition, can also be controlled. That is, the content of the remaining components excluding the solvent in the polymer composition can be controlled. The solid content of the polymer composition can be in the range of 1 wt% to 10 wt%. The lower limit of the solid content (unit: wt%) 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 solid content (unit: wt%) can be 9.5, 9.0, 8.5, or 8.0. When the solid content of the polymer composition is within the above range, a separator including the composition can be smoothly manufactured without gelation.

[0092] Another specific embodiment of the present invention is a polymer slurry.

[0093] The polymer slurry may comprise a plurality of different polymer compositions.

[0094] In this document, the fact that the plurality of polymer compositions are different from each other may mean that the types, contents, properties, and / or functions of the polymer components constituting each are different from each other.

[0095] The polymer slurry may comprise at least a first polymer composition and a second polymer composition, wherein the first polymer composition may be the polymer composition of the present invention described above.

[0096] Therefore, in the description of the polymer slurry, the content of the first polymer composition may be the same as the content of the polymer composition of the present invention described above.

[0097] The polymer slurry may further include inorganic particles. The polymer slurry may include inorganic particles to impart functions such as heat resistance to a battery separator.

[0098] The above inorganic particles may have one or more of the following properties: lithium ion transport capability, piezoelectricity, and flame retardancy.

[0099] 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.

[0100] 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 .

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] In the polymer slurry, the first polymer composition and the second polymer composition may exhibit at least different functions. The first polymer composition may act to attach a separator manufactured from the polymer slurry to an electrode. The second polymer composition may act to bind inorganic particles included in the polymer slurry.

[0106] In the polymer slurry, the first polymer composition and the second polymer composition may have different compositions. The first polymer composition may be the same as the polymer composition of the present invention, and thus, the first polymer composition may be a (meth)acrylamide-based polymer composition. The second polymer composition may have a different composition from the first polymer composition. For example, the second polymer composition may include a (meth)acrylate-based copolymer. Through this, the second polymer composition may exhibit the aforementioned binding function.

[0107] In the above polymer slurry, the contents of each of the first polymer composition and the second polymer composition can also be appropriately controlled.

[0108] The content of the first polymer composition may be in the range of 1 part by weight to 5 parts by weight relative to 100 parts by weight of the inorganic particles. The lower limit (unit: parts by weight) of the content of the first polymer composition may be 1.5, 2.0, 2.5, or 3.0 relative to 100 parts by weight of the inorganic particles. The upper limit (unit: parts by weight) of the content of the first polymer composition may be 4.5, 4.0, 3.5, or 3.0 relative to 100 parts by weight of the inorganic particles.

[0109] The content of the second polymer composition may be in the range of 1 part by weight to 5 parts by weight relative to 100 parts by weight of the inorganic particles. The lower limit (unit: parts by weight) of the content of the second polymer composition may be 1.1, 1.2, 1.3, 1.4, or 1.5 relative to 100 parts by weight of the inorganic particles. The upper limit (unit: parts by weight) of the content of the first polymer composition may be 4.5, 4.0, 3.5, 3.0, 2.5, 2.0, or 1.5 relative to 100 parts by weight of the inorganic particles.

[0110] The polymer slurry may further include other components in addition to the above components. Specifically, the polymer slurry may further include a dispersant to allow the polymer compositions to be dispersed in the polymer slurry. In addition, the polymer slurry may further include a surfactant to allow the polymer compositions to have a particle form in the polymer slurry. Known components or products may be used as the dispersant and the surfactant. The types of the dispersant and the surfactant may not be particularly limited.

[0111] Like the polymer composition of the present invention, the polymer slurry may also be based on an aqueous solvent. Accordingly, the polymer slurry may further comprise an aqueous solvent. Even if the polymer slurry is based on an aqueous solvent, it can simultaneously reduce the moisture content and thermal shrinkage of a battery separator.

[0112] Another specific embodiment of the present invention is a separator. Specifically, the separator may be a battery separator.

[0113] In this document, a battery may refer to a device that can convert electrical energy into chemical energy through an oxidation-reduction reaction, or a device that can convert chemical energy into electrical energy.

[0114] The above battery separator may include a porous substrate layer; and a polymer layer.

[0115] The porous substrate layer can support the separator and provide structural stability to the separator. The porous substrate layer can include a polyolefin-based film.

[0116] Here, polyolefin film means a film containing a polyolefin polymer as a main component.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] The polymer layer may be disposed on one or both sides of the porous substrate layer. Preferably, the polymer layer may be disposed on both sides of the porous substrate layer.

[0122] In the above-described separation membrane, the polymer layer can be prepared from the aforementioned polymer slurry. Specifically, the polymer layer can be formed by applying the aforementioned polymer slurry to one or both sides of the porous substrate layer and drying it. Accordingly, the polymer layer can contain most of the components included in the aforementioned polymer slurry.

[0123] The polymer layer may include a first polymer composition; inorganic particles; and a second polymer composition.

[0124] The first polymer composition included in the polymer layer may be a polymer composition of the present disclosure.

[0125] The inorganic particles and the second polymer composition included in the polymer layer may be the same as those described in the polymer slurry of the present disclosure.

[0126] In this way, the separator to which the polymer slurry of the present invention is applied can reduce moisture content and thermal shrinkage. When the separator is applied to a battery, side reactions of the electrolyte are reduced, thereby improving performance.

[0127] The polymer layer can exhibit sufficient performance even when formed by applying a small amount of the polymer slurry. Furthermore, applying a relatively small amount of the polymer slurry can be advantageous in reducing the moisture content of the separator. As a result, the polymer layer formed on the separator can be relatively thin. For example, the thickness of the polymer layer can be in the range of 1 μm to 1.5 μm. The thickness of the polymer layer can refer to the thickness per layer.

[0128] Another specific embodiment of the present invention is a battery. The battery may include the battery separator of the present invention.

[0129] The battery may include at least a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The battery may further include an electrolyte.

[0130] The separator may be a battery separator according to the present invention. Therefore, the above-described content may be applied to the description of the separator in the description of the battery. The battery can minimize side reactions caused by the electrolyte and have improved thermal durability. This is because the electrolyte usually undergoes side reactions with water, and the separator has reduced moisture content. Separators usually shrink due to heat, and the separator has reduced shrinkage rate.

[0131] The above battery may be a lithium ion battery. The electrolyte of a lithium ion battery may typically include a carbonate-based solvent. Water undergoes a side reaction with the carbonate-based solvent, deteriorating battery performance. However, since the battery of the present invention has a low moisture content, the performance deterioration thereof can be minimized.

[0132] In addition, the polymer layer included in the separator may be a layer having both heat resistance and adhesiveness. Therefore, the polymer layer may impart heat resistance to the separator or the battery. In addition, the polymer layer may attach the porous substrate layer of the separator and the electrode (positive electrode and / or negative electrode). A separator that exhibits heat resistance and adhesiveness as separate layers may also be included within the scope of the present invention. Such a separator may further include an inorganic layer disposed between the polymer layer and the porous layer, and including inorganic particles. In this case, the inorganic particles may be included only in the inorganic layer.

[0133] In the above battery, 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 may be attached via the polymer layer. Preferably, the positive electrode and the substrate layer, and the negative electrode and the substrate layer may be attached via the polymer layer.

[0134] Below, this document describes the present invention in more detail through examples and comparative examples. However, this document does not limit the present invention to the examples.

[0135] [Experimental sample production]

[0136] Manufacturing Example 1. Polymer Composition

[0137] (1) 69 parts by weight of acrylamide, 10 parts by weight of dimethyl acrylamide, 20 parts by weight of N-vinyl caprolactam, and 1 part by weight of benzoylphenyl methacrylate are charged into a reaction vessel.

[0138] (2) Then, 300 ppm of 3-mercaptopropionic acid is added to the reaction vessel as a molecular weight regulator.

[0139] (3) Then, distilled water is added as a reaction solvent to the reaction vessel so that the solid content of the reaction solution becomes 8 wt%.

[0140] (4) After that, the inside of the reaction vessel is replaced with nitrogen and the temperature is raised to 70 ℃.

[0141] (5) Then, 5000 ppm of potassium percarbonate (KPS) as a polymerization initiator is added to the reaction vessel, and polymerization proceeds for 8 hours.

[0142] Manufacturing Example 2. Polymer composition.

[0143] (1) The same process as Manufacturing Example 1 was repeated except that 70 parts by weight of acrylamide, 10 parts by weight of dimethyl acrylamide, and 20 parts by weight of N-vinyl caprolactam were added to the reaction vessel during the process, (2) 5000 ppm of 3-mercaptopropionic acid was added during the process, and (3) distilled water was added as a reaction solvent so that the solid content became 8 wt% during the process.

[0144] Example. Polymer slurry

[0145] A polymer slurry is obtained by mixing 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) in distilled water. The polymer composition of Preparation Example 1 is used as the first polymer composition.

[0146] Comparative example. Polymer slurry

[0147] The same process as in Example 2 was repeated except that the polymer composition of Manufacturing Example 2 was used as the first polymer composition.

[0148] [Evaluation Method]

[0149] The weight average molecular weight and polydispersity index of the polymer components of the polymer compositions of Manufacturing Examples 1 and 2 were measured by gel permeation chromatography under the conditions below.

[0150] (1) Column (maker, model no.): 2 x TSKgel SupermultiporeHZ-M + TSKgel SuperHZ-2500

[0151] (2) Eleunt: THF

[0152] (3) Temperature: 40℃

[0153] (4) Flow rate: 1.0 mL / min

[0154] (5) Injection volume, sample concentration: 30 ㎕, 1~10 mg / mL

[0155] (6) Standard: Polystyrene

[0156] (7) Detector: RI

[0157] (8) Device: PL GPC220 (Agilent Technologies) or GPC-900 (JASCO)

[0158] 2. Moisture content

[0159] The moisture content of the separation membrane made from the polymer slurry obtained in the examples and comparative examples was measured according to the following process.

[0160] (1) The polymer slurry obtained in the examples and comparative examples is coated on a polyethylene substrate layer using Meyer bar.

[0161] (2-1) The coated comparative example slurry is dried in a Mathis oven to manufacture a separation membrane.

[0162] (2-2) The slurry of the coated example is dried in a Mathis oven and irradiated with UV-A (1160 mJ) using a Miltec H type Bulb to manufacture a separation membrane.

[0163] (3) Approximately 0.2 g of the membrane is cut to obtain a measurement specimen.

[0164] (4) The measurement specimen is placed in a vial, and the moisture content is measured according to the Karl-Fischer method. The measuring device used is a Metrohm 899 Coulometer, and the moisture content can be calculated from the amount of Karl-Fischer reagent consumed.

[0165] (5) The moisture content of the membrane is determined as the average value of the three measurements in (4) above.

[0166] 3. Thermal shrinkage

[0167] The thermal shrinkage of the separator made from the polymer slurry obtained in the examples and comparative examples was measured according to the following process.

[0168] (1) The polymer slurry obtained in the examples and comparative examples is coated on a polyethylene substrate layer having a thickness of 11 ㎛ using a Meyer bar.

[0169] (2-1) The coated comparative example slurry is dried in a Mathis oven to manufacture a separation membrane.

[0170] (2-2) The slurry of the coated example is dried in a Mathis oven and irradiated with UV-A (1160 mJ) using a Miltec H type Bulb to manufacture a separation membrane.

[0171] (3) The membrane is cut into a square with an area of ​​5 X 5 ㎠ to obtain a measurement specimen.

[0172] (4) Four points at 1.5 cm intervals are marked on the measurement specimen with a permanent marker.

[0173] (5) The membrane specimen is heat treated in a Mathis oven maintained at 150°C for approximately 30 minutes.

[0174] (6) The membrane specimen is removed from the Mathis oven, and the spacing between the four points engraved on the specimen is measured with a ruler. Since the spacing change is confirmed at three points, the average value of the three points is treated as the spacing between the points after heat treatment.

[0175] (7) The change rate of the gap between four points before and after heat treatment is evaluated as the heat shrinkage rate.

[0176] [Results and Discussion]

[0177] Tables 1 and 2 below summarize the polymer compositions of the manufacturing examples and the polymer slurry evaluation results of the examples and comparative examples.

[0178] Molecular weight (*1000) Polydispersity index Manufacturing example 14502.79 Manufacturing example 25063.22

[0179] First polymer compositionPolymer layer thickness (㎛)Moisture content (ppm)Heat shrinkage rate (%)ExamplePreparation example 11.312530.5Comparative examplePreparation example 21.314204.5

[0180] Referring to Tables 1 and 2, it can be confirmed that the separator of the example reduces moisture content by approximately 167 ppm and thermal shrinkage rate by approximately 4% compared to the separator of the comparative example. Considering that even trace amounts of moisture can deteriorate battery performance, it can be seen that the difference in moisture content and thermal shrinkage rate between the separators of the example and the comparative example can impart a significant difference in battery performance.

[0181] The separator of the example is made by using the polymer composition of Manufacturing Example 1 as the first polymer composition and curing it with ultraviolet rays. The separator of the comparative example is made by using the polymer composition of Manufacturing Example 2 as the first polymer composition and thermally drying it. Through this, it was confirmed that a polymer further including a polymerization unit derived from a photoreactive functional group further reduces the moisture content and thermal shrinkage rate of a battery separator.

Claims

1. A first polymerization unit derived from a monomer containing an N-unsubstituted (meth)acrylamide group; A second polymerization unit derived from a monomer containing an N-2 substituted (meth)acrylamide group; A third polymerization unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and A fourth polymerization unit derived from a photoreactive functional group-containing monomer; A polymer component comprising; A polymer composition comprising:

2. In paragraph 1, A polymer composition wherein the first polymer unit content of the polymer component is 50 wt% or more.

3. In paragraph 1, A polymer composition wherein the content of the second polymerization unit of the polymer component is in the range of 5 to 20 parts by weight relative to 100 parts by weight of the first polymerization unit.

4. In paragraph 1 A polymer composition wherein the third polymerization unit content of the polymer component is in the range of 10 to 50 parts by weight relative to 100 parts by weight of the first polymerization unit.

5. In paragraph 1, A polymer composition wherein the content of the fourth polymerization unit of the polymer component is in the range of 0.1 to 5 parts by weight relative to 100 parts by weight of the first polymerization unit.

6. In paragraph 1, A polymer composition wherein the first polymerization unit comprises a polymerization unit derived from (meth)acrylamide.

7. In paragraph 1, A polymer composition wherein the second polymerization unit comprises a polymerization unit derived from dimethyl (meth)acrylamide.

8. In paragraph 1, A polymer composition comprising a polymerization unit derived from a monomer containing an N-substituted lactam group having a number of nuclear atoms of 6 or more, wherein the third polymerization unit is a polymerization unit.

9. In paragraph 1, The third polymerization unit is a polymer composition derived from a monomer having a lower critical solution temperature (LCST) of a single polymer within a range of 25°C to 50°C.

10. In paragraph 1, A polymer composition wherein the third polymerization unit comprises a polymerization unit derived from N-vinyl caprolactam.

11. In paragraph 1, A polymer composition wherein the fourth polymerization unit comprises a polymerization unit derived from a benzoylphenyl group-containing monomer.

12. In paragraph 1, The fourth polymerization unit is a polymer composition comprising a polymerization unit derived from a benzoylphenyl group-containing (meth)acrylate monomer.

13. In paragraph 1, A polymer composition wherein the weight average molecular weight of the polymer component is in the range of 200,000 to 500,000.

14. In paragraph 1, A polymer composition wherein the polydispersity index of the polymer component is in the range of 2 to 3.

15. In paragraph 1, A polymer composition having a solid content of the polymer composition in a range of 1 wt% to 10 wt%.

16. In paragraph 1, A polymer composition further comprising an aqueous solvent.

17. First polymer composition; inorganic particles; and Second polymer composition; Including, A polymer slurry comprising a first polymer component, wherein the first polymer composition comprises a first polymer unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymer unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymer unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymer unit derived from a photoreactive functional group-containing monomer.

18. In paragraph 17, The second polymer composition is a polymer slurry comprising a (meth)acrylate copolymer.

19. In paragraph 17, A polymer slurry wherein the content of the first polymer composition of the polymer slurry is in the range of 1 part by weight to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

20. In paragraph 17, A polymer slurry in which the content of the second polymer composition of the polymer slurry is in the range of 1 part by weight to 5 parts by weight relative to 100 parts by weight of the inorganic particles.

21. In paragraph 17, A polymer slurry having a solid content of 30 wt% to 70 wt%.

22. In paragraph 17, A polymer slurry further comprising an aqueous solvent.

23. Porous substrate layer; and A polymer layer disposed on one or both sides of the porous substrate layer; Including, The polymer layer comprises a first polymer composition; inorganic particles; and a second polymer composition; A battery separator comprising a first polymer component, wherein the first polymer composition comprises a first polymer unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymer unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymer unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymer unit derived from a photoreactive functional group-containing monomer.

24. In paragraph 23, A battery separator having a thickness per layer of the polymer layer in the range of 1 ㎛ to 1.5 ㎛.

25. Including a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte; The above separator comprises a porous substrate layer; and a polymer layer disposed on one or both sides of the porous substrate layer; The polymer layer comprises a first polymer composition; inorganic particles; and a second polymer composition; A battery comprising a first polymer component, wherein the first polymer composition comprises a first polymer unit derived from an N-unsubstituted (meth)acrylamide group-containing monomer; a second polymer unit derived from an N-2-substituted (meth)acrylamide group-containing monomer; a third polymer unit derived from a lactam group-containing monomer having a number of nuclear atoms of 6 or more; and a fourth polymer unit derived from a photoreactive functional group-containing monomer.

26. In paragraph 25, A battery wherein the electrolyte contains a carbonate solvent.

27. In paragraph 25, A battery in which the polymer layer attaches 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.