Battery separator, electrolyte membrane, battery, method for manufacturing battery separator, and method for manufacturing electrolyte membrane

Abstract

The present invention is a battery separator, an electrolyte membrane, a battery, a method of manufacturing a battery separator, and a method of manufacturing an electrolyte membrane. The battery separator of the present invention can exhibit high liquid electrolyte impregnability. The electrolyte membrane of the present invention can exhibit excellent mechanical stability and thermal characteristics. The battery of the present invention is safe and can exhibit excellent performance. The method of manufacturing a battery separator of the present invention can improve the liquid electrolyte impregnability of the battery separator. The method of manufacturing an electrolyte membrane of the present invention can improve the mechanical stability and thermal characteristics of the electrolyte membrane.

Description

Technical Field

[0001] This document claims the benefit of Korean Patent Application No. 10-2024-0193082, filed with the Korean Intellectual Property Office on December 20, 2024, the entire contents of which are incorporated herein by reference.

[0002] This invention relates to a battery separator.

[0003] This invention relates to an electrolyte membrane.

[0004] This invention relates to a battery.

[0005] This invention relates to a method for manufacturing battery separators.

[0006] This invention relates to a method for manufacturing an electrolyte membrane. Background Technology

[0007] Inorganic-coated separators are one technology used to mitigate the risk of battery fires caused by the use of liquid electrolytes. Inorganic-coated separators may comprise a porous substrate layer and inorganic particles coated on its exterior. The inorganic particles can form a dense pore structure due to interstitial volume. The pore structure of the separator can vary depending on the amount of liquid electrolyte impregnation. Summary of the Invention

[0008] Technical issues

[0009] Inorganic-coated separators exhibit poor liquid electrolyte impregnation. This can lead to rapid evaporation of residual liquid electrolyte. Furthermore, residual liquid electrolyte may undergo side reactions with the electrodes. Rapid evaporation of the liquid electrolyte reduces battery safety. Side reactions of the liquid electrolyte degrade battery performance.

[0010] Technical solution

[0011] One embodiment of the present invention is a battery separator comprising: a base layer; and a composite layer disposed on one or both surfaces of the base layer and comprising an adhesive, a crosslinking agent and inorganic particles, wherein the adhesive content (wt%) of the composite layer is in the range of 10 to 40, and wherein the porosity (%) of the composite layer is in the range of 40 to 62.

[0012] The adhesive may contain a first unit of vinylidene fluoride and a second unit of a fluorinated alkyl vinyl compound.

[0013] The weight-average molecular weight (g / mol) of the binder can be in the range of 150,000 to 600,000, and the content (wt%) of the second unit of the binder can be in the range of 10 to 25.

[0014] The number of crosslinkable functional groups in a crosslinking agent can be two or more.

[0015] Crosslinking agents may include di(meth)acrylate-based compounds, tri(meth)acrylate-based compounds, tetra(meth)acrylate-based compounds, penta(meth)acrylate-based compounds, hexa(meth)acrylate-based compounds, or combinations thereof.

[0016] Crosslinking agents may include monomeric compounds, polymeric compounds, or combinations thereof.

[0017] Crosslinking agents may include trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, tri(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and propoxylated pentaerythritol tetra(meth)acrylate. Erythritol tetra(meth)acrylate, bis(trimethylolpropane)tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, sorbitol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, poly(ethylene oxide-propylene oxide) di(meth)acrylate, polyurethane di(meth)acrylate, polycarbonate di(meth)acrylate, or combinations thereof.

[0018] The composite layer may contain an adhesive whose weight is greater than that of the crosslinking agent.

[0019] Inorganic particles may include lithium-ion transport first inorganic particles, piezoelectric second inorganic particles, flame-retardant third inorganic particles, or combinations thereof.

[0020] Another embodiment of the present invention is an electrolyte membrane comprising: a substrate layer; and an electrolyte layer disposed on one or both surfaces of the substrate layer and comprising a polymer matrix and a liquid electrolyte impregnated in the polymer matrix, wherein the electrolyte membrane exhibits a first decomposition peak at a first temperature and a second decomposition peak at a second temperature above the first temperature in differential thermal gravimetric analysis (DTG), the first temperature (°C) being 200 or higher, and the second temperature (°C) being in the range of 90 to 150.

[0021] The first temperature (°C) can be in the range of 200 to 250.

[0022] The polymer matrix may contain components derived from the binder and components derived from the crosslinking agent.

[0023] Liquid electrolytes can contain non-aqueous solvents and lithium salts.

[0024] The electrolyte layer may contain linear carbonate-based compounds with a volume larger than that of cyclic carbonate-based compounds.

[0025] Compounds based on linear carbonates may include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, or combinations thereof.

[0026] Compounds based on linear carbonates can be liquids at room temperature.

[0027] Compounds based on cyclic carbonates may include ethylene carbonate, vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, propylene carbonate, butyl carbonate, or combinations thereof.

[0028] Compounds based on cyclic carbonates can be solid at room temperature.

[0029] The volume (volume %) of the linear carbonate-based compound in the electrolyte layer can range from 55 to 95.

[0030] Another embodiment of the present invention is a battery comprising a positive electrode, a negative electrode, and an electrolyte membrane disposed between the positive and negative electrodes, wherein the electrolyte membrane comprises: a substrate layer; and an electrolyte layer disposed on one or both surfaces of the substrate layer and comprising a polymer matrix and a liquid electrolyte impregnated in the polymer matrix, wherein the electrolyte membrane exhibits a first decomposition peak at a first temperature and a second decomposition peak at a second temperature above the first temperature in differential thermal gravimetric analysis (DTG), wherein the first temperature (°C) is 200 or higher, and wherein the second temperature (°C) is in the range of 90 to 150.

[0031] Another embodiment of the present invention is a method for manufacturing a battery separator, comprising: preparing a slurry comprising a binder, a crosslinking agent, inorganic particles and a first solvent; coating the slurry onto one or both surfaces of a substrate layer to prepare a coated structure; immersing the coated structure in a first bath comprising a first solvent and a second solvent; immersing the coated structure in a second bath comprising a second solvent; and applying light to the coated structure, wherein the binder dissolves better in the first solvent than in the second solvent at room temperature.

[0032] Immersion in the second bath allows the coated structure that has been immersed in the first bath to be immersed in the second bath.

[0033] The method may further include drying the coated structure that has been immersed in the second bath.

[0034] Light can be applied to a dried coated structure.

[0035] The first solvent may include NMP, and the second solvent may include water.

[0036] Another embodiment of the present invention is a method for manufacturing an electrolyte membrane, comprising: preparing a slurry comprising a binder, a crosslinking agent, inorganic particles and a first solvent; coating the slurry onto one or both surfaces of a substrate to prepare a coated structure; immersing the coated structure in a first bath comprising a first solvent and a second solvent; immersing the coated structure in a second bath comprising a second solvent; applying light to the coated structure; and immersing the coated structure in a liquid electrolyte, wherein at room temperature, the binder dissolves better in the first solvent than in the second solvent.

[0037] Immersion in a liquid electrolyte allows the coated structure that has been photo-treated to be immersed in the liquid electrolyte.

[0038] Beneficial effects

[0039] The battery separator of the present invention can exhibit high liquid electrolyte impregnation properties.

[0040] The electrolyte membrane of the present invention exhibits excellent mechanical stability and thermal properties.

[0041] The battery of the present invention is safe and can exhibit excellent performance.

[0042] The method for manufacturing the battery separator of the present invention can improve the liquid electrolyte impregnation of the battery separator.

[0043] The method for manufacturing an electrolyte membrane according to the present invention can improve the mechanical stability and thermal properties of the electrolyte membrane. Attached Figure Description

[0044] Figure 1 The results of DTG behavior analysis for the embodiments and comparative examples are shown. Detailed Implementation

[0045] This document may use ordinal numbers such as "first" and "second" to refer to multiple components. There is no order of precedence among the components.

[0046] In this document, when a specific commercial product is used as a component, the characteristics of the component may refer to the characteristics stated in the product's Technical Data Sheet (TDS) or Certificate of Analysis (COA).

[0047] In this document, when the physical properties of a particular material vary with temperature and pressure, the measurement standard for said physical properties may be at room temperature (25°C) and atmospheric pressure (101.325 kPa). This conforms to the SATP (standard ambient temperature and pressure) as defined in the CRC Handbook of Chemistry and Physics.

[0048] In this document, the numerical range "within the range of A to B" means "A or greater and B or less".

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

[0050] The invention is described in more detail below.

[0051] One embodiment of the present invention is a battery separator.

[0052] In this document, a battery may include any device that performs an electrochemical reaction.

[0053] A battery can refer to any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor. A battery can refer to a lithium secondary battery. Lithium secondary batteries can include lithium metal secondary batteries, lithium polymer secondary batteries, lithium-ion polymer secondary batteries, or lithium-ion secondary batteries.

[0054] A battery separator can be disposed between the electrodes in a battery. Specifically, a battery separator can be disposed between the positive and negative electrodes in a battery. The battery separator prevents physical contact (short circuit) between the positive and negative electrodes in the battery. Charge carriers (e.g., lithium ions) can move between the electrodes through the battery separator.

[0055] The battery separator of the present invention includes: a base layer; and a composite layer.

[0056] The substrate layer allows fluid to move from one surface of the substrate layer to another.

[0057] The composite layer is disposed on one or both surfaces of the substrate layer. Specifically, the composite layer can be disposed on the first surface of the substrate layer, or on the first surface and a second surface facing the first surface. When the composite layer is disposed on both the first and second surfaces, the composition and thickness of each composite layer can be the same or different from each other.

[0058] The composite layer can provide a path for charge carriers to move through the battery separator.

[0059] The composite layer contains binders, crosslinking agents, and inorganic particles.

[0060] The binder, alone or together with the crosslinking agent, forms the polymer matrix. The binder can also serve as a mechanical support for the polymer matrix.

[0061] Crosslinking agents, alone or together with binders, form the polymer matrix. Crosslinking agents can connect binders and / or crosslinking agents within the polymer matrix.

[0062] Inorganic particles can impart predetermined properties to battery separators. For example, inorganic particles can impart lithium-ion transport properties, piezoelectricity, and / or thermal properties (heat resistance, flame retardancy, etc.) to battery separators.

[0063] Inorganic particles can be dispersed in a polymer matrix.

[0064] The battery separator of the present invention can exhibit high liquid electrolyte impregnation and excellent mechanical and thermal properties by adjusting the characteristics of the composite layer.

[0065] The adhesive content (by weight) of the composite layer is in the range of 10 to 40%.

[0066] The binder content of the composite layer, along with inorganic particles and the manufacturing method of the composite layer described later, can affect the porosity of the composite layer. Furthermore, the binder content of the composite layer, together with the crosslinking agent, can affect the physical strength, thermal properties, and electrochemical performance of the battery separator. Specifically, when the binder content of the composite layer is within the above range, the structure of the polymer matrix can be appropriately achieved through crosslinking of the binder and the crosslinking agent, and such a structure can improve the physical strength, thermal properties, and electrochemical performance of the composite layer.

[0067] If the binder content (by weight) of the composite layer is less than 10%, the cross-linked structure of the polymer matrix and the resulting pore distribution cannot be fully formed in the composite layer. Insufficient cross-linking structure and inadequate porosity degrade the heat resistance, ion conductivity, and long-term durability of the battery separator.

[0068] If the binder content (by weight) of the composite layer exceeds 40%, a cross-linked structure of the polymer matrix cannot be formed, or the binder may remain in the composite layer in an uncross-linked state. Residual binder may interfere with the effectiveness of the cross-linked structure. Residual binder degrades the heat resistance and durability of the battery separator. Furthermore, in this case, the inorganic particle content of the composite layer is reduced, which decreases the mechanical or structural stability of the battery separator.

[0069] Preferably, the adhesive content (by weight) of the composite layer can be 15 or more, 20 or more, or 25 or more. The adhesive content (by weight) of the composite layer can be 35 or less, 30 or less, or 25 or less.

[0070] The adhesive content of a composite layer can be referred to as the ratio (B / A) of the weight of the adhesive (B) to the weight of the total solid contents (A) of the composite layer.

[0071] The binder content of the composite layer can be adjusted by the amount of binder in the composition used to form the composite layer.

[0072] The porosity (%) of the composite layer is in the range of 40 to 62.

[0073] The porosity of the composite layer can affect the liquid electrolyte impregnation of the battery separator. Liquid electrolyte impregnation directly impacts battery safety and performance. When the porosity of the composite layer is within the above-mentioned range, the liquid electrolyte impregnation of the battery separator can be maximized while ensuring its structural stability.

[0074] If the porosity (%) of the composite layer is less than 40, the liquid electrolyte cannot be adequately impregnated in the battery separator. Insufficient liquid electrolyte impregnation reduces heat resistance, ion conductivity, and long-term durability.

[0075] If the porosity (%) of the composite layer exceeds 62, the liquid electrolyte is excessively impregnated in the battery separator. Excessive liquid electrolyte remains in the battery separator. The residual liquid electrolyte is susceptible to thermal stress and reduces heat resistance and long-term durability.

[0076] Preferably, the porosity (%) of the composite layer can be 45 or greater, 50 or greater, or 55 or greater. The porosity (%) of the composite layer can be 61 or less, 60 or less, or 55 or less.

[0077] The porosity (%) of the composite layer can be the average porosity. The average porosity can refer to the average value of the composite layer's porosity measurements based on the number of measurements taken.

[0078] The porosity of the composite layer can be a value based on length measurements. Specifically, the porosity of the composite layer can be considered in terms of the load per unit area (g / m²) of the composition used to form the composite layer. 2 The porosity (%) of the composite layer is calculated using the composition and the density of the solid contents of the composition. When the composition used to form the composite layer is referred to as 'Composition A', the porosity (%) of the composite layer can be defined as "(Coating thickness of Composition A - (Load per unit area of ​​Composition A) / (Density of solid contents of Composition A)) / (Coating thickness of Composition A) × 100 (%)".

[0079] Furthermore, the porosity of the composite layer can be measured, for example, according to ISO 15901-1:2016.

[0080] There are no particular limitations on how the composite layer exhibits the aforementioned porosity. For example, the type and content of each component in the composition used to form the composite layer, including the binder, crosslinking agent, and inorganic particles, can affect the porosity. Furthermore, the manner in which the composite layer is formed (i.e., the manner in which the composite layer is produced using the composition) (e.g., the conditions during UV curing) can also affect the porosity of the composite layer.

[0081] The following sections describe in more detail the other constructions included in the battery separator.

[0082] The substrate layer may include a polyolefin-based membrane. Specifically, the substrate layer may include a polyolefin-based porous membrane.

[0083] Here, a polyolefin-based porous membrane refers to a porous membrane that contains a polyolefin-based resin as its main component.

[0084] Polyolefin-based porous membranes may contain polyolefin-based resin in an amount of 50% or more, 90% or more, or 95% or more of the total material constituting the polyolefin-based porous membrane.

[0085] The weight-average molecular weight of the components contained in polyolefin-based resins can be 3 × 10⁻⁶. 5 Up to 15×10 6 When the weight-average molecular weight of the components contained in a polyolefin-based resin is 1,000,000 or greater, the strength of the separator, including a polyolefin-based porous membrane, can be improved.

[0086] Polyolefin-based resins may include thermoplastic resins. Thermoplastic resins may include homopolymers (e.g., polyethylene, polypropylene, polybutene) or copolymers (e.g., ethylene-propylene copolymers) formed by the polymerization of monomers (e.g., ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene).

[0087] Polyolefin-based porous membranes can be layers containing only one of these polyolefin-based resins, or layers containing two or more of these polyolefin-based resins. Polyethylene and high-molecular-weight polyethylene, with ethylene as the main backbone, can block the flow of overcurrent (shutdown) at lower temperatures. Furthermore, polyolefin-based porous membranes can further contain components other than the polyolefin-based resin that do not impair the membrane's function.

[0088] Binders can form the backbone of a polymer matrix. Binders can possess appropriate crystallinity to enhance the ionic conductivity of the battery separator. The polar portion of the binder can bond with a crosslinking agent. Binders can form crosslinked structures with crosslinking agents.

[0089] Adhesives may include fluorine-based adhesives. A fluorine-based adhesive can refer to an adhesive whose constituent units contain fluorine in whole or in part. Fluorine-based adhesives may include PVDF-based adhesives.

[0090] The binder comprises a first unit of vinylidene fluoride and a second unit of a fluorinated alkyl vinyl compound.

[0091] PVDF-based adhesives can be homopolymers or copolymers comprising polymeric units derived from vinylidene fluoride. Fluorine-based adhesives can comprise a first unit of vinylidene fluoride and a second unit of a fluorinated alkyl vinyl compound. PVDF-based adhesives can be block copolymers or random copolymers comprising the first and second units. Preferably, PVDF-based adhesives can be random copolymers comprising the first and second units.

[0092] Fluorinated alkyl vinyl compounds can refer to those in which C n H (2n+1-y) F y The compound represented by at least one fluorinated alkyl group bonded to a vinyl group. However, vinylidene fluoride is excluded.

[0093] Fluorinated alkyl vinyl compounds may include at least one selected from vinyl fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene. Preferably, the fluorinated alkyl vinyl compound may include at least one selected from hexafluoropropylene, tetrafluoroethylene, and chlorotrifluoroethylene. More preferably, the fluorinated alkyl vinyl compound may include hexafluoropropylene.

[0094] The content of the second unit in fluorine-based binders can be adjusted. The content of the second unit in fluorine-based binders can affect the crystallinity of fluorine-based binders, the ionic conductivity of battery separators, and mechanical strength.

[0095] The content (by weight%) of the second unit in the fluorine-based adhesive can be in the range of 10 to 25%. Preferably, the content (by weight%) of the second unit in the fluorine-based adhesive can be 15 or more, 16 or more, 17 or more, or 18 or more. The content (by weight%) of the second unit in the fluorine-based adhesive can be 23 or less, 21 or less, 20 or less, or 19 or less.

[0096] The content of the first and second units in the fluorine-based binder can be determined by the fluorine-based binder. 19 F-NMR analysis was used for measurement.

[0097] The weight-average molecular weight (g / mol) of the fluorine-based adhesive can also be adjusted. The weight-average molecular weight (g / mol) of the fluorine-based adhesive can be in the range of 150,000 to 600,000. Preferably, the weight-average molecular weight (g / mol) of the fluorine-based adhesive can be 200,000 or greater, 250,000 or greater, 300,000 or greater, or 350,000 or greater. The weight-average molecular weight (g / mol) of the fluorine-based adhesive can be 550,000 or less, 500,000 or less, 450,000 or less, 400,000 or less, or 350,000 or less.

[0098] The weight-average molecular weight of fluorine-based binders can be measured by gel permeation chromatography.

[0099] The melting point of the fluorine-based adhesive can also be adjusted. The melting point (°C) of the fluorine-based adhesive can be in the range of 100 to 140. Preferably, the melting point (°C) of the fluorine-based adhesive can be 110 or higher, or 115 or higher. The melting point (°C) of the fluorine-based adhesive can be 135 or lower, 130 or lower, or 125 or lower.

[0100] The number of crosslinkable functional groups in a crosslinking agent can be two or more. Here, the number of crosslinkable functional groups in a crosslinking agent can refer to the number of crosslinkable functional groups per molecule of the crosslinking agent. Crosslinkable functional groups can be functional groups used to connect binders and / or crosslinking agents in a polymer matrix.

[0101] Preferably, the crosslinking agent has 3 or more, or 4 or more crosslinkable functional groups. Alternatively, the crosslinking agent may have 6 or less, or 5 or less crosslinkable functional groups.

[0102] The crosslinkable functional group may include a photoreactive functional group. Specifically, the crosslinkable functional group may include a (meth)acryloyl group as a photoreactive functional group. The crosslinking agent may include a multifunctional (meth)acrylate-based compound. Preferably, from the viewpoint of the rate of crosslinking reaction and preventing the electrochemical properties from deteriorating due to the rigidity of the polymer network, the crosslinkable functional group may include an acryloyl group as a photoreactive functional group.

[0103] Therefore, crosslinking agents may include di(meth)acrylate-based compounds, tri(meth)acrylate-based compounds, tetra(meth)acrylate-based compounds, penta(meth)acrylate-based compounds, hexa(meth)acrylate-based compounds, or combinations thereof.

[0104] Specifically, the crosslinking agent may include diacrylate-based compounds, triacrylate-based compounds, tetraacrylate-based compounds, pentaacrylate-based compounds, hexaacrylate-based compounds, or combinations thereof.

[0105] More specifically, crosslinking agents may include triacrylate-based compounds, tetraacrylate-based compounds, pentaacrylate-based compounds, or combinations thereof.

[0106] More specifically, crosslinking agents can include triacrylate-based compounds.

[0107] Crosslinking agents can include monomeric compounds, polymeric compounds, or combinations thereof. A monomeric crosslinking agent can mean that the remainder, excluding the crosslinkable functional groups, is derived from a monomer. A polymeric crosslinking agent can mean that the remainder, excluding the crosslinkable functional groups, is derived from a polymer.

[0108] Specifically, crosslinking agents may include monomeric compounds.

[0109] Crosslinking agents may include trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, tri(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and propoxylated pentaerythritol tetra(meth)acrylate. Erythritol tetra(meth)acrylate, bis(trimethylolpropane)tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, sorbitol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, poly(ethylene oxide-propylene oxide) di(meth)acrylate, polyurethane di(meth)acrylate, polycarbonate di(meth)acrylate, or combinations thereof.

[0110] Specifically, the crosslinking agent may include trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, tri(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethyl... Oxylated pentaerythritol tetra(meth)acrylate, propoxylated pentaerythritol tetra(meth)acrylate, erythritol tetra(meth)acrylate, bis(trimethylolpropane) tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, sorbitol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, or combinations thereof.

[0111] More specifically, the crosslinking agent may include trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, glycerol triacrylate, ethoxylated glycerol triacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl) isocyanurate triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, erythritol tetraacrylate, bis(trimethylolpropane) tetraacrylate, dipentaerythritol pentaacrylate, ethoxylated dipentaerythritol pentaacrylate, sorbitol pentaacrylate, dipentaerythritol hexaacrylate, ethoxylated dipentaerythritol hexaacrylate, sorbitol hexaacrylate, or combinations thereof.

[0112] More specifically, crosslinking agents may include trimethylolpropane triacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, glycerol triacrylate, ethoxylated glycerol triacrylate, propoxylated glycerol triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, or combinations thereof.

[0113] Not only can the porosity of the composite layer be adjusted, but the size of the pores included in the composite layer can also be adjusted. The average pore size (μm) of the composite layer can be in the range of 0.1 to 1.

[0114] Preferably, the average pore size (μm) of the composite layer can be 0.2 or greater, 0.3 or greater, 0.4 or greater, or 0.5 or greater. The average pore size (μm) of the composite layer can be 0.9 or less, 0.8 or less, 0.7 or less, or 0.6 or less.

[0115] From the perspective of ensuring the heat resistance of the battery separator and delaying the evaporation of the liquid electrolyte even after impregnation, inorganic particles can be included in the composite layer in a larger amount than the binder. That is, among the inorganic particles, binder, and crosslinking agent contained in the composite layer, the inorganic particles can be included in the composite layer in a larger amount than the binder. Specifically, the composite layer can contain inorganic particles by weight greater than the binder.

[0116] The inorganic particle content (parts by weight, relative to 100 parts by weight of binder) of the composite layer can be in the range of 150 to 1000.

[0117] Preferably, the inorganic particle content (parts by weight, relative to 100 parts by weight of binder) of the composite layer can be 200 or greater, 217 or greater, 250 or greater, 300 or greater, 325 or greater, 350 or greater, 400 or greater, 450 or greater, or 500 or greater. The inorganic particle content (parts by weight, relative to 100 parts by weight of binder) of the composite layer can be 950 or less, 900 or less, 850 or less, 800 or less, 750 or less, 700 or less, 650 or less, 600 or less, 550 or less, or 500 or less.

[0118] From the perspective of forming an appropriate cross-linking structure in the composite layer, the content of binder and cross-linking agent in the composite layer can also be adjusted.

[0119] That is, among the inorganic particles, binder, and crosslinking agent contained in the composite layer, the binder may be included in the composite layer in a larger amount than the crosslinking agent, except for the inorganic particles. Specifically, the composite layer may contain inorganic particles with a weight greater than that of the binder.

[0120] The crosslinking agent content (parts by weight, relative to 100 parts by weight of adhesive) of the composite layer can be in the range of 1 to 99.

[0121] Preferably, the crosslinking agent content (parts by weight, relative to 100 parts by weight of adhesive) of the composite layer can be 10 or more, 16 or more, 20 or more, 30 or more, 40 or more, or 50 or more. The crosslinking agent content (parts by weight, relative to 100 parts by weight of adhesive) of the composite layer can be 90 or less, 80 or less, 74 or less, 70 or less, 60 or less, or 50 or less.

[0122] The type of inorganic particles can vary depending on the characteristics that the inorganic particles impart to the battery separator.

[0123] The inorganic particles may comprise lithium-ion transport first inorganic particles, piezoelectric second inorganic particles, flame-retardant third inorganic particles, or combinations thereof. Preferably, the inorganic particles may comprise lithium-ion transport first inorganic particles, flame-retardant third inorganic particles, or combinations thereof. More preferably, the inorganic particles may comprise flame-retardant third inorganic particles.

[0124] Lithium-ion transport inorganic particles may contain lithium but exhibit the function of facilitating lithium-ion movement without storing lithium. A defect may exist within these particles. Charge carriers, such as lithium ions, can utilize this defect to move. Therefore, lithium-ion transport inorganic particles can improve lithium-ion conductivity in batteries, thereby improving battery performance.

[0125] The first inorganic particle may include 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)、Li 6+x La3Zr 2-y M y O 12-z (0≤x≤1, 0≤y≤0.5, 0≤z≤0.2), or combinations thereof.

[0126] Piezoelectric inorganic particles are materials that exhibit different electrical conductivity depending on the applied pressure. Specifically, piezoelectric inorganic particles are non-conductive at atmospheric pressure and become electrically conductive when a certain pressure is applied. The dielectric constant of piezoelectric inorganic particles is relatively high, ranging from 100 to greater than 100. When piezoelectric inorganic particles are stretched or compressed under pressure, an electric charge can be generated. One side of the piezoelectric inorganic particle is positively charged while the other side is negatively charged, thus creating a potential difference within the particle. When a short circuit occurs within the positive and negative electrodes due to an external impact, the piezoelectric inorganic particles positioned in the separator prevent physical contact between the positive and negative electrodes. This potential difference allows a microcurrent to be applied between the positive and negative electrodes. When a short circuit occurs in the cell, this microcurrent can gently reduce the cell voltage, thereby improving cell safety.

[0127] The second inorganic particle may include BaTiO3, BaSO4, Pb(Zr,Ti)O3 (PZT), and Pb 1-x La x Zr 1-y Ti y O3 (PLZT) (0) <x<1,0<y<1)、Pb(Mg1 / 3 Nb 2 / 3 O3-PbTiO3 (PMN-PT), HfO2 (hafnium dioxide), or combinations thereof.

[0128] Flame-retardant inorganic particles can add flame-retardant properties to battery separators and prevent the battery's internal temperature from rising sharply.

[0129] The third inorganic particle may include SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, Zn2SnO4, ZnSnO3, ZnSn(OH)6, ZrO2, Y2O3, Al2O3, AlOOH, Al(OH)3, TiO2, or combinations thereof. Preferably, the third inorganic particle may include ZrO2, Y2O3, Al2O3, AlOOH, Al(OH)3, TiO2, or combinations thereof. More preferably, the third inorganic particle may include Al2O3, AlOOH, Al(OH)3, TiO2, or combinations thereof.

[0130] The battery separator of the present invention can further adjust the characteristics of inorganic particles.

[0131] Specifically, the inorganic particles may include flame-retardant third inorganic particles. In this case, the properties of the inorganic particles can be further modified to enhance the impregnation properties of the electrolyte solution while maintaining thermal stability.

[0132] The D50 (nm) of inorganic particles can range from 100 to 1000. Specifically, the D50 (nm) of inorganic particles can be 150 or greater, 200 or greater, 250 or greater, 300 or greater, 350 or greater, or 400 or greater. Alternatively, the D50 (nm) of inorganic particles can be 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, or 400 or less.

[0133] BET specific surface area of ​​inorganic particles (m²) 2 The BET specific surface area (m² / g) of inorganic particles can range from 5 to 20. 2 The BET specific surface area (m²) of inorganic particles can be 6 or greater, 7 or greater, 8 or greater, 9 or greater, 10 or greater, or 12 or greater. 2 The number of grams (g) can be 18 or less, 16 or less, 15 or less, 14 or less, or 12 or less.

[0134] The composite layer may further contain an initiator.

[0135] When a predetermined stimulus is applied, the initiator can initiate a reaction in which the binder forms a polymer matrix.

[0136] The initiator may include a thermal polymerization initiator, a photopolymerization initiator, or a combination thereof. Preferably, the initiator may include a photopolymerization initiator.

[0137] Photopolymerization initiators may include short-wavelength photopolymerization initiators, long-wavelength photopolymerization initiators, or combinations thereof. Preferably, the photopolymerization initiator may include a long-wavelength photopolymerization initiator.

[0138] Short-wavelength photopolymerization initiators may include IRGACURE 127 (1,1'-(methylene-di-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone]), IRGACURE 1173 (2-hydroxy-2-methylphenylacetone, HMPP), DMPA (2,2-dimethoxy-2-phenylacetophenone), HOMPP (2-hydroxy-2-methylphenylacetone), LAP (phenyl-2,4,6-trimethylbenzoylphosphine), or combinations thereof.

[0139] Long-wavelength photopolymerization initiators may include at least one selected from bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and ethyl (2,4,6-trimethylbenzoyl)phenylphosphine oxide. Preferably, the long-wavelength photopolymerization initiator may include ethyl (2,4,6-trimethylbenzoyl)phenylphosphine oxide (TPO-L).

[0140] From the perspective of properly controlling the crosslinking reaction between the binder and the crosslinking agent, the initiator content of the composite layer can also be appropriately adjusted. The composite layer can contain the crosslinking agent in a larger weight than the initiator.

[0141] The initiator content (parts by weight, relative to 100 parts by weight of crosslinking agent) of the composite layer can be in the range of 1 to 10. Preferably, the initiator content (parts by weight, relative to 100 parts by weight of crosslinking agent) of the composite layer can be 1.1 or greater, 1.3 or greater, 1.5 or greater, 1.7 or greater, 1.9 or greater, or 2.0 or greater. The initiator content (parts by weight, relative to 100 parts by weight of crosslinking agent) of the composite layer can be 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2.5 or less, 2.4 or less, 2.3 or less, 2.2 or less, or 2.1 or less.

[0142] Another embodiment of the present invention is an electrolyte membrane.

[0143] Specifically, the electrolyte membrane of the present invention can be prepared by immersing the aforementioned battery separator in a liquid electrolyte. When impregnated with a liquid electrolyte, the composite layer of the aforementioned battery separator can exhibit electrolyte properties. It can be referred to as an electrolyte layer.

[0144] Furthermore, when describing the electrolyte membrane of this embodiment, the description of the battery separator of the aforementioned embodiments can be applied verbatim in this document.

[0145] The electrolyte membrane of this embodiment includes: a base layer; and an electrolyte layer.

[0146] The electrolyte layer can provide a path for charge carriers to move through the electrolyte membrane.

[0147] An electrolyte layer is disposed on one or both surfaces of the substrate layer. Specifically, the electrolyte layer may be disposed on the first surface of the substrate layer, or on the first surface and a second surface facing the first surface. When the electrolyte layer is disposed on both the first and second surfaces, the composition and thickness of each electrolyte layer may be the same or different from each other.

[0148] The electrolyte layer contains a gel polymer electrolyte.

[0149] In this document, the gel polymer electrolyte is a gel-phase electrolyte. A gel polymer electrolyte comprises a polymer matrix and a liquid electrolyte. The liquid electrolyte may be impregnated within the polymer matrix. Here, the polymer matrix can physically support the gel polymer electrolyte. The liquid electrolyte can impart ionic conductivity to the gel polymer electrolyte.

[0150] The electrolyte membrane exhibits specific behavior in differential thermal gravimetric analysis (DTG). Specifically, the electrolyte membrane shows peaks at two different temperatures in DTG. These peaks represent decomposition peaks of the electrolyte membrane. A peak can also refer to a local minimum in the temperature versus weight rate curve plotted for the electrolyte membrane in DTG.

[0151] Specifically, the electrolyte membrane exhibits a first decomposition peak at a first temperature (T1) and a second decomposition peak at a second temperature (T2) above the first temperature in the DTG. The fact that the electrolyte membrane exhibits at least two decomposition peaks in the DTG means that the electrolyte membrane decomposes in at least two temperature ranges. Furthermore, the presence of two or more temperature ranges in which decomposition peaks occur means that the electrolyte membrane contains two or more materials with different thermal properties.

[0152] The present invention adjusts the first temperature and the second temperature. In this way, the electrolyte membrane of the present invention can simultaneously exhibit appropriate liquid electrolyte impregnation, improved ion conductivity, and heat resistance.

[0153] The decomposition peaks of the electrolyte membrane and the temperatures at which these peaks appear are determined by the thermal properties of the components contained in the electrolyte membrane. Specifically, the number of decomposition peaks and the temperatures at which they appear in the DTG of the electrolyte membrane can be determined by the quantity and type of components contained in the electrolyte membrane.

[0154] The second temperature (°C) is 200 or higher.

[0155] The fact that the second temperature (°C) is 200 or higher means that, of the at least two decomposition peaks appearing in the DTG of the electrolyte membrane, the peak appearing at the higher temperature is observed at the above temperature. Furthermore, this may mean that the electrolyte layer of the electrolyte membrane has been impregnated with an appropriate amount of liquid electrolyte to reduce the amount of residual liquid electrolyte. Additionally, this may mean that the liquid electrolyte contains a significant amount of non-aqueous solvent with a boiling point higher than the second temperature. Furthermore, this indicates that the electrolyte membrane exhibits excellent heat resistance.

[0156] If the second temperature (°C) is below 200, it means that the electrolyte membrane thermally decomposes at such a low temperature. This indicates that a large amount of residual liquid electrolyte remains in the electrolyte membrane.

[0157] Preferably, the second temperature (°C) can be 205 or higher, 210 or higher, 215 or higher, 217 or higher, 220 or higher, or 225 or higher. The second temperature (°C) can be 250 or lower, 245 or lower, 240 or lower, 235 or lower, 230 or lower, or 225 or lower.

[0158] The first temperature (°C) is in the range of 90 to 150.

[0159] The first and second temperatures can be derived from the composition of the liquid electrolyte and the thermal properties of the polymer matrix. Therefore, the first temperature can also refer to the amount of liquid electrolyte impregnating the polymer matrix, reducing the amount of residual liquid electrolyte in the electrolyte membrane. Furthermore, this can mean that the liquid electrolyte contains an appropriate amount of a non-aqueous solvent with a boiling point similar to the first temperature. Thus, the electrolyte membrane exhibits excellent heat resistance.

[0160] Preferably, the first temperature (°C) can be 95 or higher, 100 or higher, 105 or higher, 110 or higher, 115 or higher, or 120 or higher. The first temperature (°C) can be 145 or lower, 140 or lower, 135 or lower, 130 or lower, 125 or lower, or 120 or lower.

[0161] The second and first temperatures may be more meaningful when the ratio of the intensity of the first decomposition peak to the intensity of the second decomposition peak is within a specific range. The intensity of each decomposition peak may be related to the amount of component decomposed at each peak. That is, the ratio can be determined based on the composition of the components contained in the electrolyte layer.

[0162] Furthermore, the DTG behavior of the battery separator can vary depending on the method of manufacturing the electrolyte membrane (specifically, the manner in which the polymer matrix is ​​formed and impregnated with the liquid electrolyte).

[0163] The ratio of the intensity of the first decomposition peak to the intensity of the second decomposition peak can be a value reflecting the composition of the components contained in the liquid electrolyte. The ratio of the intensity of the first decomposition peak (IP1) to the intensity of the second decomposition peak (IP2) (IP2 / IP1) can be, for example, 0.5 or greater. The ratio (IP2 / IP1) can be 0.55 or greater, 0.6 or greater, 0.65 or greater, or 0.7 or greater. The ratio can be 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.9 or less, or 0.85 or less.

[0164] In the electrolyte membrane of the present invention, the composition of the electrolyte layer can be adjusted. This allows the electrolyte membrane to exhibit specific thermal behavior. Therefore, the electrolyte membrane can simultaneously exhibit appropriate liquid electrolyte impregnation, high ionic conductivity, heat resistance, and long-term durability.

[0165] The polymer matrix can be formed by the reaction of the binder and crosslinker contained in the aforementioned composite layer. That is, the polymer matrix can contain components derived from the binder and components derived from the crosslinker.

[0166] As described above, the composite layer may further contain an initiator. Therefore, the polymer matrix may further contain components derived from the initiator.

[0167] Liquid electrolytes can contain non-aqueous solvents and lithium salts. Lithium salts can be dissolved in non-aqueous solvents.

[0168] The decomposition peaks of the electrolyte membrane and the temperatures at which these peaks appear can be determined by the thermal properties of the components contained in the electrolyte membrane (specifically, the electrolyte layer). Specifically, the number of decomposition peaks and the temperatures at which they appear can be determined by the type and quantity of non-aqueous solvents contained in the liquid electrolyte. The liquid electrolyte may contain two or more types of non-aqueous solvents. The liquid electrolyte may contain two or more types of non-aqueous solvents with different boiling points. This can affect the DTG results of the electrolyte membrane.

[0169] The first and second temperatures, the intensity of the first decomposition peak, and the intensity of the second decomposition peak can be determined by the composition of the liquid electrolyte impregnated in the polymer matrix. Specifically, the type of non-aqueous solvent contained in the liquid electrolyte can affect the thermal behavior of the electrolyte membrane.

[0170] Non-aqueous solvents can refer to organic solvents that do not contain water or contain only trace amounts of water. Non-aqueous solvents can include carbonate-based compounds, ether-based compounds, ester-based compounds, compounds containing polar functional groups, or mixtures thereof. Preferably, non-aqueous solvents can include carbonate-based compounds.

[0171] Ether-based compounds may include dimethoxyethane, diethoxyethane, tetrahydrofuran, or combinations thereof.

[0172] Ester-based compounds may include N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, or combinations thereof.

[0173] Compounds containing polar functional groups may include dimethyl sulfoxide, acetonitrile, or combinations thereof.

[0174] Carbonate-based compounds may include linear carbonate-based compounds, cyclic carbonate-based compounds, or combinations thereof. Preferably, carbonate-based compounds may include both linear carbonate-based compounds and cyclic carbonate-based compounds.

[0175] The electrolyte layer can contain linear carbonate-based compounds in a larger volume than cyclic carbonate-based compounds. In this case, the miscibility of the binder with the liquid electrolyte increases, and abnormal viscosity increases in the electrolyte layer can be prevented.

[0176] In this document, linear carbonate-based compounds refer to open-chain diesters of carbonic acid. Specifically, linear carbonate-based compounds include structures in which the two hydroxyl groups of carbonic acid are esterified with different alcohols and the entire molecule does not form a ring.

[0177] In this document, compounds based on cyclic carbonates refer to lactones whose ring structure includes a -O-CO-O- skeleton of a carbonate group. Specifically, compounds based on cyclic carbonates include structures in which two hydroxyl groups in a molecule form ester bonds with the same carbonate group at both ends, and the ring includes an -O-CO-O- skeleton.

[0178] Compounds based on linear carbonates may include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, or combinations thereof.

[0179] Specifically, linear carbonate-based compounds may include dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, or combinations thereof.

[0180] More specifically, linear carbonate-based compounds may include ethyl methyl carbonate.

[0181] Compounds based on linear carbonates can be liquids at room temperature.

[0182] Compounds based on cyclic carbonates may include ethylene carbonate, vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, propylene carbonate, butyl carbonate, or combinations thereof.

[0183] Specifically, compounds based on cyclic carbonates may include ethylene carbonate, vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butyl carbonate, or combinations thereof.

[0184] More specifically, compounds based on cyclic carbonates may include ethylene carbonate, vinylene carbonate, ethylene carbonate, propylene carbonate, or combinations thereof.

[0185] From the perspectives of the miscibility of the aforementioned binder with the liquid electrolyte, the viscosity adjustment of the electrolyte layer, and the safety of the battery, combinations of linear carbonate-based compounds and cyclic carbonate-based compounds in different phases may be preferred.

[0186] Compounds based on cyclic carbonates can be solid at room temperature. Specifically, compounds based on cyclic carbonates may include ethylene carbonate.

[0187] The amounts of linear carbonate-based compounds and cyclic carbonate-based compounds used can also be appropriately adjusted within the range that the above conditions are met.

[0188] The volume (volume %) of the linear carbonate-based compound in the electrolyte layer can range from 55 to 95.

[0189] Preferably, the volume (volume %) of the linear carbonate-based compound in the electrolyte layer can be 60 or greater, 65 or greater, or 70 or greater. The volume (volume %) of the linear carbonate-based compound in the electrolyte layer can be 90 or less, 85 or less, 80 or less, or 75 or less.

[0190] The volume (volume %) of the cyclic carbonate-based compound in the electrolyte layer can range from 5 to 45. Preferably, the volume (volume %) of the cyclic carbonate-based compound in the electrolyte layer can be 10 or greater, 15 or greater, 20 or greater, or 25 or greater. The volume (volume %) of the cyclic carbonate-based compound in the electrolyte layer can be 40 or less, 35 or less, or 30 or less.

[0191] Lithium salts are soluble in non-aqueous solvents. Lithium salts can refer to materials that dissociate into lithium cations and anions upon dissociation.

[0192] Lithium salts may include LiPF6, LiBF4, LiCl, LiBr, LiI, LiClO4, LiAsF6, LiCH3CO2, LiCF3SO3, LiN(CF3SO2)2, LiN(FSO2)2, LiC(CF2SO2)3, or combinations thereof. Preferably, lithium salts may include LiPF6.

[0193] Liquid electrolytes may further contain additives.

[0194] Additives can refer to substances that are applied in small amounts to liquid electrolytes to stabilize the electrode interface, improve electrochemical stability, regulate conduction characteristics, improve temperature characteristics, and inhibit gas generation.

[0195] The additive may include vinylene carbonate, 1,3-propanesulfonyl lactone, 1,3-propenesulfonyl lactone, lithium difluorophosphate, lithium tetrafluoro(oxalate)phosphate, lithium bis(fluorosulfonyl)imide, fluoroethylene carbonate, ethylene ethylene carbonate, or combinations thereof. Preferably, the additive may include vinylene carbonate.

[0196] Because the liquid electrolyte is impregnated in the binder or a polymer matrix formed by the binder in the electrolyte layer, the thickness of the electrolyte layer can typically be thick. Specifically, the electrolyte layer can be thicker than the base layer.

[0197] Another embodiment of the present invention is a battery.

[0198] A battery may include a first electrode, a second electrode, a separator, and an electrolyte. The separator may be disposed between the first electrode and the second electrode. The polarity of the first electrode may be opposite to that of the second electrode. If the first electrode is a positive electrode (negative electrode), then the second electrode may be a negative electrode (positive electrode).

[0199] The system consisting of the battery separator and the electrolyte can be the electrolyte membrane of the present invention. Therefore, in the description of the battery, the description of the separator and the electrolyte can be completely replaced by the electrolyte membrane described above.

[0200] The positive electrode can be the electrode that undergoes a reduction reaction during discharge. The negative electrode can be the electrode that undergoes an oxidation reaction during discharge.

[0201] The electrodes of the battery may include electrode active materials attached to the electrode current collector. Specifically, the electrodes may include an electrode current collector and an electrode active material layer disposed on one or both surfaces of the electrode current collector and containing the electrode active material.

[0202] The positive electrode active material in the electrode active material may include a lithium intercalation material. The lithium intercalation material may include lithium transition metal oxides. The lithium intercalation material may include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide and lithium iron oxide, lithium nickel manganese oxide, lithium nickel cobalt oxide, lithium nickel manganese cobalt oxide, or combinations thereof. Preferably, the positive electrode active material may include lithium nickel manganese cobalt oxide.

[0203] The negative electrode active material in the electrode active material may include a lithium intercalation material. The lithium intercalation material may include lithium-based metals, including lithium metal and lithium alloys; carbon-based compounds, including carbon, petroleum coke, activated carbon, and graphite; or combinations thereof.

[0204] The positive electrode current collector can be a foil of a metal including aluminum, nickel, or a combination thereof. Preferably, the positive electrode current collector can be an aluminum foil.

[0205] The negative electrode current collector can be a foil containing metals including copper, gold, nickel, or combinations thereof. Preferably, the negative electrode current collector can be a copper foil.

[0206] Another embodiment of the present invention is a method for manufacturing a battery separator.

[0207] The manufacturing method can produce battery separators by forming a composite layer on one or both surfaces of the substrate.

[0208] The manufacturing method includes preparing a slurry.

[0209] The slurry contains binders, crosslinking agents, inorganic particles, and a primary solvent.

[0210] The slurry can be prepared directly, or obtained as a product designed and produced to have the corresponding composition and used in this invention.

[0211] When describing binders, crosslinking agents, and inorganic particles, the same content mentioned in the section on battery separators applies to this document.

[0212] Inorganic particles can be dispersed in the first solvent.

[0213] The slurry can contain inorganic particles in a greater weight than the binder.

[0214] Inorganic particles can be dispersed in the first solvent. Binders can be dissolved in the first solvent.

[0215] The method for manufacturing a battery separator according to the present invention includes coating a slurry onto one or both surfaces of a substrate layer to prepare a coated structure. The coated structure comprises a substrate layer and the slurry applied thereto.

[0216] The method for manufacturing battery separators according to the present invention involves immersing a coated structure in baths (tanks) of different compositions in a specific sequence. Therefore, the method of the present invention can manufacture battery separators that simultaneously exhibit appropriate liquid electrolyte impregnation levels, high ionic conductivity, and heat resistance.

[0217] The method for manufacturing a battery separator according to the present invention may include immersing a coated structure in a first bath and immersing the coated structure in a second bath.

[0218] The method for manufacturing battery separators according to the present invention involves immersing a coated structure in a first bath, removing the coated structure from the first bath, and then immersing the removed coated structure in a second bath. Immersion in the second bath allows the coated structure that has already been immersed in the first bath to be immersed in the second bath.

[0219] The method for manufacturing a battery separator according to the present invention further includes applying light to a coated structure. Specifically, the light can be ultraviolet light. Applying light to the coated structure can form a cross-linked structure between the binder and the cross-linking agent.

[0220] The method of manufacturing the battery separator of the present invention may further include drying the coated structure that has been immersed in a second bath. During drying, a porous layer may be formed on one or both surfaces of the substrate layer.

[0221] The method for manufacturing a battery separator according to the present invention may include drying the coated structure before applying light to it. Specifically, the method may involve removing the coated structure, which has been immersed in a second bath, drying it, and then applying light to the dried coated structure.

[0222] The method for manufacturing battery separators of the present invention configures the types of solvents contained in the first bath and the second bath to be different. The first bath contains a first solvent and a second solvent. The second bath contains a second solvent. Specifically, the second bath may consist of a second solvent.

[0223] The first and second solvents can include different types of compounds. For example, the criterion used to distinguish between the first and second solvents is the solubility of the binder in each solvent. Specifically, the binder is more soluble in the first solvent than in the second solvent. More specifically, at room temperature, the binder dissolves better in the first solvent than in the second solvent.

[0224] The first bath may contain specific components as a first solvent and a second solvent. The first solvent may include NMP (N-methyl-2-pyrrolidone). The second solvent may include water. In this case, the second bath may consist of water.

[0225] The drying, holding temperatures of the first and second baths, and immersion times can vary depending on the composition of the slurry and the ratio of the second solvent in the first bath. For example, the solids content (wt%) of the slurry can range from 10 to 50. The ratio of the second solvent in the first bath (volume%), based on the total volume of the first and second solvents, can range from 60 to 80.

[0226] Another embodiment of the present invention is a method for manufacturing an electrolyte membrane.

[0227] The method for manufacturing the electrolyte membrane further includes impregnating the polymer matrix of the composite layer of the aforementioned battery separator with a liquid electrolyte. That is, the method for manufacturing the electrolyte membrane of the present invention may further include immersing the product obtained from the method for manufacturing the battery separator according to the aforementioned embodiment into a liquid electrolyte.

[0228] That is, the method for manufacturing an electrolyte membrane according to the present invention includes: preparing a slurry comprising a binder, a crosslinking agent, inorganic particles and a first solvent; coating the slurry onto one or both surfaces of a substrate layer to prepare a coated structure; immersing the coated structure in a first bath comprising a first solvent and a second solvent; immersing the coated structure in a second bath comprising a second solvent; applying light to the coated structure; and immersing the coated structure in a liquid electrolyte.

[0229] Immersion in a liquid electrolyte allows the coated structure, which has already been immersed in a second bath, to be further immersed in the liquid electrolyte. The liquid electrolyte can impregnate the polymer matrix contained in the composite layer. Therefore, an electrolyte membrane comprising an electrolyte layer disposed on one or both surfaces of the substrate layer can be manufactured.

[0230] Here, immersion in a liquid electrolyte allows the coated structure that has been light-treated to be immersed in the liquid electrolyte. Specifically, immersion in a liquid electrolyte allows the coated structure that has been immersed in the second bath to be dried, light to be applied to the dried coated structure, and then the light-treated coated structure to be immersed in the liquid electrolyte.

[0231] Invention Embodiments

[0232] In the following document, the invention is described in more detail by way of examples and comparative examples. However, the invention is not limited to the examples.

[0233] [Preparation Example]

[0234] Example 1. Battery separator and electrolyte membrane

[0235] The battery separator and electrolyte membrane are prepared according to the following steps.

[0236] (1) 30 g of binder, 4.9 g of crosslinking agent, 0.1 g of photopolymerization initiator and 65 g of inorganic particles were mixed in NMP (N-methyl-2-pyrrolidone) to prepare a mixture with a density of 2.30 g / cm³. 3 The slurry was prepared using Kynar2501-20 (PVDF-HFP; weight-average molecular weight: 350,000 g / mol; HFP substitution rate: 18.6 wt%) from Arkema as the binder. The crosslinking agent was M340 (pentaerythritol triacrylate; PETA) from Miwon Specialty Chemical. The photopolymerization initiator was Omnirad TPO-L ((2,4,6-trimethylbenzoyl)phenylphosphine ethyl ester) from IGM. The inorganic particles were D60 (boehmite; D50: 400 nm; BET: 10 nm) from Sasol. 2 / g to 12 m 2 / g).

[0237] (2) The slurry was coated on both surfaces of the substrate layer with a thickness of 10 μm per layer to prepare the coated structure. The substrate layer was HK09G (PE film, thickness: 9 μm) from Horizon.

[0238] (3) Immerse the coated structure in the first bath. The first bath contains 40% by volume NMP and 60% by volume water. The temperature of the first bath is 20°C. The immersion time is 40 seconds.

[0239] (4) Remove the coated structure from the first bath and immerse it in the second bath. The second bath contains 100% by volume water. The temperature of the second bath is 20°C. The immersion time is 60 seconds.

[0240] (5) Remove the coated structure from the second bath and dry it in a vacuum oven to form a composite layer on both surfaces of the substrate. The drying temperature is 80°C. The drying time is 2 minutes. The average porosity of each layer of the composite layer is 60%.

[0241] (6) Apply UV to the composite layer to prepare a battery separator in which a cross-linked structure of a polymer matrix is ​​formed in the composite layer.

[0242] (7) Immerse the battery separator in a liquid electrolyte to prepare an electrolyte membrane. The liquid electrolyte is a liquid electrolyte in which 1M LiPF6 is dissolved in a non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 3:7, and 2% by weight of ethylene carbonate (VC) is added based on the total weight.

[0243] Example 2. Battery separator and electrolyte membrane

[0244] The battery separator and electrolyte membrane were prepared by repeating the same steps as in Example 1, except that in (1), 30 g of binder, 4.9 g of crosslinking agent, 0.1 g of photopolymerization initiator and 65 g of inorganic particles were mixed in NMP (N-methyl-2-pyrrolidone) to prepare a membrane with a density of 2.30 g / cm³. 3 The slurry. In (5), a composite layer is formed on both surfaces of the substrate. The average porosity of each layer of the composite layer is 50%.

[0245] Comparative Example 1. Battery separator and electrolyte membrane

[0246] The battery separator and electrolyte membrane were prepared by repeating the same steps as in Example 1, except that in (1), 35 g of binder and 65 g of inorganic particles were mixed in NMP (N-methyl-2-pyrrolidone) to prepare a membrane with a density of 2.40 g / cm³. 3 The slurry is prepared, and step (6) is omitted. In (5), a composite layer is formed on both surfaces of the substrate. The average porosity of each layer of the composite layer is 65%.

[0247] Comparative Example 2. Battery separator and electrolyte membrane

[0248] The battery separator and electrolyte membrane were prepared by repeating the same steps as in Example 1, except that in (1), 5 g of binder, 28.5 g of crosslinking agent, 1.5 g of photopolymerization initiator and 65 g of inorganic particles were mixed in NMP (N-methyl-2-pyrrolidone) to prepare a membrane with a density of 1.93 g / cm³. 3 The slurry. In (5), a composite layer is formed on both surfaces of the substrate. The average porosity of each layer of the composite layer is 30%.

[0249] [Evaluation Methodology]

[0250] Experimental Example 1. Porosity of the Composite Layer

[0251] The porosity of the composite layer is measured using the following steps.

[0252] (1) Measure the density, content, coating thickness, and weight of the composite layer of the slurry.

[0253] (2) The calculation is performed by substituting the measured values ​​into the following equation:

[0254] The porosity (%) of the composite layer can be defined as: (slurry coating thickness - (slurry load per unit area) / (slurry solid content density)) / (slurry coating thickness) × 100 (%).

[0255] Experimental Example 2. Ion Conductivity

[0256] The ionic conductivity of the electrolyte membrane is assessed according to the following steps.

[0257] (1) A coin cell with the electrolyte membrane positioned between SUS plates, as described in the embodiments and comparative examples, was manufactured. The coin cell was a 2016 type, and the area of ​​the electrolyte membrane was 2.83 cm². 2 (19pi).

[0258] (2) The resistance and ionic conductivity of the coin cell were calculated by applying resistance measurements using electrochemical impedance spectroscopy (EIS) and converting them via the Nyquist plot method. The resistance measurements were performed at AC voltage with an amplitude of 10 mV and a frequency of 1,000,000 Hz to 1,000 Hz.

[0259] Experimental Example 3. Liquid Electrolyte Impregnation Amount

[0260] The weight change rate (%) of the battery separator and electrolyte membrane in the embodiments and comparative examples is calculated as the liquid electrolyte impregnation amount according to the following steps.

[0261] (1) The battery separator was cut into 20 mm × 60 mm dimensions to prepare a sample and its weight (W1) was measured.

[0262] (2) Prepare an electrolyte membrane sample of the same size as the battery separator sample.

[0263] (3) Place the paper towels on both sides of the electrolyte membrane sample, insert them into the aluminum bag (100 mm × 80 mm), and seal it.

[0264] (3) Apply pressure to the bag using a press set at room temperature, 1 minute and 1.6 MPa.

[0265] (4) Open the bag, take out the electrolyte membrane sample, and measure its weight (W2).

[0266] (5) Convert the weight ratio (W2 / W1) to % to determine the amount of liquid electrolyte impregnation.

[0267] Experimental Example 4. Differential Thermal Gravimetric Analysis (DTG) of Electrolyte Membranes

[0268] DTG of the electrolyte membrane is performed using the following steps.

[0269] (1) Cut the electrolyte membrane into 20 mm × 60 mm pieces and attach PET release films above and below it to prepare the sample. Store the sample at 25°C.

[0270] (2) Apply pressure to the cut electrolyte membrane using a press (1.6 MPa, hold for 1 minute) to prepare a sample from which residual liquid electrolyte has been removed.

[0271] (3) Place 10 mg of the sample into a thermogravimetric analyzer (PerkinElmer Inc., TGA 4000).

[0272] (3) Perform thermogravimetric analysis of the sample in a nitrogen (N2) atmosphere. The temperature range is 30℃ to 600℃, the heating rate is 10℃ / min, and the sample is naturally cooled to room temperature after reaching 600℃ to obtain the thermogravimetric analysis chart.

[0273] Experimental Example 5. High-Temperature Thermal Shrinkage Rate of Electrolyte Membranes

[0274] The high-temperature thermal shrinkage rate of the electrolyte membrane is measured using the following steps.

[0275] (1) Cut the electrolyte membrane into 5 cm × 5 cm dimensions to prepare the sample.

[0276] (2) Draw four points in a cross shape on the surface of the sample. The four points are spaced 1.5 cm apart from the center in the top, bottom, left and right directions, respectively.

[0277] (3) Place the sample on a glass plate and heat it in an oven at 150°C for 30 minutes.

[0278] (4) Remove the heated sample from the oven and measure its length shrinkage. The shrinkage rate is calculated as a percentage of the distance from the center of the four points compared to the initial distance.

[0279] (5) Determine the average shrinkage rate of the electrolyte membrane based on the measurement direction (length direction and width direction).

[0280] Experimental Example 6. Battery Life Characteristics

[0281] The following steps are used to measure the discharge capacity and capacity retention of a battery made with an electrolyte membrane.

[0282] (1) The electrolyte membrane is stamped to a size of 32 mm × 44 mm.

[0283] (2) Positive electrode

[0284] 1) Prepare a slurry in which a mixture consisting of 94 wt% LiNiCoMnO2 (Ni:Co:Mn=8:1:1) as the positive electrode active material, 3 wt% conductive carbon black (Super P; IMERYS Graphite & Carbon) as the conductive material, and 3 wt% polyvinylidene fluoride with a weight average molecular weight of about 800,000 as the binder is uniformly dispersed in NMP.

[0285] 2) Apply the slurry to one surface of the aluminum current collector, and then dry and roll it to prepare a positive electrode plate with a positive electrode active material layer on top.

[0286] 3) The positive electrode plate is stamped to a size of 30 mm × 42 mm.

[0287] (2) Negative electrode

[0288] 1) Prepare a negative electrode material composition comprising: 95.6% by weight of a material as the negative electrode active material (composed of 90% by weight of a graphite-based material (in which artificial graphite and natural graphite are mixed in a weight ratio of 3:7) and 10% by weight of SiO); 1% by weight of acetylene black as the conductive material; 1.1% by weight of carboxymethyl cellulose (CMC) as the first binder; and 2.3% by weight of styrene-butadiene rubber (SBR) as the second binder.

[0289] 2) The negative electrode material composition was applied to one surface of a copper current collector with a thickness of 8 μm using a comma coating machine, followed by drying and calendering to prepare a negative electrode plate with a negative electrode active material layer on top. The porosity and thickness of the negative electrode active material layer were 24% and 44 μm, respectively.

[0290] 3) The negative electrode plate is stamped to a size of 31 mm × 43 mm.

[0291] (3) Assembly

[0292] 1) Manufacturing an electrode assembly having such a structure that the positive active material layer of the positive electrode plate and the negative active material layer of the negative electrode plate are arranged facing each other, and an electrolyte membrane is disposed between the positive active material layer and the negative active material layer.

[0293] 2) The electrode assembly was housed in a bag to complete the battery. The electrolyte solution was the same as that used to prepare the gel polymer electrolyte precursor composition. Five battery samples were prepared. The battery performance is the arithmetic mean of the five samples.

[0294] (4) Perform charge-discharge cycles on the battery. The conditions for repeated charge-discharge tests are room temperature and a 0.1-C rate from 2.5 V to 4.2 V.

[0295] (5) Repeat the charge-discharge cycle 10 times to measure the capacity retention rate. The charge capacity, discharge capacity and discharge capacity retention rate of the battery are determined by the capacity retention rate.

[0296] [Results and discussion]

[0297] Figure 1 The results of DTG behavior analysis of the composite electrolytes of the examples and comparative examples are shown. Figure 1 In the analysis, the local minimum values ​​of each sample were identified as decomposition peaks.

[0298] Table 1 below shows the test results for the embodiments and comparative examples.

[0299] [Table 1]

[0300]

Claims

1. A battery separator, comprising: basal layer; as well as A composite layer, wherein the composite layer is disposed on one or both surfaces of the substrate layer, and comprises an adhesive, a crosslinking agent, and inorganic particles. The adhesive content (by weight) of the composite layer is in the range of 10 to 40%, and The porosity (%) of the composite layer is in the range of 40 to 62.

2. The battery separator according to claim 1, The adhesive comprises a first unit of vinylidene fluoride and a second unit of a fluorinated alkyl vinyl compound.

3. The battery separator according to claim 1, The adhesive has a weight-average molecular weight (g / mol) in the range of 150,000 to 600,000, and The content (by weight%) of the second unit of the adhesive is in the range of 10 to 25%.

4. The battery separator according to claim 1, The number of crosslinkable functional groups in the crosslinking agent is 2 or more.

5. The battery separator according to claim 1, The crosslinking agent includes compounds based on di(meth)acrylate, compounds based on tri(meth)acrylate, compounds based on tetra(meth)acrylate, compounds based on penta(meth)acrylate, compounds based on hexa(meth)acrylate, or combinations thereof.

6. The battery separator according to claim 1, The crosslinking agent includes monomeric compounds, polymeric compounds, or combinations thereof.

7. The battery separator according to claim 1, The crosslinking agent includes trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, glycerol tri(meth)acrylate, ethoxylated glycerol tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate, tri(2-hydroxyethyl)isocyanurate tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and propoxylated pentaerythritol tetra(meth)acrylate. Ester, erythritol tetra(meth)acrylate, bis(trimethylolpropane)tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethoxylated dipentaerythritol penta(meth)acrylate, sorbitol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate, polyethylene glycol di(meth)acrylate, poly(ethylene oxide-propylene oxide) di(meth)acrylate, polyurethane di(meth)acrylate, polycarbonate di(meth)acrylate, or combinations thereof.

8. The battery separator according to claim 1, The composite layer contains an adhesive in which the weight is greater than the weight of the crosslinking agent.

9. The battery separator according to claim 1, The inorganic particles include lithium-ion transport first inorganic particles, piezoelectric second inorganic particles, flame-retardant third inorganic particles, or combinations thereof.

10. An electrolyte membrane, comprising: basal layer; and An electrolyte layer, disposed on one or both surfaces of the substrate layer, comprises a polymer matrix and a liquid electrolyte impregnated in the polymer matrix. The electrolyte membrane exhibits a first decomposition peak at a first temperature and a second decomposition peak at a second temperature above the first temperature in differential thermal gravimetric analysis (DTG). The first temperature (°C) is 200 or higher, and The second temperature (°C) is in the range of 90 to 150.

11. The electrolyte membrane according to claim 10, The first temperature (°C) is in the range of 200 to 250.

12. The electrolyte membrane according to claim 10, The polymer matrix comprises components derived from the binder and components derived from the crosslinking agent.

13. The electrolyte membrane according to claim 10, The liquid electrolyte contains a non-aqueous solvent and a lithium salt.

14. The electrolyte membrane according to claim 13, The electrolyte layer contains a linear carbonate-based compound with a volume larger than that of a cyclic carbonate-based compound.

15. The electrolyte membrane according to claim 14, The linear carbonate-based compounds mentioned above include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, or combinations thereof.

16. The electrolyte membrane according to claim 14, The linear carbonate-based compound is a liquid at room temperature.

17. The electrolyte membrane according to claim 14, The compounds based on cyclic carbonates include ethylene carbonate, vinylene carbonate, ethylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, propylene carbonate, butyl carbonate, or combinations thereof.

18. The electrolyte membrane according to claim 14, The cyclic carbonate-based compound is a solid at room temperature.

19. The electrolyte membrane according to claim 14, The volume (volume %) of the linear carbonate-based compound in the electrolyte layer is in the range of 55 to 95.

20. A battery, comprising: A positive electrode, a negative electrode, and an electrolyte membrane disposed between the positive electrode and the negative electrode. The electrolyte membrane comprises: a substrate layer; and an electrolyte layer disposed on one or both surfaces of the substrate layer, and comprising a polymer matrix and a liquid electrolyte impregnated in the polymer matrix. The electrolyte membrane exhibits a first decomposition peak at a first temperature and a second decomposition peak at a second temperature above the first temperature in differential thermal gravimetric analysis (DTG). Wherein the first temperature (°C) is 200 or higher, and The second temperature (°C) is in the range of 90 to 150.

21. A method for manufacturing a battery separator, comprising: Prepare a slurry comprising a binder, a crosslinking agent, inorganic particles, and a first solvent; The slurry is coated onto one or both surfaces of the substrate to prepare a coated structure. The coated structure is immersed in a first bath containing the first solvent and the second solvent; Immerse the coated structure in a second bath containing the second solvent; and Apply light to the coated structure, At room temperature, the adhesive dissolves better in the first solvent than in the second solvent.

22. The method for manufacturing a battery separator according to claim 21, The immersion in the second bath involves immersing the coated structure, which has already been immersed in the first bath, into the second bath.

23. The method of manufacturing a battery separator according to claim 21, further comprising: The coated structure that has been immersed in the second bath is dried.

24. The method for manufacturing a battery separator according to claim 23, The application of light involves applying light to the dried coated structure.

25. The method for manufacturing a battery separator according to claim 21, The first solvent includes NMP, and The second solvent includes water.

26. A method for manufacturing an electrolyte membrane, comprising: Prepare a slurry comprising a binder, a crosslinking agent, inorganic particles, and a first solvent; The slurry is coated onto one or both surfaces of the substrate to prepare a coated structure. The coated structure is immersed in a first bath containing the first solvent and the second solvent; The coated structure is immersed in a second bath containing the second solvent; Apply light to the coated structure; and The coated structure is immersed in a liquid electrolyte. At room temperature, the adhesive dissolves better in the first solvent than in the second solvent.

27. The method for manufacturing an electrolyte membrane according to claim 26, The immersion in the liquid electrolyte involves immersing the coated structure, which has been light-treated, into the liquid electrolyte.

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