Separator for electrochemical device and method for manufacturing same

Abstract

The separator according to the present invention comprises a porous polymer substrate, an adhesive layer, and a heat-resistant layer, wherein the adhesive layer comprises an acrylic adhesive polymer having a swelling ratio of 50% or more. The separator can ensure sufficient peel strength while being thin.

Description

Technical Field

[0001] This disclosure relates to a separator for an electrochemical device and a method for manufacturing the same.

[0002] This application is based on and claims priority to Korean Patent Application No. 10-2024-0091290, filed with the Korean Intellectual Property Office on July 10, 2024, the disclosure of which is incorporated herein by reference in its entirety. Background Technology

[0003] Recently, there has been increasing attention on energy storage technologies. With the expanding applications of energy storage in mobile phones, cameras, laptops, and electric vehicles, more efforts have been made in the research and development of electrochemical devices. In this regard, the development of rechargeable secondary batteries has become a central focus within the field of electrochemical devices, attracting the most attention. Recently, research and development in secondary batteries have concentrated on new electrode and battery designs to improve capacity density and specific energy.

[0004] An electrochemical device includes an electrode assembly and a battery housing. The electrode assembly includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes. The battery housing houses the electrode assembly, and the separator prevents short circuits caused by contact between the positive and negative electrodes and provides a path for electrolyte movement between the positive and negative electrodes. Therefore, it is important to maintain the electrode assembly structure, including the positive electrode, separator, and negative electrode in a stacked configuration, after the electrolyte has been wetted.

[0005] To improve the safety of electrochemical devices, it has been attempted to have a separator containing a ceramic heat-resistant layer on at least one surface of a porous polymer substrate. However, when a heat-resistant layer with a small thickness is formed to reduce the thickness of the separator, peeling occurs due to the low adhesion strength between the porous polymer substrate and the heat-resistant layer. Summary of the Invention

[0006] Technical issues

[0007] This disclosure relates to providing a separator with a smaller thickness and improved peel strength.

[0008] Technical solution

[0009] One aspect of this disclosure provides a separator, an electrochemical device, and a method for manufacturing the separator according to the following embodiments.

[0010] The partition according to the first embodiment includes:

[0011] Porous polymer substrate; and porous coating,

[0012] The porous coating includes: an adhesive layer on at least one surface of the porous polymer substrate; and a heat-resistant layer on one surface of the adhesive layer.

[0013] The adhesive layer includes a first adhesive polymer.

[0014] The heat-resistant layer comprises inorganic particles and a second adhesive polymer.

[0015] The first adhesive polymer comprises an acrylic polymer, and

[0016] The swelling ratio of the acrylic polymer is 50% or higher.

[0017] According to the second embodiment, in the first embodiment...

[0018] The swelling ratio of acrylic polymers can be 60% or higher.

[0019] According to the third embodiment, in the first or second embodiment...

[0020] The swelling ratio of acrylic polymers can be measured using the following formula 1:

[0021] (Equation 1)

[0022] In Equation 1, W0 represents the initial mass of the membrane made of the adhesive polymer when measured at 25°C, and W1 represents the mass of the adhesive polymer membrane measured at 25°C after the membrane has been placed in dimethyl carbonate and stored at 60°C for 48 hours.

[0023] According to the fourth embodiment, in any of the first to third embodiments,

[0024] Carbonate solvents can include dimethyl carbonate.

[0025] According to the fifth embodiment, in any of the first to fourth embodiments,

[0026] Acrylic polymers can be crosslinked and have a crosslinking degree of 0.01% to 80%.

[0027] According to the sixth embodiment, in any one of the first to fifth embodiments,

[0028] Acrylic polymers may include poly(methylmethacrylate), poly(ethylhexyl acrylate), poly(butyl acrylate), poly(acrylonitrile), copolymers of ethylhexyl acrylate and methyl methacrylate, copolymers of butyl acrylate and methyl methacrylate, ethyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(dimethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, or mixtures of two or more thereof.

[0029] According to the seventh embodiment, in any one of the first to sixth embodiments...

[0030] The peel strength between the porous polymer substrate and the porous coating can be 50 gf / 15 mm or greater.

[0031] According to the eighth embodiment, in any of the first to seventh embodiments,

[0032] The adhesive layer may not include inorganic particles.

[0033] The electrochemical device according to the ninth embodiment includes:

[0034] Positive electrode, negative electrode, and a separator inserted between the positive and negative electrodes.

[0035] The partition is any one of the partitions in the first to eighth embodiments.

[0036] The method for manufacturing a partition according to the tenth embodiment includes:

[0037] Preparation of porous polymer substrates;

[0038] Prepare a slurry for forming an adhesive layer comprising a first adhesive polymer and a first aqueous solvent; apply the slurry for forming the adhesive layer to at least one surface of a porous polymer substrate and dry the slurry to form the adhesive layer; and

[0039] A slurry for forming a heat-resistant layer is prepared, comprising inorganic particles, a second binder polymer, a second aqueous solvent, and an organic solvent. The slurry for forming the heat-resistant layer is applied to one surface of the binder layer and dried to form the heat-resistant layer.

[0040] The first adhesive polymer comprises an acrylic polymer, and

[0041] The swelling ratio of the acrylic polymer is 50% or higher.

[0042] According to the eleventh embodiment, in the tenth embodiment...

[0043] Organic solvents may include carbonate solvents.

[0044] According to the twelfth embodiment, in the tenth or eleventh embodiment...

[0045] Organic solvents may include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, or mixtures thereof.

[0046] According to the thirteenth embodiment, in any one of the tenth to twelfth embodiments,

[0047] The second aqueous solvent and organic solvent can be mixed in a volume ratio of 95:5 to 80:20.

[0048] Beneficial effects

[0049] The separator according to this disclosure can have a smaller thickness. Furthermore, the separator can have higher peel strength between the porous coating and the porous polymer substrate. Detailed Implementation

[0050] The present disclosure will be described in detail below. It should be understood that the terms or words used in the specification and appended claims should not be construed as limited to their general or dictionary meanings, but should be interpreted based on their meanings and concepts corresponding to the technical aspects of the present disclosure, based on the principle that the inventors are permitted to appropriately define terms for the best interpretation.

[0051] Therefore, the embodiments described herein are provided to illustrate this disclosure by way of example, but are not intended to be limiting, and it should be understood that other equivalents may be substituted and modified thereto at the time of filing.

[0052] It should also be understood that, unless otherwise expressly stated, “include,” “comprise,” or “have” as used in the specification designates the presence of the stated element and does not exclude the presence or addition of one or more other elements.

[0053] The terms “about” and “substantially” are used herein in the sense that they are equal to or close to the inherent manufacturing and material tolerances given in the stated context, and are used to prevent dishonest infringers from unfairly exploiting this disclosure (where exact or absolute figures are stated to aid in understanding this disclosure).

[0054] In this specification, A and / or B refers to A or B or both.

[0055] Unless otherwise stated, the temperatures used in this article refer to temperatures in Celsius, and the unit is °C.

[0056] The first aspect of this disclosure relates to a partition.

[0057] The partitions according to aspects of this disclosure include:

[0058] Porous polymer substrate; and porous coating,

[0059] The porous coating includes: an adhesive layer on at least one surface of the porous polymer substrate; and a heat-resistant layer on one surface of the adhesive layer.

[0060] The adhesive layer includes a first adhesive polymer.

[0061] The heat-resistant layer comprises inorganic particles and a second adhesive polymer.

[0062] The first adhesive polymer comprises an acrylic polymer, and

[0063] The swelling ratio of the acrylic polymer is 50% or higher.

[0064] In this disclosure, the swelling ratio can be measured by the following formula 1:

[0065] (Equation 1)

[0066] In Equation 1 above, W0 represents the initial mass of the film made of acrylic polymer when measured at room temperature (approximately 25°C), and W1 represents the mass of the acrylic polymer film when measured at room temperature (approximately 25°C) after the film has been placed in dimethyl carbonate and stored at 60°C for 48 hours.

[0067] The separator according to this disclosure includes an acrylic adhesive having a swelling ratio of 50% or greater in the adhesive layer. That is, the swollen mass can be 150% or greater relative to the initial mass of the acrylic adhesive before swelling. When the swelling ratio is 50% or greater, the acrylic adhesive can be used to fully swell the solvent included in the slurry forming the heat-resistant layer. Sufficient swelling of the acrylic polymer can improve the adhesion strength between the porous polymer substrate and the heat-resistant layer.

[0068] The partition according to this disclosure will be described in detail below.

[0069] The separator according to this disclosure includes a porous coating on at least one surface of a porous polymer substrate. Additionally, the porous coating includes an adhesive layer on at least one surface of the porous polymer substrate and a heat-resistant layer on one surface of the adhesive layer.

[0070] Porous polymer substrate

[0071] In embodiments of this disclosure, the porous polymer substrate is not limited to a specific material and may include any separator material commonly used in the art for electrochemical devices. Non-limiting examples of polymer materials used in the porous polymer substrate may include olefin polymers, polyethylene terephthalate polymers, butylene terephthalate polymers, acetal polymers, amide polymers, carbonate polymers, imide polymers, ether ether ketone polymers, ether sulfone polymers, phenyl ether polymers, phenyl sulfide polymers, or vinylnaphthalene polymers.

[0072] Furthermore, the porous polymer substrate may include a nonwoven fabric or a porous polymer membrane made of the aforementioned polymer material, or a laminate of two or more of these materials. Specifically, the porous polymer substrate may be any one of a) to e).

[0073] a) Porous membranes formed by melting and extruding polymer materials.

[0074] b) A multilayer membrane made of two or more stacked layers of the porous membrane in a),

[0075] c) Nonwoven webs produced by weaving filaments obtained from melt / spinned polymer materials;

[0076] d) A multilayer film made of two or more stacked layers of the nonwoven mesh in c)

[0077] e) Porous membranes with two or more of the multilayer structures found in a) to d).

[0078] Porous polymer substrates can be manufactured by forming pores using known methods commonly used in the art, such as wet methods using solvents, diluents or pore-forming agents, or dry methods using stretching, to ensure high permeability and porosity of the aforementioned materials.

[0079] In embodiments of this disclosure, the thickness of the porous polymer substrate is not limited to a specific range, but can be from 1 μm to 100 μm or from 1 μm to 30 μm. When the thickness of the porous polymer substrate falls within the above range, it can prevent the separator from being easily damaged during battery use and make it easier to ensure energy density.

[0080] Meanwhile, the average pore size and porosity of the porous polymer substrate are not limited to a specific range and can be within a suitable range for use in electrochemical devices. The average pore size can be from 0.01 μm to 50 μm or from 0.1 μm to 20 μm, and the porosity can be from 5% to 95%. When the pore size and porosity fall within the above ranges, it is easy to prevent the porous polymer substrate from acting as a resistor and to maintain the mechanical properties of the porous polymer substrate.

[0081] The average pore size and porosity of porous polymer substrates can be measured using scanning electron microscopy (SEM) images, a mercury porosimeter, a capillary flow porometer, or a porosimetry analyzer (Belosorp-II mini, Bell Japan Inc.) via nitrogen adsorption flow method through BET 6-point analysis.

[0082] Adhesive layer

[0083] The adhesive layer according to this disclosure includes a first adhesive polymer, the first adhesive polymer including an acrylic polymer, and the acrylic polymer having a swelling ratio of 50% or greater.

[0084] In embodiments of this disclosure, the swelling ratio of the acrylic adhesive can be 50% or greater, 60% or greater, 70% or greater, 80% or greater, or 90% or greater. Furthermore, the swelling ratio of the acrylic adhesive can be 400% or less. When the swelling ratio of the acrylic adhesive falls within the above ranges, the peel strength between the porous polymer substrate and the porous coating can be significantly improved.

[0085] In embodiments of this disclosure, the weight-average molecular weight of the acrylic adhesive polymer can be from 10,000 to 1,000,000. When the weight-average molecular weight of the acrylic adhesive polymer falls within the above range, a sufficient swelling ratio can be ensured.

[0086] In embodiments of this disclosure, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) of a solution containing 1 g of acrylic polymer can be measured using gel permeation chromatography (GPC: gelpermeation chromatography, PL GPC220, Agilent Technologies) under the following conditions, thereby allowing the calculation of the weight-average molecular weight and molecular weight distribution of the acrylic polymer.

[0087] Column: PLmixed B Х 2,

[0088] Solvent: DMF / 0.05 M LiBr (0.45 μm filtered)

[0089] Flow rate: 1.0 ml / min

[0090] Sample concentration: 4.0 mg / ml

[0091] Injection volume: 100 μl

[0092] Column temperature: 65℃

[0093] Detector: Waters RI Detector, Standard: PS

[0094] In embodiments of the present invention, the acrylic adhesive polymer may include poly(methyl methacrylate), poly(ethylhexyl acrylate), poly(butyl acrylate), poly(acrylonitrile), copolymers of ethylhexyl acrylate and methyl methacrylate, copolymers of butyl acrylate and methyl methacrylate, ethyl acrylate-N,N-dimethylacrylamide copolymer, ethyl acrylate-2-(dimethylamino)ethyl acrylate copolymer, ethyl acrylate-N,N-diethylacrylamide copolymer, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymer, or mixtures of two or more thereof, and preferably polymethyl methacrylate.

[0095] Acrylic adhesive polymers may contain hydrophilic functional groups, such as OH, CO, COH, and / or COOH groups. The presence of hydrophilic functional groups in acrylic adhesives can enhance swelling. Furthermore, acrylic adhesive polymers may include acrylic copolymers containing hydrophilic functional groups (such as OH, CO, COH, and / or COOH groups).

[0096] In embodiments of this disclosure, the first adhesive polymer may be non-crosslinked or crosslinked.

[0097] When the first adhesive polymer is crosslinked, the degree of crosslinking of the first adhesive polymer can be 0.01% or greater, 0.1% or greater, 1% or greater, 5% or greater, 10% or greater, 15% or greater, 20% or greater, 25% or greater, 30% or greater, 35% or greater, 40% or greater, 45% or greater, 50% or greater, 55% or greater, 60% or greater, and can be 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, or 20% or less.

[0098] The degree of crosslinking of the first adhesive polymer can vary depending on the properties of the adhesive polymer. For example, when the first adhesive polymer includes a small number of hydrophilic functional groups, the first adhesive polymer may not be crosslinked or may have a low degree of crosslinking. Conversely, when the first adhesive polymer includes a large number of hydrophilic functional groups, the first adhesive polymer may have a high degree of crosslinking. That is, when the degree of crosslinking of the first adhesive polymer is controlled within the above-mentioned range, the swelling ratio may be 50% or greater.

[0099] The degree of crosslinking can be calculated as the ratio of the dry weight of the film made from the first binder polymer to its initial weight, where the dry weight refers to the remaining weight after boiling in a decahydronaphthalene solution at 135°C for 4 hours according to ASTM D 2765.

[0100] In embodiments of this disclosure, based on a total of 100 wt% of adhesive layer, the adhesive layer may comprise 80 wt% or more, 85 wt% or more, 90 wt% or more, 95 wt% or more, 97 wt% or more, 98 wt% or more, or 99 wt% or more of acrylic polymer, and may substantially comprise 100 wt% of acrylic polymer. That is, the adhesive layer may comprise only acrylic polymer. However, this disclosure is not limited thereto, and in addition to acrylic polymer, the adhesive layer may also comprise adhesive polymers commonly used in the art, if desired.

[0101] In embodiments of this disclosure, the adhesive layer may consist only of an adhesive polymer and no inorganic particles.

[0102] heat-resistant layer

[0103] The heat-resistant layer according to this disclosure comprises inorganic particles and a second adhesive polymer.

[0104] In embodiments of the present disclosure, the inorganic particles are not limited to specific particles and may include any electrochemically stable particles. That is, the inorganic particles useful in the present disclosure are not limited to specific particles and may include those in which no oxidation and / or reduction reaction occurs within the operating voltage range of the applied electrochemical device (e.g., 0 to 5V vs. Li / Li + ). In particular, when inorganic particles having a high dielectric constant are used as the inorganic particles, they can contribute to an increased degree of dissociation of electrolyte salts (e.g., lithium salts) in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

[0105] For the above reasons, in embodiments of the present disclosure, the inorganic particles may include high dielectric constant inorganic particles having a dielectric constant of 5 or greater, preferably 10 or greater. Non-limiting examples of inorganic particles having a dielectric constant of 5 or greater may include BaTiO3, 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), hafnium dioxide (HfO2), SrTiO3, SnO2, CeO2, MgO, Mg(OH)2, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al₂O₃, AlOOH, Al(OH)3, SiC, TiO2, or mixtures thereof. In addition, the inorganic particles may include inorganic particles having the ability to transport lithium ions, that is, inorganic particles containing lithium but not storing lithium and having the function of promoting the movement of lithium ions. Non-limiting examples of inorganic particles having the ability to transport lithium ions may include: lithium phosphate (Li3PO4); lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3); lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3); (LiAlTiP) x O y -like glass (0 < x < 4, 0 < y < 13), such as 14Li2O-9Al2O3-38TiO2-39P2O₅; lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3); lithium germanium thiophosphate (Li x Ge y P z Sw , where 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as Li 3.25 Ge 0.25 P 0.75 S4; lithium nitride (Li x N y , where 0 < x < 4, 0 < y < 2), such as Li3N; Li3N; SiS2-based glass (Li x Si y S z , where 0 < x < 3, 0 < y < 2, 0 < z < 4), such as Li3PO4-Li2S-SiS2; P2S5-based glass (Li x P y S z , where 0 < x < 3, 0 < y < 3, 0 < z < 7), such as LiI-Li2S-P2S5; or a mixture thereof.

[0106] In an embodiment of the present disclosure, the average particle size of the inorganic particles may be from 0.01 μm to 1.5 μm. When the average particle size of the inorganic particles falls within the above range, an inorganic hybrid porous layer with a uniform thickness and optimal porosity can be easily formed, achieving good dispersion of the inorganic particles and providing the desired energy density.

[0107] In this case, the average particle size of the inorganic particles refers to D 50 particle size, and "D 50 particle size" refers to the particle size at the 50% point of the cumulative particle size distribution. The particle size can be measured using the laser diffraction method. Specifically, after dispersing the powder in a dispersion medium and feeding it into a commercially available laser diffraction particle size analyzer (e.g., Microtrac S3500), when the particles pass through the laser beam, the particle size distribution is calculated by measuring the difference in the diffraction pattern as a function of the particle size. The D50 particle size can be measured by calculating the particle diameter at the 50% point of the cumulative particle size distribution in the measuring instrument.

[0108] In an embodiment of the present disclosure, based on a total of 100 wt% of the heat-resistant layer, the inorganic particles may be included in an amount of 60 wt% to 95 wt%, 65 wt% to 95 wt%, 70 wt% to 95 wt%, or 75 wt% to 95 wt%. When the amount of the inorganic particles falls within the above range, sufficient empty space can be formed between the inorganic particles, thereby ensuring the porosity of the heat-resistant layer and sufficient heat resistance of the separator.

[0109] In embodiments of this disclosure, the second adhesive polymer may include any adhesive polymer commonly used in the art. Non-limiting examples of the second adhesive polymer may include, but are not limited to, any polymer resin selected from the group consisting of: polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl-co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethyl pullullan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullullan, and carboxymethyl cellulose. methylcellulose), or a mixture of two or more of them.

[0110] In embodiments of this disclosure, the swelling ratio of the second adhesive polymer can be 30% or less, 20% or less, 10% or less, 5% or less, or 3% or less. The swelling ratio of the second adhesive polymer can be measured using the same method as that used to measure the swelling ratio of the first adhesive polymer. When the swelling ratio of the second adhesive polymer falls within the aforementioned range, stability can be ensured during coating of the slurry due to the low swelling ratio in the slurry. Furthermore, sufficient porosity in the heat-resistant layer can be ensured, thereby ensuring low electrical resistance.

[0111] In embodiments of this disclosure, the heat-resistant layer may further comprise additives, such as dispersants and / or thickeners. For example, additives may include cyanoethyl polyvinyl alcohol (PVA-CN), citric acid, hydroxyethyl cellulose (HEC), hydroxypropyl cellulose (HPC), ethylhydroxyethyl cellulose (EHEC), methyl cellulose (MC), carboxymethyl cellulose (CMC), hydroxyalkyl methyl cellulose, or mixtures of two or more of these.

[0112] In embodiments of this disclosure, the thickness of the heat-resistant layer can be 0.5 μm to 10 μm, 0.5 μm to 5 μm, or 0.5 μm to 3 μm. When the thickness of the heat-resistant layer falls within the above range, the partition can have a sufficiently small thickness and excellent heat resistance.

[0113] In embodiments of this disclosure, the peel strength between the porous polymer substrate and the porous coating can be 50 gf / 15 mm or greater, 60 gf / 15 mm or greater, 70 gf / 15 mm or greater, 80 gf / 15 mm or greater, 90 gf / 15 mm or greater, or 100 gf / 15 mm or greater. When the peel strength falls within the above range, separator peeling can be prevented during the manufacture and operation of the secondary battery, thereby ensuring the safety of the secondary battery.

[0114] Peel strength can be measured using the following methods:

[0115] Cut the separator to a size of 15mm × 100mm. Attach double-sided tape to the glass plate and adhere the porous coating of the prepared separator to the tape. Then, place the adhered separator end on a UTM device (LLOYDInstrument LF Plus) and measure the speed at 300 mm / min at 180°. o The force required to peel the porous coating from the porous polymer substrate during stretching.

[0116] The second aspect of this disclosure relates to an electrochemical device.

[0117] The electrochemical device according to aspects of this disclosure includes a positive electrode, a negative electrode, and a separator inserted between the positive and negative electrodes.

[0118] The partition is a partition according to an aspect of this disclosure.

[0119] In embodiments of this disclosure, the electrochemical device includes any device that facilitates an electrochemical reaction, and specific examples may include any type of primary battery, secondary battery, fuel cell, solar cell, or capacitor, such as a supercapacitor. In particular, the electrochemical device may include a lithium secondary battery, including lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, lithium-sulfur batteries, or lithium-ion polymer secondary batteries.

[0120] The electrodes used in conjunction with the separators of the electrochemical devices of this disclosure are not limited to a particular type, and can be manufactured such that a layer of electrode active material comprising an electrode active material, a conductive material and a binder is bonded to the electrode current collector by methods known in the art.

[0121] Non-limiting examples of positive electrode active materials may include: layered compounds, such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides of O4 (x=0 to 0.33), such as LiMnO3, LiMn2O3, or LiMnO2; lithium copper oxides (Li2CuO2); vanadium oxides, such as LiV3O5, LiV3O4, V2O5, or Cu2V2O7; and those of the chemical formula LiNi 1-x M x Ni-site type lithium nickel oxides represented by O2 (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 to 0.3); and those with the chemical formula LiMn 2-x M x Lithium-manganese composite oxides represented by O2 (M=Co, Ni, Fe, Cr, Zn or Ta, x=0.01 to 0.1) or Li2Mn3MO5 (M=Fe, Co, Ni, Cu or Zn); LiMn2O4, wherein the Li in the chemical formula is partially replaced by an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, but not limited thereto.

[0122] Non-limiting examples of negative electrode active materials may include negative electrode active materials commonly used in the negative electrodes of electrochemical devices, and in particular, may include lithium adsorbent materials such as lithium metal or lithium alloys, carbon, petroleum cokes, activated carbon, graphite or other carbon.

[0123] Non-limiting examples of positive current collectors may include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of negative current collectors may include foils made of copper, gold, nickel, or copper alloys or combinations thereof.

[0124] In embodiments of this disclosure, the conductive materials used in the negative and positive electrodes are typically added in amounts ranging from 1% to 30% by weight, based on the total weight of each active material layer. The conductive materials are not limited to a specific type and may include any material that has conductive properties without causing chemical changes in the corresponding battery, and may include, for example: graphite, such as natural or artificial graphite; carbon black, such as acetylene black, Ketjen black, channel black, furnace black, lampblack, or thermally cracked black; conductive fibers, such as carbon fibers or metal fibers; fluorocarbons; metal powders, such as aluminum or nickel powder; conductive whiskers, such as zinc oxide whiskers or potassium titanate whiskers; conductive metal oxides, such as titanium oxides; or conductive materials, such as polyphenylene derivatives.

[0125] In embodiments of this disclosure, the binder polymer used in the negative and positive electrodes can help hold the active and conductive materials together and bond them to the current collector, and can typically be added in an amount of 1% to 30% by weight based on the total weight of each active material layer. Examples of binders may include polyvinylidene fluoride (PVdF), polyacrylic acid (PAA), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, or copolymers thereof.

[0126] In embodiments of this disclosure, the electrochemical device includes an electrolyte solution, which may include an organic solvent and a lithium salt. Furthermore, the electrolyte solution may include an organic solid electrolyte or an inorganic solid electrolyte.

[0127] Organic solvents may include, for example, aprotic organic solvents such as N-methyl-2-pyrrolidone, ethylene carbonate, propylene carbonate, butyl carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, or ethyl propionate.

[0128] Lithium salts are materials that are readily soluble in organic solvents and can include, for example, LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB. 10 Cl 10 LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylic acids, lithium tetraphenylborate, or imide.

[0129] Furthermore, to improve charge / discharge characteristics or flame retardancy, the electrolyte solution may further include, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glycol dimethyl ether (glyme), triammonium hexaphosphate, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolides, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride. If desired, halogen-containing solvents such as carbon tetrachloride or trifluoroethylene may be further included to provide non-flammability, and carbon dioxide gas may be further included to improve high-temperature storage characteristics.

[0130] Organic solid electrolytes may include, for example, polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate polymers, polyalginic acid-lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, or polymers containing ionic dissociation groups.

[0131] Inorganic solid electrolytes may include, for example, nitrides, halides or sulfates of Li, such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, or Li3PO4-Li2S-SiS2.

[0132] Electrolyte solution injection can be performed at appropriate steps in the battery manufacturing process, depending on the manufacturing process and the required properties of the final product. In other words, electrolyte solution injection can be completed before battery pack assembly or in the final stage of battery pack assembly.

[0133] A third aspect of this disclosure relates to a method for manufacturing a partition.

[0134] The method for manufacturing a partition according to aspects of this disclosure includes:

[0135] Preparation of porous polymer substrates;

[0136] Prepare a slurry for forming an adhesive layer comprising a first adhesive polymer and a first aqueous solvent; apply the slurry for forming the adhesive layer to at least one surface of a porous polymer substrate and dry the slurry to form the adhesive layer; and

[0137] A slurry for forming a heat-resistant layer is prepared, comprising inorganic particles, a second binder polymer, a second aqueous solvent, and an organic solvent. The slurry for forming the heat-resistant layer is applied to one surface of the binder layer and dried to form the heat-resistant layer.

[0138] The first adhesive polymer comprises an acrylic polymer, and

[0139] The swelling ratio of the acrylic polymer is 50% or higher.

[0140] After an adhesive layer is formed on one or both surfaces of a porous polymer substrate, a slurry for forming a heat-resistant layer is applied. In this case, the acrylic polymer included in the adhesive layer can absorb the organic solvent contained in the slurry for forming the heat-resistant layer and swell by 50% or more.

[0141] In embodiments of this disclosure, the organic solvent includes carbonate solvents. For example, the organic solvent may include: at least one linear carbonate (dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate); and / or at least one cyclic carbonate (ethylene carbonate, propylene carbonate, or butyl carbonate); or mixtures thereof. Preferably, the organic solvent may include dimethyl carbonate.

[0142] In embodiments of this disclosure, the second aqueous solvent and organic solvent in the slurry used to form the heat-resistant layer can be mixed in a volume ratio of 95:5 to 80:20, 95:5 to 90:10, or 90:10 to 80:20. When the second aqueous solvent and organic solvent are mixed in amounts within the above ranges, the first adhesive polymer contained in the adhesive layer can sufficiently absorb the organic solvent and swell during the application of the slurry used to form the heat-resistant layer to one surface of the adhesive layer.

[0143] The present disclosure will be described in more detail below by way of examples, but the scope of the disclosure is not limited thereto.

[0144] Example 1

[0145] A 9 μm thick polyethylene film was prepared as a porous polymer substrate.

[0146] Polymethyl methacrylate (PMMA) with a crosslinking degree of 60% was added to water as a first binder polymer to prepare a slurry with a solid content of 10% for forming an adhesive layer. The slurry was then applied to both surfaces of a porous polymer substrate and dried to form the adhesive layer.

[0147] Water and dimethyl carbonate were mixed at a volume ratio of 90:10, and Al₂O₃ as inorganic particles and PVDF-HFP as a second binder polymer were added to the mixture to prepare a slurry with a solids content of 35% for forming the heat-resistant layer. The slurry for forming the heat-resistant layer was then applied to one surface of the binder layer and dried to form the heat-resistant layer, thus completing the fabrication of the partition. The thickness of the binder layer was 0.5 μm, and the thickness of the heat-resistant layer, when measured, was 1.5 μm.

[0148] In this case, the swelling ratio of the first adhesive polymer PMMA in dimethyl carbonate is 60%.

[0149] Example 2

[0150] The separator was manufactured in the same manner as in Example 1, except that polymethyl methacrylate (PMMA) with a crosslinking degree of 10% was added as the first adhesive polymer.

[0151] In this case, the swelling ratio of the first adhesive polymer is calculated to be 90%.

[0152] Comparative Example 1

[0153] The separator was manufactured in the same manner as in Example 1, except that no adhesive layer was formed. The slurry used to form the heat-resistant layer was applied directly to both surfaces of the porous polymer substrate and dried to manufacture the separator.

[0154] Comparative Example 2

[0155] The separator was manufactured in the same manner as in Example 1, except that polyacrylonitrile with a crosslinking degree of 60% and a swelling ratio of 30% in dimethyl carbonate was used as the first adhesive polymer.

[0156] Comparative Example 3

[0157] The separator was manufactured in the same manner as in Example 1, except that PVDF-HFP with 85% crosslinking and a swelling ratio of 130% in dimethyl carbonate was used as the first adhesive polymer.

[0158] Comparative Example 4

[0159] The separator was manufactured in the same manner as in Example 1, except that polyvinylpyrrolidone (PVP) was used as the first adhesive polymer.

[0160] Polyvinylpyrrolidone is an adhesive polymer produced by solution polymerization, making it impossible to compare its swelling ratio with that of acrylic adhesive polymers produced by emulsion polymerization at the same scale.

[0161] Comparative Example 5

[0162] The separator was manufactured in the same manner as in Example 1, except that polymethyl methacrylate (PMMA) with a crosslinking degree of 10% was added as the first adhesive polymer.

[0163] In this case, the swelling ratio of the first adhesive polymer is calculated to be 45%.

[0164] Comparative Example 6

[0165] The separator was manufactured in the same manner as in Example 1, except that a slurry for forming the heat-resistant layer was applied to both surfaces of the porous polymer substrate and dried to form the heat-resistant layer, and a slurry for forming the adhesive layer was applied to one surface of the heat-resistant layer and dried to form the adhesive layer. That is, the stacking order of the adhesive layer and the heat-resistant layer was reversed compared to Example 1.

[0166] Swelling Measurement Method

[0167] In the examples / comparative examples, the swelling ratio was calculated by measuring the initial mass (W0) of the film made of the adhesive polymer and the mass (W1) after the film was placed in dimethyl carbonate and stored at 60°C for 48 hours, and substituting them into Equation 1 below.

[0168] (Equation 1)

[0169] Crosslinking degree measurement method

[0170] In the examples / comparative examples, the degree of crosslinking was calculated as the ratio of the dry weight of the film made from the first adhesive polymer to its initial weight, where the dry weight refers to the remaining weight after boiling in a decahydronaphthalene solution at 135°C for 4 hours according to ASTM D 2765.

[0171] Thickness measurement methods

[0172] In the examples / comparative examples, the thickness of the adhesive layer and the heat-resistant layer was measured using a thickness gauge (Mitutoyo).

[0173] Experimental Example 1: Peel Strength Measurement

[0174] For each separator manufactured in the examples and comparative examples, the peel strength between the porous polymer substrate and the porous coating was measured, and the results are summarized in Table 1 below.

[0175] Specifically, each partition manufactured in Examples 1 and 2, as well as Comparative Examples 1 to 4, was cut to a size of 15 mm × 100 mm. Double-sided adhesive tape was attached to a glass plate, and the porous coating surface of the prepared partition was adhered to the tape. Subsequently, the adhered end of the partition was placed on a UTM device (LLOYD Instrument LF Plus), and measurements were taken at a speed of 300 mm / min and a rotation speed of 180°. o The force required to peel the porous coating from the porous polymer substrate during stretching.

[0176] Table 1

[0177]

[0178] Referring to Table 1 above, it can be confirmed that the partition according to this disclosure is superior to the partition according to the comparative example in terms of peel strength.

[0179] Specifically, it can be confirmed that the separator according to Comparative Example 1 has low peel strength due to the absence of an adhesive layer. Furthermore, it can be confirmed that the separators according to Comparative Examples 2 and 5 include acrylic adhesive polymers, but have low swelling ratios of 30% or 45%, thus failing to ensure sufficient peel strength.

[0180] In Comparative Example 3, which includes PVDF-based adhesives, the PVDF-based adhesive polymer is a crystalline polymer (as opposed to acrylic adhesives), thus failing to achieve good electrolyte wetting and a high swelling ratio, resulting in insufficient peel strength.

[0181] In Comparative Example 4, which included a PVP-based adhesive polymer, very low peel strength was observed. Since the PVP-based adhesive polymer is dissolved in an organic solvent, it is presumed that during the application of the slurry used to form the heat-resistant layer, the PVP-based adhesive polymer was eluted into the dimethyl carbonate contained in the slurry. Furthermore, the PVP-based adhesive polymer is an adhesive polymer generated through solution polymerization, making it impossible to compare its swelling ratio with that of an acrylic adhesive polymer generated through emulsion polymerization at equal levels.

[0182] Comparative Example 6 involves forming a heat-resistant layer on both surfaces of a porous polymer substrate and forming an adhesive layer on the heat-resistant layer, thus the positions of the heat-resistant layer and the adhesive layer are reversed compared to Example 1. Because the heat-resistant layer is formed before the adhesive layer, the adhesive polymer in the adhesive layer does not swell sufficiently, thereby failing to ensure adequate peel strength.

[0183] Although this disclosure has been described above with reference to a number of embodiments and accompanying drawings, this disclosure is not limited thereto, and various changes and modifications will be apparent to those skilled in the art within the scope of this disclosure and the appended claims and their equivalents.

Claims

1. A partition, comprising: Porous polymer substrate; and porous coating, The porous coating includes an adhesive layer located on at least one surface of the porous polymer substrate; and a heat-resistant layer located on one surface of the adhesive layer, The adhesive layer comprises a first adhesive polymer, The heat-resistant layer comprises inorganic particles and a second adhesive polymer. The first adhesive polymer comprises an acrylic polymer, and The swelling ratio of the acrylic polymer is 50% or higher.

2. The partition according to claim 1, The swelling ratio of the acrylic polymer is 60% or higher.

3. The partition according to claim 1, The swelling ratio of the acrylic polymer is measured by the following formula 1: (Equation 1) In Formula 1, W0 represents the initial mass of the film made from the adhesive polymer when measured at 25°C, and W1 represents the mass of the adhesive polymer film measured at 25°C after the film has been placed in dimethyl carbonate and stored at 60°C for 48 hours.

4. The partition according to claim 3, The carbonate solvents mentioned therein include dimethyl carbonate.

5. The partition according to claim 1, The acrylic polymer thereon is crosslinked and has a crosslinking degree of 0.01% to 80%.

6. The partition according to claim 1, The acrylic polymers mentioned therein include poly(methyl methacrylate), poly(ethyl hexyl acrylate), poly(butyl acrylate), poly(acrylonitrile), copolymers of ethyl hexyl acrylate and methyl methacrylate, copolymers of butyl acrylate and methyl methacrylate, ethyl acrylate-N,N-dimethylacrylamide copolymers, ethyl acrylate-2-(dimethylamino)ethyl acrylate copolymers, ethyl acrylate-N,N-diethylacrylamide copolymers, ethyl acrylate-2-(diethylamino)ethyl acrylate copolymers, or mixtures of two or more thereof.

7. The partition according to claim 1, The peel strength between the porous polymer substrate and the porous coating is 50 gf / 15 mm or greater.

8. The partition according to claim 1, The adhesive layer thereof does not include inorganic particles.

9. An electrochemical device, comprising: A positive electrode, a negative electrode, and a partition inserted between the positive electrode and the negative electrode. The partition is the partition according to any one of claims 1 to 8.

10. A method for manufacturing a partition, the method comprising: Preparation of porous polymer substrates; Prepare a slurry for forming an adhesive layer comprising a first adhesive polymer and a first aqueous solvent, apply the slurry for forming the adhesive layer to at least one surface of the porous polymer substrate and dry the slurry to form the adhesive layer; and A slurry for forming a heat-resistant layer is prepared, comprising inorganic particles, a second binder polymer, a second aqueous solvent, and an organic solvent. The slurry is then applied to one surface of the binder layer and dried to form the heat-resistant layer. The first adhesive polymer comprises an acrylic polymer, and The swelling ratio of the acrylic polymer is 50% or higher.

11. The method for manufacturing a partition according to claim 10, The organic solvents mentioned include carbonate solvents.

12. The method for manufacturing a partition according to claim 10, The organic solvents mentioned therein include dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl ethyl carbonate, or mixtures thereof.

13. The method for manufacturing a partition according to claim 10, The second aqueous solvent and the organic solvent are mixed in a volume ratio of 95:5 to 80:20.

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