KR102209823B1 - Seaparator and lithium battery containing the separator - Google Patents

Abstract

Porous substrate; And a coating layer disposed on at least one surface of the porous substrate, wherein the coating layer includes a binder composition, and the elongation rate measured after standing for 10 minutes at 150° C. for a load of 50 g of the binder film made of the binder composition is 10 % Or less of a separator and a lithium battery including the same are provided.

Description

Separator and lithium battery containing the separator {Seaparator and lithium battery containing the separator}

It relates to a separator and a lithium battery employing the same.

In order to meet the miniaturization and high performance of various devices, miniaturization and weight reduction of lithium batteries are becoming important. In addition, discharge capacity, energy density, and cycle characteristics of lithium batteries are becoming important to be applied to fields such as electric vehicles. In order to meet the above use, a lithium battery having high discharge capacity per unit volume, high energy density, and excellent lifespan characteristics is required.

In a lithium battery, a separator is disposed between the positive electrode and the negative electrode to prevent a short circuit. The organic separator has a physical property that melts below 200°C, and has a function of stopping the operation of the battery due to volume change such as shrinkage or melting when the battery becomes high temperature due to internal and/or external stimulation.

As a lithium battery separator, olefin-based polymers are widely used. Although the olefin-based polymer has excellent flexibility, it has low strength when immersed in an electrolyte solution, and a short circuit of the battery may occur due to rapid thermal contraction at a high temperature of 100°C or higher.

Therefore, there is a need for a separator having improved stability by overcoming the limitations of the prior art and having improved heat resistance.

One aspect is to provide a separator having improved heat resistance.

Another aspect is to provide a lithium battery including the separator.

According to one aspect,

Porous substrate; And

It includes a coating layer disposed on at least one surface of the porous substrate,

The coating layer contains a binder composition,

A separator having an elongation of 10% or less measured after standing for 10 minutes with respect to a load of 50 g at 150° C. of the binder film made of the binder composition is provided.

According to the other side

A lithium battery including the above-described separator is provided.

According to one aspect, heat resistance of the separator may be improved by forming a coating layer including a new binder composition.

1 is a schematic diagram of a separator according to an exemplary embodiment.
Fig. 2 is a schematic diagram of a separator according to another exemplary embodiment.
3 is a schematic diagram of a lithium battery according to an exemplary embodiment.
4 is a schematic diagram of a breaking strength measuring device.
5 is a schematic diagram of a heat resistance measuring device.
<Explanation of symbols for major parts of drawings>
1: lithium battery 2: negative electrode
3: anode 4: separator
5: battery case 6: cap assembly
11: porous substrate layer 12, 13: coating layer
14, 15: adhesive layer

Hereinafter, a separator according to exemplary embodiments and a lithium battery employing the same will be described in more detail.

Polyolefin-based separators are excellent in flexibility but have a problem that heat shrinkage is large, and in consideration of the problem that flexibility is reduced in conventional separators with high Tg or high strength, the stability of the battery is improved by maintaining the flexibility of the separator while maintaining high heat resistance. As a result of examining the method that can be made, the binder film made of the binder composition was left at 150° C. for 10 minutes against a load of 50 g, and then, using a binder composition whose elongation was adjusted to 10% or less, was used on at least one side of the porous substrate. By forming the coating layer, a stable separator capable of preventing a short circuit of a battery at high temperature by suppressing heat shrinkage by realizing flexibility and heat resistance at the same time was completed. In the present specification, the binder composition included in the coating layer is defined as a concept including both a solvent-containing state and a solvent-free state.

A separator according to an embodiment is a porous substrate; And a coating layer disposed on at least one surface of the porous substrate, wherein the coating layer includes a binder composition, and the elongation rate measured after standing for 10 minutes at 150° C. for a load of 50 g of the binder film made of the binder composition is 10 % Or less. While the separator has flexibility, heat shrinkage may be suppressed and the safety of a battery may be improved by improving the heat resistance of the film.

The separator may have a structure including, for example, a porous substrate layer 11 and coating layers 12 and 13 disposed on at least one surface of the porous substrate, as shown in FIG. 1.

In the separator, the binder film made of the binder composition may have an elongation of 10% or less measured after standing at 150° C. for 10 minutes against a load of 50 g. For example, the binder film may have an elongation of 10% or less after standing for 10 minutes at 150° C. for a load of 50 g. For example, the binder film may have an elongation of 8% or less after standing for 10 minutes at 150° C. for a load of 50 g. For example, the binder film may have an elongation of 7% or less after standing for 10 minutes at 150° C. for a load of 50 g. For example, the binder film may have an elongation of 6.5% or less after standing for 10 minutes at 150° C. for a load of 50 g. For example, the binder film may have an elongation of more than 0 to 10% after being left for 10 minutes at 150° C. for a load of 50 g. For example, the separator may have an elongation of 1% to 8% after being left for 10 minutes at 150° C. for a load of 50 g. For example, the binder film may have an elongation of 2% to 7% after standing for 10 minutes at 150° C. for a load of 50 g. For example, the binder film may have an elongation of 3% to 6.5% after standing at 150° C. for 10 minutes against a load of 50 g. If the elongation of the binder film is more than 10% after standing at 150°C for 10 minutes under a load of 50 g, it is difficult to suppress melting and/or thermal contraction at high temperature of the separator.If the elongation is too small, the separator is hard and winding is difficult and the battery During manufacturing, the separator may crack. The elongation rate is a value obtained by dividing the increased length of the separator by the initial length of the separator.

As the coating layer disposed on the porous substrate in the separator additionally includes a filler, the coating layer includes a filler and a binder composition, and the binder composition has nanoparticles having an average particle diameter of 100 nm or less and a glass transition temperature of 20° C. or less. Eggplant contains a polymer binder, and the binder film made of the binder composition can have high heat resistance with an elongation of 10% or less measured after standing at 150° C. for 10 minutes against a load of 50 g, thereby suppressing heat shrinkage of the separator, Stability can be improved. In particular, the binder composition included in the coating layer in the separator may maintain a high modulus even at a high temperature of 60° C. or higher because the first polymer binder contains a functional group capable of binding to the first nanoparticle. In the binder composition, the first polymer binder does not have a special shape and may serve as a kind of matrix.

The binder composition included in the separator may increase strength, suppress heat shrinkage, and increase heat resistance by including the first nanoparticles and the first polymer binder. For example, the binder composition may have a storage modulus of 30 MPa or more at 100°C. For example, the binder composition may have a storage modulus of 30 MPa to 150 MPa at 100°C. By having a storage modulus in the above range at 100° C., the separator including the binder composition can suppress heat shrinkage at high temperatures and can implement excellent heat resistance. In addition, the binder composition may have a storage modulus of 50 MPa to 200 MPa at 40°C. If the elastic modulus of the binder composition is too high at room temperature, the separator may crack. By having the storage modulus in the above range at 40° C., cracking at room temperature of the separator including the binder composition may be prevented.

In the binder composition included in the separator, the average particle diameter of the first nanoparticles may be 1 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 5 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 10 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 20 nm to 100 nm. For example, the average particle diameter of the first nanoparticles may be 30nm to 100nm. For example, the average particle diameter of the first nanoparticles may be 30nm to 80nm. For example, the average particle diameter of the first nanoparticles may be 40nm to 80nm. For example, the average particle diameter of the first nanoparticles may be 50nm to 80nm. For example, the average particle diameter of the first nanoparticles may be 50nm to 80nm. For example, the average particle diameter of the first nanoparticles may be 60nm to 80nm. If the average particle diameter of the first nanoparticles exceeds 100 nm, the separator strength may be lowered, and if the average particle diameter is too small, manufacturing may be difficult and the solid content may be lowered, making it difficult to handle.

Heat resistance of the separator may be improved by the first nanoparticles having a glass transition temperature of 60° C. or higher in the binder composition included in the separator.

For example, in the binder composition included in the separator, the glass transition temperature of the first nanoparticles may be greater than 60°C. For example, in the binder composition, the glass transition temperature of the first nanoparticles may be 70°C or higher. For example, in the binder composition, the glass transition temperature of the first nanoparticles may be 80°C or higher. For example, in the binder composition, the glass transition temperature of the first nanoparticles may be 90°C or higher.

The first nanoparticles having a glass transition temperature of 60° C. or higher may be, for example, polymer particles. For example, the first nanoparticles having a glass transition temperature of 60°C or higher may be polyurethane particles, but are not necessarily limited thereto, and any polymer particles that can be used in the art can be used as long as the glass transition temperature is 60°C or higher. .

Alternatively, the first nanoparticles in the binder composition included in the separator may not substantially have a glass transition temperature. The fact that the first nanoparticles do not substantially have a glass transition temperature indicates that the differential scanning calorimeter (DSC) has a slight change in the slope of the heat flow according to the temperature, so that a meaningful value that can be clearly recognized cannot be measured. it means.

The first nanoparticles that do not have a glass transition temperature (Tg) refer to particles that do not soften, and include inorganic particles or polymer particles that are highly crosslinked and do not exhibit a glass transition temperature.

For example, the first nanoparticles having no glass transition temperature may be crosslinked polymethyl methacrylate. For example, the first nanoparticles that do not have a glass transition temperature are colloidal colloidal silica (SiO ₂ ), α-alumina (α-Al ₂ O ₃ ), γ-alumina (γ-Al ₂ O ₃ ), Zirconium oxide (ZrO ₂ ) and magnesium fluoride (MgF ₂ ), titania (TiO ₂ ), tin oxide (SnO ₂ ), cerium oxide (CeO ₂ ), nickel oxide (NiO), calcium oxide (CaO), zinc oxide (ZnO) ), magnesium oxide (MgO), yttrium oxide (Y ₂ O ₃ ), It may be one or more selected from the group consisting of SrTiO ₃ , BaTiO ₃ , and Mg(OH) ₂ , but is not necessarily limited thereto, and any one that can be used as an inorganic particle in the art may be used.

The purpose of using particles with a glass transition temperature of 60°C or higher or not having a glass transition temperature is to use in combination with a polymer binder with a glass transition temperature of 20°C or lower, and to suppress shrinkage of the separator, so the conditions of use of the battery are 60°C. In consideration of reaching the temperature, it is necessary to have a glass transition temperature of 60℃ or higher or not.

When the glass transition temperature is lower than 60° C., under the conditions of use of the battery, when it reaches 60° C., it softens and decreases in strength, so that shrinkage of the separator cannot be suppressed. Therefore, particles that do not soften up to a temperature of 60°C are preferred.

When the first nanoparticles are the organic particles, the first nanoparticles are the first polymer particles. In addition, when two or more different polymer particles are additionally included in the binder composition included in the separator, the additionally included polymer particles may be referred to as second polymer particles, third polymer particles, etc., if present.

In the binder composition included in the separator, since the first polymer binder has a glass transition temperature of 20° C. or less, the separator may have excellent flexibility and adhesion in addition to improved heat resistance. For example, the glass transition temperature of the first polymer binder may be -60°C to 20°C. For example, the glass transition temperature of the first polymer binder may be -60°C to less than 20°C. For example, the glass transition temperature of the first polymer binder may be -55°C to 20°C. For example, the glass transition temperature of the first polymer binder may be -50°C to 20°C. For example, the glass transition temperature of the first polymer binder may be -40°C to 20°C. For example, the glass transition temperature of the first polymer binder may be -30°C to 20°C. For example, the glass transition temperature of the first polymer binder may be -20°C to 20°C.

The first nanoparticles may contain a polar functional group capable of chemically bonding to the first polymeric binder. For example, the first nanoparticle may have a polar functional group on the surface of the particle. The polar functional group may form various bonds such as hydrogen bonds and covalent bonds with the polymer binder. For example, the polar functional group may be a carboxyl group, a hydroxyl group, an amine group, a glycidyl group, and the like, but is not limited thereto, and any polar functional group capable of forming a bond with a polymer binder may be used.

The first polymer binder may contain a polar functional group capable of chemically bonding to the first nanoparticle. For example, the first polymer binder may have a polar functional group in at least a portion of the main chain and/or side chain. The polar functional group may form various bonds such as hydrogen bonds and covalent bonds with the first nanoparticle. The polar functional group may be a carboxyl group, a hydroxyl group, an amine group, a glycidyl group, and the like, but is not necessarily limited thereto, and any polar functional group capable of forming a bond with the first nanoparticle may be used.

The first nanoparticles and the first polymer binder may form a composite. That is, the first nanoparticle and the first polymer binder are formed by reacting with each other a polar functional group on the surface of the first nanoparticle and a polar functional group on the first polymer binder in addition to a physical bond such as a van der Waals bond. It may additionally contain a chemical bond that becomes.

The binder composition included in the separator may additionally include one or more second nanoparticles having a glass transition temperature different from the first nanoparticles or not having a glass transition temperature. For example, the binder composition included in the separator may include two or more nanoparticles having a different glass transition temperature or no glass transition temperature. For example, the binder composition included in the separator may include three or more nanoparticles having different glass transition temperatures or no glass transition temperatures.

The binder composition included in the separator may additionally include at least one second polymer binder having a glass transition temperature different from that of the first polymer binder. For example, the binder composition included in the separator may include two or more polymer binders having different glass transition temperatures. For example, the binder composition included in the separator may include three or more polymer binders having different glass transition temperatures.

However, unless specifically stated below, the first polymer binder refers to the entire polymer binder further including a second polymer binder. This concept is the same for the first nanoparticle.

The binder composition included in the separator may include 7 to 60 parts by weight of the solid content of the first nanoparticles based on 100 parts by weight of the solid content of the first polymer binder. For example, the binder composition included in the separator may include 7 to 60 parts by weight of the first nanoparticles based on 100 parts by weight of the first polymer binder. For example, in the binder composition included in the separator, 10 to 60 parts by weight of the first nanoparticles may be included with respect to 100 parts by weight of the first polymer binder based on the solid content. For example, the binder composition included in the separator may include 10 to 50 parts by weight of the first nanoparticles based on 100 parts by weight of the first polymer binder. For example, the binder composition included in the separator may include 15 to 45 parts by weight of the first nanoparticles per 100 parts by weight of the first polymer binder based on the solid content. If the content of the first nanoparticles is too small, the shrinkage rate of the separator may increase, and if the content of the first nanoparticles is too high, the separator may crack.

In the negative electrode of a lithium battery, it is often used in combination with a carbon material for the purpose of suppressing the effect of a material having a large volume change during charging and discharging. However, when the proportion of use of a metal-based negative active material is high, the electrode tends to expand and lithium Since the battery may be exposed to high temperatures, it may be necessary to increase the ratio of the first nanoparticle/first polymer binder in the binder composition included in the separator to prevent shrinkage of the separator. In addition, when the use ratio of the metallic negative active material is small, since the expansion of the electrode is relatively small compared to the 100% metallic negative active material, the ratio of the first nanoparticles/first polymer binder is reduced, so that the binder composition contained in the separator is By smoothing, the flexibility of the separator can be improved. In addition, when the glass transition temperature of the first polymer binder is high, the separator becomes hard. Therefore, in order to secure the flexibility of the separator, it is necessary to reduce the ratio of the first nanoparticle/first polymer binder.

In the binder composition included in the separator, the first nanoparticles may be dispersed in the first polymer binder. The first nanoparticles may have a form dispersed in a matrix made of a first polymer binder. The first nanoparticles may exist alone within the first polymer binder, and may have a form dispersed in a matrix made of the first polymer binder after a plurality of first nanoparticles are aggregated to form secondary particles. The first nanoparticles may be uniformly dispersed in the first polymer binder.

For example, the first nanoparticles may be irregularly dispersed inside the first polymer binder.

For example, the binder composition included in the separator includes a first polymer binder assembly formed from at least two or more first polymer binders, and the first nanoparticles are included in the first polymer binder assembly. It can be placed at the interface between polymer binders. For example, the first nanoparticles may be disposed between a plurality of first polymer binders.

For example, the first polymer may be irregularly disposed on an interface between the plurality of first polymer binders.

Alternatively, the first nanoparticles may be disposed at the interface between the first polymer binder and other battery components. For example, the first nanoparticles may be present at an interface between the first polymer binder and the electrolyte. For example, the first nanoparticles may exist at an interface between the first polymer binder and the electrode active material. For example, the first nanoparticles may exist at an interface where the first polymer binder and the conductive material are in contact. For example, the first polymer may be irregularly disposed at the interface with the other battery components.

For example, the first nanoparticles have a glass transition temperature of 60° C. or higher or do not have a glass transition temperature, and a polymer material is not particularly limited as long as they are polymer particles having an average particle diameter of 100 nm or less. For example, the first nanoparticle may include a water-dispersible functional group. The first nanoparticles may be prepared by various methods such as emulsion polymerization and solution polymerization, and are not particularly limited. In addition, the reaction conditions used in the above method can be appropriately adjusted by a person skilled in the art.

For example, the first nanoparticles may be water dispersions such as (meth)acrylic acid ester-based aqueous dispersion, diene-based latex, ethylene-acrylate, carboxy-modified polyethylene, polyurethane, nylon, polyester, etc., and these may be crosslinking agents Can be crosslinked by

For example, the first nanoparticles may be prepared by polymerizing a radically polymerizable monomer in emulsion polymerization, suspension polymerization, dispersion polymerization, etc. in the case of a (meth)acrylic acid ester-based aqueous dispersion or diene-based latex. have.

The (meth)acrylic acid ester-based aqueous dispersion can be prepared by polymerizing an ethylenically unsaturated carboxylic acid ester and an ethylenically unsaturated carboxylic acid ester and other monomers capable of copolymerization.

Specific examples of ethylenically unsaturated carboxylic acid esters include methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, and isoacrylate. Acrylic acid alkyl esters and substituted alkyl esters such as amyl, n-hexyl acrylic acid, 2-ethyl hexyl acrylic acid, isobornyl acrylic acid, hydroxypropyl acrylic acid, and lauryl acrylic acid; Methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate , Methacrylic acid alkyl esters and substituted alkyl esters such as n-hexyl methacrylate, 2-ethyl hexyl methacrylate, hydroxypropyl methacrylic acid, and lauryl methacrylate; Methyl crotonate, ethyl crotonate, propyl crotonate, butyl crotonate, isobutyl crotonate, n-amyl crotonate, isoamyl crotonate, n-hexyl crotonate, 2-ethylhexyl crotonate, crotonic acid Crotonic acid alkyl esters and substituted alkyl esters such as hydroxypropyl; Amino group-containing methacrylic acid esters such as dimethyl amino ethyl methacrylate and diethyl amino ethyl methacrylate; Alkoxy group-containing methacrylic acid esters such as methoxy polyethylene glycol mono methacrylic acid ester; unsaturated dicarboxylic acid monoesters such as monooctyl maleate, monobutyl maleate, monooctyl itaconic acid, etc., but are not necessarily limited thereto. Anything that can be used as an ethylenically unsaturated carboxylic acid ester in the technical field is possible.

As a monomer copolymerizable with ethylenic unsaturated carboxylic acid ester, unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; Carboxylic acid esters having two or more carbon-carbon double bonds such as diethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate; Styrene monomers such as styrene, chloro styrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, vinyl methyl benzoate, vinyl naphtharene, chloromethyl styrene, hydroxy methyl styrene, α-methyl styrene, and divinyl benzene; Amide monomers such as acrylamide, N-methylol acrylamide, and acrylamide-2-methyl propane sulfonic acid; Α,β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; Olefins such as ethylene and propylene; Diene-based monomers such as butadiene and isoprene; Halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; Vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl benzoate; Vinyl ethers such as allyl glycidyl ether, methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether; Vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; It may be a heterocycle-containing vinyl compound such as N-vinyl pyrrolidone, vinyl pyridine, vinyl imidazole, etc., but is not necessarily limited thereto, and any one that can be used as a monomer copolymerizable with ethylenically unsaturated carboxylic acid ester in the art It is possible.

Among these copolymerizable monomers, at least one selected from the group consisting of carboxylic acid esters having two or more carbon-carbon double bonds, amide monomers, α,β-unsaturated nitrile compounds, and vinyl ethers may be used. .

The diene-based latex is a copolymer obtained from an aromatic vinyl unit, a conjugated diene unit, an ethylenically unsaturated carboxylic acid ester unit, and an ethylenically unsaturated carboxylic acid unit.

The aromatic vinyl unit may be, for example, styrene, α-methyl styrene, p-methyl styrene, vinyl toluene, chloro styrene, divinyl benzene, and the like, and for example, styrene may be used.

The conjugated diene unit may be a conjugated diene compound such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, and chloroprene, and in particular, may be 1,3-butadiene.

The ethylenically unsaturated carboxylic acid ester unit is, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, and (meth)acrylic acid. n-butyl, (meth)acrylate i-butyl, (meth)acrylate n-amyl, (meth)acrylate i-amyl, (meth)acrylate hexyl, (meth)acrylate 2-hexyl, (meth) Octyl acrylate, i-nonyl (meth)acrylate, decyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, ethylene glycol (meth)acrylate, etc. It may be a (meth) acrylic acid ester, and the like. For example, it may be methyl (meth)acrylate, butyl (meth)acrylate, and the like. In particular, methyl (meth)acrylate can be used.

The ethylenically unsaturated carboxylic acid unit may be acrylic acid, (meth)acrylic acid, itaconic acid, fumaric acid, maleic acid, or the like.

The first nanoparticle may contain another polar functional group-containing compound unit copolymerizable with the above-described monomer. Examples of the polar functional group-containing compound unit include alkyl amides of ethylenically unsaturated carboxylic acids such as (meth)acrylamide and N-methylol acrylamide; Carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate; Acid anhydrides, monoalkyl esters, and monoamides of ethylenically unsaturated dicarboxylic acids; Amino alkyl esters of ethylenically unsaturated carboxylic acids such as amino ethyl acrylate, dimethyl amino ethyl acrylate, and butyl amino ethyl acrylate; Aminoalkyl amides of ethylenically unsaturated carboxylic acids such as amino ethyl acryl amide, dimethyl amino methyl methacryl amide, and methyl amino propyl methacryl amide; Vinyl cyanide compounds such as (meth)acrylonitrile and α-crole acrylonitrile; It may be an unsaturated aliphatic glycidyl ester such as glycidyl (meth)acrylate, but is not necessarily limited thereto, and any compound containing a polar functional group in the art may be used as long as it can be used for preparing a copolymer.

The above-described monomer must contain a polar functional group necessary for chemically bonding with the first polymer binder. The polar functional group may be a polar functional group capable of chemically bonding to the first polymer binder, or bonding the first nanoparticle and the first polymer binder through a binder. For example, the monomer containing a polar functional group may be a monomer containing an OH group, a monomer containing a carboxyl group, a monomer containing a glycidyl group, a monomer containing an amino group, etc., but is not necessarily limited thereto, and a monomer containing a polar functional group in the art Anything that can be used as is possible.

The first nanoparticles may be impregnated in the electrolyte and not swelled. For example, the swelling degree of the first nanoparticles with respect to the electrolyte may be 4 times or less. For example, the degree of swelling of the first nanoparticles with respect to the electrolyte may be 3 times or less. For example, the degree of swelling of the first nanoparticles with respect to the electrolyte may be 2 times or less. When the swelling degree of the first nanoparticles with respect to the electrolyte solution is too large, the Tg of the first nanoparticles may be lowered to 60°C or less. Therefore, when the use temperature of the battery becomes high, it may be difficult to suppress heat shrinkage of the separator.

In order to suppress the degree of swelling of the first nanoparticles in the electrolyte, a diene-based latex in which styrene and butadiene are 80% by weight or more of the total monomer may be used. When an acrylic acid ester-based aqueous dispersion is used, an ethylenically unsaturated carboxylic acid ester esterified with a higher alcohol having 6 or more carbon atoms, and a polymer containing 80% by weight or more, for example, 85% by weight or more of the total monomers, are used. I can. In addition, a crosslinked structure may be introduced into the first nanoparticles by using a bifunctional monomer having two or more carbon-carbon double bonds. The bifunctional monomer having two or more carbon-carbon double bonds is 2-vinyl benzene, or two or more carbon-carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate. It may be a carboxylic acid ester having a double bond. For example, 2-vinyl benzene can be used to obtain hard particles.

In addition, for example, the first nanoparticles are polyethylene, polypropylene, ethylene propylene copolymer, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyacrylonitrile, polytetrafluoroethylene, polymethyl methacrylate, Polyvinyl acetate, polyisoprene, polychloroprene, polyester, polycarbonate, polyamide, polyacrylate, polymethylmethacrylate, polyurethane, acrylonitrile-butadiene-styrene copolymer, polyoxyethylene, polyoxy Methylene, polyoxypropylene, styrene-acrylonitrile copolymer, acrylonitrile-styrene-acrylate copolymer, styrene-butadiene copolymer, acrylated styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylic Lonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, fluorine rubber, polyvinylpyrrolidone, polyepicrohydrin, polyphosphagen, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene , Polysulfone, polyvinyl alcohol, polyvinyl acetate, thermoplastic polyester rubber (PTEE), carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropylcellulose, and diacetylcellulose, but may include at least one selected from the group consisting of It is not limited to these, and any one that can be used as a polymer particle in the art may be used. In addition, the first nanoparticles described above may be crosslinked polymers.

The first nanoparticles may be aqueous polymer particles or non-aqueous polymer particles. The aqueous polymer particles refer to water-dispersible polymer particles that can be easily dispersed or dissolved in water. Non-aqueous polymer particles are the opposite.

For example, the first nanoparticle may be a (meth)acrylic acid ester-based aqueous dispersion, a Zene-based latex, or an aqueous dispersion such as polyurethane, nylon, polyester, etc. The first nanoparticle is used to prepare the first nanoparticle. The monomer is, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, butyl methacrylate, ethyl methacrylate, 2-ethylhexyl methacrylate, etc. Unsaturated carboxylic acid alkyl ester; Cyano group-containing ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-cyanoethyl acrylonitrile; Conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene; Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and citraconic acid, and salts thereof; Aromatic vinyl monomers such as styrene, yl styrene, and vinyl naphthalene; Fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; Vinylpyridine; Non-conjugated diene monomers such as vinyl norbornene, dicyclopentadiene, and 1,4-hexadiene; Α-olefins such as ethylene and propylene; Ethylenically unsaturated amide monomers such as methacrylamide; Isocyanate-based monomers such as methylene diphenyl diisocyanate and toluene diisocyanate; Polyol-based monomers such as glycerin, ethylene glycol, and propylene glycol; And the like, but are not necessarily limited thereto, and any monomer that can be used in the art may be used.

The first nanoparticles may be prepared by various methods such as emulsion polymerization, solution polymerization, suspension polymerization, and dispersion polymerization, and are not particularly limited. In addition, the reaction conditions used in the above method can be appropriately adjusted by a person skilled in the art.

In addition, the first nanoparticles are polymer particles with a Tg of 60°C or higher, and are used to emulsify a polymer dissolved in a solvent, or to heat and dissolve a polymer having crystallinity above the melting point in a poor solvent, and then cool it. It can be produced by a method of precipitating at, or a method of obtaining a polymer containing a dissociable functional group into particles in an alkaline solution.

The first polymer binder is added to impart flexibility to the separator and at the same time secure adhesion between the porous substrate and the electrode, and the polymer material is not particularly limited if it is a polymer binder having a glass transition temperature of 20°C or less. For example, the first polymer binder may include a water-dispersible functional group. The first polymer binder may be manufactured by various methods such as emulsion polymerization and solution polymerization, and is not particularly limited. In addition, the reaction conditions used in the above method can be appropriately adjusted by a person skilled in the art. The first polymer binder may be an elastomer. For example, the monomer used in the manufacture of the first polymer binder is a monomer that can be used for radical polymerization. The monomers used in the manufacture of the first polymer binder may be used in combination with the monomers used in the manufacture of the first nanoparticles described above.

The monomer used in the manufacture of the first polymer binder necessarily contains a polar functional group necessary to chemically bond with the first nanoparticle. The polar functional group may be a polar functional group capable of chemically binding to the first nanoparticle, or bonding the first nanoparticle and the first polymer binder through a binder. For example, the monomer containing the polar functional group may be a monomer containing an OH group, a monomer containing a carboxyl group, a monomer containing a glycidyl group, a monomer containing an amino group, etc., but is not necessarily limited thereto and contains a polar functional group in the art. Anything that can be used as a monomer can be used.

The first polymer binder may not be swelled by being impregnated with the electrolyte. For example, the swelling degree of the first polymer binder with respect to the electrolyte may be 4 times or less. For example, the degree of swelling of the first polymer binder with respect to the electrolyte may be 3 times or less. For example, the degree of swelling of the first polymer binder with respect to the electrolyte may be 2 times or less. When the swelling degree of the first polymer binder with respect to the electrolyte solution is too large, the strength of the binder decreases, and it may be difficult to suppress shrinkage of the separator including the binder composition for a secondary battery.

The swelling degree is obtained from the weight ratio of the first polymer binder before and after immersion in the electrolyte. That is, it shows the degree of how much the first polymeric binder absorbs the electrolyte.

In order to suppress the degree of swelling of the first polymer binder in the electrolyte, a diene-based latex in which styrene and butadiene are 80% by weight or more of the total monomer may be used. When an acrylic acid ester-based aqueous dispersion is used, an ethylenically unsaturated carboxylic acid ester esterified with a higher alcohol having 6 or more carbon atoms, and a polymer containing 80% by weight or more, for example, 85% by weight or more of the total monomers, are used. In addition, for example, the first polymer binder is styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber , Fluororubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylate, polyacrylonitrile , Polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylmethylcellulose, hydroxypropyl It may include at least one selected from the group consisting of cellulose and diacetylcellulose, but is not limited thereto, and any one that can be used as a polymer binder in the art may be used.

However, in the case of polyvinylidene fluoride (PVDF), the strength is high, but when used as a binder because it is too hard, it may cause cracking of the separator and may be excluded.

The first polymer binder may be an aqueous polymer binder or a non-aqueous polymer binder. The water-based polymer binder refers to a water-dispersible polymer binder that can be easily dispersed or dissolved in water.

The monomers used to prepare the first polymer binder include, for example, methyl methacrylate, butyl methacrylate, ethyl methacrylate, and ethylhexyl methacrylate, and other alkyl esters of ethylenic unsaturated carboxylic acids; Cyano group-containing ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-cyanoethyl acrylonitrile; Conjugated diene monomers such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene; Ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, fumaric acid, and citraconic acid, and salts thereof; Aromatic vinyl monomers such as styrene, yl styrene, and vinyl naphthalene; Fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; Vinylpyridine; Non-conjugated diene monomers such as vinyl norbornene, dicyclopentadiene, and 1,4-hexadiene; Α-olefins such as ethylene and propylene; Ethylenically unsaturated amide monomers such as methacrylamide; And the like, but are not necessarily limited thereto, and any monomer that can be used in the art may be used.

The first polymer binder may be manufactured by various methods such as emulsion polymerization and solution polymerization, and is not particularly limited. In addition, the reaction conditions used in the above method can be appropriately adjusted by a person skilled in the art.

In the binder composition for secondary batteries, the gel content of the first polymer binder may be 90% or less. In the binder composition for secondary batteries, the first polymer binder containing a polar functional group capable of chemically binding to the first nanoparticle and the first nanoparticle are used in combination to suppress the shrinkage of the separator. May have high mobility until chemically combined with the first nanoparticle in order to facilitate bonding with the first nanoparticle.

Therefore, when the first polymer binder is a diene-based latex, the gel content may be 90% or less. For example, when the first polymeric binder is a diene-based latex, the gel content may be 80% or less. When the first polymeric binder is a diene-based latex, the gel content may be 75% or less.

In addition, when the first polymer binder is an acrylic acid ester emulsion, since a crosslinked structure is introduced into the polymer binder, the amount of bifunctional monomer used may be reduced. For example, the amount of the bifunctional monomer used may be 1% by weight or less, for example, 0.5% by weight or less of the total weight of the monomer. The bifunctional monomer is a bifunctional monomer having two or more carbon-carbon double bonds in one molecule, 2-vinyl benzene, or ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, trimethylol propane It may be a carboxylic acid ester having two or more carbon-carbon double bonds such as triacrylate.

For example, the first polymer binder can be prepared by general emulsion polymerization, suspension polymerization, and dispersion polymerization.

Emulsifiers or dispersants used in emulsion polymerization, suspension polymerization, and dispersion polymerization may be those used in ordinary emulsion polymerization, suspension polymerization, dispersion polymerization, and the like. Benzene sulfonates, such as sodium dodecyl benzene sulfonate and sodium dodecyl phenyl ether sulfonate, for example; Alkyl sulfates such as sodium lauryl sulfate and sodium tetra dodecyl sulfate; Sulfosuccinates such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate; fatty acid salts such as sodium laurate; Ethoxy sulfate salts such as polyoxyethylene lauryl ether sulfate sodium salt and polyoxyethylene nonyl phenyl ether sulfate sodium salt; Alkane sulfonate; Alkyl ether phosphoric acid ester sodium salt; Nonionic emulsifiers such as polyoxyethylene nonyl phenyl ether, polyoxyethylene sorbitan lauryl ester, polyoxyethylene-polyoxypropylene block copolymer, and the like. These may be used alone or in combination of two or more. The amount of the emulsifier or dispersant may be arbitrarily set, and thus 0.01 to 10 parts by weight may be used with respect to 100 parts by weight of the total monomer, but the emulsifier or dispersant may be omitted depending on polymerization conditions.

As the molecular weight modifier, in the case of a diene-based latex, for example, mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and n-octyl mercaptan; Halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; Terpinolene; α-methyl styrene dimer; and the like.

Such a molecular weight modifier may be added before or during polymerization. The molecular weight modifier may be used in a ratio of 0.01 to 10 parts by weight, for example, 0.1 to 5 parts by weight, based on 100 parts by weight of the monomer.

In the acrylic acid ester-based aqueous dispersion, since the molecular weight can be controlled by the polymerization reaction temperature and the rate of addition of the monomer, the molecular weight control agent can be omitted.

The polymerization initiator may be one used in ordinary emulsion polymerization, dispersion polymerization, suspension polymerization, and the like. For example, the polymerization initiator is a persulfate salt such as potassium persulfate and ammonium persulfate; Hydrogen peroxide; It may be an organic peroxide such as benzoyl peroxide and cumene hydroperoxide, and these may be used alone or as a redox polymerization initiator in combination with a reducing agent such as sodium sulfite, sodium thiosulfate, and ascorbic acid. . In addition, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2, Azo compounds such as 4-dimethylvaleronitrile), dimethyl-2,2'-azobisisobutyrate, and 4,4'-azobis(4-cyanopentanoic acid); 2,2'-azobis(2-amino-di-propane)dihydrochloride, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis(N Amidine compounds such as ,N'-dimethyleneisobutylamidine)dihydrochloride; Etc. can be used. The polymerization initiator can be used alone or in combination of two or more. The amount of the polymerization initiator used may be 0.01 to 10 parts by weight, for example 0.1 to 10 parts by weight, for example 0.1 to 5 parts by weight, based on 100 parts by weight of the total monomer weight.

Anti-aging agents, preservatives, anti-foaming agents, etc. may be optionally added to the binder composition included in the separator.

The binder composition included in the separator may additionally include a binder. The binder may react with a polar functional group present in the first nanoparticle and/or the first polymer binder to form a covalent bond. For example, the first nanoparticle and the first polymer binder may be more firmly bonded by a binder. In the binder composition included in the separator, the binder may be present in the form of a reaction product with the first nanoparticles and/or the first polymer binder. In the case of bonding using the binder, the binder is capable of crosslinking the first nanoparticles having a glass transition temperature of 60°C or higher and a first binder polymer having a glass transition temperature of 60°C or lower. 1 Any binder that can react with the reactive functional groups introduced into the polymer binder can be used.

The binder may include a functional group having reactivity with a polar functional group. For example, the binder may include a functional group having reactivity with a carboxyl group. For example, the binder may include a functional group having reactivity with a hydroxyl group. For example, the binder may include a functional group having a reactive amine group. For example, the binder may include a functional group having reactivity with water.

For example, the binder may be a carbodiimide-based compound. The binder is, for example, N,N'-di-o-tolylcarbodiimide, N,N'-difetylcarbodiimide, N,N'-dioctyldecylcarbodiimide, N,N'-di-2, 6-diketylphenylcarbodiimide, N-tolyl-N'cyclohexylcarbodiimide, N,N'-di-2,6-diisopropylphenylcarbodiimide, N,N'-di-2,6 -Di-tertiary-butylphenylcarbodiimide, N-tolyl-N'-phenylcarbodiimide, N,N'-di-p-nitrophenylcarbodiimide, N,N'-di-p-aminophenyl Carbodiimide, N,N'-di-p-hydroxyphenylcarbodiimide, N,N'-di-cyclohexylcarbodiimide, N,N'-di-p-tolylcarbodiimide, p-phenyl Ren-bis-di-o-tolylcarbodiimide, p-phenylene-bisdicyclohexylcarbodiimide, hexamethylene-bisdicyclohexylcarbodiimide, ethylene-bisdiphenylcarbodiimide, benzene-2, 4-diisocyanato-1,3,5-tris(1-methylethyl) homopolymer, 2,4-diisocyanato-1,3,5-tris(1-methylethyl) and 2,6-diiso It may be a copolymer of propyl diisocyanate or a combination thereof, but is not limited thereto, and any one that can be used as a carbodiimide compound in the art may be used. In the binder, the carbodiimide compound may be present in the form of a reaction product with the first nanoparticle and/or the first polymer binder. For example, the diimide bond of the carbodiimide-based compound may be present in the form of a reaction product in which a new covalent bond is formed by reacting with a polar functional group on the surface of the first nanoparticle.

For example, the binder may be a silane coupling agent that is a silane compound.

For example, the silane coupling agent may include at least one selected from the group consisting of an alkoxy group, a halogen group, an amino group, a vinyl group, a glycidoxy group, an acyloxy group, and a hydroxyl group.

For example, the silane coupling agent may be at least one selected from the group consisting of vinylalkylalkoxysilane, epoxyalkylalkoxysilane, mercaptoalkylalkoxysilane, vinylhalosilane, and alkylacyloxysilane.

For example, the silane coupling agent is vinyl tris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, β-(3,4- Epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, vinyl It may be one selected from the group consisting of trichlorosilane and methyltriacetoxysilane, but is not limited thereto, and any silane coupling agent that can be used in the art may be used.

For example, a silane compound, a hydrazine compound, an isocyanate compound, a melamine compound, a urea compound, an epoxy compound, a carbodiimide compound, and an oxazoline compound may be used, but are not necessarily limited thereto, and as a binder in the art. Anything that can be used can be used. These compounds may be used alone or in combination.

In particular, a silane compound, an oxazoline compound, a carbodiimide compound, an epoxy compound, and an isocyanate compound can be used.

As other binders, those having self-crosslinking properties or those having a polyvalent coordination site can also be used.

In addition, a commercially available binder can also be used.

Specifically, as the hydrazine compound, Otsuka Chemical's APA series (APA-M900, APA-M90, APA-P250, APA-P280, etc.) can be used.

As the isocyanate compound, Basonat (BASONAT) PLR88 from BASF, Vasonat HW-110, and Baihyjur (BB) from Sumitomo Bayel Urethane can be used.

As a melamine compound, Mitsui Cytec's Cymel 35, etc. can be used.

As the urea compound, beccamine series manufactured by DIC can be used.

As an epoxy compound, Nagase Chemtech's Denacor series (EM-1500, EM-101, etc.), Adeggene EM-0517, EM-0526, EM-0.51R, EM-11-50B, etc. manufactured by ADEKA can be used.

As a carbodiimide compound, Nisshinbo Chemical's carbonilite series (SV-02, V-02, V-02-L2, V-04, E-01, E-02, V-01, V-03, V- 07, V-0.09, V-0.05) can be used.

As an oxazoline compound, Nippon Shokubai's Epocross Series (WS-500, WS-700, K-10100E, K-1020E, K-10300E, K-20110E, K-2020E, KG-20E) can be used. .

These are commercially available as dispersions or solutions containing a binder.

For example, the content of the binder used to manufacture the battery binder included in the separator may be 10% by weight or less based on the total weight of the reactant based on the dry weight. For example, the content of the binder used for preparing the binder may be 5% by weight or less based on the total weight of the reactant based on the dry weight. For example, the content of the binder used to prepare the binder may be 3% by weight or less based on the total weight of the reactants based on the dry weight. For example, the content of the binder used to prepare the binder may be greater than 0 to 3% by weight based on the total weight of the reactant based on the dry weight. If the content of the binder is too low, polar functional groups required for stabilization of the particles may be insufficient, and if the content of the binder is too high, a stable electrode slurry cannot be prepared.

The binder composition obtained by combining the above-described first nanoparticles having a glass transition temperature of 60°C or higher and a first polymer binder having a glass transition temperature of 20°C or lower is 0.1% to 50% by weight based on the total weight of the coating layer included in the separator. It may be included in weight percent. For example, the content of the binder composition may be 1% to 50% by weight based on the total weight of the coating layer. For example, the content of the binder composition may be 1% to 40% by weight based on the total weight of the coating layer. For example, the content of the binder composition may be 1% to 30% by weight based on the total weight of the coating layer. For example, the content of the binder composition may be 1% to 20% by weight based on the total weight of the coating layer. For example, the content of the binder composition may be 1% to 10% by weight based on the total weight of the coating layer. If the content of the binder composition is too small in the coating layer, the filler cannot be sufficiently bound, and if the content of the binder composition is too high, the mechanical properties of the separator may be deteriorated.

In the separator, the coating layer includes a filler having an average particle diameter of 300 nm or more. The filler is not particularly limited, and any filler that can be used in the art may be used.

The filler may serve as a support in the separator. When the separator is about to shrink at a high temperature, the filler supports the separator to suppress the shrinkage of the separator. When the separator includes a filler, sufficient porosity can be secured and mechanical properties can be improved. A lithium battery including such a separator can secure improved stability.

The average particle diameter of the filler may be 300nm to 2㎛. For example, the average particle diameter of the filler may be 300nm to 1.5㎛. For example, the average particle diameter of the filler may be 300nm to 1.0㎛. This average particle diameter can be defined as the number average particle diameter of the particles measured using a laser scattering particle size distribution meter (for example, Horiba's LA-920). By using the filler having the average particle diameter, it is easy to form the coating layer to an appropriate thickness, and the separator in which the coating layer including the filler is disposed may have an appropriate porosity. When the average particle diameter of the filler is less than 300 nm, mechanical properties of the separator may be deteriorated.

The content of the filler may be 50% to 99.9% by weight based on the total weight of the coating layer. For example, the content of the filler may be 50% to 99% by weight based on the total weight of the coating layer. For example, the content of the filler may be 60% to 99% by weight based on the total weight of the coating layer. For example, the content of the filler may be 70% to 99% by weight based on the total weight of the coating layer. For example, the content of the filler may be 80% to 99% by weight based on the total weight of the coating layer. For example, the content of the filler may be 90% to 99% by weight based on the total weight of the coating layer. In the content range of the filler, physical properties of the separator may be improved.

The filler may be an inorganic particle, an organic particle, or a combination thereof.

The inorganic particles may be metal oxides, metalloid oxides, or a combination thereof. Specifically, the inorganic particles may be alumina, silica, boehmite, magnesia, or a combination thereof. The alumina, silica, etc. have a small particle size, so it is easy to prepare a dispersion. For example, the inorganic particles are Al ₂ O ₃ , SiO ₂ , TiO ₂ , SnO ₂ , CeO ₂ , NiO, CaO, ZnO, MgO, ZrO ₂ , Y ₂ O ₃ , It may be SrTiO ₃ , BaTiO ₃ , MgF ₂ , Mg(OH) ₂ or a combination thereof.

The inorganic particles may be spherical, plate, fiber, or the like, but are not limited thereto, and any form usable in the art may be used.

The plate-shaped inorganic particles include, for example, alumina and boehmite. In this case, the reduction of the separator area at high temperature can be further suppressed, a relatively large porosity can be secured, and characteristics can be improved during penetration evaluation of the lithium battery.

When the inorganic particles are plate-like or fibrous, the aspect ratio of the inorganic particles may be about 1:5 to 1:100. For example, the aspect ratio may be about 1:10 to 1:100. For example, the aspect ratio may be about 1:5 to 1:50. For example, the aspect ratio may be about 1:10 to 1:50.

The ratio of the length of the long axis to the short axis in the flat surface of the plate-shaped inorganic particles may be 1 to 3. For example, the ratio of the length of the long axis to the short axis in the flat surface may be 1 to 2. For example, the ratio of the length of the major axis to the minor axis in the flat surface may be about 1. The aspect ratio and the ratio of the length of the long axis to the short axis may be measured through a scanning electron microscope (SEM). Separator shrinkage may be suppressed in the aspect ratio and the length range of the short axis to the long axis, relatively improved porosity, and penetration characteristics of the lithium battery may be improved.

When the inorganic particles have a plate shape, an average angle of the flat surface of the inorganic particles to one surface of the porous substrate may be 0 degrees to 30 degrees. For example, the angle of the inorganic particle flat surface with respect to one surface of the porous substrate may converge to 0 degrees. That is, one surface of the porous substrate and the flat surface of the inorganic particles may be parallel. For example, when the average angle of the flat surface of the inorganic compound to one surface of the porous substrate is within the above range, heat shrinkage of the porous substrate can be effectively prevented, thereby providing a separator with reduced shrinkage.

The organic particles may be cross-linked polymers. The organic particles may be highly cross-linked polymers that do not exhibit a glass transition temperature (Tg). When a highly crosslinked polymer is used, heat resistance is improved and shrinkage of the porous substrate can be effectively suppressed at high temperatures.

The organic particles include, for example, an acrylate compound and a derivative thereof, a diallyl phthalate compound and a derivative thereof, a polyimide compound and a derivative thereof, a polyurethane compound and a derivative thereof, a copolymer thereof, or a combination thereof. It may include, but is not limited to these, and any one that can be used as a filler in the art may be used. For example, the filler may be crosslinked polystyrene particles or crosslinked polymethylmethacrylate particles.

The filler may be secondary particles formed by aggregation of primary particles. In the separator including the filler, which is the secondary particle, the porosity of the coating layer is increased, thereby providing a lithium battery having excellent high output characteristics.

The coating layer may be formed by mixing the filler and the binder composition to prepare a composition for forming a coating layer, and then applying it on a porous substrate. A method of applying the composition for forming a coating layer is not particularly limited, and any method that can be used in the art may be used. For example, it may be formed by a method such as printing, compression, press-fitting, roller coating, blade coating, bristles coating, dipping coating, spray coating, or flow flue coating.

The coating layer may be present on one or both surfaces of the porous substrate. The thickness of the coating layer may be 0.1 to 5 μm, 0.5 to 5 μm, or 1 to 5 μm based on one surface. When the thickness of the coating layer satisfies the above range, a lithium battery including the same may prevent improved heat resistance and a decrease in capacity of the lithium battery.

In the separator, the porous substrate may be a membrane containing polyolefin. Polyolefin has an excellent short-circuit prevention effect and can also improve battery stability through a shutdown effect. For example, the porous substrate may be a film made of a resin such as polyethylene, polypropylene, polybutene, polyolefin such as polyvinyl chloride, and a mixture or copolymer thereof, but is not necessarily limited thereto and may be used in the art. Any porous membrane that can be used is possible. For example, a porous membrane made of a polyolefin resin; A porous membrane made of polyolefin-based fibers; Nonwoven fabric containing polyolefin; Aggregates of insulating material particles, etc. may be used. For example, the porous membrane comprising the polyolefin has excellent applicability of a polymer solution for preparing a polymer coating layer formed on the base layer, and increases the ratio of active materials in the battery by reducing the thickness of the separator to increase capacity per volume. You can increase it.

For example, the polyolefin used as the material for the porous substrate may be a homopolymer such as polyethylene or polypropylene, a copolymer, or a mixture thereof. Polyethylene may be a low-density, medium-density, high-density polyethylene, and from the viewpoint of mechanical strength, a high-density polyethylene may be used. In addition, two or more types of polyethylene may be mixed for the purpose of imparting flexibility. The polymerization catalyst used to prepare the polyethylene is not particularly limited, and a Ziegler-Natta catalyst, a Phillips catalyst, a metallocene catalyst, or the like may be used. From the viewpoint of achieving both mechanical strength and high permeability, the weight average molecular weight of polyethylene may be 100,000 to 12 million, for example, 200,000 to 3 million. Polypropylene may be a homopolymer, a random copolymer, or a block copolymer, and may be used alone or in combination of two or more. In addition, the polymerization catalyst is not particularly limited, and a Ziegler-Natta catalyst, a metallocene catalyst, or the like can be used. Also, stereoregularity is not particularly limited, and isotactic, syndiotactic, or atactic may be used, but inexpensive isotactic polypropylene may be used. Further, polyolefins other than polyethylene or polypropylene, and additives such as antioxidants can be added to the polyolefin within the range not impairing the effects of the present invention.

For example, the porous substrate includes a polyolefin such as polyethylene and polypropylene, and a multilayer film of two or more layers may be used, and a polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, a polypropylene/polyethylene A mixed multilayer film such as a /polypropylene three-layer separator may be used, but is not limited thereto, and any material and composition that can be used as a porous substrate in the art may be used.

The thickness of the porous substrate in the separator may be 1 μm to 100 μm. For example, the thickness of the porous substrate layer may be 1 μm to 30 μm. For example, the thickness of the porous substrate layer may be 5 μm to 30 μm. If the thickness of the porous substrate layer is less than 1 μm, it may be difficult to maintain mechanical properties, and if the thickness of the porous substrate layer is more than 100 μm, battery resistance may increase.

In the separator, the porosity of the porous substrate may be 5% to 95%. If the porosity is less than 5%, battery resistance may increase, and if the porosity is more than 95%, it may be difficult to maintain the mechanical properties of the porous substrate layer.

In the separator, the pore size of the porous substrate may be 0.01 μm to 50 μm. For example, in the separator, the pore size of the porous substrate layer may be 0.1 μm to 20 μm. If the pore size is less than 0.01 μm, battery resistance may increase, and if the pore size is more than 50 μm, it may be difficult to maintain the mechanical properties of the porous substrate layer.

After allowing the separator to stand at 130° C. for 10 minutes, take it out, cool it at room temperature, and then the thermal contraction rate of the separator in the long axis direction may be 4% or less. For example, after allowing the separator to stand at 130° C. for 10 minutes, take it out, cool it at room temperature, the separator heat shrinkage in the long axis direction may be 3% or less. For example, after allowing the separator to stand at 130° C. for 10 minutes, take it out, cool it at room temperature, and then the thermal contraction rate of the separator in the long axis direction may be 2.6% or less. The heat shrinkage rate is a value obtained by dividing the change in the length of the long axis of the separator that is reduced before and after heat shrinkage by the length of the long axis of the separator before heat shrinkage.

After allowing the separator to stand at 150° C. for 10 minutes, take it out and cool it at room temperature, the separator heat shrinkage in the long axis direction may be 40% or less. For example, after allowing the separator to stand at 150° C. for 10 minutes, take it out, cool it at room temperature, the separator heat shrinkage in the long axis direction may be 30% or less. For example, after allowing the separator to stand at 150° C. for 10 minutes, take it out, cool it at room temperature, the separator heat shrinkage in the long axis direction may be 28% or less. The heat shrinkage rate is a value obtained by dividing the change in the length of the long axis of the separator that is reduced before and after heat shrinkage by the length of the long axis of the separator before heat shrinkage.

In addition, the separator may include a diene-based polymer prepared by polymerizing a monomer composition containing a diene-based monomer. The diene-based monomer may be a conjugated diene-based monomer or a non-conjugated diene-based monomer. For example, the diene-based monomers are 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1 ,3-pentadiene, chloroprene, vinylpyridine, vinyl norbornene, dicyclopentadiene, and at least one selected from the group consisting of 1,4-hexadiene, but is not necessarily limited thereto, and as a diene monomer in the art. Anything that can be used is possible.

The separator may additionally include an adhesive layer disposed on the coating layer. The separator includes, for example, a porous substrate layer 11, a coating layer 12 and 13 disposed on at least one surface of the porous substrate, and an adhesive layer 14 disposed on at least one surface of the coating layer, as shown in FIG. , 15) may have a structure including.

When the separator additionally includes an adhesive layer, the bonding strength between the electrode and the separator may be improved. For example, in a pouch-type battery in which a flexible packaging material such as a laminate film is used, the electrode and the separator are stably bonded to prevent battery deterioration due to detachment of the electrode and the separator, and the position of the separator can be fixed.

The adhesive layer is the same binder as the coating layer; A binder different from the coating layer including an acrylate-based binder, a fluorine-based binder, a rubber-based binder, or a combination thereof; A binder including inorganic particles, organic particles, or a combination thereof, and an organic polymer; Or a combination thereof.

For example, the adhesive layer may include the same binder composition as the coating layer. When the adhesive layer includes the same binder composition as the coating layer, the bonding strength between the coating layer and the adhesive layer may be further improved. Specifically, the binder composition included in the adhesive layer may include first nanoparticles having an average particle diameter of 100 nm or less; And a first polymer binder having a glass transition temperature of 20° C. or less. The description of the first nanoparticle and the first polymer binder is the same as described above.

Further, for example, the adhesive layer may include another binder instead of the binder composition including the first polymer binder, or may additionally include a binder different from the first polymer binder.

For example, the adhesive layer may be an acrylate-based binder, a fluorine-based binder, a rubber-based binder, or a combination thereof, but is not limited thereto, and any one that can be used as a binder for the adhesive layer in the art may be used.

The acrylate-based binder means an acrylate-based polymer or a copolymer, and may be, for example, poly(meth)acrylate, polyalkyl(meth)acrylate, polyacrylonitrile, or a combination thereof, but must be It is not limited, and any acrylate-based binder that can be used as a binder for an adhesive layer in the art may be used.

The fluorine-based binder may be, for example, polyvinylidene fluoride, polytetrafluoroethylene, or a combination thereof, but is not limited thereto, and any fluorine-based binder that can be used as a binder for an adhesive layer in the art may be used.

The rubber-based binder is, for example, styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, acrylic rubber, butyl rubber, fluorine rubber, or a combination thereof. It may include, but is not necessarily limited to these, and any rubber-based binder that can be used as a binder for an adhesive layer in the art may be used.

In addition, for example, the adhesive layer may include inorganic particles, organic particles, or a combination thereof; And a binder containing an organic polymer.

The inorganic particles may be the same as or different from the filler included in the coating layer. For example, the inorganic particles may be colloidal silica or alumina.

The organic particles may be the same as or different from the polymer particles included in the coating layer.

The average particle diameter of the inorganic particles, organic particles, or a combination thereof may be about 1 to 100 nm. Specifically, it may be 5 to 90 nm, 5 to 80 nm, 5 to 70 nm, and 5 to 50 nm. An inorganic compound having a size in the above range may be used to impart appropriate strength to the separator coating layer. If the particle size is less than 1 nm, the dispersibility of the composition may decrease, and if the particle size is more than 100 nm, the film strength of the separator may decrease.

The inorganic particles, organic particles, or a combination thereof may be included in 10 to 100 parts by weight based on 100 parts by weight of the organic polymer. Specifically, 20 to 80 parts by weight and 20 to 60 parts by weight may be included. When the inorganic particles, organic particles, or a combination thereof are included in the above range, they may have adequate strength and exhibit sufficient adhesive strength.

The organic polymer may include, for example, a diene polymer, an acrylate polymer, a styrene polymer, a urethane polymer, a polyolefin polymer, or a combination thereof.

The organic polymer may have, for example, a glass transition temperature (Tg) of about -50 to 60°C, and specifically about -40 to 20°C.

The organic polymer may have a particle diameter of about 0.05 µm to about 0.5 µm, specifically, about 0.08 µm to about 0.2 µm, in a state dispersed in a solvent. Particles having the above range size may be used to have an appropriate viscosity, and safety characteristics of a lithium secondary battery including a separator having an adhesive layer prepared therefrom may be improved.

The adhesive layer may be disposed on one surface of the coating layer. The thickness of the adhesive layer may be 0.1 to 5 μm, 0.5 to 5 μm, or 1 to 5 μm based on one surface. When the thickness of the adhesive layer satisfies the above range, the adhesive layer can stably maintain improved binding strength with the coating layer and the electrode.

A separator according to another embodiment is a porous substrate; A coating layer disposed on at least one surface of the porous substrate; And an adhesive layer disposed on the coating layer, wherein the adhesive layer comprises a binder composition, and the elongation measured after standing for 10 minutes against a load of 50 g at 150° C. of the binder film made of the binder composition is 10% or less. to be. While the separator has flexibility, heat shrinkage may be suppressed and the safety of a battery may be improved by improving the heat resistance of the film.

The separator includes, for example, a porous substrate layer 11, a coating layer 12 and 13 disposed on at least one surface of the porous substrate, and an adhesive layer 14 disposed on at least one surface of the coating layer, as shown in FIG. , 15) may have a structure including.

In the separator, the coating layer may include a binder including an acrylate binder, a fluorine binder, a rubber binder, or a combination thereof; A binder including inorganic particles, organic particles, or a combination thereof, and an organic polymer; Or a combination thereof. Details of the binders used in the coating layer are as described above.

The average particle diameter of the inorganic particles, organic particles, or a combination thereof may be about 1 to 100 nm. Specifically, it may be 5 to 90 nm, 5 to 80 nm, 5 to 70 nm, and 5 to 50 nm. An inorganic compound having a size in the above range may be used to impart appropriate strength to the separator coating layer. If the particle size is less than 1 nm, the dispersibility of the composition may decrease, and if the particle size is more than 100 nm, the film strength of the separator may decrease.

In the separator, the coating layer may additionally include a filler.

A lithium battery according to another embodiment includes a positive electrode; cathode; Organic electrolyte; And the above-described separator between the anode and the cathode. By including the separator, the stability and life characteristics of the lithium battery may be improved.

The lithium battery may be manufactured, for example, by the following method.

First, an anode active material composition in which an anode active material, a conductive material, a binder, and a solvent are mixed is prepared. The negative electrode active material composition is directly coated on a metal current collector to prepare a negative electrode plate. Alternatively, after the negative active material composition is cast on a separate support, a film peeled from the support may be laminated on a metal current collector to prepare a negative electrode plate. The negative electrode is not limited to the shapes listed above, but may have a shape other than the above shape.

The negative electrode active material may be a non-carbon material. For example, the negative electrode active material includes at least one selected from the group consisting of a metal capable of forming an alloy with lithium, an alloy of a metal capable of forming an alloy with lithium, and an oxide of a metal capable of forming an alloy with lithium. can do.

For example, the metal alloyable with lithium is Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13-16 element, transition metal, rare earth element, or These are a combination element, not Si), Sn-Y alloy (wherein Y is an alkali metal, alkaline earth metal, group 13-16 element, transition metal, rare earth element, or a combination element thereof, but not Sn), etc. . The element Y is Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, It may be Te, Po, or a combination thereof.

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, or the like.

For example, the non-transition metal oxide may be SnO ₂ , SiO _x (0<x<2), or the like.

Specifically, the negative electrode active material is Si, Sn, Pb, Ge, Al, SiOx (0<x≤2), SnOy (0<y≤2), Li ₄ Ti ₅ O ₁₂ , TiO ₂ , LiTiO ₃ , Li ₂ It may be one or more selected from the group consisting of Ti ₃ O ₇ , but is not necessarily limited thereto, and any material used in the art as a non-carbon-based anode active material may be used.

In addition, a composite of the non-carbon-based negative active material and the carbon-based material may be used, and a carbon-based negative active material may be additionally included in addition to the non-carbon-based material.

The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous (non-shaped), plate-shaped, flake-shaped, spherical or fibrous natural graphite or artificial graphite, and the amorphous carbon is soft carbon (low-temperature calcined carbon) Alternatively, it may be hard carbon, mesophase pitch carbide, fired coke, or the like.

As the conductive material, metal powders such as acetylene black, ketjen black, natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, copper, nickel, aluminum, silver, metal fibers, etc. may be used, In addition, one kind or a mixture of one or more conductive materials such as polyphenylene derivatives may be used, but the present invention is not limited thereto, and any material that can be used as a conductive material in the art may be used. In addition, the above-described crystalline carbonaceous material may be added as a conductive material.

As the binder, vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene and mixtures thereof, or styrene butadiene rubber-based polymer, etc. May be used, but is not limited thereto, and any one that can be used as a binder in the art may be used.

As the solvent, N-methylpyrrolidone, acetone, or water may be used, but are not limited thereto, and any solvent that can be used in the art may be used.

The contents of the negative electrode active material, the conductive material, the binder, and the solvent are generally used in lithium batteries. One or more of the conductive material, the binder, and the solvent may be omitted depending on the use and configuration of the lithium battery.

Meanwhile, the binder used for manufacturing the negative electrode may be the same as the binder composition included in the coating layer of the separator.

Next, a positive electrode active material composition in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed is prepared. The positive electrode active material composition is directly coated and dried on a metal current collector to prepare a positive electrode plate. Alternatively, after the positive electrode active material composition is cast on a separate support, a film peeled from the support may be laminated on a metal current collector to prepare a positive electrode plate.

The positive electrode active material may include at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese oxide, but is not necessarily limited thereto. All of the cathode active materials available in can be used.

For example, Li _a A _1-b B _b D ₂ (where 0.90≦a≦1.8, and 0≦b≦0.5); Li _a E _1-b B _b O _2-c D _c (in the above formula, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05); LiE _2-b B _b O _4-c D _c (where 0≦b≦0.5, 0≦c≦0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Co _b B _c O _2-α F ₂ (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B _c D _α (wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α ≤ 2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _1-bc Mn _b B _c O _2-α F ₂ (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 <α <2); Li _a Ni _b E _c G _d O ₂ (in the above formula, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein, 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≦a≦1.8, 0.001≦b≦0.1); Li _a Mn ₂ G _b O ₄ (in the above formula, 0.90≦a≦1.8 and 0.001≦b≦0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≦f≦2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≦f≦2); A compound represented by any one of the formulas of LiFePO ₄ can be used:

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or combinations thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

Of course, one having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may contain a coating element compound of oxide, hydroxide, oxyhydroxide of coating element, oxycarbonate of coating element, or hydroxycarbonate of coating element. The compound constituting these coating layers may be amorphous or crystalline. As a coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. The coating layer formation process may be any coating method as long as the compound can be coated by a method that does not adversely affect the physical properties of the positive electrode active material by using these elements (e.g. spray coating, dipping method, etc.). Since the content can be well understood by those engaged in the relevant field, detailed description will be omitted.

For example, LiNiO ₂ , LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _1-x Mn _x O ₂ (0<x<1), LiNi _1-xy Co _x Mn _y O ₂ (0 ≤x≤0.5, 0≤y≤0.5), LiFeO ₂ , V ₂ O ₅ , TiS, MoS, etc. may be used.

In the positive electrode active material composition, the conductive material, the binder, and the solvent may be the same as those of the negative electrode active material composition. On the other hand, it is also possible to form pores inside the electrode plate by adding a plasticizer to the positive electrode active material composition and/or the negative electrode active material composition.

The contents of the positive electrode active material, the conductive material, a general binder, and a solvent are generally used in lithium batteries. Depending on the use and configuration of the lithium battery, one or more of the conductive material, a general binder, and a solvent may be omitted.

Meanwhile, the binder used in manufacturing the positive electrode may be the same as the binder composition included in the coating layer of the separator.

Next, the above-described separator is inserted between the anode and the cathode.

As described above, the separator is a porous substrate; And a coating layer disposed on at least one surface of the porous substrate, the coating layer having an average particle diameter of 300 nm or more; And a first nanoparticle comprising a binder composition, wherein the binder composition has an average particle diameter of 100 nm or less; And a first polymer binder having a glass transition temperature of 20° C. or less, and a breaking strength of the binder film prepared from the binder composition and impregnated in the electrolyte solution is 25 Kg/cm ² or more.

Next, the electrolyte is prepared.

The electrolyte may be in a liquid or gel state.

For example, the electrolyte may be an organic electrolyte. In addition, the electrolyte may be a solid. For example, boron oxide, lithium oxynitride, etc. may be used, but the present invention is not limited thereto, and any solid electrolyte may be used as long as it can be used as a solid electrolyte in the art. The solid electrolyte may be formed on the negative electrode by a method such as sputtering.

For example, an organic electrolyte may be prepared. The organic electrolyte may be prepared by dissolving a lithium salt in an organic solvent.

The organic solvent may be used as long as it can be used as an organic solvent in the art. For example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate, dibutyl carbonate , Benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N,N-dimethylformamide, dimethylacetamide, dimethylsulfoxide , Dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethyl ether, or mixtures thereof.

The lithium salt may also be used as long as it can be used as a lithium salt in the art. For example, LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N, LiC ₄ F ₉ SO ₃ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _{2x +1} SO ₂ )(C _y F _{2y +1} SO ₂ ) (where x,y are natural numbers), LiCl, LiI, or a mixture thereof.

As shown in FIG. 3, the lithium battery 1 includes a positive electrode 3, a negative electrode 2, and a separator 4. The positive electrode 3, the negative electrode 2, and the separator 4 described above are wound or folded to be accommodated in the battery case 5. Subsequently, an organic electrolyte is injected into the battery case 5 and sealed with a cap assembly 6 to complete the lithium battery 1. The battery case may have a cylindrical shape, a square shape, or a thin film type. For example, the lithium battery may be a thin film type battery. The lithium battery may be a lithium ion battery. The lithium battery may be a lithium polymer battery.

A separator may be disposed between the positive electrode and the negative electrode to form a battery structure. After the battery structure is stacked or wound in a bi-cell structure, it is impregnated with an organic electrolyte, and the resulting product is accommodated in a pouch and sealed to complete a lithium ion polymer battery.

In addition, a plurality of the battery structures are stacked to form a battery pack, and the battery pack may be used in all devices requiring high capacity and high output. For example, it can be used for laptop computers, smart phones, electric vehicles, and the like.

In particular, the lithium battery is suitable for an electric vehicle (EV) because it has excellent high rate characteristics and lifetime characteristics. For example, it is suitable for hybrid vehicles such as plug-in hybrid electric vehicles (PHEV).

The present invention will be described in more detail through the following examples and comparative examples. However, the examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

(Preparation of the first polymer binder particle emulsion)

Manufacturing Example 1 (Binder A)

After nitrogen was replaced in the inside of the flask reactor equipped with a condenser, thermometer, monomer emulsion introduction pipe, nitrogen gas introduction pipe and agitator, 200 parts by weight of distilled water and 0.5 parts by weight of sodium dodecylbenzenesulfonate were added, and the temperature was reduced to 60°C. The temperature was raised. Then, potassium persulfate 1.0 parts by weight, sodium bisulfite 0.5 parts by weight, α-methylstyrene dimer 0.2 parts by weight, t-dodecylmercaptan 0.2 parts by weight, butadiene 34 parts by weight, styrene 30 parts by weight, methyl methacrylate 17 A monomer mixture consisting of parts by weight, 10 parts by weight of acrylonitrile, 7 parts by weight of methacrylic acid, and 2 parts by weight of acrylic acid was put into a reactor at 45° C. and reaction was carried out. After the polymerization conversion rate reached 40%, 0.4 parts by weight of t-dodecylmercaptan was added and the reaction was additionally performed.When the polymerization conversion rate reached 80%, the reaction temperature was raised to 60°C, and the reaction was further carried out for 6 hours. Thus, the polymerization conversion rate reached 98%. Subsequently, the reaction solution was cooled to 20° C., further reduced pressure to remove residual monomers, and the solid content concentration was adjusted to 40% while adjusting the pH to 7.0 with a 5% by weight aqueous lithium hydroxide solution to obtain an acrylic acid ester polymer emulsion. The average particle diameter of the polymer binder particles dispersed in the emulsion was 120 nm. The polymer binder particles had a Tg of 17° C. and a gel content of 70%.

The polymer binder includes a carboxyl group (-COOH) as a polar functional group.

Manufacturing Example 2 (Binder B)

After nitrogen was replaced in the inside of the flask reactor equipped with a condenser, thermometer, monomer emulsion introduction pipe, nitrogen gas introduction pipe and agitator, 200 parts by weight of distilled water and 0.5 parts by weight of sodium dodecylbenzenesulfonate were added, and the temperature was reduced to 60°C. The temperature was raised. Then, 1.0 parts by weight of potassium persulfate, 0.5 parts by weight of sodium bisulfite, 0.2 parts by weight of α-methylstyrene dimer, 0.2 parts by weight of t-dodecylmercaptan, 34 parts by weight of butadiene, 31 parts by weight of styrene, methyl methacrylate 12 A monomer mixture consisting of parts by weight, 15 parts by weight of acrylonitrile, 2 parts by weight of methacrylic acid, 2 parts by weight of acrylic acid, and 4 parts by weight of hydroxyethyl methacrylate was put into a reactor at 45° C. and reaction was carried out. After the polymerization conversion rate reaches 40%, 0.3 parts by weight of t-dodecylmercaptan is added and the reaction is additionally performed.When the polymerization conversion rate reaches 80%, the reaction temperature is raised to 60°C and the reaction is further carried out for 6 hours. Thus, the polymerization conversion rate reached 98%. Subsequently, the reaction solution was cooled to 20° C., further reduced pressure to remove residual monomers, and the solid content concentration was adjusted to 40% while adjusting the pH to 7.0 with a 5% by weight aqueous lithium hydroxide solution to obtain an acrylic acid ester polymer emulsion. The average particle diameter of the polymer particles dispersed in the emulsion was 110 nm. The polymer binder particles had a Tg of 11° C. and a gel content of 72%.

The polymer binder contains a hydroxy group (-OH) as a polar functional group.

(Preparation of the first nanoparticle emulsion)

Preparation Example 3 (Nanoparticle C)

After nitrogen was replaced in the inside of the flask reactor equipped with a condenser, thermometer, monomer emulsion introduction pipe, nitrogen gas introduction pipe and agitator, 500 parts by weight of distilled water and 3 parts by weight of sodium dodecylbenzenesulfonate were added, and the temperature was reduced to 80°C. The temperature was raised. Then, 2 parts by weight of methyl methacrylate was added to the reactor, and after stirring for 5 minutes, 20 parts by weight of an aqueous 5% ammonium persulfate solution was added to the reactor to initiate the reaction. After 1 hour, a monomer emulsion consisting of 93 parts by weight of methyl methacrylate, 2 parts by weight of acrylic acid, 4 parts by weight of methacrylic acid, 1 part by weight of ethylene dimethacrylate, 0.5 parts by weight of sodium dodecylbenzenesulfonic acid and 40 parts by weight of distilled water It was dripped into the reactor for 3 hours. At the same time, 10 parts by weight of a 5% aqueous solution of ammonium persulfate was added dropwise to the reactor for 3 hours. After the dropping of the monomer emulsion was completed, the reaction was additionally carried out for 1 hour, so that the polymerization conversion rate reached 98.9%. Then, the reaction solution was cooled to 20°C, further reduced pressure to remove residual monomers, and then the solid content concentration was adjusted to 15% while adjusting the pH to 8.0 with a 5% by weight aqueous lithium hydroxide solution, and an emulsion containing polymer particles having a Tg of 100°C. Was obtained. The average particle diameter of the polymer particles dispersed in the emulsion was 70 nm.

Preparation Example 4 (Nanoparticle D)

After nitrogen was replaced in the inside of the flask reactor equipped with a condenser, thermometer, monomer emulsion introduction pipe, nitrogen gas introduction pipe and agitator, 500 parts by weight of distilled water and 3 parts by weight of sodium dodecylbenzenesulfonate were added, and the temperature was reduced to 80°C. The temperature was raised. Then, 2 parts by weight of methyl methacrylate was added to the reactor, and after stirring for 5 minutes, 20 parts by weight of an aqueous 5% ammonium persulfate solution was added to the reactor to initiate the reaction. After 1 hour, a monomer emulsion consisting of 97 parts by weight of methyl methacrylate, 2 parts by weight of hydroxyethyl methacrylate, 1 part by weight of ethylene dimethacrylate, 2 parts by weight of sodium dodecylbenzenesulfonic acid, and 40 parts by weight of distilled water was added for 3 hours. In the meantime, it was dripped in the reactor. At the same time, 10 parts by weight of a 5% aqueous solution of ammonium persulfate was added dropwise to the reactor for 3 hours. After the dropping of the monomer emulsion was completed, the reaction was additionally carried out for 1 hour, and the polymerization conversion rate reached 98.7%. Subsequently, the reaction solution was cooled to 20°C, further reduced pressure to remove residual monomers, and then the solid content concentration was adjusted to 15% while adjusting the pH to 8.0 with a 5% by weight aqueous lithium hydroxide solution, and an emulsion containing polymer particles having a Tg of 108°C. Was obtained. The average particle diameter of the polymer particles dispersed in the emulsion was 90 nm.

(Production of binder composition and separator)

Example 1

(Preparation of binder composition)

Drying of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 70 nm prepared in Preparation Example 3 in 100 parts by weight based on the dry weight of the polymer emulsion (binder A, solid content 40%) prepared in Preparation Example 1 After adding 20 parts by weight based on weight, 1 part by weight based on dry weight of a carbodiimide binder (Carbodilite V-02-L2, Nisshinbo Chemical Inc.) was added, followed by stirring for 10 minutes to prepare a binder composition.

(Manufacture of separator)

As a filler, 6 parts by weight of alumina (AKP-3000, Sumitomo Chemical Co., Ltd.) having an average particle diameter of 0.4 to 0.6 µm (volume D50) based on the dry weight of the binder composition and a dispersant (Aron T-40, Toagosei Chemicals Industry Co., Japan) 0.5 parts by weight were mixed to prepare a composition for forming a coating layer.

The composition for forming the coating layer was gravure-printed on both sides of a 16 μm-thick polyethylene porous substrate to prepare a separator. The thickness of the coating layer was 3 μm based on one side.

Example 2

A separator was prepared in the same manner as in Example 1, except that the addition amount of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 70 nm prepared in Preparation Example 3 was changed from 20 parts by weight to 30 parts by weight.

Example 3

A separator was prepared in the same manner as in Example 1, except that the addition amount of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 70 nm prepared in Preparation Example 3 was changed from 20 parts by weight to 40 parts by weight.

Example 4

(Preparation of binder composition)

Drying of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 90 nm prepared in Preparation Example 4 in 100 parts by weight based on the dry weight of the polymer emulsion (binder B, solid content 40%) prepared in Preparation Example 2 After adding 20 parts by weight based on weight, 1 part by weight based on dry weight of γ-glycidoxypropyltrimethoxysilane, which is a silane coupling agent, was added, followed by stirring for 10 minutes to prepare a binder composition.

(Manufacture of separator)

As a filler, 6 parts by weight of alumina (AKP-3000, Sumitomo Chemical Co., Ltd.) having an average particle diameter of 0.4 to 0.6 µm (volume D50) based on the dry weight of the binder composition and a dispersant (Aron T-40, Toagosei Chemicals Industry Co., Japan) 0.5 parts by weight were mixed to prepare a composition for forming a coating layer.

The composition for forming the coating layer was gravure-printed on both sides of a 16 μm-thick polyethylene porous substrate to prepare a separator. The thickness of the coating layer was 3 μm based on one side.

Example 5

A separator was prepared in the same manner as in Example 4, except that the addition amount of the polymer emulsion (solid content 15% by weight) prepared in Preparation Example 4 was changed from 20 parts by weight to 30 parts by weight.

Example 6

A separator was manufactured in the same manner as in Example 4, except that the addition amount of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 90 nm prepared in Preparation Example 4 was changed from 20 parts by weight to 40 parts by weight.

Example 7 (MgF2)

Except for adding 40 parts by weight of magnesium fluoride (CIK NanoTek, Japan) having an average particle diameter of 50 nm instead of 20 parts by weight based on the dry weight of the polymer emulsion with an average particle diameter of 70 nm prepared in Preparation Example 3 (solid content 15% by weight) A separator was manufactured in the same manner as in Example 1.

Example 8 (crosslinked PMMA)

A crosslinked polymethyl methacrylate emulsion (Nippon Shokubai, EPOSTAR 2B20, Tg) having an average particle diameter of 50 nm instead of 20 parts by weight based on dry weight of the polymer emulsion with an average particle diameter of 70 nm prepared in Preparation Example 3 (solid content 15% by weight) ) A separator was manufactured in the same manner as in Example 1, except that 25 parts by weight based on dry weight was added.

Example 9 (PU)

In place of 20 parts by weight based on the dry weight of the polymer emulsion with an average particle diameter of 70 nm (solid content 15% by weight) prepared in Preparation Example 3, 30 parts by weight based on the dry weight of the polyurethane emulsion with an average particle diameter of 30 nm (35% by weight solid content) were added. Except for that, a separator was manufactured in the same manner as in Example 1.

The polyurethane emulsion having a solid content of 35% by weight is obtained after adding 150 parts by weight of ion-exchanged water to 100 parts by weight of a commercially available polyurethane emulsion (SUPERFLEX 130, Dai-ichi Kogyo Seiyaku Co., Ltd., Tg 101°C). It was prepared by removing the solvent until the solid content reached 35% by weight in a rotary evaporator under reduced pressure.

Comparative Example 1

A separator was prepared in the same manner as in Example 1, except that the addition amount of the polymer emulsion (solid content 15% by weight) of 70 nm prepared in Preparation Example 3 was changed from 20 parts by weight to 5 parts by weight.

Comparative Example 2

A separator was prepared in the same manner as in Example 4, except that the addition amount of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 90 nm prepared in Preparation Example 4 was changed from 20 parts by weight to 120 parts by weight.

Comparative Example 3

A separator was prepared in the same manner as in Example 1, except that the polymer emulsion (solid content 15% by weight) prepared in Preparation Example 3 was not added with an average particle diameter of 70 nm.

Example 10

The addition amount of the polymer emulsion (solid content 15% by weight) having an average particle diameter of 70 nm prepared in Preparation Example 3 was changed from 20 parts by weight to 30 parts by weight,

A coating layer was formed using a composition for forming a coating layer prepared by mixing 6 parts by weight based on the dry weight of the binder composition and 0.5 parts by weight of a dispersant (Aron T-40, Toagosei Chemicals Industry Co., Japan) without adding an alumina filler. Except for that, a separator was manufactured in the same manner as in Example 1.

(Manufacture of lithium battery)

Example 11

(Manufacture of cathode)

After mixing 97% by weight of graphite particles (C1SR, Japanese carbon) having an average particle diameter of 25 μm, 1.5% by weight of styrene-butadiene rubber (SBR) binder (ZEON), and 1.5% by weight of carboxymethylcellulose (CMC, NIPPON A&L), in distilled water Then, the mixture was stirred for 60 minutes using a mechanical stirrer to prepare a negative active material slurry. The slurry was applied on a copper current collector with a thickness of 10 μm using a doctor blade, dried for 0.5 hours in a hot air dryer at 100° C., dried again for 4 hours under vacuum and 120° C., and rolled. A negative plate was prepared.

(Manufacture of anode)

LiCoO ₂ 97% by weight, 1.5% by weight of carbon black powder and 1.5% by weight of polyvinylidene fluoride (PVdF, SOLVAY) were mixed as a conductive material and added to the N-methyl-2-pyrrolidone solvent, and then a mechanical stirrer was used. Then, the mixture was stirred for 30 minutes to prepare a positive electrode active material slurry. The slurry was applied on an aluminum current collector with a thickness of 20 μm using a doctor blade, dried for 0.5 hours in a hot air dryer at 100° C., dried again for 4 hours under vacuum and 120° C. conditions, and rolled. A positive plate was prepared.

(Battery assembly)

The separator prepared in Example 1 was faced between the positive electrode plate and the negative electrode plate prepared above, inserted into a pouch, and an electrolyte was injected, and then the pouch was vacuum-sealed and compressed at high temperature at 100°C to prepare a pouch cell.

As the electrolyte, 1.3 M LiPF ₆ was dissolved in a 3/5/2 (volume ratio) mixed solvent of ethylene carbonate (EC)/ethylmethyl carbonate (EMC)/diethyl carbonate (DEC).

Examples 12 to 20

A lithium battery was manufactured in the same manner as in Example 11, except that the separators prepared in Examples 2 to 10 were used, respectively.

Comparative Examples 4 to 6

Lithium batteries were each manufactured in the same manner as in Example 11, except that the separators prepared in Comparative Examples 1 to 3 were used, respectively.

Evaluation Example 1: Measurement of the breaking strength of the binder film

The binder compositions prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were poured into a petri dish made of a Teflon material having a diameter of 12 cm, and dried at room temperature for 2 days to prepare a binder film having a thickness of 0.6 mm. The binder film was dried in a vacuum dryer at 70° C. for 10 hours to sufficiently remove moisture. A binder specimen for strength measurement having a length of 5 cm and a width of 5 mm was prepared from the dried binder film.

The width of the specimen corresponds to B of FIG. 3, the length of the specimen corresponds to A of FIG. 3, and the thickness of the specimen corresponds to C of FIG. 3.

The binder specimen was immersed in an EC (ethylene carbonate):EMC (ethylmethyl carbonate):DEC (diethyl carbonate) (3:5:2 volume ratio) mixed solvent (electrolyte solvent) for 72 hours at 70° C., and then wiped off the electrolyte solution. Breaking strength was measured using a tensile tester under conditions of a tensile speed of 100 cm/min.

Four specimens were measured and the breaking strength of the electrolyte solution immersed film was measured according to Equation 1 below.

<Equation 1>

Strength of specimen = breaking strength of the strongest specimen × 0.5 + breaking strength of the second strongest specimen × 0.3 + breaking strength of the third strongest specimen × 0.1 + breaking strength of the weakest specimen × 0.1

Some of the measurement results are shown in Table 1 below.

Evaluation Example 2: Evaluation of heat resistance of a binder film

The binder compositions prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were poured into a petri dish made of a Teflon material having a diameter of 12 cm, and dried at room temperature for 2 days to prepare a binder film having a thickness of 0.6 mm. The binder film was dried in a vacuum dryer at 70° C. for 10 hours to sufficiently remove moisture. A binder specimen for strength measurement having a length of 5 cm and a width of 5 mm was prepared from the dried binder film.

The width of the specimen corresponds to B of FIG. 4, the length of the binder corresponds to A of FIG. 4, and the thickness of the specimen corresponds to C of FIG. 4. As shown in FIG. 4, a marker having a length of 2 cm was marked in the center of the specimen.

After applying a load of 50 g to the specimen, it was set as shown in FIG. 4 in a dryer at 150° C., and left for 10 minutes, and then the elongation of the marker was measured to evaluate heat resistance. The elongation was calculated from Equations 2 and 3 below.

<Equation 2>

Elongation = [(extended marker length-initial marker length)/initial marker length]×100

Some of the heat resistance evaluation results are shown in Table 1 below.

Immersion breaking strength
[kg/cm ² ] Elongation
[%] Example 1 84 5 Example 2 102 4.1 Example 3 126 3.2 Example 4 62 6.2 Example 5 76 5.5 Example 6 82 4 Example 7 106 3.6 Example 8 98 4.2 Example 9 102 7 Comparative Example 1 35 20 Comparative Example 2 - - Comparative Example 3 25 26 Example 10
84 5

The content of the nanoparticles of Comparative Example 2 was too high to produce a binder film.

As shown in Table 1, the binder films prepared from the binder compositions of Examples 1 to 9 significantly improved the breaking strength after immersing the electrolyte compared to the binder films of Comparative Examples 1 and 3, and thus improved strength when applied to an actual separator. By providing, it is possible to effectively suppress the shrinkage of the separator.

In addition, as shown in Table 1, the binder films of Examples 1 to 9 have reduced elongation compared to the binder films of Comparative Examples 1 and 3, resulting in improved heat resistance.

The separator prepared using the binder composition in Example 10 had the same composition as the separator of Example 2, except that no filler was added, and thus the breaking strength and heat resistance after immersion in the electrolyte solution of the binder film were excellent, but in Table 2 As can be seen, the shrinkage of the separator was sluggish.

Evaluation Example 3: Evaluation of the shrinkage rate of the separator

The separators having a thickness of 22 μm prepared in Examples 1 to 10 and Comparative Examples 1 to 3 were left in a convection oven at 130° C. and 150° C. for 10 minutes, respectively, and then taken out and cooled at room temperature, and then the thermal contraction rate was measured.

The shrinkage rate of the separator was evaluated by drawing a linear marker with a length of 10 cm in the direction of the long axis of the separator, and after leaving the separator in an oven and cooling it at room temperature, the degree of shrinkage of the marker was calculated from Equation 3 below.

<Equation 3>

Shrinkage rate = [(initial marker length-reduced marker length)/initial marker length]×100

Some of the results of measuring the thermal contraction rate are shown in Table 2 below.

Shrinkage rate
(130℃)
[%] Shrinkage rate
(150℃)
[%] Example 1 2 17 Example 2 1.8 13 Example 3 1.5 9 Example 4 2.3 21 Example 5 2.1 15 Example 6 1.8 11 Example 7 1.7 11 Example 8 1.8 12 Example 9 2.6 28 Comparative Example 1 5 54 Comparative Example 2 - - Comparative Example 3 6 60 Example 10
5 42

In Comparative Example 2, the content of the nanoparticles was too high, so it was impossible to manufacture a binder film.

In addition, as shown in Table 2, the separators of Examples 1 to 9 have improved shrinkage compared to the separators of Comparative Examples 1 and 3. In particular, the shrinkage rate at 150°C was remarkably improved.

Claims (28)

Porous substrate; And
It includes a coating layer disposed on at least one surface of the porous substrate,
The coating layer contains a binder composition,
First nanoparticles in which the binder composition has an average particle diameter of 1 to 90 nm; And
Including a first polymer binder having a glass transition temperature of 20 ℃ or less,
The binder composition comprises 7 to 60 parts by weight of the solid content of the first nanoparticles based on 100 parts by weight of the solid content of the first polymer binder,
A separator having an elongation of 10% or less measured after standing for 10 minutes against a load of 50 g at 150° C. of the binder film made of the binder composition. The separator of claim 1, wherein the coating layer further includes a filler. delete The separator according to claim 1, wherein the binder composition has a storage modulus of 30 MPa or more at 100°C. The separator according to claim 1, wherein the first nanoparticles have a glass transition temperature of 60°C or higher. The separator according to claim 5, wherein the first nanoparticles are polymer particles. The separator according to claim 6, wherein the polymer particles are polyurethane. The separator according to claim 1, wherein the first nanoparticles do not have a glass transition temperature. The separator according to claim 8, wherein the first nanoparticles are polymer particles or inorganic particles. The separator according to claim 9, wherein the polymer particles are crosslinked polymer particles. The separator according to claim 10, wherein the crosslinked polymer particles are crosslinked polymethylmethacrylate. The method of claim 9, wherein the inorganic particles are colloidal silica (SiO ₂ ), α-alumina (α-Al ₂ O ₃ ), γ-alumina (γ-Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ) and fluorinated Magnesium (MgF ₂ ), titania (TiO ₂ ), tin oxide (SnO ₂ ), cerium oxide (CeO ₂ ), nickel oxide (NiO), calcium oxide (CaO), zinc oxide (ZnO), magnesium oxide (MgO), Yttrium oxide (Y ₂ O ₃ ), SrTiO ₃ , BaTiO ₃ , and at least one separator selected from the group consisting of Mg(OH) ₂ . delete The separator according to claim 1, wherein the first polymer binder has a gel content of 90% or less. The separator of claim 1, wherein the binder composition further comprises a binder that chemically couples the first nanoparticles and the first polymer binder. The separator according to claim 2, wherein the filler has an average particle diameter of 300 nm to 2.0 μm. The separator according to claim 2, wherein the content of the filler is 50% to 99% by weight based on the total weight of the coating layer. The separator according to claim 1, wherein the porous substrate comprises polyolefin. The separator according to claim 1, wherein the first polymeric binder comprises a diene-based polymer prepared by polymerizing a monomer composition containing a diene-based monomer. The separator according to claim 1, wherein the separator is allowed to stand at 150°C for 10 minutes and has a shrinkage of 40% or less. The separator according to claim 1, further comprising an adhesive layer disposed on the coating layer. The method of claim 21, wherein the adhesive layer is the same binder as the coating layer; A binder different from the coating layer including an acrylate-based binder, a fluorine-based binder, a rubber-based binder, or a combination thereof; A binder including inorganic particles, organic particles, or a combination thereof, and an organic polymer; Or a separator comprising a combination thereof. The separator according to claim 22, wherein the organic particles have a particle diameter of 10 nm to 90 nm. Porous substrate;
A coating layer disposed on at least one surface of the porous substrate; And
It includes an adhesive layer disposed on the coating layer,
The adhesive layer comprises a binder composition,
First nanoparticles in which the binder composition has an average particle diameter of 1 to 90 nm; And
Including a first polymer binder having a glass transition temperature of 20 ℃ or less,
The binder composition comprises 7 to 60 parts by weight of the solid content of the first nanoparticles based on 100 parts by weight of the solid content of the first polymer binder,
A separator having an elongation of 10% or less measured after standing for 10 minutes against a load of 50 g at 150° C. of the binder film made of the binder composition. The method of claim 24, wherein the coating layer
A binder including an acrylate binder, a fluorine binder, a rubber binder, or a combination thereof; A binder including inorganic particles, organic particles, or a combination thereof, and an organic polymer; Or a separator comprising a combination thereof. The separator according to claim 25, wherein the organic particles have a particle diameter of 10 nm to 90 nm. The separator according to claim 23, wherein the coating layer further comprises a filler. A lithium battery comprising the separator according to any one of claims 1 to 2, 4 to 12, and 14 to 23.

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