KR102556801B1 - Dispersant for separator of non-aqueous electrolyte battery comprising 2-cyanoethyl group-containing polymer - Google Patents

Abstract

The present invention relates to a dispersant for a non-aqueous electrolyte battery separator containing a cyanoethyl group-containing polymer, a non-aqueous electrolyte battery separator using the same, and a non-aqueous electrolyte battery. Further, the present invention relates to a method for producing a cyanoethyl group-containing polymer.

Description

Dispersant for non-aqueous electrolyte battery separator containing cyanoethyl group-containing polymer

The present invention relates to a dispersant for a non-aqueous electrolyte battery separator containing a cyanoethyl group-containing polymer, a non-aqueous electrolyte battery separator using the same, and a non-aqueous electrolyte battery. Further, the present invention relates to a method for producing a cyanoethyl group-containing polymer.

Recently, a non-aqueous electrolyte battery, particularly a lithium ion secondary battery, having a high voltage and high energy density has been attracting attention as a power source for a mobile terminal such as a notebook computer or a mobile phone or a power source for a hybrid vehicle or an electric vehicle. Since a non-aqueous electrolyte battery represented by a lithium ion secondary battery has a high capacity and a high energy density, a large current flows when the battery is shorted internally or externally, and the battery generates heat due to Joule heat generated at the time, and the electrolyte solution There are problems of expansion of the battery and deterioration of characteristics due to gas generation accompanying decomposition.

In current lithium ion secondary batteries, in order to solve this problem, a separator including a porous substrate having fine pores such as a polypropylene or polyethylene film is interposed between the positive electrode and the negative electrode. Separators made of these porous substrates generate heat when short-circuited, and when the temperature rises, the separator melts and the fine pores are blocked, blocking the movement of ions, thereby preventing current from flowing and suppressing battery runaway.

Nowadays, as the use of lithium ion secondary batteries expands, batteries with higher heat resistance, particularly improved heat resistance when an internal short circuit occurs, are required. In particular, when a short circuit occurs inside the battery, the temperature may reach 600 ° C. or higher at the short circuit part due to local heat generation. The heat causes the separator in the short-circuit area to shrink or melt, and the battery is exposed to dangers such as smoke, ignition, and explosion.

As a technology to increase the reliability of a battery by preventing a short circuit due to heat shrinkage or heat melting of the separator, for example, a heat-resistant porous layer on one side or both sides (surface and back surface) of a porous substrate having fine pores such as a polyolefin film. A separator having a multi-layer structure is proposed.

On the other hand, the heat-resistant porous layer uses a cyanoethyl group-containing polymer as an inorganic material and a dispersing agent for uniformly dispersing the inorganic material. The stability of the battery separator can be sufficiently secured when the dispersing ability of the dispersing agent is at an appropriate level. Since inorganic materials are not evenly dispersed, it is difficult to sufficiently secure thermal stability of a separator, that is, a separator.

The present specification provides a dispersant for a non-aqueous electrolyte battery separator, a non-aqueous electrolyte battery separator using the same, and a non-aqueous electrolyte battery separator using the same, which can further improve the heat resistance of the separator by not only firmly adhering the inorganic filler when forming a heat-resistant porous layer of the separator, but also effectively dispersing the inorganic filler. It is intended to provide an electrolyte cell.

In addition, the present specification is intended to provide a method for producing a cyanoethyl group-containing polymer used as a dispersant for the non-aqueous electrolyte battery separator.

The present specification includes a cyanoethyl group-containing polymer comprising a first repeating unit represented by Formula 1 below, a second repeating unit represented by Formula 2 below, and a third repeating unit represented by Formula 3 below. , Dispersant compositions for non-aqueous electrolyte battery separators are provided.

[Formula 1]

In Formula 1, R1 is hydrogen or alkyl having 1 to 8 carbon atoms,

[Formula 2]

[Formula 3]

In Formula 3, R31 is an oxyethylene group (-O-CH ₂ -CH ₂ -).

In this case, the number of repetitions of the first repeating units, compared to the total number of repetitions of the first, second, and third repeating units, may be about 30 mol% or less, preferably about 29 mol% or less, or about 28 mol%. It may be mol % or less. The lower limit may be about 15 mol% or more, preferably about 20 mol% or more.

And, separately from this, the number of repetitions of the third repeating units relative to the total number of repetitions of the second and third repeating units may be about 60 mol% or more, preferably about 70 mol% or more, or about 80 mol% or more. The upper limit may be about 99 mol% or less, or about 90 mol% or less, or about 75 mol% or less.

According to one embodiment of the invention, the cyanoethyl group-containing polymer may further include a fourth repeating unit represented by Chemical Formula 4 below.

[Formula 4]

In Formula 4, R41 is an acetate (CH ₃ COO-) group.

In this case, the number of repetitions of the fourth repeating unit relative to the total number of repetitions of the first, second, third, and fourth repeating units may be about 10 mol% or less, preferably about 5 mol% or less. there is.

According to one embodiment of the invention, the cyanoethyl group-containing polymer may have a weight average molecular weight of about 50,000 to about 300,000, or about 55,000 or more and about 270,000 or less.

According to another aspect of the invention, polymerizing a first monomer represented by Formula 1-1 and vinyl acetate to form an acetate group-containing polymer; and a substitution step of adding a base to the acetate group-containing polymer and reacting with acrylonitrile.

[Formula 1-1]

In Formula 1-1, R11 is hydrogen or alkyl having 1 to 8 carbon atoms.

At this time, in the step of forming the acetate group-containing polymer, about 3 to about 15 parts by weight of the first monomer, preferably about 5 to about 10 parts by weight, based on 100 parts by weight of the vinyl acetate may be used.

And, the polymerization may be performed at about 50 to about 80 °C, or about 60 to about 70 °C.

In the substitution step, the base may be used in an amount of about 5 to about 15 parts by weight or about 5 to about 10 parts by weight based on 100 parts by weight of the acetate group-containing polymer.

Separately, in the substitution step, the acrylonitrile may be used in an amount of about 50 to about 200 parts by weight, or about 70 to about 150 parts by weight based on 100 parts by weight of the acetate group-containing polymer.

According to another embodiment of the present invention, the substitution step proceeds by dissolving the acetate group-containing polymer in a first solvent, then removing the first solvent, and introducing a second solvent and a base; The first solvent may be an acetate group-containing polymer-soluble solvent, and the second solvent may be a cyanoethyl group-containing polymer-soluble solvent.

Meanwhile, according to another aspect of the invention, a heat-resistant porous layer comprising the dispersant composition for a non-aqueous electrolyte battery separator of claim 1; and a porous substrate; A separator for a non-aqueous electrolyte battery is provided.

In this case, the heat-resistant porous layer may further include an inorganic filler.

Meanwhile, according to another aspect of the present invention, a non-aqueous electrolyte battery including a positive electrode, a negative electrode, the separator for the non-aqueous electrolyte battery, and an electrolyte is provided.

In the present invention, terms such as first and second are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

In addition, terms used in this specification are only used to describe exemplary embodiments, and are not intended to limit the present invention.

Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this specification, terms such as "comprise", "include" or "having" are intended to describe an implemented feature, number, step, component or combination thereof, and one or more other features or numbers, It does not exclude the possibility of steps, components, combinations or additions thereof.

Also, in this specification, when each layer or element is referred to as being formed "on" or "above" each layer or element, it means that each layer or element is formed directly on each layer or element, or other This means that layers or elements may be additionally formed between each layer or on the object or substrate.

Since the present invention can have various changes and various forms, specific embodiments will be exemplified and described in detail below. However, it should be understood that this does not limit the present invention to the specific disclosed form, and includes all modifications, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Hereinafter, a dispersant for a non-aqueous electrolyte battery separator, a non-aqueous electrolyte battery separator using the same, and a non-aqueous electrolyte battery according to specific embodiments of the present invention will be described in more detail.

(polymer)

According to one aspect of the present invention, a cyanoethyl group containing a first repeating unit represented by the following formula (1), a second repeating unit represented by the following formula (2), and a third repeating unit represented by the following formula (3) A dispersant composition for a non-aqueous electrolyte battery separator comprising a polymer is provided.

[Formula 1]

In Formula 1, R1 is hydrogen or alkyl having 1 to 8 carbon atoms,

[Formula 2]

[Formula 3]

In Formula 3, R31 is an oxyethylene group (-O-CH ₂ -CH ₂ -).

According to the physical properties of the cyanoethyl group-containing polymer used as a dispersant for the inorganic filler in the heat-resistant porous layer of the non-aqueous electrolyte battery separator, the inventors of the present invention not only can strengthen the bonding of the inorganic filler, but also the dispersibility of the inorganic filler It became high, and it was confirmed through experiments that the heat resistance of the separator was improved, and the invention was completed.

In a non-aqueous electrolyte battery separator, it is well known that a cyanoethyl group-containing polymer or the like serves as a binder for firmly adhering the inorganic filler, but the dispersibility of the cyanoethyl group-containing polymer and the inorganic filler is known in detail. does not exist.

The cyanoethyl group-containing polymer according to one aspect of the present invention serves not only as a binder for firmly adhering inorganic fillers when forming a heat-resistant porous layer of a separator, but also as a dispersant capable of effectively dispersing inorganic fillers. Accordingly, it is possible to implement a separator having significantly improved heat resistance compared to the prior art.

Specifically, the cyanoethyl group-containing polymer used in the non-aqueous electrolyte battery separator according to one aspect of the present invention includes a first repeating unit represented by the following formula (1), a second repeating unit represented by the following formula (2), and the following formula (3) It includes a third repeating unit represented by .

[Formula 1]

In Formula 1, R1 is hydrogen or alkyl having 1 to 8 carbon atoms,

[Formula 2]

[Formula 3]

In Formula 3, R31 is an oxyethylene group (-O-CH ₂ -CH ₂ -).

Such a cyanoethyl group-containing polymer can be prepared, for example, by a Michael addition reaction of acrylonitrile with a polymer having a hydroxyl group in the molecule as shown in the following reaction scheme.

[reaction formula]

In the reaction formula, Polymer-OH represents a polymer having a hydroxyl group, and Polymer-O-CH ₂ -CH ₂ -CN represents a cyanoethyl group-containing polymer.

In the cyanoethyl group-containing polymer according to one aspect of the present invention, the first repeating unit portion represented by Formula 1 is part of the repeating unit constituting the cyanoethyl group-containing polymer of the above reaction formula, and is represented by Formula 1- It may refer to a component derived from the monomer represented by 1.

[Formula 1-1]

In Formula 1-1, R11 is hydrogen or alkyl having 1 to 8 carbon atoms.

Since the moiety represented by Formula 1 does not have a reactive functional group, it does not react with acrylonitrile in the above-described reaction scheme and is incorporated as it is in the reaction product, that is, the cyanoethyl group-containing polymer.

And, in the cyanoethyl group-containing polymer according to one aspect of the present invention, the second repeating unit portion represented by Formula 2 is another partial repeating unit constituting the cyanoethyl group-containing polymer of the above reaction formula, After introduction from vinyl acetate, it may have been provided with a hydroxyl group by hydrolysis.

Since the part represented by Formula 2 contains a hydroxyl group as a reactive functional group, a Michael addition reaction with acrylonitrile may proceed in the above-described reaction scheme. Among them, the part that does not react with acrylonitrile is included in the output in the form of

And, in the cyanoethyl group-containing polymer according to one aspect of the present invention, the third repeating unit portion represented by Formula 3 is another partial repeating unit constituting the cyanoethyl group-containing polymer of the above reaction formula, It means the part where the cyanoethyl group was introduced into the above-mentioned hydroxyl group.

The cyanoethyl group-containing polymer used in the non-aqueous electrolyte battery separator according to one aspect of the present invention, as described above, includes a first repeating unit not involved in a substitution reaction, a second repeating unit in which a hydroxyl group remains because substitution is not performed, and a cyanoethyl group-introduced third repeating unit, which can further improve the adhesion of inorganic fillers and the like, and improve the dispersibility of the non-aqueous electrolyte battery separator, thereby improving overall performance of the non-aqueous electrolyte battery. be able to improve

In this case, the number of repetitions of the first repeating units, compared to the total number of repetitions of the first, second, and third repeating units, may be about 30 mol% or less, preferably about 29 mol% or less, or about 28 mol%. It may be mol % or less. The lower limit may be about 1 mol% or more, preferably about 10 mol% or more, or about 15 mol% or more, or about 20 mol% or more.

The repeating number ratio of the first repeating unit described above is the polymer having a hydroxyl group represented by Polymer-OH in the above reaction formula, or a polymer containing a cyanoethyl group represented by Polymer-O-CH ₂ -CH ₂ -CN. It is the repeating number ratio of repeating units derived from ethylenically unsaturated monomers constituting . That is, the cyanoethyl group-containing polymer according to one embodiment of the present invention contains repeating units derived from ethylenically unsaturated monomers at a ratio of about 30 mol% or less to the total number of moles of repeating units derived from each monomer constituting the polymer. may have been introduced.

If the ratio of the repeating number of the first repeating unit, ie, the relative content of the repeating unit derived from the ethylenically unsaturated monomer, in the entire polymer is too high, this may cause a problem in that the adhesive strength of the separator is lowered.

And, separately from this, the number of repetitions of the third repeating units, relative to the total number of repetitions of the second and third repeating units, may be 60 mol% or more, preferably about 70 mol% or more, or about 80 mol% or more. there is.

The repeating number ratio of the above-described third repeating unit is the repeating number ratio of the cyanoethyl group introduced by the hydroxyl group of Polymer-OH in the above reaction formula, and means the cyanoethyl group substitution rate of the cyanoethyl group-containing polymer. . That is, in the cyanoethyl group-containing polymer according to an embodiment of the present invention, cyanoethyl groups may be introduced at a ratio of about 70 mol% or more to less than about 100 mol% of the total hydroxyl groups.

Here, the cyanoethyl group substitution rate can be calculated from the nitrogen content of the cyanoethyl group-containing polymer measured by the Kjeldahl method, or can be derived through measurement of NMR data for the sample.

If the ratio of the repeating number of the above-described third repeating unit, that is, the cyanoethyl group substitution rate is too low, the dielectric constant of the non-aqueous electrolyte battery separator using the same may decrease, and accordingly, the ion conductivity may decrease.

According to one embodiment of the invention, the cyanoethyl group-containing polymer may further include a fourth repeating unit represented by Chemical Formula 4 below.

[Formula 4]

In Formula 4, R41 is an acetate (CH ₃ COO-) group.

The fourth repeating unit portion represented by Formula 4 is derived from a precursor used to prepare a polymer having a hydroxyl group, specifically, is introduced from vinyl acetate, is not hydrolyzed, and has an acetate group as it is may be doing

In this case, the number of repetitions of the fourth repeating unit relative to the total number of repetitions of the first, second, third, and fourth repeating units may be about 10 mol% or less, preferably about 5 mol% or less. there is. If the ratio of the repeating number of the fourth repeating unit, that is, the relative content of the vinyl acetate-derived repeating unit is too high, the non-aqueous electrolyte battery separator using the repeating unit may have reduced adhesive strength with inorganic materials and may be invaded by the electrolyte solution. there is.

According to one embodiment of the invention, the cyanoethyl group-containing polymer may have a weight average molecular weight of about 50,000 to about 300,000, or about 55,000 or more and about 270,000 or less.

If the weight average molecular weight value of the polymer is too small, the dispersion stability of the inorganic material may deteriorate and the adhesive strength after coating may decrease. problems may arise.

(Manufacturing method)

Meanwhile, the above-mentioned cyanoethyl group-containing polymer is formed by polymerizing the first monomer represented by Formula 1-1 and vinyl acetate to form an acetate group-containing polymer; and a substitution step of adding a base to the acetate group-containing polymer and reacting with acrylonitrile.

[Formula 1-1]

In Formula 1-1, R11 is hydrogen or alkyl having 1 to 8 carbon atoms, and means the above-mentioned ethylenically unsaturated monomer.

The step of forming the acetate group-containing polymer, that is, the polymerization reaction, may be performed by gas phase polymerization or solution polymerization, and may be performed in the presence of an initiator or without the use of an initiator.

In the case of solution polymerization, any solvent capable of mediating the reaction between the ethylenically unsaturated monomer used as a reactant and vinyl acetate can be used without any particular problem. For example, methanol, ethanol, propanol, isopropanol, butanol, ethyl acetate, butyl acetate, ethylene carbonate, methyl isobutyl ketone, cyclohexanone, and the like, and vinyl acetate, that is, vinyl acetate, which is a reactant, may be used as a reaction solvent, and one or more of these solvents may be mixed and used, but the present invention This is not necessarily limited to this.

In the case of using a solvent, the amount of the solvent may be about 10 to 500 parts by weight, or about 20 to about 200 parts by weight, based on 100 parts by weight of the reactant.

Examples of the initiator include 2,2-azobis(2-cyanobutane), 2,2-azobis(methylbutyronitrile), 2,2'-azoisobutyronitrile (AIBN), azo-based compounds such as azobisdimethylvaleronitrile (AMVN); peroxy-based compounds such as benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, oxidized cumyl peroxide, and hydrogen peroxide; Alternatively, hydroperoxides may be used, but the present invention is not necessarily limited thereto.

The initiator may decompose at a predetermined temperature of about 40 to about 80° C. to form radicals, and may initiate polymerization of reactants through free radical polymerization.

In the case of using an initiator, the amount of the initiator may be about 0.001 to about 1 part by weight, or about 0.01 to about 0.5 part by weight based on 100 parts by weight of the reactant.

At this time, in the step of forming the acetate group-containing polymer, about 3 to about 15 parts by weight of the first monomer, preferably about 5 to about 10 parts by weight, based on 100 parts by weight of the vinyl acetate may be used.

When the amount of vinyl acetate and the first monomer, that is, the ethylenically unsaturated monomer, is adjusted within the above range, the relative ratio of the repeating unit derived from the ethylenically unsaturated monomer, that is, the above-mentioned first repeating unit, can be adjusted in the polymer produced. there will be

And, the polymerization may be carried out at about 50 to 80 °C, or about 60 to about 70 °C.

By the above reaction, a copolymer comprising a repeating unit derived from an ethylenically unsaturated monomer, that is, a first repeating unit, and a repeating unit derived from vinyl acetate, that is, a fourth repeating unit, can be prepared.

Thereafter, a substitution step is performed in which a base is added to the acetate group-containing polymer and reacted with acrylonitrile.

In the step of adding a base to the polymer, it may be preferable to use a base having a hydroxyl group, such as sodium hydroxide or potassium hydroxide. The base having a hydroxyl group causes a saponification reaction with the acetate group of the fourth repeating unit in the acetate group-containing polymer. Accordingly, a hydroxyl group may be introduced into the acetate group-containing polymer, which may mean the Polymer-OH form in the above-described reaction scheme.

However, as soon as the hydroxyl group is introduced into the polymer, hydrogen is removed by the surrounding base to form an anion of Polymer-O-, and this anion is directly added to the unsaturated bond of acrylonitrile, resulting in Michael addition will cause a reaction.

That is, in the production method according to one aspect of the present invention, after preparing a copolymer by the reaction of an ethylenically unsaturated monomer and vinyl acetate, introducing a hydroxyl group into the copolymer, by Michael addition reaction with acrylonitrile Since a series of reactions proceeds continuously until the introduction of the cyanoethyl group, the process can be simplified.

In particular, in the case of using a base having a hydroxyl group in the continuous reaction as described above, the hydroxyl group is consumed by the saponification reaction with the acetate group, but the anion of Polymer-O- is generated as the saponification reaction with the acetate group proceeds, and the Polymer-O - As the Michael addition reaction between the form anion and acrylonitrile proceeds, the base in the form of a hydroxyl group is regenerated.

That is, in the production method of the present invention, the base having a hydroxyl group is used as a kind of catalyst, and thus the amount used can be greatly reduced compared to the existing method, thereby greatly reducing environmental pollution and costs.

In addition, since the base having a hydroxyl group is regenerated by the series of reactions described above, the pH of the reaction system can be constantly adjusted according to the amount used, and in the cyanoethyl group-containing polymer produced, the following second repeating unit The content of can be easily controlled, and the substitution rate of the cyanoethyl group in the produced cyanoethyl group-containing polymer can be greatly increased.

In this regard, the base may be used in an amount of about 5 to about 15 parts by weight, or about 5 to about 10 parts by weight, based on 100 parts by weight of the acetate group-containing polymer.

Separately, in the substitution step, the acrylonitrile may be used in an amount of about 50 to about 200 parts by weight, or about 70 to about 150 parts by weight based on 100 parts by weight of the acetate group-containing polymer.

According to another embodiment of the present invention, the substitution step proceeds by dissolving the acetate group-containing polymer in a first solvent, then removing the first solvent, and introducing a second solvent and a base; The first solvent may be a solvent dissolving the acetate group-containing polymer, and the second solvent may be a solvent dissolving the polymer having a cyanoethyl group.

At this time, it may be preferable to use, for example, water, methanol, ethanol, isopropanol, isobutanol, etc. as the first solvent, and acetonitrile, gamma-butyrolactone, dimethylphthalate, It may be preferable to use dimethyl sulfoxide, methyl ethyl ketone, N,N-dimethylformamide, tetramethylene sulfoxide, acrylonitrile, N,N-dimethylacetamide or the like. In the case of acrylonitrile, it can also be used as a reactant and as such can be used as a solvent, capable of mediating the reaction and dissolving the resulting cyanoethyl group-containing polymer.

As described above, by using the method of replacing the solvent in the middle of the substitution step, the yield of the cyanoethyl group-containing polymer can be increased, and the reaction of other solvents with acrylonitrile can prevent the formation of by-products.

The substitution step may be performed at about 0 to about 60 °C for about 2 to about 12 hours.

After completion of the reaction, the reaction solution is separated into two layers, an aqueous layer and an organic layer containing a cyanoethyl group-containing polymer. The organic layer is taken out, and water is added thereto to precipitate a product, thereby obtaining a crude product of a cyanoethyl group-containing polymer can be obtained. By washing this crude product with a large amount of water or repeating re-dissolution/re-precipitation, a cyanoethyl group-containing polymer having a content of bis-cyanoethyl ether as a by-product of 0.5% by weight or less can be obtained.

(separator)

Meanwhile, according to another aspect of the invention, a heat-resistant porous layer comprising the dispersant composition for a non-aqueous electrolyte battery separator of claim 1; and a porous substrate; A separator for a non-aqueous electrolyte battery is provided.

The composition used for forming the heat-resistant porous layer on the non-aqueous electrolyte battery separator includes not only the above-mentioned cyanoethyl group-containing polymer, but also an ethylene-vinyl acetate copolymer (EVA, structural units derived from vinyl acetate in an amount of 20 to 35 moles), if necessary. %), acrylate copolymer, styrene butadiene rubber (SBR), polyvinyl butyral (PVB), polyvinylpyrrolidone (PVP), polyurethane, polyvinylidene fluoride-hexafluoropropylene, polyvinyl Liden fluoride-trichloroethylene, polyvinylidene fluoride-chlorotrifluoroethylene copolymer, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, cellulose acetate, cellulose acetate butyrate, Resins such as cellulose acetate propionate may be further included.

When these resins are additionally used, the resins may be mixed in an amount of about 10 to about 1,000 parts by weight based on 100 parts by weight of the cyanoethyl group-containing polymer.

In addition, the heat-resistant porous layer may further include an inorganic filler.

Specifically, the separator for a non-aqueous electrolyte battery of the present invention may be a separator including a heat-resistant porous layer containing the dispersant composition and an inorganic filler, and a porous substrate. In this case, the heat-resistant porous layer is one side of the surface of the porous substrate. It may be formed on one side or both sides, and may have a structure having a plurality of pores inside due to voids between inorganic fillers.

When the heat-resistant porous layer is formed on only one side of the surface of the porous substrate, it may be provided on either the anode-side surface or the cathode-side surface.

On the other hand, the inorganic filler is not particularly limited as long as it has a melting point of about 200 ° C. or higher, has high electrical insulation, is electrochemically stable, and is stable in an electrolyte solution or a solvent used in a slurry for forming a heat-resistant porous layer.

Such inorganic fillers include, for example, iron oxide, SiO ₂ (silica), Al ₂ O ₃ (alumina), TiO ₂ , BaTiO ₃ , ZrO, PB(Mg ₃ Nb _2/3 )O ₃ -PbTiO ₃ (PMN- PT), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ and the like inorganic oxide fine particles; fine particles of inorganic nitrides such as aluminum nitride and silicon nitride; Poorly soluble ion crystal fine particles, such as calcium fluoride, barium fluoride, and barium sulfate; covalently bonded crystal fine particles such as silicon and diamond; fine clay particles such as talc and montmorillonite; Mineral resource-derived materials such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, bentonite, or lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , wherein x and y are 0 < A number that satisfies x<2, 0<y<3); or combinations thereof.

The particle diameter of the inorganic filler is not particularly limited, but in order to form a heat-resistant porous layer of uniform thickness and to obtain an appropriate porosity, an average particle diameter of about 5 nm to about 5 μm may be used. Preferably, Anything from about 0.01 to about 1 μm may be used.

Meanwhile, the average particle diameter here can be measured by a measuring device based on the laser diffraction scattering method.

If the diameter of the inorganic filler is too small, dispersibility may deteriorate, making it difficult to control the physical properties of the separator.

In addition, when the diameter of the inorganic filler is too large, the strength of the heat-resistant porous layer may decrease and the smoothness of the surface may deteriorate, and the heat-resistant porous layer produced may become thick and mechanical properties may deteriorate. .

On the other hand, the method for forming the heat-resistant porous layer is not particularly limited, but, for example, a slurry obtained by dispersing an inorganic filler in the dispersant composition described above is prepared, coated on a porous substrate, and then the solvent is dried and removed. can be used.

Here, the solvent used in the dispersant composition is not particularly limited as long as it can dissolve the above-mentioned cyanoethyl group-containing polymer, and examples thereof include acetone, tetrahydrofuran, cyclohexanone, ethylene glycol monomethyl ether, methyl ethyl ketone, Acetonitrile, furfuryl alcohol, tetrahydrofurfuryl alcohol, methyl acetoacetate, nitromethane, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone, γ-butyrolactone, propylene carbo Nate et al.

This solvent may be used in an amount of about 300 to about 5,000 parts by weight based on 100 parts by weight of the cyanoethyl group-containing polymer and resin component.

In addition, as a method of dispersing the inorganic filler in the above-described dispersant composition, a known stirrer, disperser, grinder, etc. can be used, and specifically, a ball mill method can be used.

The relative content ratio between the dispersant composition and the inorganic filler in the slurry is not particularly limited, and may be differently adjusted depending on the thickness, average pore diameter, and porosity of the heat-resistant porous layer to be produced.

Specifically, the content of the inorganic filler in the heat-resistant porous layer may be about 50% by weight or more, or about 95% by weight or less.

If the content of the inorganic filler is too low, the ratio of pores in the heat-resistant porous layer may decrease, resulting in deterioration in battery performance or insufficient heat resistance. If the content of the inorganic filler is too high, the heat-resistant porous layer may It becomes vulnerable, and a problem that handling is difficult may occur.

On the other hand, since the ion conduction path is secured by the pores in the heat-resistant porous layer, low-resistance is possible. The average pore diameter is not particularly limited as long as it is a size that allows lithium ions in the electrolyte described later to pass through, but from the viewpoint of the mechanical strength of the heat-resistant porous layer, it is about 5 nm to about 5 μm, preferably about 0.1 to about 3 μm. The porosity may be in the range of about 5 to about 95%, preferably about 20 to about 70%.

Here, the average pore diameter can be measured by a mercury porosimetry porosimetry, and the porosity is determined by the true density (d) of the inorganic filler, the volume (v) of the heat-resistant porous layer, and the mass (m) of the heat-resistant porous layer, It can be calculated by the following formula.

Porosity (%)={1-m/(vd)}Х100

As described above, a heat-resistant porous layer having an average pore diameter value and a porosity value within the above ranges can be obtained by controlling the particle size or content of the inorganic filler.

Meanwhile, the porous substrate may include a thermoplastic resin component.

The porous substrate containing the thermoplastic resin component may melt when the temperature rises above a certain level and close the pores, thereby preventing the movement of ions and preventing the flow of current, thereby suppressing heat generation or ignition.

Thermoplastic resins that can be used as the porous substrate include polyolefin resins such as low-density polyethylene, high-density polyethylene, ultra-high molecular weight polyethylene, and polypropylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; It may be a polyacetal resin, a polyamide resin, a polycarbonate resin, a polyimide resin, a polyether ether ketone resin, a polyether sulfone resin, or a combination thereof.

Meanwhile, the porous substrate may preferably have a film shape, and the thickness thereof is not particularly limited, but is preferably about 2 to about 50 μm. If the thickness is too thin, it may be difficult to maintain mechanical properties, and if the thickness is too thick, a problem of functioning as a resistance layer may occur.

In addition, the average pore diameter and porosity of the porous substrate are not particularly limited, but it may be preferable that the average pore diameter is about 0.1 to about 30 μm and the porosity is about 10% to about 90%.

If the pore size is too small or the porosity is too low, ion conductivity may deteriorate, and if the average pore diameter is too large or the porosity is too high, mechanical strength is lowered, resulting in poor function as a substrate. There may be problems that can't be done.

The average pore diameter can be measured in the same way as in the case of the heat-resistant porous layer. On the other hand, the porosity can be calculated by the following formula by obtaining the true density (d) of the porous substrate, the volume (v) of the porous substrate, and the mass (m) of the porous substrate.

Porosity (%)={1-m/(vd)}Х100

On the other hand, as a method of coating the slurry on the porous substrate, a conventional coating method in the art can be used, and any method capable of realizing the required layer thickness or coating area is not particularly limited. For example, gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, deep coater method, knife coater method, air doctor coater method, blade coater method, rod coater method, squeeze coater method, cast coater method, Methods such as a die coater method, a screen printing method, and a spray coating method can be used.

The total thickness of the non-aqueous electrolyte battery separator obtained as described above is not particularly limited and may be adjusted in consideration of the use and performance of the battery. can be within range.

(Non-aqueous electrolyte battery)

Meanwhile, the non-aqueous electrolyte battery according to one aspect of the present invention may include a positive electrode, a negative electrode, the above-described separator for a non-aqueous electrolyte battery, and an electrolyte solution.

Specifically, the non-aqueous electrolyte battery may be manufactured by disposing the separator for a non-aqueous electrolyte battery between the positive electrode and the negative electrode and impregnating the separator with an electrolyte solution.

In the case of using a separator for a non-aqueous electrolyte battery in which the heat-resistant porous layer is provided on only one side of the porous substrate, the surface having the heat-resistant porous layer may be positioned on either the anode side or the cathode side.

Examples of the nonaqueous electrolyte battery of the present invention include a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

Meanwhile, the positive electrode and the negative electrode may be manufactured by applying an electrode mixture obtained by dispersing a positive electrode or negative electrode active material and a conductive agent in a solution in which a binder is dissolved, to a current collector.

As a cathode active material, a lithium-containing transition metal having a layered structure represented by a chemical formula of Li _1+x MO ₂ (-0.1<x<0.1, M: Co, Ni, Mn, Al, Mg, Zr, Ti, Sn, etc.) It is possible to use oxides, LiMn ₂ O ₄ or spinel-structured lithium manganese oxides in which some of their elements are substituted with other elements, olivine-type compounds represented by LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.), etc. do.

The lithium-containing transition metal oxide of the layered structure is, for example, LiCoO ₂ or LiNi ₁ - _x Co _x - _y Al _y O ₂ (0.1=x≤=0.3, 0.01≤=y≤=0.2), etc., at least Oxides containing Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiNi _3/5 Mn _1/5 Co _{1 /5} O ₂ , etc.) and the like.

On the other hand, the negative electrode active material includes, for example, lithium alloys such as lithium metal and lithium aluminum alloy, carbonaceous materials capable of intercalating and deintercalating lithium, cokes such as graphite, phenol resin, and furan resin, carbon fiber, Glassy carbon, pyrolytic carbon, activated carbon, etc. are mentioned.

On the other hand, as the positive electrode current collector, for example, aluminum, nickel, or a thin metal body made of a combination thereof may be used, and the negative electrode current collector may be, for example, copper, gold, nickel, copper alloy or the like. A thin metal body or the like manufactured by a combination thereof may be used.

On the other hand, the conductive agent, for example, carbon black such as acetylene black, Ketjen Black; metal fibers such as aluminum and nickel; Natural graphite, thermally expanded graphite, carbon fiber, ruthenium oxide, titanium oxide and the like can be used. Among these, acetylene black and Ketjen Black, which can secure desired conductivity with a small amount of blending, can be preferably used.

Meanwhile, various known binders may be used as the binder, and examples thereof include polytetrafluoroethylene, polyvinylidene fluoride, carboxymethylcellulose, fluoroolefin copolymer crosslinked polymer, styrene-butadiene copolymer, polyacrylonitrile, poly Vinyl alcohol or the like may be used.

The binder may be dissolved in a solvent, and as the solvent, for example, N-methyl-2-pyrrolidone (NMP) or the like may be used.

On the other hand, as the electrolyte solution, a solution in which a lithium salt is dissolved in an organic solvent is used. The lithium salt is not particularly limited as long as it dissociates in a solvent to form Li ⁺ ions and does not cause side reactions such as decomposition in the voltage range used as a battery.

For example, inorganic lithium salts such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiC(CF ₃ SO ₂ ) ₃ , LiCnF _2n+1 SO ₃ (n=2), LiN(RfOSO ₂ ) ₂ (wherein Rf represents a fluoroalkyl group), organic lithium salts, etc. can be used Preferred lithium salts are LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , Li(CF ₃ SO ₂ ) ₂ N.

On the other hand, the organic solvent used for the electrolyte solution is not particularly limited as long as it dissolves the above lithium salt and does not cause side reactions such as decomposition in the voltage range used as a battery. Examples thereof include, but are not limited to, cyclic carbonate esters such as propylene carbonate and ethylene carbonate, chain carbonate esters such as ethylmethyl carbonate, diethyl carbonate, dimethyl carbonate and dipropyl carbonate, and mixtures thereof.

When using a mixture of cyclic carbonate and chain carbonate, the volume ratio of cyclic carbonate to chain carbonate is preferably about 4:1 to about 1:4 from the viewpoint of optimizing dielectric constant and viscosity.

On the other hand, the form of the non-aqueous electrolyte battery of the present invention may be a polyhedral or cylindrical shape using a steel can, aluminum can, etc. as an exterior body (exterior can), or a package battery using a laminate film deposited with metal as an exterior body. Not particularly limited.

The separator composition for a non-aqueous electrolyte battery of the present invention not only firmly adheres the inorganic filler when forming the heat-resistant porous layer of the separator, but also effectively disperses the inorganic filler to further improve the heat resistance of the separator.

In addition, in the method for producing a cyanoethyl group-containing polymer of the present specification, the cyanoethyl group-containing polymer used as the dispersant for the non-aqueous electrolyte battery separator can be easily produced through a series of steps.

Hereinafter, the action and effect of the invention will be described in more detail through specific examples of the invention. However, these embodiments are only presented as examples of the invention, and the scope of the invention is not determined thereby.

<Example>

Polymerization of ethylene and vinyl acetate (preparation of polymers containing acetate groups)

Polymerization Example 1

In a stainless steel polymerization reactor, 94.8 parts by weight of vinyl acetate were dissolved in 200 parts by weight of methanol, and ethylene was pressurized into the reactor to dissolve. Dissolved ethylene was added so as to be 5.2 parts by weight.

0.1 part by weight of an initiator (2,2'-azoisobutyronitrile) was added.

The copolymerization reaction proceeded for 10 hours while maintaining the reaction system at a temperature of about 60 to 70 °C.

From the polymerization solution, the solvent and unreacted substances were removed to obtain an acetate group-containing copolymer.

The obtained polymer had a weight average molecular weight of about 60,000 g/mol and a molecular weight distribution of about 1.53.

When measuring the weight average molecular weight, gel permeation chromatography GPC (measurement device name: Alliance e2695; manufacturer: WATERS) was used, and as a detector, a differential refractive index detector (measurement device name: W2414; manufacturer: WATERS), DMF column was used. A column was used, the flow rate was 1 mL / min, the column temperature was 65 ° C, the sample injection amount was 10 mg / 10 mL, 200 μL was supplied, and polystyrene (molecular weight: 9,600 / 31,420 / 113,300 / 327,300 / 1,270,000 / 6 types of 4,230,000) were used.

The relative content of ethylene repeating units in the polymer was about 21.0 mol%.

Polymerization Example 2

Dissolving 8.9 parts by weight of ethylene and 91.1 parts by weight of vinyl acetate in 45 parts by weight of t-butanol,

0.043 parts by weight of an initiator (2,2'-azobis(2,4-dimethylvaleronitrile) was added.

The copolymerization reaction proceeded for 10 hours while maintaining the reaction system at a temperature of about 60 to 70 °C.

The solvent and unreacted materials were removed from the polymerization solution to obtain an acetate group-containing copolymer.

The obtained polymer had a weight average molecular weight of about 263,000 g/mol and a molecular weight distribution of about 2.09.

The relative content of ethylene repeating units in the polymer was about 27.6 mol%.

Preparation of polymers containing cyanoethyl groups

Example 1

About 20 g of the acetate group-containing polymer obtained in Polymerization Example 1 was again dissolved in 180 g of methanol to prepare a 10% concentration solution. While stirring the solution at about 60° C., 1.8 g of sodium hydroxide (9 parts by weight) was dissolved in 180 parts by weight of methanol, and then mixed with the acetate group-containing polymer solution to proceed with hydrolysis. Again, about 180 g of dimethyl sulfoxide was slowly added while methanol was removed by distillation at 65 ° C. At the same time, 20 g of acrylonitrile was added, and the reaction was carried out at 60 ° C. for about 24 hours.

After completion of the reaction, the reaction solution was neutralized with acetic acid, and water vapor was blown to completely volatilize methanol, and then particles dispersed in water were precipitated.

This precipitate was washed with a large amount of water to obtain a cyanoethyl group-containing polymer. (Cyanoethyl substitution rate: about 81 mol%)

The cyanoethyl substitution rate was calculated as a percentage ratio with respect to the number of moles of hydroxyl groups originally present per repeating unit of the polymer after determining the nitrogen content through the Kjeldahl Method.

Comparative Example 1

20 parts by weight of polyvinyl alcohol having a polymerization degree of 1500 and 10 parts by weight of polyvinyl alcohol having a polymerization degree of 1500 were dissolved in 120 parts by weight of water and mixed until the polyvinyl alcohol was uniformly dissolved.

To this, 100 parts by weight of a 12.5 wt% sodium hydroxide aqueous solution was added and mixed uniformly with the polyvinyl alcohol aqueous solution.

After that, 150 parts by weight of acrylonitrile and 120 parts by weight of isopropanol were added and reacted at 30 DEG C for 5 hours.

To this, a 25 wt% aqueous acetic acid solution was added in an equivalent amount to the above sodium hydroxide to neutralize.

Water was added to this while stirring to precipitate cyanoethyl polyvinyl alcohol (crude product). The precipitated cyanoethyl polyvinyl alcohol (crude product) was purified by washing with a large amount of water, dissolving, and re-precipitating, and dried to obtain cyanoethyl polyvinyl alcohol. (Cyanoethyl substitution rate: about 79 mol%)

Comparative Example 2

About 20 g of the acetate group-containing polymer obtained in Polymerization Example 1 was again dissolved in 180 g of methanol to prepare a 10% concentration solution. While stirring the solution at about 60° C., 1.8 g of sodium hydroxide (9 parts by weight) was dissolved in 180 parts by weight of methanol, and then mixed with the acetate group-containing polymer solution to proceed with hydrolysis. Thereafter, 20 g of acrylonitrile was immediately added, and the reaction was performed at 60° C. for about 24 hours.

After completion of the reaction, the reaction solution was neutralized with acetic acid, and water vapor was blown to completely volatilize methanol, and then particles dispersed in water were precipitated.

This precipitate was washed with a large amount of water to obtain a cyanoethyl group-containing polymer. (Cyanoethyl substitution rate: about 5 mol%)

slurry manufacturing

Alumina having an average particle diameter of 0.7 μm and a BET of 4 m ² /g was dispersed in acetone. The polymer prepared in Examples and Comparative Examples and the alumina dispersion were mixed in a weight ratio of polymer: alumina = 10:90, and two types of zirconia beads were used (0.5 mm: 1 mm = 1:1) in a ball mill. pulverized and mixed for 20 minutes to prepare a slurry.

separator manufacturing

Using a doctor blade, the slurry prepared above was applied to one surface of the polyethylene porous substrate and dried to prepare a separator having a coating layer thereon.

dispersion stability

For the slurry, the sedimentation rate of slurry particles in the slurry was measured using a dispersion stability analyzer (Lumisizer LS651).

Film formability

A sample was prepared by cutting the manufactured separator into 1m X 1m. Thereafter, the flatness and uniformity of the coating film was visually observed in the prepared sample, and a case without a problem was evaluated as 0 to 5 points, with 5 points being scored.

adhesion

The prepared separators were cut to a size of 15 mm * 100 mm, and two sheets were prepared respectively.

The prepared separators were overlapped with each other, sandwiched between 100 μm PET films, and bonded by passing through a roll laminator at 100 °C. At this time, the speed of the roll laminator was heated for 30 seconds at 0.3 m/min, and the pressure at this time was 2 kgf/cm ² .

After mounting the distal end of the two adhered separators to a UTM device (LLOYD Instrument LF Plus), force was applied in both directions at a measurement speed of 100 mm/min to measure the force required to separate the adhered separators.

The evaluation results are summarized in the table below.

Example 1 Comparative Example 1 Comparative Example 2 substitution rate 81% 79% 5% Dispersion stability
(sedimentation velocity; μm/s) 1.2 1.1 1.1 film formation
(5-point method) 5 4 4 adhesion
(gf/15mm) 81 72 74

Referring to Table 1, the slurry according to one embodiment of the present invention, that is, the dispersant, has a relatively high substitution rate of cyanoethyl groups, so the sedimentation rate is slow compared to the comparative example, and the separator manufactured using this, It can be seen that the coating film formability is very excellent, and the adhesive strength is very excellent compared to the comparative example.

Accordingly, the separator according to one embodiment of the present invention is expected to be able to firmly adhere the inorganic filler when forming the heat-resistant porous layer, and to effectively disperse the inorganic filler to further improve heat resistance.

Claims (15)

delete delete delete delete delete delete In the presence of an initiator,
polymerizing a first monomer represented by Formula 1-1 and vinyl acetate to form an acetate group-containing polymer; and
A substitution step of adding a base to the acetate group-containing polymer and reacting with acrylonitrile,
The substitution step proceeds by dissolving the acetate group-containing polymer in a first solvent, removing the first solvent, and simultaneously introducing a second solvent and a base;
the first solvent is the acetate group-containing polymer-soluble solvent, and the second solvent is a cyanoethyl group-containing polymer-soluble solvent;
Process for preparing cyanoethyl group-containing polymers:
[Formula 1-1]

In Formula 1-1, R11 is hydrogen or alkyl having 1 to 8 carbon atoms.
According to claim 7,
A method for producing a cyanoethyl group-containing polymer, wherein 3 to 15 parts by weight of the first monomer is used with respect to 100 parts by weight of the vinyl acetate.
According to claim 7,
The polymerization is carried out at 50 to 80 ° C., a method for producing a cyanoethyl group-containing polymer.
According to claim 7,
The base is used in an amount of 5 to 15 parts by weight based on 100 parts by weight of the acetate group-containing polymer.
According to claim 7,
The acrylonitrile is used in an amount of 50 to 200 parts by weight based on 100 parts by weight of the acetate group-containing polymer.
delete delete delete delete