KR101938385B1 - Separator with a layer of binder polymers for electrochemical device and Electrochemical device comprising the same - Google Patents

Abstract

The present invention relates to a separator for an electrochemical device having a binder polymer layer and an electrochemical device comprising the same, wherein the compound used in the polymer layer of the separator has little or no elution in the electrolyte solution, have. As a result, internal short-circuiting or deterioration in performance caused by deterioration of the adhesive strength of the separator does not occur or occurs little.

Description

TECHNICAL FIELD The present invention relates to a separator for electrochemical devices having a binder polymer layer and an electrochemical device including the binder polymer layer,

The present invention relates to a separator for an electrochemical device having a binder polymer layer and an electrochemical device including the separator.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices have attracted the greatest attention in this respect, among which the development of rechargeable secondary batteries has become a focus of attention. In recent years, in order to improve the capacity density and specific energy in developing such batteries, And research and development on the design of the battery.

Such an electrochemical device includes an electrode assembly in which a separator is interposed between a cathode and an anode in a battery case. The separator prevents a short circuit due to contact between the cathode and the anode while preventing a path through which the electrolyte moves between the cathode and the anode to provide. Therefore, it is important that the structure of the electrode assembly in which the cathode, the separator and the anode are laminated is maintained even after being impregnated with the electrolyte. For this purpose, a method of forming an electrode adhesive layer on the outermost layer of the separator has been proposed in the art. However, when the separator having the electrode adhesive layer is contained in the electrode assembly and impregnated in the electrolyte, the electrode adhesive layer component such as the binder polymer component used in the electrode adhesive layer is eluted into the electrolyte solution and the adhesive force between the separator and the electrode is lowered, A phenomenon of deteriorating the performance of the chemical device occurs. Therefore, it is necessary to solve such a problem.

It is an object of the present invention to provide a separator for an electrochemical device having a binder polymer layer as an outermost layer of a separator capable of exhibiting excellent adhesion between an electrode and a separator.

Another object of the present invention is to provide a separator for an electrochemical device which can maintain an excellent adhesive force between an electrode and a separator even after the electrolytic solution is impregnated, because the binder polymeric compound of the binder polymer layer hardly elutes into the electrolytic solution even after the electrolytic solution is impregnated have.

It is still another object of the present invention to provide an electrochemical device using the separator to improve the internal short circuit phenomenon and to have excellent cell performance.

According to an aspect of the present invention, there is provided a separator for an electrochemical device, comprising: a porous polymer substrate; And a binder polymer layer formed on at least one side of the porous polymer base material and constituting an outermost layer of the separator and containing a binder polymer compound having a low electrolyte dissolution rate.

According to another aspect of the present invention, there is further provided a porous coating layer including inorganic particles and a binder polymer between the porous polymer substrate and the binder polymer layer, wherein the inorganic particles of the porous coating layer are filled with each other, The interstitial volume is formed between the inorganic particles, and the interstitial volume between the inorganic particles becomes an empty space, thereby providing a separator for forming pores.

The binder polymer compound having a low electrolyte dissolution rate is preferably a polyacrylic acid (PAA), a polymethylmethacrylate, a polyisobutylmethacrylate (PAA), or a polyisobutylmethacrylate ), Polyethylacrylate, polybutyl acrylate, poly (2-ethylhexyl acrylate), polyacrylonitrile, polyvinylpyrrolidone, polyvinylpyrrolidone, Polyvinylacetate, polyethylene-co-vinyl acetate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cellulose acetate propionate, Cyanoethyl cellulose, cyanoethyl sucrose, carboxymethyl cellulose, It can be a butadiene copolymer (acrylonitrile-styrene-butadiene copolymer), and polyimide (polyimide) 1 or two or more mixture selected from the group consisting of-room cellulose (carboxyl methyl cellulose), an acrylonitrile-styrene.

The porous polymer substrate may be formed of at least one selected from the group consisting of polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, but are not limited to, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, polyethylene naphthalene (polyethylenenaphthalene), and the like, or a film or a nonwoven fabric formed by mixing two or more of these polymers.

The binder polymer compound having a low electrolyte dissolution rate may be included in the binder polymer layer in an amount of 10 to 50 parts by weight based on 100 parts by weight of the total binder polymer component constituting the binder polymer layer.

The binder polymer layer may further include a polyvinylidene fluoride (PVdF) -based compound.

The binder polymer compound having a low electrolyte dissolution rate and the PVdF compound may be contained in the form of a mixture in the binder polymer layer.

The binder polymer compound having a low electrolyte dissolution rate and the PVdF compound may be included in the binder polymer layer in the form of a copolymer.

The PVdF-based compound may be selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polyvinylidene fluoride-co-tetrafluoroethylene, polyvinylidene fluoride- Or a mixture of two or more selected from the group consisting of trifluoroethylene, polyvinylidene fluoride-co-trifluorofluoroethylene and polyvinylidene fluoride-co-ethylene.

The particle size (D90) of the binder polymer constituting the binder polymer layer is preferably in the range of from 0.1 to 100 parts by mass, more preferably from 0.1 to 50 parts by mass, have.

Alternatively, the particle diameter (D90) of the binder polymer constituting the binder polymer layer may be larger than 1/4 of the average particle diameter of the inorganic particles.

The binder polymer layer may have an electrolyte impregnation rate ranging from 30 to 300% by weight at 25 ° C.

Alternatively, the binder polymer layer may have an electrolyte impregnation rate ranging from 50 to 500% by weight at 60 ° C.

According to another aspect of the present invention, there is provided an electrochemical device comprising a cathode, an anode, a separator interposed between the cathode and the anode, and an electrolyte, wherein the separator is the separator described above.

The binder polymer compound having a low electrolyte dissolution rate may have a dissolution rate of 0 to less than 10% when impregnated with an electrolyte at 60 캜.

The electrolytic solution may include one or more selected from the group consisting of linear carbonates, cyclic carbonates, ethers, esters, and amides.

The electrochemical device may be a lithium secondary battery.

A separator according to an embodiment of the present invention comprises a binder polymer layer formed on at least one surface of a porous polymer base material and constituting an outermost layer of the separator and serving as an electrode adhesion layer, The polymeric binder compound component contained therein is hardly or not eluted with the electrolytic solution, and thus an excellent adhesive force between the electrode and the separator can be maintained.

As a result, it is possible to realize a strong lamination between the separator and the electrode, while the problem of the internal short circuit of the electrochemical device and deterioration of the performance of the electrochemical device, which have conventionally occurred due to the elution of the electrolytic solution of the binder polymer compound, have.

For this reason, the separator according to an embodiment of the present invention can be preferably used in an electrochemical device such as an electric vehicle, a hybrid electric vehicle, and a power storage device which require a long cycle characteristic and high output characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention and are not intended to limit the scope of the invention. On the other hand, the shape, size, scale or ratio of the elements in the drawings incorporated herein can be exaggerated to emphasize a clearer description.
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a view schematically showing a separator according to an embodiment of the present invention, in which a binder polymer layer is formed on both surfaces of a porous polymer substrate.
2 is a schematic view of a separator according to another embodiment of the present invention in which a porous coating layer comprising inorganic particles and a binder polymer is formed on both surfaces of a porous polymer substrate and a binder polymer layer is formed on each of the porous coating layers to be.

Hereinafter, the present invention will be described in detail. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined.

In one aspect of the present invention, there is provided a separator for an electrochemical device, comprising: a porous polymer substrate; And a binder polymer layer formed on at least one side of the porous polymer base material and constituting an outermost layer of the separator and containing a binder polymer compound having a low electrolyte dissolution rate. Such an embodiment is shown in Fig. 1, and in the separator of Fig. 1, the binder polymer layer 100 is formed on both sides of the porous polymer substrate 10 by an interview.

In another embodiment of the present invention, a porous coating layer including inorganic particles and a binder polymer is further formed between the porous polymer substrate and the binder polymer layer, and the inorganic particles of the porous coating layer are filled with the binder polymer, Thereby forming an interstitial volume between the inorganic particles, and an interstitial volume between the inorganic particles is an empty space to provide a separator for forming pores. 2, a porous coating layer 20 including inorganic particles and a binder polymer is formed on both surfaces of the porous polymer substrate 10, and the porous coating layer 20 A binder polymer layer 100 is formed on the porous polymer layer 100, and the porous polymer layer 100 and the porous coating layer 20 are interfaced with each other.

As used herein, the term "separator" refers to a porous ion-conducting barrier used to separate an anode and a cathode from an electrochemical device. Such a separator may include not only the above-described aspects, but also any separator which meets the object of the present invention.

As used herein, the term 'separator outermost layer' is understood to mean a separator portion that comes into contact with the cathode and / or the anode when the separator is interposed between the cathode and the anode.

The porous polymer substrate may be any conventional porous polymer substrate used in a separator of an electrochemical device. Examples of the porous polymer substrate include polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, But are not limited to, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, a film or a nonwoven fabric formed by mixing two or more kinds of polymers such as polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, and polyethylenenaphthalene, either singly or in combination.

The thickness of the porous polymer base material is not particularly limited, but is preferably 1 to 100 占 퐉 or 5 to 50 占 퐉, and the pore size and porosity present in the porous polymer base material are also not particularly limited, but are 0.001 to 50 占 퐉 and 10 to 99% .

Herein, the term 'binder polymer layer' refers to a layer of a binder polymer which is formed on at least one surface of a porous polymer substrate so as to more firmly adhere to the electrode, and which forms an outermost layer of the separator and has a low- Layer and serves to improve the adhesion between the electrode and the separator.

Herein, the term "dissolution rate" of the binder polymer means that the binder polymer layer of the separator is impregnated with the electrolytic solution at 25 ° C. for 48 hours, and the mass of the binder polymer compound eluted as the electrolyte is expressed as a percentage (%) .

In the present specification, the term "high-temperature dissolution rate" means that the binder polymeric layer of the separator is impregnated with the electrolytic solution at 60 ° C. for 24 hours, and the mass of the binder polymeric compound eluted with the electrolytic solution is expressed as a percentage (%) .

In the present specification, the term 'dissolution rate' may be referred to as 'room temperature dissolution rate' for more clear distinction from the term 'high temperature dissolution rate'.

In the present specification, the term 'binder polymer compound having a low electrolyte dissolution rate' means that the binder polymer constituting the binder polymer layer of the separator is impregnated with the electrolytic solution at 25 ° C for 48 hours, ≪ / RTI >

The binder polymer compound having a low electrolyte dissolution rate is impregnated with the electrolytic solution at 25 ° C for 48 hours, and then has an elution degree of 0 to less than 5% based on the weight of the binder polymer compound, And more preferably from 0 to less than 10%, based on the weight of the binder polymer compound.

A binder polymer compound having a low electrolyte dissolution rate which can be used in one embodiment of the present invention is not particularly limited as long as it has a solubility of not less than 0% and less than 5% on a weight basis after being impregnated with an electrolytic solution at 25 캜 for 48 hours, (PAA), polyacrylic acid, polymethylmethacrylate, polyisobutylmethacrylate, polyethylacrylate, polybutyl acrylate, poly (ethylhexyl acrylate), poly (2-ethylhexyl acrylate), polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, cellulose acetate cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate e acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer and the like. Polyimide, and the like, but the present invention is not limited thereto.

The binder polymer layer according to an embodiment of the present invention may include a binder polymer compound having a low electrolyte dissolution rate, and may further include a polyvinylidene fluoride (PVdF) -based compound, if necessary.

The binder polymer compound having a low electrolyte dissolution rate may be used together with other binder polymer compounds including PVdF binder polymer compounds. The binder polymer compound having a low electrolyte dissolution rate may be used in an amount of 10 to 100 parts by weight or 20 To 100 parts by weight of the binder polymer layer.

The PVdF compound is known to have good adhesion at the time of drying. However, PVdF compound has a problem of exhibiting high elution when impregnated with an electrolytic solution at room temperature. Especially when impregnated into a high temperature (60 DEG C) electrolytic solution, So that it is not possible to make the adhesion between the substrates.

When the compound having a low electrolyte dissolution rate is used in an amount of less than 10 parts by weight, there arises a problem that the PVdF-based binder polymer is eluted into the electrolyte solution, and the adhesion between the electrode and the separator is greatly deteriorated at the time of electrolyte impregnation, There is a problem of increasing the resistance of the separator by reducing the interstitial volume formed between the particles of the PVdF compound by the swelling of the binder polymer compound by the electrolyte solution.

The 'binder polymer compound having a low electrolyte dissolution rate' in the present invention not only has a low electrolyte elution rate but also has an effect of reducing the electrolyte dissolution rate of the PVdF compound when it is mixed or crosslinked with the PVdF compound .

When such a PVdF compound is used together with a 'binder polymer compound having a low electrolyte dissolution rate', a combination of factors may be considered as a reason for lower dissolution rate of the electrolyte. Among them, a PVdF compound is used as the low- And exhibiting an effect similar to or crosslinked with that of the PVdF compound due to the use of the binder polymer compound having a dissolution rate. Thus, even if the binder polymer layer is impregnated with the electrolytic solution, the phenomenon that the binder polymer compound is eluted into the electrolytic solution can be greatly improved.

The PVdF-based compound usable in the present invention may be a PVdF-based compound commonly used in the art. Non-limiting examples of PVdF based compounds include polyvinylidene fluoride, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polyvinylidene fluoride- At least one selected from the group consisting of ethylene, polyvinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-trifluorofluoroethylene and polyvinylidene fluoride-co- But is not limited thereto.

The particle size of the binder polymer compound constituting the binder polymer layer is not particularly limited, but is larger than the pores formed in the face-contacted porous polymer base material or the porous coating layer interposed with the binder polymer layer, It is preferable that the binder polymer does not flow in. That is, when the porous polymer film or the nonwoven fabric is disposed directly below the binder polymer layer, it is preferable that the particle diameter of the binder polymer compound constituting the binder polymer layer is larger than the pores of the porous polymer film or the nonwoven fabric, . When the porous coating layer is formed directly below the binder polymer layer, the particle diameter of the binder polymer constituting the binder polymer layer is larger than the interstitial volume formed in the porous coating layer, Is preferably larger than 1/4 of the average particle diameter of the particles and does not flow into the interstitial volume formed in the porous coating layer. For example, the particle diameter (D90) of the binder polymer constituting the binder polymer layer can be independently determined within the range of 50 nm to 1000 nm, but is not limited thereto.

In the present specification, the term "particle size" is understood to mean the maximum diameter of a substance. In terms of particle diameter, D90 is understood to mean a particle diameter in an amount corresponding to 90% of the particle diameter.

The binder polymer compound used in the binder polymer layer is coated on the porous polymer base material or the porous coating layer in the form of a dispersion dispersed in a dispersion medium to form the outermost layer of the separator.

The dispersion medium may be selected from the group consisting of acetone, methanol, ethanol, isopropyl alcohol, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water or a mixture thereof. On the other hand, the solvent for dissolving the binder polymer compound is excluded from the above-mentioned dispersion medium.

The concentration at which the binder polymer constituting the binder polymer layer is dispersed in the dispersion medium is not particularly limited and may be used at a concentration ordinarily used in the art.

The dispersion of the binder polymer compound constituting the binder polymer layer may be applied to the porous polymer base material or the porous coating layer by a conventional coating method known in the art and may be a dip coating process, (roll) coating, comma coating, or a combination thereof. The coating area and / or coating pattern of the dispersion is not particularly limited in the present invention as long as the binder polymer layer can exhibit the desired electrode adhesion.

Meanwhile, the binder polymer constituting the polymer layer of the separator according to an embodiment of the present invention has a low electrolyte impregnation rate even when impregnated with an electrolytic solution, and may exhibit a low degree of swelling.

Herein, the term "impregnation rate" refers to the degree to which the binder polymer compound is impregnated with the electrolytic solution, based on an increase in weight after the binder polymer compound is impregnated with the electrolytic solution.

In one embodiment of the present invention, the binder polymer layer may exhibit an electrolyte impregnation rate ranging from 30 to 300 wt% at 25 DEG C (room temperature) or 50 to 500 wt% at 60 DEG C (high temperature).

In the present invention, the dissolution rate of the binder polymer compound or the electrolyte solution impregnation rate of the film layer made of the binder polymer compound can be determined by measuring a method including the following steps:

① Dispense a dispersion with a certain amount of binder polymer compound dispersed in a release film.

(2) Using a doctor blade, the dispersion of the above-mentioned binder polymer compound is pushed to a thickness of 1000 mu m, and is put in an oven to dry the dispersion medium. At this time, the drying conditions are 90 ° C and 12 hours.

(3) The binder polymer compound from which the dispersion medium has been removed is desorbed from the release film, and then cut into a film having a length of 1.5 cm x 8 cm. The mass (W ₁ ) of the obtained film is measured.

(4) The film is placed in a 15 mL vial, and an electrolyte is injected to impregnate the film with an electrolytic solution. At this time, an electrolytic solution containing propylene carbonate (PC): diethyl carbonate (DEC) = 1: 1 (w / w) as an organic solvent was used as the electrolyte composition and composition ratio.

In order to obtain the experimental data of the room temperature (25 ° C) dissolution rate, the result is evaluated after impregnating the electrolytic solution at 25 ° C for 48 hours. To obtain the experimental data of the high temperature dissolution rate, .

(5) The film gelled by electrolyte impregnation is allowed to stand on a # 100 mesh at room temperature for a certain time, and then the mass (W _swollen ) of the gelled film is measured.

(6) Next, after drying the film at 90 DEG C for 48 hours, the mass (W _{dry after elution} ) is measured.

The dissolution rate of the binder polymer film can be determined by applying the measured value to the following equation (1).

[Equation 1]

(%) Of the electrolytic solution of the binder polymer compound = 100- {W _{dry after elution} / W ₁ * 100}

Further, the impregnation rate of the film made of the binder polymer compound can be obtained by substituting the measured value into the following equation (2).

&Quot; (2) "

Impregnation rate (%) = {W _swollen / W ₁ - 1} * 100

The electrolytic solution used in the present invention may include electrolytic salts and organic solvent components commonly used in the art.

The lithium salt contained as an electrolyte in a non-aqueous liquid electrolyte of the present invention can be used without limitation, those which are commonly used in a lithium secondary battery electrolyte, such as the lithium salt, the anion is F ^-, Cl ^-, Br ^-, I ^{-, _{NO 3 -, N (CN)}} 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 -, (CF 3) 4 PF 2 -, ^{_{(CF 3) 5 PF -,}} (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, (FSO 2) 2 N -, CF 3 _{CF 2 (CF 3) 2 CO} -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 (CF 2) 7 SO 3 -, CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^-, and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

In the present invention, the organic solvent used together with the binder polymer layer may be any electrolyte commonly used in the art as an electrolyte for a lithium secondary ion battery. Examples of the organic solvent include, but are not limited to, linear carbonates, cyclic carbonates, ethers, esters, amides, etc., each alone or in a mixture of two or more kinds.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate or a mixture thereof may be included. Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, and halides thereof, or a mixture of two or more thereof. Specific examples of the linear carbonate compound include a group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate Any one selected, or a mixture of two or more thereof may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high viscosity organic solvent and dissociate the lithium salt in the electrolyte well, and dimethyl carbonate and diethyl carbonate When a low viscosity and a low dielectric constant linear carbonate are mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone, ε-caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

In another aspect of the present invention, there is a separator including a porous coating layer between the porous polymer substrate and the polymeric binder layer.

The porous coating layer includes inorganic particles and a binder polymer layer. In this case, the inorganic particles are bonded to each other by the binder polymer in a state of being filled with each other, thereby causing an interstitial volume And the interstitial volume between the inorganic particles becomes an empty space to form pores.

As the inorganic particles used for forming the porous coating layer, inorganic particles, that is, inorganic particles that do not undergo oxidation and / or reduction reaction in the operating voltage range of the electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ) are further added Can be used. Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance. When inorganic particles having a high dielectric constant are used as the inorganic particles, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte is also increased, and ion conductivity of the electrolyte can be improved.

For the reasons stated above, it is preferable that the inorganic particles further include high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having lithium ion transferring ability, or a mixture thereof. Non-limiting examples of inorganic particles greater than a dielectric constant of 5 is _{BaTiO 3, Pb (Zr, Ti} ) O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB (Mg 3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiC, or a mixture thereof.

Particularly, the above-mentioned BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT), PB (Mg ₃ Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT) and hafnia (HfO ₂ ) exhibit a high permittivity characteristic with a permittivity constant of 100 or more. In addition, when a certain pressure is applied, a charge is generated when being tensioned or compressed. It is possible to prevent internal short-circuiting of both electrodes due to an external impact, thereby improving the safety of the electrochemical device. Further, when the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

The inorganic particles having the lithium ion transferring ability refer to inorganic particles containing a lithium element but having a function of transferring lithium ions without storing lithium. The inorganic particles having lithium ion transferring ability can transfer and move lithium ions due to a kind of defect existing in the particle structure, so that the lithium ion conductivity in the battery is improved and the battery performance is improved thereby . Nonlimiting examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (LixTiy (PO ₄ ) ₃ , 0 <x <2, 0 <y <3) (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), Li (LiAlTiP) _x O _y series glass (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as _3.25 Ge _0.25 P _0.75 S ₄ , lithium nitride such as _{Li 3 N (Li x N y} , 0 <x <4, 0 <y <2), Li 3 PO 4 -Li 2 S-SiS 2 SiS 2 based glass (Li _x Si _y S, such as _{z, 0 <x <3,} 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 as P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3 , such , 0 <y <3, 0 <z <7), or a mixture thereof.

The inorganic particle size of the porous coating layer is not limited, but it is preferably 0.001 to 10 탆 in order to form a coating layer having a uniform thickness and a proper porosity. If it is less than 0.001 m, the dispersibility of the inorganic particles may be deteriorated. If it is more than 10 m, the thickness of the porous coating layer may increase and mechanical properties may be deteriorated. Also, due to an excessively large pore size, The probability of happening increases.

The composition ratio of the inorganic particles and the binder polymer used in the porous coating layer is, for example, in the range of 50:50 to 99: 1, more preferably 70:30 to 95: 5. If the content ratio of the inorganic particles to the binder polymer is less than 50:50, the content of the binder polymer becomes large, and the thermal stability improvement of the separator may be deteriorated. In addition, the pore size and porosity due to the reduction of the void space formed between the inorganic particles may be reduced, resulting in deterioration of the final cell performance. If the content of the inorganic particles exceeds 99 parts by weight, the fillerability of the porous coating layer may be weakened because the content of the binder polymer is too small. The thickness of the porous coating layer is not particularly limited, but is preferably in the range of 0.01 to 20 mu m. The pore size and porosity are also not particularly limited, but the pore size is preferably in the range of 0.001 to 10 μm, and the porosity is preferably in the range of 10 to 90%. The pore size and porosity mainly depend on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 탆 or less are used, pores formed are also about 1 탆 or less. Such a pore structure is filled with an electrolyte solution to be injected at a later stage, and the filled electrolyte serves as an ion transfer function. When the pore size and porosity are 0.001 탆 or less and 10% or less, respectively, it can act as a resistive layer. If the pore size and porosity exceed 10 탆 and 90% respectively, mechanical properties may be deteriorated.

Examples of the binder polymer for forming the porous coating layer include polyvinylidene fluoride-co-hexafluoropropylene (PVdF), polyvinylidene fluoride-co-trichlorethylene, Polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl (meth) acrylate, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpullulan), cyanoethylpolulan A binder polymer selected from the group consisting of cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose; or a binder polymer selected from the group consisting of Or a mixture of two or more of them may be used.

The dispersion medium used in the slurry for forming the porous coating layer preferably has a solubility index similar to that of the binder polymer to be used and a low boiling point. This is to facilitate uniform mixing and subsequent removal of the dispersion medium. Non-limiting examples of usable dispersion media include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone N-methyl-2-pyrrolidone, NMP), cyclohexane, water or a mixture thereof.

It is preferable that the inorganic particles are added to the dispersion liquid in which the binder polymer is dispersed in the dispersion medium and then the inorganic particles are crushed. In this case, the disintegration time is preferably 1 to 20 hours, and the particle size of the disintegrated inorganic particles is preferably 0.001 to 10 占 퐉 as described above. As the crushing method, a conventional method can be used, and a ball mill method is particularly preferable.

Then, the binder polymer dispersion in which the inorganic particles are dispersed is coated on at least one surface of the porous polymer base material and dried under a humidity condition of 10 to 80%. The dispersion may be coated on the porous polymer substrate by a conventional coating method known in the art. For example, a dip coating, a die coating, a roll coating, a comma coating, A coating method or a mixing method thereof may be used.

The porous coating layer component may further contain other additives such as a conductive agent in addition to the inorganic particles and the binder polymer.

The thickness of the separator which can be used in the present invention is not particularly limited, but may be 1 to 100 占 퐉 or 5 to 50 占 퐉, and the pore size and porosity present in the separator are also not particularly limited, but 0.01 to 50 占 퐉 and 10 to 95 %. &Lt; / RTI &gt;

The thus produced separator is interposed between the cathode and the anode to constitute an electrochemical device.

The electrochemical device includes all the devices that perform an electrochemical reaction, and specific examples include capacitors such as all kinds of primary, secondary cells, fuel cells, solar cells, or super-capacitor devices. Particularly, 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 among the above secondary batteries is preferable.

The electrochemical device may be manufactured according to a conventional method known in the art, and may be manufactured, for example, by assembling between the cathode and the anode with the separator interposed therebetween, and then injecting the electrolyte solution.

The electrode to be used together with the separator of the present invention is not particularly limited, and can be produced by applying the electrode active material slurry to the current collector according to a conventional method known in the art. The electrode active material particles and the anode active material particles used for the electrode may be conventional electrode active material particles that can be used for the cathode and the anode of the conventional electrochemical device, and specific examples are as described above.

The types of the lithium salt and the organic solvent included in the nonaqueous electrolyte solution of the present invention are as described above.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell. As a process for applying the separator of the present invention to a battery, lamination, stacking and folding processes of a separator and an electrode are possible in addition to a general winding process.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the invention are provided to more fully describe the present invention to those skilled in the art.

Example 1: A binder having a low electrolyte dissolution rate A separator comprising a binder polymer layer made of a polymer compound

Example 1-1: Preparation of binder polymer layer film

5 g of SX8686 (H) -10 (particle size 300 nm) of JSR Corporation, a binder polymer compound having a low electrolyte dissolution rate, was dispersed in water, and the dispersion was dropped on a polyethylene terephthalate (PET) film. Using a doctor blade, the dispersion of the above-mentioned binder polymer compound was pushed to a thickness of 1000 mu m and dried in an oven to remove the dispersion medium. At this time, drying conditions were 90 ° C and 12 hours. The binder polymer compound from which the dispersion medium had been removed was desorbed from the PET film, and then cut so as to have a length x length of 1.5 cm x 8 cm to obtain two films. The weight (W ₁ ) of one piece of the obtained film was measured. The film was impregnated with 10 g of an organic solvent consisting of propylene carbonate (PC): diethyl carbonate (DEC) = 1: 1 (w / w) in a 15 mL vial.

One film was impregnated with an electrolytic solution at room temperature (25 ° C) for 48 hours, and the other one film was impregnated with an electrolytic solution at 60 ° C for 24 hours. The weight (W _swollen ) was measured after each of the films impregnated with the electrolyte solution and left in the gel state was left for 30 minutes on a # 100 wire mesh at room temperature. Then, each of the films was dried at 90 캜 for 48 hours, and the weight (W _{dry after elution} ) was measured.

Example 1-2: Preparation of separator

A polyolefin membrane (Senior Co., SD216C, aeration time 310 sec / 100 cc) having a thickness of 16 탆 was prepared as a porous polymer base material.

A dispersion prepared by dispersing 5 g of SX8686 (H) -10 (particle diameter 300 nm) of JSR Co. in water was coated on a polyolefin film by dip coating and dried to form a binder polymer layer on both sides of the polyolefin film.

Example 2: A binder having a low electrolyte dissolution rate A separator having a binder polymer layer containing a polymeric compound and a PVdF compound

Example 2-1: Preparation of a binder polymer adhesive layer film

Except that KPX130 (particle diameter: 200 nm) of Toyo Chem, which is a binder polymer compound having a low electrolyte solubility as a binder polymer, and RC10280 of Arkema, a PVdF compound were mixed at a ratio of 1: 9 and used preparing a film-sheet 2, which was measured W _1, W _swollen, W _{dry after elution} with respect to these two pieces of film, respectively.

Example 2-2: Preparation of separator

A separator was produced in the same manner as in Example 1-2, except that the binder polymer compound described in Example 2-1 was used for the binder polymer layer.

Comparative Example 1: A separator comprising a binder polymer layer made of a PVdF compound

Comparative Example 1-1: Preparation of a binder polymer layer film

Two films were prepared in the same manner as in Example 1-1, except that PVdF-CTFE (Solve, Solef 32008) was used as a binder polymer compound and acetone was used as a dispersion medium. W ₂ , W _swollen , and W _{dry after elution} .

Comparative Example 1-2: Preparation of separator

A separator was produced in the same manner as in Example 1-2 except that the binder polymeric compound described in Comparative Example 1-1 was used in the binder polymer layer.

Comparative Example 2: A separator comprising a binder polymer layer made of a PVdF compound

Comparative Example 2-1: Preparation of binder polymer layer film

Two films were prepared in the same manner as in Example 1-1, except that PVdF-HFP (Solvey, Kynar 2500) was used as a binder polymer compound and acetone was used as a dispersion medium. W ₂ , W _swollen , and W _{dry after elution} .

Comparative Example 2-2: Preparation of separator

A separator was produced in the same manner as in Example 1-2, except that the binder polymeric compound described in Comparative Example 2-1 was used in the binder polymer adhesive layer.

Evaluation Example 1: Electrolyte dissolution rate

W _{dry after elution} , W ₁ , of the films obtained in each of Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 was applied to the following Equation 1 to determine the electrolyte dissolution rate, 1.

[Equation 1]

(%) Of the electrolytic solution of the binder polymer compound = 100- {W _{dry after elution} / W ₁ * 100}

Evaluation Example 2: Rate of electrolyte impregnation of the binder polymer layer

W _swollen and W ₁ of the binder polymer film obtained in each of Examples 1-1 and 1-2 and Comparative Examples 1-1 and 1-2 were applied to the following Equation 2 to determine the electrolyte impregnation ratio, Are shown in Table 1 below.

&Quot; (2) &quot;

Impregnation rate (%) = {W _swollen / W ₁ -1} * 100

Evaluation Example 3: Electrode adhesion

An anode slurry was prepared by dispersing 80 g of graphite as a negative active material, 5 g of styrene butadiene rubber (SBR) as a binder, 5 g of carboxymethylcellose (CMC), and 10 g of dendrimer black as a conductive material so as to have a solid content of 45%. After drying, the negative electrode slurry was coated on Cu foil so as to have a thickness of 111 mu m, dried and rolled to prepare a negative electrode having a thickness of 56 mu m.

The separator prepared in Examples 1-2 & 2-2 and Comparative Examples 1-2 & 2-2 was laminated to the negative electrode prepared above at 100 ° C, and then the separator was peeled off at 180 ° to obtain peel strength. And the results are shown in Table 1 as &quot; dry &quot; electrode adhesion. The separator prepared in Examples 1-2 & 2-2 and Comparative Examples 1-2 & 2-2 was laminated to the negative electrode prepared above at 100 占 폚, and then the laminated negative electrode and the separator were laminated with a mixture of propylene carbonate: Diethyl carbonate = 1: 1 by weight at room temperature for 1 day, and then the separator was peeled off at 180 ° to measure the peel strength. The results are shown in Table 1 as 'electrode adhesion after impregnation with electrolyte' .

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Dissolution rate (%) 25 ℃ 4.1 4.7 24 15 60 ° C 7 8 100 (dissolution) 100 (dissolution) Impregnation rate (%) 25 ℃ 121 260 450 207 60 ° C 380 260 -(Dissolution) -(Dissolution) Electrode adhesion
(gf / 25 mm) dry 89 102 83 78 After electrolyte impregnation 45 37 6 12

As a result of the evaluation examples 1 and 2, the film for the binder polymer layer formed in Examples 1-1 and 2-1 showed a slight or low electrolytic solution dissolution rate at both room temperature (25 占 폚) and high temperature (60 占 폚).

In addition, the electrode adhesiveness of the separator manufactured in Examples 1-2 and 2-2 exhibited excellent electrode adhesion at both of the drying time and the electrolyte impregnation.

On the other hand, as a result of the evaluation examples 1 and 2, according to the comparative examples 1-1 and 2-1, the film for the binder polymer layer exhibited a high electrolyte dissolution rate at room temperature (25 캜) A phenomenon that the binder polymer adhesive layer was eluted into the electrolyte was observed.

In Evaluation Example 3, the separators prepared in Comparative Examples 1-2 and 2-2 were found to be lower than the separator electrode adhesiveness in Examples 1-2 and 2-2. Particularly, after impregnation with an electrolyte, And it has a low electrode adhesion.

Claims (17)

As a separator for an electrochemical device,
Porous polymeric substrates; And
And a binder polymer layer formed on at least one surface of the porous polymer base material and constituting an outermost layer of the separator,
The binder polymer layer includes a copolymer type of a low electrolyte dissolution rate binder polymer compound and a polyvinylidene fluoride binder polymer compound, which exhibits a dissolution rate of 0 to 5% after being impregnated with an electrolytic solution at 25 DEG C for 48 hours ,
(D90) of the copolymer constituting the binder polymer layer is larger than the particle diameter of the pores formed in the porous polymer base material that is in contact with the binder polymer layer
Separator for electrochemical devices.
The method according to claim 1,
A porous coating layer containing inorganic particles and a binder polymer is further formed between the porous polymer base material and the binder polymer layer,
The inorganic particles of the porous coating layer are bonded to each other by the binder polymer in a state of being filled with each other so that an interstitial volume is formed between the inorganic particles, The volumetric volume becomes an empty space to form pores,
Wherein a particle diameter (D90) of the copolymer constituting the binder polymer layer is larger than a particle diameter of pores formed in the porous coating layer that is in contact with the binder polymer layer.
3. The method according to claim 1 or 2,
Wherein the binder polymer compound having a low electrolyte dissolution rate is selected from the group consisting of polyacrylic acid (PAA), polymethylmethacrylate, polyisobutylmethacrylate, polyethylacrylate, polybutyl acrylate polybutyl acrylate, poly (2-ethylhexyl acrylate), polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-co-vinyl acetate polyethylene-co-vinyl acetate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl cellulose, cyanoethyl sucrose, carboxyl methyl cellulose, Trill-styrene-butadiene copolymer (acrylonitrile-styrene-butadiene copolymer), and a separator for an electrochemical device, characterized in that one or two or more mixture selected from the group consisting of polyimide (polyimide).
3. The method according to claim 1 or 2,
The porous polymer substrate may be formed of at least one selected from the group consisting of polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, but are not limited to, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more of them, or a nonwoven fabric.
delete delete delete delete The method according to claim 1,
Wherein the polyvinylidene fluoride-based binder polymer is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polyvinylidene fluoride-co-tetrafluoroethylene, poly Is a mixture of at least one member selected from the group consisting of vinylidene fluoride-co-trifluoroethylene, polyvinylidene fluoride-co-trifluorofluoroethylene and polyvinylidene fluoride-co-ethylene And a separator for an electrochemical device.
The method according to claim 1,
Wherein a particle diameter (D90) of the copolymer constituting the binder polymer layer is in the range of 50 nm to 1000 nm.
3. The method of claim 2,
Wherein the particle diameter (D90) of the copolymer constituting the binder polymer layer is larger than 1/4 of the average particle diameter of the inorganic particles.
3. The method according to claim 1 or 2,
Wherein the binder polymer layer exhibits an electrolyte solution impregnation rate in the range of 30 to 300 wt% at 25 ° C.
3. The method according to claim 1 or 2,
Wherein the binder polymer layer exhibits an electrolyte solution impregnation rate in the range of 50 to 500 wt% at 60 캜.
1. An electrochemical device comprising a cathode, an anode, a separator interposed between the cathode and the anode, and an electrolyte,
Wherein the separator is the separator according to any one of claims 1 to 5. The electrochemical device according to claim 1,
The method of claim 3,
Wherein the binder polymer compound having the low electrolyte dissolution rate has a dissolution rate of 0% or more and less than 10% based on the weight of the binder polymer compound after impregnating the electrolytic solution at 60 占 폚 for 24 hours.
15. The method of claim 14,
Wherein the electrolytic solution contains at least one selected from the group consisting of linear carbonates, cyclic carbonates, ethers, esters and amides.
15. The method of claim 14,
Wherein the electrochemical device is a lithium secondary battery.

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