KR101663540B1 - A separator having porous coating and electrochemical device containing the same - Google Patents

Abstract

A porous substrate having a plurality of pores; And a binder that is formed on at least one surface of the porous substrate or at least one surface of the porous substrate and a pore of the porous substrate and includes a plurality of inorganic particles having a carbon coating and an inorganic particle having the carbon coating formed thereon, And the separator may be employed in various electrochemical devices such as a lithium secondary battery.

Description

Technical Field [0001] The present invention relates to a separator having a porous coating layer and an electrochemical device including the same.

The present invention relates to a separator having a porous coating layer and an electrochemical device including the separator. More particularly, the present invention relates to a separator having a porous coating layer formed on the surface of a separator using inorganic particles having a carbon coating, And an electrochemical device including the same.

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.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution . However, such a lithium ion battery has safety problems such as ignition and explosion when using an organic electrolytic solution, and it is disadvantageous in that it is difficult to manufacture. Recently, the lithium ion polymer battery is considered to be one of the next generation batteries by improving the weak point of the lithium ion battery. However, since the capacity of the battery is still relatively low as compared with the lithium ion battery, Is urgently required.

The lithium secondary battery has constituent elements of a cathode, an anode, a separator and an electrolyte as a power generation element. As the anode material, a graphite based material is typical, and lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, .

During the operation of the lithium battery, some metal components of the cathode material migrate to the anode surface and oxidize to form metal oxides. The metal oxide on the surface of the anode thus formed deteriorates the electrical characteristics of the anode surface, which adversely affects cycle characteristics and lifetime characteristics.

Therefore, it is necessary to reduce the amount of the metal oxide precipitated from the anode surface.

SUMMARY OF THE INVENTION The present invention provides a separator that improves electrical characteristics and lifetime characteristics by forming a porous coating layer on a surface using inorganic particles having carbon coatings formed thereon.

Another object of the present invention is to provide an electrochemical device including the separator.

According to an aspect of the present invention,

A porous substrate having a plurality of pores; And

A plurality of inorganic particles formed on at least one surface of the porous substrate or at least one surface of the porous substrate and a pore of the porous substrate and having a carbon coating and a binder for connecting and fixing the inorganic particles having the carbon coating formed thereon A separator is provided that includes a porous coating layer.

The carbon coating may be formed as a continuous phase or a non-continuous phase on the surface of the inorganic particles, and may have a crystalline or amorphous structure. The carbon coating may have a thickness of 0.1 to 1,000 nm.

The inorganic particles may be selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, and mixtures thereof. The average particle diameter of the inorganic particles may be 0.01 to 10 탆.

The inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x , Ti _{1 -x} ) O ₃ (PZT, 0 <x <1), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ , 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ (PMN- HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ . Or a mixture of two or more of them.

The inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), lithium aluminum titanium phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) x O y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , , 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y S _{z, 0 <x <3,} 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 <z <7) series glass, or a mixture of two or more thereof.

The binder may be selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, poly But are not limited to, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide Polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolylenes, Vinyl alcohol (cyanoethylpolyvinylalcohol), And may be any one selected from the group consisting of cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more thereof.

The weight ratio of the inorganic particles to the binder may be 50:50 to 99: 1.

The porous substrate may be a polyolefin-based porous membrane or a nonwoven fabric.

The porous substrate may be selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfroid and polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more thereof.

According to another aspect of the present invention,

There is provided an electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator described above.

The electrochemical device may be a lithium secondary battery.

When a separator having a porous coating layer containing inorganic particles having a carbon coating is used in an electrochemical device, the metal component from the cathode is precipitated in the porous coating layer of the separator having many pores, so that the metal component precipitates on the anode or the anode surface . Accordingly, the efficiency of the anode is prevented from being lowered, thereby improving the electrical characteristics and lifetime characteristics of the electrochemical device.

1 is a schematic view showing a separator according to an embodiment of the present invention.
2 is a schematic view showing a state in which a conventional separator is in contact with an anode.
3 is a schematic view showing a state in which a separator according to an embodiment of the present invention is in contact with an anode.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

According to an aspect of the present invention,

A porous substrate having a plurality of pores; And

A plurality of inorganic particles formed on at least one surface of the porous substrate or at least one surface of the porous substrate and a pore of the porous substrate and having a carbon coating and a binder for connecting and fixing the inorganic particles having the carbon coating formed thereon And a porous coating layer.

When the porous coating layer including the inorganic coating film having the carbon coating is formed on at least one surface of the separator, the oxidation reaction of the metallic component occurs on the surface of the inorganic particle on which the carbon coating is formed, And is precipitated. Therefore, deposition of metal oxide on the surface of the anode is suppressed, thereby improving electrical characteristics and lifetime characteristics of the electrochemical device.

The inorganic particles usable for the inorganic particles having the carbon coating may have an average particle diameter of 0.01 to 10 탆. These inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles are not particularly limited as long as oxidation and / or reduction reactions do not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance.

Further, 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, can also contribute to enhance the ionic conductivity of the electrolyte.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having lithium ion-transporting ability, or a mixture thereof.

Non-limiting examples of the inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x Ti _1-x ) O ₃ (PZT, where 0 <x <1), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where 0 a <x <1), hafnia _{(HfO 2), SrTiO 3,} SnO 2, CeO 2, MgO, NiO, CaO, ZnO, ZrO 2, Y 2 O 3, Al 2 O 3, SiC, TiO 2 , etc., respectively May be used alone or in admixture of two or more.

In particular, the above-mentioned BaTiO ₃ , Pb (Zr _x Ti _1-x ) O ₃ (PZT, where 0 <x <1), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, 1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O _3-x PbTiO ₃ (PMN- HfO ₂ ) exhibits a high dielectric constant with a dielectric constant of 100 or more, as well as a piezoelectricity in which a potential difference is generated between both surfaces due to the generation of charge when a certain pressure is applied to the piezoelectric element by being stretched or compressed. It is possible to prevent internal short-circuiting of both electrodes due to the 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 that contain a lithium element but do not store lithium but have a function of moving lithium ions. The inorganic particles having lithium ion transferring ability exist in the particle structure Since lithium ions can be transferred and transferred due to a kind of defect, the lithium ion conductivity in the battery is improved and the battery performance can be improved. Examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (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 as such (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3 _{), Li 3.25 Ge 0.25 P 0.75} S 4 lithium germanate Mani help thiophosphate _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w , such as < 5), SiS ₂ based glass such as Li ₃ N lithium nitride such as _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 -Li 2 S-SiS 2 (Li x _{Si y S z, 0 <x} <3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 P 2 S 5 based glass (Li _x P _y S _z, such as 0 < x <3, 0 <y <3, 0 <z <7), or mixtures thereof.

The carbon film formed on the surface of the inorganic particles may be formed to have a thickness of less than a micrometer, for example, 0.1 to 1,000 nm, or 1 to 10 nm. When the thickness of the carbon coating satisfies this range, it is possible to prevent precipitation of the metal particles further on the anode side while preserving the stability improving function of the existing inorganic particle layer, and to prevent deterioration in performance such as capacity reduction of the battery. It also has the effect of interfering with the delivery of lithium ions from the cathode to the anode by grabbing the metal particles from the coating layer of inorganic particles with much more internal pores than the interface between the anode and the separator. The thickness of the carbon coating may vary depending on the particle size of the inorganic particles. As the thickness becomes thinner compared to the particle size of the inorganic particles, the precipitation ability of the metal particles decreases. When the thickness is thicker than the particle size of the inorganic particles, the coated carbon particles cause other side reactions such as decomposition reaction of the electrolyte, This may lead to performance degradation.

Such a carbon coating may have a continuous phase or discontinuous phase structure, and if it is a continuous phase, the entire surface of the inorganic particle is coated with carbon.

As described above, the inorganic particles having the carbon coating formed thereon form a porous coating layer on at least one surface of the separator, and a binder is used to bond them to the separator.

In the separator according to one aspect of the present invention, the binder used for forming the porous coating layer may be a polymer commonly used in the art for forming a porous coating layer. In particular, a polymer having a glass transition temperature (T _g ) of -200 to 200 ° C can be used because it can improve mechanical properties such as flexibility and elasticity of a finally formed porous coating layer. Such a binder faithfully performs a binder function to connect and stably fix inorganic particles, thereby contributing to prevention of deterioration of mechanical properties of the separator into which the porous coating layer is introduced.

Further, the binder does not necessarily have the ion-conducting ability, but the performance of the electrochemical device can be further improved by using a polymer having ion-conducting ability. Therefore, a binder having a high permittivity constant can be used. Actually, the dissociation degree of the salt in the electrolytic solution depends on the permittivity constant of the solvent of the electrolyte. Therefore, the higher the permittivity constant of the polymer, the better the salt dissociation degree in the electrolyte. The permittivity constant of such a binder may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), in particular, 10 or more.

In addition to the functions described above, the binder may be characterized by being capable of exhibiting a high degree of swelling of the electrolyte by gelation upon impregnation with a liquid electrolyte. Accordingly, the solubility index of the binder is in the range of 15 to 45 MPa ^1/2 or 15 to 25 MPa ^1/2 and 30 to 45 MPa ^1/2 . Therefore, hydrophilic polymers having many polar groups can be used more than hydrophobic polymers such as polyolefins. If the solubility index is less than 15 MPa &lt; ^1/2 &gt; and more than 45 MPa &lt; ^1/2 &gt;, it may be difficult to swell by a common battery liquid electrolyte.

Non-limiting examples of such binders include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate but are not limited to, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, But are not limited to, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, , Cyanoethyl polyvinyl alcohol cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose can be mentioned.

The weight ratio of the inorganic particles to the binder may be 50:50 to 99: 1, or 60:40 to 90:10, or 70:30 to 80:20.

The thickness of the porous coating layer composed of the carbonaceous film-containing inorganic particles and the binder is not particularly limited, but may be in the range of 0.01 to 20 占 퐉. Also, the pore size and porosity of the porous coating layer are not particularly limited, but the pore size may be in the range of 0.01 to 10 μm, and the porosity may be in the range of 5 to 90%.

Further, in the separator of the present invention, the porous substrate on which the porous coating layer is formed may be any porous substrate commonly used in an electrochemical device. For example, a polyolefin porous membrane or a nonwoven fabric may be used However, it is not particularly limited.

Examples of the polyolefin-based porous film include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low density polyethylene, low density polyethylene and ultra high molecular weight polyethylene, One membrane can be mentioned.

The nonwoven fabric may include, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, and polyethylenenaphthalene are used alone or in combination. Or a nonwoven fabric formed of a polymer mixed with these. The structure of the nonwoven fabric may be a spun bond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The thickness of the porous substrate is not particularly limited, but may be 5 to 50 탆, and the pore size and porosity present in the porous substrate are also not particularly limited, but may be 0.01 to 50 탆 and 10 to 95%, respectively.

In the porous coating layer, the binder attaches the inorganic particles to each other so that the inorganic particles can be maintained in a state of being bonded to each other (that is, the binder binds and fixes the inorganic particles), and the porous coating layer is bound to the porous substrate by the binder . The carbonaceous coating-containing inorganic particles of the porous coating layer exist in a densely packed structure in a state of being substantially in contact with each other, and the interstitial volume generated when the inorganic particles are in contact becomes the pores of the porous coating layer.

The separator according to one aspect of the present invention may further include other additives in addition to the inorganic particles and the binder described above as the porous coating layer component.

The additive is not particularly limited as long as it is a substance required or additionally required for the operation or performance improvement of the electrochemical device and is continuously consumed due to consumption in the operation process.

Non-limiting examples of such an electrochemical device performance improving additive may include any one of additives for forming a solid electrolyte interface, a cell side reaction inhibiting additive, a thermal stability improving additive, an overcharge suppressing additive, or a mixture of two or more thereof .

As the additive for forming the solid electrolyte interface, any one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, cyclic sulfite, saturated sulphone, unsaturated sulphone, acyclic sulphone, Mixtures of two or more of these may be used, but are not limited thereto.

Examples of the cyclic sulfite include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethylethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, Diethyl propyl sulfite, 4,6-diethyl propyl sulfite, and 1,3-butylene glycol sulfite. The saturated sulphone includes, for example, 1,3-propane sultone, and 1,4-butane sultone. Examples of the unsaturated sultone include ethene sultone, 1,3-propene sultone, 1,4-butene sultone, Phenolsaltone, and the like. Examples of the non-cyclic sulfone include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone.

Examples of the cell side reaction inhibiting additive include ethylenediaminetetraacetic acid, tetramethylethylenediamine, pyridine, dipyridyl, ethylbis (diphenylphosphine), butyronitrile, succinonitrile, iodine, And derivatives thereof, or a mixture of two or more thereof, may be used, but are not limited thereto.

Examples of the thermostability-improving additive include one or two or more selected from the group consisting of hexamethyldisiloxane, hexamethoxycyclotriphosphazene, hexamethylphosphoramide, cyclohexylbenzene, biphenyl, dimethylpyrrole, and derivatives thereof But are not limited thereto.

The overcharge suppression additive may be, but is not limited to, a mixture of one or more selected from the group consisting of n-butylferrocene, a halogen-substituted benzene derivative, cyclohexylbenzene, and biphenyl.

Examples of the additives for improving the performance of the electrochemical device include derivatives in which at least one hydrogen atom bonded to the carbon atom of each compound is substituted with a halogen.

The content of the electrochemical device performance improving additive may be 2 to 20 parts by weight, 4 to 18 parts by weight, or 6 to 15 parts by weight based on 100 parts by weight of the total amount of the inorganic particles and the binder.

When the content of the additive satisfies the above range, the effect of the addition is sufficiently exhibited, the excessive additive is released to prevent the side reaction, and the cycle of the battery can be prevented from being degenerated early.

1, a separator according to an aspect of the present invention may be formed by forming a porous coating layer composed of inorganic particles 2 containing a carbon coating 3 and a binder (not shown) on one surface or both surfaces of a porous substrate 1 have. The voids between the inorganic particles 2 may further include additives as described above.

When a polyolefin-based porous film is used as the porous substrate 1, a porous coating layer composed of a carbon film-containing inorganic particle and a binder may be formed on the surface thereof. When a polyolefin-based nonwoven fabric is used as the porous substrate, The porous coating layer composed of the inorganic particles and the binder may be impregnated in the porous substrate inner pores or formed on both surfaces or one surface of the porous substrate.

At this time, the polyolefin-based nonwoven fabric used as the porous substrate may have a pore size of 500 nm to 10 탆 which is much larger than that of the polyolefin-based porous film having pores of about 100 nm or less.

2 is a schematic view showing a state in which the conventional separator 1 is in contact with the anode 4. As shown in Fig. Referring to FIG. 2, the metal component 5 generated in the cathode is oxidized in the void space between the anode 4 and the anode 2 and the adjacent inorganic particles 2, and is precipitated as an oxide.

3 is a schematic view showing a state in which a separator according to an embodiment of the present invention is in contact with an anode. Referring to FIG. 3, the separator 1 having the porous coating layer as described above may be disposed so that the porous coating layer is in contact with the anode 4. In the case of such a structure, the metal component generated in the cathode is oxidized at the surface of the inorganic particle containing carbon coating to become an oxide, so that the metal component (5) precipitates in the void space between the inorganic particles (2).

The method of manufacturing the separator according to one aspect of the present invention is illustrated below, but the present invention is not limited thereto.

First, a carbon film is formed on the surface of the inorganic particles as described above. The method of forming the carbon film may be any conventional coating method of inorganic particles, and may be applied without limitation, for example, a calcination method, a chemical vapor deposition method, a spray method, a fluidized bed method, and the like .

For example, in the firing method, a polymer material such as a pitch flow and a thermosetting resin is baked together with the inorganic particles to form a carbon film on the inorganic particles. Examples of pitch types are coal tar pitches ranging from soft to deep pitch carbonized in liquid phase. As the thermosetting resin, phenol resin, furan resin vinyl resin, tar resin, polyvinyl alcohol resin and the like are used.

When the carbon film is directly formed on the surface of the inorganic particles through a deposition process such as a CVD (Chemical Vapor Deposition) process, the carbon film is formed on the surface of the inorganic particles without performing a predetermined process .

Next, the above-mentioned binder is dissolved in a solvent to prepare a binder solution. As the solvent, a solubility index similar to that of a binder to be used may be used, and a solvent having a low boiling point may be used. This is because the mixing can be made uniform and then the solvent can be easily removed. Non-limiting examples of the solvent include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (N- methyl-2-pyrrolidone (NMP), cyclohexane, water or a mixture thereof.

Then, the carbonaceous coating-containing inorganic particles and other additives are added to the prepared binder solution to prepare a coating solution in which inorganic particles and additives are dispersed.

At this time, inorganic particles may be added to the binder solution, followed by pulverization of the inorganic particles. The crushing time is suitably from 1 to 20 hours, and the particle size of the crushed inorganic particles may be 0.01 to 10 탆 as mentioned above. As the crushing method, a conventional method can be used, and in particular, a ball mill method can be used.

On the other hand, when the inorganic particles are coated using a coupling agent so that the inorganic particles can be easily dispersed in the binder solution, the coating solution can be prepared by simply mixing the inorganic particles in the binder solution.

Then, a coating solution in which inorganic particles and other additives are dispersed is applied to at least one side of the porous substrate to form a porous coating layer.

The coating liquid may be coated on the porous substrate using a conventional coating method known in the art, for example, a dip coating, a die coating, a roll coating, a comma coating Or a mixture method thereof may be used. Further, the porous coating layer can be selectively formed on both or only one side of the porous substrate.

When a solvent is added to the coating liquid, it is needless to say that a drying process of the coating layer is further required. Drying conditions are possible in a batch or continuous manner using an oven or a heated chamber in a temperature range that takes into account the vapor pressure of the solvent used.

The separator according to one aspect of the present invention thus manufactured can be usefully used as a separator of an electrochemical device, that is, as a separator interposed between a cathode and an anode.

An electrochemical device according to one aspect of the present invention includes all devices that perform an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of primary, secondary, fuel cell, solar cell, or super capacitor devices. ). In particular, 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 may be included in the secondary battery.

The electrode to be applied together with the separator according to one aspect of the present invention is not particularly limited, and the electrode active material may be bound to an electrode current collector according to a conventional method known in the art. Examples of the cathode active material include, but are not limited to, lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, or a combination thereof A lithium complex oxide may be used. As a non-limiting example of the anode active material, a conventional anode active material that can be used for an anode of an electrochemical device can be used. In particular, lithium metal or a lithium alloy, carbon, petroleum coke, activated carbon, Lithium adsorbing materials such as graphite or other carbon-based materials and the like can be used. Non-limiting examples of the cathode current collector include aluminum, nickel, or a combination thereof, and examples of the anode current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

The electrolytic solution which can be used in the electrochemical device according to one aspect of the present invention is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ is an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ And B ^- is a metal ion such as PF ₆ ^- , BF ₄ ^- , Cl ^- , Br ^- , I ^- , ClO ₄ ^- , AsF ₆ ^- , CH ₃ CO ₂ ^- , CF ₃ SO ₃ ^- , N (CF ₃ SO ₂ ) _{^{2 -, C (CF 2 SO}} 2) 3 - anion, or a salt containing an ion composed of a combination of propylene carbonate (PC) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC ), Dimethyl carbonate (DPC), dimethylsulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (G-butyrolactone), or an organic solvent composed of a mixture thereof, but is not limited thereto It is not.

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 according to one aspect of the present invention to a battery, a lamination, stacking and folding process of a separator and an electrode can be performed 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 may 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. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

Example 1. Preparation of separator

(1) Production of inorganic particle containing carbon coating film

100 parts by weight of Al ₂ O ₃ having an average particle diameter of 0.5 탆 as inorganic particles were charged into a fluidized bed chamber (BUCHI mini spar dryer B-290), and the internal temperature of the chamber was raised to 215 캜 while flowing the inorganic particles, So that the process temperature was stabilized.

Then, 15 parts by weight of sucrose as a carbon coating material was sprayed into the chamber at a pressure of 600 L / h using a spray nozzle having a diameter of 0.7 mm to uniformly form a carbon coating on the surfaces of the inorganic particles, .

At this time, the obtained inorganic particles had a carbon film thickness of 30 nm.

(2) Production of separator

5 parts by weight of PVdF-CTFE (polyvinylidene fluoride-chlorotrifluoroethylene copolymer) were added to 95 parts by weight of acetone and dissolved at 50 DEG C for 12 hours or more to prepare 5 parts by weight of a binder solution. The inorganic powder was added to the prepared binder solution so that the weight ratio of binder / inorganic particles = 20/80, and the inorganic particles were crushed and dispersed in an average particle size of about 300 nm by ball milling for 12 hours or longer, Slurry.

The slurry thus prepared was coated on a polyethylene porous film (porosity of 40%) having a thickness of 20 m by a dip coating method. The coating thickness was adjusted to about 10 mu m.

Example 2: Manufacture of electrochemical device (lithium secondary battery)

(1) Manufacture of cathode

90 parts by weight of a lithium cobalt composite oxide as cathode active material particles, 5 parts by weight of carbon black as a conductive material and 5 parts by weight of PVDF as a binder were added to 40 parts by weight of N-methyl-2-pyrrolidone (NMP) A cathode active material slurry was prepared. The cathode active material slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 100 탆 and dried to produce a cathode, followed by roll pressing.

(2) Manufacture of anode

95 parts by weight, 2 parts by weight and 3 parts by weight, respectively, of a carbon powder as an anode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were respectively dissolved in N-methyl- 100 parts by weight of NMP to prepare an anode active material slurry. The anode active material slurry was coated on a copper (Cu) thin film as an anode current collector having a thickness of 90 占 퐉 and dried to produce an anode, followed by roll pressing.

(3) Production of lithium secondary battery

The unit cells were assembled by the stacking method using the cathode, the anode and the separator manufactured by the above-described method. Then, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio) and 1 mol of lithium hexafluorophosphate (LiPF ₆ ) A battery was prepared.

Comparative Example 1

A lithium secondary battery was produced in the same manner as in Example 2 except that inorganic particles having no carbon coating were used.

1: porous substrate, 2: inorganic particles, 3: carbon coating
4: anode, 5: metal component

Claims (16)

A porous substrate having a plurality of pores; And
A plurality of inorganic particles formed on at least one surface of the porous substrate or at least one surface of the porous substrate and a pore of the porous substrate and having a carbon coating and a binder for connecting and fixing the inorganic particles having the carbon coating formed thereon And a porous coating layer containing the porous coating layer. The method according to claim 1,
Wherein the carbon coating is a continuous phase or a discontinuous phase. The method according to claim 1,
Wherein the carbon film has a thickness of 0.1 to 1,000 nm. The method according to claim 1,
Wherein the inorganic particles have an average particle diameter of 0.01 to 10 占 퐉. The method according to claim 1,
Wherein the inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transporting ability, and mixtures thereof. 6. The method of claim 5,
Wherein the inorganic particles having a dielectric constant of 5 or more are BaTiO ₃ , Pb (Zr _x , Ti _{1 -x} ) O ₃ (PZT, 0 <x <1), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ , 0 <x <1, 0 <y <1), (1-x) Pb (Mg _1/3 Nb _2/3 ) O ₃ -xPbTiO ₃ (PMN- HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , SiO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC and TiO ₂ . Or a mixture of two or more of them. 6. The method of claim 5,
Wherein the inorganic particles having lithium ion transferring ability are lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), lithium aluminum titanium phosphate _{(Li x Al y Ti z (} PO 4) 3, 0 <x <2, 0 <y <1, 0 <z <3), (LiAlTiP) x O y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate (Li _x La _y TiO ₃ , 0 <x <2, 0 <y <3), lithium germanium thiophosphate (Li _x Ge _y P _z S _w , , 0 <y <1, 0 <z <1, 0 <w <5), lithium nitrides _{(Li x N y, 0 <} x <4, 0 <y <2), SiS 2 (Li x Si y S _{z, 0 <x <3,} 0 <y <2, 0 <z <4) based glass, and _{P 2 S 5 (Li x P} y S z, 0 <x <3, 0 <y <3, 0 <z &Lt; 7) -glass, or a mixture of two or more thereof. The method according to claim 1,
Wherein the binder is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, polymethylmethacrylate, poly But are not limited to, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide Polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolylether, Vinyl alcohol (cyanoethylpolyvinylalcohol), Wherein the separator is any one selected from the group consisting of cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or a mixture of two or more thereof. The method according to claim 1,
Wherein the weight ratio of the inorganic particles to the binder is 50:50 to 99: 1. The method according to claim 1,
Wherein the thickness of the porous coating layer is 0.01 to 20 占 퐉. The method according to claim 1,
Wherein the porous coating layer further comprises any one selected from the group consisting of an additive for forming a solid electrolyte interface, a cell side reaction inhibiting additive, a thermal stability improving additive, and an overcharge inhibiting additive, or two or more of the additives. 12. The method of claim 11,
Wherein the content of the additive is 2 to 20 parts by weight based on 100 parts by weight of the total amount of the inorganic particles and the binder. The method according to claim 1,
Wherein the porous substrate is a polyolefin-based porous film or a nonwoven fabric. The method according to claim 1,
Wherein the porous substrate is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfroid and polyethylene naphthalene (polyethylenenaphthalene), or a mixture of two or more thereof. An electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator according to any one of claims 1 to 14. 16. The method of claim 15,
Wherein the electrochemical device is a lithium secondary battery.

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