KR20160130716A - A separator for electrochemical device comprising a porous coating layer comprising heat-resistant particles and electrochemical device comprising the same - Google Patents

Abstract

The present invention relates to a complex separation film for an electrochemical device and an electrochemical device comprising the same. More specifically, the complex separation film reduces the amount of gas generated during an activation process of a battery to have internal resistance increase and battery capacity degradation preventing effects.

Description

TECHNICAL FIELD The present invention relates to a composite separator having a porous coating layer containing a heat-resistant particle and an electrochemical device including the same, and a separator for electrochemical device comprising a porous coating layer,

The present invention relates to a composite separator for an electrochemical device and an electrochemical device including the same. More particularly, the present invention relates to a composite separator having an effect of preventing an increase in internal resistance and deterioration of battery capacity due to a decrease in the amount of gas generated during the activation process of the battery.

The secondary battery is based on anode / cathode / separator / electrolytic solution, and it is widely used for small electronic equipment such as mobile phones and notebooks. In recent years, hybrid electric vehicles (HEV), plug-in EVs, electric bikes (e-bikes) and energy storage systems (Energy Storage System, ESS) is rapidly expanding.

As the potential risks of safety accidents such as ignition and explosion accidents of the electrochemical devices have been rapidly increased, safety evaluation and safety of the electrochemical devices have become important issues. Therefore, as the demand for safety confirmation centered on the consumer as well as the national level is increasing, enforcement and enforcement of regulations on forced certification are progressing centering on the government, and standardization of technology is also being promoted. Such an electrochemical device may cause a malfunction according to the operating environment, and when thermal breakdown occurs due to overheating in the case of malfunction, when the separation membrane provided in the device is decomposed, the electric energy due to the potential difference of the electrode, There is a fear that the internal explosion may be caused by the vaporization of the electrolyte caused. Particularly, a polyolefin-based porous substrate produced by a thermodynamic phase separation method of a material, which is currently used as a separator of a general electrochemical device, is excellent in mechanical properties, chemical stability,

It has a characteristic of proper production cost. However, due to the characteristics of the material to be melted at 200 ° C or lower and the characteristics of the manufacturing process of the stretch for controlling the pore size and porosity, the material exhibits extreme heat shrinkage behavior at a temperature of 100 ° C or higher, The stability is poor, and the mechanical strength is weak for application to medium and large electrochemical devices, and there is a risk of an internal short circuit.

In order to complement the thermal and mechanical properties of the polyolefin-based separator provided in the electrochemical device, Japanese Patent Laid-Open No. 2003-022707 and Polymer Journal, vol. 42, pp. 425-437, 2010, and the like, a method of manufacturing an organic / inorganic hybrid membrane having a microporous structure using inorganic particles and a polyolefin resin and thermodynamic phase separation of a solvent, a polymer and an inorganic particle has been proposed. In addition, Korean Patent Laid-Open Nos. 10-2006-72065, 10-2007-231, 10-2008-0010166, and the like disclose a porous substrate made of a mixture of inorganic filler particles and a polymeric binder on one surface or both surfaces thereof, A separation membrane having a coating layer is proposed. The inorganic filler particles of the microporous coating layer formed on the porous substrate serve as a kind of passivation that can maintain the physical form, thereby suppressing heat shrinkage of the porous substrate upon overheating due to malfunction of the electrochemical device, Together, there is an empty space between the inorganic filler particles to form micropores. Thus, the microporous coating layer formed on the porous substrate contributes to the improvement of the safety of the electrochemical device. Al ₂ O ₃ is mainly used as the inorganic filler particles used in the formation of the microporous coating layer according to the prior art. However, the higher the specific surface area of alumina, the greater the amount of gas generated during the initial activation process of the battery .

It is an object of the present invention to provide a composite separator in which the amount of gas generated during the initial activation process of the cell is reduced. Other objects and advantages of the present invention will become apparent from the following description. On the contrary, it is to be understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

The present invention is directed to a composite separator for an electrochemical device comprising a core-shell structure heat-resistant particle including a core portion and a shell portion formed on at least a part of a surface of the core portion. Here, the core portion comprises a non-conductive particles, the shell portion comprising a barium titanate (BaTiO _3).

Here, the non-conductive particles do not cause an oxidation and / or reduction reaction within an operating voltage range of the electrochemical device.

Wherein the non-conductive particles may comprise inorganic particles or organic particles or both.

In the present invention, the inorganic particles may be at least one selected from the group consisting of aluminum oxide (alumina), aluminum hydroxide hydrate (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, Titanium oxide (titania), oxides which are at least one kind of calcium oxide, nitrides which are at least one kind of aluminum nitride, silicon nitride, silica, barium sulfate and calcium fluoride, and potassium fluoride.

Here, the organic particles are polymer particles.

The present invention also relates to a porous polymer substrate; And a porous coating layer formed on at least one surface of the porous polymer substrate; Wherein the porous coating layer has a porous structure due to an interstitial volume between particles, wherein the heat-resistant particles are bound to each other via a binder resin and are integrated and layered, Wherein the particles include a core portion and a shell portion formed on at least a part of a surface of the core portion, the core portion is non-conductive particle, and the shell portion includes barium titanate (BaTiO ₃ ) .

Here, the non-conductive particles do not cause an oxidation and / or reduction reaction within an operating voltage range of the electrochemical device.

Further, the non-conductive particles may include inorganic particles or organic particles or both of them.

The inorganic particles may be at least one selected from the group consisting of aluminum oxide (alumina), hydrated aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, (Titania), an oxide that is at least one kind of calcium oxide, at least one selected from the group consisting of nitride, at least one of aluminum nitride and silicon nitride, silica, barium sulfate and calcium fluoride, and potassium fluoride.

Here, the organic particles are polymer particles.

The polymeric polymer particles may include at least one selected from the group consisting of polystyrene, polyethylene, polyimide, melamine resin and phenol resin.

The polymeric polymer particles have a glass transition temperature of 150 ° C or higher.

The polymeric polymer particles may include at least one selected from polystyrene, polyethylene, polyimide, melamine resin and phenol resin.

Here, the polymeric polymer particles have a glass transition temperature of 150 ° C or higher.

Further, in the present invention, the porous polymer substrate is any one of the following a) to e):

a) a porous film formed by melting / extruding a polymer resin,

b) a multi-layered film in which two or more porous films of a)

c) a nonwoven web prepared by integrating filaments obtained by melting / spinning a polymer resin,

d) a multi-layered film in which two or more layers of the nonwoven web of b)

e) a multi-layered composite porous substrate comprising at least two of a) to d).

Here, the inorganic particles may include inorganic particles having ion transport capability and / or high-permittivity inorganic particles having a dielectric constant of 5 or more.

The present invention also relates to an electrode assembly including a cathode, an anode, and a separator interposed between the cathode and the anode. Here, the separation membrane is a composite separation membrane having the above-described characteristics. The present invention also provides an electrochemical device including the electrode assembly.

The separation membrane according to the present invention is provided with a porous coating layer including heat-resistant particles coated with BTO. When the separation membrane is applied to a battery, the amount of gas generated during the activation process is greatly reduced. In addition, since the conventional inorganic particles such as alumina are coated with BTO, there is an advantage that the increase in cost due to material change is not large.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles 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.
1 schematically shows a cross section of a heat-resistant particle according to the present invention.
2 is a graph showing a correlation between the D ₅₀ of the particles and the gas generation amount.
3 is a graph showing the relationship between the BET of the particles and the gas generation amount.
FIG. 4 is a graph comparing the amounts of gases generated in Examples and Comparative Examples according to the present invention.

The terms or words used in the present specification and claims should not be construed to be limited to ordinary or dictionary terms and the inventor shall properly define the concept of the term in order to best explain its invention The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

The present invention relates to a separation membrane for an electrochemical device having a porous coating layer containing heat-resistant particles. The heat resistant particles have a barium titanate coating layer formed on the surface of the non-conductive particles, so that the amount of gas generated during the activation process of the battery is small, and the internal resistance increase rate and battery capacity degradation are low.

1 schematically shows a cross section of heat resistant particles contained in the porous coating layer in the composite separation membrane. Hereinafter, the present invention will be described in detail with reference to the drawings.

The separation membrane according to one aspect of the present invention includes a porous polymer base material including a polymer material, and a porous coating layer including heat resistant particles is formed on one side surface or both side surfaces of the porous polymer base material. In the present invention, the separation membrane serves as a porous ion-conducting barrier for passing ions while blocking electrical contact between the cathode and the anode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

1. Porous polymer substrate

According to a specific embodiment of the present invention, the porous polymer substrate can provide a path for lithium ion migration while electrically insulating the negative electrode and the positive electrode to prevent short-circuiting. Normally, Can be used without limit. Examples of such a porous substrate include polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyether sulfone, polyphenylene oxide, polyphenyl A porous substrate formed of at least one of polymer resins such as rhenium sulfide, polyethylene naphthalene, and the like, but the present invention is not limited thereto.

As the porous polymer substrate, any of a nonwoven fabric in which a film in the form of a film formed by melting a polymer resin or a filament obtained by melt spinning a polymer resin is integrated can be used. The porous substrate is preferably a porous substrate produced by melting / molding the polymer resin to form a sheet.

Specifically, the porous polymer substrate is any one of the following a) to e).

a) a porous film formed by melting / extruding a polymer resin

b) a multi-layered film in which two or more porous films of a)

c) a nonwoven web prepared by integrating filaments obtained by melting / spinning a polymer resin,

d) a multi-layered film in which two or more layers of the nonwoven web of b)

e) a porous composite membrane of a multi-layer structure comprising at least two of a) to d).

In the present invention, the thickness of the porous polymer substrate may be 5 to 50 탆. Although the range of the porous substrate is not particularly limited to the above-mentioned range, if the thickness is too thin than the lower limit described above, the mechanical properties are deteriorated and the separator may be easily damaged during use of the battery. On the other hand, the pore size and porosity present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

2. Porous coating layer

The porous coating layer is formed as a layer on one surface or both surfaces of the polymer substrate and includes a mixture of a plurality of heat resistant particles and a binder resin. The surface of the porous polymer substrate is covered with the heat-resistant particles, so that the heat resistance and mechanical properties of the separation membrane are further improved.

The porous coating layer not only has a microporous structure due to the interstitial volume between the heat resistant particles, but also serves as a kind of spacer capable of maintaining the physical form of the porous coating layer. The interstitial volume means a space in which adjacent non-conductive particles are substantially interposed and confined. Further, since the heat-resistant particles generally have the property that their physical properties do not change even at a high temperature of 200 DEG C or more, the separator has excellent heat resistance due to the formed porous coating layer. In the present invention, the porous coating layer has a thickness of 1 탆 to 50 탆, or 2 탆 to 30 탆, or 2 탆 to 20 탆.

In the porous coating layer, the content ratio of the heat resistant particles to the binder resin is determined in consideration of the thickness, pore size, and porosity of the porous coating layer of the present invention, wherein the inorganic particles are contained in an amount of 50 to 99.9% 70 to 99.5 wt%, and the polymer resin is 0.1 to 50 wt% or 0.5 to 30 wt%. By setting the content ratio of the heat-resistant particles in the porous coating layer within the above range, the interstitial volume can be formed to such an extent that the heat-resistant particles have a contact portion therebetween and the movement of ions is not hindered. When the content of the heat resistant particles is less than 50% by weight, the content of the polymer is excessively increased, and the pore size and the porosity due to the reduction of the interstitial volume formed between the heat resistant particles are decreased, Can be caused. On the other hand, if it exceeds 99.9% by weight, the mechanical properties of the final porous coating layer are deteriorated due to the weak adhesion between the inorganic materials because the polymer content is too small.

On the other hand, the pore size and porosity of the porous coating layer depend on the size of the heat-resistant particles contained therein. For example, when heat-resistant particles having a particle diameter of 1 탆 or less are used, pores to be formed also become 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. Therefore, the pore size and porosity are important factors for controlling the ionic conductivity of the porous inorganic coating layer. The porosity and porosity of the porous coating layer of the present invention are preferably 0.001 to 10 μm, and preferably 5 to 95%.

3. Heat Resistance Particles

In the present invention, the heat resistant particle has a core-shell structure including a core portion and a shell portion formed on at least a part of the surface of the core portion. In the present invention, the core portion is non-conductive particles, and the shell portion includes barium titanate (BaTiO ₃ ). Fig. 1 schematically shows a structure of a heat-resistant particle according to an embodiment of the present invention.

The average particle diameter (D50 average particle diameter of the volume average) of the heat resistant particles is 5 nm to 10 탆, or 50 nm to 5 탆, or 100 nm to 5 탆, or 500 nm to 2 탆 or 500 nm to 1.5 탆 . By setting the average particle diameter of the heat resistant particles within the above range, it becomes easy to control the dispersion state, and it becomes easy to obtain a porous coating layer in which the internal resistance of a uniform predetermined thickness is suppressed. Also, it is possible to prevent the occurrence of an internal short circuit due to an excessively large pore formation. When the average particle diameter of the heat resistant particles is in the range of 50 nm to 5 占 퐉, it is more preferable since it is excellent in dispersion, ease of application and controllability of the pores.

The average particle diameter of the heat-resistant particles in the present invention is the number average particle diameter calculated as the arithmetic mean value by measuring the diameters of 100 heat-resistant particle images randomly selected by a transmission electron microscope photograph.

The BET specific surface area of these heat resistant particles is preferably from 0.9 to 200 m 2 / g or from 1 to 100 m 2 / g, or from 1 to 100 m 2 / g, from the viewpoint of suppressing aggregation of the particles and making the fluidity of the heat resistant layer slurry private, Lt; 2 > / g or 1 to 10 m < 2 > / g.

According to a specific embodiment of the present invention, the heat resistant particles may be formed by a conventional mechanical alloying method such as ball milling or planetary milling, and may be formed by a method such as electrolysis, chemical or physical vapor deposition As shown in FIG.

4. Core portion - Non-conductive  particle

The non-conductive particles forming the core portion are stably present under the environment of use of the secondary battery, and if they are electrochemically stable, non-conductive inorganic particles or organic particles or both may be used. That is, the non-conductive particles are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li +).

As the material of the inorganic particles in the present invention, a material suitable for preparing a slurry composition for heat resistance layer by electrochemically stabilizing and mixing with another material, for example, a viscosity adjusting agent described later is preferable. From such a viewpoint, the inorganic particles include aluminum oxide (alumina), hydrate of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, , Oxides such as titanium oxide (titania) and calcium oxide, nitrides such as aluminum nitride and silicon nitride, silica, barium sulfate, calcium fluoride, potassium fluoride, etc. Among them, from the viewpoint of stability in the electrolyte solution and dislocation stability, Among them, alumina, titanium oxide, boehmite, magnesium oxide and magnesium hydroxide are preferable from the viewpoints of low water absorption and excellent heat resistance (for example, resistance to high temperature of 180 DEG C or more), and alumina, boehmite, magnesium oxide And magnesium hydroxide are particularly preferable.

According to a specific embodiment of the present invention, the inorganic particle is alumina. Alumina has desirable physical properties as an insulating material for a separator because it has a resistance higher than that of other insulators even when it has a volume resistivity of 10? 占 cm m or more at room temperature. In addition, alumina has a melting point of about 2,047 ° C and is excellent in strength at high temperature and stable to corrosive gases and liquids such as acids and alkalis and does not react well, and thus has high electrochemical safety. In addition, alumina is the next most abundant minerals of silicon oxide in the crustal minerals, making it easy to refine, making it possible to produce products of high purity with low cost and relatively simple fixing.

On the other hand, in the case of using the inorganic particles having an ion-transferring ability, the ionic conductivity in the electrochemical device can be increased and the performance can be improved. 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. Accordingly, according to a specific embodiment of the present invention, 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 transferring ability, or a mixture thereof. Nonlimiting examples of inorganic particles having a dielectric constant of 5 or more include Pb (Zr, Ti) O ₃ (PZT), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, MgO, and MgO), Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), HfO ₂ , CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, and TiO ₂ may be used alone or in combination of two or more. 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.

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 Mani lithium germanium thiophosphate Titanium _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w such as <5), Li ₃ N lithium nitride _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 SiS 2 family, such as _{-Li 2 S-SiS 2 glass (} Li , such as _{x Si y S z, 0 <} x <3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 , etc., such as P ₂ S ₅ based glass (Li _x P _y S _z, 0 <x <3, 0 <y <3, 0 <z <7), or a mixture thereof.

In the present invention, particles of a polymer (polymer) are usually used as the organic particles. The organic particles can control the affinity to water by controlling the kind and amount of functional groups on the surface thereof, and furthermore, the amount of water contained in the heat resistant layer of the present invention can be controlled. Preferable examples of the organic material of the non-conductive particles include various high-molecular compounds such as polystyrene, polyethylene, polyimide, melamine resin and phenol resin. The polymer compound forming the particles may be a mixture, a modified product, a derivative, a random copolymer, an alternate copolymer, a graft copolymer, a block copolymer, a crosslinked product and the like. The organic particles may be formed by a mixture of two or more kinds of polymer compounds.

When organic particles are used as the non-conductive particles, they may or may not have a glass transition temperature. When the polymer compound forming the organic particles has a glass transition temperature, the glass transition temperature is usually 150 ° C or higher, Preferably 200 DEG C or higher, and more preferably 250 DEG C or higher.

The non-conductive particles may be subjected to element substitution, surface treatment, solidification or the like as necessary. The non-conductive particles may contain one kind of the above-described materials singly in one particle, or two or more kinds may be combined in an arbitrary ratio. The non-conductive particles may be used in combination of two or more kinds of particles formed of different materials.

In the present invention, the non-conductive form is not particularly limited, but may be spherical, needle-like, rod-like, scaly, flake-like, tabular or Tetrapod (connected particle). In the case of using inorganic particles as heat- Phase (connecting particle), plate-like shape, and scaly shape are preferable. By having the inorganic particles in the above-described shape, porosity (porosity) of the porous coating layer can be ensured, and deterioration of the ionic conductivity can be suppressed.

5. Shell part - BTO  Coating layer

Coating layer to form the shell of barium titanate (BaTiO _3, BTO). Barium titanate (BTO) is a ceramic material having a tetragonal phase at room temperature and a very high dielectric constant. FIG. 4 is a graph comparing the amount of gas generated in the separation membrane having a porous coating layer containing alumina particles and barium titanate particles, respectively. As shown in FIG. 4, barium titanate has a gas generation amount of only 20% as compared with alumina.

6. Manufacturing method of porous coating layer

In one specific embodiment of the present invention, the porous coating layer is formed by mixing heat-resistant particles and a binder resin in a dispersion medium to prepare a slurry for the porous coating layer, applying the slurry to the porous substrate, and drying the mixture.

The binder resin contained in the porous coating layer is preferably a polymer resin having a low glass transition temperature (Tg), and the glass transition temperature is preferably -200 ° C to 200 ° C. This is because mechanical properties such as flexibility and elasticity of the composite membrane can be improved. The binder resin stably fixes the adhesion between the inorganic particles, thereby contributing to prevention of deterioration of the mechanical properties of the porous coating layer finally produced. In the present invention, the binder resin does not necessarily have ion conductivity, but when the polymer resin having ion conductivity is used, the performance of the electrochemical device can be further improved. Therefore, it is preferable that the binder resin has a high permittivity constant. Accordingly, a solubility parameter of 15 to 45 MPa ^1/2 of a polymer resin is preferable, and more preferably 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range. Therefore, hydrophilic polymer resins having many polar groups are preferred over hydrophobic polymer resins such as polyolefins. If the solubility is more than 15 MPa ^1/2 and less than 45 MPa ^1/2 hard to be impregnated with a conventional liquid electrolyte batteries.

Non-limiting examples of binder resins that can be used in the present invention include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, Polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-vinyl acetate copolymer, and the like. vinyl acetate, co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethyl Cyanoethylsucrose, pullulan and carboxy Butyl cellulose may be a (carboxyl methyl cellulose) any of the polymeric resin or a mixture of two or more of those selected from the group consisting of. However, the present invention is not limited thereto.

In the present invention, the dispersion medium is an organic solvent and is not particularly limited as long as it can uniformly disperse the heat-resistant particles and the binder resin.

Examples of the organic solvent include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene and ethylbenzene; aromatic hydrocarbons such as acetone, ethylmethylketone, diisopropylketone, cyclohexanone, methylcyclohexane, Ethylcyclohexane and the like; chlorinated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; esters such as ethyl acetate, butyl acetate,? -Butyrolactone and? -Caprolactone; acylonitrile such as acetonitrile and propionitrile Ethers such as tetrahydrofuran and ethylene glycol diethyl ether; alcohols such as methanol, ethanol, isopropanol, ethylene glycol and ethylene glycol monomethyl ether; and alcohols such as N-methylpyrrolidone and N, N-dimethylformamide Amides of the formula

These dispersion media may be used alone, or two or more of them may be mixed and used as a mixed solvent. Among them, a solvent having a low boiling point and a high volatility can be preferably removed at a low temperature in a short period of time. Concretely, acetone, toluene, cyclohexanone, cyclopentane, tetrahydrofuran, cyclohexane, xylene, N-methylpyrrolidone, or a mixed dispersion thereof is preferable.

The method of forming the porous coating layer by applying the slurry on the porous substrate is not particularly limited and may be any one of a dip coating method, a die coating method, a roll coating method, a comma coating method, a doctor blade Coating method, reverse roll coating method, direct roll coating method and the like.

The composite separator of the present invention thus produced can be used as a separator of an electrochemical device. The electrochemical device includes all devices that perform an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary, fuel cell, solar cell, and capacitor. 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 is preferable.

Further, in one specific embodiment according to the present invention, the lithium secondary battery may be manufactured according to a conventional method known in the art. According to an embodiment of the present invention, the secondary battery may be manufactured by preparing the electrode assembly by interposing the separation membrane between the anode and the cathode, charging the electrode assembly into the battery case, and injecting the electrolyte solution.

In one embodiment of the present invention, the electrode of the secondary battery may be manufactured by adhering an electrode active material 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, A lithium intercalation material such as a composite oxide formed by a combination thereof, and the like are preferable. As a non-limiting example of the negative electrode active material, a conventional negative electrode active material that can be used for a negative electrode 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 are preferable. Non-limiting examples of the positive current collector include aluminum, nickel, or a combination thereof. Examples of the negative current collector include copper, gold, nickel, or a copper alloy or a combination thereof Foil to be manufactured, and the like.

Electrolyte that may be used in the present invention is A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF _{6 ^{-, BF 4 -, Cl -}} , Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, NCF 3 SO 2) 2 -, CCF 2 SO 2) 3 - (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone (gamma -butyrolactone), or a mixture of these compounds. Or dissolving or dissociating in an organic solvent composed of a mixture, but the present invention is not limited thereto.

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 electrode assembly 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 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. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

Manufacture of heat resistant particles

Heat-resistant particles having BTO-coated on the surface of alumina particles were obtained through a vacuum deposition method. The vacuum deposition method was performed by heating and evaporating the metal (BTO) in a vacuum and attaching the generated metal evaporation molecules to the alumina surface having a temperature lower than the vapor temperature. At this time, the heating temperature was controlled to 700-1,000 ° C. and BTO was coated on the surface of alumina particles with a thickness of about 50-100 nm by using a vacuum evaporator. The deposition time was controlled to 5 to 10 seconds.

Gas emission measurement

The heat-resistant particles prepared above were impregnated with an electrolyte (ethylene carbonate: ethylpropionate = 3: 7, weight ratio), and the electrolyte solution was allowed to stand at 85 ° C for 3 days. The amount of particles used was 0.7 g, and the electrolyte was 1.5 g. The amount of gas generated is summarized in Table 1 below.

Comparative Example

Al2O3 particles and BTO particles were each impregnated with an electrolyte (ethylene carbonate: ethylpropionate = 3: 7, weight ratio), and then allowed to stand at 85 ℃ for 3 days. The amount of particles used was 0.7 g, and the electrolyte was 1.5 g. The amount of gas generated is summarized in Table 1 and FIG.

Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Mineral Type Al2O3 / BTO
(9: 1 weight ratio) Al2O3 BTO Inorganic material penetration
Electrolyte D50 (占 퐉) 0.65 0.50 1.00 - BET (m &lt; 2 &gt; / g) 3.50 5.89 2.20 - water(%) 99.99 99.99 99.99 - CH (ul) 113.4 103.6 00 26.2 CO2 (μl) 1724.0 3189.4 710.4 49.5 CO (μl) 17.9 7.7 38.9 0.8 Total 1855.3 3300.7 749.3 76.5

From the above experimental results, it was confirmed that the Al ₂ O ₃ / BTO composite particles were significantly reduced in gas generation as compared with Al ₂ O ₃ . On the other hand, it can be seen that the gas generation amount of the example particles is higher than that of the BTO particles of Comparative Example 2, but the use of only 10% of the BTO component in Comparative Example 2 is more effective than the BTO injection amount, . Therefore, by combining alumina particles with BTO, it is possible to reduce costs and reduce gas generation.

Experimental Example

Confirmation of the relationship between D50 and BET surface area of particles and gas generation amount

The amount of gas generated in the electrolytic solution was measured for five different alumina particle samples. The amount of the particle sample was 0.7 g, and the electrolyte used for each sample was 1.5 g each. The D50 and BET surface area of the alumina particle samples used are summarized in Table 2 below.

sample A B C D E D50 (占 퐉) 0.49 0.58 0.51 0.99 0.69 BET (m &lt; 2 &gt; / g) 5.9 5.0 5.4 4.8 4.5 water(%) 99.00 99.99 99.90 99.99 99.94

The alumina particles A to E were each impregnated with an electrolyte (ethylene carbonate: ethylpropionate = 3: 7, weight ratio), and then allowed to stand at 85 ° C for 3 days. The amount of gas generated is summarized in Table 3 below.

sample A B C D E CH (ul) 103.6 197.1 167.9 159.6 126.0 CO2 (μl) 3189.4 3245.1 3450.6 2246.4 2429.9 CO (μl) 7.7 52.1 173.1 255.7 138.7 Total 3300.7 3494.4 3791.6 2661.7 2694.6

2 is a graph showing the correlation between the diameter of the heat resistant particles and the gas generation amount. According to this, as the diameter of the heat-resistant particles decreases, the amount of gas generated tends to increase. Therefore, in order to reduce the amount of generated gas, it is preferable that the diameter of the particles is large.

On the other hand, FIG. 3 is a graph showing a correlation between the specific surface area of the heat resistant particles and the gas generation amount. According to this, as the specific surface area of the heat resistant particles increases, the gas generation amount tends to increase, so that the BET specific surface area of the particles is preferably low in order to reduce the gas generation amount. The BET specific surface area of the heat resistant particles was measured by a BET measurement method by adsorbing nitrogen gas to heat resistant particles using a specific surface area measuring device (Jimini 2310, manufactured by Shimadzu Corporation).

100 ... Heat-resistant particle
11 ... shell part
12 ... core portion

Claims (16)

Porous polymeric substrates; And
A porous coating layer formed on at least one surface of the porous polymer substrate; / RTI &gt;
Here, the porous coating layer is formed as a layered structure in which heat-resistant particles are bound to each other via a binder resin and are integrated and have a porous structure due to an interstitial volume between particles,
The heat-resistant particles have a core portion and a non-conductive particles comprise a shell portion and a core portion formed on at least a portion of the core portion surface, it said shell portion of barium titanate is, an electrochemical device composite separator for comprises (BaTiO _3).
The method according to claim 1,
Wherein the non-conductive particles do not cause an oxidation and / or reduction reaction within an operating voltage range of the electrochemical device.
The method according to claim 1,
Wherein the non-conductive particles comprise inorganic particles or organic particles or both.
The method of claim 3,
The inorganic particles may be at least one selected from the group consisting of aluminum oxide (alumina), aluminum hydroxide hydrate (AlOOH), gibbsite (Al (OH) ₃ ), bakeite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide, , An oxide which is at least one kind of calcium oxide, a nitride which is at least one kind of aluminum nitride, silicon nitride, silica, barium sulfate and calcium fluoride, and potassium fluoride.
The method of claim 3,
Wherein the organic particles are polymer particles.
6. The method of claim 5,
Wherein the polymeric polymer particles comprise at least one selected from the group consisting of polystyrene, polyethylene, polyimide, melamine resin and phenol resin.
6. The method of claim 5,
Wherein the polymeric polymer particles have a glass transition temperature of 150 DEG C or higher.
The method according to claim 1,
Wherein the porous polymer substrate is any one of the following a) to e):
a) a porous film formed by melting / extruding a polymer resin,
b) a multi-layered film in which two or more porous films of a)
c) a nonwoven web prepared by integrating filaments obtained by melting / spinning a polymer resin,
d) a multi-layered film in which two or more layers of the nonwoven web of b)
e) a multi-layered composite porous substrate comprising at least two of a) to d).
The method of claim 3,
Wherein the inorganic particles include inorganic particles having ion transport capability and / or high-permittivity inorganic particles having a dielectric constant of 5 or more.
A cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the composite separator according to any one of claims 1 to 9.
An electrochemical device comprising an electrode assembly according to claim 10.
Heat-resistant particles of a core-shell structure including a core portion and a shell portion formed on at least a part of a surface of the core portion,
Here, the core portion comprises a non-conductive particle, and the shell portion of barium titanate, an electrochemical device for the composite separator comprises (BaTiO _3).
13. The method of claim 12,
Wherein the non-conductive particles do not cause an oxidation and / or reduction reaction within an operating voltage range of the electrochemical device.
13. The method of claim 12,
Wherein the non-conductive particles comprise inorganic particles or organic particles or both.
13. The method of claim 12,
The inorganic particles may be at least one selected from the group consisting of aluminum oxide (alumina), aluminum hydroxide hydrate (AlOOH), gibbsite (Al (OH) ₃ ), bakeite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide, , An oxide which is at least one kind of calcium oxide, a nitride which is at least one kind of aluminum nitride, silicon nitride, silica, barium sulfate and calcium fluoride, and potassium fluoride.
13. The method of claim 12,
Wherein the organic particles are polymer particles.

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