KR102017239B1 - 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 composite separator for an electrochemical device and an electrochemical device comprising the same. More particularly, the present invention relates to a composite separator having an effect of reducing the amount of gas generated during activation of a battery, thereby increasing internal resistance and preventing battery capacity deterioration.

Description

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

The present invention relates to a composite separator for an electrochemical device and an electrochemical device comprising the same. More particularly, the present invention relates to a composite separator having an effect of reducing the amount of gas generated during activation of a battery, thereby increasing internal resistance and preventing battery capacity deterioration.

Secondary battery is composed of anode / cathode / membrane / electrolyte based on the reversible conversion of chemical energy and electrical energy, which can be charged and discharged with high energy density energy storage body, which is widely used in small electronic equipment such as mobile phones and laptops. In recent years, combined electric vehicles (hybrid electric vehicles (HEV), plug-in EVs, e-bikes and energy storage systems) have been developed to address environmental issues, high oil prices, energy efficiency and storage. Applications to energy storage systems (ESS) are expanding rapidly.

In the secondary battery as described above, as the potential risk of safety accidents such as ignition and explosion accidents of electrochemical devices has rapidly increased, safety evaluation and safety of electrochemical devices have emerged as a very important issue. Accordingly, as the demand for safety verification not only at the national level but also at the consumer level is increasing worldwide, the government is enforcing and expanding the mandatory certification regulations and standardizing technology. Such an electrochemical device may cause a malfunction depending on the operating environment.In case of malfunction, a thermal runaway occurs due to overheating, and when a separator provided in the device is decomposed, electrical energy is discharged due to the potential difference of the electrode, which is rapidly narrowed due to an internal short circuit. There is a fear that internal explosion may occur due to vaporization of the electrolyte solution. In particular, polyolefin-based porous substrates prepared by thermodynamic phase separation of materials, which are currently used as separators of general electrochemical devices, have suitable mechanical properties, chemical stability,

Although it has the property of reasonable production cost, it is characterized by extreme heat shrinkage behavior at temperatures above 100 ° C due to the material properties that are usually melted below 200 ° C and the nature of the drawing process to control pore size and porosity. The stability is weak and the mechanical strength is insufficient to be applied to medium and large electrochemical devices, and the risk of internal short circuit exists.

In order to complement the thermal and mechanical properties of the polyolefin-based separator provided in the electrochemical device as described above, Japanese Patent Publication No. 2003-022707 and Polymer Journal, vol. 42, P. 425-437, 2010, etc. have proposed a method for producing an organic / inorganic composite membrane having a microporous structure by mixing the inorganic particles and the polyolefin resin, using thermodynamic phase separation of a solvent, a polymer, and inorganic particles. In addition, the Republic of Korea Patent Publication Nos. 10-2006-72065, 10-2007-231, 10-2008-0010166, etc., the porous material consisting of a mixture of inorganic filler particles and a polymeric binder on one or both sides of the porous substrate A separator having a coating layer has been proposed. Inorganic filler particles of the microporous coating layer formed on the porous substrate serve as a kind of passivation to maintain physical shape, thereby inhibiting thermal shrinkage of the porous substrate during overheating due to malfunction of the electrochemical device, and Together, an empty space exists between the inorganic filler particles to form fine pores. As such, the microporous coating layer formed on the porous substrate contributes to improving the safety of the electrochemical device. According to the prior art, Al ₂ O ₃ is mainly used as the inorganic filler particles used to form the microporous coating layer. The higher the specific surface area of the alumina, the more the amount of gas generated during the initial activation of the battery has a problem. .

An object of the present invention is to provide a composite membrane in which the amount of gas generated during the initial activation of the battery is reduced. Other objects and advantages of the invention will be understood by the following description. On the other hand, it will be readily apparent that the objects and advantages of the present invention may be realized by the means or method described in the claims, and combinations thereof.

The present invention is to solve the above technical problem, and relates to a composite separator for an electrochemical device comprising heat-resistant particles of the core-shell structure including a core portion and a shell portion formed on at least part of the surface of the core portion. Here, the core portion includes non-conductive particles, and the shell portion includes barium titanate (BaTiO ₃ ).

Herein, the non-conductive particles do not undergo oxidation and / or reduction reactions within the operating voltage range of the electrochemical device.

Herein, the non-conductive particles may include inorganic particles or organic particles or both.

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

Herein, the organic particles are high molecular polymer particles.

In addition, the present invention is 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 is formed of layers in which heat-resistant particles are bound and integrated with each other through a binder resin and have a porous structure due to an interstitial volume between the particles. Particles include a core portion and a shell portion formed on at least a portion of the surface of the core portion, wherein the core portion is a non-conductive particle, the shell portion is a composite separator for an electrochemical device, including barium titanate (BaTiO ₃ ). .

Herein, the non-conductive particles do not undergo oxidation and / or reduction reactions within the operating voltage range of the electrochemical device.

In addition, the non-conductive particles may include inorganic particles or organic particles or both thereof.

Herein, the inorganic particles include aluminum oxide (alumina), hydrate of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide, titanium oxide (Titania), at least one oxide of calcium oxide, at least one of aluminum nitride, at least one nitride of silicon nitride, silica, barium sulfate and calcium fluoride, and potassium fluoride.

Herein, the organic particles are high molecular polymer particles.

In addition, the polymer particles may include at least one selected from polystyrene, polyethylene, polyimide, melamine resin, and phenol resin.

In addition, the polymer particles are the glass transition temperature is 150 ℃ or more.

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

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

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

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

b) a multilayer film in which two or more porous films of a) are laminated;

c) nonwoven web made by integrating filament obtained by melting / spinning polymer resin,

d) a multilayer film in which two or more layers of the nonwoven web of b) are laminated;

e) A composite porous substrate having a multilayer structure comprising two or more of a) to d).

Herein, the inorganic particles may include inorganic particles having ion transfer ability and / or high dielectric constant inorganic particles having a dielectric constant of 5 or more.

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

The separator according to the present invention has a porous coating layer including heat-resistant particles coated on the surface of BTO. When the separator is applied to a battery, the amount of gas generated during the activation process is greatly reduced. In addition, since conventional inorganic particles such as alumina are coated with BTO, the cost increase due to material change is not significant.

The accompanying drawings illustrate preferred embodiments of the invention, and together with the description serve to explain the principles of the invention, but the scope of the invention is not limited thereto. On the other hand, the shape, size, scale or ratio of the elements in the drawings included in this specification may be exaggerated to emphasize a more clear description.
Figure 1 schematically shows the cross section of the heat-resistant particles according to the present invention.
2 is a graph showing the correlation between D ₅₀ of particles and the amount of gas generated.
3 is a graph showing the correlation between the BET of the particles and the gas generation amount.
Figure 4 is a graph comparing the amount of gas generated in the Examples and Comparative Examples according to the present invention.

The terms or words used in this specification and claims are not to be construed as being limited to the common or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that it can. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

The present invention relates to a separator for an electrochemical device equipped with 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 of the battery is small, so that the internal resistance increase rate and the battery capacity deterioration are low.

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

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

Hereinafter, the present invention will be described in detail for each component.

1. Porous Polymer Base

According to one specific embodiment of the present invention, the porous polymer substrate is capable of providing a migration path of lithium ions while electrically insulating the negative electrode and the positive electrode to prevent a short circuit. Can be used without limitation. Examples of such porous substrates include polyolefins, polyethylene terephthalates, polybutylene terephthalates, polyacetals, polyamides, polycarbonates, polyimides, polyetheretherketones, polyethersulfones, polyphenylene oxides, and polyphenyls. Porous substrates formed of at least one of polymer resins such as rensulphide and polyethylene naphthalene, but are not particularly limited thereto.

In addition, as the porous polymer substrate, any of a sheet-like film in which a polymer resin is melted and formed into a film or a nonwoven fabric in which filaments obtained by melting and spinning a polymer resin may be used. Preferably it is a porous substrate prepared in the form of a sheet by melting / molding the polymer resin.

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

a) Porous film formed by melting / extruding polymer resin

b) a multilayer film in which two or more porous films of a) are laminated;

c) nonwoven web made by integrating filament obtained by melting / spinning polymer resin,

d) a multilayer film in which two or more layers of the nonwoven web of b) are laminated;

e) A porous composite membrane having a multilayer structure comprising two or more of a) to d).

In the present invention, the thickness of the porous polymer substrate may be 5 to 50 ㎛. Although the range of the porous substrate is not particularly limited to the above-mentioned range, when the thickness is too thin than the above-described lower limit, the mechanical properties may be degraded and the separator may be easily damaged during battery use. On the other hand, the pore size and pore present in the porous substrate is also not particularly limited, but may be 0.01 to 50 ㎛ 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 comprises a mixture of a plurality of heat resistant particles and a binder resin. As such, the surface of the porous polymer substrate is coated with heat-resistant particles to further improve heat resistance and mechanical properties of the separator.

The porous coating layer not only has a microporous structure by interstitial volume between 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 nonconductive particles are substantially interviewed and defined. In addition, since the heat-resistant particles generally have a property that physical properties do not change even at a high temperature of 200 ° C. or more, the separator has excellent heat resistance by the formed porous coating layer. In the present invention, the porous coating layer has a thickness of 1 μm to 50 μm, or 2 μm to 30 μm, or 2 μm to 20 μm.

In the porous coating layer, the content ratio of the heat-resistant particles and the binder resin is determined in consideration of the thickness, pore size and porosity of the porous coating layer of the present invention to be finally produced, based on the weight ratio of inorganic particles 50 to 99.9% by weight or 70 to 99.5% by weight, polymer resin is 0.1 to 50% by weight or 0.5 to 30% by weight. By setting the content ratio of the heat-resistant particles in the porous coating layer within the above range, it is possible to form an interstitial volume to the extent that the movement of ions is not inhibited while the heat-resistant particles have contact portions. When the content of the heat-resistant particles is less than 50% by weight, the content of the polymer is excessively large, and the pore size and porosity due to the reduction of the interstitial volume formed between the heat-resistant particles are reduced, resulting in deterioration of final cell performance. May be caused. On the other hand, if it exceeds 99.9% by weight, the polymer content is too small, the mechanical properties of the final porous coating layer is reduced due to the weakening of the adhesion between the inorganic materials.

On the other hand, the pore size and porosity of the porous coating layer depends on the size of the heat-resistant particles included, for example, when using the heat-resistant particles having a particle size of 1㎛ or less, the pore formed is also 1㎛ or less. The pore structure is filled with the electrolyte solution to be poured later, the electrolyte thus filled serves to transfer the ion. Therefore, the pore size and porosity are important factors in controlling ion conductivity of the porous inorganic coating layer. The pore size and porosity of the porous coating layer of the present invention is 0.001 to 10㎛, respectively, preferably in the range of 5 to 95%.

3. Heat resistant particles

In the present invention, the heat resistant particles have a core-shell structure including a core portion and a shell portion formed on at least a portion 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 ). Figure 1 schematically shows the configuration of the heat-resistant particles according to an embodiment of the present invention.

The average particle diameter (D50 average particle diameter of the volume average) of the said heat resistant particle is 5 nm-10 micrometers, or 50 nm-5 micrometers, or 100 nm-5 micrometers, or 500 nm-2 micrometers, or 500 nm-1.5 micrometers . By making the average particle diameter of heat resistant particle | grains into the said range, control of a dispersion state becomes easy and it becomes easy to obtain the porous coating layer which suppressed the internal resistance of a uniform predetermined thickness. In addition, it is possible to prevent the occurrence of internal short circuit due to the formation of too large pores. When the average particle diameter of heat resistant particle | grains is made into the range of 50 nm-5 micrometers, since it is excellent in dispersion | distribution, ease of application | coating, and controllability of a space | gap, it is more preferable.

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

In addition, the BET specific surface area of these heat resistant particles is specifically 0.9 to 200 m 2 / g or 1 to 100 m 2 / g or 1 to 1 from the viewpoint of suppressing the aggregation of the particles and making the fluidity of the slurry for the heat resistant layer suitable. 50 m <2> / g or 1-10 m <2> / g.

According to one 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 the method of electrolysis, chemical or physical vapor deposition, etc. It can be formed by.

4. Core part - Non-conductive  particle

The non-conductive particles forming the core part may be non-conductive inorganic particles or organic particles, or both, as long as they are stably present in a secondary battery environment and are electrochemically stable. In other words, the non-conductive particles are not particularly limited as long as the oxidation and / or reduction reactions do not occur in the operating voltage range (for example, 0 to 5 V on the basis of Li / Li +) of the electrochemical device to be applied.

In this invention, the material of inorganic particle is electrochemically stable, and the material suitable for preparing the slurry composition for heat-resistant layers by mixing with another material, for example, a viscosity modifier etc. which are mentioned later is preferable. From such a viewpoint, the inorganic particles include aluminum oxide (alumina), hydrates of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide Oxides such as titanium oxide (titania), calcium oxide, nitrides such as aluminum nitride, silicon nitride, silica, barium sulfate, calcium fluoride, potassium fluoride, etc. Among these, oxides are considered from the viewpoint of stability in electrolyte solution and potential stability. Among them, alumina, titanium oxide, boehmite, magnesium oxide and magnesium hydroxide are preferable from the viewpoint of low water absorption and excellent heat resistance (for example, resistance to high temperature of 180 ° C or higher), and alumina, boehmite, magnesium oxide are preferred. And magnesium hydroxide are particularly preferred.

According to one specific embodiment of the present invention, the inorganic particles are alumina. Alumina has a bulk resistance of 10 Ω · cm or more at room temperature, and thus has a higher physical resistance than other insulators even at elevated temperatures, and thus has preferable physical properties as an insulating material for separators. In addition, the alumina has a melting point of about 2,047 ° C., which is excellent in strength at high temperatures and stable to corrosive gases and liquids such as acids and alkalis and does not react well. In addition, alumina is a mineral that is next to silicon oxide among the minerals in the earth's crust, so it is easy to purify, and thus the raw material price is low and high purity products can be produced with relatively simple fixation.

On the other hand, the inorganic particles, in particular, when using the inorganic particles having ion transfer ability can be improved performance by increasing the ionic conductivity in the electrochemical device. In addition, when inorganic particles having a high dielectric constant are used as the inorganic particles, the ionic conductivity of the electrolyte may be improved by contributing to an increase in the dissociation degree of the electrolyte salt such as lithium salt in the liquid electrolyte. Accordingly, according to one specific embodiment of the present invention, the inorganic particles may include high dielectric constant inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having a lithium ion transfer ability, or a mixture thereof. Non-limiting 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, where 0 <x <1, 0 <y <1), Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ (PMN-PT), Hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ , and the like may be used alone or in combination of two or more thereof. In addition, synergistic effects of the high dielectric constant inorganic particles and the inorganic particles having lithium ion transfer ability may be doubled.

Non-limiting examples of the inorganic particles having a lithium ion transfer capacity is 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), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P (LiAlTiP) _x O _y series glass such as 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 _{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), lithium nitrides such as Li ₃ N (Li _x N _y , 0 <x <4, 0 <y <2), and SiS ₂ based glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li P ₂ S ₅ series glass (Li _x P _y S _z , 0, such as _x Si _y S _z , 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S _5, etc. <x <3, 0 <y <3, 0 <z <7) or mixtures thereof.

In addition, in this invention, the particle | grains of a polymer (polymer) are used normally as said organic substance particle | grains. The organic particle | grains can control affinity with water by adjusting the kind and quantity of the functional group of the surface, and can also control the moisture content contained in the heat-resistant layer of this invention. As an organic material of a nonelectroconductive particle, various high molecular compounds, such as polystyrene, polyethylene, a polyimide, a melamine resin, a phenol resin, etc. are mentioned, for example. The polymer compound forming the particles may be a mixture, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, a crosslinked product or the like. The organic particle | grains may be formed of the mixture of 2 or more types of high molecular compounds.

When using organic particle | grains as a nonelectroconductive particle, although it may or may not have a glass transition temperature, when the high molecular compound which forms the said organic particle has a glass transition temperature, the glass transition temperature is 150 degreeC or more normally, Preferably it is 200 degreeC or more, More preferably, it is 250 degreeC or more.

As for the said nonelectroconductive particle, element substitution, surface treatment, solid solution, etc. may be given as needed. Moreover, a nonelectroconductive particle may contain one type of the said material independently in one particle | grain, and may contain it combining two or more types by arbitrary ratios. In addition, you may use a nonelectroconductive particle combining 2 or more types of particle | grains formed from the different material.

In the present invention, the non-conductive shape is spherical, acicular, rod-shaped, flaky, plate-like, tetrapod (registered trademark) phase (linked particles) and the like, but is not particularly limited, but in the case of using inorganic particles as heat-resistant particles, tetrapod Phase (connected particle), plate shape, and flaky phase are preferable. When the inorganic particles have the above-described shape, the porosity (porosity) of the porous coating layer can be ensured, and the decrease in ion conductivity can be suppressed.

5. Shell - BTO  Coating layer

The coating layer forming the shell portion is barium titanate (BaTiO ₃ , BTO). Barium titanate (BTO) is a ceramic material having a tetragonal phase at room temperature and having a very high dielectric constant. Figure 4 shows the gas generation amount of the separator having a porous coating layer comprising alumina particles and barium titanate particles, respectively, it can be seen that in the case of barium titanate gas generation amount is only 20% compared to alumina.

6. Manufacturing method of porous coating layer

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

The binder resin included in the porous coating layer may be preferably a low polymer resin capable of a glass transition temperature (Tg), and the glass transition temperature is preferably in the range of -200 ° C to 200 ° C. This is because mechanical properties such as flexibility and elasticity of the composite separator can be improved. The binder resin stably fixes the adhesion between the inorganic particles, thereby contributing to the prevention of mechanical property deterioration of the final porous coating layer. In the present invention, the binder resin does not necessarily have an ion conductivity, but when using a polymer resin having an ion conductivity, it is possible to further improve the performance of the electrochemical device. Therefore, the binder resin is preferably as high as possible dielectric 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 more polar groups are preferable than 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 the binder resin usable in the present invention include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene , Polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene vinyl acetate copolymer co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethyl Sucrose (cyanoethylsucrose), pullulan and carboxyl 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, it is not particularly 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 cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene and ethylbenzene; acetone, ethyl methyl ketone, diisopropyl ketone, cyclohexanone, methylcyclohexane, Ketones such as ethylcyclohexane; chlorine aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; esters such as ethyl acetate, butyl acetate, γ-butyrolactone and ε-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; N-methylpyrrolidone, N, N-dimethylformamide and the like; Amides may be mentioned.

These dispersion mediums may be used alone, or two or more thereof may be mixed and used as a mixed solvent. Among these, especially a solvent with low boiling point and high volatility can be removed in a short time and at low temperature, and it is preferable. Specifically, acetone, toluene, cyclohexanone, cyclopentane, tetrahydrofuran, cyclohexane, xylene, N-methylpyrrolidone, or a mixed dispersion medium thereof is preferable.

The method of forming the porous coating layer by applying the slurry on the porous substrate is not limited, and may be a dip coating method, a die coating method, a roll coating method, a comma coating method, or a doctor blade. The coating method, the reverse roll coating method, the direct roll coating method, etc. are mentioned.

The composite separator of the present invention prepared as described above may be used as a separator of an electrochemical device. The electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors. 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 among the secondary batteries is preferable.

In addition, in one specific embodiment according to the present invention, the lithium secondary battery may be manufactured according to conventional methods known in the art. According to an embodiment of the present invention, a secondary battery may be manufactured by preparing an electrode assembly by interposing the aforementioned separator between a positive electrode and a negative electrode, inserting the same into a battery case, and then injecting an electrolyte solution.

In one embodiment of the present invention, the electrode of the secondary battery can be prepared in the form of the electrode active material adhered to the electrode current collector according to a conventional method known in the art. Non-limiting examples of the positive electrode active material of the electrode active material may be used a conventional positive electrode active material that can be used for the positive electrode of the conventional electrochemical device, in particular lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or Lithium intercalation materials such as composite oxides formed by combination are preferred. Non-limiting examples of the negative electrode active material may be a conventional negative electrode active material that can be used for the negative electrode of the conventional electrochemical device, in particular lithium metal or lithium alloys, carbon, petroleum coke, activated carbon, Lithium adsorbents such as graphite or other carbons are preferred. Non-limiting examples of the positive electrode current collector is a foil made by aluminum, nickel or a combination thereof, and non-limiting examples of the negative electrode current collector by copper, gold, nickel or copper alloy or a combination thereof Foils produced.

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 - Salts containing ions consisting of anions or combinations thereof such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide , Acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone (γ-butyrolactone) or their Some are dissolved or dissociated in an organic solvent composed of a mixture, but are not limited thereto.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and the required physical properties of the final product. That is, it may be applied before the battery assembly or at the end of battery assembly. As a process of applying the electrode assembly of the present invention to a battery, a lamination (stacking) and folding (folding) process of the separator and the electrode may be performed in addition to the general winding process.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

Preparation of heat resistant particles

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

Gas generation measurement

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

Comparative example

Al2O3 particles and BTO particles were impregnated in an electrolyte solution (ethylene carbonate: ethylpropionate = 3: 7, weight ratio), and then allowed to stand for 3 days in an electrolyte solution at 85 ° C., and gas generation was measured. The amount of particles used was 0.7 g, and the electrolyte solution was 1.5 g. The amount of gas generated is as summarized in Table 1 below and FIG. 4.

Example Comparative Example 1 Comparative Example 2 Comparative Example 3 Mineral type Al2O3 / BTO
(9: 1 weight ratio) Al2O3 BTO No mineral input
Electrolyte D50 (μm) 0.65 0.50 1.00 - BET (m2 / g) 3.50 5.89 2.20 - water(%) 99.99 99.99 99.99 - CH (μl) 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

Through the experimental results, it was confirmed that the Al ₂ O ₃ / BTO composite particles significantly reduced gas generation compared to Al ₂ O ₃ . On the other hand, compared with the BTO particles of Comparative Example 2, the amount of gas generated in the Example particles is higher, but in the case of Example, only 10% of the BTO component is used compared to Comparative Example 2, it can be seen that the gas generation amount reduction effect is very high compared to the BTO input amount. . Therefore, by combining the alumina particles with BTO it is possible to increase the cost reduction and gas generation amount reduction effect.

Experimental Example

Confirmation of particle D50 and BET surface area and gas generation

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

sample A B C D E D50 (μm) 0.49 0.58 0.51 0.99 0.69 BET (m2 / 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 of A to E were impregnated in an electrolyte solution (ethylene carbonate: ethylpropionate = 3: 7, weight ratio), respectively, and left for 3 days at 85 ° C. in an electrolyte solution. The gas generation amount is as summarized in Table 3 below.

sample A B C D E CH (μl) 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 amount of gas generated. According to this, since the gas generation amount tends to increase as the diameter of the heat resistant particles decreases, it is preferable that the diameter of the particles be large to reduce the gas generation amount.

3 is a graph showing the correlation between the specific surface area of the heat-resistant particles and the gas generation amount. According to this, since the gas generation amount tends to increase as the specific surface area of the heat-resistant particles increases, it is preferable that the BET specific surface area of the particles is low in order to reduce the gas generation amount. The BET specific surface area of the heat-resistant particles was measured by BET measurement method by adsorbing nitrogen gas to the heat-resistant particles using a specific surface area measuring device (Jamini 2310: manufactured by Shimadzu Corporation).

100 ... heat-resistant particles
11.shell part
12 ... core part

Claims (16)

Porous polymer substrates; And
A porous coating layer formed on at least one surface of the porous polymer substrate; Including;
Here, the porous coating layer is a heat-resistant particles are bound to each other via a binder resin and are integrated with each other formed in a layered form having a porous structure due to the interstitial volume between the particles,
The heat-resistant particles include a core portion and a shell portion formed on at least a portion of a surface of the core portion, the core portion is non-conductive particles, and the shell portion includes barium titanate (BaTiO ₃ ),
The non-conductive particles are composite particles for an electrochemical device which is an inorganic particle as the oxidation and / or reduction does not occur within the operating voltage range of the electrochemical device.
delete delete The method of claim 1,
The inorganic particles are aluminum oxide (alumina), hydrate of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide, titanium oxide (titania) At least one selected from oxides of aluminum oxide, aluminum nitride, at least one nitride of silicon nitride, silica, barium sulfate and calcium fluoride, potassium fluoride, composite separator for an electrochemical device.
delete delete delete The method of claim 1,
The porous polymer substrate is any one of the following a) to e), the composite separator for an electrochemical device:
a) porous film formed by melting / extruding polymer resin,
b) a multilayer film in which two or more porous films of a) are laminated;
c) nonwoven web made by integrating filament obtained by melting / spinning polymer resin,
d) a multilayer film in which two or more layers of the nonwoven web of b) are laminated;
e) A composite porous substrate having a multilayer structure comprising two or more of a) to d).
The method of claim 1,
Wherein the inorganic particles include inorganic particles having ion transfer ability and / or high dielectric constant inorganic particles having a dielectric constant of 5 or more, composite separator for an electrochemical device.
An electrode assembly comprising a cathode, an anode and a separator interposed between the cathode and the anode, wherein the separator is a composite separator according to any one of claims 1, 4, 8 and 9.
An electrochemical device comprising the electrode assembly of claim 10.
It comprises a core-shell structured heat-resistant particles comprising a core portion and a shell portion formed on at least a portion of the surface of the core portion,
Wherein the core portion includes non-conductive particles, the shell portion includes barium titanate (BaTiO ₃ ),
The non-conductive particles are composite particles for an electrochemical device which is an inorganic particle as the oxidation and / or reduction does not occur within the operating voltage range of the electrochemical device.
delete delete The method of claim 12,
The inorganic particles are aluminum oxide (alumina), hydrate of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide, titanium oxide (titania) At least one selected from oxides of aluminum oxide, aluminum nitride, at least one nitride of silicon nitride, silica, barium sulfate and calcium fluoride, potassium fluoride, composite separator for an electrochemical device.


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