KR102121277B1 - Organic/inorganic composite porous separator and electrochemical device including the same - Google Patents

Abstract

The present invention relates to an organic/inorganic composite porous separator and an electrochemical device comprising the same, more specifically, (a) a porous polymer substrate; And (b) a porous coating layer formed on at least one surface of the porous polymer substrate and comprising a mixture of basic particles of inorganic particles and a binder polymer; and an organic/inorganic composite porous separator having an electrochemical device comprising the same. will be.
According to the present invention, if an organic/inorganic composite porous separator is prepared by applying a basic oxide instead of a positive oxide such as Al ₂ O ₃ that was previously used as an inorganic particle, HF generated by side reaction can be neutralized and thus an electrochemical device. It is possible to improve the lifespan, and to reduce the amount of gas generated, it is possible to suppress the swelling (swelling) phenomenon that the thickness of the electrochemical device is thick.

Description

Organic/inorganic composite porous separator and electrochemical device comprising the same{ORGANIC/INORGANIC COMPOSITE POROUS SEPARATOR AND ELECTROCHEMICAL DEVICE INCLUDING THE SAME}

The present invention relates to an organic/inorganic composite porous separator and an electrochemical device comprising the same, and more particularly, an organic/inorganic composite porous separator capable of improving the life of the electrochemical device and reducing the amount of gas generated, and It relates to an electrochemical device comprising him.

Recently, interest in energy storage technology has been increasing. Mobile phones, camcorders and notebook PCs, and furthermore, the field of application to the energy of electric vehicles has been expanded, and efforts for research and development of electrochemical devices are gradually becoming concrete. The electrochemical device is the area that is receiving the most attention in this aspect, and among them, the development of a rechargeable battery capable of charging and discharging has become a focus of interest, and recently, in developing such a battery, in order to improve capacity density and specific energy, new Research and development are being conducted on the design of electrodes and batteries.

Among currently used secondary batteries, lithium secondary batteries developed in the early 1990s have the advantage of higher operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries that use aqueous electrolyte solutions. Is in the limelight. However, such a lithium ion battery has safety problems such as ignition and explosion caused by the use of an organic electrolytic solution, and has a disadvantage in that it is difficult to manufacture. In recent years, lithium ion polymer batteries are considered as one of the next generation batteries by improving the weakness of such lithium ion batteries, but the capacity of the batteries is still relatively low compared to lithium ion batteries, and in particular, the discharge capacity at low temperatures is insufficient, thereby improving it. This is urgently required.

Although the above electrochemical devices are produced by many companies, their safety characteristics show different aspects. It is very important to evaluate the safety and safety of these electrochemical devices. The most important consideration is that the electrochemical device should not cause injury to the user in case of malfunction, and for this purpose, the safety standard strictly regulates ignition and smoke in the electrochemical device. In the safety characteristics of the electrochemical device, there is a high possibility that an electrochemical device will overheat and cause a thermal runaway or an explosion when the separator penetrates. In particular, the polyolefin-based porous polymer substrate commonly used as a separator of an electrochemical device exhibits extreme heat shrinkage behavior at a temperature of 100° C. or higher due to material properties and manufacturing process characteristics, including stretching, between an anode and a cathode. There is a problem that causes a short circuit.

In order to solve the safety problem of the electrochemical device, a porous coating layer is formed by coating a mixture of inorganic particles that are positive oxides such as Al ₂ O ₃ and a binder polymer on at least one surface of a porous polymer substrate having a large number of pores. One separator was proposed.

However, the inorganic particles, which are these positive oxides, cause side reactions with moisture present in the electrolyte as the electrochemical device is activated to generate HF, and the HF thus generated has a great influence on the deterioration of the life of the electrochemical device.

Therefore, the problem to be solved by the present invention is to provide an organic/inorganic composite porous separator and an electrochemical device including the same, by solving the above-mentioned problems to neutralize the generated HF and lower the amount of gas generated.

In order to solve the above problems, according to an aspect of the present invention, (a) a porous polymer substrate; And (b) a porous coating layer formed on at least one surface of the porous polymer substrate and comprising a mixture of inorganic particles, which are basic oxides, and a binder polymer.

Here, the porous coating layer, the inorganic particles are filled and bound to each other by the binder polymer in contact with each other, an interstitial volume (interstitial volume) is formed between the inorganic particles, the interstitial volume May be an empty space to form pores.

And, the pore size of the porous coating layer is 0.001 to 10 ㎛, porosity may be 10 to 90%.

In addition, the weight ratio of the inorganic particles and the binder polymer may be 50:50 to 99:1.

In addition, the basic oxide may be any one selected from the group consisting of Mg(OH) ₂ , Ca(OH) ₂ , MgO, CaO, K ₂ O, Na ₂ O, MnO and BaO, or a mixture of two or more of them. Can be.

In addition, the average particle diameter of the inorganic particles may be 0.001 to 10 μm.

In addition, the binder polymer is polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichloro ethylene, polyvinylidene fluoride-co-trichloro ethylene, poly Methyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinylacetate, polyimide , Polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl poly A group consisting of vinyl alcohol (cyanoethyl polyvinylalcohol), cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose and polyvinylalcohol It may be any one selected from or a mixture of two or more of them.

In addition, the porous polymer substrate may be a porous polymer film substrate or a porous nonwoven fabric substrate.

And, the porous polymer substrate, polyethylene (polyethylene), polypropylene (polypropylene), polybutylene (polybutylene), polypentene (polypentene), polyethylene terephthalate (polyethyleneterephthalate), polybutylene terephthalate (polybutyleneterephthalate), polyester (polyester), polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide , Polyphenylene sulfide (polyphenylenesulfide) and polyethylene naphthalate (polyethylenenaphthalate) may be formed of any one or a mixture of two or more selected from the group consisting of.

In addition, the thickness of the porous polymer substrate may be 5 to 50 μm.

Meanwhile, according to another aspect of the present invention, an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode; A non-aqueous electrolyte that impregnates the electrode assembly; And an electrode assembly and a battery case incorporating the non-aqueous electrolyte, wherein the separator is an organic/inorganic composite porous separator of the present invention described above.

Here, the non-aqueous electrolyte solution may include an organic solvent and an electrolyte salt.

At this time, the organic solvent, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinyl Ethylene carbonate, fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, Ethylpropyl ether, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone And ε-caprolactone, or a mixture of two or more of them.

In addition, the electrolyte salt is a negative ^{ion, F -, Cl -, Br} -, I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 _{^{PF 4 -, (CF 3)}} 3 PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 _{^{-, (CF 3 SO 2)}} 2 N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, _{(CF 3 SO 2) 3 C} -, CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- may include any one or two or more selected from the group consisting of.

In addition, the electrochemical device may be a lithium secondary battery.

According to the present invention, if an organic/inorganic composite porous separator is prepared by applying a basic oxide instead of a positive oxide such as Al ₂ O ₃ that was previously used as an inorganic particle, HF generated by side reaction can be neutralized and thus an electrochemical device. It is possible to improve the lifespan, and to reduce the amount of gas generated, it is possible to suppress the swelling (swelling) phenomenon that the thickness of the electrochemical device is thick.

Hereinafter, the present invention will be described in detail. The terms or words used in the specification and claims should not be interpreted as being limited to ordinary or lexical meanings, and the inventor can appropriately define the concept of terms in order to explain his or her invention in the best way. Based on the principle that it should be interpreted as meanings and concepts consistent with the technical spirit of the present invention.

Therefore, the configuration described in the embodiments described in this specification is only one of the most preferred embodiments of the present invention, and does not represent all of the technical spirit of the present invention, and various equivalents that can replace them at the time of this application It should be understood that there may be and variations.

An organic/inorganic composite porous separator according to an aspect of the present invention, (a) a porous polymer substrate; And (b) a porous coating layer formed on at least one surface of the porous polymer substrate and comprising a mixture of inorganic particles that are basic oxides and a binder polymer.

Conventionally, an organic/inorganic composite porous separator having a porous coating layer was formed by coating a mixture of inorganic particles, which are positive oxides such as Al ₂ O ₃ , and a binder polymer, on a porous polymer substrate. As the electrochemical device is activated, HF is generated by causing side reactions with moisture present in the electrolyte, and the generated HF has been a problem because it has a great influence on the deterioration of the life of the electrochemical device.

However, in the present application, by using a basic oxide instead of a positive oxide previously used as an inorganic particle, neutralization of the HF generated by a side reaction can improve the life of the electrochemical device. In addition, the swelling phenomenon in which the thickness of the electrochemical device becomes thicker by reducing the amount of gas generated can be suppressed.

On the other hand, the porous coating layer, the binder polymer is attached to each other so that the inorganic particles can be bound to each other (that is, the binder polymer is connected and fixed between the inorganic particles), the porous coating layer is also by the binder polymer It remains bound to the porous polymer substrate.

Then, an interstital volume is formed between the inorganic particles, and this interstitial volume can be an empty space, thereby forming the porosity of the porous coating layer, and the interstital volume. Is a space defined by inorganic particles substantially interviewed in a closed structure (closed packed or densely packed) by inorganic particles.

The inorganic particles used herein are not particularly limited as long as they are basic oxides and are electrochemically stable. That is, the inorganic particles are not particularly limited as long as they do not undergo oxidation and/or reduction reactions in the operating voltage range of the applied electrochemical device (eg, 0 to 5 V based on Li/Li ⁺ ), for example, Mg( OH) ₂ , Ca(OH) ₂ , MgO, CaO, K ₂ O, Na ₂ O, MnO, and BaO.

In addition, the average particle diameter of the inorganic particles is not limited, but for the formation of a uniform thickness coating layer and proper porosity, it is preferable that it is in the range of 0.001 to 10 μm as much as possible. If it is less than 0.001 μm, dispersibility may decrease, and when it exceeds 10 μm, the thickness of the porous coating layer may increase.

And, the composition ratio of the inorganic particles of the porous coating layer of the present invention and the binder polymer is, for example, preferably in the range of 50:50 to 99:1, more preferably 70:30 to 95:5. When the content ratio of the inorganic particles to the binder polymer is less than 50:50, the content of the binder polymer increases, so that the pore size and porosity of the porous coating layer may be reduced. When the content of the inorganic particles exceeds 99 parts by weight, since the binder polymer content is small, the peeling resistance of the porous coating layer may be weakened. The loading amount of the porous coating layer on the porous substrate is preferably 5 to 20 g/m ² in consideration of the function of the porous coating layer and compatibility with a high-capacity battery, but is not limited thereto.

In addition, the pore size and porosity of the porous coating layer are not particularly limited, but the pore size is preferably in the range of 0.001 to 10 μm, and the porosity is preferably in the range of 10 to 90%. The pore size and porosity mainly depend on the size of the inorganic particles. For example, when using inorganic particles having a particle diameter of 1 µm or less, the pores formed also show approximately 1 µm or less. The pore structure is filled with an electrolyte to be injected later, and the filled electrolyte serves as ion transport. When the pore size and porosity are less than 0.001 μm and 10%, respectively, it can act as a resistive layer, and when the pore size and porosity exceeds 10 μm and 90%, respectively, mechanical properties of the porous coating layer may be deteriorated.

Meanwhile, as the binder polymer used for forming the porous coating layer, a polymer commonly used for forming a porous coating layer in the art may be used. In particular, a polymer having a glass transition temperature (T _g ) of -200 to 200°C may be used, because mechanical properties such as flexibility and elasticity of the finally formed porous coating layer can be improved. These binder polymers faithfully perform the role of a binder that connects and stably fixes the inorganic particles, thereby contributing to the prevention of deterioration in mechanical properties of the separator in which the porous coating layer is introduced.

In addition, the binder polymer does not necessarily have an ion conducting ability, but when a polymer having an ion conducting ability is used, the performance of the electrochemical device can be further improved. Therefore, a binder polymer having a high dielectric constant is possible. Indeed, since the degree of dissociation of a salt in an electrolyte is dependent on the dielectric constant of the electrolyte solvent, the higher the dielectric constant of the polymer, the better the salt dissociation in the electrolyte. The dielectric constant of the binder polymer may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), and may be 10 or more.

In addition to the above-described functions, the binder polymer may have a characteristic that can exhibit a high degree of swelling of the electrolyte by being gelled upon impregnation of the liquid electrolyte. Accordingly, the solubility of the binder polymer may be 15 to 45 MPa ^1/2 or 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range. Therefore, hydrophilic polymers having many polar groups may be used more than hydrophobic polymers such as polyolefins. If the solubility is more than 15 MPa ^1/2 and less than 45 MPa ^1/2, because it can be difficult to swell (swelling) by conventional liquid electrolyte batteries.

Non-limiting examples of such a binder polymer include polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichloro ethylene , Polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinylacetate, polyimide ( polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl pullulan Ethyl polyvinyl alcohol (cyanoethyl polyvinylalcohol), cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, polyvinylalcohol, etc. Can be heard.

In this case, when a basic binder polymer is used as the binder polymer, HF generated by a side reaction of the electrochemical device can be more efficiently neutralized.

Meanwhile, the porous polymer substrate may be any porous polymer substrate used in the electrochemical device, and for example, a polyolefin-based porous polymer film substrate or a porous non-woven fabric substrate may be used, but is not particularly limited thereto.

In addition, the porous polymer substrate may be a porous polymer substrate formed of a single layer, or may be formed of a multilayer of two or more layers.

The porous polymer substrate, polyethylene (polyethylene), polypropylene (polypropylene), polybutylene (polybutylene), polypentene (polypentene), polyethylene terephthalate (polyethyleneterephthalate), polybutylene terephthalate (polybutyleneterephthalate), polyester (polyester) ), polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, poly It may be formed of phenylene sulfide (polyphenylenesulfide), polyethylene naphthalate (polyethylenenaphthalate).

In particular, examples of the polyolefin-based porous polymer substrate include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-high-molecular-weight polyethylene, respectively, or mixing them. And a membrane formed of one polymer.

The porous non-woven fabric substrate includes, in addition to polyolefin-based non-woven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate (polycarbonate), polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, polyethylenenaphthalate, etc. And nonwoven fabrics formed of polymers alone or in combination. The structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a melt blown nonwoven fabric.

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

Meanwhile, according to another aspect of the present invention, an electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode; A non-aqueous electrolyte that impregnates the electrode assembly; And an electrode assembly and a battery case incorporating the non-aqueous electrolyte, wherein the separator is an organic/inorganic composite porous separator of the present invention described above.

At this time, the positive electrode has a structure in which a positive electrode active material layer including a positive electrode active material, a conductive material, and a binder is formed on one or both surfaces of a positive electrode current collector plate.

The positive electrode active material may be a lithium-containing oxide, and a lithium-containing transition metal oxide may be preferably used. For example, the lithium-containing transition metal oxide is Li _x CoO ₂ (0.5<x<1.3), Li _x NiO ₂ (0.5<x<1.3), Li _x MnO ₂ (0.5<x<1.3), Li _x Mn ₂ O ₄ (0.5<x<1.3), Li _x (Ni _a Co _b Mn _c )O ₂ (0.5<x<1.3, 0<a<1, 0<b<1, 0<c<1, a +b+c=1), Li _x Ni _{1 -y} Co _y O ₂ (0.5<x<1.3, 0<y<1), Li _x Co _{1 -y} Mn _y O ₂ (0.5<x<1.3, 0 ≤y<1), Li _x Ni _{1 -y} Mn _y O ₂ (0.5<x<1.3, O≤y<1), Li _x (Ni _a Co _b Mn _c )O ₄ (0.5<x<1.3, 0 <a<2, 0<b<2, 0<c<2, a+b+c=2), Li _x Mn _{2 -z} Ni _z O ₄ (0.5<x<1.3, 0<z<2), Group consisting of Li _x Mn _{2 -z} Co _z O ₄ (0.5<x<1.3, 0<z<2), Li _x CoPO ₄ (0.5<x<1.3) and Li _x FePO ₄ (0.5<x<1.3) It may be any one selected from or a mixture of two or more of them, the lithium-containing transition metal oxide may be coated with a metal or metal oxide such as aluminum (Al). Further, in addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

In addition, the conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in the electrochemical device. In general, carbon black, graphite, carbon fiber, carbon nanotubes, metal powders, conductive metal oxides, organic conductive materials, etc. can be used. As a commercially available product, acetylene black series (Chevron Chemical) Company (such as Chevron Chemical Company or Gulf Oil Company), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cavity Company) (Product of Cabot Company) and Super P (product of MMM). Examples include acetylene black, carbon black, and graphite.

Meanwhile, the negative electrode has a structure in which a negative electrode active material layer including a negative electrode active material, a conductive material, and a binder is formed on one side or both sides of a negative electrode current collector plate.

As the negative electrode active material, a lithium metal, a carbon material, a metal compound, or a mixture thereof, which can normally occlude and release lithium ions, can be used.

Specifically, both low-crystalline carbon and high-crystalline carbon may be used as the carbon material. Soft carbon and hard carbon are typical examples of low crystalline carbon, and natural graphite, Kish graphite, pyrolytic carbon, and liquid crystal pitch-based carbon fibers are examples of high crystalline carbon. High-temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, Mesophase pitches and petroleum or coal tar pitch derived cokes are typical examples.

The metal compounds include metal elements such as Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, Sr, Ba, etc. And compounds containing at least one of them. These metal compounds are simple substance, alloy, oxide (TiO ₂ , SnO ₂ Etc.), nitrides, sulfides, borides, alloys with lithium, etc. can be used in any form, but simple substances, alloys, oxides, alloys with lithium can be increased in capacity. Among them, one or more elements selected from Si, Ge and Sn can be contained, and one or more elements selected from Si and Sn can further increase the capacity of the battery.

The binder used for the positive electrode and the negative electrode has a function of maintaining a positive electrode active material and a negative electrode active material in each current collector plate and connecting between the active materials, and a commonly used binder can be used without limitation.

For example, polyvinylidene fluoride-hexapuloropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate Various types of binders such as (polymethyl methacrylate), styrene-butadiene rubber (SBR), and carboxyl methyl cellulose (CMC) can be used.

The current collector plate used for the positive electrode and the negative electrode is a metal having high conductivity, and can be used as long as it is a metal to which the electrode active material slurry can be easily adhered and is not reactive in the voltage range of the electrochemical device. Specifically, a non-limiting example of a current collector plate for a positive electrode includes aluminum, nickel, or a foil manufactured by a combination thereof, and a non-limiting example of a current collector plate for a negative electrode is copper, gold, nickel, or a copper alloy or these. And foils produced by the combination of Further, the current collector plate may be used by laminating substrates made of the materials.

The positive electrode and the negative electrode may be prepared by kneading using an active material, a conductive material, a binder, and a high boiling point solvent to prepare an electrode active material slurry, and then applying the electrode active material slurry to the current collector plate in the manner described above.

Meanwhile, the non-aqueous electrolyte solution may include an organic solvent and an electrolyte salt, and the electrolyte salt is a lithium salt. The lithium salt may be used without limitation those commonly used in the non-aqueous electrolyte for lithium secondary batteries. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF _{^{4 -, (CF 3) 3}} PF 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 - _{, (CF 3 SO 2) 2} N -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, ( ^{_{CF 3 SO 2) 3 C -}} , CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- may include any one or two or more selected from the group consisting of.

And, as the organic solvent included in the above-described non-aqueous electrolyte solution, those commonly used in the non-aqueous electrolyte solution for lithium secondary batteries can be used without limitation, for example, ether, ester, amide, linear carbonate, cyclic carbonate, etc. It can be used by mixing two or more kinds.

Among them, a carbonate compound which is representatively a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and any one selected from the group consisting of halides or mixtures of two or more of them. Examples of these halides include, but are not limited to, fluoroethylene carbonate (FEC).

In addition, specific examples of the linear carbonate compound may be any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate and ethylpropyl carbonate or these Among them, a mixture of two or more kinds may be representatively used, but is not limited thereto.

Particularly, among the carbonate-based organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are high-viscosity organic solvents and have a high dielectric constant, so that lithium salts in the electrolyte can be better dissociated, such as dimethyl carbonate and diethyl carbonate. When a low-viscosity, low-permittivity linear carbonate is mixed and used in an appropriate ratio, an electrolyte having a higher electrical conductivity can be prepared.

In addition, as the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether and ethylpropyl ether, or a mixture of two or more of them can be used. , But is not limited thereto.

And among the organic solvents, esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ -Any one or a mixture of two or more selected from the group consisting of valerolactone and ε-caprolactone may be used, but is not limited thereto.

The injection of the non-aqueous electrolyte may be performed at an appropriate step in the manufacturing process of the electrochemical device, depending on the manufacturing process of the final product and the required physical properties. That is, it can be applied before the assembly of the electrochemical device or at the final stage of assembly of the electrochemical device.

In this case, the electrochemical device includes all devices that undergo an electrochemical reaction, and specific examples include capacitors such as all types of secondary cells, fuel cells, solar cells, 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 is preferable among the secondary batteries.

Hereinafter, examples will be described in detail to specifically describe the present invention. However, the embodiments according to the present invention may be modified in 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 more fully describe the present invention to those skilled in the art.

One. Example

(1) Preparation of separator

A slurry for forming a porous coating layer was prepared by mixing Mg(OH) ₂ as inorganic particles, PVdF-HFP as a binder polymer, and acetone as a solvent. At this time, the content of the inorganic particles and the binder polymer was adjusted to a weight ratio of 90:10.

Subsequently, the porous polymer film substrate having a thickness of 9 μm was coated with the slurry for forming the porous coating layer, and then dried to prepare a separator having a porous coating layer formed on the surface.

(2) Preparation of anode and cathode

90 parts by weight of LiCoO ₂ as a positive electrode active material, 5 parts by weight of acetylene black as a conductive material, and 5 parts by weight of PVDF as a binder were added to NMP (Nmethyl-2-pyrrolidone) and mixed to prepare a positive electrode active material slurry, followed by aluminum (Al) An anode was prepared by applying and drying on a current collector.

95 parts by weight of graphite as a negative electrode active material, 2.5 parts by weight of acetylene black as a conductive material, and 2.5 parts by weight of SBR as a binder were added and mixed in water to prepare a negative electrode active material slurry, and then coated and dried on a copper (Cu) current collector. A negative electrode was prepared.

(3) Preparation of lithium secondary battery

Using the prepared positive electrode, negative electrode, and separator, a pouch-shaped cell was manufactured, and an electrolyte (EC/EMC = 1/2 volume ratio, LiPF ₆ 1 mol) was injected into the produced cell to prepare a lithium secondary battery.

2. Comparative example

A lithium secondary battery was manufactured in the same manner as in Example except that Al ₂ O ₃ was used instead of Mg(OH) ₂ as the inorganic particles in the production of the separator.

3. Analysis of gas generation during assembly, storage and cycle evaluation of lithium secondary batteries

Table 1 below shows the amount of gas generated after the electrolyte injection process of the lithium secondary battery according to the Examples and Comparative Examples, after the activation process of the battery and after degassing, and after high temperature (60°C) storage and after 100 cycles. It is shown by comparing the measured gas generation amount. For reference, the type of gas generated at this time is H ₂ , CO, CO ₂ , hydrocarbon gas (CH ₄ , C ₂ H ₆ , C ₂ H ₄ , C ₂ H ₂ , C ₃ H ₈ , C ₃ H ₆ ) to be.

Main amount Activation Degas 60 ℃, 500 hr storage 23 ℃, 100 cycle Example 41.2 μl 1186.8 μl 167.5 μl 722.3 μl 233.9 μl Comparative example 52.6 μl 1344.4 μl 178.5 μl 1100.4 μl 387.0 μl

Referring to Table 1, even when the battery was activated, more gas was generated in the case of the comparative example. After degassing, although almost similar, the storage evaluation at high temperature (60°C) and the gas generation amount analysis after the cycle progress at room temperature (23°C) showed that the gas generation amount of the comparative example was significantly higher than that of the example. Can be.

4. Comparison of thickness and capacity of the lithium secondary battery after high temperature storage and cycle

Table 2 below shows a comparison of the thickness and capacity of the batteries measured after high temperature (60° C.) storage and after 100 cycles of the lithium secondary battery according to Examples and Comparative Examples.

Immediately after assembly (SOC100) 60 ℃, after 500 hr storage 23 ℃, after 100 cycles Thickness(mm) Capacity (mAh) Thickness(mm) Capacity (mAh) Thickness(mm) Capacity (mAh) Example 3.81 1150.2 3.85 1001.9 3.91 1093.3 Comparative example 3.82 1148.9 3.90 923.3 3.94 1083.6

Referring to Table 2, since the gas generation amount of the example is less, even after comparing the thickness and capacity of the battery after high temperature storage and after the cycle, the thickness of the battery of the example was less than that of the comparative example, and the capacity was less. It can be seen.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the scope of the technical spirit of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical spirits within the equivalent range should be interpreted as being included in the scope of the present invention.

Claims (15)

(a) porous polymer substrate; And
(b) a porous coating layer formed on at least one surface of the porous polymer substrate and composed of a mixture of inorganic particles, which are basic oxides, and a binder polymer;
The basic oxide inorganic particles are Mg(OH) ₂ ,
The binder polymer is PVDF-HFP,
The porous coating layer is formed by applying and drying the organic solvent in which the Mg(OH) ₂ and the PVDF-HFP are dissolved,
The porous coating layer is bound to each other by the binder polymer in a state where the Mg(OH) ₂ particles are filled and in contact with each other, thereby forming an interstitial volume between the Mg(OH) ₂ particles, and the interstitial The organic/inorganic composite porous separator characterized in that the volume becomes an empty space to form pores.
delete According to claim 1,
An organic/inorganic composite porous separator, wherein the porous coating layer has a pore size of 0.001 to 10 μm, and a porosity of 10 to 90%. According to claim 1,
The organic/inorganic composite porous separator, characterized in that the weight ratio of the inorganic particles and the binder polymer is 50:50 to 99:1. delete According to claim 1,
The average particle diameter of the inorganic particles is an organic / inorganic composite porous separator, characterized in that 0.001 to 10 ㎛. delete According to claim 1,
The porous polymer substrate is an organic / inorganic composite porous separator, characterized in that the porous polymer film substrate or a porous non-woven substrate. According to claim 1,
The porous polymer substrate, polyethylene (polyethylene), polypropylene (polypropylene), polybutylene (polybutylene), polypentene (polypentene), polyethylene terephthalate (polyethyleneterephthalate), polybutylene terephthalate (polybutyleneterephthalate), polyester (polyester) ), polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, poly Organic/inorganic composite porous separator, characterized in that it is formed of any one or a mixture of two or more selected from the group consisting of phenylenesulfide and polyethylenenaphthalate. According to claim 1,
The thickness of the porous polymer substrate, organic / inorganic composite porous separator, characterized in that 5 to 50 ㎛. An electrode assembly including an anode, a cathode, and a separator interposed between the anode and the cathode;
A non-aqueous electrolyte that impregnates the electrode assembly; And
In the electrochemical device comprising; a battery case incorporating the electrode assembly and the non-aqueous electrolyte,
The separator is an electrochemical device, characterized in that the organic / inorganic composite porous separator of any one of claims 1, 3 to 4, 6 and 8 to 10. The method of claim 11,
The non-aqueous electrolyte is an electrochemical device comprising an organic solvent and an electrolyte salt. The method of claim 12,
The organic solvent is ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate , Fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, dimethyl ether, diethyl ether, dipropyl ether, methylethyl ether, methylpropyl ether, ethylpropyl Ether, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε -Any one selected from the group consisting of caprolactone or a mixture of two or more of them. The method of claim 12,
The electrolyte salt includes, as ^{anions, F -, Cl -, Br} -, I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 ^{_{-, (CF 3) 3 PF}} 3 -, (CF 3) 4 PF 2 -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, _{(CF 3 SO 2) 2 N} -, (FSO 2) 2 N -, CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF ^{_{3 SO 2) 3 C -,}} CF 3 (CF 2) 7 SO 3 -, CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- Electrochemical device characterized in that it comprises any one or two or more selected from the group consisting of. The method of claim 11,
The electrochemical device is an electrochemical device, characterized in that a lithium secondary battery.