KR20160025079A - Heat-resistant, nonflammable, coated separator and battery - Google Patents

Abstract

An embodiment of the present invention provides a separator including a polyolefin-based base film and a heat-resistant porous layer including a binder formed on one surface or both surfaces of the base film. The binder includes a polymer composed of a repeating unit containing a first component and a second component. The first component includes at least one between tetraphosphate and phosphonate. The second component includes nitrogen. The purpose of the present invention is to provide the separator with high thermal resistance, flame resistance, an excellent adhesive strength to the base film, and excellent oxidation resistance and including inorganic particles of the heat-resistant porous layer with improved dispersibility and to provide an electrochemical cell using the separator.

Description

TECHNICAL FIELD [0001] The present invention relates to a heat-resistant and flame-resistant separator and an electrochemical cell,

The present invention relates to a separator having high heat resistance and flame resistance and an electrochemical cell including the same.

A separator for an electrochemical cell means an interlayer capable of charging and discharging the battery by keeping the ion conductivity constant while isolating the positive electrode and the negative electrode from each other in the battery.

In recent years, electrochemical cells for increasing the portability of electronic devices have become more lightweight and miniaturized, and there is a tendency to require high-output large capacity batteries for use in electric vehicles and the like. [0003] Lithium secondary batteries that provide a high output relative to a capacity as a unit battery (battery cell) of a middle- or large-sized battery pack for high-output large-capacity applications have been studied extensively.

The lithium secondary battery is a candidate for a unit cell of a middle- or large-sized battery pack due to various advantages as described above. However, when the temperature of the battery rises during charging and discharging, a combustible gas due to the decomposition reaction of the electrolyte, There is a problem that explosion or fire occurs due to generation of oxygen due to decomposition of the anode. In addition, when a polyolefin-based material is used as the base film of the separation membrane of the secondary battery, there is a problem that the film is melted down at a relatively low temperature (Korean Patent Registration No. 10-0775310).

Accordingly, there is a need to provide a new separator that prevents or suppresses ignition and improves heat resistance in an electrochemical cell, particularly a medium to large capacity cell, while maintaining or improving the original performance of the cell.

Korean Patent No. 10-0775310

An object of the present invention is to provide a separator having flame retardancy and high heat resistance, excellent adhesion to base film and oxidation resistance, and improved dispersibility of inorganic particles in heat resistant porous layer, and an electrochemical cell using the same.

In one embodiment of the present invention, the heat resistant porous layer includes a polyolefin based film and a heat resistant porous layer formed on one surface or both surfaces of the substrate film, wherein the heat resistant porous layer comprises a polymeric resin comprising a repeating unit containing a first component and a second component Wherein the first component contains phosphate or phosphonate and the second component comprises nitrogen.

Yet another embodiment of the present invention provides an electrochemical cell formed from the separator according to the above embodiment.

The separator according to one embodiment of the present invention and the electrochemical cell using the same have flame retardancy and high heat resistance. They have excellent adhesion between the base film and the heat resistant porous layer, improved dispersibility of inorganic particles and excellent oxidation resistance .

1 is an exploded perspective view of an electrochemical cell according to one embodiment. The electrochemical cell 100 includes an electrode assembly 40 wound around a separator 30 between an anode 10 and a cathode 20 and a case 50 in which the electrode assembly 40 is embedded . The anode 10, the cathode 20 and the separator 30 are impregnated with an electrolyte (not shown).

According to one embodiment of the present invention, there is provided a polyolefin-based substrate film and a heat-resistant porous layer formed on one or both surfaces of the substrate film, wherein the heat-resistant porous layer comprises a polymer comprising a repeating unit including a first component and a second component Wherein the first component contains a phosphate or a phosphonate, and the second component comprises a nitrogen-containing separation membrane.

In one embodiment of the present invention, the heat resistant porous layer may be formed of a heat resistant porous layer composition, wherein the heat resistant porous layer composition comprises a first component containing a phosphate or a phosphonate and a second component containing a nitrogen And a solvent. Specifically, in another example, the heat-resistant porous layer composition may further include inorganic particles. Thus, according to an embodiment of the present invention, there is provided a separation membrane heat resistant porous layer composition comprising a polymer resin composed of a first component containing a phosphate or a phosphonate and a second component containing a nitrogen component and a solvent, / RTI >

The polyolefin-based film includes a polyolefin-based resin. Non-limiting examples of the polyolefin-based resin include polyethylene (PE), polypropylene (PP), polybutylene (PB), and poly-4-methyl -1-pentene, PMP). These may be used alone or in combination of two or more. That is, the polyolefin-based resin may be used alone, or a copolymer or a mixture thereof may be used.

In another example, the polyolefin-based film may contain other resins besides the polyolefin resin. Examples of other resins include polyimide, polyester, polyamide, polyetherimide, polyamideimide, and polyacetal. When other resins are included, the polyolefin resin composition may be prepared by blending the polyolefin resin and other resins in an appropriate solvent.

In another example, the polyolefin-based resin may comprise a copolymer of an olefin and a non-olefin monomer. The thickness of the polyolefin-based film may be 1 to 40 탆, more specifically 5 to 15 탆. When a base film within the above-mentioned thickness range is used, it is possible to produce a separator having an appropriate thickness which is thick enough to prevent a short circuit between the positive and negative electrodes of the battery, but not thick enough to increase the internal resistance of the battery.

The separation membrane of one embodiment of the present invention includes a polymer resin composed of a repeating unit containing a first component containing a phosphate or a phosphonate and a second component containing nitrogen in a heat-resistant porous layer formed on one surface or both surfaces of a base film can do.

Since the polymer resin contains phosphate or phosphonate, it is possible to prevent the battery from exploding or generating a fire due to the generation of oxygen due to decomposition of the anode, and further, by containing nitrogen, the adhesive strength to the polyolefin- In addition, when the heat resistant porous layer contains inorganic particles, the dispersibility of the inorganic particles can be improved. While not wishing to be bound by any particular theory, a phosphate or phosphonate structure containing a phosphate group in the separator can produce a polymetaphosphate by pyrolysis. The resulting polymetaphosphoric acid may form a protective layer on the separation membrane, or the carbon film generated by dehydration accompanied by the polymetaphosphoric acid production may block oxygen, resulting in flame retardance. Further, although it is not bound to a particular theory, it is presumed that the provision of a pair of non-covalent electrons of nitrogen when containing nitrogen improves the adhesion to the polyolefin-based film and the dispersibility of the inorganic particles.

The separation membrane according to an embodiment of the present invention may be formed by using a polymer resin composed of a repeating unit including a first component containing a phosphate or a phosphonate and a second component containing nitrogen in the heat resistant porous layer, , It is advantageous in that sufficient adhesion to the separator substrate, ignition suppression, and heat resistance can be ensured at the same time without any additional flame retardant or separate inorganic particles.

Examples of the first component containing a phosphate or phosphonate in the polymer resin of an embodiment of the present invention are as follows.

[Chemical Formula 1]

(2)

In Formula 1 and Formula 2, R ₁ and R ₂ are each independently hydrogen; Substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-20 cycloalkyl, and C _6-30 aryl. . In one embodiment, in Formula 1 and Formula 2, R ₁ and R ₂ are each independently hydrogen; C _1-6 alkyl, C _6-30 aryl or C _3-10 alkyl, which is unsubstituted or substituted one or more times by halogen, OH, C _1-6 alkyl, alkoxy, nitro, cyano, Lt; / RTI > In embodiments, R ₁ and R ₂ are each independently hydrogen; Naphthyl, cyclopropyl, cyclobutyl, methyl, ethyl, propyl, butyl, etc., which are unsubstituted or substituted one or more times by halogen, OH, or C _1-6 alkyl.

In the polymer resin of one embodiment of the present invention, the nitrogen-containing second component may be an imide- or amide-containing structure. When the second component is an imide- or amide-containing structure, the bonding strength between the molecules is high due to imide bond or amide bond between them, so that the substrate film can have high heat resistance that can not be melted down even at a relatively high temperature.

In an embodiment, the second component is a phthalimide-containing structure, which may be an alkylamide containing residue having 1 to 10 carbon atoms, an alkenylamide containing residue or an arylamide containing residue. Particularly, the second component may be a phthalimide-containing structure. In the case of a phthalimide-containing structure, since the number of hydrogen atoms in the amine group is small, the compound can have a wider dislocation window and is stable at high voltage, have.

Another embodiment of the second component containing nitrogen is as follows.

(3)

In Formula 3, R ₃ is hydrogen; Substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-10 cycloalkyl, and C _6-30 aryl . In one example, in Formula 3, R ₃ is hydrogen; An unsubstituted, halogen, OH, C _1-6 alkyl, one or more times with C _2-6 alkenyl, alkoxy, nitro, cyano, carbonyl, thiol or substituted C _2-6 alkynyl, C _{1-6 Lt; /} RTI > alkyl, C _6-30 aryl or C _3-10 cycloalkyl. In embodiments, R < ₃ > is hydrogen; Naphthyl, cyclopropyl, cyclobutyl, cyclopentyl, methyl, ethyl, propyl, butyl, or phenyl which is unsubstituted or substituted one or more times by halogen, OH, C _1-6 alkyl or C _2-6 alkenyl. Decyl, propenyl, heptenyl or butenyl.

As another example of the nitrogen-containing second component, there may be mentioned a nitrogen-containing heteroaromatic hydrocarbon ring-containing structure. As used herein, the term "nitrogen-containing heteroaromatic hydrocarbon ring" refers to a heteroaromatic hydrocarbon ring in which at least one carbon of the aromatic hydrocarbon ring compound is substituted with nitrogen. The aromatic hydrocarbon ring compound may be a monocyclic, bicyclic or tricyclic ring structure. As an example, two or more nitrogen-containing heteroaromatic hydrocarbon rings are directly bonded; A structure in which at least one nitrogen-containing heteroaromatic hydrocarbon ring and at least one aromatic hydrocarbon ring compound are substituted for hydrogen in the methyl group can be exemplified. In embodiments, poly-aromatic hydrocarbons include structures wherein at least one carbon of at least one aromatic hydrocarbon ring is substituted with nitrogen.

In a more specific example, the nitrogen-containing second component may be selected from:

In one example, the polymer resin may include a repeating unit represented by the formula (4) or (5).

[Chemical Formula 4]

[Chemical Formula 5]

In Formula 4 and 5, R _1, R ₂ and the definition of the R ₃ substituents are the same as R _1, R ₂ and the definition of the R ₃ substituent in Formula 1-3.

The polymer resin may have a glass transition temperature of 180 to 300 캜, specifically 200 to 280 캜, more specifically 220 to 250 캜. In the case of the separation membrane containing the polymer resin satisfying the above range in the heat resistant porous layer, the relatively high temperature is not melted down, so that it can have high heat resistance characteristics.

The weight average molecular weight of the polymer resin may be in the range of 5,000 to 350,000 g / mol, and if it is within the above range, it may be advantageous in terms of adhesion and heat resistance.

The polymer resin may be contained in an amount of from 2 to 100% by weight, for example, from 2 to 70% by weight, based on the total solid weight of the separable membrane heat resistant porous layer composition. In a more specific example, it may be contained in an amount of 5 to 30% by weight.

In another embodiment of the present invention, in addition to the polymeric resin comprising a repeating unit comprising a first component containing a phosphate or a phosphonate and a second component containing a nitrogen, an additional binder component may be included, Polyvinylidene fluoride (PVdF) homopolymer, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), polymethylmethacrylate, polyacrylonitrile, polyvinylidene fluoride But are not limited to, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate (cellulose acetate propionate), cyano But are not limited to, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and the like. Acrylonitrile-butadiene copolymer, or a mixture thereof. These acrylonitrile-butadiene copolymers may be used alone or in combination.

In another embodiment of the present invention, the heat resistant porous layer composition may further contain inorganic particles. The kind of the inorganic particles contained in the heat resistant porous layer is not particularly limited, and inorganic particles commonly used in the art can be used. Non-limiting examples of the inorganic particles include Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Ga ₂ O ₃ , TiO _2, and SnO ₂ . These may be used alone or in combination of two or more. For example, Al ₂ O ₃ (alumina) may be used. The inorganic particles in the heat resistant porous layer serve as a kind of spacer capable of maintaining the physical shape of the heat resistant porous layer. As a result, it is possible to prevent the problem that the inorganic particles in the heat resistant porous layer are removed during the assembly process of the battery or the like, thereby securing the form stability, and by giving sufficient adhesion force between the heat resistant porous layer and the film, There is an advantage of being able to prevent the short circuit of the electrode and to have high temperature safety.

The size of the inorganic particles is not particularly limited, but may be an average particle diameter of 100 nm to 1000 nm, specifically 300 nm to 600 nm. When the inorganic particles having the above-mentioned size range are used, the dispersibility of the inorganic particles in the heat-resistant porous layer composition liquid and the coating processability can be prevented from being lowered, and the thickness of the heat-resistant porous layer can be appropriately controlled.

The inorganic particles may be contained in the heat resistant porous layer in an amount of 70 to 98% by weight, specifically 85 to 95% by weight. Within the above range, the shape stability of the separator can be ensured and a sufficient adhesive force can be given between the heat resistant porous layer and the film to suppress shrinkage of the film due to heat as well as short-circuiting of the electrode effectively.

According to another embodiment of the present invention, a heat resistant porous layer composition containing a solvent and a polymer resin comprising a repeating unit containing a first component containing a phosphate or a phosphonate and a second component containing a nitrogen is prepared And forming a heat resistant porous layer with the heat resistant porous layer composition on one side or both sides of the polyolefin.

Specifically, the separation membrane may be formed by applying a heat resistant porous layer composition on a polyolefin film and then drying the composition. The polyolefin-based film may be porous, and the porous film may be formed by a generally known production method. As a non-limiting example, a dry method and a wet method are known. Specifically, the porous film can be produced by extruding and stretching a composition for a base film to form fine pores in the film.

The heat-resistant porous layer composition for forming the heat-resistant porous layer of the separator may include the above-mentioned polymer resin and solvent, and in another example, the composition may further include inorganic particles. There is no particular limitation on the method for producing the heat resistant porous layer composition, but it is also possible to use a polymer solution in which a polymer resin is dissolved in a solvent as a heat resistant porous layer composition, or to disperse inorganic particles in the polymer solution and use it as a heat resistant porous layer composition, The heat resistant porous layer composition may be prepared by preparing each of the polymer solution and the inorganic particle dispersion in which the inorganic particles are dispersed and then mixing them together with an appropriate solvent. One method for preparing the heat resistant porous layer composition may include further mixing the polymeric resin and the solvent disclosed herein or inorganic particles thereto and stirring at 10 to 40 DEG C for 30 minutes to 5 hours.

The polymer solution and the solvent used for preparing the dispersion of the inorganic particles are not particularly limited as far as they are capable of dissolving the polymer resin and capable of sufficiently dispersing the inorganic particles. Non-limiting examples of the solvent usable in the present invention include dimethyl formamide, dimethyl sulfoxide, dimethylacetamide, dimethyl carbonate or N-methylpyrrolidone (N-methylpyrrolidone). The content of the solvent based on the weight of the heat resistant porous layer composition may be 20 to 99% by weight, specifically 50 to 95% by weight, and more specifically 70 to 95% by weight. When the solvent is contained in the above range, the production of the heat resistant porous layer composition is facilitated and the heat resistant porous layer can be smoothly dried.

The polymer solution and the inorganic particle dispersion are further mixed with a solvent and then sufficiently stirred using a ball mill, a beads mill, a screw mixer or the like to obtain a heat-resistant porous layer A composition liquid can be prepared.

The method of forming the heat resistant porous layer on the polyolefin based film is not particularly limited and a method commonly used in the technical field of the present invention such as a coating method, lamination, coextrusion and the like can be used . Non-limiting examples of the coating method include a dip coating method, a die coating method, a roll coating method, and a comma coating method. These may be applied alone or in combination of two or more methods. The heat-resistant porous layer of the separator of the present invention may be formed by, for example, a dip coating method.

The thickness of the heat-resistant porous layer according to the embodiments of the present invention may be 0.01 to 20 탆, specifically 1 to 15 탆. The heat resistant porous layer having an appropriate thickness can be formed within the above-mentioned thickness range to obtain excellent thermal stability and adhesion, and the thickness of the entire separation membrane can be prevented from becoming excessively thick, and the increase in the internal resistance of the battery can be suppressed.

In the embodiments of the present invention, drying of the heat resistant porous layer may be carried out by drying, vacuum drying or irradiating far infrared ray or electron beam by hot wind, hot wind, low humidity wind or the like. The drying temperature may vary depending on the kind of the solvent, but it can be generally dried at a temperature of 60 to 120 ° C. Drying time may vary depending on the type of solvent but can be generally 1 minute to 1 hour. In embodiments, it may be dried at a temperature of 90 to 120 DEG C for 1 to 30 minutes, or for 1 to 10 minutes.

The heat shrinkage rate in the machine direction (MD) or in the transverse direction (TD) after leaving the separation membrane containing the heat resistant porous layer according to the present invention at 200 占 폚 for 30 minutes is 10 Or less, specifically 5% or less, more specifically, 3% or less. Within the above range, there is an advantage that the short circuit of the electrode is effectively prevented and the safety of the battery is improved.

The method of measuring the heat shrinkage percentage of the separation membrane is not particularly limited, and a method commonly used in the technical field of the present invention can be used.

A method of measuring the heat shrinkage ratio of the separation membrane is as follows: The separation membrane is cut into a size of about 5 cm in length (MD) about 5 cm in length (TD) For 30 minutes, and measuring the degree of shrinkage in the MD and TD directions of the separator to calculate the heat shrinkage ratio.

When the flame retardancy of the separator comprising the heat resistant porous layer described in the embodiments of the present invention is measured according to the UL94 VB flame retardant specification, it may be an excellent flame retardancy grade of V0 or more. Within this range, the combustion of the separation membrane is effectively prevented, so that the safety of the battery can be improved.

The method for measuring the flame retardancy of the separation membrane is not particularly limited, and a method commonly used in the technical field of the present invention can be used.

A method of measuring the flame retardancy of the separator is as follows: A 10 cm x 50 cm separator is folded to make a size of 10 cm x 2 cm and the upper and lower portions are fixed to prepare a specimen. According to UL94 VB Flammability class is measured based on specimen burning time.

The air permeability of the separation membrane including the heat resistant porous layer described in the embodiments of the present invention may be 400 sec / 100cc or less. Within the above range, ion and electron flow in the cell including the separation membrane can be smooth and battery performance can be improved.

The method for measuring the air permeability of the separation membrane is not particularly limited, and a method commonly used in the technical field of the present invention can be used.

A non-limiting example of the method for measuring the air permeability of the separator is as follows: The air permeability is determined by measuring the time taken for 100 cc of air to pass through the separator to the prepared separator.

According to another embodiment of the present invention, there is provided a polyolefin-based porous separator comprising a polyolefin-based porous separator comprising a heat-resistant porous layer comprising a polymer resin composed of a repeating unit including a first component and a second component, To provide an electrochemical cell.

The type of the electrochemical cell is not particularly limited and may be a battery of a kind known in the technical field of the present invention.

The electrochemical cell according to an embodiment of the present invention may be a lithium secondary battery such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

The method of manufacturing the electrochemical cell according to an embodiment of the present invention is not particularly limited, and a method commonly used in the technical field of the present invention can be used.

1 is an exploded perspective view of an electrochemical cell according to one embodiment. The electrochemical cell according to one embodiment is explained as an example of square type, but the present invention is not limited thereto, and may be applied to various types of cells such as a lithium polymer battery and a cylindrical battery.

1, an electrochemical cell 100 according to an embodiment includes an electrode assembly 40 wound around a separator 30 between an anode 10 and a cathode 20, (Not shown). The anode 10, the cathode 20 and the separator 30 are impregnated with an electrolyte (not shown).

The separation membrane 30 is as described above.

The anode 10 may include a cathode current collector and a cathode active material layer formed on the cathode current collector. The cathode active material layer may include a cathode active material, a binder, and optionally a conductive material.

The cathode current collector may be aluminum (Al), nickel (Ni) or the like, but is not limited thereto.

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Concretely, at least one of cobalt, manganese, nickel, aluminum, iron or a composite oxide or composite phosphorus of a metal and lithium in combination thereof may be used. More specifically, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate or a combination thereof may be used.

The binder not only adheres the positive electrode active materials to each other well but also adheres the positive electrode active material to the positive electrode current collector. Specific examples thereof include polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride , Carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, Acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like. These may be used alone or in combination of two or more.

The conductive material imparts conductivity to the electrode. Examples of the conductive material include, but are not limited to, natural graphite, artificial graphite, carbon black, carbon fiber, metal powder, and metal fiber. These may be used alone or in combination of two or more. The metal powder and the metal fiber may be made of metals such as copper, nickel, aluminum, and silver.

The cathode 20 may include a negative electrode collector and a negative electrode active material layer formed on the negative collector.

The negative electrode current collector may be copper (Cu), gold (Au), nickel (Ni), copper alloy, or the like, but is not limited thereto.

The negative electrode active material layer may include a negative electrode active material, a binder, and optionally a conductive material.

Examples of the negative electrode active material include a material capable of reversibly intercalating and deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, a transition metal oxide, Can be used.

Examples of the material capable of reversibly intercalating and deintercalating lithium ions include carbonaceous materials, and examples thereof include crystalline carbon, amorphous carbon, and combinations thereof. Examples of the crystalline carbon include amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite. Examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like. As the lithium metal alloy, a lithium-metal alloy may be selected from the group consisting of lithium, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, An alloy of a selected metal may be used. As the material capable of doping and dedoping lithium, Si, SiO _x (0 <x <2), Si-C composite, Si-Y alloy, Sn, SnO ₂ , Sn-C composite, Sn- And at least one of them may be mixed with SiO ₂ . The element Y may be at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Se, Te, Po, and combinations thereof. Examples of the transition metal oxide include vanadium oxide, lithium vanadium oxide, and the like.

The kinds of the binder and the conductive material used for the cathode are the same as those used for the anode and the conductive material.

The positive electrode and the negative electrode may be prepared by mixing each active material and a binder with a conductive material in a solvent to prepare each active material composition and applying the active material composition to each current collector. The solvent may be N-methyl pyrrolidone or the like, but is not limited thereto. The method of manufacturing the electrode is well known in the art, and therefore, a detailed description thereof will be omitted herein.

The electrolytic solution includes an organic solvent and a lithium salt.

The organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Specific examples thereof may be selected from a carbonate-based solvent, an ester-based solvent, an ether-based solvent, a ketone-based solvent, an alcohol-based solvent and an aprotic solvent.

Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate Carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Specifically, when a mixture of a chain carbonate compound and a cyclic carbonate compound is used, it can be prepared from a solvent having a high viscosity and a high dielectric constant. Here, the cyclic carbonate compound and the chain carbonate compound may be mixed in a volume ratio of 1: 1 to 1: 9.

Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone, decanolide, valerolactone, Mevalonolactone, caprolactone, and the like. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran and the like. Examples of the ketone-based solvent include cyclohexanone, and examples of the alcohol-based solvent include ethyl alcohol, isopropyl alcohol, and the like.

The organic solvents may be used alone or in combination of two or more. When two or more of them are used in combination, the mixing ratio may be appropriately adjusted according to the performance of the desired cell.

The lithium salt is dissolved in an organic solvent to act as a source of lithium ions in the battery to enable the operation of a basic electrochemical cell and to accelerate the movement of lithium ions between the positive electrode and the negative electrode.

For example the lithium salt _{is, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiN (SO 3 C 2 F 5) 2, LiN (CF 3 SO 2) 2, LiC 4 F 9 SO 3, LiClO 4, LiAlO 2 , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) where x and y are natural numbers, LiCl, LiI, LiB (C ₂ O ₄ ) _2, .

The concentration of the lithium salt can be used within the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, the electrolytic solution has an appropriate conductivity and viscosity, and thus can exhibit excellent electrolytic solution performance, and lithium ions can effectively move.

Hereinafter, the present invention will be described in more detail by describing Production Examples, Examples, Comparative Examples and Experimental Examples. However, the following Production Examples, Examples, Comparative Examples and Experimental Examples are merely examples of the present invention, and the present invention should not be construed as being limited thereto.

Production Example 1: Preparation of Polymer Resin 1

Phenolphthalein (100 g, 314 mmol) was dissolved in 28% aqueous ammonia solution and the purplish solution was stirred at room temperature for 20 days. When the purple solution became almost transparent, the reaction solution was poured into concentrated hydrochloric acid and ice to terminate the reaction. The resultant was washed with distilled water to neutralize, and recrystallized from ethanol and water to synthesize PI01 of formula (3-1). The synthesized compound of Formula 3-1 (44.4 g, 140 mmol) and triethylamine (35.8 g, 350 mmol) were added to methylenechloride (210 mL) and then cooled to 0 ° C. A solution of 28.1 g of phenylphosphonic dichloride (BPOD) in methylenechloride (15 mL) was added slowly for 1 hour and then reacted at room temperature for 4 hours. The reaction solution was washed several times with diluted HCl solution and distilled water. The washed polymer was dried in a vacuum oven at 80 캜 for 48 hours to obtain a polymer resin having a repeating unit represented by formula (6) having a weight average molecular weight of 125,000 g / mol and a glass transition temperature of 248 캜.

[Formula 3-1]

[Chemical Formula 6]

Production Example 2: Preparation of Polymeric Resin 2

To phenolphthalein (100 g, 314 mmol) was added 40% methylamine aqueous solution. The reaction solution was reacted at 30 ° C. for 24 hours, and then the reaction solution was poured into concentrated hydrochloric acid and ice to terminate the reaction. The precipitated solid was filtered, washed with distilled water, and recrystallized using ethanol and water to synthesize PI02 of formula (3-2). The thus-synthesized compound of Formula 3-2 (46.4 g, 140 mmol) was reacted under the same conditions as in Preparation Example 1 to obtain a compound of Formula 7 having a weight average molecular weight of 138,000 g / mol and a glass transition temperature of 210 ° C. A polymer resin having repeating units was obtained.

[Formula 3-2]

(7)

Production Example 3: Preparation of Polymeric Resin 3

Aniline (300 mL, 3287 mmol) and aniline hydrochloride (100 g, 965 mmol) were added to phenolphthalein (100 g, 314 mmol). The reaction solution was reacted at 185 degrees for 5 hours. After completion of the reaction, the temperature was lowered, and the reaction solution was poured into concentrated hydrochloric acid and ice to terminate the reaction. After filtering out the precipitated solids. Washed with distilled water, and then recrystallized using ethanol to synthesize PI03 of Formula 3-3. The synthesized compound of Formula 3-3 (55.1 g, 140 mmol) was reacted under the same conditions as in Preparation Example 1 to obtain a compound of Formula 8 having a weight average molecular weight of 148,000 g / mol and a glass transition temperature of 202 ° C A polymer resin having repeating units was obtained.

[Formula 3-3]

[Chemical Formula 8]

Example 1: Preparation of separation membrane (polymer resin + inorganic particle-containing separation membrane)

The polymer resin 1 prepared in Preparation Example 1 was dissolved in tetrahydrofuran (THF) in an amount of 10% by weight to prepare a polymer solution. 25 wt% of Al ₂ O ₃ (LS235A, manufactured by Nippon Light Metal Co., Ltd.) was added to acetone (manufactured by Daikin Fine Chemicals Co., Ltd.) and milled for 3 hours at 25 ° C using a bead mill to prepare an inorganic dispersion. The prepared polymer resin solution and inorganic dispersion were mixed so that the mixed solvent of N, N-dimethylacetamide (DMAc) and THF was 2.5: 5: 2.5 by weight and stirred at 25 ° C for 1 hour by a power mixer A heat resistant porous layer composition was prepared.

The heat resistant porous layer composition was coated on both sides of a 9 μm-thick polyethylene single-film base film to a thickness of 1.5 μm by dip coating method and dried at 110 ° C. for 1 minute to prepare a separator.

Example 2: Preparation of separation membrane (polymer resin + inorganic particle-containing separation membrane)

Except that the polymer resin 2 of Production Example 2 was used in place of the polymer resin of Production Example 1 in Example 1, a separation membrane having a total thickness of 12 탆 was produced.

Example 3: Preparation of separator (polymer resin + separator containing inorganic particles)

Except that the polymer resin 3 of Production Example 3 was used instead of the polymer resin of Production Example 1 in Example 1, a separation membrane having a total thickness of 12 탆 was produced.

Comparative Example 1: Preparation of separation membrane

Membrane membrane A membrane was prepared in the same manner as in Example 1, except that poly (butyl acrylate-co-methyl methacrylate-co-vinyl acetate) was used in place of polymer resin 1 prepared in Preparation Example 1.

Experimental Example

(Mw), glass transition temperature (Tg), and flame retardancy were measured for the polymer resin of Production Examples 1 to 3 and the poly (butyl acrylate-co-methyl methacrylate-co-vinyl acetate) The results are shown in Table 1 below.

(1) Weight average molecular weight (Mw): expressed in terms of polystyrene as measured by gel permeation chromatography (GPC).

(2) Glass transition temperature (Tg): Measured by differential scanning calorimetry (DSC).

(3) Flammability (1/8 "): Measured according to the UL94 VB flame retardant specification.

Separator binder Mw (g / mol) Tg (占 폚) Flame retardancy of polymer resin The polymer resin of Production Example 1 125,000 248 V0 The polymer resin of Production Example 2 138,000 210 VO The polymer resin of Production Example 3 148,000 202 VO Poly (butyl acrylate-co-methyl methacrylate-co-vinyl acetate) 450,000 35 V2

The flame retardancy, heat shrinkage, and air permeability of the membranes prepared in Examples 1 to 3 and Comparative Example 1 were measured by the measurement method described below, and the results are shown in Table 2.

Experimental Example 1: Measurement of Flammability

Specimens were prepared as described below for the membranes prepared in Examples 1 to 3 and Comparative Example 1, and flame retardancy was evaluated according to the UL94 VB flame retardancy specification.

The 10 cm x 50 cm separation membrane prepared in Examples 1 to 3 and Comparative Example 1 was folded to make 10 cm x 2 cm, and the upper and lower portions were fixed to prepare specimens. Based on UL94 VB, the flame retardancy grade was measured based on specimen burn time

Experimental Example 2: Measurement of Heat Shrinkage

In order to measure the heat shrinkage of the separator prepared in Examples 1 to 3 and Comparative Example 1, the following methods were performed. Each of the membranes prepared according to the above Examples and Comparative Examples was cut into 5 cm (MD) 5 cm (length) (TD) 5 cm to prepare 7 samples. Each of the samples was stored in a chamber at 200 ° C. for 30 minutes, and the degree of shrinkage in each of the MD and TD directions was measured to calculate the heat shrinkage ratio.

Experimental Example 3: Measurement of air permeability

The air permeability of the separator prepared in Examples 1 to 3 and Comparative Example 1 was measured by measuring the time taken for 100 cc of air to pass through the separator using EG01-55-1 MR (Asahi Seiko) Respectively.

Flame retardancy of membrane Air permeability (sec / 100cc) Shrinkage (%) Example 1 V0 220 Less than 1 Example 2 V0 240 Less than 1 Example 3 V0 250 Less than 1 Comparative Example 1 V2 255 55

Referring to Table 2, when a separator is manufactured using a polymer resin including a first component containing a phosphonate and a second component containing nitrogen, the flame retardancy is excellent at V0. Also, it was confirmed that the heat shrinkage rate was less than 1% and the air permeability was 310 sec / 100cc or less.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that such detail is solved by the person skilled in the art without departing from the scope of the invention. will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

Claims (14)

A polyolefin based film; And
And a heat-resistant porous layer formed on one or both sides of the substrate film,
Wherein the heat resistant porous layer comprises a polymer resin composed of a repeating unit containing a first component and a second component,
Wherein the first component comprises a phosphate or a phosphonate,
Wherein the second component comprises nitrogen. The separator according to claim 1, wherein the first component comprises a compound represented by Formula (1) or Formula (2).
[Chemical Formula 1]

(2)

In Formula 1 and Formula 2, R ₁ and R ₂ are each independently hydrogen; Substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-20 cycloalkyl, and C _6-30 aryl . The separator according to claim 1, wherein the second component comprises an imide or amide group. 4. The separation membrane according to claim 3, wherein the imide comprises phthalimide. The separator of claim 1, wherein the second component comprises Formula (3).
(3)

In Formula 3, R ₃ is hydrogen; Substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-10 cycloalkyl, and C _6-30 aryl . The separation membrane according to claim 1, wherein the repeating unit is a repeating unit of any one of formulas (4) and (5).
[Chemical Formula 4]

[Chemical Formula 5]

In Formula 4 and Formula 5, R ₁ to R ₃ are each independently hydrogen; Substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-20 cycloalkyl, and C _6-30 aryl . The separator according to claim 1, wherein the polymer resin has a glass transition temperature of 180 to 300 ° C. The separator according to claim 1, wherein the heat resistant porous layer further comprises polyvinylidene fluoride. The separation membrane according to claim 1, wherein the heat resistant porous layer further contains inorganic particles. The separation membrane according to claim 9, wherein the inorganic particles comprise at least one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Ga ₂ O ₃ , TiO ₂ and SnO ₂ . [Claim 11] The separation membrane according to claim 10, wherein the content of the inorganic particles is 70 to 98% by weight based on the total solid weight of the heat resistant porous layer. A heat resistant porous layer composition comprising a polymer resin composed of a repeating unit containing a first component containing a phosphate or a phosphonate and a second component containing a nitrogen and a solvent,
And forming a heat resistant porous layer with the heat resistant porous layer composition on one surface or both surfaces of the polyolefin. An electrochemical cell comprising an anode, a cathode, a separator, and an electrolyte, wherein the separator is the separator according to any one of claims 1 to 11. 14. The electrochemical cell of claim 13, wherein the electrochemical cell is a lithium secondary battery.

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