WO2016032166A1 - Separator membrane having high heat resistance and flame retardancy, and electrochemical battery - Google Patents

Abstract

Provided is a separator membrane comprising a heat-resistant porous layer having a binder which is formed on one or both sides of a porous substrate, and the porous substrate, wherein the binder has a polymer comprising a repeating unit which contains a first component and a second component, wherein the first component comprises phosphate or phosphonate and the second component comprises nitrogen.

Description

High heat and flame retardant membranes and electrochemical cells

The present invention relates to a high heat resistant and flame retardant separator and an electrochemical cell comprising the same.

A separator for an electrochemical cell refers to an interlayer membrane which maintains ion conductivity while allowing the cathode and the cathode to be separated from each other in the cell, thereby allowing the battery to be charged and discharged.

In recent years, along with the trend of lightening and miniaturization of electrochemical cells for increasing the portability of electronic devices, there is a tendency to require high output large capacity batteries for use in electric vehicles. As a unit cell (battery cell) of a medium-large battery pack for the high-output large-capacity use, a lithium secondary battery providing high output to capacity has been studied.

Lithium secondary battery is a strong candidate as a unit cell of a medium-large battery pack due to various advantages as described above, but the internal temperature of the battery increases during charging and discharging, and flammable gas due to the decomposition reaction of electrolyte, flammable gas due to reaction of electrolyte and electrode, There is a problem that an explosion or fire occurs due to generation of oxygen due to decomposition of the anode. In addition, when a polyolefin-based film is used as a separator of a secondary battery, there is a problem in that the film is melted down at a relatively low temperature (Korean Patent No. 10-0775310).

Therefore, there is a need to provide a new separator that prevents or suppresses ignition and improves heat resistance in electrochemical cells, especially in medium and large capacity batteries, while improving or maintaining the intrinsic performance of the battery.

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

In one embodiment of the present invention, a porous substrate and a porous heat-resistant layer formed on one or both sides of the porous substrate, the porous heat-resistant layer comprises a polymer 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 contains nitrogen.

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

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

1 is an exploded perspective view of an electrochemical cell according to one embodiment. The electrochemical cell 100 includes an electrode assembly 40 wound through a separator 30 between the positive electrode 10 and the negative electrode 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 an embodiment of the present invention, the polymer includes a porous substrate and a porous heat resistant layer formed on one or both surfaces of the porous substrate, wherein the porous heat resistant layer includes a repeating unit containing a first component and a second component. Wherein the first component contains phosphate or phosphonate, and the second component is provided with a separator containing nitrogen.

The porous substrate may use a porous substrate having a plurality of pores and can be used in an electrochemical device. Porous substrates include, but are not limited to, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide , Polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, and any one polymer selected from the group consisting of polyethylene naphthalene or a polymer membrane formed of a mixture of two or more thereof Can be. In one example, the porous substrate may be a polyolefin-based substrate, the polyolefin-based substrate is excellent in the shutdown (shut down) function may contribute to the improvement of the safety of the battery. The polyolefin-based substrate may be selected from the group consisting of, for example, polyethylene monolayer, polypropylene monolayer, polyethylene / polypropylene double membrane, polypropylene / polyethylene / polypropylene triple membrane, and polyethylene / polypropylene / polyethylene triple membrane. In another example, the polyolefin resin may include a non-olefin resin in addition to the olefin resin, or may include a copolymer of an olefin and a non-olefin monomer. The porous substrate may have a thickness of 1 μm to 40 μm, more specifically 5 μm to 15 μm, even more specifically 5 μm to 10 μm. When using a porous substrate within the thickness range, it is possible to produce a separator having a suitable thickness, 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 porous heat resistant layer may include a polymer resin including a repeating unit containing a first component containing phosphate or phosphonate and a second component containing nitrogen. In this case, one repeating unit containing the first repeating unit containing the first component and the second repeating unit containing the second component, or one repeating unit containing the first component and the second component at the same time It may be in the form of a polymer comprising a. The polymer resin may contain a phosphate or a phosphonate to prevent the battery from being exploded or fired due to the generation of oxygen due to decomposition of the positive electrode, or the like, and also to improve adhesion to the porous substrate by containing nitrogen. In addition, when the porous heat-resistant layer includes inorganic particles, it is possible to improve the dispersibility of the inorganic particles. Without being bound by a particular theory, phosphate or phosphonate structures comprising phosphate groups in the separator can produce polymethaic acid by pyrolysis. The produced polymethacrylic acid may form a protective layer on the separation membrane, or the carbon film generated by dehydration in the process of producing polymethacrylic acid may block oxygen, thereby resulting in flame retardancy. In addition, although not bound by a specific theory, it is speculated that the adhesion to the porous substrate and the dispersibility of the inorganic particles are improved by providing a non-covalent electron pair of nitrogen when nitrogen is contained. In addition, the separation membrane according to an embodiment of the present invention by using a polymer resin including a repeating unit containing a first component containing phosphate or phosphonate and a second component containing nitrogen in the porous heat-resistant layer as described above There is an advantage in that sufficient adhesion, fire suppression, and heat resistance with the separator substrate can be secured simultaneously without a separate binder, a separate flame retardant, or a separate inorganic particle.

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

[Formula 1]

[Formula 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 Can be. 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 unsubstituted or substituted one or more times with halogen, OH, C _1-6 alkyl, alkoxy, nitro, cyano, carbonyl, thiol It may be cycloalkyl. In specific examples, R ₁ and R ₂ are each, independently, hydrogen; Phenyl, naphthyl, cyclopropyl, cyclobutyl, methyl, ethyl, propyl, butyl and the like, unsubstituted or substituted one or more times with 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, since the bonding strength is strong by imide bonds or amide bonds between molecules, the porous substrate may have high heat resistance that may not melt down even at a relatively high temperature.

In a specific example, the second component is a phthalimide-containing structure, and may be an alkyl amide-containing residue, an alkenylamide-containing residue, or an arylamide-containing residue having 1 to 10 carbon atoms. In particular, the second component may be a phthalimide-containing structure, and in the case of the phthalimide-containing structure, the number of hydrogens in the amine group is small, which may have a wider potential window, and thus may not be easily decomposed because it is stable at high voltage. have.

Other specific examples of the second component containing nitrogen are as follows.

[Formula 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 embodiment, in Chemical 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 Alkyl, C _6-30 aryl or C _3-10 cycloalkyl. In specific examples, R ₃ is hydrogen; Phenyl, naphthyl, cyclopropyl, cyclobutyl, cyclopentyl, methyl, ethyl, propyl, butyl, to unsubstituted or substituted one or more times with halogen, OH, C _1-6 alkyl or C _2-6 alkenyl Tenyl, propenyl, heptenyl or butenyl.

Another example of the nitrogen-containing second component is a nitrogen-containing heteroaromatic hydrocarbon ring-containing structure. As used herein, "nitrogen-containing heteroaromatic hydrocarbon ring" refers to a heteroaromatic hydrocarbon ring in which one or more carbons of an aromatic hydrocarbon ring compound are replaced with nitrogen. The aromatic hydrocarbon ring compound may have a monocyclic, bicyclic or tricyclic structure. For example, two or more, nitrogen-containing heteroaromatic hydrocarbon rings may be directly bonded; And structures in which at least one nitrogen-containing heteroaromatic hydrocarbon ring and at least one aromatic hydrocarbon ring compound are substituted for hydrogen of the methyl group. In a specific example, there may be mentioned a structure in which at least one carbon of at least one aromatic hydrocarbon ring is substituted with nitrogen in poly-aromatic hydrocarbons.

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

The polymer resin may include repeating units of Formula 4 or Formula 5 in one example.

[Formula 4]

[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 ° C to 300 ° C, specifically 200 ° C to 280 ° C, more specifically 220 ° C to 250 ° C. In the case of the separator including the polymer resin satisfying the above range in the porous heat resistant layer, since the relatively high temperature does not melt down, it may have a high heat resistance.

The weight average molecular weight of the polymer resin may be in the range of 5,000 to 350,000, it may be advantageous in terms of adhesion and heat resistance.

Hereinafter, a separator according to another embodiment of the present invention will be described. The separator according to the present embodiment includes a porous substrate and a porous heat resistant layer formed on the porous substrate, and the porous heat resistant layer contains a first component containing phosphate or phosphonate and a second component containing nitrogen. It differs from the separator according to the embodiment of the present invention in that it includes an additional binder component in addition to the polymer resin including the repeating unit. Hereinafter, this will be described with reference to the center, and detailed description of the same elements as those of the exemplary embodiment will be omitted. The present embodiment further includes an additional binder component to further improve adhesion to the porous substrate, as well as to improve heat resistance and cycle characteristics.

The further binder component can be, for example, a polyvinylidene fluoride (PVdF) based polymer. The polyvinylidene fluoride polymer may include a polyvinylidene fluoride (PVdF) homopolymer, a polyvinylidene fluoride copolymer, or a mixture thereof. The polyvinylidene fluoride homopolymer refers to a polymer containing only repeating units derived from vinylidene fluoride (VDF) or containing 5 wt% or less of repeating units other than vinylidene fluoride derived repeating units. do. Here, the polyvinylidene fluoride homopolymer does not include hexafluoropropylene (HFP) -derived repeating units as the other types of repeating units. The polyvinylidene fluoride copolymer means polymerized using other monomers in addition to vinylidene fluoride, and specifically, includes a hexafluoropropylene-derived repeating unit, or a vinylidene fluoride repeating unit and hexafluoropropylene. It means to include more than 5% by weight of other types of repeating units in addition to the derived repeating units. The polyvinylidene fluoride copolymer is a polyvinylidene fluoride-hexaxapropylene containing a repeating unit derived from vinylidene fluoride and a repeating unit derived from hexafluoropropylene. HFP) based copolymers. The polyvinylidene fluoride-hexapropylene copolymer is a polyvinylidene fluoride-hexaxa propylene (PVdF-HFP) binary copolymer, or vinylidene fluoride-derived repeating units and hexafluoro In addition to the propylene-derived repeating unit, all three or more copolymers further including other repeating units may be included. As another example of the additional binder component, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene oxide, Cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethyl Alone or selected from the group consisting of cellulose (cyanoethylcellulose), cyanoethylsucrose, pullulan, carboxyl methyl cellulose, and acrylonitrilestyrene-butadiene copolymer Of these There may be mentioned compounds.

Hereinafter, a separator according to another embodiment of the present invention will be described. The separator according to the present embodiment includes a porous substrate and a porous heat resistant layer, and the porous heat resistant layer is different from an embodiment of the present invention in that it further contains inorganic particles. Hereinafter, this will be described with reference to the center, and detailed description of the same elements as those of the exemplary embodiment will be omitted. The separator according to the present embodiment is advantageous in ensuring adequate permeability to include not only inorganic particles but also heat resistance, and to improve conductivity of ions.

The kind of the inorganic particles contained in the porous heat resistant layer is not particularly limited, and inorganic particles commonly used in the art may 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 or SnO ₂ . These may be used alone or in combination of two or more thereof, for example, Al ₂ O ₃ (alumina) may be used. The inorganic particles in the porous heat resistant layer serve as a kind of spacer capable of maintaining the physical form of the porous heat resistant layer. Accordingly, it is possible to secure morphological stability by preventing the inorganic particles in the porous heat-resistant layer from being detached during the assembly process of the battery, and by providing sufficient adhesive force between the porous heat-resistant layer and the porous substrate to suppress shrinkage of the porous substrate by heat. Not only can it prevent the short circuit of the electrode and there is an advantage of excellent high temperature safety.

The size of the inorganic particles is not particularly limited, but the average particle diameter may be 100 nm to 1000 nm, specifically 300 nm to 600 nm. When using the inorganic particles in the size range, it is possible to prevent the dispersibility and coating processability of the inorganic particles in the porous heat-resistant layer composition solution can be prevented and the thickness of the porous heat-resistant layer can be adjusted appropriately.

The inorganic particles may be contained in 70% by weight to 98% by weight in the porous heat-resistant layer, specifically, may be contained in 80% by weight to 95% by weight. It is possible to secure the shape stability of the separator within the above range, to impart sufficient adhesive force between the porous heat-resistant layer and the porous substrate can not only suppress the shrinkage of the porous substrate by heat, but also effectively prevent the short circuit of the electrode.

Hereinafter, a method of manufacturing a separator according to an embodiment of the present invention will be described. Method for manufacturing a separator according to an embodiment of the present invention is a porous heat-resistant layer containing a polymer resin and a solvent comprising a repeating unit containing a first component containing phosphate or phosphonate and a second component containing nitrogen Preparing a composition, and forming a porous heat resistant layer with the porous heat resistant layer composition on one or both surfaces of the porous substrate.

Specifically, the separator may be formed by applying a porous heat-resistant layer composition on a porous substrate, and then drying it. Fine pores of the porous substrate may be formed by a generally known manufacturing method. As a non-limiting example, a dry method and a wet method are known, and specifically, the porous substrate may be prepared by extruding and stretching the composition for the porous substrate to form fine pores in the porous substrate.

The porous heat resistant layer composition for forming the porous heat resistant layer of the separator may include the above-described polymer resin and a solvent, and in another example, may further include inorganic particles in the composition. Although there is no particular limitation on the method for preparing the porous heat resistant layer composition, a polymer solution in which a polymer resin is dissolved in a solvent is used as the porous heat resistant layer composition, or the inorganic particles are dispersed in the polymer solution and used as the porous heat resistant layer composition, The porous heat-resistant layer composition may be prepared by preparing the polymer solution and the inorganic particle dispersion in which the inorganic particles are dispersed, and then mixing them with an appropriate solvent. One method of preparing the porous heat-resistant layer composition may include further mixing the polymer resin and the solvent, or inorganic particles disclosed herein, and stirring at 10 ° C. to 40 ° C. for 30 minutes to 5 hours.

The solvent used for preparing the polymer solution and the inorganic particle dispersion is not particularly limited as long as it can dissolve the polymer resin and can disperse the inorganic particles sufficiently. Non-limiting examples of the solvent that can be used in the present invention is dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, dimethyl carbonate or N-methylpyrrolidone (N-methylpyrrolydone) etc. are mentioned. The content of the solvent may be 20 wt% to 99 wt%, specifically 50 wt% to 95 wt%, and more specifically 70 wt% to 95 wt%, based on the weight of the porous heat-resistant layer composition. . When the solvent is contained in the above range, the porous heat resistant layer composition may be easily manufactured, and the drying process of the porous heat resistant layer may be performed smoothly. In addition, the polymer resin may be contained in 2% by weight to 100% by weight, for example, 2% by weight to 70% by weight based on the total weight of solids of the porous heat-resistant layer composition. In a more specific example, it may be contained in 5% to 30% by weight.

After mixing the solvent with the polymer solution and the inorganic particle dispersion, the porous heat-resistant layer in the form of a mixture is subjected to a sufficiently stirring process using a ball mill, a beads mill, a screw mixer, or the like. The composition liquid can be prepared.

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

The thickness of the porous heat resistant layer according to the embodiments of the present invention may be 0.01 μm to 20 μm, and specifically 1 μm to 15 μm. Within the thickness range, an excellent thermal stability and adhesion can be obtained by forming a porous heat resistant layer having an appropriate thickness, and the thickness of the entire separator can be prevented from becoming too thick to suppress an increase in the internal resistance of the battery.

Drying the porous heat-resistant layer in the embodiments of the present invention may be a method of irradiating dry or vacuum drying or far-infrared rays or electron beams by hot air, hot air, low humidity wind. And the drying temperature is different depending on the type of the solvent, but can be dried at a temperature of approximately 60 ℃ to 120 ℃. The drying time also varies depending on the type of solvent, but may generally be dried for 1 minute to 1 hour. In a specific example, it may be dried for 1 minute to 30 minutes, or 1 minute to 10 minutes at a temperature of 90 ℃ to 120 ℃.

After leaving the separator comprising the porous heat-resistant layer described in the embodiments of the present invention for 30 minutes at 200 ℃ in the machine direction (Machine Direction, MD) or the transverse direction (TD), respectively, the heat shrinkage rate is 10 % Or less, specifically 5% or less, and more specifically 3% or less. Within this range, there is an advantage of effectively preventing a short circuit of the electrode to improve the safety of the battery.

The method for measuring the thermal contraction rate of the separator is not particularly limited, it can be used a method commonly used in the art.

A non-limiting example of a method of measuring the thermal contraction rate of the separator is as follows: The prepared separator is cut into a width of about 5 cm × length (TD) of about 5 cm, which is 200 ° C. chamber. After storing for 30 minutes, the shrinkage in the MD direction and the TD direction of the separator can be measured by calculating the heat shrinkage rate.

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

The method for measuring the flame retardancy of the separator is not particularly limited, and a method commonly used in the art may be used.

A non-limiting example of a method for measuring the flame retardancy of the separator is as follows: Fold the prepared 10cm × 50cm separator into 10cm × 2cm, and then prepare the specimen by fixing the upper and lower parts, based on UL94 VB Flame retardant ratings are measured based on specimen burn time.

The air permeability of the separator including the porous heat resistant layer described in the embodiments of the present invention may be 400 sec / 100 cc or less, specifically 310 sec / 100 cc or less, and more specifically 280 sec / 100 cc or less. Within this range, ion and electron flow inside the battery including the separator may be smooth, and battery performance may be improved.

The method for measuring the air permeability of the separator is not particularly limited, and may be used a method commonly used in the art.

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

According to still another embodiment of the present invention, a porous separator including a porous heat-resistant layer comprising a polymer resin including a repeating unit containing a first component and a second component disclosed herein, and a positive electrode, a negative electrode and the electrolyte Provide a filled electrochemical cell.

The kind of the electrochemical cell is not particularly limited, and may be a battery of a kind known in the art.

The electrochemical battery according to an embodiment of the present invention may be specifically 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.

Method for manufacturing an electrochemical cell according to an embodiment of the present invention is not particularly limited, it can be used a method commonly used in the art.

1 is an exploded perspective view of an electrochemical cell according to one embodiment. Although an electrochemical cell according to an embodiment is described as an example of being rectangular, the present invention is not limited thereto and may be applied to various types of batteries such as a lithium polymer battery and a cylindrical battery.

Referring to FIG. 1, an electrochemical cell 100 according to an embodiment includes an electrode assembly 40 wound through a separator 30 between a positive electrode 10 and a negative electrode 20, and the electrode assembly 40. It includes a case 50 is built. The anode 10, the cathode 20, and the separator 30 are impregnated with an electrolyte (not shown).

The separator 30 is as described above.

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

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

As the cathode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specifically, at least one of cobalt, manganese, nickel, aluminum, iron, or a combination of metal and lithium composite oxide or phosphoric acid 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 material particles to each other but also serves to adhere the positive electrode active material to the positive electrode current collector, and specific examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and polyvinyl chloride. , Carboxylated polyvinylchloride, polyvinylfluoride, ethylene oxide containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride polymer, polyethylene, polypropylene, styrene-butadiene Rubber, styrene-butadiene rubber, epoxy resin, nylon, and the like, but is not limited thereto. These can be used individually or in mixture of 2 or more types.

The conductive material provides conductivity to the electrode, and examples thereof include natural graphite, artificial graphite, carbon black, carbon fiber, metal powder, and metal fiber, but are not limited thereto. These can be used individually or in mixture of 2 or more types. As the metal powder and the metal fiber, metals such as copper, nickel, aluminum, and silver may be used.

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

The negative electrode current collector may include copper (Cu), gold (Au), nickel (Ni), a 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.

The negative electrode active material may be a material capable of reversibly intercalating and deintercalating lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, a transition metal oxide, or a combination thereof. Can be used.

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

Kinds of the binder and the conductive material used in the negative electrode are the same as the binder and the conductive material used in the above-described positive electrode.

The positive electrode and the negative electrode may be prepared by mixing each active material, a binder, and optionally a conductive material in a solvent to prepare each active material composition, and applying the active material composition to each current collector. In this case, N-methylpyrrolidone may be used as the solvent, but is not limited thereto. Since such an electrode manufacturing method is well known in the art, detailed description thereof will be omitted.

The electrolyte solution contains 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 carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents and aprotic solvents.

Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), ethylene Carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like. Specifically, when a mixture of the chain carbonate compound and the cyclic carbonate compound is used, the dielectric constant may be increased, and the solvent may have a low viscosity. In this case, the cyclic carbonate compound and the chain carbonate compound may be mixed and used in a volume ratio of 1: 1 to 1: 9.

Examples of the ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, and meronate. Melononolactone, caprolactone, and the like. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran and the like. Cyclohexanone etc. are mentioned as said ketone solvent, Ethyl alcohol, isopropyl alcohol, etc. are mentioned as said alcohol solvent.

The organic solvents may be used alone or in combination of two or more thereof, and the mixing ratio in the case of mixing two or more kinds may be appropriately adjusted according to the desired battery performance.

The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery to enable operation of a basic electrochemical cell and to promote the movement of lithium ions between the positive electrode and the negative electrode.

Examples of the lithium salt include 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 ) (x and y are natural numbers), LiCl, LiI, LiB (C ₂ O ₄ ) ₂ or a combination thereof Can be mentioned.

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, since the electrolyte has an appropriate conductivity and viscosity, it can exhibit excellent electrolyte performance, and lithium ions can move effectively.

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

Production Example  1: Preparation of Polymer Resin 1

The solution prepared by adding 28% aqueous ammonia solution to phenolphthalein (100 g, 314 mmol) was stirred at room temperature for 20 days. When the solution became almost clear, the solution was poured into concentrated hydrochloric acid and ice to terminate the reaction. The resultant was washed with distilled water to be neutral, and then recrystallized with ethanol and water to synthesize a compound 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 methylene chloride (210 mL), and then cooled to 0 ° C. A solution of 28.1 g of phenylphosphonic dichloride (benzene phosphorus oxydichloride, BPOD) in methylene chloride (15 mL) was added slowly for 1 hour, followed by 4 hours at room temperature. Reacted. 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 ° C. for 48 hours to obtain polymer resin 1 having a repeating unit of formula 6 having a weight average molecular weight of 125,000 g / mol and a glass transition temperature of 248 ° C.

[Formula 3-1]

[Formula 6]

Production Example  2: Preparation of Polymer Resin 2

A solution prepared by adding 40% aqueous methylamine solution to phenolphthalein (100 g, 314 mmol) was reacted at 30 ° C. for 24 hours. Thereafter, the solution was poured into concentrated hydrochloric acid and ice to terminate the reaction. The resultant was filtered, washed with distilled water, and recrystallized with ethanol and water to synthesize a compound of Chemical Formula 3-2. The synthesized compound of Formula 3-2 (46.4 g, 140 mmol) was reacted under the same conditions as in Preparation Example 1, where the weight average molecular weight was 138,000 g / mol and the glass transition temperature was 210 ° C. Polymer resin 2 having repeating units was obtained.

[Formula 3-2]

[Formula 7]

Production Example  3: Preparation of Polymer Resin 3

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

[Formula 3-3]

[Formula 8]

Example  1: Preparation of Separator (Polymer Resin 1+ Inorganic Particle Separation Membrane)

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

The prepared porous heat-resistant layer composition was coated on both sides of a polyethylene single membrane porous substrate having a thickness of 9 μm with a thickness of 1.5 μm in a dip coating manner, and then dried at 110 ° C. for 1 minute to prepare a separator.

Example  2: Preparation of Separator (Polymer Resin 2+ Inorganic Particle-Containing Separator)

Except for using the polymer resin 2 of Preparation Example 2 instead of the Polymer Resin 1 of Preparation Example 1 in Example 1 to prepare a separator having a total thickness of 12㎛.

Example  3: Preparation of Separation Membrane

Except for using the polymer resin 3 of Preparation Example 3 instead of the polymer resin 1 of Preparation Example 1 in Example 1 to prepare a separator having a total thickness of 12㎛.

Comparative example  1: Preparation of Separator

A separator was manufactured in the same manner as in Example 1, except that poly (butylacrylate-co-methylmethacrylate-co-vinylacetate) was used instead of the polymer resin 1 prepared in Preparation Example 1.

Experimental Example

The weight average molecular weight (Mw), glass transition temperature (Tg) and flame retardance of the polymer resins of Preparation Examples 1 to 3 and poly (butyl acrylate-co-methylmethacrylate-co-vinylacetate) of Comparative Example 1 Each measured by the following method, and the results are shown in Table 1 below.

(1) Weight average molecular weight (Mw): It was shown by the polystyrene conversion value measured by the gel permeation chromatography (GPC).

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

(3) Flame retardancy (1/8 "): Measured according to UL94 VB flame retardant regulations.

Membrane Binder	Mw (g / mol)	Tg (℃)	Flame retardancy of polymer resin
Polymer resin 1 of Preparation Example 1	125,000	248	V0
Polymer resin 2 of Preparation Example 2	138,000	210	V0
Polymer resin 3 of Preparation Example 3	148,000	202	V0
Poly (butyl acrylate-co-methylmethacrylate-co-vinylacetate)	450,000	35	V2

Flame retardance, heat shrinkage, and air permeability of the separators prepared in Examples 1 to 3 and Comparative Example 1 were measured by the methods described below, and the results are shown in Table 2.

Experimental Example  1: flame retardancy measurement

With respect to the separator prepared in Examples 1 to 3 and Comparative Example 1 to prepare a specimen in the following manner to evaluate the flame retardancy according to the UL94 VB flame retardant regulations.

After folding the separation membrane of 10cm X 50cm prepared in Examples 1 to 3 and Comparative Example 1 to make 10cm X 2cm, a specimen was prepared by fixing the upper and lower portions. Flame retardant ratings were measured on the basis of specimen burn time in accordance with UL94 VB.

Experimental Example  2 : Heat shrinkage  Measure

In order to measure the thermal shrinkage of the separator prepared in Examples 1 to 3, and Comparative Example 1 was carried out the following method. A total of seven samples were prepared by cutting each of the separators prepared according to the Examples and Comparative Examples at a width of 5 cm and a length of 5 cm. Each sample was stored in a chamber at 200 ° C. for 30 minutes, and then heat shrinkage was calculated by measuring the shrinkage in the MD and TD directions of each sample.

Experimental Example 3  Breathability measurement

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

	Flame Retardant of Membrane	Breathability (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 the separation membrane is manufactured using a polymer resin including a first component containing phosphonate and a second component containing nitrogen, the flame retardancy is excellent as V0. In addition, the heat shrinkage was less than 1% and the ventilation was confirmed to be less than 250 sec / 100cc.

Having described the specific parts of the present invention in detail, it will be apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. will be. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (14)

1. Porous substrates; And

   It includes a porous heat-resistant layer formed on one side or both sides of the porous substrate,

   The porous heat resistant layer includes a polymer resin including a repeating unit containing a first component and a second component,

   The first component contains phosphate or phosphonate,

   The second component is a separator containing nitrogen.
2. The separation membrane of claim 1, wherein the first component comprises Formula 1 or Formula 2. 8.

   [Formula 1]

   

   [Formula 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 .
3. The separation membrane of claim 1, wherein the second component comprises an imide or an amide group.
4. The separator of claim 3, wherein the imide comprises phthalimide.
5. The separation membrane of claim 1, wherein the second component comprises Formula 3. 3.

   [Formula 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 .
6. The separation membrane of claim 1, wherein the repeating unit is any one of Formulas 4 and 5.

   [Formula 4]

   

   [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 .
7. The separation membrane of claim 1, wherein the polymer resin has a glass transition temperature of 180 ° C to 300 ° C.
8. The separator of claim 1, wherein the porous heat-resistant layer further comprises a polyvinylidene fluoride polymer.
9. The separator of claim 1, wherein the porous heat resistant layer further contains inorganic particles.
10. The separation membrane of claim 9, wherein the inorganic particles include one or more 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 .
11. The separation membrane of claim 10, wherein the content of the inorganic particles is 70 wt% to 98 wt% with respect to the total weight of solids of the porous heat-resistant layer.
12. Preparing a porous heat-resistant layer composition containing a polymer resin and a solvent comprising a repeating unit containing a first component containing phosphate or phosphonate and a second component containing nitrogen,

    A method of manufacturing a separator comprising forming a porous heat resistant layer with the porous heat resistant layer composition on one or both surfaces of the porous substrate.
13. An electrochemical cell comprising a positive electrode, a negative electrode, 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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