JP6657185B2 - High heat resistant and flame retardant separation membrane and electrochemical cell - Google Patents

Description

  The present invention relates to a high heat-resistant and flame-retardant separation membrane and an electrochemical cell including the same.

  The separator for an electrochemical cell refers to an intermediate layer that maintains the conductivity of ions while separating a positive electrode and a negative electrode from each other in the cell, thereby enabling charging and discharging of the cell.

  2. Description of the Related Art Recently, there has been a trend toward a need for a high-output large-capacity battery for use in an electric vehicle and the like along with a trend toward a reduction in the weight and size of an electrochemical battery for improving the portability of electronic devices. Many studies have been made on lithium secondary batteries that provide high output compared to the capacity of a unit battery (battery cell) of a medium- to large-sized battery pack for the high-output large-capacity application.

  Lithium secondary batteries are promising candidates as unit batteries for medium- and large-sized battery packs due to the various advantages described above.However, the internal temperature of the battery rises during charging and discharging, causing flammable gas and electrolytic There is a problem that explosion or fire occurs due to generation of flammable gas due to reaction between the liquid and the electrode and oxygen due to decomposition of the positive electrode. In addition, when a polyolefin-based film is used as a separation membrane of a secondary battery, there is a problem that the film melts at a relatively low temperature (Korean Registered Patent No. 10-0775310).

  Therefore, there is a need to provide a new separation membrane that prevents or suppresses ignition in electrochemical cells, especially in medium- to large-capacity cells, and that improves or maintains the original performance of the battery while improving heat resistance. .

Republic of Korea registered patent No. 10-0775310

  The present invention provides a separation membrane having flame retardancy and high heat resistance, excellent adhesion to a porous substrate and excellent oxidation resistance, and improved dispersibility of inorganic particles in a porous heat-resistant layer. The purpose of the present invention is to provide an electrochemical cell.

  In one embodiment of the present invention, including a porous substrate, a porous heat-resistant layer formed on one or both surfaces of the porous substrate, the porous heat-resistant layer, the first component and the first A separation membrane containing a polymer resin containing a repeating unit containing two components, wherein the first component contains phosphate or phosphonate, and the second component contains nitrogen is provided.

  According to another embodiment of the present invention, there is provided an electrochemical cell formed from the separator according to the above aspect.

  A separation membrane according to an embodiment of the present invention and an electrochemical battery using the same have flame retardancy and high heat resistance, have excellent adhesion between a porous substrate and a porous heat-resistant layer, and have a dispersion of inorganic particles. It has improved properties and excellent properties in oxidation resistance.

FIG. 1 is an exploded perspective view of an electrochemical cell according to one embodiment. The electrochemical cell (100) includes an electrode assembly (40) wound with a separation membrane (30) interposed between a positive electrode (10) and a negative electrode (20), and the electrode assembly (40). Includes built-in case (50). The positive electrode (10), the negative electrode (20), and the separation membrane (30) are impregnated with an electrolytic solution (not shown).

  According to one embodiment of the present invention, a porous substrate, and a porous heat-resistant layer formed on one surface or both surfaces of the porous substrate, wherein the porous heat-resistant layer comprises a first component And a polymer resin containing a repeating unit containing a second component and a second component, wherein the first component contains a phosphate or a phosphonate, and the second component contains a nitrogen-containing separation membrane.

  The porous substrate has a large number of pores, and may be a porous substrate that can be generally used for an electrochemical device. Examples of the porous substrate include, but are not limited to, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, and poly (imide). Polymer membrane formed from any one polymer selected from the group consisting of benzimidazole, polyether sulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide and polyethylene naphthalene, or a mixture of two or more thereof It may be. For example, the porous substrate may be a polyolefin-based substrate, and the polyolefin-based substrate has an excellent shutdown down function and contributes to an improvement in battery safety. The polyolefin-based substrate is selected from the group consisting of, for example, a single film of polyethylene, a single film of polypropylene, a double film of polyethylene / polypropylene, a triple film of polypropylene / polyethylene / polypropylene, and a triple film of polyethylene / polypropylene / polyethylene. Is also good. As another example, the polyolefin-based 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 thickness of the porous substrate may be 1 μm to 40 μm, more specifically, 5 μm to 15 μm, and more specifically, 5 μm to 10 μm. When using a porous substrate within the above thickness range, the appropriate thickness is not thick enough to increase the internal resistance of the battery, while being thick enough to prevent a short circuit between the positive electrode and the negative electrode of the battery. Can be manufactured.

  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. At this time, it is in the form of a copolymer containing a first repeating unit containing the first component and a second repeating unit containing the second component, or contains the first component and the second component simultaneously. It may be in the form of a polymer containing one repeating unit. The polymer resin can prevent a battery from exploding or generating a fire due to generation of oxygen due to decomposition of the positive electrode by containing phosphate or phosphonate, and also contains nitrogen. The adhesive strength with the porous substrate can be improved, and when the porous heat-resistant layer contains inorganic particles, the dispersibility of the inorganic particles can be improved. Without being bound by any particular theory, the phosphate or phosphonate structure containing phosphate groups in the separation membrane may generate polymetaphosphate by thermal decomposition. The generated polymetaphosphoric acid forms a protective layer on the separation membrane, and the carbon coating generated by the dehydration action during the polymetaphosphoric acid generation process blocks oxygen and shows flame retardancy. Can be. Also, without being bound by any particular theory, it is speculated that when nitrogen is contained, the provision of lone pairs of nitrogen improves the adhesion to the porous substrate and the dispersibility of the inorganic particles. . Further, the separation membrane according to one embodiment of the present invention includes a polymer resin containing 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. Use of such a material is advantageous in that sufficient adhesive strength to a separation membrane substrate, ignition suppression, and heat resistance can be simultaneously secured without using another binder, another flame retardant, or another inorganic particle.

前記化学式１および化学式２で、Ｒ₁およびＲ₂は、それぞれ独立して、水素、または、置換もしくは非置換の、Ｃ_1-6のアルキル、Ｃ_2-6のアルケニル、Ｃ_2-6のアルキニル、Ｃ_3-20のシクロアルキル、およびＣ_6-30のアリールからなる群より選択されてもよい。一例として、前記化学式１および化学式２で、Ｒ₁およびＲ₂は、それぞれ独立して、水素、または、非置換もしくは、ハロゲン、ＯＨ、Ｃ_1-6アルキル、アルコキシ、ニトロ、シアノ、カルボニル、チオールで１つ以上置換された、Ｃ_1-6のアルキル、Ｃ_6-30アリールまたはＣ_3-10のシクロアルキルであってもよい。具体的な例として、Ｒ₁およびＲ₂は、それぞれ独立して、水素、または、非置換もしくは、ハロゲン、ＯＨ、またはＣ_1-6アルキルで１つ以上置換されたフェニル、ナフチル、シクロプロピル、シクロブチル、メチル、エチル、プロピル、ブチルなどであってもよい。 Examples of the first component containing a phosphate or a phosphonate in the polymer resin of one embodiment of the present invention are as follows.

In the above formulas 1 and 2, R ₁ and R ₂ are each independently hydrogen or substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl. , C _3-20 cycloalkyl, and C _6-30 aryl. For example, in Formulas 1 and 2, R ₁ and R ₂ are each independently hydrogen or unsubstituted or halogen, OH, C _1-6 alkyl, alkoxy, nitro, cyano, carbonyl, thiol. _May be a C _1-6 alkyl, a C _6-30 aryl or a C _3-10 cycloalkyl substituted with one or more of As specific examples, R ₁ and R ₂ are each independently hydrogen or phenyl, naphthyl, cyclopropyl, unsubstituted or substituted with one or more halogen, OH, or C _1-6 alkyl. It may be cyclobutyl, methyl, ethyl, propyl, butyl and the like.

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

  As a specific example, the second component may have a phthalimide-containing structure and may be an alkylamide-containing residue, an alkenylamide-containing residue or an arylamide-containing residue having 1 to 10 carbon atoms. In particular, the second component may have a phthalimide-containing structure. If the second component has a phthalimide-containing structure, the amine group has a small number of hydrogen atoms and can have a wider potential window. There is an advantage that it is not easily disassembled.

前記化学式３で、Ｒ₃は、水素、または、置換もしくは非置換の、Ｃ_1-6のアルキル、Ｃ_2-6のアルケニル、Ｃ_2-6のアルキニル、Ｃ_3-10のシクロアルキル、およびＣ_6-30のアリールからなる群より選択される。一例として、前記化学式３で、Ｒ₃は、水素、または、非置換もしくは、ハロゲン、ＯＨ、Ｃ_1-6アルキル、Ｃ_2-6アルケニル、アルコキシ、ニトロ、シアノ、カルボニル、チオールまたはＣ_2-6アルキニルで１つ以上置換された、Ｃ_1-6のアルキル、Ｃ_6-30アリールまたはＣ_3-10のシクロアルキルであってもよい。具体的な例として、Ｒ₃は、水素、または、非置換もしくは、ハロゲン、ＯＨ、Ｃ_1-6アルキルまたはＣ_2-6アルケニルで１つ以上置換された、フェニル、ナフチル、シクロプロピル、シクロブチル、シクロペンチル、メチル、エチル、プロピル、ブチル、エテニル、プロフェニル、ヘプテニルあるいはブテニルであってもよい。 Other specific examples of the second component containing nitrogen are as follows.

In the above formula 3, R ₃ is hydrogen or substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-10 cycloalkyl, and C _3-10. Selected from the group consisting of _6-30 aryls. For example, in Formula 3, R ₃ is hydrogen or unsubstituted or halogen, OH, C _1-6 alkyl, C _2-6 alkenyl, alkoxy, nitro, cyano, carbonyl, thiol or C _2-6 It may be C _1-6 alkyl, C _6-30 aryl or C _3-10 cycloalkyl substituted with one or more alkynyl. As a specific example, R ₃ is hydrogen, or phenyl, naphthyl, cyclopropyl, cyclobutyl, unsubstituted or substituted with one or more halogen, OH, C _1-6 alkyl or C _2-6 alkenyl. It may be cyclopentyl, methyl, ethyl, propyl, butyl, ethenyl, prophenyl, heptenyl or butenyl.

  Still another example of the nitrogen-containing second component includes 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 one or more carbon atoms of an aromatic hydrocarbon ring compound are substituted with nitrogen. The aromatic hydrocarbon ring compound may have a monocyclic, bicyclic or tricyclic structure. Examples are two or more nitrogen-containing heteroaromatic hydrocarbon rings directly attached, or one or more nitrogen-containing heteroaromatic hydrocarbon rings and one or more aromatic hydrocarbon rings. Examples include a structure in which a compound is substituted for hydrogen in a methyl group. A specific example is a structure in which at least one carbon of at least one aromatic hydrocarbon ring is substituted with nitrogen in poly-aromatic hydrocarbons.

As a more specific example, the second component containing nitrogen may be selected from the following.

前記化学式４および５で、Ｒ₁、Ｒ₂およびＲ₃置換基の定義は、前記化学式１〜３でのＲ₁、Ｒ₂およびＲ₃置換基の定義と同一である。 For example, the polymer resin may include a repeating unit of Formula 4 or Formula 5.

In Formulas 4 and 5, the definition of R _1, R ₂ and R ₃ substituents are the same definition of R _1, R ₂ and R ₃ substituents 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, and more specifically, 220 ° C to 250 ° C. In the case of a separation membrane in which the porous heat-resistant layer contains a polymer resin satisfying the above range, since the melt-down is not performed even at a relatively high temperature, it can have high heat resistance.

  The weight average molecular weight of the polymer resin may be in the range of 5,000 to 350,000, and if it is in the range, it may be advantageous from the viewpoint of adhesive strength and heat resistance.

  Hereinafter, a separation membrane according to another embodiment of the present invention will be described. The separation membrane according to the present embodiment includes a porous substrate, and a porous heat-resistant layer formed on the porous substrate, wherein the porous heat-resistant layer contains a phosphate or a phosphonate-containing first component and nitrogen. There is a difference from the separation membrane according to the embodiment of the present invention in that an additional binder component is included in addition to the polymer resin including the repeating unit containing the second component. Hereinafter, this will be mainly described, and detailed description of components substantially the same as those of the embodiment will be omitted. In the present embodiment, by further including an additional binder component, not only the adhesive strength with the porous substrate can be further improved, but also the heat resistance and the cycle characteristics are improved.

  The additional binder component may be, for example, a polyvinylidene fluoride (PVdF) -based polymer. The polyvinylidene fluoride-based 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 a repeating unit derived from vinylidene fluoride (VDF) or containing 5% by weight or less of other types of repeating units other than the repeating unit derived from vinylidene fluoride. I do. Here, the polyvinylidene fluoride homopolymer does not include a hexafluoropropylene (Hexafluoropropylene, HFP) -derived repeating unit as the other type of repeating unit. Polyvinylidene fluoride copolymer means a polymer obtained by polymerizing 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 those containing more than 5% by weight of other types of repeating units in addition to the derived repeating units. The polyvinylidene fluoride copolymer may include a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) copolymer containing a repeating unit derived from vinylidene fluoride and a repeating unit derived from hexafluoropropylene. . The polyvinylidene fluoride-hexapropylene copolymer includes a polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP) binary copolymer, or a vinylidene fluoride-derived repeating unit and a hexafluoropropylene-derived repeating unit. It may include all ternary or higher copolymers additionally containing other repeating units. Other examples of the additional binder component include polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, oxide, polyethylene oxide, polyethylene oxide, polyethylene oxide, polyethylene oxide, polyethylene oxide, polyethylene oxide, polyethylene oxide, polyethylene oxide and polyethylene oxide. Cellulose acetate butyrate (cellulose acetate butyrate), cellulose acetate propionate (cellulose acetate propionate), cyanoethyl pullulan (cyanoethyl pullulan), Ano ethyl polyvinylalcohol (cyanoethylpolyvinylalcohol), cyanoethyl cellulose (cyanoethylcellulose), cyanoethyl sucrose (cyanoethylsucrose), pullulan (pullulan), from the group consisting of carboxymethyl cellulose (carboxyl methyl cellulose), and acrylonitrile-styrene-butadiene copolymer (acrylonitrilestyrene-butadiene copolymer) Selected alone or mixtures thereof are mentioned.

  Hereinafter, a separation membrane according to another embodiment of the present invention will be described. The separation membrane according to the present embodiment includes a porous substrate and a porous heat-resistant layer, and differs from the embodiment of the present invention in that the porous heat-resistant layer additionally contains inorganic particles. Hereinafter, this will be mainly described, and detailed description of components substantially the same as those of the embodiment will be omitted. The separation membrane according to the present embodiment is advantageous not only for improving the heat resistance by containing the inorganic particles, but also for securing appropriate permeability to the extent that the ion conductivity can be improved. .

The type of inorganic particles contained in the porous heat-resistant layer is not particularly limited, and inorganic particles generally used in the art may be used. . Non-limiting examples of the inorganic _{particles, Al 2 O 3, SiO 2} , B 2 O 3, Ga 2 O 3, etc. TiO ₂ or SnO ₂ and the like. These can be used alone or in combination of two or more. For example, Al ₂ O ₃ (alumina) can be used. The inorganic particles in the porous heat-resistant layer serve as a kind of spacer that can maintain the physical form of the porous heat-resistant layer. In this way, it is possible to prevent the problem of inorganic particles in the porous heat-resistant layer being detached in the process of assembling a battery or the like, to secure morphological stability, and to provide a sufficient space between the porous heat-resistant layer and the porous substrate. In addition to providing a strong adhesive force, it is possible not only to suppress the shrinkage of the porous base material due to heat, but also to prevent short-circuiting of the electrodes, which is advantageous in high-temperature safety.

  The size of the inorganic particles is not particularly limited, but may have an average particle size of 100 nm to 1000 nm, or specifically 300 nm to 600 nm. When using the inorganic particles of the size range, it is possible to prevent the dispersibility and coating processability of the inorganic particles in the porous heat-resistant layer composition liquid from being reduced, and to appropriately adjust the thickness of the porous heat-resistant layer. Can be adjusted.

  The inorganic particles may be included in the porous heat-resistant layer in an amount of 70% by weight to 98% by weight, specifically, 80% by weight to 95% by weight. Within the above range, the morphological stability of the separation membrane can be ensured, and sufficient adhesion between the porous heat-resistant layer and the porous base material is provided to suppress shrinkage of the porous base material due to heat. In addition to this, it is possible to effectively prevent short-circuiting of the electrodes.

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

  Specifically, the separation membrane may be formed by applying a porous heat-resistant layer composition on a porous substrate and then drying the composition. The micropores 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.Specifically, the porous substrate extrudes and stretches the composition for a porous substrate to form fine pores in the porous substrate. It may be formed and manufactured.

  The porous heat-resistant layer composition for forming the porous heat-resistant layer of the separation membrane may include the above-described polymer resin and a solvent. In another example, the composition may further include inorganic particles. Although there is no particular limitation on the method for producing the porous heat-resistant layer composition, a polymer solution obtained by dissolving a polymer resin in a solvent can be used as the porous heat-resistant layer composition, or inorganic particles can be dispersed in the polymer solution. This is used as a porous heat-resistant layer composition, or after preparing the polymer solution and an inorganic particle dispersion liquid in which inorganic particles are dispersed, and mixing these with an appropriate solvent. A layer composition may be manufactured. . One method of preparing the porous heat-resistant layer composition is as follows: a polymer resin and a solvent disclosed herein, or an inorganic particle is additionally added thereto, and the mixture is heated at 10 to 40 ° C. for 30 minutes to 5 hours. Stirring may be included.

  The solvent used for producing the polymer solution and the inorganic particle dispersion is not particularly limited as long as the solvent is capable of dissolving the polymer resin and sufficiently dispersing the inorganic particles. Non-limiting examples of the solvent that can be used in the present invention include dimethylformamide, dimethylsulfoxide, dimethylacetamide, dimethylcarbonate or dimethyl carbonate (N-methyl carbonate). N-methylpyrrolydone) and the like. Based on the weight of the porous heat-resistant layer composition, the content of the solvent may be 20% by weight to 99% by weight, specifically, 50% by weight to 95% by weight, and more specifically. May be 70% to 95% by weight. When the solvent is contained in the above range, the production of the porous heat-resistant layer composition becomes easy, and the drying step of the porous heat-resistant layer can be performed smoothly. Further, the polymer resin may be contained in an amount of 2% by weight to 100% by weight, for example, 2% by weight to 70% by weight based on the total weight of the solid content of the porous heat-resistant layer composition. In a more specific example, it may be contained at 5% by weight to 30% by weight.

  After the solvent is added to the polymer solution and the inorganic particle dispersion, the mixture is thoroughly stirred using a ball mill, a beads mill, a screw mixer, or the like. Can be produced.

  The method for forming the porous heat-resistant layer on the porous substrate is not particularly limited, and may be a method usually used in the technical field of the present invention, for example, using a coating method, lamination, coextrusion, or the like. Good. 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 can be applied alone or as a mixture of two or more methods. The porous heat-resistant layer of the separation membrane 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 embodiment of the present invention may be 0.01 μm to 20 μm, and specifically, may be 1 μm to 15 μm. Within the thickness range, a porous heat-resistant layer having an appropriate thickness can be formed to obtain excellent thermal stability and adhesive strength, and prevent the entire separation membrane from being excessively thick. Thus, it is possible to suppress an increase in the internal resistance of the battery.

  To dry the porous heat-resistant layer in the embodiment of the present invention, a method of drying with warm air, hot air, low-humidity air, vacuum drying, or irradiation with a far-red electron beam may be used. Although the drying temperature varies depending on the type of the solvent, the drying can be performed at a temperature of approximately 60C to 120C. The drying time also varies depending on the type of the solvent, but it can be dried in about 1 minute to 1 hour. In a specific example, drying can be performed at a temperature of 90C to 120C for 1 minute to 30 minutes, or 1 minute to 10 minutes.

  The heat shrinkage in the machine direction (Machine Direction, MD) or the perpendicular direction (Transverse Direction, TD) after leaving the separation membrane including the porous heat-resistant layer described in the embodiment of the present invention at 200 ° C. for 30 minutes is as follows. , Each may be 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 for measuring the heat shrinkage of the separation membrane is not particularly limited, and a method usually used in the technical field of the present invention may be used.

  A non-limiting example of a method for measuring the heat shrinkage of a separation membrane is as follows. That is, the manufactured separation membrane is cut into a size of about 5 cm in width (MD) × about 5 cm in length (TD), and stored in a 200 ° C. chamber for 30 minutes, and then in the MD direction of the separation membrane. And the degree of shrinkage in the TD direction is measured to calculate the heat shrinkage.

  When the flame retardancy of the separation membrane including the porous heat-resistant layer described in the embodiment of the present invention is measured in accordance with UL94VB flame retardancy regulations, it may be an excellent flame retardancy grade of V0 or more. Within the above 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 generally used in the technical field of the present invention can be used.

  A non-limiting example of a method for measuring the flame retardancy of the separation membrane is as follows. In other words, after the manufactured 10 cm x 50 cm separation membrane is folded to make 10 cm x 2 cm, the upper and lower parts are fixed to produce a test piece, and the flame-retardant grade conforms to UL94VB, Measure with time as a guide.

  The air permeability of the separation membrane including the porous heat-resistant layer described in the embodiment of the present invention may be 400 sec / 100 cc or less, specifically, 310 sec / 100 cc or less, and more specifically. May be 280 sec / 100 cc or less. Within this range, the flow of ions and electrons inside the battery including the separation membrane may be smooth, and the battery performance may be improved.

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

  A non-limiting example of a method for measuring the air permeability of the separation membrane is as follows. That is, the air permeability is obtained by measuring the time required for 100 cc of air to pass through the separation membrane with respect to the manufactured separation membrane.

  According to yet another embodiment of the present invention, a porous separation membrane including a porous heat-resistant layer including a polymer resin including a repeating unit containing a first component and a second component disclosed herein, and a positive electrode , An electrochemical cell including an anode and filled with an electrolyte.

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

  The electrochemical cell according to an embodiment of the present invention is 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. There may be.

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

  FIG. 1 is an exploded perspective view of an electrochemical cell according to an embodiment. An electrochemical battery according to an embodiment will be described by taking a prismatic battery as an example, but 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. It is possible.

  Referring to FIG. 1, an electrochemical battery 100 according to an embodiment includes an electrode assembly 40 wound between a positive electrode 10 and a negative electrode 20 with a separator 30 interposed therebetween, and the electrode assembly 40 is incorporated therein. Case 50. The positive electrode 10, the negative electrode 20, and the separation membrane 30 are impregnated with an electrolyte (not shown).

  The separation membrane 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 agent.

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

  As the positive electrode active material, a compound capable of reversibly inserting and removing lithium may be used. Specifically, at least one of a complex oxide or a complex phosphor of lithium and a metal of cobalt, manganese, nickel, aluminum, iron or a 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 phosphorus oxide, or a combination thereof may be used.

  The binder not only makes the positive electrode active material particles adhere well to each other, but also plays a role of making the positive electrode active material adhere well to the positive electrode current collector. Specific examples include polyvinyl alcohol, carboxymethyl cellulose, and hydroxypropyl. Cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride-based polymer, polyethylene, polypropylene, styrene-butadiene rubber, Examples include, but are not limited to, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like. These may be used alone or in combination of two or more.

The conductive agent imparts conductivity to the electrode, and examples thereof 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 use a metal such as copper, nickel, aluminum, and silver.

  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 use 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 agent.

  As the negative electrode active material, a material capable of reversibly inserting and removing lithium ions, a lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, a transition metal oxide, or a transition metal oxide thereof Combinations can be used.

Examples of the substance capable of reversibly inserting and removing lithium ions include a carbon-based substance, and examples thereof include crystalline carbon, amorphous carbon, and a combination thereof. Examples of the crystalline carbon include amorphous, plate-like, flake-like, 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 lithium metal include a group consisting of lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn. An alloy of a more selected metal can be used. Examples of the substance capable of doping and undoping lithium include Si, SiO _x (0 <x <2), Si—C composite, Si—Y alloy, Sn, SnO ₂ , Sn—C composite, and Sn. —Y and the like, and at least one of them may be mixed with SiO ₂ for use. 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, It may be selected from the group consisting of S, Se, Te, Po and combinations thereof. Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide.

  The types of the binder and the conductive agent used for the negative electrode are the same as the binder and the conductive agent used for the positive electrode described above.

  The positive electrode and the negative electrode are manufactured by mixing each active material and a binder and a conductive agent in a solvent to prepare each active material composition, and applying the active material composition to each current collector. can do. At this time, the solvent may be N-methylpyrrolidone or the like, but is not limited thereto. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted in this specification.

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

  Examples of the carbonate-based solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), ethyl methyl carbonate (EMC), and ethylene. Carbonate (EC), propylene carbonate (PC), butylene carbonate (BC) and the like. Specifically, when a mixture of a chain carbonate compound and a cyclic carbonate compound is used, it can be produced as a solvent having a low viscosity while increasing the dielectric constant. At this time, the cyclic carbonate compound and the chain carbonate compound can be mixed and used at 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, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, and 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 and isopropyl alcohol.

  The organic solvents may be used singly or as a mixture of two or more kinds. When two or more kinds are used in combination, the mixing ratio may be appropriately adjusted according to the intended battery performance.

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

Examples of the lithium _{salt, 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.

  The concentration of the lithium salt can be used in the range of 0.1M to 2.0M. When the concentration of the lithium salt is within the above range, since the electrolyte has appropriate conductivity and viscosity, excellent electrolyte performance can be exhibited, and lithium ions can move effectively.

  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.

Preparation Example 1: Preparation of Polymer Resin 1 A solution prepared by adding a 28% aqueous ammonia solution to phenolphthalein (100 g, 314 mmol) was stirred at room temperature for 20 days. When the solution became almost transparent, the solution was poured into concentrated hydrochloric acid and ice to terminate the reaction. The resulting product was washed with distilled water so as to be neutral, and then recrystallized using ethanol and water to synthesize a compound of the formula 3-1. The 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 prepared by dissolving 28.1 g of phenylphosphonic dichloride (benzenephosphorus oxydichloride, BPOD) in methylene chloride (15 mL) was gradually added over 1 hour, and then reacted at room temperature for 4 hours. . The solution after the reaction was washed several times with a diluted HCl solution and distilled water. The washed polymer is dried in an 80 ° C. vacuum oven for 48 hours to obtain a polymer resin 1 having a weight average molecular weight of 125,000 g / mol and a glass transition temperature of 248 ° C. and having a repeating unit of the formula (6). Was.

Preparation Example 2 Preparation of Polymer Resin 2 A solution prepared by adding a 40% aqueous solution of methylamine 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 resulting product was filtered, washed with distilled water, and recrystallized using ethanol and water to synthesize a compound of 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 to have a weight average molecular weight of 138,000 g / mol and a glass transition temperature of 210 ° C. A polymer resin 2 having a repeating unit of the formula 7 was obtained.

Preparation Example 3: Preparation of Polymer Resin 3 A solution prepared by adding aniline (300 mL, 3287 mmol) and aniline hydrochloride (100 g, 965 mmol) to phenolphthalein (100 g, 314 mmol). The reaction was performed 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. The resulting product was filtered, washed with distilled water, and recrystallized using ethanol to synthesize a compound 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 have a weight average molecular weight of 148,000 g / mol and a glass transition temperature of 202 ° C. A polymer resin 3 having a repeating unit of the formula 8 was obtained.

Example 1: Production of separation membrane (polymer resin 1 + separation membrane containing inorganic particles)
The polymer resin 1 prepared in Preparation Example 1 was dissolved at 10% by weight in tetrahydrofuran (THF) to prepare a polymer solution. Also, Al ₂ O ₃ (LS235A, manufactured by Nippon Light Metal Co., Ltd.) was added to acetone (manufactured by Oi Kakin Co., Ltd.) at 25% by weight, and the mixture was milled and dispersed at 25 ° C. for 3 hours using a bead mill to produce an inorganic dispersion. . The prepared polymer resin solution and inorganic dispersion were mixed with a mixed solvent of N, N-dimethylacetamide (DMAc) and THF at a weight ratio of 2.5: 5: 2.5, respectively. The mixture was stirred at 25 ° C. for 1 hour with a mixer to produce a porous heat-resistant layer composition.

  The prepared porous heat-resistant layer composition was coated on both surfaces of a 9 μm-thick polyethylene single-layer porous base material by a dip coating method to a thickness of 1.5 μm, respectively, and then applied at 110 ° C. for 1 minute. After drying, a separation membrane was manufactured.

Example 2: Production of separation membrane (polymer resin 2 + inorganic particle-containing separation membrane)
A separator having a total thickness of 12 μm was manufactured in the same manner as in Example 1, except that the polymer resin 2 of Production Example 2 was used instead of the polymer resin 1 of Production Example 1.

Example 3: Production of separation membrane (polymer resin 3 + separation membrane containing inorganic particles)
A separation membrane having a total thickness of 12 μm was manufactured in the same manner as in Example 1, except that the polymer resin 3 of Production Example 3 was used instead of the polymer resin 1 of Production Example 1.

Comparative Example 1 Preparation of Separation Membrane Example 1 except that poly (butyl acrylate-co-methyl methacrylate-co-vinyl acetate) was used instead of the polymer resin 1 prepared in Preparation Example 1. A separation membrane was produced in the same manner as described above.

Experimental Example Weight average molecular weight (Mw), glass transition temperature (Tg), and flame retardancy of the polymer resins of Production Examples 1 to 3 and poly (butyl acrylate-co-methyl methacrylate-co-vinyl acetate) of Comparative Example 1 The properties were measured by the following methods, and the results are shown in Table 1 below.
(1) Weight average molecular weight (Mw): expressed as a polystyrene converted value measured by gel permeation chromatography (GPC).
(2) Glass transition temperature (Tg): measured by differential scanning calorimetry (DSC).
(3) Flame retardancy (1/8 "): Measured in accordance with UL94VB flame retardant regulations.

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

Experimental Example 1: Measurement of Flame Retardancy A test piece was produced from the separation membranes produced in Examples 1 to 3 and Comparative Example 1 by the following method, and the flame retardancy was determined in accordance with UL94VB flame retardancy regulations. Was evaluated.

  The 10 cm × 50 cm separation membranes manufactured in Examples 1 to 3 and Comparative Example 1 were folded to form 10 cm × 2 cm, and the upper and lower portions were fixed to manufacture test pieces. Flame-retardant grades were measured in accordance with UL94VB with reference to the burning time of test pieces.

Experimental Example 2: Measurement of heat shrinkage The following method was used to measure the heat shrinkage of the separation membranes manufactured in Examples 1 to 3 and Comparative Example 1. Each of the separation membranes manufactured according to the example and the comparative example was cut into a width (MD) of 5 cm and a length (TD) of 5 cm to prepare a total of seven samples. After each sample was stored in a 200 ° C. chamber for 30 minutes, the degree of shrinkage of each sample in the MD and TD directions was measured to calculate the heat shrinkage.

Experimental Example 3: Measurement of air permeability 100 cc of air passed through the separation membrane by using EG01-55-1MR (manufactured by Asahi Seiko Co., Ltd.) for the air permeability of the separation membranes manufactured in Examples 1 to 3 and Comparative Example 1. It was measured by a method of measuring the time required to perform the measurement.

  Referring to Table 2, when a separation membrane is manufactured using a polymer resin containing a first component containing a phosphonate and a second component containing nitrogen, the flame retardancy is excellent at V0. Further, it was confirmed that the heat shrinkage was less than 1% and the air permeability was 250 sec / 100 cc or less.

  Having described in detail the specific parts of the present invention, those skilled in the art will appreciate that such specific descriptions are merely preferred embodiments, which limit the scope of the present invention. It is clear that this is not the case. Thus, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

REFERENCE SIGNS LIST 100 Electrochemical battery 10 Positive electrode 20 Negative electrode 30 Separation membrane 40 Electrode assembly 50 Case

Claims (10)

A porous substrate;
A porous heat-resistant layer formed on one surface or both surfaces of the porous substrate,
Including
The porous heat-resistant layer includes a polymer resin comprising at least one of a structural unit represented by the following chemical formula 1 or a structural unit represented by the following chemical formula 2 and a structural unit represented by the following chemical formula 3. No separation membrane.

(In Formulas 1 and 2, R ₁ and R ₂ are each independently hydrogen, or a substituted or unsubstituted alkyl of C _1-6, alkenyl C _2-6, the C _2-6 Selected from the group consisting of alkynyl, _C3-20 cycloalkyl, and _C6-30 aryl.)

(Wherein R ₃ is hydrogen or substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-10 cycloalkyl, and Selected from the group consisting of C _6-30 aryl.) The separation membrane according to claim 1, wherein the polymer resin comprises at least one of a structural unit represented by the following chemical formula 4 or a structural unit represented by the following chemical formula 5 .

(In the above formulas 4 and 5, R ₁ to R ₃ are each independently hydrogen or substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 Selected from the group consisting of alkynyl, _C3-20 cycloalkyl, and _C6-30 aryl.)   The separation membrane according to claim 1, wherein the polymer resin has a glass transition temperature of 180C to 300C.   The separation membrane according to claim 1, wherein the porous heat-resistant layer additionally includes a polyvinylidene fluoride-based polymer.   The separation membrane according to claim 1, wherein the porous heat-resistant layer additionally contains inorganic particles. The inorganic _{particles, Al 2 O 3, SiO 2} , B 2 O 3, Ga 2 O 3, contains at least one element selected from the group consisting of TiO ₂ and SnO _2, the separation membrane according to claim 5. The separation membrane according to claim 6 , wherein the content of the inorganic particles is 70% by weight to 98% by weight based on the total weight of the solid content of the entire porous heat-resistant layer. Porosity containing a polymer resin comprising a structural unit represented by the following chemical formula 1 or one or more structural units represented by the following chemical formula 2, and a structural unit represented by the following chemical formula 3, and a solvent Producing a heat-resistant layer composition,
A method for producing a separation membrane, comprising forming a porous heat-resistant layer with the porous heat-resistant layer composition on one or both surfaces of a porous substrate.

(In Formulas 1 and 2, R ₁ and R ₂ are each independently hydrogen, or a substituted or unsubstituted alkyl of C _1-6, alkenyl C _2-6, the C _2-6 Selected from the group consisting of alkynyl, _C3-20 cycloalkyl, and _C6-30 aryl.)

(Wherein R ₃ is hydrogen or substituted or unsubstituted C _1-6 alkyl, C _2-6 alkenyl, C _2-6 alkynyl, C _3-10 cycloalkyl, and Selected from the group consisting of C _6-30 aryl.) An electrochemical battery including a positive electrode, a negative electrode, a separation membrane, and an electrolyte, wherein the separation membrane is the separation membrane according to any one of claims 1 to 7 . The electrochemical cell according to claim 9 , wherein the electrochemical cell is a lithium secondary battery.

Images