WO2015076573A1

WO2015076573A1 - Secondary battery

Info

Publication number: WO2015076573A1
Application number: PCT/KR2014/011178
Authority: WO
Inventors: 천지현; 김양섭; 윤효상
Original assignee: 삼성에스디아이 주식회사
Priority date: 2013-11-21
Filing date: 2014-11-20
Publication date: 2015-05-28

Abstract

The present invention relates to a secondary battery comprising: an anode comprising an anode active material; a cathode comprising a cathode active material; an electrolyte; and a separation film arranged between the anode and the cathode, wherein the separation film comprises a porous adhesive layer having a plurality of pores adhered to the anode or the cathode, the electrolyte is contained in the pores of the porous adhesive layer, and the porous adhesive layer comprises an acrylate-acetate copolymer.

Description

Secondary battery

The present invention relates to a secondary battery.

BACKGROUND ART In general, portable electronic devices such as video cameras, mobile phones, and portable computers have been researched about secondary batteries used as driving power sources as light weights and high functionalities are advanced. As such a secondary battery, a nickel-cadmium battery, a nickel-hydrogen battery, a nickel-zinc battery, a lithium secondary battery, etc. are used, for example. Among these, lithium secondary batteries have been used in many fields because of their advantages such as small size and large size, high operating voltage, and high energy density per unit weight.

The secondary battery uses a rigid packaging material such as, for example, a metal square, as a method of bringing the positive electrode and the negative electrode into close contact with each other. Without the packaging material, the electrodes are peeled off and it is difficult to maintain the electrical connection between the electrodes through the separator, and the battery performance is reduced (see Korean Patent Application Laid-Open No. 10-2013-0099543). In addition, due to such an exterior material, the weight and volume of the entire battery are increased, and the shape of the battery is limited due to the rigidity, which makes it difficult to manufacture any shape.

Accordingly, it is possible to manufacture a shape in any shape by maintaining the shape without an exterior material, and there is a need to provide a rechargeable battery with reduced weight and increased energy density.

In the present invention, the shape of the secondary battery can be maintained even without a rigid exterior material, and can be used in any form. The secondary battery has a strong adhesive strength between the positive electrode or the negative electrode and the separator, without increasing the ion conductivity resistance between the electrodes. And to provide a method of manufacturing the same.

According to an embodiment of the present invention, a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; Electrolyte solution; And a separator disposed between the anode and the cathode,

The separator includes a porous adhesive layer having a plurality of pores adhered to the anode or the cathode, the pore of the porous adhesive layer contains an electrolyte solution,

The porous adhesive layer is provided with a secondary battery comprising an acrylate-acetate copolymer.

According to another example of the present invention, a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; Electrolyte solution; And a separator disposed between the anode and the cathode,

The separator includes a porous adhesive layer having a plurality of pores adhered to the cathode or the anode, and the separator provides a secondary battery having a transfer rate of at least 75% of the cathode or anode active material of Formula 1, respectively.

[Equation 1]

Transfer rate (%) = (A ₁ / A ₀ ) X 100

In Equation 1, A ₀ is the total area of the negative electrode or the positive electrode, A ₁ forms an electrode assembly in which the positive electrode, the separator and the negative electrode are sequentially stacked and at a temperature of 20 ℃ to 110 ℃, for 1 second to 5 seconds, First crimping with a force of 1 kgf / cm ² to 30 kgf / cm ² , injecting an electrolyte solution into the pressed electrode assembly, 60 ° C. to 110 ° C., 30 seconds to 180 seconds, and 1 kgf / cm ² to 30 kgf / It is the area of the positive electrode or negative electrode active material transferred to the separator after the second pressing with a force of cm ² .

According to another example of the present invention, a positive electrode is formed by forming a positive electrode active material layer on a positive electrode current collector, a negative electrode is prepared by forming a negative electrode active material layer on a negative electrode current collector, and a separator is disposed between the positive electrode and the negative electrode. After the secondary battery is pressed at a pressure of 1 kgf / cm ² to 30 kgf / cm ² for 1 second to 5 seconds at 20 to 110 ℃, and a secondary battery comprising injecting an electrolyte solution to the laminated structure of the cathode / separator / cathode A method for producing is provided.

Secondary battery according to one embodiment of the present invention can be maintained in any shape without having a rigid outer material can be used in any shape and excellent in shape stability, between the positive or negative electrode and the separator without increasing the ion conductivity resistance between the electrodes Each has strong adhesive force and has high efficiency charge and discharge characteristics.

1 is a cross-sectional view of a part of a secondary battery according to an embodiment of the present invention, wherein the secondary battery 200 includes a positive electrode 6 having a positive electrode active material layer 5 formed on a positive electrode current collector 4; A negative electrode 12 having a negative electrode active material layer 10 formed on the negative electrode current collector 11; And a separator 9 disposed between the positive electrode 6 and the negative electrode 12 and bonded to the positive electrode or the negative electrode, respectively.

2 is a perspective view of a secondary battery according to an embodiment of the present invention, wherein the secondary battery 200 includes a positive electrode 6; Cathode 12; And a separator 9 disposed between the positive electrode 6 and the negative electrode 12 and bonded to the positive electrode or the negative electrode, respectively, in the case 50 together with the sealing member 40.

3 is a cross-sectional view of a part of a secondary battery according to another embodiment of the present invention, the secondary battery comprising: a positive electrode 6 having a positive electrode active material layer 5 formed on a positive electrode current collector 4; A negative electrode 12 having a negative electrode active material layer 10 formed on the negative electrode current collector 11; And a separator 9 disposed between the anode 6 and the cathode 12 and bonded to the anode or the cathode, respectively, and including a porous substrate 8 and a porous adhesive layer 7 formed on one surface of the porous substrate. do.

Hereinafter, the present invention will be described in more detail. The content not described in the present specification may be sufficiently recognized and inferred by those skilled in the art or similar fields of the present invention, and thus description thereof is omitted.

The transfer rate of the negative electrode active material or the positive electrode active material in the separator herein refers to the percentage of the area of the negative electrode or positive electrode active material transferred to the separator based on the area of the positive electrode or the negative electrode when the prepared secondary battery is disassembled in the order of negative electrode-separation membrane-anode-separation membrane. it means. The transfer rate of the negative electrode active material or the positive electrode active material in the separator of 75% or more shows that the shape stability is improved by maintaining the integrated form of the positive electrode / membrane / cathode in the actual secondary battery environment.

Hereinafter, a rechargeable battery according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 2.

Referring to FIG. 1, the secondary battery 200 according to the present embodiment includes a positive electrode 6 having a positive electrode active material layer 5 formed on a positive electrode current collector 4; A negative electrode 12 having a negative electrode active material layer 10 formed on the negative electrode current collector 11; And a separator 9 disposed between the anode 6 and the cathode 12 and bonded to the anode or the cathode, respectively. The separator 9 may include a porous substrate 8 and a porous adhesive layer 7, 7 ′ formed on the porous substrate 8. Referring to FIG. 2, the secondary battery 200 according to the present embodiment includes an electrode assembly wound between a cathode 6 and an anode 12 with a separator 9 interposed therebetween, and a case 50 in which the electrode assembly is embedded. It includes. The positive electrode 6, the negative electrode 12, and the separator 9 are impregnated with an electrolyte (not shown). Secondary battery according to the present embodiment can maintain the shape even without a separate outer packaging material by disassembling the separator and the negative electrode, or the transfer rate between the separator and the positive electrode is 75% or more during disassembly in the state holding the electrolyte as shown in Equation 1 above, It can have high efficiency charge and discharge characteristics. In addition, since the separator and the positive electrode or the separator and the negative electrode are present in an integrated form without being separated, the electrical connection between the electrodes can be stably maintained through the separator and the degradation of battery performance can be prevented.

The method of measuring the transfer rate is not limited thereto, for example, as follows: An electrode assembly of 7 cm * 6.5 cm is prepared by interposing a separator between the positive electrode and the negative electrode, and at a temperature of 20 ° C. to 110 ° C. for 1 second to 1 second. 5 seconds, first crimped with a force of 1 kgf / cm ² to 30 kgf / cm ² , placed in a case, for example an aluminum coated pouch (8 cm * 12 cm), and sealing two adjacent corners at a temperature of 143 ° C. Add 6.5 g of electrolyte. Thereafter, the sealing is performed so that no air is left in the battery using a degassing machine for at least 3 minutes, and the prepared battery is aged for 10 hours to 30 hours, specifically 12 hours or 24 hours, and 20 to 25 ° C. After secondary compression at a pressure of 1 kgf / cm ² to 30 kgf / cm ² for 30 seconds to 180 seconds at 30 ° C. to 110 ° C., the battery is dismantled to measure the area of the negative electrode or positive electrode active material transferred to the separator. The area of the positive or negative electrode active material may be taken by a known image analyzer (eg, lumenera high resolution camera) and measured using an area calculation program (eg, Easy Measure converter 1.0.0.4). This is not restrictive.

In the separator of the secondary battery disclosed in this embodiment, the transfer rate of the negative electrode active material or the positive electrode active material may be 75% or more, respectively. Specifically, the transfer rate of the negative electrode active material or the positive electrode active material may be 80% or more, and more specifically, the transfer rate of the negative electrode active material or the positive electrode active material may be 90% or more, respectively. In one example, the transfer rate of the negative electrode active material may be 90% or more, and the transfer rate of the positive electrode active material may be 98% or more.

Subsequently, referring to FIG. 1, the separator 9 may include a porous substrate 8 and porous adhesive layers 7 and 7 ′ containing acrylate-acetate copolymers formed on both surfaces of the porous substrate.

As the porous substrate 8, those having a plurality of pores and which can be used for an electrochemical device can be used. Non-limiting examples of porous substrates include polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyether Formed of any one polymer selected from the group consisting of mid, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide and polyethylene naphthalene or mixtures of two or more thereof It may be a polymer film. 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 to 15 μm. When using the 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 adhesive layers 7 and 7 'may be formed of an adhesive layer composition, and the adhesive layer composition may include an organic binder and a solvent.

Specifically, the organic binder may be an acrylate-acetate copolymer, and may be, for example, an acrylic copolymer including a (meth) acrylate-based monomer-derived repeating unit and an acetate group-containing monomer-derived repeating unit. When the acrylic copolymer having a (meth) acrylate-based monomer-derived repeating unit and an acetate group-containing monomer-derived repeating unit is used as a binder, a separate adhesive may be obtained due to strong adhesion to a positive electrode or a negative electrode in a secondary battery, which is an environment in which a separator is actually used. The shape can be maintained even without a rigid exterior material. In addition, since the porous adhesive layer retains the electrolyte solution, good ionic conductivity between electrodes can be maintained, and porosity of the base film may not be impaired. Glass transition temperature (Tg) of the acrylic copolymer may be in the range of less than 100 ℃, for example, 20 to 60 ℃, specifically 30 to 45 ℃. Within this range, the separator may be positioned between the electrodes to form good adhesion at a temperature at which the separator is compressed, thereby ensuring shape stability. The acrylic copolymer having a (meth) acrylate-based monomer-derived repeating unit and an acetate group-containing monomer-derived repeating unit which can be used in the present embodiment is particularly suitable as long as it can form a good adhesive force at a temperature pressed between the anode and the cathode. For example, but not limited to, the acrylic copolymer is one or more selected from the group consisting of butyl (meth) acrylate, propyl (meth) acrylate, ethyl (meth) acrylate and methyl (meth) acrylate (meth) ) And a copolymer produced by polymerizing an acrylate-based monomer with at least one acetate group-containing monomer selected from the group consisting of vinyl acetate and allyl acetate.

The acetate group-containing monomer-derived repeating unit may be a repeating unit of Formula 1:

[Formula 1]

In Formula 1, R ₁ is a single bond, linear or branched alkyl having 1 to 6 carbon atoms, R ₂ is hydrogen or methyl, and l is an integer between 1 and 100, respectively.

For example, the acetate group-containing monomer-derived repeating unit may be a repeating unit derived from an acetate group-containing monomer selected from at least one selected from the group consisting of vinyl acetate and allyl acetate.

The acrylic copolymer is a (meth) acrylate monomer and an acetate group-containing monomer, for example, vinyl acetate and / or allyl acetate in a molar ratio of 3: 7 to 7: 3, specifically 4: 6 to 6: 4 More specifically, by polymerization in a ratio of about 5: 5. The acrylic copolymer may be, for example, a butyl (meth) acrylate monomer, a methyl (meth) acrylate monomer, and a vinyl acetate and / or allyl acetate monomer in a molar ratio of 3 to 5: 0.5 to 1.5: 4 to 6, specifically In addition, it can be prepared by polymerization reaction in a molar ratio of 4: 1: 5.

The thickness of the porous adhesive layers 7 and 7 ′ may be 1 μm to 15 μm, specifically 1 to 10 μm, more specifically 1 to 8 μm and 1 μm to 5 μm. In the case of using the porous adhesive layer within the thickness range, it is possible to obtain an excellent thermal stability and adhesion by forming a porous adhesive layer of an appropriate thickness, and to prevent the internal resistance of the battery from increasing by preventing the thickness of the entire separator from being too thick. Can be.

Non-limiting examples of the solvent include acetone, dimethyl formamide, dimethyl sulfoxide, dimethyl acetamide, dimethyl carbonate or N-methylpyrrolidone (N- methylpyrrolydone), and the like. The content of the solvent may be 20 to 99% by weight, specifically 50 to 95% by weight, and more specifically 70 to 95% by weight based on the weight of the adhesive layer composition. When the solvent is contained in the above range, the preparation of the adhesive layer composition may be facilitated, and the drying process of the porous adhesive layer may be smoothly performed.

Hereinafter, a secondary battery according to another embodiment of the present invention will be described. Secondary battery according to another embodiment of the present invention is substantially a secondary battery according to an embodiment of the present invention described above, except that the porous adhesive layer may be formed from an adhesive layer composition comprising an organic binder, inorganic particles and a solvent. Since the same configuration as described above will be described with respect to the inorganic particles. In this embodiment, the porous adhesive layer may include inorganic particles, and thus may be effective in forming excellent pores in the porous adhesive layer.

The inorganic particles are not particularly limited, and inorganic particles commonly used in the art may be used. Non-limiting examples of the inorganic particles usable in the present invention include Al ₂ O ₃ , SiO ₂ , B ₂ O ₃ , Ga ₂ O ₃ , TiO ₂ , SnO ₂ , and the like. These can be used individually or in mixture of 2 or more types. As the inorganic particles used in the present invention, for example, Al ₂ O ₃ (alumina) can be used. The size of the inorganic particles used in the present invention is not particularly limited, but the average particle diameter may be 1 nm to 2,000 nm, for example, 100 nm to 1,000 nm, 100 nm to 500 nm. In the case of using the inorganic particles in the size range, it is possible to prevent the dispersibility of the inorganic particles in the adhesive layer composition and the fairness of the formation of the adhesive layer to be lowered, and the thickness of the porous adhesive layer is appropriately adjusted to reduce the mechanical properties and the electrical resistance. The increase can be prevented. In addition, the size of the pores generated in the separator is appropriately adjusted, there is an advantage that can lower the probability of the internal short circuit occurs during the charge and discharge of the battery. In preparing the adhesive layer composition, the inorganic particles may be used in the form of an inorganic dispersion in which it is dispersed in a suitable solvent. The appropriate solvent is not particularly limited and may be a solvent commonly used in the art. Acetone can be used as a suitable solvent for dispersing the inorganic particles, for example. The inorganic dispersion may be prepared by a conventional method without any particular limitation. For example, Al ₂ O ₃ may be added to acetone in an appropriate amount, and the inorganic dispersion may be milled and dispersed using a bead mill. Dispersions can be prepared. The inorganic particles in the porous adhesive layer may be included in 70 to 99% by weight, specifically 75 to 95% by weight, more specifically 80 to 90% by weight based on the total weight of the porous adhesive layer. When the inorganic particles are contained within the above range, the heat dissipation characteristics of the inorganic particles may be sufficiently exhibited, and when the adhesive layer is formed using the separator, heat shrinkage of the separator may be effectively suppressed.

Hereinafter, a rechargeable battery according to still another embodiment of the present invention will be described. The secondary battery according to the present embodiment may further include other types of organic binders in addition to the acrylic copolymer described above as the organic binder in the porous adhesive layer of the separator. The porous adhesive layer and the adhesive layer composition according to the present embodiment are distinguished from the embodiment of the present invention in that another binder is added in addition to the above-described acrylic copolymer. By including another binder in addition to the acrylic copolymer, the adhesive force and heat resistance can be further improved. This will be described below with reference to other binders added.

Examples of binders that may be added in addition to the acrylic copolymers include polyvinylidene fluoride (PVdF) homopolymers, polyvinylidene fluoride-hexaxapropylene (Polyvinylidene fluoride-Hexafluoropropylene copolymers, PVdF-HFP), Polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene oxide, cellulose acetate, cellulose acetate butyl Cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethyl sucrose cyanoethylsucrose) grass Is (pullulan), there may be mentioned carboxymethyl cellulose, alone or a mixture thereof selected from the group consisting of (carboxyl methyl cellulose), and styrene-butadiene-acrylonitrile copolymer (acrylonitrilestyrene-butadiene copolymer). The weight ratio of the acrylic copolymer and the added binder is 9: 1 to 5: 5, specifically 8.5: 1.5 to 5: 5, 8: 2 to 5: 5, and more specifically 7: 3 to 5: 5 Can be. For example, when the PVdF-based binder is further included, the PVdF-based binder may have a weight average molecular weight (Mw) of 500,000 to 1,500,000 (g / mol). In embodiments, the PVdF-based binder may have a weight average molecular weight (Mw) of 100,000 to 1,500,000 (g / mol). In another example, two or more kinds having different weight average molecular weights may be used in combination. For example, one or more types of weight average molecular weights of 1,000,000 g / mol or less and one or more types of 1,000,000 g / mol or more can be mixed and used. The use of the PVdF-based binder within the above molecular weight range enhances the adhesion between the porous adhesive layer and the porous substrate, thereby effectively suppressing thermal shrinkage of the porous substrate, for example, the polyolefin-based substrate, which is weak to heat, and also impregnates the electrolyte. It is possible to produce a sufficiently improved separator and there is an advantage that can produce a battery that uses an efficient electrical output by using this.

Hereinafter, a rechargeable battery according to another exemplary embodiment of the present invention will be described with reference to FIG. 3. The secondary battery according to the embodiment includes a positive electrode 6 having a positive electrode active material layer 5 formed on a positive electrode current collector 4; A negative electrode 12 having a negative electrode active material layer 10 formed on the negative electrode current collector 11; And a separator 9 disposed between the positive electrode 6 and the negative electrode 12 and adhered to the positive electrode or the negative electrode. The separator 9 may include a porous substrate 8 and a porous adhesive layer 7 formed on one surface of the porous substrate 8. Since the secondary battery of the present embodiment differs only in that the secondary battery and the porous adhesive layer of the embodiment with reference to FIG. 2 are formed on one side of the porous substrate rather than both sides, the description of the above-described secondary battery may be applied to the present embodiment as it is.

The separator of the secondary battery according to the embodiments of the present invention may have a ventilation of 500 sec / 100cc or less, specifically 50 to 400 sec / 100cc, and more specifically 50 to 300 sec / 100cc. In addition, the tensile strength of the separator in the MD direction may be 1750 kg / cm ² or more, and the tensile strength in the TD direction may be 1700 kg / cm ^{2 or} more. The tensile strength of the separator in the MD direction may be 1750 kg / cm ² to 2550 kg / cm ^2, and the tensile strength in the TD direction may be 1700 kg / cm ² to 2500 kg / cm ² . Therefore, the separator according to the embodiments of the present invention has excellent adhesiveness and excellent mechanical properties without deteriorating air permeability.

A secondary battery according to embodiments of the present invention includes a positive electrode including a positive electrode active material; A negative electrode including a negative electrode active material; Electrolyte solution; And a separator disposed between the positive electrode and the negative electrode, wherein the separator includes a porous adhesive layer having a plurality of pores adhered to the positive electrode or the negative electrode, wherein the separator is a separator of the positive electrode or the negative electrode active material of Formula 1 as a separator. The transcription rate may each be at least 75%.

[Equation 1]

Transfer rate (%) = (A ₁ / A ₀ ) X 100

Hereinafter, a method of manufacturing a secondary battery according to an embodiment of the present invention will be described. In the method of manufacturing a secondary battery according to an embodiment of the present invention, a positive electrode is formed by forming a positive electrode active material layer on a positive electrode current collector, a negative electrode is formed by forming a negative electrode active material layer on a negative electrode current collector, and the positive electrode and The separator is disposed between the cathodes, and then compressed under a pressure of 1 kgf / cm ² to 30 kgf / cm ² at 20 to 110 ° C. for 1 second to 5 seconds, and an electrolyte solution is injected into the laminated structure of the compressed anode / separator / cathode. It may include doing.

The positive electrode or negative electrode constituting the secondary battery of the present invention can be produced in a form in which an electrode active material is bound to an electrode current collector by a method commonly used in the technical field of the present invention.

The positive electrode active material that can be used in the examples of the present invention is not particularly limited, and a positive electrode active material commonly used in the art may be used. Non-limiting examples of the positive electrode active material include lithium manganese oxide, lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or a lithium composite oxide in combination thereof.

The negative electrode active material that can be used in the examples of the present invention is not particularly limited, and may be a negative electrode active material commonly used in the art.

Non-limiting examples of the negative electrode active material include lithium adsorption materials such as lithium metal or lithium alloy, carbon, petroleum coke, graphite, activated carbon, graphite or other carbons, and the like. Can be.

The electrode current collector that can be used in the examples of the present invention is not particularly limited, and an electrode current collector commonly used in the art may be used.

Non-limiting examples of the positive electrode current collector material of the electrode current collector may be a foil made of aluminum, nickel or a combination thereof. Non-limiting examples of the negative electrode current collector material of the electrode current collector may be a foil produced by copper, gold, nickel, copper alloy or a combination thereof.

The electrolyte solution used in the present invention is not particularly limited, and the electrolyte solution for a secondary battery commonly used in the technical field of the present invention may be used.

The electrolyte solution may be one in which a salt having a structure such as A ⁺ B ⁻ is dissolved or dissociated in an organic solvent. Non-limiting examples of A ⁺ include a cation consisting of an alkali metal cation such as Li ⁺ , Na ⁺ or K ⁺ , or a combination thereof. The B ^- Non-limiting examples of _{^{_{^{the, PF 6 -, BF 4 -}}}} , Cl -, Br -, I -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF ₃ SO _{₂₎ 2} ^- or _{_{_{C (CF 2 SO 2) 3}}} - anions, such as, or may be an anion consisting of a combination thereof. Non-limiting examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate DPC), dimethyl sulfoxide Acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC) or gamma-butyrolactone (-Butyrolactone ), And the like. These may be used alone or in combination of two or more thereof.

The separator that can be used in the production of the secondary battery of the present invention is a binder comprising an acrylic copolymer having a repeating unit derived from a (meth) acrylate monomer and a repeating unit derived from an acetate group-containing monomer such as vinyl acetate or allyl acetate monomer. Porous adhesive layer comprising a, may be formed on one side or both sides of the porous substrate. By using the binder containing the acrylic copolymer as described above, it is possible to maintain an integrated form of the anode / separator / cathode even in a secondary battery including an electrolyte by exhibiting excellent adhesive strength when heated and pressurized in a stack structure of the cathode / separator / cathode. . The acrylic copolymer disclosed herein may be present at 7% or more, specifically 10% or more, more specifically 12 to 90% based on the total solid weight of the porous adhesive layer.

The porous adhesive layer of the separator may be formed from an adhesive layer composition, and the adhesive layer composition may be formed by adding a binder and a solvent including an acrylic copolymer, or adding inorganic particles thereto, and stirring at 10 to 40 ° C. for 30 minutes to 5 hours. It may include doing. At this time, the content of solids may be 10 to 20 parts by weight with respect to the adhesive layer composition, when the inorganic particles, the weight ratio of the binder and the inorganic particles may be 3: 7 to 0.5: 9.5.

Alternatively, an inorganic dispersion in which the inorganic particles are dispersed in a dispersion medium may be prepared, and then mixed with a polymer solution containing a binder and a solvent including an acrylic copolymer to prepare an adhesive layer composition. When the inorganic dispersion is prepared separately as described above, the dispersibility and crude liquid stability of the inorganic particles and the binder may be improved. Therefore, in another embodiment, in preparing the adhesive layer composition of the present invention, the binder component and the inorganic particles may be prepared and mixed in a dissolved or dispersed state in a suitable solvent, respectively.

For example, an acrylic copolymer, a polyvinylidene fluoride homopolymer, and / or a polyvinylidene fluoride-hexafluoropropylene copolymer are prepared by dissolving each in an appropriate solvent, and an inorganic dispersion in which inorganic particles are dispersed. The adhesive layer compositions can then be prepared by mixing them with a suitable solvent. A ball mill, a beads mill, a screw mixer, or the like may be used for the mixing.

Subsequently, a porous adhesive layer is formed of one or both surfaces of the porous substrate using the adhesive layer composition.

The method of forming the porous adhesive layer on the porous substrate using the adhesive layer composition is not particularly limited, and methods commonly used in the technical field of the present invention, for example, a coating method, lamination, coextrusion, and the like. Can 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 adhesive layer of the separator of the present invention may be formed by, for example, a dip coating method.

In the present invention, the porous adhesive layer may be dried by hot air, hot air, low wet air, vacuum drying, or a method of irradiating far infrared rays or electron beams. And the drying temperature is different depending on the type of the solvent, it 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 embodiments, it may be dried for 1 minute to 30 minutes, or 1 minute to 10 minutes at a temperature of 90 to 120 ℃.

After placing the separator prepared by the above method between the positive electrode and the negative electrode at 20 to 110 ℃ pressed for 1 second to 5 seconds under a pressure of 1kgf / cm ² to 30 kgf / cm ² , the acrylic copolymer of the present application Formability of the secondary battery may be improved by forming strong adhesion with the positive electrode or the negative electrode. The crimping conditions are 4 kgf / cm ² to 20 kgf for 1 second to 5 seconds at room temperature (20 to 30 ° C.) or 80 to 100 ° C, in consideration of the temperature at which the thermal contraction of the substrate is not significant when the porous substrate of the separator is polyolefin-based. It may be to apply a pressure of / cm ² .

In another example, a method of manufacturing a secondary battery includes injecting an electrolyte into the laminated structure of the compressed cathode / separator / cathode and applying a pressure of 1 kgf / cm ² to 30 kgf / cm ² at 60 to 110 ° C. for 30 seconds to 180 seconds. Secondary compression may further comprise.

In another example, a method of manufacturing a secondary battery may further include storing an electrolyte solution in a range of 10 to 30 ° C. for 6 hours to 48 hours after injecting an electrolyte solution into the laminated structure of the first compressed cathode / separation membrane / cathode. . Secondary compression may be performed on the stored secondary battery at a pressure of 1 kgf / cm ² to 30 kgf / cm ² for 30 seconds to 180 seconds at 60 to 110 ° C.

Specifically, the secondary battery of the present invention may be a lithium secondary battery such as a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.

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

실시예 Example

제조예 1: 분리막의 제조Preparation Example 1 Preparation of Separator

Butyl methacrylate (BMA), methyl methacrylate (MMA), vinyl acetate (Vinyl Acetate, VAc) polymerized acrylic copolymer binder (Tg: 35 ° C) at a 4/1/5 molar ratio , Mw: 600K (GPC)) was dissolved in acetone (acetone) in a solid content of 10% by weight and stirred for 2 hours at 40 ℃ using a stirrer to prepare a first binder solution. PVdF-based binder KF9300 (Kurehasa, Mw: 1,000,000 ~ 1,200,000 g / mol) was dissolved in acetone, DMAc mixed solvent to 7% by weight solid solution, and stirred for 2 hours at 40 ℃ using a stirrer to prepare a second binder solution It was. An alumina dispersion was prepared by adding alumina (LS235, Nippon Light Metal) to acetone at 25% by weight, followed by bead mill dispersion at 25 ° C. for 2 hours. The first and second binder solutions and the alumina dispersion were mixed so that the weight ratio of the acrylic binder and the PVdF-based binder was 8/2, and the binder solid content and the alumina solid content were 1/5 weight ratio, and the total solid content was 10% by weight. Acetone was added to prepare an adhesive layer composition. 12 μm in thickness was coated on both sides of the polyethylene fabric (W scope) with the adhesive layer composition, each having a thickness of 2 μm to prepare a separator having a total thickness of about 16 μm.

제조예 2: 분리막의 제조Preparation Example 2 Preparation of Separator

5 wt% solution in which an acrylic binder in which butyl methacrylate (BMA), methyl methacrylate (MMA) and vinyl acetate (VAc) was polymerized at a 4/1/5 molar ratio was dissolved in acetone, and PVdF binder 5130 ( Solvay, Mw: 1,000,000 to 1,200,000 g / mol) was prepared in a 10% by weight solution in which acetone and DMAc mixed solvent were dissolved. Alumina dispersion was prepared by adding alumina (LS235, Nippon Light Metal) to acetone at 25% by weight and dispersing the beads for 3 hours. The binder solution and the alumina dispersion were mixed so that the weight ratio of the acrylic binder and the 5130 binder was 7/3, the binder solid content and the alumina solid content were 1/6 weight ratio, and acetone was added so that the total solid content was 10% by weight. An adhesive layer composition was prepared. A separator having a total thickness of about 16 μm was prepared using the above adhesive layer composition on both sides of a polyethylene cloth having a thickness of 12 μm (W scope).

제조예 3: 분리막의 제조Preparation Example 3 Preparation of Separator

5 wt% solution of an acrylic binder in which butyl methacrylate (BMA), methyl methacrylate (MMA) and vinyl acetate (VAc) were polymerized at a 4/1/5 molar ratio in acetone, and a PVdF binder KF9300 7 wt% solution dissolved in acetone, DMAc mixed solvent, PVdF-HFP binder (21216 (Solbay), weight average molecular weight: 500,000-700,000 g / mol) were prepared in 10 wt% solution dissolved in acetone, respectively. Alumina dispersion was prepared by adding alumina (LS235, Nippon Light Metal) to acetone at 25% by weight and dispersing the beads for 3 hours. The binder solution and the alumina dispersion were mixed so that the weight ratio of the acrylic binder and the KF9300, 21216 binder was 5/3/2, and the binder solid content and the alumina solid content were 1/5 weight ratio, and the total solid content was 10% by weight. Acetone was added to prepare an adhesive layer composition. A separator having a total thickness of about 16 μm was prepared using the above adhesive layer composition on both sides of a polyethylene cloth having a thickness of 12 μm (W scope).

제조예 4: 분리막의 제조Preparation Example 4 Preparation of Separator

In Preparation Example 1, the weight ratio of the acrylic binder and PVdF-based binder 9300 was 7/3, and the same procedure as in Preparation Example 1 except that the binder solid content and the alumina solid content were 1/6 weight ratio. A separator having a total thickness of about 16 μm was prepared.

제조예 5: 분리막의 제조Preparation Example 5 Preparation of Separator

In Preparation Example 1, except for producing a membrane having a total thickness of about 14 ㎛ by coating a thickness of 2 ㎛ with an adhesive layer composition on one side of the polyethylene fabric (W scope) having a thickness of 12 ㎛ (W scope) The same process as in the preparation of the separator formed with a porous adhesive layer on only one surface.

비교제조예 1: 분리막의 제조Comparative Production Example 1: Preparation of Separator

A 7 wt% solution in which KF9300, a PVdF-based binder, was dissolved in acetone and DMAc mixed solvent, and a 10 wt% solution, in which 21216 binder was dissolved in acetone, were prepared. Alumina dispersion was prepared by adding alumina (LS235, Nippon Light Metal) to acetone at 25% by weight and dispersing the beads for 3 hours. The binder solution and the alumina dispersion were mixed such that the weight ratio of the above KF9300 and 21216 binders was 5/5, the binder solids and the alumina solids were 1/4 weight ratio, and the adhesive layer was added with acetone so that the total solids was 11% by weight. The composition was prepared. A separator having a total thickness of about 16 μm was prepared using an adhesive layer composition having a thickness of 12 μm polyethylene fabric (W scope).

비교제조예 2: 분리막의 제조Comparative Preparation Example 2: Preparation of Separator

In Preparation Example 1, instead of the acrylic copolymer in which butyl methacrylate (BMA), methyl methacrylate (MMA), and vinyl acetate (Vinyl Acetate, VAc) were polymerized with an acrylic binder, Methyl methacrylate-co-ethyl acrylate) was added to acetone in a solid content of 10% by weight and the same procedure as in Preparation Example 1 was carried out in the same manner as in Preparation Example 1 except that the mixture was stirred at 40 ° C for 4 hours using a stirrer. A degree of separation membrane was produced.

비교제조예 3: 분리막의 제조Comparative Production Example 3 Preparation of Separator

In Preparation Example 1, polybutyl instead of an acrylic copolymer in which butyl methacrylate (BMA), methyl methacrylate (MMA) and vinyl acetate (Vinyl Acetate, VAc) were polymerized with an acrylic binder. Except that the methacrylate was added to acetone in a solid content of 10% by weight and the mixture was stirred at 40 ° C for 4 hours using a stirrer, the same procedure as in Preparation Example 1 was carried out to prepare a separator having a total thickness of about 16 μm.

The composition of each membrane coating according to Preparation Examples 1 to 5 and Comparative Preparation Examples 1 to 3 is shown in Table 1 below.

Table 1

	Fabric / thickness (㎛)	Binder composition
Preparation Example 1	PE / 12	Acrylic-Acetate Copolymer / PVdF-Based Binder, 80/20%	BMA + MMA + VAc
Preparation Example 2	PE / 12	Acrylic-Acetate Copolymer / PVdF Type Binder, 70/30%	BMA + MMA + VAc
Preparation Example 3	PE / 12	Acrylic-Acetate Copolymer / PVdF Binder + PVdF-HFP, 50/50%	BMA + MMA + VAc
Preparation Example 4	PE / 12	Acrylic-Acetate Copolymer / PVdF Type Binder, 70/30%	BMA + MMA + VAc
Preparation Example 5	PE / 12	Acrylic-Acetate Copolymer / PVdF-Based Binder, 80/20%	BMA + MMA + VAc
Comparative Production Example 1	PE / 12	PVdF binder, 100%
Comparative Production Example 2	PE / 12	PMMAEA / PVdF binder, 80/20%
Comparative Production Example 3	PE / 12	PBMA / PVdF binder, 80/20%

실시예Example

실시예 1: 이차 전지의 제조Example 1 Fabrication of Secondary Battery

As a positive electrode active material, LCO (LiCoO 2) was coated on both sides of an aluminum foil having a thickness of 14 μm with a thickness of 94 μm, dried, and rolled to prepare a positive electrode having a total thickness of 108 μm. As the negative electrode active material, natural graphite and artificial graphite (1: 1) were coated on both sides of a copper foil having a thickness of 8 μm at 120 μm, dried, and rolled to prepare a negative electrode having a total thickness of 128 μm. As electrolyte, 1.5M LiPF6 mixed with organic solvent of EC / EMC / DEC + 0.2% LiBF4 + 5.0% FEC + 1.0% VC + 3.00% SN + 1.0% PS + 1.0% SA (PANAX ETEC CO., LTD.) Was used.

The separator prepared in Preparation Example 1 was wound between 7 cm * 6.5 cm electrode assemblies between the positive electrode and the negative electrode. After pressing the electrode assembly at 100 ° C. under a pressure of 9 kgf / cm ² for 3 seconds, the electrode assembly was placed in an aluminum coated pouch (8 cm * 12 cm), and the two adjacent corners were sealed at a temperature of 143 ° C., and 6.5 g of the electrolyte was added thereto. The degassing machine was used to seal the air in the battery for at least 3 minutes. The secondary battery of Example 1 was prepared by aging the prepared battery at 25 ° C. for 12 hours and then pressing it at 100 ° C. for 30 seconds at a pressure of 9 kgf / cm ² .

실시예 2: 이차 전지의 제조Example 2: Preparation of Secondary Battery

In Example 1, the secondary battery of Example 2 was prepared in the same manner as in Example 1 except that the separator of Preparation Example 2 was used as the separator.

실시예 3: 이차 전지의 제조Example 3: Fabrication of Secondary Battery

In Example 1, the secondary battery of Example 3 was prepared in the same manner as in Example 1 except that the separator of Preparation Example 3 was used as the separator.

실시예 4: 이차 전지의 제조Example 4: Fabrication of Secondary Battery

In Example 1, the secondary battery of Example 4 was prepared in the same manner as in Example 1 except that the separator of Preparation Example 4 was used as the separator.

실시예 5: 이차 전지의 제조Example 5: Preparation of Secondary Battery

In Example 1, using the separator of Preparation Example 5 as a separator, and replacing the anode on the separator surface on which the porous adhesive layer is formed, the same as in Example 1 except for replacing the cathode on the separator surface without the porous adhesive layer It carried out to manufacture the secondary battery of Example 5.

비교예 1: 이차 전지의 제조Comparative Example 1: Fabrication of Secondary Battery

In Example 1, a secondary battery of Comparative Example 1 was prepared in the same manner as in Example 1 except that the separator of Comparative Preparation Example 1 was used as the separator.

비교예 2: 이차 전지의 제조Comparative Example 2: Fabrication of Secondary Battery

In Example 1, the secondary battery of Comparative Example 2 was prepared in the same manner as in Example 1 except that the separator of Comparative Preparation Example 2 was used as the separator.

비교예 3: 이차 전지의 제조Comparative Example 3: Fabrication of Secondary Battery

In Example 1, the secondary battery of Comparative Example 3 was prepared in the same manner as in Example 1 except that the separator of Comparative Preparation Example 3 was used as the separator.

실험예 Experimental Example

For the secondary batteries prepared in Examples 1 to 5 and Comparative Examples 1 to 3, the active material transfer rate and the cell performance after the cycle were measured by the measurement method disclosed below, and the results are shown in Table 2.

TABLE 2

		Example 1	Example 2	Example 3	Example 4	Example 5	Comparative Example 1	Comparative Example 2	Comparative Example 3
Active material transfer rate (%)	anode	100%	100%	100%	100%	100%	0%	0%	0%
Active material transfer rate (%)	cathode	98%	96%	100%	100%	-	0%	0%	0%
Capacity after 200 cycles (%)		88%	85%	88%	88%	85%	85%	87%	88%

1. Positive or negative electrode active material transfer rate

For each of the secondary batteries prepared in Examples and Comparative Examples, the pouch was cut out and the compressed electrode assembly was taken out and disassembled. After separating and releasing between cathode and separator, disassemble in order of cathode-membrane-anode-membrane.Then, the area where the active material of cathode or anode is transferred to separator and separated is taken by using image analyzer (lumenera high resolution camera). The transferred area was calculated using an image analyzer (Easy Measure converter 1.0.0.4) and calculated as a percentage.

2. Battery Performance Evaluation After Cycle

The battery characteristics of the secondary battery manufactured by the separator prepared in Examples and Comparative Examples obtained a capacity value of 2300 mAh to 2600 mAh at a current value of 1C, the discharge capacity after the charge and discharge of 0.7C 200 times more than 85% As a result, it was confirmed that the cycle characteristics of the battery were not weakened even after the adhesive force was applied.

Claims

A positive electrode including a positive electrode active material;

A negative electrode including a negative electrode active material;

Electrolyte solution; And

A separator disposed between the anode and the cathode;

The separator includes a porous adhesive layer having a plurality of pores adhered to the anode or the cathode,

An electrolyte is contained in the pores of the porous adhesive layer,

The porous adhesive layer is a secondary battery comprising an acrylate-acetate copolymer.
The secondary battery according to claim 1, wherein the acrylate-acetate copolymer includes a repeating unit derived from a (meth) acrylate monomer and a repeating unit derived from an acetate group-containing monomer.
The secondary battery according to claim 1, wherein the glass transition temperature of the acrylate-acetate copolymer is less than 100 ° C.
The secondary battery of claim 1, wherein the porous adhesive layer further includes inorganic particles, and the inorganic particles are 70 to 99 wt% based on the total weight of the porous adhesive layer.
The method of claim 1, wherein the porous adhesive layer is a polyvinylidene fluoride homopolymer, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, poly Vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose And at least one binder selected from the group consisting of acrylonitrile styrene butadiene copolymer.
The repeating unit derived from the (meth) acrylate-based monomer according to claim 2, wherein the repeating unit derived from the group consisting of butyl (meth) acrylate, propyl (meth) acrylate, ethyl (meth) acrylate and methyl (meth) acrylate A secondary battery, which is a repeating unit derived from at least one monomer selected.
The secondary battery according to claim 2, wherein the acrylate-acetate copolymer is prepared by polymerizing a (meth) acrylate monomer and an acetate group-containing monomer in a molar ratio of 3: 7 to 7: 3.
The secondary battery according to any one of claims 1 to 7, wherein a transfer rate of the positive electrode or the negative electrode active material of Formula 1 to the separator is 75% or more, respectively.

[Equation 1]

Transfer rate (%) = (A 1 / A 0 ) X 100

In Formula 1,

A 0 is the total area of the cathode or anode,

A 1 forms an electrode assembly in which the positive electrode, the separator, and the negative electrode are sequentially stacked, and at the temperature of 20 ° C. to 110 ° C. for 1 second to 5 seconds, with a force of 1 kgf / cm 2 to 30 kgf / cm 2 . After pressing, the electrolyte solution is injected into the compressed electrode assembly, and the second electrode is pressed with a force of 1 kgf / cm 2 to 30 kgf / cm 2 for 60 ° C. to 110 ° C., 30 seconds to 180 seconds, and then the anode transferred to the separator. Or the area of the negative electrode active material.
A positive electrode including a positive electrode active material;

A negative electrode including a negative electrode active material;

Electrolyte solution; And

A separator disposed between the anode and the cathode;

The separator includes a porous adhesive layer having a plurality of pores adhered to the anode or the cathode,

The separator is a secondary battery, the transfer rate of the positive electrode or negative electrode active material of Formula 1 to the separator, respectively, 75% or more.

[Equation 1]

Transfer rate (%) = (A 1 / A 0 ) X 100

In Formula 1,

A 0 is the total area of the cathode or anode,

A 1 forms an electrode assembly in which the positive electrode, the separator, and the negative electrode are sequentially stacked, and at the temperature of 20 ° C. to 110 ° C. for 1 second to 5 seconds, with a force of 1 kgf / cm 2 to 30 kgf / cm 2 . After pressing, the electrolyte solution is injected into the compressed electrode assembly, and the second electrode is pressed with a force of 1 kgf / cm 2 to 30 kgf / cm 2 for 60 ° C. to 110 ° C., 30 seconds to 180 seconds, and then the anode transferred to the separator. Or the area of the negative electrode active material.
The secondary battery according to any one of claims 1 to 7, wherein the secondary battery is a lithium secondary battery.