KR101731982B1 - Electrode-separator assembly, secondary battery comprising the same, and manufacturing method thereof - Google Patents

Abstract

electrode; Separation membrane; And an adhesive layer disposed between the electrode and the separator, wherein the adhesive layer is formed of an electrospun polymer fiber, and a secondary battery including the electrode-separator composite.

Description

ELECTRODE SEPARATOR ASSEMBLY, SECONDARY BATTERY COMPRISING THE SAME, AND MANUFACTURING METHOD THEREOF BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode-

The present invention relates to an electrode-separator composite, a secondary battery including the same, and more particularly to an electrode-separator composite including an adhesive layer formed of an electrospun polymer fiber between an electrode and a separator, Battery and a method of manufacturing the same.

The secondary battery has many advantages such as high energy density, high operating voltage, excellent storage and life characteristics, and is widely used in various portable electronic devices such as a personal computer, a camcorder, a portable telephone, a portable CD player and a PDA have.

Generally, a lithium secondary battery includes an electrode assembly accommodated in the case together with a cylindrical or prismatic case and an electrolyte. Here, the electrode assembly is formed by stacking a cathode, a separator and an anode, and has a winding structure or a stack structure of a jelly-roll type.

The electrode assembly composed of the cathode / separator / anode may have a laminated structure. However, it is also possible to stack a plurality of electrodes (cathodes and anodes) with the separator interposed therebetween, have. In this case, the bonding of the electrode and the separator is achieved by heating / pressing the electrode and the adhesive layer applied on the separator in face-to-face relationship. Here, the separation membrane is usually formed by an extrusion process using a polyolefin resin as a raw material, and a material such as a binder is coated to improve characteristics such as adhesion with an electrode.

In order to realize an adhesive layer with a binder, an adhesive layer is formed by dissolving a binder in an organic solvent such as acetone and coating the resultant with an electrode or a separator. In this case, a binder in the form of a polymer copolymer dissolved in an organic solvent is mainly used. However, depending on the content of the monomers to be copolymerized, it is difficult to dissolve in a solvent, so that it is difficult to realize an adhesive layer.

Disclosure of the Invention The present invention addresses the above problems and provides an electrode-separator composite having excellent mechanical strength and high stability including an adhesive layer formed of an electrospun polymer fiber between an electrode and a separator, and a secondary battery having the electrode- .

It is also an object of the present invention to provide an adhesive layer comprising a low weight ratio comonomer unit using electrospinning.

Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

According to an aspect of the present invention, there is provided an electrode-separator composite comprising an electrode, a separator, and an adhesive layer provided between the electrode and the separator, wherein the adhesive layer is formed of an electrospun polymer.

The separation membrane may include a porous polymer base material or a porous polymer base material and a porous coating layer formed on at least one surface of the porous polymer base material.

The electrospinning polymer fiber may be a polyvinylidene fluoride-based polymer. The polyvinylidene fluoride-based polymer may contain, in addition to the vinylidene fluoride monomer unit, at least one of hexafluoropropylene, chlorotrifluoroethylene, tetrafluoroethylene, trifluoroethylene, hexafluoroisobutylene, perfluorobutylethylene , Perfluoropropyl vinyl ether, perfluoroethyl vinyl ether, perfluoromethyl vinyl ether, perfluoro-2,2-dimethyl-1,3-dioxol and perfluoro-2-methylene- -1,3-dioxolane. ≪ / RTI >

The weight ratio of the vinylidene fluoride monomer unit and the comonomer unit may be 80:20 to 99.9: 0.1.

The polyvinylidene fluoride-based polymer may be a copolymer including a vinylidene fluoride monomer unit and a hexafluoropropylene monomer unit.

The weight ratio of the vinylidene fluoride monomer unit and the hexafluoropropylene monomer unit may be 90:10 to 99: 1.

The diameter of the electrospun polymer fiber may be 10 to 1,000 nm.

The adhesive layer may be formed on all or a part of both surfaces of the electrode and the separator facing each other

The adhesive layer may have a circular, elliptical or polygonal cross-section.

The adhesive layer may be formed so that both ends of the electrode and the separation membrane can pass through each other.

The electrode may be a cathode or an anode.

The electrode-separator composite may be a cathode-separator composite, an anode-separator composite or a cathode-separator-anode composite.

According to another aspect of the present invention, there is provided a secondary battery including the electrode-separator composite.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode-separator composite, comprising: supplying a spinning solution of a polymer binder to a spinneret; applying a voltage to the polymer binder spinning solution, The polymer binder fibers may be coated on at least one surface of an electrode or a separation membrane to form an adhesive layer; and pressing and bonding the electrode and the separation membrane with the adhesive layer interposed therebetween.

The voltage may be between 10 and 1000 volts.

The bonding step may be carried out by pressing at a pressure of 1 to 100 Pa.

The present invention relates to a PVDF-HFP polymer binder which is used as an adhesive layer through a solution coating and has an HFP content of less than 5%, which is advantageous for cell performance because of a low side reaction, but is poor in solubility and melts only in a polar solvent having a high breaking point. Do. In order to overcome this problem, PVDF-HFP binder having HFP content of less than 5% is coated by electrospinning method rather than solution coating.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to better understand the spirit of the invention. The present invention is not limited thereto.
1 is an example of a cross-sectional view of an electrode-separator composite according to an embodiment of the present invention.
2 is an example of a cross-sectional view of an electrode-separator composite according to an embodiment of the present invention.
3 is an example of a cross-sectional view of an electrode-separator composite according to an embodiment of the present invention.
4 is a flowchart of a method of manufacturing an electrode-separator composite according to another embodiment of the present invention.

Hereinafter, the present invention will be described. The terms and words used in the specification and claims should not be construed to be limited to ordinary or dictionary terms, and the inventor should properly define the concept of the term to describe its own invention in the best way possible. It should be construed as meaning and concept consistent with the technical idea of the present invention. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

According to an aspect of the present invention, there is provided an electrode-separator composite comprising an electrode, a separator, and an adhesive layer provided between the electrode and the separator, wherein the adhesive layer comprises an adhesive layer formed of an electrospun polymeric fiber.

1 is an example of a cross-sectional view of an electrode-separator composite including an electrode 100, a separator 200, and an adhesive layer 300 according to an embodiment of the present invention.

1, an electrode-separator composite according to an embodiment of the present invention includes an electrode 100, a separator 200, and an adhesive layer 300 disposed between the electrode 100 and the separator 200, The adhesive layer 300 is formed of an electrospun polymer fiber.

The electrode used in the present invention may be a cathode or an anode. Accordingly, the electrode-separator composite may be formed of a cathode-separator composite or an anode-separator composite depending on the type of the electrode when one kind of electrode and the separator are bound to each other through an adhesive layer. Further, in addition to the cathode-separator composite or the anode-separator composite, the anode and the cathode may be formed of a cathode-separator-anode composite, respectively, when the anode and the cathode are further bound through the adhesive layer.

The electrode may include an electrode current collector and an electrode active material layer, wherein the electrode current collector is made of stainless steel, aluminum, nickel, titanium, sintered carbon, copper, carbon, nickel, titanium or silver; Aluminum-cadmium alloy or the like can be used.

The anode active material layer may be an anode active material layer or a cathode active material layer. In the case of the anode active material layer, natural graphite, artificial graphite, a carbonaceous material, a lithium-containing titanium composite oxide (LTO) Cd, Ce, Ni or Fe (Me); An alloy composed of the metal (Me); An oxide of the metal (Me) (MeOx); And a composite of the metal (Me) and carbon, and the like.

In the case where the electrode active material layer of the present invention is a cathode active material layer, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiCoPO ₄ , LiFePO ₄ , LiNiMnCoO ₂ and LiNi _{1-x- y z} Co _x M _y M2 _z O ₂ M1 and M2 are independently selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg and Mo; x, y and z are, independently of each other, 0 < y < 0.5, 0 < z &lt; 0.5, and x + y + z &lt; = 1 as atomic fractions of the elements).

2, the separation membrane 200 used in an embodiment of the present invention may further include a porous polymer substrate 210 or a porous coating layer 220 formed on the surface of the porous polymer substrate 210 .

Here, the porous polymer base material may be a porous polymeric film base or a porous polymer nonwoven base.

As well known, a separator made of a porous polymer film made of a polyolefin such as polyethylene or polypropylene can be used as the porous polymer film substrate. Such a polyolefin porous polymer film substrate has a shutdown function at a temperature of, for example, 80 to 130 Lt; / RTI &gt; Such a polyolefin porous polymer film may be obtained by polymerizing polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polyphenylene, such as high density polyethylene, linear low density polyethylene, low density polyethylene and ultra high molecular weight polyethylene, either individually or as a mixture of two or more thereof . In addition, the porous polymeric film substrate may be produced by using various polymers such as polyesters in addition to polyolefin. In addition, the porous polymeric film substrate may have a structure in which two or more layers of a fl ow layer are laminated, and each film layer may be formed of a polymer such as the polyolefin or polyester described above alone or a mixture of two or more thereof It is possible.

The porous polymer nonwoven fabric substrate may be made of a polyolefin-based polymer or a fiber using a polymer such as polyester such as polyethylene terephthalate (PET) having a higher heat resistance. The porous polymer nonwoven substrate may be produced by mixing single fibers or two or more kinds of fibers.

The material and shape of the porous polymer film substrate may be variously selected depending on the purpose.

The thickness of the porous substrate is not particularly limited, but is about 1 to about 100 占 퐉 or about 5 to about 50 占 퐉.

The size and porosity of the pores existing in the porous substrate are also not particularly limited, but may be about 0.001 to about 50 탆 and about 10 to about 95%, respectively.

The porous coating layer may be formed by coating a solution of a binder polymer in which electrochemically stable inorganic particles are dispersed on at least one surface of a porous polymer substrate and drying the same.

The inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles usable in the present invention are not particularly limited as long as oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ) . Particularly, when inorganic particles having a high dielectric constant are used as the inorganic particles, the dissociation of the electrolyte salt, for example, the lithium salt in the liquid electrolyte, can be increased, and the ion conductivity of the electrolyte can be improved.

For the reasons stated above, it is preferable that the inorganic particles include high-permittivity inorganic particles having a dielectric constant of 5 or more, preferably 10 or more. Nonlimiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _{1 -x} La _x Zr _{1 -y} Ti _y O ₃ (PLZT, 0 < , 0 <y <1), Pb (Mg 1/3 Nb 2/3) O 3 -PbTiO 3 (PMN-PT), hafnia _{(HfO 2), SrTiO 3,} SnO 2, CeO 2, MgO, NiO, _{CaO, ZnO, ZrO 2, Y} 2 O 3, Al 2 O 3, boehmite (γ-AlO (OH)) , TiO 2, SiC Or a mixture thereof.

As the inorganic particles, inorganic particles having a lithium ion transferring ability, that is, inorganic particles containing a lithium element but having a function of transferring lithium ions without storing lithium can be used. Non-limiting examples of inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O _5, including (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3) (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5) such as Li _3.25 Ge _0.25 P _0.75 S ₄ ), Li ₃ lithium nitride such as _{N (Li x N y, 0} <x <4, 0 <y <2), Li 3 PO 4 SiS 2 family, such as _{-Li 2 S-SiS 2 glass (} Li x Si _{y S z, 0 <x <} 3, 0 <y <2, 0 <z <4), LiI-Li 2 SP 2 S 5 , etc., such as P ₂ S ₅ based _{glass (Li x P y S z} , 0 <x <3, 0 <y <3, 0 <z <7), or a mixture thereof.

In addition, the average particle diameter of the inorganic particles is not particularly limited, but may be in the range of 0.001 to 10 mu m for the formation of the porous coating layer of uniform thickness and proper porosity.

The binder polymer preferably has a glass transition temperature (T _g ) of -200 to 200 ° C. This improves the mechanical properties such as flexibility and elasticity of the finally formed porous coating layer. It is because.

In addition, the binder polymer does not necessarily have ion conductivity, but the performance of the electrochemical device can be further improved by using a polymer having ion conductivity. Therefore, it is preferable that the binder polymer has a high permittivity constant. In fact, since the dissociation degree of the salt in the electrolyte depends on the permittivity constant of the electrolyte solvent, the higher the permittivity constant of the binder polymer, the better the salt dissociation in the electrolyte. The dielectric constant of such a binder polymer may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), preferably 10 or more.

Non-limiting examples of such a binder polymer include polyvinylidene fluoride-cohexafluoropropylene, polyvinylidene fluoride-cotrichloroethylene, polymethylmethacrylate, Polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide (polyvinylpyrrolidone), polyvinylacetate polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl Polyvinyl Call (cyanoethylpolyvinylalcohol), cyanoethyl cellulose (cyanoethylcellulose), cyanoethyl and the like may be used sucrose (cyanoethylsucrose), pullulan (pullulan) or carboxymethyl cellulose (carboxyl methyl cellulose).

The content ratio of the inorganic particles and the polymeric binder solution constituting the porous coating layer is 50:50 to 99: 1, preferably 60:40 to 99: 1, more preferably 70:30 to 99: 1 to be.

The adhesive layer of the electrode-separator composite according to an embodiment of the present invention is an electrospun polymeric fiber, which bonds the electrode and the separator to improve the stability and heat resistance of the electrode-separator composite.

The electrospun polymer fiber may be formed by electrospinning and may be formed of microfine fiber without limitation. Preferably, the electrospun polymer fiber is made of polyvinylidene fluoride (PVdF) polymer, styrene-butadiene rubber (SBR) Polytetrafluoroethylene (PTFE), polyethylene glycol (PEG), polypropylene glycol (PPG), toluene diisocyanate (TDI), polymethylmethacrylate, But are not limited to, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose (cellulose acetate) acetate, cellulose acetate butyrate, Cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and the like. A carboxyl methyl cellulose, an acrylonitrile-styrene-butadiene copolymer, and a polyimide. In the present invention, it is also possible to use a mixture of two or more selected from the group consisting of polyvinyl alcohol,

Further, non-limiting examples of the polyvinylidene fluoride (PVDF) polymer include vinylidene fluoride monomer units, hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE ), Trifluoroethylene, trichlorethylene (TCE), ethylene, hexafluoroisobutylene, perfluorobutyl ethylene, perfluoropropyl vinyl ether (PPVE), perfluoroethyl vinyl ether (PEVE) (PMD), perfluoro-2,2-dimethyl-1,3-dioxole (PDD) and perfluoro-2-methylene- &Lt; / RTI &gt; and a comonomer unit selected from the group consisting of &lt; RTI ID = 0.0 &gt;

In this case, the weight ratio of the vinylidene fluoride monomer unit and the comonomer unit may be 80:20 to 99.9: 0.1, preferably 95: 5 to 99: 1. This is because when the weight ratio of the comonomer unit is less than 0.1, the crystallinity is high and there is a problem that the solution coating does not dissolve in a solvent having a low boiling point such as acetone. At this time, it dissolves in a polar solvent having a high boiling point such as dimethylacetamide, but since such a solvent corresponds to a solvent unsuitable for use in solution coating, the weight ratio of the comonomer unit may be less than 0.1. Further, when the weight ratio of the comonomer unit is more than 20, the side reaction is increased in the secondary battery and the performance is deteriorated.

In particular, the polyvinylidene fluoride-based polymer is preferably a copolymer comprising a vinylidene fluoride monomer unit and a hexafluoropropylene monomer unit, and the weight ratio of the vinylidene fluoride monomer unit and the hexafluoropropylene monomer unit is May be 80:20 to 99.9: 0.1, preferably 90:10 to 99: 1, more preferably 95: 5 to 99: 1.

Conventionally, in an organic solvent such as acetone When the PVDF polymer binder is used as an adhesive layer for bonding the electrode and the separator after dissolving the PVDF polymer binder, when the amount of the comonomer of the PVDF polymer binder is less than 5 wt%, it is difficult to dissolve in the solvent, There was an unacceptable problem.

To solve this problem, it has been attempted to form an adhesive layer by dissolving a PVDF-based polymer containing less than 5% by weight of a comonomer in a polar solvent such as NMP. However, since a polar solvent such as NMP has a high boiling point, , There is a problem that the stability in the process is lowered and the cost is increased.

However, when the coating is carried out by electrospinning, when the content of the comonomer of the PVDF polymer binder is less than 5% by weight, not only can it be used together with a solvent having a low boiling point such as acetone but also the content of the comonomer is low It is possible to use a PVDF polymer binder having a high crystallinity and a low side reaction, thereby providing a lithium secondary battery exhibiting excellent electrochemical characteristics.

The adhesive layer is a web-shaped polymer fiber extruded by electrospinning, and the diameter of the electrospun polymer fiber is 1 to 1,000 nm, preferably 100 to 500 nm. When the diameter of the polymer fiber exceeds 1,000 nm, there is a problem that the surface area of the polymer fiber decreases in the case of electrospinning on the surface of the porous coating layer of 10000 nm or less to decrease the adhesive force. In order to increase the surface area, There is a problem that the thickness of the adhesive layer relatively increases and the electrical resistance increases. When the diameter of the polymer fibers is less than 1 nm, there arises a problem that the movement of lithium ions is interrupted.

The adhesive layer is formed on the surface of the electrode and the separator facing each other, and may be formed on all or a part of each of the opposite surfaces. In detail, an adhesive layer may be formed on one surface of an electrode or a separator and may be bonded to each other, or an adhesive layer may be formed on both surfaces of the electrode and the separator to bond the adhesive layer and the adhesive layer.

3 (a), 3 (b), and 3 (c) are sectional views showing a state in which the electrode 100 and the separator 200 are separated from each other so as to allow both ends of the electrode and the separator to pass therethrough. As an example of the partitioned formed adhesive layer 300, this facilitates the passage of the metal / metal cations so that the charge / discharge characteristics are improved.

In addition, the cross-section of the adhesive layer is not limited to the shape that the electrospinning polymer fibers can be formed under the pressure when the electrodes and the separator are bonded to each other, but may be circular, elliptical or polygonal.

According to another aspect of the present invention, there is provided a secondary battery including the above-described electrode-separator composite.

The secondary battery includes a cathode, an anode, and a separator interposed between the cathode and the anode. At this time, one of the cathode and the anode has an adhesive layer between the cathode and the anode, Or an anode-separator complex. Further, both the cathode and the anode may be provided with an adhesive layer between the separator and a cathode-separator-anode composite.

In addition, the electrolyte is injected into the secondary battery including the electrode-separator composite, and the electrolyte injection can be performed at an appropriate stage of the battery manufacturing process depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

According to an embodiment of the present invention, the electrolyte is a salt having a structure such as A ⁺ B ^- , wherein A ⁺ includes an ion of an alkali metal cation such as Li ⁺ , Na ⁺ , K ⁺ B ^- is _{^{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 -, _{C (CF 2 SO 2) 3} - anion, or a salt containing an ion composed of a combination of propylene carbonate (PC) such as, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), di (DMP), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone g-butyrolactone) or an organic solvent composed of a mixture thereof, but the present invention is not limited thereto.

According to another aspect of the present invention, there is provided a method of manufacturing an electrode-separator composite including an adhesive layer formed of an electrospun polymer fiber.

4 is a flowchart illustrating a method of manufacturing an electrode-separator composite according to an embodiment of the present invention.

Referring to FIG. 4, the method for manufacturing an electrode-separator composite according to the present invention includes the steps of supplying a polymeric binder spinning solution S10, discharging polymer binder fibers S20, forming an adhesive layer S30, and adhering S40 .

The step (S10) of supplying the polymeric binder spinning solution is a step of supplying the polymeric binder spinning solution to the electrospinning nozzle, wherein the polymeric binder spinning solution is prepared by heating the polymeric binder spinning raw material and melting it, Or by dissolving them.

As described above, the polymeric binder used in the polymeric binder spinning solution may include a polymer such as polyvinylidene fluoride (PVdF), styrene-butadiene rubber (SBR), polytetrafluoroethylene Polytetrafluoroethylene (PTFE), polyethylene glycol (PEG), polypropylene glycol (PPG), toluene diisocyanate (TDI), polymethylmethacrylate, polyacrylonitrile, Polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, polyvinylpyrrolidone, cellulose acetate butyrate, cellulose acetate propionate cetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxylmethyl cellulose (carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, and polyimide, may be used.

In addition, non-limiting examples of the polyvinylidene fluoride (PVDF) polymer include vinylidene fluoride monomer units, hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), tetrafluoroethylene (TFE ), Trifluoroethylene, trichlorethylene (TCE), ethylene, hexafluoroisobutylene, perfluorobutyl ethylene, perfluoropropyl vinyl ether (PPVE), perfluoroethyl vinyl ether (PEVE) (PMD), perfluoro-2,2-dimethyl-1,3-dioxole (PDD) and perfluoro-2-methylene- &Lt; / RTI &gt; and a comonomer unit selected from the group consisting of &lt; RTI ID = 0.0 &gt;

The solvent may be a chlorinated organic solvent such as chloroform, methylene chloride, carbon tetrachloride, dichloromethane, trichloroethane, vinyl chloride, ethylene dichloride, trichlorethylene and tetrachlorethylene, dimethylacetamide (DMAC) At least one of an aliphatic organic solvent, an aromatic organic solvent, an ether, a ketone and an ester, and a mixture thereof, such as an aliphatic organic solvent including 2-dichloromethane, benzene, toluene, carbon tetrachloride, xylene, tetrahydrofuran, hexane, But is not limited thereto.

The polymeric binder spinning solution may contain the polymer binder in an amount of 10 to 30% by weight based on 100% by weight of the total spinning solution, but is not limited thereto. The above contents are the characteristics (molecular weight, molecular structure, glass transition temperature and solubility) of the polymeric binder and the characteristics of the solvent (viscosity, elasticity, concentration, surface tension and conductivity). And may be determined in consideration of process conditions such as electrospinning conditions.

Next, the polymer binder fiber discharging step (S20) is a step of applying voltage to the polymeric binder spinning solution supplied to the electrospinning apparatus to discharge the polymer binder fiber in a fiber form.

Specifically, the polymeric binder spinning solution is connected to an electrospinning nozzle by using a feeding device, and a high electric field (high electric field, ~ 100 kV) is formed between the nozzle and the current collector by using a high voltage generating device to perform electrospinning do. Filaments are radiated from nozzles at high voltage and integrated into a collecting plate positioned at a predetermined distance to form a web. The size of the electric field is related to the distance between the nozzle and the current collector, and the relationship between them is used in combination to facilitate electrospinning.

The electrospinning device to be used at this time is not particularly limited, and a generally used electrospinning device may be used, and an electro-bronzing method or a centrifugal electrospinning method may be used.

According to a specific embodiment of the present invention, the spinning conditions include a spinning voltage of 10 kV to 1000 kV, a spinning distance of 10 cm to 100 cm, and a spinning speed of 0.5 ml / hr to 10 ml / hr. Adjustable. According to the above method, filament fibers having a diameter of less than 1 mu m can be obtained.

The adhesive layer forming step S30 is a step in which the polymeric binder fibers formed through the polymeric binder fiber discharging step S20 form an adhesive layer by coating at least one surface of an electrode or a separation membrane, Alternatively, one surface of the separator may be coated to form a web, or an adhesive layer web may be separately formed and then coated on the surface of the electrode or separator.

In addition, it may further include a rolling step of performing at least one hot rolling or at least one cold rolling after the adhering step (S30). Alternatively, hot rolling and cold rolling may be used in combination of two or more times. According to a specific embodiment, preferably, at least one hot rolling step is carried out. At this time, at least a part of the solvent contained in the adhesive layer web can be removed by the hot rolling.

According to a specific embodiment, the rolling may be performed using a rolling roller. The rolling temperature, the pressure, the contact time of the adhesive layer web and the roller, and the rotational speed of the roller, and may be varied depending on the state of the adhesive layer obtained from the preliminary step and suitable for obtaining an adhesive layer web having properties suitable for the intended use .

The bonding step S40 is a step of pressing and bonding the electrodes and / or the separation layer coated with the adhesive layer on the surface so that the adhesive layer is interposed therebetween. The binding force between the binder polymer fibers constituting the adhesive layer is improved by the pressing, thereby increasing the durability of the secondary battery.

The step of curing the adhesive layer web after the bonding step (S40) may be further performed. In the curing step, the adhesive layer web is dried, and the solvent that has not been removed during the rolling process is additionally removed. In the process according to the present invention, since the solvent is removed in the bonding step (S30), which is the previous step, and a separate drying step is not performed, there is a favorable aspect in the process execution. Further, as the adhesive layer web is dried, the polymeric binder is cured and the physical properties of improving the tensile strength are reinforced. According to a specific embodiment of the present invention, the curing step is performed under heating conditions. As an example of the heating conditions, the temperature can be raised to 300 캜 at a rate of 5 캜 and maintained for 1 hour or more, preferably 3 hours or more. Preferably, the heating can be carried out under constant pressure conditions.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiments according to the present invention can be modified in various other forms, and the scope of the present invention should not be construed as being limited by the above-described embodiments. The embodiments of the present invention are provided to explain the present invention more fully to those skilled in the art.

Preparation of electrode-separator composite

[Example 1]

A polyvinylidene fluoride-hexafluoropropylene copolymer containing 95% by weight of a vinylidene fluoride monomer unit and containing 5% by weight of a hexafluoropropylene monomer unit was melted to prepare a polymer binder spinning solution, which was subjected to electrospinning And injected into a nozzle. Thereafter, a voltage was applied between the electrospinning nozzle and the current collector to perform electrospinning. Polymeric binder fibers were radiated from the electrospinning nozzle at a high voltage, and the surface of the separator disposed on the current collector was coated with the electrospun polymer web Thereby forming an adhesive layer.

90 parts by weight of a lithium cobalt composite oxide as cathode active material particles, 5 parts by weight of carbon black as a conductive material and 5 parts by weight of PVDF as a binder were added to 40 parts by weight of N-methyl-2-pyrrolidone (NMP) A cathode active material slurry was prepared. The cathode active material slurry was applied to an aluminum (Al) thin film of a cathode current collector having a thickness of 100 m, dried, and rolled to produce a cathode.

Then, the prepared cathode was disposed so as to face the separation membrane having the adhesive layer formed thereon, and by applying pressure, the cathode and the separator were bonded to each other to prepare an electrode-separator composite (cathode-separator composite).

[Example 2]

An electrode-separator composite was prepared in the same manner as in Example 1 except that the polyvinylidene fluoride-hexafluoropropylene copolymer contained 96% by weight of a vinylidene fluoride monomer unit and 4% by weight of a hexafluoropropylene monomer unit % &Lt; / RTI &gt;

[Example 3]

The polyvinylidene fluoride-hexafluoropropylene copolymer contained 97 wt% of a vinylidene fluoride monomer unit, and the hexafluoropropylene monomer unit was used in an amount of 3 % &Lt; / RTI &gt;

[Example 4]

The electrode-separator composite was prepared in the same manner as in Example 1 except that the polyvinylidene fluoride-hexafluoropropylene copolymer contained 98% by weight of the vinylidene fluoride monomer unit and 2% by weight of the hexafluoropropylene monomer unit % &Lt; / RTI &gt;

[Example 5]

The polyvinylidene fluoride-hexafluoropropylene copolymer contained 99% by weight of a vinylidene fluoride monomer unit, and the hexafluoropropylene monomer unit was replaced with 1% by weight of a vinylidene fluoride monomer unit. % &Lt; / RTI &gt;

[Example 6]

95 parts by weight, 2 parts by weight and 3 parts by weight, respectively, of a carbon powder as an anode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were respectively dissolved in N-methyl- 100 parts by weight of NMP to prepare an anode active material slurry. The anode active material slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 90 탆, dried, and rolled to produce an anode.

An adhesive layer composed of a web of an electrospun polymer fiber was formed on the active material layer of the anode prepared above by an electrospinning method under the same conditions as in Example 1.

Thereafter, the electrode-separator composite prepared in Example 1 was placed so as to face the anode on which the adhesive layer was formed, and the anode and the electrode (cathode) Anode composite).

[Comparative Example 1]

A polyvinylidene fluoride-hexafluoropropylene copolymer containing 90% by weight of a vinylidene fluoride monomer unit and containing 10% by weight of a hexafluoropropylene monomer unit was dissolved in acetone to prepare a polymeric binder coating liquid, The coating solution was coated on the surface of the separator by spin coating to form an adhesive layer. Thereafter, pressure was applied between the electrode and the separator to place the adhesive layer therebetween, and the electrode and separator were bonded to each other to prepare an electrode-separator composite.

[Comparative Example 2]

An electrode-separator composite was prepared in the same manner as in Comparative Example 1 except that the polyvinylidene fluoride-hexafluoropropylene copolymer contained 80 wt% of a vinylidene fluoride monomer unit, 20 wt% of a hexafluoropropylene monomer unit % Was used.

[Comparative Example 3]

An electrode-separator composite was prepared in the same manner as in Comparative Example 1 except that a dip coating method was used instead of the spin coating method to form an adhesive layer.

[Comparative Example 4]

An electrode-separator composite was prepared in the same manner as in Comparative Example 2, except that a dip coating method was used instead of the spin coating method to form an adhesive layer.

Manufacture of Secondary Battery

[Example 7]

95 parts by weight, 2 parts by weight and 3 parts by weight, respectively, of a carbon powder as an anode active material, polyvinylidene fluoride (PVdF) as a binder and carbon black as a conductive material were respectively dissolved in N-methyl- 100 parts by weight of NMP to prepare an anode active material slurry. The anode active material slurry was applied to a copper (Cu) thin film as an anode current collector having a thickness of 90 占 퐉, dried, and rolled to produce an anode.

The unit cells were assembled using the electrode-separator composite (cathode-separator composite) prepared in Example 1 and the anode using the stacking method. Then, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio) and 1 mol of lithium hexafluorophosphate (LiPF ₆ ) .

[Examples 8 to 11]

A secondary battery was manufactured in the same manner as in Example 7, except that the electrode-separator composite prepared in Examples 2 to 5 was used.

[Example 12]

The unit cells were assembled using the electrode-separator composite (cathode-separator-anode composite) prepared in Example 6. Then, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio) and 1 mol of lithium hexafluorophosphate (LiPF ₆ ) .

[Comparative Examples 5 to 8]

A secondary battery was fabricated in the same manner as in Example 7, except that the electrode-separator composite prepared in Comparative Examples 1 to 4 was used.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. And various modifications and variations are possible within the scope of the appended claims.

100: electrode
200: separator
210: Porous polymer substrate
220: Porous coating layer
300: adhesive layer

Claims (16)

electrode;
Separation membrane; And
And an adhesive layer disposed between the electrode and the separator,
Wherein the adhesive layer is formed of an electrospun polymer fiber,
Wherein the electrospun polymer fiber is a copolymer comprising a vinylidene fluoride monomer unit and a hexafluoropropylene monomer unit in a weight ratio of 95: 5 to 99: 1. The method according to claim 1,
The separator may be a porous polymeric substrate or
A porous polymer substrate, and a porous coating layer formed on at least one surface of the porous polymer substrate. delete delete delete delete delete The method according to claim 1,
Wherein the diameter of the electrospun polymer fiber is 10 to 1,000 nm. The method according to claim 1,
Wherein the adhesive layer is formed on all or a part of both surfaces of the electrode and the separator facing each other. The method according to claim 1,
Wherein the adhesive layer has a circular, elliptical or polygonal cross-section. The method according to claim 1,
Wherein the adhesive layer is formed so that both ends of the electrode and the separation membrane can pass through each other. The method according to claim 1,
Wherein the electrode is a cathode or an anode. The method according to claim 1,
Wherein the electrode-separator composite is a cathode-separator composite, an anode-separator composite or a cathode-separator-anode composite. 14. A secondary battery comprising the electrode-separator composite according to any one of claims 1, 2, and 8 to 13. Supplying a polymeric binder spinning solution to the spinning nozzle;
Applying a voltage to the polymeric binder spinning solution to discharge the polymeric binder fibers;
Coating the polymeric binder fiber with at least one surface of the electrode or the separation membrane to form an adhesive layer; And
And pressing and bonding the electrode and the separator with the adhesive layer interposed therebetween,
Wherein the polymeric binder spinning solution is a copolymer comprising a vinylidene fluoride monomer unit and a hexafluoropropylene monomer unit at a weight ratio of 95: 5 to 99: 1. 16. The method of claim 15,
Wherein the voltage is between 10 and 1000 volts.

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