KR100470314B1 - A complex membrane for electrochemical device, manufacturing method and electrochemical device having the same - Google Patents

Abstract

The present invention relates to a composite membrane that can be used in an electrochemical device such as a lithium secondary battery, a method for manufacturing the same, and an electrochemical device having the same. The composite membrane for an electrochemical device of the present invention includes a polyolefin-based microporous membrane; And a porous membrane on a web made of nanofibers bonded to at least one surface of the polyolefin-based microporous membrane. Since the composite membrane according to the present invention can absorb the electrolyte uniformly, the performance of the battery is greatly improved when used in an electrochemical device, and the mechanical strength is good and the binding with the electrode is good, thereby increasing the process speed of battery manufacturing. have.

Description

A composite membrane for an electrochemical device, a manufacturing method and an electrochemical device having the same {A complex membrane for electrochemical device, manufacturing method and electrochemical device having the same}

The present invention relates to a composite membrane that can be used in an electrochemical device, such as a lithium secondary battery, a method of manufacturing the same, and an electrochemical device having the same.

In recent years, the miniaturization, thinning, and weight reduction of electronic devices have been made rapidly, and in the field of office automation, in particular, small size and light weight have been reduced from desktop computers to laptop and notebook computers. In addition, with the emergence of electronic notebooks, electronic still cameras, and the like, the miniaturization of conventional hard disks and floppy disks, and the development of memory cards, which are new small memory media, are also in progress.

In accordance with the tendency of light and short of electronic devices, high performance is also required for electrochemical devices that supply power to them. Lithium secondary batteries are the batteries that best meet these requirements.

Lithium secondary batteries are classified into lithium ion batteries made of a liquid electrolyte and lithium polymer batteries made of a solid or gel polymer electrolyte according to the electrolyte composition, and a separator having a different polymer material and structure is used for each battery.

Lithium ion batteries are homopolymers such as polyethylene [poly (ethylene): PE], polypropylene [poly (propylene): PP], ethylene / butene copolymers, ethylene / hexene copolymers, ethylene / methacrylate copolymers. A microporous film made of a polyolefin-based polymer made of a copolymer such as is used as a separator. If necessary, the separator may have a single layer structure or a multilayer structure such as PE / PP and PP / PE / PP. However, since the polyolefin-based separator has no affinity with the electrolyte, there is a disadvantage in that various types of batteries other than cans cannot be manufactured by leakage of the liquid electrolyte.

In order to overcome this problem, a gel polymer electrolyte membrane having affinity with the impregnated electrolyte has been proposed.

The gel polymer electrolyte membrane is polyvinylidene fluoride [poly (vinylidene fluoride); PVDF] type, polyvinylidene fluoride-hexafluoropropylene (poly (vinylidenefluoride) -co- (hexafluoropropylene); P (VDF-HFP)] copolymer , Phase inversion method, solution cating from polymers such as poly (acrylonitrile), PAN, poly (ethylene oxide), PEO, and acrylate ) Method, in-situ crosslinking method, hot melting method and the like.

As a method for producing a PVDF-based gel polymer electrolyte by a phase transfer method, a process technology of Belcore (now, Telcordia Technologies) is representative. That is, U.S. Patent Nos. 5,456,000 and 6,322,923 have prepared a polymer film of a P (VDF-HFP) copolymer to which a dibutyl phthalate (DBP) plasticizer was added, and then inserted the membrane between a cathode and an anode to laminate A method of producing a cell is then carried out through a plasticizer extraction process to make the membrane porous and dried, and then subjected to an electrolyte solution injection process under anhydrous atmosphere.

U.S. Patent No. 5,429,891 also discloses a silica inorganic filler in P (VDF-HFP) copolymer, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, or glycerol triglyceride. Disclosed is a method of preparing an electrolyte membrane by adding a crosslinking agent such as glycerol trimethacrylate, film casting, drying, and three-dimensional crosslinking by irradiation with an electron beam.

In addition, Korean Patent Laid-Open Publication No. 2002-0069601 discloses a PVDF or P (VDF-HFP) copolymer, a porous silica and a plasticizer dissolved in acetone, and then coated and dried on a PET film to extract a plasticizer to form a porous polymer membrane. Next, a method of preparing a gel polymer electrolyte in which a nitrile-based thermosetting polymer is coated or dropped on a polymer membrane to prepare a membrane, and then the membrane is placed between a cathode and an anode, and heat and pressure are applied to integrate the cathode / polymer membrane / anode is disclosed.

However, the gel polymer electrolyte has a limitation in increasing the process speed in the battery manufacturing process due to the low mechanical strength of the membrane, as well as the complicated manufacturing process of the battery, such as the addition of a plasticizer extraction process, the electrolyte is unevenly penetrated into the separator. There is a problem.

In order to improve this problem, a multicomponent composite polymer electrolyte membrane in which a polyolefin-based porous membrane is used as a strength support layer and a PVDF polymer is coated or laminated on both surfaces or one end of the support layer membrane has been proposed.

For example, US Pat. No. 5,681,357, US Pat. No. 5,688,293 and US Pat. No. 5,716,421 produce a composite hybrid electrolyte by immersing or coating a polyolefin-based porous separator in a polymerization composition, and polymerizing the composition with heat and pressure applied during the packaging process. Disclosed is a manufacturing method in which the polymer is bonded to the electrode while the polymerization is performed. However, the heat and pressure applied during the packaging process not only impair the packaging of the cell, but also cause the problem that gas is generated from the composition during curing.

In addition, US Patent No. 5,853,916 discloses a multilayer polymer gel electrolyte prepared by laminating a porous gelation PVDF-based polymer layer and a microporous non-gelling polymer layer. However, such a porous gelling membrane has a problem in that the electrolyte content cannot be increased because of its low porosity.

In addition, Korean Patent Laid-Open Publication No. 2000-0077418 applies an electrolyte to a cathode and an anode, respectively, and a two-layer structure consisting of a polyolefin-based separator, that is, a porous polyethylene (PE) film or polyethylene / polypropylene (PE / PP). A method of improving the low mechanical strength of a polymer electrolyte by inserting a porous film of is disclosed. However, since the gel electrolyte applied to the electrode reacts sensitively to moisture, there is a problem in that the process must be carried out in an anhydrous atmosphere, and since the gel electrolyte layer must be coated on both electrodes, it is difficult to manufacture a thin battery.

WO 99/54953 discloses polymer suspensions containing lithium mixtures in acetone and n-methyl pyrrolidone (NMP) mixed solvents, for example lithium phosphohexafluoride (LiPF ₆ ). Polyethylene oxide (PEO) suspension solution containing lithium salt, polyvinylidene fluoride (PVDF) suspension solution containing lithium salt, or polymethyl methacrylate containing lithium salt ( PMMA; polymethyl methacrylate) suspension solution is coated on a microporous polypropylene (PP) film or a multi-layered microporous laminate film made of PP / PE / PP and dried to prepare a composite polymer electrolyte, and the prepared composite polymer electrolyte membrane A method of finally manufacturing a battery is disclosed by placing it between an electrode of a positive electrode and a negative electrode and then immersing them in an organic electrolyte solution. . However, since the polymer layer coated in the composite polymer electrolyte is particulate, it takes a long time to absorb the organic electrolyte, and there is a problem in that a non-uniform gelling layer is formed by impregnation.

As described above, the conventional composite multicomponent separator formed by coating a PVDF-based gelling polymer layer on the strength support layer or by laminating and bonding in a membrane form has a low absorption rate when the electrolyte is injected since the electrolyte absorbing layer does not have internal pores. However, there is a problem in that battery performance is lowered due to non-uniform absorption of the electrolyte.

Therefore, the technical problem to be achieved by the present invention was devised to solve the above problems, uniformly absorb the electrolyte solution when used in the electrochemical device not only greatly improve the performance of the battery, but also excellent mechanical strength and binding force with the electrode The present invention provides a composite membrane for an electrochemical device, a method for manufacturing the same, and an electrochemical device having the same, which can increase a process speed of battery manufacturing.

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 is a cross-sectional view schematically showing the configuration of an electrospinning apparatus for producing a porous membrane on a web made of nanofibers constituting the composite membrane for an electrochemical device of the present invention.

Figure 2 is a schematic view showing the configuration of a vertical electrospinning apparatus for producing a vertical electrospinning apparatus for producing a porous film on the web consisting of nanofibers constituting the composite membrane for an electrochemical device of the present invention.

<Description of main reference numerals in the drawings>

10 Solution solution 11 Solution distribution 12 Radiation nozzle pack

12a Radiation nozzle 14 Voltage application 15a, 15b Jet stream control

16a, 16b..stream induction part 17.collector 18.air injection part

19 Solvent exhaust 20 Condensed object

In order to achieve the above object, the present invention provides a composite membrane for an electrochemical device composed of a strength support and an electrospinning membrane on a polymer web bonded to at least one surface of the strength support. The strength support is a polyolefin microporous membrane having an average pore size of 0.005 to 3 µm, a porosity of 30 to 80%, a tensile strength of 700 kg / cm 2 or more in the mechanical direction, and a tensile strength of 150 kg / cm 2 or more in the transverse direction. In addition, the electrospinning film is a porous film on a web in which nanofibers having a diameter of 50 to 2,000 nm are integrated by electrospinning so that the average flow pore size (MFPS) is 0.01 to 3 µm and the porosity is 60 to 95%. Therefore, the composite membrane according to the present invention has an average flow pore size of 0.01 to 1.5 μm, a porosity of 40% or more, a tensile strength of 1,000 kg / cm 2 or more in the mechanical direction, and a tensile strength of 100 kg / cm 2 in the lateral direction. More than It becomes a multilayer film with phosphorus thickness of 5-70 micrometers.

In addition, the polyolefin-based microporous membrane is composed of at least one or more layers made of polyethylene-based polymer and / or polypropylene-based polymer. In another aspect of the present invention, the method for preparing a composite membrane for an electrochemical device includes (a) an average pore size. Preparing a polyolefin-based microporous membrane having a thickness of 5 to 50 µm having a thickness of 0.005 to 3 µm, a porosity of 30 to 80%, a tensile strength of 700 kg / cm 2 or more in the mechanical direction, and a tensile strength of 150 kg / cm 2 or more in the transverse direction step; (b) Electrospinning nanofibers having a diameter of 50 to 2,000 nm on one side and / or both sides of the polyolefin-based microporous membrane to form a porous membrane on a polymer web (thickness of 50 μm or less and average flow pore size (MFPS). ) Porous layer having a porosity of 60 to 95% and 0.01 to 2㎛); And (c) laminating the polyolefin-based microporous membrane and the porous membrane on the web by applying a predetermined pressure and temperature to the resultant of step (b).

Another aspect of the present invention relates to an electrochemical device containing a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an organic electrolyte solution in a case.

Hereinafter, a composite membrane for an electrochemical device, a method of manufacturing the same, and an electrochemical device having the same will be described in detail.

The composite membrane for an electrochemical device of the present invention includes a polyolefin-based microporous membrane, which serves to support the strength of the composite membrane. The first property required as a strength support layer film is mechanical strength. That is, the puncture or puncture strength must be high to prevent the short circuit of the positive electrode and the negative electrode, the tensile strength must be high to increase the speed of the battery manufacturing process, and the thermal strain such as the thermal contraction of the membrane must be small. Also, considering stability issues such as battery explosion, it is desirable that the membrane configuration as a support has a shut down function so that pores can be closed at a particular temperature. Here, the shutdown function is a means for controlling thermal runaway that may occur due to battery physical damage, internal defects or short circuits due to overcharging. As a result, most of the pores are closed at a specific temperature (90 to 120 ° C.) to reduce ion or current flow. Refers to the function being blocked. As the film forming material capable of performing such a function, a polyolefin-based polymer is suitable. For example, in the case of PP / PE / PP membranes, the PE layer is melted at a certain temperature and the pores are closed, thereby providing a shutdown function. Polyolefin-based polymers or polypropylene-based polymers are suitable as the polyolefin-based polymers used in the composite membrane of the present invention. For example, uniaxial or biaxially-stretched PE monolayers, PP monolayers, PE / PP two-layer structure membranes, PP / PE / PP three-layer structure film, or polyolefin-based porous membrane film or nonwoven fabric having a composite multilayer structure composed of PE and PP, a composite material laminated with the same nonwoven fabric on the film, a polyamide-based porous membrane film or nonwoven fabric, or Polyester-based porous membrane film or nonwoven fabric may be used. Preferably, a porous polyolefin-based membrane film of a PE single membrane, a PE / PP two-layer structure film, and a PP / PE / PP three-layer structure film having a shutdown function is used to prevent a short circuit between the positive electrodes. Such a polyolefin-based microporous membrane is one of the conventional methods disclosed in EP 1,146,577, US 6,368,742, US 5,691,077, US 6,180,280, US 5,667,911, US 6,080,507. The membrane produced can be provided. As the polyolefin-based microporous membrane of the present invention, a commercially available polyolefin-based microporous film can be used. For example, Celgard's Celgard Film (PE film, PP film, PP / PE / PP triple layer film) or Hipore of Asahi Kasaei Film (PE), Setela of Tonen / ExxonMobil Film (PE), Teklon from Entek International The film PE may be provided as a polyolefin-based microporous membrane serving as a strength support layer.

The thickness of the polyolefin microporous membrane used in the composite membrane of the present invention is 5 to 50 µm, porosity (porosity) (porosity (%)) = 1- (membrane density / resin density) x100] is 30 It is preferable that it is -80%. In addition, the tensile strength is 700 kg / cm 2 or more in the mechanical direction (MD), 150 kg / cm 2 or more in the transverse direction (CD), the punching strength is 200 g or more per mil (mil, 1 mil = 25.4 μm), and the shrinkage ratio is 100 ° C. Less than 10% for 1 hour, the average pore size is 0.005 ~ 3㎛ physical properties and electrical resistance is 130 ~ 185 ℃ more than 10,000Ω-cm ² It is particularly suitable for use for electrochemical devices.

One or both surfaces of the aforementioned polyolefin-based microporous membrane are bonded to a porous membrane on a web made of nanofibers.

Porous membranes on the web of nanofibers include poly (vinylidene fluoride); PVDF], or polyvinylidene fluoride-hexafluoropropylene copolymer [poly (vinylidene) -co- (hexafluoropropylene); P (VDF-HFP)], or a composite composition thereof, or polyacrylonitrile (PAN), polyvinylidene chloride-acrylonitrile copolymer [poly (vinylidene) -co- (acrylonitrile); P (VDF-AN)], polyethylene oxide [poly (ethylene oxide); PEO], polyurethane [poly (urethane); PU], polymethyl acrylate [poly (methylacrylate)], polymethyl methacrylate [poly ( methyl methacrylate); PMMA], polyacrylamide; PAA, polyvinyl chloride; PVC, polyvinylacetate; PVAc], poly (vinylpyrrolidone), polytetraethylene glycol diacrylate, polyethylene glycol dimethacrylate [poly (ethylene glycol dimethacrylate; PEGDMA], acrylate [acrylate] type Or a solution of a copolymer thereof, cellulose, cellulose acetate, or a composite of the polymer (preferably a PVDF-based polymer that is homogeneous with the binder of the electrode, or a composite polymer including the same) It can be obtained by electrospinning or electrostatic spinning in order to increase the mechanical strength of the resulting polymer solution in the preparation of silicon oxide (SiO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), BaTiO ₃ , for _{LiO 2, LiF, LiOH, LiN} , BaO, Na 2 O, MgO, Li 2 CO 3, LiAlO 3, PTFE, or a filler, such as mixtures of these polymers Can be added in. Is preferred to be less than 20% compared to the configuration with a polymer weight ratio to the amount of the filling material.

The basic mechanism of electrospinning has already been introduced in the literature (JMDeitzel, JDKleinmeyer, JKHirvonen, NCBeck Tan, Polymer 42 , 8163-8170 (2001)), JMDeitzel, JDKleinmeyer, D. Harris, NCBeck Tan, Polymer 42 , 261-272 (2001), YMShin, MMHohman, MPBrenner, GCRutledge, Polymer 42 , 9955-9967 (2001).

The basic principle of the electrospinning method will be described in detail as follows.

Electrospinning is directly applied a high voltage of positive or negative polarity ((+)) of thousands to tens of thousands of volts to charge the polymer solution, and then discharge the charged solution to the air layer through the capillary nozzle, The discharged charged filament is a spinning method in which ultrafine fibers having a diameter of several tens of nanometers to several thousand nanometers are manufactured while being stretched and branched by mutual repulsion between adjacent filaments in the air layer. At this time, the microfibers charged with the (+) or (-) charge are grounded to have a potential difference, or are integrated on the collector charged with the opposite polarity to prepare a porous membrane of the web structure [P.K. Baumgarten, Journal of Colloid and Interface Science, Vol. 36, No. 1, 71 (1971); G. Taylor, Proc. Roy. Soc. London A, 313, 453 (1969); D.H. Reneker, A.L. Yarine, H. Fong, and S. Koombhongse, J Applied Physics, 876 (190, 909 (2000); J. Doshi and D. H. Reneker, J. Electrostatics, 35, 151 (1995)).

An example of an electrospinning apparatus for implementing such an electrospinning method is described in detail in Korean Patent Application No. 10-2002-48594. Referring to the attached electrospinning Figure 1 as follows.

Electrospinning is a solution supply unit for supplying a solution in which a polymer material to be a fiber raw material dissolved; A spinning nozzle pack (12) comprising a plurality of spinning nozzles (12a) for receiving a solution from the solution supply unit and discharging the solution in a filament form; A voltage applying unit 14 for charging the solution by applying a predetermined voltage to the spinning nozzle pack; It is installed in a symmetrical manner with the spinneret pack interposed therebetween, and a voltage is applied to apply or charge with the same polarity as the charged filament, so that the jet filament discharged from the nozzle has a uniform spinning state, while lowering integration of the charged filament. Jetstream controllers 15a and 15b for controlling the plane; A collector 17 installed at a lower side with a predetermined distance from the spinneret pack and grounded to generate a potential difference with the charged filament so that the charged filament discharged from the spinneret is integrated on an upper surface thereof; A porous stream guide unit (16a, 16b) installed to surround the charged filament stream discharged to the collector, and installed to form a uniform stack by inducing the filament integration direction; A supply circular tube tube portion 18 for injecting air into the air layer between the spinneret pack and the collector to increase the volatilization of the solvent contained in the charged filament; And an exhaust circular tube tube portion 19 for sucking and exhausting the solvent from the air layer between the spinneret pack and the collector.

The finely charged filaments branched from the air layer may be integrated on the collector or on the film 20 or the grasping paper installed on the collector.

The nanofibers constituting the integrated porous film on the web are preferably 50 to 2,000 nm in diameter, and more preferably 50 to 1500 nm. If the fiber diameter is too large, the specific surface area is reduced with respect to the weight, and thus the pore size constituting the membrane is increased, and thus leakage may occur due to insufficient content of the electrolyte.

The porous membrane on the web bonded to one or both sides of the polyolefin-based microporous membrane can absorb the electrolyte uniformly and sufficiently to greatly improve the performance of the electrochemical device, and also have excellent binding power with the electrode to improve the process speed. The thickness of the porous membrane on the web (web) is preferably 50㎛ or less, but finally should be set in consideration of the total thickness of the composite membrane to be prepared, if the membrane is too thick it is difficult to manufacture a thin electrochemical device. The porosity of the porous membrane on the web is preferably 60 to 95%, more preferably 65 to 90%. The average flow pore size (MFPS) of the porous membrane on the web is preferably 0.01 to 3 μm, more preferably 0.05 to 2 μm. If the pore size is too small, the rate of absorption of the electrolyte is slow during impregnation of the electrolyte, and if the pore size is too large, leakage of the electrolyte may occur.

The mechanical strength of the porous membrane on the web constituting the composite membrane is preferably 50 kg / cm ² or more in the mechanical direction (MD), and 20 kg / cm ² or more in the transverse direction (CD). In particular, it is preferable to pass the press roll in order to impart the strength and shape stability of the membrane. Pressurization is carried out in the pressure range of 0.1 ~ 10kgf / cm. The thickness reduction ratio of the film after pressurization is preferably 10 to 60%. On the other hand, the pressurized membrane may additionally go through the stretching step. Stretching is preferably uniaxial or biaxial stretching, and the total stretching ratio is preferably 1 to 20 times, more preferably 2 to 10 times.

The porous membrane on the web thus prepared is laminated on one or both sides of the polyolefin-based microporous membrane, and then the two membranes are bonded to each other through a lamination process applying a predetermined pressure and temperature, thereby manufacturing a composite membrane for an electrochemical device of the present invention. The lamination has a linear pressure load of 0.1 to 30 kgf / cm, preferably at a temperature of 3 to 30 ° C. lower than the melting point of the constituent polymer. If the temperature during the pressurization is high, the membrane melts, and if the pressure is too high, the porosity decreases, which is undesirable. The porous membrane on the web may be formed by laminating the porous membrane on the web by electrospinning directly onto the polyolefin-based microporous membrane and laminating under the above conditions. At this time, the polyolefin-based microporous membrane may be transferred together with the collector, or may be integrated while being spaced apart or passed within 1 cm from the upper surface of the collector.

The composite membrane for an electrochemical device thus prepared is a composite of a two-layered composite membrane consisting of a porous membrane / polyolefin-based microporous membrane on a web, a porous membrane on a web / polyolefin-based microporous membrane / a porous membrane on a web. It may be a multilayer composite membrane in which a membrane or a porous membrane on a web and a polyolefin-based microporous membrane are alternately stacked and stacked in three or more layers. The porosity of the composite membrane is preferably 40% or more. If the porosity is low, the impregnation rate of the electrolyte is low, making the membrane unsuitable for use as a high performance battery separator.

It is preferable that the total thickness of a composite film shall be 5-70 micrometers. If the thickness of the film is thinner than 5㎛ may be a problem in the battery manufacturing process due to the film strength is weak, if the thickness is more than 70㎛ may decrease the ion conductivity. More preferable thickness is 10-30 micrometers. The tensile strength is preferably at least 1000 kg / cm 2 in the mechanical direction and at least 100 kg / cm 2 in the transverse direction. The average flow pore size is preferably 0.01 ~ 1.5㎛.

The composite membrane prepared by the above-described method may be used as an electrolyte membrane for a lithium secondary battery according to a general battery manufacturing process, for example, and used to manufacture an electrochemical device such as a lithium secondary battery. The composite film is interposed between the positive electrode and the negative electrode to form an electrode structure in which the electrode and the film are integrated through a lamination process. The composite membrane is placed in a battery case, and then injected and sealed with an organic electrolyte to manufacture an electrochemical device. At this time, the porous membrane on the web forms a gelling polymer layer after the injection of the electrolyte due to the affinity with the electrolyte. The injected organic electrolyte is lithium phospho hexafluoride (LiPF ₆ ), lithium perchlorate (LiClO ₄ ; lithiumperchlorate), lithium tetrafluoroborate (LiBF ₄ ; lithiumtetrafluoroborate) and lithium trifluoromethanesulfonate in an organic solvent. Lithium salts such as (LiCF ₃ SO ₃ ; lithiumtrifluoromethanesulfonate) are dissolved. Organic solvents are propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl Ethylene (ethylmethyl carbonate, EMC), γ-butyrolactone, or a combination of these solvents.

Hereinafter, the present invention will be described in detail with reference to Examples. However, embodiments according to the present invention can be modified in many different forms, the scope of the present invention should not be construed as limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art.

Example

The electrospinning apparatus used in the embodiment used the apparatus shown in FIG. 1, and specific specifications thereof are as follows.

The spinning solution is transferred from the tank to the spinning nozzle pack by a precision feeder equipped with a metering pump. The spinneret pack was equipped with a capillary nozzle with an inner diameter of 0.2 mm, an outer diameter of 0.4 mm and a capillary length of 10 mm, with a gap of 26 mm between nozzle tips. The distance between the spin packs was 20 cm. The spinneret pack moves repeatedly from side to side at a speed of 6 meters per minute.

Each spinneret pack was connected to a high voltage generator section (DEL Global Technologies, model name: RLPS50-300P, output voltage 50KV, output current 3mA, positive polarity) to charge the spinning solution. At this time, the applied voltage is a positive DC voltage of 20 ~ 40kv.

A jet stream control panel consisting of an aluminum metal plate 0.4 mm thick and 40 mm wide at 3 cm from the left and right sides of the spinneret pack was installed in a vertical direction parallel to the pack. At this time, the position of the lower end of the control panel is the same as the position of the lower end of the nozzle tip. This jet stream control panel was applied with the same voltage applied to the spinning solution.

In addition, the stream guides 6a and 6b were installed at a distance of 5 cm apart from the left and right sides of the discharged charged filament stream, and were located within the range of 1 cm below the spinneret pack to 1 cm above the collector. The collector was grounded as a conveyor employing a metal belt (SUS 304) and was installed 20 cm away from the nozzle tip.

On the other hand, Figure 2 is an electrospinning device in which the spinneret pack and the collector of the above-described electrospinning device is vertically continuous, and was used to directly form a porous film on the web on both sides of the polyolefin membrane.

The property test method of the prepared composite membrane is as follows.

1. Pore size

Mean pore size (MFPS) and maximum pore size were measured using an automated capillary flow porometer (PMI (Porous Materials Inc.), Model CFP-1200AEL (CFP-34RTF8A-X-6-L4)] It was. The wetting fluid used for the measurement was galwick acid (surface tension 15.9 dynes / cm). The diameter of the adapter plate was 21 mm and measured by wet-up / dry-up method.

2.SEM

Fiber diameter was analyzed using SEM (Spectroscan Leica Model 440) instrument. Magnification was observed at x10k and x20k.

3. Mechanical property

Tensile strength and elongation of the porous membrane on the web was measured using a tensile tester (Instron Model 4201). At this time, the capacity of the used load cell was 2.5kg.

Example 1

Polyolefin-based microporous PP membrane acting as a strength support layer has a thickness of 25㎛, porosity 55%, pore size 0.209x0.054㎛, air flow resistance value Gurley 9 sec, tensile strength 1200kg / ㎠ in MD direction, tensile strength in CD direction A porous film (Celgard, trade name Celgard 2500) having physical properties of 115 kg / cm 2 and shrinkage of 3% was used.

On the other hand, the porous membrane on the web was prepared using the above-described electrospinning using a PVDF (poly (vinylidene fluoride))-based polymer. That is, PVDF-HFP (88 mol%: 12 mol%) [poly (vinylidenefluoride- co- hexafluoro propylene)] copolymer [Elf Atochem North America, Inc., trade name Kynar Flex 2801: number average molecular weight (Mn) = 120,000, Weight average molecular weight (Mw) = 380,000, specific gravity 1.77 g / cc, melting point 143 캜] was dissolved in a mixed solvent of acetone (acetone) and dimethylacetamide (DMAc) having a weight ratio of 7: 3 to prepare a 13% by weight polymer solution. It was prepared and electrospun. At this time, the discharge amount per spinning nozzle was 20 μl / min, and the applied voltage was 28 kv.

The membrane integrated in the collector was separated from the collector, and the prepared web-like porous membrane had a diameter of 70-500 nm, a porosity of 80%, and a MFPS of 1 μm. The thickness was 10 micrometers.

After laminating porous membranes on the web on both sides of the aforementioned PP microporous membrane to form a three-layer structure, the laminator (GMP company, model: EXCEL AM) at a temperature of 140 ° C., a linear pressure of 0.5 kg / cm, and a feed rate of 20 cm / min. -655Q) to produce a composite membrane in which the porous membrane on the web is bonded to both sides of the PP microporous membrane.

The total thickness of the composite membrane was 33 μm, porosity 58%, average flow pore size 0.136 μm, maximum pore size 2.65 μm, and mechanical properties were the same as those of the PP porous film.

Example 2

Polyolefin-based microporous PP membrane acting as a strength support layer has a thickness of 25㎛, porosity 55%, pore size 0.209x0.054㎛, air flow resistance value Gurley 9 sec, tensile strength 1200kg / ㎠ in MD direction, tensile strength in CD direction A porous film (Celgard, trade name Celgard 2500) having physical properties of 115 kg / cm 2 and shrinkage of 3% was used.

On the other hand, the porous membrane on the web was prepared by complex spinning a heterogeneous PVDF-based polymer. That is, a polymer solution obtained by dissolving 15% by weight of 100% PVDF homopolymer [Elf Atochem North America, Inc., trade name Kynar 761] in a mixed solvent having a weight ratio of acetone and dimethylacetamide 5: 5, and PVDF-HFP (88 mol%) : 12 mol%) [poly (vinylidenefluoride- co- hexafluoro propylene)] copolymer [Elf Atochem North America, Inc., trade name Kynar Flex 2801: number average molecular weight (Mn) = 120,000, weight average molecular weight (Mw) = 380,000, Specific gravity 1.77 g / cc, melting point 143 ° C.] was used as a polymer solution obtained by dissolving 13 wt% in acetone solvent. The polymer solution was supplied to a separate spinning nozzle pack and spun using the same electrospinning apparatus as in Example 1. At this time, the interval between the spinning nozzle pack was 20cm, each 20μl / min was discharged per spinning nozzle. The applied voltage was 28 kv for 100% PVDF homopolymer solution and 21 kv for 88% PVDF copolymer. The distance between the tip and the collector was 20 cm.

Membrane integrated in the collector by the composite spinning was 70 ~ 700nm diameter of the constituent fibers, a mixture of thin and coarse diameter. The thickness of the membrane produced was 10 μm.

Thus prepared membrane is laminated on both sides of the PP microporous membrane (film) to form a three-layer structure, laminator (GMP company, model: EXCEL under conditions of temperature 140 ℃, linear pressure 1kg / 10cm, feed rate 20cm / min) AM-655Q) to produce a composite membrane in which the PVDF porous membrane on the web is bonded to both sides of the PP microporous membrane.

The total thickness of the composite membrane thus prepared was 33 μm, porosity 60%, MFPS 0.136 μm, maximum pore size of 2.65 μm, and mechanical properties were the same as those of the PP porous film.

Example 3

Polyolefin microporous PE membrane acting as a strength support layer has a thickness of 21㎛, porosity 43%, pore size 0.110x0.054㎛, air flow resistance value Gurley 22 sec, tensile strength in MD direction 1700㎏ / ㎠, tensile strength in CD direction A porous film (Celgard, trade name Celgard 2730) having physical properties of 120 kg / cm 2, shrinkage of 5%, and melting temperature of 135 ° C. was used.

The porous membrane on the web was PVDF-HFP (88 mol%: 12 mol%) [poly (vinylidenefluoride- co -hexafluoro propylene)] copolymer [Elf Atochem North America, Inc., trade name KynarFlex 2801: number average molecular weight (Mn) = 120,000 , Weight average molecular weight (Mw) = 380,000, specific gravity 1.77 g / cc, melting point 143 ° C.] was prepared as a 13 wt% polymer solution prepared by dissolving acetone and dimethylacetamide in a mixed solvent having a weight ratio of 4: 6.

As shown in FIG. 2, the spinneret pack 12 and the conveyor-type metal (SUS 304) collector 17 are vertically and continuously installed, and the PE film is disposed on the upper surface of the collector to pass along with the collector. It is. Spinning was done directly on both sides on the PE film on the upper surface of the collector. At this time, the discharge amount per spinning nozzle was 50 mu l / min, the applied voltage was 28 kv, and the distance between the tip and the collector was 20 cm. The diameters of the filaments constituting the film on the PE film produced through the above apparatus were 300 to 1,000 nm, and the cross-sectional thicknesses of the films were 10 µm, respectively.

The three-layer structure having a porous membrane on the web on both sides of the PE porous film is passed through a laminator (GMP company, model: EXCEL AM-655Q) at a temperature of 120 ° C., a linear pressure of 1 kg / cm, and a feed rate of 20 cm / min. The composite membrane was produced by bonding together.

The total thickness of the composite membrane thus prepared was 30 μm, porosity 45%, MFPS 0.304 μm, maximum pore size of 1.10 μm, and the mechanical properties were the same as that of the PE porous film.

Example 4

The polyolefin-based microporous membrane serving as the strength support layer has a thickness of 25 µm, a porosity of 36%, a pore size of 0.05x0.11 µm, and a mechanical direction (MD) made of a multilayer of polyethylene (PE) / polypropylene (PP) / polyethylene (PE). Shrinkage rate of 5% (90 ℃, 60min), air flow resistance value Gurley 25 seconds, tensile strength 1560㎏ / ㎠ (22kpsi) in MD direction, tensile strength 135㎏ / ㎠ (2kpsi) in CD direction, melting temperature 135 ℃ ( A porous film (Celgard, trade name Celgard 2300) having physical properties of PE) / 165 ° C. (PP) was used.

The porous membrane on the web was PVDF-HFP (88 mol%: 12 mol%) [poly (vinylidenefluoride- co -hexafluoro propylene)] copolymer [Elf Atochem North America, Inc., trade name Kynar Flex 2801: number average molecular weight (Mn) = 120,000, weight average molecular weight (Mw) = 380,000, specific gravity 1.77 g / cc, melting point 143 ° C.] was prepared as a 13 wt% polymer solution prepared by dissolving acetone and dimethylacetamide in a weight ratio of 4: 6.

The electrospinning device used the same apparatus as in Example 3, but the PP / PE / PP film was configured to pass 5 mm away from the top surface of the collector. At this time, the discharge amount per spinning nozzle was 20 mu l / min, the applied voltage was 28 kv, and the distance between the tip and the collector was 20 cm. Spinning was done directly on the PP / PE / PP film passing through the top of the collector, and the charged filaments were integrated on both sides of the PP / PE / PP film while passing through each set of spinning nozzle packs and collectors. The diameter of the fibers integrated on the film was 300-700 nm, and the cross-sectional thicknesses of the films were 5 mu m, respectively.

The three-layer structure thus manufactured was passed through a laminator (GMP company, model: EXCEL AM-655Q) at a temperature of 100 ° C., a linear pressure of 1 kg / cm, and a feed rate of 20 cm / min. Prepared.

The total thickness of the composite membrane thus prepared was 30 μm, porosity 37%, MFPS 0.127 μm, maximum pore size of 2.31 μm, and the mechanical properties were the same as those of the PP / PE / PP porous film.

Example 5

Polyolefin microporous PE membrane acting as a strength support layer has a thickness of 21㎛, porosity 43%, pore size 0.110x0.054㎛, air flow resistance value Gurley 22 sec, tensile strength in MD direction 1700㎏ / ㎠, tensile strength in CD direction A porous film (Celgard, trade name Celgard 2730) having physical properties of 120 kg / cm 2, shrinkage of 5%, and melting temperature of 135 ° C. was used.

The porous membrane on the web was PVDF-HFP (88 mol%: 12 mol%) [poly (vinylidenefluoride- co -hexafluoro propylene)] copolymer [Elf Atochem North America, Inc., trade name Kynar Flex 2801: number average molecular weight (Mn) = 120,000, weight average molecular weight (Mw) = 380,000, specific gravity 1.77 g / cc, melting point 143 ° C.] was prepared as a 13 wt% polymer solution prepared by dissolving acetone and dimethylacetamide in a weight ratio of 6: 4.

The electrospinning value is the same as that used in Example 1. At this time, the discharge amount per spinning nozzle was 50 mu l / min, the applied voltage was 28 kv, and the distance between the tip and the collector was 20 cm.

The fibrous porous membrane prepared through the above device had a diameter of 300 to 1,000 nm and a thickness of 10 μm.

The porous membrane on the web was fed and laminated on both sides of the porous PE film, and the laminated three-layer structure was passed through a laminator at a temperature of 100 ° C., a linear pressure of 1 kg / 10 cm, and a feed rate of 20 cm / min so that the porous membrane on the web was PE microporous. A composite membrane bonded to the membrane was prepared.

The total thickness of the composite membrane thus prepared was 23 μm, porosity 43%, MFPS 0.304 μm, maximum pore size of 1.10 μm, and mechanical properties were the same as that of the PE porous film.

Example 6

The spinning conditions were the same as those of Example 2, but instead of PVDF-HFP copolymer, PMMA [poly (methyl methacrylate), Mw = 120,000] was used for the complex spinning at an 8: 2 ratio. The physical properties of the composite membrane in which the porous membrane formed on the web is bonded to both sides of the PP microporous membrane were found to be the same as the PP porous film supplied to the inner support layer.

The total thickness of the composite membrane thus prepared was 33 μm, porosity 60%, MFPS 0.136 μm, and maximum pore size of 2.65 μm.

As described above, the composite membrane according to the present invention has a polyolefin-based microporous membrane as a strength support layer, and the porous membrane on the web made of nanofibers having high porosity is bonded to one or both surfaces thereof, so that the strength and absorption rate of the liquid electrolyte are high. Is fast, and the electrolyte may be uniformly diffused and penetrated to improve the performance of the electrochemical device. In addition, when the porous membrane on the web, which is the outer layer of the composite membrane, is provided as an electrolyte membrane of an electrochemical device such as a lithium secondary battery, when the porous membrane on the web is formed of a material having a binding property with the electrode binder material, the manufacturing speed of the battery may be increased.

Claims (10)

In a composite membrane for an electrochemical device comprising a strength support and an electrospinning membrane on a polymer web bonded to at least one surface of the strength support, (1) The strength support has an average pore size of 0.005 to 3㎛, porosity of 30 to 80%, mechanical tensile strength of 700kg / ㎠ or more, transverse tensile strength of 150kg / ㎠ or more fine polyolefin-based fine Porous membrane; (2) The electrospun film has a porosity on a web in which nanofibers having a diameter of 50 to 2,000 nm are integrated by electrospinning so that the average flow pore size (MFPS) is 0.01 to 3 µm and the porosity is 60 to 95%. Membrane; For this reason, the composite membrane has an average flow pore size of 0.01 to 1.5 µm, a porosity of 40% or more, a tensile strength of 1,000 kg / cm 2 or more in the mechanical direction, and a thickness of 5 to 100 kg / cm 2 or more in the transverse direction A composite membrane for an electrochemical device, characterized in that the multilayer membrane of 70㎛. The method of claim 1, The polyolefin-based microporous membrane is a composite membrane for an electrochemical device, characterized in that at least one layer consisting of a polyethylene-based polymer and / or a polypropylene-based polymer. The method of claim 1, The composite membrane for an electrochemical device, characterized in that the thickness of the support 5 ~ 50㎛. delete The method of claim 1, The nanofibers are polyvinylidene fluoride, polyvinylidene fluoride-hexafluoro propylene copolymer, polyacrylonitrile, polyvinylidene chloride-acrylonitrile copolymer, polyethylene oxide, polyurethane, polymethyl acrylate, poly From the group consisting of methyl methacrylate, polyacrylamide, polyvinylchloride, polyvinylacetate, polyvinylpyrrolidone, polytetraethylene glycol diacrylate, polyethyleneglycol dimethacrylate, cellulose, cellulose acetate and mixtures thereof Composite membrane for an electrochemical device, characterized in that consisting of the selected polymer. The polymer constituting the nanofiber is SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaTiO ₃ , LiO ₂ , LiF, LiOH, LiN, BaO, Na ₂ O, MgO, Li ₂ CO ₃ , LiAlO ₃ , PTFE and a composite membrane for an electrochemical device, characterized in that it further comprises a filler selected from the group consisting of these. The method of claim 1, The electrospinning film has a thickness of 50 μm or less, a tensile strength of 50 kg / cm 2 or more in the mechanical direction, and a tensile strength of 20 kg / cm 2 or more in the lateral direction, wherein the composite membrane for an electrochemical device. (a) Polyolefins having a mean pore size of 0.005 to 3 μm, porosity of 30 to 80%, tensile strength in the mechanical direction of 700 kg / cm 2 or more, and transverse tensile strength of 150 kg / cm 2 or more in thickness of 5 to 50 μm. Preparing a system-based microporous membrane; (b) Electrospinning nanofibers having a diameter of 50 to 2,000 nm on one side and / or both sides of the polyolefin-based microporous membrane to form a porous membrane on a polymer web (thickness of 50 μm or less and average flow pore size (MFPS). ) Porous layer having a porosity of 60 to 95% and 0.01 to 2㎛); And and (c) laminating the polyolefin-based microporous membrane and the porous membrane on the web by applying a predetermined pressure and temperature to the resultant of step (b). The method of claim 8, The polyolefin-based microporous membrane is at least one or more layers made of polyethylene-based polymer and / or polypropylene-based polymer; The polymer constituting the nanofibers may be polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyacrylonitrile, polyvinylidene chloride-acrylonitrile copolymer, polyethylene oxide, polyurethane, polymethyl Acrylate, polymethylmethacrylate, polyacrylamide, polyvinylchloride, polyvinylacetate, polyvinylpyrrolidone, polytetraethylene glycol diacrylate, polyethyleneglycol dimethacrylate, cellulose, cellulose acetate and mixtures thereof Method selected from the group consisting of. In the electrochemical device containing a positive electrode, a negative electrode, a separator and an organic electrolyte interposed between the positive electrode and the negative electrode in a case, The separator is an composite membrane according to claim 1, characterized in that the electrochemical device.