KR102447851B1 - Ultra-thin electric double layer capacitor of high voltage using gel electrolyte and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a high voltage ultra-thin electric double layer capacitor using a gel electrolyte and a manufacturing method thereof. According to the present invention, provided are the ultra-thin electric double layer capacitor and the manufacturing method thereof. The ultra-thin electric double layer capacitor comprises: an exterior material including a pouch film; an electrode assembly embedded in the exterior material; and an electrolyte embedded in the exterior material. In addition, the electrode assembly comprises: two electrodes, positive electrode and negative electrode; a separation film interposed between the positive electrode and negative electrode; and a lead tab coupled to the positive electrode and negative electrode and having one side drawn out of the exterior material. The electrolyte is a gel electrolyte formed by gelation of an electrolyte solution, and the pouch film and the lead tab are sealed with a sealing film. According to the present invention, provided are the ultra-thin electric double layer capacitor and the manufacturing method thereof. Moreover, by removing a tab film fixed to a conventional lead tab and minimizing the thickness of each component, the ultra-thin electric double layer capacitor is ultra-thin with a thickness of less than 0.3 mm and has electrical characteristics improved to be usefully applied to thin devices such as credit cards and smart cards.

Description

ULTRA-THIN ELECTRIC DOUBLE LAYER CAPACITOR OF HIGH VOLTAGE USING GEL ELECTROLYTE AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a high voltage ultra-thin electric double layer capacitor using a gel electrolyte and a method for manufacturing the same, and a tab film fixed to a lead tab using a gel electrolyte according to one embodiment. film) and minimizing the thickness of each component, an ultra-thin electric double-layer capacitor with a thickness of 0.3 mm or less and a method for manufacturing the same that can be usefully applied to thin devices such as credit cards and smart cards by improving electrical properties is about

Electric double layer capacitors (EDLCs) as electric energy storage devices capable of charging/discharging are widely used in various industrial fields. Unlike general secondary batteries, electric double layer capacitors (EDLCs) have high output and semi-permanent long lifespan, and they do not deteriorate due to repeated charging and discharging and require little maintenance.

In general, an electric double layer capacitor (EDLC) includes an electrode having a symmetrical structure of an anode and a cathode, and a separator made of a porous material that is interposed between the two electrodes to allow only ion conduction and prevent short circuit (insulation). separator) and an electrolyte that conducts ions between the anode and the cathode. The positive electrode and the negative electrode are configured in the same way, and they are mainly formed by coating an electrode active material containing activated carbon as a main component on a metal current collector (Al, etc.).

In addition, the electric double layer capacitor (EDLC) includes a casing for supporting and accommodating the above components, and a lead-out terminal (or also referred to as an electrode terminal) is drawn out of the casing. Electric double layer capacitors (EDLCs) are classified according to the shape of the exterior material, and these are the most common of a cylindrical type, a coin type, and a pouch type. The pouch type has a thinner thickness and a larger area than a coil type or a coin type, and can have high output. Accordingly, the pouch type is mainly applied to thin products that are limited by the thickness of the product or products requiring high output.

1 shows a conventional pouch-type electric double layer capacitor (EDLC), and FIG. 2 shows a lead-out terminal. 1 and 2 , a pouch-type electric double layer capacitor (EDLC) includes an exterior material 1 composed of a pouch film (mainly, an aluminum laminate film), an anode 2 embedded in the exterior material 1, and The two electrodes of the negative electrode 3, the separator 4 interposed between the positive electrode 2 and the negative electrode 3, and the ions between the positive electrode 2 and the negative electrode 3 embedded in the casing 1 It contains an electrolyte that conducts. Further, lead tabs 2a and 3a as lead terminals are coupled to each of the electrodes 2 and 3 .

The most important purpose of the exterior material (1) is to seal the electrodes (2) (3), the separator (4), and the electrolyte accommodated therein so that they do not come into contact with the outside, and to prevent the electrolyte from leaking. To this end, a tab film 5 is fixed to the lead tabs 2a and 3a for sealing property between the exterior material 1 and the lead tabs 2a and 3a. As shown in FIG. 2 , the tab film 5 is bent to cover both surfaces of the lead tabs 2a and 3a and is fixed to the lead tabs 2a and 3a. The tab film 5 is heat-sealed to the pouch film to seal between the exterior material 1 and the lead tabs 2a and 3a.

For example, Korean Patent Application Laid-Open No. 10-2014-0035605, Korean Patent Application Laid-Open No. 10-2015-0041291, and Korean Patent Application Laid-Open No. 10-2018-0050842 disclose the above-related technology.

Recently, as electronic devices become thinner, the demand for a thinner electric double layer capacitor (EDLC) is spreading. In particular, in the case of components applied to thin devices such as credit cards and smart cards, which are rapidly expanding the market recently, the thickness of the mounted components is limited according to international standards. The international card standard is limited to 0.76mm in thickness. It is difficult to change for compatibility with other devices used.

In order for an electric double layer capacitor (EDLC) to be applied to a thin device such as a credit card, it may vary depending on the composition of the plastic and film materials constituting the credit card, but it must have a thickness of at most 0.4mm or less, and depending on the customer's configuration method, is required to have an ultra-thin thickness of 0.3 mm or less. Factors determining the thickness of the pouch-type electric double layer capacitor (EDLC) may include the thickness of the electrodes 2 and 3 and the thickness of the separator 4 and the thickness of the pouch film. However, even if the thickness of the electrodes 2 and 3 and the separator 4 among these components is minimized, when the thickness of the lead-out terminal becomes thick, there is inevitably a limit to the reduction in thickness. That is, the lead tabs 2a and 3a of the lead-out terminal according to the prior art are made of aluminum (Al) metal, which is soldered with the electrodes 2 and 3 while the tab film 5 is fixed on both sides thereof. It is coupled through, and must have a predetermined thickness for soldering with the electrodes (2) and (3). At this time, the total thickness of the lead-out terminal is a thickness obtained by adding the thickness of the lead tabs 2a and 3a and the thickness of the tab film 5 .

In the case of an electric double layer capacitor (EDLC) for thin devices such as credit cards and smart cards, the thickness of the product is generally determined by the thickness of the pouch film, the lead tabs 2a and 3a and the tab film 5 . No matter how minimized the thickness of the electrodes 2 and 3 and the separator 4 built into the exterior material 1, the thickness of the pouch film, the lead tab 2a, 3a, and the tab film 5 is not lowered. product configuration is not possible.

In the case of a pouch-type electric double layer capacitor (EDLC) for thin devices currently on the market, in general, 1 sheet of positive electrode (2), 1 sheet of negative electrode (3), 1 sheet of separator (4), and 2 sheets of pouch film as exterior material (1) (upper/lower pouch film). In most cases, the pouch film uses an aluminum laminate film having a thickness of about 75 to 80 μm, and the lead tabs 2a and 3a have a thickness of 0.05 to 0.1 mm for the lead-out terminals 2a, 3a, and 5. Since it has a thickness and a thickness of the tab film 5 of 50 μm, the overall thickness of the lead-out terminals 2a, 3a, and 5 has a thickness of at least 0.15 to 0.2 mm. Accordingly, the minimum thickness of the edge of the exterior material 1, that is, the minimum thickness of the portion where the lead-out terminals 2a, 3a, and 5 are formed, has a thickness of about 0.3 to 0.36 mm considering the thickness of the pouch film. has been This is the theoretical minimum thickness, and when the thinnest product is applied, there is a concern about the deterioration of the sealing property, so the product with a thickness of about 0.4mm is generally marketed as the thinnest product. However, in the case of these products, since they are made of thin aluminum to minimize the thickness of the lead tabs 2a and 3a, the actual soldering process between the lead tabs 2a and 3a and the electrodes 2 and 3 is impossible. Many are pointed out as problems in use.

In addition, in the pouch-type electric double layer capacitor (EDLC), a liquid electrolyte obtained by dissolving the electrolyte in an organic solvent is used. However, in the case of using a liquid electrolyte, there is a chronic problem of leakage (leakage) of the electrolyte due to weakening of the sealing property of the exterior material 1 according to the use environment such as high temperature and/or high humidity or long-term use. To solve this, a case of applying a solid electrolyte can be considered, but the solid electrolyte has a very low electrical conductivity compared to a liquid electrolyte, so it is difficult to implement a low internal resistance for high output.

Korean Patent Publication No. 10-2014-0035605 Korean Patent Publication No. 10-2015-0041291 Korean Patent Publication No. 10-2018-0050842

Accordingly, the present invention uses a gel electrolyte, but removes the tab film fixed to the lead tab, heat-seals the sealing film to the pouch film to have sealing properties, and adjusts the thickness of each component. To provide a high-output ultra-thin electric double layer capacitor (EDLC) and a method for manufacturing the same, which can be usefully applied to thin devices such as credit cards and smart cards by improving electrical properties while being ultra-thin with a thickness of 0.3 mm or less by minimizing it There is a purpose.

In order to achieve the above object, the present invention

exterior material consisting of a pouch film;

an electrode structure embedded in the exterior material; and

Containing an electrolyte built into the exterior material,

The electrode assembly is an ultra-thin electric double layer capacitor comprising two electrodes, a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a lead tab coupled to the positive electrode and the negative electrode and having one side drawn out of the exterior material. provides In this case, the electrolyte is a gel electrolyte formed by gelling the electrolyte, and the pouch film and the lead tab are sealed by a sealing film.

In addition, the present invention,

A first step of preparing an electrode assembly including two electrodes of a positive electrode and a negative electrode, a separator interposed between the positive electrode and the negative electrode, and a lead tab coupled to the positive electrode and the negative electrode and having one side drawn out of the exterior material;

a second step of attaching a sealing film to one side of the lower pouch film and the upper pouch film constituting the exterior material;

a third step of installing an electrode assembly on the lower pouch film, laminating an upper pouch film on the electrode assembly, and thermally sealing three sides of the upper/lower pouch film to form a pouch-type exterior material;

a fourth step of injecting an electrolyte into the exterior material and then heat-sealing it in a vacuum to seal the upper/lower pouch film and the lead tab with a sealing film; and

It provides a method of manufacturing an ultra-thin electric double layer capacitor comprising a fifth step of thermocompression bonding the exterior material, forming a gel electrolyte by gelation of the electrolyte, and compressing the gel electrolyte and the electrode assembly.

According to the present invention, it has an effect of improving electrical properties while being ultra-thin with a thickness of 0.3 mm or less. Accordingly, it can be usefully applied to thin devices such as credit cards and smart cards.

1 is a cut-away perspective view showing a conventional pouch-type electric double layer capacitor (EDLC).
2 is a conventional drawing terminal, showing a state in which the tab film is fixed to the lead tab.
3 is a plan view illustrating a manufacturing process of an electric double layer capacitor (EDLC) according to an embodiment of the present invention.
4 is a plan view of an electric double layer capacitor (EDLC) according to an embodiment of the present invention.
5 is an SEM photograph of the activated carbon used in Examples.
6 is an SEM photograph of activated carbon used in Comparative Example.

The term "and/or" used in the present invention is used in the sense of including at least one or more of the components listed before and after. As used herein, the term “one or more” refers to one or a plurality of two or more.

In addition, in the present invention, "formed on", "formed on", "installed on", and "installed on", etc. do not mean only that the components are laminated (installed) in direct contact with each other, It includes the meaning that other components are further formed (installed) between the components. For example, "formed on." and "Installed on." means that the second component is formed (installed) in direct contact with the first component, as well as the third component is formed between the first component and the second component. It includes meanings that can be further formed (installed).

3 is a plan view illustrating a manufacturing process of an electric double layer capacitor (EDLC) according to an embodiment of the present invention, and FIG. 4 is a plan view of an electric double layer capacitor (EDLC) according to an embodiment of the present invention. 3 and 4 , an electric double layer capacitor (EDLC) according to the present invention includes a casing 10 composed of pouch films 11 and 12; an electrode assembly 20 built in (accommodated) in the exterior material 10; and an electrolyte embedded in the exterior material 10 .

The electrode assembly 20 includes two electrodes, an anode 21 and a cathode (not shown), a separator (not shown) interposed between the anode 21) and the cathode, the anode 21 and It is coupled to the negative electrode and includes lead tabs 21a and 22a having one side drawn out of the casing 10 . In this case, the lead tabs 21a and 22a include a positive lead tab 21a coupled to the positive electrode 21 and a negative lead tab 22a coupled to the negative electrode. The electrolyte is a gel electrolyte formed by gelling the electrolyte, and the pouch films 11 and 12 and the lead tabs 21a and 22a are sealed by a sealing film 30 .

In addition, the manufacturing method of the electric double layer capacitor (EDLC) according to the present invention, the first step of manufacturing the electrode assembly 20; a second step of attaching the sealing film 30 to the pouch films 11 and 12; a third step of forming a pouch-type exterior material 10 in which the electrode assembly 20 is embedded; a fourth step of injecting an electrolyte into the exterior material 10 and then sealing; and a fifth step of thermocompression bonding the exterior material 10 . In this case, the first step is not limited to the order, and this may be performed before the third step. By the thermocompression bonding in the fifth step, the electrolyte is gelled to form a gel electrolyte, and the gel electrolyte and the electrode assembly 20 are compressed (adhered) together to improve electrical properties.

The electric double layer capacitor (EDLC) according to the present invention is an ultra-thin pouch type, and specifically has an exterior form in which the electrode assembly 20 and the gel electrolyte are built-in (accommodated) in the pouch type exterior material 10 . According to one embodiment of the present invention, the thick tab film 5 ( FIG. 2 ) is not attached to the lead tabs 21a and 22a as in the prior art, but is sealed through a thin sealing film 30 to have sealing properties. and has an ultra-thin thickness.

In general, in the pouch-type electric double layer capacitor (EDLC), the thickness of the lead tabs 21a and 22a determines the overall thickness of the product. In the present invention, the thickness of the lead tabs 21a and 22a is the thickness of the portion (top in the drawing) where the lead tabs 21a and 22a are formed, which is the thickness of the portion indicated by "T" in FIG. (T) means. Specifically, this means the sum of the thickness of the upper pouch film 11, the thickness of the lower pouch film 12, the thickness of one selected from the positive and negative lead tabs 21a and 22a, and the thickness of two sealing films 30 do.

The electric double layer capacitor (EDLC) according to the present invention has an ultra-thin thickness by minimizing the thickness T of at least portions of the lead tabs 21a and 22a. The electric double layer capacitor (EDLC) according to the present invention may have, for example, an ultra-thin thickness T of 0.3 mm or less, or 0.27 mm or less. The electric double layer capacitor (EDLC) according to the present invention may have a thickness T of, for example, 0.25 mm to 0.3 mm.

In addition, the present invention uses a gel electrolyte as an electrolyte, and after injecting the electrolyte into the packaging material 10, gelation is performed to form a gel electrolyte, and the density of each component is improved through compression together with improved electrical properties. It has technical significance. In addition, the present invention has a technical significance even though it has low resistance and high output and prevents electrolyte leakage by adding a specific crosslinked polymer capable of gelling an electrolyte (liquid electrolyte) and then gelling it to form a gel electrolyte. have.

The electric double layer capacitor (EDLC) according to the present invention may have an ultra-thin thickness T of 0.3 mm or less and an internal resistance of 4.2 Ω or less. The electric double layer capacitor (EDLC) according to the present invention may have an internal resistance of, for example, 3.5Ω to 4.2Ω. The electric double layer capacitor (EDLC) according to the present invention may preferably have an internal resistance of 4.0 Ω or less. This internal resistance value is a value measured by a measurement method commonly used in the art (eg, measurement using an ohmmeter).

Hereinafter, an electric double layer capacitor (EDLC) according to an embodiment of the present invention will be described together while describing a method of manufacturing an electric double layer capacitor (EDLC) according to an embodiment of the present invention. In describing the embodiments of the present invention, detailed descriptions of related well-known general-purpose functions and/or configurations will be omitted.

(1) Preparation of the electrode assembly 20

The electrode assembly 20 is composed of one positive electrode 21, one negative electrode, and one separator interposed between the positive electrode 21 and the negative electrode as usual. A positive lead tab 21a and a negative lead tab 22a are coupled to upper ends of the positive electrode 21 and the negative electrode, respectively. Such an electrode assembly 20 may be manufactured according to a conventional method.

The positive electrode 21 and the negative electrode have the same configuration, and they have a structure in which an electrode active material layer is formed on a metal current collector such as aluminum. The electrode active material layer may be formed by coating a composition (slurry form) including at least activated carbon on a metal current collector. In this case, the activated carbon preferably has an average particle size of, for example, 0.5 to 3 μm through a fine grinding process such as a jet mill and/or a ball mill. The thickness of the electrode can be minimized by the activated carbon of such fine particles.

The lead tabs 21a and 22a are made of nickel metal, and may have a thickness of, for example, 75 to 95 μm. In addition, as the separator, for example, a nonwoven separator may be used, which may have a thickness of 20 to 40 μm.

(2) Attachment of the sealing film 30

First, the lower pouch film 11 and the upper pouch film 12 constituting the exterior material 10 are prepared. These lower/upper pouch films 11 and 12 may have the same size (horizontal and vertical), and they may use an aluminum laminate film, for example, having a thickness of 70 to 80 μm.

A sealing film 30 is attached to each of the lower pouch film 11 and the upper pouch film 12 to be fixed. As shown in FIG. 3 , the sealing film 30 is attached to one side (the upper end in FIG. 3 ) of the lower/upper pouch films 11 and 12 . The sealing film 30 may be attached to the pouch films 11 and 12 through, for example, heat sealing or an adhesive. In one example, the sealing film 30 may be attached and fixed to the pouch films 11 and 12 through the fixing part 32 formed by thermally sealing both ends of the sealing film 30 .

Heat shrinkage of the pouch films 11 and 12 is prevented by the sealing film 30 while having sealing properties. Specifically, when the pouch films 11 and 12 are heat-sealed without attaching the sealing film 30 and laminated to the lead tabs 21a and 22a, the pouch films 11 and 12 are heat-shrinked and adhered. Sealability may deteriorate. The sealing film 30 prevents heat shrinkage as described above and has sealing properties.

The sealing film 30 is a film selected from polyethylene (PE; Poly Ethylene), polypropylene (PP; Poly Propylene), polyimide (PI; Poly Imide) and/or cast polypropylene (CPP; Cast Poly Propylene). Can be used. The sealing film 30 may preferably be a cast polypropylene (CPP) film. When the cast polypropylene (CPP) film is used, the sealing property is more advantageous than when a film such as polyethylene (PE) or polypropylene (PP) is used.

The sealing film 30 preferably has a thickness of 1 μm to 12 μm. In this case, when the thickness of the sealing film 30 is less than 1 μm, the sealing property is deteriorated, and electrolyte leakage may occur. And, when the thickness of the sealing film 30 exceeds 12 μm, it may be difficult to achieve the desired ultra-thin thickness, for example, a thickness T of 0.3 mm (300 μm) or less in the present invention.

According to a preferred embodiment of the present invention, the sealing film 30 is preferably a cast polypropylene (CPP) film having a thickness of 1㎛ ~ 5㎛. When a cast polypropylene (CPP) having such a thickness is used, the sealing property is excellent and a thickness (T) of 0.3 mm or less, preferably an ultra-thin thickness (T) of 0.27 mm or less, can be realized, which is also of the electrical properties. It is also desirable for improvement.

(3) Formation of the exterior material (10)

Referring to FIG. 3 , the electrode assembly 20 is installed (laminated) on the lower pouch film 11 to which the sealing film 30 is attached, and then the upper pouch film 12 is placed on the electrode assembly 20 . are stacked Thereafter, the three side surfaces 10a, 10b, and 10c of the upper/lower pouch film are heat-sealed to form the pouch-shaped exterior material 10 . Thermal fusion may be performed, for example, at a temperature of 150 to 200°C.

(4) Injection and sealing of electrolyte

Next, the electrolyte is injected into the exterior material 10 . Thereafter, the sealing portion 35 is formed by heat-sealing in a vacuum state. Specifically, after injecting an appropriate amount of electrolyte into the exterior material 10, the interior of the exterior material 10 is maintained in a vacuum state, and then the upper/lower pouch films 11 and 12 and the lead tabs 21a and 22a) The sealing portion 35 is formed by thermally sealing the portion (the upper end in FIGS. 3 and 4 ) on which the lead tabs 21a and 22a are formed so as to be sealed by the sealing film 30 . Thereby, the four surfaces of the exterior material 10 are sealed, and sealing property is achieved.

Further, in the present invention, the electrolyte is an electrolyte for a gel electrolyte capable of forming a gel electrolyte, and includes a polymer and an electrolyte solution. The polymer is not particularly limited as long as it can gel with the electrolyte solution. According to a preferred embodiment of the present invention, the polymer comprises a crosslinked polymer of an acrylate-based monomer and a thiol-ene monomer. Specifically, the polymer is selected from an acrylate-thiol copolymer in which an acrylate-based monomer and a thiol-ene monomer are crosslinked according to the present invention.

According to the present invention, the acrylate-thiol copolymer, for example, in comparison with other polymers such as polyvinyl alcohol (PVA) or polyurethane (PU), forms a good electrolyte solution and a colloidal network structure, which In addition, interfacial stability and flexibility are improved. Accordingly, the acrylate-thiol copolymer has lower resistance and higher capacitance than the case of using polyvinyl alcohol (PVA) or polyurethane (PU), thereby improving the electrical properties of the electric double layer capacitor (EDLC). .

The acrylate-based monomer is, for example, trimethylolpropane triacrylate, poly (ethylene glycol) dimethacrylate, trimethylolpropane propoxylate triacrylate (Trimethylolpropane) At least one selected from propoxylate (2PO/OH) triacrylate) and bisphenol A ethoxylate (15EO/phenol) dimethacrylate may be used.

In addition, the thiol-ene monomer is not particularly limited as long as it has one or more thiol groups (-SH) in the molecule. The thiol-ene monomer may be, for example, one or more selected from alkyl-3-mercaptopropionate, alkylthioglycolate, and alkylthiol. The thiol-ene monomer is, for example, methyl-3-mercaptopropionate, ethyl-3-mercaptopropionate, butyl-3-mercaptopropionate, methylthioglycolate, ethylthioglycolate At least one selected from , butylthioglycolate and 2-butyl-4-ethylbenzene-1-thiol may be used.

In the present invention, the acrylate-thiol copolymer is a cross-linked polymer of the acrylate-based monomer and the thiol-ene monomer as described above, which may be cross-linked in the presence of a reaction initiator. In this case, the thiol-ene monomer may act as a crosslinking agent or the acrylate-based monomer may act as a crosslinking agent.

In addition, the reaction initiator is not limited as long as it can promote a crosslinking reaction between the acrylate-based monomer and the thiol-ene monomer, for example, benzoyl peroxide, acetyl peroxide, dilauryl Peroxide (dilauryl peroxide), di-tert-butyl peroxide (di-tert-butyl peroxide), cumyl hydroperoxide (cumyl hydroperoxide), hydrogen peroxide (hydrogen peroxide) and potassium persulfate (potassium persulfate), etc. One or more selected from may be used.

According to one embodiment, the acrylate-thiol copolymer may be synthesized using an acrylate-based monomer and a thiol-ene monomer in a weight ratio of 2-8:8-2. That is, the acrylate-thiol copolymer may be a crosslinked polymer synthesized in a weight ratio of acrylate-based monomer: thiol-ene monomer = 2 to 8: 8 to 2, for example, acrylate-based monomer: thiol-ene Monomer = 4 to 6: It may be a crosslinked polymer synthesized in a weight ratio of 6 to 4.

In addition, the reaction initiator may be used in an amount of about 0.2 wt % to 5 wt % based on the total amount of the mixed monomer of the acrylate-based monomer and the thiol-ene monomer. The reaction initiator may be used, for example, in an amount of 0.5 wt% to 2 wt% based on the total amount of the mixed monomers.

On the other hand, the electrolyte solution is not particularly limited as long as it contains an electrolyte salt (solute) and a solvent. The electrolytic solution is, specifically, an electrolytic salt dissolved in a solvent, which may be commonly used in the art.

The electrolytic salt has ionicity, and is selected from ionic salts selected from organic substances, inorganic substances and/or organic-inorganic complexes. Examples of the electrolytic salt include quaternary ammonium salts such as tetraethylammonium and triethylmethylammonium; (C ₂ H ₅ ) ammonium tetrafluoride salts such as ₄ NBF ₄ ; aliphatic cyclic ammonium salts such as N-ethyl-N-methylpyrrolidinium and N,N-tetramethylene pyrrolidinium; quaternary imidazoles such as 1,3-dimethylimidazole and 1-ethyl-3-methylimidazole; and/or derivatives thereof.

As the electrolytic salt, for example, one or more selected from tetraethylammonium tetrafluoroborate, tetramethylammonium tetrafluoroborate, tetraphosphonium tetrafluoroborate and tetraethylmethylammonium tetrafluoroborate may be used. . In addition, the electrolyte salt may be included (dissolved) in the electrolyte in an amount of, for example, 0.1 to 4.0 mol/L, preferably 0.5 to 3.0 mol/L.

The solvent is an organic solvent, which is not particularly limited as long as it can dissolve (dilute) the electrolyte salt. The solvent is, for example, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, gamma butyrolactone, tetrahydrofuran, dimethyl sulfoxide, sulfolane, dimethyl form selected from amide, dimethylacetamide, phosphoric acid triester, maleic anhydride, succinic anhydride, phthalic anhydride, 1,3-propanesultone, nitrobenzene, 1,2-dimethoxyethane, nitromethane and/or derivatives thereof, etc. can be

According to an embodiment of the present invention, the acrylate-thiol copolymer and the electrolyte solution (electrolyte salt + solvent) may be mixed and used in a weight ratio of 0.5 to 3: 7 to 9.5. That is, the electrolyte solution for a gel electrolyte for forming the gel electrolyte may include the acrylate-thiol copolymer: the electrolyte solution (electrolyte salt + solvent) = 0.5 to 3: 7 to 9.5 in a weight ratio. At this time, when the amount (weight ratio) of the electrolyte solution is low, the resistance property may not be good, and when the amount (weight ratio) of the electrolyte solution is high, the amount of the acrylate-thiol copolymer is relatively low, and the gelation characteristic can be lowered. have.

After the above electrolyte is injected into the exterior material 10 , a vacuum state is maintained to uniformly vacuum impregnate the electrode assembly 20 . By vacuum impregnation, the electrolyte may be sufficiently dispersed in the anode 21 , the cathode and the separator to improve electrical properties. The impregnated electrolyte is gelled by heat to form a gel electrolyte.

(5) thermocompression bonding

After the electrolyte is injected and sealed as described above, the exterior material 10 is thermocompression-bonded. By such thermocompression bonding, the electrolyte is gelled to form a gel electrolyte, and the gel electrolyte and the electrode assembly 20 are compressed (adhered) to improve electrical properties.

The heat applied during the thermocompression bonding may be any temperature capable of gelling the electrolyte, which may be performed by, for example, applying heat at a temperature of 60° C. to 80° C. for 30 minutes to 3 hours.

In addition, the pressure applied at the time of the thermocompression bonding may be enough to allow the gel electrolyte and the electrode assembly 20 to adhere well. The exterior material 10 may be pressurized, for example, at a pressure of 2 kgf/cm ² or more, or 5 kgf/cm ² or more. The gel electrolyte and the electrode assembly 20 are brought into close contact by this pressurization, and the positive electrode 21, the negative electrode, and the separator constituting the electrode assembly 20 are in close contact with each other to improve electrical properties and minimize the thickness. .

According to the present invention described above, the thickness (T) 0.3mm or less, preferably 0.27mm or less, while having an ultra-thin thickness (T) is improved. The electric double layer capacitor (EDLC) according to the present invention may be usefully applied to, for example, a thin device such as a credit card and a smart card.

Hereinafter, Examples and Comparative Examples of the present invention are exemplified. The following examples are provided for illustrative purposes only to help the understanding of the present invention, and the technical scope of the present invention is not limited thereby. In addition, the following comparative examples do not mean the prior art, and are provided only for comparison with the examples.

[Examples 1 to 5]

(1) Preparation of the electrode assembly 20

As a metal current collector, an aluminum (Al) foil having a thickness of about 20 μm was prepared. After coating the slurried electrode active material composition on the prepared aluminum (Al) foil, rolling rolling was performed to prepare an electrode sheet in which an electrode active material layer having a thickness of about 28 μm was formed on the aluminum (Al) foil. Thereafter, the electrode sheet was cut into two of an appropriate size to prepare one positive electrode and one negative electrode. In this case, the electrode active material layer used an activated carbon slurry, and the activated carbon had an average particle size of about 1 μm. 5 is an SEM photograph of the activated carbon used in this example.

Next, the upper ends of each of the positive electrode 21 and the negative electrode were stripped, and lead tabs 21a and 22a were attached to the stripped portion as lead-out terminals through ultrasonic welding. At this time, the lead tabs 21a and 22a do not have the conventional tab film 5 attached thereto, and nickel metal (without a tab film) having a thickness of 90 μm is used. A separator was laminated between the prepared positive electrode and one negative electrode to prepare a thin electrode assembly 20 composed of one positive electrode, one separator, and one negative electrode. As the separator, a non-woven fabric separator having a thickness of 40 μm was used.

(2) Attachment of the sealing film 30

A lower pouch film 11 and a lower pouch film 12 were prepared, and a sealing film 30 was attached to the top of each film. The pouch films 11 and 12 had a size of 15 x 15 mm (width x length), and an aluminum laminate film having a thickness of 76 μm was used. The sealing film 30 was attached and fixed to the pouch films 11 and 12 through the fixing part 32 formed by heat-sealing both ends of the sealing film 30 . At this time, the sealing film 30 is PE (Poly Ethylene): 10㎛, PP (Poly Propylene): 10㎛, CPP (Cast Poly Propylene): 10㎛, CPP (Cast Poly Propylene): 3㎛ and PI (Poly Imide) ): 20 μm, and a material and a thickness of the sealing film 30 different according to each embodiment were used. The material and thickness of the sealing film 30 according to each of Examples (1 to 5) are shown in Table 1 below.

(3) Forming the exterior material (10)

First, an electrode assembly 20 is laminated on the lower pouch film 11 so that one side of the lead tabs 21a and 22a is drawn out toward the upper end of the lower pouch film 11 , and then the upper portion on the electrode assembly 20 . A pouch film 12 was laminated. Thereafter, the three side surfaces 10a, 10b, and 10c of the pouch films 11 and 12 were heat-sealed to form the pouch-shaped exterior material 10 .

(4) sealing

After injecting the electrolyte into the exterior material 10 and maintaining the vacuum state, the pouch films 11 and 12 and the lead tabs 21a and 22a were sealed by thermal fusion. At this time, the sealing film 30 was heat-sealed at about 180° C. so that the sealing film 30 was fused to each of the films 11 and 12 and the lead tabs 21a and 22a. Meanwhile, the electrolytic solution prepared as follows was used.

In a reactor equipped with a stirrer, trimethylolpropane triacrylate as an acrylate-based monomer and ethyl-3-mercaptopropionate as a thiol-ene monomer 6: After adding in a weight ratio of 4, stirring and mixing for 1 hour, a reaction initiator is added here in an amount of 1% by weight based on the total weight of the two monomers, followed by stirring and reaction for 1 hour to synthesize an acrylate-thiol copolymer did. As the reaction initiator, benzoyl peroxide was used.

Next, an electrolyte solution (liquid electrolyte) was added to the synthesized acrylate-thiol copolymer and mixed, but the acrylate-thiol copolymer: electrolyte solution = 1.5: 8.5 was added and mixed in a weight ratio. In this case, as the electrolyte solution, a solution obtained by dissolving tetraethylammonium tetrafluoroborate (1.0M) as an electrolyte salt in propylene carbonate (PC) as a solvent was used. After adding the electrolytic solution to the acrylate-thiol copolymer as described above, the electrolytic solution for the gel electrolyte was prepared by mixing and stirring for 1 hour. An appropriate amount of this electrolyte solution for a gel electrolyte was injected into the exterior material 10 .

(5) Thermocompression bonding - EDLC cell manufacturing

The manufacturing of the pouch-type EDLC cell was completed by thermocompression bonding the packaging material 10 into which the electrolyte was injected. Specifically, by applying heat of about 60° C. to the exterior material 10 for 1 hour, the electrolyte was gelled (cured) to form a gel electrolyte. At the same time, pressure was applied to the exterior material 10 to allow the gel electrolyte to penetrate into the electrode assembly 20 well, while the positive electrode/separator/cathode constituting the electrode assembly 20 was compressed (adhered). Through this process, an ultra-thin pouch-type EDLC cell was manufactured.

[Comparative Example 1]

(a) Preparation of electrode assembly

As a metal current collector, an aluminum (Al) foil having a thickness of about 20 μm was prepared. After coating the slurried electrode active material composition on the prepared aluminum (Al) foil, rolling rolling was performed to prepare an electrode sheet in which an electrode active material layer having a thickness of about 40 μm was formed on the aluminum (Al) foil. Thereafter, the electrode sheet was cut into two of an appropriate size to prepare one positive electrode and one negative electrode. In this case, the electrode active material layer used an activated carbon slurry, and the activated carbon had an average particle size of about 11 μm. 6 is an SEM photograph of the activated carbon used in this comparative example.

Next, the upper ends of each of the positive and negative electrodes were stripped, and lead tabs 2a and 3a were attached to the stripped portion as lead-out terminals through soldering. At this time, as the lead tabs 2a and 3a, a tab film 5 is fixed as in the prior art, and a 50 μm thick tab film 5 attached to 90 μm thick aluminum metal was used. A separator was laminated between the prepared positive electrode and one negative electrode to prepare an electrode assembly composed of positive electrode/separator/negative electrode, and a 40 μm-thick nonwoven separator was used as the separator.

(b) Formation of exterior material

An electrode assembly was laminated on the lower pouch film, and then an upper pouch film was laminated on the electrode assembly. Thereafter, three sides of the pouch film were heat-sealed to form a pouch-type exterior material.

(c) Sealing and EDLC cell fabrication

After injecting the electrolyte into the exterior material, the pouch film and the lead tabs 2a and 3a were sealed by heat-sealing the tab film 5 as in the prior art. In this case, as the electrolyte, a liquid electrolyte obtained by dissolving tetraethylammonium tetrafluoroborate (1.0M) as an electrolyte salt in propylene carbonate (PC) as a solvent was used.

For the pouch-type EDLC cells according to each of Examples and Comparative Examples prepared as above, thickness, capacity, internal resistance, and sealing properties were evaluated. The results are shown in [Table 1] below. The thickness shown in Table 1 below represents the thickness (T) of the lead-out terminal portion, that is, the portion where the lead tabs 21a and 22a are formed. Capacitance (mF) and internal resistance (Ω) were measured using a capacitive meter and an ohmmeter according to a conventional method in the art. On the other hand, sealing performance was performed by visual evaluation. Specifically, the sealing property is “X” when leakage of electrolyte is visibly observed after the thermocompression bonding (gelation and compression of electrolyte) or thermocompression bonding (manufacture of EDLC cell), and “Δ” when a very small amount is observed. ", when no leakage of the electrolyte was observed, it was evaluated as "double-circle" and is shown in [Table 1].

< Characteristic evaluation result of pouch-type EDLC cell specimen > division sealing film thickness
(μm) electrolyte Volume
(mF) internal resistance
(Ω) hermeticity Example 1 PE 10㎛ 278 gel electrolyte 2.8 6.3 X (liquid) Example 2 PP 10㎛ 281 gel electrolyte 2.9 5.2 X (liquid) Example 3 CPP 10㎛ 281 gel electrolyte 4.2 4.1 ◎ Example 4 CPP 3㎛ 267 gel electrolyte 4.1 3.8 ◎ Example 5 PI 20㎛ 302 gel electrolyte 4.1 4.1 △ Comparative Example 1 Existing Leads tab
(Fixed tab film) 370 liquid electrolyte 4.3 4.8 ◎

As shown in [Table 1], the EDLC cells (Examples 1 to 5) in which the lead tabs 21a and 22a were sealed using the sealing film 30 according to the embodiment were about 300 μm (0.3 mm) It was found to have an ultra-thin thickness (T) as follows. On the other hand, in the case of using the lead tabs 2a and 3a to which the tab film 5 is fixed as in the prior art, it had a thickness greater than that of the embodiments as 370 μm.

Meanwhile, it can be seen that the sealing properties and electrical properties (capacitance and internal resistance) vary depending on the type of the sealing film 30 in comparison with the embodiments. It was found that Examples 3 and 4 in which CPP was used as the sealing film 30 had superior sealing properties and electrical properties compared to the cases in which PE, PP, and PI were used (Examples 1, 2, and 5). In the case of internal resistance, Examples 3 and 4 showed improved results compared to the case of using the conventional liquid electrolyte (Comparative Example 1) as 4.2Ω or less. This is considered to be due to the excellent sealing properties and sufficient thermocompression bonding.

In particular, in the case of Example 4 using CPP having a thickness of 3 μm, it has an ultra-thin thickness T of 270 μm or less (about 267 μm) and excellent sealing properties, which also shows the best results in internal resistance. could That is, in Example 4 using CPP having a thickness of 3 μm, it was found that the internal resistance was significantly improved as 3.8 Ω.

Through the above results, according to the present invention, it has excellent sealing properties without using the conventional tab film 5, and the thickness (T) is 300 μm or less, preferably 270 μm or less, and ultra-thinning is realized, along with the conventional ( Compared to Comparative Example 1), it was found that the internal resistance was significantly reduced (Example 4) to have high output characteristics. Accordingly, it is expected that it will be possible to enter markets such as thin devices such as credit cards and smart cards, as well as health patches and flexible capacitors that require ultra-thinness.

10: exterior material 11, 12: pouch film
20: electrode structure 21: positive electrode
21a, 22a: lead tab 30: sealing film
32: sealing film fixing part T: thickness

Claims (5)

an exterior material 10 composed of pouch films 11 and 12;
an electrode assembly 20 embedded in the exterior material 10; and
Including an electrolyte built into the exterior material (10),
The electrode assembly 20 includes two electrodes, a positive electrode 21 and a negative electrode, a separator interposed between the positive electrode 21 and the negative electrode, and the positive electrode 21 and the negative electrode coupled to one side of the exterior material 10 Includes lead tabs (21a) and (22a) drawn to the outside of
The electrolyte is a gel electrolyte formed by gelling the electrolyte,
The pouch films 11 and 12 and the lead tabs 21a and 22a are sealed by a sealing film 30 ,
The sealing film 30 is a pouch-type electric double layer capacitor, characterized in that it is a cast polypropylene (CPP) film having a thickness of 1㎛ to 12㎛.
According to claim 1,
The sealing film 30 is a cast polypropylene (CPP) film having a thickness of 1 μm to 5 μm,
The thickness (T) of the portion where the lead tabs 21a and 22a are formed is 0.3 mm or less,
The pouch-type electric double-layer capacitor is a pouch-type electric double-layer capacitor, characterized in that it has an internal resistance of 4.0Ω or less.
Two electrodes of the positive electrode 21 and the negative electrode, a separator interposed between the positive electrode 21 and the negative electrode, and a lead tab coupled to the positive electrode 21 and the negative electrode and having one side drawn out of the casing 10 ( a first step of preparing an electrode assembly 20 including 21a) and 22a;
a second step of attaching the sealing film 30 to one side of the lower pouch film 11 and the upper pouch film 12 constituting the exterior material 10;
After installing the electrode assembly 20 on the lower pouch film 11 , and then laminating the upper pouch film 12 on the electrode assembly 20 , the upper/lower pouch films 11 and 12 are A third step of heat-sealing the three side surfaces (10a, 10b, 10c) to form a pouch-shaped exterior material (10);
After injecting an electrolyte into the exterior material 10, heat-sealing in a vacuum state to seal the upper/lower pouch films 11 and 12 and the lead tabs 21a and 22a by the sealing film 30 Step 4; and
A fifth step of thermocompression bonding the exterior material 10 to form a gel electrolyte by gelation of the electrolyte, and compressing the gel electrolyte and the electrode assembly 20;
The sealing film 30 is a method of manufacturing a pouch-type electric double layer capacitor, characterized in that the cast polypropylene (CPP) film having a thickness of 1㎛ ~ 12㎛.
delete 4. The method of claim 3,
The electrolyte uses an electrolyte for a gel electrolyte capable of forming a gel electrolyte,
The electrolyte includes a polymer and an electrolyte,
The polymer includes an acrylate-thiol copolymer in which an acrylate-based monomer and a thiol-ene monomer are crosslinked,
The acrylate-thiol copolymer is synthesized using an acrylate-based monomer and a thiol-ene monomer in a weight ratio of 2 to 8: 8 to 2 in the presence of a reaction initiator,
The thiol-ene monomer is a method of manufacturing a pouch-type electric double layer capacitor, characterized in that at least one selected from alkyl-3-mercaptopropionate, alkylthioglycolate and alkylthiol is used.

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