KR101493976B1 - Manufacturing method of Asymmetrical Super Capacitor with Cylindrical Type - Google Patents

Abstract

The present invention relates to a cylindrical asymmetric super capacitor. The present invention provides the cylindrical asymmetric super capacitor for winding an anode formed of a first current collector and an active carbon layer, and a cathode formed of a second current collector and a lithium layer in a coil type across a separator inside a container. The lithium layer is formed on either or both one end or/and the other end of the second current collector surface to be located in either or both the center part or/and the outermost part of the coil. The carbon layer is formed on the second current collector surface and is formed on the remaining part where the lithium is not formed to free-dope a lithium ion.

Description

{Manufacturing method of Asymmetrical Super Capacitor with Cylindrical Type}

The present invention relates to a cylindrical asymmetric supercapacitor and more particularly to a cylindrical asymmetric supercapacitor in which a lithium layer is wound on the outermost side of the coil with a coil shape in which an anode and a cathode are wound to pre- Capacitor.

As the conventional super capacitors, electric double layer capacitors using activated carbon symmetrically for the positive electrode and the negative electrode have been most commonly used. This is because the ions contained in the electrolytic solution are adsorbed and desorbed on the activated carbon surface by impregnating the activated carbon electrode with the electrolytic solution, thereby securing fast charge / discharge and long-term reliability.

The electrolytic solution for the electric double layer capacitor can be classified into an aqueous system and an organic system. Of aqueous liquid electrolyte is H ₂ SO _4, and KOH, and the electrolyte is generally used, an organic electrolytic solution, there is used an electrolyte mainly TEABF ₄ (Tetraethylammonium Tetrafluoroborate) or SBPBF ₄ (Spirobipyrrolidinium tetrafluoroborate).

A water-based electric double layer capacitor using a water-based electrolyte having a small ion size and a high ionic conductivity has a high electrostatic capacitance, but the decomposition voltage of the solvent (H ₂ O) is low and is limited to less than 1 V, In the case of the organic system, the electrostatic capacity is small as opposed to the water system, but generally exhibits high energy characteristics by using up to 2.7V.

The development of supercapacitors with higher energy than the conventional electric double layer capacitors is progressing due to the expansion of application fields of supercapacitors and demands for higher characteristics. As energy (E) is proportional to 1 / 2CV ² , an asymmetric supercapacitor that realizes a high voltage by hybridizing an anode and a cathode is a common study for realizing a recent high energy.

The most typical configuration of the asymmetric supercapacitor is composed of an activated carbon electrode for an electric double layer capacitor on the anode and a carbon electrode for a lithium secondary battery on the cathode.

This asymmetric supercapacitor has a Li-pre-doping process of storing a certain amount of lithium ions in the carbon, which is an anode active material, in the manufacturing step. This increases the energy density by lowering the cathode potential of the asymmetric supercapacitor and increasing the potential difference with the anode by pre-doping lithium ions to the cathode. These asymmetric supercapacitors typically have a working voltage of 3.8 to 4.0V.

As a method of pre-doping lithium ions in these asymmetric supercapacitors, the following methods are best known commercially.

1) A method in which an anode made of an activated carbon anode and a cathode made of a carbon material are stacked in parallel and a structure in which lithium metal poles are arranged at both ends is deposited in an electrolyte and an electric current is flowed between the electrodes to electrochemically dope lithium ions.

2) A method of chemically doping a carbon material by ionizing a lithium foil by immersing it in an electrolyte in a state in which a lithium foil is in contact with a negative electrode prepared using a carbon material.

As prior art document information related to these applications, for example, it is well known in Patent Document 1 (Japanese Patent Laid-Open Nos. 8-107048 and 2) (Japanese Patent No. 3689948).

The lithium pre-doping process described in Patent Document 1 is a technique applied to an asymmetric supercapacitor of a pouch type, and the lithium pre-doping process disclosed in Patent Document 2 is a technique applied to a cylindrical asymmetric supercapacitor.

The electrode structure for lamination described in Patent Document 1 has a problem of being applied to a cylindrical shape.

The pre-doping process of the cylindrical asymmetric supercapacitor described in Patent Document 2 is generally performed by depositing lithium on the surface of the Cu current collector of the negative electrode at a thickness of less than about 1 탆 and forming the carbon electrode / Cu current collector / There is a problem that a high manufacturing cost is required due to the introduction of a mass production process by lithium vapor deposition by winding the cathode of the lithium foil structure together with the anode again and the contact resistance due to the change of the cathode thickness during the pre- come.

Japanese Patent Application Laid-Open No. 8-107048 Japanese Patent No. 3689948

SUMMARY OF THE INVENTION It is an object of the present invention to provide a cylindrical asymmetric supercapacitor which is improved in productivity and pre-doped with stable lithium ions to a cathode.

In order to achieve the above object, the present invention provides a positive electrode comprising a first current collector and an active carbon layer, a negative electrode comprising a second current collector, a carbon layer and a lithium layer, Wherein the lithium layer is formed at one or both ends of the surface of the second current collector so as to be located at one or both of a center side and an outermost side of the coil, The second current collector is formed on the surface of the second current collector, and the remaining portion of the lithium secondary battery is not formed.

And the lithium layer is formed so as to be wound by at least one revolution.

The lithium layer is characterized in that a lithium foil is attached to the surface of the second current collector by mechanical pressing or vapor deposition.

The lithium layer has a purity of 99% or more and a thickness of 1 to 200 mu m.

And the carbon layer and the activated carbon layer are disposed and wound around each other.

The first current collector and the second current collector may include aluminum (Al) and copper (Cu), respectively, and may have porosity.

According to the present invention having the above-described configuration, the following effects can be expected.

The present invention relates to a method of manufacturing an asymmetric supercapacitor using a lithium pre-doping technique, characterized in that the lithium foil for lithium pre-doping is formed at one or both predetermined positions on the surface of an anode current collector, The cylindrical asymmetric supercapacitor manufactured by using the above-described method has an effect of exhibiting high capacity and output characteristics.

1 is an internal structural view of a cylindrical asymmetric supercapacitor according to an embodiment of the present invention;
2 is a front view of a positive and negative electrode structure for a cylindrical asymmetric supercapacitor according to an embodiment of the present invention.
Fig. 3 is a winding state diagram of Fig. 2; Fig.
4 is an electrode, separator, element and cell photograph for an asymmetric supercapacitor in the embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Figure 1 shows an internal structure through some cut-away sides of an asymmetric cylindrical asymmetric supercapacitor according to an embodiment of the present invention.

A positive electrode 10 having a polarized active carbon layer 14 formed on upper and lower surfaces of a first current collector 120 made of a metal foil and a carbon layer (30) is inserted between the positive electrode (22) and the negative electrode (20) having the lithium layer (26)

The lead wires 52 and 54 are attached to the positive electrode 10 and the negative electrode 20 described in FIG.

The lead wires 52 and 54 bind to the positive electrode 10 and the negative electrode 20, respectively. Lead wires 52 for binding the positive electrode 10 are made of aluminum (Al) The lead wire 54 that bonds to the base 20 is made of copper (Cu), nickel (Ni), or nickel-plated material.

An electrolytic solution containing a winding element and a lithium salt is contained in the Al container 40. The sealing member 60 having the lead wire drawn out to seal the container 40 is brought into close contact with the opening of the container 40, Structure.

In this case, the electrolytic solution generally uses electrolyte composed of Li ⁺ and anion BF4 ^- or PF6 ^- and a solvent composed of EC (Ethylene Carbonate) and DEC (Diethyl Carbonate) in a weight ratio of 1: 1.

2 shows a front view of a positive and negative electrode structure for a cylindrical asymmetric supercapacitor according to an embodiment of the present invention.

Referring to FIG. 2, the anode 10 has a structure in which the active carbon layer 14 is applied on the top and bottom surfaces of the first current collector 12.

In this case, the anode 10 is formed in a thin plate shape and can be formed of a cathode sheet, and the cathode 20 described above can also be formed of a thin plate or a cathode sheet.

The first current collector 12 uses 99% or more of high purity aluminum (Al) foil, and can be used in a thickness range of 20 to 50 탆.

The aluminum foil is a circle having a diameter of 0.3 mm or less, preferably 0.2 mm or less, or a square with a side length of 0.3 mm or less, preferably 0.2 mm or less, and an aperture ratio of 10 to 30% Is 10 to 20%.

In the figure, the thickness of the active carbon layer 14 is in the range of 60 to 120 mu m, preferably 70 to 100 mu m.

Here, the activated carbon layer 14 is composed of activated carbon, a conductive material, and a binder.

Here, the activated carbon layer 14 has a porosity of 1,500 to 2,000 m ² / g and an average particle size of 5 to 10 μm. The conductive material may be carbon black having an average size of 0.1 to 0.5 μm, Is composed of CMC (Carboxymethyl Cellulose) and SBR (Styrenebutadiene Rubber), or a mixed binder in which a small amount of PTFE (Polytetrafluoroethylene) is added to these mixed binders.

The mixing ratio of the constituent components of the anode 10 of the base material can be adjusted in the range of 80 to 95% by weight of the activated carbon powder, 3 to 10% by weight of the conductive material and 3 to 10% by weight of the binder. Also, the mixing ratio of the binder can be adjusted in the range of 30 to 50 wt% for CMC, 50 to 70 wt% for SBR, and 0 to 2 wt% for PTFE.

The cathode 20 shows a structure in which a carbon layer 24 and a lithium layer 26 are formed on the top and bottom surfaces of the second current collector 22 made of a metal foil.

The cathode 20 firstly applies carbon to the center portion of the upper and lower surfaces of the second current collector 22 to a predetermined thickness, and forms a carbon layer 24 through drying and rolling.

The lithium layer 26 is attached to one or both ends of the second current collector 22, and one or both ends of the lithium layer 26 are wound by one or more turns at the time of winding. In the present invention, .

The lithium layer 26 can be selectively formed on the center side (center) of the coil or at the outermost side of the coil at the time of winding, and is formed so as to be located on both sides in the present invention.

At this time, the lithium layer 26 is attached to the second current collector 22 by mechanical pressing and, of course, can be attached by various methods such as vapor deposition.

At this time, the lithium layer 26 may be deposited on the carbon layer 24 and one or both ends of the second current collector 22 without the carbon layer 24 may be attached to the position.

In detail, the attachment of the lithium layer 26 can be attached through roll pressing, or can be attached by a pressing jig applying a vertical load.

In the figure, 99% or more of high-purity copper (Cu) or nickel (Ni) can be used as the second current collector 22, and a thickness range of 20 to 50 μm is used.

Of course, the second current collector 22 may be made of aluminum.

The second current collector 22 is porous and has a through-hole of a circular shape with a diameter of 0.3 mm or less, preferably 0.2 mm or less, or a square shape with a side length of 0.3 mm or less, preferably 0.2 mm or less, Is 10 to 30%, preferably 10 to 20%.

In the figure, the thickness of the carbon layer 24 is in the range of 20 to 80 mu m, preferably 20 to 50 mu m.

Carbon, which is an anode active material, includes lithium (Li) ions which can be doped between carbon layers such as graphite, hard carbon, soft carbon, carbon nanotube, carbon nanofiber, Nano Fiber) powders may be used in combination.

The carbon layer may have a d _{002 value} of 0.335 to 1.2 nm and an average particle size of 5 to 20 μm.

The conductive material may be carbon black having an average size of 0.1 to 0.5 탆, and the binder is characterized by using a mixed binder composed of CMC and SBR.

The mixing ratio between the constituent components of the negative electrode of the base material can be controlled in the range of 85 to 96% by weight of the carbon powder, 2 to 5% by weight of the conductive material and 2 to 10% by weight of the binder. In addition, the mixing ratio of the binder can be adjusted in the range of 30 to 50 wt% for CMC and 50 to 70 wt% for SBR.

99% or more of high purity lithium foil can be used in a thickness range of 10 to 200 mu m. The thickness and area of the lithium foil can be determined in consideration of the lithium doping amount of the negative electrode carbon.

The weight of the lithium foil required for lithium doping is calculated by the following equation (1), and the thickness and area can be calculated from the volume of the lithium foil obtained from the equation (2).

On the other hand, a front view of a laminated structure composed of the anode 10, the cathode 20 and the separator 30 is shown.

The active carbon layer 14 of the anode 10 and the carbon layer 24 of the cathode 20 are stacked so that they can face each other with the separator 30 interposed therebetween and the lithium layer 26 of the cathode 20 is stacked And does not face the activated carbon layer 14 of the substrate 10.

The separator 30 is located on the intermediate surface between the anode 10 and the cathode 20 and the lower surface of the cathode 20. The separator 30 on the lower surface is located at a distance of 1 / And two or more circumferential lengths.

FIG. 3 is a view showing a winding state diagram of FIG. 2. FIG.

In FIG. 3, the separation membrane is omitted for the sake of understanding, and the first current collector and the second current collector of the cathode are omitted from the anode.

In Fig. 3, the stacked structure is wound in the rotational direction, and the lithium layer 26 is positioned at least one turn at the center side and the outermost side of the coil.

The lithium layer 26 may be located on the center side (center of gravity) or on the outermost side of at least one circumference, and in the present invention, it is located at least one circumference at the center side and the outermost side.

As shown in the drawing, the lithium layer extends from both ends of the carbon layer 24 to form a wound state.

The lithium layer 26 located at least on the center and the outermost side of the lithium layer 26 passes through each electrode layer in the state of a lithium layer in the electrochemical pre-doping process of the cylindrical asymmetric supercapacitor, .

Thus, the lithium layer 26 can pre-dope lithium ions radially from the center side, and can radially pre-dope the lithium ions from the outermost side.

As a result, the lithium layer 26 can stably implant the lithium ion into the carbon layer 24 of the anode, and can uniformly dope the entire area.

(Example)

The method of manufacturing the electrode and the cell, and the evaluation method of each characteristic in the embodiment of the present invention are as follows. However, the following description is provided only to illustrate the present invention more specifically, and does not limit the technical scope of the present invention.

<Manufacturing Method>

(a) cathode manufacturing

The anode active carbon electrode was prepared using activated carbon (2,000 m ² / g, average particle D ₅₀ = 8 μm), acetylene black, and mixed binder (CMC, SBR). First, SBR was added to CMC dissolved in water to mix CMC: SBR = 40: 60 weight ratio. Acetylene black and activated carbon were added to adjust the weight ratio of activated carbon: acetylene black: mixed binder to 86: 10: 6 .

The positive electrode slurry was agitated in a mixer (Thinky machine, Japan) for 10 minutes or more, and then coated on top and bottom of an aluminum current collector (thickness: 30 μm, aperture ratio: 20%). The coated electrode was dried for 60 minutes in a dryer and then rolled to a final thickness of 80 μm through a roll press.

The electrode was cut in a longitudinal direction (28 mm? 500 mm) in order to use it as a positive electrode for a cylindrical asymmetric supercapacitor (Radial 1840 type, 18 mm? 40 mml). The lead wire was made of aluminum terminal, and the lead wire was attached to the surface of the current collector not coated with the activated carbon electrode by mechanical pressing.

(b) Negative electrode fabrication

Negative electrode The carbon electrode was prepared using graphite carbon (d ₀₀₂ = 0.34 nm, average particle D ₅₀ = 5 μm), acetylene black, and a mixed binder (CMC, SBR). SBR was added to CMC dissolved in water to make CMC: SBR = 40: 60 weight ratio. Acetylene black and graphite carbon were added to prepare a mixture of graphite carbon: acetylene black: mixed binder in a weight ratio of 96: 1: 3 .

The negative electrode slurry was stirred in a mixer (Thinky machine, Japan) for 10 minutes or more and then coated on a copper collector (thickness: 20 μm, aperture ratio: 20%). The slurry was coated on the current collector area (30 mm? 占 520 mm) except for the current collector area to which the lithium foil was to be adhered in the subsequent step. The graphite-based carbon electrode layer of the negative electrode is designed to be slightly larger because it exists on the outer periphery of the positive electrode at the time of winding.

The coated electrode was dried at room temperature and rolled through a roll press so that the final thickness of the electrode cross section was 30 μm. In order to use the electrode as a negative electrode for a cylindrical asymmetric supercapacitor (Radial 1840 type, 18 mmφ × 40 mm), a certain area was cut in the lengthwise direction. At this time, when the electrode was wound, The collector was cut to expose the surface. When the lithium layer formed by the lithium foil is bound by the upper and lower mechanical pressing at the surface area of the current collector exposed to the surface, the roll press was finally performed to increase the binding strength.

The area and thickness of the lithium layer by the lithium foil were determined in the calculation of equations (1) and (2) of the above description, based on the lithium weight corresponding to the intercalation capacity of the lithium ion of the graphite carbon of the negative electrode. When the lithium capacity (0.59 g / cm ³ ) is divided by the lithium weight, which is calculated as the specific capacity of the graphite carbon at 400 mAh / g and the total weight of the graphite carbon at the cathode is 81 mg, The volume of the lithium foil necessary for the lithium ion battery can be obtained. The thickness of the lithium battery can be adjusted in accordance with one or two divisions according to the center or outermost attachment position of the negative electrode current collector during winding.

On the other hand, the lead wire was made of nickel-plated copper terminal, and the lead wire was mechanically crimped to a certain portion where the graphite carbon electrode was not coated.

(c) Manufacture of cylindrical asymmetric supercapacitors

The anode and the cathode (graphite carbon electrode + Li foil) cut in the longitudinal direction are laminated in the order of anode / separator / cathode / separator together with the separator, and the anode and the cathode of the cathode are connected to each other Position, and the lithium foil of the cathode is disposed at a predetermined position at both ends of the cathode. The separator used was a pp series Celgard 3501 and the separator located at the bottom of the cathode was cut to a length of more than one circumference than the length of the cathode. The electrodes and separator are arranged so that the terminal positions of the positive electrode and the negative electrode are aligned by 180 ° using a winder, and the outside of the wound element is fixed with an imide tape.

The finished device was inserted into a Radial 1840 aluminum case and the protruded terminals were discharged to the outside through a rubber bat- tery. After injecting a 1.0M LiPF6 in EC: DEC (1: 1) electrolyte, A cylindrical asymmetric supercapacitor (Radial 1840 type) was completed.

<Measurement method>

(a) Discharge capacity (F) measurement

After the cylindrical asymmetric supercapacitor was left at room temperature for 24 hours, the charging and discharging characteristics of the cell were measured using a charge and discharge tester (MACCOR, Model MC-4). The driving voltage was measured in the range of 2.2 to 3.8 V, and the applied current was measured in the condition of 0.2 C current (15 mA). The discharge capacity was calculated by the following equation in the time-voltage curve in the third discharge.

(b) High rate characteristic (C-rate)

The high-rate discharge characteristics of the asymmetric supercapacitor were calculated by the following equation after the third 0.2C charge and discharge of the cell were completed and then the fourth 0.2C charge and the 5C (375mA) discharge.

(b) AC resistance

The internal resistance of the asymmetric supercapacitor was measured using an impedance analyzer (Zahner IM6) after the third constant current discharge. The internal resistance behavior was performed in the frequency range of 100 kHz to 2.5 mHz, and the values specified in the present invention indicate the AC resistance value at 1 kHz.

&Lt; Example 1 >

The asymmetric supercapacitor is a lithium foil (26 mm x 60 mm l × 0.117 mm) was adhered to the center of the copper current collector at the center position (lithium foil + graphite carbon electrode layer). Other manufacturing conditions are the same as described above. The capacitance and high-rate characteristics of this asymmetric supercapacitor (Radial, Model 1840) were 135F and 90%, respectively, and the internal resistance was 120mΩ.

&Lt; Example 2 >

The asymmetric supercapacitor was manufactured by using a negative electrode (graphite carbon electrode layer + Li foil) in which a lithium foil (26 mmw x 60 mm x 0.117 mm t ) was bonded to the outermost position of the copper current collector. Other manufacturing conditions are the same as described above. The capacitance and high-rate characteristics of this asymmetric supercapacitor (Radial, Model 1840) were 138F and 90%, respectively, and the internal resistance was 126mΩ.

&Lt; Example 3 >

In the asymmetric supercapacitor, a lithium foil (26 mmw x 60 mm x 0.117 mm t ) was divided into two parts (primary core: 26 mmw x 15 mm x 0.117 mm t , outermost: 26 mmw x 45 mm x 0.117 mm t ) To prepare a negative electrode (lithium foil + graphite carbon electrode layer + lithium foil). Other manufacturing conditions are the same as described above.

Fig. 4 shows photographs of the anode, cathode and separator of Example 3, and a photograph of the upper plan view and the asymmetric supercapacitor (Radial, Model 1840) of the small electrode composed of the anode / separator / cathode / separator. Capacity and high-rate characteristics of this asymmetric supercapacitor were 140F and 95%, respectively, and the internal resistance was 90mΩ.

<Comparative Example>

The asymmetric supercapacitor was fabricated using a negative electrode (graphite carbon layer) without lithium foil for pre-doping. Other manufacturing conditions are the same as described above. The capacity and the high rate characteristics of this asymmetric supercapacitor (Radial, Model 1840) were 120F and 70%, respectively, and the internal resistance was 220mΩ.

(Comparative explanation)

Embodiments 1, 2 and 3 of an asymmetric supercapacitor pre-doped with lithium have superior capacity and resistance characteristics as compared with Comparative Examples in which Li is not pre-doped. By pre-doping lithium, the electrochemical characteristics of the asymmetric supercapacitor are improved because the fluctuation of the negative electrode potential is small and the output characteristic of the negative electrode is improved.

The electrochemical characteristics of the asymmetric supercapacitor of the embodiment shown in Table 1 are shown.

case Capacity (F) High rate characteristic (%) Resistance (mΩ) Example 1 135 90 120 Example 2 138 90 123 Example 3 140 95 90 Comparative Example 120 70 220

On the other hand, in the case of the embodiment in which the lithium foil was arranged on the cathode, the electrochemical characteristics of the asymmetric supercapacitor of Example 3 in which the lithium foil was disposed on both sides of the cathode as compared with Examples 1 and 2 in which the lithium foil was disposed on one side of the cathode Is excellent.

It is judged that the lithium pre-doping rate and the lithium ion are uniformly dispersed in the inside and outside of the device when the center of the coil of the device and the outermost side of the device are arranged as in the third embodiment.

As described above, it can be seen that the present invention provides a cylindrical asymmetric supercapacitor as a basic technical idea, and within the scope of the basic idea of the present invention, Of course, many variations are possible.

10: anode 12: first current collector
14: activated carbon layer 20: cathode
22: second collector 24: carbon layer
26: lithium layer 30: separator

Claims (6)

A cylindrical supercapacitor wound in a coil shape inside a container with a separator interposed therebetween, the positive electrode comprising a first current collector and an activated carbon layer, and a cathode comprising a second current collector, a carbon layer and a lithium layer,
The lithium-
One or both of one end and the other end of the surface of the second current collector is located at one or both of the center side and the outermost side of the coil,
The carbon layer
And the second collector is formed on a surface of the second collector, the remaining portion of the second collector being not formed with the lithium layer. The method according to claim 1,
The lithium-
And at least one turn of the cylindrical asymmetric supercapacitor is wound. The method according to claim 1,
The lithium-
And a lithium foil is attached to the surface of the second current collector by mechanical pressing or vapor deposition. The method according to claim 1,
The lithium-
A purity of 99% or more, and a thickness of 1 to 200 mu m. The method according to claim 1,
Wherein the carbon layer and the activated carbon layer comprise
Are arranged and wound in mutually confronted positions. The method according to claim 1,
Wherein the first current collector and the second current collector are made of a metal,
Each of which comprises aluminum (Al) and copper (Cu), and has porosity.

Images