JP2005026343A - Activated carbon for electrochemical element electrodes, electrochemical element electrode using it, and electrochemical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide activated carbon for electrochemical element electrode of sufficiently low internal resistance which is useful for formation of an electrochemical element electrode having superior electric characteristic, an electrochemical element electrode using it, and an electrochemical element and electrochemical capacitor provided with the electrode. <P>SOLUTION: The activated carbon is contained in the electrochemical element electrode, an composition material is activated carbon 100 for electrochemical element electrode which is a fiber, and whose aspect ratio is at most 8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００９７】
表１に示した結果から明らかなように、アスペクト比が１０以上になると電極表面に筋が入ったり、電極形成用塗布液が作製できなくなることが確認された。また、アスペクト比が１、すなわち、略球状の活性炭の場合は、電気抵抗の著しい増加と、レート特性（充放電特性）が劣化することが確認された。これに対して、実施例１〜３は、内部抵抗が十分に低減されており、優れたレート特性を示すことが確認された。
【００９８】
【発明の効果】
以上説明したように、本発明によれば、内部抵抗が十分に低減されており、優れた電極特性を有する電気化学素子電極の作製に有用な、電気化学素子電極用活性炭、それを用いた電気化学素子電極を提供することができる。さらに、本発明の電極を用いることで、内部抵抗が十分に低減されており、優れた充放電特性を示す電気化学素子並びに電気化学キャパシタを提供することができる。
【図面の簡単な説明】
【図１】本発明の電気化学素子電極用活性炭を示す模式図である。
【図２】本発明の電極の基本構成の一例を示す模式断面図である。
【図３】本発明の電気化学素子（電気化学キャパシタ）の好適な一実施形態を示す正面図である。
【図４】図３に示す電気化学キャパシタの内部をアノード１０の表面の法線方向からみた場合の展開図である。
【図５】図３に示す電気化学キャパシタを図３のＸ１−Ｘ１線に沿って切断した場合の模式断面図である。
【図６】図３に示す電気化学キャパシタを図３のＸ２−Ｘ２線に沿って切断した場合の要部を示す模式断面図である。
【図７】図３に示す電気化学キャパシタを図３のＹ−Ｙ線に沿って切断した場合の要部を示す模式断面図である。
【図８】図３に示す電気化学キャパシタのケースの構成材料となるフィルムの基本構成の一例を示す模式断面図である。
【図９】図３に示す電気化学キャパシタのケースの構成材料となるフィルムの基本構成の別の一例を示す模式断面図である。
【符号の説明】
１００…電気化学素子電極用活性炭、１０…電気化学素子電極、１…電気化学素子（電気化学キャパシタ）、１０…アノード、１２…アノード用リード、１４…絶縁体、２０…カソード、２２…カソード用リード、２４…絶縁体、３０…電解質溶液、４０…セパレータ、５０…ケース、６０…素体。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to activated carbon for an electrochemical element electrode, an electrochemical element electrode using the activated carbon, and an electrochemical element.
[0002]
[Prior art]
Electrochemical elements such as electrochemical capacitors and non-aqueous secondary batteries can be easily reduced in size and weight. For example, backup power supplies for portable devices (small electronic devices), electric vehicles, etc. It is expected as an auxiliary power source for automobiles and hybrid vehicles, and various studies are being made to improve its performance.
[0003]
For example, reduction of the internal resistance of the electrochemical element electrode and improvement of electrode characteristics such as capacitance per unit mass of the electrode and capacitance per unit volume have been studied. In order to reduce the internal resistance (impedance) of the electrode and improve the electrode characteristics, it has been proposed to use substantially spherical activated carbon as a constituent material of the electrode (see, for example, Patent Documents 1 and 2). It has also been proposed to use fine carbon fiber as a constituent material of the electrode (see, for example, Patent Document 3).
[0004]
[Patent Document 1]
JP 2001-180923 A
[Patent Document 2]
JP 2002-231589 A
[Patent Document 3]
JP-A-11-322314
[0005]
[Problems to be solved by the invention]
However, in the electric double layer capacitor using the electrode containing the substantially spherical activated carbon described in Patent Documents 1 and 2 as a constituent material, the internal resistance cannot be sufficiently reduced, and sufficient charge / discharge characteristics are still obtained. I couldn't do it. Moreover, even the conventional lithium ion secondary battery using the electrode containing the fine carbon fiber described in Patent Document 3 as a constituent material is described as a fine carbon fiber that is not activated and is not activated carbon. The actual state of the material is substantially spherical, and it does not have a sufficient specific surface area like activated carbon. Therefore, the internal resistance has not been sufficiently reduced, and sufficient charge / discharge characteristics have not yet been obtained.
[0006]
The present invention has been made in view of the above-described problems of the prior art, and has an internal resistance sufficiently reduced, which is useful for producing an electrochemical element electrode having excellent electrode characteristics. An object is to provide activated carbon, an electrochemical element electrode using the activated carbon, an electrochemical element including the electrode, and an electrochemical capacitor.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventors have found that the above object can be achieved by using activated carbon having a specific shape as a constituent material of an electrochemical element electrode. Reached.
[0008]
That is, the present invention provides activated carbon for an electrochemical element electrode, which is an activated carbon contained as a constituent material in an electrochemical element electrode and is fibrous and has an aspect ratio of 8 or less. Here, the “aspect ratio” indicates a value (b / a) obtained by dividing the major axis (length) b of the fibrous activated carbon by the minor axis (diameter) a.
[0009]
The electrochemical element electrode containing the activated carbon for an electrochemical element electrode of the present invention as a constituent material has an internal resistance sufficiently reduced, has excellent electrode characteristics, and further includes an electrochemical device equipped with this electrochemical element electrode. The element has a sufficiently reduced internal resistance and can obtain excellent charge / discharge characteristics.
[0010]
The reason why the above effect is obtained by using the activated carbon for an electrochemical element electrode of the present invention is not clear, but the present inventors speculate as follows. That is, in the conventional electrode using substantially spherical activated carbon, the contact between the activated carbons in the electrodes is a point contact, and since the contact area is small, the amount of electricity transmitted between the activated carbons is small, and thus the internal resistance of the electrodes is large. it is conceivable that. In addition, activated carbon expands and contracts due to desorption of electrolyte ions during charge and discharge, and the activated carbon tends to lose contact with each other, which is considered to be one of the causes of high internal resistance.
[0011]
On the other hand, since the activated carbon for an electrochemical element electrode of the present invention is in a fibrous form, the contact between the activated carbons in the electrode is often a line contact, and the contact area is larger than that of the substantially spherical activated carbon. Therefore, it is considered that the amount of electricity transmitted between the activated carbons increases and the internal resistance is sufficiently reduced practically. Furthermore, in the activated carbon for electrochemical element electrodes of the present invention, the entire activated carbon does not easily expand and contract due to desorption of electrolyte ions during charge and discharge, and contact between activated carbons is not easily lost. Accordingly, it is possible to sufficiently reduce the internal resistance of the electrode, and even when used for a long time, the contact area between the activated carbons is constant, so that it is considered that excellent electrode characteristics can be obtained.
[0012]
Further, the activated carbon of the present invention has (1) an aspect ratio of 1.5 or more, (2) a minor axis of activated carbon of 15 μm or less, and (3) a density of activated carbon of 1.2 g / cm. ³ It is preferable that at least one of the following conditions is satisfied. By satisfying the condition (1), the area of the line contact of the activated carbon increases, and the internal resistance of the electrode can be further reduced. In addition, by satisfying the condition (2), it is possible to more easily achieve the thinning of the electrode. Moreover, since it becomes easy to ensure the specific surface area in activated carbon enough by satisfy | filling the conditions of said (3), it becomes possible to further improve an electrode characteristic.
[0013]
The present invention also includes a current collector having electron conductivity, and a porous layer having electron conductivity formed on the current collector, and the porous layer is the electric current of the present invention. An electrochemical element electrode characterized by containing activated carbon for a chemical element electrode is provided. Since the electrode of the present invention contains the activated carbon for an electrochemical element electrode of the present invention, the internal resistance is sufficiently reduced and the electrode characteristics are excellent.
[0014]
In addition, the electrode of the present invention has a plate shape, and the thickness of the porous body layer is preferably 200 μm or less (more preferably 100 μm or less). Such an electrode is useful for reducing the size and weight of an electrochemical element.
[0015]
Furthermore, in the electrode of the present invention, a porous body layer is prepared with a coating liquid for forming a porous body layer containing at least the activated carbon for electrochemical element electrodes, and the coating liquid for forming a porous body layer is applied onto a current collector. It is preferably formed by a process. By using fibrous activated carbon having an aspect ratio of 8 or less and formed by the above-described coating step, it is possible to form a thin electrode without aggregation while reducing internal resistance as described above.
[0016]
The present invention also provides a first electrode and a second electrode facing each other, a separator disposed between the first electrode and the second electrode, an electrolyte solution, a first electrode, a second electrode An electrode, a separator and a case for containing the electrolyte solution in a sealed state, and
Provided is an electrochemical element, wherein at least one of the first electrode and the second electrode is the electrochemical element electrode of the present invention. Since the electrochemical device of the present invention has the above-described electrochemical device electrode of the present invention, the internal resistance is sufficiently reduced and excellent charge / discharge characteristics are exhibited.
[0017]
In the electrochemical device of the present invention, both the first electrode and the second electrode may be the electrochemical device electrode of the present invention. In this case, the electrochemical element functions as an electrochemical capacitor.
[0018]
Here, in the present invention, the “electrochemical element” means a first electrode and a second electrode facing each other, a separator disposed between the first electrode and the second electrode, and an electrolyte solution. And an element provided with at least. Furthermore, in the present invention, the electrochemical element may have a module configuration in which a plurality of unit cells are arranged in series or in parallel in one case.
[0019]
More specifically, the “electrochemical element” preferably represents a secondary battery or an electrochemical capacitor. The secondary battery is preferably a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte such as a lithium ion secondary battery, a secondary battery using an aqueous electrolyte solution, or the like. Examples of the electrochemical capacitor include an electric double layer capacitor, a pseudo capacitance capacitor, and a redox capacitor.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of an activated carbon for an electrochemical element electrode of the present invention, an electrochemical element electrode using the same, and an electrochemical element will be described with reference to the drawings. In the following description, the same or corresponding parts are denoted by the same reference numerals, and duplicate descriptions are omitted.
[0021]
(Activated carbon for electrochemical device electrodes)
FIG. 1 is a schematic diagram of activated carbon for an electrochemical element electrode of the present invention. As shown in FIG. 1, the activated carbon 100 for electrochemical element electrodes of the present invention is fibrous. Further, this activated carbon 100 has an aspect ratio (b / a) of 8 or less (preferably 1.5 to 8, more preferably 2 to 6, and further preferably 2 to 4).
[0022]
When the aspect ratio is more than 8, aggregation flaws are likely to occur in the electrode-forming coating solution used to produce the electrode, making it difficult to produce the electrode (especially thin film). On the other hand, when the ratio is less than 1.5, the contact between the activated carbons becomes close to point contact, and the internal resistance of the electrode tends to be insufficiently reduced.
[0023]
Moreover, it is preferable that the short axis a of the activated carbon 100 of this invention is 15 micrometers or less, It is more preferable that it is 0.1-12 micrometers, It is further more preferable that it is 1-10 micrometers. If the short axis a exceeds 15 μm, it tends to be difficult to make the electrode thin, whereas if it is less than 0.1 μm, it tends to be difficult to produce activated carbon.
[0024]
The density of the activated carbon 100 is 1.2 g / cm. ³ Or less, preferably 0.1 to 1.0 g / cm ³ More preferably, 0.5 to 0.8 g / cm ³ It is more preferable that Such density is 1.2 g / cm ³ Exceeding the above range, the electrode characteristics tend to be insufficient. On the other hand, 0.1 g / cm ³ If it is less than 1, the production of activated carbon tends to be difficult.
[0025]
Moreover, the activated carbon 100 has a specific surface area of 1000 to 3000 m. ² ・ G ^-1 It is preferable that it is 1000-2000m ² ・ G ^-1 It is preferable that it is 1000-1200m. ² ・ G ^-1 It is preferable that Specific surface area is 1000m ² ・ G ^-1 If it is less than 1, the electrode characteristics tend to be insufficient, while the specific surface area is 3000 m. ² ・ G ^-1 If it exceeds, the electrolyte solution tends to be unstable.
[0026]
As the material of the activated carbon, raw coal (for example, carbonized petroleum coke or resin produced from a delayed coker made from bottom oil of fluid catalytic cracking equipment of petroleum heavy oil or residual oil of vacuum distillation equipment) It is preferable to use as a main component what is obtained by activation treatment (such as phenol resin) or carbonized natural material (for example, coconut shell charcoal).
[0027]
The activated carbon 100 of the present invention first performs an activation treatment by cutting a fibrous material having a short axis a within a predetermined range into a predetermined length. In addition, a cutting | disconnection and activation process can be performed by a well-known method. Next, the activated carbon 100 of the present invention is obtained by further pulverizing the material after the activation treatment using a rotor having a predetermined rotational speed.
[0028]
(Electrochemical element electrode)
FIG. 2 is a schematic cross-sectional view of the electrochemical device electrode of the present invention. As shown in FIG. 2, the electrochemical device electrode 10 of the present invention comprises a current collector 16 having electron conductivity and a porous layer 18 having electron conductivity formed on the current collector. This porous layer 18 contains activated carbon 100 of the present invention having electron conductivity as a constituent material. Thereby, an electrochemical element provided with the electrode 10 having the porous body layer 18 has sufficiently reduced internal resistance and has excellent charge / discharge characteristics.
[0029]
The current collector 16 is not particularly limited as long as it is a good conductor capable of sufficiently transferring charges to the porous body layer 18, and a current collector used for a known electrochemical element electrode can be used. For example, the current collector 16 may be a metal foil such as aluminum, and the metal foil may be any one that has been etched or rolled, without particular limitation.
[0030]
The thickness of the current collector 16 is preferably 20 to 50 μm and more preferably 20 to 30 μm from the viewpoint of reducing the size and weight of the electrode 10.
[0031]
As long as the porous layer 18 includes the activated carbon 100 of the present invention in its constituent materials, the other structural conditions are not particularly limited, but from the viewpoint of obtaining the effects of the present invention more reliably, the porous layer 18 The content of the activated carbon 100 of the present invention is preferably 70 to 90% by mass based on the total mass of the porous body layer 18.
[0032]
Moreover, the porous body layer 18 is exhibiting plate shape, The thickness is preferably 200 micrometers or less, More preferably, it is 100 micrometers or less, It is more preferable that it is 20-100 micrometers. If the thickness of the porous layer 18 exceeds 200 μm, it is difficult to reduce the size of the electrode, and streaks or the like are generated during the electrode preparation, which tends to make the electrode preparation difficult. On the other hand, when the thickness is less than 20 μm, unevenness of the surface such as streaks is produced during electrode production, and the electrode production tends to be difficult.
[0033]
Further, the porous body layer 18 may contain a carbon material other than the activated carbon 100 of the present invention, or may contain a constituent material other than the carbon material such as a binder. The type and content thereof are not particularly limited. For example, a conductive auxiliary agent (carbon black or the like) for imparting conductivity to the carbon powder, and a binder (polytetrafluoroethylene, hereinafter referred to as PTFE), for example. And) may be added.
[0034]
The porous body layer 18 is formed on the current collector 16 (undercoat layer when an undercoat layer is provided). And the porous body layer 18 is formed as follows, for example. That is, first, a coating liquid for forming a porous body layer containing at least the activated carbon 100 of the present invention, a binder and a liquid capable of dissolving the binder is prepared, and then this is applied onto the current collector 16 and then the liquid is removed. It is formed by doing. In addition, it is preferable that the porous body layer 18 further contains a conductive additive in order to obtain better electronic conductivity.
[0035]
The electrode 10 of the present invention may be provided with an undercoat layer (not shown). The undercoat layer is a layer disposed between the current collector 16 and the porous multilayer 18, and provides physical and electrical adhesion of each layer (the current collector 16 and the porous body layer 18) in the electrode 10. It is a layer to be applied, and contains at least conductive particles and a binder capable of binding to the conductive particles as a constituent material. The undercoat layer is formed as follows. That is, first, a coating liquid for forming an undercoat layer containing conductive particles, a binder, and a liquid capable of dissolving the binder is prepared. Then, this is applied onto the surface of the current collector 16, and then the liquid is removed. It is formed by doing.
[0036]
(Electrochemical element)
FIG. 3 is a front view showing a preferred embodiment (electrochemical capacitor) of the electrochemical device of the present invention. 4 is a development view when the inside of the electrochemical capacitor shown in FIG. 3 is viewed from the normal direction of the surface of the anode 10. 5 is a schematic cross-sectional view of the electrochemical capacitor shown in FIG. 3 taken along the line X1-X1 of FIG. 6 is a schematic cross-sectional view showing the main part when the electrochemical capacitor shown in FIG. 3 is cut along the line X2-X2 of FIG.
[0037]
As shown in FIGS. 3 to 7, the electrochemical capacitor 1 is mainly composed of a plate-like anode 10 and a plate-like cathode 20 facing each other, and a plate disposed adjacently between the anode 10 and the cathode 20. Separator 40, electrolyte solution 30, case 50 containing these in a sealed state, and one end of the anode 10 is electrically connected to the anode 10, and the other end protrudes outside the case 50. The anode lead 12 and the cathode 20 having one end electrically connected to the cathode 20 and the other end protruding to the outside of the case 50 are configured. Here, the “anode” 10 and the “cathode” 20 are determined based on the polarity when the electrochemical capacitor 1 is discharged. Note that the electrochemical element electrode 10 of the present invention shown in FIG. 2 is applied to the anode 10 and the cathode 20.
[0038]
And the electrochemical capacitor 1 has the structure demonstrated below, in order to achieve the objective of this invention described previously.
[0039]
Details of each component of the present embodiment will be described below with reference to FIGS.
[0040]
The case 50 has a first film 51 and a second film 52 that face each other. Here, as shown in FIG. 4, the first film 51 and the second film 52 in this embodiment are connected. That is, the case 50 in the present embodiment is formed by bending a rectangular film 53 made of a single composite packaging film along a fold line X3-X3 shown in FIG. 4 and a pair of edges of the rectangular film facing each other. (The edge part 51B of the 1st film 51 and the edge part 52B of the 2nd film in a figure) are overlapped, and it forms by using an adhesive agent or performing heat sealing.
[0041]
And the 1st film 51 and the 2nd film 52 show the part of this film which has the mutually opposing surface (F51 and F52) which is formed when one rectangular film is bent as mentioned above, respectively. . Here, in this specification, each edge part of the 1st film 51 after bonding and the 2nd film 52 is called "seal part."
[0042]
Thereby, since it becomes unnecessary to provide the seal part for joining the 1st film 51 and the 2nd film 52 in the part of bending line X3-X3, the seal part in case 50 can be reduced more. As a result, the energy density per unit volume of the installation space in which the electrochemical capacitor 1 to be described later is to be installed (hereinafter referred to as “volume energy density based on the volume of the space to be installed”) can be improved. .
[0043]
In the case of this embodiment, as shown in FIGS. 3 and 4, one end of each of the anode lead 12 and the cathode lead 22 connected to the anode 10 is connected to the edge portion 51 </ b> B of the first film 51 described above. It arrange | positions so that it may protrude outside from the seal part which joined the edge part 52B seal part of the 2nd film.
[0044]
Furthermore, the film which comprises the 1st film 51 and the 2nd film 52 is a film which has a flexibility. By including a case 50 formed using a flexible film that is lightweight and easy to be thinned, and further, each of the anode 10, the cathode 20, and the separator 40 is formed into a plate shape, The shape of the electrochemical capacitor 1 itself can be a thin film. Since the film is lightweight and easy to thin, the electrochemical capacitor itself can be made into a thin film. Therefore, the original volume energy density can be easily improved, and the volume energy density based on the volume of the space in which the electrochemical capacitor is to be installed can be easily improved.
[0045]
Here, the “volume energy density” of the electrochemical capacitor is originally defined by the ratio of the total output energy to the total volume including the container of the electrochemical capacitor. On the other hand, “volume energy density based on the volume of the space to be installed” means the electrochemical capacitor for the apparent volume determined based on the maximum length, width, and thickness of the electrochemical capacitor. Means the ratio of the total output energy. In fact, when an electrochemical capacitor is mounted on a small electronic device, in addition to improving the original volume energy density described above, improving the volume energy density based on the volume of the space to be installed is This is important from the viewpoint of effectively using the limited space with the dead space sufficiently reduced.
[0046]
This film is not particularly limited as long as it is a flexible film. However, while ensuring sufficient mechanical strength and light weight of the case, moisture and air can enter from the outside of the case to the inside of the case and from the inside of the case to the outside of the case. From the standpoint of effectively preventing the electrolyte component from escaping, the “composite packaging” has at least an innermost layer made of synthetic resin in contact with the electrolyte solution and a metal layer disposed above the innermost layer. A “film” is preferred.
[0047]
Examples of the composite packaging film that can be used as the first film 51 and the second film 52 include a composite packaging film having a configuration shown in FIGS. 8 and 9. The composite packaging film 53 shown in FIG. 8 is disposed on the innermost layer 50a made of synthetic resin that contacts the electrolyte solution on the inner surface F50a, and on the other surface (outer surface) of the innermost layer 50a. It has the metal layer 50c. Further, the composite packaging film 54 shown in FIG. 9 has a configuration in which an outermost layer 50b made of synthetic resin is further arranged on the outer surface of the metal layer 50c of the composite packaging film 53 shown in FIG.
[0048]
The composite packaging film that can be used as the first film 51 and the second film 52 includes two or more layers including one or more synthetic resin layers including the innermost layer described above and a metal layer such as a metal foil. Although it will not specifically limit if it is the composite packaging material which has a layer, From the viewpoint of obtaining the same effect as the above more reliably, like the composite packaging film 54 shown in FIG. A synthetic resin outermost layer 50b disposed on the outer surface side of the case 50 farthest from the layer, and at least one metal layer 50c disposed between the innermost layer and the outermost layer. More preferably, it is composed of three or more layers.
[0049]
The innermost layer is a layer having flexibility, and the constituent material can express the above-mentioned flexibility, and chemical stability (chemical reaction, dissolution, It is not particularly limited as long as it is a synthetic resin having a characteristic that does not cause swelling) and chemical stability to oxygen and water (water in the air), but oxygen, water (water in the air) and electrolyte Materials having low permeability to the components of the solution are preferred. Examples thereof include thermoplastic resins such as polyethylene, polypropylene, polyethylene acid modified product, polypropylene acid modified product, polyethylene ionomer, and polypropylene ionomer.
[0050]
Further, when a synthetic resin layer such as the outermost layer 50b is further provided in addition to the innermost layer 50a as in the composite packaging film 54 shown in FIG. 9 described above, this synthetic resin layer Alternatively, the same constituent material as the innermost layer may be used. Further, as the synthetic resin layer, for example, a layer made of engineering plastic such as polyethylene terephthalate (PET) or polyamide (nylon) may be used.
[0051]
Moreover, the sealing method of all the sealing parts in the case 50 is not particularly limited, but the heat sealing method is preferable from the viewpoint of productivity.
[0052]
The metal layer is preferably a layer formed of a metal material having corrosion resistance against oxygen, water (water in the air) and an electrolyte solution. For example, a metal foil made of aluminum, aluminum alloy, titanium, chromium, or the like may be used.
[0053]
Next, the anode 10 and the cathode 20 will be described. As the anode 10 and the cathode 20 in the electrochemical capacitor of this embodiment, the above-described electrochemical element electrode 10 of the present invention shown in FIG. 2 is applied.
[0054]
The electrochemical device of the present invention may be such that at least one of the anode 10 and the cathode 20 is the electrochemical device electrode 10 of the present invention. For example, a porous layer is formed on one surface of the current collector. A conventionally known electrode having the structure described above may be used as the anode or the cathode. However, from the viewpoint of further reducing the size and weight while maintaining sufficient electrode characteristics, it is preferable that both the anode and the cathode are the electrochemical element electrodes 10 of the present invention as shown in the present embodiment. .
[0055]
The separator 40 disposed between the anode 10 and the cathode 20 is not particularly limited as long as it is formed of an insulating porous body, and a separator used in a known electrochemical capacitor can be used. For example, as the insulating porous body, at least one constituent material selected from the group consisting of a laminate of films made of polyethylene, polypropylene or polyolefin, a stretched film of a mixture of the above resins, or cellulose, polyester and polypropylene The fiber nonwoven fabric which consists of is mentioned.
[0056]
However, from the viewpoint of ensuring a sufficient contact interface with the electrolyte solution, the void volume Z of the porous body layer 18 is preferably 50 to 75 μL and more preferably 60 to 70 μL when the porous body layer volume is 100 μL. preferable. The method for obtaining the void volume Z is not particularly limited, and can be obtained by a known method.
[0057]
The current collector 28 of the cathode 20 is electrically connected to one end of a cathode lead 22 made of, for example, aluminum, and the other end of the cathode lead 22 extends to the outside of the case 50. On the other hand, the current collector 18 of the anode 10 is also electrically connected to one end of an anode lead 12 made of, for example, aluminum, and the other end of the anode lead 12 extends to the outside of the encapsulating bag 14.
[0058]
The electrolyte solution 30 is filled in the internal space of the case 50, and a part of the electrolyte solution 30 is contained in the anode 10, the cathode 20, and the separator 40.
[0059]
The electrolyte solution 30 is not particularly limited, and an electrolyte solution (electrolyte aqueous solution, electrolyte solution using an organic solvent) used in a known electrochemical capacitor can be used. However, the electrolyte aqueous solution is preferably an electrolyte solution (non-aqueous electrolyte solution) that uses an organic solvent because the electrochemical breakdown voltage is low, which limits the capacitor withstand voltage.
[0060]
Further, the type of the electrolyte solution 30 is not particularly limited, but is generally selected in consideration of the solubility, dissociation degree, and liquid viscosity of the solute, and has a high conductivity and a high potential window (a high decomposition start voltage). The electrolyte solution is desirable. For example, as a typical example, a quaternary ammonium salt such as tetraethylammonium tetrafluoroborate dissolved in an organic solvent such as propylene carbonate, diethylene carbonate, acetonitrile, γ-butyrolactone, or sulfolane is used. In this case, it is necessary to strictly manage the moisture content.
[0061]
Further, as shown in FIGS. 3 and 4, the portion of the portion of the anode lead 12 that contacts the sealing portion of the encapsulating bag composed of the edge portion 51 </ b> B of the first film 51 and the edge portion 52 </ b> B of the second film An insulator 14 for preventing contact between the anode lead 12 and the metal layer in the composite packaging film constituting each film is coated. Further, the cathode lead 22 and the composite constituting each film are formed on the portion of the cathode lead 22 that comes into contact with the sealing portion of the sealing bag composed of the edge 51B of the first film 51 and the edge 52B of the second film. An insulator 24 for preventing contact with the metal layer in the packaging film is coated.
[0062]
The configurations of the insulator 14 and the insulator 24 are not particularly limited. For example, the insulator 14 and the insulator 24 may be made of a synthetic resin. It should be noted that the insulator 14 and the insulator 24 may not be disposed as long as the metal layer in the composite packaging film can be sufficiently prevented from contacting the anode lead 12 and the cathode lead 22 respectively.
[0063]
Furthermore, from the viewpoint of enabling installation in a limited installation space within a portable small electronic device, the thickness of the laminate composed of the anode 10, the separator 40, and the cathode 20 (the laminate composed of the anode, the separator, and the cathode). The thickness (the thickness of the element body 60) is preferably 0.1 to 0.4 mm, and more preferably 0.1 to 0.3 mm.
[0064]
The electrochemical capacitor 1 has a capacitor capacity of 1 × 10 ^-3 It is preferably ˜1F, and more preferably 0.01 to 0.10F. Thereby, an electric double layer capacitor having a large capacity while being in the form of a film is obtained. These can be used for IC cards, IC tags, etc. by utilizing their thin characteristics. In addition, applications for toys and portable devices will be expanded.
[0065]
Next, a method for manufacturing the case 50 and the electrochemical capacitor 1 described above will be described.
[0066]
The manufacturing method of the element body 60 (a stacked body in which the anode 10, the separator 40, and the cathode 20 are sequentially stacked in this order) is not particularly limited, and is a known thin film manufacturing technique that is employed for manufacturing a known electrochemical capacitor. Can be used.
[0067]
First, the anode lead 12 and the cathode lead 22 are electrically connected to the anode 10 and the cathode 20, respectively. The separator 40 is disposed between the anode 10 and the cathode 20 (in an unbonded state), and the element body 60 is manufactured.
[0068]
Next, an example of a method for manufacturing the case 50 will be described. First, when the first film and the second film are composed of the composite packaging film described above, a dry lamination method, a wet lamination method, a hot melt lamination method, and an extrusion lamination method are used. It is produced using a known production method such as
[0069]
For example, a film that becomes a synthetic resin layer constituting the composite packaging film, and a metal foil made of aluminum or the like are prepared. The metal foil can be prepared, for example, by rolling a metal material.
[0070]
Next, a composite packaging film (multilayer film) is preferably obtained by laminating a metal foil via an adhesive on a film that becomes a layer made of a synthetic resin so as to have a configuration of a plurality of layers described above. Is made. Then, the composite packaging film is cut into a predetermined size, and one rectangular film 53 is prepared.
[0071]
Next, as described above with reference to FIG. 4, one film 53 is folded, and the element body 60 is placed in the folded film 53 (between the first film 51 and the second film 52). Is inserted. At this time, a part of the lead portion (the anode lead 12 and the cathode lead 22) of the element body 60 is projected from the seal portion 51B and the seal portion 52B to the outside of the case 50. Next, the seal portion 51B (edge portion 51B) of the first film 51 and the seal portion 52B (edge portion 52B) of the second film are made to have a desired seal width under a predetermined heating condition using, for example, a sealing machine. Heat seal. At this time, in order to secure an opening for introducing the electrolyte solution 30 into the case 50, a part where heat sealing is not performed is provided. As a result, the case 50 having an opening is obtained.
[0072]
Then, the electrolyte solution 30 is injected from the opening of the case 50 containing the element body 60. Subsequently, with the anode lead 12 and the cathode lead 22 partially inserted into the case 50, the opening of the case 50 is sealed using a sealing machine. In this way, the production of the case 50 and the electrochemical capacitor 1 is completed.
[0073]
The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the above embodiment. For example, in the description of the above embodiment, a configuration suitable for the case where the present invention is applied to an electrochemical capacitor (electric double layer capacitor) has been mainly described. However, the electrochemical element of the present invention is limited to an electrochemical capacitor. For example, a non-aqueous secondary battery (for example, a lithium ion secondary battery) and the like, an anode and a cathode facing each other, and a plate-like separator disposed adjacent to each other between the anode and the cathode The present invention can be applied to an electrochemical device having an electrolyte solution and a configuration in which these are accommodated in a case.
[0074]
When the electrochemical device is configured as a non-aqueous secondary battery as described above, an electrode active material having oxidation-reduction ability is further included in the electrode, if necessary, in addition to the activated carbon of the present invention. Also good. The electrode active material may be any material that can occlude or release (intercalate or dope / dedope) metal ions (lithium ions) involved in the electrode reaction, for example.
[0075]
In addition to the three-layer structure in which the separator 40 is disposed between the anode 10 and the cathode 20, the electrochemical element has five or more layers in which electrodes (anode 10 or cathode 20) and separators are alternately stacked. You may have the structure which consists of these laminated bodies.
[0076]
【Example】
Hereinafter, the contents of the electrochemical device of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
[0077]
(Example 1)
By the following procedure, an electrochemical capacitor having the same configuration as the electrochemical element (electrochemical capacitor) shown in FIG. 3 was produced.
[0078]
(1) Production of electrodes
The electrodes to be the anode (polarizable electrode) and the cathode (polarizable electrode) were prepared by the following procedure. Fibrous activated carbon (specific surface area: 2000 m ² / G, aspect ratio: 2, fiber average length: 15 μm, density: 0.7 g / cm ³ ), A binder {fluorine resin, manufactured by DuPont, product name: “Viton-GF”}, and a conductive additive (acetylene black, manufactured by Denki Kagaku Kogyo Co., Ltd., product name: “DENKABLACK”), and their mass The composition is such that the ratio is carbon material: binder: conducting aid = 80: 10: 10, and this is put into NMP (N-methylpyrrolidone) as a solvent and kneaded to apply for electrode formation. A liquid (hereinafter referred to as “coating liquid L1”) was prepared.
[0079]
The aspect ratio was measured by the following method. That is, the aspect ratio was obtained from the particle size distribution measurement, and the aspect ratio was obtained from the fiber average length and the average fiber diameter of the fibrous activated carbon. The average fiber diameter is actually measured with a microscope. The average fiber length was obtained by dispersing fibrous activated carbon in an ethanol solution and measuring it with a particle size distribution analyzer (HORIBA LA920).
[0080]
Next, this coating liquid L1 was uniformly applied on one surface of a current collector (thickness: 50 μm) made of an aluminum foil. Thereafter, NMP is removed from the coating film by a drying treatment, and a laminate comprising the current collector and the dried coating film is pressed using a rolling roll, and a current collector made of aluminum foil (thickness: 50 μm). ) Was formed on one surface of the electrode conductive layer (thickness: 0.120 mm) (hereinafter referred to as “electrode E1”).
[0081]
Next, the electrode E1 is cut so as to have a rectangular shape (size: 17.5 mm × 32.3 mm), and further vacuum-dried at a temperature of 150 ° C. to 175 ° C. for 12 hours or more to thereby conduct electron conduction. Moisture adsorbed on the surface of the porous layer was removed, and electrodes (anode and cathode) mounted on the electrochemical capacitor of Example 1 were produced.
[0082]
(2) Production of electrochemical capacitor
First, a tab portion (width 4 mm, length 3 mm) made of an aluminum foil is formed on the outer edge of the surface of the current collector on the side of the anode and cathode where the electron conductive porous layer is not formed. The tab portion was disposed in an electrically connected state. Moreover, the lead which consists of an aluminum ribbon (width 3mm, length 20mm) was electrically connected to each tab part of an anode and a cathode, respectively by ultrasonic welding. Next, the anode and the cathode are opposed to each other, and a separator (18.0 mm × 33.5 mm, thickness: 0.05 mm, manufactured by Nippon Kogyo Kogyo Co., Ltd., trade name: “TF4050”) is disposed between them. Then, a laminated body (element body) was formed in which the anode, the separator, and the cathode were laminated in this order (non-bonded state).
[0083]
Next, a sealant material was thermocompression bonded to the tab portion. Next, the laminated body (element body) was put into a case formed of a composite packaging film having flexibility, and the tab portions were heat sealed. As a flexible composite packaging film, the innermost layer made of synthetic resin (a layer made of modified polypropylene) in contact with the electrolyte solution, a metal layer made of aluminum foil, and a layer made of polyamide are sequentially laminated in this order. A laminate was used. And two sheets of this composite packaging film were piled up, and the edge part was heat-sealed and produced.
[0084]
Injecting electrolyte solution (1.2 mol / L propylene carbonate solution of triethylmethylammonium tetrafluoroborate) into the above case, then vacuum-sealing completes the production of an electrochemical capacitor (electric double layer capacitor) did.
[0085]
(Example 2)
First, the fibrous activated carbon used in producing the electrode of Example 1 has a specific surface area of 2000 m. ² / G, aspect ratio of 4, fiber average length of 30 μm, density of 0.7 g / cm ³ An electrode was produced in the same manner as in Example 1 except that the activated carbon was used. Next, an electrochemical capacitor was produced in the same manner as in Example 1 using the electrode.
[0086]
(Example 3)
First, the fibrous activated carbon used in producing the electrode of Example 1 has a specific surface area of 2000 m. ² / G, aspect ratio of 8, fiber average length of 70 μm, density of 0.7 g / cm ³ An electrode was produced in the same manner as in Example 1 except that the activated carbon was used. Next, an electrochemical capacitor was produced in the same manner as in Example 1 using the electrode.
[0087]
(Comparative Example 1)
First, the fibrous activated carbon used in producing the electrode of Example 1 has a specific surface area of 2000 m. ² / G, aspect ratio is 10, fiber average length is 110 μm, density is 0.7 g / cm ³ An electrode was produced in the same manner as in Example 1 except that the activated carbon was used. Next, an electrochemical capacitor was produced in the same manner as in Example 1 using the electrode.
[0088]
(Comparative Example 2)
First, the fibrous activated carbon used in producing the electrode of Example 1 has a specific surface area of 2000 m. ² / G, aspect ratio is 15, fiber average length is 180 μm, density is 0.7 g / cm ³ An electrode was produced in the same manner as in Example 1 except that the activated carbon was used. Next, an electrochemical capacitor was produced in the same manner as in Example 1 using the electrode.
[0089]
(Comparative Example 3)
First, the fibrous activated carbon used in producing the electrode of Example 1 has a specific surface area of 2000 m. ² / G, aspect ratio is 1, average particle size is 6 μm, density is 0.7 g / cm ³ An electrode was produced in the same manner as in Example 1, except that the spherical activated carbon was used. Next, an electrochemical capacitor was produced in the same manner as in Example 1 using the electrode.
[0090]
[Characteristic evaluation test of electric double layer capacitor]
The following various characteristics were measured about each electrochemical capacitor of Examples 1-3 and Comparative Examples 1-3.
[0091]
For the measurement of charge / discharge, a charge / discharge test apparatus (HJ-101SM6, manufactured by Hokuto Denko Co., Ltd.) was used. First, a constant current charge of 0.5 C is performed, and the voltage rise is monitored as the electric charge is accumulated in the electric double layer capacitor. After the potential reaches 2.5 V, the constant voltage charge (relaxation charge) is performed. The charging was terminated when the current became 1/10 of the charging current. The discharge was also a constant current discharge of 0.5 C, and the final voltage was set to 0V. After this test, the battery was charged with a current of 1 C. After the potential reached 2.5 V, the charging was switched to constant voltage charging, and the charging was terminated when the current became 1/10 of the charging current. The discharge was also a constant current discharge of 1 C, and the final voltage was set to 0V. Charging was started again and this was repeated 10 times.
[0092]
The capacitor capacity (electrostatic capacitor cell capacitance) was determined as follows. That is, the discharge energy (discharge voltage × current time integral of the discharge energy (W · s) is obtained from the discharge curve (discharge voltage−discharge time), and the capacitor capacity [F] = 2 × total discharge energy [W · s]. / (Discharge start voltage [V]) ² The capacitor capacity [F] of the evaluation cell was obtained using the following relational expression.
[0093]
Next, the internal resistance (impedance) of each electrochemical capacitor was determined by the following method. That is, a value at a frequency of 1 KHz measured using Solartron (trade name, manufactured by Toyo Technica Co., Ltd.) at a measurement environment temperature of 25 ° C. and a relative humidity of 60% is shown.
[0094]
The “rate characteristic” (C2 / C1) was calculated based on the following definition. That is, “C1” refers to an electrochemical capacitor having a capacitance of αF, a discharge current value: α × 10 ^-3 The electrostatic capacity when discharged with A is shown. In addition, “C2” means that the same electrochemical capacitor (electrochemical capacitor whose capacitor capacity is αF) from which C1 is measured is a discharge current value: 100 × α × 10 ^-3 The electrostatic capacity when discharged with A is shown. The “rate characteristic” indicates a value (C2 / C1) obtained by dividing C2 by C1. An electrochemical capacitor having a large “rate characteristic” value can be evaluated as having excellent charge / discharge characteristics. For example, in the electrochemical capacitor of Example 1, since α = 1.8F, C1 is a capacitance measured when discharged at a current value of 1.8 mA, and C2 is discharged at a current value of 180 mA. It becomes the electrostatic capacity measured at the time.
[0095]
Table 1 shows the internal resistance and rate characteristics of the electrochemical capacitors of Examples 1 to 3 and Comparative Examples 1 to 3. Note that, among the internal resistance values in Table 1, the internal resistance value described as “initial” indicates a value measured immediately after manufacturing the cell. Moreover, among the internal resistance values in Table 1, the internal resistance value described as “internal resistance after 120 cycles” indicates a value after 120 cycles of 1C charge / discharge. In addition, “−” in the table indicates that the measurement was not possible because the surface of the electrode was streaked or the electrode could not be prepared without preparing the coating liquid for forming the porous layer. .
[0096]
[Table 1]

[0097]
As is clear from the results shown in Table 1, it was confirmed that when the aspect ratio was 10 or more, streaks entered the electrode surface or the electrode forming coating solution could not be produced. It was also confirmed that when the aspect ratio was 1, that is, substantially spherical activated carbon, the electrical resistance was remarkably increased and the rate characteristics (charge / discharge characteristics) deteriorated. On the other hand, in Examples 1 to 3, it was confirmed that the internal resistance was sufficiently reduced and excellent rate characteristics were exhibited.
[0098]
【The invention's effect】
As described above, according to the present invention, the internal resistance is sufficiently reduced, and the activated carbon for an electrochemical element electrode useful for the production of an electrochemical element electrode having excellent electrode characteristics, and the electric power using the same A chemical element electrode can be provided. Furthermore, by using the electrode of the present invention, the internal resistance is sufficiently reduced, and an electrochemical element and an electrochemical capacitor exhibiting excellent charge / discharge characteristics can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic view showing activated carbon for an electrochemical element electrode of the present invention.
FIG. 2 is a schematic cross-sectional view showing an example of a basic configuration of an electrode of the present invention.
FIG. 3 is a front view showing a preferred embodiment of the electrochemical element (electrochemical capacitor) of the present invention.
4 is a development view when the inside of the electrochemical capacitor shown in FIG. 3 is viewed from the normal direction of the surface of the anode 10. FIG.
5 is a schematic cross-sectional view when the electrochemical capacitor shown in FIG. 3 is cut along line X1-X1 in FIG. 3;
6 is a schematic cross-sectional view showing the main part when the electrochemical capacitor shown in FIG. 3 is cut along the line X2-X2 of FIG. 3;
7 is a schematic cross-sectional view showing the main part when the electrochemical capacitor shown in FIG. 3 is cut along the YY line of FIG. 3;
8 is a schematic cross-sectional view showing an example of a basic configuration of a film that is a constituent material of the case of the electrochemical capacitor shown in FIG. 3. FIG.
9 is a schematic cross-sectional view showing another example of the basic structure of a film that is a constituent material of the case of the electrochemical capacitor shown in FIG. 3. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 ... Activated carbon for electrochemical element electrodes, 10 ... Electrochemical element electrode, 1 ... Electrochemical element (electrochemical capacitor), 10 ... Anode, 12 ... Lead for anode, 14 ... Insulator, 20 ... Cathode, 22 ... For cathode Lead, 24 ... insulator, 30 ... electrolyte solution, 40 ... separator, 50 ... case, 60 ... element body.

Claims (9)

An activated carbon contained in an electrochemical element electrode as a constituent material, which is fibrous and has an aspect ratio of 8 or less. The activated carbon for an electrochemical element electrode according to claim 1, wherein the aspect ratio is 1.5 or more. The activated carbon for an electrochemical element electrode according to claim 1 or 2, wherein the activated carbon has a minor axis of 15 µm or less. The activated carbon for an electrochemical element electrode according to any one of claims 1 to 3, wherein the activated carbon has a density of 1.2 g / cm ³ or less. A current collector having electron conductivity, and a porous layer having electron conductivity formed on the current collector,
The said porous body layer contains the activated carbon for electrochemical element electrodes as described in any one of Claims 1-4, The electrochemical element electrode characterized by the above-mentioned. The said porous body layer prepares the coating liquid for porous body layer formation containing the activated carbon for electrochemical element electrodes as described in any one of Claims 1-4, This coating liquid for porous body layer formation The electrochemical device electrode according to claim 5, wherein the electrochemical device electrode is formed by a step of coating the current collector on the current collector. The electrochemical element electrode according to claim 5 or 6, wherein the electrochemical element electrode has a plate shape, and the thickness of the porous layer is 200 µm or less. A first electrode and a second electrode facing each other;
A separator disposed between the first electrode and the second electrode;
An electrolyte solution;
A case for containing the first electrode, the second electrode, the separator, and the electrolyte solution in a sealed state;
Have
The electrochemical element according to claim 5, wherein at least one of the first electrode and the second electrode is the electrochemical element electrode according to claim 5. The electrochemical element according to claim 8, wherein both the first electrode and the second electrode are electrochemical element electrodes according to claim 5. .

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