JP2011029408A - Electrochemical capacitor and electrode layer used therefor, and method of manufacturing the electrode layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrochemical capacitor that has high energy density, has low internal resistance and a high breakdown voltage in a wide temperature environment from high temperature to low temperature, can be rapidly charged and discharged with a large current, and generates stable high output, to provide an electrode layer used for the electrochemical capacitor, and to provide a method of manufacturing the electrode layer. <P>SOLUTION: The electrochemical capacitor includes: a positive electrode layer containing lithium-containing transition metal oxide, a conductivity auxiliary, fibrous carbon, crystalline active carbon and a binder; a negative electrode layer containing a carbon material capable of occluding and desorbing lithium ions, a conductivity auxiliary, fibrous carbon, crystalline active carbon and a binder; and an organic electrolyte containing lithium salt and quaternary onium salt. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrochemical capacitor having a capacity by accumulating charges by a non-Faraday reaction without oxidation-reduction and a capacity by accumulating charges by a Faraday reaction with oxidation-reduction, an electrode layer used therefor, and an electrode layer thereof It relates to the manufacturing method. The present invention has a high energy density, a low internal resistance, a high withstand voltage, a rapid charge / discharge with a large current, and a stable high output in a wide temperature environment from a high temperature to a low temperature. The present invention relates to an electrochemical capacitor to be obtained, an electrode layer used therefor, and a method for producing the same.

Secondary batteries and electrochemical capacitors are actively developed as main power sources and auxiliary power sources for electric vehicles (EV) and hybrid vehicles (HEV), or as power storage devices for renewable energy such as solar power generation and wind power generation. It is advanced to.
As the electrochemical capacitor, an electric double layer capacitor, a hybrid capacitor, and a redox capacitor are known.
An electric double layer capacitor (sometimes called a symmetrical capacitor) uses a material having a large specific surface area such as activated carbon for both positive and negative electrode layers. An electric double layer is formed at the interface between the electrode layer and the electrolytic solution, and electricity is stored by a non-Faraday reaction without redox. An electric double layer capacitor generally has a higher output density and excellent rapid charge / discharge characteristics than a secondary battery.
The electrostatic energy J of the capacitor is defined by the formula: J = (1/2) × CV ² . C is a capacitance and V is a withstand voltage. The withstand voltage of the electric double layer capacitor is as low as about 2.7 to 3.3V. Therefore, the electrostatic energy of the electric double layer capacitor is 1/10 or less of the secondary battery.

  A hybrid capacitor (sometimes referred to as an asymmetric capacitor) has a positive electrode layer and a negative electrode layer made of different materials facing each other in an electrolyte solution containing lithium ions via a separator. With such a configuration, power storage by non-Faraday reaction that does not involve oxidation / reduction is performed in the positive electrode layer, and power storage by Faraday reaction that involves oxidation / reduction is performed in the negative electrode layer, thereby generating a large capacitance C. For this reason, it is expected that the hybrid capacitor will obtain a larger energy density than the electric double layer capacitor.

Various materials used for the positive electrode layer and the negative electrode layer of the hybrid capacitor have been proposed.
For example, in Patent Document 1, activated carbon is used for the positive electrode layer, and a carbon material that can occlude and desorb lithium ions in the negative electrode layer is used in which lithium ions are occluded by a chemical method or an electrochemical method. Proposed.
Patent Document 2 proposes using activated carbon for the positive electrode layer and using a carbon material capable of inserting and extracting lithium ions and lithium titanate for the negative electrode layer.
Patent Document 3 proposes using activated carbon and a lithium-containing transition metal oxide for the positive electrode layer and using a carbon material capable of inserting and extracting lithium ions for the negative electrode layer.

Patent Document 4 discloses a battery positive electrode including a battery positive electrode layer mainly composed of a lithium-containing transition metal oxide capable of occluding and releasing lithium ions in the same exterior material, and a carbonaceous material capable of adsorbing and desorbing anions. Capacitor positive electrode including a capacitor positive electrode layer mainly composed of lithium, a battery including a battery negative electrode layer mainly composed of an active material made of at least one of a carbonaceous material capable of occluding and releasing lithium ions or lithium-containing titanium oxide A negative electrode, a capacitor negative electrode including a capacitor negative electrode layer mainly composed of an active material composed of at least one of a carbonaceous material or lithium-containing titanium oxide capable of occluding and inserting lithium ions, and an organic electrolyte containing a lithium salt The battery positive electrode and the capacitor positive electrode are electrically connected, and the battery negative The above capacitor negative even complex energy elements are electrically connected have been proposed.
In Patent Document 5, a slurry mixture containing lithium cobalt oxide, activated carbon, a conductive agent and a binder is used for the positive electrode layer, a slurry mixture made of graphite, activated carbon and a binder is used for the negative electrode layer, and lithium ions are used for the electrolyte. A battery / capacitor composite element using a material including the above is described.

Japanese Patent Laid-Open No. 11-144759 JP 2002-270175 A JP 2000-106218 A JP 2004-55541 A JP 2001-351688 A

In the hybrid capacitor described in Patent Document 1, a carbon material in which lithium ions are occluded in the negative electrode layer is used. This occlusion process in the negative electrode layer is a process generally called lithium ion doping. This lithium ion doping requires a long time of one week to two weeks, and there is a problem that must be solved in industrial mass production, such as difficult process control.
The hybrid capacitor described in Patent Document 2 has a withstand voltage of about 2.5 to 3.0V. The specific capacity of lithium titanate is about 5 times the specific capacity of activated carbon, but the withstand voltage is low, so the energy density is not different from the conventional electric double layer capacitor and is insufficient.
On the other hand, the hybrid capacitor described in Patent Document 3 and the composite element described in Patent Document 4 or 5 have a high withstand voltage, but have a low cell capacity, resulting in an insufficient energy density.

As described above, the electrochemical capacitor described in the above-mentioned patent document has an energy density of about 10 Wh / L, and stabilizes an energy density of 30 Wh / L or more which is required for environmentally-friendly automobiles and natural energy storage applications. Have not been able to get.
The object of the present invention is to have a high energy density, a low internal resistance, a high withstand voltage, a rapid charge and discharge at a large current, and a stable high in a wide temperature environment from a high temperature to a low temperature. It is an object to provide an electrochemical capacitor capable of obtaining an output, an electrode layer used therefor, and a method for producing the same.

  The present inventors diligently studied to achieve the above object. As a result, a carbon material and a conductive auxiliary agent capable of inserting and extracting lithium ions in the negative electrode layer using a lithium-containing transition metal oxide, a conductive auxiliary agent, fibrous carbon, and crystalline activated carbon in the positive electrode layer And carbon fiber and crystalline activated carbon, and when the electrolyte contains a lithium salt and a quaternary onium salt, a high energy density is obtained without performing lithium ion doping. In addition, it is possible to provide an electrochemical capacitor that has a low internal resistance, a high withstand voltage, can be rapidly charged / discharged with a large current, and can obtain a stable high output in a wide temperature environment from high temperature to low temperature. I found it. The present invention has been completed by further study based on this finding.

That is, the present invention includes the following aspects.
[1] A positive electrode layer containing a lithium-containing transition metal oxide, a conductive aid, fibrous carbon, and crystalline activated carbon, a carbon material capable of inserting and extracting lithium ions, a conductive aid, fibrous carbon, and a crystal An electrochemical capacitor comprising: a negative electrode layer containing conductive activated carbon; and an organic electrolyte containing a lithium salt and a quaternary onium salt.
[2] The electrochemical capacitor according to [1], wherein the fibrous carbon contained in the positive electrode layer and / or the negative electrode layer is a carbon fiber or a carbon nanotube obtained by a vapor phase method.
[3] The fibrous carbon contained in the positive electrode layer and / or the negative electrode layer has a specific surface area of 10 to 20 m ² / g, an average fiber diameter of 1 to 500 nm, and a powder resistance value of 0.02Ω · mass ratio of carbon fiber V having a specific surface area of 100 to 1000 m ² / g, carbon fiber A having an average fiber diameter of 1 to 500 nm and a powder resistance value of 0.025 Ω · cm or more. The electrochemical capacitor according to [1] or [2], wherein the electrochemical capacitor is mixed in a range of 1: 2 to 1:10.
[4] The lithium-containing transition metal oxide is a composite oxide containing at least one element selected from the group consisting of Ti, V, Mn, Fe, Co, Ni, Zn, and W and a lithium element [ [1] The electrochemical capacitor according to any one of [3].
[5] The electrochemical capacitor according to any one of [1] to [4], wherein 10 to 60% by mass of the lithium-containing transition metal oxide is contained in the positive electrode layer.
[6] The carbon material capable of occluding and desorbing lithium ions has a true density of 1.45 to 1.6 g / cm ³ according to a liquid phase substitution method, according to any one of the above [1] to [5] The electrochemical capacitor as described.
[7] The electrochemical capacitor according to any one of [1] to [6], wherein the negative electrode layer contains 10 to 60% by mass of a carbon material capable of inserting and extracting lithium ions.
[8] The conductive assistant contained in the positive electrode layer and / or the negative electrode layer is a conductive carbon having a porosity of 55 to 85%, a specific surface area of 700 to 1400 m ² / g, and a hollow shell structure. The electrochemical capacitor according to any one of the above [1] to [7].
[9] The electricity according to any one of [1] to [8], wherein the crystalline activated carbon contained in the positive electrode layer and / or the negative electrode layer has a specific surface area of 800 to 2200 m ² / g. Chemical capacitor.
[10] In the organic electrolyte, the sum of the concentration of lithium ions and the concentration of quaternary onium ions is 2 to 4 mol / L, and the amount of lithium ions is mol relative to the amount of quaternary onium ions. The electrochemical capacitor according to [9], which has a ratio of 0.5 to 1.
[11] The electrochemical capacitor according to any one of [1] to [10], wherein the capacity of the negative electrode layer is 1.1 to 1.5 in a ratio to the capacity of the positive electrode layer.

[12] A positive electrode layer for an electrochemical capacitor containing a lithium-containing transition metal oxide, fibrous carbon, a conductive auxiliary, crystalline activated carbon, and a binder.
[13] The amount of the conductive auxiliary is 20 to 75% by mass with respect to the amount of the lithium-containing transition metal oxide, and the amount of fibrous carbon is 2 to 40% by mass with respect to the amount of the lithium-containing transition metal oxide. The positive electrode layer for an electrochemical capacitor as described in [12] above.
[14] The electricity according to [12] or [13], wherein the amount of the lithium-containing transition metal oxide is 10 to 50% by mass with respect to the total amount of the crystalline activated carbon and the lithium-containing transition metal oxide. Positive electrode layer for chemical capacitors.
[15] The electricity according to any one of [12] to [14], wherein the surface of the secondary particles of the lithium-containing transition metal oxide includes fibrous carbon and a conductive auxiliary agent attached thereto. Positive electrode layer for chemical capacitors.
[16] A lithium-containing transition metal oxide, fibrous carbon, and a conductive auxiliary agent are mixed, and a mixture obtained by mixing the crystalline activated carbon and a binder is obtained, and then the mixture The manufacturing method of the positive electrode layer of any one of said [12]-[15] including shape | molding.

[17] A negative electrode layer containing a carbon material capable of inserting and extracting lithium ions, fibrous carbon, a conductive auxiliary agent, crystalline activated carbon, and a binder.
[18] The amount of the carbon material capable of inserting and extracting lithium ions when the amount of the conductive auxiliary agent is 20 to 75% by mass with respect to the amount of the carbon material capable of inserting and extracting lithium ions. The negative electrode layer for an electrochemical capacitor according to [17], which is 2 to 40% by mass based on the total amount.
[19] The above [17], wherein the amount of the carbon material capable of inserting and extracting lithium ions is 10 to 60% by mass with respect to the total amount of the crystalline activated carbon and the carbon material capable of inserting and extracting lithium ions. Or the negative electrode layer for electrochemical capacitors as described in [18].
[20] Any one of [17] to [19] above, wherein the surface of secondary particles of a carbon material capable of occluding and desorbing lithium ions includes fibrous carbon and a conductive auxiliary agent attached thereto. A negative electrode layer for an electrochemical capacitor as described in 1.

[21] A carbon material capable of occluding and desorbing lithium ions, fibrous carbon, and a conductive auxiliary agent are mixed, and a mixture obtained by mixing the obtained carbonaceous material with crystalline activated carbon and a binder is obtained, Next, the method for producing a negative electrode layer according to any one of [17] to [20], comprising forming the mixture.

[22] An automobile having the electrochemical capacitor according to any one of [1] to [11] (an electric vehicle, a hybrid electric vehicle (HEV), a micro hybrid vehicle having an idling stop function, a power energy regeneration, Strong hybrid vehicles with brake regeneration, plug-in hybrid vehicles, fuel cell vehicles, etc.).
[23] A power generation system (solar power generation system, wind power generation system, etc.) having the electrochemical capacitor according to any one of [1] to [11].
[24] A transport engine (railway, ship, aircraft, etc.) provided with the electrochemical capacitor according to any one of [1] to [11].

Since the electrochemical capacitor of the present invention has a high withstand voltage and a large capacity, a high energy density of 30 Wh / L or more can be obtained. In the electrochemical capacitor of the present invention, activated carbon is mainly involved in rapid charge / discharge. The lithium-containing transition metal oxide is involved only when charging / discharging at a low current, and is not substantially involved during rapid charging / discharging. As a result, the electrochemical capacitor of the present invention has excellent charge / discharge cycle durability.
In the electrochemical capacitor of the present invention, a sufficient withstand voltage can be obtained without performing lithium doping on the negative electrode carbon material. Therefore, the production efficiency of the negative electrode layer is high and suitable for industrial mass production.

The figure which shows the scanning electron microscope image of what was obtained by mixing lithium titanate, a conductive support agent, and fibrous carbon It is sectional drawing of the apparatus for measuring powder resistance.

  The electrochemical capacitor of the present invention includes a positive electrode layer containing a lithium-containing transition metal oxide, a conductive auxiliary, fibrous carbon, and crystalline activated carbon, a carbon material capable of inserting and extracting lithium ions, and a conductive auxiliary. It has a negative electrode layer containing fibrous carbon and crystalline activated carbon, and an organic electrolyte solution containing a lithium salt and a quaternary onium salt.

(Crystalline activated carbon)
The crystalline activated carbon used for the positive electrode layer and the negative electrode layer preferably has a specific surface area of 800 to 2200 m ² / g, more preferably 850 to 1100 m ² / g. If the specific surface area of the crystalline activated carbon is too small, the capacity per mass (F / g) tends to be insufficient. Conversely, if the specific surface area is too large, the capacity per mass (F / g) increases, but the electrode density (g / ml) decreases, resulting in a decrease in capacity per volume (F / ml).
The crystalline activated carbon used in the present invention shows the maximum value of the pore volume in the range of the pore diameter of 1.0 to 1.5 nm in the logarithmic differential pore volume distribution obtained by the BJH method analysis from the N ₂ adsorption isotherm. There is a peak A, and the peak value of the peak A is preferably in the range of 0.012 to 0.05 ml / g and is preferably 2 to 32% of the total pore volume.
The crystalline activated carbon used for this invention is not limited by the manufacturing method, What has the said characteristic can be selected from the activated carbon obtained by the well-known manufacturing method. As a raw material of activated carbon, coconut shell, pitch, coal coke, petroleum coke, and synthetic resin (for example, vinyl chloride) can be used. Examples of the activation method include a steam activation method and an alkali activation method. Particularly preferred is activated carbon obtained by alkali activation using coal coke as a raw material.

Furthermore, the crystalline activated carbon used in the present invention has a plurality of crystallites having a graphite structure in amorphous carbon, and parameters indicating the orientation composition state and interlayer distance of these crystallites are the following (a) to (a) to It is preferable that at least one of (c) is satisfied.
(A) The crystallite size La (the size of the hexagonal network surface) in the a-axis direction on the (10) plane and the (11) plane in X-ray diffraction measurement is 5.5 nm or less.
(B) a peak intensity ratio of 1345cm ^-1 to the peak intensity of G-band 1600 cm ^-1 by laser Raman spectrum (R value) is 0.9 to 1.0.
(C) In the limited field electron diffraction of the bright field image of the transmission electron microscope, the area ratio of the graphite crystalline carbon portion / the specific crystalline carbon portion is 7/3 to 9/1.
When the La of X-ray diffraction of crystalline activated carbon exceeds 5.5 nm, the orientation structure of the carbonized material and the interlayer distance are narrow, so that the permeability of the molten alkali into the carbonized material becomes poor in the alkali activation treatment. Since the discharge of the generated gas to the outside of the carbonized product is delayed, the electric capacity (F / cc) per volume tends to decrease.
When the laser Raman G band peak ratio (R value) exceeds 1.0, the ratio of the amorphous turbulent layer structure increases, and the electric capacity (F / cc) per volume tends to decrease.
When the area ratio is smaller than 7/3, it is difficult to obtain a high discharge capacity. In addition, when the area ratio is larger than 9/1, the graphite volume is too much, so that the pore volume distribution is hardly optimized.

(Conductive aid)
The conductive auxiliary agent used for the positive electrode layer and the negative electrode layer is a conductive carbon capable of reducing the resistance of the positive electrode layer and the negative electrode layer. The conductive auxiliary agent may be selected from known conductive carbons used in electric double layer capacitors, lithium ion batteries and the like. Examples of the conductive carbon include acetylene black, channel black, furnace black, and ketjen black. Of these, ketjen black is particularly preferred.

The conductive carbon used in the present invention preferably has a specific surface area of 700 to 1400 m ² / g, and more preferably 800 to 1000 m ² / g. If the specific surface area is too small, the conductivity of the negative electrode layer tends to decrease. If the specific surface area is too large, the structure is disturbed, and problems such as electrode formability are likely to occur when mixed with activated carbon.
Furthermore, the conductive carbon used in the present invention preferably has a hollow shell structure. The hollow shell structure is constituted by a shell having a space inside the particle and a thin outer periphery as observed with an electron microscope. The shell is composed of a carbon hexagonal plane layer.

The conductive carbon suitably used in the present invention preferably has a porosity of 55% to 85%, and more preferably 60% to 70%. When the porosity of the conductive carbon is too small, the conductivity of the electrode layer is insufficient and the output tends to decrease. On the other hand, when the porosity of the conductive carbon is too large, the density of the electrode layer becomes low and the capacity per volume tends to decrease.
The porosity of the conductive carbon was calculated according to the following formula based on the BET specific surface area determined from the nitrogen adsorption isotherm and the external specific surface area determined from the electron micrograph.
Porosity (%) = (External specific surface area / BET specific surface area) × 100
As a commercial product having such characteristics, Ketjen Black (Ketjen Black International Co., Ltd.), which is a kind of furnace black, is preferable, and in particular, Ketjen Black EC300JP (porosity: 66.3%; porosity: 69) 0.1%) and Ketjen Black EC600JP (porosity: 81.9%; porosity: 81.6%) (both manufactured by Ketjen Black International).

  Moreover, the conductive carbon used in the present invention preferably has a primary particle size of 20 to 50 nm, and more preferably 30 to 40 nm. If the primary particle diameter of the conductive carbon is too small, the kneadability at the time of producing the electrode layer is lowered, so that aggregates increase and it is difficult to uniformly disperse. As a result, the conductive effect corresponding to the blending amount may not be obtained. On the other hand, if the particle diameter of the conductive carbon is too large, the density of the molded electrode is lowered, and the mechanical properties tend to be lowered.

(Fibrous carbon)
The fibrous carbon used for the positive electrode layer and the negative electrode layer can be selected from known fibrous carbons used in electric double layer capacitors, lithium ion batteries, and the like. The fibrous carbon used in the present invention has an aspect ratio of preferably 10 to 15000, more preferably 50 to 100; its specific surface area is preferably 10 to 1000 m ² / g, more preferably 50 to 500 m ^2. The average fiber diameter is preferably 1 to 500 nm, more preferably 150 to 200 nm.

In the present invention, it is preferable to use a combination of at least two types of carbon fibers having different characteristics. Specifically, it is preferable to use the following carbon fiber V and carbon fiber A in combination.
The carbon fiber V has a specific surface area of 10 to 20 m ² / g, an average fiber diameter of 1 to 500 nm, and a powder resistance value of 0.02 Ω · cm or less. The carbon fiber V is excellent in electrical conductivity and has an effect of improving the conductive path of the electrode layer. A preferable powder resistance value of the carbon fiber V is 0.015 Ω · cm or less. The lower limit of the powder resistance value of the carbon fiber V is preferably 0.011 Ω · cm.
Carbon fiber A has a specific surface area of 100 to 1000 m ² / g, an average fiber diameter of 1 to 500 nm, and a powder resistance value of 0.025 Ω · cm or more. Since the carbon fiber A has a pore structure similar to activated carbon on the surface of the carbon fiber, the organic electrolyte solution can easily permeate, thereby improving the electrical conductivity. The upper limit of the powder resistance value of the carbon fiber A is preferably 0.03 Ω · cm.
The mass ratio of carbon fiber V: carbon fiber A is preferably in the range of 1: 2 to 1:10, more preferably 1: 2 to 1: 5.

The fibrous carbon used in the present invention is preferably a carbon fiber or carbon nanotube obtained by a gas phase method.
The gas phase method is a method in which a carbon source such as ethylene is thermally decomposed in a gas phase, and carbon is grown in a fiber shape using catalyst particles such as iron and iron alumina as nuclei.
The carbon fiber V can be obtained, for example, by firing fibrous carbon obtained by a vapor phase method at 1000 to 1500 ° C. and then graphitizing at a temperature of 2500 ° C. or higher.
The carbon fiber A can be obtained, for example, by firing fibrous carbon obtained by a gas phase method at 1000 to 1500 ° C., and then subjecting the carbon to an alkali activation treatment at a temperature of 700 ° C. or higher.

<Positive electrode layer>
(Lithium-containing transition metal oxide)
The lithium-containing transition metal oxide contained in the positive electrode layer is a composite oxide containing a transition metal element and a lithium element. The transition metal element is preferably at least one element selected from the group consisting of Ti, V, Mn, Fe, Co, Ni, Zn and W, and at least one element selected from the group consisting of Mn, Ti and Fe. Elements are more preferred. Specific examples of the lithium-containing transition metal oxide include lithium manganese composite oxide (for example, LiMn ₂ O ₄ or LiMnO ₂ ), lithium nickel composite oxide (for example, LiNiO ₂ ), lithium cobalt composite oxide (for example, LiCoO). ₄ ), lithium titanium composite oxide (for example, Li ₄ Ti ₅ O ₁₂ ), lithium phosphorus oxide having an olivine structure (for example, LiFePO ₄ ), lithium vanadium oxide (for example, Li _x V ₂ O ₅ ), etc. Can be mentioned. Of these, Li _x Ti _y O _(1-y) or Li _z Mn ₂ O ₄ (where 0 <x <2, 0 ≦ y ≦ 1, 0 <z <2) is particularly preferable.

  The amount of the lithium-containing transition metal oxide in the positive electrode layer is preferably 10 to 60% by mass, more preferably 10 to 40% by mass, from the viewpoint of increasing the capacity, reducing the capacity decrease in the charge / discharge cycle, and increasing the durability. Preferably, 10 to 20% by mass is more preferable. If the amount of the lithium-containing transition metal oxide is too small, the amount of lithium ions desorbed in the first charge is insufficient relative to the amount of lithium ions that can be occluded by the negative electrode, and the withstand voltage tends to be lowered. When the amount of the lithium-containing transition metal oxide is too large, the amount of activated carbon in the positive electrode layer is relatively small, so that the capacity reduction in the charge / discharge cycle tends to be large.

  The amount of the conductive auxiliary in the positive electrode layer is preferably 20 to 75% by mass, more preferably 20 to 40% by mass with respect to the lithium-containing transition metal oxide. When the amount of the conductive auxiliary agent is too small, the conductivity of the positive electrode layer is insufficient and the high rate characteristic tends to be lowered. Moreover, when there are too many electroconductive auxiliary agents, since the compounding quantity of a lithium containing transition metal oxide will fall relatively, it will become difficult to obtain a high capacity | capacitance.

The amount of fibrous carbon in the positive electrode layer is preferably 2 to 40% by mass, more preferably 3 to 8% by mass with respect to the lithium-containing transition metal oxide.
If the amount of fibrous carbon is too small, the conductivity of the positive electrode layer tends to decrease. If the amount of fibrous carbon is too large, the electrode density decreases and the volume per volume (F / ml) tends to decrease.

  The amount of the crystalline activated carbon in the positive electrode layer is preferably 50 to 90% by mass, more preferably 75 to 90% by mass with respect to the total amount of the crystalline activated carbon and the lithium-containing transition metal oxide. If the amount of crystalline activated carbon in the positive electrode layer is too small, the energy density tends to decrease. If the amount of crystalline activated carbon in the positive electrode layer is too large, the withstand voltage tends to decrease.

In the positive electrode layer, it is preferable that the surface of the secondary particles of the lithium-containing transition metal oxide contains fibrous carbon and a conductive auxiliary agent attached thereto.
There are no particular restrictions on the method for allowing the positive electrode layer to include the surface of the secondary particles of the lithium-containing transition metal oxide to which the fibrous carbon and the conductive auxiliary agent are attached, but the positive electrode layer is formed by the following method. When manufactured, the above can be easily obtained.
First, a lithium-containing transition metal oxide, fibrous carbon, and a conductive aid are mixed. What was obtained by the mixing, crystalline activated carbon and a binder are mixed to obtain a positive electrode mixture. Next, the mixture is formed into a positive electrode layer having a predetermined size. As described above, by carrying out two-stage mixing in the preparation of the positive electrode mixture, the positive electrode layer includes a lithium particle-containing transition metal oxide secondary particle surface to which fibrous carbon and a conductive auxiliary agent are attached. Can be made.

The means for mixing (primary mixing) of the lithium-containing transition metal oxide, the conductive auxiliary agent and the fibrous carbon is not particularly limited. Examples thereof include a mixer such as a ball mill, a vibration mill, a sand mill, a bead mill, a pigment disperser, an ultrasonic disperser, a homogenizer, a planetary mixer, and a sample mill. The primary mixing can usually be performed in a temperature range of 20 to 30 ° C. for 20 seconds to 5 minutes. In addition, as a lithium containing transition metal oxide, it is preferable to use what a primary particle aggregates, ie, what is a secondary particle.
Primary mixing may be performed by mechanochemical treatment. Mechanochemical treatment is a treatment method that changes the structure / bonding state of substances constituting the solid by applying mechanical energy such as compressive force or frictional force to the solid, and changes the interaction with surrounding substances. It is. Examples of the mechanochemical treatment method include a hybridization method, a mechanofusion method, a theta composa method, and a mechanomill method.
By this primary mixing, what has fibrous carbon and a conductive support agent adhered to the secondary particle surface of the lithium-containing transition metal oxide is obtained. FIG. 1 is a view showing a scanning electron micrograph observation image of what was obtained by primary mixing of lithium titanate 15, conductive assistant 17 and fibrous carbon 16.

Next, what was obtained by the said primary mixing, crystalline activated carbon, and a binder are mixed (secondary mixing), and the positive mix is obtained. If only a portion of the conductive aid and / or fibrous carbon is used in the primary mixing, the remainder is secondary mixed together. The means for mixing (secondary mixing) of the primary mixture, crystalline activated carbon and binder is not particularly limited, and examples thereof include a ball mill, a sand mill, a bead mill, a pigment disperser, a grinder, an ultrasonic disperser, a homogenizer, and a planetar. Mixing equipment such as a Lee mixer may be mentioned. The secondary mixing is usually performed in a temperature range of 20 to 30 ° C., usually for 20 seconds to 5 minutes. .
The binder can be selected from known binders used in electric double layer capacitors, lithium secondary batteries and the like. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyamideimide, polyimide, acrylate rubber, butadiene rubber, and the like can be given. The amount of the binder contained in the positive electrode layer is preferably 1 to 20% by mass from the viewpoint of a balance between the strength of the positive electrode body and characteristics such as capacity.

  In order to obtain a mixture, a solvent can be appropriately used. Solvents include N-methylpyrrolidone; hydrocarbons such as toluene, xylene and benzene; ketones such as acetone, methyl ethyl ketone and butyl methyl ketone; alcohols such as methanol, ethanol and butanol; esters such as ethyl acetate and butyl acetate And organic solvents such as

  Next, the positive electrode mixture is formed. The forming can be performed by the same method as the forming method of the electrode layer of the conventional electric double layer capacitor or lithium secondary battery. Examples thereof include an extrusion molding method, a compression molding method, and a cast molding method. The obtained positive electrode layer and current collector joined together are called a positive electrode body.

Aluminum, stainless steel, titanium, tantalum, niobium, etc. can be used for the current collector for the positive electrode. A particularly preferable positive electrode current collector is made of aluminum. The thickness of the current collector is preferably 5 to 30 μm, and more preferably 5 to 10 μm. If the current collector is too thin, mechanical strength, heat resistance and the like are insufficient, and the electrode layer and terminal portion are liable to break. If the current collector is too thick, the capacity per volume of the electrochemical capacitor tends to decrease.
It is preferable to interpose a conductive adhesive layer between the positive electrode layer and the current collector. The contact resistance between the positive electrode layer and the current collector can be reduced by the conductive adhesive layer. The conductive adhesive is not particularly limited. For example, a varnish obtained by dissolving polyamideimide, polyimide or a precursor thereof in a solvent, or a conductive material such as conductive carbon particles, silver, or copper is dispersed in the varnish. Etc. For example, it is possible to obtain a positive electrode body by applying a conductive adhesive to the surface of a current collector by a doctor blade method or the like, drying the coating film to form an adhesive layer, and forming a positive electrode layer thereon. it can.

<Negative electrode layer>
(Carbon material capable of inserting and extracting lithium ions)
The carbon material that can occlude and desorb lithium ions used for the negative electrode layer can be appropriately selected from known carbon materials used for the negative electrode layer of the lithium secondary battery. In general, as a carbon material capable of inserting and extracting lithium ions, those having relatively high crystallinity are used. Specifically, petroleum coke, mesophase pitch-based carbon material or vapor-grown carbon fiber is used at 800 to 2000 ° C. Examples of the heat-treated material include natural graphite, artificial graphite, non-graphitizable carbon material (hard carbon), and graphitizable carbon material (soft carbon). Among these, artificial graphite is preferable in the present invention.
The carbon material that can occlude and desorb lithium ions preferably has a true density of 1.45 to 1.6 g / cm ³ by a liquid phase substitution method. Since the carbon material with too low true density has an undeveloped crystal structure, the capacity to intercalate Li ions is insufficient and the capacity tends to decrease. On the other hand, a carbon material having a too high true density has a graphite structure developed, so that it is difficult for Li ions to be inserted between the graphite layers, and the durability and reliability tend to decrease.

  The carbon material capable of inserting and extracting lithium ions is preferably contained in the negative electrode layer in an amount of 10 to 60% by mass, and more preferably 20 to 40% by mass. If the amount of the carbon material that can occlude and desorb lithium ions is too small, the negative electrode potential does not decrease and gas tends to be generated during high-voltage charge / discharge, and the reliability tends to decrease. When the amount of the carbon material capable of inserting and extracting lithium ions is too large, the cell capacity tends to decrease, and as a result, the energy density and output density tend to decrease.

The amount of the conductive auxiliary in the negative electrode layer is preferably 20 to 75% by mass, more preferably 20 to 40% by mass, based on the amount of the carbon material capable of inserting and extracting lithium ions.
If the amount of the conductive auxiliary is too small, the output tends to decrease. Moreover, when there is too much conductive auxiliary agent, there exists a tendency for a capacity | capacitance to fall.

The amount of fibrous carbon in the negative electrode layer is preferably 2 to 40% by mass, more preferably 3 to 8% by mass, based on the amount of carbon material capable of inserting and extracting lithium ions.
If the amount of fibrous carbon is too small, the conductivity of the negative electrode layer tends to decrease. If the amount of fibrous carbon is too large, the electrode density decreases and the volume per volume (F / ml) tends to decrease.

  The amount of the crystalline activated carbon in the negative electrode layer is preferably 40 to 90% by mass, more preferably 75 to 90% by mass with respect to the total amount of the crystalline activated carbon and the carbon material capable of inserting and extracting lithium ions. %. If the amount of crystalline activated carbon in the negative electrode layer is too small, the energy density tends to decrease, and if it is too large, the negative electrode potential does not decrease and gas tends to be generated by high-voltage charge / discharge, and the reliability tends to decrease. .

In the negative electrode layer, it is preferable that a carbon material capable of occluding and desorbing lithium ions has a fibrous particle and a conductive auxiliary agent attached to the surface of secondary particles.
The method for allowing the negative electrode layer to include a carbon particle secondary particle surface capable of occluding and desorbing lithium ions attached to fibrous carbon and a conductive auxiliary agent is not particularly limited. When the negative electrode layer is manufactured with the above, the above can be easily obtained.
First, a carbon material capable of inserting and extracting lithium ions, fibrous carbon, and a conductive aid are mixed. What was obtained by this mixing, crystalline activated carbon, and a binder are mixed, and the mixture for negative electrodes is obtained. Next, the mixture is formed into a negative electrode layer having a predetermined size. As described above, fibrous carbon and a conductive auxiliary agent adhere to the secondary particle surface of the carbon material capable of inserting and extracting lithium ions in the negative electrode layer by performing two-stage mixing in the preparation of the negative electrode mixture. Can be included.

  Means and methods for mixing (primary mixing) a carbon material capable of occluding and desorbing lithium ions, a conductive additive and fibrous carbon (primary mixing), and mixing (secondary mixing) the primary mixture, crystalline activated carbon and binder, It does not restrict | limit in particular, The same thing as the means and method in the preparation method of the positive electrode compound material can be mentioned. The primary mixing in the preparation of the negative electrode mixture can be usually performed at a temperature range of 20 to 30 ° C. for 20 seconds to 5 minutes, and the secondary mixing is usually performed at a temperature range of 20 to 30 ° C. for 20 seconds to Can be done in 5 minutes. In addition, it is preferable to use secondary particles in which the primary particles of the carbon material capable of inserting and extracting lithium ions are aggregated.

Next, the negative electrode mixture is formed. Molding can be performed by the same method as that for the positive electrode layer described above. The obtained negative electrode layer and the current collector are joined and integrated together is referred to as a negative electrode body.
For the current collector for the negative electrode, copper, nickel, stainless steel, and alloys thereof can be used. A particularly preferable negative electrode current collector is made of copper. The thickness of the current collector is preferably 5 to 30 μm, and more preferably 5 to 10 μm. If the current collector is too thin, mechanical strength, heat resistance and the like are insufficient, and the electrode layer and terminal portion are liable to break. If the current collector is too thick, the capacity per volume of the electrochemical capacitor tends to decrease. It is preferable to interpose a conductive adhesive layer between the negative electrode layer and the current collector. The contact resistance between the negative electrode layer and the current collector can be reduced by the conductive adhesive layer. The type of the conductive adhesive is not particularly limited, and examples thereof include the same ones used in the positive electrode layer.

(Organic electrolyte)
The organic electrolytic solution used in the present invention contains a quaternary onium salt and a lithium salt. Lithium salt contained in the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiN (SO 2 CF 3) 2, CF 3 SO 3 Li, LiC (SO 2 CF 3) 3, the group consisting of LiAsF ₆ and LiSbF ₆ One or more compounds selected from are preferred.
The quaternary onium salts contained in the electrolytic solution are (C ₂ H ₅ ) ₄ PBF ₄ , (C ₃ H ₇ ) ₄ PBF ₄ , (CH ₃ ) (C ₂ H ₅ ) ₃ NBF ₄ , (C ₂ H ₅ ) one or more compounds selected from the group consisting of ₄ NBF ₄ , (C ₂ H ₅ ) ₄ PPF ₆ , (C ₂ H ₅ ) ₄ PCF ₃ SO ₄ , and (C ₂ H ₅ ) ₄ NPF ₆ preferable.
The solvent for dissolving the quaternary onium salt and the lithium salt is at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, sulfolane, and dimethoxyethane. It is preferable to contain.

The molar ratio of lithium ions / quaternary onium ions in the electrolytic solution is preferably 0.5-1.
The total concentration of lithium ions and quaternary onium ions in the organic electrolyte is preferably 2 to 4 mol / L, more preferably 2.5 to 3.6 mol / L.

  In order to prevent overcharge of the negative electrode layer, it is preferable to set the capacity of the negative electrode layer larger than the capacity of the positive electrode layer. The capacity ratio of the negative electrode layer to the positive electrode layer (the capacity of the negative electrode layer / the capacity of the positive electrode layer) is more preferably in the range of 1.1 to 1.5. If the capacity ratio is too small, the diffusion of lithium ions in the negative electrode layer cannot catch up with the current when charging with a large current, the potential in the vicinity of the negative electrode layer is lowered, and the electrolytic solution is likely to be decomposed. On the other hand, if the capacity ratio is too large, the energy density of the entire electrochemical capacitor tends to decrease.

The electrochemical capacitor of the present invention is configured by immersing a positive electrode layer and a negative electrode layer in an organic electrolyte. A separator can be interposed between the positive electrode layer and the negative electrode layer. In the electrochemical capacitor of the present invention, a plurality of positive electrode layers, negative electrode layers, and separators can be alternately stacked (stacked type), and the positive electrode layer, negative electrode layer, and separator can be wound (winding type). The electrochemical capacitor is not limited to one having a pair of positive electrode layer and negative electrode layer in the cell, and two or more pairs in the cell may be connected in parallel. Further, a plurality of cells of the electrochemical capacitor may be connected in parallel and / or in series.
The container for housing the positive electrode layer, the negative electrode layer, and the organic electrolyte is not particularly limited by the shape and material thereof, but an aluminum laminate case or a metal case is preferable from the viewpoint of high heat dissipation.

(Li ion doping and means to lower the negative electrode potential)
Since the conventional hybrid capacitor is mainly composed of activated carbon without the lithium-containing transition metal oxide in the positive electrode layer, the lithium ions occluded in the carbon material of the negative electrode layer are derived from the lithium salt in the electrolyte. It was only what to do. Lithium ions stored in the carbon material of the negative electrode layer are insufficient. Therefore, in the conventional hybrid capacitor, it was necessary to dope lithium ions into the negative electrode layer.
On the other hand, in the electrochemical capacitor of the present invention, the lithium salt anion is adsorbed on the activated carbon in the positive electrode layer during charging, and lithium ions are desorbed from the lithium-containing transition metal oxide. Lithium ions are occluded in a carbon material that can occlude and desorb lithium ions in the negative electrode layer. The lithium ions occluded by the carbon material of the negative electrode layer are both derived from lithium salts in the electrolyte and derived from desorption from lithium-containing transition metal oxides. Therefore, the electrochemical capacitor of the present invention can store a sufficient amount of lithium ions in the negative electrode only by charging without performing lithium ion doping in the negative electrode layer. The potential of the negative electrode becomes base, and the oxidative decomposition voltage of the electrolyte solution of the positive electrode of the electrochemical capacitor can be increased, and the reductive decomposition voltage of the electrolyte solution of the negative electrode can be decreased, so that the operating voltage range can be widened.

A conventional lithium ion secondary battery having a positive electrode layer mainly composed only of a lithium-containing transition metal oxide and a negative electrode layer mainly composed of a carbon material capable of occluding and desorbing lithium ions performs a rapid charge / discharge cycle. And deterioration is remarkable compared with the case where a gentle charging / discharging cycle is performed. The main cause is deterioration due to the oxidation-reduction reaction of the lithium-containing transition metal oxide performed at the time of charging / discharging.
On the other hand, in the electrochemical capacitor of the present invention, activated carbon in the positive electrode layer is involved during rapid charge / discharge at a large current, and lithium-containing transition metal oxide in the positive electrode layer is involved during charge / discharge at a relatively small current. As a result of such a charge / discharge mechanism, the burden on the lithium-containing transition metal oxide of the positive electrode layer is reduced, deterioration due to the charge / discharge cycle can be suppressed, high voltage, high capacity, and long life of the charge / discharge cycle. Chemical capacitors are possible.

The electrochemical capacitor of the present invention is used in hybrid vehicles, plug-in hybrid vehicles, electric vehicles, various vehicles equipped with an idling stop mechanism, mild hybrid vehicles equipped with power energy regeneration and brake energy regeneration functions, fuel cell vehicles, and the like. Suitable for power storage devices. The electrochemical capacitor of the present invention is preferably used in combination with a secondary battery such as a lithium secondary battery.
The electrochemical capacitor of the present invention is used in a vehicle power supply system for railways, a ship power supply system, an aircraft power supply system, and the like, and also uses a renewable natural energy such as a solar power generation power system and a wind power generation power system. Used in the system. Furthermore, the electrochemical capacitor of the present invention is used in robots, toys, medical equipment, sensors, industrial equipment, communication equipment, and non-contact rechargeable power storage devices.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. The cells were all produced in an argon glove box with a dew point of −40 ° C. or lower.

In this example and the comparative example, characteristic values were obtained by the following method.
〔Specific surface area〕
Using NOVA1200, manufactured by Quantachrome, an adsorption isotherm of nitrogen at a liquid nitrogen temperature (77.4 K) was determined, and based on this, the specific surface area was calculated using the BET method.
[Secondary particle size]
Using MICROTRAC HRC MODEL 9320-X100 manufactured by Honeywell, the particle size distribution was obtained by the light scattering method, and the volume-based average value was calculated therefrom, which was used as the secondary particle size.
[Primary particle size]
The particle size distribution was obtained by observation with an electron microscope, and the median diameter was defined as the primary particle diameter.

[Porosity]
Calculated from the formula: (total pore volume / apparent volume) × 100 [%]. The total pore volume was measured using an autosorb (manufactured by Quantachrome), and the true specific gravity of carbon 1.9 was used for the calculation. The apparent volume is the sum of the total pore volume and the carbon volume.
[Porosity]
The external specific surface area was calculated by electron microscope observation. Based on the BET specific surface area based on the above-mentioned nitrogen adsorption isotherm and the external specific surface area, it was determined by the formula: (external specific surface area / BET specific surface area) × 100 [%].

[True density]
The true density was determined by measuring the butanol liquid phase replacement method (pycnometer method) according to JIS Z2601.
[Powder resistance]
As shown in FIG. 2, a fixed amount of powder is put into a measuring cell consisting of a cell 4 of 10 mm × 50 mm square and a depth of 100 mm, a compression rod 2 for pushing in, and a receiver 3, and the compression rod is placed from above. The pressure is applied to 2 and the powder is compressed. Then, while measuring the pressure and volume, a current of 100 mA is passed from the electrode 1 installed in the direction perpendicular to the pressurizing direction, and the voltage difference (E) V between the two measuring terminals 6 installed at an interval of 10 mm. And the resistance value (R) Ω · cm was calculated from the following equation.
R = E / 100
Since the powder resistance varies depending on the density, the evaluation is made with a constant density value. The powder resistance in the present invention is a value when the powder density is 0.8 g / cm ³ .

In the examples and comparative examples, the following substances were used.
Carbon fiber A: specific surface area 226 m ² / g, average fiber diameter 150 nm, aspect ratio = 60, powder resistance 0.025 Ω · cm, laser Raman G band peak ratio (R value) 1.32, from N ₂ adsorption isotherm In the logarithmic differential pore volume distribution obtained by BJH analysis, there is no pore volume peak at a pore diameter of 1 to 2 nm.
Carbon fiber V: specific surface area 13 m ² / g, fiber diameter 150 nm, aspect ratio = 60, powder resistance 0.012 Ω · cm, laser Raman G band peak ratio (R value) 1.32, N ₂ adsorption isotherm from BJH In the logarithmic differential pore volume distribution obtained by the method analysis, there is no pore volume peak at a pore diameter of 1 to 2 nm.

Conductive auxiliary agent (Ketjen Black EC300JP; manufactured by Ketjen Black International): Primary particle diameter = 39.5 nm, specific surface area 828 m ² / g, DBP oil absorption 360 ml / 100 g, porosity 66.3%, porosity 69.1%, volume resistivity 3.9Ω · cm (10% by weight polycarbonate)

[Lithium-containing transition metal oxide]
Lithium titanate (Li ₄ Ti ₅ O ₁₂ [XA105] manufactured by Ishihara Sangyo): secondary particle size 5.8 μm, specific surface area 3.1 m ² / g, tap density (200 times) 1.4 g / cm ³
Lithium manganate (LiMn ₂ O ₄ ): manufactured by Yunan Yuxihuilong Techonology; secondary particle size 11.8 μm, specific surface area 0.6 m ² / g, tap density 2.03 g / cm ³
Lithium cobaltate (LiCoO ₂ ): manufactured by Nippon Chemical Industry Co., Ltd .; Cell seed C-10, secondary particle diameter 23.3 μm, specific surface area 0.241 m ² / g, tap density 2.23 g / cm ³

[Carbon material capable of inserting and extracting lithium ions]
SCMG-AR (4RF): Showa Denko Prototype; secondary particle size of 15.5 μm, specific surface area of 1.4 m ² / g, true density of 1.59 g / cm ³ ; heat treatment of coal coke carbon material at 1000 ° C. SCMG-AR: manufactured by Showa Denko KK; secondary particle size 15.5 μm, specific surface area 1.39 m ² / g, true density 2.2 g / cm ³ , tap density (400 times) 1.28 g / cm ³ ： Obtained by heat treatment of coal coke carbon material at 3000 ℃ or higher

Crystalline activated carbon: Showa Denko Prototype; secondary particle size = 9.7 μm, specific surface area = 802 m ² / g, with a pore size of 1. in the logarithmic differential pore volume distribution determined by BJH analysis from the N ₂ adsorption isotherm. There is a peak A showing the maximum value of the pore volume in the range of 0 to 1.5 nm, the peak value of the peak A is in the range of 0.012 to 0.05 ml / g and 2% of the total pore volume. It is a size. Laser Raman G band peak ratio (R value) = 0.92, X-ray diffraction measurement (10) plane and (11) plane crystallite size La (hexagonal network size) Are 5.095 nm and 4.555 nm, respectively.
Phenol resin / steam activated activated carbon RP20: manufactured by Kuraray Chemical Co., Ltd .; secondary particle size = 6.4 μm, specific surface area = 1724 m ² / g, fine in logarithmic differential pore volume distribution determined by BJH method analysis from N ₂ adsorption isotherm There is no peak A indicating the maximum value of the pore volume in the pore diameter range of 1.0 to 1.5 nm.
Coal coke / alkali activated activated carbon SK331: manufactured by Kuraray Chemical Co., Ltd .; secondary particle size = 10.6 μm, specific surface area = 1116 m ² / g, fine in logarithmic differential pore volume distribution determined by BJH method analysis from N ₂ adsorption isotherm There is no peak A indicating the maximum value of the pore volume in the pore diameter range of 1.0 to 1.5 nm.

[Example 1]
(Method for producing positive electrode layer)
40 parts by mass of lithium titanate, 1 part by mass of carbon fiber A and 1 part by mass of ketjen black were put into a small pulverizer (sample mill SK-M2; manufactured by Kyoritsu Riko Co., Ltd.) and mixed at 15000 rpm for 20 seconds (primary mixing) ).
To 42 parts by mass of this primary mixture, 40 parts by mass of crystalline activated carbon, 0.5 parts by mass of carbon fiber V, 7.5 parts by mass of ketjen black, and 10 parts by mass of polytetrafluoroethylene (PTFE) as a binder are added. Ethanol was added to the mixture and kneaded at a pressure kneader (manufactured by Nishiyama) at 0.6 MPa (secondary mixing).
Next, the sheet was rolled to ² ton / cm ^{2 with} a roll rolling machine (manufactured by Daito Seisakusho) to produce a sheet having a thickness of 300 ± 10 μm. The sheet was vacuum-dried at 200 ° C. for 12 hours to obtain an electrode sheet for the positive electrode layer. This sheet was punched out to obtain a disk having a diameter of 20 mm. The disk was vacuum dried at 200 ° C. and 0.1 Mpa or less for 15 hours, and then the mass, thickness and diameter were measured. Electrode density = mass / volume (g / cm ³ ). The electrode density was 1.07 g / cm ³ . The electrode sheet was bonded to a current collector made of aluminum foil using a conductive adhesive to obtain a positive electrode body.

(Method for producing negative electrode layer)
40 parts by mass of carbon material SCMG-AR (4RF) capable of inserting and extracting lithium ions, 1 part by mass of carbon fiber A and 1 part by mass of Ketjen black (sample mill SK-M2; manufactured by Kyoritsu Riko) And mixed for 20 seconds at 15000 rpm (primary mixing).
To 42 parts by mass of this primary mixture, 40 parts by mass of crystalline activated carbon, 0.5 parts by mass of carbon fiber V, 7.5 parts by mass of ketjen black, and 10 parts by mass of binder (PTFE) are added, and ethanol is added to this mixture. The mixture was kneaded at a pressure kneader (Nishiyama Co., Ltd.) at 0.6 MPa (secondary mixing).
Next, the sheet was rolled to ² ton / cm ^{2 with} a roll rolling machine (manufactured by Daito Seisakusho) to produce a sheet having a thickness of 300 ± 10 μm. The sheet was vacuum dried at 200 ° C. for 12 hours to obtain an electrode sheet for the negative electrode layer. This sheet was punched out to obtain a disk having a diameter of 20 mm. The disk was vacuum-dried at 200 ° C. and 0.1 Mpa or less for 15 hours, and then the mass, thickness and diameter were measured, whereby electrode density = mass / volume (g / cm ³ ) was determined. The electrode density was 1.00 g / cm ³ . The electrode sheet was joined to a current collector made of copper foil using a conductive adhesive to obtain a negative electrode body.

(Electrochemical capacitor cell assembly)
A polyethylene separator (065E-2 made by Nippon Sheet Glass) was sandwiched between the positive electrode body and the negative electrode body obtained above, and they were overlapped so that the positive electrode layer and the negative electrode layer were opposed to each other. This was encapsulated in an aluminum laminate film to produce a cell.
An electrolyte solution was prepared by dissolving LiPF ₆ in propylene carbonate at a concentration of 1.5 mol / L and (CH ₃ ) (C ₂ H ₅ ) ₃ NBF ₄ at a concentration of 1.8 mol / L. The electrode layer was sufficiently immersed in the electrolytic solution. The initial capacity (F / cell) was measured in the range of 3.8V to 1.5V.

[Cycle characteristics and gas generation]
Charging / discharging was repeated 100 times at 25 ° C. in the range of 3.8 V to 1.5 V at a current density of 0.4 mA / cm ² .
The ratio (namely, capacity | capacitance retention) with respect to the capacity | capacitance at the time of the 100th charge / discharge with respect to the capacity | capacitance at the time of the 3rd charge / discharge was computed.
Moreover, the ratio (namely, volume expansion coefficient) after performing 100 times charging / discharging with respect to the volume before charging / discharging of a laminate cell was computed. The amount of gas generation was estimated from the volume expansion coefficient of the laminate cell. With respect to gas generation, 1 ml / cycle or less was represented as ◯ (Good), and 1 ml / cycle or more as x (Bad). The results are shown in Table 1.

[Examples 2 to 5, Comparative Examples 1 to 6]
An electrochemical capacitor cell was obtained in the same manner as in Example 1 except that the formulation of the positive electrode layer, the negative electrode layer, and the electrolytic solution was changed to that shown in Table 1, and the characteristic values thereof were measured. The results are shown in Table 1.

1 Electrode 2 Compression rod 3 Receiver 4 Cell 5 Measured substance 6 Measurement terminal

Claims (24)

A positive electrode layer containing a lithium-containing transition metal oxide, a conductive auxiliary, fibrous carbon, and crystalline activated carbon;
A negative electrode layer containing a carbon material capable of inserting and extracting lithium ions, a conductive auxiliary, fibrous carbon, and crystalline activated carbon, and an organic electrolyte containing a lithium salt and a quaternary onium salt,
An electrochemical capacitor.   The electrochemical capacitor according to claim 1, wherein the fibrous carbon contained in the positive electrode layer and / or the negative electrode layer is a carbon fiber or a carbon nanotube obtained by a vapor phase method. The fibrous carbon contained in the positive electrode layer and / or the negative electrode layer has a specific surface area of 10 to 20 m ² / g, an average fiber diameter of 1 to 500 nm, and a powder resistance value of 0.02 Ω · cm or less. A carbon fiber V,
Carbon fiber A having a specific surface area of 100 to 1000 m ² / g, an average fiber diameter of 1 to 500 nm, and a powder resistance value of 0.025 Ω · cm or more,
The electrochemical capacitor according to claim 1 or 2, which is mixed in a mass ratio of 1: 2 to 1:10.   The lithium-containing transition metal oxide is a composite oxide containing at least one element selected from the group consisting of Ti, V, Mn, Fe, Co, Ni, Zn, and W and a lithium element. The electrochemical capacitor according to any one of the above.   5. The electrochemical capacitor according to claim 1, wherein 10 to 60 mass% of the lithium-containing transition metal oxide is contained in the positive electrode layer. The electrochemical capacitor according to any one of claims 1 to 5, wherein a carbon material capable of inserting and extracting lithium ions has a true density of 1.45 to 1.6 g / cm ³ by a liquid phase substitution method.   The electrochemical capacitor according to any one of claims 1 to 6, wherein a carbon material capable of inserting and extracting lithium ions is contained in the negative electrode layer in an amount of 10 to 60% by mass. The conductive auxiliary agent contained in the positive electrode layer and / or the negative electrode layer is a conductive carbon having a porosity of 55 to 85%, a specific surface area of 700 to 1400 m ² / g, and having a hollow shell structure. Item 10. The electrochemical capacitor according to any one of Items 1 to 7. 9. The electrochemical capacitor according to claim 1, wherein the crystalline activated carbon contained in the positive electrode layer and / or the negative electrode layer has a specific surface area of 800 to 2200 m ² / g.   In the organic electrolyte, the total concentration of lithium ions and quaternary onium ions is 2 to 4 mol / L, and the amount of lithium ions is 0.1 by mole with respect to the amount of quaternary onium ions. The electrochemical capacitor according to claim 9, which is 5-1.   The electrochemical capacitor according to any one of claims 1 to 10, wherein a capacity of the negative electrode layer is 1.1 to 1.5 in a ratio to a capacity of the positive electrode layer.   A positive electrode layer for an electrochemical capacitor containing a lithium-containing transition metal oxide, a conductive auxiliary agent, fibrous carbon, crystalline activated carbon, and a binder.   The amount of the conductive auxiliary is 20 to 75% by mass with respect to the amount of the lithium-containing transition metal oxide, and the amount of fibrous carbon is 2 to 40% by mass with respect to the amount of the lithium-containing transition metal oxide. The positive electrode layer for an electrochemical capacitor according to claim 12.   The positive electrode layer for an electrochemical capacitor according to claim 12 or 13, wherein the amount of the lithium-containing transition metal oxide is 10 to 50% by mass with respect to the total amount of the crystalline activated carbon and the lithium-containing transition metal oxide. .   The positive electrode layer for an electrochemical capacitor according to any one of claims 12 to 14, wherein the surface of secondary particles of the lithium-containing transition metal oxide contains fibrous carbon and a conductive auxiliary agent attached thereto. .   Lithium-containing transition metal oxide, fibrous carbon, and conductive auxiliary are mixed, and the mixture obtained by mixing the above, crystalline activated carbon, and binder are mixed to obtain a mixture, and then the mixture is molded. The manufacturing method of the positive electrode layer of any one of Claims 12-15 containing this.   A negative electrode layer for an electrochemical capacitor, comprising a carbon material capable of inserting and extracting lithium ions, a conductive auxiliary agent, fibrous carbon, crystalline activated carbon, and a binder.   The amount of the conductive assistant is 20 to 75% by mass with respect to the amount of the carbon material capable of inserting and extracting lithium ions, and the amount of the fibrous carbon is based on the amount of the carbon material capable of inserting and extracting lithium ions. The negative electrode layer for an electrochemical capacitor according to claim 17, which is 2 to 40% by mass.   The amount of the carbon material capable of inserting and extracting lithium ions is 10 to 60% by mass with respect to the total amount of the crystalline activated carbon and the carbon material capable of inserting and extracting lithium ions. Negative electrode layer for electrochemical capacitors.   The electrochemical capacitor according to any one of claims 17 to 19, wherein a carbon material capable of inserting and extracting lithium ions includes a surface of secondary particles attached to fibrous carbon and a conductive auxiliary agent. Negative electrode layer.   A carbon material capable of occluding and desorbing lithium ions, fibrous carbon, and a conductive aid are mixed, and a mixture obtained by mixing the above, a crystalline activated carbon, and a binder is obtained, and then the mixture is obtained. The manufacturing method of the negative electrode layer of any one of Claims 17-20 including shape | molding an agent.   The motor vehicle which has the electrochemical capacitor of any one of Claims 1-11.   The power generation system which has an electrochemical capacitor of any one of Claims 1-11.   The transport organization provided with the electrochemical capacitor of any one of Claims 1-11.

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