JP2003331849A - Current collecting structure, electrode structure, and method for manufacturing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance attaching strength of a conducting assistant to a current collector. <P>SOLUTION: The current collecting structure, the electrode structure, and the method for manufacturing them are provided in such a way that the current collector having an oxide film on the surface; the conducting assistant having conductivity; an anchor material being bitten into the current collector; and a binder binding the current collector, the anchor material, and the conducting assistant are arranged, and the conducting assistant is fixed to the surfaces of the anchor material and the current collector. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current collecting structure which is a constituent element of a battery or a capacitor, and an electrode structure.

[0002]

2. Description of the Related Art Conventionally, in order to increase the conductivity of the surface of a current collector, even if a large amount of conductive auxiliary agent such as Ketchin Black is attached, even if a conductive agent and a binder are mixed and applied to the surface of the current collector, It was difficult to attach the conductive auxiliary agent to the entire surface of the current collector because the conductive auxiliary agent aggregated to form clusters. Further, even if a conductive substance is attached to the surface of the current collector by vapor deposition or sputtering, it is difficult to sufficiently fix it so as to function as an electrode.

Further, conventionally, in the production of an electrode structure, a mixture of an electrode active material, a conductive additive and a binder is applied to a current collector to form a coating layer in order to increase the density of the electrode active material and the conductive additive. Pressing. However, this pressing force increases the densities of the electrode active material and the conductive additive, and it was difficult to attach the conductive additive in large amounts to the surface of the electrode active material and the surface of the current collector. In particular, it has been difficult to reduce the resistance at the interface of the current collector.

[0004]

<A> The present invention is to increase the adhesion strength of a conductive additive used for an electrode to a current collector. <B> Further, the present invention is to increase the adhesion density of the conductive additive used for the electrode to the current collector. <C> Further, the present invention is to bring the conductive auxiliary agent used for the electrode closer to the current collector. <D> Further, the present invention is to prevent corrosion of the current collector of the electrode and to maintain low impedance of the current collector structure.

[0005]

The present invention is directed to a current collector having an oxide film on its surface, a conductive auxiliary agent having conductivity, an anchor substance digging into the current collector, a current collector, an anchor substance and a conductive substance. A binder for adhering an auxiliary agent, characterized in that the conductive auxiliary agent is fixed to the surface of the anchor material and the current collector, or the current collecting structure, or the present invention, in the current collecting structure, the conductive auxiliary The agent is a carbon particle having a particle diameter smaller than that of the anchor material, or a fibrous carbon having a diameter smaller than the particle diameter of the anchor material, or a current collecting structure, or the present invention has an oxide film on the surface. Apply a mixture of a conductive auxiliary agent having an electrical conductivity and an anchor substance and a binder to the current collector to press and cause the anchor material to bite into the current collector, and bond the current collector, the anchor substance and the conductive auxiliary agent with a binder, Conductive aid A method for producing a current collecting structure, which comprises fixing the car material surface and a current collecting material surface close to each other, or the present invention, in the method for producing the current collecting structure, an anchor having a conductive auxiliary agent attached to the surface thereof. A method for producing a current collecting structure, which comprises applying a mixture of a substance, a conductive auxiliary agent and a binder to a current collecting material, or the present invention has a current collecting material having an oxide film on its surface, and having conductivity. It has a conductive additive and an anchor substance that digs into the current collector.Apply a mixture of the anchor substance, conductive additive and binder to the current collector and press it to let the anchor substance dig into the current collector and A current collecting structure fixed on the surface of the anchor material and the current collecting material, and an electrode layer formed by applying a mixture of an electrode active material, a conductive auxiliary agent and a binder on the current collecting structure and pressing them to adhere them, The pressing force for forming the current collecting structure depends on the shape of the electrode layer. The electrode structure, or the present invention is characterized in that the current collector has a passivation film on the surface, a conductive auxiliary agent having conductivity, and an anchor substance that digs into the current collector. A current collector that has a mixture of an anchor substance, a conductive auxiliary agent, and a binder applied to the current collector and presses it to cause the anchor material to bite into the current collector and fix the conductive auxiliary agent to the anchor substance surface and the current collector surface. Structure, and an electrode layer formed by applying a mixture of an electrode active material, a conductive auxiliary agent and a binder on the current collecting structure and pressing the mixture to form a current collecting structure. Electrode structure, characterized in that it is greater than the pressing force of
Or, the present invention, a current collector having an oxide film on the surface,
It will bite into the current collector.Apply a mixture of an anchor substance, a conductive auxiliary agent that has conductivity and a binder, and press it to make the anchor substance bite into the current collector to create a current collecting structure. And a mixture of conductive aid and binder is applied and pressed to create an electrode layer.
It is a method for manufacturing an electrode structure, which is characterized in that it is larger than the pressing force for forming the electrode layer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

<A> Electrodes of Battery and Capacitor The electrodes of a battery and a capacitor are capable of delivering and receiving electricity to and from ions. Therefore, the electrode has a current collecting structure 2 in which a current collecting layer 21 is formed on a current collecting material 3 as shown in FIG.
Further, the electrode structure 1 is formed by forming the electrode layer 11 capable of passing ions.

The electrode layer of the positive electrode structure 12 of the battery is LiC.
An electrode active material such as oO ₂ is used and the negative electrode structure 13
In this case, an electrode active material such as graphite or hard carbon is used. Further, for the positive electrode structure electrode layer and the negative electrode structure electrode layer of the capacitor, a high surface area electrode active material capable of adhering a large amount of ions such as lithium is used. In a battery or a capacitor, for example, as shown in FIG. 1B, a positive electrode structure 12 and a negative electrode structure 13 are arranged to face each other with a separator 42 interposed therebetween, and an electrolytic substance 4 such as an electrolytic solution is interposed therebetween.
It is configured by arranging 1.

<B> Current-collecting structure The current-collecting structure 2 has a current-collecting layer 21 formed on the current-collecting material 3, and reduces the electrical resistance at the interface of the current-collecting material 3. In the current collecting structure 2, a part of the anchor substance 22 is bitten into the current collecting material 3 by a strong pressing force, and the conductive auxiliary agent 23 is firmly fixed near the surface of the current collecting material 3. When aluminum is the current collector 3, a thin oxide film is inevitably formed on the surface of aluminum. The anchor substance 22 is firmly fixed to the current collector 3 by partially intruding the anchor substance 22 on the surface of the aluminum current collector 3 and utilizing the adhesive force of the binder. A large amount of the conductive auxiliary agent 23 adheres to the periphery of the anchor substance 22 and can be fixed in large amounts near the surface of the current collector 3 together with the anchor substance 22. Further, the conductive auxiliary agent 23 can be brought closer to the surface of the current collector 3.
By forming the current collecting layer 21, the electric resistance at the interface of the current collector 3 can be significantly reduced.

The current collecting layer 21 may be multi-layered. For example,
As the first layer close to the current collector 3, a layer made of the conductive additive 23 and the binder is thinly attached. For example, the thickness is about several microns. Next, a second layer composed of the anchor substance 22, the conductive additive 23 and the binder is attached on the first layer, and the anchor substance 22 is made to bite into the first layer or the current collector 3. In this way, by forming the current collecting layer 21 into two layers, it is possible to fix the conductive auxiliary agent 23 closer to the current collecting material 3 with high density.

<C> Anchor substance The anchor substance 22 is hooked on the surface of the current collector 3, that is, is firmly fixed to the surface. For example, the anchor substance 22 partially digs into the surface of the current collector 3 with a strong pressing force. Then, the adhesive force of the binder is used to firmly fix it. The anchor material 22 is
It is preferable that the conductive additive 23 is easily attached to the surface. For that purpose, it is preferable that the surface has unevenness and is larger than the conductive additive 23. The anchor material 22 is preferably a conductive material or an electrode active material. The conductive material can enhance the function of the anchor and the conductivity with the interface of the current collector. In addition, the electrode active material can function as an anchor and also as an electrode layer capable of exchanging ions. It is considered that the anchor substance 22 breaks a film such as an oxide film on the surface of the current collector 3 by directly digging into the surface of the current collector 3 together with the attached conductive auxiliary agent 23 and comes into direct contact with the metal portion of the current collector. The anchor substance 22 only needs to have an anchor function, and preferably, a single particle having a particle size of 0.5 μm to 30 μm or a tufted bonded particle such as a tuft of grapes can be used.

<D> Electrode Active Material The electrode active material transfers and receives ions.
In the case of a lithium battery, the positive electrode active material is LiCoO 2.
₂ , LiNiO ₂ , LiMn ₂ O _4, and the like. Examples of the negative electrode active material include carbon materials.

A high surface area material can be used as the electrode active material of the capacitor. In particular, activated carbon obtained by activating a carbon material by a steam activation treatment method, a molten KOH activation treatment method, or the like is preferable. Examples of the activated carbon include coconut husk activated carbon, phenol activated carbon, petroleum coke activated carbon, polyacene and the like, and it is possible to use one of these alone or in combination of two or more. Of these, phenol-based activated carbon, petroleum coke-based activated carbon, and polyacene are preferable for achieving a large electrostatic capacity.

<E> Conductivity Auxiliary Agent The conductive auxiliary agent 23 has conductivity and enhances the conductivity of the electrode structure 1. When the conductive auxiliary agent 23 is used in the current collecting layer 21, it is preferable that the conductive auxiliary agent 23 has a diameter smaller than that of the anchor substance 22 and easily adheres to the periphery of the anchor substance 22. Conductive agent 2
When 3 is in contact with the aluminum passivation film, the conductive aid 23 is preferably a carbon substance, and it is considered that the conductivity of the passivation film is increased at the place where the carbon substance is attached to the passivation film. Examples of the conductive aid 23 include carbon black, Ketjen black, acetylene black, carbon whiskers, natural graphite, artificial graphite, carbon fibers such as VGCF and carbon nanotubes, and one of these may be used alone or in combination of two or more. Can be used in combination. Of these, Ketjen black and acetylene black, which are types of carbon black, are preferable. The average particle diameter (in the case of fibers, the cross-sectional area diameter) of the powdery conductive additive is preferably 10 nm to 100 nm, more preferably 20 n.
m to 40 nm is preferable.

<F> Electrolyte Material The electrolyte material 41 is an electrolytic liquid, gel or solid, and allows ions to move between the positive electrode structure 12 and the negative electrode structure 13, for example, dibutyl ether, 1,2-
Examples include dimethoxyethane and the like.

<G> Current collector The current collector 3 is made of a material having extremely high conductivity. As the current collector for the positive electrode, for example, aluminum foil or copper foil is used. An oxide film is naturally formed on the surface of the aluminum foil at the stage of manufacturing an electrode. It is assembled as a battery or capacitor, and when an electrolyte is injected and a current flows, a passive film is formed on the surface. The passivation film can prevent corrosion of the current collector by the electrolytic solution, and can improve the corrosion resistance of the current collector.
Since the passivation film has an insulating property, the current of the electrode is limited, but the electric resistance can be reduced by contacting the passivation film with carbon particles. It is considered that this reduction is due to the fact that the passivation film near the contact with the carbon particles has a defect and the conductivity is increased. Therefore, it is considered that when a large amount of the conductive auxiliary agent is fixed near the interface of the current collector using an anchor substance, the electrical resistance of the interface is reduced. The current collector is preferably hard so that the anchor substance can be bitten more firmly. In the case of aluminum foil for electrodes, for example, aluminum foil 3003-H1
8 (manufactured by Showa Denko KK) can be used.

<H> Separator The separator is for preventing electronic contact between the positive and negative electrode structures and allowing the passage of ions, and for example, a porous material such as polyethylene or polypropylene can be used.

The method of manufacturing the electrode structure will be described below.

<A> Production of Current Collection Structure First, for example, as shown in FIG.
Anchor substance 22, conductive aid 23, and binder (eg PV
A solvent (eg, NMP) 25 is added to a mixture with DF) 24 to be liquefied, that is, made into a paste, and a mixture for current collecting structure is manufactured. Preferably, the conductive auxiliary agent 23 is used as the anchor material 2
It is advisable to pre-deposit on No. 2 and mix with the binder 24. The current collecting structure mixture is applied to the current collecting material 3 with a doctor knife applicator or the like, and the current collecting layer 21 is applied to the surface of the current collecting material 3.
To form. The current collector 3 coated with the current collecting layer 21 is put into the drying device 6, the current collecting layer 21 is dried, and the solvent 25 is evaporated. When the solvent 25 is evaporated, the binder 24 and the conductive additive 23 are prevented from moving to the surface of the current collecting layer 21. Therefore, it is preferable to gradually warm the entire current collecting layer 21 and gradually evaporate the solvent 25.

The current collecting structure 2 having the dried current collecting layer 21 is strongly pressed by the pressing device 7. As a result, the anchor material 22 bites into the current collector 3 and is fixed to the current collector 3 in cooperation with the adhesive force of the binder 24. It is considered that the conductive additive 23 is firmly fixed near the surface of the current collector by adhering to the periphery of the fixed anchor substance 22. Also,
The conduction aid 23 is fixed closer to the current collector 3.
In the case of aluminum oxide film 31, it usually occurs naturally,
The thickness is considered to be about 0.01 μm, and it is considered that the anchor substance 22 penetrates into the metal through the oxide film 31 due to the pressing force. The pressing force that pushes the current collecting layer 21 is the current collecting material 3
Depending on the hardness of the current collector 3, if the current collector 3 is a hard aluminum foil, our super press (small diameter roll: diameter 15c
m and a large diameter roll: a pair of work rolls having a diameter of 25 cm), it is preferably 500 kg / cm to 1500 kg / cm. Particularly, 700 kg / cm to 1500 kg / cm is more preferable.

<B> Manufacturing of Electrode Structure In manufacturing the electrode structure 1, first, an electrode active material and a conductive auxiliary agent 23 are used.
Liquefaction by adding the solvent 25 to the mixture of the binder 24 and
That is, it is made into a paste and an electrode structure mixture is manufactured. The electrode layer 11 is formed on the surface of the current collecting structure 2 by applying this mixture onto the surface of the current collecting structure 2 with a doctor knife applicator or the like. The current collecting structure 2 coated with the electrode layer 11 is put into the drying device 6, the electrode layer 11 is dried, and the solvent 25 is evaporated.
When the solvent 25 is evaporated, like the formation of the current collecting layer 21,
It is preferable to gradually warm the entire electrode layer 11 and gradually evaporate the solvent 25.

The electrode structure 1 having the dried electrode layer 11 is pressed by the pressing device 7 to increase the density of the electrode layer 11. This pressing force is a value smaller than the force pressing the current collecting layer 21, and in the case of our super press, it is 300 kg / c.
m to 1000 kg / cm is desirable. Especially 300 kg /
cm to 800 kg / cm is more preferable. Further, in order to more reliably attach the conductive auxiliary agent 23 to the periphery of the electrode active material, the electrode active material and the conductive auxiliary agent 23 may be previously mixed together as in the formation of the current collecting layer 21. .

<C> Manufacturing of Battery or Capacitor Positive electrode structure 12 and negative electrode structure 1 of battery or capacitor
3 is manufactured, the separator 42 is arranged between the electrode structures as shown in FIG. 1 (B), and the electrolytic solution is injected to manufacture a battery or a capacitor. A passivation film is formed on the surface of the current collector 3 by the electrolytic solution or the current flowing between the electrode structures. Current collector 3
When is aluminum, the passive film is aluminum,
It is considered that the oxide film and the components of the electrolytic solution are chemically changed and generated.

<D> Drying Method The drying performed when manufacturing the current collecting structure 2 and the electrode structure 1 is as follows.
For example, by using breeze heating, breeze with heat, that is, warm air 61
Is applied to the current collector structure mixture. The drying device creates a breeze (warm air) with heat and applies it to the mixture for the current collecting structure. For example, as shown in FIG. 3, air is taken in from the outside air intake 69 and the dry air generator 68 is used. Dry the air,
Air is heated by the air heater 62, and the warm air 61 is injected into the housing 66 through the injection pipe 63. The current collecting layer applied to the current collector 3 moves inside the housing by a transfer means such as a conveyor 65. The warm air 61 is poured into the current collecting layer to gradually evaporate the solvent contained in the current collecting layer, and the solvent collecting device 6 is passed through the discharge pipe 64.
7, the evaporated solvent is recovered. The hot air from which the solvent has been removed is partially exhausted to the outside through the exhaust port 60, and the rest returns to the dry air generator 68.

When hot air is used, the dried current collecting layer 21 adheres well to the current collecting material 3, and the impedance of the electrode layer 11 becomes low. The reason is that when the surface of the mixture is irradiated with warm air, the entire mixture is gradually heated and the solvent 25
Gradually evaporates from the surface of the mixture. Therefore, the concentrations of the binder 24 and the conductive additive 23 are uniform throughout. That is, it is possible to prevent the migration of the binder 24 and the conductive additive 23. As a result, in the electrode layer formed by drying the mixture, since the binder concentration near the current collector does not become thin, the electrode layer adheres well to the current collector, and
It is considered that the impedance of the entire electrode layer becomes low because the concentration of the conductive additive in the vicinity of the current collector does not decrease. In addition,
The drying device is described in detail in the specification of which the applicant has already filed a patent (WO 01/22506).
See A1).

<E> Pressing method The pressing method performed when manufacturing the current collecting structure 2 and the electrode structure 1 can be performed by the pressing device 7 shown in FIG. 4, for example.
The pressing device 7 of FIG. 4 includes a pair of small-diameter work rolls 71,
The work roll 71 is provided with a pair of large diameter backup rolls 72, 72. The backup roll 72 is made by adhering a super-hard elastic material to the surface of a material having an extremely high hardness, corrects the bending of the work roll 71 by contact with the work roll 71, and uniformly presses it over the entire roll surface length. be able to. As the ultra-hard elastic material, modified urethane, polyimide, or the like can be used, and the hardness thereof can be, for example, JIS rubber hardness or a material having a Shore D scale of 90 to 98. The thickness of the super hard elastic material is, for example, 6 mm to 30 mm. As the work roll 71, a small diameter steel roll is used, and by pressing these with two large diameter rolls, a large effective pressure can be applied to the current collecting structure 2 and the electrode structure 1. Voids in the current collecting layer and electrode layer of the electrode structure can be almost filled. Instead of the pair of small diameter work rolls, a pair of a small diameter roll and a large diameter roll may be used as the work roll. The pressing device 7 is described in detail in the specification of which the present applicant has already applied for a patent (Japanese Patent Application No. 2001-222992, Japanese Patent Application No. 20922).
No. 01-345095).

[0027]

According to the present invention, the following effects can be obtained. <A> In the present invention, the adhesion strength of the conductive additive used for the electrode to the current collector can be increased. <B> Further, according to the present invention, the adhesion density of the conductive additive used for the electrode to the current collector can be increased. <C> Further, in the present invention, the conductive auxiliary agent used for the electrode can be brought closer to the current collector. <D> Further, the present invention prevents corrosion of the current collector by the passivation film on the surface of the current collector of the electrode, and fixes a large amount of the conductive auxiliary agent to the passivation film by the anchor substance, so that the impedance is low. A current collecting structure can be provided.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an electrode structure of an electrode.

FIG. 2 is an explanatory view showing a manufacturing process of a current collecting structure.

FIG. 3 is an explanatory view of a drying device.

FIG. 4 is an explanatory view of a pressing device.

[Explanation of symbols]

1 ... Electrode structure 11 ... Electrode layer 12 ... Positive electrode structure 13 ... Negative electrode structure 2 ... Current collecting structure 21 ... Current collecting layer 22..Anchor material 23..Conduction aid 24 ... Binder 25 ... Solvent 3 ... Current collector 31..Oxide film 4 ... Batteries 41..Electrolyte 42 ... Separator 5: Mixer 51..Mixture 6 ... Drying device 7 ... Pressing device 71 ... Work roll 72 ... Backup roll 73 ··· Pressure device 74 · · Drive unit 75 ... Motor

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Claims (7)

[Claims] 1. A current collector having an oxide film on its surface, a conductive auxiliary agent having conductivity, an anchor substance digging into the current collector, and a binder for adhering the current collector, the anchor substance and the conductive auxiliary agent. And a conductive auxiliary agent fixed to the surface of the anchor material and the surface of the current collector. 2. The current collecting structure according to claim 1, wherein the conductive auxiliary agent is carbon particles having a particle size smaller than that of the anchor substance, or fibrous carbon having a diameter smaller than that of the anchor substance. The current collecting structure. 3. A current collector having an oxide film on its surface is coated with a mixture of a conductive auxiliary agent having conductivity, an anchor substance and a binder and pressed to cause the anchor substance to dig into the current collector.
A method for producing a current collecting structure, characterized in that a current collecting material, an anchor substance, and a conductive auxiliary agent are bonded with a binder, and the conductive auxiliary agent is brought close to the anchor material surface and the current collecting material surface and fixed. 4. The method for producing a current collecting structure according to claim 3, wherein a mixture of an anchor substance having a conductive additive attached to its surface, a conductive additive and a binder is applied to the current collector. Method of manufacturing current collecting structure. 5. A mixture of a current collecting material having an oxide film on its surface, a conductive auxiliary agent having conductivity, and an anchor substance that digs into the current collecting material, and a mixture of the anchor substance, the conductive auxiliary agent, and the binder in the current collecting material. And press to make the anchor material dig into the current collector, and fix the conductive auxiliary agent by bringing it close to the anchor material surface and the current collector surface, and the electrode active material and the conductive material on the current collector structure. An electrode structure comprising: an electrode layer formed by applying a mixture of an auxiliary agent and a binder, and pressing and adhering the mixture. The pressing force for forming the current collecting structure is larger than the pressing force for forming the electrode layer. . 6. A current collector having a passivation film on the surface thereof, a conductive auxiliary agent having conductivity, and an anchor substance that digs into the current collector. The current collector comprises an anchor substance, a conductive agent and a binder. The mixture is applied and pressed to cause the anchor substance to bite into the current collector, and the conductive auxiliary agent is brought close to the anchor substance surface and the current collector surface and fixed, and an electrode active material is provided on the current collector structure. An electrode layer formed by applying a mixture of a conductive auxiliary agent and a binder and pressing the mixture to make it adhere, and the pressing force for forming the current collecting structure is larger than the pressing force for forming the electrode layer. Construction. 7. A current collector having an oxide film on its surface is coated with a mixture of an anchor substance, a conductive auxiliary agent having electric conductivity, and a binder, which bites into the current collector, and is pressed to dig the anchor substance into the current collector. To create a current collecting structure, apply a mixture of an electrode active material, a conductive auxiliary agent and a binder to the current collecting structure and press it to create an electrode layer.The pressing force for creating the current collecting structure is to create the electrode layer. A method for manufacturing an electrode structure, wherein the pressing force is larger than the pressing force of.