JPH11144708A - Electrode structure for electrochemical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode structure for an electrochemical element that reduces the contact resistance between an electrode and a current collector and also to stabilize a contact between them. SOLUTION: A carbonic nonwoven fabric is made as a current collector 1. An electrode 2 including an active material, an electroconductive assistant, and a binder is integrated with the current collector 1. The one formed by carbonizing a phenol-resin material nonwoven fabric is used as the carbonic nonwoven fabric. Also, a current collector may also be formed by coating a conductive coating onto the phenol-based resin material nonwoven fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode structure for an electrochemical device applicable to a lithium ion battery, an electric double layer capacitor and the like, and more particularly to a sheet-like electrode structure.

[0002]

2. Description of the Related Art At present, various types of batteries are widely used from the field of electronics to large ones intended for automobile use or power storage.

[0003] In such a battery, a liquid is usually used as an electrolytic solution. By replacing this with a solid electrolyte, it is expected that liquid leakage can be prevented or a sheet structure can be formed. It is attracting attention as a battery. In particular, it is expected that application of lithium-ion secondary batteries and the like, which are rapidly used in notebook personal computers and the like, can be further accelerated if they can be made into sheets or miniaturized. When such a solid electrolyte is used, a ceramic material, a polymer material, or a composite material thereof has been proposed. Among them, a gel electrolyte obtained by plasticizing a polymer electrolyte using an electrolytic solution or the like has both high liquid-based electrical conductivity and high polymer-based plasticity, and is considered promising in electrolyte development.

By the way, an example in which a gel electrolyte is used for a battery has already been described in G. Feuillade, J. Appl. Electrochem.
5) disclosed on pages 63-69 and further US Pat.
Practical systems are also presented in 296318.

[0005]

In such a method of manufacturing a sheet-type battery, a positive electrode, a negative electrode, and a solid electrolyte are sequentially laminated. Therefore, unlike the conventional cylindrical type, a flat type and a large-area type are possible. However, when a gel electrolyte is used, the internal resistance of the electrolyte part is inevitably increased because the electrolyte is not essentially a solution system. Therefore, in order to make the battery more suitable for practical use, it has been a technical problem to reduce the resistance of the electrode portion as much as possible.

The following four items can be considered as factors that cause the resistance of the electrode portion to be exhibited. (1) Resistance of the electrolyte part inside the electrode (2) Resistance due to the reaction rate of the electrode active material (3) Resistance due to dispersion of conductive additives added to improve the electronic conductivity inside the electrode ( 4) Contact resistance between electrode sheet and current collector

Although it is difficult to separate these factors as a practical problem, it is expected that the contribution of the item (4) will be large especially when considering a large-area sheet type. That is, it is difficult to uniformly contact a current collector such as a metal grid with an electrode mainly composed of an active material and a binder.

For this reason, the prior art, for example, US Pat.
In 37692 and the like, it is considered that a conductive paint is applied to the interface between the electrode and the current collector. Although it is certain that the resistance can be reduced by such a method, it is difficult to uniformly contact the conductive paint, especially when the conductive paint is made to have a large area, since the conductive paint is usually a main component. In this case, since there is a limitation on the baking or heat treatment, an unstable factor still occurs in the contact.

Conventionally, it has been attempted to use a metal punched metal or grid as a current collector.
The high cost of these materials and the difficulty in embedding them in the case of grids have hampered their practical use.

The inventors of the present invention have studied in view of the above background, and as a result, have found an electrode and a current collector which are optimal as an electrode structure of a sheet type battery (or an electric double layer capacitor).

It is an object of the present invention to provide an electrode structure for an electrochemical device capable of reducing the contact resistance between an electrode and a current collector and stabilizing the contact between the two.

Other objects and novel features of the present invention will be clarified in embodiments described later.

[0013]

In order to achieve the above object, a first electrode structure for an electrochemical element according to the present invention comprises a carbon nonwoven fabric as a current collector, and comprises an active material, a conductive auxiliary agent, and a binder. An electrode is integrated with the current collector.

In the first electrode structure for an electrochemical device, the carbon nonwoven fabric is preferably formed by carbonizing a phenolic resin material nonwoven fabric.

A second electrode structure for an electrochemical element according to the present invention is characterized in that a conductive paint is applied to a phenolic resin material non-woven fabric to form a current collector, and the electrode containing an active material, a conductive auxiliary agent and a binder is used as the current collector. The structure is integrated with the body.

A third electrode structure for an electrochemical element according to the present invention is characterized in that a metal film made of any one of aluminum, nickel, copper, titanium and tungsten is formed on a phenolic resin nonwoven fabric by thermal spraying to form a current collector. An electrode including an active material, a conductive assistant, and a binder is integrated with the current collector.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an electrode structure for an electrochemical device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of an electrode structure for an electrochemical device according to the present invention, wherein 1 is a current collector, which is a carbon nonwoven fabric obtained by carbonizing a phenolic resin material nonwoven fabric.
Reference numeral 2 denotes an electrode serving as a positive electrode or a negative electrode. The positive electrode or negative electrode active material, a binder, and a conductive auxiliary are formed into a paste using a solvent and directly applied to and impregnated into the carbon nonwoven fabric current collector 1 to form a sheet on the current collector 1. Formed and integrated.

In the first embodiment, the current collector 1 is basically composed of a carbon non-woven fabric obtained by carbonizing a non-woven fabric of a phenolic resin material to form an electric conductor. It has a high efficiency and is suitable for an electrode in the case of using a gel electrolyte, and it is possible to embed a current collector inside the electrode. In addition, it is electrochemically stable because it is a carbon-based material. Furthermore, since the nonwoven fabric has a three-dimensional structure, a three-phase interface is formed by the electrolyte, the conductive additive and the current collector, so that the discharge rate characteristics are also improved. In addition, since it has an appropriate strength even after carbon treatment, it can be applied to a process such as bending or punching, and burrs are less generated at the time of cutting or the like.

FIG. 2 shows a second embodiment of the present invention, wherein 1A is a current collector, and a phenolic resin material nonwoven fabric 11A.
The conductive paint 12 is applied by dipping or the like to form a conductive material. 2 is an electrode serving as a positive electrode or a negative electrode,
The positive electrode or negative electrode active material, a binder, and a conductive assistant are formed into a paste by using a solvent as a paste and directly applied to and impregnated into the current collector 1A, thereby being integrated with the current collector 1A in a sheet shape.

In the second embodiment, the current collector 1A is formed by coating the phenolic resin material nonwoven fabric 11 with the conductive paint 12, and also has a high porosity when a gel electrolyte is used. It is suitable for an electrode, and a current collector can be embedded inside the electrode. In addition, since the nonwoven fabric forms a three-dimensional structure, a three-phase interface is formed by the electrolyte, the conductive additive, and the current collector, so that the discharge rate characteristics are also improved. Further, since it has an appropriate strength, it can be applied to a process such as bending or punching.

FIG. 3 shows a third embodiment of the present invention, wherein 1B denotes a current collector, and a phenolic resin material nonwoven fabric 11B.
A metal film 13 made of any of aluminum, nickel, copper, titanium and tungsten is formed by thermal spraying. Reference numeral 2 denotes an electrode serving as a positive electrode or a negative electrode. The positive electrode or negative electrode active material, a binder, and a conductive auxiliary are formed into a paste using a solvent and directly applied to and impregnated into the current collector 1B to form a sheet on the current collector 1B. Formed and integrated.

In the third embodiment, the current collector 1B is formed by forming a metal film 13 by thermal spraying on a phenolic resin material nonwoven fabric 11, and also uses a gel electrolyte having a high porosity. It is suitable for an electrode in such a case, and a current collector can be embedded inside the electrode. In addition, since the nonwoven fabric forms a three-dimensional structure, a three-phase interface is formed by the electrolyte, the conductive additive, and the current collector, so that the discharge rate characteristics are also improved. Further, since it has an appropriate strength, it can be applied to a process such as bending or punching. The metal film 13 is any of aluminum, nickel, copper, titanium, and tungsten, and is a material having corrosion resistance to the gel electrolyte of a lithium ion battery.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to a case where a sheet-like electrode of a lithium ion secondary battery is formed.

Example 1 In this example, a positive electrode was produced with the following composition. Positive electrode active material LiCoO ₂ binder PVDF Kynar 741 (vinylidene fluoride homopolymer) Conductive aid Acetylene black These materials are used as a paste at a ratio of 80:10:10 by weight using NMP (normal methylpyrrolidone) as a solvent and carbon. It was applied directly to the non-woven fabric current collector. The carbon nonwoven fabric current collector is manufactured through the following steps. A phenolic resin material nonwoven fabric (manufactured by Nippon Kainol) was used and carbonized at 900 ° C. in a reducing atmosphere. Next, a negative electrode was manufactured. Negative electrode active material Graphite Binder PVDF Kynar 741 Conductive aid Acetylene black These materials are mixed in a weight ratio of 82: 9: 9, and the solvent is N
A paste was formed using MP (normal methylpyrrolidone) and applied in the same manner as the positive electrode to form an electrode.

[Example 2] In this example, production was performed in the same manner as in Example 1, but the binder was PVDF Kynar 2801 (a copolymer of vinylidene fluoride and propylene hexafluoride). Other conditions are exactly the same.

Comparative Example Similar positive and negative electrodes were prepared using an expanded metal (metal mesh) as a normal electrode, that is, a current collector.

With respect to the electrode of Example 1 manufactured by the above manufacturing method, a normal electrode, that is, an electrode of a comparative example using expanded metal as a current collector was manufactured to evaluate the difference in internal resistance and to evaluate the polymer solid. The sheet-type battery using the electrolyte was evaluated and is shown in Table 1 below. Table 1 compares the internal resistance difference and the discharge capacity increase rate.

Table 1 Internal resistance (relative value%) Capacity increase rate (%) (Example / Sample 1) 82 10 (Example / Sample 2) 84 13 (Example / Sample 3) 78 15 (Comparative Example / Sample) 4) 93 0 (Comparative Example / Sample 5) 100 0 (However, the internal resistance is a relative value with the case of Comparative Example / Sample 5 being 100)

When the electrode according to the present invention is used, it can be seen that the internal resistance is reduced and the capacity is increased.

Although the embodiments of the present invention have been described above, it is obvious to those skilled in the art that the present invention is not limited to the embodiments and various modifications and changes can be made within the scope of the claims. There will be.

[0032]

As described above, according to the electrode structure for an electrochemical device of the present invention, it is possible to reduce the contact resistance between the electrode and the current collector and to stabilize the contact between the two. In addition, when applied to a secondary battery, discharge rate characteristics can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of an electrode structure for an electrochemical device according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a third embodiment of the present invention.

[Explanation of symbols]

 1, 1A, 1B Current collector 2 Electrode 11 Non-woven fabric of phenolic resin material 12 Conductive paint 13 Metal film

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01M 4/66 H01G 9/00 301B 10/40 301F (72) Inventor Makoto Kobayashi 1-13-1 Nihonbashi tee, Chuo-ku, Tokyo DK Corporation

Claims (4)

[Claims] 1. An electrode structure for an electrochemical element, wherein a carbon nonwoven fabric is used as a current collector, and an electrode containing an active material, a conductive auxiliary agent, and a binder is integrated with the current collector. 2. The electrode structure for an electrochemical device according to claim 1, wherein said carbon nonwoven fabric is obtained by carbonizing a phenolic resin material nonwoven fabric. 3. An electrochemical device wherein a current collector is formed by applying a conductive paint to a non-woven fabric of a phenolic resin material, and an electrode containing an active material, a conductive auxiliary agent and a binder is integrated with the current collector. Electrode structure. 4. A phenolic resin material nonwoven fabric made of aluminum,
A metal film made of nickel, copper, titanium, or tungsten is formed by thermal spraying to form a current collector, and an electrode containing an active material, a conductive auxiliary, and a binder is integrated with the current collector. Electrode structure for electrochemical device.