JPH117939A - Manufacture of electrode plate for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the quality and processing yield of an electrode plate for a battery by easily and reliably peeling part of mix layers applied over the metallic foil collector of the electrode plate and dried up so as to strengthen the mechanical and electrical connection of the collecting elements to the electrode plate. SOLUTION: A battery plate is manufactured by the coating of a collector made up of metallic foil 1 with a mix paste, which is then dried up to form mix layers 2. On part of the electrode plate, a heating plate is pressed, heated up to the temperature at which the binder begins to soften to soften the mix layer 2 such that it partly separates from the collector surface. That separated portion is thereafter removed away by a method, typically, of mechanically scraping off the mix at that portion so that the collector surface is partly exposed, to which a collecting element 5 is connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrode plate for a battery, and more particularly to a method for producing a sheet-like electrode plate having a mixture layer formed on a metal foil current collector.

[0002]

2. Description of the Related Art In recent years, with the reduction in size and weight of various electronic devices such as VTRs and communication devices, lithium secondary batteries have been demanded as high-energy-density power supplies used for them.

FIG. 6 shows an example of a battery configuration of a lithium secondary battery. In this battery, a positive electrode plate 10 in which a positive electrode mixture mainly composed of LiCoO2 was applied to the surface of a metal foil at a predetermined thickness, and a positive electrode mixture mainly composed of graphite was applied in a predetermined thickness to the surface of a metal foil. The negative electrode plate 10 'is spirally wound via a separator 11 made of a porous film of a polyolefin resin to form an electrode plate group.

As shown in FIG. 3, strip-like elongated positive and negative electrode plates 10 'and 10 used in such a battery are composed of a metal foil 1 serving as a core material, a mixture 2 formed thereon, and a current collector. And a piece 5. In order to firmly adhere the mixture 2 to the metal foils 1 of the positive and negative electrode plates 10 ′ and 10, a mixture paste is applied / dried and then pressed with a roll press or the like to be combined with the metal foil 1. The bonding strength with Agent 2 is increased.

As shown in FIG. 2, the lead 5 is attached to the electrode plate by caulking the mixture 2 and sandwiching the mixture 2 between the metal foil 1 and the current collecting piece 5. After bonding or mechanical scraping of a part of the mixture 2 on the metal foil 1 with a tool 4 such as a scraper as shown in FIG. A method of connecting the current collecting pieces 5 by welding or caulking the foil 1 is generally used.

In Japanese Patent Application Laid-Open No. Hei 8-138655, ethanol or other solvent is locally applied to a predetermined position on the mixture to wet the mixture to weaken the binding force with the metal foil 1. , Mechanically scraping this part with a peeling tool,
A method of connecting the current collecting piece 5 to the exposed metal foil 1 has been proposed.

[0007]

However, when the current collector is crimped on the mixture and joined, sufficient electrical contact between the current collector and the metal foil cannot be obtained, and as a result, the The internal impedance rises.

On the other hand, when the mixture is peeled off from the metal foil, the mechanical scraping method and the peeling method using ultrasonic vibration described above, particularly, the metal foil of the electrode plate and the mixture are roll-pressed or the like. Since peeling after strengthening the bond, at the time of peeling,
Problems such as tearing of the metal foil occurred, and the electrode plate was easily damaged and became unusable, resulting in poor yield.

In the method of removing the mixture after wetting the organic solvent with the mixture, the ethanol penetrates not only into the part of the mixture layer which should be originally peeled off, but also into the parts which should not be removed. Therefore, there is a problem that the swelling of the electrode plate occurs from the peeling edge portion to several mm. As a result, when the electrode plate hoop after peeling is wound up, stress is applied to the outer periphery of the raised portion of the electrode plate, and there is a problem that the mixture falls off from the raised portion.

[0010] The present invention solves the above-mentioned problems in attaching the current collector to the electrode plate for a lithium secondary battery,
An object of the present invention is to provide a battery electrode plate that has good electrical contact with a current collecting piece and a good yield in the process.

[0011]

SUMMARY OF THE INVENTION In order to solve these problems, the present invention relates to a method in which a mixture paste is applied to a metal foil as a current collector and dried to form an electrode plate on which a mixture layer is formed. Prior to attaching the electric piece, a hot plate heated to a temperature at which the binder in the mixture softens is locally pressed against the current collecting piece mounting position on the electrode plate, and the local mixture is applied to the electrode body. The mixture layer is locally peeled off by removing the released mixture and the metal foil is exposed, and the current collecting piece is connected to the exposed portion.

According to this method for manufacturing an electrode plate, the mixture can be reliably removed without damaging the electrode plate, and the exposed portion of the metal foil can be easily provided with a high yield at a predetermined portion to which the current collector is connected. It becomes possible. Further, the connection between the electrode plate body and the current collecting piece by welding or the like can be firmly performed, and highly reliable electrical conduction can be obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, after forming an electrode mixture layer on a current collector on a thin metal plate such as a metal foil, a part of the mixture layer is peeled off to form a part of the current collector. Exposed, can be applied to all the production of positive and negative electrode plates for non-aqueous electrolyte batteries configured by connecting a current collector to the exposed portion, for example, lithium cobaltate, lithium nickelate, lithium manganate, and the like, Positive electrode plates containing various metal compounds that can release and occlude lithium by charge and discharge as main materials, and various substances that can occlude and release lithium by charge and discharge, for example, various carbon materials such as graphite, and metals such as iron oxide and tin oxide Oxides, polyaniline,
The present invention can also be applied to the production of a negative electrode plate containing a polymer such as polypyrrole as a main material.

In one specific embodiment of the present invention, a powder of the above carbon material is used as a main component of a mixture, and a synthetic rubber resin obtained by dispersing the powder in water or an organic solvent is kneaded with a binder. The above-mentioned manufacturing method is applied to a negative electrode plate prepared using a mixture paste. This makes it possible to manufacture a carbon negative electrode plate for a lithium secondary battery that can reliably secure electrical conduction with the current collecting piece without damaging the electrode plate main body with a good process yield.

Further, in an embodiment of the heating method for raising the temperature of the hot plate to a temperature at which the binder softens, it is necessary to equalize the heat in the width and longitudinal directions as much as possible. It is most preferable to use electromagnetic induction heating which is fast, has good work efficiency, and can make the heat distribution of the hot plate uniform. However, even if the temperature of the hot plate is increased by heating medium circulation heating or microwave heating, the same is true. The mixture layer can be partially released from the current collector by the method. The material of the hot plate may be any heat conductor that does not deform at the elevated temperature.

Furthermore, a composite tool, a hard rubber, a high-density polyethylene, or the like in which ceramic powder is dispersed in the material of the end portion is used as a polyhedron for the peeling tool, and the end portion is separated by a hot plate. By employing an embodiment in which the agent is mechanically removed, the mixture can be efficiently and reliably removed from the exposed surface of the current collector, and the current collector piece is firmly attached to the exposed surface by welding or caulking. Can be connected to

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the production method according to the present invention will be described with reference to FIG. In this embodiment, a mixture paste was used in which spherical graphite (mesocarbon microbeads) as the main material of the electrode was kneaded with a liquid in which styrene butadiene rubber as a binder was dispersed in water.

The metal foil of the current collector 1 has a thickness of 0.01 mm.
The above-mentioned mixture paste is applied to both sides of the copper foil, dried, and then pressed between the upper roll 7 and the lower roll 8 shown in FIG. The mixture 2
Closely adheres to the current collector 1. A hot plate (50 mm long, 100 mm wide, 20 mm thick) made of SUS316 stainless steel heated to a temperature (130 ° C.) at which the binder softens against the roll-pressed mixture layer is used as an electrode plate. On the other hand, the mixture is pressed locally to soften the mixture layer at that portion and release it from the current collector surface. Then, using the edge portion of the hexahedral (50 mm long, 100 mm wide, 20 mm thick) stripping tool 4 made of a composite resin in which ceramic powder is dispersed, the separated mixture layer and the front surface of the stripping tool 4 are separated. Keep the angle between 20 and 90 degrees to the moving direction of the peeling tool,
The peeling tool is moved while pressing with a load of 0.5 to 5 kg to scrape the mixture 2. As a result, the current collecting piece 5 made of nickel is formed on the surface of the metal foil 1 where the mixture is peeled off and exposed.
Was attached by ultrasonic welding.

An electrode plate manufactured according to this embodiment, a conventional manufacturing method in which leads are directly caulked without removing the mixture (FIG. 2), and a conventional method in which the mixture is directly peeled off with a metal plate Table 1 shows the results of measuring the resistance between the end of the current collecting lead and the surface of the electrode plate mixture for the electrode plate produced by the manufacturing method (FIG. 3).

As can be seen from Table 1, the resistance between the current collecting lead end and the electrode plate was clearly smaller in the electrode plate manufactured according to the present invention. This is considered to be due to the fact that the state of contact between the current collecting lead piece and the surface of the core copper foil was improved as compared with the prior art. As a result, the battery characteristics (particularly, high-rate charge / discharge characteristics) are considered to be stable.

Further, the electrode plate manufactured according to the present embodiment,
The number of defective samples in the process of peeling the mixture from the electrode plate according to the conventional manufacturing method shown in FIGS.
Table 2 shows the results of the test performed on 000 sheets. The comparison between the defective product and the non-defective product was determined based on the presence or absence of breakage such as tearing of the current collector metal foil after the mixture layer was peeled off. As can be seen from the results shown in (Table 2), the electrode plate manufactured according to the present invention showed almost no damage to the metal foil. This is because the softening and release of the mixture layer by the hot plate were sufficiently promoted, and thus the peeling could be performed without applying excessive stress to the electrode plate.

[0022]

[Table 1]

[0023]

[Table 2]

An example of the present invention has been described in the above embodiment.
The invention can be implemented in various ways. For example,
Laser welding or spot welding may be used to connect the current collecting pieces. The heating plate can be heated in the same manner as in the case of thermal cycling heating or microwave heating, in which case the mixture can be released. it can.

The metal foil used for the current collector of the negative electrode plate for a lithium secondary battery may be nickel, stainless steel or the like instead of copper. Also in the case of forming a positive electrode plate, for example, an electrode plate containing lithium cobaltate, lithium nickelate, lithium manganate or the like as a main component, the mixture layer is peeled off in the same manner as in this embodiment, and the current collector piece is removed. In the case where the present invention is applied to these positive electrode plates, a foil of aluminum, titanium, or the like can be used for the current collector. Further, the present invention can be applied to general electrode plates for batteries such as lithium primary batteries and alkaline storage batteries in addition to the electrode plates for lithium secondary batteries.

Further, the material of the hot plate may be any heat conductor that can withstand the elevated temperature, such as SUS3 used in the embodiment.
A stainless steel material other than 16, a steel plate, an aluminum plate, or the like can be used, and the same effect can be obtained by using a hard rubber or the like as the peeling tool in addition to a composite resin in which ceramic powder is dispersed.

In this embodiment, the hexahedral stripping tool is used. However, the angle formed by the edge portion of the tool and the plane of the electrode plate is 20 to 90 degrees with respect to the traveling direction of the stripping tool. For example, a similar result can be obtained even if the shape is as shown in FIGS. 5A, 5B, and 5C, for example. FIG. 5 (A)
5B illustrates a peeling tool having a triangular cross section, FIG. 5B illustrates a peeling tool having a semicircular cross section, and FIG. 5C illustrates a peeling tool having a wedge-shaped cross section.

[0028]

As described above, according to the production method of the present invention,
A hot plate heated to a temperature that causes the binder in the mixture to soften is locally pressed against the electrode plate with the mixture layer formed on the current collector metal foil to soften the mixture. In the state of being separated from the current collector surface, the softened portion of the mixture layer is easily removed without leaving the mixture by a method such as mechanical scraping, so that the current collector metal foil becomes clean. An exposed part is formed, and the exposed part and the current collecting piece lead are firmly joined to each other,
The quality and productivity of the electrode plate for a lithium secondary battery can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for manufacturing an electrode plate according to an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional electrode plate with lead terminals.

FIG. 3 is a diagram showing a conventional mechanical peeling method.

FIG. 4 is a diagram showing a roll press pressing method for an electrode plate.

FIG. 5 (A) is a view showing a state when the mixture layer is peeled off by a peeling tool. (B) is a view showing another example of the peeling. (C) is a view showing another example of the peeling.

FIG. 6 is a sectional view of a lithium secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal foil 2 Mixture layer 3 Dielectric heating coil 4 Peeling tool 5 Current collecting piece 6 End of peeling tool 7 Upper roll 8 Lower roll 9 Hot plate 10 Positive plate 10 'Negative plate 11 Separator

Claims (3)

[Claims] A mixture of an electrode plate having a mixture layer formed by applying an electrode mixture paste obtained by kneading a main material of an electrode mixture with a binder and a dispersion medium onto a metal foil and drying the paste. The mixture layer is softened by locally pressing a hot plate heated to a temperature that causes the softening of the binder to the surface, and the mixture is released from the metal foil. A method for manufacturing an electrode plate for a battery, characterized in that a metal foil is partially exposed by removing the metal foil using a peeling tool, and a current collecting piece is connected to the exposed surface. 2. The method according to claim 1, wherein a main material of the electrode mixture is carbon powder, and an electrode paste kneaded with a dispersion obtained by dispersing a synthetic rubber resin as a binder in water or an organic solvent is used. The method for producing an electrode plate for a battery according to claim 1. 3. The method for producing an electrode plate for a battery according to claim 1, wherein the heating method of the hot plate is electromagnetic induction heating.