JPH05225998A - Manufacture of spiral type electrode structure for battery - Google Patents

Abstract

PURPOSE:To reduce the defects generation percentage by inserting a two-stage tapered forming pin into a split-pin post draw-off space at the central part of a spiral type electrode structure to thereby cause a starting portion of a separator winding to be conveniently laid along the inner peripheral surface. CONSTITUTION:After a split pin is drawn off, a two stage tapered forming pin 10c is inserted into a split-pin post draw-off space 8 formed at a central portion of a spiral type electrode structure 7 for battery. At this time, an end portion 4 of a separator in the split-pin post draw-off space 8 of the spiral type electrode structure is laid along the inner peripheral surface of the space 8 by the use of the two-stage tapered forming pin 10c. The forming pin 10c serves to widen an entrance portion 8a of the post draw-off space 8, thus facilitating insertion of a welding bar.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a spiral electrode structure for a battery. More specifically, the present invention relates to a method for manufacturing a spiral wound electrode structure for a battery in which a welding rod for spot welding the inner bottom portion of a metal battery container and an electrode lead can be easily inserted.

[0002]

2. Description of the Related Art In recent years, with the progress of electronic technology, electronic devices have been improved in performance, downsized, and made portable, and high energy density secondary batteries for use in these electronic devices have been developed. .. In particular, non-aqueous electrolyte type lithium secondary batteries, which can achieve higher discharge voltage and higher energy density than conventional nickel-cadmium batteries and lead batteries, have been actively developed.

In such a lithium secondary battery, a material capable of doping and dedoping lithium ions such as lithium, a lithium alloy or a carbon material is used as a negative electrode, and a lithium composite oxide such as a lithium cobalt composite oxide is used as a positive electrode. It is the one that used the thing. The electrode structure is a spiral electrode structure to increase the electrode area and enable heavy load discharge, and also as a separator to increase the capacity by filling the electrode active material more. Microporous polymeric films have been used.

A method of manufacturing such a spiral electrode structure is shown in FIGS. 7 and 8. That is, as shown in FIG. 7, the end 4 of the separator 3 is sandwiched between the split grooves 2 of the split pin 1 for winding the electrode, and the separator 3 is started to be wound. Here, the split groove 2 is provided at the central portion of the split pin 1, that is, at the position of the central axis in the longitudinal direction thereof.

In this way, the separator 3 is wound up,
Further, after winding the negative electrode 5 and the positive electrode 6 as well, the split pin 1
And the spiral electrode structure are separated from each other. FIG. 8 shows the split pin trace space 8 formed in the center of the spirally wound electrode structure 7 manufactured in this manner. An end portion 4 of the separator 3, which is sandwiched between the split grooves 2 of the split pin 1, is present at approximately the center of this space 8.

Usually, a welding rod for spot-welding the inner bottom portion of the metallic battery container accommodating it and the electrode lead of the positive electrode or the negative electrode to the spiral type electrode structure manufactured as described above is provided. Inserting into the split pin trace space is performed.

However, as shown in FIG. 8, in the spiral type electrode structure 7 in which the end 4 of the separator 3 exists in the center of the split pin trace space 8, the end 4 of the separator 3 becomes an obstacle and spot welding is performed. I could not insert the welding rod for
There was a problem of reduced productivity.

In order to solve this problem, before inserting the welding rod for spot welding, as shown in FIG. 9, while heating the molding pin (expansion rod) 9 having a sharp tip, the spiral electrode structure is heated. It is proposed that the split pin trace space 8 is inserted into the split pin trace space 8 and the end 4 of the separator is aligned with the inner peripheral surface of the split pin trace space 8 as shown in FIG. 10 (Japanese Patent Publication No. 3-510).
No. 65).

[0009]

However, even if the split pin trace space 8 is expanded by the molding pin 9 described in Japanese Patent Publication No. 3-51065, the welding rod is made into the split pin trace space of the spiral type electrode. When inserting, the end 4 of the separator 3
There has been a problem that an insertion failure occurs in which the device cannot be inserted because it is caught in the above.

The present invention is intended to solve the problems of the prior art, and the electrode lead of the spiral electrode structure and the metal battery for housing the electrode lead in the space of the split pin of the spiral electrode structure. It is an object of the present invention to manufacture a spiral electrode structure so as to reduce defects when inserting a welding rod for spot welding the inner bottom portion of a container.

[0011]

Means for Solving the Problems The present inventor has formed a molding having a sharp tip like a conventional molding pin and forming a second taper in a portion distant from the tip so as to further expand the diameter. By using a pin (hereinafter, referred to as a two-step tapered molding pin), the end of the separator of the split pin trace space of the spirally wound electrode structure is arranged along the inner peripheral surface of the space, and the split pin trace space is formed into a second space. The inventors have found that if the taper is further spread, the welding rod can be easily inserted, and the present invention has been completed.

That is, according to the present invention, the separator is sandwiched in the split groove of the split pin for winding the electrode and the winding is started, and the strip-shaped positive electrode and negative electrode are wound while interposing the separator so as not to contact each other. In a method for manufacturing a spiral-wound electrode structure for a battery, which includes removing the split pin later, in a split-pin trace space formed in the center of the spiral electrode structure for a battery after removing the split pin. A spiral electrode structure for a battery, characterized in that a winding start portion of the separator in the cotter pin trace space is aligned with an inner peripheral surface of the cotter pin trace space by inserting a two-step tapered molding pin into the cotter pin trace space. A method of manufacturing a body is provided.

The manufacturing method of the present invention will be described below in detail with reference to the drawings. In the drawings, the same reference numerals represent the same or equivalent constituent elements.

As described above, the present invention is characterized in that the two-stage tapered forming pin is used as the forming pin to be inserted into the split pin trace space of the spiral type electrode structure. This 2
A side view of the stepped tapered forming pin is shown in FIG. As shown in the figure, the two-stage tapered molding pin 10 is composed of a front end portion 10a, an intermediate portion 10b and a rear end portion 10c, and its cross section is generally circular.

Tip part 1 of two-step tapered molding pin 10
The taper 0a is formed so as to expand toward the intermediate portion 10b, and the tip end portion has the sharpest point. Therefore, as shown in FIG. 2, the split pin trace space 8 can be smoothly inserted.

As shown in FIG. 3, the intermediate portion 10b is for pushing the end portion 4 of the separator 3 against the inner peripheral surface of the split pin trace space 8 to follow it. Therefore, it is preferable to have a length equal to or longer than the length of the end portion 4 of the separator 3 to be pressed.

The rear end 10c is provided with a taper that expands as it moves away from the front end 10a. That is,
The cross-sectional area of the rear end portion 10c is wider than that of the middle portion 10b. As shown in FIG. 4, this taper is for further expanding the entrance portion 8a of the split pin trace space 8 on the side where the welding rod is inserted. As a result, defective insertion of the welding rod can be reduced.

When inserting such a two-step tapered molding pin 10, in view of the fact that the separator 3 is mainly composed of a microporous polymer film, it is heated to such an extent that it can be plastically deformed. It is preferable that Further, the number of times of insertion into one split pin mark space is not limited to once, and may be inserted a plurality of times.

In the method of manufacturing the spiral wound electrode structure for a battery of the present invention, the constituent elements of the conventional manufacturing method are used as the constituent elements other than the use of the two-stage tapered molding pin 9. You can For example, Japanese Patent Publication No. 3-51
The means described in Japanese Patent No. 065 can be used.

As a split pin for winding the electrode, FIG.
Although it is parallel to the central axis of the longitudinal direction of the split pin 1 as shown in (3), it is preferable to use the one in which the split groove 2 is provided at a position not overlapping the central axis. When such a split pin 1 is used, the position of the end 4 of the separator 3 in the split pin trace space 8 is displaced from the center as shown in FIG. Therefore, when the tip A of the two-stage tapered molding pin 10 is inserted, the tip does not get caught on the end 4 of the separator 3.

[0021]

In the method for manufacturing the spiral wound electrode structure for a battery of the present invention, the split pin is removed after the electrode is wound in a spiral shape by using the split pin, and the split pin trace space formed thereby, As the heated two-step tapered molding pin is inserted as needed, the end of the separator located in the middle of the cotter pin trace space is pressed against the inner surface of the cotter pin trace space and the inner circumference It follows the surface. Moreover, the taper at the rear end of the molding pin further expands the split pin trace space.

[0022]

EXAMPLES The method of manufacturing the spiral wound electrode structure for a battery according to the present invention will be specifically described below based on examples.

Example 1 Petroleum pitch was subjected to an oxygen crosslinking treatment to introduce 10 to 20% of functional groups containing oxygen into petroleum pitch, and then fired in an inert gas stream at a temperature of 1000 ° C. to form a glass. A non-graphite carbon material having properties close to carbon was obtained. According to the X-ray diffraction result of this carbon material, the interplanar spacing of the (002) plane is 3.
The thickness was 76 angstrom and the true specific gravity was 1.58 g / cm ³ . This carbon material was pulverized into powder having an average particle size of 10 μm.

90 parts by weight of the carbon material powder thus obtained was mixed with polyvinylidene fluoride (PVDF) 1 as a binder.
0 parts by weight were mixed and dispersed in N-methyl-2-pyrrolidone to obtain a negative electrode mixture slurry. Add this slurry to a thickness of 10
Uniformly coated on both sides of a copper foil (negative electrode current collector) of μm band,
It was dried and compression-molded with a roll press to produce a strip-shaped negative electrode.

As the positive electrode active material, lithium carbonate and cobalt carbonate were mixed so that Li / Co (molar ratio) = 1, and the mixture was fired in air at a temperature of 900 ° C. for 5 hours to obtain LiCoO _2. Got Obtained LiCoO ₂ , 9
91 parts by weight of a mixture of 9.5 parts by weight and lithium carbonate, 0.5 parts by weight, 6 parts by weight of graphite as a conductive agent and 3 parts by weight of PVDF as a binder were mixed with N-methyl-2-. It was dispersed in pyrrolidone to obtain a positive electrode mixture slurry. This slurry was uniformly applied to both surfaces of a strip-shaped copper foil (negative electrode current collector) having a thickness of 20 μm, dried, and further compression-molded by a roll press machine to produce a strip-shaped positive electrode.

As the separator, a microporous polypropylene film (Celgard 2400, manufactured by Hoechst Celanese) was used.

These strip-shaped negative electrode, strip-shaped positive electrode and separator are adjusted to have a length and a width so that they can be properly accommodated in a battery can having an outer diameter of 20 mm and a height of 51 mm, and they are spirally wound by using a split pin according to a conventional method. It was used as a mold electrode.

Next, as shown in FIG. 1, a circular cross section 2
The stepped tapered molding pin was heated to 113 ° C. and inserted into the space left after removing the split pin of the spirally wound electrode from the tip as shown in FIG. This operation was repeated once again to form a split pin mark space.

When a welding rod for spot-welding the negative electrode lead to the bottom of the battery can was inserted into 100 spirally-wound electrode structures manufactured as described above, no defective insertion occurred.

Example 2 Using a microporous polyethylene film (Hypore 4030U, manufactured by Asahi Kasei Kogyo Co., Ltd.) as a separator, a two-stage tapered molding pin as shown in FIG. 1 was used.
100 spirally wound electrode structures were manufactured in the same manner as in Example 1 except that heating was performed at 3 ° C.

When a welding rod for spot-welding the negative electrode lead to the bottom of the battery can was inserted into 100 spirally-wound electrode structures thus manufactured, no defective insertion occurred.

Comparative Example Example 1 except that molding was not performed with a two-step tapered molding pin.
100 spiral electrode structures were manufactured in the same manner as in.

When a welding rod for spot-welding the negative electrode lead to the bottom of the battery can was inserted into 100 spiral electrode structures thus manufactured, the welding rod was a spiral electrode structure. The number of defective products was exactly 40, which was obstructed by the end of the separator in the split pin trace space.

[0034]

According to the present invention, the welding rod for spot welding the electrode lead of the spiral electrode structure and the inner bottom portion of the metal battery container accommodating the electrode lead is provided with the split pin of the spiral electrode structure. It is possible to reduce the occurrence rate of defects when inserting into the trace space.

[Brief description of drawings]

FIG. 1 is a side view of a two-step tapered forming pin used in the present invention.

FIG. 2 is an explanatory diagram showing a state in which a two-step tapered forming pin starts to be inserted into a spirally wound electrode structure.

FIG. 3 is an explanatory view showing a state in which an intermediate portion of a two-step tapered forming pin is inserted into a spiral electrode structure.

FIG. 4 is an explanatory view showing a state in which a tapered portion of a rear end portion of a two-step tapered forming pin is inserted into a spiral electrode structure.

FIG. 5 is a perspective view of a split pin for winding an electrode according to a preferred embodiment.

FIG. 6 is a top view of a spiral electrode structure having a split pin trace space when the split pin of FIG. 5 is used.

FIG. 7 is a diagram illustrating a conventional method for manufacturing a spirally wound electrode structure.

FIG. 8 is a top view of a split pin trace space of the spiral electrode structure.

FIG. 9 is an explanatory diagram showing how a conventional molding pin in a split pin trace space is inserted into a split pin trace space in a spiral electrode structure.

FIG. 10 is an explanatory view showing a state where a conventional molding pin is inserted into a split pin mark space of a spirally wound electrode structure.

[Explanation of symbols]

 1 Split pin 2 Split groove of split pin 3 Separator 4 Separator end 5 Negative electrode 6 Positive electrode 7 Spiral type electrode structure 8 Split pin trace space 9 Molded pin 10 Molded pin with 2 steps taper

Claims (2)

[Claims] 1. A separator is sandwiched in a split groove of a split pin for winding an electrode to start winding, and further, the strip-shaped positive electrode and negative electrode are wound while interposing the separator so as not to contact each other, and then the split In a method for manufacturing a spiral-wound electrode structure for a battery, including removing pins, in a split pin trace space formed in a central portion of the spiral-wound electrode structure for batteries after separating the split pins, two steps are provided. Manufacture of a spiral-wound electrode structure for a battery, characterized in that a winding start portion of the separator in the cotter pin trace space is aligned with an inner peripheral surface of the cotter pin trace space by inserting a tapered molding pin. Method. 2. The spiral electrode structure for a battery according to claim 1, wherein the split groove of the split pin is provided so as to be parallel to the central axis in the longitudinal direction of the split pin but not to overlap the central axis. Body manufacturing method.