WO2015133568A1

WO2015133568A1 - Accumulator element

Info

Publication number: WO2015133568A1
Application number: PCT/JP2015/056484
Authority: WO
Inventors: 雅彰関谷; 櫻井　淳; 徳孝江口; 貴史増井; 若松　喜美
Original assignee: 新神戸電機株式会社
Priority date: 2014-03-06
Filing date: 2015-03-05
Publication date: 2015-09-11
Also published as: JPWO2015133568A1

Abstract

Provided is an accumulator element allowing the tension applied to a sheet-formed separator during initial winding to be higher than in prior art. An axial core (7) has a shape in which the external diameter dimension decreases at a predetermined ratio from a central region (R2) in the longitudinal direction toward the two ends (11) and (13) in the longitudinal direction. The predetermined decreasing ratio is set to such a value that no wrinkles occur in the sheet-formed separator (3) during the initial winding in which an electrode plate group (5) is wound around the axial core (7).

Description

Electricity storage element

The present invention relates to a storage element such as a lithium ion capacitor element and a lithium ion battery element configured by winding an electrode plate group around an axis.

Japanese Patent Laying-Open No. 2012-079943 (Patent Document 1) discloses a wound-type power storage device in which a laminate in which positive and negative electrode plates are laminated through a paper separator is wound around an axis. An example is shown. In this type of conventional power storage element, a tubular shaft core having a constant outer diameter is used.

JP 2012-079943 A

In a wound-type power storage device in which a laminated body in which such positive and negative electrode plates are stacked via a papermaking separator is wound around the shaft core, the winding density of the stacked body is increased to improve the performance of the power storage device. Therefore, when the electrode plate group is wound around the shaft core, a predetermined tension is applied to the papermaking separator.

However, as the tension increases, there is a problem that wrinkles occur in the paper separator at the initial stage of winding the paper separator around the shaft core. This problem becomes more prominent as the paper separator becomes thinner. When wrinkles occur during such initial winding, the wrinkles are not eliminated even if the winding is continued, and in the portion where wrinkles have occurred, a part of the positive electrode plate or the negative electrode plate bites into the paper separator This will cause a short circuit in the future. Therefore, the electricity storage element in which wrinkles are generated in the papermaking separator is disposed as a defective product, and conventionally, the production yield of the electricity storage device cannot be increased.

An object of the present invention is to provide a power storage device capable of increasing the tension applied to a papermaking separator as compared with the prior art at the time of initial winding of the papermaking separator around an axis.

Another object of the present invention is to reduce the thickness of the paper separator and increase the tension applied to the paper separator as compared with the prior art. An object of the present invention is to provide a power storage element in which no soot is generated.

The inventor examined why wrinkles occur when using a papermaking separator, even though so-called resin separators are used, so that wrinkles do not occur at the initial stage of winding. As a result, it was discovered that the papermaking separator has a characteristic that the stretchability is lower than that of the resin separator, and this characteristic causes wrinkles. In particular, the distribution of the force applied to the end of the separator varies along the width direction of the end depending on the joined state or the fixed state of the end of the separator and the shaft core. Thus, it is presumed that wrinkles are generated at the initial winding stage of the papermaking separator having low elasticity.

An object of the present invention is to improve a power storage device in which a laminated body formed by laminating a belt-like positive electrode plate and a belt-like negative electrode plate via a belt-shaped paper separator is wound around an axis. . In the present invention, the shaft core has a shape in which the outer diameter dimension decreases from the central region in the longitudinal direction toward both ends in the longitudinal direction at a predetermined reduction rate. In addition, the center area | region of an axial center is an area | region of the predetermined range containing the center position of the longitudinal direction of an axial center. In this central region, the outer diameter of the shaft core may or may not decrease. The predetermined reduction rate is set to a value that does not generate wrinkles in the paper separator during the initial winding of winding the electrode plate group around the axis. The decreasing rate may be constant or may vary. If the outer diameter of the shaft core is determined in this way, even if there is a large variation in the force applied to the end of the papermaking separator during the initial winding, the force applied to the papermaking separator is directed from the central region of the shaft core toward both ends. Shows a decreasing distribution trend. The inventor believes that such a force distribution tendency prevents wrinkles from forming on the low-stretch paper-making separator even when the paper-making separator is thinned and the tension is increased. .

The predetermined reduction rate is determined so that the difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the winding portion of the shaft core is a value in a range of 30% ± 10% of the thickness dimension of the papermaking separator. It is preferable. Experiments have confirmed that such a value can more effectively prevent wrinkles.

In addition, the papermaking separator may be any material as long as it is produced by a papermaking method used in the production of paper, and the raw material to be made may be any material as long as it has insulating properties. When a so-called paper separator formed using the cellulose fiber as a main raw material is used, a power storage element can be manufactured at low cost. In addition, when using this papermaking separator, this invention is especially suitable when the thickness is thinner than 35 micrometers. Moreover, it is preferable that the length of the reduction | decrease area | region which is located in the both sides of a center area | region and whose outer diameter dimension reduces is longer than 1/4 of the length dimension of an axial center. This is because the effect of providing the reduction region cannot be obtained if the length of the reduction region in the longitudinal direction becomes too short.

It should be noted that the present invention can also be understood as an axial core having a shape in which the outer diameter dimension decreases from the central region in the longitudinal direction toward both ends in the longitudinal direction at a predetermined reduction rate. Also in this case, the predetermined reduction rate is that when the laminated body constituted by laminating the belt-like positive electrode plate and the belt-like negative electrode plate through the belt-like papermaking separator is wound, the papermaking separator is wrinkled. The value is not set.

The present invention is suitable for application to a lithium ion capacitor element, which often uses a paper separator.

It is a perspective view which shows roughly the structure of the lithium ion capacitor element which is 1 type of the electrical storage element of embodiment of this invention. It is a front view of the shaft core used in the embodiment of the present invention. FIG. 4 is a partially omitted enlarged cross-sectional view schematically showing exaggerated changes in the outer diameter of the shaft center. 6 is a table showing the presence or absence of wrinkles in the paper separators of Examples 1 and 2 and Comparative Examples 1 to 3 using a paper separator having a thickness of 30 μm.

Hereinafter, an embodiment in which the present invention is applied to a lithium ion capacitor element which is a kind of power storage element will be described with reference to the drawings. FIG. 1 is a perspective view of a lithium ion capacitor element schematically showing a structure when the present invention is applied to a lithium ion capacitor element. FIG. 2 is a front view in which a part of the shaft core 7 used in the embodiment of the present invention is omitted. FIG. 3 is a partially omitted enlarged sectional view schematically showing exaggerated changes in the outer diameter of the shaft core 7. 2 and 3, R1 indicates a first end region, R2 indicates a central region, and R3 indicates a second end region. The first end region R1, the central region R2, and the second end region R3 each have a length that is 1/3 of the total length of the axial center 7 in the longitudinal direction. The first end region R1, the central region R2, and the second end region R3 form a winding portion of the axial core.

In the lithium ion capacitor element 1 of the present embodiment, a laminated body configured by laminating a belt-like positive electrode plate and a belt-like negative electrode plate via a belt-like papermaking separator 3 is wound around the shaft core 7. Thus, a tabless type electrode plate group 5 is configured.

The positive electrode plate in the electrode plate group 5 is configured by forming a positive electrode active material layer on a belt-shaped current collector plate so as to leave a welded portion on one end side in the width direction. Similarly, the negative electrode plate is configured by forming a negative electrode active material layer on a belt-shaped current collector plate so as to leave a welded portion on one end side in the width direction. Then, a laminated body formed by laminating the positive electrode plate and the negative electrode plate via the papermaking separator 3 so that the welded portion of the positive electrode plate and the welded portion of the negative electrode plate are located at both end portions of the electrode plate group 5 is provided. The electrode group 5 is formed by winding around 7.

In the present embodiment, the thickness dimension of the positive electrode plate and the negative electrode plate is in the range of 50 μm to 115 μm, the thickness dimension of the papermaking separator 3 is less than 50 μm, and the positive electrode plate, the negative electrode plate, and the papermaking separator 3 The width dimension is in the range of 90.3 mm to 133.3 mm. As the papermaking separator 3, a so-called paper separator formed using cellulose fibers spun by treatment with a solvent as a main raw material is used. In addition, as the papermaking separator 3, what uses PPS (poly phenylene sulfide) resin etc. which have insulation as a raw material can be used.

The shaft core 7 of the present embodiment is integrally formed of a hollow cylindrical PPS (polyphenylene sulfide) resin. The shaft core 7 may be made of other resins such as polypropylene and polyimide. A pair of fitting grooves 12 into which jigs for rotating the shaft core 7 are fitted are formed at both

end portions

11 and 13 of the shaft core 7 so as to face each other in the radial direction. Further, at both

end portions

11 and 13 of the shaft core 7, a small-diameter protruding portion 14 on which the electrode plate group 5 is not mounted is integrally provided.

Further, a tapered surface that is continuous from the central region R2 to the first end region R1 and the second end region R3 is formed on the outer surface of the region where the electrode plate group 5 of the shaft core 7 is mounted. That is, the outer diameter dimension decreases from the central portion 17 in the longitudinal direction of the central region R2 toward the end portion 11 at a predetermined decreasing rate from the first end region R1. Similarly, the outer diameter dimension decreases from the central portion 17 in the longitudinal direction of the central region R2 toward the end portion 13 at a predetermined decreasing rate from the second end region R3. In the central region R2, the reduction rate of the outer diameter dimension gradually decreases toward the central portion 17, and finally the reduction rate becomes zero. Therefore, in the shaft core 7 of the present embodiment, no ridge line appears at the center of the central region R2. In the present embodiment, the reduction ratio of the outer diameter dimension in the first end region R1 and the reduction ratio of the outer diameter dimension in the second end region R3 are constant, and the central portion 17 of the central region R2 is The reduction rate of the outer diameter dimension of the excluded portion is also constant, as is the reduction rate in the first and second end regions.

In the present embodiment, the outer diameter size of the central portion 17 in the longitudinal direction of the central region R2 of the shaft core 7 is the maximum outer diameter size of the shaft core 7, and the end portions of the first and second end regions R1 and R3. The outer diameter dimension at the extreme end position in 11 and 13 is the minimum outer diameter dimension. In each of the first and second end regions R1 and R3, the outer diameter dimension decreases from the central region R2 at a constant decreasing rate in a direction in which both end

portions

11 and 13 are located.

The predetermined reduction ratio of the outer diameter dimension of the shaft core 7 is set to a value that does not cause wrinkles in the papermaking separator 3 during the initial winding of the electrode plate group 5 around the shaft core 7. Specifically, in the present embodiment, the reduction ratio of the outer diameter dimension of the shaft core 7 is such that the difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the shaft core 7 is 30 mm of the thickness dimension of the papermaking separator 3. It is determined to be a value in the range of ± 10%. When the outer diameter dimension of the shaft core 7 is determined in this way, even if tension is applied to the papermaking separator 3 during the initial winding, the force that generates wrinkles is directed from the central region R2 of the shaft core 7 toward both ends 11 and 13. A tendency to decrease appears. As a result, wrinkles can be prevented from occurring in the papermaking separator 3.

When the difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the shaft core 7 is larger than 30% + 10% of the thickness dimension of the papermaking separator 3, there is a tendency that wrinkles tend to occur due to the dimensional difference. It has been confirmed by experiments. Further, when the difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the shaft core 7 is smaller than 30% -10% of the thickness dimension of the papermaking separator 3, the tendency to generate wrinkles is suppressed and the generation of wrinkles is prevented. Experiments have confirmed that no effect can be obtained.

The reduction ratio of the main portion excluding the central portion 17 of the outer diameter dimension in the central region R2 may be different from the reduction ratio of the outer diameter dimension in the first end region R1 and the second end region R3. That is, when the outer diameter dimension continuously decreases when the transition from the first end region R1 to the central region R2, and the decreasing rate gradually approaches 0 in the central portion 17 of the central region R2, the central region The aspect of the change in the decrease rate in R2 is arbitrary. Of course, the reduction ratio of the outer diameter may be zero in a relatively wide region including the central portion 17 of the central region R2. In the present invention, at least in the first and second end regions R1 and R3, the outer diameter may be reduced at a predetermined reduction rate.

In the examples of the present embodiment, specifically, the maximum outer diameter of the shaft core 7 is in the range of 13.03 mm to 13.20 mm, and the minimum outer diameter is in the range of 13.01 mm to 13.18 mm. The length of the shaft core 7 is in the range of 97.25 mm to 139.45 mm. The decreasing rate is constant in the first and second end regions R1 and R3. That is, in the first and second end regions R1 and R3, the angles of the tapered surfaces 15 and 19 appearing on the outer surface (the tangential plane in the central portion 17 of the central region R2 and the

tapered surfaces

15 and 19 of the end regions R1 and R3) The angle between 19) is constant. In the central region R <b> 2, the reduction rate is set so that the reduction rate gradually becomes 0 toward the central portion 17. That is, the taper angle appearing on the outer surface of the central region R2 becomes 0 as it approaches the central portion 17.

FIG. 4 shows the result of an experiment conducted on the ease of occurrence of wrinkles in the paper separator for the lithium ion capacitor element of the example of the above embodiment and the lithium ion capacitor element of the comparative example. FIG. 4 shows the tension during winding of the lithium ion capacitor elements of Examples 1 and 2 and Comparative Examples 1 to 3 and the presence or absence of wrinkling of the paper separator using a paper separator having a thickness of 30 μm. It is a table.

In this experiment, lithium ion capacitor elements of Examples 1 and 2 and Comparative Examples 1 to 3 were prepared, and the presence or absence of wrinkles in the paper separator was examined while changing the tension during winding. The lithium ion capacitor element of Example 1 is the lithium ion capacitor element of the above embodiment shown in FIGS. That is, the maximum outer diameter dimension of the shaft core 7 is 13.11 mm, the minimum outer diameter dimension is 13.09 mm, and the length dimension of the shaft core 7 is 97.25 mm. The outer diameters of the first end region R1 and the second end region R3 are set such that the difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the shaft core 7 is 30% of the thickness dimension of the papermaking separator 3. The reduction ratio of the diameter dimension and the reduction ratio of the central region R2 were determined. The reduction ratio of the outer diameter dimension of the first end region R1 and the second end region R3 is constant, and in the central region R2, the reduction ratio of the outer diameter dimension gradually increases toward the central portion 17 in the longitudinal direction. The reduction rate was determined to be 0.

The lithium ion capacitor element of Example 2 has a taper at the end region of a quarter near the both ends in the longitudinal direction of the axial core (the outer diameter dimension decreases from the central region toward both ends in the longitudinal direction at a predetermined reduction rate. Has a smaller shape). In Example 2, wrinkles are observed when the tension is increased. According to experiments, it is confirmed that if the first end region R1 and the second end region R3 are longer than ¼ of the longitudinal dimension of the shaft core 7, a certain effect of the present invention can be obtained. Has been. In particular, as in Example 1, when the first end region R1 and the second end region R3 are about 1/3 of the longitudinal dimension of the shaft core 7, particularly good results can be obtained.

The lithium ion capacitor element of Comparative Example 1 uses a shaft core whose outer diameter increases at a constant rate from the central region in the longitudinal direction of the shaft core toward both ends in the longitudinal direction. The specific increase ratio was such that the difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the shaft core was 30% of the thickness dimension of the papermaking separator.

For the lithium ion capacitor element of Comparative Example 2, a shaft core having a constant outer diameter dimension was used.

In the lithium ion capacitor element of Comparative Example 3, the outer diameter decreases from the central region in the longitudinal direction of the shaft core toward both ends in the longitudinal direction as in the embodiment, but the reduction ratio is large (the maximum of the shaft core). A shaft core is used in which the difference between the outer diameter dimension and the minimum outer diameter dimension is 60% larger than the range of 30% ± 10% of the thickness dimension of the papermaking separator.

As shown in FIG. 4, when a paper separator having a thickness of 30 μm was used, the lithium ion capacitor element of Example 1 did not generate wrinkles even when wound with a tension of 3100 g. . In addition, the lithium ion capacitor element of Example 2 was wrinkled on the papermaking separator for the first time when it was wound with a tension of 2200 g. In contrast, the lithium ion capacitor elements of Comparative Examples 1 to 3 were wrinkled on the paper separator with a tension of 2000 g or less. Therefore, even in the case of Example 2, it is possible to increase the tension during winding of the papermaking separator as compared with the comparative example to which the present invention is not applied.

According to the inventors' experiments, it has been confirmed that when the thickness of the papermaking separator exceeds 35 μm, there is almost no difference in wrinkling conditions between Example 1 and Comparative Example 2.

In the above experiment, a paper separator having a thickness of 30 μm was used. However, when the thickness of the paper separator increases beyond 30 μm, wrinkles are less likely to occur. Decrease. On the other hand, when the thickness of the papermaking separator is reduced, wrinkles are likely to occur, and it is natural that the effect of the present invention becomes more remarkable than the above experiment.

As described above, the lithium ion capacitor elements of Examples 1 and 2 are more effective than the lithium ion capacitor elements of Comparative Examples 1 to 3, even when a strong tension is applied or the thickness of the paper separator is reduced. It can be seen that wrinkles are less likely to occur.

According to the present invention, there is provided a power storage device in which wrinkles are not easily generated in a papermaking separator at the initial winding time when the papermaking separator is wound around an axis even when the papermaking separator is thinned and the tension is increased. be able to.

DESCRIPTION OF SYMBOLS 1 Lithium ion capacitor element 3 Papermaking separator 5 Electrode board group 7 Shaft core

Claims

A laminated body constituted by laminating a belt-like positive electrode plate and a belt-like negative electrode plate via a belt-shaped paper separator is a power storage element formed by winding around a shaft core,
The shaft core has a shape in which the outer diameter dimension decreases from the central region in the longitudinal direction toward both ends in the longitudinal direction at a predetermined reduction rate,
The storage element according to claim 1, wherein the predetermined reduction rate is set to a value that does not generate wrinkles in the paper separator during initial winding of the electrode plate group around the shaft core.
The predetermined reduction ratio is determined so that a difference between the maximum outer diameter dimension and the minimum outer diameter dimension of the winding portion of the shaft core is a value in a range of 30% ± 10% of the thickness dimension of the papermaking separator. The electrical storage element according to claim 1, wherein the electrical storage element is provided.
3. The electricity storage device according to claim 1, wherein the papermaking separator is formed using cellulose fibers spun by treatment with a solvent as a main raw material.
The electric storage element according to claim 3, wherein the paper separator has a thickness of less than 35 µm.
5. The length in the longitudinal direction of a decreasing region located on both sides of the central region and having a reduced outer diameter is longer than ¼ of the length of the shaft core. 6. Power storage element.
The power storage element according to claim 1, wherein the power storage element is a lithium ion capacitor element.
The outer diameter dimension has a shape that decreases at a predetermined reduction rate from the central region in the longitudinal direction toward both ends in the longitudinal direction,
The predetermined reduction rate is a value that does not generate wrinkles in the papermaking separator when a laminate composed of a beltlike positive electrode plate and a beltlike negative electrode plate laminated via a beltlike papermaking separator is wound. The shaft core specified in