JP2002231211A - Separator with collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a secondary battery using a compact electrode including no collector support. SOLUTION: An electrode group structure for the secondary battery is characterized in that the collector is stuck to the separator and the power is collected by the whole surface in contact with a negative electrode. A positive electrode is wrapped by using the separator with the collector stuck thereto and the negative electrode is stuck to its outside so as to secure the power collection of the negative electrode. When this separator with the collector stuck thereto is used for the electrode of the conventional type, it is formed into a sandwich power collection system from the collector support existing in the negative electrode and the collector stuck to the separator existing in the external circumferential surface part of the negative electrode so that the power collection effective area is increased to be favorable in drawing out a large current. This results in that the compact positive electrode including no collector support can adopt the similar method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a secondary battery.

[0002]

2. Description of the Related Art Components of a secondary battery include a positive electrode, a negative electrode, a separator, and an electrolyte. In the related art, a paste made of an active material, a binder, a conductive material, and the like is applied to a current collecting support for both a positive electrode and a negative electrode, dried, and then rolled by a roll press or the like to produce an electrode. A separator is sandwiched between the positive and negative electrodes, inserted into a battery can as an electrode group, injected with an electrolytic solution, and then sealed to produce a secondary battery. In the case of a cylindrical secondary battery, a wound type electrode group is formed, and in the case of a square secondary battery, a stacked electrode group is formed. A current is taken out to an external circuit by welding a lead wire coming out of the current collecting support to the positive electrode cover and the negative electrode can.
In the case where a current collecting support is not used, there is a structure in which a portion such as an end of a positive electrode or a negative electrode is in contact with the current collector.

FIG. 9 shows a sectional view of a conventional electrode group. In the case of a conventional electrode group, a structure is provided in which a separator 105 is provided and lead wires 103 and 104 are protruded from a current collecting support inside the positive electrode 101 and the negative electrode 102.

[0004]

When a positive electrode or a negative electrode containing no current-collecting support is used for a secondary battery, it is necessary to provide a current collector on the positive and negative electrodes by some method. For example, when a molded body or sintered body that does not contain a current collecting support is used as a negative electrode, a method for collecting the negative electrode is to enclose the outer periphery of the negative electrode with a current collector and extend a lead wire extending from the current collector. To the negative electrode can. In this case, when the outer periphery of the negative electrode is wrapped with the current collector, a volume space for the current collector is formed. When a large number of negative electrodes are used as in a prismatic battery, such a current collecting method is employed for each negative electrode, and the volume space loss due to the current collector increases. This is disadvantageous when producing a high capacity secondary battery.

[0005]

According to the present invention, there is provided an electrode group structure for a secondary battery, wherein a current collector is attached to a separator and current is collected over the entire surface in contact with the negative electrode. I will provide a. The current collector of the negative electrode is secured by wrapping the positive electrode using a separator to which the current collector is attached and attaching the negative electrode to the outside of the positive electrode. Furthermore, when the separator with the current collector attached thereto is used for a conventional electrode, a sandwich current collection method is used in which the current collector is attached to the current collector support existing inside the negative electrode and the current collector attached to the separator on the outer peripheral surface of the negative electrode. When taking out a large current, the effective current collecting area increases, which is advantageous. For these reasons, a similar method can be adopted for a molded positive electrode that does not contain a current collecting support.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments shown in the drawings. Examples of the sectional view of the electrode group of the present invention are shown in FIGS. The electrode group of FIG. 1 has a structure in which a current collector 6 is attached to a separator 5, and the current collector adheres to the surface of the negative electrode 2 which does not include a current collecting support (conductive core material). Thus, current collection of the negative electrode is ensured. The lead wire 4 extending from the current collector attached to the separator 5 is shown. FIG. 1 shows a positive electrode 1 containing a current collecting support (conductive core material) and a lead wire 3 extending from the current collecting support of the positive electrode. FIG.
The current collector 6 is attached to the separator 5, and the current collector adheres to the surface of the positive electrode 7 that does not include the current collecting support (conductive core material), so that the current collection of the positive electrode is ensured. Is done. FIG. 2 shows a negative electrode 8 containing a current collecting support (conductive core material) and a lead wire 9 extending from the current collecting support of the negative electrode.
FIG. 3 shows a structure in which current collectors 6 are attached to both surfaces of a separator 5, and the current collectors are provided on the surface of a positive electrode 7 which does not contain a current collecting support (conductive core material) and a current collecting support ( Conductive core material)
Is attached to the surface of the negative electrode 2 that does not contain, the current collection of both electrodes is secured.

FIG. 4 shows a structural diagram in which a current collector 6 is attached to a separator 5. By pressing the separator and the current collector, a current collector-attached separator can be produced. The current collector material used in the present invention is not particularly limited, but is preferably a conductive material such as nickel, copper, or carbon, and has air permeability such as fibrous, mesh, or perforated sheet. The amount of the current collecting material used needs to be about the area of the electrode that requires current collection. The separator used in the present invention is not particularly limited, but nonwoven fabrics such as polyamide, polypropylene, and nylon are used. Further, the thickness of the separator may be any thickness as long as the current collector does not protrude to the side opposite to the press surface by pressing and the insulation is not broken. The separator and the current collector adhere to each other in such a manner that the separator bites into the gap between the holes by pressing. In order to improve the adhesion between the current collector and the separator, the current collector and the separator may be temporarily adhered with an adhesive or the like, and then pressed and adhered. Further, it is characterized in that the total thickness of the separator thickness and the current collector thickness before pressing can be reduced by pressing. In the present invention, the current collector may be attached to one side, both sides, or a part of the separator.

[0008] Figs. 5 and 6 show the configuration of an electrode group in a case where a separator with a current collector is applied to a columnar or plate-shaped negative electrode containing no current collecting support. In the plan view of the cylindrical electrode group shown in FIG. 5, the separator 13 is located on the inner peripheral side of the hollow cylindrical positive electrode, and the columnar negative electrode 12 is located inside the separator 13. The current collector is attached to the negative electrode side of the separator.
When the positive electrode 14 is in contact with the battery can 11, current collection is secured. As for the negative electrode, the current collector attached to the separator adheres to the outer peripheral surface of the negative electrode, so that the current can be collected.

In the sectional view of the hexagonal electrode group shown in FIG. 6, in the case of a positive / negative electrode type using plate electrodes, one surface of the outermost negative electrode 22A is in contact with the battery can 21 and the other surface is a separator. Current collection is ensured by contacting the current collector attached to 23. As for the negative electrode 22B located inside, current collection is ensured in such a manner that the current collector attached to the negative electrode side of the separator enclosing the positive electrode contacts both surfaces of the negative electrode 22A. The external negative electrode 22 </ b> A and the internal negative electrode 22 </ b> B ensure electrical conductivity by the current collector attached to the separator 23. FIG. 6 also shows a positive electrode 24 containing a current collecting support and a positive electrode lead wire 25.

FIG. 5 shows a case in which the positive electrode is disposed at the outer periphery of the negative electrode at the center in the case of the cylindrical electrode group. However, a cylindrical positive electrode comes to the center and a hollow cylindrical negative electrode is provided at the outer periphery. The collector-attached separator can be applied to the arranged electrode group, and further to a cylindrical electrode group having a positive / negative electrode multilayer structure in which positive and negative electrodes are arranged on the outer periphery thereof. In the case of a plate-like electrode, an electrode group having two positive electrodes and three negative electrodes has been described as an example. However, a collector-attached separator can be applied to a multilayer electrode group using more positive and negative electrodes.

Further, as an application example, FIG. 7 shows a configuration diagram of a square electrode group when a collector-attached separator is applied to a conventional electrode having a current-collecting support. Since current collection from inside the electrode and from outside the electrode is ensured, current collection efficiency is improved. FIG. 7 shows a negative electrode 31 and a negative electrode lead 32 containing a current collecting support. As an improvement for improving the high rate discharge characteristics, the present invention can be applied to a wound electrode group of a cylindrical battery and a laminated electrode group of a square battery.

[0012]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Example 1 (Preparation of square plate electrode containing no current collecting support) Hydrogen storage alloy ingot (La)
Assuming that the total of 63% by weight, 7% by weight of Ce, 22% by weight of Pr, and 8% by weight of Nd is an atomic ratio of 1.0, Ni is 3.75;
0.75 for Co, 0.20 for Mn, 0.30 for Al)
Was heat-treated in argon to prepare a uniform hydrogen storage alloy ingot. The alloy ingot was coarsely pulverized in a nitrogen atmosphere. Further, the mixture was pulverized to a size of 1 mm or less with a brown mill to obtain a raw material for a jet mill. Further, in the present invention, the hydrogen storage alloy is dry-pulverized by a jet mill under a gas pressure of 5.8 kgf / cm ² and a nitrogen gas atmosphere to obtain an average particle diameter of 6 μm.
A hydrogen storage alloy fine powder having a particle size distribution of 1 to 30 μm was obtained. Next, the pulverized fine powder was put in a mold, and a square plate molded body having a vertical width of 20 mm, a horizontal width of 10 mm, and a thickness of 0.5 mm was produced at a molding pressure of 6.0 ton / cm ² . The bulk density of the molded body is 5.5 g / cm ³ . This hydrogen storage alloy porous square plate compact is put into a 5% by weight aqueous solution of polyvinyl alcohol,
After degassing for a certain period of time and immersing for 24 hours to confirm that the aqueous binder solution had sufficiently penetrated into the inside of the molded product, the molded product was taken out and dried under vacuum. The binder impregnation amount (solid content) is about 0.3% by weight of the molded body weight. Three porous square plate electrodes were produced.

(Preparation of Positive Electrode Containing Current-Supporting Support) Next, commercially available nickel hydroxide powder and cobalt monoxide powder were mixed at a weight ratio of 9: 1, and the powder was mixed with a V mixer. After 30 minutes, the mixture is well kneaded with a 1% aqueous solution of methylcellulose and has a vertical width of 20 m with a nickel lead wire.
m, a width of 10 mm and a thickness of 1.7 mm were applied to a foamed nickel current collector, dried to remove moisture, and then press-molded to produce two 1.2 mm-thick positive electrodes. The electrode capacity density of the positive electrode containing the current collecting support is about 600 mAh / cm ³
Therefore, the design capacity per positive electrode is about 144 mA
h.

(Preparation of separator with current collector)
A polypropylene separator having a width of 50 mm, a width of 15 mm and a thickness of 0.23 mm, a width of 42 mm and a width of 10
mm, 0.18 mm thick nickel mesh (# 10
In a state where 0) was overlapped, pressing was performed at a pressing pressure of 6 ton / cm ² to attach a nickel mesh and a separator. It was found that the thickness after pressing was 0.17 mm, which was extremely thin with respect to the separator plus nickel mesh thickness of 0.41 mm before pressing. In addition, it was found that the adhesion was improved by part of the separator biting into the mesh holes by pressing. As a result of surface observation using a microscope, it was confirmed that the separator and the nickel mesh were crushed by pressing.

(Preparation of Square Sealed Battery) The current collector-attached separator was folded in two such that the current collector-attached portion was on the outer peripheral side, and the positive electrode was wrapped. Next, a rectangular battery can having an inner size of 25 mm in depth, 12 mm in width, and 4.8 mm in thickness was prepared. Two positive electrodes wrapped with the current collector-attached separator and three square plate molded bodies were inserted therein (square electrode group structure in FIG. 6). The design capacity of the positive electrode is 28
8 mAh. At this time, the thickness of the negative electrode was 1.5 mm, the thickness of the positive electrode was 3.08 mm (including the separator with a current collector), and the total thickness of the electrode group was 4.58 mm, so that the electrode group could be easily inserted into the battery can. Since the battery can still has an extra space of 0.22 mm in the thickness direction, the thickness of the positive electrode or the negative electrode can be increased accordingly. The fact that the thickness of the positive electrode or the negative electrode can be increased allows the battery capacity or the battery reserve to be increased accordingly. After injecting 7N caustic potash electrolyte into the battery can, the battery was sealed to produce a square sealed battery. This battery is assumed to be A (design capacity: 288 mAh).

Comparative Example 1 The negative electrode was the same as in Example 1 in a width of 20 mm and a width of 1
Three square plate molded bodies having a thickness of 0 mm and a thickness of 0.5 mm were prepared.
As the positive electrode, two sheets of the same one as in Example 1 were prepared. Next, a vertical width of 50 mm, a horizontal width of 15 mm, and a thickness of 0.23
A 2 mm-thick polypropylene separator was folded and the positive electrode was wrapped, and the electrode group having two positive electrodes and three conventional negative electrodes was inserted into the battery can in the same manner as in Example 1. Here, the method for collecting the negative electrode was such that one end of the negative electrode was in contact with the fibrous nickel when the electrode group was inserted by laying a thin layer of fibrous nickel on the bottom of the battery can. FIG. 8 shows a cross-sectional view of the square electrode group using the negative electrode end current collecting method. FIG. 8 shows the battery can 4
1. Negative electrodes 42A and 42B containing no current collecting support,
Shown are a separator 43, a positive electrode 44 containing a current collecting support, a positive electrode lead wire 45, and a current collector 46 at the negative electrode end. The thickness of the negative electrode was 1.5 mm, the thickness of the positive electrode was 3.32 mm (including the separator), and the total thickness of the electrode group was 4.82 mm.
And insertion into the battery can was possible. However, Embodiment 1
No extra space was created in the thickness direction of the battery can as indicated by. After injecting 7N caustic potash electrolyte into the battery can, the battery was sealed to produce a square sealed battery. This battery is designated as B (design capacity: 288 mAh).

(Battery Test) For Battery A and Battery B having a designed capacity of 288 mAh, a charge rate of 0.2 at room temperature of 25 ° C.
C at a charge rate of 120%, and 30 minutes after the end of charging, charge / discharge at a discharge rate of 0.2 C and a 1.0 V cut was performed for 1 minute.
00 cycles (charge rate 1C = 288m)
A). Table 1 shows the results.

[0018]

[Table 1]

In the nickel-hydrogen secondary battery using the collector-attached separator of Example 1, a discharge capacity close to the designed capacity was obtained from the beginning, and the capacity retention rate after 100 cycles ((discharge at the 100th cycle) (Capacitance / discharge capacity at the first cycle) × 100%), the discharge capacity of Comparative Example 1 at the time of 100-cycle charge / discharge was drastic, and did not function satisfactorily as a secondary battery. For this reason, in the prismatic electrode group structure battery shown in FIG. 8, the outermost negative electrode 42A is in direct contact with the battery can and current collection can be properly performed, whereas the internal negative electrode 42B is only the negative electrode end current collector. Therefore, it is considered that the current was not collected properly, and the negative electrode 42B did not function, resulting in a decrease in the negative electrode capacity, that is, a decrease in the cycle of the discharge capacity accompanying a decrease in the battery reserve. On the other hand, in Example 1, the current collector adhered to the separator was in contact with the negative electrode over a large area, and the current collection was performed well.
It is considered that the capacity retention rate after 0 cycles was high.

[0020]

As described above, by using the collector-attached separator according to the present invention, it is possible to manufacture a secondary battery using a molded electrode containing no current-collecting support. Furthermore, an efficient current collection method becomes possible by bringing the current collector into close contact with the negative electrode surface, and a secondary battery with a small decrease in discharge capacity due to charge and discharge cycles can be provided.

[Brief description of the drawings]

FIG. 1 shows a sectional view of an electrode group of the present invention.

FIG. 2 shows a sectional view of an electrode group according to the present invention.

FIG. 3 shows a sectional view of an electrode group of the present invention.

FIG. 4 is a structural view in which a current collector 6 is attached to a separator 5;

FIG. 5 is a plan view of a cylindrical electrode group when a separator with a current collector is applied to a columnar negative electrode that does not contain a current collecting support.

FIG. 6 is a cross-sectional view of a square electrode group when a separator with a current collector is applied to a plate-shaped negative electrode that does not contain a current collecting support.

FIG. 7 is a configuration diagram of a square electrode group when a collector-attached separator is applied to a conventional electrode having a current-collecting support.

FIG. 8 shows a sectional view of a square electrode group by a negative electrode end current collecting method.

FIG. 9 is a sectional view of a conventional electrode group.

[Explanation of symbols]

1 Positive electrode containing current collecting support (conductive core material) 2 Negative electrode not containing current collecting support (conductive core material) 3 Lead wire extending from current collecting support of positive electrode 4 Current collector adhered to separator 5 Lead wire extending from 5 Current collector adhered to separator 6 Current collector adhered to separator 7 Positive electrode not containing current collecting support (conductive core material) 8 Negative electrode containing current collecting support (conductive core material) 9 Lead wire extending from the current-collecting support of the negative electrode 11 Battery can 12 Negative electrode without current-collecting support 13 Separator with current collector attached 14 Positive electrode without current-collecting support 21 Battery can 22A Outermost Negative electrode 22B Negative electrode located inside 23 Separator to which current collector is adhered 24 Positive electrode containing current collecting support 25 Lead wire of positive electrode 31 Negative electrode containing current collecting support 32 Negative electrode lead 41 Battery can 42 Outermost negative electrode 42B that does not contain a current collecting support 42B Internal negative electrode 43 that does not contain a current collecting support 43 Separator 44 Positive electrode 44 that contains a current collecting support 44 45 Positive electrode lead wire 46 Current collector 101 at negative electrode end 101 Positive electrode containing current supporting body (conductive core material) 102 Negative electrode containing current collecting support (conductive core material) 103 Lead wire extending from current collecting support 104 Lead wire extending from current collecting support 105 Separator

Continued on the front page (72) Inventor Satoshi Shima 2-5-1, Kitafu, Takefu-shi, Fukui Prefecture Shin-Etsu Chemical Co., Ltd. Magnetic Materials Research Laboratory F-term (Reference) 5H017 AA02 AS02 HH05 5H021 AA02 CC04 EE02 EE21 5H022 AA04 CC12 CC19 CC23 5H028 AA05 CC05 CC08 CC11 EE01

Claims (3)

[Claims] 1. A battery separator to which a current collector is attached. 2. The battery separator according to claim 1, wherein the current collector is obtained from a conductive material having a shape having air permeability. 3. A secondary battery using the separator with a current collector according to claim 1 or 2.