JPH1031996A - Battery - Google Patents

Abstract

(57) [Problem] To provide a battery capable of improving the reliability by increasing the strength of a current collector of a positive electrode of the battery. SOLUTION: In a battery 1 in which a current collecting portion of a positive electrode 20 is made of aluminum, the current collecting portion of the positive electrode 20 is formed by adding alumina fiber to aluminum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a battery in which a current collector of a positive electrode is made of aluminum.

[0002]

2. Description of the Related Art A battery, for example, a lithium ion secondary battery is used for driving a portable personal computer, for example, and a large lithium ion secondary battery is used for driving a motor of an electric vehicle.

[0003]

In the case of a large secondary battery, the amount of current supplied to the device to be operated is large, so that a large amount of current is supplied between the large lithium ion secondary battery and the device to be operated. The connection (referred to as a bus bar) connected to is naturally increased. Moreover, if the contact area between the connection and the terminal of the lithium ion secondary battery is not sufficiently secured,
The large amount of current flowing to the equipment to be operated may cause unexpected heat generation. For this reason, in the case where the connection is fastened to a terminal of a large-sized lithium ion secondary battery, there is an example in which a screw connection is used.

[0004] Conventional large-sized lithium ion secondary batteries are:
Aluminum is used as the material of the current collecting part (terminal part) of the positive electrode. In order to strongly and reliably connect the screw to the current collector of the positive electrode with screws, it is conceivable to use an aluminum alloy for the terminal of the lithium ion secondary battery fastened to the current collector. Even if the battery terminals to be joined to this current collector are made of aluminum alloy, it is necessary to prevent the aluminum alloy from being eluted in the electrolytic solution. Has usage restrictions. In addition to the strength, if the type of alloy with good conductivity is not selected to cope with the flow of a large amount of current, it is necessary to increase the cross-sectional area of the current collector to reduce the heating resistance. Some problems arise, and in view of the volume energy density and the weight energy density, it is desired that the current collector of the positive electrode be made of a material having high rigidity and good conductivity. Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a battery capable of increasing the strength of a positive electrode current collector of a battery and improving reliability.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a battery in which the current collector of the positive electrode is made of aluminum, wherein the current collector of the positive electrode is formed by adding alumina fibers to aluminum. This is achieved by the battery being used.
If the current collector of the battery's positive electrode is made of aluminum,
The current collector of the positive electrode is formed by adding alumina fibers to aluminum. By doing so, the current collector of the positive electrode made by adding alumina fiber to aluminum has a higher strength and rigidity than the current collector of the positive electrode made of genuine aluminum. Even when connecting to the electrical part, the connection can be firmly fixed.

[0006] Even if the current collecting portion of the positive electrode has a screw portion and the connection for transmitting electricity is connected to the current collecting portion of the positive electrode, at least one of a bolt and a nut is used. The current collecting part of the positive electrode made by adding alumina fiber to the positive electrode has higher rigidity than the current collecting part of the positive electrode made of pure aluminum. For this reason, the creep can be reduced, and the highly reliable fastening state in the current collector of the positive electrode of the battery can be maintained even in a place where the temperature fluctuation is large. Since the current collecting portion of the positive electrode has high rigidity, it is possible to prevent the bolts and nuts from being loosened in the screw portion even when vibration is applied, and to maintain the connection state with high reliability.

[0007]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 shows a preferred embodiment of a lithium ion secondary battery which is the battery of the present invention, and FIG. 2 is a side view of the lithium ion secondary battery of FIG. FIG. 3 is an enlarged view showing a region including a portion of the positive electrode 20 of the lithium ion secondary battery of FIG.

1 and 2, the lithium ion secondary battery 1 includes a battery case (battery container) 17, an electrode roll (electrode element) 35, a positive electrode 20, and a negative electrode 21.
The positive electrode 20 is disposed at one end of the cylindrical battery case 17, and the negative electrode 21 is disposed at the other end of the cylindrical battery case 17. The battery case 17 is, for example, a cylindrical tube made of stainless steel (SUS304), in which an electrode roll body 35 is housed. First, this electrode roll 3
5 will be described. The electrode roll body 35 is formed in a roll shape (spiral shape) using the core 31 of FIG. As shown in FIG. 5, the electrode roll body 35 includes a positive electrode sheet 13, a negative electrode sheet 14, and separators 30, 30.
4. A roll body as shown in FIG. 1 is obtained by stacking the separators 30 in order and winding the separator 30 around the core 31.

When the core 31 of FIG. 4 forms the electrode roll body 35, the rotation stopper 24 of the power shaft 25 is fitted into the groove 23 at one end of the core 31 as shown in FIG. The hollow member 26 at the other end of the core 31 is pressed against the pressing member 22.
Is fitted. When the motor M operates, the core 31 rotates in the R direction to form the electrode roll body 35. The core 31 is also called an inner core. For example, the outer diameter is 17 mm, the inner diameter is 14 mm, and the axial length is 354.
mm.

An active material 13 a is applied to the positive electrode sheet 13, and an active material 14 a is applied to the negative electrode sheet 14. Positive electrode sheet 1 not coated with active material 13a
A portion 3 is cut into a strip shape to form a lead 11. Similarly, the uncoated portion of the negative electrode sheet 14 on which the active material 14a is not formed is cut into a strip shape to form the lead 11. The lead 11 of the positive electrode sheet 13 is a positive electrode lead, and the lead 11 of the negative electrode sheet 14 is a negative electrode lead. The leads 11 of the positive electrode sheet 13 and the leads 11 of the negative electrode sheet 14 are guided in opposite directions. When the electrode roll body 35 is formed, the leads 11 of the positive electrode sheet 13 gather and the leads 11 of the negative electrode sheet 14 They are getting together.

Next, the positive electrode sheet 13 and the negative electrode sheet 1 shown in FIG.
4 and the material of the separator 30 will be described. The negative electrode sheet 14 was baked in an inert gas stream and then pulverized to obtain 90 parts by weight of carbon having an average particle diameter of 20 μm, and 10 parts by weight of vinylidene fluoride resin as a binder. By applying a slurry dispersed in methylpyrrolidone to both sides of a 10 μm thick copper foil current collector,
An electrode base plate having a thickness of 180 μm is prepared, and is cut to (348 mm + uncoated portion 35 mm) × 6940 mm, for example, leaving an uncoated portion serving as a negative electrode lead portion in a part of the electrode base plate.

The positive electrode sheet 13 is made of L having an average particle size of 15 μm.
A slurry in which iCoO2 powder was 91 parts by weight, graphite was 6 parts by weight as a conductive material, vinylidene fluoride resin was 3 parts by weight as a binder, and these were dispersed in N-methylpyrrolidone was used as a current collector of aluminum foil. By coating on both surfaces of the substrate, a non-coated portion serving as a lead portion of a positive electrode is left on a part of the electrode plate, leaving (344 mm + uncoated portion 35 mm) × 7150 mm
It is formed by cutting. The separator 30 is a sheet of polyethylene having a thickness of 38 μm, which is cut into a width of 353 mm × 7600 mm and formed with minute holes.

Electrode roll body 3 made as shown in FIG.
5 is the pole 10 of the positive electrode 20 and the pole 10 of the negative electrode 21 in FIG.
During this time, laser welding is performed using the holding bracket 33 shown in FIGS. At this time, the holding bracket 33 connects the lead 11 to the pole 10
Sandwich it. Electrode roll body 35 and pole 1 welded
After the caps 0 and 10 are assembled with the caps 1 and 1, the seal 8, the ceramic spacer 6 and the like and tightened with the nut 7 via the ceramic washer 5, the caps 1 and 1 are laser-welded to the end of the battery case 17. Is done. The electrolyte solution injected into the battery case 17 is a mixture of propylene carbonate and diethyl carbonate containing LiPF6 at a ratio of 1 mol / 1.
And dissolved at a ratio of The electrolyte is supplied to the inlet 32 of the valve 4.
Open and inject.

Next, the structure of the pole 10 of the positive electrode 20 and its peripheral structure will be described in more detail with reference to FIGS. Since the structure of the positive electrode 20 and the structure of the negative electrode 21 are the same, the description of the structure of the negative electrode 21 is omitted. However, the pole 10 of the positive electrode is made of pure aluminum and alumina fiber, whereas the pole 10 is made of pure copper. 1 and 3,
The cap 1 includes a stopper 4, a metal seal 2, an opening valve 9, a metal seal 3, and the like. The electrolytic solution can be injected into the battery case 17 by opening the stopper 4. After the electrolyte is injected, the stopper 4 is closed.

The pole 10 is substantially T-shaped when viewed in cross section. The pole 10 is closely attached to the cap 1 via a seal 8. The seal 8 is disposed between the backup ring 51 and the ceramic spacer 6. The pole 10 is fixed to the cap 1 by a nut 7 and a ceramic washer 5. The nut 7 is in close contact with the outer surface of the cap 1 via the ceramic washer 5. The nut 7 is a tip 15 of the base material 70 of the pole 10.
a meshes with the male screw 15 formed in FIG. Pole 10
The center of the base material 70 is provided with bolts 19 along its axial direction.
Are detachably attached. The bolt 19 is for fixing a connection CN that connects the positive electrode 20 of the battery 1 to a device (not shown, for example, a motor of an electric vehicle) to be operated.

The bolt 19 meshes with a female screw 16 formed inside the base material 70, and the female screw 16
Is a female thread of M6 (thread size of fastening screw) based on the notation method of JIS (Japanese Industrial Standard). The male screw 15 provided on the outer periphery of the base material 70 meshes with the nut 7, and the nut 7 is connected to the ceramic washer 5 and the ring 50.
It is firmly fixed to the pole 10 through the like. This prevents the electrolyte in the battery case 17 from leaking from the cap 1 to the outside.

The base material 70, particularly the female thread 16 of the base material 70,
It greatly contributes to the fastening of the connection CN, and the fastening force must be strong. Because, for example, the battery 1 in FIG.
Has a power supply capacity of 100 Ah class, and even if the current is taken out at a discharge rate of 1 C, if the connection of the connection CN to the base material 70 is incomplete, a contact failure occurs, which is dangerous. In particular, if the battery 1 is mounted on an electric vehicle (EV), it must be strong against vibration, and the fastening force of the connection CN to the pole 10 by the bolt 19 and the female screw 16 must be strong. Must.

When the battery 1 is used as a power source mounted on an electric vehicle, the allowable current in continuous use of the battery 1 can be about 3C discharge rate. Must be available. Even if the pole column 10 is made of pure aluminum, a cross-sectional area of 50 mm ² or more is necessary so that even if such a large current continuously flows through the pole column 10, heat generation does not increase (for example, 80 ° C. or less). . Otherwise, it is necessary to join with a heat radiating plate for improving heat radiation.

Here, the 1C discharge rate and the 3C discharge rate will be described. Indicates the discharge rate when taking out the battery current,
In general, the amount of power that can be taken out from the fully charged state of the battery until it reaches the usage limit by using it continuously for 3 hours is defined as the capacity of the battery. Is called a 1C discharge rate, and a discharge rate at a current setting used up in 1/3 hour is called a 3C discharge rate. In general, in the case of 1 / 3C discharge, the amount of power corresponding to the capacity can be taken out of the battery, but when the load becomes heavy such as 1C or 3C, generally less power than the actual capacity can be taken out. In this case, the battery capacity is 100A
h, a current of 3000 A is discharged at a constant discharge rate of 3C.

In the embodiment of the present invention, in order to increase the fastening force of the connection CN, a portion including the female thread 16 of the base material 70 constituting the pole 10 (shown by hatching in FIG. 3).
In the case of the pole 10 of the positive electrode 20, the pole is made by melting and forging an alumina fiber mixed with 5% with respect to pure aluminum, and its elastic limit is limited to the base of the pole made of pure aluminum only. It is very expensive compared to wood. Specifically, as compared with the case of the pole 10, the pole 10 in which alumina fibers are mixed with pure aluminum is used. Since the compounding ratio of this alumina fiber is about 5% as described above, the electrical resistivity is only about 95% of that of pure aluminum, so the required cross-sectional area is 50 / 0.95 = 5.
It can be achieved with an area of 2.6 mm ² .

FIG. 6 shows a comparison between rigidity (proof stress, ie, elastic limit) and electric conductivity of the pole column 10 made of pure aluminum containing alumina fibers of the present invention and a conventional aluminum alloy. The material of the pure aluminum containing the alumina fiber in the embodiment of the present invention has a higher electrical conductivity required as an electrode element material for the same proof stress as compared with other typical alloy aluminum (for example, A5052). It can be said that it is suitable for a current collector (terminal) of a battery that requires a screw portion such as a large battery.

As an effective method of manufacturing the pole column 10 made of pure aluminum containing alumina fibers in the embodiment of the present invention, a two-stage molding method as shown in FIGS. 7 and 8 can be proposed.

The two-stage molding method will be described below. First, FIG. 7 shows the pole 10 corresponding to FIG. 3, and the pole 10 is composed of a base material 70 indicated by a broken line and a remaining portion 90 thereof. First, the base material 70 is
And a mold for preparing only a portion which is easily subjected to a force such as a compression or a tensile force when fastening the connection CN of FIG. 3 is prepared. Harden. That is, as shown in FIG.
Make 0A.

The alumina core 70A is arranged in a main die 100 for forging molten metal shown in FIG. This main mold 100 is an upper mold 1
01 and a lower mold 102, and an alumina core 70A is arranged between the upper mold 101 and the lower mold 102. Then, a pure aluminum melt is injected from an inlet 103 of the lower mold 102, and the pure aluminum permeates the alumina core 70A to form the pole 10 as shown in FIG. At this time, if the porosity of the alumina core 70A is 90%, the alumina mixing ratio of the prepared base material (also referred to as a core portion) 70 of the pole 10 is 10%, and the porosity is 95%. For example, the alumina content can be 5%. Thereafter, the female screw 16 and the male screw 15 are machined on the base material 70. By using such a manufacturing method, the amount of alumina fiber used can be saved. That is, rather than making the whole pole column a material containing alumina fibers, the amount of alumina fibers can be inevitably saved by partially including the alumina fibers.

Further, as shown in FIG. 3, since the exposed portion of the alumina fiber can be limited to a place where the exposed portion does not come into contact with the electrolyte in the battery case 1, it is controlled whether or not the alumina fiber contains impurities which react with the electrolyte. There is also a merit that it is not necessary to make strict.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, a lithium ion secondary battery is used as a battery, but the present invention is not limited to this, and can be applied to other types of secondary batteries, for example, lithium metal batteries, non-aqueous solvent batteries, and polymer batteries. . The battery is not limited to a secondary battery, but may be another type of battery, such as a lithium-based primary coin battery. The connection is fixed to the pole not only by using a bolt, but also by screwing a nut into the pole to fix the connection to the pole. The connection may be fixed to the pole using both the nut and the bolt. When fixing the pole to the battery case, bolts may be used instead of nuts.

By proposing a battery having such a structure, by using an aluminum pole 10 containing alumina fiber as compared with a pole made of pure aluminum, the battery is used for fastening the connection CN shown in FIG. Since the internal thread 16 (also referred to as a threaded portion) and the external thread (also referred to as a fastening portion) 15 for firmly fixing the pole 10 itself to the cap 1 can be reinforced, the rigidity is increased, and the internal thread 16 of the internal thread 16 and the external thread 1 are increased.
5 can be avoided as much as possible. Therefore, the creep of the pole 10 can be reduced, and the reliability of the connection of the connection CN and the reliability of fixing the pole can be improved even when used in a place where the temperature fluctuation is large. Further, since the pole 10 has high rigidity, even if vibration is applied, the bolt 19 engaged with the female thread 16 may be loosened or the male screw 1 may be loosened.
The loosening of the nut 7 meshing with the nut 5 can be prevented. Accordingly, it can be expected that the embodiment of the battery of the present invention is used as, for example, a battery for an electric vehicle or a starter of a car.

[0029]

As described above, according to the present invention,
The reliability can be improved by increasing the strength of the current collector of the positive electrode of the battery.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a lithium ion secondary battery as a battery of the present invention.

FIG. 2 is a side view of the lithium ion secondary battery of FIG.

FIG. 3 is an enlarged view showing the vicinity of a positive electrode of the lithium ion secondary battery of FIG. 1;

FIG. 4 is a perspective view showing a core for forming an electrode roll body of a lithium ion secondary battery.

FIG. 5 is a perspective view showing an electrode roll body formed by winding the core shown in FIG. 4;

FIG. 6 is a diagram showing a comparative example of the characteristics of a pole made of pure aluminum and an aluminum pole containing alumina fibers.

FIG. 7 is a diagram showing a structural example of a pole according to the present invention.

FIG. 8 is a diagram showing an example of a method for manufacturing the pole shown in FIG.

[Explanation of symbols]

1 ... lithium ion secondary battery (battery), 10 ...
Pole, 15 ... male screw, 16 ... female screw, 17 ...
・ Battery case, 20 ・ ・ ・ Positive electrode, 21 ・ ・ ・ Negative electrode, 35
... Roll body, 70 ... Base material, 90 ... Remainder

Claims (4)

[Claims] 1. A battery in which a current collector of a positive electrode is made of aluminum, wherein the current collector of the positive electrode is formed by adding alumina fibers to aluminum. 2. A lithium ion secondary battery according to claim 1.
The battery according to 1. 3. The current collector of claim 1, wherein the current collector of the positive electrode includes a screw, and at least one of a bolt and a nut is used when connecting a wire for transmitting electricity to the current collector of the positive electrode. battery. 4. The current collector of the positive electrode includes a bolt or a nut for holding the current collector of the positive electrode in the battery case.
The battery according to 1.