JP4195963B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a current collecting structure.
[0002]
[Prior art]
In recent years, electronic devices such as AV devices and personal computers are rapidly becoming portable and cordless, and there is an increasing demand for secondary batteries having a small size, light weight, and high energy density as power sources for driving these devices. Among them, a lithium ion secondary battery using lithium as an active material is particularly expected as a battery having a high voltage and a high energy density. Also, as a new requirement, high output is desired for use in electric tools and the like.
In order to meet this requirement, it is important to reduce the internal resistance of the battery. In a general lithium ion secondary battery current collecting method, current is collected from each of a positive electrode plate and a negative electrode plate using leads.
On the other hand, in a high-power nickel-metal hydride storage battery or the like, current collection is performed with the ends of the positive and negative electrode plates protruding from the group. Although this current collection method can reduce the resistance compared to the case of using a lead, it is necessary to weld the current collector plate and the bottom of the case.
[0003]
[Problems to be solved by the invention]
In the current collecting method as described above, when there is a gap penetrating the group like a cylindrical battery, it is easy to weld the current collector plate and the bottom of the case, but the gap penetrating the group like a square battery. If there is no power, such a current collecting method cannot be taken. In addition, a resistance component is generated between the current collector plate and the bottom of the case because both are integrated only in the welded portion.
[0004]
The present invention has been made in view of the above-described conventional problems, and enables a current collecting structure such as a nickel-metal hydride storage battery to be used even in a lithium ion secondary battery, particularly a square battery. Is the purpose.
[0005]
Furthermore, the volume of the current collector plate that is used as the space in the battery can be deleted, and the junction between the current collector plate of the positive electrode plate or the negative electrode plate and the bottom of the case can be deleted to reduce the resistance, and the battery capacity and battery characteristics can be improved. The object is to provide a current collection method.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention assumes that the current collector plate also serves as the bottom of the case, and further inserts an electrode plate group having the current collector plate into the bottomless case and welds the current collector plate and the case. Thus, the current collector plate and the case bottom are combined.
Thus, in the lithium ion secondary battery, a current collecting structure like a nickel metal hydride battery can be used even if it is a prismatic battery. Furthermore, it is possible to reduce the volume of the current collector plate that fills the battery internal space and to eliminate the junction between the current collector plate of the positive electrode plate or the negative electrode plate and the bottom of the case, thereby reducing the resistance and improving the battery capacity and battery characteristics. It is possible to provide a method for collecting current.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The non-aqueous electrolyte secondary battery according to the present invention is an electrode plate group in which a positive electrode plate and a negative electrode plate are wound through a separator, and an uncoated portion at an end of at least one of the positive electrode plate and the negative electrode plate In the electrode plate group in which the uncoated portion protrudes from the electrode plate group and is welded to the current collector plate, the current collector plate also serves as a case bottom.
In this battery, it is possible to reduce the portion of the battery internal volume that has been occupied by the current collector plate, and the capacity can be increased by increasing the electrode plate group height.
In addition, the battery internal resistance can be greatly reduced as compared with a battery that collects current using leads. Thus, by reducing battery internal resistance, the polarization at the time of charging / discharging is suppressed and battery characteristics like high load charging / discharging can be improved. Furthermore, since Joule heat generated during large current charge / discharge can be reduced, an increase in battery temperature during charge / discharge can be suppressed.
It is also preferable that the current collector plate also serves as the case bottom by inserting the electrode plate group into the bottomless case and welding the current collector plate and the opening of the bottomless case.
In this case, the current collector plate can easily serve as the bottom of the case, and even a prismatic battery can use a current collecting structure such as a nickel-metal hydride storage battery.
In this case, the thickness of the current collector plate is 0.1 mm or more and preferably 0.7 mm or less from the viewpoint of the strength of the case bottom and the condition range where welding is possible.
In the non-aqueous electrolyte secondary battery described above, when the current collector plate is connected to the negative electrode plate, the current collector plate must be made of a material that does not react with the electrolyte solution at the negative electrode potential. A metal plated with nickel is preferable.
Further, when the current collector plate is connected to the positive electrode plate, it is necessary that the current collector plate is made of a material that does not react with the electrolyte solution or the like at the positive electrode potential. Among them, aluminum, nickel-chromium steel or aluminum is the main component. It is preferable that it is an alloy.
[0008]
【Example】
Hereinafter, specific examples of the present invention will be described with reference to the drawings.
[0009]
FIGS. 1 to 3 are process schematic diagrams showing the manufacturing process of the non-aqueous electrolyte secondary battery of the present invention in the order of processes, and each process is schematically illustrated in an easy-to-understand manner.
[0010]
FIG. 1 shows the structure of a positive electrode plate, a negative electrode plate, and a separator constituting the electrode plate group. The negative electrode uncoated portion 2 was formed on the negative electrode plate 1, and the upper lead 5 was attached to the positive electrode plate 4 with a part uncoated. The positive electrode plate 4 and the negative electrode plate 1 were wound through a separator 3 to form an electrode plate group 6. At that time, the negative electrode uncoated portion 2 was wound so as to protrude from the electrode plate group 6.
[0011]
In FIG. 2, the uncoated protrusions of the electrode plate group 6 obtained in the process of FIG. 1 were flattened, and a nickel current collector plate 7 having a thickness of 0.3 mm was welded by laser welding. Thereafter, the electrode plate group 6 to which the current collector plate 7 was welded was inserted into a bottomless case 8 made of nickel-plated iron.
[0012]
In FIG. 3, the current collector plate 7 and the case opening are joined to the bottomless case 8 in which the electrode plate group 6 obtained in FIG. 2 is inserted by laser welding. Although welding can be performed from the bottom direction and from the side, it was performed from the bottom. Of course, you can go from the side.
[0013]
Next, the battery intermediate obtained in the above step was grooved for caulking the sealing plate by a conventional known method. Subsequently, a sealing plate was welded to the upper lead, a predetermined amount of non-aqueous electrolyte was injected, and caulking was performed, and test batteries of Examples 1 to 9 described in detail later were produced.
[0014]
Here, only the example where the current collector plate also serving as the bottom of the case is connected to the negative electrode is shown, but when the positive current collector plate also serves as the bottom of the case, an appropriate material can be selected for the case and the current collector plate. went.
[0015]
In addition, although the structure of the electrode group has shown an example in which the bottom is collected from an uncoated part and the upper part is collected by a lead, the same applies to a structure in which the upper part is collected from an uncoated part. .
[0016]
For comparison, a comparative battery A having the same configuration as that of the battery described above was prepared except that both the upper part and the bottom part were collected using leads. Furthermore, although the bottom current is collected from the uncoated part, a comparative battery B having the same configuration as the above battery is also prepared except that the current collector plate and the case bottom are welded as in the conventional nickel metal hydride storage battery. did. Furthermore, comparative batteries C and D having the same current collecting structure as comparative batteries A and B but made into square batteries were respectively prepared.
Next, Examples 1 to 9 created by the above-described method will be described in detail.
[0017]
Example 1 A current collector plate that also serves as the bottom of the case was connected to the negative electrode, and the positive electrode current was collected using a lead. Graphite was used as the negative electrode active material, and LiCoO ₂ was used as the positive electrode active material. The capacity of the battery 1 was 1020 mA when a constant current discharge of 200 mA was performed. The internal resistance of the battery 1 measured by the 1 kHz alternating current method was 15 mΩ, which was lower than the 24 mΩ measured in the same manner as the comparative battery A. The comparative battery B had a resistance value of 13 mΩ, which was lower than this.
[0018]
Furthermore, a battery excellent in high load discharge characteristics performed at a discharge current of 10 A was obtained. Further, the temperature rise at this time was 9 ° C. lower than that of Comparative Battery A.
In addition, since each Example demonstrated below changes only a part in the said Example 1, in the following description of each Example, only the content changed with respect to Example 1 is listed. To do.
[0019]
(Example 2) In contrast to Example 1, a positive electrode current collector was not a lead, but a battery 2 was produced using a current collector plate welded to an uncoated part similar to the negative electrode. This battery had an internal resistance of 11 mΩ, which is lower than that of the battery 1 of Example 1, and exhibited further excellent high load characteristics.
(Example 3) Compared to Example 1, using a current collector plate in which the case was changed from iron to aluminum, the current collector plate also serving as the bottom of the case was connected to the positive electrode, and the current collector of the negative electrode was also welded to the uncoated part The battery 3 to be produced was created. The internal resistance of the battery 3 was 10 mΩ, and the battery 3 also showed higher load characteristics than the comparative battery A and the comparative battery B.
(Example 4) In contrast to Example 1, a battery 4 was prepared in which the case was changed from iron to aluminum, a current collector plate also serving as the bottom of the case was connected to the positive electrode, and the negative electrode was collected using a lead. The battery 4 showed 20 mΩ which is an internal resistance lower than that of the comparative battery A, and showed excellent high load characteristics.
(Example 5) A group configuration of prismatic batteries was performed, and a prismatic battery 5 having a capacity of 480 mA, a thickness of 6 mm, a width of 34 mm, and a height of 50 mm, which was the same as that of Example 1, was produced. The battery 5 showed 30 mΩ which is an internal resistance lower than those of the comparative batteries C and D, and had a high load discharge performance superior to these.
(Example 6) A square battery group configuration was performed, and a square battery 6 having a thickness of 6 mm, a width of 34 mm, and a height of 50 mm similar to that of Example 3 was produced. The battery 6 had an internal resistance of 28 mΩ lower than that of the comparative battery C, and had excellent high load discharge performance.
Example 7 A battery having a nickel current collector plate thickness of 0.1 mm, 0.7 mm, and 1 mm with respect to Example 1 was prepared. Both the internal resistances of the batteries using the current collector plates of 0.1 mm and 0.7 mm were 11 mΩ.
Although a battery could be produced even with a 0.1 mm current collector, the thickness of the current collector is preferably thicker than 0.1 mm in consideration of the bottom strength. In addition, although the battery could be produced even at 0.7 mm, the welding of the uncoated part and the current collector plate did not have sufficient strength with the current collector of 1 mm. Therefore, the thickness of the current collector is preferably 0.1 mm or more and 0.7 mm or less.
(Example 8) For Example 7, an iron plate plated with nickel was used as a negative electrode current collector. In either case, it was possible to produce a battery in a thickness range of 0.1 mm to 0.7 mm. The internal resistance was 12 mΩ.
(Example 9) For Example 7, a test was performed using an aluminum plate as a positive electrode current collector and an aluminum alloy containing 3% magnesium. Negative electrode current collection was performed by lead. In either case, it was possible to produce a battery in a thickness range of 0.1 mm to 0.7 mm. Both internal resistances were 33 mΩ.
In any of the batteries obtained in each of these Examples, the required charge / discharge cycle life could be ensured, good storage characteristics were obtained, and it was confirmed that the discharge capacity was improved.
[0020]
【The invention's effect】
As described above, according to the nonaqueous electrolyte secondary battery of the present invention, the internal resistance of the battery can be reduced, so that particularly high load discharge performance can be improved, and the battery temperature rise during large current discharge can be improved. Can be suppressed. In addition, since the volume corresponding to the current collector plate is reduced, the volume can be effectively utilized to improve the capacity. Furthermore, a current collecting method using an uncoated portion, which could not be employed in a conventional prismatic battery, is possible.
[Brief description of the drawings]
FIG. 1 is a process schematic diagram showing a first step in a battery manufacturing process according to an embodiment of the present invention. FIG. 2 shows a second step in a battery manufacturing process according to an embodiment of the present invention. FIG. 3 is a process schematic diagram showing the third step in the battery manufacturing process according to one embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Negative electrode plate 2 Negative electrode uncoated part 3 Separator 4 Positive electrode plate 5 Upper lead 6 Electrode plate group 7 Current collecting plate 8 Bottomless case

Claims (4)

In the electrode plate group in which the positive electrode plate and the negative electrode plate are wound through a separator, an uncoated portion is provided at an end portion of at least one of the positive electrode plate or the negative electrode plate, and the uncoated portion is In the electrode plate group protruding from the electrode plate group and directly connected to the current collector plate,
The current collector plate also serves as a case bottom , the electrode plate group is inserted into a bottomless case, and the current collector plate is welded to the opening of the bottomless case, whereby the current collector plate is A nonaqueous electrolyte secondary battery characterized by also serving as a battery.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the current collector plate has a thickness of 0.1 mm or more and 0.7 mm or less.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the current collector plate is connected to a negative electrode plate, and the material of the current collector plate is nickel or a metal plated with nickel.   The non-aqueous electrolysis according to claim 1, wherein the current collector plate is connected to a positive electrode plate, and the material of the current collector plate is made of aluminum, nickel-chromium steel, or an alloy mainly composed of aluminum. Liquid secondary battery.

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