JPH1116577A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate deterioration of an output characteristic caused by increase of internal resistance due to a shape of a lead terminal portion and a welding condition, or generation of internal short circuit in the case of forming an electrode group using a foil-like collector base body in a nonaqueous electrolye battery. SOLUTION: A lead terminal portion Ba of an electrode is formed to be projected from an electrode without applying an active material to a portion of a collector base body, and formed is a continuous curve line E (1 mm<= radius of curvature <=10 mm) ranging from a top side periphery C of an active material-applied portion A to a periphery of the lead terminal portion Ba. An effective collector terminal shape is provided thereby without impairing strength of the electrode to improve an output characteristic and reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery, and more particularly to a non-aqueous electrolyte battery having a laminated or wound electrode group structure using a foil-like current collector.

[0002]

2. Description of the Related Art Conventionally, aqueous secondary batteries such as lead-acid batteries, nickel-cadmium batteries, and the like are mainly used as secondary batteries that are widely used. However, these aqueous secondary batteries have a drawback that the energy density is low because an operating voltage exceeding the decomposition potential of water cannot be obtained. Therefore, recently, research and development of non-aqueous electrolyte secondary batteries represented by lithium ion batteries have been actively conducted. This non-aqueous electrolyte secondary battery has a high operating voltage, a high energy density, and excellent cycle characteristics. Therefore, development is expected not only for small-sized batteries for consumer use but also for high-voltage, high-energy density, and high-output batteries used for power storage and electric vehicles from the viewpoint of energy saving and environmental conservation.

However, a non-aqueous electrolyte secondary battery has a low internal conductivity due to the low ionic conductivity of the electrolyte.
It is difficult to obtain a high output compared to an aqueous battery. In order to improve this point, generally, in a non-aqueous electrolyte secondary battery, the electrode area is made as large as possible to reduce the internal resistance of the battery and to improve the output characteristics. In order to increase the electrode area, it is necessary to reduce the electrode thickness, and therefore, it is necessary to make the current collecting substrate as thin as possible. For this reason, a foil-shaped current collecting base having a thickness of about 1 μm to 100 μm is generally used, as disclosed in, for example, Japanese Patent Publication No. Hei 4-52592.

[0004]

In order to connect the electrode having the foil-shaped current collecting base to the battery current collecting terminal, generally, a solid portion where no active material layer is provided on the electrode is secured, and a lead terminal is provided there. Means such as welding by ultrasonic welding or the like and further welding the lead terminal to the battery current collecting terminal are used.
However, in this method, there is a concern about resistance loss in a welded portion, and it is difficult to apply the method to a battery aimed at high output characteristics. Also,
When the lead terminal is welded to the uncoated portion of the electrode, a sharp projection is easily formed at that portion, and there is a structural defect that a short circuit is easily caused when forming the electrode group. Further, the formation of the active material layer on these foil-like current collectors is carried out by continuously applying the active material slurry to the band-like foil before being cut and divided into the foil-like current collectors. In order to form the uncoated portion, a special coating device having an intermittent coating function is required, which complicates the manufacturing process and reduces the production speed. The present invention provides a means for solving these problems.

[0005]

In order to solve the above problems, the present invention has a structure in which at least one of a positive electrode plate and a negative electrode plate has an active material layer formed on the surface of a foil-like electrode current collecting substrate. In a non-aqueous electrolyte battery in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween or spirally wound to form an electrode group, the active material layer is formed as a part of the foil-like current collecting base The uncoated solid portion is protruded from the electrode group, has a structure in which this is directly connected to the battery current collecting terminal to collect current, and extends from the periphery of the protruded solid portion to the periphery of the portion having the active material layer. To form a continuous curve. In the foil-like current collecting base, the radius of curvature of a curve formed from the periphery of the protruding solid portion to the periphery of the portion having the active material layer is 1 mm or more and 10 mm or less.

[0006]

Embodiments of the present invention will be described. FIG. 1 shows the structure of the electrode used in the battery according to the present invention, and FIGS. 2 and 3 show the structure of the electrode used in the battery according to the prior art. The description will be made with reference to these drawings. In the following description, it is assumed that a stacked electrode group is formed. However, the present invention does not limit the structure of the electrode group (such as a stacked type or a wound type). In the prior art, as shown in FIG. 2, an uncoated portion F was provided on an electrode A, and a lead terminal G was welded thereto by ultrasonic welding or the like. In this case, if the weld H is not reliably conducted, the battery characteristics, particularly the output characteristics, are greatly affected. Since the welding state easily changes depending on the operating state of the welding machine, the surface state of the work, and the like, it is necessary to perform extremely strict process control to ensure stable performance during mass production.

As shown in FIG. 1, when the lead terminal G is welded to the surface of the uncoated portion F, a sharp projection I is formed depending on the shape of the lead terminal. Generally, a separator used for a non-aqueous electrolyte secondary battery is a resin film having a thickness of several tens of microns, and depending on the material, there is a concern that the protrusion I may damage the separator and cause a short circuit. Therefore, conventionally, after welding the lead terminal G, a protective tape was applied to the surface of the uncoated portion F so as to cover the lead terminal G to prevent short circuit. For this reason, the manufacturing process has been further complicated.

As an alternative method, a method of protruding a part of the current collecting base and using it as a lead terminal B as shown in FIG. According to this, there is no fear that the battery characteristics may be degraded due to poor welding of the lead terminal portion B, and the steps such as tape covering can be omitted. However, as described above, the current collecting base used for the non-aqueous electrolyte secondary battery has a thickness of 10
As thin as a micron. For this reason, for example, when the lead terminal portion B is welded to the battery current collecting terminal arranged on the battery upper cover or the like during the assembling process, or when a shock is applied from outside the battery in a normal use state, the electrode plate A
There is a disadvantage that torsional or tensile stress tends to concentrate on the protruding lead terminal portion B, and the lead terminal portion B is broken. Such a problem is not discussed in conventional batteries having a similar lead terminal structure, for example, in lead storage batteries and alkaline storage batteries, because the thickness of the current collector is as large as several hundred microns to several millimeters. This is a problem inherent to a non-aqueous electrolyte battery using a foil as a current collecting substrate.

In the embodiment of the present invention shown in FIG. 1, a continuous curve E is formed from the periphery D of the base projection used as the lead terminal Ba to the periphery C of the electrode plate. In order to obtain such a shape, there is a method of punching out with a mold in a shape having a projection shape used in advance as a lead terminal portion, or cutting while continuously forming a curve with a cutter, laser, ultrasonic wave or the like. Conceivable. In either method, the strength of the protruding lead portion Ba is increased by forming and cutting a continuous curve, and the lead portion is welded to the battery current collecting terminal, or even when an external impact is applied to the completed battery. There is no risk of breaking or cracking. Also, since the processing shape is determined at the time of cutting the electrode, continuous application of the active material becomes possible,
The process is simplified, and the productivity is improved.

[0010]

An embodiment of the present invention will be described. The types, shapes, and dimensions of the batteries described below are merely examples, and do not limit the present invention. In the following description,
In consideration of the use of a foil having an uneven surface such as an electrolytic foil, the “thickness” of the current collector was calculated by the following formula. Thickness = weight per unit area of current collecting substrate / true density of current collecting substrate As a positive electrode plate, an aluminum foil with a thickness of 20 µm was formed on both sides with an active material layer mainly composed of lithium cobalt oxide, and as a negative electrode plate A lithium secondary battery is manufactured using a copper foil having a thickness of 20 μm and an active material layer mainly composed of carbon formed on both sides. Each electrode is 100m long
m, width 200 mm, thickness 0.18 mm. The bipolar plates are alternately laminated via a 0.02 mm-thick polyethylene porous film to form an electrode group. The number of layers is 80 positive electrodes and 81 negative electrodes. The battery a of the present invention was manufactured by using electrodes having the shape shown in FIG. 1 for both electrodes as the electrodes used for the electrode group configured as described above. At this time, the value of the radius r in FIG. 1 was 4 mm.

As shown in FIG. 2, a lead terminal (thickness: 20 μm, material: Al for a positive electrode, Ni for a negative electrode) is ultrasonically welded to an electrode provided with a solid portion in advance by intermittent application of an active material. A conventional battery "b" was manufactured using electrodes of a shape welded by the method for both electrodes. For this battery only, the electrode lateral dimension is 210
mm and the uncoated part width was 10 mm. A conventional battery c was manufactured using electrodes having the shape shown in FIG. 3 for both electrodes. At this time, the angle between the upper edge C of the electrode and the outer edge D of the lead terminal portion is 90 degrees, and no continuous curve is formed from the outer edge C to the outer edge D. The shape of each of the batteries a, b, and c is as shown in FIG.
The batteries a and c connect the lead terminal portions Ba and B, and the battery b connects the lead terminal G to the battery current collecting terminal K. The opening of the battery container J is closed by the upper lid L. The connection shape between the electrode group M and the battery current collecting terminal K, the battery outer shape (top cover L, battery container J), the type of electrolyte,
All amounts were the same.

FIG. 5 is a diagram showing the discharge rate characteristics of the battery of the present invention and the conventional battery. It can be seen that the battery a of the present invention is superior to the conventional battery b in high-rate discharge characteristics, and is almost at the same level as the conventional battery c. FIG. 6 shows the results of measuring the internal resistance of the battery a of the present invention and the conventional batteries b and c by an impedance measurement method (ambient temperature: 20 ° C., frequency: 10 kHz). It can be seen that the battery a of the present invention has lower internal resistance than the conventional battery b. The conventional battery c has substantially the same internal resistance as the battery a of the present invention, but the battery a of the present invention
The variation is large compared to. As a result of disassembling the battery and examining it in more detail, it was found that some of the lead terminals of the conventional battery c had cracks or breaks which were not observed in the battery a of the present invention. It is considered that the conductivity was impaired and the internal resistance varied.

With respect to the aluminum foil used as the current collecting base of the positive electrode plate, test pieces as shown in FIG. 7 were prepared, and the tensile strength was examined by changing the radius r in the figure. This test assumes that a force is applied to the lead terminal during the battery assembly process, such as mechanically correcting the position of the lead terminal during welding to the battery current collecting terminal. FIG. 8 shows the result. At r = 0, it was found that the strength was extremely reduced and the variation was large. R ≧ 1m to obtain stable strength
m. FIG. 9 shows a battery a of the present invention prepared by changing the value of the radius of curvature r of the lead terminal in FIG.
It is a result of examining a change in internal resistance after applying vibration in a fixed direction at 0 Hz for 60 minutes. This test is based on the assumption that external vibration is applied during normal battery use. r =
The fact that the variation is large at 0 is the same as in FIG. 6, but it can be seen that the variation increases as the value of r increases, and a battery with zero resistance is generated. This is presumably because the strength of the lead terminal portion was increased, so that vibration from the outside was easily transmitted to the active material application portion, and a short circuit was likely to occur due to the falling off of the active material. From this, the value of the radius r is 10 m
m.

In the above embodiment, the thickness of the current collecting base is 2
Although the thickness is set to 0 μm, it goes without saying that the effects of the present invention can be exerted even when a foil having any other thickness is used. However, if the thickness is too thin, the output characteristics may deteriorate,
In consideration of the handling in manufacturing, the thickness of the current collecting substrate is 1 μm.
m or more. On the other hand, if the thickness is too large, the energy density of the battery decreases, and there is no significance in using the foil substrate. Therefore, the upper limit is desirably 100 μm or less. The material of the current collecting base is not limited as long as it is stable in the average operating potential range of the nonaqueous electrolyte battery (about 2 V to 5 V) and can form electrodes. Further, there is no limitation on the surface shape of the foil (such as the presence or absence of irregularities and perforations).

Further, in the above-described embodiment, results regarding a battery having a structure in which strip-shaped electrodes are stacked and accommodated in a rectangular battery container are shown. However, a long electrode is spirally wound to form an electrode group. A similar effect can be obtained in a battery that performs the same. The electrode group may be substantially circular, or may be wound in an elliptical shape. Furthermore, in the above embodiment, the electrode 1
Although an example in which one lead terminal portion is formed per sheet is shown, the technology of the present invention disclosed above can be applied to a battery in which a plurality of lead terminal portions are formed for the purpose of improving current collection performance and the like. It is.

[0016]

According to the present invention, in a non-aqueous electrolyte battery, the output characteristics can be improved, and the production process can be simplified to improve the productivity, thereby providing a high-performance and highly reliable battery. be able to.

[Brief description of the drawings]

FIG. 1 is a view showing an electrode structure of a battery of the present invention.

FIG. 2 is an electrode structure of a conventional battery, (a) is a front view, (b)
FIG.

FIG. 3 is a view showing an electrode structure of a conventional battery.

FIG. 4 is an explanatory view for assembling the battery of the present invention and a conventional battery.

FIG. 5 is a diagram showing discharge rate characteristics of the battery of the present invention and a conventional battery.

FIG. 6 is a diagram showing the internal resistance of the battery of the present invention and the conventional battery.

FIG. 7 is a view showing a test piece shape for a tensile test.

FIG. 8 is a diagram showing the relationship between the shape of aluminum foil and tensile strength.

FIG. 9 is a diagram showing the relationship between the shape of an electrode lead and the internal resistance of a battery.

[Explanation of symbols]

A is an electrode (active material application portion), Ba is a lead terminal portion, C is a peripheral edge of the upper side of the electrode (active material application portion), D is a peripheral edge of the lead terminal portion, E is a curve provided at the lead portion rising, F
Is a solid portion (active material-uncoated portion), J is a battery container, K is a battery collecting terminal, L is a top cover, and M is an electrode group.

Claims (2)

[Claims] At least one of a positive electrode plate and a negative electrode plate has a structure in which an active material layer is formed on a surface of a foil-like electrode current collecting base, and a plurality of positive electrode plates and negative electrode plates are laminated via a separator. Alternatively, in a non-aqueous electrolyte battery that is spirally wound to form an electrode group, a plain portion that is a part of the foil-shaped current collecting base and has no active material layer formed thereon is protruded from the electrode group, and It has a structure for directly collecting power by directly connecting to the current collecting terminal, and is characterized in that a continuous curve is formed from the periphery of the protruding solid portion to the periphery of the portion having the active material layer, Non-aqueous electrolyte battery. 2. The foil-shaped current collecting base according to claim 1, wherein a radius of curvature of a curve formed from the periphery of the protruding solid portion to the periphery of the portion having the active material layer is 1 mm or more and 10 mm or less. The non-aqueous electrolyte battery according to claim 1, wherein