JPH0331008Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> This invention relates to a cylindrical battery, and more specifically, it has an electrode group formed by spirally winding an anode and a cathode formed into strips with a separator in between. At least one of the anode and the cathode has a plurality of lead pieces, and by changing the width of the lead pieces between the inner circumference and the outer circumference of the electrode group, it is possible to reduce the occurrence of assembly defects. This invention relates to a wound electrode group for cylindrical batteries.

<Prior Art> Cylindrical batteries currently on the market have a strip-shaped anode 6 and a cathode 7 arranged in a spiral shape with a separator 3 in between, as shown in FIGS. 4A and 4B, in order to effectively utilize the electrode area. A type that uses a wound electrode group as an electrode group is widely used for both primary and secondary batteries.The electrode group obtained in this way is inserted into a metal outer can, and the electrolyte solution is After that, the opening of the outer can is sealed with a metal sealing plate, a synthetic resin sealing gasket, etc. to complete the battery. By the way, in this type of battery, the sealing plate and the outer case can be used as anode terminals and cathode terminals by electrically connecting them to the anode or cathode (or vice versa) constituting the electrode group through lead pieces. It is common, and it is also known that the current collection effect of a battery is increased by taking out multiple lead pieces from one electrode (anode or cathode) and connecting them to each terminal. It is publicly known as disclosed in No. 39174, Utility Model Publication No. 57-1402, etc. In FIGS. 4A and 4B, 8a is a lead piece located at the inner circumference of the anode 6, and 8b is a lead piece located at the outer circumference of the anode 6. Naturally, a lead piece is similarly arranged on the cathode 7, but it is omitted for the sake of simplifying the explanation. The width of the lead piece of such an electrode is set to a certain appropriate size depending on the type of battery, battery size, etc. Also, the width of the multiple lead pieces provided on one electrode,
That is, the lead pieces 8a and 8b in FIGS. 4A and 4B have exactly the same dimensions.

<Problems to be solved by the invention> By the way, looking at the winding state of the wound electrode group near where the lead piece is located, the winding curvature is steep at the inner circumference of the winding, that is, the winding of the electrode and separator is It can be seen that the radius of rotation is small and the curvature becomes gentler towards the outer periphery. Since the lead piece is formed integrally with the electrode, mechanical stress is applied to the lead piece according to the winding state. However, in current batteries, the widths of the lead pieces located at the inner and outer peripheries of the wound electrode group are the same, so compared to the lead pieces at the outer periphery that are loosely wound, the inner periphery Since the lead piece in the section has a large winding curvature of the electrode, unreasonable mechanical stress is applied in the winding direction. On the other hand, since the lead piece itself has a certain length, the degree of freedom of mechanical displacement in the width direction is restricted. For this reason, the winding curvature between the electrode and the lead piece will be misaligned near the base of the lead piece on the inner periphery of the winding, and the active material of the electrode will crumble and the separator will break near the lead piece, resulting in damage to the battery. This causes poor assembly, deterioration of battery performance, and, in the case of storage batteries, deterioration of cycle characteristics. In particular, recently, a configuration in which a perforated punched plate is used as a current collector plate for the electrode has been widely used, and this punched plate is cut due to misalignment between the electrode and the lead piece, resulting in the above-mentioned assembly failure. tends to encourage

<Means for Solving the Problems> The present invention provides a wound electrode group for a cylindrical battery having a band-shaped metal current collector plate, in which the band-shaped metal current collector plate has a plurality of lead pieces integrally formed at the side ends. It is something that
This is a current collector plate for a positive electrode or a negative electrode, and the width of the plurality of lead pieces is gradually decreased from the outer circumference to the inner circumference of the winding.

<Operation> The above means allows the lead piece to have a degree of freedom in mechanical displacement in the width direction that is adapted to the winding curvature of the electrode and separator on which the lead piece is located. This reduces the mechanical force at the base of the lead piece and eliminates misalignment between the electrode and the lead piece, preventing collapse of the electrode active material near the lead piece during electrode assembly, and preventing damage to the separator and electrode current collector plate. Prevents damage etc.

<Example> As an example, a case will be described in which this invention is applied to a nickel-zinc storage battery of size AA. Figure 1 shows the electrode group of a storage battery. 1 is a nickel electrode constructed by filling a band-shaped metal current collector plate with a nickel sintered body with an active material, and 2 is an active material whose main component is zinc oxide. A zinc electrode formed by pressing a material layer onto a current collector plate; 3 is a separator; 4a and 4b are leads integrally formed on the band-shaped metal current collector plate of nickel electrodes located at the inner and outer windings of the electrode group The width of the lead piece 4b is 4.0 mm, and the width of the lead piece 4b is 4.0 mm.
The a width was set to 2.0 mm. A storage battery using the above electrode group (the battery of the present invention) and a width of the lead piece 4a of 4.0 mm.
The table below shows a comparison of the number of defects during battery assembly with a storage battery (conventional battery) that uses the same electrode group except for the above.

Conventional battery Inventive battery Number of assembly defects: 4/100 (cell) 0/100 (cell) As is clear from the table above, the inventive battery can reduce or prevent assembly defects when compared to the conventional battery. The reason for this seems to be as follows. In the battery of the present invention, the width of the lead piece located on the inner circumference of the winding of the electrode group is smaller than the width of the lead piece located on the outer circumference of the winding. The base of the lead piece is
Compared to conventional batteries, it has a greater degree of freedom regarding mechanical displacement, and is easily deformed to accommodate the large curvature of the inner circumferential portion of the electrode winding. Therefore, collapse of the active material of the electrode near the base of the lead piece and damage to the separator and current collector plate can be prevented.

Further, FIG. 3 shows a comparison of the charge/discharge cycle characteristics between the battery A of the present invention and the conventional battery B. As is clear from the figure, the battery of the present invention is superior to the conventional battery in terms of cycle life. When conventional batteries with degraded lifespans were disassembled and the causes of their characteristic deterioration were investigated, it was confirmed that most of the causes were located near the lead piece located on the inner circumference of the winding.

What is shown in FIG. 2 is an electrode used in a battery in which three or more lead pieces are formed on a band-shaped metal current collector plate 5. In the figure, R is the winding start side of the electrode 5, and the widths x1 to _xo of each lead piece 5a to 5n are x1<x2<x3...
It is defined as x _o-1 < x _o .

<Effects of the Invention> As detailed above, the present invention provides a wound electrode group for a cylindrical battery having a band-shaped metal current collector plate, in which the band-shaped metal current collector plate has a plurality of lead pieces integrated at the side ends. It is a current collector plate for a positive electrode or a negative electrode, and the width of the plurality of lead pieces is gradually decreased from the outer circumference to the inner circumference of the winding. This prevents the electrode active material from collapsing near the lead piece and damage to the separator and electrode current collector plate during battery assembly.
Therefore, the occurrence of battery assembly defects can be reduced, battery performance can be improved, and in the case of storage batteries, cycle characteristics can be improved.

[Brief explanation of the drawing]

Figure 1 is a plan view showing the electrode group of the example, Figure 2 is a plan view showing the electrode group of the example.
The figure is a plan view showing another example of the electrode, FIG. 3 is a graph showing charge/discharge cycle characteristics, and FIGS. 4A and 4B are a perspective view and a plan view showing a conventional example of the electrode group. 1...Nickel electrode, 2...Zinc electrode, 3...Separator, 4a, 4b, 5a~ _5o , 8a, 8b...
... Lead piece, 5 ... Band-shaped metal current collector plate, 6 ... Anode, 7 ... Cathode.

Claims (1)

[Claims for Utility Model Registration] A wound electrode group for a cylindrical battery having a band-shaped metal current collector plate 5, wherein the band-shaped metal current collector plate 5 includes a plurality of lead pieces 4a, 4.
b, 5a, 5b, 5c...5n are integrally formed on the side end, and are a current collector plate for a positive electrode or a negative electrode, and a plurality of lead pieces 4a, 4b, 5a, 5
The widths of b, 5c...5n are gradually reduced from the outer circumference to the inner circumference of the wound electrode group for a cylindrical battery.