JPH11135101A - Electrode structure of secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the increase in electric resistance and local concentration of current unlikely to occur and to avoid the deterioration of electrodes caused by generation, even in high rate charge/discharge by connecting a current collec tor to the electrode terminal of a battery without decreasing the cross-sectional area of the current collector. SOLUTION: A non-coating part 1 serving as a current collecting part is formed in each winding starting part and winding ending part of the positive electrode and negative electrode of a secondary battery, and the non-coating part 1 is bent by 90 deg. and connected to the electrode terminal of the battery. Thereby, both positive and negative electrodes can be taken out together in one direction of the battery and without setting lead wires.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary device used as a power source for products such as mobile devices such as electric vehicles and electric carts, portable devices such as video cameras and personal computers, backup devices in the event of a power failure, and security devices. In batteries,
The present invention relates to a current collecting structure which can be processed relatively easily and has a small connection electric resistance.

[0002]

2. Description of the Related Art In a conventional current collecting structure of a secondary battery, an uncoated portion in which only a current collector is exposed is provided at a winding start portion of a positive electrode and a winding end portion of a negative electrode, and the uncoated portion is represented by Al or Ni. And a lead wire connected to the battery electrode terminal.

As a method for connecting a power generating element and a battery electrode terminal without a lead wire, Japanese Patent Laid-Open Publication No. 3-49151 discloses a method in which a current collector is loaded with an electrode active material on one side in a direction perpendicular to the winding direction. Discloses a method in which a current collector is exposed from the electrode active material portion to at least 1/4 or more of the current collector length in a chevron shape, and the current collector exposed portion and the electrode terminal portion are directly welded.

[0004]

However, in the connection method using a lead wire, the cross-sectional area of the lead wire is structurally smaller than the cross-sectional area of the current collector, so that the electrical resistance at the lead wire portion increases. Also, the current is concentrated on the lead wire and the welding portion between the lead wire and the current collector. Therefore, when charging and discharging with a large current, local heat is generated around the above-mentioned lead wire and a welding portion between the lead wire and the current collector, which may cause deterioration of the active material or the electrolyte applied to the electrode. . Also,
When the welding strength is insufficient, there is a problem that the lead wire is peeled off during the winding operation, and the performance of the battery is deteriorated due to an increase in the electric resistance of the welded portion.

In the case where the current collector is exposed in one direction perpendicular to the winding direction and connected to the electrode terminal as shown in Japanese Patent Application Laid-Open No. 3-49151, Current concentration and the problem of welding strength can be avoided, but since the current collectors processed into a mountain shape in both directions along the axis of the wound body directly protrude from the wound body, the winding A crack is likely to be formed at the base of the mountain-shaped current collector during the turning operation or when connecting the battery electrode terminals.

In the above current collecting structure, in order to avoid a short circuit between the exposed positive and negative current collectors, electrodes are provided in two directions with the positive electrode on one side and the negative electrode on one side along the axis of the wound body. It is necessary and suitable for batteries having positive and negative terminals in two directions, such as up and down, as shown in JP-A-3-49151. When a battery is provided with both positive and negative electrodes in one direction, which is possible only on one side, there is a problem that the connection of electrodes inside the battery becomes complicated and the external dimensions of the battery become large.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to use a wound body composed of a positive electrode, a negative electrode, and a separator coated with an active material, a conductive additive, and a binder on a current collector. In the next battery, an uncoated portion is provided only at the current collecting portion at the winding start portion and the winding ending portion of the positive electrode and the negative electrode, and the non-coated portion is bent by 90 ° and the battery electrode terminal is connected thereto, thereby obtaining a current collecting portion. An object of the present invention is to provide an electrode structure of a secondary battery which can easily cope with a battery having no lead wire and having both positive and negative electrodes in one direction without increasing the external dimensions.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings, taking an electrode and a battery structure as an example.
FIG. 1 is an electrode structure diagram showing one embodiment of the present invention, and FIG.
a and FIG. 2b show the processing method. In FIG. 1, reference numeral 2 denotes a portion (hereinafter, referred to as an application portion) in which a current collector is coated with a mixture (hereinafter, referred to as a mixture) in which an active material, a binder, and a conductive assistant are mixed as necessary. Is an uncoated portion where only the current collector is exposed without applying the mixture (hereinafter, referred to as an uncoated portion).
Is shown. Reference numeral 1a denotes a current collecting lead portion formed by bending an uncoated portion of 1, and when a battery is manufactured using the present electrode, the portion of 1a is directly connected to a battery electrode terminal. Thus, it is not necessary to provide a current collecting lead wire of another component by welding.

Next, a method of manufacturing an electrode according to an embodiment of the present invention will be described with reference to FIGS. 2A and 2B. Reference numerals 3 and 4 denote an applied portion and an uncoated portion, respectively. First, as shown in FIG. 2A, an uncoated portion 4 longer than the electrode width W is provided in at least one portion of the electrode, and a part of the uncoated portion is defined as a starting point at a portion L from an end of the uncoated portion. 2b with respect to the reference line 5 having an inclination of 45 ° with respect to the electrode shown in FIG.
The convex portion 7 of the uncoated portion which is bent by 0 ° is created.

At this time, L> W is satisfied, and L may be determined to be an extra length for W in consideration of the distance between the wound body of the battery to which the present electrode is applied and the battery electrode terminal and the ease of battery assembly. Further FIG.
In FIG. 1B, the electrode shown in FIG. 1 can be manufactured by performing valley folding with reference to a reference line 6 provided at W / n in the width direction from the end of the convex portion and repeating this n-1 times. In addition, when battery terminals are taken out in the upper and lower two directions of the wound body, or when W is 以下 or less of the outermost circumferential length of the wound body, n = 1 may be set.

Next, an embodiment of a method for manufacturing a wound body in which both positive and negative poles are taken out in one direction will be described with reference to FIGS. 8
Indicates a wound body in the middle of winding. The wound body is manufactured by winding a positive electrode 10 and a negative electrode 11 around a center pin 9 with a separator 12 interposed therebetween. ΔL indicates the difference between the total electrode lengths of the negative electrode and the positive electrode. Here, in order to align the negative current collecting lead portion 14 and the positive current collecting lead portion 15 with respect to the wound body 13 in the opposite directions about the winding axis as shown in FIG. 4, ΔL is provided as follows. I just need.

[0012]

１L = ((circumferential length of negative electrode) − (circular length of positive electrode)) +
(The outermost circumference of the wound body) / 2 In the above description, the case where the current collecting lead portion is one is described. However, as shown in FIG. Two portions, such as the lead portions 17 and 18, may be provided.

Finally, an embodiment of a secondary battery using the present invention will be described with reference to FIG. After a roll formed by winding the separator 23, the positive electrode 24, and the negative electrode 25 around the center pin 22 is inserted into the battery can 20, the battery cover 19 and the battery can 2 are inserted.
0 is sealed by welding. The lower part of the wound body and the battery can 20 are insulated by a donut-shaped insulating plate 21.

The battery cover 19 has a battery negative terminal 27,
Two battery electrode terminals, that is, a battery positive terminal 28, are provided, and are insulated from the battery lid 19 by an insulating sealing material 29. The negative electrode current collecting lead portion 2 provided on the outermost periphery of the negative electrode described earlier with reference to FIG.
5a, a positive electrode current collecting lead 24a provided on the outermost periphery of the positive electrode
Are directly connected to the battery negative terminal 27 and the battery positive terminal 28, respectively. At this time, as a connection method, any of ultrasonic welding, laser welding, and caulking connection using rivets may be used.

[0015]

As described above, according to the present invention, in a secondary battery using a wound body composed of a positive electrode, a negative electrode and a separator coated with an active material, a conductive additive, and a binder on a current collector, a positive electrode, a negative electrode, A current collecting structure in which only the current collecting portion was provided with an uncoated portion at the winding start portion and the winding end portion, and a current collecting lead portion formed by bending the uncoated portion by 90 ° was directly connected to the battery electrode terminal. This eliminates the necessity of providing a separate current collecting lead wire, thereby eliminating the need to control welding strength and area. In addition, since the current collector can be connected to the battery electrode terminal without reducing its cross-sectional area, an increase in electric resistance and local concentration of current are unlikely to occur, and deterioration of the electrode due to heat generation during charging and discharging with a large current is prevented. Can be avoided.

Further, by changing the direction in which both or one of the positive and negative current collectors is bent, both a battery having positive and negative electrodes in two directions and a battery having both positive and negative electrodes in one direction can be easily formed. Can be handled.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electrode structure according to one embodiment of the present invention.

FIG. 2A is a diagram showing a processing procedure of a method for processing the current collecting structure in FIG. 1; FIG. 2B is a view showing a processing procedure of the processing method of the current collecting structure of FIG. 2A according to the present invention.

FIG. 3 is a view showing a schematic structure of a wound body according to one embodiment of the present invention.

FIG. 4 is a diagram showing an appearance of FIG. 3;

FIG. 5 is a diagram showing an electrode structure according to one embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a structure of a secondary battery according to one embodiment of the present invention.

[Explanation of symbols]

1. Uncoated portion, 1a, 17, 18 ... Current collecting lead portion, 2,
3 ‥‥ applied part, 4… unapplied part, 5,6… bending reference line, 7… projected part created by bending the unapplied part by 90 °,
8 ... wound body in the middle of winding, 9, 22 ... center pin, 1
0, 24: positive electrode, 11, 25: negative electrode, 12, 23: separator, 13: wound body, 14, 25a: negative electrode current collecting lead portion, 15: positive electrode current collecting lead portion, 16: composite material application portion, 19
... Battery lid, 20 ... Battery can, 21 ... Insulating plate, 24a ... Positive electrode current collecting lead part, 26 ... Battery cover Battery can fitting part, 27 ... Battery negative electrode terminal, 28 ... Battery positive electrode terminal, 29 ... Insulating sealing material.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Michiko Sakairi 800, Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Pref.Hitachi, Ltd.

Claims (1)

[Claims] 1. A secondary battery comprising a power generation element (hereinafter referred to as a wound body) formed by winding a positive electrode, a negative electrode, and a separator coated with an active material, a conductive auxiliary material, and a binder on a current collector.
An uncoated portion where the current collector is exposed is provided at at least one of a winding start portion and a winding end portion of the positive electrode and the negative electrode, and the uncoated portion is bent at 90 ° to connect a battery electrode terminal. The electrode structure of the secondary battery.