JP2003338276A - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery to carry out a stable electroconductive connection simply, easily and inexpensively in a battery requiring high output power. <P>SOLUTION: As for an electrode plate having the same polarity as the battery can, there are non-coated parts at one end in the longitudinal direction and one end in the width-wise direction, the non-coated part in the longitudinal direction and the bottom part of the battery can are connected with a lead, and the non-coated part in the width-wise direction protrudes and forms a spiral protruded part at the bottom end side end part, and this is the wound lithium ion battery in which one part or the whole part of the non-coated parts in the protruded part opposed by winding are electrically connected with each other. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery, and more particularly to a current collecting structure for an electrode plate.

[0002]

2. Description of the Related Art In recent years, portable and cordless AV equipment or electronic equipment such as personal computers have been rapidly developed, and there has been a demand for a secondary battery having a small size, a light weight and a high energy density as a power source for driving them. It is rising. Among them, a lithium ion secondary battery using lithium as an active material is mainly used as a battery having a high voltage and a high energy density.

The current-collecting structure of current lithium ion secondary batteries is mainly of the lead type. As shown in FIG. 2, this is not applied to one end in the longitudinal direction of the positive electrode plate manufactured by adhering the positive electrode material to the positive electrode current collector or the negative electrode plate manufactured by adhering the negative electrode material to the negative electrode current collector. The working portion 1a is formed, and the current collecting tab 2 is welded thereto. The current collecting tab 2 is connected to a positive electrode terminal or a negative electrode terminal to form a lead. This method is advantageous in terms of construction method, low cost, and reliable connection between the electrode plate and the terminal.

Further, among secondary batteries such as nickel-hydrogen storage battery, nickel-cadmium storage battery and lithium-ion secondary battery which require high output for electric tools, a current collecting structure has been devised conventionally. . Among them, a general one is called a tabless structure, and is manufactured by attaching a negative electrode material to a positive electrode plate or a negative electrode current collector manufactured by attaching a positive electrode material to a positive electrode current collector as shown in FIG. The uncoated portion 1b is formed on one end of the negative electrode plate in the width direction. The positive electrode plate and the negative electrode plate are vertically shifted from each other and spirally wound via a separator to form an electrode plate group, and then a current collector including an uncoated portion 1b at the edge of the positive electrode plate of the spiral electrode plate group. A flat positive electrode current collector plate is welded to the protruding portion of the body, and the uncoated portion 1 at the edge of the negative electrode plate 1
A plate-shaped negative electrode current collector plate is welded to the current collector protruding portion of b to form an electrode body. This electrode body was inserted into a metal outer can, the negative electrode current collector plate was spot-welded to the bottom of the outer can, and the positive electrode current collector plate was welded to the sealing plate that also served as the positive electrode terminal by the positive electrode tab. With this structure, the current distribution in the positive electrode plate and the current distribution in the negative electrode during use become uniform, and the high rate discharge characteristics are improved.

Among these tabless structures, Japanese Patent Laid-Open No.
No. 0-323117 discloses that a positive electrode or a negative electrode current collector plate is made to have a size such that it does not come into contact with a metal outer can, or even if a current collector plate is not used, the electrode plates are collected from all the electrode plates. It is described that, in order to enable charging, the current collector protrusion is turned from the inner peripheral portion to the outer peripheral portion and sequentially bent at a right angle to form a flat portion. Further, a structure has been proposed in which a current collector plate is welded to the flat portion. In addition, JP-A-200
As described in Japanese Patent Application Laid-Open No. 0-294222, in order to improve the current collection efficiency and reduce the temperature rise during charging and discharging,
A structure has been proposed in which a current collector protrusion is pressed to form a flat portion by the tip of the protrusion itself, and a current collector plate is welded to this flat portion.

[0006]

SUMMARY OF THE INVENTION
When used in applications requiring high output, the current collection efficiency was poor and the discharge characteristics were poor. Further, in the above-mentioned tabless structure, a current collector plate or a lead must be welded to the uncoated portion in order to connect with the terminal, but in this process, if the welding strength is increased, the separator has holes. However, there is a problem in that adjustment is difficult and the cost is high. Further, when a shock is applied to the battery by dropping or the like and a twisting force is applied to the electrode plate group and the battery case, there is a problem that welding is likely to be dislocated.

An object of the present invention is to solve the above-mentioned problems and to provide a lithium-ion secondary battery in which stable conductive connection is performed simply and at low cost.

[0008]

In order to solve the above problems, in the lithium ion secondary battery of the present invention, the electrode plate having the same polarity as that of the battery can has one end in the longitudinal direction and one in the width direction. There is an uncoated part at one end, the uncoated part in the longitudinal direction and the bottom of the battery can are connected by leads, and,
At the bottom side end of the electrode plate group, the uncoated portion in the width direction projects to form a spiral projecting portion, and one of the uncoated portions in the projecting portions facing each other by winding is Some or all of them are electrically connected.

With this configuration, it is possible to provide a lithium ion secondary battery which is suitable for large current discharge, is low in cost, and has less defects in welding loss due to impact such as dropping.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium ion secondary battery of the present invention comprises a positive electrode plate manufactured by adhering a positive electrode material to a positive electrode current collector and a negative electrode plate manufactured by adhering a negative electrode material to a negative electrode current collector. In a lithium-ion secondary battery in which the electrode plate group that is created by winding through a separator is housed in a battery container consisting of a battery can and a sealing plate together with an electrolytic solution, the electrode plate with the same polarity as the battery can is There is an uncoated portion at one end and one end in the width direction, the uncoated portion in the longitudinal direction and the bottom of the battery can are connected by leads, and the electrode plate group The uncoated part in the width direction projects at the bottom end to form a spiral projecting part, and some or all of the uncoated parts in the projecting parts facing each other by winding are electrically connected. It is characterized by being connected to.

In this embodiment, the electrode plate is firmly and electrically and mechanically connected to the bottom of the battery can by the lead. In addition, the uncoated portion in the width direction projects in the width direction to form a spiral projecting portion, and some or all of the uncoated portions in the projecting portions facing each other by winding are electrically conductive. Since they are electrically connected to each other, the electrode plates can efficiently collect electricity. At this time, if the electrical connection of the protrusions is made in at least the end face of the electrode plate group in a direction perpendicular to the winding core, that is, in a direction radially extending from the winding core, the total current collection path is statistically short. Therefore, it is preferable.

In the present embodiment, the electrode plate having the same polarity as that of the battery can is preferably a negative electrode because a strong steel can or the like can be used as the battery can.

Further, as a method of electrically connecting, a method of welding a burring to a protruding portion, a method of using a collector plate,
A method of filling the conductive paste between the uncoated parts, a method of spraying a metal on the end surface can be used, but by bending a part or all of the uncoated parts in the protruding parts facing each other by the winding. It is preferable that the parts are electrically connected by pressure contact, because parts such as a current collector and a conductive paste and a process for mounting the parts are unnecessary, and the cost is reduced.

FIG. 1 shows a structural diagram of an electrode plate having the same polarity as the battery can in this embodiment. In FIG. 1, there is a current collecting tab 2 previously attached to an uncoated portion 1a at one end in the longitudinal direction, and the uncoated portion 1 is also provided at one end in the width direction.
There is b.

Further, FIG. 4 shows a vertical sectional view of the lithium ion secondary battery in the present embodiment. In FIG.
Reference numeral 3 denotes a positive electrode plate, 4 a negative electrode plate, which are spirally wound in a state of being opposed to each other with a separator 5 made of a microporous polyethylene film interposed therebetween to form an electrode plate group 6. The electrode plate group 6 is electrolyzed. It is housed and arranged in the battery container 7 together with the liquid. The battery container 7 is a cylindrical container-shaped battery can 8 serving as a negative electrode terminal.
And a battery lid 9 serving as a positive electrode terminal, which is insulated from each other by an insulating packing 10 interposed between the inner circumference of the upper end opening of the battery can 8 and the outer circumference of the battery lid 9 and the battery container 7
Is sealed. The separator 5 is also interposed between the electrode plate group 6 and the inner circumference of the battery can 8.

The positive electrode plate 3 is formed by applying a positive electrode material on both sides of a positive electrode current collector, and is attached to the uncoated portion 1a at the longitudinal end of the electrode plate in advance as shown in FIG. The collected current collecting tab 2 serves as the positive electrode lead 2 a in FIG. 4 and connects the positive electrode plate 3 and the battery lid 9. In the positive electrode plate 3,
The positive electrode lead 2a is located in the winding core portion 13 at the beginning of winding, and is drawn out from the central hole of the upper insulating plate 11a.

The negative electrode plate 4 is formed by coating a negative electrode material on both surfaces of a negative electrode current collector, and as shown in FIG. 1, the uncoated portion 1a at the longitudinal end of the electrode plate. There is a current collecting tab 2 attached in advance and an uncoated portion 1b in the width direction, and the current collecting tab 2 serves as the negative electrode lead 2b in FIG. 4 and connects the negative electrode plate 4 and the battery lid 9. In the negative electrode plate 4, the negative electrode lead 2b is located at the outermost peripheral portion at the end of winding, and is extended from the periphery of the lower insulating plate 11b toward the winding core portion 13, and at the winding core portion 13, a bottom portion of the battery can 8 is formed by a welding rod. It is welded. Further, the uncoated part 1b projects from the electrode plate group 6 to form a projecting part 12, and the projecting part 12 is bent and pressure-contacted so that all of the uncoated parts in the projecting part 12 are completely bonded to each other. It is electrically connected. The separator 5 is projected outward from both side edges of the coated portions of the positive electrode plate 3 and the negative electrode plate 4.

In the battery as described above, the discharge characteristic is better than that of the lead type electrode plate. The reason for this will be schematically described below.

For example, when the active material at point A, which is the farthest point from the conductive tab 2 in FIG. 1, absorbs and desorbs lithium, the emitted electrons flow to the external terminal by the shortest conduction path. It flows along the shortest path to the uncoated part 1b, and then the electrical connection between the uncoated parts is
It becomes a short path and flows from the conductive tab 2 to the external terminal. On the other hand, in the lead method as shown in FIG. 2, as the active material at point A, which is the farthest point from the conductive tab 2, absorbs and releases lithium, the emitted electrons are emitted from the electrode plate wound in the current collector. Since it flows along the longitudinal direction to the conductive tab 2, the conductive path becomes long and its electrical resistance becomes large. Therefore, it is preferable that all the uncoated portions of the protruding portion 12 are electrically connected to each other so that the shortest route can be taken in all the portions in terms of current collection. Since it takes a lot of time and labor to process, a part may be used. At this time, as shown in FIG.
However, it is preferable that it is performed in a direction that extends radially from the winding core portion 13 (in FIG. 5, symmetrically, four directions), because the total current collecting path is statistically shortened.

In the present embodiment and the tabless system, the tabless system is superior in current collection, but the electrode plate is firmly and electrically and mechanically connected to the bottom of the battery can by the conductive tab 2. Conductive tab 2 to the electrode plate before processing
Since it can be carried out by welding and bottom welding with a welding rod after winding, it is simple and low cost.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A lithium ion secondary battery as an embodiment of the secondary battery of the present invention will be specifically described below with reference to the accompanying drawings.

In FIG. 1, the size of this battery is 1 in diameter.
8mm, battery height 65mm, battery capacity 120
It is 0 mAh. The battery can 2 is a steel can whose inside is nickel plated and has a thickness of 0.2 mm on the side surface and a thickness of 0.
It is 5 mm.

The positive electrode plate 3 is made of electrolytic manganese dioxide (EM
D: MnO ₂ ) and lithium carbonate (Li ₂ CO ₃ ) as Li
/ Mn = 1/2, and LiMn ₂ O _{4 of} the positive electrode active material produced by firing in air at 800 ° C. for 20 hours
A positive electrode material was prepared by mixing acetylene black as a conductive agent and polyvinylidene fluoride as a binder at a weight ratio of 92: 3: 5.

For kneading the positive electrode material into a paste, N-methylpyrrolidone dispersion liquid was used as polyvinylidene fluoride as a binder. The above mixing ratio is a ratio as a solid content. This positive electrode material paste,
A positive electrode current collector made of an aluminum foil having a thickness of 15 μm was coated on both sides to form a positive electrode material layer. Both thicknesses of the positive electrode material layer were the same, the sum of both thicknesses after coating and drying was 150 μm, and the thickness of the positive electrode plate was 165 μm. Then, compression molding was performed with a press roll having a diameter of 300 mm so that the positive electrode plate had a thickness of 100 μm. At this time, the positive electrode material density is 2.8.
It was g / cm ³ . One end of the positive electrode plate was scraped off to form an uncoated portion 1a, and the positive electrode lead 2a was attached by ultrasonic welding.

The negative electrode plate 4 was prepared by mixing artificial graphite and styrene-butadiene rubber (SBR) as a binder in a weight ratio of 97: 3 as a negative electrode material. A water-soluble dispersion liquid was used as styrene-butadiene rubber as a binder for kneading the negative electrode material into a paste. The above mixing ratio is a ratio as a solid content. This negative electrode material mixture paste was applied to both surfaces of a negative electrode current collector made of a copper foil having a thickness of 14 μm, leaving an uncoated portion 1b having a width of 4 mm at one side edge portion to form a negative electrode material layer. Then, the negative electrode plate was compression-molded with a press roll having a diameter of 300 mm so that the thickness of the negative electrode plate was 110 μm. At this time, the negative electrode material density was 1.3.
It was g / cm ³ . Further, one end of the negative electrode plate was scraped off to form an uncoated portion 1a, and the negative electrode lead 2b was attached by ultrasonic welding.

The electrolyte is ethylene carbonate (EC).
And a mixture of diethylene carbonate (DEC) at a volume ratio of 1: 1 and lithium hexafluorophosphate (LiPF ₆ ) as a solute dissolved at a concentration of 1 mol / dm ³ were used.

The positive electrode plate and the negative electrode plate produced as described above are spirally wound in a state where the uncoated portion 1b of the negative electrode current collector is projected with the positive electrode plate and the negative electrode plate facing each other with the separator interposed therebetween. Group 6 was formed. The length of the protrusion 12 was 2 mm.

Further, a part of the current collector of the protruding portion 12 was bent and pressure-welded to form a bent portion 14.

The electrode plate group 6 is connected to the lower insulating plate 11b.
Along with it, it was housed in the battery can 8 and a welding rod was inserted into the winding core having a diameter of about 3.5 mm, and the negative electrode lead 2b was bottom-welded to the battery can 8.

Then, the positive electrode lead 2a was passed through the upper insulating plate 11a made of PP and having a thickness of 0.5 mm, and it was placed on the electrode plate group 6.

After that, the battery can 8 was grooved for caulking, the positive electrode lead 2a was welded to the battery lid 9, and the above-mentioned electrolytic solution was injected. Finally, the battery lid 9 together with the insulating packing 10 was caulked and sealed to seal the battery.

As described above, in the present embodiment, the processing of the current collecting structure could be performed easily and at low cost.

After activating the battery by charging and discharging several times, the internal resistance was measured and found to be 15 mΩ, which was equivalent to the tabless method and about half the value of the lead method. In addition, as a durability test, rotate for 2 hours in the test drum (60
The lead did not come off even after the rotation (rpm).

[0034]

As described above, according to the lithium ion secondary battery of the present invention, the current collecting structure of the electrode plate is excellent, so that stable conductive connection can be easily and inexpensively performed in a battery requiring high output. It is possible to provide a lithium-ion secondary battery that performs the above.

[Brief description of drawings]

FIG. 1 is a structural diagram of an electrode plate according to an embodiment of the present invention.

FIG. 2 is a structural diagram of a conventional lead-type electrode plate.

FIG. 3 is a structural diagram of a conventional tabless type electrode plate.

FIG. 4 is a vertical sectional view of a lithium-ion secondary battery according to an embodiment of the present invention.

FIG. 5 is a front view of a protrusion according to the embodiment of the present invention.

[Explanation of symbols]

1a, 1b Uncoated part 2 Current collection tab 2a Positive lead 2b Negative electrode lead 3 Positive plate 4 Negative plate 5 separator 6 plate group 7 Battery container 8 battery cans 9 Battery lid 10 Insulating packing 11a Upper insulating plate 11b Lower insulating plate 12 Projection 13 winding core 14 Bent section

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Futoshi Tanikawa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Shinji Murashige             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5H017 AA03 AS02 BB00 CC03 EE05                       EE06 HH05                 5H022 AA09 AA18 BB11 BB17 CC12                 5H029 AJ06 AJ14 AK03 AL07 BJ02                       BJ14 DJ05 DJ07 DJ12 EJ04                       EJ12 HJ12

Claims (3)

[Claims] 1. An electrode plate group formed by winding a positive electrode plate manufactured by adhering a positive electrode material on a positive electrode current collector and a negative electrode plate manufactured by adhering a negative electrode material on a negative electrode current collector through a separator. In a lithium-ion secondary battery in which a battery can and a sealing plate are housed together with an electrolytic solution, an electrode plate having the same polarity as the battery can has one end in the longitudinal direction and one end in the width direction. There is an uncoated part in the longitudinal direction, the uncoated part in the longitudinal direction and the bottom part of the battery can are connected by leads, and the uncoated part in the width direction at the bottom side end of the electrode plate group. A lithium ion secondary battery in which the parts project to form a spiral projecting part, and some or all of the uncoated parts in the projecting parts facing each other by winding are electrically connected. 2. The lithium-ion secondary battery according to claim 1, wherein the electrode plate having the same polarity as that of the battery can is a negative electrode. 3. The lithium ion secondary battery according to claim 1, wherein some or all of the uncoated parts in the protruding parts facing each other by the winding are bent and pressed to be electrically connected. .