JP2003157902A - Flat cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat cell that is free from causing fractures at the winding start side of a connection piece when winding a group of electrode plates into flat shape, and prevents deposition of metallic lithium. SOLUTION: A positive electrode plate 11 and a negative electrode plate 12 are wound into flat shape so that positive electrode lamination faces 22a-22e and negative electrode lamination faces 23a-23f can be laminated through a separator, then, a resin tape 45 is stuck to a positive electrode piece 24a at the topmost part of winding start side. There is a risk of causing fractures at a positive electrode current collector made of aluminum foil, as the positive electrode piece 24a is curved with small radius of curvature. However, the fractures are prevented by sticking the resin tape 45, and it is effective for preventing the negative electrode 12 from a deposition of metallic lithium.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coin-type battery and a method for manufacturing the coin-type battery, and more particularly, to an increase in discharge current using an electrode group having a winding structure in which a positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween. The present invention relates to a coin-shaped battery.

[0002]

2. Description of the Related Art A coin type battery, as shown in FIG. 9, has a disk-shaped positive electrode pellet 32 and a negative electrode pellet 33.
An electrode plate structure in which and are arranged to face each other via a separator 34 is generally adopted. This coin-shaped battery has a positive electrode pellet 3 in a sealing case 35 formed in a circular half shell.
2 and the negative electrode pellet 33 are opposed to each other with the separator 34 interposed therebetween, the electrolytic solution is injected, the gasket 36 is arranged on the side peripheral portion of the sealing case 35, and the cap case 31 is put on the gasket 36. The internal space is sealed by the crimping process in which the open end is bent inward, and the battery is formed into a coin-shaped appearance.

In the electrode plate structure in which the positive electrode pellets 32 and the negative electrode pellets 33 face each other at a ratio of 1: 1 as described above, a large discharge capacity is generated due to factors such as a small reaction area where the positive electrode plate and the negative electrode plate are opposed. I could not get it. In order to obtain a large discharge capacity, it is necessary to increase the facing area between the positive electrode plate and the negative electrode plate. For relatively large batteries other than coin type batteries, a plurality of positive electrode plates and negative electrode plates are laminated with a separator in between. A structure in which a reaction area is enlarged and an energy density in a high rate discharge is improved by a laminated structure or a winding structure in which a strip-shaped positive electrode plate and a negative electrode plate are wound with a separator interposed therebetween is widely used. If the electrode plates having such a laminated structure or a wound structure can be housed in a flat coin-shaped case, the discharge capacity of the coin-shaped battery can be increased. The battery in which the electrode group having the winding structure is housed in a flat case such as a coin shape is disclosed by the applicant of the present application.
No. 00-241678, Japanese Patent Application No. 2000-241679, etc.

As shown in FIG. 7, the electrode group having the winding structure has a positive electrode plate in which a plurality of positive electrode stacking surfaces 17a to 17e are connected by connecting pieces 19a to 19d in order to accommodate it in a circular case. 7, and a negative electrode plate 8 in which a plurality of negative electrode stacking surfaces 18a to 18f formed in a larger area than the positive electrode stacking surfaces 17a to 17e are connected by connecting pieces 20a to 20e, as shown schematically in FIG. It is wound in a flat shape via 9 to form the electrode plate group 1. By using this electrode plate group 1, it is possible to contribute to miniaturization and high functionality of portable electronic devices and the like as a battery that is small and flat but can take out a large discharge current.

[0005]

However, when the positive electrode plate 7 and the negative electrode plate 8 are flatly wound, the connecting piece 19a of the positive electrode plate 7 and the negative electrode plate 8 at the bending position closest to the winding start side.
Since the connecting piece 20a is bent to 180 degrees with a small bending radius, the current collector, which is the core material of the electrode plate, may be broken. In particular, since the positive electrode plate 7 uses an aluminum foil as a current collector and has a low breaking strength, breakage easily occurs.

The positive electrode plate 7 is formed by applying a positive electrode active material layer on both sides of a positive electrode current collector, and when this is bent 180 degrees with a small bending radius by a connecting piece 19a, the positive electrode active material layer on the inside is formed. Since the positive electrode active material layer on the outer side is compressed, the force also acts on the positive electrode current collector in the direction of expansion, and the positive electrode current collector of the aluminum foil having low breaking strength may be broken.

Further, when the flat battery is constructed as a lithium ion secondary battery, a transition metal oxide such as lithium cobalt oxide is used as a positive electrode active material, and graphite capable of absorbing and releasing lithium ions is used as a negative electrode active material. The carbon material of is used. In a secondary battery using such a positive electrode active material and a negative electrode active material, the potential of the graphite material during charging is used at a low potential that is almost the same as the potential at which lithium is deposited. Therefore, in a secondary battery in which the negative electrode active material has deteriorated due to repeated charge and discharge cycles, lithium ions inserted in the negative electrode active material during charging cause an inactivation reaction with the electrolytic solution, and the surface of the negative electrode plate 8 is inactivated. It is known that a phenomenon in which dendrite-like lithium metal is deposited occurs, and an internal short circuit resulting from this causes the safety and the life of the secondary battery to be shortened. Compared with the case of a cylindrical battery in which a positive electrode plate and a negative electrode plate are wound in a cylindrical shape, when the electrode plate group is formed by flatly winding the flat battery like the flat battery of the present invention, the lithium dendrite is It was discovered that the charging / discharging cycle occurs in a few states.

Whether the electrode plate group is wound in a cylindrical shape or in a flat wound state, the areas of the electrode plates facing each other are almost the same, and the capacity between the positive electrode and the negative electrode is almost the same. It is kept. However, when the electrode plate group is formed in a flat shape, the end of the negative electrode plate 8 on the winding start side is confronted so as to be surrounded by the connecting piece 19a on the winding start side of the positive electrode plate 7, and If limited, the capacity balance between the positive electrode and the negative electrode is greatly inclined to the positive electrode side. For this reason, it was found that the lithium ions desorbed from the positive electrode during charging could not be fully occluded between the layers of the carbon material of the negative electrode, and excessive lithium ions were deposited on the surface of the negative electrode.

The present invention was devised in view of the above problems that occur when the electrode plate group is formed by flatly winding, and has a structure for preventing breakage and lithium dendrites that occur in the current collector during winding. It aims at providing the flat type battery provided with.

[0010]

In order to achieve the above object, the first invention of the present application is to connect a plurality of positive electrode laminated surfaces by using a positive electrode plate material having positive electrode active material layers formed on both surfaces of a positive electrode current collector. A positive electrode plate formed by connecting one piece in a strip shape and a negative electrode plate material in which a negative electrode active material layer is formed on both surfaces of a negative electrode current collector are used to form a strip shape by connecting a plurality of negative electrode laminated surfaces by a connecting piece. A negative electrode plate, the positive electrode laminated surface and the negative electrode laminated surface is bent by the connecting piece so as to be alternately laminated via a separator, a group of electrode plates wound flatly, via a gasket in the sealing case. In a flat battery housed in an internal space formed by covering a cap case, an insulating resin tape is adhered to at least the inner surface side of the connection piece located at the most winding start side of the positive electrode plate. It is characterized by that.

According to the first aspect of the invention, when the positive electrode plate and the negative electrode plate are flatly wound with the separator interposed therebetween, the connecting piece located closest to the winding start side is bent with a small bending radius, and the electrode plate When the aluminum foil is used for the current collector that is the core material of the current collector, especially for the positive electrode plate, the current collector may be broken due to pulling due to bending,
Since the resin tape is attached to the inner surface where the connecting piece is bent, the bending radius is increased by the thickness of the resin tape and it is not bent at an acute angle, so aluminum foil is used as the collector of the positive electrode plate. Even if it is present, it is possible to prevent breakage of the current collector due to bending. Further, since the connecting piece on the winding start side of the positive electrode plate is arranged so as to wrap around the winding start end portion of the negative electrode plate, if it is limited to the end portion, the cut surface is exposed by the cutting process of the current collector. Therefore, there is a problem that the capacity balance between the positive electrode and the negative electrode largely tilts toward the positive electrode side, and lithium ions desorbed from the positive electrode during charging cannot be fully absorbed in the negative electrode, and excess lithium metal is deposited on the negative electrode surface. However, since the resin tape is attached to the connecting piece of the positive electrode plate, the lithium ions released from the positive electrode can be reduced, and the deposition of lithium metal on the opposing negative electrode can be suppressed. Further, even if there is precipitation, the tape can firmly insulate, so that no short circuit occurs.

In the above structure, the resin tape is formed by forming a non-adhesive surface on the positive electrode plate in which about ½ of the winding direction does not adhere to the connecting piece, so that the resin tape adheres to the positive electrode active material layer and is bent. Sometimes, the movement of the positive electrode active material layer is not restricted, and the positive electrode active material layer inside the connecting piece is not compressed into a bump shape when bent, and it is possible to suppress the force in the extending direction applied to the current collector.

The second invention of the present application is a positive electrode plate formed by using a positive electrode material in which a positive electrode active material layer is formed on both surfaces of a positive electrode current collector and connecting a plurality of positive electrode laminated surfaces with connecting pieces to form a strip shape. ,
A negative electrode plate in which a plurality of negative electrode laminated surfaces are connected by connecting pieces using a negative electrode material in which a negative electrode active material layer is formed on both surfaces of a negative electrode current collector to form a strip shape, the positive electrode laminated surface and the negative electrode laminated surface. A group of electrode plates that are bent and flatly wound by the connecting pieces so that and are alternately stacked via a separator are housed in an internal space formed by covering a cap case with a gasket on a sealing case. In the flat battery consisting of, the separator located between the most winding start side of the positive electrode plate and the winding start side end portion of the negative electrode plate facing this, the pores present in the separator are formed. It is characterized in that it is subjected to a pore sealing treatment for closing.

According to the second aspect of the invention, since the connecting piece on the winding start side of the positive electrode plate is arranged so as to wrap around the winding start end of the negative electrode plate, the capacity balance between the positive electrode and the negative electrode largely tilts toward the positive electrode side, Lithium ions desorbed from the positive electrode during charging could not be fully occluded in the negative electrode, and there was a problem that excess lithium metal was deposited on the negative electrode surface, but the pores of the separator in the portion facing the connecting piece of the positive electrode plate were By blocking, the lithium ions separated from the positive electrode do not pass through the separator, so that the lithium ions occluded at the winding start end of the negative electrode plate are reduced and the deposition of lithium metal on the negative electrode plate is suppressed. Therefore, it is possible to improve the decrease in charge / discharge cycle life and the occurrence of internal short circuit due to the deposition of lithium metal.

The pore-sealing treatment in the above-mentioned structure is a treatment of invading the pores in a part of the separator and applying a coating agent for closing the pores, a process of thermally melting a part of the separator to close the pores, the separator Any of the treatments of attaching the resin tape to a part of the can be applied.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention.
The embodiments described below are examples of embodying the present invention and do not limit the technical scope of the present invention.

As shown in FIG. 1, the coin-type battery according to the present embodiment has a positive electrode group 10 housed in a sealing case 5 formed in a circular half-shell, and the positive electrode group pulled out from the positive electrode group 10. The lead 26 and the negative electrode lead 27 are welded to the cap case 4 and the sealing case 5, respectively, and the electrolytic solution is injected into the sealing case 5, and the cap case 4 is placed on the gasket 6 arranged on the side peripheral portion of the sealing case 5. And the inner space is sealed by a crimping process in which the open end of the cap case 4 is bent inward.

As shown in FIG. 2A, the electrode plate group 10 is formed by using a negative electrode plate material in which a negative electrode active material layer is formed on both surfaces of a negative electrode current collector which is a copper foil, as shown in FIG. As shown in 6
The negative electrode stacking surfaces 23a to 23f are connected to the negative electrode connecting pieces 25a to 2f.
5e, the negative electrode plate 12 having the negative electrode lead 27 formed at the end of winding and the positive electrode plate material in which the positive electrode active material layers are formed on both surfaces of the positive electrode current collector, which is an aluminum foil, are used.
As shown in (b), the five positive electrode stacking surfaces 22a to 22f formed in an area smaller than the areas of the negative electrode stacking surfaces 23a to 23f.
22e are connected by the positive electrode connecting pieces 24a to 24d, and the positive electrode plate 11 having the positive electrode lead 26 formed at the winding end is wound flatly via the separator. Positive electrode stacking surface 2
The positive electrode connecting pieces 24a to 24d and the negative electrode connecting pieces 25a to 25e are wound so as to be alternately laminated with the separators 2a to 22e and the negative electrode laminated surfaces 23a to 23f via the separator.
Is formed so that the width thereof gradually increases from the winding start side to the winding end side as illustrated. Further, small-diameter negative electrode displacement detection holes 43, 44 are formed on the winding start side and the winding end side of the negative electrode plate 12, and the negative electrode stacking surfaces 23a, 23 in which the negative electrode displacement detection holes 43, 44 are formed.
the positive electrode stacking surfaces 22a, 22b of the positive electrode plate 11 facing the f,
22e includes positive electrode displacement detection holes 41a, 41 having a large diameter.
b and 42 are formed, and after winding, the negative electrode position deviation detection holes 43 and 44 and the positive electrode laminated surfaces 22a, 22b, and 22e are subjected to X-ray inspection to detect the misalignment when flatly wound. I am able to do it.

FIG. 3 is a schematic view showing a state in which the positive electrode plate 11 and the negative electrode plate 12 are flatly wound with the separator 13 in between, and each positive electrode connecting piece 24a-2 of the positive electrode plate 11 is shown.
4d and the negative electrode connecting pieces 25a to 25e of the negative electrode plate 12 are bent and wound to form the positive electrode laminated surfaces 22a to 22.
e and the negative electrode stacking surfaces 23a to 23f are stacked alternately with the separator 13 interposed therebetween. When the positive electrode plate 11 and the negative electrode plate 12 are thus flatly wound, the positive electrode connecting piece 24a located on the winding start side of the positive electrode plate 11 and the negative electrode connecting piece 25a located on the winding start side of the negative electrode plate 12. Will be bent 180 degrees with a small bend radius. As described above, the aluminum foil used as the positive electrode current collector of the positive electrode plate 11 has low bending strength and tensile strength, and when it is bent with a small bending radius, the positive electrode active material layer inside the bending is compressed and the aluminum There was a possibility that the positive electrode current collector would be broken due to the force in the pulling direction.

In order to prevent the breakage of the positive electrode current collector, suppress the generation of dendrites, and enhance the insulating property, as shown in FIG. 2B, the positive electrode on the winding start side of the positive electrode plate 11 is formed. A resin tape 45 made of an insulating resin is attached to the inner surface of the connecting piece 24a when the connecting piece 24a is bent. As shown in FIG. 4, the positive electrode connecting piece 24a to which the resin tape 45 is attached is bent so as to wrap around the winding start end of the negative electrode plate 12, and thus has a small bending radius, and when bent at an acute angle, the positive electrode connecting piece 24a. Since the positive electrode active material layer 11b existing inside is compressed and a force acts on aluminum, which is the positive electrode current collector 11a, in the extending direction, the positive electrode current collector 11a may be broken. However, the positive electrode active material layer 11 existing inside
Since the resin tape 45 is attached to the surface of b, the bending radius of the positive electrode connecting piece 24a is increased by the thickness of the resin tape 45, and the positive electrode current collector is not bent at an acute angle. It is possible to prevent breakage of 11a, suppress generation of dendrites, and enhance insulation.

It is preferable that the resin tape 45 be adhered so that there is no adhesive surface in about 1/2 of the length direction of the positive electrode plate 11, and the positive electrode active material layer 11b is not restricted by the adhesion. When the positive electrode connecting piece 24a is bent, the positive electrode active material layer 11b is not restricted from being compressed and expanding in a bump shape. When the positive electrode active material layer 11b is compressed and there is no escape,
Although a force in the pulling direction acts on the positive electrode current collector 12a to break the positive electrode current collector 12a, the movement of the positive electrode active material layer 11b is not restricted by reducing the adhesive surface. The method of partially removing the adhesive surface of the resin tape 45 is the resin tape 4
It is also possible to partially apply an adhesive to 5,
As shown in FIG. 5, a method is suitable in which the resin tape 45 is folded back from one end thereof to the adhesive surface side, and about ½ of the adhesive tapes adhere to each other to cover the adhesive surface.

Further, the resin tape 45 is made of a material having an ion impermeable property that impedes the permeation of lithium ions, and is preferably one having a chemical stability to a non-aqueous solvent. This resin tape 45 is used as the positive electrode connecting piece 24a.
By being adhered on the top, the lithium ions that are detached from the positive electrode connecting piece 24a can be reduced.
Since the end of the negative electrode plate 12 on the winding start side is wrapped in the positive electrode connecting piece 24a, the capacity balance largely tilts toward the positive electrode side, and the lithium ions released from the positive electrode at the time of charging cannot be fully absorbed in the negative electrode. Is deposited as lithium metal on the surface of the negative electrode, and deterioration of charge / discharge cycle characteristics and safety due to the deposition of lithium metal becomes a problem, but the resin tape 45 is attached to the positive electrode connecting piece 24a that wraps around the end of the negative electrode plate 12. By being adhered, the lithium ions released from the positive electrode connecting piece 24a can be reduced, and the precipitation of lithium metal on the facing negative electrode plate 12 can be suppressed.

As shown in FIG. 6, the deposition of the lithium metal is fine in a portion 47 located between the end of the separator 13 on the winding start side of the negative electrode plate 12 and the positive electrode connecting piece 24a of the positive electrode plate 11. It can also be suppressed by performing a hole sealing process. Since the separator 13 holds an electrolytic solution and does not hinder the ionic conductivity, a microporous film made of a polyolefin resin having a sufficient opening area is used.
By moving the end of the separator 13 on the winding start side of the negative electrode plate 12 and the positive electrode connecting piece 24a of the positive electrode plate 11 to close the pores, the positive electrode connecting piece 24a moves to the end of the negative electrode plate. Lithium ions can be limited, and lithium metal can be prevented from depositing on the negative electrode plate 12.

In the pore-sealing treatment, the negative electrode plate 12 of the separator 13 is coated with a coating agent that penetrates into the separator 13 and closes the pores.
Method for applying to the portion 47 located between the end portion on the winding start side of the positive electrode and the positive electrode connecting piece 24a of the positive electrode plate 11, the separator 1
No. 3 winding end side of the negative electrode plate 12 and the positive electrode connecting piece 24a of the positive electrode plate 11 which is melted by heat to close the pores, and the winding start side of the negative electrode plate 12 of the separator 13. It is possible to apply a method of attaching a resin tape to a portion 47 located between the end portion of the positive electrode plate 11 and the positive electrode connecting piece 24a of the positive electrode plate 11. However, the effect of preventing breakage of the positive electrode connecting piece 24a on the winding start side of the positive electrode plate 11 due to the pore sealing treatment cannot be expected.

[0025]

As described above, according to the present invention, when a flat rechargeable battery is constructed by using a wound electrode group, when the electrode group is wound flatly, The problem that the bent portion of the electrode plate is broken can be solved by a simple means of attaching the resin tape. Further, the adhesion of the resin tape can also suppress the generation of lithium dendrites. The generation of this lithium dendrite can be suppressed by the pore sealing treatment such as sticking a resin tape or applying a resin to the pores of the separator.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a flat battery.

FIG. 2A is a development view showing a negative electrode plate and FIG.

FIG. 3 is a schematic diagram showing a wound state of an electrode plate group.

FIG. 4 is a partial cross-sectional view showing a stuck state of a resin tape.

FIG. 5 is a partial cross-sectional view showing a method of attaching a resin tape.

FIG. 6 is a partial cross-sectional view showing a structure in which a separator is subjected to pore sealing treatment.

FIG. 7 is a developed view showing a conventional negative electrode plate and a positive electrode plate.

FIG. 8 is a schematic diagram showing a wound state of a conventional electrode plate group.

FIG. 9 is a sectional view of a conventional coin battery.

[Explanation of symbols]

10 electrode group 11 Positive plate 12 Negative electrode plate 13 separator 22a-22e Positive electrode laminated surface 23a to 23f Negative electrode laminated surface 24a-24d Positive electrode connecting piece 25a to 25e Negative electrode connecting piece 45 resin tape

Continued front page    (72) Inventor Satoshi Ogawa             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. (72) Inventor Akio Hakada             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5H029 AJ05 AJ11 AK03 AL06 AL07                       BJ03 BJ14 CJ02 CJ05 CJ07                       DJ04 DJ07 EJ12                 5H050 AA14 AA15 BA17 CA08 CB08                       DA02 DA09 DA12 DA19 EA23                       FA04 FA05 GA03 GA07 GA09                       GA22 GA23 HA04 HA12

Claims (6)

[Claims] 1. A positive electrode plate in which a plurality of positive electrode laminated surfaces are connected by connecting pieces using a positive electrode plate material in which a positive electrode active material layer is formed on both surfaces of a positive electrode current collector, and a strip-shaped positive electrode plate, and a negative electrode current collector. A negative electrode plate formed by using a negative electrode plate material having a negative electrode active material layer formed on both sides of the negative electrode laminated surface by connecting pieces to form a strip, the positive electrode laminated surface and the negative electrode laminated surface are separators. A flat type in which a group of electrode plates that are bent and flatly wound by the connecting pieces so that they are alternately stacked via a cap is housed in an internal space formed by covering a sealing case with a cap case through a gasket. In the battery, the flat battery is characterized in that an insulating resin tape is adhered to at least the inner surface side of the connecting piece located on the most winding start side of the positive electrode plate. 2. The resin tape comprises about 1 in the winding direction of the positive electrode plate.
The flat battery according to claim 1, wherein / 2 is formed on a non-adhesive surface that does not adhere to the connecting piece. 3. A positive electrode plate in which a plurality of positive electrode laminated surfaces are connected by connecting pieces using a positive electrode plate material in which a positive electrode active material layer is formed on both surfaces of the positive electrode current collector, and which is formed in a strip shape, and a negative electrode current collector. A negative electrode plate formed by using a negative electrode plate material having a negative electrode active material layer formed on both sides of the negative electrode laminated surface by connecting pieces to form a strip, the positive electrode laminated surface and the negative electrode laminated surface are separators. A flat plate group that is folded and flatly wound by the connecting pieces so as to be alternately laminated via a flat plate and is housed in an internal space formed by covering a sealing case with a cap case through a gasket. In the shaped battery, a separator interposed between at least the winding start side of the positive electrode plate and a winding start side end portion of the negative electrode plate facing the positive electrode plate is provided with a separator that closes pores existing in the separator. The feature is that it is hole-sealed. Flat-shaped battery to be. 4. The flat battery according to claim 3, wherein the pore sealing treatment applies a coating agent that penetrates into a part of the pores of the separator and closes the pores. 5. The flat battery according to claim 3, wherein in the pore sealing treatment, a part of the separator is heat-melted to close the pores. 6. The flat battery according to claim 3, wherein a resin tape is attached to a part of the separator for the pore sealing treatment.