JPH08273697A - Winding type battery - Google Patents

Abstract

PURPOSE: To provide a winding type battery whose safety can be secured by restraining a temperature rise in a positive electrode active material when a short circuit is caused by crushing in the layering direction in the winding type battery having a coil-shaped electrode plate layered body in which positive- negative electrode plates and a separator are layered by winding. CONSTITUTION: A center pin 3a composed of a coil spring is arranged in the winding center of an electrode plate layered body 1A. When a battery is crushed in the layering direction of the electrode plate layered body 1A, an inner peripheral side part of the electrode plate layered body 1A bites into a clearance of the coil spring 3a, and in this condition, the coil spring 3a inclines by extending in the axial direction while being crushed. Therefore, since the electrode plate layered body 1A is ruptured over a wide range from inside, a positive electrode plate 11 and a negative electrode plate 12 are short-circuited to each other over a wide range.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode plate having a collector foil coated with a positive electrode active material, a negative electrode plate having a collector foil coated with a negative electrode active material, and a separator. The present invention relates to a wound-type battery in which a coil-shaped electrode plate laminate is formed by stacking and is housed in a battery can, and more particularly to a wound battery that can be safely internally discharged even when crushed in the stacking direction.

[0002]

2. Description of the Related Art Lithium ion using a non-aqueous electrolyte
Rechargeable batteries have high voltage, high capacity and high output
Because it is light, it has been adopted as a power source for portable electronic devices.
is there. In such a lithium ion secondary battery,
Generally, aluminum foil is used as the current collector for the positive electrode.
In addition, the lithium composite oxide (LiCoO
₂Etc.) to form a positive electrode plate.
In addition, copper foil was used as the current collector of the negative electrode, and the negative electrode active material
Is applied to form a negative electrode plate by applying a material containing carbon.
A porous polyethylene with a fine pore size as a separator between
The electrode plate laminate wound in a spiral shape with a
It is housed in a cylindrical cylindrical metal battery can.

As a structure of an electrode plate laminate in a lithium ion secondary battery currently in circulation, there is one positive electrode plate having an active material coating on both sides of an aluminum foil and an active material coating on both sides of a copper foil. There is one in which one negative electrode plate and two separators are layered in the order of a negative electrode plate, a separator, a positive electrode plate, and a separator, and are spirally wound so that the negative electrode plate is on the outside. Further, two positive electrode plates having an active material coating on one side of the aluminum foil, one negative electrode plate having an active material coating on both sides of the copper foil, and two separators, a negative electrode plate,
There is also a separator, two positive electrode plates (the aluminum foil sides are aligned with each other, the active material film side is arranged outward), the separators are stacked in this order, and the negative electrode plate is wound outward in a spiral shape. .

That is, there is a difference in whether a current collector foil has active material coatings on both sides or two current collector foils having an active material coating on one surface are stacked, but in any case, the electrode is The plate laminate has a positive electrode active material, a positive electrode side current collector foil, a positive electrode active material,
The separator, the negative electrode active material, the negative electrode side current collector foil, the negative electrode active material, the separator, and the positive electrode active material are laminated in this order.

[0005]

In such a lithium ion secondary battery, the safety in the case where the temperature inside the battery rises due to a short circuit between the positive electrode and the negative electrode due to circuit abnormality or incorrect usage, etc. To ensure the safety valve,
Although it is equipped with a thermal fuse, a PTC element, etc., further safety measures are required in preparation for various operating environments and unexpected accidents.

For example, when a nail such as a conductor is stabbed in a battery, the tip of the nail penetrates the battery can, which is the negative electrode, and comes into contact with the internal positive electrode plate in the negative electrode state.
A short circuit occurs through this nail. Further, when the battery is abnormally heated from the outside, the separator, which is an organic material, first melts, so that the positive electrode plate and the negative electrode plate, which are insulated by the separator, come into contact with each other to cause a short circuit. Furthermore, when the battery is crushed in the stacking direction of the electrode plate laminate, a large stress is applied to the inner peripheral side of the electrode plate laminate, the separator is broken, and the positive electrode plate and the negative electrode plate come into contact with each other to cause a short circuit.

At the time of such a short circuit, the lithium composite oxide (positive electrode active material) has a relatively high resistance value among the members constituting the electrode plate laminate, so that the temperature of the lithium composite oxide is reduced by the passage of the short circuit current. Easy to rise. Then, the heat generated by this temperature rise easily causes the decomposition reaction of the organic solvent inside the battery. Further, when such a short circuit occurs in the battery in the charged state, the lithium composite oxide in the charged state is in an unstable state in which lithium is released as ions to some extent. It is liable to be generated, and the oxygen easily causes a reaction in the aluminum foil or the organic solvent to which the lithium composite oxide is adhered.

From the above, a large amount of energy (chemical energy) is likely to be generated inside the battery due to the temperature rise of the positive electrode active material caused by the short circuit between the positive electrode active material and the negative electrode in the battery in the charged state, and It becomes difficult to secure the safety of. Therefore, as a safety measure in response to various use environments and unexpected accidents, in particular, the short circuit between the positive electrode active material and the negative electrode does not occur in the charged state, and when the short circuit occurs, the positive electrode active material rises. It is important to keep the temperature low, but the conventional structure does not take any measures against it.

The present invention has been made in view of the above-mentioned problems of the prior art, and has a wound type battery having a coiled electrode plate laminate in which a positive and negative electrode plates and a separator are laminated by winding. In the above, it is an object of the present invention to provide a material capable of suppressing the temperature rise of the positive electrode active material and ensuring safety when a short circuit occurs due to crushing in the stacking direction.

[0010]

In order to achieve the above object, the invention of claim 1 provides a positive electrode plate having a positive electrode active material deposited on a current collector foil, and a negative electrode active material on the current collector foil. In a wound type battery having an electrode plate laminate in which a deposited negative electrode plate and a separator are laminated by winding in a battery can, in a winding center of the electrode plate laminate, a peripheral surface of a bar material. The present invention provides a wound type battery, characterized in that a center pin having a concave portion continuous in the circumferential direction is provided on the.

The center pin having the above-mentioned shape has, for example, a screw shaft in which a concave portion having a predetermined width is spirally formed on the peripheral surface of the bar material, or not a spiral shape but along a circle of a cross section of the bar material. A large number of circumferential grooves are formed in the length direction. The rod may be solid or hollow, but it is preferable that the rod is hollow because the gas in the battery can is guided from the hollow portion toward the safety valve when the internal pressure rises. Incidentally, when the bar is hollow, the recess is
It is limited to the bar formed from the outer peripheral surface toward the inner peripheral surface side so as not to penetrate the inner peripheral surface.

According to a second aspect of the present invention, the positive electrode plate having the positive electrode active material deposited on the current collector foil, the negative electrode plate having the negative electrode active material deposited on the current collector foil, and the separator are wound. A wound-type battery having a laminated electrode plate laminate in a battery can, wherein a center pin made of a coil spring is provided at the winding center of the electrode-plate laminate. To do.

The coil spring is preferably one having a pitch larger than the diameter of the wire rod and having a gap between adjacent wire rods when no load is applied. The sectional shape of the wire is not particularly limited, and may be a circle or a polygon such as a rhombus.

[0014]

According to the battery of the first aspect, when the battery is crushed in the stacking direction of the electrode plate laminate (direction intersecting the axis), a large stress is applied to the inner peripheral side of the electrode plate laminate to cause the separator. Is broken, and the positive electrode plate and the negative electrode plate come into contact with each other to cause a short circuit. At that time, the inner peripheral side portion of the electrode plate laminate bites into the recess of the center pin and is broken in a wide range.

As a result, the center pin does not have such a recess, or the short circuit occurs in a wider range than in a wound battery having a structure without the center pin itself, so that the resistance value of the positive electrode active material is the current collector. Even when it is higher than the resistance value of the foil, the current flowing per unit volume of the positive electrode active material is small, and the temperature rise of the positive electrode active material is suppressed. According to the battery of claim 2, in the case of a short circuit caused by the above-mentioned crushing, the inner peripheral side portion of the electrode plate laminated body is pressed against the peripheral surface of the coil spring forming the center pin, and the gap is provided when the coil spring is unloaded. , The coil spring extends axially while being crushed with the above-mentioned portion biting into the gap, and tilts in the electrode plate laminate (the center axis of the coil spring is displaced from the winding center). From a wide range to the inside. Even if the pitch of the coil spring is equal to the diameter of the wire rod and there is no gap when there is no load, the inside of the electrode plate laminate will bite into the gap if the gap occurs between the wire rods, so that the same effect as above can be obtained. .

As a result, the short circuit occurs in a wider area than in the wound battery having the structure in which the center pin is not such a coil spring, so that the resistance value of the positive electrode active material is higher than that of the current collector foil. However, the current flowing per unit volume of the positive electrode active material is reduced, and the temperature rise of the positive electrode active material is suppressed.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an inner portion of a cylindrical wound battery corresponding to a first embodiment of the present invention, and FIG.
It is a front view which shows the center pin in this Example.

This battery is a non-aqueous lithium ion secondary battery in which the spirally wound electrode plate laminate 1 is housed in a cylindrical battery can. In FIG. 1, only the inner peripheral side of the electrode plate laminate 1 is shown, and the outer peripheral side and the battery can are omitted. The electrode plate laminate 1 includes a single positive electrode plate 11C in which a material containing LiCoO ₂ is applied as a positive electrode active material 11b on both sides of a current collector foil 11a made of aluminum,
A sheet of negative electrode plate 1 in which a material containing carbon particles is applied as a negative electrode active material 12b on both surfaces of a collector foil 12a made of copper.
2, two separators 13A and 13B composed of a polyethylene microporous film (thickness 35 μm) arranged between the positive electrode active material 11b and the negative electrode active material 12b, and connected to the separators 13A and 13B on the inner peripheral side, respectively. And insulating films 14A and 14B made of a polyethylene resin film (film thickness 12 μm) having no ion conductivity.

The layer structure of this electrode plate laminated body 1 has a separator 13B, a negative electrode active material 12b, a negative electrode side current collector foil 12a, a negative electrode active material 12b and a separator 13 except for the inner peripheral portion.
A, the positive electrode active material 11b, the positive electrode side current collector foil 11a, the positive electrode active material 11b, the separator 13B ... Regarding the inner peripheral portion, a current collector exposed portion 15 is formed on the positive electrode plate 11C, and a current collector exposed portion 16 is also formed on the negative electrode plate 12 facing inside the positive electrode plate 11C. The current collector exposed portion 15 on the positive electrode side is the positive electrode active material 1 on both surfaces of the positive electrode plate 11C.
It is formed by not depositing 1b on that portion. Similarly, the current collector exposed portion 16 on the negative electrode side is also formed by not depositing the negative electrode active material 12b on both surfaces of the negative electrode plate 12 at that portion.

The positive and negative electrode collector foil exposed portions 15,
In the portion adjacent to 16, each separator 13
Insulating films 14A and 14B (polyethylene resin film having no ion conductivity) connected to A and 13B are arranged.
Thereby, the separators (that is, the insulating films 14A and 14B) adjacent to the positive and negative electrode collector foil exposed portions 15 and 16 are formed.
Are separators 13A, 13 interposed between the active materials of both electrodes.
It is thinner than B.

On the other hand, a center pin 3 made of stainless steel as shown in FIG. 2 is inserted in the winding center of the electrode plate laminate 1. The center pin 3 is a solid screw shaft having a diameter of about 4 mm and a pitch of 0.7 mm, and has a spiral recess 31 on the peripheral surface. The depth ((“outer diameter” − “valley diameter”) / 2) of the recess 31 is about 0.5 mm. Also,
The tab 5 is fixed to the outer surface of the positive electrode side current collector 11a adjacent to the center pin 3.

Therefore, when the battery is crushed in the stacking direction, generally, the stress applied to the innermost insulating films 14A and 14B adjacent to the center pin 3 is the largest. Membrane 14A, 1
4B is broken, but the positive and negative electrode current collector foils 11a, 11a,
Only a short circuit between 12a occurs, and each substance of positive and negative electrodes 11
No short circuit between b and 12b occurs.

At this time, the inner peripheral portion of the electrode plate laminate 1 bites into the recess of the center pin 3 and is broken extensively. As a result, with respect to the crushing, most of the electric current is generated even in the short-circuited portion in the collector foils 11a, 1
2a and a short circuit current may also flow to the center pin 3. Therefore, the positive electrode active material 1 made of LiCoO ₂
The current flowing in 1b is reduced, and the temperature rise of LiCoO ₂ is suppressed. Therefore, even if the state of charge is short-circuited,
Generation of oxygen due to temperature rise of LiCoO ₂ and reaction of aluminum (positive electrode side current collector foil) and organic solvent (electrolyte solvent) due to this oxygen are suppressed, so that large energy is prevented from being generated inside the battery, The safety of the battery is ensured.

In this embodiment, the film thickness of the separators (that is, the insulating films 14A and 14B) adjacent to at least the outside of the positive and negative electrode current collector foil exposed portions 15 and 16 are interposed between the both electrode active materials. Since the separators 13A and 13B are thinner than the separators 13A and 13B, they can be stacked in a battery can of the same size as compared with the case where the separators 13A and 13B are directly extended to the outside of the positive and negative electrode collector foil exposed portions 15 and 16. Can increase the total length of the body. As a result, the electric capacity can be increased while ensuring the safety of the battery as described above.

FIG. 3 is a cross-sectional view showing a cylindrical wound battery corresponding to the second embodiment of the present invention, and FIG. 4 is a perspective view showing the center pin in this embodiment. This battery is a non-aqueous lithium-ion secondary battery as in the first embodiment, and the electrode plate laminate 1A has only one surface of a collector foil 11a made of aluminum, as shown in FIG. A positive electrode plate 11 coated with a material containing LiCoO ₂ as a positive electrode active material 11b, and a collector foil 12a made of copper
The material containing carbon particles is formed on only one surface of the negative electrode active material 12b.
As the negative electrode plate 12, a separator 13 composed of a polyethylene microporous film disposed between the positive electrode active material 11b and the negative electrode active material 12b, a positive electrode side current collector foil 11a and a negative electrode side current collector foil 12a. And an insulating film 14 made of the same film as that of the separator 13 disposed between and.

In this electrode plate laminate 1A, the positive electrode side current collector foil 11a, the positive electrode active material 11b, the separator 13, the negative electrode active material 12b, the negative electrode side current collector foil 12a and the insulating film 14 are laminated in this order for insulation. It is produced by setting the film 14 inside (that is, the positive electrode side current collector foil 11a outside), spirally winding it by a winding machine, and further winding the insulating film 14 on the outermost periphery. Accordingly, the layer structure of the electrode plate laminate 1A is
From the battery can 2 side toward the inside, the insulating film 14, the positive electrode side current collector foil 11a, the positive electrode active material 11b, the separator 13, the negative electrode active material 12b, the negative electrode side current collector foil 12a, the insulating film 14, the positive electrode side current collector. The electric foils 11a are in this order.

Further, in this electrode plate laminated body 1A,
A battery action occurs in the unit battery layer 4 formed of the positive electrode 11 and the negative electrode 12 in which the positive electrode active material 11b and the negative electrode active material 12b are arranged to face each other, and the separator 13 arranged therebetween, but the insulating film 14 Between the unit battery layers 4 that are interposed (that is, between the positive and negative current collector foils 11a and 12a)
Does not cause battery action.

The center pin 3a inserted into the winding center of this electrode plate laminate 1A is a stainless steel coil spring made of a wire having a circular cross section as shown in FIG. 4, and the diameter of the wire is 0. The pitch is 6 mm and the pitch is 1.6 mm. Therefore, 1.0 mm between adjacent wire rods when no load is applied.
There is a gap. Therefore, when the battery is crushed in the stacking direction, the innermost separator 13 adjacent to the center pin 3a and the insulating film 14 generally receive the largest stress. And the insulating film 14 is broken, and a short circuit occurs between the positive electrode active material 11b and the negative electrode active material 12b.
Almost at the same time, a short circuit occurs between the positive and negative current collector foils 11a and 12a.

At this time, the inner peripheral side portion of the electrode plate laminated body 1A is pressed against the peripheral surface of the coil spring 3a, and the coil spring 3a is crushed in a state in which this portion bites into the gap between the adjacent wire rods. The electrode plate laminated body 1A is extensively broken from the inside since it extends in the direction and tilts in the electrode plate laminated body 1A (the central axis of the coil spring 3a is displaced from the winding center).

Accordingly, regarding the crushing,
Most of the current is collected in the short-circuited portions as the collector foils 11a and 12a.
Flow into the positive electrode active material 11b made of LiCoO ₂ because a short circuit current may also flow to the center pin 3.
The current flowing through the device decreases and the temperature rise of LiCoO ₂ is suppressed. Therefore, even if the battery is short-circuited in the charged state, a large amount of energy is prevented from being generated inside the battery and the safety of the battery is ensured, as in the first embodiment.

In this embodiment, the electrode plate laminated body 1A is used.
When a conductor such as a sharp nail penetrates the battery can 2 and enters the inside of the battery, the tip of the conductor that becomes the negative electrode at the time of penetrating the battery can 2 has the insulating film 14 and the positive electrode. Side collector foil 11a, positive electrode active material 11b, separator 1
3, the negative electrode active material 12b, the negative electrode side current collector foil 12a, the insulating film 14 ... In this way, the positive electrode active material 11b and the negative electrode active material 1 via the conductor.
Although a short circuit with 2b occurs, as described above, since a short circuit occurs between the positive and negative current collectors 11a and 12a almost at the same time, most of the current is also collected in the short circuit portion.
It flows to a and is safely discharged internally. As a result, even in the case of a short circuit due to a nail piercing in a charged state, similar to the above, generation of large energy inside the battery is suppressed,
The safety of the battery is ensured.

Although the lithium ion secondary battery has been described in the above embodiment, the non-aqueous secondary battery or the non-aqueous primary battery other than the lithium ion secondary battery has a positive electrode active material having a relatively high resistance value. Can ensure the safety of the battery by the same operation as described above. Also,
The structure of the electrode plate laminated body is not limited to the special structure as in the above-mentioned embodiment, and may have a conventional structure. Further, it goes without saying that the combination of the electrode plate laminate and the center pin in each of the above embodiments may be different.

Then, in the electrode plate laminate having the conventional structure,
When the battery is crushed in the stacking direction (the direction intersecting the axis) of the electrode plate laminate, a short circuit occurs between the positive electrode active material and the negative electrode plate inside the electrode plate laminate. Since the center pin is made to rupture in a wide range from the inner peripheral side, a short circuit is promoted in a wider range as compared with a wound battery having a structure in which the center pin is made of a cylinder without a recess on the peripheral surface or having a center pin itself. Occurs in

As a result, even when the resistance value of the positive electrode active material is higher than that of the current collector foil, the current flowing per unit volume of the positive electrode active material is reduced and the temperature rise of the positive electrode active material is increased. Is suppressed, the safety of the battery is secured. Further, in each of the above-mentioned examples, since the stainless steel center pin is used, there is an effect that the corrosion resistance is high and a short-circuit current flows therethrough, but the material of the center pin in the present invention is not limited to this. It may be plastic or spring steel.

The coil spring that can be used as the center pin is not limited to the one described above, and it is assumed that a saw tooth-shaped recess is formed on the outer peripheral surface like a spring in which the wire rod has a rhombic cross section. Even in the case of a coil spring in which there is no gap between the adjacent wire rods when there is no load, the inner peripheral portion of the electrode plate laminate is likely to bite into the recessed portion during the crushing, which is preferable.

Further, in the center pin according to the first aspect, the degree of biting into the concave portion of the inner peripheral portion of the electrode plate laminate differs depending on the depth of the concave portion, and the deeper the concave portion, the higher the degree of biting, which is preferable. Further, in the center pin according to claim 2, the degree of biting differs depending on the gap between the adjacent wire rods of the coil spring, and the gap is 2 to the wire rod diameter.
It is preferably three times.

When both axial ends of the center pins 3 and 3a are formed into a tapered cylindrical body having a diameter smaller toward the end side, they can be easily inserted into the winding center of the electrode plate laminate 1, 1A. Become. In addition, when the center pin is made of a coil spring, the weight of the battery can be reduced.

[0038]

As described above, according to the first and second aspects.
According to the wound type battery, by devising the shape of the center pin, even if a short circuit occurs between the positive electrode active material and the negative electrode due to crushing in the stacking direction of the battery, the temperature rise of the positive electrode active material can be suppressed. Therefore, particularly when the battery is a lithium ion secondary battery, even if a short circuit occurs in the charged state, generation of a large amount of energy inside the battery is suppressed, and battery safety can be ensured.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a wound type battery according to a first embodiment of the present invention.

FIG. 2 is a front view showing a center pin in the first embodiment.

FIG. 3 is a schematic cross-sectional view showing a wound type battery according to a second embodiment of the present invention.

FIG. 4 is a perspective view showing a center pin according to a second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrode plate laminated body 1A Electrode plate laminated body 2 Battery can 3 Center pin 3a Coil spring (center pin) 31 Recessed portion 11 Positive electrode plate 11C Positive electrode plate 11a Positive electrode side current collector foil 11b Positive electrode active material 12 Negative electrode plate 12a Negative electrode side collection Electrical foil 12b Negative electrode active material 13 Separator 13A Separator 13B Separator

Claims (2)

[Claims] 1. An electrode plate in which a positive electrode plate having a collector foil coated with a positive electrode active material, a negative electrode plate having a collector foil coated with a negative electrode active material, and a separator are laminated by winding. A wound type battery having a laminated body in a battery can, characterized in that a center pin having a concave portion continuous in the circumferential direction on the peripheral surface of the rod is provided at the winding center of the electrode plate laminated body, A wound type battery. 2. An electrode plate in which a positive electrode plate having a current collector foil coated with a positive electrode active material, a negative electrode plate having a current collector foil coated with a negative electrode active material, and a separator are laminated by winding. A wound type battery having a laminate in a battery can, wherein a center pin made of a coil spring is provided at a winding center of the electrode plate laminate.