JP3419272B2 - Battery - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to batteries.

[0002]

2. Description of the Related Art Lithium secondary batteries have recently attracted attention as batteries having a high battery capacity. In such a lithium secondary battery, an electrode laminated body which is a laminated body of a positive electrode plate and a negative electrode plate, a battery can that accommodates the electrode laminated body and is electrically connected to any one of the positive electrode plate and the negative electrode plate, and the positive electrode plate And a terminal that is electrically connected to the other side of the negative electrode plate and is led to the outside of the battery can in an insulated state from the battery can.

Such a structure is used not only for lithium secondary batteries but also for many batteries, but for some reason, the active material of the electrode (whether it is the positive electrode or the negative electrode, either electrode) When a short circuit occurs through
Since an active material having a high resistance is often used, it is considered that high heat is generated in the active material due to electric resistance. This high heat is not only dangerous, but depending on the active material, it is decomposed at a high temperature to release oxygen gas or the like, or abnormal gas is generated from the electrolyte or the like. Particularly in high-capacity batteries such as lithium secondary batteries, it is assumed that abnormal reaction occurs rapidly due to their high reaction activity, and a large amount of abnormal gas suddenly occurs in the battery can, causing rupture. It

Therefore, conventionally, such a battery is equipped with a safety device such as a fuse for shutting off an abnormal current to shut off an abnormal current or a safety valve for letting gas generated in a battery can escape to the outside to prevent accidents such as rupture. Has been done. By the way, when the fuselage of a device loaded with a battery is damaged by being subjected to a strong pressure such as a collision, the damaged part made of a conductor such as metal and having a sharp tip will be stabbed into the battery. It is possible that Examples of the case where such a sharp conductor pierces the battery include the following three piercing methods.

One is the case where a sharp conductor penetrates the battery can and penetrates into the inside of the electrode laminate. In this case, the collector of the positive electrode plate, the collector of the negative electrode plate, and the battery can are short-circuited via the pierced conductor. Therefore, a short-circuit current does not flow in the active material of the electrode, and the active material does not generate high heat due to electric resistance. the other one is,
This is the case when the battery can penetrates but the sharp conductor is pierced only up to the outermost peripheral surface of the electrode laminate.
This also includes a state in which the tip of the sharp conductor is not sticking firmly to the outermost peripheral surface of the electrode laminated body and is in contact therewith. in this case,
If there is an active material layer on the outermost peripheral surface, the electrode laminate and the battery can are short-circuited through this active material layer, and high heat is generated by the active material. In such a short circuit, the short circuit current may flow around the fuse and the fuse may fail.

The other one is the case where a sharp conductor is stuck in a place where a safety valve or a fuse is provided. In this case, the safety valve and the fuse may be destroyed and their accident prevention function may not work. This does not necessarily mean that this does not actually occur because the connection part with the electrode terminal of the device is provided from the metal conductor and the safety valve and the fuse are often provided in the position close to the electrode terminal. .

If the safety valve and the fuse do not function well as in the latter two cases, it may be possible to induce a secondary accident such as a battery rupture. Therefore, only providing the safety valve and the fuse is not sufficient as a safety measure when a sharp conductor is stuck in the battery. In order to solve such a problem, in JP-A-8-153542, JP-A-8-203541, JP-A-8-203562, and JP-A-8-264206, a strip-shaped electrode plate is wound and formed. In the battery including the electrode laminated body or the electrode laminated body formed by laminating plate-shaped electrode plates, and the battery can that conducts to the negative electrode of the electrode laminated body, the positive electrode plate is arranged on the outermost surface of the electrode laminated body. Then, a battery is disclosed in which the current collector is exposed outside the positive electrode plate, and an insulator is interposed between the exposed current collector and the battery can.
If a sharp conductor such as a nail pierces this battery, a short-circuit current will flow between the collector of the electrode laminate, the exposed collector and the battery can through the sharp conductor, causing a short circuit in the electrode active material. Almost no short-circuit current flows. As a result, heat generation due to a short circuit current flowing through the electrode active material is suppressed, and the battery is prevented from bursting.

By the way, in the battery having the insulator interposed between the exposed current collector and the battery can as described above, PE (polyethylene), PP (polypropylene) and PP- are used as the material of the insulator. It is common to use a copolymer of PE, but the tensile elongation of PE and PP is 70 to 160% in the MD (winding) direction and 500 to 1000% in the TD (film width) direction. So big. In a battery using an insulator made of a material having such a large tensile elongation, for example, when the tip of a sharp conductor is pierced slightly slowly, the insulator is stretched and exposed as a sharp conductor pierced. An insulator may be caught between the collector and the collector. As a result, the contact resistance between the sharp conductor and the exposed current collector increases, and it can be considered that high-temperature heat is generated when a short-circuit current flows there. Such high heat may affect the electrode active material, the electrolytic solution, etc., and may cause a danger such as ignition of the battery.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and even if a sharp conductor is stuck in a battery to cause a short circuit, high-temperature heat is generated when a short-circuit current flows. The purpose of the present invention is to provide a battery that is free from the dangers such as ignition of the battery.

[0010]

A battery according to the present invention is an electrode laminate which is a laminate of a positive electrode plate and a negative electrode plate, and the electrode laminate is housed to conduct electricity to either the positive electrode plate or the negative electrode plate. A battery can, and a terminal that is electrically connected to the other of the positive electrode plate and the negative electrode plate and is led to the outside of the battery can in an insulated state from the battery can.
An equipotential body that is disposed along the inner peripheral surface of the battery can so as to cover the electrode laminated body and is electrically connected to the other of the positive electrode plate and the negative electrode plate, and completely encloses the periphery of the equipotential body. And a bag-shaped insulator that is disposed in the battery can and the electrode laminate to insulate the battery can and the electrode laminate, and the insulator has a tensile elongation of less than 50%.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The battery of the present invention is not particularly limited by the type of battery, and can be applied to known batteries such as lithium secondary batteries. The overall shape of the battery is also not particularly limited, and it may be a prismatic or cylindrical battery. The form of the battery will be described below for each component.

The electrode laminate, which is a laminate of the positive electrode plate and the negative electrode plate, is not particularly limited in its laminated form, and known ones can be used. It is possible to use a sheet formed by winding a sheet with a separator or the like interposed therebetween, or a sheet in which a positive electrode plate and a negative electrode plate each having a rectangular shape are laminated with a separator provided therebetween.

As the positive electrode plate, an electrode formed by applying a positive electrode active material on at least one surface of a positive electrode current collector can be used. The material and the like of the positive electrode current collector and the positive electrode active material can be appropriately selected according to the type of battery, and known materials can be used. For example, in the case of a lithium secondary battery, a metal foil of aluminum, titanium, stainless steel or the like can be used for the positive electrode current collector, and LiC for the positive electrode active material.
It is possible to use oO ₂ , lithium composite oxides such as Mn, Ni and Fe, and chalcogenide.

As the negative electrode plate, an electrode formed by applying a negative electrode active material to at least one surface of a negative electrode current collector can be used. For the negative electrode current collector and the negative electrode active material, the material and the like can be appropriately selected according to the type of battery, and known materials can be used. For example, if it is a lithium secondary battery,
A metal foil such as copper can be used, and a carbonaceous material such as graphite or amorphous carbon can be used as the negative electrode active material. The shape of the carbonaceous material is not particularly limited, and may be spherical, scaly, lumpy, fibrous, or the like.

The battery can can also have a known form, and the material and the like can be appropriately selected according to the type of battery. The terminals can also have a known form. The material of the equipotential body is not particularly limited as long as it has conductivity, and for example, a metal conductor having excellent conductivity such as aluminum, titanium, and stainless can be used. The thickness is also not particularly limited and can be appropriately selected.

As the insulator, one having a tensile elongation of less than 50% is used.
Examples include aramid resin (aromatic polyamide-based polymer), polyimide resin, glass, ceramics, and paper, and it is preferable to use at least one of the materials listed here. Aramid resin is particularly preferable because it has a small tensile elongation. The thickness is not particularly limited and can be appropriately selected.

[0017] In addition, if non-aqueous electrolyte secondary battery such as a lithium secondary battery, ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, a mixed organic solvent such as dimethyl carbonate,
An electrolytic solution in which a lithium salt such as LiPF ₆ or LiBF ₄ is dissolved as a solute can be used.

[0018]

In the battery of the present invention, even if a sharp conductor is stabbed to cause a short circuit, high temperature heat is not generated when a short circuit current flows. For example, even when the tip of a sharp conductor is pierced slightly slowly, the insulator does not stretch because the insulator has a relatively small tensile elongation of less than 50%. The insulator is not caught in the body. Therefore, the wound insulator does not increase the contact resistance between the sharp conductor and the exposed current collector, and the short-circuit current flowing therethrough does not generate high-temperature heat. Therefore, there is no danger of ignition of the battery.

[0019]

EXAMPLES The present invention will be specifically described below with reference to examples. In the following description, the vertical direction is defined by the vertical direction in the reference diagram. (Embodiment 1) As shown in the longitudinal sectional view of FIG. 1, the battery of this embodiment is a battery can which is a spirally laminated electrode laminate 110, and which houses the electrode laminate 110 and is electrically connected to the negative electrode plate 114. 12
0, and a terminal 130 that is electrically connected to the positive electrode plate 112 and is guided to the outside of the battery can 120 in an insulated state from the battery can 120, and is a cylindrical lithium secondary battery.

This lithium secondary battery 100 has a battery can 1
The positive electrode plate 112 and the negative electrode plate 114 are arranged along the inner peripheral surface of the electrode stack 20 so as to substantially cover the side peripheral surface of the electrode laminate 110.
Of the equipotential body 140 electrically connected to the other of the
And an insulator 150 that is disposed around the battery can 120 and insulates the battery can 120 and the electrode stack 110 from each other. The electrode laminate 110 is formed by stacking a strip-shaped positive electrode plate 112 and a negative electrode plate 114 with a separator 116 interposed between them and winding them. Positive electrode plate 112
Is a current collector 1 made of an aluminum foil having a thickness of 20 μm.
A positive electrode active material 112b containing LiCoO ₂ as a main component was applied to both surfaces of 12a to a thickness of 180 μm to form a positive electrode active material 112b. On the other hand, the negative electrode plate 114 was formed by applying a negative electrode active material 114b made of a carbonaceous material to a thickness of 170 μm on both surfaces of a current collector 114a made of a copper foil having a thickness of 18 μm. The negative electrode plate 114 located at the outermost periphery of the electrode stack has the negative electrode active material 114b only on the inner side, and the negative electrode current collector is exposed on the outer side. In addition, the separator 116 has a thickness of 25 μm.
m polyethylene porous membrane was used.

The battery can 120 is composed of a main body portion 122 of a cylindrical bottomed container and a lid portion 124. Both the main body portion 122 and the lid portion 124 are made of nickel-plated steel plate. A through hole into which the terminal 130 can be fitted is provided at the center of the lid portion 124. The main body 122 of the battery can 120 is electrically connected to the negative electrode on the outermost surface of the electrode stack 110 via the conductive member 160. The terminal 130 is a positive electrode terminal made of aluminum and having a cylindrical shape.
A fixing member 132 made of an insulating material is joined and fixed to the through hole of the lid portion 124 on the side peripheral surface thereof.

The equipotential body 140b is formed by winding a strip-shaped aluminum foil having a thickness of 20 μm around the electrode laminated body 110. This equipotential body is the electrode stack 110.
Connected to the outermost positive electrode current collector 112a of
It has the same potential as the positive electrode plate 112. The insulator 150 is
It is made of an aramid resin having a tensile elongation of 10%, has a bag shape, and completely encloses the equipotential body 140. This insulator has a thickness of 12 μm per layer.

As the electrolytic solution (not shown), a solution prepared by dissolving 1 mol / l of LiPF ₆ as a solute in a mixed organic solvent of ethylene carbonate and propylene carbonate was used. (Example 2) The battery of this example is the same as Example 1 except that the insulator is made of a polyimide resin having a tensile elongation of 40%. (Comparative Example 1) In the battery of Comparative Example 1, the insulator is 100%.
Other than polyethylene resin, which has a tensile elongation of
It is the same battery as that of Example 1 .

[ Evaluation of Battery Safety] For each of the batteries of Example 1, Example 2 and Comparative Example 1, φ was applied to each battery.
A 2.5 mm nail was slowly pierced at a rate of about 0.1 mm / sec until the tip of the nail pierced through the insulator and reached an equipotential body. At this time, the electrical resistance between the nail and the equipotential body was measured, and the presence or absence of ignition of the battery due to a short circuit was observed. FIG. 2 shows the measurement result of the electric resistance of each battery. Further, in the invention described in claim 3,
Thermal expansion of the layer closest to the substrate (10) in the protective layer (60)
Characteristic is that the coefficient is in the same order as the substrate
There is. According to it, even when the device operates at high temperature,
The protective film is also deformed along with the substrate and the layered material that covers
Therefore, it is preferable to prevent the occurrence of pinholes.

In the batteries of Examples 1 and 2, the insulator was not caught between the nail and the equipotential body.
As can be seen from the above, the electric resistance of 29 mΩ was measured for the battery of Example 1, and the electric resistance of 7 mΩ was measured for the battery of Example 2. In the batteries of these examples, high-temperature heat was not generated even when a short-circuit current flowed between the nail and the equipotential body. The short circuit stopped after a while, the fever subsided and no ignition occurred.

On the other hand, in the battery of Comparative Example 1, an insulator was wound between the nail and the equipotential body, and an electric resistance of 67 mΩ was measured. In the battery of Comparative Example 1, as a short-circuit current flows between the nail and the equipotential body, heat is generated and high heat is generated in this portion, which leads to ignition. From this result, using an insulator having a tensile elongation of less than 50% prevents the insulator from being caught between the sharp conductor and the equipotential body,
It can be seen that high-temperature heat is prevented from being generated when a short-circuit current flows through this, and ignition is prevented.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing a vertical cross section of a battery of Example 1.

FIG. 2 is a graph showing the results of measuring the electric resistance between the nail and the equipotential body for each of the batteries of Example 1, Example 2 and Comparative Example 1.

[Explanation of symbols]

100: Lithium secondary battery 110: Electrode laminated body 11
2: Positive electrode plate 114: Negative electrode plate 120: Battery can 13
0: Terminal 140: Equipotential body 150: Insulator

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Hasegawa, 1-1, Showa-cho, Kariya city, Aichi prefecture, Denso Co., Ltd. (72) Inventor, Naoki Ueda, 1-1, Showa-cho, Kariya city, Aichi prefecture, Denso company ( 56) References JP-A-8-153542 (JP, A) JP-A-7-335228 (JP, A) JP-A-9-161757 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 10/40 H01M 2/14-2/18 H01M 2/20-2/34

Claims (3)

(57) [Claims] 1. An electrode laminated body, which is a laminated body of a positive electrode plate and a negative electrode plate, a battery can containing the electrode laminated body and conducting with either one of the positive electrode plate and the negative electrode plate, the positive electrode plate and the A terminal that is electrically connected to the other of the negative electrode plate and is guided to the outside of the battery can in an insulated state from the battery can, and the positive electrode plate is provided along the inner peripheral surface of the battery can so as to cover the electrode laminate. And the equipotential body that is electrically connected to the other of the negative electrode plate and the periphery of the equipotential body.
And a bag-shaped insulator that is disposed so as to be wrapped around the battery can and insulates it from the electrode stack, the insulator having a tensile elongation of less than 50%. battery. 2. The battery according to claim 1, wherein the insulator is made of at least one of aramid resin, polyimide resin, glass, ceramics and paper. 3. The battery according to claim 1, wherein the insulator is integrally formed on a surface of the equipotential body.