JPH1197066A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease risks such as firing of a battery without generating high- temperature heat when short-circuit current is allowed to flow, even if short circuit is generated caused by sticking of a sharp conductor in the battery, by setting the tensile extension degree of an insulator to a specified value. SOLUTION: An insulator having the tensile extension degree not more than 50% is used for an insulator 150. As the material, Alamid resin, polyimide resin, glass, ceramics, and paper can be included. Accordingly, since the insulator 150 has the relative low tensile extension degree not more than 50%, the insulator is not extended even if the tip of a sharp conductor is slowly stuck in it, and the insulator is not caught between the sharp conductor and a positive electrode collector 112a. Accordingly, the contact resistance of the sharp conductor and the positive electrode collector 112a is not increased caused by the caught insulator, and high-temperature heat is not generated caused by short- circuit current to be allowed to flow to it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a battery.

[0002]

2. Description of the Related Art A lithium secondary battery has recently attracted attention as a battery having a high battery capacity. In such a lithium secondary battery, an electrode laminate that is a laminate of a positive electrode plate and a negative electrode plate, a battery can that houses the electrode laminate and conducts with one of the positive electrode plate and the negative electrode plate, And a terminal electrically connected to the other of the negative electrode plates and led out of the battery can insulated from the battery can.

[0003] Such a configuration is employed not only for lithium secondary batteries but also for many batteries, but for some reason the active material of the electrode (whether positive or negative or either electrode). When a short circuit occurs via
Since an active material having a high resistance is often used, high heat may be generated in the active material due to electric resistance. This high heat is not only dangerous, but also decomposes at a high temperature depending on the active material to release oxygen gas or the like, or an abnormal gas is generated from the electrolyte or the like. In particular, in high capacity batteries such as lithium secondary batteries, the abnormal reaction of the battery occurs rapidly due to its high reaction activity. You.

Conventionally, such batteries have been provided with safety devices such as a fuse for interrupting the current path to stop abnormal current and a safety valve for releasing gas generated in the battery can to the outside to prevent accidents such as rupture. It has been done. By the way, when the body of a device loaded with a battery is damaged by being subjected to strong pressure such as a collision or the like, a damaged portion made of a conductor such as a metal and having a sharp tip stabs the battery. Something like that is possible. Examples of the case where such a sharp conductor stabs the battery include the following three stab methods.

[0005] One is a case where a sharp conductor penetrates through a battery can and penetrates into the electrode laminate. In this case, the current collector of the positive electrode plate, the current collector of the negative electrode plate, and the battery can are short-circuited via the pierced conductor. Therefore, no short-circuit current flows through 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 where the battery can penetrated, but the sharp conductor was only pierced up to the outermost peripheral surface of the electrode laminate.
This includes a state in which the tip of the sharp conductor is not firmly stuck and is in contact with the outermost peripheral surface of the electrode laminate. in this case,
If there is an active material layer on the outermost peripheral surface, the electrode laminate and the battery can short-circuit through the active material layer, and high heat is generated by the active material. In such a short circuit, a short circuit current may flow around the fuse, and the fuse may not function.

[0006] The other case is a case where a sharp conductor pierces 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 functions may not work. This does not necessarily occur in practice because the connection between the terminal of the electrode of the device and the terminal is provided from a metal conductor, and the safety valve and the fuse are often provided at a position close to the electrode terminal. .

[0007] As in the latter two examples, when the safety valve or the fuse does not work well, it is conceivable that a secondary accident such as a rupture of the battery is induced. Therefore, simply providing a safety valve or a fuse is not sufficient as a safety measure when a sharp conductor pierces a battery. To cope with such a problem, Japanese Patent Application Laid-Open Nos. 8-153542, 8-203541, 8-203562, 8-264206, and the like disclose a method in which a belt-shaped electrode plate is wound. A positive electrode plate is disposed on the outermost surface of the electrode laminate in a battery including: an electrode laminate, or an electrode laminate formed by laminating plate-like electrode plates; and a battery can that conducts with a negative electrode of the electrode laminate. A battery is disclosed in which a current collector is exposed outside the positive electrode plate, and an insulator is interposed between the exposed current collector and a battery can.
When a sharp conductor such as a nail is pierced into this battery, a short-circuit current flows between the current collector of the electrode stack, the exposed current collector, and the battery can through the sharp conductor, and the Has almost no short-circuit current. As a result, heat generation due to a short-circuit current flowing through the electrode active material is suppressed, and rupture of the battery is prevented.

By the way, in a battery provided with an insulator interposed between the exposed current collector and the battery can, PE (polyethylene), PP (polypropylene) and PP- Generally, a copolymer using PE is used. The tensile elongation of PE or PP is 70 to 160% in the MD (winding) direction and 500 to 1000% in the TD (film width) direction. So big. In such a battery using an insulator made of a material having a high tensile elongation, for example, when the tip of a sharp conductor is stabbed a little slowly, the insulator is stretched and exposed to the pierced sharp conductor. An insulator may be entangled between the current collector. As a result, the contact resistance between the sharp conductor and the exposed current collector increases, and it is conceivable that high-temperature heat is generated when a short-circuit current flows through the current collector. Such high heat affects the electrode active material, the electrolyte, and the like, and may cause danger such as ignition of the battery.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. Even when a sharp conductor pierces a battery to cause a short circuit, high-temperature heat is generated when a short-circuit current flows. It is an object of the present invention to provide a battery that does not have any danger such as ignition of the battery.

[0010]

According to the present invention, there is provided a battery according to the present invention comprising: an electrode laminate which is a laminate of a positive electrode plate and a negative electrode plate; A battery can, and a terminal led out of the battery can in an insulated state with the other of the positive electrode plate and the negative electrode plate and insulated from the battery can,
An equipotential body disposed along the inner peripheral surface of the battery can so as to cover the electrode stack and electrically connected to the other of the positive electrode plate and the negative electrode plate; and an equipotential body disposed around the equipotential body. A battery comprising: the battery can and an insulator that is insulated from the electrode stack, wherein 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 a lithium secondary battery. Also, the overall shape of the battery is not particularly limited, and may be a square or cylindrical battery. Hereinafter, the form of the battery will be described for each component.

[0012] The electrode laminate, which is a laminate of the positive electrode plate and the negative electrode plate, is not particularly limited in the form of lamination, and a known one may be used. May be formed by winding with a separator or the like interposed therebetween, or may be formed by laminating a square-shaped positive electrode plate and a rectangular negative electrode plate with a separator or the like interposed therebetween.

As the positive electrode plate, an electrode formed by applying a positive electrode active material to at least one surface of a positive electrode current collector can be used. Materials and the like for the positive electrode current collector and the positive electrode active material can be appropriately selected according to the type of the 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 is used for the positive electrode active material.
oO ₂ , lithium composite oxides such as Mn, Ni and Fe, chalcogenides and the like can be used.

As the negative electrode plate, an electrode formed by applying a negative electrode active material on at least one surface of a negative electrode current collector can be used. Materials and the like can be appropriately selected for the negative electrode current collector and the negative electrode active material according to the type of the 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, flaky, massive, or fibrous.

[0015] The battery can can also be in a known form, and the material and the like can be appropriately selected according to the type of the battery. The terminal may be in a known form. The material of the equipotential body is not particularly limited as long as it has conductivity. For example, a metal conductor having excellent conductivity such as aluminum, titanium, and stainless steel can be used. The thickness is not particularly limited and can be appropriately selected.

As the insulator, one having a tensile elongation of less than 50% is used.
Examples thereof include an aramid resin (aromatic polyamide-based polymer), a polyimide resin, glass, ceramics, and paper, and are preferably made of at least one of the materials mentioned here. In particular, aramid resin is preferable because of its low tensile elongation. The thickness is not particularly limited and can be appropriately selected.

Further, the insulator may be integrally formed on the surface of the equipotential body. Such an insulator can be formed by a film formation method such as a chemical vapor deposition method (CVD method). In the case of a non-aqueous electrolyte secondary battery such as a lithium secondary battery, a mixed organic solvent such as ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, or dimethyl carbonate contains L.
An electrolyte in which a lithium salt such as iPF ₆ or LiBF ₄ is dissolved as a solute can be used.

[0018]

In the battery of the present invention, even when a sharp conductor is pierced and short-circuited, high-temperature heat is not generated when a short-circuit current flows. For example, even when the tip of a sharp conductor is pierced a little slowly, the insulator does not stretch because the insulator has a relatively small tensile elongation of less than 50%. No insulator is trapped between the body. Therefore, the contact resistance between the sharp conductor and the exposed current collector is not increased by the wound insulator, and high-temperature heat is not generated by the short-circuit current flowing therethrough. Therefore, there is no danger such as ignition of the battery.

[0019]

The present invention will be described below in detail with reference to examples. In the following description, the vertical direction is defined by the vertical direction in the reference diagram. (Example 1) As shown in a longitudinal sectional view of FIG. 1, a battery of this example has a wound laminated electrode laminate 110 and a battery can that houses the electrode laminate 110 and conducts with a negative electrode plate 114. 12
0 and a terminal 130 electrically connected to the positive electrode plate 112 and led out of the battery can 120 in an insulated state with respect to the battery can 120.

The lithium secondary battery 100 includes a battery can 1
The positive electrode plate 112 and the negative electrode plate 114 are disposed along the inner peripheral surface of the electrode stack 20 so as to substantially cover the side peripheral surface of the electrode laminate 110.
An 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 laminating a strip-shaped positive electrode plate 112 and a strip-shaped negative electrode plate 114 with a separator 116 interposed therebetween, and winding these. 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 the layer 12a to a thickness of 180 μm to form a film. 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 laminate has the negative electrode active material 114b only on the inner side, and the negative electrode current collector is exposed on the outer side. The separator 116 has a thickness of 25 μm.
m of polyethylene porous membrane was used.

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

The equipotential body 140b is formed by winding a strip-shaped aluminum foil having a thickness of 20 μm around the electrode laminate 110. This equipotential body is the electrode stack 110
Is connected to the outermost positive electrode current collector 112a of
It has the same potential as the positive electrode plate 112. The insulator 150
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 an 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. (Embodiment 2) The battery of this embodiment is the same as that of Embodiment 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 was 100%
Other than polyethylene resin with tensile elongation of
This is the same battery as in Example 1. (Embodiment 3) The battery of this embodiment is the same as Embodiment 1 except that an insulator 250 is integrally formed on the surface of the equipotential body 240 as shown in a longitudinal sectional view of FIG. A wound electrode stack 210, a battery can 220 containing the electrode stack 210 and conducting with the negative electrode plate 214, and a positive electrode plate 212.
And a terminal 230 led out of the battery can 220 in an insulated state with the battery can 220 and a cylindrical lithium secondary battery.

The insulator 250 is made of S formed by the CVD method.
This is a thin film made of iN and has a thickness of 20 μm per film. Note that the positive electrode current collector 212 located at the center of the positive electrode 212
a has an extension extending upward, and the tip of this extension is connected to the terminal 230. A conductive member 260 is attached to a part of the extension, and the equipotential body 240 The conductive member 260 is electrically connected to the positive electrode plate. [Evaluation of Battery Safety] For each of the batteries of Example 1, Example 2, and Comparative Example 1, a nail of φ2.5 mm was slowly inserted into each battery at a speed of about 0.1 mm / sec.
The nail was pierced until the tip of the nail penetrated the insulator and reached the equipotential body. At this time, the electric resistance between the nail and the equipotential body was measured to observe whether or not the battery was ignited due to the short circuit. FIG. 3 shows the measurement results of the electric resistance of each battery.

In the batteries of Examples 1 and 2, the insulator is not entangled between the nail and the equipotential body,
As can be seen from the graph, the battery of Example 1 measured an electric resistance of 29 mΩ, and the battery of Example 2 measured an electric resistance of 7 mΩ. 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 ceased after a while, and the fever subsided and no fire occurred.

On the other hand, in the battery of Comparative Example 1, an insulator was involved 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 flowed between the nail and the equipotential body, heat was generated at this portion and high heat was generated, leading to ignition. From this result, the use of the 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 when a short-circuit current flows, generation of high-temperature heat is prevented, and ignition is prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a longitudinal section of a battery of Example 1.

FIG. 2 is a longitudinal sectional view schematically showing a longitudinal section of the battery of Example 3.

FIG. 3 is a graph showing the results of measuring the electrical resistance between the nail and the equipotential body for each of the batteries of Example 1, Example 2, and Comparative Example 1.

[Description of Signs] 100: Lithium secondary battery 110: Electrode laminate 11
2: positive electrode plate 114: negative electrode plate 120: battery can 13
0: terminal 140: equipotential 150: insulator

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Takeshi Hasegawa 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Naoki Ueda 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Denso Corporation Inside

Claims (3)

[Claims] An electrode laminate, which is a laminate of a positive electrode plate and a negative electrode plate, a battery can that houses the electrode laminate and conducts with one of the positive electrode plate and the negative electrode plate; A terminal connected to the other of the negative electrode plates and led out of the battery can in an insulated state with the battery can; and a positive electrode plate disposed so as to cover the electrode laminate along an inner peripheral surface of the battery can. A battery comprising: an equipotential body electrically connected to the other of the negative electrode plates; and an insulator disposed around the equipotential body and insulated from the battery can and the electrode stack. A battery, wherein the body has a tensile elongation of less than 50%. 2. The battery according to claim 1, wherein said 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.