JP2000021386A - Battery - Google Patents

Abstract

(57) [Summary] [Problem] A coating layer 4 can be formed even when nailing or crushing occurs.
Provided is a battery capable of preventing a large current from flowing between electrodes due to elongation of the battery and improving safety. SOLUTION: A coating layer 4 which is a microporous non-electrically conductive polymer compound having a tensile elongation of 200% or more is formed on the surfaces of positive and negative electrodes 1 and 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery such as a wound type non-aqueous electrolyte secondary battery in which positive and negative electrodes are superposed and arranged in an electrolytic solution.

[0002]

2. Description of the Related Art A non-aqueous electrolyte secondary battery has a positive electrode in which a positive electrode active material such as lithium cobalt oxide is supported on a current collector such as aluminum foil, and a negative electrode active material such as graphite on a current collector such as copper foil. A power generating element is formed by winding or laminating a negative electrode carrying the same with a separator interposed therebetween.
Then, the power generation element is housed in a battery container and filled with a non-aqueous electrolyte to form a battery.

[0003] Since this non-aqueous electrolyte secondary battery uses a material that is more reactive than an aqueous electrolyte secondary battery, it is necessary to provide a particularly strict safety device. For this reason, conventionally, a safety valve for extracting high-pressure gas from the inside of the battery container has been provided, and a PTC element or a shutdown separator has been used to limit the current flowing when an external short circuit or an internal short circuit occurs. That is, the PTC element is a PTC ([Positiv
e Temperature Coefficient) This element has a characteristic. When the temperature inside the battery rises, the resistance increases, so the current that flows when an external short circuit occurs can be limited. In addition, the shutdown separator is a separator that melts at high temperatures and loses ion permeability.If it is inserted between the electrodes, the current that flows when an external short circuit or an internal short circuit occurs can be limited. Can be.

[0004]

However, when a sharp metal rod such as a nail is pierced into the battery, the metal rod 5 penetrates the separator 3 from the positive electrode 1 and reaches the negative electrode 2 as shown in FIG. become. Then, the current collector 1a and the positive electrode active material 1b of the positive electrode 1 directly contact the metal rod 5, and the current collector 2a and the negative electrode active material 2b of the negative electrode 2 directly contact the metal rod 5. An internal short circuit occurs between the negative electrode 2 and the metal rod 5. However, since the current flows only in the battery, the current limitation by the PTC element does not help, and even the shutdown separator cannot prevent a large current from flowing when the metal bar 5 pierces.

[0005] When the battery is crushed and crushed, the separator 3 may be broken. As a result, if the positive electrode 1 and the negative electrode 2 are internally short-circuited, the PTC element is not useful and the Even the separator cannot prevent a large current from flowing at first.

For this reason, in a conventional battery, particularly in the case of a large-capacity non-aqueous electrolyte secondary battery or the like used in an electric vehicle or the like, an extremely large short-circuit current flows at once if nailing or crushing occurs. There is a problem that sufficient safety cannot be maintained because the temperature instantaneously rises to high temperature and pressure.

The present invention has been made in view of such circumstances, and provides a battery capable of preventing a large current from flowing between electrodes and improving safety even when nailing or crushing occurs. It is intended to be.

[0008]

According to a first aspect of the present invention, there is provided a battery provided with an electrode group and an electrolyte solution in which positive and negative electrodes are stacked with a separator interposed therebetween, and at least one of the positive and negative electrodes is provided. The surface has ion permeability,
A coating layer having a tensile elongation of 200% or more is formed.

According to the first aspect of the present invention, since the coating layer having high elasticity or high ductility is formed on the positive and negative electrode surfaces,
Even when a nail or the like pierces these electrodes, the coating layer expands along the nail or the like. Since the film surface of the coating layer extending between the nail and the like and the current collector and the active material is interposed, a large short-circuit current is prevented from flowing between the positive and negative electrodes due to the low electric conductivity of the coating layer. be able to. Further, even when the battery is crushed and the separator is broken, the coating layer on the electrode surface extends and intervenes between the positive and negative electrodes instead of the separator, so that a large short-circuit current can be prevented from flowing. When the coating layer has high elasticity such as rubber, the rubber elasticity causes an extremely large elongation up to the breaking limit. Further, when the coating layer has a high ductility, the elastic layer exceeds the elastic limit and causes extremely large elongation due to plasticity.

The invention according to claim 2 is characterized in that the coating layer has a heat resistance of 150 ° C. or higher.

According to the second aspect of the present invention, it is possible to provide a safety device suitable for a non-aqueous electrolyte secondary battery requiring particularly high safety.

The invention according to claim 3 is characterized in that the coating layer is made of a fluorine-based polymer compound.

The invention according to claim 4 is characterized in that the coating layer contains a filler.

Further, the invention according to claim 5 provides a filler.
Is calcium carbonate, magnesium carbonate, magnesium oxide
Or aluminum oxide or a mixture thereof.

According to a sixth aspect of the present invention, there is provided a battery provided with an electrode group and an electrolytic solution in which positive and negative electrodes are stacked via a separator, and a tensile elongation of 200% or more and 150 ° C.
It is characterized by using a separator having the above heat resistance.

According to the sixth aspect of the present invention, the separator having high elasticity or high ductility is arranged between the positive and negative electrodes, so that even if a nail or the like pierces these electrodes, the separator can be directly penetrated. And elongation occurs along nails and the like. Since the film surface of the separator extends between the nail or the like and the current collector or active material, a large short-circuit current can be prevented from flowing between the positive and negative electrodes due to the insulating properties of the separator. Further, even when the battery is crushed, the separator is stretched, so that the battery is not broken. Thus, the insulation between the positive and negative electrodes can be maintained and a large short-circuit current can be prevented from flowing. When the separator has a high elasticity such as rubber, the rubber elasticity causes an extremely large elongation to the breaking limit. When the separator has high ductility, extremely large elongation occurs due to plasticity exceeding the elastic limit.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 3 show an embodiment of the present invention. FIG. 1 is a partially enlarged longitudinal sectional view showing the structure of positive and negative electrodes, and FIG. 2 is a view showing a power generating element of a non-aqueous electrolyte secondary battery. FIG. 3 is a partially enlarged longitudinal sectional view showing the state of the positive and negative electrodes when nail penetration has occurred.
Components having the same functions as those of the conventional example shown in FIG. 4 are denoted by the same reference numerals.

In this embodiment, a large-capacity non-aqueous electrolyte secondary battery used for an electric vehicle or the like will be described. As shown in FIG. 2, the nonaqueous electrolyte secondary battery forms a wound power generating element by winding a positive electrode 1 and a negative electrode 2 via a separator 3. As shown in FIG.
Is obtained by supporting a positive electrode active material 1b on the front and back surfaces of a current collector 1a made of a belt-like aluminum foil or the like. As the positive electrode active material 1b, lithium cobalt oxide or the like is used, and the positive electrode active material 1b is supported on the current collector 1a as a mixture layer to which a conductive auxiliary such as acetylene black and a binder are added. Also, as shown in FIG. 1, the negative electrode 2 has a current collector 2 a made of a strip-shaped copper foil or the like and the front and back surfaces of a current collector 2 a carrying a negative electrode active material 2 b. Graphite or the like is used as the negative electrode active material 2b, and the negative electrode active material 2b is supported on the current collector 2a as a mixture layer to which a binder is added. The separator 3 is a band-shaped insulating material having ion permeability. Here, a shutdown separator is used. The shutdown separator is an insulating resin film that is microporous to ensure ion permeability, and melts at high temperatures to close the microporosity and lose ion permeability, thus suppressing short-circuit current. Can be. In the present embodiment, as the separator 3, 15
Use a shutdown separator that melts at a temperature of 0 ° C.

Many shutdown separators have been subjected to ductile processing to increase porosity. For this reason, the tensile elongation is small, generally a low value of 50 to 200%. In addition, the elongation varies depending on the tensile direction.

The active materials 1 b on the front and back of the positive electrode 1 and the negative electrode 2,
The coating layer 4 is formed on the surface of 2b. Coating layer 4
Is a mono- or multi-component fluorine-based polymer compound having rubber elasticity, coated on the surfaces of the active materials 1b and 2b in a microporous layer having a thickness of about 0.005 to 0.2 mm. In addition, the degree of microporosity can be adjusted by uniformly dispersing and adding a non-electrically conductive reinforcing material such as calcium carbonate that does not participate in the charge / discharge reaction of the battery to the polymer compound. . The coating layer 4 undergoes large elongation when subjected to stress due to rubber elasticity, and the elongation at the breaking limit is 200% or more. Moreover, since it is a non-electrically conductive polymer compound, the electric conductivity is extremely low even if such elongation occurs. Furthermore, it has ion permeability in a non-aqueous electrolyte due to its microporosity. In addition, the heat resistance of the coating layer 4 is preferably preferably higher than that of the separator 3. In the case of the present embodiment, a material having a heat resistance of 150 ° C. or more is used.

In the non-aqueous electrolyte secondary battery of this embodiment, a power generating element is formed by winding the positive electrode 1 and the negative electrode 2 through a separator 3, and the power generating element is stored in a battery container. Is filled. As shown in FIG. 3, the non-aqueous electrolyte secondary battery configured as described above has a positive electrode 1 and a negative electrode 2, for example, in which a metal rod 5 such as a nail is pierced from the outside of a battery container and overlapped via a separator 3. However, even when the metal layer 5 penetrates, the coating layer 4 on the surfaces of the positive and negative electrodes 1 and 2 extends along the metal bar 5, so that the side surface of the metal bar 5 can be covered. Then, this metal rod 5
And the active material 1b, 2b of the positive and negative electrodes 1 and 2 and the current collectors 1a, 2a penetrating therethrough, the film surface of the stretched coating layer 4 having extremely low electric conductivity is interposed. As a result, it is possible to prevent a large short-circuit current from flowing between the positive and negative electrodes 1 and 2.

The coating layer 4 needs to have a tensile elongation of 200% or more. A larger elongation can accommodate a thicker electrode, and a tensile elongation of 250% or more can accommodate most electrodes. When the tensile elongation rate was less than 200%, the elongation was insufficient, and the short circuit could not be completely prevented. As a filler added for reinforcing the coating layer 4, calcium carbonate is inexpensive and is most suitable for non-aqueous electrolyte type secondary batteries. In addition, a simple substance of magnesium carbonate, magnesium oxide, and aluminum oxide or a mixture thereof may be used.

When a conventional non-aqueous electrolyte secondary battery in which the coating layer 4 is not formed on the surfaces of the positive and negative electrodes 1 and 2 is subjected to a nail penetration test in a fully charged state, 25 seconds after the nail penetration, a highly reactive non-aqueous non-aqueous battery is output from the safety valve. Water electrolyte gushes out, battery temperature up to 390 ° C
Up. However, when a nail penetration test was performed on the nonaqueous electrolyte secondary battery of the present embodiment, 5 to 11
Even after a lapse of minutes, the battery temperature rose only to a maximum of 109 ° C., and no ejection of the non-aqueous electrolyte from the safety valve was observed. In this test, the maximum battery temperature was 109 ° C.
The separator 3 that shuts down at 150 ° C. or higher did not melt because it only rose to 150 ° C. However, in this embodiment, since the heat resistance of the coating layer 4 is 150 ° C. or higher, the separator 3 shuts down. It is possible to suppress the short-circuit current even after performing.

Further, even when the separator 3 is broken by crushing and crushing the nonaqueous electrolyte secondary battery together with the battery container, the coating layer 4 on the surfaces of the positive and negative electrodes 1 and 2 is extended to cut the broken portion. To cover. Therefore, even if the separator 3 breaks, a large short-circuit between the positive and negative electrodes 1 and 2 is caused between the positive electrode 1 and the negative electrode 2 because the film surface of the extended coating layer 4 having extremely low electric conductivity is interposed between the positive electrode 1 and the negative electrode 2. The current can be prevented from flowing.

When a conventional non-aqueous electrolyte secondary battery in which the coating layer 4 is not formed on the surfaces of the positive and negative electrodes 1 and 2 is subjected to a crush test in a fully charged state, an internal short circuit occurs due to breakage of the separator 3 and the battery temperature decreases. As the temperature rose to 370 ° C., a non-aqueous electrolyte squirted from the safety valve. However, when the crush test was performed on the nonaqueous electrolyte secondary battery of the present embodiment, the separator 3 was broken, but the battery temperature was 85 ° C at the maximum.
And the non-aqueous electrolyte was not ejected from the safety valve.

Therefore, according to the non-aqueous electrolyte secondary battery of the present embodiment, a large short-circuit current flows between the positive and negative electrodes 1 and 2 even in an extremely severe situation such as nail penetration or crushing. Therefore, high safety can be ensured even in the case of a large-capacity non-aqueous electrolyte secondary battery.

In the above embodiment, a non-aqueous electrolyte secondary battery using a wound-type power generating element has been described. However, a stacked-type power generating element in which the positive electrode 1 and the negative electrode 2 are stacked via the separator 3 is used. The present invention can be similarly applied to a non-aqueous electrolyte secondary battery. Further, the present invention is not limited to a large-capacity large-capacity non-aqueous electrolyte secondary battery, but can be applied to a small-sized non-aqueous electrolyte secondary battery, and is similarly applicable to an aqueous electrolyte secondary battery and these primary batteries. It is possible.

Further, in the above embodiment, the case where the fluorine-based polymer compound is used for the coating layer 4 has been described.
Other materials having high permeability such as rubber elasticity as well as ion permeability and low electric conductivity can be used. Further, instead of high elasticity such as rubber elasticity, it is also possible to use a material having high extensibility, which causes large elongation by plasticity.

Materials having a high elongation include polyolefin, vinyl acetate, various fluororesins, ionomer, polybutadiene, polybutylene, and polybutylene terephthalate.
, Silicone rubber, styrene-butadiene elastomer, polyurethane and the like can be used. These materials are made porous by additives, pores, and various processes, and are formed on the electrodes. In order to obtain the effects of the present invention, it is necessary to provide sufficient ion permeability and low electrical conductivity (low electron conductivity).
A tensile elongation of at least 00% is required. Further, in order to mechanically protect the electrode surface, a tensile strength of 5 Mp or more is required. With a tensile strength of 5 Mp or less, it was easily broken by nail penetration or crushing, and short-circuit prevention yesterday was insufficient.

Further, in the above embodiment, the positive and negative electrodes 1, 1
Although the case where the coating layer 4 is formed on the surface of No. 2 has been described, the same effect can be obtained when the separator 3 having high elasticity or high ductility is used instead of the coating layer 4.

The properties required for the separator 3 are the same as those required for the coating layer 4. Some conventional separators show large elongation in one direction. However,
Separators exhibiting an elongation of 200% or more in all directions have never been used. Conventionally, when a separator having a large elongation is used, it is difficult to manufacture a battery, and the number of defective products increases. In the present invention, a manufacturing apparatus capable of extending the tension of the separator at the time of assembling the battery has been developed to solve the problem of assembling the battery.

[0033]

As is apparent from the above description, according to the battery of the present invention, even when nailing or crushing occurs, the separator or the coating layer extends and blocks between the positive and negative electrodes. Short circuit current can be prevented from flowing. In addition, the present invention contributes to enhancing the safety of a large-capacity non-aqueous electrolyte secondary battery.

[Brief description of the drawings]

FIG. 1, showing one embodiment of the present invention, is a partially enlarged longitudinal sectional view showing a configuration of positive and negative electrodes.

FIG. 2, showing one embodiment of the present invention, is an assembled perspective view for explaining the structure of a power generating element of a nonaqueous electrolyte secondary battery.

FIG. 3, showing an embodiment of the present invention, is a partially enlarged longitudinal sectional view showing a state of positive and negative electrodes when nail penetration occurs.

FIG. 4 is a partially enlarged longitudinal sectional view showing a conventional example and showing a state of a positive electrode and a negative electrode when nail penetration occurs.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Coating layer 5 Metal rod

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masanao Terasaki 1 No. 1 Nishinosho Inono Babacho, Kichijoin, Minami-ku, Kyoto F-term (reference) in Nippon Battery Co., Ltd. 5H014 AA04 CC01 EE01 EE10 HH00 HH08 5H021 AA06 CC04 EE04 EE05 EE22 HH00 HH01 HH06 5H022 AA09 BB22 CC16 EE00 EE06 EE07 5H028 AA05 AA08 CC12 EE05 EE06 HH00 HH01 HH08 5H029 AJ11 AK03 AL07 AM01 BJ14 CJ21 DJ04 DJ13 EJ12 HJ00 HJ14

Claims (6)

[Claims] Claims: 1. A battery comprising an electrode group and an electrolytic solution in which positive and negative electrodes are stacked with a separator interposed therebetween, wherein at least one of the positive and negative electrodes has ion permeability. A battery comprising a coating layer having a tensile elongation of 200% or more. 2. The battery according to claim 1, wherein the coating layer has a heat resistance of 150 ° C. or higher. 3. The battery according to claim 1, wherein the coating layer is a fluorine-based polymer compound. 4. The battery according to claim 2, wherein the coating layer contains a filler. 5. The filler according to claim 5, wherein the filler is a simple substance of calcium carbonate, magnesium carbonate, magnesium oxide, aluminum oxide or a mixture thereof.
The battery according to 1. 6. A battery provided with an electrode group and an electrolyte solution in which positive and negative electrodes are overlapped via a separator, wherein a separator having a tensile elongation of 200% or more and a heat resistance of 150 ° C. or more is used. Battery.