JPH09274935A - Lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high capacity lithium ion secondary battery having such structure that the damage of the battery itself and the influence to the environment due to the internal short-circuit may be minimized. SOLUTION: A positive electrode 2 with positive electrode active material 4 applied to one side of a positive electrode collector 5, and a negative electrode 3 with negative electrode active material applied to one side of a negative electrode collector 7 are separately incorporated in a baggy separator 8 so that active materials 4, 6 of different electrodes are in opposition each to other, and these are layered to form the lamination 10. When the electrode pairs (electrode units 25) are laminated, the opposing section of the positive electrode collector 5 and the negative electrode collector 7 exists for each electrode unit 25. Since the opposing section of this positive electrode collector 5 and the negative electrode collector 7 is excellent in heat-sinking, if a particular electrode unit 25 short-circuits internally, it prevents the influence of short-circuit to adjacent electrode units 25.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-capacity lithium ion secondary battery suitable for use in, for example, electric vehicles, UPS (Uninterruptible Power Supply), load leveling and the like.

[0002]

2. Description of the Related Art Conventionally, lithium-ion secondary batteries have been researched and developed in many fields related to environmental problems such as electric vehicles, UPS, load leveling, and have large capacity, high output, high voltage, and long-term storability. What is excellent is required.

In this lithium ion secondary battery, lithium is dissolved as lithium ions from the positive electrode active material of the positive electrode into the electrolyte solution in the separator during charging and enters the negative electrode active material of the negative electrode, and during discharge, the negative electrode is discharged. The lithium ion that has entered the negative electrode active material is released into the electrolytic solution, and returns to the positive electrode active material of the positive electrode again.

In a conventional small-sized lithium ion secondary battery, a sheet-shaped positive electrode and negative electrode formed by coating an active material on a current collector of a metal foil are sequentially laminated through a polyethylene or polypropylene separator. A known type battery or a cylindrical battery in which a long positive electrode and a negative electrode are wound with a separator interposed therebetween is also known. In addition, in these small lithium ion secondary batteries, in order to increase the energy density, both the positive electrode and the negative electrode are coated with an active material on both the front and back surfaces of the current collector.

[0005]

The structure similar to that of the above-mentioned small lithium ion secondary battery is used.
A lithium ion secondary battery capable of achieving a large capacity of up to 40 A · h can also be manufactured. However, in such a large capacity lithium ion secondary battery,
If an internal short circuit occurs at one location, the internal short circuit may spread to the surrounding area and damage the battery itself.

Therefore, it is an object of the present invention to provide a large-capacity lithium ion secondary battery having a structure capable of minimizing the damage to the battery itself and the influence on the surroundings due to an internal short circuit. .

[0007]

As a result of intensive studies to achieve the above object, the present inventor has clarified the cause of a large amount of heat and a large amount of gas being ejected due to an internal short circuit, and prevents it. We have found a lithium-ion secondary battery that has a possible structure.

Generally, as a simulated test of an internal short circuit of a battery,
There is a so-called nail penetration test in which a positive electrode and a negative electrode are artificially short-circuited by piercing a nail from the outside, but such a nail piercing test is performed on a large-capacity lithium-ion secondary battery. Then, a large amount of gas is ejected together with a large amount of heat. As a result of pursuing the cause of such a phenomenon, the present inventor melts the separator between adjacent electrodes due to the heat generated by the resistance of the nail piercing portion, and the positive electrode and the negative electrode directly react to generate further heat. It was also found that this heat generation causes a sequential heat generation such that the separator between the next electrodes is melted by heat, and finally an exothermic reaction occurs over all the electrodes. And
In order to prevent this, the present inventors have found that even if a part of heat is generated, this heat should be diffused to prevent further exothermic reaction in an adjacent region, and this is made possible. We have come to propose a lithium-ion secondary battery with a configuration.

That is, the lithium ion secondary battery according to the present invention comprises a positive electrode having a positive electrode current collector coated with a positive electrode active material, and a negative electrode current collector having a negative electrode active material coated on the surface. The negative electrode and the negative electrode are laminated via a separator, and the positive electrode current collector and the negative electrode current collector face each other via the separator at at least one location.

As described above, in the region where the current collectors face each other without the heteropolar active material interposed therebetween, the current collectors are made of a material having a small electric resistance and hardly accumulating heat. Even if heat is generated near this area, it can be diffused. Therefore, it is possible to prevent the separator from melting in a region adjacent thereto, and to prevent further exothermic reaction from occurring.

In the lithium ion secondary battery as described above, a conductive heat dissipating material may be interposed between the positive electrode current collector and the negative electrode current collector facing each other. This allows the heat to be diffused more efficiently.

Further, a heat resistant separator may be interposed between the positive electrode active material and the negative electrode active material facing each other. As a result, even if heat is generated in the vicinity of this region, if the contact between the positive electrode active material and the negative electrode active material is prevented, further exothermic reaction can be prevented.

Of course, between the positive electrode current collector and the negative electrode current collector facing each other, a heat dissipation material having conductivity is interposed, and the positive electrode active material and the negative electrode active material are opposed to each other. A heat resistant separator may be interposed therebetween.

By the way, at least one location where the positive electrode current collector and the negative electrode current collector are opposed to each other with the separator interposed therebetween may be present in the battery, and a pair of positive electrode electrode and negative electrode electrode may be used as electrodes. If it is made into a pair, it may exist for each electrode pair, or may exist for every two electrode pairs. That is, when one electrode unit is formed from a region where the current collectors face each other to a region where the current collectors face each other next, at least in the electrodes existing at both ends of each electrode unit, the electrode unit Any number of electrode pairs may be present in this electrode unit as long as the active material is applied only to the inner surface of the electrode and the active material is not applied to the outer surface. The more the current collectors face each other in the battery, the more the exothermic reaction can be suppressed in the initial stage.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below with reference to the drawings.

First Embodiment First, a flat-angle lithium-ion secondary battery in which a positive electrode current collector and a negative electrode current collector face each other for each electrode pair is shown in FIG. This will be described with reference to FIGS.

In this lithium ion secondary battery, a laminated body 10 in which a positive electrode 2 and a negative electrode 3 are laminated via a separator 8 is housed in a flat rectangular battery case 11.

Here, the positive electrode 2 is composed of a positive electrode current collector 5 coated with a positive electrode active material 4 on one surface thereof. To manufacture this positive electrode 2, first, lithium carbonate and cobalt carbonate are mixed so that Li / Co (molar ratio) = 1,
After firing in air at 900 ° C. for 5 hours, it is crushed using an automatic mortar to obtain LiCo ₂ powder. And this Li
95% by weight of Co ₂ powder, 91% by weight of a mixture obtained by mixing 5% by weight of lithium carbonate, 6% by weight of graphite as a conductor material, and 3% by weight of polyvinylidene fluoride as a binder were mixed, and Disperse in N-methyl-2-pyrrolidone to form a slurry. Further, the slurry of the positive electrode active material 4 thus obtained is applied to one surface of a sheet-shaped positive electrode current collector 5 made of aluminum foil, leaving a portion to be a lead portion, dried, and then a roller press machine. It can be compression molded. In the positive electrode 2 thus manufactured, the size of the coated portion of the positive electrode active material 4 is 107 mm ×
Die cut to 265 mm.

The negative electrode 3 is formed by coating the negative electrode current collector 7 with one side of the negative electrode active material 6. This negative electrode 3
In order to produce the above, first, oxygen was introduced into the petroleum pitch to crosslink 10 to 20% of the functional groups with oxygen, and then in an inert gas,
By firing at 1000 ° C., a non-graphitizable carbon material having properties close to those of glassy carbon is obtained. Then, 90% by weight of this carbon material and 3% by weight of polyvinylidene fluoride as a binder are mixed, and this is dispersed in N-methyl-2-pyrrolidone to form a slurry. Further, the slurry of the negative electrode active material 6 thus obtained is applied to one surface of the sheet-shaped negative electrode current collector 5 made of a copper foil, leaving a portion to be a lead portion,
After drying, compression molding may be performed with a roller press. The negative electrode 3 thus manufactured is die-cut so that the size of the coated portion of the negative electrode active material 6 is 109 mm × 265 mm.

The size of the separator 8 is 112 mm × 2.
Two 73 mm polypropylene microporous films are stuck together to form a bag.

Then, the coating portions of the active materials 4 and 6 of the positive electrode 2 and the negative electrode 3 described above are housed in the bag-shaped separator 8 so that the lead portions are exposed. In this way, 70 pairs of positive electrode 2 and negative electrode 3 respectively housed in the bag-shaped separator 8 are laminated such that the coated surfaces of the active materials 4 and 6 of the respective electrodes face each other, thereby forming a rectangular parallelepiped laminated body. 10 are configured. At this time, the laminated body 1
The lead portions of the positive electrode 2 are aligned on one end side of 0, and the lead portions of the negative electrode 3 are aligned on the other end side.

The lead portion of the positive electrode 2 exposed on one end side of the laminated body 10 is connected to the positive electrode lead body 12 made of an aluminum prism, and the lead portion of the negative electrode 3 exposed on the other end side is made of copper. It is connected to the negative electrode lead body 13 made of a prism. In addition, the lead portion of each pole and the lead body 1 of each pole
2 and 13 may be connected by welding by ultrasonic welding.

On the other hand, the laminated body 1 having the above-mentioned structure
The battery case 11 for accommodating 0 is made of a stainless steel plate having a thickness of 300 μm, and has a flat rectangular tube-shaped main body 11a having a horizontal length of approximately 300 mm, a vertical length of approximately 115 mm, and a width of approximately 12 mm. , An upper lid 11b made of a stainless steel plate having a thickness of 1.5 mm.

The laminated body 10 as described above is covered on its outer periphery with an insulating sheet (not shown), and each pole lead body 1
At the parts 2 and 13, on the upper lid 11b of the battery case 11,
It is bolted through an O-ring and an insulating ring (not shown) and inserted into the main body 11a of the battery case 11.
At this time, in the main body 11a, 1% LiPF ₆ was added to the mixed solvent of propylene carbonate and diethyl carbonate.
An organic electrolyte solution dissolved at a concentration of mol / l is injected,
Then, the upper lid 11b is welded and fixed to the main body 11a by laser welding.

In this lithium ion secondary battery, the positive electrode terminal 14 and the negative electrode terminal 15 connected to the positive electrode lead body 12 and the negative electrode lead body 13 are provided, and the internal pressure becomes higher than a predetermined value. A safety valve 16 is also provided for venting the internal gas when the lamp is opened.

In the lithium ion secondary battery having the above structure, a large capacity of 50 A · h can be realized.

In the laminated body 10 of the lithium ion secondary battery according to the present embodiment, as shown in FIG. 1, the active materials 4 and 6 are applied to only one surface of the current collectors 5 and 7 of each electrode, respectively. The positive electrode 2 and the negative electrode 3 are paired so that the active materials 4 and 6 of different polarities face each other to form an electrode pair. Therefore, one electrode pair becomes one electrode unit 25, the active materials 4 and 6 of each pole are provided inside the electrode unit 25, and the current collectors 5 and 7 of each pole are provided outside thereof. Become. Therefore, when such electrode units 25 are stacked, the positive electrode current collector 5 and the negative electrode current collector 7 are necessarily opposed to each other between the electrode units 25, that is, the positive electrode current collector 5 and the negative electrode current collector 5 are arranged for each electrode pair. There will be a portion facing the current collector 7. It should be noted that the description "active materials 4, 6 face each other" or "current collectors 5, 7 face each other" omits the description "through separator 8", and the same applies hereinafter. .

Therefore, in the lithium ion secondary battery according to this embodiment, even if an internal short circuit occurs in a specific electrode unit 25, the current collector 5 is present at the interface between this electrode unit 25 and the adjacent electrode unit 25. , 7 face each other, so that heat can be diffused at this interface. As a result, if the melting of the separator 8 inside the adjacent electrode unit 25 can be prevented, a new direct reaction between the positive electrode active material 4 and the negative electrode active material 6 will not occur here. That is, the internal short circuit is prevented from spreading to the adjacent electrode units 25, and the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Second Embodiment Here, a lithium ion secondary battery having an excellent heat diffusing ability at the interface between the electrode units 25 will be described with reference to FIG. It should be noted that members common to those of the first embodiment will be denoted by common reference numerals, and redundant description will be omitted.

The laminated body 20 of this lithium ion secondary battery
In the same manner as in the first embodiment, the active materials 4 and 6 are applied to only one surface of the current collectors 5 and 7 of the respective poles so that the active materials 4 and 6 of the different polarities face each other. To form an electrode pair. Further, since there is a portion where the positive electrode current collector 5 and the negative electrode current collector 7 face each other for each electrode pair, this electrode pair serves as the electrode unit 25. However, in the present embodiment, all of the electrode units 25 are laminated with the heat radiating material 18 interposed therebetween.

The heat radiating material 18 may be made of any material as long as it has conductivity and resistance to the electrolytic solution, and examples thereof include stainless steel and titanium foil. Here, the thickness is 15 μm and the size is 112.
A mm × 273 mm stainless steel sheet was used as the heat dissipation material 18.

Also in the lithium ion secondary battery according to this embodiment, when an internal short circuit occurs in a specific electrode unit 25, heat can be diffused at the interface between the electrode units 25. Further, in the lithium-ion secondary battery according to the present embodiment, since the heat radiating material 18 is interposed between the positive electrode current collector 5 and the negative electrode current collector 7 which face each other, the heat diffusing ability is further improved. improves. Therefore, the internal short circuit is prevented from spreading to the adjacent electrode units 25, and the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Third Embodiment Here, a lithium ion secondary battery having a structure excellent in the ability to prevent a direct reaction between the positive electrode active material 4 and the negative electrode active material 6 will be described with reference to FIG. It should be noted that members common to those of the first embodiment will be denoted by common reference numerals, and redundant description will be omitted.

A laminated body 30 of this lithium ion secondary battery
In the same manner as in the first embodiment, the active materials 4 and 6 are applied to only one surface of the current collectors 5 and 7 of the respective poles so that the active materials 4 and 6 of the different polarities face each other. To form an electrode pair. Further, since there is a portion where the positive electrode current collector 5 and the negative electrode current collector 7 face each other for each electrode pair, this electrode pair serves as the electrode unit 25. However, in the present embodiment, not only the positive electrode 2 and the negative electrode 3 are housed in the bag-shaped separator 8, but also the separator 8 housing the positive electrode 2 is stored.
A heat-resistant separator 19 is further interposed between the separator 8 and the separator 8 that houses the negative electrode 3 to form a laminated body 30.

As the heat resistant separator 19, a microporous film or sheet using a heat resistant resin such as a thermoplastic resin or a thermosetting resin, a cloth using an inorganic fiber or a cellulose fiber, a paper or the like can be used. However, when used alone, it is necessary to use a material having electrolytic solution resistance that does not dissolve in the electrolytic solution, as the thermoplastic resin, polyethylene, a polyolefin resin such as polypropylene, a polyimide resin such as a thermoplastic polyimide. Fluorine-based resins such as resin, tetrafluoroethylene resin, and tetrafluoroethylene-hexafluoropropylene copolymer can be used. A polyimide resin can be used as the thermosetting resin, and alumina fibers, glass fibers, ceramic fibers, silicon carbide fibers, carbon fibers and the like can be used as the inorganic fibers. When cellulose fibers are used, it is necessary to use high-purity fibers with reduced impurities such as hemicellulose. Here, a polyimide film having a thickness of 25 μm (trade name: Kapton, heat-resistant temperature: about 800 ° C.) is provided with 1.2 mm holes having a diameter of 1.2 mm.
Provided on the entire surface with a pitch of 7 mm, and this is 109 mm x 270
Heat-resistant separator made by punching out to a size of 1 mm
Used as 9.

Also in the lithium ion secondary battery according to this embodiment, when an internal short circuit occurs in a specific electrode unit 25, heat can be diffused at the interface between the electrode units 25.

Further, in the lithium ion secondary battery according to this embodiment, since the heat resistant separator 19 is interposed between the positive electrode active material 4 and the negative electrode active material 6 which face each other, the positive electrode active material 4 has an excellent ability to prevent a direct reaction between the negative electrode active material 6 and the negative electrode active material 6. As a result, even if an internal short circuit occurs in a specific electrode unit 25, the direct reaction between the positive electrode active material 4 and the negative electrode active material 6 is prevented in the electrode unit 25 adjacent to this, and the internal short circuit does not spread. It is possible to minimize the damage to the ion secondary battery itself and the influence on the surroundings.

Fourth Embodiment Here, a lithium ion secondary battery having both a heat dissipation material and a heat resistant separator in a laminated body will be described with reference to FIG. It should be noted that members common to those of the first embodiment will be denoted by common reference numerals, and redundant description will be omitted.

This lithium ion secondary battery laminate 40
In the same manner as in the first embodiment, the active materials 4 and 6 are applied to only one surface of the current collectors 5 and 7 of the respective poles so that the active materials 4 and 6 of the different polarities face each other. To form an electrode pair. Further, since there is a portion where the positive electrode current collector 5 and the negative electrode current collector 7 face each other for each electrode pair, this electrode pair serves as the electrode unit 25. And in this Embodiment, the laminated body 40
However, all of the electrode units 25 are laminated via the heat dissipation material 18, and a heat-resistant separator 19 is interposed between the separator 8 that houses the positive electrode 2 and the separator 8 that houses the negative electrode 3. ing.

Here, a stainless steel sheet was used as the heat dissipation material 18, and a glass cloth was used as the heat resistant separator 19. The glass cloth is a film having a thickness of 51 μm and a porosity of 11% in which glass fibers are woven in a density of 78 lengthwise and 73 widthwise per inch.

In the lithium ion secondary battery according to the present embodiment, the ability to diffuse heat at the interface between the electrode units 25 is high, and the positive electrode active material 4 and the negative electrode active material 6 are used.
It also has excellent ability to prevent direct reaction with. For this reason, even if an internal short circuit occurs in the specific electrode unit 25, the internal short circuit does not spread, so that the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Fifth Embodiment Here, a flat-angle lithium-ion secondary battery in which a positive electrode current collector and a negative electrode current collector face each other for every two electrode pairs is provided. , FIG. 7 will be described.
It should be noted that members common to those of the first embodiment will be denoted by common reference numerals, and redundant description will be omitted.

This lithium ion secondary battery laminate 50
In the same manner as in the first embodiment, the positive electrode 2 and the negative electrode 3 in which the active materials 4 and 6 are provided on only one surface of the current collectors 5 and 7 of each electrode respectively are also provided. It also has a positive electrode 22 and a negative electrode 23 in which the active materials 4 and 6 are provided on both surfaces of the current collectors 5 and 7, respectively.

Specifically, the positive electrode electrode 2 having the positive electrode active material 4 provided on one surface of the positive electrode current collector 5, the negative electrode electrode 23 having the negative electrode active material 6 provided on both surfaces of the negative electrode current collector 7, and the positive electrode current collector Electric body 5
Of the positive electrode 22 having the positive electrode active material 4 provided on both surfaces thereof, and the negative electrode 3 having the negative electrode active material 6 provided on one surface of the negative electrode current collector 7.
However, one electrode unit 35 is formed by stacking the active materials 4 and 6 having different polarities in this order so as to face each other, and the stacked body 50 is formed by stacking these. In this case, the electrode unit 35 is composed of two electrode pairs.

Even when such electrode units 35 are laminated, the positive electrode current collector 5 must be provided between the electrode units 35.
And the negative electrode current collector 7 face each other. Therefore,
Also in the lithium ion secondary battery according to the present embodiment, even if an internal short circuit occurs in a specific electrode unit 35, the electrode unit 3 adjacent to this electrode unit 35
Since the current collectors 5 and 7 face each other at the interface with 5,
Heat can be diffused at this interface. Therefore, the internal short circuit is prevented from spreading to the adjacent electrode units 35, and the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Sixth Embodiment Here, an example in which a heat radiating material is added to the fifth embodiment will be described with reference to FIG. It should be noted that members common to those of the fifth embodiment are denoted by common reference numerals, and redundant description will be omitted.

A laminated body 60 of this lithium ion secondary battery
Also in the above, the electrode unit 35 is formed similarly to the fifth embodiment. However, in the present embodiment, the heat dissipation material 18 is interposed between the electrode units 35. Here, a stainless steel sheet was used as the heat dissipation material 18.

Also in the lithium ion secondary battery according to this embodiment, when an internal short circuit occurs in a specific electrode unit 35, heat can be diffused at the interface between the electrode units 35. Further, in the lithium-ion secondary battery according to the present embodiment, since the heat radiating material 18 is interposed between the positive electrode current collector 5 and the negative electrode current collector 7 which face each other, the heat diffusing ability is further improved. improves. Therefore, the internal short circuit is prevented from spreading to the adjacent electrode units 35, and the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Seventh Embodiment Here, an example in which a heat resistant separator is added to the fifth embodiment will be described with reference to FIG. It should be noted that members common to those of the fifth embodiment are denoted by common reference numerals, and redundant description will be omitted.

A laminated body 70 of this lithium ion secondary battery
Also in the above, the electrode unit 35 is formed similarly to the fifth embodiment. However, in the present embodiment, in each electrode unit 35, the heat-resistant separator 19 is interposed between the separator 8 containing the positive electrode 2 or 22 and the separator 8 containing the negative electrode 3 or 23. . Here, glass cloth was used as the heat resistant separator 19.

Also in the lithium ion secondary battery according to this embodiment, when an internal short circuit occurs in a specific electrode unit 35, heat can be diffused at the interface between the electrode units 35. Further, in the lithium ion secondary battery according to the present embodiment, since the heat resistant separator 19 is interposed between the positive electrode active material 4 and the negative electrode active material 6 facing each other, the positive electrode active material 4 and the negative electrode It has an excellent ability to prevent a direct reaction with the active material 6. Therefore, the spread of the internal short circuit to the adjacent electrode unit 35 is prevented, and the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Eighth Embodiment Here, an example in which both the heat dissipation material and the heat resistant separator are added to the fifth embodiment will be described with reference to FIG. It should be noted that members common to those of the fifth embodiment are denoted by common reference numerals, and redundant description will be omitted.

Laminate 80 of this lithium-ion secondary battery
Also in the above, the electrode unit 35 is formed similarly to the fifth embodiment, but in the present embodiment,
Each of the electrode units 35 is laminated via a heat dissipation material 18, and a heat-resistant separator 19 is provided between the separator 8 containing the positive electrodes 2 and 22 and the separator 8 containing the negative electrodes 3 and 23. Intervened. Here, a stainless steel sheet was used as the heat dissipation material 18, and a glass cloth was used as the heat resistant separator 19.

In the lithium ion secondary battery according to the present embodiment, the ability to diffuse heat at the interface between the electrode units 35 is high, and the positive electrode active material 4 and the negative electrode active material 6 are used.
It also has excellent ability to prevent direct reaction with. For this reason, even if an internal short circuit occurs in the specific electrode unit 35, the internal short circuit does not spread, so that the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Ninth Embodiment Here, with respect to a cylindrical lithium ion secondary battery,
This will be described with reference to FIG. It should be noted that members common to those of the first embodiment will be denoted by common reference numerals, and redundant description will be omitted.

In this lithium ion secondary battery,
Instead of sequentially stacking a plurality of positive electrode electrodes 2 and negative electrode electrodes 3, long positive electrode electrodes 32 and negative electrode electrodes 33 are stacked via a separator 28, which is wound to form a spiral laminated body 90. It is configured.

Specifically, the size is 280 mm × 1745
a positive electrode electrode 32 having a positive electrode active material 4 provided on one surface of a positive electrode current collector 5 of mm and a negative electrode electrode 33 having a negative electrode active material 6 provided on one surface of a negative electrode current collector 7 having a size of 283 mm × 1750 mm. , The size of each active material 4 and 6 is 2
The separators 28 made of a polyethylene film of 87 mm × 1755 mm are overlapped with each other and wound, and the spiral laminated body 90 is formed. Then, although not shown, a negative electrode lead body made of nickel is welded to the lead portion of the negative electrode 33 by resistance welding, and a positive electrode lead body made of aluminum is welded to the lead portion of the positive electrode 32 by resistance welding. The laminated body 90 to which the lead bodies of the respective electrodes are thus welded is made of nickel-plated iron, and is formed in the body of a cylindrical battery case having a diameter of 50 mm and a height of 300.5 mm, and an insulating plate at the bottom. Is inserted and then inserted. Further, an organic electrolytic solution prepared by dissolving LiPF ₆ at a concentration of 1 mol / l in a mixed solvent of 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate was injected into the battery case, and then asphalt was applied. The upper lid is caulked and fixed to the main body via the insulating sealing gasket.

The lithium ion secondary battery is provided with a positive electrode terminal and a negative electrode terminal connected to the positive electrode lead body and the negative electrode lead body, respectively, and
A safety valve is also provided for venting the internal gas when the internal pressure becomes higher than a predetermined value.

In the lithium ion secondary battery having the above structure, a large capacity of 20 A · h can be realized.

In the lithium-ion secondary battery according to the present embodiment, as shown in FIG. 11, active materials 4 and 6 are provided on only one surface of the current collectors 5 and 7 of each electrode, respectively.
The active materials 4 and 6 having different polarities are paired so as to face each other. Therefore, in the laminated body 90, the collectors 5 and 7 of the respective electrodes face each other on both sides of the region where the active materials 4 and 6 of the respective electrodes face each other at any position in the radial direction. That is, in the radial direction, the current collectors 5 of the respective poles for each electrode pair,
It can be said that there is a location where 7 is facing.

Therefore, in the lithium ion secondary battery according to the present embodiment, even if an internal short circuit occurs at a specific position in the radial direction of the laminate 90, the current collectors 5, 7 face each other in the vicinity thereof. Since there is a region that is doing so, heat can be diffused here. Therefore, melting of the separator 28 in the adjacent region can be prevented, and a new direct reaction between the positive electrode active material 4 and the negative electrode active material 6 does not occur here. That is, the internal short circuit is prevented from spreading to the adjacent region, and the damage to the lithium ion secondary battery itself and the influence on the surroundings can be minimized.

Although various embodiments to which the present invention is applied have been described above, it goes without saying that the present invention is not limited to the above-mentioned embodiments. For example,
The material, manufacturing method, etc. of each component may be changed, and the thickness, size, etc. may be changed.

Further, in the embodiment in which the heat radiating material 18 is interposed, the heat radiating material 18 is interposed for each electrode unit 25 (or electrode unit 35, the same applies hereinafter), but not all electrode units are required. It is not necessary to interpose the heat radiating material 18 at the interface between the plurality of electrode units 25, and the heat radiating material 18 is provided at at least one place among the interfaces between the plural electrode units 25.
Should be interposed. Similarly, in the embodiment in which the heat-resistant separator 19 is interposed, the heat-resistant separator 19 is interposed in all the facing portions of the different-polarity active materials 4 and 6, but there are a plurality of opposite-polarity active materials 4 and 6 facing each other. The heat-resistant separator 19 may be interposed in at least one of the parts.

Further, in the embodiment in which the heat dissipating material 18 is interposed, the heat diffusing ability at the interface between the electrode units 25 can be improved. However, the material composing the heat dissipating material 18 and the current collection of each pole. Since the same material as the material forming the bodies 5 and 7 can be used, even if the thickness of the current collectors 5 and 7 of each pole is increased in the range of 1 to 3 times the normal range, the thermal diffusivity is the same. Can be improved.

Further, in the ninth embodiment, the example in which the present invention is applied to the cylindrical lithium ion secondary battery is shown. The laminated body 19 of this cylindrical lithium ion secondary battery is shown.
Also in 0, a heat dissipation material may be interposed between the opposite electrode current collectors 5 and 7 or a heat resistant separator may be interposed between the opposite electrode active materials 4 and 6.

Further, in the above-described embodiment, the example in which the current collectors are opposed to each other for each electrode pair and for each two electrode pairs has been described.
At least one location where the current collectors face each other may be present in the battery. Therefore, one electrode unit may be configured with three or more electrode pairs. Further, as shown in FIG. 12, one electrode unit 45 may be composed of 1.5 electrode pairs. In this lithium ion secondary battery, the positive electrode 2 having the positive electrode active material 4 provided on only one surface of the positive electrode current collector 5, the negative electrode 23 having the negative electrode active material 6 provided on both surfaces of the negative electrode current collector 7, Positive electrode 2 in which the positive electrode active material 4 is provided only on one surface of the positive electrode current collector 5.
However, one electrode unit 45 is formed by laminating the active materials 4 and 6 of different polarities in this order so as to face each other. However, the electrode unit 45 'adjacent thereto has a negative electrode 3 having a negative electrode active material 6 applied only on one side, a positive electrode 22 having a positive electrode active material 4 applied on both sides, and a negative electrode active material 6 on only one side. The negative electrode 3 formed by coating is laminated. Then, the electrode unit 45 and the electrode unit 45 ′ are alternately laminated to form a laminated body 100. Also in such a lithium-ion secondary battery, as in the case of the above-described embodiment, even if an internal short circuit occurs in the specific electrode unit 45 (45 ′),
A short circuit is prevented from spreading to the adjacent electrode units 45 '(45), and damage to the lithium ion secondary battery itself and its influence on the surroundings can be minimized.

[0067]

EXAMPLES Here, a lithium-ion secondary battery having various configurations as described above was actually prepared and a nail penetration test was conducted.

Specifically, the lithium-ion secondary battery shown in the first embodiment is prepared and used in Example (1).
Sample battery of Further, the lithium ion secondary battery shown in the second embodiment was prepared, and this was used as the sample battery of Example (2), except that titanium foil was used instead of stainless steel as the heat dissipation material 18. A lithium-ion secondary battery having the same configuration as that of the second embodiment was prepared and used as a sample battery of Example (3).

Further, the lithium ion secondary battery shown in the third embodiment was prepared, and this was used as the sample battery of Example (4), and aramid was used instead of the punched polyimide film as the heat resistant separator 19. Lithium ion secondary batteries each having the same configuration as that of the third embodiment except that a fiber sheet, an alumina powder sheet, a glass cloth, a ceramic cloth, and a punched aluminum foil were used were prepared, and these were sequentially used in Examples. (5)
-The sample battery of Example (9) was used. The aramid fiber sheet used as the heat-resistant separator 19 in Example (5) was obtained by making a para-aramid fiber (trade name: Technora) into paper and heat-treating it, and having a thickness of 50 μm.
m wet non-woven fabric. The alumina powder sheet used as the heat resistant separator 19 in Example (6) was rapidly solidified by heating and solidifying a suspension of polytetrafluoroethylene powder and alumina powder having an average particle size of 10 μm. It is a powder-containing porous film having a thickness of 50 μm obtained by the above. The glass cloth used as the heat-resistant separator 19 in Example (7) was 78 in length and 7 in width per inch.
Glass fiber woven with a density of three, thickness 51μ
It is a film having m and a porosity of 11%. The ceramic cloth used as the heat resistant separator 19 in Example (8) was Al ₂ O ₃ : SiO ₂ : B ₂ O ₃ = 68: 27:
The suspension obtained by dispersing the feces of No. 5 in water was dropped by a nozzle, dried and baked to prepare a filament bundle of 80 filaments having a diameter of 11 μm, and the thickness obtained by weaving the filament bundle. It is a woven fabric of 80 μm continuous alumina fibers. The punched aluminum foil used as the heat-resistant separator 19 in Example (9) had a thickness of 25 μm.
The aluminum foil of m is provided with holes having a diameter of 0.8 mm on the entire surface at a pitch of 1.27 mm.

Further, the lithium ion secondary batteries shown in the fourth to ninth embodiments were prepared, and these were sequentially used as the sample batteries of Examples (10) to (15). .

Further, for comparison, a conventional flat rectangular lithium-ion secondary battery was prepared. FIG. 13 shows a laminated body 110 in this lithium ion secondary battery. The laminated body 110 includes a positive electrode electrode 102 formed by applying a positive electrode active material 104 on both surfaces of a positive electrode current collector 105, and a negative electrode electrode 103 formed by applying a negative electrode active material 106 on both surfaces of a negative electrode current collector 107. Each of them is housed in a bag-shaped separator 108 and laminated. Therefore, the laminated body 110
There is no location where the positive electrode current collector 105 and the negative electrode current collector 107 face each other. This lithium-ion secondary battery is used as a sample battery of Comparative Example (1).

Similarly, for comparison, a conventional cylindrical lithium ion secondary battery was prepared. FIG. 14 shows a laminated body 190 in this lithium ion secondary battery. This laminated body 190 includes a long first separator 128, a positive electrode 132 in which the positive electrode active material 104 is applied to both surfaces of a long positive electrode current collector 105, and a long second separator 1.
29, the negative electrode active material 1 on both surfaces of the elongated negative electrode current collector 107.
The negative electrode 133 to which 06 is applied is superposed in this order, and is wound. Therefore, the laminated body 1
There is no place where the positive electrode current collector 105 and the negative electrode current collector 107 face each other in any part of 90. This lithium-ion secondary battery is used as a sample battery of Comparative Example (2).

Then, a nail penetration test was conducted on the sample batteries of Examples 1 to 15 and Comparative Examples 1 and 2 described above, and the weight reduction rate of each sample battery due to the nail penetration was examined. In addition,
The weight reduction rate was based on the weight of the organic electrolyte injected into each sample battery. Table 1 shows the results.

[0074]

[Table 1]

Table 1 shows the characteristics of the constitution of each sample battery,
The capacity is also shown.

From Table 1, when Comparative Example 1 which is a flat type lithium ion secondary battery is compared with Examples 1 to 14, in Comparative Example 1, the weight is 135% by the nail penetration test.
However, in Examples 1 to 14, it can be seen that the weight reduction is suppressed to 2 to 5%. Further, comparing Comparative Example 2 which is a cylindrical lithium ion secondary battery with Example 15, in Comparative Example 2,
It can be seen that, while the weight was reduced by 140% by the nail penetration test, the weight reduction was suppressed to 5% in Example 15. From this result, when there is a location where the positive electrode current collector and the negative electrode current collector face each other in the laminate, even if an internal short circuit occurs due to a nail stick, this expansion is suppressed, and gas ejection is suppressed. I understand.

Further, when comparison is made in Examples 1 to 10,
It is understood that the effect of suppressing the expansion of the internal short circuit is improved by interposing the heat dissipation material between the different polar current collectors facing each other and by interposing the heat resistant separator between the different polar active materials facing each other.

Further, Examples 1 to 10 and Examples 11 to 1
Comparing with No. 4, it can be seen that the more frequently the opposite electrode current collectors face each other, the more the effect of suppressing the expansion of the internal short circuit is improved.

[0079]

As is apparent from the above description, when the present invention is applied, even if an internal short circuit occurs in a specific area,
The expansion of the internal short circuit to the adjacent area can be suppressed.

As a result, it becomes possible to minimize the damage to the battery itself and the influence on the surroundings due to the internal short circuit, and it is possible to improve the reliability and safety of the large capacity lithium ion secondary battery. Becomes

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a structure of a laminate in a lithium ion secondary battery according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a state where the laminated body of FIG. 1 is connected to a lead body and fixed to an upper lid of a battery case.

FIG. 3 is a schematic perspective view showing a state where the laminated body of FIG. 2 is inserted into a battery case body.

FIG. 4 is a schematic cross-sectional view showing a structure of a laminate in a lithium ion secondary battery according to a second embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing a structure of a laminated body in a lithium ion secondary battery according to a third embodiment of the present invention.

FIG. 6 is a schematic cross-sectional view showing the structure of a laminate in a lithium ion secondary battery according to a fourth embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing a structure of a laminate in a lithium ion secondary battery according to a fifth embodiment of the present invention.

FIG. 8 is a schematic cross-sectional view showing the structure of a laminate in a lithium ion secondary battery according to a sixth embodiment of the present invention.

FIG. 9 is a schematic cross-sectional view showing the structure of a laminate in a lithium ion secondary battery according to a seventh embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view showing the structure of a laminate in a lithium ion secondary battery according to an eighth embodiment of the invention.

FIG. 11 is a schematic cross-sectional view showing the structure of a laminate in a lithium ion secondary battery according to a ninth embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view showing still another configuration example of the laminate of the lithium ion secondary battery according to the present invention.

FIG. 13 is a schematic cross-sectional view showing the structure of a laminated body of a conventional flat rectangular lithium-ion secondary battery.

FIG. 14 is a schematic view showing a structure of a laminate of a conventional cylindrical lithium ion secondary battery.

[Explanation of symbols]

2 positive electrode, 3 negative electrode, 4 positive electrode active material,
5 positive electrode current collector, 6 negative electrode active material, 7 negative electrode current collector,
8 bag-shaped separator, 10 laminated body, 25 electrode unit, 18 heat dissipation material, 19 heat-resistant separator

Claims (6)

[Claims] 1. A positive electrode having a surface of a positive electrode current collector coated with a positive electrode active material, and a negative electrode having a surface of a negative electrode current collector coated with a negative electrode active material are laminated with a separator interposed therebetween. In the lithium ion secondary battery, the lithium ion secondary battery is characterized in that the positive electrode current collector and the negative electrode current collector face each other via the separator at at least one location. 2. The lithium-ion secondary battery according to claim 1, wherein a heat dissipation material having conductivity is interposed between the positive electrode current collector and the negative electrode current collector facing each other. . 3. The lithium ion secondary battery according to claim 1, wherein a heat-resistant separator is interposed between the positive electrode active material and the negative electrode active material facing each other. 4. A positive electrode active material and a negative electrode active material, in which a heat dissipation material having conductivity is interposed between the positive electrode current collector and the negative electrode current collector facing each other. The lithium-ion secondary battery according to claim 1, wherein a heat-resistant separator is interposed between and. 5. When a pair of the positive electrode and the negative electrode is an electrode pair, a portion where the positive electrode current collector and the negative electrode current collector face each other via the separator is provided for each electrode pair. It exists, The lithium ion secondary battery of Claim 1 characterized by the above-mentioned. 6. Where the pair of the positive electrode and the negative electrode is an electrode pair, the position where the positive electrode current collector and the negative electrode current collector face each other through the separator for every two electrode pairs. The lithium-ion secondary battery according to claim 1, wherein: