JP2000277161A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery whose safety can be significantly enhanced by preventing sudden voltage drop and recovery from being repeated even in the event of a short circuit inside the battery due to application of stresses from the outside. SOLUTION: In this nonaqueous electrolyte battery having a generating element 4 in which a positive electrode 1 having positive electrode active material layers 1b, 1b capable of storing and releasing lithium ion, on both sides of a positive electrode core 1a made from metallic foil, and a negative electrode 2 having negative electrode active material layers 2b, 2b capable of storing and releasing lithium ion, on both sides of a negative electrode core 2a made from metallic foil, are spirally rolled with the intervention of a separator 3 impregnated with a nonaqueous electrolytic solution, a safety piece 10 having a metallic rising part 12 which, when locally exerted with a force, rises and tears the positive electrode 1 and the negative electrode 2, is inserted into the generating element 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode having a positive electrode active material layer capable of occluding and releasing lithium ions on both surfaces of a positive electrode core made of metal foil, and a lithium electrode having both surfaces of a negative electrode core made of metal foil. The present invention relates to a nonaqueous electrolyte battery including a power generation element in which a negative electrode having a negative electrode active material layer capable of occluding and releasing ions is spirally wound through a separator impregnated with a nonaqueous electrolyte.

[0002]

_2. Description of the Related Art In recent years, nonaqueous electrolyte batteries using a lithium-containing composite oxide such as LiCoO ₂ as a positive electrode active material and an alloy or a carbon material capable of occluding and releasing metallic lithium or lithium ions as a negative electrode active material. However, attention has been paid to batteries capable of increasing capacity. The specific structure of such a nonaqueous electrolyte battery includes a positive electrode in which the positive electrode active material layer and the negative electrode active material layer are formed on both surfaces of a positive electrode core and a negative electrode core made of metal foil, respectively. The structure is such that the negative electrode is wound via a separator.

Here, when stress is applied to the non-aqueous electrolyte battery having the above-described structure from the outside, the separator may be damaged and a short circuit may occur inside the battery. In such a case, in a conventional non-aqueous electrolyte battery, the positive electrode active material layer and the negative electrode active material layer are in direct contact with each other, which is a so-called short-circuit between the active materials. Therefore, as shown in FIG. And voltage return are repeated (that is, a state where a short circuit occurs in the battery and a state where no short circuit occurs) are repeated. However, if a short circuit occurs inside the battery, a large current will flow locally, causing the battery temperature to rise and gas to be generated. When flowing, the generated gas may ignite. Therefore, the conventional nonaqueous electrolyte battery has a problem in terms of safety.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has been made in consideration of the above-mentioned circumstances. An object of the present invention is to provide a non-aqueous electrolyte battery that can dramatically improve the safety of a battery by preventing repetition of return.

[0005]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present invention provides a positive electrode active material capable of inserting and extracting lithium ions on both surfaces of a positive electrode core made of a metal foil. A positive electrode provided with a material layer and a negative electrode provided with a negative electrode active material layer capable of inserting and extracting lithium ions on both surfaces of a negative electrode core made of a metal foil are swirled through a separator impregnated with a non-aqueous electrolyte. In a non-aqueous electrolyte battery having a power generating element wound in a shape, the power generating element has a metallic rising portion that rises when a force is locally applied and breaks through the positive electrode and the negative electrode. The safety piece provided is inserted.

With the above structure, when stress is applied from the outside and the rising portion breaks through the positive electrode and the negative electrode, the positive electrode core and the negative electrode core are directly short-circuited via the metallic rising portion. Therefore, the internal resistance of the battery when a short circuit occurs inside the battery is small, and almost all the current flows instantaneously as shown in FIG. 9 (that is, the same phenomenon as when an external short circuit occurs) occurs. Will be). As a result, short-circuiting does not occur again inside the battery after gas generation, and the rise in battery temperature is also suppressed, so that the generated gas can be prevented from igniting and the like, and the safety of the battery is significantly improved. I do.

According to a second aspect of the present invention, in the first aspect of the invention, the safety piece is made of metal, and the safety piece is provided with a cut to constitute the rising portion. As described above, if the raised portion is formed by providing a cut in the metal safety piece, a highly safe battery can be easily manufactured. However, the structure of the rising portion is not limited to the above structure, for example, by combining a metal with high hardness and a low metal, even a structure in which the metal portion with high hardness is the rising portion, There is a similar effect.

According to a third aspect of the present invention, in the first or second aspect of the invention, the rising portion is tapered. As described above, if the rising portion is tapered, the positive electrode and the negative electrode can be easily pierced, so that safety is further improved.

[0009] The invention described in claim 4 is based on claim 1,
In the invention described in 2 or 3, the safety piece also serves as a positive electrode current collecting tab and / or a negative electrode current collecting tab. With such a structure, the number of parts of the battery does not increase, and there is no need to provide a new space for inserting a safety piece, so that the manufacturing cost of the battery increases and the volume energy density decreases. , And safety can be improved without inviting.

[0010] The invention described in claim 5 is based on claim 1,
In the invention described in 2, 3, or 4, at least one part of the power generating element wound in a spiral shape is provided.
For the number of turns, a positive electrode core exposed portion where the positive electrode active material layer is not formed and a negative electrode core exposed portion where the negative electrode active material layer is not formed are provided, and positions corresponding to these two core exposed portions are provided. Characterized in that the above-mentioned safety piece is inserted therein.

As described above, if the safety piece is inserted at a position corresponding to the exposed portion of the positive electrode core and the exposed portion of the negative electrode core, the active material layer is present when the rising portion breaks through the positive electrode and the negative electrode. Instead, a short circuit occurs at the portion where the resistance is the smallest, so that the internal resistance is further reduced and the safety of the battery can be further improved. In addition, the position corresponding to the exposed portion of the positive electrode core and the exposed portion of the negative electrode core is preferably at least one turn from the winding start end of the power generating element that is spirally wound. This is because the area of one round becomes smaller toward the inner circumference, which is advantageous for battery capacity.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an exploded perspective view of a nonaqueous electrolyte battery according to the present invention, FIG. 2 is a front view showing a relationship between a safety piece and a negative electrode, FIG. 3 is a plan view of a safety piece according to another example used in the present invention, FIG. 4 is a plan view of a safety piece according to another example used in the present invention, FIG. 5 is a cross-sectional view showing a relationship between the safety piece and a power generating element before external pressure is applied, and FIG. It is sectional drawing which shows the relationship between a safety piece and a power generation element later.

As shown in FIG. 1, the lithium ion battery of the present invention has a cylindrical outer can 8 having a bottom. The outer can 8 has a positive electrode 1, a negative electrode 2, Electrode 1 ・
2 and a polyethylene microporous membrane (thickness:
And a separator 3 made of 25 .mu.m). Further, 40 parts by weight of ethylene carbonate (EC) and 60 parts by weight
An electrolyte in which LiPF ₆ is dissolved at a ratio of 1 M (mol / liter) is injected into a mixed solvent with dimethyl carbonate (DMC) in parts by weight. Further, an insulating gasket 1 made of polypropylene is provided in the opening of the outer can 8.
The sealing body 7 is fixed by caulking via 3, thereby sealing the battery.

Here, as shown in FIG.
Is a positive electrode core made of aluminum (thickness: 20 μm)
Positive electrode active material layer 1 mainly composed of LiCoO ₂ on both surfaces of 1a
b · 1b is formed, while the negative electrode 2
Has a structure in which negative electrode active material layers 2b, 2b mainly composed of natural graphite are formed on both surfaces of a negative electrode core (thickness: 20 μm) 2a made of copper. A safety piece 10 is inserted between the negative electrode 2 and the separator 3.
As shown in FIG. 2, has a structure in which a number of cuts 11 are formed in a thin plate (thickness: 300 μm) made of stainless steel. The safety piece 10 exists in a planar shape in the power generating element 4 in a normal state (see FIG. 5), but when a power is locally applied and the power generating element 4 is deformed, a rising portion 12 is formed. In this configuration, the positive and negative electrodes 1.2 are pierced through the separator and the positive and negative electrodes 1.2 are smoothly short-circuited (see FIG. 6).

A negative current collector tab 6 electrically connected to the negative electrode 2 is connected to the outer can 8, while a positive electrode electrically connected to the positive electrode 1 is connected to the sealing body 7. The current collecting tab 5 is connected, so that chemical energy generated inside the battery is converted into electrical energy. Insulating plates 9 and 10 are disposed near the upper and lower ends of the power generating element 4 to prevent a short circuit from occurring in the battery.

Here, the non-aqueous electrolyte battery having the above structure was manufactured as follows. First, L as a positive electrode active material
and the iCoO ₂ 90 wt%, and 5 wt% of carbon black or graphite as a conductive agent, and polyvinylidene fluoride as a binding agent (PVDF) 5 wt%, of organic solvent N- methyl-2 After mixing with a pyrrolidone (NMP) solution to prepare a slurry, the slurry is converted to an aluminum foil (thickness: 1 mm) as a positive electrode current collector 1a using a die coder, a doctor blade, or the like.
20 μm). Then, after drying in a dryer to remove the organic solvent, the positive electrode 1 (thickness: 0.17 m) was rolled using a roll press.
m) was prepared. Thereafter, a positive electrode current collector tab 5 made of aluminum was welded to the positive electrode 1.

In parallel with this, 95% by weight of natural graphite powder (d ₀₀₂ value = 3.36 °) as a negative electrode active material, 5% by weight of PVDF as a binder and NM as a solvent
After mixing with the P solution to prepare a slurry, the slurry was applied to both surfaces of a copper foil (thickness: 20 μm) as the negative electrode current collector 2a using a die coder or a doctor blade or the like. Thereafter, this was dried in a dryer to remove the organic solvent, and then rolled using a roll press to produce a negative electrode 2 (thickness: 0.14 mm). Thereafter, a negative electrode current collector tab 6 made of nickel was welded to the negative electrode 2.

Next, the positive electrode 1 and the negative electrode 2 are connected to both electrodes 1 ·
The separator 3 (thickness: 25 μm) made of a polyethylene microporous membrane while the center lines of
m) and then wound by a winder to produce a power generating element 4. At this time, the safety piece 10 is inserted into a predetermined position. Next, after the insulating plates 9 and 10 are arranged above and below the power generating element 4, the power generating element 4 and the insulating plates 9 and 10 are disposed.
10 was inserted into the outer can 8. Thereafter, the negative electrode current collecting tab 6 is welded to the bottom of the outer can 8 and the positive electrode current collecting tab 5 is welded.
Was welded to the bottom of the sealing plate 7.

Thereafter, 40 parts by weight of ethylene carbonate (EC) and 60 parts by weight of dimethyl carbonate (DM)
An electrolyte in which LiPF ₆ is dissolved at a ratio of 1 M (mol / liter) into a mixed solvent with C) is injected through the opening of the outer can 8, and then sealed via an insulating gasket 13 made of polypropylene (PP). The plate 7 was fixed by caulking to the open end of the outer can 8. Thus, a cylindrical non-aqueous electrolyte battery was manufactured.

The shape of the safety piece 10 is shown in FIG.
The shape is not limited to the shape shown in FIG. 3, for example, the shape shown in FIG. 3 or FIG.
Further, a structure in which a metal part having a high hardness is used as a rising part by combining a metal having a high hardness and a metal having a low hardness may be employed.

In the above embodiment, the safety piece 10 is inserted into the power generating element 8. However, the present invention is not limited to such a structure, and the safety piece 10 may include the positive current collecting tab 5 and / or the negative electrode. A configuration that also serves as the current collecting tab 6 may be used. Further, the present invention is not limited to a cylindrical non-aqueous electrolyte battery, but may be applied to a square non-aqueous electrolyte battery. However, when applied to a square type, it is necessary to press a spiral power generating element with a press machine to form a flat spiral.

In addition, as the positive electrode material, the above LiCoO
_TwoIn addition, for example, LiNiO_Two, LiMn_TwoO_FourOr
These composites and the like are preferably used and used as a negative electrode material.
In addition to the above carbon materials, lithium metal, lithium alloy,
Alternatively, a metal oxide (such as a tin oxide) is preferably used.
You. Further, the solvent of the electrolytic solution is not limited to the above,
Propylene carbonate, vinylene carbonate, γ-
A solution with a relatively high dielectric constant, such as butyrolactone,
Methyl carbonate, methyl ethyl carbonate, tet
Lahydrofuran, 1,2-dimethoxyethane, 1,3-
Dioxolan, 2-methoxytetrahydrofuran, diee
Mix with a low-viscosity low-boiling solvent such as tyl ether in an appropriate ratio
Combined solvents can be used. In addition, electrolytic solution
The quality is LiPF₆And LiAsF₆, Li
ClO_Four, LiBF_Four, LiCF _ThreeSO_ThreeUse
Can be.

In addition to the above-mentioned aluminum foil, an aluminum mesh or the like can be used as the positive electrode core. Further, the separator is not limited to the above-mentioned polyethylene microporous membrane, but it is preferable to use a microporous membrane made of an inexpensive polyolefin resin having low reactivity with an organic solvent.

[0024]

[Example 1] In Example 1, a battery manufactured by the same method as that described in the embodiment of the present invention was used. The battery fabricated in this manner is hereinafter referred to as Battery A1 of the invention.

[Embodiment 2] As shown in FIG. 7, the positive electrode core exposed portion 1c where the positive electrode active material layer 1b is not formed and the negative electrode active material are formed at least one turn from the winding start end 4a of the power generating element 4. Exposed negative electrode core 2c on which layer 2b is not formed
And a battery was fabricated in the same manner as in Example 1 except that the safety piece 10 was inserted at positions corresponding to the exposed portions 1c and 2c. The battery fabricated in this manner is hereinafter referred to as Battery A2 of the invention.

Comparative Example Except that the safety piece 10 was not inserted,
A battery was manufactured in the same manner as in Example 1. The battery fabricated in this manner is hereinafter referred to as Comparative Battery X.

[Experiment] After charging the batteries A1 and A2 of the present invention and the comparative battery X, a thermocouple was attached to the surface of the battery in an environment of 20 ° C., and as shown in FIG.
The central portion of the battery 15 was crushed by a metal round bar 16 of m, causing a short circuit in the battery 15 and the maximum attained temperature of each battery was examined. The results are shown in Table 1. The charging conditions were such that each battery had a constant current of 1600 mA and a battery voltage of 4.2.
V, and after the battery voltage reaches 4.2 V, constant-voltage charging is performed, for a total of three hours. The number of samples is five for each battery.

[0028]

[Table 1]

As apparent from Table 1 above, the comparative battery X
Although the maximum temperature is high, the battery A1 of the present invention
It can be seen that the maximum attainable temperature is low in A2, and particularly the maximum attainable temperature is extremely low in the battery A2 of the present invention.

Such a result is considered to be due to the following reason. That is, in the comparative battery X,
When a short circuit occurs inside the battery, the positive electrode active material layer and the negative electrode active material layer come into contact with each other (so-called short-circuit between the active materials). As shown in FIG. (That is, a state in which a short circuit occurs inside the battery and a state in which no short circuit occurs) are repeated. As a result, a large current locally flows to increase the maximum temperature.

On the other hand, in the batteries A1 and A2 of the present invention, when a stress is applied from the outside, the rising portion made of metal breaks through the positive electrode and the negative electrode. Short circuit directly with the core. Therefore, when a short circuit occurs in the battery, the internal resistance of the battery is small, and almost current flows instantaneously as shown in FIG. Furthermore, the battery A2 of the present invention is particularly excellent when the rising portion breaks through the positive electrode and the negative electrode,
This is considered to be because the short circuit occurs in the portion where the resistance is the smallest because the active material layer does not exist, and the internal resistance is further reduced.

[0032]

As described above, according to the present invention,
Even if a short circuit occurs inside the battery due to external stress, it is possible to prevent sudden voltage drop and voltage return from being repeated, thereby dramatically improving the safety of non-aqueous electrolyte batteries. It has an excellent effect that it can be performed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a nonaqueous electrolyte battery according to the present invention.

FIG. 2 is a front view showing a relationship between a safety piece and a negative electrode.

FIG. 3 is a plan view of a safety piece according to another example used in the present invention.

FIG. 4 is a plan view of a safety piece according to another example used in the present invention.

FIG. 5 is a cross-sectional view showing a relationship between a safety piece and a power generating element before pressure is applied from the outside.

FIG. 6 is a cross-sectional view showing the relationship between the safety piece and the power generating element after externally applying pressure.

FIG. 7 is an explanatory diagram of a power generating element according to another example used in the present invention.

FIG. 8 is an explanatory diagram showing an experimental method for examining the highest attainment temperatures of the batteries A1 and A2 of the present invention and the comparative battery X.

FIG. 9 is a graph showing the relationship between voltage and time when the battery of the present invention is short-circuited inside the battery.

FIG. 10 is a graph showing the relationship between voltage and time when a comparative battery short-circuits inside the battery.

[Explanation of symbols]

 1: Positive electrode 1a: Positive electrode core 1b: Positive electrode active material layer 2: Negative electrode 2a: Negative electrode core 2b: Negative electrode active material layer 3: Separator 4: Power generating element 5: Positive current collecting tab 6: Negative current collecting tab 7: Sealing Body 8: Outer can 10: Safety piece 11: Cut 12: Stand up

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H022 AA09 AA18 BB02 CC08 CC13 CC19 EE01 KK00 5H029 AJ12 AK03 AL02 AL07 AL12 AM02 AM03 AM04 AM05 AM07 BJ02 BJ14 BJ27 DJ05 DJ07 DJ12 EJ01 HJ12 5H030 AA06 AS20

Claims (5)

[Claims] 1. A positive electrode having a positive electrode active material layer capable of inserting and extracting lithium ions on both surfaces of a positive electrode core made of metal foil, and inserting and releasing lithium ions on both surfaces of a negative electrode core made of metal foil. A negative electrode provided with a negative electrode active material layer, and a non-aqueous electrolyte battery including a power generation element spirally wound through a separator impregnated with the non-aqueous electrolyte, A sealed battery comprising a safety piece having a metallic rising portion that rises when a force is applied and breaks through the positive electrode and the negative electrode. 2. The non-aqueous electrolyte battery according to claim 1, wherein the safety piece is made of a metal, and the safety piece is provided with a notch to constitute the rising portion. 3. The non-aqueous electrolyte battery according to claim 1, wherein the rising portion has a tapered shape. 4. The non-aqueous electrolyte battery according to claim 1, wherein the safety piece also functions as a positive electrode current collecting tab and / or a negative electrode current collecting tab. 5. A positive electrode core exposed portion where the positive electrode active material layer is not formed and the negative electrode active material layer are formed in at least one turn in any part of the spirally wound power generating element. 5. The sealed battery according to claim 1, wherein an unexposed negative electrode core exposed portion is provided, and the safety piece is inserted at a position corresponding to the both core exposed portions.