JP2002134072A - Flattened non-aqueous electrolytic secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flattened non-aqueous electrolytic secondary battery, by which disruption is prevented, safety is improved and a larger amount of electric current can be discharged, while maintaining sealability. SOLUTION: In the flattened non-aqueous electrolytic secondary battery wherein a set of electrodes with strip positive electrodes and negative electrodes wound via a separator are housed in a battery case, a cutaway is provided at a side face of a positive electrode case. When the width of this cutaway is 0.1 to 0.9 π radius in central angle to the circumference of the positive electrode case and the depth of the cutaway is 5 to 30% of the height of the positive electrode case, disruption of the battery can be prevented, and safety of the battery can be improved as no leakage by storage is also caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat nonaqueous electrolyte secondary battery excellent in heavy load discharge characteristics and safety thereof.

[0002]

MnO ₂ and V ₂ O metal oxide such as ₅ of the Related Art cathode agent, or inorganic compounds such as fluorinated graphite, or using Porianin and polyacene structure such as an organic compound of a metal lithium on the negative electrode or, Lithium alloy, or an organic compound such as a polyacene structure, or a carbonaceous material capable of absorbing and releasing lithium, or an oxide such as lithium titanate or lithium-containing silicon oxide, and propylene carbonate, ethylene carbonate, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ S in a non-aqueous solvent such as butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, and γ-butyl lactone
A coin-shaped or button-shaped flat non-aqueous electrolyte secondary battery using a non-aqueous electrolyte in which a supporting salt such as O ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ is dissolved is It is used as a backup for an SRAM which discharges with a light load of several to several tens of μA, a main power supply of a wristwatch, and the like.

[0003] These conventional coin-shaped or button-shaped flat nonaqueous electrolyte secondary batteries have the advantages of simple manufacturing, excellent mass productivity, long-term reliability and safety, and the simple structure. Miniaturization is possible.

However, on the other hand, medium to heavy load discharge is impossible due to the limited electrode area, and it cannot be used as a main power source for information terminals such as mobile phones and PDAs, which have a large need for small batteries. Was.

Therefore, the present inventors have provided a coin-shaped or button-shaped flat non-aqueous electrolyte secondary battery capable of discharging a heavy load by increasing the electrode area without changing the battery shape. That is, when a cross section in a direction perpendicular to the flat surface of the flat battery is viewed, an electrode group having a positive / negative electrode facing surface where at least three or more positive electrodes and a negative electrode face each other with a separator interposed therebetween, and By making the total area of the positive and negative electrode facing areas larger than the opening area of the insulating gasket, a flat nonaqueous electrolyte secondary battery with remarkably improved heavy load discharge characteristics could be provided. However, while such a battery can provide a large current, if it is used improperly and is placed in an abnormal situation such as a short circuit, a remarkable temperature rise occurs, causing a thermal runaway phenomenon, which may cause a burst or explosion.

[0006]

Conventionally, in a cylindrical non-aqueous electrolyte secondary battery having a caulking structure, a safety element is provided inside the battery. In addition, some cylindrical alkaline manganese primary batteries avoid rupture of the battery by compressing the battery container only in the radial direction and caulking the insulating gasket.

As a safety element, an element having a P 有 す る C characteristic in which a resistance value increases with a rise in temperature is generally used. This is a resin in which insulating resin and conductive carbon are blended, sandwiched between metal electrode plates, and shows a very small resistance value under normal use conditions, but because the resistance value increases when overcurrent occurs or when the temperature rises The current is cut off, which has the effect of preventing thermal runaway. However, when this means is applied to a coin-type or button-type small battery, the structure becomes complicated, so that miniaturization becomes difficult.

On the other hand, in the latter method of caulking only in the radial direction, since the insulating gasket is not compressed in the height direction of the battery, it is easily released when the internal pressure rises, and rupture can be prevented beforehand. . In addition, a step is formed by projecting about 50% of the circumference of the opening of the battery container, and furthermore, the projecting portion is inclined inward, and even when the insulating gasket comes off from the caulked portion, the insulating gasket is brought into contact with the projecting portion to thereby separate the insulating gasket from the battery container. Batteries are also being manufactured that prevent their coming off.
However, in the battery having such a structure, since the compression ratio of the insulating gasket is low, problems such as frequent occurrence of electrolyte leakage occur.

The above-mentioned safety measures cannot be applied to the flat non-aqueous electrolyte secondary battery by the safety element described above, and when the latter means is adopted, the flat type, which has excellent sealing performance and high reliability, is used. The characteristics of the non-aqueous electrolyte secondary battery are impaired.

SUMMARY OF THE INVENTION The present invention has been made to address the above circumstances, and a flat non-aqueous electrolyte capable of discharging a large current capable of preventing rupture and improving safety while maintaining battery sealing properties. The challenge is to provide a secondary battery.

[0011]

In order to solve the above-mentioned problems, the present invention is characterized in that a conventional flat battery caulking method is improved, and a notch is provided on a side surface portion of a positive electrode case to perform caulking. . That is, since the insulating packing is compressed in the radial direction and the height direction, no liquid leakage occurs in a normal state, but the notched portion of the positive electrode case is easily deformed. Can be opened to prevent rupture.

Further, it is possible to reliably avoid a burst in a thermal runaway state,
In addition, in order to prevent problems such as liquid leakage during normal use, as shown in the following experiment, the width of the notch provided on the side of the positive electrode case is centered with respect to the circumference of the positive electrode case. It is desirable that the angle is 0.1π to 0.9πrad and the notch depth is 5 to 30% of the height of the positive electrode case.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention and comparative examples will be described in detail. (Example 1) FIG. 1 is a sectional view of a battery according to Example 1 of the present invention.
FIG. 2 shows a perspective view of the positive electrode case. Example 1 below
The method for manufacturing the battery described above will be described.

First, 5 parts by mass of acetylene black and 5 parts by mass of graphite powder were added as conductive agents to 100 parts by mass of LiCoO ₂ , 5 parts by mass of polyvinylidene fluoride was added as a binder, and the mixture was diluted with N-methylpyrrolidone and mixed. Thus, a slurry-like positive electrode mixture was obtained. Next, this positive electrode mixture is applied to both surfaces of a 0.02 mm thick aluminum foil as a positive electrode current collector by a doctor blade method and dried, and the coating thickness of the positive electrode active material-containing layer is reduced to 0 on both surfaces. A .15 mm double-sided coated positive electrode was produced. Next, a 10 mm portion of the active substance-containing layer was removed from one end of one side of the electrode body, and the aluminum layer was stripped to serve as a current-carrying part. The positive electrode plate 2 was cut out to a width of 15 mm and a length of 120 mm.

Next, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were used as binders in 100 parts by mass of the graphitized mesophase pitch carbon fiber powder.
Were added and diluted with ion-exchanged water and mixed to obtain a slurry-like negative electrode mixture. The obtained negative electrode mixture is applied to both sides of a copper foil having a thickness of 0.02 mm as a negative electrode current collector by a doctor blade method and dried, and a double-sided coated negative electrode having an active substance-containing layer having a thickness of 0.15 mm is applied. Was prepared. Next, the active substance-containing layer of 10 mm portion was removed from one end of the electrode body, and the copper layer was exposed to form a current-carrying part.
A negative electrode plate 4 cut out to a width of 15 mm and a length of 120 mm was produced.

Next, the current-carrying surface of the positive / negative plate is set to the outer peripheral winding end side, and spirally wound between the positive electrode plate 2 and the negative electrode plate 4 via a separator 3 made of a 25 μm-thick polyethylene microporous film. Then, pressure was applied in a fixed direction so that the space at the center of the wound electrode was exhausted so as to have the positive and negative electrode facing portions in the horizontal direction with respect to the flat surface of the flat battery.

After the produced electrode group is dried at 85 ° C. for 12 hours, it is arranged so that the active substance-containing layer removed portion of the negative electrode plate of the electrode group is in contact with the inner bottom surface of the negative electrode metal case 5 in which the insulating gasket 6 is integrated. A non-aqueous electrolyte obtained by dissolving LiPF ₆ at a rate of 1 mol / l as a supporting salt in a solvent in which ethylene carbonate and methyl ethyl carbonate are mixed at a volume ratio of 1: 1 is injected, and the function of the positive electrode plate of the electrode group The positive electrode case 1 made of stainless steel was fitted so as to be in contact with the material-containing layer-removed portion, and after turning upside down, the positive electrode case 1 was subjected to caulking in the radial direction and the height direction and sealed. The positive electrode case 1 has a height of 3 mm, a diameter of 24.5 mm, and a second
As shown in the figure, the central angle is 0.1πrad and the depth is 0.15.
A notch 1a of mm is provided. This gives a thickness of 3
Fifty flat nonaqueous electrolyte secondary batteries of Example 1 having a diameter of 24.5 mm and a diameter of 24.5 mm were produced.

(Embodiment 2) The dimensions of the notched portion 1a formed in the positive electrode case 1 are such that the central angle is 0.1πrad and the depth is 0.90.
Except for mm, 50 batteries having the structure shown in FIG.

(Embodiment 3) The dimensions of the notched portion 1a formed on the positive electrode case 1 are such that the central angle is 0.9πrad and the depth is 0.15.
Except for mm, 50 batteries having the structure shown in FIG.

(Embodiment 4) The dimensions of the notched portion 1a formed in the positive electrode case 1 are such that the central angle is 0.9πrad and the depth is 0.90.
Except for mm, 50 batteries having the structure shown in FIG.

Comparative Example 1 Fifty batteries having the structure shown in FIG. 1 were produced in the same manner as in Example 1 except that the positive electrode case 1 shown in FIG. 3 was used.

(Comparative Example 2) The dimensions of the notched portion 1a formed in the positive electrode case 1 were such that the central angle was 0.1πrad and the depth was 0.10.
Except for mm, 50 batteries having the structure shown in FIG.

(Comparative Example 3) The dimensions of the notched portion 1a formed on the positive electrode case 1 were such that the central angle was 0.1πrad and the depth was 0.95.
Except for mm, 50 batteries having the structure shown in FIG.

(Comparative Example 4) The dimensions of the notched portion 1a formed in the positive electrode case 1 were such that the central angle was 0.05πrad and the depth was 0.9.
Except for 0 mm, 50 batteries having the same structure as that of Example 1 and shown in FIG. 1 were produced.

(Comparative Example 5) The dimensions of the notched portion 1a formed on the positive electrode case 1 were such that the central angle was 0.95πrad and the depth was 0.1.
Except for 5 mm, 50 batteries having the same structure as that of Example 1 and shown in FIG. 1 were produced.

(Comparative Example 6) The dimensions of the notched portion 1a provided on the positive electrode case 1 are such that the central angle is 0.1πrad and the depth is 0.15.
mm, and 50 batteries having the structure shown in FIG. 4 were produced in the same manner as in Example 1 except that the positive electrode case 1 was caulked only in the radial direction and sealed.

For these batteries, 4.2 V, 3 mA
After initial charging for 48 hours at constant current and constant voltage of 45 ℃ -9
It was stored at 3% Rh for 100 days, and the number of occurrences of electrolyte leakage was examined. Further, a constant current forced discharge test at 300 mA for 6 hours and a heating test at 160 ° C. for 10 minutes at a rate of temperature increase of 5 ° C./min were performed to examine the occurrence of rupture.

Table 1 shows the test results. In the batteries of this example and comparative examples 1, 2, and 4, no liquid leakage due to storage occurred. On the other hand, in Comparative Example 3, since the notch was too deep, the electrolyte leaked from the notched portion. In Comparative Example 5, the width of the notch was too wide, and in Comparative Example 6, the compressibility of the insulating gasket did not increase, and the airtightness was low, so that the electrolyte leaked.

In the forced discharge test and the heating test, the batteries of this example and Comparative Examples 3, 5, and 6 did not burst,
In the batteries of Comparative Examples 1, 2, and 4, the positive electrode case was not deformed and the insulating gasket was not opened, so that rupture was observed.

[0030]

[Table 1]

As described above, the notch of the positive electrode case is formed such that the width is equal to the central angle of 0.1π to 0.9πr with respect to the circumference of the positive electrode case.
By setting the ad to a depth of 5 to 30% of the height of the positive electrode case, it is possible to obtain a flat nonaqueous solvent secondary battery that does not burst at the time of an abnormality and that does not leak during storage.

Although the embodiment of the present invention has been described using a flat non-aqueous solvent secondary battery using a non-aqueous solvent as a non-aqueous electrolyte, a polymer secondary battery using a polymer electrolyte as a non-aqueous electrolyte has been described. A similar effect can be obtained for a solid electrolyte secondary battery using a solid electrolyte. Further, it is also possible to use a polymer thin film or a solid electrolyte membrane instead of the resin separator. Also, the case where the notch is singular has been described, but even when a plurality of notches are provided, the sum of the widths is 0.1 π to 0.9π rad with respect to the circumference of the positive electrode case.
Then, the same effect can be obtained. Furthermore, the shape of the battery has been described based on the coin-type non-aqueous electrolyte secondary battery that is sealed by swaging the positive electrode case, but it is also possible to replace the positive and negative electrodes and provide a notch in the negative electrode case and seal by swaging. It is possible.

[0033]

As described above, according to the present invention,
It is possible to prevent the flat nonaqueous electrolyte secondary battery from being ruptured, and it is possible to prevent the liquid from leaking due to storage.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a flat nonaqueous electrolyte secondary battery according to Embodiment 1 of the present invention.

FIG. 2 is a perspective view of the positive electrode case of FIG.

FIG. 3 is a perspective view of a conventional positive electrode case.

FIG. 4 is a cross-sectional view of a flat nonaqueous electrolyte secondary battery of Comparative Example 6.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode case, 1a ... Notch part of positive electrode case, 2 ... Positive electrode plate, 3 ... Separator, 4 ... Negative electrode plate, 5 ... Negative electrode case, 6
... an insulating gasket.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masami Suzuki 3-4-1-10 Minamishinagawa, Shinagawa-ku, Tokyo Inside Toshiba Battery Corporation (72) Inventor Kazuo Iizuka 3-4-1 Minamishinagawa, Shinagawa-ku, Tokyo F-term in Toshiba Battery Corporation (reference) 5H011 AA13 CC06 DD15 FF03 GG02 HH02 KK00 KK01 KK02 5H029 AJ12 AK02 AL06 AL12 AL16 AM03 AM05 AM07 BJ03 BJ16 DJ02 DJ12 DJ14 EJ01 HJ00 HJ04 HJ12

Claims (1)

[Claims] 1. A metal negative electrode case also serving as a negative electrode terminal and a metal case also serving as a positive electrode terminal are fitted via an insulating gasket, and the insulating gasket is compressed in a radial direction and a height direction by the positive electrode case. It has a sealing structure swaged by swaging, and a positive electrode of a lithium-containing oxide, a separator, and a negative electrode of a carbonaceous material therein,
In a flat non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte, an electrode group in which a strip-shaped positive electrode and a negative electrode are wound via a separator is housed, and a notch is provided on a side surface portion of the positive electrode case. The width of the notch is 0.1π to 0.9πrad with respect to the circumference of the positive electrode case, and the depth of the notch is 5 to 30% of the height of the positive electrode case. Flat non-aqueous electrolyte secondary battery.