JPH11265700A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery capable of surely preventing the occurrence of a leak of electrolyte to improve the reliability of the battery, and also surely operating a current interrupting mechanism to improve the safety of the battery. SOLUTION: This nonaqueous electrolyte secondary battery has a bottomed cylindrical facing can 5 containing a generating element 4 consisting of positive and negative electrodes 1, 2 wound through a separator 3 and an electrolyte and a sealing body 6 for sealing the opening part of the facing can 5 and having a current cutoff valve 8 for interrupting the contact between the generating element 4 and a positive electrode gap 7 to stop the further charging when the pressure inside the battery increased. In this battery, excessive electrolyte is housed in the facing can 5, and a liquid absorptive insulator 15 for absorbing the electrolyte is arranged in hollow part 14 situated in the winding center of 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 bottomed cylindrical outer can containing a power generating element whose positive and negative electrodes are wound via a separator and an excess electrolyte, and an opening of the outer can. The present invention relates to a non-aqueous electrolyte secondary battery having a sealing body and a sealing body provided with a current interrupting mechanism for interrupting charging by cutting off the contact between the power generating element and a current extraction terminal when the pressure in the battery increases.

[0002]

2. Description of the Related Art In recent years, non-aqueous electrolyte secondary batteries have been used for electronic devices such as mobile phones. In this case, it is necessary to ensure the safety of the batteries during overcharge. Therefore, as shown in Japanese Patent Application Laid-Open No. 2-112151, when an amount of electricity equal to or more than a predetermined value is charged from a fully charged state, the contact between the power generation element and the current extraction terminal is made use of the pressure increase in the battery. There has been proposed a device provided with a current cut-off mechanism for stopping the further charging. However, in the battery having the above structure, the current cutoff mechanism may not always operate reliably.

Therefore, as disclosed in JP-A-4-328278, a carbonate is added to the positive electrode to generate carbon dioxide gas when a predetermined amount of electricity is charged, or the additive is added to the electrolyte. Has been proposed to generate gas when a predetermined amount of electricity is charged, thereby reliably operating the current cutoff mechanism.

However, when an additive is added to the positive electrode or the electrolytic solution, the additive does not often contribute to the charge / discharge reaction of the electrode as long as normal charge / discharge is performed. Thus, there is a problem that the battery capacity is reduced, and further, various characteristics of the battery are reduced, and therefore, it is impossible to improve the performance of the battery. Therefore, in order to solve this problem, a battery having a structure in which a slightly larger amount of electrolyte is injected into the outer can than the amount required for smoothly progressing charge / discharge can be considered. With such a configuration, no additive is required, so that the battery capacity can be prevented from lowering, the space volume in the battery can be reduced, and the low boiling point in the electrolyte due to heat generation during overcharge. Since the gas generation due to the evaporation of the components and the decomposition of the electrolytic solution at a high voltage is further facilitated, the above-described current interruption mechanism can be reliably operated. However, the battery with the above configuration has a problem that the amount of the electrolyte increases, the electrolyte leaks, and the reliability of the battery decreases.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is intended to prevent the occurrence of electrolyte leakage to improve the reliability of a battery and to cut off current. An object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of reliably operating a mechanism and improving battery safety.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a power generating element in which both positive and negative electrodes are wound via a separator and an electrolyte are housed. The bottomed cylindrical outer can and the opening of the outer can are sealed, and when the pressure in the battery increases, the contact between the power generating element and the current extracting terminal is cut off to stop further charging. In a non-aqueous electrolyte secondary battery having a sealing body provided with a current interrupting mechanism, an excess electrolyte is stored in the outer can, and a hollow portion at the winding center of the power generation element includes: A liquid-absorbing insulator for absorbing the electrolytic solution is provided.

As described above, if the liquid-absorbing insulator that absorbs the electrolytic solution is disposed in the hollow portion, the amount of the electrolytic solution (excess electrolytic solution) is larger than that required for smoothly progressing charge and discharge. )
Even if is stored in the outer can, excess electrolyte is absorbed by the liquid-absorbing insulator, so that leakage of the electrolyte can be prevented. Furthermore, the amount of gas generated at the time of overcharging increases due to the presence of excess electrolyte, and the volume of the space in the battery decreases due to the presence of the liquid-absorbing insulator.
Therefore, the current cutoff mechanism can be reliably operated. In addition, due to the presence of the excess electrolyte, battery abnormality such as battery ignition does not occur, battery safety is improved, and battery cycle deterioration is suppressed.

According to a second aspect of the present invention, in the first aspect of the present invention, the amount of the electrolyte is 0.0035 cm ³ or more and 0.005 c per mAh of the theoretical capacity of the battery.
characterized in that m ³ or less. The amount of the electrolytic solution is regulated within such a range for the following reason.
That is, when the amount of the electrolytic solution is less than 0.0035 cm ³ per 1 mAh of the theoretical capacity of the battery, the discharge capacity is reduced due to the exhaustion of the electrolytic solution, and ignition or the like due to overcharging occurs. The liquid volume is 1 mAh, the theoretical capacity of the battery.
If it exceeds 0.005 cm ³ per cell, an electrolyte that is not absorbed by the liquid-absorbing insulator will be present in the battery, and as a result, the electrolyte will leak.

[0009]

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 non-aqueous electrolyte secondary battery according to the present invention, FIG. 2 is an enlarged cross-sectional view of a battery current interrupting mechanism, and FIG. 3 is an enlarged cross-sectional view of the battery when the current interrupting mechanism operates. .

As shown in FIG. 1, the nonaqueous electrolyte secondary battery of the present invention has a bottomed cylindrical outer can 5, which is made of nickel-plated iron. . In the outer can 5, a core body made of aluminum is coated with LiCo.
A positive electrode 1 on which an active material layer mainly composed of O ₂ is formed; a negative electrode 2 on which an active material layer mainly composed of graphite is formed on a core made of copper; and a separator 3 which separates these electrodes 1 and 2 Are stored. In addition, ethylene carbonate (E
In C) and dimethyl carbonate and (DMC) is a volume ratio of 4: 6 to mixed mixed solvent at a ratio of, LiPF ₆ is 1
An electrolyte dissolved at a rate of M (mol / liter) is injected. Furthermore, the battery is sealed by caulking the sealing body 6 into the opening of the outer can 5.

Here, as shown in FIG. 2, the sealing body 6 has a positive electrode cap 7 also serving as a positive electrode terminal, and a current cutoff valve 8 having a substantially semi-spherical shape is provided on the positive electrode cap 7. It is electrically connected. In a normal state, the current cutoff valve 8 is a thin plate 9 electrically connected to the positive electrode current collecting tab 10.
On the other hand, when the pressure inside the battery becomes a predetermined value (10 to 20 kgf / cm ² ) or more at the time of abnormality such as overcharging, as shown in FIG. As a result, charging is stopped. The sealing body 6 is provided with an insulating packing 11.

In the hollow part 14 of the power generating element 4,
Absorbent insulator 15 made of polyethylene fiber in a cylindrical shape
Are arranged, and the liquid-absorbing insulator 15 is configured to absorb excess electrolytic solution. Further, a negative electrode current collecting tab 13 electrically connected to the negative electrode 2 is connected to the outer can 5, and insulating plates 16 and 17 are disposed near upper and lower ends of the power generating element 4. .

Here, the non-aqueous electrolyte battery having the above structure was manufactured as follows. First, L as a positive electrode active material
90% by weight of iCoO ₂ , 5% by weight of carbon black as a conductive agent, 5% by weight of polyvinylidene fluoride as a binder, and N-methyl-2-pyrrolidone (NMP) solution as a solvent After mixing to prepare a slurry, the above-mentioned slurry was removed from an aluminum foil (thickness: 20 μm) as a positive electrode current collector, except for a welding portion of the positive electrode current collector tab 10.
m). Thereafter, the solvent was dried, compressed to a predetermined thickness by a roller, cut into a predetermined width and length, and then a positive electrode current collector tab 10 (width: 3 mm) made of aluminum was welded.

At the same time, a slurry was prepared by mixing 95% by weight of graphite powder as a negative electrode active material, 5% by weight of polyvinylidene fluoride as a binder, and an NMP solution as a solvent. Thereafter, the above-mentioned slurry was applied to both surfaces of a copper foil (thickness: 16 μm) as a negative electrode current collector, except for a welding portion of the negative electrode current collector tab 13. Thereafter, the solvent was dried, compressed to a predetermined thickness by a roller, cut into a predetermined width and length, and a nickel negative electrode current collecting tab 13 (width: 3 mm) was welded.

Next, the positive electrode 1 and the negative electrode 2 are separated by a separator 3 (thickness: 25 μm) made of a microporous polyethylene film.
Then, the power generating element 4 was fabricated by inserting the power generating element 4 together with the insulating plate 16 into the outer can 5, and the negative electrode current collecting tab 13 was welded to the bottom of the outer can 5. Thereafter, the positive electrode current collecting tab 10 is welded to the thin plate 9 of the sealing plate 6 provided with a current interrupting mechanism, and the liquid-absorbing insulator 15 is inserted into the hollow portion 14 of the power generation element 4. Thereafter, LiP was added to a mixed solvent in which EC and DMC were mixed at a volume ratio of 4: 6.
An electrolyte in which F ₆ is dissolved at a rate of 1 M (mol / liter) is applied at a rate of 0.0035 cm per 1 mAh of theoretical battery capacity.
³ and then sealed with a sealing plate 6 to form a cylindrical battery (diameter: 18 mm,
A height of 65 mm and a theoretical capacity of 1400 mAh) were produced.

In the above embodiment, the positive electrode current collecting tab 1
Although the current cutoff valve 8 is provided through the thin plate 9 electrically connected to the positive electrode 0, the present invention is not limited to such a structure. For example, the positive current collecting tab 10 and the current cutoff valve 8 are directly welded. Such a structure may be adopted. In this case, the pressure inside the battery is increased to a predetermined value (10 to 20) at the time of abnormality such as overcharging.
When the pressure exceeds kgf / cm ² ), the welded portion between the positive electrode current collecting tab 10 and the current cutoff valve 8 is disengaged and the current cutoff mechanism operates.

Further, the liquid-absorbing insulator 15 is not limited to a polyethylene fiber formed into a cylindrical shape, but may be, for example, a polyolefin resin fiber such as a polypropylene fiber formed into a cylindrical shape, polyethylene, or the like. Polyolefin resin non-woven fabric such as polypropylene resin non-woven fabric formed by winding into a cylindrical shape, a polymer absorber that absorbs an electrolytic solution and becomes a gel, or a ceramic porous body processed into a cylindrical shape can be used. It is possible. In addition, as the cathode material, in addition to the above LiCoO ₂ , for example,
LiNiO ₂ , LiMn ₂ O ₄ or a composite thereof is preferably used. As the negative electrode material, in addition to the above-mentioned carbon materials, lithium metal, lithium alloys, metal oxides (tin oxides and the like) are preferably used. Used.

Further, the solvent of the electrolytic solution is not limited to the above-mentioned ones. A solution having a relatively high relative dielectric constant such as propylene carbonate, ethylene carbonate, vinylene carbonate, γ-butyrolactone, and diethyl carbonate,
Dimethyl carbonate, methyl ethyl carbonate, tetrahydrofuran, 1,2-dimethoxyethane, 1,3
A solvent in which low-viscosity low-boiling solvents such as -dioxolan, 2-methoxytetrahydrofuran, and diethyl ether are mixed at an appropriate ratio can be used. As the electrolyte of the electrolytic solution, in addition to the above-mentioned LiPF ₆ , LiAsF ₆ , L
iClO ₄ , LiBF ₄ , LiCF ₃ SO _{3 and the} like can be used.

[0019]

[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. Example 2 A battery was manufactured in the same manner as in Example 1 except that the amount of the electrolyte was adjusted to be 0.0040 cm ³ per 1 mAh of the theoretical capacity of the battery. The battery fabricated in this manner is hereinafter referred to as Battery A2 of the invention.

Example 3 A battery was manufactured in the same manner as in Example 1 except that the amount of the electrolyte was adjusted to 0.0050 cm ³ per 1 mAh of the theoretical capacity of the battery. The battery fabricated in this manner is hereinafter referred to as Battery A3 of the invention. Example 4 A battery was manufactured in the same manner as in Example 1 except that the amount of the electrolyte was adjusted to 0.0055 cm ³ per 1 mAh of the theoretical capacity of the battery. The battery fabricated in this manner is hereinafter referred to as Battery A4 of the invention.

[Comparative Examples 1 to 3] Examples 1 to 3 except that no liquid-absorbing insulator was disposed in the hollow portion of the power generating element.
In the same manner as in the above, a battery was produced. The batteries fabricated in this manner are hereinafter referred to as comparative batteries X1 to X3, respectively. Comparative Example 4 A battery was fabricated in the same manner as in Example 1 except that the amount of the electrolytic solution was 0.0030 cm ³ per 1 mAh of the theoretical capacity of the battery. The battery fabricated in this manner is hereinafter referred to as Comparative Battery X4.

Comparative Example 5 A battery was manufactured in the same manner as in Comparative Example 4 except that no liquid-absorbing insulator was disposed in the hollow portion of the power generating element. The battery fabricated in this manner is hereinafter referred to as Comparative Battery X5. Comparative Example 6 A battery was manufactured in the same manner as in Example 4 except that no liquid-absorbing insulator was disposed in the hollow portion of the power generating element.
The battery fabricated in this manner is hereinafter referred to as Comparative Battery X6.

[Experiment 1] Overcharging tests were performed on the batteries A1 to A4 of the present invention and the comparative batteries X1 to X6, and the results are shown in Table 1 below. The experimental condition was 270.
The condition is that the battery is continuously charged with a constant current of 0 mA, and the number of samples is 5 for each battery.

[0024]

[Table 1]

As apparent from Table 1 above, in the batteries A1 to A4 of the present invention, the comparative batteries X1 to X3 and the comparative battery X6, no abnormality occurred in the batteries. In X5, it is recognized that an abnormality of the battery occurs due to a small amount of the electrolyte.

[Experiment 2] Drop tests were performed on the batteries A1 to A4 of the present invention and the comparative batteries X1 to X6.
The results are shown in Table 1 above. The experimental conditions were 1 m
And the number of samples is 50 for each battery.

As is clear from Table 1 above, in the batteries A1 to A3 of the present invention, no leakage of the electrolyte was observed, whereas the batteries of Comparative Examples X1 to X3 and Comparative Battery X6 (the batteries of Experiment 1 described above were used). In the case of a comparative battery in which no abnormality occurs, the electrolyte leaks due to the absence of the liquid-absorbing insulator that absorbs the excess electrolyte. However, in the battery A4 of the present invention in which the amount of the electrolyte is too large, leakage of the electrolyte is observed.

[Experiment 3] A cycle test was performed on the batteries A1 to A4 of the present invention and the comparative batteries X1 to X6, and the results are shown in FIG. The charging and discharging conditions are as follows. Charging conditions: Battery voltage of 4.1 V at constant current of 1350 mA
, And then charge at a constant voltage of 4.1 V. When the current value drops to 27 mA, the charging is completed. Then rest for 10 minutes. Discharge conditions: 1.75 mA constant current and battery voltage of 2.75
Discharge to V, then rest for 10 minutes.

As is clear from FIG. 4, the battery A1 of the present invention
A4 and comparative batteries X1 to X3 and comparative battery X6,
While good cycle characteristics are shown, in Comparative Battery X4 and Comparative Battery X5, it is recognized that the decrease in discharge capacity is large and the cycle is deteriorated due to the small amount of electrolyte.

[0030]

As described above, according to the present invention,
Excess electrolyte is absorbed by the absorbent insulator, so that leakage of the electrolyte can be prevented. In addition, due to the presence of excess electrolyte, the amount of gas generated during overcharge increases,
Since the volume of the space in the battery is reduced by the presence of the liquid-absorbing insulator, the current cutoff mechanism can be reliably operated. In addition, due to the presence of the excess electrolyte, there is no battery abnormality such as ignition of the battery, so that the battery is improved in safety and the cycle deterioration of the battery is suppressed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a non-aqueous electrolyte secondary battery according to the present invention.

FIG. 2 is an enlarged sectional view of a current interrupting mechanism of a battery.

FIG. 3 is an enlarged cross-sectional view when a current cutoff mechanism of a battery is operated.

FIG. 4 shows batteries A1 to A4 of the present invention and comparative batteries X1 to X6.
5 is a graph showing cycle characteristics of the present invention.

[Explanation of symbols]

 1: Positive electrode 2: Negative electrode 3: Separator 4: Power generation element 5: Outer can 8: Current cutoff valve 15: Liquid absorbing insulator

Continuation of front page (72) Inventor Naoyama Yamaguchi 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A bottomed cylindrical outer can containing an electric power generating element and an electrolytic solution in which both positive and negative electrodes are wound via a separator, an opening of the outer can is sealed, and pressure inside the battery is reduced. In the non-aqueous electrolyte secondary battery having a sealing body provided with a current cutoff mechanism that cuts off the contact between the power generation element and the current extraction terminal when the power generation element rises and stops further charging, Is a non-aqueous electrolyte characterized in that an excess electrolyte is stored and a liquid-absorbing insulator that absorbs the electrolyte is disposed in a hollow portion at the winding center of the power generation element. Rechargeable battery. 2. The battery according to claim 1, wherein the amount of the electrolyte is the theoretical capacity of the battery.
mAh per 0.0035cm ³ more than 0.005cm ³
The non-aqueous electrolyte secondary battery according to claim 1, wherein: