JPH11102728A - Organic electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a production process and prevent electrolyte leakage in the last stage of life by using a clad material of a stainless steel plate and a hard aluminum plate in a negative electrode can. SOLUTION: In an organic electrolyte secondary battery, in which the peripheral hanging part of a negative can 2 inside which a negative electrode is housed and the peripheral standing part 1a of a positive can 1 inside which a positive electrode 7 is housed, are sealed via a gasket 6, the negative can 2 is formed with a clad material of a hard aluminum plate or a hard aluminum alloy plate 2b and a stainless steel plate 2a so that the aluminum plate side faces the inside of a battery, and the longitudinal cross section of the peripheral part is formed, so that a shoulder part 3 is formed in the one step lower part than the top surface, a corner part 4 bent at an angle of 90 ±10 deg. is formed in the outer periphery, and a surrounding wall 5 hanging down from the corner part 4 and terminate at the lower end edge is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a button-type or coin-type small organic electrolyte secondary battery used for a main power supply of an electronic device or a power supply for memory backup.

[0002]

2. Description of the Related Art In general, organic electrolyte batteries have a high energy density, can be reduced in size and weight, and have excellent reliability such as storage characteristics and leakage resistance. The demand for a main power supply of a device and a power supply for memory backup is increasing year by year. Primary batteries that cannot be charged in this type of battery are predominant, and typical battery systems used lithium metal for the negative electrode, manganese dioxide, carbon fluoride, thionyl chloride, sulfur dioxide, silver chromate, and the like for the positive electrode. Batteries are known. Furthermore, rechargeable secondary batteries have recently been developed, and among them, lithium secondary batteries using a lithium alloy or the like for the negative electrode have been actively developed.

When a lithium metal similar to a lithium primary battery is used as a negative electrode of a secondary battery, lithium ions in an electrolytic solution are deposited unevenly on the lithium surface of the negative electrode during charging to form dendrites. However, there is a problem in that an internal short circuit may occur through the separator, or the discharge reaction may become non-uniform at the time of discharge, causing lithium to fall off, thereby deteriorating the cycle life.

[0004] Therefore, as a negative electrode of a lithium secondary battery, lithium and a metal capable of inserting and extracting lithium,
For example, a technique has been proposed in which an alloy with aluminum is used and lithium ions are electrochemically occluded in the alloy during charging to prevent lithium dendrite from depositing on the negative electrode surface.

When a button-type lithium secondary battery is actually manufactured, the structure of the negative electrode portion is hardened so that lithium ions can be occluded and released in order to obtain a lithium aluminum alloy as a negative electrode active material. Punched hard aluminum that has been treated, or a hard aluminum alloy that has been added with metal manganese to increase the hardness and improve the charge-discharge cycle life, into a circle with a diameter smaller than the inner diameter of the flat part of the inner surface of the negative electrode can It is fixed so that electrical contact can be obtained inside the negative electrode can, and furthermore, a lithium foil punched out in a circular shape so as to have a predetermined size is press-bonded to the surface of the hard aluminum, and electrochemically in the presence of an electrolytic solution. By inserting, a lithium aluminum alloy as a negative electrode active material is obtained.

[0006] By the way, hard aluminum stamped in a disk shape is attached to the inside of the negative electrode can to obtain electrical contact, and a generally used method is to use a stainless steel net as a current collector. It is. That is, a circular stainless steel net punched slightly smaller than hard aluminum is attached by resistance welding to the inside of the negative electrode can, and then the hard aluminum punched in a disk shape is placed on the stainless steel net, and it varies depending on the battery diameter. However, electrical contact is obtained by indenting a stainless steel net into hard aluminum with a push pin, usually with a force of about 3 to 10 tons.

[0007]

However, in the above-mentioned conventional method, it is difficult to handle a stainless steel net punched in a circular shape in a production line, and the process becomes complicated due to deformation or fraying of the net. is there. In addition, when pressurizing with a push pin, there is a problem that dents and scratches are likely to occur in the negative electrode can, and there is a problem that the current collecting net is expensive and leads to an increase in cost. .

Therefore, as a method without using a stainless steel net, a method of maintaining electrical contact between hard aluminum and the negative electrode can by welding or the like has been recently developed.

However, since the hard aluminum and the stainless steel of the negative electrode can have a different melting point and cannot be joined by resistance welding, the hard aluminum and the thin stainless steel foil are stuck together by a clad, and the stainless steel negative electrode can and the stainless steel of the clad material are bonded together. Are electrically connected by resistance welding. However, in this method, although the current collecting net can be abolished, maintenance of resistance welding during the manufacturing process is important, so that there is a problem that the process is not solved.

[0010] Further, there has been proposed a method of eliminating the resistance welding step. That is, this is a method in which the negative electrode can itself is formed using the stainless steel plate and the hard aluminum clad material, and the hard aluminum surface is formed on the inner side and formed. The general structure of a button type secondary battery is
As shown in FIG. 2, the periphery of the negative electrode can 11 in which the hard aluminum or hard aluminum alloy disk 12 and the lithium disk 13 are arranged on the inner surface is hung down via a small shoulder portion 14 and U Folded part 15
Are formed, and a rising portion 18 is formed on a peripheral portion of a positive electrode can 17 in which the positive electrode 16 is disposed on the inner surface.
And a gasket 19 between the upper portion 18 and the gasket 19, but the hard aluminum or hard aluminum alloy disk 12 is omitted, and as shown in FIG. One using a cladding material of 21 and hard aluminum 22 has been proposed. According to this, in the battery manufacturing process, a predetermined negative electrode can be easily formed by pressing a predetermined lithium foil 13 on the hard aluminum surface 22 on the inner surface of the negative electrode can 11 and injecting an electrolytic solution.

However, in the configuration shown in FIG. 3, since the sealing surface between the negative electrode can 11 after sealing and the gasket 19 made of a polymer material becomes an alloy surface of the hard aluminum 22 and the lithium 13, especially when the battery is used, As the charge / discharge cycle progresses, the hard aluminum 22 is pulverized,
At the end of the charge / discharge cycle life, the sealing part may be insufficient, and the electrolyte may leak from this part in some cases.Therefore, it has not yet been put to practical use, and improvement is desired. .

[0012] In view of the above-mentioned conventional problems, the present invention can simplify the manufacturing process by using a stainless steel plate and a hard aluminum clad material for a negative electrode can, and can prevent electrolyte leakage at the end of life. An object of the present invention is to provide an electrolyte secondary battery.

[0013]

The organic electrolyte secondary battery of the present invention comprises a positive electrode capable of inserting and extracting lithium through a separator and a hard aluminum or hard aluminum alloy capable of inserting and extracting lithium. A negative electrode having an active material of electrochemically occluded lithium, and an organic electrolyte solution in which a lithium salt is dissolved in an organic solvent; An organic electrolyte secondary battery in which the rising edge of the peripheral portion of the positive electrode can disposed on the inner surface is sealed via a gasket, and the negative electrode can is bonded to a hard aluminum plate or a hard aluminum alloy plate and a stainless steel plate. It is composed of a molded product using the combined clad material and oriented so that the aluminum surface side is housed inside the battery, and the vertical cross-sectional shape of the peripheral part is one step below the upper surface of the negative electrode plate. Has a shoulder was, and on its outer peripheral edge 9
It has a shape in which a corner bent at an angle of 0 ± 10 degrees is formed, and has a peripheral wall hanging down from the corner and ending at the lower end edge.

With such a structure, the manufacturing process can be simplified because the steps such as welding are unnecessary and the manufacturing cost can be reduced, and the sealing surfaces of the gasket and the negative electrode can are made of an alloy surface of hard aluminum and lithium. Instead of a stainless steel plate, even if hard aluminum is pulverized at the end of the charge / discharge cycle life, it is possible to reliably prevent the occurrence of situations such as insufficient sealing and electrolyte leakage. Since the outer peripheral edge of the shoulder portion of the plate peripheral portion is formed as a corner bent at an angle of 90 ± 10 degrees, the gasket is strongly squeezed and compressed by the corner and the inner surface of the positive electrode can, so that the electrolytic solution is formed. Leakage can be prevented.

Further, since the hanging portion of the peripheral portion of the negative electrode can is not folded back into a U-shape, the internal capacity of the battery can be increased, and as a result, the charged electric capacity can be increased.

This is more effective as the battery becomes ultra-small with a diameter of 6 mm or less. In addition, since the inner surface of the negative electrode can is entirely made of hard aluminum, the reaction area can be widened, so that the miniaturization of the lithium aluminum alloy due to the charge / discharge cycle does not progress easily and deterioration can be prevented. The charge / discharge cycle life can be extended.

Preferably, the radius of curvature at the corner of the outer peripheral edge of the shoulder is set to 0.2 mm or less, so that the above-mentioned sealing performance is further ensured.

The lithium salt is LiN (CF ₃ SO
₂ ) If it is any one selected from ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ , the charge / discharge cycle life can be remarkably improved.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the organic electrolyte secondary battery of the present invention will be described below with reference to FIG.

In FIG. 1, the battery size is a battery diameter of 6.8.
mm and a thickness of 2.6 mm. Reference numeral 1 denotes a positive electrode can also serving as a positive electrode terminal, which is formed of a molded product made of a stainless steel plate having excellent corrosion resistance. Reference numeral 2 denotes a negative electrode can that also serves as a negative electrode terminal, and is formed of a molded product made of a clad material of a stainless steel plate of the same material as the positive electrode can 1 and a hard aluminum alloy containing 5% by weight of manganese metal.
a is a stainless steel surface, 2b is a hard aluminum alloy surface, and the hard aluminum alloy surface 2b is formed so as to face the inside of the battery.

The peripheral section of the negative electrode can 2 has a shoulder 3 which is one step lower than the upper surface of the negative electrode plate.
A corner 4 bent at an angle of 0 ± 10 degrees is formed, and has a peripheral wall 5 that hangs down from the corner 4 and ends at the lower edge thereof. The whole is a stainless steel surface 2a. The radius of curvature of the corner 4 is 0.2 mm or less. 6 is the positive electrode can 1
And a gasket made of polypropylene that insulates and seals the anode can 2 and seals the gasket 6 between the inner surface of the rising portion 1 a of the periphery of the cathode can 1 and the shoulder 3 of the anode can 2 to the outer surface of the peripheral wall 5. The battery is sealed by squeezing the rising portion 1a in the mounted state.

Reference numeral 7 denotes a positive electrode, in which lithium black manganate composite oxide as an active material is mixed with carbon black as a conductive agent and a fluororesin powder as a binder, and has a diameter of 3.7 m.
m, after molding into a 1.5 mm thick pellet
It was dried at 24 ° C for 24 hours. Reference numeral 8 denotes a lithium metal of the negative electrode, which lithium is occluded in a hard aluminum alloy in the presence of an electrolytic solution to electrochemically produce a lithium aluminum alloy, which is used as a negative electrode active material. 9
Is a separator made of a polypropylene nonwoven fabric, and 10 is a carbon layer also serving as a positive electrode current collector. As an electrolytic solution, LiN (CF ₃ SO ₂ ) ₂ as a lithium salt was added at 1 mol / L to a binary mixed solvent in which propylene carbonate and 1,2-dimethoxyethane were mixed at a volume ratio of 1: 1.
1 dissolved was used. This battery is referred to as Example A.
Here, the radius of curvature of the corner portion 4 in Example A is 0.18 mm.

Next, a configuration similar to that of the embodiment A, except that the radius of curvature of the corner portion 4 is 0.25 mm is referred to as embodiment B.

Next, Example C has the same structure as that of Example A except that 1 mol / l of LiBF ₄ is dissolved as a lithium salt.

Next, the negative electrode can 2 is made of a molded product of the same clad material as that of Example A, and the hanging portion of the peripheral portion has a U-shaped folded portion as shown in FIG. This is referred to as Comparative Example D.

Next, as shown in FIG. 2, the negative electrode can is made of stainless steel and has a U-shaped weave portion at the periphery thereof, and a hard aluminum alloy punched in a circular shape is formed inside the negative electrode can. A comparative example E has the same configuration as that of the example C except that the pressure contact is performed via a current collecting net.

[0027] Twenty prototype batteries were manufactured under each condition. The battery was evaluated after being aged for about one week in an atmosphere of 60 ° C. so that aluminum and lithium sufficiently react after the battery was manufactured, taken out, and further left at room temperature for 12 hours or more. As the evaluation, charge / discharge cycle performance and liquid leakage resistance were performed. The charge and discharge cycle conditions were a charge of 3.5 V at a constant current of 0.5 mA and a discharge of 2.0 V at a constant current of 0.5 mA. The number of cycles when the discharge capacity reached about 50% in the first cycle was defined as the charge / discharge cycle life. Table 1 shows the results.

[0028]

[Table 1]

As shown in Table 1, the charge / discharge cycle life was excellent in A, B and D, and about 100 charge / discharge cycles were possible. Next, 61 times of C, E
Was the worst 42 times. From this result, the case where the clad material was used for the negative electrode can had a large reaction area of the lithium aluminum alloy, and further, as the lithium salt, LiN (C
It is understood that a synergistic effect can be obtained by using F ₃ SO ₂ ) ₂ .

Next, in the liquid leakage resistance test, the battery after the completion of the charge / discharge cycle life test was stored under a heat cycle condition of 70 ° C. for 1 hour / −10 ° C. for 1 hour. The number of batteries was measured. Table 2 shows the results.

[0031]

[Table 2]

As shown in Table 2, A and C showed the best liquid leakage performance. Next, the radius of curvature of the corner 4 is 0.25 mm.
B, then E, and D was the worst, resulting in all of the test pieces leaking. D was disassembled after the test was completed, and observed. As a result, it was found that lithium aluminum was finer on the sealing surface between the negative electrode can and the gasket, the shape was collapsed, and the sealing effect was lost. On the other hand, in the negative electrode cans of A, B and C, it is considered that the stainless steel surface and the gasket adhered firmly, and no liquid leakage occurred. The radius of curvature of the corner 4 is 0.25 mm.
Even with this, the leakage resistance performance is better than that of the comparative product, but a better result is obtained with 0.2 mm or less.

From the above results, according to this embodiment, the button-type lithium secondary battery not only simplifies the manufacturing process of the battery, but also has excellent charge-discharge cycle performance in battery characteristics, and also has excellent leakage resistance. You can get a battery.

[0034]

According to the organic electrolyte secondary battery of the present invention,
As is clear from the above description, the negative electrode can was formed of a molded product using a clad material in which a hard aluminum plate or a hard aluminum alloy plate and a stainless steel plate were bonded together, and having an aluminum surface side to be housed inside the battery. ,
The vertical cross-sectional shape of the peripheral portion has a shoulder portion which is one step lower than the upper surface of the negative electrode plate, and a corner portion bent at an angle of 90 ± 10 degrees is formed on the outer peripheral edge and is drooped from the corner portion. Since the shape has a peripheral wall that ends at the lower edge, the use of a clad material eliminates the need for welding and other steps, thereby simplifying the manufacturing process, thereby reducing the manufacturing cost, and reducing the gasket and anode. Since the sealing surface of the can is made of stainless steel instead of the alloy surface of hard aluminum and lithium, even if hard aluminum is pulverized at the end of the charge / discharge cycle life, the sealing performance will be insufficient and the electrolyte will leak. And the outer peripheral edge of the shoulder at the peripheral portion of the negative electrode plate is 90 ± 10
Since the corners are bent at an angle of degrees, the gasket is strongly pressed and compressed by the corners and the inner surface of the positive electrode can, thereby preventing leakage of the electrolyte. In addition, since the hanging part of the periphery of the negative electrode can is not folded back into a U-shape, the internal volume of the battery can be increased,
As a result, the charged electric capacity can be increased, and this is particularly effective in the case of a very small battery having a battery diameter of 6 mm or less. In addition, since the inner surface of the negative electrode can is entirely made of hard aluminum, the reaction area can be widened, so that the miniaturization of the lithium aluminum alloy due to the charge / discharge cycle does not progress easily and deterioration can be prevented. Effects such as prolonging the charge / discharge cycle life are obtained.

When the radius of curvature of the corner of the outer peripheral edge of the shoulder is set to 0.2 mm or less, the above-mentioned sealing performance can be further improved.

The lithium salt is converted to LiN (CF ₃ SO
₂ ) When any one selected from ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ is used, the charge / discharge cycle life can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of an organic electrolyte secondary battery of the present invention.

FIG. 2 is a longitudinal sectional view of a conventional organic electrolyte secondary battery.

FIG. 3 is a longitudinal sectional view of another conventional organic electrolyte secondary battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode can 1a Rise 2 Negative electrode can 2a Stainless steel surface 2b Hard aluminum alloy surface 3 Shoulder 4 Corner 5 Peripheral wall 6 Gasket 7 Positive electrode 8 Lithium metal 9 Separator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Fumio Oo 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] Claims: 1. A method for storing and storing lithium through a separator.
A positive electrode capable of releasing, and a negative electrode using an active material obtained by electrochemically storing lithium in hard aluminum or a hard aluminum alloy capable of storing and releasing lithium,
An organic electrolytic solution in which a lithium salt is dissolved in an organic solvent,
An organic electrolyte secondary battery in which a hanging portion of a peripheral portion of a negative electrode can in which a negative electrode is disposed on an inner surface and a rising portion of a peripheral portion of a positive electrode can in which a positive electrode is disposed on an inner surface are sealed via a gasket. ,
The negative electrode can is made of a molded product using a clad material in which a hard aluminum plate or a hard aluminum alloy plate and a stainless steel plate are bonded together, and the aluminum surface is oriented so as to be housed inside the battery. To
It has a shoulder that is one step down from the upper surface of the negative electrode plate, and has a corner that is bent at an angle of 90 ± 10 degrees on its outer peripheral edge, and has a peripheral wall that hangs down from that corner and ends at its lower edge. An organic electrolyte secondary battery having a shape. 2. A curvature radius of a corner portion of an outer peripheral edge of a shoulder portion is 0.2.
mm or less. 3. The lithium salt is LiN (CF ₃ SO ₂ ).
_2. The organic electrolyte secondary battery according to claim 1, wherein the secondary battery is any one selected from ₂ and LiN (C ₂ F ₅ SO ₂ ) ₂ .