JP2001338674A - Method of manufacturing secondary battery and seal stopper for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To drastically simplify a manufacturing process, especially a process around initial charging, and to avoid corruption of a production facility and lowering of cell capacity, and also, to avoid futility of further removing seal stopper which is once equipped. SOLUTION: In the method of manufacturing a secondary battery in which an initial charging process is performed after containing the power generation component including an electrolyte in an exterior container 21 of a sealing structure, the above exterior container 21 is temporarily sealed by a seal stopper 4 of a quality of rubber elasticity which has a full-time closed valve 41 structure which can be opened by forced deformation operation from outside. After performing the above initial charging process by the temporarily sealed state, a gas-liquid separation operation of the above exterior container 21 is performed. Then, gas discharge in the above exterior container 21 is performed by operating the above seal stopper 4, and further, after this, the full-time closed valve 41 structure of the seal stopper 4 is closed, and a complete seal of the exterior container 21 is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a secondary battery and a sealing plug for a battery, and more particularly to a method of manufacturing a sealed secondary battery of a type in which initial charging with gas generation is performed during manufacturing and a battery used therefor. The present invention relates to a sealing plug for use, for example, to a technique which is effective when applied to a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, with the remarkable progress of electronic technology, electronic devices have been reduced in size and weight, and accordingly, batteries have also been reduced in size and weight, and the demand for high energy density batteries has increased. I have. In response to such demands, recently, non-aqueous electrolyte secondary batteries represented by lithium ion batteries have been provided and widely used.

Among them, a lithium ion battery can be used as a secondary battery, and has a higher energy density and a higher battery voltage, a longer memory life and a longer cycle life than other types of secondary batteries.
It has advantages such as a small loss of electrons and a small self-discharge, and is particularly used for portable electronic devices.

[0004] In the manufacture of this type of secondary battery, it is necessary to perform an initial charge at the final stage of the manufacture in order to complete a ready-to-use charged product. In the case of the above-described lithium ion secondary battery, initial charging is performed at the final stage of manufacturing, and this initial charging involves gas generation. This gas generation occurs intensively, especially at the time of initial charging. Therefore, in a sealed secondary battery using a sealed outer container, it is necessary to release the generated gas before sealing the outer container.

[0005] However, when the battery is initially charged with the battery outer container opened to release the generated gas, the electrolyte in the outer container spills, and the spilled electrolyte adheres to the production equipment and corrodes. Etc. may be damaged. In order to prevent this, the initial charge needs to be performed with the outer container of the battery sealed, but in this case, it is necessary to degas the outer container after the first charge.

Therefore, conventionally, prior to the first charge, the outer container of the battery is hermetically sealed with a removable sealing plug, and after the first charge, the sealing plug is once removed to release the gas in the container. This has been dealt with by resealing the outer container again.

[0007]

However, it has been found that the above technique has the following problems. That is, a double process of removing the sealing plug once attached to the battery outer container and resealing the outer container is required. Also, once the sealing stopper is attached,
Since it may be damaged or damaged during its removal, it cannot be reused. Furthermore, at the moment when the sealing stopper is removed, the pressure inside the container is released at a stretch, and the electrolyte in the container squirts to the outside, thereby contaminating the production equipment and reducing the amount of electrolyte in the completed battery. The capacity may be reduced.

The present invention has been made in view of the above-mentioned problems, and has as its object to greatly simplify the manufacturing process, particularly before and after initial charging, and to reduce the contamination of production facilities and the reduction of battery capacity. It is an object of the present invention to provide a method of manufacturing a secondary battery and a battery sealing plug which can avoid waste and can also avoid waste of removing the sealing plug once attached.

[0009]

Means for Solving the Problems In order to achieve the above object, the present invention provides a method for manufacturing a secondary battery, in which a power generation element containing an electrolyte is contained in an outer container having a closed structure and then a first charging step is performed. The outer container is temporarily sealed by a rubber elastic sealing stopper having a normally closed valve structure that can be opened by a force deformation operation from the outside, and after performing the first charging step in this temporarily sealed state, After performing the gas-liquid separation operation in the outer container, the sealing stopper is operated to release the gas in the outer container, and thereafter, the normally closed valve structure of the sealing stopper is closed to close the outer container. The container was completely sealed. With this configuration, it is possible to eliminate the double process of removing the sealing plug once attached and resealing it, and to minimize the loss of the electrolyte during degassing. In addition, it is possible to hermetically seal the completed battery while leaving the sealing plug as it is. This greatly simplifies the manufacturing process, especially before and after initial charging, and avoids the contamination of production equipment and the reduction of battery capacity, as well as the waste of removing the sealing plug once installed. (Claim 1).

The sealing plug is a rubber-elastic sealing plug for closing a gas vent hole provided in an outer container of a battery, and the valve is opened by an externally applied deformation operation. If a battery sealing plug having a normally closed valve structure for forming a gas vent path of the outer container is used, for example, it can be obtained by integral molding of synthetic rubber, and has a configuration suitable for cost reduction and mass production. In addition, the degassing operation in a state where the battery is attached to the outer container of the battery can be smoothly performed by a simple operation from the outside (claim 2).

Further, the sealing plug is formed integrally with an embedding portion for closing the gas vent hole and a projection projecting from an outer wall surface of the outer container. A very simple structure in which a normally closed valve structure is cut into a notch that is opened by elastic deformation when a side portion of the portion is pressed from a specific direction to form the gas vent path. In addition to this, it is possible to easily and reliably construct the apparatus, and it is possible to more smoothly perform the operation of selectively removing the gas in the outer container from the electrolyte by selectively controlling the pressing operation (claim 3). .

Further, if the sealing plug is made of a heat-fusible material and has a normally-closed valve structure which is closed by heat melting, for example, an appropriately heated iron may be applied. With a very simple process of heat-sealing the surface of the sealing plug, the final sealing of the outer container can be performed instantaneously and efficiently (claim 4).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the portions denoted by the same reference numerals between the drawings indicate the same or corresponding portions. FIG. 1 is a sectional view of a main part of a secondary battery to which the manufacturing method of the present invention is applied.

The secondary battery 1 shown in FIG. 1 is a prismatic lithium ion secondary battery. First, a power generating element containing an electrolyte is housed in an outer container 21 having a sealed structure. Outer container 2
1 is a bottomed rectangular cylindrical metal can also serving as a negative electrode terminal,
The opening is closed by the lid 22. Lid 22
, A positive electrode terminal 24 is attached via a gasket 23. A small hole (gas vent hole) 26 for venting gas is provided in a part of the lid portion 22, and the vent hole 26 is closed by a rubber elastic sealing plug 4. .

Inside the outer container 21, as a power generating element, a positive electrode 31 made of lithium cobalt oxide (LiCoO ₂ ) as an active material, a separator 32 made of a porous film made of polypropylene, and carbon (graphite) as an active material. Negative electrode 3
3 is stored together with the electrolyte. In this case, the positive electrode 3
The negative electrode 1 and the negative electrode 33 are formed in a sheet shape with the separator 32 interposed therebetween, and are wound in a spiral shape. The wound element is accommodated in the outer container 21.

Although not shown, each of the positive electrode 31 and the negative electrode 33 is formed in a layered state in contact with a current collector surface of a metal foil. The current collector on the positive electrode side is connected to the positive electrode terminal 24 via the positive electrode lead 35, and the current collector on the negative electrode side is connected to the negative electrode lead 3.
7 is connected to an outer container 21 also serving as a negative electrode terminal.

The sealing plug 4 has the structure of a normally closed valve 41 which is opened by an externally applied deforming operation to form a gas vent path for the outer container 21. As shown, it is fixed to the lid 22 by a pressing member 27. The holding member 27 is formed using a metal plate, and is fixed to the lid 22 by welding with the sealing plug 4 fitted in the gas vent small hole 26.

FIG. 2 shows a part of the sealing plug 4 taken out. First, as shown in FIG.
Is formed of a rubber elastic material such as ethylene propylene rubber, fluorine rubber, or silicon rubber. The sealing plug 4 made of rubber elastic material is used for the gas vent small hole 2.
An embedding part 45 for closing the outer case 6 and a projection 43 protruding from the surface of the lid part 22 forming the upper outer wall surface of the outer container 21 are integrally formed. Further, a flange portion 44 for fixing with the pressing member 27 (FIG. 1) is integrally formed between the embedding portion 45 and the protruding portion 43.

A notch 42 is formed in the sealing plug 4 so as to penetrate in the vertical direction. The cut 42 is closed tightly by the rubber elasticity of the sealing plug 4 in the steady state where no external force is applied, as shown in FIG. As shown in FIG. 3B, when the side portion of the projection 43 is squeezed from a specific direction, that is, in this case, from the side, the projection 43 is opened by elastic deformation due to the squeezing operation, and the outer container is opened. 21 gas vent paths are formed. That is, the notch 42 has a structure of the normally closed valve 41 which is opened by an externally applied deformation operation.

The normally-closed valve 41 configured as described above is opened only when a force is applied from the side of the projection 43 to apply a mechanical force, and the gas in the container 21 is opened. Although forming an escape path, the force other than the above-described force operation, that is, the force acting due to the internal pressure of the outer container 21,
The notch 42 remains tightly closed and no valve opening operation is performed. In other words, the valve is opened only when a predetermined force operation is performed from the outside to form a gas vent path, and the sealed state is maintained in other steady states.

In this case, the pressing operation is performed by the protrusion 4
A simple operation of simply pinching 3 with forceps or tweezers is sufficient, and the degree of opening of the cut 42, that is, the degree of valve opening, can be arbitrarily adjusted by adjusting the pinching force.

Next, a method of manufacturing a secondary battery using the battery sealing plug 4 will be described. First, FIGS. 1 and 2
As shown in (A), the battery 1 structure before the initial charge in which the power generation element containing the electrolytic solution is stored in the outer container 21 having a closed structure is formed, and the battery 1 is provided in advance on the lid portion 22 of the outer container 21. The gas vent small hole 26 is closed and sealed by the sealing plug 4. In this case, attachment of the sealing plug 4 to the outer container 21 is simple when forming the lid portion 22, but may be performed immediately before the first charge. Thereafter, the battery 1 sealed with the sealing plug 4 is initially charged.

After the initial charge, a gas-liquid separation operation such as standing or centrifugation is performed for a predetermined time, and then, as shown in FIG. And open the valve. Thereby, the gas generated at the time of the first charge and accumulated in the outer container 21 can be released. At this time, the gas is released relatively slowly through the slit-shaped scrap removing path formed by the force operation, unlike the case where the sealing stopper is removed and the internal pressure of the container is released at a stretch. In addition, the electrolyte in the container 21 does not spout vigorously.

After the degassing after the initial charge is completed, after that, the structure of the normally closed valve 41 of the sealing plug 4 is closed and the outer container 21 is fully sealed. In this final sealing, for example, a suitable sealing material or an adhesive may be applied to the upper end (outer end) of the cut 42, but when the sealing plug 4 is made of a heat-meltable material, the sealing plug 4 shown in FIG. As shown in (C) of
A part of the sealing plug 4 can permanently close the normally closed valve structure by thermal melting. In this case, the main sealing can be instantaneously and efficiently performed by a very simple process operation such as applying a suitably heated iron to thermally seal the surface of the sealing plug 4. Reference numeral 46 in FIG.
Indicates a permanent block formed by the heat fusion.

As described above, in the method for manufacturing a secondary battery according to the present invention, the double step of removing the sealing plug once attached and resealing it can be omitted, and the degassing process can be performed. In this case, the loss of the electrolyte can be minimized, and the sealed battery can be hermetically sealed while the sealing plug is left as it is. This greatly simplifies the manufacturing process, especially before and after initial charging, and avoids the contamination of production equipment and the reduction of battery capacity, as well as the waste of removing the sealing plug once installed. .

[0026]

The present invention will be described below in more detail with reference to typical examples.

EXAMPLE A rectangular lithium ion secondary battery having the structure shown in FIG. 1 was manufactured in dimensions of 34 mm in width, 48.0 mm in height, and 8.6 mm in thickness.

In this case, the positive electrode 31 was manufactured as follows. LiCoO _{2 as a} positive electrode active material, carbon powder as a conductive agent, and polytetrafluoroethylene (hereinafter, PTF)
E)) and a mixture in a weight ratio (mass ratio) of 100: 10: 10 is stirred, and the mixture is kneaded into a paste with water. This kneading mixture is applied to both sides of the aluminum foil. This is dried and rolled and cut into a predetermined shape and size. The aluminum foil was used as a positive electrode current collector. A part of the mixture on the surface was scraped off, and the positive electrode lead 35 was spot-welded thereto. In the above mixing ratio, the ratio of the aqueous PTFE dispersion is the ratio of the solid components.

The negative electrode 33 was manufactured as follows. The carbon powder and the PTFE aqueous dispersion are in a weight ratio of 100:
The mixture prepared at a ratio of 3 is kneaded with water. This kneading mixture is applied to a copper foil. This is dried and rolled and cut into a predetermined shape and size. The copper foil was used as a negative electrode current collector. A part of the mixture on the surface was scraped off, and the negative electrode lead 37 was spot-welded thereto.

The electrolyte was a non-aqueous electrolyte and was prepared as follows. Lithium hexafluorophosphate (LiPF ₆ ) was dissolved at a ratio of 1 M / L in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a ratio of 40:40:20. One used.

The sealing plug 4 having the cut 42 shown in FIG. 2 was made of a heat-fusible synthetic rubber, and the surface thereof was permanently closed by heat fusion after the initial charging step.

(Comparative Example) Instead of the sealing plug 4 with the notch 42 used in the above embodiment, an ordinary completely closed rubber plug having no notch 42 was used. A battery was manufactured. Except for the sealing stopper, the configuration is the same as that of the above-described embodiment.

The following tests were performed using the batteries of the above-described examples and the batteries of the comparative examples. (Test 1) In this test 1, the cut 42 according to the present invention was used.
It was confirmed by the following Test 2 whether or not the sealing stopper 4 functions as the normally closed valve 41. First, as Reference Example 1, a pressure sensor was directly attached to the gas vent small hole 26 of the outer container 21, and the pressure inside the container 21 increased by the initial charge was measured. In this case, the vent hole 26 of the outer container 21 is not closed by the sealing plug 4, but is completely airtightly closed by the attachment of the pressure sensor. Next, as Test Example 1, the sealing plug 4 with the notch 42 of the present invention was used.
The first charging was performed in a state where the vent hole 26 of the outer container 21 was sealed. After the initial charging is completed, the sealing plug 4
The pressure inside the container 21 increased by the initial charge was indirectly measured from the pressure of the gas released when the sealing plug 4 was opened by a force operation. The above measurement was performed three times in each of the reference example and the test example, and the following result 1 was obtained. The unit of the pressure is kgf / cm ² .

[0034]

[Table 1]

From the above results, it can be seen that the gas generated by the initial charge is almost completely confined in the outer container 21 by the sealing plug 4 with the notch 42 of the present invention. This means that the sealing plug 4 of the present invention can securely temporarily seal the outer container 21.

(Test 2) In the degassing step after the initial charge, the amount of the electrolytic solution which was ejected and lost with the release of gas was evaluated by the following Test 2. As Test Example 2, the secondary battery 1 having the structure of the above-described embodiment was used, and after the total weight of the battery was precisely measured, initial charging was performed. Thereafter, after a slight gas-liquid separation time, the notched 42 sealing stopper 4 of the present invention was opened by a force operation to release gas. Then, the weight of the battery after degassing was precisely measured again, and a weight loss -ΔW from the weight before the first charge was obtained.
During that time, there is no other weight loss factor, so the weight loss ΔW
Can be regarded as a reduction in the amount of the electrolyte. Reference example 2
In the same manner as in Test Example 2 above, using a secondary battery having the structure of the above-described comparative example, that is, a battery in which only the sealing plug 4 of the battery 1 of the above-described embodiment was replaced with a normal completely closed rubber plug was used. Precise measurement of the total battery weight was performed before the first charge and after degassing, respectively, and a weight loss -ΔW from the weight before the first charge was obtained. In this case, degassing after the first charge was performed by removing the completely closed rubber stopper. Also, the total weight measurement after degassing is
The test was performed with the rubber stopper removed. The measurement described above was performed three times in each of the reference example and the test example, and the following result 2 was obtained. The unit of the weight loss -ΔW is g.

[0037]

[Table 2]

According to the above results, in the manufacturing method using the sealing plug 4 of the present invention, it is possible to greatly reduce the amount of electrolyte solution due to degassing as compared with the conventional method, thereby greatly reducing the battery capacity. It has been demonstrated that it can be made smaller.

(Test 3) It was confirmed by the following test 3 whether or not the main sealing after degassing was completely performed. As Test Example 3, the secondary battery 1 having the structure of the above-described embodiment was used, and after the initial charge and the subsequent degassing process, the normally closed valve structure with the cut 42 of the sealing plug 4 of the present invention was heated and fused. The main sealing was performed by closing. The completely sealed battery was stored in a thermostat at 80 ° C. for 3 months, and the weight loss −ΔW of the battery due to the storage was measured. Reference example 3
In the same manner as in Test Example 3 above, a secondary battery having the structure of the above-described comparative example, that is, a battery in which only the sealing plug 4 of the battery 1 of the above embodiment was replaced with a normal completely closed rubber plug, The sealed battery was stored at 80 ° C. for 3 months in a thermostat, and the weight loss ΔW of the battery due to the storage was measured. In this case, the amount of decrease in battery weight -ΔW reflects the decrease in the amount of electrolyte that is lost when sealing is incomplete. Therefore, it can be used as an index that the smaller the amount of decrease -ΔW, the more complete the sealing. The above measurement was performed three times in each of the reference example and the test example, and the following result 3 was obtained.
The unit of the weight loss -ΔW is g.

[0040]

[Table 3]

According to the above results, Test Example 3 and Reference Example 3
Show almost the same tendency to decrease in weight, and there is no significant difference between them. This means that the sealed state obtained by the sealing plug 4 of the present invention is not inferior to the sealing state obtained by a normal completely closed rubber plug.

[0042]

As described above, according to the method of manufacturing a secondary battery according to the present invention, the secondary battery is subjected to the initial charging step after the power generation element containing the electrolyte is housed in the outer container having the closed structure. In the manufacturing method, the outer container is temporarily sealed with a rubber elastic sealing stopper having a normally closed valve structure that can be opened by an externally applied deformation operation, and the first charging step is performed in the temporarily sealed state. After performing, after performing the gas-liquid separation operation in the outer container, gas is released in the outer container by operating the sealing plug, and further thereafter, the normally closed valve structure of the sealing plug By performing the main sealing of the outer container while closing, the double process of removing the sealing plug once mounted and resealing can be omitted, and the loss of the electrolyte during degassing is achieved. Can be minimized. It can be in a state in which the leave of the responsible for the hermetic sealing of the finished battery.

This greatly simplifies the manufacturing process, especially before and after the first charge, and avoids contamination of production equipment and reduction of battery capacity, and also avoids wasteful removal of the once installed sealing plug. be able to.

The sealing plug is a rubber-elastic sealing plug for closing a gas vent hole provided in an outer container of the battery, and is opened by an externally applied deformation operation. If a battery sealing plug having a normally closed valve structure for forming a gas vent path of the outer container is used, for example, it can be obtained by integral molding of synthetic rubber, and has a configuration suitable for cost reduction and mass production. In addition, the degassing operation in a state of being mounted on the battery outer container can be smoothly performed by a simple operation from the outside.

Further, the sealing plug is formed integrally with an embedding portion for closing the gas vent hole and a projection projecting from an outer wall surface of the outer container. A very simple structure in which a normally closed valve structure is cut into a notch that is opened by elastic deformation when a side portion of the portion is pressed from a specific direction to form the gas vent path. Thus, the configuration can be made simpler and more reliable, and the operation of selectively removing the gas in the outer container from the electrolyte by selectively controlling the pressure operation can be performed more smoothly.

Further, the sealing plug is made of a heat-fusible material and has a normally-closed valve structure which is closed by the heat melting, so that, for example, an appropriately heated iron can be applied. In a very simple step of heat-sealing the surface of the sealing plug, the final sealing of the outer container can be performed instantaneously and efficiently.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a secondary battery to which a manufacturing method of the present invention is applied.

FIG. 2 is a side view and a top view showing an embodiment of the sealing plug according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery 21 Outer container (also serving as negative electrode terminal) 22 Lid 23 Gasket 24 Positive electrode terminal 26 Degassing small hole 27 Pressing member 31 Positive electrode 32 Separator 33 Negative electrode 35 Positive electrode lead 37 Negative electrode lead 4 Sealing plug 41 Normally closed valve 42 Normally closed Notch forming a valve 43 Projection 44 Flange 45 Embedding 46 Permanent closure

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H012 AA01 BB02 BB04 CC01 DD02 EE01 GG05 JJ02 JJ06 5H028 AA01 BB01 BB10 CC00 EE06 FF04 5H029 AJ14 AK03 AL06 AM03 AM05 AM07 BJ02 BJ14 CJ16 DJ03 EJ12

Claims (4)

[Claims] 1. A method of manufacturing a secondary battery in which a power generation element containing an electrolyte is stored in an outer container having a closed structure and a first charging step is performed, wherein a normally-closed valve is opened by an externally applied deformation operation. The outer container is temporarily sealed with a rubber-elastic sealing stopper having a structure, and after performing the first charging step in this temporarily sealed state, performing a gas-liquid separation operation in the outer container, Operate a sealing stopper to release gas in the outer container, and thereafter, further close the normally closed valve structure of the sealing stopper to perform the main sealing of the outer container. Production method. 2. A rubber-elastic sealing plug for closing a gas vent hole provided in an outer container of a battery, wherein the valve is opened by an externally applied deforming operation and the gas vent path of the outer container. A sealing plug for a battery having a normally closed valve structure for forming a sealing plug. 3. An embedding portion for closing the gas vent hole and a projection projecting from an outer wall surface of the outer container are integrally formed, and a side portion of the projection is specified as the normally closed valve structure. The sealing plug for a battery according to claim 2, wherein a notch is formed to be opened by elastic deformation when the pinching operation is performed from the direction to form the gas vent path. 4. The sealing plug for a battery according to claim 2, wherein the sealing plug for a battery is formed of a heat-fusible material and has a normally-closed valve structure which is closed by the heat melting.