JPH0370345B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a flat non-aqueous electrolyte battery in which a power generation element using lithium as a negative electrode is housed in a sheet-like packaging material and sealed. Conventional structure and problems Nonaqueous electrolyte batteries generally use lithium for the negative electrode, and various halides such as carbon fluoride, manganese dioxide, copper oxide, iron sulfide, silver chromate, etc. for the positive electrode. Oxides and sulfides can be used, and various properties can be obtained depending on the type. In addition, the electrolyte contains a relatively high-boiling point, high-viscosity solvent such as γ-butyrolactone and propylene carbonate, and a relatively low-boiling point, low-viscosity solvent such as tetrahydrofuran and dimethoxyethane, either singly or in combination with lithium borofluoride. , a non-aqueous electrolyte in which a solute such as lithium perchloride is dissolved is used. The structures of these battery types can be roughly divided into cylindrical and button-shaped, which are becoming more common, but as electronic devices have become smaller and thinner in recent years, development of thinner batteries has become more active. is being carried out. Thin batteries can be constructed by, for example, using a film made by laminating thermoplastic resin on aluminum foil as the battery container, and then thermally welding the laminated resin to each other to encapsulate the power generation element, or by placing the power generation element inside the film between the peripheral edges of two metal foils. The power generation element is housed in a battery chamber with a thermoplastic resin window-wake-like sealant interposed.
A typical method proposed is to seal a battery by thermally welding a sealing material and metal foil. The sealing materials and laminate resins used in these batteries must be able to be thermally welded and chemically stable against non-aqueous electrolytes. To satisfy this requirement, polyolefin resins, especially polyethylene and polypropylene, are suitable. ing. However, in order to ensure better weldability, it is necessary to select a polyolefin resin that has been modified by adding a carboxyl group to the above resin by copolymerizing with maleic anhydride, etc., and this is especially true for metals and resins. It is essential for welding. However, among the solvents in the electrolytic solution, the modified polyolefin resin can withstand relatively high boiling point and high viscosity solvents, but reacts slightly with low boiling point and low viscosity solvents, resulting in loss of weldability. However, since the sealing reliability of the battery is insufficient, it is necessary to use only a solvent belonging to the former category, or an electrolytic solution using a solvent mainly composed of these solvents. In this case, since the viscosity of the electrolytic solution is high, the rate of impregnation of the electrolytic solution into the separator and the positive electrode is slow, so it takes a long time for the electrolytic solution injected in the manufacturing process to impregnate the power generation element. At this time, if the seal is sealed with insufficient impregnation, the electrolyte may overflow during sealing, or the battery may be sealed with air left inside, resulting in poor discharge performance due to leakage or insufficient liquid volume, or battery expansion. cause On the other hand, sealing after sufficient impregnation with the electrolytic solution poses a problem in that the time required for impregnation is long, which significantly impairs mass productivity. OBJECTS OF THE INVENTION An object of the present invention is to improve mass productivity and stabilize battery quality by smoothly impregnating the power generation element of the thin non-aqueous electrolyte battery with electrolyte. Structure of the Invention The present invention relates to a method for manufacturing a flat battery that uses lithium as a negative electrode and a non-aqueous electrolyte as an electrolyte, and seals a power generating element by thermally welding thermoplastic resins to each other or a thermoplastic resin and a metal. With at least the positive electrode, separator, and negative electrode stored in the opened bag-shaped battery container, the separator is crimped and fixed to the negative electrode in advance before the step of injecting the electrolyte from the opening part. , both sides of the battery container are suctioned with a vacuum pipe with a suction cup to forcibly open the unsealed part to create a gap between the separator and the positive electrode, and the non-aqueous electrolyte is introduced between the separator and the positive electrode through this opening. It is characterized by injection. The present invention is capable of shortening the impregnation time by injecting the electrolytic solution between the separator and the positive electrode using the above method, thereby simultaneously impregnating the separator and the positive electrode with the electrolytic solution. As a result, during heat welding at the unsealed part, or during the depressurization step to degas the battery that is performed prior to this, the electrolyte may leak to the outside, or welding failure may occur due to leakage at the unsealed part. This makes it possible to manufacture high-quality batteries with good mass production. Next, an embodiment of the present invention will be described in comparison with a conventional method. DESCRIPTION OF EMBODIMENTS FIG. 1 is a sketch of a flat non-aqueous electrolyte battery according to an embodiment of the present invention, and FIG. 2 is a diagram showing A-A in FIG.
FIG. 3 is a sectional view taken along line A'. Figure 3 is like Figure 1,
This is a sketch of the electrolyte injection step in the manufacturing process of the battery shown in FIG. 2, and FIGS. FIG. 5 depicts each embodiment of the invention. In Figures 1 and 2, 1 is a negative electrode container made of stainless steel foil that serves as a negative electrode current collector and a negative electrode terminal plate, 2 is a sheet-shaped negative electrode lithium crimped to the inner surface of 1, and 3 is a polypropylene nonwoven fabric. The separator 4 uses manganese dioxide as an active material, to which are added acetylene black as a conductive material, fluororesin dispersion as a binder, and carboxymethyl cellulose as a thickener, and kneaded to form a paste, which is placed on one side of the positive electrode container 5. This is the positive electrode that has been coated and dried. The positive electrode container is made of stainless steel foil and serves as both a positive electrode current collector and a positive terminal plate. 6
is a sealing material made by adding maleic anhydride to polyethylene to give it heat-weldability to metal. It is processed into a window frame shape, and is heat-welded to the peripheral edges of the negative electrode container 1 and the positive electrode container 5, and is used to generate electricity. The elements are sealed.
Inside the battery, propylene carbonate contains 1 mole/
A non-aqueous electrolyte containing dissolved lithium perchlorate is sealed. Next, the manufacturing process of this battery is shown in Figures 3 and 4.
FIG. 5 will be explained. First, the sealing material 6 is thermally welded to the entire peripheral edge of the negative electrode container 1 to integrate it, and then the lithium sheet 2 is crimped to the surface of the negative electrode container 1 in the area surrounded by the sealing material 6 to integrate the three parts. The steps up to this point are the same for both the embodiment of the present invention and the conventional method. Next, the embodiment of the present invention differs from the conventional method in that a step of press-bonding and fixing the separator 3 to the surface of the lithium sheet 2 is provided. On the other hand, the step of providing the positive electrode 4 on the surface of the positive electrode container 5 is performed in the same manner in both the embodiment of the present invention and the conventional example. and each member on the negative electrode container side are superimposed, and three sides of the periphery of the positive electrode container 5 are thermally welded to the sealing material 6 to form a bag-shaped container with one side unwelded and opened. In the case of the present invention, the separator 3 and the lithium sheet 2 are overlapped in advance and pressure bonded using a roll or other means, so that the fibers constituting the separator 3 are press-fitted into the flexible lithium sheet, and the separator 3 and the lithium sheet are bonded together. 2 are integrated, the integrated members on the positive electrode container side and the negative electrode container side are overlapped and the peripheral edge of the positive electrode container 5 is sealed to form a bag-shaped container with one side opened. Third
The figure shows a bag-like container containing battery components as described above, in order to easily inject the electrolyte into the container by suctioning both sides of the container with a vacuum pipe equipped with a suction cup to open the unsealed part and create a void inside the container. 7 and 7' are decompression pipes, 8 is an electrolyte injection nozzle, and 9 is an electrolyte. At this time, among the constituent elements of the battery, the positive electrode container 5 and the negative electrode container 1 are thin and have spring properties, the separator 3, the negative electrode 2, and the positive electrode 4
Since it is thin, soft, and flexible, it can be easily opened during injection using the operations described above, and if the vacuum is released after injection, it will return to the state before the vacuum. Thereafter, by welding the unsealing part 10, a battery as shown in FIGS. 1 and 2 is completed. Fig. 4 is a cross section taken along the line B-B' in Fig. 3 when the opening operation on one side is performed as described above in the case of the conventional method.
Since the separator 3 is not fixed, the gap in the battery chamber exists in an irregular shape. Therefore, the electrolytic solution 9 injected through the opening 11 exists between the positive electrode 4 and the separator 3 and between the negative electrode 2 and the separator 3 at an undefined ratio. On this occasion,
Since the negative electrode 2 is non-porous lithium, it does not essentially have the property of being impregnated with an electrolyte, and the electrolyte 9' present on the negative electrode 2 side is impregnated into the separator 3. Impregnation is started only after it penetrates into the separator 3, and since the rate of penetration of the electrolyte 9' into the separator 3 is originally slow, the impregnation rate of the electrolyte 9' is significantly slowed down, making it difficult for mass production. Due to time constraints, we had no choice but to weld the unsealed part with a large amount of free electrolyte remaining, and when the open state was restored during welding, there was no void.
At least a portion of the free electrolyte may leak out of the battery or leak through the surface of the unwelded sealing material, resulting in a battery with insufficient performance due to insufficient electrolyte, or a battery with unreliable storage due to insufficient sealing. will be manufactured. On the other hand, FIG. 5 is a cross-sectional view of the battery according to the embodiment of the present invention in an open state. Since the separator 3 is fixed in advance to the surface of the negative electrode 2, the gap created by the opening is always between the positive electrode 4 and the separator 3. The electrolytic solution is always injected between the positive electrode 4 and the separator 3. Therefore, the injected electrolyte comes into contact with both the separator 3 and the positive electrode 4, and is impregnated into both at the same time. Therefore, the impregnation speed of the electrolyte is faster than in the conventional example, and the welding process can be started with less free electrolyte, and there is no electrolyte leakage or leakage on the surface of the sealing material 6. Since it can be welded and sealed, it is possible to manufacture batteries with excellent discharge performance and storage performance. Next, the results of a comparative evaluation of a battery according to an example of the present invention and a conventional battery produced as prototypes will be explained.
The shape of the battery was 1.0 mm thick, 25 mm long, and 50 mm wide, the positive electrode container 5 and the negative electrode container 1 each had a thickness of 50 μm, and the reduced pressure maintained in the reduced pressure pipe after the electrolyte was poured was 1 minute. The following table shows the discharge duration when discharging at a temperature of 20°C and a load resistance of 5KΩ, and the weight loss and leakage rate of the battery when stored at 60°C for one month.

[Table] As shown in this table, in the conventional method, there is a shortage of electrolyte necessary for the discharge reaction due to leakage of electrolyte during battery manufacturing, and there is large variation, and the performance is significantly inferior to that of the battery of the example of the present invention. It's on. Furthermore, with conventional methods, many batteries are sealed with the surface of the sealing material wet with electrolyte, so welding is incomplete and the electrolyte evaporates during storage and is prone to escaping or leaking. In contrast, the present invention has been proven to have extremely high reliability in storage performance. In the above example, the explanation was mainly given to a thin battery of the type in which a power generation element is sealed by interposing a frame-shaped sealing material between two sheets of metal foil, but in addition to this, the present invention can be applied to The present invention can also be applied to batteries in which battery elements are wrapped and sealed with a film in which resin is laminated on foil or resin films, and similar effects can be obtained. Effects of the Invention As described above, the present invention is an extremely effective method for manufacturing high-quality flat non-aqueous electrolyte batteries with excellent discharge performance and storage stability with good mass productivity.

[Brief explanation of drawings]

Figure 1 is a sketch showing an example of a flat non-aqueous electrolyte battery, Figure 2 is a sectional view taken along line A-A' in Figure 1, and Figure 3 is a battery and liquid injection device during the liquid injection process. 4 is a cross-sectional view of the conventional battery manufacturing method taken along line BB' in Figure 3, and Figure 5 is a cross-sectional view of the battery manufacturing method of the present invention taken along line BB' in Figure 3 1 is a cross-sectional view of a battery according to the method. 1... Negative electrode container, 2... Negative electrode, 3... Separator, 4... Positive electrode, 5... Positive electrode container, 6... Seal material, 7, 7'...... Decompression pipe, 8... Electrolyte injection nozzle, 9... Nonaqueous electrolyte, 9'... Electrolyte injected into the negative electrode side, 10... Opening part (unwelded sealing material surface), 11... Opening (liquid injection port).

Claims (1)

[Claims] 1 A method for manufacturing a flat battery that uses lithium for the negative electrode, a non-aqueous electrolyte for the electrolyte, and seals the power generation element by thermally welding thermoplastic resins or thermoplastic resins and metals, one end of which is unwelded. Prior to the step of injecting the electrolyte from the opening part with at least a positive electrode, a separator, and a negative electrode housed in a bag-shaped battery container serving as an opening part, the separator is crimped and fixed to the negative electrode in advance. , a flat type characterized in that when pouring liquid, both sides of the container are adsorbed with a vacuum pipe to forcibly open the unsealed part, and the non-aqueous electrolyte is injected into the gap formed between the separator and the positive electrode. Battery manufacturing method.