JP2009187711A - Method of manufacturing electrochemical device, and electrochemical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacture for enhancing reliability of an electrochemical device using laminate films as an outer packaging. <P>SOLUTION: The manufacturing method includes the steps of: arranging a laminate formed by arranging sheet-like positive electrode and negative electrode through a separator between almost rectangular laminate films facing with the upper ends made uniform, and forming the laminate films in a bag having an opening in the upper end; pouring an electrolyte in the bag of the laminate film in a vacuum and sealing the laminate film by mechanical crimp in almost a parallel line to the periphery of the upper end in the lower part than the opening; aging by generating gas by chemical reaction within the bag of the laminate film in the sealed state; exhausting gas by opening the mechanical crimp in the line; and fusion-bonding the laminate bag opened in the exhaust step along the parallel line in the upper part than the parallel line in a vacuum. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrochemical device in which a laminate formed by arranging a positive electrode and a negative electrode formed in a sheet shape so as to face each other with a separator interposed therebetween and an electrolyte solution are sealed in a degassed body of a laminate film. More specifically, the present invention relates to an improved technique for improving the sealing characteristics of an exterior body. The present invention is applicable to, for example, a non-aqueous electrolyte electricity storage device.

  FIG. 2 shows a basic structure of a nonaqueous electrolyte electricity storage device as an example of an electrochemical device having a laminate film as an outer package. (A) is a perspective plan view of the nonaqueous electrolyte electricity storage device 1b, and (B) is a side sectional view thereof. Each of the positive and negative electrodes (10p, 10n) in the nonaqueous electrolyte electricity storage device 1b is formed by applying an active material of each electrode on the surface of a sheet-like conductor (11p, 11n) serving as a current collector. The electricity storage device 1b has a basic structure of a laminated body 50 in which the positive and negative electrodes (10p, 10n) are arranged to face each other via a separator 30, and the laminated body 50 is stored in a bag-like laminated film 100 together with an electrolyte. The bag is assembled by heat-sealing (heat-sealing) the opening 102 of the upper end 101 of the bag in a vacuum. In addition, the sheet-like conductors (11p, 11n) in the nonaqueous electrolyte electricity storage device 1b are formed with electrode portions (12p, 12n) serving as power outlets, and the tabs 40 extend beyond the electrode portions (12p, 12n). It is welded by a method such as sonic welding. The laminate film is heat-sealed at a predetermined position 103 in the middle of the extending direction of the tab 40, so that the tip of the tab 40 is exposed outside the exterior body 100.

  In the illustrated example, for ease of explanation, the stacked body 50 is shown as a single-layer structure in which a pair of positive electrode 10p and negative electrode 10n are disposed to face each other with a separator 30 interposed therebetween. This power storage element of the laminated structure type usually has a multilayer structure. And in the state which laminated | stacked each electrode part (12p, 12n) of the positive electrode and negative electrode in each layer of the laminated body of a multilayer structure, it welds to the tab 40 collectively, and the tab 40 is the bag-shaped laminate film 100. It is structured to be exposed to the outside.

  By the way, in the nonaqueous electrolyte electricity storage device of the said structure, after the assembly, it is left for a certain period and it preserve | saves for a certain period until an electric power generation element becomes chemically stabilized, or a nonaqueous electrolyte electricity storage device for the purpose of initial charge or electrolytic activation An aging process for charging the battery may be performed. As is well known, in this aging process, a gas originating from some chemical reaction is generated. When the generated gas fills the exterior body, the laminate film is deformed so as to swell outward, and the adhesion between the positive electrode and the negative electrode that are stacked in close contact with each other by vacuum sealing is reduced, and the nonaqueous electrolyte electricity storage device Performance deteriorates. In addition, since the reaction gas may contain components that are generated by the reaction of the water or impurities remaining in the non-aqueous electrolyte power storage device with the electrolyte, the aging treatment is performed in the non-aqueous electrolyte power storage device. Another purpose is to remove impurities and moisture in the device in a gas state. Therefore, in an electrochemical device such as a non-aqueous electrolyte electricity storage device, after assembling, a gas is generated by an aging treatment, the outer body is opened, the gas is exhausted, and the vacuum sealing is performed again. Become a product.

  FIG. 3 shows a conventional method for manufacturing the nonaqueous electrolyte electricity storage device. This figure shows a process of encapsulating the laminate 50 and the electrolyte in the laminate body outer package. First, the laminated body 50 is disposed between the substantially rectangular laminate films (100a, 100b) facing each other with the upper end 101 aligned (A) with the tab 40 exposed to the outside (A). In this example, two substantially rectangular laminate films (100a, 100b) are used to face each other. Of course, one laminate film may be folded in two so that the upper end 101 is aligned, and face each other. Next, by laminating the edges 104 other than the upper end 101, a laminate film (100a, 100b) is formed in a bag having the upper end 101 as the opening 102 (B). Then, an electrolyte is injected from the opening 102 in a vacuum, and the laminate film 100 is heat-sealed along the upper end 101 to seal the laminate 50 in the bag of the laminate film 100 (C). An aging process is performed in this state, and a reactive gas is generated in the bag of the laminate film 100. In order to exhaust this gas, the laminate film 100 is cut below the upper end 101 of the laminated film 100 being sealed, along a line 105 parallel to the edge of the upper end, and newly put below the original opening 102. An opening 106 is formed (D). When the gas is exhausted from the opening 106, the portion of the previous cutting line 105 is heat-sealed in vacuum to complete the nonaqueous electrolyte electricity storage device 1b (E).

  As described above, in the conventional manufacturing method in an electrochemical device such as a nonaqueous electrolyte electricity storage device, the final sealing line is located below the first sealing line of the bag-shaped laminate film. Therefore, the portion of the final sealing line inside the laminate film is highly likely to come into contact with the electrolytic solution. And when the part is heat-sealed, if the electrolytic solution adheres between the laminate films before and after facing in the final sealing line, the attached electrolytic solution may inhibit the fusion. There is. There is a possibility that the electrolytic solution adhering to the inside of the laminate film at the time of heat fusion boils with the heat at the time of heat sealing, and bubbles are generated at the heat fusion part. Such poor fusion at the sealed portion causes leakage of the electrolyte during long-term storage of the electrochemical device.

  Therefore, the present invention relates to an electrochemical device in which a laminated body in which a positive electrode and a negative electrode formed into a sheet shape are arranged opposite to each other with a separator interposed therebetween and an electrolyte solution are sealed in a degassed state in a laminate film outer package. In this manufacturing method, an object of the present invention is to provide a highly reliable electrochemical device by reliably sealing a laminate film as an outer package.

In order to achieve the above object, the present invention seals a laminate and an electrolyte solution, in which a positive electrode and a negative electrode formed in a sheet shape face each other via a separator, in a degassed state in an outer package of a laminate film. And a method for producing an electrochemical device in which tabs connected to the positive and negative electrodes of the laminate are led out of the exterior body,
The laminated film is disposed between the substantially rectangular laminated films facing each other with the upper ends aligned with the tabs exposed to the outside, and the edges other than the upper ends are heat-sealed so that the laminated films are Forming a bag having an opening in
In a vacuum, the electrolyte is injected into the bag of the laminate film, and a line substantially parallel to the upper edge below the opening is used as a first sealing line to mechanically pressure-bond the line. A temporary vacuum sealing step for sealing the laminate film;
An aging process for generating a gas due to a chemical reaction in the bag of the laminated film sealed by the temporary vacuum sealing process;
An exhausting step of exhausting the gas by releasing mechanical pressure bonding in the first sealing line;
A final vacuum sealing step of heat-sealing the laminated film bag opened by the evacuation step in a vacuum along a line substantially parallel to the line above the first sealing line. It is out.
Further, an electrochemical device produced by the manufacturing method is also included in the scope of the present invention.

  According to the method for producing an electrochemical device of the present invention, it is possible to reliably seal the outer package of the laminate film and prevent liquid leakage. Therefore, the electrochemical device manufactured by the manufacturing method can ensure high reliability.

=== Example ===
As an example of the present invention, a method for manufacturing a non-aqueous electrolyte electricity storage device (hereinafter, electricity storage element) is shown. FIG. 1 shows steps in the method. In this figure, the process from the state (A) which sealed the laminated body 50 between the facing laminate films (100a, 100b) and formed the laminate film 100 in the bag shape is shown. Then, in a vacuum, an electrolyte is injected below the upper end 101 of the laminate film 100 so as not to exceed a line (first sealing line) 110 parallel to the edge of the upper end 101, and along the line 110. The laminate film 100 is sealed by mechanical pressure (B). That is, it is not sealed by heat sealing, but is mechanically pressure-bonded / sealed, for example, by pressing and clamping at the portion of the first sealing line 110 from before and after the laminate film 100 facing the elongated bar 200. It stops. In this state, an aging treatment is performed, and then the mechanical pressure in the first sealing line 110 is released, and the upper end 101 of the laminate film 100 is made the bag opening 102 again, and the reaction gas is exhausted. Then, in a portion above the first sealing line 110, that is, a portion not touching the electrolyte solution inside the laminate film, a line parallel to the line (for example, the upper end 101 of the laminate film) is heated in a vacuum. Sealing is performed to complete the storage element 1a (D).

=== Evaluation of reliability ===
Here, in order to evaluate the reliability of the power storage device manufactured by the method of the present invention, the power storage device manufactured by the conventional method (conventional product) and the power storage device manufactured by the method of the above embodiment (invention product) 100 samples were prepared, and each sample was stored for 120 days in a temperature environment of 70 ° C. to check for leakage. The conventional product and the invention product are the same in the structure of the laminate and the electrolytic solution except for the manufacturing method. In this evaluation, the power storage element has a structure equivalent to that of a known power storage element called a lithium ion capacitor, and the laminated body can store and release lithium and a positive electrode in which activated carbon is formed into an aluminum foil shape. The negative electrode active material mixture containing a carbon material is a structure in which a negative electrode applied and molded into a copper foil sheet is formed facing each other through a separator, and the electrolyte is a non-aqueous electrolyte containing a lithium salt It is. Moreover, the lithium metal is stuck to the part where the negative electrode active material mixture is not applied on the copper foil of the negative electrode.

Table 1 shows the results of the liquid leakage test.

  In the conventional product, leakage occurred in 3 samples on the 90th day, and leakage occurred in 9 samples on the 120th day. On the other hand, in the inventive product, there was no sample in which leakage occurred even after 120 days. That is, in the electricity storage device manufactured by the method of the above example, the laminate film is surely heat-sealed and completely sealed because the part that is finally sacrificed by heat sealing does not touch the electrolyte. .

=== Applicability of the present invention ===
In the above embodiment, as the electrochemical device, a non-aqueous electrolyte electricity storage device capable of charging / discharging has been taken as an example.However, the present invention requires an aging treatment in which a power generation element is housed in an outer package of a laminate film. It is intended for electrochemical devices that generate gas during the process. Therefore, the electrochemical device may be a primary battery.

It is a figure which shows the manufacturing method of the electrochemical device in the Example of this invention. It is a schematic structure figure of a nonaqueous electrolyte electrical storage device. It is a figure which shows the conventional manufacturing method of an electrochemical device.

Explanation of symbols

1a, 1b Nonaqueous electrolyte electricity storage device 10p Positive electrode 10n Negative electrode 40 Tab 50 Laminate 100, 100a, 100b Laminate film 102 Opening 110 First sealing line

Claims (2)

The laminate and electrolyte solution, in which the positive and negative electrodes formed in a sheet form are placed opposite to each other via a separator, are sealed in a degassed state inside the laminate film exterior and connected to the positive and negative electrodes of the laminate. A method for producing an electrochemical device in which a tab is led out of an exterior body,
The laminated film is disposed between the substantially rectangular laminated films facing each other with the upper ends aligned with the tabs exposed to the outside, and the edges other than the upper ends are heat-sealed so that the laminated films are Forming a bag having an opening in
In a vacuum, the electrolyte is injected into the bag of the laminate film, and a line substantially parallel to the upper edge below the opening is used as a first sealing line to mechanically pressure-bond the line. A temporary vacuum sealing step for sealing the laminate film;
An aging process for generating a gas due to a chemical reaction in the bag of the laminated film sealed by the temporary vacuum sealing process;
An exhausting step of exhausting the gas by releasing mechanical pressure bonding in the first sealing line;
A final vacuum sealing step in which the laminated film bag opened by the exhausting step is heat-sealed along a line substantially parallel to the line above the first sealing line in a vacuum; and
A method for producing an electrochemical device, comprising:   An electrochemical device made by the method of claim 1.

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