JP2004071301A - Manufacturing method of case for storage element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a case for a storage element in which the case for the storage element can be manufactured without bringing about a tear or a pin hole at a part between a plurality of storage element housing parts. <P>SOLUTION: As for the manufacturing method of the case for the storage element in which the case for the storage element having at least two storage element housing parts is manufactured by simultaneously applying a drawing process at least at two places of a film, the film is applied to the drawing process in a state that a waviness which does not abut on a molding die surface of the drawing is added at a part between at least two places to become the storage element housing parts. The tear or the pin hole does not occur in the film between storage element housing parts manufactured by the drawing process in the manufacturing method of the case for the storage element. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a storage element case.
[0002]
[Prior art]
In some batteries, a power generating element having a positive electrode, a negative electrode, and an electrolyte is covered with a film such as a laminate film, with only the tips of leads connected to the positive and negative electrodes of the power generating element protruding and sealed. For example, a card type battery is formed by housing a battery formed by sealing a power generation element with a laminate film in a card type outer case.
[0003]
As a battery formed by sealing a power generating element with a laminate film, for example, there is a battery in which a laminate film is bent as it is and a peripheral edge is heat-sealed with the power generating element arranged on the surface of the laminate film.
[0004]
The configuration of a battery in which a power generation element is sealed with a laminate film is also employed in a capacitor. That is, a capacitor is formed by sealing the electrolytic solution and the charge / discharge element having a pair of electrodes with a laminate film.
[0005]
In general, a laminated film used for a battery and a capacitor (hereinafter, referred to as an electric storage element) having the above-described configuration is formed by laminating a metal layer and a resin layer in order to ensure water resistance and insulation. Is formed. Specifically, it has a structure in which resin layers are laminated on at least both surfaces of a metal layer. In this laminated film, the metal layer secures water resistance and the resin layer secures insulation.
[0006]
However, since the innermost peripheral surface of the laminated film facing the power generation element and the charge / discharge element (hereinafter, referred to as a power storage element) is required to have electrical insulation, the innermost peripheral surface is formed of a resin layer. Is required.
[0007]
In recent years, higher performance has been demanded for power storage elements, and an increase in capacity has been achieved by increasing the size of power storage elements of batteries and capacitors. When the physique of the electricity storage element becomes large (thickness becomes large), the sealing is performed in a state in which the laminate film on the periphery of the electricity storage element is wrinkled. Sealing in a wrinkled state tends to cause poor sealing, and when poor sealing occurs, power storage elements, especially electrolyte leaks out, or water is mixed in, and the performance of the power storage element deteriorates. .
[0008]
In order to suppress the occurrence of such poor sealing, a substantially concave-shaped storage element housing portion for housing the storage element is formed in advance on the laminate film by performing drawing processing, and the storage element is stored in the storage element housing section. There has been developed an electric storage element in which a laminated film is sealed with the laminate.
[0009]
For example, Japanese Patent Application Laid-Open No. 2001-291497 discloses that a polymer battery is folded in two using at least a laminate comprising a base material layer, a barrier layer, and a heat seal layer having a concave portion formed on one surface or concave portions formed on both surfaces. A polymer battery is shown in which the main body is housed and the sides other than the bent sides are heat-sealed and sealed.
[0010]
Since the power storage element generates heat when charging and discharging are repeated, a pair of power storage element housings are formed from the viewpoint of cooling performance, and the power storage element is formed in a space formed in the pair of power storage element housings. Is preferable.
[0011]
The production of a laminated film having a storage element housing portion (hereinafter, referred to as a storage element case) can be performed by subjecting the laminated film to processing such as drawing, vacuum forming, and pressure forming.
[0012]
During the processing of forming a plurality of power storage element housings on the laminate film, the laminate film at a portion between the plurality of power storage element housings is pulled in the direction of the power storage element housings facing each other. For this reason, there has been a problem that tears and pinholes are likely to occur in a portion between the plurality of power storage element housings.
[0013]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has an object to manufacture a power storage element case that can manufacture a power storage element case without causing breakage or pinholes in a portion between a plurality of power storage element housings. It is an object to provide a method.
[0014]
[Means for Solving the Problems]
As a result of repeated studies to solve the above-described problems, the present inventor has found that a manufacturing method for manufacturing a power storage element housing section by drawing in a state in which a slack is provided between a plurality of power storage element housing sections. Found that the above problems could be solved.
[0015]
In other words, the method for manufacturing a case for a storage element of the present invention is a method for manufacturing a case for a storage element having at least two storage elements accommodating portions by simultaneously drawing at least two locations of a film. In the above, the film is subjected to a drawing process in a state in which a slack is given to at least a portion between at least two locations serving as a power storage element housing portion.
[0016]
In the method for manufacturing a power storage element case according to the present invention, since the drawing process is performed at a plurality of locations in a state where the sag is given, the sag is formed even when the film is pulled in the facing direction during the working. The film flows into the storage element housing. As a result, the storage element case manufactured by the manufacturing method of the present invention is free from breakage and pinholes.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The method for manufacturing a power storage element case according to the present invention is a method for manufacturing a power storage element case having at least two power storage element housing portions by simultaneously drawing at least two locations of a film. That is, by simultaneously drawing at least two portions of the film, a case for a power storage element having at least two power storage element housing portions can be manufactured at a time.
[0018]
In the method for manufacturing a power storage element case according to the present invention, the drawing is performed in a state where the film has a slack at least between two locations serving as power storage element housing portions. That is, in the manufacturing method of the present invention, since the drawing is performed in a state where the sag is given to the film, even if the film is pulled in the facing direction at the time of the working, the film that has formed the sag remains in the electricity storage element. It will start to flow into the storage. As a result, in the manufacturing method of the present invention, breakage and pinholes do not occur.
[0019]
The drawing process is a process of pressing a punch while the film is supported by a die and a wrinkle holding plate, and it is preferable that the wrinkle holding plate has a ridge (bead). The die has a mold surface corresponding to the ridge of the wrinkle holding plate. Since the wrinkle-holding plate has the ridge, when the film is supported by the wrinkle-holding plate and the die, the film comes to rise from the wrinkle-holding plate (a drawing die) near the ridge. The lifting of the film creates a gap between the film and the wrinkle holding plate. That is, sag is given to the film at the time of drawing.
[0020]
In the manufacturing method of the present invention, in the drawing process, the punch is displaced upward from the lower side in the vertical direction to press the film.
[0021]
Also, by performing drawing using the wrinkle holding plate provided with the ridge, a groove corresponding to the ridge is formed between the power storage element housing portions of the processed case. This groove can be used as a fold when the case is bent to manufacture a power storage device. By folding along the groove, positioning of the electricity storage element housing portion can be easily performed.
[0022]
The ridge is preferably provided at the center of each of the plurality of punches. By providing a ridge at the center of each of the plurality of punches, the distance from the ridge to the punch becomes equal, the amount of film flowing in the direction of each storage element housing during drawing is uniform, and breakage is less likely to occur. The positioning of the power storage element housing portion when bent can be easily performed.
[0023]
In the manufacturing method of the present invention, the cross-sectional shape of the ridge is not particularly limited. That is, any cross-sectional shape may be used as long as the film can be given a slack enough to secure the amount of the film flowing in the direction of the power storage element accommodating portion during drawing. This is because the flow depth of the film at the time of the drawing changes because the processing depth of the drawing differs depending on the size of the power storage element accommodated in the power storage element housing portion.
[0024]
The film is preferably a composite sheet in which a metal layer and a resin layer are laminated. When the film is made of the composite sheet, the water storage resistance and the electric insulation of the electric storage element can be secured. Specifically, it has a structure in which resin layers are laminated on at least both surfaces of a metal layer. In this composite sheet, the metal layer secures water resistance and the resin layer secures insulation. More preferably, it is a composite sheet in which a resin layer is laminated on at least both surfaces of a metal layer.
[0025]
In the composite sheet, the type of the metal and the resin constituting each of the metal layer and the resin layer is not particularly limited as long as the material can ensure water resistance and electrical insulation.
[0026]
The film is not particularly limited as long as it is a composite sheet, and a laminate sheet (laminate film) that seals the electrode body in a conventional polymer battery can be used.
[0027]
The power storage element manufactured using the power storage element case manufactured by the manufacturing method of the present invention may be any element that can hold power. For example, a capacitor and a battery can be given.
[0028]
The storage element in the capacitor has a pair of electrodes and an electrolyte. The pair of electrodes and the electrolytic solution are not particularly limited, and conventionally known members can be used.
[0029]
In the battery, the storage element is a member having positive and negative electrodes and an electrolyte. The positive and negative electrodes and the electrolyte are not particularly limited, and conventionally known materials can be used.
[0030]
The power storage element case manufactured by the manufacturing method of the present invention is bent in a state where the power storage element is arranged in the power storage element accommodating portion, and by sealing the peripheral edge of the power storage element peripheral edge other than the bent side, A power storage element in which the power storage element is sealed can be manufactured. Further, it is preferable to seal the storage element fusion case by heat fusion.
[0031]
It is preferable that the interval between a pair of adjacent power storage element housing portions that house the same power storage element when bent is short. By reducing the distance between the pair of power storage element housing portions, the amount of film used is reduced, and material costs can be reduced. Further, even if the electrolytic solution contained in the power storage element enters the bent portion that is not welded, the bent portion is short, so that the amount of the electrolytic solution that deteriorates the performance of the power storage element does not come out of the power storage element housing portion. That is, there is an effect that the price of the power storage performance of the power storage element is suppressed.
[0032]
In the method for manufacturing a case for a storage element of the present invention, the drawing process is performed in a state in which the sag is given, so that even if the film is pulled in the facing direction at the time of working, the film forming the sag is charged. It will flow into the element housing. As a result, in the manufacturing method of the present invention, breakage and pinholes do not occur.
[0033]
【Example】
Hereinafter, the present invention will be described using examples.
[0034]
As an example of the present invention, a case for a lithium battery was manufactured.
[0035]
(Example)
As a material for the battery case, a laminate film having a thickness of 110 μm was cut into a size of 210 × 290 mm in length × width. The laminated film has a structure in which a 30 μm-thick nylon layer is formed on the surface of an aluminum layer having a thickness of 40 μm, and a polypropylene (PP) layer having a thickness of 40 μm is formed on the back surface. FIG. 1 shows a cross section of the laminate film.
[0036]
Subsequently, drawing was performed on the laminated film using the mold shown in FIG.
[0037]
The mold shown in FIG. 2 is vertically opposed and has two punches 2, 2 having a pressing surface formed upward and a pressing surface of the two punches 2, 2. And a die 3 having a die surface corresponding to the pressing surfaces of the punches 2 and 2, and a wrinkle holding plate 4 holding the two punches 2 and 2 and supporting the laminate film 1 between the die 3 and the die 3. Have. The interval between the punches 2 and 2 was 10 mm.
[0038]
A bead 5 is formed on the surface of the wrinkle holding plate 4 and at the center between the two dies 2. This bead 5 has a substantially triangular cross-sectional shape with a base of 4 mm and a height of 3 mm.
[0039]
In the drawing process, first, the laminate film 1 is placed on the wrinkle holding plate 4 by P.P. P. The layer was placed in the mold with the layer facing the wrinkle holding plate 4. The placed laminate film 1 was placed in a state where the center portion was raised by the beads 5.
[0040]
Subsequently, the die 3 was displaced vertically downward, and the laminate film 1 was supported between the die 3 and the wrinkle holding plate 4 so as not to cause wrinkles. At this time, the slack of the laminate film 1 caused by the beads 5 remained.
[0041]
Thereafter, the die 3 was further displaced vertically downward. Due to the displacement of the die 3, the pressing surfaces of the two punches 2, 2 were pushed into the die 3. At this time, the wrinkle holding plate 4 was displaced downward together with the die 3. By pressing the punches 2 and 2 into the die 3, a concave-shaped battery element housing portion was formed in the laminate film 1. The displacement of the die 3 was 10 mm, and the depth of the battery element housing formed by the punches 2 and 2 was also 10 mm. FIG. 3 shows a state in which the punches 2 and 2 press the laminate film 1.
[0042]
By the above drawing, the lithium battery case of the example was manufactured. FIG. 4 shows the manufactured lithium battery case.
[0043]
The manufactured lithium battery case has a shape having a groove 11 formed by the bead 5 and battery element housings 12, 12 formed symmetrically to the groove 11.
[0044]
In the manufactured lithium battery case of the example, no breakage or pinholes were observed near the groove 11 formed by the bead 5. That is, it can be seen that the laminate film constituting the lithium battery case also has a sufficient thickness in the vicinity of the groove 11.
[0045]
(Manufacture of batteries)
A lithium secondary battery was manufactured using the lithium battery case manufactured in the example.
[0046]
First, a cathode active material made of LiNiO ₂ , a conductive agent made of carbon, and a binder made of polyvinylidene fluoride (PVDF) are dissolved in an N-methyl-2-pyrrolidone (NMP) solution, A paste was made. This paste was applied to both surfaces of a positive electrode current collector made of aluminum foil using a comma coater. Thereafter, the electrode was passed through a roll press to apply a load, and a positive electrode plate with an improved electrode density was prepared.
[0047]
This positive electrode plate was cut into a predetermined size, and a sheet-shaped positive electrode was manufactured by scraping off the electrode mixture at a portion to be a lead tab weld for current extraction.
[0048]
Subsequently, a negative electrode active material made of graphite and a binder made of PVDF were dissolved in an NMP solution to prepare a negative electrode active material paste. This paste was applied to both surfaces of a negative electrode current collector made of copper foil using a comma coater in the same manner as the positive electrode. Thereafter, the copper foil to which the paste was applied was passed through a roll press to apply a load, thereby producing a negative electrode plate having an increased electrode density.
[0049]
This negative electrode plate was cut into a predetermined size, and a sheet-shaped negative electrode was manufactured by scraping off the electrode mixture at a portion to be a lead tab weld for current extraction.
[0050]
The sheet-shaped positive electrode and the sheet-shaped negative electrode obtained as described above were wound in a flat shape with a separator made of microporous polypropylene having a thickness of 25 μm interposed therebetween to form a flat wound electrode body. Then, an electrode tab was fused to an uncoated portion of the flat wound electrode body where the electrode mixture of the positive electrode and the negative electrode was scraped off. In addition, the electrode tabs fused to the positive electrode and the negative electrode were attached so as to protrude in the same direction.
[0051]
In addition, an electrolyte was prepared by dissolving LiPF ₆ as an electrolyte in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at an equal volume ratio at a rate of 1 mol / liter.
[0052]
Subsequently, the produced flat wound electrode body 6 was housed in the battery element housing section of the above-described lithium battery case. The flat spirally wound electrode body was housed by bending the lithium battery case in a groove formed by a bead with the flat spirally wound electrode body arranged at a position corresponding to the battery element housing portion. At this time, the electrode tabs 61, 61 attached to the flat spirally wound electrode body 6 were exposed from the lithium battery case whose ends not joined to the flat spirally wound electrode body were bent. FIG. 4 shows a state in which the flat spirally wound electrode body 6 is accommodated in a lithium battery case.
[0053]
Then, in the state where the flat wound electrode body is housed, an electrolytic solution is injected into the inside of the battery element housing part, and the periphery of the battery element housing part other than the side where the groove of the lithium battery case is formed is removed. The electrode body and the electrolyte were sealed by welding.
[0054]
By the above procedure, a lithium secondary battery was manufactured.
[0055]
In the manufactured lithium secondary battery, no break or pinhole was observed near the groove of the lithium battery case.
[0056]
(Other forms of the embodiment)
Further, a die having a triangular cross-sectional shape of the bead and a concave groove having an inner peripheral surface substantially matching the outer peripheral shape of the bead may be used in a corresponding portion of the die facing the bead.
[0057]
Also in the embodiment having the bead and the groove, no breakage or pinhole was found in the laminated film after molding.
[0058]
In the laminate film formed in this mode, a clear broken line is formed in a portion pressed by the bead.
[0059]
The bent line facilitates bending and positioning when forming a lithium secondary battery. That is, in the present embodiment, not only the drawing process is enabled, but also the productivity in assembling the lithium secondary battery is improved.
[0060]
In the present embodiment, the description has been made using a laminated film. However, a single-layer film can be used as long as the material can ensure water resistance and insulation.
[0061]
【The invention's effect】
The method for manufacturing a power storage element case according to the present invention is characterized in that the drawing process is performed in a state where the sag is provided, so that even when the laminate film is pulled in the facing direction at the time of working, the laminated film that formed the sag Flows into the storage element housing. As a result, the storage element case manufactured by the manufacturing method of the present invention is free from breakage and pinholes.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross section of a laminate film.
FIG. 2 is a diagram showing a configuration of a mold.
FIG. 3 is a view showing a state where a punch of a mold presses a laminate film.
FIG. 4 is a view showing a lithium battery case according to an embodiment.
FIG. 5 is a diagram showing a state in which the flat wound electrode body is housed in a lithium battery case.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Laminate film 11 ... Groove 12 ... Battery element accommodating part 2 ... Punch 3 ... Dice 4 ... Wrinkle holding plate 5 ... Bead 6 ... Flat wound electrode body 61 ... Electrode tab

Claims (3)

At least two places of the film are simultaneously subjected to drawing processing, a method for manufacturing a storage element case for manufacturing a storage element case having at least two storage element housing portions,
A method for manufacturing a case for a storage element, wherein the film is subjected to the drawing process in a state in which a slack is given to at least a portion between at least two places serving as the storage element housing portion. The method according to claim 1, wherein the drawing is a process of pressing a punch while the film is supported by a die and a wrinkle holding plate, and the wrinkle holding plate has a ridge. The method according to claim 2, wherein the ridge is provided at a center between each of the plurality of punches.

Images