JP2018129203A - Film-clad battery manufacturing method and film-clad battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corner portions 2A, 2B, 2C, 2D of an electrode laminated body 2 from being strongly pressed by a laminate film 10 while reducing a die required for drawing an outer casing 3. SOLUTION: An outer package 3 of a film-sheathed battery 1 is configured by folding a single laminated film 10 having a size twice as large as that of an electrode laminated body 2 along a folding line 23. Before being folded in two, the laminate film 10 is formed by drawing a gusset portion 21 along a folding line 23 and four corner bulging portions 22 for accommodating the corner portions 2C and 2D of the electrode laminate 2. Keep it. The size of the mold is smaller than that in the case where a cup-shaped drawing process corresponding to the overall shape of the electrode laminate 2 is performed. [Selection diagram] Figure 1

Description

  The present invention relates to a method for manufacturing a film-clad battery in which an electrode laminate (power generation element) is housed together with an electrolyte in an exterior body made of a laminate film having flexibility. The present invention relates to a film-clad battery manufacturing method and a film-clad battery in which a film is folded in two and an electrode laminate is disposed therein.

  For example, as a lithium ion secondary battery, an electrode laminate (also referred to as a power generation element) in which a plurality of positive electrodes and negative electrodes are laminated via a separator is electrolyzed in an outer package made of a laminate film having a heat-sealing layer. A film-sheathed battery having a flat shape housed together with a liquid is known. In one example, two laminated films are arranged so that each heat-sealing layer is on the inside and the electrode laminate is sandwiched, and heat-sealed along each peripheral side to form an exterior body. Composed. On the other hand, there is also known a configuration in which a relatively large laminate film is used, folded in half, and an electrode laminate is sandwiched inside, and then three sides are heat sealed.

  Further, in Patent Document 1, a cup portion that is recessed in a rectangular shape corresponding to the outer shape of the electrode laminate is formed by deep drawing in advance on each of the two laminate films sandwiching the electrode laminate from both sides. Is disclosed.

Japanese Patent Laying-Open No. 2006-122492

  In the method of drawing a rectangular cup portion corresponding to the outer shape of the electrode laminate as in Patent Document 1, the size of the laminate film is used as a die (die and punch) for drawing processing. Therefore, a large mold with a size almost equal to the above is required.

  In particular, when one laminated film is used by folding it in two, if two cup parts arranged in each of the two pieces that are abutted when folded into two are drawn simultaneously, a larger size is required. A mold is required. If the two cup parts are to be processed sequentially, the large cup parts will be drawn adjacent to each other, so that the peripheral material will be stretched or drawn during the second drawing of the cup part. This is not realistic because of problems such as holding down the material.

  Therefore, in the present invention, the gusset portion is drawn into a bead shape having a length extending over two corners of the electrode laminate along the central fold line in the rectangular laminate film before being folded in two, The corner bulges that accommodate the corners were drawn at four positions corresponding to the remaining two corners of the electrode laminate.

  That is, in the present invention, the drawing process is locally performed on one laminated film that is folded in half.

  Assuming that a flat laminate film is folded in half and a thick electrode laminate is sandwiched, the four corners of the electrode laminate are strongly pressed in the thickness direction by the laminate film. A laminate film obtained by laminating a heat-sealing layer or the like on a metal foil has flexibility, and when a force is applied, a certain degree of elongation occurs. However, the corners tend to be pressed locally. Thus, when an electrode laminated body contacts a laminated film strongly, the performance as a battery will fall.

  Therefore, conventionally, the cup portion as in Patent Document 1 has been formed.

  On the other hand, in the present invention, of the four corners of the electrode laminate, the two corners located away from the fold line of the laminate film are two pieces that are abutted when folded in two. By drawing the corner bulging portions in advance, a space is generated in the thickness direction of the battery, and the laminate film does not strongly press the corner portions. In addition, for the two corners located near the fold line of the laminate film, the bead-shaped gusset portion is drawn in advance along the fold line, so that the thickness direction of the battery is also reduced when folded in two. Thus, there is no space and the laminate film does not press the corners strongly.

  Therefore, an action substantially equivalent to the case of forming the cup part as in Patent Document 1 is obtained by the local drawing process of the gusset part and the corner bulge part.

  In the present invention, since each individual drawing process is small, the necessary mold size is very small compared to the size of the laminate film, and the drawing process itself is easy. In addition, since each drawing process is performed at a position distant from each other, it is not always necessary to perform all the drawing processes simultaneously.

  According to this invention, the laminate film strongly presses the four corners of the electrode laminate by locally drawing the gusset portion and the corner bulge portion in advance into the laminate film to be folded in half. The battery performance can be effectively avoided. Therefore, compared with the conventional case where the cup portion is drawn, the mold can be downsized and the drawing can be facilitated.

The top view which shows the laminate film before folding in half. The top view in the completion state of a film-clad battery. The figure which looked at the film-clad battery of FIG. 2 from the arrow X direction. The perspective view of the corner bulging part formed in the laminate film. The perspective view of the gusset part formed in the laminate film. The top view of the gusset part formed in the laminate film. The front view of a gusset part similarly. Sectional drawing which showed the cross section (a) along the aa line | wire of FIG. 6, and the cross section (b) along the bb line | wire by contrast. The top view (a) and sectional drawing (b) of the die | dye for a corner bulging part process. Plane (a), front view (b), rear view (c), sectional view along line dd, right side view (e), and ff of a punch for corner bulge processing Sectional drawing (f) along the line. The top view (a) and sectional drawing (b) of the die | dye for a gusset part process. The top view (a), front view (b), and side view (c) of the punch for a gusset part processing.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 2 shows a film-clad battery 1 completed through the battery manufacturing method of one embodiment. In this embodiment, as an example of the film-clad battery 1, a film-clad lithium ion secondary battery having a flat shape that constitutes a power pack for driving a vehicle such as an electric vehicle or a hybrid vehicle is targeted. A film-clad battery 1 of one embodiment has basically the same configuration as that described in Patent Document 1 and the like, and a plurality of positive and negative electrodes cut into a rectangular sheet are stacked via a separator. An electrode laminate 2 (which is also referred to as a power generation element) is configured, and this electrode laminate 2 is accommodated together with an electrolytic solution in a bag-like exterior body 3 made of a laminate film. In the description of the following examples, the battery after the electrode laminate 2 is accommodated in the film-shaped outer package 3 is simply referred to as a “cell” regardless of the manufacturing process.

  The outline of the battery manufacturing process will be described. First, the electrode laminate 2 is configured in the electrode lamination process. Here, a positive electrode, a negative electrode, and a separator wound in a roll shape are sequentially stacked while being cut into a rectangular sheet, so that a power generation element, that is, an electrode, in which a plurality of positive electrodes and negative electrodes are stacked via a separator. The laminated body 2 is formed. The positive electrode is obtained by applying a positive electrode active material as a slurry containing a binder to both surfaces of an aluminum foil serving as a current collector, and drying and rolling to form an active material layer having a predetermined thickness. Similarly, the negative electrode is obtained by applying a negative electrode active material as a slurry containing a binder to both surfaces of a copper foil serving as a current collector, and drying and rolling to form an active material layer having a predetermined thickness. The separator has a function of preventing a short circuit between the positive electrode and the negative electrode and at the same time holding the electrolytic solution. For example, the separator is a microporous film or a nonwoven fabric of a synthetic resin such as polyethylene (PE) or polypropylene (PP). Consists of.

  These positive electrodes, negative electrodes, and separators are laminated in a predetermined number to form a power generation element, that is, an electrode laminate 2 having a rectangular shape (more specifically, a rectangular parallelepiped shape having a relatively small thickness). The ends of the current collectors of the plurality of positive electrodes are overlapped with each other, and the electrode tab serving as the positive terminal, that is, the positive electrode tab 4 is ultrasonically welded. Similarly, the ends of the current collectors of the plurality of negative electrodes are overlapped with each other, and the electrode tab that is the negative terminal, that is, the negative electrode tab 5 is ultrasonically welded. The positive electrode tab is made of a strip-like thin aluminum plate, and the negative electrode tab is made of a strip-like thin copper plate. That is, each is comprised from the same kind of metal as an electrical power collector.

  The electrode laminate 2 configured as described above is accommodated in a flexible film-shaped outer package 3 in the next sealing step. The exterior body is made of, for example, a laminate film having a four-layer structure in which a heat-sealing layer made of polypropylene is laminated inside an aluminum foil and a polyamide resin layer and a polyethylene terephthalate resin layer are laminated on the outside as a protective layer. . The thickness of the entire laminate film is, for example, about 0.15 mm. A metal foil other than aluminum may be used.

  Here, in the sealing process of the present invention, a relatively large single laminate film 10 (see FIG. 1) having a size slightly more than twice that of the electrode laminate 2 is used, and the film is folded in two so as to protrude from each other. The electrode laminate 2 is sandwiched between two pieces to be combined. That is, the laminate film 10 is folded in two so that the heat-sealing layer is on the inside, and the electrode laminate 2 is disposed on the inside, and then, as shown in FIG. 11 and 12, heat sealing is performed. Specifically, the laminate film 10 folded in half is sandwiched between a pair of heat blocks with a built-in electric heater, pressed and heated to fuse the two pieces of the laminate film 10 together, and to form an elongated strip-shaped seal line 15, 16 is formed. Thereby, the exterior body 3 is comprised by the bag shape which the remaining edge | side 13 opened as an injection hole. In the illustrated example, the positive electrode tab 4 and the negative electrode tab 5 of the electrode laminate 2 are drawn out from one side 11 of the outer package 3 to the outside. Therefore, the seal line 15 on the side 11 is set so as to form a straight line across the positive electrode tab 4 and the negative electrode tab 5, and the two pieces of laminate film 10 sandwich the positive electrode tab 4 and the negative electrode tab 5. Joined into an oval shape. The side 14 shown on the lower side of the cell 1 in FIG. 2 is a place where the laminate film 10 is folded in half, and therefore the side 14 is not heat-sealed.

  The cell 1 configured in such a manner that the electrode laminate 2 is accommodated in the bag-shaped outer package 3 in the sealing step is then transferred to the liquid injection step. In the liquid injection process, for example, the cell 1 is placed in a vacuum chamber, and the liquid injection nozzle of the dispenser is inserted into the injection port (that is, the opening of the side 13) of the outer package 3 under a predetermined pressure reduction. Fill the liquid (injection).

  When the liquid injection is completed, the side 13 serving as the injection port is heat-sealed with a heat block as the injection port sealing step while maintaining the posture of the cell 1 as it is. Note that the sealing here is a so-called temporary sealing, and after the initial charging, the inlet (or the vicinity thereof) is opened in order to vent the gas generated with the charging. The side 13 is sealed. Both ends of the seal line 17 provided along the side 13 by thermal fusion are exposed to the ends of the seal lines 15 and 16, thereby obtaining a continuous seal line on three sides.

  After the cell 1 configured as shown in FIG. 2 is left for a predetermined time (for example, several hours to several tens of hours) in order to wait for sufficient penetration of the electrolyte into the electrode laminate 2, Proceed to charging and aging process.

  Next, the sealing process by the laminate film 10 which is the main part of the present invention will be described in more detail. FIG. 1 shows a single laminate film 10 used as a double fold for sealing the electrode laminate 2. In FIG. 1, in order to show the positional relationship with the electrode laminate 2, the electrode laminate 2 is also illustrated on each piece. The laminate film 10 is composed of a single laminate film 10 (that is, a rectangular blank) cut into a rectangular shape having a predetermined size, and before being folded in half, a central gusset portion 21 and four corner corner bulging portions 22 are formed. These are drawn using dies (die and punch) which will be described later. Note that the gusset portion 21 and the corner bulge portion 22 bulge toward the outside (protective layer side) of the laminate film 10.

  The gusset portion 21 is drawn into a narrow bead shape along a central fold line 23 (note: this is a virtual line before the fold is folded). It has a length extending over two corners 2A and 2B of the adjacent electrode laminate 2. 5 to 8 show the three-dimensional shape of the gusset portion 21 drawn into the laminate film 10, that is, a rectangular blank, slightly exaggeratedly. The gusset portion 21 has a central straight portion 21a and end portions 21b at both ends, and the straight portion 21a swells to form an arcuate cross section in a cross section perpendicular to the folding line 23 (see FIG. 8 (a), FIG. 5), and extends linearly along the fold line 23 with a constant cross-sectional shape. In addition, the arch-shaped curve in FIG. 5 is an auxiliary line showing the cross-sectional shape of each part. As shown in FIG. 8B, the end portions 21b at both ends have a cross-sectional arc shape as shown in FIG. 8B, and the size of the cross-sectional shape is continuously reduced. Thus, it terminates at the end point 21c (see FIGS. 5 to 7). That is, the cross-sectional shape of the end portion 21b gradually decreases from the boundary with the straight portion 21a to the end point 21c. In other words, the end 21b has a shape that approximates a shape that bisects the conical surface.

  The end points 21c on both sides of the gusset portion 21 are desirably in the vicinity of the seal lines 15 and 16 (for example, positions in contact with the seal lines 15 and 16) when heat sealed. Further, the boundary between the straight portion 21a and the end portion 21b is desirably in the vicinity of the corner portions 2A and 2B of the electrode laminate 2. In other words, it is desirable that the straight portion 21a extends slightly outside the corner portions 2A and 2B.

  Drawing of the gusset portion 21 is performed using a die 31 shown in FIG. 11 and a punch 32 shown in FIG. The die 31 has a slit-shaped mold opening 33, and the punch 32 has a plate-shaped mold protrusion 34 combined with the mold opening 33. The die opening 33 of the die 31 is gradually narrowed at both ends 33a in the longitudinal direction, and the opening edge 33b is appropriately chamfered. The mold projecting portion 34 of the punch 32 protrudes from the base portion 32a of the punch 32 with a constant protrusion amount, and both end portions 34a in the longitudinal direction recede obliquely and form a conical surface. Further, as is apparent from FIG. 12C, the tip that enters the mold opening 33 has a circular arc cross section, specifically a semicircular shape.

  The gusset portion 21 shown in FIGS. 5 to 8 is obtained by performing drawing with an appropriate amount of pressing (drawing depth) using such a die 31 and punch 32. At this time, the laminate film 10 (blank) is pressed by a stripper (not shown) around the mold opening 33 and the mold protrusion 34, but is stretched into a blank by drawing the gusset part 21 into a bead shape. (Elongation in a direction perpendicular to the fold line 23) occurs. That is, the gusset portion 21 is obtained in a form in which the laminate film 10 is stretched in a direction orthogonal to the folding line 23. Desirably, the drawing process of the gusset portion 21 is set so that an elongation slightly longer than the thickness (for example, about several mm) of the electrode laminate 2 is obtained.

  By forming the gusset portion 21 in this way, the side 13 of the cell 1 is constituted by the gusset portion 21 when folded in half as shown in FIG. That is, the gusset portion 21 is expanded in the thickness direction of the cell 1 from both ends that are crushed by the seal lines 15 and 16, and the corner portions 2A and 2B of the electrode laminate 2 are not pressed strongly. Sufficient space is secured. In addition, since the gusset portion 21 expands in a band shape having a curved cross-sectional shape in the folded state, the fold line 23 that is sharply folded is actually the both side portions of the side 13 of the cell 1 (the portions other than the gusset portion 21). ) Only occurs.

  The corner bulging portion 22 is positioned corresponding to the remaining two corner portions 2C and 2D of the electrode laminate 2. In other words, two corner bulging portions 22 are formed on one piece 10A of the laminate film 10 around the fold line 23, and two corner bulging portions 22 are formed on the other piece 10B. When the laminate film 10 is folded in half, the bulging portion 22 has a positional relationship that faces the corner portions 2C and 2D of the electrode laminate 2 so as to sandwich from both sides. In other words, the corner bulging portion 22 of each piece 10A, 10B is configured symmetrically about the folding line 23.

  As shown in FIGS. 1, 2 and 4, each corner bulging portion 22 accommodates the corresponding corner portions 2C and 2D of the electrode laminate 2, and is perpendicular to the corner portions 2C and 2D in plan view. Is formed in a substantially right-angled triangle shape (more specifically, a shape approximated to a right-angled isosceles triangle), and the apex angle portion 22a of the triangle projects most greatly. The amount of protrusion gradually decreases from the apex portion 22a toward the central portion of the laminate film 10 (more specifically, the central portion of each piece 10A, 10B), and the general portion of the laminate film 10 is formed at the triangular bottom portion 22b. Smoothly continuous. The protrusion amount (that is, the drawing depth) of the apex angle portion 22a is desirably set to a value slightly exceeding 1/2 of the thickness of the electrode laminate 2. The size of the corner bulging portion 22 having a shape approximating a right-angled isosceles triangle in plan view is such that excessive elongation of the material and generation of wrinkles can be avoided when obtaining a desired protrusion amount at the apex angle portion 22a. Is set. The apex angle portion 22a is rounded so as to form an arc shape with an appropriate radius in plan view.

  The corner bulging portion 22 is drawn using a die 41 shown in FIG. 9 and a punch 42 shown in FIG. The die 41 has a rectangular mold opening 43, and the punch 42 has a rectangular mold protrusion 44 combined with the mold opening 43. In the illustrated example, the die 41 is based on two mold openings 43 so that two corner bulging portions 22 in one piece 10A, 10B of the laminate film 10 are formed by one die 41 and a punch 42. The punch 42 has two mold projections 44 symmetrically at both ends of the base portion 42a.

  The die opening 43 of the die 41 has two orthogonal sides 43b and 43c in which a corner 43a is rounded into an arc shape. The corner 43a corresponds to the apex angle portion 22a of the corner bulging portion 22, and the remaining three corners and two sides of the mold opening 43 do not substantially contribute to the drawing. The opening edge 43d of the mold opening 43 is appropriately chamfered.

  The mold protrusion 44 of the punch 42 has a rectangular shape smaller than the mold opening 43 in plan view, and two orthogonal sides 44b and 44c adjacent to the two sides 43b and 43c of the mold opening 43, and the mold And a corner 44a adjacent to the corner 43a of the opening 43. The remaining two sides of the mold projection 44 are located away from the corresponding sides of the mold opening 43 and do not substantially contribute to the drawing process. The corner 44a is rounded into an arc shape with a curvature corresponding to the corner 43a of the mold opening 43 in plan view (see FIG. 10A). Further, the top surface 44d of the mold projecting portion 44 is a flat surface inclined with respect to the surface of the base portion 42a. Specifically, the corner 43a portion protrudes the largest, and is inclined so as to gradually recede along the diagonal line of the mold protrusion 44 (see FIG. 10F). The two sides 44b and 44c and the edge 44e of the corner 44a are appropriately chamfered as shown in FIG. 10 (b).

  By using such a die 41 and punch 42 and performing a drawing process with an appropriate pushing amount (drawing depth), the corner bulging portion 22 shown in FIGS. 1 and 4 is obtained. The corner bulging portion 22 has a shape approximating a right-angled isosceles triangle formed by the corners 43a and 44a and the apex angle portion 22a is formed, and the punch 42 for the die 41 can be easily understood from the shapes of the die 41 and the punch 42. As the amount of pushing increases, the corner bulging portion 22 becomes larger. As described above, the push-in amount is desirably set so that the apex angle portion 22a has a depth that is slightly larger than ½ of the thickness of the electrode laminate 2.

  By forming the corner bulging portion 22 in this way, as shown in FIG. 2, the two corners 2C and 2D of the electrode stack 2 are arranged in the thickness direction of the cell 1 when folded in half. It is accommodated in the corner bulging portion 22 on both sides. Therefore, even when the three sides 11, 12, and 13 of the laminated film 10 folded in half are crushed by the seal lines 15, 16, and 17, a space that is expanded in the thickness direction of the cell 1 is secured. The corners 2C and 2D of the electrode laminate 2 are not strongly pressed. As shown in FIG. 2, an appropriate margin is provided between the corners 2C and 2D of the electrode laminate 2 and the rounded corner portion 22a of the corner bulging portion 22 in a plan view. Yes.

  The drawing process of the two corner bulging parts 22 and the drawing process of the central gusset part 21 in each of the pieces 10A and 10B of the laminate film 10 can be performed individually, that is, sequentially, but it is preferable. In one example, the drawing processing of the four corner bulging portions 22 and the drawing processing of the central gusset portion 21 are performed simultaneously. By simultaneously drawing in this way, the number of steps is reduced, and the shape obtained by the drawing performed earlier is not deformed by the drawing performed later. According to the present invention, even if all the drawing processes are performed simultaneously as described above, the mold (die and punch) has a small configuration as shown in FIGS. Compared with the conventional method of drawing into a rectangular cup shape corresponding to the above, the cost of the mold is reduced. In addition, only a part of the molds can be exchanged due to wear of the molds.

  As mentioned above, although one Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible.

  For example, in the above embodiment, both the positive electrode tab 4 and the negative electrode tab 5 are derived from one side 11 orthogonal to the side 14 that is folded in half, and these tabs 4 and 5 are arranged on any of the three sides. It is also possible to adopt a configuration in which the positive electrode tab 4 and the negative electrode tab 5 are derived from different sides. Further, the place where the liquid injection is performed is not limited to the side 13 as in the above-described embodiment, but can be performed from another place, and the sealing order of the seal lines 15, 16, and 17 is arbitrary.

DESCRIPTION OF SYMBOLS 1 ... Film exterior battery 2 ... Electrode laminated body 2A, 2B, 2C, 2D ... Corner | angular part 3 ... Exterior body 4 ... Positive electrode tab 5 ... Negative electrode tab 10 ... Laminate film 15, 16, 17 ... Seal wire 21 ... Machi part 22 ... Corner bulge 23 ... Folding line 31 ... Die 32 ... Punch 41 ... Die 42 ... Punch

Claims (9)

A rectangular electrode laminate in which a plurality of positive electrodes and negative electrodes are laminated via a separator is placed in an outer package formed by folding a laminate film made of a metal foil provided with a heat-fusible layer. A method for manufacturing a film-clad battery that constitutes an exterior body by heat-sealing along a side,
While drawing the gusset part into a bead shape having a length extending over two corners of the electrode laminate along the central fold line in the rectangular laminate film before being folded in two,
A method for producing a film-clad battery, characterized in that corner bulging portions that accommodate the corner portions are respectively drawn at four positions corresponding to the remaining two corner portions of the electrode laminate.   The manufacturing method of the film-clad battery of Claim 1 which performs the drawing process of a gusset part, and the drawing process of four corner bulging parts simultaneously.   The corner bulging portion has a substantially right triangle shape in plan view, and the apex portion protrudes the largest, and the amount of protrusion gradually decreases toward the center portion of the laminate film. The manufacturing method of the film-clad battery of Claim 1 or 2 which continues smoothly to a general part.   The method for producing a film-clad battery according to claim 3, wherein the apex angle portion has a rounded shape in plan view.   The method of manufacturing a film-clad battery according to any one of claims 1 to 4, wherein the gusset portion has a circular arc cross section in a cross section perpendicular to the folding line.   The manufacturing method of the film-clad battery according to any one of claims 1 to 4, wherein an end portion of the gusset portion is terminated so that a size of a cross-sectional shape in a cross section orthogonal to a fold line is continuously reduced.   The gusset portion is drawn using a slit-shaped die and a plate-like punch whose tip is arc-shaped in cross section and whose longitudinal ends are receded obliquely. The manufacturing method of the film-clad battery in any one of. A die having a rectangular opening having two orthogonal sides with rounded corners;
A rectangular punch that is combined with the die along the corner and inclined so that the top surface gradually recedes diagonally from the corner;
The manufacturing method of the film-clad battery in any one of Claims 1-7 which performs the drawing process of the said corner bulging part using. An electrode laminate in which a plurality of positive electrodes and negative electrodes are laminated via a separator;
It is configured by folding in half and laminating a laminate film made of a metal foil provided with a heat-fusible layer and heat-sealing three sides, and an exterior body containing the electrode laminate,
A film-clad battery comprising:
The exterior body is
While having a gusset portion formed by expanding a laminate film into a bead shape over two corners of the electrode laminate along a fold line,
Each of the two folded pieces has a corner bulging portion that locally bulges outward so that the corner portions respectively enter at positions corresponding to the remaining two corner portions of the electrode laminate.
Film outer battery.

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