JP2018176215A - Ultrasound joint method for metallic foil and film exterior battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress cracking and opening on current collectors 14, 15 upon ultrasound joint of the current collectors 14, 15 made of metallic foil with electrode tubs 3, 4 and to avoid problems, such as burr, due from a conventional protect metal plate.SOLUTION: Current collectors 14, 15 comprising a large number of positive electrodes and negative electrodes are respectively laminated on electrode tubs 3, 4 and jointed by ultrasound in thickness direction of the electrode tubs 3, 4 together with a heat resistance fiber reinforcement resin sheet 5. The sheet 5 is that whose fiber layer where glass fiber is woven in flat to form a grid shape is coated with PTFE and whose surface is uneven due to the fiber. Thereby, cracking and opening due to ultrasound energy on the current collectors 14, 15 are suppressed. The sheet 5 is flexible rather than the metal plate, thus no damage is provided on an inside layer of a laminate film 6 to be an outer body 2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an improvement of an ultrasonic bonding method in which a large number of metal foils and a relatively thick metal plate are laminated and ultrasonically bonded to each other, and further, a film sheath manufactured using this ultrasonic bonding method It relates to the battery.

  For example, as a lithium ion secondary battery, an electrode laminate (also referred to as a power generation element) formed by laminating a plurality of positive electrodes and negative electrodes with a separator interposed therebetween is electrolyzed in an outer package made of a laminate film provided with a heat fusion layer. There is known a film-shaped battery having a flat shape which is accommodated with a liquid. In this type of film-clad battery, the end of the metal foil constituting the current collector of the positive electrode or the negative electrode protrudes like a tongue from the active material layer, and a plurality of such tongue-like portions are stacked. Above, the structure ultrasonically bonded on the electrode tab which consists of a relatively thick metal plate is common.

  Here, since thin metal foils are susceptible to cracks and holes due to ultrasonic bonding, according to Patent Document 1, a protective metal layer made of similar metals having a thickness of about 50 μm to 200 μm is formed on a large number of metal foils. It is proposed to arrange the metal plate of the above and perform ultrasonic bonding between the horn and the anvil.

Japanese Patent Application Laid-Open No. 10-244380

  The above-mentioned protective metal plate is, for example, cut into an elongated rectangular shape and stacked on a metal foil, but if the cut metal plate is used as it is, sharp burrs and edges are present at the corners and the periphery. Therefore, new problems occur due to the burrs and edges, and measures for these problems are required.

  For example, in the case of the film-clad battery described above, since the laminate film is superimposed on the ultrasonic bond of the electrode tab, the resin layer on the inner surface of the laminate film (usually heat) However, the metal layer inside the laminate film may come in contact with the electrolytic solution to cause corrosion. Therefore, for example, it is necessary to take measures such as sticking a resin film for protecting the laminate film locally to the corresponding part of the laminate film.

  Therefore, in the present invention, when a large number of metal foils and relatively thick metal plates are laminated and ultrasonically bonded, a heat resistant fiber reinforced resin sheet is overlapped on the outermost metal foils instead of the metal plates. Ultrasonic bonding was performed.

  By superposing the heat-resistant fiber-reinforced resin sheets in this manner and ultrasonically bonding them, it is possible to prevent cracks and holes in the metal foil at the time of ultrasonic bonding, as in the case of conventional metal plates for protection. And in the heat resistant fiber reinforced resin sheet, since it becomes much more flexible as compared with the conventional metal plate for protection, it does not damage other members by the corner or the edge.

  The ultrasonic bonding method of the present invention can be applied to, for example, bonding of an electrode tab of a film-clad battery including an electrode laminate and an outer package made of a laminate film. In this case, there is no possibility that the heat-resistant fiber-reinforced resin sheet overlapped on the metal foil at the joint portion of the electrode tab may damage the inner layer of the laminate film, so no resin tape for laminate film protection is necessary. The inner layer of the above can be exposed to the heat resistant fiber reinforced resin sheet.

  According to the present invention, the heat-resistant fiber reinforced resin sheet is used in place of the conventional protective metal plate to protect the metal foil of the ultrasonic bonding portion. It is possible to avoid the occurrence of new issues.

The perspective view of the film-clad battery concerning this invention. The disassembled perspective view of this film-clad battery. Sectional drawing of the principal part of this film-clad battery. The perspective view of the principal part of the electrode laminated body which showed the junction part of the edge part of an electrical power collector, and an electrode tab. Explanatory drawing which showed roughly the joining process using the ultrasonic bonding apparatus. The drawing substitute photograph which showed the state of the metallographic structure of a junction. Explanatory drawing which shows the modification to which the collector was each arrange | positioned at the both sides of an electrode tab.

  Hereinafter, an embodiment in which the bonding method of the present invention is applied to the bonding of electrode tabs of a film-clad battery will be described.

  FIG. 1 shows a film-clad battery to which the present invention is applied. This film-clad battery is, for example, a film-clad lithium ion secondary battery having a flat shape that constitutes a power supply pack for driving a vehicle such as an electric car or a hybrid car. The film-clad battery of one embodiment has basically the same structure as that described in JP-A-2013-140782, JP-A-2015-37047, etc., and a positive electrode formed in a rectangular sheet shape. A plurality of negative electrodes are stacked via a separator to form an electrode laminate 1, and the electrode laminate 1 is housed together with an electrolytic solution in a bag-like outer package 2 made of a laminate film. The electrode laminate 1 has a pair of electrode tabs, that is, a positive electrode tab 3 and a negative electrode tab 4, and the pair of electrode tabs 3 and 4 are drawn out from the bonding surface of the laminate film constituting the package 2. There is.

  FIG. 2 is an exploded perspective view of the film-clad battery, and FIG. 3 is a cross-sectional view of the main part. As shown in FIG. 3, in the electrode stack 1, the positive electrodes 11 and the negative electrodes 12 are alternately stacked via the separators 13. The positive electrode 11 is a metal foil to be the current collector 14. Specifically, a positive electrode active material is applied as a slurry containing a binder on both sides of an aluminum foil, dried and rolled to form an active material layer of a predetermined thickness. is there. Similarly, the negative electrode 12 is a metal foil that becomes the current collector 15 (not shown in FIG. 3). Specifically, a negative electrode active material is applied as a slurry containing a binder on both sides of a copper foil, dried and rolled. An active material layer having a predetermined thickness is formed. The separator 13 has a function of preventing a short circuit between the positive electrode 11 and the negative electrode 12 and at the same time holding an electrolytic solution. For example, fine particles of thermoplastic synthetic resin such as polyethylene (PE) or polypropylene (PP) are used. It consists of a porous membrane or a nonwoven fabric.

  At one end portion of the current collector 14 of the positive electrode 11, a tongue piece portion 14 a to be welded to the positive electrode tab 3 is provided. The tongue portion 14 a is exposed without the active material layer. Similarly, at one end of the current collector 15 of the negative electrode 12, a tongue piece portion 15 a to be welded to the negative electrode tab 4 is provided. The tongue piece 15a is exposed without the active material layer. The tongue piece 14a on the positive electrode 11 side and the tongue piece 15a on the negative electrode 12 side are disposed so as not to overlap each other on one side of the electrode stack 1, as shown in FIG.

  Then, the plurality of tongue pieces 14 a located at mutually overlapping positions are stacked on the positive electrode tab 3 and integrally joined in the thickness direction of the positive electrode tab 3 by ultrasonic bonding. At the time of this ultrasonic bonding, a heat-resistant fiber-reinforced resin sheet 5 in the form of an elongated rectangle is superimposed on the tongue piece portion 14a made of a thin metal foil in order to prevent cracks and holes in the metal foil. The heat-resistant fiber-reinforced resin sheet 5, the tongue portions 14a, and the positive electrode tab 3 are integrally ultrasonically bonded. The same applies to the negative electrode 12 side, and a plurality of tongue pieces 15a at mutually overlapping positions are stacked on the negative electrode tab 4, and a heat-resistant fiber-reinforced resin sheet 5 in an elongated rectangular shape is stacked on the top. Then, they are integrally joined in the thickness direction of the negative electrode tab 4 by ultrasonic bonding.

  The positive electrode tab 3 is made of a thin aluminum plate, and the negative electrode tab 4 is made of a thin copper plate. That is, they are made of the same kind of metal as the current collectors 14 and 15, respectively. The positive electrode tab 3 and the negative electrode tab 4 are relatively thick as compared to the current collectors 14 and 15 made of metal foil. For example, the aluminum foil serving as the current collector 14 on the positive electrode 11 side has a thickness of about 15 μm, and the copper foil serving as the current collector 15 on the negative electrode 12 side has a thickness of about 8 μm. On the other hand, the positive electrode tab 3 made of an aluminum plate has a thickness of about 400 μm, and the negative electrode tab 4 made of a copper plate has a thickness of about 200 μm.

  As shown in FIG. 2, the exterior body 2 is composed of upper and lower two sheet-like laminate films 6, 7 and is formed into a bag shape by heat-sealing four sides of the peripheral edge. In more detail, the heat sealing of 3 sides is performed in the form which leaves the injection port of one side in the state which accommodated the electrode laminated body 1, and an injection port is sealed after injection. In the example shown in FIG. 2, the recessed part corresponding to the external shape of the electrode laminated body 1 is cup-shaped in advance in the laminate films 6 and 7. As shown in FIG. Note that one large laminate film may be used, and this may be folded in two, and the three sides may be heat-welded. The laminate films 6 and 7 to be the outer package 2 are, for example, a laminate of a heat seal layer made of polypropylene on the inside of aluminum foil and a laminate of a polyamide resin layer and a polyethylene terephthalate resin layer on the outside as a protective layer. It has a layered structure.

  As shown in FIG. 2, in order to protect the heat fusion layer from the sharp edges of the positive electrode tab 3 and the negative electrode tab 4 at the corresponding portions of the lower laminate film 7 in contact with the positive electrode tab 3 and the negative electrode tab 4. A protective tape 17 made of a relatively strong resin such as a polyamide resin is attached.

  In addition, on the surfaces of the electrode tabs 3 and 4 sandwiched by the bonding surfaces of the laminate films 6 and 7, a synthetic resin layer 18 called “first attached resin” is band-shaped in advance corresponding to the portion crossed by the seal line at the time of heat sealing. Provided in Where the peripheral edges of the laminate films 6 and 7 intersect the electrode tabs 3 and 4, the heat seal layer of the laminate films 6 and 7 is bonded onto the synthetic resin layer 18. For example, by sticking two strip-like polypropylene films on both surfaces of the electrode tabs 3 and 4, the synthetic resin layer 18 is formed in such a shape as to sandwich the electrode tabs 3 and 4.

  In addition, FIG. 3 has shown the structure of the cross section in the part of the positive electrode tab 3 typically. The configuration of the negative electrode tab 4 is basically the same. In FIG. 3, the dimensional relationship of each part, the number of positive electrodes 11 and negative electrodes 12, etc. are not necessarily accurate. For example, in one example, about 20 positive electrodes 11 and about 20 negative electrodes 12 are alternately stacked.

  FIG. 4 shows the joint portion of the positive electrode tab 3 and the negative electrode tab 4 joined to the tongue piece portions 14a and 15a of the current collectors 14 and 15 by ultrasonic bonding. An elongated rectangular portion indicated by reference numeral 21 is a welded portion by ultrasonic bonding, and three welded portions 21 are respectively disposed on a straight line at intervals along the width direction of the electrode tabs 3 and 4. The heat-resistant fiber-reinforced resin sheet 5 is cut into an elongated rectangular shape having a length that can cover the entire three welds 21.

  FIG. 5 shows an example of an ultrasonic bonding apparatus 25 that performs ultrasonic bonding. The ultrasonic bonding device 25 includes an anvil 26 disposed on the lower surface side of the welding portion 21 and a horn 27 connected to a vibration device (not shown), and the tip of the horn 27 is a tool for ultrasonic bonding. That is, the chip 28 is provided. The horn 27 is in the form of a substantially horizontally extending round rod, and is vibrated by a vibration device (not shown) along its longitudinal direction (left and right direction in the figure). And, at a position that is the antinode of the vibration of the horn 27, a tip 28 which is to be a substantially processed portion in contact with the work is disposed. In FIG. 5, the horn 27 and the anvil 26 are drawn in the mutually open position, but at the time of processing, the anvil 26 ascends to a predetermined height position, and the horn 27 is anvil 26 by a pressing mechanism (not shown). It is pressurized with a predetermined load toward the end. That is, the ultrasonic bonding apparatus 25 applies ultrasonic vibration while pressing the workpiece between the horn 27 and the anvil 26.

  The ultrasonic bonding device 25 holds the electrode tabs 3 and 4 as work pieces, the plurality of current collectors 14 and 15 (the tongues 14a and 15a), and the heat resistant fiber reinforced resin sheet 5 in a mutually laminated state. Clamp mechanism 29 is provided. The clamp mechanism 29 holds the work at a position not interfering with the anvil 26 and the horn 27.

  In one embodiment, the electrode tabs 3 and 4 are located on the anvil 26, and the heat-resistant fiber reinforced resin sheet 5 is disposed on the top where the horn 27 contacts. Alternatively, the horn 27 may be reversely disposed so as to be in contact with the electrode tabs 3 and 4, and the heat resistant fiber reinforced resin sheet 5 may be disposed between the current collectors 14 and 15 and the anvil 26.

  The tips 28 are in the form of elongated rectangular plates corresponding to the size of the individual welds 21. The tip 28 can be formed as a component separate from the horn 27 using, for example, tool steel or the like, and can be attached to the horn 27 and used. Alternatively, it may be formed directly on the horn 27 as a part of the horn 27. In the example of FIG. 5, the vibration direction of the horn 27 is along the width direction of the chip 28 (the direction orthogonal to the longitudinal direction of the chip 28).

  The machined surface of the chip 28 is provided with a plurality of regularly arranged pyramidal (i.e., quadrangular pyramidal) convex portions (not shown), and has a so-called knurled configuration. In one embodiment, the convexes are arranged vertically and horizontally so that the base of the quadrangular pyramid is parallel to the long and short sides of the chip 28. The base of the quadrangular pyramid may be inclined at about 45 ° with respect to the long side and the short side of the tip 28.

  Further, in one embodiment, the machining surface of the anvil 26 is provided with a plurality of pyramid-shaped (that is, quadrangular pyramidal) convex portions regularly arranged in the same manner as the machining surface of the tip 28. The anvil 26 may have a flat processing surface.

  The heat-resistant fiber-reinforced resin sheet 5 disposed between the current collectors 14 and 15 and the horn 27 is made of glass fibers or ceramics as reinforcing fibers in a layer of synthetic resin having excellent heat resistance such as fluorocarbon resin. It contains fibers and is configured in a thin sheet. As a synthetic resin, you may use heat resistant resins other than a fluorine resin. In a preferred embodiment, the glass fibers are configured as a grid-like woven fabric (in other words plain woven fabric) with appropriately sized eyes, and on both sides or one side of this woven fabric as a heat resistant resin It is coated with polytetrafluoroethylene (PTFE). The thickness of the sheet 5 is about 75 μm in one example, and since the heat resistant resin is coated relatively thinly, unevenness due to the plain weave glass fiber appears on the surface of the sheet 5. That is, the surface of the sheet 5 is not smooth but rough. The size of the grid-like eye is set to, for example, about several tens of μm to several hundreds of μm.

  The heat-resistant fiber-reinforced resin sheet 5 may have a configuration in which the fibers are mixed as they are or in the form of threads and irregularly mixed in the synthetic resin layer, in addition to the above-mentioned form of the woven fabric.

  When such heat-resistant fiber-reinforced resin sheet 5 is disposed between it and the anvil 26 and ultrasonic bonding is performed, the synthetic resin portion of the sheet 5 is locally localized by the energy applied from the processing surface of the tip 28 by ultrasonic vibration. Although the fiber layer contained in the sheet 5 protects the metal foil (current collectors 14 and 15) together with the softened and melted synthetic resin, cracks and holes in the metal foil are suppressed. In addition, the heat-resistant fiber-reinforced resin sheet 5 does not impair the transmission of vibrational energy to the metal foil in the lower layer, and ultrasonic waves are supplied with the same energy and processing time as in the case of stacking metal plates for protection in the prior art. Bonding is possible. The unevenness on the surface of the sheet 5 suppresses slippage on the surface of the sheet 5 and contributes to the efficient transfer of vibrational energy from the chip 28 to the metal foil in the lower layer.

  FIG. 6 is a photograph of the actual welded portion 21 by ultrasonic bonding as viewed from the heat resistant fiber reinforced resin sheet 5 side. In this example, 20 current collectors 14 on the side of positive electrode 11 made of aluminum foil with a thickness of 15 μm are laminated, stacked on positive electrode tab 3 with a thickness of 400 μm, and the top of current collector 14 The heat-resistant fiber reinforced resin sheet 5 is disposed, and ultrasonic bonding is performed. As processing conditions for ultrasonic bonding, a pressure of 700 N, an amplitude of 45 μm, and a supplied energy of 100 J were used. As shown in the drawing, pyramidal depressions are produced corresponding to the pyramidal projections of the tips 28 of the horn 27. However, glass fibers are also present around the individual indentations together with the synthetic resin. The current collector 14 does not have any cracks or holes.

  According to the inventor's experiments, if the synthetic resin sheet does not contain the fiber layer, the resin is softened and melted by ultrasonic energy and spreads, and the effect of protecting the metal foil is not obtained. Also, conversely, if the woven fabric is a glass fiber that does not contain a synthetic resin, the fiber is only dispersed as powder by ultrasonic energy, and the effect of protecting the metal foil is not obtained.

  Thus, according to the present invention using the heat resistant fiber reinforced resin sheet 5 for protecting the current collectors 14 and 15 at the time of ultrasonic bonding, it is similar to the conventional protective metal plate disclosed in Patent Document 1 It is possible to achieve suppression of cracks and holes in the current collectors 14 and 15.

  And in the heat resistant fiber reinforced resin sheet 5, since it is much softer compared with the metal plate for protection disclosed in patent documents, other members will not be damaged by the peripheral edge or corner. More specifically, there is no risk of damaging the inner layer of the laminate film 6, that is, the heat seal layer, which overlaps the welds 21 of the electrode tabs 3 and 4. Therefore, it is not necessary to apply a protective tape to the inner surface of the laminate film 6 to protect the heat seal layer. As shown in FIG. 3, in the state where the electrode laminate 1 is accommodated in the exterior body 2, the inner side surface (heat fusion layer) of the laminate film 6 is exposed to the heat resistant fiber reinforced resin sheet 5.

  Further, in the heat-resistant fiber-reinforced resin sheet 5 described above, generation of dust is suppressed at the time of processing by the ultrasonic bonding device 25. That is, when the tip 28 applies ultrasonic vibration to a metal work such as metal foil, fine metal powder is generated and scattered. It is not desirable for the metal powder to intrude into the film-clad battery, and it needs to be removed by some means. On the other hand, in the above embodiment in which the heat-resistant fiber reinforced resin sheet 5 is stacked on the metal foil, the synthetic resin melted at the time of processing intervenes near the contact point between the chip 28 and the metal surface. While the generation itself is reduced, the generation of dust is suppressed because it is encased in the molten resin and does not scatter even if it occurs temporarily.

  Furthermore, in the automated line, when the position of the heat-resistant fiber-reinforced resin sheet 5 is confirmed by image inspection after ultrasonic bonding, the heat-resistant fiber-reinforced resin sheet 5 reflects the surrounding metal foil and the electrode tabs 3, 4 The position detection is reliable and easy, and there are few false detections. For example, in the case of using a protective metal plate made of the same kind of metal as the metal foil or electrode tab as a collector as disclosed in Patent Document 1, the difference in reflectance between the protective metal plate and the surroundings, Since there is no color difference, erroneous detection is likely to occur when detecting the position of the protective metal plate by image inspection.

  As mentioned above, although one Example of this invention was described, the ultrasonic bonding method of this invention is not limited to the said Example, Also in the field | area other than a battery, many metal foil and a relatively thick metal plate It can be applied to various applications of laminating and ultrasonic bonding. The present invention is applicable even when the processing surfaces of the horn and the anvil are flat, and the same effects as those of the above-described embodiment can be obtained.

  Further, as illustrated in FIG. 7, the present invention is also applicable to the case where multiple metal foils 52 are laminated on both sides of a relatively thick metal plate 51 and ultrasonic bonding is integrally performed in the thickness direction of the metal plate 51. It is applicable. In this case, the heat resistant fiber reinforced resin sheet 53 is overlapped on both the horn side and the anvil side.

DESCRIPTION OF SYMBOLS 1 ... Electrode laminated body 2 ... Exterior body 3, 4 ... Electrode tab 5 ... Heat resistant fiber reinforced resin sheet 11 ... Positive electrode 12 ... Negative electrode 13 ... Separator 14, 15 ... Current collector 21 ... Welding part 25 ... Ultrasonic bonding apparatus 26 ... anvil 27 ... horn 51 ... metal plate 52 ... metal foil 53 ... heat resistant fiber reinforced resin sheet

Claims (6)

In a bonding method in which a large number of metal foils and a relatively thick metal plate are laminated, and ultrasonic vibration is applied while bonding between a horn and an anvil of an ultrasonic bonding device to bond them.
A method of ultrasonically bonding a metal foil, comprising superposing a heat resistant fiber reinforced resin sheet between the horn or anvil and the outermost metal foil on the horn side or the anvil side.   The said heat-resistant fiber reinforced resin sheet has the unevenness | corrugation by a fiber on the surface, The ultrasonic bonding method of metal foil of Claim 1 characterized by the above-mentioned.   The ultrasonic bonding method of metal foil according to claim 1 or 2, wherein the heat-resistant fiber-reinforced resin sheet has a structure in which a glass fiber woven fabric is coated with a heat-resistant synthetic resin.   The said heat-resistant fiber reinforced resin sheet is using the fluororesin as a synthetic resin, The ultrasonic bonding method of the metal foil in any one of the Claims 1-3 characterized by the above-mentioned.   The ultrasonic wave of the metal foil according to any one of claims 1 to 4, wherein a plurality of pyramidal convex portions are provided side by side on at least one of the processing surfaces of the horn and the anvil. Bonding method. A plurality of positive and negative electrodes cut into a sheet are laminated via a separator, and an electrode tab made of a relatively thick metal plate is joined to an end of a current collector made of a metal foil of these electrodes. An electrode stack,
An exterior body made of a laminated film in which the electrode stack is accommodated together with an electrolytic solution and the electrode tab is pulled out from the bonding surface;
In a film-clad battery provided with
The end portions of the current collector and the electrode tab are provided with a heat resistant fiber reinforced resin sheet on the outermost surface of the current collector, while the ends of the plurality of current collectors are stacked together with the electrode tab. These are integrated in the thickness direction of the electrode tab,
An inner layer of a laminate film of the outer package is exposed to the heat resistant fiber reinforced resin sheet, A film outer battery characterized in that: