JP2015199095A - Ultrasonic welding apparatus and method of manufacturing battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic welding apparatus capable of suppressing tear of a weld part and enhancing bond strength, and a method of manufacturing a battery.SOLUTION: An ultrasonic welding apparatus comprises a first pressing part (10) having a first joint surface (11) on which a joint material (3) and a jointed material (4) are placed so as to be laminated, and a second pressing part (20) having a second joint surface (21) holding and pressing the joint material and the jointed material with the first joint surface, and joints the joint material and the jointed material by applying ultrasonic vibration to the first pressing part and/or the second pressing part. The first joint surface and the second joint surface have a plurality of protrusions (12, 22) which are vertically and horizontally arranged. The joint material is a laminate which contacts the second joint surface and consists of a plurality of pieces of foil. One or a plurality of recesses (13, 23) existing between the plurality of protrusions consist of surfaces having no corner part on at least the second joint surface.

Description

  The present invention relates to an ultrasonic welding apparatus and a battery manufacturing method using the apparatus.

  Conventionally, ultrasonic welding has been widely used as a method for joining metal plates. An ultrasonic welding apparatus that performs ultrasonic welding gives ultrasonic vibration energy in parallel to the bonding surface while holding the bonding material and the material to be bonded with a tool made of a horn and an anvil under moderate pressure. It is an apparatus for joining a joining material and a material to be joined without causing melting on the surfaces. And the joining surface of the horn of this ultrasonic welding apparatus and an anvil generally has an uneven | corrugated shape in order to clamp a joining material and a to-be-joined material reliably. With an ultrasonic welding apparatus having such a joining surface, when the joining material and the material to be joined are relatively thick, they can be joined with good reliability.

  By the way, in recent years, secondary batteries such as lithium secondary batteries and nickel metal hydride batteries have become increasingly important as power sources for electric vehicles or personal computers, portable terminals, and other electric products. In particular, a lithium secondary battery that is lightweight and has a high energy density is expected to be preferably used as a high-output power source for mounting on a vehicle.

  As one form of this type of battery, a positive or negative electrode sheet in which an electrode active material layer is held on a long current collector (typically a foil current collector) is laminated or wound together with a separator to form an electrode. 2. Description of the Related Art Secondary batteries are known in which a body is formed and the electrode body is housed in a battery case having a predetermined shape (for example, a square shape or a cylindrical shape) together with an electrolyte. Thus, by laminating electrode sheets with a plurality of separators interposed between them or making the electrode body spiral, the area contributing to the battery reaction is increased, the energy density is increased, and high output is possible.

  The electrode body and the current collecting terminal are joined as follows. That is, first, an active material layer non-formation part in which no electrode active material layer is formed is provided along one end in the width direction of each of the positive electrode current collector and the negative electrode current collector. Next, the electrode body is configured such that the active material layer non-forming portion of the current collector protrudes from the separator and the other electrode. Then, the current collector laminated portion including the active material layer non-forming portion is joined to the current collecting terminal.

  The ultrasonic welding method mentioned above is mentioned as one of the means of forming the connection structure of the collector laminated part formed by laminating this foil-like collector and the plate-like collector terminal. Here, the thickness of a general current collector used for a lithium secondary battery or the like is 50 μm or less, and ultrasonic waves are obtained using a laminate of a plurality of thin metal foils and a plate-like metal plate. When welding is performed, the current collector foil may be partially broken. In particular, tearing is likely to occur in the current collector foil portion in contact with the top surface of the convex portion provided on the joint surface of the horn and the current collector foil portion in contact with the peripheral portion of the horn joint surface where stress tends to concentrate. Such partial breakage of the current collector foil may cause peeling of the joint portion during actual use or battery assembly operation, resulting in problems such as product reliability and safety.

  As a method for solving this problem, the convex portion provided on the joint surface of the horn is formed in an arc shape, or a margin region is provided in which no concavo-convex portion is provided at the end of the horn joint surface (Patent Literature). 1).

JP 2012-125801 A

  However, when the thickness of one current collector foil is thinner, for example, when the thickness is 30 μm or less, the current collector foil may still be broken or damaged. In view of such circumstances, the inventors have intensively studied and occur in the current collector foil in contact with the peripheral portion of the joint surface of the horn or the current collector foil portion in contact with the top surface of the convex portion provided on the joint surface. It was discovered that not only the tear but also the current collector foil in contact with the concave portion existing between the convex portions on the joint surface has a tear. The cause of the breakage observed in the current collector laminated portion in contact with the concave portion of the horn joint surface is considered as follows.

  The terminal placed on the anvil joint surface and the current collector laminated portion are sandwiched between the horn joint surface and the anvil joint surface, and further apply ultrasonic vibration while pressing them. By this pressurization and ultrasonic vibration, the terminal and the current collector laminated portion are welded. At the same time, a plurality of current collector foils on the horn side, that is, on the current collector laminated portion that is in contact with the horn joint surface, is the side facing away from the surface where the terminal and current collector laminated portion are in contact with each other. Plastic flow is caused by pressure and ultrasonic vibration. Then, the plurality of current collector foils constituting the current collector laminated portion on the horn side flows into the concave portion of the horn joint surface. As a result, the current collector foil that has caused plastic flow and has flowed into the concave portion acts as an anchor in the vibration direction, so that the current collector laminated portion is securely held by the horn joint surface, and the current collector laminated portion Ultrasonic vibration can be transmitted effectively.

  On the other hand, the concave portion of the horn joint surface is surrounded by convex portions and convex portions, and has a shape in which the space becomes narrower toward the back, for example, a valley shape, a groove shape, or a substantially mortar shape. And the base part of a convex part and the back | inner part of a recessed part is a surface which has a corner | angular part. Due to such a shape, the plurality of current collector foils that flow plastically flow into the concave portion, so that the space in which the current collector foil can vibrate becomes narrower and its movement is restricted. As a result, among the current collector foils flowing into the recesses, the current collector foil in contact with both ends of the recesses in the vibration direction is raised, and the current collector foil located in the back center portion of the recesses is shown sinking A new stacking occurs. For this reason, among the plurality of current collector foils that are in contact with the concave portion of the horn joint surface when ultrasonic welding is finished, in particular, the plurality of current collector foils that are in contact with the back of the concave portion are in an irregular laminated state. Will be shown. And the irregular lamination | stacking state of this several collector foil is the cause of a tear (refer Fig.6 (a) and (b)). Attention is paid to such breakage of the current collector foil, and no invention has been found yet.

  In view of this, the present invention aims to improve the bonding strength by preventing the current collector foil in contact with the concave portion provided on the bonding surface, thereby improving the bonding strength, thereby reducing the bonding area. A device is provided. In addition, the present invention provides a battery manufacturing method that can improve reliability and safety as a product by using this device.

  In order to solve the above problems, an ultrasonic welding apparatus of the present invention is provided between a first pressing portion having a first bonding surface on which a bonding material and a material to be bonded are stacked and placed, and the first bonding surface. And a second pressing portion having a second bonding surface that sandwiches and presses the bonding material and the material to be bonded, and applies ultrasonic vibration to the first pressing portion and / or the second pressing portion to apply the bonding material and the material to be bonded. An ultrasonic welding apparatus for joining a joining material, wherein the first joining surface and the second joining surface have a plurality of convex portions arranged vertically and horizontally, and the joining material is in contact with the second joining surface and from a plurality of foils In the laminated body, at least in the second bonding surface, one or a plurality of concave portions existing between the plurality of convex portions is formed of a surface having no corner portion.

  As a result of earnest research to solve the above-described problems, the present inventors have made the recesses present at least on the second joint surface exemplified by the horn into a surface having no corners, so that It has been found that breakage of the current collector laminated part in contact can be prevented. That is, by adopting this configuration, the plastic flowable space of the bonding material in the concave portion of the second bonding surface can be expanded, and a plurality of current collector foils constituting the bonding material are not formed in the concave portion of the horn bonding surface. It can suppress becoming a regular lamination | stacking state. Therefore, the tear which may arise in the recessed part of a 2nd joint surface can be prevented.

  Further, the battery manufacturing method of the present invention includes a positive electrode having a positive electrode active material layer on a partial surface of a positive electrode current collector, a negative electrode having a negative electrode active material layer on a partial surface of a negative electrode current collector, a separator, A positive electrode terminal that is electrically connected to an electrolyte, a positive electrode current collector laminated portion in which a plurality of positive electrode current collector junctions in which the positive electrode current collector in the positive electrode is exposed, and a negative electrode current collector in which the negative electrode current collector in the negative electrode is exposed A negative electrode terminal electrically connected to a negative electrode current collector laminated portion in which a plurality of junctions are laminated, and a positive electrode current collector laminated portion, a positive electrode terminal, and / or a negative electrode current collector The laminated portion and the negative electrode terminal have a joining step in which ultrasonic welding is performed using the above-described ultrasonic welding apparatus of the present invention.

  If the manufacturing method of the battery adopting this configuration, it is possible to perform the ultrasonic welding corresponding to each of the positive and negative current collecting joints and the positive and negative electrode terminals while suppressing the breakage of the current collector foil. The joint strength of the joint part corresponding to each of the joint part and the positive and negative electrode terminals can be improved. Therefore, the battery manufacturing method of the present invention has improved reliability and safety.

It is the side view which showed typically the conjugate | zygote of the ultrasonic welding apparatus of this invention, and its vicinity. It is the perspective view which showed typically the 2nd press part of the ultrasonic welding apparatus of this invention. It is sectional drawing which showed typically the cross section by AA of FIG. It is sectional drawing which showed typically the schematic structure of the welding part of the negative electrode collector lamination part and negative electrode terminal in the manufacturing method of the battery of this invention, and its vicinity. It is the side view which showed typically the ultrasonic welding method for forming the welding part shown in FIG. Both (a) and (b) are photographs showing a cross-sectional structure of a welded portion between a current collector laminated portion and an electrode terminal by a conventional ultrasonic welding apparatus. It is a photograph which shows the cross-sectional structure of the welding site | part of the collector laminated part and electrode terminal by the ultrasonic welding apparatus of this invention. 1 is a perspective plan view showing a schematic configuration of a laminated lithium secondary battery which is an example of the present invention.

  Hereinafter, a preferred embodiment of the ultrasonic welding apparatus 1 of the present invention will be described with reference to FIGS. It should be noted that matters other than matters specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  The ultrasonic welding apparatus of the present invention is similar to a normal ultrasonic welding apparatus in which a bonding material 3 and a material to be bonded 4 (hereinafter, collectively referred to as “joined body”) to be bonded are placed. 1 press part 10 and the 2nd press part 20 which applies an ultrasonic vibration to a joined body while pressing a joined body are provided.

  The first pressing portion 10 has a first bonding surface 11 on which the bonding material 3 and the bonded material 4 are stacked and placed. Of the joined body, the material to be joined 4 is placed on the first joining surface 11. And the joining material 3 is arrange | positioned on the predetermined position of the to-be-joined material 4 mounted in the 1st joining surface 11 among the joined bodies.

  The second pressing portion 20 includes a second bonding surface 21 that sandwiches and presses the bonding material 3 and the material to be bonded 4 with the first bonding surface 11.

  The 1st press part 10 is an anvil, for example, and hold | maintains the to-be-joined material 4. FIG. The second pressing portion 20 is a horn and applies pressure and ultrasonic vibration to the bonding material 3. Specifically, the second pressing unit 20 is applied with ultrasonic vibrations that vibrate substantially parallel to the first joint surface 11 of the first pressing unit 10 by an ultrasonic wave generation source (not shown), an actuator, and the like. A pressing operation is performed toward the first joint surface 11 of the first pressing portion 10 by the driving device (not shown). Note that, similarly to the second pressing unit 20, the first pressing unit 10 may be configured to pressurize the bonded body to be sandwiched and apply ultrasonic vibration to the bonded body. In this case, it is desirable that the pressurizing directions of the first pressing portion 10 and the second pressing portion 20 are opposite to each other. Moreover, the 1st press part 10 and the 2nd press part 20 move relatively by applying an ultrasonic vibration.

  The bonding material 3 is a laminated body composed of a plurality of foils. For example, a plurality of Al metal foils constituting a positive electrode current collector in a lithium ion battery or Cu metal foils constituting a negative electrode current collector are laminated. Moreover, the to-be-joined material 4 is a ribbon-shaped lead by which ultrasonic welding is made | formed with respect to the joining material 3 which comprises a collector, for example, for example, is a metal plate which comprises Al lead and Cu lead.

  As shown in FIG. 1, the bonding material 3 includes a bonding material first surface 31 that contacts the second bonding surface 21 of the second pressing portion 20 and a bonding material second surface 32 that faces away from the bonding material first surface 31. Have. The bonded material 4 includes a bonded material first surface 41 that contacts the first bonded surface 11 of the first pressing portion 10 and a bonded material second surface 42 that faces away from the bonded material first surface 41. . The joined body is formed by welding the joining material second surface 32 and the joined material second surface 42.

  The welding method of the joining material 3 and the to-be-joined material 4 of the ultrasonic welding apparatus of this invention is as follows. First, the second pressing portion 20 to which ultrasonic vibration is applied presses the bonding material 3. Thereby, pressure and amplitude are given to the bonding material 3. Then, the bonding material 3 oscillates in synchronization with the ultrasonic vibration. Next, the amplitude of the bonding material 3 rubs against the bonded portion 4 held by the first pressing portion 10, the bonding material second surface 32, and the bonded material second surface 42. As a result, the oxide film at the bonding interface between the bonding material second surface 32 and the bonded material second surface 42 is removed. Then, the atoms at the bonding interface between the bonding material second surface 32 and the bonded material second surface 42 are close to each other, and a strong attractive force is generated between the atoms. Due to the attractive force between the atoms, the bonding material 3 and the bonded material 4 are bonded by the bonding material second surface 32 and the bonded material second surface 42.

  As shown in FIG. 1, the first bonding surface 11 of the first pressing portion 10 and the second bonding surface 21 of the second pressing portion 20 are provided with a plurality of convex portions 12 and 22 arranged vertically and horizontally. Concave portions 13 and 23 are provided between the convex portions 12 and 22. As described above, the first bonding surface 11 and the second bonding surface 21 have uneven surfaces.

  The shape of the protrusions 12 and 22 is not particularly limited as long as it is a protrusion that can be pressed against a member to be joined. For example, a shape such as a polygonal pyramid or cone, a polygonal pyramid or cone with a tip portion cut off, or a cylinder or a hemisphere is preferable. Moreover, it is more preferable that it is a shape which has the form which rounded off the front-end | tip of a tapered truncated cone.

  The number of the convex parts 12 and 22 is not specifically limited, It can adjust suitably according to the area which the welding site | part welds. Further, the arrangement of the convex portions 12 and 22 is not particularly limited. For example, the convex portions 12 and 22 may be arranged in a single row or a double row (arrangement having a pattern such as a staggered pattern or a checkered pattern, or without regularity). May be used).

  The ultrasonic welding apparatus of the present invention is particularly characterized by the shape of the recess 23 provided in the second joint surface 21 of the second pressing portion 20. That is, the shape of the recess 23 is formed from a surface having no corners. The features of the present invention will now be described in further detail with reference to FIGS.

  FIG. 2 is a perspective view schematically showing the second pressing portion 20, and is an embodiment showing the shape of the second bonding surface 21. In the embodiment, the convex portions 22 are regularly arranged on the second joint surface 21, and the concave portions 23 are regularly arranged between the convex portions 22. In addition, the convex part 22 and the recessed part 23 may be arrange | positioned irregularly. Here, the recess 23 includes a first recess 24 and a second recess 25. The 1st recessed part 24 exists between the two convex parts 22 adjacently arranged vertically or horizontally. The second concave portion 25 is surrounded by three or four or more convex portions 22.

  At the time of ultrasonic welding, a plurality of laminated metal foils in the vicinity of the bonding material first surface 31 undergoes a plastic flow by receiving a pressing force and ultrasonic vibration, and the first concave portion 24 and the second concave portion 25 are subjected to plastic flow. Flows in. The shape of the recessed part provided in the horn joint surface of the conventional ultrasonic welding apparatus is a substantially mortar shape with a corner | angular part, for example. For this reason, the space becomes narrower toward the back of the recess. Therefore, a restriction is added to the viable range of the plurality of metal foils flowing into the back of the recess. As a result, as shown in FIGS. 6 (a) and 6 (b), irregular lamination of the metal foil occurs in the inner part of the recess. This irregular and disturbed lamination of the metal foil causes the tearing of the bonding material.

  Therefore, in the present invention, the shapes of the first recess 24 and the second recess 25 are surfaces having no corners. That is, the back portions of the first recess 24 and the second recess 25 have a shape that draws a loose arc. By adopting such a shape, the space in the back part of the first recess 24 and the second recess 25 becomes wider than a recess having a conventional corner. Accordingly, the plurality of metal foils that plastically flow during ultrasonic welding and flow into the first recess 24 and the second recess 25 have a certain amount of vibration space at the back of the recess, so the restriction on the amplitude motion is relaxed. Is done. For this reason, the plurality of metal foils flowing into the first recess 24 and the second recess 25 do not show an irregular and disordered laminated structure. Therefore, it is possible to suppress breakage that can occur in the bonding material 3 formed by the first recess 24 and the second recess 25 of the present invention. Furthermore, by suppressing the tearing, the bonding strength can be improved, and therefore the bonding area can be reduced.

  As for the shape of the 1st recessed part 24 and the 2nd recessed part 25 which exist in multiple numbers, it is desirable that all make it the surface which does not have a corner | angular part. However, it is possible to improve the bonding strength and reduce the bonding area by setting at least one of these concave portions to a surface having no corners. Further, the present inventors have found that the portion of the bonding material 3 in contact with the second recess 25 in the recess 23 is often broken. Therefore, it is more preferable that at least one of the plurality of second recesses 25 is a surface having no corners. FIG. 3 is a schematic diagram of a cross section taken along line AA of FIG. As shown in FIG. 3, it is desirable that the second recess 25 has a surface that does not have a corner.

  Further, the concave portion 23 having a surface having no corner portion can also be applied to the concave portion 13 of the first pressing portion. By doing in this way, also in the to-be-joined material 4, it can anticipate that the effect similar to the joining material 3 is acquired.

  Here, the “corner” can be defined by the radius of curvature. That is, the “corner portion” of the present invention desirably has a radius of curvature smaller than the thickness of one foil constituting the bonding material 3. That is, it is desirable that the thickness of one foil constituting the bonding material 3 is the lower limit value of the radius of curvature of the “surface not having a corner” of the present invention. Specifically, in the case where the ultrasonic welding apparatus of the present invention is applied to the welded portion of the current collector laminated portion and the electrode terminal of the battery as an example, the curvature radius of the “corner portion” is the current collector foil. It is desirable that the thickness of each sheet is smaller than 15 μm, 10 μm, 8 μm, 4 μm, and 2 μm. That is, the radius of curvature of the “surface having no corners” is desirably 15 μm, 10 μm, 8 μm, 4 μm, 2 μm or more, which is the thickness of one current collector foil. However, it can be designed as appropriate depending on the type of current collector used.

  In addition, the upper limit value of the curvature radius of the “surface having no corner” can be the height from the first joint surface 11 and the second joint surface 21 to the vertices of the corresponding convex portions 12 and 22. . The height of the convex portion 12 is smaller than the thickness of the bonding material 3, and the height of the convex portion 22 needs to be smaller than the thickness of the material to be bonded 4. If the heights of the convex portions 12 and 22 are smaller than the thicknesses of the bonding material 3 and the material to be bonded 4 corresponding to each of the convex portions 12 and 22, when the bonded body is sandwiched during the ultrasonic welding, the convex portion 12 There is no possibility that 22 breaks through the material 4 to be joined. Therefore, it is desirable that the upper limit value of the radius of curvature of the “surface having no corner” is the thinner one of the bonding material 3 and the material to be bonded 4. Further, in each of the bonding material 3 and the material to be bonded 4, it is preferable to define an upper limit value of the radius of curvature of the “surface having no corner”. Here, in the case where the ultrasonic welding apparatus of the present invention is applied to the current collector laminated portion of the battery and the welded portion of the electrode terminal as an example, the curvature radius of the “surface having no corner” is plural. The thickness is preferably smaller than the thickness of the laminated current collector foil. For these reasons, it is desirable to appropriately design the upper limit value of the radius of curvature of the “surface having no corner” depending on the type of current collector, the number of current collectors to be stacked, and the like.

  A well-known method can be used to obtain the curvature radius. For example, fitting is performed while changing the radius of the arc having a central angle of 90 degrees with respect to the tip (rear part) of the recess. The radius when at least two points at the end of the arc coincide with one point at the center can be obtained as the radius of curvature.

  Thus, according to the ultrasonic welding apparatus by this embodiment, generation | occurrence | production of a hole and a tear can be suppressed and favorable welding can be performed. In addition, since the occurrence of holes and tears can be suppressed, the bonding strength can be improved, thereby reducing the bonding area.

  The ultrasonic welding apparatus of the present embodiment described above is an electrode body formed by laminating and / or winding a positive electrode and a negative electrode each having an electrode active material layer formed on the surface of a foil-shaped current collector together with a separator (hereinafter simply referred to as an electrode body). And a method of manufacturing a battery having a configuration including a current collecting terminal joined to the electrode body. In particular, the ultrasonic welding apparatus of the present embodiment is suitable for a method for manufacturing a secondary battery. As the secondary battery, a storage battery such as a lithium secondary battery or a nickel secondary battery, or an electric storage such as an electric double layer capacitor. A battery including the element can be mentioned. Hereinafter, in a preferred embodiment of the battery manufacturing method of the present invention, the laminated lithium secondary battery 80 shown in FIG. 8 will be described as an example. However, the present invention is not intended to be limited to the embodiment.

  The general configuration of the lithium secondary battery will be outlined. In the present specification, the “lithium secondary battery” refers to a secondary battery that uses lithium ions as electrolyte ions and is charged / discharged by movement of charges accompanying the lithium ions between the positive and negative electrodes. Secondary batteries generally referred to as lithium ion batteries (or lithium ion secondary batteries), lithium polymer batteries, lithium-air batteries, lithium-sulfur batteries, and the like can be included in the lithium secondary batteries in this specification. Further, in this specification, the “active material” refers to a substance (compound) involved in power storage on the positive electrode side or the negative electrode side. That is, it refers to a substance that is involved in the insertion and extraction of electrons during battery charge / discharge. In addition, the lithium secondary battery in this invention is not limited to what was shown to the following embodiment, In the range which does not change the summary, it can change suitably and can implement.

  FIG. 8 is a perspective plan view showing a schematic configuration of a general laminated lithium secondary battery 80. In FIG. 8, 51p is a positive electrode and 51n is a negative electrode. The positive electrode 51p and the negative electrode 51n have a positive electrode current collector 52p and a negative electrode current collector 52n made of metal foil as a base material layer, and an electrode mixture layer (53p, 53p, 53n) is formed by coating. The positive electrode 51p and the negative electrode 51n are alternately stacked via the separator 60 to constitute the electrode body 50. The positive electrode current collector junction 61p and the negative electrode current collector junction 61n, which are part of the current collector protruding from the electrode body 50, are not formed with the electrode mixture layer (53p, 53n), and the positive electrode current collector 52p and the negative electrode The current collector 52n is exposed. A positive electrode current collector laminate portion 62p in which a plurality of positive electrode current collector junction portions 61p are laminated is welded by a positive electrode terminal 71p and a positive electrode weld portion 54p. Similarly, a negative electrode current collector laminated portion 62n in which a plurality of negative electrode current collector joining portions 61n are laminated is welded by a negative electrode terminal 71n and a negative electrode welded portion 54n. The exterior 81 accommodates the electrode body 50. The exterior 81 is made of two laminate sheets (exterior materials) having flexibility. The two laminate sheets are heat-sealed and sealed at a heat seal portion along the outer peripheral edge.

  FIG. 4 is a cross-sectional view along the thickness direction showing a schematic configuration of the negative electrode weld 54n and the vicinity thereof. The positive electrode 51p includes a positive electrode current collector 52p and a positive electrode mixture layer 53p applied to the surface of the positive electrode current collector 52p. The negative electrode 51n is applied to both surfaces of the negative electrode current collector 52n and the negative electrode current collector 52n. The negative electrode mixture layer 53n. A plurality of negative electrode current collector joining portions 61n from which the negative electrode current collector 52n is exposed are stacked on the negative electrode terminal 63n to constitute a negative electrode current collector stacked portion 62n.

  The negative electrode current collector laminated portion 62n and the negative electrode terminal 63n are integrally welded and electrically connected at the negative electrode welded portion 54n. Here, as shown in FIG. 5, the negative electrode weld portion 54n includes a negative electrode weld portion first surface 55n in contact with the second joint surface 21 of the second pressing portion 20, and a negative electrode weld portion second surface 56n in contact with the negative electrode terminal 71n. have.

  Although not shown, the configuration of the positive electrode weld 54p is substantially the same as that shown in FIG. That is, a plurality of positive electrode current collector junctions 61p from which the positive electrode current collector 52p is exposed are stacked on the positive electrode terminal 63p to constitute a positive electrode current collector stacked portion 62p. The positive electrode current collector laminated portion 62p and the positive electrode terminal 63p are integrally welded and electrically connected by the positive electrode welded portion 54p. Here, the positive electrode weld portion 54p has a positive electrode weld portion first surface 55p in contact with the second joint surface 21 of the second pressing portion 20, and a positive electrode weld portion second surface 56p in contact with the positive electrode terminal 71p.

(Positive electrode)
In the positive electrode 51p, for example, a layer (positive electrode mixture layer) 53p made of a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like is formed on one surface or a part of both surfaces of the current collector 52p. It has a structure. Further, the positive electrode current collector 52p has a positive electrode current collector junction 61p protruding from the electrode body 50 and exposing the positive electrode current collector 52p.

A positive electrode active material consists of an active material which can occlude / release lithium ion. Such a positive electrode active material includes, for example, lithium having a layered structure represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, etc.) Transition metal oxide, LiMn ₂ O ₄ , lithium manganese oxide having a spinel structure in which part of the element is replaced with another element, and olivine type represented by LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.) It is desirable to consist of any one of compounds.

  The positive electrode current collector 52p of the positive electrode 51p is preferably made of, for example, an aluminum foil or an aluminum alloy foil. The thickness of the positive electrode current collector 52p varies depending on the size and capacity of the battery, but is preferably 1 to 20 μm, for example.

  The positive electrode 51p is manufactured by the following method. A positive electrode mixture containing the above-described positive electrode active material, a conductive additive such as graphite, acetylene black, carbon black, and fibrous carbon, and a binder such as polyvinylidene fluoride (PVDF) is used as N-methyl-2-pyrrolidone. A paste-like or slurry-like composition uniformly dispersed using a solvent such as (NMP) is prepared (the binder may be dissolved in the solvent). This composition is intermittently applied onto the belt-like positive electrode current collector 52p and dried. You may adjust the thickness of the positive mix layer 53p by press processing as needed. The long positive electrode substrate (electrode substrate) thus obtained is cut into a predetermined shape to obtain the positive electrode 51p.

  The thickness of the positive electrode mixture layer 53p in the positive electrode 51p is preferably 30 to 100 μm per side. Moreover, as for content of each structural component in the positive mix layer 53p, it is desirable that they are positive electrode active material: 90-98 mass parts, conductive support agents: 1-5 mass parts, binder: 1-5 mass parts.

  The positive electrode terminal 71p is preferably made of aluminum or an aluminum alloy. The thickness of the positive electrode terminal 71p is desirably 20 to 300 μm.

(Negative electrode)
The negative electrode 51n has, for example, a structure in which a layer (negative electrode mixture layer) 53n containing a negative electrode active material capable of occluding and releasing lithium ions is formed on a part of one surface or both surfaces of the negative electrode current collector 52n. The negative electrode current collector 52n has a positive electrode current collector junction 61n protruding from the electrode body 50 and exposing the negative electrode current collector 52n.

Negative electrode active materials include graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon that can occlude and release lithium ions such as carbon fibers. It is desirable to consist of one or a mixture of two or more system materials. Alternatively, the negative electrode active material is made of an element such as Si, Sn, Ge, Bi, Sb, or In, an alloy containing one or more of Si, Sn, Ge, Bi, Sb, and In, lithium-containing nitride, and lithium. It is preferably made of any one of a compound that can be charged and discharged at a low voltage close to lithium metal such as oxide (such as LiTi ₃ O ₁₂ ), lithium metal, and a lithium / aluminum alloy.

  As the negative electrode current collector 52n of the negative electrode 51n, a copper foil is suitable. Copper foils are roughly classified into electrolytic copper foils and rolled copper foils depending on the manufacturing method. Electrolytic copper foil is relatively inexpensive. The thickness of the negative electrode current collector 52n varies depending on the size or capacity of the battery, but is preferably 1 to 20 μm, for example.

  The negative electrode 51n is manufactured by the following method. The negative electrode active material described above, a binder (such as a mixed binder of rubber binder such as PVDF or styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC)), and graphite, acetylene black, carbon black, etc. A paste-like or slurry-like composition in which a negative electrode mixture containing a conductive aid or the like is uniformly dispersed using a solvent such as NMP or water is prepared (the binder may be dissolved in the solvent). . This composition is intermittently applied onto the strip-shaped negative electrode current collector 52n and dried. You may adjust the thickness or the density of the negative mix layer 53p by press processing as needed. The long negative electrode substrate (electrode substrate) thus obtained is cut into a predetermined shape to obtain a negative electrode 51n.

  The thickness of the negative electrode mixture layer 53n in the negative electrode 51n is preferably 30 to 100 μm per side. Moreover, it is preferable that content of each structural component in the negative mix layer 53n is negative electrode active material: 90-98 mass parts, binder: 1-5 mass parts. Moreover, when using a conductive support agent, it is preferable that content of the conductive support agent in the negative mix layer 53n is 1-5 mass parts.

  The negative electrode terminal 71n is preferably made of copper. If necessary, nickel plating or the like may be applied to the surface. The thickness of the negative electrode terminal 71n is preferably 20 to 300 μm.

(Separator)
The separator 60 includes a porous film that is interposed between the positive electrode 51p and the negative electrode 51n and transmits lithium ions. The porous film is preferably made of a thermoplastic resin having a melting point of about 80 to 140 ° C., and specifically, preferably made of a polyolefin polymer such as polypropylene or polyethylene. Although the thickness of a porous film does not have a restriction | limiting in particular, It is desirable that it is 10-50 micrometers.

  The separator 60 may be formed by coating a plate-like inorganic particle layer on the porous film. Thereby, the heat shrink of the separator 60 at the time of abnormal heat generation can be suppressed, and safety can be improved. Alternatively, the separator 60 may have a laminated structure of the porous film and the heat-resistant porous substrate. As the heat resistant porous substrate, for example, a fibrous material having a heat resistant temperature of 150 ° C. or higher can be used. Examples of the fibrous material include cellulose and its modified products, polyolefin, polyethylene terephthalate, polybutylene terephthalate, polypropylene, polyester, polyacrylonitrile, aramid, polyamideimide, polyimide, and the like. Specifically, it is preferably made of a nonwoven fabric made of the above materials.

(Electrolyte)
As the electrolytic solution, for example, a solution (nonaqueous electrolytic solution) in which a solute such as LiPF ₆ or LiBF ₄ is dissolved in a high dielectric constant solvent or an organic solvent can be used. As the high dielectric constant solvent, any of ethylene carbonate (EC), propylene carbonate (PC), and γ-butyrolactone (BL) can be used. As the organic solvent, a low viscosity solvent such as linear dimethyl carbonate (DMC), diethyl carbonate (DEC), or methyl ethyl carbonate (EMC) can be used.

  As the solvent of the electrolytic solution, it is preferable to use a mixed solvent of the above-described high dielectric constant solvent and low viscosity solvent. Alternatively, PVDF, a rubber-based material, an alicyclic epoxy, a material having an oxetane-based three-dimensional crosslinked structure, and the like may be mixed and solidified into the above-described solution to form a polymer electrolyte.

(Manufacture of batteries)
The separator 60 is interposed between the positive electrode 51p and the negative electrode 51n, and the positive electrode 51p and the negative electrode 51n are alternately stacked to form the electrode body 50.

  There is no restriction | limiting in particular in the production method of the electrode body 50. FIG. For example, the strip-shaped separator 60 is alternately zigzag-folded by alternately repeating mountain folds and valley folds at regular intervals, and the positive electrode 51p is sandwiched between the one side of the separator 60 and each valley fold, and the other side Thus, the electrode body 50 can be prepared by sandwiching the negative electrode 51n between the valley folds. Alternatively, the electrode body 50 may be formed by forming a plurality of rectangular bags with the separator 60 and inserting the positive electrodes 51p into the bags made of the separators 60 alternately with the negative electrodes 51n. Alternatively, the electrode body 50 may be formed by winding the laminated positive electrode 51p, negative electrode 51n, and separator 66.

  A positive electrode terminal 71p is electrically connected to a positive electrode current collector laminated portion 62p formed by laminating a plurality of positive electrode current collector joining portions 61p protruding from the electrode body 50 thus obtained by a positive electrode welding portion 54p. More specifically, the positive electrode welded portion second surface 56p and the surface of the positive electrode terminal 71p opposed thereto are welded. Similarly, the negative electrode terminal 71n is electrically connected to the negative electrode current collector laminated portion 62n formed by laminating the plurality of negative electrode current collector joining portions 61n protruding from the electrode body 50 through the negative electrode welding portion 54n. More specifically, the negative electrode welded portion second surface 56n and the surface of the positive electrode terminal 71n opposed thereto are welded.

  Here, the ultrasonic welding apparatus of the present invention described above can be used as a joining process in the welded portions 54p and 54n. That is, in FIG. 5, the uneven surface formed on the second bonding surface 21 of the second pressing portion 20 is composed of the first concave portion 24 and the second concave portion 25 which are surfaces having no corner portions shown in FIGS. Or it is desirable to provide a plurality. In particular, it is desirable that at least one or more of the second recesses 25 is a surface having no corners. A concave portion that is a surface that does not have a corner portion by applying a pressing force and ultrasonic vibration to the positive electrode current collector laminated portion 62p or the negative electrode current collector laminated portion 62n by the second pressing portion 20 having such an uneven surface. It is considered that the positive electrode current collector laminated portion 62p or the negative electrode current collector laminated portion 62n in the portion in contact with the electrode does not break.

  FIG. 7 is a photograph of a cross section of the welded portion after the joining step in the battery manufacturing method of the present invention, taken with a digital microscope. On the other hand, FIGS. 6A and 6B are photographs taken by a digital microscope of a cross section of a welded portion after performing a joining step in a battery manufacturing method using a conventional ultrasonic welding apparatus. As can be understood by comparing these photographs, in FIGS. 6A and 6B, the current collector foil in contact with the concave portion shows an irregular lamination, and this portion is broken. However, in FIG. 7, the current collector foil in contact with the recesses shows an orderly lamination, and no tearing occurs. This is because, as described above, the inner portion of the concave portion formed on the joint surface of the horn in the conventional ultrasonic welding apparatus has a substantially mortar shape with a corner portion, for example. This is because the back portion of the concave portion formed on the second joint surface of the second pressing portion in the ultrasonic welding apparatus has a shape including a surface having no corner portion.

  As described above, according to the battery manufacturing method of the present invention, since the joining process can be performed without causing breakage of the welded portions 54p and 54n, the joining strength at the welded portions 54p and 54n can be improved. Further, since the joining strength can be improved, peeling of the welded portions 54p and 54n can be suppressed during actual use or battery assembly operation, and the reliability and safety of the product can be improved. Furthermore, since joint strength can be improved, the joint area of the welding parts 54p and 54n can also be made small, and it can contribute also to size reduction of a battery.

  Here, as shown in FIG. 7, the positive electrode welded portion 54p and the negative electrode welded portion 54n are the positive electrode welded portion first surface 55p and the negative electrode welded portion formed by at least one recess 23 of the second joint surface 21. The convex portion of the first surface 55n is preferably a surface having no corners. The positive electrode welded portion first surface 55p of the positive electrode welded portion 54p and the negative electrode welded portion first surface 55n of the negative electrode welded portion 54n are uneven shapes provided on the second joint surface 21 of the second pressing portion 20 after ultrasonic welding. Thus, a concavo-convex shape opposite to this is formed. And it is desirable for the convex part formed in this positive electrode welding part 1st surface 55p and negative electrode welding part 1st surface 55n to be a surface which does not have a corner | angular part. Further, among the recesses 23 of the second joint surface 21, the convex portions of the positive electrode welded portion first surface 55p and the negative electrode welded portion first surface 55n formed by the first recess 24 and the second recess 25 have corner portions. It is preferable that there is no surface. Furthermore, it is more preferable that the convex portions of the positive electrode welded portion first surface 55p and the negative electrode welded portion first surface 55n formed by at least the second concave portion 25 are surfaces having no corners.

  By adopting such a configuration, the positive and negative electrode current collector foils forming the convex portions of the positive electrode welded portion first surface 55p and the negative electrode welded portion first surface 55n exhibit a regular laminated state, and do not cause the portions to be torn. . Therefore, it is possible to improve the joining height, improve the reliability and safety of the product, and improve the battery performance.

  Two substantially rectangular laminate sheets (exterior) 81 are arranged above and below the electrode body 50 thus obtained, and two sheets are provided along three sides excluding the side where the positive electrode terminal 71p and the negative electrode terminal 71n are formed. The laminate sheet (exterior) 81 is heat-sealed to form the laminate sheet (exterior) 81 in a bag shape. Alternatively, instead of using two laminate sheets, one rectangular laminate sheet is folded and overlapped so as to sandwich the electrode body 50, and heat-sealed along two opposite sides to form a laminate sheet in a bag shape You may form in. Thereafter, an electrolytic solution is injected into the bag of the laminate sheet (exterior) 81. Finally, the laminate sheet is heat-sealed together with the positive and negative terminals 71p and 71n along the side that is not heat-sealed to obtain the lithium secondary battery 80.

  In the above example, the positive electrode terminal 71p and the negative electrode terminal 71n are drawn from the same short side of the substantially rectangular laminate sheet (exterior) 81, but may be drawn from different sides.

  Although the example of the laminate type lithium secondary battery has been described above, the battery of the present invention may be a lithium secondary battery other than the laminate type.

10: 1st press part 11: 1st joint surface 12, 22: Convex part 13, 23: Recess 20: 2nd press part 21: 2nd joint surface 24: 1st recessed part 25: 2nd recessed part 3: Bonding material 31 : Joining material first surface 32: Joining material second surface 4: Joined material 41: Joined material first surface 42: Joined material second surface 50: Electrode body 51 n: Negative electrode 51 p: Positive electrode 52 n: Negative electrode collection Electric current 52p: Positive electrode current collector 53n: Negative electrode mixture layer 53p: Positive electrode mixture layer 54n: Negative electrode welded portion 55n: Negative electrode welded portion first surface 56n: Negative electrode welded portion second surface 60: Separator 61n: Negative electrode current collector junction Part 62n: Negative electrode current collector lamination part 71n: Negative electrode terminal 80: Laminate type lithium secondary battery 81: Exterior

Claims (6)

A first pressing portion (10) having a first bonding surface (11) on which the bonding material (3) and the bonded material (4) are stacked and placed;
A second pressing portion (20) having a second bonding surface (21) that sandwiches and presses the bonding material and the material to be bonded between the first bonding surface, and the first pressing portion and / or Or an ultrasonic welding device that applies ultrasonic vibration to the second pressing portion to join the joining material and the material to be joined,
The first joint surface and the second joint surface have a plurality of convex portions (12, 22) arranged vertically and horizontally,
The bonding material is a laminate that is in contact with the second bonding surface and includes a plurality of foils,
At least in the second joining surface, the ultrasonic welding apparatus characterized in that one or a plurality of concave portions (13, 23) existing between the plurality of convex portions are formed of surfaces having no corners. The plurality of concave portions include a first concave portion (24) existing between two convex portions adjacent vertically or horizontally, and a second concave portion (25) surrounded by three or four or more convex portions. )
The ultrasonic welding apparatus according to claim 1, wherein at least one of the second recesses has a surface having no corners.   The ultrasonic welding apparatus according to claim 1, wherein the convex portion has a form in which a tip of a tapered truncated cone is rounded.   The ultrasonic welding apparatus according to any one of claims 1 to 3, wherein a radius of curvature of the corner is smaller than a thickness of one of the foils constituting the bonding material. A positive electrode provided with a positive electrode mixture layer (53p) on a partial surface of a positive electrode current collector (52p), a negative electrode provided with a negative electrode mixture layer (53n) on a partial surface of a negative electrode current collector (52n), and a separator ( 60), an electrolyte, and a positive electrode terminal (71p) electrically connected to a positive electrode current collector laminated portion (62p) in which a plurality of positive electrode current collecting junctions (61p) in which the positive electrode current collector of the positive electrode is exposed are laminated. And a negative electrode terminal (71n) electrically connected to a negative electrode current collector laminated portion (62n) in which a plurality of negative electrode current collector junctions (61n) in which the negative electrode current collector of the negative electrode is exposed are laminated. A battery manufacturing method comprising:
The said positive electrode collector lamination part and the said positive electrode terminal, and / or the said negative electrode collector lamination part and the said negative electrode terminal are ultrasonically welded using the ultrasonic welding apparatus of Claims 1-4. The manufacturing method of the battery which has a process. In the positive electrode welded portion first surface (55p) of the positive electrode welded portion (54p) and the negative electrode welded portion first surface (55n) of the negative electrode welded portion (54n) welded by the joining step,
The battery manufacturing method according to claim 5, wherein the positive electrode welded portion first surface formed by at least one or more of the concave portions and the convex portion of the negative electrode welded portion first surface are formed of surfaces having no corners.