JP2014212012A - Method of manufacturing secondary battery and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a secondary battery in which a collector laminate and a collector terminal can be bonded well with high bond strength, and to provide a secondary battery.SOLUTION: A method of manufacturing a battery 100 includes a step for preparing a wound electrode body 110 having a positive electrode collector laminate 136 at one end, a step for forming a first welding mark region 10 and a second welding mark region 20 having a recess 22 in the positive electrode collector laminate by using a horn 41 having an anvil 45 and a plurality of protrusions 42, and a step performing resistance-welding while holding the first welding mark region 10 and second welding mark region 20, together with a positive electrode collector terminal 191, by using a pair of electrodes 51. In the step for forming a recess, both welding mark regions are formed to satisfy the relations; S1≥S2 and 1<S2/S3<6 (S1:area of first welding mark, S2:contact area of the first welding mark and an electrode during resistance-welding, S3:contact area of the second welding mark and the positive electrode collector terminal during resistance-welding).

Description

  The present invention relates to a method for manufacturing a secondary battery and a secondary battery. Specifically, the present invention relates to a secondary battery manufacturing method and a secondary battery that can satisfactorily join a current collector terminal to a current collector laminate.

  In recent years, secondary batteries such as lithium ion secondary batteries have been used in various fields such as electronic devices such as mobile phones and personal computers, vehicles such as hybrid cars and electric cars. In particular, a lithium ion secondary battery has a high energy density and is suitable for mounting in various devices.

  Conventionally, a secondary battery having a configuration in which an electrode body is accommodated in a rectangular battery case is known as such a secondary battery. Examples of the electrode body include a positive electrode plate coated with a positive electrode active material layer on the surface of a foil-shaped positive electrode current collector, a negative electrode plate coated with a negative electrode active material layer on the surface of a foil-shaped negative electrode current collector, In addition, there is a wound electrode body in which separators that insulate a positive electrode plate and a negative electrode plate are overlapped and wound. This wound electrode body has a positive electrode current collector laminated portion formed by winding a positive electrode active material layer non-coated portion on which a positive electrode active material layer is not formed on one end side along the winding axis direction, A negative electrode current collector laminated portion formed by winding a negative electrode active material layer non-coated portion on which a negative electrode active material layer is not formed is provided on the other end side along the winding axis direction. A positive electrode current collector terminal is joined to the positive electrode current collector laminated portion, and a negative electrode current collector terminal is joined to the negative electrode current collector laminated portion.

  Here, as a method of joining the current collector terminal to the current collector laminated portion, a method shown in Patent Document 1 below has been conventionally known. In Patent Document 1 below, as shown in FIG. 1, a plurality of laminated “aluminum foils 1 a, 1 a...” Are placed between “ultrasonic heads H, H” together with “aluminum base plate B” for terminals. While being sandwiched and pressed, it is vibrated by ultrasonic vibration. As a result, the “oxide films 2a, 2a...” Of the aluminum foils 1a, 1a... Are destroyed and a plurality of laminated aluminum foils 1a, 1a. Then, as shown in FIG. 2 of the same document, the temporarily attached portions of the aluminum foils 1a, 1a... Are sandwiched between a pair of “electrodes E, E” together with the aluminum base plate B, and a current is passed between the electrodes E, E. , And the laminated aluminum foils 1a, 1a... And the aluminum base plate B are joined by resistance welding. According to this joining method, it is supposed that a plurality of laminated aluminum foils 1a, 1a... Can always be joined by resistance welding with stable welding strength.

JP 2010-184260 A

  However, the joining method described in Patent Document 1 has the following problems. That is, in the above joining method, the laminated aluminum foil and the aluminum base plate are sandwiched between the ultrasonic heads. For this reason, the ultrasonic head does not contact the aluminum base plate side surface of the aluminum foil. In addition, the contact surface to the aluminum foil and the contact surface to the aluminum base plate in the ultrasonic head are flat surfaces having no projections. Therefore, a weld mark having a recess is not formed on the aluminum foil after ultrasonic welding.

  For this reason, in resistance welding after ultrasonic welding, even if the location where the aluminum foil is temporarily attached is positioned between a pair of electrodes, the location where the current flows is not stable at the initial stage of energization between the electrodes. For example, current flows in a concentrated manner at one location where the oxide film in the laminated aluminum foil is destroyed, or currents of different sizes are present at multiple locations where the oxide film is destroyed in the laminated aluminum foil. It flows in a distributed manner.

  When the current flows concentrated on one location where the oxide film is broken, only the location where the concentrated current flows becomes very hot. As a result, the aluminum melts as it is ejected, and as shown in FIG. 23, one large nugget 201 having a thin portion 200 having no meat may be instantaneously formed. If the lacking part 200 is formed, the welding strength between the aluminum foil 202 and the aluminum base plate 203 is significantly reduced. Also, the molten aluminum that has been ejected may adhere to the electrode of the resistance welding apparatus, and as shown in FIG. 24, the aluminum foil 202 may be joined to the electrode 205 of the resistance welding apparatus. In FIG. 24, an alternate long and short dash line indicates a joint location between the aluminum foil 202 and the electrode 205. If the aluminum foil 202 is joined to the electrode 205 of the resistance welding apparatus, the productivity of the battery is lowered.

  In addition, when currents of different sizes flow in a plurality of locations where the oxide film is broken, the location where a large current flows becomes higher than the location where a small current flows. As a result, a difference occurs in the molten state of aluminum, and a plurality of nuggets 210 having different sizes are formed as shown in FIG. The formation of such a non-uniform nugget 210 causes a variation in welding strength among products. Note that, in the joining method described in Patent Document 1 above, the portion where current flows in the resistance welding process (see FIG. 25) rather than the surface area of the portion temporarily attached in the ultrasonic attachment step (see the cross-hatching portion 211 in FIG. 25). 25, the surface area of the portion 212) indicated by the broken line is smaller. This is also one of the reasons that the location where current flows during resistance welding is not stable.

  The present invention has been made to solve the above-described problems. That is, an object of the present invention is to provide a secondary battery manufacturing method and a secondary battery that can satisfactorily bond the current collector laminated portion and the current collector terminal with high bonding strength.

In order to solve this problem, a method for manufacturing a secondary battery according to an embodiment of the present invention includes a positive electrode coated portion in which a positive electrode active material layer is coated on a positive electrode current collector and a positive electrode active material on the positive electrode current collector. A negative electrode active material layer is applied to a negative electrode coated portion and a negative electrode current collector in which a negative electrode active material layer is coated on a positive electrode plate, a negative electrode current collector, and a negative electrode non-coated portion. A negative electrode plate including a negative electrode non-coated portion and a separator interposed between the positive electrode coated portion and the negative electrode coated portion, and the positive electrode non-coated portion is laminated in a state of protruding from the negative electrode plate. A preparatory step of preparing an electrode body having a positive electrode current collector laminated portion at one end and a negative electrode current collector laminated portion laminated at the other end with the negative electrode non-coated portion protruding from the positive electrode plate; Using an ultrasonic welding apparatus equipped with a horn having a plurality of convex portions, the plurality of convex portions possessed by the horn are pressed. The current collector laminated portion is obtained by vibrating the horn while sandwiching the current collector laminated portion of one of the positive electrode current collector laminated portion or the negative electrode current collector laminated portion between the anvil and the horn so as to be applied. Forming a first weld trace region on the contact surface with the anvil in the step, and forming a second weld trace region having a concave portion on the contact surface with the horn in the current collector laminated portion; A resistance welding apparatus comprising a pair of electrodes composed of a first electrode and a second electrode while contacting a current collecting terminal of a pole corresponding to the current collector laminated portion in a region including at least the second welding mark region A resistance welding process in which resistance welding is performed by sandwiching the current collector laminated portion and the current collector terminal between the pair of electrodes so that the first welding trace region and the second welding trace region are positioned between the pair of electrodes. In this order, in the recess formation process, As 1) and (2) are satisfied, to form the first welding mark area and a second welded mark regions.
S1 ≧ S2 (1)
1 <S2 / S3 <6 (2)
S1: Area of the first welding trace area to be formed S2: Contact area in the resistance welding process between the first welding trace area to be formed and the first electrode to which the first welding trace area is abutted in the resistance welding process S3: Contact area in the resistance welding process between the second welding mark area to be formed and the current collector terminal where the second welding mark area is scheduled to abut in the resistance welding process

  In the secondary battery manufacturing method described above, the second welding trace region having a recess in the current collector laminated portion is formed by ultrasonic welding before resistance welding. In the resistance welding process, the second welding mark region is positioned between the pair of electrodes. The contact area S3 between the second welding trace area and the current collecting terminal is smaller than the contact area S2 between the first welding trace area and the first electrode. Therefore, when performing resistance welding, the contact resistance of the contact surface with the current collector terminal (electrical resistance at the contact surface) in the current collector laminated portion is determined by the contact resistance of the contact surface with the first electrode in the current collector laminated portion. Also grows. Therefore, sufficient Joule heat can be generated on the contact surface between the current collector stack and the current collector terminal. Therefore, the current collector laminated portion and the current collector terminal can be sufficiently melted. As a result, a nugget of an appropriate size can be formed, and the current collector laminated portion and the current collector terminal can be firmly bonded (bonding can be performed with sufficient welding strength).

  Moreover, when 1 ≧ S2 / S3, the contact resistance of the contact surface between the current collector stack and the first electrode becomes too high, and the temperature of the contact surface becomes too high. There is a possibility that the portion melts excessively and is joined to the first electrode. However, since 1 <S2 / S3 in this configuration, such a problem does not occur.

  Further, when S2 / S3 ≧ 6, the contact resistance of the contact surface between the current collector stack and the current collector terminal becomes too high, and the temperature of the contact surface becomes too high. May melt excessively, and the melted current collector laminated portion may be ejected and bonded to the first electrode or a nugget with a lacking portion may be formed. However, in this configuration, since S2 / S3 <6, such a problem does not occur.

  Here, in the recess forming step in the manufacturing method of the secondary battery described above, the contact area S3 is reduced by increasing the pitch of the plurality of protrusions included in the horn, and the pitch of the plurality of protrusions included in the horn is decreased. Therefore, it is desirable to increase the contact area S3.

  In this way, the second welding mark region satisfying the above-described expression (2) is compared with changing other parameters (such as the pressing force of the horn in ultrasonic welding, the vibration frequency, and the welding time). It is because it can form reliably.

  In the recess forming step in the method for manufacturing a secondary battery described above, the anvil having a plurality of projections is used, and the current collector is laminated between the anvil and the horn so as to press the plurality of projections of the anvil. It is desirable to form a first weld mark region having a concave portion by sandwiching the portion.

  If it does in this way, the contact area S2 of the 1st welding trace area | region and 1st electrode at the time of resistance welding can be made smaller than the area S1 of a 1st welding trace area | region (S1> S2). Therefore, compared with the case where S1 = S2, the contact resistance of the contact surface between the current collector stack and the first electrode can be increased. As a result, heat generation in the current collector laminated portion can be promoted and good welding can be performed. In addition, as long as the said Formula (2) is satisfy | filled, a collector laminated part is not melted so that a collector laminated part and a 1st electrode may join.

  Further, in the recess forming step in the method for manufacturing a secondary battery described above, the contact area S2 is reduced by increasing the pitch of the plurality of protrusions included in the anvil, and the pitch of the plurality of protrusions included in the anvil is decreased. It is desirable to increase the contact area S2.

  In this way, the above formulas (1) and (2) are satisfied as compared to changing other parameters (such as horn pressing force, vibration frequency, and welding time in ultrasonic welding). This is because the first welding mark region can be formed reliably.

Moreover, in the recessed part formation process in the manufacturing method of an above-described secondary battery, it is desirable to form a 1st welding trace area | region so that following Formula (3) may be satisfy | filled further.
A> S1 (3)
A: The area of the end surface in contact with the joining target in the first electrode scheduled to be used in the resistance welding process

  In the case of A ≦ S1, the current density of the current flowing in the first welding mark region is reduced. For this reason, the current collector laminated portion cannot be sufficiently melted. As a result, a smaller nugget is formed. Moreover, in the contact part with the periphery of the 1st electrode in a 1st welding trace area | region, the location where the periphery of a 1st electrode does not contact | connect a 1st welding trace area | region arises because of the recessed part of a 1st welding trace area | region. For this reason, the first electrode cannot sufficiently press the current collector laminated portion, and the nugget formed at that location is significantly smaller than the other nuggets. For these reasons, when A ≦ S1, the bonding strength between the current collector stack and the current collector terminal decreases. However, since A> S1 in the above manufacturing method, such a problem does not occur.

  Further, in the preparation step in the method for manufacturing a secondary battery described above, an aluminum foil is used as the positive electrode current collector, and in the recess forming step, the first welding mark region and the second welding mark region are formed in the positive electrode current collector laminated portion. In the resistance welding process, a positive electrode current collector terminal made of aluminum may be joined to the positive electrode current collector laminated portion.

  Aluminum has a lower thermal conductivity than other metals such as copper, so it is not suitable for resistance welding compared to copper. In addition, since aluminum has an oxide film with a high electric resistance on the surface, there is a possibility that the current collector laminated portion and the first electrode of the resistance welding apparatus are welded if resistance welding is performed as it is. However, in the above-described secondary battery manufacturing method, since the contact resistance of the contact surface between the current collector laminated portion and the current collector terminal is increased by forming a recess in the aluminum foil by ultrasonic welding, resistance welding is not used. However, the current collector laminated portion can be sufficiently heated and melted. Moreover, since the oxide film of the aluminum foil is destroyed by ultrasonic welding, it is possible to prevent welding of the current collector laminated portion and the first electrode. As a result, it is possible to join the current collector laminate portion and the current collector terminal with sufficient strength while preventing the current collector laminate portion and the first electrode from being welded. The reason why resistance welding is used for joining the positive electrode current collector laminated portion made of aluminum, which is not suitable for resistance welding compared to copper, and the positive electrode current collector terminal is as follows. That is, some recent positive electrode current collecting terminals have a structure incorporating a current interrupting mechanism for interrupting current in the event of an abnormality. When such a positive electrode current collector terminal is joined to the positive electrode current collector laminated portion by ultrasonic welding, a force is applied to the current interruption mechanism by ultrasonic waves during welding, and there is a risk that the current interruption mechanism may be defective. However, if resistance welding is used instead of ultrasonic welding, the positive electrode current collector terminal having the current interruption mechanism and the positive electrode current collector laminated portion can be joined without causing such a problem.

The present invention also includes a positive electrode plate including a positive electrode coated portion in which a positive electrode active material layer is coated on a positive electrode current collector and a positive electrode non-coated portion in which the positive electrode current collector is not coated with a positive electrode active material layer, A negative electrode plate including a negative electrode coated portion in which a negative electrode active material layer is coated on a negative electrode current collector, and a negative electrode non-coated portion in which the negative electrode current collector is not coated with a negative electrode active material layer, and positive electrode coating Including a separator interposed between the negative electrode coating portion and the negative electrode coating portion, the positive electrode non-coating portion being laminated in a state protruding from the negative electrode plate at one end, An electrode body having a negative electrode current collector laminated part laminated in a state protruding from the positive electrode plate at the other end, a positive electrode current collector terminal joined to the positive electrode current collector laminated part, and a negative electrode current collector laminated part And a negative electrode current collector terminal, and a current collector laminate portion of at least one of the positive electrode current collector laminate portion and the negative electrode current collector laminate portion , Of the positive electrode current collector terminal or the negative electrode current collector terminal, a first welding mark region having a concave portion or no concave portion is provided on the back surface of the joint surface with the current collector terminal of the electrode corresponding to the current collector laminated portion. In addition, the joint surface has a second weld trace region where a nugget is formed, and the first weld trace region and the second weld trace region satisfy the following expressions (4) and (5): It extends to the secondary battery characterized by being.
S1 ≧ S4 (4)
1 <S4 / S5 <2 (5)
S1: Area of the first welding trace area S4: Area of the non-dented area in the first welding trace area S5: Area of the non-nugget area in the second welding trace area

  This secondary battery is a secondary battery manufactured by the above-described manufacturing method. Therefore, in this battery, as described above, the current collector laminated portion and the current collector terminal are well bonded with high bonding strength.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method and secondary battery of a secondary battery which can favorably join a collector lamination part and a current collection terminal with high joining strength are provided.

It is sectional drawing which shows the secondary battery which concerns on embodiment. It is a figure which shows the structure of the winding electrode body with which the secondary battery is equipped. It is a figure which shows a mode that ultrasonic welding is carried out in embodiment, and is a figure which shows a mode that the collector laminated part is inserted | pinched with the horn and the anvil. It is a top view which shows the front end surface of a horn. It is a top view which shows the front end surface of an anvil. It is a figure which shows the 1st welding trace area | region formed in the location which was in contact with the anvil. It is a figure which shows the 2nd welding trace area | region formed in the location which was in contact with the horn. It is a figure which shows a mode that resistance welding is carried out in embodiment, and is a figure which shows a mode that the collector laminated part and the current collection terminal are inserted | pinched by a pair of electrodes. It is a figure which shows the diameter of the electrode of a resistance welding apparatus, and the diameter of a welding trace area | region. It is a figure which shows the positional relationship of a 1st electrode and a 1st welding trace area | region. It is a figure which shows the positional relationship of a 2nd electrode and a 2nd welding trace area | region. It is a figure which shows typically the joined state of the collector laminated part and current collection terminal after resistance welding. It is a figure which shows typically a mode that resistance welding is carried out in Example 5 in experiment. It is a figure which shows the positional relationship of the 1st electrode and 1st welding trace area | region in Example 5 in experiment. It is a figure which shows the positional relationship of the 2nd electrode and 2nd welding trace area | region in Example 5 in experiment. It is a figure which shows typically the joining state of the collector laminated part and current collection terminal after resistance welding in Example 5 in experiment. It is a figure which shows typically a mode that resistance welding is performed in the comparative example 1 in experiment. It is a figure which shows typically the joined state of the collector laminated part and current collection terminal after resistance welding in the comparative example 1 in experiment. It is a figure which shows typically a mode that resistance welding is performed in the comparative example 2 in experiment. It is a figure which shows typically the joining state of the collector laminated part and current collection terminal after resistance welding in the comparative example 2 in experiment. It is a figure which shows the 1st welding trace area | region after resistance welding in embodiment. It is a figure which shows the 2nd welding trace area | region after resistance welding in embodiment, and is the figure which looked at the 2nd welding trace area | region in the AA cross section of FIG. It is a figure which shows typically one of the subjects of a prior art. It is a figure which shows typically one of the subjects of a prior art. It is a figure which shows typically one of the subjects of a prior art.

  Hereinafter, embodiments of the secondary battery of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a secondary battery 100 according to the embodiment. As shown in FIG. 1, the secondary battery 100 according to the embodiment (hereinafter also simply referred to as “battery 100”) includes a rectangular battery case 180 and a flat wound electrode housed in the battery case 180. A prismatic lithium ion secondary battery including the body 110. The battery 100 is mounted as a power source in a vehicle such as a hybrid car or an electric vehicle, or a battery-powered device such as a hammer drill. In this specification, unless otherwise specified, the top, bottom, left, and right refer to FIG. 1, and the front side of the page in FIG. 1 is the front and the back side of the page is the back.

  The battery case 180 is made of aluminum and has a battery case main body 181 and a sealing lid 182. More specifically, the battery case 180 is a flat rectangular type in which two of the surfaces other than the sealing lid 182 form a flat surface having a larger area than the other surfaces. The sealing lid 182 has a rectangular plate shape, closes the upper opening of the battery case body 181, and is welded to the battery case body 181. A rectangular plate-shaped safety valve 197 is sealed on the sealing lid 182.

  The battery case body 181 has a bottomed rectangular box shape with an open top, and houses a flat wound electrode body 110 therein. More specifically, the battery case main body 181 includes a rectangular plate-like case bottom wall portion 181b facing the sealing lid 182, and four case side wall portions 181c standing upward from the periphery of the case bottom wall portion 181b. ing.

  The wound electrode body 110 is a wound electrode body in which a belt-like positive electrode plate 130 and a negative electrode plate 120 are wound into a flat shape via a belt-like separator 150. The wound electrode body 110 is housed in the battery case 180 in a state where the wound axis direction AX is in the horizontal direction. A plate-like positive current collecting terminal 191 bent in a crank shape is joined to the positive electrode plate 130. A method for joining the positive electrode current collecting terminal 191 to the positive electrode plate 130 will be described later. Further, a plate-shaped negative electrode current collecting terminal 192 bent in a crank shape is joined to the negative electrode plate 120 by resistance welding. Note that the positive electrode current collector terminal 191 is made of the same material (aluminum in this embodiment) as the positive electrode current collector 131 described later. The negative electrode current collector terminal 192 is made of the same material (copper in this embodiment) as the negative electrode current collector 121 described later.

  Of the positive electrode current collecting terminal 191 and the negative electrode current collecting terminal 192, the positive electrode external terminal portion 191a and the negative electrode external terminal portion 192a located at the respective leading ends (upper ends) penetrate the sealing lid 182 of the battery case 180 and cover surface 182A. Protruding from. Insulating members 195 made of an electrically insulating resin are interposed between the positive external terminal portion 191a and the sealing lid 182 and between the negative external terminal portion 192a and the sealing lid 182, respectively.

FIG. 2 is a view showing the structure of the wound electrode body 110. As shown in FIG. 2, the positive electrode plate 130 includes a strip-shaped positive electrode current collector (positive electrode current collector plate) 131 made of an aluminum foil extending in the longitudinal direction DA (vertical direction in FIG. 2), and the positive electrode current collector. And a positive electrode active material layer 132 coated on a part of the surface of 131. The positive electrode active material layer 132 includes, for example, a positive electrode active material 133 made of lithium cobalt oxide (LiCoO ₂ ), a conductive material made of acetylene black, and a binder made of polyvinylidene fluoride (PVDF).

  A portion of the positive electrode current collector 131 on which the positive electrode active material layer 132 is applied is referred to as a positive electrode coating portion (positive electrode active material layer forming portion) 131a. On the other hand, a portion where the positive electrode active material layer 132 is not coated is referred to as a positive electrode non-coated portion (positive electrode active material layer non-formed portion) 131b. The positive electrode non-coating portion 131b is located at the end portion (left end portion in FIG. 2) of the positive electrode current collector 131 (positive electrode plate 130) in the width direction DB (left and right direction in FIG. 2). The plate 130) extends in a strip shape along the longitudinal direction DA.

  The negative electrode plate 120 includes a strip-shaped negative electrode current collector (negative electrode current collector plate) 121 made of a copper foil extending along the longitudinal direction DA, and a negative electrode active material coated on a part of the surface of the negative electrode current collector 121. The material layer 122 is included. The negative electrode active material layer 122 includes, for example, a negative electrode active material 123 made of graphite (graphite), a binder made of SBR, and a thickener made of CMC.

  A portion of the negative electrode current collector 121 where the negative electrode active material layer 122 is coated is referred to as a negative electrode coating portion (negative electrode active material layer forming portion) 121a. On the other hand, a portion of the negative electrode current collector 121 where the negative electrode active material layer 122 is not coated is referred to as a negative electrode non-coated portion (negative electrode active material layer non-formed portion) 121b. The negative electrode non-coating portion 121b is located at the end portion (right end portion in FIG. 2) of the negative electrode current collector 121 (negative electrode plate 120) in the width direction DB, and the longitudinal direction DA of the negative electrode current collector 121 (negative electrode plate 120). It extends in the shape of a belt along.

The separator 150 is made of polyethylene, for example, and is interposed between the positive electrode plate 130 and the negative electrode plate 120 to separate them. The separator 150 is impregnated with an electrolytic solution 160 having lithium ions as shown in FIG. The electrolyte 160 is, for example, lithium hexafluorophosphate (LiPF) as a solute in a mixed organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are adjusted to EC: EMC = 3: 7 by volume ratio. ₆ ) is a non-aqueous electrolyte with a lithium ion concentration of 1 mol / L.

  As shown in FIG. 1, the wound electrode body 110 configured as described above includes a positive electrode current collector stack 136 formed by winding the positive electrode non-coated portion 131 b so as to protrude from the negative electrode plate 120. At one end (left end) along the rotational axis direction AX. The positive electrode current collector laminated portion 136 is a portion where the lower end portion of the positive electrode current collector terminal 191 is joined by a welding method described later. In FIG. 1, a portion indicated by reference numeral 137 indicates the welding mark. By this welding, the positive electrode current collecting terminal 191 and the wound electrode body 110 are electrically and mechanically connected.

  In addition, the wound electrode body 110 includes a negative electrode current collector laminated portion 126 formed by winding the negative electrode non-coated portion 121b so as to protrude from the positive electrode plate 130, and the other end portion (right end) along the winding axis direction AX. Part). The negative electrode current collector laminated portion 126 is a portion where the lower end portion of the negative electrode current collector terminal 192 is welded by resistance welding. In FIG. 1, a portion indicated by reference numeral 127 indicates the welding mark. By this welding, the negative electrode current collector terminal 192 and the wound electrode body 110 are electrically and mechanically connected.

  In the wound electrode body 110, the power generation unit 116 is located between the positive electrode current collector stacking portion 136 and the negative electrode current collector stacking portion 126. The power generation unit 116 includes a positive electrode coating unit 131a (a portion where the positive electrode active material layer 132 of the positive electrode plate 130 is formed, see FIG. 2) and a negative electrode coating unit 121a (the negative electrode active material layer 122 of the negative electrode plate 120 is formed). 2 (see FIG. 2) and a portion where the separator 150 is wound.

  Next, the manufacturing process of the battery 100 of this embodiment will be briefly described. First, the wound electrode body 110, the battery case body 181, and the sealing lid 182 configured as described above are prepared. Current collecting terminals 191 and 192 are assembled to the sealing lid 182 in advance.

  Next, as shown in FIG. 1, the positive electrode current collector terminal 191 is joined to the positive electrode current collector laminated portion 136 of the wound electrode body 110 by a welding method described later. Further, the negative electrode current collector terminal 192 is joined to the negative electrode current collector laminated portion 126 of the wound electrode body 110 by resistance welding.

  Subsequently, the wound electrode body 110 is accommodated in the battery case body 181 and the battery case body 181 is closed by the sealing lid 182. Then, the sealing lid 182 and the battery case body 181 are joined by laser welding.

  After the sealing lid 182 and the battery case main body 181 are joined by laser welding, the electrolytic solution 160 is injected into the battery case main body 181 through a liquid injection port (not shown) to impregnate the wound electrode body 110. Then, the liquid inlet is sealed with a liquid stopper. Thereafter, the battery 100 of this embodiment (see FIG. 1) is completed by performing predetermined processing.

  Next, a method for joining the positive current collector terminal 191 to the positive current collector laminated portion 136 will be described in detail. For joining the positive current collector terminal 191 to the positive current collector laminated portion 136, first, ultrasonic welding is performed only on the positive current collector laminated portion 136 (FIGS. 3 to 7), and then the positive current collector laminated portion 136 and the positive electrode This is done by performing resistance welding on the current collecting terminal 191 (FIGS. 6 to 12). First, the ultrasonic welding will be specifically described.

(Ultrasonic welding)
In the embodiment, before the positive electrode current collector terminal 191 is bonded to the positive electrode current collector stacking portion 136, the layers constituting the positive electrode current collector stacking portion 136 are bonded by ultrasonic welding. This is because concave portions are formed in the form of dots on the front and back surfaces of the positive electrode current collector stack 136 (front surface 136a and rear surface 136b, see FIG. 3). That is, as shown in FIGS. 6 and 7, the concave portions 12 and 22 as welding marks are formed on the front surface 136 a and the rear surface 136 b of the positive electrode current collector laminated portion 136 after ultrasonic welding. A region where the concave portion 12 is formed in the front surface 136a of the positive electrode current collector laminated portion 136 is referred to as a first welding mark region 10 (see FIG. 6). Moreover, the area | region where the recessed part 22 is formed in the rear surface 136b of the positive electrode collector lamination part 136 is called the 2nd welding trace area | region 20 (refer FIG. 7).

  First, prepare an ultrasonic welding device for ultrasonic welding. As shown in FIG. 3, the ultrasonic welding apparatus 40 includes a horn 41 that is a vibrating body and an anvil 45 that cooperates with the horn 41. In ultrasonic welding using this ultrasonic welding apparatus 40, a work (positive electrode current collector stacking portion 136) to be joined is sandwiched between a horn 41 and an anvil 45. At this time, the plurality of convex portions 42 provided on the horn 41 and the plurality of convex portions 46 provided on the anvil 45 are pressed against the work (positive electrode current collector stacking portion 136) with high pressure. The horn 41 is vibrated along the surface direction of the work (left and right along the surface direction of the rear surface 136b of the positive electrode current collector stacking portion 136). That is, it is vibrated in the direction of arrow V in the figure.

  As a result, the layers 138 constituting the positive electrode current collector stacking portion 136 are welded, and the front surface 136a of the positive electrode current collector stacking portion 136 has a concave portion corresponding to the convex portion 46 of the anvil 45 as shown in FIG. The first welding mark area 10 having 12 is formed, and the second welding mark area 20 having the recess 22 corresponding to the protrusion 42 of the horn 41 is formed on the rear surface 136b as shown in FIG. In the embodiment, the vibration direction V of the horn 41 is set in the same direction as the winding axis direction AX. This prevents the positive electrode current collector laminated portion 136 from being cracked or broken by the vibration of the horn 41.

  Here, the plurality of convex portions 42 formed on the front end surface (contact end surface with respect to the workpiece) 41 a of the horn 41 and the plurality of convex portions 46 formed on the front end surface (contact end surface with respect to the workpiece) 45 a of the anvil 45. Describe in detail. FIG. 4 shows a plurality of convex portions 42 (hereinafter also referred to as “first convex portions 42”) formed on the front end surface 41 a of the horn 41. FIG. 5 shows a plurality of convex portions 46 (hereinafter also referred to as “second convex portions 46”) formed on the front end surface 45 a of the anvil 45. Both the first convex portion 42 and the second convex portion 46 are quadrangular pyramidal projections. As shown in FIGS. 4 and 5, the pitch P <b> 2 of the second protrusions 46 is smaller than the pitch P <b> 1 of the first protrusions 42. However, the tip surface 41a of the horn 41 (region where the convex portion 42 is provided in the horn 41) and the tip surface 45a of the anvil 45 (region where the convex portion 46 is provided in the anvil 45) are the same size. is there. Further, the number of convex portions 46 provided on the anvil 45 is larger than the number of convex portions 42 provided on the horn 41. Further, the convex portion 46 provided on the anvil 45 is shorter in height (length along the vertical direction) than the convex portion 42 provided on the horn 41.

  In the embodiment, the positive electrode current collector laminated portion 136 is welded using the horn 41 having the first convex portion 42 and the anvil 45 having the second convex portion 46. Therefore, a welding mark (first welding mark region 10) as shown in FIG. 6 is formed on the front surface 136a of the positive electrode current collector stack 136 where the anvil 45 is pressed. On the other hand, a welding mark (second welding mark region 20) as shown in FIG. 7 is formed on the rear surface 136b of the positive electrode current collector stack 136 where the horn 41 is pressed. The depression of the recess 22 in the second welding trace area 20 is deeper than the depression of the depression 12 in the first welding trace area 10. In addition, the area of the opening surface of the recess 22 in the second welding trace region 20 is larger than the area of the opening surface of the recess 12 in the first welding trace region 10. That is, the area S2 of a portion not recessed in the first welding mark region 10 formed on the front surface 136a of the positive electrode current collector stacking portion 136 (a portion excluding the recess 12 in the first welding mark region 10) (see FIG. 10). Is the area S3 of the non-recessed portion (the portion excluding the recessed portion 22 in the second welding trace region 20) in the second welding trace region 20 formed on the rear surface 136b of the positive electrode current collector stack 136 (see FIG. 11). Bigger than.

  In the present embodiment, a particularly preferable quadrangular pyramid (pyramid type) is adopted as the shape of the convex portions 42 and 46. However, as the protruding shape of the convex portions 42 and 46 in the horn 41 and the anvil 45, a workpiece ( There is no particular limitation as long as it is a projection that can be pressed against the positive electrode current collector stack 136). For example, the shape may be a polygonal pyramid or cone other than a quadrangular pyramid, a polygonal pyramid or cone with the tip cut off, or a cylinder or hemisphere.

  In the present embodiment, the horn 41 and the anvil 45 are each provided with a plurality of convex portions 42 and 46, and are provided on the horn 41 rather than the number of the convex portions 42 provided on the anvil 45. The number of convex portions 46 is smaller. However, the number of each convex part 42 and 46 is not limited, It can adjust suitably according to a welding area. Further, in this embodiment, the horn 41 has a convex portion (12 pieces) arranged as shown in FIG. 4, and the anvil 45 has a convex portion 46 smaller than the convex portion 42 of the horn 41 as shown in FIG. However, the arrangement of the convex portions 42 and 46 is not particularly limited. For example, the convex portions may be arranged in a single row, or may be arranged in a double row. When it is a double row, it may be arranged with a pattern such as a staggered pattern or a checkered pattern, or may be arranged without regularity.

  As described above, in the ultrasonic welding according to the embodiment, the convex portion 42 of the horn 41 and the convex portion 46 of the anvil 45 are pressed against the positive electrode current collector stacking portion 136, so that the foil-shaped positive electrode current collector 131 is pressed. The convex portion 42 of the horn 41 and the convex portion 46 of the anvil 45 are firmly bitten into the positive electrode current collector laminated portion 136 in which are stacked. By the way, in the conventional secondary battery in which the positive electrode current collector made of aluminum and the positive electrode current collector terminal are ultrasonically welded, the vibration due to the ultrasonic wave is caused by the oxide film formed on the surface of the aluminum. In some cases, it was not propagated to the inner layer portion on the positive electrode current collector terminal side, and the bonding was not strong. However, according to the manufacturing method of this embodiment, the convex portions 42 of the horn 41 and the convex portions 46 of the anvil 45 break the oxide film on the surface of the aluminum, so that all the layers of the positive electrode current collector laminated portion 136 are satisfactorily solid-phased. Join. That is, the adjacent layers 138 of the positive electrode current collector stacked portion 136 can be firmly bonded. As a result, a highly reliable secondary battery that can stably exhibit high output can be obtained.

(Resistance welding)
Subsequently, the positive electrode current collector terminal 191 is joined by resistance welding (spot welding) to the positive electrode current collector laminated portion 136 in which the first weld mark region 10 and the second weld mark region 20 are formed as described above. First, prepare resistance welding equipment for resistance welding. As shown in FIG. 8, the resistance welding apparatus 50 includes a pair of electrodes 51 including a first electrode 52 that abuts on the positive electrode current collector laminated portion 136 and a second electrode 55 that abuts on the positive electrode current collector terminal 191. is there.

  In resistance welding using this resistance welding apparatus 50, as shown in FIG. 8, a pair of electrodes 51 (first electrode 52 and second electrode 55) are joined (positive current collector terminal 191 and positive current collector laminated portion 136). ). This sandwiching is performed so that the first welding trace region 10 and the second welding trace region 20 of the positive electrode current collector laminated portion 136 are positioned between the pair of electrodes 51. Moreover, it carries out so that the junction location of the 2nd welding trace area | region 20 of the positive electrode collector lamination part 136 and the positive electrode current collection terminal 191 may contact | connect.

  That is, in the state shown in FIG. 8, the front end surface of the first electrode 52 (with the object to be joined) is located in the region including the first welding mark region 10 on the front surface 136 a (the surface on the back side of the bonding surface) of the positive electrode current collector stack 136. Contact end face) 52a is in contact. In addition, the positive electrode current collector terminal 191 is in contact with a region including the second welding mark region 20 on the rear surface 136b (corresponding to the bonding surface) of the positive electrode current collector stack 136. Further, the tip surface (contact end surface with the object to be joined) 55a of the second electrode 55 is in contact with the region on the back side of the region of the positive electrode current collecting terminal 191 that is in contact with the second welding mark region 20.

  In the present embodiment, the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 are sandwiched between the pair of electrodes 51 so as to be in the above-described state, and the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 are added. Pressure is applied (pressing force is applied to the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191). And along with this, between the electrodes 52 and 55, it supplies with electricity. As a result, Joule heat is generated in the objects to be joined (the positive current collector laminated portion 136 and the positive current collector terminal 191) to melt the joined object, thereby connecting the positive current collector laminated portion 136 and the positive current collector terminal 191. Join.

  FIG. 12 shows the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 after bonding. As shown in FIG. 12, the upper surface (front surface 136 a) of the positive electrode current collector stack 136 after bonding is recessed because the first electrode 52 is pressed. A nugget 70 is formed at the boundary between the positive electrode current collector stack 136 and the positive electrode current collector terminal 191. The nugget 70 is obtained by solidifying the objects to be joined (positive electrode current collector laminated portion 136 and positive electrode current collector terminal 191) melted by resistance welding. In the embodiment, a plurality of good-sized nuggets 70 as shown in FIG. 12 are formed without variation. This is due to the following reason.

  That is, in the embodiment, as shown in FIG. 9, the diameter d1 of the first welding scar region 10 and the second welding scar region 20 is equal to the diameter d2 of the contact end surface 52a of the first electrode 52 and the contact end surface 55a of the second electrode 55. Smaller than. That is, as shown in FIG. 10, the area S1 of the entire first welding mark region 10 is smaller than the area A of the contact end face 52a of the first electrode 52 (A> S1). Moreover, as shown in FIG. 10, the first welding mark region 10 is in contact with the first electrode 52 so that the peripheral edge 10 a is located inside the peripheral edge 52 b of the first electrode 52. Therefore, during resistance welding, the current flows evenly over the entire first welding mark region 10 having the recess 12. As shown in FIG. 11, the area of the second welding trace region 20 (equal to the area S1 of the first welding trace region 10) is also the area of the contact end face 55a of the second electrode 55 (contact end face 52a of the first electrode 52). The second welding scar region 20 is in contact with the second electrode 55 such that the peripheral edge 20a is located inside the peripheral edge 55b of the second electrode 55.

  In addition, the contact area (contact area) S2 between the positive electrode current collector laminate 136 and the first electrode 52 during resistance welding (see the hatched portion in FIG. 10) is the positive electrode current collector laminate 136 and the positive electrode current collector. It is larger than the contact area (contact area) S3 with the terminal 191 (see the hatched portion in FIG. 11) (S2> S3). More specifically, the ratio of S2 to S3 (S2 / S3) is in the range of 1 <S2 / S3 <6. Therefore, at the time of resistance welding, the contact resistance between the positive electrode current collector laminate portion 136 and the positive electrode current collector terminal 191 is appropriately larger than the contact resistance between the positive electrode current collector laminate portion 136 and the first electrode 52. Become. Contact resistance is the electrical resistance at the contact surface. Note that S2 is smaller than S1 because the recess 12 is formed in the first welding mark region 10 (S2 <S1).

  As a result, the contact portion between the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 generates heat to an appropriately high temperature and melts. For this reason, as shown in FIG. 12, a plurality of good-sized nuggets 70 are formed without variation, and the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 are favorably bonded with high bonding strength. On the other hand, heat generation at the contact portion between the positive electrode current collector stack 136 and the first electrode 52 is suppressed. Therefore, the positive electrode current collecting terminal 191 does not adhere to the first electrode 52.

  Next, the results of tests conducted to confirm the effects of the method for manufacturing the battery 100 of the present embodiment (particularly, the method for bonding the positive electrode current collector stacking portion 136 and the positive electrode current collector terminal 191) are shown in Table 1 below. I will explain.

  In this experiment, 40 aluminum foils having a thickness of 15 μm were laminated, and the aluminum foil was cut into a size of 40 mm × 30 mm to obtain a test piece for the positive electrode current collector lamination part 136. In addition, an aluminum plate having a thickness of 1.5 mm was prepared as a test piece for the positive electrode current collecting terminal 191.

  The prepared aluminum foil laminate was subjected to ultrasonic welding as follows. That is, ultrasonic welding was performed using the ultrasonic welding apparatus 40 described above, with the horn 41 having an amplitude of 80 μm, vibration energy of 100 J (joule), and pressure of 1000 N (Newton).

  In each example and each comparative example shown in Table 1, the pitch P2 (see FIG. 5) of the convex portion 46 of the anvil 45 and the pitch P1 (see FIG. 4) of the convex portion 42 of the horn 41 are changed in ultrasonic welding. . Changing the pitch P2 of the anvil 45 changes the area S2 (see FIG. 10). Further, when the pitch P1 of the horn 41 is changed, the area S3 (see FIG. 11) is changed. The relationship between the anvil pitch P2 and the area S2 is as shown in Table 2 below. The relationship between the horn pitch P1 and the area S3 is as shown in Table 3 below.

Specifically, in each example and each comparative example shown in Table 1, the anvil pitch P2 and the horn pitch P1 were set as follows.
Example 1:
Anvil pitch P2: 0.9 mm (S2: 3.4 mm ² )
Horn pitch P1: 1.0 mm (S3: 3.1 mm ² )
Example 2
Anvil pitch P2: 0.7 mm (S2: 5.1 mm ² )
Horn pitch P1: 1.2 mm (S3: 1.8 mm ² )
Example 3
Anvil pitch P2: 0.4 mm (S2: 7.0 mm ² )
Horn pitch P1: 1.3 mm (S3: 1.2 mm ² )
Example 4
Anvil pitch P2: 0 mm, that is, a flat surface without the convex portion 46 (S2: 9.6 mm ² )
Horn pitch P1: 1.2 mm (S3: 1.8 mm ² )
Example 5
Anvil pitch P2: 0.7 mm (S2: 5.1 mm ² )
Horn pitch P1: 1.2 mm (S3: 1.8 mm ² )
Comparative Example 1
Anvil pitch P2: 1.0 mm (S2: 3.1 mm ² )
Horn pitch P1: 0.9 mm (S3: 3.4 mm ² )
Comparative Example 2
Anvil pitch P2: 0.1 mm (S2: 8.5 mm ² )
Horn pitch P1: 1.3 mm (S3: 1.4 mm ² )

  By such ultrasonic welding, the first weld mark region 10 (see FIG. 10) is formed on the front and back surfaces of the aluminum foil laminate, which is a test piece of the positive electrode current collector laminate 136, and the second weld trace is formed. Region 20 (see FIG. 11) was formed.

  And after this ultrasonic welding, the aluminum plate which is a test piece of the positive electrode current collection terminal 191 was joined to the laminated body of aluminum foil by resistance welding. This resistance welding was performed as follows. That is, by using the resistance welding apparatus 50 described above, the applied pressure of the first electrode 52 is fixed to 2.5 kN (kilonewton), and energization is performed so that current flows from the aluminum foil laminate toward the aluminum plate. Resistance welding was performed.

Then, this resistance welding was evaluated. The evaluation items are “welding strength”, “adhesion to electrode”, and “spatter scattering” as shown in Table 1 above. The meanings of “◎”, “◯”, and “×” in the above Table 1 showing the evaluation results of each evaluation item are as follows. In this experiment, bonding was performed 10 times under the conditions shown in each example and each comparative example.
Weld strength ◎: All 10 times showed a weld strength of 200 N (Newton) or more ○: All 10 times showed a weld strength of 150 N or more ×: 5 times or more of 10 times showed a weld strength of less than 100 N Adhesion to the indicated electrode ○: No adhesion between the aluminum foil laminate and the first electrode 52 during 10 times ×: Adhesion between the aluminum foil laminate and the first electrode 52 during 5 or more times Spatter scattering ○: No spatter scattering in 10 times ×: Spatter scattering in 5 times or more out of 10 times

  Examples 1 to 5 shown in Table 1 above are cases where the ratio of S2 to S3 (S2 / S3) is greater than 1 and less than 6, that is, 1 <S2 / S3 <6. In each of these examples, good results were obtained for all items of “welding strength”, “adhesion to electrodes”, and “spatter scattering”. However, in Example 5, the size of the formed nugget was smaller than that of Examples 1 to 4 (that is, it had a small diameter). Therefore, the weld strength of Example 5 was lower than that of Examples 1 to 4.

  The fifth embodiment is a case where the area S1 of the first welding mark region is larger than the area A of the contact end face 52a of the first electrode 52, that is, A <S1. In other examples (Examples 1 to 4), A> S1. Specifically, as shown in FIG. 13, the first welding formed on the aluminum foil laminated body 136A (the test piece of the positive electrode current collector laminated portion 136) rather than the diameter d2 of the contact end face 52a of the first electrode 52. The diameter d11 of the scar region 10A is larger. Therefore, as shown in FIG. 14, the area S1 of the first welding mark region 10A is larger than the area A of the contact end face 52a of the first electrode 52. In this case, as shown in FIG. 15, the area of the second welding mark region 20A (same as S1) is larger than the area of the contact end face 55a of the second electrode 55 (same as A).

  When welding is performed under such conditions, as shown in FIG. 16, the nugget 70A formed at the boundary portion between the laminated body 136A and the aluminum plate 191A (the test piece of the positive electrode current collecting terminal 191) becomes the nugget 70 shown in FIG. Smaller than that. This is because the entire area of the contact end face 52a of the first electrode 52 comes into contact with the first weld trace area 10A because the first weld trace area 10A is larger than the contact end face 52a of the first electrode 52. This is because the current density of the current flowing through the first welding mark region 10A is lower than that in the case shown in FIG. 8, and the laminated body 136A and the aluminum plate 191A are less likely to generate heat, and their melting becomes insufficient. Particularly in this case, the nugget 70B (see FIG. 16) formed at the contact point between the peripheral edge 52b (see FIG. 14) of the contact end surface 52a of the first electrode 52 and the first welding mark region 10A is remarkably reduced. This is because the peripheral edge 52b of the contact end surface 52a and the concave portion 12A of the first welding mark region 10A overlap along the vertical direction, so that the portion cannot be sufficiently pressed down. Since this occurs in the fifth embodiment, the welding strength is smaller than in the first to fourth embodiments.

  Further, Comparative Example 1 shown in Table 1 is a case where S2 / S3 is 1 or less (S2 / S3 ≦ 1). That is, this is a case of S2 ≦ S3. Specifically, as shown in FIG. 17, the reverse of what is shown in FIG. 8, the first welding mark region 10 </ b> B formed in the aluminum foil laminate 136 </ b> B (the test piece of the positive electrode current collector laminate 136). The number of the concave portions 22B of the second welding mark region 20B is smaller than the number of the concave portions 12B.

  When welding is performed under such conditions, the nugget 70C formed by resistance welding as shown in FIG. 18 becomes smaller than that shown in FIG. 12, and its position is biased toward the first electrode 52. This is because the contact resistance between the laminated body 136B and the aluminum plate 191B (the test piece of the positive electrode current collecting terminal 191) is smaller than the contact resistance between the laminated body 136B and the first electrode 52. This is because it becomes difficult to generate heat at the boundary of the plate 191B and its melting becomes insufficient. On the other hand, heat is easily generated at the boundary between the stacked body 136 </ b> B and the first electrode 52. For this reason, the first electrode 52 side of the stacked body 136B is melted, and a problem that the stacked body 136B and the first electrode 52 are joined also occurs. In addition, the dashed-dotted line in FIG. 18 has shown the location joined. Therefore, in Comparative Example 1, as shown in Table 1, the welding strength is “x” and the adhesion to the electrode is “x”. In Comparative Example 1, there is no spatter scattering.

  Moreover, the comparative example 2 shown in the said Table 1 is a case where S2 / S3 is 6 or more (S2 / S3> = 6). That is, S3 is excessively small compared to S2. Specifically, as shown in FIG. 19, compared with the one shown in FIG. 8, the second weld trace region 20 </ b> C formed in the aluminum foil laminate 136 </ b> C (the test piece of the positive electrode current collector laminate 136). The number of recesses 22C is increased and the number thereof is decreased.

  When welding is performed under such conditions, the nugget 70D formed by resistance welding as shown in FIG. 20 becomes larger than that shown in FIG. This is because the contact resistance between the laminated body 136C and the aluminum plate 191C (the test piece of the positive electrode current collecting terminal 191) is too large compared to that shown in FIG. 8, and excessively at the boundary between the laminated body 136C and the aluminum plate 191C. This was due to heat generation and excessive melting. As a result, molten aluminum is ejected (spatter is scattered), and a lacking portion 71 lacking in meat is generated in the nugget 70D. Further, the ejected aluminum adheres to the first electrode 52 and solidifies, thereby causing a problem that the stacked body 136C is joined to the first electrode 52. The one-dot chain line in FIG. 20 shows the part where it has joined. Therefore, in Comparative Example 2, as shown in Table 1, adhesion to the electrode is “x” and spatter scattering is “x”. In the second comparative example, the welding strength is “◯”. This is because the weld strength decreases due to the occurrence of the lacking portion 71 and the weld strength of “の” cannot be secured.

  The example shown as the prior art at the bottom in Table 1 is a case where there are no recesses on the front and back surfaces of the positive electrode current collector stack (S2 / S3 = 1 case). In such a case, all items of welding strength, adhesion to electrodes, and spatter scattering are “x”.

  The following can be understood from the experimental results as described above. That is, as in Examples 1 to 5, if the first welding trace region 10 and the second welding trace region 20 are formed so that S2 / S3 is greater than 1 and less than 6 (1 <S2 / S3 <6), It can be seen that good bonding can be performed. Specifically, it can be seen that the welding strength is strong, the positive electrode current collector laminated portion 136 does not adhere to the electrode, and the spatter does not scatter. In particular, when A> S1 (see Examples 1 to 4), it can be seen that the nugget 70 formed by resistance welding has an appropriate size and no variation, and the welding strength increases.

  Here, when resistance welding is performed by forming the first welding trace region 10 and the second welding trace region 20 so that 1 <S2 / S3 <6, there is no depression in the first welding trace region 10 after resistance welding. The area of the part (area excluding the recess 12) S4 (see the hatched part in FIG. 21) and the area of the part other than the nugget 70 in the second weld mark region 20 after welding (area excluding the nugget 70) S5 (hatched in FIG. As shown in Table 1, the ratio (S4 / S5) with respect to (refer to the location) has a relationship of 1 <S4 / S5 <2. Therefore, if the relationship of “1 <S4 / S5 <2” is established in the battery 100 after resistance welding, it can be said that the battery has high bonding strength in which good bonding as described above is performed. The reason why the range of “1 <S2 / S3 <6” before resistance welding changes to the range of “1 <S4 / S5 <2” after resistance welding is as follows. .

  That is, when resistance welding is performed, the first welding mark region 10 is softened by heat generated by resistance welding. Therefore, the area S4 (see FIG. 21) of the non-recessed portion in the first welding mark region 10 after resistance welding is the area (the area excluding the recess 12) of the non-recessed portion in the first welding mark region 10 before resistance welding. ) Increased compared to S2 (see FIG. 10) (see Table 1). Further, when resistance welding is performed, a nugget 70 (see FIGS. 12 and 22) is formed around the recess 22 (see FIG. 11) in the second welding mark region 20. Therefore, the area S5 (refer to FIG. 22) of the portion other than the nugget 70 in the second welding trace region 20 after resistance welding is the area (the area excluding the recess 22) of the non-recessed portion in the second welding trace region 20 before resistance welding. ) Increased compared to S3 (see Table 1). FIG. 22 is a diagram showing a state of the second welding scar region 20 after resistance welding, and is a diagram of the second welding scar region 20 as seen in the AA cross section of FIG.

  As a result, the relationship “1 <S2 / S3 <6” before resistance welding changes to the relationship “1 <S4 / S5 <2” after resistance welding as shown in Table 1. Therefore, a battery in which the relationship of “1 <S4 / S5 <2” is established after resistance welding is that the relationship of “1 <S2 / S3 <6” is established at the time of resistance welding. This is a battery in which the laminated portion 136 and the positive electrode current collecting terminal 191 are well bonded. Incidentally, S4 is less than S1 (S1> S4) when the concave portion 12 is formed in the first welding trace region 10, and is equal to S1 when the concave portion 12 is not formed in the first welding trace region 10. (S1 = S4).

  In Comparative Example 1 shown in Table 1, S4 / S5 after resistance welding is 1 or less (S4 / S5 ≦ 1). Therefore, the battery of S4 / S5 ≦ 1 is in a joined state as shown in FIG. 18, and is not a good joined battery. In Comparative Example 2, S4 / S5 after resistance welding is 2 or more (S4 / S5 ≧ 2). Therefore, a battery with S4 / S5 ≧ 2 is in a joined state as shown in FIG. 20, and is not a good joined battery.

As described above in detail, the method for manufacturing the secondary battery 100 of the embodiment includes the following steps 1 to 3.
[1. Preparation Step] A positive electrode coated portion 131a in which the positive electrode current collector 131 is coated with the positive electrode active material layer 132 and a positive electrode non-coated portion 131b in which the positive electrode current collector 131 is not coated with the positive electrode active material layer 132 The negative electrode coating part 121a in which the negative electrode active material layer 122 was coated on the positive electrode plate 130, the negative electrode current collector 121, and the negative electrode non-coated part 121b in which the negative electrode current collector 121 was not coated with the negative electrode active material layer 122 And a separator 150 interposed between the positive electrode coating part 131a and the negative electrode coating part 121a, and a positive electrode laminated with the positive electrode non-coating part 131b protruding from the negative electrode plate 120 A wound electrode body 110 having a current collector laminated portion 136 at one end and having a negative electrode current collector laminated portion 126 laminated at the other end with the negative electrode non-coated portion 121b protruding from the positive electrode plate 130 is prepared. Process.
[2. Concave forming step] Using an ultrasonic welding apparatus 40 including an anvil 45 and a horn 41 having a plurality of convex portions 42, the space between the anvil 45 and the horn 41 so as to press the plurality of convex portions 42 included in the horn 41. In addition, the horn 41 is vibrated while sandwiching the positive electrode current collector laminated portion 136 between the first current collector trace portion 136 and the contact surface (front surface 136a) with the anvil 45 in the positive electrode current collector laminated portion 136. A step of forming the second welding mark region 20 having the recess 22 on the contact surface (rear surface 136b) with the horn 41 in the positive electrode current collector laminated portion 136.
[3. Resistance Welding Step] A pair of electrodes 51 composed of the first electrode 52 and the second electrode 55 is formed while the positive electrode current collector terminal 191 is brought into contact with the region including at least the second welding mark region 20 in the positive electrode current collector laminated portion 136. Using the resistance welding apparatus 50 provided, a pair of the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 are placed so that the first welding scar region 10 and the second welding scar region 20 are positioned between the pair of electrodes 51. A process of performing resistance welding by sandwiching the electrodes 51.

In the recess forming step, the first welding trace region 10 and the second welding trace region 20 are formed so that the following expressions (1) and (2) are satisfied.
S1 ≧ S2 (1)
1 <S2 / S3 <6 (2)
S1: Area of the first welding mark region 10 to be formed (see FIG. 10)
S2: Contact area in the resistance welding process between the first welding trace area 10 to be formed and the first electrode 52 that the first welding trace area 10 is scheduled to contact in the resistance welding process (see FIG. 10).
S3: Contact area in the resistance welding process between the second welding trace area 20 to be formed and the positive electrode current collector terminal 191 to which the second welding trace area 20 is scheduled to contact in the resistance welding process (see FIG. 11).

  In the manufacturing method of the secondary battery 100 of such an embodiment, the second welding mark region 20 having the recess 22 is formed in the positive electrode current collector laminated portion 136 by ultrasonic welding before resistance welding. In the resistance welding process, the second welding mark region 20 is positioned between the pair of electrodes 51. The contact area S3 between the second welding trace region 20 and the positive electrode current collector terminal 191 is smaller than the contact area S2 between the first welding trace region 10 and the first electrode 52. For this reason, when performing resistance welding, the contact resistance of the contact surface with the positive electrode current collector terminal 191 in the positive electrode current collector stacking portion 136 is greater than the contact resistance of the contact surface with the first electrode 52 in the positive electrode current collector stacking portion 136. Also grows. Therefore, sufficient Joule heat can be generated on the contact surface between the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191. Therefore, the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 can be sufficiently melted. As a result, the nugget 70 having an appropriate size can be formed, and the positive electrode current collector laminated portion 136 and the positive electrode current collector terminal 191 can be firmly bonded (bonding can be performed with sufficient welding strength). .

  In addition, when 1 ≧ S2 / S3, the contact resistance of the contact surface between the positive electrode current collector stack 136 and the first electrode 52 becomes too high, and the temperature of the contact surface becomes too high. There is a possibility that the current collector stack 136 is excessively melted and joined to the first electrode 52 (see FIG. 18). However, since 1 <S2 / S3 in the manufacturing method of the embodiment, such a problem does not occur.

  In addition, when S2 / S3 ≧ 6, the contact resistance of the contact surface between the positive electrode current collector stack 136 and the positive electrode current collector terminal 191 becomes too high, and the temperature of the contact surface becomes too high. As shown in FIG. 20, the current collector laminated portion 136 is melted excessively, and the molten positive electrode current collector laminated portion 136 is ejected to join the first electrode 52 or to form the nugget 70D having the lacking portion 71. There is a risk of However, in the manufacturing method of the embodiment, since S2 / S3 <6, such a problem does not occur.

  Moreover, in the recessed part formation process in the manufacturing method of the above-mentioned secondary battery 100, what has the some convex part 46 is used as the anvil 45, and the anvil 45, the horn 41, and so on are pressed against the some convex part 46 which the anvil 45 has. The positive electrode current collector laminated portion 136 is sandwiched between them to form the first weld mark region 10 having the recess 12.

  Therefore, the contact area S2 between the first welding trace region 10 and the first electrode 52 during resistance welding can be made smaller than the area S1 of the first welding trace region 10 (S1> S2). Therefore, the contact resistance of the contact surface between the positive electrode current collector stack 136 and the first electrode 52 can be increased as compared with the case where S1 = S2. As a result, heat generation of the positive electrode current collector laminated portion 136 can be promoted and good welding can be performed. In addition, as long as the said Formula (2) is satisfy | filled, the positive electrode collector lamination part 136 is not melted so that the positive electrode collector lamination part 136 and the 1st electrode 52 will join.

  In the recess forming step in the method for manufacturing the secondary battery 100 described above, the contact area S3 can be reduced by increasing the pitch P1 (see FIG. 4) of the plurality of protrusions 42 of the horn 41. The contact area S3 can be increased by reducing the pitch P1 of the plurality of convex portions 42 included in 41 (see Table 3 above). If the size of the contact area S3 is adjusted in this way, the above formula (in comparison with changing other parameters (pressing force of the horn 41, vibration frequency, welding time, etc. in ultrasonic welding)) ( The second weld mark region 20 that satisfies 2) can be reliably formed.

  Moreover, in the recessed part formation process in the manufacturing method of the above-mentioned secondary battery 100, the contact area S2 can be made small by enlarging pitch P2 (refer FIG. 5) of the some convex part 46 which the anvil 45 has, and the anvil 45 The contact area S2 can be increased by reducing the pitch P2 of the plurality of convex portions 46 included in (see Table 2 above). If the size of the contact area S2 is adjusted in this way, the above formula is compared to changing other parameters (such as the pressing force of the horn 41 in ultrasonic welding, the vibration frequency, and the welding time). The 1st welding trace area | region 10 which satisfy | fills (1) and Formula (2) can be formed reliably.

Moreover, in the recessed part formation process in the manufacturing method of the above-mentioned secondary battery 100, the 1st welding trace area | region 10 is formed so that following Formula (3) may be satisfy | filled.
A> S1 (3)
A: Area of the end surface 52a in contact with the joining target (the positive electrode current collector laminated portion 136) in the first electrode 52 to be used in the resistance welding process

  In the case of A ≦ S1, the current density of the current flowing through the first welding mark region 10 decreases. Therefore, the positive electrode current collector laminated portion 136 cannot be sufficiently melted. As a result, a nugget 70A (see FIG. 16) smaller than the nugget 70 shown in FIG. 12 is formed. Further, at the contact portion with the peripheral edge 52 b of the first electrode 52 in the first welding trace area 10, the peripheral edge 52 b of the first electrode 52 is in contact with the first welding trace area 10 because of the concave portion 12 of the first welding trace area 10. The part which does not occur arises. Therefore, the 1st electrode 52 cannot fully press the positive electrode collector lamination part 136, and the nugget 70B formed in the location will become smaller than other nuggets 70A. For these reasons, when A ≦ S1, the bonding strength between the positive electrode current collector stack 136 and the positive electrode current collector terminal 191 decreases. However, since A> S1 in the above manufacturing method, such a problem does not occur.

  In the preparation step in the manufacturing method of the secondary battery 100 described above, an aluminum foil is used as the positive electrode current collector 131, and in the concave portion formation step, the first welding mark region 10 and the second welding mark are formed on the positive electrode current collector laminated portion 136. The region 20 is formed, and in the resistance welding process, the positive electrode current collector terminal 191 made of aluminum is joined to the positive electrode current collector laminated portion 136. Aluminum has a lower thermal conductivity than other metals such as copper, so it is not suitable for resistance welding compared to copper. Further, since aluminum has an oxide film with high electrical resistance on the surface, if resistance welding is performed as it is, the positive electrode current collector laminated portion 136 and the first electrode 52 of the resistance welding apparatus 50 may be welded. However, in the manufacturing method of the secondary battery 100 described above, the contact between the positive electrode current collector stack 136 and the positive electrode current collector terminal 191 is obtained by applying the recess 22 to the positive electrode current collector stack 136 that is an aluminum foil by ultrasonic welding. The contact resistance of the surface is increased. Therefore, even with resistance welding, the positive electrode current collector laminated portion 136 can be sufficiently heated and melted. Further, since the oxide film of the aluminum foil is broken by ultrasonic welding, it is possible to prevent the positive electrode current collector laminated portion 136 and the first electrode 52 from being welded. As a result, it is possible to join the positive current collector stack 136 and the positive current collector terminal 191 with sufficient strength while preventing the welding of the positive current collector stack 136 and the first electrode 52.

  The reason why the resistance welding is used for joining the positive electrode current collector laminated portion 136 made of aluminum, which is not suitable for resistance welding compared to copper, and the positive electrode current collecting terminal 191 is as follows. That is, some recent positive electrode current collecting terminals have a structure incorporating a current interrupting mechanism for interrupting current in the event of an abnormality. When such a positive electrode current collector terminal is joined to the positive electrode current collector laminated portion 136 by ultrasonic welding, a force is applied to the current interruption mechanism by the ultrasonic wave during welding, and there is a possibility that a problem occurs in the current interruption mechanism. However, if resistance welding is used instead of ultrasonic welding, the positive current collector terminal having the current interrupt mechanism and the positive current collector laminated portion 136 can be joined without causing such a problem.

  As mentioned above, although this invention was demonstrated according to embodiment, it cannot be overemphasized that this invention is not limited to the above-mentioned embodiment, It can change suitably and apply in the range which does not deviate from the summary. For example, in the above embodiment, a lithium ion secondary battery is exemplified as the secondary battery. However, the technical idea of the present invention can be applied to other types of secondary batteries such as a nickel hydride secondary battery. .

  In the embodiment, the current collecting terminals 191 and 192 include the external terminal portions 191a and 192a, but may not include the external terminal portions 191a and 192a. In other words, a current collecting terminal disposed inside the battery case 180 is provided separately from the external terminal portion exposed to the outside of the battery case 180, and the external terminal portion and the current collecting terminal are provided inside or outside the battery case. May be electrically joined.

  In the embodiment, the negative electrode current collector laminated portion 126 is not subjected to ultrasonic welding, and the negative electrode current collector laminated portion 126 and the negative electrode current collector terminal 192 are joined by resistance welding. However, ultrasonic welding similar to that performed for the positive electrode current collector layered portion 136 was also performed on the negative electrode current collector layered portion 126, and the positive electrode current collector stacked portion 136 and the positive electrode current collector terminal 191 were joined. The negative electrode current collector laminated portion 126 and the negative electrode current collector terminal 192 may be joined by resistance welding similar to the above.

  In the embodiment, the convex portion 46 is provided on the tip surface 45a of the anvil 45 to form the first weld mark region 10 having the concave portion 12. However, the tip surface 45a of the anvil 45 is flat with no flat portion (flat surface). 1st welding trace area | region 10 (1st welding trace area | region 10 of S1 = S2) without the recessed part 12 may be formed. This is because even if the concave portion 12 is not formed in the first weld mark region 10, as long as the above formulas (1) and (2) are satisfied, good bonding can be performed (the implementation of Table 1). (See Example 4). In this case, the first welding mark region 10 after resistance welding is S1 = S4.

  In the embodiment, the overall size of the first welding scar region 10 and the overall size of the second welding scar region 20 are the same, but may be different. In the embodiment, the prismatic battery 100 is used, but a cylindrical battery may be used. In the embodiment, a wound-type wound electrode body 110 in which the positive electrode plate 130, the negative electrode plate 120, and the separator 150 are wound is used as the electrode body, but the positive electrode plate, the negative electrode plate, and the separator are stacked. Alternatively, a laminated electrode body may be used.

DESCRIPTION OF SYMBOLS 10 ... 1st welding trace area | region 20 ... 2nd welding trace area | region 40 ... Ultrasonic welding apparatus 41 ... Anvil 42 ... Convex part 45 ... Horn 46 ... Convex part 50 ... Resistance welding apparatus 51 ... Pair of electrodes 52 ... 1st electrode 55 ... second electrode 100 ... battery 110 ... wound electrode body 120 ... negative electrode plate 121 ... negative electrode current collector 121a ... negative electrode coating part 121b ... negative electrode non-coating part 122 ... negative electrode active material layer 126 ... negative electrode current collector laminate part DESCRIPTION OF SYMBOLS 130 ... Positive electrode plate 131 ... Positive electrode collector 131a ... Positive electrode coating part 131b ... Positive electrode non-coating part 132 ... Positive electrode active material layer 136 ... Positive electrode collector laminated part 136a ... Front surface 136b ... Rear surface 150 ... Separator 191 ... Positive electrode collector Electrical terminal 192 ... Negative current collector terminal

Claims (7)

A positive electrode plate, a negative electrode current collector, comprising a positive electrode coated portion in which a positive electrode active material layer is coated on a positive electrode current collector and a positive electrode non-coated portion in which the positive electrode current collector is not coated with the positive electrode active material layer A negative electrode plate comprising: a negative electrode coated portion coated with a negative electrode active material layer; and a negative electrode non-coated portion where the negative electrode current collector is not coated with the negative electrode active material layer; and the positive electrode coated Including a separator interposed between the negative electrode coating portion and the negative electrode coating portion, the positive electrode non-coating portion being laminated in a state protruding from the negative electrode plate at one end, and the negative electrode non-coating portion A preparation step of preparing an electrode body having, at the other end, a negative electrode current collector laminated portion laminated in a state where the coating portion protrudes from the positive electrode plate;
Using an ultrasonic welding apparatus including an anvil and a horn having a plurality of convex portions, the positive electrode current collector laminated portion or the positive electrode current collector stack portion between the anvil and the horn so as to press the plurality of convex portions of the horn Forming a first weld mark region on the contact surface with the anvil in the current collector laminate portion by vibrating the horn while sandwiching the current collector laminate portion of one of the negative electrode current collector laminate portions And forming a second weld trace region having a recess on the contact surface with the horn in the current collector laminate,
A pair of electrodes composed of a first electrode and a second electrode while contacting a current collector terminal of a pole corresponding to the current collector laminate portion in a region including at least the second welding mark region in the current collector laminate portion The pair of electrodes is connected to the current collector laminated portion and the current collector terminal so that the first welding mark area and the second welding mark area are positioned between the pair of electrodes using a resistance welding apparatus comprising: A resistance welding process in which resistance welding is performed by sandwiching between
In the recess forming step, the first welding trace region and the second welding trace region are formed so that the following expressions (1) and (2) are satisfied.
S1 ≧ S2 (1)
1 <S2 / S3 <6 (2)
S1: Area of the first welding trace area to be formed S2: Resistance of the first welding trace area to be formed and the first electrode to which the first welding trace area is abutted in the resistance welding process Contact area in the welding process S3: Contact area in the resistance welding process between the second welding trace region to be formed and the current collector terminal with which the second welding trace region is scheduled to abut in the resistance welding process A method of manufacturing a secondary battery according to claim 1,
In the recess forming step, the contact area S3 is reduced by increasing the pitch of the plurality of protrusions included in the horn, and the contact area S3 is increased by decreasing the pitch of the plurality of protrusions included in the horn. A method for manufacturing a secondary battery. A method of manufacturing a secondary battery according to claim 1 or claim 2,
In the concave portion forming step, the anvil having a plurality of convex portions, the current collector laminated portion is sandwiched between the anvil and the horn so as to press the plural convex portions of the anvil, A method for manufacturing a secondary battery, comprising forming the first welding mark region having a recess. A method of manufacturing a secondary battery according to claim 3,
In the recess forming step, the contact area S2 is reduced by increasing the pitch of the plurality of protrusions included in the anvil, and the contact area S2 is increased by decreasing the pitch of the plurality of protrusions included in the anvil. A method for manufacturing a secondary battery. In the manufacturing method of the secondary battery as described in any one of Claim 1- Claim 4,
In the recess forming step, the first welding mark region is formed so that the following expression (3) is further satisfied.
A> S1 (3)
A: The area of the end surface in contact with the joining target in the first electrode scheduled to be used in the resistance welding process A method for manufacturing a secondary battery according to any one of claims 1 to 5,
In the preparation step, an aluminum foil is used as the positive electrode current collector,
In the recess forming step, the first welding trace region and the second welding trace region are formed in the positive electrode current collector laminated portion,
In the resistance welding step, a positive electrode current collector terminal made of aluminum is joined to the positive electrode current collector laminated portion. A positive electrode plate, a negative electrode current collector, comprising a positive electrode coated portion in which a positive electrode active material layer is coated on a positive electrode current collector and a positive electrode non-coated portion in which the positive electrode current collector is not coated with the positive electrode active material layer A negative electrode plate comprising: a negative electrode coated portion coated with a negative electrode active material layer; and a negative electrode non-coated portion where the negative electrode current collector is not coated with the negative electrode active material layer; and the positive electrode coated Including a separator interposed between the negative electrode coating portion and the negative electrode coating portion, the positive electrode non-coating portion being laminated in a state protruding from the negative electrode plate at one end, and the negative electrode non-coating portion An electrode body having, on the other end, a negative electrode current collector laminated portion laminated in a state where the coating portion protrudes from the positive electrode plate;
A positive current collector terminal joined to the positive current collector laminated portion;
A negative electrode current collector terminal joined to the negative electrode current collector laminate,
The current collector laminate portion of at least one of the positive electrode current collector laminate portion and the negative electrode current collector laminate portion is the current collector laminate portion of the positive electrode current collector terminal or the negative electrode current collector terminal. And a second welding trace region where a nugget is formed on the joint surface, the first welding trace region having a recess or not having the recess on the back surface of the joint surface with the current collector terminal of the electrode corresponding to Having
The secondary battery, wherein the first welding mark area and the second welding mark area satisfy the following expressions (4) and (5).
S1 ≧ S4 (4)
1 <S4 / S5 <2 (5)
S1: Area of the first welding mark area S4: Area of a non-dented area in the first welding mark area S5: Area of a non-nugget area in the second welding mark area

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