JP2009277596A - Method of manufacturing electrode group for secondary battery and secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture an electrode group for a secondary battery by reliably, stably, and efficiently connecting a collector end of a positive electrode plate or a negative electrode plate and a collector terminal plate, and obtain a secondary battery suited for large-current charge and discharge with the use of the electrode group. <P>SOLUTION: In the electrode structure 10 including a positive electrode plate 11 and the negative electrode plate 15 as electrode plates, a collector terminal plate is made in contact with a collector exposed part 12a of the positive electrode plate 11 arranged at one end and/or a chip of a collector exposed part 16c of the negative electrode plate 15 arranged at the other end, abutment parts of the collector terminal plates with at least the collector exposed parts 12a, 16a are to be melted, and at the same time, molten parts are pulled into an electrode plate side to have the electrode plates and the collector terminal plates connected. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a secondary battery electrode group and a secondary battery. More specifically, the present invention mainly relates to an improvement in a method for attaching a current collector terminal plate to an electrode plate.

  Recently, a secondary battery used for a drive power source or the like has been developed as an important key device. Among them, nickel-metal hydride storage batteries and lithium ion secondary batteries are small and light and have high energy density, so they are widely used not only for consumer devices such as mobile phones but also for electric vehicles and power tools. In particular, lithium ion secondary batteries are attracting attention as power sources for driving, and development for higher capacity and higher output is being actively conducted. A secondary battery used as a driving power source is required to discharge a large current. For this reason, secondary batteries have been proposed in which the structure of the secondary battery, in particular, the current collecting structure is modified.

  For example, a tabless current collecting structure is known. The tabless current collecting structure is an electrode group including a positive electrode plate, a negative electrode plate, and a separator, wherein a current collector exposed portion of the positive electrode plate is disposed at one end of the electrode group, and a current collector of the negative electrode plate is disposed at the other end. A body exposed portion is arranged, and a current collector terminal plate is connected to each current collector exposed portion without a tab. In the tabless current collecting structure, the current collector exposed portions are arranged on almost the entire surface of both ends thereof, so that a current collecting terminal plate can be connected to the entire surfaces of both ends, and the electric resistance can be reduced. Therefore, the tabless current collecting structure is suitable for large current discharge. In order for the tabless current collecting structure to function efficiently, it is necessary to securely connect the ends of the current collector exposed portions of the positive electrode plate and the negative electrode plate to the current collecting terminal plate, respectively.

  Various proposals have been made for an electrode group having a tabless current collecting structure. For example, the current collector exposed portion and the current collector terminal plate include a stacked electrode group in which the current collector exposed portions of the positive electrode plate and the negative electrode plate are arranged at one and the other end, and two current collector terminal plates. In the connection portion, a battery in which a fillet made of metal contained in the current collector terminal plate is formed around the end of the current collector exposed portion has been proposed (for example, see Patent Document 1). This battery is manufactured by forming a recess in the connection surface of the current collector terminal plate with the current collector exposed portion, inserting the end of the current collector exposed portion into this recess, and welding by electron beam or laser irradiation. Is done. According to the technique of Patent Document 1, the current collector and the current collector terminal plate can be reliably connected.

  However, in the battery manufacturing method described in Patent Document 1, since the distance between the current collectors varies depending on the thickness of the positive electrode plate or the negative electrode plate or the thickness of the separator, the concave portion of the current collector terminal plate is formed accordingly. There is a need. Further, in the electrode group having a tabless current collecting structure, a plurality of end portions of the current collector exposed portions of the positive electrode plate and the negative electrode plate are arranged at both end portions, so that these end portions are formed on the current collecting terminal plate. In order to insert into the recess, precise alignment is required. Therefore, the manufacturing process becomes complicated, and problems such as a partial connection failure, an increase in defective product rate, and an increase in manufacturing cost may occur.

  Further, in the wound electrode group having a tabless current collecting structure, the ends of the positive and negative electrode collector exposed portions arranged at both ends of the electrode group are pressed from the winding axis direction of the electrode group. A secondary battery in which a flat portion is formed and the flat portion and a current collecting terminal plate are welded has been proposed (for example, see Patent Document 2). In Patent Document 2, it is not necessary to align the current collector exposed portion of the electrode group and the current collector terminal plate as in Patent Document 1, and the current collector terminal plate is connected to the end of the current collector by a simple method. it can.

  However, at present, in order to increase the capacity and size of the secondary battery, it is essential to further reduce the thickness of the current collectors included in the positive electrode plate and the negative electrode plate. Since the thinned current collector does not have sufficient mechanical strength, when it is pressed from the winding axis direction, the bending method becomes uneven and it becomes difficult to form a flat portion. In particular, in a lithium ion secondary battery, an aluminum foil or copper foil having a thickness of about 20 μm is used as a current collector, so that it is very difficult to form a flat portion by pressing. If the flat portion is not formed, the connection between the current collector and the current collector terminal plate may be insufficient.

JP 2006-172780 A JP 2000-294222 A

  An object of the present invention is to provide a method for producing a secondary battery electrode group capable of reliably and efficiently connecting a current collector end of a positive electrode plate or a negative electrode plate and a current collector terminal plate, and an electrode produced by the production method. A secondary battery including a group and suitable for high-current discharge is provided.

The present invention provides an electrode structure manufacturing step for manufacturing an electrode structure in which a current collector exposed portion of a positive electrode plate is disposed at one end and a current collector exposed portion of a negative electrode plate is disposed at the other end. When,
The current collector terminal plate is brought into contact with the current collector exposed portion of at least one electrode plate selected from the positive electrode plate and the negative electrode plate, and at least the contact portion of the current collector terminal plate with the current collector exposed portion is melted. The present invention relates to a method for manufacturing an electrode group for a secondary battery including an electrode connecting step of drawing a molten portion toward the electrode plate and connecting the electrode plate and a current collecting terminal plate.

In the electrode connection step, it is preferable to melt at least a contact portion of the current collector terminal plate with the current collector exposed portion by arc welding.
In the electrode connection step, it is preferable to draw the molten portion of the current collector terminal plate toward the electrode plate side by reducing the pressure inside the electrode structure.
It is preferable that through holes in the thickness direction are formed in the current collecting terminal plate.
The current collector terminal plate for the positive electrode is preferably made of a metal having a specific gravity equal to or smaller than that of copper.

Moreover, this invention relates to the secondary battery containing the electrode group for secondary batteries manufactured by the manufacturing method of the electrode group for secondary batteries of this invention.
The secondary battery of the present invention is preferably a lithium ion secondary battery or a nickel hydride storage battery.

  According to the present invention, the exposed portion of the current collector disposed at the end of the electrode group and the current collector terminal plate can be reliably and stably connected by a simple method, and the secondary battery electrode group can be It can be manufactured efficiently with few steps. In addition, the connection area between the current collector exposed portion and the current collector terminal plate can be increased. Therefore, the secondary battery including the electrode group for the secondary battery manufactured by the manufacturing method of the present invention has low resistance and stable output characteristics, and is particularly suitable for large current discharge.

The manufacturing method of the electrode group for secondary batteries of this invention includes an electrode structure preparation process and an electrode connection process.
[Electrode structure manufacturing process]
In this step, the electrode assembly 10 is produced. FIG. 1 is a drawing showing a simplified configuration of an electrode structure 10. FIG. 1A is a plan view of the positive electrode plate 11 included in the electrode structure 10. FIG. 1B is a plan view of the negative electrode plate 15 included in the electrode structure 10. FIG. 1C is a perspective view showing the appearance of the electrode structure 10.

  The electrode structure 10 is a wound electrode group including a positive electrode plate 11, a negative electrode plate 15, and a separator (not shown). In the direction in which the winding axis (axial center) of the electrode structure 10 extends, the current collector exposed portion 12a of the positive electrode plate 11 is disposed at one end of the electrode structure 10, and the negative electrode plate 15 is disposed at the other end. A current collector exposed portion 16a is disposed. The current collector exposed portion 12 a of the positive electrode plate 11 is disposed in a spiral shape over the entire surface of one end of the electrode structure 10. The current collector exposed portion 16 a of the negative electrode plate 15 is also arranged in a spiral shape on the entire surface of the other end of the electrode structure 10.

  Moreover, the electrode structure 10 has the hollow part 10a extended along the winding axis | shaft. The hollow portion 10a penetrates the electrode structure 10 in the direction in which the winding axis of the electrode structure 10 extends. The direction in which the winding axis of the electrode structure 10 extends is the same as the longitudinal direction of the electrode structure 10.

  The positive electrode plate 11 includes a current collector 12 and a positive electrode active material layer 13. The current collector 12 is a long metal sheet having a long direction and a short direction. Specifically, the metal sheet is a metal foil, a metal film, or the like. The positive electrode active material layer 13 is formed on both surfaces of the current collector 12 in the thickness direction. However, a current collector exposed portion 12 a where the positive electrode active material layer 13 is not formed is present at one end of the positive electrode plate 11 in the short direction. The current collector exposed portion 12 a is a portion extending in a strip shape in the longitudinal direction of the positive electrode plate 11 at one end in the short direction of the positive electrode plate 11.

  The negative electrode plate 15 includes a current collector 16 and a negative electrode active material layer 17. The current collector 16 is a long metal sheet having a longitudinal direction and a lateral direction. Specifically, the metal sheet is a metal foil, a metal film, or the like. The negative electrode active material layer 17 is formed on both surfaces of the current collector 16 in the thickness direction. However, the current collector exposed portion 16 a where the negative electrode active material layer 17 is not formed is present at one end of the negative electrode plate 15 in the short direction. The current collector exposed portion 16 a is a portion extending in a strip shape in the longitudinal direction of the negative electrode plate 15 at one end in the short direction of the negative electrode plate 15.

  As the separator, for example, a porous film, a porous insulating film, a laminate of a porous film and a porous insulating film, or the like can be used. The porous film is, for example, a microporous film made of a synthetic resin. As the synthetic resin, for example, polyolefin such as polyethylene and polypropylene can be used. The porous insulating film is formed from an inorganic filler such as a metal oxide and a binder such as a synthetic resin. As the synthetic resin used as the binder, the same resin as the binder for forming the active material layer can be used.

  The electrode assembly 10 can be produced, for example, by stacking the positive electrode plate 11 and the negative electrode plate 15 with a separator interposed therebetween and winding the same. At this time, the positive electrode active material layer 13 and the negative electrode active material layer 17 face each other with a separator interposed therebetween, and the current collector exposed portions 12a and 16a are positioned at one and the other end portions in the lateral direction of the stacked product, respectively. Thus, the positive electrode plate 11 and the negative electrode plate 15 are overlapped. Thereby, current collector exposed portions 12a and 16a protrude in a spiral shape from between the separators at both ends of the electrode assembly 10 in the direction in which the winding shaft extends.

  In the present embodiment, the electrode assembly 10 is formed as a substantially circular wound electrode group, but is not limited thereto, and may be formed as a flat or flat wound electrode group. Moreover, it is not limited to a wound type electrode group, You may form the electrode structure 10 as a laminated type electrode group. The stacked electrode group is produced by stacking the positive electrode plate 11 and the negative electrode plate 15 with a separator interposed therebetween. For example, when the shape of the stacked electrode group is a rectangle, the current collector exposed portion 12a is disposed at an end corresponding to one side of the rectangle, and the current collector exposed portion 16a corresponds to a side facing one side of the rectangle. It is arranged at the end.

[Electrode connection process]
In this step, the current collector terminal plate is connected to the tip portions of the current collector exposed portions 12a and 16a respectively disposed at both ends of the electrode assembly 10 in the direction in which the winding axis extends. An electrode connection process may be implemented with respect to any one of a positive electrode plate and a negative electrode plate, and may be implemented to both. It is preferable to carry out both. Moreover, when implementing to either one, it is preferable to implement with respect to a positive electrode plate.

  The positive electrode and the positive electrode current collector terminal plate can be connected by, for example, a method including a contact process, a melting process, and a bonding process. In the contact step, one surface of a positive current collector terminal plate (not shown) is brought into contact with the tip of the current collector exposed portion 12a. In the melting step, the positive electrode current collector terminal plate is partially melted. In the joining step, the melted portion of the positive electrode current collector terminal plate is drawn to the positive electrode plate 11 side, and the current collector exposed portion 12a and the positive electrode current collector terminal plate are joined. Thereby, the positive electrode plate 11 and the positive electrode current collector terminal plate are stably and firmly connected.

  For connection between the negative electrode and the negative electrode current collector terminal plate, one surface of the negative electrode current collector terminal plate (not shown) is brought into contact with the tip of the current collector exposed portion 16a (contact process). The melting step and the joining step are performed to join the negative electrode plate 15 and the negative electrode current collector terminal plate. Either the positive electrode connection or the negative electrode connection may be performed first.

  FIG. 2 is a perspective view illustrating an example of an electrode connection process. In FIG. 2A to FIG. 2C, the contact step is performed. In FIG.2 (d), a melting process and a joining process are implemented. In the present embodiment, FIG. 2 shows a positive electrode connection step.

  In the step shown in FIG. 2A, the electrode assembly 10 is accommodated in the decompressor 20. The decompressor 20 includes a storage container 21, a first pipe 22, a second pipe 23, a three-way cock 24, and an O-ring 25. The storage container 21 is a cylindrical container and stores the electrode structure 10 so that the direction in which the winding axis of the electrode structure 10 extends matches the vertical direction. At this time, the electrode structure 10 is arranged such that the upper end portion (the current collector exposed portion 12a or the current collector exposed portion 16a tip portion) of the electrode structure 10 is positioned about 5 mm above the upper end portion of the storage container 21. Is preferably accommodated. In the present embodiment, the electrode assembly 10 is housed in the housing container 21 with the current collector exposed portion 12a facing upward.

  The first pipe 22 has one end connected to the storage container 21 and the other end connected to a vacuum pump (not shown). The internal space of the first pipe 22 communicates with the internal space of the storage container 21. When suction is performed by the vacuum pump, the internal space of the container 21 is in a decompressed state in which the airflow is directed downward in the vertical direction. Thereby, the inside of the electrode structure 10 accommodated in the container 21 is also in a reduced pressure state.

  The second pipe 23 has one end connected to the first pipe 22 and the other end opened. The three-way cock 24 is attached to a connection portion between the first pipe 22 and the second pipe 23. By appropriately adjusting the direction of the three-way cock 24, the degree of decompression of the internal space of the container 21 is adjusted, or the decompressed state of the internal space is eliminated. In this Embodiment, the pressure reduction degree of the internal space of the storage container 21 is adjusted in the range of about 800 hPa-500 hPa. The O-ring 25 is disposed along the upper end portion of the storage container 21 and is stored when the upper end portion of the storage container 21 and the horizontal base 27 of the welding base 26 are brought into contact with each other in the step shown in FIG. The adhesion between the container 21 and the horizontal base 27 is improved.

  In the step shown in FIG. 2B, the decompressor 20 containing the electrode structure 10 is placed under the welding base 26 in a state where it is placed on the elevating means 29. The welding base 26 includes a horizontal base 27 and a support member 28. The horizontal base 27 is a substantially rectangular plate-like member in the present embodiment, and a hole 27a is formed at the center thereof. The current collector exposed portion 12a of the electrode assembly 10 is inserted through the hole 27a. Therefore, the hole 27a preferably has a shape corresponding to the cross-sectional shape of the current collector exposed portion 12a.

  The four support members 28 are attached to the lower surfaces of the four corners of the horizontal table 27 and support the horizontal table 27 in the horizontal direction. The elevating means 29 moves the decompressor 20 up and down in the vertical direction. For the elevating means 29, for example, a hydraulic press or the like is used. When the decompressor 20 is raised, the current collector exposed portion 12a of the electrode assembly 10 is disposed under the welding base 26 so that the current collector exposed portion 12a can be inserted into the hole 27a of the horizontal base 27.

  In the step shown in FIG. 2C, first, the decompressor 20 is raised by the elevating means 29, and the current collector exposed portion 12a of the electrode structure 10 is inserted into the hole 27a of the horizontal base 27. At this time, the decompressor 20 is raised so that at least the tip of the current collector exposed portion 12 a is positioned above the upper surface of the horizontal base 27. In addition, the O-ring 25 disposed at the upper end of the storage container 21 of the decompressor 20 and the lower surface of the horizontal table 27 are in close contact with each other. Thereby, the decompression state inside the container 21 is efficiently maintained.

  Next, the positive electrode current collector terminal plate 30 is placed on the front end portion of the current collector exposed portion 12a, and the presser plate 31 causes the front end portion of the current collector exposed portion 12a and one surface of the positive electrode current collector terminal plate 30 to contact each other. The positive electrode current collector terminal plate 30 is fixed in the contact state. Furthermore, a vacuum pump is operated and the inside of the storage container 21 is made into a pressure reduction state. In the present embodiment, the inside of the container 21 is preferably in a reduced pressure state of about 800 hPa to 500 hPa.

  FIG. 3 is a perspective view showing the configuration of the positive electrode current collector terminal plate 30. The positive electrode current collector terminal plate 30 is a metal plate-like member having a shape corresponding to the cross-sectional shape of the current collector exposed portion 12a. In the present embodiment, the positive electrode current collector terminal plate 30 is substantially circular. The positive current collector terminal plate 30 is formed with a through hole 30a so as to communicate with the hollow portion 10a of the electrode structure 10 when the terminal plate 30 is placed on the tip of the current collector exposed portion 12a. Has been. Thereby, even after the positive electrode current collector terminal plate 30 is connected, the air permeability of the hollow portion 10a of the electrode assembly 10 is maintained. As a result, in the subsequent negative electrode connection step, it is easy to adjust the degree of reduced pressure in the electrode assembly 10, and the negative electrode connection step can be easily performed. A positive electrode lead 33 is connected to the positive electrode current collector terminal plate 30 in advance. In FIG. 2, the positive electrode lead 33 is not shown.

  The material of the positive electrode current collector terminal plate 30 is not particularly limited as long as it is a metal, but a metal having a specific gravity equal to or lower than that of copper is preferable, and a metal having a specific gravity lower than that of copper is more preferable. When the positive electrode current collector terminal plate 30 is made of a metal having a specific gravity similar to copper or iron, the amount of sag (pulling) toward the positive electrode plate 11 increases due to its own weight. Further, the drawn melted portion expands without being bounced on the surface of the current collector exposed portion 12a. Therefore, even if the degree of decompression is reduced, a sufficient bonding area can be obtained.

  On the other hand, if the specific gravity is the same as that of copper or a metal having a specific gravity smaller than copper, the molten portion spreads on the surface of the positive electrode current collector terminal plate 30, and the amount drawn into the positive electrode plate 11 side is reduced. In addition, the drawn melted portion is easily repelled on the surface of the current collector exposed portion 12a. Therefore, a sufficient bonding area can be secured by increasing the degree of decompression and increasing the amount drawn into the positive electrode plate 11 side. In this way, the positive electrode plate 11 and the positive electrode current collector terminal plate 30 are connected stably and reliably.

  The positive electrode plate 11 and the positive electrode current collector terminal plate 30 can be connected even when a metal having a specific gravity greater than that of copper is used. However, when such a metal is melted, its own weight is heavy, so that there is a possibility that the melted portion falls off, which may cause an internal short circuit.

  In the present embodiment, the positive electrode current collector terminal plate 30 is made of aluminum. When the positive electrode current collector terminal plate 30 is made of a metal having a low surface tension such as aluminum, the molten metal flows more easily in the horizontal direction than in the vertical direction, so the tip of the current collector exposed portion 12a and the positive electrode current collector terminal There is a possibility that the bonding with the plate 30 becomes insufficient. However, in the present invention, the molten metal is pushed in the vertical direction and drawn to the positive electrode plate 11 side by bringing the inside of the electrode structure 10 into a reduced pressure state in which the airflow is directed downward in the vertical direction. Therefore, regardless of the surface tension, a sufficient amount of molten metal adheres to the periphery of the tip portion of the current collector exposed portion 12a and solidifies. As a result, the current collector exposed portion 12a and the positive electrode current collector terminal plate 30 are stably and reliably joined.

  FIG. 4 is a cross-sectional view showing a contact state between the front end portion of the current collector exposed portion 12 a and the positive electrode current collector terminal plate 30. As shown in FIG. 4, the entire tip of the current collector exposed portion 12 a is in contact with the surface of the positive electrode current collector terminal plate 30. Thereby, the resistance of the connection part of the positive electrode plate 11 and the positive electrode current collection terminal plate 30 becomes low, and the electrode group for secondary batteries which can discharge a large current is obtained.

  Returning to the description of FIG. In the step shown in FIG. 2D, the tip portion of the current collector exposed portion 12a and the positive electrode current collector terminal plate 30 are joined, and the positive electrode plate 11 and the positive electrode current collector terminal plate 30 are connected. This is performed, for example, using a welding electrode commonly used in arc welding, preferably TIG (Tungsten Inert Gas) welding.

  Specifically, as shown in FIG. 2D, on the surface opposite to the contact surface of the positive electrode current collector terminal plate 30 to the current collector exposed portion 12a (hereinafter referred to as "opposite surface"), Energy is irradiated from the welding electrode 32. At this time, it is not necessary to irradiate the entire opposite surface with energy, and for example, energy may be partially irradiated according to the interval between the current collector exposed portions 12a. For example, energy may be applied to a portion of the opposite surface corresponding to the contact portion with the current collector exposed portion 12a. Thereby, the positive electrode current collector terminal plate 30 is melted in the thickness direction, and at least the contact portion with the tip portion of the current collector exposed portion 12a is melted.

  At this time, since the inside of the electrode assembly 10 is in a depressurized state in which the airflow is directed downward in the vertical direction, the molten portion of the positive electrode current collector terminal plate 30 is drawn to the positive electrode plate 11 side, and the current collector exposed portion 12a It sticks around the tip and solidifies. By making the inside of the electrode assembly 10 in a reduced pressure state as described above, the amount of the melted portion of the positive electrode current collector terminal plate 30 drawn into the positive electrode plate 11 side increases, and the current collector exposed portion 12a and the positive electrode current collector are increased. It is possible to increase the bonding area with the terminal board 30. Thereby, the front-end | tip part of the collector exposed part 12a and the positive electrode current collection terminal board 30 are joined reliably and stably.

FIG. 5 is a cross-sectional view showing a joined state between the tip portion of the current collector exposed portion 12 a and the positive electrode current collector terminal plate 30. According to FIG. 5, by melting the positive electrode current collector terminal plate 30, the melted portion is drawn to the current collector exposed portion 12a (positive electrode plate 11) side and adheres to the periphery of the tip portion of the current collector exposed portion 12a. And the front-end | tip part of the collector exposed part 12a and the positive electrode current collection terminal board 30 are joined.
Thereby, a positive electrode connection process is complete | finished and the joined body (henceforth "a positive electrode joined body") of the electrode structure 10 and the positive electrode current collection terminal board 30 is obtained.

  The negative electrode connection step can be performed in the same manner as the positive electrode connection step. That is, as shown in FIG. 2A, the positive electrode assembly is accommodated in the decompressor 20 again so that the current collector exposed portion 16a is positioned upward in the vertical direction. Next, as shown in FIG. 2 (b), the decompressor 20 containing the positive electrode assembly is placed under the welding base 26 in a state where it is placed on the lifting means 29. Further, as shown in FIG. 2 (c), the negative electrode current collector terminal plate 35 shown in FIG. 6 is placed on the tip of the current collector exposed portion 16 a, and the negative electrode current collector terminal plate 35 is fixed by the presser plate 31. . At this time, the contact state between the tip of the current collector exposed portion 16a and one surface of the negative electrode current collector terminal plate 35 is the same as shown in FIG.

  FIG. 6 is a perspective view showing the configuration of the negative electrode current collector terminal plate 35. The negative electrode current collector terminal plate 35 is a metal plate-like member having a shape corresponding to the cross-sectional shape of the current collector exposed portion 16a. In the present embodiment, the shape of the negative electrode current collector terminal plate 35 is substantially circular. The negative electrode current collector terminal plate 35 has a through hole 35a. The through-hole 35a has a U-shape, and is formed so that the distance between two straight lines at both ends of the U-shape is slightly larger than the maximum diameter of the hollow portion 10a of the electrode structure 10. preferable. Thereby, it becomes easy to create a reduced pressure state in which the direction of the airflow is downward in the vertical direction inside the electrode structure 10.

  In the present embodiment, the through-hole 35a has a U-shape, but is not limited to this, and can have any shape. When the negative electrode current collector terminal plate 35 is joined before the positive electrode current collector terminal plate 30, a through hole similar to the through hole 30 a of the positive electrode current collector terminal plate 30 is formed in the negative electrode current collector terminal plate 30. The through hole 35 a of the negative electrode current collector terminal plate 35 may be formed in the positive electrode current collector terminal plate 30. In the present embodiment, the negative electrode current collector terminal plate 35 is made of copper.

  Subsequently, as shown in FIG. 2D, the negative electrode current collector terminal plate 35 is melted, and the current collector exposed portion 16a and the negative electrode current collector terminal plate 35 are joined. The joining state is the same as that shown in FIG. At the time of melting and bonding, the inside of the electrode structure 10 is preferably in a reduced pressure state of about 900 hPa to 700 hPa.

  Thereby, the negative electrode current collector terminal plate 35 is connected to the electrode structure 10, the negative electrode plate 15 and the negative electrode current collector terminal plate 35 are connected, and the secondary battery electrode group of the present invention having a tabless current collection structure is obtained. It is done. The electrode group for a secondary battery of the present invention is preferably used for a secondary battery. Moreover, you may use the electrode group for secondary batteries of this invention for the electrochemical element which has the current collection structure similar to a secondary battery. Examples of such electrochemical elements include capacitors.

FIG. 7 is a vertical cross-sectional view showing a simplified configuration of a secondary battery 1 that is one embodiment of the present invention. The secondary battery 1 includes a secondary battery electrode group 2 having a tabless current collecting structure manufactured by the method for manufacturing a secondary battery electrode group of the present invention.
The secondary battery 1 includes an electrode group 2, a sealing plate 3, a gasket 4 and a battery can 5.

  The electrode group 2 includes an electrode structure 10, a positive electrode current collector terminal 30, and a negative electrode current collector terminal 35. As described above, the electrode assembly 10 is produced by stacking the positive electrode plate 11 and the negative electrode plate 15 with the separator 34 interposed therebetween and further winding the electrode plate 10 and the negative electrode plate 15. In the direction in which the winding axis of the electrode structure 10 extends, the current collector exposed portion 12a of the positive electrode plate 11 is disposed at one end of the electrode structure 10, and the current collector exposed portion of the negative electrode plate 15 is disposed at the other end. 16a is arranged. The tip end portion of the current collector exposed portion 12a is directly joined to the surface of the positive electrode current collector terminal plate 30 without using a tab. The tip of the current collector exposed portion 16a is directly joined to the surface of the negative electrode current collector terminal plate 35 without using a tab. The electrode assembly 10 is impregnated with an appropriate electrolyte depending on the battery type of the secondary battery 1.

  The separator 34 included in the electrode assembly 10 includes a synthetic resin porous film, a porous insulating film containing a metal oxide and a binder, and a laminate of the synthetic resin porous film and the porous insulating film. The body can be used.

  The positive electrode current collector terminal plate 30 is a disk-shaped metal plate, and a through hole 30 a communicating with the hollow portion 10 a extending along the winding axis of the electrode group 2 is formed at the center thereof. One end of a positive electrode lead 33 is connected to the positive electrode current collecting terminal plate 30. The other end of the positive electrode lead 33 is connected to a sealing plate 3 having a positive electrode terminal. In the present embodiment, the positive electrode current collector terminal plate 30 is made of aluminum. On the other hand, the negative electrode current collecting terminal plate 35 is a disk-shaped metal plate, and is directly connected to the inner wall of the bottom portion that becomes the negative electrode terminal of the battery can 5. In the present embodiment, the negative electrode current collector terminal plate 35 is made of copper.

  After the electrode group 2 is housed inside the battery can 5, the sealing plate 3 is attached to the opening of the battery can 5 through the gasket 4 to seal the battery can 5, and has a protrusion serving as a positive electrode terminal on the top. Have. The gasket 4 is made of, for example, a synthetic resin. The battery can 5 is a bottomed cylindrical container member that accommodates the electrode group 2 and the electrolytic solution therein. The bottom surface of the battery can 5 is a negative electrode terminal. The battery can 5 is made of, for example, iron.

The secondary battery 1 is produced, for example, as follows. First, the electrode group 2 is accommodated in the battery can 5. At this time, the negative electrode current collector terminal plate 35 is brought into contact with the inner wall of the lower surface of the battery can 5, and the negative electrode current collector terminal plate 35 and the battery can 5 are joined by resistance welding. Further, the positive electrode current collector terminal plate 30 is connected to the sealing plate 3 through the positive electrode lead 33 attached to the positive electrode current collector terminal plate 30. Then, after the nonaqueous electrolyte solution is injected into the battery can 5, the opening of the battery can 5 is sealed with the sealing plate 3 through the gasket 4. Thereby, the secondary battery 1 can be manufactured.
The secondary battery of the present invention is not particularly limited, but is preferably applied to a lithium ion secondary battery, a nickel metal hydride storage battery, and the like.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
Example 1
(1) Production of positive electrode plate 85 parts by weight of lithium cobaltate powder (positive electrode active material), 10 parts by weight of carbon powder (conductive agent) and 5 parts by weight of polyvinylidene fluoride (PVDF, binder) are added in appropriate amounts of N-methyl- A positive electrode mixture slurry was prepared by dissolving or dispersing in 2-pyrrolidone. This positive electrode mixture slurry was applied to both sides of an aluminum foil (positive electrode current collector) having a thickness of 15 μm and a width of 56 mm with a width of 50 mm in the short direction, and the positive electrode mixture slurry was dried and rolled to produce a positive electrode plate. . The positive electrode mixture slurry was not applied to one end in the short direction of the positive electrode plate over a width of 6 mm to form a strip-shaped current collector exposed portion. The thickness of the portion of the positive electrode plate where the positive electrode active material layer was formed was 100 μm.

(2) Production of negative electrode plate 95 parts by weight of artificial graphite powder (negative electrode active material) and 5 parts by weight of PVDF (binder) are dispersed or dissolved in an appropriate amount of N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry. did. This negative electrode mixture slurry was applied to both sides of a copper foil (negative electrode current collector) having a thickness of 10 μm and a width of 57 mm with a width of 52 mm in the short direction, and the negative electrode mixture was dried and rolled to prepare a negative electrode plate. . A negative electrode mixture slurry was not applied to one end in the short direction of the negative electrode plate over a width of 5 mm to form a strip-shaped current collector exposed portion. The thickness of the portion of the negative electrode plate on which the negative electrode active material layer was formed was 100 μm.

(3) Preparation of electrode structure The positive electrode plate and the negative electrode plate were overlapped via a separator, and this was wound in a spiral shape to prepare an electrode structure. As the separator, a microporous film made of polypropylene resin having a width of 53 mm and a thickness of 25 μm was used. The separator was disposed between the positive electrode active material layer of the positive electrode plate and the negative electrode active material layer of the negative electrode plate. In the direction in which the winding axis of the electrode structure extends, the current collector exposed portion of the positive electrode plate is spirally arranged at one end of the electrode structure, and the current collector exposed portion of the negative electrode plate is spirally arranged at multiple ends. It had been.

(4) Production of current collector terminal plate An aluminum plate was molded into a disk shape having a thickness of 1 mm and a diameter of 24 mm, and this aluminum plate was punched out by a press to form a through hole having a diameter of 7 mm in the center of the disk.
Similarly, a copper plate was molded into a disk shape having a thickness of 0.5 mm and a diameter of 24 mm, and this copper plate was punched out with a press to form a U-shaped through hole in the center. The through hole was processed so that the midpoint of the straight line connecting the two U-shaped ends and the end of the curved portion was the center of the disk-shaped current collector terminal plate. The distance between the two U-shaped tips is 5 mm, the distance from the midpoint of the straight line connecting the two tips to the tip of the R portion is 5 mm, and the width of the U-shaped through hole is 1 mm.

(5) Production of electrode group The positive electrode current collector terminal plate is brought into contact with the front end portion of the current collector plate exposed portion of the positive electrode plate disposed at one end of the electrode structure, and the front end portion and the positive electrode current collector terminal plate are subjected to TIG welding. And joined. TIG welding was performed at a current value of 150 A and a welding time of 100 ms. In addition, TIG welding was performed with the inside of the electrode structure in a reduced pressure state of 600 hPa.

  Next, the negative electrode current collector terminal plate was brought into contact with the tip portion of the current collector exposed portion of the negative electrode plate arranged at the multi-end of the electrode structure, and the tip portion and the negative electrode current collector terminal plate were joined by TIG welding. TIG welding was performed at a current value of 200 A and a welding time of 50 ms. In addition, TIG welding was performed with the inside of the electrode structure in a reduced pressure state of 800 hPa.

(6) Production of Cylindrical Lithium Ion Secondary Battery The electrode group obtained above was inserted into a cylindrical battery can whose one end in the longitudinal direction was opened. Thereafter, the negative electrode current collector terminal plate was resistance-welded to the bottom inner wall of the battery can. Subsequently, the other end of the aluminum positive electrode lead attached to the positive electrode current collector terminal plate was laser welded to the sealing plate. At this time, a voltage of 500 V was applied between the positive electrode current collector terminal plate and the negative electrode current collector terminal plate, the insulation resistance of the electrode group was measured, and the electrode group of 50 MΩ or less was determined to be poorly insulated.

  Subsequently, after heating and drying the battery can, injecting a non-aqueous electrolyte into the battery can, the sealing plate was fitted into the opening of the battery can with the gasket attached to the peripheral edge of the sealing plate. The battery can was sealed by crimping the open end. Thus, a cylindrical lithium ion secondary battery of the present invention having a diameter of 26 mm and a height of 65 mm was produced. This battery had a design capacity of 2600 mAh.

The non-aqueous electrolyte was prepared by mixing ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 1 as a non-aqueous solvent, and lithium hexafluorophosphate (LiPF ₆ , solute) 1 A solution dissolved at a rate of 2 mol / liter was used.

(Example 2)
When joining the negative electrode current collector terminal plate to the electrode structure, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the inside of the electrode structure was not put under reduced pressure.
(Example 3)
A lithium ion secondary battery was produced in the same manner as in Example 1 except that when the positive electrode current collector terminal plate was joined to the electrode structure, the inside of the electrode structure was not put under reduced pressure.
(Comparative Example 1)
When joining the positive electrode current collector terminal plate and the negative electrode current collector terminal plate to the electrode structure, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the inside of the electrode structure was not put under reduced pressure.

(7) Evaluation of bonding strength of current collecting terminal plate Electrode groups prepared in Examples 1 to 3 and Comparative Example 1 (a positive current collecting terminal plate and a negative current collecting terminal plate joined to an electrode structure) Ten pieces were used, and a tensile test was performed to measure the bonding strength of the positive electrode current collector terminal plate and the negative electrode current collector terminal plate. A tensile tester (trade name: Autograph AG-IS, manufactured by Shimadzu Corporation) was used for the test. The electrode terminal group was pulled at a speed of 1 mm / min until the current collector terminal plate was completely removed, and the maximum value at that time was used as data.
Table 1 shows the tensile strength of the positive electrode (positive electrode current collector terminal plate) and the negative electrode (negative electrode current collector terminal plate).

  From Table 1, it was found that the battery of the example had stronger bonding strength of the current collector terminal plate and less variation in strength than the battery of the comparative example. This is considered to indicate that the pressure treatment during TIG welding deepened the penetration into the electrode plate side, and the current collector exposed portion and the current collector terminal plate were firmly joined in a wider range. . In general, the tensile strength of the negative electrode is higher than that of the positive electrode because aluminum is used for the positive electrode current collector plate and copper is used for the negative electrode current collector plate. Conceivable.

  The tensile strength on the positive electrode side is greatly improved in the example compared to the comparative example. In Example 3 and Comparative Example 1, since the specific gravity of aluminum, which is a raw material for the positive electrode current collector terminal plate, is light and no pressure reduction treatment is performed, even if the current collector terminal plate is melted by TIG welding, the current collector exposed portion side It is thought that it is hard to sag. On the other hand, when the decompression process is performed as in Examples 1 and 2, it is considered that the amount of sagging increases even with aluminum having a low specific gravity, and as a result, the bonding area also increases.

  As an effect of reducing the pressure at the time of TIG welding on the negative electrode side, in addition to increasing the welding strength, it can be mentioned that the variation in welding strength is suppressed to be very small as compared with the case where the pressure reducing treatment is not performed. Copper is a metal whose specific gravity is originally large, so that when it is melted, the sag increases. However, since the current collector exposed portion is positioned vertically downward, it may be repelled by the tip portion of the current collector exposed portion, and the bonding strength is considered to be unstable. On the other hand, the molten metal is forced to sag to the current collector exposed portion side by the method of the present invention, and it is considered that the bonding strength is stabilized.

(8) Initial charging / discharging About the battery obtained in Examples 1-3 and Comparative Example 1, the following initial charging / discharging of (a)-(d) was repeated 3 times at room temperature.
(A) Charging until the battery voltage reaches 4.2V at a constant current of 650 mA (b) No load for 20 minutes (c) Discharging until the battery voltage reaches 3.0 V at a constant current of 650 mA (c) 20 minutes no load

(9) Aging The batteries obtained in Examples 1 to 3 and Comparative Example 1 were subjected to the above initial charge / discharge, and then the above charge (a) was performed once again to bring the battery into a charged state. The battery was aged by being left for 7 days in an environment at a temperature of 45 ° C.

(10) Battery evaluation (initial capacity)
The battery after aging was allowed to stand for 10 hours in an environment of 25 ° C., and then charged and discharged with the following (e) to (h) as one cycle, and the discharge capacity at the third cycle was defined as the battery capacity.
(E) Discharge until battery voltage reaches 3.0 V at a constant current of 650 mA (f) No load for 20 minutes (g) Charge until battery voltage reaches 4.2 V at a constant current of 650 mA (h) 20 minutes No load condition

(DC-IR)
The batteries obtained in Examples 1 to 3 and Comparative Example 1 were charged by 60% of the battery capacity by constant current charging of 650 mA. This was left for 10 hours in an environment of 25 ° C., and then charged and discharged at a constant current according to the following procedures (i) to (t). When the battery voltage fell below 2.0V during discharge, the test was terminated and no further discharge was performed.

(I) Discharge for 10 seconds at 1 hour rate (2.6A), then no load for 30 seconds (j) Charge for 10 seconds at 1 hour rate (2.6A), then no load for 30 seconds (k) 1 / 2 hour rate (5.2A) 10 seconds discharge, then 30 seconds no load condition (l) 1/2 hour rate (5.2A) 10 seconds charge, then 30 seconds no load condition (m) 1 Discharged for 10 seconds at / 5 hour rate (13A), then unloaded for 30 seconds (n) Charged for 10 seconds at 1/5 hour rate (13A), then unloaded for 30 seconds (o) 1/10 hour rate (26A) 10 seconds discharge, then 60 seconds unloaded condition (p) 1/5 hour rate (13A) 20 seconds charged, then 60 seconds unloaded condition (q) 1/20 hour rate (52A) 10 seconds of discharge, then 60 seconds of no load (r) 1/5 hour rate (13A Charged for 40 seconds, then unloaded for 60 seconds (s) discharged for 10 seconds at 1/30 hour rate (78A), then unloaded for 60 seconds (t) 60 seconds at 1/5 hour rate (13A), No load for 60 seconds

In the discharge under the above-described conditions, the voltage 10 seconds after the current was applied at each current value was read to create a current-voltage characteristic (IV characteristic) diagram. The slope of the graph of this IV characteristic diagram was DC-IR. Table 2 shows the initial capacity and DC-IR value of each 10 cells.

  From Table 2, it was found that the batteries of Examples 1 to 3 had the same initial capacity and no difference compared to the battery of Comparative Example 1, but the DC-IR was reduced. This is considered to be due to the effect of reducing the electrical resistance at the interface by increasing the bonding area between the current collector terminal plate and the current collector exposed portion by reducing the pressure during TIG welding. Since Example 2 and Example 3 also have lower DC-IR than Comparative Example 1, even if the production method of the present invention is applied to only one of the positive electrode and the negative electrode, it is effective for reducing the resistance. It is clear that

  The electrode group for secondary batteries obtained by the production method of the present invention has a current collecting structure suitable for large current charge / discharge. Therefore, the secondary battery including the electrode group for the secondary battery is useful as, for example, an electric power tool that requires high output, a driving power source for an electric vehicle, a large-capacity backup power source, a power storage power source, and the like. .

It is drawing which simplifies and shows the structure of an electrode structure. FIG. 1A is a plan view of the positive electrode plate. FIG. 1B is a plan view of the negative electrode plate. FIG.1 (c) is a perspective view of an electrode structure. It is a perspective view which shows an example of an electrode connection process. It is a perspective view which shows the structure of a positive electrode current collection terminal plate. It is sectional drawing which shows the contact state of the front-end | tip part of an electrical power collector exposure part, and a positive electrode current collection terminal plate. It is sectional drawing which shows the joining state of the front-end | tip part of an electrical power collector exposure part, and a positive electrode current collection terminal plate. It is a perspective view which shows the structure of a negative electrode current collection terminal plate. It is a longitudinal cross-sectional view which simplifies and shows the structure of the secondary battery which is one of the embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Secondary battery 2 Electrode group 3 Sealing plate 4 Gasket 5 Battery can 10 Electrode structure 11 Positive electrode plate 12a, 16a Current collector exposed part 15 Negative electrode plate 20 Depressurizer 26 Welding base 29 Lifting means 30 Positive electrode current collecting terminal plate 35 Negative current collector terminal board

Claims (7)

An electrode assembly producing step for producing an electrode assembly in which the current collector exposed portion of the positive electrode plate is disposed at one end and the current collector exposed portion of the negative electrode plate is disposed at the other end;
The current collector terminal plate is brought into contact with the current collector exposed portion of at least one electrode plate selected from the positive electrode plate and the negative electrode plate, and at least the contact portion of the current collector terminal plate with the current collector exposed portion is melted. A manufacturing method of an electrode group for a secondary battery including an electrode connecting step of drawing a molten portion toward the electrode plate and connecting the electrode plate and the current collector terminal plate. The manufacturing method of the electrode group for secondary batteries of Claim 1 which fuse | melts the contact part to the collector exposed part at least of a collector terminal board by arc welding.   The manufacturing method of the electrode group for secondary batteries of Claim 1 or 2 which draws in the molten part of a current collection terminal plate to the electrode plate side by making the inside of an electrode structure into a pressure-reduced state.   The manufacturing method of the electrode group for secondary batteries as described in any one of Claims 1-3 by which the through-hole of the thickness direction is formed in the current collection terminal board.   The method for producing an electrode group for a secondary battery according to any one of claims 1 to 3, wherein the positive electrode current collector terminal plate is made of a metal having a specific gravity equal to or smaller than copper.   The secondary battery containing the electrode group for secondary batteries manufactured by the manufacturing method of the electrode group for secondary batteries as described in any one of Claims 1-5.   The secondary battery according to claim 6, which is a lithium ion secondary battery or a nickel metal hydride storage battery.