JP2007324015A - Secondary battery and manufacturing method thereof - Google Patents

Abstract

The present invention provides a secondary battery having a current collecting structure with small resistance and excellent reliability that enables charging and discharging with a large current at a high output.
A positive electrode plate having a positive electrode mixture coated portion 1b on a positive electrode current collector and a positive electrode mixture uncoated portion 1a provided at one end in the width direction, and a negative electrode mixture on the negative electrode current collector. A negative electrode plate 2 having a negative electrode mixture uncoated portion 2 a provided at one end in the width direction with the coating portion 2 b, and a negative electrode mixture coating of at least the positive electrode mixture coated portion 1 b of the positive electrode plate 1 and the negative electrode plate 2. Cutting edge shape smaller than the width of the electrode group 4 constituted by winding the separator 3 provided facing the portion 2b in the longitudinal direction, and the positive electrode mixture uncoated portion 1a and the negative electrode mixture uncoated portion 2a A positive electrode current collecting member 10 and a negative electrode current collecting member 11 each having a protruding portion 12a, and the protruding portion 12a of the positive electrode current collecting member 10 and the negative electrode current collecting member 11, the positive electrode mixture uncoated portion 1a, and It connects and comprises via the notch provided in the electrode group 4 of the negative electrode mixture uncoated part 2a.
[Selection] Figure 1

Description

  The present invention relates to a lithium ion secondary battery with high output, and particularly relates to a current collecting structure that is low resistance and suitable for large current charge / discharge.

  In recent years, with the reduction in size and weight of various electronic devices, a secondary battery serving as a driving power source has been developed as one of important key devices. Among them, secondary batteries such as nickel metal hydride storage batteries and lithium-ion secondary batteries are lightweight, compact, and have high energy density, so power supplies for driving electric vehicles and power tools from consumer devices such as mobile phones It is deployed in various applications. Recently, in particular, lithium ion secondary batteries have been attracting attention as driving power sources, and development has been actively promoted toward higher capacity and higher output.

  A battery used as a power source for driving requires a large output current, and a battery in which a device structure, particularly a current collecting structure, has been devised has been proposed.

  For example, to obtain a large output current, the electrode area can be increased, and a positive electrode plate coated with a positive electrode mixture on a positive electrode current collector and a negative electrode plate coated with a negative electrode mixture on a negative electrode current collector are opposed to each other through a separator. A wound electrode group configuration is used. The electrode group is housed in a cylindrical battery container that also serves as one battery terminal, and the opening of the battery container is sealed with a sealing plate that also serves as the other battery terminal, whereby a secondary battery is manufactured. In general, the negative electrode current collector is electrically connected to the battery container, and the positive electrode current collector is electrically connected to the sealing plate, either directly or via a current collecting member such as a current collecting plate, a current collecting tab or a lead plate. It is connected to the.

  Furthermore, the current collector is connected to the battery container or the sealing plate with a low resistance, and a current flows uniformly over the entire surface of the positive electrode plate and the negative electrode plate, and the volume of the connecting portion in the battery is made as small as possible. A current collecting structure is required.

  Conventionally, a secondary battery having a tabless structure as described below has been disclosed as a current collecting structure that satisfies such requirements (see, for example, Patent Document 1 and Patent Document 2).

  That is, in the secondary battery described in Patent Document 1, the positive electrode current collector and the negative electrode current collector are provided with cutout portions at a plurality of positions, and the edge portions are formed by bending the plate members of the cutout portions with respect to the plane. is doing. And it has the current collection structure which welded this bent edge part with the end surface of the current collecting strip protruded from the both ends of the electrode group.

  Moreover, the secondary battery described in Patent Document 2 is provided with a plurality of rectangular cutout portions extending from the vicinity of the center of the current collector plate to the outer edge portion, and downward rib-shaped protrusions on the edge portions of the cutout portion. A piece is formed. And it has the current collection structure which made this rib-shaped projection piece bite into the end surface part of the electrical power collector which protruded from the both ends of the electrode group, and was welded.

  By these, the reactive current at the time of resistance welding with the current collecting strip and current collector of the electrode group connected with each current collecting member is made small, and it is supposed that it can weld efficiently and uniformly.

In addition, in this specification, when it is not necessary to show a positive electrode and a negative electrode independently, it describes as a mixture coating part, a mixture uncoated part, a collector, and a current collection member. There is a case.
JP-A-10-188997 Japanese Patent Laid-Open No. 11-167914

  However, Patent Document 1 and Patent Document 2 relate to a current collecting structure of an alkaline storage region, and the current collector strips of the electrode group connected to each current collecting member and the plate thickness of the current collector have about 200 μm. Yes. Therefore, when resistance collecting is performed between the current collecting member and the current collector strip and the current collector of the electrode group, the resistance to pressurization is large, and the current collector strip of the electrode group and the current collector are not easily bent.

  However, in a lithium ion secondary battery or the like, the volume occupied by each current collector needs to be as small as possible in order to achieve high capacity. A thin metal foil of about micron is used.

  Therefore, the current collector which is each mixture uncoated part protruding from the electrode group is weak in mechanical strength, and the mixture uncoated part is bent by the pressure applied when connecting the current collecting member, There was a problem that distortion occurred in the mixture layer of the mixture coating portion, and the mixture was peeled off or damaged from the current collector.

  In addition, when the current collecting members shown in Patent Document 1 and Patent Document 2 are connected to each current collector protruding from the electrode group, the current collector cannot be uniformly contacted due to bending of the current collector. Therefore, there is a problem that reliable and uniform welding cannot be performed. As a result, the connection resistance was increased and large current charge / discharge characteristics could not be obtained.

  The present invention solves the above-described problem, prevents the current collector that is an uncoated part of the electrode group from being bent, and ensures uniform current connection between the current collector and the current collector. It aims at providing the secondary battery which implement | achieved discharge.

  In order to achieve the above object, the secondary battery of the present invention comprises a positive electrode plate having a positive electrode mixture coated part and a positive electrode mixture uncoated part on a positive electrode current collector, and a negative electrode compound on a negative electrode current collector. An electrode group in which a negative electrode plate having an agent coating portion and a negative electrode mixture uncoated portion, a positive electrode mixture coating portion and a separator provided opposite to the negative electrode mixture coating portion, Positive electrode current collector member and negative electrode current collector member having a blade-shaped protrusion smaller than the width of the uncoated agent portion and negative electrode mixture uncoated portion, and uncoated positive electrode mixture portion and negative electrode mixture uncoated portion It has the structure connected through the notch provided in the electrode group of the part.

  Thereby, even if the pressurization at the time of welding is added to the mixture uncoated part protruded from the electrode group, bending of a collector can be prevented. Moreover, since the notch part is previously provided in the collector which is a mixture uncoated part, a uniform connection with the protrusion part of a current collection member is obtained.

  According to the secondary battery and the manufacturing method thereof of the present invention, charging and discharging at a large current is realized by reliably connecting the current collecting member and the current collector, which is an uncoated part of the electrode group, by welding. A secondary battery is obtained.

  A first invention of the present invention includes a positive electrode plate having a positive electrode mixture coated portion and a positive electrode mixture uncoated portion provided at one end in the width direction on the positive electrode current collector, and a negative electrode on the negative electrode current collector. A negative electrode plate having a negative electrode mixture uncoated portion provided at one end in the width direction with the mixture coated portion, and at least facing the positive electrode mixture coated portion of the positive electrode plate and the negative electrode mixture coated portion of the negative electrode plate. A positive electrode current collector having an electrode group formed by winding a separator provided in the longitudinal direction and a blade-shaped protrusion that is smaller than the width of the positive electrode mixture uncoated part and the negative electrode mixture uncoated part At least a member and a negative electrode current collecting member, and a cut portion provided in a protruding portion of the positive electrode current collecting member and the negative electrode current collecting member, and an electrode group of the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion It has the structure connected via this.

  Accordingly, it is possible to prevent the uncoated portion from being bent due to pressurization during welding and to achieve uniform connection between the protruding portion of the current collecting member and the current collector. As a result, a secondary battery capable of charging and discharging a large current with a small connection resistance is obtained.

  According to a second aspect of the present invention, in the first aspect, the brazing material is provided at least at the position of the edge shape of the protrusion.

  As a result, the area where the brazing material melts and spreads at the cut portion of the mixture uncoated portion is increased, so that a connection with lower resistance can be realized. Also, since the brazing material melts at a relatively low temperature, a reliable secondary battery is obtained without affecting the separator with heat.

  The third invention of the present invention is the first invention and the second invention, wherein the positive electrode mixture coated portion, the positive electrode mixture uncoated portion, the negative electrode mixture coated portion, the negative electrode mixture uncoated portion, A reinforcing layer is provided between the boundary portion of the electrode and the cut portions of the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion.

  Thereby, the secondary battery excellent in reliability can be obtained by reliably preventing the uncoated portion from being bent by pressurization during welding.

  According to a fourth aspect of the present invention, there is provided a step of forming a positive electrode plate having a positive electrode mixture coated portion and a positive electrode mixture uncoated portion provided at one end in the width direction on a positive electrode current collector; Forming a negative electrode plate having a negative electrode mixture coated portion and a negative electrode mixture uncoated portion provided at one end in the width direction on the body, and at least a positive electrode mixture coated portion of the positive electrode plate and a negative electrode of the negative electrode plate A step of winding the separator provided facing the mixture coating portion in the longitudinal direction to form an electrode group, and a cut portion in the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion of the electrode group Forming a positive electrode current collector and a negative electrode current collector member with protrusions and notches having a blade-shaped protrusion smaller than the width of the positive electrode mixture uncoated part and the negative electrode mixture uncoated part, And a step of connecting the two.

  This prevents bending of the uncoated part due to the pressurization during welding and realizes a uniform connection between the ridges of the current collector and the current collector, resulting in low connection resistance and high current charge / discharge A secondary battery that enables the above can be manufactured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As the secondary battery, a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery will be described as an example. Further, the present invention is not limited to the contents described below as long as it is based on the basic characteristics described in the present specification.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view of a secondary battery according to Embodiment 1 of the present invention. 2A is a development view of the positive electrode plate used in the embodiment, and FIG. 2B is a development view of the negative electrode plate used in the embodiment. 3A is a perspective view of an electrode group used in the embodiment, and FIG. 3B is a partial enlarged view of the AA line in FIG. 3A. Further, FIG. 4A is a plan view of a current collecting member used in the embodiment, and FIG. 4B is a cross-sectional view taken along line AA in FIG.

  In FIG. 1, a cylindrical nonaqueous electrolyte secondary battery (hereinafter referred to as “battery”) includes a positive electrode plate 1 in which a positive electrode mixture is applied to a positive electrode current collector made of, for example, an aluminum foil, and a copper foil, for example. A negative electrode plate 2 coated with a negative electrode mixture on a negative electrode current collector, and a separator 3 made of a microporous film made of polypropylene resin having a thickness of 25 μm, for example, between the positive electrode plate 1 and the negative electrode plate 2 The electrode group 4 wound in the shape is provided.

  Here, the positive electrode plate 1 includes a positive electrode mixture uncoated portion 1 a and a positive electrode mixture coated portion provided in a band shape in the longitudinal direction from one end in the width direction of the positive electrode current collector as shown in FIG. 1b is provided.

  Moreover, as shown in FIG. 2 (b), the negative electrode plate 2 includes a negative electrode mixture uncoated portion 2a and a negative electrode mixture coated portion 2b provided in a band shape in the longitudinal direction from one end in the width direction of the negative electrode current collector. Is provided. In addition, the positive electrode mixture uncoated portion 1a and the negative electrode mixture uncoated portion 2a are portions where the positive electrode current collector and the negative electrode current collector are exposed. Represents.

  At this time, as shown in FIG. 3A, the electrode group 4 includes at least a separator 3 interposed between the positive electrode mixture coating portion 1 b of the positive electrode plate 1 and the negative electrode mixture coating portion 2 b of the negative electrode plate 2. Thus, in the width direction, the positive electrode mixture uncoated portion 1a and the negative electrode mixture uncoated portion 2a are wound in a state of protruding from the edge of the separator 3 in opposite directions.

  Moreover, as shown in FIG.3 (b), the electrode group 4 is provided with the notch part 9 from the end surface of the positive electrode mixture uncoated part 1a and the negative electrode mixture uncoated part 2a. Here, the cut portion 9 needs to be provided so as not to reach the positive electrode mixture coating portion 1 b and the negative electrode mixture coating portion 2 b of the electrode group 4.

  Then, as shown in FIG. 4A, the positive electrode current collecting member 10 and the negative electrode current collecting member 11 having protrusions 12 a provided corresponding to the positions of the cut portions 9 of the electrode group 4 are brought into contact with each other. Then, in the state of contact, the current collectors and the uncoated portions of each mixture and the respective uncoated portions are formed by, for example, resistance welding through the notch portions 12 formed in the positive electrode current collector member 10 and the negative electrode current collector member 11. The current collecting member is connected to constitute an electrode group unit. Here, the protrusion 12a provided on the positive electrode current collecting member 10 and the negative electrode current collecting member 11 has a cutting edge shape at the tip so that it can be attached to the notch 9 provided on the electrode group 4 with low pressure, It is provided smaller (narrower) than at least the width of each mixture uncoated portion.

  Furthermore, since the notch part 9 can be formed with the jig | tool of the same shape as each current collection member, the notch part 9 can be provided in uniform height with low pressurization. Thereby, the protrusion 12a of the positive electrode current collecting member 10 and the negative electrode current collecting member 11, and the current collectors which are the positive electrode mixture uncoated portion 1a and the negative electrode mixture uncoated portion 2a are in contact with each other on a uniform surface. it can. As a result, each current collector can be prevented from being bent at the time of resistance welding between each current collector and the current collector. Furthermore, uniform electrical connection can be reliably obtained by uniform contact.

  In the above description, the example in which the protrusion 12a is brought into contact with the notch 9 has been described. However, when there is no problem in bending of each current collector, the protrusion of the current collector may be pushed into the notch. Thereby, the uniformity of contact between the current collector and the current collecting member is further improved, and a more reliable connection can be obtained.

  Further, an electrode group unit including the positive electrode current collecting member 10 and the negative electrode current collecting member 11 is built in the battery container 13, the negative electrode current collecting member 11 is provided at the bottom of the battery container 13, and the positive electrode current collecting member 10 is provided with the insulating plate 14. It is provided in between and connected to the sealing plate 16 via the positive electrode lead 15. Then, a nonaqueous electrolyte (not shown) is injected into the battery container 13 and the sealing plate 16 is caulked through the gasket 17.

  According to the above configuration, the positive electrode current collector that is the positive electrode mixture uncoated portion and the negative electrode current collector that is the negative electrode mixture uncoated portion are uniformly connected to the positive electrode current collector member and the negative electrode current collector member. Thus, a secondary battery that achieves charging and discharging with a large current can be obtained. In addition, since the blade-shaped ridges can be brought into contact with the cut portions or evenly contacted with low pressure, the current collector can be prevented from being bent.

  According to Embodiment 1 of the present invention, the positive electrode current collector shown by the positive electrode mixture uncoated part and the negative electrode current collector shown by the negative electrode mixture uncoated part, the positive electrode current collecting member, and the negative electrode current collecting member, Therefore, a secondary battery suitable for charging / discharging a large current can be realized. It is done. In addition, since the blade-shaped protrusions can be brought into contact with the cut portions or evenly contacted with low pressure, the current collector can be prevented from being bent, and a secondary battery with excellent reliability can be obtained.

  Here, as the positive electrode current collector, an aluminum foil or a perforated body made of a metal thin foil can be used. Moreover, aluminum etc. are used for a positive electrode current collection member.

  The positive electrode mixture includes a positive electrode active material, a conductive agent, and a binder. Specifically, as the positive electrode active material, composite oxides such as lithium cobaltate, lithium nickelate, and lithium manganate, and modified products thereof can be used. As a modified body, elements such as aluminum and magnesium can be contained. Further, cobalt, nickel and manganese elements can be mixed and contained. As the conductive agent, graphite, carbon black, metal powder or the like that is stable under the positive electrode potential is used. Furthermore, as the binder, polyvinylidene fluoride (PVDF) / polytetrafluoroethylene (PTFE) which is stable under a positive electrode potential is used.

  On the other hand, the negative electrode current collector can be a copper foil or a copper perforated body made of a metal thin foil. Moreover, copper, nickel, a nickel plating steel plate, etc. are used for a negative electrode current collection member.

  And a negative electrode mixture consists of a negative electrode active material, a electrically conductive agent, and a binder. Specifically, as the negative electrode active material, natural graphite, artificial graphite, aluminum, various alloys mainly composed thereof, metal oxides such as tin oxide, and metal nitrides can be used. As the conductive agent, graphite, carbon black, metal powder, etc. that are stable under a negative electrode potential are used. Further, as the binder, styrene-butadiene copolymer rubber (SBR) / carboxymethyl cellulose (CMC) which is stable under a negative electrode potential is used.

As the non-aqueous electrolyte, a non-aqueous electrolyte solution or a gel electrolyte in which a non-aqueous electrolyte solution is included in a polymer material is used. The non-aqueous electrolyte solution includes a non-aqueous solvent, a solute, and an additive. As the solute, lithium salts such as lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ) are used. As the non-aqueous solvent, it is preferable to use cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, but it is not limited thereto. In addition, a non-aqueous solvent may be used individually by 1 type, but may combine 2 or more types. As the additive, vinylene carbonate, cyclohexylbenzene, diphenyl ether, or the like is used.

  Hereinafter, a method for manufacturing the secondary battery according to Embodiment 1 of the present invention will be described. In particular, the electrode group unit of the secondary battery in Embodiment 1 of the present invention will be described in detail with reference to FIG. FIG. 5 is a fragmentary process cross-sectional view illustrating the method for manufacturing the electrode group unit of the secondary battery.

  First, for example, lithium cobaltate as a positive electrode active material, graphite as a conductive agent and polyvinylidene fluoride (PVDF) as a binder are kneaded to prepare a positive electrode mixture, and a positive electrode current collector such as an aluminum foil Apply to. At this time, the positive electrode mixture uncoated portion 1a is formed in the longitudinal direction at one end in the width direction of the positive electrode current collector to produce the positive electrode plate 1.

  Next, for example, natural graphite is used as the negative electrode active material, graphite is used as the conductive agent, and styrene-butadiene copolymer rubber (SBR) is used as the binder to prepare a negative electrode mixture. Apply to negative electrode current collector. At this time, the negative electrode mixture uncoated portion 2a is formed in the longitudinal direction at one end in the width direction of the negative electrode current collector to produce the negative electrode plate 2.

  Next, the positive electrode plate 1 and the negative electrode plate 2 are separated from each other in the width direction in a direction opposite to the positive electrode mixture uncoated portion 1a and the negative electrode mixture uncoated portion 2a through a separator made of a microporous film such as polyolefin. And electrode group 4 is formed.

  Hereinafter, a method for manufacturing the electrode group unit will be described with reference to FIGS.

  First, as shown in FIG. 5 (a), the notch forming treatment is performed on each current collector, which is the positive electrode mixture uncoated portion 1a and the negative electrode mixture uncoated portion 2a, which protrude from the electrode group 4 in opposite directions. The tool 20 is pressed to form a cut portion 9 as shown in FIG. Here, it is preferable that the notch | incision part formation jig | tool 20 has the same shape as the positive electrode current collection member and negative electrode current collection member which are described below, for example. Thereby, while being able to form a notch part by low pressurization, since the position of a notch part can be made the same, incorporation of each current collection member becomes easy. Specifically, the notch forming jig 20 includes a convex portion 21 having a taper of 25 ° from the tip and a width of 50 μm.

  Next, as shown in FIG.5 (c), the positive electrode current collection member 10 which has the protrusion part 12a of the same shape as the notch | incision part 9, and the protrusion part 12a of the negative electrode current collection member 11 are each mixture uncoated. It arrange | positions according to the position of the notch part 9 of the electrical power collector shown by a part.

  Next, as shown in FIG. 5 (d), the protruding portion 12 a of each current collecting member is fitted into the cut portion 9. In this case, as shown in FIG. 5E, each current collecting member may be pressurized and pushed into the cut portion.

  And in the state of FIG.5 (d) or FIG.5 (e), an electric current is sent through the protrusion part 12a which opposes by the notch part 12 shown to Fig.4 (a), and each current collection member and each mixture Resistance welding is performed on the current collector indicated by the uncoated portion. The electrode group unit is manufactured through the above steps.

  Next, the electrode group unit provided with each current collecting member is inserted into the battery container 13 made of, for example, iron, nickel, stainless steel, and the negative electrode current collecting member 11 is resistance-welded to the bottom of the battery container 13. Similarly, the sealing plate 16 that also serves as the positive electrode terminal and the positive electrode current collector 10 are connected by laser welding.

Next, a nonaqueous electrolyte composed of a nonaqueous solvent such as ethylene carbonate and a solute such as lithium hexafluorophosphate (LiPF ₆ ) is injected into the battery container 13 under reduced pressure.

  Next, a sealing plate 16 that also serves as a positive electrode terminal is inserted into the battery container 13, and the secondary battery is manufactured by, for example, crimping the sealing plate 16 and the periphery of the battery container 13 via a resin gasket 17. it can.

  In the above description, the example in which the cut portion is formed using the cut portion forming jig has been described. However, the present invention is not limited to this. For example, the cut portion may be formed using a laser. In this case, it is preferable to form the current collector melted by the laser so that it does not remain in the electrode group, for example, while being sucked or held downward so as to fall by its own weight.

(Embodiment 2)
FIG. 6 is a cross-sectional view of a current collecting member of the secondary battery according to Embodiment 2 of the present invention. Here, the second embodiment is different from the first embodiment in that a brazing material is provided at least at the tip position of the protruding portion of the current collecting member, and the other configurations are the same.

  That is, as shown in FIG. 6, a brazing material 25 made of, for example, an aluminum alloy was formed on the protrusion 12 a of the positive electrode current collector 10. A brazing material 25 made of, for example, a nickel alloy was formed on the protrusion 12a of the negative electrode current collecting member 11. Then, the positive electrode current collector 10 and the positive electrode current collector indicated by the positive electrode mixture uncoated portion 1a are connected to the negative electrode current collector 11 and the negative electrode mixture uncoated portion 2a via the brazing material 25. The electrode group unit is manufactured by, for example, resistance welding the electric body.

  Then, the electrode group unit is configured as a secondary battery by the same method as in the first embodiment.

  According to the second embodiment of the present invention, since the brazing material melts and spreads at the cut portions of the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion, the connection area increases, and the connection with low resistance is further achieved. Is obtained. In addition, since the brazing material melts at a relatively low temperature, the influence of heat on the separator can be reduced, so that a highly reliable secondary battery can be realized.

  Below, the formation method of the brazing material 25 is demonstrated.

  First, the oil component of the positive electrode current collecting member 10 is washed and removed, and a required amount of an aluminum alloy φ0.5 mm wire is cut and installed at a required location, for example, at a bending angle of 90 ° of the protrusion 12a.

  Next, the positive electrode current collector 10 provided with the brazing material 25 is heated in a vacuum furnace at 615 ° C. for about 11 minutes and reflowed.

  And after reflowing, while pressing the positive electrode current collection member 10 and correcting the curvature, the reflow part of the brazing material 25 is smoothed and the positive electrode current collection member 10 is obtained.

  Further, the oil content of the negative electrode current collecting member 11 is washed and removed, and a required amount of a slurry of nickel alloy powder with a binder is applied to a required portion, for example, a position at a bending angle of 90 ° of the protrusion 12a.

  Next, the negative electrode current collector 11 coated with the brazing material 25 is heated at 450 ° C. to 800 ° C. for about 30 minutes to 10 minutes in a vacuum furnace and reflowed.

  And after reflowing, while negative electrode current collection member 11 is pressed and the curvature is corrected, the reflow part of brazing material 25 is smoothed and negative electrode current collection member 11 is obtained.

  In the present embodiment, the example in which the brazing material is reflowed to the positive electrode current collecting member 10 and the negative electrode current collecting member 11 has been described, but the present invention is not limited thereto. For example, the brazing material may be attached using heat welding or an adhesive. Further, an alloy of a material close to an aluminum brazing sheet or a brazing material may be formed by an electroless plating method or the like.

(Embodiment 3)
FIG. 7 is a schematic cross-sectional view of the secondary battery according to Embodiment 3 of the present invention. FIG. 8A is a development view of the positive electrode plate used in the embodiment, and FIG. 8B is a development view of the negative electrode plate used in the embodiment. Here, the third embodiment is different from the first embodiment in that a reinforcing layer is provided between the boundary between the mixture coated portion and the mixture uncoated portion of each current collector and at least the cut portion. The other configurations are the same.

  That is, as shown to Fig.8 (a), between the boundary part 1c of the positive electrode mixture coating part 1b of the positive electrode plate 1, and the positive electrode mixture uncoated part 1a to at least a notch part (not shown). The reinforcement layer 30 is provided. Similarly, as shown in FIG. 8 (b), at least from the boundary portion 2c between the negative electrode mixture coated portion 2b and the negative electrode mixture uncoated portion 2a of the negative electrode plate 2 to a notch (not shown). In this configuration, the reinforcing layer 30 is provided. Here, the reinforcing layer 30 is preferably formed to a thickness that is the same as or thinner than the thickness of each mixture coating portion. Thereby, it is possible to improve the reliability by preventing the current collector from being bent while maintaining the battery characteristics without reducing the number of times the electrode group is wound.

  And the said positive electrode plate 1 and the negative electrode plate 2 are wound by the method similar to Embodiment 1, and an electrode group unit is comprised, and a secondary battery as shown in FIG. 7 is comprised.

  According to Embodiment 3 of the present invention, bending of the current collector shown in each mixture uncoated portion that is likely to occur due to pressurization during resistance welding between each current collector and each current collecting member by the reinforcing layer. A secondary battery that is reliably prevented and further excellent in reliability can be obtained.

  Hereinafter, a method for forming the reinforcing layer will be described.

  First, for example, an inorganic oxide filler such as alumina, a binder, and an appropriate amount of N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”) were kneaded to prepare a slurry for a reinforcing layer.

  Next, the obtained slurry is subjected to the following steps from the boundary portion of the positive electrode mixture uncoated portion 1a, the negative electrode mixture uncoated portion 2a with the positive electrode mixture coated portion 1b, and the negative electrode mixture coated portion 2b. After applying so that it may become the same thickness as the thickness of the positive mix application part 1b and the negative mix application part 2b between the notch parts formed by (2), it is made to dry and a reinforcement layer is formed.

  Specific examples in the embodiment of the present invention will be described below.

Example 1
Example 1 is an example in which Embodiment 1 is embodied.

(1) Production of positive electrode plate A positive electrode plate capable of inserting and extracting lithium ions was produced by the following method.

  First, 85 parts by weight of lithium cobaltate powder as a positive electrode mixture, 10 parts by weight of carbon powder as a conductive agent, and 5% of PVDF as an NMP solution of polyvinylidene fluoride (hereinafter referred to as “PVDF”) as a binder. Equivalent parts by weight were mixed.

  Next, the obtained mixture was applied to both sides of a positive electrode current collector of aluminum foil having a thickness of 15 μm and a width of 56 mm using a doctor blade method on a positive electrode mixture coating portion having a width of 50 mm, dried, and then rolled. A positive electrode plate having a thickness of 150 μm and a positive electrode mixture uncoated portion with a width of 6 mm was obtained.

(2) Production of negative electrode plate A negative electrode plate capable of inserting and extracting lithium ions was produced by the following method.

  First, 95 parts by weight of artificial graphite powder was mixed as a negative electrode mixture, and 5 parts by weight of PVDF was mixed with an NMP solution of PVDF as a binder.

  Next, the obtained mixture was applied to both sides of a negative electrode current collector of copper foil having a thickness of 10 μm and a width of 57 mm using a doctor blade method on a negative electrode mixture coating portion having a width of 52 mm, and dried, and then the negative electrode mixture The coated part was rolled to prepare a negative electrode plate having a thickness of 160 μm and a negative electrode mixture uncoated part having a width of 5 mm.

(3) Production of Electrode Group Microporous polypropylene resin having a width of 53 mm and a thickness of 25 μm so as to cover at least the positive electrode mixture coated part of the positive electrode plate produced as described above and the negative electrode mixture coated part of the negative electrode plate. A separator made of a film was placed oppositely and wound in a spiral shape. Then, it is wound in a spiral shape, and is pressed from the end surfaces of the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion protruding from both ends with a pressing force 2N using a notch forming jig. A taper-shaped cut portion having a thickness of 1 mm was formed to obtain an electrode group. At this time, as the notch forming jig, a jig having the same shape as the protruding portion of the current collecting member described below was used.

(4) Production of current collector The positive electrode current collector was produced by the following method.

  First, an aluminum plate having a thickness of 24 mm and a hole having a diameter of 7 mm in the central portion was punched out with a press to form a donut-shaped disk. Next, four notches were formed in a rectangular shape from the position not contacting the hole of the donut-shaped disk toward the outer peripheral edge. Then, the aluminum plate was bent at 90 ° with respect to the flat surface from the end face of the cutout portion to form a ridge portion having a height of 0.7 mm. Furthermore, the tip of the ridge portion was polished at an inclination of 25 ° with respect to the flat surface, and a positive electrode current collecting member with a thickness of 50 μm having a tip shape of the tip was produced.

  Moreover, the negative electrode current collection member was produced by the same method as the positive electrode current collection member using a copper plate having a thickness of 0.2 mm.

(5) Preparation of electrode group unit The notch part of the electrode group produced as described above and the protruding part of each current collecting member were aligned and connected by resistance welding to obtain an electrode group unit. At this time, the resistance welding conditions were as follows. In the case of the positive electrode current collector and the positive electrode current collector member, welding was performed at a pressure of 2 N at a voltage of 3.5 V, a current of 0.54 A, and a time of 5.0 ms. In the case of the negative electrode current collector and the negative electrode current collector member, welding was performed at a pressure of 3.5 N at a voltage of 5 V, a current of 0.85 kA, and a time of 5.0 ms.

(6) Production of battery As described above, the electrode group unit was inserted into a cylindrical battery container (material: iron / Ni plating, diameter 26 mm, height 65 mm) opened on only one side, and the battery container and electrode group unit were After the negative electrode current collecting member and the battery container were resistance welded, an insulating plate was disposed, and the positive electrode current collecting member and the sealing plate were laser welded via an aluminum positive electrode lead to obtain a battery container.

Next, ethylene carbonate and ethyl methyl carbonate are mixed at a volume ratio of 1: 1 as a non-aqueous solvent, and dissolved therein so that lithium hexafluorophosphate (LiPF ₆ ) is 1 mol / L as a solute. A non-aqueous electrolyte was prepared.

  Next, after the obtained battery container was dried by heating to 60 ° C. in a vacuum, 4.5 ml of the adjusted nonaqueous electrolyte was injected.

  Then, the sealing plate was squeezed and sealed with a battery container through a gasket to produce a cylindrical secondary battery having a diameter of 26 mm, a height of 65 mm, and a design capacity of 2600 mAh.

  This is sample 1.

(Example 2)
Example 2 is an example in which Embodiment 2 is embodied. And it is the same as that of Example 1 except having provided the brazing material in the protrusion part of the current collection member with the following method.

  First, an aluminum alloy φ0.5 mm wire was cut at 5 mg at a position at a bending angle of 90 ° of the protruding portion of the positive electrode current collecting member from which oil was washed and removed with ethanol.

  Next, the positive electrode current collecting member provided with the brazing material was heated in a vacuum furnace at 615 ° C. for about 11 minutes and reflowed.

  And after reflowing, the positive electrode current collection member was pressed, the curvature was corrected, and the reflow part of the brazing material was smoothed, and the positive electrode current collection member was obtained.

  Next, 5 mg of a negative electrode current collecting member in which oil was washed and removed with ethanol, for example, a nickel alloy powder made into a slurry with a binder was applied to the ridge.

  Then, the negative electrode current collecting member coated with the brazing material was heated in a vacuum furnace at 450 ° C. to 800 ° C. for about 30 minutes to 10 minutes and reflowed.

  Furthermore, after reflowing, the negative electrode current collecting member was pressed to correct warpage due to heating, and the reflow part of the brazing material was smoothed to obtain a negative electrode current collecting member.

  Further, a secondary battery was produced by the same method as in Example 1 using the obtained negative electrode current collector.

  This is Sample 2.

(Example 3)
Example 3 is an example in which the third embodiment is embodied. And it is the same as that of Example 1 except having provided the reinforcement layer in the positive electrode plate and the negative electrode plate.

  Hereinafter, a method for forming the reinforcing layer will be described.

  First, alumina having a median diameter of 0.3 μm, which is an inorganic oxide filler, and polyacrylonitrile-modified rubber binder BM-720H (manufactured by Nippon Zeon Co., Ltd., solid content: 8% by weight) at a weight ratio of 8: 3, an appropriate amount of NMP Together with a planetary mixer, a white reinforcing layer slurry was prepared.

  Next, the obtained slurry is placed on the positive electrode mixture uncoated portion to a width of 4 mm between the boundary portion with the positive electrode mixture coated portion and the cut portion formed in the positive electrode mixture uncoated portion. After coating with a thickness of 62.5 μm per side so as to be the same as the thickness of the agent-coated portion, it was dried at 100 ° C. for 2 minutes to produce a positive electrode plate having a reinforcing layer. Similarly, on the negative electrode mixture uncoated portion, a width of 4 mm between a boundary portion with the negative electrode mixture coated portion and a cut portion formed in the negative electrode mixture uncoated portion is formed with a thickness of 75 μm per side. A negative electrode plate having a reinforcing layer was prepared.

  Furthermore, a secondary battery was produced in the same manner as in Example 1 using the obtained positive electrode plate and negative electrode plate.

  This is designated as Sample 3.

(Comparative Example 1)
The positive electrode current collector member and the negative electrode current collector member ridges that are not formed with a notch in the positive electrode mixture uncoated part and the negative electrode mixture uncoated part of the wound electrode group, and the tip does not have a cutting edge shape A secondary battery manufactured in the same manner as in Example 1 is designated as Sample C1.

  Fifty secondary batteries each prepared as described above were prepared and evaluated as follows.

(Measurement of tensile strength)
In the production stage of each secondary battery, the tensile strength when each current collecting member and each current collector were connected was extracted and measured, for example, in accordance with JIS Z2241. Specifically, a gripping device having a shape suitable for the electrode group was attached to one of the tensile testers to hold the electrode group. And the holding device of the shape suitable for a current collection member was attached to the other side of a tension test machine, and the current collection member was hold | maintained. In this state, the tensile strength was defined as the load when the tensile welded part was released in the axial direction at a constant speed.

  As a result, any of the secondary batteries of Sample 1 to Sample 3 had a tensile strength of 20 N or more. This is due to the effect that uniform contact is realized by the cut portion and the blade-shaped protrusion, and resistance welding is performed uniformly.

  On the other hand, in sample C1, 3/5 pieces had a welded portion with a tensile strength of 10 N or less.

(Observation of current collector bent state)
In the production stage of each secondary battery, the connection state between each current collector and each current collector and the bent state of each current collector are observed by the cross section of the current collector indicated by each unmixed portion of the mixture did.

  As a result, almost no bending was observed in any of the secondary batteries of Sample 1 to Sample 3, and Sample 3 was not bent at all by the reinforcing layer. Further, no peeling or damage between each mixture in each mixture coating part and each current collector was observed. This is due to the effect of resistance welding performed at a low pressure and the effect of providing a reinforcing layer by the cut portion and the edge-shaped protrusion.

  On the other hand, in the sample C1, a large number of current collectors that were bent and peeled off or not connected to the current collecting member were observed.

(Measurement of battery internal resistance)
First, each secondary battery was charged to 4.2 V with a constant current of 1250 mA, and then charging and discharging for discharging to 3.0 V with a constant current of 1250 mA was taken as one cycle, and charging and discharging for 3 cycles were repeated.

  Thereafter, the internal resistance of the secondary battery was measured with an alternating current of 1 kHz, and the connection state was evaluated.

  As a result, the average internal resistance values of the secondary batteries of Sample 1 and Sample 3 were 10 mΩ, and the variation was about 10%. In sample 2, the average internal resistance value of the secondary battery was 9 mΩ, and the variation was about 5%. This is a result of realizing a uniform connection between each current collecting member and each current collector, and in particular, Sample 2 is due to an even more uniform connection obtained by enlarging the connection area by the brazing material. .

  On the other hand, the average internal resistance of sample C1 was 15 mΩ, and the variation was 30% or more.

(Fall evaluation)
Each secondary battery was subjected to a 10-cycle drop test with a single cycle of dropping in an upright state, an inverted state, and a side-standing state from a height of 60 cm as one cycle. Thereafter, the tested secondary battery was disassembled, and the connection state between each current collector and each current collector and the bending state of each current collector were observed.

  As a result, in any of the secondary batteries of Sample 1 to Sample 3, almost no bending or welding failure was observed, and in Sample 3, none. Moreover, neither peeling nor damage between each mixture and each current collector in each mixture coating part was observed. This is due to the effect of resistance welding performed at a low pressure and the effect of providing a reinforcing layer by the cut portion and the edge-shaped protrusion.

  On the other hand, in the sample C1, a large number of current collectors that were bent or peeled off and disconnected from the current collecting member were observed.

  In the above description, the configuration and the configuration procedure of the wound cylindrical lithium ion secondary battery have been described as examples. However, the present invention is not limited to this. For example, the same effect can be utilized for various types of wound batteries in which the current collector is thin and easily bent.

  In the present invention, charging and discharging with a large current can be realized by uniformly connecting each current collecting member and each current collector indicated by each uncoated part of the mixture with low resistance. Thus, it is useful as a battery for driving power tools, electric vehicles, and the like that require high output, which is expected to be in great demand in the future.

Schematic cross-sectional view of the secondary battery in Embodiment 1 of the present invention (A) Development view of positive electrode plate used in the embodiment (b) Development view of negative electrode plate used in the embodiment (A) Perspective view of electrode group used in same embodiment (b) AA line cross-sectional partial enlarged view of FIG. 3 (a) (A) Plan view of current collecting member used in the embodiment (b) AA line sectional view of FIG. 4 (a) Cross-sectional view of main steps for explaining a method for producing an electrode group unit of a secondary battery in the same embodiment Sectional drawing of the current collection member of the secondary battery in Embodiment 2 of this invention Schematic cross-sectional view of a secondary battery according to Embodiment 3 of the present invention (A) Development view of positive electrode plate used in the embodiment (b) Development view of negative electrode plate used in the embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 1a Positive electrode mixture uncoated part 1b Positive electrode mixture applied part 1c, 2c Boundary part 2 Negative electrode plate 2a Negative electrode mixture uncoated part 2b Negative electrode mixture applied part 3 Separator 4 Electrode group 9 Cut part 10 Positive electrode current collecting member 11 Negative electrode current collecting member 12 Notch portion 12a Projection portion 13 Battery container 14 Insulating plate 15 Positive electrode lead 16 Sealing plate 17 Gasket 20 Cutting portion forming jig 21 Protruding portion 25 Brazing material 30 Reinforcing layer

Claims (4)

A positive electrode plate having a positive electrode mixture coated portion and a positive electrode mixture uncoated portion provided at one end in the width direction on the positive electrode current collector, and a negative electrode mixture coated portion and a width direction on the negative electrode current collector A negative electrode plate having a negative electrode mixture uncoated portion provided at one end, and a separator provided at least facing the positive electrode mixture coated portion of the positive electrode plate and the negative electrode mixture coated portion of the negative electrode plate And an electrode group configured by winding in the longitudinal direction;
A positive electrode current collecting member and a negative electrode current collecting member having at least a blade-shaped protruding strip portion smaller than a width of the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion,
The protrusions of the positive electrode current collecting member and the negative electrode current collecting member are connected to each other through notches provided in the electrode group of the positive electrode mixture uncoated part and the negative electrode mixture uncoated part. A secondary battery characterized by. The secondary battery according to claim 1, wherein a brazing material is provided at least at a position of the blade edge shape of the protruding portion. The positive electrode mixture uncoated portion and the negative electrode mixture from the boundary between the positive electrode mixture coated portion, the positive electrode mixture uncoated portion, and the negative electrode mixture coated portion and the negative electrode mixture uncoated portion. The secondary battery according to claim 1, wherein a reinforcing layer is provided between the not-coated part and the notched part. Forming a positive electrode plate having a positive electrode mixture coated portion and a positive electrode mixture uncoated portion provided at one end in the width direction on the positive electrode current collector;
Forming a negative electrode plate having a negative electrode mixture coated portion and a negative electrode mixture uncoated portion provided at one end in the width direction on the negative electrode current collector;
Winding at least the positive electrode mixture coating portion of the positive electrode plate and the separator provided facing the negative electrode mixture coating portion of the negative electrode plate in the longitudinal direction to form an electrode group;
Forming a notch in the positive electrode mixture uncoated part and the negative electrode mixture uncoated part of the electrode group;
The positive electrode current collector and the negative electrode current collector having the blade-shaped protrusions smaller than the width of the positive electrode mixture uncoated part and the negative electrode mixture uncoated part are connected to the protrusions and the cut parts. And steps to
The manufacturing method of the secondary battery characterized by including.

Images