JP2008010400A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery having a collector structure which has a low resistance to enable to charge/discharge in a high output and large current and is highly reliable. <P>SOLUTION: The secondary battery is composed at least of an electrode group 4 in which a cathode plate 1 and an anode plate 2 and a porous insulation layer 3 are arranged so that an exposed part of a collector provided at least at one end of one of the cathode plate 1 and the anode plate 2 may be extruded out from the porous insulation layer 3, a cathode collector member 10 as well as an anode collector member 11 connected to the cathode plate 1 and the anode plate 2, and a bending prevention part which is provided at an exposed part of the collector and is narrow than that of the exposed part of the collector. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a secondary battery with high output, and more particularly to a current collection structure suitable for high current charge / discharge with low resistance.

  In recent years, with the reduction in size and weight of various electric devices, a secondary battery 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 driving power source is required to have a large output current and a large battery capacity, and a battery having a contrivance for a battery structure, particularly a current collecting structure, has been proposed.

  For example, the electrode area can be increased to obtain a large output current, 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.

  Further, in order to increase the capacity of the secondary battery, it is necessary to make the volume occupied by each current collector as small as possible in order to increase the amount of the positive electrode mixture and the negative electrode mixture. For this reason, a thin metal foil having a thickness of about several tens of μm is used for each current collector.

  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 shown in FIGS. 10 and 11 has been disclosed as a current collecting structure satisfying such requirements (see, for example, Patent Document 1).

  That is, as shown in FIG. 10, in the secondary battery, the positive electrode current collecting member 60 is welded to the positive electrode mixture uncoated portion 51 a of the positive electrode plate 51 and the negative electrode mixture uncoated portion 52 a of the negative electrode plate 52 is welded. The electric member 61 is welded to be embedded in the battery container 62. And it has the tabless structure which connected the negative electrode current collection member 61 to the inner bottom part of the battery container 62, and the positive electrode current collection member 60 to the sealing board 63. FIG.

  Therefore, in the positive electrode plate 51 shown in FIG. 11 (a) and the negative electrode plate 52 shown in FIG. 11 (b), the positive electrode mixture uncoated portion 51a and the negative electrode mixture uncoated in the longitudinal direction of one end in the width direction, respectively. A portion 52a is formed. And each positive electrode mixture uncoated part 51a of the positive electrode plate 51 and the negative electrode plate 52 and the negative electrode mixture uncoated part 52a are arranged in opposite directions, for example, shifted in the vertical direction and wound through the separator 53, Each positive electrode mixture uncoated portion 51a and negative electrode mixture uncoated portion 52a protrude from the separator 53 to constitute an electrode group. Here, the positive electrode mixture uncoated portion is an exposed portion of the positive electrode current collector of the positive electrode plate, and the negative electrode mixture uncoated portion means an exposed portion of the negative electrode current collector of the negative electrode plate.

  Further, the electrode group configured as described above is sequentially bent from the outer peripheral portion toward the winding axis to form a surface that contacts each positive electrode current collecting member 60 and negative electrode current collecting member 61, and each positive electrode current collector is formed on this surface. The electric member 60 and the negative electrode current collecting member 61 are welded.

  Thereby, the current distribution in the positive electrode plate 51 and the negative electrode plate 52 becomes uniform, and charge / discharge characteristics are improved.

  However, when a thin foil is used for the current collector to realize a high capacity, sufficient mechanical strength cannot be obtained. Therefore, in the structure where the exposed portion end of each current collector disclosed in Patent Document 1 is sequentially bent and welded to the current collector member, the current collector is not uniformly bent, and is caused by the distortion generated in the mixture coating portion. There was a problem that peeling and breakage of the mixture from the current collector occurred.

  Therefore, as shown in FIG. 12, the positive electrode mixture uncoated portion 71a of the positive electrode plate 71 and the negative electrode mixture uncoated portion 72a of the negative electrode plate 72 are formed by being folded along the width direction, thereby providing mechanical strength. Has been disclosed (see, for example, Patent Document 2).

In addition, in this specification, when it is not necessary to show a positive electrode plate and a negative electrode plate independently, an electrode plate, a mixture coating part, a mixture uncoated part (exposed part), a current collector Body, current collector member.
JP 2000-323117 A JP-A-4-324248

  However, in the current collector structure in which the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion disclosed in Patent Document 2 are folded, the mechanical strength of the portion where the thickness is increased by folding is improved. The thickness of the boundary portion between the mixture-coated portion and the mixture-uncoated portion does not change. Therefore, the mechanical strength is still weak against the load at the boundary, and it is bent at the boundary with the mixture coating portion. As a result, distortion occurred in the mixture coating portion, and there were problems such as peeling from the current collector.

  The present invention solves the above-mentioned problem, prevents bending of the current collector by avoiding bending of the current collector, and prevents peeling of the material coated portion from the current collector. To do. It is another object of the present invention to provide a secondary battery that realizes uniform connection by welding a current collector and a current collecting member, and is suitable for charging and discharging with a large current and low resistance.

  In order to achieve the above object, the secondary battery of the present invention includes a positive electrode plate and a negative electrode so that an exposed portion of a current collector provided at one end of at least one of the positive electrode plate and the negative electrode plate protrudes from the porous insulating layer. Less than the width of the exposed portion of the current collector provided at the position of the electrode group in which the plate and the porous insulating layer are disposed, the current collector connected to the positive electrode plate and the negative electrode plate, and the current collector exposed portion It is set as the structure which has a bending prevention part at least.

  With this configuration, the strength of the exposed portion of the current collector protruding from the electrode group can be improved, and non-uniform bending due to a load generated when the current collecting member is connected can be prevented, and a highly reliable tabless structure can be obtained. .

  According to the secondary battery of the present invention, it is possible to obtain a secondary battery that prevents charging of the mixture from the current collector and realizes charging and discharging with a large current by realizing a highly reliable tabless structure. .

  According to a first aspect of the present invention, there is provided a positive electrode plate, a negative electrode plate, a porous insulating layer, and an exposed portion of a current collector provided at one end of at least one of a positive electrode plate and a negative electrode plate protruding from the porous insulating layer. At least, a current collecting member connected to the positive electrode plate and the negative electrode plate, and a bending preventing portion smaller than the width of the exposed portion of the current collector provided at the position of the exposed portion of the current collector. It is the structure which has.

  As a result, the mechanical strength against the load of the exposed portion of the current collector connected to the current collector is improved, and the current collector and current collector can be connected uniformly, so charging and discharging of a large current with low resistance is possible. A suitable secondary battery is obtained.

  According to a second aspect of the present invention, in the first aspect of the invention, as a bending prevention portion, a wedge-shaped portion inserted into an intermediate portion between a ring body fitted on the outer periphery of the electrode group and an exposed portion of the wound current collector. This is a configuration using a spring material. Accordingly, the mechanical strength can be improved by collecting the current collector by the wedge-shaped spring material inserted in the middle of the exposed portion of the current collector.

  According to a third aspect of the present invention, in the first aspect, as the bending preventing portion, a rib provided on a current collecting member fitted on the outer periphery of the exposed portion of the current collector of the electrode group, and a current collector inserted into the intermediate portion. It is comprised by the rib provided in the electrical power member, and the rib provided in the electrical power collection member fitted by the inner peripheral part of the exposed part of an electrical power collector. Thereby, mechanical strength can be improved by collecting the current collector wound by the rib provided in the current collecting member inserted in the middle of the exposed portion of the current collector.

  According to a fourth aspect of the present invention, in the first aspect, a contraction ring body that is fitted to the outer periphery of the electrode group is used as the bending prevention section, and the exposed portions of the current collector are assembled by thermal contraction of the contraction ring body. Accordingly, the exposed portion of the current collector can be shaped and reinforced to improve mechanical strength.

  According to a fifth aspect of the present invention, in the first aspect, a fastening member mounted on the outer periphery of the electrode group is used as the bending prevention portion, and the exposed portion of the current collector is assembled by fastening the fastening member. Thereby, the exposed part of the current collector can be shaped and reinforced to improve the mechanical strength.

  According to a sixth aspect of the present invention, in the first aspect, the push nut-shaped ring body is mounted on the outer periphery of the electrode group as the bending preventing portion, and a plurality of protrusions provided on the inner periphery of the push nut-shaped ring body. The exposed part of the current collector is assembled at the part. Accordingly, the exposed portion of the current collector can be shaped and reinforced to improve mechanical strength.

  According to a seventh aspect of the present invention, in the first aspect, as a bend preventing portion, at a boundary portion between the exposed portion of the current collector of the positive electrode plate and the negative electrode plate and the mixture coating portion of the positive electrode plate and the negative electrode plate It has a configuration in which a reinforcing layer is provided. At this time, the thickness of the reinforcing layer is preferably about the same as the thickness of the mixture coating portion. Thereby, the clearance gap between the exposed parts of an adjacent electrical power collector is eliminated, and a mutual fall and bending can be prevented.

  According to an eighth aspect of the present invention, in the first through seventh aspects, the electrode group is provided with an inner diameter holding member. Thereby, the bending prevention part and the inner diameter holding member constitute a reinforcing wall, and the exposed part of the current collector due to the load is prevented from falling in the winding axis direction.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As the secondary battery, a non-aqueous electrolyte secondary battery such as a lithium ion 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. FIG. 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.

  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. Between the negative electrode plate 2 coated with the negative electrode mixture on the negative electrode current collector and the positive electrode plate 1 and the negative electrode plate 2, a porous insulating layer (hereinafter referred to as a 25 μm-thick polypropylene resin microporous film, for example) An electrode group 4 is provided, which is wound around in a spiral shape.

  Here, as shown in FIG. 2A, the positive electrode plate 1 includes a positive electrode mixture uncoated portion 5a and a positive electrode mixture coated portion provided in a strip shape in the longitudinal direction from one end in the width direction of the positive electrode current collector. 5b is provided.

  Moreover, as shown in FIG. 2 (b), the negative electrode plate 2 includes a negative electrode mixture uncoated portion 6a and a negative electrode mixture coated portion 6b provided in a strip shape in the longitudinal direction from one end in the width direction of the negative electrode current collector. Is provided. The positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a show the exposed portions of the respective current collectors where the positive electrode current collector and the negative electrode current collector are exposed. To help, it is expressed in a different way.

  At this time, the electrode group 4 has at least a positive electrode mixture in the width direction via the separator 3 interposed between the positive electrode mixture coating portion 5b of the positive electrode plate 1 and the negative electrode mixture coating portion 6b of the negative electrode plate 2. The uncoated portion 5a and the negative electrode mixture uncoated portion 6a are wound in a state of protruding from the edge of the separator 3 in opposite directions.

  A central portion of the winding axis of the electrode group 4 has an inner diameter holding member 7 made of, for example, resin, and the outer periphery of the wound electrode group 4 is not coated with a positive electrode mixture protruding from the separator 3. A ring body 8 for restricting the positions of the work part 5a and the negative electrode mixture uncoated part 6a is fitted. Furthermore, at least the positive electrode current collecting member and the negative electrode current collector, which will be described later, are provided in the intermediate portion between the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a wound between the inner diameter holding member 7 and the ring body 8. For example, a spring material 9 having a wedge shape such as a U shape or a V shape shown in FIG. 3 is provided at the lower surface position of the electric member.

  Here, the spring material 9 is preferably a resin spring material such as polycarbonate resin having excellent elasticity and chemical resistance. In addition, when the metal spring material 9 is used, the aluminum spring material is exposed to the negative electrode composite in which the current collector of the negative electrode plate is exposed in the positive electrode mixture uncoated portion where the current collector of the positive electrode plate is exposed. A spring material made of copper or nickel is preferable in the agent-uncoated portion because it has low reactivity with the positive electrode plate and the negative electrode plate and high conductivity.

  In addition, it is important that the height of the inner diameter holding member 7, the ring body 8, and the spring material 9 is smaller than the widths of the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a. This is because if the height is high, it cannot be connected to each current collecting member.

  Then, the positive electrode current collecting member 10 and the negative electrode current collecting member 11 are welded to at least the positions where the spring material 9 is disposed in the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a of the electrode group 4. Connect to. Here, for example, arc welding (TIG (Tungsten Inert Gas) welding method), laser welding method, or electron beam welding method can be used for welding the current collector and the current collecting member. Furthermore, the electrode group 4 including the positive electrode current collecting member 10 and the negative electrode current collecting member 11 is built in the battery container 12, the negative electrode current collecting member 11 is disposed at the bottom of the battery container, and the positive electrode current collecting member 10 is disposed between the insulating plates 13. And is connected to the sealing plate 14. Then, a nonaqueous electrolyte is injected into the battery container 12 and the sealing plate 14 is caulked through the gasket 15.

  With the above configuration, the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion are gathered while the position and height are regulated by the inner diameter holding member 7, the ring body 8, and the spring material 9, respectively. A secondary battery with improved strength can be obtained.

  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, it is possible to prevent the bending that occurs at the time of connection, and to obtain a uniform connection. Moreover, since the height of the electrode group can be made constant by the inner diameter holding member, the ring body, and the spring material, a secondary battery having uniform battery characteristics can be realized with high productivity.

  Here, as the positive electrode current collector, an aluminum foil or a perforated body made of a thin metal 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 thin metal foil. Moreover, nickel, copper, copper / nickel plating, 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.

In addition, 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.

  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 the body. At this time, the positive electrode mixture uncoated portion 5a 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 a negative electrode active material, graphite is used as a conductive agent, and styrene-butadiene copolymer rubber (SBR) is used as a binder to prepare a negative electrode mixture, copper foil, etc. The negative electrode current collector is coated. At this time, the negative electrode mixture uncoated portion 6a 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 the opposite direction to the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a through a separator made of a microporous film such as polyolefin. And electrode group 4 is formed.

  Next, the bending prevention part shown below is formed. That is, for example, the resin-made inner diameter holding member 7 is inserted into the central portion of the winding shaft center of the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a protruding from the electrode group 4 in opposite directions. . And the ring body 8 is engage | inserted in the outer peripheral part of the positive mix uncoated part 5a and the negative mix uncoated part 6a. Further, the spring material 9 is inserted into at least the lower surface on which the positive electrode current collecting member 10 and the negative electrode current collecting member 11 are arranged at an intermediate portion between the inner diameter holding member 7 and the ring body 8. As a result, the positive electrode current collector and the negative electrode current collector indicated by the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a are assembled to reinforce the current collector, and the height and the like are corrected. Is done.

  Next, in the bending prevention portion of the assembled positive electrode mixture uncoated portion 5a and negative electrode mixture uncoated portion 6a, a positive electrode current collecting member such as an aluminum plate and a negative electrode current collecting member such as a copper plate, for example, by TIG welding Weld and connect electrically.

  Next, the electrode group 4 having each current collecting member is inserted into the battery container 12 made of, for example, iron, nickel, stainless steel, etc., and the negative electrode current collecting member is welded to the bottom of the battery container 12 by, for example, resistance welding. Connect. Similarly, the sealing plate 14 that also serves as the positive electrode terminal and the positive electrode current collecting member are electrically connected by welding, for example, 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 12 under reduced pressure.

  Next, a sealing plate 14 that also serves as a positive electrode terminal is inserted into the battery container 12, and the secondary battery is manufactured by, for example, sealing the sealing plate 14 and the battery container 12 by caulking the periphery of the sealing plate 14 with a resin gasket 15. it can.

(Embodiment 2)
FIG. 4A is a cross-sectional view for explaining the state of the electrode group provided with the bending prevention portion according to the second embodiment of the present invention, and FIG. 4B is a collection including the bending prevention portion used in the same embodiment. It is sectional drawing which shows an electric member. Here, the configuration of the second embodiment is different from that of the first embodiment in that the bending prevention portion is also used as a current collecting member, and the other configurations are the same.

  That is, as shown in FIG. 4B, the positive electrode current collecting member 10 and the negative electrode current collecting member 11 are inserted at positions of the outer periphery or middle part of the electrode group 4, for example, conical, cylindrical, spherical ribs 16. It has. At this time, the rib 16 functions as a bending prevention part. And the rib 16 is fitted in the position of the exposed part of the collector of the electrode group 4, and the positive electrode mixture uncoated part 5a of the electrode group 4, the positive electrode current collecting member 10, the negative electrode mixture uncoated part 6a, and the negative electrode The current collecting member 11 is electrically connected by welding, for example, by TIG welding. That is, the exposed part of the positive electrode current collector and the exposed part of the negative electrode current collector are gathered together by the ribs, and bending can be prevented. The ribs 16 of the positive electrode current collecting member and the negative electrode current collecting member may be formed along the circumference of the electrode group in the winding direction or may be formed radially. As described above, a secondary battery can be manufactured as in the first embodiment.

  The height of the ribs is determined so that the positive electrode mixture uncoated part and the negative electrode mixture uncoated part and the positive electrode current collector member and the negative electrode current collector member are uniformly connected. It is important to make it smaller than the width of the part and the negative electrode mixture uncoated part. That is, the height of the electrode group is regulated by the rib, and an electrode group having a uniform shape can be obtained.

  4A illustrates an example in which ribs are formed at positions where the inner peripheral portion, the intermediate portion, and the outer peripheral portion of the electrode group are fitted. However, the present invention is not limited to this, and the exposed portion of the current collector is bent. A rib may be provided at an arbitrary position as long as the position can be prevented.

  Further, in the case of the second embodiment, it is not necessary to provide the inner diameter holding member, but it goes without saying.

  According to Embodiment 2 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, Bending that occurs at the time of connection is prevented by the rib, and a uniform connection can be obtained. In addition, since the height of the electrode group can be regulated by the rib, a secondary battery having a stable battery characteristic by the electrode group having a uniform shape can be realized with high productivity.

(Embodiment 3)
FIG. 5A is a perspective view illustrating the configuration of the electrode group of the secondary battery according to Embodiment 3 of the present invention, and FIG. 5B is a partially enlarged perspective view of FIG. 5A. Here, the third embodiment is different from the first embodiment in the configuration of the bending prevention unit, and the other configurations are the same.

  That is, as shown in FIG. 5A, for example, a resin-made shrink ring body 17 is attached to the outer periphery of the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a protruding in the electrode group 4. . Then, the shrink ring body 17 is heated and contracted, and the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a are assembled to form a bending prevention portion.

  Here, the shrink ring body 17 is not particularly limited. For example, fluororesin, PFA, FEP, polyolefin, polyvinyl chloride, or the like can be used.

  In this case, the inner diameter holding member is preferably a material that does not shrink by heating, and more preferably a material that expands on the contrary.

  According to the third embodiment of the present invention, the positive electrode current collector indicated by the positive electrode mixture uncoated part and the negative electrode current collector indicated by the negative electrode mixture uncoated part are assembled by contraction of the contraction ring body to mechanically Improve the strength. As a result, bending that occurs at the time of connection between the positive electrode current collecting member and the negative electrode current collecting member is prevented, and a uniform connection can be realized. In addition, since the height of the electrode group can be regulated by the contraction ring body, a secondary battery with stable battery characteristics by the electrode group having a uniform shape can be realized with high productivity.

(Embodiment 4)
FIG. 6A is a perspective view for explaining the configuration of the electrode group of the secondary battery according to Embodiment 4 of the present invention, and FIG. 6B is a partially enlarged perspective view of FIG. 6A. Here, the fourth embodiment is different from the first embodiment in the configuration of the bending preventing portion, and the other configurations are the same.

  That is, as shown in FIG. 6A, a fastening member made of, for example, a resin fastening band on the outer periphery of the positive electrode mixture uncoated portion 5 a and the negative electrode mixture uncoated portion 6 a protruding from the electrode group 4. 18 is installed. Then, by fastening the fastening member 18, the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a are gathered to form a bending prevention portion.

  In addition to the fastening band, a thread or string may be wound around the fastening member 18 in a band shape.

  According to the fourth embodiment of the present invention, the positive electrode current collector indicated by the positive electrode mixture uncoated part and the negative electrode current collector indicated by the negative electrode mixture uncoated part are assembled by tightening the fastening member to mechanically Improve the strength. As a result, bending that occurs at the time of connection between the positive current collecting member and the negative current collecting member is prevented, and a uniform connection is realized. In addition, since the height of the electrode group can be regulated by the fastening member and the inner diameter holding member, a secondary battery with stable battery characteristics can be realized with high productivity by the electrode group having a uniform shape.

(Embodiment 5)
FIG. 7A is a perspective view illustrating the configuration of the electrode group of the secondary battery according to Embodiment 5 of the present invention, and FIG. 7B is a partially enlarged perspective view of FIG. 7A. Here, the fifth embodiment is different from the first embodiment in the configuration of the bending prevention unit, and the other configurations are the same.

  That is, as shown in FIG. 7A, for example, a resin-made push nut-shaped ring body 19 is provided on the outer periphery of the positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a protruding in the electrode group 4. Installing. And by the protrusion part 20 provided in the inner periphery of the push nut-shaped ring body 19, the positive electrode mixture uncoated part 5a and the negative electrode mixture uncoated part 6a are gathered, and it is set as a bending prevention part.

  According to the fifth embodiment of the present invention, the positive electrode current collector indicated by the positive electrode mixture uncoated portion and the negative electrode current collector indicated by the negative electrode mixture uncoated portion are arranged on the inner periphery of the push nut-shaped ring body 19. Aggregated by the protrusions 20 improves the mechanical strength. As a result, bending that occurs at the time of connection between the positive electrode current collecting member and the negative electrode current collecting member is prevented, and a uniform connection can be realized. Further, since the push nut-like ring body 19 and the inner diameter holding member 7 can correct the height variation due to the bending of the electrode group 4, a secondary battery having a uniform battery characteristic and a stable battery characteristic can be realized with high productivity. .

(Embodiment 6)
FIG. 8A is a development view of the positive electrode plate of the secondary battery according to Embodiment 6 of the present invention, and FIG. 8B is a development view of the negative electrode plate. FIG. 9 is a cross-sectional view showing the configuration of the secondary battery in the same embodiment. Here, the sixth embodiment is different from the first embodiment in the configuration of the positive electrode plate and the negative electrode plate, and the other configurations are the same.

  That is, as shown in FIG. 8A, the reinforcing layer 21 is provided at least near the boundary between the positive electrode mixture coated portion 5b and the positive electrode mixture uncoated portion 5a in the positive electrode plate 1. Similarly, as shown in FIG. 8B, a reinforcing layer 21 is provided at least in the vicinity of the boundary between the negative electrode mixture coated portion 6 b and the negative electrode mixture uncoated portion 6 a in the negative electrode plate 2. .

  Here, the reinforcing layer 21 is, for example, an inorganic oxide filler such as alumina, a binder, and an appropriate amount of N-methyl-2-pyrrolidone (N-Methyl-2-Pyrrolidone, hereinafter referred to as “NMP”). To prepare a slurry. Then, the slurry is applied to the boundary between the positive electrode mixture coated portion 5b and the positive electrode mixture uncoated portion 5a and the boundary between the negative electrode mixture coated portion 6b and the negative electrode mixture uncoated portion 6a and dried. Thereby, the reinforcing layer 21 is formed. At this time, the reinforcing layer 21 is preferably formed to have a thickness equal to or less than the thickness of the positive electrode mixture coating portion 5b and the negative electrode mixture coating portion 6b.

  According to the sixth embodiment, by providing the reinforcing layer 21, it is possible to suppress a decrease in the mechanical strength of the exposed portion of the current collector. Moreover, since the bending of each positive electrode mixture uncoated portion 5a and the negative electrode mixture uncoated portion 6a at the time of joining can be prevented, the production yield of the secondary battery can be further improved.

  Specific examples in each 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 produce a negative electrode plate having a thickness of 140 μm and a negative electrode mixture uncoated part having a width of 5 mm.

(3) Production of Battery The positive electrode plate and the negative electrode plate produced as described above were spirally wound with a separator made of a polypropylene resin microporous film having a thickness of 25 μm to obtain a cylindrical electrode group. .

  The inner diameter is maintained at the center of the winding axis φ5 mm of the positive electrode current collector of the positive electrode mixture uncoated portion and the negative electrode current collector of the negative electrode mixture uncoated portion protruding from both ends of the wound electrode group As a member, a cylinder having an outer diameter of 4.8 mm, an inner diameter of 4.4 mm, and a height of 3 mm was attached to a ring body having an outer diameter of 25.5 mm, an inner diameter of 24 mm, and a height of 3 mm. In addition, a wedge-shaped spring material having a thickness of 0.2 mm and a height of 3 mm was attached at least at a position where the positive electrode current collector and the negative electrode current collector were connected at an intermediate portion between the inner periphery and the outer periphery of the electrode group. Furthermore, TIG welding was performed on the positive electrode current collector member made of a disc-shaped aluminum plate having an outer diameter of 25.5 mm and a thickness of 0.5 mm at the position of the spring material attached to the electrode group obtained above, and the outer diameter was 25.5 mm. A negative electrode current collector made of a disc-shaped copper plate having a thickness of 0.3 mm was TIG welded. At this time, as the welding conditions for TIG welding, the current value was 100 A for the positive electrode, the time was 100 msec, the current value was 130 A for the negative electrode, and the time was 50 msec.

  Then, the obtained electrode group is inserted into a cylindrical battery container (material: iron / Ni plating, diameter 26 mm, height 65 mm) opened on only one side, and an insulating plate is disposed between the battery container and the electrode group. The negative electrode current collector and the battery container were resistance welded, and then the positive electrode current collector and the sealing plate were laser welded 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 heating the obtained battery container at 60 degreeC in vacuum and drying, the adjusted nonaqueous electrolyte was inject | poured.

  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.

  First, a positive electrode current collecting member made of a disc-shaped aluminum plate having an outer diameter of 25.5 mm and a thickness of 0.5 mm, and a negative electrode current collecting member made of a disc-shaped copper plate having an outer diameter of 25.5 mm and a thickness of 0.3 mm Conical ribs having a diameter of 2 mm and a depth of 1 mm were provided radially.

  Then, at both ends of the electrode group produced by the same method as in Example 1, the positive electrode current collector and the negative electrode current collector are fitted into the outer peripheral part, the intermediate part, and the inner peripheral part of the electrode group via the positive electrode current collector. A secondary battery was fabricated in the same manner as in Example 1, except that the electric member and the positive electrode mixture uncoated part and the negative electrode current collecting member and the negative electrode mixture uncoated part were TIG welded. This is Sample 2.

(Example 3)
Example 3 is an example in which the third embodiment is embodied.

  A shrink ring body having an outer diameter of 25.5 mm and a thickness of 0.1 mm made of polyolefin on the outer periphery of the positive electrode mixture uncoated part and the negative electrode mixture uncoated part at both ends of the electrode group produced by the same method as in Example 1. A secondary battery was fabricated in the same manner as in Example 1 except that the bending prevention portion was formed by heating at 150 ° C. This is designated as Sample 3.

Example 4
Example 4 is an example in which Embodiment 4 is embodied.

  A fastening member having a width of 3 mm and a length of 80 mm made of polypropylene is attached to the outer periphery of the positive electrode mixture uncoated portion and the negative electrode mixture uncoated portion on both ends of the electrode group produced in the same manner as in Example 1, and fastened. Then, a secondary battery was fabricated in the same manner as in Example 1 except that the bending prevention portion was formed. This is designated as sample 4.

(Example 5)
Example 5 is an example in which Embodiment 5 is embodied.

  A push nut-like ring body having an outer diameter of 25.5 mm made of polypropylene is attached to the outer periphery of the positive electrode mixture uncoated part and the negative electrode mixture uncoated part on both ends of the electrode group produced in the same manner as in Example 1. A secondary battery was fabricated in the same manner as in Example 1 except that the bending prevention portion was formed at the protruding portion on the inner periphery. This is designated as Sample 5.

(Example 6)
Example 6 is an example in which the sixth embodiment is embodied.

(1) Preparation of positive electrode plate and negative electrode plate First, alumina, which is an inorganic oxide filler, a polyacrylonitrile-modified rubber binder, and an NMP solution were kneaded to prepare a slurry for a reinforcing layer.

  Next, a slurry for reinforcing layer is applied in a width of 4 mm and a thickness per side of 67.5 μm on a part of the positive electrode mixture uncoated portion in contact with the positive electrode mixture coated portion, and then the slurry is dried to be reinforced. A layer was formed. At this time, the thickness of the reinforcing layer was substantially the same as the thickness of the positive electrode mixture coating portion. In the same manner, a reinforcing layer having a width of 4 mm and a thickness per side of 62 μm was also formed on the negative electrode plate.

(2) Production of Battery A secondary battery was produced in the same manner as in Example 1 except that the positive electrode plate and the negative electrode plate produced by the above method were used. This is designated as Sample 6.

(Comparative Example 1)
Comparative Example 1 is an example in which Patent Document 2 is embodied. That is, a secondary battery was produced in the same manner as in Example 1 except that the wound positive electrode mixture uncoated part and negative electrode mixture uncoated part were folded along the width direction. This is designated as sample C1.

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

  The evaluation results of Sample 1 to Sample 6 and Sample C1 are shown in (Table 1) below.

(Observation of bent state of electrode plate)
The electrode group was taken out from the battery container of the produced secondary battery, and the electrode plate was visually observed. The measurement results are shown in the column of the electrode plate state in (Table 1).

  As shown in (Table 1), almost all of the secondary batteries of Sample 1 to Sample 6 were not observed to be bent so as to cause distortion in the mixture portion. At this time, a slightly bent portion of the electrode plate was observed, but this bending is considered to be caused by bringing the current collecting member into contact with the end face of the electrode group during welding. Therefore, since the reinforcing layer was provided in the sample 6, there was no bending of the electrode plate. On the other hand, in sample C1, bending occurred at the boundary between the mixture-coated portion and the uncoated portion, and many peeling and breakage of the mixture were observed.

(Measurement of tensile strength)
Five samples were taken from each sample, and the tensile strength at the weld was measured based on JIS Z2241. Specifically, the electrode group is held on one side of the tensile tester, and the current collecting member is held on the other side of the tensile tester. In this state, the electrode group and the current collecting member are pulled in the axial direction of the tensile tester at a constant speed. And the load when a welding part destroyed was made into tensile strength. The measurement results are shown in the column of tensile strength in (Table 1).

  As shown in (Table 1), in any of Sample 1 to Sample 6, the tensile strength was 50 N or more. On the other hand, in sample C1, three of the five pieces had a tensile strength of 10 N or less, and the welded portion was detached.

(Measurement of battery internal resistance)
The internal resistance was measured for samples 1 to 6 and sample C1. Specifically, first, after charging to 4.2 V with a constant current of 1250 mA for each sample, a charge / discharge cycle of discharging to 3.0 V with a constant current of 1250 mA was repeated three times. And the alternating current of 1 kHz was applied to each sample, the internal resistance of the secondary battery was measured, and the connection state was evaluated. The measurement results are shown in the column of internal resistance in (Table 1).

  As shown in Table 1, in Sample 1 and Sample 2, the average value of the internal resistance was 5 mΩ, and the variation was about 10%. In samples 3 to 6, the average value of the internal resistance was 5.8 mΩ, and the variation was about 5%.

  On the other hand, in sample C1, the average value of the internal resistance was 11 mΩ, and the variation was 20%.

  Further, the average output current (I) was calculated from the measured internal resistance (R) of each sample. Specifically, when the battery is charged to 4.2V and then discharged to 1.5V, it is calculated from I = (4.2-1.5) / R. The result is shown in the column of output current in (Table 1).

  As shown in (Table 1), it was found that if Sample 1 to Sample 6 were used, large current discharge could be performed.

  In the secondary battery of each example, the example in which the inner diameter holding member is inserted at the center of the winding axis of the electrode group has been described. However, there is no particular problem even if the inner diameter holding member is omitted, and the same effect is obtained. It was.

  However, in the secondary battery composed only of the inner diameter holding member as the bending prevention portion described in each of the above embodiments, the effect of the present invention cannot be obtained, and the current collector is bent or peeled off at the mixture coating portion. It has occurred.

  As described above, the cylindrical battery has been described in the above embodiment, but the present invention is not limited to this. For example, the effects of the present invention can be similarly obtained for secondary batteries such as prismatic batteries, nickel metal hydride storage batteries, and nickel cadmium storage batteries.

  The present invention provides a uniform and reliable connection between each current collecting member and each current collector indicated by each material uncoated portion by means of a bend preventing portion, and also prevents each material from being separated from each current collector. Can be prevented. Thereby, charging / discharging with a large current is realized by a low resistance connection, and it is useful as a driving battery for electric 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 The perspective view which shows an example of the spring material used in the embodiment (A) Sectional drawing explaining the state of the electrode group which provided the bending prevention part in Embodiment 2 of this invention (b) Sectional drawing which shows the current collection member provided with the bending prevention part used for the embodiment (A) Perspective view for explaining the configuration of the electrode group of the secondary battery according to Embodiment 3 of the present invention (b) Partial enlarged perspective view of FIG. 5 (a) (A) Perspective view for explaining the configuration of the electrode group of the secondary battery in Embodiment 4 of the present invention (b) Partial enlarged perspective view of FIG. 6 (a) (A) Perspective view for explaining the configuration of the electrode group of the secondary battery according to Embodiment 5 of the present invention (b) Partial enlarged perspective view of FIG. 7 (a) (A) Development view of the positive electrode plate of the secondary battery in the sixth embodiment of the present invention (b) Development view of the negative electrode plate in the same embodiment Sectional drawing which shows the structure of the secondary battery in the same embodiment The figure explaining the secondary battery by the conventional tabless system (A) Development view of the positive electrode plate of the secondary battery of FIG. 10 (b) Development view of the negative electrode plate of the secondary battery of FIG. (A) The perspective view explaining the current collection structure of the positive electrode plate of the conventional secondary battery (b) The perspective view explaining the current collection structure of the negative electrode plate of the conventional secondary battery

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 2 Negative electrode plate 3 Separator (porous insulating layer)
DESCRIPTION OF SYMBOLS 4 Electrode group 5a Positive electrode mixture uncoated part 5b Positive electrode mixture coated part 6a Negative electrode mixture uncoated part 6b Negative electrode mixture coated part 7 Inner diameter holding member 8 Ring body 9 Spring material 10 Positive electrode current collecting member 11 Negative electrode Current collecting member 12 Battery container 13 Insulating plate 14 Sealing plate 15 Gasket 16 Rib 17 Shrink ring body 18 Fastening member 19 Push nut-shaped ring body 20 Protruding portion 21 Reinforcing layer

Claims (8)

An electrode group in which the positive electrode plate, the negative electrode plate, and the porous insulating layer are arranged so that an exposed portion of a current collector provided at one end of at least one of the positive electrode plate and the negative electrode plate protrudes from the porous insulating layer When,
A current collecting member connected to the positive electrode plate and the negative electrode plate;
A bending prevention portion smaller than the width of the exposed portion of the current collector provided at the position of the exposed portion of the current collector;
A secondary battery characterized by comprising: As the bending prevention part,
The ring-shaped body fitted in the outer periphery of the said electrode group, and the wedge-shaped spring material inserted in the intermediate part of the exposed part of the said collector currently wound are used. Next battery. As the bending prevention part,
A rib provided on the current collecting member fitted on the outer periphery of the exposed portion of the current collector of the electrode group, and a rib provided on the current collecting member inserted in an intermediate portion of the exposed portion of the current collector. The secondary battery according to claim 1, comprising a rib provided on the current collecting member inserted into a peripheral portion. As the bending prevention part,
2. The secondary battery according to claim 1, wherein an exposed portion of the current collector is gathered by heat contraction of the contraction ring body using a contraction ring body fitted on an outer periphery of the electrode group. As the bending prevention part,
2. The secondary battery according to claim 1, wherein a fastening member mounted on an outer periphery of the electrode group is used to gather the exposed portions of the current collector by fastening the fastening member. As the bending prevention part,
The push nut-shaped ring body is mounted on the outer periphery of the electrode group, and the exposed portions of the current collector are assembled by a plurality of protrusions provided on the inner periphery of the push nut-shaped ring body. 2. The secondary battery according to 1. As the bending prevention part,
The reinforcing layer is provided at a boundary portion between the exposed portion of the current collector of the positive electrode plate and the negative electrode plate and a mixture coating portion of the positive electrode plate and the negative electrode plate. Secondary battery. As the bending prevention part,
The secondary battery according to any one of claims 1 to 7, wherein an inner diameter holding member is provided in the electrode group.

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