Secondary battery

Abstract

A secondary battery that is obtained by having a power storage element, which charges and discharges electricity, contained in an outer package is provided with: a box, one surface of which is opened, and a cover which closes the surface of the box, the box and the cover constituting the outer package; an external terminal which is fitted to the cover in such a manner that at least a part thereof is exposed from the cover to the outside; and a collector which electrically connects the power storage element and the external terminal to each other. With respect to this secondary battery, the collector comprises a first extending part which is electrically connected to the power storage element and a plate-like second base part which is arranged along the cover and is electrically connected to the external terminal; the base part comprises a first base part constituent part which forms one end portion of the base part in the longitudinal direction, while being continued from the first extending part, and a second base part constituent part which forms the other end portion of the base part in the longitudinal direction, while being connected to the external terminal; and the second base part constituent part is formed to have a thinner thickness than the first base part constituent part.

Description

Technical Field

[0001] The present invention relates to secondary batteries, and is particularly suitable for application to, for example, lithium-ion secondary batteries.

Background Art

[0002] In recent years, large-capacity secondary batteries used as power sources for electric vehicles (EVs) and hybrid vehicles have been developed, and among them, lithium-ion secondary batteries with high energy density have attracted attention. For lithium-ion secondary batteries for automobiles, from the viewpoint of emphasizing environmental performance, which has been increasing in recent years, higher safety as well as higher energy density is required.

[0003] A lithium-ion secondary battery generally includes a positive electrode, a negative electrode, and a separator for electrically insulating these electrodes, and has a basic configuration in which the positive electrode and the negative electrode are stacked via the separator. Usually, an active material layer is formed on the surface of a strip-shaped metal foil by applying a slurry containing an active material into which lithium ions can be inserted and detached. These positive electrode, negative electrode, and separator are formed, for example, as an electrode group wound in a state of being overlapped with each other, and are enclosed in a can or a laminate exterior body in a state of being impregnated with an electrolytic solution.

[0004] As the background art in this technical field, there is Patent Document 1. In this Patent Document 1, a thin portion is provided in the base portion of a positive electrode current collector plate that connects between the positive electrode of a wound electrode body, which is a power storage body housed in a square exterior body of a secondary battery, and the positive electrode terminal of the secondary battery. After inserting the tip of the positive electrode terminal into a through hole provided in the thin portion, caulking is performed to fix the positive electrode terminal to the positive electrode current collector plate.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] In the secondary battery disclosed in such Patent Document 1, only the connection portion with the positive electrode terminal is thinned, so that the volume and weight of the positive electrode current collector plate become excessive, and it is difficult to reduce the size and weight of the rectangular secondary battery. Further, as disclosed in Patent Document 1, when the entire periphery of the base of the terminal caulking fixing portion is thickened, there is also a problem that the effect of suppressing heat generation cannot be obtained.

[0007] The present invention has been made in consideration of the above points, and intends to propose a secondary battery capable of suppressing heat generation while reducing the size and weight.

MEANS FOR SOLVING THE PROBLEMS

[0008] In order to solve such problems, in the present invention, in a secondary battery in which a power storage element for charging and discharging electricity is housed in an exterior body, the exterior body is configured to include a box body having one side open, and a lid for closing the one side of the box body, and an external terminal attached to the lid so that at least a part thereof is exposed to the outside from the lid, and a current collector for electrically connecting between the power storage element and the external terminal, the current collector has an extending portion electrically connected to the power storage element, and a plate-shaped base portion disposed along the lid and electrically connected to the external terminal, the base portion includes a first base portion constituting one end side in the longitudinal direction of the base portion and being a portion continuous from the extending portion, and a second base portion constituting the other end side in the longitudinal direction of the base portion and connected to the external terminal, and the second base portion is formed to have a thinner plate thickness than the first base portion.

[0009] According to the secondary battery of the present invention, it is possible to suppress an increase in the electrical resistance of the current path from the current collector to the external terminal, and to suppress heat generation of the current collector. Further, since the plate thickness of the second base portion of the current collector is formed to be thinner than the plate thickness of the first base portion, the weight of the current collector can be reduced.

Advantages of the Invention

[0010] According to the present invention, a secondary battery capable of suppressing heat generation while being reduced in size and weight can be realized.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Modes for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0013] (1) First Embodiment (1-1) Configuration of the Secondary Battery According to the Present Embodiment In FIGS. 1 and 2, reference numeral 1 denotes a secondary battery according to the present embodiment as a whole. This secondary battery is, for example, a flat rectangular lithium-ion secondary battery mounted as a power source in an electric vehicle or a hybrid vehicle.

[0014] In the following description, the configuration of each part of the secondary battery 1 may be described using an xyz orthogonal coordinate system in which the width direction of the secondary battery is the x direction, the thickness direction is the y direction, and the height direction is the z direction. Also, the directions of up, down, left, and right in the following description are for convenience in explaining the configuration of each part of the secondary battery 1 based on the drawings, and are not limited to the vertical or horizontal directions.

[0015] The secondary battery 1 includes a battery container 2 that forms a sealed container and houses a power storage element 5 to be described later. The battery container 2 is, for example, a metal container having a flat rectangular box shape. The battery container 2 has a pair of wide side surfaces 3A along the width direction (x direction), a pair of narrow side surfaces 3B along the thickness direction (y direction), and an elongated rectangular upper surface 3C and a bottom surface 3D. Among these wide side surfaces 3A, narrow side surfaces 3B, upper surface 3C, and bottom surface 3D, the wide side surfaces 3A have the largest area.

[0016] The battery container 2 is composed of, for example, a battery can 3 that is a flat rectangular box body with one side in the height direction (z direction) open, and a rectangular plate-shaped battery lid 4 that closes the opening 3E of the battery can 3. The battery can 3 and the battery lid 4 are made of a metal material such as an aluminum alloy, and are formed by deep drawing or pressing.

[0017] After the power storage element 5 for storing electricity is loaded into the battery can 3 through the opening 3E, the opening 3E is sealed by the battery lid 4 by joining the periphery of the battery lid 4 over the entire circumference of the opening 3E by laser welding or the like.

[0018] The battery cover 4 is provided with through holes 4A through which a part of a positive electrode external terminal 7 and a negative electrode external terminal 8, which will be described later, are inserted at both longitudinal ends in the longitudinal direction (x direction) of the secondary battery 1 in the width direction, and a gas discharge valve 4B is formed at the central portion in the longitudinal direction. The gas discharge valve 4B is, for example, a portion where a part of the battery cover 4 is press-processed to be thinned and a slit is formed, and is integrally formed with the battery cover 4. When the internal pressure of the battery container 2 rises to a predetermined pressure, the gas discharge valve 4B cracks and discharges the gas in the battery container 2 to the outside of the container, whereby the internal pressure of the battery container 2 is reduced and the safety of the secondary battery 1 is ensured.

[0019] Further, the battery cover 4 is provided with a liquid injection hole 4C, for example, between the through hole and the gas discharge valve. The liquid injection hole 4C is a hole for injecting an electrolytic solution into the inside of the battery cover 4, and after the injection of the electrolytic solution, it is sealed by joining a liquid injection plug 6, for example, by laser welding. As the electrolytic solution to be injected into the battery container 2, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF6) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.

[0020] In addition, a positive electrode external terminal 7 and a negative electrode external terminal 8 are fixed to the battery cover 4. These positive electrode external terminal 7 and negative electrode external terminal 8 are arranged at intervals in the longitudinal direction on the outer surface of the battery cover 4 (the upper surface 3C of the battery container 2), and are electrically and physically connected to the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12 inside the battery container 2 through the battery cover 4. The positive electrode external terminal 7 is made of, for example, aluminum or an aluminum alloy, and the negative electrode external terminal 8 is made of, for example, copper or a copper alloy.

[0021] The positive electrode external terminal 7 and the negative electrode external terminal 8 each have, for example, joint portions 7A and 8A connected to a bus bar, and connection portions 7B and 8B connected to the positive electrode current collector plate 11 or the negative electrode current collector plate 12, respectively. The joint portions 7A and 8A are formed in a substantially rectangular parallelepiped shape and are fixed to the outer surface of the battery lid 4 via gaskets 9 and 10 made of an insulating member. The connection portions 7B and 8B are columnar or cylindrical portions extending in a direction penetrating the battery lid 4 from the bottom surface side of the joint portions 7A and 8A facing the battery lid 4, and are integrally formed with the joint portions 7A and 8A.

[0022] As shown in FIG. 2, the positive electrode current collector plate 11 and the negative electrode current collector plate 12 are plate-like members bent into predetermined shapes, respectively, and are connected to the power storage element 5. The positive electrode current collector plate 11 connects between the positive electrode external terminal 7 and a positive electrode electrode laminated portion 5A, which will be described later, that is the positive electrode of the entire power storage element 5, and the negative electrode current collector plate 12 connects between the negative electrode external terminal 8 and a negative electrode electrode laminated portion 5B, which will be described later, that is the negative electrode of the entire power storage element 5. The positive electrode current collector plate 11 is made of, for example, aluminum or an aluminum alloy, and the negative electrode current collector plate 12 is made of, for example, copper or a copper alloy.

[0023] The positive electrode current collector plate 11 and the negative electrode current collector plate 12 are each bent and formed so as to be positioned along the battery lid 4, and are composed of base portions 11A and 12A connected to the corresponding positive electrode external terminal 7 or negative electrode external terminal 8, and extending portions 11B and 12B extending toward the bottom surface 3D along the wide side surface 3A of the battery can 3. The joint portions 11BA and 12BA of the extending portions 11B and 12B are joined to the positive electrode electrode laminated portion 5A in which the positive electrode foil exposed portion 23B (FIG. 3) of the power storage element 5 is wound and flatly laminated, and the negative electrode of the power storage element 5 by ultrasonic bonding or the like.

[0024] FIG. 3 shows a state in which a part of the power storage element 5 is developed. The power storage element 5 is formed in a flat shape by stacking a first separator 20, a negative electrode 21, a second separator 22, and a positive electrode 23, each formed in a strip shape, in this order, and winding these with the positive electrode 23 on the inside. In this case, the first and second separators 20 and 22 are formed of an insulating material, whereby the negative electrode 21 and the positive electrode 23 are wound in an insulated state.

[0025] The negative electrode 21 is configured to include a negative electrode mixture layer 21A formed by applying a negative electrode active material (negative electrode mixture) to both surfaces of a negative electrode metal foil, which is a negative electrode current collector, and a negative electrode foil exposed portion 21B provided on one end side in the width direction (x direction) of the negative electrode metal foil, where the negative electrode mixture is not applied.

[0026] The negative electrode metal foil is made of, for example, copper foil having a thickness of about 10 μm. The negative electrode mixture layer 21A is formed to a thickness of about 70 μm by applying a slurry negative electrode mixture to the negative electrode metal foil, drying the applied negative electrode mixture, and pressing it. The negative electrode 21 is manufactured by appropriately cutting the negative electrode metal foil on which the negative electrode mixture layer 21A has been formed.

[0027] As a slurry of the negative electrode mixture, for example, a mixture can be used in which 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder is added to 100 parts by weight of non-reinforced carbon powder as the negative electrode mixture, and N-methylpyrrolidone (NMP) is further added as a dispersion solvent and kneaded.

[0028] The negative electrode active material contained in the negative electrode mixture layer 21A is not limited to the amorphous carbon described above. For example, the negative electrode active material may be natural graphite capable of inserting and extracting lithium ions, various artificial graphite materials, carbonaceous materials such as coke, compounds of Si or Sn (e.g., SiO, TiSi), or composite materials thereof. The particle shape of the negative electrode active material is not particularly limited and may be, for example, flaky, spherical, fibrous, or lumpy.

[0029] On the other hand, the positive electrode 23 is configured to include a positive electrode mixture layer 23A formed by applying a positive electrode active material (positive electrode mixture) to both surfaces of a positive electrode metal foil, which is a positive electrode current collector, and a positive electrode foil exposed portion 23B provided on the other end side in the width direction (x direction) of the positive electrode metal foil, where the positive electrode mixture is not applied.

[0030] The positive electrode metal foil is composed of, for example, an aluminum foil having a thickness of about 20 μm. Also, the positive electrode mixture layer 23A is formed to have a thickness of about 90 μm by applying a slurry-like positive electrode mixture, drying the applied positive electrode mixture, and pressing it. The positive electrode 23 is manufactured by appropriately cutting the positive electrode metal foil on which the positive electrode mixture layer 23A is formed.

[0031] As the slurry of the positive electrode mixture, for example, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganate (LiMn2O4) which is the positive electrode mixture, and further NMP is added as a dispersion solvent and kneaded, and the resulting mixture can be used.

[0032] Note that the positive electrode active material contained in the positive electrode mixture layer 23A is not limited to the above-mentioned lithium manganate. For example, as the positive electrode active material, other lithium manganates having a spinel crystal structure, lithium manganese composite oxides partially substituted or doped with metal elements can be used. Also, as the positive electrode active material, lithium cobaltate or lithium titanate having a layered crystal structure, lithium-metal composite oxides partially substituted or doped with metal elements may be used.

[0033] Also, the binder used for the negative electrode mixture and the positive electrode mixture is not limited to PVDF. As the binder, for example, polymers such as polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene-butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, or acrylic resins, or mixtures thereof can be used.

[0034] Although illustration is omitted, the power storage element 5 may have an axis for winding by laminating a first separator 20, a negative electrode 21, a second separator 22, and a positive electrode 23. As the axis, for example, a resin sheet having higher bending rigidity than the positive electrode metal foil, the negative electrode metal foil, and the first and second separators 20 and 22 can be used after being wound. Further, in the power storage element 5, the dimension of the negative electrode mixture layer 21A is larger than the dimension of the positive electrode mixture layer 23A in the winding axis 24 direction (x direction), and the positive electrode mixture layer 23A is always configured to be sandwiched between the negative electrode mixture layers 21A.

[0035] In the power storage element 5, the positive electrode foil exposed portion 23B of the positive electrode 23 and the negative electrode foil exposed portion 21B of the negative electrode 21 are wound and laminated on one end side and the other end side in the winding axis 24 direction (x direction) as shown in FIG. 3, respectively. Further, the positive electrode foil exposed portion 23B and the negative electrode foil exposed portion 21B are each flattened and bundled as shown in FIG. 2, and are joined to the joining portions 11BA and 12BA of the extending portions 11B and 12B of the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12 by, for example, ultrasonic bonding or resistance bonding.

[0036] In the winding axis 24 direction (x direction), the dimensions of the first and second separators 20 and 22 are larger than the dimension of the negative electrode mixture layer 21A of the negative electrode 21. However, the ends of the first and second separators 20 and 22 are arranged at positions inside the power storage element 5 in the winding axis 24 direction (x direction) rather than the ends of the positive electrode foil exposed portion 23B of the positive electrode 23 or the negative electrode foil exposed portion 21B of the negative electrode 21. Therefore, when the positive electrode foil exposed portion 23B of the positive electrode 23 and the negative electrode foil exposed portion 21B of the negative electrode 21 are bundled and joined to the joining portion 11BA of the extending portion 11B of the positive electrode current collector plate 11 and the joining portion 12BA of the extending portion 12B of the negative electrode current collector plate 12, respectively, the first and second separators 20 and 22 do not cause any trouble.

[0037] The base portions 11A of the positive electrode current collector plate 11 and the base portions 12A of the negative electrode current collector plate 12 are each fixed to the battery lid 4 via plate-shaped insulating members 13 and 14 and are connected to the corresponding positive electrode external terminal 7 or negative electrode external terminal 8. More specifically, the connection portions 7B of the positive electrode external terminal 7 and the connection portions 8B of the negative electrode external terminal 8 are inserted through, for example, the through holes 9A and 10A of the gaskets 9 and 10, the through hole 4A of the battery lid 4, the through holes 13A and 14A of the insulating members 13 and 14, and the through holes 11AA and 12AA of the base portions 11A and 12A of the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12, and caulked so as to be plastically deformed to expand the diameter of the tip at the lower surface of the base portions 11A and 12A of the positive electrode current collector plate 11 and the negative electrode current collector plate 12. As a result, the positive electrode external terminal 7 and the positive electrode current collector plate 11, and the negative electrode external terminal 8 and the negative electrode current collector plate 12 are electrically connected to each other, and the positive electrode external terminal 7 and the positive electrode current collector plate 11, and the negative electrode external terminal 8 and the negative electrode current collector plate 12 are fixed to the battery lid 4 in a state of being electrically insulated from each other via the gaskets 9 and 10 and the insulating members 13 and 14.

[0038] Also, the joint portions 11BA of the extending portions 11B of the positive electrode current collector plate 11 and the joint portions 12BA of the extending portions 12B of the negative electrode current collector plate 12 are joined to the positive electrode electrode laminate portion 5A formed by laminating the positive electrode foil exposed portions 23B of the power storage element 5 and the negative electrode electrode laminate portion 5B formed by laminating the negative electrode foil exposed portions 21B, respectively. Thus, the positive electrode 23 and the negative electrode 21 constituting the power storage element 5 are electrically connected to the corresponding positive electrode external terminal 7 or negative electrode external terminal 8 via the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12. The materials of the gaskets 9 and 10 and the insulating members 13 and 14 are resins having electrical insulation properties such as polybutylene terephthalate, polyphenylene sulfide, and perfluoroalkoxy fluororesin.

[0039] The power storage element 5 is joined to the positive electrode current collector plate 11 and the negative electrode current collector plate 12 respectively, and is covered by an insulating cover 15 (Fig. 2) made of resin having electrical insulation in a state of being fixed to the battery lid 4 via the corresponding positive electrode current collector plate 11 or negative electrode current collector plate 12, and is loaded into the battery can 3 from the opening 3E of the battery can 3. The insulating cover 15 is created by assembling, for example, a single sheet made of synthetic resin such as polypropylene or a plurality of film members. The insulating cover 15 has dimensions and a shape that can cover substantially the entire power storage element 5 to which the positive electrode current collector plate 11 and the negative electrode current collector plate 12 are joined, integrally with these positive electrode current collector plate 11 and negative electrode current collector plate 12.

[0040] As shown in Figs. 2 and 3, the power storage element 5 is wound in a flat shape, and has semi-cylindrical curved portions 5C provided at both ends in the height direction (z direction) of the battery container 2 and a flat portion 5D between these curved portions 5C. The power storage element 5 is loaded into the battery can 3 from one curved portion 5C so that the winding axis 24 direction is along the width direction (x direction) of the secondary battery 1, and the other curved portion 5C is accommodated in the battery can 3 so as to face the battery lid 4. Thereafter, the battery container 2 is configured by joining the battery lid 4 over the entire circumference of the opening 3E of the battery can 3 as described above, an electrolytic solution is injected into the battery container 2 through the liquid injection hole 4C, and the battery container 2 is sealed by joining a liquid injection plug 6 to the liquid injection hole 4C.

[0041] With the above configuration, the secondary battery 1 charges the power storage element 5 by supplying power to the positive electrode 23 and the negative electrode 21 of the power storage element 5 via the positive electrode external terminal 7 and the positive electrode current collector plate 11, and the negative electrode external terminal 8 and the negative electrode current collector plate 12 respectively, or outputs power to the outside from the positive electrode 23 and the negative electrode 21 of the power storage element 5 via the positive electrode current collector plate 11 and the positive electrode external terminal 7, and the negative electrode current collector plate 12 and the negative electrode external terminal 8.

[0042] (1-2) Detailed Configuration of Current Collector Plate Next, the detailed configuration of the positive electrode current collector 11 in the secondary battery 1 will be described. Note that the negative electrode current collector 12 has the same configuration as the positive electrode current collector 11, and since the relationship between the positive electrode current collector 11 and the positive electrode external terminal 7 is the same as the relationship between the negative electrode current collector 12 and the negative electrode external terminal 8, the description of the negative electrode current collector 12 will be omitted.

[0043] FIG. 4 and FIG. 5 show the state in which the positive electrode current collector 11 and the positive electrode external terminal 7 of the secondary battery 1 are connected. Specifically, FIG. 4 shows a cross section in a plane parallel to the xz plane of the positive electrode current collector 11 and the positive electrode external terminal 7 in a state where the positive electrode external terminal 7 is connected to the positive electrode current collector 11, and FIG. 5 shows a cross section in a plane parallel to the yz plane of the positive electrode current collector 11 and the positive electrode external terminal 7 in such a state.

[0044] As described above, the positive electrode current collector 11 includes a base portion 11A bent to face parallel to the battery lid 4, and an extending portion 11B extending in the direction of the bottom surface 3D along the wide side surface 3A of the battery can 3.

[0045] The base portion 11A of the positive electrode current collector 11 includes a first base configuration portion C1 that constitutes one end side in the longitudinal direction of the base portion 11A and is a portion continuous from the extending portion 11B, a second base configuration portion C2 that constitutes the other end side in the longitudinal direction of the base portion 11A and to which the positive electrode external terminal 7 is connected, and a third base configuration portion C3 that is a configuration portion of the base portion 11A between the first base configuration portion C1 and the second base configuration portion C2.

[0046] And the positive electrode current collector 11 of the present embodiment is characterized in that the plate thickness of the first base configuration portion C1 (the thickness of the first base configuration portion C1 in the z direction) is the same as the plate thickness of the extending portion 11B, while the second base configuration portion C2 is formed thinner (thinned) than the first base configuration portion C1 throughout the entire region in the direction from the first base configuration portion C1 to the second base configuration portion C2 (that is, in the longitudinal direction of the base portion 11A of the positive electrode current collector 11) by pressing or cutting.

[0047] Specifically, the second base component C2 is thinned such that the facing surface (lower surface) with the power storage element 5 is positioned in a direction away from the power storage element 5 compared to the facing surface (lower surface) with the power storage element 5 in the first base component C1. For this reason, the lower surface side of the third base component C3 is formed in a tapered shape that slopes from the first base component C1 toward the second base component C2.

[0048] Thus, in the secondary battery 1 of this embodiment, by thinning the entire second base component C2 of the positive electrode current collector plate 11 more than the first base component C2, the internal capacity of the battery container 2 can be reduced by that amount, and thus it can be made smaller than before.

[0049] Also, when thinning the second base component C2 by pressing, since the second base component C2 extends in a direction perpendicular to the pressing direction, it is necessary to cut off the excess. And by cutting off the excess in this way, the positive electrode current collector plate 11, and thus the entire secondary battery 1, can be lightened. Also, even when the second base component C2 is formed by cutting, naturally the positive electrode current collector plate 11, and thus the entire secondary battery 1, can be lightened.

[0050] FIG. 6 schematically shows with arrows the state of the current flowing between the positive electrode current collector plate 11 and the positive electrode external terminal 7. The direction of the current flowing between the negative electrode current collector plate 12 and the negative electrode external terminal 8 is opposite to that in FIG. 6, but the current path is the same.

[0051] In the secondary battery 1 of this embodiment, since the second base component C2 is thinner than the first base component C1 in the base 11A of the positive electrode current collector plate 11, compared to the case where the second base component C2 has the same thickness as the first base component C1, the current path flowing from the caulking portion 7BA of the positive electrode external terminal 7 to the positive electrode external terminal 7 becomes shorter. As a result, it is possible to suppress an increase in the electrical resistance of the current path from the positive electrode current collector plate 11 to the positive electrode external terminal 7, and it is also possible to suppress heat generation of the positive electrode current collector plate 11.

[0052] Actually, according to simulations, by setting the thickness ratio of the second base component C2 to the plate thickness of the first base component C1 to be 5:2 or more and 5:3 or less, it was confirmed that the heat generation suppression effect is enhanced.

[0053] Therefore, according to the present embodiment, since the volume and weight of the positive electrode current collector plate 11 and the negative electrode current collector plate 12 of the secondary battery 1 can be effectively reduced, it is possible to make the battery smaller and lighter than before, and it is possible to realize a secondary battery that suppresses heat generation and can withstand large current charging and discharging.

[0054] In addition, in the case of the present embodiment, the second base component C2 in the base 11A of the positive electrode current collector 11 is formed thicker than the second base component C2 in the base 12A of the negative electrode current collector plate 12. This is because the resistivity of aluminum or an aluminum alloy, which is the material of the positive electrode current collector plate 11, is higher than the resistivity of copper or a copper alloy, which is the material of the negative electrode current collector plate 12. Therefore, by forming the second base component C2 in the base 11A of the positive electrode current collector plate 11 thicker than the second base component C2 in the base 12A of the negative electrode current collector plate 12, the resistance value of the second base component C1 of the positive electrode current collector plate 11 can be reduced.

[0055] Thus, according to the present secondary battery 1, heat generation in the base 11A of the positive electrode current collector plate 11 can be further suppressed, and thus a secondary battery that can further withstand large current charging and discharging can be realized.

[0056] (2) Second Embodiment FIGS. 7 and 8, in which the same reference numerals are given to the corresponding parts as in FIG. 4, show a positive electrode current collector plate 30 according to a second embodiment applied to the secondary battery 1 described above with reference to FIGS. 1 to 3 instead of the positive electrode current collector plate 11 of the first embodiment described above with reference to FIGS. 4 and 5. FIG. 7 shows a cross section of the positive electrode current collector plate 30 and the positive electrode external terminal 7 in a plane parallel to the xz plane with the positive electrode external terminal 7 connected to the positive electrode current collector plate 30 of the present embodiment, and FIG. 8 shows a cross section of the positive electrode current collector plate 30 and the positive electrode external terminal 7 in a plane parallel to the yz plane in such a state.

[0057] The configuration of the positive current collector plate according to the present embodiment applied to the secondary battery 1 described above with respect to FIGS. 1 to 3, instead of the negative current collector plate 12 of the first embodiment, is the same as that of the positive current collector plate 30. Therefore, detailed description here is omitted.

[0058] The positive current collector plate 30 of the present embodiment has the same configuration as the positive current collector plate 11 of the first embodiment in that it is composed of a base portion 30A bent so as to face the battery lid 4 in parallel and an extending portion 30B extending in the direction of the bottom surface 3D along the wide side surface 3A of the battery can 3 described above with respect to FIG. 1.

[0059] Also, the base portion 30A of the positive current collector plate 30 is, similar to the positive current collector plate 11 of the first embodiment, a first base configuration portion C10 that constitutes one end side in the longitudinal direction of the base portion 30A and is a part continuous with the extending portion 30B, a second base configuration portion C11 that constitutes the other end side in the longitudinal direction of the base portion 30A and to which the positive external terminal 7 is connected, and a third base configuration portion C12 that is a configuration part of the base portion 30A between the first base configuration portion C10 and the second base configuration portion C11.

[0060] And also in the positive current collector plate 30 of the present embodiment, the first base configuration portion C10 is formed to have the same thickness as the extending portion 30B, while the second base configuration portion C11 is formed thinner than the first base configuration portion C10 by press working or cutting working or the like. For this reason, the lower surface side of the third base configuration portion C12 is formed in a tapered shape that slopes from the first base configuration portion C10 toward the second base configuration portion C11.

[0061] In addition to such a configuration, on the lower surface side of the second base configuration portion C11 in the positive current collector plate 30, ribs 30AA protruding in a direction away from the battery lid 4 are provided along each end side in the width direction (y direction) of the second base configuration portion C11. In the case of the present embodiment, the height of such ribs 30AA is selected to be the same as the difference between the thickness of the first base configuration portion C10 and the thickness of the second base configuration portion C11, but any height can be applied as the height of the ribs 30AA.

[0062] Thus, according to the positive electrode current collector plate 30 of the present embodiment, the deformation of the second base component C11 caused by making the second base component C11 of the base 30A thinner than the first base component C10 can be suppressed by the rib 30AA. Thereby, it is possible to effectively prevent the deformation of the second base component C11 when caulking the connection part 7B of the positive electrode external terminal 7 so as to plastically deform with the tip diameter-expanded on the lower surface of the base 30A.

[0063] As described above, according to the present embodiment, in addition to the effects obtained by the first embodiment, when connecting the positive electrode external terminal 7 to the base 30A of the positive electrode current collector plate 30 or when connecting the negative electrode external terminal 8 to the base of the negative electrode current collector plate, it is possible to obtain the effect of suppressing the deformation of the second base component C11 of the base 30A, and thus the deformation of the entire base 30A.

[0064] (3) Third Embodiment FIG. 9, in which the same reference numerals are given to the corresponding parts as in FIG. 4, shows a partial configuration of a positive electrode current collector plate 40 according to a third embodiment applied to the secondary battery 1 described above with reference to FIGS. 1 to 3 instead of the positive electrode current collector plate 11 of the first embodiment described above with reference to FIGS. 4 and 5. FIG. 9 is an enlarged view of a cross-sectional portion in a plane parallel to the xz plane of the positive electrode current collector plate 40 and the positive electrode external terminal 7 in a state where the positive electrode external terminal 7 is connected to the positive electrode current collector plate 40 of the present embodiment.

[0065] Note that the configuration of the negative electrode current collector plate according to the present embodiment applied to the secondary battery 1 described above with reference to FIGS. 1 to 3 instead of the negative electrode current collector plate 12 of the first embodiment is the same as that of the positive electrode current collector plate 30, and thus the detailed description thereof is omitted here.

[0066] The positive electrode current collector plate 40 of the present embodiment has the same configuration as the positive electrode current collector plate 11 of the first embodiment in that it includes a base 40A bent so as to face the battery lid 4 in parallel and an extending portion 40B extending along the wide side surface 3A of the battery can 3 toward the bottom surface 3D.

[0067] However, the base portion 40A of the positive current collector plate 40 is composed of only a first base portion component C20 that constitutes one end side in the longitudinal direction of the base portion 40A and is continuous with the extending portion 40B, and a second base portion component C21 that constitutes the other end side in the longitudinal direction of the base portion 40A and to which the positive external terminal 7 is connected. That is, the boundary between the first base portion component C20 and the second base portion component C21 is an inclined surface 40C with an inclination angle of 90 degrees that connects between the lower surfaces of the first base portion component C20 and the second base portion component C21.

[0068] When the base portion 40A of the positive current collector plate 40 is configured in this way, since it is difficult to form the inclined surface 40C when thinning the second base portion component C21 by pressing, the second base portion component C21 is formed by cutting, and the inclined surface 40C is formed at this time.

[0069] Also, with the positive current collector plate 40 of the present embodiment having the above configuration and the negative current collector plate having a similar configuration, similar to the positive current collector plate 11 and the negative current collector plate 12 of the first embodiment, the volume and weight of the positive current collector plate 11 and the negative current collector plate 12 of the secondary battery 1 can be effectively reduced. Therefore, it is possible to make the secondary battery smaller and lighter than before, and also to suppress heat generation and realize a secondary battery that can withstand high-current charging and discharging.

[0070] (4) Fourth Embodiment FIG. 10, in which the same reference numerals are given to corresponding parts as in FIG. 4, shows a partial configuration of a positive current collector plate 50 according to a fourth embodiment applied to the secondary battery 1 described above with reference to FIGS. 1 to 3, instead of the positive current collector plate 11 of the first embodiment described above with reference to FIGS. 4 and 5. FIG. 10 is an enlarged view of a cross-sectional portion in a plane parallel to the xz plane of the positive current collector plate 50 and the positive external terminal 7 with the positive external terminal 7 connected to the positive current collector plate 50 of the present embodiment.

[0071] Note that the configuration of the negative current collector plate according to the present embodiment applied to the secondary battery 1 described above with reference to FIGS. 1 to 3, instead of the negative current collector plate 12 of the first embodiment, is the same as that of the positive current collector plate 50, and thus the detailed description here is omitted.

[0072] The positive current collector 50 of this embodiment has the same configuration as the positive current collector 11 of the first embodiment in that it is composed of a base portion 50A bent to face the battery lid 4 in parallel and an extending portion 50B extending along the wide side surface 3A of the battery can 3 toward the bottom surface 3D.

[0073] Also, the base portion 50A of the positive current collector 50 is composed of a first base configuration portion C30 that constitutes one end side in the longitudinal direction of the base portion 50A and is a part continuous with the extending portion 50B, a second base configuration portion C31 that constitutes the other end side in the longitudinal direction of the base portion 50A and to which the positive external terminal 7 is connected, and a third base configuration portion C32 that is a configured part of the base portion 50A between the first base configuration portion C30 and the second base configuration portion C31, which is also the same as the positive current collector 11 of the first embodiment.

[0074] However, in the case of the positive current collector 50 of this embodiment, the third base configuration portion C32 is not an inclined surface, but is formed in a curved surface shape connecting the lower surface of the first base configuration portion C30 and the lower surface of the second base configuration portion C31. By configuring the positive current collector 50 in this way, when thinning the second base configuration portion C31 of the base portion 50A, not only cutting but also pressing can be used as a method. And when thinning the second base configuration portion C31 of the base portion 50A, by applying pressing, the manufacturing time of the positive current collector 50 can be shortened compared to cutting, and accordingly, the manufacturing cost of the positive current collector 50 can be reduced.

[0075] (5) Other embodiments In the above-described first to fourth embodiments, the case where the present invention is applied to the rectangular secondary battery configured as shown in FIGS. 1 to 3 has been described. However, the present invention is not limited to this, and can be widely applied to secondary batteries with various other configurations.

[0076] In the above-described first to fourth embodiments, a current collector (positive current collector plate 11) that electrically connects between the positive electrode electrode laminate portion 5A of the power storage element 5 and the positive external terminal 7, and a current collector that electrically connects between the negative electrode electrode laminate portion 5B of the power storage element 5 and the negative external terminal 8 (negative current collector plate 12) have been described as being formed by bending a plate-like member. However, the present invention is not limited to this. As long as it is possible to electrically connect between the positive electrode electrode laminate portion 5A of the power storage element 5 and the positive external terminal 7, and between the negative electrode electrode laminate portion 5B of the power storage element 5 and the negative external terminal 8, various other configurations can be widely applied as the configuration of such a current collector.

[0077] Furthermore, in the above-described first to fourth embodiments, the case where the lower surface sides of the second base constituent portions C2, C11, C21, C31 of the bases 11A, 30A, 40A, 50A of the positive current collector plates 11, 30, 40, 50 and the second base constituent portion of the base 12A of the negative current collector plate 12 are thinned by pressing or cutting has been described. However, the present invention is not limited to this. The entire upper surface side or both the upper surface side and the lower surface side of such second base constituent portions C2, C11, C21, C31 may be thinned.

[0078] Furthermore, in the above-described second embodiment, the case where the rib 30AA is provided on the lower surface side of the second base constituent portion C11 of the base 30A of the positive current collector plate 30 has been described. However, the present invention is not limited to this. Such a rib 30AA may be provided on the upper surface side of such second base constituent portion C11 so as to protrude in a direction approaching the battery lid 4.

[0079] Furthermore, in the above-described second embodiment, the case where the rib 30AA is provided only on the lower surface side of the second base constituent portion C11 of the base 30A of the positive current collector plate 30 has been described. However, the present invention is not limited to this. A rib integral with such a rib 30AA may also be formed on the lower surface of the third base constituent portion C12 and / or the first base constituent portion C10.

[0080] Furthermore, in the above-described second embodiment, the case where the ribs 30AA are provided at both end portions in the width direction on the lower surface of the second base component C11 of the base portion 30A of the positive current collector 30 has been described. However, the present invention is not limited thereto, and the ribs 30AA may be provided only on one end side in the width direction on the lower surface of such a second base component C11. Further, the ribs 30AA may be provided at a location other than the end portions in the width direction on the lower surface of such a second base component C11 and at a location where it does not interfere with the connection of the positive external terminal 7.

Industrial Applicability

[0081] The present invention can be widely applied to prismatic secondary batteries and other forms of secondary batteries.

Explanation of Reference Numerals

[0082] 1... Secondary battery, 2... Battery container, 3... Battery can, 4... Battery lid, 5... Power storage element, 5A... Positive electrode laminate, 5B... Negative electrode laminate, 7... Positive external terminal, 7A, 8A... Joint portion, 7B, 8B... Connection portion, 8... Negative external terminal, 11, 30, 40, 50... Positive current collector, 11A, 12A, 30A, 40A, 50A... Base portion, 12... Negative current collector, 30AA... Rib, 11B, 12B, 30B, 40B, 50B... Extension portion, 40C... Inclined surface, C1~C3, C10~C12, C20, C21, C30~C32... Base component.

Claims

1. In a secondary battery in which a power storage element that charges and discharges electricity is housed in an exterior body, a box body that constitutes the exterior body and has one side open, and a lid that closes the one side of the box body, an external terminal attached to the lid so that at least a part thereof is exposed to the outside from the lid, and a current collector that electrically connects between the power storage element and the external terminal, wherein the current collector has an extending portion electrically connected to the power storage element, and a plate-shaped base portion disposed along the lid and electrically connected to the external terminal, wherein the base portion has a first base portion component that forms one end side in the longitudinal direction of the base portion and is a portion continuous from the extending portion, and a second base portion component that forms the other end side in the longitudinal direction of the base portion and is connected to the external terminal, the second base portion component is formed to be thinner in plate thickness than the first base portion component, and a rib that protrudes in a direction approaching or separating from the lid is provided on at least one end side in the width direction of a first surface of the second base portion component facing the lid or a second surface on the opposite side of the first surface. A secondary battery characterized by the above.

2. The second base portion component is formed to be thinner than the first base portion component throughout the longitudinal direction of the base portion. The secondary battery according to claim 1, characterized by the above.

3. The second base portion component is thinned such that a surface facing the power storage element is positioned in a direction away from the power storage element compared to a surface facing the power storage element in the first base portion component. The secondary battery according to claim 1, characterized by the above.

4. The ratio of the plate thickness of the first base portion component to the plate thickness of the second base portion component is 5:2 or more and 5:3 or less. The secondary battery according to claim 1, characterized by the above.

5. A third base portion component is provided between the first base portion component and the second base portion component of the base portion, and at least one surface side is formed in a tapered shape that slopes from the first base portion component toward the second base portion component. The secondary battery according to claim 1, characterized by the above.

6. One surface side of the first base portion component and one surface side of the second base portion component are connected by an inclined surface with an inclination angle of 90 degrees. The secondary battery according to claim 1, characterized by the above.

7. A third base component is provided between the first base component and the second base component of the base, and is formed in a curved surface shape that connects at least one surface side to one surface of the first base component and one surface of the second base component. The secondary battery according to claim 1, characterized in that.

8. The current collector is a positive current collector connected to the positive electrode of the power storage element and a negative current collector connected to the negative electrode of the power storage element, The external terminal is a positive external terminal connected to the positive current collector and a negative external terminal connected to the negative current collector, The plate thickness of the second base component of the base in the positive current collector is thicker than the plate thickness of the second base component of the base in the negative current collector. The secondary battery according to any one of claims 1 to 5, characterized in that.

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