JP2015103420A - Square secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a square secondary battery which ensures excellent electrolyte permeability to a wound electrode group, while preventing fracture of the positive electrode uncoated part and negative electrode uncoated due to vibration ot impact in the market environment.SOLUTION: A square secondary battery C1 has a through hole 40 for introducing the electrolyte into a wound electrode group 3, in a region from the end 70 on the bottom side 22 of a battery can 1 in the positive electrode side weld zone 31c of a positive electrode uncoated part 31c to the top 71 of a bend 50 on the bottom side 22 of a battery can 1 of the positive electrode side weld zone 31c, and a region from the end 70 on the bottom side 22 of a battery can 1 in the negative electrode side weld zone 32d of a negative electrode uncoated part 32c to the top 71 of a bend 50 on the bottom side 22 of a battery can 1 of the negative electrode uncoated part 32c. Furthermore, the through hole 40 is immersed in the free liquid electrolyte.

Description

  The present invention relates to a prismatic secondary battery.

  Since lithium ion secondary batteries have a higher energy density than other secondary batteries, they are now mainly used in portable devices such as digital cameras, notebook computers and mobile phones. In recent years, research and development of large-sized lithium ion secondary batteries for the purpose of electric vehicles and power storage have been actively conducted in order to cope with environmental problems. In particular, in the automobile industry, the development of electric vehicles using a motor as a power source and hybrid electric vehicles using both an internal combustion engine and a motor are underway, some of which have already been put into practical use. Yes.

  As a conventional lithium ion secondary battery, a wound electrode group formed by winding a belt-like positive electrode and a negative electrode through a separator, and a prismatic secondary battery in which the wound electrode group and an electrolytic solution are accommodated in a can. It has been known. In this type of prismatic secondary battery, as an in-vehicle lithium ion secondary battery that mainly requires high output, uncoated portions of the positive electrode and the negative electrode are provided at both ends in the winding axis direction of the wound electrode group. A simple configuration is made possible by projecting and connecting the projected uncoated portion to a current collector.

  In a lithium ion secondary battery, an electrolytic solution is injected in order to advance the battery reaction. The electrolyte solution penetrates inside the wound electrode group and causes a battery reaction. However, in the general wound electrode group, the electrolyte solution penetrates mainly from the end in the winding axis direction. There is a problem that it takes.

  In Patent Document 1, a plurality of through holes are formed along a winding direction between a welded portion with a positive electrode current collector in a positive electrode uncoated portion and the positive electrode coated portion, and a negative electrode uncoated portion. An invention is disclosed in which a plurality of through holes are formed along a winding direction between a welded portion with a negative electrode current collector and a negative electrode coating portion. According to the invention described in Patent Document 1, since the electrolytic solution permeates through the through-holes, the penetration of the electrolytic solution in the wound electrode group is accelerated, and the liquid injection operation is shortened.

JP 2013-171733 A

  However, in the invention described in Patent Document 1, a plurality of through holes are provided on the center side in the winding axis direction with respect to the current collecting weld holding the wound electrode group, and the coating is not applied by the through holes. Since the area of the part is reduced, the mechanical strength is low. There is a possibility that the wound electrode group is shaken in the battery can due to vibration or impact in the market environment, and as a result, the positive electrode uncoated portion or the negative electrode uncoated portion may be broken.

  The prismatic secondary battery according to the invention of claim 1 includes an electrolyte, a positive electrode having a positive electrode coated part in which a positive electrode active material is coated on a positive electrode foil, and a non-coated positive electrode uncoated part, and A wound electrode group in which a negative electrode having a negative electrode coated portion coated with a negative electrode active material and a non-coated negative electrode uncoated portion is wound in a flat shape with a separator interposed therebetween, A battery can that houses the rotating electrode group, a battery lid that seals the battery can, a positive electrode current collector connected to the positive electrode uncoated part via the positive electrode side welded part, and a negative electrode side welded part A negative electrode current collector connected to the negative electrode uncoated part, and the wound electrode group is outside the region between the positive electrode side welded part and the positive electrode coated part in the positive electrode uncoated part, or the negative electrode uncoated part. The through hole has a through hole anywhere outside the region between the negative electrode side welded portion and the negative electrode coated portion, and at least a part of the through hole is an electrolyte solution. Characterized in that it is immersed in free liquid. That is, the through hole is a region from the winding direction battery can bottom side end of the positive electrode side welded portion to the apex of the curved portion of the winding electrode group on the winding direction battery can bottom side, the positive electrode side in the positive electrode uncoated portion Winding direction battery lid side end of the winding electrode group on the winding direction battery lid side of the welding part to the apex of the curved part of the winding electrode group on the winding direction battery lid side The region from the end to the apex of the curved portion of the wound electrode group on the bottom side of the winding direction battery can, and the winding direction of the negative electrode side welded portion in the negative electrode uncoated portion It is provided in any of the regions up to the apex of the curved portion of the wound electrode group on the battery lid side.

  According to the present invention, it is possible to provide a prismatic secondary battery having excellent electrolyte solution permeability to a wound electrode group while preventing breakage of a positive electrode uncoated portion and a negative electrode uncoated portion due to vibration or impact in a market environment.

The external appearance perspective view of a square secondary battery. The disassembled perspective view of a square secondary battery. The figure which shows the winding electrode group before welding a collector. The figure of the winding electrode group of 1st Embodiment which provided the through-hole. Schematic which shows the process of providing a through-hole. The figure of the winding electrode group of 2nd Embodiment which provided the through-hole in the top part of the curved part. The figure of the winding electrode group of 3rd Embodiment which provided the through-hole which penetrates the winding electrode group uncoated part from one outer peripheral surface to another outer peripheral surface. The figure of the winding electrode group of 4th Embodiment which provided the square through-hole. The figure of the winding electrode group of 5th Embodiment which provided the several through-hole. The figure which shows the modification of how to provide a through-hole.

-First embodiment-
FIG. 1 is a perspective view showing the external appearance of the prismatic secondary battery C1, and FIG. 2 is an exploded perspective view showing the configuration of the prismatic secondary battery C1 of FIG.

  As shown in FIGS. 1 and 2, the square secondary battery C <b> 1 has a flat rectangular parallelepiped shape and includes a battery container including a battery can 1 and a battery lid 6. The material of the battery can 1 and the battery lid 6 is aluminum or an aluminum alloy.

  As shown in FIG. 2, the wound electrode group 3 is accommodated in the battery can 1. The battery can 1 has a pair of wide surfaces 21a, a pair of narrow surfaces 21b, and a bottom surface 22, and is formed in a bottomed box shape having one end opened as an opening 1a. The wound electrode group 3 is accommodated in the battery can 1 while being covered with the insulating protective film 2. The material of the insulating protective film 2 is an insulating resin such as polypropylene or polyethylene terephthalate. Thereby, the bottom face and side face of the battery can 1 and the wound electrode group 3 are electrically insulated.

  As shown in FIGS. 1 and 2, the battery lid 6 has a rectangular flat plate shape and is laser-welded so as to close the opening of the battery can 1. That is, the battery lid 6 seals the opening of the battery can 1. The battery lid 6 is provided with a positive external terminal 8A and a negative external terminal 8B.

  The positive electrode external terminal 8A is electrically connected to the positive electrode side weld 31d of the wound electrode group 3 via the positive electrode current collector 4A, and the negative electrode external terminal 8B is connected to the wound electrode group 3 via the negative electrode current collector 4B. It is electrically connected to the negative electrode side welding part 32d. Therefore, electric power is supplied to the external load via the positive external terminal 8A and the negative external terminal 8B, or external generated power is supplied to the wound electrode group 3 via the positive external terminal 8A and the negative external terminal 8B. Charged.

As shown in FIG. 2, the battery lid 6 is provided with a liquid injection port 9 for injecting an electrolytic solution into the battery container. The liquid injection port 9 is sealed with a liquid injection stopper 11 after the electrolytic solution is injected. As the electrolytic solution, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a carbonate-based organic solvent such as ethylene carbonate can be used.

  As shown in FIG. 1, a gas discharge valve 10 is recessed on the surface of the battery lid 6. The gas discharge valve 10 is formed by partially thinning the battery lid 6 by press work so that the degree of stress concentration at the time of internal pressure action is relatively high. The gas discharge valve 10 generates heat when the square secondary battery C1 generates heat due to an abnormality such as overcharge, and when the pressure in the battery container rises and reaches a predetermined pressure, the gas discharge valve 10 is opened and gas is discharged from the inside. By discharging, the pressure in the battery container is reduced.

  As shown in FIG. 2, a positive electrode external terminal 8A, a negative electrode external terminal 8B, a positive electrode current collector 4A, and a negative electrode current collector 4B are attached to the battery lid 6. Gaskets 5 are disposed between the positive external terminal 8A and the battery cover 6 and between the negative external terminal 8B and the battery cover 6, respectively. Insulating plates 7 are disposed between the positive electrode current collector 4 </ b> A and the battery lid 6 and between the negative electrode current collector 4 </ b> B and the battery lid 6.

  The material of the positive electrode external terminal 8A and the positive electrode current collector 4A is an aluminum-based metal, that is, aluminum or an aluminum alloy. 8 A of positive electrode external terminals have a rectangular parallelepiped external terminal part and the protrusion part which protrudes toward the battery cover 6 side from the battery cover 6 side surface of an external terminal part. The protrusion is inserted into the through hole of the gasket 5, the positive side through hole 6A of the battery lid 6, the through hole of the insulating plate 7, and the positive side opening hole 43A of the positive current collector base 41A of the positive current collector 4A. The tip is caulked to the positive electrode current collector base 41A of the positive electrode current collector 4A in the battery container to form the positive electrode connection portion 12A. The positive electrode connecting portion 12A and the positive electrode current collector base portion 41A are fixed by caulking and then spot welded by a laser. Thus, the positive external terminal 8A and the positive current collector 4A are electrically connected, and the positive external terminal 8A and the positive current collector 4A are fixed to the battery cover 6.

  The material of the negative electrode external terminal 8B and the negative electrode current collector 4B is a copper-based metal, that is, copper or a copper alloy. The negative electrode external terminal 8B has a rectangular parallelepiped external terminal portion and a protrusion protruding from the surface of the external terminal portion on the battery lid 6 side toward the battery lid 6 side. The protrusion is inserted into the through hole of the gasket 5, the positive electrode side through hole 6A of the battery cover 6, the through hole of the insulating plate 7, and the negative electrode side opening hole 43B of the negative electrode current collector base 41B of the negative electrode current collector 4B. The tip is caulked to the negative electrode current collector base 41B of the negative electrode current collector 4B in the battery container to form the negative electrode connection portion 12B. The negative electrode connection portion 12B and the negative electrode current collector base portion 41B are caulked and fixed, and then spot welded by a laser. Thereby, the negative electrode external terminal 8B and the negative electrode current collector 4B are electrically connected, and each of the negative electrode external terminal 8B and the negative electrode current collector 4B is fixed to the battery lid 6.

  The material of the gasket 5 and the insulating plate 7 is a resin having insulation properties such as polybutylene terephthalate, polyphenylene sulfide, perfluoroalkoxy fluororesin. A gasket 5 is disposed between each of the positive external terminal 8 </ b> A and the negative external terminal 8 </ b> B and the battery cover 6. For this reason, each of the positive electrode external terminal 8A and the negative electrode external terminal 8B is electrically insulated from the battery lid 6. An insulating plate 7 is disposed between each of the positive electrode current collector base 41A of the positive electrode current collector 4A and the negative electrode current collector base 41B of the negative electrode current collector 4B and the battery lid 6. Therefore, each of positive electrode current collector 4A and negative electrode current collector 4B is electrically insulated from battery cover 6.

  As shown in FIG. 2, the positive electrode current collector 4 </ b> A includes a rectangular flat plate-shaped positive electrode current collector base 41 </ b> A disposed along the inner surface of the battery lid 6, and substantially from the long side of the positive electrode current collector base 41 </ b> A. The positive electrode side flat plate portion 44A that is bent at a right angle and extends toward the bottom surface 22 of the battery can 1 along the wide surface 21a of the battery can 1, and the positive electrode side connecting portion 45A provided at the lower end of the positive electrode side flat plate portion 44A. And a positive electrode side connection end 42A to be connected. The positive electrode side connection end portion 42 </ b> A is a portion that is ultrasonically welded to the positive electrode side welding portion 31 d of the wound electrode group 3.

  Similarly, the negative electrode current collector 4B is bent at a substantially right angle from the rectangular flat plate negative electrode current collector base portion 41B arranged along the inner surface of the battery lid 6 and the long side of the negative electrode current collector base portion 41B. The negative electrode side plate portion 44B extending toward the bottom surface 22 of the battery can 1 along the wide surface 21a of the battery can 1, and the negative electrode connected by the negative electrode side connecting portion 45B provided at the lower end of the negative electrode side flat plate portion 44B Side connection end 42B. The negative electrode side connection end portion 42 </ b> B is a portion that is ultrasonically welded to the negative electrode side welding portion 32 d of the wound electrode group 3.

  FIG. 3A shows a wound electrode group before the positive electrode current collector 4A is welded to the positive electrode uncoated part 31c and before the negative electrode current collector 4B is welded to the negative electrode uncoated part 32c. It is a disassembled perspective view which shows the state which expand | deployed the winding end side of 3. FIG. The wound electrode group 3 is configured by winding in a flat shape via a separator 33 between the negative electrode 32 and the positive electrode 31. As the shaft core for winding, one formed by winding a resin sheet having higher bending rigidity than any of the positive electrode foil 31a, the negative electrode foil 32a, and the separator 33 can be used. In the wound electrode group 3, the outermost electrode is the negative electrode 32, and the separator 33 is wound outside thereof. The separator 33 has a role of insulating between the positive electrode 31 and the negative electrode 32. The positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c are regions where the metal surface of the electrode foil is exposed. In the wound electrode group 3, the positive electrode uncoated portion 31 c is disposed on one side in the winding axis direction, and the negative electrode uncoated portion 32 c is wound on the other side in the winding axis direction. Is done.

  Here, the winding direction will be described. The winding direction is similar in terms to the winding axis direction, but the concept is different. As shown in FIG. 3A, the winding axis direction is a direction parallel to the winding axis of the wound electrode group, whereas the wound direction is a direction in which the wound electrode group is wound. means.

In order to fabricate the positive electrode 31, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of polyfluoride as a binder with respect to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material A positive electrode mixture was prepared by adding vinylidene (hereinafter referred to as PVDF), adding N-methylpyrrolidone (hereinafter referred to as NMP) as a dispersion solvent, and kneading. This positive electrode mixture was applied to both surfaces of a positive electrode foil 31a made of an aluminum foil having a thickness of 20 μm to provide a positive electrode mixture coating portion 31b. In that case, the positive electrode uncoated part 31c was provided in both surfaces of the one edge part of the width direction of the positive electrode foil 31a by not coating a positive mix. Then, the positive electrode 31 was obtained through the drying, the press, and the cutting process. In addition, the thickness of the positive mix application part 31b which deducted the thickness of the positive electrode foil 31a was 90 micrometers.

  In order to produce the negative electrode 32, 10 parts by weight of PVDF as a binder was added to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and NMP was added and kneaded as a dispersion solvent thereto. A mixture was prepared. This negative electrode mixture was applied to both surfaces of a negative electrode foil 32a made of a copper foil having a thickness of 10 μm to provide a negative electrode mixture coating portion 32b. In that case, the negative electrode uncoated part 32c was provided in both surfaces of the one end part of the width direction of the negative electrode foil 32a by not coating a negative electrode mixture. Then, the negative electrode 32 was obtained through the drying, the press, and the cutting process. In addition, the thickness of the negative electrode mixture coating part 32b which deducted the thickness of the negative electrode foil 32a was 70 micrometers.

  The negative electrode mixture coating portion 32b is larger in the width direction than the positive electrode mixture coating portion 31b, and the positive electrode mixture coating portion 31b extends from the negative electrode mixture coating portion 32b in the winding axis direction in the wound electrode group 3. It is arranged so as not to protrude. The positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c are bundled and connected to the positive electrode current collector 4A and the negative electrode current collector 4B, respectively, by welding. The separator 33 is larger in the width direction than the negative electrode mixture coating portion 32b. However, since the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c in the wound electrode group 3 are arranged so as to protrude outward in the winding axis direction from the separator 33, the separator 33 is the positive electrode uncoated portion. This does not hinder the welding of 31c and negative electrode uncoated portion 32c.

  FIG. 3B shows a wound electrode group before the positive electrode current collector 4A is welded to the positive electrode uncoated part 31c and before the negative electrode current collector 4B is welded to the negative electrode uncoated part 32c. It is the figure which looked at 3 from the winding axis direction. In this specification, the bending portion refers to a region 50 surrounded by a dotted line provided above and below the drawing, that is, a region 50 at both ends of the wound electrode group 3, and is hereinafter referred to as a bending portion 50. . When the curved portion 50 is defined in consideration of after welding of the positive electrode uncoated portion 31c and after welding of the negative electrode uncoated portion 32c, “the positive electrode mixture coated portion 31b, the negative electrode mixture coated portion 32b, A curved region in the central portion of the wound electrode direction 3 of the wound electrode group 3 constituted by the separator 33, and a positive electrode uncoated portion 31c extending from the region in the wound axial direction and the negative electrode It becomes an area | region of the coating part 32c. The definition is such that the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c are the central portions of the positive electrode uncoated portion 31 and the negative electrode uncoated portion 32c shown in the center of FIG. 3B. This is because it is not preferable to use the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c as a reference because the vicinity of 51 is bundled, welded, and deformed. Note that an end portion of the bending portion 50 in the illustrated vertical direction is referred to as a vertex 71.

  FIG. 4A is a front view of the wound electrode group 3 of the first embodiment. FIG.4 (b) is AA sectional drawing of Fig.4 (a). Note that the BB cross-sectional view of FIG. 4A is the same as FIG. That is, the description of the through hole 40 provided in the negative electrode uncoated portion 32c of the wound electrode group 3 is the same as the description of the through hole 40 provided in the positive electrode uncoated portion 31c of the wound electrode group 3. Therefore, it is omitted.

  As shown in FIG. 4 (a), in the wound electrode group 3 of the first embodiment, the negative electrode is not formed from the end portion 70 on the bottom surface 22 side of the battery can 1 in the negative electrode side welded portion 32d of the negative electrode uncoated portion 32c. A round through-hole 40 is provided as a passage for guiding the electrolyte to the inside of the wound electrode group 3 in the region up to the vertex 71 of the curved portion 50 on the bottom surface 22 side of the battery can 1 of the coating portion 32c. Yes. The through hole 40 is provided at a position where it is difficult to receive a load from the wound electrode group. To reduce the influence, the winding direction of the battery can 1 in the negative electrode side welded part 32d of the negative electrode uncoated part 32c is provided. The through hole 40 may be provided in a region from the end portion 70 on the bottom surface 22 side to the apex 71 of the curved portion 50 on the bottom surface 22 side in the winding direction of the battery can 1 of the negative electrode uncoated portion 32c. By setting it as the winding direction bottom face 22 side, the limitation of the area | region from the winding axial direction edge part 72 of the negative electrode side welding part 32d to the winding axial direction edge part 73 of the negative electrode side welding part 32d is added. Note that the through hole 40 provided in the positive electrode uncoated portion 31c is also provided in the same manner as the negative electrode side. That is, from the end portion 70 on the bottom surface 22 side of the battery can 1 in the positive electrode side welding portion 31d of the positive electrode uncoated portion 31c to the apex 71 of the curved portion 50 on the bottom surface 22 side of the battery can 1 in the positive electrode uncoated portion 31c. A through hole 40 is provided in the region.

  As shown in FIG. 4B, the through hole 40 is provided so as to penetrate from the outer peripheral side surface to the inner peripheral side surface of the positive electrode uncoated portion 31 c of the wound electrode group 3. Therefore, only one of the through-holes 40 of the outer peripheral surface of the wound electrode group 3 facing the wide surface 21a of the battery can 1 is opened. By opening the outer peripheral surface in this way, the electrolytic solution can be guided to the inside of the wound electrode group 3.

  The square secondary battery C1 is generally placed so that the bottom surface 22 of the battery can 1 is perpendicular to the direction of gravity, that is, so-called vertical placement. Therefore, since the electrolyte free solution is collected on the bottom surface 22 side of the battery can 1, the electrolyte solution collected at the bottom of the battery can 1 is more provided by providing the through hole 40 on the bottom surface 22 side of the battery can 1. It becomes easy to be immersed in the free liquid.

  FIG. 5A is a schematic diagram illustrating a process of providing the through hole 40. FIG. 5B shows the wound electrode group 3 after the through hole 40 and before press molding. The wound electrode group 3 is produced by winding the negative electrode 32 and the positive electrode 31 in a flat shape via the separator 33. The through hole 40 is provided after the winding process and before press molding. As shown in FIG. 5A, the positive electrode foil 31a and the negative electrode foil 32a are formed on the wound electrode group 3 after the winding process and before press molding using the passage processing punch 61 and the passage processing jig 62. A through hole 40 is provided. And as shown in FIG.5 (b), in order to position the through-hole 40 provided in the positive electrode uncoated part 31c and the negative electrode uncoated part 32c in the above-mentioned area | region, a winding axis | shaft is used as a rotating shaft. After adjusting the position of the through hole 40 by rotating the wound electrode group 3 by the rotation described above, the wound electrode group 3 is press-molded.

  In the case where the hole is provided before winding the electrode as in the invention described in Patent Document 1, alignment for forming the through hole is required when the electrode is wound. However, since the through hole 40 according to the first embodiment of the present invention is provided after winding the electrode, the above-described alignment is not required, and the through hole 40 can be easily provided in the positive electrode uncoated portion 31c.

  The positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c are bundled at the central portion 51 shown in FIG. 3B and connected to the positive electrode current collector 4A and the negative electrode current collector 4B by welding. At this time, it is preferable that the welding position and the portion where the through hole 40 is provided do not interfere with each other. As a welding method, ultrasonic welding or resistance welding can be used. Considering the influence of the material of the current collector, ultrasonic welding is preferable.

  After the through hole 40 is provided and the positive electrode uncoated portion 31 c and the negative electrode uncoated portion 32 c are welded, the wound electrode group 3 is inserted into the battery can 1 with the through hole 40 facing the bottom of the battery can 1. . The wound electrode group 3 has pores in each of the positive electrode 31, the negative electrode 32, and the separator 33, and the battery characteristics are exhibited by impregnating the pores with the electrolytic solution. Therefore, it is preferable to inject an amount of the electrolytic solution that is equal to or larger than the pore volume of the wound electrode group 3. However, from the viewpoint of weight reduction, it is preferable not to add an amount of the electrolyte that fills the entire volume of the battery can 1.

According to the square secondary battery C1 shown in the first embodiment, the following operational effects are obtained.
(1) In the square secondary battery C1, the bottom surface 22 side of the battery can 1 of the positive electrode uncoated portion 31c from the end portion 70 on the bottom surface 22 side of the battery can 1 in the positive electrode side welding portion 31d of the positive electrode uncoated portion 31c. And the bottom surface of the battery can 1 of the negative electrode uncoated portion 32c from the end portion 70 on the bottom surface 22 side of the battery can 1 in the negative electrode side welded portion 32d of the negative electrode uncoated portion 32c. A round through hole 40 is provided as a passage for guiding the electrolytic solution to the inside of the wound electrode group 3 in a region up to the vertex 71 of the curved portion 50 on the 22 side.
Thereby, since there is no through hole in the winding axis direction with respect to the positive electrode welded portion and the negative electrode welded portion, the mechanical strength of the uncoated portion is maintained, and the positive electrode uncoated portion and the negative electrode uncoated portion due to vibration and impact are maintained. Can be prevented from breaking.

(2) Since the through hole 40 is provided on the bottom surface 22 side of the battery can 1 and the outer peripheral surface side of the wound electrode group 3 is open, the through hole 40 is easily immersed in the electrolyte free liquid. As a result, the electrolytic solution can be easily guided into the wound electrode group 3, and the electrolytic solution in the wound electrode group 3 can be easily replaced.

  As another form of the through hole 40 shown in the first embodiment, the through hole 40 of the second to fifth embodiments shown below will be described. Explanations similar to those in the first embodiment are omitted.

-Second embodiment-
FIG. 6A is a front view of the wound electrode group 3 in which the through hole 40 is provided at the top of the curved portion 50 of the positive electrode uncoated part 31 c and the negative electrode uncoated part 32 c of the wound electrode group 3. FIG.6 (b) is AA sectional drawing of Fig.6 (a). Note that the BB cross-sectional view of FIG. 6A is the same as FIG. That is, the description of the through hole 40 provided in the negative electrode uncoated portion 32c of the wound electrode group 3 is the same as the description of the through hole 40 provided in the positive electrode uncoated portion 31c of the wound electrode group 3. Therefore, it is omitted.

  In the first embodiment, the curved portion 50 on the bottom surface 22 side of the battery can 1 in the positive electrode uncoated portion 31c from the end portion 70 on the bottom surface 22 side of the battery can 1 in the positive electrode side welded portion 31d of the positive electrode uncoated portion 31c. A region from the end 70 on the bottom surface 22 side of the battery can 1 to the bottom surface 22 side of the negative electrode uncoated portion 32c on the bottom surface 22 side in the region up to the vertex 71 and the negative electrode side welded portion 32d of the negative electrode uncoated portion 32c. A through hole 40 was provided in a region up to 50 vertices 71. In 2nd Embodiment, it provided in the top part of the curved part 50 of them. Thereby, the through-hole 40 becomes easy to be immersed in the free solution of the electrolytic solution, and the electrolytic solution more easily penetrates into the wound electrode group 3.

-Third embodiment-
FIG. 7A shows a wound electrode provided with a through-hole 40 that penetrates from one outer peripheral surface to the other outer peripheral surface in the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c of the wound electrode group 3. It is a front view of a group. FIG.7 (b) is AA sectional drawing of Fig.7 (a). Note that the BB cross-sectional view of FIG. 7A is the same as FIG. That is, the description of the through hole 40 provided in the negative electrode uncoated portion 32c of the wound electrode group 3 is the same as the description of the through hole 40 provided in the positive electrode uncoated portion 31c of the wound electrode group 3. Therefore, it is omitted.

  In the first embodiment, the through-hole 40 is provided so that only one of the two outer peripheral surfaces of the wound electrode group 3 facing the wide surface 21a of the battery can 1 is opened (FIG. 4B). . In 3rd Embodiment, as shown in FIG.7 (b), the through-hole 40 was provided so that it might penetrate from one outer peripheral surface to the other outer peripheral surface. Thereby, it becomes easier for the electrolytic solution to penetrate into the wound electrode group 3 than in the first embodiment.

-Fourth embodiment-
FIG. 8 is a front view of the wound electrode group 3 provided with the rectangular through holes 40. The shape of the through hole 40 of the first embodiment was a round shape. The shape of the through hole 40 of this embodiment is a square. Compared with the round shape, the square shape can provide a large passage in the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c for the four corners of the square shape, so that the electrolytic solution is contained in the wound electrode group 3 by that amount. Easy to penetrate. The square through hole 40 can be provided by a square hole processing punch 61.

-Fifth embodiment-
FIG. 9 is a front view of the wound electrode group 3 provided with a plurality of through holes 40. In the first embodiment, one through hole 40 is provided in each of the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c. In the present embodiment, a plurality of through holes 40 are provided for each uncoated portion. Thereby, compared with 1st Embodiment, when the total area of the cross-sectional area of a channel | path is the same, the direction of providing a plurality of small through-holes can maintain mechanical strength rather than providing one large through-hole. Moreover, since the area of the inner peripheral surface of the through-hole 40 increases, the electrolytic solution easily penetrates into the wound electrode group 3. The hole diameter into which the electrolytic solution penetrates and can be processed is preferably 1 mm, and the hole interval is preferably at least twice the hole diameter in consideration of the strength of the uncoated part. If the width of the positive electrode uncoated portion or the negative electrode uncoated portion protruding from the separator from the wound electrode group is 6 mm and the position of the through hole 40 is 2 mm from the separator, the separator is involved during processing. There is no. Since the length from the welded portion end to the apex of the curved portion is 20 mm, when a plurality of through-holes 40 are formed at the same position in the winding axis direction and in the winding direction, with respect to one uncoated portion Two to three places, preferably 5 to 7 places when the positions are shifted with respect to the winding axis direction and a plurality of places are formed in the winding direction. When a plurality of through-holes are provided at the same position in the winding direction and in the winding axis direction, the electrolyte that has permeated from the outer holes in the winding axis direction is discharged through the inner holes. The effect of liquid penetration cannot be expected. Further, it is necessary to consider that the plurality of through-holes are closer to the welded portion on the inner peripheral side than the outer peripheral side with the vertex of the curved portion being the center when press-molding. For this reason, when eight or more through-holes 40 are provided, there is a possibility that the mechanical strength is lowered due to the narrowing of the hole interval, and the through-holes interfere with the welded portion.

-Modification of how to provide through hole 40-
FIG. 10 is a view showing a modification of how to provide the through hole 40. In the first embodiment, the through-hole 40 is provided before the wound electrode group 3 is pressed and flattened, whereas in the present modification, the wound electrode group 3 is pressed and flattened. A through hole 40 was provided. Thereby, the position shift of the hole at the time of press molding can be prevented. The through-hole 40 of the third embodiment shown in FIG. 7 can be easily provided with the through-hole 40 if this modification is applied.

―Other variations―
In addition, the following modifications may be made in the present invention.

  In 1st, 3rd-5th embodiment, the bottom face 22 of the battery can 1 of the positive electrode uncoated part 31c from the edge part 70 by the side of the bottom face 22 of the battery can 1 in the positive electrode side welding part 31d of the positive electrode uncoated part 31c. Of the battery can 1 of the negative electrode uncoated portion 32c from the end portion 70 on the bottom surface 22 side of the battery can 1 in the negative electrode side welded portion 32d of the negative electrode uncoated portion 32c Although the through hole 40 is provided in the region up to the vertex 71 of the curved portion 50 on the bottom surface 22 side, it is more preferable to provide the curved portion 50 among them. By doing in this way, the through-hole 40 becomes easy to be immersed with the free liquid of electrolyte solution.

  The angle at which the through hole 40 is formed is preferably perpendicular to the outer surface of the uncoated part, that is, parallel to the stacking direction of the layers of the uncoated part constituting the wound electrode group 3. However, it is not limited to this. By providing the through hole 40 perpendicularly to the surface of the uncoated part, it can be provided easily and efficiently. On the other hand, since the surface area of the inner peripheral surface of the through hole 40 is increased by providing the through hole 40 at an angle with respect to the surface of the uncoated portion, the surface area of the inner peripheral surface of the through hole 40 is increased. The contact area with the electrolyte increases, and the electrolyte penetration efficiency increases.

  The size of the through hole 40 is preferably as large as possible within the range of the width of the uncoated portion from the viewpoint of facilitating the passage of the electrolyte free solution. However, the through hole 40 may be small if the through hole 40 has a sufficient passage through which the electrolyte free liquid flows.

  The through hole 40 is preferably provided on the bottom side of the battery can 1 from the lower end of the positive electrode current collector 4A or the negative electrode current collector 4B. There are two reasons for this. The first reason is to avoid the proximity of the positive electrode current collector 4A, the negative electrode current collector 4B, and the through hole 40. The positive electrode current collector 4A and the negative electrode current collector 4B are provided in the vicinity of the center of the battery can 1 in the bottom-battery lid 6 direction in the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c, respectively. When the through hole 40 is provided near the center of the battery can 1 in the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c in the direction of the battery lid 6 (the central portion 51 in FIG. 3B), This is because the positive electrode current collector 4 </ b> A or the negative electrode current collector 4 </ b> B is welded onto the hole 40, so that the welding strength may be lowered. Secondly, since the electrolyte free solution accumulates on the bottom side of the battery can 1, the through hole 40 is easily immersed in the electrolyte free solution. By providing the through hole 40 on the bottom side of the battery can 1, interference between the through hole 40 and the positive electrode current collector 4A or the negative electrode current collector 4B can be avoided, so that the welding strength is reduced, the metal foil is broken, and the like. This makes it possible to perform welding stably, and further makes it easy to immerse in the electrolyte free solution.

  It is preferable that the through hole 40 is provided in the center portion in the winding axis direction of the positive electrode uncoated portion 31c and the negative electrode uncoated portion 32c. As can be seen from FIG. 3 (a), the through hole 40 is near the boundary between the positive electrode uncoated portion 31c and the positive electrode mixture coated portion 31b, or the negative electrode uncoated portion 32c and the negative electrode mixture coated portion 32b. The separator 33 and the through-hole 40 may interfere with each other.

  The square secondary battery C1 is generally placed so that the bottom surface 22 of the battery can 1 is perpendicular to the direction of gravity, that is, so-called vertical placement. Therefore, as shown in the above embodiment, it is considered preferable to provide the through hole 40 on the bottom surface 22 side of the battery can 1. However, if the through hole 40 is immersed in the electrolyte free solution, the battery lid 6 side of the region other than the welded portion in the positive electrode uncoated portion 31c and the region other than the welded portion in the negative electrode uncoated portion 32c. A through hole 40 may be provided. As an example in which this is possible, for example, the prismatic secondary battery C1 is placed so that the wide surface 21a of the prismatic secondary battery C1 is perpendicular to the direction of gravity, that is, the prismatic secondary battery. It is conceivable that C1 is placed in a so-called horizontal orientation.

  The through hole 40 may be provided only in one of the region other than the welded portion in the positive electrode uncoated portion 31c and the region other than the welded portion in the negative electrode uncoated portion 32c. The electrolytic solution permeates from the wound electrode group 3 in which the through hole 40 is not provided in any of the region other than the welded portion in the positive electrode uncoated portion 31c and the region other than the welded portion in the negative electrode uncoated portion 32c. Because.

  As a positive electrode active material, other lithium manganate having a spinel crystal structure, a lithium manganese composite oxide partially substituted or doped with a metal element, lithium cobaltate having a layered crystal structure, lithium titanate, and the like A lithium-metal composite oxide in which a part of the metal is substituted or doped with a metal element may be used.

As a negative electrode active material, natural graphite capable of inserting and removing lithium ions, various artificial graphite materials, carbonaceous materials such as coke, and compounds such as Si and Sn (for example, SiO, TiSi _2, etc.) Or a composite material thereof. Also in the particle shape, there is no particular limitation such as a scale shape, a spherical shape, a fiber shape, or a lump shape.

  As a binder for the coating part in the positive electrode and the negative electrode, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes Polymers such as acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof can be used.

C1: prismatic secondary battery, 1: battery can, 1a: opening, 2: insulating protective film,
3: wound electrode group, 4A: positive electrode current collector, 4B: negative electrode current collector, 5: gasket
6: Battery cover, 6A: Positive electrode side through hole, 6B: Negative electrode side through hole, 7: Insulating plate,
8A: positive electrode external terminal, 8B: negative electrode external terminal, 9: injection port, 10: gas discharge valve,
11: Injection plug, 12A: Positive electrode connection part, 12B: Negative electrode connection part, 21a: Wide surface,
21b: narrow surface, 22: bottom surface, 31: positive electrode, 31a: positive foil,
31b: Positive electrode mixture coated part, 31c: Positive electrode uncoated part, 31d: Positive electrode side welded part,
32: Negative electrode, 32a: Negative electrode foil, 32b: Negative electrode mixture coating part,
32c: negative electrode uncoated portion, 32d: negative electrode side welded portion, 33: separator,
40: Through hole, 50: Curved part, 51: Center part, 61: Punch for passage processing,
62: Passage processing jig 71: Vertex

Claims (8)

An electrolyte,
A positive electrode having a positive electrode coated part coated with a positive electrode active material on a positive electrode foil and a non-coated positive electrode uncoated part; and a negative electrode coated part coated with a negative electrode active material on a negative electrode foil; A wound electrode group in which a negative electrode having an uncoated negative electrode uncoated portion is wound into a flat shape with a separator interposed therebetween,
A battery can containing the wound electrode group;
A battery lid for sealing the battery can;
A positive electrode current collector connected to the positive electrode uncoated part via a positive electrode side welding part;
A negative electrode current collector connected to the negative electrode uncoated portion via a negative electrode side weld,
The wound electrode group includes:
Outside the region between the positive electrode side welded portion and the positive electrode coated portion in the positive electrode uncoated portion, or
In the negative electrode uncoated part has a through hole in any one of the areas outside the negative electrode side welded part and the negative electrode coated part,
A rectangular secondary battery in which at least a part of the through hole is immersed in a free solution of the electrolytic solution. The prismatic secondary battery according to claim 1,
The through hole is a region from the end of the battery can bottom surface side in the winding direction of the positive electrode side welded portion to the apex of the curved portion of the wound electrode group on the bottom surface side of the battery can in the winding direction, the positive electrode uncoated Winding direction of the positive electrode side welded portion in the region from the battery lid side end portion to the apex of the curved portion of the wound electrode group on the battery lid side in the winding direction, the negative electrode side in the negative electrode uncoated portion Winding direction of the welded part The region from the bottom of the battery can bottom side to the apex of the curved part of the wound electrode group on the bottom of the battery can in the winding direction, and the negative electrode side welding in the negative electrode uncoated part A prismatic secondary battery provided in one of the regions from the battery lid side end of the winding part to the apex of the curved part of the winding electrode group on the battery lid side in the winding direction. The prismatic secondary battery according to claim 1,
The through hole extends from the battery can bottom surface side end portion of the positive electrode side welded portion in the positive electrode uncoated portion to the apex of the curved portion of the wound electrode group on the battery can bottom surface side in the winding direction. A region, and a region from the negative electrode side welded portion of the negative electrode side welded portion to the apex of the curved portion of the wound electrode group on the bottom surface side of the battery can in the winding direction A prismatic secondary battery provided in at least one of them. The prismatic secondary battery according to claim 2,
The through hole is a prismatic secondary battery provided in the curved portion of the wound electrode group. The prismatic secondary battery according to claim 3,
The through hole is a prismatic secondary battery provided at the top of the curved portion of the wound electrode group. In the square secondary battery according to any one of claims 1 to 5,
A square secondary battery in which a plurality of the through holes are provided. In the square secondary battery according to any one of claims 1 to 5,
The shape of the through hole is a rectangular secondary battery that is round or square. In the square secondary battery according to any one of claims 1 to 5,
The said through-hole is a square secondary battery provided in parallel with the lamination direction of each layer which comprises the said winding electrode group.

Images