JP6944998B2 - Rechargeable battery - Google Patents

Description

The present invention relates to a secondary battery.

In recent years, large-capacity and high-output lithium-ion secondary batteries have been attracting attention as a power source for hybrid electric vehicles and pure electric vehicles. In a lithium ion secondary battery, for example, positive and negative electrodes having metal leaf exposed parts are wound by winding through a separator to form a winding group, and the positive and negative metal foil exposed parts are laminated and collected. It has a structure that is welded to the electric plate.
In such a secondary battery, if metal foreign matter or the like generated during the production process is mixed inside the electrode group, a minute internal short circuit occurs and the performance deteriorates. In particular, when a metal foreign substance is mixed in the positive electrode, metal ions oxidized at the positive electrode diffuse in the electrolytic solution, and when they come into contact with the negative electrode, they are reduced and precipitated. The precipitated metal grows in the pores of the separator toward the positive electrode, and when it comes into contact with the positive electrode, it forms a minute short-circuit path.

There is also a document that an internal short circuit occurs not only when a metallic foreign substance is mixed into the inside but also when a thin separator is used. In this document, it is stated that in a thin separator, when the temperature of the battery rises, an internal short circuit occurs due to a portion where the separator does not intervene between the positive and negative electrodes due to the shrinkage of the separator. Therefore, as a countermeasure, one side edge of the separator is projected from the ends of the positive and negative electrodes, and the protruding portion and the positive electrode or the negative electrode are fixed with an adhesive tape to regulate the shrinkage of the separator. (See, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2003-168411

Patent Document 1 does not disclose a structure capable of suppressing foreign matter from entering the positive electrode.

According to one aspect of the present invention, in the secondary battery, a positive electrode and a negative electrode are laminated via a separator, and an electrode group provided with a flat portion having a pair of flat surfaces on the front and back surfaces and the positive electrode. A positive electrode current collector to be connected is provided, and a surface side portion of the separator is arranged on the surface side of the positive electrode electrode on the outermost surface side of the electrode group, and the positive electrode electrode is a positive electrode foil exposed portion and a positive electrode combination. The positive electrode foil exposed portion has an agent layer, and is provided on one side edge of the electrode group between a laminated portion having a thickness thinner than the flat portion of the electrode group and the laminated portion and the flat portion. The positive electrode current collector plate is arranged on one surface of the laminated portion of the positive electrode foil exposed portion, and is directed from the flat surface of the flat portion of the electrode group toward the laminated portion side. The surface side portion of the separator is deformed so as to approach the exposed positive electrode foil portion on the outermost surface side.

According to the present invention, it is possible to prevent metal foreign matter from being mixed between the outer peripheral portion of the separator and the exposed positive electrode foil portion on the outermost periphery.

The external perspective view of the 1st Embodiment of the secondary battery of this invention. The exploded perspective view of the secondary battery illustrated in FIG. The exploded perspective view of the wound electrode group illustrated in FIG. The plan view which shows the bonding state of a positive electrode / negative electrode current collector plate and a wound electrode group. (A) is a cross-sectional view taken along the line Va-Va of FIG. 4, and (b) is an enlarged view of the region Vb of (a). FIG. 4 is an enlarged cross-sectional view taken along the line VI-VI of FIG. FIG. 5 is a plan view showing a state in which a tape for controlling foreign matter contamination is provided on the wound electrode group shown in FIG. (A) is a sectional view taken along line VIIIa-VIIIa of FIG. 7, and (b) is an enlarged view of region VIIIb of (a). The figure which shows the relationship between the tape length and the number of mixed foreign matters. The plan view which shows the 2nd Embodiment of this invention. FIG. 10 is a cross-sectional view taken along the line XI-XI of FIG. The plan view which shows the 3rd Embodiment of this invention. The plan view which shows the 4th Embodiment of this invention. (A) is a cross-sectional view taken along the line XIVa-XIVa of FIG. 13, and (b) is an enlarged view of region XIVb of (a). A fifth embodiment of the present invention is shown, (a) is a cross-sectional view of the vicinity of a welded portion on the positive electrode side corresponding to FIG. 5 of the first embodiment, and (b) is an enlarged view of region XVb of (a). .. FIG. 5 is a cross-sectional view of the vicinity of the outermost periphery of the wound electrode group 3 including the winding start portion of the positive electrode electrode corresponding to FIG. 6 of the first embodiment, showing a fifth embodiment of the present invention.

Hereinafter, embodiments of the secondary battery of the present invention will be described with reference to the drawings.
− First Embodiment −
The first embodiment of the present invention will be described with reference to FIGS. 1 to 9.
FIG. 1 is an external perspective view of a flat winding type secondary battery. The secondary battery 100 includes a battery can 1 and a battery lid 6 that form a battery container. The battery can 1 is a square secondary battery having a flat box shape, and has a pair of opposing wide side surfaces 1b having a relatively large area, a pair of opposing narrow side surfaces 1c having a relatively small area, and the like. It has a bottom surface 1d and an opening 1a (see FIG. 2) above it.
The winding electrode group 3 is housed in the battery can 1, and the opening 1a of the battery can 1 is sealed by the battery lid 6. The battery lid 6 has a substantially rectangular flat plate shape, is welded by closing the opening 1a of the battery can 1, and seals the battery can 1 to the outside. The battery lid 6 is provided with a positive electrode external terminal 14 and a negative electrode external terminal 12. The positive electrode external terminal 14 and the negative electrode external terminal 12 are connected to an external device via a bus bar (not shown). The wound electrode group 3 is charged via the positive electrode external terminal 14 and the negative electrode external terminal 12, and electric power is supplied to the external load. The battery lid 6 is integrally provided with a gas discharge valve 10. When the pressure inside the battery container rises, the gas discharge valve 10 opens to discharge gas from the inside, and the pressure inside the battery container is reduced. As a result, the safety of the flat winding type secondary battery 100 is ensured. The battery lid 6 is provided with a liquid injection plug 11 for sealing the liquid injection hole 9 (see FIG. 2).

FIG. 2 is an exploded perspective view of the secondary battery illustrated in FIG.
The wound electrode group 3 is housed in the battery can 1 of the secondary battery 100 via the insulating protective film 2.
The wound electrode group 3 is formed by winding a negative electrode 32 and a positive electrode 34 between both members via separators 33 and 35 (see FIG. 3). The winding electrode group 3 has a flat flat portion 36 and curved portions 37 having a semicircular cross section formed at both ends of the flat portion 36 in the winding direction. The flat portion 36 has a pair of flat surfaces 36U and 36L (see also FIG. 5 and the like) facing each other in the thickness direction. The winding electrode group 3 is inserted into the battery can 1 from one curved portion 37 side so that the winding axis direction is along the lateral width direction of the battery can 1, and the other curved portion 37 side is the opening of the battery can 1. It is arranged on the part 1a side.

Although the details will be described later, the positive electrode electrode 34 has a positive electrode foil exposed portion 34c, and the negative electrode electrode 32 has a negative electrode foil exposed portion 32c.
The positive electrode foil exposed portion 34c of the wound electrode group 3 is electrically connected to the positive electrode external terminal 14 provided on the battery lid 6 via the positive electrode current collector plate 44. Further, the negative electrode foil exposed portion 32c of the wound electrode group 3 is electrically connected to the negative electrode external terminal 12 provided on the battery lid 6 via the negative electrode current collector plate 24. As a result, electric power is supplied from the wound electrode group 3 to the external load via the positive electrode current collecting plate 44 and the negative electrode current collecting plate 24, and the wound electrode group 3 is supplied via the positive electrode current collecting plate 44 and the negative electrode current collecting plate 24. Externally generated power is supplied to and charged.

A gasket 5 is attached to one side of the battery lid 6, and the positive electrode external terminal 14 and the negative electrode external terminal 12 are each insulated from the battery lid 6. Further, an insulating plate 7 is attached to the other surface side of the battery lid 6, and the positive electrode current collector plate 44 and the negative electrode current collector plate 24 are each insulated from the battery lid 6. The battery lid 6 is provided with a liquid injection hole 9 for injecting an electrolytic solution into the battery container. After injecting the electrolytic solution into the battery can 1 from the liquid injection hole 9, the liquid injection plug 11 is joined to the battery lid 6 by laser welding to seal the liquid injection hole 9, and the secondary battery 100 is sealed.

Examples of the material for forming the positive electrode external terminal 14 and the positive electrode current collector plate 44 include an aluminum alloy, and examples of the material for forming the negative electrode external terminal 12 and the negative electrode current collector plate 24 include a copper alloy. Examples of the material for forming the insulating plate 7 and the gasket 5 include resin materials having insulating properties such as polybutylene terephthalate, polyphenylene sulfide, and perfluoroalkoxy fluororesin.

As the electrolytic solution to be injected into the battery container, for example, a non-aqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF6) is dissolved in a carbonic acid ester-based organic solvent such as ethylene carbonate can be applied. can. When the pressure inside and outside the battery container is appropriately adjusted, the replacement of the air and the electrolytic solution in the wound electrode group 3 is promoted, and the electrolytic solution can be efficiently injected into the battery container.

The positive electrode external terminal 14 and the negative electrode external terminal 12 are formed with a positive electrode connecting portion 14a and a negative electrode connecting portion 12a, which project downward, respectively. The positive electrode connection portion 14a and the negative electrode connection portion 12a each have a cylindrical shape, and the tips thereof are inserted into the positive electrode side through hole 46 and the negative electrode side through hole 26 of the battery cover 6. The positive electrode connection portion 14a penetrates the battery lid 6 and projects toward the inside of the battery can 1 from the positive electrode current collector plate base 41 of the positive electrode current collector plate 44. The tip of the positive electrode connection portion 14a is crimped to integrally fix the positive electrode external terminal 14 and the positive electrode current collector plate 44 to the battery cover 6. The negative electrode connecting portion 12a penetrates the battery lid 6 and projects toward the inside of the battery can 1 from the negative electrode current collecting plate base 21 of the negative electrode current collecting plate 24. The tip of the negative electrode connecting portion 12a is crimped to integrally fix the negative electrode external terminal 12 and the negative electrode current collector plate 24 to the battery cover 6.

The positive electrode current collector plate 44 has a positive electrode current collector plate base 41 and a positive electrode side connection end 42. The positive electrode side connection end 42 is bent at the side end of the positive electrode current collector plate base 41 and extends along the wide side surface 1b of the battery can 1 toward the bottom surface 1d side, and the positive electrode of the wound electrode group 3 It is connected in a state of being overlapped with the foil exposed portion 34c facing each other. The positive electrode current collector plate base 41 is formed with a positive electrode side opening hole 43 through which the positive electrode connection portion 14a is inserted.
The negative electrode current collector plate 24 has a negative electrode current collector plate base portion 21 and a negative electrode side connection end portion 22. The negative electrode side connection end 22 is bent at the side end of the negative electrode current collector plate base 21 and extends along the wide side surface 1b of the battery can 1 toward the bottom surface 1d, and the negative electrode foil of the wound electrode group 3 It is connected in a state of being overlapped with the exposed portion 32c facing each other. The negative electrode side opening hole 23 through which the negative electrode connecting portion 12a is inserted is formed in the negative electrode current collector plate base portion 21.

The insulation protective film 2 has a winding electrode group 3 having a winding center in a direction along the flat surfaces 36U and 36L of the flat portion 36 of the winding electrode group 3 and a direction orthogonal to the winding axis direction of the winding electrode group 3. It is wrapped around the. The insulating protective film 2 is made of a single sheet or a plurality of film members made of synthetic resin such as PP (polypropylene), and is in a direction parallel to the flat surfaces 36U and 36L of the winding electrode group 3 and in the winding axis direction. It has a length that allows it to be wound around the direction orthogonal to the winding center.

FIG. 3 is an exploded perspective view of the wound electrode group illustrated in FIG. FIG. 3 shows a state in which the outer peripheral side of the wound electrode group 3 is expanded.
The winding electrode group 3 is configured by winding the negative electrode 32 and the positive electrode 34 in a flat shape with the separators 33 and 35 in between. That is, the wound electrode group 3 is wound by repeating the separator 35, the negative electrode 32, the separator 33, the positive electrode 34, the separator 35, the negative electrode 32, the separator 33, the positive electrode 34, and so on in this order from the outer peripheral side. There is. The separators 33 and 35 have a role of insulating between the positive electrode 34 and the negative electrode 32.

The negative electrode electrode 32 has a negative electrode mixture layer 32b coated on both sides of the negative electrode foil 32a, and a negative electrode foil exposed portion 32c in which the negative electrode foil 32a is exposed from the negative electrode mixture layer 32b. The positive electrode electrode 34 has a positive electrode mixture layer 34b coated on both sides of the positive electrode foil 34a, and a positive electrode foil exposed portion 34c in which the positive electrode foil 34a is exposed from the positive electrode mixture layer 34b.
The negative electrode mixture layer 32b is larger in the width direction (length in the direction orthogonal to the winding direction) than the positive electrode mixture layer 34b, whereby the positive electrode mixture layer 34b is arranged in the region of the negative electrode mixture layer 32b. Has been done. The positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c are arranged on opposite sides in the width direction. In the positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c, adjacent inner and outer peripheral portions of the flat portion 36 are laminated with each other. In the laminated portion in which the positive electrode foil exposed portion 34c is laminated, the adjacent inner and outer peripheral portions are welded to each other, and the positive electrode current collector plate 44 is welded to one surface of the laminated portion. In the laminated portion in which the negative electrode foil exposed portion 32c is laminated, the adjacent inner and outer peripheral portions are welded to each other, and the negative electrode current collector plate 24 is welded to one surface of the laminated portion.

The length of the separators 33 and 35 in the width direction is larger than that of the negative electrode mixture layer 32b. However, the separators 33 and 35 are arranged so that their ends are located inside the end of the positive electrode foil exposed portion 34c and the end of the negative electrode foil exposed portion 32c, and the positive electrode foil exposed portion 34c and the negative electrode foil are exposed. Each of the portions 32c has a region exposed to the outside in the width direction from the separators 33 and 35. Therefore, it does not hinder the welding of the positive electrode current collector plate 44 and the negative electrode current collector plate 24 to the positive electrode foil exposed portion 34c and the negative electrode foil exposed portion 32c, respectively.

The negative electrode electrode 32 could be obtained by the following method.
To 100 parts by weight of amorphous carbon powder as a negative electrode active material, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) was added as a binder, and N-methylpyrrolidone (hereinafter referred to as PVDF) was added as a dispersion solvent. NMP) was added and kneaded to prepare a negative electrode mixture. This negative electrode mixture is applied to both sides of a copper foil (negative electrode foil 32a) having a thickness of 10 μm, leaving a welded portion (negative electrode foil exposed portion 32c). Then, through the drying, pressing, and cutting steps, a negative electrode 32 having a thickness of 70 μm in the negative electrode active material coating portion containing no copper foil was obtained.

In this embodiment, the case where amorphous carbon is used as the negative electrode active material has been illustrated, but the present invention is not limited to this, and natural graphite capable of inserting and removing lithium ions and various artificial graphite materials are used. , A carbonaceous material such as coke, a compound such as Si or Sn (for example, SiO, TiSi2, etc.), or a composite material thereof, and the particle shape thereof is particularly limited to scaly, spherical, fibrous, lumpy, etc. It is not something that is done.

The positive electrode 34 could be obtained by the following method.
To 100 parts by weight of lithium manganate (chemical formula LiMn2O4) as a positive electrode active material, 10 parts by weight of scaly graphite as a conductive material and 10 parts by weight of PVDF as a binder were added, and NMP was added as a dispersion solvent. , A kneaded positive electrode mixture was prepared. This positive electrode mixture was applied to both sides of an aluminum foil (positive electrode foil 34a) having a thickness of 20 μm, leaving welded portions (exposed positive electrode foil 34c). Then, through a drying, pressing, and cutting steps, a positive electrode 34 having a thickness of 90 μm in the positive electrode active material coating portion containing no aluminum foil was obtained.

In this embodiment, the case where lithium manganate is used as the positive electrode active material has been illustrated, but other lithium manganate having a spinel crystal structure, a lithium manganese composite oxide obtained by partially substituting or doping with a metal element, or a layered crystal structure Lithium cobaltate, lithium titanate, or a lithium-metal composite oxide obtained by substituting or doping a part thereof with a metal element may be used.

Further, in the present embodiment, the case where PVDF is used as a binder for the coated portion in the positive electrode electrode 34 and the negative electrode electrode 32 has been illustrated, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, and nitrile rubber have been exemplified. , Styrene butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latex, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, polymers such as acrylic resin, and mixtures thereof. Can be used.

Further, as the shaft core, for example, a resin sheet having a higher bending rigidity than any of the positive electrode foil 34a, the negative electrode foil 32a, and the separators 33 and 35 can be used.

FIG. 4 is a plan view showing a bonding state between the positive / negative electrode current collector plate and the wound electrode group.
The positive electrode foil exposed portion 34c and the positive electrode current collecting plate 44, and the negative electrode foil exposed portion 32c and the negative electrode current collecting plate 24 are joined by, for example, ultrasonic welding. Ultrasonic welding is a method in which the positive and negative electrode current collector plates 44 and 24 are fixed by anvil, and a horn is pressed against the positive and negative electrode foil exposed portions 34c and 32c to bond the metal interface by ultrasonic vibration. .. The positive electrode current collector 64, which is the joint surface between the positive electrode foil exposed portion 34c and the positive electrode current collector plate 44, and the negative electrode current collector 62, which is the joint surface between the negative electrode foil exposed portion 32c and the negative electrode current collector plate 24, are positive and negative electrodes. In the process of fixing the current collector plates 44 and 24 with anvil and pressing the horn to vibrate, the positive and negative electrode current collector plates 44 and 24 and the positive and negative electrode exposed portions 34c and 32c are scraped to generate metallic foreign matter.
As a method of joining the current collector, another method such as resistance welding may be applied.

A part of the generated metal foreign matter may invade the inside of the wound electrode group 3 by the flow of the electrolytic solution, for example, in the step of injecting the electrolytic solution. If it penetrates into the wound electrode group 3, it may penetrate the separator and lead to an internal short circuit depending on the size and shape of the metal foreign matter. Further, when the invaded metallic foreign matter is the negative electrode foil 32a, copper or the like constituting the negative electrode current collecting plate 24, it is oxidized at the positive electrode potential, diffuses in the electrolytic solution, and is reduced and precipitated at the negative electrode. The deposited copper may connect the negative electrode and the positive electrode to form a minute internal short circuit. The precipitation and growth form differ depending on the metal species and the like, but for example, when growing in a dendritic shape in the voids of the separator, an internal short circuit may occur even if a small foreign substance does not physically penetrate the separator.

That is, there are the following two causes of internal short circuit due to foreign matter.
Factors 1. Metallic foreign matter generated on the negative electrode side flows in the electrolytic solution, mixes from the positive electrode side into the wound electrode group 3, is oxidized by the positive electrode potential, is reduced and precipitated on the negative electrode, and short-circuits the positive electrode and the negative electrode.
Factor 2. Metallic foreign matter generated on the positive electrode side or foreign matter generated during the manufacturing process is mixed into the wound electrode group 3 from the positive electrode side, and is in a state of substantially penetrating the separator to short-circuit the positive electrode and the negative electrode.
While an internal short circuit is a serious problem that causes a loss of function of the secondary battery, it is not easy to take measures against foreign matter contamination to prevent it.

5 (a) is a sectional view taken along line Va-Va of FIG. 4, and FIG. 5 (b) is an enlarged view of the region Vb of FIG. 5 (a). FIG. 5A shows the welded portion side of the positive electrode electrode 34.
The positive electrode foil exposed portion 34c of the positive electrode electrode 34 is laminated so that the flat portions on the inner and outer circumferences to be wound are in close contact with each other. The thickness of the laminated portion 38 is naturally thinner than the thickness of the flat portion 36 of the wound electrode group 3. In the state shown in FIG. 5, the positive electrode current collector plate 44 arranged on one surface of the laminated portion 38 is fixed with an anvil, and while pressurizing with a horn from the other surface side of the positive electrode foil exposed portion 34c constituting the laminated portion 38. Gives ultrasonic vibration. As a result, frictional heat is generated between adjacent metal members, and a solid phase welding state is created. By this action, the positive electrode foil exposed portions 34c constituting the laminated portion 38 are joined to each other, and the positive electrode current collector plate 44 is joined to one surface of the laminated portion 38.

When forming the laminated portion 38 of the positive electrode foil exposed portion 34c, the flat surfaces 36U and 36L of the flat portion 36 are formed between the laminated portion 38 and the flat portion 36 of the wound electrode group 3 in the positive electrode foil exposed portion 34c. A deformed portion 39 that curves toward the laminated portion 38 is formed. As shown in FIG. 5B, in the deformed portion 39, the positive electrode foil exposed portion 34c and the separators 33 and 35 are curved toward the laminated portion 38 so that the distance between them gradually becomes smaller. Therefore, in the deformed portion 39, the sizes of the gaps 54a and 54b between the positive electrode foil exposed portion 34c and the separators 33 and separators 35 arranged on both sides thereof are limited by the positive electrode foil exposed portions 34c joined to each other at the tips. NS.

On the other hand, on the outer periphery of the outermost peripheral portion 34d of the positive electrode 34, the outermost peripheral portion 33a of the separator 33, the outermost outer peripheral portion 32d of the negative electrode 32, and the outermost outer peripheral portion 35a of the separator 35 are formed from the inner peripheral side to the outer peripheral side. , In this order, it is wound around once. Since the outermost peripheral portion 33a of the separator 33, the outermost peripheral portion 32d of the negative electrode electrode 32, and the outermost outer peripheral portion 35a of the separator 35 do not form the laminated portion 38 of the positive electrode foil exposed portion 34c, they are directed toward the laminated portion 38 side. It does not deform and remains flat.

Therefore, a large gap 54c is formed between the outermost peripheral portion 33a of the separator 33 and the deformed portion 39, that is, the positive electrode foil exposed portion 34c on the outermost circumference of the wound electrode group 3. The gap 54c is open to the outside as shown in FIG. 5 (b). Therefore, there is a high possibility that metal foreign matter will enter the gap 54 from the outside.

FIG. 6 is an enlarged cross-sectional view taken along the line VI-VI of FIG. FIG. 6 shows the vicinity of the outermost periphery of the winding electrode group 3 including the winding end portion 74 of the positive electrode electrode 34 shown in FIG.
At the end of winding the positive electrode 34, the outermost peripheral portion 33a of the separator 33 arranged on the outer periphery of the positive electrode electrode 34, the outermost peripheral portion 32d of the negative electrode electrode 32, and the outermost outer peripheral portion 35a of the separator 35 are from the end of the positive electrode 34. , Extends in the winding direction. For this reason, in particular, at the winding end portion 74 of the positive electrode electrode 34, there is a high possibility that a metallic foreign substance will enter the gap 54d from the outside.

As described above, when the positive electrode foil exposed portion 34c of the wound electrode group 3 is laminated and joined to the positive electrode current collector plate 44, the gap 54c formed between the deformed portion 39 and the outermost peripheral portion 33a of the separator 33 is formed. , 54d has a high risk of metal foreign matter being mixed from the outside. Therefore, an embodiment of the present invention capable of suppressing the mixing of metallic foreign matter into the wound electrode group 3 is shown below.

FIG. 7 is a plan view showing a state in which a tape for controlling foreign matter contamination is provided on the wound electrode group shown in FIG. 8 (a) is a sectional view taken along line VIIIa-VIIIa of FIG. 7, and FIG. 8 (b) is an enlarged view of the region VIIIb of FIG. 8 (a).
As shown in FIGS. 8A and 8B, a tape 200 for controlling foreign matter contamination is attached to the upper surface of the outermost peripheral portion 35a of the separator 35. The tape 200 is arranged on the flat surface 36U side of the flat portion 36 where the positive electrode current collector plate 44 joined to the laminated portion 38 is arranged.
Further, as shown in FIG. 7, the tape 200 covers one side edge of the positive electrode current collector plate 44 side and straddles the winding end portion 74 of the positive electrode electrode 34 in the winding direction and the winding direction. It extends in the opposite direction. Further, the tape 200 is arranged in the region 64R of the positive electrode current collector 64 in the winding direction.

The tape 200 deforms the outermost peripheral portion 35a of the separator 35 toward the outermost peripheral portion 33a side of the separator 33, and the tip end side (side edge portion side in the width direction) becomes the outermost peripheral portion 33a of the separator 33. Make a contact. The tape 200 further presses the outermost peripheral portion 35a of the separator 35 against the outermost peripheral portion 33a of the separator 33 so that the tip end side of the outermost peripheral portion 33a of the separator 33 approaches the positive electrode foil exposed portion 34c on the outermost circumference. Deform. As a result, the gap 54c formed between the outermost peripheral portion 33a of the separator 33 and the positive electrode foil exposed portion 34c on the outermost circumference is reduced and becomes closed to the outside. Further, the tape 200 is arranged so as to cover the positive electrode side end portion 74T of the winding end portion 74 of the positive electrode electrode 34. Therefore, the gap 54d formed at the end of the winding end portion 74 of the positive electrode electrode 34 shown in FIG. 6 is reduced and closed on the positive electrode current collector plate 44 side.
Therefore, the tape 200 suppresses the mixing of metal foreign matter into the wound electrode group 3 from the gap 54c and the gap 54d.

The effect of suppressing the mixing of metallic foreign matter into the wound electrode group 3 by the above-mentioned tape 200 was confirmed by the method shown below.
Three samples were prepared by attaching the tape 200 having the following conditions 1 to 3 to the winding electrode group 3 shown in FIG. 7 with a length in the winding direction.
Condition 1: The length of the tape is 23% of the length of the flat portion 36 of the wound electrode group 3.
Condition 2: The length of the tape is 62% of the length of the flat portion 36 of the wound electrode group 3.
Condition 3: The length of the tape is 100% of the length of the flat portion 36 of the wound electrode group 3.
The sample of condition 3 corresponds to the third embodiment described later.
In addition, a wound electrode group 3 to which the tape 200 is not attached was also produced.
In the sample under each condition, the tape 200 is arranged on the flat surface 36U side of the flat portion 36 on the side where the positive electrode current collector plate 44 is joined. Further, all the tapes 200 were arranged so as to cover the winding end portion 74 of the positive electrode electrode 34.

The number of metallic foreign substances mixed in the wound electrode group 3 was determined after the wound electrode group 3 was housed in the battery can 1 and the battery can 1 and the battery lid 6 were welded to each other. Normally, in the as-made state, the probability that a metallic foreign substance is mixed in the wound electrode group 3 is very low. Therefore, in order to promote confirmation of the effect, about 1 mg of a copper foreign substance was added from the liquid injection hole 9 and diffused into the battery can 1. The copper foreign matter used was sieved with a 70 μm sieve. Subsequently, the electrolytic solution was injected into the battery can 1 and the electrolytic solution was permeated into the wound electrode group 3 by appropriately adjusting the pressure inside and outside the battery container, and then sealed by the liquid injection plug 11. Next, the secondary battery 100 was charged and allowed to stand for a certain period of time in a state where the positive electrode potential exceeded the dissolution potential of copper. Then, the wound electrode group 3 was taken out from the secondary battery 100 and disassembled, and the number of copper that was dissolved and precipitated in the voids 54c and 54d and became apparent was confirmed.

FIG. 9 shows the results of the above test, and is a diagram showing the relationship between the tape length and the number of mixed foreign substances. The horizontal axis indicates the length of the tape 200 with respect to the length of the flat portion 36 of the wound electrode group 3 in the winding direction, and the vertical axis indicates the total number of metal foreign substances mixed in the wound electrode group 3 without tape. Is shown as a relative value with.
From FIG. 9, it can be seen that in the sample to which any of the tapes of the conditions 1 to 3 was attached, the number of copper mixed was reduced to less than 1/5 with respect to the wound electrode group 3 without the tape. Comparing the samples of conditions 1 to 3, the results show that the sample of condition 2 has a slightly higher mixing rate of metallic foreign substances than the samples of conditions 1 and 3. However, in the samples of Condition 1 and Condition 3, when the result that the mixing rate of the metallic foreign matter is 0 is seen, it is judged that the mixing number of copper does not depend on the length of the tape 200. In conclusion, the tape 200 is attached to at least a part of the flat portion 36 of the wound electrode group 3, and the tip end side of the outermost peripheral portion 33a of the separator 33 arranged outside the positive electrode foil exposed portion 34c on the outermost periphery is the positive electrode. It can be said that if the foil is deformed so as to approach the exposed portion 34c, the gap 54c is reduced and the mixing of metallic foreign matter is suppressed. Further, if the gap is limited to 54d, the contamination of foreign matter can be reduced to zero by sticking the tape. That is, the tape 200 is attached to the flat surface 36U side on which the positive electrode current collector plate 44 is arranged, and the tip end side of the outermost peripheral portion 33a of the separator 33 is deformed so as to approach the positive electrode foil exposed portion 34c. Not only the side where the positive electrode current collector plate 44 is arranged, but also the side where the positive electrode current collector plate 44 is not arranged, it is possible to suppress advancing and mixing of metal foreign matter into the wound electrode group 3 from the outside. Was confirmed.

According to the first embodiment of the present invention, the following effects are obtained.
(1) The outermost peripheral portion 33a of the separator 33 is arranged on the outer periphery of the outermost peripheral positive electrode electrode 34, and the positive electrode foil exposed portion 34c of the positive electrode electrode 34 is laminated with a thickness thinner than the flat portion 36 of the wound electrode group 3. It has a portion 38 and a deformed portion 39 provided between the laminated portion 38 and the flat portion 36, and the positive electrode current collecting plate 44 is arranged on one surface of the laminated portion 38 of the positive electrode foil exposed portion 34c and rolled up. The outer peripheral portion 33a of the separator 33 is deformed so as to approach the outermost positive electrode foil exposed portion 34c from the flat surface 36U of the flat portion 36 of the rotating electrode group 3 toward the laminated portion 38 side. Therefore, the tape 200 deforms the tip end side of the outermost peripheral portion 33a of the separator 33 so as to approach the outermost positive electrode foil exposed portion 34c, thereby suppressing the mixing of metal foreign matter into the wound electrode group 3. can do.
According to the first embodiment, as described above, it is possible to obtain an effect of suppressing both the factor 1 and the factor 2 of the internal short circuit due to the metal foreign matter.

-Second embodiment-
10 is a plan view of the second embodiment, and FIG. 11 is a cross-sectional view taken along the line XI-XI of FIG. 10 and 11 correspond to FIGS. 7 and 8 (a) of the first embodiment, respectively.
In the second embodiment, the tape 201 for controlling foreign matter is mixed with the positive electrode current collector plate 44 and the positive electrode from above one flat surface 36U of the flat portion 36 of the wound electrode group 3 in the direction orthogonal to the winding direction. It extends to a region covering the upper surface of the positive electrode current collecting portion 64 formed on the joint surface with the foil exposed portion 34c. The intermediate portion of the tape 201 in the longitudinal direction is deformed in a curved shape in a direction in which the positive electrode current collecting portion 64 side descends from the flat surface 36U of the flat portion 36, following the shape of the outer surface of the deformed portion 39.
Also in the second embodiment, the tape 201 deforms the separator 33 so that the tip end side of the outermost peripheral portion 33a approaches the positive electrode foil exposed portion 34c on the outermost circumference. Further, the tape 201 is arranged so as to cover the winding end portion 74 of the positive electrode electrode 34.
Therefore, the second embodiment also has the same effect as the first embodiment.
In addition, in the second embodiment, since the tape 201 covers the positive electrode current collector 64 formed on the joint surface between the positive electrode current collector plate 44 and the positive electrode foil exposed portion 34c, it adheres to the positive electrode current collector 64. The movement of metal foreign matter can be restricted. Therefore, it is possible to further enhance the effect of suppressing the mixing of metal foreign substances into the wound electrode group 3.

-Third embodiment-
FIG. 12 shows a third embodiment of the present invention. FIG. 12 corresponds to FIG. 7 of the first embodiment.
In the third embodiment, the tape 202 for controlling foreign matter contamination has a length over the entire length of the flat portion 36 of the wound electrode group 3 in the winding direction. In the third embodiment, the outermost peripheral portion 33a of the separator 33 approaches the outermost peripheral positive electrode foil exposed portion 34c over the entire length of the flat portion 36 of the wound electrode group 3 in the winding direction. It transforms like this. This structure is the same as the sample of the above-mentioned condition 3. In the test, the total number of metallic foreign substances mixed in the wound electrode group 3 was 0, which was the same as that of the first embodiment. However, in the third embodiment, the gap 54c, which is a path for mixing metal foreign matter, is reduced over the entire length of the flat portion 36 of the wound electrode group 3, so that the certainty of the effect of suppressing foreign matter mixing is the first. There is an expectation that it will be improved from the embodiment.

− Fourth Embodiment −
13 is a plan view showing a fourth embodiment of the present invention, FIG. 14A is a sectional view taken along line XIVa-XIVa of FIG. 13, and FIG. 14B is FIG. 14A. It is an enlarged view of the region XIVb of.
In the fourth embodiment, the foreign matter mixing control portion 44a is integrally molded on the positive electrode current collector plate 44. The foreign matter mixing restricting portion 44a is a flat surface of the flat portion 36 from above one flat surface 36U of the flat portion 36 of the winding electrode group 3 in a direction orthogonal to the winding direction, following the outer surface shape of the deformed portion 39. It is curved in the direction of descending from 36U and is connected to the positive electrode current collector plate 44. The foreign matter mixing restricting portion 44a deforms the outermost peripheral portion 33a of the separator 33 so that the tip end side thereof approaches the positive electrode foil exposed portion 34c on the outermost circumference. As a result, the gap 54c formed between the outermost peripheral portion 33a of the separator 33 and the positive electrode foil exposed portion 34c on the outermost circumference is reduced to form a closed shape. Further, the foreign matter mixing restricting portion 44a is arranged so as to cover the winding end portion 74 of the positive electrode electrode 34.
Therefore, the fourth embodiment also has the same effect as the first embodiment.
In addition, since the foreign matter mixing control portion 44a is formed by integrally molding with the positive electrode current collector plate 44, the foreign matter mixing control portion 44a is a group of wound electrodes at the same time as the step of joining the positive electrode current collector plate 44 to the positive electrode foil exposed portion 34c. Since it is fixed to 3, the efficiency of the assembly process can be improved.

-Fifth Embodiment-
FIG. 15 shows a fifth embodiment of the present invention, and FIG. 15 (a) is a cross-sectional view of the vicinity of the welded portion on the positive electrode side corresponding to FIG. 5 of the first embodiment, FIG. 15 (b). Is an enlarged view of the region XVb of FIG. 15 (a).
FIG. 16 is a cross-sectional view of the vicinity of the welded portion on the positive electrode side corresponding to FIG. 5 of the first embodiment, FIG. 16 shows the fifth embodiment of the present invention, and the positive electrode corresponding to FIG. 6 of the first embodiment. It is sectional drawing of the vicinity of the outermost periphery of the winding electrode group 3 including the winding start part of an electrode.
In the fifth embodiment, the deformed portions 39 and the laminated portions 38 of the positive and negative electrodes of the wound electrode group 3 in the first embodiment are polarized in two stages in the thickness direction. That is, on the positive electrode side, the positive electrode foil exposed portion 34c of the positive electrode electrode 34 and the separators 33 and 35 are bundled separately on the upper side and the lower side at substantially the center in the thickness direction of the wound electrode group 3. There is. The positive electrode foil exposed portion 34cU and the separators 33 and 35 of the positive electrode electrode 34 bundled on the upper side form the upper deformed portion 39a, and the positive electrode foil exposed portion 34cU is extended to form the upper laminated portion 38a. The positive electrode foil exposed portion 34 cL and the separators 33 and 35 of the positive electrode electrode 34 bundled on the lower side form the lower deformed portion 39b, and the positive electrode foil exposed portion 34 cL is extended to form the lower laminated portion 38b.

Positive electrode current collection is performed on the positive electrode foil exposed portion 34cU on the innermost circumference (lowermost layer in FIG. 15) of the upper laminated portion 38a and the positive electrode foil exposed portion 34cL on the innermost circumference (uppermost layer in FIG. 15) of the lower laminated portion 38b. The plates 44 are joined by welding. To bond the upper and lower laminated portions 38a and 38b and the positive electrode current collector plate 44 by ultrasonic welding, fix the positive electrode current collector plate 44 with anvil and horn on the opposite side of the upper and lower laminated portions 38a and 38b. Is pressed against it to give ultrasonic vibration while pressurizing.

Although not shown, the same applies to the negative electrode side. The negative electrode foil exposed portion 32c and the separators 33 and 35 of the negative electrode electrode 32 bundled on the upper side form an upper deformed portion, and the negative electrode foil exposed portion 32cU is extended. Form the upper laminated part. The negative electrode foil exposed portion 32c and the separators 33 and 35 of the negative electrode electrode 32 bundled on the lower side form a lower deformed portion, and the negative electrode foil exposed portion 32cL is extended to form a lower laminated portion. Further, the negative electrode foil exposed portion 32c on the innermost circumference in the upper laminated portion on the negative electrode side.
The negative electrode current collector plate 44 is joined to the innermost peripheral negative electrode foil exposed portion 32c in the lower laminated portion by welding.

As shown in FIG. 15, the tape 200 is attached to the side 39aL on the positive electrode side of the wound electrode group 3 where the positive electrode current collector plate 44 of the upper deformed portion 39a is arranged. The tape 200 is attached to the outer surfaces of the separators 33 and 35 on the inner peripheral side of the positive electrode foil exposed portion 34cU on the innermost circumference (lowermost layer in FIG. 15) from the flat portion 36 to the upper deformed portion 39aL. Therefore, the tape 200 is deformed so that the tip end side of the separators 33 and 35 approaches the positive electrode foil exposed portion 34cU on the innermost circumference (the lowermost layer in FIG. 15). As a result, the gap 54e formed between the separators 33 and 35 and the positive electrode foil exposed portion 34cU on the innermost circumference is reduced and becomes closed to the outside. Further, although not shown, the tape 200 is arranged so as to cover the positive electrode side end portion of the winding start portion 75 of the positive electrode electrode 34. Therefore, the gap 54f formed in the winding start portion 75 of the positive electrode electrode 34 shown in FIG. 16 is reduced and closed on the positive electrode current collector plate 44 side.
Therefore, the tape 200 suppresses the mixing of metal foreign matter into the wound electrode group 3 from the gap 54e and the gap 54f.

Further, as shown by the alternate long and short dash line in FIG. 15A, the tape 200 is also attached to the side 39bU where the positive electrode current collector plate 44 of the lower deformed portion 39b is arranged. The tape 200 attached to the lower deformed portion 39bU suppresses the mixing of metal foreign matter into the wound electrode group 3 also in the lower deformed portion 39b.
Therefore, the fifth embodiment also has the same effect as the first embodiment.

In the fifth embodiment, the tape 200 attached to the upper deformed portion 39aL and the lower deformed portion 39bU has the separator 33 on the inner peripheral side of the positive electrode foil exposed portions 34cU and 34cL on the innermost circumferences of the deformed portions 39a and 39b, respectively. It is affixed to 35. Here, since the innermost peripheral side of each of the deformed portions 39a and 39b is also the outermost surface side, the tape 200 is a separator 33 on the surface side of the positive electrode foil exposed portions 34cU and 34cL on the outermost surface side of the deformed portions 39a and 39b. , 35 can be expressed as being attached.

In the fifth embodiment, the positive and negative electrode groups are exemplified as a structure polarized in two stages. However, the positive and negative electrode groups may be polarized in three or more stages.

In the first to fourth embodiments, the outermost peripheral portion 33a of the separator 33 is deformed by the tapes 200 to 202 or the foreign matter mixing restricting portion 44a so that the tip end portion side approaches the outermost peripheral positive electrode foil exposed portion 34c. It was illustrated as a structure to be constructed. However, without using the tapes 200 to 202 or the foreign matter mixing restricting portion 44a, the outermost peripheral portion 33a of the separator 33 may be deformed by a hot press, or the outermost peripheral portion 33a of the separator 33 may be adhered to the outermost peripheral positive electrode foil exposed portion 34c. You may try to do it.

In the first to fourth embodiments, the tapes 200 to 202 are attached only to the flat surface 36U side on which the positive electrode current collector plate 44 joined to the laminated portion 38 is arranged in the deformed portion 39. .. However, the tapes 200 to 202 may be attached to both flat surfaces 36U and 36L of the deformed portion 39.

In the first to fourth embodiments, the winding end portion 74 of the positive electrode electrode 34 is illustrated as a configuration in which the winding end portion 74 of the positive electrode electrode 34 is arranged in the region 64R of the positive electrode current collecting portion 64 in the winding direction. However, the winding end portion 74 of the positive electrode electrode 34 may be arranged outside the region 64R of the positive electrode current collecting portion 64 in the winding direction.

In the first to fourth embodiments, the winding end portion 74 of the positive electrode electrode 34 is illustrated as a configuration in which the winding end portion 74 of the positive electrode group 3 is arranged on the flat surface 36U side on which the positive electrode current collector plate 44 of the winding electrode group 3 is arranged. However, the winding end portion 74 of the positive electrode electrode 34 may be arranged on the flat surface 36L side opposite to the flat surface 36U side on which the positive electrode current collector plate 44 of the winding electrode group 3 is arranged. It is known that more dust is generated by ultrasonic welding on the anvil side used to fix the workpiece. Therefore, if the winding end portion 74 of the positive electrode electrode 34 is kept away from the positive electrode current collecting plate 44 supported by the anvil, the risk of metal foreign matter being mixed into the winding electrode group 3 during ultrasonic welding can be reduced. Can be expected.

In the first to fourth embodiments, the separator 33 and the separator 35 are wound around the outer periphery of the outermost peripheral portion 34d of the positive electrode electrode 34. However, one or both of the separator 33 and the separator 35 may be wound around the outer periphery of the outermost peripheral portion 34d of the positive electrode electrode 34 several times.

In each of the above embodiments, the positive electrode 34 and the negative electrode 32 are exemplified as a secondary battery 100 having a wound electrode group 3 wound via separators 33 and 35. However, the present invention can be applied to a secondary battery including a group of electrodes in which a rectangular sheet-shaped positive electrode and a rectangular sheet-shaped negative electrode are stacked flatly via a separator.

In each of the above embodiments, the secondary battery is exemplified as a lithium ion battery. However, the present invention can be applied to other secondary batteries such as nickel-cadmium batteries and nickel-metal hydride batteries.

Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included within the scope of the present invention.

3 Winding electrode group (electrode group)
32 Negative electrode 33, 35 Separator 34 Positive electrode 34a Positive electrode 34b Positive mixture layer 34c, 34cU, 34cL Positive electrode exposed part 34d Outermost part (outermost surface side part)
36 Flat part 36U, 36L Flat surface 38 Laminated part 38a Upper laminated part 38b Lower laminated part 39 Deformed part 39a Upper deformed part 39b Lower deformed part 44 Positive electrode current collector plate 44a Foreign matter mixing control part (regulatory part)
64 Positive electrode current collector (joint)
74 Winding end part 75 Winding start part 100 Secondary battery 200-202 Tape

Claims (7)

A group of electrodes in which a positive electrode and a negative electrode are laminated via a separator and a flat portion having a pair of flat surfaces is provided on the front and back surfaces.
A positive electrode current collector plate connected to the positive electrode is provided.
The surface side portion of the separator is arranged on the surface side of the positive electrode electrode on the outermost surface side of the electrode group.
The positive electrode has a positive electrode foil exposed portion and a positive electrode mixture layer.
The positive electrode foil exposed portion includes a laminated portion having a thickness thinner than the flat portion of the electrode group and a deformed portion provided between the laminated portion and the flat portion on one side edge of the electrode group. Have and
The positive electrode current collector plate is arranged on one surface of the laminated portion of the positive electrode foil exposed portion.
The surface side portion of the separator is deformed so as to approach the positive electrode foil exposed portion on the outermost surface side from the flat surface of the flat portion of the electrode group toward the laminated portion side.
A regulating portion for deforming the surface side portion of the separator so as to approach the exposed positive electrode foil portion on the outermost surface side is provided.
The regulatory part is a tape
The positive electrode current collector plate and the positive electrode foil exposed portion are electrically connected at the joint portion, and the tape is at least one of the positive electrode current collector plates in a region corresponding to the joint portion in a direction along the one side edge of the electrode group. The secondary battery where the part is arranged. In the secondary battery according to claim 1,
A secondary battery in which the flat surface of the flat portion is a flat surface on the side on which the positive electrode current collector plate is arranged. In the secondary battery according to claim 1,
The tape is a secondary battery provided on the side where the positive electrode current collector plate of the electrode group is arranged over the entire region of the flat portion in a direction along the one side edge of the electrode group. A group of electrodes in which a positive electrode and a negative electrode are laminated via a separator and a flat portion having a pair of flat surfaces is provided on the front and back surfaces.
A positive electrode current collector plate connected to the positive electrode is provided.
The surface side portion of the separator is arranged on the surface side of the positive electrode electrode on the outermost surface side of the electrode group.
The positive electrode has a positive electrode foil exposed portion and a positive electrode mixture layer.
The positive electrode foil exposed portion includes a laminated portion having a thickness thinner than the flat portion of the electrode group and a deformed portion provided between the laminated portion and the flat portion on one side edge of the electrode group. Have and
The positive electrode current collector plate is arranged on one surface of the laminated portion of the positive electrode foil exposed portion.
The surface side portion of the separator is deformed so as to approach the positive electrode foil exposed portion on the outermost surface side from the flat surface of the flat portion of the electrode group toward the laminated portion side.
A regulating portion for deforming the surface side portion of the separator so as to approach the exposed positive electrode foil portion on the outermost surface side is provided.
The regulating portion is a secondary battery integrally formed with the positive electrode current collector plate. In the secondary battery according to claim 1,
The electrode group is a secondary battery in which the positive electrode and the negative electrode are wound by the separator. A group of electrodes in which a positive electrode and a negative electrode are laminated via a separator and a flat portion having a pair of flat surfaces is provided on the front and back surfaces.
A positive electrode current collector plate connected to the positive electrode is provided.
The surface side portion of the separator is arranged on the surface side of the positive electrode electrode on the outermost surface side of the electrode group.
The positive electrode has a positive electrode foil exposed portion and a positive electrode mixture layer.
The positive electrode foil exposed portion includes a laminated portion having a thickness thinner than the flat portion of the electrode group and a deformed portion provided between the laminated portion and the flat portion on one side edge of the electrode group. Have and
The positive electrode current collector plate is arranged on one surface of the laminated portion of the positive electrode foil exposed portion.
The surface side portion of the separator is deformed so as to approach the positive electrode foil exposed portion on the outermost surface side from the flat surface of the flat portion of the electrode group toward the laminated portion side.
A regulating portion for deforming the surface side portion of the separator so as to approach the exposed positive electrode foil portion on the outermost surface side is provided.
The electrode group is a wound electrode in which the positive electrode and the negative electrode are wound via the separator.
Wherein having said regulating portion covering the surface side of the separator of the region corresponding to at least a portion of the seeded end portion or Maki start portion of the positive electrode foil exposed portion of the outermost surface side, the secondary battery. In the secondary battery according to claim 1,
A secondary battery in which the positive electrode foil exposed portion and the separator of the electrode group are polarized so as to form the deformed portion in a plurality of stages, and the surface side portion of the separator in each of the deformed portions is deformed.

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