JP2016152170A - Square secondary battery and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-life square secondary battery which makes possible to ensure the liquid inpouring easiness and impregnatability of an electrolyte while suppressing the winding loosening of a wound group.SOLUTION: A square secondary battery 100 of the present invention comprises: a flat wound group 3 arranged by winding a positive electrode 34 and a negative electrode 32 with separators 33 and 35 put therebetween. The positive electrode 34 has: a positive electrode mixture layer 34b applied to a piece of positive electrode metal foil; and a positive electrode metal foil-exposure part 34c from which the piece of positive electrode metal foil is exposed. On the positive electrode metal foil-exposure part 34c, adhesion layers 50 are provided for bonding between the piece of positive electrode metal foil and the separators 33 and 35.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a rectangular secondary battery and a method for manufacturing the same.

  In recent years, as a power source for electric vehicles and the like, development of a high energy density prismatic secondary battery including a winding group produced by interposing a separator between a positive electrode and a negative electrode and winding them has been promoted. ing. In addition to high energy, establishment of high production efficiency is required while ensuring safety.

  Patent Document 1 aims to suppress the slackening of a flat wound electrode body having a heat-resistant layer between positive and negative electrodes in a square secondary battery, and to avoid a decrease in production efficiency due to a decrease in can insertability. A heat-resistant layer containing an acrylic binder and a rosin ester-based tackifier is disposed between at least one of the positive electrode and the negative electrode and the separator, and the heat-resistant layer is brought into close contact with the positive and negative electrodes and / or separator by the adhesive force. Technology is shown.

JP 2014-137988

  However, in the case of Patent Document 1, since the separator and the electrode active material are bonded via an adhesive, there is a concern that the electrolyte pouring property and the impregnating property into the pores of the separator and the electrode may be reduced. There is. If charging / discharging is repeated in this state, the electrolyte solution due to expansion and contraction of the electrode becomes insufficient, which may adversely affect the life characteristics.

  It is an object of the present invention to provide a prismatic secondary battery having a long life and a method for manufacturing the same, while ensuring the pouring / impregnation properties of the electrolyte while suppressing the loosening of the wound group.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present invention includes a plurality of means for solving the above-mentioned problems. For example, a square secondary having a flat wound group in which a separator is wound between a positive electrode and a negative electrode. The positive electrode includes a positive electrode mixture layer coated on a positive metal foil, and a positive metal foil exposed portion from which the positive metal foil is exposed, and the separator of the positive metal foil exposed portion An adhesive layer is provided at a position facing the surface.

  According to the present invention, the separator can be bonded to the exposed portion of the positive electrode metal foil by the adhesive layer, so that the positive electrode and the separator can be integrated. Therefore, the loosening of the winding group due to the separation of the positive electrode and the separator is suppressed. And since the surface of a positive mix layer and the surface of a separator are not adhere | attached, a long life battery can be produced by ensuring sufficient liquid injection property / impregnation property. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

The external appearance perspective view of a square secondary battery. The disassembled perspective view of a square secondary battery. The exploded perspective view of a winding group. The figure explaining the structure of a separator. The figure explaining the structure of a negative electrode. The figure explaining the structural example of a positive electrode. The figure which expands and shows the C section of FIG. The figure which shows the cross section of a winding group typically. The figure which expands and shows the D section of FIG. The figure explaining the other structural example of a positive electrode.

  Examples will be described below with reference to the drawings. In the following examples, a case of a lithium ion secondary battery will be described as an example of a square secondary battery, but the present invention is not limited to this, and the positive electrode and the negative electrode are wound with a separator interposed therebetween. The present invention can be applied to any battery having a flat wound group.

FIG. 1 is an external perspective view of a prismatic secondary battery, and FIG. 2 is an exploded perspective view of the prismatic secondary battery.
The prismatic secondary battery 100 includes a battery can 1 and a battery lid 6. The battery can 1 has a pair of opposed wide side surfaces 1b having a relatively large area, a pair of opposed narrow side surfaces 1c and a bottom surface 1d having a relatively small area, and an opening that opens upward at the top. Part 1a.

  A wound group 3 is accommodated in the battery can 1, and an opening 1 a of the battery can 1 is sealed by a battery lid 6. The battery lid 6 has a substantially rectangular flat plate shape, and is welded so as to close the opening 1 a of the battery can 1 to seal the battery can 1. The battery lid 6 is provided with a positive external terminal 14 and a negative external terminal 12. The wound group 3 is charged through the positive external terminal 14 and the negative external terminal 12, and power is supplied to the external load.

  The battery cover 6 is integrally provided with a gas discharge valve 10, and when the pressure in the battery container rises to a preset value or more, the gas discharge valve 10 is opened and gas is discharged from the inside, so that the inside of the battery container The pressure of is reduced. Thereby, the safety of the prismatic secondary battery 100 is ensured.

  A wound group 3 is accommodated in the battery can 1 via an insulating protective film 2. Since the wound group 3 is wound in a flat shape, the wound group 3 has a pair of opposed curved portions having a semicircular cross section and a flat portion formed continuously between the pair of curved portions. ing. The winding group 3 is inserted into the battery can 1 from one curved portion side so that the winding axis direction is along the lateral width direction of the battery can 1, and the other curved portion side is disposed on the upper opening side.

  The positive electrode metal foil exposed portion 34 c of the winding 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 metal foil exposed portion 32 c of the wound 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. Thereby, electric power is supplied from the winding group 3 to the external load via the positive electrode current collecting plate 44 and the negative electrode current collecting plate 24, and externally supplied to the wound group 3 via the positive electrode current collecting plate 44 and the negative electrode current collecting plate 24. The generated power is supplied and charged.

  In order to electrically insulate the positive electrode current collector plate 44 and the negative electrode current collector plate 24, and the positive electrode external terminal 14 and the negative electrode external terminal 12 from the battery lid 6, a gasket 5 and an insulating plate 7 are provided on the battery lid 6. It has been.

  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.

The battery lid 6 is provided with a liquid injection port 9 for injecting the electrolytic solution into the battery container. The liquid injection port 9 is injected by the liquid injection plug 11 after the electrolytic solution is injected into the battery container. Sealed. The liquid injection plug 11 is joined to the battery lid 6 by laser welding to seal the liquid injection port 9 and seal the rectangular secondary battery 100. For example, a nonaqueous electrolytic solution in which a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in an organic carbonate-based organic solvent such as ethylene carbonate is used as the electrolytic solution injected into the battery container. Can do.

  The positive electrode connecting portion 14 a and the negative electrode connecting portion 12 a have a cylindrical shape that protrudes from the lower surface of the positive electrode external terminal 14 and the negative electrode external terminal 12 and can be inserted into the positive electrode side through hole 46 and the negative electrode side through hole 26 of the battery lid 6. Have. The positive electrode connecting portion 14 a and the negative electrode connecting portion 12 a penetrate the battery lid 6 and are more inside the battery can 1 than the positive electrode current collector plate 44, the positive electrode current collector plate base 41 of the negative electrode current collector plate 24, and the negative electrode current collector plate base 21. The positive electrode external terminal 14, the negative electrode external terminal 12, the positive electrode current collector plate 44, and the negative electrode current collector plate 24 are integrally fixed to the battery lid 6. A gasket 5 is interposed between the positive electrode external terminal 14 and the negative electrode external terminal 12 and the battery cover 6, and an insulating plate is interposed between the positive electrode current collector plate 44, the negative electrode current collector plate 24 and the battery cover 6. 7 is interposed.

  The positive electrode current collector plate 44 and the negative electrode current collector plate 24 are a rectangular plate-shaped positive electrode current collector plate base 41, a negative electrode current collector plate base 21, and a positive electrode current collector plate base 41 that are arranged to face the lower surface of the battery lid 6. The negative electrode current collector plate base 21 is bent at the side end and extends toward the bottom surface along the wide side surface of the battery can 1, and the positive electrode metal foil exposed portion 34c of the wound group 3, the negative electrode metal foil exposed portion It has the positive electrode side connection end part 42 and the negative electrode side connection end part 22 which are connected in the state which overlapped facing 32c. The positive electrode current collector plate base 41 and the negative electrode current collector plate base 21 are respectively formed with a positive electrode side opening hole 43 and a negative electrode side opening hole 23 through which the positive electrode connection part 14a and the negative electrode connection part 12a are inserted.

  The insulating protective film 2 is wound around the winding group 3 with the direction along the flat plane of the winding group 3 and the direction perpendicular to the winding axis direction of the winding group 3 as the central axis direction. 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), for example, and is a direction parallel to the flat surface of the wound group 3 and perpendicular to the winding axis direction. Is wound around at least one round.

FIG. 3 is an exploded perspective view showing a state in which a part of the wound group is developed.
The winding group 3 is configured by winding in a flat shape with separators 33 and 35 sandwiched between the negative electrode 32 and the positive electrode 34. In the winding group 3, the positive electrode mixture layer 34b and the negative electrode mixture layer 32b overlap each other, and the positive electrode metal foil exposed portion 34c and the negative electrode metal foil exposed portion 32c are arranged separately on one side and the other side in the winding axis direction. Has been. In the winding group 3, the outermost electrode is the negative electrode 32, and the separators 33 and 35 are wound outside thereof. The separators 33 and 35 have a role of insulating between the positive electrode 34 and the negative electrode 32.

  The negative electrode mixture layer 32b of the negative electrode 32 is larger in the width direction than the positive electrode mixture layer 34b of the positive electrode 34, and the positive electrode mixture layer 34b is always sandwiched between the negative electrode mixture layers 32b. Yes. That is, the negative electrode 32 has a negative electrode mixture layer 32b that is wider than the positive electrode mixture layer 34b, and ends of the negative electrode mixture layer 32b on both sides in the winding axis direction are wound around the positive electrode mixture layer 34b. The positive electrode 34 is overlapped and wound so as to protrude from both end portions in the axial direction.

  The positive electrode metal foil exposed portion 34c and the negative electrode metal foil exposed portion 32c are bundled in a flat thickness direction at a plane portion and connected to the positive electrode current collector plate 44 and the negative electrode current collector plate 24 by welding or the like (see FIG. 2). . Although the separators 33 and 35 are wider than the negative electrode mixture layer 32b in the width direction, the separators 33 and 35 are wound to positions where the metal foil surface at the end is exposed at the positive metal foil exposed portion 34c and the negative metal foil exposed portion 32c. , It does not hinder bundled welding. Moreover, it is also possible to arrange | position an axial center in the innermost periphery of the winding group 3 as needed. As the shaft core, for example, a material obtained by winding a resin sheet having higher bending rigidity than any of the positive electrode metal foil, the negative electrode metal foil, and the separators 33 and 35 can be used.

  4A and 4B are diagrams illustrating the configuration of the separator 33. FIG. 4A is a front view of the separator 33, and FIG. 4B is a cross-sectional view taken along the line BB of FIG. 4A. Since the separators 33 and 35 have the same configuration, the separator 33 is shown in FIG. 4, and the illustration of the separator 35 is omitted by showing it in parentheses. The separators 33 and 35 are made of a soft belt-like sheet member, and are provided by laminating heat-resistant layers 33b and 35b made of an inorganic material and a binder on one surface of the porous polyolefin resin layers 33a and 35a serving as a base material. It has been. The separators 33 and 35 are disposed in a direction in which the heat-resistant layers 33b and 35b face the positive electrode 34 (see FIG. 9).

  5A and 5B are diagrams illustrating the configuration of the negative electrode. FIG. 5A is a front view of the negative electrode, and FIG. 5B is a cross-sectional view taken along line BB in FIG.

  The negative electrode electrode 32 is provided with a negative electrode mixture layer 32b formed by applying a negative electrode mixture containing a negative electrode active material on both surfaces of a negative electrode metal foil which is a negative electrode current collector. And the negative electrode metal foil exposure part 32c which is the uncoated part in which the negative mix is not apply | coated is provided in the edge part of the width direction one side of negative electrode metal foil. That is, the negative electrode 32 has a negative electrode mixture layer 32b applied to the negative electrode metal foil and a negative electrode metal foil exposed portion 32c where the negative electrode metal foil is exposed. The negative electrode metal foil exposed portion 32c is a region where the negative electrode metal foil protrudes from the negative electrode mixture layer 32b. In the wound group 3, the negative electrode metal foil exposed portion 32c is disposed at the other side position in the winding axis direction of the wound group 3.

  Regarding the negative electrode 32, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as a binder to 100 parts by weight of amorphous carbon powder as a negative electrode active material, and N as a dispersion solvent. -A negative electrode mixture in which methylpyrrolidone (hereinafter referred to as NMP) was added and kneaded was prepared. This negative electrode mixture was applied on both sides of a 10 μm thick copper foil (negative electrode metal foil) leaving a negative electrode metal foil exposed portion 32c (negative electrode uncoated portion) as a welded portion. Then, the negative electrode 32 with a thickness of 70 μm of the negative electrode active material application part not including the copper foil was obtained through drying, pressing, and cutting processes.

In this embodiment, the case where amorphous carbon is used as the negative electrode active material is exemplified, but the present invention is not limited to this, and natural graphite capable of inserting and removing lithium ions and various artificial graphite materials , Carbonaceous materials such as coke, compounds such as Si and Sn (for example, SiO, TiSi ₂ etc.), or composite materials thereof may be used. It is not limited.

  Moreover, although the case where PVDF was used as a binder of the coating part in a negative electrode was illustrated, polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber, nitro Polymers such as cellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof can be used.

Further, while an example has been shown where used NMP as dispersion solvent of the coating unit in the negative electrode, not limited thereto, for example in a solvent H _{2 O,} it was added carboxymethylcellulose (CMC) as a thickener A thing may be used.

  6A and 6B are diagrams illustrating a configuration example of the positive electrode. FIG. 6A is a front view of the positive electrode, and FIG. 6B is a cross-sectional view taken along the line BB in FIG. .

  The positive electrode 34 is provided with a positive electrode mixture layer 34b formed by applying a positive electrode mixture containing a positive electrode active material on both surfaces of a positive electrode metal foil which is a positive electrode current collector. And the positive electrode metal foil exposure part 34c which is the uncoated part in which the positive mix is not apply | coated is provided in the edge part of the width direction one side of positive electrode metal foil. That is, the positive electrode 34 has a positive electrode mixture layer 34b applied to the positive metal foil and a positive metal foil exposed portion 34c where the positive metal foil is exposed. The positive electrode metal foil exposed portion 34c is a region where the positive electrode metal foil protrudes from the positive electrode mixture layer 34b, and in the wound group 3, is disposed at one position in the winding axis direction.

  The positive electrode 34 is provided with an adhesive layer 50 for bonding the separators 33 and 35 to the positive metal foil exposed portion 34c as one of the characteristic configurations of the present invention. The adhesive layer 50 is provided so as to extend along the longitudinal direction of the positive electrode 34 with a constant width along the end of the positive electrode mixture layer 34b. The adhesive layer 50 is disposed at a position facing the separators 33 and 35 of the positive electrode metal foil exposed portion 34 c in the wound group 3 and a position facing the negative electrode 32 with the separators 33 and 35 interposed therebetween. The adhesive layer 50 does not have adhesiveness before heating, and has a configuration in which adhesiveness is expressed by heating once. In this embodiment, thermoplasticity that exhibits adhesiveness by heating is used. Contains resin.

FIG. 7 is an enlarged view of a portion C in FIG.
The adhesive layer 50 and the positive electrode mixture layer 34b are provided on a positive electrode metal foil that is a conductor, and are in contact with each other. In this embodiment, since the positive electrode mixture layer 34b is applied first and the adhesive layer 50 is applied later, the end portion of the adhesive layer 50 overlaps the end portion of the positive electrode mixture layer 34b. Yes. Thus, if there are overlapping portions w between the adhesive layer 50 and the positive electrode mixture layer 34b, the sum of the thickness t ₃ of the thickness t ₂ and the adhesive layer 50 of the positive electrode mixture layer 34b in such overlapping portions w is the maximum thickness _{t 1} is set to be less than the thickness of the central portion of the positive electrode mixture layer _{34b (t 1> t 2 +} t 3).

As for the positive electrode 34, 10 parts by weight of flaky graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganate (chemical formula LiMn ₂ O ₄ ) as a positive electrode active material. Then, NMP was added as a dispersion solvent and kneaded to prepare a slurry-like positive electrode mixture. This slurry-like positive electrode mixture was applied to both surfaces of an aluminum foil (positive metal foil) having a thickness of 20 μm, leaving a positive metal foil exposed portion 34c (positive electrode uncoated portion) as a welded portion. Then, the positive electrode 34 with a thickness of 90 μm of the positive electrode mixture layer 34b not containing the aluminum foil was obtained through drying, pressing, and cutting processes.

The adhesive layer 50 is configured by applying a slurry adhesive and drying it. In this embodiment, the positive electrode mixture is first applied and dried for a predetermined time, and then the adhesive is applied. However, the adhesive may be applied simultaneously with the positive electrode mixture. The adhesive layer 50 is cold-pressed after the adhesive is applied and dried, and is adjusted to the same thickness t ₁ as the positive electrode mixture layer 34b.

  Since the adhesive layer 50 contains a thermoplastic resin that exhibits adhesiveness when heated, depending on the type or formulation of the thermoplastic resin, adhesiveness is manifested by compression by a press, particularly by pressing in an overheated state. Adhering to a press machine or the like may cause a decrease in productivity. Accordingly, the adhesive layer 50 is preferably dried and pressed at room temperature.

  Further, in this example, the case where lithium manganate is used as the positive electrode active material is exemplified, but other lithium manganate having a spinel crystal structure or a lithium manganese composite oxide or layered in which a part is substituted or doped with a metal element A lithium cobalt oxide or lithium titanate having a crystal structure, or a lithium-metal composite oxide obtained by substituting or doping a part thereof with a metal element may be used.

  Further, in this example, the case where PVDF is used as the binder in the positive electrode mixture is exemplified, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene butadiene rubber, polysulfide rubber. Polymers such as nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride, chloroprene fluoride, and acrylic resins, and mixtures thereof can be used.

  Next, the adhesive layer 50 in the present embodiment will be described. The adhesive layer 50 contains a thermoplastic resin having a melting point lower than the shutdown temperature (about 120 ° C.) of the separator. Examples include low density polyethylene (95 ° C), polystyrene (100 ° C), polyvinyl chloride (PVC: 85 ° C), acrylic resin, methacrylic resin (90 to 105 ° C).

  In the present embodiment, particulate methacrylic resin is included as the thermoplastic resin, and PVDF is included as the metal foil binder. NMP was added thereto as a dispersion solvent, and a dispersed slurry-like adhesive material was prepared. After applying to a target portion, the adhesive layer 50 was formed by drying at room temperature and evaporating the dispersion solvent.

  In this example, a particulate methacrylic resin having an average particle diameter of about 3 to 10 μm was used. In this embodiment, the NMP dispersion solvent containing particulate methacrylic resin and PVDF was used as the configuration of the adhesive layer 50. However, the present invention is not limited to this, and the resin material softened at a high temperature. There is also a method in which the adhesive layer 50 is obtained by directly applying to the exposed metal foil exposed portion 34c and cooling. In this example, in order to easily control the thickness of the adhesive layer 50, a dispersion solvent made of particulate resin was selected. When the particulate resin is used, the thickness can be easily adjusted when pressed, and can be easily adjusted when the thickness of the adhesive layer 50 is adjusted to be the same as the thickness of the positive electrode mixture layer 34b.

FIG. 8 is a cross-sectional view of the wound group 3 in the embodiment, and FIG. 9 is an enlarged view of a portion D in FIG.
In the wound group 3, the negative electrode mixture layer 32b protrudes on both sides in the winding axis direction of the wound group 3 rather than the positive electrode mixture layer 34b. The positive metal foil exposed portion 34c protrudes outward in the winding axis direction from the negative electrode mixture layer 32b. The coating-side end portion 32e of the negative electrode mixture layer 32b is disposed at a position on the outer side in the winding axis direction than the uncoated side end portion 34d of the positive electrode mixture layer 34b. The separators 33 and 35 are oriented so that the heat-resistant layers 33b and 35b face the positive electrode mixture layer 34b and sandwich the positive electrode mixture layer 34b therebetween.

  The adhesive layer 50 is provided on the positive electrode metal foil exposed portion 34c of the positive electrode 34, and is located at a position facing the separators 33 and 35, with the separators 33 and 35 interposed therebetween, and the negative electrode mixture layer 32b of the negative electrode 32. It is arrange | positioned in the position facing. In this embodiment, the negative electrode side of the positive electrode mixture layer 34b is connected to the negative electrode side 34d so that the end of the adhesive layer 50 is aligned with the coating side end 32e of the negative electrode mixture layer 32b in the wound group 3. It is arrange | positioned by the coating width ranging to the position which opposes the coating side edge part 32e of the mixture layer 32b. The edge of the adhesive layer 50 is set at a position that does not protrude beyond the edges of the separators 33 and 35, and the negative electrode metal foil exposed portion 32c is bundled in the flat thickness direction and connected to the negative electrode current collector plate 24. The weldability is not impaired.

Next, the manufacturing method of the winding group which has the said structure is demonstrated.
The manufacturing method of the winding group 3 includes a winding step S1 and an adhesion step S2. In the winding process S1, the positive electrode 34 and the negative electrode 32 having the above-described configuration are wound in a flat shape with the separators 33 and 35 interposed therebetween to form a wound group 3 wound in a flat shape.

  In the bonding step S2, the wound group 3 wound in a flat shape has a melting point lower than the shutdown temperature of the separators 33 and 35 and a temperature equal to or higher than the melting point of the thermoplastic resin constituting the adhesive layer 50 for several seconds. Heat compression in the flat thickness direction. Thereby, adhesiveness is expressed in the adhesive layer 50, and the adhesive layer 50 is adhered to the heat-resistant layers 33b and 35b of the separators 33 and 35. Therefore, the positive electrode 34 and the separators 33 and 35 are integrated with each other.

  Since the adhesive layer 50 is disposed at a position facing the negative electrode mixture layer 32b of the negative electrode 32 with the separators 33 and 35 interposed therebetween, pressure can be applied in the flat thickness direction during the heat compression. The separators 33 and 35 can be reliably pressed and bonded. Therefore, it is possible to suppress the loosening caused by the separation between the positive electrode 34 and the separators 33 and 35. In addition, since the surface of the electrode active material and the separator are not adhered to each other with respect to the electrolyte injection, sufficient injection / impregnation can be secured, and as a result, an increase in DCR can be suppressed. .

  According to the present embodiment, in the wound group 3, the coating width of the adhesive layer 50 so that the position of the end portion of the adhesive layer 50 is aligned with the position of the coating-side end portion 32e of the negative electrode mixture layer 32b in the thickness direction. Therefore, when the wound group 3 is heated and compressed, the adhesive layer 50 can be pressed against the separators 33 and 35 over the entire coating width, and is securely adhered to the separators 33 and 35. be able to.

  When the separators 33 and 35 have the heat-resistant layers 33b and 35b as in this embodiment, the friction coefficient with the positive electrode mixture layer 34b is small. With respect to this problem, in the present invention, since the adhesive layer 50 is provided on the positive electrode metal foil exposed portion 34c and the separators 33 and 35 are adhered, it is possible to prevent the occurrence of whistling and Compared with the case where the adhesive is interposed between and adhering to the positive electrode mixture layer as in the described technique, there is a possibility that the liquid injection property of the electrolytic solution and the impregnation property to the pores of the separator and the electrode may be reduced. In addition, it is possible to extend the life of the battery by suppressing an increase in DCR.

  In addition, although the present Example demonstrated the case where the separators 33 and 35 have the heat resistant layers 33b and 35b, this invention is not limited to this, The structure where a separator does not have a heat resistant layer is also included. Applicable.

  10A and 10B are diagrams illustrating another configuration example of the positive electrode. FIG. 10A is a front view of the positive electrode, and FIG. 10B is a cross-sectional view taken along the line BB in FIG. It is.

The adhesive layer 50 may not be in contact with the positive electrode mixture layer 34b and may have a gap 34e. For example, as shown in FIG. 7, when there is an overlapping portion w between the positive electrode mixture layer 34b and the adhesive layer 50, the thickness (t ₂ + t ₃ ) of the overlapping portion w is set to the maximum of the positive electrode mixture layer 34b. it is necessary to control the thickness t ₁ below.

If the thickness of the overlapping portion w is larger than the maximum thickness t ₁ (see FIG. 7) of the positive electrode mixture layer 34b, the overlapping portion w protrudes and becomes bulky in the radial direction when wound, There is a risk of affecting durability and can insertion property of the wound group 3.

Since the present configuration example is provided with a gap 34e between the adhesive layer 50 and the positive electrode mixture layer 34b, it is not necessary to control the thickness of the portion w below the maximum thickness t ₁ of the positive electrode mixture layer 34b overlap, positive Manufacture of the electrode 34 becomes easy.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various designs can be made without departing from the spirit of the present invention described in the claims. It can be changed. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Furthermore, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 Battery can 3 Winding group 32 Negative electrode 32b Negative electrode mixture layer 32c Negative electrode metal foil exposed part 33 Separator 34 Positive electrode 34a Positive electrode mixture layer 34b Positive electrode metal foil exposed part 35 Separator 50 Adhesive layer 100 Rectangular secondary battery

Claims (8)

A prismatic secondary battery having a flat wound group wound by sandwiching a separator between a positive electrode and a negative electrode,
The positive electrode has a positive electrode mixture layer coated on a positive metal foil, and a positive metal foil exposed portion where the positive metal foil is exposed, and is located at a position facing the separator of the positive metal foil exposed portion. A prismatic secondary battery comprising an adhesive layer.   The prismatic secondary battery according to claim 1, wherein the separator has a heat-resistant layer, and the heat-resistant layer is disposed to face the positive electrode. The negative electrode has a negative electrode mixture layer coated on a negative electrode metal foil and wider than the positive electrode mixture layer, and a negative electrode metal foil exposed portion where the negative electrode metal foil is exposed,
In the winding group, the positive electrode metal foil exposed portion and the negative electrode metal foil exposed portion are divided into one side and the other side in the winding axis direction, and the negative electrode mixture layer is wound more than the positive electrode mixture layer. It protrudes on both sides in the axial direction, and the positive electrode metal foil exposed part is arranged so as to protrude outward in the winding axis direction than the negative electrode mixture layer,
The prismatic secondary battery according to claim 2, wherein the adhesive layer is provided at a position facing the negative electrode mixture layer with the separator interposed therebetween.   The prismatic secondary battery according to claim 3, wherein the adhesive layer is disposed between an end portion of the positive electrode mixture layer and a position facing the end portion of the negative electrode mixture layer.   When there is an overlapping portion between the positive electrode mixture layer and the adhesive layer, the sum of the thicknesses of the positive electrode mixture layer and the adhesive layer in the overlapping portion is not more than the maximum thickness of the positive electrode mixture layer. The prismatic secondary battery according to claim 4.   The prismatic secondary battery according to claim 5, wherein the adhesive layer includes a thermoplastic resin having a melting point lower than a shutdown temperature of the separator.   The prismatic secondary battery according to claim 6, wherein the thermoplastic resin is particulate. A method for manufacturing a prismatic secondary battery having a flat wound group wound with a separator interposed between a positive electrode and a negative electrode,
The positive electrode is provided with an adhesive layer having a thermoplastic resin at a position facing the separator of the exposed portion of the positive metal foil,
Winding the separator between the positive electrode and the negative electrode in a flat shape; and
Heating and compressing the wound group wound in a flat shape at a melting point lower than the shutdown temperature of the separator and at a temperature equal to or higher than the melting point of the thermoplastic resin in a flat thickness direction;
The manufacturing method of the square secondary battery characterized by including.

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