JP2012119080A - Secondary battery, and secondary battery manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery of a high energy density, which has a group of wound electrodes formed so that an active material mixture layer is prevented from coming loose and falling, and which is decreased in weight by providing a plurality of bores in a current collector foil.SOLUTION: The secondary battery includes a wound electrode group formed by winding a positive electrode sheet and a negative electrode sheet, each consisting of a long length of current collector foil 9(10) coated with an active material mixture, with a separator interposed therebetween. The current collector foil 9(10) has: a belt-like coating region 3 which is coated with the active material mixture so that one of belt-like long side edge portions of the current collector foil 9(10) is left exposed; and a boring region 60 where a plurality of bores 2 are provided within the coating region 3 except for both the long sides of the belt-like coating region 3.

Description

  The present invention relates to a secondary battery mounted on a vehicle such as an electric vehicle (EV) or a hybrid electric vehicle (HEV), and a method for manufacturing the secondary battery.

  In recent years, secondary batteries having high energy density have attracted attention as power sources for electric vehicles (EV) and hybrid electric vehicles (HEV).

  In a secondary battery such as a lithium ion battery, a positive electrode sheet and a negative electrode are usually obtained by applying a slurry-like active material mixture to a current collector foil made of a long metal foil, drying, pressing, and cutting. A sheet is formed. A wound electrode group is formed by winding the positive electrode sheet and the negative electrode sheet through a microporous separator between the two electrode sheets. A secondary battery is formed by injecting an electrolyte into a battery container containing a wound electrode group and then sealing the battery.

  In the positive electrode sheet and the negative electrode sheet, the weight of the positive electrode current collector foil and the negative electrode current collector foil is larger than the weight of the active material mixture. In order to improve the energy density, weight reduction of the positive electrode current collector foil and the negative electrode current collector foil is an important issue. Therefore, a current collector foil for a lithium ion battery has been proposed in which weight reduction is realized by providing a plurality of holes in the positive electrode current collector foil and the negative electrode current collector foil (Patent Document 1).

JP-A-11-67222

  In the current collector foil described in Patent Document 1, it is possible to reduce the weight of the current collector foil by providing a plurality of holes in a portion of the long current collector foil excluding the peripheral portion on the long side. However, nothing is shown about the relationship between the hole processing region in which holes are formed in the current collector foil and the coating region where the active material mixture is applied.

  Usually, application, drying, pressing, and cutting of the active material mixture are performed in a state where a predetermined tension is applied to the positive electrode and the negative electrode sheet. When the active material mixture is applied to the current collector foil provided with a plurality of holes, a band-shaped active material mixture layer is formed. Since the thickness of the active material mixture layer is thicker than that of the current collector foil, tension is applied to the positive electrode and the negative electrode sheet when the roller contacts the active material mixture layer.

  When the edge of the active material mixture layer is positioned on the hole, the strength of the active material mixture layer in the hole is weaker than the strength of the active material mixture layer formed on the current collector foil. In the manufacturing process of the wound electrode group, it is difficult to ensure the tension balance, and the active material mixture layer at the edge portion may fall off.

  The secondary battery according to the invention of claim 1 includes a secondary electrode group comprising a positive electrode sheet coated with an active material mixture on a long current collector foil and a negative electrode sheet obtained by winding the negative electrode sheet through a separator. In the battery, the current collector foil has a belt-shaped coating region to which the active material mixture is coated so that one long side edge of the current collector foil is left exposed in a belt shape, It is characterized by having a hole processing region in which a plurality of holes are provided in the coating region except on both long sides of the region.

  A secondary battery according to a third aspect of the invention includes a secondary electrode provided with a wound electrode group formed by winding a positive electrode sheet and a negative electrode sheet coated with an active material mixture on a long current collector foil through a separator. In the battery, the current collector foil includes a strip-shaped coating region coated with an active material mixture so that one long side edge of the current collector foil remains exposed in a strip shape, and a strip-shaped coating region. It is characterized by comprising a non-porous region set along both long sides and a hole processing region in which a plurality of holes are provided in a coating region other than the non-porous region.

  The method of manufacturing a secondary battery according to the invention of claim 6 is the method of manufacturing a secondary battery according to any one of claims 1 to 5, wherein the active material mixture is applied to the coating region. It includes at least a step of winding the positive electrode sheet, the negative electrode sheet, and the separator while overlapping each other while bringing a roller into contact therewith.

  According to the present invention, the secondary battery is reduced in weight by providing a plurality of holes in the current collector foil, and the wound electrode group formed in a state in which the active material mixture layer is prevented from falling off. A secondary battery having a high energy density and a method for manufacturing the secondary battery can be provided.

It is a perspective view which shows the external appearance of the secondary battery which concerns on embodiment of this invention. 1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention. It is a perspective view which shows the winding electrode group of the secondary battery which concerns on embodiment of this invention. It is a flowchart which shows the procedure which produces the winding electrode group of the secondary battery which concerns on embodiment of this invention. It is a top view which shows the positive electrode current collector foil (or negative electrode current collector foil) which concerns on embodiment of this invention. It is a top view which shows the positive electrode current collector foil (or negative electrode current collector foil) by which the punching process which concerns on embodiment of this invention was given. It is a top view which shows the positive electrode sheet (or negative electrode sheet) before the cutting which concerns on embodiment of this invention. It is a perspective view of the positive electrode sheet and negative electrode sheet after cutting concerning an embodiment of the present invention. It is a perspective view which shows the winding process for creating the winding electrode group of the secondary battery which concerns on embodiment of this invention.

Hereinafter, an embodiment in which a secondary battery according to the present invention is applied to a prismatic lithium ion battery will be described with reference to the drawings.
[Configuration of secondary battery]
With reference to FIGS. 1-3, the structure of the secondary battery 40 which concerns on embodiment of this invention is demonstrated. FIG. 1 is a perspective view showing an appearance of a secondary battery 40 according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the secondary battery 40 according to the embodiment of the present invention. FIG. 3 is a perspective view showing the wound electrode group 20 of the secondary battery 40 according to the embodiment of the present invention.

  As shown in FIG. 1, the secondary battery 40 includes a battery container including a can 38 and a lid 32. As shown in FIG. 2, the can 38 accommodates the wound electrode group 20 covered with the insulating sheet 37, and is formed in a rectangular box shape having one end opened. The lid 32 has a rectangular flat plate shape and is welded so as to close the opening of the can 38. Both the can 38 and the lid 32 are made of an aluminum alloy.

  As shown in FIGS. 1 and 2, the lid 32 is provided with a positive external terminal 31a and a negative external terminal 31b. The positive electrode external terminal 31a and the negative electrode external terminal 31b are connected to a positive electrode connection plate 35a and a negative electrode connection plate 35b disposed in the can 38, respectively. The positive electrode external terminal 31a and the positive electrode connection plate 35a are both formed of an aluminum alloy, and the negative electrode external terminal 31b and the negative electrode connection plate 35b are both formed of a copper alloy.

  The positive electrode connection plate 35a and the negative electrode connection plate 35b are connected to the joint 36 of the wound electrode group 20 by ultrasonic welding. Prior to ultrasonic welding, the joining portion 36 is formed by crushing a laminate in an uncoated region where the active material mixture is not applied at both ends in the axial direction of the wound electrode group 20. That is, the joining portion 36 is formed by crushing the exposed regions of the positive electrode current collector foil 9 and the negative electrode current collector foil 10 in a superimposed state.

  Since the positive and negative external terminals 31a and 31b are electrically connected to the wound electrode group 20 via the positive and negative connection plates 35a and 35b, power is supplied to the external load via the positive and negative external terminals 31a and 31b. Or externally generated power is supplied to the wound electrode group 20 via the positive and negative external terminals 31a and 31b and charged. The positive electrode external terminal 31a, the positive electrode connection plate 35a, the negative electrode external terminal 31b, and the negative electrode connection plate 35b are electrically insulated from the lid 32 by an insulating material (not shown).

  The lid 32 is provided with a liquid injection hole 33 for injecting an electrolytic solution into the battery container. The liquid injection hole 33 is sealed by the liquid injection plug 30 after the electrolyte solution is injected. The lid 32 is also provided with a gas discharge valve 34. The gas discharge valve 34 generates heat when the secondary battery 40 generates heat due to an abnormality such as overcharge, and is cleaved when the pressure in the battery container increases and reaches a predetermined pressure. The pressure in the battery container is reduced by discharging.

  As shown in FIG. 3, the wound electrode group 20 is configured by winding the positive electrode sheet 12 and the negative electrode sheet 13 in a flat shape via separators 14 and 15. The positive electrode sheet 12 and the negative electrode sheet 13 are formed by coating an active material mixture on both surfaces of a positive electrode current collector foil 9 and a negative electrode current collector foil 10 which are long metal foils. The positive electrode current collector foil 9 is an aluminum foil or an aluminum alloy foil having a thickness of about 20 μm, and the negative electrode current collector foil 10 is a copper foil or a copper alloy foil having a thickness of about 15 μm. The separators 14 and 15 are porous polyethylene resins.

  A number of holes 2 shown in FIG. 7 are regularly formed in the positive electrode current collector foil 9. A belt-like positive electrode active material mixture layer 23 is applied so as to cover these holes 2, and the positive electrode sheet 12 shown in FIG. The positive electrode active material mixture layer 23 is formed by applying a positive electrode active material mixture so that one long side edge of the long positive electrode current collector foil 9 remains exposed in a strip shape. ing. The positive electrode active material mixture layer 23 is a mixture of lithium-containing complex oxide powder, scaly graphite as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 85: 10: 5. A slurry obtained by adding and kneading N-methylpyrrolidone (NMP) as a dispersion solvent is applied to both surfaces of the positive electrode current collector foil 9 and dried and pressed.

  A large number of holes 2 shown in FIG. 7 are regularly formed in the negative electrode current collector foil 10. A belt-like negative electrode active material mixture layer 24 is applied so as to cover these holes 2, and the negative electrode sheet 13 shown in FIG. The negative electrode active material mixture layer 24 is formed by applying a negative electrode active material mixture so that one long side edge of the long negative electrode current collector foil 10 remains exposed in a strip shape. ing. The negative electrode active material mixture layer 24 is prepared by mixing a slurry obtained by mixing amorphous carbon powder and PVDF as a binder at a weight ratio of 90:10, adding NMP as a dispersion solvent thereto, and kneading the mixture. It is formed by applying to both sides of 10 and dry pressing. The formed positive electrode and negative electrode active material mixture layers 23 and 24 each have a thickness of about 40 μm on one side.

  One end of the positive electrode and negative electrode current collector foils 9 and 10 in the width direction (direction orthogonal to the winding direction) is, as shown in FIG. 3, a positive electrode uncoated region 9a to which no active material mixture is applied. And the negative electrode uncoated region 10a. The positive electrode uncoated region 9a and the negative electrode uncoated region 10a are portions where the metal foil is exposed, and as described above, are the joints 36 that are electrically connected to the positive and negative electrode connecting plates 35a and 35b. (See FIG. 2). As described above, the positive and negative electrode connecting plates 35a and 35b are connected to the positive and negative external terminals 31a and 31b.

  Various processes for producing the wound electrode group 20 will be described with reference to FIG. 4 shows procedures S50 and S100 to 500 for producing the positive electrode sheet 12 and the negative electrode sheet 13 constituting the wound electrode group 20, and a procedure S600 for producing the wound electrode group 20 by winding the positive and negative electrode sheets 12 and 13. It is a flowchart which shows. Since the positive electrode sheet 12 and the negative electrode sheet 13 are produced by the same procedure, the flowchart of FIG. 4 will be described as a procedure for producing the positive and negative electrode sheets 12 and 13.

[Manufacturing process]
As shown in FIG. 4, the positive and negative electrode sheets 12 and 13 include an electrode foil material preparation step S50, a punching step S100, a positive and negative electrode active material mixture coating step S200, a drying step S300, a pressing step S400, and a slitting step S500. It is produced through.

  In the electrode foil material preparation step S50, as shown in FIG. 5, positive and negative electrode current collector foils 9 and 10, which are long electrode foil materials having a width twice that of the positive and negative electrode sheets 12 and 13, are prepared. Reference numeral 70 in FIG. 5 is a dividing line between the two positive and negative current collecting foils 9 and 10. The dividing line 70 is an imaginary line for dividing the strip of current collector foils 9 and 10 into two, and when cut on this line, this line becomes one of the long sides of the positive and negative electrode sheets 12 and 13.

  A band-shaped active material coating region 3 having a width of 2 × WK is set in the upper and lower regions sandwiching the dividing line 70, and an active material mixture is applied to the active material coating region 3 as described later. An active material uncoated region 1 where no active material is applied is set on the upper and lower long side edges of the long positive and negative current collector foils 9 and 10, respectively. The uncoated region 1 is a region corresponding to the above-described joint portion 36, and a width necessary for connection with the positive electrode connection plate 35a or the negative electrode connection plate 35b is secured.

  A hole machining area 60 having a width WP is set in each of the areas above and below the dividing line 70, and a plurality of small holes 2 are formed in each hole machining area 60 as described later. The hole processing region 60 is secured in a strip shape in the coating region 3 so as not to include the parting line 70 and the both long sides of the coating region 3. That is, the non-perforated area 61 where no hole machining is performed is set along both long sides of the coating area 3 and the dividing line 70. The width of the non-porous region 61 was 2 to 10 mm, respectively. As described above, since the dividing line 70 becomes the long side of the positive and negative electrode sheets 12 and 13 after cutting, both long sides that are not the hole processing region 60 in the coating region 3 of the positive and negative electrode sheets 12 and 13 after cutting. The side edge portion is a non-porous region 61.

  In the punching step S100, as shown in FIG. 6, punching is performed on the hole processing region 60 of the positive and negative current collector foils 9 and 10. When punching is performed on the hole processing region 60, a large number of circular holes 2 are formed in the current collector foils 9 and 10 in a matrix.

  In the active material mixture coating step S200, as shown in FIG. 7, the active material mixture is applied to the coating region 3 including the hole processing region 60 of the positive and negative electrode current collector foils 9 and 10, and the positive and negative electrode sheets 12 are applied. , 13 are formed. The positive and negative electrode active material mixture layers 23 and 24 are formed so as to cover the hole 2. That is, the active material mixture is filled not only in the surfaces of the current collector foils 9 and 10 but also in the holes 2.

  In the drying step S300, the coated active material mixture is dried, and the active material mixture layers 23 and 24 are pressure-molded in the pressing step S400.

  In the slitting process S500, the material of the positive and negative electrode sheets 12 and 13 is cut along the dividing line 70, that is, the material is cut in the longitudinal direction at the center in the width direction, and the positive electrode sheet 12 shown in FIG. Each of the negative electrode sheets 13 shown in FIG.

  In the winding step S600, as shown in FIG. 9, the coating region 3 coated with the active material mixture is brought into contact with a roller (not shown) to apply tension, and the positive electrode sheet 12 and the negative electrode sheet 13 A wound electrode group 20 is created by winding the separators 14 and 15 while overlapping them.

  In winding, first, separators 14 and 15 are wound a plurality of times around a winding shaft 16 that rotates about a horizontal axis to form an axis. Next, the positive electrode sheet 12 is wound on the upper side of the separator 15 from one side of the winding shaft 16, and the negative electrode sheet 13 is wound on the lower side of the separator 14. By rotating the winding shaft 16, the separator 15 and the positive electrode sheet 12, and the separator 14 and the negative electrode sheet 13 are respectively wound around the shaft core while being guided by the guide rollers 17 installed horizontally.

  At the time of winding, the positive electrode sheet 12, the negative electrode sheet 13, and the separators 14 and 15 are stretched by applying a load of 10 N in the longitudinal direction, and the positive and negative electrode sheets 12, 13 and the separators 14 and 15 are extended in the longitudinal direction. The meandering is controlled so that the side edge is at a fixed position.

  Each treatment in the positive and negative electrode active material mixture coating step S200 to the winding step S600 is performed by coating the positive electrode and the negative electrode current collector foils 9 and 10 with the positive electrode and negative electrode active material mixture layers 23 and 24. This is performed in a state where a predetermined tension is applied in the longitudinal direction of the sheets 12 and 13. Tension is applied by a roller (not shown).

  In the positive electrode and negative electrode sheets 12 and 13, the thickness of the region where the positive electrode and negative electrode active material mixture layers 23 and 24 are formed is thicker than that of the positive electrode and negative electrode current collector foils 9 and 10. The agent layers 23 and 24 come into contact with the roller, and tension is applied to the positive and negative electrode sheets 12 and 13.

According to this Embodiment described above, there can exist the following effects.
(1) A non-porous region 61 was provided along both long sides of the coating region 3, and the coating region 3 was secured so as to include the hole processing region 60. Thereby, since the tension balance added to the positive electrode and negative electrode active material mixture layers 23 and 24 in the active material mixture coating step S200 to the winding step S600 can be appropriately maintained, the positive electrode and negative electrode active material mixture layer 23 is maintained. , 24 can be prevented from peeling off or falling off.
That is, according to the present embodiment, the secondary battery 40 is reduced in weight by providing the current collector foils 9 and 10 with the plurality of holes 2, and the active material mixture layers 23 and 24 are prevented from falling off. It is possible to provide a secondary battery 40 having a high energy density and having a wound electrode group 20 formed in the formed state, and a method for manufacturing the secondary battery 40.

  (2) The hole processing region 60 was secured so that the hole 2 was not formed on the dividing line 70 at the center in the width direction of the positive electrode or negative electrode current collector foils 9 and 10. Thereby, in slit process S500, peeling of the positive electrode and negative electrode active material mixture layers 23 and 24 in a cutting part, and dropping off can be prevented.

  (3) Since the tension balance applied to the positive electrode and the negative electrode sheets 12 and 13 in the winding step S600 can be properly maintained, winding slippage can be prevented.

  (4) Since the hole processing region 60 is in the coating region 3, the hole 2 is not formed in the uncoated region 1. Thereby, the joining part 36 which overlaps the collector foil exposed surface which is the uncoated area | region 1 can be easily connected with the positive electrode and negative electrode connection part 35a, 35b by ultrasonic welding.

  (5) The width | variety of the non-porous area | region 61 provided in the both long side edge part of the coating area | region 3 was 2-10 mm, respectively. Thereby, the tension balance can be reliably ensured when the wound electrode group 20 is formed, and the positive electrode and the negative electrode active material mixture layers 23 and 24 can be prevented from being peeled off and dropped off.

  (6) Since the positive electrode and negative electrode active material mixture layers 23 and 24 are formed on both surfaces of the positive electrode and negative electrode current collector foils 9 and 10, the secondary battery 40 having a high energy density can be provided.

The embodiment described above can be modified as follows.
[Modification]
(1) The present invention is not limited to the case where the positive electrode sheet 12 and the negative electrode sheet 13 are formed by two strips. Even in the case where the positive electrode sheet 12 and the negative electrode sheet 13 are formed by a single strip, a hole is formed inside the coating region 3 so that the long sides of the active material mixture layers 23 and 24 are not positioned on the hole 2. By setting the non-porous region 61 along both long sides of the coating region 3 so as to secure the region 60, an appropriate balance of tension is secured during coating and winding, and the active material mixture layer 23 and 24 can be prevented from peeling off and dropping off. Winding can be prevented during winding. In the case of a single strip, the slit process S500 is omitted.

  (2) In the above embodiment, the prismatic secondary battery has been described as an example, but the present invention is not limited to this. When creating a wound electrode group of a cylindrical lithium ion secondary battery, it is also possible to ensure a proper tension balance and prevent the active material mixture layer from peeling off or falling off.

(3) The shape of the hole 2 is not limited to a circular shape. Various shapes such as an elliptical shape and a rectangular shape can be adopted.
(4) The holes 2 may be provided at unequal pitches without being provided in a matrix shape with an equal pitch.
(5) It is not limited to the case where punching is performed on both the positive electrode current collector foil 9 and the negative electrode current collector foil 10 constituting the wound electrode group 20. The wound electrode group 20 may be formed by punching one of the positive electrode current collector foil 9 and the negative electrode current collector foil 10.

  DESCRIPTION OF SYMBOLS 1 Uncoated area | region, 2 hole, 3 coated area | region, 9 positive electrode current collection foil, 9a positive electrode uncoated area | region, 10 negative electrode current collection foil, 10a negative electrode uncoated area | region, 12 positive electrode sheet | seat, 13 negative electrode sheet | seat, 14 separator , 15 separator, 20 wound electrode group, 23 positive electrode active material mixture layer, 24 negative electrode active material mixture layer, 40 secondary battery, 60 hole processing region, 70 dividing line

Claims (6)

In a secondary battery comprising a wound electrode group formed by winding a positive electrode sheet and a negative electrode sheet coated with an active material mixture on a long current collector foil through a separator,
The current collector foil has a belt-shaped coating region to which an active material mixture is applied so that one long side side edge of the current collector foil remains exposed in a belt shape, and the belt-shaped coating A secondary battery comprising a hole processing region in which a plurality of holes are provided in a coating region except on both long sides of the region. The secondary battery according to claim 1,
The secondary battery according to claim 2, wherein the width of both long side edges where the hole is not formed in the coating region is 2 to 10 mm. In a secondary battery comprising a wound electrode group formed by winding a positive electrode sheet and a negative electrode sheet coated with an active material mixture on a long current collector foil through a separator,
The current collector foil includes a belt-shaped coating region coated with an active material mixture so that one long side edge of the current collector foil remains exposed in a belt shape, and the belt-shaped coating region. A secondary battery comprising: a non-porous region set along both long sides; and a hole processing region in which a plurality of holes are provided in the coating region other than the non-porous region. The secondary battery according to claim 3,
The non-porous region has a width of 2 to 10 mm, respectively. The secondary battery according to any one of claims 1 to 4,
The active material mixture is coated on both surfaces of a positive electrode current collector foil and a negative electrode current collector foil. The method of manufacturing a secondary battery according to any one of claims 1 to 5,
The method includes at least a step of winding the positive electrode sheet, the negative electrode sheet, and the separator while superimposing them while bringing a tension into contact with the application region where the active material mixture has been applied. A method for manufacturing a secondary battery.

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