JP6765268B2 - Rechargeable battery - Google Patents

Description

The present invention relates to a method for manufacturing a secondary battery and an electrode, and more particularly to a secondary battery used as a power source for power of an electric vehicle, a hybrid electric vehicle, or the like.

In recent years, large-capacity (Wh) secondary batteries have been developed as power sources for hybrid electric vehicles and pure electric vehicles. Among them, non-aqueous lithium-ion batteries with high energy density (Wh / kg) have been developed. The next battery is drawing attention. In addition, from the viewpoint of suppressing exhaust gas and emphasizing environmental performance, automobiles are oriented toward running by electrification, and a large capacity battery is required. Further, a battery used as a power source for driving an electric motor is required to have characteristics capable of outputting a large current.

A group of flat wound electrodes is generally housed in a battery container of a square lithium ion secondary battery. The wound electrode group is composed of a positive electrode and a negative electrode which are wound and laminated in a roll shape, and a separator for electrically insulating them. An active material mixture capable of inserting and removing lithium ions is applied to the surfaces of the strip-shaped metal foils of the positive electrode and the negative electrode to form a mixture layer. The wound electrode group is provided by winding these positive electrode and negative electrode electrodes around an axis in a state of being overlapped with each other via a separator and forming them flat.

The flatly formed winding electrode group is housed in a container such as a metal can. For example, in Patent Document 1, in order to prevent a short circuit between electrodes even if a separator having a thin thickness is used in order to increase the capacity, an electrode having a porous insulating layer is formed on the electrode surface to withstand resistance. It is disclosed to improve the short circuit property.

Japanese Unexamined Patent Publication No. 2008-226566

In the process of manufacturing a secondary battery in which a group of wound electrodes is stored in a container such as a square metal can, a mixture containing an active material capable of inserting and removing lithium ions is slurried and applied to the surface of a band-shaped metal foil. The positive electrode and the negative electrode having the mixture layer formed in the above are manufactured. Then, the wound electrode group is formed by electrically insulating them and winding them flatly through a microporous resin film separator through which lithium ions and an electrolytic solution can pass. After that, the winding electrode group housed in the can is electrically connected so that the current collector plate electrically connected to the outside is joined to the winding electrode group by a method such as welding to allow current to pass through. It is necessary to be there.

The positive electrode and negative electrode current collector plates are fixed to the inside of the battery lid of the battery container via an insulating material, and are electrically connected to the positive electrode and negative electrode external terminals provided on the outside of the battery lid. The winding electrode group fixed to the battery lid via the current collector plate is housed in the battery can through the upper opening of the battery can of the battery container, and the battery lid is sealed and welded to the upper opening of the battery can. , Housed in a battery container. The battery container is sealed by injecting an electrolytic solution into the inside through a liquid injection port provided on the battery lid and then sealing and welding a liquid injection plug to the liquid injection port.

However, in order to increase the capacity, it is necessary to increase the internal volume of the electrodes provided in the can. That is, the mixture layer is formed thick, or the electrode length is extended to increase the number of turns of the wound electrode group in order to increase the electrode area. Further, in order to cope with high output, it is also effective to increase the electrode area by extending the electrode length or widening the electrode width. Furthermore, it is necessary to increase the joint area of the welded portion and thicken the current collector in order to take out a large current to the outside, and the battery can is provided with necessary parts other than the wound electrode group.

The secondary battery according to the present invention is a secondary battery provided with a positive electrode and a negative electrode having a mixture layer arranged on the electrode foil and an insulating layer provided on the mixture layer, respectively. An exposed portion is provided at one end of the electrode and the negative electrode electrode so that the electrode foil is exposed from the mixture layer, and the other ends of the positive electrode electrode and the negative electrode electrode are directed toward the end of the electrode foil, respectively. As the thickness of the mixture layer decreases, an inclined portion is provided, and the insulating layer is arranged on each of the mixture layers including the inclined portion, and the electrode winding composed of the positive electrode and the negative electrode. The separator interposed between the positive electrode and the negative electrode of the group is formed to have a thickness thinner than the thickness of the insulating layer.

Patent Document 1 describes a point of providing an insulating layer on the surface of electrodes to protect short circuits between electrodes. On the other hand, there is no description about the protection of the cut end portion that occurs during electrode processing.

The present invention has been made in view of the above points, and provides a battery in which an insulating layer can be efficiently formed even at an electrode cut end portion that is easily exposed, and the insulation reliability is further improved. Is the subject.

The secondary battery according to the present invention includes an electrode having a mixture layer arranged on the electrode foil and an insulating layer provided on the mixture layer, and the electrode current collecting foil is exposed from the active material at one end of the electrode. It is characterized in that it has an exposed portion, and the other end of the electrode has an inclined portion in which the thickness of the mixture layer decreases toward the end of the electrode foil, and an insulating layer is arranged on the inclined portion. To do.

By using the present invention, it is possible to provide a secondary battery having improved insulation reliability.

According to the present invention, an insulating layer can be efficiently formed even at an electrode cut end portion that is easily exposed, and it is possible to provide a battery with further improved insulation reliability.

The external perspective view of the square secondary battery which concerns on Embodiment 1 of the secondary battery of this invention. An exploded perspective view of the square secondary battery shown in FIG. It is an exploded perspective view of the electrode winding group of the square secondary battery shown in FIG. FIG. 3 is a cross-sectional model diagram showing an electrode facing portion constituting the electrode winding group shown in FIG. An electrode cross-sectional schematic diagram and an electrode surface external view showing the first embodiment. An electrode cross-sectional schematic diagram and an electrode surface external view showing the second embodiment.

Hereinafter, embodiments of the secondary battery of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is an external perspective view of the square secondary battery 100 of the present embodiment. The battery can 11 includes a pair of wide surfaces 11b, a pair of narrow surfaces 11c, and a bottom surface 11d. The upper surface portion has an opening for accommodating the electrode group 40. The upper surface of the battery can 11 is covered with the battery lid 12. Further, the battery lid 12 is provided with an external terminal 21, a positive electrode external terminal 22, a liquid injection plug 15 for closing the liquid injection hole 14, and a gas discharge valve 13.

Next, FIG. 2 will be described. FIG. 2 shows a flat electrode group 40 in which the battery can 11 is removed from the square secondary battery 100 shown in FIG. 1 and positive and negative electrodes are wound around, a flat square battery can 11 accommodating the electrode group 40, and the like. An exploded perspective view showing an exploded state of a secondary battery including a battery lid 12 that seals an opening 11a of the battery can 11 and an insulating member 3 that is fixed to the battery lid 12 and housed in the battery can 11. is there. The negative electrode external terminal 21 is arranged on the battery lid 12 via the insulating member 2, and is connected to the negative electrode current collector plate 31 inside the battery can 11. The negative electrode current collector plate 31 is welded and connected to the negative electrode current collector foil of the electrode group 40. The same applies to the positive electrode external terminal 22 side, and the positive electrode external terminal 22 is arranged on the battery lid 12 via the insulating member 2 and is connected to the positive electrode current collector plate 32 inside the battery can 11. The positive electrode current collector plate 32 is welded and connected to the positive electrode current collector foil of the electrode group 40. The electrode group 40 is housed in the battery can 11 in a state of being housed in the bag-shaped insulating sheet 4. With such a configuration, the current collector plate and the electrode group are not short-circuited to the battery can 11. The insulating sheet 4 is composed of a side surface portion 4c, a bottom surface portion 4b, and an opening portion 4a.

FIG. 3 is an exploded perspective view showing a wound structure in which a part of the electrode group 40 shown in FIG. 2 is developed.

The negative electrode 41 formed by forming the negative electrode mixture layer 412 on the negative electrode current collecting foil 411 and the positive electrode 42 formed by forming the positive electrode mixture layer 422 on the positive electrode current collecting foil 421 face each other via the separators 43 and 44. The electrodes are laminated around the shaft A while maintaining the arranged arrangement, forming the electrode group 40.

More specifically, the electrode group 40 is an electrode group formed into a flat shape by winding positive and negative electrodes 41 and 42 laminated with separators 43 and 44 around an axis parallel to the winding axis A. It is 40. The separators 43 and 44 are made of, for example, a porous polyethylene resin to insulate between the negative electrode 41 and the positive electrode 42, and the separators 43 and 44 are also provided on the outside of the negative electrode 41 wound around the outermost periphery. Is being rolled up.

The negative electrode electrode 41 is provided with a negative electrode mixture layer 412 on the surface of the current collector foil 411, and although not specified in FIG. 3, an insulating layer 413 is provided so as to cover the negative electrode mixture layer 412. .. Further, the positive electrode electrode 42 is provided with a positive electrode mixture layer 422 on the surface of the current collector foil 421.

Subsequently, the features of the present invention will be described with reference to FIGS. 4 and 5. FIG. 4 is a view of the negative electrode electrode 41 before cutting.

Negative electrode mixture layers 412 are formed by coating on both sides of the negative electrode current collector foil 411, and an insulating layer 413 is formed on the surface of the negative electrode mixture layer 412 to cover the negative electrode mixture layer 412. Is. FIG. 4-a is a cross-sectional view, and FIG. 4-b shows a plan view of the negative electrode as viewed from above.

FIG. 4-b shows the electrode before the cutting process, and the portion indicated by the dotted line of SS ′ on the cut end portion of the electrode is provided with a groove portion 415 whose thickness is slightly thinner than that of the flat portion of the mixture layer. There is.

After that, the insulating layer 413 is applied to the entire surface of the negative electrode mixture layer 412 to form the insulating layer 413 together with the covering portion of the insulating layer 413 of the groove portion 415 over the cut portion. The cut portion is indicated by the dotted line of SS'. With such a structure, a part of the mixture layer of the cut surface is exposed, but the inclined portion 415a formed by the cutting is covered with the insulating layer 413. Therefore, even if the cut end portion appears after electrode processing and molding, the coating of the insulating layer 413 can be left at the end portion of the negative electrode electrode 41, and the exposed portion can be suppressed.

In addition, the area of the exposed portion is smaller than that of a structure in which the cut surface is simply vertical. Therefore, the insulation reliability at the end of the negative electrode electrode 41 is improved.

Since the other end portion 414 of the mixture layer is the end portion on the side where the exposed portion of the negative electrode current collector foil 411 is formed, the insulating layer 413 is provided to the outside of the mixture layer. The exposure of the agent layer can be prevented. The end of the mixture layer on this side is not cut because it is welded and joined to the current collector plate 31 connected to the external terminal 21 shown in FIG. 2 in a later step.

Subsequently, FIG. 5 will be described. FIG. 5 is a cross-sectional model diagram showing an electrode facing portion in which the negative electrode electrode 41 after cutting at the S portion shown in FIG. 4 faces the positive electrode electrode 42.

In FIG. 4, the portion indicated by the dotted line of the cutting portion S—S ′ that is cut along the groove portion 415 is the end face indicated by the cutting portion S—S ′ in FIG. Has been done. That is, the thickness of the insulating layer 413 of the groove portion 415 can be made thicker than the thickness of the insulating layer 413 on the flat portion of the mixture layer, and the insulating property is improved. With such a structure, the inclined portion 415a formed by cutting is covered with the insulating layer 413. Therefore, conventionally, the end portion of the mixture layer is exposed by the thickness T1 of the flat portion, but the thickness of the exposed portion at the end portion of the mixture layer can be reduced to T2. Therefore, the mixture layer is exposed only for T2 as compared with the conventional one, so that the insulation reliability can be further improved.

A negative electrode mixture layer 412 is provided on the surface of the negative electrode current collector foil 411, and an insulating layer 413 is provided on the surface of the negative electrode mixture layer 412 so as to be covered. As shown in FIG. 4, the negative electrode electrode 41 is formed by cutting at the S portion of FIG.

In the present embodiment, since the negative electrode mixture layer 412 is provided so that the thickness of the mixture layer decreases toward the cut end face and is inclined, the insulating layer 413 spreads from the flat portion and covers the vicinity of the cut end face. The exposure of the mixture layer is suppressed.

The winding electrode group 40 is configured so that the negative electrode electrode 41 faces the positive electrode 42 via the separators 43 and 44. A positive electrode mixture layer 422 is provided on the surface of the positive electrode current collector foil 421, and the wound electrode group 40 is configured so as to face the negative electrode electrode 41. The mixture layer portion is arranged so as to face each other with the separators 43 and 44 interposed therebetween, and since the current collector foil portion serves as an electrode joint portion, it is derived and arranged so as to come out of the separators 43 and 44. The derived current collector foil portion is joined to the current collector plate shown in FIG. 2 and connected to the external terminal 21.

The negative electrode mixture layer 412 shown in FIGS. 4 and 5 can be manufactured, for example, as follows. First, to 100 parts by weight of graphite carbon powder as a negative electrode active material, an aqueous solution of carboxymethyl cellulose (CMC) was added as a thickening adjuster, and after mixing, 1 part by weight of SBR was added as a binder, and after kneading, the viscosity was increased. Adjust to prepare a negative electrode slurry. Next, the negative electrode mixture layer 412 is formed by applying this negative electrode slurry to, for example, on both sides of a copper foil having a thickness of 10 μm, leaving exposed foil portions. The insulating layer 413 can be formed by applying the negative electrode mixture layer 412, drying, and then applying a dispersion liquid in which the insulating particles constituting the insulating layer are dispersed. After that, through each step of drying, pressing, and cutting, for example, a negative electrode 41 having a thickness (total of both front and back surfaces) of a negative electrode active material coating portion containing no copper foil of 40 μm can be obtained. It is necessary to create the groove portion 415 shown in FIG. 5 when forming the negative electrode mixture layer. The groove portion 415 may be created when the negative electrode mixture layer 412 is formed, or when the negative electrode mixture layer 412 and the insulating layer 413 are formed at the same time, the groove portion 415 extends in the same direction as the coating direction at that time. Need to be created in.

Porous inorganic particles are preferably used as the insulating particles constituting the insulating layer, ceramic particles can be more preferably used, and boehmite particles can be selected. It is preferable to use spherical particles for the shape of the particles in order to prepare a stable dispersion liquid, but when forming the insulating layer, an angular rhedron is used to provide an insulating layer having a thinner film thickness and good coating property. It is more preferable to use the polyhedral particles having.

The insulating particles are dispersed in a solvent containing one or both resin-based and rubber-based binders to prepare a dispersion liquid for an insulating layer.

The positive electrode mixture layer 422 can be manufactured, for example, as follows. First, the layered lithium nickel cobalt manganese oxide (chemical formula _{Li (Ni x Co y Mn 1} -xy) O 2) as a positive electrode active material relative to 100 parts by weight of scaly graphite and acetylene black and forming a total of 7 parts by weight as the conductive material 3 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) is added as a coating agent, N-methylpyrrolidone (hereinafter referred to as NMP) is added as a dispersion solvent, and the mixture is kneaded to prepare a positive electrode slurry. Next, the positive electrode mixture layer 422 is formed by applying this positive electrode slurry to, for example, on both sides of an aluminum foil having a thickness of 15 μm, leaving exposed foil portions. After that, through each step of drying, pressing, and cutting, for example, a positive electrode 42 having a thickness (total of both front and back surfaces) of a positive electrode active material coating portion containing no aluminum foil of 70 μm can be obtained.

In order to manufacture the wound electrode group 40 by superimposing and winding the positive electrode 42 and the negative electrode 41 via the separators 43 and 44, first, the tips of the separators 43 and 44 are welded to a shaft core (not shown). The separators 43 and 44 and the positive and negative electrodes 42 and 41 are alternately stacked and wound. At this time, the winding start side end of the positive electrode 42 is located inside the winding electrode group 40 after winding so that the winding start side end of the positive electrode 42 is located inside the winding electrode group 40 after winding. Is arranged on the axis side of the negative electrode electrode 41 on the axis side of the winding start side end and wound.

As shown in FIG. 2, the wound electrode group 40 is housed in the insulating bag 4, the battery lid 12 is joined to the battery can 11, the battery lid 12 is sealed and welded to the upper opening of the battery can 11, and the liquid injection port 14 The square battery 100 is manufactured by injecting a non-aqueous electrolytic solution into the battery can 11 and then sealing and welding the injection plug 15 to the injection port 14. The non-aqueous electrolyte solution injected from the injection port 14 infiltrates the winding electrode group 40 housed in the battery can 11. As a non-aqueous electrolyte solution, for example, lithium hexafluorophosphate (LiPF ₆ ) was dissolved at a concentration of 1 mol / liter in a mixed solution in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2. Can be used.

[Embodiment 2]
Although the insulating layer covering the negative electrode mixture layer is shown in the first embodiment, the above-mentioned insulating layer can be formed on the surface of the positive electrode mixture layer 422 in the same manner as shown in FIG. FIG. 6 shows a case where the positive electrode insulating layer 423 is provided in this way.

In the case of the electrode configuration as shown in FIG. 6, the total thickness of the insulating layer is the sum of the thicknesses of the insulating layer provided on the positive electrode mixture layer and the insulating layer provided on the negative electrode mixture layer, and the positive electrode is positive. Insulation is improved as compared with the case where it is provided only on either the mixture layer or the negative electrode mixture layer. That is, in the case of this configuration, the separators 43 and 44 can be made thinner.

Further, in the case of this configuration, the layer thickness of the insulating layer should be thicker than that of the separators 43 and 44. That is, (T3-T4)> T4. With such a configuration, an effect of reducing the resistance between the electrodes can be obtained.

Further, in the above-described embodiment, the thickness of the electrode is constant, that is, the thickness of the insulation layer on the SS'side of the negative electrode 41 is thicker than the thickness of other portions, but this is not necessarily the case. There is no need to take such a configuration. For example, the structure may be such that the insulating layer is also inclined according to the inclination of the mixture layer.

The present invention will be briefly summarized above. The secondary battery described in the present invention includes an electrode having a mixture layer arranged on an electrode foil and an insulating layer provided on the mixture layer, and one end of the electrode collects electrodes from the mixture layer. The foil has an exposed portion, and the other end of the electrode has an inclined portion 415a in which the thickness of the mixture layer decreases toward the end portion of the electrode foil, and an insulating layer is arranged on the inclined portion 415a. It is characterized by that. With such a structure, the area of the exposed portion of the mixture layer is smaller than that of a structure in which the cut surface is simply vertical. Therefore, the insulation reliability at the end of the negative electrode electrode 41 is improved.

Further, in the secondary battery described in the present invention, the thickness of the insulating layer provided on the inclined portion 415a is equal to or larger than the thickness of the insulating layer provided on the other portion. With such a structure, the thickness of the insulating layer at the electrode end can be ensured, and the insulation reliability of the electrode end can be improved.

Further, the separator interposed between the electrodes of the electrode winding group composed of the electrodes includes a separator having a film thickness thinner than the thickness of the insulating layer. With such a configuration, an effect of reducing the resistance between the electrodes can be obtained.

Further, the method for manufacturing an electrode according to the present invention has a mixture layer arranged on the electrode foil and an insulating layer provided on the mixture layer, and the mixture layer is applied on the electrode foil. Further, a groove portion is continuously formed in the direction in which the mixture layer is applied, an insulating layer is applied on the mixture layer, and the electrode is cut on the groove portion. By adopting such a manufacturing method, the electrode described in the present invention can be produced.

Although the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within a range not deviating from the gist of the present invention. Also, they are included in the present invention.

11 ... Battery can 12 ... Battery lid 14 ... Liquid injection port 15 ... Liquid injection plug 21 ... Negative electrode external terminal 22 ... Positive electrode external terminal 31 ... Negative electrode current collector plate 32 ... Positive electrode current collector plate 40 ... Winding electrode group 41 ... Negative electrode 411 ... Negative electrode current collector foil 412 ... Negative electrode mixture layer 413 ... Insulation layer 42 ... Positive electrode electrode 421 ... Positive electrode current collector foil 422 ... Positive electrode mixture layer
43, 44 ... Separator 100 ... Square battery

Claims (4)

In a secondary battery provided with a positive electrode and a negative electrode having a mixture layer arranged on the electrode foil and an insulating layer provided on the mixture layer, respectively.
An exposed portion in which the electrode foil is exposed from the mixture layer is provided at one end of the positive electrode electrode and the negative electrode electrode, and the end portions of the electrode foil are provided at the other ends of the positive electrode electrode and the negative electrode electrode, respectively. An inclined portion is provided in which the thickness of the mixture layer decreases toward the direction, and the insulating layer is arranged on each of the mixture layers including the inclined portion.
The separator interposed between the positive electrode and the negative electrode of the electrode winding group composed of the positive electrode and the negative electrode is formed to have a thickness thinner than the thickness of the insulating layer. Next battery. In the secondary battery according to claim 1,
A secondary battery characterized in that the thickness of the insulating layer provided on the inclined portion is equal to or larger than the thickness of the insulating layer provided on the other portion. In the secondary battery according to claim 1 or 2.
A secondary battery, wherein the mixture layer of the negative electrode is a negative electrode mixture layer. In the secondary battery according to claim 3,
A secondary battery characterized in that the insulating layer is formed of ceramic particles.

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