JP2005129393A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve rigidity of a secondary battery having an electrode laminated body in which a positive electrode plate and a negative electrode plate are laminated alternately through a separator. <P>SOLUTION: The secondary battery 10 comprises the electrode laminated body 101 in which the positive electrode plate 102 and the negative electrode plate 104 are laminated alternately through a separator. The positive electrode plate 102 has a positive electrode layer 102b including a positive electrode active material formed on a main surface of a positive electrode side collector 102a. The negative electrode plate 104 has a negative electrode layer 104b including a negative electrode active material formed on a main surface of a negative electrode side collector 104a. The positive electrode plate 102 and the negative electrode plate 104 have rigid parts 102c, 104c formed by bending at least one side of each periphery of the positive electrode plate 102 and the negative electrode plate 104, like nearly wavy shape. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a secondary battery including an electrode laminate in which a positive electrode plate and a negative electrode plate are alternately laminated via separators.

  An electrode laminate in which a positive electrode plate coated with a positive electrode active material on the main surface of the positive electrode side current collector and a negative electrode plate coated with a positive electrode active material on the main surface of the negative electrode side current collector are alternately stacked via separators There is known a thin secondary battery provided with (for example, see Patent Document 1).

In such a thin secondary battery, the strength of the battery itself is maintained by the rigidity of the electrode laminate, but in order to further reduce the thickness, the number of laminated electrode laminates can be reduced, When the area of the electrode stack is increased in order to increase the capacity, there is a problem that the rigidity of the electrode stack decreases and the secondary battery is distorted.
Japanese Patent Laid-Open No. 9-259859

An object of the present invention is to increase the rigidity of a secondary battery.
In order to achieve the above object, according to the present invention, a positive electrode plate in which a positive electrode layer containing a positive electrode active material is formed on the main surface of a positive electrode side current collector, and a negative electrode layer containing a negative electrode active material are arranged in a negative electrode side current collector. A negative battery formed on a main surface of the body is a secondary battery comprising at least an electrode laminate in which separators are alternately stacked, the positive electrode plate and / or the negative electrode plate being the positive electrode plate A secondary battery having a rigid portion in which at least one side of the outer peripheral edge of the negative electrode terminal is formed in a non-planar shape is provided.

  In the present invention, at least one of the positive electrode plate and the negative electrode plate constituting the electrode laminate of the secondary battery is provided with a rigid portion in which at least one side of the outer peripheral edge is formed in a non-planar shape. By laminating the positive electrode plate and the negative electrode plate provided with the rigid portion to constitute the electrode laminated body, it becomes possible to improve the rigidity of the electrode laminated body maintaining the strength of the secondary battery itself, The rigidity can be increased.

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

  1 is a plan view of an entire secondary battery according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the secondary battery taken along line II-II in FIG. 1, and FIG. 3 is taken along line III-III in FIG. 4A is a plan view of a positive electrode plate used in the secondary battery according to the embodiment of the present invention, and FIG. 4B is a IVB-IVB line in FIG. 4A. 5A is a plan view of the negative electrode plate used in the secondary battery according to the embodiment of the present invention, and FIG. 5B is a VB-VB line in FIG. 5A. FIG. 6A is an exploded perspective view of the electrode laminate of the secondary battery shown in FIG. 1, and FIG. 6B is an assembled state of FIG. 6A. FIG. 1 to 3 show one secondary battery 10 (unit battery), and a plurality of the secondary batteries 10 are stacked and connected to form an assembled battery having a desired voltage and capacity.

  A secondary battery 10 according to the present embodiment is a lithium-based thin secondary battery, and as shown in FIGS. 1 to 3, three positive plates 102, seven separators 103, and three sheets The electrode laminate 101 having the negative electrode plate 104, the positive electrode terminal 105 and the negative electrode terminal 106 respectively connected to the electrode laminate 101, and the electrode power generator 101 and the electrode terminals 105 and 106 are accommodated and sealed. It is comprised from the upper exterior member 107 and the lower exterior member 108, and the electrolyte which is not specifically shown.

  As shown in FIGS. 2 to 4A and 4B, the positive electrode plate 102 constituting the electrode laminate 101 includes a positive electrode current collector 102a extending to the positive electrode terminal 105, and the positive electrode current collector. The positive electrode layer 102b is formed on a part of the main surface of the positive electrode 102a, and the rigid portion 102c is formed on two long side portions facing each other on the outer peripheral edge of the positive electrode plate 102.

  The positive electrode side current collector 102 a of the positive electrode plate 102 is an electrochemically stable metal foil such as an aluminum foil, an aluminum alloy foil, a copper foil, or a nickel foil having a thickness of about 20 μm.

  When the positive electrode side current collector 102a is configured as shown in FIGS. 2 and 3, the electrode stack 101 has one short side portion located on the upper side in FIG. Two long side portions located on both the left and right sides have an outer shape that protrudes from the electrode laminate 101.

  The positive electrode layer 102b is formed on both main surfaces of the positive electrode current collector 102a, but the positive electrode layer 102b is formed over the entire main surfaces of the positive electrode current collector 102a. Instead, when the electrode laminate 101 is configured as shown in FIGS. 2 and 3, it is formed only on the substantially rectangular portion (the shaded portion in FIG. 4A) where the separator 103 substantially overlaps in the positive electrode plate 102. Has been. Therefore, as shown in FIG. 4 (A), at the outer peripheral edge of the positive electrode side current collector 102a, one short side portion located on the upper side in FIG. The positive electrode layer 102b is not formed on the long side portion. One short side portion on the upper side of the outer peripheral edge of the positive current collector 102a is connected to the positive terminal 105, and rigid portions 102c are formed on the two long side portions on the left and right sides of the outer peripheral edge. Yes.

The positive electrode layer 102b of the positive electrode plate 102 is formed by mixing a positive electrode active material such as a metal oxide, a conductive agent such as carbon black, and an adhesive such as an aqueous dispersion of polytetrafluoroethylene on the positive electrode side. It is formed by applying to a part of the main surface of the current collector 102a, drying and rolling. Examples of the positive electrode active material include lithium composite oxides such as lithium nickelate (LiNiO ₂ ), lithium manganate (LiMnO ₂ ), and lithium cobaltate (LiCoO ₂ ), and chalcogen (S, Se, Te) compounds. Etc. can be mentioned. These materials are relatively easy to dissipate the heat generated in the secondary battery, and can suppress the stress accompanying expansion due to the heat generated in the secondary battery. It is particularly effective.

  As shown in FIGS. 4 (A) and 4 (B), the rigid portion 102c of the positive electrode plate 102 has two lengths located on the left and right sides in FIG. 4 (A) at the outer peripheral edge of the positive current collector 102a. The side portion is formed by being bent into a substantially wavy shape in cross section by, for example, pressing.

  As shown in FIGS. 2, 3, 5 (A) and (B), the negative electrode plate 104 constituting the electrode laminate 101 includes a negative electrode current collector 104 a extending to the negative electrode terminal 106, and the negative electrode side It has a negative electrode layer 104b formed on both main surfaces of a part of the current collector 104a, and a rigid portion 104c formed on one short side of the outer peripheral edge of the negative electrode plate 104.

  The negative electrode side current collector 104a of the negative electrode plate 104 is an electrochemically stable metal foil such as a nickel foil, a copper foil, a stainless steel foil, or an iron foil having a thickness of about 10 μm.

  When the negative electrode side current collector 104 a is configured as shown in FIGS. 2 and 3, the short side portion positioned on the lower side in FIG. It has an outer shape that protrudes from.

  The negative electrode layer 104b is formed on both main surfaces of the negative electrode current collector 104a, but the negative electrode layer 104b is formed over the entire main surfaces of the negative electrode current collector 104a. Instead, when the electrode laminate 101 is configured as shown in FIGS. 2 and 3, it is formed only on the substantially rectangular portion (the shaded portion in FIG. 5A) where the separator 103 substantially overlaps in the negative electrode plate 104. Has been. Accordingly, as shown in FIG. 5 (A), the negative electrode layer 104b is not formed on one short side portion positioned on the lower side in the outer peripheral edge of the negative electrode side current collector 104a, The portion of the negative electrode plate 104 where the negative electrode layer 104b is formed and the portion of the positive electrode plate 102 where the positive electrode layer 102b is formed have substantially the same shape. Note that a rigid portion 104 c is formed on one lower side portion of the outer peripheral edge of the negative electrode side current collector 104 a and is further connected to the negative electrode terminal 106.

  The negative electrode layer 104b of the negative electrode plate 104 includes, for example, a negative electrode active material that occludes and releases lithium ions of the positive electrode active material, such as amorphous carbon, non-graphitizable carbon, graphitizable carbon, or graphite. In addition, an aqueous dispersion of styrene butadiene rubber resin powder as a precursor material of an organic fired body is mixed, dried and then pulverized, so that the carbon particles are supported by carbonized styrene butadiene rubber. In addition, a binder such as an acrylic resin emulsion is further mixed therewith, the mixture is applied to both main surfaces of a part of the negative electrode side current collector 104a, and dried and rolled.

  If amorphous carbon or non-graphitizable carbon is used as the negative electrode active material, the flatness of the potential during charge / discharge is poor, and the output voltage decreases with the amount of discharge. Is not suitable, but it is advantageous when used as a power source for an electric vehicle because there is no sudden drop in output.

  As shown in FIGS. 5A and 5B, the rigid portion 104c of the negative electrode plate 104 is a short one located on the lower side in FIG. 5A on the outer peripheral edge of the negative electrode current collector 104a. The side portion is formed by being bent into a substantially wavy shape in cross section by, for example, pressing.

  As described above, the outer peripheral edges of the positive electrode side current collector 102a and the negative electrode side current collector 104a are bent into a substantially wave shape to form the rigid portions 102c and 104c, and the positive electrode plate 102 and the negative electrode on which the rigid portions 102c and 104c are formed. By configuring the electrode laminate 101 using the plate 104, the rigidity of the electrode laminate 101 that maintains the strength of the secondary battery 10 itself can be improved, and the rigidity of the secondary battery 10 can be increased. Become.

  Further, by forming neither the positive electrode layer 102b nor the negative electrode layer 104b in the rigid portion 102c of the positive electrode plate 102 and the rigid portion 104c of the negative electrode plate 104, the rigid portions 102c and 104c are substantially wave-shaped by pressing or the like. And the rigid portions 102c and 104c are easily formed.

  Further, when the electrode laminate 101 is configured in the positive plates 102 and 104, the total thickness of the secondary battery 10 is maintained by forming the rigid portions 102c and 104c in portions protruding from the electrode laminate 101. The rigidity of the secondary battery 10 can be increased as it is.

  In the present embodiment, the rigid portion has been described as having a substantially wavy cross section. However, in the present invention, any rigid portion that is formed in a non-planar shape that imparts rigidity to the outer peripheral edge of the current collector may be used. For example, the outer peripheral edge of the current collector may be formed in a curved shape to constitute the rigid portion. Further, in the present embodiment, the rigid portion is formed on the two long side portions of the outer peripheral edge of the positive electrode plate, and the rigid portion is formed on one short side portion of the outer peripheral edge of the negative electrode plate. The invention is not particularly limited to this. For example, a rigid portion is formed on one short side portion of the outer peripheral edge of the positive electrode plate, and a rigid portion is formed on two long side portions of the outer peripheral edge of the negative electrode plate. Also good.

  The separator 103 of the electrode laminate 101 prevents the short-circuit between the positive electrode plate 102 and the negative electrode plate 104 described above, and may have a function of holding an electrolyte. The separator 103 is a microporous film made of, for example, a polyolefin such as polyethylene (PE) or polypropylene (PP) having a thickness of about 25 μm. Has a function of blocking the current.

  The separator of the present invention is not limited to a single-layer film such as polyolefin, but a three-layer structure in which a polypropylene film is sandwiched with a polyethylene film, or a laminate of a polyolefin microporous film and an organic nonwoven fabric can also be used. By forming the separator in multiple layers, various functions such as an overcurrent prevention function, an electrolyte holding function, and a separator shape maintenance (rigidity improvement) function can be provided.

  As shown in FIG. 2, the electrode laminate 101 has the positive plates 102 and the negative plates 104 alternately laminated via the separators 103, and the separators 103 are laminated on the uppermost layer and the lowermost layer, respectively. ing. At the time of this lamination, as shown in FIGS. 6A and 6B, the positive electrode plate 102 and the negative electrode plate 104 include a rigid portion 102c included in each positive electrode plate 102 and a rigid portion 104c included in each negative electrode plate 104. Are stacked so as to be shifted from each other by 90 °.

  The three positive plates 102 are respectively connected to the positive terminal 105 made of metal foil through the short side portion located on the upper side in FIG. 4A on the outer peripheral edge of the positive current collector 102a. On the other hand, the three negative electrode plates 104 are respectively connected to the negative electrode terminal 106 also made of metal foil through a short side portion positioned on the lower side in FIG. 5A on the outer periphery of the negative electrode side current collector 104a. It is connected. 6A and 6B, only one positive plate 102, one separator 103, and one negative plate 104 are shown in order to clarify the laminated structure of the electrode laminate 101. Not shown.

  Thus, when laminating the electrode laminate 101, the positive electrode plate 102 and the negative electrode plate 104 are arranged so that the rigid portion 102c of each positive electrode plate 102 and the rigid portion 104c of each negative electrode plate 104 are shifted from each other by 90 °. By laminating, it is possible to prevent the rigid portion 102c of the positive electrode plate 102 and the rigid portion 104c of the negative electrode plate 104 from coming into contact with each other and causing a short circuit, and any of the longitudinal direction and the width direction of the secondary battery 10 can be prevented. It is possible to impart strength also in the direction.

  The positive electrode plate 102, the separator 103, and the negative electrode plate 104 of the electrode laminate 101 are not limited to the above number in the present invention. For example, one positive electrode plate 102, three separators 103, and The electrode laminate 101 can also be configured with a single negative electrode plate 104, and the number of positive electrode plates, separators, and negative electrode plates can be selected as necessary.

  The positive electrode terminal 105 and the negative electrode terminal 106 are not particularly limited as long as they are electrochemically stable metal foils. Examples of the positive electrode terminal 105 include an aluminum foil having a thickness of about 0.2 mm, an aluminum alloy foil, a copper foil, or And nickel foil. Examples of the negative electrode terminal 106 include a nickel foil, a copper foil, a stainless steel foil, or an iron foil having a thickness of about 0.2 mm. These metals are suitable as a constituent element of a secondary battery in terms of the resistance value, linear expansion coefficient, and resistivity of the metal, and particularly can suppress the stress accompanying expansion due to heat generation in the secondary battery. This is particularly effective for a thin secondary battery as in this embodiment.

  In this embodiment, the electrode plates 102 and 104 are directly connected to the electrode terminals 105 and 106 by extending the metal foil itself constituting the current collectors 102a and 104a of the electrode bodies 102 and 104 to the electrode terminals 105 and 106. Although connected, the current collectors 102a and 104a of the electrode plates 102 and 104 and the electrode terminals 105 and 106 are connected by a material or a part different from the metal foil constituting the current collectors 102a and 104a. Also good.

  The electrode laminate 101 configured as described above is housed and sealed in the upper exterior member 107 and the lower exterior member 108. As shown in FIG. 2, the upper exterior member 107 in the present embodiment has a cup shape in which the outer shape is provided with a convex portion that accommodates the electrode laminate 101, whereas the lower exterior member 108 has the same As shown in the figure, the outer shape is a flat plate shape. Both the upper exterior member 107 and the lower exterior member 108 are not particularly illustrated, but are directed to the outside of the secondary battery 10, for example, an anti-electrolytic solution such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer. An inner layer composed of a resin film excellent in heat resistance and heat fusion, an intermediate layer composed of a metal foil such as an aluminum foil, and an electrical insulation such as a polyamide resin and a polyester resin It has a three-layer structure including an outer layer made of a resin film having excellent properties. Therefore, in both the upper exterior member 107 and the lower exterior member 108, one surface of the metal foil (the inner surface of the secondary battery 10) is laminated with a material excellent in electrolytic solution resistance and heat fusion property, The surface (the outer surface of the secondary battery 10) is made of a resin-metal thin film laminate material having a thickness of about 125 μm, for example, laminated with a material having excellent electrical insulation.

  As described above, when the exterior member includes the metal layer in addition to the resin layer, it is possible to improve the strength of the exterior member itself. Further, the inner layer of the exterior member is made of, for example, a synthetic resin material such as polyethylene, modified polyethylene, polypropylene, modified polypropylene, or ionomer, thereby ensuring good fusion property with a metal electrode terminal. It becomes possible.

  As shown in FIGS. 1 and 2, the positive terminal 105 is led out from one end of the sealed exterior members 107 and 108, and the negative terminal 106 is led out from the other end. Since a gap is generated between the upper exterior member 107 and the lower exterior member 108 by the thickness of 105, 106, the electrode terminals 105, 106 and the exterior member are maintained in order to maintain the sealing performance inside the secondary battery 10. For example, a seal film made of polyethylene, polypropylene, or the like may be interposed between the portions 107 and 108 in contact with each other. It is preferable from the viewpoint of heat-sealing property that this seal film is made of a synthetic resin material of the same system as the inner layers of the exterior members 107 and 108 on either side of the positive electrode terminal 105 and the negative electrode terminal 106.

These exterior members 107 and 108 wrap the electrode laminate 101 described above and a part of the electrode terminals 105 and 106, and while injecting a liquid electrolyte into the space formed by the exterior members 107 and 108, After vacuuming the inside of the space, as shown in FIG. 1, the exterior members 107 and 108 are heat-sealed and sealed. Examples of the solute of the liquid electrolyte include lithium salts such as lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), and lithium borofluoride (LiBF ₄ ). Examples of the organic liquid solvent for the liquid electrolyte include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC). However, the organic liquid solvent of the present invention is not particularly limited to this, and is an organic solvent prepared by mixing an ester solvent with an ether solvent such as γ-butylactone (γ-BL) or dietoshikitan (DEE) and the like. A liquid solvent can also be used.

  As described above, in the secondary battery according to the present embodiment, the outer peripheral edges of the positive electrode plate and the negative electrode plate are bent into a non-planar shape to form a rigid portion, and the positive electrode plate and the negative electrode plate on which the rigid portion is formed are used. By configuring the electrode stack, the rigidity of the electrode stack that maintains the strength of the secondary battery itself can be improved, and the rigidity of the secondary battery can be increased.

  In the secondary battery according to the present embodiment, the positive electrode layer and the negative electrode layer are not formed on any of the rigid portion of the positive electrode plate and the rigid portion of the negative electrode plate, thereby forming the non-planar rigid portion. It becomes easy to bend, and it becomes easy to form a rigid part.

  Further, in the secondary battery according to the present embodiment, when the electrode laminate is configured in the positive electrode plate and the negative electrode plate, a rigid portion is formed in a portion protruding from the electrode laminate, so that the total capacity of the secondary battery is increased. The rigidity of the secondary battery can be increased while maintaining the thickness.

  In the secondary battery according to the present embodiment, the positive electrode plate and the negative electrode plate are laminated so that the rigid portion of the positive electrode plate and the rigid portion of the negative electrode plate face in different directions when the electrode laminate is laminated. Accordingly, it is possible to prevent the positive electrode plate and the negative electrode plate each having a rigid portion from coming into contact with each other and short-circuiting, and to impart strength in various directions of the secondary battery.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

FIG. 1 is a plan view of an entire secondary battery according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the secondary battery taken along line II-II in FIG. FIG. 3 is a cross-sectional view of the secondary battery taken along line III-III in FIG. 4A is a plan view of a positive electrode plate used in the secondary battery according to the embodiment of the present invention, and FIG. 4B is a positive electrode plate taken along line IVB-IVB in FIG. 4A. FIG. 5A is a plan view of a negative electrode plate used in the secondary battery according to the embodiment of the present invention, and FIG. 5B is a negative electrode plate taken along the line VB-VB in FIG. 5A. FIG. 6A is an exploded perspective view of the electrode stack of the secondary battery shown in FIG. 1, and FIG. 6B is a perspective view showing a state in which FIG. 6A is assembled.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Secondary battery 101 ... Electrode laminated body 102 ... Positive electrode plate 102a ... Positive electrode side collector 102b ... Positive electrode layer 102c ... Rigid part 103 ... Separator 104 ... Negative electrode plate 104a ... Negative electrode side collector 104b ... Negative electrode layer 104c ... Rigidity Part 105 ... Positive electrode terminal 106 ... Negative electrode terminal 107 ... Upper exterior member 108 ... Lower exterior member

Claims (6)

A positive electrode plate in which a positive electrode layer containing a positive electrode active material is formed on the main surface of the positive electrode side current collector, and a negative electrode plate in which a negative electrode layer containing a negative electrode active material is formed on the main surface of the negative electrode side current collector A secondary battery comprising at least an electrode laminate laminated alternately via
The positive electrode plate and / or the negative electrode plate is a secondary battery having a rigid portion in which at least one side of the outer peripheral edge of the positive electrode plate and / or the negative electrode terminal is formed in a non-planar shape.   The secondary battery according to claim 1, wherein the rigid portion is formed by being bent into a substantially wave shape.   The secondary battery according to claim 1, wherein the positive electrode layer and the negative electrode layer are not formed in the rigid portion.   The secondary battery according to claim 1, wherein the rigid portion protrudes from the electrode laminate when the positive electrode plate and the negative electrode plate are alternately laminated via the separator. The portion where the positive electrode layer is formed in the positive electrode plate and the portion where the negative electrode layer is formed in the negative electrode plate have substantially the same outer shape,
5. The electrode laminate according to claim 1, wherein the rigid portion of the positive electrode plate and the rigid portion of the negative electrode plate are laminated so as to face in different directions. Next battery. The portion where the positive electrode layer is formed on the positive electrode plate and the portion where the negative electrode layer is formed on the negative electrode plate have substantially the same substantially rectangular shape,
The secondary electrode according to any one of claims 1 to 5, wherein the electrode laminate is laminated such that the rigid portion of the positive electrode plate and the rigid portion of the negative electrode plate are shifted from each other by 90 °. battery.

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