JP2015011924A - Battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery pack capable of minimizing heat generation at the inside of a battery at the penetration of a conductive foreign substance therethrough and expansion due to internal pressure rise, while reducing the number of members.SOLUTION: A battery pack includes: a bipolar battery obtained by stacking a plurality of electric cells, in each of which a positive electrode layer, a negative electrode layer, and a separator sandwiched between the positive electrode layer and the negative electrode layer are stacked; and a case accommodating the bipolar battery. The separator comprises a separator layer (1) that is a porous layer having conductivity and a separator layer (2) having ion conductivity, the case has conductivity, an end part of the separator layer (1) having conductivity is electrically connected to the case, and insulation between electrodes is provided by an insulation member for covering a conductor imparting the conductivity.

Description

  The present invention relates to an assembled battery, and more particularly, to an assembled battery capable of suppressing expansion due to heat generation inside the battery and an increase in internal pressure when the number of members is reduced and a conductive foreign object is penetrated.

In recent years, lithium batteries have been put into practical use as batteries having high voltage and high energy density. Due to the expansion of the use of lithium batteries in a wide range of fields and the demand for high performance, various studies have been conducted to further improve the performance of lithium batteries.
Among them, the reduction of the resin thickness in the electrode thickness direction is the most effective for improving the energy density of lithium batteries, and a plurality of single cells (those in which a positive electrode layer, a separator and a negative electrode layer are sequentially laminated) are laminated. Bipolar batteries have been proposed.
On the other hand, in a battery in which such single cells are stacked, a short-circuit current due to a short circuit occurs when a conductive foreign object comes into contact with the battery, so that a bipolar current occurs when a conductive foreign substance penetrates the battery. Measures to increase battery reliability are necessary.

  For this reason, for example, in Patent Document 1, a plurality of bipolar electrodes in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface are stacked in series with an electrolyte layer held by a separator in between. In such a bipolar battery, there is described a bipolar battery in which a sealing resin is molded and arranged on the outer periphery of the electrolyte layer in order to prevent the electrolyte from seeping out.

  Patent Document 2 includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a non-aqueous electrolyte. On the surface of at least one of the electrodes on the separator side, A non-aqueous electrolyte secondary battery in which an ion conductive porous layer containing a conductive material is described, and when a foreign object such as a nail penetrates the battery, a short circuit current is not only a foreign object but also a porous layer Therefore, it is shown that the heat generation inside the battery can be suppressed when the foreign object penetrates.

  Furthermore, Patent Document 3 includes a battery laminate in which a plurality of secondary batteries using a laminate film having a laminate film having a synthetic resin and a metal layer as an exterior material are stacked, and a case. In addition, an assembled battery is described in which the upper surface and the lower surface of both side surfaces in the stacking direction of the case are made of a conductive member, and the upper surface and the lower surface are electrically connected.

  However, when these known techniques are applied as they are to obtain a bipolar battery, if foreign matter such as a nail penetrates the battery, there is a risk of expansion due to heat generation and internal pressure increase inside the battery. In a bipolar (electrode) that is not encapsulated, the number of parts increases if an insulator for covering the conductor is provided for each unit cell. For this reason, according to the prior art, it is difficult to obtain a battery pack that can suppress expansion due to heat generation inside the battery and increase in internal pressure while reducing the number of members and penetrating conductive foreign matter.

International Publication No. 2006/062204 JP 2006-179432 A JP 2006-344520 A

  Accordingly, an object of the present invention is to provide an assembled battery that can suppress expansion due to heat generation inside the battery and increase in internal pressure when the conductive foreign matter is penetrated while reducing the number of members.

  The present invention includes a bipolar battery formed by laminating a plurality of unit cells each including a positive electrode layer, a negative electrode layer, and a separator sandwiched between the positive electrode layer and the negative electrode layer, and a case for housing the bipolar battery. An assembled battery, wherein the separator includes a separator layer (1) that is a porous layer having conductivity and a separator layer (2) that has ion conductivity, and the case has conductivity. The assembled battery is formed of an insulating member for covering the conductive layer with an end portion of the conductive separator layer (1) electrically connected to the case. About.

  ADVANTAGE OF THE INVENTION According to this invention, the assembled battery which can suppress the expansion | swelling by the heat_generation | fever inside a battery at the time of a conductive foreign material penetration and internal pressure rise, reducing the number of members can be obtained.

FIG. 1 is a schematic diagram of a cross section of an assembled battery according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a flow of a short-circuit current when a conductive foreign object (such as a nail) passes through the assembled battery according to the embodiment of the present invention.

  An assembled battery according to an embodiment of the present invention includes a bipolar battery formed by laminating a plurality of unit cells each including a positive electrode layer, a negative electrode layer, and a separator sandwiched between the positive electrode layer and the negative electrode layer, and the bipolar battery An assembled battery, and the separator is composed of a separator layer (1) which is a porous layer having conductivity and ion conductivity and a separator layer (2) having ion conductivity. The case has conductivity, the end of the separator layer (1) having conductivity and ion conductivity is electrically connected to the case, and the insulation between the electrodes is the conductivity. Because of the insulating member for covering the layer having a conductive layer, when a conductive foreign matter such as a nail penetrates the battery with a simple configuration, a short-circuit current is applied to the external case via the conductive separator layer (1). flow Therefore, it is considered possible to suppress the expansion due to heat generation and increase in internal pressure inside the battery when conductive foreign substance penetration.

As shown in FIG. 1, an assembled battery 1 according to an embodiment of the present invention includes a single battery 5 in which a positive electrode layer 2, a negative electrode layer 3, and a separator 4 sandwiched between the positive electrode layer 2 and the negative electrode layer 3 are stacked. A separator battery (1) is a battery pack comprising a bipolar battery 10 formed by laminating a plurality of layers and a case 11 for housing the bipolar battery 10, wherein the separator 4 is a porous layer having conductivity and ion conductivity. ) 41 and an ion conductive separator layer (2) 42, the case 11 has conductivity, and the end of the separator layer (1) 41 having conductivity and ion conductivity. The part is electrically connected to the case 11, and the insulation between the electrodes is due to the insulating member 12 for covering the conductive layer.
In the assembled battery 1, the insulator 13 can be disposed in the case 11.

In the present invention, a single cell can be composed of a negative electrode layer, a positive electrode layer, and a separator.
Preferred examples of the unit cell include a lithium secondary battery, a sodium secondary battery, a potassium secondary battery, a magnesium secondary battery, and a calcium secondary battery.
The positive electrode layer may have a positive electrode current collector and a positive electrode active material layer provided on at least one surface thereof.
The positive electrode current collector is made of, for example, a metal material such as aluminum, nickel, or stainless steel.

As the positive electrode active material, at least one transition metal selected from manganese, cobalt, nickel and titanium and a metal oxide containing lithium, such as lithium cobaltate (Li _x CoO ₂ ), lithium nickelate (Li _x NiO _2). ), Lithium nickel manganese cobaltate (Li _{1 + x} Ni _1/3 Mn _1/3 Co _1/3 O ₂ ), lithium nickel cobaltate (LiCo _0.3 Ni _0.7 O ₂ ), lithium manganate (Li _x Mn ₂ O _4), lithium titanate _{(Li 4/3 Ti 5/3 O 4)} , lithium manganese oxide compound _{(Li 1 + x M y Mn} 2-x-y O 4; M = Al, Mg, Fe, Cr, Co , Ni, Zn), lithium titanate _(Li x _TiO y), phosphate metal lithium _(LiMPO 4, M = Fe, n, Co, Ni), vanadium oxide _{(V 2 O} 5), molybdenum oxide _(MoO 3), titanium sulfide _(TiS 2), lithium cobalt nitride (LiCoN), lithium silicon nitride (LiCoN), lithium metal, lithium Alloys (LiM, M = Sn, Si, Al, Ge, Sb, P), lithium-storable intermetallic compounds (MgxM, M = Sn, Ge, Sb, or XySb, X = In, Cu, Mn) and their Derivatives.

  In addition, the positive electrode active material layer usually has a binder, for example, a polymer material such as polyaniline, polythiophene styrene butadiene rubber (SBR), polyacrylate, polyvinylidene fluoride (PVdF), or a conductive agent such as graphite or carbon black. In addition, a carbon material in which acetylene black or ketjen black, carbon nanotube, carbon nanofiber, fullerene and the like are used alone or in combination of two or more thereof may be included.

The negative electrode layer may include a negative electrode current collector and a negative electrode active material layer including a negative electrode active material provided on at least one surface thereof.
Examples of the negative electrode current collector include copper or an alloy containing copper as a main component. When used as a vehicle-mounted high-output power source, a copper foil having a thickness of about 5 to 100 μm is suitably used as the current collector for the negative electrode layer.

The negative electrode active material layer may include a negative electrode active material capable of occluding and releasing ions serving as charge carriers, such as lithium ions.
Examples of the negative electrode active material include one or more of materials conventionally used in lithium ion secondary batteries. An example is carbon particles. Particulate carbon materials (carbon particles) including a graphite structure (layered structure) at least partially may be mentioned. Any carbon material of a so-called graphitic material (graphite), a non-graphitizable carbonaceous material (hard carbon), a graphitizable carbonaceous material (soft carbon), or a combination of these materials can be suitably exemplified. . Of these, graphite particles are particularly preferred. Graphite particles (eg, graphite) are excellent in conductivity because they can suitably occlude lithium ions as charge carriers. Further, since the particle size is small and the surface area per unit volume is large, it can be a negative electrode active material suitable for high-rate pulse charge / discharge.

Moreover, the said negative electrode active material layer typically may contain arbitrary components, such as a binder and a solvent, as needed in addition to the said negative electrode active material as the structural component. The binder may be the same as the binder used in the negative electrode of a general lithium ion secondary battery, and various polymer materials that can function as a binder in the positive electrode component are preferably exemplified. .
Examples of the conductive agent include carbon materials, metals that are difficult to alloy with lithium, conductive polymer materials, and the like, and carbon materials are preferred. As the carbon material, graphite, carbon black, carbon nanotube, carbon nanofiber, fullerene and the like can be used alone or in combination of two or more.

In an embodiment of the present invention, the separator needs to be composed of a separator (1) layer which is a porous layer having conductivity and ion conductivity and a separator layer (2) having ion conductivity. is there.
Examples of the base material of the separator layer (2) include a porous film made of polyolefin such as polypropylene (PP) and polyethylene (PE), and a ceramic porous film soaked with an electrolyte. It is done. In particular, a multilayer structure film made of polyolefin, for example, a porous film made of polyolefin having a three-layer structure of PE / PP / PE is preferably used.

Examples of the separator (1) layer, which is a porous layer having conductivity and ionic conductivity, include those obtained by immersing an ion conductive material (electrolytic solution, solid electrolyte) in a conductive porous body. Examples of the conductive porous body include foamed metals such as Ni and Al, and resins containing conductive carbon.
As the conductive carbon particles, for example, carbon black is preferable because of its low electrical resistance and low cost. Examples of the carbon black include acetylene black such as Denka Black and Ketjen Black manufactured by Denki Kagaku Kogyo Co., Ltd., such as Ketjen Black and furnace black, such as Vulcan XC72 manufactured by CABOT. Can be mentioned.

The thermosetting resin may have any function as a binder for binding carbon black. For example, phenol resin, epoxy resin, melanin resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane resin Is mentioned.
In the embodiment of the present invention, the separator (1) layer, which is a conductive porous layer, is provided with a conductive ink containing conductive carbon particles and a thermosetting resin as main components on the porous substrate, if necessary. It is possible to obtain the film by applying heat treatment, removing the dispersion medium or solvent, and curing the thermosetting resin.

As the separator layer having ion conductivity, for example, an ion conductive polymer or oligomer polymerized after impregnating a base material of the separator with an ionic liquid having a group imparting ion conductivity and a polymerizable group. The separator to contain is mentioned.
Examples of the group imparting ion conductivity include an amino acid as an anion, an anion portion derived from an amino acid, imidazolium, quaternary ammonium, and quaternary phosphonium.
Moreover, a double bond containing group is mentioned as said polymeric group.

  The separator layer may further contain an electrolytic solution, a gel-like or solid electrolyte, preferably an electrolytic solution as the electrolyte. The electrolytic solution contains a solvent and an electrolyte salt, and preferred examples of the solvent include ethylene carbonate (EC), propylene carbonate, dimethyl carbonate (DMC), diethyl carbonate, and ethyl methyl carbonate (EMC). Among them, a mixed solvent obtained by mixing a high-viscosity solvent such as ethylene carbonate or propylene carbonate and at least one or two or more low-viscosity solvents such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, or ethyl methyl carbonate is preferable. .

Examples of the electrolyte include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), Bis (pentafluoroethanesulfonyl) imidolithium (LiN (C ₂ F ₅ SO ₂ ) ₂ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ ), lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ), lithium chloride (LiCl) or lithium bromide (LiBr), preferably lithium hexafluorophosphate (LiPF ₆ ) Can be mentioned.

The gel electrolyte can be formed, for example, by preparing a positive electrode layer and a negative electrode layer, applying an electrolytic solution containing a solvent and an electrolyte salt thereto, and then volatilizing the solvent.
As examples of the solid electrolyte, for example, is not limited as long as the powder material that may be used as a solid electrolyte material of a lithium secondary battery, for example, _{Li 2 O-B 2 O 3} -P 2 O 5, Li 2 O- _{SiO 2, Li 2 O-B} 2 O 3, Li 2 O-B 2 O 3 solid oxide-based amorphous electrolyte powder such as _{-ZnO, Li 2 S-SiS 2} , LiI-Li 2 S-SiS 2, _{liI-li 2 S-P 2} S 5, LiI-Li 2 S-B 2 S 3, Li 3 PO 4 -Li 2 S-Si 2 S, Li 3 PO 4 -Li 2 S-SiS 2, LiPO 4 - Solid sulfide amorphous such as Li ₂ S—SiS, LiI—Li ₂ S—P ₂ O ₅ , LiI—Li ₃ PO ₄ —P ₂ S ₅ , Li ₃ PS ₄ , Li ₂ S—P ₂ S ₅ Electrolyte electrolyte powder.

Further, as the solid _{electrolyte, LiI, LiI-Al 2 O} 3, Li 3 N, Li 3 N-LiI-LiOH, Li 1.3 Al 0.3 Ti 0.7 (PO 4) 3, Li 1 + x + y A x Ti _2-x Si _y P _3-y O ₁₂ (A = Al or Ga, 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6), [(B _1/2 Li _1/2 ) _{1-z C z] TiO 3 (B =} La, Pr, Nd, Sm, C = Sr or _{Ba, 0 ≦ x ≦ 0.5)} , Li 5 La 3 Ta 2 O 12, Li 7 La 3 Zr 2 O 12, Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li ₃ PO _{(4-3 / 2w)} N _w (w <1), Li _3.6 Si _0.6 P _0.4 O ₄ and other crystalline oxide powders and oxynitrides Preferably, a solid sulfide electrolyte powder is used.

A bipolar battery according to an embodiment of the present invention includes a separator layer (1) that is a porous layer sandwiched between the positive electrode layer, the negative electrode layer, and the positive electrode layer and the negative electrode layer and having conductivity and ion conductivity. And a plurality of unit cells, for example, 4 to 10 layers, each having a separator composed of a separator layer (2) having ion conductivity.
In the assembled battery according to the embodiment of the present invention, a bipolar battery is accommodated in a case accommodating the bipolar battery, and an end portion of the conductive separator layer (1) is electrically connected to the case. Insulation between the electrodes is due to an insulating member for covering the conductor giving the conductivity.

  The electrical connection between the end of the separator layer (1) having conductivity and the ionic conductivity and the case is performed by mechanically joining or thermally melting the end of the separator layer (1) having conductivity to the case. It can be carried out by adhesion or fusion using a conductive adhesive.

The case may be a synthetic resin case containing conductive powder, for example, metal powder or carbon powder.
An insulating member may be disposed in the case. The insulating member may be made of a polyolefin that is a porous layer.

  ADVANTAGE OF THE INVENTION According to this invention, the assembled battery which can suppress the expansion | swelling by the heat_generation | fever inside a battery and internal pressure rise at the time of electroconductive foreign material penetration can be obtained, reducing the number of members.

DESCRIPTION OF SYMBOLS 1 assembled battery 2 positive electrode layer 3 negative electrode layer 4 separator 5 single cell 10 bipolar battery 11 case 12 insulating member 41 Separator layer (1) which is a porous layer which has electroconductivity and ion conductivity
42 Separator layer having ion conductivity (2)

Claims (1)

  An assembled battery comprising a bipolar battery formed by laminating a plurality of unit cells each including a positive electrode layer, a negative electrode layer, and a separator sandwiched between the positive electrode layer and the negative electrode layer, and a case for housing the bipolar battery. The separator is composed of a separator layer (1) which is a porous layer having conductivity and a separator layer (2) having ion conductivity, and the case has conductivity, The assembled battery is formed of an insulating member for covering an electric conductor in which an end portion of the separator layer (1) having electrical properties is electrically connected to the case and insulation between the electrodes gives the conductivity.

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