JP2005347018A - Manufacturing method of bipolar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar battery wherein liquid junction between unit cells is prevented even when a plurality of unit cells using a polymer electrolyte are laminated to form the battery. <P>SOLUTION: A positive electrode 3 is provided on one side of one collector 2, and a negative electrode 4 is provided on the other side. Pregel is applied to and impregnated into the positive electrode 3 and the negative electrode 4, respectively, and on the other hand, the pregel is also applied to and impregnated into a separator 5a. After that, the pregel of the positive electrode 3, the negative electrode 4, and the separator 5a is gelled, and a gelled gel-electrolyte impregnated separator (electrolyte layer 5) is held between the electrode 3 and the negative electrode 4 to laminate them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bipolar battery, a method for manufacturing a bipolar battery, an assembled battery, and an automobile using the assembled battery.

  Some lithium secondary batteries use a polymer gel electrolyte as the electrolyte encapsulated therein.

  The polymer gel electrolyte is, for example, polyvinylidene fluoride (PVDF) itself having an electrolyte solution held in a polymer skeleton that does not have lithium ion conductivity (see, for example, Patent Document 1).

  In recent years, a bipolar electrode having two electrodes on one current collector in which a positive electrode is provided on one surface of one current collector and a negative electrode on the other surface is used. There is a bipolar battery in which an electrolyte is sandwiched between a positive electrode and a negative electrode.

  In such a bipolar battery, when the electrolyte contained in the electrolyte of each layer oozes out, it electrically connects each layer and does not function as a battery. This is called a liquid junction. For this reason, it is difficult to manufacture a bipolar battery using an electrolyte containing an electrolytic solution.

  From such a point of view, there is a conventional technique in which the electrolyte is gelled in the electrolyte, thereby eliminating the fluidity of the electrolyte in each layer and facilitating the manufacture of a bipolar battery (see, for example, Patent Document 2). . Such a gelled electrolyte is called a gel electrolyte. For example, a solid electrolyte such as PEO (polyethylene oxide) containing an electrolyte solution usually used in a lithium ion battery, or lithium ion conductivity such as PVDF. A polymer gel electrolyte is one in which an electrolyte solution is held in a polymer skeleton that does not have a polymer. On the other hand, the ratio of the polymer constituting the polymer gel electrolyte to the electrolyte solution is wide. When 100% of the polymer is an all solid polymer electrolyte and 100% of the electrolyte solution is a liquid electrolyte, the intermediates are all polymer gel electrolytes.

  If a bipolar battery using such a gel electrolyte is to be manufactured, the electrolyte must be kept in a non-fluid state from the stage of laminating each layer during manufacturing.

  The gel electrolyte is usually prepared by preparing a highly fluid pregel solution in which the electrolyte and polymer are mixed, and then creating a gel electrolyte having no fluidity by crosslinking the polymer, or the electrolyte and polymer are highly volatile. After preparing a pregel dispersion solution dissolved in a solvent and uniformly dispersed, the solvent was volatilized to obtain a gel electrolyte having no fluidity.

For this reason, in the conventional bipolar battery manufacturing method, when a gel electrolyte is used to prevent liquid junction, first, a fluid pregel is made into a non-fluid gel electrolyte and then sandwiched between bipolar electrodes. The bipolar batteries were manufactured by a method of alternately bonding them together.
JP-A-11-204136 Japanese Patent Laid-Open No. 2000-1000047

  However, since the bipolar battery manufactured by the conventional manufacturing method has the gel electrolyte layer manufactured separately from the electrode, the electrolyte does not sufficiently penetrate inside the electrode, the resistance increases, and the rate characteristic decreases during large current discharge. There was a problem to do.

  Moreover, when using a gel electrolyte layer with a very high ratio of the electrolyte, when trying to stack a plurality of unit cell layers, the electrolyte exudes from the gel electrolyte, and the unit cells become liquid junctions, There was also a problem that the bipolar battery could not be completed.

  Accordingly, an object of the present invention is to provide a method for manufacturing a bipolar battery in which even when a gel electrolyte layer is used, the electrolyte enters the electrode well, and the resistance at the interface between the electrode and the electrolyte layer can be lowered. is there.

  Another object of the present invention is to provide a bipolar battery manufacturing method in which a plurality of single battery layers can be easily stacked without causing liquid junction during manufacturing when a gel electrolyte layer is used. It is to be.

  The object of the present invention is to form a positive electrode on the first surface of one current collector, to form a negative electrode on a second surface of the current collector that faces the surface on which the positive electrode is formed, A step of impregnating the positive electrode and the negative electrode with pregel, a step of gelling the pregel impregnated with the positive electrode and the negative electrode, a step of impregnating the base material for holding the electrolyte with the pregel, and the base material Forming a gel electrolyte layer by gelling the impregnated pregel, and sandwiching the gel electrolyte between the positive electrode of the first current collector and the negative electrode of the second current collector It is achieved by the manufacturing method of the bipolar battery characterized by having.

  According to the bipolar battery manufacturing method of the present invention, the electrode and the electrolyte holding substrate are impregnated with the electrolyte in the pregel state, and then gelled. Therefore, in the electrode and the electrolyte holding substrate Since the electrolyte component sufficiently permeates into the electrode, the electrical resistance between the electrode and the electrolyte layer can be lowered. Moreover, since gelation occurs after impregnation with the pregel, there is no leakage of the electrolyte from the electrode and the electrolyte layer, and a liquid junction is generated when a plurality of unit cell layers are laminated. Can be prevented.

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

  FIG. 1 is an explanatory diagram for explaining a manufacturing method of a bipolar battery in an embodiment to which the present invention is applied.

  In the bipolar battery manufacturing method according to the present embodiment, first, as shown in FIG. 1A, the positive electrode 3 is provided on one surface of the current collector 2, and the negative electrode 4 is provided on the other surface. A pre-gel solution with high fluidity that will later become a gel electrolyte is applied and impregnated.

  Thereafter, the applied pregel is gelled, and as shown in FIG. 1B, the positive electrode 3 and the negative electrode 4 are provided on one current collector 2, and the gel electrolyte-impregnated bipolar electrode 1 is manufactured.

  On the other hand, as shown in FIG. 1 (c), the base material for holding the electrolytic solution such as the separator 5a is impregnated with the pregel solution in the same manner, and then the pregel is gelled. As shown, a gel electrolyte layer 5 (gel electrolyte impregnated separator) is formed.

  Then, as shown in FIG. 1 (e), an electrolyte layer 5 in which a separator 5a is impregnated with a gel electrolyte is sandwiched between a bipolar electrode 1 having a positive electrode 3 and a negative electrode 4 impregnated with the gelled electrolyte. Thus, the bipolar battery 10 is completed by stacking a plurality of layers as shown in FIG.

  FIG. 2 is a diagram showing an internal configuration of the completed bipolar battery 10.

  In the finally completed bipolar battery, as shown in FIG. 2, a positive electrode 3 and a negative electrode 4 are formed on both surfaces of one current collector 2 except at both ends, and the positive electrode 3 of the current collector 2 is formed. A unit cell 6 is configured by sandwiching an electrolyte layer 5 between the anode 4 and the anode 4. A plurality of the unit cells 6 are stacked. Further, a sealing material 9 for preventing liquid leakage is provided around each unit cell 6. This sealing material does not have a sealing function when a plurality of bipolar electrodes 1 and electrolyte layers 5 are laminated, and is only disposed between the laminated current collectors 2. Each unit cell 6 is sealed by thermocompression bonding the portions where the sealing materials 9 of 2 and 7 are located from above and below. A current collector (referred to as an end current collector 7) at both ends has only the positive electrode 3 or the negative electrode 4 on one surface, and is connected to the electrodes of the entire bipolar battery.

  FIG. 3 is a schematic diagram for explaining the state of impregnation of the electrolyte using such a pregel.

  As shown in FIG. 3A, the electrode layer 300 (positive electrode or negative electrode) provided on the current collector 2 contains an active material 301, and a pregel solution 304 having high fluidity is applied thereto. As a result, the pregel enters into the active material 301. Then, by gelling this, as shown in FIG. 3B, the active material 301 is sufficiently covered with the gel electrolyte 305 obtained by gelling the pregel. Therefore, when the electrolyte layer 5 is placed on the electrode layer 300, the interface 306 between the electrode layer 300 and the electrolyte layer 5 is practically indistinguishable as shown in FIG. The electrical resistance at this interface can be reduced.

  Here, when impregnating the pregel solution into the positive electrode, the negative electrode, and the separator, a die coater coating method, a spray coating method, an ink jet printing method, or the like can be used. These methods are preferable because the application amount of the pregel solution can be strictly controlled. And the current density distribution of a battery becomes uniform by apply | coating a pregel solution uniformly.

  When using the die coater coating method, it is possible to easily and evenly apply a pregel solution having a high viscosity by applying the pregel solution to the electrodes and the separator with the die coater. When the spray coating method is used, since the pregel solution is sprayed using a spray coater, the droplets of the pregel solution can be made small. For this reason, it becomes possible to saturate the pregel even deeper in the electrode and the separator. In the case of using the ink jet printing method, by using an ink jet printer, the pregel droplets can be made small as in the case of using the spray coater, and the pregel can be infiltrated to the deep part of the electrode or the separator.

  The amount of the pregel solution to be impregnated is preferably 100% by volume or more based on the total amount of voids of the positive electrode, the negative electrode, and the separator. This is because when the amount of pregel to be impregnated is smaller than the total amount of voids, the electrolyte itself impregnated with the pregel is preferred, and voids remain as they are, which may hinder ion migration. In addition, about the upper limit of the amount of pregel solution to impregnate, it is necessary to make below the limit with which a pregel solution is hold | maintained with respect to an electrode or a separator by the surface tension. This is not preferable when a large amount of pregel is applied beyond the holding force of the electrode or separator, because part of the pregelling may be liquefied and leaked from the electrode or separator due to subsequent gelation.

  Moreover, the volume in the case of the gel battery produced by the process which volatilizes a solvent and gelatinizes is made into the volume of the gel electrolyte after a solvent volatilizes.

  In addition, the amount of the pregel solution impregnated in the positive electrode and the negative electrode is preferably at least 90% by volume or more with respect to the respective void amounts in both the positive electrode and the negative electrode. This is because, by setting it to 90% by volume or more, as can be seen from the examples described later, it is possible to increase the output of the battery and to improve the rate characteristics. In addition, about the upper limit of the amount of pregel solution to impregnate, it is necessary to make below the limit with which a pregel solution is hold | maintained with respect to an electrode or a separator by the surface tension. This is not preferable because when a large amount of pregel is applied beyond the holding power of the electrode or separator, some of the pregelling may be liquefied and leaked from the electrode or separator due to subsequent gelation. is there.

After application of the pregel, the electrode and separator are introduced under reduced pressure at a temperature of about 45 ° C. and a pressure of about 1 × 10 ² to 1 × 10 ³ Pa for about 10 to 30 minutes, and the pregel is completely placed inside the electrode and separator. Let it soak. Here, the decompression condition varies depending on the physical properties of the solvent used for the electrolyte, the viscosity of the pregel, and the porosity of the electrode. Therefore, it is necessary to check the optimum conditions against the performance.

  In addition, when introducing an electrode under reduced pressure, a positive electrode and a negative electrode may be formed on one current collector, and after applying a pregel solution to each current collector, the current collector may be introduced under reduced pressure.

  In the gelation method of the electrolyte, an initiator is added to the pregel, and the gel can be gelled by the chemically crosslinked polymer. Chemically cross-linked polymers have good liquid retention and facilitate the lamination of bipolar electrodes and gel electrolyte layers without liquid junction after gelation.

  As another gelation method, the pregel is applied to the electrode in a state of being dispersed in a solvent, and then the pregel soaked into the electrode is heated, so that the solvent component is skipped and the gel is physically crosslinked. May be. In the case of this physical crosslinking, since the gel is uniformly formed in the electrode, the output of the battery can be increased and the rate characteristics can be further improved.

  In this way, at the stage of laminating electrodes and electrolytes, the pregels impregnated in each are processed into a gel state and then laminated, so that there is no oozing out of the electrolyte during production, and the single gel during production is not. A liquid junction between battery layers can be prevented. In addition, by defining the amount of electrolyte applied to the porosity of the electrode and electrolyte, it becomes easier to manufacture a bipolar battery without a liquid junction.

  Here, the polymer gel electrolyte is one in which an electrolytic solution is held in a polymer matrix, and the ratio of the electrolytic solution in the gel electrolyte is about several% to 98% by mass. In particular, it is effective for gel electrolytes having a large amount of electrolytic solution with an electrolytic solution ratio of 70% by mass or more. This means that when the electrolytic solution is 70% by weight or less, the electrolyte holding power is necessary and sufficient for both the chemically crosslinked gel electrolyte and the physically crosslinked gel electrolyte. However, since there is a possibility that the electrolyte solution leaks when the content is 70% by weight or more, the present invention is particularly effective for the gel electrolyte having a large amount of the electrolyte solution having a ratio of 70% by mass or more.

  Hereinafter, the current collector, the positive electrode, the negative electrode, the electrolyte, and other components used here will be described.

  Basically, members (materials) constituting these batteries are those used in lithium ion secondary batteries.

  These will be described below with specific examples.

[Current collector]
The current collector needs to be formed by laminating and stacking whatever shape it has, such as aluminum, copper, titanium, nickel, stainless steel (for example, by a thin film manufacturing technique such as spray coating). SUS), a metal powder such as an alloy thereof as a main component, and a current collector metal paste containing a binder (resin) and a solvent is heated and molded. In addition, these metal powders may be used alone or in combination of two or more, and moreover, different types of metal powders are laminated in multiple layers taking advantage of the characteristics of the manufacturing method. It may be a thing.

  The binder is not particularly limited. For example, a conventionally known resin binder material such as an epoxy resin can be used, and a conductive polymer material may be used.

  Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.

[Positive electrode (positive electrode active material layer)]
The positive electrode includes a positive electrode active material. In addition, a conductive auxiliary agent, a binder, and the like can be included. After impregnating this electrode with the pregel as described above, it is sufficiently infiltrated into the positive electrode and the negative electrode as a gel electrolyte by chemical crosslinking or physical crosslinking.

As the positive electrode active material, a composite oxide of transition metal and lithium, which is also used in a solution-type lithium ion battery, can be used. Specifically, Li · Co-based composite oxide such as LiCoO _2, Li · Ni-based composite oxide such as LiNiO _2, Li · Mn-based composite oxide such as spinel LiMn ₂ O _4, Li · such LiFeO ₂ Examples thereof include Fe-based composite oxides. In addition, transition metal and lithium phosphate compounds and sulfate compounds such as LiFePO ₄ ; transition metal oxides and sulfides such as V ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , and MoO ₃ ; PbO ₂ , AgO, NiOOH etc. are mentioned.

  The positive electrode active material may have any particle size as long as the positive electrode material can be formed into a paste by spray coating and the like, but in order to reduce the electrode resistance of the bipolar battery, the electrolyte is not a solid solution type. What is smaller than the generally used particle size used in the lithium ion battery of the present invention may be used. Specifically, the average particle diameter of the positive electrode active material is preferably 10 to 0.1 μm.

  The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity containing an electrolyte solution usually used in a lithium ion battery. Further, in the polymer skeleton having no lithium ion conductivity, In addition, those holding the same electrolytic solution are also included.

Here, the electrolyte solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte may be any one that is normally used in lithium ion batteries. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , inorganic acid anion salts such as LiAlCl ₄ and Li ₂ B ₁₀ Cl ₁₀ , organic acid anions such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ) ₂ N Including at least one lithium salt (electrolyte salt) selected from ionic salts, cyclic carbonates such as propylene carbonate and ethylene carbonate; chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxa , Ethers such as 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; esters such as methyl propionate; amides such as dimethylformamide; Those using an organic solvent (plasticizer) such as an aprotic solvent in which at least one selected from methyl and methyl formate are mixed can be used. However, it is not necessarily limited to these.

  Examples of the polymer having ion conductivity include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof.

  For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used in the polymer gel electrolyte. it can. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be a polymer having the above ionic conductivity, but here, they are used for a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.

As the lithium salt, for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 and the like inorganic acid anion _{salts, Li (CF 3 SO 2)} 2 N, An organic acid anion salt such as Li (C ₂ F ₅ SO ₂ ) ₂ N or a mixture thereof can be used. However, it is not necessarily limited to these.

  Examples of the conductive assistant include acetylene black, carbon black, and graphite. However, it is not necessarily limited to these.

  In this embodiment, these electrolyte solution, lithium salt, and polymer (polymer) are mixed to prepare a pregel solution, and the positive electrode and the negative electrode are impregnated.

  The blending amount of the positive electrode active material, the conductive additive, and the binder in the positive electrode should be determined in consideration of the intended use of the battery (output importance, energy importance, etc.) and ion conductivity. For example, if the amount of the electrolyte in the positive electrode, particularly the solid polymer electrolyte, is too small, the ionic conduction resistance and the ionic diffusion resistance in the active material layer will increase, and the battery performance will deteriorate. On the other hand, when the amount of the electrolyte in the positive electrode, particularly the solid polymer electrolyte, is too large, the energy density of the battery decreases. Therefore, in consideration of these factors, the solid polymer electrolytic mass meeting the purpose is determined.

  The thickness of the positive electrode is not particularly limited, and should be determined in consideration of the intended use of the battery (emphasis on output, emphasis on energy, etc.) and ion conductivity, as described for the blending amount. A typical positive electrode active material layer has a thickness of about 10 to 500 μm.

[Negative electrode (negative electrode active material layer)]
The negative electrode 4 includes a negative electrode active material. In addition, a conductive auxiliary agent, a binder, and the like can be included. Since the contents other than the type of the negative electrode active material are basically the same as the contents described in the section “Positive electrode”, the description is omitted here.

  As the negative electrode active material, a negative electrode active material that is also used in a solution-type lithium ion battery can be used. For example, metal oxide, lithium-metal composite oxide metal, carbon and the like are preferable. More preferred are carbon, transition metal oxide, and lithium-transition metal composite oxide. More preferred are titanium oxide, lithium-titanium composite oxide, and carbon. These may be used alone or in combination of two or more.

[Electrolytes]
The electrolyte is a polymer gel electrolyte. As described above, in this embodiment, a separator as a base material is impregnated with a pregel solution and then used as a polymer gel electrolyte layer by chemical crosslinking or physical crosslinking.

  As such a polymer gel electrolyte, a solid polymer electrolyte having ion conductivity includes an electrolytic solution usually used in a lithium ion battery. Those in which the same electrolyte solution is held in the molecular skeleton are also included. Since these are the same as the polymer gel electrolyte described as one type of electrolyte contained in the positive electrode, description thereof is omitted here.

  These polymer gel electrolytes can be included in the positive electrode and / or the negative electrode as described above in addition to the polymer electrolyte constituting the battery. However, different polymer electrolytes are used depending on the polymer electrolyte, positive electrode, and negative electrode constituting the battery. The same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layer.

  The thickness of the electrolyte constituting the battery is not particularly limited. However, in order to obtain a compact bipolar battery, it is preferable to make it as thin as possible as long as the function as an electrolyte can be secured. The thickness of a general solid polymer electrolyte layer is about 10 to 100 μm. However, the shape of the electrolyte can be easily formed so as to cover the upper surface of the electrode (positive electrode or negative electrode) as well as the outer periphery of the side surface, taking advantage of the characteristics of the manufacturing method. It is not always necessary to have a substantially constant thickness.

[Battery exterior material (battery case)]
Furthermore, in this battery, in order to prevent the external impact and environmental degradation during use in order to prevent the components and the external impact and environmental degradation of the bipolar battery shown in FIG. The entire battery stack including the template is accommodated in a battery exterior material or battery case (not shown).

  As a battery case for this purpose, from the viewpoint of weight reduction, a polymer-metal composite laminate film or aluminum laminate in which metals (including alloys) such as aluminum, stainless steel, nickel and copper are coated with an insulator such as a polypropylene film. It is preferable to use a conventionally known battery exterior material such as a pack, and a part or the whole of its peripheral part is joined by heat fusion so that the battery stack is housed and sealed.

  In this case, the positive electrode and the negative electrode lead may be structured to be sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, the use of polymer-metal composite laminate films and aluminum laminate packs with excellent thermal conductivity allows heat to be efficiently transferred from the heat source of the automobile and the inside of the battery to be quickly heated to the battery operating temperature. preferable.

[Positive electrode and negative electrode terminal plate]
A positive electrode and a negative electrode terminal plate (not shown) are attached to the outermost end collector 7. The positive electrode and negative electrode terminal plates (not shown) have functions as terminals and should be as thin as possible from the viewpoint of thinning, but the electrodes, electrolytes, and current collectors laminated by film formation are all mechanical. Since the strength is weak, it is desirable to have a strength sufficient to sandwich and support them from both sides. Furthermore, it can be said that the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm from the viewpoint of suppressing internal resistance at the terminal portion.

  As the material of the positive electrode and the negative electrode terminal plate, materials usually used in lithium ion batteries can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like.

  The material of the positive electrode terminal plate and the negative electrode terminal plate may be the same material or different materials. Furthermore, the positive electrode and the negative electrode terminal plate may be a laminate of different materials.

  The shape of the positive electrode and the negative electrode terminal plate is a shape obtained by tracing the outer surface of a heat source of an automobile when used also as a template, and the terminal plate is installed in a terminal plate provided at a position opposite to the template. Any shape that traces the outer surface of the current collector may be used, and it may be formed by tracing by press molding or the like. Note that the terminal plate provided at a position opposite to the template may be formed by spray coating in the same manner as the current collector.

[Positive electrode and negative electrode lead]
As for the positive electrode and the negative electrode lead, known leads usually used in lithium ion batteries can be used. In addition, since the part taken out from the battery exterior material (battery case) does not have a distance from the heat source of the automobile, it does not affect the automobile parts (particularly electronic equipment) by contacting with them and causing electric leakage. In addition, it is preferable to coat with a heat-resistant insulating heat-shrinkable tube or the like.

  FIG. 4 is an external view when the bipolar battery 10 manufactured by the above-described manufacturing method is configured as the battery 20 by an aluminum laminate pack. In the battery 20, the positive electrode terminal plate and the negative electrode terminal plate are provided on the end current collector of the bipolar battery 15, and leads are attached to form electrodes 23 and 24.

(Reference Example 1)
Reference Example 1 is an assembled battery in which a plurality of bipolar batteries manufactured according to the above-described embodiment are connected.

  FIG. 5 is a perspective view of the assembled battery according to Reference Example 1, and FIG. 6 is a view of the internal configuration as viewed from above.

  As shown in the figure, this assembled battery 50 is a battery in which a plurality of batteries 20 (refer to FIG. 4) in which the bipolar battery 1 manufactured according to the above-described embodiment is packaged with a laminate pack are connected in parallel. is there. Between the batteries 20, the electrodes 23 and 24 of each battery are connected by a conductive bar 53. The assembled battery 50 is provided with electrode terminals 51 and 52 on one side of the assembled battery 50 as electrodes of the assembled battery 50.

  In this assembled battery, ultrasonic welding, heat welding, laser welding, rivet, caulking, electron beam, etc. can be used as a connection method when the battery 20 is directly connected and connected in parallel. By adopting such a connection method, a long-term reliable assembled battery can be manufactured.

  According to the assembled battery according to the first reference example, each bipolar battery 20 itself has no liquid junction at the manufacturing stage, and the internal resistance of the battery 20 is low. Therefore, the assembled battery is connected in series or in parallel. As a result, it is possible to obtain high capacity and high output, and each battery is highly reliable because the liquid junction in the internal cell is prevented, improving long-term reliability as an assembled battery. Can be made.

  In addition, connection of the battery 20 as an assembled battery may connect all the batteries 20 in parallel, and may connect all the batteries 20 in series.

(Reference Example 2)
Reference Example 2 is an assembled battery module in which a plurality of assembled batteries according to Reference Example 1 described above are connected.

  FIG. 7 is a perspective view of an assembled battery module according to Reference Example 2.

  This assembled battery module 60 is a module in which a plurality of assembled batteries 50 according to the fifth embodiment described above are stacked and the electrode terminals 51 and 52 of each assembled battery 50 are connected by conductive bars 61 and 62. .

  As described above, by modularizing the assembled battery 50, battery control is facilitated, and for example, an assembled battery module optimal for in-vehicle use such as an electric vehicle or a hybrid vehicle is obtained. Since the assembled battery module 60 uses the above-described assembled battery, it has high long-term reliability.

  Such an assembled battery module is also a kind of assembled battery.

(Reference Example 3)
Reference Example 3 is an automobile on which the assembled battery module according to Reference Example 2 described above is mounted and used as a motor power source. An automobile using the assembled battery module as a power source for a motor is an automobile whose wheels are driven by a motor, such as an electric vehicle and a hybrid vehicle.

  For reference, FIG. 8 shows a schematic diagram of an automobile 100 on which the assembled battery module 60 is mounted. The assembled battery module 60 mounted on the automobile has the characteristics described above. For this reason, the automobile on which the assembled battery module 60 is mounted has high durability, and can provide a sufficient output even after being used for a long period of time.

  Bipolar batteries were manufactured based on the above-described embodiment, and charge / discharge cycle characteristics were tested for liquid junction evaluation between single cells.

[Sample preparation]
The actually manufactured bipolar battery is as follows.

<Basic configuration>
The current collector 2 is made of stainless steel (SUS) foil (thickness 20 μm), and the end current collector 7 is formed with either the following positive electrode 3 or negative electrode 4 to produce a terminal positive electrode and a negative electrode. A positive electrode 3 and a negative electrode 4 were formed on the current collector 2 to produce a bipolar electrode.

Here, the positive electrode 3 is composed of LiMn ₂ O ₄ (85% by mass), acetylene black (5% by mass) as a conductive additive, polyvinylidene fluoride (PVDF) (10% by mass) as a binder, and N— as a viscosity adjusting solvent. Methyl-2-pyrrolidone (NMP) (appropriate amount) is added, and these are mixed to prepare a positive electrode slurry. This is used as a positive electrode active material and applied to one side of a stainless steel foil (thickness 20 μm) that is a current collecting holiday. The positive electrode 3 was obtained by drying.

  In the negative electrode 4, hard carbon (90% by mass), PVDF (10% by mass) as a binder, NMP (appropriate amount) as a viscosity adjusting solvent are mixed, and these are mixed to prepare a negative electrode slurry. Was applied to the opposite surface of the coated stainless steel foil and dried to obtain a negative electrode 4.

  Thus, a bipolar electrode having a thickness of 20 μm was produced.

  The completed electrode was cut into 130 mm × 80 mm, and the electrode portion was scraped off in order to form a seal layer at the outer periphery of 10 mm.

  Therefore, a bipolar electrode having an electrode area of 120 mm × 70 mm was completed.

  From the porosity of the positive electrode and the volume of the electrode, there is a 0.2268 ml void in the positive electrode. In addition, the negative electrode has 0.2268 ml of void from the porosity of the negative electrode and the volume of the electrode.

  Next, a nonwoven fabric having a thickness of 22 μm, a porosity of 33%, and 125 mm × 75 mm was used as a separator. Therefore, from the porosity and volume of the separator, there is 0.20625 ml of void in the separator. Therefore, the amount of voids in each layer is 0.65985 ml.

In addition, each current collector is provided with a tab for voltage monitoring that extends to the outside with a width of 5 mm so as not to be in contact with each layer on one side of 120 mm. Further, the end current collector 7 provided with the terminal positive electrode and the negative electrode is provided with a high-power tab made of Al and having a width of 20 mm and a thickness of 200 μm by ultrasonic welding.
<Formation of pregel solution>
The pregel solution is a monomer solution (copolymer of polyethylene oxide and polypropylene oxide) having an average molecular weight of 7500 to 9000 which is a precursor of an ion conductive polymer matrix, 10% by mass of PC + EC (1: 1) as an electrolyte, A solution composed of 1.0 M Li (C ₂ F ₅ SO ₂ ) ₂ N and a polymerization initiator (perhexyl PV) was used.

(Example 1)
0.2268 ml of pregel solution is uniformly applied to each of the positive electrodes of the bipolar electrode and the electrode provided with only the positive electrode (or the negative electrode) on the end current collector (hereinafter collectively referred to simply as electrodes) by a spray coater. did. Similarly, 0.2268 ml of pregel solution was uniformly applied to each negative electrode by a spray coater. 0.20625 ml of pregel was applied to the separator.

These were introduced at a pressure of 1 × 10 ² Pa for 30 minutes under reduced pressure, completely impregnated with pregel, sealed in a laminate material, and heated at 80 ° C. for 1 hour, whereby gel electrolytes were respectively applied to the electrode and the separator. Formed.

  Each electrode was laminated so that the positive electrode and the negative electrode faced each other with the gel electrolyte interposed therebetween to form a unit cell layer. In addition, the sealing material by a 3 layer film was inserted | pinched and arrange | positioned between the electrical power collectors at the peripheral part of the cell layer.

  This was repeated, and the electrodes were laminated so that three cell layers were formed, thereby forming an electrode laminate. Thereafter, the sealing material portion was thermally fused while applying pressure from above the end current collector, and each layer was sealed to seal the electrolyte of each layer.

  Finally, these were vacuum sealed in an aluminum laminate exterior to complete a three-layer 12.8V bipolar battery.

(Comparative example)
0.2268 ml of the pregel solution was uniformly applied to each positive electrode of the electrode by a spray coater, and 0.2268 ml of the pregel solution was also uniformly applied to each negative electrode by a spray coater. 0.20625 ml of pregel was applied to the separator.

  Each electrode was laminated so that the positive electrode and the negative electrode faced each other with the gel electrolyte interposed therebetween to form a unit cell layer.

  A sealing material composed of a three-layer film was disposed between the current collector foil and the current collector foil at the periphery of the single cell layer.

  This was repeated, and the electrodes were laminated so that three cell layers were formed, thereby forming an electrode laminate.

  However, the pregel solution having a low viscosity leaks out in the process of stacking these layers, and the electrolyte solution (pregel) inevitably comes into contact between the end battery layers, so that the bipolar battery itself cannot be produced. .

(Example 2)
A die coater was used for the pregel application. Otherwise, the bipolar battery was fabricated in the same manner as in Example 1.

(Example 3)
An ink jet was used for the pregel application. Otherwise, the bipolar battery was fabricated in the same manner as in Example 1.

Example 4
A 0.2268 ml pregel solution was dropped on each positive electrode of each electrode with a dropper, and a 0.2268 ml pregel solution was dropped on each negative electrode with a dropper. 0.20625 ml of pregel was dropped on the separator with a dropper. A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

(Example 5)
0.21 ml of pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.2268 ml of pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.23 ml of pregel. That is, the amount of the pregel solution applied to the positive electrode is less than the amount of voids in the positive electrode, the amount of the pregel solution is the same as the amount of voids in the negative electrode, and the separator has more pregel solution than the amount of voids. As a whole, the amount of the pregel solution is increased with respect to the void amount.

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

(Example 6)
0.2268 ml of pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.21 ml of pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.23 ml of pregel. That is, the positive electrode is applied so that the amount of the applied pregel solution is the same as the void amount, the negative electrode is such that the amount of the pregel solution is smaller than the void amount, and the separator is such that the pregel solution is larger than the void amount. As a whole, the amount of the pregel solution is increased with respect to the void amount.

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

(Example 7)
0.21 ml of pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.2268 ml of pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.20625 ml of pregel. That is, the amount of the applied pregel solution is less than the amount of voids in the positive electrode, the amount of the pregel solution is the same as the amount of voids in the negative electrode, and the pregel solution is smaller in the separator than the amount of voids. As a whole, the amount of the pregel solution is reduced with respect to the void amount.

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

(Example 8)
0.2268 ml of pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.21 ml of pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.20625 ml of pregel. That is, the amount of the pregel solution applied to the positive electrode is the same as the amount of voids, the amount of the pregel solution is less than the amount of voids, and the separator has less pregel solution than the amount of voids. As a whole, the amount of the pregel solution is reduced with respect to the void amount.

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

Example 9
A 0.2268 ml pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.2268 ml of a pregel solution was also uniformly applied to each negative electrode by a spray coater. Further, 0.19 ml of pregel was applied to the separator. That is, the amount of the pregel solution applied to the positive electrode and the negative electrode is set to be the same as the amount of voids, and the separator has less pregel solution than the amount of voids. Is to reduce the number of

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

(Example 10)
0.205 ml of pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.205 ml of pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.27 ml of pregel. That is, the positive electrode and the negative electrode are applied so that the amount of the pregel solution applied is less than the amount of voids and is about 90% by mass, and the separator is larger in amount of the pregel solution than the amount of voids. Thus, the amount of the pregel solution is slightly increased.

  Other than this, a bipolar battery was produced as in Example 1.

(Example 11)
A 0.19 ml pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.205 ml of a pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.27 ml of pregel. That is, the amount of the pregel solution applied to the positive electrode is less than the void amount and about 83% by mass, and the amount of the applied pregel solution is less than the void amount to about 90% by mass, As a whole, the amount of the pregel solution is slightly increased with respect to the void amount so that the separator has more pregel solution than the void amount.

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

(Example 12)
0.205 ml of pregel solution was uniformly applied to each positive electrode of each electrode by a spray coater, and 0.19 ml of pregel solution was also uniformly applied to each negative electrode by a spray coater. The separator was coated with 0.27 ml of pregel. That is, the amount of the pregel solution applied to the positive electrode is less than the void amount and about 90% by mass, and the amount of the applied pregel solution is less than the void amount to about 83% by mass, As a whole, the amount of the pregel solution is slightly increased with respect to the void amount so that the separator has more pregel solution than the void amount.

  A bipolar battery was fabricated in the same manner as in Example 1 except for these components.

<Evaluation of charge / discharge>
The bipolar battery of the above example was fully charged by constant current and constant voltage (CCCV) charging up to 12.8 V for 10 hours at a current of 2.5 mA (equivalent to 0.1 C). Further, the charged battery was discharged to 7.5 V at 25 mA (equivalent to 1 C) and the capacity was measured. Then, the battery was fully charged by constant current and constant voltage (CCCV) charging at 25 mA for 2 hours.

  Thereafter, the battery was further discharged at a current of 1.25 A (equivalent to 50 C), and the discharge amount with respect to 1 C discharge is shown in Table 1 in%.

  In addition, about the comparative example, since the liquid junction generate | occur | produced in the manufacture stage as already demonstrated, such charging / discharging evaluation was not able to be performed.

<Result>
First, in the case of the comparative example, even if an attempt was made to serialize with a bipolar electrode using a pregel solution with high fluidity, the liquid was connected before sealing each layer, and the policy of bipolar electrons itself could not be made. That is, in the comparative example in which the pressure reduction and the heat treatment were not performed after the pregel application, it was difficult to perform serialization using the bipolar electrode. On the other hand, in Examples 1 to 12, it was possible to easily perform serialization using bipolar electrodes.

  Moreover, when the results of charge / discharge evaluation (see Table 1) and Examples 1 to 3 and 4 are compared, almost the same capacity is obtained, and it can be seen that the contact between the active material and the electrolyte is maintained.

  However, when a large current was passed, the discharge capacity of Example 4 decreased. This is considered to be due to the difference in the method of applying the pregel to the electrode and the separator. In Example 4, it was considered that the discharge amount was reduced because the pregel could not be uniformly dispersed.

  Therefore, it turns out that the coating method of Examples 1-3 which can apply a uniform and exact quantity of a pregel, ie, a spray coater, a die coater, and an inkjet is good.

  In addition, compared with Examples 5 and 6, in Examples 7 to 9, both the discharge capacity of 1C and the discharge rate of 50C are decreased. This is because in Examples 5 and 6, the electrolytes completely covered the voids in the respective layers, whereas in Examples 7 to 9, there was not enough electrolyte, so the electrolyte was not spread over all active materials. Conceivable. Therefore, it can be seen that it is preferable to apply the pregel to 100% or more of the voids at least.

  In Examples 11 and 12, a discharge capacity of 1 C is obtained as compared with Example 10, but the capacity decreases when a large current is passed. In Examples 11 and 12, the electrolyte inside the electrode covers all the active material, but since the amount of pregel with respect to one electrode is reduced, either the positive electrode or the negative electrode has more voids. It is thought that the amount of movement has decreased. Therefore, it was found from the results of Example 10 that it is possible to produce a bipolar battery having a larger current when applying a pregel solution of 90% or more of the void amount of each electrode.

  As described above, according to the embodiments and examples to which the present invention is applied, since the electrode is impregnated with the pregel and then gelled, the bipolar electrode in which the electrolyte is sufficiently infiltrated is formed. Can be manufactured. In addition, since the separator to be the electrode and the gel electrolyte layer is individually impregnated with pregel and then gelled, the electrolyte solution leaks out from the bipolar electrode and the gel electrolyte layer during battery manufacture. There is no.

It is sectional drawing for demonstrating the manufacturing method of the bipolar battery by embodiment to which this invention is applied. It is sectional drawing for demonstrating the structure of the bipolar battery by embodiment to which this invention is applied. It is a schematic diagram for demonstrating the state of the electrolyte impregnation using a pregel. It is a perspective view which shows the external appearance of the battery which made the said bipolar battery the laminate pack. 5 is a perspective view of an assembled battery of Reference Example 1. FIG. It is drawing which looked at the internal structure of the said assembled battery from upper direction. It is a perspective view of the assembled battery module of the reference example 2. 10 is a drawing of an automobile provided with the assembled battery module of Reference Example 3.

Explanation of symbols

1 Bipolar electrode,
2 ... current collector,
3 ... positive electrode,
4 ... negative electrode,
5 ... electrolyte layer,
6 ... single cell,
7 ... End current collector,
9 ... sealing material,
10 ... Bipolar battery,
20 ... Battery,
50 ... assembled battery,
60 ... assembled battery module,
100 ... an automobile.

Claims (7)

Forming a positive electrode on the first surface of one current collector;
Forming a negative electrode on a second surface of the current collector opposite to the surface on which the positive electrode is formed;
Impregnating the positive electrode and the negative electrode with pregel;
Gelling the pregel impregnated in the positive electrode and the negative electrode;
Impregnating a base material for retaining an electrolyte with a pregel;
Forming a gel electrolyte layer by gelling the pregel impregnated in the substrate;
Sandwiching the gel electrolyte between the positive electrode of the first current collector and the negative electrode of the second current collector;
A method for producing a bipolar battery, comprising:   2. The bipolar battery according to claim 1, wherein the gelation is performed by heating after the step of impregnating the pregel using a pregel solution in which a polymerization initiator is preliminarily contained in the pregel. Manufacturing method.   The gelling is characterized in that after the step of impregnating the pregel using a pregel dispersion solution in which the pregel is dispersed in a solvent, the gelation is performed by evaporating the solvent by heating. Manufacturing method of bipolar battery.   In the step of impregnating the positive electrode and the negative electrode with pregel and the step of impregnating the base material with pregel, the amount of the pregel to be impregnated is 100 volumes with respect to the total amount of voids of the positive electrode, the negative electrode, and the base material. The bipolar battery according to any one of claims 1 to 3, wherein the positive electrode, the negative electrode, and the base material are not more than an amount capable of holding the pregel. Method.   In the step of impregnating the positive electrode and the negative electrode with pregel, the amount of the pregel to be impregnated is 90% by volume or more with respect to the respective void amounts of the positive electrode and the negative electrode, and the positive electrode and the negative electrode hold the pregel. The method for producing a bipolar battery according to any one of claims 1 to 4, wherein the amount is less than or equal to a possible amount.   The step of impregnating the positive electrode and the negative electrode with pregel and the step of impregnating the base material with pregel are performed by any one of a die coater coating method, a spray coating method, and an ink jet printing method. The method for manufacturing a bipolar battery according to claim 1, further comprising a step of applying to the base material. The positive electrode includes a lithium-transition metal composite oxide as a positive electrode active material,
The method for manufacturing a bipolar battery according to any one of claims 1 to 6, wherein the negative electrode contains carbon or a lithium-transition metal composite oxide as a negative electrode active material.

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