JP2006185854A - Bipolar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bipolar battery of which corrosion of a cathode-side collecting foil and contact resistance between a collector and an electrode active material are reduced. <P>SOLUTION: The bipolar battery uses a metal foil having coating layers 3a, 3b consisting of a non-ion-conductive polymer and electron conductive particles for the collector 2; lithium-transition metal complex oxide as a cathode active material; and carbon or lithium transition metal complex oxide as an anode active material. A battery pack using the bipolar battery, and a vehicle mounting the battery pack are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a bipolar battery, an assembled battery using the battery, and a vehicle using the battery.

  In recent years, the demand for batteries has increased due to the development of the advanced electronics industry. In particular, a battery having a high energy density is required. As one of such batteries, a bipolar battery using an electrode in which a positive electrode active material is applied to one surface of a current collector and a negative electrode active material is applied to the other surface has been proposed.

  Bipolar battery current collector foils are required to be excellent in corrosion resistance on the positive electrode side and not to be alloyed with lithium on the negative electrode. Therefore, materials that can be used as the current collector foil are very limited, and examples include stainless steel.

  However, even when a stainless steel current collector foil is used, there is a problem in that the positive electrode side cannot withstand a high potential (about 4 V) and the metal is eluted due to corrosion. As a result, battery characteristics are degraded.

Patent Document 1 describes that a protective film made of an aluminum oxide film is provided on the current collector in order to suppress the reaction between the Al current collector foil for positive electrode and the active material paste. However, the purpose of providing the aluminum oxide film is to suppress the reaction between the current collector and the active material paste in the step of forming the active material mixture layer on the current collector (paragraph “0023”). When used, it does not suppress the reaction between the current collector and the active material. That is, since aluminum oxide itself has electrical insulation, it is unsuitable as a current collector (paragraph “0027”). Therefore, there is a description that in order to impart electrical conductivity, such a protective coating preferably has carbon particles and a binder that binds the carbon particles (paragraph “0033”).
JP 2003-157852 A

  However, the aluminum oxide film is preferably formed by heating the current collector in water vapor or water (Patent Document 1, Paragraph “0062”). Means are not described.

  Therefore, an object of the present invention is to provide a bipolar battery that reduces corrosion of the positive electrode when used as a battery.

  Another object of the present invention is to provide an assembled battery using such a bipolar battery.

  Furthermore, an object of the present invention is to provide a vehicle using such a bipolar battery or an assembled battery.

  In order to achieve the above object, a bipolar battery characterized in that a metal foil coated with a layer having non-ion conductivity and electron conductivity is used as a current collector has been devised.

  In order to achieve the above object, an assembled battery using the above bipolar battery has been devised.

  Furthermore, in order to achieve the above object, a vehicle characterized by using the bipolar battery or the assembled battery has been devised.

  In a bipolar battery, a metal foil coated with a layer having non-ion conductivity and electron conductivity is used as a current collector. Therefore, when used as a battery, corrosion of the current collector foil on the positive electrode side should be reduced. Can do. Furthermore, the contact resistance between the current collector and the electrode active material can be reduced.

  Since the bipolar battery is used in the assembled battery, the battery characteristics are excellent.

  Since the bipolar battery or the assembled battery is used in the vehicle, the battery characteristics are excellent.

  The bipolar battery of the present invention will be described separately for a bipolar current collector and a bipolar battery using such a bipolar current collector. A lithium ion battery will be described as a representative example.

(Bipolar current collector)
The bipolar current collector used in the bipolar battery of the present invention is a metal foil coated with a layer having nonionic conductivity and electron conductivity.

  The metal foil does not include aluminum, but is preferably a metal foil that is harder than aluminum. Specific examples include stainless steel (SUS), copper, nickel, titanium, and the like. Since the reaction with Li ions can be prevented by providing a coating layer on the metal foil, not only stainless steel but also other metal foils can be used. The thickness of the metal foil is usually in the range of 1 to 100 μm.

  The material that imparts nonionic conductivity is not particularly limited as long as it is a material that does not conduct ions, and examples thereof include a nonionic conductive polymer. Such polymers are poorly compatible with the electrolyte and can be sufficiently repelled. Specific examples include fluorine resins such as polytetrafluoroethylene; olefin resins such as polyethylene, polypropylene, and copolymers thereof; silicone resins; acrylic resins; polyester resins; aramid resins; epoxy resins; it can. These resins may be used alone or in combination.

  Examples of the material that imparts electron conductivity include carbon-based particle materials such as carbon black, acetylene black, graphite, carbon nanotube, and carbon fiber; metal fine particles such as gold and platinum; and ceramic fine particles such as conductive ceramics. it can. By dispersing this material in the coating layer, the layer is given sufficient electronic conductivity. The size of the particles is usually in the range of 10-20 μm.

  Since the usage ratio of the material which gives nonionic conductivity and the material which gives electronic conductivity changes with metal foils and electrode electrolyte to be used, it selects suitably. The ratio (mass ratio) is usually 50:50 to 90:10, preferably 70:30.

  These materials are coated on the metal foil by the following method. If necessary, these materials can be dispersed in a solvent such as N-methylpyrrolidone (NMP) to prepare a dispersion, and the dispersion can be coated on the positive electrode side or both surfaces of the metal foil with a coater or the like and dried. The thickness of the coating layer is usually in the range of 0.1 to 10 μm.

  In addition, as the coating layer, a gold plating layer or a platinum plating layer can be used instead of the above layer. It is obtained by plating on the positive electrode side or both surfaces of the metal foil. The thickness of the coating layer is usually in the range of 0.1 to 10 μm.

  Thus, by providing the coating layer on the metal foil, direct contact between the metal foil and the electrode electrolyte can be prevented. In addition, the generated electrons or current can be easily taken out.

As a characteristic required for a current collector (metal) foil for a lithium ion secondary battery, the positive electrode side has a very high potential of 4 V or more with respect to Li / Li ⁺ , so that there is no corrosion, that is, no metal elution, on the negative electrode side. Then, it may not be alloyed with Li metal at a low potential. That is, the bipolar current collector foil needs to satisfy these requirements. For this reason, stainless steel has conventionally been used as a bipolar current collector foil. However, there is a problem that the positive electrode side cannot withstand a high potential, corrodes metal, and battery characteristics deteriorate. It was. On the other hand, if the coating layer of the present invention is used, corrosion of the positive electrode current collector foil can be suppressed. Moreover, if a coating layer is provided on both surfaces of the current collector foil, alloying with Li metal can be suppressed on the negative electrode side.

  Furthermore, the following effects are recognized by providing a coating layer on the current collector foil. By closing the pinhole of the current collector foil, it is possible to prevent a short circuit or a liquid junction between adjacent batteries due to the bipolar battery. Furthermore, according to the method using a material that imparts nonionic conductivity, when the battery is manufactured, the active material particles for the electrode are embedded in the soft coating layer, so that the active material for the electrode and the current collector foil Contact resistance can be reduced.

  FIG. 1 is a diagram illustrating the contact resistance between an electrode active material and a current collector. Including the figure, the thickness of the layer is enlarged for easy understanding. In FIG. 1, a positive electrode active material layer 4 is laminated on a current collector 2 having a coating layer 3. Since the coating layer 3 is soft, the granular material of the positive electrode active material layer 4 is brought into contact with the current collector 2 by pressing, and the state is stably maintained. With such a configuration, the contact resistance between the positive electrode active material and the current collector can be reduced.

(Bipolar battery)
FIG. 2 is a cross-sectional view for explaining the bipolar electrode of the present invention. In FIG. 2, a positive electrode active material layer 4 is formed on one surface of a current collector 2 having coating layers 3a and b formed on both surfaces, and a negative electrode active material layer 5 is formed on the remaining surface. The coating layer may cover the entire current collector, if necessary. Except for the bipolar electrode, the materials and manufacturing methods used in conventional batteries can be used. In the present invention, the coated current collector foil described in the bipolar current collector is used as the current collector foil.

  FIG. 3 is a partially broken sectional view for explaining an example of layer stacking in the bipolar battery of the present invention. 3A, the coating layer 3a, the current collector 2, the coating layer 3b, the negative electrode active material layer 5, the electrolyte 7, the positive electrode active material layer 4, the coating layer 3a, the current collector 2, and the coating layer 3b are arranged in this order. It is laminated from the bottom to the bottom. Here, the electrolyte layer 7 is formed of a solid electrolyte. FIG. 3B shows a bipolar battery using a separator impregnated with a gel electrolyte. In FIG. 3B, since the electrolyte layer 7 has a gel shape, unlike FIG. 3A, the leakage preventing portion 15 is provided so that the gel electrolyte does not leak to the outside. The leakage prevention unit 15 is made of a heat sealing resin such as a polyolefin resin. Here, the negative electrode active material layer 5, the electrolyte layer 7, and the positive electrode active material layer 4 are sequentially stacked and referred to as a unit cell.

The active material for the negative electrode is not particularly limited as long as it is a conventionally known material, but a carbon material such as lithium metal, lithium alloy, lithium-transition metal composite oxide such as Li ₄ Ti ₅ O ₁₂ , hard carbon, graphite or the like. In addition, an oxide material can be selected as appropriate. Further, if necessary, conductive aids such as acetylene black, carbon black, graphite, and carbon fiber for enhancing electron conductivity; binders such as polyvinylidene fluoride and styrene butadiene rubber; polyethylene oxide (PEO), polypropylene oxide (PPO) ), a solid electrolyte such as a copolymer _{thereof; LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10, LiCF 3 SO 3, Li (CF 3 SO 2) 2 An electrolyte supporting salt for enhancing ion conductivity such as N and Li (C ₂ F ₅ SO ₂ ) ₂ N can be used. In addition, the film thickness of the active material layer for negative electrodes is about 1-500 micrometers normally.

The positive electrode active material is not particularly limited, and a conventionally known material, for example, a composite oxide of a transition metal and lithium can be suitably used. Specifically, Li · Mn-based composite oxides such as LiMn ₂ O ₄ , Li · Co-based composite oxides such as LiCoO ₂ , Li · Cr-based composite oxides such as Li ₂ Cr ₂ O ₇ and Li ₂ CrO ₄ Products, Li / Ni-based composite oxides such as LiNiO ₂ , Li / Fe-based composite oxides such as LiFeO ₂ , and parts of these transition metals substituted with other elements (for example, LiNi _x Co _1-x O ₂ (0 <x <1) or the like can be used. Furthermore, if necessary, a conductive additive for increasing electron conductivity, a binder, a solid electrolyte, an electrolyte supporting salt for increasing ion conductivity, and the like can be used. The film thickness of the positive electrode active material layer is usually about 1 to 500 μm.

  It is preferable to use lithium-transition metal composite oxide as the positive electrode active material and carbon or lithium-transition metal composite oxide as the negative electrode active material. This is because a battery having excellent capacity and output characteristics can be configured.

  The electrolyte is not particularly limited, and conventionally known materials such as (a) a polymer gel electrolyte, (b) a polymer solid electrolyte, or (c) a separator impregnated with these electrolytes (including a nonwoven fabric separator). (D) A liquid electrolyte can be used.

(A) Polymer gel electrolyte Gel electrolyte means what held electrolyte solution in a polymer matrix. Examples of the polymer matrix include PEO, PPO, polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), PVdF, poly (methyl methacrylate) (PMMA), and a combination thereof. A polymer is desirable, and among them, PEO, PPO and their copolymers, or PVdF-HFP is desirably used. The electrolyte solution, which electrolyte salt dissolved in a solvent, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl ₁₀ and the like inorganic acid anion As the solvent, at least one selected from organic acid anion salts such as salts, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, etc. Ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC) and mixtures thereof are desirable.

  The ratio of the electrolytic solution in the gel electrolyte in the present invention is not particularly limited, but is preferably about several mass% to 98 mass% from the viewpoint of ionic conductivity. The present invention is particularly effective for a gel electrolyte having a large amount of electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more.

(B) Polymer solid electrolyte Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as PEO, PPO, and copolymers thereof. The solid polymer electrolyte contains a lithium salt in order to ensure ionic conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used.

(C) Separator impregnated with the electrolyte (including non-woven separator)
As the electrolyte that can be impregnated in the separator, the same electrolytes as those already described (a) and (b) can be used.

  Examples of the separator include a porous sheet and a nonwoven fabric made of a polymer that absorbs and holds the electrolyte.

  As the porous sheet, for example, a microporous separator can be used. Examples of the polymer include polyolefins such as polyethylene (PE) and polypropylene (PP); laminates having a three-layer structure of PP / PE / PP, polyimide, and aramid. The thickness of the separator cannot be unambiguously defined because it varies depending on the intended use. However, in the case of a secondary battery for driving a motor such as an electric vehicle (EV) or a hybrid electric vehicle (HEV), a single layer is used. Or it is desirable that it is 4-60 micrometers in a multilayer. The separator preferably has a fine pore size of 1 μm or less (usually a pore size of about several tens of nanometers) and a porosity of 20 to 70%.

  As the nonwoven fabric, cotton, rayon, acetate, nylon, polyester; polyolefin such as PP and PE; conventionally known materials such as polyimide and aramid are used alone or in combination. Further, the bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. The porosity of the nonwoven fabric separator is preferably 50 to 90%. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm. When the thickness is less than 5 μm, the electrolyte retention deteriorates, and when it exceeds 200 μm, the resistance increases.

(D) Liquid electrolyte (electrolytic solution)
Examples of the electrolytic solution include those obtained by dissolving an electrolyte salt in a solvent. Here, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _{as, LiCF 3 SO 3, Li (} CF 3 SO 2 ) At least one selected from organic acid anion salts such as ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, and the solvent is EC, PC, GBL, DMC, DEC and mixtures thereof Is desirable.

  Among electrolytes, a separator impregnated with a gel electrolyte is preferable. This is because a battery having excellent capacity and output characteristics can be configured.

  FIG. 4 is a cross-sectional view schematically showing the overall structure of a bipolar lithium ion secondary battery (hereinafter also simply referred to as a bipolar battery). In FIG. 4, in the bipolar battery 1, a coating layer 3b and a positive electrode active material layer 4 are sequentially laminated on one surface of a current collector 2, and a coating layer 3a and a negative electrode active material layer 5 are formed on the other surface. The electrode assembly (bipolar battery main body) 8 has a structure in which a plurality of sequentially stacked bipolar electrodes 6 are stacked via an electrolyte layer 7. Note that the number of stacked bipolar electrodes 6 (including the electrodes 6a and 6b) is adjusted according to a desired voltage. Further, the uppermost layer and the lowermost layer electrodes 6a and 6b of the electrode laminate 8 in which a plurality of such bipolar electrodes 6 are laminated may not have a bipolar electrode structure, and only one side necessary for the current collector 2 or the terminal plate may be used. The cover layer 3b and the positive electrode active material layer 4 or the cover layer 3a and the negative electrode active material layer 5 may be arranged.

  In the bipolar battery 1, positive and negative electrode leads 12 and 11 are joined to current collectors 2 at both upper and lower ends, respectively.

  Further, in the bipolar battery 1 of the present invention, the electrode laminate 8 portion is sealed in a battery exterior material (exterior case) 13 under reduced pressure in order to prevent external impact and environmental degradation during use.

  The initial charging of the battery is performed after enclosing it in the battery outer packaging material. Thereafter, pressing is performed while heating the exterior material. A method such as hot pressing is the same as that of a conventional battery.

  The basic configuration of the bipolar battery 1 can be said to be a configuration in which a plurality of stacked single battery layers or single cells are connected in series.

  As the current collector, the positive electrode active material, the negative electrode active material, and the electrolyte used in the stacked battery, the materials described in the bipolar battery can be used.

  It is preferable to use lithium-transition metal composite oxide as the positive electrode active material and carbon or lithium-transition metal composite oxide as the negative electrode active material. This is because a battery having excellent capacity and output characteristics can be configured.

  Other layers will be described.

[Battery exterior materials]
As a battery exterior material, a conventionally well-known case can be used, and a bag-like case that can cover a unit cell using a laminate film containing aluminum can be given. The laminate film is, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order.

[Insulation layer]
The insulating layer is formed around each electrode for the purpose of preventing current collectors adjacent in the battery from contacting each other and short-circuiting due to slight unevenness at the end of the laminated electrode. If necessary, an insulating layer is provided around the electrode. As the insulating layer, for example, polyolefin resin such as PE and PP, epoxy resin, rubber, polyimide and the like can be used, and polyolefin resin is preferable from the viewpoint of corrosion resistance, chemical resistance, film-forming property, economy and the like. .

[Positive electrode and negative electrode terminal plate]
The positive electrode and the negative electrode terminal plate are used as necessary. For example, when the electrode terminals are directly taken out from the outermost current collector, the positive electrode and negative electrode terminal plates are not used (see FIG. 4).

  As a material for the positive electrode and the negative electrode terminal plate, a material used in a conventionally known lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, SUS, or an alloy thereof is used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like. Furthermore, from the viewpoint of suppressing internal resistance at the terminal portion, the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm.

[Positive electrode and negative electrode lead]
Regarding the positive electrode and the negative electrode lead, a lead used in a known lithium ion battery can be used. In addition, the parts removed from the battery exterior material should be heat-insulating so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

  The lithium ion secondary battery according to the present invention is a power source for driving a vehicle or an auxiliary device that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle and the like. It can utilize suitably for a power supply.

(Battery)
In the present invention, an assembled battery (vehicle submodule) can be formed by using at least one of a plurality of the lithium ion secondary batteries in parallel connection, series connection, parallel-series connection, or series-parallel connection.

  Hereinafter, embodiments of the assembled battery will be described with reference to the drawings. Typical assembled batteries include a battery combining bipolar batteries (FIG. 5), a battery combining bipolar batteries and non-bipolar batteries (FIG. 6), and a composite assembled battery (FIG. 7).

  FIG. 5 is a schematic diagram of an assembled battery (42V1Ah) in which the bipolar batteries (24V, 50 mAh) of the present invention are connected in two lines and 20 lines. (A) is a plan view, (b) is a front view, and (c) is a right side view. Here, the battery pack connected in parallel with 2 in 20 means that 40 bipolar batteries are used, and each battery is divided into 20 sets of 2 pieces, and the two batteries are connected in series and 20 sets are connected in series. A battery in which all batteries are connected in parallel. In FIG. 5, 40 bipolar batteries are prepared, arranged in 2 rows and 5 columns, and stacked in four stages. In the first stage, two sets of upper and lower are connected in series, all five sets connected in series are connected in parallel, and the second to fourth stages are similarly performed, and finally 20 sets of batteries connected in series All are connected in parallel to obtain an assembled battery. The tabs 48 and 49 are connected by vibration welding in the series part, and the tabs in the parallel part are connected by copper bus bars 56 and 58.

  The obtained battery assembly is stored in a metal battery assembly case 55. Thus, the assembled battery 51 which can respond to a desired electric current, voltage, and capacity | capacitance can be provided by connecting the some bipolar battery 41 in series and parallel.

  The end of the series portion is connected to terminals 62 and 64 attached to the assembled battery case to constitute positive and negative terminals. Specifically, each of the positive terminal 62 and the negative terminal 64 formed on the front side of the side surface of the assembled battery case 55 is connected to each bus bar 56 via each terminal lead 59.

  Further, in the assembled battery 51, a detection tab terminal 54 is installed at the front side of the assembled battery case 55 in order to monitor the battery voltage such as the voltage between terminals of each single cell layer and the bipolar battery. The detection tab terminal 54 is connected to the voltage detection tab 60 of each bipolar battery 41 via the detection line 53.

  An external elastic body 52 such as synthetic rubber is attached to the bottom of the assembled battery case 55. When forming a composite battery pack by stacking a plurality of battery packs 51, the distance between the battery packs 51 can be kept constant, improving vibration proofing, impact resistance, insulation, heat dissipation, and the like.

  The assembled battery 51 can be provided with various measuring devices and control devices in addition to the detection tab terminal 54, depending on the intended use.

  Further, the method of connecting the electrode tabs (48, 49) of the bipolar battery 1, the detection tab 60, the detection line 53, the bus bars 56, 58, the terminal lead 59, etc. is not particularly limited. Examples thereof include welding, heat welding, laser welding or electron beam welding, a method using bus bars 56 and 58 such as rivets, and a caulking method.

  In the assembled battery of the present invention, the bipolar battery of the present invention is the same as the lithium ion battery of the present invention, wherein the bipolar battery and the positive and negative electrode materials are the same, and the number of structural units of the bipolar battery is set in series. A secondary battery (hereinafter also simply referred to as a non-bipolar battery) may be connected in parallel. That is, the battery forming the assembled battery may be a mixture of the bipolar battery of the present invention and a non-bipolar battery (however, not all batteries need to be the battery of the present invention). As a result, an assembled battery that compensates for each other's weaknesses can be obtained by combining a bipolar battery that emphasizes output and a non-bipolar battery that emphasizes energy, and the mass and size of the assembled battery can be reduced. The ratio of the bipolar battery and the non-bipolar battery is determined according to the safety performance and output performance required for the assembled battery.

  FIG. 6 is a drawing showing an example of an assembled battery in which a bipolar battery A (42 V, 50 mAh) and a non-bipolar battery B (4.2 V, 1 Ah) 10 series (42 V) are connected in parallel. Here, (a) is a plan view, (b) is a front view, and (c) is a right side view. In FIG. 6, 10 non-bipolar type batteries B are vibration welded in order from the end through a bus bar 56 and connected in series. Further, the bipolar battery A and the non-bipolar battery B at both ends connected in series are connected in parallel by the bus bar 56 and then housed in a metal battery assembly case 55. Also in this assembled battery 51 ′, the tabs of the parallel portion and the non-bipolar battery B adjacent in the horizontal direction in the figure are connected in series by the copper bus bar 56, and between the general batteries B adjacent in the vertical direction in the figure. The portions to be connected in series are connected by vibration welding of the tabs 39 and 40. With such a configuration, the non-bipolar battery B and the bipolar battery A have the same voltage, and a parallel connection is formed at that portion. The assembled battery 51 ′ has a structure in which the bipolar battery A has an output sharing and the non-bipolar battery B has an energy sharing. This is a very effective means in an assembled battery in which it is difficult to achieve both output and energy. In this way, by connecting an arbitrary number of bipolar batteries A in series and parallel, an assembled battery 51 ′ that can handle a desired current, voltage, and capacity can be provided.

  The tab 60 for detecting the voltage of each layer of the bipolar battery A is taken out on both sides of the bipolar battery A, and the detection lines (not shown) are taken out at the front part of the assembled battery 51 ′, as shown in FIG. Since it is the same as that of the assembled battery 51, the same symbol is attached to the same member.

  Also in the assembled battery 51 ′, a positive terminal 62 and a negative terminal 64 are formed at the front side of the assembled battery case 55, and each bus bar 56 is connected to each terminal by a terminal lead 59, for example. The tabs 48 and 49 are connected to the bus bar 56, respectively.

  The assembled battery 51 ′ includes a detection tab terminal 54 for monitoring battery voltages such as voltage between terminals of each of the bipolar batteries A and further between the terminals of the bipolar battery A and the non-bipolar battery B. It is installed at the front side of the case 55. And all the detection tabs 60 of each bipolar battery A (and non-bipolar type battery B) are connected to the detection tab terminal 54 via the detection line (not shown).

  An external elastic body 52 such as a synthetic rubber is attached to the lower part of the assembled battery case 55. When forming a composite battery pack by stacking a plurality of battery packs 51 ', the distance between the battery packs 51' can be kept constant, improving vibration proofing, impact resistance, insulation, heat dissipation, and the like. .

  Furthermore, in the assembled battery of the present invention, the above assembled battery is used as a first assembled battery unit, and secondary batteries other than the bipolar battery having the same voltage and voltage between the terminals of the first assembled battery unit are connected in series and parallel. The second assembled battery unit is formed, and the first assembled battery unit and the second assembled battery unit are connected in parallel to form an assembled battery.

  In addition, regarding the other structural requirements of an assembled battery, it should not be restrict | limited at all and the conventionally well-known structural member and manufacturing technique for assembled batteries can be utilized.

  Next, at least two or more of the above assembled batteries can be combined in series, parallel, or combined in series and in parallel (a combined battery for vehicles). By using a composite assembled battery, it is possible to respond to the demands for battery capacity and output for each purpose of use relatively inexpensively without producing a new assembled battery. That is, the composite battery pack is composed of at least two or more battery packs in series (parallel or non-bipolar batteries of the present invention, or bipolar and non-bipolar batteries of the present invention). Or a series and parallel composite connection. Therefore, the specification of an assembled battery can be tuned by manufacturing a reference assembled battery and combining it into a composite assembled battery. Thereby, it is not necessary to manufacture assembled battery types having different specifications, and the combined assembled battery cost can be reduced.

  FIG. 7 is a drawing showing an example of a composite battery pack. For example, FIG. 7 is a schematic diagram of a composite assembled battery (42V, 6Ah) in which six assembled batteries (42V, 1Ah) using the bipolar battery shown in FIG. 5 are connected in parallel. Here, (a) is a plan view, (b) is a front view, and (c) is a right side view. Each assembled battery constituting the composite assembled battery is integrated by a connecting plate and a fixing screw, and an elastic body is installed between the assembled batteries to form a vibration-proof structure. The tabs of the assembled battery are connected by a plate-like bus bar. That is, in FIG. 7, in order to connect the six assembled batteries 51 in parallel to form the composite assembled battery 70, the tabs (the positive terminal 62 and the positive terminal 62 and the tabs of the assembled batteries 51 provided on the lid of each assembled battery case 55. The negative electrode terminal 64) is electrically connected using an assembled battery positive electrode terminal connecting plate 72 having an external positive electrode terminal portion which is a plate-shaped bus bar and an assembled battery negative electrode terminal connecting plate 74 having an external negative electrode terminal portion. Further, a connecting plate 76 having an opening corresponding to the fixing screw hole is fixed to each screw hole (not shown) provided on both side surfaces of each assembled battery case 55 with a fixing screw 77, and The batteries 51 are connected to each other. Moreover, the positive electrode terminal 62 and the negative electrode terminal 64 of each assembled battery 51 are protected by a positive electrode and a negative electrode insulating cover, respectively, and are identified by color-coding into appropriate colors, for example, red and blue. Further, an anti-vibration structure is formed by installing an external elastic body 52 such as a synthetic rubber between the assembled batteries 51, specifically, at the bottom of the assembled battery case 55.

  In this way, by combining the basic lithium secondary battery, it is possible to satisfy the demands for capacity and voltage for various vehicles. As a result, it is not necessary to design and produce different batteries for various vehicles, and it becomes possible to mass-produce basic batteries and to reduce costs by mass production.

  Moreover, in the said composite assembled battery, it is desirable to connect the some assembled battery which comprises this so that attachment or detachment is possible respectively. As described above, in the composite assembled battery in which a plurality of assembled batteries are connected in series and parallel, even if some of the batteries and the assembled battery fail, the repair can be performed only by replacing the failed part.

  In addition, the vehicle used in the present invention can be mounted with the assembled battery and / or the composite assembled battery. This makes it possible to meet a large vehicle demand for space by using a light and small battery. By reducing the battery space, the weight of the vehicle can be reduced.

(vehicle)
FIG. 8 is a view showing an example in which a composite assembled battery or a battery is mounted under a seat at the center of the body of an electric vehicle. If the composite battery pack 70 is mounted under the seat of the electric vehicle 80, the interior space and the trunk room can be widened. The place where the battery is mounted is not limited to the position under the seat, but may be the floor under the vehicle, the back of the seat back, the lower part of the rear trunk room, or the engine room in front of the vehicle.

  In the present invention, the composite assembled battery alone, the assembled battery alone, or the composite assembled battery and the assembled battery can be mounted on the vehicle. Moreover, as a vehicle in which the battery can be mounted as a driving power source or an auxiliary power source, the above-described electric vehicle, fuel cell vehicle, and hybrid vehicle thereof are preferable, but are not limited thereto. By using the battery of the present invention for an electric vehicle, a fuel cell vehicle or a hybrid vehicle thereof, a vehicle having a long life and high reliability can be obtained.

  Hereinafter, the present invention will be described in detail using examples.

  A bipolar electrode slurry and a gel electrolyte are prepared in advance.

<Bipolar electrode slurry>
○ Positive electrode ・ The following materials are mixed at a mass ratio shown in parentheses to prepare a positive electrode slurry.
- as a positive electrode active _{material, LiMn 2 O 4 (85wt%} ).
-Acetylene black (5 wt%) as a conductive assistant.
-PVdF (10 wt%) as a binder.
・ NMP (appropriate amount) as slurry viscosity adjusting solvent
○ Negative electrode-The following materials are mixed at a mass ratio shown in parentheses to prepare a negative electrode slurry.
-Hard carbon (90 wt%) as the negative electrode active material.
-PVdF (10 wt%) as a binder.
・ NMP (appropriate amount) as slurry viscosity adjusting solvent
<Formation of gel electrolyte>
A nonwoven fabric having a thickness of 20 μm is used as a separator. 5% by weight of PEO macromonomer (copolymer of PEO and PPO) having a number average molecular weight of about 8000 as a polymer and 1.0M LiBF ₄ dissolved in EC + PC (1: 1) as an electrolytic solution in the separator. A gel electrolyte is formed by impregnating a pregel solution consisting of 95 wt% and 2000 ppm of a polymerization initiator and photocrosslinking in an inert atmosphere.

Example 1
A conductive paint (thickness 2 μm) was coated on both sides of a SUS foil (thickness 10 μm) as a current collector. The conductive paint used was a sufficiently dispersed carbon black (30 wt%) in polypropylene (70 wt%). The negative electrode slurry was applied to one side of the coated current collector foil, and a negative electrode having a thickness of 15 μm was formed by drying and pressing. The positive electrode slurry was applied to the opposite surface of the current collector foil coated with the negative electrode, and a positive electrode having a thickness of 15 μm was formed by drying and pressing. As described above, bipolar electrodes having a positive electrode and a negative electrode were formed on both sides of the current collector foil.

  The bipolar electrode and the gel electrolyte were laminated so that the positive electrode and the negative electrode sandwiched the gel electrolyte. After stacking five layers, the laminate was sealed with a laminate pack to form a bipolar battery.

(Example 2)
Gold plating (thickness 2 μm) was applied to both surfaces of a SUS foil (thickness 10 μm) as a current collector. In the same manner as in Example 1, bipolar electrodes having a positive electrode and a negative electrode were formed on both surfaces of the gold-plated current collector foil.

  In the same manner as in Example 1, five layers of bipolar electrode and gel electrolyte were laminated and laminated to form a bipolar battery.

(Comparative example)
The SUS foil (thickness 10 μm) as a current collector was used as it was. In the same manner as in Example 1, bipolar electrodes having a positive electrode and a negative electrode were formed on both sides of the current collector foil.

  In the same manner as in Example 1, five layers of bipolar electrode and gel electrolyte were laminated and laminated to form a bipolar battery.

(Evaluation 1)
Each battery was subjected to a cycle test (1C CC charge / discharge). None of the batteries had any problems in the first charge / discharge, and showed good battery characteristics. However, as the number of cycles increased to 100 cycles and 200 cycles, the capacity of the battery of the comparative example was reduced, and this was noticeable at 500 cycles. When the battery was disassembled, SUS corrosion was observed on the positive electrode side. On the other hand, the batteries of Example 1 and Example 2 maintained a capacity equivalent to the initial value even after exceeding 500 cycles, and exhibited good cycle characteristics. Even when the battery was disassembled, corrosion on the positive electrode side was not observed.

(Evaluation 2)
A full charge storage test was performed on each battery. After 30 days, the battery voltage of the comparative example was significantly reduced. When the battery was disassembled, SUS corrosion was observed on the positive electrode side. On the other hand, the batteries of Example 1 and Example 2 maintained the battery voltage even after 30 days and exhibited a good voltage maintenance rate. Even when the battery was disassembled, corrosion on the positive electrode side was not observed.

(Evaluation 3)
In each battery, the battery resistance was measured. Assuming that the battery resistance of the comparative example was 100%, the battery resistance of Example 1 was 95%, and the battery resistance of Example 2 was 90%.

It is drawing explaining the contact resistance between an electrode active material and a collector. It is sectional drawing for demonstrating the bipolar electrode of this invention. FIG. 5 is a partially broken cross-sectional view for explaining an example of layer stacking in the bipolar battery of the present invention. It is sectional drawing which shows typically an example of the whole structure of a bipolar type lithium ion secondary battery. It is a schematic diagram of an example of the assembled battery in which the bipolar battery of the present invention is connected in two lines and 20 lines. It is drawing which shows an example of the assembled battery which connected the bipolar battery A and the non-bipolar type battery B in parallel. It is drawing which shows an example of a composite assembled battery. It is drawing which shows an example by which the composite assembled battery or the battery was mounted under the seat of the vehicle body center part of an electric vehicle.

Explanation of symbols

1 Bipolar battery,
2 current collector,
3 coating layer,
4 active material layer for positive electrode,
5 active material layer for negative electrode,
7 Electrolyte layer.

Claims (9)

  A bipolar battery characterized in that a metal foil coated with a layer having nonionic conductivity and electron conductivity is used as a current collector.   The battery according to claim 1, wherein the layer includes a non-ion conductive polymer and electron conductive particles.   The battery according to claim 1, wherein the layer is a gold plating layer or a platinum plating layer.   The nonionic conductive polymer is at least one selected from the group consisting of a fluororesin, an olefin resin, a silicone resin, an acrylic resin, a polyester resin, an aramid resin, an epoxy resin, and a urethane resin. 2. The battery according to 2.   5. The battery according to claim 2, wherein the electron conductive particles are particles made of at least one material selected from the group consisting of a carbon material, a metal, and a conductive ceramic.   The lithium-transition metal composite oxide is further used as the positive electrode active material, and carbon or lithium-transition metal composite oxide is used as the negative electrode active material. The battery described.   Furthermore, gel electrolyte is used as electrolyte, The battery of any one of Claims 1-6 characterized by the above-mentioned.   An assembled battery comprising a plurality of the batteries according to claim 1 connected to each other.   A vehicle comprising the battery according to any one of claims 1 to 8 as a driving power source.

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