JP2004158307A - Bipolar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-reliability bipolar battery capable of preventing a liquid junction (short circuit) caused by oozing of an electrolytic solution from an electrolyte, in a bipolar battery using a gel electrolyte. <P>SOLUTION: This bipolar battery is composed by serially stacking, by interposing electrolyte layers 4, a plurality of bipolar electrodes each composed by forming a positive electrode on one surface of a collector and a negative electrode on the other surface thereof. The bipolar battery is characterized in that the electrolyte layer has a structure wherein a polymer gel electrolyte 4c is held in the vicinity of the center part of a non-woven fabric; and a resin for sealing the electrolyte is held in the circumferential part of the part of the non-woven fabric with the gel electrolyte held. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bipolar battery in which a positive electrode active material and a negative electrode active material are arranged on both sides of a current collector, and more specifically, a polymer gel electrolyte having excellent ionic conductivity compared to a polymer solid electrolyte. The present invention relates to a bipolar battery used.
[0002]
[Prior art]
In recent years, reduction of carbon dioxide emission has been urgently required for environmental protection. The automobile industry is expected to reduce carbon dioxide emissions through the introduction of electric vehicles (EVs) and hybrid electric vehicles (HEVs), and is keen to develop secondary batteries for motor drives, which are key to their practical use. Is being done. As a secondary battery, attention has been focused on a lithium ion secondary battery capable of achieving high energy density and high output density. However, in order to apply it to an automobile, it is necessary to use a plurality of secondary batteries connected in series in order to secure a large output.
[0003]
However, when a battery is connected via the connection, the output decreases due to the electrical resistance of the connection. Also, batteries with connections have spatial disadvantages. That is, the connection portion lowers the output density and energy density of the battery.
[0004]
As a solution to this problem, a bipolar battery in which a positive electrode active material and a negative electrode active material are arranged on both sides of a current collector has been developed.
[0005]
Among them, a bipolar battery using a polymer solid electrolyte containing no solution as an electrolyte has been proposed (for example, see Patent Document 1). According to this, since no solution (electrolyte solution) is contained in the battery, there is no need to worry about liquid leakage or gas generation, and a highly reliable bipolar battery that does not require a hermetically sealed structure can be provided. is there. However, the ionic conductivity of the polymer solid electrolyte is lower than that of the gel electrolyte, and the output density and energy density of the battery are not sufficient in a normal use environment, and the battery has not yet reached the stage of practical use. The improvement of ionic conductivity is expected.
[0006]
On the other hand, a bipolar battery using an electrolyte having an electrolytic solution has been proposed (for example, see Patent Documents 2 and 3). If an electrolyte having an electrolytic solution, particularly a gel electrolyte, is used, it is expected to be a bipolar battery which is excellent in ionic conductivity and sufficiently obtains the output density and energy density of the battery, which is the closest to the practical use stage.
[0007]
[Patent Document 1]
JP 2000-100471 A
[Patent Document 2]
JP-A-2002-75455
[Patent Document 3]
JP-A-11-204136
[0008]
[Problems to be solved by the invention]
However, when an attempt is made to construct a bipolar battery using a gel electrolyte, the electrolyte may seep out from the electrolyte portion, come into contact with the electrolyte of another unit cell layer, and cause a liquid junction (short circuit).
[0009]
Therefore, an object of the present invention is to provide a bipolar battery using a gel electrolyte, which prevents a liquid junction (short circuit) due to seepage of an electrolyte solution from the electrolyte and provides a highly reliable bipolar battery. .
[0010]
[Means for Solving the Problems]
The present invention provides a bipolar lithium ion secondary battery in which a positive electrode is formed on one surface of a current collector, and a bipolar electrode in which a negative electrode is formed on the other surface is stacked in series with an electrolyte layer interposed therebetween.
The electrolyte layer has a structure in which a polymer gel electrolyte is held in the vicinity of the center of the nonwoven fabric, and a resin for electrolyte sealing is held on the outer periphery of the same nonwoven fabric holding the gel electrolyte. This is a bipolar battery.
[0011]
【The invention's effect】
In the bipolar battery of the present invention, the structure of the electrolyte layer, the gel electrolyte is held in the nonwoven fabric, and the resin for the electrolyte seal is immersed in the outer periphery of the same nonwoven fabric to form the electrolyte seal portion. A liquid junction (short circuit) due to leakage of the electrolyte can be easily and effectively prevented. In addition, by forming the electrolyte seal portion integrally with the polymer gel electrolyte, the battery manufacturing process is greatly simplified. In other words, in order to prevent self-discharge due to a liquid junction (short circuit) between the unit cell layers, it is conceivable to newly form an insulator layer around the outer periphery between the unit cell layers to have a sealing property with respect to the electrolytic solution. The configuration and manufacturing process of the bipolar battery become complicated or complicated. On the other hand, the bipolar battery of the present invention can prevent a liquid junction between unit cells without providing a special member, is excellent in ionic conductivity, and is a compact battery excellent in battery characteristics such as charge and discharge characteristics. Bipolar batteries can be provided. Therefore, it has high reliability, can maintain excellent energy density and power density, and is a useful power source in various industries.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0013]
The bipolar battery according to the present invention is a bipolar battery in which a positive electrode is formed on one surface of a current collector, and a bipolar electrode in which a negative electrode is formed on the other surface is stacked in series with a plurality of electrolytes sandwiched therebetween.
(1) The electrolyte layer has a structure in which a polymer gel electrolyte is held near the center of the nonwoven fabric, and a resin for electrolyte sealing is held on the outer periphery of a portion of the same nonwoven fabric holding the gel electrolyte. Characterized by having (first embodiment), and / or
(2) The electrolyte layer has a structure in which a polymer gel electrolyte is held near the center of the nonwoven fabric, and an all-solid polymer electrolyte is held on the outer periphery of a portion of the same nonwoven fabric holding the gel electrolyte. (Second embodiment).
[0014]
In the first embodiment, the electrolyte seal portion (the portion where the resin for the electrolyte seal is held) can be easily formed at the time of manufacturing the battery (at the time of laminating the electrodes). Short circuit) can be prevented. In addition, by forming the electrolyte seal portion integrally with the gel electrolyte, the battery manufacturing process is simplified.
[0015]
Further, in the second embodiment, the all solid polymer electrolyte in the outer peripheral portion can prevent the liquid of the internal gel electrolyte from seeping out, and can prevent a liquid junction (short circuit) due to leakage of the electrolyte. . In addition, it is advantageous in that a battery reaction can be performed even in the all solid polymer electrolyte portion on the outer peripheral portion.
[0016]
The outline of the basic configuration of the bipolar battery according to the present invention will be briefly described with reference to FIGS. FIG. 1 is a schematic cross-sectional view schematically showing the structure of a bipolar electrode constituting a bipolar battery, and FIG. 2 is a schematic sectional view showing the structure of a unit cell layer constituting a bipolar battery. FIG. 3 is a schematic cross-sectional view, FIG. 3 is a schematic cross-sectional view schematically showing the entire structure of a bipolar battery, and FIG. 4 is a diagram in which a plurality of unit cell layers stacked in a bipolar battery are connected in series. FIG. 1 shows a schematic diagram conceptually (in symbolic form) of what happens.
[0017]
As shown in FIGS. 1 to 4, the bipolar electrode 5 (see FIG. 1) in which the positive electrode layer 2 is provided on one surface of one current collector 1 and the negative electrode layer 3 is provided on the other surface is connected to the electrolyte. The electrode layers 2 and 3 of the bipolar electrode 5 adjacent to each other with the layer 4 interposed therebetween are opposed to each other. That is, in the bipolar battery 11, a plurality of bipolar electrodes (electrode layers) 5 having the positive electrode layer 2 on one surface of the current collector 1 and the negative electrode layer 3 on the other surface are provided via the electrolyte layer 4. It is composed of an electrode laminate (bipolar battery body) 7 having a laminated structure. The electrodes 5a and 5b of the uppermost layer and the lowermost layer do not have a bipolar electrode structure, but have a structure in which an electrode layer (positive electrode layer 2 or negative electrode layer 3) on only one side required for the current collector 1 (or terminal plate) is formed. I have.
[0018]
Also, the uppermost and lowermost electrodes 5a and 5b of the electrode stack 7 in which a plurality of such bipolar electrodes 5 and the like are stacked need not have a bipolar electrode structure, and are necessary for the current collector 1 (or terminal plate). A structure in which only one electrode layer (the positive electrode layer 2 or the negative electrode layer 3) is provided (see FIG. 3). In the bipolar battery 11, the positive and negative electrode leads 8, 9 are respectively joined to the current collectors 1 at the upper and lower ends.
[0019]
The number of laminations of the bipolar electrode is adjusted according to a desired voltage. If a sufficient output can be ensured even if the thickness of the sheet-shaped battery is made as thin as possible, the number of times of laminating the bipolar electrodes may be reduced.
[0020]
Further, in the bipolar battery 11 of the present invention, in order to prevent external impact and environmental degradation during use, the electrode laminate 7 is sealed in a battery exterior material (exterior package) 10 under reduced pressure, and the electrode leads 8, It is preferable to adopt a structure in which 9 is taken out of the battery exterior material (exterior package) 10 (see FIGS. 3 and 4). From the viewpoint of weight reduction, conventionally known batteries such as a polymer-metal composite laminate film such as an aluminum laminate pack in which a metal (including an alloy) such as aluminum, stainless steel, nickel and copper is coated with an insulator such as a polypropylene film; A part or all of the peripheral portion is joined by heat fusion using an exterior material, thereby housing and laminating the electrode laminate 7 under reduced pressure (sealing), and attaching the electrode leads 8 and 9 to the battery exterior material 10. It is preferable to adopt a configuration taken out to the outside. The basic configuration of the bipolar battery 11 can be said to be a configuration in which a plurality of stacked unit cell layers (single cells) 6 are connected in series, as shown in FIG. The bipolar battery of the present invention is used for a bipolar lithium ion secondary battery in which charging and discharging are mediated by movement of lithium ions. However, this does not prevent application to other types of batteries as long as effects such as improvement in battery characteristics can be obtained.
[0021]
In a conventional bipolar battery using a polymer gel electrolyte layer, as shown in FIG. 11, a positive electrode layer 2 is formed on one surface of a current collector 1 using one type of positive electrode material, and one type is formed on an opposite surface. A negative electrode layer 3 is formed using the negative electrode material to form a bipolar electrode 5, and these are laminated with a polymer gel electrolyte (layer) 4 'interposed therebetween. Therefore, the electrolyte contained in the polymer gel electrolyte may ooze out and come into contact with the electrolyte of the other unit cell layer 6 to cause a short circuit (liquid junction). However, in the present invention, the conventional problems can be solved by forming an electrolyte layer as described below with reference to the drawings. Here, FIG. 5 is a schematic plan view and a schematic cross-sectional view schematically showing a state of a process of manufacturing a typical electrolyte layer used in the bipolar battery of the present invention.
[0022]
As shown in FIGS. 5 to 7, the electrolyte layer used in the bipolar battery of the present invention is provided on the outer peripheral portion of the nonwoven fabric 4a (see FIGS. 5A and 5B) corresponding to the size used for the electrolyte layer. The electrolyte seal resin portion 4b is formed by an appropriate method (for example, a method of applying a resin (solution) for electrolyte seal and drying and curing) (FIGS. 5C, 5D, and 5 '). )checking). Next, a suitable method (for example, a raw material slurry for a polymer gel electrolyte (also simply referred to as a pregel solution)) is applied to the vicinity of the central portion of the nonwoven fabric 4a (the inside surrounded by the electrolyte seal resin portion 4b) and polymerized and cured. To form a gel electrolyte portion 4c (see FIGS. 5 (E), (F) and (F ′)). As a result, the polymer gel electrolyte is held near the central portion of the nonwoven fabric 4a, and the outer periphery (electrolyte sealing resin portion 4b) of the portion (gel electrolyte portion 4c) of the same nonwoven fabric 4a holding the gel electrolyte is sealed with the electrolyte. Electrolyte layer 4 of the present invention having a structure in which a resin for use is held.
[0023]
In the present invention, an appropriate method (for example, a raw material polymer (solution) for an all solid polymer electrolyte) is applied to the outer peripheral portion of the nonwoven fabric 4a corresponding to the size used for the electrolyte layer instead of the electrolyte seal resin portion 4b. The electrolyte layer 4 may be manufactured using an all-solid polymer electrolyte portion 4b 'that does not contain a solution (electrolyte solution) formed by a method of applying and heating and drying.
[0024]
In the present invention, the electrolyte sealing resin portion 4b, the entirety of the electrolyte sealing resin portion 4b, and the like are hardly changed by impregnating the nonwoven fabric 4a with a resin for electrolyte sealing, a raw material polymer for all solid polymer electrolyte, a pregel solution or the like. The solid polymer electrolyte portion 4b 'and the gel electrolyte portion 4c may be formed (see FIGS. 5D and 5F), and the electrolyte sealing resin portion is made thicker than the thickness of the nonwoven fabric 4a. 4b, an all-solid polymer electrolyte portion 4b ', and a gel electrolyte portion 4c may be formed (see FIGS. 5 (D') and (F ')). In particular, when the thickness is made larger than the thickness of the nonwoven fabric 4a, the operation from the formation of the electrolyte sealing resin portion 4b and the all-solid polymer electrolyte portion 4b 'to the formation of the gel electrolyte portion 4c is repeated several times. There is no particular limitation, for example, the number may be increased, or a predetermined thickness may be obtained by a single operation using an appropriate thickness adjusting jig.
[0025]
The thickness of the polymer gel electrolyte layer is not particularly limited. However, in order to obtain a compact bipolar battery, it is preferable to make the battery as thin as possible as long as the function as the electrolyte layer can be secured. From such a viewpoint, the thickness of the polymer gel electrolyte layer of the present invention is about 5 to 200 μm.
[0026]
In the bipolar battery of the present invention using the polymer gel electrolyte 4, as shown in FIGS. 6 and 7, similarly to the conventional bipolar battery using the polymer gel electrolyte layer 4 '(see FIG. 11 for comparison). .), A positive electrode layer 2 is formed on one surface of the current collector 1 using a positive electrode material, and a negative electrode layer 3 is formed on the opposite surface using a negative electrode material to form a bipolar electrode 5. What is necessary is just to laminate with the layer 4 interposed. As a result, the electrolyte contained in the gel electrolyte portion 4c of the gel electrolyte layer 4 cannot move into the outer peripheral portion by the electrolyte seal resin portion 4b or the polymer solid electrolyte portion 4b 'on the outer peripheral portion, and cannot move to the outside. Can be effectively prevented from oozing out. Therefore, it is possible to provide a high-quality bipolar battery that does not come into contact with the electrolytic solution of the other unit cell layer 6 and has high safety without causing a short circuit (liquid junction).
[0027]
In particular, in the present invention, as shown in FIG. 8, the outer periphery (peripheral portion) of the electrolyte seal resin portion 4b or the solid polymer electrolyte portion 4b 'of the electrolyte layer 4 where the positive electrode layer 2 and the negative electrode layer 3 are not formed. It is particularly desirable that the length has a width of about 1 mm to 2 cm, preferably 5 mm to 1 cm. This is because, for example, as shown in FIG. 8, a preferable thickness of each unit cell layer 6 is about 100 to 200 μm. On the other hand, the general size of the electrode layers 2 and 3 is about 10 cm × 10 cm. Therefore, when the electrode layers 2 and 3 are stacked, the electrolyte sealing resin portion 4b or the polymer solid electrolyte portion 4b ′ on the outer peripheral portion (peripheral portion) of the electrolyte layer 4 is more intense than the positive electrode layer 2 and the negative electrode layer 3. By making it longer (wider), the outer peripheral portion (peripheral portion; see the portion circled in the drawing) of the electrolyte layer 4 where the positive electrode layer 2 and the negative electrode layer 3 are not formed. The electrolyte seal resin portion 4b or the solid polymer electrolyte portion 4b 'and the current collector 1 inevitably adhere to each other, and even if the electrolyte seeps out from the electrode layers 2, 3 side, this can be sealed. Therefore it is extremely useful. This is because the current collector 1 is inevitably adhered to the electrolyte seal resin portion 4b or the solid polymer electrolyte portion 4b 'at the outer peripheral portion (peripheral portion) of the electrolyte layer 4 by sealing with the battery exterior material. This is because a heavy load is applied. If necessary, the current collector 1 may be brought into close contact with the electrolyte sealing resin portion 4b or the solid polymer electrolyte portion 4b 'around the electrolyte layer 4 by applying appropriate pressure or the like. Good.
[0028]
Here, the nonwoven fabric (nonwoven fabric) 4a constituting the electrolyte layer 4 of the present invention is not particularly limited. In other words, any sheet may be used as long as the fibers are arranged in a web (thin cotton) or mat shape by an appropriate method, and are joined by an appropriate adhesive or the fusion force of the fibers themselves. The adhesive is not particularly limited as long as it has sufficient heat resistance at the temperature during production and use, and is stable without any reactivity or solubility even for the gel electrolyte. Instead, a conventionally known one can be used. The fibers used are not particularly limited, and for example, conventionally known fibers such as cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, and aramid can be used. Used alone or in combination depending on the mechanical strength required for the above). 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. That is, if the bulk density of the nonwoven fabric is too large, the proportion of the non-electrolyte material in the electrolyte layer becomes too large, which may impair the ionic conductivity and the like in the electrolyte layer.
[0029]
In FIG. 5, for convenience of explanation, a nonwoven fabric having the same size as the electrolyte layer is used. However, in actual production, a roll-shaped nonwoven fabric is used by using various printing / coating techniques or thin film forming techniques. Various mass production techniques may be applied, such as forming an electrolyte layer continuously on the nonwoven fabric, or using a larger nonwoven fabric to form a large amount of electrolyte layer at a time. be able to.
[0030]
In addition, the gel electrolyte constituting the electrolyte layer 4 (also simply referred to as a gel electrolyte) is not particularly limited, and a gel electrolyte used in a conventional gel electrolyte layer can be appropriately used. Here, the gel electrolyte refers to a gel electrolyte in which an electrolyte is held in a polymer matrix. In the present invention, the difference between an all solid polymer electrolyte (also simply referred to as a polymer solid electrolyte) and a gel electrolyte is as follows.
[0031]
A gel electrolyte containing an all-solid polymer electrolyte such as polyethylene oxide (PEO) and an electrolyte used in a normal lithium ion battery.
[0032]
-A polymer electrolyte such as polyvinylidene fluoride (PVDF) having no lithium ion conductivity and having an electrolyte retained therein is also a gel electrolyte.
[0033]
The ratio of the polymer constituting the gel electrolyte (also referred to as a host polymer or a polymer matrix) and the electrolyte is wide, and if 100% by weight of the polymer is an all solid polymer electrolyte and 100% by weight of the electrolyte is a liquid electrolyte, the intermediate Every body is a gel electrolyte.
[0034]
The host polymer of the gel electrolyte is not particularly limited, and a conventionally known host polymer can be used. Preferably, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG) is used. ), Polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) (PMMA) and copolymers thereof are desirable, and the solvent is ethylene carbonate (EC), propylene Carbonate (PC), gamma-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof are preferred.
[0035]
The electrolytic solution (electrolyte salt and plasticizer) of the gel electrolyte is not particularly limited, and conventionally known ones can be used. More specifically, it may be any one that is usually used in a lithium ion battery. ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ Acid anion salts such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ Cyclic carbonates such as propylene carbonate, ethylene carbonate and the like containing at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as N; chains such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; Esters such as methyl propionate; amides such as dimethylformamide; and organic solvents (plasticizers) such as aprotic solvents in which at least one or more selected from methyl acetate and methyl formate are mixed. You can use what you used However, it is not limited to these.
[0036]
The proportion of the electrolyte 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 and the like. The present invention is particularly effective for a gel electrolyte containing a large amount of an electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more.
[0037]
Further, in the present invention, the amount of the electrolytic solution contained in the gel electrolyte may be made substantially uniform inside the gel electrolyte as shown in FIG. 9, or may be gradually reduced from the center to the outer periphery. You may do. The former is preferable because reactivity can be obtained in a wider range, and the latter is preferable in that the sealing property of the all-solid polymer electrolyte portion 4b 'on the outer peripheral portion with respect to the electrolytic solution can be enhanced. When the concentration is gradually reduced from the center toward the outer periphery, polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof having lithium ion conductivity are used as the host polymer. It is desirable.
[0038]
Next, the resin for the electrolyte sealing constituting the electrolyte layer of the first embodiment is not particularly limited as long as it can seal the electrolyte solution (alkaline solution). A conventionally known sealing resin having a certain property can be used. Specifically, for example, it is desirable to use a resin selected from silicon, epoxy, urethane, polybutadiene, polypropylene, polyethylene, paraffin wax and the like. These resins have excellent sealing properties (liquid tightness), chemical resistance, durability / weather resistance, heat resistance, etc., can effectively prevent the electrolyte solution from seeping out of the gel electrolyte, This is because a liquid junction (short circuit) due to leakage can be prevented for a long time.
[0039]
The all solid polymer electrolyte constituting the electrolyte layer of the second embodiment is not particularly limited, and a conventionally known one can be used. Specifically, it is a layer composed of a polymer having ion conductivity, and the material is not limited as long as it exhibits ion conductivity. Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof. The solid polymer electrolyte contains a lithium salt in order to secure ion 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. However, it is not limited to these. Polyalkylene oxide polymers such as PEO and PPO are made of LiBF. ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ And other lithium salts. Further, by forming a crosslinked structure, excellent mechanical strength is exhibited.
[0040]
The ratio between the gel electrolyte portion near the center of the electrolyte layer and the electrolyte seal resin portion or the all solid polymer electrolyte portion at the outer periphery cannot be uniquely determined because the ratio varies depending on the material of the outer periphery. It is desirable in terms of battery characteristics that the portion be as small as possible within a range where a sealing effect can be obtained. Therefore, a sufficient sealing effect can be obtained if the width of the outer peripheral portion is about 1 mm to 1 cm even in consideration of the close contact with the current collector.
[0041]
The foregoing has been described mainly with respect to the electrolyte layer which is a component of the characteristic portion of the bipolar battery according to the present invention. However, other components of the bipolar battery according to the present invention are not particularly limited and are conventionally known. Is widely applicable to bipolar batteries.
[0042]
Hereinafter, each component of the bipolar battery of the present invention will be briefly described, but it goes without saying that the present invention should not be limited to these components.
[0043]
[Current collector]
The current collector that can be used in the present invention is not particularly limited, and a conventionally known current collector can be used. For example, aluminum foil, stainless steel foil, a clad material of nickel and aluminum, copper and aluminum Or a plating material of a combination of these metals is preferably used. Alternatively, a current collector in which aluminum is coated on a metal surface may be used. In some cases, a current collector in which two or more metal foils are bonded may be used. It is preferable to use an aluminum foil as a current collector from the viewpoints of corrosion resistance, ease of production, economy, and the like.
[0044]
The thickness of the current collector is not particularly limited, but is usually about 1 to 100 μm.
[0045]
[Positive electrode layer]
The positive electrode layer contains a positive electrode active material. In addition, a conductive auxiliary agent for improving electron conductivity, a lithium salt for improving ionic conductivity, a binder, a polymer electrolyte, and the like may be included, but when a polymer gel electrolyte is used for the polymer electrolyte layer, It is sufficient that the binder contains a conventionally known binder for binding the fine particles of the positive electrode active material, a conductive auxiliary agent for enhancing electron conductivity, and the like. It does not have to be included.
[0046]
Among these, as the positive electrode active material, a composite oxide of a transition metal and lithium (lithium-transition metal composite oxide), which is also used in a solution-based lithium ion battery, can be used. Specifically, LiCoO ₂ Li-Co based composite oxides such as LiNiO ₂ Li-Ni based composite oxide such as spinel LiMn ₂ O ₄ Li-Mn based composite oxides such as LiFeO ₂ Li.Fe-based composite oxides such as In addition, LiFePO ₄ Phosphoric acid compounds and sulfuric acid compounds of transition metals and lithium; ₂ O ₅ , MnO ₂ , TiS ₂ , MoS ₂ , MoO ₃ Transition metal oxides and sulfides such as PbO ₂ , AgO, NiOOH and the like.
[0047]
In order to reduce the electrode resistance of a bipolar battery, it is preferable to use a positive electrode active material having a particle size smaller than a particle size generally used in a solution type lithium ion battery. Specifically, the average particle diameter of the positive electrode active material fine particles is preferably 0.1 to 5 μm.
[0048]
Examples of the conductive assistant include acetylene black, carbon black, and graphite. However, it is not limited to these.
[0049]
As the binder, polyvinylidene fluoride (PVDF) or the like can be used. However, it is not limited to these.
[0050]
The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity, as defined above, containing an electrolyte solution usually used in lithium ion batteries. Also, those in which a similar electrolyte is held in a polymer skeleton having no polymer are also included.
[0051]
Here, the electrolyte solution (electrolyte salt and plasticizer) contained in the polymer gel electrolyte may be any one that is usually used in a lithium ion battery. For example, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ Acid anion salts such as LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ Cyclic carbonates such as propylene carbonate, ethylene carbonate and the like containing at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as N; chains such as dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate Ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; lactones such as γ-butyrolactone; nitriles such as acetonitrile; Esters such as methyl propionate; amides such as dimethylformamide; and organic solvents (plasticizers) such as aprotic solvents in which at least one or more selected from methyl acetate and methyl formate are mixed. You can use what you used However, it is not limited to these.
[0052]
Examples of the polymer having no lithium ion conductivity used for the polymer gel electrolyte include polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and polymethyl methacrylate (PMMA). it can. However, it is not limited to these. Since PAN, PMMA, and the like fall into the category of having little ionic conductivity, they can be the above-mentioned polymers having ionic conductivity, but are used here as polymer gel electrolytes. This is exemplified as a polymer having no lithium ion conductivity.
[0053]
Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiTaF ₆ , LiAlCl ₄ , Li ₂ B ₁₀ Cl ₁₀ Inorganic acid anion salts such as Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ Organic acid anions such as N, and mixtures thereof can be used. However, it is not limited to these.
[0054]
The ratio (mass ratio) between the host polymer and the electrolyte in the polymer gel electrolyte may be determined according to the purpose of use and the like, but is in the range of 2:98 to 90:10. In other words, as described with reference to FIG. 8, the leakage of the electrolytic solution from the outer periphery of the electrode layer is also effectively sealed by appropriately making the outer periphery of the gel electrolyte layer of the present invention longer than the end of the electrode. can do. Therefore, the battery characteristics can be given a relatively high priority also in the ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte.
[0055]
The amount of the positive electrode active material, conductive auxiliary agent, binder, polymer electrolyte (host polymer, electrolyte solution, etc.), and lithium salt in the positive electrode layer depends on the intended use of the battery (output-oriented, energy-oriented, etc.) and ionic conductivity. The decision should be taken into account. For example, if the blending amount of the polymer electrolyte in the positive electrode layer is too small, the ionic conduction resistance and the ionic diffusion resistance in the positive electrode layer increase, and the battery performance decreases. On the other hand, if the blending amount of the polymer electrolyte in the positive electrode layer is too large, the energy density of the battery decreases. Therefore, a polymer gel electrolysis mass that meets the purpose is determined in consideration of these factors.
[0056]
The thickness of the positive electrode layer is not particularly limited, and should be determined in consideration of the intended use of the battery (e.g., emphasis on output, energy, etc.) and ionic conductivity, as described for the blending amount. The thickness of a general positive electrode layer is about 10 to 500 μm.
[0057]
[Negative electrode layer]
The negative electrode layer contains a negative electrode active material active material. In addition, a conductive auxiliary agent for improving electron conductivity, a binder, a polymer electrolyte (such as a host polymer and an electrolyte), and a lithium salt for improving ionic conductivity may be included. In the case of using a polymer gel electrolyte, it is sufficient that a conventionally known binder that binds the negative electrode active material fine particles to each other, a conductive auxiliary agent for increasing electron conductivity, and the like are included, and a host polymer as a raw material of the polymer electrolyte is used. , Electrolyte and lithium salt may not be contained.
[0058]
Except for the type of the negative electrode active material, the content is basically the same as that described in the section of “Positive electrode layer”, and thus the description is omitted here.
[0059]
As the negative electrode active material, a negative electrode active material used in a solution-type lithium ion battery can be used. Specifically, carbon, a metal oxide, a lithium-metal composite oxide, or the like can be used, but carbon or a lithium-transition metal composite oxide is preferable. By using these, a battery excellent in capacity and output characteristics (for example, battery voltage can be increased) can be configured. As the lithium-transition metal composite oxide, for example, a lithium-titanium composite oxide or the like can be used. As the carbon, for example, graphite, graphite, acetylene black, carbon black, and the like can be used.
[0060]
[Polymer gel electrolyte layer]
The polymer gel electrolyte layer of the present invention, that is, (1) the polymer gel electrolyte is held near the center of the nonwoven fabric, and the resin for electrolyte sealing is placed on the outer periphery of the same nonwoven fabric holding the gel electrolyte. And (2) a polymer gel electrolyte held near the center of the nonwoven fabric, and an all-solid polymer on the outer periphery of the portion of the same nonwoven fabric holding the gel electrolyte. An electrolyte layer having a structure in which an electrolyte is held can be employed, and these are as described above.
[0061]
The electrolyte layers (1) and (2) may be used together in one battery.
[0062]
Further, the polymer electrolyte may be contained in the polymer gel electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer, but the same polymer electrolyte may be used, or different polymer electrolytes may be used depending on the layers. Good.
[0063]
Meanwhile, a host polymer for a polymer gel electrolyte which is preferably used at present is a polyether polymer such as PEO or PPO. For this reason, the oxidation resistance on the positive electrode side under high temperature conditions is weak. Therefore, when using a positive electrode agent having a high oxidation-reduction potential, which is generally used in a solution-based lithium ion battery, the capacity of the negative electrode is preferably smaller than the capacity of the positive electrode opposed via the polymer gel electrolyte layer. preferable. When the capacity of the negative electrode is smaller than the capacity of the opposed positive electrode, it is possible to prevent the positive electrode potential from excessively rising at the end of charging. In addition, the capacity of the positive electrode and the negative electrode can be obtained from the manufacturing conditions as a theoretical capacity at the time of manufacturing the positive electrode and the negative electrode. The capacity of the finished product may be measured directly by a measuring device.
[0064]
However, if the capacity of the negative electrode is smaller than the capacity of the opposite positive electrode, the potential of the negative electrode may be too low and the durability of the battery may be impaired. For example, the average charge voltage of one cell (single cell layer) is set to an appropriate value for the oxidation-reduction potential of the positive electrode active material to be used, and care is taken so that the durability does not decrease.
[0065]
[Insulating layer]
The insulating layer is formed around each electrode for the purpose of preventing current collectors from contacting each other, leaking out of the electrolytic solution, and short-circuiting due to slight irregularities at the ends of the stacked electrodes. Things.
[0066]
As the insulating layer, any material having an insulating property, a sealing property (sealing property) against leakage of an electrolyte solution or moisture permeation from the outside, heat resistance at a battery operating temperature, and the like may be used. Although rubber, polyethylene, polypropylene and the like can be used, epoxy resins are preferred from the viewpoints of corrosion resistance, chemical resistance, ease of production (film formation), economy, and the like.
[0067]
[Positive and negative terminal plates]
The positive and negative electrode terminal plates may be used as needed. When used, it is better to have as thin as possible from the viewpoint of thinning in addition to having the function as a terminal, but since the laminated electrodes, electrolyte and current collector all have low mechanical strength, It is desirable to have enough strength to sandwich and support from above. Further, from the viewpoint of suppressing the internal resistance at the terminal portion, it can be said that the thickness of the positive electrode and negative electrode terminal plates is usually preferably about 0.1 to 2 mm.
[0068]
As the material of the positive electrode terminal and the negative electrode terminal plate, a material usually used in a lithium ion battery can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), alloys thereof, and the like can be used. It is preferable to use aluminum from the viewpoints of corrosion resistance, ease of production, economy, and the like.
[0069]
The materials of the positive electrode terminal plate and the negative electrode terminal plate may be the same or different. Further, these positive and negative electrode terminal plates may be formed by laminating different materials from each other in multiple layers.
[0070]
The positive and negative electrode terminal plates may have the same size as the current collector.
[0071]
[Positive and negative electrode leads]
As the positive and negative electrode leads, known leads that are usually used in lithium ion batteries can be used. In addition, since the part taken out of 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 (especially electronic devices) by contacting them and causing a short circuit. It is preferable to coat with a heat-shrinkable heat-shrinkable tube or the like.
[0072]
[Battery exterior material (battery case)]
In order to prevent external shock and environmental degradation, the bipolar battery body must be entirely covered with a battery exterior material or battery case in order to prevent external impact and environmental degradation during use. (Not shown). From the viewpoint of weight reduction, a conventionally known battery package such as a polymer-metal composite laminate film or an aluminum laminate pack in which a metal (including an alloy) such as aluminum, stainless steel, nickel, or copper is coated with an insulator such as a polypropylene film. It is preferable that the battery laminate is housed and sealed by using a material and joining a part or all of its peripheral portion by heat fusion. In this case, the positive electrode and the negative electrode lead may have a structure sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, the use of a polymer-metal composite laminate film or aluminum laminate pack with excellent thermal conductivity allows the heat to be efficiently transmitted from the heat source of the vehicle and quickly heats the inside of the battery to the battery operating temperature. preferable.
[0073]
Next, in the present invention, an assembled battery formed by connecting a plurality of the above bipolar batteries can be provided. That is, by using at least two or more bipolar batteries of the present invention and connecting them in series and / or in parallel to form an assembled battery, it is possible to respond to the demand for battery capacity and output for each purpose of use relatively inexpensively. It becomes possible to do.
[0074]
Specifically, for example, the above-mentioned N bipolar batteries are connected in parallel, and N parallel bipolar batteries are further connected in series to be stored in a metal or resin battery pack case to form a battery pack. . At this time, the number of series / parallel connected bipolar batteries is determined according to the purpose of use. For example, a large-capacity power supply such as an electric vehicle (EV) or a hybrid electric vehicle (HEV) may be combined so as to be applicable to a driving power supply of a vehicle requiring a high energy density and a high output density. Further, the positive electrode terminal and the negative electrode terminal for the assembled battery and the electrode lead of each bipolar battery may be electrically connected using a lead wire or the like. When the bipolar batteries are connected in series / parallel, they may be electrically connected using a suitable connecting member such as a spacer or a bus bar. However, the battery pack of the present invention should not be limited to the battery described here, and a conventionally known battery can be appropriately used. In addition, the assembled battery may be provided with various measuring devices and control devices according to the intended use, for example, a voltage measuring connector or the like may be provided to monitor the battery voltage. There is no particular limitation.
[0075]
According to the present invention, a vehicle equipped with the bipolar battery and / or the assembled battery as a driving power source can be provided. The bipolar battery and / or assembled battery of the present invention has various characteristics as described above, and is particularly a compact battery. For this reason, it is suitable as a power source for driving vehicles that have particularly strict requirements regarding energy density and output density, for example, electric vehicles and hybrid electric vehicles. For example, as shown in FIG. 10, it is convenient to mount the battery pack 13 as a drive power source under a seat at the center of the body of an electric vehicle or a hybrid electric vehicle 15 because the internal space and the trunk room can be widened. However, the present invention is not limited to these, and may be mounted at the lower part of the rear trunk room, or if the engine is not mounted like an electric vehicle, the engine at the front of the vehicle body is mounted. It can also be mounted on parts that were used. In the present invention, not only the battery pack 13 but also a bipolar battery may be mounted depending on the intended use, or these battery packs 13 and the bipolar battery may be mounted in combination. Further, as the vehicle on which the bipolar battery and / or the assembled battery of the present invention can be mounted as a driving power source, the above-described electric vehicle or hybrid electric vehicle is preferable, but is not limited thereto.
[0076]
The method for manufacturing the bipolar battery of the present invention is not particularly limited, and various conventionally known methods can be appropriately used. The following is a brief description. However, the method for manufacturing the polymer gel electrolyte layer is the same as that described with reference to FIG. 5, and a description thereof will not be repeated.
[0077]
(1) Application of positive electrode composition
First, an appropriate current collector is prepared. The positive electrode composition is usually obtained as a slurry (positive electrode slurry), and is applied to one surface of the current collector.
[0078]
The positive electrode slurry is a solution containing a positive electrode active material. Other components include a conductive auxiliary agent, a binder, a polymerization initiator, a raw material of a polymer gel electrolyte (a host polymer, an electrolyte solution, and the like), and a lithium salt. When used, it is sufficient that a conventionally known binder for binding the fine particles of the positive electrode active material, a conductive auxiliary agent for increasing electron conductivity, a solvent, and the like are included, and a host polymer as a raw material of the polymer gel electrolyte, an electrolyte solution And lithium salts may not be contained.
[0079]
Examples of the raw material of the polymer gel electrolyte include PEO, PPO, and a copolymer thereof, and the polymer gel electrolyte preferably has a crosslinkable functional group (such as a carbon-carbon double bond) in the molecule. By cross-linking the polymer gel electrolyte using this cross-linkable functional group, the mechanical strength is improved.
[0080]
As for the positive electrode active material, the conductive additive, the binder, and the lithium salt, the compounds described above can be used.
[0081]
The polymerization initiator needs to be selected according to the compound to be polymerized. For example, benzyldimethyl ketal is used as a photopolymerization initiator, and azobisisobutyronitrile is used as a thermal polymerization initiator.
[0082]
The solvent such as NMP is selected according to the type of the positive electrode slurry.
[0083]
The amounts of the positive electrode active material, the lithium salt, and the conductive additive may be adjusted according to the purpose of the bipolar battery or the like, and may be generally used. The amount of the polymerization initiator to be added is determined according to the number of crosslinkable functional groups contained in the polymer material. Usually, it is about 0.01 to 1% by mass relative to the polymer raw material.
[0084]
(2) Formation of positive electrode layer
The current collector coated with the positive electrode slurry is dried to remove the contained solvent. At the same time, depending on the slurry for the positive electrode, a cross-linking reaction may be advanced to increase the mechanical strength of the solid polymer electrolyte. For drying, a vacuum dryer or the like can be used. Drying conditions are determined according to the applied slurry for the positive electrode and cannot be uniquely defined, but are usually from 40 to 150 ° C. for 5 minutes to 20 hours.
[0085]
(3) Application of composition for negative electrode
A negative electrode composition (negative electrode slurry) containing a negative electrode active material is applied to the surface opposite to the surface on which the positive electrode layer is applied.
[0086]
The negative electrode slurry is a solution containing a negative electrode active material. As other components, a conductive auxiliary, a binder, a polymerization initiator, a raw material (a host polymer, an electrolytic solution, and the like) of a polymer gel electrolyte, a lithium salt, and the like are optionally included. The raw materials used and the amounts added are the same as those described in the section of “(1) Application of positive electrode composition”, and thus description thereof is omitted here.
[0087]
(4) Formation of negative electrode layer
The current collector coated with the negative electrode slurry is dried to remove the contained solvent. At the same time, depending on the slurry for the negative electrode, the crosslinking reaction may be advanced to increase the mechanical strength of the polymer gel electrolyte. By this operation, a bipolar electrode is completed. For drying, a vacuum dryer or the like can be used. The drying conditions are determined according to the applied slurry for the negative electrode, and cannot be uniquely defined, but are usually at 40 to 150 ° C. for 5 minutes to 20 hours.
[0088]
(5) Lamination of bipolar electrode and polymer gel electrolyte layer
Separately, a polymer gel electrolyte layer to be laminated between the electrodes is prepared. The polymer gel electrolyte layer may be prepared by the procedure already described with reference to FIG.
[0089]
After sufficiently heating and drying the bipolar electrode produced as described above under a high vacuum, a plurality of bipolar electrodes and a plurality of polymer gel electrolyte layers are cut into appropriate sizes. The width of the polymer gel electrolyte layer is often slightly smaller than the current collector size of the bipolar electrode (see FIG. 8). A predetermined number of the cut-out bipolar electrodes and polymer gel electrolyte are attached to each other to produce a bipolar battery body (battery laminate). The number of layers is determined in consideration of battery characteristics required for a bipolar battery. A bipolar electrode having a polymer gel electrolyte layer formed on one or both sides may be directly bonded. Electrodes are arranged on the outermost polymer gel electrolyte. In the outermost layer on the positive electrode side, an electrode in which only the positive electrode layer is formed on the current collector is arranged. In the outermost layer on the negative electrode side, an electrode in which only the negative electrode layer is formed on the current collector is arranged. The step of obtaining a bipolar battery by laminating a bipolar electrode and a polymer gel electrolyte is preferably performed in an inert atmosphere. For example, a bipolar battery is preferably manufactured in an argon atmosphere or a nitrogen atmosphere.
[0090]
(6) Packing (completion of battery)
Finally, a positive electrode terminal plate and a negative electrode terminal plate are respectively disposed on both outermost electron conductive layers of the bipolar battery body (battery laminate), and a positive electrode lead and a negative electrode lead are further provided on the positive electrode terminal plate and the negative electrode terminal plate. Are joined (electrically connected) and taken out. The method for joining the positive electrode lead and the negative electrode lead is not particularly limited, but ultrasonic welding or the like having a low joining temperature can be suitably used, but is not limited to this. A known joining method can be appropriately used.
[0091]
The entire battery stack is sealed with a battery exterior material or a battery case in order to prevent external impact and environmental degradation, thereby completing a bipolar battery. The material of the battery exterior material (battery case) is preferably a metal (aluminum, stainless steel, nickel, copper, or the like) whose inner surface is covered with an insulator such as a polypropylene film.
[0092]
【Example】
The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.
[0093]
Example 1 (example of the first embodiment)
<Formation of electrode>
1. Positive electrode layer
Spinel LiMn having an average particle diameter of 2 μm as a positive electrode active material ₂ O ₄ [85% by mass], acetylene black [5% by mass] as a conductive aid, PVDF [10% by mass] as a binder, and N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent (NMP is (Because it is removed by volatilization, an appropriate amount was added so as to obtain an appropriate slurry viscosity instead of the constituent material of the electrode.) A material composed of the above ratio (indicated by a ratio converted by a component excluding the slurry viscosity adjusting solvent). To prepare a positive electrode slurry.
[0094]
The positive electrode slurry was applied to one surface of a SUS foil (thickness: 20 μm) as a current collector, placed in a vacuum oven, and dried at 120 ° C. for 10 minutes to form a positive electrode layer having a dry thickness of 50 μm.
[0095]
2. Negative electrode layer
Li as negative electrode active material ₄ Ti ₅ O ₁₂ [85% by mass], acetylene black [5% by mass] as a conductive additive, PVDF [10% by mass] as a binder, and NMP (an appropriate amount was added so as to obtain an appropriate slurry viscosity) as a slurry viscosity adjusting solvent. The negative electrode slurry was prepared by mixing the materials in the above-described ratio (the ratio was calculated in terms of components excluding the slurry viscosity adjusting solvent). In addition, Li used for the negative electrode active material was used. ₄ Ti ₅ O ₁₂ Has an average particle size of 10 μm, and has a structure in which primary particles of 0.2 to 0.5 μm are necked to some extent.
[0096]
The negative electrode slurry was applied to the opposite surface of the SUS foil on which the positive electrode layer was formed, placed in a vacuum oven, and dried at 120 ° C. for 10 minutes to form a negative electrode layer having a dry thickness of 50 μm.
[0097]
A bipolar electrode was formed by forming a positive electrode layer and a negative electrode layer on both sides of a SUS foil as a current collector (see FIG. 1).
[0098]
<Formation of seal part>
Four sides of an outer peripheral portion of a 50 μm-thick polypropylene nonwoven fabric were immersed in an epoxy resin as a resin for electrolyte sealing with a width of 10 cm from the outer edge, and then the epoxy resin was cured to form an electrolyte seal portion. (See FIG. 5C).
[0099]
<Formation of gel electrolyte layer>
As a raw material for the gel electrolyte, a copolymer of polyethylene oxide and polypropylene oxide (copolymerization ratio: 5: 1, weight average) as a raw material for the gel electrolyte, inside the non-woven fabric having an electrolyte seal portion formed on the outer periphery. [5% by mass], EC + DMC (EC: DMC (volume ratio) = 1: 3) as an electrolyte, and 1.0 M Li (C) as a lithium salt (supporting salt). ₂ F ₅ SO ₂ ) ₂ N (the total amount of the electrolyte and the lithium salt was 95% by mass. The amount of the lithium salt was 1.0 M with respect to the electrolyte). 1% by mass), and thermally polymerized at 90 ° C. for 1 hour in an inert atmosphere to hold the gel electrolyte at the center of the nonwoven fabric to form a gel electrolyte layer (FIG. 5 ( See E)). The thickness of the obtained gel electrolyte layer was 50 μm, which was not thicker than the nonwoven fabric.
[0100]
<Formation of bipolar battery>
The bipolar electrode and a gel electrolyte layer as an electrolyte-retaining nonwoven fabric were laminated so that the positive electrode layer and the negative electrode layer of the electrode sandwiched the gel electrolyte layer.
[0101]
After laminating five layers (equivalent to five cells), the battery laminate was sealed with a laminate pack (aluminum laminated with a polypropylene film; battery exterior material) to form a bipolar battery.
[0102]
Example 2 (example of the second embodiment)
<Formation of electrode>
1. Positive electrode layer
Spinel LiMn having an average particle diameter of 2 μm as a positive electrode active material ₂ O ₄ [85% by mass], acetylene black [5% by mass] as a conductive aid, PVDF [10% by mass] as a binder, and N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent (to obtain an appropriate slurry viscosity) Was mixed in the above ratio (showing a ratio converted by a component excluding the solvent for adjusting the slurry viscosity) to prepare a positive electrode slurry.
[0103]
The positive electrode slurry was applied to one surface of a SUS foil (thickness: 20 μm) as a current collector, placed in a vacuum oven, and dried at 120 ° C. for 5 minutes to form a positive electrode layer having a dry thickness of 50 μm.
[0104]
2. Negative electrode layer
Li as negative electrode active material ₄ Ti ₅ O ₁₂ [85% by mass], acetylene black [5% by mass] as a conductive additive, PVDF [10% by mass] as a binder, and NMP (an appropriate amount was added so as to obtain an appropriate slurry viscosity) as a slurry viscosity adjusting solvent. The negative electrode slurry was prepared by mixing the materials in the above-described ratio (the ratio was calculated in terms of components excluding the slurry viscosity adjusting solvent). In addition, Li used for the negative electrode active material was used. ₄ Ti ₅ O ₁₂ Has an average particle size of 10 μm, and has a structure in which primary particles of 0.2 to 0.5 μm are necked to some extent.
[0105]
The negative electrode slurry was applied to the opposite surface of the SUS foil on which the positive electrode layer was formed, placed in a vacuum oven, and dried at 120 ° C. for 5 minutes to form a negative electrode layer having a dry thickness of 50 μm.
[0106]
A bipolar electrode was formed by forming a positive electrode layer and a negative electrode layer on both sides of a SUS foil as a current collector (see FIG. 1).
[0107]
<Formation of all solid electrolyte part>
Li (C) is used as a supporting salt on the outer periphery of a 50 μm-thick polypropylene nonwoven fabric. ₂ F ₅ SO ₂ ) ₂ Polymer (copolymer of polyethylene oxide and polypropylene oxide) containing N [28% by mass] and an organic peroxide (specifically, t-hexylperoxypiparate) [0.7% by mass] as a polymerization initiator (A material having a copolymerization ratio of 5: 1 and a weight-average molecular weight of 8000 was used.) A material for an all-solid electrolyte was immersed in a width of 10 mm from the outer periphery and dried by heating at 80 ° C. for 10 hours in a vacuum atmosphere. Simultaneously, polymerization (acceleration of the cross-linking reaction) was carried out to form an all solid electrolyte portion (see FIG. 5C).
[0108]
<Formation of gel electrolyte layer>
As a raw material for a gel electrolyte, a copolymer of polyethylene oxide and polypropylene oxide (copolymerization ratio: 5: 1, as a host polymer) as a raw material for a gel electrolyte of a nonwoven fabric having an all solid electrolyte portion formed on the outer peripheral portion. [5% by mass], EC + DMC (EC: DMC (volume ratio) = 1: 3) as an electrolytic solution, and 1.0 M Li (as a lithium salt (supporting salt)) C ₂ F ₅ SO ₂ ) ₂ N (the total amount of the electrolyte and the lithium salt was 95% by mass. The amount of the lithium salt was 1.0 M with respect to the electrolyte). 1% by mass] to form a gel electrolyte layer (see FIG. 5E). The thickness of the obtained gel electrolyte layer was 50 μm, which was not thicker than the nonwoven fabric.
[0109]
<Formation of bipolar battery>
The bipolar electrode and a gel electrolyte layer as an electrolyte-retaining nonwoven fabric were laminated so that the positive electrode layer and the negative electrode layer of the electrode sandwiched the gel electrolyte layer.
[0110]
After laminating five layers (equivalent to five cells), the battery laminate was sealed with a laminate pack (aluminum laminated with a polypropylene film; battery exterior material) to form a bipolar battery.
[0111]
Comparative Example 1
After laminating 5 layers (for 5 single battery layers) in the same manner as in Example 1 except that a gel electrolyte layer having no electrolyte seal portion was used as Comparative Example 1, a battery pack was laminated with a laminate pack (aluminum made of polypropylene film). (A battery exterior material) to form a bipolar battery (see FIG. 11).
[0112]
<Evaluation>
Each of the batteries of Examples 1 and 2 and Comparative Example 1 was subjected to a charge / discharge cycle test. The charge / discharge cycle test was performed at 25 ° C., and the charge / discharge current value was 0.5 CA.
[0113]
In the battery of Comparative Example 1 having no electrolyte seal portion, during the initial charging, the electrolyte oozes out of the unit cell layer and comes into contact with the electrolyte of another unit cell layer to cause a liquid junction, Battery voltage dropped significantly.
[0114]
In the bipolar batteries of Examples 1 and 2 having another electrolyte sealing layer, it was confirmed that the voltage of each unit cell layer was maintained even after more than 50 cycles, and no liquid junction occurred.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view schematically showing a basic structure of a bipolar electrode constituting a bipolar battery of the present invention.
FIG. 2 is a schematic cross-sectional view schematically showing a basic structure of a unit cell layer (single cell) constituting the bipolar battery of the present invention.
FIG. 3 is a schematic sectional view schematically showing a basic structure of a bipolar battery of the present invention.
FIG. 4 is a schematic diagram schematically showing a basic configuration of a bipolar battery of the present invention.
FIG. 5 is a schematic plan view and a schematic cross-sectional view schematically showing a state of a manufacturing process of a typical electrolyte layer used in the bipolar battery of the present invention. FIG. 5A is a schematic plan view illustrating a nonwoven fabric that is a base material of an electrolyte layer before production. FIG. 5B is a schematic cross-sectional view along the line AA in FIG. FIG. 5C is a schematic plan view schematically showing a state of a process of manufacturing an electrolyte layer at a stage where an electrolyte sealing resin portion or an all-solid polymer electrolyte portion is formed on an outer peripheral portion of a nonwoven fabric. FIGS. 5D and 5D ′ are schematic cross-sectional views taken along line BB of FIG. 5C. FIG. 5E is a schematic plan view schematically showing a state in which a gel electrolyte portion is formed near the center of the nonwoven fabric to complete the electrolyte layer. FIGS. 5F and 5F ′ are schematic cross-sectional views taken along line CC of FIG. 5E.
FIG. 6 is a schematic cross-sectional view schematically illustrating a basic structure of a bipolar battery using the polymer gel electrolyte (first embodiment) of the present invention.
FIG. 7 is a schematic cross-sectional view schematically showing a basic structure of a bipolar battery using the polymer gel electrolyte (second embodiment) of the present invention.
FIG. 8 is a schematic cross-sectional view schematically illustrating a structure near an outer peripheral portion of an electrode laminate (part) constituting a bipolar battery of the present invention.
FIG. 9 is a schematic plan view schematically showing a typical electrolyte layer used in the bipolar battery of the present invention. FIG. 9B shows the amount of electrolyte contained in the electrolyte layer in FIG. 2) is a drawing displayed along the line AA.
FIG. 10 is a schematic diagram schematically showing a vehicle equipped with a bipolar battery and / or a battery pack according to the present invention as a driving power supply.
FIG. 11 is a schematic sectional view schematically showing the basic structure of a bipolar battery of the present invention using a conventional polymer gel electrolyte.
[Explanation of symbols]
1 ... current collector (metal foil)
2 ... Positive electrode layer,
3: Negative electrode layer,
4 ... Electrolyte layer (electrolyte membrane),
4a: non-woven fabric,
4b: electrolyte sealing resin part,
4b ': all solid polymer electrolyte part,
4c: gel electrolyte part,
4 ': polymer gel electrolyte layer,
5 ... Bipolar electrode,
5a: an electrode having a positive electrode layer disposed only on one required surface of the current collector;
5b: an electrode in which a negative electrode layer is arranged on only one required surface of the current collector,
6 ... unit cell layer (single cell),
7 ... electrode laminate,
8 Positive electrode lead,
9 ... negative electrode lead,
10. Battery exterior material,
11. Bipolar lithium ion secondary battery,
13 ... battery pack,
15 Vehicle (electric vehicle or hybrid electric vehicle).

Claims (6)

In a bipolar battery in which a positive electrode is formed on one surface of a current collector and a bipolar electrode having a negative electrode formed on the other surface, a plurality of bipolar electrodes are stacked in series with an electrolyte layer interposed therebetween.
The electrolyte layer has a structure in which a polymer gel electrolyte is held in the vicinity of a central portion of the nonwoven fabric, and a resin for electrolyte sealing is held in an outer peripheral portion of a portion of the same nonwoven fabric holding the gel electrolyte. Features a bipolar battery. The bipolar battery according to claim 1, wherein a resin selected from silicone, epoxy, urethane, polybutadiene, polypropylene, polyethylene, and paraffin wax is used as the resin for the electrolyte seal. In a bipolar battery in which a positive electrode is formed on one surface of a current collector and a bipolar electrode having a negative electrode formed on the other surface, a plurality of bipolar electrodes are stacked in series with an electrolyte layer interposed therebetween.
The electrolyte layer has a structure in which a polymer gel electrolyte is held near the center of the nonwoven fabric, and the same nonwoven fabric has a structure in which an all-solid polymer electrolyte is held on the outer periphery of the portion holding the gel electrolyte. Features a bipolar battery. Using a lithium-transition metal composite oxide as the positive electrode active material,
The bipolar battery according to any one of claims 1 to 3, wherein carbon or a lithium-transition metal composite oxide is used as the negative electrode active material. An assembled battery comprising a plurality of the bipolar batteries according to claim 1 connected to each other. A vehicle comprising the bipolar battery according to claims 1 to 4 and / or the assembled battery according to claim 5 as a driving power supply.

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