JP4258204B2 - Bipolar battery - Google Patents

Description

[0001]
BACKGROUND 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. More specifically, the present invention relates to a polymer gel electrolyte having excellent ionic conductivity as compared with a polymer solid electrolyte. The present invention relates to a bipolar battery used.
[0002]
[Prior art]
In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion secondary battery that can achieve a high energy density and a high output density. However, in order to apply to an automobile, it is necessary to use a plurality of secondary batteries connected in series in order to ensure a large output.
[0003]
However, when a battery is connected via the connection portion, the output is reduced due to the electrical resistance of the connection portion. Further, the battery having the connection portion has a disadvantage in terms of space. That is, the connection portion causes a reduction in 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 these, a bipolar battery using a polymer solid electrolyte containing no solution as an electrolyte has been proposed (see, for example, Patent Document 1). According to this, since the battery (electrolytic solution) is not included in the battery, there is no worry of liquid leakage or gas generation, and it is possible to provide a bipolar battery that is highly reliable and does not require a hermetic seal structurally. is there. However, the ionic conductivity of solid polymer electrolytes is lower than that of gel electrolytes. Under normal conditions of use, the output density and energy density of the battery are not sufficient, and the practical use stage has not been reached. Improvement of ionic conductivity is expected.
[0006]
On the other hand, a bipolar battery using an electrolyte having an electrolytic solution has been proposed (see, for example, 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 that is closest to the practical application stage because it has excellent ionic conductivity and sufficient battery output density and energy density.
[0007]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-1000047
[Patent Document 2]
JP 2002-75455 A
[Patent Document 3]
JP-A-11-204136
[0008]
[Problems to be solved by the invention]
However, when a bipolar battery is constructed using a gel electrolyte, there is a possibility that the electrolyte solution oozes out from the electrolyte portion and comes into contact with the electrolyte of another single cell layer, resulting in a liquid junction (short circuit).
[0009]
Accordingly, an object of the present invention is to provide a highly reliable bipolar battery in a bipolar battery using a gel electrolyte by preventing a liquid junction (short circuit) due to leakage of the electrolyte from the electrolyte. .
[0010]
[Means for Solving the Problems]
The present invention provides a bipolar lithium ion secondary battery in which a plurality of bipolar electrodes each having a positive electrode formed on one surface of a current collector and a negative electrode formed on the other surface 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 the center of the nonwoven fabric, and an electrolyte sealing resin is held in the outer peripheral portion of the same nonwoven fabric where the gel electrolyte is held,
The outer peripheral edge of the electrolyte sealing resin is located on the outer side (of the nonwoven fabric) from the outer peripheral edges of the positive electrode and the negative electrode. This is a bipolar battery.
[0011]
【The invention's effect】
In the bipolar battery of the present invention, the structure of the electrolyte layer is such that the gel electrolyte is held in a non-woven fabric, and an electrolyte sealing resin is immersed in the outer periphery of the same non-woven fabric to form an electrolyte seal portion. A liquid junction (short circuit) due to leakage of the electrolyte can be easily and effectively prevented. Moreover, the battery manufacturing process is greatly simplified by configuring the electrolyte seal portion integrally with the polymer gel electrolyte. That is, in order to prevent self-discharge due to liquid junction (short circuit) between the unit cell layers, it may be possible to form a new insulator layer around the outer periphery of the unit cell layer to have a sealing property against the electrolyte, The structure and manufacturing process of the bipolar battery are complicated or complicated. On the other hand, the bipolar battery of the present invention can prevent liquid junction between the single cell layers without providing a special member, is excellent in ion conductivity, and compact in battery characteristics such as charge / discharge characteristics. A bipolar battery can be provided. Therefore, it is highly reliable and can maintain an excellent energy density and output density, which makes it a useful power source in various industries.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0013]
A 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 negative electrode is formed on the other surface, and a plurality of bipolar electrodes stacked in series with an electrolyte interposed therebetween.
(1) 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 an electrolyte sealing resin is held in the outer peripheral portion of the same nonwoven fabric where the gel electrolyte is held. Characterized by having (first embodiment), and / or
(2) The electrolyte layer has a structure in which the polymer gel electrolyte is held in the vicinity of the center of the nonwoven fabric, and the whole solid polymer electrolyte is held in the outer peripheral portion of the same nonwoven fabric where the gel electrolyte is held. It is characterized by having (2nd embodiment).
[0014]
In the first embodiment, an electrolyte seal portion (portion where a resin for electrolyte seal is held) can be easily formed at the time of battery production (electrode lamination), and a liquid junction due to leakage of the electrolyte ( Short circuit) can be prevented. Moreover, a battery manufacturing process is simplified by comprising an electrolyte seal part integrally with a gel electrolyte.
[0015]
In the second embodiment, the all-solid polymer electrolyte in the outer peripheral portion can prevent the internal gel electrolyte from leaking out and can prevent a liquid junction (short circuit) due to leakage of the electrolyte. . In addition, it is advantageous in that the battery reaction is possible even in the all solid polymer electrolyte portion of the outer peripheral portion.
[0016]
1-4, the basic configuration of the bipolar battery according to the present invention will be briefly described with reference to the drawings. Among these, FIG. 1 shows a schematic cross-sectional view schematically showing the structure of the bipolar electrode constituting the bipolar battery, and FIG. 2 schematically showing the structure of the single cell layer constituting the bipolar battery. FIG. 3 is a schematic cross-sectional view schematically showing the overall structure of the bipolar battery. FIG. 4 shows a plurality of unit cell layers stacked in the bipolar battery connected in series. A schematic diagram conceptually representing this (symbolized) is shown.
[0017]
1-4, the bipolar electrode 5 (refer FIG. 1) which provided the positive electrode layer 2 in the one surface of the collector 1 and provided the negative electrode layer 3 in the other surface was made into 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 disposed via the electrolyte layer 4. The electrode laminate (bipolar battery main body) 7 having a laminated structure is formed. The uppermost and lowermost electrodes 5a and 5b have a structure in which an electrode layer (positive electrode layer 2 or negative electrode layer 3) of only one side necessary for the current collector 1 (or terminal plate) is formed instead of the bipolar electrode structure. Yes.
[0018]
In addition, the uppermost layer and the lowermost layer electrodes 5a and 5b of the electrode laminate 7 in which a plurality of such bipolar electrodes 5 and the like are laminated may not have a bipolar electrode structure, and are necessary for the current collector 1 (or terminal plate). It is good also as a structure which has arrange | positioned the electrode layer (the positive electrode layer 2 or the negative electrode layer 3) of only one side (refer FIG. 3). In the bipolar battery 11, positive and negative electrode leads 8 and 9 are joined to the current collectors 1 at both upper and lower ends, respectively.
[0019]
The number of stacked bipolar electrodes is adjusted according to the desired voltage. If sufficient output can be ensured even if the thickness of the sheet-like battery is made as thin as possible, the number of laminated 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 portion is sealed under reduced pressure in a battery exterior material (exterior package) 10, and electrode leads 8, It is preferable that 9 be taken out of the battery exterior material (exterior package) 10 (see FIGS. 3 and 4). From the viewpoint of weight reduction, a conventionally known battery 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, or copper is covered with an insulator such as a polypropylene film. By using an exterior material, a part or all of the peripheral part thereof is joined by thermal fusion so that the electrode laminate 7 is accommodated and sealed (sealed) under reduced pressure. It is preferable that the configuration is 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 single battery 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 / discharging is mediated by movement of lithium ions. However, as long as effects such as improvement of battery characteristics can be obtained, application to other types of batteries is not prevented.
[0021]
In a conventional bipolar battery using a polymer gel electrolyte layer, as shown in FIG. 11, a positive electrode layer 2 is formed using one type of positive electrode material on one side of a current collector 1, and one type is provided on the opposite side. The negative electrode layer 3 is formed using the negative electrode material to form the bipolar electrode 5, which are stacked with the polymer gel electrolyte (layer) 4 ′ interposed therebetween. Therefore, the electrolytic solution contained in the polymer gel electrolyte oozes out and comes into contact with the electrolytic solution of the other unit cell layer 6, which may cause a short circuit (liquid junction). However, in the present invention, conventional problems can be solved by forming an electrolyte layer as will be described below with reference to the drawings. Here, FIG. 5 is a schematic plan view and a schematic cross-sectional view schematically showing a manufacturing process of 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 formed on the outer peripheral portion of the nonwoven fabric 4 a corresponding to the size used for the electrolyte layer (see FIGS. 5A and 5B). The electrolyte seal resin portion 4b is formed by an appropriate method (for example, a method of applying a resin (solution) for electrolyte sealing and drying and curing) (FIGS. 5C, 5D, 5D). )checking). Next, an appropriate method (for example, a raw material slurry for polymer gel electrolyte (also simply referred to as a pregel solution) is applied to the vicinity of the center of the nonwoven fabric 4a (inside the area surrounded by the electrolyte seal resin portion 4b), and polymerization hardening The gel electrolyte part 4c is formed by a method (see FIGS. 5E, 5F, and 5F ′). As a result, the polymer gel electrolyte is held near the center of the nonwoven fabric 4a, and an electrolyte seal is applied to the outer peripheral portion (electrolyte sealing resin portion 4b) of the same nonwoven fabric 4a that holds the gel electrolyte (gel electrolyte portion 4c). The electrolyte layer 4 of the present invention having a structure in which a resin for use is held can be produced.
[0023]
In the present invention, instead of the electrolyte seal resin portion 4b, an appropriate method (for example, a raw 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. The electrolyte layer 4 may be produced by using the all solid polymer electrolyte part 4b ′ which does not contain a solution (electrolytic solution) formed by a method such as coating and drying by heating.
[0024]
In the present invention, the non-woven fabric 4a is impregnated with a resin for electrolyte sealing, a raw polymer for all solid polymer electrolyte, a pregel solution, or the like, so that the thickness of the non-woven fabric 4a is hardly changed. The solid polymer electrolyte portion 4b ′ and the gel electrolyte portion 4c may be formed (see FIGS. 5D and 5F), or the electrolyte seal resin portion so as to be thicker than the thickness of the nonwoven fabric 4a. 4b, an all solid polymer electrolyte part 4b ′, and a gel electrolyte part 4c may be formed (see FIGS. 5D ′ and 5F ′). In particular, when the thickness is made thicker than that of the nonwoven fabric 4a, the thickness of the electrolyte sealing resin portion 4b and the all solid polymer electrolyte portion 4b ′ from the formation to the gel electrolyte portion 4c is repeated several times. There is no particular limitation such that the predetermined thickness 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 it as thin as possible as long as the function as the electrolyte layer can be secured. From this viewpoint, the thickness of the polymer gel electrolyte layer of the present invention is about 5 to 200 μm.
[0026]
As shown in FIGS. 6 and 7, the bipolar battery of the present invention using the polymer gel electrolyte 4 is similar to the bipolar battery using the conventional polymer gel electrolyte layer 4 ′ (see FIG. 11 for comparison). .), The positive electrode layer 2 is formed on one surface of the current collector 1 using the positive electrode material, the negative electrode layer 3 is formed on the opposite surface using the negative electrode material, and the bipolar electrode 5 is formed. What is necessary is just to laminate | stack on both sides of the layer 4. As a result, the electrolyte contained in the gel electrolyte part 4c of the gel electrolyte layer 4 cannot be moved into the outer peripheral part by the electrolyte seal resin part 4b or the polymer solid electrolyte part 4b 'on the outer peripheral part, Can be effectively prevented. Therefore, it is possible to provide a high-quality bipolar battery having high safety without coming into contact with the electrolyte solution of the other single battery layer 6 and without causing a short circuit (liquid junction).
[0027]
In particular, in the present invention, as shown in FIG. 8, the electrolyte seal resin portion 4b or the polymer solid electrolyte portion 4b ′ in the outer peripheral portion (peripheral portion) of the electrolyte layer 4 in which the positive electrode layer 2 and the negative electrode layer 3 are not formed. It is particularly desirable to have a length of about 1 mm to 2 cm, preferably 5 mm to 1 cm. For example, as shown in FIG. 8, the preferred thickness of each single 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 laminated, the electrolyte seal resin portion 4b or the polymer solid electrolyte portion 4b ′ on the outer peripheral portion (peripheral portion) of the electrolyte layer 4 is more than the positive electrode layer 2 and the negative electrode layer 3 described above. The outer peripheral portion (periphery) of the electrolyte layer 4 in which the positive electrode layer 2 and the negative electrode layer 3 are not formed is made long (wide). Part) The electrolyte seal resin part 4b or the polymer solid electrolyte part 4b ′ and the current collector 1 are in intimate contact with each other, and even when the electrolyte solution oozes out from the electrode layers 2 and 3 side, it can be sealed. Therefore, it is extremely useful. This is because the electrolyte seal resin portion 4b or the polymer solid electrolyte portion 4b ′ on the outer peripheral portion (peripheral portion) of the electrolyte layer 4 and the current collector 1 are necessarily in close contact with each other 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 seal resin portion 4b or the polymer solid electrolyte portion 4b ′ around the electrolyte layer 4 by appropriately applying pressure or the like. Good.
[0028]
Here, the nonwoven fabric (non-woven fabric) 4a constituting the electrolyte layer 4 of the present invention is not particularly limited. In other words, it may be in the form of a sheet formed by arranging fibers in a web (thin cotton) shape or mat shape by an appropriate method, and joining them using an appropriate adhesive or the fusing force of the fibers themselves. The adhesive is not particularly limited as long as it has sufficient heat resistance at the temperature during manufacture and use, and is stable without any reactivity or solubility with respect to the gel electrolyte. In addition, conventionally known ones can be used. Further, the fiber used is not particularly limited, and for example, conventionally known fibers such as cotton, rayon, acetate, nylon, polyester, polypropylene, polyethylene, polyimide, and aramid can be used. Depending on the mechanical strength required for the 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. 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 in the electrolyte layer.
[0029]
In FIG. 5, a non-woven fabric having the same size as the electrolyte layer is used for convenience of explanation. However, in actual manufacturing, a roll-shaped non-woven fabric is used by utilizing various printing / coating techniques or thin film forming techniques. Thus, an electrolyte layer may be continuously formed on the nonwoven fabric, or various mass production techniques may be applied such as a larger amount of electrolyte layer may be formed at once using a larger nonwoven fabric. be able to.
[0030]
Further, the gel electrolyte constituting the electrolyte layer 4 (also simply referred to as gel electrolyte) is not particularly limited, and those used in conventional gel electrolyte layers can be appropriately used. Here, the gel electrolyte refers to one in which an electrolytic solution 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 is an all-solid polymer electrolyte such as polyethylene oxide (PEO) containing an electrolytic solution used in a normal lithium ion battery.
[0032]
A gel electrolyte is also one in which an electrolytic solution is held in a polymer skeleton having no lithium ion conductivity, such as polyvinylidene fluoride (PVDF).
[0033]
-The ratio of the polymer constituting the gel electrolyte (also referred to as host polymer or polymer matrix) to the electrolytic solution is wide. When 100% by mass of the polymer is the total solid polymer electrolyte and 100% by mass of the electrolytic solution is the liquid electrolyte, the intermediate All bodies are gel electrolytes.
[0034]
A host polymer of the gel electrolyte is not particularly limited, and a conventionally known one can be used. Preferably, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG ), Polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) (PMMA) and copolymers thereof are preferable, and the solvents include ethylene carbonate (EC), propylene Carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof are desirable.
[0035]
The electrolyte solution (electrolyte salt and plasticizer) of the gel electrolyte is not particularly limited, and conventionally known ones can be used. Specifically, any material that is normally used in lithium ion batteries may be used. For example, LiPF ₆ , LiBF _Four LiClO _Four , LiAsF ₆ , LiTaF ₆ LiAlCl _Four , Li ₂ B _Ten Cl _Ten Inorganic acid anion salt such as LiCF _Three SO _Three , Li (CF _Three SO ₂ ) ₂ N, Li (C ₂ F _Five SO ₂ ) ₂ Including at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as N; cyclic carbonates such as propylene carbonate and ethylene carbonate; chains such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate Carbonates; 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; Organic solvents (plasticizers) such as aprotic solvents mixed with at least one selected from methyl acetate and methyl formate We can use what we used However, it is not necessarily limited to these.
[0036]
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.
[0037]
Further, in the present invention, the amount of the electrolyte contained in the gel electrolyte may be made substantially uniform inside the gel electrolyte as shown in FIG. You may do it. 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 part 4b ′ on the outer peripheral part with respect to the electrolytic solution can be improved. When decreasing gradually from the central part toward the outer peripheral part, polyethylene oxide (PEO), polypropylene oxide (PPO) and copolymers thereof having lithium ion conductivity are used as the host polymer. It is desirable.
[0038]
Next, the electrolyte sealing resin constituting the electrolyte layer of the first embodiment is not particularly limited as long as it can seal the electrolytic solution (alkaline solution), and is resistant to alkali. A conventionally known sealing resin having the following 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., and can effectively prevent the electrolyte from seeping out from the gel electrolyte. This is because a liquid junction (short circuit) due to leakage can be prevented over a long period of 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 copolymers thereof. The solid polymer electrolyte contains a lithium salt in order to ensure ionic conductivity. As the lithium salt, LiBF _Four , LiPF ₆ , LiN (SO ₂ CF _Three ) ₂ , LiN (SO ₂ C ₂ F _Five ) ₂ Or a mixture thereof. However, it is not necessarily limited to these. Polyalkylene oxide polymers such as PEO and PPO are LiBF _Four , LiPF ₆ , LiN (SO ₂ CF _Three ) ₂ , LiN (SO ₂ C ₂ F _Five ) ₂ Lithium salt such as can be dissolved well. Moreover, excellent mechanical strength is exhibited by forming a crosslinked structure.
[0040]
The ratio of the gel electrolyte portion in the vicinity of the center of the electrolyte layer and the electrolyte seal resin portion or the all solid polymer electrolyte portion in the outer peripheral portion cannot be uniquely determined because it varies depending on the material of the outer peripheral portion. It is desirable from the standpoint of battery characteristics that the portion be as small as possible within the range where the 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 described above.
[0041]
The above description has been made centering on the electrolyte layer that is a component of the characteristic part of the bipolar battery according to the present invention. However, the other components of the bipolar battery of the present invention are not particularly limited and are conventionally known. The present invention can be widely applied to bipolar batteries.
[0042]
Hereinafter, although it demonstrates easily for every component of the bipolar battery of this invention, it cannot be overemphasized that this invention should not be restrict | limited to these at all.
[0043]
[Current collector]
The current collector that can be used in the present invention is not particularly limited, and conventionally known ones can be used. For example, aluminum foil, stainless steel foil, clad material of nickel and aluminum, copper and aluminum A clad material or a plating material of a combination of these metals can be preferably used. Moreover, the collector which made the metal surface coat | cover aluminum may be sufficient. Moreover, you may use the electrical power collector which bonded 2 or more metal foil depending on the case. From the viewpoint of corrosion resistance, ease of production, economy, etc., it is preferable to use an aluminum foil as a current collector.
[0044]
Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.
[0045]
[Positive electrode layer]
The positive electrode layer includes a positive electrode active material. In addition to this, a conductive additive for enhancing electron conductivity, a lithium salt for enhancing ion 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 Need only contain a conventionally known binder that binds the fine particles of the positive electrode active material, a conductive aid for increasing the electronic conductivity, and the host polymer, electrolyte solution and lithium salt of the raw material of the polymer electrolyte are It does not have to be included.
[0046]
Among these, as a positive electrode active material, the composite oxide (lithium-transition metal composite oxide) of a transition metal and lithium which is used also with a solution-type lithium ion battery can be used. Specifically, LiCoO ₂ Li / Co complex oxides such as LiNiO ₂ Li / Ni composite oxides such as spinel LiMn ₂ O _Four Li · Mn based complex oxide such as LiFeO ₂ And Li / Fe-based composite oxides. In addition, LiFePO _Four Transition metal and lithium phosphate compounds and sulfuric acid compounds; V ₂ O _Five , MnO ₂ TiS ₂ , MoS ₂ , MoO _Three Transition metal oxides and sulfides such as PbO ₂ , AgO, NiOOH and the like.
[0047]
In order to reduce the electrode resistance of the bipolar battery, the positive electrode active material may have a particle diameter smaller than that generally used for 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 necessarily limited to these.
[0049]
As the binder, polyvinylidene fluoride (PVDF) or the like can be used. However, it is not necessarily limited to these.
[0050]
As described above, the polymer gel electrolyte includes a solid polymer electrolyte having ion conductivity and an electrolyte solution usually used in lithium ion batteries. In the polymer skeleton having no saponification, the same electrolyte solution is held.
[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 _Four LiClO _Four , LiAsF ₆ , LiTaF ₆ LiAlCl _Four , Li ₂ B _Ten Cl _Ten Inorganic acid anion salt such as LiCF _Three SO _Three , Li (CF _Three SO ₂ ) ₂ N, Li (C ₂ F _Five SO ₂ ) ₂ Including at least one lithium salt (electrolyte salt) selected from organic acid anion salts such as N; cyclic carbonates such as propylene carbonate and ethylene carbonate; chains such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate Carbonates; 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; Organic solvents (plasticizers) such as aprotic solvents mixed with at least one selected from methyl acetate and methyl formate We can use what we used However, it is not necessarily limited to these.
[0052]
For example, polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), etc. are used as the polymer having no lithium ion conductivity used for the polymer gel electrolyte. it can. However, it is not necessarily limited to these. Note that PAN, PMMA, etc. are in a class that has almost no ionic conductivity, and therefore can be a polymer having the above ionic conductivity, but here, they are used for a polymer gel electrolyte. This is exemplified as a polymer having no lithium ion conductivity.
[0053]
Examples of the lithium salt include LiPF. ₆ , LiBF _Four LiClO _Four , LiAsF ₆ , LiTaF ₆ LiAlCl _Four , Li ₂ B _Ten Cl _Ten Inorganic acid anion salts such as Li (CF _Three SO ₂ ) ₂ N, Li (C ₂ F _Five SO ₂ ) ₂ An organic acid anion salt such as N or a mixture thereof can be used. However, it is not necessarily limited to these.
[0054]
The ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte may be determined according to the purpose of use, but is in the range of 2:98 to 90:10. In other words, the leakage of the electrolyte from the outer peripheral portion of the electrode layer can be effectively sealed by making the outer peripheral portion of the gel electrolyte layer of the present invention appropriately longer than the end portion of the electrode as described in FIG. can do. Therefore, it is possible to give priority to battery characteristics relatively with respect to the ratio (mass ratio) between the host polymer and the electrolytic solution in the polymer gel electrolyte.
[0055]
The amount of positive electrode active material, conductive additive, binder, polymer electrolyte (host polymer, electrolyte, etc.), and lithium salt in the positive electrode layer depends on the intended use of the battery (output priority, energy priority, etc.) and ion conductivity. It should be decided in consideration. For example, if the blending amount of the polymer electrolyte in the positive electrode layer is too small, the ion conduction resistance and the ion diffusion resistance in the positive electrode layer are increased, and the battery performance is deteriorated. On the other hand, when the blending amount of the polymer electrolyte in the positive electrode layer is too large, the energy density of the battery is lowered. Therefore, in consideration of these factors, the polymer gel electrolysis mass suitable for the purpose is determined.
[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 (emphasis on output, emphasis on energy, etc.) and ion conductivity as described for the blending amount. A typical positive electrode layer has a thickness of about 10 to 500 μm.
[0057]
[Negative electrode layer]
The negative electrode layer includes a negative electrode active material active material. In addition to this, a conductive auxiliary agent for increasing electron conductivity, a binder, a polymer electrolyte (host polymer, electrolytic solution, etc.), a lithium salt for increasing ion conductivity, and the like may be included. In the case of using a polymer gel electrolyte, it is sufficient that a conventionally known binder for linking the negative electrode active material fine particles, a conductive auxiliary agent for enhancing electronic conductivity, etc. are contained. In addition, an electrolytic solution or a lithium salt may not be contained.
[0058]
Since the contents other than the type of the negative electrode active material are basically the same as the contents described in the section “Positive electrode layer”, the description is omitted here.
[0059]
As the negative electrode active material, a negative electrode active material that is also used in a solution-type lithium ion battery can be used. Specifically, carbon, metal oxide, lithium-metal composite oxide, and the like can be used, and carbon or lithium-transition metal composite oxide is preferable. This is because a battery excellent in capacity and output characteristics (for example, the battery voltage can be increased) can be configured by using these. As the lithium-transition metal composite oxide, for example, a lithium-titanium composite oxide can be used. Moreover, as carbon, graphite, graphite, acetylene black, carbon black etc. can be used, for example.
[0060]
[Polymer gel electrolyte layer]
The polymer gel electrolyte layer of the present invention, that is, (1) a polymer gel electrolyte is held in the vicinity of the center of the nonwoven fabric, and an electrolyte sealing resin is placed on the outer periphery of the same nonwoven fabric where the gel electrolyte is held. An electrolyte layer having a held structure, and / or (2) a polymer gel electrolyte is held in the vicinity of the center of the nonwoven fabric, and an all-solid polymer on the outer periphery of the same nonwoven fabric where the gel electrolyte is held 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 in a single battery.
[0062]
In addition, the polymer electrolyte may be included 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 layer. Good.
[0063]
By the way, a host polymer for a polymer gel electrolyte that is preferably used at present is a polyether polymer such as PEO and 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 that is generally used in a solution-based lithium ion battery, the capacity of the negative electrode may be less than the capacity of the positive electrode facing through the polymer gel electrolyte layer. preferable. If the capacity of the negative electrode is less than the capacity of the opposing positive electrode, it is possible to prevent the positive electrode potential from rising excessively at the end of charging. In addition, the capacity | capacitance of a positive electrode and a negative electrode can be calculated | required from manufacturing conditions as theoretical capacity | capacitance at the time of manufacturing a positive electrode and a negative electrode. You may measure the capacity | capacitance of a finished product directly with a measuring device.
[0064]
However, if the capacity of the negative electrode is smaller than the capacity of the opposing positive electrode, the negative electrode potential may be lowered too much and the durability of the battery may be impaired, so it is necessary to pay attention to the charge / discharge voltage. For example, care should be taken not to lower the durability by setting an appropriate value for the oxidation-reduction potential of the positive electrode active material using the average charging voltage of one cell (single cell layer).
[0065]
[Insulation layer]
The insulating layer is formed around each electrode for the purpose of preventing current collectors from coming into contact with each other, electrolyte leaking out, and short-circuiting due to slight unevenness at the end of the laminated electrode. Is.
[0066]
The insulating layer may have any insulating property, sealing performance against leakage of electrolyte solution or moisture permeation from the outside (sealing property), heat resistance under battery operating temperature, etc., for example, epoxy resin Rubber, polyethylene, polypropylene, and the like can be used, but an epoxy resin is preferable from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming property), economy, and the like.
[0067]
[Positive electrode and negative electrode terminal plate]
The positive electrode and the negative electrode terminal plate may be used as necessary. When used, it has a function as a terminal and should be as thin as possible from the viewpoint of thinning. However, the laminated electrode, electrolyte, and current collector all have weak mechanical strength. It is desirable to have sufficient strength to pinch and support from above. Furthermore, it can be said that the thickness of the positive electrode and the negative electrode terminal plate is usually preferably about 0.1 to 2 mm from the viewpoint of suppressing the internal resistance at the terminal portion.
[0068]
As the material of the positive electrode and the negative electrode terminal plate, materials usually used in lithium ion batteries can be used. For example, aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof can be used. Aluminum is preferably used from the viewpoints of corrosion resistance, ease of production, economy, and the like.
[0069]
The material of the positive electrode terminal plate and the negative electrode terminal plate may be the same material or different materials. Furthermore, the positive electrode and the negative electrode terminal plate may be a laminate of different materials.
[0070]
The positive electrode and the negative electrode terminal plate may be the same size as the current collector.
[0071]
[Positive electrode and negative electrode lead]
As for the positive electrode and the negative electrode lead, known leads usually used in lithium ion batteries can be used. In addition, since the part taken out from the battery exterior material (battery case) does not have a distance from the heat source of the automobile, it does not affect the automobile parts (particularly electronic equipment) by contacting with them and causing electric leakage. In addition, it is preferable to coat with a heat-resistant insulating heat-shrinkable tube or the like.
[0072]
[Battery exterior material (battery case)]
In order to prevent external impact and environmental degradation when using a bipolar battery, in order to prevent external impact and environmental degradation during use, the entire battery stack, which is the body of the bipolar battery, is used as a battery exterior material or battery case. (Not shown). From the viewpoint of weight reduction, conventionally known battery exteriors such as polymer-metal composite laminate films and aluminum laminate packs in which metals (including alloys) such as aluminum, stainless steel, nickel, and copper are coated with an insulator such as polypropylene film It is preferable that the battery stack is housed and sealed by joining a part or the whole of the peripheral part by heat fusion using a material. In this case, the positive electrode and the negative electrode lead may be structured to be sandwiched between the heat-sealed portions and exposed to the outside of the battery exterior material. In addition, the use of polymer-metal composite laminate films and aluminum laminate packs with excellent thermal conductivity allows heat to be efficiently transferred from the heat source of the automobile and the inside of the battery to be quickly heated to the battery operating temperature. preferable.
[0073]
Next, in the present invention, an assembled battery in which a plurality of the above bipolar batteries are connected can be obtained. In other words, by using an assembled battery in which at least two or more bipolar batteries of the present invention are connected in series and / or in parallel, the battery capacity and output requirements for each purpose of use can be handled relatively inexpensively. It becomes possible to do.
[0074]
Specifically, for example, N bipolar batteries are connected in parallel, and N parallel bipolar batteries are further connected in series in a metal or resin battery case to form a battery pack. . At this time, the number of series / parallel connections of the bipolar battery is determined according to the purpose of use. For example, a large-capacity power source such as an electric vehicle (EV) or a hybrid electric vehicle (HEV) may be combined so as to be applicable to a driving power source for a vehicle that requires high energy density and high output density. Moreover, what is necessary is just to electrically connect the positive electrode terminal and negative electrode terminal for assembled batteries, and the electrode lead of each bipolar battery using a lead wire. Further, when the bipolar batteries are connected in series / parallel, they may be electrically connected using an appropriate connecting member such as a spacer or a bus bar. However, the assembled battery of the present invention should not be limited to those described here, and conventionally known ones can be appropriately employed. In addition, the assembled battery may be provided with various measuring devices and control devices according to usage, for example, a voltage measuring connector may be provided to monitor the battery voltage, etc. There is no particular limitation.
[0075]
In 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 the 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 a vehicle, for example, an electric vehicle or a hybrid electric vehicle, which has particularly strict requirements regarding energy density and output density. For example, as shown in FIG. 10, it is convenient to install the assembled battery 13 as a driving power source under the seat at the center of the body of the electric vehicle or hybrid electric vehicle 15 because the in-house space and the trunk room can be widened. However, the present invention is not limited to these, and may be mounted in the lower part of the rear trunk room, or if the engine is not mounted like an electric vehicle, the engine in front of the vehicle body is mounted. It can also be mounted on parts that have been damaged. In the present invention, not only the assembled battery 13 but also a bipolar battery may be mounted depending on the usage, or the assembled battery 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 and hybrid electric vehicle are preferable, but are not limited thereto.
[0076]
The method for producing the bipolar battery of the present invention is not particularly limited, and various conventionally known methods can be appropriately used. This will be briefly described below. However, the method for producing the polymer gel electrolyte layer is as already described with reference to FIG.
[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 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 conductive aids, binders, polymerization initiators, polymer gel electrolyte materials (host polymers, electrolytes, etc.), and lithium salts, etc., but polymer gel electrolyte is added to the polymer electrolyte layer. When used, it may contain a conventionally known binder that binds the positive electrode active material fine particles, a conductive aid for increasing electron conductivity, a solvent, and the like. Or lithium salt may not be contained.
[0079]
Examples of the raw material for the polymer gel electrolyte include PEO, PPO, and copolymers thereof, and preferably have 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]
With respect to the positive electrode active material, the conductive additive, the binder, and the lithium salt, the above-described compounds can be used.
[0081]
The polymerization initiator needs to be selected according to the compound to be polymerized. For example, benzyl dimethyl ketal is used as the photopolymerization initiator, and azobisisobutyronitrile is used as the thermal polymerization initiator.
[0082]
A solvent such as NMP is selected according to the type of the positive electrode slurry.
[0083]
The addition amount of the positive electrode active material, the lithium salt, and the conductive additive may be adjusted according to the purpose of the bipolar battery, and may be added in a commonly used amount. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer raw material. Usually, it is about 0.01-1 mass% with respect to a polymeric 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 positive electrode slurry, the cross-linking reaction may be advanced to increase the mechanical strength of the polymer solid electrolyte. For drying, a vacuum dryer or the like can be used. The drying conditions are determined according to the applied positive electrode slurry and cannot be uniquely defined, but are usually 40 to 150 ° C. and 5 minutes to 20 hours.
[0085]
(3) Application of negative electrode composition
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 aid, a binder, a polymerization initiator, a raw material for a polymer gel electrolyte (host polymer, electrolytic solution, etc.), a lithium salt, and the like are optionally included. Since the raw materials used and the amounts added are the same as those described in the section “(1) Application of positive electrode composition”, the 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. This work completes the bipolar electrode. For drying, a vacuum dryer or the like can be used. The drying conditions are determined according to the applied slurry for negative electrode and cannot be uniquely defined, but are usually 40 to 150 ° C. and 5 minutes to 20 hours.
[0088]
(5) Lamination of bipolar electrode and polymer gel electrolyte layer
Separately, a polymer gel electrolyte layer laminated between the electrodes is prepared. What is necessary is just to produce this polymer gel electrolyte layer in the procedure already demonstrated using FIG.
[0089]
The bipolar electrode produced as described above is sufficiently heated and dried under high vacuum, and then a plurality of bipolar electrodes and polymer gel electrolyte layers are cut into appropriate sizes. In many cases, the width of the polymer gel electrolyte layer is slightly smaller than the current collector size of the bipolar electrode (see FIG. 8). A predetermined number of the cut bipolar electrodes and polymer gel electrolyte are bonded together to produce a bipolar battery body (battery laminate). The number of stacked layers is determined in consideration of battery characteristics required for the bipolar battery. A bipolar electrode having a polymer gel electrolyte layer formed on one side or both sides may be directly bonded. Electrodes are disposed 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 disposed. 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 disposed. 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, the bipolar battery may be manufactured in an argon atmosphere or a nitrogen atmosphere.
[0090]
(6) Packing (Battery completion)
Finally, a positive electrode terminal plate and a negative electrode terminal plate are installed on the outermost electron conductive layers of the bipolar battery main body (battery laminate), respectively, and a positive electrode lead and a negative electrode lead are further added to 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 having a low bonding temperature can be suitably used. A known bonding method can be used as appropriate.
[0091]
In order to prevent external impact and environmental degradation, the entire battery stack is sealed with a battery exterior material or battery case to complete a bipolar battery. The material of the battery exterior material (battery case) is preferably a metal (aluminum, stainless steel, nickel, copper, etc.) 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 with an average particle size of 2 μm as positive electrode active material ₂ O _Four [85% by mass], acetylene black [5% by mass] as a conductive additive, PVDF [10% by mass] as a binder, and N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent (NMP is all when the electrode is dried) Since it is volatilized and removed, an appropriate amount is added so as to obtain an appropriate slurry viscosity, not an electrode constituent material.) The above ratio (the ratio converted by the component excluding the slurry viscosity adjusting solvent is shown.) To prepare a positive electrode slurry.
[0094]
The positive electrode slurry was applied to one side 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 _Four Ti _Five O ₁₂ [85% by mass], acetylene black [5% by mass] as a conductive additive, PVDF [10% by mass] as a binder, and NMP as a slurry viscosity adjusting solvent (an appropriate amount was added so as to obtain an appropriate slurry viscosity). The materials were mixed at the above ratios (showing ratios converted with components excluding the slurry viscosity adjusting solvent) to prepare a negative electrode slurry. In addition, Li used for the negative electrode active material _Four Ti _Five O ₁₂ The average particle diameter of the secondary particles was 10 μm, and the primary particles of 0.2 to 0.5 μm were 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 surfaces of a SUS foil as a current collector (see FIG. 1).
[0098]
<Formation of seal part>
From the outer side of the four sides of the outer periphery of a 50 μm thick polypropylene nonwoven fabric 10mm And immersed in an epoxy resin as a resin for electrolyte sealing, 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 as a host polymer (copolymerization ratio is 5: 1, weight average) on the inside of the electrolyte seal portion of the nonwoven fabric having an electrolyte seal portion formed on the outer periphery. A molecular weight of 8000 was used.) [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 _Five SO ₂ ) ₂ N (electrolytic solution and lithium salt combined to 95 mass%. The amount of lithium salt was 1.0 M with respect to the electrolytic solution) and AIBN [0. 1 mass%] was immersed and thermally polymerized at 90 ° C. for 1 hour under 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 obtained gel electrolyte layer had a thickness of 50 μm and was not thicker than the nonwoven fabric.
[0100]
<Formation of bipolar battery>
The bipolar electrode and a gel electrolyte layer that is an electrolyte-holding 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 5 layers (single battery layer 5 cells) were laminated, the battery laminate was sealed with a laminate pack (aluminum laminated with 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 with an average particle size of 2 μm as positive electrode active material ₂ O _Four [85% by mass], acetylene black [5% by mass] as a conductive additive, PVDF [10% by mass] as a binder, and N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent (to achieve an appropriate slurry viscosity) An appropriate amount was added to the mixture.) And a mixture of the above materials (showing the ratio converted by the component excluding the slurry viscosity adjusting solvent) to prepare a positive electrode slurry.
[0103]
The positive electrode slurry was applied to one side 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 _Four Ti _Five O ₁₂ [85% by mass], acetylene black [5% by mass] as a conductive additive, PVDF [10% by mass] as a binder, and NMP as a slurry viscosity adjusting solvent (an appropriate amount was added so as to obtain an appropriate slurry viscosity). The materials were mixed at the above ratios (showing ratios converted with components excluding the slurry viscosity adjusting solvent) to prepare a negative electrode slurry. In addition, Li used for the negative electrode active material _Four Ti _Five O ₁₂ The average particle diameter of the secondary particles was 10 μm, and the primary particles of 0.2 to 0.5 μm were 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 surfaces of a SUS foil as a current collector (see FIG. 1).
[0107]
<Formation of all solid electrolyte part>
Li (C) as a supporting salt on the outer periphery of a polypropylene nonwoven fabric having a thickness of 50 μm ₂ F _Five SO ₂ ) ₂ N [28% by mass] and a polymer (polyethylene oxide and polypropylene oxide copolymer) containing an organic peroxide (specifically, t-hexylperoxypiparate) [0.7% by mass] as a polymerization initiator When an all-solid electrolyte material consisting of (a copolymerization ratio of 5: 1 and a weight average molecular weight of 8000 was used) was immersed at a width of 10 mm from the outer side and heated and dried at 80 ° C. for 10 hours in a vacuum atmosphere. At the same time, polymerization (accelerating the crosslinking reaction) was performed to form an all-solid electrolyte part (see FIG. 5C).
[0108]
<Formation of gel electrolyte layer>
As a raw material for the gel electrolyte, a non-woven fabric having an all solid electrolyte part formed on the outer peripheral part, a raw material for gel electrolyte, a copolymer of polyethylene oxide and polypropylene oxide as a host polymer (copolymerization ratio is 5: 1, The weight average molecular weight was 8000.) [5% by mass], EC + DMC (EC: DMC (volume ratio) = 1: 3) as an electrolytic solution, and 1.0 M Li (as a supporting salt) as a lithium salt (supporting salt) C ₂ F _Five SO ₂ ) ₂ N (electrolytic solution and lithium salt combined to 95 mass%. The amount of lithium salt was 1.0 M with respect to the electrolytic solution) and AIBN [0. 1% by mass] was held to form a gel electrolyte layer (see FIG. 5E). The obtained gel electrolyte layer had a thickness of 50 μm and was not thicker than the nonwoven fabric.
[0109]
<Formation of bipolar battery>
The bipolar electrode and a gel electrolyte layer that is an electrolyte-holding 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 5 layers (single battery layer 5 cells) were laminated, the battery laminate was sealed with a laminate pack ((aluminum laminated with polypropylene film; battery outer packaging material) to form a bipolar battery.
[0111]
Comparative Example 1
As Comparative Example 1, except that a gel electrolyte layer having no electrolyte seal portion was used, 5 layers (single cell layer for 5 cells) were laminated in the same manner as in Example 1, and then the battery laminate was laminated with a laminate pack (aluminum made of polypropylene film). A bipolar battery was formed by sealing with a battery outer packaging material (see FIG. 11).
[0112]
<Evaluation>
The batteries of Examples 1 and 2 and Comparative Example 1 were 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 that does not have an electrolyte seal portion, during the initial charging, the electrolyte oozes out of the unit cell layer, and contacts with the electrolyte of the other unit cell layer to cause a liquid junction, The battery voltage has dropped significantly.
[0114]
In the bipolar batteries of Examples 1 and 2 having other electrolyte seal layers, it was confirmed that the voltage of each single battery layer was maintained even when 50 cycles were exceeded, and no liquid junction occurred.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view schematically showing the 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 single battery layer (single cell) constituting the bipolar battery of the present invention.
FIG. 3 is a schematic cross-sectional view schematically showing the basic structure of the bipolar battery of the present invention.
FIG. 4 is a schematic view schematically showing a basic configuration of a bipolar battery of the present invention.
FIGS. 5A and 5B are a schematic plan view and a schematic cross-sectional view schematically showing a manufacturing process of a typical electrolyte layer used in the bipolar battery of the present invention. FIGS. FIG. 5A is a schematic plan view showing a nonwoven fabric corresponding to the base material of the electrolyte layer before production. FIG. 5B is a schematic cross-sectional view taken along line AA in FIG. FIG. 5C is a schematic plan view schematically showing the state of the manufacturing process of the electrolyte layer at the stage where the electrolyte sealing resin part or the all solid polymer electrolyte part is formed on the outer peripheral part of the nonwoven fabric. FIG. 5D and FIG. 5D ′ are schematic cross-sectional views taken along line BB in FIG. FIG. 5E is a schematic plan view schematically showing a state where a gel electrolyte part is formed in the vicinity of the center part of the nonwoven fabric and the electrolyte layer is completed. FIG. 5F and FIG. 5F ′ are schematic cross-sectional views along the line CC in FIG.
FIG. 6 is a schematic cross-sectional view schematically showing the basic structure of a bipolar battery using the polymer gel electrolyte of the present invention (first embodiment).
FIG. 7 is a schematic cross-sectional view schematically showing the basic structure of a bipolar battery using the polymer gel electrolyte of the present invention (second embodiment).
FIG. 8 is a schematic cross-sectional view schematically showing the structure in the vicinity of the outer peripheral portion of an electrode laminate (part) constituting the 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. 9 (B) shows the amount of electrolyte contained in the electrolyte layer. It is the drawing displayed along the AA line in FIG.
FIG. 10 is a schematic view schematically showing a vehicle on which the bipolar battery and / or the assembled battery according to the present invention is mounted as a driving power source.
FIG. 11 is a schematic cross-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 seal resin part,
4b '... all solid polymer electrolyte part,
4c ... gel electrolyte part,
4 '... polymer gel electrolyte layer,
5 ... Bipolar electrode,
5a: an electrode in which a positive electrode layer is disposed only on one side of the current collector,
5b ... an electrode in which a negative electrode layer is disposed only on one side of the current collector,
6 ... Single 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 ... assembled battery,
15 ... Vehicle (electric vehicle or hybrid electric vehicle).

Claims (5)

In a bipolar battery in which a plurality of bipolar electrodes in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface are stacked in series across an electrolyte layer,
The electrolyte layer has a structure in which the polymer gel electrolyte is held in the vicinity of the center of the nonwoven fabric, and the whole solid polymer electrolyte is held in the outer peripheral portion of the same nonwoven fabric where the gel electrolyte is held. Bipolar battery features.   2. The bipolar battery according to claim 1, wherein a thickness of the non-woven fabric holding the all solid polymer electrolyte of the electrolyte layer is equal to or greater than a thickness of the non-woven fabric holding the gel electrolyte. Using a lithium-transition metal composite oxide as a positive electrode active material,
3. The bipolar battery according to claim 1, wherein carbon or lithium-transition metal composite oxide is used as the negative electrode active material. Assembled cell constituted by connecting a plurality of bipolar battery according to any one of claims 1 to 3. Vehicle, characterized by comprising mounting the assembled battery according as a driving power source to the bipolar battery and / or claim 4 according to any one of 請 Motomeko 1-3.

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