JP2004247209A - Laminated battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-safety battery with a structure of not leaving voltage (electric capacity), quickly discharging, and surely turning into 0V, when the battery gets into a destructive state such as being pierced by a matter from outside. <P>SOLUTION: Of the laminated battery structured by forming an electrode on a metal foil as a current collector and laminating it with an electrolyte in between, a part of the current collector is extended, and it is constructed so that an electrode-forming part is wrapped by the extended. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a stacked battery, particularly to a polymer battery using a polymer electrolyte as an electrolyte.
[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 polymer battery using a polymer electrolyte as an electrolyte has been proposed (for example, see Patent Documents 1 and 2). Among them, the bipolar polymer battery using a solid polymer electrolyte has high reliability because there is no solution (electrolyte solution) in the battery, so there is no risk of liquid leakage or gas generation, and the structure is sealed. This has the advantage of providing a bipolar polymer battery that does not require a seal. In addition, a bipolar polymer battery using a polymer gel electrolyte as the polymer electrolyte has excellent ionic conductivity and sufficient output density and energy density of the battery, so it is expected to be the bipolar polymer battery closest to the practical application stage Have been.
[0006]
[Patent Document 1]
JP 2000-100471 A
[Patent Document 2]
JP-A-11-204136
[0007]
[Problems to be solved by the invention]
However, when such a bipolar polymer battery is in a state like a nail penetration, the polymer electrolyte covers the fractured surface of the nail or the electrode, a short circuit does not occur, and the voltage of the battery remains. In particular, in the case of a bipolar battery in which each cell layer is independent as a battery, there is a very high possibility that there is a cell layer in which a voltage remains.
[0008]
Therefore, an object of the present invention is to have a structure in which, when a battery is in a destructive state such as an object pierced from the outside, the battery is discharged quickly without leaving a voltage (electric capacity) and reliably reaches 0V. It is to provide a highly safe battery.
[0009]
[Means for Solving the Problems]
The present invention provides a stacked battery in which an electrode is formed on a metal foil that is a current collector, and the electrode is stacked with an electrolyte interposed therebetween. A stacked battery having a structure in which a portion surrounds an electrode forming portion.
[0010]
【The invention's effect】
In the battery of the present invention, a part of the current collector on which the electrode is formed is extended, and the extended part is bent so as to wrap the electrode forming part with the extended part. When this state is reached, the current collector extension surrounding the electrode forming portion also breaks. However, since the polymer electrolyte does not cover the nail or the like or the fractured surface of the current collector extension, a short circuit surely occurs at this portion and discharge occurs quickly. As a result, the voltage (electric capacity) of the battery (all the cell layers constituting it) does not remain, and the voltage can be reliably set to 0 V, and the safety of the battery in a broken state can be enhanced. Therefore, even if a battery mounted as a drive power source such as an EV or an HEV capable of extracting a large current with a high energy density and a high output density is destroyed by an accident or the like, electric shock or ignition caused by the battery (furthermore, flammability) Secondary disasters such as fuel ignition) can be prevented. Therefore, it is possible to maintain excellent energy density and power density, and furthermore, to have high reliability and safety at the time of an accident or disaster, and thereby to be a useful power source in various industries.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0012]
In the stacked battery according to the present invention, an electrode is formed on a metal foil that is a current collector, and in the stacked battery configured by stacking the electrode with an electrolyte interposed therebetween, a part of the current collector is extended. In this case, the extended portion surrounds the electrode forming portion. This is advantageous in that the battery can be completely short-circuited when foreign matter pierces from the outside.
[0013]
The stacked battery to be used in the present invention is a bipolar lithium ion secondary battery, preferably a bipolar lithium ion secondary battery using a polymer electrolyte (specifically, a polymer solid electrolyte or a polymer gel electrolyte) for the electrolyte layer. is there.
[0014]
This is because a bipolar lithium ion secondary battery can constitute a battery having excellent capacity and output characteristics. Further, even when a foreign object is pierced from the outside, the battery can be completely short-circuited even in a bipolar lithium ion secondary battery in which the battery is unlikely to be completely short-circuited. Furthermore, in a bipolar lithium ion secondary battery using a polymer solid electrolyte as an electrolyte, there is no liquid junction problem, so that a bipolar battery having high reliability and excellent output characteristics with a simple configuration can be formed. It is. In addition, even when a foreign substance pierces from the outside, the battery is unlikely to be completely short-circuited, and can be completely short-circuited even in a battery using a polymer electrolyte. That is, it can be said that such a battery can sufficiently exhibit the true value and effectiveness of the present invention.
[0015]
However, the present invention should not be limited to these, and can be applied to conventionally known stacked batteries. That is, by employing the structure of the present invention, it is possible to discharge by short-circuiting the current collector extension. Therefore, even if a large current is generated at the broken part of the current collector extension and a heat generation phenomenon occurs, only the peripheral part generates heat, abnormal combustion of the electrode active material such as a short circuit at the electrode part, and gas of electrolyte solution. This is because it is possible to reduce the risk of battery rupture or the like due to gasification.
[0016]
Therefore, the present invention is not limited to a stack type battery using a polymer electrolyte. For example, a bipolar lithium ion battery using an electrolyte solution (more specifically, a separator in which an electrolyte solution is impregnated) is used as the electrolyte. Stackable batteries such as secondary batteries, non-bipolar polymer lithium ion secondary batteries, non-bipolar electrolyte type lithium ion secondary batteries, and non-bipolar lithium secondary batteries can also be objects of the present invention. is there. Hereinafter, a preferred embodiment of the stacked battery according to the present invention is a bipolar lithium ion secondary battery using a polymer electrolyte (specifically, a polymer solid electrolyte or a polymer gel electrolyte) (hereinafter simply referred to as a bipolar battery). (Referred to as a battery) will be briefly described, but the present invention is not limited thereto.
[0017]
1 to 4 briefly explain the basic configuration of a bipolar battery with reference to the drawings. 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, and FIG. 3 is a schematic cross-sectional view schematically showing the entire structure of the bipolar battery (a part in which the electrode forming part is wrapped around the current collector extension is not shown). This point will be described in detail with reference to FIG. 5.) and FIG. 4 is a schematic diagram conceptually (in symbolized) showing a plurality of unit cell layers stacked in a bipolar battery connected in series. Is shown.
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
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.
[0022]
In the present invention, as described with reference to FIGS. 1 to 4, a plurality of bipolar electrodes in which a positive electrode is formed on one surface of a current collector and a negative electrode is formed on the other surface are stacked in series with an electrolyte interposed therebetween. In the bipolar lithium ion secondary battery, as shown in FIG. 5B, a part of the current collector 1 is extended, and the extended portion (also referred to as a current collector extension) forms an electrode. It is characterized in that it has a structure surrounding the formed part. Here, FIG. 5A is a developed view (or a manufacturing process) schematically showing a state where a part of the current collector 1 is extended so that the structure of the characteristic portion of the present invention can be easily understood. 5 (b) is a schematic sectional side view of a battery schematically showing a structure in which an electrode forming portion is wrapped by a current collector extension portion.
[0023]
In the present invention, as shown in FIG. 5A, a part of the current collector 1 is extended. Specifically, both left and right (or front and rear) ends of the electrode forming portion (= the positive electrode layer 2 and the negative electrode layer 3) 21 on the current collector 1 may be respectively extended (this extended portion is referred to as a current collector extension portion). 23a and 23b). In the present invention, the current collector extension portions 23a and 23b do not have to be provided on both left and right (or front and rear) ends of the electrode forming portion 21 on the current collector 1, for example, on the right side of the electrode forming portion on the current collector 1. The ends of (or the left side) and the front (or the rear side) may be extended (in other words, the ends may be extended into an L-shape). However, the former can be said to be desirable from the viewpoints of productivity and ease of handling of the current collector. Further, the current collector extension portions 23 may be provided at four positions on both sides of the electrode forming portion 21 on the current collector 1 in front, rear, left and right.
[0024]
Note that the thickness of the current collector 1 may be the same or different between the electrode forming portion 21 and the current collector extending portion 23. That is, depending on how the terminal lead is taken out, the current collector extension 23 may not be used as a terminal for taking out current in a normal state. It is also possible to reduce the thickness of the part to reduce the thickness and weight of the entire battery.
[0025]
In the present invention, as shown in FIGS. 5A and 5B, the current collector extension portions 23a and 23b have a structure in which the electrode forming portion 21 is wrapped from above and below (a structure in which the electrode forming portion 21 is sandwiched). That is, for the purpose of preventing the upper and lower current collector extension portions 23 from contacting each other (and, in some cases, the current collector extension portion and the electrode forming portion) in a normal state, for example, the insulating separator 25 is placed ( Or pinching). Thereafter, at positions where the load due to bending is not applied to the electrode forming portion (folded line portion in FIG. 5A), the current collector extension portions 23a and 23b and the insulating separator 25 are moved to the thick arrow in FIG. As shown in the figure, the electrode forming portion 21 is bent upward and downward, respectively, and the current collector extending portions 23a and 23b (and the insulating separator 25) wrap (enclose) the electrode forming portion 21 from above and below. 5 (b)).
[0026]
Therefore, the length of the current collector extension portions 23a and 23b can cover and hide the electrode forming portion when the current collector extension portions are bent at both ends as shown in FIG. 5B. Any length is acceptable. On the other hand, in the case where the current collector extension portions 23 are provided at the four front, rear, left, and right ends of the electrode formation portion 21 on the current collector 1, the electrode formation portion 21 is covered by two current collector extension portions 23. Any length is acceptable. As shown in FIG. 5B, the outer side of the current collector extension may be longer than the inner side of the current collector extension in consideration of the difference between the inner and outer bending allowances. Since the difference length of the bent margin portion is extremely small, it is not necessary to particularly consider this point.
[0027]
Here, as the insulation processing part installed for the purpose of preventing the stacked upper and lower current collector extension parts from contacting each other and short-circuiting, the insulation separator described above is installed and the insulation processing part is used. It is not limited to any one, and various conventionally known insulation treatment techniques can be appropriately applied. For example, an insulating film previously coated on the surface of the current collector extension portion 23 of the current collector 1 may be used as the insulating portion, or the current collector extension portion 23 may be provided with a spacing such as a spacer during lamination. An insulating member having a function may be provided to serve as an insulation-treated portion, or a resin-coated portion obtained by immersing the current collector extension portion 23 in a precursor solution of an insulating resin and hardening the resin before bending is used as the insulation-treated portion. It is not particularly limited. Preferably, the current collector extension laminated in the manufacturing stage is easy to bend, and when foreign matter pierces from the outside as shown in FIG. It is preferable that the structure be such that it can be short-circuited. For this purpose, it is preferable that an insulating separator be provided as the insulating portion as shown in FIG. 5A. Note that such an insulating separator is sufficient on one side of the current collector extension 23, but may be provided on both sides. In particular, as shown in FIGS. 5C and 5D, if one separator is folded into two and the fold is set so as to hit one end face of the current collector extension 23, the alignment is achieved. It is excellent in that it becomes easy. In this case, from the viewpoint of reducing the thickness, it is not necessary to install all the current collector extension portions 23 of the electrodes to be stacked, but it is sufficient to install them every other (one by one) for the electrodes to be stacked.
[0028]
At this time, the insulating separator may be simply adhered with glue or the like so as not to be displaced, and it is not always necessary to fix the entire surface of the insulating separator with glue or the like, but is appropriately glued with glue or the like at several places. It is enough to keep it fixed. This is because the separator is pinched by bending and there is no possibility that the separator will be displaced after assembly. From this point of view, it can be said that the used insulating separator should be larger than the current collector extension.
[0029]
The insulating separator used is desirably as thin as possible and non-viscous (hard). If it is viscous, the separator or the adhesive may cover the foreign material or the fractured surface of the current collector extension part, if not a soft and viscous polymer electrolyte, so that a short circuit may not easily occur. .
[0030]
From this point of view, as the insulating separator to be used, an insulating material having no viscosity and a hard property is desirable, and specifically, a polypropylene film, a polyimide film, a polyethylene film, or the like can be suitably used.
[0031]
In addition, the thickness of the insulating separator is desirably as thin as possible because it is laminated above and below the electrode forming portion, and specifically, it is desirably 100 μm or less.
[0032]
In addition, the insulating separator to be used is preferably one having high insulating property so as not to cause a short circuit due to oozing out of the electrolytic solution. However, it is desirable that the electrolyte has high liquid retention, permeability, and high insulating properties without ionic conductivity.
[0033]
Since the adhesive used is desirably an insulating material having a property of being hard and having no viscosity, specifically, a glue, a resin tape or the like can be suitably used.
[0034]
It should be noted that when performing insulation treatment other than the above-mentioned insulation separator, it can be said that the material and thickness may be selected based on the same standards as those for the insulation separator.
[0035]
The mounting positions of the electrode leads 8 and 9 may be provided on one or both of the current collector extension portions as shown in FIG. 5B, or as shown in FIG. 5A. The body 1 may be provided on one or both sides where the body 1 is not extended. However, the latter is not particularly limited, but is the latter from the viewpoint of reducing the electric resistance from the electrode forming portion to the terminal.
[0036]
Although the above has been described mainly with respect to the structure of the current collector extension portion which is a component of the characteristic portion of the present invention, other components of the bipolar battery of the present invention are not particularly limited, It is widely applicable to known bipolar batteries.
[0037]
Hereinafter, other components of the bipolar battery of the present invention will be briefly described, but it is needless to say that the present invention should not be limited to these components.
[0038]
[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.
[0039]
The thickness of the current collector is not particularly limited, but is usually about 1 to 100 μm.
[0040]
Further, the length (or shape) of the current collector may be a length obtained by adding the length necessary for the left and right (or front and rear) extension portions of the current collector to the electrode forming portion as described above. Further, in the case of the L-shaped shape as described above, the electrode forming portion may be formed into a shape obtained by adding a necessary length as a current collector extension portion to one of left and right and one of front and rear. Similarly, in the case of front, rear, left and right, the length may be the length obtained by adding the length required for the current collector extension. In addition, in the case where a current collector extension portion of the current collector coated with an insulating film is used as the insulation processing portion other than the insulating separator, the current collector 1 is formed in the current collector production stage. May be coated with an insulating film. In this case, the insulating film may be coated on one side of the current collector extension 23 of the current collector 1 or on both sides.
[0041]
[Insulation processing part]
The insulation treatment part (insulation separator, etc.), which is a part of the current collector and is installed for the purpose of preventing the current collector extension parts from coming into contact with each other and causing a short circuit, is as described above. Is omitted.
[0042]
[Positive electrode layer]
The positive electrode layer contains a positive electrode active material. In addition, a conductive auxiliary material for improving electron conductivity, a binder, a polymer electrolyte, a lithium salt for improving ionic conductivity, and the like may be included.
[0043]
As the positive electrode active material, a composite oxide of a transition metal and lithium (lithium-transition metal composite oxide) can be suitably 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 those described above, and those obtained by partially replacing these transition metals with other elements can be used. These lithium-transition metal composite oxides are excellent in reactivity and cycle durability, and are low-cost materials. Therefore, using these materials for the electrode is advantageous in that a battery having excellent output characteristics can be formed. 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.
[0044]
The particle size of the positive electrode active material is preferably smaller than the particle size generally used in a solution type lithium ion battery in order to reduce the electrode resistance of a bipolar battery. Specifically, the average particle diameter of the positive electrode active material fine particles is preferably 0.1 to 5 μm.
[0045]
Examples of the conductive additive include acetylene black, carbon black, and graphite. However, it is not limited to these.
[0046]
As the binder, polyvinylidene fluoride (PVDF), SBR, polyimide or the like can be used. However, it is not limited to these.
[0047]
When a polymer solid electrolyte is used for the electrolyte layer, it is desirable that the positive electrode layer also contains the polymer solid electrolyte. By filling the gap between the positive electrode active materials in the positive electrode layer with the solid polymer electrolyte, the ionic conduction in the positive electrode layer becomes smooth, and the output of the entire bipolar battery can be improved.
[0048]
On the other hand, in the case where the electrolyte layer is used by impregnating the polymer gel electrolyte or the electrolytic solution into the separator, the positive electrode layer may not include the electrolyte, but includes a conventionally known binder that binds the positive electrode active material particles. It should just be.
[0049]
The polymer for a polymer solid electrolyte is not particularly limited, and examples thereof include polyethylene oxide (PEO), polypropylene oxide (PPO), and a copolymer thereof. Such a polyalkylene oxide-based polymer is 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. In the present invention, the polymer solid electrolyte is contained in at least one of the positive electrode active material layer and the negative electrode active material layer. However, in order to further improve the battery characteristics of the bipolar battery, it is preferable that both are included.
[0050]
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. However, it is not limited to these.
[0051]
The polymer gel electrolyte is a solid polymer electrolyte having ion conductivity containing an electrolyte solution usually used in lithium ion batteries, and further contains a polymer skeleton having no lithium ion conductivity. And those holding similar electrolytes.
[0052]
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. 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.
[0053]
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. It is exemplified as a polymer having no lithium ion conductivity.
[0054]
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.
[0055]
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. That is, leakage of the electrolytic solution from the outer peripheral portion of the electrode layer can be effectively sealed by providing the insulating layer and the insulating portion. 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.
[0056]
In the positive electrode layer, the compounding amounts of the positive electrode active material, the conductive auxiliary material, the binder, the polymer electrolyte (host polymer, electrolyte solution, etc.), the lithium salt, and the like are determined according to the purpose of use of the battery (output-oriented, energy-oriented, etc.), ionic conduction Should be determined with gender in mind. 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.
[0057]
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.
[0058]
[Negative electrode layer]
The negative electrode layer contains a negative electrode active material active material. In addition, a conductive auxiliary material for improving electron conductivity, a binder, a polymer electrolyte (a host polymer, an electrolytic solution, or the like), a lithium salt for improving ionic conductivity, and the like can be included.
[0059]
When a polymer solid electrolyte is used for the polymer electrolyte layer, it is desirable that the negative electrode layer also contains the polymer solid electrolyte. By filling the gap between the negative electrode active materials in the negative electrode layer with the solid polymer electrolyte, the ionic conduction in the negative electrode layer becomes smooth, and the output of the entire bipolar battery can be improved.
[0060]
On the other hand, when the polymer electrolyte layer is used by impregnating the separator with a polymer gel electrolyte or an electrolytic solution, the electrolyte does not need to be contained in the negative electrode layer, and a conventionally known binder that binds the negative electrode active material particles to each other is used. It only has to be included. 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.
[0061]
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. These carbon or lithium-transition metal composite oxides are excellent in reactivity and cycle durability, and are low-cost materials. Therefore, by using these materials for the electrodes, a battery having excellent output characteristics can be formed. In addition, as the lithium-transition metal composite oxide, for example, Li ₄ Ti ₅ O ₁₂ And the like can be used. As the carbon, for example, graphite (graphite), hard carbon, soft carbon, or the like can be used.
[0062]
[Electrolyte layer]
The electrolyte layer of the present invention is desirably a polymer electrolyte layer, which will be described below.However, it is also possible to use a separator impregnated with an electrolyte by forming an insulating layer. . By using a polymer solid electrolyte (all solid polymer) for the polymer electrolyte layer, there is no liquid leakage, so that a bipolar battery can be formed with a simple configuration. Further, by using an all-solid polymer, there is no problem of liquid junction, so that a battery having high reliability and excellent output characteristics can be formed. In addition, by using a polymer gel electrolyte for the polymer electrolyte layer, a battery having excellent ionic conductivity, high output density and high energy density can be formed.
[0063]
(1) Polymer solid electrolyte layer
The all-solid polymer used for the polymer electrolyte layer is composed of a polymer having ion conductivity, and the material is not limited as long as it has ion conductivity. As the all solid polymer (polymer solid electrolyte), for example, a known polymer (polymer solid electrolyte) such as polyethylene oxide (PEO), polypropylene oxide (PPO), or a copolymer thereof can be used. .
[0064]
The polymer solid electrolyte layer 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. However, it is not limited to these.
[0065]
Polyalkylene oxide-based 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.
[0066]
The polymer solid electrolyte can be contained in the polymer solid electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer, but the same polymer solid electrolyte may be used. Is also good.
[0067]
The thickness of the polymer solid electrolyte layer is not particularly limited. However, in order to obtain a compact solid polymer battery, it is preferable to make the battery as thin as possible as long as the function as a polymer solid electrolyte layer can be secured. The thickness of a general polymer solid electrolyte layer is about 5 to 200 μm.
[0068]
By the way, the polymer for the polymer solid electrolyte which 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 a positive electrode agent having a high oxidation-reduction potential 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 solid 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. Here, the “positive electrode opposed via the polymer solid electrolyte layer” refers to a positive electrode that is a component of the same unit cell layer (cell). 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.
[0069]
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 layer (cell) 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.
[0070]
(2) Polymer gel electrolyte layer
The polymer gel electrolyte is not particularly limited, and those used in conventional gel electrolyte layers 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.
[0071]
A gel electrolyte containing an all-solid polymer electrolyte such as polyethylene oxide (PEO) and an electrolyte used in a normal lithium ion battery.
[0072]
-A polymer electrolyte such as polyvinylidene fluoride (PVDF) having no lithium ion conductivity and having an electrolyte retained therein is also a gel electrolyte.
[0073]
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.
[0074]
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.
[0075]
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.
[0076]
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.
[0077]
In the present invention, the amount of the electrolytic solution contained in the gel electrolyte may be made substantially uniform inside the gel electrolyte, or may be gradually reduced from the center to the outer periphery. . The former is preferable because the 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 in the outer peripheral portion with respect to the electrolytic solution can be improved. 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.
[0078]
[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. In the present invention, it is effective to provide an insulating layer around the electrode on the side where the current collector extension is not bent (the side on which the terminal of FIG. 5A is formed). Note that an insulating layer may be provided on the current collector extension side. This is because, when used as a vehicle drive power source, considering that a longer battery life is desired, during the period of use, the electrolyte layer is used to extend the current collector or the insulating separator. It is because there is no danger of seeping out to the outside, though very slowly. In the case where an insulating layer is also formed on the current collector extension portion side, it is preferable to install the insulating layer on the electrode forming portion side with respect to the folding line in FIG.
[0079]
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. , Rubber, polyethylene, polypropylene, polyimide and the like can be used, but from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming property), economy, etc., epoxy resins are preferred.
[0080]
[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.
[0081]
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.
[0082]
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.
[0083]
The positive and negative electrode terminal plates only need to have the same size as the range up to the electrode forming portion of the current collector or the vicinity of the folding line set outside the electrode forming portion.
[0084]
[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.
[0085]
[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.
[0086]
Next, in the present invention, an assembled battery formed by connecting a plurality of the above bipolar batteries can be provided. That is, a high-capacity, high-output battery module can be formed by using at least two or more bipolar batteries connected in series and / or in parallel to constitute a battery pack. Therefore, it is possible to respond to the demand for the battery capacity and output for each purpose of use relatively inexpensively.
[0087]
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.
[0088]
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, the present invention provides an electric vehicle and a hybrid vehicle which are suitable as a drive power source for a vehicle, for example, an electric vehicle or a hybrid electric vehicle, which has particularly strict requirements regarding energy density and output density, and which are excellent in fuel efficiency and running performance. it can. For example, it is convenient to mount a battery pack as a driving power source under a seat in the center of the body of an electric vehicle or a hybrid electric vehicle, because it is possible to widen a company space and a trunk room. However, the present invention is not limited to these, and the battery can be installed under the floor of the vehicle, in a trunk room, in an engine room, on a roof, in a hood, or the like. In the present invention, not only the assembled battery but also a bipolar battery may be mounted depending on the intended use, or the assembled battery 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.
[0089]
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, when laminating the bipolar electrode and the electrolyte layer, an insulation treatment section such as an insulating separator is provided on the current collector extension part where a part of the current collector is extended, and the bipolar electrode and the electrolyte layer are further laminated. The method of folding the current collector extension portion and the insulating separator to enclose the electrode forming portion later is the same as that described with reference to FIG. 5, and thus description thereof will be omitted or simplified.
[0090]
(1) Application of positive electrode composition
First, a suitable current collector to which the current collector extension has been added 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.
[0091]
The positive electrode slurry is a solution containing a positive electrode active material. As other components, a conductive auxiliary, a binder, a polymerization initiator, a raw material of a polymer electrolyte (a polymer for a solid electrolyte or a host polymer for a gel electrolyte, an electrolyte solution, and the like), and a lithium salt are optionally included. When a polymer gel electrolyte is used for the polymer electrolyte layer, it is sufficient that the polymer electrolyte layer contains a conventionally known binder for binding the positive electrode active material fine particles to each other, a conductive auxiliary agent for increasing electron conductivity, a solvent, and the like. The host polymer, the electrolyte, the lithium salt, and the like as the raw material of the gel electrolyte may not be contained.
[0092]
Examples of the polymer raw material for the polymer electrolyte include PEO, PPO, and a copolymer thereof, and the polymer material preferably has a crosslinkable functional group (such as a carbon-carbon double bond) in the molecule. By cross-linking the polymer electrolyte using the cross-linkable functional group, the mechanical strength is improved.
[0093]
As for the positive electrode active material, the conductive additive, the binder, and the lithium salt, the compounds described above can be used.
[0094]
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.
[0095]
The solvent such as NMP is selected according to the type of the positive electrode slurry.
[0096]
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 with respect to the polymer raw material.
[0097]
(2) Formation of positive electrode layer (electrode formation part)
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. By such a drying treatment, a positive electrode layer (electrode forming portion) is formed on the current collector.
[0098]
(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.
[0099]
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 of a polymer electrolyte (a polymer for a solid electrolyte or a host polymer for a gel electrolyte, an electrolyte solution, and the like), and a lithium salt 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.
[0100]
(4) Formation of negative electrode layer (electrode formation part)
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 cross-linking reaction may proceed to increase the mechanical strength of the polymer 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. By such a drying process, a negative electrode layer (electrode forming portion) is formed on the current collector.
[0101]
(5) Formation of electrolyte layer
When the polymer solid electrolyte layer is used, the polymer solid electrolyte layer is produced by, for example, curing a solution prepared by dissolving a raw material polymer of the polymer solid electrolyte, a lithium salt, or the like in a solvent such as NMP. When a polymer gel electrolyte layer is used, for example, as a raw material of the polymer gel electrolyte, a pre-gel solution comprising a host polymer and an electrolyte solution, a lithium salt, a polymerization initiator, and the like are simultaneously heated and dried under an inert atmosphere. It is produced by polymerizing (promoting a crosslinking reaction).
[0102]
For example, the prepared solution or pregel solution is applied on the electrode (positive electrode and / or negative electrode), and an electrolyte layer having a predetermined thickness or a part thereof (an electrolyte membrane having a thickness of about half the electrolyte layer thickness) is formed. Form. Thereafter, by curing or heating and drying the electrode on which the electrolyte layer (membrane) is laminated and polymerizing (promoting a crosslinking reaction), the mechanical strength of the electrolyte is increased, and the electrolyte layer (membrane) is formed into a film (completed). Let it do).
[0103]
Alternatively, an electrolyte layer laminated between the electrodes or a part thereof (an electrolyte membrane having a thickness of about half the electrolyte layer thickness) is separately prepared. The electrolyte layer (membrane) is produced by applying the above solution or pregel solution on a suitable film such as a PET film, and curing (or accelerating the crosslinking reaction) at the same time as heating and drying.
[0104]
For curing or heat drying, a vacuum dryer (vacuum oven) or the like can be used. The conditions of the heat drying are determined according to the solution or the pregel solution and cannot be uniquely defined, but are usually at 30 to 110 ° C. for 0.5 to 12 hours.
[0105]
The thickness of the electrolyte layer (membrane) can be controlled using a spacer or the like. When a photopolymerization initiator is used, it is poured into a light-transmitting gap and irradiated with ultraviolet rays using an ultraviolet irradiation device capable of drying and photopolymerization, thereby photopolymerizing the polymer in the electrolyte layer and performing a crosslinking reaction. It is advisable to proceed the film formation. However, it is a matter of course that the present invention is not limited to this method. Depending on the type of the polymerization initiator, radiation polymerization, electron beam polymerization, thermal polymerization, and the like are properly used.
[0106]
Further, since the film used above may be heated to about 80 ° C. during the manufacturing process, the film has sufficient heat resistance at the temperature, and has no reactivity with the solution or the pregel solution. It is desirable to use a material excellent in releasability from the necessity of peeling and removing with, for example, polyethylene terephthalate (PET), a polypropylene film and the like can be used, but it is not limited thereto.
[0107]
The width of the electrolyte layer is often slightly smaller than the size of the electrode forming portion of the current collector of the bipolar electrode.
[0108]
The composition of the above solution or pregel solution and the amount thereof should be appropriately determined according to the purpose of use.
[0109]
The separator impregnated with the electrolytic solution has the same configuration as the electrolyte layer used for the conventional non-bipolar type solution-based bipolar battery, and conventionally known various manufacturing methods, for example, a separator impregnated with the electrolytic solution is used. Since it can be manufactured by a method of sandwiching and stacking between bipolar electrodes or a vacuum injection method, a detailed description thereof will be omitted below.
[0110]
(6) Lamination of bipolar electrode and polymer electrolyte layer
{Circle around (1)} In the case of a bipolar electrode having an electrolyte layer (membrane) formed on one or both sides, sufficiently heat and dry under a high vacuum, and then form a plurality of electrodes having the electrolyte layer (membrane) in an appropriate size. The bipolar battery main body (electrode laminate) is manufactured by cutting out the individual pieces and directly attaching the cut out electrodes.
[0111]
(2) In the case where the bipolar electrode and the electrolyte layer (membrane) are separately manufactured, they are sufficiently heated and dried under a high vacuum, and then each of the bipolar electrode and the electrolyte layer (membrane) is cut into a plurality of appropriate sizes. . A predetermined number of the cut-out bipolar electrodes and the electrolyte layer (membrane) are attached to each other to produce a bipolar battery main body (electrode laminate).
[0112]
In addition, at the time of lamination, an insulating film such as a polyimide film of an appropriate thickness is laminated while being glued with glue at several places on the surface of the current collector extension portion so that the current collectors are not in contact with each other and short-circuited. (See FIG. 5). However, in the present invention, the present invention is not limited to this, and as described above, in the production stage of the current collector, if the insulating portion such as an insulating film is coated on the current collector extension, In the step of laminating the bipolar electrode and the polymer electrolyte layer, the operation can be performed without any difference from the conventional bipolar battery.
[0113]
The number of layers of the electrode stack is determined in consideration of battery characteristics required for a bipolar battery. 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 an electrolyte layer (membrane) or laminating an electrode on which an electrolyte layer (membrane) is formed is difficult from the viewpoint of preventing moisture and the like from being mixed into the battery. It is preferable to carry out under an active atmosphere. For example, a bipolar battery is preferably manufactured in an argon atmosphere or a nitrogen atmosphere.
[0114]
(7) Formation of insulating layer
In the present invention, for example, four or two sides (two sides adjacent to the current collector extension) around the electrode forming portion of the electrode laminate are immersed in an epoxy resin (precursor solution) or the like with a predetermined width. Is injected or impregnated. In any case, the current collector extension is previously masked using a releasable masking material or the like. After that, the epoxy resin is cured to form an insulating portion, and then the masking material may be peeled off.
[0115]
(8) Lead terminal connection
A positive electrode terminal plate and a negative electrode terminal plate are respectively installed on both outermost electron conductive layers of the bipolar battery body (battery laminate), and sides of the positive electrode terminal plate and the negative electrode terminal plate that are not on the current collector extension side. Then, the positive electrode lead and the negative electrode lead are joined (electrically connected) (see FIG. 5). As a joining method of the positive electrode lead and the negative electrode lead, ultrasonic welding or the like having a low joining temperature can be preferably used, but it is not limited to this, and a conventionally known joining method may be appropriately used. Can be.
[0116]
(9) Encapsulation of electrode forming part by current collector extension
Insulating portions such as a current collector extension portion and an insulating separator of the electrode laminate are bent up and down to wrap the electrode forming portion from above and below (see FIGS. 5A and 5B). Since this point has already been described, description thereof will be omitted here.
[0117]
(10) Packing (completion of battery)
Finally, in order to prevent external impact and environmental degradation, the entire battery stack, which is configured to enclose the electrode forming portion with the current collector extension, is sealed with a battery exterior material or battery case, Complete the battery. At the time of sealing, a part of the positive electrode lead and the negative electrode lead is taken out of the 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.
[0118]
【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.
[0119]
Example 1
<Manufacture of batteries>
1. Formation of positive electrode layer
Spinel LiMn having an average particle diameter of 2 μm as a positive electrode active material ₂ O ₄ [41.7% by mass], acetylene black [8.3% by mass] as a conductive additive, a raw material of a polymer electrolyte, and a copolymer of polyethylene oxide (PEO) and polypropylene oxide (PPO) as a host polymer (copolymer). A polymer having a polymerization ratio of 5: 1 and a weight average molecular weight of 8000 was used.) [33.3% by mass], and Li (C ₂ F ₅ SO ₂ ) ₂ N [16.7% by mass], N-methyl-2-pyrrolidone (NMP) as a slurry viscosity adjusting solvent (NMP is volatilized and removed when the electrode is dried, so it is not a constituent material of the electrode but an appropriate slurry viscosity. And a material composed of AIBN (1000 mass ppm based on the amount of the host polymer) as a thermal polymerization initiator was converted into the above ratio (components excluding the slurry viscosity adjusting solvent and the thermal polymerization initiator). The ratio is shown below.) To prepare a positive electrode slurry.
[0120]
The positive electrode slurry is applied to one side of a SUS foil (thickness: 20 μm) as a current collector, placed in a vacuum oven, dried at 120 ° C. for 10 minutes, and simultaneously cured by thermal polymerization to form a positive electrode layer having a dry thickness of 50 μm. did.
[0121]
2. Formation of negative electrode layer
Li as negative electrode active material ₄ Ti ₅ O ₁₂ [21.8% by mass], acetylene black [8.4% by mass] as a conductive additive, and a copolymer (copolymerization) of polyethylene oxide (PEO) and polypropylene oxide (PPO) as a host polymer as a raw material of a polymer electrolyte A ratio of 5: 1 and a weight average molecular weight of 8000 were used.) [42.1% by mass], and Li (C ₂ F ₅ SO ₂ ) ₂ N [21.3% by mass], NMP as a slurry viscosity adjusting solvent (NMP is volatilized and removed at the time of electrode drying. Therefore, an appropriate amount was added so as to obtain an appropriate slurry viscosity instead of a constituent material of the electrode. ) And a material consisting of AIBN (1000 mass ppm based on the amount of the host polymer) as the thermal polymerization initiator are mixed in the above-mentioned ratio (the ratio is expressed by components excluding the slurry viscosity adjusting solvent and the thermal polymerization initiator). Thus, a negative electrode slurry was prepared. 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.
[0122]
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, dried at 120 ° C. for 10 minutes, and simultaneously cured by thermal polymerization to form a negative electrode layer having a dry thickness of 50 μm.
[0123]
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 FIGS. 1 and 5A).
[0124]
3. Formation of polymer electrolyte (layer) membrane
An electrolyte membrane having a thickness of 50 μm was laminated on each of the positive electrode and the negative electrode of the bipolar electrode having the positive electrode and the negative electrode formed on both surfaces.
[0125]
The production of the polymer electrolyte membrane was performed as follows. 53% by mass of the following polymer raw material, and LiN (SO ₂ C ₂ F ₅ ) ₂ Was added, and benzyldimethyl ketal as a photopolymerization initiator was added in an amount of 0.1% by mass of a polymer material. A solution was prepared using dry acetonitrile as a solvent, and then acetonitrile was removed by vacuum distillation. The thickness is regulated using a Teflon (registered trademark) spacer, and the highly viscous solution is filled on the positive electrode layer of a bipolar electrode having a positive electrode layer and a negative electrode layer formed on both sides, and irradiated with ultraviolet rays for 20 minutes to perform photopolymerization. (Crosslinked). The membrane was taken out, placed in a vacuum vessel, and heated and dried under high vacuum at 90 ° C. for 12 hours to remove residual moisture and solvent, thereby forming an electrolyte membrane having a thickness of 50 μm. Similarly, the above highly viscous solution was filled also on the negative electrode layer of the bipolar electrode, and irradiated with ultraviolet rays for 20 minutes to perform photopolymerization (crosslinking). The membrane was taken out, placed in a vacuum vessel, and heated and dried under high vacuum at 90 ° C. for 12 hours to remove residual moisture and solvent, thereby forming an electrolyte membrane having a thickness of 50 μm.
[0126]
As the polymer raw material, a polyether-type network polymer raw material synthesized according to the method described in the literature (J. Electrochem. Soc., 145 (1998) 1521.) was used.
[0127]
4. Formation of bipolar battery
The bipolar electrode on which the electrolyte membrane was formed was laminated so that the positive electrode and the negative electrode faced each other with the electrolyte interposed therebetween, thereby forming a unit cell layer.
[0128]
A 10 μm-thick polyimide film was laminated as an insulating film on the current collector extension so as to prevent the current collectors from contacting each other and causing a short circuit (see FIG. 5).
[0129]
The electrodes were stacked so that 10 unit cell layers (10 unit cell layers) were formed. Thereafter, the current collector extension and the polyimide film are bent vertically along the fold line as shown in FIG. 5 (a), and as shown in FIG. A battery laminate having a structure in which the applied portion was wrapped from above and below was obtained.
[0130]
This battery laminate was sealed with a laminate pack (aluminum laminated with a polypropylene film; battery exterior material) to form a bipolar battery. In addition, as shown in FIG. 5B, the electrode lead was formed on the current collector extension side and taken out of the battery exterior material.
[0131]
Comparative Example 1
A laminate pack (aluminum made of a polypropylene film made of aluminum) was obtained by laminating a battery laminate in which 10 layers (10 single battery layers) were laminated in the same manner as in Example 1 except that a current collector having no current collector extension was used as Comparative Example 1. (A battery exterior material) to form a bipolar battery.
[0132]
<Evaluation>
A nail piercing test was performed on the conventional polymer electrolyte bipolar battery without the current collector extension of Example 1 and Comparative Example 1 at full charge (see FIG. 5B).
[0133]
In a conventional bipolar battery, the voltage of each cell layer was measured after nail penetration, and the voltage of three layers was 0 V, and the remaining seven layers maintained a voltage of 3 V or more.
[0134]
On the other hand, in the bipolar battery of the present invention, the voltages of all the cell layers became 0 V after nail penetration.
[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 (a) is a developed view (or a manufacturing view) schematically showing a state where a part of the current collector 1 is extended so that the structure of a characteristic portion of the present invention can be easily understood. FIG. 5B is a schematic side sectional view schematically showing a structure in which an electrode forming portion is wrapped by a current collector extension, and FIG. FIG. 5D is a schematic explanatory view showing a state in which one sheet of separator is folded into two parts and the fold is set so as to hit one end face of the current collector extension, and FIG. FIG. 7 is a schematic explanatory view showing another state in which the separator is folded into two and the fold is set so as to hit one end face of the current collector extension.
[Explanation of symbols]
1 ... current collector (metal foil)
2 ... Positive electrode layer,
3: Negative electrode layer,
4 ... Electrolyte layer (electrolyte membrane),
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 battery,
21 ... electrode forming part (positive electrode layer and negative electrode layer),
23, 23a, 23b ... current collector extension,
25 ... insulating separator.

Claims (6)

An electrode is formed on a metal foil that is a current collector, and in a stacked battery configured by stacking the electrode with an electrolyte interposed therebetween,
A stacked battery, wherein a part of the current collector is extended, and the extended portion surrounds the electrode forming portion. 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 interposed therebetween. Item 2. The stacked battery according to Item 1. The stacked battery according to claim 1, wherein a polymer electrolyte is used as the electrolyte. The laminated type according to any one of claims 1 to 3, wherein a lithium-transition metal composite oxide is used as the positive electrode active material, and carbon or a lithium-transition metal composite oxide is used as the negative electrode active material. battery. An assembled battery comprising a plurality of the stacked batteries according to claim 1 connected to each other. A vehicle comprising the stacked battery according to any one of claims 1 to 4 and / or the assembled battery according to claim 5 as a driving power supply.

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