JP4032931B2 - Bipolar battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an all-solid-state polymer battery configured using a polymer electrolyte as an electrolyte and an electrode internal structure thereof. More specifically, the present invention relates to a highly reliable all solid polymer battery and its internal electrode structure because it does not contain an electrolytic solution and thus does not leak or generate gas.
[0002]
[Prior art]
In recent years, lithium ion secondary batteries that can achieve high energy density and high output density have been developed as large-capacity power supplies for electric vehicles and the like. The basic configuration of the lithium ion secondary battery is that a positive electrode in which a positive electrode active material such as lithium cobaltate and a conductive additive such as acetylene black are applied to an aluminum current collector using a binder, and carbon fine particles are bonded to a copper current collector. A negative electrode coated with a resin is placed through a polyolefin-based porous membrane separator, and LiPF ₆ It is what filled the non-aqueous electrolyte containing etc. When applied to an electric vehicle or the like, unit cells (cells) having this configuration are connected in series, and a battery module unit and modules are connected in series to form a battery pack.
[0003]
From the viewpoint of the energy density and output density of the battery, it is desired to improve connection resistance, space, and weight of connection between cells and connection between modules. Recently, a battery that employs a bipolar electrode unit that can reduce the resistance of connection between cells and can be expected to be compact has been proposed (see, for example, Patent Document 1). In this proposal, so-called clad material is used to roll two types of metal foil for the current collector, and gel electrolyte is used for the electrolyte. Therefore, a hermetic seal for each cell unit is indispensable. Tangles can occur. If a polymer solid electrolyte is used instead of the gel electrolyte, a hermetic seal is not required and a realistic bipolar battery can be constructed (for example, see Patent Documents 2 and 3). A bipolar battery, which is an all-solid polymer battery configured using a polymer electrolyte as such an electrolyte, has the advantage of extremely high reliability because it does not contain an electrolyte solution and thus does not leak or generate gas. Yes. (For example, refer to Patent Documents 2 and 3.)
[0004]
[Patent Document 1]
JP-A-11-204136
[Patent Document 2]
Japanese Patent Laid-Open No. 2000-1000047
[Patent Document 3]
JP 2002-75455 A
[0005]
[Problems to be solved by the invention]
However, in an all-solid polymer type bipolar battery constructed using a polymer solid electrolyte, the electrodes are stacked in series in the battery, and therefore the capacity is lower than that of a normal battery.
[0006]
In order to increase the battery capacity, it is conceivable to increase the thickness of the electrode and increase the amount of active material applied.
[0007]
However, in an electrode of a solid polymer battery (hereinafter, also simply referred to as an electrode for a solid polymer battery) configured using a polymer solid electrolyte, a polymer (binder, binder, polymer) included in the electrode is included. (It is also called electrolyte etc.)) Since the ionic conductivity is low, there is a problem that when the electrode film is thick, the deep part of the electrode is difficult to react and the utilization factor of the electrode is lowered.
[0008]
Therefore, in view of these problems, the present invention improves the electrode reactivity, improves the electrode utilization rate, and improves the output characteristics and charge / discharge efficiency using the electrode. An object of the present invention is to provide a solid polymer battery.
[0009]
[Means for Solving the Problems]
In the present invention, a positive electrode and a negative electrode including a polymer electrolyte are electrodes of a solid polymer battery configured by sandwiching a solid polymer electrolyte layer (hereinafter, a solid polymer electrolyte layer sandwiched between a positive electrode and a negative electrode) Is also referred to as an interelectrode electrolyte, and in order to distinguish it from the interelectrode electrolyte, the polymer electrolyte contained in the electrode is also referred to as an in-electrode electrolyte).
The polymer electrolyte in a portion near the current collector of the positive electrode and / or the negative electrode is gelled,
The above object can be achieved by a solid polymer battery electrode characterized in that the polymer electrolyte in a portion close to the solid polymer electrolyte layer of the positive electrode and / or the negative electrode is totally solidified.
[0010]
【The invention's effect】
According to the present invention, only the portion of the electrode close to the current collector (also referred to as a deep portion of the electrode in this specification) is gelled, so that the film thickness must be increased in order to increase the battery capacity. Even with no electrode, the reactivity of the electrode can be sufficiently improved. Therefore, by using such an electrode for a solid polymer battery, the reactivity of the electrode is improved, and the output characteristics and charge / discharge efficiency of the battery are improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The solid polymer battery electrode of the present invention is a solid polymer battery in which a positive electrode and a negative electrode including a polymer electrolyte are sandwiched between solid polymer electrolyte layers.
The portion of the polymer electrolyte close to the positive electrode and / or negative electrode current collector is gelled, and the portion of the positive electrode and / or negative electrode close to the solid polymer electrolyte layer is solidified. It is a feature.
[0012]
FIGS. 1 to 4 show a basic cross-sectional structure of a bipolar battery in which a bipolar electrode, a single battery layer, a plurality of bipolar electrodes (or single battery layers) according to the present invention are stacked, and a basic schematic structure of the bipolar battery. 1-4, a bipolar electrode 5 having a positive electrode layer 2 provided on one side of a current collector 1 and a negative electrode layer 3 provided on the other side is adjacent to the polymer electrolyte layer 4 sandwiched between them. The electrode layers 2 and 3 of the matching bipolar electrode 5 are opposed to each other (see FIG. 2). That is, in the bipolar battery, a bipolar electrode (electrode layer) 5 having a positive electrode layer 2 on one surface of the current collector 1 and a negative electrode layer 3 on the other surface is interposed via the polymer electrolyte layer 4. It consists of the electrode laminated body 7 of the structure which laminated | stacked two or more sheets (refer FIG. 3). 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 is formed, not a bipolar electrode structure. In the bipolar battery 11, positive and negative electrode leads 11 and 12 are joined to the current collectors 1 at both upper and lower ends, respectively.
[0013]
Further, in the bipolar battery of the present invention, in order to prevent external impact and environmental degradation during use, the electrode laminate 7 portion is sealed in the battery outer packaging material 10 under reduced pressure, and the electrode leads 8 and 9 are connected to the battery outer packaging material. (Exterior package) It is good to make it the structure taken out outside 10 (refer FIG. 3, 4). From the viewpoint of weight reduction, a conventionally known material such as a polymer-metal composite laminate film such as an aluminum laminate pack or a metal (including an alloy) such as aluminum, stainless steel, nickel, or copper coated with an insulator such as a polypropylene film. By using a battery exterior material, a part or all of the peripheral part thereof is bonded by thermal fusion so that the electrode laminate is accommodated and sealed (sealed) under reduced pressure, and the electrode lead is taken out of the battery exterior material. A configuration is preferable. The basic configuration of the bipolar battery 11 is a configuration in which single battery layers (single cells) 6 are connected in series as shown in FIG.
[0014]
In a conventional bipolar battery using a polymer electrolyte, the positive electrode layer 2 is formed on one side of the current collector 1 using one type of positive electrode material, and the negative electrode layer 3 is formed using one type of negative electrode material on the opposite side. The bipolar electrode 5 is formed and laminated with the polymer electrolyte (membrane) layer 4 interposed therebetween. That is, in these battery electrodes, when the electrode (film) layer becomes thick, there is a problem that a deep portion of the electrode (portion close to the current collector) does not react. Therefore, one feature of the present invention that differs from the conventional one is that the electrode electrolyte near the electrode current collector is gelled, and the electrode electrolyte near the solid polymer electrolyte of the electrode is totally solidified. An electrode is provided. Hereinafter, it demonstrates using drawing.
[0015]
As shown in FIG. 5A, the all-solid polymer battery electrode (= positive electrode layer 2) includes a solid polymer electrolyte 52 in the electrode 2 so that ions can be conducted through the electrode 2. Yes. Although FIG. 5 shows the positive electrode layer 2, the same applies to the negative electrode layer 3.
[0016]
As shown in FIG. 5B, when the electrode film thickness is thin, ions can be conducted through the entire electrode, so that the entire electrode functions effectively as a reacting portion.
[0017]
However, since bipolar batteries have electrodes stacked in series in the battery, the capacity is lower than that of ordinary batteries. To increase battery capacity, the electrode film thickness is increased and the amount of active material applied is increased. It is necessary to increase it. On the other hand, since the ionic conductivity of the solid polymer electrolyte is low, increasing the electrode film thickness (increasing the active material coating amount) to increase the battery capacity as shown in FIG. The reactivity is lowered in a portion (distant from the electrolyte layer and close to the current collector). Therefore, in the present invention, as shown in FIG. 5 (C), only the non-reacting portion 54 (the deep portion of the electrode) is gelled to improve the conductivity so that it can react. It is. This improves the reactivity of the entire electrode, and improves the output characteristics and charge / discharge efficiency of a battery using such an electrode.
[0018]
In the present invention, it is particularly effective when the electrode (film thickness) is increased as described above, but the thickness of the entire electrode is desirably 30 μm or more. The upper limit is not particularly limited, and should be determined in consideration of the purpose of use of the battery (emphasis on output, emphasis on energy, etc.) and ion conductivity. Although the thickness of a general electrode (a positive electrode and a negative electrode) is about 10 to 500 μm, it can be said that it is effective at a thickness of about 30 to 500 μm.
[0019]
In the present invention, the portion of the electrode close to the solid polymer electrolyte is fully solidified. In the specific liquid, the electrolyte in the portion from the surface layer of the electrode (boundary portion with the solid polymer electrolyte layer) to about 20 μm (corresponding to the reacting portion 53 in FIG. 5C) is completely solidified. desirable. However, in this invention, even if it is a case outside the said range, if the reactivity of the deep part of an electrode can be improved, it is included in the scope of the present invention. That is, the all-solid-state all-solid polymer battery does not contain an electrolytic solution, and therefore has very high reliability and heat resistance. For this reason, it is desirable to minimize the portion of the electrode that gels the electrolyte. From the viewpoint of reliability and heat resistance, even if the part that solidifies the electrolyte exceeds the part from the electrode surface layer to about 20 μm, the reactivity of the battery is improved by improving the reactivity of the deeper part. If output characteristics and charge / discharge efficiency are improved, it can be said to be included in the scope of the present invention.
[0020]
Moreover, in this invention, the electrolyte of the part close | similar to the electrical power collector of an electrode is gelatinized. In the specific liquid, the electrolyte in the portion deeper than about 20 μm (corresponding to the non-reacting portion 54 in FIG. 5C) from the electrode surface layer (the lower surface or boundary surface of the solid polymer electrolyte layer 4 in FIG. 5) gels. The configuration is desirable. However, in the present invention, even if it is out of the above range, if the reactivity of the deep portion of the electrode (corresponding to the non-reactive portion 54 in FIG. 5C) can be improved, It is included in the scope of the present invention. That is, the all-solid-state all-solid polymer battery does not contain an electrolytic solution, and therefore has very high reliability and heat resistance. Therefore, it is desirable to minimize the portion of the electrode that gels the electrolyte. From the viewpoint of reliability and heat resistance, even if the portion to be gelled is only a portion deeper than about 20 μm from the electrode surface layer, the reactivity of the entire electrode is efficiently improved by the gelation. If the output characteristics and charge / discharge efficiency are improved, it can be said that it is included in the scope of the present invention.
[0021]
From the above, in the present invention, it can be said that the thickness of the whole electrode is 30 μm or more, the portion from the electrode surface layer to about 20 μm is solidified, and the deeper portion is gelled. For example, when the thickness of the entire electrode is 100 μm, it is desirable that the portion from the electrode surface layer to about 20 μm is solidified, and the deeper portion (the portion from the electrode surface layer to about 20 μm to 100 μm) is gelled. become. In addition, when all the electrodes are gelled, the amount of the solvent contained in the battery increases, and the reliability decreases. In addition, the solvent inside the electrode may permeate the solid electrolyte layer and soften the solid electrolyte, which may cause an internal short circuit.
[0022]
In the present invention, the ratio of the host polymer and the solvent constituting the gel electrolyte in the gelled portion of the electrode (corresponding to the non-reacting portion 54 in FIG. 5C) is polymer: solvent = The range of 3% by mass: 97% by mass to polymer: solvent = 50% by mass: 50% by mass is desirable. This is a highly reliable electrode with high electrode reactivity and low leakage by adjusting the ratio of the host polymer and solvent constituting the gel electrolyte of the gelled part of the electrode to the above range. It is because it can comprise.
[0023]
Further, as the host polymer of the gelled portion of the electrode in the present invention, polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoro Propylene (PVdF-HFP), poly (methyl methacrylate) (PMMA) and copolymers thereof are desirable.
[0024]
As the solvent (electrolytic solution) of the gelled portion of the electrode in the present invention, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (GBL), dimethyl carbonate (DMC), diethyl carbonate (DEC) , And mixtures thereof are desirable.
[0025]
As described above, in the positive electrode layer 2 and the negative electrode layer 3, the portion of the electrolyte close to the current collector of the electrode is gelled, and the portion of the electrode close to the solid polymer electrolyte is solidified. Each includes a positive electrode active material and a negative electrode active material, respectively, and both include a solid polymer electrolyte and a gelled gel electrolyte in the layer. In addition to this, a lithium salt, a conductive additive or the like may be included in order to increase the ionic conductivity.
[0026]
Among these, the solid polymer electrolyte is made of a polymer containing a lithium salt and a polar group. In order to make the movement of ions smoothly in the electrode layer, the space between the active material fine particles in a portion close to the solid polymer electrolyte in the electrode layer is filled so that this polymer solid electrolyte fills.
[0027]
The gelled gel electrolyte contains a host polymer (the polymer solid electrolyte) constituting the gel electrolyte and a solvent. Above (all solid polymer electrolyte and gelled gel electrolyte serve as electrolyte and binder in electrolyte battery. For smooth ion movement in electrode layer In the present invention, in particular, the gel electrolyte is filled so that the gap between the active material fine particles in the portion near the current collector in the electrode layer is filled.
[0028]
Fully solidified polymer solid electrolyte in the electrode layer (ionic conductivity: 10 ^-Five -10 ^-Four S / cm) and gelled gel electrolyte (ionic conductivity: 10 ^-2 -10 ^-Four The optimal filling ratio of S / cm) depends on the intended use of the battery (for high power or high energy) and ion conductivity, but if it is too small, the ion conduction resistance and the ion diffusion resistance in the electrode When it becomes large and is too much, the energy density of the battery constituting the battery is lowered. In the case where the total solid polymer electrolyte of the present invention and the gelled gel electrolyte are used in combination, the ionic conductivity level of each battery is a gelled gel electrolyte. It is desirable to increase the area in which the solvent is used, or to increase the solvent in the ratio of the host polymer and the solvent constituting the gelled gel electrolyte. In addition, the conductive material is increased or the bulk density of the active material is lowered to keep the electron conduction resistance between the active material fine particles high. At the same time, the voids are increased, and a solid polymer electrolyte or gel electrolyte is formed there. As a filled structure, the filling ratio of the solid polymer electrolyte or gel electrolyte to the active material fine particles may be increased.
[0029]
Examples of the polymer used in the polymer solid electrolyte of the part of the electrode that is fully solidified in the present invention include polyethylene oxide (PEO), polypropylene oxide (PPO), and their copolymer polymers, A polymer synthesized by a radical polymerization method using a raw material polymer having a crosslinkable carbon-carbon double bond can be used, but is not limited thereto. This type of polyalkylene oxide polymer is LiBF. _Four , LiPF ₆ , LiN (SO ₂ CF _Three ) ₂ , LiN (SO ₂ C ₂ F _Five ) ₂ Lithium salts such as can be dissolved well, and mechanical properties are also good by making a crosslinked structure.
[0030]
Note that, in the solid polymer battery electrode of the present invention and the solid polymer battery using the same, as shown in FIG. 5, the electrolyte in a portion close to the current collector of the electrode is gelled. The portion of the electrolyte close to the molecular electrolyte is solidified. Therefore, the solid polymer battery electrode and other components of the solid polymer battery using the same are not limited at all. Therefore, although each constituent element of the solid polymer battery using the electrode for the solid polymer battery will be briefly described below, it goes without saying that the present invention should not be limited thereto.
[0031]
[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. Further, a current collector in which a metal surface is coated with aluminum may be used. 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.
[0032]
Although the thickness of a collector is not specifically limited, Usually, it is about 1-100 micrometers.
[0033]
[Positive electrode active material layer]
The positive electrode active material layer includes a positive electrode active material, a solid polymer electrolyte formed into a solid, and a gel electrolyte formed into a gel. In addition, a lithium salt may be included to enhance ion conductivity, and a conductive aid may be included to enhance electrical conductivity.
[0034]
The positive electrode active material is not particularly limited, but a lithium-transition metal composite oxide is preferably used. This is because the material is excellent in reactivity and cycle durability and is low in cost. Therefore, a battery having excellent output characteristics can be formed by using these materials for the positive electrode.
[0035]
Examples of the lithium-transition metal composite oxide include spinel LiMn. ₂ O _Four There is, but is not limited to this. Spinel LiMn ₂ O _Four In addition, any lithium-transition metal composite oxide used in a solution-type lithium ion battery can be used. Specifically, LiCoO ₂ Li / Co complex oxides such as LiNiO ₂ Li / Ni based complex oxide such as spinel LiMn ₂ O _Four Li / Mn based composite oxides such as those obtained by substituting some of these transition metals with other elements can be used.
[0036]
Other positive electrode active materials that can be used include, for example, LiFeO. ₂ Li / Fe complex oxides such as 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.
[0037]
The particle diameter of the fine particles of the positive electrode active material is preferably smaller than that used in a normal solution type lithium ion battery in order to reduce the electrode resistance of the battery. Specifically, the average particle diameter of the positive electrode active material is preferably 0.1 to 10 μm.
[0038]
The polymer solid electrolyte obtained by making it all solid is not particularly limited as long as it is a polymer having ion conductivity. Examples of the polymer having ion conductivity include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. Such polyalkylene oxide polymer is 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. In addition, excellent mechanical strength is exhibited by forming a crosslinked structure. 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 to be included in both.
[0039]
The gel polymer formed by gelation is as described above as a characteristic part of the present invention.
[0040]
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.
[0041]
Examples of the conductive assistant include acetylene black, carbon black, and graphite. However, it is not necessarily limited to these.
[0042]
The amount of positive electrode active material, polymer solid electrolyte, gel electrolyte, lithium salt, and conductive additive in the positive electrode active material layer is determined in consideration of the intended use of the battery (emphasis on output, energy, etc.) and ion conductivity. Should. For example, if the blending amount of the polymer solid electrolyte or gel electrolyte in the active material layer is too small, the ion conduction resistance and ion diffusion resistance in the active material layer increase, and the battery performance decreases. On the other hand, when the amount of the polymer solid electrolyte or gel electrolyte in the active material layer is too large, the energy density of the battery is lowered. Therefore, in consideration of these factors, the polymer solid electrolysis mass and the gel electrolysis mass suitable for the purpose are determined.
[0043]
The thickness of the positive electrode active material layer is as already described.
[0044]
[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode active material, a solid polymer electrolyte formed into a total solid, and a gel electrolyte formed into a gel. In addition, a lithium salt may be included to enhance ion conductivity, and a conductive aid may be included to enhance electrical conductivity. Except for the type of the negative electrode active material, the contents are basically the same as those described in the section “Positive electrode active material”, and thus the description thereof is omitted here.
[0045]
The negative electrode active material is not particularly limited, and a negative electrode active material that is also used in a solution-type lithium ion battery can be used. Preferably, since the polymer solid battery of the present invention uses a polymer solid electrolyte, carbon, a metal oxide, and a lithium-metal composite oxide are preferable, and more preferably carbon, considering the reactivity with the polymer solid electrolyte. , Transition metal oxides, lithium-transition metal composite oxides. More preferred are carbon and lithium-titanium composite oxide. Specifically, hard carbon, graphite, Li _Four Ti _Five O ₁₂ It is desirable to use This is because these are excellent in reactivity and cycle durability and are low-cost materials. Therefore, a battery having excellent output characteristics can be formed by using these materials for the negative electrode.
[0046]
[Polymer electrolyte layer]
The polymer electrolyte layer of the present invention is desirably a polymer solid electrolyte layer using an all solid polymer. By using an all solid polymer in the polymer electrolyte layer, there is no liquid leakage, so that a solid polymer battery, preferably a bipolar lithium ion secondary battery can be formed with a simple configuration. Furthermore, by using a solid polymer, there is no problem of liquid junction, so that a battery having high reliability and excellent output characteristics can be formed.
[0047]
The all solid polymer used in the polymer electrolyte layer is composed of a polymer having ion conductivity, and the material is not limited as long as it exhibits ion conductivity. As the all solid polymer (polymer solid electrolyte), for example, known polymers (polymer solid electrolyte) such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof can be used. .
[0048]
The polymer solid electrolyte layer 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.
[0049]
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.
[0050]
The polymer solid electrolyte may be included 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, and different polymer solid electrolytes are used depending on the layer. Also good.
[0051]
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 it as thin as possible within a range in which the function as the polymer solid electrolyte layer can be secured. The thickness of a general polymer solid electrolyte layer is about 5 to 200 μm.
[0052]
By the way, a polymer for a solid polymer 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 solution-type lithium ion batteries, the capacity of the negative electrode may be less than the capacity of the positive electrode facing through the polymer solid 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. Here, the “positive electrode facing through the polymer solid electrolyte layer” refers to a positive electrode that is a component of the same single battery layer (cell). 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.
[0053]
However, if the capacity of the negative electrode is smaller than the capacity of the opposing positive electrode, the negative electrode potential will be too low 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 so that the durability is not lowered by setting an appropriate value for the oxidation-reduction potential of the positive electrode active material using the average charging voltage of one single battery layer (cell).
[0054]
In the present invention, a gel electrolyte may be used for the polymer electrolyte layer. In particular, by reducing the ratio of the solvent to the ratio of the host polymer and the solvent constituting the gel electrolyte, it is possible to construct a highly reliable electrode with high ionic conductivity inside the polymer electrolyte layer and reduced leakage. Because. The ratio of the host polymer and the solvent constituting the gel electrolyte is preferably in the range of polymer: solvent = 5 mass%: 95 mass% to polymer: solvent = 95 mass%: 5 mass%. Needless to say, the polymer electrolyte layer may have a structure in which a solid polymer electrolyte and the gel electrolyte are combined in an arbitrary ratio.
[0055]
The battery of the present invention can be applied to any solid polymer battery using a polymer solid electrolyte for the electrolyte layer. Preferably, a plurality of bipolar electrodes in which the positive electrode is formed on one surface of the current collector and the negative electrode is formed on the other surface are stacked in series with the electrolyte interposed therebetween, using the electrode for the solid polymer battery of the present invention. The battery is a bipolar lithium ion secondary battery having the above structure. This is because the cell voltage is higher than that of a lithium ion secondary battery using a normal electrolyte, and a battery with excellent output characteristics can be configured. This is because a high power density can be achieved. Further, in the bipolar lithium ion secondary battery of the present invention, since the electrodes are stacked in series in the battery, the battery capacity is lower than that of a lithium ion secondary battery using a normal electrolytic solution, and the battery capacity is increased. Even when it is necessary to increase the coating amount of the active material by increasing the thickness (film thickness) of the electrode, the reactivity of the entire electrode is improved, and the output characteristics and charge / discharge efficiency of the battery can be improved. But there is.
[0056]
[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. What is necessary is just to use it as needed.
[0057]
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.
[0058]
[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.
[0059]
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.
[0060]
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.
[0061]
The positive electrode and the negative electrode terminal plate may be the same size as the current collector.
[0062]
[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.
[0063]
[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. It is good to accommodate in. 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.
[0064]
The second of the present invention is an assembled battery constituted by connecting a plurality of bipolar lithium ion secondary batteries of the present invention. This is because a battery module with a high capacity and a high output can be formed by forming an assembled battery. The battery assembly of the bipolar lithium ion secondary battery of the present invention is not particularly limited, and the bipolar lithium ion secondary battery of the present invention is appropriately connected in series according to the purpose of use of the battery pack. Can be connected in parallel, or in series-parallel (a combination of series and parallel).
[0065]
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.
[0066]
A third aspect of the present invention is a vehicle in which the bipolar lithium ion secondary battery and / or the assembled battery of the present invention is mounted as a driving power source. Thereby, the vehicle (for example, electric vehicle, hybrid vehicle) excellent in fuel consumption and running performance can be provided. In addition, the bipolar lithium ion secondary battery of the present invention has various characteristics as described above, and is a particularly compact battery. For this reason, it is suitable as a power source for driving a vehicle, for example, an electric vehicle, a hybrid electric vehicle, or the like that has particularly strict requirements regarding energy density and power density. In addition, the solid polymer electrolyte has the disadvantage that its ionic conductivity is lower than that of the gel electrolyte, but when used as a power source for driving a vehicle, the ambient environment of the bipolar lithium ion secondary battery is kept at a certain high temperature. can do. Also from this point of view, it can be said that the bipolar lithium ion secondary battery of the present invention is preferably used as a power source for driving a vehicle. For example, as shown in FIG. 7, it is convenient to install the assembled battery 73 as a driving power source under the seat (under the floor) at the center of the body of the electric vehicle or hybrid electric vehicle 71 because the interior space and the trunk room can be widened. It is. However, the present invention is not limited to these, and can be installed in the engine room, the hood inside the hood, the roof, or the like, or can be installed in the lower part of the rear trunk room, or the electric vehicle. If the engine is not mounted as in the case of the above, it can be mounted on the part where the engine is mounted in front of the vehicle body. In the present invention, not only the assembled battery but also a bipolar battery may be mounted depending on the intended use, or a combination of these assembled battery and bipolar battery may be mounted. In addition, as the vehicle on which the bipolar lithium ion secondary 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 not limited thereto. .
[0067]
In the fourth aspect of the present invention, a gel electrode is formed on the current collector, an all-solid electrode is formed on the solid polymer electrolyte membrane, and the electrodes are gelled to form a solid battery. A method for producing a polymer battery. By this manufacturing method, an electrode in which only the electrolyte inside the electrode (that is, the portion close to the current collector) is gelled (that is, the electrode for the solid polymer battery according to claim 1 or 2) can be formed. . Thereby, the reactivity of the whole electrode improves, and the output characteristic and charging / discharging efficiency of a battery improve. The fourth aspect of the present invention will be described below with reference to the drawings.
[0068]
FIG. 6 is a schematic cross-sectional view of a part of the battery structure at the battery assembly stage or the completed battery after battery assembly, schematically showing the outline of each main process of the method for producing a solid polymer battery of the present invention.
[0069]
(1) Formation of electrode (positive electrode) having gelled gel electrolyte (hereinafter also referred to as gel electrode (positive electrode)) (see FIG. 6A)
(1) Preparation of slurry for gel electrode (positive electrode)
The slurry for gel electrode (positive electrode) is a solution containing a polymer (polymer raw material) that is a raw material of gel electrolyte, a solvent (electrolytic solution), a positive electrode active material 51, and a lithium salt (supporting salt). As other components, a conductive assistant and a polymerization initiator are optionally included. Examples of the raw material polymer for the 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 (polymer solid electrolyte) using this cross-linkable functional group, the mechanical strength is improved. As the gel electrolyte raw material solvent (electrolytic solution), positive electrode active material, lithium salt, and conductive additive, the aforementioned compounds can be used. 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. The amount of polymer and the amount of solvent, which are raw materials for the gel electrolyte, are adjusted so that the ratio of the host polymer and the solvent (electrolytic solution) constituting the gel electrolyte is within the above range. The addition amount of the positive electrode active material, the lithium salt, and the conductive auxiliary agent may be adjusted according to the purpose of the solid polymer battery (preferably a bipolar lithium ion secondary battery), and may be added in a commonly used amount. The amount of the gel electrolyte material added is selected in consideration of the relationship between the energy density of the gel electrode and the volume fraction of the gel electrolyte. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer (polymer raw material). Usually, it is about 0.01-1 mass% with respect to a polymer (polymer raw material).
[0070]
(2) Formation of gel electrode (positive electrode) 2a
A slurry for a gel electrode (positive electrode) is applied to one surface of the current collector 1 with a predetermined thickness. After determining the thickness of the entire electrode from the purpose of use of the battery, etc., the thickness of the applied gel electrode is determined in consideration of the thickness (about 20 μm) of the all solid electrode (positive electrode) defined above. What is necessary is just to determine application | coating thickness suitably so that the thickness of a (positive electrode) part can be formed.
[0071]
Next, the current collector 1 coated with the slurry for the gel electrode (positive electrode) is heated and dried, and the cross-linking reaction of the polymer proceeds to increase the mechanical strength of the gel electrolyte, thereby increasing the mechanical strength of the current collector 1. In addition, the gel electrode (positive electrode) 2 a containing the polymer gel electrolyte 53 in addition to the positive electrode active material 51 is formed. The heating and drying atmosphere can be performed in an inert gas atmosphere such as an argon gas atmosphere, but is not limited thereto. The heating and drying conditions are determined according to the composition of the applied slurry for the gel electrode (positive electrode) and cannot be uniquely defined, but are usually 40 to 150 ° C. and 5 minutes to 20 hours.
[0072]
In addition, although the example which apply | coats the slurry for gel electrodes (positive electrode) on the electrical power collector 1 was shown here, the slurry for gel electrodes (positive electrode) is formed on a film similarly to the all-solid-state electrode (positive electrode) 2b mentioned later. May be applied and heated and dried to form a gel electrode (positive electrode), and then laminated on the current collector. However, from the viewpoint of simplifying the manufacturing procedure and handling the gel electrode (positive electrode), etc. It can be said that it is better to apply on the electric body.
[0073]
The gel electrode 2a may be formed as a single layer, or if necessary, two or more types of gel electrolyte layers having different ratios of the host polymer and solvent constituting the gel electrolyte, the amount of active material, and the like may be used. Needless to say, it may be formed in multiple layers. Thus, the concentration of the electrolyte in the portion near the current collector of the electrode (and hence the ionic conductivity of the gel electrolyte portion) may have a concentration distribution.
[0074]
(2) Formation of an electrode (hereinafter also referred to as an all-solid electrode (positive electrode)) having an electrolyte that has been solidified (see FIG. 6B).
(1) Preparation of slurry for all solid electrode (positive electrode)
The slurry for an all solid electrode (positive electrode) is a polymer (polymer raw material), a positive electrode active material, and a lithium salt (supporting salt), which are raw materials of a polymer electrolyte (also referred to as an all polymer solid electrolyte) that has been solidified. It is a solution containing a slurry viscosity adjusting solvent. As other components, a conductive assistant and a polymerization initiator are optionally included. Examples of the polymer (polymer raw material) of the raw material of the all-polymer solid electrolyte include PEO, PPO, and copolymers thereof, and the polymer has a crosslinkable functional group (such as a carbon-carbon double bond). preferable. By cross-linking the polymer (polymer raw material) using this cross-linkable functional group, the mechanical strength is improved. With respect to the positive electrode active material, the lithium salt, and the conductive additive, the above-described compounds can be used. 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. As the slurry viscosity adjusting solvent, for example, a conventionally known solvent such as NMP may be appropriately selected according to the type of slurry for all solid electrode (positive electrode). The addition amount of the positive electrode active material, the lithium salt, and the conductive auxiliary agent may be adjusted according to the purpose of the solid polymer battery (preferably a bipolar lithium ion secondary battery), and may be added in a commonly used amount. The amount of polymer (polymer raw material) added to the raw material of the all-polymer solid electrolyte is selected in consideration of the relationship between the energy density of the all-solid electrode (positive electrode) and the volume fraction of the all-polymer solid electrolyte. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer (polymer raw material) of the raw material of the all polymer solid electrolyte. Usually, it is about 0.01-1 mass% with respect to this polymer (polymer raw material).
[0075]
(2) Preparation of polymer electrolyte layer
Separately, a polymer solid electrolyte layer part 4a (generally, a polymer solid electrolyte membrane having a thickness of about half the target polymer solid electrolyte layer thickness) to be laminated between the electrodes 2 and 3 is prepared. The polymer solid electrolyte membrane (a part of the polymer solid electrolyte) 4a is a PET film prepared by dissolving a polymer (polymer material) as a raw material of the polymer solid electrolyte and a lithium salt in a solvent such as NMP. It is manufactured by applying on a suitable film 61 and curing. The thickness of the polymer solid electrolyte membrane (a part of the polymer solid electrolyte) can be controlled using a spacer or the like. In the case of using a photopolymerization initiator, the film may be formed by pouring into a light-transmitting gap and irradiating with ultraviolet rays to advance the crosslinking reaction. However, it is needless to say that the method is not limited to this. Depending on the type of polymerization initiator, radiation polymerization, electron beam polymerization, thermal polymerization, etc. are used properly. Since the solid polymer electrolyte, lithium salt, blending amount, and the like used are as described above, description thereof is omitted here. In addition, since the film used above may be heated to about 80 ° C. in the manufacturing process, it has sufficient heat resistance at about the temperature, and further has reactivity with the raw material slurry and the polymer solid electrolyte. In addition, it is desirable to use a material having excellent releasability because it needs to be peeled off and removed in the manufacturing process. For example, polyethylene terephthalate (PET), polypropylene film, etc. can be used, but should be limited to these. It is not a thing.
[0076]
(3) Formation of all solid electrode (positive electrode)
On the solid polymer electrolyte membrane 4a having the predetermined thickness (about half of the target solid polymer electrolyte layer thickness of 5 to 200 μm) prepared on the film 61 in the above (2), the all solid electrode ( A positive electrode) slurry is applied at a predetermined thickness. The thickness of the slurry for all solid electrode (positive electrode) by coating is determined by determining the thickness of the entire electrode 2 from the purpose of use of the battery, and then the thickness of the all solid electrode (positive electrode) 2b defined above (about 20 μm). The coating thickness may be determined as appropriate so that the degree can be formed.
[0077]
Next, the polymer solid electrolyte membrane 4a coated with the slurry for the all-solid-state electrode (positive electrode) is heated and dried to advance the cross-linking reaction of the polymer, thereby increasing the mechanical strength of the polymer solid electrolyte. On the molecular solid electrolyte membrane 4a, an all solid electrode (positive electrode) 2b containing a polymer solid electrolyte 52 in addition to the positive electrode active material 51 is formed. The heat drying can be performed using a vacuum dryer or the like, but is not limited thereto. The heating and drying conditions are determined according to the composition of the applied slurry for the all-solid-state electrode (positive electrode) and cannot be uniquely defined, but are usually 40 to 150 ° C. and 5 minutes to 20 hours.
[0078]
(3) Bonding of electrodes (positive electrode) (see FIG. 6C)
The solid electrode (positive electrode) 2b prepared in (2) above is bonded onto the gel electrode (positive electrode) 2a prepared in (1) so that the electrode portions face each other, and the polymer solid electrolyte membrane 4a The pasted film 61 is peeled off, and the polymer electrolyte 53 in a portion close to the current collector 1a of the electrode (positive electrode) 2 (electrode (positive electrode) 2) is gelled on one surface of the current collector 1. An electrode (positive electrode) 2) in which a portion of the polymer electrolyte 52 in the (positive electrode) 2 close to the solid polymer electrolyte layer 4a is solidified and a part 4a of the polymer solid electrolyte layer are formed (FIG. 6 ( See C).
[0079]
(4) Formation of electrode (negative electrode) having gelled gel electrolyte (hereinafter also referred to as gel electrode (negative electrode)) (see FIG. 6 (A) to FIG. 6 (C) by replacing the positive electrode with the negative electrode) thing.)
(1) Preparation of slurry for gel electrode (negative electrode)
The slurry for a gel electrode (negative electrode) is a solution containing a polymer (polymer raw material) that is a gel electrolyte raw material, a solvent (electrolytic solution), a negative electrode active material, and a lithium salt (supporting salt). As other components, a conductive assistant and a polymerization initiator are optionally included. Examples of the raw material polymer for the 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 (polymer solid electrolyte) using this cross-linkable functional group, the mechanical strength is improved. Regarding the solvent (electrolyte solution), the negative electrode active material, the lithium salt, and the conductive additive of the gel electrolyte raw material, the above-described compounds can be used. 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. The amount of polymer and the amount of solvent, which are raw materials for the gel electrolyte, are adjusted so that the ratio of the host polymer and the solvent (electrolytic solution) constituting the gel electrolyte is within the above range. The addition amount of the negative electrode active material, the lithium salt, and the conductive auxiliary agent may be adjusted according to the purpose of the solid polymer battery (preferably a bipolar lithium ion secondary battery), and may be added in a commonly used amount. The amount of the gel electrolyte material added is selected in consideration of the relationship between the energy density of the gel electrode (negative electrode) and the volume fraction of the gel electrolyte. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer (polymer raw material). Usually, it is about 0.01-1 mass% with respect to a polymer (polymer raw material).
[0080]
(2) Formation of gel electrode (negative electrode)
A slurry for gel electrode (negative electrode) is applied to one surface of current collector 1b with a predetermined thickness. The thickness of the applied electrode is determined by determining the thickness of the entire electrode from the intended use of the battery, and the remaining gel electrode in consideration of the thickness (about 20 μm) of the all solid electrode (negative electrode) defined above. What is necessary is just to determine application | coating thickness suitably so that the thickness of a (negative electrode) part can be formed.
[0081]
The current collector includes (i) a negative electrode active material on the other surface (the surface opposite to the positive electrode forming side) of the current collector 1a of the electrode (positive electrode) 2a formed in (1) to (3). In addition to the substance 55, a bipolar electrode may be formed by forming a gel electrode (negative electrode) 3a having a polymer gel electrolyte 53, or (ii) a current collector different from the current collector 1a of the electrode (positive electrode) 2a. A current collector 1b is prepared, and a gel electrode (negative electrode) 3a having a polymer gel electrolyte 53 in addition to the negative electrode active material 55 may be formed on one surface of the current collector 1b (particularly, both ends of the bipolar battery). This is effective when forming the electrode.) Here, for the convenience of explanation, the latter has been described as an example (see FIG. 6D). However, even in the case of (i) above, when forming a bipolar battery, except for the case described later, It goes without saying that it is necessary to form a plurality of bipolar electrodes formed by forming an electrode (positive electrode) on one side of the body and an electrode (negative electrode) on the other side. Since this is possible, the description of each case will be omitted. A bipolar battery may be formed by stacking a plurality of single cells formed in (ii). In this case, since the current collectors at both ends of each unit cell are bonded together, the thickness of the current collector used for each unit cell is reduced to about half the normal thickness as necessary. Is desirable. Further, when the current collectors are bonded to each other, they may be bonded more firmly using an electrically conductive adhesive or the like. As the electrically conductive adhesive, a paste obtained by dispersing a metal powder such as aluminum in a resin solution (preferably a conductive resin solution) can be used. Further, other joining means may be used. In addition, in order to avoid the need to attach the current collectors to each other, a PET film is used instead of the current collector for any one of the electrodes facing the current collectors. The current collector on the side may be laminated.
[0082]
Next, the current collector coated with the slurry for the gel electrode (negative electrode) is heated and dried, and the cross-linking reaction of the polymer is advanced to increase the mechanical strength of the gel electrolyte. An electrode (negative electrode) is formed. The heating and drying atmosphere can be performed in an inert gas atmosphere such as an argon gas atmosphere, but is not limited thereto. The conditions for heat drying are determined according to the composition of the applied slurry for the gel electrode (negative electrode) and cannot be uniquely defined, but are usually 40 to 150 ° C. and 5 minutes to 20 hours.
[0083]
(5) Formation of an electrode having an electrolyte that is solidified (hereinafter also referred to as an all-solid electrode (negative electrode))
(1) Preparation of slurry for all solid electrode (negative electrode)
The slurry for an all solid electrode (negative electrode) is a polymer (polymer raw material), a negative electrode active material, and a lithium salt (supporting salt) that are raw materials for a polymer electrolyte (also referred to as an all polymer solid electrolyte) that has been solidified. It is a solution containing a slurry viscosity adjusting solvent. As other components, a conductive assistant and a polymerization initiator are optionally included. Examples of the polymer (polymer raw material) of the raw material of the all-polymer solid electrolyte include PEO, PPO, and copolymers thereof, and the polymer has a crosslinkable functional group (such as a carbon-carbon double bond). preferable. By cross-linking the polymer (polymer raw material) using this cross-linkable functional group, the mechanical strength is improved. With respect to the negative electrode active material, the lithium salt, and the conductive additive, the above-described compounds can be used. 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. As the slurry viscosity adjusting solvent, for example, a conventionally known solvent such as NMP may be appropriately selected according to the type of slurry for all solid electrode (negative electrode). The addition amount of the negative electrode active material, the lithium salt, and the conductive auxiliary agent may be adjusted according to the purpose of the solid polymer battery (preferably a bipolar lithium ion secondary battery), and may be added in a commonly used amount. The amount of polymer (polymer raw material) added to the raw material of the all-polymer solid electrolyte is selected in consideration of the relationship between the energy density of the all-solid electrode (negative electrode) and the volume fraction of the all-polymer solid electrolyte. The addition amount of the polymerization initiator is determined according to the number of crosslinkable functional groups contained in the polymer (polymer raw material) of the raw material of the all polymer solid electrolyte. Usually, it is about 0.01-1 mass% with respect to this polymer (polymer raw material).
[0084]
(2) Preparation of polymer electrolyte
Separately, the remaining part 4b of the polymer solid electrolyte layer laminated between the electrodes 2 and 3 is prepared. The polymer solid electrolyte membrane (the remaining part of the polymer solid electrolyte layer) 4b is a slurry prepared by dissolving a polymer (polymer material) as a raw material of the polymer solid electrolyte and a lithium salt in a solvent such as NMP. It is manufactured by coating on a suitable film and curing. The thickness of the polymer solid electrolyte membrane (the remaining part of the polymer solid electrolyte layer) can be controlled using a spacer or the like. In the case of using a photopolymerization initiator, the film may be formed by pouring into a light-transmitting gap and irradiating with ultraviolet rays to advance the crosslinking reaction. However, it is needless to say that the method is not limited to this. Depending on the type of polymerization initiator, radiation polymerization, electron beam polymerization, thermal polymerization, etc. are used properly. Since the solid polymer electrolyte, lithium salt, blending amount, and the like used are as described above, description thereof is omitted here. In addition, since the film used above may be heated to about 80 ° C. in the manufacturing process, it has sufficient heat resistance at about the temperature, and further has reactivity with the raw material slurry and the polymer solid electrolyte. In addition, it is desirable to use a material having excellent releasability because it needs to be peeled off and removed in the manufacturing process. For example, polyethylene terephthalate (PET), polypropylene film, etc. can be used, but should be limited to these. It is not a thing.
[0085]
The remaining part of the polymer solid electrolyte layer is a polymer solid electrolyte membrane that is about half the thickness of the target polymer solid electrolyte layer. The total thickness of the polymer solid electrolyte membrane obtained in the above is adjusted to the target polymer solid electrolyte layer thickness. However, the total thickness of the polymer solid electrolyte membrane prepared in the above (2) (2) and the polymer solid electrolyte membrane prepared in (4) (2) is the target polymer solid electrolyte layer thickness. It can be said that the thickness of each layer is not particularly limited. Therefore, in some cases, when a polymer solid electrolyte membrane having a target polymer solid electrolyte layer thickness is formed by either (2) (2) or (4) (2), the other The manufacturing process of the polymer solid electrolyte membrane is omitted. In this case, it can be said that an all solid electrode (positive electrode) or an all solid electrode (negative electrode) may be formed directly without providing a solid polymer electrolyte membrane on the film.
[0086]
(3) Formation of all solid electrode (negative electrode)
On the polymer solid electrolyte membrane 4b having a predetermined thickness (about half of the target polymer solid electrolyte layer thickness of 5 to 200 μm) prepared on the film in (2) above, the all solid electrode (negative electrode) ) Slurry is applied at a predetermined thickness. The thickness of the slurry for all solid electrode (negative electrode) by coating is determined by determining the thickness of the entire electrode from the purpose of use of the battery, and then the thickness of the all solid electrode (negative electrode) portion defined above (about 20 μm) The coating thickness may be determined as appropriate so that can be formed.
[0087]
Next, the polymer solid electrolyte membrane 4b coated with the slurry for the all solid electrode (negative electrode) is heated and dried to advance the crosslinking reaction of the polymer, thereby increasing the mechanical strength of the polymer solid electrolyte. An all solid electrode (positive electrode) 3 having a solid polymer electrolyte 52 in addition to the negative electrode active material 55 is formed on the molecular solid electrolyte membrane 4b. The heat drying can be performed using a vacuum dryer or the like, but is not limited thereto. The heating and drying conditions are determined according to the composition of the applied slurry for the all-solid-state electrode (negative electrode) and cannot be uniquely defined, but are usually 40 to 150 ° C. and 5 minutes to 20 hours.
[0088]
(6) Bonding of electrodes (negative electrode) (see FIG. 6D)
On the gel electrode (negative electrode) 3a, the all-solid-state electrode (negative electrode) 3b is bonded so that the electrode portions face each other, and the film bonded on the polymer solid electrolyte membrane 4b is peeled off to obtain a current collector. A portion of the polymer electrolyte 53 near the current collector 1b of the electrode (negative electrode) 3 (electrode (negative electrode) 3 is gelled on one side of 1b, and a portion near the solid polymer electrolyte layer 4b of the electrode (negative electrode) 3 The electrode (negative electrode) 3) in which the polymer electrolyte 52 is completely solidified, and the remaining part 4b of the polymer solid electrolyte layer are formed.
[0089]
(7) Lamination of bipolar electrode and polymer solid electrolyte layer
The electrode (positive electrode) 2 and the electrode (negative electrode) 3 obtained by the above (1) to (6) are sufficiently heated and dried under high vacuum, and then each of them is cut into a suitable size as necessary. After that, the electrolyte membranes 4a and 4b of the electrode (positive electrode) 2 and the electrode (negative electrode) 3 are bonded together to form a battery (unit cell). Further, the width of the electrode and the solid polymer electrolyte layer may be made slightly smaller than the current collector. This is because a gel electrolyte is used for a part of the electrodes, and thus the periphery of these electrodes and the solid polymer electrolyte layer is insulated by an insulating layer, which can further improve safety and reliability. This is because this is advantageous.
[0090]
Further, as described in the above unit cell (the electrode (positive electrode) and the electrode (negative electrode)) or the bipolar electrode ((4) (2) above), the electrode (positive electrode) is formed on one side of the current collector, A bipolar battery body (battery laminate) is fabricated by laminating (attaching) a plurality of electrodes (with negative electrodes formed on the surface). The number of stacked layers is determined in consideration of battery characteristics required for the bipolar battery. Electrodes are respectively disposed on the outermost polymer solid 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 solid electrolyte is preferably performed in an inert atmosphere. For example, the bipolar battery may be manufactured in an argon atmosphere or a nitrogen atmosphere.
[0091]
(8) Packing (Battery completion)
Finally, a positive electrode terminal plate and a negative electrode terminal plate are installed on the outermost current collectors of the bipolar battery main body (battery laminate) as necessary, and the positive electrode lead plate and the negative electrode terminal plate are further connected to the positive electrode lead. Then, the negative electrode lead is 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.
[0092]
In order to prevent external impact and environmental degradation, the entire battery stack is sealed with a battery exterior material or battery case (not shown) 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.
[0093]
【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.
[0094]
<Formation of gel electrode (positive electrode)>
(1) Preparation of slurry for gel electrode (positive electrode)
Spinel LiMn with an average particle size of 2 μm as positive electrode active material ₂ O _Four [41.7% by mass], acetylene black [8.3% by mass] as a conductive assistant, polyethylene oxide / propylene oxide copolymer as a polymer (copolymerization ratio 5: 1, weight average molecular weight 8000) [12.5% by mass], EC and DMC mixed at 1: 3 (volume ratio) [20.8% by mass], and Li (C) as the supporting salt (lithium salt) ₂ F _Five SO ₂ ) ₂ N [16.7% by mass] and an organic peroxide (specifically, t-hexylperoxypiparate) [1% by mass with respect to the polymer] as a polymerization initiator are mixed in the above ratio. Thus, a slurry for gel electrode (positive electrode) was prepared.
[0095]
The polymer and the electrolytic solution are mixed so that the weight ratio of polymer: electrolytic solution = 2: 8.
[0096]
(2) Formation of gel electrode (positive electrode)
As the current collector, an aluminum foil with a thickness of 20 μm was used.
[0097]
The gel electrode (positive electrode) slurry obtained above was applied to one side of the current collector so as to have a film thickness of 40 μm. After the application, the polymer was polymerized at the same time by heating and drying at 80 ° C. for 3 hours under an argon atmosphere, and the electrode was gelled to form a gel electrode (positive electrode) (see FIG. 6A).
[0098]
<Formation of all solid electrode (positive electrode)>
(1) Slurry preparation for all solid electrode (positive electrode)
Spinel LiMn with an average particle size of 2 μm as positive electrode active material ₂ O _Four [41.7% by mass], acetylene black [8.3% by mass] as a conductive assistant, polyethylene oxide / propylene oxide copolymer as a polymer (copolymerization ratio 5: 1, weight average molecular weight 8000) [33.3% by mass], Li (C as a supporting salt (lithium salt) ₂ F _Five 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. A suitable amount was added so that the amount of the polymerization initiator was an organic peroxide (specifically, t-hexylperoxypiparate) [1% by mass with respect to the polymer]. The ratio in terms of components excluding the viscosity adjusting solvent is shown.) To prepare a slurry for an all solid electrode (positive electrode).
[0099]
(2) Formation of all solid electrode (positive electrode)
A 50 μm all-solid polymer electrolyte membrane (a copolymer of polyethylene oxide and propylene oxide (copolymerization ratio of 5: 1 and weight average molecular weight of 8000) prepared in advance on a PET film was used. The slurry for an all-solid-state electrode (positive electrode) was applied onto a support salt [28.6 mass%] containing [71.4 mass%]. After coating, the polymer was polymerized at the same time as drying by heating at 80 ° C. for 5 hours in a vacuum atmosphere to form an all-solid electrode (positive electrode) (see FIG. 6B).
[0100]
<Lamination of electrode (positive electrode)>
On the gel electrode (positive electrode), an all solid electrode (positive electrode) was bonded so that the electrode portions face each other, and the PET film adhered on the electrolyte membrane was peeled off to form an electrode (positive electrode) ( (See FIG. 6C.)
[0101]
<Battery formation>
Lithium anode active material _Four Ti _Five O ₁₂ Other than that, the gel electrode (negative electrode) slurry and the all solid electrode (positive electrode) slurry were prepared with the same composition as the gel electrode (positive electrode) slurry and the all solid electrode (positive electrode) slurry.
[0102]
Using the obtained slurry for gel electrode (negative electrode) and slurry for all solid electrode (positive electrode), an electrode (negative electrode) was formed in the same procedure as that for forming the electrode (positive electrode) (FIG. 6A). Refer to the positive electrode up to (C) as the negative electrode.)
[0103]
An electrode (positive electrode) + electrolyte membrane and an electrode (negative electrode) + electrolyte membrane were bonded together so that the electrolyte membranes face each other to form a battery (single cell) (see FIG. 6D).
[0104]
In addition, by laminating a plurality of obtained single cells, the electrolyte in the portion close to the current collector of the electrode is gelled, and the electrolyte in the portion close to the solid polymer electrolyte of the electrode is fully solidified A bipolar lithium ion secondary battery having a structure 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 It was also confirmed that it could be formed. Note that as shown in FIG. 6D, the current collectors can be electrically connected by stacking, but the current collectors are connected to each other using an electrically conductive adhesive or the like so as not to move due to vibration or the like. Joined.
[0105]
<Evaluation>
An all-solid positive electrode having a thickness of 80 μm with no gelation inside and an internal gelation positive electrode having a thickness of 80 μm in which 40 μm inside was gelled were prepared, and charge / discharge characteristics were evaluated using a coin cell.
[0106]
That is, a coin cell was prepared using Li metal as a counter electrode, and charged to 4.2 V at 25 ° C. Then, when constant current discharge was performed at 0.1 CA, the discharge rate relative to the theoretical capacity of each electrode (the amount of electricity actually discharged / theoretical electric capacity charged to the electrode) was as follows: 45% and coin cells using an internal gelled electrode were 83%.
[0107]
Thereby, it was confirmed that the reactivity of a thick electrode can be improved by gelatinizing the inside of an electrode (part which does not react especially).
[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.
FIG. 5 is an explanatory diagram of electrode (positive electrode) thickness and reactivity of a conventional solid polymer battery, and FIG. 5 (A) is a diagram illustrating the structure of the periphery of the electrode (positive electrode) of the solid polymer battery. Yes. FIG. 5B shows the reactivity when the positive electrode layer is thin, and FIG. 5C shows the reactivity when the positive electrode layer is thick.
FIG. 6 is a schematic cross-sectional view of a part of a battery structure in a battery assembly stage or a finished battery after battery assembly, schematically showing the outline of each main process of the method for producing a solid polymer battery of the present invention; FIG. 6 (A) is a schematic cross-sectional view schematically showing a state where a gel electrode (positive electrode) is formed, and FIG. 6 (B) schematically shows a state where an all solid electrode (positive electrode) is formed. FIG. 6C is a schematic cross-sectional view schematically showing a state in which an electrode (positive electrode) is formed by laminating a gel electrode (positive electrode) and an all-solid electrode (positive electrode), FIG. 6D is a schematic cross-sectional view schematically showing a state in which a battery is formed by bonding an electrode (positive electrode) and an electrode (negative electrode).
FIG. 7 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.
[Explanation of symbols]
1 ... current collector,
1a, 1b ... current collector (part),
2 ... positive electrode layer,
2a ... Gel electrode (positive electrode),
2b: all solid electrode (positive electrode),
3 ... negative electrode layer,
3a ... Gel electrode (negative electrode),
3b ... all solid electrode (negative electrode),
4 ... electrolyte layer,
4a, 4b ... electrolyte layer (part),
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 battery,
51 ... positive electrode active material,
52 ... Solid polymer electrolyte contained in the electrode,
53 ... the part that reacts in the electrode,
54 ... the part which does not react in the electrode,
55 ... a polymer gel electrolyte contained in the electrode,
56 ... negative electrode active material,
61 ... PET film,
71 ... Electric vehicle or hybrid electric vehicle,
73: An assembled battery.

Claims (8)

In a solid polymer battery in which a positive electrode and a negative electrode including a polymer electrolyte are sandwiched between solid polymer electrolyte layers,
The portion of the polymer electrolyte near the current collector of the positive electrode and / or negative electrode is gelled, and the portion of the polymer electrolyte near the solid polymer electrolyte layer of the positive electrode and / or negative electrode is fully solidified. A bipolar lithium ion secondary battery electrode. The ratio of the host polymer constituting the gel electrolyte to the solvent in the gelled portion of the electrode is in the range of polymer: solvent = 3 mass%: 97 mass% to polymer: solvent = 50 mass%: 50 mass%. The electrode for bipolar lithium ion secondary battery according to claim 1, wherein the electrode is provided. By forming a gel electrolyte-containing electrode on the current collector, forming an all-solid electrolyte-containing electrode on the solid polymer electrolyte layer, and bonding them together, the portion of the inside of the electrode that is close to the current collector of the electrode A method for producing a solid polymer battery, comprising: a battery in which a polymer electrolyte is gelled and a portion of the polymer electrolyte close to the solid polymer electrolyte layer of the electrode is solidified. A bipolar electrode in which the positive electrode is formed on one surface of the current collector and the negative electrode is formed on the other surface is sandwiched between the solid polymer electrolyte layer using the electrode according to any one of claims 1 to 3. A bipolar lithium ion secondary battery having a structure in which a plurality of the batteries are stacked in series. 5. The battery according to claim 4, 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. 6. The battery according to claim 4, wherein an all solid polymer is used for the electrolyte. An assembled battery formed by connecting a plurality of the batteries according to claim 4. A vehicle equipped with the battery according to claim 4 and / or the assembled battery according to claim 7 as a driving power source.

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