JP2010113939A - Bipolar secondary battery and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for suppressing the occurrence of problems caused by gas generation in a bipolar secondary battery. <P>SOLUTION: The bipolar secondary battery 10 includes a power generating element in which a bipolar electrode and an electrolyte containing electrolyte layer 17 are laminated so as to form at least one single cell layer 19 formed by laminating a positive electrode active material layer 13, the electrolyte layer and a negative electrode active material layer 15 in this order and a sealing part 31 is formed on an outer peripheral pat of the single cell layer. As the electrolyte constituting the electrolyte layer, an electrolyte whose loss obtained when stationarily set for one hour at 25°C and under a pressure condition of 10 Torr is at least 1 mass.% relative to the mass before set stationarily is used. The electrolyte is subjected to pressure reduction treatment at a pressure of <20 Torr before a sealing part forming process or simultaneously with this process in the manufacture of the battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a bipolar secondary battery and a method for manufacturing the same. In particular, the present invention relates to an improvement for improving durability and long-term reliability of a bipolar secondary battery.

  In recent years, hybrid vehicles, electric vehicles, and fuel cell vehicles have been manufactured and sold from the viewpoints of environment and fuel efficiency, and new developments are continuing. In these so-called electric vehicles, it is indispensable to use a power supply device capable of discharging and charging. As the power supply device, a secondary battery such as a lithium ion battery or a nickel metal hydride battery, an electric double layer capacitor, or the like is used. In particular, lithium ion secondary batteries are considered suitable for electric vehicles because of their high energy density and high durability against repeated charging and discharging, and various developments have been intensively advanced. However, in order to apply to the power sources for driving motors of various automobiles as described above, it is necessary to use a plurality of secondary batteries connected in series in order to ensure a large output.

  However, when a battery is connected via the connection portion, the output is reduced due to the electrical resistance of the connection portion. Further, the battery having the connection portion has a disadvantage in terms of space. That is, the connection portion causes a reduction in the output density and energy density of the battery.

  As a solution to this problem, a bipolar lithium ion secondary battery (bipolar battery) has been developed (see, for example, Patent Document 1). The bipolar battery has a power generation element having a configuration in which a plurality of bipolar electrodes each having a positive electrode active material layer formed on one surface and a negative electrode active material layer formed on the other surface are stacked via an electrolyte layer. In order to prevent a short circuit between adjacent unit cell layers, the outer peripheral portion of a unit cell (unit cell layer) in which a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer are stacked in this order is provided. Generally, a seal portion is provided. Such a power generation element is usually vacuum-packed in an exterior made of a laminate film.

  In the bipolar battery, since a plurality of single battery layers are electrically connected in series in the stacking direction of the power generation elements, the battery can be increased in voltage and resistance. Furthermore, since such a series connection is made without going through a connection portion, the battery can be made compact and the output density can be improved.

  By the way, in the lithium ion secondary battery, when the first charge / discharge or repeated charge / discharge, the battery components (for example, an organic solvent constituting the electrolyte) and inevitable components (for example, moisture) are included. Gas is generated due to the decomposition. When such a gas stays inside the power generation element, there is a problem that the electrode is peeled off or the contact between the electrode and the electrolyte is deteriorated, and the battery performance is deteriorated.

  Here, the parallel connection type lithium ion secondary battery which is not a bipolar type does not have a seal portion. For this reason, for example, when using a liquid electrolyte or a gel electrolyte, an electrode and an electrolyte layer are laminated to prepare a laminated body, and after drying this, an electrolytic solution or a pregel solution is injected to install a power generation element. It is possible to produce. Thereby, the mixing of moisture during the production of the power generation element can be prevented to some extent. As a result, it is possible to suppress gas generation due to moisture mixing.

  In addition, since the battery of the parallel connection type does not have a seal part, even if gas is generated during the first charge / discharge, it is possible to open the vacuum pack once and degas it after degassing. It is. Thereby, it is possible to avoid the problem caused by the gas generated during the first charge / discharge. Further, at least a part of the gas generated during repeated charging / discharging can escape to the outside of the power generation element even though it is inside the exterior. Thus, in the parallel connection type battery, it is possible to reduce problems caused by gas generation to some extent.

  On the other hand, the situation is different for bipolar batteries. That is, the bipolar battery has a unique structural feature that the outer peripheral portion of the single cell layer must be sealed by the seal portion. In general, such a seal portion is formed simultaneously with the formation of a laminate of a bipolar electrode and an electrolyte layer. For this reason, like a battery of parallel connection type, it is practically impossible to produce a laminated body first, dry it, and then inject a liquid component. Therefore, a liquid component must be included in the electrode or the electrolyte layer in advance before the laminate is manufactured, and then a laminate process must be performed to form the laminate. As a result, moisture in the atmosphere is mixed in the power generation element in the stacking process. In addition, for the purpose of removing such moisture, it seems likely to dry the laminate obtained in the laminating step, but then the organic solvent in the electrolyte and pregel solution will volatilize, which is preferable. Absent.

In addition, due to the structural restriction that the seal portion exists, even if the gas is degassed after the first charge / discharge, the generated gas cannot escape to the outside of the seal portion and remains in the generated single cell layer. . This applies not only to the first charge / discharge, but also to repeated charge / discharge thereafter, and problems such as electrode peeling and poor battery performance due to poor contact between the electrode and electrolyte are connected in parallel. It can occur significantly compared to the type of battery. Further, when the battery is exposed to high temperature during use, even if the organic solvent constituting the electrolyte is volatilized, the volatilized organic solvent cannot escape to the outside of the unit cell layer. As a result, the internal pressure of the single cell layer rises, and the same problem of battery performance degradation as described above occurs.
JP-A-11-204136

  Therefore, an object of the present invention is to provide means capable of suppressing the occurrence of at least one problem caused by gas generation due to various causes as described above in a bipolar secondary battery.

  In order to solve the above problems, in the bipolar secondary battery of the present invention, as the electrolyte constituting the electrolyte layer, the weight loss when left under a pressure condition of 10 Torr at 25 ° C. for 1 hour is An electrolyte that is 1% by mass or less based on the previous mass is used. A bipolar secondary battery including such an electrolyte can be manufactured by subjecting the electrolyte to a reduced pressure at a pressure of less than 20 Torr before or simultaneously with the process of forming the seal portion when manufacturing the battery. Alternatively, when the electrolyte contains a solvent or dehydrating agent having a boiling point lower than that of water, the electrolyte is included when the electrolyte is decompressed at a pressure of less than 20 Torr before or simultaneously with the step of forming the seal portion. A bipolar secondary battery can be manufactured.

  According to the bipolar secondary battery and the method of manufacturing the same of the present invention, the mixing of moisture that causes gas generation is prevented. As a result, a bipolar secondary battery in which the occurrence of at least one problem due to gas generation is suppressed can be provided.

  Hereinafter, embodiments of the present invention will be described. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following embodiments.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the description of the scope of claims, and is not limited to the following embodiments. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a schematic cross-sectional view schematically showing an outline of a bipolar lithium ion secondary battery which is a typical embodiment of a bipolar secondary battery. In the present specification, a bipolar lithium ion secondary battery will be described in detail as an example, but the technical scope of the present invention is not limited to such a form.

  The bipolar secondary battery 10 of this embodiment shown in FIG. 1 has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is a battery exterior material. .

  As shown in FIG. 1, a power generation element 21 of a bipolar secondary battery 10 according to the present embodiment includes a positive electrode active material layer 13 electrically coupled to one surface of a current collector 11, and the current collector 11 has a plurality of bipolar electrodes formed with a negative electrode active material layer 15 electrically coupled to the opposite surface. Each bipolar electrode is stacked via the electrolyte layer 17 to form the power generation element 21. At this time, each bipolar type is formed such that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. Electrodes and electrolyte layers 17 are alternately stacked. That is, the electrolyte layer 17 is disposed between the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar secondary battery 10 has a configuration in which the single battery layers 19 are stacked. Further, in order to prevent a liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17, a seal portion 31 is disposed around the single cell layer 19. By providing the seal portion 31, the adjacent current collectors 11 can be insulated and a short circuit due to contact between adjacent electrodes can be prevented. A positive electrode active material layer 13 is formed only on one side of the positive electrode outermost layer current collector 11 a located in the outermost layer of the power generation element 21. The negative electrode active material layer 15 is formed only on one surface of the outermost current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21.

  Furthermore, in the bipolar secondary battery 10 shown in FIG. 1, the positive electrode side outermost layer current collector 11a is extended to be a positive electrode current collecting plate 25, which is led out from a laminate sheet 29 which is a battery outer packaging material. On the other hand, the negative electrode side outermost layer current collector 11b is extended to form a negative electrode current collector plate 27, which is similarly derived from a laminate sheet 29 which is a battery exterior material.

[Current collector]
The current collector 11 is made of a conductive material, and an active material layer is formed on both sides thereof to serve as a battery electrode, and finally forms a battery. In the present embodiment, the current collector is used for a battery (bipolar battery) in which active material layers having different polarities (positive electrode and negative electrode) are formed on the surface of each layer. As shown in FIG. 1, in the battery having a power generation element formed by laminating a plurality of single battery layers, the electrode located in the outermost layer does not participate in the battery reaction, so in the current collector located in the outermost layer, The active material layer only needs to exist inside the power generation element.

  Further, the size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used.

  There is no restriction | limiting in particular in the material which comprises the electrical power collector 11. FIG. For example, a metal or a conductive polymer can be employed. Specifically, metal materials, such as aluminum, nickel, iron, stainless steel, titanium, copper, are mentioned, for example. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum, stainless steel, and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.

  There is no particular limitation on the thickness of the current collector 11. The thickness of the current collector is usually about 1 to 100 μm.

[Positive electrode active material layer and negative electrode active material layer]
The active material layers 13 and 15 contain an active material, and further contain other additives as necessary.

The positive electrode active material layer 13 includes a positive electrode active material. As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium-such as those in which a part of these transition metals are substituted with other elements Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material. Of course, positive electrode active materials other than those described above may be used.

The negative electrode active material layer 15 includes a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite, soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, and lithium-metal alloy materials. . In some cases, two or more negative electrode active materials may be used in combination. Preferably, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Of course, negative electrode active materials other than those described above may be used.

  Although the average particle diameter of each active material contained in each active material layer 13 and 15 is not particularly limited, it is preferably 1 to 20 μm and more preferably 1 to 5 μm from the viewpoint of increasing the output. However, it goes without saying that a form outside this range may be adopted. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the active material particles. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

  Examples of the additive that can be included in the positive electrode active material layer 13 and the negative electrode active material layer 15 include a binder, a conductive additive, an electrolyte salt (lithium salt), and an ion conductive polymer.

  Examples of the binder include polyvinylidene fluoride (PVdF), a synthetic rubber binder, and an epoxy resin.

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer 13 or the negative electrode active material layer 15. Examples of the conductive assistant include carbon materials such as carbon black such as acetylene black, graphite, and vapor grown carbon fiber. When the active material layer (13, 15) contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to the improvement of the output characteristics of the battery.

As an electrolyte salt (lithium salt), Li (FSO ₂ ) ₂ N), Li (CF ₃ SO ₂ ) ₂ N), Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiAsF ₆ LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₂ F ₅ SO _3, LiClO ₄ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (C ₃ F ₇ ) ₃ , LiPF ₃ C ₄ F ₉ ) _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

  The compounding ratio of the components contained in the positive electrode active material layer 13 and the negative electrode active material layer 15 is not particularly limited. The blending ratio can be adjusted in consideration of the intended use of the battery (emphasis on output, emphasis on energy, etc.) and ion conductivity by appropriately referring to known knowledge about the bipolar secondary battery.

  The thickness of each active material layer 13, 15 is not particularly limited, and conventionally known knowledge about the battery can be referred to as appropriate. As an example, the thickness of each active material layer (13, 15) is about 2 to 100 μm.

[Electrolyte layer]
The electrolyte layer 17 functions as a spatial partition (spacer) between the positive electrode active material layer 13 and the negative electrode active material layer 15. In addition, it also has a function of holding an electrolyte that is a lithium ion transfer medium between the positive and negative electrodes during charging and discharging. A liquid electrolyte or a polymer electrolyte can be used as the electrolyte constituting the electrolyte layer 17. Details of the constituent material of the electrolyte layer 17 will be described later.

  The bipolar secondary battery 10 of the present embodiment is characterized in that the reduced-pressure drying loss of the electrolyte contained in the electrolyte layer 17 is not more than a predetermined value. Specifically, the weight loss when the electrolyte contained in the electrolyte layer 17 of the bipolar secondary battery 10 of the present embodiment is allowed to stand under a pressure condition of 10 Torr at 25 ° C. for 1 hour (in this specification, “ Is also 1% by mass or less with respect to the mass of the electrolyte before standing. The said weight loss becomes like this. Preferably it is 0.5 mass% or less, More preferably, it is 0.1 mass% or less. In addition, the value of reduced-pressure drying loss can be calculated by allowing the electrolyte to stand under the above-described conditions and measuring the mass before and after that.

  If the reduced-pressure drying loss at 25 ° C. of the electrolyte is within such a range, problems such as gas generation during initial charge / discharge and repeated charge / discharge and deterioration of battery performance due to this are effectively generated. Can be suppressed.

  In a preferred form, reduced pressure loss under more severe conditions is also defined. That is, in a preferred embodiment, the weight loss under reduced pressure when the electrolyte contained in the electrolyte layer 17 of the bipolar secondary battery 10 of the present embodiment is allowed to stand under a pressure condition of 10 Torr at 60 ° C. for 1 hour is It is 1 mass% or less with respect to the mass of the said electrolyte before installation. The said weight loss becomes like this. Preferably it is 0.5 mass% or less, More preferably, it is 0.1 mass% or less.

  Further, in a more preferred form, the reduced weight loss upon drying when the electrolyte contained in the electrolyte layer 17 of the bipolar secondary battery 10 of the present embodiment is allowed to stand at 150 ° C. for 1 hour under a pressure condition of 10 Torr, It is 1 mass% or less with respect to the mass of the said electrolyte before standing still. The said weight loss becomes like this. Preferably it is 0.5 mass% or less, More preferably, it is 0.1 mass% or less.

  In addition, the method of obtaining the electrolyte which shows the reduced pressure drying loss of the form mentioned above is mentioned later.

  There is no restriction | limiting in particular about the specific material which comprises electrolyte, The material which shows the reduced pressure drying loss of the form mentioned above can be selected suitably. Hereinafter, although an example of the material which comprises an electrolyte layer is demonstrated, the technical scope of this invention is not restrict | limited only to the following form.

  The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in a plasticizer. Examples of the plasticizer include carbonates such as diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylene carbonate (EC) and propylene carbonate (PC); lactones such as γ-butyrolactone, and ionic liquids. The When the electrolyte contains a plasticizer, EC, PC, lactones or ionic liquids having a relatively high boiling point are preferably used as the plasticizer. Among these, it is more preferable to use an ionic liquid. This is because high boiling point solvents and ionic liquids have a relatively low vapor pressure (ionic liquids are very small). As a result, the high boiling point solvent and the ionic liquid can remain in the electrolyte without being volatilized even under reduced pressure and high temperature conditions for the purpose of removing moisture during battery manufacture. In addition, unlike an ordinary organic solvent, the ionic liquid has a very low vapor pressure, so that it hardly volatilizes even when it is exposed to a high temperature during battery use. Therefore, it is also preferable from the viewpoint of suppressing the occurrence of problems such as battery swelling, electrode peeling, and poor contact between the electrode and the electrolyte.

  Here, the ionic liquid is also called a normal temperature molten salt, and is a salt that shows a liquid state at normal temperature. The ionic liquid itself is a well-known material, and a great number of documents are distributed. Examples of ionic liquids preferably used in the present embodiment include cations constituting the ionic liquids such as ammonium (imidazolium, pyridinium, aliphatic quaternary ammonium [piperidinium, pyrrolidinium, quaternary alkylammonium. , Quaternary alkyl ammonium having an alkoxy group]), phosphonium cation and sulfonium cation. Specific examples of the imidazolium cation include 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-butyl-3. -Methylimidazolium, 1-hexyl-3-methylimidazolium, 1-ethyl-2,3-dimethylimidazolium. Specific examples of the pyridinium cation include N-ethyl-N-methylpyridinium, N-methyl-N-propylpyridinium, N-butyl-N-methylpyridinium, and N-hexyl-N-methylpyridinium. Specific examples of the pyrrolidinium cation include N-ethyl-N-methylpyrrolidinium, N-methyl-N-propylpyrrolidinium, N-butyl-N-methylpyrrolidinium, N-hexyl-N-methyl. Pyrrolidinium is mentioned. Specific examples of piperidinium include N-ethyl-N-methylpiperidinium, N-methyl-N-propylpiperidinium, N-butyl-N-methylpiperidinium, N-hexyl-N-methylpiperidinium Is mentioned. Specific examples of the pyrrolidinium cation include N-ethyl-N-methylpyrrolidinium, N-methyl-N-propylpyrrolidinium, N-butyl-N-methylpyrrolidinium, N-hexyl-N-methyl. Pyrrolidinium is mentioned. Specific examples of the quaternary alkyl ammonium include N, N, N-trimethyl-N-ethylammonium, N, N, N-trimethyl-N-propylammonium, N, N, N-trimethyl-N-butylammonium, N, N, N-trimethyl-N-hexylammonium, N, N, N-triethyl-N-methylammonium may be mentioned. Specific examples of the quaternary alkyl ammonium having an alkoxy group include N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium. Specific examples of the phosphonium cation include triethylmethylphosphonium and triethylhexylphosphonium. Specific examples of the sulfonium cation include triethylmethylsulfonium and triethylhexylsulfonium.

Examples of the anion constituting the ionic liquid include BF ₄ ⁻ , AlF ₄ −, PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , ClO ₄ ⁻ , AlCl ₄ ⁻ , CF ₃ SO ₃ ⁻ and C ₂ F. ₅ SO ₃ ⁻ _, C ₃ F ₇ SO ₃ ⁻ _, C ₄ F ₉ SO ₃ ⁻ _, CH ₃ SO ₃ ⁻ _, C ₂ H ₅ SO ₃ ⁻ _, CH ₃ OSO ₃ ⁻ _, C ₂ H ₅ OSO ₃ ⁻ _, ( ^{_{FO 2 S) 2 N - (}} FSI), (CF 3 SO 2) 2 N - (TFSI), CF 3 CO 2 -, (C 2 F 5 SO 2) 2 N - (BETI), (C 4 F 9 SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , (C ₂ F ₅ SO ₂ ) ₃ C ⁻ , (CN) ₂ N ⁻ , (CF ₃ ) ₃ PF ₃ ⁻ , (C ₂ F _{5 ^{) 3 PF 3 -, (C}} 3 F 7) 3 PF 3 - Contact Beauty _{(C 4 F 9) 3 PF} 3 - , etc. are exemplified. Each of these cations and anions may be used alone or in combination of two or more. Among these, ionic liquids are N-ethyl-N-methylpiperidinium, N-methyl-N-propylpiperidinium, N-butyl-N from the viewpoint of low viscosity and excellent oxidation resistance and reduction resistance. -Methylpiperidinium, N-hexyl-N-methylpiperidinium, N-ethyl-N-methylpyrrolidinium, N-methyl-N-propylpyrrolidinium, N-butyl-N-methylpyrrolidinium, N-hexyl-N-methylpyrrolidinium, N, N, N-trimethyl-N-ethylammonium, N, N, N-trimethyl-N-propylammonium, N, N, N-trimethyl-N-butylammonium, N, N, N-trimethyl-N-hexylammonium, N, N, N-triethyl-N-methylammonium, N, N-diethyl-N-methyl-N One or more selected from the group consisting of (2-methoxyethyl) ammonim, and the anion constituting the ionic liquid is one or more selected from the group consisting of FSI, TFSI, and BETI It is preferable that The plasticizers described above are ethylene carbonate (EC), diethylene carbonate (DEC), vinylene carbonate (VC), lithium bisoxalate borate (LiBOB), ethylene sulfite (ES), chloroethylene carbonate (Cl- EC) and other conventionally known additives may be included.

As the supporting salt (lithium salt) dissolved in the above-described plasticizer (organic solvent or ionic liquid) in the liquid electrolyte, a compound that can be added to the active material layer of the electrode, such as LiPF ₆ or LiBETI, can be similarly employed. There is no restriction | limiting in particular also in the addition amount of the supporting salt to a plasticizer, A conventionally well-known knowledge can be referred suitably.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and a solid electrolyte containing no electrolytic solution.

  The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer made of an ion conductive polymer. Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), Examples thereof include a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) (PMMA), and a copolymer thereof. In these polymers, lithium salts can be dissolved well. Especially, it is preferable that PEO, PPO or these copolymers, or PVdF-HFP is used as a matrix polymer.

  In addition, the content rate in particular of electrolyte solution (components other than a matrix polymer) in a gel electrolyte is not restrict | limited. From the viewpoint of ionic conductivity and the like, it may be about several mass% to 98 mass%, preferably 80 mass% or more.

  The solid electrolyte is also called an intrinsic polymer electrolyte, and has a structure in which a supporting salt (lithium salt) is dissolved in the above matrix polymer, and does not contain a plasticizer. As the matrix polymer, an ion conductive solid electrolyte such as ceramics may be used. Since the solid electrolyte does not contain a liquid component, when the electrolyte layer is composed of a solid electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

  In addition, when an electrolyte layer is comprised from a liquid electrolyte or a gel electrolyte, you may use a separator for an electrolyte layer. Specific examples of the separator include a microporous film made of polyolefin such as polyethylene or polypropylene.

  The matrix polymer of gel electrolyte or solid electrolyte can express excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a polymerization process such as thermal polymerization, ultraviolet polymerization, radiation polymerization, or electron beam polymerization may be performed on a matrix polymer (for example, PEO or PPO) using an appropriate polymerization initiator.

  The specific form of the electrolyte constituting the electrolyte layer 17 has been described above in detail by classifying it into a liquid electrolyte, a gel electrolyte, and a solid electrolyte. However, the electrolyte is preferably a polymer electrolyte. In other words, the electrolyte preferably includes a polymer. This is because the polymer itself also has a very low vapor pressure, and is not easily affected even under reduced pressure and high temperature conditions for the purpose of removing moisture during battery manufacture.

  In another preferred embodiment of the present invention, the electrolyte constituting the electrolyte layer 17 includes a solvent having a boiling point lower than that of water (hereinafter, also simply referred to as “low boiling point solvent”). According to such a form, when a reduced pressure treatment is performed for the purpose of removing moisture during battery production, moisture is easily volatilized and removed from the electrolyte due to the presence of the low boiling point solvent.

  There is no restriction | limiting in particular about the specific form of a low boiling point solvent, A conventionally well-known knowledge can be referred suitably. For example, alcohol solvents such as methanol, ethanol, 1-propanol and 2-propanol; ketone solvents such as acetone and methyl ethyl ketone; n-hexane, 2-methylpentane, 3-methylpentane and 2,2-dimethyl Hydrocarbon solvents such as butane, 2,3-dimethylbutane, n-heptane, cyclohexane, methylcyclopentane, cyclopentane; ethers such as tetrahydrofuran, diisopropyl ether, methyl-tert-butyl ether, 1,2-dimethoxyethane A solvent or the like can be used as the low boiling point solvent. These low-boiling solvents are preferable because they are inert to other components such as electrodes and separators even if they are contained in the electrolyte. Of course, other low-boiling solvents may be used as long as they can promote volatilization and removal of water. Of these, methanol, ethanol, acetone, methyl ethyl ketone, and n-hexane are preferably used, and methanol, ethanol, and acetone are more preferably used. In addition, as for these low boiling-point solvents, only 1 type may be used independently and 2 or more types may be used together.

  When the electrolyte contains a low boiling point solvent, the content of the low boiling point solvent is not particularly limited. As a preferred range, when the electrolyte contains an electrolytic solution (plasticizer + supporting salt), the amount of the low boiling point solvent added is preferably 5 to 50 parts by mass, more preferably 100 parts by mass of the electrolytic solution. Is 5 to 20 parts by mass. Further, when the electrolyte does not contain an electrolytic solution (that is, a solid electrolyte), the amount of the low boiling point solvent added is preferably 5 to 80 parts by mass with respect to 100 parts by mass of the (solid) electrolyte, and more Preferably it is 5-20 mass parts. If the content of the low boiling point solvent is within such a range, the decrease in lithium ion conductivity, which is the original function of the electrolyte, can be minimized. On the other hand, it is possible to achieve the purpose of removing moisture, which is a function as a low boiling point solvent.

  In still another preferred embodiment of the present invention, the electrolyte constituting the electrolyte layer 17 includes a dehydrating agent. According to such a form, even if moisture exists in the electrolyte, the moisture changes to a low boiling point compound having a vapor pressure higher than that of water by reaction with the dehydrating agent. The low boiling point compound can be volatilized and removed by a reduced pressure (high temperature) treatment during battery manufacture. As a result, it becomes possible to reduce the amount of moisture remaining in the electrolyte.

  The dehydrating agent that can be used in the present embodiment is not particularly limited as long as it can exhibit the above-described effects, and an example is an alkoxide compound represented by the following chemical formula 1.

  In Chemical Formula 1, M is Si, Ge, Sn, Pb, Al, Ga, In, or Tl, preferably Si or Ge, and particularly preferably Si. R is an alkyl group having 1 to 4 carbon atoms. Examples of such an alkyl group include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. Among them, preferred is a methyl group, an ethyl group, or an n-propyl group, particularly preferred is a methyl group or an ethyl group, and most preferred is a methyl group. In Chemical Formula 1, Rs may be the same as or different from each other. In Chemical Formula 1, x is 3 or 4.

As specific examples of the alkoxide compound that can be used as the dehydrating agent, examples in which M is Si include tetramethyl orthosilicate (TMOS; Si (OCH ₃ ) ₄ ), tetraethyl orthosilicate (TEOS; Si (OCH ₂ CH ₃ ) ₄ ), tetra -n- propyl orthosilicate _{(Si (OCH 2 CH 2 CH} 3) 4), tetra -iso- propyl orthosilicate _{(Si (OCH (CH 3)} 2) 4), tetra -n- butyl orthosilicate ( _{Si (OCH 2 CH 2 CH 2} CH 3) 4), tetra -sec- butyl orthosilicate _{(Si (OCH 2 CH (CH} 3) 2) 4), tetra -tert- butyl orthosilicate (Si _(OCH 2 C ( CH _{3) 3) 4),} ethyl trimethyl silicate, diethyl dimethylsilylene Over DOO, methyl tri ethyl silicate or the like. Examples of M that is Ge include tetramethoxygermanium (Ge (OCH ₃ ) ₄ ), tetraethoxygermanium (Ge (OCH ₂ CH ₃ ) ₄ ), tetra-n-propoxygermanium, tetra-iso-propoxygermanium, Examples include tetra-n-butoxygermanium, tetra-sec-butoxygermanium, tetra-tert-butoxygermanium, ethoxytrimethoxygermanium, diethoxydimethoxygermanium, methoxytriethoxygermanium, and the like. Among these, from the viewpoint of easy availability, TEOS, tetraethoxygermanium, and tetra-n-butoxygermanium are preferably used, and TEOS is particularly preferably used.

  Here, for reference, a chemical reaction formula showing a reaction between TEOS and water when TEOS is used as a dehydrating agent is shown in the following reaction formula 1.

  When the electrolyte contains a dehydrating agent, the content of the dehydrating agent is not particularly limited. As a preferred range, when the electrolyte contains an electrolytic solution (plasticizer + supporting salt), the amount of the dehydrating agent added is preferably 1 to 20 parts by mass, more preferably 100 parts by mass of the electrolytic solution. 1 to 5 parts by mass. Further, when the electrolyte does not contain an electrolytic solution (that is, a solid electrolyte), the amount of the dehydrating agent added is preferably 1 to 20 parts by mass, more preferably 100 parts by mass of the (solid) electrolyte. Is 1-5 parts by mass. If the content of the dehydrating agent is within such a range, the decrease in lithium ion conductivity, which is the original function of the electrolyte, can be minimized. On the other hand, it is possible to achieve the purpose of removing moisture, which is a function as a dehydrating agent.

  In the bipolar secondary battery 10 of the present embodiment, the amount of water in the electrolyte is controlled to a value that is small because the electrolyte has the above-described configuration. Specifically, the water content in the electrolyte contained in the electrolyte layer 17 of the bipolar secondary battery 10 of the present embodiment is preferably 50 ppm by mass or less, more preferably based on the total amount of the electrolyte. It is 20 mass ppm or less, and particularly preferably 10 mass ppm or less. As described above, since the moisture content in the electrolyte is controlled to an extremely small value compared to the conventional one, the occurrence of various problems due to the mixing of moisture as described above is effective according to the present invention. Can be suppressed. In addition, the value measured by the Karl Fischer method shall be employ | adopted for content of the water | moisture content in electrolyte.

[Seal part]
The seal portion 31 is disposed on the periphery of the unit cell layer 19 in order to prevent leakage of the electrolyte layer 17. In addition to this, it is possible to prevent current collectors adjacent in the battery from coming into contact with each other and a short circuit due to a slight unevenness at the end of the laminated electrode. Examples of the constituent material of the seal portion 31 include polyolefin resins such as PE and PP, epoxy resins, rubber, and polyimide. Of these, polyolefin resins are preferred from the viewpoints of corrosion resistance, chemical resistance, film-forming properties, economy, and the like.

[Positive electrode and negative electrode current collector]
In the bipolar secondary battery 10, current collecting plates (a positive current collecting plate 25 and a negative current collecting plate 27) electrically connected to the outermost layer current collectors (11 a, 11 b) for the purpose of extracting current to the outside of the battery. ) Is taken out of the laminate sheet 29 which is an exterior material. Specifically, a positive electrode current collector plate 25 electrically connected to the positive electrode outermost layer current collector 11a, and a negative electrode current collector plate 27 electrically connected to the negative electrode outermost layer current collector 11b, It is taken out of the exterior material 29.

  The material constituting the current collector plates (the positive electrode current collector plate 25 and the negative electrode current collector plate 27) is not particularly limited, and a known highly conductive material conventionally used as a current collector plate for a bipolar secondary battery can be used. Can be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum is more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Copper or the like is preferable, and aluminum is particularly preferable. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be made of the same material or different materials. The outermost layer current collectors (11a, 11b) may be extended to form current collector plates (25, 27), or a separately prepared current collector plate may be connected to the outermost layer current collector.

[Positive electrode and negative electrode terminal plate]
The positive electrode and the negative electrode terminal plate are used as necessary. For example, when the positive electrode current collector plate 25 and the negative electrode current collector plate 27 are directly taken out from the outermost current collectors 11a and 11b, the positive electrode and negative electrode terminal plates need not be used.

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

[Positive electrode and negative electrode lead]
The positive electrode and the negative electrode lead are also used as necessary. For example, when the output electrode terminals (the positive electrode current collector plate 25 and the negative electrode current collector plate 27) are directly taken out from the outermost current collectors 11a and 11b (see FIG. 7), the positive electrode and the negative electrode lead are not used. Also good.

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

[Battery exterior materials]
A conventionally known metal can case can be used as the battery exterior material. In addition, the power generation element 21 may be packed using a laminate sheet 29 as shown in FIG. The laminate sheet 29 can be composed of, for example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order.

[Appearance structure of bipolar secondary battery]
FIG. 2 is a perspective view showing the appearance of a laminated flat bipolar secondary battery which is a typical embodiment of the bipolar secondary battery according to the present invention.

  As shown in FIG. 2, the laminated flat bipolar secondary battery 10 has a rectangular flat shape, and a positive current collector 25 for taking out electric power from both sides thereof, a negative current collector, and the like. The electric plate 27 is pulled out. The power generation element 21 is wrapped by a battery outer packaging material 29 of the bipolar secondary battery 10, and the periphery thereof is heat-sealed. The power generation element is sealed in a state where the positive current collector plate 25 and the negative current collector plate 27 are drawn out. Has been. Here, the power generation element corresponds to the power generation element 21 of the bipolar secondary battery shown in FIG. 1 described above, and includes a current collector 11, a positive electrode active material layer 13, an electrolyte layer 17, and a negative electrode active material layer. A plurality of unit cell layers 19 made of 15 are stacked.

  The bipolar secondary battery 10 of the present invention is not limited to the laminated flat shape as shown in FIGS. 1 and 2, but in the wound bipolar secondary battery, a cylindrical type is used. There is no particular limitation, for example, it may be a shape, or it may be such that a cylindrical shape is deformed into a rectangular flat shape. In the cylindrical shape, a laminate sheet may be used for the exterior material, and a conventional cylindrical can (metal can) may be used.

  Further, the extraction of the current collector plates 25 and 27 shown in FIG. 2 is not particularly limited, and the positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be drawn from the same side, or the positive electrode current collector plate. 25 and the negative electrode current collector plate 27 may be divided into a plurality of parts and taken out from each side, and the present invention is not limited to the one shown in FIG. Further, in a wound bipolar secondary battery, a terminal may be formed using, for example, a cylindrical can (metal can) instead of the current collector plate.

  The bipolar secondary battery 10 of the present embodiment is a power source for driving a vehicle that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, and the like. And can be suitably used for an auxiliary power source.

[Battery]
The assembled battery of this embodiment is configured by connecting a plurality of bipolar secondary batteries 10 of the above-described embodiment. In detail, at least two or more are used and it is comprised by serialization or parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of this embodiment, in addition to the bipolar secondary battery of the above embodiment, other secondary batteries (for example, a normal lithium ion secondary battery that is not bipolar) are used and these are connected in series. The assembled battery can be configured by combining a plurality of them in parallel or in series and in parallel.

  The number of bipolar secondary batteries and the manner of connection in the assembled battery of this embodiment may be determined according to the output and capacity required of the battery. When the assembled battery of this invention is comprised, the stability as a battery increases compared with a bipolar secondary battery single (unit cell). In addition, by configuring the assembled battery of the present embodiment, it is possible to reduce the influence on the entire assembled battery due to deterioration of one single battery layer (single cell) in the assembled battery of the present invention.

  FIG. 3 is an external view of a typical embodiment of the assembled battery according to this embodiment. FIG. 3A is a plan view of the assembled battery, FIG. 3B is a front view of the assembled battery, and FIG. It is a side view of a battery.

  In the form shown in FIG. 3, a small assembled battery 35 that can be attached and detached by connecting a plurality of bipolar secondary batteries 10 of the above embodiment in series and / or in parallel is formed. A plurality of small assembled batteries 35 that can be attached and detached are connected in series and / or in parallel to form an assembled battery 37. As a result, the assembled battery 37 is an assembled battery 37 having a large capacity and a large output suitable for a vehicle driving power source and an auxiliary power source that require high volume energy density and high volume output density. The small assembled batteries 35 that can be attached and detached are connected to each other using an electrical connection means such as a bus bar, and the assembled batteries 35 are stacked in a plurality of stages using a connection jig 39. How many bipolar secondary batteries are connected to create the assembled battery 35 and how many assembled batteries 35 are stacked to create the assembled battery 37 depends on the vehicle (electric vehicle) to be mounted. It may be determined according to the battery capacity and output. According to this embodiment, an assembled battery having excellent durability can be provided.

[vehicle]
The bipolar secondary battery 10 or the assembled battery 37 of the present invention can be used as a power source for driving a vehicle. The bipolar secondary battery 10 or the assembled battery 37 of the present invention is, for example, a hybrid vehicle, a fuel cell vehicle, and an electric vehicle (all are four-wheel vehicles (passenger vehicles, commercial vehicles such as trucks and buses, light vehicles, etc.)). In addition, it can be used for motorcycles (including motorcycles) and tricycles. Thereby, a long-life and highly reliable automobile can be provided. However, the application is not limited to automobiles. For example, if it is another vehicle, it can be applied to various power sources for moving bodies such as trains, and it can be used for mounting uninterruptible power supplies and the like. It can also be used as a power source.

  FIG. 4 is a conceptual diagram of a vehicle equipped with the assembled battery 37 of the present invention.

  As shown in FIG. 4, in order to mount the assembled battery 37 in a vehicle such as the electric vehicle 40, the battery pack 37 is mounted under the seat at the center of the vehicle body of the electric vehicle 40. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 37 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 40 using the assembled battery 37 as described above has excellent durability and can provide a sufficient output even when used for a long time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance.

[Production method of bipolar secondary battery]
Hereinafter, although an example of the preferable form of the manufacturing method of the bipolar secondary battery of this invention is demonstrated, the technical scope of the bipolar secondary battery of this invention is limited only to what was manufactured with the following manufacturing method. Do not mean. Further, the technical scope of the manufacturing method of the present invention to be described later is not limited to only the form in which the above-described bipolar secondary battery of the present invention is manufactured.

(I) Application of positive electrode active material slurry First, an appropriate current collector is prepared. On the other hand, a positive electrode active material slurry is prepared and applied to one surface of the current collector.

  The positive electrode active material slurry is a slurry containing a constituent material of the positive electrode active material layer. In addition to the positive electrode active material, the slurry may optionally include a conductive additive, binder, polymerization initiator, gel electrolyte raw material (matrix polymer, plasticizer (organic solvent or ionic liquid), supporting salt (lithium salt)), and the like. included. Since the specific form of each of these components is as described above, detailed description is omitted here. The slurry generally contains a slurry viscosity adjusting solvent such as N-methyl-2-pyrrolidone (NMP) for the purpose of adjusting the viscosity of the slurry. The polymerization initiator needs to be selected according to the compound to be polymerized. For example, benzyl dimethyl ketal (BDK) is mentioned as a photoinitiator, and azobisisobutyronitrile (AIBN) is mentioned as a thermal polymerization initiator. The addition amount of these polymerization initiators is determined according to the number of crosslinkable functional groups contained in the matrix polymer. The addition amount of the polymerization initiator is usually about 0.01 to 1% by mass with respect to the total amount of the matrix polymer.

  Examples of the method for applying the slurry to the surface of the current collector include screen printing and ink jet printing in addition to bar coating and spray coating. Further, in some cases, it can be formed using a vacuum process. Specifically, PVD (Physical Vapor Deposition method) or CVD (Chemical Vapor Deposition method) or Chemical Vapor Deposition method represented by vapor deposition, ion plating, thermal spraying, etc. Vapor deposition method) may be used.

(Ii) Formation of positive electrode active material layer The current collector coated with the positive electrode active material slurry is dried to remove the contained slurry viscosity adjusting solvent, thereby forming a positive electrode active material layer. At the same time, when the polymerization initiator is contained in the slurry, the cross-linking reaction may be advanced to increase the mechanical strength of the polymer electrolyte. A vacuum dryer or the like can be used for drying. The drying conditions can be determined according to the composition of the applied positive electrode active material slurry, but are usually 40 to 150 ° C. for 5 minutes to 20 hours.

  The produced positive electrode may be subjected to a press operation in order to improve surface smoothness and thickness uniformity. The press operation may be either a cold press roll method or a hot press roll method. In the case of hot-rolling, it is preferably performed under a temperature condition not higher than the temperature at which the supporting salt or matrix polymer decomposes. The press pressure may be about 200 to 1000 kg / cm in terms of linear pressure.

(Iii) Application of negative electrode active material slurry On the other hand, a negative electrode active material slurry is prepared and applied to the surface of the current collector opposite to the surface on which the positive electrode active material layer is formed.

  The negative electrode active material slurry is a slurry containing a constituent material of the negative electrode active material layer. In addition to the negative electrode active material, the various components described above for the positive electrode active material slurry can be similarly blended in the slurry. The application method is also as described above.

(Iv) Formation of negative electrode active material layer The current collector coated with the negative electrode active material slurry is dried to remove the contained slurry viscosity adjusting solvent, thereby forming a negative electrode active material layer. At the same time, when the polymerization initiator is contained in the slurry, the cross-linking reaction may be advanced to increase the mechanical strength of the polymer electrolyte. The drying and the subsequent pressing operation are as described above. Thereby, a bipolar electrode is completed. The press operation described in the above section “(ii) Formation of positive electrode active material layer” is performed, for example, after a positive electrode active material layer is formed on one side of a current collector and then a plurality of positive electrode active material layers used in a battery. The whole may be performed together. The same applies to the negative electrode active material layer. Further, after the positive electrode active material layer is formed on one side of the current collector and the negative electrode active material layer is formed on the other side, the positive electrode active material layer and the negative electrode active material layer may be pressed together. . Thereby, the man-hour required for press operation can be reduced significantly. On the other hand, from the viewpoint of ensuring a predetermined film thickness for each layer constituting the positive electrode active material layer and the negative electrode active material layer, it is possible to perform a pressing operation for each layer constituting the positive electrode active material layer and the negative electrode active material layer. preferable. Thus, what is necessary is just to select suitably the object and time of press operation as needed.

(V) Production of bipolar electrode and electrolyte layer (production of electrolyte)
Next, the liquid electrolyte and the gel raw material are disposed at predetermined positions (center portion; electrode area or larger area portion) of the positive electrode active material layer, the negative electrode active material layer, or the separator on both sides of the bipolar electrode prepared as described above. A solution (pregel solution) or a precursor solution of a solid electrolyte is impregnated. These solutions penetrate into electrodes and separators. In addition, in the impregnation operation, if an applicator or a coater is used, a very small amount can be supplied.

  The pregel solution used when the electrolyte is a gel electrolyte means a solution prepared by dissolving a gel electrolyte raw polymer (matrix polymer), a supporting salt, a polymerization initiator and the like in a solvent. Since the matrix polymer, the supporting salt, and the like are as described in the section of the bipolar secondary battery, detailed description thereof is omitted here.

  When the electrolyte is a solid electrolyte, the precursor solution of the solid electrolyte impregnated in the bipolar electrode means a solution prepared by mixing a solid electrolyte raw material polymer (matrix polymer), a supporting salt, a polymerization initiator, and the like. . Since the matrix polymer, the supporting salt, and the like are as described in the section of the bipolar secondary battery, detailed description thereof is omitted here.

  Thereafter, the matrix polymer contained in the electrode and the separator impregnated with the pregel solution or the solid electrolyte precursor solution is polymerized (crosslinked) by heat, ultraviolet rays, radiation, electron beams, or the like. Thereby, the ion conductivity of the electrode can be increased and a desired electrolyte layer can be formed.

  The bipolar electrode produced as described above is sufficiently heated and dried under a high vacuum, and then the bipolar electrode and the electrolyte layer are cut into appropriate sizes. The size of the electrolyte layer (separator) is preferably slightly larger than the size of the current collector of the bipolar electrode.

(Vi) Formation of Seal Part Precursor A seal part precursor (for example, one liquid) is applied to the electrode uncoated part (all four sides) of the positive electrode peripheral part of the bipolar electrode obtained in (v) above using a dispenser or the like. A non-curable epoxy resin).

  Next, the electrolyte layer (separator) obtained in (v) is installed on the positive electrode side so as to cover the current collector. In addition, when using a separator for an electrolyte layer, you may perform the impregnation process of the liquid electrolyte mentioned above, a pregel solution, and a solid electrolyte precursor solution after installation of a separator.

  Next, a seal portion precursor (for example, one-component uncured epoxy resin) is applied from above the outer peripheral portion of the separator (portion not including the electrolyte) using a dispenser or the like, and impregnated in the outer peripheral portion of the separator. You may apply | coat in several times as needed so that a seal | sticker part precursor may be located in a separator inside (impregnation) and the upper part (position corresponding to the electrode non-application part of a negative electrode peripheral part).

  Note that the steps (i) to (vi) are preferably performed in an inert atmosphere such as argon or nitrogen from the viewpoint of preventing moisture and the like from entering the battery.

(Vii) Production of power generation element The bipolar electrode and the electrolyte layer obtained above are alternately and sequentially laminated so that the positive electrode active material layer and the negative electrode active material layer face each other with the electrolyte layer interposed therebetween. Thereafter, if necessary, hot pressing is performed by a hot press machine. As a result, the uncured seal portion precursor is cured to form a seal portion.

  According to one aspect of the present invention, there is provided a method for manufacturing a bipolar secondary battery characterized by reduced pressure treatment conditions when the bipolar electrode and the electrolyte layer are stacked. That is, the manufacturing method provided by the present invention includes a step of preparing a bipolar electrode, a step of preparing an electrolyte, and a laminate including a single battery layer by laminating the bipolar electrode and an electrolyte layer or a precursor thereof. A step of obtaining a body, and a step of forming a seal portion on the outer periphery of the unit cell layer. And it is characterized in that it further includes a step of depressurizing the electrolyte at a pressure of less than 10 Torr before or simultaneously with the step of forming the seal portion.

  The electrolyte decompression process may be performed at a pressure of less than 10 Torr. Note that 1 Torr is about 133.32 Pa, and thus 10 Torr corresponds to about 1333.2 Pa. The reduced pressure treatment step is preferably performed at a pressure of less than 5 Torr. By setting it as such a form, it becomes possible to remove the water | moisture content in electrolyte effectively. As a result, it is possible to suppress the occurrence of various problems due to gas generation due to moisture mixing.

  As a means for achieving reduced pressure in the reduced pressure treatment step, it is preferable to use an apparatus that can perform a series of steps from the lamination step of the bipolar electrode and the electrolyte layer to the hot press step under reduced pressure conditions. As such a decompression means, for example, a vacuum laminating apparatus provided with a laminating mechanism inside a vacuum chamber using a high performance vacuum pump can be mentioned.

  There are no particular restrictions on the temperature conditions in the decompression process, but the vapor pressure curves of the components in the electrolyte that are to be volatilized / removed (for example, moisture) and the components that are not to be volatilized / removed (for example, the plasticizer for the electrolyte). The temperature condition may be determined with reference to (see also FIG. 5 described later). In general, even under the same reduced pressure condition, if the temperature of the system is raised, it will evaporate. Therefore, the temperature condition during the decompression process can vary depending on the components contained in the electrolyte, so it is difficult to determine uniquely. However, if general temperature conditions for volatilizing and removing moisture are given, it is usually about 25 to 150 ° C, preferably 60 to 130 ° C.

  Moreover, there is no restriction | limiting in particular also about the time of the pressure reduction process in a pressure reduction processing process. As an example, the treatment time is about 30 to 120 minutes, preferably 30 to 60 minutes. According to such a form, it is possible to remove moisture from the electrolyte economically and efficiently.

  When performing the electrolyte decompression process, the electrolyte may be subjected to decompression alone. However, preferably, in the case of a liquid electrolyte or a gel electrolyte, after the impregnation of the electrode active material layer or the separator, in the case of a solid electrolyte, a reduced pressure treatment step is performed after the crosslinking step. More preferably, after the bipolar electrode and the electrolyte layer are stacked, the reduced pressure treatment step is performed. This is because, by adopting such a form, mixing of moisture in the atmosphere into the electrolyte can be minimized. In the production process of the present invention, the “electrolyte layer precursor” means a separator that does not contain an electrolyte, a solid electrolyte precursor that has not been cross-linked, and a gel electrolyte that has not been cross-linked. Means an electrolyte layer that has a configuration different from its final form when it is laminated with a bipolar electrode.

  The decompression process is performed before or simultaneously with the process of forming the seal portion. This is because, after the seal portion is formed, even if the decompression process is performed, the volatilized water can no longer escape out of the seal portion. As a form of performing the pressure reduction treatment step before the seal portion forming step, for example, a form in which the electrode and the electrolyte layer are laminated as described above, the pressure reduction treatment is performed, and then the laminated body is hot pressed to complete the power generation element. Can be mentioned. At this time, it is preferable that hot pressing is also performed in an atmosphere that has been subjected to a reduced pressure treatment to some extent. If the pressure condition at the time of hot pressing is less than 10 Torr, the pressure reducing process step is performed "simultaneously" with the seal portion forming step. However, the pressure condition at the time of hot pressing may be looser than the above-described pressure reduction process. For example, the pressure condition at the time of hot pressing may be about 10 to 50 Torr.

There is no particular restriction as to the other conditions at the time of hot pressing, press pressure (surface pressure) is about 0.1 to 2.0 / cm ^2, is preferably 0.5~1.0kg / cm ² . Moreover, press temperature is about 25-150 degreeC, Preferably it is 45-100 degreeC, More preferably, it is 60-80 degreeC. The pressing time is about 0.1 to 2 hours, preferably 0.5 to 1 hour. In addition, these conditions at the time of a hot press can be determined according to the kind of material used as a seal | sticker part precursor.

  The seal portion precursor is cured by the hot pressing process, and a seal portion having a predetermined thickness is formed. As a result, a power generation element in which a single cell layer is stacked in a desired number of cells is completed. The number of single battery layers is determined in consideration of battery characteristics required for the bipolar secondary battery.

  As described in the column of the configuration of the bipolar secondary battery of the present invention, when the electrolyte contains a low boiling point solvent or a dehydrating agent, volatilization / removal of moisture from the electrolyte during the decompression process can be promoted. Therefore, when the electrolyte contains a low boiling point solvent or a dehydrating agent, it is possible to effectively remove moisture from the electrolyte even by a decompression process under a milder decompression condition compared to the above-described manufacturing method. Become. That is, a manufacturing method provided by still another embodiment of the present invention includes a step of preparing a bipolar electrode, a step of preparing an electrolyte containing a low boiling point solvent with water or a dehydrating agent, and the bipolar electrode and the electrolyte. Including a step of laminating a layer or a precursor thereof to obtain a laminate including a single cell layer, and a step of forming a seal portion on the outer periphery of the single cell layer. And it is characterized in that it further includes a step of depressurizing the electrolyte at a pressure of less than 20 Torr before or simultaneously with the step of forming the seal portion.

  In the manufacturing method of the present embodiment, the pressure reduction treatment step of the electrolyte may be performed at a pressure less than 20 Torr that is looser than the above-described embodiment. This reduced pressure treatment step is preferably performed at a pressure of less than 10 Torr, more preferably less than 5 Torr. By adopting such a form, it becomes possible to effectively remove moisture in the electrolyte even under relatively gentle pressure reduction conditions. As a result, it is possible to suppress the occurrence of various problems due to gas generation due to moisture mixing.

  As for the temperature condition in the decompression process, a condition looser than that of the above-described embodiment can be adopted. Specifically, it is usually about 25 to 130 ° C, preferably 60 to 120 ° C. As for other specific modes, the above-described modes can be adopted in the same manner, and thus detailed description thereof is omitted here.

(Viii) Attachment of electrode current collector plate A positive electrode current collector plate and a negative electrode current collector plate are disposed (electrically connected) to the current collectors located on both outermost layers of the obtained power generation element. The current collector plate is disposed, for example, by adhesion using a carbon-based conductive adhesive or the like.

  If necessary, a positive electrode lead and a negative electrode lead may be further joined (electrically connected) to the positive electrode current collector plate and the negative electrode current collector plate, respectively. Although there is no restriction | limiting in particular about the joining method of a positive electrode lead and a negative electrode lead, Ultrasonic welding etc. with low joining temperature can be utilized suitably. In addition, as with the current collector plate, the leads may be joined by adhesion using a carbon-based conductive adhesive or the like.

(Ix) Manufacture of Bipolar Secondary Battery Next, a battery exterior member or battery case made of a laminate sheet or the like is used to prevent the power generation element to which the electrode current collector plate is attached from external impact or environmental degradation. Vacuum-packed inside. And the outer peripheral part of an exterior material is sealed by heat sealing | fusion. Thereby, a bipolar secondary battery is completed.

  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 only the forms shown in the following examples.

<Example 1>
・ Production of electrolyte type bipolar electrode (Production of bipolar electrode)
LiMn ₂ O ₄ (average particle diameter 10 μm) (85% by mass) as a positive electrode active material, acetylene black (5% by mass) as a conductive additive, and polyvinylidene fluoride (PVdF) (10% by mass) as a binder Next, an appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, was added to prepare a positive electrode active material slurry.

  On the other hand, hard carbon (average particle diameter 10 μm) (90% by mass) as a negative electrode active material and PVdF (10% by mass) as a binder are mixed, and then an appropriate amount of NMP as a slurry viscosity adjusting solvent is added, A negative active material slurry was prepared.

  The positive electrode active material slurry prepared above is applied to one surface of a stainless steel foil (thickness 20 μm) as a current collector in a size of 135 mm long × 105 mm wide and dried to form a positive electrode active material layer having a thickness of 30 μm. did. Next, the negative electrode active material slurry prepared above was applied to the other surface of the current collector in a size of 140 mm long × 110 mm wide and dried to form a negative electrode active material layer having a thickness of 20 μm. Note that the negative electrode active material layer was formed so that the centers of the positive electrode active material layer and the negative electrode active material layer overlapped.

  Next, the current collector coated with the positive electrode active material layer and the negative electrode active material layer is cut into a size of 160 mm in length and 130 mm in width, and a current collector having a width of 20 mm is formed on the outer periphery of the positive electrode active material layer and the negative electrode active material layer. An exposed portion (uncoated portion) was provided to complete a bipolar electrode.

(Preparation of electrolyte)
An equivalent volume mixed solution (90% by mass) of propylene carbonate (PC) and ethylene carbonate (EC) containing LiPF ₆ at a concentration of 1.0 M was prepared as an electrolytic solution.

(Formation of seal part precursor)
The seal part precursor (one-component uncured epoxy resin) was applied to the positive electrode side uncoated part (all four sides) of the bipolar electrode obtained above using a dispenser.

  Next, a polyethylene separator (thickness 12 μm, length 145 mm × width 115 mm) as a precursor of the electrolyte layer was placed on the positive electrode side of the bipolar electrode provided with the seal portion precursor so as to cover all the current collectors. .

  Then, from the top of the separator, a non-electrode-applied portion (all four sides) (the same portion as the portion where the seal portion precursor is applied) is used with a dispenser, and a seal portion precursor (one-component uncured epoxy resin) ) Was further applied.

(Set to electrode holding mechanism)
With the bipolar electrode-separator laminate obtained above, with the negative electrode face up, the electrodes do not contact and are not displaced in the direction perpendicular to the electrode surface direction. Six sheets were set in a bipolar electrode holding mechanism provided with a clip mechanism capable of chucking the outside of the precursor application portion. Here, the bipolar electrode positioned at the lowermost portion was used without a seal portion precursor applied and without a separator.

(Introduction of electrolyte)
On the negative electrode surface of six bipolar electrodes set in the electrode holding mechanism, 1 mL of the electrolyte prepared as described above was dropped with a micropipette and soaked into the negative electrode active material layer of each bipolar electrode.

(Lamination of electrodes)
While lowering the electrode holding mechanism, the six bipolar electrodes were stacked on the electrode base so as not to be displaced. Thus, a power generation element in which five single cell layers were laminated was produced.

(Introduction to vacuum)
The power generation element obtained above was introduced together with the electrode cradle into a vacuum chamber having a hot press part. Thereafter, the inside of the vacuum chamber was heated and decompressed, and decompressed at 60 ° C. for 30 minutes and at a pressure of 10 Torr.

(Power generation element press)
The power generation element subjected to the pressure reduction treatment was moved together with the electrode cradle to a hot press site in the vacuum chamber under a pressure condition of 30 Torr. Thereafter, the power generation element was hot pressed at 80 ° C. for 1 hour at a surface pressure of 1 kg / cm ² by the hot press portion. As a result, the seal portion precursor (one-component uncured epoxy resin) was pressed to a predetermined thickness and cured, and a seal portion was formed on the outer peripheral portion of the single cell layer. Moreover, the electrolytic solution penetrated the entire single cell layer (that is, the negative electrode active material layer, the separator, and the positive electrode active material layer) by this hot pressing.

(Encapsulation in exterior)
After the inside of the vacuum chamber was leaked and returned to atmospheric pressure, the power generation element was taken out from the vacuum chamber, and current collecting plates and leads for current extraction were connected to both ends of the power generation element. Next, the entire power generation element was placed in an exterior (aluminum laminate film) so that the leads were led out, and the interior of the exterior was packed as a vacuum to complete a liquid electrolyte type bipolar laminate battery. When the electrolyte in the completed battery was allowed to stand at 25 ° C. for 1 hour under a pressure condition of 10 Torr, the weight loss was 0.5% by mass.

<Example 2>
In Example 1 described above, the electrolytic solution was changed to N-methyl-N-propylpiperidinium.TFSI, which is an ionic liquid, containing LiTFSI at a concentration of 0.5 M. In addition, the decompression condition in the vacuum chamber was changed to 120 ° C. and 5 Torr. Otherwise, a liquid electrolyte type bipolar laminate battery was completed in the same manner as in Example 1 described above. The weight loss when the electrolyte in the completed battery was allowed to stand at 25 ° C. for 1 hour under a pressure condition of 10 Torr was 0.1% by mass.

<Test example>
Using the bipolar laminate battery obtained in Examples 1 and 2, a charge / discharge cycle test was conducted.

  Specifically, first, charging was performed at 25 ° C. by a constant current constant voltage method (CCCV, current: 0.5 C, voltage: 4.2 V) for 3 hours. Thereafter, the battery was discharged to 2.5 V with a constant current (CC, current: 0.5 C) and rested for 30 minutes after the discharge. This charging / discharging process was defined as one cycle, and 100 cycles were repeated for a charge / discharge cycle test.

(Measurement of expansion coefficient)
The thickness of the laminate battery was measured at the end of the first charge / discharge (1 cycle) and at the end of 100 cycles. And the increase percentage (expansion coefficient) with respect to the thickness after battery preparation (before a charge-and-discharge test) of the measured thickness was computed. The calculation results of the expansion rate (%) are shown in Table 1 below.

  From the results shown in Table 1, it can be seen that according to the present invention, the expansion coefficient of the thickness of the battery after the charge / discharge cycle test can be suppressed to a very low value. This is considered to be because, in the bipolar battery provided by the present invention, the generation of gas during the first charge / discharge or repeated charge / discharge is suppressed. In addition, it can be seen that when the ionic liquid is used as compared with the case where an organic solvent is used as the plasticizer of the electrolytic solution, the expansion coefficient can be further suppressed to a smaller value. That is, when an electrolyte is constituted by using an ionic liquid, gas generation accompanying charging / discharging can be suppressed more significantly, and a bipolar battery with higher reliability can be provided.

(Measurement of capacity maintenance rate)
Moreover, the discharge capacity of the first charge / discharge (first cycle) and the discharge capacity of the 100th cycle were measured. From the first cycle to the 100th cycle, the ratio at which the discharge capacity was maintained was calculated as a percentage (capacity maintenance ratio). The calculation results of the capacity retention rate (%) are shown in Table 2 below.

  From the results shown in Table 2, it can be seen that according to the present invention, the capacity retention rate after the charge / discharge cycle is maintained at a high value. This is because, in the bipolar battery provided by the present invention, the generation of gas at the time of the first charge / discharge or repeated charge / discharge is suppressed, and peeling of the electrode due to gas generation or poor contact between the electrode and the electrolyte This is considered to be because the occurrence of such a problem is prevented. In addition, compared with the case where an organic solvent is used as a plasticizer of electrolyte solution, when an ionic liquid is used, it turns out that a capacity | capacitance maintenance factor is maintained at a still higher value. That is, when an electrolyte is formed using an ionic liquid, the occurrence of a problem due to gas generation can be more significantly suppressed, and a bipolar battery with higher reliability can be provided.

<Reference example>
Hereinafter, as a modification of Examples 1 and 2 described above for reference, what performance (expansion rate, capacity maintenance rate) is obtained when the composition of the electrolyte, the conditions of the reduced pressure treatment, and the like are changed. The theoretically predicted result is described along with whether the result corresponds to the example or the comparative example.

<Reference Example 1>
In Example 1 mentioned above, the liquid mixture which added acetone (10 mass parts) and methanol (10 mass parts) which are low boiling point solvents with respect to 100 mass parts of said electrolyte solutions is used as electrolyte solution. Otherwise, a liquid electrolyte type bipolar laminate battery is completed by the same method as in Example 1 described above.

<Reference Example 2>
In Example 2 mentioned above, the liquid mixture which added acetone (10 mass parts) and methanol (10 mass parts) which are low boiling point solvents with respect to 100 mass parts of said electrolyte solutions is used as electrolyte solution. Otherwise, a liquid electrolyte type bipolar laminate battery is completed by the same method as in Example 2 described above.

<Reference Example 3>
-Preparation of gel electrolyte type bipolar electrode In Example 1 mentioned above, electrolyte solution is changed into a pregel solution. The pregel solution includes an electrolytic solution (90% by mass) in which LiPF ₆ is dissolved at a concentration of 1.0 M in an equal volume mixture of PC and EC, and a host polymer (polyvinylidene fluoride containing 10% by mass of an HFP component). Hexafluoropropylene copolymer (PVdF-HFP)) (10% by mass) is mixed, and a suitable amount of dimethyl carbonate (DMC) is added as a viscosity adjusting solvent. This pregel solution is applied to the negative electrode surface, and the DMC is dried. The remaining electrolyte and host polymer are plasticized during hot pressing in a vacuum and penetrate into the entire single cell layer. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Example 1 described above.

<Reference Example 4>
In Reference Example 3 described above, acetone (10 parts by mass) and methanol (10 parts by mass), which are low boiling point solvents, are added to 100 parts by mass of the pregel solution, and an appropriate amount of dimethyl carbonate (DMC) is added as a viscosity adjusting solvent. The added one is used as a pregel solution. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 3 described above.

<Reference Example 5>
In Reference Example 3 described above, the electrolytic solution constituting the pregel solution is changed to N-methyl-N-propylpiperidinium.TFSI, which is an ionic liquid, containing LiTFSI at a concentration of 0.5M. In addition, the decompression condition in the vacuum chamber is changed to 120 ° C. and 5 Torr. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 3 described above.

<Reference Example 6>
In Reference Example 4 described above, the electrolytic solution constituting the pregel solution is changed to N-methyl-N-propylpiperidinium.TFSI, which is an ionic liquid, containing LiTFSI at a concentration of 0.5M. In addition, the decompression condition in the vacuum chamber is changed to 120 ° C. and 5 Torr. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 4 described above.

<Reference Example 7>
In Reference Example 6 described above, the host polymer constituting the pregel solution is changed to polyethylene oxide (PEO) which is a lithium ion conductive polymer. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 6 described above.

<Reference Example 8>
・ Production of solid electrolyte type bipolar electrode (Production of bipolar electrode)
LiMn ₂ O ₄ (average particle diameter 10 μm) (22% by mass) as a positive electrode active material, acetylene black (6% by mass) as a conductive auxiliary agent, PEO (18% by mass) as a host polymer, Li as a supporting salt (C ₂ F ₅ SO ₂ ) ₂ N (9% by mass), NMP (45% by mass) as a slurry viscosity adjusting solvent, and azobisisobutyronitrile (AIBN) (a trace amount) as a thermal polymerization initiator are mixed Then, a positive electrode active material slurry is prepared.

On the other hand, Li ₄ Ti ₅ O ₁₂ (14% by mass) as a negative electrode active material, acetylene black (4% by mass) as a conductive auxiliary agent, PEO (20% by mass) as a host polymer, Li (C ₂ F ₅ SO ₂ ) ₂ N (11% by mass), NMP (51% by mass) which is a slurry viscosity adjusting solvent, and azobisisobutyronitrile (AIBN) (a trace amount) which is a thermal polymerization initiator are mixed. A negative electrode active material slurry is prepared.

  The positive electrode active material slurry prepared above is applied to one surface of a stainless steel foil (thickness 20 μm) as a current collector in a size of 135 mm long × 105 mm wide and dried to form a positive electrode active material layer having a thickness of 30 μm. To do. Next, the negative electrode active material slurry prepared above is applied to the other surface of the current collector in a size of 140 mm long × 110 mm wide and dried to form a negative electrode active material layer having a thickness of 20 μm. Note that the negative electrode active material layer is formed so that the centers of the positive electrode active material layer and the negative electrode active material layer overlap. And the obtained laminated body is heat-polymerized at 110 degreeC for 4 hours, and PEO is thermally polymerized.

  Next, the current collector coated with the positive electrode active material layer and the negative electrode active material layer described above is cut into a size of 160 mm in length and 130 mm in width, and a current collector having a width of 10 mm is formed on the outer periphery of the positive electrode active material layer and the negative electrode active material layer. The exposed portion (uncoated portion) is provided to complete the bipolar electrode.

(Formation of solid electrolyte layer)
Host polymer is a PEO (64.5 wt%), and a supporting salt _{Li (C 2 F 5 SO 2} ) 2 N and (35.5 wt%) were mixed, acetone 20% by weight and a low boiling point solvent 20% by weight of methanol is added. Furthermore, an appropriate amount of acetonitrile is added as a slurry viscosity adjusting solvent to prepare a solid electrolyte slurry.

  The solid electrolyte slurry prepared above is applied onto the positive electrode active material of the bipolar electrode prepared above and dried to form an electrolyte layer having a thickness of 40 μm. In addition, a Kapton tape made of polyimide (thickness: 50 μm) is attached to the electrode uncoated portion (all four sides) on the positive electrode side of the bipolar electrode to form a seal portion.

(Set to electrode holding mechanism)
The bipolar electrode-electrolyte layer laminate obtained above, with the negative electrode facing up, the electrodes are not in contact with each other and there is no deviation in the direction perpendicular to the electrode surface direction. 6 pieces are set in a bipolar electrode holding mechanism equipped with a clip mechanism capable of chucking. Here, no seal portion is attached to the bipolar electrode located at the lowermost portion, and no electrolyte layer is formed.

(Lamination of electrodes)
While lowering the electrode holding mechanism, the six bipolar electrodes are stacked on the electrode base so as not to be displaced. As a result, a power generation element in which five cell layers are stacked is manufactured.

(Introduction to vacuum)
The power generation element obtained as described above is introduced together with the electrode pedestal into a vacuum chamber having a hot press part. Thereafter, the inside of the vacuum chamber is heated and depressurized, and a depressurizing process is performed at 120 ° C. for 30 minutes and a pressure of 5 Torr.

(Power generation element press)
The power generation element subjected to the pressure reduction treatment is moved together with the electrode cradle to a hot press site in the vacuum chamber under a pressure condition of 30 Torr. Thereafter, the power generation element is hot-pressed at 80 ° C. for 1 hour at a surface pressure of 1 kg / cm ^{2 by} the hot-press portion. As a result, the negative electrode active material layer and the electrolyte layer in the adjacent bipolar electrode are brought into close contact with each other.

(Encapsulation in exterior)
After the inside of the vacuum chamber is leaked and returned to the atmospheric pressure, the power generation element is taken out from the vacuum chamber, and a current collecting current collecting plate and a lead are connected to both ends of the power generation element. Next, the entire power generation element is placed in an exterior (aluminum laminate film) so that the leads are led out, and the interior of the exterior is packed as a vacuum to complete a solid electrolyte type bipolar laminate battery.

<Reference Example 9>
In the first embodiment described above, an electrolytic solution, tetraethyl orthosilicate is dehydrating agent based on the total amount of the electrolytic solution (before addition); changes to that of _{(TEOS Si (OCH 2 CH 3} ) 4) was added 1 wt% To do. Otherwise, a liquid electrolyte type bipolar laminate battery is completed by the same method as in Example 1 described above.

<Reference Example 10>
In Example 2 mentioned above, electrolyte solution is changed into what added 1 mass% of TEOS with respect to the whole quantity of electrolyte solution (before addition). In addition, the decompression condition in the vacuum chamber is changed to 100 ° C. and 3 Torr. Otherwise, a liquid electrolyte type bipolar laminate battery is completed by the same method as in Example 2 described above.

<Reference Example 11>
In Reference Example 3 described above, a pregel solution further added with TEOS is used. At this time, the addition amount of TEOS is 1% by mass with respect to the total amount of the electrolyte components (excluding DMC) in the pregel solution. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 3 described above.

<Reference Example 12>
In Reference Example 11 described above, the electrolytic solution constituting the pregel solution is changed to N-methyl-N-propylpiperidinium.TFSI, which is an ionic liquid, containing LiTFSI at a concentration of 0.5M. In addition, the decompression condition in the vacuum chamber is changed to 100 ° C. and 3 Torr. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 11 described above.

<Reference Example 13>
In Reference Example 12 described above, the host polymer constituting the pregel solution is changed to PEO. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 12 described above.

<Comparative Reference Example 1>
In the first embodiment described above, the depressurization condition in the vacuum chamber is changed to 25 ° C. and 20 Torr. Otherwise, a liquid electrolyte type bipolar laminate battery is completed by the same method as in Example 1 described above.

<Comparative Reference Example 2>
In the reference example 3 described above, the decompression condition in the vacuum chamber is changed to 25 ° C. and 20 Torr. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 3 described above.

<Comparative Reference Example 3>
In the reference example 5 described above, the decompression process condition in the vacuum chamber is changed to 25 ° C. and 20 Torr. Otherwise, a gel electrolyte type bipolar laminate battery is completed by the same method as in Reference Example 5 described above.

<Prediction of impact of charge / discharge cycle test>
For the bipolar laminate batteries obtained in Reference Examples 1 to 13 (corresponding to Examples of the present application) and Comparative Reference Examples 1 to 3 (corresponding to Comparative Examples of the present application), the charge / discharge cycle test described above was performed. The values of the expansion coefficient and the capacity maintenance ratio were predicted. The prediction results are shown in Table 3 below.

  In addition, the prediction of the expansion rate and the capacity retention rate in the batteries of the above reference examples and comparative reference examples is based on the results of Examples 1 and 2 described above and the logarithmic graph representing the vapor pressure curves of various solvents shown in FIG. This was carried out from the viewpoint of how much moisture remained during battery production.

  Here, the vapor pressure curves of ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (GBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and water are shown in FIG.

  Referring to FIG. 5, the vapor pressure curve of the solvent represents the relationship of the vapor pressure (vertical axis) at a certain temperature (horizontal axis) of the solvent. Therefore, the solvent is a liquid under the condition located on the upper left side of the vapor pressure curve of a certain solvent, and the solvent is a gas under the condition located on the lower right side of the curve. Therefore, the more the vapor pressure curve is located on the left, the greater the vapor pressure at a certain temperature, and it can be volatilized and removed even under milder pressure reduction conditions. For example, taking a decompression condition of about 10 Torr as an example, water can be removed under the condition of point A (about 20 ° C.) shown in FIG. Further, under the condition of point B (about 60 ° C.) shown in FIG. 5, it is possible to remove the low boiling point solvent (DEC, DMC) in addition to water. On the other hand, in order to remove the high boiling point solvents (EC, PC, GBL), it is necessary to set the system to a high temperature condition of about point C (about 150 ° C.) shown in FIG. Further, as shown in FIG. 5, it is estimated that the vapor pressure curve of the ionic liquid is located on the considerably high temperature side. Therefore, it is considered that the ionic liquid is hardly volatilized / removed when the battery is manufactured.

  The prediction results shown in Table 3 described in each reference example are the composition of the electrolyte and the conditions of the decompression treatment based on the test results in Examples 1 and 2 described above and the past experimental data possessed by the applicant. If the change is made as described above, it is estimated how much gas is generated, and the values of the expansion rate and capacity retention rate in each reference example are predicted from the gas generation amount thus estimated.

  From the prediction results shown in Table 3 for each reference example, it is expected that the bipolar battery provided by the present invention is excellent in the expansion rate and capacity retention rate after the charge / discharge cycle test. Further, it is expected that the expansion rate and the capacity retention rate are further improved when an ionic liquid is used as compared with a case where an organic solvent is used as a plasticizer for the electrolytic solution. Such a prediction can be predicted only after the results of Examples 1 and 2 described above are obtained. Therefore, even if the above prediction is possible based on the results of Examples 1 and 2 and past experimental data, it cannot be predicted from the technical level at the time of filing this application.

BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic which represented typically the outline | summary of the bipolar lithium ion secondary battery which is one typical embodiment of the bipolar secondary battery of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an appearance of a stacked flat bipolar secondary battery that is a typical embodiment of a bipolar secondary battery according to the present invention. FIG. 3A is an external view schematically showing a typical embodiment of a battery pack according to the present invention, FIG. 3A is a plan view of the battery pack, FIG. 3B is a front view of the battery pack, and FIG. It is a side view of a battery. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention. It is a graph which shows the vapor pressure curve of ethylene carbonate (EC), propylene carbonate (PC), gamma butyrolactone (GBL), diethyl carbonate (DEC), dimethyl carbonate (DMC), and water.

Explanation of symbols

10 Bipolar secondary battery,
11 Current collector,
11a The outermost layer current collector on the positive electrode side,
11b The outermost layer current collector on the negative electrode side,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21 power generation elements,
25 positive current collector,
27 negative current collector,
29 Laminate sheet,
31 seal part,
35 A small assembled battery that can be attached and detached,
37 battery pack,
39 Connecting jig,
40 Electric car.

Claims (20)

A bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte layer containing an electrolyte, the positive electrode active material layer, the electrolyte layer, A bipolar power generation element having a power generation element that is laminated so that at least one unit cell layer is formed by laminating the anode active material layer in this order, and a seal portion is formed on the outer periphery of the unit cell layer. A secondary battery,
The bipolar type battery is characterized in that a weight loss when the electrolyte is allowed to stand at 25 ° C. for 1 hour under a pressure condition of 10 Torr is 1% by mass or less with respect to the mass of the electrolyte before standing. Next battery. A bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte layer containing an electrolyte, the positive electrode active material layer, the electrolyte layer, A bipolar power generation element having a power generation element that is laminated so that at least one unit cell layer is formed by laminating the anode active material layer in this order, and a seal portion is formed on the outer periphery of the unit cell layer. A secondary battery,
A bipolar secondary battery, wherein a weight loss when the electrolyte is allowed to stand at 60 ° C. for 1 hour under a pressure condition of 10 Torr is 1% by mass or less with respect to a mass of the electrolyte before standing. A bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte layer containing an electrolyte, the positive electrode active material layer, the electrolyte layer, A bipolar power generation element having a power generation element that is laminated so that at least one unit cell layer is formed by laminating the anode active material layer in this order, and a seal portion is formed on the outer periphery of the unit cell layer. A secondary battery,
A bipolar secondary battery, wherein a weight loss when the electrolyte is allowed to stand at 150 ° C. for 1 hour under a pressure condition of 10 Torr is 1% by mass or less based on a mass of the electrolyte before standing.   The battery according to claim 1, wherein the electrolyte contains a solvent having a boiling point lower than that of water.   The battery according to claim 4, wherein the solvent is one or more selected from the group consisting of alcohol solvents, ketone solvents, ether solvents, and hydrocarbon solvents.   The solvent is methanol, ethanol, 1-propanol, 2-propanol, acetone, methyl ethyl ketone, n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, n- 6. One or more selected from the group consisting of heptane, cyclohexane, methylcyclopentane, cyclopentane, toterahydrofuran, diisopropyl ether, methyl-tert-butyl ether, and 1,2-dimethoxyethane. The battery described in 1.   The battery according to claim 1, wherein the electrolyte includes a dehydrating agent. The dehydrating agent has the following chemical formula 1:

Where M is Si, Ge, Sn, Pb, Al, Ga, In, or Tl, R is independently an alkyl group having 1 to 4 carbon atoms, and x is 3 or 4.
The battery of Claim 7 which is an alkoxide compound represented by these.   The battery according to claim 8, wherein M is Si or Ge.   The battery according to claim 8 or 9, wherein R is a methyl group or an ethyl group.   The battery according to any one of claims 1 to 10, wherein a water content in the electrolyte is 50 mass ppm or less with respect to a total amount of the electrolyte.   The battery according to claim 1, wherein the electrolyte includes an ionic liquid. The cation constituting the ionic liquid is one or more selected from the group consisting of ammonium, phosphonium cation and sulfonium cation, and the anions constituting the ionic liquid are BF ₄ ⁻ , AlF ₄ −, PF ₆ ^−. , AsF ₆ ⁻ , SbF ₆ ⁻ , ClO ₄ ⁻ , AlCl ₄ ⁻ , CF ₃ SO ₃ ⁻ , C ₂ F ₅ SO ₃ ⁻ _, C ₃ F ₇ SO ₃ ⁻ _, C ₄ F ₉ SO ₃ ⁻ _, CH ₃ SO ^{_{3 -, C 2 H 5 SO}} 3 -, CH 3 OSO 3 -, C 2 H 5 OSO 3 -, (FO 2 S) 2 N - (FSI), (CF 3 SO 2) 2 N - (TFSI), ^{_{CF 3 CO 2 -, (C}} 2 F 5 SO 2) 2 N - (BETI), (C 4 F 9 SO 2) 2 N -, (CF 3 SO 2) 3 C -, (C 2 F ^{_{SO 2) 3 C -, (}} CN) 2 N -, (CF 3) 3 PF 3 -, (C 2 F 5) 3 PF 3 -, (C 3 F 7) 3 PF 3 -, and _(C 4 F _{9) 3} PF ₃ ^- is one or more selected from the group consisting of battery of claim 12.   The cation constituting the ionic liquid is N-ethyl-N-methylpiperidinium, N-methyl-N-propylpiperidinium, N-butyl-N-methylpiperidinium, N-hexyl-N-methylpiper Peridinium, N-ethyl-N-methylpyrrolidinium, N-methyl-N-propylpyrrolidinium, N-butyl-N-methylpyrrolidinium, N-hexyl-N-methylpyrrolidinium, N, N , N-trimethyl-N-ethylammonium, N, N, N-trimethyl-N-propylammonium, N, N, N-trimethyl-N-butylammonium, N, N, N-trimethyl-N-hexylammonium, N , N, N-triethyl-N-methylammonium, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium Is one or more selected from an anion constituting the ionic liquid, FSI, TFSI, cell of claim 13 is one or more selected from the group consisting of BETI.   The battery according to claim 1, wherein the electrolyte includes a polymer.   The battery according to claim 1, which is a bipolar lithium ion secondary battery.   The assembled battery using the battery of any one of Claims 1-16.   A vehicle equipped with the battery according to any one of claims 1 to 16, or the assembled battery according to claim 17. A bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte layer containing an electrolyte, the positive electrode active material layer, the electrolyte layer, And a bipolar secondary battery having a power generation element that is laminated to form at least one single cell layer in which the negative electrode active material layers are laminated in this order, and a seal portion is formed on the outer periphery of the single cell layer. A battery manufacturing method comprising:
Preparing a bipolar electrode; and
Preparing the electrolyte; and
Laminating the bipolar electrode and an electrolyte layer or a precursor thereof to obtain a laminate including the single battery layer;
Forming a seal portion on the outer periphery of the unit cell layer,
A method for manufacturing a bipolar secondary battery, further comprising a step of reducing the electrolyte at a pressure of less than 10 Torr before or simultaneously with the step of forming the seal portion. A bipolar electrode having a positive electrode active material layer formed on one surface of a current collector and a negative electrode active material layer formed on the other surface, and an electrolyte layer containing an electrolyte, the positive electrode active material layer, the electrolyte layer, And a bipolar secondary battery having a power generation element that is laminated to form at least one single cell layer in which the negative electrode active material layers are laminated in this order, and a seal portion is formed on the outer periphery of the single cell layer. A battery manufacturing method comprising:
Preparing a bipolar electrode; and
Preparing the electrolyte; and
Laminating the bipolar electrode and an electrolyte layer or a precursor thereof to obtain a laminate including the single cell layer;
Forming a seal portion on the outer periphery of the unit cell layer,
The bipolar secondary, wherein the electrolyte contains a solvent or dehydrating agent having a boiling point lower than that of water, and further includes a step of reducing the electrolyte at a pressure of less than 20 Torr before or simultaneously with the step of forming the seal portion. Battery manufacturing method.

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