JP2006210089A - Electrode for intrinsic polymer battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means which facilitates the purge of gas generated from an electrode of an intrinsic polymer battery during initial charge and discharge to the outside, prevents various problems caused by the generation of gas from occurring, and improves the durability of the battery. <P>SOLUTION: The electrode of the intrinsic polymer battery has a collector and an active material layer formed on the surface of the collector and including an active material, where the voidage of the active material layer is 60% or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an intrinsic polymer battery electrode. In particular, the present invention relates to an improvement for improving the durability of an intrinsic polymer battery.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of secondary batteries for motor drive that holds the key to their practical application is thriving. Has been done.

As a secondary battery for driving a motor, a lithium ion secondary battery having the highest theoretical energy among all the batteries is attracting attention, and is currently being developed rapidly. Generally, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. However, it has the structure connected through the electrolyte layer and accommodated in a battery case (for example, refer patent document 1).
JP 2003-7345 A

  It is known that gas is generated from the electrolyte layer and the electrodes constituting the battery element during the initial charge / discharge of the lithium ion secondary battery. If this gas is left as it is, the active material of the electrode is peeled off, which causes deterioration of battery characteristics such as charge / discharge performance and battery life. For this reason, it is necessary to open the battery case once after the first charge / discharge and let the generated gas escape to the outside of the battery case.

  Here, when the electrolyte contained in the electrode is a liquid electrolyte, it is relatively easy to remove the gas generated in the electrode during the initial charge to the outside of the electrode.

  On the other hand, when a gel polymer electrolyte or an intrinsic polymer electrolyte is included in the electrode, it is difficult to extract the gas generated in the electrode to the outside of the electrode. In particular, the gas generated in the electrode containing the intrinsic polymer electrolyte is very difficult to escape to the outside of the electrode. This is considered due to the structure of the electrode in which the binder and the solid polymer electrolyte surround the active material particles. In addition, development is advanced from the viewpoint of improving output characteristics, and this problem is remarkable in a bipolar battery in which the area of the electrode continues to increase.

  Therefore, an object of the present invention is to improve the durability of the battery by preventing the occurrence of various problems due to gas generation by making the gas generated during the first charge / discharge easy to escape to the outside in the intrinsic polymer battery electrode. It is to provide a means.

  The present invention is an intrinsic polymer battery electrode having a current collector and an active material layer containing an active material formed on the surface of the current collector, wherein the active material layer has a porosity of 60%. It is the electrode for intrinsic polymer batteries characterized by the above.

  The present invention also includes a step of preparing an active material slurry by adding an active material, an ion conductive polymer, and a foaming agent to a solvent, and applying the active material slurry to the surface of the current collector. By this, it is the manufacturing method of the electrode for intrinsic polymer batteries which has the process of forming the coating film, the process of drying the said coating film, and the process of decomposing | disassembling the said foaming agent contained in the said coating film.

  In the intrinsic polymer battery electrode of the present invention, the porosity of the active material layer is 60% or more, which is larger than the conventional one. For this reason, the gas generated in the active material layer of the electrode is likely to escape outside the electrode. Therefore, the electrode of the present invention can contribute to improvement of battery durability.

  Embodiments of the present invention will be described below.

(First embodiment)
(Constitution)
The present invention is an intrinsic polymer battery electrode having a current collector and an active material layer containing an active material formed on the surface of the current collector, wherein the active material layer has a porosity of 60%. It is the electrode for intrinsic polymer batteries characterized by the above.

  First, the structure of the intrinsic polymer battery electrode of the present invention will be described with reference to the drawings. In the present invention, the drawings are exaggerated for convenience of explanation, and the technical scope of the present invention is not limited to the forms shown in the drawings. Also, embodiments other than the drawings may be employed.

  FIG. 1 is a cross-sectional view showing an embodiment of an intrinsic polymer battery electrode of the present invention. 1 is a bipolar electrode in which a positive electrode active material layer 13 is formed on one surface of a current collector 11 and a negative electrode active material layer 15 is formed on the other surface. .

  In the present embodiment, the porosity of the positive electrode active material layer 13 and the negative electrode active material layer 15 is 60% or more. With such a configuration, the gas generated in the active material layer at the time of the first charge / discharge can easily escape to the outside of the active material layer. As a result, various problems associated with gas generation are prevented, and the durability of the battery is improved. In the present application, the porosity of the active material layer can be calculated from, for example, the volume and mass of the active material layer, and the density and blending ratio of each material included in the active material layer.

  The electrode for an intrinsic polymer battery of the present invention is applied to a battery having an electrolyte layer made of an intrinsic polymer electrolyte. That is, the electrode of the present invention can be employed in a battery that does not contain a liquid component in either the electrode or the electrolyte layer.

  The bipolar electrode as shown in FIG. 1 can be employed in, for example, a bipolar lithium ion secondary battery (hereinafter also simply referred to as “bipolar battery”). Of course, it may be adopted for other batteries.

  Hereinafter, the configuration of the intrinsic polymer battery electrode of the present invention will be described by taking as an example a case where it is employed in a lithium ion secondary battery. The intrinsic polymer battery electrode of the present invention is characterized in that the porosity of the active material layer is 60% or more. There is no particular limitation on the selection of the current collector, active material, binder, supporting salt (lithium salt), intrinsic polymer electrolyte, and other compounds added as necessary. Depending on the intended use, it may be selected by appropriately referring to conventionally known knowledge. The intrinsic polymer battery electrode of the present invention can be applied to both the positive electrode and the negative electrode. For example, when applied to the positive electrode, the positive electrode current collector and the positive electrode active material are used as the current collector and the active material. A compound known to act as a substance may be employed.

[Current collector]
The current collector 11 is made of a conductive material such as an aluminum foil, a nickel foil, a copper foil, or a stainless steel (SUS) foil. The general thickness of the current collector is 1 to 30 μm. However, a current collector having a thickness outside this range may be used.

  The size of the current collector is determined according to the intended use of the battery. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. If a small electrode is produced, a current collector with a small area is used.

[Active material layer]
An active material layer (13, 15) is formed on the current collector 11. The active material layers (13, 15) are layers containing an active material that plays a central role in the charge / discharge reaction. In the present invention, the porosity of the active material layers (13, 15) is 60% or more, preferably 65% or more, more preferably 70% or more, and particularly preferably 75% or more. If the porosity of the active material layer (13, 15) is less than 60%, the gas generated in the active material layer may not sufficiently escape to the outside, which may cause problems such as separation of components of the active material layer. . This is presumably due to the fact that when the porosity of the active material layer is too small, the voids existing in the active material layer are not connected to each other, so that a passage through which gas escapes is not effectively formed.

  From the viewpoint of improving the gas venting performance, the upper limit of the porosity of the active material layer (13, 15) is not defined. However, in consideration of characteristics such as battery capacity and mechanical strength from the viewpoint of practicality, the porosity of the active material layer is preferably 85% or less, more preferably 80% or less, and still more preferably. 75% or less. However, depending on the case, a form out of such a range may be adopted.

  The porosity of the active material layers (13, 15) is affected by the concentration of the active material, the binder, and the like in the active material slurry used to form the active material layer. Therefore, these concentrations may be adjusted at the time of manufacturing the electrode according to the desired porosity.

  The active material layers (13, 15) include an active material. When the electrode of the present invention is used as a positive electrode, the active material layer contains a positive electrode active material. On the other hand, when the electrode of the present invention is used as a negative electrode, the active material layer contains a negative electrode active material.

As the positive electrode active material, a lithium-transition metal composite oxide is preferable, and examples thereof include a Li—Mn composite oxide such as LiMn ₂ O ₄ and a Li—Ni composite oxide such as LiNiO ₂ . In some cases, two or more positive electrode active materials may be used in combination.

  As the negative electrode active material, the above lithium transition metal-composite oxide or carbon is preferable. Examples of carbon include graphite-based carbon materials such as natural graphite, artificial graphite, and expanded graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon.

  The active material layers (13, 15) may contain other materials if necessary. For example, a binder, a conductive additive, a supporting salt (lithium salt), an ion conductive polymer, and the like can be included. When an ion conductive polymer is included, a polymerization initiator for polymerizing the polymer may be included.

  Examples of the binder include polyvinylidene fluoride (PVdF) and a synthetic rubber binder.

  A conductive support agent means the additive mix | blended in order to improve the electroconductivity of an active material layer. Examples of the conductive aid include carbon powder such as graphite and various carbon fibers.

  In a more preferred form, the active material layers (13, 15) further contain carbon fibers having a fiber diameter of 500 nm or less, preferably 300 nm or less, more preferably 200 nm or less. According to such a form, the said carbon fiber functions as a conductive support agent, and the electron conduction network between active materials can fully be ensured in an active material layer. At this time, if the fiber diameter of the carbon fiber exceeds 500 nm, the flexibility of the carbon fiber is lowered, and the contact property between the carbon fiber and the active material may be lowered. Specific examples of such carbon fibers include vapor grown carbon fibers (VGCF), vapor grown nano carbon fibers (VGNF), carbon nanotubes (CNT), and the like.

Examples of the supporting salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers. Here, the polymer may be the same as or different from the ion conductive polymer used in the intrinsic polymer electrolyte layer of the battery in which the electrode of the present invention is employed, but is preferably the same.

  The polymerization initiator is blended to act on the crosslinkable group of the ion conductive polymer and advance the crosslinking reaction. Depending on the external factor for acting as an initiator, it is classified into a photopolymerization initiator, a thermal polymerization initiator and the like. Examples of the polymerization initiator include azobisisobutyronitrile (AIBN), which is a thermal polymerization initiator, and benzyl dimethyl ketal (BDK), which is a photopolymerization initiator.

  The compounding ratio of the components contained in the active material layers (13, 15) is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.

  However, when the carbon fiber is included in the active material layer, the ratio of the content of the carbon fiber to the content of the active material is preferably 0.2 or more, more preferably 0.2 to 3. Yes, more preferably 0.5-2. When this ratio is 0.2 or more, even when a large amount of solvent is mixed with the active material slurry prepared at the time of electrode production, complication of the coating process due to a decrease in slurry viscosity is prevented, and more voids are generated. It is preferable because an active material layer having a high rate can be manufactured.

(Production method)
Then, the manufacturing method of the electrode for intrinsic polymer batteries of this invention is demonstrated.

  In the electrode of the present invention, for example, an active material and an intrinsic polymer electrolyte are added to a solvent to prepare an active material slurry (active material slurry preparation step), and the active material slurry is applied to the surface of the current collector. It can be manufactured by forming a coating film by coating (coating process) and drying the coating film (drying process). For the purpose of crosslinking the intrinsic polymer electrolyte added to the active material slurry, when a polymerization initiator is further added to the active material slurry, a polymerization treatment is performed simultaneously with the drying step or before or after the drying step. (Polymerization step).

  Hereinafter, although such a manufacturing method is demonstrated in detail in order of a process, it is not restrict | limited only to the following form.

[Active material slurry preparation process]
In this step, a desired active material, an ion conductive polymer, and other components (for example, a binder, a conductive assistant, a supporting salt (lithium salt), a polymerization initiator, etc.) are mixed in a solvent as necessary. Then, an active material slurry is prepared. Since the specific form of each component blended in the active material slurry is as described in the column of the configuration of the electrode of the present invention, detailed description is omitted here.

  Carbon fiber is excellent in solvent absorbability. For this reason, when carbon fiber is mix | blended in an active material slurry, compared with the case where it does not mix | blend, it is possible to increase the compounding quantity of a solvent, without reducing the viscosity of a slurry. Since this solvent is removed in the drying step described later, the porosity of the active material layer can be further increased by blending carbon fibers, particularly carbon fibers having the above-mentioned predetermined fiber diameter, into the active material slurry. .

  The kind of solvent and the mixing means are not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. As an example of the solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide and the like can be used. When adopting polyvinylidene fluoride (PVdF) as a binder, NMP is preferably used as a solvent.

  In this manufacturing method, the porosity of the active material layer of the manufactured electrode can be controlled by adjusting the compounding ratio between the solid content and the solvent in the active material slurry prepared in the active material slurry preparation step. Specifically, when it is desired to reduce the porosity of the active material layer to be formed, the blending amount of the solid content in the active material slurry may be increased. On the other hand, when it is desired to increase the porosity of the active material layer to be formed, the blending amount of the solid content in the active material slurry is preferably decreased.

[Coating process]
Subsequently, a current collector is prepared, and the active material slurry prepared above is applied to the surface of the current collector. Thereby, the coating film which consists of an active material slurry is formed on the surface of an electrical power collector. This coating film becomes an active material layer through a drying step described later.

  The specific form of the current collector to be prepared is as described in the column of the configuration of the electrode of the present invention, and thus detailed description thereof is omitted here.

  The application means for applying the active material slurry is not particularly limited. For example, a commonly used means such as a coater can be adopted.

  A coating film is formed according to the desired arrangement | positioning form of the electrical power collector and active material layer in the electrode manufactured. For example, when the manufactured electrode is a bipolar electrode, a coating film containing a positive electrode active material is formed on one surface of the current collector, and a coating film containing a negative electrode active material is formed on the other surface. On the other hand, when manufacturing a non-bipolar electrode, a coating film containing either the positive electrode active material or the negative electrode active material is formed on both surfaces of one current collector.

[Drying process]
Thereafter, the coating film formed on the surface of the current collector is dried. Thereby, the solvent in a coating film is removed.

  The drying means for drying the coating film is not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. For example, heat treatment is exemplified. Drying conditions (drying time, drying temperature, etc.) can be appropriately set according to the application amount of the active material slurry and the volatilization rate of the solvent of the slurry.

  When a coating film does not contain a polymerization initiator, the electrode of this invention is completed with completion of a drying process. When a coating film contains a polymerization initiator, the ion conductive polymer in a coating film is bridge | crosslinked by a crosslinkable group by performing a superposition | polymerization process, and the electrode of this invention is completed.

  The polymerization treatment in the polymerization step is not particularly limited, and conventionally known knowledge may be referred to as appropriate. For example, when the coating film contains a thermal polymerization initiator (AIBN or the like), the coating film is subjected to heat treatment. Moreover, when a coating film contains a photoinitiator (BDK etc.), light, such as an ultraviolet light, is irradiated. In addition, the heat processing for thermal polymerization may be performed simultaneously with said drying process, and may be performed before or after the said drying process.

  This application provides the more preferable form of said manufacturing method. This more preferable embodiment is characterized in that a foaming agent is used as a means for improving the porosity of the active material layer. That is, the second aspect of the present invention is a step of preparing an active material slurry (active material slurry preparation step) by adding an active material, an ion conductive polymer, and a foaming agent to a solvent, and the active material. By applying substance slurry to the surface of the current collector, a step of forming a coating film (application step), a step of drying the coating layer (drying step), and decomposing the foaming agent contained in the coating layer And a step (decomposing step of foaming agent) for producing an intrinsic polymer battery electrode. According to the second manufacturing method of the present invention, the porosity of the active material layer of the electrode can be easily controlled.

  Hereinafter, such a manufacturing method will be described in detail, but the description of the same steps as the above manufacturing method will be omitted, and a characteristic form of the manufacturing method will be described in detail.

[Active material slurry preparation process]
In the active material slurry preparation step of this production method, a foaming agent is further added to the solvent. This foaming agent is blended for the purpose of decomposing in a foaming agent decomposing step described later to form voids in the active material layer.

  The “foaming agent” is a compounding agent that can be decomposed in the coating film formed on the surface of the current collector and discharged as a gas from the coating film to form a large number of bubbles in the coating film.

  The specific form of the foaming agent is not particularly limited, and conventionally known knowledge can be referred to as appropriate. For example, it is preferable to use a foaming agent that decomposes by heat treatment because the treatment in the foaming agent decomposition step described later is simple. However, it is not limited only to such a form.

  Specific examples of the foaming agent include 4,4′-oxybis (benzenesulfonylhydrazide) (decomposition temperature: 118 ° C.), N, N′-dinitrosopentamethylenetetramine (decomposition) that can be decomposed by heat treatment. Temperature: 125 ° C.). Only 1 type of these foaming agents may be used independently, and 2 or more types may be used together.

  The blending amount of the foaming agent in the active material slurry is not particularly limited. The blending amount of the foaming agent can be adjusted in consideration of a desired porosity of the formed active material layer. Specifically, when the amount of the foaming agent added is increased, the porosity of the active material layer can be increased. On the other hand, when the addition amount of the foaming agent is reduced, the porosity of the active material layer can be reduced.

  In some cases, a foaming aid such as urea may be further added to the solvent. By adding such a foaming aid, the decomposition temperature of the foaming agent can be lowered. Further, the decomposition temperature of the foaming agent can be controlled by adjusting the amount of foaming aid added. Therefore, by adding the foaming aid, the workability of the foaming aid decomposition step described later can be improved.

[Foaming agent decomposition process]
In this step, the foaming agent in the coating film made of the active material slurry is decomposed. Many bubbles are formed in the coating film by the decomposition of the foaming agent. Thereby, the porosity of an active material layer can be increased reliably.

  The means for decomposing the foaming agent is not particularly limited, and can be appropriately selected according to the characteristics of the used foaming agent. For example, when the coating film contains a foaming agent that can be decomposed by heat, the foaming agent may be decomposed by heat treatment.

  The treatment temperature during the heat treatment is not particularly limited and can be appropriately set according to the characteristics of the foaming agent used. However, when the coating film contains an ion conductive polymer and a thermal polymerization initiator, it is preferable in terms of working time, manufacturing cost, etc., to perform the heat treatment in this step and the heat treatment for thermal polymerization at once. Although depending on the type of thermal polymerization initiator used, the operating temperature of the thermal polymerization initiator is generally about 100 to 130 ° C. Therefore, if a foaming agent that decomposes in this temperature range is employed, the decomposition of the foaming agent and the polymerization of the ion conductive polymer can be achieved by a single heat treatment. In some cases, further drying of the coating can be achieved simultaneously. However, it is not limited only to such a form, heat treatment for the purpose of drying the coating film in the drying step, heat treatment for the purpose of polymerizing the ion conductive polymer, and heat treatment for the purpose of decomposing the foaming agent. May be performed in separate steps, or may be performed in any combination at the same time.

(Second Embodiment)
In 2nd Embodiment, a battery is comprised using the electrode for intrinsic polymer batteries of said 1st Embodiment.

  That is, a third aspect of the present invention is an intrinsic polymer battery having at least one unit cell in which a positive electrode, a solid polymer electrolyte layer, and a negative electrode are laminated in this order, and at least one of the positive electrode and the negative electrode is a main battery. It is an intrinsic polymer battery which is an electrode of the invention. The electrode of the present invention can be applied to any of a positive electrode, a negative electrode, and a bipolar electrode as long as it constitutes an intrinsic polymer battery. An intrinsic polymer battery including the electrode of the present invention as at least one electrode belongs to the technical scope of the present invention. However, preferably, all of the electrodes constituting the intrinsic polymer battery are the electrodes of the present invention. By adopting such a configuration, the durability of the battery can be effectively improved.

  The intrinsic polymer battery of the present invention may be a bipolar lithium ion secondary battery (hereinafter also referred to as “bipolar battery”). FIG. 2 is a cross-sectional view showing a third intrinsic polymer battery of the present invention, which is a bipolar battery. Hereinafter, the bipolar battery shown in FIG. 2 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 battery 10 of this embodiment shown in FIG. 2 has a structure in which a substantially rectangular battery element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior.

  As shown in FIG. 2, the battery element 21 of the bipolar battery 10 of the present embodiment has a positive electrode active material layer 13 formed on one surface of a current collector 11 and a negative electrode active material layer 15 formed on the other surface. It has a plurality of bipolar electrodes. Each bipolar electrode is laminated via an intrinsic polymer electrolyte layer 17 to form a battery element 21. At this time, each bipolar electrode and 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 intrinsic polymer electrolyte layer 17. An intrinsic polymer electrolyte layer 17 is laminated.

  The adjacent positive electrode active material layer 13, intrinsic polymer electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar battery 10 has a configuration in which the single battery layers 19 are stacked. In addition, an insulating layer 31 for insulating adjacent current collectors 11 is provided on the outer periphery of the unit cell layer 19. The current collector (outermost layer current collector) (11a, 11b) located in the outermost layer of the battery element 21 has a positive electrode active material layer 13 (positive electrode side outermost layer current collector 11a) or a negative electrode only on one side. One of the active material layers 15 (negative electrode side outermost layer current collector 11b) is formed.

  Further, in the bipolar battery 10 shown in FIG. 2, the positive electrode side outermost layer current collector 11a is extended to form a positive electrode tab 25, which is led out from a laminate sheet 29 which is an exterior. On the other hand, the negative electrode side outermost layer current collector 11 b is extended to form a negative electrode tab 27, which is similarly derived from the laminate sheet 29.

  Hereinafter, members constituting the bipolar battery 10 of the present embodiment will be briefly described. However, since the components constituting the electrode are as described above, the description thereof is omitted here. Further, the technical scope of the present invention is not limited to the following forms, and conventionally known forms can be similarly adopted.

[Intrinsic polymer electrolyte layer]
The electrolyte constituting the intrinsic polymer electrolyte layer 17 is composed of an ion conductive polymer (matrix polymer), and the material is not limited as long as it exhibits ionic conductivity. Made by forming a cross-linked structure by polymerizing a polymerizable polymer for forming a polymer electrolyte by thermal polymerization, ultraviolet polymerization, radiation polymerization, or electron beam polymerization because it can exhibit excellent mechanical strength. Are preferably used. Intrinsic polymer electrolyte layer formed of such a polymer electrolyte has almost no risk of liquid leakage, so that the battery reliability is improved, and bipolar battery 10 having a simple configuration and excellent output characteristics is formed.

  The intrinsic polymer electrolyte is not particularly limited, and examples thereof include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts can be well dissolved. In addition, these polymers can exhibit excellent mechanical strength by forming a crosslinked structure. As described above, it is preferable that the ion conductive polymer constituting the intrinsic polymer electrolyte is included in both the positive electrode active material layer 13 and the negative electrode active material layer 15 from the viewpoint of further improving the electrode characteristics. The ion conductive polymer constituting the intrinsic polymer electrolyte layer 17 may be one in which crosslinkable groups are crosslinked by chemical bonds.

The supporting salt (lithium salt) dissolved in the ion conductive polymer in the intrinsic polymer electrolyte layer 17 is Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO. ₃ etc. are mentioned.

[Insulation layer]
In the bipolar battery 10, an insulating layer 31 is usually provided around each unit cell layer 19. The insulating layer 31 is provided for the purpose of preventing the adjacent current collectors 11 in the battery from contacting each other and short-circuiting due to a slight unevenness at the end of the battery cell layer 19 in the battery element 21. It is done. The installation of such an insulating layer 31 ensures long-term reliability and safety, and can provide a high-quality bipolar battery 10.

  The insulating layer 31 only needs to have insulating properties, sealing properties against falling off of the solid electrolyte, sealing properties against moisture permeation from the outside (sealing properties), heat resistance under battery operating temperature, etc. Urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber and the like can be used. Of these, urethane resins and epoxy resins are preferred from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming properties), economy, and the like.

[tab]
In the bipolar battery 10, tabs (positive electrode tab 25 and negative electrode tab 27) electrically connected to the outermost layer current collector (11 a, 11 b) are taken out of the exterior for the purpose of taking out current outside the battery. Specifically, a positive electrode tab 25 electrically connected to the positive electrode outermost layer current collector 11a and a negative electrode tab 27 electrically connected to the negative electrode outermost layer current collector 11b are provided outside the exterior. It is taken out.

  The material of the tabs (the positive electrode tab 25 and the negative electrode tab 27) is not particularly limited, and a known material conventionally used as a tab for a bipolar battery can be used. Examples thereof include aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof. The positive electrode terminal 25 and the negative electrode terminal 27 may be made of the same material or different materials. As in the present embodiment, the outermost layer current collectors (11a, 11b) may be extended to form tabs (25, 27), or a separately prepared tab may be connected to the outermost layer current collector. Good.

[Exterior]
In the bipolar battery 10, the battery element 21 is preferably housed in an exterior such as a laminate sheet 29 in order to prevent external impact and environmental degradation during use. The exterior is not particularly limited, and a conventionally known exterior can be used. A polymer-metal composite laminate sheet or the like excellent in thermal conductivity can be preferably used in that heat can be efficiently transferred from a heat source of an automobile and the inside of the battery can be rapidly heated to the battery operating temperature.

(Third embodiment)
In the third embodiment, a plurality of the bipolar batteries of the second embodiment are connected in parallel and / or in series to constitute an assembled battery.

  FIG. 3 is a perspective view showing the assembled battery of the present embodiment.

  As shown in FIG. 3, the assembled battery 40 is configured by connecting a plurality of bipolar batteries described in the second embodiment. Each bipolar battery 10 is connected by connecting the positive electrode tab 25 and the negative electrode tab 27 of each bipolar battery 10 using a bus bar. On one side surface of the assembled battery 40, electrode terminals (42, 43) are provided as electrodes of the entire assembled battery 40.

  The connection method when connecting the plurality of bipolar batteries 10 constituting the assembled battery 40 is not particularly limited, and a conventionally known method can be appropriately employed. For example, a technique using welding such as ultrasonic welding or spot welding, or a technique of fixing using rivets, caulking, or the like can be employed. According to such a connection method, the long-term reliability of the assembled battery 40 can be improved.

  According to the assembled battery 40 of this embodiment, since each bipolar battery 10 which comprises the assembled battery 40 is excellent in durability, the assembled battery excellent in durability can be provided.

  The connection of the bipolar batteries 10 constituting the assembled battery 40 may be all connected in parallel, all may be connected in series, or a combination of series connection and parallel connection may be used. Also good.

(Fourth embodiment)
In the fourth embodiment, the bipolar battery 10 of the second embodiment or the assembled battery 40 of the third embodiment is mounted as a motor driving power source to constitute a vehicle. As a vehicle using the bipolar battery 10 or the assembled battery 40 as a motor power source, for example, a complete electric vehicle that does not use gasoline, a hybrid vehicle such as a series hybrid vehicle or a parallel hybrid vehicle, and a fuel cell vehicle, etc., wheels are driven by a motor. A driving car can be mentioned.

  For reference, FIG. 4 shows a schematic diagram of an automobile 50 on which the assembled battery 40 is mounted. The assembled battery 40 mounted on the automobile 50 has the characteristics as described above. For this reason, the automobile 50 equipped with the assembled battery 40 is excellent in durability, and can provide a sufficient output even after being used for a long period of time.

  As described above, some preferred embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications, omissions, and additions can be made by those skilled in the art. .

  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 only to the following examples.

Example 1
<Production of negative electrode>
Graphite (average particle size: 20 μm) (100 parts by mass) as a negative electrode active material, polyethylene oxide (PEO) (800 parts by mass) as an intrinsic polymer electrolyte raw material, LiN (SO ₂ C ₂ ) as a supporting salt (lithium salt) F ₅ ) ₂ (LiBETI) (400 parts by mass), polyvinylidene fluoride (PVdF) as a binder (200 parts by mass), vapor grown carbon fiber (VGCF) (fiber diameter: 150 nm) (200 parts by mass), thermal polymerization 2,2′-azobisisobutyronitrile (AIBN) (4 parts by mass) as an initiator and N-methyl-2-pyrrolidone (NMP) (2000 parts by mass) as a slurry viscosity adjusting solvent are mixed, The slurry was sufficiently stirred to prepare a negative electrode active material slurry.

  The negative electrode active material slurry prepared above was applied onto a nickel foil (thickness: 20 μm) as a negative electrode current collector by a coater, dried, and then vacuum polymerized at 120 ° C. for 5 hours to produce a negative electrode. did. Next, the obtained negative electrode was punched out to 16 mmφ using a punch to obtain a test negative electrode. In addition, it was 75% when the porosity of the active material layer of the obtained negative electrode for a test was measured.

<Production of test cell>
A lithium metal foil (thickness: 500 μm, 16 mmφ) was prepared as a counter electrode for the test negative electrode prepared above.

  Furthermore, the intrinsic polymer electrolyte raw material (PEO) (100 parts by mass), the supporting salt (LiBETI) (50 parts by mass), and the photopolymerization initiator benzyldimethyl ketal (BDK) (0.5 parts by mass) A precursor solution was prepared by adding to and mixing with some NMP (100 parts by mass). This precursor solution was applied onto a suitable substrate, dried, photopolymerized by irradiation with ultraviolet light, and peeled from the substrate to produce an intrinsic polymer electrolyte layer (thickness: 100 μm). Next, the obtained electrolyte layer was punched out to 18 mmφ using a punch to obtain an electrolyte layer.

  The test negative electrode, the electrolyte layer, and the counter electrode obtained above were laminated in this order, and a current extraction terminal was connected to each of the test negative electrode and the counter electrode. Next, the battery element was placed in an aluminum laminate film so that the current extraction terminals were exposed to the outside, and sealed in a vacuum to prepare a test cell.

<Example 2>
A test cell was produced in the same manner as in Example 1 except that the amount of each component in the negative electrode active material slurry was changed to the value shown in Table 1 below. In addition, it was 70% when the porosity of the active material layer of the obtained negative electrode for a test was measured.

<Example 3>
A test cell was produced in the same manner as in Example 1 except that the amount of each component in the negative electrode active material slurry was changed to the value shown in Table 1 below. In addition, it was 65% when the porosity of the active material layer of the obtained negative electrode for a test was measured.

<Example 4>
A test cell was produced in the same manner as in Example 1 except that the amount of each component in the negative electrode active material slurry was changed to the value shown in Table 1 below. In addition, it was 60% when the porosity of the active material layer of the obtained negative electrode for a test was measured.

<Comparative Example 1>
A test cell was produced in the same manner as in Example 1 except that the amount of each component in the negative electrode active material slurry was changed to the value shown in Table 1 below. In addition, it was 50% when the porosity of the active material layer of the obtained negative electrode for a test was measured.

<Comparative example 2>
A test cell was produced in the same manner as in Example 1 except that the amount of each component in the negative electrode active material slurry was changed to the value shown in Table 1 below. In addition, when the porosity of the active material layer of the obtained test negative electrode was measured, it was 40%.

<Evaluation of battery characteristics of test cell>
Using the test cells prepared in each of the above Examples and Comparative Examples, the discharge capacity at the first discharge and the discharge capacity after 30 charging / discharging cycles were measured by the following methods.

In the charge / discharge test of this example, the battery is charged to a voltage of 0.005 V (vs. Li / Li ⁺ ) with a constant current of 0.1 C, and is maintained at that voltage so that the total charge time is 15 h. A series of operations of discharging to a voltage of 3.0 V (vs. Li ^/ Li ⁺ ) at a constant current of 0.1 C and resting for 10 minutes after a pause of 10 minutes was taken as one cycle. Note that “1C” refers to a current value at which the battery is fully charged (100% charged) when charged at that current value for 1 hour. For example, 2C is twice the current value of 1C, and the battery can be fully charged in 30 minutes.

  First, the discharge capacity at the first discharge was measured. The results are shown in Table 2 below.

  Next, a hole was made in the laminate film, and the gas generated at the first charge / discharge was released to the outside of the cell, and then sealed again in vacuum.

  Subsequently, the above charge / discharge cycle was further repeated 29 times, and the discharge capacity at the 30th discharge was measured. The results are shown in Table 2 below.

<Effect caused by increase in porosity of electrode active material layer>
From the comparison between each example and the comparative example, by increasing the porosity of the active material layer of the electrode, specifically by setting it to 60% or more, the gas generated in the battery element at the first charge / discharge is external It can be seen that the battery capacity after charging / discharging cycle is maintained at a high value.

  Therefore, the electrode of the present invention can effectively contribute to the improvement of battery durability.

It is sectional drawing which shows one Embodiment of the electrode for intrinsic polymer batteries of this invention. It is sectional drawing which shows one preferable embodiment of the intrinsic polymer battery of 2nd Embodiment. It is a perspective view which shows the assembled battery of 3rd Embodiment. It is the schematic of the motor vehicle of 4th Embodiment carrying the assembled battery of 3rd Embodiment.

Explanation of symbols

1 Bipolar electrode,
10 Bipolar battery,
11 Current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 solid electrolyte layer,
19 cell layer,
21 battery elements,
25 positive electrode tab,
27 negative electrode tab,
29 Laminate sheet,
31 insulating layer,
40 battery packs,
50 cars.

Claims (9)

An intrinsic polymer battery electrode comprising a current collector and an active material layer containing an active material formed on a surface of the current collector,
An intrinsic polymer battery electrode, wherein the active material layer has a porosity of 60% or more.   The intrinsic polymer battery electrode according to claim 1, wherein the active material layer further includes carbon fibers having a fiber diameter of 500 nm or less.   The intrinsic polymer battery electrode according to claim 2, wherein in the active material layer, a ratio of the content of the carbon fiber to the content of the active material is 0.2 or more. An intrinsic polymer battery having at least one unit cell in which a positive electrode, a solid polymer electrolyte layer, and a negative electrode are laminated in this order,
An intrinsic polymer battery, wherein at least one of the positive electrode and the negative electrode is the electrode according to claim 1.   The intrinsic polymer battery according to claim 4, which is a bipolar lithium ion secondary battery.   An assembled battery using the intrinsic polymer battery according to claim 4 or 5.   A vehicle equipped with at least one of the intrinsic polymer battery according to claim 4 or 5 or the assembled battery according to claim 6. A step of preparing an active material slurry by adding an active material, an ion conductive polymer, and a foaming agent to a solvent;
A step of forming a coating film by applying the active material slurry to the surface of the current collector;
Drying the coating film;
Decomposing the foaming agent contained in the coating film;
The manufacturing method of the electrode for intrinsic polymer batteries which has these.   The manufacturing method of Claim 8 whose heating temperature in the process of decomposing | disassembling the said foaming agent is 100-130 degreeC.

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