JP4352972B2 - Electrode and battery using the same - Google Patents

Description

  The present invention relates to an electrode and a battery using the electrode. In particular, the electrode of the present invention is suitably used for a secondary battery as a power source for driving a motor of a vehicle.

  In recent years, there has been a strong demand for the introduction of electric vehicles (EV), hybrid vehicles (HEV), and fuel cell vehicles (FCV) against the background of the growing environmental protection movement, and the development of power sources for driving these motors has been underway. . As these motor driving power sources, rechargeable secondary batteries are used. Since EV, HEV, and FCV require high output and high energy density, it is virtually impossible to cope with a single large battery. Therefore, it is common to use an assembled battery composed of a plurality of batteries connected in series.

  As a secondary battery, a lithium ion secondary battery has attracted attention. In a lithium ion secondary battery, charge and discharge proceed as lithium ions travel between the positive electrode active material and the negative electrode active material. When microscopically observed, for example, at the time of discharging, the lithium ions diffuse from the electrolyte to the active material disposed on the surface of the current collector, so that discharge in the lithium ion secondary battery proceeds.

  In other words, the diffusion of ions between the active material and the electrolyte plays an important role in charging and discharging in the lithium ion secondary battery, and the ion mobility between the active material and the electrolyte depends on the charge and discharge of the battery. The discharge characteristics are greatly affected.

  Here, as a method for producing an electrode of a lithium ion secondary battery, for example, a slurry obtained by adding an appropriate solvent to a mixture of an active material, a binder, and a conductive auxiliary agent is applied onto a metal foil, A method of drying is known (see, for example, Patent Document 1).

  When a discharge reaction is allowed to proceed using a battery having an electrode produced by the method as described above, there is no particular problem in ion mobility under low output conditions, and the electrode reaction can proceed sufficiently. However, there is a problem that the internal resistance of the battery rapidly increases and the battery capacity decreases under high output conditions (see Non-Patent Documents 1 and 2).

On the other hand, attempts have been made to improve the battery capacity and other characteristics by using a foam metal or metal fiber sintered body as the current collector constituting the electrode and applying the slurry containing the active material thereto. (For example, see Patent Documents 2 to 4). However, each of these electrodes aims to improve electron conductivity by applying or filling an active material into the pores of the current collector, thereby improving battery performance such as charge / discharge performance. It is not intended to improve ion mobility, which is a rate-determining step during charge and discharge.
JP-A-7-220722 JP-A-8-170126 Japanese Patent Laid-Open No. 9-213307 Japanese Patent No. 3387724 Osawa et al., 41st Battery Discussion Meeting, 3C15, p358 (2000) Nagayama et al., 44th Battery Discussion Meeting, 3C22, p418 (2003)

  Accordingly, an object of the present invention is to provide means for suppressing an increase in internal resistance around an electrode and exhibiting sufficient charge / discharge characteristics even under high output conditions.

The electrode of the present invention includes a porous current collector that holds an electrolyte, and an active material layer that includes the active material and is formed on the current collector. The porous current collector includes a coarse pore current collector and fine pore current collectors located on both sides of the coarse pore current collector. Furthermore, the porosity of the coarse pore current collector is larger than the porosity of the fine pore current collector.

  In a battery using the electrode of the present invention, an electrolyte is held in a current collector. For this reason, an increase in internal resistance is suppressed even under high output conditions. As a result, sufficient charge / discharge characteristics can be exhibited even under high output conditions.

  A first aspect of the present invention is an electrode having a current collector holding an electrolyte and an active material layer containing an active material formed on the current collector.

  The configuration and effect of the electrode of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing a laminated state of an electrode and an electrolyte layer inside a battery using the electrode of the present invention. Here, a lithium ion battery will be described as an example, but the present invention is not necessarily limited thereto, and the present invention can be applied to a general secondary battery.

  In the electrodes (positive electrode 1 and negative electrode 2) of the present invention shown in FIG. 1, an active material layer 4 containing an active material is formed on a current collector 3. In the battery, the electrodes (positive electrode 1 and negative electrode 2) of the present invention are laminated via an electrolyte layer 5 as shown in FIG. In the active material layer 4 (the positive electrode active material layer 4a and the negative electrode active material layer 4b), a battery reaction, that is, a cathode reaction or an anode reaction proceeds. Electrons generated by the battery reaction in the active material layer 4 are collected through the current collector 3 and perform electrical work on an external load.

  Note that FIG. 1 is exaggerated for convenience of explanation, and the ratio of the current collector 3 and the thickness of the active material layer 4 and the number of stacked positive electrodes 1 and 2 are different from actual ones. In some cases. The same applies to the following drawings.

  The electrodes (positive electrode 1 and negative electrode 2) of the present invention are characterized in that the current collector 3 holds an electrolyte. Thereby, the mobility of ions can be improved.

  In conventional electrodes, generally, a metal foil or the like in which an active material layer is formed on both surfaces is used as a current collector. This metal foil is smooth or roughened for the purpose of improving adhesion, but it does not hold the electrolyte inside. For this reason, when a battery having a conventional electrode is discharged under high output conditions, there is a problem that the internal resistance of the battery rapidly increases and the battery capacity decreases. This is presumably due to the following mechanism. It should be noted that the following explanation is just an estimation, and even if problems such as an increase in internal resistance and a decrease in battery capacity are caused by a mechanism different from the following estimation, there is no influence on the technical scope of the present invention. It does not affect. Moreover, in the following description, the case where an electrolyte is also contained in the active material layer of the electrode will be described as an example.

  In the positive electrode, the lithium ions in the electrolyte contained in the active material layer are first absorbed into the active material by high-rate discharge, and contribute to the battery reaction. In order to maintain the reaction in the positive electrode active material after this reaction has progressed and the lithium ion concentration in the electrolyte contained in the active material layer has decreased, lithium ions are migrated from the electrolyte layer adjacent to the active material layer. Need to be replenished.

On the other hand, an anion (for example, PF ₆ ⁻ ) which is a counter ion of lithium ion moves toward the negative electrode due to discharge. Since the transport number of lithium ions very low usually about 0.2, the current during discharge, most part PF ₆ ^- are carried by anions such. Further, if the vicinity of the electrode is observed microscopically, it needs to be electrically neutral. Therefore, large PF ₆ of transport number ^- anions and the like in association with diffusing into negative direction, also lithium ion moves to the negative electrode direction, a phenomenon that lithium ions are depleted occurs in the vicinity of the active material of positive electrode. As a result, it is presumed that the discharge reaction does not proceed in the positive electrode, the internal resistance increases, and the problem of a decrease in battery capacity occurs. This problem becomes prominent when the current collector becomes thick in the conventional electrode.

In the negative electrode during high-rate discharge, anions such as PF ₆ ⁻ that have diffused as the discharge progresses are saturated around the active material. As a result, it is presumed that the discharge reaction does not proceed as in the positive electrode, the internal resistance increases, and the battery capacity decreases.

  On the other hand, according to the electrode of the present invention, the above-described problems can be solved, and deterioration of charge / discharge characteristics under high output conditions can be prevented.

  That is, in the electrode of the present invention, the current collector holds the electrolyte. For this reason, in the positive electrode to which the electrode of the present invention is applied, even when the lithium ion concentration around the active material is lowered, lithium ions are supplied from the electrolyte held in the current collector. As a result, the depletion of lithium ions is prevented, and the increase in internal resistance and the accompanying decrease in battery capacity are suppressed.

  In addition, in the negative electrode to which the electrode of the present invention is applied, even if anions are concentrated around the active material by electrophoresis, some of the anions move into the electrolyte held by the current collector. sell. As a result, the saturation state of the anion around the active material of the negative electrode is relaxed, and the increase in internal resistance and the accompanying decrease in battery capacity can be suppressed.

  Therefore, the electrode of the present invention can be applied to both the positive electrode and the negative electrode. Although the mechanism is different between when applied to the positive electrode and when applied to the negative electrode, the charge / discharge characteristics of the battery can be improved regardless of which mechanism is applied.

  Next, the current collector and the active material layer constituting the electrode of the present invention will be described in detail.

  First, the current collector will be described. The current collector is formed of a conductive material and mediates the movement of electrons between the active material layer and an external load.

  In the electrode of the present invention, the current collector holds an electrolyte. By holding the electrolyte, as described above, depletion of lithium ions at the positive electrode and saturation of anions at the negative electrode can be suppressed. As a result, the charge / discharge characteristics of the battery can be improved.

  Examples of the form in which the electrolyte is held include a form in which a porous current collector is used as a current collector and the electrolyte is filled with pores of the porous current collector. Hereinafter, although such a form is mentioned as an example and it demonstrates in detail, the technical scope of this invention is not restrict | limited only to this form. For example, a current collector having a shape in which a large number of small openings are provided on the surface of a hollow box-shaped metal capable of holding an electrolyte solution, or a current collector in which a gel electrolyte is wrapped with a metal mesh It can also be employed.

  “Porous current collector” refers to a current collector having a large number of pores. Specific forms such as the size and shape of the pores of the porous current collector and the ratio of the volume of the pores to the apparent volume of the porous current collector (porosity) are not particularly limited, and are adjusted as appropriate. Can be done. The porous current collector may have pores uniformly throughout, or may have pores of different sizes throughout. The porous current collector may have pores only near the surface and may not have pores inside. In addition, as a porous electrical power collector, a commercially available thing may be used and what was produced itself may be used.

  The average diameter of the pores of the porous current collector is preferably smaller than the average particle diameter of the active material contained in the active material layer described later. If the average diameter of the pores is greater than or equal to the average particle diameter of the active material, the active material may be filled in the pores of the porous current collector, and the electrolyte may not be sufficiently retained. On the other hand, if the vacancies are too small, the ion flow rate may be lowered, and the production becomes difficult. Considering these points, the average diameter of the pores is preferably 0.05 to 20 μm, more preferably 0.1 to 10 μm. Moreover, the porosity of the porous current collector is preferably 10 to 90%, more preferably 20 to 80%. Note that the average diameter and porosity of the pores of the porous current collector can be measured by a conventionally known method such as observation with an electron microscope.

  The porous current collector may be an etching foil whose surface is etched by various methods. The etching foil generally has a large number of pores inside the foil while leaving the surface layer of the foil, and such pores are particularly suitable as a means for holding the electrolyte in the present invention. . It is usually difficult to obtain such holes by physical drilling or sandblasting. However, when a current collector having a large number of fine holes as in the etching foil is obtained by means such as physical perforation or sandblasting, the current collector obtained using such means is It may be adopted. For reference, a photograph of a cross section of the electrode of the present invention produced using an etching foil taken with an electron microscope is shown in FIG. FIG. 2 is a photograph of a cross section of an electrode produced in an example described later. In the photograph of FIG. 2, the etching foil 6, which is the material of the current collector 3, has an unetched core portion 7 and a hole portion 8 having holes formed by etching located on both sides of the core portion 7. And have. An active material layer 4 is formed on the surface of the etching foil 6. In the photograph shown in FIG. 2, the active material layer 4 is formed only on one surface of the etching foil 6. Of course, the active material layer 4 may be formed on both surfaces of the etching foil 6. Good.

  When the etching foil 6 is used as the current collector 3 constituting the electrode of the present invention, as shown in FIG. 2, the etching foil 6 may have a core portion 7 or may not have the core portion 7. You may consist only of the void | hole part 8 etched completely. From the viewpoint of improving the strength of the foil and facilitating the production of the electrode and the battery, the etching foil 6 preferably has the core portion 7, but is not limited thereto. The thickness of the core 7 is not particularly limited, but is usually about 5 to 20 μm.

  The current collector may be composed of only one layer as shown in FIG. 1 or may be composed of two or more layers. Examples of the form of the electrode having a current collector composed of two or more layers include the form shown in FIG. In the form shown in FIG. 3, the current collector 3 includes a current collector 3 a having a relatively coarse hole (hereinafter abbreviated as “coarse hole current collector”) positioned in the center, and the coarse sky. A current collector 3b having relatively fine holes located on both sides of the hole current collector 3a (hereinafter abbreviated as "fine hole current collector"), and both of the fine hole current collectors. An active material layer 4 is formed on the surface of 3b facing the coarse hole current collector 3a. That is, the electrode is configured by laminating the active material layer 4 / the fine hole current collector 3b / the coarse hole current collector 3a / the fine hole current collector 3b / the active material layer 4 in this order. In the electrode having such a current collector 3, the presence of the fine hole current collector 3 b can prevent the holes from being blocked by the active material contained in the active material layer 4. On the other hand, the presence of the coarse pore current collector 3 a allows the electrolyte to be sufficiently held in the current collector 3. As a result, more excellent effects of the present invention can be exhibited.

  In the above embodiment, the specific diameter of the coarse hole current collector 3a and the fine hole current collector 3b constituting the current collector 3 is such that the average diameter of the holes of the coarse hole current collector 3a is There is no particular limitation except that it is larger than the average diameter of the holes of the fine hole current collector 3b. Preferred forms such as the porous current collector and the etching foil described above can be similarly employed. In addition, when the form shown in FIG. 3 is adopted, the average diameter of the pores of the coarse pore current collector 3a is preferably 10 to 500 μm, and more preferably 20 to 200 μm. If the average pore diameter of the coarse pore current collector 3a is too small, there is a possibility that the merit obtained by providing the coarse pore current collector 3a cannot be sufficiently obtained. On the other hand, if the average diameter of the pores of the coarse pore current collector 3a is too large, the strength of the current collector may be reduced, which may cause damage during manufacture or use.

  In addition to the above-described materials, the coarse pore current collector 3a may be a through-etched foil having a through-hole penetrating from one surface of the foil to the other surface, a metal mesh, a punching metal, or an expanded metal. Etc. can be used. These materials have relatively large pores, and can sufficiently retain the electrolyte in the pores.

  The conductive material constituting the current collector is not particularly limited, but the positive electrode of the battery is required to have oxidation resistance against a high potential. For this reason, when the electrode of this invention is used as a positive electrode, it is preferable that a collector is comprised with the valve metal which forms an oxide film in a metal surface. Specific examples of the valve metal include aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, and the like, or a stainless alloy. These may be used alone or in combination of two or more. Moreover, you may use together with the simple substance or alloy of another metal. When the electrode of the present invention is used as a positive electrode, the current collector is particularly preferably composed of aluminum.

  On the other hand, in the negative electrode of the battery, it is required that the current collector does not form an alloy with lithium at the potential at which the battery reaction proceeds. For this reason, when the electrode of this invention is used as a negative electrode, it is preferable that a collector is comprised with copper, nickel, titanium, stainless steel, etc. These may be used alone or in combination of two or more. When the electrode of the present invention is used as a negative electrode, the current collector is particularly preferably composed of copper or nickel.

  The thickness of the current collector (the total thickness of all layers when the current collector comprises two or more layers) is not particularly limited, but is preferably 5 to 200 μm, more preferably 10 to 50 μm. If the current collector is too thin, the electrolyte may not be sufficiently retained, and it may not be able to withstand the stress when the active material layer is formed on the surface of the current collector, which may cause cutting or cracking. On the other hand, if the current collector is too thick, the manufacturing cost increases and the battery may be enlarged. Further, when a porous current collector is used, if the current collector is too thick, the current collector becomes brittle and may be difficult to handle. However, a current collector having a thickness outside the above range may be used.

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

  The electrolyte filled in the porous current collector is not particularly limited. Conventionally, an electrolyte similar to the electrolyte included in the electrolyte layer of the secondary battery can be used. The electrolyte is preferably a non-aqueous electrolyte. The non-aqueous electrolyte contains an electrolyte salt such as a lithium salt. Nonaqueous electrolytes are classified into liquid electrolytes, gel polymer electrolytes, and all solid polymer electrolytes depending on the presence or absence of a nonaqueous solvent (plasticizer) or a polymer for electrolyte (host polymer).

  Content of the said various components in electrolyte is not restrict | limited in particular, According to desired battery performance etc., it can adjust suitably. The electrode of the present invention can be applied to only the positive electrode, to the negative electrode only, and to the two electrodes. The application to the positive electrode can improve the performance during charging. When it is desired, it is effective to lower the electrolyte salt concentration than usual to suppress the increase in the salt concentration during charging. Further, when it is desired to improve the performance at the time of discharge by application to the positive electrode side, it is effective to increase the concentration of the electrolyte salt more than usual to suppress the decrease in the salt concentration at the time of discharge. When applied to the negative electrode, the direction of ion movement is reversed, and therefore, it is preferable to adjust the salt concentration, contrary to the description of the application to the positive electrode. However, this is merely an example, and the salt concentration can be appropriately determined in consideration of the balance between the charging and discharging performance. This is the same when the electrode of the present invention is applied to both the positive electrode and the negative electrode.

  Next, the active material layer will be described. The active material layer is formed on the current collector and includes an active material. The specific form of the active material layer is not particularly limited as long as the battery reaction can proceed. The form employed in the conventional active material layer can be used similarly. Specifically, the active material layer may include a conductive additive, a binder, an electrolyte salt, a solvent, and the like in addition to the active material. In order to improve the ionic conductivity in the active material layer, a polymer electrolyte may be included. There is no limitation in particular about the compounding quantity of each of these components. Based on the knowledge already obtained, the blending amount of each component may be determined. In the electrode of the present invention, the active material layer may be formed only on one side of the current collector, or may be formed on both sides. Moreover, when an active material layer is formed on both surfaces of one current collector, both active material layers may be the same electrode (positive electrodes or negative electrodes), or different electrodes (positive electrode and negative electrode). There may be. For example, as described later, when employed in a general lithium ion battery, the electrode of the present invention is an electrode in which active material layers having the same electrode are formed on both surfaces of a current collector. On the other hand, when employed in a bipolar battery, the electrode of the present invention is an electrode (bipolar electrode) in which active material layers having different electrodes are formed on both surfaces of a current collector.

  The thickness of the active material layer is not particularly limited. Here, if the active material layer is too thin, the battery capacity may be insufficient. On the other hand, if the active material layer is too thick, the ionic conductivity in the active material layer may be lowered, and the charge / discharge characteristics under high output conditions may be insufficient. However, according to the electrode of the present invention, since the current collector holds the electrolyte, even when the active material layer is relatively thick, the charge / discharge characteristics accompanying the decrease in ion conductivity in the active material layer Can be suppressed. From such a viewpoint, the thickness of the active material layer is preferably 1 to 100 μm, more preferably 5 to 50 μm.

  Other members are disposed on the electrode as necessary. For example, when a battery is manufactured by enclosing an electrode in a battery outer package, a tab that is drawn out of the battery is disposed for the purpose of extracting electric power to the outside of the battery outer layer body. In addition, various improvements may be made to the electrode.

  Then, the manufacturing method of the electrode of this invention is demonstrated.

  The electrode of the present invention can be produced, for example, by holding an electrolyte in a current collector and applying a slurry containing an active material to the surface of the current collector.

  Hereinafter, a case where a porous current collector is used as the current collector will be described as an example, and a preferable embodiment of the above manufacturing method will be described. However, the technical scope of the present invention is not limited to the following embodiment.

  First, a porous current collector is prepared. As a preferable form of the porous current collector, the same form as described above is used, and thus the description thereof is omitted here.

  As described above, the porous current collector may be a commercially available one. However, when the porous current collector is manufactured by itself, it may be manufactured by using an etching method. In the following, a preferred mode for producing a porous current collector by an etching method will be described.

  As the etching method, for example, an AC etching method is used. In the AC etching method, an electrolytic bath provided with opposing electrodes to which an AC current can be applied is filled with an etching electrolytic solution such as a hydrochloric acid solution, and a foil made of a desired conductive material is filled in this solution. In this method, the foil is etched by dipping and applying an alternating current. According to the AC etching method, holes are evenly formed on both sides of the foil in the thickness direction of the foil. For this reason, the AC etching method can be suitably used in the production of the electrode of the present invention. When the porous current collector constituting the electrode of the present invention is produced by an etching method, the foil made of a conductive material described in the section of the preferred form of the current collector can be used.

There are no particular restrictions on the etching conditions when the porous current collector is produced by the alternating current etching method. Known knowledge about the conventional AC etching method can be referred to as appropriate. For example, the etching electrolyte preferably contains about 1 to 10% by mass of hydrochloric acid. The temperature of the electrolytic solution for etching is preferably about 15 to 80 ° C. The current density of the current applied during etching is preferably about 50 to 5000 A / m ² , and the etching time is preferably about 1 to 60 minutes. These conditions are merely examples, and conditions out of these ranges may be employed. Further, the etching method is not limited to the AC etching method, and other etching methods such as a DC etching method and a chemical etching method may be used.

  As shown in FIG. 3, when the current collector 3 is composed of two or more layers, the layers, for example, between the coarse hole current collector 3a and the fine hole current collector 3b are simply stacked. Therefore, it may not be further fixed by other means. Moreover, as long as the effect of this invention is not inhibited, the other means for fixing between each layer may be employ | adopted.

  Subsequently, an electrolyte for holding the porous current collector prepared above is prepared.

  The specific form of the electrolyte held by the porous current collector is not particularly limited. As described above, the electrolyte is preferably a non-aqueous electrolyte such as a liquid electrolyte, a gel polymer electrolyte, and an all solid polymer electrolyte.

In general, the liquid electrolyte includes a non-aqueous solvent and an electrolyte salt. Examples of the non-aqueous solvent include cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC); chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC); Lactones such as butyrolactone; nitriles such as acetonitrile; esters such as methyl acetate, methyl formate, methyl propionate, ethyl propionate; tetrahydrofuran, 2-methyltetrahydrofuran 1,4-dioxane, 1,2-dimethoxyethane, And aprotic organic solvents such as ethers such as 1,2-diethoxyethane; amides such as dimethylformamide; and mixtures thereof. Moreover, as said electrolyte salt, an alkali salt is preferable and lithium salt is especially preferable. Examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiClO ₄ , LiBETI (Li (C ₂ F ₅ SO ₂ ) ₂ N), LiN (SO ₂ CF ₃ ), Li (SO ₂ C ₂ F ₅ ). , LiBOB (lithium bisoxide borate) and the like.

  The gel polymer electrolyte includes a polymer for electrolyte (host polymer), a non-aqueous solvent (plasticizer), and an electrolyte salt. Examples of the electrolyte polymer (host polymer) include ion conductive polymers such as polyethylene oxide (PEO) and polypropylene oxide (PPO); polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), and polyacrylonitrile (PAN). And polymers having no ion conductivity such as polymethyl methacrylate (PMMA); and copolymers thereof. Preferred forms of the non-aqueous solvent (plasticizer) and the electrolyte salt are the same as in the case of the liquid electrolyte.

  The all solid polymer electrolyte does not include a non-aqueous solvent as a plasticizer, but includes an electrolyte polymer (host polymer) and an electrolyte salt. Preferred forms of the electrolyte polymer (host polymer) and the electrolyte salt are the same as in the case of the gel polymer electrolyte. At this time, a physical cross-linked gel in which the polymer is cross-linked by physical bonds such as van der Waals force may be used.

  In the electrolyte retained in the current collector of the present invention, the ratio of the content of each of the above components is not particularly limited, and depends on the intended use and desired battery characteristics based on the knowledge already obtained. Can be appropriately determined.

  The specific method of filling the electrolyte into the porous current collector is not particularly limited, and is appropriately determined according to the amount and size of the pores of the porous current collector, the type and amount of the electrolyte to be filled, and the like. Can be selected.

  When a liquid electrolyte is used as the electrolyte, for example, the electrolyte can be filled into the porous current collector by dropping the liquid electrolyte onto the surface of the porous current collector prepared above. When the electrode of the present invention is used in a battery that employs a liquid electrolyte in the electrolyte layer, the liquid electrolyte is placed in the pores of the porous current collector when the electrolyte layer is sandwiched by the electrode of the present invention. The porous current collector may be filled with a liquid electrolyte by permeation.

  When a gel polymer electrolyte is used as the electrolyte, first, a monomer (electrolyte polymer raw material) that becomes an electrolyte polymer by polymerization and a polymerization initiator in a non-aqueous solvent (plasticizer) containing an electrolyte salt. To prepare a pregel solution. Here, the polymerization initiator is added in order to act on the crosslinkable group of the polymer raw material for electrolyte and advance the crosslinking reaction. The polymerization initiator is classified into a photopolymerization initiator, a thermal polymerization initiator, and the like according to an external factor for causing it to act as an initiator. Examples of the polymerization initiator include azobisisobutyronitrile (AIBN) and benzyldimethyl ketal (BDK).

  Next, the porous current collector prepared above is filled with this pregel solution, and the polymer material for electrolyte is polymerized by an appropriate external factor to obtain a polymer for electrolyte. As a result, a porous current collector filled with the gel polymer electrolyte is obtained.

  Further, when an all solid polymer electrolyte is used as the electrolyte, for example, the physical cross-linking gel described above is melted by heating, the melted physical cross-linking gel is filled in the porous current collector, and then cooled. As a result, a porous current collector filled with the all solid polymer electrolyte is obtained.

  On the other hand, a slurry containing an active material for forming an active material layer (hereinafter also referred to as “active material slurry”) is prepared.

  The active material slurry is prepared by adding at least the active material into a suitable slurry viscosity adjusting solvent. Further, if necessary, the active material slurry may contain other components such as a binder, a conductive additive, and a lithium salt (supporting electrolyte). In order to improve ion conductivity in the active material layer, a polymer electrolyte raw material that becomes a polymer electrolyte by polymerization and a polymerization initiator may be contained in the active material slurry.

The active material is not particularly limited in the present application. Examples of the positive electrode active material include Li—Mn complex oxides such as LiMn ₂ O ₄ and Li—Ni complex oxides such as LiNiO ₂ . In some cases, two or more positive electrode active materials may be used in combination. Examples of the negative electrode active material include a crystalline carbon material and an amorphous carbon material. Specific examples include natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon. In some cases, two or more negative electrode active materials may be used in combination.

  Examples of the binder include polyvinylidene fluoride (PVdF).

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

Examples of the lithium salt (supporting electrolyte) include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , and LiN (SO ₂ C ₂ F ₅ ) ₂ .

  The polymer electrolyte raw material is not particularly limited as long as it is a compound that can become a polymer electrolyte by polymerization after slurry application. Moreover, about a polymerization initiator, since the form similar to having demonstrated in the column of description of the preferable form of said electrolyte can be employ | adopted, description is abbreviate | omitted here.

  The compounding ratio of the components contained in the active material slurry is not particularly limited. The content of the active material in the active material slurry is not particularly limited, but is usually about 30 to 70% by mass.

  In addition, when preparing the said active material slurry, the order of addition of each component in particular is not restrict | limited. For example, after preparing a mixture of all components other than the solvent contained in the slurry, a solvent may be added to the mixture and mixed to prepare an active material slurry. Also, after preparing a mixture of several components other than the solvent contained in the slurry, add a solvent to the mixture, mix, and then add the remaining components and mix to prepare an active material slurry May be. At this time, the apparatus used for adding or mixing each component is not particularly limited, and examples thereof include a homomixer.

  Next, the active material slurry prepared above is applied to the surface of the porous current collector that is also prepared as described above and filled with the electrolyte. As a specific form at the time of application, a conventionally known method and apparatus can be appropriately employed. Thereafter, the porous current collector coated with the active material slurry is dried to remove the solvent contained in the slurry. For drying, for example, a vacuum dryer can be used. Moreover, since drying conditions change according to the various properties of the slurry, they cannot be uniquely determined, but are usually about 1 minute to 2 hours at 50 to 180 ° C.

  Here, in the case where the polymer electrolyte raw material contained in the active material layer and a polymerization initiator for polymerizing the polymer electrolyte raw material are contained in the active material layer, after the application of the active material slurry, the polymer is obtained by various methods. The electrode is completed by polymerizing (crosslinking) the electrolyte raw material. The polymerization (crosslinking) method at this time is not particularly limited, and can be appropriately selected according to the kind of the polymerization initiator contained in the active material layer. In some cases, in this polymerization step, the polymer electrolyte raw material filled in the porous current collector may be polymerized.

  As mentioned above, the case where a porous current collector is used as a current collector has been described as an example, and a preferred embodiment of the method for producing an electrode of the present invention has been described. Not limited to. For example, as shown in FIG. 3, when the current collector 3 is laminated with the fine hole current collector 3b / the coarse hole current collector 3a / the fine hole current collector 3b, the electrode of the present invention is used. Can be manufactured in the form shown in FIG. Hereinafter, although this form is demonstrated in detail, it is not restrict | limited only to this form.

  First, a fine hole current collector 3b is prepared. The active material slurry is applied to one surface of the fine hole current collector 3b in the same manner as described above, and dried to form the active material layer 4. Similarly, the active material layer 4 is formed on the other fine hole current collector 3b. Next, a coarse hole current collector 3a is prepared. A porous current collector of the form shown in FIG. 3 can be produced by sandwiching the coarse hole current collector 3a between two fine hole current collectors 3b.

  Moreover, if necessary, you may perform press operation to the electrode manufactured by said method. By performing this pressing operation, the surface of the obtained electrode can be further flattened, the thickness can be adjusted, or when the current collector is composed of two or more layers, peeling between the layers can be prevented. It becomes possible. The apparatus and conditions used for the press operation are not particularly limited, and conventionally known apparatuses and methods can be appropriately used.

  In an industrial production process, in order to improve productivity, an electrode larger than the final battery size may be produced and cut into a predetermined size.

  A second aspect of the present invention is a battery in which a positive electrode, an electrolyte layer, and a negative electrode are laminated in this order, and at least one of the positive electrode and the negative electrode is the electrode described above. The electrode of the present invention may be a positive electrode or a negative electrode. The electrode of this invention should just be employ | adopted for at least one of the positive electrode and the negative electrode. Preferably, both the positive electrode and the negative electrode are the electrodes of the present invention.

  When the battery element is accommodated inside the exterior material, the battery element is accommodated in such a manner that the tab is pulled out of the exterior material. And in order to ensure internal sealing performance, the exterior material of the site | part in which the battery element is not accommodated is sealed. As the exterior material, a polymer metal composite film can be used. The polymer metal composite film is a film in which at least a metal thin film and a resin film are laminated. With such an exterior material, a thin laminated battery can be formed.

  In a general battery, a positive electrode, an electrolyte layer, and a negative electrode are arranged in this order, and these are sealed in an exterior material. The form of the electrolyte contained in the electrolyte layer is not particularly limited, and a conventionally known form can be adopted. The electrolyte may be a liquid electrolyte, a gel polymer electrolyte, or an all solid polymer electrolyte. Specifically, an electrolyte that can be retained in the electrode of the present invention can be used as well. The electrolyte contained in the electrolyte layer and the electrolyte held by the electrode may be different, but are preferably the same. In addition, the number of stacked positive electrodes, electrolyte layers, and negative electrodes stacked in the battery is not particularly limited, and can be appropriately determined according to a desired battery voltage.

  The battery of the present invention is preferably a lithium ion secondary battery. More preferably, it is a bipolar lithium ion secondary battery (bipolar battery). For reference, FIG. 5 shows a schematic sectional view of a non-bipolar lithium ion secondary battery (general lithium ion battery) 10, and FIG. 6 shows a schematic sectional view of a bipolar lithium ion secondary battery (bipolar battery) 20. The figure is shown. As can be seen from FIGS. 5 and 6, the general lithium ion battery 10 and the bipolar battery 20 differ only in the arrangement of the electrodes. Generally, a general lithium ion battery is a high-energy battery having a large battery capacity, and is excellent in performance of supplying power for a long period of time. On the other hand, a bipolar battery is a battery with a high output density and is excellent in performance of supplying a large amount of power in a short time. Therefore, which form is adopted can be appropriately determined according to the form of required power. The technical scope of the present invention is not limited to the contents of these drawings.

  A plurality of the batteries of the present invention, or at least one battery of the present invention and another type of battery are connected in parallel connection, series connection, parallel-series connection, or series-parallel connection to form a battery module. Also good. That is, the 3rd of this invention is a battery module containing the battery of this invention. Thereby, it becomes possible to respond to the demand for the battery capacity and output for each purpose of use relatively inexpensively without producing a new battery. The specific form at the time of manufacturing a battery module is not specifically limited, The well-known knowledge currently used about a battery module can be employ | adopted. Furthermore, a plurality of battery modules of the present invention may be connected to form a composite battery module.

  The battery and battery module of the present invention can be preferably used in a vehicle as a driving power source or an auxiliary power source. That is, the 4th of this invention is a vehicle carrying the battery of this invention or the battery module of this invention.

  The vehicle on which the battery or the assembled battery of the present invention can be mounted is not particularly limited, but an electric vehicle, a fuel cell vehicle and a hybrid electric vehicle thereof are preferable.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the following embodiment only illustrates one embodiment, and the technical scope of the present invention is not limited to the following form.

<Example>
A coin-type battery 40 shown in FIG. 7 was produced by the following procedure.

In 40 ° C. electrolytic solution containing 10% by mass hydrochloric acid, 0.1% by mass sulfuric acid and 2% by mass aluminum chloride in aluminum foil (purity: 99.9% by mass, thickness: 50 μm), An etching foil as a porous current collector was produced by applying a current having a current density of 50 A / m ^{2 at} an alternating current of 50 Hz for 1 minute.

  Moreover, lithium manganate (average particle size: 5 μm) as a positive electrode active material, acetylene black as a conductive additive, and polyvinylidene fluoride as a binder are mixed at a mass ratio of 90: 5: 5 to adjust slurry viscosity. An appropriate amount of N-methyl-2-pyrrolidone as a solvent was added to prepare a positive electrode active material slurry.

  The positive electrode active material slurry prepared above was applied to the porous current collector (etching foil) similarly produced above and dried at 150 ° C. for 10 minutes to form an active material layer having a thickness of 30 μm. For use in the coin-type battery 40, the obtained electrode was punched out at 15 mmφ to produce the positive electrode 41 of the present invention. The photograph which image | photographed the cross section of the obtained positive electrode of this invention with the electron microscope is shown in FIG. In addition, in the obtained electrode, the average diameter of the void | hole which the etching foil which is a collector has had was measured by observing using an electron microscope. As a result, the average diameter of the pores in the etching foil was 0.8 μm.

  On the other hand, as the negative electrode 42, a lithium metal foil (thickness: 100 μm) was fitted into a stainless steel battery lid 43 and pressed.

The positive electrode 41 produced above was placed in a stainless steel outer can 44, and a separator 45 of a polypropylene microporous film (thickness: 20 μm) was placed thereon. The separator 45 was defoamed by injecting an electrolyte of 1M LiPF ₆ / EC + DEC (1: 1 (volume ratio)) and evacuating it once. Thereafter, the battery lid 43 was placed and sealed by filling a sealant 46 made of a mixture of styrene butadiene rubber and pitch without any gaps, thereby producing a coin-type battery 40 shown in FIG. The battery has a diameter of 25 mm and a height of 2 mm.

<Comparative Example 1>
A coin-type battery was produced in the same manner as in Example 1 except that an aluminum foil (purity: 99.9 mass%, thickness: 50 μm) was used instead of the etching foil as the porous current collector. did.

<Evaluation of battery capacity>
The coin-type batteries of Example 1 and Comparative Example 1 produced above were charged and discharged with currents of 0.1 mA, 1 mA, 5 mA, 10 mA, 50 mA, and 100 mA, respectively, and the battery capacity was measured. The results are shown in Table 1 below.

  As can be seen from Table 1, as the current value during charging / discharging increases, the battery employing the electrode of the present invention as the positive electrode suppresses the decrease in battery capacity compared to the comparative example, and at a current value of 100 mA. It shows about twice the battery capacity. This shows that the electrode of the present invention and the battery using the same can suppress a decrease in battery characteristics such as battery capacity even under high output conditions.

It is a schematic cross section which shows the lamination | stacking state of the electrode and electrolyte layer in the inside of the battery which uses the electrode of this invention. It is the photograph which image | photographed the cross section of the positive electrode of this invention obtained in the Example with the electron microscope. It is a schematic cross section which shows one preferable form of the electrode of this invention. It is a schematic cross section which shows one preferable form at the time of manufacturing the electrode of the form shown in FIG. It is a schematic cross section of a lithium ion secondary battery (general lithium ion battery) that is not bipolar. It is a schematic cross section of a bipolar type lithium ion secondary battery. It is a schematic cross section of the coin type battery produced in the Example and the comparative example.

Explanation of symbols

1 positive electrode,
2 negative electrode,
3 Current collector,
3a Coarse pore current collector,
3b Fine hole current collector,
4 active material layer,
4a positive electrode active material layer,
4b negative electrode active material layer,
5 electrolyte layer,
6 Etching foil,
7 core,
8 hole part,
10 General lithium ion battery,
13 positive electrode,
15 negative electrode,
17 electrolyte layer,
21 positive electrode current collector,
23 negative electrode current collector,
25 positive electrode tab,
29 negative electrode tab,
30 bipolar battery,
31 current collector,
33 single battery (cell),
35 insulation layer,
37 laminate (battery element),
40 coin cell battery,
41 positive electrode,
42 negative electrode,
43 Battery cover,
44 exterior cans,
45 separator,
46 Sealant.

Claims (13)

A porous current collector holding an electrolyte;
An active material layer containing an active material formed on the current collector;
A that electrodes having a,
The porous current collector has a coarse pore current collector, and a fine pore current collector located on both surfaces of the coarse pore current collector,
An electrode, wherein the porosity of the coarse pore current collector is larger than the porosity of the fine pore current collector. 2. The electrode according to claim 1, wherein an average diameter of pores of the coarse pore current collector is larger than an average diameter of pores of the fine pore current collector. The electrode according to claim 1 or 2, wherein an average diameter of pores of the fine-hole current collector is equal to or less than an average diameter of the active material. The electrode according to any one of claims 1 to 3, wherein an average diameter of pores of the porous current collector is 0.05 to 20 µm. The electrode according to any one of claims 1 to 4, wherein the porous current collector is an etching foil. The porous current collector is etched through the foil, metal mesh, punching metal, and one or more members selected from the group consisting of expanded metal, according to any one of claims 1-4 electrode. The material which comprises the said porous electrical power collector is aluminum, The electrode of any one of Claims 1-6 used as a positive electrode. The material which comprises the said porous electrical power collector is copper or nickel, The electrode of any one of Claims 1-6 used as a negative electrode. The battery using the electrode of any one of Claims 1-8.   The battery according to claim 9, which is a lithium ion secondary battery.   The battery according to claim 10, which is a bipolar battery.   The battery module containing the battery of any one of Claims 9-11.   A vehicle on which the battery according to any one of claims 9 to 11 or the battery module according to claim 12 is mounted.