JP5326450B2 - Electrode and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrode, and more particularly to an electrode that can increase the output of a battery by reducing the contact resistance between a current collector and an active material layer.

  In recent years, reduction of carbon dioxide emissions has been strongly desired for environmental protection. In the automobile industry, there are high expectations for reducing carbon dioxide emissions by introducing electric vehicles (EVs) and hybrid electric vehicles (HEVs), and we are eager to develop secondary batteries for motor drives that hold the key to their practical application. Has been done. As a secondary battery, attention is focused on a lithium ion secondary battery that can achieve a high energy density and a high output density.

  In general, a lithium ion secondary battery is configured by applying a positive electrode or a negative electrode active material or the like to a current collector using a binder.

In such a lithium ion secondary battery, conventionally, a metal foil has been used as a current collector. In recent years, conductive current collectors containing a resin have been used instead of metal foil (see, for example, Patent Document 1).
JP-A-63-43257

  However, when an active material layer is formed on a conductive current collector containing the resin by a conventional method, contact resistance between the conductive current collector containing the resin and the active material layer becomes a problem.

  Accordingly, an object of the present invention is to reduce the contact resistance between the current collector and the active material layer and improve the output of the battery.

  In view of the above problems, the present inventors have conducted intensive research, and as a result, an electrode in a form in which a part of the active material contained in the active material layer is taken into the resin layer by the conductive resin layer is the above problem. The present invention has been completed.

  In the electrode of the present invention, the adhesion between the current collector and the active material is improved, and the contact resistance between the resin layer and the active material layer can be reduced. In particular, when applied to an electrode for a bipolar battery, an excellent effect is exhibited.

  First, a bipolar lithium ion secondary battery electrode which is a preferred embodiment of the present invention will be described, but is not limited to the following embodiment. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  FIG. 1 is a schematic view showing a bipolar lithium ion secondary battery electrode (hereinafter also referred to as a bipolar electrode) which is a preferred embodiment (hereinafter also referred to as a first embodiment) of the present invention. The bipolar electrode 1 has a structure in which a positive electrode (positive electrode active material layer) 3 is provided on one surface of a resin layer 2 and a negative electrode (negative electrode active material layer) 4 is provided on the other surface. The resin layer 2 has conductivity and serves as a current collector. The positive electrode active material layer 3 contains a positive electrode active material 5, and the negative electrode active material layer 4 contains a negative electrode active material 6. A part of the positive electrode active material 5 and the negative electrode active material 6 is incorporated into the resin layer.

  Since part of the active material particles forming the active material layer is taken into the resin layer, the contact resistance between the resin layer and the active material interlayer can be reduced. In addition, a lithium ion secondary battery containing an active material is caused by expansion and contraction of the positive electrode and negative electrode active material layers due to insertion and extraction of lithium ions into and from the positive electrode and negative electrode active materials during charging and discharging processes. In some cases, the current collector and the active material layer were peeled off due to the stress. According to the electrode of the present invention, since part of the active material particles forming the active material layer is taken into the resin layer, the adhesion between the resin layer and the active material can be improved by the anchor effect of the active material. In addition, electronic conductivity between the resin layer and the active material layer can be increased. When applied to a battery, the contact resistance between the resin layer and the active material layer is reduced and the adhesion is improved, so that the charge / discharge durability can be improved and the output of the battery can be improved.

  In the present invention, the maximum depth at which the active material is taken into the resin layer is preferably 1/4 to 1/2 of the average particle diameter of the active material in the thickness direction. More preferably, it is 1/4 to 1/3. Within this range, the active material layer is unlikely to peel off from the resin layer, and since the amount of the active material that does not function as a battery is small, a decrease in energy and output can be suppressed. Note that “the maximum depth at which the active material is taken into the resin layer is 1/4 to 1/2 of the average particle diameter of the active material in the thickness direction” is the deepest uptake in FIG. It means that the depth of the active material in the thickness direction (X in FIG. 1) is 1/4 to 1/2 of the average particle diameter of the active material. 1 in FIG. 1 can be easily measured by separating the resin layer and the active material layer from the electrode, and measuring the length in the thickness direction in the trace of the active material remaining in the resin layer. Can do.

  Moreover, the numerical value measured with the particle size distribution meter (model number SALD-2200, manufacturer Shimadzu Corporation) using a laser diffraction is employ | adopted for the average particle diameter of an active material here.

  The average particle diameter of the active material is not particularly limited, but is preferably 1 to 20 μm, more preferably 1 to 10 μm, and further preferably 1 to 5 μm from the viewpoint of output.

  Alternatively, the maximum depth at which the active material is taken into the resin layer is preferably 5 to 20 μm in the thickness direction. More preferably, it is 5-15 micrometers, More preferably, it is 5-10 micrometers. Within this range, the active material layer is unlikely to peel off from the resin layer, and since the amount of the active material that does not function as a battery is small, a decrease in energy and output can be suppressed. In addition, the above-mentioned “the maximum depth in which the active material is taken into the resin layer is 5 to 20 μm in the thickness direction” means that the depth in the thickness direction of the active material taken in the deepest in FIG. X) in 1 means 5 to 20 μm.

  In the first embodiment, the positive electrode and the negative electrode active material are incorporated in the resin layer. However, the electrode of the present invention is not limited to such a form, and at least one of the positive electrode and the negative electrode active material is a resin. It only has to be incorporated in the layer. For example, although not particularly limited, there is a form in which at least one of the positive electrode and the negative electrode active material is taken into the resin layer in the current collector made of the resin layer. From the viewpoint of peel strength and resistance reduction, a form in which both the positive electrode and the negative electrode active material are taken into the resin layer as in the first embodiment is preferable. The member functioning as a current collector may include at least a resin layer, and specifically includes a current collector made of a resin layer, a laminate of a resin layer and a metal foil, and the like. A current collector made of a resin layer is preferable from the viewpoint of weight reduction. In the case of a laminate composed of a resin layer and a metal foil, the active material of the active material layer on the side in contact with the resin layer is taken into the resin layer.

  The current collector of a normal battery that is not a bipolar type transfers charge through a tab attached to the end of the current collector, and the current collector collects the charge generated on the negative electrode side into the tab or supplies it from the tab. A function of transmitting the generated electric charge to the positive electrode side. Therefore, the current collector needs to have a low electric resistance in the horizontal direction (surface direction) in which charges move, and a metal foil having a certain thickness is used to reduce the electric resistance in the horizontal direction. On the other hand, in a current collector of a bipolar battery, unlike a normal battery, the charge generated on the negative electrode side is directly supplied to the positive electrode existing on the opposite side of the current collector. For this reason, the current flows in the stacking direction of the components of the bipolar battery, and does not need to flow in the horizontal direction. Therefore, in order to reduce the electrical resistance in the horizontal direction, the conventional metal foil is not necessarily used, and therefore the electrode of the present invention can be used. Further, by applying the resin layer current collector of the present invention to a bipolar battery, the weight of the battery can be reduced. Bipolar batteries have an energy density that is more than twice that of conventional batteries. The energy released during anomalies is large and the temperature tends to rise excessively. Compared with metal foil current collectors. And when a resin layer electrical power collector is applied, such a temperature rise is suppressed.

  For the reasons described above, the electrode of the present invention is preferably an electrode applied to a bipolar battery, but it should be understood that the present invention can be applied to other types of electrodes as long as it is a configuration of the present invention. include.

  Next, each element constituting the electrode will be described.

(Resin layer)
The resin layer 2 has conductivity, essentially contains a resin, and serves as a current collector. In order for the resin layer 2 to have conductivity, specific forms include 1) a form in which the polymer material constituting the resin is a conductive polymer, and 2) a form in which the resin layer includes a resin and conductive particles. It is done.

  The conductive polymer is selected from materials that are conductive and have no conductivity with respect to ions used as charge transfer media. These conductive polymers are considered to be conductive because the conjugated polyene system forms an energy band. As a typical example, a polyene-based conductive polymer that has been put into practical use in an electrolytic capacitor or the like can be used. Specifically, polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, polyoxadiazole, or a mixture thereof is preferable, from the viewpoint that it can be used stably in an electronic conductivity and battery. , Polyaniline, polypyrrole, polythiophene, and polyacetylene are more preferable.

  The conductive particles are selected from materials that are conductive and have no conductivity with respect to the ions used as the charge transfer medium. The conductive particles are selected from materials that can withstand the applied positive electrode potential and negative electrode potential. Specific examples include aluminum particles, SUS particles, carbon particles, silver particles, gold particles, copper particles, and titanium particles, but are not limited thereto. These electroconductive particles may be used individually by 1 type, and may be used together 2 or more types. Moreover, these alloy particles may be used. The conductive particles are not limited to the above-described form, and those that are put into practical use as so-called filler-based conductive resin compositions such as carbon nanotubes may be used.

  The distribution of the conductive particles in the current collector may not be uniform, and the particle distribution may be changed inside the current collector. A plurality of conductive particles may be used, and the distribution of the conductive particles may be changed inside the current collector. For example, preferable conductive particles may be properly used in a portion in contact with the positive electrode and a portion in contact with the negative electrode. As the conductive particles used on the positive electrode side, aluminum particles, SUS particles, and carbon particles are preferable, and carbon particles are particularly preferable. As the conductive particles used for the negative electrode, silver particles, gold particles, copper particles, titanium particles, SUS particles, and carbon particles are preferable, and carbon particles are particularly preferable. Carbon particles such as carbon black and graphite have a very wide potential window, are stable in a wide range with respect to both the positive electrode potential and the negative electrode potential, and are excellent in conductivity. Also, since the carbon particles are very light, the increase in mass is minimized. Furthermore, since carbon particles are often used as a conductive aid for electrodes, even if they come into contact with these conductive aids, the contact resistance is very low because of the same material. When carbon particles are used as conductive particles, it is possible to reduce the compatibility of the electrolyte by applying a hydrophobic treatment to the surface of the carbon, making it difficult for the electrolyte to penetrate into the pores of the current collector. is there.

  In the case where the resin layer includes conductive particles, the resin forming the resin layer may include a non-conductive polymer material that binds the conductive particles in addition to the conductive particles. Good. By using a polymer material as the constituent material of the resin layer, the binding property of the conductive particles can be improved and the reliability of the battery can be improved. The polymer material is selected from materials that can withstand the applied positive electrode potential and negative electrode potential.

  Examples of the polymer material are preferably polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide (PI), polyamide (PA), polytetrafluoroethylene (PTFE). ), Styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or mixtures thereof. .

  The ratio of the conductive particles in the resin layer is not particularly limited, but preferably 5 to 20% by mass, more preferably 10 to 15% by mass of the conductive particles with respect to the total of the polymer material and the conductive particles. Exists. By allowing a sufficient amount of conductive particles to be present, sufficient conductivity in the resin layer can be secured.

The volume resistivity of the resin layer is not particularly limited, but is preferably 10 ^{−2 to} 1.0 Ωcm. If it is such a range, it will become a level applicable as a battery electrical power collector.

  The resin layer may contain other additives in addition to the conductive particles and the resin, but preferably includes the conductive particles and the resin.

  The thickness of the resin layer is not particularly limited, but it is preferably as thin as possible to increase the output density of the battery. In the bipolar battery, since the resin layer existing between the positive electrode and the negative electrode may have a high electric resistance in the direction parallel to the stacking direction, the thickness of the resin layer can be reduced. Specifically, the thickness of the resin layer is preferably 50 μm or less, and preferably 0.1 to 20 μm.

(Active material layer)
[Positive electrode (positive electrode active material layer) and negative electrode (negative electrode active material layer)]
The positive electrode active material layer 3 or the negative electrode active material layer 4 contains an active material, and further contains other additives as necessary.

The positive electrode active material layer 3 includes a positive electrode active material 5. Examples of the positive electrode active material 5 include LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium such as those in which a part of these transition metals is substituted with other elements. -Transition metal complex oxides, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, etc. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material. Of course, positive electrode active materials other than those described above may be used.

The negative electrode active material layer 4 includes a negative electrode active material 6. Examples of the negative electrode active material include carbon materials such as graphite, soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, and lithium-metal alloy materials. . In some cases, two or more negative electrode active materials may be used in combination. Preferably, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Of course, negative electrode active materials other than those described above may be used.

  Examples of the additive that can be included in the positive electrode active material layer 3 and the negative electrode active material layer 4 include a binder, a conductive additive, an electrolyte salt (lithium salt), and an ion conductive polymer.

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

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer 3 or the negative electrode active material layer 4. Examples of the conductive assistant include carbon materials such as carbon black such as acetylene black, graphite, and vapor grown carbon fiber. When the active material layer (3, 4) contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of output characteristics of the battery.

Examples of the electrolyte 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.

  The compounding ratio of the components contained in the positive electrode active material layer 3 and the negative electrode active material layer 4 is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about the non-aqueous solvent secondary battery. The content of the active material in the active material layer is preferably 90 to 98% by weight, and more preferably 92 to 96% by weight. Such a range is preferable because the active material is easily taken into the resin layer, and the anchor effect of the active material between the resin layer and the active material layer is appropriately exhibited.

  The porosity of the active material layer is not particularly limited, but is preferably 30 to 55%, and more preferably 30 to 45%. When the porosity of the active material layer is in such a range, a high energy or high output battery can be obtained when applied to the battery. The porosity of the active material layer can be easily obtained by appropriately adjusting the pressing pressure in the pressing step described in the column of the electrode manufacturing method described later. .

  The thickness of each active material layer 3, 4 is not particularly limited, and conventionally known knowledge about the battery can be referred to as appropriate. As an example, the thickness of each active material layer (3, 4) is about 2 to 150 μm.

  The bipolar lithium ion secondary battery electrode according to a preferred embodiment of the present invention has been described above, but the electrode of the present invention is not limited to the bipolar type. For example, you may apply to the positive electrode which has arrange | positioned the positive electrode active material layer on both surfaces of the resin layer, or the negative electrode which has arrange | positioned the negative electrode active material layer on both surfaces of the resin layer. As described above, the bipolar electrode has a remarkable effect of the present invention.

  Next, a battery to which the electrode of the present invention is applied will be described. The type of battery to which the electrode of the present invention is applied is not particularly limited, and examples thereof include nonaqueous electrolyte batteries. Further, when distinguished by the structure and form of the non-aqueous electrolyte battery, it is not particularly limited, such as a stacked (flat) battery or a wound (cylindrical) battery, and can be applied to any conventionally known structure. .

  Similarly, there is no particular limitation in the case of distinguishing by the form of the electrolyte of the nonaqueous electrolyte battery. For example, the present invention can be applied to any of a liquid electrolyte type battery in which a separator is impregnated with a nonaqueous electrolytic solution, a polymer gel electrolyte type battery also called a polymer battery, and a solid polymer electrolyte (all solid electrolyte) type battery. With respect to the polymer gel electrolyte and the solid polymer electrolyte, these can be used alone, or the polymer gel electrolyte or the solid polymer electrolyte can be used by impregnating the separator.

  The battery of the present invention may be either a primary battery or a secondary battery. Furthermore, when it sees with the electrode material of a battery, or the metal ion which moves between electrodes, it does not restrict | limit in particular, It can apply to any well-known electrode material. Examples include lithium ion secondary batteries, sodium ion secondary batteries, potassium ion secondary batteries, nickel metal hydride secondary batteries, nickel cadmium secondary batteries, nickel metal hydride batteries, and the like, preferably lithium ion secondary batteries. . This is because in the lithium ion secondary battery, the voltage of the cell (single cell layer) is large, high energy density and high output density can be achieved, and it is excellent as a vehicle driving power source or an auxiliary power source. Furthermore, as described above, the effect of the present invention is remarkably exhibited in the bipolar type.

  Therefore, a bipolar lithium ion secondary battery, which is a preferred embodiment, will be described below.

  The bipolar lithium ion secondary battery 30 of this embodiment shown in FIG. 2 has a structure in which a substantially rectangular power generation element 37 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 42 that is an exterior. .

  As shown in FIG. 2, the power generation element 37 of the bipolar lithium ion secondary battery of the present embodiment includes a plurality of bipolar electrodes 34 (the bipolar electrode 1 of the first embodiment described above). The bipolar electrode 34 is provided with the positive electrode active material layer 32 (the positive electrode active material layer 3 of the first embodiment described above) on one surface of the resin layer 31 (the resin layer 2 of the first embodiment described above) and on the other surface. The negative electrode active material layer 33 (the negative electrode active material layer 4 of the first embodiment described above) is provided. The bipolar lithium ion secondary battery 30 has a positive electrode active material layer 32 on one surface of a resin layer 31 and a bipolar electrode 34 having a negative electrode active material layer 33 on the other surface, and an electrolyte layer 35. A power generation element 37 having a structure in which a plurality of layers are stacked via the power generation element 37 is provided.

  The adjacent positive electrode active material layer 32, electrolyte layer 35, and negative electrode active material layer 33 constitute one single battery layer (= battery unit or single cell) 36. Therefore, it can be said that the bipolar lithium ion secondary battery 30 has a configuration in which the single battery layer 36 is laminated. In addition, an insulating layer (seal part) 43 is disposed around the single cell layer 36 in order to prevent liquid junction due to leakage of the electrolyte from the single cell layer 36. By providing the insulating layer (seal part) 43, it is possible to insulate between the adjacent resin layers 31 and prevent a short circuit due to contact between the adjacent electrodes (the positive electrode 32 and the negative electrode 33).

  The outermost layer current collector 31a on the positive electrode side is connected to the positive electrode tab 38 that is electrically connected, and the outermost layer current collector 31b on the negative electrode side is connected to the negative electrode tab 39 that is electrically connected. In addition, regarding outermost layer current collectors 31a and 31b that finally extract current, it is preferable to use a metal foil in order to reduce the electrical resistance in the horizontal direction (plane direction). And the electric power generation element 37 is sealed in the exterior material which consists of the laminate sheet 42 so that these positive electrode tabs 38 and negative electrode tabs 39 may lead out outside. The outermost layer current collector (31a, 31b) and the tab (38, 39) may be electrically connected via a positive terminal lead and a negative terminal lead. The outermost layer current collector may also serve as a tab.

  In the bipolar lithium ion secondary battery, current flows in the vertical direction due to the above-described configuration. Therefore, the path of electronic conduction is significantly shorter than that of the non-bipolar stacked battery, and the output is correspondingly higher.

  Hereinafter, although the member which comprises the bipolar lithium ion secondary battery 30 of this embodiment is demonstrated easily, the member which comprises an electrode among the components of the said bipolar lithium ion secondary battery was described above. Since it is the same as the contents, the description is omitted here.

[Electrolyte layer]
As an electrolyte constituting the electrolyte layer 35, a liquid electrolyte or a polymer electrolyte can be used.

  The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent that can be used as the plasticizer include carbonates such as ethylene carbonate (EC) and propylene carbonate (PC). Further, as the supporting salt (lithium salt), a compound that can be added to the active material layer of the electrode, such as LiBETI, can be similarly employed.

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

  The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer made of an ion conductive polymer. Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such polyalkylene oxide polymers, electrolyte salts such as lithium salts can be well dissolved.

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

  The intrinsic polymer electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the matrix polymer, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer is composed of an intrinsic polymer electrolyte, there is no fear of liquid leakage from the battery, and the reliability of the battery can be improved.

  The matrix polymer of the gel electrolyte or the intrinsic polymer electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator. A polymerization treatment may be performed.

[Outermost layer current collector]
Examples of the outermost layer current collector include an aluminum foil, a stainless steel (SUS) foil, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals. In particular, a stainless steel foil is preferable in order to obtain a current collector that can withstand both positive and negative electrode potentials. The resin layer may be used as the outermost layer current collector. The general thickness of the current collector is 1 to 30 μm.

[Tab (positive tab and negative tab)]
Tabs (positive electrode tab 38 and negative electrode tab 39) that are electrically connected to each current collector are taken out of the battery exterior material for the purpose of taking out the current outside the battery. Specifically, as shown in FIG. 2, a positive electrode tab 38 electrically connected to the outermost layer positive electrode current collector 31a and a negative electrode tab 39 electrically connected to the outermost layer negative electrode current collector 31b It is taken out of the laminate sheet which is the exterior material 42.

  The material constituting the tabs (the positive electrode tab 38 and the negative electrode tab 39) is not particularly limited, and a known highly conductive material conventionally used as a tab for a lithium ion secondary battery can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, copper, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferred. In addition, the same material may be used for the positive electrode tab 38 and the negative electrode tab 39, and different materials may be used. Further, the outermost layer current collectors 31a and 31b may be extended to form a positive electrode tab 38 and a negative electrode tab 39, or a separately prepared positive electrode tab 38 and negative electrode tab 39 are connected to the outermost layer current collectors 31a and 31b. Also good.

[Positive electrode and negative electrode lead]
The positive terminal lead and the negative terminal lead are also used as necessary. For example, when the positive electrode tab 38 and the negative electrode tab 39 serving as output electrode terminals are directly taken out from the outermost layer current collectors 31a and 31b, the positive electrode terminal lead and the negative electrode terminal lead may not be used.

  As the material of the positive terminal lead and the negative terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. It should be noted that the portion taken out from the battery outer packaging material 42 has a heat insulating property so as not to affect a product (for example, an automobile part, particularly an electronic device, etc.) by contacting with a peripheral device or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

[Battery exterior materials]
As the battery exterior member 42, a known metal can case can be used, and a bag-like case using a laminate film containing aluminum that can cover a power generation element (battery element) can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto. In the present invention, a laminate film that is excellent in high output and cooling performance and that can be suitably used for a battery for large equipment for EV and HEV is desirable.

  Although the bipolar lithium ion secondary battery according to the preferred embodiment of the present invention has been described above, it is needless to say that a non-bipolar lithium ion secondary battery may be used. As an example of a non-bipolar lithium ion secondary battery, a positive electrode in which a positive electrode active material layer is formed on both sides of a positive electrode current collector, an electrolyte layer, and a negative electrode active material layer on both sides of a negative electrode current collector A configuration in which a plurality of negative electrodes thus formed is laminated is exemplified. At this time, the positive electrode, the electrolyte layer, and the negative electrode are laminated in this order so that the positive electrode active material layer on one side of one positive electrode and the one negative electrode adjacent to the one positive electrode face each other through the electrolyte layer. Similarly to the bipolar type, the positive electrode tab and the negative electrode tab connected to each electrode (positive electrode and negative electrode) are connected to the positive electrode current collector and the negative electrode current collector of each electrode via the positive electrode terminal lead and the negative electrode terminal lead. It is attached by ultrasonic welding or resistance welding. Thereby, the positive electrode tab and the negative electrode tab have a structure exposed to the exterior of said battery exterior material from the site | part joined by heat sealing | fusing of the peripheral part of the laminate film.

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

  A preferred method for producing the electrode of the present invention includes an active material slurry preparation step of preparing an active material slurry by adding an active material to a solvent, and applying the active material slurry to the surface of a conductive resin layer. And a pressing step of pressing the laminated body produced through the coating step in the laminating direction so that the active material is taken into the resin layer. By such a manufacturing method, the electrode of the first embodiment can be easily manufactured. Hereinafter, each step will be described.

  The resin layer can be manufactured by a conventionally known method. For example, it can be manufactured by using a spray method or a coating method. Specifically, there is a technique in which a slurry containing a polymer material is prepared, applied and cured. Since the specific form of the polymer material used for the preparation of the slurry is as described above, the description thereof is omitted here. Examples of other components contained in the slurry include conductive particles. Since specific examples of the conductive particles are as described above, description thereof is omitted here. Alternatively, the polymer material, conductive particles and other additives are mixed by a conventionally known mixing method, and the obtained mixture is formed into a film. Further, for example, as in the method described in JP-A-2006-190649, the resin layer may be produced by an inkjet method.

(Active material slurry preparation process)
The active material slurry is prepared by adding an active material to a solvent. Desired active material, conductive assistant, and other components as required (for example, binder, ion conductive polymer, supporting salt (lithium salt), dispersant (polyoxystearylamine, etc.), polymerization initiator, etc.) Mix in a solvent to prepare an active material slurry. 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. In addition, when an ion conductive polymer is added to the active material slurry and a polymerization initiator is further added for the purpose of crosslinking the ion conductive polymer, simultaneously with drying in the coating process or before the drying or Later, a polymerization treatment may be performed (polymerization step).

  The solvent of each slurry is not particularly limited, and conventionally known knowledge about electrode production can be referred to appropriately. 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. It is possible to control the viscosity of the slurry by increasing or decreasing the amount of solvent. Although not particularly limited, specifically, the viscosity of the active material slurry is preferably from 3,000 to both the positive electrode and the negative electrode in order to achieve a suitable porosity of the active material layer described later. 6,000 cPs.

  Although the compounding ratio of the components contained in each slurry is not particularly limited, the ratio (weight ratio) between the solvent and the other components in the positive electrode is solvent: other components = 0.8: 1 to 1. 2: 1 is preferable, and 0.9: 1 to 1.1: 1 is more preferable. In the negative electrode, solvent: other components = 1.5: 1 to 2.0: 1 is preferable, and 1.8: 1 to 2.0: 1 is more preferable.

(Coating process)
Subsequently, the active material slurry is applied to the resin layer. The application means for applying the active material slurry to the surface of the resin layer is not particularly limited, and a conventionally known method can be appropriately employed in the battery manufacturing field. For example, methods such as a doctor blade method, an ink jet method, a screen printing method, and a die coater method are exemplified.

  After the electrodes are formed, the solvent is removed by drying. When the raw material of the solid electrolyte is polymerized by this stage and does not become a solid electrolyte, the polymerization reaction may be advanced. For example, when a photopolymerization initiator is contained in the ink, the polymerization reaction of the raw material may be advanced by irradiating predetermined light.

  A drying means for drying the active material slurry applied to the surface of the active material layer is not particularly limited, and a conventionally known method can be appropriately employed. As an example, natural drying, air drying, hot air drying, reduced pressure drying and the like can be mentioned. When forming an active material on both surfaces of an active material layer, you may form an active material layer in order, and may form simultaneously. Further, the drying temperature may be appropriately set so that the solvent is dried.

(Pressing process)
In the pressing step, the laminate produced through the coating film forming step is pressed in the laminating direction so that the active material is taken into the resin layer. Although it does not specifically limit as a press method, A roll press method, a flat plate press method, a hot roll method etc. can be used. The press linear pressure at the time of the roll press is appropriately set depending on the material of the resin layer or the state of the coating film, but is preferably 2,000 to 30,000 N / cm, and 10,000 to 30,000 N. More preferably, it is / cm. By setting the pressing pressure in such a range, the active material layer is unlikely to peel off from the resin layer, and the amount of active material that does not function as a battery is small, so that reduction in energy and output can be suppressed. The press pressure N / cm is a unit when a roll press is applied, and is a linear pressure. For example, 2,000 N / cm is a condition in which a roller having a width of 30 cm has a pressing force of 60,000 N. The pressing pressure during flat plate pressing is preferably 4.0 × 10 ^{7 to} 6.0 × 10 ⁸ Pa, and more preferably 2.0 × 10 ^{8 to} 6.0 × 10 ⁸ Pa.

  Moreover, it is preferable to press so that the electrode thickness ratio after pressing when the electrode thickness when not pressing is 1 is 0.5 to 0.8 in both the positive electrode and the negative electrode. It is more preferable to press so that it may become 6-0.7.

  The press conditions are preferably such that the maximum depth at which the active material is taken into the resin layer is 1/4 to 1/2 of the average particle diameter of the active material in the thickness direction, more preferably the active material It is preferable to perform the pressing so that the average particle diameter is ¼ to ３. The press linear pressure for adjusting the average particle diameter of the active material to ¼ to ½ is appropriately adjusted and set depending on the state of the coating film, but is 2,000 to 30,000 N / cm. It is preferable that it is 10,000 to 30,000 N / cm.

  The temperature at the time of pressing is usually about 20 to 30 ° C.

  When the electrode thus obtained is used for a battery, the battery can be produced by a conventionally known production method.

[Appearance structure of lithium ion secondary battery]
FIG. 3 is a perspective view showing the appearance of a stacked flat non-bipolar or bipolar lithium ion secondary battery which is a typical embodiment of the battery according to the present invention.

  As shown in FIG. 3, the stacked flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power from both sides thereof. Has been pulled out. The power generation element (battery element) 57 is wrapped by the battery outer packaging material 52 of the lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element (battery element) 57 includes a positive electrode tab 58 and a negative electrode tab 59. It is sealed in a state where it is pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation element (battery element) 37 of the bipolar lithium ion secondary battery 30 shown in FIG. 2 described above. In addition, a plurality of single battery layers (single cells) 36 including a positive electrode (positive electrode active material layer) 32, an electrolyte layer 35, and a negative electrode (negative electrode active material layer) 33 are stacked.

  The battery of the present invention is not limited to the stacked flat shape as shown in FIG. The wound lithium ion battery may have a cylindrical shape, or may be a rectangular flat shape obtained by deforming such a cylindrical shape. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit.

  Also, the removal of the tabs 58 and 59 shown in FIG. 3 is not particularly limited. The positive electrode tab 58 and the negative electrode tab 59 may be drawn out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side, as shown in FIG. It is not limited to. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The battery of the present invention is suitably used as a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, etc. Can be used.

[Battery]
The assembled battery of the present invention is formed by connecting a plurality of the batteries of the present invention. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of the present invention, a non-bipolar lithium ion secondary battery and a bipolar lithium ion secondary battery are used, and these are combined in series, in parallel, or in series and in parallel. A battery can also be constructed.

  4 is an external view of a typical embodiment of the assembled battery according to the present invention, FIG. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. It is a side view of an assembled battery.

  As shown in FIG. 4, an assembled battery 300 according to the present invention forms a small assembled battery 250 that can be attached and detached by connecting a plurality of lithium ion secondary batteries of the present invention in series or in parallel. A large capacity and large output suitable for a vehicle driving power source and an auxiliary power source that require a high volume energy density and a high volume output density by connecting a plurality of these detachable small assembled batteries 250 in series or in parallel. It is also possible to form an assembled battery 300 having 4A is a plan view of the assembled battery, FIG. 4B is a front view, and FIG. 4C is a side view. The small assembled battery 250 that can be attached / detached has an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many non-bipolar or bipolar lithium ion secondary batteries are connected to produce the assembled battery 250, and how many assembled batteries 250 are stacked to produce the assembled battery 300 are mounted. What is necessary is just to determine according to the battery capacity and output of the vehicle (electric vehicle) to be.

[vehicle]
The vehicle of the present invention is equipped with the battery of the present invention or an assembled battery formed by combining a plurality of these. When the electrode of the present invention is used, a high-output battery can be configured. Therefore, when such a battery is mounted, a plug-in hybrid electric vehicle having a long EV travel distance or an electric vehicle having a long one-charge travel distance can be configured. In other words, the battery of the present invention or the assembled battery formed by combining a plurality of these can be used as a power source for driving a vehicle. Examples of vehicles include hybrid vehicles, fuel cell vehicles, and electric vehicles (all are automobiles (commercial vehicles such as passenger cars, trucks, buses, light vehicles, etc.), motorcycles, and tricycles. ). However, the application is not limited to automobiles, and it can be applied to various power sources for other vehicles, for example, moving bodies such as trains, and can be used as a power source for mounting such as an uninterruptible power supply. It is also possible to do.

  FIG. 5 is a conceptual diagram of a vehicle equipped with the assembled battery of the present invention.

  As shown in FIG. 5, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance. A vehicle equipped with the assembled battery of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

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
The resin layer used was a resin layer (thickness: 50 μm) made of ketjen black (average particle size: 1 μm, 10 mass%) as the polymer material and polypropylene (90% by mass) as the conductive filler.

Next, as a positive electrode active material, lithium manganate (LiMnO ₄ ) (average particle size 5 μm, 96 mass%), acetylene black (2.2 mass%) as a conductive additive, PVdF (1.8 mass%) as a binder Prepared. The viscosity of the slurry was adjusted (slurry viscosity 5,000 cps) using NMP (50% by mass with respect to the total of other components) as the slurry viscosity adjusting solvent.

  The slurry was applied on both sides of the resin layer using a coater. The coating thickness was 100 μm. After coating, drying was performed at 120 ° C. to obtain an electrode.

  This electrode was pressed by a roll press at various press line pressures. The results are shown in FIG. The horizontal axis in FIG. 6 is the pressing linear pressure, and the vertical axis is the electrode thickness ratio after pressing when the electrode thickness is 1 when the pressing linear pressure is 10 N / cm.

Referring to FIG. 6, the region where the press linear pressure is low is a region where the void in the active material layer shrinks (press linear pressure less than 2,000 N / cm). It becomes a region where the substance bites into (pressing linear pressure: 2,000 N / cm to 30,000 N / cm). Finally, there is no shrinkage of the active material layer and the resin layer, followed by a region where the change in thickness is small (press linear pressure: over 30,000 N / cm). An electrode in which an appropriate amount of the active material is taken into the resin layer can be obtained by obtaining this relationship in advance and pressing the material under a pressing pressure condition in which an appropriate amount of the active material bites into the current collector or shrinkage scissors.
(Example 2)
(1) Production of Electrode As a positive electrode active material, lithium manganate (LiMnO ₄ ) (average particle diameter 5 μm) (96 mass%), acetylene black (2.2 mass%) as a conductive additive, PVdF (binder as a binder) 1.8% by mass). To the mixture, NMP was added as a solvent and sufficiently stirred to prepare a slurry. The obtained slurry was applied to the resin layer and dried at 120 ° C. After drying, pressing was performed at various press linear pressures described in Table 2 below to obtain a positive electrode.

  Graphite (average particle size 5 μm) (93% by mass) was mixed as the negative electrode active material, and PVdF (7.0% by mass) was mixed as the binder. To the mixture, NMP was added as a solvent and sufficiently stirred to prepare a slurry. The obtained slurry was applied to the resin layer and dried at 120 ° C. After drying, pressing was performed at various press linear pressures described in Table 2 below to obtain a negative electrode.

  The resin layer used was a resin layer (thickness 50 μm) made of ketjen black (average particle size 1 μm, 10% by mass) as the polymer material and polypropylene (90% by mass) as the conductive filler.

(3) Production of battery A positive electrode, a separator, and a negative electrode were laminated in this order. After this laminate was placed on the outer case, an electrolytic solution (electrolytic solution composition: EC: DEC = 4: 6 (volume ratio) mixed solution in which LiPF ₆ was dissolved as a lithium salt in a concentration of 1.0 M) was poured. Liquid. Thereafter, a coin-type battery was produced by sealing with an insulating gasket.

(4) Measurement of internal resistance The internal resistance of the battery was measured by the following method.

  The battery was charged to 100% state of charge (SOC). When SOC 100% is defined as 4.2 Volt, 1C charge is performed, and when 4.2 Volt is reached, constant voltage charge of 4.2 Volt is performed from 1 hour to 1 hour 30 minutes. From this SOC 100% state, pulse discharge of 10C, 20C, 30C for 5 to 10 seconds is performed. When the coulomb capacity of the battery is Ah, the current value of 10C is 10 × Ah, the current value of 20C is 20 × Ah, and the current value of 30C is 30 × Ah.

  The current value and battery terminal voltage after 5 seconds of each pulse discharge are plotted in the figure. For example, as shown in FIG. For the three plotted points, a straight line is drawn by the method of least squares to obtain the slope. This inclination is the internal resistance of the battery. It is important to measure the internal resistance to select a current value at which the battery is frequently used as the current value. Next, the internal resistance at SOC 90% is measured. For that purpose, it is necessary to lower the SOC by 10%. The discharge capacity Ah1 discharged by 10 second pulses of 10C, 20C, and 30C is removed from 0.1 * Ah, which is the capacity for 10% SOC, and 1C is discharged (0.1 * Ah-Ah), and the SOC is 90%. Set to. When SOC reaches 90%, pulse discharge is performed for 10C, 20C, and 30C for 5 to 10 seconds, and the current value and battery terminal voltage after 5 seconds of each pulse discharge are shown in the figure in the same manner as in the case of SOC 100%. Plot. For the three plotted points, a straight line is drawn by the method of least squares to obtain the slope. This inclination becomes the internal resistance of the battery. This method is repeated to determine the internal resistance of each SOC. The results are shown in Table 2 below. The data on the internal resistance ratio in Table 2 below is the value at SOC 50%.

  In Table 2, “ratio to active material particle diameter” means the ratio of the maximum depth at which the active material is taken into the resin layer to the average active material particle diameter. Moreover, the figure which showed the relationship between ratio with respect to an active material particle size and battery output ratio was shown in FIG. The ratio to the active material particle size is a value for both the positive electrode and the negative electrode. The ratio to the active material particle size was determined by cutting out the electrode and observing the cut surface with a microscope. At this time, although the unevenness of the resin layer was somewhat present, it was sufficiently small with respect to the amount of active material taken up.

  In Table 2, the “durable capacity reduction rate” is obtained from the time from when the battery is discharged at the current value of the discharge rate for 1 hour until the battery voltage reaches the lower limit of 2.5 V from the state of SOC 100%.

  From the above results, it was found that when the active material in the active material layer is taken into the resin layer, the internal resistance can be reduced and the output of the battery is improved. In particular, when the active material is incorporated in the resin layer in a ratio of 1/4 to 1/2 of the active material particle size, the internal resistance value can be significantly reduced and the output is also significantly improved. .

(Examples 3-5 and Comparative Examples 1-2)
About Examples 3-5 and Comparative Examples 1-2, it carried out similarly to Example 2, and obtained the battery. However, in Examples 3 to 5, the press line pressures were 7,500 N / cm, 50,000 N / cm, and 50,000 N / cm, respectively. Moreover, about Example 5, the corona treatment was performed to the resin layer. The corona treatment conditions are a generator output of 1,000 W, a line speed of 3.0 m / min, and a process output of 1,100 W / m ² / min. The corona treatment is a treatment conventionally used for improving the adhesion with a metal (for example, JP-A-3-2229).

The depth of incorporation of the active material in each example into the resin layer was as follows with respect to the average particle diameter of the active material. Example 4: 0.7, Example 5: 0.7. Moreover, the porosity of the active material layer was as follows. Example 4: 30%, Example 5: 30%,
For Comparative Example 1, no pressing was performed. The comparative example 2 used what performed the corona treatment to the resin layer (corona treatment conditions are the same as Example 6), and did not press. The porosity of the active material layer was as follows. Comparative Example 1: 80%, Comparative Example 2: 80%.

  About the obtained battery, internal resistance was measured similarly to the above. Table 3 below shows the results of the output ratios of the examples and the comparative example when the internal resistance of the example 3 is 1.

  Comparative Example 1, which is a condition without pressing, has a large internal resistance and a low battery output. Corona treatment is performed on the surface of the resin layer, and the output of Comparative Example 2, which is a condition without pressing, is not improved as compared with Comparative Example 1. On the other hand, the output of the batteries of Examples 3 to 5 increased compared to the comparative example. This is presumably because the electronic network between the active materials was improved. The output of the battery (Example 5) when the resin layer surface was subjected to corona treatment was almost the same as that without corona treatment (Example 4). In Example 3, since the press was set to the optimum condition, the output of the battery was remarkably improved. This is presumably because the electronic network between the active materials was improved and the amount of the active material taken into the resin layer was optimized.

It is a conceptual diagram which shows 1st embodiment of this invention. It is a schematic diagram which shows the bipolar battery of this invention. It is an external view of the bipolar battery of the present invention. It is an external view of the assembled battery of this invention. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention. It is the figure which showed the relationship between the electrode thickness ratio in an Example, and a press line pressure. It is an example of the plot used when calculating the internal resistance of a battery. It is the figure which showed the relationship between the output ratio of the battery in an Example, and the ratio with respect to an active material particle size.

Explanation of symbols

1, 34 Bipolar electrode,
2, 31 resin layer,
3, 32 positive electrode active material layer,
4, 33 negative electrode active material layer,
5 cathode active material,
6 negative electrode active material,

30 Bipolar lithium ion secondary battery,
31a, 31b outermost layer current collector,
35 electrolyte layer,
36 single battery layer (= battery unit or single cell),
37, 57 Power generation element (battery element; laminate),
38, 58 positive electrode tab,
39, 59 negative electrode tab,
40 Positive terminal lead,
41 Negative terminal lead,
42, 52 Battery exterior material (for example, laminate film),
43 Sealing part (insulating layer),
50 lithium ion secondary battery,
250 small battery pack,
300 battery packs,
310 connection jig,
400 Electric car.

Claims (8)

A current collector made of a resin layer having conductivity,
An active material layer formed on the resin layer and containing an active material;
An electrode, wherein a part of the active material is incorporated in the resin layer.   The electrode according to claim 1, wherein a maximum depth in which the active material is taken into the resin layer is ¼ to ½ of an average particle diameter of the active material in a thickness direction.   The electrode according to claim 1, wherein the resin layer includes conductive particles.   The electrode according to claim 1, wherein the active material layer has a porosity of 30 to 55%. An active material slurry preparation step of preparing an active material slurry by adding an active material to a solvent;
A coating step of applying the active material slurry to the surface of a current collector made of a conductive resin layer;
A pressing process for pressing the laminate produced through the coating process in the stacking direction so that the active material is taken into the resin layer;
The manufacturing method of the electrode containing this.   The method for producing an electrode according to claim 5, wherein in the pressing step, a press linear pressure is set to 2000 to 30000 N / cm.   The battery using the electrode of any one of Claims 1-4, or the electrode obtained by the manufacturing method of Claim 5 or 6.   The battery according to claim 7, which is a bipolar battery.

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