JP2015069833A - Method and apparatus for manufacturing lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a mixed layer of an electrode material and an insulation material from being formed in the vicinity of the interface between an electrode material layer and an insulation material layer when an electrode layer of a lithium ion secondary battery is coated on a current collector foil and the insulation material which becomes a separator is coated on the electrode layer.SOLUTION: A method for manufacturing a lithium ion secondary battery includes the steps of: coating an electrode material ES containing a binding material on the surface of a current collector foil EP; coating an insulation material IF1 containing a first component which precipitates the binding material on the electrode material ES; solidifying the electrode material ES by supplying spray liquid LIQ containing a second component which precipitates the binding material to the electrode material ES; and drying the electrode material ES and the insulation material IF1.

Description

  The present invention relates to a method for manufacturing a lithium ion secondary battery and a lithium ion secondary battery manufacturing apparatus, and in particular, a lithium ion secondary battery having a positive electrode, a negative electrode, and a separator for electrically separating the positive electrode and the negative electrode. The present invention relates to a manufacturing method, a manufacturing apparatus, and a technology effective when applied to a lithium ion secondary battery.

  With the development of portable electronic devices, small secondary batteries that can be repeatedly charged are used as power supply sources for these portable electronic devices. Among these, lithium ion secondary batteries have been attracting attention because they have the advantages of high energy density, long cycle life, low self-discharge characteristics, and high operating voltage. Lithium ion secondary batteries have the advantages described above, and are therefore widely used in portable electronic devices such as digital cameras, notebook personal computers, and mobile phones.

  Furthermore, in recent years, research and development of large-sized lithium ion secondary batteries capable of realizing high capacity, high output, and high energy density as electric vehicle batteries and power storage batteries have been promoted. In particular, in the automobile industry, development of an electric vehicle using a motor as a power source or a hybrid vehicle using both an engine (internal combustion engine) and a motor as a power source is underway in order to cope with environmental problems. . Lithium ion secondary batteries have attracted attention as power sources for such electric vehicles and hybrid vehicles. Similarly, lithium ion secondary batteries are becoming increasingly important in applications such as solar power generation or power storage for efficient use of nighttime power. However, since the lithium ion secondary battery has a high operating voltage and high energy density, sufficient countermeasures against abnormal heat generation due to an internal short circuit or an external short circuit are required.

The lithium ion secondary battery is a kind of non-aqueous electrolyte secondary battery, and is a secondary battery in which lithium ions in the electrolyte bear electric conduction. A lithium metal oxide is used for the positive electrode material (active material), a carbon material such as graphite is used for the negative electrode material (active material), and an organic solvent such as ethylene carbonate and lithium hexafluorophosphate (LiPF ₆ ) are used for the electrolyte. It is known to use lithium salts such as Lithium-ion secondary batteries, for example, electrically separate a positive electrode plate and a negative electrode plate from a strip-shaped positive electrode plate coated with a positive electrode material on a metal foil and a strip-shaped negative electrode plate coated with a negative electrode material on a metal foil. It has the laminated body which piled up through the separator for doing. This laminated body is wound to constitute an electrode winding body having a spiral cross section in the outer can of the lithium ion secondary battery.

  In Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-054991), a positive electrode film and a negative electrode film are individually formed, a separator film is bonded to the negative electrode film, and the positive electrode film is applied to the negative electrode film with a separator. It is described that an electrode winding body is formed by laminating layers. Here, the above configuration can improve the point that it is difficult to uniformly inject a solution-like electric field substance into a current collector in which a plurality of electrode winding bodies are laminated, and the number of manufacturing steps is large. Have been described.

  In Patent Document 1, a positive electrode material-containing solution and a solution containing an electrolytic substance and an insulating substance are applied to both surfaces of a positive electrode sheet using a coater having a solution discharge slit, It is described that a positive electrode sheet is formed through a heating process. Similarly, a negative electrode substance-containing solution and a solution containing an electrolytic substance and an insulating substance are applied to both surfaces of the negative electrode sheet-like material using a coater, and then subjected to a heating step to form a negative electrode sheet It is described to form an object. Further, a secondary battery manufacturing method and a secondary battery manufacturing apparatus are described in which both electrode sheet-like materials are laminated to form an electrode winding body.

JP 2003-054991 A

  Lithium ion secondary batteries are, for example, a positive electrode plate coated with a positive electrode active material on the surface of a current collector foil, a negative electrode plate coated with a negative electrode active material on the surface of a current collector foil, and the contact between the positive electrode plate and the negative electrode plate The electrode winding body which wound the plate-shaped separator which prevents this is provided. Here, it is possible to prepare each of the positive electrode plate, the negative electrode plate, and the separator as separate parts, that is, separate bodies. In this case, for example, due to the cutting process of the positive electrode plate, the positive electrode plate and the separator are separated. There arises a problem such that a metal foreign substance enters the gap between them and the positive electrode and the negative electrode are short-circuited.

  In contrast, in the coating process of the electrode material of the lithium ion secondary battery, as described in Patent Document 1, the positive electrode or the negative electrode material is applied to the surface of the current collector foil as the carrier material. It is conceivable to form an electrode plate by forming a coating film and applying an insulating material to be a separator on the coating film. Thereby, it is possible to prevent the occurrence of a short circuit problem due to the foreign matter, and it is possible to improve the production efficiency and downsize the manufacturing apparatus.

  However, when a positive or negative electrode material is applied to the surface of the current collector foil, which is a carrier material, and an insulating material that is to be a separator is applied continuously, the electrode material and the insulating material layer are Since the mixed layer of the insulating material is formed, the layer of the insulating material that functions as a separator is thinned. Thereby, the short circuit of a positive electrode and a negative electrode becomes easy to generate | occur | produce, and since the possibility that a defect will generate | occur | produce becomes high, the problem which the reliability of a lithium ion secondary battery falls arises. As a configuration for preventing the short circuit, it is conceivable to increase the thickness of the separator, but in this case, it is difficult to reduce the size of the lithium ion secondary battery.

  The above object and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

  Of the embodiments disclosed in the present application, the outline of typical ones will be briefly described as follows.

  A method of manufacturing a lithium ion secondary battery according to a representative embodiment includes a step of applying an electrode material containing a binder on the surface of a current collector foil, and a step of depositing the binder on the electrode material. A step of applying an insulating material containing one component, a step of solidifying the electrode material by supplying a spray liquid containing a second component for precipitating the binder to the electrode material, and drying the electrode material and the insulating material And a step of causing

  Furthermore, the manufacturing apparatus of a lithium ion secondary battery according to a representative embodiment includes a first coating unit that applies an electrode material slurry containing a binder to the surface of the current collector foil, and an electrode material slurry. By supplying the electrode material slurry with a second coating portion for applying an insulating material slurry containing a first component for precipitating the binder, and a solidified liquid containing a second component for precipitating the binder, A solidification part for solidifying the electrode material slurry, a drying chamber for drying the electrode material slurry and the insulating material slurry, and a current collector foil in the order of the first coating part, the second coating part, the solidification part and the drying room. And a transport unit for transporting.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  According to the present invention, the reliability of a lithium ion secondary battery can be improved.

  Moreover, according to this invention, the performance of a lithium ion secondary battery can be improved.

It is a schematic diagram which shows the manufacturing apparatus of the lithium ion secondary battery which is one embodiment of this invention. It is sectional drawing of the electrode plate which comprises a lithium ion secondary battery. The graph which shows the relationship between the thickness of a mixed layer and the conveyance speed of current collection foil of each of the lithium ion secondary battery which is Embodiment 1 of this invention, and the lithium ion secondary battery which is a 2nd comparative example It is. It is a schematic diagram which shows the structure of a lithium ion secondary battery. It is a flowchart which shows the manufacturing process of the lithium ion secondary battery which is a 1st comparative example. It is a schematic diagram which shows the manufacturing apparatus of the lithium ion secondary battery in a 2nd comparative example.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiments, and the repetitive description thereof will be omitted. Also, in the following embodiments, the description of the same or similar parts will not be repeated in principle unless particularly necessary.

  In addition, the thickness as used in this application refers to the length of each structure in the direction perpendicular | vertical with respect to the surface of the current collector foil which comprises a lithium ion secondary battery.

  Below, the manufacturing method and manufacturing apparatus of the lithium ion secondary battery in this Embodiment are demonstrated using FIG. In this embodiment, as the lithium ion secondary battery is downsized, a method for reducing the thickness of the mixed layer in the vicinity of the interface between the electrode material layer and the insulating material layer even when the insulating material layer serving as a separator is designed to be thin. Will be explained. FIG. 1 is a diagram showing a configuration of a single-side coating type electrode plate manufacturing apparatus according to the present embodiment. That is, FIG. 1 is a schematic diagram showing a lithium ion secondary battery manufacturing apparatus according to the present embodiment.

  As shown in FIG. 1, the manufacturing apparatus of the lithium ion secondary battery according to the present embodiment includes a current collector foil delivery roll RL1 for delivering a current collector foil EP, which is an electrode plate, and a winding roll for winding the current collector foil EP. RL4. The current collector foil EP, which is a thin plate-like metal foil, is conveyed between the current collector foil feed roll RL1 and the take-up roll RL4 while being supported by a plurality of rollers such as rollers RL2 and RL3. Here, in order to convey the current collector foil EP at a constant speed, the plurality of rollers are referred to as a roller conveyance system, that is, a conveyance unit.

  In the transport path of the current collector foil EP, a coater DC1, a coater DC2, a spray nozzle SPR in the solidification chamber SD, and a drying chamber DRY are arranged in this order from the current collector foil feed roll RL1 side to the take-up roll RL4 side. Yes. The conveyed current collecting foil EP passes between the coater DC1 and the roller RL2, between the coater DC2 and the roller RL3, in the solidification chamber SD, and in the drying chamber DRY.

  Each of the positive electrode and the negative electrode constituting the lithium ion secondary battery differs in the material of the current collector foil EP and the material of the film applied to the current collector foil EP, but is basically manufactured by the same process. . For this reason, below, it demonstrates without dividing each manufacturing process of a positive electrode and a negative electrode. For example, the electrode material ES, which is a coating material to be described later, includes a case where it is a positive electrode material and a case where it is a negative electrode material. In each case, the electrode material ES is composed of different materials. Here, it goes without saying that, in the positive electrode manufacturing process, the current collector foil EP and the coating material made of the positive electrode material are used, and the material used only in the negative electrode manufacturing process is not used. Similarly, in the negative electrode manufacturing process, a material used only for the positive electrode manufacturing process is not used.

  In the manufacturing process of the lithium ion secondary battery in the present embodiment, first, the electrode material ES for forming the positive electrode or the negative electrode of the lithium ion secondary battery is adjusted. Next, the collected slurry electrode material ES is supplied from the collector foil feed roll RL1 by using the coater DC1 which is the first coating portion disposed so as to face the roller RL2. Apply thinly and evenly on the surface of the EP. Below, this process is called a 1st coating process. Moreover, the film | membrane which consists of electrode material ES apply | coated on current collection foil EP by the 1st coating process is called an electrode material layer or a 1st coating film. For example, a slit die coater can be used for the first coating part, but another apparatus may be used as an apparatus for supplying the electrode material ES.

  Next, on the surface of the first coating film, the insulating material IF1 supplied from the coater DC2, which is the second coating portion provided so as to face the roller RL3, is thinly and uniformly applied. This process is called a second coating process. In addition, the film made of the insulating material IF1 applied on the first coating film in the second coating process is referred to as an insulating material layer or a second coating film. For the second coating part, for example, a slit die coater or the like can be used. In FIG. 1, the first coating film and the second coating film are not shown.

  Here, insulating material IF1 contains the component which deposits the binder component of the surface layer of the 1st coating film which is an electrode material layer. Here, the component which precipitates a binder component is called a solidification material or a solidification liquid. One of the features of the lithium ion secondary battery of the present embodiment is that the insulating material IF1 includes a solidifying material as described above. In the second coating process, the insulating material IF1 including the solidifying material is in contact with the surface of the first coating film. When the solidifying material comes into contact with the surface layer of the first coating film, the solidified liquid enters the first coating film while dissolving in the solvent in the first coating film.

  As a result, when the concentration of the solidified liquid in the surface layer of the first coating film increases, the solubility of the binder in the first coating film decreases, so that the binder is deposited and only the surface layer of the first coating film is fixed. That is, the binder of the surface layer of the first coating film is deposited, so that the active material constituting the first coating film that is the electrode material is fixed. Therefore, solidification of the surface layer of the first coating film can prevent the active material constituting the first coating film from being mixed into the second coating film on the first coating film. The surface layer of the first coating film means the first coating film in the vicinity of the surface including the surface of the first coating film.

  The binder is a component having a role of binding between the powder components constituting the first coating film and further binding between the powder component and the current collector foil after the first coating film is dried. It is. When the electrode material contains a conductive additive, the binder has a role of binding the powder and the conductive additive. The powder constituting the first coating film is, for example, a positive electrode active material powder or a negative electrode active material powder.

  Next, a component for precipitating the binder in the electrode material layer, that is, the spray liquid LIQ containing the solidifying material is supplied from the spray nozzle SPR in the solidification chamber SD to the laminated film composed of the first coating film and the second coating film. To do. Here, the spray liquid LIQ is sprayed from the spray nozzle SPR. As a result, the binder inside the first coating film that is the electrode material layer is deposited, so that not only the surface layer of the first coating film but also the active material inside the first coating film is fixed. That is, in this solidification step, the entire first coating film that is the electrode material layer is solidified. In the present application, a configuration in which the spray liquid LIQ that is a solidification material is sprayed using the spray nozzle SPR in the solidification chamber SD and the coating film to be sprayed is solidified is referred to as a solidification unit.

  Next, the current collector foil EP is transported into a drying chamber DRY which is a hot air drying furnace. In the drying chamber DRY, the solvent component and the solidified liquid in the first coating film and the second coating film are heated and evaporated to dry and solidify the first coating film and the second coating film, An insulating layer is formed in a lump. Below, this process is called a drying process. That is, the first coating film becomes an electrode layer by a drying process, and the second coating film becomes an insulating layer, that is, a separator, by a drying process. Thereby, the electrode plate which consists of the current collection foil EP and the electrode layer and insulating layer which were laminated | stacked in order on one side of the current collection foil EP, ie, a positive electrode plate or a negative electrode plate, is formed. Then, the said electrode plate is wound up by winding roll RL4. In the present application, the electrode, the positive electrode, and the negative electrode may be referred to as an electric plate, a positive electrode plate, and a negative electrode plate, respectively.

  After the drying step, a film-like positive electrode or negative electrode plate is produced by performing a processing step such as compression or cutting on the current collecting foil EP. Thereafter, in the assembly process of the electrode cell, a positive electrode and a negative electrode having a size necessary for the battery cell are cut out from the film-like positive electrode plate and negative electrode plate formed by the above process in a process called winding. At this time, the insulating layer which is a separator for separating the positive electrode plate and the negative electrode plate is cut out together with the positive electrode plate and the negative electrode plate. Subsequently, after stacking the positive electrode plate and the negative electrode plate on which the separator is laminated on the electrode layer, the laminate including the positive electrode plate and the negative electrode plate is put together.

  Next, a group of electrode pairs including the combined positive electrode and negative electrode is assembled and welded. In this welding process, for example, an aluminum ribbon is wound around the positive electrode current collecting tab, and the positive electrode current collecting tab is connected to the aluminum ribbon by ultrasonic welding. Then, after arranging the group of these electrode pairs welded in the battery can, the electrolyte is injected. Subsequently, a battery cell of a lithium ion secondary battery is formed by completely sealing the battery can.

  In the battery cell inspection process, the cells of the lithium ion secondary battery created in the cell assembly process are repeatedly charged and discharged. Thereby, the cell inspection process regarding the performance and reliability of a battery cell is performed. In the unit cell inspection step, for example, the capacity or voltage of the battery cell is inspected, or the current or voltage at the time of charging or discharging is inspected. Thereby, the battery cell of a lithium ion secondary battery, ie, a single battery, is completed.

  Below, each material used in order to manufacture the lithium ion secondary battery in this Embodiment is demonstrated.

  The electrode material ES in the present embodiment includes a positive electrode active material powder or a negative electrode active material powder that can release and occlude lithium ions by charging and discharging. In addition, the electrode material ES includes a binder component that binds between the powder components after drying, or binds between the powder component and the current collector foil. Further, in some cases, the electrode material ES includes a powder of a conductive additive.

  When forming the positive electrode plate, the electrode material ES to be applied in the first coating step, that is, the positive electrode material is, for example, a mixture of an active material made of a lithium-containing composite oxide and carbon as a conductive additive. Is included. The positive electrode material is, for example, a slurry obtained by kneading the mixture in a solution in which a binder (binder) made of polyvinylidene fluoride is dissolved in N-methylpyrrolidone (NMP).

In the manufacturing process of the positive electrode, the insulating material IF1 is a binder (binder) made of styrene butadiene rubber, and is added to a component for precipitating the binder component of the surface layer of the electrode material, that is, ethanol-added water which is one of solidifying materials. A slurry in which silica (SiO ₂ ) powder is kneaded is used in the dissolved solution. Moreover, the spray liquid LIQ which is a solidification liquid supplied in the solidification chamber SD which is a solidification part uses a component for precipitating the binder component of the electrode material, that is, ethanol-added water which is one of the solidification materials.

  Moreover, when forming a negative electrode plate, electrode material ES applied in a 1st coating process, ie, negative electrode material, contains the negative electrode active material which consists of carbon materials (carbon material), for example. The negative electrode material is, for example, a slurry obtained by kneading the negative electrode active material in a solution in which a binder (binder) made of polyvinylidene fluoride is dissolved in N methylpyrrolidone (NMP).

In the negative electrode manufacturing process, a binder (binder) made of styrene butadiene rubber is used as the insulating material IF1 as a component for precipitating the binder component of the surface layer of the electrode material, that is, ethanol-added water which is one of solidifying materials. A slurry in which silica (SiO ₂ ) powder is kneaded is used in the dissolved solution. The spray liquid LIQ, which is a solidified liquid supplied in the solidifying chamber SD, uses a component that deposits the binder component of the electrode material, that is, ethanol-added water that is one of the solidified materials.

  Below, the specific example of each material mentioned above is shown.

  The positive electrode active material used in this embodiment includes a lithium-containing composite oxide having a spinel structure containing lithium cobaltate or Mn (manganese), or Ni (nickel), Co (cobalt), or Mn (manganese). A composite oxide or the like can be used. Moreover, olivine type compounds, such as olivine type iron phosphate, can also be used for a positive electrode active material. However, the positive electrode active material is not limited to these materials, and other materials may be used. Since the lithium-containing composite oxide having a spinel structure containing manganese is excellent in thermal stability, for example, a highly safe battery can be configured.

In addition, as the positive electrode active material, only a lithium-containing composite oxide having a spinel structure containing manganese may be used, but another positive electrode active material may be used in combination. Examples of other positive electrode active materials include olivine type compounds represented by Li ₁ + xMO ₂ (−0.1 <x <0.1). Examples of the metal M in this formula include Co (cobalt), Ni (nickel), Mn (manganese), Al (aluminum), Mg (magnesium), Zr (zirconium) or Ti (titanium).

Further, a lithium-containing transition metal oxide having a layered structure can be used for the positive electrode active material. Specific examples of the lithium-containing transition metal oxide having a layered structure, LiCoO ₂ or _{LiNi 1 -xCo x -yAl y O 2} (0.1 ≦ x ≦ 0.3,0.01 ≦ y ≦ 0.2) such as Can be used. As the lithium-containing transition metal oxide having a layered structure, an oxide containing at least Co, Ni, and Mn can be used. Examples of the oxide containing Co, Ni, and Mn include LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , or LiNi _3/5 Examples thereof include Mn _1/5 Co _1/5 O ₂ .

  The conductive aid is used as an electron conductive aid to be contained in the positive electrode film, and is preferably a carbon material such as carbon black, acetylene black, graphite, carbon fiber, or carbon nanotube. Among the above carbon materials, acetylene black is particularly preferable from the viewpoints of the amount of addition and conductivity, and the productivity of the positive electrode mixture slurry for coating. This conductive auxiliary agent can also be contained in the negative electrode film.

  The binder as the binder preferably contains a binder for binding the active material and the conductive additive to each other. As the binder material, for example, a polyvinylidene fluoride polymer or a rubber polymer is preferably used. The polyvinylidene fluoride-based polymer is, for example, a polymer of a fluorine-containing monomer group containing 80% by mass or more of vinylidene fluoride whose main component is a monomer. Two or more of the above polymers may be used in combination. The binder of the present embodiment is preferably provided in the form of a solution dissolved in a solvent.

  The fluorine-containing monomer group for synthesizing the polyvinylidene fluoride-based polymer includes vinylidene fluoride or a mixture of vinylidene fluoride and another monomer, and a monomer mixture containing 80% by mass or more of vinylidene fluoride. Is mentioned.

  Examples of the other monomer include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether.

  Examples of the rubber-based polymer include styrene butadiene rubber (SBR), ethylene propylene diene rubber, and fluorine rubber.

  The binder content in the electrode material layer, that is, the first coating film is preferably 0.1% by mass or more and 10% by mass or less based on the electrode layer after drying. More preferably, the binder content is 0.3% by mass or more and 5% by mass or less. If the binder content is too small, not only will the solidification in the pre-solidification step of the present embodiment be insufficient, but the mechanical strength of the electrode film after drying will be insufficient, and the electrode layer will peel off from the current collector foil. Problems arise. Moreover, when there is too much content of a binder, there exists a possibility that the amount of active materials in an electrode layer may reduce and battery capacity may become low.

For the insulating material IF1 used in this embodiment, an inorganic oxide such as alumina (Al ₂ O ₃ ) or silica (SiO ₂ ) can be used. Further, by using a slurry in which fine particles of polypropylene or polyethylene are mixed, the insulating layer can be provided with a shutdown property. The insulating layer is a porous film, and in the completed lithium ion secondary battery, the electrolytic solution is held in the pores of the insulating layer and constitutes a lithium ion conduction path between the electrodes. The shutdown property here refers to a function of melting the insulating layer and closing the hole when the lithium ion secondary battery generates abnormal heat. By shutting off permeation of lithium ions in the insulating layer by this shutdown function, the reaction in the battery is stopped, and further increase in battery temperature can be prevented.

  Further, a resin is used as a binder for fixing inorganic oxide particles used for the insulating material IF1. As the binder, the above-mentioned polyvinylidene fluoride polymer or rubber polymer is preferably used in the negative electrode as well as the positive electrode.

  In the present embodiment, it is important to use the material of the solidified liquid contained in the insulating material IF1 that is appropriately selected for the solvent and binder in the first coating film. The solidifying liquid should be selected in consideration of the solubility of the binder component in the first coating film and the mutual solubility of the solvent. The solvent in the first coating film used in a general solvent-based slurry is an aprotic polar solvent such as N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, dimethylformamide, or γ-butyrolactone, or a mixture thereof. Liquid. Considering the mutual solubility in these solvents and the solubility of the binder used, water, alcohols such as ethanol and isopropyl alcohol, or a mixture thereof can be selected as the solidified liquid, but are limited to the examples given here. I don't mean.

  In addition, in order to uniformly spray the solidified liquid, that is, the spray liquid LIQ from the spray nozzle SPR in the solidification chamber SD, the wettability between the solidified liquid and the laminated film composed of the first coating film and the second coating film is also considered. Thus, a solidified liquid should be selected. For example, a mixture of water and alcohol is preferably used as the spray liquid LIQ. When the wettability between the laminated film consisting of the first coating film and the second coating film and the solidified liquid is poor, the solidified liquid is dispersed in a plurality of locations on the surface of the laminated film and adheres in an island shape. This is because the solidified liquid cannot be supplied uniformly to the surface of the laminated film. That is, the solidified liquid constituting the spray liquid LIQ needs to be a component having good affinity with the surface of the laminated film.

  The concentration of alcohol in the mixture is preferably 20 to 80%, for example. However, more preferably, the concentration of the alcohol is 40 to 60%. When the alcohol concentration is lower than the above concentration range, the wettability between the laminated film and the solidified liquid deteriorates. If the alcohol concentration is higher than the above concentration range, handling of the solidified liquid becomes difficult due to an increase in the concentration of combustible alcohol, and the risk of explosion in the manufacturing process and the like increases.

  When the solidifying liquid constituting the spray liquid LIQ has high wettability with the surface of the laminated film, that is, the surface of the second coating film, that is, when the affinity is good, the spray liquid LIQ is composed only of water. May be. Further, when the solidified liquid can be handled safely, the spray liquid LIQ may be composed of only alcohol.

  Specifically, when forming the negative electrode plate in the present embodiment, for example, a graphite material such as natural graphite (flaky graphite), artificial graphite, or expanded graphite is used as the negative electrode active material constituting the electrode material ES. be able to. Also, as the negative electrode active material, an easily graphitizable carbonaceous material such as coke obtained by firing pitch can be used. In addition, examples of the negative electrode active material include amorphous carbon obtained by low-temperature firing of furfuryl alcohol resin (PFA: Poly Furfuryl Alcohol) or polyparaphenylene (PPP: Poly-Para-Phenylen) and a phenol resin. The non-graphitizable carbonaceous material can be used.

  In addition to the above carbon material, Li (lithium) or a lithium-containing compound can also be used as the negative electrode active material. Examples of the lithium-containing compound include a lithium alloy such as Li—Al or an alloy containing an element that can be alloyed with Li (lithium) such as Si (silicon) or Sn (tin). Furthermore, oxide-based materials such as Sn oxide and Si oxide can also be used for the negative electrode active material. This oxide-based material may not contain Li (lithium).

  The current collector foil EP used in the present embodiment is not limited to a sheet-like foil, and examples of the substrate include pure aluminum (Al), copper (Cu), stainless steel, titanium (Ti), and the like. Metal or alloy conductive materials can be used. For the current collector foil EP, for example, a net, a punched metal, a foam metal, a foil processed into a plate shape, or the like is used. The thickness of the conductive substrate constituting the current collector foil EP is, for example, 5 to 30 μm.

  Here, FIG. 2 shows the mixed layer formed at the interface between the electrode layer and the insulating layer in the manufacturing method of the present embodiment, and FIG. 3 shows the result of the evaluation of the thickness of the mixed layer. The evaluation is performed by cutting out a cross section of the completed electrode plate and calculating the thickness of the mixed layer from an image observed with an SEM (Scanning Electron Microscope).

  FIG. 2 shows a cross-sectional view of an electrode plate constituting a lithium ion secondary battery. As shown in FIG. 2, an electrode layer EL having a thickness L1 and an insulating layer SEL that is a separator having a thickness L2 are sequentially stacked on the current collector foil EP. The electrode layer EL is a film formed by drying the first coating film described above, and the insulating layer SEL is a film formed by drying the second coating film described above.

  Further, a mixed layer MIX having a thickness L3 formed by mixing the constituent material of the electrode layer EL and the constituent material of the insulating layer SEL is formed in the vicinity of the interface between the electrode layer EL and the insulating layer SEL. In FIG. 2, the upper end and the lower end of the mixed layer MIX are indicated by broken lines. The mixed layer MIX is a region including the interface between the electrode layer EL and the insulating layer SEL, and is formed from the inside of the electrode layer EL to the inside of the insulating layer SEL. In the present embodiment, the thickness L1 of the electrode layer constituting the positive electrode plate after the drying step is, for example, 30 to 500 μm, and the thickness L2 of the insulating layer is, for example, 10 to 20 μm.

  Moreover, the result of having evaluated the film thickness of the mixed layer MIX by the said SEM observation based on sectional drawing shown in FIG. 2 is shown in FIG. FIG. 3 shows the thickness of each mixed layer MIX (see FIG. 2) of the lithium ion secondary battery of the present embodiment described above and a lithium ion secondary battery of a second comparative example described later, and a current collector foil. It is a graph which shows the relationship with the conveyance speed. The vertical axis of the graph shown in FIG. 3 indicates the thickness of the mixed layer, and the horizontal axis indicates the conveyance speed of the current collector foil.

  As a result of the above evaluation, the present inventors have found the following matters.

  That is, as shown by a square plot in FIG. 3, in the second comparative example described later, the film thickness of the mixed layer varies depending on the conveying speed of the current collector foil. That is, the thickness of the mixed layer MIX increases as the conveying speed of the current collector foil decreases. On the other hand, even if the conveyance speed of the current collector foil is 100 m / min, the thickness of the mixed layer does not become 10 μm or less. Moreover, the thickness of the mixed layer is 10 μm or more even at a practical speed of conveying the current collector foil.

  The mixed layer MIX is a film that has lost its insulating property when the electrode layer EL is mixed with the insulating layer SEL. When the mixed layer MIX is formed with a relatively large thickness, the thickness of the insulating layer SEL having an insulating function may be thinner than originally intended. Further, when the insulating layer SEL is thinned, the electrode material constituting the mixed layer MIX may be exposed above the insulating layer SEL. That is, if the insulating layer is made thin, the possibility of occurrence of a short circuit increases.

  On the other hand, as shown by a round plot in FIG. 3, the thickness L3 (see FIG. 2) of the mixed layer MIX in the manufacturing method of the present embodiment is always 4 μm or less regardless of the conveying speed of the current collector foil. It has become. From this, the present inventors can prevent the occurrence of a short circuit when the insulating layer SEL (see FIG. 2) is thinned if the lithium ion secondary battery is formed by the manufacturing method of the present embodiment. I found out that I can.

  In the manufacturing process described with reference to FIG. 1, an example is described in which the electrode material ES and the insulating material IF1 are sequentially coated on one surface of the current collector foil EP to manufacture a positive electrode or negative electrode sheet. When the electrode material ES and the insulating material IF1 are applied to both surfaces of the current collector foil EP, the electrode sheet wound around the take-up roll RL4 is reversed after the manufacturing process described above, and again the same It is conceivable that the surface opposite to the one surface of the current collector foil EP is applied through the process.

  Here, the basic operation principle of the lithium ion secondary battery will be described with reference to FIG. FIG. 4 is a schematic diagram showing the structure of a lithium ion secondary battery.

As shown in FIG. 4, the lithium ion secondary battery is a kind of non-aqueous electrolyte secondary battery, and is a secondary battery in which lithium ions in the electrolyte bear electric conduction. A lithium metal oxide is used for the active material PA that is the amount of the positive electrode material, and a carbon material such as graphite is used for the active material NA that is the negative electrode material. Further, an organic solvent such as ethylene carbonate and a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) are used for the electrolyte ELQ made of an electrolyte. In the battery, lithium ions exit from the positive electrode PE and enter the negative electrode NE during charging, and conversely during discharge, the lithium ions exit from the negative electrode NE and enter the positive electrode PE. Al foil AF made of Al (aluminum) is used for the current collector foil of the positive electrode PE, and Cu foil CF made of Cu (copper) is used for the current collector foil of the negative electrode NE.

  In the lithium ion secondary battery, for example, a positive electrode plate coated with a positive electrode material, a negative electrode plate coated with a negative electrode material, and a separator SP such as a polymer film that prevents contact between the positive electrode plate and the negative electrode plate are wound. An electrode winding body is provided. The lithium ion secondary battery has a configuration in which the electrode winding body is inserted into the outer can and the electrolyte is injected into the outer can. In other words, a lithium ion secondary battery has a positive electrode plate coated with a positive electrode material on a metal foil and a negative electrode plate coated with a negative electrode material on a metal foil. The positive electrode plate and the negative electrode plate formed into a band shape. In order to prevent direct contact with each other, the laminated body is stacked via separators. The electrode winding body having a spiral cross section is formed by winding the laminated body.

  Below, the manufacturing method of the lithium ion secondary battery of a 1st comparative example is demonstrated.

  FIG. 5 is a flowchart schematically showing specific steps until a lithium ion secondary battery is manufactured. As shown in FIG. 5, the manufacturing process of the lithium ion secondary battery includes a positive electrode sheet manufacturing process, a negative electrode sheet manufacturing process, a battery cell assembly process, and a module assembly process.

  In the manufacturing process of the lithium ion secondary battery in the first comparative example, first, the electrode material is adjusted. The electrode material used to form the electrode layer constituting the positive electrode or the negative electrode of the lithium ion secondary battery is composed of an active material capable of releasing and occluding lithium ions by charge and discharge, and a conductive auxiliary powder. It is a high-viscosity slurry-like liquid formed by kneading and dispersing with a binder and a solvent for binding (kneading and blending step shown in FIG. 5). Next, the slurry material is applied to a film-like metal foil, followed by drying (a coating process shown in FIG. 5). Thereafter, the metal foil coated with the slurry material is subjected to processing such as compression or cutting (processing step shown in FIG. 5) to form a film-like positive electrode sheet.

  On the other hand, a negative electrode sheet manufacturing process is performed in the same procedure as the positive electrode sheet manufacturing process mentioned above. However, the various materials used in the positive electrode sheet manufacturing process described above may be different from the various materials used in the negative electrode sheet manufacturing process. That is, first, a slurry material (negative electrode material) is prepared by kneading and preparing various materials as raw materials for the negative electrode material (kneading and preparing step shown in FIG. 5). Thereafter, the slurry material is applied to a film-like metal foil and dried (application step shown in FIG. 5). Subsequently, the metal foil coated with the slurry material is subjected to processing such as compression or cutting (processing step shown in FIG. 5) to produce a film-like negative electrode sheet.

  Thereafter, in the electrode cell assembly process, a positive electrode and a negative electrode having a size necessary for the battery cell are cut out from the positive electrode sheet and the negative electrode sheet in a process called winding. Along with this, a separator having a size necessary for the battery cell is cut out from the film-like separator material for separating the positive electrode sheet and the negative electrode sheet, and the cut separator is sandwiched between the positive electrode and the negative electrode. (A winding process shown in FIG. 5). Thereafter, a group of electrode pairs composed of the joined positive electrode, negative electrode, and separator is assembled and welded (welding / assembly process shown in FIG. 5). Then, after arranging the group of these electrode pairs welded in the battery can into which the electrolytic solution has been injected (the injection step shown in FIG. 5), the battery can is completely sealed (the sealing step shown in FIG. 5). Thereby, a battery cell is created.

  In the battery cell inspection step, the cells of the lithium ion secondary battery created in the cell assembly step are repeatedly charged and discharged (charge / discharge step shown in FIG. 5). Thereby, the cell inspection process regarding the performance and reliability of a battery cell is performed (cell inspection process shown in FIG. 5). In the unit cell inspection step, for example, the capacity or voltage of the battery cell is inspected, or the current or voltage at the time of charging or discharging is inspected. Thereby, the battery cell of a lithium ion secondary battery, ie, a single battery, is completed.

  Next, in the module assembly process, a battery module is configured by combining a plurality of battery cells in series, and a battery system is configured by connecting a controller for charge / discharge control (module assembly process shown in FIG. 5). Thereafter, in the module inspection process, the battery module assembled in the module assembly process is inspected for performance and reliability (module inspection process shown in FIG. 5). In this module inspection step, for example, the capacity or voltage of the battery module is inspected, or the current or voltage during charging or discharging is inspected.

  In the manufacturing method and the manufacturing apparatus of the lithium ion secondary battery according to the present embodiment, in the electrode sheet manufacturing process of the positive electrode or the negative electrode, the insulating material layer is applied on the electrode material layer, and then the drying process is performed. An electrode plate in which a layer and an insulating layer as a separator are integrated can be formed. For this reason, in the battery cell assembling step, the step of preparing the processed separator can be omitted in the step of winding the separator in the battery cell assembly step. Thereby, the throughput of the manufacturing process of a lithium ion secondary battery can be improved.

  Below, the manufacturing method of the lithium ion secondary battery of a 2nd comparative example is demonstrated using FIG. FIG. 6 is a schematic diagram showing a lithium-ion secondary battery manufacturing apparatus in a second comparative example.

  In FIG. 6, the structure of the single-sided application type electrode plate manufacturing apparatus in the 2nd comparative example is shown. An example of a manufacturing process in which the electrode material ES and the insulating material IF2 are applied to one surface of the current collector foil EP that is a carrier material will be described. In the manufacturing process of the second comparative example, coating is performed on one side of the electrode sheet. In the manufacturing process of the second comparative example, first, the electrode material ES supplied from the coater DC1 that opposes the roller RL2 is applied to one surface of the current collector foil EP fed from the current collector foil feed roll RL1. The

  Subsequently, the insulating material IF2 supplied from the coater DC2 at a position facing the roller RL3 is applied on the applied electrode material ES. Next, when the current collector foil EP passes through the drying chamber DRY, the electrode material ES and the insulating material IF2 are dried, wound on the winding roll RL4, and the positive electrode sheet is manufactured. In this drying step, the first coating film made of the electrode material ES is dried to form an electrode layer, and the second coating film made of the insulating material IF2 is dried to form an insulating layer, that is, a separator.

  As described above, after the slurry-like positive electrode material and the insulating material are applied in layers, both coating films can be dried and fixed simultaneously through the heating / drying process in the drying chamber DRY. The example is more efficient in the manufacturing process than the first comparative example.

  However, when the slurry-like electrode material and the insulating material are continuously applied on the current collector foil as in the second comparative example, the current on the current collector foil EP of the electrode plate as shown in FIG. A mixed layer MIX that has lost its insulating function is formed in the vicinity of the interface between the electrode layer EL and the insulating layer SEL applied to the substrate. The present inventors have found that the mixed layer MIX is a layer generated due to the coating pressure of the slit die coater described with reference to FIG. As shown by a square plot in FIG. 3, the film thickness of the mixed layer MIX (see FIG. 2) generated in the second comparative example varies depending on the conveying speed of the current collector foil. That is, the slower the current collecting foil transport speed, the longer the time during which the pressure applied by the coater is applied to the coating film at a specific location, and the thickness of the mixed layer MIX also increases. Even if the conveying speed of the current collector foil is relatively high, 100 m / min, the thickness of the mixed layer MIX is 10 μm or more.

  When the mixed layer MIX is formed with a relatively large thickness, the insulating layer SEL having an insulating function becomes thinner than originally intended, and when the insulating layer SEL is thinned, the insulating layer There is a problem that the electrode material constituting the mixed layer MIX may be exposed at the top of the SEL.

  Like the second comparative example described above, the internal short circuit is prevented by eliminating the gap between the electrode layer and the separator (insulating layer), and the productivity of the lithium ion secondary battery is improved. Although it is conceivable to make the manufacturing apparatus of the lithium ion secondary battery compact, in this configuration, it is difficult to reduce the thickness of the insulating layer due to the problem of the mixed layer. That is, the second comparative example has a problem that it is difficult to increase the capacity and size of the lithium ion secondary battery.

  Below, the effect of this Embodiment demonstrated using FIG. 1 is demonstrated.

  In contrast to the second comparative example described above, the method of manufacturing the lithium ion secondary battery of the present embodiment, as shown in FIG. 1, after applying the first coating film of the first layer that becomes the electrode layer, An insulating material IF1 including a solidifying material is applied as the second coating film of the second layer that becomes the insulating layer. Thereby, the surface layer of the first coating film is solidified. As described above, when the insulating material IF1 is applied, the electrode layer ES and the insulating material IF1 are mixed by solidifying the surface layer of the first coating film, and the mixed layer MIX (see FIG. 2) has a large thickness. Can be prevented.

  In the present embodiment, after the coating process, the first coating film and the second coating film are supplied by supplying the first coating film and the second coating film with the spray liquid LIQ that is a solidifying material in the solidification chamber SD. Allow the membrane to solidify completely. Thereby, in the drying process in the drying chamber DRY, the electrode material ES and the insulating material IF1 are mixed due to the flow of the binder inside each of the electrode material ES and the insulating material IF1, and the mixed layer MIX (FIG. 2) Can be prevented from being formed with a large thickness.

  As described above, in the present embodiment, the thickness L3 of the mixed layer MIX shown in FIG. 2 can be reduced as compared with the second comparative example. Specifically, the thickness of the mixed layer MIX can be less than 5 μm. On the other hand, in the second comparative example, the thickness L3 of the mixed layer MIX is 10 μm or more even at a practical speed of transporting the current collector foil. Therefore, when the thickness L2 of the insulating layer SEL is reduced, The possibility of occurrence of a short circuit between the negative electrodes is increased.

  Therefore, in this embodiment mode, the risk of a short circuit can be prevented even if the separator, which is an insulating layer, is thinned, so that the reliability of the lithium ion secondary battery can be improved. Moreover, since the separator which is an insulating layer can be thinned while preventing a short circuit, the lithium ion secondary battery can be miniaturized. Therefore, the performance of the lithium ion secondary battery can be improved.

  Further, in the present embodiment, as shown in FIG. 1, since each coating film is completely solidified by supplying the spray liquid LIQ before the drying process, the drying process is performed at a high speed. Even if it exists, the movement of the electrode material in a 1st coating film and the insulating material in a 2nd coating film can be suppressed. That is, when the solidification process using the solidification chamber SD is not performed, the components such as the binder in each film move during the drying process because the inside of the first coating film and the second coating film are liquid during drying. Thus, convection or diffusion occurs in each membrane. For this reason, variation occurs in the distribution of the electrode material ES after drying, and the mixed layer MIX (see FIG. 2) may be formed with a large thickness. In this case, in order to suppress the convection or diffusion of the electrode material ES due to the movement or remelting of the binder, it is necessary to suppress the evaporation rate. However, when the evaporation rate is slowed, there is a problem that the drying time becomes long.

  On the other hand, in this embodiment, since each coating film is completely solidified in the solidification chamber SD before the drying step, it is possible to prevent the electrode material ES from moving during the drying step in the drying chamber DRY. It is possible to increase the evaporation rate of solvents and the like. Therefore, the drying time can be shortened, and the drying equipment can be downsized. Thereby, the throughput in the manufacturing process of the lithium ion secondary battery can be improved. Further, the manufacturing cost of the lithium ion secondary battery can be reduced by shortening the drying time or downsizing the drying equipment.

  In addition, said effect is not only acquired with the positive electrode plate which consists of positive electrode materials, but the same effect can be acquired also with a negative electrode plate. The manufacturing apparatus and the manufacturing method described in this embodiment are merely examples for implementing this embodiment, and various forms can be used without departing from the technical idea or main features thereof. Even in the embodiment, the above effect can be obtained.

  Further, here, a lithium ion secondary battery has been described as an example, but the effect of this embodiment is not limited to a lithium ion secondary battery. For example, the positive electrode, the negative electrode, and the positive electrode and the negative electrode are electrically connected. It can be widely applied to an electricity storage device including a separator that is separated into two. Examples of the power storage device include other types of batteries or capacitors.

  Although the invention made by the present inventors has been specifically described based on the embodiment, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention is effective when applied to a manufacturing technique of a lithium ion secondary battery in which an insulating layer is applied on an electrode layer to form an electrode plate.

AF Al foil CF Cu foil DC1 Coater (first coating part)
DC2 coater (second coating part)
DRY Drying chamber EL Electrode layer ELQ Electrolytic solution EP Current collecting foil ES Electrode material IF1 Insulating material LIQ Spray liquid MIX Mixed layer NA Active material NE Negative electrode PA Active material PE Positive electrode RL1 Current collecting foil feed roll RL2 Roller RL3 Roller RL4 Winding roll SD Solidification chamber SEL Insulating layer SP Separator SPR Spray nozzle

Claims (7)

(A) The process of apply | coating the electrode material slurry containing a binder using the 1st coating part on the surface of current collection foil,
(B) A step of applying an insulating material slurry containing a first component for precipitating the binding material on the electrode material slurry using a second coating portion;
(C) a step of solidifying the electrode material slurry by supplying a solidified liquid containing a second component for precipitating the binder to the electrode material slurry after the step (b);
(D) a step of drying the electrode material slurry and the insulating material slurry after the step (c);
A method for producing a lithium ion secondary battery. In the manufacturing method of the lithium ion secondary battery of Claim 1,
The method for manufacturing a lithium ion secondary battery, wherein the first component and the second component contain water or alcohol. In the manufacturing method of the lithium ion secondary battery according to claim 2,
A method for producing a lithium ion secondary battery, wherein the alcohol contains methanol, ethanol, propanol, butanol, hexanol, heptanol or octanol. In the manufacturing method of the lithium ion secondary battery of Claim 1,
In the step (d), the electrode material slurry is dried to form an electrode layer, the insulating material slurry on the electrode material slurry is dried to form an insulating layer,
(E) A method for producing a lithium ion secondary battery, further comprising a step of stacking a plurality of electrode plates having the current collector foil, the electrode layer, and the insulating layer. A first coating portion for applying an electrode material slurry containing a binder to the surface of the current collector foil;
A second coating portion for applying an insulating material slurry containing a first component for precipitating the binder on the electrode material slurry;
A solidifying part for solidifying the electrode material slurry by supplying a solidified liquid containing a second component for precipitating the binder to the electrode material slurry;
A drying chamber for drying the electrode material slurry and the insulating material slurry;
A transport unit that transports the current collector foil in the order of the first coating unit, the second coating unit, the solidifying unit, and the drying chamber;
An apparatus for producing a lithium ion secondary battery. In the manufacturing apparatus of the lithium ion secondary battery according to claim 5,
The said 1st component and the said 2nd component are the manufacturing apparatuses of a lithium ion secondary battery containing water or alcohol. In the manufacturing apparatus of the lithium ion secondary battery according to claim 6,
An apparatus for producing a lithium ion secondary battery, wherein the alcohol contains methanol, ethanol, propanol, butanol, hexanol, heptanol or octanol.

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