JP2015069797A - Method and apparatus for manufacturing lithium ion secondary battery, and 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 electrode material slurry on the surface of a current collector coil EP using a first coating part; supplying solidified liquid containing a component which precipitates a binder component contained in the electrode material slurry to the electrode material slurry to thereby solidify a surface layer of the electrode material slurry; coating an insulation material slurry on the electrode material slurry whose surface layer is solidified; and drying the electrode material slurry and the insulation material slurry.

Description

  The present invention relates to a method for manufacturing a lithium ion secondary battery, a lithium ion secondary battery manufacturing apparatus, and a lithium ion secondary battery, and particularly includes a positive electrode, a negative electrode, and a separator that electrically separates the positive electrode and the negative electrode. The present invention relates to a method and apparatus for manufacturing a lithium ion secondary battery, and a technology effective when applied to the 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.

  As a background art in this technical field, there is Patent Document 1 (Japanese Patent Laid-Open No. 2003-054991). In Patent Document 1, a positive electrode sheet 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 die coater having a solution discharge slit, followed by a heating step. The formation of a positive electrode sheet is described. Similarly, a negative electrode material containing solution and a solution containing an electrolytic substance and an insulating substance are applied to both surfaces of the negative electrode sheet using a die coater, followed by a heating step, followed by a negative electrode sheet material. Is described. Here, the electrode winding body is formed by laminating both electrode sheets of the positive electrode and the negative electrode.

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 conceivable that each of the positive electrode plate, the negative electrode plate, and the separator is prepared as a separate part, that is, a separate body. In this case, for example, due to the cutting process of the positive electrode plate, the positive electrode plate and the separator There arises a problem that a metal foreign substance enters the gap between the positive electrode and the negative electrode, causing a short circuit.

  In contrast, a positive electrode plate formed by sequentially applying a positive electrode active material and a separator to the surface of the current collector foil, and a negative electrode plate formed by sequentially applying a negative electrode active material and a separator to the surface of another current collector foil To form a lithium ion secondary battery. If it is such a lithium ion secondary battery, it can prevent that the metal foreign material produced by cut | disconnecting a positive electrode plate or a negative electrode plate penetrate | invades between a positive electrode plate or a negative electrode plate, and a separator.

  However, when the electrode material slurry containing the positive electrode active material or the negative electrode active material is applied to the surface of the current collector foil, and the insulating material slurry that becomes the separator continuously is applied on the slurry, the electrode layer and the insulating layer A mixed layer of an electrode material and an insulating material is formed at the interface. In this case, since the insulating material layer functioning as a separator becomes thin, a short circuit between the positive electrode and the negative electrode is likely to occur, thereby causing a problem that the reliability of the lithium ion secondary battery is lowered. 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 typical embodiment includes a step of applying an electrode material slurry on the surface of a current collector foil using a first coating part, and the electrode material slurry A step of solidifying a surface layer of the electrode material slurry by supplying a first solidified liquid containing a component for precipitating a binder component to the electrode material slurry; and on the electrode material slurry on which the surface layer is solidified. And a step of applying an insulating material slurry using the second coating part, and a step of drying the electrode material slurry and the insulating material slurry.

  Further, the lithium ion secondary battery manufacturing apparatus according to the representative embodiment deposits a first coating part for applying an electrode material slurry to the surface of the current collector foil, and a binder component contained in the electrode material slurry. A first solidification liquid containing a component to be fed is supplied to the electrode material slurry, whereby a first solidification chamber for solidifying the surface layer of the electrode material slurry, and the electrode material slurry on which the surface layer is solidified, A second coating section for applying an insulating material slurry; a drying chamber for drying the electrode material slurry and the insulating material slurry; and the current collector foil, the first coating section, the first solidification chamber, It has a conveyance part which conveys in order of the said 2nd coating part and the said drying chamber.

  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 Embodiment 1 of this invention. It is a schematic diagram which shows the manufacturing apparatus of the lithium ion secondary battery which is Embodiment 2 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 manufacturing apparatus of the lithium ion secondary battery which is a 1st comparative example. 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. It is an expanded sectional view 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.

(Embodiment 1)
Below, the manufacturing method and manufacturing apparatus of the lithium ion secondary battery in this Embodiment are demonstrated using FIG. 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 in the present embodiment includes a current collecting metal foil roll RL1 for feeding out the current collecting foil EP and a winding roll RL4 for winding up the current collecting foil EP. Have. The current collecting foil EP, which is a thin plate-like metal foil, is conveyed between the current collecting metal foil 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.

  A die coater DC1, a spray nozzle NZ1, a die coater DC2 and a drying chamber DRY in the solidification chamber SD1 are arranged in this order from the current collecting metal foil roll RL1 side to the take-up roll RL4 side in the conveying path of the current collecting foil EP. ing. The conveyed current collecting foil EP passes between the die coater DC1 and the roller RL2, inside the solidification chamber SD1, between the die coater DC2 and the roller RL3, and inside 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-like electrode material ES is collected from the current-collecting metal foil roll RL1 using the die coater DC1, which is the first coating portion disposed so as to face the roller RL2. Apply thin and evenly on the surface of the foil 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 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, the current collector foil EP coated with the electrode material ES is transported into the solidification chamber SD1, and the solidified liquid supplied from the spray nozzle NZ1 is sprayed onto the electrode material ES on the current collector foil EP. The surface layer of the first coating film made of the electrode material ES is solidified. Below, this process is called a pre-solidification process. The solidified liquid as used in the present application is a liquid containing a solidifying material contained in a slurry such as a first coating film, that is, a component that precipitates a binder component as a binder. That is, the solidified liquid and the solidified material are different materials, and the solidified material is included in the first coating film, for example, and the solidified liquid supplied from the spray nozzle NZ1 does not include the solidified material.

  Next, the insulating material IF supplied from the die coater DC2, which is the second coating portion provided so as to face the roller RL3, is thinly and uniformly applied on the surface of the first coating film whose surface layer is solidified. Work. This process is called a second coating process. A film made of the insulating material IF applied on the first coating film in the second coating process is referred to as 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.

  Next, the current collector foil EP coated with the second coating film in the second coating step is conveyed into a drying chamber DRY that 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.

  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.

  The solidification liquid used in the pre-solidification step needs to have a property that the binder component contained in the first coating film is insoluble and a property of mutual dissolution with the solvent in the first coating film. When the solidified liquid comes into contact with the first coating film, the solidified liquid enters the first coating film while being dissolved in the solvent in the first coating film. When the concentration of the solidified liquid increases in the surface layer of the first coating film, the solubility of the binder decreases, so that the binder is precipitated and only the surface layer of the first coating film is fixed.

  This embodiment has a feature that a pre-solidification step is introduced between the first coating step and the second coating step. Thereby, a 2nd coating process can be performed in the state in which the surface of a 1st coating film does not flow. For this reason, as will be described later, it is possible to suppress the generation of a mixed layer formed by applying a coating pressure to the first coating film and the second coating film by the die coater which is the second coating section described above. It becomes.

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

  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 .

  As the negative electrode active material used in the present embodiment, for example, a graphite material such as natural graphite (flaky graphite), artificial graphite, or expanded graphite can be used. 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 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 used for the electrode of this embodiment 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 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.

As the insulating material IF 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 binding the inorganic oxide particles used for the insulating material IF. 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.

  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, and more preferably 8 to 16 μm.

  It is important that the solidifying liquid of the present embodiment is appropriately selected and used with respect to 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 order to spray the solidified liquid uniformly, the solidified liquid should be selected in consideration of the wettability between the first coating film and the solidified liquid, and it is preferable to use a mixture of water and alcohol. This is because when the wettability between the first coating film and the solidified liquid is poor, the solidified liquid is dispersed at a plurality of locations on the surface of the first coated film and adheres in an island shape, and is uniform on the surface of the first coated film. This is because the solidified liquid cannot be supplied to the container. The concentration of the alcohol in the mixture is desirably 20 to 80%, more preferably 40 to 60%. When the concentration of alcohol is lower than the above concentration range, the wettability between the first coating film and the solidified liquid is deteriorated. 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.

  Here, the pre-solidification process of this Embodiment is demonstrated.

  The pre-solidification process of this Embodiment is a process introduce | transduced between a 1st coating process and a 2nd coating process. In the pre-solidification step, the solidification liquid is sprayed on the surface of the first coating film to solidify the surface layer of the first coating film. The surface layer of the first coating film means a first coating film in the vicinity of the surface including the surface of the first coating film.

  At this time, it is important to perform the pre-solidification step by appropriately selecting the amount of the solidification liquid to be sprayed and the spray particle size of the solidification liquid. As the type of the spray nozzle, a one-fluid nozzle that ejects only liquid or a two-fluid nozzle that ejects mixed liquid and gas can be used. From the viewpoint of reducing the impact when water contacts the solidified film by spraying, it is desirable to use a two-fluid nozzle that can spray finer droplets.

  Further, the average particle diameter D50 of the sprayed particles sprayed from the nozzle is 20 μm or less, more preferably 10 μm or less, so that damage such as a coating film defect can be prevented. The coating film defect is the surface of the coating film because the sprayed particles are struck against the surface of the coating film when the spray pressure, spraying force, or average particle size of the droplet sprayed on the surface of the coating film is large. Means that it is recessed. In this case, problems such as variations in insulation between electrodes occur. Here, the spray hitting force refers to a pressure that the target receives per unit area by hitting a droplet against the target by spraying.

  From the above, it is necessary to select an appropriate spray amount of the solidified liquid depending on the type of binder and solidified liquid used for the electrode material. Specifically, the concentration is not more than the solidified solution concentration at which all the binder in the first coating film is deposited. More preferably, the concentration is 40 to 90% of the concentration of the solidified solution in which all the binder in the first coating film is deposited. When the amount of the solidified liquid to be sprayed is too large, the solidified liquid accumulates on the first coating film, making it difficult to apply the insulating material. When the amount of the solidified liquid is too small, the solidified liquid spreads on the front surface of the first coating film. There is a risk of not.

  The lithium ion secondary battery that can be provided by the present embodiment is manufactured in the same process as the lithium ion secondary battery of the second comparative example described later, except that it includes the positive electrode and the negative electrode manufactured by the above-described method. can do. There is no particular limitation on the structure and size of the container of the battery, or the structure of the electrode body having positive and negative electrodes as main components.

  The manufacturing method of the lithium ion secondary battery of the present embodiment, after applying the first coating film to be the first electrode layer as described above, through the step of solidifying only the surface layer of the electrode layer, A second coating film to be a second insulating layer is applied. Moreover, the manufacturing apparatus of the lithium ion secondary battery according to the present embodiment includes the first coating portion that coats the first coating film serving as the first electrode layer as described above, and the second layer insulation. Between the 2nd coating part which coats the 2nd coating film used as a layer, it has a means to solidify only the surface layer of a 1st coating film, It is characterized by the above-mentioned. In such a manufacturing apparatus, by using the above manufacturing method, the thickness of the mixed layer generated at the interface between the electrode layer and the insulating layer can be reduced, as described later, and the insulating layer can be made thinner and highly reliable. Can be realized.

  Below, an example of the manufacturing process of the lithium ion secondary battery of this Embodiment is described. Here, an example of the positive electrode forming step will be described.

  First, in the step of adjusting the electrode material ES, in the positive electrode manufacturing step, nickel cobalt lithium manganate as a lithium transition metal composite oxide can be used for the positive electrode active material constituting the electrode material ES. In the first adjustment process of the electrode material ES, the positive electrode active material, a conductive additive containing graphite powder and acetylene black, and polyvinylidene fluoride (hereinafter simply referred to as PVdF) serving as a binder serving as a solidifying material, Mix. Further, N-methyl-2-pyrrolidone (hereinafter simply referred to as NMP), which is the first solvent of the present embodiment, is added to the mixture. The components of the positive electrode active material, the conductive additive, the solidifying material, and the first solvent thus mixed are further kneaded with a planetary mixer to adjust the positive electrode slurry, that is, the electrode material ES.

  Here, the positive electrode active material, graphite powder, acetylene black, and PVdF are mixed at a weight ratio of 85: 8: 2: 5. In the positive electrode slurry, a binder component as a solidifying material is dissolved in NMP, and the slurry is a high-viscosity liquid. The viscosity of the slurry measured with a rotational viscometer is about 10 Pa · s.

  Next, a first coating process is performed. Here, an aluminum foil having a thickness of 20 μm and a width of 200 mm, for example, is used for the current collector foil EP to be applied in the first coating process. In the first application step, the electrode material ES is applied to the surface of the current collector foil EP with a thickness of 100 μm and a width of 150 mm using the die coater DC1 which is a slit die coater. Thereby, the 1st coating film which consists of electrode material ES is formed on current collection foil EP. The above process is the 1st coating process of this Embodiment. Here, the width of the current collector foil EP and the first coating film is a direction orthogonal to the traveling direction of the current collector foil EP being conveyed, and each structure in a direction along the upper surface of the current collector foil EP. Refers to the length of

  Next, a pre-solidification step is performed. That is, the current collector foil EP coated with the first coating film is transported into the solidification chamber SD1, and only the surface layer of the first coating film is solidified. Here, 40% ethanol-containing water is used for the solidified liquid supplied from the spray nozzle NZ1. The 40% ethanol-containing water is a liquid in which ethanol and water are mixed, and ethanol constitutes 40% of the liquid.

As the spray nozzle NZ1, an internal mixing type two-fluid nozzle is used. The average particle diameter D50 of the spray particles that are the solidified liquid ejected from the two-fluid nozzle is 10 μm. Further, the distance from the spray nozzle to the first coating film is adjusted to 100 mm, the spray pressure is adjusted to 0.1 MPa, and the spray hitting force is adjusted to 1 g / cm ² . The spray amount of the solidified liquid was set to an amount that would be 50% of the amount of 40% ethanol-containing water required for the precipitation of PVdF as a binder. That is, the spray amount of the solidified liquid is made half of the amount used for depositing all the binder. Thereby, only the surface layer of the first coating film is solidified. The above process is the pre-solidification process of this Embodiment.

  Further, on the surface including the surface of the first coating film, which is an electrode material slurry, to which the spray nozzle NZ1 sprays the solidified liquid, the solidified liquid spray area has a uniform flow distribution. That is, the distribution of the spray amount of the solidified liquid is sprayed in an equal amount within a certain range from the center of the spray nozzle NZ1 in the width direction of the first coating film. Here, the solidified liquid is sprayed uniformly over the entire top surface of the first coating film by keeping the entire width of the first coating film within the certain range in which spraying in an equal amount is possible. .

  For this purpose, the position where the flow rate is 50% of the flow rate at the center of the spray nozzle NZ1 is outside the end of the first coating film in the width direction of the first coating film, which is the direction perpendicular to the conveying direction of the current collector foil EP. Position. This is because there is a possibility that the solidified liquid cannot be sprayed in an equal amount in a region outside the position where the flow rate is 50% of the total flow rate of the solidified liquid in the width direction from the center of the spray nozzle NZ1. Because there is. That is, the solidified liquid can be sprayed in an equal amount from the center of the spray nozzle NZ1 within a range of 50% of the total flow rate of the solidified liquid.

Next, a second coating process is performed. Silica (SiO ₂ ) powder is used for the insulating material IF. Here, the insulating material IF and polyvinylidene fluoride (PVdF) serving as a binder are mixed at a weight ratio of 90:10, and N-methyl-2-pyrrolidone (NMP) is sequentially added as a solvent. Then, these components are kneaded with a planetary mixer to adjust the insulating material slurry. The insulating material slurry is a high-viscosity liquid, and the viscosity of the slurry measured with a rotational viscometer is about 2 Pa · s.

  Here, the insulating material slurry, that is, the insulating material IF is applied on the first coating film whose surface is solidified by using a die coater DC2 which is a slit die coater so as to have a thickness of 80 μm and a width of 160 mm. Thereby, the second coating film made of the insulating material IF is formed on the first coating film. The above process is the second coating process of the present embodiment.

  Next, a drying process is performed. Here, the first coating film and the second coating film are dried by heating at 120 ° C. for 10 minutes in a drying chamber DRY which is a hot air drying furnace. Thereby, the solvent contained in the first coating film and the second coating film is removed by evaporation, so that the entire first coating film and the second coating film are completely solidified. A positive electrode plate for a lithium ion secondary battery is manufactured. That is, the positive electrode plate is formed by drying and solidifying the current collector foil EP, the electrode layer formed by drying and solidifying the first coating film containing the electrode material ES, and the second coating film containing the insulating material IF. And an insulating layer. The above process is the drying process of the present embodiment in which the solvent component is removed from the electrode material ES and the insulating material IF and the process is dried.

  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.

  Here, the thickness of the mixed layer formed at the interface between the electrode layer and the insulating layer in the manufacturing method of the present embodiment is evaluated. 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. 3 shows a cross-sectional view of an electrode plate constituting a lithium ion secondary battery. As shown in FIG. 3, an electrode layer EL having a thickness L1 and an insulating layer SEL which is a separator having a thickness L2 are sequentially stacked on the current collector foil EP. This configuration is the same for the lithium ion secondary battery of the present embodiment described above and the lithium ion secondary battery of the second comparative example described later. 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. 3, the upper end and the lower end of the mixed layer MIX are indicated by broken lines, respectively.

  In the present embodiment, the thickness L1 of the electrode layer constituting the positive electrode plate after the drying step is, for example, 50 μm, and the thickness L2 of the insulating layer is, for example, 40 μm. The mixed layer MIX is a layer formed from the inside of the electrode layer EL to the inside of the insulating layer SEL near the interface between the electrode layer EL and the insulating layer SEL.

  FIG. 4 shows the result of evaluating the film thickness of the mixed layer MIX by the SEM observation based on the cross-sectional view shown in FIG. FIG. 4 shows the thickness of each mixed layer MIX (see FIG. 3) of the lithium ion secondary battery of the present embodiment described above and a lithium ion secondary battery of a second comparative example, which will be 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. 4 indicates the film 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 inventors of the present invention, as shown by a round plot in FIG. 4, determines the thickness L3 (see FIG. 3) of the mixed layer in the manufacturing method of the present embodiment as the conveyance speed of the current collector foil. Regardless, it was always 5 μm or less, and it was found that even if the insulating layer SEL (see FIG. 3) is thinned, the possibility of occurrence of a short circuit is low.

  Here, the example in which the positive electrode material slurry and the insulating material slurry are sequentially coated on one surface of the positive electrode current collector foil to manufacture the positive electrode plate has been described. When coating the positive electrode material slurry and the insulating material slurry on both surfaces of the positive electrode current collector foil, after performing the above-described steps, before performing a processing step such as compression or cutting of the current collector foil, It is conceivable to reverse the positive electrode plate wound on the winding roll and apply the back surface again through the same process.

  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. Thereafter, the welded electrode pair group is placed in the battery can, and then 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, the manufacturing process of the lithium ion secondary battery of a 1st comparative example is demonstrated using FIG. 5 and FIG.

  FIG. 6 is a flowchart schematically showing specific steps until a lithium ion secondary battery is manufactured. As shown in FIG. 6, the manufacturing process of the lithium ion secondary battery includes a positive electrode plate manufacturing process, a negative electrode plate manufacturing process, and a battery cell assembly process.

  In FIG. 5, the lithium ion secondary battery manufacturing apparatus of the 1st comparative example is shown. That is, FIG. 5 is a schematic view showing a lithium ion secondary battery manufacturing apparatus in the first comparative example. In the manufacturing process of the lithium ion secondary battery in the first comparative example, first, the electrode material ES is adjusted. An electrode material ES used for forming an electrode layer constituting a positive electrode or a negative electrode of a lithium ion secondary battery is composed of an active material capable of releasing and occluding lithium ions by charging and discharging, and a conductive auxiliary powder. It is a high-viscosity slurry-like liquid formed by kneading and dispersing with a binder, a solvent and the like for binding (a kneading and blending step shown in FIG. 6).

  Next, the slurry-like electrode material ES is thinly and uniformly applied on the surface of the current collector foil EP supplied from the current collector metal foil roll RL1 using the die coater DC1 which is a coating portion. Thereafter, a current collector foil coated with a coating film made of a slurry-like electrode material ES using a roller transport system for transporting the current collector foil EP at a constant speed while contacting the back surface of the current collector foil EP, that is, a transport unit. EP is dried and solidified in a hot-air drying furnace which is a drying chamber DRY. In this drying step, the solvent component in the coating film is evaporated by heating, whereby the electrode material is dried and solidified to form the electrode layer. Thus, an electrode layer is formed on current collection foil EP by performing a series of processes of application of electrode material ES, and a drying process (application process shown in Drawing 6). Then, a film-like positive electrode or negative electrode plate is manufactured by performing a process such as compression on the current collector foil on which the electrode layer is formed.

  In the manufacturing process of the electrode plate of the first comparative example, the process as described above is performed separately on one surface of the current collector foil EP and the surface opposite to the surface, and on both surfaces of the current collector foil EP. A positive electrode plate and a negative electrode plate on which an electrode layer is formed are manufactured.

  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 in a process called winding (the processing step shown in FIG. 6). ). At this time, a separator for separating the positive electrode plate and the negative electrode plate was cut out from the film-like separator material in a size necessary for the battery cell, and cut into the positive electrode plate and the negative electrode plate. After stacking with the separator in between, they are rolled together (winding step shown in FIG. 6).

  Next, a group of electrode pairs of the positive electrode, the negative electrode, and the separator assembled together is assembled and welded (welding / assembly process shown in FIG. 6). Then, after arranging the group of these electrode pairs welded in a battery can, electrolyte solution is inject | poured (injection process shown in FIG. 6). Subsequently, the battery can of the lithium ion secondary battery is formed by completely sealing the battery can (sealing step shown in FIG. 6).

  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 (charge / discharge process shown in FIG. 6). Thereby, the test | inspection regarding the performance and reliability of a battery cell is performed (single cell test process shown in FIG. 6). 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, a battery cell, that is, a single battery is completed, and the assembly process of the battery cell of the lithium ion secondary battery is completed.

  In the manufacturing process which is the first comparative example, there is a problem that the possibility of a metal foreign substance entering the inside of the electrode winding body increases due to the steps performed before and after forming the electrode winding body. That is, since the positive electrode plate, the negative electrode plate, and the separator are configured as separate parts, for example, there is a gap between the positive electrode plate and the separator, and a metal foreign object easily enters the gap.

  Specifically, in the first comparative example in which the electrode winding body is formed by winding the positive electrode plate, the negative electrode plate, and the separator around the axis, the positive electrode plate, the negative electrode plate, and the separator are separate components. For example, there is a gap between the positive electrode plate and the separator. In the manufacturing process of the lithium ion secondary battery, the positive electrode plate and the negative electrode plate are cut into a predetermined size (the processing step shown in FIG. 6) before forming the wound body described above, and in addition, the positive electrode and the negative electrode The current collecting tab is formed by cutting the positive electrode plate and the negative electrode plate.

  Then, after forming the electrode winding body described above, for example, a step of ultrasonically welding a positive electrode current collecting tab formed on the positive electrode plate to the positive electrode current collecting ring, and a negative electrode current collecting tab formed on the negative electrode plate And a step of ultrasonic welding to the negative electrode current collector ring (welding / assembly step shown in FIG. 6). Subsequently, the electrode winding body is inserted into the outer can (container), and after injecting the electrolyte into the outer can, the outer can and the lid are connected by welding or the like to seal the inside of the outer can. Perform the process.

  In the above welding and assembling process, the positive electrode current collector tab and the positive electrode current collector ring are welded by, for example, attaching an aluminum ribbon to the positive electrode current collector tab and then connecting the positive electrode current collector tab to the aluminum ribbon by ultrasonic welding. It is done by doing. The ultrasonic welding used at this time connects the aluminum ribbon and the positive electrode current collector tab by atomic interdiffusion by rubbing the aluminum ribbon and the positive electrode current collector tab.

  Therefore, when the positive electrode current collector tab and the aluminum ribbon are connected by ultrasonic welding, a metal foreign matter (aluminum) is generated by rubbing between the aluminum ribbon and the positive electrode current collector tab. The same phenomenon occurs in the process of connecting the negative electrode current collecting tab and the copper ribbon. That is, when connecting a negative electrode current collection tab and a copper ribbon by ultrasonic welding, a metal foreign material (copper) generate | occur | produces by friction with a copper ribbon and a negative electrode current collection tab. Furthermore, in welding (arc welding) used in the process of connecting the outer can and the lid, for example, welding scraps are likely to be generated.

  From the above, the possibility of metal foreign matter entering the inside of the electrode winding body is increased by the steps performed before and after forming the electrode winding body. When the positive electrode plate, the negative electrode plate, and the separator are configured as separate parts as in the first comparative example, for example, there is a gap between the positive electrode plate and the separator. Metal foreign matter generated in the process is likely to enter. In this way, when a metal foreign object enters the inside of the electrode winding body, the metal foreign object that has penetrated breaks through the separator, and the positive electrode and the negative electrode are short-circuited via the metal foreign object. In addition, for example, when a metal foreign matter that has entered the gap between the positive electrode and the separator adheres to the positive electrode, a phenomenon occurs in which the attached metal foreign matter is dissolved in the electrolytic solution and then deposited on the negative electrode. And when the metal which grew by precipitation from a negative electrode reaches a positive electrode, the problem which a positive electrode and a negative electrode short-circuit will arise.

  Furthermore, when assembling the positive electrode plate, the negative electrode plate, and the separator as separate parts, it is necessary to wind a total of four sheets of the positive electrode plate, the negative electrode plate, and the two separators at the same time, making it difficult to align the parts. There's a problem. Moreover, it is necessary to arrange a total of four film rolls of a positive electrode plate roll, a negative electrode plate roll, and two separator rolls, and there is a problem that a manufacturing apparatus becomes large.

  As a configuration for solving the above problem, it is conceivable to form a separator by directly applying a separator to the positive electrode plate and the negative electrode plate. In this case, the positive electrode plate or the negative electrode plate and the separator are continuously formed and integrated with each other, thereby eliminating a gap between the positive electrode plate or the negative electrode plate and the separator. Thereby, since it can prevent that a metal foreign material penetrate | invades between a positive electrode plate or a negative electrode plate, and a separator, the short circuit with a positive electrode and a negative electrode can be prevented. Furthermore, by applying a slurry containing a positive electrode active material or a negative electrode active material on a metal, and then applying an insulating material to be a separator, it may be possible to improve productivity and reduce manufacturing equipment. it can.

  As described above, a method for forming the electrode plate by directly applying the separator to the positive electrode plate and the negative electrode plate will be described below with reference to FIG. FIG. 7 is a schematic view showing an apparatus for manufacturing a lithium ion secondary battery in a second comparative example.

  In FIG. 7, the structure of the single-side coating type electrode plate manufacturing apparatus in the 2nd comparative example is shown. In the manufacturing process of the lithium ion secondary battery of the second comparative example, the current collector foil EP is fed from the current collector metal foil roll RL1. The current collector foil EP is an aluminum foil having a thickness of 20 μm and a width of 200 mm, for example. Subsequently, the electrode material ES supplied from the die coater DC1 facing the roller RL2 is applied on the surface of the current collector foil EP, thereby forming a first coating film. The first coating film has a thickness of 100 μm and a width of 150 mm, for example.

  Subsequently, the insulating material IF supplied from the die coater DC2, which is a coating portion at a position facing the roller RL3, is coated on the first coating film, thereby forming a second coating film made of the insulating material IF. The second coating film has a thickness of 20 μm and a width of 160 mm, for example. Thereafter, the first coating film and the second coating film on the current collector foil EP are dried by passing through the drying chamber DRY and wound around the winding roll RL4, whereby the electrode plate is manufactured. In this drying step, drying is performed at 120 ° C. for 10 minutes.

  As described above, the configuration of the second comparative example includes the die coater DC2 that is the second coating portion as compared with the first comparative example described with reference to FIG. The difference is that a second coating film serving as a separator is directly formed on the coating film.

  For the die coater DC1 (see FIG. 7), for example, a slit die coater is used. The slit die coater is a coating apparatus used for thick film coating or for applications where a high viscosity material is coated.

  In the die coating method of the second comparative example, as shown in FIG. 8, an electrode is connected to the manifold 3 of the base 1 by a metering pump (not shown) from a tank (not shown) in which an electrode material ES as a slurry material is stored. Material ES is supplied. Here, after the pressure distribution of the electrode material ES is made uniform in the manifold 3, the electrode material ES is supplied to the slit 4 provided in the base 1 and discharged. The discharged electrode material ES forms an electrode material reservoir 5 called a bead between the base 1 and the current collector foil EP that travels relatively at a constant interval h1, and in this state the current collector foil EP With the running, the electrode material ES is pulled out to form a coating film. FIG. 8 is an enlarged cross-sectional view of the die coater DC1 that constitutes the lithium ion secondary battery manufacturing apparatus in the second comparative example.

  In the coating process, the coating film is continuously formed by supplying the same amount of electrode material ES as consumed by the coating film formation from the slit 4. At this time, in order to stably apply the organic solvent-based thin film having a high evaporation rate, it is important to stabilize the formation of the downstream meniscus 9 which is the bending of the liquid surface of the electrode material reservoir 5. Therefore, the pressure for supplying the positive electrode material to the manifold 3 is slit 4 pressure loss + downstream lip 8 pressure loss of the cap 1 + downstream meniscus 9 pressure. That is, in order to apply the electrode material ES stably, it is necessary to apply a certain pressure from the electrode material ES to the current collector foil EP. This configuration is the same for the die coater DC2.

  In the manufacturing process described with reference to FIG. 7, the insulating material is continuously applied by the die coater DC2, which is the second coating part. The die coating method therefor is the die coater which is the first coating part. The conditions are the same as in DC1. That is, a slurry material made of an insulating material discharged from the slit 4 (see FIG. 8) of the die coater DC2, that is, an insulating material IF, is applied onto the electrode material ES applied to the current collector foil EP by the die coater DC1. To do.

  In the second comparative example described above, the slurry-like electrode material ES and the insulating material IF shown in FIG. 7 are applied in layers, followed by a heating / drying process in the drying chamber DRY. Since it can be dried and fixed, the manufacturing process is more efficient than the first comparative example. In addition, since processing such as cutting or welding of the electrode can be performed in a state where there is no gap between the electrode layer and the insulating layer which is a separator, an internal short circuit due to intrusion of a metal foreign object can be prevented.

  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, 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 the square plot in FIG. 4, the film thickness of the mixed layer MIX (see FIG. 3) 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 die 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.

  Specifically, when the thickness L3 of the mixed layer MIX is larger than 20% of the thickness L2 of the insulating layer SEL that is the separator, the total thickness of the insulating layer SEL between the positive electrode and the negative electrode Among them, since the region where the insulating function is lost becomes large, the insulating property of the insulating layer SEL is lowered, and the problem that a short circuit occurs between the positive electrode and the negative electrode becomes significant.

  That is, the thickness L3 of the mixed layer MIX is desirably 20% or less of the thickness L2 of the insulating layer SEL that is a separator. Therefore, when the thickness L2 of the insulating layer SEL is 40 μm, the thickness L3 of the mixed layer MIX is desirably 8 μm or less. In the second comparative example, in order to prevent the above problems from occurring and to ensure the reliability of the insulating layer SEL, it is conceivable that the insulating layer is a thick film of, for example, 50 μm or more.

  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 according to the present embodiment applies the first coating film of the first layer to be the electrode layer, and then the surface layer of the first coating film. The second coating film of the second layer that becomes the insulating layer is applied through a process of solidifying only the first layer. Thus, after applying the positive electrode or negative electrode material ES, the pre-solidification step is performed, and only the surface layer of the first coating film is solidified, as described with reference to FIGS. 3 and 4. The thickness L3 of the layer MIX can be reduced as compared with the second comparative example. Specifically, the thickness of the mixed layer MIX can be 5 μm or less. 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.

  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.

(Embodiment 2)
In the present embodiment, similarly to the first embodiment, after forming the insulating layer on the positive electrode layer or the negative electrode layer at once, a step of completely solidifying the coating film by bringing it into contact with the solidifying liquid is provided. Then, a manufacturing method and a manufacturing apparatus for performing drying will be described.

  FIG. 2 shows a schematic diagram showing a lithium ion secondary battery manufacturing apparatus of the present embodiment. In the manufacturing process of the lithium ion secondary battery of the present embodiment, after adjusting the electrode material ES in the same manner as in the first embodiment, the slurry-like electrode material ES is used by using the die coater DC1 facing the roller RL2. Then, coating is performed on the surface of the current collector foil EP supplied from the current collector metal foil roll. Thereby, the 1st coating film which consists of electrode material ES is formed on current collection foil EP. The thickness and width of each of the current collector foil EP and the first coating film are the same as those in the first embodiment.

  Next, as in the first embodiment, a pre-solidification step is performed in the solidification chamber SD1. Here, only the surface layer of the first coating film is solidified. The solidified liquid and spraying conditions are the same as those in the first embodiment. Using the die coater DC2, a second coating film made of the insulating material IF is applied on the first coating film whose surface is solidified. The thickness and width of the second coating film are the same as those in the first embodiment.

  Next, the current collector foil EP coated with the first coating film and the second coating film is carried into the solidification chamber SD2, and the solidification liquid is laminated by using the spray nozzle NZ2 and is composed of the first coating film and the second coating film. A step of solidifying the first coating film and the second coating film is performed by spraying on the film. Here, this process is called a solidification process. For example, 40% ethanol-containing water is used as the solidified liquid. As the solidification liquid used here, water, alcohols such as ethanol or isopropyl alcohol, or a mixed liquid thereof are used in the same manner as the solidification liquid sprayed in the solidification chamber SD1 (see FIG. 1) in the first embodiment. be able to.

An internal mixing type two-fluid nozzle is used as the spray nozzle NZ2. The average particle diameter D50 of the spray particles ejected from the two-fluid nozzle is 10 μm. Here, the distance from the spray nozzle NZ2 to the upper surface of the second coating film is 100 mm, the spray pressure of the solidified liquid is 0.1 MPa, and the spray hitting force is adjusted to 1 g / cm ² .

  The amount of the solidified liquid sprayed is 200% of the 40% ethanol-containing water amount in which all PVdF is precipitated in order to completely solidify the first coating film that is the electrode material layer and the second coating film that is along the insulating material. . That is, each coating film is completely solidified by supplying a solidification liquid twice as much as 40% ethanol-containing water, which is a solidification liquid necessary for precipitating PVdF. In FIG. 2, the spray nozzle NZ2 is shown more than the spray nozzle NZ1 in order to increase the number of nozzles and supply a large amount of solidified liquid as described above.

  Next, the first coating film and the second coating film are dried in a drying chamber DRY at 120 ° C. for 10 minutes to evaporate and remove the solvent contained in the first coating film and the second coating film, An electrode plate for a lithium ion secondary battery is manufactured. Here, the thickness of the electrode layer constituting the electrode plate after the drying step is 50 μm, and the thickness of the insulating layer on the electrode layer is 40 μm. Said process is applicable to each manufacturing process of a positive electrode plate and a negative electrode plate.

  As described above, the configuration of the present embodiment is substantially the same as that of the first embodiment. However, a second solidification chamber SD2 different from the first solidification chamber SD1 is provided between the die coater DC2 which is the second coating part and the drying chamber DRY, and on the current collector foil EP in the solidification chamber SD2. This is different from the first embodiment in that the coating film is solidified. Further, in the pre-solidification step performed in the first solidification chamber SD1, only the surface layer of the first coating film is solidified and the inside of the first coating film is not solidified, whereas the second solidification chamber SD2 is performed. In the solidification step, the entire structure including the inside of each of the first coating film and the second coating film is solidified. That is, all the binders contained in each of the first coating film and the second coating film are deposited.

  In the electrode plate obtained in the manufacturing process of the present embodiment, the thickness of the mixed layer MIX (see FIG. 3) formed in the vicinity of the interface between the electrode layer EL and the insulating layer SEL is the same as that of the first embodiment. In addition, it is always 5 μm or less regardless of the conveying speed of the current collector foil. Therefore, even if the insulating layer SEL is thinned, the possibility of occurrence of a short circuit between the positive electrode and the negative electrode can be reduced.

  In addition, since each coating film is completely solidified before the drying process as in the present embodiment, the electrode material and the second material in the first coating film can be used even when the drying process is performed at high speed. The movement of the insulating material in the coating film can be suppressed. That is, when the solidification process using the second solidification chamber SD2 shown in FIG. 2 is not performed, the inside of the first coating film and the second coating film are in a liquid state at the time of drying, and therefore the binder in each film during the drying process. The movement of components such as convection or diffusion occurs in each film. For this reason, the distribution of the electrode material ES after drying may vary. In this case, in order to suppress the convection or diffusion of the electrode material ES, it is necessary to suppress the evaporation rate, which causes a problem that the drying time becomes longer.

  On the other hand, in the second embodiment, since each coating film is completely solidified to the inside before the drying process, it is possible to prevent the electrode material ES from moving during the drying process in the drying chamber DRY. It is possible to increase the evaporation rate of the. 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.

  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.

1 Base 3 Manifold 4 Slit 5 Electrode Material Pool 8 Lip Part 9 Downstream Meniscus (Liquid Bend)
DC1 die coater (first coating part)
DC2 die coater (second coating part)
DRY Drying chamber EL Electrode layer EP Current collecting foil ES Electrode material IF Insulating material MIX Mixed layer NZ1 Spray nozzle NZ2 Spray nozzle RL1 Current collecting metal foil roll RL2 Roller RL3 Roller RL4 Winding roll SD1 Solidification chamber SD2 Solidification chamber SEL Insulation layer

Claims (13)

(A1) A step of applying an electrode material slurry on the surface of the current collector foil using the first coating portion,
(B1) a step of solidifying the surface layer of the electrode material slurry by supplying the electrode material slurry with a first solidified liquid containing a component that precipitates a binder component contained in the electrode material slurry;
(C1) After the step (b1), a step of applying an insulating material slurry on the electrode material slurry using a second coating part,
(D1) drying the electrode material slurry and the insulating material slurry;
A method for producing a lithium ion secondary battery. In the manufacturing method of the lithium ion secondary battery of Claim 1,
(C2) After the step (c1) and before the step (d1), the binder contained in each of the electrode material slurry and the insulating material slurry with respect to the electrode material slurry and the insulating material slurry The manufacturing method of a lithium ion secondary battery which further has the process of solidifying the said electrode material slurry and the said insulating material slurry by supplying the 2nd solidification liquid containing the component which deposits a component. In the manufacturing method of the lithium ion secondary battery of Claim 1,
The solvent contained in the electrode material slurry is an aprotic polar solvent,
The method for producing a lithium ion secondary battery, wherein the solvent used in the first solidified liquid is water, alcohols, or a mixture thereof. In the manufacturing method of the lithium ion secondary battery of Claim 1,
The solvent contained in the electrode material slurry is N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, dimethylformamide, or γ-butyrolactone, or a mixture thereof.
The method for producing a lithium ion secondary battery, wherein the solvent used in the first solidified solution is water, ethanol, isopropyl alcohol, or a mixture thereof. In the manufacturing method of the lithium ion secondary battery of Claim 1,
The method for producing a lithium ion secondary battery, wherein the alcohol concentration of the first solidified liquid supplied in the step (b1) is 20 to 80%. A first coating part for applying an electrode material slurry to the surface of the current collector foil;
A first solidification chamber for solidifying a surface layer of the electrode material slurry by supplying a first solidification liquid containing a component for precipitating a binder component contained in the electrode material slurry to the electrode material slurry;
A second coating portion for applying an insulating material slurry on the electrode material slurry on which the surface layer is solidified;
A drying chamber for drying the electrode material slurry and the insulating material slurry;
A transport section for transporting the current collector foil in the order of the first coating section, the first solidification chamber, the second coating section, 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 6,
The electrode material slurry and the insulating material slurry are supplied to the electrode material slurry and the insulating material slurry by supplying a second solidified liquid containing a component for precipitating the binder component contained in the electrode material slurry and the insulating material slurry. A second solidification chamber for solidifying the slurry;
The transport unit transports the current collector foil in the order of the first coating unit, the first solidification chamber, the second coating unit, the second solidification chamber, and the drying chamber. Secondary battery manufacturing equipment. In the manufacturing apparatus of the lithium ion secondary battery according to claim 6,
The solvent contained in the electrode material slurry is an aprotic polar solvent,
The manufacturing apparatus of a lithium ion secondary battery, wherein the solvent used in the first solidified liquid is water, alcohols, or a mixture thereof. In the manufacturing apparatus of the lithium ion secondary battery according to claim 6,
The solvent contained in the electrode material slurry is N-methylpyrrolidone, dimethyl sulfoxide, propylene carbonate, dimethylformamide, or γ-butyrolactone, or a mixture thereof.
The lithium ion secondary battery manufacturing apparatus, wherein the solvent used in the first solidified liquid is water, ethanol, isopropyl alcohol, or a mixture thereof. In the manufacturing apparatus of the lithium ion secondary battery according to claim 6,
The spray nozzle provided in the first solidification chamber for supplying the first solidification liquid is an internal mixing type two-fluid nozzle,
The spray region by the spray nozzle has a uniform flow distribution, and the position where the flow rate is 50% of the flow rate at the center of the spray nozzle is the end of the electrode material slurry in a direction orthogonal to the conveying direction of the current collector foil. Located outside the
The spray particle diameter of the first solidified liquid supplied from the spray nozzle is 10 μm or less,
The apparatus for producing a lithium ion secondary battery, wherein the spray hitting force of the first solidified liquid is 1 g / cm ² or less.   The lithium ion secondary battery formed using the manufacturing apparatus of the lithium ion secondary battery of Claim 8. The lithium ion secondary battery according to claim 11,
An electrode layer formed by drying the electrode material slurry on the current collector foil;
An insulating layer formed by drying the insulating material slurry on the electrode material slurry;
A mixed layer of the electrode layer and the insulating layer formed in the vicinity of the interface between the electrode layer and the insulating layer;
Have
The lithium ion secondary battery, wherein a thickness of the mixed layer is 20% or less of a thickness of the insulating layer. The lithium ion secondary battery according to claim 11,
The current collector foil;
An electrode layer formed by drying the electrode material slurry on the current collector foil;
An insulating layer formed by drying the insulating material slurry on the electrode material slurry;
A lithium ion secondary battery having a structure in which a plurality of electrode plates having a plurality of layers are stacked.

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