JP7257159B2 - Granulated particles for electrode and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to granulated particles for electrodes and a method for producing the same.

2. Description of the Related Art In recent years, various electric vehicles are expected to spread toward solving environmental and energy problems. Development of a secondary battery is earnestly carried out as an in-vehicle power source such as a power source for driving a motor, which holds the key to popularization of these electric vehicles.

As a method for manufacturing a battery electrode, for example, a method of manufacturing an electrode using a powdery electrode material is known. For example, Patent Document 1 below discloses a method for producing a battery electrode, in which granulated particles containing an electrode active material and a conductive aid are used as an electrode material, and the granulated particles are supplied onto a current collector and deposited. It is

JP 2016-062654 A

The inventors of the present invention conducted studies using granulated particles in a powder state as disclosed in Patent Document 1, and found that there is still room for improvement in the resistance value of the granulated particles. . If it is possible to reduce the resistance value between granulated particles containing an electrode active material and a conductive aid or between granulated particles, it is expected that the internal resistance value of electrodes and batteries produced using the granulated particles can be reduced. It is preferable because

Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a means capable of reducing the resistance value of granulated particles containing an electrode active material and a conductive aid.

To achieve the above object, the electrode granulated particles according to the present invention contain a solid content of 70% by mass or more including an electrode active material and a conductive aid. The granulated particles are characterized by having a volume average particle diameter D50 of 310 μm or less and an angle of repose of 35 to 51°.

According to the granulated particles for electrode according to the present invention, it is possible to manufacture an electrode having a low internal resistance value.

1 is a cross-sectional view showing an outline of the overall structure of a battery according to one embodiment of the present invention; FIG. 1 is a cross-sectional view schematically showing a stirring device for producing granulated particles according to one embodiment of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention should be determined based on the description of the claims and is not limited only to the following embodiments. In the following, for the sake of convenience, the battery according to the present invention will be described, and then the method for manufacturing the battery electrode according to the present invention will be described in detail. Note that the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from the actual ratios. In this specification, "X to Y" indicating a range means "X or more and Y or less".

<Battery>
A bipolar lithium ion secondary battery, which is one type of non-aqueous electrolyte secondary battery, will be described as an example of a battery according to an embodiment of the present invention. Here, a bipolar lithium ion secondary battery is a secondary battery that includes a bipolar electrode and is charged or discharged by moving lithium ions between a positive electrode and a negative electrode. In the following description, the bipolar lithium ion secondary battery is simply referred to as "battery".

FIG. 1 is a cross-sectional view schematically showing a battery 10 according to one embodiment of the invention. As shown in FIG. 1, the battery 10 preferably has a structure in which the power generation element in which the charge/discharge reaction actually progresses is sealed inside the exterior body 12 in order to prevent external impact and environmental deterioration. preferable.

As shown in FIG. 1, the power generation element of the battery 10 of this embodiment is a laminate 11 formed by stacking a plurality of single cells 20 . Hereinafter, the power generating element is also referred to as "laminate 11". It is preferable to adjust the number of times the unit cells 20 are stacked according to the desired voltage.

As shown in FIG. 1, positive electrode 30a and negative electrode 30b are formed with positive electrode active material layer 32a electrically coupled to one surface of current collector 31, and electrically connected to the opposite surface of current collector 31. A bipolar electrode 35 having a bonded negative electrode active material layer 32b is formed.

In FIG. 1, the current collector 31 is illustrated as a laminated structure (two-layer structure) in which the positive electrode current collector 31a and the negative electrode current collector 31b are combined, but it is a single layer structure made of a single material. may

Furthermore, in the battery 10 shown in FIG. 1 , a positive electrode current collector plate (positive electrode tab) 34 a is arranged adjacent to the positive electrode current collector 31 a on the positive electrode side, and this is extended and led out from the package 12 . On the other hand, a negative electrode current collector plate (negative electrode tab) 34b is arranged so as to be adjacent to the negative electrode current collector 31b on the negative electrode side.

[Current collector]
The current collector 31 (adjacent positive electrode current collector 31a and negative electrode current collector 31b) mediates transfer of electrons from one surface in contact with the positive electrode active material layer 32a to the other surface in contact with the negative electrode active material layer 32b. It has the function to The material constituting the current collector 31 is not particularly limited, but for example, conductive resin or metal can be used.

From the viewpoint of reducing the weight of the current collector 31, the current collector 31 is preferably a resin current collector made of a conductive resin. From the viewpoint of blocking the movement of lithium ions between the single cells 20, a metal layer may be provided on a part of the resin current collector.

Specifically, examples of the conductive resin that is the constituent material of the resin current collector include a resin obtained by adding a conductive filler to a conductive polymer material or a non-conductive polymer material as necessary. . Examples of conductive polymer materials include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, and polyoxadiazole. Such a conductive polymer material has sufficient conductivity without adding a conductive filler, and is therefore advantageous in terms of facilitating the manufacturing process and reducing the weight of the current collector.

Examples of non-conductive polymer materials include polyethylene (PE; high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), and polyimide. (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethylacrylate (PMA), polymethylmethacrylate (PMMA) , polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or polystyrene (PS). Such non-conductive polymeric materials can have excellent electrical potential or solvent resistance.

Any electrically conductive filler can be used without particular limitation. Examples of materials having excellent conductivity, potential resistance, or lithium ion blocking properties include metals and conductive carbon. The metal is not particularly limited, but at least one metal selected from the group consisting of nickel, titanium, aluminum, copper, platinum, iron, chromium, tin, zinc, indium, antimony, and potassium, or these metals It preferably contains an alloy or metal oxide containing Also, the conductive carbon is not particularly limited. Preferably, from the group consisting of acetylene black, Vulcan (registered trademark), Black Pearl (registered trademark), carbon nanofiber, Ketjenblack (registered trademark), carbon nanotube (CNT), carbon nanohorn, carbon nanoballoon, and fullerene It is preferable to include at least one selected.

The amount of the conductive filler added is not particularly limited as long as it is an amount that can impart sufficient conductivity to the current collector 31, and is preferably about 5 to 35% by mass, more preferably 10 to 30% by mass. Yes, more preferably 15 to 20% by mass.

When the current collector 31 is made of metal, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plated material of these metals can be preferably used. Alternatively, a foil in which a metal surface is coated with aluminum may be used. Among them, aluminum, stainless steel, copper, and nickel are preferable from the viewpoint of electronic conductivity, battery operating potential, adhesion of the negative electrode active material to the current collector 31 by sputtering, and the like.

[Electrode active material layer (positive electrode active material layer, negative electrode active material layer)]
The electrode active material layer (positive electrode active material layer 32a, negative electrode active material layer 32b) 32 has electrode active material (positive electrode active material or negative electrode active material) and electrode granulated particles containing a conductive aid. The electrode granulated particles may further contain an electrolytic solution and/or an adhesive, if necessary. Moreover, the electrode active material layer 32 may contain an ion conductive polymer or the like, if necessary.

(Granulated particles for electrodes)
The electrode granulated particles (also simply referred to as “granulated particles”) according to the present invention contain a solid content containing an electrode active material and a conductive aid in an amount of 70% by mass or more, and have a volume average particle diameter D50 of 310 μm or less. It has an angle of repose of 35-51°. The granulated particles are powdery granulated particles that essentially contain an electrode active material and a conductive aid, and may further contain a liquid component (preferably an electrolytic solution) and an adhesive.

As used herein, the term “powder state” refers to an aggregate of granulated particles in which the components present in the system exhibit substantially solid properties, and the aggregate includes a single granulated particle and a plurality of granulated particles. It is defined as including at least one of aggregates in which the granulated particles are aggregated. For example, when a system is in a solution state or a slurry state due to the presence of a relatively large amount of a liquid component, it is not in a "powder state". As long as this definition is satisfied, the granulated particles may contain a liquid component such as an electrolytic solution. In particular, the granulated particles preferably contain a liquid component such as an electrolytic solution (preferably, an electrolytic solution) from the viewpoint of facilitating adjustment of the particle size. The content of the liquid component at this time is not particularly limited as long as the "powder state" is maintained, but it is preferably 0 to 10% by mass, more preferably 0% by mass based on 100% by mass of the granulated particles. 0.01 to 8% by mass, more preferably 0.1 to 5% by mass, and particularly preferably 0.1 to 3% by mass. Correspondingly, the amount of solids contained in the granulated particles for electrodes is preferably 90 to 100% by mass, more preferably 92 to 99.99% by mass with respect to 100% by mass of the granulated particles. %, more preferably 95 to 99.9% by mass, particularly preferably 97 to 99.9% by mass. In the present specification, the term "solid content" refers to a component excluding granulated particles, such as a solvent contained in an electrolytic solution, which volatilizes at room temperature or by heating if necessary. Contains an adhesive (binder) that

The volume average particle diameter D50 (also simply referred to as “D50”) of the granulated particles according to the present invention is 310 μm or less. As the value of this D50, a value measured by the method described in the section of Examples to be described later shall be adopted. D50 is preferably 300 μm or less, more preferably 280 μm or less, still more preferably 240 μm or less, still more preferably 200 μm or less, and particularly preferably 180 μm or less. If the particle size of the granulated particles is too large, the gaps between the particles become large, which is considered to be the cause of the increase in the resistance value. Although the lower limit of D50 is not particularly limited, if the particle diameter of the granulated particles is too small, the fluidity will be poor and it will be difficult to form the electrode when producing the electrode. From the above viewpoint, the particle size of the granulated particles is preferably 43 μm or more, more preferably 45 μm or more, and still more preferably 50 μm or more.

The volume-average particle diameter D50 of the granulated particles is measured by the method described in the following examples carried out according to the method described in JISZ8815-1994 General rules for sieving test methods.

The angle of repose of the granulated particles according to the present invention is 35 to 51°. The angle of repose is preferably 50° or less, more preferably 48° or less, and even more preferably 46° or less. If the angle of repose of the granulated particles is too large, the fluidity will decrease, making it difficult to mold the electrode during electrode production. The angle of repose of the granulated particles is preferably 36° or more, more preferably 40° or more, and even more preferably 44° or more. If the angle of repose of the granulated particles is too small, it is considered to cause an increase in the resistance value.

In the present invention, the angle of repose refers to the maximum angle of the slope at which the granulated particles are spontaneously kept stable without collapsing when they are piled up. Also, the angle of repose shall be measured using the method of JIS R9301-2-2.

(Positive electrode active material)
As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li(Ni—Mn—Co)O ₂ and those obtained by partially replacing these transition metals with other elements, such as lithium- Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, and the like. In some cases, two or more positive electrode active materials may be used together. From the viewpoint of capacity and output characteristics, lithium-transition metal composite oxides are preferably used as the positive electrode active material. A composite oxide containing lithium and nickel is more preferably used. More preferably, Li(Ni-Mn-Co)O ₂ and those in which a portion of these transition metals are replaced with other elements (hereinafter simply referred to as "NMC composite oxide"), or lithium-nickel-cobalt - Aluminum composite oxide (hereinafter simply referred to as "NCA composite oxide") or the like is used. The NMC composite oxide has a layered crystal structure in which lithium atomic layers and transition metal (Mn, Ni and Co are arranged in an orderly manner) atomic layers are alternately stacked via oxygen atomic layers. In addition, one Li atom is contained per transition metal atom, and the amount of Li that can be taken out is double that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, and a high capacity can be obtained.

(Negative electrode active material)
Examples of the negative electrode active material include carbon materials such as graphite (graphite), soft carbon and hard carbon, lithium-transition metal composite oxides (eg, Li ₄ Ti ₅ O ₁₂ ), metal materials (tin, silicon), lithium Alloy negative electrode materials (eg, lithium-tin alloys, lithium-silicon alloys, lithium-aluminum alloys, lithium-aluminum-manganese alloys, etc.). In some cases, two or more kinds of negative electrode active materials may be used together. Carbon materials, lithium-transition metal composite oxides, and lithium alloy negative electrode materials are preferably used as the negative electrode active material from the viewpoint of capacity and output characteristics. Needless to say, negative electrode active materials other than those described above may be used. In addition, coating resins such as (meth)acrylate copolymers have the property of being particularly prone to adhere to carbon materials. Therefore, from the viewpoint of providing a structurally stable electrode material, it is preferable to use a carbon material as the negative electrode active material.

(Conductivity aid)
The conductive aid forms an electron conduction path and reduces the electron transfer resistance of the electrode active material layer 32, thereby contributing to the improvement of high-rate output characteristics of the battery.

Examples of conductive aids include metals such as aluminum, stainless steel, silver, gold, copper, and titanium, alloys containing these metals, and metal oxides; carbon fibers (specifically, vapor grown carbon fibers (VGCF) etc.), carbon nanotubes (CNT), carbon nanofibers, carbon black (specifically, acetylene black, Ketjenblack (registered trademark), furnace black, channel black, thermal lamp black, etc.). , but not limited to. In addition, a particulate ceramic material or resin material coated with the above metal material by plating or the like can also be used as a conductive aid. Among these conductive aids, from the viewpoint of electrical stability, it is preferable to include at least one selected from the group consisting of aluminum, stainless steel, silver, gold, copper, titanium, and carbon. , silver, gold, and carbon, and more preferably at least one selected from the group consisting of carbon. These conductive aids may be used alone or in combination of two or more.

The shape of the conductive aid is preferably particulate or fibrous. When the conductive agent is particulate, the shape of the particles is not particularly limited, and may be powdery, spherical, rod-like, needle-like, plate-like, columnar, amorphous, scaly, spindle-like, or the like. I don't mind. The average particle size (primary particle size) of the conductive aid in the form of particles is preferably 100 nm or less, more preferably 60 nm or less, and even more preferably 40 nm or less. Further, when the conductive additive is fibrous, the aspect ratio is preferably 300 or less, more preferably 150 or less, and even more preferably 90 or less. When the conductive additive is fibrous, the average fiber diameter is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 150 nm or less. When the conductive additive is fibrous, the average fiber length is preferably 50 µm or less, more preferably 20 µm or less, and even more preferably 10 µm or less.

In addition, the "particle size" of the conductive aid means the maximum distance among the distances between any two points on the outline of the conductive aid. The value of "average particle size" is the average value of the particle size of particles observed in several to several tens of fields of view using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. The fiber diameter and fiber length of the fibrous conductive additive can be the average value of several to several tens of fiber diameters actually measured using a transmission electron microscope (TEM) or a scanning electron microscope (SEM). .

The content of the conductive additive in the electrode granulated particles is not particularly limited, but the conductive additive is preferably contained in an amount of 0.01 to 10% by mass based on the total mass of the solid content of the electrode granulated particles. 1 to 8% by mass, more preferably 1 to 6% by mass. Within such a range, the conductive aid can satisfactorily form an electron conduction path in the electrode active material layer 32 .

(Electrolyte)
The granulated particles according to the present invention may further contain an electrolytic solution in order to adjust the particle size. As the content of the electrolytic solution increases, the particle size of the granulated particles tends to increase. The content of the electrolytic solution is not particularly limited as long as the "powder state" is maintained. 01 to 8% by mass, more preferably 0.1 to 5% by mass, particularly preferably 0.1 to 3% by mass.

The electrolytic solution has a form in which a lithium salt is dissolved in a solvent. Examples of the solvent that constitutes the electrolytic solution of the present invention include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethylmethyl carbonate. Lithium salts include inorganic acid lithium salts such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ LiClO ₄ , Li[(FSO ₂ ) ₂ N] (LiFSI), LiN(CF ₃ SO ₂ ) ₂ , LiN( C ₂ F ₅ SO ₂ ) ₂ and lithium salts of organic acids such as LiC(CF ₃ SO ₂ ) ₃ and the like. The lithium salt concentration in the electrolytic solution is preferably 0.1 to 3.0M, more preferably 0.8 to 2.2M. In addition, when using an additive, the amount used is preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass, with respect to 100% by mass of the electrolytic solution before adding the additive. be.

Examples of additives include vinylene carbonate, methylvinylene carbonate, dimethylvinylene carbonate, phenylvinylene carbonate, diphenylvinylene carbonate, ethylvinylene carbonate, diethylvinylene carbonate, vinylethylene carbonate, 1,2-divinylethylene carbonate, 1-methyl- 1-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-1-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, vinylvinylene carbonate, allylethylene carbonate, vinyloxymethylethylene carbonate, allyloxymethylethylene carbonate, acryloxymethylethylene carbonate, methacryloxymethylethylene carbonate, ethynylethylene carbonate, propargylethylene carbonate, ethynyloxymethylethylene carbonate, propargyloxyethylene carbonate, methyleneethylene carbonate, 1,1-dimethyl-2-methylene ethylene carbonate and the like. Among them, vinylene carbonate, methylvinylene carbonate and vinylethylene carbonate are preferred, and vinylene carbonate and vinylethylene carbonate are more preferred. These cyclic carbonates may be used alone or in combination of two or more.

(adhesive)
The granulated particles according to the present invention may further contain an adhesive (binder) as a solid content in order to adjust the particle size. When the content of the adhesive is increased, the particle size of the granulated particles tends to increase.

Examples of adhesives include (meth)acrylic acid ester-based pressure-sensitive adhesives such as Polysic (registered trademark) series. The content of the adhesive in the granulated particles is preferably 0.01 to 10% by mass, more preferably 0.01 to 8% by mass, based on the total mass of the solid content of the granulated particles. Yes, more preferably 0.1 to 5% by mass, particularly preferably 0.1 to 3% by mass.

(ion conductive polymer)
Ion-conducting polymers include, for example, known polyoxyalkylene oxide polymers based on polyethylene oxide (PEO) and polypropylene oxide (PPO).

The method for producing the electrode granulated particles described above is not particularly limited as long as it includes the step of obtaining granulated particles having the characteristics described above (granulation step). An example of a preferred method for producing granulated particles will be briefly described below.

[Granulation process]
In the granulation step, raw materials containing the electrode active material and the conductive aid are mixed using a stirring device to produce granulated particles in a powder state.

FIG. 2 is a schematic cross-sectional view showing an example of a stirring device. The stirring device 100 shown in FIG. 2 includes a rotating container 110 that rotates about a central axis O1 in a state in which granulated particles are accommodated, and a central axis housed in the rotating container 110 and arranged at a position different from the central axis O1. and a stirring blade 120 that rotates around O2. Stirring blade 120 is attached to shaft 121 extending along central axis O2. The stirring device 100 can generate a turbulent flow as indicated by an arrow F in FIG. . Thereby, the stirring effect of the stirring device 100 can be improved. That is, according to another aspect of the present invention, there is provided a method for manufacturing granulated particles for batteries, which includes a granulating step performed using a stirring device as shown in FIG. Specifically, the manufacturing method includes a rotating container that rotates about a central axis while containing a raw material, and a central axis that is housed in the rotating container and arranged at a position different from the central axis of the rotating container. It includes granulating a solid content containing an electrode active material and a conductive aid using an agitating device having a centrally rotating agitating blade.

Note that the configuration of the stirring device is not limited to the stirring device 100 shown in FIG. can be used.

In the granulation step, an electrode active material and a conductive aid are put into a rotating container of a stirring device and stirred to produce granulated particles in a powder state (hereinafter also referred to as "first granulated particles"). (hereinafter also referred to as "first granulation step"). In the granulation step, an electrode active material, a conductive agent and a liquid component (preferably an electrolytic solution) are put into a rotating container of a stirring device and stirred to form granulated particles in a powder state (hereinafter referred to as "second (also referred to as "granulated particles") (hereinafter also referred to as "second granulation step"). Further, in the granulation step, an electrode active material, a conductive aid, a liquid component (preferably an electrolytic solution) and an adhesive are put into a rotating container of a stirring device and stirred to form granulated particles in a powder state (hereinafter referred to as A granulation step (hereinafter also referred to as a "third granulation step") for producing "third granulated particles") may be included. In addition, the first granulation step, the second granulation step and the third granulation step are independent steps for producing different granulated particles (first granulated particles, second granulated particles, third granulated particles). Only one of the steps can be performed as the granulation step. Each granulation step will be briefly described below.

(First Granulation Step)
In the first granulation step, an electrode active material and a conductive aid are put into a rotating container 110 of a stirring device 100 and stirred to produce first granulated particles in a powder state. In the first granulation step, a dry mixing process is performed. The treatment conditions for the mixing treatment are determined so that the electrode active material and the conductive aid are uniformly mixed and have a particle size and fluidity that facilitate molding into an electrode.

The treatment conditions for the mixing treatment include stirring speed, stirring time, stirring temperature, and the like. The stirring speed is the peripheral speed of the stirring blades 120 of the stirring device 100 . Here, the “peripheral speed” is the speed at the outermost peripheral position (maximum radius position) of the stirring blade 120, which is a rotating body. can be expressed as peripheral speed=2πnr. The peripheral speed is set to a value that can generate enough shear energy to granulate without destroying the granulated particles, depending on device conditions such as the size and shape of the rotating container 110 and the shape, number, and arrangement of the stirring blades 120. It can be set as appropriate. The peripheral speed is not particularly limited, but is preferably 1 to 100 m/s, more preferably 10 to 50 m/s, even more preferably 15 to 30 m/s, and particularly preferably 17 to 25 m/s. be. Moreover, when the peripheral speed increases, the particle size of the granulated particles tends to decrease. If the peripheral speed is within the above range, granulated particles having an appropriate particle size can be obtained in combination with conditions such as the contents of the pressure-sensitive adhesive and the electrolytic solution.

The stirring time can be appropriately set to a time sufficient to granulate the electrode active material and the conductive aid. The stirring time is not particularly limited, but preferably 1 to 20 minutes, more preferably 1 to 10 minutes, even more preferably 3 to 8 minutes, and particularly preferably 5 to 7 minutes. As for the stirring time, the stirring may be performed continuously once, or may be divided into several times and stirred for the total stirring time. The stirring temperature is also not particularly limited, but can be set to 10 to 25° C., for example.

(Second granulation step)
In the second granulation step, the electrode active material, the conductive aid and the liquid component (preferably the electrolytic solution) are stirred in the rotating container 110 of the stirring device 100 to produce second granulated particles in a powder state. In the second granulation step, since liquid components are used, a wet mixing process is performed.

In the second granulation step, a liquid component may be added to the first granulated particles granulated in the first granulation step to perform a mixing treatment, or the electrode active material, the conductive aid and the liquid before the mixing treatment may be mixed. The ingredients may be mixed together.

The treatment conditions for the mixing treatment are determined so that the electrode active material, the conductive aid and the liquid component are uniformly mixed and have a particle size and fluidity that facilitate molding into the electrode. The stirring speed (peripheral speed) is not particularly limited, but is preferably 1 to 100 m/s, more preferably 5 to 50 m/s, still more preferably 10 to 30 m/s, particularly preferably 10 to 20 m/s. Moreover, when the peripheral speed increases, the particle size of the granulated particles tends to decrease. If the peripheral speed is within the above range, granulated particles having an appropriate particle size can be obtained in combination with conditions such as the contents of the pressure-sensitive adhesive and the electrolytic solution.

The stirring time can be appropriately set to a time sufficient to granulate the electrode active material, conductive aid and liquid component. The stirring time is not particularly limited, but preferably 1 to 20 minutes, more preferably 1 to 10 minutes, even more preferably 3 to 8 minutes, and particularly preferably 5 to 7 minutes. As for the stirring time, the stirring may be performed continuously once, or may be divided into several times and stirred for the total stirring time. The stirring temperature is also not particularly limited, but can be set to 10 to 25° C., for example.

(Third granulation step)
In the third granulation step, the electrode active material, the conductive aid, the liquid component (preferably the electrolytic solution), and the adhesive are stirred in the rotating container 110 of the stirring device 100 to produce third granulated particles in a powder state. manufacture. In the third granulation step, a wet mixing process is performed because liquid components are used. In the third granulation step, the pressure-sensitive adhesive may be diluted with a liquid component as a solvent and then mixed, and the liquid component may be dried after the mixing process.

In the third granulation step, a pressure-sensitive adhesive may be added to the second granulated particles granulated in the second granulation step and mixed, or the first granulated particles granulated in the first granulation step may be mixed. A liquid component and an adhesive may be added to the granules and mixed. Alternatively, the electrode active material, the conductive aid, the liquid component and the adhesive may be mixed at the same time before being mixed.

The treatment conditions for the mixing treatment are determined so that the electrode active material, the conductive aid and the liquid component are uniformly mixed and have a particle size and fluidity that facilitate molding into the electrode. The stirring speed (peripheral speed) is not particularly limited, but is preferably 1 to 100 m/s, more preferably 5 to 50 m/s, still more preferably 10 to 30 m/s, particularly preferably 10 to 20 m/s. Moreover, when the peripheral speed increases, the particle size of the finally obtained granulated particles tends to decrease. If the peripheral speed is within the above range, granulated particles having an appropriate particle size can be obtained in combination with conditions such as the contents of the pressure-sensitive adhesive and the electrolytic solution.

In the mixing process, stirring may be continuously performed at one time, or may be performed intermittently with a rest time during which the stirring is temporarily stopped. The stirring time can be appropriately set to a time sufficient to granulate the electrode active material, conductive aid and liquid component. The stirring time is not particularly limited, but is preferably 3 to 60 minutes, more preferably 5 to 30 minutes, even more preferably 10 to 15 minutes, particularly preferably 15 minutes. As for the stirring time, the stirring may be performed continuously once, or may be divided into several times and stirred for the total stirring time.

The stirring temperature is also not particularly limited, but can be set to 10 to 25° C., for example. When the liquid component is dried after the mixing process, the drying temperature can be, for example, 40 to 70° C., and the drying time can be, for example, 90 to 140 minutes.

The granulated particles described above can be used as a raw material for manufacturing an electrode. That is, according to still another aspect of the present invention, an electrode containing the electrode granulated particles according to one aspect described above can be provided. The manufacturing method of the electrode according to this embodiment is not particularly limited, and a manufacturing method capable of forming an electrode active material layer containing the above-described granulated particles on at least one surface of a current collector can be appropriately employed. As an example, a method for manufacturing an electrode includes a step of supplying the above-described granulated particles for an electrode to the surface of a current collector (supplying step), and pressing the granulated particles supplied to the surface of the current collector in the thickness direction. and a step (pressing step).

[Supply process]
In the supplying step, the granulated particles obtained above are supplied to the surface of the current collector 31 . Specifically, for example, a parts feeder is used to supply a fixed amount of granulated particles to the surface of the current collector 31 that moves relative to the parts feeder. Here, "quantitative supply" means that the supply amount per unit time is substantially the same. The granulated particles may be supplied continuously or intermittently to the current collector 31 . The current collector 31 is transported by a transport device such as a conveyor. The supply speed of the parts feeder and the transport speed of the current collector 31 are determined in consideration of the fluidity of the particles, the required thickness of the electrode active material layer, etc., so that the granulated particles are distributed to the surface of the current collector 31 at a uniform density. (thickness and amount) can be deposited. The parts feeder for carrying out the supply step is not particularly limited, and conventionally known parts feeders can be used as appropriate.

Note that the particle size of the granulated particles supplied between the parts feeder and the current collector 31 may be sorted through a sieve or the like. By selecting the particle size of the granulated particles, it is possible to eliminate aggregates in which granulated particles are aggregated together and granulated particles with an excessively large particle size, thereby supplying granulated particles with a more uniform particle size. can.

Further, the surface of the granulated particles supplied to the current collector 31 may be leveled by a squeegee, a rotating roller, or the like so that the thickness is constant.

[Pressing process]
In the pressing step, the granulated particles supplied to the surface of the current collector 31 are pressed in the thickness direction to fabricate the electrode. By pressing the granulated particles deposited on the surface of the current collector 31, the granulated particles can be densified and the thickness can be made more uniform. A press device for carrying out the pressing step is not particularly limited, and a conventionally known press device can be used as appropriate. For example, a roll press device equipped with a pressure roller, a surface press device equipped with a pressure surface, and the like can be used. From the viewpoint of applying pressure without interfering with the transport (movement) of the current collector 31, it is preferable to use a roll press device. The pressure per unit area applied to the granulated particles during pressing is not particularly limited, but is preferably 0.01 to 40 MPa, more preferably 1 to 30 MPa, and still more preferably 10 to 20 MPa. When the pressure is within the above range, the porosity and density of the electrode active material layer according to the preferred embodiment described above can be easily achieved.

<Constituent elements other than electrodes>
The current collector and the electrode active material layer among the constituent elements of the bipolar secondary battery according to the preferred embodiment of the present invention have been described in detail above. can be

[Electrolyte layer]
The electrolyte layer 40 is a layer in which an electrolyte is held in a separator, and is located between the positive electrode active material layer 32a and the negative electrode active material layer 32b to prevent the two from coming into direct contact with each other. The electrolyte used for the electrolyte layer 40 of the present embodiment is not particularly limited, and examples thereof include electrolyte solutions and gel polymer electrolytes. By using these electrolytes, high lithium ion conductivity can be ensured.

As the electrolytic solution, the same electrolytic solution that may be contained in the granulated particles described above may be used.

The separator has a function of retaining the electrolyte to ensure lithium ion conductivity between the positive electrode 30a and the negative electrode 30b, and a function of a partition wall between the positive electrode 30a and the negative electrode 30b.

Examples of the form of the separator include porous sheet separators and non-woven fabric separators made of polymers or fibers that absorb and retain the electrolyte.

[Positive collector plate and negative collector plate]
The material constituting the current collectors 34a and 34b is not particularly limited, and known highly conductive materials conventionally used as current collectors for lithium ion secondary batteries can be used. Metal materials such as aluminum, copper, titanium, nickel, stainless steel, and alloys thereof are preferable as the constituent material of the current collector plates 34a and 34b. From the viewpoint of light weight, corrosion resistance and high conductivity, aluminum and copper are more preferred, and aluminum is particularly preferred. The same material or different materials may be used for the positive electrode collector plate 34a and the negative electrode collector plate 34b.

[Seal part]
The sealing portion 50 has a function of preventing contact between the current collectors 31 and short circuiting at the ends of the unit cells 20 . The material constituting the sealing portion 50 may be any material that has insulating properties, sealing properties (liquid-tightness), heat resistance under the battery operating temperature, and the like. For example, acrylic resin, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber (ethylene-propylene-diene rubber: EPDM), and the like can be used. Alternatively, an isocyanate-based adhesive, an acrylic resin-based adhesive, a cyanoacrylate-based adhesive, or the like may be used, or a hot-melt adhesive (urethane resin, polyamide resin, polyolefin resin) or the like may be used. Among them, polyethylene resin and polypropylene resin are preferably used as constituent materials of the insulating layer from the viewpoint of corrosion resistance, chemical resistance, ease of production (film forming property), economy, etc., and amorphous polypropylene resin is the main component. It is preferable to use a resin obtained by copolymerizing ethylene, propylene, and butene.

[Exterior body]
In the present embodiment shown in FIG. 1, the exterior body 12 is configured in a bag shape with a laminated film, but the exterior body 12 is not limited to this, and for example, a known metal can case or the like may be used. The exterior body 12 is preferably made of a laminate film from the viewpoint of high output and excellent cooling performance, and being suitable for use in batteries for large equipment such as EVs and HEVs. As the laminate film, for example, a laminate film having a three-layer structure in which polypropylene (PP), aluminum, and nylon are laminated in this order can be used, but the film is not limited to these. Further, the outer package 12 is more preferably a laminate film containing aluminum because the group pressure applied to the laminate 11 from the outside can be easily adjusted and the thickness of the electrolyte layer 40 can be easily adjusted to a desired thickness.

A bipolar lithium ion secondary battery, which is one type of non-aqueous electrolyte secondary battery, has been described as an example of the battery according to the embodiment of the present invention, but the battery to which the present invention is applied is limited to the bipolar lithium ion secondary battery. not. For example, the present invention can be applied to any conventionally known secondary battery such as a so-called parallel stacked battery in which electrodes are connected in parallel in a power generating element. Among them, the battery according to the present invention is preferably a nonaqueous electrolyte secondary battery, more preferably a lithium ion secondary battery.

The present invention will be described in more detail below with reference to examples. However, the technical scope of the present invention is not limited only to the following examples. In addition, "parts" means "parts by mass" unless otherwise specified.

Example 1
[Production of positive electrode granulated particles 1]
Lithium-nickel-cobalt-aluminum composite oxide (NCA composite oxide) as a positive electrode active material is placed in a stirring tank of a stirring device (manufactured by Eirich Japan Co., Ltd., Eirich Intensive Mixer, see JP-A-2013-017923). (BASF Toda Battery Materials LLC) 98.0 parts, acetylene black (AB) as a conductive agent (Denka Black (registered trademark) manufactured by Denka Co., Ltd., average particle size (primary particle size): 0.036 μm ) 1.0 part and carbon nanofiber (CNF) as a conductive agent (manufactured by Showa Denko K.K., VGCF (registered trademark), aspect ratio 60, average fiber diameter: about 150 nm, average fiber length: about 9 μm, electrical 1.0 part of resistivity of 40 μΩm and bulk density of 0.04 g/cm ³ ) was added and stirred at room temperature at a stirring speed of 20 m/s for 7 minutes. By this stirring, the positive electrode granulated particles 1 were produced.

[Evaluation of positive electrode granulated particles 1: measurement of angle of repose]
Using the method of JIS R9301-2-2, the angle of repose of the positive electrode granulated particles 1 was measured. Specifically, in a dry room, 5 g of the powder of the positive electrode granulated particles 1 was placed in a funnel, dropped onto a tray while being vibrated, and the angles of the mountain slopes were measured in four directions using a laser displacement meter. The average value of the angles was calculated as the angle of repose. Table 1 shows the results.

[Evaluation of Granulated Particles 1 for Positive Electrode: Volume Average Particle Size (D50)]
3 g of the positive electrode granulated particles 1 powder was set in a robot shifter (manufactured by Seishin Enterprise Co., Ltd.), and sonic vibration was applied to the sieve to classify the powder. At this time, three metal sieve nets with different openings are used, and the openings of the three metal sieve nets are 500 μm/425 μm/355 μm/250 μm/200 μm/150 μm/100 μm/63 μm, respectively. The weight of the sieve was measured before and after the classification, and the particle size distribution of the introduced powder was calculated. Table 1 shows the value of the volume average particle diameter (D50) calculated from this particle size distribution.

[Evaluation of positive electrode granulated particles 1: DC resistance]
30 mg of positive electrode granulated particles 1 were placed in a polypropylene cylinder having an inner diameter of 15 mm and a height of 30 mm, and tapped 50 times. The positive electrode granulated particles 1 after tapping were further sandwiched from both sides by SUS316 cylinders, and a pressure of 100 kN was applied. The cylinder was removed, and an electrochemical measuring device (1280C manufactured by Solartron) was used to measure the DC resistance value [Ω·cm ² ] above and below the positive electrode granulated particles 1 formed into a cylindrical mass. The resistance value of was confirmed. Table 1 shows the results.

[Electrode production]
Using a twin-screw extruder, polypropylene [trade name “SunAllomer (registered trademark) PL500A” manufactured by SunAllomer Co., Ltd.] (B-1) 75% by mass, acetylene black (AB) (Denka Black (registered trademark) NH-100 ) 20% by mass, and 5% by mass of a modified polyolefin resin (Umex (registered trademark) 1001 manufactured by Sanyo Chemical Industries, Ltd.) as a dispersant (A) for a resin current collector under the conditions of 180 ° C., 100 rpm, and a residence time of 10 minutes. A material for a resin current collector was obtained by melt-kneading. The obtained resin current collector material was extruded to obtain a resin current collector (20% AB-PP) having a thickness of 90 μm. The positive electrode granulated particles 1 obtained above were quantitatively supplied to the surface of the resin current collector using a parts feeder, and then pressed. Specifically, using a roll press, the granulated particles supplied to the surface of the resin current collector were pressed so that the pressure per unit area in the thickness direction was 15 MPa. Thus, a positive electrode 1 was obtained. Thus, it was confirmed that an electrode can be produced using the positive electrode granulated particles 1 .

Example 2
[Production of positive electrode granulated particles 2]
Positive electrode granulated particles 2 were prepared in the same manner as positive electrode granulated particles 1 except that the stirring speed during preparation of the granulated particles was changed to 17 m/s.

Thereafter, the positive electrode granulated particles 2 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Example 3
[Preparation of positive electrode granulated particles 3]
A positive electrode granulated particle 3 was produced in the same manner as the positive electrode granulated particle 1, except that the stirring speed in producing the granulated particles was changed to 15 m/s.

Thereafter, the positive electrode granulated particles 3 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Example 4
[Preparation of positive electrode granulated particles 4]
A positive electrode granulated particle 4 was produced in the same manner as the positive electrode granulated particle 1, except that the stirring speed in producing the granulated particles was changed to 11 m/s.

After that, the positive electrode granulated particles 4 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Example 5
[Preparation of electrolytic solution]
Li[(FSO ₂ ) ₂ N] (LiFSI) was dissolved at a ratio of 2 mol/L in a mixed solvent of ethylene carbonate (EC) and propylene carbonate (PC) (volume ratio 1:1) to form an electrolytic solution. Obtained.

[Preparation of positive electrode granulated particles 5]
Lithium-nickel-cobalt-aluminum composite oxide (NCA composite oxide) as a positive electrode active material is placed in a stirring tank of a stirring device (manufactured by Eirich Japan Co., Ltd., Eirich Intensive Mixer, see JP-A-2013-017923). (BASF Toda Battery Materials LLC) 98.0 parts, acetylene black (AB) as a conductive agent (Denka Black (registered trademark) manufactured by Denka Co., Ltd., average particle size (primary particle size): 0.036 μm ) 1.0 part and carbon nanofiber (CNF) as a conductive agent (manufactured by Showa Denko K.K., VGCF (registered trademark), aspect ratio 60, average fiber diameter: about 150 nm, average fiber length: about 9 μm, electrical 1.0 part of resistivity 40 μΩm, bulk density 0.04 g/cm ³ ) and 1.01 part of the electrolytic solution obtained above were added, and stirred at room temperature at a stirring speed of 17 m/s for 7 minutes. rice field. By this stirring, the positive electrode granulated particles 5 were produced.

Thereafter, the positive electrode granulated particles 5 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Example 6
[Preparation of positive electrode granulated particles 6]
The positive electrode granulated particles 6 were produced in the same manner as the positive electrode granulated particles 5 except that the stirring speed during the production of the granulated particles was changed to 15 m/s.

Thereafter, the positive electrode granulated particles 6 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Example 7
[Preparation of positive electrode granulated particles 7]
Lithium-nickel-cobalt-aluminum composite oxide (NCA composite oxide) as a positive electrode active material is placed in a stirring tank of a stirring device (manufactured by Eirich Japan Co., Ltd., Eirich Intensive Mixer, see JP-A-2013-017923). (BASF Toda Battery Materials LLC) 92.0 parts, acetylene black (AB) as a conductive agent (Denka Black (registered trademark) manufactured by Denka Co., Ltd., average particle size (primary particle size): 0.036 μm ) 3.0 parts and carbon nanofiber (CNF) as a conductive agent (manufactured by Showa Denko K.K., VGCF (registered trademark), aspect ratio 60, average fiber diameter: about 150 nm, average fiber length: about 9 μm, electrical Resistivity 40 μΩm, bulk density 0.04 g/cm ³ ) 3.0 parts, Polysic (manufactured by Sanyo Chemical Industries, Ltd. Polysic 311) 2.0 parts as an adhesive, and 1.01 parts of the electrolytic solution obtained above were added, and stirred at room temperature at a stirring speed of 17 m/s for 5 minutes x 3 times (15 minutes in total). Then, it was dried at 60° C. for 120 minutes to prepare granulated particles 7 for positive electrode.

Thereafter, the positive electrode granulated particles 7 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Comparative example 1
[Production of positive electrode granulated particles C1]
The positive electrode granulated particles C1 were produced in the same manner as the positive electrode granulated particles 7, except that the stirring speed during the production of the granulated particles was changed to 15 m/s.

After that, the positive electrode granulated particles C1 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results. In addition, the electrode was not able to be produced using the granulated particle C1 for positive electrodes.

Comparative example 2
[Production of positive electrode granulated particles C2]
A positive electrode granulated particle C2 was produced in the same manner as the positive electrode granulated particle 7, except that the stirring speed in producing the granulated particles was changed to 13 m/s.

After that, the positive electrode granulated particles C2 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

Comparative example 3
[Production of positive electrode granulated particles C3]
Positive electrode granulated particles C3 were produced in the same manner as the positive electrode granulated particles 7, except that the stirring speed in producing the granulated particles was changed to 11 m/s.

After that, the positive electrode granulated particles C3 were subjected to the respective measurements and evaluations performed in Example 1. Table 1 shows the results.

The positive electrode granulated particles 1 to 7 of Examples 1 to 7 exhibited extremely small DC resistance values, and electrodes could be produced using these granulated particles. It is considered that this is because the angle of repose and the volume average particle size (D50) of the positive electrode granulated particles produced in each example are within the predetermined ranges. On the other hand, when the positive electrode granulated particles C1 produced in Comparative Example 1 were used, an electrode could not be produced, and the DC resistance value could not be measured. It is considered that this is because the electrode does not have a predetermined shape because the particle size is too small and the angle of repose is too large. In addition, when the positive electrode granulated particles C2 and C3 produced in Comparative Examples 2 and 3 were used, electrodes could be produced, but the particle diameter was too large and the angle of repose was too small. It can be seen that the DC resistance value of the granulated particles became a high value.

10 batteries,
11 laminate,
12 outer body,
20 single cells,
30 electrodes,
30a positive electrode,
30b negative electrode,
31 current collector,
31a positive electrode current collector,
31b negative electrode current collector,
32 electrode active material layer,
32a positive electrode active material layer,
32b negative electrode active material layer,
40 electrolyte layer,
50 seal part.

Claims (7)

Granulated particles for an electrode containing an electrode active material , an electrolytic solution , and a conductive aid, wherein the mass ratio of solids contained in the granulated particles is 70% by mass or more based on the total mass of the granulated particles, and Granulated particles for electrodes, wherein the volume average particle diameter D50 of the granulated particles is 310 μm or less, and the angle of repose of the powder composed of the granulated particles is 46.1 to 51°. 2. The granulated particles for electrodes according to claim 1, comprising 0.01 to 10% by mass of said conductive aid with respect to the total mass of the solid content of said granulated particles for electrodes. 3. The granulated particles for electrodes according to claim 1 , wherein the content of said electrolytic solution is 0.01 to 10% by mass with respect to the total mass of the granulated particles for electrodes. The electrode granulated particles according to any one of claims 1 to 3 , further comprising an adhesive. 5. The granulated particles for electrodes according to claim 4 , comprising 0.01 to 10% by mass of the adhesive with respect to the total mass of the solid content of the granulated particles for electrodes. a rotating container that rotates around a central axis while containing raw materials;
a stirring blade housed in the rotating container and rotating around a central axis arranged at a position different from the central axis of the rotating container;
The method for producing granulated particles for a battery according to any one of claims 1 to 5 , comprising producing the granulated particles using a stirring device having An electrode comprising the electrode granulated particles according to any one of claims 1 to 5 .

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