Composite particles for non-aqueous secondary battery electrode, method for manufacturing same, and use thereof

Abstract

These composite particles for a non-aqueous secondary battery electrode contain electrode active material particles and a binder, and have an adhesion index of 22 or higher. The D50 particle diameter of the composite particles is preferably 75-80 μm, and the percentage of particles having a particle diameter of 45 μm or less is preferably 8% or less. The occupancy rate of the binder on the surface of the composite particles is preferably 50% or less. Also provided are: a method for manufacturing the composite particles; a negative electrode for non-aqueous secondary batteries in which the composite particles are used; a method for manufacturing the negative electrode; and a non-aqueous secondary battery.

Description

Composite particles for non-aqueous secondary battery electrodes, their manufacturing method and uses

[0001] The present invention relates to composite particles for non-aqueous secondary battery electrodes, a method for producing the same, and uses thereof.

[0002] Non-aqueous secondary batteries such as lithium ion secondary batteries are used in a wide range of applications, and there is a demand for further improvement in their performance.

[0003] A non-aqueous secondary battery typically includes positive and negative electrodes, and in many cases, one or both of the electrodes includes a current collector and an electrode mixture layer provided on the surface thereof.

[0004] Conventionally, wet molding methods have been widely used to provide electrode mixture layers, but dry molding methods are also being used as more efficient molding methods.

[0005] The wet molding method referred to here is a method in which a slurry composition containing an electrode active material, a binder, and a solvent is applied to the surface of a current collector, and the slurry composition is dried to form an electrode mixture layer.

[0006] On the other hand, the dry molding method is a method in which composite particles containing an electrode active material and a binder are prepared, deposited on the surface of a current collector to form a particle layer, and then pressed to compress the thickness, thereby forming an electrode mixture layer. When electrodes are continuously produced as long members on a transport path by the dry molding method, specifically, the composite particles can be deposited to a certain thickness on the surface of a transported long current collector using a feeder and a squeegee, and then compressed using a press roll provided downstream of the transport path.

[0007] While the wet molding method requires a drying step after the application of the slurry, the dry molding method does not require such a drying step, allowing for efficient production. This feature is particularly advantageous when continuously producing electrodes as long members on a conveying path, as it allows for a shortening of the conveying path and an increase in conveying speed. Various composite particles have been proposed for use in the dry molding method (see, for example, Patent Documents 1 to 6).

[0008] JP 2004-311427 A, International Publication No. 2013 / 076958, JP 2017-204331 A (Corresponding Publication: US Patent Application Publication No. 2017 / 324091), JP 2017-188445 A (Corresponding Publication: US Patent Application Publication No. 2017 / 288223), JP 2011-155003 A, JP 2006-278031 A

[0009] While dry molding has the advantage of enabling efficient manufacturing, it can result in insufficient bonding between the composite particles and between the composite particles and the current collector, which can lead to various problems. Specifically, when powdered composite particles are deposited and then pressed to form an electrode mixture layer, the thickness of the layer can become non-uniform. A battery having an electrode mixture layer with a non-uniform thickness can have poor performance.

[0010] More specifically, when manufacturing a long electrode, a defect called crosshatching can occur on the surface of the electrode mixture layer. Here, crosshatching refers to a streaky uneven structure that occurs on the surface of the electrode mixture layer along multiple directions oblique to the longitudinal direction of the long electrode. When such an uneven structure occurs, the thickness of the electrode mixture layer becomes non-uniform, resulting in a decrease in the accuracy of the weight per unit area. Furthermore, dry molding methods also have the problem of difficulty in handling the composite particles in a powder state from the time they are deposited until they are pressed.

[0011] Therefore, an object of the present invention is to provide composite particles for non-aqueous secondary battery electrodes that are easy to handle, can suppress defects such as crosshatching, and enable easy production of an electrode mixture layer with a uniform thickness, and a method for producing such composite particles for non-aqueous secondary battery electrodes that can easily produce such composite particles. Another object of the present invention is to provide a negative electrode for a non-aqueous secondary battery that suppresses defects such as crosshatching, has a uniform thickness, and can be easily produced, and a non-aqueous secondary battery that includes such a negative electrode and has good performance and can be easily produced.

[0012] In order to solve the above problems, the present inventors have conducted studies and found that composite particles for a non-aqueous secondary battery electrode containing specific components and having specific physical properties can suppress defects such as crosshatching and enable the production of an electrode mixture layer with a uniform thickness, thereby completing the present invention.

[0013] (1) Composite particles for a non-aqueous secondary battery electrode, comprising electrode active material particles and a binder, and having an adhesive index of 22 or more. (2) Composite particles for a non-aqueous secondary battery electrode according to (1), having an adhesive index of 32 or less. (3) Composite particles for a non-aqueous secondary battery electrode according to (1) to (2), having a D50 particle size of 70 μm or more and 80 μm or less, and a proportion of particles having a particle size of 45 μm or less being 8% or less. (4) Composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (3), having a surface occupancy rate of the binder of 50% or less. (5) Composite particles for a non-aqueous secondary battery electrode according to (4), having a surface occupancy rate of the binder of 24% or less. (6) Composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (5), having a tap porosity of 65% or more. (7) The composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (6), further comprising a water-soluble polymer, wherein the electrode active material particles comprise at least one of a carbon-based active material and a silicon-based active material, and the binder is a particulate binder that is a polymer containing an aliphatic conjugated diene monomer unit, and the water-soluble polymer has a carboxyl group. (8) A method for producing composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (7), comprising a step of granulating a granulation material containing the electrode active material particles and the binder by a spray drying method to obtain particles. (9) The method for producing composite particles for a non-aqueous secondary battery electrode according to (8), further comprising a step of classifying the particles. (10) A method for producing composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (7), comprising a step of granulating a granulation material containing electrode active material particles and a binder by a fluidized bed granulation method to obtain particles. (11) A method for producing composite particles for a non-aqueous secondary battery electrode according to (10), further comprising a step of classifying the particles. (12) A negative electrode for a non-aqueous secondary battery, comprising an electrode mixture layer which is a molded product of the composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (7).(13) A method for producing a negative electrode for a non-aqueous secondary battery, the method comprising dry-molding the composite particles for a non-aqueous secondary battery electrode according to any one of (1) to (7) to form an electrode mixture layer. (14) A non-aqueous secondary battery, comprising a positive electrode, a negative electrode, an electrolyte solution, and a separator, wherein the negative electrode is the negative electrode for a non-aqueous secondary battery according to (12).

[0014] According to the present invention, there are provided composite particles for non-aqueous secondary battery electrodes that are easy to handle, can suppress defects such as crosshatching, and enable easy production of an electrode mixture layer with a uniform thickness, and a method for producing such composite particles for non-aqueous secondary battery electrodes that can easily produce such composite particles.The present invention also provides a non-aqueous secondary battery negative electrode that suppresses defects such as crosshatching, has a uniform thickness, and can be easily produced, and a non-aqueous secondary battery that includes such a negative electrode and has good performance and can be easily produced.

[0015] FIG. 1 is a side view showing an example of a method and apparatus for producing a negative electrode using the composite particles of the present invention.

[0016] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0017] In the following description, the term "(meth)acrylic" is meant to encompass "acrylic", "methacrylic" and combinations thereof, for example, (meth)acrylic acid means acrylic acid, methacrylic acid or a mixture thereof.

[0018] In the following description, a polymerized unit produced by polymerization of a certain monomer may be expressed using the name of the monomer. For example, an aromatic vinyl monomer unit means a polymerized unit having a structure obtained by polymerizing an aromatic vinyl monomer. However, in this application, the compound is not limited by its production method.

[0019] In a polymer produced by copolymerizing multiple types of monomers, the ratio of structural units formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of the certain monomer to all the monomers used in the polymerization of the polymer, unless otherwise specified.

[0020] In this application, the "solid content" of a mixture in which a solid is dispersed in a liquid, such as a slurry composition, is defined as the components remaining after the dispersion medium and solvent in the composition evaporate and harden, and the "solid content concentration" is defined as the concentration of such components. For example, when such a composition consists of water and components dissolved or dispersed in water, the solid content concentration is the concentration of components other than water.

[0021] In the following description, the term "solvent" is interpreted in a broad sense and also includes the meaning of a dispersion medium. That is, "solvent" includes not only a medium in a solution (i.e., a mixture of a liquid medium substance and a solute substance dissolved therein), but also a medium in a dispersion (i.e., a mixture of a liquid medium substance and a dispersion substance dispersed therein as solid particles or emulsion particles), and a medium in a mixture containing both a solute and a dispersion substance.

[0022] In this application, a "long" member refers to a film-like member having a length that is 5 times or more its width, preferably 10 times or more its width, and specifically refers to a member having a length that can be wound into a roll for storage or transportation. There is no particular upper limit to the length of a long member, and it can be, for example, 100,000 times or less its width.

[0023] (Outline of Composite Particles for Non-Aqueous Secondary Battery Electrodes) The composite particles for non-aqueous secondary battery electrodes of the present invention (hereinafter also simply referred to as "composite particles") contain electrode active material particles and a binder. The binder may be entirely or partially a particulate binder. Typically, a single composite particle contains a plurality of electrode active material particles and a plurality of particulate binders that are adhered to each other.

[0024] (Adhesion Index) The composite particles of the present invention have an adhesion index of 22 or more. The adhesion index is preferably 28 or more, more preferably 30 or more. When the adhesion index discovered by the present inventors is equal to or greater than the lower limit, the composite particles can be uniformly leveled, and the weight accuracy can be improved. In particular, in a dry manufacturing method, it is possible to improve the weight accuracy when depositing the composite particles on the surface of a current collector using a squeegee. The upper limit of the adhesion index is not particularly limited, but from the viewpoint of suppressing powder falling in a dry manufacturing method, it is preferable that the value be lower than a certain level, specifically, 32 or less.

[0025] The adhesive index value of the composite particles is affected by factors such as the manufacturing conditions of the composite particles and the particle size of the composite particles. Therefore, by adjusting the manufacturing conditions of the composite particles and the particle size of the composite particles, composite particles having a desired adhesive index can be manufactured. For example, composite particles having a desired adhesive index can be obtained by operations such as adjusting the heating temperature during granulation and adjusting the particle size by classification after granulation.

[0026] The adhesive index of a composite particle can be determined together with the fluidity index by measuring the change in density due to tapping the composite particle. The adhesive index can be measured using a powder tester (for example, Hosokawa Micron Corporation, product name "PT-S"). Specifically, the loose bulk density (bulk density at tapping count 0) ρ0 of the composite particle and the packed bulk density ρN at tapping count N are measured, the degree of bulk loss C (C = (ρN - ρ0) / ρ0) at each tapping count is determined, and the relationship between N and N / C is plotted. The plotted results are approximated to a straight line, whereby the values ​​of the slope 1 / a and intercept 1 / ab in the Kawakita formula below can be determined. From these values, the fluidity index 1 / a and adhesive index 1 / b can be determined. Kawakita formula... N / C = 1 / ab + (1 / a)N

[0027] (Tap Density) The composite particles of the present invention preferably have a tap porosity that is at least somewhat large. When the tap porosity is large, the occurrence of crosshatching can be suppressed when forming an electrode mixture layer using the composite particles, thereby further improving the accuracy of the basis weight. The tap porosity is preferably 60% or more, more preferably 65% ​​or more. The upper limit of the tap porosity is not particularly limited, but can be set to 70% or less from the viewpoint of obtaining an electrode mixture layer with good density.

[0028] The tapped porosity is the porosity at the time when the composite particles are tapped to a certain extent. Specifically, in the density measurement described above, the packed bulk density ρ180 at 180 taps and the theoretical density ρ Ｔ Based on this, the porosity at 180 tapping times is calculated by the following formula, and this can be used as the tapped porosity. Ｔ can be obtained by calculating or measuring the density when the materials constituting the composite particles have a lump-like shape rather than a particulate shape. Specifically, the theoretical density can be calculated by obtaining the density of each of the materials constituting the composite particles as a literature value or an actual measurement value, calculating the product of the mass ratio and density of each material, and then calculating the sum of these values ​​for all materials. Tapped porosity (%) = (1 - (ρ180 / ρ Ｔ )) x 100

[0029] The particle size of the composite particles of the present invention is not particularly limited and can be appropriately adjusted to a particle size suitable for the production of electrodes. However, from the viewpoint of obtaining a desired adhesive index and obtaining good basis weight accuracy, it is preferable that the D50 particle size is within a certain range. Specifically, the D50 particle size is preferably 70 μm or more, more preferably 75 μm or more, and is preferably 85 μm or less, more preferably 80 μm or less.

[0030] Furthermore, from the viewpoint of obtaining good basis weight accuracy, it is preferable that the particle size distribution is narrow, and that the proportion of particles with small particle sizes is particularly small. Specifically, the proportion of particles with a particle size of 45 μm or less is preferably 8% or less, more preferably 7% or less, even more preferably 3% or less, and ideally 0%.

[0031] The particle size of the composite particles can be determined by laser scattering and diffraction. Specifically, it can be measured in a dry state using a particle size distribution analyzer (e.g., Microtrac MT3300EX II; manufactured by Microtrac Bell Co., Ltd.). The integral particle size distribution (volume basis) of the composite particles can be obtained, and the particle size at which the cumulative frequency, calculated from the smallest diameter side, is 50% can be used as the D50 particle size. In addition, the volume-based occupancy frequency of particles with a particle size of 45 μm or less can be calculated in the particle size distribution, and the proportion of particles with a particle size of 45 μm or less can be determined.

[0032] (Binder Occupancy Rate) The composite particles of the present invention may have a structure in which a part or all of the particle surface is coated with a binder. Therefore, a part or all of the particle surface may be occupied by the binder. From the viewpoint of obtaining desired physical properties such as a desired adhesive index, it is preferable that the composite particles of the present invention have a binder occupancy rate that is at least somewhat low. Here, the binder occupancy rate refers to the proportion of the area where the binder is present relative to the total surface area of ​​the particle. This binder occupancy rate may also be referred to as the binder coverage rate. The binder occupancy rate may be preferably 50% or less, more preferably 24% or less. On the other hand, from the viewpoint of increasing the strength of the obtained electrode mixture layer, the lower limit of the binder occupancy rate is preferably 8% or more.

[0033] The binder occupancy rate can be determined by observing the composite particles with a microscope such as a scanning electron microscope, after staining the binder with osmium staining or the like, as necessary.

[0034] (Electrode active material) The electrode active material can be appropriately selected from known electrode active materials used in secondary batteries. When the secondary battery is a lithium ion secondary battery, the electrode active material can usually be particles (electrode active material particles) made of a material capable of absorbing and releasing lithium ions. The following describes an example in which the secondary battery is a lithium ion secondary battery, but the present invention is not limited to the following example. Examples of negative electrode active materials for lithium ion secondary batteries include carbon-based active materials, silicon-based active materials, metal-based active materials, and negative electrode active materials that are combinations of these.

[0035] (Carbon-based active material) A carbon-based active material refers to an active material having a carbon skeleton that can insert (also referred to as "doping") lithium. Examples of carbon-based active materials include carbonaceous materials and graphite materials.

[0036] Examples of carbonaceous materials include graphitizable carbon, whose carbon structure can be easily changed by heat treatment temperature, and non-graphitizable carbon, which has a structure close to an amorphous structure, such as glassy carbon.

[0037] Examples of graphitizable carbon include carbon materials made from tar pitch obtained from petroleum or coal, and more specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, and pyrolytic vapor-grown carbon fiber.

[0038] Examples of non-graphitizable carbon include phenolic resin sintered bodies, polyacrylonitrile carbon fibers, pseudo-isotropic carbon, furfuryl alcohol resin (PFA) sintered bodies, and hard carbon.

[0039] Examples of graphite materials include graphite such as natural graphite and artificial graphite.

[0040] (Silicon-based active material) Examples of silicon-based active materials include silicon (Si), silicon-containing alloys, SiO, SiOx, and composites of Si-containing materials and conductive carbon. Here, the composites are materials obtained by coating or compounding Si-containing materials with conductive carbon.

[0041] Examples of alloys containing silicon include alloy compositions containing silicon, aluminum, and a transition metal such as iron, and further containing tin and a rare earth element such as yttrium.

[0042] SiOx is SiO and SiO ２and Si, where x is usually 0.01 or more and less than 2. SiOx can be formed by utilizing the disproportionation reaction of silicon monoxide (SiO). Specifically, SiOx can be prepared by heat-treating SiO, optionally in the presence of a polymer such as polyvinyl alcohol, to produce silicon and silicon dioxide. The heat treatment can be carried out by pulverizing and mixing SiO and, optionally, a polymer, in an atmosphere containing organic gas and / or steam at a temperature of 900°C or higher, preferably 1000°C or higher.

[0043] (Metal-based active material) Metal-based active material is an active material containing a metal, and usually contains an element capable of inserting lithium in its structure, and when lithium is inserted, the theoretical electric capacity per unit mass is 500 mAh / g or more. Examples of metal-based active materials include lithium metal, elemental metals that can form lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.) and their alloys, as well as their oxides, sulfides, nitrides, silicides, carbides, phosphides, etc.

[0044] The above-described negative electrode active materials may be used singly or in combination of two or more. In particular, from the viewpoint of increasing the capacity of the resulting secondary battery, it is preferable that the negative electrode active material contains at least one of a carbon-based active material and a silicon-based active material.

[0045] The content of the electrode active material in the composite particles is preferably 90% by mass or more, and more preferably 95% by mass or more, when the total mass of the composite particles is 100% by mass. If the content of the electrode active material particles in the composite particles is equal to or more than the above lower limit, the capacity of the resulting secondary battery can be further increased.

[0046] (Binder) The composite particles of the present invention contain a binder in addition to the electrode active material particles. The binder is usually formed of a polymer. The binder is usually a particulate binder, that is, a material that exists in a particulate form in the composite particles, all or part of which, preferably all of which, is a particulate binder. The binder is a component that, when an electrode mixture layer is produced using the composite particles of the present invention, prevents components contained in the composite particles from being detached from the composite particles and can favorably bind the electrode mixture layer to the current collector.

[0047] The particulate binder can be made into polymer particles that can be dispersed in an aqueous medium such as water while maintaining a particulate shape. The particulate binder usually has an insoluble content of 90 mass% or more when 0.5 g of the particulate binder is dissolved in 100 g of water at 25° C. In this specification, the "particulate" shape refers to a shape having an aspect ratio of 1 or more and less than 10 as measured by a scanning electron microscope.

[0048] The particle size of the particulate binder can be appropriately adjusted to a value that allows the composite particles to exhibit the desired properties. The particle size is preferably 0.001 μm or more, more preferably 0.1 μm or more, and is preferably 10 μm or less, more preferably 1 μm or less. The particle size can be a volume-based average particle size. The particle size of the particulate binder can be measured wet using a particle size distribution measuring device (e.g., Microtrac MT3300EX II; manufactured by Microtrac Bell Co., Ltd.).

[0049] Examples of the polymer that constitutes the binder include conjugated diene polymers and acrylic polymers.

[0050] Conjugated diene polymers are polymers containing conjugated diene monomer units. Specific examples of conjugated diene polymers include copolymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene copolymer (SBR), butadiene rubber (BR), acrylic rubber (NBR), and hydrogenated products thereof.

[0051] Examples of acrylic polymers include polymers containing crosslinkable monomer units, (meth)acrylic acid ester monomer units, and acidic group-containing monomer units.

[0052] Additionally, the polymer may include monomers such as, for example, nitrile group-containing monomer units.

[0053] In particular, the polymer preferably contains an aliphatic conjugated diene monomer unit. If the binder composition contains a polymer containing an aliphatic conjugated diene monomer unit, the electrical characteristics of the secondary battery can be further improved. The content ratio of the monomer unit in the polymer is １ It can be measured using a nuclear magnetic resonance (NMR) method such as H-NMR.

[0054] (Aromatic vinyl monomer unit) Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include styrene, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinylnaphthalene, vinyltoluene, and chlorostyrene. Among these, styrene is preferred. These can be used alone or in combination of two or more.

[0055] The content of aromatic vinyl monomer units in the polymer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, when the total of all monomer units contained in the polymer is 100% by mass.

[0056] (Aliphatic Conjugated Diene Monomer Unit) Examples of conjugated diene monomers that can form aliphatic conjugated diene monomer units include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, 2-chloro-1,3-butadiene (chloroprene), and piperylene. Among these, 1,3-butadiene is preferred. These can be used alone or in combination of two or more.

[0057] The content of the aliphatic conjugated diene monomer units in the polymer is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, when the total of all monomer units contained in the polymer is 100% by mass.

[0058] (Crosslinkable Monomer Unit) Examples of crosslinkable monomers capable of forming crosslinkable monomer units include polyfunctional ethylenically unsaturated carboxylic acid ester monomers having two or more ethylenically unsaturated bonds.

[0059] Examples of bifunctional ethylenically unsaturated carboxylic acid ester monomers having two ethylenically unsaturated bonds in the molecule include allyl acrylate, allyl methacrylate, ethylene diacrylate, ethylene dimethacrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, polyethylene glycol diacrylate, propoxylated ethoxylated bisphenol A diacrylate, ethoxylated bisphenol A diacrylate, 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, propoxylated bisphenol A diacrylate, tricyclodecane dimethanol diacrylate, 1,10-decanediol diacrylate, and 1,6-hexanediol diacrylate. , 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, polytetramethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, ethoxylated bisphenol A dimethacrylate, tricyclodecane dimethanol dimethacrylate, 1,10-decanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, ethoxylated polypropylene glycol dimethacrylate, and glycerin dimethacrylate.

[0060] Examples of trifunctional ethylenically unsaturated carboxylic acid ester monomers having three ethylenically unsaturated bonds in the molecule include ethoxylated isocyanuric acid triacrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, ethoxylated glycerin triacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate.

[0061] Examples of tetrafunctional or higher ethylenically unsaturated carboxylic acid ester monomers having four or more ethylenically unsaturated bonds in the molecule include ditrimethylolpropane tetraacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol polyacrylate, and dipentaerythritol hexaacrylate. These may be used alone or in combination of two or more.

[0062] The content of the crosslinkable monomer unit in the polymer is not particularly limited and can be set appropriately.

[0063] ((Meth)acrylic acid ester monomer unit) Examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include methyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and 2-hydroxyethyl acrylate. These can be used alone or in combination of two or more.

[0064] The content of the (meth)acrylic acid ester monomer units in the polymer is not particularly limited and can be set appropriately.

[0065] (Acidic Group-Containing Monomer Unit) Examples of acidic group-containing monomer units include unsaturated carboxylic acid monomer units. Examples of unsaturated carboxylic acid monomers that can form unsaturated carboxylic acid monomer units include unsaturated monocarboxylic acids and derivatives thereof, unsaturated dicarboxylic acids and acid anhydrides thereof, and derivatives thereof. Examples of unsaturated monocarboxylic acids and derivatives thereof include acrylic acid, methacrylic acid, crotonic acid, 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of unsaturated dicarboxylic acids and derivatives thereof include maleic acid, fumaric acid, itaconic acid, methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate. Examples of the acid anhydride of an unsaturated dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride, which can be used alone or in combination of two or more.

[0066] Among these, preferred unsaturated carboxylic acid monomers are unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid.

[0067] The content of the acidic group-containing monomer unit in the polymer is not particularly limited, but is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, when the total of all monomer units contained in the polymer is taken as 100% by mass.

[0068] (Nitrile Group-Containing Monomer Unit) Examples of nitrile group-containing monomers that can form nitrile group-containing monomer units include α,β-ethylenically unsaturated nitrile monomers. α,β-Ethylenically unsaturated nitrile monomers are α,β-ethylenically unsaturated compounds having a nitrile group. Examples include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. These can be used alone or in combination of two or more.

[0069] The content of the nitrile group-containing monomer unit in the polymer is not particularly limited and can be set appropriately.

[0070] (Method for Preparing Polymer) The method for preparing the above-mentioned polymer is not particularly limited, and for example, the polymer can be prepared by polymerizing a monomer composition containing the above-mentioned monomer. Here, the content ratio of each monomer in the monomer composition used to prepare the polymer can be determined according to the content ratio of each repeating unit in the polymer. The polymerization method is not particularly limited, and any method such as solution polymerization, suspension polymerization, bulk polymerization, or emulsion polymerization can be used. Furthermore, any addition polymerization method such as ionic polymerization, radical polymerization, or living radical polymerization can be used as the polymerization method.

[0071] The binder content in the composite particles is preferably 1.0% by mass or more, and more preferably 1.5% by mass or more, when the total mass of the composite particles is 100% by mass. If the binder content in the composite particles is equal to or greater than the above lower limit, the binding strength between the current collector and the composite particles can be further improved. The upper limit of the binder content is not particularly limited, but can be, for example, 5.0% by mass or less.

[0072] (Optional Component: Water-Soluble Polymer) The composite particles of the present invention may contain optional components in addition to the essential components described above. As an example of an optional component, the composite particles of the present invention may contain a water-soluble polymer. The water-soluble polymer, together with the binder, is a component that prevents the components contained in the composite particles from detaching from the composite particles and can favorably bind an electrode mixture layer formed using the composite particles to a current collector. The water-soluble polymer may exist in a non-particulate form in the composite particles. Here, in the present invention, a polymer being "water-soluble" means that when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is less than 1.0 mass%.

[0073] Examples of water-soluble polymers include cellulose-based polymers such as cellulose compounds such as carboxymethyl cellulose (CMC), carboxyethyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, and carboxyethyl methyl cellulose, and salts thereof (ammonium salts, alkali metal salts, etc.); starches such as oxidized starch and starch phosphate; casein; various modified starches; polyethylene oxide, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, polysulfonic acid, polycarboxylic acid, polyacrylic acid; (meth)acrylic acid copolymers, acrylic acid-acrylamide copolymers, and other (meth)acrylamide-based polymers, and salts thereof (ammonium salts, alkali metal salts, etc.). These may be used alone or in combination of two or more. Among these, cellulose-based polymers, (meth)acrylic acid copolymers, (meth)acrylamide-based polymers, and combinations thereof are preferred as water-soluble polymers.

[0074] Furthermore, the water-soluble polymer more preferably has a carboxyl group, which can improve the electrical characteristics of the secondary battery.

[0075] The content of the water-soluble polymer in the composite particles is preferably 0.5% by mass or more, and more preferably 1.0% by mass or more, when the total mass of the composite particles is taken as 100% by mass. When the content of the water-soluble polymer in the composite particles is equal to or more than the above lower limit, the binding strength between the current collector and the composite particles can be further improved.

[0076] (Optional Component: Conductive Material) The composite particle of the present invention may contain a conductive material as an optional component. The conductive material is intended to promote electrical contact between electrode active materials. Examples of conductive materials include conductive carbon materials such as carbon black (e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.), graphite, carbon fiber, and carbon flakes; as well as fibers and foils of various metals. Among these, the conductive material preferably contains carbon fiber, more preferably contains ultrashort carbon fibers such as carbon nanotubes and vapor-grown carbon fibers, even more preferably contains carbon nanotubes, and particularly preferably contains single-walled carbon nanotubes. These may be used alone or in combination of two or more types.

[0077] The content of the conductive material in the composite particles is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more, when the total mass of the composite particles is taken as 100% by mass. If the content of the conductive material in the composite particles is equal to or more than the above lower limit, electrical contact between the electrode active materials can be further promoted.

[0078] (Optional Components: Additives) In addition to those described above, the composite particles of the present invention may contain additives as optional components. Examples of additives include antifoaming agents, preservatives, antioxidants, reinforcing materials, leveling agents, viscosity modifiers, and electrolyte additives. These are not particularly limited as long as they do not affect the battery reaction, and known additives can be used. These additives can be used alone or in combination of two or more.

[0079] The content of the additive in the composite particles is preferably 1.0 mass % or less, and more preferably 0.5 mass % or less, when the total mass of the composite particles is 100 mass %. When the content of the additive in the composite particles is the above upper limit or less, the electrical characteristics of the secondary battery can be further improved.

[0080] (Method for producing composite particles for non-aqueous secondary battery electrodes) The method for producing the composite particles of the present invention is not particularly limited, and the particles can be produced by any production method. Specifically, the composite particles can be produced by a production method including a step of granulating a granulation material containing electrode active material particles and a binder. The granulation material is sometimes called a "granulation material." The granulated particles can be used as the composite particles of the present invention as is, but from the viewpoint of obtaining composite particles having the desired particle size and particle size distribution, it is preferable to use the granulated particles as bulk powder and further perform a step of classifying this. Examples of the granulation step include a granulation step using a spray drying method (hereinafter referred to as "granulation step A") and a granulation step using a fluidized bed granulation method (hereinafter referred to as "granulation step B").

[0081] The granulation step A, the granulation step B, and the classification step will be described in order below.

[0082] (Granulation step A) In the granulation step A, the granulation material is granulated by a spray drying method to obtain particles of the composite particle bulk powder. In the spray drying method, the granulation material is sprayed into hot air and dried to perform granulation. Here, the granulation material may be a slurry composition A described below.

[0083] (Slurry Composition A) The slurry composition A used in the granulation step A contains electrode active material particles and a binder, and may further contain optional components of the composite particles. The slurry composition A may further contain a solvent. The electrode active material particles, binder, and optional components may be those described above as components of the composite particles.

[0084] The solvent that can be contained in the slurry composition A is not particularly limited, and either water or an organic solvent can be used. Examples of the organic solvent that can be used include acetonitrile, N-methyl-2-pyrrolidone, tetrahydrofuran, acetone, acetylpyridine, cyclopentanone, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, ethylenediamine, dimethylbenzene (xylene), methylbenzene (toluene), cyclopentyl methyl ether, and isopropyl alcohol. Of these, water is preferably used. These solvents can be used alone or in combination of two or more at any desired ratio.

[0085] (Method for Preparing Slurry Composition A) The method for preparing the slurry composition A is not particularly limited, and for example, the slurry composition A can be prepared by mixing the above-mentioned components.

[0086] From the viewpoint of uniformly dispersing each component in the slurry composition A and more efficiently producing the composite particles of the present invention, the granulation step A preferably includes a kneading step. Specifically, the granulation step A preferably includes, for example, a kneading step in which all of the above-mentioned components except the binder are mixed, and a preparation step in which a binder and an additional solvent are added to the mixture obtained through the kneading step and further mixed to prepare the slurry composition A. In the present invention, "kneading" means mixing the components in a state in which the solids concentration is higher than that of the slurry composition A finally obtained.

[0087] The solid content concentration in the kneading step is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more. The upper limit of the solid content concentration in the kneading step is not particularly limited, but may be, for example, 95% by mass or less, or 90% by mass or less.

[0088] The solid content of the final slurry composition A is preferably 40% by mass or more, more preferably 45% by mass or more, and even more preferably 50% by mass or more. The upper limit of the solid content of the slurry composition A is not particularly limited, but may be, for example, 70% by mass or less, or 60% by mass or less.

[0089] (Operation of Granulation Step A) The hot air temperature during spray drying in the spray drying method is preferably 25 to 250°C, more preferably 50 to 220°C, and even more preferably 80 to 200°C. In the spray drying method, the method of blowing the hot air is not particularly limited. Examples of the blowing method include a method in which the hot air blowing direction and the spraying direction of the granulation material flow sideways parallel to each other, a method in which the granulation material is sprayed at the top of the drying tower and then descends together with the hot air, a method in which the sprayed droplets come into countercurrent contact with the hot air, and a method in which the sprayed droplets first flow parallel to the hot air and then fall by gravity to come into countercurrent contact.

[0090] The temperature of the slurry composition A to be sprayed is not limited, and may be room temperature or may be heated to a temperature higher than room temperature.

[0091] Spray drying can be carried out using a known spray dryer. An example of a device used to spray the slurry composition A is an atomizer. Examples of atomizer types include a rotating disk type, a cup type, a two-fluid nozzle type, and a pressurized type.

[0092] (Granulation step B) In the granulation step B, the granulation material is granulated by a fluidized bed granulation method to obtain a bulk powder of composite particles. In the fluidized bed granulation method, the electrode active material particles are fluidized by hot air, and then the slurry composition B is sprayed from a spraying device onto the particles to cause aggregation, thereby carrying out granulation.

[0093] (Slurry Composition B) The slurry composition B used in the granulation step B contains a binder and may further contain optional components of the composite particles. The slurry composition B may further contain a solvent. However, the slurry composition B may not contain electrode active material particles. As the binder, optional components, and solvent, those described above as components of the slurry composition A may be used.

[0094] (Method for Preparing Slurry Composition B) The method for preparing the slurry composition B is not particularly limited, and for example, the slurry composition B can be prepared by mixing the components described above.

[0095] The solid content concentration of the slurry composition B is preferably 40% by mass or more, more preferably 50% by mass or more. When the solid content concentration of the slurry composition B is equal to or higher than the above-mentioned lower limit, the components contained in the slurry composition B can be uniformly dispersed. The upper limit of the solid content concentration of the slurry composition B is not particularly limited, but can be, for example, 80% by mass or less.

[0096] (Operation of Granulation Step B) As the electrode active material particles to be subjected to the granulation step B, those components described above as components of the composite particles can be used.

[0097] The method for fluidizing the electrode active material is not particularly limited, and the fluidization can be carried out by a known method.

[0098] The temperature of the hot air used to fluidize the electrode active material is preferably 80°C or higher, and more preferably 100°C or higher.

[0099] The bulk powder of the composite particles obtained in the granulation step A or the granulation step B contains, as constituent materials, the solid components of the materials used in their production. On the other hand, the solvent of the materials used in their production is evaporated in the granulation step, and therefore, is not contained at all or only a trace amount is contained.

[0100] (Classification step) In the classification step, the raw powder of the composite particles obtained in the granulation step A or the granulation step B is classified. The classification method is not particularly limited, and any known classification method can be appropriately adopted. Examples of classification methods include dry classification methods such as gravity classification, inertial classification, and centrifugal classification; wet classification methods such as sedimentation classification, mechanical classification, and hydraulic classification; and sieving classification methods using a sieve mesh such as a vibrating sieve or an in-plane moving sieve. Among these, sieving classification methods are preferred. By performing the classification step, composite particles having the desired particle size and particle size distribution and capable of further improving the basis weight precision of the electrode mixture layer can be easily produced.

[0101] (Negative electrode for non-aqueous secondary battery and manufacturing method thereof) The negative electrode for a non-aqueous secondary battery of the present invention (hereinafter also simply referred to as "negative electrode") includes an electrode mixture layer. The electrode mixture layer is a molded product of the composite particles of the present invention described above. That is, the negative electrode of the present invention can be manufactured by subjecting the composite particles of the present invention to a molding step and molding the electrode mixture layer.

[0102] The negative electrode of the present invention may include an electrode mixture layer and a current collector. The current collector may be selected from conductive and electrochemically durable materials depending on the type of secondary battery. The current collector may typically be in the form of a foil. The electrode mixture layer is typically provided on one or both sides of the foil-shaped current collector. Examples of materials constituting the current collector of a lithium-ion secondary battery negative electrode include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum. Of these, copper foil is particularly preferred as the current collector used for the negative electrode. One of the above materials may be used alone, or two or more may be used in any combination in any ratio.

[0103] The negative electrode of the present invention can be produced by molding the composite particles of the present invention to form an electrode mixture layer. Specifically, the composite particles are deposited on the surface of a current collector to form a layer of the composite particles, and the layer is further pressurized as necessary to form the electrode mixture layer.

[0104] The electrode mixture layer can be formed by a wet molding method or a dry molding method, but when manufacturing using the composite particles of the present invention, a dry molding method is preferred. When a dry molding method is adopted, the advantages of the dry molding method, such as manufacturing efficiency, can be enjoyed, while by adopting the composite particles of the present invention as the composite particles, it is possible to reduce disadvantages such as a decrease in basis weight accuracy due to the occurrence of crosshatching, and the difficulty in handling the composite particles in a powder state after depositing them and pressing them, so it is possible to carry out particularly preferable manufacturing.

[0105] An example of a method for manufacturing a negative electrode of the present invention will be described with reference to Fig. 1. Fig. 1 is a side view showing an example of a method for manufacturing a negative electrode using the composite particles of the present invention and a manufacturing apparatus therefor. In Fig. 1, a manufacturing apparatus 10 has a conveying path along which a long current collector 11 is unwound from a unwinding roll 111 and continuously conveyed. Downstream of the unwinding roll 111 on the conveying path, a feeder 123 for depositing the composite particles, a squeegee plate 121 and a squeegee roll 122, press rolls 131 and 132 for pressing a layer of the composite particles, and a winding device 141 are arranged in this order.

[0106] In an example of operation of the manufacturing apparatus 10 shown in FIG. 1 , an electrode composite layer is formed by a dry forming method. Specifically, a current collector 11 is unwound from a feed roll 111 rotating in the direction of arrow A1 and transported in the direction of arrow A2. Downstream, composite particles 21 are dropped from a feeder 123 in the direction of arrow A9. Using a squeegee plate 121 with its end abutting a press roll 131 and a squeegee roll 122, the composite particles 21 are deposited on the current collector 11 to form a layer 22. The layer 22 is then roll-pressed using the press rolls 131 and 132 to form a negative electrode composite layer 23, thereby producing a negative electrode 20 consisting of the negative electrode composite layer 23 and the current collector 11. The produced negative electrode 20 is collected by a winding device 141 rotating in the direction of arrow A5.

[0107] During deposition of layer 22, by rotating squeegee roll 122 in the direction of arrow A8, composite particles 21 can be leveled to a uniform thickness to form layer 22. However, when performing the step of leveling layer 22 in this manner, dusting, i.e., composite particles flying up from layer 22, can occur. Specifically, dusting can occur near squeegee roll 122 and at the stage before layer 22 reaches press rolls 131 and 132. If such dusting occurs, the thickness of layer 22, and therefore the thickness of negative electrode composite layer 23, becomes non-uniform. Furthermore, in such a dry molding step, dusting, i.e., composite particles falling off from layer 22, can occur. Specifically, composite particles can fall off from layer 22 downstream of squeegee roll 122 before layer 22 reaches press rolls 131 and 132. If such dusting occurs, the thickness of layer 22, and therefore the thickness of negative electrode composite layer 23, becomes non-uniform. In particular, as in the example of Figure 1, when the composite particles are deposited on the upper side of the nearly horizontal peripheral surface of the press roll 131 and then the press roll 131 is rotated to subject the layer 22 to the pressing process, powder fall-off is particularly likely to occur before the layer 22 is subjected to the pressing process, and thickness uniformity is likely to be impaired. In addition, when an electrode mixture layer is formed using such a dry forming method, phenomena such as the occurrence of crosshatching on the surface can reduce the basis weight accuracy. Here, the inventors have found that when the composite particles of the present invention satisfy the above-mentioned requirements of the present invention, the occurrence of such powder fall-off, powder fall-off, and crosshatching can all be suppressed. Therefore, it is possible to efficiently manufacture high-quality electrodes.

[0108] (Non-aqueous secondary battery) The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a separator, and the negative electrode is the above-described negative electrode for a non-aqueous secondary battery of the present invention. Therefore, the secondary battery of the present invention can be easily manufactured and has good performance. Below, as an example, a case where the non-aqueous secondary battery is a lithium ion secondary battery will be described, but the present invention is not limited to the following example.

[0109] (Positive Electrode) The positive electrode is not particularly limited, and a known positive electrode can be used. Specifically, the positive electrode can be a positive electrode obtained by forming a positive electrode mixture layer on a current collector using a known method.

[0110] (Negative Electrode) As the negative electrode, the above-described negative electrode for a secondary battery of the present invention is used.

[0111] (Electrolyte) As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. Examples of the supporting electrolyte include lithium salts. Examples of the lithium salt include LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, and (C ２ F ５ SO ２ Among them, LiPF is preferred because it is easily soluble in solvents and shows a high degree of dissociation. ６ , LiClO ４ , and CF ３ SO ３ Li is preferred, and LiPF ６ The electrolyte may be used alone or in combination of two or more kinds in any ratio.

[0112] The organic solvent used in the electrolyte can be appropriately selected from solvents capable of dissolving the supporting electrolyte. Suitable examples include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. A mixture of these solvents may also be used. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. Known additives, such as vinylene carbonate, fluoroethylene carbonate, and ethyl methyl sulfone, may also be added to the electrolyte.

[0113] (Separator) The separator may be appropriately selected from known separators such as those described in JP 2012-204303 A. Among these, a microporous film made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred, as it allows the thickness of the entire separator to be thin, thereby increasing the proportion of electrode active material in the secondary battery and increasing the capacity per volume.

[0114] (Method for manufacturing lithium ion secondary battery) The lithium ion secondary battery of the present invention can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the resulting assembly as necessary according to the battery shape, placing it in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent internal pressure rise, overcharge / discharge, and the like in the secondary battery, a fuse, an overcurrent prevention element such as a PTC element, an expanded metal, a lead plate, or the like may be provided as necessary. The shape of the secondary battery may be, for example, any of a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, and the like.

[0115] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, the operations described below were performed under conditions of room temperature and normal pressure unless otherwise specified.

[0116] (Evaluation method) (D50 particle size and proportion of particles of 45 μm or less) Using a particle size distribution measuring device (Microtrac MT3300EX II; manufactured by Microtrac Bell Co., Ltd.) based on the laser scattering and diffraction method, the integrated particle size distribution (volume basis) of the composite particles was obtained in a dry state with the dispersion air pressure during measurement set to 0.05 MPa. The particle size at which the cumulative frequency, calculated from the smallest diameter side, was 50% was adopted as the D50 particle size. Furthermore, in the particle size distribution, the volume-based occupancy frequency of particles of 45 μm or less was calculated and adopted as the proportion of particles with a particle size of 45 μm or less.

[0117] (Flowability Index and Tapped Porosity) Measurements were performed using a powder tester (manufactured by Hosokawa Micron Corporation, product name "PT-S"). The composite particles whose mass was weighed were placed in the device, and the loose bulk density ρ0 (bulk density at tapping count 0) and the packed bulk density ρN at tapping count N were measured. The tapping count N was 10, 30, 120, 180, 300, 600, and 900. The tapping conditions were a stroke of 18 mm and 1 tap / second. The degree of bulk loss C (C = (ρN - ρ0) / ρ0) at each tapping count was determined, and the relationship between N and N / C was plotted. The plot results were approximated to a straight line to determine the values ​​of the slope 1 / a and intercept 1 / ab in the Kawakita formula below. From these values, the flowability index 1 / a and adhesiveness index 1 / b were calculated. Kawakita style... N / C=1 / ab+(1 / a)N

[0118] In addition, the compacted bulk density ρ180 at 180 tapping times and the theoretical density ρ Ｔ Based on this, the tap porosity was calculated using the following formula: Tap porosity (%) = (1-(ρ180 / ρ Ｔ ))×100 Theoretical density ρ Ｔwas calculated by obtaining the density of each of the materials (active material, conductive additive, organic component) constituting the composite particle from literature values, calculating the product of the mass ratio (relative value with the total amount taken as 1) and density of each material, and then calculating the sum of these values ​​for all materials.

[0119] (Method for measuring binder occupancy rate) The composite particles were placed in an osmium tetroxide vapor atmosphere for 8 hours and stained with osmium. A backscattered electron image of the stained composite particles was taken using a scanning electron microscope (manufactured by JEOL Ltd., product name "FE-SEM7800F"), and an image in which the binder portion was shown in white was obtained. The image was binarized using image processing software (ImageJ). The proportion of the area of ​​the white portion in the area of ​​the composite particle in the processed image was measured, and the binder occupancy rate was calculated.

[0120] (Dust Flying) In the examples and comparative examples, a negative electrode for a non-aqueous secondary battery electrode was produced using the molding apparatus shown in Fig. 1 over a length of 40 m, and the number of times that dust flying of the composite particles occurred around the squeegee roll 122 was measured and evaluated according to the following evaluation criteria: A: During production of 40 m at 60 m / min, dust flying occurred 0 times. B: During production of 40 m at 60 m / min, dust flying occurred 1 to 5 times. C: During production of 40 m at 60 m / min, dust flying occurred 6 or more times.

[0121] (Adhesion from Squeegee to Press) In the examples and comparative examples, a negative electrode for a non-aqueous secondary battery electrode was manufactured over a length of 40 m using the molding apparatus shown in FIG. 1 . Manufacturing was performed under multiple conditions with different conveying speeds. During the 40 m manufacturing, the number of times that powder fall occurred along the conveying path from when the composite particles deposited by the squeegee roll 122 were pressed by the downstream press rolls 131 and 132 was measured, and the result was evaluated according to the following evaluation criteria. A+: No powder fall occurred in the manufacturing of 40 m at 60 m / min, and no powder fall occurred in the manufacturing of 40 m at 80 m / min. A: Among those that had no powder fall in the manufacturing of 40 m at 60 m / min, those other than A+ were evaluated. B: 1 to 10 powder fall occurred in the manufacturing of 40 m at 60 m / min. C: 11 or more powder fall occurred in the manufacturing of 40 m at 60 m / min.

[0122] (Moldability) In the examples and comparative examples, a negative electrode for a non-aqueous secondary battery electrode was manufactured over a length of 40 m using the molding apparatus shown in FIG. 1 . Manufacturing was performed under multiple conditions with different conveying speeds. The negative electrodes obtained after manufacturing over a length of 40 m were observed, and the number of crosshatching locations was counted and evaluated according to the following evaluation criteria. A+: No crosshatching occurred in the manufacturing of 40 m at 60 m / min, and no crosshatching occurred in the manufacturing of 40 m at 80 m / min. A: Of those that had no crosshatching in the manufacturing of 40 m at 60 m / min, those other than A+. B: No crosshatching occurred in the manufacturing of 40 m at 60 m / min, 1 to 5 times. C: No crosshatching occurred more than 6 times in the manufacturing of 40 m at 60 m / min.

[0123] (Examples 1 to 3 and Comparative Examples 1 to 4) (1-1. Preparation of Slurry Composition for Lithium Ion Secondary Battery Negative Electrode) As negative electrode active materials, 94.5 parts of artificial graphite as a carbon-based active material, 3.0 parts of SiOx as a silicon-based negative electrode active material, 0.5 parts in solids equivalent of a 1% aqueous solution of carboxymethylcellulose sodium salt (CMC-Na) as a water-soluble polymer, and 0.5 parts in solids equivalent of a 4% aqueous solution of sodium polyacrylate (PAA-Na) were placed in a planetary mixer equipped with a disperser. Further, ion-exchanged water was added to obtain a mixed solution adjusted to a solids concentration of 65%. The mixed solution was mixed at 25°C for 60 minutes. Next, to the above mixture was added 1.5 parts in terms of solids of a binder composition consisting of an aqueous dispersion of styrene-butadiene-methacrylic acid copolymer (SBR, manufactured by Zeon Corporation, product name "BM-451B", volume-based average particle size 0.15 μm, measured by wet method using a Microtrac MT3300EX II (manufactured by Microtrac Bell Co., Ltd.)), and ion-exchanged water was added, adjusting the final solids concentration to 50%, and further mixing for 10 minutes. This was subjected to a degassing treatment under reduced pressure to obtain a negative electrode slurry composition.

[0124] (1-2. Preparation of Composite Particles for Non-Aqueous Secondary Battery Electrodes) The negative electrode slurry composition obtained in (1-1) was spray-dried to prepare composite particle bulk powder. Spray drying was performed using a spray dryer (OUDT-25, manufactured by Okawara Co., Ltd.) equipped with a rotating disk atomizer (diameter: 50 mm). The spray drying conditions were a rotation speed of 20,000 to 25,000 rpm, and the hot air temperature (outlet temperature) was set to the temperatures shown in Table 1. The obtained composite particle bulk powder was classified using a sieve with a nominal mesh size of 125 μm (JIS Z8801-1) to obtain composite particles for non-aqueous secondary battery electrodes having a D50 particle size shown in Table 1. By changing the drying conditions, such as the rotation speed of the dryer during spray drying, within the above ranges, the D50 particle size was obtained as shown in Table 1 for each of the Examples and Comparative Examples.

[0125] The adhesive index, tap porosity, proportion of particles with a particle size of 45 μm or less, and binder occupancy of the obtained composite particles were measured. The results are shown in Table 1.

[0126] (1-3. Negative Electrode Production and Evaluation) The composite particles for a non-aqueous secondary battery electrode obtained in (1-2) were dry-molded using a molding apparatus shown in FIG. 1 to produce a negative electrode for a non-aqueous secondary battery electrode. In FIG. 1, a copper foil with a thickness of 8 μm was used as the current collector 11. Composite particles 21 were dropped from a feeder 123 and deposited on the current collector 11 using a squeegee plate 121 and a squeegee roll 122 to form a layer 22. Thereafter, the layer 22 was roll-pressed using press rolls 131 and 132 to form a negative electrode composite layer 23, and a negative electrode 20 consisting of the negative electrode composite layer 23 and the current collector 11 was produced. The roll press load applied by the press rolls 131 and 132 was 3.5 MPa. The temperature during pressing was 50°C. By adjusting various conditions such as the supply amount of the composite particles 21, the basis weight was adjusted to a target value of 11.5 mg / cm. ２ The conveying speed of the current collector 11 was set to two speeds: 60 m / min and 80 m / min. In the production of the negative electrode, dusting, adhesion from the squeegee to the press, and moldability were evaluated. The results are shown in Table 1.

[0127]

[0128] As is clear from the above results, the composite particles of Examples 1 to 3, which satisfy the requirements of the present invention, are easy to handle, can suppress defects such as crosshatching, and enable the easy production of an electrode mixture layer with a uniform thickness.

[0129] REFERENCE SIGNS LIST 10 Manufacturing apparatus 11 Current collector 20 Negative electrode 21 Composite particles 22 Layer 23 Negative electrode composite layer 111 Pay-off roll 121 Squeegee plate 122 Squeegee roll 123 Feeder 131 Press roll 132 Press roll 141 Winding device

Claims

1. A composite particle for a non-aqueous secondary battery electrode, comprising electrode active material particles and a binder, and having an adhesion index of 22 or more.

2. The composite particles for use in a non-aqueous secondary battery electrode according to claim 1, wherein the adhesive index is 32 or less.

3. Composite particles for non-aqueous secondary battery electrodes according to claim 1, having a D50 particle size of 70 μm or more and 80 μm or less, and a ratio of particles having a particle size of 45 μm or less being 8% or less.

4. The composite particles for a non-aqueous secondary battery electrode according to claim 1, wherein the surface occupancy rate of said binder is 50% or less.

5. The composite particles for a non-aqueous secondary battery electrode according to claim 4, wherein the surface occupancy rate of said binder is 24% or less.

6. The composite particles for use in a non-aqueous secondary battery electrode according to claim 1, having a tap porosity of 65% or more.

7. The composite particle for a non-aqueous secondary battery electrode according to claim 1, further comprising a water-soluble polymer, wherein the electrode active material particles comprise at least one of a carbon-based active material and a silicon-based active material, and the binder is a particulate binder which is a polymer containing an aliphatic conjugated diene monomer unit, and the water-soluble polymer has a carboxyl group.

8. A method for producing composite particles for a non-aqueous secondary battery electrode according to any one of claims 1 to 7, comprising a step of granulating a granulating material containing electrode active material particles and a binder by a spray drying method to obtain particles.

9. The method for producing composite particles for a non-aqueous secondary battery electrode according to claim 8, further comprising a step of classifying the particles.

10. A method for producing composite particles for use in a non-aqueous secondary battery electrode according to any one of claims 1 to 7, comprising a step of granulating a granulation material containing electrode active material particles and a binder by a fluidized bed granulation method to obtain particles.

11. The method for producing composite particles for a non-aqueous secondary battery electrode according to claim 10, further comprising a step of classifying the particles.

12. A negative electrode for a non-aqueous secondary battery, comprising an electrode mixture layer which is a molded product of the composite particles for a non-aqueous secondary battery electrode according to any one of claims 1 to 7.

13. A method for producing a negative electrode for a non-aqueous secondary battery, comprising subjecting the composite particles for a non-aqueous secondary battery electrode according to any one of claims 1 to 7 to dry molding to form an electrode mixture layer.

14. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the negative electrode is the negative electrode for a non-aqueous secondary battery according to claim 12.

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