Composite particles, electrodes for electrochemical elements, and electrochemical elements

Abstract

The present invention relates to composite particles containing an electrode active material, a conductive material, and a binder. These composite particles have an average area equivalent diameter of 20 μm to 250 μm, inclusive. Formula 1: The coefficient of variation of the area equivalent diameter, which is calculated according to (standard deviation of area equivalent diameter / average of area equivalent diameter) × 100, is 5% to 50%, inclusive. Formula 2: The value of the density coefficient, which is calculated according to pressed density / bulk density, is 1.3 to 3.5, inclusive.

Description

[Technical Field]

[0001] This invention relates to composite particles, electrodes for electrochemical elements, and electrochemical elements. [Background technology]

[0002] Electrochemical elements such as lithium-ion secondary batteries are small, lightweight, have high energy density, and can be repeatedly charged and discharged, making them suitable for a wide range of applications.

[0003] To improve the performance of electrochemical elements, various improvements have been made to the materials used to form electrodes for electrochemical elements. Electrodes for electrochemical elements have a structure in which an electrode composite layer is arranged on an electrode substrate, with the electrode active material as the main component, and, if necessary, containing other components such as conductive materials and binders to impart specific functions to the electrode, such as conductivity, adhesion, and flexibility. From the viewpoint of improving the performance of electrochemical elements, it is preferable that the electrode active material and other components are uniformly dispersed in the electrode composite layer.

[0004] Conventionally, methods for forming an electrode composite layer have been investigated, including applying and drying a slurry composition containing an electrode active material, a conductive material, a binder, and a solvent onto an electrode substrate, and forming an electrode composite layer by pressure molding composite particles containing an electrode active material, a conductive material, a binder, and a solvent onto an electrode substrate.

[0005] As composite particles, various types with different attributes have been considered according to various manufacturing methods (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2005 / 124801 [Patent Document 2] Japanese Patent Publication No. 2006-060193 [Patent Document 3] International Publication No. 2015 / 029829 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] However, there was still room for further improvement in the properties of the electrodes formed using such composite particles and the electrochemical elements provided with such electrodes among the conventional granulated particles.

[0008] Therefore, an object of the present invention is to provide composite particles capable of enhancing the flexibility of an electrode, suppressing cracks in an electrode active material in the electrode, and further improving the cycle characteristics and rate characteristics of an electrochemical element provided with such an electrode. Another object of the present invention is to provide an electrode for an electrochemical element containing the composite particles of the present invention and an electrochemical element provided with the same. [Means for Solving the Problems]

[0009] The present inventor conducted intensive studies for the purpose of solving the above problems. As a result, the present inventor newly found that the properties of the obtained electrodes and electrochemical elements can be improved by composite particles in which the average value of the area equivalent diameter, the coefficient of variation of the area equivalent diameter, and the density coefficient are within predetermined ranges, and completed the present invention.

[0010] [1] That is, this invention aims to advantageously solve the above problems, and the composite particles of the present invention are composite particles containing an electrode active material, a conductive material, and a binder, and the average value of the area equivalent diameter of the composite particles is 20 μm or more and 250 μm or less, Formula 1: (Standard deviation of area equivalent diameter / Average value of area equivalent diameter) × 100 The coefficient of variation of the area equivalent diameter calculated according to the above is 5% or more and 50% or less, Formula 2: Compression density / Bulk density The density coefficient, calculated according to the formula, is characterized by being between 1.3 and 3.5. Composite particles in which the average value of the area-equivalent diameter, the coefficient of variation of the area-equivalent diameter, and the density coefficient are each within a predetermined range can enhance the flexibility of the electrode, suppress cracking of the electrode active material in the electrode, and further improve the cycle characteristics and rate characteristics of an electrochemical element equipped with such an electrode. The average value of the area-equivalent diameter, the coefficient of variation of the area-equivalent diameter, and the density coefficient can each be measured according to the methods described in the examples of this specification.

[0011] [2] Here, the composite particles of the present invention described in [1] above preferably have a volume resistivity of 1 Ω·cm or more and 3000 Ω·cm or less. The volume resistivity of the composite particles can be measured according to the methods described in the examples of this specification.

[0012] [3] Furthermore, the composite particles of the present invention described in [1] or [2] above preferably have an area circularity of 0.50 or more and an perimeter length envelope of 0.70 or more and 0.97 or less. If the area circularity and perimeter length envelope of the composite particles are within the above ranges, the flexibility of the electrode can be further enhanced, cracking of the electrode active material in the electrode can be further suppressed, and the cycle characteristics and rate characteristics of the electrochemical element equipped with such electrodes can be further improved. The area circularity and perimeter length envelope of the composite particles can be measured according to the methods described in the examples of this specification.

[0013] [4] Furthermore, in the composite particles of the present invention described in any of [1] to [3] above, it is preferable that the binder is a polymer material that dissolves in a non-aqueous solvent with a boiling point of 95°C or less at 1 atm. If the binder is a polymer material that dissolves in a non-aqueous solvent with a boiling point of 95°C or less at 1 atm, degradation of the polymer material due to residual solvent is suppressed, and the long-term life characteristics of the resulting electrochemical element can be improved.

[0014] [5] Furthermore, the present invention aims to advantageously solve the above problems, and the electrode for an electrochemical element of the present invention is characterized by comprising an electrode composite layer containing composite particles as described in any of [1] to [4] above. An electrode for an electrochemical element comprising an electrode composite layer containing composite particles has excellent flexibility, less cracking of the contained electrode active material, and can further improve the cycle characteristics and rate characteristics of an electrochemical element comprising such an electrode.

[0015] [6] Furthermore, this invention aims to advantageously solve the above problems, and the electrochemical element of the present invention is characterized by comprising the electrodes for the electrochemical element of the present invention described above. The electrochemical element comprising the electrodes for the electrochemical element of the present invention has excellent cycle characteristics and rate characteristics. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide composite particles that can increase the flexibility of electrodes, suppress cracking of the electrode active material in the electrodes, and further improve the cycle characteristics of an electrochemical element equipped with such electrodes. Furthermore, according to the present invention, it is possible to provide an electrode for an electrochemical element containing the composite particles of the present invention and an electrochemical element equipped therewith. [Brief explanation of the drawing]

[0017] [Figure 1] This is a top view of a granulation tank used in one example. [Figure 2] This is a cross-sectional view following the AA cutting line shown in Figure 1. [Modes for carrying out the invention]

[0018] Embodiments of the present invention will be described in detail below. Herein, the composite particles of the present invention can be suitably used as a compounding component in an electrode composite layer provided for the electrodes of an electrochemical element such as a secondary battery.

[0019] (composite particles) The composite particles of the present invention include an electrode active material, a conductive material, and a binder. The average area equivalent diameter of the composite particles of the present invention is 20 μm or more and 250 μm or less. Equation 1: (Standard deviation of area-equivalent diameter / Average value of area-equivalent diameter) × 100 The coefficient of variation of the area equivalent diameter, calculated according to the formula, is 5% or more and 50% or less. Equation 2: Compression density / Bulk density The density coefficient calculated according to the formula is characterized by being between 1.3 and 3.5. Composite particles in which the average value of the area-equivalent diameter, the coefficient of variation of the area-equivalent diameter, and the density coefficient are all within predetermined ranges can increase the flexibility of the electrode, suppress cracking of the electrode active material in the electrode, and further improve the cycle characteristics and rate characteristics of an electrochemical element equipped with such an electrode.

[0020] <Average value of area equivalent diameter> The composite particles must have an average area-equivalent diameter of 20 μm or more and 250 μm or less, preferably 30 μm or more, more preferably 40 μm or more, preferably 200 μm or less, and more preferably 150 μm or less. If the average area-equivalent diameter of the composite particles is above the lower limit, the flexibility of the electrode formed using the composite particles can be increased, and the rate characteristics of the electrochemical element equipped with such an electrode can be improved. If the average area-equivalent diameter of the composite particles is below the upper limit, cracking of the electrode active material in the electrode composite layer can be suppressed, and the cycle characteristics and rate characteristics of the resulting electrochemical element can be improved.

[0021] <Coefficient of variation of area equivalent diameter> The coefficient of variation of the area-equivalent diameter of the composite particles must be between 5% and 50%, preferably 7% or more, more preferably 10% or more, preferably 45% or less, and more preferably 40% or less. If the coefficient of variation of the area-equivalent diameter is above the lower limit, cracking of the electrode active material in the electrode formed using the composite particles can be effectively suppressed. Furthermore, a coefficient of variation above the lower limit means that the composite particles do not have a perfectly uniform particle size, but rather have a certain degree of variation. Therefore, even when a high-density electrode composite layer is formed, the electrode active material is efficiently filled within the electrode composite layer, and the cycle characteristics of the electrochemical element containing such an electrode composite layer can be improved. In addition, if the coefficient of variation of the area-equivalent diameter is below the upper limit, the flexibility of the resulting electrode and the rate characteristics of the electrochemical element equipped with such an electrode can be improved.

[0022] <Ratio of composite particle area equivalent diameter to primary particle diameter of electrode active material> The area-equivalent diameter of the composite particles is preferably 10 times or more the primary particle diameter of the electrode active material, more preferably 20 times or more, even more preferably 50 times or more, preferably 3000 times or less, more preferably 1000 times or less, and even more preferably 500 times or less. If the area-equivalent diameter of the composite particles is 10 times or more the primary particle diameter of the electrode active material, the handling properties of the composite particles can be improved while maintaining the homogeneity of the composite particles. Furthermore, if the area-equivalent diameter of the composite particles is 3000 times or less the primary particle diameter of the electrode active material, density control during electrode manufacturing becomes easier, and swelling during lithium-ion battery cycle testing can be suppressed.

[0023] <Density coefficient> The density coefficient of the composite particles must be between 1.3 and 3.5, preferably 1.4 or higher, more preferably 1.5 or higher, preferably 3.0 or lower, and even more preferably 2.7 or lower. If the density coefficient is above the lower limit, the flexibility of the resulting electrode and the cycle characteristics of the electrochemical element equipped with such electrode can be improved. If the density coefficient is below the upper limit, the occurrence of cracking of the active material in the resulting electrode can be effectively suppressed.

[0024] <Bulk density> The bulk density of the composite particles is preferably between 1.0 and 4.0. If the bulk density is above the lower limit, cracking of the electrode active material in the electrode formed using the composite particles can be suppressed. Furthermore, if the bulk density is below the upper limit, the flexibility of the resulting electrode can be increased.

[0025] <Homogeneity> The homogeneity of composite particles can affect the cycle characteristics of the resulting electrochemical element. The homogeneity of composite particles can be evaluated by observing them with a scanning electron microscope (SEM). For example, by observing the external appearance of the composite particles with an SEM, the segregation and dispersion of the binder and conductive material on the surface of the composite particles can be evaluated. Furthermore, by observing the cross-section of the composite particles with an SEM, the segregation and dispersion of the binder and conductive material inside the composite particles can be evaluated.

[0026] <Liquidity> The fluidity of composite particles can be evaluated by measuring the angle of repose and collapse angle using a powder tester, as well as by the thinnest doctor blade thickness at which no streaks are formed in the composite particle layer obtained when the composite particle layer is smoothed with a doctor blade, as described in the embodiment of this application. The thinner the doctor blade thickness at which a streaky composite particle layer can be formed, the better the fluidity of the composite particles, and the more homogeneous the electrode composite layer can be formed. The doctor blade thickness evaluated by this method is preferably 400 μm or less, more preferably 330 μm or less, and even more preferably 250 μm or less. If the doctor blade thickness evaluated by the above method is below these upper limits, a homogeneous electrode composite layer can be formed. Furthermore, a homogeneous electrode composite layer can improve the rate characteristics of the electrochemical element. In addition, as described in the embodiment of this application, the fluidity of composite particles can also be evaluated based on the surface roughness of the surface smoothed with a doctor blade. The surface roughness is 5.4 mm. 2 The spatial volume per unit area is 0.50 μm 3 Preferably, the following: 0.30 μm 3 The following is more preferable: 0.20 μm 3 The following is even more preferable: If the composite particles have excellent fluidity, the smoothness of the surface of the resulting electrode can be increased, thereby reducing the internal resistance of the electrochemical element and improving its rate characteristics.

[0027] <Volume resistivity> The volume resistivity of the composite particles is preferably 3000 Ω·cm or less, more preferably 1000 Ω·cm or less, even more preferably 500 Ω·cm or less, even more preferably 250 Ω·cm or less, and particularly preferably 100 Ω·cm or less. The lower limit of the volume resistivity of the composite particles is not particularly limited, but for example, it may be 1 Ω·cm or more. If the volume resistivity of the composite particles is below the above upper limit, the rate characteristics of the resulting electrochemical element can be improved. The volume resistivity of the composite particles can be measured by the method described in the examples.

[0028] <Area circularity> The circularity of the area of the composite particles is preferably 0.50 or more, more preferably 0.60 or more, still more preferably 0.70 or more, preferably 0.93 or less, more preferably 0.92 or less, and still more preferably 0.91 or less. If the circularity of the area of the composite particles is at least the above lower limit value, cracking of the electrode active material in the electrode formed using the composite particles can be suppressed. Further, if the circularity of the area of the composite particles is at most the above upper limit value, the rate characteristics of the obtained electrochemical device can be enhanced.

[0029] <Perimeter envelope degree> The perimeter envelope degree of the composite particles is preferably 0.70 or more, more preferably 0.72 or more, still more preferably 0.75 or more, preferably 0.97 or less, more preferably 0.94 or less, and still more preferably 0.92 or less. If the perimeter envelope degree of the composite particles is at least the above lower limit value, the flexibility of the electrode formed using the composite particles can be enhanced. Further, if the perimeter envelope degree of the composite particles is at most the above upper limit value, the cycle characteristics of the obtained electrochemical device can be enhanced.

[0030] <Electrode active material> The electrode active material is not particularly limited, and examples thereof include various active materials that can be used for the positive and negative electrodes of electrochemical devices such as secondary batteries. The positive electrode active material is not particularly limited, and examples thereof include, for example, lithium-containing cobalt oxide (lithium cobalt oxide, LiCoO2), lithium manganate (LiMn2O4), lithium-containing nickel oxide (LiNiO2), lithium-containing composite oxide of Co-Ni-Mn (Li(Co Mn Ni)O2), lithium-containing composite oxide of Ni-Mn-Al, lithium-containing composite oxide of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO4), olivine-type lithium manganese phosphate (LiMnPO4), Li2MnO3-LiNiO2-based solid solution, Li 1+x Mn 2-x O4 (0 < X < 2) represented by a lithium-excess spinel compound, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 O2, LiNi 0.5 Mn1.5 Examples of known positive electrode active materials include O4. Examples of negative electrode active materials include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials that combine these.

[0031] The particle size of the electrode active material is preferably 0.03 μm or larger, more preferably 0.1 μm or larger, even more preferably 0.5 μm or larger, preferably 500 μm or smaller, more preferably 200 μm or smaller, and even more preferably 30 μm or smaller. The particle size of the electrode active material can be measured by laser diffraction. More specifically, it is preferable that the particle size D50, where the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured using a laser diffraction particle size distribution analyzer becomes 50%, is used as the volume-average particle size, and this value satisfies the above particle size range. If the particle size of the electrode active material is below the above upper limit, the composition within the composite particles can be made more homogeneous. Furthermore, if the particle size of the electrode active material is below the above upper limit, the electrode density of the resulting electrode can be increased, and because the specific surface area of ​​the electrode active material is sufficiently large, the electrochemical reaction when forming the electrochemical element can be optimized. If the particle size of the electrode active material is above the lower limit mentioned above, the handling properties of the powder material used in manufacturing composite particles will improve, and the productivity of the composite particles will also improve. Furthermore, if the particle size of the electrode active material is above the lower limit mentioned above, the degradation of the electrode active material when the electrochemical element is repeatedly charged and discharged can be effectively suppressed.

[0032] <Conductive material> The conductive material is not particularly limited and can be a conductive carbon material such as carbon black (e.g., acetylene black, Ketjenblack®, furnace black, etc.), single-walled or multi-walled carbon nanotubes (multi-walled carbon nanotubes include cup-stacked types), carbon nanohorns, vapor-grown carbon fibers, milled carbon fibers obtained by crushing polymer fibers after firing, single-walled or multi-walled graphene, carbon nonwoven fabric sheets obtained by firing nonwoven fabrics made of polymer fibers, and various metal fibers or foils. These can be used individually or in combination.

[0033] When electrode active materials and conductive materials are used in combination, the ratio of these materials is not particularly limited and can be the general ratio used for electrodes in electrochemical devices.

[0034] <Binder> Examples of binders include conjugated diene polymers, acrylic polymers, aromatic vinyl block polymers, fluorine polymers, cellulose polymers, and cyclic olefin polymers. Binders may be used individually or in combination of two or more types.

[0035] A conjugated diene polymer refers to a polymer containing conjugated diene monomer units. Specific examples of conjugated diene polymers are, without particular limitation, copolymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene copolymer (SBR), butadiene rubber (BR), acrylic rubber (NBR) (a copolymer containing acrylonitrile units and butadiene units), and their hydrides.

[0036] The acrylic polymer is not particularly limited, and examples include polymers containing crosslinkable monomer units, (meth)acrylic acid ester monomer units, and acidic group-containing monomer units. The proportion of (meth)acrylic acid ester monomer units in the acrylic polymer is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 58% by mass or more, preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less.

[0037] Examples of aromatic vinyl block polymers include block polymers containing block regions consisting of aromatic vinyl monomer units. Examples of aromatic vinyl monomers include styrene, styrene sulfonic acid and its salts, α-methylstyrene, pt-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene, with styrene being preferred. Preferred aromatic vinyl block polymers include styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene copolymers, and their hydrides.

[0038] A fluorinated polymer refers to a polymer that contains fluorine-containing monomer units and may also contain fluorine-free monomer units. Examples of fluorine-containing monomers are not particularly limited and include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride, vinyl fluoride, trifluoroethylene, trifluorochloroethylene, 2,3,3,3-tetrafluoropropene, and perfluoroalkyl vinyl ethers. Examples of fluorinated polymers are not particularly limited and include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesins, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer (vinylidene fluoride-hexafluoropropylene copolymer).

[0039] Cellulose polymers are not particularly limited, but include, for example, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethylcellulose, cyanoethyl sucrose, pullulan, and carboxymethylcellulose.

[0040] The cyclic olefin polymers are not particularly limited and include, for example, polymers (addition polymers or ring-opening polymers) synthesized using cyclic olefin compounds as monomers and their hydrides, as well as hydrides of polymers using aromatic vinyl compounds as monomers. Among these, hydrides of ring-opening polymers using cyclic olefin compounds as monomers and hydrides of polymers using aromatic vinyl compounds as monomers are preferred because they allow for easy adjustment of the electrolyte swelling degree and glass transition temperature to appropriate levels.

[0041] The cyclic olefin compound is not particularly limited, but for example, Norbornene compounds, including unsubstituted or alkyl groups such as norbornene, 5-methylnorbornene, 5-ethylnorbornene, 5-butylnorbornene, 5-hexylnorbornene, 5-decylnorbornene, 5-cyclohexylnorbornene, and 5-cyclopentylnorbornene; norbornenes having alkenyl groups, such as 5-ethylidene norbornene, 5-vinyl norbornene, 5-propenyl norbornene, 5-cyclohexenyl norbornene, and 5-cyclopentenyl norbornene; Norbornenes containing aromatic rings, such as 5-phenylnorbornene; Norbornenes containing an oxygen atom and having a polar group, such as 5-methoxycarbonylnorbornene, 5-ethoxycarbonylnorbornene, 5-methyl-5-methoxycarbonylnorbornene, 5-methyl-5-ethoxycarbonylnorbornene, norbornenyl-2-methylpropionate, norbornenyl-2-methyloctanate, 5-hydroxymethylnorbornene, 5,6-di(hydroxymethyl)norbornene, 5,5-di(hydroxymethyl)norbornene, 5-hydroxy-i-propylnorbornene, 5,6-dicarboxynorbornene, and 5-methoxycarbonyl-6-carboxynorbornene; Norbornenes containing a nitrogen atom in a polar group, such as 5-cyanonorbornene; Polycyclic norbornenes with three or more rings that do not contain aromatic ring structures, such as dicyclopentadiene, methyldicyclopentadiene, and tricyclo[5.2.1.02,6]deca-8-ene; Polycyclic norbornenes with three or more aromatic rings, such as tetracyclo[9.2.1.02,10.03,8]tetradeca-3,5,7,12-tetraene (also known as 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene) and tetracyclo[10.2.1.02,11.04,9]pentadeca-4,6,8,13-tetraene (also known as 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene); Tetracyclododecenes that are unsubstituted or have alkyl groups, such as tetracyclododecene, 8-methyltetracyclododecene, 8-ethyltetracyclododecene, 8-cyclohexyltetracyclododecene, 8-cyclopentyltetracyclododecene, and 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.12,5.17,10]-3-dodecene; Tetracyclododecene compounds having double bonds outside the ring, such as 8-methylidenetetracyclododecene, 8-ethylidenetetracyclododecene, 8-vinyltetracyclododecene, 8-propenyltetracyclododecene, 8-cyclohexenyltetracyclododecene, and 8-cyclopentenyltetracyclododecene; Tetracyclododecenes having aromatic rings, such as 8-phenyltetracyclododecene; Tetracyclododecene compounds having substituents containing an oxygen atom, such as 8-methoxycarbonyltetracyclododecene, 8-methyl-8-methoxycarbonyltetracyclododecene, 8-hydroxymethyltetracyclododecene, 8-carboxytetracyclododecene, tetracyclododecene-8,9-dicarboxylic acid, and tetracyclododecene-8,9-dicarboxylic acid anhydride; Tetracyclododecene compounds having substituents containing nitrogen atoms, such as 8-cyanotetracyclododecene and tetracyclododecene-8,9-dicarboxylateimide; Tetracyclododecenes having substituents containing halogen atoms, such as 8-chlorotetracyclododecene; Tetracyclododecenes having substituents containing silicon atoms, such as 8-trimethoxysilyltetracyclododecene; Hexacycloheptadecenes such as the Diels-Alder adducts of the aforementioned tetracyclododecenes and cyclopentadienes; These are some examples.

[0042] Among the cyclic olefin compounds, nonpolar norbornene monomers are preferred, with unsubstituted or alkyl-containing norbornenes (e.g., norbornene, 8-ethyltetracyclododecene), norbornenes having an alkenyl group (e.g., ethylidenetetracyclododecene (8-ethylidenetetracyclododecene)), dicyclopentadiene, norbornene derivatives having an aromatic ring (e.g., tetracyclo[9.2.1.02,10.03,8]tetradeca-3,5,7,12-tetraene (also known as 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene)), and unsubstituted or alkyl-containing tetracyclododecenes (e.g., tetracyclododecene, 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.12,5.17,10]-3-dodecene) being more preferred.

[0043] Furthermore, a polymer using a cyclic olefin compound as a monomer, which can be optionally hydrogenated, may be a polymer using only a cyclic olefin compound as a monomer, or a polymer using a cyclic olefin compound and a copolymerizable compound other than a cyclic olefin compound as a monomer, but it is preferable that the polymer uses only a cyclic olefin compound as a monomer.

[0044] Furthermore, polymers using cyclic olefin compounds as monomers, which can be optionally hydrogenated, are preferably polymers using tetracyclododecene, dicyclopentadiene, and norbornene as monomers, and more preferably ring-opening polymers using tetracyclododecene, dicyclopentadiene, and norbornene as monomers.

[0045] Among the above, a polymer material that dissolves in a non-aqueous solvent with a boiling point of 95°C or lower, more preferably 90°C or lower, and even more preferably 85°C or lower at 1 atm is preferred as the binder. By using a binder that is soluble in a non-aqueous solvent with a boiling point of 1 atm below the above upper limit, the degradation of the polymer material due to residual solvent is suppressed, and the long-term life characteristics of the resulting electrochemical element can be improved. The lower limit of the boiling point of the non-aqueous solvent in which the binder is soluble at 1 atm is not particularly limited, but can be 50°C or higher. Examples of solvents that satisfy these conditions include cyclohexane, n-hexane, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, methylene chloride, and chloroform.

[0046] <Method for manufacturing composite particles> The composite particles of the present invention described above can be manufactured according to any manufacturing method, without being particularly limited, as long as they satisfy the above-mentioned essential and preferred attributes. In particular, it is preferable to manufacture the composite particles of the present invention using a granulation tank equipped with two or more stirring blades with different stirring shafts. Below, as an example of a manufacturing method that can efficiently manufacture the composite particles of the present invention, a manufacturing method using a granulation tank equipped with two or more stirring blades with different stirring shafts will be described.

[0047] <Granulation tank> The granulation tank is equipped with two or more stirring blades with opposite stirring axes. By providing two or more stirring blades with opposite stirring axes, the uniformity of the composition of the resulting composite particles is increased, and as a result, the cycle characteristics of an electrochemical element equipped with electrodes formed using such composite particles can be improved. An example of such a granulation tank will be described with reference to Figures 1 and 2. Figure 1 is a top view of the granulation tank 1, and Figure 2 is a cross-sectional view following the AA cutting line shown in Figure 1. The granulation tank 1 is equipped with a main stirring blade 2 and a secondary stirring blade 3 with opposite stirring axes to the main stirring blade 2. The number of stirring blades is not particularly limited as long as there are two or more. By having two or more stirring blades, the uniformity of the composition of the composite particles is increased, and as a result, the cycle characteristics of an electrochemical element equipped with electrodes formed using such composite particles can be improved.

[0048] Furthermore, although not shown in the figures, the granulation tank 1 is equipped with at least one supply means capable of supplying a liquid composition. Examples of such supply means include a spray nozzle configured to supply a mist-like liquid and a dropping funnel. The number of supply means is not particularly limited, but depending on the size of the granulation tank, multiple supply means may be arranged dispersed from one another. Furthermore, although not shown in the figures, the granulation tank 1 may be equipped with a supply port for powder material and a discharge port configured to discharge the formed composite particles.

[0049] In Figure 2, the stirring axis of the main stirring blade 2 is shown by a dashed line as the first stirring axis RA1, and the stirring axis of the auxiliary stirring blade is shown by a dashed line as the second stirring axis RA2. In Figure 2, the angle θ between the first stirring axis RA1 and the second stirring axis RA2 is approximately 90 degrees. The angle between the first stirring axis RA1 and the second stirring axis RA2 refers to the acute angle of the angle formed by these two axes. Here, in this specification, "different stirring axes" means that the angle θ between the stirring axes is between 20° and 90°. Preferably, the angle θ between the stirring axes is 30° or more, more preferably 45° or more, and even more preferably 85° or more. If the angle θ between the stirring shafts is within the above range, the powder material can be effectively stirred, and the particle size and coefficient of variation of the resulting composite particles can be well controlled. As a result, the flexibility of the electrode formed using such composite particles and cracking of the electrode active material in the electrode can be suppressed, and furthermore, the cycle characteristics of the resulting electrochemical element can be improved. The "coefficient of variation" refers to the coefficient of variation of the particle size distribution of the composite particles, and can be calculated as a percentage by dividing the standard deviation of the area-equivalent diameter of the composite particles by the average value of the area-equivalent diameter, according to the method described in the examples of this specification.

[0050] The shape of the granulation tank is not particularly limited, as long as it can accommodate powder material containing electrode active material for a predetermined period of time and can be stirred by at least two stirring blades. For example, the shape of the granulation tank may be a cylindrical shape with a circular bottom and top surface and a tapered top in the height direction, as shown in granulation tank 1 in Figures 1-2. When the shape of the granulation tank is a predetermined cylindrical shape as shown in Figures 1-2, at least one of the two stirring shafts may coincide with the central axis of the cylinder, and the other stirring shaft may coincide perpendicular to this central axis. Furthermore, when the shape of the granulation tank is a predetermined cylindrical shape as shown in Figures 1-2, the value obtained by dividing the diameter of the bottom surface by the height (diameter / height) is preferably 0.1 or more, more preferably 0.3 or more, even more preferably 0.5 or more, preferably 2.5 or less, more preferably 2.0 or less, and even more preferably 1.5 or less. This is because the powder material can be effectively stirred.

[0051] The main stirring blade 2 comprises three main blades 21. The shape and number of the main blades 21 are not particularly limited. The secondary stirring blade 3 comprises two secondary blades 31. The secondary blades 31 are shown as anchor blades in Figures 1 and 2, but are not limited to this. The number of secondary blades 31 is also not limited to the illustrated configuration and may be one or three or more. Furthermore, although not shown, the granulation tank 1 may be equipped with a ventilation mechanism configured to suppress the mixing of powder material into the drive units of the main stirring blade 2 and secondary stirring blade 3 by venting air.

[0052] Examples of granulation tanks that meet the above conditions include the Earth Technica high-speed mixer, the Mitsui Sanko Henschel mixer, the Pauleck vertical granulator, the Freund Industrial CF granulator, the Nara Machine Works high-speed stirring and mixing granulator, the Dalton SP granulator, and the Freund Industrial Balance Gran.

[0053] The following describes the various operations that can be performed inside the granulation tank.

[0054] <(i) Preliminary stirring procedure> In the preliminary stirring operation, the powder material is stirred to achieve a stirred state. Here, the powder material must contain an electrode active material, and optionally, a conductive material may also be included. The above-mentioned materials can be used as the electrode active material and conductive material. By performing the preliminary stirring operation, the cycle characteristics of the electrochemical element equipped with electrodes formed using the resulting composite particles can be improved.

[0055] In the preliminary stirring operation, it is preferable not to incorporate liquid components. Powder materials inevitably contain small amounts of liquid components due to the influence of moisture that may adhere to them during manufacturing and storage. In other words, the solid content concentration of the powder material at the start of the preliminary stirring operation is highly likely to be less than 100% by mass. Here, from the viewpoint of improving the properties of the resulting composite particles and the manufacturing efficiency of the composite particles, it is preferable to increase the solid content concentration of the powder material by performing the preliminary stirring operation. Specifically, it is preferable that the solid content concentration of the powder material at the end of the preliminary stirring operation be 95% by mass or more, more preferably 97% by mass or more, and even more preferably 98% by mass or more. The solid content concentration of the powder material can be measured by the method described in the examples.

[0056] The peripheral speed of the main and auxiliary impellers during the pre-stirring operation is preferably between 1 m / s and 20 m / s. Within this peripheral speed range, the homogeneity of the composition of the resulting composite particles can be increased, thereby suppressing cracking of the electrode active material in the resulting electrode, and consequently improving the cycle characteristics of the electrochemical element equipped with such electrode. Here, the peripheral speeds of the main and auxiliary impellers during the pre-stirring operation may be the same or different, and may be different, but if they are different, it is preferable that the peripheral speed of the auxiliary impeller is faster than that of the main impeller.

[0057] In the preliminary stirring operation, the aeration rate is preferably such that the flow rate of air flowing into the granulation tank divided by the capacity of the granulation tank (flow rate / capacity) is 0.1 / min or more and 100 / min or more. Within this range of aeration rate, the solid content concentration of the powder material can be increased effectively during the preliminary stirring operation. The aeration rate may be the aeration rate due to the aeration mechanism that prevents the powder material from entering the drive section of the main and auxiliary stirring blades, as described above. Furthermore, the temperature of the aeration air is preferably less than 50°C, more preferably 45°C or less, even more preferably 40°C or less, and particularly preferably 30°C or less.

[0058] The time required for the preliminary stirring operation (preliminary stirring time) is not particularly limited. For example, the preliminary stirring time is preferably a time that allows the solid content concentration to reach or exceed the preferred threshold mentioned above. For example, the preliminary stirring time may be 5 minutes or more and 60 minutes or less.

[0059] The preliminary stirring operation may be carried out in multiple stages. In that case, it is preferable to carry out the preliminary stirring operation using a stirring device different from the one used in the granulation tank equipped with the aforementioned stirring blades (hereinafter also referred to as "stirring device A") prior to the preliminary stirring operation in the granulation tank equipped with the aforementioned stirring blades. Stirring device A is not particularly limited as long as it is a stirring device different from the one used in the granulation tank equipped with the aforementioned stirring blades, and examples include dry mixing devices and wet mixing devices. Examples of dry mixing devices include the Miracle KCK manufactured by Asada Iron Works Co., Ltd. and the Hybridization System manufactured by Nara Machinery Co., Ltd. Examples of wet mixing devices include the Planetary Despa manufactured by Asada Iron Works Co., Ltd. By carrying out such preliminary stirring operation using stirring device A before the preliminary stirring operation using the granulation tank equipped with the aforementioned stirring blades, the rate characteristics of the resulting electrochemical elements can be improved. This is thought to be because the volume resistivity of the resulting composite particles can be reduced by carrying out the preliminary stirring operation using stirring device A.

[0060] (ii) Pre-composite particle formation operation In the pre-composite particle formation operation, a composition containing a binder and a solvent is added to a stirred powder material to form pre-composite particles. The binder can be the one described above. Furthermore, the method of adding the composition containing the binder and solvent to the powder material in the pre-composite particle formation operation is not particularly limited, as long as it is not a single-composite addition. For example, this could be a continuous addition throughout the pre-composite particle formation operation, or an intermittent addition with one or more periods of interruption between additions during the pre-composite particle formation operation. Among these, the continuous addition method is preferred. While the pre-composite particle formation operation is being carried out, that is, in an atmosphere where the powder material, solvent, and binder are all stirred, pre-composite particles of the powder material and binder are gradually formed, and a particle sizing effect can occur as particles collide with each other and with the solvent. In other words, during the pre-composite particle formation operation, the formation of pre-composite particles and the particle sizing effect can proceed simultaneously in the presence of the solvent. In this way, the pre-composite particle formation operation allows for the formation of pre-composite particles while maintaining their uniform size.

[0061] As mentioned above, spray nozzles and dropping funnels are examples of means for adding a composition containing a binder and a solvent to a powder material. In particular, when using a spray nozzle such as a two-fluid spray that has a mechanism for crushing and atomizing the liquid by the flow of gas and ejecting it, the gas-liquid ratio (gas volume / liquid volume) is preferably 1.30 or higher, more preferably 1.40 or higher, even more preferably 1.45 or higher, preferably 1.80 or lower, more preferably 1.70 or lower, and even more preferably 1.60 or lower. If the gas-liquid ratio is above the lower limit above, it is possible to suppress the enlargement of the particle size of the composite particles. Also, if the gas-liquid ratio is below the upper limit above, it is possible to suppress the particle size of the composite particles from becoming excessively small. Furthermore, the spray surface density (g / mm²), which is the value corresponding to the amount of composition sprayed per unit area on a stationary surface, is also important. 2 The value of ( / min) is 0.20 (g / mm³). 2 It is preferable that it be 0.25 (g / mm³) or more, and 0.25 (g / mm³)2 It is more preferable that it be 0.38 (g / mm³) or more. 2 It is even more preferable that it be 0.60 (g / mm³) or more. 2 It is preferable that the concentration be less than or equal to 0.50 (g / mm³) per minute. 2 It is more preferable that it be less than or equal to 0.41 (g / mm³) / min. 2 It is even more preferable that the spray surface density (g / mm³) is less than or equal to the spray surface density (g / mm³). 2 If the value of ( / min) is greater than or equal to the lower limit above, it is possible to suppress the particle size of the composite particles from becoming excessively small. In other words, by controlling the gas-liquid ratio and / or spray surface density within an appropriate range, the particle size of the resulting composite particles can be well controlled.

[0062] Any solvent can be used, without any particular limitations. For example, organic solvents such as N-methyl-2-pyrrolidone, cyclohexane, n-hexane, acetone, methyl ethyl ketone, ethyl acetate, tetrahydrofuran, methylene chloride, and chloroform, as well as water, can be used as solvents. Among these, non-aqueous solvents with a boiling point of 95°C or lower at 1 atm, where the binder is soluble, can be preferably used. It is more preferable that the boiling point of the non-aqueous solvent at 1 atm be 90°C or lower, and even more preferable that it be 85°C or lower. If the boiling point at 1 atm is below the above upper limit, the solvent can be efficiently removed in the granulation tank, reducing the drying energy when forming pre-composite particles. The lower limit of the boiling point of the non-aqueous solvent at 1 atm is not particularly limited, but it is preferable to be 50°C or higher from the viewpoint of improving the stability when forming pre-composite particles. The solvents listed above are examples of solvents that satisfy these conditions. One type of solvent may be used alone, or two or more types may be used in any ratio.

[0063] The viscosity index of the composition containing the binder and solvent, which is continuously added to the granulation tank during the pre-composite particle formation operation, is preferably between 100 mPa·s and 1000 mPa·s. By keeping the viscosity index of the composition containing the binder and solvent within the above range, the particle size and coefficient of variation of the resulting composite particles can be well controlled. The viscosity index of the composition is the value obtained by dividing the viscosity of the composition by the solid content concentration and multiplying by 100, and can be measured and calculated by the method described in the examples.

[0064] In the pre-composite particle formation operation, the peripheral speed of the main and auxiliary stirring blades is preferably between 1 m / s and 20 m / s. If the peripheral speed of the main stirring blade is within the above range, the particle size of the resulting composite particles can be controlled well. Furthermore, if the peripheral speed of the auxiliary stirring blade is within the above range, the coefficient of variation of the resulting composite particles can be controlled well. Moreover, from the viewpoint of enhancing the particle sizing effect that occurs during the pre-composite particle formation operation and suppressing gas generation during high-temperature storage of electrodes formed using composite particles, the peripheral speed of the main stirring blade is preferably 6 m / s or higher.

[0065] In the pre-composite particle formation operation, the aeration rate is preferably such that the ratio of the airflow rate into the granulation tank to the tank's capacity (flow rate / capacity) is 0.1 / min or more and 100 / min or more. Within this aeration rate range, the amount of solvent vapor in the granulation layer can be well controlled during the pre-composite particle formation operation, and pre-composite particles can be formed efficiently.

[0066] The duration of the pre-composite particle formation operation (pre-composite particle formation time) is not particularly limited. For example, the pre-composite particle formation time may be between 5 minutes and 60 minutes.

[0067] <(iii) Sizing operation> In the particle sizing operation, the pre-composite particles are stirred after the addition of the composition is complete (i.e., after the completion of (ii) the pre-composite particle formation operation) to sizing them into composite particles.

[0068] In the particle sizing operation, the peripheral speeds of the main and auxiliary stirring blades are preferably between 0.1 m / s and 10 m / s. If the peripheral speed of the main stirring blade is within the above range, the density coefficient and area circularity of the resulting composite particles can be controlled well. Furthermore, if the peripheral speed of the auxiliary stirring blade is within the above range, the coefficient of variation and perimeter envelope of the resulting composite particles can be controlled well.

[0069] In the granulation process, the aeration rate is preferably such that the ratio of the airflow rate into the granulation tank to the tank's capacity (flow rate / capacity) is between 0.1 / min and 100 / min. Within this aeration range, the wetness of the composite particles can be well controlled during the granulation process, and the composite particles can be formed efficiently.

[0070] The duration of the particle sizing operation (sizing time) is not particularly limited. For example, the sizing time may be 10 seconds or more, 60 minutes or less, preferably 20 minutes or less, preferably 8 minutes or less, and more preferably 3 minutes or less. By keeping the sizing operation time below the above upper limit, the amount of gas generated when electrodes formed using composite particles are stored under high-temperature conditions can be reduced.

[0071] <Temperature inside the granulation tank> Through the operations (i) to (iii) described above, the temperature inside the granulation tank is preferably less than 50°C, more preferably 45°C or lower, and even more preferably 40°C or lower. By satisfying these temperature conditions, the degradation of the electrode active material contained in the resulting composite particles can be effectively suppressed, and cracking of the electrode active material in the electrode formed using the composite particles can be effectively suppressed.

[0072] (Electrodes for electrochemical devices) The electrode for the electrochemical element of the present invention comprises an electrode composite layer containing the composite particles of the present invention described above. The electrode for the electrochemical element of the present invention has excellent flexibility, less cracking of the contained electrode active material, and can further improve the cycle characteristics and rate characteristics of the electrochemical element equipped with such an electrode.

[0073] <Method for manufacturing electrodes for electrochemical elements> The electrode for the electrochemical element of the present invention can be manufactured by pressurizing composite particles produced according to the manufacturing method of the present invention described above on an electrode substrate to form an electrode composite layer (pressure molding operation).

[0074] [Pressure molding operation] The pressure molding operation can be carried out according to known methods. For example, composite particles manufactured according to the manufacturing method of the present invention can be subjected to a roll press and roll-pressed on an electrode substrate to pressure-molde the composite particles on the electrode substrate and form an electrode composite layer. The pressure during pressing can be appropriately set according to the desired electrode density.

[0075] As the electrode substrate, a material that is conductive and electrochemically durable is used. Specifically, as the electrode substrate, a current collector made of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum may be used. Note that one of the above materials may be used alone, or two or more may be used in any ratio.

[0076] (Electrochemical element) Furthermore, the electrochemical element of the present invention comprises the electrodes for the electrochemical element described above. Because the electrochemical element of the present invention comprises the electrodes for the electrochemical element of the present invention, it exhibits excellent cycle characteristics and rate characteristics. The electrochemical element is not particularly limited and may be, for example, a lithium-ion secondary battery, an electric double-layer capacitor, or a lithium-ion capacitor, and may preferably be a lithium-ion secondary battery.

[0077] Herein, we will describe an example in which the electrochemical element is a lithium-ion secondary battery, but the present invention is not limited to the example below. The lithium-ion secondary battery as the electrochemical element of the present invention usually comprises electrodes (positive electrode and negative electrode), an electrolyte, and a separator, and at least one of the positive electrode and the negative electrode uses the electrode for the electrochemical element of the present invention.

[0078] <Electrode> Here, as electrodes other than the electrochemical element electrodes of the present invention described above, which can be used in lithium-ion secondary batteries as electrochemical elements, known electrodes can be used without particular limitation. Specifically, as electrodes other than the electrochemical element electrodes described above, electrodes formed by forming an electrode composite layer on a current collector using a known manufacturing method can be used.

[0079] <Electrolyte> Typically, an organic electrolyte is used as the electrolyte, which is obtained by dissolving a supporting electrolyte in an organic solvent. For example, lithium salts are used as the supporting electrolyte. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred because they are easily soluble in the solvent and exhibit a high degree of dissociation, with LiPF6 being particularly preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in any ratio.

[0080] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte, but 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. In addition, known additives such as vinylene carbonate, fluoroethylene carbonate, and ethyl methyl sulfone may be added to the electrolyte.

[0081] <Separator> As the separator, there are no particular limitations and any known types can be used. Among them, a microporous membrane made of polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred. Furthermore, as the separator, a separator with a functional layer may be used, in which a functional layer (porous membrane layer or adhesive layer) is provided on one or both sides of the separator substrate.

[0082] <Manufacturing method for lithium-ion secondary batteries> A lithium-ion secondary battery can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. To prevent pressure rise inside the secondary battery, overcharging and discharging, etc., fuses, overcurrent protection elements such as PTC elements, expanded metal, lead plates, etc., may be provided as needed. The shape of the secondary battery can be any of the following: coin type, button type, sheet type, cylindrical type, prismatic type, flat type, etc. [Examples]

[0083] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" used to express quantities refer to mass unless otherwise specified. Furthermore, in polymers produced by copolymerizing multiple types of monomers, the proportion of repeating units (monomer units) formed by polymerizing a certain monomer in the polymer is, unless otherwise specified, usually equal to the ratio of that particular monomer to the total monomers used in the polymerization of the polymer (starting ratio). In the examples and comparative examples, the measurement and evaluation of various attributes were carried out according to the methods described below.

[0084] <Solid content concentration of powdered material> The sample to be measured was weighed in Wo[g] onto an aluminum dish with a mass of Wa[g] and heated on a hot plate at 130°C for 1 hour. The mass W[g] after heating was measured, and the solid content concentration Cs[%] of the powder material was calculated using the following formula. Cs = (W - Wa) / Wo × 100 [%]

[0085] <Viscosity index Cη of a composition containing a binder and solvent> The viscosity index of the composition containing the binder and solvent (binder solution) was calculated using the following formula based on the viscosity measured by the method described below and the solid content concentration measured by the method described above. Viscosity measurement: Viscosity η was measured at 25°C and 60 rpm using a Type B viscometer (TVB-10M, manufactured by Toki Sangyo Co., Ltd.). The rotor used was changed as appropriate according to the viscosity. Calculation of viscosity index: Cη = η / Cs × 100 [mPa·s]

[0086] <Area-equivalent diameter of composite particles, coefficient of variation of particle size distribution, area circularity, and perimeter envelope> Based on the image analysis method conforming to JIS Z 8827-1, image analysis was performed on the composite particles created in the examples and comparative examples, and the specified physical properties were calculated. Specifically, using Malvern's "Morphologi G3," 4000 images of the composite particles prepared in each example and comparative example were binarized and analyzed to determine the following physical properties. The definitions of terms conform to JIS Z 8890, "Evaluation of Particle Properties of Powders - Terminology." Average value of area-equivalent diameter: The average value of the area-equivalent diameter of 4000 composite particles analyzed (D) A (μm) Coefficient of variation of area-equivalent diameter: The average value D of the area-equivalent diameter of 4000 composite particles analyzed. A The value CV calculated from its standard deviation σ Coefficient of variation of area-equivalent diameter CV = Standard deviation of area-equivalent diameter σ / Mean value of area-equivalent diameter D A ×100(%) Average area circularity: For 4000 particles analyzed, 4πA / P 2 The average value of area circularity C is calculated using (A: projected area, P: perimeter). A Mean Perimeter Envelopment: The average value obtained by dividing the perimeter of the convex circumscribed figure (least convex hull) of all particles within the observed field of view by the perimeter P.

[0087] <Ratio of composite particle area equivalent diameter to primary particle diameter of electrode active material> The primary particle diameter of the electrode active material was calculated by observing the composite particles obtained in the examples and comparative examples using SEM. Specifically, 10 target composite particles were selected at a magnification of 500x, and these target composite particles were further observed at 10,000x magnification. The particle diameter (diameter of the circumscribed circle enclosing the particle) of 100 primary electrode active material particles was measured, and the average value of these measurements was calculated. The obtained primary particle diameter of the electrode active material was then divided by the area equivalent diameter of the composite particle calculated according to the above procedure to determine how many times larger the area equivalent diameter of the composite particle was than the primary particle diameter of the electrode active material.

[0088] <Density coefficient> Density coefficient Cρ = Compression density ρ p / Bulk density ρ a [Bulk density ρ a ] Based on the constant volume measurement method described in JIS R 1628-1997, the bulk density of composite particles (g / cm³) 3 ) Measured. [Compression density ρ p ] 4.00 g of the composite particles prepared in the examples and comparative examples were pressurized at 50 MPa and the bottom surface area was 2 cm². 2 Cylindrical pellets with a diameter of 15.97 mm were prepared, their thickness was measured, and their compressed density was calculated.

[0089] <Fluidity (evaluated based on doctor blade thickness)> On a 20cm square glass plate with a smooth surface, 5g of the composite particles produced in the example and comparative example were placed so that each had a diameter of approximately 20mm. When the mixture was leveled with a doctor blade, it was determined whether or not streaks appeared in the leveled composite particle layer, and the thinnest doctor blade thickness that did not produce streaks was determined.

[0090] <Fluidity (evaluation based on surface roughness)> On a 20cm square smooth glass plate, 25g of the composite particles produced in the examples and comparative examples were placed so that each particle had a diameter of approximately 20mm, and then smoothed with a 280μm doctor blade. The smoothed surface was then examined using a laser microscope at 5.4mm. 2 Space volume per unit area (μm 3 ) was measured.

[0091] <Volume resistivity> The composite particles prepared in the examples and comparative examples were measured to have a diameter of 25.4 mm and a density of 3.2 g / cm³. 2 Pellets were produced by pressure molding in the following manner. The electrical resistance of these pellets was measured using a digital LCR meter (Yokogawa HP Corporation, model name "4261A"). The measured electrical resistance values ​​were converted to volume resistivity (Ω·cm).

[0092] <Electrode flexibility> The positive electrodes prepared in the examples and comparative examples were evaluated for cracking of the positive electrode composite layer when wrapped around rods of different diameters. The smaller the diameter of the rod in which the positive electrode composite layer did not crack when wrapped around it, the more flexible and windable the electrode is. The flexibility of the electrode was evaluated according to the following criteria, based on the diameter of the thinnest rod in which the positive electrode composite layer did not crack. A: It won't break even when wrapped around a rod with a diameter of 1.50 mm. B: It won't break even when wrapped around a rod with a diameter of 1.80 mm. C: It won't break even when wrapped around a 2.10mm diameter rod. D: It won't break even when wrapped around a 3.00mm diameter rod.

[0093] <Presence or absence of active material cracking> Cross-sectional SEM images of the cathodes prepared in the examples and comparative examples were observed at 1000x magnification, and evaluated as follows according to the number of cracks observed in the active material. A: No fractured electrode active material was observed. B: The number of fractured electrode active materials is 1 or more, but less than 3. C: The number of broken positive electrode active materials is 3 or more, but less than 5. D: The number of broken positive electrode active material pieces is 5 or more.

[0094] <Cycle Characteristics> The lithium-ion secondary batteries, which were prepared as electrochemical elements in the examples and comparative examples, were left to stand at 25°C for 5 hours after electrolyte injection. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then aged at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times to obtain evaluation cells. Next, under conditions of 45°C, the evaluation cell described above underwent 100 charge-discharge cycles with a cell voltage of 4.20-3.00V and a charge-discharge rate of 0.5C. The discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle as X2. Using these discharge capacities X1 and X2, the capacity retention rate = (X2 / X1) × 100 (%) was calculated and evaluated according to the following criteria. A higher capacity retention rate indicates superior cycle characteristics of the lithium-ion secondary battery. A: Capacity retention rate of 90% or more B: Capacity retention rate is 85% or more but less than 90% C: Capacity retention rate is 80% or more but less than 85% D: Capacity retention rate is less than 80%

[0095] <Gas generation during high-temperature storage> The evaluation cells prepared in the <Cycle Characteristics> section described above were charged using the CC-CV method at a constant current of 0.2C at a temperature of 25°C (maximum cell voltage 4.20V), and then stored in a constant temperature environment of 60°C for one week. The increase in cell volume measured before and after storage was used as the amount of gas generated, and was evaluated according to the following criteria. A: Gas generation is less than 5% B: Gas generation amount is 5% or more but less than 10% C; Gas generation amount is 10% or more but less than 20% D: Gas generation is 20% or more

[0096] <Rate Characteristics> The lithium-ion secondary batteries, which were prepared as electrochemical elements in the examples and comparative examples, were left to stand at 25°C for 5 hours after electrolyte injection. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then aged at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times. Next, under a temperature of 25°C, the cells were charged to 4.2V using a constant current method at 0.1C, and then discharged to 3.0V at 0.1C to determine the 0.1C discharge capacity. Furthermore, the cells were charged to 4.2V at 0.1C and then discharged to 3.0V at 1C to determine the 1C discharge capacity. These measurements were performed on 10 cells each of the lithium-ion secondary batteries used as electrochemical elements in the examples and comparative examples, and the average values ​​of each measurement were defined as the 0.1C discharge capacity a and the 1C discharge capacity b. The ratio of electrical capacities = b / a × 100 (%) was then calculated and evaluated according to the following criteria. A larger ratio of electrical capacities indicates that the lithium-ion secondary battery used as an electrochemical element has superior rate characteristics. A: The ratio of electrical capacity is 90% or more. B: The ratio of electrical capacity is 80% or more but less than 90% C: The ratio of electrical capacity is between 70% and less than 80%. D: The ratio of electrical capacity is less than 70%

[0097] (Example 1) <Manufacturing of Binder A1> In a reactor equipped with a stirring device and thoroughly purged with nitrogen, 270 parts of dehydrated cyclohexane and 0.53 parts of ethylene glycol dibutyl ether were added, followed by 0.47 parts of n-butyllithium (15% cyclohexane solution). While stirring the entire mixture at 60°C, 12.5 parts of dehydrated styrene were continuously added to the reactor over 40 minutes. After the addition was complete, the mixture was stirred for another 20 minutes at 60°C. The polymerization conversion rate at this point was measured by gas chromatography and found to be 99.5%. Next, 75.0 parts of dehydrated isoprene were continuously added to the reaction mixture over 100 minutes, and stirring was continued for 20 minutes after the addition was complete. The polymerization conversion rate at this point was 99.5%. Subsequently, 12.5 parts of dehydrated styrene were continuously added over 60 minutes, and the mixture was stirred for 30 minutes after the addition was complete. The polymerization conversion rate at this point was approximately 100%. Here, 0.5 parts of isopropyl alcohol were added to the reaction solution to stop the reaction. Of the total isoprene-derived structural units in the obtained block copolymer [C1], the proportion of structural units derived from 1,2- and 3,4-addition polymerization was 58%. Next, the polymer solution was transferred to a pressure reactor equipped with a stirring device, and 7.0 parts of diatomaceous earth-supported nickel catalyst (manufactured by JGC Catalysts & Chemicals, product name "E22U", nickel load 60%) and 80 parts of dehydrated cyclohexane were added and mixed as hydrogenation catalysts. The inside of the reactor was purged with hydrogen gas, and hydrogen was supplied while stirring the solution, and the hydrogenation reaction was carried out at a temperature of 190°C and a pressure of 4.5 MPa for 6 hours. After the hydrogenation reaction was complete, the reaction solution was filtered to remove the hydrogenation catalyst. To the filtrate, 1.0 part of a xylene solution containing 0.1 parts of the phenolic antioxidant pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (manufactured by Koyo Chemical Research Institute, product name "Songnox1010") was added and dissolved. Further addition of cyclohexane was then used to prepare a binder A1 solution of the specified concentration.

[0098] <Evaluation of Binder A1> -Proportion of structural units derived from 1,2- and 3,4-addition polymerization among the structural units derived from chain-like conjugated diene compounds in polymer block [B]- Of the structural units derived from the chain-like conjugated diene compound in polymer block [B], the proportion of structural units derived from 1,2- and 3,4-addition polymerization is as follows: 1 From the 1H-NMR spectrum (in deuterated chloroform), it was found that the carbon atoms bonded to the carbon-carbon unsaturated bonds in the polymer backbone are 1 H and the carbon atoms of the carbon-carbon unsaturated bond in the polymer side chain 1 It was calculated from the ratio of H.

[0099] <Fabrication of composite particles> A composite particle manufacturing apparatus was prepared using a cylindrical container with an inner diameter of 180 mm and a capacity of 2 L as a granulation tank. The apparatus had stirring blades on two axes, vertically and horizontally, with the axis of the cylindrical container being the vertical direction (the vertical direction being the main stirring blade and the horizontal direction being the secondary stirring blade). The main stirring blade was an inclined paddle with three main blades of 170 mm in diameter, and the secondary stirring blade was a V-shaped anchor blade with a diameter of 30 mm. To prevent raw material contamination of the drive parts of the main and secondary stirring blades, a sealing mechanism was installed that allowed air to pass through. Using the above composite particle manufacturing apparatus, composite particles were manufactured by performing (i) a preliminary stirring operation, (ii) a pre-composite particle formation operation, and (iii) a sizing operation in this order. First, (i) in the preliminary stirring operation, 96 parts by mass (1344 g) of NMC532 (average particle size 6 μm) as a positive electrode active material for lithium-ion batteries was added to the granulation tank, and carbon black (BET specific surface area: 62 m²) was added as a conductive material. 2 / g, bulk density 0.16g / cm³ 3 Two parts by mass (28 g) of the material were added. Next, room temperature air (hereinafter also referred to as "sealing air") was circulated at a rate of 20 L / min (airflow rate of 10 g / min) to seal the drive units of the main and auxiliary stirring blades, and the mixture was stirred for 15 minutes under operating conditions of a peripheral speed of 5 m / s for the main stirring blade and a peripheral speed of 6 m / s for the auxiliary stirring unit. The solid content concentration of the powder material after stirring was measured to be 99% by mass or higher. Next, (ii) as a pre-composite particle formation operation, sealing air at room temperature was flowed at 20 L / min (airflow rate 10 / min), and the main impeller was operated at a peripheral speed of 5 m / s and the secondary impeller at a peripheral speed of 6 m / s. A composition containing binder A1 and solvent (solid content concentration: 10% by mass, viscosity index: 200 mPa·s, solvent: cyclohexane) was continuously added as solid content at a rate of 280 g over 15 minutes using a dropwise funnel. Next, (iii) as a granulation operation, sealing air at room temperature was circulated at 20 L / min (airflow rate 10 / min), and the system was operated for 10 minutes under the operating conditions of the main stirring blade at a peripheral speed of 2 m / s and the auxiliary stirring blade at a peripheral speed of 2 m / s. Composite particles prepared by performing the above operations (i) to (iii) in this order were subjected to various measurements. The results are shown in Table 1.

[0100] <Fabrication of positive electrodes for lithium-ion secondary batteries> The prepared composite particles were supplied to the press rolls (roll temperature 100°C, press linear pressure 500kN / m) of a roll press machine (Hirano Giken Kogyo Co., Ltd. "Oshikiri Rough Surface Hot Roll") using a quantitative feeder (Nikka Spray KV, Nikka Co., Ltd.). A 20μm thick aluminum foil was inserted between the press rolls, and the composite particles supplied from the quantitative feeder were attached to the aluminum foil. The mixture was then pressure-molded at a molding speed of 1.5m / min, resulting in a basis weight of 30mg / cm². 2 A positive electrode raw material for lithium-ion secondary batteries having a positive electrode active material layer was obtained. This positive electrode raw material was rolled using a roll press, and a density of 3.5 g / cm³ was obtained. 3 A sheet-like positive electrode was fabricated consisting of a positive electrode composite layer and aluminum foil. <Fabrication of the negative electrode> In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 3.5 parts of itaconic acid as an acidic group-containing monomer, 63.5 parts of styrene as an aromatic vinyl monomer, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized water, and 0.5 parts of potassium persulfate as a polymerization initiator were added and thoroughly stirred. Polymerization was then started by heating to 50°C. When the polymerization conversion rate reached 96%, the mixture was cooled to stop the polymerization reaction, and a mixture containing particulate binder (styrene-butadiene copolymer) was obtained. A 5% aqueous sodium hydroxide solution was added to this mixture to adjust the pH to 8, and unreacted monomers were removed by heated vacuum distillation. The mixture was then cooled to below 30°C to obtain an aqueous dispersion containing a binder for the negative electrode. Next, 48.75 parts of artificial graphite as the negative electrode active material, 48.75 parts of natural graphite, and 1 part of carboxymethylcellulose as a thickener were added to a planetary mixer. Furthermore, the mixture was diluted with deionized water to a solid content concentration of 60%, and then kneaded at a rotation speed of 45 rpm for 60 minutes. Subsequently, 1.5 parts of the aqueous dispersion containing the negative electrode binder obtained according to the above procedure were added in terms of solid content, and the mixture was kneaded at a rotation speed of 40 rpm for 40 minutes. Finally, deionized water was added to achieve a viscosity of 3000 ± 500 mPa·s (measured with a B-type viscometer at 25°C and 60 rpm) to prepare a slurry for the negative electrode composite layer. Next, a copper foil with a thickness of 15 μm was prepared as the current collector. The amount of the above-mentioned slurry for the negative electrode composite layer applied to the copper foil after drying was 15 mg / cm². 2 The material was applied and dried at 60°C for 20 minutes and then at 120°C for 20 minutes. After that, it was heat-treated at 150°C for 2 hours to obtain a negative electrode base. This negative electrode base was rolled in a roll press to obtain a density of 1.6 g / cm³. 3 A sheet-like negative electrode was fabricated consisting of a negative electrode composite layer (on both sides) and copper foil. <Manufacturing of lithium-ion secondary batteries> A single-layer laminate cell (equivalent to a discharge capacity of 250 mAh) was fabricated using the above-mentioned positive electrode, negative electrode, and separator (made of polyethylene, 12 μm thick) and placed inside an aluminum packaging. Subsequently, a 1.0 M LiPF6 solution (solvent: mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), additive: containing 2 vol% vinylene carbonate (solvent ratio)) was filled into the aluminum packaging as the electrolyte. Furthermore, the opening of the aluminum packaging was sealed by heat sealing at a temperature of 150°C to fabricate a lithium-ion secondary battery. The cycle characteristics and rate characteristics were evaluated using this lithium-ion secondary battery. The results are shown in Table 1.

[0101] (Example 2) In the (ii) pre-composite particle formation operation in <Preparation of composite particles>, the same operations, measurements, and evaluations as in Example 1 were performed, except that a composition prepared using Binder A2 (solid content concentration 10% by mass, binder liquid viscosity: 400 mPa·s, solvent: acetone), prepared according to the following, was used instead of Binder A1. The results are shown in Table 1. <Manufacturing of Binder A2> In a 10-liter reactor, 100 parts of deionized water, 35 parts of acrylonitrile as a nitrile group-containing monomer, and 65 parts of 1,3-butadiene as an aliphatic conjugated diene monomer were charged. 2 parts of potassium oleate as an emulsifier, 0.1 parts of potassium phosphate as a stabilizer, and 0.4 parts of tert-dodecyl mercaptan (TDM) as a molecular weight modifier were added. Emulsion polymerization was carried out at 530 °C in the presence of 0.35 parts of potassium persulfate as a polymerization initiator, copolymerizing acrylonitrile and 1,3-butadiene. When the polymerization conversion rate reached 95%, polymerization was stopped by adding 0.2 parts of hydroxylamine sulfate per 100 parts of monomer. Subsequently, the mixture was heated and steam distilled under reduced pressure at approximately 90 °C to recover the residual monomer. Then, 0.1 parts of dibutylhydroxytoluene (BHT) was added as a substituted phenol to obtain an aqueous dispersion of the polymer. To 100 parts of the polymer solids in the obtained aqueous dispersion, 3 parts of a 25% by mass aqueous solution of calcium chloride (CaCl2) was added as a coagulant while stirring, and the polymer in the aqueous dispersion was coagulated. After that, the mixture was filtered, and the obtained polymer was washed with 50 times the amount of deionized water, and then dried under reduced pressure at a temperature of 90°C to obtain a polymer precursor. Next, the polymer precursor was hydrogenated using the oil layer hydrogenation method. The polymer precursor was dissolved in acetone to a concentration of 12% to obtain an acetone solution of the polymer precursor to be hydrogenated, which was placed in an autoclave, and 500 ppm of palladium silica (Pd / SiO2) was added as a catalyst to 100% of the polymer precursor to be hydrogenated. A hydrogenation reaction was then carried out at a temperature of 90°C for 6 hours under a hydrogen pressure of 3.0 MPa to obtain the hydrogenated product. After the hydrogenation reaction was completed, the palladium silica was filtered off, and acetone was added to obtain a binder A2 solution to a predetermined solid content concentration.

[0102] (Example 3) In the <Preparation of Composite Particles>, the same operations, measurements, and evaluations as in Example 2 were performed, except that (i) conductive material was not added to the stirring tank during the preliminary stirring operation, and (ii) the composition added to the stirring tank during the pre-composite particle formation operation was changed to a composition containing a binder, solvent, and conductive material prepared as described below. The results are shown in Table 1. <Preparation of compositions containing conductive materials> Carbon black as a conductive material (BET specific surface area: 62 m²) 2 / g, bulk density 0.16g / cm³ 3 Two parts of the conductive material and two parts of binder solution A2 prepared in the same manner as in Example 2 were mixed in terms of solid content, and acetone was added as a solvent to prepare a mixture of conductive material, binder, and solvent with a solid content concentration of 10% and a total volume of 1 kg. Next, the obtained mixture was dispersed for 1 hour at a peripheral speed of 12 m / s using a bead mill (LMZ015, manufactured by Ashizawa Fine Tech) with zirconia beads with a diameter of 0.5 mm, to prepare a composition containing conductive material, binder, and solvent. The obtained composition had a solid content concentration of 10% by mass and a viscosity index of 300 mPa·s.

[0103] (Example 4) In (ii) the pre-composite particle formation operation in <Composite Particle Preparation>, the peripheral speed of the main stirring blade was changed to 3 m / s and the peripheral speed of the secondary stirring blade to 5 m / s, and the airflow rate for sealing was changed to 5 m / min. Otherwise, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0104] (Example 5) In the (ii) pre-composite particle formation operation in <Composite Particle Preparation>, the same operations, measurements, and evaluations as in Example 1 were performed, except that the peripheral speed of the main impeller was changed to 9 m / s and the peripheral speed of the secondary impeller to 5 m / s. The results are shown in Table 1.

[0105] (Example 6) In the (ii) pre-composite particle formation operation in <Composite Particle Preparation>, the same operations, measurements, and evaluations as in Example 1 were performed, except that the peripheral speed of the auxiliary stirring blade was changed to 2 m / s. The results are shown in Table 1.

[0106] (Example 7) In the <Preparation of Composite Particles>, (ii) the pre-composite particle formation operation was changed to 10 m / s, and (iii) the particle sizing operation was performed, followed by the classification operation as described below. Except for these points, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 1. <Classification operation> (iii) The composite particles obtained after the sizing operation were sieved using a sieve with a mesh size of 100 μm to remove coarse particles on the sieve. Furthermore, the composite particles below the sieve were sieved using a sieve with a mesh size of 50 μm to remove the particles below the sieve, and the composite particles remaining on the sieve were obtained.

[0107] (Example 8) Except for changing the peripheral speed of the main stirring blade to 0.4 m / s during the particle sizing operation in (iii) <Composite particle preparation>, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0108] (Example 9) Except for changing the peripheral speed of the main stirring blade to 6 m / s during the particle sizing operation in (iii) <Composite particle preparation>, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0109] (Example 10) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In the <Preparation of Composite Particles>, (i) the preliminary stirring operation was performed in two stages. Specifically, the preliminary stirring operation in the granulation tank under the same conditions as in Example 1 was shortened to 1 minute. Furthermore, prior to this operation, a mixture of NMC532 as a positive electrode active material for lithium-ion batteries and carbon black as a conductive material was mixed using Miracle KCK (registered trademark) (model: M·KCK-L) manufactured by Asada Iron Works Co., Ltd., under the conditions of a rotation speed of 40 rpm, a processing speed of 1 L / h, and a processing time of 10 minutes, and the resulting powder material was subjected to a preliminary stirring operation with a stirring time of 1 minute. Furthermore, (ii) in the pre-composite particle formation operation, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. Also, (ii) in the pre-composite particle formation operation, the peripheral speed of the main stirring blade was changed to 8 m / s and the airflow rate was changed to 5 / min. Furthermore, (iii) in the granulation operation, the operating time was changed to 1 minute. The highest temperature in the system throughout these processes was 40°C.

[0110] (Example 11) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In the <Preparation of Composite Particles>, (i) the preliminary stirring operation was performed in two stages. Specifically, the preliminary stirring operation in the granulation tank under the same conditions as in Example 1 was shortened to 1 minute. Furthermore, prior to this operation, a mixture of NMC532 as a positive electrode active material for lithium-ion batteries and carbon black as a conductive material was mixed using Miracle KCK (registered trademark) (model: M·KCK-L) manufactured by Asada Iron Works Co., Ltd., under the conditions of a rotation speed of 40 rpm, a processing speed of 1 L / h, and a processing time of 10 minutes, and the resulting powder material was subjected to a preliminary stirring operation with a stirring time of 1 minute.

[0111] (Example 12) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Composite particle preparation>, the peripheral speed of the main stirring blade was changed to 8 m / s and the airflow rate was changed to 5 m / min. Furthermore, (iii) in the granulation operation, the operating time was changed to 1 minute. The highest temperature in the system throughout processes (i) to (iii) was 40°C.

[0112] (Example 13) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Composite Particle Preparation>, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. The highest temperature in the system throughout processes (i) to (iii) was 40°C.

[0113] (Example 14) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Composite Particle Preparation>, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. The highest temperature in the system throughout processes (i) to (iii) was 36°C.

[0114] (Example 15) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Preparation of composite particles>, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. In addition, in (ii) the pre-composite particle formation operation, the peripheral speed of the main impeller was changed to 15 m / s, and the peripheral speed of the secondary impeller was changed to 2 m / s. Furthermore, (iii) during the grain sizing operation, the peripheral speed of the auxiliary stirring blade was changed to 10 m / s. The highest temperature in the system throughout processes (i) to (iii) was 42°C.

[0115] (Example 16) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Preparation of composite particles>, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. In addition, in (ii) the pre-composite particle formation operation, the peripheral speed of the main impeller was changed to 3 m / s, and the peripheral speed of the secondary impeller was changed to 10 m / s. The highest temperature in the system throughout processes (i) to (iii) was 34°C.

[0116] (Example 17) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Composite Particle Preparation>, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. Also, in (ii) the pre-composite particle formation operation, the peripheral speed of the main stirring blade was changed to 8 m / s. Furthermore, (iii) during the grain sizing operation, the peripheral speed of the main stirring blade was changed to 0.4 m / s. The highest temperature in the system throughout processes (i) to (iii) was 38°C.

[0117] (Example 18) Except for the following changes to the <Composite Particle Preparation> process, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 2. In (ii) the pre-composite particle formation operation in <Composite Particle Preparation>, the means of adding the composition was changed to a two-fluid spray, and the composition was continuously added to the system with the gas-liquid ratio (gas volume / liquid volume) and spray surface density shown in Table 2. Also, in (ii) the pre-composite particle formation operation, the peripheral speed of the auxiliary stirring blade was changed to 10 m / s. Furthermore, (iii) during the grain sizing operation, the peripheral speed of the main stirring blade was changed to 6 m / s. The highest temperature in the system throughout processes (i) to (iii) was 38°C.

[0118] (Comparative Example 1) (ii) Except for changing the duration of the pre-composite particle formation operation to 5 minutes and the flow rate of sealing air at room temperature to 40 L / min (airflow rate 20 L / min), the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 3.

[0119] (Comparative Example 2) (ii) In the pre-composite particle formation operation, the peripheral speed of the main stirring blade was changed to 25 m / s and the flow rate of sealing air at room temperature was changed to 100 L / min (airflow rate 50 / min), but the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 3.

[0120] (Comparative Example 3) Except for the following changes, various operations, measurements, and evaluations were carried out in the same manner as in Example 1: (ii) the peripheral speed of the auxiliary stirring blade in the pre-composite particle formation operation was changed to 2 m / s, (iii) the peripheral speed of the auxiliary stirring blade in the particle sizing operation was changed to 0.05 m / s, (iii) the duration of the operation was changed to 5 minutes, and the flow rate of sealing air at room temperature was changed to 30 L / min (airflow rate 15 L / min). The results are shown in Table 3.

[0121] (Comparative Example 4) (ii) In the pre-composite particle formation operation, the peripheral speed of the auxiliary stirring blade was changed to 10 m / s, (iii) in the particle sizing operation, the peripheral speed of the auxiliary stirring blade was changed to 15 m / s, (iii) the duration of the operation was changed to 15 minutes, and the flow rate of sealing air at room temperature was changed to 10 L / min (airflow rate 5 / min). Furthermore, (iii) the classification operation was performed after the completion of the particle sizing operation. Except for these points, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 3. <Classification operation> (iii) The composite particles obtained after the sizing operation were sieved using a sieve with a mesh size of 90 μm to remove coarse particles on the sieve. Furthermore, the composite particles below the sieve were sieved using a sieve with a mesh size of 60 μm to remove the particles below the sieve, and the composite particles remaining on the sieve were obtained.

[0122] (Comparative Example 5) (iii) The peripheral speed of the main stirring blade during the granulation sizing operation was changed to 0.05 m / s, the duration of (iii) was set to 2 minutes, and the flow rate of sealing air at room temperature was changed to 100 L / min (airflow rate 50 / min). Except for these changes, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 3.

[0123] (Comparative Example 6) (iii) The peripheral speed of the main stirring blade during the granulation sizing operation was changed to 12 m / s, the duration of (iii) was set to 15 minutes, and the flow rate of sealing air at room temperature was changed to 10 L / min (airflow rate 5 / min). Except for these changes, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 3.

[0124] [Table 1]

[0125] [Table 2]

[0126] [Table 3]

[0127] Tables 1-3 show that composite particles in which the average value of the area-equivalent diameter, the coefficient of variation of the area-equivalent diameter, and the density coefficient are all within predetermined ranges can improve the flexibility of the electrodes, suppress cracking of the electrode active material in the electrodes, and further improve the cycle characteristics and rate characteristics of electrochemical elements equipped with such electrodes. [Industrial applicability]

[0128] According to the present invention, it is possible to provide composite particles that can increase the flexibility of electrodes, suppress cracking of the electrode active material in the electrodes, and further improve the cycle characteristics of an electrochemical element equipped with such electrodes. Furthermore, according to the present invention, it is possible to provide an electrode for an electrochemical element containing the composite particles of the present invention and an electrochemical element equipped therewith. [Explanation of Symbols]

[0129] 1 Granulation tank 2 Main stirring blades 21 Main blade 3. Auxiliary stirring blades 31 Sub-blade RA1 First stirring shaft RA2 Second stirring shaft

Claims

1. A composite particle comprising an electrode active material, a conductive material, and a binder, wherein the composite particle is The average value of the area equivalent diameter is 20 μm or more and 250 μm or less. Formula 1: (Standard deviation of area-equivalent diameter / Average value of area-equivalent diameter) × 100 The coefficient of variation of the area equivalent diameter, calculated according to the formula, is 5% or more and 50% or less. Equation 2: Compression density / Bulk density The density coefficient value calculated according to is between 1.3 and 3.

5. composite particles.

2. The composite particle according to claim 1, wherein the volume resistivity is 1 Ω·cm or more and 3000 Ω·cm or less.

3. The composite particle according to claim 1, wherein the area circularity is 0.50 or more and 0.93 or less, and the perimeter envelope is 0.70 or more and 0.97 or less.

4. The composite particle according to claim 1, characterized in that the binder is a polymer material that dissolves in a non-aqueous solvent having a boiling point of 95°C or lower at 1 atm.

5. An electrode for an electrochemical element, comprising an electrode composite layer containing composite particles according to any one of claims 1 to 4.

6. An electrochemical element comprising an electrode for an electrochemical element as described in claim 5.

Images