Particulate binder for nonaqueous secondary battery electrode, binder composition for nonaqueous secondary battery electrode, slurry composition for nonaqueous secondary battery electrode, composite particles for nonaqueous secondary battery electrode, electrode for nonaqueous secondary battery, and nonaqueous secondary battery

Abstract

The purpose of the present invention is to provide a particulate binder for a nonaqueous secondary battery electrode that allows an electrode for a nonaqueous secondary battery to exhibit excellent peel strength, that offers excellent electrode producibility, and enables the internal resistance of the nonaqueous secondary battery to be reduced. The present invention is a particulate binder for a nonaqueous secondary battery electrode, the particulate binder being configured from a polymer, wherein: the degree of electrolyte swelling in a test film A composed of the particulate binder for a nonaqueous secondary battery electrode lies within a prescribed numerical range; when an elastic modulus image is obtained by measuring, with an atomic microscope, the elastic modulus in a cross-section of a test film B composed of the particulate binder for the nonaqueous secondary battery electrode, a prescribed low elastic modulus region and a prescribed high elastic modulus region form a sea-island structure in all regions of the elastic modulus image; the average value of the elastic modulus is within a prescribed numerical range; and the proportion of the prescribed region A is within a prescribed numerical range.

Description

Particulate binder for non-aqueous secondary battery electrodes, binder composition for non-aqueous secondary battery electrodes, slurry composition for non-aqueous secondary battery electrodes, composite particles for non-aqueous secondary battery electrodes, electrodes for non-aqueous secondary batteries, and non-aqueous secondary batteries

[0001] The present invention relates to particulate binders for non-aqueous secondary battery electrodes, binder compositions for non-aqueous secondary battery electrodes, slurry compositions for non-aqueous secondary battery electrodes, composite particles for non-aqueous secondary battery electrodes, electrodes for non-aqueous secondary batteries, and non-aqueous secondary batteries.

[0002] Non-aqueous secondary batteries, such as lithium-ion batteries (hereinafter sometimes simply referred to as "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. As applications expand and develop, there is a growing demand for further improvements in areas such as lower resistance, higher capacity, improved mechanical properties, and increased productivity. In this context, there is a need for more productive manufacturing methods for electrodes used in secondary batteries.

[0003] Here, electrodes for secondary batteries typically consist of electrode composite layers formed by bonding an electrode active material and an arbitrary conductive material with a binder, which are then laminated on a current collector. For example, there are coated electrodes for secondary batteries, which are obtained by coating a slurry composition containing an electrode active material, a binder, a solvent, and an arbitrary conductive material onto a current collector and then removing the solvent from the coated slurry composition. However, with such coated electrodes, it has been difficult to form a uniform electrode composite layer due to migration of the binder and other components.

[0004] In contrast, it has been proposed to obtain composite particles containing electrode active material and binder, and to form a uniform electrode composite layer by powder molding. As a method for forming such an electrode composite layer, for example, Patent Document 1 discloses a method for forming an electrode composite layer by spraying and drying a slurry composition containing electrode active material, binder and solvent to remove the solvent, and then performing dry pressure molding such as roll pressure molding using the obtained composite particles.

[0005] Patent No. 4929792

[0006] In the case of electrodes equipped with an electrode composite layer obtained using composite particles, it is desirable to increase productivity from a cost perspective. However, if the molding speed of the electrode composite layer is increased to improve productivity, problems such as streaks and chips may occur in the electrode composite layer, which can lead to a decrease in the battery performance of the secondary battery. Therefore, it is necessary to increase the productivity of electrodes without causing such problems.

[0007] Furthermore, when electrodes are fabricated by forming an electrode composite layer, it is required to ensure high adhesion between the electrode composite layer and the current collector (i.e., the peel strength of the electrode). However, conventional binders had room for further improvement in terms of increasing the peel strength of the electrode.

[0008] Furthermore, there was room for further improvement in conventional binders in terms of reducing the internal resistance of secondary batteries.

[0009] Therefore, the present invention aims to provide a particulate binder for non-aqueous secondary battery electrodes that exhibits excellent peel strength, excellent electrode productivity, and can reduce the internal resistance of non-aqueous secondary batteries. The present invention also aims to provide a binder composition for non-aqueous secondary battery electrodes, a slurry composition for non-aqueous secondary battery electrodes, and composite particles for non-aqueous secondary battery electrodes using the above-mentioned particulate binder for non-aqueous secondary battery electrodes. Furthermore, the present invention aims to provide an electrode for a non-aqueous secondary battery comprising an electrode composite layer containing the above-mentioned composite particles for non-aqueous secondary battery electrodes. Furthermore, the present invention aims to provide a non-aqueous secondary battery comprising the above-mentioned electrode for a non-aqueous secondary battery.

[0010] The inventors diligently conducted studies to achieve the above objectives. The inventors have newly discovered that the above problems can be solved by using a particulate binder for non-aqueous secondary battery electrodes composed of a polymer, wherein the degree of electrolyte swelling of test film A made of the particulate binder for non-aqueous secondary battery electrodes is within a predetermined numerical range, and when the elastic modulus of the cross-section of test film B made of the particulate binder for non-aqueous secondary battery electrodes is measured with an atomic microscope to obtain an elastic modulus image, a predetermined low elastic modulus region and a predetermined high elastic modulus region form a sea-island structure throughout the entire region of the elastic modulus image, the average value of the elastic modulus is within a predetermined numerical range, and the proportion of a predetermined region A is within a predetermined numerical range. With this discovery, the inventors have completed the present invention.

[0011] In other words, the present invention aims to advantageously solve the above problems, and [1] the present invention is a particulate binder for non-aqueous secondary battery electrodes composed of a polymer, wherein when a test film A made of the particulate binder for non-aqueous secondary battery electrodes is prepared, the electrolyte swelling degree of the test film A is 200% or more and 400% or less, and when a test film B made of the particulate binder for non-aqueous secondary battery electrodes is prepared and the elastic modulus in the cross-section of the test film B is measured with an atomic microscope to obtain an elastic modulus image, in the entire region of the elastic modulus image, a low elastic modulus region with an elastic modulus of less than 60 MPa and a high elastic modulus region with an elastic modulus of 60 MPa or more form a sea-island structure, the average value of the elastic modulus is 20 MPa or more and 100 MPa or less, and the proportion of region A with an elastic modulus of 10 MPa or more and less than 60 MPa is 50% or more and 90% or less. If a particulate binder for non-aqueous secondary battery electrodes is used as described above, it will exhibit excellent peel strength for electrodes of non-aqueous secondary batteries, have excellent electrode productivity, and reduce the internal resistance of non-aqueous secondary batteries. In this specification, the degree of electrolyte swelling of test film A made of particulate binder for non-aqueous secondary battery electrodes can be measured by the method described in the examples of this specification. In this specification, the elastic modulus in the cross-section of test film B made of particulate binder for non-aqueous secondary battery electrodes is measured using an atomic force microscope (AFM), and can be measured in more detail by the method described in the examples of this specification. In this specification, the elastic modulus image is obtained from the above elastic modulus values ​​at each measurement point of the atomic force microscope, and can be obtained in more detail by the method described in the examples of this specification. In this specification, "sea-island structure" means a state in which discontinuous dispersed phases, namely island parts, are dispersed within a continuous phase, namely sea parts. In other words, when a low modulus region with an elastic modulus of less than 60 MPa (hereinafter sometimes simply referred to as the "low modulus region") and a high modulus region with an elastic modulus of 60 MPa or more (hereinafter sometimes simply referred to as the "high modulus region") form a sea-island structure, it means that the island portion is composed of the high modulus region and the sea portion is composed of the low modulus region, or conversely, the island portion is composed of the low modulus region and the sea portion is composed of the high modulus region.In this specification, the proportion of region A (hereinafter sometimes simply referred to as "region A"), in which the elastic modulus is 10 MPa or more and less than 60 MPa, can be calculated by the method described in the examples of this specification.

[0012] [2] In the particulate binder for non-aqueous secondary battery electrodes described in [1] above, it is preferable that the proportion of region B, where the elastic modulus is 60 MPa or more and 200 MPa or less, within the entire region of the elastic modulus image is 10% or more and 30% or less. If the proportion of region B, where the elastic modulus is 60 MPa or more and 200 MPa or less, within the entire region of the elastic modulus image is above the lower limit, the resistance increase rate of the non-aqueous secondary battery can be effectively reduced. On the other hand, if the proportion of region B, where the elastic modulus is 60 MPa or more and 200 MPa or less, within the entire region of the elastic modulus image is below the upper limit, the peel strength of the electrode for non-aqueous secondary battery can be effectively improved. In this specification, the proportion of region B, where the elastic modulus is 60 MPa or more and 200 MPa or less (hereinafter sometimes simply referred to as "region B"), can be calculated by the method described in the examples of this specification.

[0013] [3] In the particulate binder for non-aqueous secondary battery electrodes described in [1] or [2] above, the ratio of the average diameter Da measured by dynamic light scattering to the median diameter Db measured by laser diffraction scattering (Da / Db) is preferably 1.05 or more and 2.00 or less. If Da / Db is above the lower limit, the peel strength of the electrode for non-aqueous secondary battery and the capacity retention rate of the non-aqueous secondary battery can be effectively improved. On the other hand, if Da / Db is below the upper limit, the electrode productivity can be effectively improved. In this specification, the "average diameter Da" of the particulate binder means the cumulant average particle diameter obtained by cumulant analysis of the particle size distribution (volume basis) measured by dynamic light scattering, and can be measured by the method described in the examples of this specification. In this specification, the "median diameter Db" of the particulate binder refers to the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by laser diffraction scattering method becomes 50%, and can be measured by the method described in the examples of this specification.

[0014] [4] In any of the particulate binders for non-aqueous secondary battery electrodes described in [1] to [3] above, the polymer preferably contains aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units. If the polymer contains the above monomer units, the peel strength and electrode productivity of the non-aqueous secondary battery electrode can be improved. In addition, the internal resistance of the non-aqueous secondary battery can be further reduced.

[0015] [5] In the particulate binder for non-aqueous secondary battery electrodes described in [4] above, it is preferable that the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less, and the proportion of vinyl cyanide monomer units is 15% by mass or more and 30% by mass or less. With a particulate binder for non-aqueous secondary battery electrodes as described above, it is possible to achieve a suitable range for both the elastic modulus and the degree of electrolyte swelling, thereby effectively reducing the resistance of the non-aqueous secondary battery. The proportion of specific monomer units (repeating units) in the polymer is, １ H-NMR and １３ It can be measured using nuclear magnetic resonance (NMR) methods such as 13C-NMR.

[0016] [6] In the particulate binder for non-aqueous secondary battery electrodes described in [5] above, the total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units is preferably more than 30% by mass and less than 60% by mass, and the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units (vinyl cyanide monomer units / aqueous vinyl monomer units) is preferably more than 0.8 and less than 2.0. With a particulate binder for non-aqueous secondary battery electrodes as described above, the resistance of the non-aqueous secondary battery can be effectively reduced, and the coverage rate of the particulate binder on the electrode active material can be set to a suitable range, thereby effectively reducing the resistance increase rate of the non-aqueous secondary battery.

[0017] [7] In the particulate binder for non-aqueous secondary battery electrodes described in [6] above, it is preferable that the proportion of aliphatic conjugated diene monomer units is 40% by mass or more and 70% by mass or less, and the proportion of ethylenically unsaturated carboxylic acid monomer units is 1% by mass or more and 5% by mass or less. With a particulate binder for non-aqueous secondary battery electrodes as described above, the resistance and resistance increase rate of the non-aqueous secondary battery can be effectively reduced, and flexibility can be provided while improving the binding properties of the electrode composite layer, so that a non-aqueous secondary electrode with superior peel strength and higher electrode productivity can be obtained.

[0018] [8] In any of the particulate binders for non-aqueous secondary battery electrodes described in [1] to [7] above, when an aqueous dispersion containing 30% by mass of the particulate binder for non-aqueous secondary battery electrodes is obtained, the viscosity of the aqueous dispersion at 25°C is preferably 200 mPa·s or more and 2000 mPa·s or less. If the viscosity of the aqueous dispersion is above the lower limit, the peel strength of the electrode for non-aqueous secondary battery can be effectively improved. Also, the rate of resistance increase of the non-aqueous secondary battery can be effectively reduced. On the other hand, if the viscosity of the aqueous dispersion is below the upper limit, the electrode productivity can be effectively improved. Also, the internal resistance of the non-aqueous secondary battery can be effectively reduced. In this specification, the viscosity of the aqueous dispersion can be measured by the method described in the examples of this specification.

[0019] [9] Preferably, any of the particulate binders for non-aqueous secondary battery electrodes described in [1] to [8] above has a core-shell structure comprising a core portion and a shell portion that at least partially covers the outer surface of the core portion. If the particulate binder for non-aqueous secondary battery electrodes has a core-shell structure, the peel strength and electrode productivity of the electrodes for non-aqueous secondary batteries can be improved. In addition, the resistance increase rate of the non-aqueous secondary battery can be reduced.

[0020] Moreover, the present invention aims to advantageously solve the above problems, and

[10] the present invention is a binder composition for a non-aqueous secondary battery electrode containing any one of the particulate binders for a non-aqueous secondary battery electrode of [1] to [9] above and a solvent. For a binder composition for a non-aqueous secondary battery electrode as described above, it can exhibit excellent peel strength for an electrode for a non-aqueous secondary battery, has excellent electrode productivity, and can reduce the internal resistance of a non-aqueous secondary battery.

[0021] Moreover, the present invention aims to advantageously solve the above problems, and

[11] the present invention is a slurry composition for a non-aqueous secondary battery electrode containing any one of the particulate binders for a non-aqueous secondary battery electrode of [1] to [9] above, an electrode active material, and a solvent. For a slurry composition for a non-aqueous secondary battery electrode as described above, it can exhibit excellent peel strength for an electrode for a non-aqueous secondary battery, has excellent electrode productivity, and can reduce the internal resistance of a non-aqueous secondary battery.

[0022] Moreover, the present invention aims to advantageously solve the above problems, and

[12] the present invention is a composite particle for a non-aqueous secondary battery electrode containing any one of the particulate binders for a non-aqueous secondary battery electrode of [1] to [9] above and an electrode active material, wherein the particulate binder for a non-aqueous secondary battery electrode partially covers the outer surface of the electrode active material. For a composite particle for a non-aqueous secondary battery electrode as described above, it can exhibit excellent peel strength for an electrode for a non-aqueous secondary battery, has excellent electrode productivity, and can reduce the internal resistance of a non-aqueous secondary battery.

[0023]

[13] In the composite particles for non-aqueous secondary batteries of

[12] above, the coating rate of the particulate binder for non-aqueous secondary battery electrodes is preferably 20% or more and 60% or less. If the coating rate of the particulate binder for non-aqueous secondary battery electrodes is at least the above lower limit, the peel strength of the electrode for non-aqueous secondary batteries can be effectively improved. On the other hand, if the coating rate of the particulate binder for non-aqueous secondary battery electrodes is at most the above upper limit, the rate of increase in resistance of non-aqueous secondary batteries can be effectively reduced. And if the coating rate of the particulate binder for non-aqueous secondary battery electrodes is within the above range, the internal resistance of non-aqueous secondary batteries can be effectively reduced. In this specification, the coating rate of the particulate binder for non-aqueous secondary battery electrodes can be measured by the method described in the examples of this specification.

[0024] Further, this invention aims to advantageously solve the above problems, and

[14] this invention is an electrode composite layer for non-aqueous secondary batteries including the composite particles for non-aqueous secondary battery electrodes of

[12] or

[13] above. The electrode for non-aqueous secondary batteries as described above is excellent in peel strength and productivity and can reduce the internal resistance of non-aqueous secondary batteries.

[0025] Further, this invention aims to advantageously solve the above problems, and

[15] this invention is a non-aqueous secondary battery including a positive electrode, a negative electrode, a separator, and an electrolytic solution, wherein at least one of the positive electrode and the negative electrode is the electrode for non-aqueous secondary batteries of

[14] above. The non-aqueous secondary battery as described above is excellent in performance.

[0026] According to the present invention, it is possible to provide a particulate binder for non-aqueous secondary battery electrodes that exhibits excellent peel strength in electrodes for non-aqueous secondary batteries, is excellent in electrode productivity, and can reduce the internal resistance of non-aqueous secondary batteries. Further, according to the present invention, it is possible to provide a binder composition for non-aqueous secondary battery electrodes, a slurry composition for non-aqueous secondary battery electrodes, and composite particles for non-aqueous secondary battery electrodes using the above particulate binder for non-aqueous secondary battery electrodes. Further, according to the present invention, it is possible to provide an electrode for non-aqueous secondary batteries including an electrode composite layer containing the above composite particles for non-aqueous secondary battery electrodes. Further, according to the present invention, it is possible to provide a non-aqueous secondary battery including the above electrode for non-aqueous secondary batteries.

[0027] This figure shows the elastic modulus image obtained in Example 1. This figure shows the image after binarization of the elastic modulus image in Figure 1.

[0028] Each component disclosed herein, as well as preferred embodiments, numerical ranges, and thresholds defining such numerical ranges, can be independently combined with each other in any manner.

[0029] Embodiments of the present invention will be described in detail below.

[0030] Here, the particulate binder for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "particulate binder") can be used in the preparation of the binder composition for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "binder composition") and the slurry composition for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "slurry composition"). Furthermore, the binder composition of the present invention can be used in the preparation of the slurry composition of the present invention. The slurry composition of the present invention can be used to form composite particles for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "composite particles"). Furthermore, the composite particles of the present invention can be used to form the electrode composite layer of the electrode for non-aqueous secondary battery electrodes of the present invention (hereinafter sometimes simply referred to as "electrode"). Moreover, the non-aqueous secondary electrode of the present invention comprises the electrode of the present invention. Note that the particulate binder, binder composition, slurry composition, and composite particles of the present invention can be used to form both the negative electrode and the positive electrode, but it is preferable to use them to form the negative electrode.

[0031] (Particulate binder for non-aqueous secondary battery electrodes) The particulate binder for non-aqueous secondary battery electrodes of the present invention is composed of a polymer. When a test film A made of the particulate binder is prepared, the electrolyte swelling degree of test film A is 200% or more and 400% or less. When a test film B made of the particulate binder is prepared and the elastic modulus of the cross-section of test film B is measured with an atomic microscope to obtain an elastic modulus image, in the entire region of the elastic modulus image, a low elastic modulus region with an elastic modulus of less than 60 MPa and a high elastic modulus region with an elastic modulus of 60 MPa or more form a sea-island structure, the average value of the elastic modulus is 20 MPa or more and 100 MPa or less, and the proportion of region A with an elastic modulus of 10 MPa or more and less than 60 MPa is 50% or more and 90% or less. With a particulate binder as described above, the electrodes can exhibit excellent peel strength, have excellent electrode productivity, and reduce the internal resistance of secondary batteries. The reasons for these are not clear, but are presumed to be as follows.

[0032] First, the particulate binder of the present invention exhibits an electrolyte swelling degree of 200% to 400% in test film A. This 200% to 400% electrolyte swelling degree in test film A results in good wettability of the electrode composite layer to the electrolyte, which is presumed to reduce the internal resistance of the secondary battery. Second, when the elastic modulus of the particulate binder of the present invention is measured using an atomic microscope to obtain an elastic modulus image, the entire area of ​​the elastic modulus image shows a sea-island structure with low-elastic modulus regions (with an elastic modulus of less than 60 MPa) and high-elastic modulus regions (with an elastic modulus of 60 MPa or more). The average elastic modulus is between 20 MPa and 100 MPa, and the proportion of region A (with an elastic modulus of 10 MPa to less than 60 MPa) is between 50% and 90%. Such a particulate binder can have a soft (low-elastic) region on the inside and a hard (high-elastic) region on the outside in an appropriate ratio. Therefore, it is presumed that in an electrode composite layer formed using composite particles containing the particulate binder and electrode active material of the present invention, the particulate binder deforms appropriately, allowing the electrode active materials to adhere well to each other and firmly to the current collector, thereby increasing the peel strength of the electrode. Furthermore, it is presumed that the appropriate deformation of the particulate binder prevents it from completely covering the surface of the electrode active material, thus reducing the internal resistance of the secondary battery. Moreover, it is presumed that the presence of a hard region outside the particulate binder in the composite particle state effectively suppresses excessive aggregation of the composite particles, thereby increasing the productivity of electrodes obtained using the composite particles.

[0033] In the above-described sea-island structure, (1) the island portion may be composed of a high modulus region and the sea portion may be composed of a low modulus region, or (2) the island portion may be composed of a low modulus region and the sea portion may be composed of a high modulus region. However, from the viewpoint of electrode peel strength, electrode productivity, and the internal resistance of the secondary battery, (1) the island portion of the dispersed phase is composed of a high modulus region and the sea portion of the continuous phase is composed of a low modulus region.

[0034] <Properties of the particulate binder> The electrolyte swelling degree of test film A made of the particulate binder of the present invention is 200% or more, preferably 220% or more, more preferably 250% or more, preferably 400% or less, preferably 350% or less, and more preferably 300% or less. If the electrolyte swelling degree of test film A is above the lower limit above, the internal resistance of the secondary battery can be effectively reduced. On the other hand, if the electrolyte swelling degree of test film A is below the upper limit above, the capacity retention rate of the secondary battery can be effectively improved. The numerical value of the electrolyte swelling degree of test film A can be adjusted, for example, by changing the type and amount of monomers used to form the polymer constituting the particulate binder described later, as well as the polymerization method and conditions.

[0035] In the test film B made of the particulate binder of the present invention, the average value of the elastic modulus is 20 MPa or more, preferably 30 MPa or more, more preferably 40 MPa or more, preferably 100 MPa or less, preferably 80 MPa or less, and more preferably 70 MPa or less. If the average value of the elastic modulus is above the lower limit, electrode productivity can be effectively improved. Furthermore, the rate of resistance increase of the secondary battery can be effectively reduced. On the other hand, if the average value of the elastic modulus is below the upper limit, the peel strength of the electrode can be effectively improved. The average value of the elastic modulus can be adjusted, for example, by changing the type and amount of monomers used to form the polymer constituting the particulate binder described later, as well as the polymerization method and conditions.

[0036] In the test film B made of the particulate binder of the present invention, the proportion of region A (the region with an elastic modulus of 10 MPa or more and less than 60 MPa) in the entire region of the elastic modulus image is 50% or more, preferably 60% or more, more preferably 70% or more, preferably 90% or less, preferably 85% or less, and more preferably 80% or less. If the proportion of region A is above the lower limit, the peel strength of the electrode can be effectively improved. On the other hand, if the proportion of region A is below the upper limit, the resistance increase rate of the secondary battery can be effectively reduced. The proportion of region A can be adjusted, for example, by changing the type and amount of monomers used to form the polymer constituting the particulate binder described later, as well as the polymerization method and conditions.

[0037] In the test film B made of the particulate binder of the present invention, the proportion of region B (the region with an elastic modulus of 60 MPa or more and 200 MPa or less) in the total area of ​​the elastic modulus image is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, preferably 30% or less, more preferably 27% or less, and even more preferably 25% or less. If the proportion of region B is above the lower limit, the resistance increase rate of the secondary battery can be effectively reduced. On the other hand, if the proportion of region B is below the upper limit, the peel strength of the electrode can be effectively improved. The proportion of region B can be adjusted, for example, by changing the type and amount of monomers used to form the polymer constituting the particulate binder described later, as well as the polymerization method and conditions.

[0038] The average diameter Da of the particulate binder of the present invention is preferably 120 nm or more, more preferably 130 nm or more, even more preferably 140 nm or more, preferably 400 nm or less, more preferably 350 nm or less, and even more preferably 250 nm or less. If the average diameter Da of the particulate binder is above the lower limit, the peel strength of the electrode and the capacity retention rate of the secondary battery can be effectively improved. On the other hand, if the average diameter Da of the particulate binder is below the upper limit, the internal resistance of the secondary battery can be effectively reduced. Here, the value of the average diameter Da measured by dynamic light scattering relatively strongly reflects the spatial extent of molecular chains in the surface layer of the particulate binder. The value of the average diameter Da of the particulate binder can be adjusted, for example, by changing the type and amount of monomers used to form the polymer constituting the particulate binder (especially the polymer constituting the surface layer of the particulate binder), the polymerization method and conditions, etc.

[0039] The median diameter Db of the particulate binder of the present invention is preferably 100 nm or more, more preferably 120 nm or more, even more preferably 130 nm or more, preferably 250 nm or less, more preferably 180 nm or less, and even more preferably 160 nm or less. If the median diameter Db of the particulate binder is above the lower limit, the internal resistance of the secondary battery can be effectively reduced. On the other hand, if the median diameter Db of the particulate binder is below the upper limit, the peel strength of the electrode can be effectively improved. Here, the median diameter Db measured by laser diffraction scattering is a value that is not significantly affected by the spatial extent of molecular chains in the surface layer of the particulate binder. The value of the median diameter Db of the particulate binder can be adjusted, for example, by changing the type and amount of monomers used to form the polymer constituting the particulate binder (particularly the polymer constituting the inside of the surface layer of the particulate binder), the polymerization method and conditions, etc.

[0040] In the particulate binder of the present invention, the ratio of the average diameter Da to the median diameter Db (Da / Db) is preferably 1.05 or more, more preferably 1.10 or more, even more preferably 1.20 or more, preferably 2.00 or less, more preferably 1.80 or less, and even more preferably 1.60 or less. If Da / Db is above the lower limit, the peel strength of the electrode and the capacity retention rate of the secondary battery can be effectively improved. On the other hand, if Da / Db is below the upper limit, the internal resistance of the secondary battery can be effectively reduced.

[0041] When an aqueous dispersion containing 30% by mass of the particulate binder of the present invention is obtained, the viscosity of the aqueous dispersion at 25°C is preferably 200 mPa·s or more, more preferably 300 mPa·s or more, even more preferably 500 mPa·s or more, preferably 2000 mPa·s or less, more preferably 1500 mPa·s or less, and even more preferably 1000 mPa·s or less. If the viscosity of the aqueous dispersion is above the lower limit, the peel strength of the electrode can be effectively improved. Furthermore, the rate of resistance increase of the secondary battery can be effectively reduced. On the other hand, if the viscosity of the aqueous dispersion is below the upper limit, the electrode productivity can be effectively improved. Furthermore, the internal resistance of the secondary battery can be effectively reduced.

[0042] The glass transition temperature of the particulate binder of the present invention is preferably -40°C or higher, more preferably -20°C or higher, even more preferably -10°C or higher, preferably 50°C or lower, more preferably 30°C or lower, and even more preferably 10°C or lower. If the glass transition temperature of the particulate binder is above the lower limit above, electrode productivity can be effectively improved. Furthermore, the internal resistance of the secondary battery can be effectively reduced. Also, if the glass transition temperature of the particulate binder is within the above range, the peel strength of the electrode can be effectively improved. In this specification, the glass transition temperature of the polymer can be measured by the method described in the examples.

[0043] <Structure of Particulate Binding Material> The structure of the particulate binding material is not particularly limited as long as the test film A and test form B, which consist of the particulate binding material, satisfy the above-mentioned requirements. However, typically, the particulate binding material has a soft region on the inside and a hard region on the outside. Here, the low modulus region in the elastic modulus image of test film B may be composed of the soft region on the inside of the particulate binding material, and the high modulus region in the elastic modulus image of test film B may be composed of the hard region on the outside of the particulate binding material. It should be noted that the particulate binding material having a soft region on the inside and a hard region on the outside is not limited to one that is completely separated into a region with a specific low modulus and a region with a specific high modulus. For example, the elastic modulus may increase in stages from the center of the particulate binding material outwards.

[0044] In one embodiment of the present invention, the particulate binder preferably has a core-shell structure comprising a core portion and a shell portion that at least partially covers the outer surface of the core portion. If the particulate binder has a core-shell structure, the peel strength and electrode productivity of the electrode can be improved. Furthermore, the resistance increase rate of the secondary battery can be reduced. In particulate binders having a core-shell structure, the shell portion is usually harder than the core portion. That is, the elastic modulus of the shell portion is usually higher than that of the core portion. Although not particularly limited, it is preferable that the elastic modulus of the core portion of the particulate binder having a core-shell structure is less than 60 MPa and the elastic modulus of the shell portion is 60 MPa or higher. In this specification, the elastic moduli of the core portion and the shell portion can be confirmed using the elastic modulus image described above, and the deformation rate image obtained by measuring the cross-section of the test film B with an atomic microscope.

[0045] When the particulate binder has a core-shell structure, the proportion of the core portion in the particulate binder is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, particularly preferably 90% by mass or more, preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 95% by mass or less. If the proportion of the core portion in the particulate binder is within the above range, the peel strength of the electrode and the electrode productivity can be effectively improved. In addition, the internal resistance of the secondary battery can be effectively reduced.

[0046] When the particulate binder has a core-shell structure, the proportion of the shell portion in the particulate binder is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, preferably 50% by mass or less, more preferably 25% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less. If the proportion of the shell portion in the particulate binder is within the above range, the peel strength of the electrode and the electrode productivity can be effectively improved. In addition, the internal resistance of the secondary battery can be effectively reduced.

[0047] <Composition of Polymer Constituting the Particulate Binder> The particulate binder of the present invention is composed of a polymer. The composition of the polymer is not particularly limited as long as the test film A and test form B made of the particulate binder satisfy the above-mentioned requirements. Examples of monomer units included in the polymer include aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, ethylenically unsaturated carboxylic acid monomer units, etc. These may be used individually or in combination of two or more. The polymer may optionally contain monomer units other than aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units (hereinafter sometimes referred to as "other monomer units").

[0048] <<Aliphatic Conjugated Diene Monomer Units>> Aliphatic conjugated diene monomer units can be formed from aliphatic conjugated diene monomers. Examples of aliphatic conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. These can be used individually or in combination of two or more. Among these, 1,3-butadiene, isoprene, and 1,3-pentadiene are preferred, and 1,3-butadiene is more preferred. That is, an aliphatic conjugated diene monomer unit is preferably at least one monomer unit selected from the group consisting of 1,3-butadiene units, isoprene units, and 1,3-pentadiene units, and is more preferably a 1,3-butadiene unit.

[0049] When the polymer contains aliphatic conjugated diene monomer units, the proportion of aliphatic conjugated diene monomer units in the polymer is preferably 40% by mass or more, more preferably 42% by mass or more, even more preferably 45% by mass or more, preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less, based on 100% by mass of all repeating units (monomer units) in the polymer.

[0050] <<Aromatic Vinyl Monomer Units>> Aromatic vinyl monomer units can be formed from aromatic vinyl monomers. Examples of aromatic vinyl monomers include aromatic monovinyl compounds such as styrene, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. These can be used individually or in combination of two or more. Among these, styrene is preferred. In other words, aromatic vinyl monomer units are preferably styrene units.

[0051] When the polymer contains aromatic vinyl monomer units, the proportion of aromatic vinyl monomer units in the polymer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of all repeating units (monomer units) in the polymer.

[0052] <<Vinyl Cyanide Monomer Units>> The polymer constituting the particulate binder of the present invention preferably contains vinyl cyanide monomer units. If the polymer contains vinyl cyanide monomer units, electrode productivity and other factors can be further improved.

[0053] Vinyl cyanide monomer units can be formed from vinyl cyanide monomers. Examples of vinyl cyanide monomers include acrylonitrile; α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitriles such as methacrylonitrile and α-ethylacrylonitrile. These can be used individually or in combination of two or more. Among these, acrylonitrile is preferred. That is, vinyl cyanide monomer units are preferably acrylonitrile units.

[0054] When the polymer contains vinyl cyanide monomer units, the proportion of vinyl cyanide monomer units in the polymer is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, preferably 40% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less, based on 100% by mass of all repeating units (monomer units) in the polymer.

[0055] <<Ethylene-Unsaturated Carboxylic Acid Monomer Units>> Ethylene-unsaturated carboxylic acid monomer units can be formed from ethylenically unsaturated carboxylic acid monomers. Examples of ethylenically unsaturated carboxylic acid monomers include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. These can be used individually or in combination of two or more. Among these, acrylic acid, methacrylic acid, and itaconic acid are preferred, with methacrylic acid being more preferred. That is, the ethylenically unsaturated carboxylic acid monomer unit is preferably at least one monomer unit selected from the group consisting of acrylic acid units, methacrylic acid units, and itaconic acid units, and is more preferably a methacrylic acid unit. The carboxylic acid of the ethylenically unsaturated carboxylic acid monomer unit may, in part or in whole, form a salt with an alkali metal or ammonia.

[0056] When the polymer contains ethylenically unsaturated carboxylic acid monomer units, the proportion of ethylenically unsaturated carboxylic acid monomer units in the polymer is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, preferably 5% by mass or less, more preferably 4.5% by mass or less, and even more preferably 4% by mass or less, based on 100% by mass of all repeating units (monomer units) in the polymer.

[0057] <<Other Monomer Units>> Other monomer units that may be included in the polymer are not particularly limited. Examples of other monomer units include (meth)acrylic acid ester monomer units and crosslinkable monomer units. In this specification, "(meth)acrylic acid" means acrylic acid and / or methacrylic acid.

[0058] (Meth)acrylic acid ester monomer units can be formed from (meth)acrylic acid ester monomers. Examples of (meth)acrylic acid ester monomers include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, and 2-ethylhexyl acrylate; and alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, and 2-ethylhexyl methacrylate. These can be used individually or in combination of two or more types.

[0059] Crosslinkable monomer units can be formed from crosslinkable monomers. Here, a crosslinkable monomer is a monomer having two or more polymerizable double bonds (e.g., olefinic double bonds) per molecule. Examples of crosslinkable monomers include polyfunctional (meth)acrylates such as allyl (meth)acrylate, ethylene di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and trimethylolpropane-tri(meth)acrylate; polyfunctional allyl / vinyl ethers such as dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, and tetraallyloxyethane; divinylbenzene; vinyl glycidyl ether; allyl glycidyl ether; N-methylolacrylamide; and acrylamide. These can be used individually or in combination of two or more types.

[0060] If the polymer contains other monomer units, the proportion of other monomer units in the polymer is preferably greater than 0% by mass, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, preferably 10% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, with the total repeating units (monomer units) in the polymer being 100% by mass.

[0061] <<Total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units>> The total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units in the polymer is preferably more than 30% by mass, more preferably more than 35% by mass, even more preferably 40% by mass or more, even more preferably more than 40% by mass, preferably less than 60% by mass, more preferably 56% by mass or less, even more preferably less than 55% by mass, and even more preferably less than 50% by mass. If the total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units in the polymer is greater than the lower limit above, the internal resistance of the secondary battery can be effectively reduced. On the other hand, if the total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units in the polymer is less than the upper limit above, the capacity retention rate of the secondary battery can be effectively improved, and the resistance increase rate of the secondary battery can be effectively reduced.

[0062] <<Total proportion of aliphatic conjugated diene monomer units and aromatic vinyl monomer units>> The total amount of aliphatic conjugated diene monomer units and aromatic vinyl monomer units in the polymer is preferably 50% by mass or more, more preferably 63% by mass or more, preferably 90% by mass or less, and more preferably 85% by mass or less, based on 100% by mass of all repeating units (monomer units) in the polymer.

[0063] <<Total proportion of aliphatic conjugated diene monomer units, aromatic vinyl monomer units, and vinyl cyanide monomer units>> The total proportion of aliphatic conjugated diene monomer units, aromatic vinyl monomer units, and vinyl cyanide monomer units in the polymer is preferably 80% by mass or more, more preferably 90% by mass or more, preferably 99% by mass or less, and more preferably 96% by mass or less, with the total repeating units (monomer units) in the polymer being 100% by mass.

[0064] <<Mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units>> The mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units (vinyl cyanide monomer units / aromatic vinyl monomer units) is preferably greater than 0.8, more preferably greater than 0.9, even more preferably greater than 1.0, preferably less than 3.0, more preferably less than 2.0, and even more preferably less than 1.5. If the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is greater than the lower limit above, the capacity retention rate of the secondary battery can be effectively improved. Furthermore, if the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is within the above range, the resistance increase rate of the secondary battery can be effectively reduced.

[0065] <<Preferred Polymer Composition>> In one embodiment of the present invention, the polymer constituting the particulate binder preferably contains aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units. If the polymer contains the above monomer units, the peel strength and electrode productivity of the electrode can be improved. In addition, the internal resistance of the secondary battery can be further reduced.

[0066] In one embodiment of the present invention, when the polymer constituting the particulate binder contains aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units, it is preferable that, with the total repeating units (monomer units) in the polymer being 100% by mass, the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less, and the proportion of vinyl cyanide monomer units is 15% by mass or more and 30% by mass or less. With such a particulate binder, it is possible to achieve a suitable range for both the elastic modulus and the degree of electrolyte swelling, thereby effectively reducing the resistance of the battery.

[0067] In one embodiment of the present invention, the polymer constituting the particulate binder contains aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units, and with the total repeating units (monomer units) in the polymer being 100% by mass, the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less, and the proportion of vinyl cyanide monomer units is 15% by mass or more and 30% by mass or less. In this case, the total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units is more than 30% by mass and less than 60% by mass, and the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is more than 0.8 and less than 2.0. With such a particulate binder, the resistance of the secondary battery can be effectively reduced, and the coating rate of the particulate binder on the electrode active material can be set to a suitable range, thereby effectively reducing the rate of resistance increase of the battery.

[0068] In one embodiment of the present invention, the polymer constituting the particulate binder contains aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units, and with the total repeating units (monomer units) in the polymer being 100% by mass, the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less, the proportion of vinyl cyanide monomer units is 15% by mass or more and 30% by mass or less, the total proportion of aromatic vinyl monomer units and vinyl cyanide monomer units is more than 30% by mass and less than 60% by mass, and the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is more than 0.8 and less than 2.0, in which case it is preferable that the proportion of aliphatic conjugated diene monomer units is 40% by mass or more and 70% by mass or less, and the proportion of ethylenically unsaturated carboxylic acid monomer units is 1% by mass or more and 5% by mass or less. With particulate binders like those described above, the battery's resistance and resistance increase rate can be effectively reduced, and flexibility can be added while improving the bonding properties of the electrode composite layer. As a result, electrodes with superior peel strength and higher electrode productivity can be obtained.

[0069] <Method for preparing particulate binder> The method for preparing particulate binder is not particularly limited, but for example, it can be carried out by the following procedure, which includes two-step polymerization. First, the predetermined monomers described above are mixed with a solvent (water, etc.), an emulsifier, a chain transfer agent, and a polymerization initiator, and the mixture is heated to carry out a polymerization reaction until a predetermined amount of monomer is consumed. Next, further monomers, and optionally emulsifiers and solvents (water, etc.), are continuously added to the reaction solution to continue polymerization. When the predetermined amount of monomer is consumed, the reaction is stopped by cooling to obtain a mixture containing particulate binder. Next, a dispersion of particulate binder can be obtained by removing unreacted monomers from the obtained mixture. Optionally, the solvent in the obtained dispersion of particulate binder may be removed. When water is used as the solvent, after removing unreacted monomers from the mixture, the pH of the mixture may be adjusted to a preferred range to obtain an aqueous dispersion of particulate binder.

[0070] Examples of emulsifiers include alkyldiphenyl ether disulfonic acid, dodecylbenzenesulfonic acid, lauryl sulfate, or salts thereof (e.g., potassium salts, sodium salts). Among these, alkyldiphenyl ether disulfonates are preferred. One type of emulsifier may be used alone, or two or more types may be used in any ratio. The amount of emulsifier added is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, based on 100 parts by mass of the total amount of monomers of the polymer constituting the particulate binder.

[0071] The polymerization initiator is not particularly limited and includes known polymerization initiators such as potassium persulfate, sodium persulfate, n-butyllithium, and ammonium persulfate. One type of polymerization initiator may be used alone, or two or more types may be used in any ratio. The amount of polymerization initiator added is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, preferably 5 parts by mass or less, and more preferably 1 part by mass or less, based on 100 parts by mass of the total amount of monomers of the polymer constituting the particulate binder.

[0072] The chain transfer agent is not particularly limited and includes known chain transfer agents such as α-methylstyrene dimer, tert-dodecyl mercaptan, and 3-mercapto-1,2-propanediol. The amount of chain transfer agent added is preferably 0.05 parts by mass or more, and more preferably 0.5 parts by mass or less, based on 100 parts by mass of the total amount of monomers of the polymer constituting the particulate binder.

[0073] (Binder composition for non-aqueous secondary battery electrodes) The binder composition for non-aqueous secondary battery electrodes of the present invention comprises the particulate binder of the present invention described above and a solvent, and may optionally contain components other than the particulate binder and solvent (hereinafter sometimes referred to as "other components"). Because the binder composition of the present invention contains the particulate binder of the present invention, it exhibits excellent peel strength in electrodes, has excellent electrode productivity, and can reduce the internal resistance of secondary batteries. The binder composition of the present invention usually does not contain the electrode active material described later.

[0074] <Particulate Binding Agent> The particulate binding agent contained in the binder composition of the present invention is the particulate binding agent of the present invention described above. Here, the content ratio of the particulate binding agent in the binder composition is, for example, 20% by mass or more, may be 30% by mass or more, for example, 60% by mass or less, and may be 50% by mass or less.

[0075] <Solvent> The solvent included in the binder composition of the present invention is not particularly limited, and either water or an organic solvent can be used, or a mixed solvent of water and an organic solvent can be used. As an organic solvent, for example, aqueous solvents such as methanol, ethanol, and lower alcohols such as isopropanol can be used. However, it is preferable that the solvent included in the binder composition of the present invention is water.

[0076] <Other Components> In addition to the particulate binder and solvent described above, the binder composition of the present invention may also contain other components such as antioxidants and preservatives. These other components may be used individually or in combination of two or more components in any ratio.

[0077] <pH of Binder Composition> The pH of the binder composition is preferably 6.0 or higher, more preferably 7.0 or higher, preferably 10.0 or lower, more preferably 9.0 or lower, and even more preferably 8.0 or lower. The pH can be adjusted, for example, by adding an alkaline species to the binder composition. Examples of alkaline species include lithium hydroxide, sodium hydroxide, potassium hydroxide, and aqueous ammonia. Ammonia is preferred because it is less likely to generate aggregates due to the shock of addition during alkali neutralization.

[0078] <Method for preparing the binder composition> The method for preparing the binder composition is not particularly limited. For example, the binder composition can be obtained by mixing the particulate binder described above, a solvent, and any other component in a predetermined ratio. The dispersion of the particulate binder (a water dispersion if the solvent is water) described in the section "Method for preparing the particulate binder" above may also be used as the binder composition of the present invention.

[0079] (Slurry composition for non-aqueous secondary battery electrodes) The slurry composition for non-aqueous secondary battery electrodes of the present invention comprises the particulate binder of the present invention described above, an electrode active material, and a solvent, and may optionally contain components other than the electrode active material, particulate binder, and solvent (hereinafter sometimes referred to as "other components"). Because the slurry composition of the present invention contains the particulate binder of the present invention, it exhibits excellent peel strength for electrodes, has excellent electrode productivity, and can reduce the internal resistance of secondary batteries. In the following description, as an example, the case in which the slurry composition for non-aqueous secondary battery electrodes is a slurry composition for the negative electrode of a lithium-ion secondary battery will be described, but the present invention is not limited to the following example.

[0080] <Electrode Active Material> Electrode active material is a substance that transfers electrons at the electrodes of a secondary battery. For lithium-ion secondary batteries, the negative electrode active material is usually a substance that can intercalate and release lithium. Specifically, examples of negative electrode active materials for lithium-ion secondary batteries include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials that combine these.

[0081] Here, a carbon-based anode active material refers to an active material with a carbon-based skeleton that can be doped with lithium. Examples of carbon-based anode active materials include carbonaceous materials and graphite materials.

[0082] Examples of carbonaceous materials include easily graphitizable carbon and non-graphitizable carbon with a structure close to an amorphous structure, such as glassy carbon. Here, examples of easily graphitizable carbon include carbon materials made from tar pitch obtained from petroleum or coal. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fibers, and pyrolysis vapor-grown carbon fibers. Examples of non-graphitizable carbon include phenolic resin calcined bodies, polyacrylonitrile-based carbon fibers, pseudoisotropic carbon, furfuryl alcohol resin calcined bodies (PFA), and hard carbon.

[0083] Furthermore, examples of graphitic materials include natural graphite and artificial graphite. Examples of artificial graphite include artificial graphite obtained by heat-treating carbon containing easily graphitizable carbon at 2800°C or higher, graphitized MCMB obtained by heat-treating MCMB at 2000°C or higher, and graphitized mesophase pitch carbon fibers obtained by heat-treating mesophase pitch carbon fibers at 2000°C or higher.

[0084] Furthermore, a metallic anode active material is an active material containing a metal, and typically contains an element in its structure that allows for lithium insertion, and has a theoretical electrical capacity of 500 mAh / g or more per unit mass when lithium is inserted. Examples of metallic active materials include lithium metal, elemental metals that can form lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.) and their alloys, as well as their oxides, sulfides, nitrides, silicides, carbides, phosphides, etc. Among these, silicon-containing active materials (silicon-based anode active materials) are preferred as metallic anode active materials. This is because using silicon-based anode active materials allows for higher capacity lithium-ion secondary batteries.

[0085] Examples of silicon-based negative electrode active materials include silicon (Si), silicon-containing alloys, SiO₂, and SiO₂. ｘ Examples include composites of Si-containing material and conductive carbon, which are obtained by coating or compounding Si-containing material with conductive carbon. These silicon-based negative electrode active materials may be used individually or in combination of two or more types.

[0086] The volume-average particle diameter of the electrode active material is preferably 0.1 μm or more, more preferably 1.0 μm or more, even more preferably 3.0 μm or more, preferably 100.0 μm or less, more preferably 50.0 μm or less, and even more preferably 30.0 μm or less. The volume-average particle diameter of the electrode active material can be measured, for example, using the "Microtrac MT-3200II" manufactured by Nikkiso Co., Ltd.

[0087] The content of the electrode active material in the slurry composition is preferably 85.0% by mass or more, more preferably 90.0% by mass or more, even more preferably 95.0% by mass or more, preferably 99.5% by mass or less, more preferably 99.0% by mass or less, and even more preferably 98.5% by mass or less, based on the total solid content in the slurry composition being 100.0% by mass.

[0088] <Particulate Binding Agent> The particulate binding agent contained in the slurry composition of the present invention is the particulate binding agent of the present invention described above.

[0089] The content of particulate binder in the slurry composition is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 2% by mass or less, based on the total solid content in the slurry composition being 100% by mass.

[0090] <Solvent> The solvent included in the slurry composition of the present invention is not particularly limited, and the same solvent as that included in the binder composition of the present invention can be used.

[0091] <Other Components> Other components that may be included in the slurry composition of the present invention are, without particular limitation, the same components as those that may be included in the binder composition of the present invention. The slurry composition may also further contain other components such as water-soluble polymers, phosphite-based antioxidants, metal scavengers, and conductive additives. These components may be used individually or in combination of two or more in any ratio. In this specification, "water-soluble polymer" means a polymer in which the undissolved portion is less than 10.0% by mass when 0.5 g of polymer is dissolved in 100 g of pure water at 25°C.

[0092] Examples of water-soluble polymers include cellulosic polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose, and hydroxypropylcellulose; ammonium salts or alkali metal salts of these cellulosic polymers; alginate esters such as propylene glycol alginate; alginates such as sodium alginate; polyacrylic acid, polymethacrylic acid; poly(meth)acrylic acid salts such as sodium polyacrylate and polysodium methacrylate; polyvinyl alcohol; modified polyvinyl alcohol; poly-N-vinylacetamide; polyethylene oxide; polyvinylpyrrolidone; starch oxide; starch phosphate; casein; various modified starches; chitin; chitosan derivatives, etc. These may be used individually or in combination of two or more in any ratio. Among these, ammonium salts or alkali metal salts of cellulosic polymers are preferred, ammonium salts or alkali metal salts of carboxymethylcellulose are more preferred, and ammonium salts of carboxymethylcellulose are even more preferred.

[0093] If the slurry composition contains a water-soluble polymer, the content of the water-soluble polymer in the slurry composition may be, for example, 0.5% by mass or more, 1% by mass or more, or 10% by mass or less, or 5% by mass or less, when the total solid content in the slurry composition is taken as 100% by mass.

[0094] Examples of conductive additives include furnace black, acetylene black, Ketjenblack (a registered trademark of AkzoNobel Chemicals Bethlotenfennotschap), carbon nanotubes, carbon nanohorns, graphene, and other conductive carbons. These may be used individually or in combination of two or more types in any ratio.

[0095] If the slurry composition contains a conductive additive, the content of the conductive additive in the slurry composition is preferably more than 0 parts by mass, more preferably more than 0.1 parts by mass, even more preferably more than 0.2 parts by mass, preferably 2 parts by mass or less, more preferably 1.5 parts by mass or less, and even more preferably 1 part by mass or less, based on the total solid content in the slurry composition being 100% by mass.

[0096] <Preparation of Slurry Composition> The method for preparing the slurry composition is not particularly limited. For example, a slurry composition can be prepared by mixing the electrode active material, the particulate binder of the present invention described above, a solvent, and any other component. Alternatively, a slurry composition can be prepared by mixing the binder composition of the present invention described above, the electrode active material, and any other component in the presence of the solvent contained in the binder composition. The mixing method is not particularly limited, but mixing can be done using a stirrer or disperser that can be commonly used.

[0097] (Composite particles for non-aqueous secondary battery electrodes) The composite particles for non-aqueous secondary battery electrodes of the present invention include the particulate binder of the present invention described above and an electrode active material, wherein the particulate binder partially coats the outer surface of the electrode active material. With composite particles as described above, the electrode exhibits excellent peel strength, excellent electrode productivity, and can reduce the internal resistance of the secondary battery.

[0098] Here, the composite particles of the present invention include an electrode active material and a particulate binder, but the electrode active material and the particulate binder do not exist as separate, independent particles. Rather, each particle is composed of two or more components, including the electrode active material and the particulate binder. Specifically, multiple individual particles of the above two or more components are bound together while substantially maintaining their shape to form secondary particles, and it is preferable that multiple (preferably several to several thousand) electrode active materials are bound together by a binder or the like to form particles. The composite particles of the present invention may also contain components other than the electrode active material and the particulate binder (other components).

[0099] <Particulate Binding Agent> The particulate binding agent contained in the composite particles of the present invention is the particulate binding agent of the present invention as described above.

[0100] <Electrode Active Material> Examples of electrode active materials included in the composite particles of the present invention include electrode active materials similar to those included in the slurry composition of the present invention described above.

[0101] <Other Components> Other components that may be included in the composite particles of the present invention include, without particular limitation, the same components as those that may be included in the slurry composition of the present invention.

[0102] <Properties of Composite Particles> In the composite particles of the present invention, the coverage rate of the particulate binder is preferably 20% or more, more preferably 25% or more, even more preferably 30% or more, preferably 60% or less, more preferably 55% or less, and even more preferably 50% or less. If the coverage rate of the particulate binder is above the lower limit above, the peel strength of the electrode can be effectively improved. On the other hand, if the coverage rate of the particulate binder is below the upper limit above, the resistance increase rate of the secondary battery can be effectively reduced. Furthermore, if the coverage rate of the particulate binder is within the above range, the internal resistance of the secondary battery can be effectively reduced. The coverage rate of the particulate binder can be adjusted by the composition of the slurry composition used to produce the composite particles and the hot air temperature during spray drying of the slurry composition when producing the composite particles.

[0103] The median diameter Dc of the composite particles of the present invention, as measured by laser diffraction scattering, is, for example, 10 μm or more, may be 30 μm or more, for example, 300 μm or less, or 150 μm or less. In this specification, the "median diameter Dc" of the composite particles means the particle diameter (D50) at which the cumulative volume calculated from the smallest diameter side in the particle size distribution (volume basis) measured by laser diffraction scattering accounts for 50%, and can be measured by the method described in the examples of this specification.

[0104] <Method for producing composite particles> The composite particles of the present invention can be obtained, for example, by drying and granulating the slurry composition of the present invention described above. The drying and granulation method is not particularly limited, but examples include spray granulation, fluid bed granulation, rolling bed granulation, compression granulation, agitation granulation, extrusion granulation, crushing granulation, fluid bed multifunctional granulation, and melt granulation. Among these, spray granulation is preferred from the viewpoint of good drying efficiency.

[0105] Specifically, in the formation of composite particles using spray granulation, the slurry composition of the present invention described above is spray-dried and granulated. Spray drying is a method of drying by spraying the slurry into hot air. Examples of devices used for spraying the slurry include atomizers. Examples of atomizers include rotary disc type, cup type, two-fluid nozzle type, and pressurized type devices, and among these, the rotary disc type device is preferred.

[0106] The rotating disk method involves introducing a slurry composition to the approximate center of a rapidly rotating disk. The centrifugal force of the disk then ejects the slurry composition outwards, atomizing it. In the rotating disk method, the rotation speed of the disk depends on its size, but is preferably 5,000 rpm to 30,000 rpm, and more preferably 15,000 rpm to 30,000 rpm. Generally, the lower the rotation speed of the disk, the larger the spray droplets become, resulting in larger particle sizes for the resulting composite particles.

[0107] Examples of rotating disc type atomizers include pin type and vane type, but a pin type atomizer is preferred. A pin type atomizer is a type of centrifugal spraying device that uses a spray disc, and the spray disc is composed of a plurality of spray rollers that are detachably attached between upper and lower mounting discs in substantially concentric circles along its periphery. The slurry composition is introduced from the center of the spray disc, adheres to the spray rollers by centrifugal force, moves outward along the roller surface, and finally separates from the roller surface and is sprayed. The temperature of the sprayed slurry composition is, for example, 25°C or higher, may be 70°C or higher, and may be, for example, 150°C or lower, or 110°C or lower.

[0108] The hot air temperature during spray drying is usually higher than the temperature of the slurry composition being sprayed, preferably 50°C or higher, more preferably 100°C or higher, even more preferably 170°C or higher, preferably 250°C or lower, more preferably 230°C or lower, and even more preferably 190°C or lower. If the hot air temperature during spray drying is within the above range, the coverage rate of the particulate binder in the composite particles can be easily adjusted.

[0109] In spray drying, the method of blowing in hot air is not particularly limited. Examples include a method in which the hot air and spray direction are parallel in the lateral direction, a method in which the spray is applied at the top of the drying tower and descends with the hot air, a method in which the sprayed droplets and hot air are in countercurrent contact, and a method in which the sprayed droplets initially flow parallel to the hot air and then fall by gravity and come into countercurrent contact.

[0110] (Electrodes for Non-Aqueous Secondary Batteries) The electrode for non-aqueous secondary batteries in the present invention comprises an electrode composite layer containing the composite particles of the present invention described above. Such a non-aqueous secondary battery electrode has excellent peel strength and productivity, and can reduce the internal resistance of the secondary battery. The electrode of the present invention may be a negative electrode or a positive electrode, but it is preferably a negative electrode.

[0111] In the electrode of the present invention, the electrode composite layer is usually laminated on a current collector. That is, the electrode of the present invention is usually made by laminating the electrode composite layer and a current collector. The electrode of the present invention may optionally include an adhesive layer between the electrode composite layer and the current collector.

[0112] <Current Collector> Current collectors are usually in the form of a sheet. Examples of materials for current collectors include copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum. For example, if the material for the current collector is copper, copper foil can be used as the current collector. The above-mentioned materials for current collectors may be used individually, or two or more may be used in any ratio.

[0113] <Electrode Mixture Layer> The electrode mixture layer contains the composite particles of the present invention as described above. When laminating the electrode mixture layer onto the current collector, the composite particles may be formed into a sheet and then laminated onto the current collector, but a method of directly press-molding the composite particles on the current collector is preferred.

[0114] As a method of pressure molding, for example, a roll pressure molding method can be used in which composite particles are supplied onto the current collector by a supply device such as a feeder while the current collector is transported at a predetermined speed, and the composite particles are pressure-molded with a press roll to laminate an electrode composite layer on the current collector. In the roll pressure molding method, optionally, before pressure molding the composite particles with the press roll, a step may be performed to level the composite particles on the current collector using a squeegee roll that rotates so that its surface moves in the opposite direction to the transport direction of the current collector, and after pressure molding the composite particles with the press roll, a step may be performed to further pressurize the electrode composite layer with the press roll to increase the density of the electrode composite layer. Alternatively, optionally, an adhesive layer may be formed on the surface of the current collector to create a current collector with an adhesive layer, and the electrode composite layer may be laminated on top of the adhesive layer of the current collector with an adhesive layer.

[0115] The press line pressure of the press roll during pressure molding is preferably 1 kN / m or more, more preferably 30 kN / m or more, even more preferably 100 kN / m or more, preferably 1000 kN / m or less, more preferably 900 kN / m or less, and even more preferably 600 kN / m or less.

[0116] The roll temperature of the press rolls used in pressure molding is preferably 20°C or higher, more preferably 40°C or higher, preferably 100°C or lower, and more preferably 70°C or lower.

[0117] The conveyance speed of the current collector is preferably 3 m / min or more, more preferably 5 m / min or more, still more preferably 10 m / min or more, still more preferably 30 m / min or more, even more preferably 50 m / min or more, yet even more preferably 60 m / min or more, and preferably 200 m / min or less, more preferably 180 m / min or less.

[0118] The roll temperature of the squeegee roll is preferably 10°C or more, more preferably 20°C or more, preferably 50°C or less, more preferably 30°C or less.

[0119] The peripheral speed of the surface of the squeegee roll is preferably 0.01 m / min or more, more preferably 0.1 m / min or more, preferably 5 m / min or less, more preferably 2 m / min or less.

[0120] The density of the electrode mixture layer is not particularly limited. For example, it is 0.30 g / cm ３ or more, may be 0.60 g / cm ３ or more, may be 1.00 g / cm ３ or more. For example, it is 10.00 g / cm ３ or less, may be 5.00 g / cm ３ or less, may be 3.00 g / cm ３ or less.

[0121] (Non-aqueous secondary battery) The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution, and at least one of the positive electrode and the negative electrode is the electrode of the present invention described above. The secondary battery as described above is excellent in performance. Hereinafter, as an example, the case where the secondary battery is a lithium ion secondary battery will be described, but the present invention is not limited to the following example.

[0122] <Electrodes> As described above, in the secondary battery of the present invention, at least one of the positive electrode and the negative electrode is the electrode of the present invention as described above. That is, the positive electrode of the lithium-ion secondary battery may be the electrode of the present invention and the negative electrode may be another known negative electrode, the negative electrode of the lithium-ion secondary battery may be the electrode of the present invention and the positive electrode may be another known positive electrode, and both the positive and negative electrodes of the lithium-ion secondary battery may be the electrodes of the present invention, but it is preferable that at least the negative electrode is the electrode of the present invention. As a known electrode other than the electrode for the secondary battery of the present invention, an electrode formed by forming an electrode composite layer on a current collector using a known manufacturing method can be used.

[0123] <Electrolyte> Typically, an organic electrolyte is used as the electrolyte, which is obtained by dissolving a supporting electrolyte in an organic solvent. As a supporting electrolyte, for example, lithium salts are used in lithium-ion secondary batteries. LiPF is an example of a lithium salt. ６ LiAsF ６ LiBF ４ LiSbF ６ LiAlCl ４ LiClO ４ CF ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Examples include NLi. Among them, LiPF is highly soluble in solvents and exhibits a high degree of dissociation. ６ LiClO ４ CF ３ SO ３ Li is preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in combination. Generally, the lithium ion conductivity tends to increase as the degree of dissociation of the supporting electrolyte increases; therefore, the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0124] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. However, in lithium-ion secondary batteries, for example, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and ethyl methyl 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 are preferably used. A mixture of these solvents may also be used. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range. Generally, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted by the type of solvent. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. In addition, known additives may be added to the electrolyte.

[0125] <Separator> The separator is not particularly limited, and for example, the separator described in Japanese Patent Application Publication No. 2012-204303 can be used. Among these, a microporous membrane made of polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows for a thinner overall film thickness of the separator, thereby increasing the ratio of electrode active material in the secondary battery and thus increasing the capacity per unit volume.

[0126] <Method for Manufacturing a Non-Aqueous Secondary Battery> The non-aqueous secondary battery of the present invention 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. In the non-aqueous secondary battery of the present invention, at least one of the positive electrode and the negative electrode, preferably the negative electrode, is the electrode for non-aqueous secondary batteries described above. In addition, the non-aqueous secondary battery of the present invention may be provided with an overcurrent prevention element such as a fuse or PTC element, expanded metal, lead plate, etc., as needed, to prevent pressure rise inside the secondary battery, overcharging and discharging, etc. The shape of the secondary battery may be, for example, coin type, button type, sheet type, cylindrical type, rectangular type, flat type, etc.

[0127] (Exemplary Embodiments) The present invention is further illustrated by the following exemplary embodiments [1] to

[56] . However, the present invention is not limited to the following embodiments [1] to

[56] .

[0128] [1] A particulate binder for non-aqueous secondary battery electrodes composed of a polymer, wherein when a test film A made of the particulate binder for non-aqueous secondary battery electrodes is prepared, the electrolyte swelling degree of the test film A is 200% or more and 400% or less, and when a test film B made of the particulate binder for non-aqueous secondary battery electrodes is prepared and the elastic modulus in the cross-section of the test film B is measured with an atomic microscope to obtain an elastic modulus image, in the entire region of the elastic modulus image, a low elastic modulus region with an elastic modulus of less than 60 MPa and a high elastic modulus region with an elastic modulus of 60 MPa or more form a sea-island structure, the average value of the elastic modulus is 20 MPa or more and 100 MPa or less, and the proportion of region A with an elastic modulus of 10 MPa or more and less than 60 MPa is 50% or more and 90% or less.

[0129] [2] The particulate binder for non-aqueous secondary battery electrodes according to [1], wherein the electrolyte swelling degree of the test film A is 220% or more and 350% or less.

[0130] [3] The particulate binder for non-aqueous secondary battery electrodes according to [1] or [2], wherein the degree of electrolyte swelling of the test film A is 250% or more and 300% or less.

[0131] [4] The particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [3], wherein the average value of the elastic modulus is 30 MPa or more and 80 MPa or less.

[0132] [5] The particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [4], wherein the average value of the elastic modulus is 40 MPa or more and 70 MPa or less.

[0133] [6] A particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [5], wherein the proportion of region A is 60% or more and 85% or less.

[0134] [7] A particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [6], wherein the proportion of region A is 70% or more and 80% or less.

[0135] [8] The particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [7], wherein the proportion of region B, in which the elastic modulus is 60 MPa or more and 200 MPa or less, to the entire region of the elastic modulus image is 10% or more and 30% or less.

[0136] [9] A particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [8], wherein the ratio (Da / Db) of the average diameter Da measured by dynamic light scattering to the median diameter Db measured by laser diffraction scattering is 1.05 or more and 2.00 or less.

[0137]

[10] A particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to [9], wherein the polymer contains an aliphatic conjugated diene monomer unit, an aromatic vinyl monomer unit, a vinyl cyanide monomer unit, and an ethylenically unsaturated carboxylic acid monomer unit.

[0138]

[11] The particulate binder for non-aqueous secondary battery electrodes according to

[10] , wherein the aliphatic conjugated diene monomer unit is at least one monomer unit selected from the group consisting of 1,3-butadiene unit, 2-methyl-1,3-butadiene (isoprene) unit, 2,3-dimethyl-1,3-butadiene unit, and 1,3-pentadiene unit.

[0139]

[12] The particulate binder for non-aqueous secondary battery electrodes according to

[10] or

[11] , wherein the aliphatic conjugated diene monomer unit is at least one monomer unit selected from the group consisting of 1,3-butadiene units, isoprene units and 1,3-pentadiene units.

[0140]

[13] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[12] , wherein the aliphatic conjugated diene monomer unit is a 1,3-butadiene unit.

[0141]

[14] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[13] , wherein the aromatic vinyl monomer unit is at least one monomer unit selected from the group consisting of styrene units, α-methylstyrene units, p-t-butylstyrene units, butoxystyrene units, vinyltoluene units, chlorostyrene units, and vinylnaphthalene units.

[0142]

[15] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[14] , wherein the aromatic vinyl monomer unit is a styrene unit.

[0143]

[16] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[15] , wherein the vinyl cyanide monomer unit is at least one monomer unit selected from the group consisting of acrylonitrile units, α-halogenoacrylonitrile units, and α-alkylacrylonitrile units.

[0144]

[17] The particulate binder for non-aqueous secondary battery electrodes according to

[16] , wherein the α-halogenoacrylonitrile unit is at least one monomer unit of an α-chloroacrylonitrile unit and an α-bromoacrylonitrile unit.

[0145]

[18] The particulate binder for non-aqueous secondary battery electrodes according to

[16] or

[17] , wherein the α-alkylacrylonitrile unit is at least one monomer unit of methacrylonitrile unit and α-ethylacrylonitrile unit.

[0146]

[19] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[18] , wherein the vinyl cyanide monomer unit is an acrylonitrile unit.

[0147]

[20] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[19] , wherein the ethylenically unsaturated carboxylic acid monomer unit is at least one monomer unit selected from the group consisting of acrylic acid unit, methacrylic acid unit, itaconic acid unit, maleic acid unit, fumaric acid unit, and crotonic acid unit.

[0148]

[21] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[20] , wherein the ethylenically unsaturated carboxylic acid monomer unit is at least one monomer unit selected from the group consisting of acrylic acid units, methacrylic acid units, and itaconic acid units.

[0149]

[22] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[21] , wherein the ethylenically unsaturated carboxylic acid monomer unit is a methacrylic acid unit.

[0150]

[23] The carboxylic acid of the ethylenically unsaturated carboxylic acid monomer unit is partially or entirely formed into a salt, as described in any of

[20] to

[22] , particulate binder for non-aqueous secondary battery electrodes.

[0151]

[24] The particulate binder for non-aqueous secondary battery electrodes according to

[23] , wherein the salt is formed of at least one of an alkali metal and ammonia.

[0152]

[25] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[24] , wherein the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less.

[0153]

[26] A particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[25] , wherein the proportion of aromatic vinyl monomer units is 15% by mass or more and 35% by mass or less.

[0154]

[27] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[26] , wherein the proportion of aromatic vinyl monomer units is 20% by mass or more and 30% by mass or less.

[0155]

[28] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[27] , wherein the proportion of vinyl cyanide monomer units is 10% by mass or more and 40% by mass or less.

[0156]

[29] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[28] , wherein the proportion of vinyl cyanide monomer units is 15% by mass or more and 35% by mass or less.

[0157]

[30] A particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[29] , wherein the proportion of vinyl cyanide monomer units is 20% by mass or more and 30% by mass or less.

[0158]

[31] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[30] , wherein the total proportion of the aromatic vinyl monomer units and the vinyl cyanide monomer units is greater than 30% by mass and less than 60% by mass.

[0159]

[32] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[31] , wherein the total proportion of the aromatic vinyl monomer units and the vinyl cyanide monomer units is greater than 35% by mass and less than 55% by mass.

[0160]

[33] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[32] , wherein the total proportion of the aromatic vinyl monomer units and the vinyl cyanide monomer units is 40% by mass or more and 56% by mass or less.

[0161]

[34] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[33] , wherein the total proportion of the aromatic vinyl monomer units and the vinyl cyanide monomer units is greater than 40% by mass and less than 50% by mass.

[0162]

[35] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[34] , wherein the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is greater than 0.8 and less than 3.0.

[0163]

[36] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[35] , wherein the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is greater than 0.9 and less than 2.0.

[0164]

[37] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[36] , wherein the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units is greater than 1.0 and less than 1.5.

[0165]

[38] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[37] , wherein the proportion of the aliphatic conjugated diene monomer units is 40% by mass or more and 75% by mass or less.

[0166]

[39] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[38] , wherein the proportion of the aliphatic conjugated diene monomer units is 42% by mass or more and 70% by mass or less.

[0167]

[40] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[39] , wherein the proportion of the aliphatic conjugated diene monomer units is 45% by mass or more and 60% by mass or less.

[0168]

[41] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[40] , wherein the proportion of ethylenically unsaturated carboxylic acid monomer units is 1% by mass or more and 5% by mass or less.

[0169]

[42] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[41] , wherein the proportion of ethylenically unsaturated carboxylic acid monomer units is 2% by mass or more and 4.5% by mass or less.

[0170]

[43] The particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[42] , wherein the proportion of ethylenically unsaturated carboxylic acid monomer units is 3% by mass or more and 4% by mass or less.

[0171]

[44] A particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[43] , wherein the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less, and the proportion of vinyl cyanide monomer units is 15% by mass or more and 30% by mass or less.

[0172]

[45] A particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[44] , wherein the total proportion of the aromatic vinyl monomer units and the vinyl cyanide monomer units is greater than 30% by mass and less than 60% by mass, and the mass ratio of the vinyl cyanide monomer units to the aromatic vinyl monomer units is greater than 0.8 and less than 2.0.

[0173]

[46] A particulate binder for non-aqueous secondary battery electrodes according to any one of

[10] to

[45] , wherein the proportion of aliphatic conjugated diene monomer units is 40% by mass or more and 70% by mass or less, and the proportion of ethylenically unsaturated carboxylic acid monomer units is 1% by mass or more and 5% by mass or less.

[0174]

[47] A particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to

[46] , wherein when an aqueous dispersion containing 30% by mass of the particulate binder for non-aqueous secondary battery electrodes is obtained, the viscosity of the aqueous dispersion at 25°C is 200 mPa·s or more and 2000 mPa·s or less.

[0175]

[48] ​​A particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to

[47] , having a core-shell structure comprising a core portion and a shell portion that at least partially covers the outer surface of the core portion.

[0176]

[49] The particulate binder for non-aqueous secondary battery electrodes according to

[48] , wherein the elastic modulus of the shell portion is higher than the elastic modulus of the core portion.

[0177]

[50] The particulate binder for non-aqueous secondary battery electrodes according to any one of [1] to

[49] , wherein in the sea-island structure, the island portion is composed of the high modulus region and the sea portion is composed of the low modulus region.

[0178] A binder composition for non-aqueous secondary battery electrodes comprising a particulate binder for non-aqueous secondary battery electrodes as described in any of

[51] [1] to

[50] and a solvent.

[0179] A slurry composition for non-aqueous secondary battery electrodes comprising a particulate binder for non-aqueous secondary battery electrodes as described in any of

[52] [1] to

[50] , an electrode active material, and a solvent.

[0180] A composite particle for a non-aqueous secondary battery electrode, comprising a particulate binder for a non-aqueous secondary battery electrode described in any of

[53] [1] to

[50] and an electrode active material, wherein the particulate binder for a non-aqueous secondary battery electrode partially covers the outer surface of the electrode active material.

[0181]

[54] The composite particle for non-aqueous secondary battery electrode according to

[53] , wherein the coverage rate of the particulate binder for non-aqueous secondary battery electrode is 20% or more and 60% or less.

[0182] An electrode for a non-aqueous secondary battery, comprising an electrode composite layer containing composite particles for non-aqueous secondary battery electrodes as described in

[55] ,

[53] , or

[54] .

[0183]

[56] A non-aqueous secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is an electrode for a non-aqueous secondary battery as described in

[55] .

[0184] 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" representing quantities refer to mass unless otherwise specified. In addition, in polymers produced by polymerizing multiple types of monomers, the proportion of a monomer unit formed by polymerizing a certain monomer in the polymer is usually equal to the ratio of that certain monomer to the total monomers used in the polymerization of that polymer (charging ratio), unless otherwise specified. In the examples and comparative examples, the degree of electrolyte swelling, presence or absence of sea-island structure, regions forming sea and island parts, average value of elastic modulus, proportion of region A and proportion of region B, average diameter Da, median diameter Db, viscosity of aqueous dispersion, glass transition temperature, median diameter Dc, and coverage rate of particulate binder were measured or confirmed by the following methods, and the peel strength, electrode productivity, internal resistance, capacity retention rate, and resistance increase rate were evaluated by the following methods.

[0185] <Electrolyte Swelling Degree> The negative electrode binder compositions (aqueous dispersions of particulate binders) prepared in the examples and comparative examples were dried in an environment of 50% humidity and 23-25°C to obtain test film A with a thickness of approximately 0.1 mm. This was cut into approximately 2 cm squares and its weight (weight before immersion) was measured. Then, it was immersed in an electrolyte at a temperature of 60°C for 72 hours. The immersed test film A was removed, the electrolyte was wiped off, and its weight (weight after immersion) was measured immediately. The value of (weight after immersion) / (weight before immersion) × 100 (%) was defined as the electrolyte swelling degree. The electrolyte was a 1:1 wt% mixed solvent of ethylene carbonate and diethyl carbonate with LiPF ６ A solution was used in which the substance was dissolved at a concentration of 1 mole / liter.

[0186] <Elastic Modulus> The negative electrode binder compositions (aqueous dispersions of particulate binders) prepared in the examples and comparative examples were dried for 3 days in an environment of 50% humidity and 23-25°C to obtain test film B with a thickness of approximately 0.3 mm. The obtained test film B was cut in the cross-sectional direction using a cryomicrotome in an atmosphere of -80°C to prepare film sections with a thickness of 1 μm. The film sections were picked up on a clean Si wafer and used as measurement samples. Using an atomic force microscope (Burker, product name "Dimension Icon®"), measurements were taken in a 500 nm square area approximately in the center of the cross-section of the film section, so that the number of measurement points was 16,384, and a force curve was obtained. The elastic modulus at each measurement point was calculated by analyzing the obtained force curve based on the JKR theory, and an elastic modulus image was obtained from the elastic modulus values ​​at each measurement point. The obtained elastic modulus images were then binarized into a low elastic modulus region (region with elastic modulus less than 60 MPa) and a high elastic modulus region (region with elastic modulus of 60 MPa or more) to confirm the presence or absence of sea-island structures and the regions forming the sea and island areas. The average value of the elastic modulus was also calculated from the elastic modulus values ​​at each of the measurement points mentioned above. Furthermore, out of 16,384 measurement points, the number of measurement points with an elastic modulus of 10 MPa or more and less than 60 MPa was defined as N1, and the number of measurement points with an elastic modulus of 60 MPa or more and 200 MPa was defined as N2. The percentage of region A (region with elastic modulus of 10 MPa or more and less than 60 MPa) and the percentage of region B (region with elastic modulus of 60 MPa or more and 200 MPa) were calculated using the following formulas (A) and (B): Percentage of region A (%) = (N1 / 16384) × 100 ... (A) Percentage of region B (%) = (N2 / 16384) × 100 ... (B) The percentage of region A (region with elastic modulus of 10 MPa or more and less than 60 MPa) and the percentage of region B (region with elastic modulus of 60 MPa or more and 200 MPa) were calculated using the following formulas (A) and (B): Percentage of region A (%) = (N1 / 16384) × 100 ... (B) The measurement conditions for AFM were as follows. Measurement mode: PeakForceQNM (force curve method) Cantilever: AC240TS (spring constant: approx. 1.4 N / m) Resolution: 128 x 128 Maximum compressive load: 1 nN

[0187] <Average Diameter Da> Using a particle size distribution analyzer (manufactured by Otsuka Electronics Co., Ltd., model "nanoSAQLA") that employs dynamic light scattering as its measurement principle, the particle size distribution (volume basis) of the particulate binder in the negative electrode binder compositions (aqueous dispersion of particulate binder) prepared in the examples and comparative examples was measured, and the average particle diameter obtained by cumulant analysis was defined as the average diameter Da (nm). The measurement conditions for the dynamic light scattering method were as follows: Dispersion medium: Ion-exchanged water Measurement temperature: 25±1℃ Measurement concentration (solid content concentration): 0.5% Scattering angle: 168.8° Light source laser wavelength: 660nm

[0188] <Median Diameter Db> Using a particle size distribution analyzer (Beckman Coulter, product name "LS13 320 XR") that employs laser diffraction scattering as its measurement principle, the particle size distribution (volume basis) of the particulate binder in the negative electrode binder compositions (aqueous dispersion of particulate binder) prepared in the examples and comparative examples was measured. The median diameter Db (nm) was defined as the median diameter at which the cumulative volume calculated from the smallest diameter side reached 50% in the measured particle size distribution (D50).

[0189] <Viscosity of Aqueous Dispersion> A binder composition for the negative electrode (an aqueous dispersion containing 30% by mass of particulate binder) with a solid content concentration adjusted to 30% by mass was measured using a single cylindrical rotational viscometer (manufactured by Eiko Seiki Co., Ltd., product name "DV2T", measurement conditions: 25°C, rotation speed = 60 rpm, spindle shape: 1-4) in accordance with JIS Z8803:1991. The value obtained 1 minute after the start of measurement was determined and defined as the viscosity of the aqueous dispersion.

[0190] <Glass Transition Temperature> The glass transition temperature (Tg) of the particulate binders obtained in the examples and comparative examples was measured using a differential scanning calorimetry analyzer (DSC6220, manufactured by SII Nanotechnology, Inc.) in accordance with JIS K7121:1987.

[0191] <Median Diameter Dc> The particle size distribution (volume-based) of the composite particles obtained in the examples and comparative examples was measured using a laser diffraction / scattering particle size distribution analyzer ("Microtrac MT-3200II" manufactured by Nikkiso Co., Ltd.). The median diameter Dc (μm) was defined as the median diameter at which the cumulative volume calculated from the smallest diameter side reached 50% in the obtained particle size distribution (D50).

[0192] <Coverage of Particulate Binding Material> 1 g of composite particles was placed in a 1 cm square cage made of aluminum foil, and 5 g of a 4% osmium tetroxide aqueous solution was placed in a 1 cm square cage made of Parafilm. These were placed in a glass petri dish (φ120 mm) and left for 8 hours to stain with osmium. Backscattered electron images of the stained composite particles were captured using a scanning electron microscope (JEOL, product name "FE-SEM7800F"), and an image was obtained in which the particulate binding material portion was shown in white. The image was binarized using image processing software (ImageJ) to show the particulate binding material portion in white and the electrode active material portion in black. Note that by staining the particulate binding material with osmium, the particulate binding material portion and the electrode active material portion can be clearly distinguished by the difference in brightness. Therefore, in the above binarization process, the brightness threshold separating the particulate binder portion and the electrode active material portion was carefully set while visually confirming it, and the ratio of the area of ​​the white portion to the area of ​​the composite particles was measured from the binarized image. This area measurement was performed on 10 composite particles, and the average value obtained was taken as the coverage rate of the particulate binder portion.

[0193] <Peel Strength> The negative electrodes prepared in the examples and comparative examples were cut into rectangles 100 mm long and 10 mm wide to serve as test specimens. These test specimens were placed with the surface of the negative electrode composite layer facing downwards, and cellophane tape was applied to the surface of the negative electrode composite layer. The cellophane tape used was that specified in JIS Z1522. The cellophane tape was fixed to the test stand. Then, the stress was measured when one end of the current collector was pulled vertically upwards at a pulling speed of 50 mm / min and peeled off. This measurement was performed three times, and the average value was calculated. This average value was used as the peel strength and evaluated according to the following criteria: A: Peel strength of 15 N / m or more B: Peel strength of 12 N / m or more and less than 15 N / m C: Peel strength of 9 N / m or more and less than 12 N / m D: Peel strength of 6 N / m or more and less than 9 N / m E: Peel strength less than 6 N / m

[0194] <Electrode Productivity> Using a roll press machine described later, copper foil with the adhesive layer (current collector with adhesive layer) was transported, and it was confirmed that the set speed was reached. Then, granulated particles for the negative electrode (composite particles for the negative electrode) obtained in the examples and comparative examples were supplied onto the current collector with the adhesive layer (on the surface where the adhesive layer is formed) being transported by a quantitative feeder described later. The surface was leveled with a squeegee roll (roll temperature 25°C, peripheral speed 1.0 m / min) rotating in the opposite direction to the transport direction of the current collector with the adhesive layer, and then press-molded with a press roll (roll temperature 50°C, press wire pressure 500 kN / m) to obtain a 50 m negative electrode. At this time, the mass per unit area of ​​the negative electrode composite layer was 10.5 mg / cm². ２ The gap between the squeegee roll and the copper foil was adjusted to achieve the following. The resulting negative electrode was visually inspected over a 40m section (excluding the first and last approximately 5m of the 50m negative electrode), and the highest molding speed at which no streaks or chips occurred was evaluated according to the following criteria. Note that a higher highest molding speed at which no streaks or chips occur indicates better electrode productivity. A: 60m / min or more B: 50m / min or more but less than 60m / min C: 30m / min or more but less than 50m / min D: 10m / min or more but less than 30m / min E: Less than 10m / min

[0195] <Internal Resistance> The lithium-ion secondary batteries in the examples and comparative examples were left standing 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, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 25°C and 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This 0.2C charge-discharge was repeated three times. After that, charging was performed in a 25°C environment to achieve a SOC of 50% at 0.2C, and the voltage V0 in the open circuit state was measured after standing in a 25°C environment for 3 hours. After that, discharge was performed at a discharge rate of 1C, and the voltage V1 was measured 10 seconds after the start of discharge. Low-temperature IV resistance (Ω) is evaluated using the formula: (V0 - V1) / discharge current. A smaller value indicates better internal resistance. A: Less than 2.0Ω B: 2.0Ω or more and less than 2.2Ω C: 2.2Ω or more and less than 2.4Ω D: 2.4Ω or more and less than 2.5Ω E: 2.5Ω or more

[0196] <Capacity Retention Rate> The lithium-ion secondary batteries prepared 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, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 25°C and 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. After that, the charging and discharging operation was performed 100 times in an environment of 45°C with a cell voltage of 4.20-3.00V and a charge / discharge rate of 1.0C. At that time, the discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle was defined as X2. Using the discharge capacities X1 and X2, the capacity retention rate, expressed as ΔC = (X2 / X1) × 100 (%), was calculated and evaluated according to the following criteria. A higher value for this capacity retention rate ΔC indicates better performance. A: ΔC is 94% or higher B: ΔC is 92% or higher but less than 94% C: ΔC is 90% or higher but less than 92% D: ΔC is 88% or higher but less than 90% E: ΔC is less than 88%

[0197] <Resistance Increase Rate> The lithium-ion secondary batteries in the examples and comparative examples were left standing 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, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 25°C and 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This 0.2C charge-discharge was repeated three times. After that, charging was performed in a 25°C environment to achieve a SOC of 50% at 0.2C, and the voltage V0 in the open circuit state was measured after standing in a 25°C environment for 3 hours. After that, discharge was performed at a discharge rate of 1C, and the voltage V1 10 seconds after the start of discharge was measured, and the resistance R1 before the cycle test was calculated using the formula: Resistance R1 (Ω) = (V0 - V1) / discharge current. Then, under a temperature of 45°C, 100 charge-discharge cycles were performed with a cell voltage of 4.20–3.00V and a charge-discharge rate of 1.0C. Subsequently, under a temperature of 25°C, charging was performed at 0.2C to achieve a SOC of 50%, and the voltage V0 in the open circuit state was measured after standing for 3 hours under the temperature of 25°C. After that, discharge was performed at a discharge rate of 1C, and the voltage V1 was measured 10 seconds after the start of discharge. The resistance R2 (Ω) after the cycle test was calculated using the formula R2 = (V0 - V1) / discharge current. Using the resistance R1 before the cycle test and the resistance R2 after the cycle test, the resistance increase rate, expressed as ΔR = (R2 / R1) × 100 (%), was determined and evaluated according to the following criteria. A smaller value of this resistance increase rate ΔR indicates better performance. A: Less than 110% B: 110% or more but less than 113% C: 113% or more but less than 116% D: 116% or more but less than 120% E: 120% or more

[0198] (Example 1) <Preparation of a binder composition for the negative electrode (aqueous dispersion of particulate binder)> [First stage polymerization] In a 5 MPa pressure vessel equipped with a stirrer, 48.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 24.0 parts of styrene as an aromatic vinyl monomer, 24.0 parts of acrylonitrile as a vinyl cyanide monomer, 1.0 part of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer, 1.0 part of alkyl diphenyl ether disulfonate as an emulsifier, 150.0 parts of deionized water, 0.1 part of tert-dodecyl mercaptan as a chain transfer agent, and 0.1 part of potassium persulfate as a polymerization initiator were added and thoroughly stirred, then heated to 55°C to start polymerization and reacted for 10 hours. Next, the pressure vessel was heated to 65°C and reacted for a further 6 hours, and it was confirmed that the monomer consumption was 80.0% or more.

[0199] [Second Stage Polymerization] Subsequently, the pressure vessel was heated to 85°C, and 3.0 parts of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer were continuously added to the polymerization system over 1 hour. The reaction was then continued for a further 8 hours, and it was confirmed that the monomer consumption was 95.0% or more. After that, unreacted monomers were removed by heated vacuum distillation. A mixture containing a particulate binder having a core-shell structure was obtained.

[0200] [pH Adjustment] The mixture containing the obtained particulate binder was neutralized with ammonia water to adjust the pH to 7.0, thereby obtaining a binder composition for the negative electrode (aqueous dispersion of particulate binder). Using the obtained binder composition, the degree of electrolyte swelling, presence or absence of sea-island structure, regions forming the sea and island parts, average value of elastic modulus, proportion of region A and region B, average diameter Da, median diameter Db, viscosity of aqueous dispersion, and glass transition temperature were measured or confirmed. The results are shown in Table 1. Figure 1 shows the elastic modulus image obtained in Example 1, and Figure 2 shows the image of the elastic modulus image in Figure 1 after binarization. In the image in Figure 2, a sea-island structure is formed. The island part 1 of the dispersed phase is composed of high elastic modulus regions, and the sea part 2 of the continuous phase is composed of low elastic modulus regions.

[0201] <Preparation of the anode slurry composition> 97.5 parts of artificial graphite (volume average particle size: 15 μm, theoretical capacity: 370 mAh / g) and 1.0 part (equivalent to solid content) of ammonium carboxymethylcellulose salt (Nippon Paper Industries Co., Ltd., product number "MAC-350HC") were added to a planetary mixer as the anode active material. The mixture was then diluted with deionized water to a solid content concentration of 67%, and kneaded at a rotation speed of 45 rpm for 60 minutes. Subsequently, 1.5 parts (equivalent to solid content) of the binder composition obtained above was added, and the mixture was kneaded at a rotation speed of 40 rpm for 40 minutes. Finally, deionized water was added to adjust the viscosity (using a B-type viscometer; temperature: 25°C, rotor rotation speed: 60 rpm) to 500 ± 100 mPa·s to prepare the anode slurry composition.

[0202] <Preparation of Granulated Particles for Neutral Electrodes (Composite Particles for Neutral Electrodes)> The obtained slurry composition for the negative electrode was supplied to a spray dryer (Okawara Chemical Machinery Co., Ltd., product name "ODB-25") and spray-dried using a rotating disc type pin atomizer (Okawara Chemical Machinery Co., Ltd., diameter 65 mm) under the conditions of a rotation speed of 20,000 rpm, a hot air temperature of 180°C, and a particle recovery outlet temperature of 90°C to obtain granulated particles for negative electrodes (composite particles for negative electrodes) with a volume average particle diameter of 70 μm. Using the obtained composite particles for negative electrodes, the median diameter Dc and the coverage rate of the particulate binder were measured to evaluate electrode productivity. The results are shown in Table 1.

[0203] <Preparation of the binder for the adhesive layer> 90 parts of deionized water and 0.23 parts of ammonium persulfate were supplied to a reactor equipped with a stirrer, the gas phase was replaced with nitrogen gas, and the temperature was raised to 70°C. Meanwhile, in a separate container, 50 parts of deionized water, 1.0 part of sodium dodecylbenzenesulfonate (Kao Chemical Co., Ltd., "Neoperex G-15") as an emulsifier, 20.1 parts of styrene, 75 parts of 2-ethylhexyl acrylate, 1.7 parts of allyl glycidyl ether, 0.2 parts of allyl methacrylate, and 3.0 parts of acrylic acid were mixed to obtain a monomer composition. This monomer composition was continuously added to the reactor over 4 hours to carry out polymerization. The reaction was carried out at 80°C during the addition. After the addition was completed, the reaction was terminated by stirring at 80°C for a further 3 hours. Subsequently, by adding a 5% sodium hydroxide aqueous solution and adjusting the pH to 8, an aqueous dispersion containing a binder for adhesive layers (glass transition temperature Tg: -40°C) was obtained.

[0204] <Formation of the negative electrode> An adhesive coating solution was obtained by mixing a binder for the adhesive layer at a solid content of 30% and a nonionic surfactant, Dispanol TOC (manufactured by NOF Corporation), at a concentration of 0.5%. The obtained adhesive coating solution was applied to copper foil using a direct gravure method at a coating speed of 40 m / min and a drying temperature of 50°C, so that the adhesive layer was arranged in a staggered pattern of square holes (square holes: 30 μm × 100 μm, pitch 50 μm), thereby obtaining a current collector with an adhesive layer. The current collector with an adhesive layer obtained above was inserted between the press rolls of a roll press machine (Hirano Giken Kogyo Co., Ltd. "Oshikiri Rough Surface Hot Roll") and transported at a speed of 5.0 m / min. The composite particles for the negative electrode obtained above were supplied onto a current collector with an adhesive layer (on the surface where the adhesive layer was formed) being transported by a quantitative feeder (Nikka Spray K-V manufactured by Nikka Inc.), leveled with a squeegee roll (roll temperature 25°C, peripheral speed 1.0 m / min), and pressure-molded with a press roll (roll temperature 50°C, press wire pressure 500 kN / m) to obtain the negative electrode. At this time, the gap between the squeegee roll and the copper foil was set such that the mass per unit area of ​​the negative electrode composite layer was 10.5 mg / cm². ２ The adjustments were made so that the density of the negative electrode composite layer was 1.65 g / cm³ using the press rolls again. ３The negative electrode was obtained by pressing in the manner described. The peel strength was evaluated using the obtained electrode. The results are shown in Table 1.

[0205] <Formation of the positive electrode> In the planetary mixer, the lithium composite oxide active material NMC532 (LiNi) of Co-Ni-Mn is used as the positive electrode active material. ０．５ Co ０．２ Mn ０．３ O ２ 97 parts of ) were added, along with 1 part of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name "Li-400") as a conductive material, and 2 parts of polyvinylidene fluoride (manufactured by Kureha Corporation, product name "#7208") (equivalent to solid content) as a binder, and mixed. Furthermore, N-methyl-2-pyrrolidone (NMP) as an organic solvent was gradually added, and the mixture was stirred at a temperature of 25±3°C and a rotation speed of 25 rpm to obtain a cathode slurry composition with a viscosity (using a B-type viscometer; temperature: 25±3°C, rotor: M4, rotor rotation speed: 60 rpm) of 3600 mPa·s. The obtained cathode slurry composition was coated onto a 15 μm thick aluminum foil current collector using a comma coater at a rate of 19.4±0.5 mg / cm². ２ The material was applied in such a manner. Furthermore, the slurry composition for the positive electrode on the aluminum foil was dried by transporting it at a speed of 0.3 m / min in an oven at 120°C for 4 minutes, and then in an oven at 130°C for another 4 minutes, thereby obtaining a positive electrode base roll with a positive electrode composite layer formed on the current collector. Subsequently, the positive electrode composite layer side of the prepared positive electrode base roll was roll-pressed in an environment with a temperature of 25 ± 3°C, and the density of the positive electrode composite layer was obtained to be 3.50 g / cm³. ３ The positive electrode was obtained.

[0206] <Preparation of Separator> A single-layer polypropylene separator (manufactured by Cellguard, product name "Cellguard 2500") was prepared as the separator, which consists of a separator base material.

[0207] <Fabrication of Lithium-ion Secondary Battery> Using the negative electrode and positive electrode obtained above, and the separator prepared above, a laminate cell (equivalent to an initial design discharge capacity of 30 mAh) was fabricated by stacking the negative electrode composite layer and the positive electrode composite layer so that they faced the separator. This cell was placed in an aluminum packaging material and vacuum dried at 60°C for 10 hours. After that, a 1.0 M LiPF4 solution was used as the electrolyte. ６ The solution (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (by weight ratio), additive: containing 2% by volume of vinylene carbonate (solvent ratio)) was filled into the container. Furthermore, to seal the opening of the aluminum packaging, the packaging was closed by heat sealing at a temperature of 150°C, and the lithium-ion secondary battery was manufactured. The internal resistance, capacity retention rate, and resistance increase rate were evaluated using the manufactured lithium-ion secondary battery. The results are shown in Table 1.

[0208] (Example 2) In the first polymerization step of preparing the binder composition for the negative electrode, the amount of 1,3-butadiene was changed from 48.0 parts to 56.0 parts, the amount of styrene was changed from 24.0 parts to 20.0 parts, and the amount of acrylonitrile was changed from 24.0 parts to 20.0 parts. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0209] (Example 3) In the first polymerization step of preparing the binder composition for the negative electrode, the amount of 1,3-butadiene was changed from 48.0 parts to 70.0 parts, the amount of styrene was changed from 24.0 parts to 13.0 parts, and the amount of acrylonitrile was changed from 24.0 parts to 13.0 parts. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0210] (Example 4) In the first polymerization step of preparing the binder composition for the negative electrode, the amount of 1,3-butadiene was changed from 48.0 parts to 63.0 parts, styrene from 24.0 parts to 13.0 parts, and acrylonitrile from 24.0 parts to 20.0 parts. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0211] (Example 5) In the first polymerization step of preparing the negative electrode binder composition, the amount of styrene was changed from 24.0 parts to 28.0 parts and the amount of acrylonitrile was changed from 24.0 parts to 20.0 parts. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0212] (Example 6) In the first polymerization step of preparing the negative electrode binder composition, the amount of 1,3-butadiene was changed from 48.0 parts to 40.0 parts, styrene from 24.0 parts to 28.0 parts, and acrylonitrile from 24.0 parts to 28.0 parts. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0213] (Example 7) In the first polymerization step of the preparation of the binder composition for the negative electrode, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed, except that 48.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 15.0 parts of styrene as an aromatic vinyl monomer, 28.0 parts of acrylonitrile as a vinyl cyanide monomer, 1.0 part of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer, and 5.0 parts of methyl methacrylate as other monomers were used as monomers for the first polymerization step. The results are shown in Table 1.

[0214] (Example 8) In the first polymerization step of preparing the negative electrode binder composition, the amount of 1,3-butadiene was changed from 48.0 parts to 50.0 parts, styrene from 24.0 parts to 33.0 parts, and acrylonitrile from 24.0 parts to 15.0 parts. In the second polymerization step of preparing the negative electrode binder composition, the amount of methacrylic acid was changed from 3.0 parts to 1.0 part. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0215] (Example 9) In the first polymerization step of preparing the negative electrode binder composition, the amount of styrene was changed from 24.0 parts to 22.0 parts, and in the second polymerization step of preparing the negative electrode binder composition, the amount of methacrylic acid was changed from 3.0 parts to 5.0 parts. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0216] (Example 10) In the first polymerization step of preparing the negative electrode binder composition, the amount of acrylonitrile was changed from 24.0 parts to 26.5 parts, and in the second polymerization step of preparing the negative electrode binder composition, the amount of methacrylic acid was changed from 3.0 parts to 0.5 parts. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0217] (Example 11) In the first polymerization step of preparing the negative electrode binder composition, the amount of styrene was changed from 24.0 parts to 26.0 parts and the amount of acrylonitrile was changed from 24.0 parts to 22.0 parts. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0218] (Example 12) In the first polymerization step of preparing the negative electrode binder composition, the amount of styrene was changed from 24.0 parts to 15.0 parts and the amount of acrylonitrile was changed from 24.0 parts to 33.0 parts. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0219] (Example 13) In the first polymerization step of preparing the binder composition for the negative electrode, 48.0 parts of 1,3-butadiene were replaced with 48.0 parts of isoprene. The same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0220] (Example 14) In the preparation of granulated particles for the negative electrode, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed, except that the hot air temperature was changed from 180°C to 100°C. The results are shown in Table 1.

[0221] (Comparative Example 1) The same operations, measurements, confirmations, and evaluations as in Example 1 were performed, except that the binder composition for the negative electrode was prepared as described below. The results are shown in Table 1.

[0222] <Preparation of Binder Composition for Negative Electrode (Aqueous Dispersion of Particulate Binding Agent)> [First Stage Polymerization] In a 5 MPa pressure vessel equipped with a stirrer, 32.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 18.0 parts of acrylonitrile as a vinyl cyanide monomer, 5.0 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150.0 parts of deionized water, 0.3 parts of tert-dodecyl mercaptan as a chain transfer agent, and 1.0 part of potassium persulfate as a polymerization initiator were added and thoroughly stirred. The mixture was then heated to 55°C to start polymerization and reacted for 10 hours. Next, the pressure vessel was heated to 65°C and reacted for a further 6 hours, and it was confirmed that the monomer consumption was 80.0% or more.

[0223] [Second Stage Polymerization] Subsequently, an aqueous dispersion prepared by pre-mixing 13.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 15.0 parts of styrene as an aromatic vinyl monomer, 7.0 parts of acrylonitrile as a vinyl cyanide monomer, 3.0 parts of acrylic acid as an ethylenically unsaturated carboxylic acid monomer, 12.0 parts of methyl methacrylate as another ene monomer, 5.0 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150.0 parts of deionized water, 0.4 parts of tert-dodecyl mercaptan as a chain transfer agent, and 1.0 part of potassium persulfate as a polymerization initiator was added and reacted for 8 hours, confirming that the monomer consumption was 95.0% or more. After that, unreacted monomers were removed by heated vacuum distillation. A mixture containing a particulate binder having a core-shell structure was obtained.

[0224] [pH Adjustment] The mixture containing the obtained particulate binder was neutralized with an aqueous sodium hydroxide solution to adjust the pH to 8.0, thereby obtaining a binder composition for the negative electrode (aqueous dispersion of particulate binder).

[0225] (Comparative Example 2) In the first polymerization step of preparing the binder composition for the negative electrode, the amount of 1,3-butadiene was changed from 48.0 parts to 60.0 parts, and the amount of styrene was changed from 24.0 parts to 36.0 parts. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0226] (Comparative Example 3) In the first polymerization step of preparing the binder composition for the negative electrode, the amount of 1,3-butadiene was changed from 48.0 parts to 70.0 parts, the amount of styrene was changed from 24.0 parts to 16.0 parts, and the amount of acrylonitrile was changed from 24.0 parts to 10.0 parts. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0227] (Comparative Example 4) In the first polymerization step of preparing the negative electrode binder composition, 40.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 24.0 parts of styrene as an aromatic vinyl monomer, 15.0 parts of acrylonitrile as a vinyl cyanide monomer, and 1.0 part of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer were used as monomers for the first polymerization step. In the second polymerization step of preparing the negative electrode binder composition, 16.0 parts of styrene as an aromatic vinyl monomer, 3.0 parts of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer, and 1.0 part of divinylbenzene as another monomer were used as monomers for the second polymerization step. Otherwise, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0228] (Comparative Example 5) In the first polymerization step of preparing the negative electrode binder composition, the amount of 1,3-butadiene was changed from 48.0 parts to 34.0 parts, and the amount of styrene was changed from 24.0 parts to 38.0 parts. Except for these changes, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0229] (Comparative Example 6) In the first polymerization step of preparing the negative electrode binder composition, 48.0 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 31.0 parts of styrene as an aromatic vinyl monomer, 1.0 part of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer, and 10.0 parts of methyl methacrylate as other monomers were used as monomers for the first polymerization step. In the second polymerization step of preparing the negative electrode binder composition, 7.0 parts of styrene as an aromatic vinyl monomer and 3.0 parts of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer were used as monomers for the second polymerization step. Except for these differences, the same operations, measurements, confirmations, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0230] In Table 1 below, "BD" represents 1,3-butadiene units, "IP" represents isoprene units, "ST" represents styrene units, "AN" represents acrylonitrile units, "MAA" represents methacrylic acid units, "AA" represents acrylic acid units, "MMA" represents methyl methacrylate units, "DVB" represents divinylbenzene units, "B+C" represents the total ratio of aromatic vinyl monomer units and vinyl cyanide monomer units, "C / B" represents the mass ratio of vinyl cyanide monomer units to aromatic vinyl monomer units, "Tg" represents the glass transition temperature of the particulate binder for non-aqueous secondary battery electrodes, "High Elasticity" represents the high modulus region, "Low Elasticity" represents the low modulus region, and "Da" represents the average diameter Da of the particulate binder for non-aqueous secondary battery electrodes. "Db" represents the median diameter Db of the particulate binder for non-aqueous secondary battery electrodes, and "Dc" represents the median diameter Dc of the composite particles for non-aqueous secondary batteries.

[0231]

[0232] As is clear from Table 1, using the particulate binders of Examples 1 to 14 allows for excellent peel strength in electrodes for non-aqueous secondary batteries, resulting in superior electrode productivity and reduced internal resistance of non-aqueous secondary batteries.

[0233] According to the present invention, it is possible to provide a particulate binder for non-aqueous secondary battery electrodes that exhibits excellent peel strength, excellent electrode productivity, and can reduce the internal resistance of non-aqueous secondary batteries. Furthermore, according to the present invention, it is possible to provide a binder composition for non-aqueous secondary battery electrodes, a slurry composition for non-aqueous secondary battery electrodes, and composite particles for non-aqueous secondary battery electrodes using the above-mentioned particulate binder for non-aqueous secondary battery electrodes. Furthermore, according to the present invention, it is possible to provide an electrode for a non-aqueous secondary battery comprising an electrode composite layer containing the above-mentioned composite particles for non-aqueous secondary battery electrodes. Furthermore, according to the present invention, it is possible to provide a non-aqueous secondary battery comprising the above-mentioned electrode for a non-aqueous secondary battery.

[0234] 1. Island areas 2. Coastal areas

Claims

1. A particulate binder for non-aqueous secondary battery electrodes composed of a polymer, wherein when a test film A made of the particulate binder for non-aqueous secondary battery electrodes is prepared, the electrolyte swelling degree of the test film A is 200% or more and 400% or less, and when a test film B made of the particulate binder for non-aqueous secondary battery electrodes is prepared and the elastic modulus of the cross-section of the test film B is measured with an atomic microscope to obtain an elastic modulus image, in the entire region of the elastic modulus image, a low elastic modulus region with an elastic modulus of less than 60 MPa and a high elastic modulus region with an elastic modulus of 60 MPa or more form a sea-island structure, the average value of the elastic modulus is 20 MPa or more and 100 MPa or less, and the proportion of region A with an elastic modulus of 10 MPa or more and less than 60 MPa is 50% or more and 90% or less.

2. The particulate binder for non-aqueous secondary battery electrodes according to claim 1, wherein the proportion of region B, in which the elastic modulus is 60 MPa or more and 200 MPa or less, within the entire region of the elastic modulus image is 10% or more and 30% or less.

3. The particulate binder for non-aqueous secondary battery electrodes according to claim 1, wherein the ratio (Da / Db) of the average diameter Da measured by dynamic light scattering to the median diameter Db measured by laser diffraction scattering is 1.05 or more and 2.00 or less.

4. The particulate binder for non-aqueous secondary battery electrodes according to claim 1, wherein the polymer contains aliphatic conjugated diene monomer units, aromatic vinyl monomer units, vinyl cyanide monomer units, and ethylenically unsaturated carboxylic acid monomer units.

5. The particulate binder for non-aqueous secondary battery electrodes according to claim 4, wherein the proportion of aromatic vinyl monomer units is 10% by mass or more and 40% by mass or less, and the proportion of vinyl cyanide monomer units is 15% by mass or more and 30% by mass or less.

6. The particulate binder for non-aqueous secondary battery electrodes according to claim 5, wherein the total proportion of the aromatic vinyl monomer units and the vinyl cyanide monomer units is greater than 30% by mass and less than 60% by mass, and the mass ratio of the vinyl cyanide monomer units to the aromatic vinyl monomer units is greater than 0.8 and less than 2.

0.

7. The particulate binder for non-aqueous secondary battery electrodes according to claim 6, wherein the proportion of aliphatic conjugated diene monomer units is 40% by mass or more and 70% by mass or less, and the proportion of ethylenically unsaturated carboxylic acid monomer units is 1% by mass or more and 5% by mass or less.

8. The particulate binder for non-aqueous secondary battery electrodes according to claim 1, wherein when an aqueous dispersion containing 30% by mass of the particulate binder for non-aqueous secondary battery electrodes is obtained, the viscosity of the aqueous dispersion at 25°C is 200 mPa·s or more and 2000 mPa·s or less.

9. The particulate binder for non-aqueous secondary battery electrodes according to claim 1, having a core-shell structure comprising a core portion and a shell portion that at least partially covers the outer surface of the core portion.

10. A binder composition for non-aqueous secondary battery electrodes, comprising a particulate binder for non-aqueous secondary battery electrodes according to any one of claims 1 to 9, and a solvent.

11. A slurry composition for a non-aqueous secondary battery electrode, comprising a particulate binder for a non-aqueous secondary battery electrode according to any one of claims 1 to 9, an electrode active material, and a solvent.

12. A composite particle for a non-aqueous secondary battery electrode, comprising a particulate binder for a non-aqueous secondary battery electrode according to any one of claims 1 to 9 and an electrode active material, wherein the particulate binder for a non-aqueous secondary battery electrode partially covers the outer surface of the electrode active material.

13. The composite particle for non-aqueous secondary battery electrode according to claim 12, wherein the coating rate of the particulate binder for non-aqueous secondary battery electrodes is 20% or more and 60% or less.

14. An electrode for a non-aqueous secondary battery, comprising an electrode composite layer containing composite particles for non-aqueous secondary battery electrodes as described in claim 12.

15. A non-aqueous secondary battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode and the negative electrode is an electrode for a non-aqueous secondary battery as described in claim 14.

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