Production method for electrochemical element positive electrode composite particles, production methods for electrochemical element positive electrode and electrochemical element, electrochemical element positive electrode composite particles, electrochemical element positive electrode, and electrochemical element

Abstract

Provided is a production method for electrochemical element positive electrode composite particles that include a positive electrode active material, a carbon-based electroconductive material, and a binder resin. The production method for electrochemical element positive electrode composite particles includes a step for obtaining pre-classification composite particles that include a positive electrode active material, a carbon-based electroconductive material, and a binder resin, a step for classifying the pre-classification composite particles to obtain a classified powder (a1) and a coarse powder, a step for crushing the coarse powder to obtain a crushed powder (b1), and a step for combining the classified powder (a1) and the crushed powder (b1). Also provided are: a production method for electrochemical element positive electrode composite particles that includes a step for combining specific particles (a2) and (b2); and the resulting composite particles. Also provided are: a positive electrode and an electrochemical element that use the composite particles; and production methods therefor.

Description

Method for manufacturing composite particles for electrochemical element positive electrodes, methods for manufacturing positive electrodes for electrochemical elements and electrochemical elements, and composite particles for electrochemical element positive electrodes, positive electrodes for electrochemical elements and electrochemical elements

[0001] The present invention relates to a method for producing composite particles for electrochemical element positive electrodes, a method for producing a positive electrode for an electrochemical element and an electrochemical element, and a composite particle for electrochemical element positive electrodes, a positive electrode for an electrochemical element and an electrochemical element.

[0002] Electrochemical devices such as lithium ion secondary batteries usually include electrodes as their constituent elements. Such electrodes typically have a structure in which a composite layer containing an active material and a binder resin is provided on the surface of a current collector having a thin film shape.

[0003] Wet molding has traditionally been widely used as a method for providing a composite layer, but dry molding has also been used as a more efficient molding method. The dry molding method involves preparing composite particles containing an electrode active material and a binder resin, depositing them on the surface of a current collector to form a particle layer, and then pressing the layer to compress the thickness, thereby forming a composite layer. When electrodes are continuously produced as long members on a conveying path using a dry molding method, specifically, composite particles are deposited to a certain thickness on the surface of a conveyed long current collector, and then compressed by a press roll installed downstream of the conveying path. While wet molding requires a drying step after coating the slurry, dry molding does not require such a drying step, allowing for efficient production (see, for example, Patent Document 1).

[0004] International Publication No. 2021 / 172208 (corresponding publication: U.S. Patent Application Publication No. 2023 / 0138078)

[0005] In addition to improving the performance of electrochemical devices manufactured using the composite particles, they are also required to be manufactured efficiently at low manufacturing costs. For example, manufacturing an electrochemical device using composite particles that have poor moldability and are prone to defects during dry molding can not only reduce the manufacturing yield but also adversely affect the characteristics of the resulting electrochemical device, such as reducing the cycle characteristics of the secondary battery. For example, if the composite particles contain coarse particles with relatively large particle sizes, poor moldability can occur when the particles are deposited on the surface of a current collector to form a particle layer, causing problems such as clogging in the slits of a lamination device.

[0006] To improve the moldability of composite particles, it is conceivable to classify the produced composite particles, remove coarse particles, and narrow the particle size distribution. However, removing coarse particles results in an increase in the amount of material that is not used in the manufacturing process. Many of the materials that make up the composite particles, especially the active material that makes up the positive electrode, are expensive, so the increase in manufacturing costs due to the removal of coarse particles can be a significant disadvantage.

[0007] Therefore, an object of the present invention is to provide composite particles that can be used to produce a positive electrode for an electrochemical device having good performance at low cost, and a method for producing the same.

[0008] A further object of the present invention is to provide a method for producing a positive electrode for an electrochemical element, which allows an electrochemical element having good performance to be produced at low cost, a method for producing an electrochemical element, and a positive electrode for an electrochemical element and an electrochemical element having good performance and which can be produced at low cost.

[0009] In order to solve the above problems, the present inventors have conducted research and come up with the idea of ​​crushing and utilizing the coarse powder obtained by classifying composite particles, and have found that this makes it possible to manufacture electrochemical elements with good performance at low cost, thereby completing the present invention. That is, the present invention provides the following.

[0010] <1> A method for producing composite particles for an electrochemical element positive electrode, comprising a positive electrode active material, a carbon-based conductive material, and a binder resin, the method comprising the steps of mixing classified powder and pulverized powder. <2> The method for producing composite particles for an electrochemical element positive electrode according to <1>, comprising the steps of: obtaining pre-classified composite particles comprising the positive electrode active material, the carbon-based conductive material, and the binder resin (S1-1); classifying the pre-classified composite particles to obtain classified powder (a1) as the classified powder and coarse powder (S1-2); crushing the obtained coarse powder to obtain pulverized powder (b1) as the pulverized powder (S1-3); and mixing the classified powder (a1) and the pulverized powder (b1) (S1-4). <3> The method for producing composite particles for electrochemical element positive electrodes according to <2>, wherein the particle size distribution D90 / D10 of the classified powder (a1) is 1 or more and 6 or less, the particle size distribution D90 / D10 of the pulverized powder (b1) is 8 or more and 20 or less, and the mixing ratio Wa1 / Wb1 of the mass Wa1 of the classified powder (a1) to the mass Wb1 of the pulverized powder (b1) in the step (S1-4) is 80 / 20 or more and 98 / 2 or less. <4> The method for producing composite particles for electrochemical element positive electrodes according to <2> or <3>, wherein the D50 particle size of the classified powder (a1) is 30 μm or more and 100 μm or less, and the D50 particle size of the pulverized powder (b1) is 50 μm or more and 120 μm or less. <5> The method for producing composite particles for an electrochemical element positive electrode according to any one of <2> to <4>, wherein the step (S1-1) comprises stirring and granulating the positive electrode active material, the carbon-based conductive material, the binder resin, and a solvent. <6> The method for producing composite particles for an electrochemical element positive electrode according to <5>, wherein the step (S1-1) comprises: a step (S1-1a) of stirring the positive electrode active material in a granulation tank to obtain a stirred state; and a step (S1-1b) of spraying a liquid composition containing the carbon-based conductive material, the binder resin, and the solvent onto the cathode active material in the stirred state.<7> A method for producing composite particles for an electrochemical element positive electrode, the method including: a step (S2-4) of mixing particles (a2) and particles (b2), wherein the particles (a2) and the particles (b2) are particles containing the positive electrode active material, the carbon-based conductive material, and the binder resin, respectively; the particle size distribution D90 / D10 of the particles (a2) is 1 or more and 6 or less; the particle size distribution D90 / D10 of the particles (b2) is 8 or more and 20 or less; and the mixing ratio Wa2 / Wb2 of a mass Wa2 of the particles (a2) to a mass Wb2 of the particles (b2) in the step (S2-4) is 80 / 20 or more and 98 / 2 or less. <8> A method for producing composite particles for electrochemical element positive electrodes according to <7>, wherein the particles (a2) have a D50 particle size of 30 μm or more and 100 μm or less, and the particles (b2) have a D50 particle size of 50 μm or more and 120 μm or less. <9> A method for producing a positive electrode for electrochemical elements comprising a current collector and a positive electrode mixture layer, the method comprising: obtaining composite particles for electrochemical element positive electrodes by the method for producing composite particles for electrochemical element positive electrodes according to any one of <1> to <8>; depositing the composite particles for electrochemical element positive electrodes on the surface of the current collector to form a composite particle layer; and applying pressure to the composite particle layer to form the positive electrode mixture layer. <10> A method for producing an electrochemical element comprising a positive electrode and a negative electrode, the method comprising: obtaining a positive electrode for electrochemical elements by the method for producing a positive electrode for electrochemical elements according to <9>; and constructing an electrochemical element using the positive electrode for electrochemical elements. <11> Composite particles for electrochemical element positive electrodes, produced by the method for producing composite particles for electrochemical element positive electrodes according to any one of <1> to <8>. <12> A positive electrode for electrochemical elements, comprising a current collector and a positive electrode mixture layer, wherein the positive electrode mixture layer is a layer containing the composite particles for electrochemical element positive electrodes according to <11>. <13> An electrochemical element, comprising the positive electrode for electrochemical elements according to <12>.

[0011] According to the present invention, there are provided composite particles and a method for producing the same, which allow for the production of a positive electrode for an electrochemical device having good performance at low cost; a method for producing a positive electrode for an electrochemical device and a method for producing an electrochemical device, which allow for the production of an electrochemical device having good performance at low cost; and a positive electrode for an electrochemical device and an electrochemical device which have good performance and can be produced at low cost.

[0012] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0013] In this application, the "solid content" of a mixture in which a solid is dispersed in a liquid is defined as the components remaining after the dispersion medium and solvent in the composition evaporate and the composition hardens, and the "solid content concentration" is defined as the concentration of such components. When such a composition consists of water and components dissolved or dispersed in water, the solid content concentration is the concentration of components other than water.

[0014] In the following description, the term "(meth)acrylic" is meant to encompass "acrylic", "methacrylic", and combinations thereof. For example, (meth)acrylic acid means acrylic acid, methacrylic acid, or a mixture thereof. (Meth)acrylic acid ester means acrylic acid ester, methacrylic acid ester, or a mixture thereof. (Meth)acryloyl means acryloyl, methacryloyl, or a mixture thereof. (Meth)allyl means allyl, methallyl, or a mixture thereof.

[0015] In the following description, the D50 particle size is the median value based on particle volume, and refers to the particle size at which the integrated value from the small diameter side is 50% in a histogram showing the relationship between particle size and relative particle amount on a volume basis. The D90 particle size and the D10 particle size refer to the particle sizes at which the integrated values ​​from the small diameter side are 90% and 10%, respectively, in the histogram.

[0016] In the following description, a polymerization unit produced by polymerization of a certain monomer may be expressed using the name of the monomer. For example, when an aromatic vinyl compound is used as a monomer, a polymerization unit derived from one aromatic vinyl compound produced by polymerization of the monomer is expressed as an aromatic vinyl monomer unit. Also, when an aliphatic conjugated diene compound is used as a monomer, a polymerization unit derived from one aliphatic conjugated diene compound produced by polymerization of the monomer is expressed as an aliphatic conjugated diene monomer unit.

[0017] (Outline of method for producing composite particles) The method for producing composite particles of the present invention is a method for producing composite particles for electrochemical element positive electrodes containing a positive electrode active material, a carbon-based conductive material, and a binder resin. The method for producing composite particles of the present invention is production method (1) or production method (2) including step (S2-4). These production methods will be described in order below.

[0018] (Steps of Manufacturing Method (1)) Manufacturing method (1) includes a step of mixing classified powder and pulverized powder. The classified powder can be prepared by the following steps (Sx-1) to (Sx-2). Step (Sx-1): Obtaining pre-classified composite particles containing a positive electrode active material, a carbon-based conductive material, and a binder resin. Step (Sx-2): Obtaining classified powder and coarse powder by classifying the pre-classified composite particles.

[0019] The crushed powder can be prepared by the following steps (Sy-1) to (Sy-3). Step (Sy-1): Obtain pre-classified composite particles containing a positive electrode active material, a carbon-based conductive material, and a binder resin. Step (Sy-2): Obtain classified powder and coarse powder by classifying the pre-classified composite particles. Step (Sy-3): Obtain crushed powder by crushing the obtained coarse powder.

[0020] The specific operations of steps (Sx-1) and (Sy-1) may be the same as step (S1-1) described below. The specific operations of steps (Sx-2) and (Sy-2) may be the same as step (S1-2) described below. The specific operations of step (Sy-3) may be the same as step (S1-3) described below. The specific operations of the step of mixing the classified powder and the pulverized powder may be the same as step (S1-4) described below.

[0021] Steps (Sx-1) and (Sx-2) can be performed as a combined step of steps (Sy-1) and (Sy-2). Alternatively, steps (Sy-1) and (Sy-2) can be performed as separate steps from steps (Sx-1) and (Sx-2). That is, in the former case, the coarse powder of the classified powder and coarse powder obtained in step (Sx-2) is used as the coarse powder obtained in step (Sy-2). On the other hand, in the latter case, the classified powder obtained in steps (Sx-1) and (Sx-2) is mixed with the coarse powder obtained in steps (Sy-1) and (Sy-2), which are performed separately.

[0022] In the former case, more specifically, the manufacturing method (1) can be a process including the following steps (S1-1) to (S1-4). Step (S1-1): Obtaining pre-classified composite particles containing a positive electrode active material, a carbon-based conductive material, and a binder resin. Step (S1-2): Obtaining classified powder (a1) and coarse powder by classifying the pre-classified composite particles. Step (S1-3): Obtaining crushed powder (b1) by crushing the obtained coarse powder. Step (S1-4): Mixing the classified powder (a1) and the crushed powder (b1).

[0023] (Steps of Production Method (2)) The production method (2) includes the following step (S2-4): Step (S2-4): Specific particles (a2) and particles (b2) are mixed in a specific ratio.

[0024] (Production Method (1): Step (S1-1)) In step (S1-1) of Production Method (1), pre-classified composite particles containing a positive electrode active material, a carbon-based conductive material, and a binder resin are obtained. The method for producing the pre-classified composite particles is not particularly limited, and a known granulation method for producing composite particles can be appropriately selected and used. Examples of granulation methods include spray-drying granulation, tumbling bed granulation, compression granulation, agitation granulation, extrusion granulation, crushing granulation, fluidized bed granulation, fluidized bed multifunctional granulation, and melt granulation. Among these, agitation granulation is preferred from the viewpoint of increasing the strength of the composite particles.

[0025] The production of pre-classified composite particles by the agitation granulation method can be carried out by subjecting a positive electrode active material, a carbon-based conductive material, a binder resin, and a solvent to agitation granulation. More specifically, step (S1-1) can be carried out by a granulation method including a step (S1-1a) of agitating the positive electrode active material in a granulation tank to obtain an agitated state, and a step (S1-1b) of spraying a liquid composition containing a carbon-based conductive material, a binder resin, and a solvent onto the agitated positive electrode active material. Examples of equipment for agitation granulation include known agitation granulators such as batch-type agitation granulators and continuous agitation granulators. Details of the materials used to produce the pre-classified composite particles will be described in detail later.

[0026] Step (S1-1) may further include any optional step in addition to steps (S1-1a) and (S1-1b). For example, it may include a particle size regulating step for further adjusting the particles obtained in step (S1-1b) to a desired particle size. The particle size regulating step may be performed by a method of continuing stirring after the end of step (S1-1b), a method of performing preliminary classification prior to step (S1-2), or the like.

[0027] The particle size and particle size distribution of the pre-classified composite particles to be subjected to step (S1-2) can be appropriately adjusted in step (S1-1) so as to obtain the desired composite particles. Specifically, the D50 particle size of the pre-classified composite particles is preferably 30 μm or more, more preferably 45 μm or more, and is preferably 95 μm or less, more preferably 80 μm or less. The particle size distribution D90 / D10 of the pre-classified composite particles is preferably 1 or more, more preferably 2.6 or more, and is preferably 5.2 or less, more preferably 4.7 or less. By having the particle size and particle size distribution of the pre-classified composite particles within the above-mentioned ranges, the particle size and particle size distribution of the resulting classified powder and crushed powder can be easily adjusted to within the desired ranges.

[0028] In order to set the particle size and particle size distribution of the pre-classified composite particles within the above-described preferred ranges, the conditions of the above-described steps (S1-1a) and (S1-1b) and any other steps can be appropriately adjusted. When preliminary classification is performed, the classification can be performed by sieving fine particles with small particle sizes through a sieve with a mesh size of 10 μm to 40 μm and removing them.

[0029] Since fine particles are difficult to reuse, it is particularly preferable from the viewpoint of efficient granulation to adjust the conditions of steps (S1-1a) and (S1-1b) and the step of continuing stirring after the completion of steps (S1-1a) and (S1-1b) so that pre-classified composite particles having a particle size and particle size distribution not less than the above-mentioned lower limit can be obtained without preliminary classification, or so that the amount of fine particles removed in the preliminary classification to obtain pre-classified composite particles having a particle size and particle size distribution not less than the above-mentioned lower limit can be reduced. If the process conditions are reduced to reduce the generation of fine particles, it is difficult to avoid the generation of a relatively large amount of coarse powder. However, in the production method of the present invention, by performing the following steps (S1-2) and onwards, it is possible to efficiently obtain composite particles of the desired particle size even if a large amount of coarse powder is generated.

[0030] (Production Method (1): Step (S1-2)) In step (S1-2), the pre-classified composite particles are classified to obtain a classified powder (a1) and a coarse powder. The specific classification procedure can be performed by classifying the pre-classified composite particles using a sieve with a predetermined mesh size, recovering the particles that passed through the sieve as the classified powder (a1), and recovering the particles that remained on the sieve as the coarse powder. The mesh size of the sieve can be appropriately selected so as to obtain the desired classified powder (a1). Specifically, the mesh size is preferably 100 μm or more, more preferably 130 μm or more, and is preferably 300 μm or less, more preferably 250 μm or less.

[0031] The D50 particle size of the classified powder (a1) is preferably 30 μm or more, more preferably 40 μm or more, even more preferably 50 μm or more, and is preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. Therefore, the D50 particle size of the classified powder (a1) is preferably in the range of 30 μm or more and 100 μm or less, more preferably 40 μm or more and 80 μm or less, and even more preferably 50 μm or more and 70 μm or less. In particular, the D50 particle size of the classified powder (a1) is preferably in the range of 48 μm or more and 60 μm or less. By having the particle size of the classified powder (a1) within the above-mentioned range, the particle size and particle size distribution of the obtained composite particles can be set within the desired range. In particular, by having the D50 particle size of the classified powder (a1) be equal to or greater than the above-mentioned lower limit, the moldability of the composite particles can be improved. When the D50 particle size of the classified powder (a1) is equal to or less than the upper limit, the formation of streaks in the positive electrode mixture layer can be effectively suppressed, and the uniformity of the positive electrode mixture layer can be effectively improved.

[0032] The particle size distribution D90 / D10 of the classified powder (a1) is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 2.5 or more, and preferably 6.0 or less, more preferably 5.5 or less, and even more preferably 5.0 or less. Therefore, the particle size distribution D90 / D10 of the classified powder (a1) is preferably in the range of 1.0 to 6.0, more preferably 2.0 to 5.5, and even more preferably 2.5 to 5.0. In particular, the particle size distribution D90 / D10 of the classified powder (a1) is preferably in the range of 4.0 to 5.5. By having the particle size distribution of the classified powder (a1) within the above-mentioned range, the particle size and particle size distribution of the obtained composite particles can be set to the desired range. In particular, by setting the particle size distribution D90 / D10 of the classified powder (a1) to be above the lower limit, the resistance of the obtained positive electrode composite layer can be reduced and production can be facilitated. By setting the particle size distribution D90 / D10 of the classified powder (a1) to the above upper limit or less, the moldability of the composite particles can be improved.

[0033] (Production method (1): step (S1-3)) In step (S1-3), the coarse powder obtained in step (S1-2) is crushed to obtain crushed powder (b1). The D50 particle size of the crushed powder (b1) is preferably 50 μm or more, more preferably 60 μm or more, even more preferably 70 μm or more, and is preferably 120 μm or less, more preferably 100 μm or less, and even more preferably 90 μm or less. Therefore, the D50 particle size of the crushed powder (b1) can be preferably in the range of 50 μm or more and 120 μm or less, more preferably in the range of 60 μm or more and 100 μm or less, and even more preferably in the range of 70 μm or more and 90 μm or less. In particular, the D50 particle size of the crushed powder (b1) is preferably in the range of 65 μm or more to 89 μm or less. When the particle size of the crushed powder (b1) is within the above-mentioned range, the particle size and particle size distribution of the obtained composite particles can be set within the desired range, and good resistance reduction can be achieved. In particular, when the particle size of the pulverized powder (b1) is equal to or larger than the lower limit, the moldability of the composite particles can be improved. When the particle size of the pulverized powder (b1) is equal to or smaller than the upper limit, the yield of the composite particles can be improved.

[0034] The particle size distribution D90 / D10 of the pulverized powder (b1) is preferably 8 or more, more preferably 9 or more, even more preferably 10 or more, and preferably 20 or less, more preferably 18 or less, and even more preferably 15 or less. Therefore, the particle size distribution D90 / D10 of the pulverized powder (b1) can be preferably in the range of 8 to 20, more preferably in the range of 9 to 18, and even more preferably in the range of 10 to 15. In particular, the particle size distribution D90 / D10 of the pulverized powder (b1) is preferably in the range of 12.9 to 17.5. By having the particle size distribution of the pulverized powder (b1) within the above-mentioned range, the particle size and particle size distribution of the obtained composite particles can be set within the desired range. In particular, by setting the particle size distribution D90 / D10 of the pulverized powder (b1) to be equal to or greater than the lower limit, the resistance of the obtained positive electrode composite layer can be reduced and production can be facilitated. By setting the particle size distribution D90 / D10 of the pulverized powder (b1) to the above upper limit or less, the moldability of the composite particles can be improved.

[0035] In addition, the present inventors have found that when the particle size and particle size distribution of the pulverized powder (b1) are within the above-mentioned ranges, even if the mixing ratio of the pulverized powder (b1) in step (S1-4) is set to a high value of 2 mass% or more, it is possible to suppress undesirable phenomena such as a decrease in electrical conductivity and a decrease in cycle characteristics and to improve the yield, thereby enabling particularly preferable production.

[0036] Generally, when crushed coarse powder is mixed with other particles in the production of composite particles for an electrode, it is thought that the performance of the resulting electrode may be reduced. However, the present inventors have found that, when the classified powder (a1) and the crushed powder (b1) satisfy the above-mentioned preferable characteristics, the reduction in the performance of the resulting electrode and electrochemical element is suppressed, and as a result, it is possible to more easily achieve the production of an electrochemical element with good performance at low cost.

[0037] The specific crushing operation can be carried out using a crusher such as a pin mill crusher. By adjusting the crushing conditions (for example, the peripheral speed of a pin mill crusher), the degree of crushing can be controlled to obtain crushed powder (b1) having the desired particle size and particle size distribution. Alternatively, auxiliary classification may be carried out before or after crushing.

[0038] (Production Method (1): Step (S1-4)) In step (S1-4), the classified powder (a1) and the pulverized powder (b1) are mixed. The mixing ratio can be adjusted appropriately so as to obtain composite particles having the desired particle size and particle size distribution. The ratio Wa1 / Wb1 of the mass Wa1 of the classified powder (a1) to the mass Wb1 of the pulverized powder (b1) is preferably 80 / 20 or more, more preferably 85 / 15 or more, even more preferably 88 / 12 or more, and is preferably 98 / 2 or less, more preferably 97 / 3 or less, and even more preferably 95 / 5 or less. By setting Wa1 / Wb1 to the above lower limit or more and increasing the proportion of the classified powder (a1) to a certain extent or more, the moldability of the composite particles can be improved. By setting Wa1 / Wb1 to the above upper limit or less and increasing the proportion of the pulverized powder (b1) to a certain extent or more, the yield of the composite particles can be improved.

[0039] (Production Method (2)) In the production method (2), in step (S2-4), specific particles (a2) and particles (b2) are mixed in a specific ratio. In step (S2-4), the particle size distribution D90 / D10 of the particles (a2) is 1 or more and 6 or less, and the particle size distribution D90 / D10 of the particles (b2) is 8 or more and 20 or less. In step (S2-4), the mixing ratio Wa2 / Wb2 of the mass Wa2 of the particles (a2) to the mass Wb2 of the particles (b2) is 80 / 20 or more and 98 / 2 or less.

[0040] The preferred materials, particle sizes, and particle size distributions of the particles (a2) and (b2) may be the same as those described above for the classified powder (a1) and the crushed powder (b1). Therefore, each of the particles (a2) and (b2) may be a particle containing a positive electrode active material, a carbon-based conductive material, and a binder resin. The preferred Wa2 / Wb2 mixing ratio may be the same as those described above for the Wa1 / Wb1 mixing ratio.

[0041] The method for producing the particles (a2) and (b2) used in production method (2) is not particularly limited. As an example, all or part of the particles (a2) and (b2) can be produced by a production method including the following steps (S2-1) to (S2-3). Preferred examples of steps (S2-1) to (S2-3) can be the same as those described for steps (S1-1) to (S1-3) of production method (1). Step (S2-1): Pre-classified composite particles containing a positive electrode active material, a carbon-based conductive material, and a binder resin are obtained. Step (S2-2): The pre-classified composite particles are classified to obtain particles (a2) and coarse powder. Step (S2-3): The obtained coarse powder is crushed to obtain particles (b2).

[0042] However, particles (a2) and (b2) may be obtained, in whole or in part, by a manufacturing method other than the manufacturing method including steps (S2-1) to (S2-3). For example, particles having the desired particle size and particle size distribution produced by a granulation process other than steps (S2-1) to (S2-3) may be used as particles (a2) and (b2). Alternatively, if there is a production line carrying out manufacturing method (1) separate from the production line carrying out manufacturing method (2), the classified powder (a1), coarse powder, and crushed powder (b1) surplus generated in manufacturing method (1) may be used as is, or after being subjected to appropriate processing such as classification or crushing, to prepare particles that meet the requirements for particles (a2) and (b2), and then used. In this way, by obtaining and utilizing particles (a2) and (b2) by various manufacturing methods, composite particles with excellent performance can be produced at low cost.

[0043] (Material of Pre-Classified Composite Particles: Positive Electrode Active Material) Hereinafter, each material used in granulating the pre-classified composite particles will be described. The positive electrode active material used in granulating the pre-classified composite particles is a material that transfers electrons at the positive electrode of the electrochemical element. For example, as a positive electrode active material for a lithium ion secondary battery, a material that can absorb and release lithium is usually used. Hereinafter, a positive electrode active material when the electrochemical element is a lithium ion secondary battery will be described as an example, but the present invention is not limited to the following example.

[0044] The positive electrode active material for lithium ion secondary batteries can be a compound containing a transition metal, such as a transition metal oxide, a transition metal sulfide, or a composite metal oxide of lithium and a transition metal, such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, or Mo.

[0045] As the transition metal oxide, transition metal sulfide, and composite metal oxide of lithium and transition metal, for example, those described in JP-A-2020-198315 can be used.

[0046] When the positive electrode active material is subjected to granulation of pre-classified composite particles by the stirring granulation method, the positive electrode active material is in the form of particles. The D50 particle size of the positive electrode active material particles is preferably 0.1 μm or more, more preferably 1.0 μm or more, and is preferably 50 μm or less, more preferably 20 μm or less.

[0047] (Material of Pre-Classified Composite Particles: Carbon-Based Conductive Material) Examples of carbon-based conductive materials used in granulating the pre-classified composite particles include carbon black (e.g., acetylene black, Ketjen Black (registered trademark), furnace black, etc.), graphite (graphene), carbon fiber (carbon nanofiber), carbon flakes, and ultrashort carbon fibers (e.g., carbon nanotubes (CNT) and vapor-grown carbon fibers, etc.). Among these, from the viewpoint of conductivity and output characteristics, carbon black, carbon fiber (carbon nanofiber), graphite (graphene), and carbon nanotubes (CNT) are preferred, carbon black and carbon nanotubes (CNT) are more preferred, and carbon black is particularly preferred. These can be used alone or in combination of two or more.

[0048] The amount of the carbon-based conductive material used to granulate the pre-classified composite particles is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and preferably 3 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the positive electrode active material. If the amount of the carbon-based conductive material is equal to or greater than the above-mentioned lower limit, the output characteristics of the electrochemical element can be further improved. Furthermore, if the amount of the carbon-based conductive material is equal to or less than the above-mentioned upper limit, the dispersion stability of the carbon-based conductive material can be further improved.

[0049] (Material of Pre-Classified Composite Particles: Binder Resin) Examples of binder resins used for granulating the pre-classified composite particles include various resins known to be usable as binder resins in composite particles for electrochemical element positive electrodes.

[0050] The range of the binder resin content is preferably 0.01 wt % or more, more preferably 0.1 wt % or more, and even more preferably 0.5 wt % or more, and is preferably 5 wt % or less, more preferably 4 wt % or less, and even more preferably 3 wt % or less, relative to 100 wt % of the composite particles. When the binder resin content is within the above range, it is possible to effectively improve moldability and cycle characteristics, and usually also to effectively reduce powder resistance.

[0051] As the binder resin, a polymer or a composition containing a polymer as a main component is usually used. Examples of polymers that can be used as the binder resin include conjugated diene polymers, acrylic polymers, aromatic vinyl block polymers, fluorine-containing polymers, cellulose polymers, and cyclic olefin polymers.

[0052] The conjugated diene polymer refers to a polymer containing conjugated diene monomer units. Examples of conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, 2-chloro-1,3-butadiene (chloroprene), and piperylene. Specific examples of conjugated diene polymers include copolymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene copolymer (SBR); butadiene rubber (BR); acrylic rubber (NBR) (a copolymer containing acrylonitrile units and butadiene units); and hydrogenated products thereof.

[0053] Examples of acrylic polymers include polymers containing crosslinkable monomer units, (meth)acrylic acid ester monomer units, and acidic group-containing monomer units. The proportion of (meth)acrylic acid ester monomer units in the acrylic polymer is preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 58% by mass or more, and is preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less.

[0054] Examples of aromatic vinyl block polymers include block polymers containing block regions composed of aromatic vinyl monomer units. Examples of aromatic vinyl monomers include styrene, styrene sulfonic acid and its salts, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene, with styrene being preferred. Examples of aromatic vinyl block polymers include styrene-isoprene-styrene block copolymers, styrene-butadiene-styrene copolymers, and hydrogenated versions of these.

[0055] The term "fluorine-containing polymer" refers to a polymer that contains fluorine-containing monomer units and may further contain fluorine-free monomer units (fluorine-free monomers). Examples of fluorine-containing monomers include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride, vinyl fluoride, trifluoroethylene, trifluorochloroethylene, 2,3,3,3-tetrafluoropropene, and perfluoroalkyl vinyl ether. Examples of fluorine-containing polymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoroalkoxy fluororesin, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, and vinylidene fluoride-hexafluoropropylene copolymer (vinylidene fluoride-hexafluoropropylene copolymer).

[0056] Examples of the cellulose-based polymer include cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, and carboxylmethyl cellulose.

[0057] Examples of cyclic olefin polymers include polymers (addition polymers or ring-opening polymers) obtained by polymerizing cyclic olefin compounds and hydrogenated polymers thereof, as well as hydrogenated polymers obtained by polymerizing aromatic vinyl compounds. Among these, hydrogenated polymers obtained by ring-opening polymerization of cyclic olefin compounds and hydrogenated polymers obtained by polymerizing aromatic vinyl compounds are preferred because they allow for easy adjustment of the electrolyte swelling degree and glass transition temperature to appropriate levels.

[0058] Examples of the cyclic olefin compounds include norbornenes that are unsubstituted or have an alkyl group, such as norbornene, 5-methylnorbornene, 5-ethylnorbornene, 5-butylnorbornene, 5-hexylnorbornene, 5-decylnorbornene, 5-cyclohexylnorbornene, and 5-cyclopentylnorbornene; norbornenes that have an alkenyl group, such as 5-ethylidenenorbornene, 5-vinylnorbornene, 5-propenylnorbornene, 5-cyclohexenylnorbornene, and 5-cyclopentenylnorbornene; norbornenes that have an aromatic ring, such as 5-phenylnorbornene; 5-methoxycarbonylnorbornene, 5-ethoxycarbonylnorbornene, 5-methylnorbornene, and 5-methylnorbornene. norbornenes having a polar group containing an oxygen atom, such as norbornene-5-methoxycarbonylnorbornene, 5-methyl-5-ethoxycarbonylnorbornene, norbornenyl-2-methylpropionate, norbornenyl-2-methyloctanate, 5-hydroxymethylnorbornene, 5,6-di(hydroxymethyl)norbornene, 5,5-di(hydroxymethyl)norbornene, 5-hydroxy-i-propylnorbornene, 5,6-dicarboxynorbornene, and 5-methoxycarbonyl-6-carboxynorbornene; norbornenes having a polar group containing a nitrogen atom, such as 5-cyanonorbornene; dicyclopentadiene, methyldicyclopentadiene, tricyclo[5.2.1.0]di ... ２，６ ]dec-8-ene and other polycyclic norbornenes having three or more rings and not containing an aromatic ring structure; tetracyclo[9.2.1.0 ２，１０ .0 ３，８]tetradeca-3,5,7,12-tetraene (also known as 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene), tetracyclo[10.2.1.0 ２，１１ .0 ４，９ ]pentadeca-4,6,8,13-tetraene (also called 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene), and other polycyclic norbornenes having three or more aromatic rings; tetracyclododecene, 8-methyltetracyclododecene, 8-ethyltetracyclododecene, 8-cyclohexyltetracyclododecene, 8-cyclopentyltetracyclododecene, 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.1 ２，５ .1 ７，１０ tetracyclododecenes having an unsubstituted or alkyl group such as 8-methylidenetetracyclododecene, 8-ethylidenetetracyclododecene, 8-vinyltetracyclododecene, 8-propenyltetracyclododecene, 8-cyclohexenyltetracyclododecene, 8-cyclopentenyltetracyclododecene; tetracyclododecenes having an exocyclic double bond such as 8-phenyltetracyclododecene; tetracyclododecenes having an aromatic ring such as 8-methoxycarbonyltetracyclododecene, 8-methyl-8-methoxycarbonyltetracyclododecene, 8-hydroxymethyltetracyclododecene, 8-carboxytetracyclododecene, ... tetracyclododecenes having a substituent containing an oxygen atom, such as tetracyclododecene-8,9-dicarboxylic acid and tetracyclododecene-8,9-dicarboxylic anhydride; tetracyclododecenes having a substituent containing a nitrogen atom, such as 8-cyanotetracyclododecene and tetracyclododecene-8,9-dicarboxylic imide; tetracyclododecenes having a substituent containing a halogen atom, such as 8-chlorotetracyclododecene; tetracyclododecenes having a substituent containing a silicon atom, such as 8-trimethoxysilyltetracyclododecene; and hexacycloheptadecenes such as Diels-Alder adducts of the above-mentioned tetracyclododecenes and cyclopentadiene.

[0059] Among these, non-polar norbornene-based monomers are preferred as cyclic olefin compounds; for example, norbornenes having unsubstituted or alkyl groups (e.g., norbornene, 8-ethyltetracyclododecene), norbornenes having alkenyl groups (e.g., ethylidenetetracyclododecene (8-ethylidenetetracyclododecene)), dicyclopentadiene, norbornene derivatives having aromatic rings (e.g., tetracyclo[9.2.1.0], ２，１０ .0 ３，８ ]tetradeca-3,5,7,12-tetraene (also called 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene)), unsubstituted or alkyl-substituted tetracyclododecenes (e.g., tetracyclododecene, 8-methoxycarbonyl-8-methyltetracyclo[4.4.0.1 ２，５ .1 ７，１０ ]-3-dodecene) is more preferred.

[0060] The polymer of a cyclic olefin compound that can be optionally hydrogenated may be a polymer using only a cyclic olefin compound as a monomer, or a polymer using a cyclic olefin compound and any copolymerizable compound other than a cyclic olefin compound as a monomer, among which a polymer using only a cyclic olefin compound as a monomer is preferred.

[0061] The polymer of a cyclic olefin compound that can be optionally hydrogenated is preferably a polymer using tetracyclododecene, dicyclopentadiene, and norbornene as monomers, and more preferably a ring-opening polymer using tetracyclododecene, dicyclopentadiene, and norbornene as monomers.

[0062] Among the above-mentioned polymers, copolymers containing aromatic vinyl monomer units and conjugated diene monomer units and hydrogenated products thereof are preferred; block copolymers containing aromatic vinyl monomer blocks and conjugated diene monomer blocks and hydrogenated products thereof are more preferred; and hydrogenated products of block copolymers containing aromatic vinyl monomer blocks and conjugated diene monomer blocks are particularly preferred. The aromatic vinyl monomer block is a block region containing aromatic vinyl monomer units and may contain only aromatic vinyl monomer units. Furthermore, the conjugated diene monomer block is a block region containing conjugated diene monomer units and may contain only conjugated diene monomer units.

[0063] The aromatic vinyl monomer unit represents a structural unit having a structure formed by polymerizing an aromatic vinyl monomer. The type of aromatic vinyl monomer unit may be one type or two or more types. The content of the aromatic vinyl monomer unit is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, relative to 100% by mass of the total of all structural units contained in the copolymer, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

[0064] The conjugated diene monomer unit represents a structural unit having a structure formed by polymerizing a conjugated diene monomer. The type of conjugated diene monomer unit may be one type or two or more types. The content of the conjugated diene monomer unit is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, relative to 100% by mass of the total of all structural units contained in the copolymer, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0065] When the copolymer is a block copolymer, the block structure may be, for example, a two-block structure having an aromatic vinyl monomer block-conjugated diene monomer block; a three-block structure having an aromatic vinyl monomer block-conjugated diene monomer block-aromatic vinyl monomer block; or a five-block structure having an aromatic vinyl monomer block-conjugated diene monomer block-aromatic vinyl monomer block-conjugated diene monomer block-aromatic vinyl monomer block.

[0066] The hydrogenation rate of the hydrogenated copolymer is not particularly limited, but is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. １ It can be measured by H-NMR.

[0067] The binder resin may be used alone or in combination of two or more.

[0068] (Particularly Preferred Example of Binder Resin: Binder Composition for Electrochemical Device) Particularly preferred examples of binder resins include specific binder compositions for electrochemical devices (hereinafter also simply referred to as "binder compositions") described below.

[0069] The binder composition includes a first polymer and a second polymer, each of which is a hydrogenated block copolymer. The first polymer has a mass average molecular weight of 120,000 or more and 550,000 or less, and the ratio of the mass average molecular weight of the first polymer to the mass average molecular weight of the second polymer (mass average molecular weight of the first polymer / mass average molecular weight of the second polymer) is 1.2 or more and 8 or less.

[0070] Since the binder composition contains two types of polymers (a first polymer and a second polymer) having different mass-average molecular weights, the molecular weight distribution thereof measured by gel permeation chromatography has at least two peaks, one attributable to the first polymer and the other to the second polymer.

[0071] By using such a binder composition as a binder resin, it is possible to improve the flexibility of a positive electrode produced using the obtained composite particles, and also to allow the electrochemical device to exhibit excellent cycle characteristics.

[0072] (First Polymer) The first polymer is a polymer obtained by hydrogenating a block copolymer.

[0073] The mass average molecular weight of the first polymer is preferably 120,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 550,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. When the mass average molecular weight of the first polymer is within the above range, the flexibility and cycle characteristics of the resulting positive electrode and electrochemical device are improved.

[0074] The first polymer is a polymer having a structure obtained by hydrogenating a block copolymer as a precursor. However, in the present invention, the structure of the compound is not limited by its production method. The block of the block copolymer preferably contains aromatic vinyl monomer units and monomer units derived from an aliphatic conjugated diene monomer, and may optionally further contain repeating units other than the aromatic vinyl monomer units and the monomer units derived from the aliphatic conjugated diene monomer (hereinafter also referred to as "other repeating units"). "Containing monomer units" means that "structural units derived from the monomer are contained in a polymer obtained using that monomer."

[0075] Examples of aromatic vinyl monomers that can form aromatic vinyl monomer units include styrene, styrene sulfonic acid and its salts, α-methylstyrene, p-t-butylstyrene, butoxystyrene, vinyltoluene, chlorostyrene, and vinylnaphthalene. These may be used alone or in combination of two or more in any ratio. Among these, styrene is preferred from the viewpoint of further improving the flexibility of the resulting positive electrode and further improving the cycle characteristics of the electrochemical element.

[0076] The proportion of aromatic vinyl monomer units in the first polymer is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 55% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, when the amount of all repeating units (monomer units) in the first polymer is taken as 100% by mass. When the content of aromatic vinyl monomer units is within the above range, the flexibility of the positive electrode can be further improved while the cycle characteristics of the electrical device can be further improved. When the first polymer has a block A described below that is composed of aromatic vinyl monomer units, the proportion of the aromatic vinyl monomer units in the first polymer typically coincides with the proportion of the block A in the first polymer.

[0077] Examples of aliphatic conjugated diene monomers capable of forming monomer units derived from an aliphatic conjugated diene monomer include aliphatic conjugated diene compounds having 4 or more carbon atoms, such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 1,3-pentadiene. These may be used alone, or two or more may be used in combination in any ratio. Among these, 1,3-butadiene and isoprene are preferred from the viewpoint of further improving the flexibility of the positive electrode. "Monomer units derived from an aliphatic conjugated diene monomer" refers to aliphatic conjugated diene monomer units and / or structural units obtained by hydrogenating aliphatic conjugated diene monomer units (aliphatic conjugated diene monomer hydrogenated units).

[0078] Here, the structural unit (hydrogenated aliphatic conjugated diene monomer unit) obtained by hydrogenating the aliphatic conjugated diene monomer unit is usually represented by the general formula: -C ｎ H ２ｎ - [where n is an integer of 2 or greater]. The alkylene structural unit may be linear or branched, but the alkylene structural unit is preferably linear, i.e., a linear alkylene structural unit. The alkylene structural unit preferably has 4 or more carbon atoms (i.e., n in the above general formula is an integer of 4 or greater).

[0079] The proportion of monomer units derived from an aliphatic conjugated diene monomer in the first polymer (the total proportion of aliphatic conjugated diene monomer units and structural units obtained by hydrogenating the aliphatic conjugated diene monomer units) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 45% by mass or less, when the amount of all repeating units in the first polymer is taken as 100% by mass. When the content of monomer units derived from an aliphatic conjugated diene monomer is within the above range, the flexibility of the positive electrode can be further improved while the cycle characteristics of the electrochemical device can be further improved. When the first polymer has a block B described below consisting of monomer units derived from an aliphatic conjugated diene monomer, the proportion of monomer units derived from the aliphatic conjugated diene monomer in the first polymer usually matches the proportion of the block B in the polymer.

[0080] Examples of monomers capable of forming other repeating units (hereinafter also referred to as "other monomers") include, but are not limited to, (meth)acrylic acid ester monomers and polymerizable monomers having a hydrophilic group. These monomers can be used alone or in combination of two or more.

[0081] Examples of the (meth)acrylic acid ester monomer include alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate; and alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. Among these, preferred (meth)acrylic acid ester monomers are ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate, with n-butyl acrylate being more preferred.

[0082] Examples of polymerizable monomers having a hydrophilic group include monomers having a carboxylic acid group, monomers having a sulfonic acid group, monomers having a phosphoric acid group, and monomers having a hydroxyl group. From the viewpoint of increasing the binding strength of the polymer, the hydrophilic group is preferably a carboxylic acid group or a sulfonic acid group, and more preferably a carboxylic acid group.

[0083] Examples of monomers having a carboxylic acid group include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, and maleic acid esters such as methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleates. Examples of dicarboxylic acid anhydrides include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. As a monomer having a carboxylic acid group, an acid anhydride that generates a carboxyl group upon hydrolysis can also be used. Other examples include monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids, such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate.

[0084] Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid.

[0085] Examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate.

[0086] Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, and di-2-hydroxypropyl itaconate; and compounds of the general formula: CH ２ =CR １ -COO-(C ｎ H ２ｎ O) ｍ -H (wherein m is an integer from 2 to 9, n is an integer from 2 to 4, R １represents hydrogen or a methyl group) and (meth)acrylic acid esters; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; alkyl ethers such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether; mono(meth)allyl ethers of ethylene glycol; polyoxyalkylene glycol mono(meth)allyl ethers such as diethylene glycol mono(meth)allyl ether and dipropylene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen- and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol, and halogen-substituted products thereof; and (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether.

[0087] The proportion of the other repeating units in the first polymer is preferably 10% by mass or less, and more preferably 5% by mass or less, when the amount of all repeating units in the first polymer is taken as 100% by mass. If the proportion of the other repeating units is equal to or less than the upper limit, it is preferable because effects such as good cycle characteristics are easily obtained.

[0088] From the viewpoint of further improving the flexibility of the positive electrode and the cycle characteristics of the electrochemical device, the first polymer is preferably a hydrogenated block copolymer containing one or more blocks A composed of first repeating units and one or more blocks B composed of second repeating units. Here, the number of blocks A in the first polymer is usually three or less, preferably two. The number of blocks B in the first polymer is usually two or less, preferably one. The first polymer may further contain a block or random region composed of the other repeating units.

[0089] The block structure of the first polymer is not particularly limited, and may be either a chain block or a radial block. However, a chain block is preferred, and a linear block is more preferred. From the viewpoint of further improving the flexibility of the positive electrode and the cycle characteristics of the electrochemical device, the first polymer preferably has a diblock structure having one of each of two types of blocks (e.g., a structure consisting of block A and block B), or a triblock structure consisting of three blocks. Among these, a structure in which block A is bonded to both ends of block B is more preferred. Preferred examples of such a structure in which block A is bonded to both ends of block B include a triblock structure represented by [A]-[B]-[A] and a pentablock structure represented by [A]-[B]-[A]-[B]-[A], with a triblock structure represented by [A]-[B]-[A] being more preferred. From the same viewpoint, the first polymer preferably has a triblock structure, and more preferably a triblock structure represented by [A]-[B]-[A]. The triblock structure or pentablock structure may be a symmetric block structure or an asymmetric block structure. For example, the triblock structure represented by [A]-[B]-[A] may be a symmetric triblock structure in which the two blocks A have the same degree of polymerization and / or the same type of structural unit, or an asymmetric triblock structure in which the two blocks A have different degrees of polymerization and / or the same type of structural unit. Among these, it is preferable that the first polymer has an asymmetric triblock structure.

[0090] The first polymer may be a mixture of two or more types selected from the group consisting of a block copolymer having a pentablock structure, a block copolymer having a triblock structure, and a block copolymer having a diblock structure. Preferably, the first polymer comprises 90% by mass or more, more preferably 95% by mass or more, of a block copolymer having a triblock structure, and even more preferably comprises a block copolymer having a triblock structure.

[0091] From the viewpoint of further improving the flexibility of the positive electrode and enabling the electrochemical device to exhibit even better cycle characteristics, the first repeating unit constituting block A is preferably an aromatic vinyl monomer unit. That is, block A is preferably composed of aromatic vinyl monomer units. Here, block A may be composed of only one type of aromatic vinyl monomer unit or may be composed of multiple types of aromatic vinyl monomer units, but is preferably composed of only one type of aromatic vinyl monomer unit. Furthermore, when the first polymer has multiple blocks A, the types and proportions of the aromatic vinyl monomer units constituting these multiple blocks A may be the same or different, but are preferably the same.

[0092] The weight average molecular weight of block A in the first polymer is not particularly limited, but is preferably at least 8,000, more preferably at least 10,000, and is preferably at most 300,000, more preferably at most 250,000. In the present invention, the weight average molecular weight of block A in the polymer can be measured by the method described in the examples.

[0093] When the first polymer has multiple blocks A, the weight-average molecular weights of the multiple blocks A (A1, A2, ...) may be the same or different, but are preferably different. Specifically, for example, when the first polymer includes two blocks A1 and A2 (e.g., when the first polymer has a structure represented by [A1]-[B]-[A2] in which blocks A1 and A2 are bonded to both ends of block B), from the viewpoint of further improving the flexibility of the positive electrode and further improving the cycle characteristics of the electrochemical device, the weight-average molecular weight of block A1 is preferably 8,000 or more, more preferably 10,000 or more, and preferably 30,000 or less, more preferably 15,000 or less; on the other hand, the weight-average molecular weight of block A2 is preferably 100,000 or more, more preferably 200,000 or more, and preferably 300,000 or less, more preferably 250,000 or less.

[0094] From the viewpoint of further improving the flexibility of the positive electrode and improving the cycle characteristics of the electrical element, the ratio of the mass average molecular weight of the block A2 to the mass average molecular weight of the block A1 (mass average molecular weight of block A2 / mass average molecular weight of block A1) is preferably 8 or more, more preferably 14 or more, and is preferably 30 or less, more preferably 25 or less.

[0095] From the viewpoint of enabling the electrochemical device to exhibit even better cycle characteristics, the second repeating unit constituting block B is preferably a monomer unit derived from an aliphatic conjugated diene monomer. That is, block B is preferably composed of monomer units derived from an aliphatic conjugated diene monomer. Here, the monomer units derived from the aliphatic conjugated diene monomer contained in block B may be composed of only one type, or may be composed of multiple types. Furthermore, when the first polymer has multiple blocks B, the types and proportions of the monomer units derived from the aliphatic conjugated diene monomer constituting these multiple blocks B may be the same or different, but are preferably the same.

[0096] The mass average molecular weight of the block B in the first polymer is preferably 50,000 or more, more preferably 70,000 or more, and even more preferably 100,000 or more, and is preferably 250,000 or less, and more preferably 200,000 or less. When the mass average molecular weight of the block B is equal to or greater than the above-mentioned lower limit, the flexibility of the positive electrode can be further improved. When the mass average molecular weight of the block B is equal to or less than the above-mentioned upper limit, a decrease in the strength of the polymer can be suppressed. In the present invention, the mass average molecular weight of the block B of the polymer can be measured by the method described in the Examples. When the polymer contains multiple blocks B, the mass average molecular weights of the multiple blocks B may be the same or different, but are preferably the same.

[0097] The content of block A in the first polymer (the total content when there are multiple blocks A) is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 55% by mass or more, and is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. When the content of block A in the first polymer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrical device can be further improved.

[0098] Furthermore, the content of block B in the first polymer (the total content when there are multiple blocks B) is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, and is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 45% by mass or less. When the content of block B in the first polymer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrochemical device can be further improved.

[0099] The mass ratio of block A to block B (block A / block B) in the first polymer is preferably 0.8 or more, more preferably 1.5 or more, and is preferably 3.5 or less, more preferably 2.5 or less. When the mass ratio of block A to block B in the first polymer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrochemical device can be further improved.

[0100] (Second Polymer) The second polymer is a polymer obtained by hydrogenating a block copolymer.

[0101] From the viewpoint of further improving the flexibility of the positive electrode and enabling the electrochemical device to exhibit even better cycle characteristics, the mass average molecular weight of the second polymer is preferably 70,000 or more, and more preferably 100,000 or more, and is preferably 300,000 or less, and more preferably 250,000 or less.

[0102] The second polymer is a polymer obtained by hydrogenating a block copolymer, and the units constituting such a polymer may be the same as those of the first polymer described above. That is, the second polymer preferably contains aromatic vinyl monomer units and monomer units derived from an aliphatic conjugated diene monomer, and may optionally further contain other repeating units.

[0103] The preferred types of aromatic vinyl monomer units in the second polymer are the same as those in the first polymer. Furthermore, the proportion of aromatic vinyl monomer units in the second polymer, when the amount of all repeating units in the second polymer is taken as 100% by mass, is preferably 10% by mass or more, more preferably 12% by mass or more, and even more preferably 14% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less. If the proportion of aromatic vinyl monomer units in the second polymer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrochemical device can be further improved.

[0104] The preferred types of monomer units derived from an aliphatic conjugated diene monomer in the second polymer are the same as those in the first polymer. The proportion of monomer units derived from an aliphatic conjugated diene monomer in the second polymer (the total proportion of aliphatic conjugated diene monomer units and structural units obtained by hydrogenating the aliphatic conjugated diene monomer units) is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 75% by mass or more, and is preferably 90% by mass or less, more preferably 88% by mass or less, and even more preferably 86% by mass or less, when the amount of all repeating units in the second polymer is taken as 100% by mass. If the content proportion of monomer units derived from an aliphatic conjugated diene monomer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrochemical device can be further improved.

[0105] The block structure of the second polymer can be the same as that of the first polymer described above. That is, the second polymer is preferably a hydrogenated block copolymer containing one or more blocks A consisting of the first repeating unit and one or more blocks B consisting of the second repeating unit, and optionally further containing blocks or random regions consisting of other repeating units. Here, the preferred numbers of blocks A and B in the second polymer and the preferred block configurations are the same as those of the first polymer. In particular, the second polymer preferably has a symmetric triblock structure.

[0106] Preferred types of the first repeating units constituting the block A in the second polymer are the same as those in the first polymer described above. The mass-average molecular weight of the block A in the second polymer is not particularly limited, but is preferably 8,000 or more, more preferably 10,000 or more, and preferably 30,000 or less, more preferably 20,000 or less. When the mass-average molecular weight of the block A in the second polymer is equal to or greater than the above-mentioned lower limit, the flexibility of the positive electrode can be further improved. When the mass-average molecular weight of the block A in the second polymer is equal to or less than the above-mentioned upper limit, the flexibility of the positive electrode can be further improved. Here, when the second polymer has multiple blocks A, the mass-average molecular weights of the multiple blocks A (A1, A2, ...) may be the same or different, but are preferably the same.

[0107] The preferred type of the second repeating unit constituting the block B in the second polymer, the preferred weight average molecular weight of the block B, etc. are the same as those of the first polymer.

[0108] The content of block A in the second polymer (the total content when there are multiple blocks A) is preferably 10% by mass or more, more preferably 12% by mass or more, and even more preferably 14% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less. When the content of block A in the second polymer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrochemical device can be further improved.

[0109] The content of block B in the second polymer (the total content when there are multiple blocks B) is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 75% by mass or more, and is preferably 90% by mass or less, more preferably 88% by mass or less, and even more preferably 86% by mass or less. When the content of block B in the second polymer is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrical device can be further improved.

[0110] The ratio of the mass average molecular weight of the first polymer to the mass average molecular weight of the second polymer (mass average molecular weight of the first polymer / mass average molecular weight of the second polymer) can be 1.2 or more and 8 or less. When the ratio of the mass average molecular weight of the first polymer to the mass average molecular weight of the second polymer is within the above range, the flexibility of the positive electrode and the cycle characteristics of the electrochemical device can be improved. From the viewpoint of further improving the flexibility of the positive electrode and the cycle characteristics of the electrochemical device, the ratio of the mass average molecular weight of the first polymer to the mass average molecular weight of the second polymer is preferably 1.5 or more, more preferably 2 or more, and is preferably 4 or less, more preferably 3 or less.

[0111] The proportion of aromatic vinyl monomer units in the binder composition in the total of the first polymer and the second polymer is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 35% by mass or more, and is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less, when the total proportion of repeating units in the first polymer and the second polymer is taken as 100% by mass. If the content of aromatic vinyl monomer units is within the above range, the flexibility of the positive electrode can be further improved, and the cycle characteristics of the electrochemical device can be further improved.

[0112] From the viewpoint of further improving the flexibility of the positive electrode and enabling the electrochemical element to exhibit even better cycle characteristics, the mass ratio of the first polymer to the second polymer (first polymer / second polymer) in the binder composition is preferably 10 / 90 or more, more preferably 20 / 80 or more, and is preferably 70 / 30 or less, more preferably 60 / 40 or less.

[0113] The binder composition can be prepared, for example, by preparing a solution containing two types of block copolymers as precursors of a first polymer and a second polymer, hydrogenating each block copolymer, and then removing the solvent used in preparing the polymers. Here, the solution containing two types of block copolymers may be prepared by preparing a solution containing a block copolymer as a precursor of the first polymer and a solution containing a block copolymer as a precursor of the second polymer and then mixing the two solutions, or by sequentially synthesizing the two types of block copolymers in one solvent. Alternatively, the binder composition may be prepared by preparing a solution containing the first polymer and a solution containing the second polymer, mixing the two solutions to obtain a mixed solution, and then removing the solvent from the mixed solution.

[0114] The method for preparing the block copolymer is not particularly limited, and for example, a block copolymer can be prepared by adding a second monomer component different from the first monomer component to a solution obtained by polymerizing a first monomer component, and optionally repeating the addition and polymerization of the monomer component. Specifically, examples of methods for producing block copolymers include those described in WO 2003 / 018656, WO 2011 / 096389, and WO 2021 / 065623.

[0115] A hydrogenated block copolymer can be obtained by hydrogenating at least the carbon-carbon unsaturated bonds derived from the aliphatic conjugated diene monomer units of the above-mentioned block copolymer. Here, each hydrogenated block copolymer may be a polymer in which only the non-aromatic carbon-carbon unsaturated bonds in the main chain and side chain derived from the aliphatic conjugated diene monomer units of the block copolymer are selectively hydrogenated, or a polymer in which the non-aromatic carbon-carbon unsaturated bonds in the main chain and side chain derived from the aliphatic conjugated diene monomer units of the block copolymer and the aromatic carbon-carbon unsaturated bonds in the aromatic ring derived from the aromatic vinyl monomer units of the block copolymer are hydrogenated. However, a polymer in which only the non-aromatic carbon-carbon unsaturated bonds in the main chain and side chain derived from the aliphatic conjugated diene monomer units of the block copolymer are selectively hydrogenated is preferred.

[0116] Specifically, during hydrogenation, the hydrogenation rate of the aromatic carbon-carbon unsaturated bonds in each block copolymer (i.e., the proportion of hydrogenated carbon-carbon unsaturated bonds in the aromatic rings of the aromatic vinyl monomer units, etc.) is preferably 50% or less, more preferably 30% or less, even more preferably 15% or less, even more preferably 3% or less, and particularly preferably 0%. When the hydrogenation rate of the aromatic carbon-carbon unsaturated bonds in the aromatic vinyl monomer units is equal to or less than the above upper limit, the cycle characteristics of the electrochemical device can be further improved. When each hydrogenated block copolymer is composed of a block A consisting of aromatic vinyl monomer units and a block B consisting of monomer units derived from an aliphatic conjugated diene compound, the hydrogenation rate of the aromatic carbon-carbon unsaturated bonds usually matches the hydrogenation rate of the aromatic carbon-carbon unsaturated bonds in block A.

[0117] Furthermore, during hydrogenation, the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds in the main chain and side chain derived from the aliphatic conjugated diene monomer units, etc. of each block copolymer (i.e., the proportion of hydrogenated carbon-carbon unsaturated bonds in the main chain and side chain derived from the aliphatic conjugated diene monomer units, etc.) is preferably 50% or more, more preferably 80% or more, even more preferably 90% or more, and particularly preferably 95% or more. When the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds is equal to or greater than the above-mentioned lower limit, the flexibility of the positive electrode can be further improved while the cycle characteristics of the electrochemical device can be further improved. When each hydrogenated block copolymer is composed of a block A composed of aromatic vinyl monomer units and a block B composed of monomer units derived from an aliphatic conjugated diene monomer, the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds usually matches the hydrogenation rate of the non-aromatic carbon-carbon unsaturated bonds of block B.

[0118] The hydrogenation rate is １ The H-NMR spectrum is measured, and the amount of change can be calculated based on the decrease in the integrated values ​​of the signals corresponding to the unsaturated bonds in the main chain and side chain portions and the unsaturated bonds in the aromatic ring before and after the hydrogenation reaction.

[0119] The method and reaction form for hydrogenating the unsaturated bonds in the block copolymer are not particularly limited, and known methods and reaction forms can be adopted. Examples of methods for selectively hydrogenating the non-aromatic carbon-carbon unsaturated bonds in the main chain and side chain derived from the aliphatic conjugated diene monomer of the block copolymer include known hydrogenation methods described in JP-A-2015-78090, etc. Furthermore, any known selective hydrogenation catalyst can be used without limitation, and a palladium-based catalyst or a rhodium-based catalyst can be used. Furthermore, for example, Ni(AcAc) ２ Nickel-based catalysts such as TIBAL and nickel(II) acetylacetonate, and aluminum-based catalysts such as triisobutylaluminum can also be used. Two or more of these hydrogenation catalysts can also be used in combination.

[0120] The reaction liquid after the hydrogenation reaction may then be optionally subjected to a catalyst removal (decalcification) treatment by a known method, and the resulting polymer may be filtered, washed, dried, etc. to recover the binder composition. The binder composition may be used as a binder solution in which the first polymer and the second polymer are dispersed and / or dissolved in a solvent.

[0121] (Solvent Used in Producing Pre-Classified Composite Particles) When the pre-classified composite particles are produced by a granulation method including the above-described steps (S1-1a) and (S1-1b), the carbon-based conductive material and binder resin are dispersed and dissolved in a solvent to prepare a liquid composition, which is then subjected to step (S1-1b). Examples of the solvent include organic solvents such as cyclohexane, N-methylpyrrolidone (NMP), N,N-dimethylformamide, and acetone. Among these, cyclohexane is preferred from the viewpoint of dispersion stability of the carbon-based conductive material.

[0122] (Composite particles) The composite particles for electrochemical element positive electrodes of the present invention are produced by the above-mentioned production method (1) or (2). The composite particles are obtained by subjecting pre-classified composite particles to steps such as classification and crushing, and therefore their components are the same as those described above for the pre-classified composite particles.

[0123] The D50 particle size of the composite particles is preferably 30 μm or more, more preferably 45 μm or more, and is preferably 95 μm or less, more preferably 80 μm or less. The particle size distribution D90 / D10 of the composite particles is preferably 1 or more, more preferably 2.6 or more, and is preferably 5.2 or less, more preferably 4.7 or less. When the particle size and particle size distribution of the composite particles are within the above-mentioned ranges, the moldability of the composite particles is good, and it is possible to produce a positive electrode for an electrochemical device with good performance.

[0124] (Positive electrode for electrochemical device and manufacturing method thereof) The positive electrode for electrochemical device of the present invention comprises a current collector and a positive electrode mixture layer. The positive electrode mixture layer is a layer containing the composite particles for electrochemical device positive electrode of the present invention.

[0125] The method for producing a positive electrode for an electrochemical element of the present invention is a method for producing a positive electrode for an electrochemical element comprising a current collector and a positive electrode composite layer, and includes the steps of: obtaining composite particles for a positive electrode for an electrochemical element by the method for producing composite particles for a positive electrode for an electrochemical element of the present invention; depositing the composite particles for a positive electrode for an electrochemical element on a surface of the current collector to form a composite particle layer; and applying pressure to the composite particle layer to form a positive electrode composite layer.

[0126] Examples of materials for the current collector include metal, carbon, and conductive polymer. Metal is preferably used as the current collector. Common examples of metals include copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, and other alloys. Among these, copper, aluminum, or aluminum alloys are preferred in terms of conductivity and voltage resistance.

[0127] Specific examples of methods for forming the composite particle layer and subsequent pressurization include a roll pressure molding method using a roll pressure molding device equipped with a pair of rolls, in which the current collector is fed by the rolls while the composite particles are fed into the roll pressure molding device by a feeder such as a vibration feeder or screw feeder to form an electrode mixture layer on the current collector; a method in which the composite particles are spread on the current collector, smoothed with a tool such as a blade to adjust the thickness, and then molded in a pressure device; and a method in which the composite particles are filled into a mold and the mold is pressurized to form. Of these, the roll pressure molding method is preferred from the viewpoint of being able to easily and efficiently carry out production.

[0128] Furthermore, to eliminate variations in the thickness of the formed electrode and increase the density of the positive electrode composite layer to achieve high capacity, post-pressing may be performed as needed. A preferred method of post-pressing is a roll pressing process. In the roll pressing process, two cylindrical rolls are arranged parallel to each other with a small gap between them, rotated in opposite directions, and pressed by clamping the electrode between them. In this process, the temperature of the rolls may be adjusted, for example, by heating or cooling.

[0129] In the positive electrode mixture layer obtained as a result of the pressing step, the composite particles are deformed as a result of the pressing, and exist in a state in which the particles are adhered to each other and to the current collector. The thickness, basis weight, and density of the obtained positive electrode mixture layer can be appropriately adjusted to obtain the desired performance. In the case of a normal positive electrode, the thickness is preferably 30 μm or more, more preferably 50 μm or more, and is preferably 150 μm or less, more preferably 100 μm or less. The basis weight is preferably 1 mg / cm as the basis weight per layer. ２ More preferably, 5 mg / cm ２ or more, while preferably 100 mg / cm ２ or less, more preferably 50 mg / cm ２ The density is preferably 2 g / cm ３ More preferably, 3 g / cm ３ or more, and preferably 5 g / cm ３ or less, more preferably 4 g / cm ３ The following is the result.

[0130] In the method for producing a positive electrode for an electrochemical device of the present invention, the composite particles of the present invention are used in the step of forming the composite particle layer, so that an efficient formation step can be carried out with reduced defects due to the presence of coarse particles. As a result, the positive electrode for an electrochemical device of the present invention has good performance and can be produced at low cost.

[0131] (Electrochemical element and manufacturing method thereof) The electrochemical element of the present invention includes the positive electrode for electrochemical elements of the present invention. The electrochemical element of the present invention may include, in addition to the positive electrode, a negative electrode, an electrolyte, and a separator. The manufacturing method of the electrochemical element of the present invention includes the steps of obtaining a positive electrode for electrochemical elements by the manufacturing method of a positive electrode for electrochemical elements of the present invention, and constructing an electrochemical element using the obtained positive electrode for electrochemical elements.

[0132] In the method for producing an electrochemical element of the present invention, the positive electrode of the present invention produced using the composite particles of the present invention is used as the positive electrode, so that an electrochemical element having good performance can be produced at low cost. As a result, the electrochemical element of the present invention has good performance and can be produced at low cost.

[0133] An example in which the electrochemical element is a lithium ion secondary battery will be described below. The negative electrode paired with the positive electrode can be selected from various types of electrodes known for use in lithium ion secondary batteries. Specifically, the negative electrode can include a negative electrode composite layer and a current collector. The negative electrode composite layer can be a layer containing a known negative electrode active material, such as a carbon-based negative electrode active material. The current collector can be a foil made of the same material as the positive electrode current collector described above, but copper foil is particularly preferred.

[0134] The electrolyte solution is usually an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent. For example, a lithium salt is used as the supporting electrolyte. For example, LiPF ６ , LiAsF ６ , LiBF ４ , LiSbF ６ , LiAlCl ４ , LiClO ４ , C.F. ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Among them, LiPF is particularly preferred because it is easily soluble in solvents and shows a high degree of dissociation. ６ , LiClO ４ , C.F. ３ SO ３ Li is preferred, and LiPF ６ is particularly preferred. One type of electrolyte may be used alone, or two or more types may be used in combination in any ratio. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0135] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (EMC) are preferred. Other suitable solvents include 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. Mixtures of these solvents may also be used. Among these, carbonates are preferred because of their high dielectric constant and wide stable potential range, and a mixture of ethylene carbonate and ethyl methyl carbonate is even more preferred. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate, and is preferably 0.5 to 15% by mass, more preferably 2 to 13% by mass, and even more preferably 5 to 10% by mass.

[0136] The separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, a microporous film made of a polyolefin resin (polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferred because it allows the thickness of the entire separator to be thin, thereby increasing the ratio of the electrode active material in the electrochemical device and increasing the capacity per volume.

[0137] The electrochemical element can be manufactured, for example, by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the resulting assembly as necessary according to the shape of the electrochemical element, placing it in a container, injecting an electrolyte into the container, and sealing it. To prevent internal pressure buildup, overcharging and discharging, and the like, a fuse, an overcurrent protection element such as a PTC element, expanded metal, lead plates, and the like may be provided as necessary. The shape of the assembled electrochemical element may be, for example, a coin type, a button type, a sheet type, a cylindrical type, a rectangular type, a flat type, or the like.

[0138] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, the operations described below were performed under conditions of room temperature and normal pressure unless otherwise specified.

[0139] (Evaluation Method) (D10, D50, and D90 of Composite Particles) The integrated particle size distribution (volume basis) of the composite particles was obtained using a particle size distribution measuring device (Microtrac MT3300EX II; manufactured by Microtrac Bell Co., Ltd.) based on a laser scattering / diffraction method, in a dry state, with the pressure of the dispersion air during measurement set to 0.1 MPa. The particle sizes at which the cumulative frequency, calculated from the smallest diameter side, was 10%, 50%, and 90% were adopted as the D10 particle size, D50 particle size, and D90 particle size, respectively.

[0140] (Weight-average molecular weight of polymer) The weight-average molecular weight of the first polymer and the second polymer prepared in the examples and comparative examples was determined as a polystyrene-equivalent molecular weight by high-performance liquid chromatography using tetrahydrofuran as a carrier at a flow rate of 0.35 ml / min. The apparatus used was a Tosoh HLC8320, the column consisted of three connected Shodex (registered trademark) KF-404HQ columns manufactured by Showa Denko K.K. (column temperature: 40°C), and the detectors used were a differential refractometer and an ultraviolet detector. The molecular weight was calibrated at 12 points using standard polystyrenes (5 million to 3 million) manufactured by Polymer Laboratory.

[0141] (Mass Ratio of First Polymer to Second Polymer) The mass ratio of the first polymer to the second polymer (first polymer / second polymer) was determined from the area ratio of the peaks corresponding to the first polymer and the second polymer in the chart obtained by the above-mentioned high performance liquid chromatography.

[0142] (Weight-Average Molecular Weight of Block (Block A) Composed of Aromatic Vinyl Monomer Units) According to the method described in Rubber Chem. Technol., 45, 1295 (1972), the first polymer and the second polymer (hydrogenated block copolymer) were each reacted with ozone and reduced with lithium aluminum hydride to decompose the block (Block B) composed of monomer units derived from the aliphatic conjugated diene monomer in each polymer. Specifically, the procedure was as follows: 300 mg of a sample was dissolved in a reaction vessel containing 100 ml of dichloromethane treated with molecular sieves. The reaction vessel was then placed in a cooling bath and cooled to −25°C. Ozone generated by an ozone generator was then introduced into the reaction vessel while oxygen was flowing into the reaction vessel at a flow rate of 170 ml / min. Thirty minutes after the start of the reaction, the completion of the reaction was confirmed by introducing the gas flowing out of the reaction vessel into an aqueous potassium iodide solution. Next, 50 ml of diethyl ether and 470 mg of lithium aluminum hydride were placed in a nitrogen-purged reaction vessel. While cooling the reaction vessel with ice water, the solution reacted with ozone was slowly added dropwise to the reaction vessel. The reaction vessel was then placed in a water bath, gradually heated, and refluxed at 40°C for 30 minutes. Dilute hydrochloric acid was then added dropwise to the reaction vessel while stirring the solution, and the addition was continued until hydrogen generation was almost completely eliminated. After the reaction, the solid product formed in the solution was filtered and extracted with 100 ml of diethyl ether for 10 minutes. This extract and the filtrate were combined, and the solvent was distilled off to obtain a solid sample. The mass average molecular weight of the sample thus obtained was measured according to the above-mentioned method for measuring mass average molecular weight, and the resulting value was taken as the mass average molecular weight of the block composed of aromatic vinyl monomer units.

[0143] (Mass Average Molecular Weight of Block (Block B) Composed of Monomer Units Derived from Aliphatic Conjugated Diene Monomer) The mass average molecular weight of the block composed of monomer units derived from an aliphatic conjugated diene monomer was determined by subtracting the mass average molecular weight of the block composed of the corresponding aromatic vinyl monomer units from each of the values ​​of the mass average molecular weights of the first polymer and the second polymer determined as described above.

[0144] (Moldability) Approximately 5 g of the composite particles produced in the Examples and Comparative Examples were placed on a clamped glass table (254 x 355 mm), and an applicator (standard film thickness 50 μm, coating width: 80 mm) was used to form a thin layer of the composite particles. The obtained thin layer was observed and evaluated based on the following evaluation criteria. When forming a thin layer by spreading a sample placed on a glass table, smearing may occur at the edges even if good molding is achieved, so the evaluation was made assuming that there was no smearing at the edges during observation. A: A uniform thin layer of composite particles was formed. B: There were some unevenness and / or streaks, but a thin layer was formed overall. C: A thin layer was not formed.

[0145] (Electrical Resistance) The powder resistance of the composite particles produced in the Examples and Comparative Examples was measured. For the measurement, 4.0 g of the composite particles prepared in the Examples and Comparative Examples was placed in a probe unit of a powder resistance measurement system MCP-PD51 manufactured by Mitsubishi Chemical Analytech Co., Ltd., and the powder resistance was measured when a pressure of 20 kN was applied. The obtained measured values ​​were evaluated based on the following evaluation criteria. A: 18.0 Ω or less B: More than 18.0 Ω and less than 22.0 Ω C: More than 22.0 Ω and less than 24.5 Ω D: More than 24.5 Ω

[0146] (Cycle Characteristics) The lithium ion secondary batteries as electrochemical elements prepared in the Examples and Comparative Examples were left standing at 25°C for 5 hours. Next, they were charged to a cell voltage of 3.65V at a constant current of 0.2C at 25°C, and then aged for 12 hours at 60°C. Next, they were discharged to a cell voltage of 3.00V at a constant current of 0.2C at 25°C. Next, they were CC-CV charged (upper limit cell voltage 4.20V) at a constant current of 0.2C at 25°C, and CC discharged to 3.00V at a constant current of 0.2C. The cells that had been subjected to this 0.2C charge-discharge cycle three times were used as evaluation cells.

[0147] Next, the evaluation cell was subjected to 100 cycles of charge / discharge at a cell voltage of 4.20-3.00V and a charge / discharge rate of 0.5C in an environment at a temperature of 45°C. Based on the discharge capacity X1 of the first cycle out of the 100 cycles and the discharge capacity X2 of the 100th cycle, the capacity retention rate = (X2 / X1) x 100 (%) was calculated. The obtained capacity retention rate values ​​were evaluated based on the following criteria. A larger capacity retention rate value indicates better cycle characteristics of the lithium ion secondary battery. A: Capacity retention rate is 90% or more B: Capacity retention rate is 85% or more but less than 90% C: Capacity retention rate is 80% or more but less than 85% D: Capacity retention rate is less than 80%

[0148] Example 1 (1-1. Preparation of Binder Solution) 120 parts of dehydrated cyclohexane, 0.2 parts of dibutyl ether, and 5.2 parts of dehydrated styrene as an aromatic vinyl monomer were placed in a reactor equipped with a stirrer and the inside of which had been thoroughly purged with nitrogen. 0.05 parts (solids content) of n-butyllithium (15% cyclohexane solution) as a polymerization initiator was then added. The entire solution was then stirred at 50°C for 30 minutes (first-stage polymerization). Measurement of the reaction solution by gas chromatography revealed that the polymerization conversion at this point was 99.5%. Next, 21.4 parts of dehydrated 1,3-butadiene as an aliphatic conjugated diene monomer was continuously added to the reaction solution over 30 minutes, and after completion of the addition, the entire solution was stirred for 30 minutes (second-stage polymerization). The polymerization conversion at this point was 99.5%. Next, 5.2 parts of dehydrated styrene as an aromatic vinyl monomer was added and stirred for 30 minutes (third-stage polymerization). The polymerization conversion rate at this point was 99.7%. 0.1 parts of ethanol were added to the reaction solution to partially terminate the reaction. This resulted in a polymer solution (M1) containing a block copolymer having an A1-B-A2 triblock structure of styrene-butadiene styrene as a precursor of the second polymer. 9 parts of dehydrated styrene as an aromatic vinyl monomer was added to the polymer solution (M1) and stirred for 30 minutes (fourth polymerization stage). The polymerization conversion rate at this point was almost 100%. 0.2 parts of ethanol were added to the reaction solution to terminate the reaction. This resulted in a polymer solution (M2) containing, in addition to the precursor of the second polymer, a block copolymer having an A1-B-A2 triblock structure of styrene-butadiene styrene as a precursor of the first polymer.

[0149] The polymer solution (M2) was transferred to a pressure-resistant reactor equipped with a stirring device, and Ni(AcAc) was added as a hydrogenation catalyst. ２A TIBAL catalyst was added at a ratio of 0.5% relative to the block copolymer composition before hydrogenation, and the hydrogenation reaction was carried out for 6 hours at a temperature of 80°C and a pressure of 0.9 MPa. Next, to remove metal components derived from the hydrogenation catalyst, 1.1 parts of malic acid and 0.2 parts of a nonionic surfactant block copolymer of ethylene oxide and propylene oxide (manufactured by ADEKA Corporation, product name "L-64") were dissolved in 500 parts of ion-exchanged water, and the mixture was then added to the reactor and stirred for 5 hours. Subsequently, 1 part of a xylene solution containing 0.1 parts of a phenolic antioxidant pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate (manufactured by Koyo Chemical Laboratory, product name "Songnox 1010") was added and dissolved. Next, cyclohexane was added to dilute the mixture to an appropriate concentration suitable for handling, and a binder solution containing a first polymer and a second polymer (binder composition) was prepared.

[0150] Using a portion of the binder solution, the weight average molecular weights of the first polymer and the second polymer, the mass ratio between the first polymer and the second polymer, and the weight average molecular weight of each block contained in the first polymer and the second polymer were determined. The weight average molecular weights of block A1, block B, and block A2 of the first polymer were 13,000, 84,000, and 98,000, respectively. The weight average molecular weight of the first polymer was 195,000. The weight average molecular weights of blocks A1 and A2 of the second polymer were 13,000, and the weight average molecular weight of block B was 84,000. The weight average molecular weight of the second polymer was 84,000. The content of the aromatic vinyl monomer in a total of 100% by mass of the first polymer and the second polymer was 48% by mass. The mass ratio of the first polymer to the second polymer was 45 / 55. The ratio (weight average molecular weight of the first polymer) / (weight average molecular weight of the second polymer) was 1.8.

[0151] (1-2. Preparation of Conductive Material Dispersion) Carbon black (BET specific surface area: 62 m) was used as a carbon-based conductive material. ２ / g, bulk density 0.16 g / cm ３) and 1.5 parts (solids content equivalent) of the binder solution obtained in (1-1) were mixed, and cyclohexane was further added as a solvent to obtain a mixture of a carbon-based conductive material, a binder composition, and a solvent (solids content concentration 10%, total amount 1 kg). Next, the obtained mixture was dispersed for 1 hour using a bead mill (LMZ015, manufactured by Ashizawa Fine Tech) using zirconia beads with a diameter of 0.5 mm at a peripheral speed of 12 m / s, to prepare a conductive material dispersion containing a carbon-based conductive material, a binder composition, and a solvent.

[0152] (1-3. Production of Pre-Classified Composite Particles: Step (S-1)) A composite particle production apparatus was prepared, which consisted of a cylindrical vessel with an inner diameter of 180 mm and a capacity of 2 L as a granulation vessel, with the axis of the cylindrical vessel being the vertical direction, and stirring blades on two axes, one vertical and one horizontal (the main stirring blade is the one in the vertical direction, and the auxiliary stirring blade is the one in the horizontal direction). The main stirring blade was an inclined paddle with three main blades each 170 mm in diameter, and the auxiliary stirring blade had a V-shaped anchor blade with a diameter of 30 mm, and was configured with a mechanism that was sealed by ventilating air to prevent raw materials from being mixed into the drive parts of the main stirring blade and auxiliary stirring blade. Using the composite particle production apparatus, (i) a preliminary stirring operation, (ii) a granulation operation, and (iii) a sizing operation were carried out in this order to produce pre-classified composite particles.

[0153] Specifically, first, (i) in the preliminary stirring operation, NMC532 (LiNi) as a positive electrode active material for a lithium ion secondary battery is added to a granulation tank. ０．５ Mn ０．３ Co ０．２ O ２96.5 parts by mass (1344 g) of a conductive material having a D50 particle size of 6 μm was added. Next, room temperature (25° C.) air (hereinafter also referred to as "sealing air") for sealing the drive parts of the main and auxiliary stirring blades was circulated at 20 L / min (airflow rate 10 / min), and stirring was carried out for 15 minutes under operating conditions of a main stirring blade peripheral speed of 5 m / s and a auxiliary stirring blade peripheral speed of 6 m / s. Next, (ii) as a granulation operation, room temperature (25° C.) sealing air was circulated at 20 L / min (airflow rate 10 / min), and the main stirring blade peripheral speed was circumferentially 5 m / s and the auxiliary stirring blade peripheral speed was 6 m / s. 4 parts (560) g of the conductive material dispersion obtained above (solid content concentration: 10% by mass, solvent: cyclohexane) was continuously added to the pre-stirred positive electrode active material over 15 minutes using a dropping funnel. Finally, (iii) as a particle size adjustment operation, room temperature (25°C) sealing air was circulated at 20 L / min (airflow rate 10 / min), and the system was operated for 10 minutes under the operating conditions of a main stirring impeller peripheral speed of 2 m / s and a sub-stirring impeller peripheral speed of 2 m / s, to produce pre-classified composite particles. The maximum temperature in the system throughout steps (i) to (iii) was 38°C. The pre-classified composite particles had a D50 particle size of 68 μm and a particle size distribution D90 / D10 of 4.7.

[0154] (1-4. Classification and Crushing: Steps (S-2) to (S-4)) The pre-classified composite particles obtained in (1-3) were classified using a vibrating sieve (mesh opening: 32 μm), and the particles remaining on the sieve were further classified using a vibrating sieve (mesh opening: 180 μm), and the particles that passed through the sieve were treated as classified powder to obtain particles (a). In addition, the coarse powder remaining on the sieve of the vibrating sieve (mesh opening: 180 μm) was crushed using a pin mill type crusher at a peripheral speed of 20 m / s to obtain particles (b) as crushed powder. The obtained particles (a) and particles (b) were mixed at the mixing ratios shown in Table 1 to obtain composite particles. The obtained composite particles were evaluated for electrical resistance and moldability.

[0155] (1-5. Preparation of a positive electrode for a lithium ion secondary battery) The composite particles prepared in (1-4) were supplied to a press roll (roll temperature 100°C, press linear pressure 500 kN / m) of a roll press machine ("Oshikuri Rough Surface Heat Roll" manufactured by Hirano Giken Kogyo Co., Ltd.) using a quantitative feeder ("Nikka Spray K-V" manufactured by Nikka Corporation). A 20 μm thick aluminum foil was inserted between the press rolls as a current collector. The composite particles supplied from the quantitative feeder were adhered to the aluminum foil to form a composite particle layer, which was then pressure-molded at a molding speed of 1.5 m / min to form a composite particle layer with a basis weight of 30 mg / cm. ２ This positive electrode raw sheet was rolled by a roll press to form a layer of aluminum foil and a layer of a positive electrode active material having a density of 3.5 g / cm3 on one surface of the aluminum foil. ３ A sheet-shaped positive electrode for a lithium ion secondary battery was produced.

[0156] (1-6. Preparation of Negative Electrode) In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene as an aliphatic conjugated diene monomer, 3.5 parts of itaconic acid as an acidic group-containing monomer, 63.5 parts of styrene as an aromatic vinyl monomer, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 parts of potassium persulfate as a polymerization initiator were placed, thoroughly stirred, and then heated to 50 ° C to initiate polymerization. When the polymerization conversion rate reached 96%, the mixture was cooled to stop the polymerization reaction, and a mixture containing a particulate binder (styrene-butadiene copolymer) was obtained. A 5% aqueous sodium hydroxide solution was added to this mixture to adjust the pH to 8, and unreacted monomer was removed by heated vacuum distillation. The mixture was then cooled to 30 ° C or below to obtain an aqueous dispersion containing a binder for the negative electrode. Next, 48.75 parts of artificial graphite as a negative electrode active material, 48.75 parts of natural graphite, and 1 part of carboxymethyl cellulose as a thickener were added to a planetary mixer. The mixture was then diluted with ion-exchanged water to a solids concentration of 60%, and then kneaded for 60 minutes at a rotation speed of 45 rpm. Then, 1.5 parts of the aqueous dispersion containing the negative electrode binder obtained as described above, equivalent to the solids content, was added, and kneaded for 40 minutes at a rotation speed of 40 rpm. Then, ion-exchanged water was added to obtain a viscosity of 3000±500 mPa·s (measured with a Brookfield viscometer at 25°C and 60 rpm), thereby preparing a negative electrode composite layer slurry. Next, a 15 μm thick copper foil was prepared as a current collector. The negative electrode composite layer slurry was applied to one surface of the copper foil in a coating amount of 15 mg / cm per layer after drying. ２ The negative electrode blank was then rolled with a roll press to form a copper foil having a density of 1.6 g / cm3 and coated on both sides of the copper foil. ３ A sheet-shaped negative electrode was fabricated comprising the negative electrode mixture layer.

[0157] (1-7. Preparation of Lithium-ion Secondary Battery) Using the positive electrode prepared in (1-5), the negative electrode prepared in (1-6), and a separator (made of polyethylene, thickness 12 μm), a laminate (discharge capacity equivalent to 250 mAh) having a layer structure of (positive electrode) / (separator) / (negative electrode) / (separator) / (positive electrode) was prepared and placed in an aluminum package. Then, a 1.0 M concentration of LiPF 6 was added as an electrolyte to the aluminum package. ６ A solution (solvent: a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) = 3 / 7 (volume ratio), to which vinylene carbonate was further added so as to be 2 volume %) was filled. Heat sealing was performed at a temperature of 150°C, and the aluminum packaging material was closed, thereby producing a lithium ion secondary battery. The cycle characteristics were evaluated using this lithium ion secondary battery.

[0158] (Examples 2 and 3) Composite particles and lithium ion secondary batteries were produced and evaluated by the same operations as in Example 1, except that the mixing ratio of particles (a) and particles (b) in (1-4) was changed as shown in Table 1.

[0159] Example 4 Composite particles and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1, except that the peripheral speed of the pulverizer in crushing the coarse powder in (1-4) was changed to 40 m / s.

[0160] (Example 5) Composite particles and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1, except that classification using a vibrating sieve (mesh opening: 32 μm) was not performed in (1-4) and the pre-classified composite particles obtained in (1-3) were directly subjected to classification using a vibrating sieve (mesh opening: 180 μm).

[0161] Reference Experimental Example 1 Composite particles and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1, except that the peripheral speed of the pulverizer in crushing the coarse powder in (1-4) was changed to 10 m / s.

[0162] Table 1 shows the outline and evaluation results of the Examples and Reference Experiments.

[0163]

[0164] According to the method for producing composite particles for electrochemical element positive electrodes of the present invention, the crushed coarse powder can be reused by the above-described steps, so that production can be carried out at low cost. In addition, the above results show that, even when produced at such low cost, composite particles can be obtained that can be used to produce electrochemical elements and positive electrodes for electrochemical elements with good performance.

Claims

1. A method for producing composite particles for electrochemical element positive electrodes, comprising a positive electrode active material, a carbon-based conductive material, and a binder resin, the method comprising a step of mixing classified powder and crushed powder.

2. The method for producing composite particles for an electrochemical element positive electrode according to claim 1, comprising: a step (S1-1) of obtaining pre-classified composite particles containing the positive electrode active material, the carbon-based conductive material, and the binder resin; a step (S1-2) of obtaining classified powder (a1) as the classified powder and coarse powder by classifying the pre-classified composite particles; a step (S1-3) of crushing the obtained coarse powder to obtain crushed powder (b1) as the crushed powder; and a step (S1-4) of mixing the classified powder (a1) and the crushed powder (b1).

3. The method for producing composite particles for electrochemical element positive electrodes according to claim 2, wherein the particle size distribution D90 / D10 of the classified powder (a1) is 1 or more and 6 or less, the particle size distribution D90 / D10 of the pulverized powder (b1) is 8 or more and 20 or less, and the mixing ratio Wa1 / Wb1 of the mass Wa1 of the classified powder (a1) to the mass Wb1 of the pulverized powder (b1) in the step (S1-4) is 80 / 20 or more and 98 / 2 or less.

4. The method for producing composite particles for an electrochemical element positive electrode according to claim 2, wherein the classified powder (a1) has a D50 particle size of 30 μm or more and 100 μm or less, and the pulverized powder (b1) has a D50 particle size of 50 μm or more and 120 μm or less.

5. The method for producing composite particles for an electrochemical element positive electrode according to claim 2, wherein the step (S1-1) comprises stirring and granulating the positive electrode active material, the carbon-based conductive material, the binder resin, and a solvent.

6. The method for producing composite particles for an electrochemical element positive electrode according to claim 5, wherein the step (S1-1) comprises: a step (S1-1a) of stirring the positive electrode active material in a granulation tank to obtain a stirred state; and a step (S1-1b) of spraying a liquid composition containing the carbon-based conductive material, the binder resin, and the solvent onto the stirred positive electrode active material.

7. A method for producing composite particles for electrochemical element positive electrodes, comprising a positive electrode active material, a carbon-based conductive material, and a binder resin, the method comprising: step (S2-4) of mixing particles (a2) and particles (b2), wherein the particles (a2) and the particles (b2) are particles each comprising the positive electrode active material, the carbon-based conductive material, and the binder resin; wherein the particle size distribution D90 / D10 of the particles (a2) is 1 or more and 6 or less; the particle size distribution D90 / D10 of the particles (b2) is 8 or more and 20 or less; and the mixing ratio Wa2 / Wb2 of the mass Wa2 of the particles (a2) to the mass Wb2 of the particles (b2) in the step (S2-4) is 80 / 20 or more and 98 / 2 or less.

8. The method for producing composite particles for electrochemical element positive electrodes according to claim 7, wherein the particles (a2) have a D50 particle size of 30 μm or more and 100 μm or less, and the particles (b2) have a D50 particle size of 50 μm or more and 120 μm or less.

9. A method for manufacturing a positive electrode for an electrochemical element comprising a current collector and a positive electrode composite layer, the method comprising: obtaining composite particles for a positive electrode for an electrochemical element by the method for manufacturing composite particles for a positive electrode for an electrochemical element according to any one of claims 1 to 8; depositing the composite particles for a positive electrode for an electrochemical element on the surface of the current collector to form a composite particle layer; and applying pressure to the composite particle layer to form the positive electrode composite layer.

10. A method for manufacturing an electrochemical element having a positive electrode and a negative electrode, the method comprising: obtaining a positive electrode for an electrochemical element by the method for manufacturing a positive electrode for an electrochemical element according to claim 9; and constructing an electrochemical element using the positive electrode for an electrochemical element.

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