Composition for electrochemical element functional layer, production method therefor, functional layer for electrochemical element, multilayer body for electrochemical element, and electrochemical element

Abstract

This composition for a functional layer contains a particulate polymer that has a core-shell structure, a volume-based median diameter of 1.0-20.0 μm, and the Raman spectrum satisfying a prescribed characteristic.

Description

Composition for functional layer of electrochemical element and method for manufacturing the same, functional layer for electrochemical element, laminate for electrochemical element, and electrochemical element

[0001] The present invention relates to a composition for a functional layer of an electrochemical element, a method for producing the same, a functional layer for an electrochemical element, a laminate for an electrochemical element, and an electrochemical element.

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

[0003] Here, for example, a lithium-ion secondary battery generally includes battery components such as a positive electrode, a negative electrode, and a separator that isolates the positive electrode and the negative electrode to prevent a short circuit between them.

[0004] In recent years, further improvements to electrochemical element components such as positive electrodes, negative electrodes, and separators have been considered with the aim of further enhancing the performance of lithium secondary batteries. In such improvements, attempts have been made to laminate layers (functional layers) on a substrate to exhibit desired functions such as heat resistance and adhesiveness. For example, Patent Documents 1 and 2 propose a composition for a functional layer that can be applied to separators and the like, which includes a particulate polymer having a core-shell structure.

[0005] International Publication No. 2022 / 181560, Japanese Patent Publication No. 2018-200796

[0006] In the manufacturing process of electrochemical elements, functional layers are sometimes formed on substrates such as separators, wound up, and stored temporarily. If the substrates do not easily block each other via the functional layer, it is easier to unwind and use them in subsequent processes. Functional layers that have the property of not easily blocking even when laminated are called functional layers with excellent blocking resistance. Furthermore, functional layers are required to exhibit excellent adhesion at room temperature and to reduce the internal resistance when an electrochemical element is formed. However, conventional electrochemical element components equipped with functional layers according to the above prior art had room-temperature adhesive strength and blocking resistance, as well as room-temperature adhesive strength and blocking resistance, and room-temperature adhesive strength

[0007] Therefore, the present invention aims to provide an electrochemical element functional layer composition that can form an electrochemical element functional layer with excellent adhesive strength at room temperature and blocking resistance, and furthermore, can reduce the internal resistance of an electrochemical element equipped with such an electrochemical element functional layer.

[0008] The inventors diligently conducted studies to achieve the above objectives. As a result, the inventors discovered that a functional layer composition containing a particulate polymer having a core-shell structure, a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, and whose Raman spectrum satisfies predetermined characteristics, makes it possible to form an electrochemical element functional layer with excellent room-temperature adhesive strength and blocking resistance, and furthermore, it is possible to reduce the internal resistance of an electrochemical element equipped with such an electrochemical element functional layer, thus completing the present invention.

[0009] In other words, the present invention aims to advantageously solve the above problems, and [1] the electrochemical element functional layer composition of the present invention is an electrochemical element functional layer composition comprising a particulate polymer, wherein the particulate polymer is a particulate polymer having a core-shell structure comprising core particles having a shell on its surface, wherein the particulate polymer has a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, and when the particulate polymer before shell formation is measured by Raman spectroscopy, the wavenumber is 996 cm⁻¹. －１ 1005cm－１ The intensity of the peak detected within the following range is P1, and the wavenumber is 678 cm⁻¹. －１ 684 cm －１ The intensity of the peak detected within the following range is defined as P2, and furthermore, when the particulate polymer having the core-shell structure is subjected to Raman spectroscopy, the wavenumber is 678 cm⁻¹. －１ 684 cm －１ The composition is characterized in that the intensity of the peak detected in the following range, P3, is given by the value given by the following formula (1), which is 0.001% or more and 200% or less: (P3 - P2) / P1 × 100 ... (1) Such an electrochemical element functional layer composition can form an electrochemical element functional layer with excellent room-temperature adhesive strength and blocking resistance, and furthermore, can reduce the internal resistance of an electrochemical element equipped with such an electrochemical element functional layer. The "volume-based median diameter" and "Raman spectrum" of the particulate polymer can be measured by the method described in the examples of this specification. The "core-shell structure" of the particulate polymer can be confirmed by the method described in the examples.

[0010] [2] In the electrochemical element functional layer composition described in [1] above, it is preferable that the pH is 5.0 or higher and 11.0 or lower. If the pH of the functional layer composition is within the above range, the room-temperature adhesive strength and blocking resistance of the resulting functional layer can be further improved. The pH of the functional layer composition can be measured by the method described in the examples of this specification.

[0011] [3] In the electrochemical element functional layer composition of [1] or [2] above, it is preferable that the particle size distribution of the particulate polymer having the core-shell structure is 5 or less. If the particle size distribution of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced. The particle size distribution of the particulate polymer can be measured according to the method described in the examples of this specification.

[0012] [4] In any of the electrochemical element functional layer compositions described in [1] to [3] above, it is preferable that the glass transition temperature of the particulate polymer having the core-shell structure is between -65°C and 60°C. If the glass transition temperature of the particulate polymer is within the above range, the room-temperature adhesive strength of the resulting functional layer can be further increased. The glass transition temperature of the particulate polymer can be measured according to the method described in the examples of this specification.

[0013] [5] In any of the electrochemical element functional layer compositions described in [1] to [4] above, it is preferable that the ratio of core particles to shells in the particulate polymer is within the range of 99.9:0.1 to 50:50 by mass. If the ratio of core particles to shells in the particulate polymer is within the above range, the room-temperature adhesive strength and blocking resistance of the resulting functional layer can be further improved. The ratio of core particles to shells (by mass) in the particulate polymer can be measured according to the method described in the examples of this specification.

[0014] [6] In any of the electrochemical element functional layer compositions described in [1] to [5] above, it is preferable that the core particles contain 5% by mass or more and 60% by mass or less of aromatic monomer units. If the core particles contain 5% by mass or more and 60% by mass or less of aromatic monomer units, the room-temperature adhesive strength of the resulting functional layer can be further increased. In this specification, "core particles containing a certain monomer unit" means "the core particles obtained using that monomer contain repeating units derived from the monomer." Furthermore, the percentage of monomer units contained in the core particles is: 1 H-NMR and 13 It can be measured using nuclear magnetic resonance (NMR) methods such as C-NMR.

[0015] [7] In any of the electrochemical element functional layer compositions described in [1] to [6] above, it is preferable that the core particles contain 40% to 90% by mass of ester bond-containing monomer units. If the core particles contain 40% to 90% by mass of ester bond-containing monomer units, the room-temperature adhesive strength of the resulting functional layer can be further increased.

[0016] [8] In the composition for an electrochemical element functional layer according to any one of [1] to [7] above, it is preferable that the particulate polymer before shell formation contains a carboxyl group-containing monomer unit or a hydroxyl group-containing monomer unit. If the particulate polymer before shell formation contains a carboxyl group-containing monomer unit or a hydroxyl group-containing monomer unit, the blocking resistance of the resulting functional layer can be further enhanced, and the resistance of the resulting electrochemical element can be further reduced.

[0017] [9] The present invention further provides a functional layer for an electrochemical element formed using the composition for an electrochemical element functional layer according to any one of [1] to [8] above. Such a functional layer for an electrochemical element is excellent in normal temperature adhesive strength and blocking resistance, and further, the internal resistance of an electrochemical element provided with such an electrochemical element functional layer can be reduced.

[0018]

[10] The present invention further provides a laminate for an electrochemical element including a base material and the functional layer for an electrochemical element according to [9] formed on the base material. Such a laminate for an electrochemical element can reduce the internal resistance of an electrochemical element provided with such a laminate.

[0019]

[11] The present invention provides an electrochemical element including the laminate for an electrochemical element according to

[10] above. Such an electrochemical element has a low internal resistance.

[0020]

[12] The present invention is a method for producing a composition for an electrochemical element functional layer containing a particulate polymer having a core-shell structure, the method for producing a composition for an electrochemical element functional layer containing a particulate polymer having a core-shell structure, comprising obtaining a solution containing core particles and a shell-forming compound, and including a reaction step of forming a shell on the surface of the core particles, wherein, when the core particles at the start of the reaction step are measured by Raman spectrum, the intensity of the peak detected in the following range is P1, the intensity of the peak detected in the range of wave number 678 cm －１ 1005 cm －１ [[ID=十六]] The intensity of the peak detected in the following range is P1, the intensity of the peak detected in the range of wave number 678 cm －１ or more and 684 cm －１ or less is defined as P2, and further, when the particulate polymer having the core-shell structure formed at the end of the reaction step is measured by Raman spectrum, wave number 6,78 cm－１ 684 cm －１ The present invention is characterized in that the intensity of the peak detected within the following range is denoted as P3, and the value I given by the following formula (1) is between 0.001% and 200%. I(%) = (P3 - P2) / P1 × 100 ... (1) According to this manufacturing method, the electrochemical element functional layer composition of the present invention can be efficiently manufactured.

[0021] According to the present invention, it is possible to form an electrochemical element functional layer that has excellent adhesive strength at room temperature and blocking resistance, and furthermore, it is possible to provide a composition for an electrochemical element functional layer that can reduce the internal resistance of an electrochemical element equipped with such an electrochemical element functional layer.

[0022] This is a conceptual diagram illustrating a case where a particulate polymer, as an example, breaks down and becomes adhesive. It is a schematic diagram illustrating a conventional particulate polymer.

[0023] Embodiments of the present invention will be described in detail below. Here, the electrochemical element functional layer composition of the present invention (hereinafter also simply referred to as the "functional layer composition") is used when forming the electrochemical element functional layer (hereinafter also simply referred to as the "functional layer") provided on the electrochemical element laminate of the present invention. The electrochemical element laminate of the present invention comprises a functional layer formed using the electrochemical element functional layer composition of the present invention. Furthermore, the electrochemical element of the present invention is an electrochemical element comprising at least the electrochemical element laminate of the present invention. Moreover, the method for manufacturing the electrochemical element functional layer composition of the present invention allows for the efficient production of the electrochemical element functional layer composition of the present invention.

[0024] (Composition for Electrochemical Element Functional Layer) The electrochemical element functional layer composition of the present invention includes a particulate polymer having a core-shell structure and a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, wherein the Raman spectrum satisfies predetermined characteristics. Furthermore, the electrochemical element functional layer composition of the present invention may optionally further contain other components. By using the functional layer composition of the present invention, it is possible to form an electrochemical element functional layer with excellent room-temperature adhesive strength and blocking resistance, and furthermore, the internal resistance of an electrochemical element equipped with such an electrochemical element functional layer can be reduced.

[0025] <Particulate Polymer> The particulate polymer contained in the functional layer composition is a particulate polymer that has a core-shell structure, a median diameter based on volume within a predetermined range, and a Raman spectrum that satisfies predetermined characteristics, as detailed below. After bonding the components together via the functional layer formed using the functional layer composition, the particulate polymer may remain in particulate form or take on any other arbitrary shape.

[0026] <<Core-Shell Structure>> Particulate polymers have a core-shell structure in which core particles are covered by a shell. The shell may completely cover the surface of the particulate polymer or partially cover it. From the viewpoint of improving the blocking resistance of the functional layer, it is considered preferable that the shell completely covers the surface of the particulate polymer. The state of the core and shell in the particulate polymer can be confirmed by microscopic observation and by the test method involving film formation described in the examples below.

[0027] <<Median diameter by volume of particulate polymer>> The median diameter by volume of the particulate polymer must be 1.0 μm or more and 20.0 μm or less, preferably 2.0 μm or more, more preferably 4.0 μm or more, preferably 15.0 μm or less, and more preferably 8.0 μm or less. If the median diameter by volume of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be reduced. The reason for this is not clear, but it is presumed to be as follows: If the median diameter by volume of the particulate polymer is above the lower limit, when an electrochemical element such as a secondary battery is formed, a certain space can be formed between the electrode and the substrate such as a separator. This space can promote the even distribution of the electrolyte when it is poured, and contribute to reducing the resistance of electrical conductive ions to move within the element. Also, if the median diameter by volume of the particulate polymer is below the upper limit, it is thought that the formation of an excessively large space between the electrode and the substrate can be suppressed. Large spaces may expand further due to gas generation associated with the charging and discharging of electrochemical elements such as secondary batteries. Therefore, suppressing the formation of large spaces can contribute to reducing the resistance to the movement of electrically conductive ions within the element. Furthermore, if the median diameter of the volume standard of the particulate polymer is above the lower limit, the particulate polymer can be crushed well during adhesion between components via the functional layer, promoting adhesion between components. Also, if the median diameter of the volume standard of the particulate polymer is below the upper limit, the particles become more prone to crushing when substrates with functional layers are laminated, effectively suppressing deterioration of blocking resistance. In addition, when forming large-diameter particulate polymers, large-diameter core particles are often used. However, when forming a shell on large-diameter core particles, the frequency of shell monomers reaching the core particle surface decreases. As a result, the shell monomers polymerize with each other, making it easier to form small-diameter particles. Such small-diameter particles may reduce the air permeability of the resulting functional layer. Furthermore, the median diameter of the volume standard for particulate polymers can be adjusted, for example, by the amount of suspension stabilizer, such as polyvinyl alcohol, used when preparing the particulate polymers.For example, increasing the amount of suspension stabilizer can reduce the particle size. Conversely, decreasing the amount of suspension stabilizer can increase the particle size.

[0028] <<Particle Size Distribution of Particulate Polymers>> The particle size distribution of particulate polymers is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less. If the particle size distribution is below the above upper limit, the internal resistance of the resulting electrochemical element can be further reduced. This is because, when the particle size distribution is wide, the frequency of small particles tends to be relatively high, and such small particles tend to clog pores in substrates such as separators, which can consequently hinder the movement of electrically conductive ions such as lithium ions within the electrochemical element. Furthermore, since small particles contribute less to adhesive strength, reducing the frequency of such small particles can increase the adhesive strength at room temperature. The lower limit of the particle size distribution is not particularly limited, but for example, it may be 1 or more. The particle size distribution of particulate polymers can be controlled by the amount of dispersant added during the synthesis of the particulate polymer. Specifically, increasing the amount of dispersant can increase the value of the particle size distribution.

[0029] <<Raman Spectral Characteristics of Particulate Polymers>> When the particulate polymer before shell formation, in other words, the core particles, are measured using Raman spectroscopy, the wavenumber is 996 cm⁻¹. －１ 1005cm －１ The intensity of the peak detected within the following range is P1, and the wavenumber is 678 cm⁻¹. －１ 684 cm －１ The intensity of the peak detected within the following range is defined as P2. Furthermore, when a particulate polymer having a core-shell structure is measured using Raman spectroscopy, the peak intensity is determined at wavenumber 678 cm⁻¹. －１ 684 cm －１ Let P3 be the intensity of the peak detected within the following range. The value given by the following formula (1) must be between 0.001% and 200%: (P3 - P2) / P1 × 100 ... (1)

[0030] Here, the wave number is 996 cm. －１ 1005cm－１ The peaks detected within the following range are thought to correspond to the benzene rings present in the monomer units contained in the core particles, as will be discussed later regarding the composition of the particulate polymer. Also, at wavenumber 678 cm⁻¹, the peaks are considered to correspond to the benzene rings present in the monomer units contained in the core particles. －１ 684 cm －１ The peaks detected within the following range are thought to correspond to the "-O-" bonding groups contained in ether or ester bonds. Equation (1) above calculates the percentage increase in the "-O-" bonding groups before and after shell formation. As will be described later regarding the composition of the particulate polymer, during shell formation, a wavenumber of 678 cm² is formed, such as with a certain melamine compound. －１ 684 cm －１ In systems containing compounds that do not contain ether or ester bonds detected within the following range, it means that an "-O-" bond is formed by the reaction between the core particles and the melamine compound. In such cases, it is considered that the core particles and the shell are cross-linked by an "-O-" bond. If the particulate polymer satisfies this structure, the shell is considered to have appropriate strength and elasticity. The particulate polymer consists of a core that does not have adhesiveness, or has low adhesiveness, and exhibits adhesiveness due to the shell, and when the shell breaks, the core is exposed and can exhibit adhesiveness. As described above, if the shell has appropriate strength and elasticity, the shell of the particulate polymer will not collapse and exhibit adhesiveness when stored in a storage environment in a lower pressure range than the conditions for performing room-temperature bonding, which contributes to improving the blocking resistance of the functional layer. On the other hand, regarding room-temperature bonding strength, the shell collapses due to the pressure action such as flat plate pressing when performing room-temperature bonding, and strength can be achieved when the core particles come into contact with the electrode.

[0031] Furthermore, in Raman spectral measurements, wavenumber 600 cm －１ More than 800cm －１Compounds that may exhibit peaks in this region include, for example, alkanes, cis-alkenes, trisubstituted alkenes, monosubstituted alkynes, monocyclic aromatics, oxirane ring ethers, primary amides, aliphatic primary amines, aromatic primary amines, aliphatic secondary amines, alkyl isocyanates, nitrate esters, nitrite esters, halogen compounds, silicon compounds, and phosphorus compounds. Furthermore, in Raman spectroscopy, at a wavenumber of 800 cm⁻¹, the peaks may be observed. －１ More than 1200cm －１ Compounds that may exhibit peaks in this region include, for example, alkanes, vinyl alkenes, trans alkenes, vinylidene alkenes, trisubstituted alkenes, monocyclic aromatics, alcohols, phenols, acetals, ethers, ketones, dimeric carboxylic acids, esters, acid chlorides, acid anhydrides, amines, isocyanate aromatic esters, nitrate esters, nitrite esters, thiocarbonyl groups, sulfoxides, sulfones, sulfonyl chlorides, sulfonamides, sulfonic acid esters, halogen compounds, silicon compounds, and phosphorus compounds. If multiple peaks originating from each compound are observed in the relevant wavenumber region, the largest peak will be used as the target.

[0032] Figure 1 shows a conceptual diagram of a particulate polymer according to one example of the present application when it has collapsed and exhibited adhesive properties. Figure 2 shows a conceptual diagram of a particulate polymer according to a reference example when it has collapsed. Figures 1 and 2 show how the particulate polymers 1 and 1' are interposed between a material to be adhered 2, such as an electrode composite layer, and a substrate 3, such as a separator having voids. In the particulate polymer of the present application shown in Figure 1, it can be seen that the particulate polymer 1 interposed between the material to be adhered 2 and the substrate 3 collapses in the stacking direction of the material to be adhered 2 and the substrate 3, and can effectively adhere the material to be adhered 2 and the substrate 3. In the particulate polymer 1, the shell is broken at the shell collapse apex 4. On the other hand, when using the particulate polymer 1' shown in Figure 2, it can be seen that the particulate polymer 1' is broken in a direction horizontal to the stacking direction, rather than in the stacking direction of the material to be adhered 2 and the substrate 3. In the particulate polymer 1', the lateral shell rupture portion 4' is located horizontally to the stacking direction. As is clear from Figures 1 and 2, the particulate polymer of the present invention is more efficient at bonding the material to be bonded 2 and the substrate 3. This is thought to be because, as described above, the particulate polymer of the present invention satisfies the specific Raman spectral characteristics described above, and the shell provided has appropriate strength and elasticity.

[0033] Here, the value given by formula (1) above must be between 0.001% and 200%, preferably 0.05% or more, more preferably 0.1% or more, preferably 150% or less, and more preferably 130% or less. If the value given by formula (1) above is greater than or equal to the lower limit, the elasticity of the shell can be moderately increased, and the blocking resistance of the functional layer can be improved. Also, if the value given by (1) above is less than or equal to the upper limit, it is possible to suppress the excessive increase in the elasticity of the shell. As a result, when manufacturing an electrochemical element, when a substrate having a functional layer is laminated with an adhesive material such as an electrode composite layer, with the functional layer interposed between the adhesive material and the substrate, and pressed at room temperature in the lamination direction, the substrate and the adhesive material can be bonded well. The value given by formula (1) above can be adjusted by controlling the blending ratio of the compound blended to form the shell, based on the mass of the monomers constituting the core particles. Specifically, the value given by equation (1) can be increased by increasing the amount of the compound used to form the shell. This is presumed to be because a higher amount of the compound used to form the shell promotes the formation of "-O-" bonds on the surface of the core particles.

[0034] Furthermore, the value given by equation (1) can be identified by reverse engineering, which involves cross-sectional analysis of the particulate polymer using embedding resin and analysis using high-resolution NMR and nano-IR to identify the compounds used during shell formation and the monomer composition used during core formation.

[0035] The glass transition temperature of the particulate polymer, particularly the glass transition temperature of the core particles constituting the particulate polymer, is preferably -65°C or higher, more preferably -50°C or higher, even more preferably -30°C or higher, particularly preferably -28°C or higher, preferably 60°C or lower, more preferably 50°C or lower, even more preferably 35°C or lower, even more preferably 25°C or lower, and particularly preferably 18°C ​​or lower. If the glass transition temperature of the core particles is above the above lower limit, it is thought that the crushing of the particulate polymer in a specific direction, as described above (see Figure 1), can be promoted. In other words, by having a moderate elasticity in the core particles, it is possible to effectively suppress the load escaping to the side of the particulate polymer when pressed, preventing the shell from cracking laterally. As a result, even if the particulate polymer collapses due to pressing, it is possible to suppress the state in which the core particles and the adhesive material, such as the electrode composite layer, cannot come into contact, thereby improving the adhesive properties. Furthermore, if the glass transition temperature of the core particles is below the above upper limit, it is possible to suppress an excessive increase in the elasticity of the core particles. As a result, it is thought that a good anchoring effect can be achieved when the bonded material, such as the electrode composite layer, comes into contact with the core particles by pressing. The glass transition temperature of the core particles can be adjusted according to the composition of the core particles. For example, the glass transition temperature of the core particles can be increased by increasing the proportion of aromatic monomer units.

[0036] <<Composition of Core Particles>> The polymer constituting the core particles (hereinafter also referred to as "polymer A") is not particularly limited and can be composed of any monomer units.

[0037] Polymer A may include, for example, at least one of aromatic monomer units, ester bond-containing monomer units, carboxyl group-containing monomer units, and hydroxyl group-containing monomer units, as well as crosslinkable monomer units.

[0038] [Aromatic Monomer Units] Examples of aromatic monomers that can form aromatic monomer units include, without particular limitation, aromatic vinyl monomer units, such as styrene, styrene sulfonic acid and its salts (e.g., sodium styrene sulfonate), α-methylstyrene, vinyltoluene, and 4-(tert-butoxy)styrene. These may be used individually or in combination of multiple types. Among these, styrene, vinyltoluene, and α-methylstyrene are preferred, with styrene being more preferred. These aromatic monomers may be used individually or in combination of two or more types in any ratio.

[0039] The content of aromatic monomer units in polymer A is not particularly limited. For example, the content of aromatic monomer units is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, even more preferably 25.0% by mass or more, particularly preferably 28.0% by mass or more, preferably 60.0% by mass or less, more preferably 55.0% by mass or less, even more preferably 50.0% by mass or less, and particularly preferably 48.0% by mass or less, based on the total repeating units contained in polymer A as 100% by mass. If the content of aromatic vinyl monomer units in polymer A is above the above lower limit, the elasticity of the core particles can be appropriately increased, thereby increasing the room-temperature adhesive strength by a mechanism similar to the mechanism described above regarding the "glass transition temperature of particulate polymers". Furthermore, if the content of aromatic vinyl monomer units in polymer A is below the above upper limit, it is possible to suppress an excessive increase in the elasticity of the core particles, and the room-temperature adhesive strength can be increased by a mechanism similar to the mechanism described in the section on "Glass transition temperature of particulate polymers".

[0040] [Ester bond-containing monomer units] As ester bond-containing monomer units, (meth)acrylic acid ester monomers capable of forming (meth)acrylic acid ester monomer units can be suitably used, without particular limitations. In this specification, "(meth)acrylic" means acrylic or methacrylic. As (meth)acrylic acid ester monomers, without particular limitations, alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-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 can be suitably used. Examples include 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. These may be used individually or in combination of multiple types. Among these, ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate are preferred, with 2-ethylhexyl acrylate being more preferred. These may also be used individually or in combination of two or more types in any ratio.

[0041] The content of ester bond-containing monomer units in polymer A is not particularly limited, but for example, with the total repeating units contained in polymer A being 100% by mass, it is preferably 40.0% by mass or more, more preferably 45.0% by mass or more, even more preferably 50.0% by mass or more, preferably 90.0% by mass or less, more preferably 80.0% by mass or less, and most preferably 78.0% by mass or less. If the content of ester bond-containing monomer units in polymer A is above the lower limit, it is possible to suppress an excessive increase in the elasticity of the core particles, and the room-temperature adhesive strength can be increased by a mechanism similar to the mechanism described in the section on "Glass transition temperature of particulate polymers". Also, if the content of ester bond-containing monomer units in polymer A is below the upper limit, the elasticity of the core particles can be moderately increased, and the room-temperature adhesive strength can be increased by a mechanism similar to the mechanism described in the section on "Glass transition temperature of particulate polymers".

[0042] [Carboxyl group-containing monomer units and hydroxyl group-containing monomer units] Polymer A preferably contains at least one of carboxyl group-containing monomer units and hydroxyl group-containing monomer units. If polymer A contains at least one of these, it becomes possible to efficiently form a shell. Carboxyl group-containing monomer units are not particularly limited and can be formed from monomers having carboxyl groups. Similarly, hydroxyl group-containing monomer units are not particularly limited and can be formed from monomers having hydroxyl groups.

[0043] Monomers having a carboxyl group include ethylenically unsaturated monocarboxylic acids and their derivatives, ethylenically unsaturated dicarboxylic acids and their acid anhydrides, and their derivatives. Examples of ethylenically unsaturated monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of derivatives of ethylenically unsaturated monocarboxylic acids include 2-ethyl acrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of ethylenically unsaturated dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, and mesaconic acid. Examples of acid anhydrides of ethylenically unsaturated dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Furthermore, examples of derivatives of ethylenically unsaturated dicarboxylic acids include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleic acid, nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, fluoroalkyl maleic acid, styrene-maleic anhydride copolymer, and acrylamide copolymer. Among these, acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and fumaric acid are preferred as carboxylic acid units. Methacrylic acid is more preferred among these. These monomers may be used individually or in combination of two or more in any ratio.

[0044] Examples of monomers having a hydroxyl group include N-methylol(meth)acrylamide, N-butoxymethylol(meth)acrylamide; alkyl (meth)acrylate esters having a hydroxyl group, such as β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, β-hydroxyethyl methacrylate, and β-hydroxypropyl methacrylate; polyvinyl alcohol, alkyl chain-modified polyvinyl alcohol, carboxymethylcellulose, and hydroxypropyl methylcellulose. Among these, vinyl alcohol units, N-methylol(meth)acrylamide, and β-hydroxyethyl acrylate are preferred, with vinyl alcohol units being more preferred. These may be used individually or in combination of two or more in any ratio.

[0045] The content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is preferably as follows: if either one is included, the content ratio of that unit; if both are included, the total content ratio. For example, with the total repeating units contained in polymer A as 100% by mass, the content ratio may be 0.5% by mass or more, preferably 20.0% by mass or less, and more preferably 15.0% by mass or less. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is above the lower limit, a good shell can be formed, and the blocking resistance of the resulting functional layer can be improved. Furthermore, if the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is below the upper limit, the formation of small-diameter by-product particles during the synthesis of particulate polymers can be suppressed, and the air permeability of the resulting functional layer and the internal resistance of the resulting electrochemical element can be effectively reduced.

[0046] [Crosslinkable Monomer Units] Furthermore, polymer A may optionally have crosslinkable monomer units. Crosslinkable monomers that can form crosslinkable monomer units are not particularly limited and include monomers that can form a crosslinked structure by polymerization. More specifically, examples include monomers that are typically thermally crosslinkable. More specifically, examples include crosslinkable monomers that have two or more olefinic double bonds per molecule. Examples of such crosslinkable monomers include allyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane-tri(meth)acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl ether, glycol di(meth)acrylate of glycidyl group-containing units other than those mentioned above, allylglycidyl(meth)acrylate, and allyl or vinyl ethers of polyfunctional alcohols other than those mentioned above, triallylamine, methylenebisacrylamide, and divinylbenzene. Among these, allyl methacrylate, ethylene glycol dimethacrylate, and divinylbenzene are preferred, and ethylene glycol dimethacrylate is more preferred among them. These crosslinkable monomers may be used individually or in combination of two or more types in any ratio.

[0047] The content of crosslinkable monomer units in polymer A is not particularly limited, but is preferably 10.0% by mass or less, and more preferably 5.0% by mass or less, based on the total repeating units contained in polymer A being 100% by mass. If the content of crosslinkable monomer units in polymer A is below the above upper limit, it is possible to suppress an excessive increase in the elasticity of the core particles, and the room-temperature adhesive strength can be increased by a mechanism similar to the mechanism described in the section on "Glass transition temperature of particulate polymers".

[0048] Polymer A may also contain other monomer units besides those mentioned above. Such monomer units are not limited to nitrile group-containing monomer units, amino group-containing monomer units, amide group-containing monomer units, and amine group-containing monomer units.

[0049] <<Composition of the shell>> The shell can be constructed using any shell-forming compound, without any particular limitations. Examples of shell-forming compounds include urethane / urea films, melamine compounds, gelatin / gum arabic, alginic acid / sodium chloride films, etc. Examples of melamine compounds, without any particular limitations, include hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, trimethylolmelamine, hexamethylolmelamine, dimethylolmelamine, N,N',N''-trimethyl-N,N',N''-trimethylolmelamine, N-methylolmelamine, N,N'-(methoxymethyl)melamine, N,N',N''-tributyl-N,N',N''-trimethylolmelamine, etc. Among these, trimethylolmelamine, hexamethylmelamine, and dimethylolmelamine are preferred, with trimethylolmelamine being more preferred.

[0050] The content of melamine compound-derived components in the shell is not particularly limited. For example, with the total components contained in the shell being 100% by mass, it is preferably 40.0% or more, more preferably 80.0% or more, even more preferably 90.0% or more, and it may be 100.0% by mass to be composed of melamine compound-derived components. If the content of melamine compound-derived components in the shell is above the lower limit mentioned above, the blocking resistance of the resulting functional layer can be further enhanced.

[0051] Furthermore, the shell may contain components other than those derived from melamine compounds, and such components include those derived from various monomers that can be used in the preparation of "polymer A" that forms the core particles.

[0052] <<Mass Ratio of Core Particles to Shell>> The mass ratio of core particles to shell constituting the particulate polymer is preferably in the range of 99.95:0.05 to 50:50, more preferably in the range of 99.9:0.1 to 55:45, and even more preferably in the range of 99.7:0.3 to 60:40. If the proportion of shell is 0.05% by mass or more, sufficient shell thickness can be secured, and the blocking resistance can be further improved. Furthermore, it is possible to suppress the breaking of the shell during operations such as coating and drying when forming the functional layer, and effectively suppress the blocking of pores in the substrate such as the separator. Also, if the proportion of shell is less than 50% by mass, it becomes possible to efficiently crush the particulate polymer by pressing, and the core particles can be brought into contact with the electrode composite layer which is the adhesive material, and the room-temperature adhesive strength can be further improved. The mass ratio of core particles to shell can be controlled by adjusting the amount ratio of the two when adding the shell-forming composition to the core particles during the preparation of the particulate polymer.

[0053] (Method for producing particulate polymer) The present invention provides a method for producing particulate polymer, characterized by a reaction step of obtaining a solution containing core particles and a shell composition, and forming a shell on the surface of the core particles. In the reaction step, when the core particles at the start of the reaction step are measured by Raman spectroscopy, the wavenumber is 996 cm⁻¹. －１ 1005cm －１ The intensity of the peak detected within the following range is P1, and the wavenumber is 678 cm⁻¹. －１ 684 cm －１ The intensity of the peak detected within the following range is defined as P2. Furthermore, when the particulate polymer having the core-shell structure formed at the end of the reaction step is subjected to Raman spectroscopy, the peak intensity is 678 cm⁻¹. －１ 684 cm －１The manufacturing method is characterized by setting the intensity of the peak detected within the following range as P3, and ensuring that the value I, given by the following formula (1), is between 0.001% and 200%. According to this manufacturing method, the particulate polymer of the present invention described above can be efficiently produced. I(%) = (P3 - P2) / P1 × 100 ... (1)

[0054] Furthermore, in the reaction process, it is preferable to control the value given by formula (1) to the range described in the section on "<<Raman spectral characteristics of particulate polymer>>". This can be achieved by measuring the change in the Raman spectrum over time during the reaction process.

[0055] <Preparation of Core Particles> When preparing particulate polymers, it is preferable to prepare the core particles to a desired composition. For example, core particles can be prepared by polymerizing a monomer composition containing the monomers described above in an aqueous solvent such as water. Here, the proportion of each monomer in the monomer composition is usually the same as the proportion of each monomer unit in the particulate polymer.

[0056] Furthermore, the polymerization method is not particularly limited, and any of the following methods can be used, for example, suspension polymerization, emulsion polymerization, and dispersion polymerization. Among these, suspension polymerization and emulsion polymerization are preferred, and suspension polymerization is more preferred. In addition, any polymerization reaction can be used, such as radical polymerization and living radical polymerization.

[0057] Furthermore, the monomer composition used to prepare the particulate polymer can contain other additives such as suspension stabilizers, polymerization initiators, and dispersants in any amount. The suspension stabilizer is not particularly limited, but polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, alkyl chain-modified polyvinyl alcohol, polyacrylic acid, methylcellulose, ethylcellulose, hydroxypropylcellulose, polyvinylpyrrolidone, and styrene-malean anhydride copolymer can be suitably used. By increasing or decreasing the amount of suspension stabilizer, the median diameter of the particulate polymer by volume can be adjusted. While the amount of suspension stabilizer is not particularly limited, it is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, preferably 6.0 parts by mass or less, more preferably 3.0 parts by mass or less, and even more preferably 2.0 parts by mass or less, per 100 parts by mass of monomer contained in the monomer composition for core particle formation. If the amount of suspension stabilizer is above the above lower limit, it is possible to suppress the excessive increase in the particle size of the core particles, and consequently the particulate polymer. If the amount of suspension stabilizer is below the above upper limit, it is possible to suppress the excessive reduction in the particle size of the core particles, and consequently the particulate polymer, and to further improve the air permeability of the resulting functional layer. As a result, it becomes possible to reduce the internal resistance of the resulting electrochemical element.

[0058] Furthermore, the dispersant is not particularly limited and can be a nonionic surfactant, anionic surfactant, cationic surfactant, or amphoteric surfactant. Among these, anionic surfactants are preferably used as the dispersant. Specific examples of anionic surfactants include sulfate ester salts of higher alcohols such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium octyl sulfate, sodium decyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, and sodium octadecyl sulfate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, sodium laurylbenzenesulfonate, and sodium hexadecylbenzenesulfonate; and aliphatic sulfonates such as sodium lauryl sulfonate, sodium dodecylsulfonate, and sodium tetradecylsulfonate. The dispersant is an optional component and does not need to be included, but if it is included, it is preferable to include an amount that does not excessively increase the particle size distribution of the particulate polymer.

[0059] Here, as an example, we will describe a method for preparing core particles by suspension polymerization.

[0060] (1) Preparation of monomer composition First, prepare monomer composition (A) having a composition corresponding to the composition of polymer A constituting the core particles as described above. At this time, various monomers are blended according to the composition of polymer A, and other compounding agents are added as needed. (2) Preparation of aqueous solution Next, a suspension stabilizer is added to water and stirred to dissolve the suspension stabilizer without stirring to prepare an aqueous solution. (3) Formation of droplets To the aqueous solution obtained in (2) above, monomer composition (A) is added and stirred, then dispersed in water with a polymerization stabilizer, and a polymerization initiator is added to obtain a mixture. Examples of polymerization initiators to be used include oil-soluble polymerization initiators such as t-butylperoxy-2-ethylhexanoate and azobisisobutyronitrile. The obtained mixture is stirred at high shear to form droplets of monomer composition (A).

[0061] (4) Polymerization After forming droplets of monomer composition (A), the water containing the formed droplets is heated to start polymerization. When the polymerization conversion rate has increased sufficiently, it is cooled. The polymerization reaction temperature is preferably 50°C to 95°C. The polymerization reaction time is preferably 1 hour to 10 hours, preferably 8 hours or less, and more preferably 6 hours or less.

[0062] <Shell Formation Reaction Step> In the shell formation reaction step, a solution containing the polymerization reaction solution of core particles obtained through the above polymerization and a shell-forming compound is obtained, and a shell is formed on the surface of the core particles. Here, as the shell-forming compound, melamine compounds can be suitably used, as described above in the section on <<Composition of Shell>>.

[0063] The amount of shell-forming compound added in the shell-forming reaction step is preferably such that it matches the mass ratio of core particles to shell as described above. Furthermore, the reaction temperature in this step is preferably between 30°C and 95°C.

[0064] The timing for terminating the reaction is determined by monitoring the change in the Raman spectrum of the reaction system over time, and determining when the value given by formula (1) reaches the desired value. The specific reaction time is not particularly limited as long as the value given by formula (1) is within a predetermined range, but is preferably 1 hour or more and 10 hours or less, preferably 8 hours or less, and more preferably 6 hours or less.

[0065] To terminate the reaction, the system is cooled. Furthermore, it is preferable to add a pH adjusting agent to adjust the pH of the obtained functional layer composition to 5.0 or higher and 11.0 or lower. Here, the pH of the functional layer composition is more preferably 6.0 or higher, even more preferably 7.0 or higher, preferably 10.5 or lower, and most preferably 10.0 or lower. If the pH is above the lower limit, it is possible to suppress excessive increase in the elasticity of the shell and further increase the room-temperature adhesive strength of the obtained functional layer. Also, if the pH is below the upper limit, hydrolysis of the "-O-" bond formed between the core particles and the shell is less likely to proceed, effectively suppressing thinning of the shell and maintaining the elasticity of the shell appropriately, thereby further increasing the blocking resistance of the obtained functional layer. Furthermore, because the elasticity of the shell is appropriately maintained, it is possible to suppress the shell from breaking during operations such as coating and drying during functional layer formation and effectively suppress blockage of pores in substrates such as separators.

[0066] <Other Ingredients> In addition to the ingredients listed above, the functional layer composition may contain any additives as needed.

[0067] (Slurry Composition) The functional layer composition of the present invention can be suitably used as a slurry composition containing non-conductive particles, any binder, etc. When the electrochemical element is a secondary battery, such a slurry composition can be applied to a separator as a substrate to form a heat-resistant adhesive layer well.

[0068] <Method for preparing the slurry composition> The method for preparing the slurry composition is not particularly limited. For example, it can be prepared by mixing the particulate polymer described above, water as a dispersion medium, a binder described later in the section on (functional layer for electrochemical elements), heat-resistant fine particles, and other components used as needed. When particulate polymers are prepared by polymerizing monomer compositions in an aqueous solvent, the particulate polymers may be mixed directly with other components in the form of an aqueous dispersion. When mixing particulate polymers in the form of an aqueous dispersion, the water in the aqueous dispersion may be used as the dispersion medium.

[0069] Here, the method of mixing the above-mentioned components is not particularly limited, but it is preferable to use a disperser as the mixing device in order to efficiently disperse each component. The disperser is preferably a device that can uniformly disperse and mix the above-mentioned components. Examples of dispersers include ball mills, sand mills, pigment dispersers, grinders, ultrasonic dispersers, homogenizers, and planetary mixers.

[0070] Furthermore, when mixing the aforementioned particulate polymer with the heat-resistant fine particles and binder described later, it is preferable to pre-mix the heat-resistant fine particles with a water-soluble polymer such as sodium polyacrylate. It is also preferable to include a dispersant when mixing the particulate polymer, optionally pre-mixed heat-resistant fine particles, and binder. The amounts of the water-soluble polymer and dispersant can be set to any amount as needed.

[0071] (Functional layer for electrochemical elements) The functional layer for electrochemical elements of the present invention is formed using the electrochemical element functional layer composition of the present invention. More specifically, the functional layer for electrochemical elements may be a dried product of the functional layer composition as a slurry composition containing non-conductive particles, an arbitrary binder, etc.

[0072] <Heat-resistant fine particles> The heat-resistant fine particles included in the functional layer are not particularly limited and include fine particles made of inorganic materials (i.e., inorganic fine particles) and fine particles made of organic materials (i.e., organic fine particles) that are stable and electrochemically stable under the operating environment of the electrochemical element. Inorganic fine particles and organic fine particles may be used individually, or inorganic fine particles and organic fine particles may be used in combination.

[0073] [Inorganic Fine Particles] Examples of inorganic fine particles include aluminum oxide (alumina, Al ２ O ３ ), aluminum oxide hydrate (boehmite, AlOOH), gibbsite (Al(OH) ３ ), silicon dioxide, magnesium oxide (magnesia), magnesium hydroxide, calcium oxide, titanium dioxide (titania), barium titanate (BaTiO) ３Examples include inorganic oxide particles such as ZrO and alumina-silica composite oxides; nitride particles such as aluminum nitride and boron nitride; covalent crystalline particles such as silicon and diamond; sparingly soluble ionic crystalline particles such as barium sulfate, calcium fluoride, and barium fluoride; and clay fine particles such as talc and montmorillonite. These particles may be subjected to elemental substitution, surface treatment, solid solution treatment, etc., as needed. Inorganic fine particles may be used individually or in combination of two or more types.

[0074] [Organic Fine Particles] Unlike the specified particulate polymers and binders described above, organic fine particles are made of polymers that do not have adhesive properties. Examples of organic fine particles include various crosslinked polymer particles such as crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked products, polystyrene, polyimide, polyamide, polyamideimide, melamine resin, phenol resin, and benzoguanamine-formaldehyde condensate, as well as heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide, and modified and derivative products thereof. Organic fine particles may be used individually or in combination of two or more types. As described above, organic fine particles are made of polymers that do not have adhesive properties. Specifically, the glass transition temperature of the polymer constituting the organic fine particles is preferably 150°C or higher.

[0075] Among the heat-resistant fine particles mentioned above, from the viewpoint of further improving the heat resistance of the element material consisting of a laminate, inorganic fine particles and organic fine particles composed of polymers having a glass transition temperature of 150°C or higher are preferred, inorganic fine particles are more preferred, and particles made of alumina (alumina particles), particles made of boehmite (boehmite particles), particles made of barium sulfate (barium sulfate particles), and particles made of magnesium hydroxide (magnesium hydroxide particles) are even more preferred.

[0076] [Properties of Heat-Resistant Fine Particles] The heat-resistant fine particles preferably have a volume-based median diameter of 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, preferably 1.0 μm or less, more preferably 0.9 μm or less, and even more preferably 0.8 μm or less. If the volume-based median diameter of the heat-resistant fine particles is 0.1 μm or more, it is possible to suppress the decrease in the ionic conductivity of the functional layer caused by excessive density packing of the heat-resistant fine particles in the functional layer, thereby reducing the internal resistance of the electrochemical element. On the other hand, if the volume-based median diameter of the heat-resistant fine particles is 1.0 μm or less, even if the functional layer is thinned, the element member consisting of a laminate equipped with the functional layer can sufficiently exhibit excellent heat resistance. Therefore, it is possible to increase the capacitance of the electrochemical element while ensuring sufficient heat resistance of the element member.

[0077] <Mixing ratio of heat-resistant fine particles and particulate polymer> The mixing ratio of heat-resistant fine particles and particulate polymer in the functional layer composition is preferably 80:20 to 60:40 by volume (heat-resistant fine particles:particulate polymer). If the mixing ratio of heat-resistant fine particles and particulate polymer is within the above range by volume, a good balance between the heat resistance and adhesion of the functional layer will be achieved.

[0078] <Binding Agent> The binding agent binds heat-resistant fine particles together in the functional layer. Examples of known polymers used as binding agents include conjugated diene polymers, acrylic polymers, polyvinylidene fluoride (PVDF), and polyvinyl alcohol (PVOH). The binding agent may be used alone or in combination of two or more types. Preferably, the binding agent is a polymer that is not water-soluble and can be dispersed in a dispersion medium such as water, such as conjugated diene polymers, acrylic polymers, and polyvinylidene fluoride (PVDF). Conjugated diene polymers and acrylic polymers are more preferred, and acrylic polymers are even more preferred. When the functional layer formed using the functional layer composition is adjacent to the positive electrode, it is preferable to use a binding agent other than a conjugated diene polymer. In this invention, a polymer is considered "water-insoluble" if, when 0.5 g of the polymer is dissolved in 100 g of water at a temperature of 25°C, the insoluble content is 90% by mass or more.

[0079] Here, a conjugated diene polymer refers to a polymer containing conjugated diene monomer units. Specific examples of conjugated diene polymers are, without particular limitation, copolymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene copolymer (SBR), butadiene rubber (BR), acrylic rubber (NBR) (a copolymer containing acrylonitrile units and butadiene units), and their hydrides. Acrylic polymers refer to polymers containing (meth)acrylic acid ester monomer units. These binders may be used individually or in combination of two or more types in any ratio.

[0080] Among these, acrylic polymers are preferred. The proportion of (meth)acrylic acid ester monomer units in the acrylic polymer is preferably 50% by mass or more, more preferably 55% by mass or more, even more preferably 58% by mass or more, preferably 98% by mass or less, more preferably 97% by mass or less, and even more preferably 96% by mass or less. By setting the proportion of (meth)acrylic acid ester monomer units to be above the lower limit of the above range, the room-temperature adhesive strength of the functional layer can be further increased. Furthermore, by setting it to be below the upper limit, the electrochemical properties of the electrochemical element equipped with the functional layer can be further enhanced.

[0081] Furthermore, the glass transition temperature (Tg) of the binder is preferably -100°C or higher, more preferably -90°C or higher, even more preferably -80°C or higher, preferably less than 30°C, more preferably 20°C or lower, and even more preferably 15°C or lower. If the glass transition temperature of the binder is above the lower limit, the blocking resistance of the functional layer can be further improved. On the other hand, if the glass transition temperature of the binder is below the upper limit, the room-temperature adhesive strength of the functional layer can be further improved.

[0082] The median diameter of the binder by volume is not particularly limited, but is, for example, less than 1.0 μm, preferably 0.8 μm or less, more preferably 0.5 μm or less, even more preferably 0.3 μm or less, preferably 0.05 μm or more, and even more preferably 0.1 μm or more. If the median diameter of the binder by volume satisfies the above upper limit, the blocking resistance of the functional layer can be further improved. If the median diameter of the binder by volume is equal to or greater than the above lower limit, the internal resistance of the resulting electrochemical element can be further reduced. The median diameter of the binder by volume can be measured by the method described in the examples.

[0083] The binder content is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of heat-resistant fine particles. If the binder content is above the lower limit, it is possible to sufficiently prevent the particulate polymer from falling off the functional layer and to sufficiently improve the adhesion of the functional layer. On the other hand, if the binder content is below the upper limit, it is possible to suppress the decrease in the ionic conductivity of the functional layer and reduce the internal resistance of the electrochemical element.

[0084] The binder is not particularly limited, and can be prepared, for example, by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent such as water. Here, the proportion of each monomer in the monomer composition is usually the same as the proportion of each monomer unit in the binder.

[0085] Furthermore, the shape of the binder may be particulate or non-particulate, but from the viewpoint of effectively suppressing the detachment of components contained in the functional layer, the shape of the binder is preferably particulate. Note that the shape of the binder within the functional layer may be crushed and is not limited to particulate.

[0086] The method for forming the functional layer for electrochemical elements will be explained in the section on (Laminates for Electrochemical Elements) along with the method for manufacturing the laminate.

[0087] (Laminate for Electrochemical Elements) The laminate for electrochemical elements comprises a substrate and a functional layer for electrochemical elements formed on the substrate using the functional layer composition described above. The functional layer for electrochemical elements contains at least the particulate polymer, binder, heat-resistant fine particles described above, and other components used as needed. The components contained in the functional layer are those contained in the functional layer composition and slurry composition, and the preferred ratio of each component is the same as the preferred ratio of each component in the functional layer composition and slurry composition. Because the laminate for electrochemical elements includes a functional layer formed using the functional layer composition described above, the internal resistance can be reduced when an electrochemical element is formed.

[0088] <Substrate> The substrate can be appropriately selected depending on the type of electrochemical element member using the laminate of the present invention. For example, when the laminate of the present invention is used as a separator, a separator substrate is used as the substrate. Also, for example, when the laminate of the present invention is used as an electrode, an electrode substrate is used as the substrate.

[0089] <<Separator Substrate>> The separator substrate is not particularly limited, and known separator substrates such as organic separator substrates can be used. The organic separator substrate is a porous member made of organic material. Examples of organic separator substrates include microporous membranes or nonwoven fabrics containing polyolefin resins such as polyethylene, polypropylene, polybutene, and polyvinyl chloride, and aromatic polyamide resins. Among these, microporous membranes made of polyolefin resins are preferred from the viewpoint that the ratio of electrode active material in the electrochemical element can be increased and the capacity per unit volume can be increased. The thickness of the separator substrate can be any thickness, preferably 5 μm to 30 μm, more preferably 5 μm to 20 μm, and even more preferably 5 μm to 18 μm.

[0090] <<Electrode Substrate>> The electrode substrate (positive electrode substrate and negative electrode substrate) is not particularly limited, but examples include an electrode substrate in which an electrode composite layer is formed on a current collector. Here, known methods can be used for the current collector, the electrode active material in the electrode composite layer (positive electrode active material, negative electrode active material), the binder for the electrode composite layer (binder for the positive electrode composite layer, binder for the negative electrode composite layer), and the method for forming the electrode composite layer on the current collector. For example, the method described in Japanese Patent Application Publication No. 2013-145763 can be used.

[0091] <Method for Manufacturing Laminates> The method for manufacturing the laminate of the present invention is not particularly limited, and for example, a method in which a functional layer is formed on a release sheet and the functional layer is transferred onto a substrate can be used. However, from the viewpoint of eliminating the need for a transfer and improving manufacturing efficiency, it is preferable to manufacture the laminate by a step of supplying a functional layer composition onto a substrate (supply step) and a step of drying the functional layer composition supplied onto the substrate (drying step).

[0092] <<Supply Process>> In the supply process, the functional layer composition of the present invention described above is supplied onto a substrate to form a film of the functional layer composition on the substrate. The method of supplying the functional layer composition onto the substrate is not particularly limited; the functional layer composition may be applied to the surface of the substrate, or the substrate may be immersed in the functional layer composition. It is preferable to apply the functional layer composition to the surface of the substrate because it is easier to control the thickness of the manufactured functional layer. There are no particular limitations on the method of applying the functional layer composition to the surface of the substrate; for example, methods such as the doctor blade method, reverse roll method, direct roll method, gravure coating method, bar coating method, extrusion method, and brush coating method can be used. In the supply process, the film of the functional layer composition may be formed on only one side of the substrate, or on both sides of the substrate.

[0093] <<Drying Process>> In the drying process, the film of the functional layer composition formed on the substrate in the supply process is dried to remove the dispersion medium and form the functional layer. The method for drying the film of the functional layer composition is not particularly limited and known methods can be used, such as drying with hot air, hot air, low humidity air, vacuum drying, and drying by irradiation with infrared rays or electron beams. The drying conditions are not particularly limited, but the drying temperature is preferably 40 to 100°C and the drying time is preferably 1 to 30 minutes.

[0094] Furthermore, when manufacturing the laminate of the present invention, a functional layer may be formed on one side of the substrate by performing a supply process and a drying process, and then a functional layer may be formed on the other side of the substrate by performing a supply process and a drying process again.

[0095] In the functional layer formed using the functional layer composition, a plurality of heat-resistant fine particles are typically arranged so as to be stacked in the thickness direction of the functional layer. The thickness of the layer formed by the stacking of heat-resistant fine particles in the thickness direction of the functional layer (hereinafter also referred to as the "heat-resistant fine particle layer") is preferably 0.3 μm or more, more preferably 0.5 μm or more, even more preferably 1 μm or more, preferably 6 μm or less, more preferably 5 μm or less, and even more preferably 3.5 μm or less. If the thickness of the heat-resistant fine particle layer is above the lower limit, the heat resistance of the functional layer becomes extremely good. On the other hand, if the thickness of the heat-resistant fine particle layer is below the upper limit, the ion diffusion of the functional layer can be ensured, and the internal resistance of the electrochemical element can be further reduced.

[0096] (Electrochemical element) The electrochemical element of the present invention comprises an electrode and a separator, and is characterized in that at least one of the electrode and the separator is the laminate of the present invention described above. Because the electrochemical element of the present invention uses the laminate of the present invention described above as at least one of the element material of the electrode and the separator, the internal resistance is low.

[0097] Furthermore, the electrochemical element of the present invention is not particularly limited, and includes, for example, a lithium-ion secondary battery, an electric double-layer capacitor, and a lithium-ion capacitor, and is preferably a lithium-ion secondary battery.

[0098] Hereinafter, we will describe a case in which a lithium-ion secondary battery is used as an example of the electrochemical element of the present invention, and the laminate of the present invention described above is used as the separator of the lithium-ion secondary battery, but the electrochemical element of the present invention is not limited to this.

[0099] <Positive and Negative Electrodes> As the positive and negative electrodes, electrodes made of the known electrode substrates (positive electrode substrate and negative electrode substrate) described in the "Substrate" section can be used.

[0100] <Electrolyte> Typically, an organic electrolyte is used as the electrolyte, which is obtained by dissolving a supporting electrolyte in an organic solvent. As the supporting electrolyte, for example, lithium salts are used in lithium-ion secondary batteries. LiPF is an example of a lithium salt. ６ LiAsF６ LiBF ４ LiSbF ６ LiAlCl ４ LiClO ４ CF ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Examples include NLi. Among them, LiPF is particularly well-soluble in solvents and exhibits a high degree of dissociation. ６ LiClO ４ CF ３ SO ３ Li is preferred. Note that the electrolyte may be used alone or in combination of two or more types. Generally, the lithium ion conductivity tends to increase as the degree of dissociation of the supporting electrolyte increases; therefore, the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0101] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte, but for example in lithium-ion secondary batteries, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (ethyl methyl carbonate (EMC)), vinylene carbonate, etc.; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; etc. are preferably used.

[0102] A mixture of these solvents may also be used. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range. Generally, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted by the type of solvent used. The concentration of the electrolyte in the electrolyte solution can be adjusted as appropriate. In addition, known additives may be added to the electrolyte solution.

[0103] <Method for Manufacturing an Electrochemical Element> The method for manufacturing the electrochemical element of the present invention is not particularly limited. For example, a lithium-ion secondary battery, which is an example of the electrochemical element of the present invention as described above, can be manufactured by stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. At least one of the element components among the positive electrode, negative electrode, and separator is made into the laminate of the present invention. Furthermore, the battery container may contain expanded metal, fuses, overcurrent prevention elements such as PTC elements, lead plates, etc., as needed, to prevent pressure rise inside the battery and overcharging / discharging. The shape of the battery may be any of the following: coin type, button type, sheet type, cylindrical type, prismatic type, flat type, etc.

[0104] (Exemplary Embodiment 1) The present invention is further illustrated by the following exemplary embodiments [1] to

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

[29] .

[0105] [1] A composition for an electrochemical element functional layer comprising a particulate polymer, wherein the particulate polymer is a particulate polymer having a core-shell structure, comprising core particles having a shell on its surface, wherein the particulate polymer has a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, and when the particulate polymer before shell formation is measured by Raman spectroscopy, the wavenumber is 996 cm⁻¹. －１ 1005cm －１ The intensity of the peak detected within the following range is P1, and the wavenumber is 678 cm⁻¹. －１ 684 cm －１The intensity of the peak detected within the following range is defined as P2, and furthermore, when the particulate polymer having the core-shell structure is subjected to Raman spectroscopy, the wavenumber is 678 cm⁻¹. －１ 684 cm －１ A composition for an electrochemical element functional layer, wherein the intensity of the peak detected within the following range is denoted as P3, and the value given by the following formula (1) is 0.001% or more and 200% or less: (P3 - P2) / P1 × 100 ... (1)

[0106] [2] The electrochemical element functional layer composition according to [1], wherein the particulate polymer has a volume-based median diameter of 2.0 μm or more and 15.0 μm or less. If the volume-based median diameter of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0107] [3] The particulate polymer has a volume-based median diameter of 4.0 μm or more and 8.0 μm or less, as described in [1] or [2], for use as a functional layer for an electrochemical element. If the volume-based median diameter of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0108] [4] The particulate polymer has a particle size distribution of 5 or less, more preferably 1 or more and 3 or less, in the electrochemical element functional layer composition according to any one of [1] to [3]. If the particle size distribution of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0109] [5] The particulate polymer is a composition for an electrochemical element functional layer according to any one of [1] to [4], wherein the particulate polymer has a particle size distribution of 1 or more and 2 or less. If the particle size distribution of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0110] [6] The electrochemical element functional layer composition according to any one of [1] to [5], wherein when the particulate polymer is interposed between a material to be adhered, such as an electrode composite layer, and a substrate such as a separator having voids, the particulate polymer interposed between the material to be adhered and the substrate is crushed in the stacking direction of the material to be adhered and the substrate, thereby effectively adhering the material to be adhered and the substrate 3.

[0111] [7] The particulate polymer is an electrochemical element functional layer composition according to any one of [1] to [6], wherein the value given by formula (1) is 0.05% or more and 150% or less. If the value given by formula (1) is equal to or greater than the lower limit, the blocking resistance of the functional layer can be further improved. Also, if the value given by (1) is equal to or less than the upper limit, the adhesion of the functional layer can be further improved.

[0112] [8] The particulate polymer is an electrochemical element functional layer composition according to any one of [1] to [7], wherein the value given by formula (1) is 0.1% or more and 130% or less. If the value given by formula (1) is greater than or equal to the lower limit, the blocking resistance of the functional layer can be further improved. Also, if the value given by (1) is less than or equal to the upper limit, the adhesion of the functional layer can be further improved.

[0113] [9] The particulate polymer is an electrochemical element functional layer composition according to any one of [1] to [8], wherein the value given by formula (1) is 0.15% or more and 9.5% or less. If the value given by formula (1) is greater than or equal to the lower limit, the blocking resistance of the functional layer can be further improved. Also, if the value given by (1) is less than or equal to the upper limit, the adhesion of the functional layer can be further improved.

[0114]

[10] The particulate polymer is preferably such that the glass transition temperature of the core particles constituting the particulate polymer is -65°C or higher and 60°C or lower, more preferably -50°C or higher and 50°C or lower, more preferably -50°C or higher and 35°C or lower, even more preferably -30°C or higher and 25°C or lower, even more preferably -28°C or higher and 20°C or lower, particularly preferably -20°C or higher and 18°C ​​or lower, and particularly preferably -20°C or higher and 10°C or lower, as described in any of [1] to [9] for an electrochemical element functional layer composition. If the glass transition temperature of the core particles is above the lower limit, the crushing of the particulate polymer in a specific direction can be promoted, and the adhesion of the functional layer can be further enhanced. Also, if the glass transition temperature of the core particles is below the upper limit, when the material to be adhered, such as an electrode composite layer, comes into contact with the core particles by pressing, a good anchoring effect can be exhibited, and consequently the adhesion of the functional layer can be further enhanced.

[0115]

[11] The electrochemical element functional layer composition according to any one of [1] to

[10] , wherein the core particles include units formed using aromatic monomer units, preferably aromatic vinyl monomer units, more preferably styrene, styrene sulfonic acid and its salts, α-methylstyrene, vinyltoluene, and 4-(tert-butoxy)styrene.

[0116]

[12] The electrochemical element functional layer composition according to any one of [1] to

[11] , wherein the core particles include units formed using at least one of styrene, vinyltoluene, and α-methylstyrene as aromatic monomer units.

[0117]

[13] The electrochemical element functional layer composition according to any one of [1] to

[12] , wherein the core particles include units formed using styrene as aromatic monomer units.

[0118]

[14] The electrochemical element functional layer composition according to any one of [1] to

[13] , wherein the core particles contain aromatic monomer units in a proportion preferably of 5% to 60% by mass, more preferably of 10.0% to 55.0% by mass, even more preferably of 25.0% to 50.0% by mass, even more preferably of 28.0% to 48.0% by mass, or for example, 30% to 45% by mass, or 15% to 40% by mass, and even more preferably of 30% to 40% by mass. This is because the room-temperature adhesive strength of the resulting functional layer can be further increased.

[0119]

[15] The core particles preferably contain (meth)acrylic acid ester monomer units as ester bond-containing monomer units, specifically alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-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, stearyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isopropyl methacrylate A composition for an electrochemical element functional layer according to any one of [1] to

[14] , comprising a unit formed using at least one selected from the group comprising alkyl methacrylates such as ethyl 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, more preferably comprising a unit formed using at least one selected from the group comprising ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate, and even more preferably comprising a unit formed using 2-ethylhexyl acrylate.

[0120]

[16] The electrochemical element functional layer composition according to any one of [1] to

[15] , wherein the core particles preferably contain ester bond-containing monomer units in a proportion of 40.0% by mass or more and 90.0% by mass or less, more preferably 45.0% by mass or more and 80.0% by mass or less, and even more preferably 50.0% by mass or more and 78.0% by mass or less. Within this range, the adhesive strength at room temperature can be further increased.

[0121]

[17] The electrochemical element functional layer composition according to any one of [1] to

[16] , wherein the core particles preferably contain ester bond-containing monomer units in a proportion of 40% to 90% by mass, more preferably 48% to 83% by mass, even more preferably 53% to 73% by mass, and even more preferably 58% to 68% by mass. Within this range, the adhesive strength at room temperature can be further increased.

[0122]

[18] The electrochemical element functional layer composition according to any one of [1] to

[17] , wherein the particulate polymer before shell formation comprises carboxyl group-containing monomer units.

[0123]

[19] The electrochemical element functional layer composition according to

[18] , wherein the carboxyl group-containing monomer unit is a unit formed using any of the following monomers. By satisfying such a composition, a shell can be efficiently formed and adhesion can be improved. - Monomers having a carboxyl group selected from ethylenically unsaturated monocarboxylic acids and their derivatives, ethylenically unsaturated dicarboxylic acids and their acid anhydrides and their derivatives - Ethylene unsaturated monocarboxylic acids selected from acrylic acid, methacrylic acid, and crotonic acid - Derivatives of ethylenically unsaturated monocarboxylic acids selected from 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid - Selected from maleic acid, fumaric acid, itaconic acid, and mesaconic acid Ethylene-unsaturated dicarboxylic acids: Acid anhydrides of ethylenically unsaturated dicarboxylic acids selected from maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride; Derivatives of ethylenically unsaturated dicarboxylic acids selected from methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleic acid, nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, fluoroalkyl maleic acid, styrene maleic anhydride copolymer, and acrylamide copolymer.

[0124]

[20] The electrochemical element functional layer composition according to

[19] , wherein the carboxyl group-containing monomer unit is a unit formed using any monomer from acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and fumaric acid as the carboxylic acid unit, and preferably a unit formed using methacrylic acid.

[0125]

[21] A composition for an electrochemical element functional layer according to any one of [1] to

[20] , wherein the particulate polymer before shell formation contains hydroxyl group-containing monomer units. By satisfying such a composition, a shell can be efficiently formed and adhesion can be improved.

[0126]

[22] The electrochemical element functional layer composition according to any one of [1] to

[21] , wherein the particulate polymer before shell formation contains hydroxyl group-containing monomer units, and the hydroxyl group-containing monomer units are units formed using any of N-methylol(meth)acrylamide, N-butoxymethylol(meth)acrylamide; alkyl (meth)acrylate esters having hydroxyl groups such as β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, β-hydroxyethyl methacrylate, and β-hydroxypropyl methacrylate; polyvinyl alcohol, alkyl chain-modified polyvinyl alcohol, carboxymethylcellulose, and hydroxypropyl methylcellulose, preferably units formed using at least one of vinyl alcohol units, N-methylol(meth)acrylamide units, and β-hydroxyethyl acrylate units, and more preferably units formed using vinyl alcohol.

[0127]

[23] The composition for an electrochemical element functional layer according to any one of [1] to

[22] , wherein the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in the particulate polymer before shell formation is preferably 0.5% by mass or more and 20.0% by mass or less, and more preferably 0.5% by mass or more and 15.0% by mass or less, if either one is included, or if both are included, the total content ratio.

[0128]

[24] The composition for an electrochemical element functional layer according to any one of [1] to

[23] , wherein the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in the particulate polymer before shell formation is preferably 0.7% by mass or more and 17% by mass or less, and more preferably 2% by mass or more and 17% by mass or less, if either one is included, or if both are included, the content ratio of the units is 0.7% by mass or more and 17% by mass or less. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is above the lower limit, the blocking resistance of the resulting functional layer can be improved. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is below the upper limit, the air permeability of the resulting functional layer and the internal resistance of the resulting electrochemical element can be effectively reduced.

[0129]

[24] The electrochemical element functional layer composition according to any one of [1] to

[23] , wherein the shell is formed of a shell-forming compound that has the property of condensing with carboxyl group-containing monomer units or hydroxyl group-containing monomer units contained in the particulate polymer before shell formation, and also contains heteroatoms.

[0130]

[25] The electrochemical element functional layer composition according to any one of [1] to

[24] , wherein the shell is composed of any one of a urethane / urea film, a melamine compound, gelatin / gum arabic, and an alginic acid / sodium chloride film.

[0131]

[26] The electrochemical element functional layer composition according to

[25] , wherein the shell is formed comprising at least one selected from melamine compounds including hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, trimethylolmelamine, hexamethylolmelamine, dimethylolmelamine, N,N',N''-trimethyl-N,N',N''-trimethylolmelamine, N-methylolmelamine, N,N'-(methoxymethyl)melamine, and N,N',N''-tributyl-N,N',N''-trimethylolmelamine, more preferably at least one selected from trimethylolmelamine, hexamethylolmelamine, and dimethylolmelamine, and even more preferably trimethylolmelamine.

[0132]

[27] The electrochemical element functional layer composition according to any one of [1] to

[26] , wherein the content of the melamine compound-derived component in the shell is preferably 40.0% by mass or more and 100.0% by mass or less, more preferably 80.0% by mass or more and 100.0% by mass or less, and even more preferably 90.0% by mass or more and 100.0% by mass or less. If the content of the melamine compound-derived component in the shell is above the lower limit value, the blocking resistance of the resulting functional layer can be further improved.

[0133]

[28] The electrochemical element functional layer composition according to any one of [1] to

[27] , wherein the ratio of the core particles to the shell in the particulate polymer is preferably in the range of 99.95:0.05 to 50:50 by mass, more preferably in the range of 99.9:0.1 to 55:45, even more preferably in the range of 99.7:0.3 to 60:40, and even more preferably in the range of 99.5:0.5 to 65.0:35.0.

[0134]

[29] A composition for an electrochemical element functional layer according to any one of [1] to

[28] , wherein the pH is preferably 5.0 or more and 11.0 or less, more preferably 6.0 or more and 10.5 or less, and even more preferably 7.0 or more and 10.0 or less.

[0135] (Exemplary Embodiment 2) The present invention is further illustrated by the following exemplary embodiments <1> to <25>. However, the present invention is not limited to the following exemplary embodiments <1> to <25>.

[0136] <1> A composition for an electrochemical element functional layer comprising a particulate polymer, wherein the particulate polymer is a particulate polymer having a core-shell structure, comprising core particles having a shell on its surface, the particulate polymer having a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, and the shell being composed of one of a urethane / urea film, a melamine compound, gelatin / gum arabic, and an alginic acid / sodium chloride film, for use as an electrochemical element functional layer.

[0137] <2> The electrochemical element functional layer composition according to <1>, wherein the shell is formed by comprising at least one selected from melamine compounds including hexamethoxymethylolmelamine, pentamethoxymethylolmelamine, hexamethoxymethylmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, trimethylolmelamine, hexamethylolmelamine, dimethylolmelamine, N,N',N''-trimethyl-N,N',N''-trimethylolmelamine, N-methylolmelamine, N,N'-(methoxymethyl)melamine, and N,N',N''-tributyl-N,N',N''-trimethylolmelamine, more preferably at least one selected from trimethylolmelamine, hexamethylolmelamine, and dimethylolmelamine, and even more preferably trimethylolmelamine.

[0138] <3> The electrochemical element functional layer composition according to <1> or <2>, wherein the content of the melamine compound-derived component in the shell is preferably 40.0% by mass or more and 100.0% by mass or less, more preferably 80.0% by mass or more and 100.0% by mass or less, and even more preferably 90.0% by mass or more and 100.0% by mass or less.

[0139] <4> The electrochemical element functional layer composition according to any one of <1> to <3>, wherein the ratio of the core particles to the shell in the particulate polymer is preferably in the range of 99.95:0.05 to 50:50 by mass, more preferably in the range of 99.9:0.1 to 55:45, even more preferably in the range of 99.7:0.3 to 60:40, and even more preferably in the range of 99.5:0.5 to 65.0:35.0.

[0140] <5> The particulate polymer is a composition for an electrochemical element functional layer according to any one of <1> to <4>, wherein the particulate polymer has a volume-based median diameter of 2.0 μm or more and 15.0 μm or less. If the volume-based median diameter of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0141] <6> The particulate polymer is a composition for an electrochemical element functional layer according to any one of <1> to <5>, wherein the particulate polymer has a volume-based median diameter of 4.0 μm or more and 8.0 μm or less. If the volume-based median diameter of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0142] <7> The particulate polymer has a particle size distribution of 5 or less, more preferably 1 or more and 3 or less, in the electrochemical element functional layer composition according to any one of <1> to <6>. If the particle size distribution of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0143] <8> The particulate polymer is an electrochemical element functional layer composition according to any one of <1> to <7>, wherein the particle size distribution is 1 or more and 2 or less. If the particle size distribution of the particulate polymer is within the above range, the internal resistance of the resulting electrochemical element can be further reduced.

[0144] <9> The electrochemical element functional layer composition according to any one of <1> to <8>, wherein when the particulate polymer is interposed between a material to be adhered, such as an electrode composite layer, and a substrate such as a separator having voids, the particulate polymer interposed between the material to be adhered and the substrate is crushed in the stacking direction of the material to be adhered and the substrate, thereby effectively adhering the material to be adhered and the substrate 3.

[0145] <10> The particulate polymer is preferably such that the glass transition temperature of the core particles constituting the particulate polymer is -65°C or higher and 60°C or lower, more preferably -50°C or higher and 50°C or lower, more preferably -50°C or higher and 35°C or lower, even more preferably -30°C or higher and 25°C or lower, even more preferably -28°C or higher and 20°C or lower, particularly preferably -20°C or higher and 18°C ​​or lower, and particularly preferably -20°C or higher and 10°C or lower, as described in any of <1> to <9>. If the glass transition temperature of the core particles is above the lower limit, the crushing of the particulate polymer in a specific direction can be promoted, and the adhesion of the functional layer can be further enhanced. Also, if the glass transition temperature of the core particles is below the upper limit, when the material to be adhered, such as the electrode composite layer, comes into contact with the core particles by pressing, a good anchoring effect can be exhibited, and consequently the adhesion of the functional layer can be further enhanced.

[0146] <11> The electrochemical element functional layer composition according to any one of <1> to <10>, wherein the core particles include units formed using aromatic monomer units, preferably aromatic vinyl monomer units, more preferably styrene, styrene sulfonic acid and its salts, α-methylstyrene, vinyltoluene, and 4-(tert-butoxy)styrene.

[0147] <12> The electrochemical element functional layer composition according to any one of <1> to <11>, wherein the core particles include units formed using at least one of styrene, vinyltoluene, and α-methylstyrene as aromatic monomer units.

[0148] <13> The electrochemical element functional layer composition according to any one of <1> to <12>, wherein the core particles include units formed using styrene as aromatic monomer units.

[0149] <14> The electrochemical element functional layer composition according to any one of <1> to <13>, wherein the core particles contain aromatic monomer units preferably in a proportion of 5% to 60% by mass, more preferably in a proportion of 10.0% to 55.0% by mass, even more preferably in a proportion of 25.0% to 50.0% by mass, even more preferably in a proportion of 28.0% to 48.0% by mass, or for example in a proportion of 30% to 45% by mass, or in a proportion of 15% to 40% by mass, and even more preferably in a proportion of 30% to 40% by mass. This is because the room-temperature adhesive strength of the resulting functional layer can be further increased.

[0150] <15> The core particles preferably contain (meth)acrylic acid ester monomer units as ester bond-containing monomer units, specifically alkyl acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-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, stearyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, isopropyl methacrylate A composition for an electrochemical element functional layer according to any one of <1> to <14>, comprising a unit formed using at least one selected from the group comprising alkyl methacrylates such as ethyl 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; more preferably comprising a unit formed using at least one selected from the group comprising ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate; and even more preferably comprising a unit formed using 2-ethylhexyl acrylate.

[0151] <16> The electrochemical element functional layer composition according to any one of <1> to <15>, wherein the core particles preferably contain ester bond-containing monomer units in a proportion of 40.0% by mass or more and 90.0% by mass or less, more preferably 45.0% by mass or more and 80.0% by mass or less, and even more preferably 50.0% by mass or more and 78.0% by mass or less. Within this range, the adhesive strength at room temperature can be further increased.

[0152] <17> The electrochemical element functional layer composition according to any one of <1> to <16>, wherein the core particles preferably contain ester bond-containing monomer units in a proportion of 40% to 90% by mass, more preferably 48% to 83% by mass, even more preferably 53% to 73% by mass, and even more preferably 58% to 68% by mass. Within this range, the adhesive strength at room temperature can be further increased.

[0153] <18> The particulate polymer before shell formation comprises carboxyl group-containing monomer units, according to any one of <1> to <17>, for use as a functional layer for an electrochemical element.

[0154] <19> The electrochemical element functional layer composition according to <18>, wherein the carboxyl group-containing monomer unit is a unit formed using any of the following monomers. By satisfying such a composition, a shell can be efficiently formed and adhesion can be improved. - Monomers having a carboxyl group selected from ethylenically unsaturated monocarboxylic acids and their derivatives, ethylenically unsaturated dicarboxylic acids and their acid anhydrides and their derivatives - Ethylene unsaturated monocarboxylic acids selected from acrylic acid, methacrylic acid, and crotonic acid - Derivatives of ethylenically unsaturated monocarboxylic acids selected from 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid - Selected from maleic acid, fumaric acid, itaconic acid, and mesaconic acid Ethylene-unsaturated dicarboxylic acids: Acid anhydrides of ethylenically unsaturated dicarboxylic acids selected from maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride; Derivatives of ethylenically unsaturated dicarboxylic acids selected from methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleic acid, nonyl maleic acid, decyl maleic acid, dodecyl maleic acid, octadecyl maleic acid, fluoroalkyl maleic acid, styrene maleic anhydride copolymer, and acrylamide copolymer.

[0155] <20> The electrochemical element functional layer composition according to <19>, wherein the carboxyl group-containing monomer unit is a unit formed using any monomer from acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and fumaric acid as the carboxylic acid unit, and preferably a unit formed using methacrylic acid.

[0156] <21> The particulate polymer before shell formation comprises hydroxyl group-containing monomer units. A composition for an electrochemical element functional layer according to any one of <1> to <20>.

[0157] <22> The electrochemical element functional layer composition according to any one of <1> to <21>, wherein the particulate polymer before shell formation contains hydroxyl group-containing monomer units, and the hydroxyl group-containing monomer units are units formed using any of N-methylol(meth)acrylamide, N-butoxymethylol(meth)acrylamide; alkyl (meth)acrylate esters having hydroxyl groups such as β-hydroxyethyl acrylate, β-hydroxypropyl acrylate, β-hydroxyethyl methacrylate, and β-hydroxypropyl methacrylate; polyvinyl alcohol, alkyl chain-modified polyvinyl alcohol, carboxymethylcellulose, and hydroxypropyl methylcellulose, preferably units formed using at least one of vinyl alcohol units, N-methylol(meth)acrylamide units, and β-hydroxyethyl acrylate units, and more preferably units formed using vinyl alcohol.

[0158] <23> The composition for an electrochemical element functional layer according to any one of <1> to <22>, wherein the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in the particulate polymer before shell formation is preferably 0.5% by mass or more and 20.0% by mass or less if either one is included, and more preferably 0.5% by mass or more and 15.0% by mass or less if both are included. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is above the lower limit, the blocking resistance of the resulting functional layer can be improved. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is below the upper limit, the air permeability of the resulting functional layer and the internal resistance of the resulting electrochemical element can be effectively reduced.

[0159] <24> The composition for an electrochemical element functional layer according to any one of <1> to <23>, wherein the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in the particulate polymer before shell formation is preferably 0.7% by mass or more and 17% by mass or less if either one is included, and more preferably 2% by mass or more and 17% by mass or less if both are included. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is above the lower limit, the blocking resistance of the resulting functional layer can be improved. If the content ratio of carboxyl group-containing monomer units and hydroxyl group-containing monomer units in polymer A is below the upper limit, the air permeability of the resulting functional layer and the internal resistance of the resulting electrochemical element can be effectively reduced.

[0160] <25> A composition for an electrochemical element functional layer according to any one of <1> to <24>, wherein the pH is preferably 5.0 or more and 11.0 or less, more preferably 6.0 or more and 10.5 or less, and even more preferably 7.0 or more and 10.0 or less.

[0161] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing quantities refer to mass unless otherwise specified. In addition, in a polymer produced by copolymerizing multiple types of monomers, the proportion of a structural unit formed by polymerizing a certain monomer in the polymer is usually equal to the ratio of that particular monomer to the total monomers used in the polymerization of the polymer (starting ratio), unless otherwise specified.

[0162] In the examples and comparative examples, the measurement and evaluation of various attributes were carried out according to the following.

[0163] <Median Diameter and Particle Size Distribution> The particulate polymers and binders prepared in the examples and comparative examples were used as measurement samples. After dispersing the measurement samples for 15 minutes, an amount equivalent to 0.1 g was weighed and placed in a beaker, and 0.1 mL of an aqueous alkylbenzene sulfonic acid solution (Fujifilm Corporation, "Drywell") was added as a dispersant. To the above beaker, 10 to 30 mL of diluent (Beckman Coulter Corporation, "Isoton II") was added, and the mixture was dispersed for 3 minutes using a 20 W (Watt) ultrasonic disperser. Subsequently, the volume-based median diameter (Dv) and number-average particle size (Dn) were measured using a particle size analyzer (Beckman Coulter Corporation, "Multisizer") under the conditions of aperture diameter: 20 μm, medium: Isoton II, and number of measured particles: 100,000. The particle size distribution (Dv / Dn) was also calculated. <Glass Transition Temperature> The binders prepared in the examples and comparative examples, and the core particles synthesized when preparing the particulate polymers, were used as measurement samples. 10 mg of the measurement sample was weighed into an aluminum pan, and a differential thermal analysis (DSC6220, manufactured by SII Nanotechnology Co., Ltd.) was used to perform the measurement under the conditions specified in JIS Z 8703, using an empty aluminum pan as a reference, within the measurement temperature range of -100°C to 500°C, at a heating rate of 10°C / min, to obtain a differential scanning calorimetry (DSC) curve. During this heating process, the glass transition temperature (°C) was determined by finding the intersection point between the baseline just before the endothermic peak of the DSC curve, where the differential signal (DDSC) is 0.05 mW / min / mg or higher, and the tangent to the DSC curve at the first inflection point that appears after the endothermic peak. The measurement results for the glass transition temperature of the core particles and the measurement results for the glass transition temperature of the core portion when particulate polymers with a core-shell structure are measured can be considered equivalent. <Confirmation of Core-Shell Structure> Microscopic observation confirmed that in all examples and comparative examples 1-3 and 5, the particulate polymers prepared had the shell completely covering the surface of the core particles. In contrast, the particulate polymer prepared in comparative example 4 had the shell partially covering the surface of the core particles. The state of the core-shell structure of the particulate polymers was determined according to the following method.At 25°C and RH 50±10%, aqueous dispersions of core particles and particulate polymers prepared in the examples and comparative examples were dried on a horizontal platform for 72 hours. The amount of aqueous dispersion to be dried was adjusted to produce a film with a thickness of 800 μm, taking into account the capacity of the horizontal platform. After that, the films were stored at 0°C for 24 hours to produce films with a thickness of 800 μm. Each film was visually inspected to see if cracks had occurred. If cracks had occurred in the film, it was considered that a shell with appropriate rigidity had been formed. <Core-Shell Ratio> Particulate polymers prepared in the examples and comparative examples were used as measurement samples. The shell ratio was calculated by measuring the nitrogen content in the particulate polymer having a core-shell structure using the Dumas method, in accordance with JIS K6451-1:2016.

[0164] <Raman Spectroscopy> In the examples and comparative examples, Raman spectroscopy and the progress of the reaction were confirmed during the reaction process for forming the shell layer. The progress of the reaction was monitored using a Mettler Toledo ReactRaman 802L (hereinafter referred to as ReactRaman) having the following configuration. The conditions were as follows: Probe: Standard immersion sensor; Optical range: 150 cm －１ ~3400cm －１ Sampling; Cosmic ray removal: Enabled; Laser power: 400 mW; Gain: High; Dark correction: Auto; Scattering correction: SNV; Baseline correction: Active Baseline Correction; Differentialization: Second derivative <Confirmation of reaction progress> Raman spectra were collected in situ throughout the reaction using ReactRaman. The ReactRaman probe was inserted into one neck of the flask, and the tip of the Raman probe was maintained below the surface of the reaction solution. After the addition of trimethylolmelamine, the shell-forming compound, a new peak appeared at 679 cm⁻¹. －１ The progress of the reaction was confirmed by observation. The reaction progressed to 679 cm⁻¹. －１ New peak at 998 cm －１ This was confirmed by calculating the increase rate using the peak derived from aromatic monomers at the following wavenumber of 678 cm⁻¹.－１ Above 684 cm －１ In the following range, 679 cm －１ One peak was confirmed at, and the peak size increased significantly as the reaction progressed. Also, at the time of adding trimethylol melamine, the wavenumber was 996 cm －１ Above 1005 cm －１ In the following range, 998 cm －１ One peak was confirmed at. The intensity of the peak detected at the wavenumber 998 cm at the time of adding trimethylol melamine －１ is designated as P1, the intensity of the peak detected at the wavenumber 679 cm －１ is designated as P2, and the intensity of the peak detected at the wavenumber 679 cm at the stage where the reaction process has advanced －１ is designated as P3. According to the following formula (1), the increase rate of the peak intensity detected at the wavenumber 679 cm －１ was calculated. (P3 - P2) / P1 × 100... (1) Incidentally, the peak height at the wavenumber 679 cm －１ is defined by the peak height from 678 cm －１ to 684 cm －１ defined from the two-point baseline of 670 cm －１ to 693 cm －１ The peak height of 998 cm －１ is defined by the peak height from 996 cm －１ to 1005 cm －１ defined from the two-point baseline of 992 cm －１ to 1010 cm －１ In this Example and Comparative Example, single peaks were confirmed in the above wavenumber ranges, respectively. However, if multiple peaks were confirmed respectively, the maximum peak was targeted for each.

[0165] <Measurement of pH of the composition for the functional layer> The pH of the composition for the functional layer prepared in the Example and Comparative Example was measured at a temperature of 25°C using a bench-top pH meter LAQUA-PH-SE manufactured by Horiba, Ltd.

[0166] <Room Temperature Bonding Strength of Functional Layers> The functional layer-coated separators obtained in the examples and comparative examples were cut into strips measuring 10 mm x 50 mm. Next, a negative electrode coating surface was attached to the functional layer-coated surface of the functional layer-coated separator to create a laminate, which was used as a test specimen. This test specimen was placed in a laminate packaging material, and the packaging material was heated and pressed for 1 minute at a temperature of 25°C and a load of 1.0 MPa using a flat plate press. After that, the test specimen was removed, and then, with the uncoated separator side facing down, cellophane tape was applied to the surface. The cellophane tape used was the one specified in JIS Z1522. The cellophane tape was fixed to a horizontal test stand. The stress was measured when one end of the separator of the functional layer-coated separator was pulled vertically upward at a tensile speed of 50 mm / min and peeled off. This measurement was performed three times, and the average value of the stress was calculated as the peel strength P, which was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2. A higher peel strength P indicates higher room-temperature bonding strength. A: Peel strength P1 is 5.0 N / m or higher. B: Peel strength P1 is 4.0 N / m or higher but less than 5.0 N / m. C: Peel strength P1 is 3.0 N / m or higher but less than 4.0 N / m. D: Peel strength P1 is less than 3.0 N / m.

[0167] <Blocking Resistance of Functional Layer> The functional layer-coated separators obtained in the examples and comparative examples were cut into strips measuring 10 mm x 50 mm. Next, a laminate was created with the coated surfaces of the functional layer-coated separators facing each other, and this was used as a test specimen. This test specimen was placed in a laminate packaging material, and the packaging material was heated and pressed using a flat plate press at a temperature of 40°C and a load of 0.2 MPa for 5 minutes. After that, the test specimen was removed, and then, with the uncoated separator side facing down, cellophane tape was applied to the surface. The cellophane tape used was the type specified in JIS Z1522. The cellophane tape was fixed to a horizontal test stand. The stress was measured when one end of the functional layer-coated separator was pulled vertically upward at a tensile speed of 50 mm / min and peeled off. This measurement was performed three times, and the average value of the stress was calculated as the peel strength P, which was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2. A smaller peel strength P indicates better blocking resistance. A: The separator falls off before the peel strength test. B: Peel strength P2 is 0.0 N / m or more and less than 0.2 N / m. C: Peel strength P2 is 0.2 N / m or more and less than 0.5 N / m. D: Peel strength P2 is 0.5 N / m or more.

[0168] <Air Permeability of Functional Layer> The Gurley values ​​(sec / 100cc) of the functional layer-equipped separators obtained in the examples and comparative examples were measured using a digital Ogura-type air permeability and smoothness tester (EYO-5-1M-R, manufactured by Asahi Seiko Co., Ltd.). Specifically, the increase in Gurley value ΔG (= G1 - G0) was determined from the Gurley value G0 of the "separator substrate" and the Gurley value G1 of the manufactured "functional layer-equipped separator," and evaluated according to the following criteria. A smaller increase in this Gurley value ΔG indicates better ionic conductivity of the separator. A: The increase in the Gurley value is less than 70 seconds / 100cc. B: The increase in the Gurley value is 70 seconds / 100cc or more but less than 85 seconds / 100cc. C: The increase in the Gurley value is 85 seconds / 100cc or more but less than 100 seconds / 100cc. D: The increase in the Gurley value is 100 seconds / 100cc or more.

[0169] <Aging and Conditioning of Secondary Batteries> Prior to measuring the internal resistance described below, the lithium-ion secondary batteries prepared in the examples and comparative examples were left standing at 25°C for 5 hours after electrolyte injection. Next, they were charged to a cell voltage of 3.65V using a constant current method at 25°C and 0.2C, and then aged at 60°C for 12 hours. Then, they were discharged to a cell voltage of 3.00V using a constant current method at 25°C and 0.2C. After that, CC-CV charging (upper limit cell voltage 4.20V) was performed using a constant current method at 0.2C, and CC discharge was performed to 3.00V using a constant current method at 0.2C. This charging and discharging at 0.2C was repeated three times. <Internal Resistance of Electrochemical Elements (Secondary Batteries)> Secondary batteries were charged to 50% of their State of Charge (SOC) at 1C (C is a value expressed as rated capacity (mA) / 1h (hour)) in a 25°C atmosphere. Then, charging and discharging were performed for 15 seconds at 0.5C, 1.0C, 3.0C, and 6.0C, centered around 50% SOC, for 15 seconds each. In each case (charging and discharging), the battery voltage after 0.1 seconds was plotted against the current value, and the slope was determined as the IV resistance (Ω) (IV resistance during charging and IV resistance during discharging). The obtained IV resistance values ​​(Ω) were evaluated according to the following criteria. A smaller IV resistance value indicates lower internal resistance and lower DC resistance. A: IV resistance of 5Ω or less B: IV resistance greater than 5Ω and 6Ω or less C: IV resistance greater than 6Ω and 7.5Ω or less D: IV resistance greater than 7.5Ω

[0170] (Example 1) <Preparation of binder> 70 parts of deionized water, 0.15 parts of sodium lauryl sulfate (Kao Chemical Co., Ltd., "Emal® 2F") as an emulsifier, and 0.5 parts of ammonium persulfate as a polymerization initiator were supplied to a reactor equipped with a stirrer, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Meanwhile, in a separate container, 50 parts of deionized water, 0.5 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate, 2 parts of methacrylic acid, 2 parts of acrylonitrile, 1 part of allyl methacrylate, and 1 part of allyl glycidyl ether were mixed to prepare a monomer composition. The obtained monomer composition was continuously added to the reactor equipped with a stirrer over 4 hours to carry out polymerization. The reaction was carried out at 60°C during the addition. After the addition was completed, the mixture was stirred at 70°C for 3 hours before the reaction was terminated to obtain a binder. The obtained particles had a volume-based median diameter of 0.25 μm and a glass transition temperature of -40°C.

[0171] <Production of particulate polymer> (1) Preparation of monomer composition for core particles A monomer composition for core particles was prepared by mixing 40.0 parts of styrene as an aromatic vinyl monomer unit, 58.0 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 2.0 parts of methacrylic acid as a carboxyl group-containing monomer. (2) Preparation of aqueous solution An aqueous solution was prepared by adding 1.0 part of polyvinyl alcohol as a suspension stabilizer to 700 parts of ion-exchanged water prepared at 60°C, stirring for 2 hours, and dissolving at 200 rpm. (3) Formation of droplets Polymers (core particles) that will become the core of the particulate polymer were prepared by suspension polymerization. Specifically, the above monomer composition was added to the aqueous solution, and after further stirring, 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, product name "Perbutyl O") as a polymerization initiator was added to obtain a mixture. The resulting mixture was subjected to high-shear stirring at a rotational speed of 12,000 rpm for 50 seconds using an in-line emulsifying disperser (manufactured by Taiheiyo Kiko Co., Ltd., product name "Cavitron") to form droplets of the monomer composition. (4) Polymerization The droplets of the monomer composition prepared above were placed in a reactor and the temperature was raised to 90°C for 5 hours to carry out the polymerization reaction. Cooling was started when the reaction conversion rate reached 99.5% or more. The obtained core particles had a glass transition temperature of 0°C. (5) Shell formation reaction process The aqueous dispersion of the core particles obtained by the suspension polymerization above was made to a solid content concentration of 15%. 2.0 parts by mass of trimethylolmelamine as a shell-forming compound was added to 98 parts by mass of core particles. The system was raised to 70°C for 6 hours to carry out the polymerization reaction, and then cooled. An aqueous solution of sodium hydroxide was added as a pH adjusting agent to make the pH 8.5 to obtain an aqueous dispersion containing particulate polymer having a core-shell structure. The pH of the aqueous dispersion was measured according to the above procedure, using the aqueous dispersion as the functional layer composition.

[0172] <Preparation of Slurry Composition> 70 parts of alumina (Sumitomo Chemical Co., Ltd., "AKP3000", median diameter by volume: 0.7 μm) as heat-resistant fine particles were added to 0.5 parts of sodium polyacrylate as a water-soluble polymer. Ion-exchanged water was added to achieve a solid content concentration of 55%, and the mixture was mixed using a ball mill to obtain the slurry before mixing. Furthermore, 25 parts of the particulate polymer having a core-shell structure obtained above, 5.0 parts of binder (particulate polymer: binder = 100:20 (by mass)), 1.5 parts of carboxymethylcellulose as a thickener, and 0.2 parts of sodium dodecylbenzenesulfonate (Kao Chemical Co., Ltd., "Neoperex G-15") as a dispersant were added to the 70 parts of heat-resistant fine particles. The mixture was mixed to achieve a solid content concentration of 40% to obtain the slurry composition.

[0173] <Preparation of Separators with Functional Layers> A polyethylene microporous membrane (thickness: 12 μm) was prepared as a separator substrate. The slurry composition obtained above was applied to one side of the prepared separator substrate by bar coating. The coating was dried at 50°C for 5 minutes. The same procedure was then performed on the other side of the separator substrate to prepare separators with functional layers, each having a heat-resistant fine particle layer with a thickness of 2.0 μm on both sides of the separator substrate. Various measurements and evaluations were performed on the obtained separators with functional layers according to the above procedure. The results are shown in Table 1.

[0174] <Fabrication of the positive electrode> LiCoO as the positive electrode active material ２100 parts of (volume average particle size: 12 μm), 2 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., "HS-100") as a conductive material, 2 parts of polyvinylidene fluoride (manufactured by Kureha Corporation, "#7208") as a binder for the positive electrode composite layer (based on solid content), and N-methylpyrrolidone as a solvent were mixed to obtain a total solid content concentration of 70%. These were mixed using a planetary mixer to prepare a slurry composition for the positive electrode. The slurry composition for the positive electrode was applied using a comma coater to a 20 μm thick aluminum foil to be used as a current collector, so that the film thickness after drying would be approximately 150 μm, and then dried. This drying was performed by transporting the aluminum foil in a 60°C oven at a speed of 0.5 m / min for 2 minutes. After that, it was heat-treated at 120°C for 2 minutes to obtain the positive electrode raw material before pressing. This cathode raw material before pressing was rolled in a roll press to obtain a pressed cathode having a cathode composite layer (thickness: 60 μm).

[0175] <Preparation of the negative electrode> In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 parts of sodium dodecylbenzenesulfonate as a dispersant, 150 parts of deionized water, and 0.5 parts of potassium persulfate as a polymerization initiator were added and thoroughly stirred. The mixture was then heated to 50°C to start polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing a binder for the negative electrode composite layer (SBR). A 5% aqueous sodium hydroxide solution was added to this mixture containing the binder for the negative electrode composite layer to adjust the pH to 8, and unreacted monomers were removed by heated vacuum distillation. After that, the mixture was cooled to below 30°C to obtain an aqueous dispersion containing the desired binder for the negative electrode composite layer. 80 parts of artificial graphite (volume average particle size: 15.6 μm) as negative electrode active material (1) and 16 parts of silicon-based active material SiOx (volume average particle size: 4.9 μm) as negative electrode active material (2) were blended together. 2.5 parts of a 2% aqueous solution of carboxymethylcellulose sodium salt (manufactured by Nippon Paper Industries, "MAC350HC") as a viscosity modifier, in terms of solid content, and deionized water were added to adjust the solid content to 68%, and the mixture was further mixed at 25°C for 60 minutes. The solid content was further adjusted to 62% with deionized water, and the mixture was further mixed at 25°C for 15 minutes to obtain a mixed solution. To this mixed solution, 1.5 parts of an aqueous dispersion containing the above-mentioned binder for the negative electrode composite layer, in terms of solid content, and deionized water were added to adjust the final solid content to 52%, and the mixture was further mixed for 10 minutes to obtain a mixed solution. This mixed solution was defoamed under reduced pressure to obtain a smooth negative electrode slurry composition. The above-mentioned slurry composition for the negative electrode was applied using a comma coater to a copper foil with a thickness of 20 μm, which was to be used as a current collector, so that the film thickness after drying would be approximately 150 μm, and then dried. This drying was carried out by transporting the copper foil in a 60°C oven at a speed of 0.5 m / min for 2 minutes. After that, it was heat-treated at 120°C for 2 minutes to obtain a negative electrode base roll before pressing. This negative electrode base roll before pressing was rolled using a roll press to obtain a pressed negative electrode having a negative electrode composite layer (thickness: 80 μm).

[0176] <Fabrication of Lithium-Ion Secondary Battery> As the battery exterior, an aluminum packaging exterior was prepared. The positive electrode obtained in the above process was cut out into a 4×4 cm square and arranged so that the surface on the current collector side was in contact with the aluminum packaging exterior. On the surface of the positive electrode active material layer of the positive electrode, the square separator obtained in the above process was arranged. Further, the pressed negative electrode obtained in the above process was cut out into a 4.2×4.2 cm square, and this was arranged on the separator so that the surface on the negative electrode active material layer side faced the separator. After pressing this battery at 50°C and 1 MPa to form a flat body, it was wrapped with the aluminum packaging exterior as the battery exterior, and an electrolytic solution [solvent: ethylene carbonate / ethyl methyl carbonate / (weight ratio)= ６ 3 / 7, vinylene carbonate 2.0 vol%, electrolyte: LiPF with a concentration of 1 mol)] was injected so that no air remained. Then, the opening of the aluminum packaging exterior was heat-sealed at a temperature of 150°C to close it, and a lithium-ion secondary battery as an electrochemical device was fabricated. The obtained secondary battery was evaluated according to the above. The results are shown in Table 1.

[0177] (Example 2) <Manufacture of particulate polymer> Various operations, measurements, and evaluations similar to those in Example 1 were carried out except that the blending amount of polyvinyl alcohol blended in "Preparation of aqueous solution" was changed from 1.0 part by mass to 5.0 parts by mass. The results are shown in Table 1.

[0178] (Example 3) <Manufacture of particulate polymer> Various operations, measurements, and evaluations similar to those in Example 1 were carried out except that the blending amount of polyvinyl alcohol blended in "Preparation of aqueous solution" was changed from 1.0 part by mass to 1.8 parts by mass. The results are shown in Table 1.

[0179] (Example 4) <Manufacture of particulate polymer> The blending amount of polyvinyl alcohol blended in "Preparation of aqueous solution" was changed from 1.0 part by mass to 0.6 part by mass. Also, the shear stirring time using an in-line emulsifying disperser in "Formation of droplets" was changed from 50 seconds to 38 seconds. Various operations, measurements, and evaluations similar to those in Example l were carried out except for these points. The results are shown in Table 1.

[0180] (Example 5) <Production of particulate polymer> In "(2) Preparation of aqueous solution," the amount of polyvinyl alcohol added was changed from 1.0 part by mass to 0.4 parts by mass. Also, in "(3) Formation of droplets," the shear stirring time using the in-line emulsifier / disperser was changed from 50 seconds to 27 seconds. Except for these points, the same operations, measurements, and evaluations as in Example 1 were performed. The results are shown in Table 1.

[0181] (Examples 6-11) <Production of particulate polymer> The blending ratio of trimethylolmelamine, which is used as a shell-forming compound in the "(5) Shell formation reaction step," was changed so that the mass ratio of core particles to shells was as shown in Table 1. Except for this point, the same operations, measurements, and evaluations as in Example 1 were carried out. The results are shown in Table 1.

[0182] (Examples 12-15) <Production of particulate polymer> The pH in the "shell formation reaction step" was adjusted to the pH shown in Table 1. Except for this point, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0183] (Example 16) <Production of particulate polymer> In "(2) Preparation of aqueous solution", 0.2 parts by mass of sodium dodecylbenzenesulfonate was added as a dispersant to polyvinyl alcohol. Except for this point, the same operations, measurements, and evaluations as in Example 1 were carried out. The results are shown in Table 1.

[0184] (Example 17) <Production of particulate polymer> In "(2) Preparation of aqueous solution", 0.4 parts by mass of sodium dodecylbenzenesulfonate was added as a dispersant to polyvinyl alcohol. Except for this point, the same operations, measurements, and evaluations as in Example 1 were carried out. The results are shown in Table 1.

[0185] (Example 18) <Production of particulate polymer> In "(2) Preparation of aqueous solution", 0.9 parts by mass of sodium dodecylbenzenesulfonate was added as a dispersant to polyvinyl alcohol. Except for this point, the same operations, measurements, and evaluations as in Example 1 were carried out. The results are shown in Table 1.

[0186] (Examples 19-31) <Production of particulate polymer> In "(1) Preparation of monomer composition for core particles," the composition of the monomer composition for core particles was changed as shown in Table 2. Except for this point, various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2. In Examples 24, 29-31, ethylene glycol dimethacrylate was added as the crosslinkable monomer unit.

[0187] (Comparative Example 1) 70 parts of deionized water, 0.15 parts of sodium lauryl sulfate (Kao Chemical Co., Ltd., "Emal® 2F") as an emulsifier, and 0.5 parts of ammonium persulfate as a polymerization initiator were supplied to a reactor equipped with a stirrer, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Meanwhile, in a separate container, 50 parts of deionized water, 0.2 parts of sodium dodecylbenzenesulfonate as a dispersant, 40.0 parts of styrene, 58.0 parts of 2-ethylhexyl acrylate, and 2.0 parts of methacrylic acid were mixed to prepare a monomer composition. The obtained monomer composition was continuously added to the above-mentioned reactor equipped with a stirrer over 4 hours to carry out polymerization. During the addition, the reaction was carried out at 60°C. After the addition was completed, the reaction was further stirred at 70°C for 3 hours before ending, and core particles were obtained. The obtained particles had a volume-based median diameter of 0.5 μm and a glass transition temperature of 0°C. Except for the points mentioned above, the shell was formed in the same manner as in Example 1 to obtain a particulate polymer having a core-shell structure, and various operations, measurements, and evaluations were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0188] (Comparative Example 2) Using 38 parts by mass of the core particles prepared in Example 5, 317 g of a dispersion with a solid content of 12% was prepared. To this, 40.0 parts of styrene, 58.0 parts of 2-ethylhexyl acrylate, and 2.0 parts of methacrylic acid were mixed to prepare a mixture. The obtained mixture was stirred at 40°C for 72 hours. To the stirred mixture, 2.0 parts of t-butyl peroxy-2-ethylhexanoate (manufactured by NOF Corporation, product name "Perbutyl O") was added as a polymerization initiator. The obtained mixture was stirred at high shear for 50 seconds at a rotation speed of 12,000 rpm using an in-line emulsifying disperser (manufactured by Taiheiyo Kiko Co., Ltd., product name "Cavitron") to obtain core particles. The obtained particles had a volume-based median diameter of 23 μm and a glass transition temperature of 0°C. Except for these points, various operations, measurements, and evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0189] (Comparative Examples 3 and 4) <Production of particulate polymer> The blending ratio of trimethylolmelamine, which is used as a shell-forming compound in the "shell-forming reaction step," was changed so that the mass ratio of core particles to shells was as shown in Table 2. Except for this point, the same operations, measurements, and evaluations as in Example 1 were carried out. The results are shown in Table 2.

[0190] (Comparative Example 5) <Production of particulate polymer> In the "shell formation reaction step," 2 parts by mass of methyl methacrylate were added instead of trimethylolmelamine, and 2.0 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride were added as an initiator. Except for these points, the same operations, measurements, and evaluations as in Example 1 were carried out. The results are shown in Table 2.

[0191] In Tables 1 and 2, "Tg" indicates the glass transition temperature.

[0192]

[0193]

[0194] Tables 1 and 2 show that a functional layer composition containing a particulate polymer having a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, and whose Raman spectrum satisfies predetermined characteristics, makes it possible to form an electrochemical element functional layer with excellent room-temperature adhesive strength and blocking resistance, and furthermore, it is possible to reduce the internal resistance of the resulting electrochemical element. In Comparative Examples 1 and 2, where the volume-based median diameter was outside the above range, and Comparative Examples 3 to 5, where the Raman spectral characteristics did not have the predetermined characteristics, it was not possible to simultaneously achieve the effect of improving the room-temperature adhesive strength and blocking resistance of the functional layer, as well as the effect of reducing the internal resistance of the resulting electrochemical element.

[0195] According to the present invention, it is possible to form an electrochemical element functional layer that has excellent adhesive strength at room temperature and blocking resistance, and furthermore, it is possible to provide a composition for an electrochemical element functional layer that can reduce the internal resistance of an electrochemical element equipped with such an electrochemical element functional layer.

[0196] 1. Particulate polymer 1' Particulate polymer in a reference example 2. Adhered material 3. Substrate 4. Shell crushing apex 4' Lateral shell rupture site

Claims

1. A composition for an electrochemical element functional layer comprising a particulate polymer, wherein the particulate polymer is a particulate polymer having a core-shell structure, comprising core particles having a shell on its surface, wherein the particulate polymer has a volume-based median diameter of 1.0 μm or more and 20.0 μm or less, and when the particulate polymer before shell formation is measured by Raman spectroscopy, the wavenumber is 996 cm⁻¹. －１ 1005cm －１ The intensity of the peak detected within the following range is P1, and the wavenumber is 678 cm⁻¹. －１ 684 cm －１ The intensity of the peak detected within the following range is defined as P2, and furthermore, when the particulate polymer having the core-shell structure is subjected to Raman spectroscopy, the wavenumber is 678 cm⁻¹. －１ 684 cm －１ A composition for an electrochemical element functional layer, wherein the intensity of the peak detected within the following range is denoted as P3, and the value given by the following formula (1) is 0.001% or more and 200% or less: (P3 - P2) / P1 × 100 ... (1) 2. The electrochemical element functional layer composition according to claim 1, wherein the pH is 5.0 or higher and 11.0 or lower.

3. The electrochemical element functional layer composition according to claim 1, wherein the particle size distribution of the particulate polymer having the core-shell structure is 5 or less.

4. The electrochemical element functional layer composition according to claim 1, wherein the glass transition temperature of the particulate polymer having the core-shell structure is -65°C or higher and 60°C or lower.

5. The electrochemical element functional layer composition according to claim 1, wherein the ratio of core particles to shells in the particulate polymer is in the range of 99.95:0.05 to 50:50 by mass.

6. The electrochemical element functional layer composition according to claim 1, wherein the core particles contain 5% by mass or more and 60% by mass or less of aromatic monomer units.

7. The electrochemical element functional layer composition according to claim 1, wherein the core particles contain 40% by mass or more and 90% by mass or less of ester bond-containing monomer units.

8. The electrochemical element functional layer composition according to claim 1, wherein the particulate polymer before shell formation contains carboxyl group-containing monomer units or hydroxyl group-containing monomer units.

9. A functional layer for an electrochemical element formed using the composition for an electrochemical element functional layer described in any one of claims 1 to 8.

10. A laminate for an electrochemical element comprising a substrate and a functional layer for an electrochemical element formed on the substrate, wherein the functional layer for an electrochemical element is the functional layer for an electrochemical element described in claim 9.

11. An electrochemical element comprising the laminate for an electrochemical element described in claim 10.

12. A method for producing a composition for an electrochemical device functional layer containing a particulate polymer having a core-shell structure, comprising a reaction step of obtaining a solution containing core particles and a shell-forming compound and forming a shell on the surface of the core particles, wherein, when the core particles at the start of the reaction step are measured by Raman spectrum, the intensity of the peak detected in the range of 996 cm －１ or more and 1005 cm －１ or less is defined as P1, and the intensity of the peak detected in the range of 678 cm －１ or more and 684 cm －１ or less is defined as P2. Further, when the particulate polymer having the formed core-shell structure is measured by Raman spectrum at the end of the reaction step, the intensity of the peak detected in the range of 678 cm －１ or more and 684 cm －１ or less is defined as P3, and a method for producing a composition for an electrochemical device functional layer is provided such that the value I given by the following formula (1) is 0.001% or more and 200% or less. I(%) = (P3 - P2) / P1 × 100... (1)

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