Hollow organic particle for electrochemical element functional layer, composition for electrochemical element functional layer, functional layer for electrochemical element, and electrochemical element

Abstract

A hollow organic particle for an electrochemical element functional layer according to the present invention which comprises a shell part and a hollow part surrounded by the shell part, said hollow organic particle for an electrochemical element functional layer being characterized in that the shell part has at least one through-hole communicating with the hollow part, and that the volume-average particle diameter is 0.8μm or more.

Description

Hollow organic particles for the functional layer of an electrochemical element, composition for the functional layer of an electrochemical element, functional layer for an electrochemical element, electrochemical element

[0001] The present invention relates to hollow organic particles for the functional layer of an electrochemical element, a composition for the functional layer of an electrochemical element, a functional layer for an electrochemical element, and an electrochemical element.

[0002] Electrochemical elements such as lithium-ion secondary batteries, electric double-layer capacitors, and lithium-ion capacitors are small, lightweight, have high energy density, and can be repeatedly charged and discharged, making them suitable for a wide range of applications. Generally, electrochemical elements consist of multiple electrodes, element components such as separators that isolate these electrodes to prevent internal short circuits, and an electrolyte.

[0003] As element components of an electrochemical element, for example, a component is used that includes a functional layer comprising a binder capable of providing adhesiveness and optionally containing particles (hereinafter referred to as "functional particles") that are blended to give the element component a desired function. Specifically, as a separator for an electrochemical element, a separator is used that comprises an adhesive layer containing a binder or a porous film layer containing a binder and non-conductive particles as functional particles on a separator substrate. Furthermore, as an electrode for an electrochemical element, an electrode is used that comprises an electrode composite layer containing a binder and electrode active material particles as functional particles on a current collector, or an electrode substrate that has an electrode composite layer on a current collector and further comprises the aforementioned adhesive layer or porous film layer.

[0004] For example, Patent Document 1 describes a separator for an energy storage device having a porous substrate layer (A) and a porous layer (B) containing an inorganic filler (b-2) and a resin binder (b-1), wherein the resin binder (b-1) contains two or more types of resin binders, the surface softening temperature of the porous layer (B) is in the range of 30 to 60°C, and the cross-sectional area of ​​the porous layer (B) is 0.01 μm². ２Disclosed is a separator for an electricity storage device, wherein, among the pores described above, the proportion of pores satisfying that an angle θ formed by the major axis of each pore and an axis parallel to the interface between said porous substrate layer (A) and the porous layer (B) is not less than 60 degrees and not more than 120 degrees is 30% or more. Patent Document 1 discloses that the separator for an electricity storage device is excellent in adhesion to an electrode, adhesive strength to the porous substrate layer, and binding strength of an inorganic filler, does not cause stickiness, is excellent in handleability, and further exhibits good cycle characteristics.

[0005] Japanese Unexamined Patent Publication No. 2016-72197

[0006] In recent years, along with the diversification of applications of electrochemical devices such as lithium ion secondary batteries, there has been an increasing demand for suppressing an increase in internal resistance. However, the above-mentioned conventional technique still has room for further improvement in terms of suppressing an increase in the internal resistance of electrochemical devices.

[0007] Accordingly, an object of the present invention is to provide a new technology related to an electrochemical device that can suppress an increase in the internal resistance of the electrochemical device.

[0008] The present inventors conducted intensive studies for the purpose of solving the above problems. The present inventors have newly found that when an electrochemical device is charged and discharged, the electrolyte solution may flow out from a functional layer provided in a member (separator, electrode, etc.) of the electrochemical device, which may cause an increase in the internal resistance of the electrochemical device. As a result of further studies, the present inventors have newly found that hollow organic particles having predetermined properties can suppress the outflow of the electrolyte solution from the functional layer and thereby suppress an increase in the internal resistance of the electrochemical device, and thus completed the present invention.

[0009] That is, the present invention aims to advantageously solve the above problems. The present invention provides [1] hollow organic particles for a functional layer of an electrochemical element, comprising a shell part and a hollow part surrounded by the shell part, wherein the shell part has at least one through hole communicating with the hollow part, and a volume-average particle diameter of 0.8 μm or more. The hollow organic particles, in which the shell part has at least one through hole communicating with the hollow part and the volume-average particle diameter is not less than the above lower limit, can suppress an increase in internal resistance of an electrochemical element including a functional layer containing said hollow organic particles. In the present invention, the fact that the shell part of the hollow organic particles for a functional layer of an electrochemical element has at least one through hole can be confirmed by the method described in the Examples. Further, in the present invention, the volume-average particle diameter of the hollow organic particles for a functional layer of an electrochemical element can be measured by the method described in the Examples.

[0010] [2] In the hollow organic particles for a functional layer of an electrochemical element according to the above [1], the volume-average particle diameter is preferably 20 μm or less. When the volume-average particle diameter is not more than the above upper limit, it is possible to suppress the decrease in peel strength of the obtained functional layer and the cycle characteristics of the obtained electrochemical element.

[0011] [3] The hollow organic particles for a functional layer of an electrochemical element according to the above [1] or [2] preferably have a porosity of 40% or more and 90% or less. When the porosity is not less than the above lower limit, the increase in internal resistance of the electrochemical element can be further suppressed. Further, when the porosity is not more than the above upper limit, the breaking strength of the hollow organic particles for a functional layer of an electrochemical element is improved, and the cycle characteristics of the electrochemical element can be improved. In the present invention, the porosity of the hollow organic particles for a functional layer of an electrochemical element can be measured by the method described in the Examples.

[0012] [4] Preferably, any of the hollow organic particles for the electrochemical element functional layer described in [1] to [3] above have a fracture strength of 5 MPa or more. If the fracture strength is equal to or greater than the lower limit, the hollow organic particles for the electrochemical element functional layer can function well as a buffer, and the contact between functional particles can be improved to further suppress the increase in the internal resistance of the electrochemical element. In this invention, the fracture strength of the hollow organic particles for the electrochemical element functional layer can be measured by the method described in the examples.

[0013] [5] In any of the hollow organic particles for the functional layer of an electrochemical element according to [1] to [4] above, the shell portion is preferably made of a polymer having a glass transition temperature of 50°C or higher. If the glass transition temperature of the shell portion is made of a polymer that is equal to or greater than the above lower limit, the increase in the internal resistance of the electrochemical element can be further suppressed. In this invention, the glass transition temperature of the polymer constituting the shell portion can be measured by the method described in the examples.

[0014] [6] In any of the hollow organic particles for the functional layer of an electrochemical element described in [1] to [5] above, it is preferable that the shell portion is made of a polymer containing at least one monomer unit selected from the group consisting of epoxy group-containing monomer units, crosslinkable monomer units other than epoxy group-containing monomer units, hydroxyl group-containing monomer units, aromatic monovinyl monomer units, and conjugated diene monomer units. If the hollow organic particles for the functional layer of an electrochemical element are made of a polymer containing the above-described predetermined monomer units, the increase in the internal resistance of the electrochemical element can be further suppressed.

[0015] Furthermore, this invention aims to advantageously solve the above problems, and the present invention is [7] a composition for an electrochemical element functional layer containing any of the hollow organic particles for electrochemical element functional layers described in [1] to [6] above. By using the above composition for an electrochemical element functional layer containing hollow organic particles for electrochemical element functional layers, an electrochemical element functional layer capable of suppressing an increase in the internal resistance of the electrochemical element can be easily obtained.

[0016] [8] The electrochemical element functional layer composition described in [7] above preferably further contains functional particles. By including functional particles, a functional layer can be formed that can perform functions attributable to the functional particles and suppress an increase in the internal resistance of the electrochemical element.

[0017] Furthermore, this invention aims to advantageously solve the above problems, and the present invention is a functional layer for an electrochemical element formed using the electrochemical element functional layer composition described in [7] or [8] above. A functional layer formed from the above-described electrochemical element functional layer composition can suppress an increase in the internal resistance of an electrochemical element equipped with the functional layer.

[0018] Furthermore, this invention aims to advantageously solve the above problems, and the present invention is an electrochemical element comprising the functional layer for electrochemical elements described in [9] above. In an electrochemical element comprising the functional layer described above, the increase in internal resistance is suppressed.

[0019] According to the present invention, it is possible to provide hollow organic particles for an electrochemical element functional layer that can form a functional layer for an electrochemical element that can suppress an increase in the internal resistance of the electrochemical element. Furthermore, according to the present invention, it is possible to provide a composition for an electrochemical element functional layer that can form a functional layer for an electrochemical element that can suppress an increase in the internal resistance of the electrochemical element. Furthermore, according to the present invention, it is possible to provide a functional layer for an electrochemical element that can suppress an increase in the internal resistance of the electrochemical element. And according to the present invention, it is possible to provide an electrochemical element in which an increase in internal resistance is suppressed.

[0020] Embodiments of the present invention will be described in detail below. Herein, the hollow organic particles for the functional layer of the electrochemical element of the present invention (hereinafter also simply referred to as "hollow organic particles") are used in the manufacture of the functional layer for the electrochemical element of the present invention (hereinafter also simply referred to as "functional layer"), and can be used, for example, in the preparation of the composition for the functional layer of the electrochemical element of the present invention (hereinafter also simply referred to as "composition for the functional layer"). The functional layer for the electrochemical element of the present invention is formed using the composition for the functional layer of the electrochemical element of the present invention, and the electrochemical element of the present invention is equipped with the functional layer for the electrochemical element of the present invention.

[0021] In this invention, a functional layer containing electrode active material particles as functional particles is referred to as an "electrode composite layer," a functional layer that does not contain electrode active material particles but contains non-conductive particles as functional particles is referred to as a "porous film layer," a functional layer that does not contain either electrode active material particles or non-conductive particles but contains a binder described later and contributes to the adhesion between components of an electrochemical element is referred to as an "adhesive layer," and a functional layer that does not belong to any of these is referred to as an "other functional layer."

[0022] (Hollow Organic Particles for Functional Layers of Electrochemical Elements) The hollow organic particles of the present invention are organic particles having a shell portion (outer shell) and a hollow portion surrounded by the shell portion, wherein the shell portion has at least one through-hole communicating with the hollow portion, and the volume average particle diameter is 0.8 μm or more. Furthermore, in the present invention, by incorporating the above-mentioned hollow organic particles into the functional layer of the component of an electrochemical element, it is possible to suppress the increase in the internal resistance of the electrochemical element.

[0023] The reason is not entirely clear, but it is presumed to be as follows: In electrochemical elements such as lithium-ion secondary batteries, components such as electrodes and separators are usually impregnated with electrolyte, so the gaps between particles that may be contained in the functional layer of these components are usually filled with electrolyte. However, as the electrochemical element charges and discharges, the electrolyte is discharged from the functional layer, resulting in a state of electrolyte depletion. As a result, it is presumed that the conductivity within the functional layer decreases and the internal resistance of the electrochemical element increases. Therefore, by having a shell portion with at least one through-hole and including hollow organic particles with a volume-average particle diameter of a predetermined value or larger in the functional layer, a predetermined amount of electrolyte can flow into and be stored inside the hollow organic particles through the through-hole. As a result, it is presumed that the occurrence of electrolyte depletion in the functional layer due to the charging and discharging of the electrochemical element is suppressed, and the increase in the internal resistance of the electrochemical element is suppressed.

[0024] <Shell portion> The shell portion constitutes the outer shell of the hollow organic particle and has at least one through-hole communicating with the hollow portion. The shell portion may be dense or have a porous structure. The shell portion is made of a polymer.

[0025] The through-holes in the shell are holes that connect the external space outside the shell to the hollow part, and when hollow organic particles are incorporated into the functional layer of the electrochemical element and the functional layer comes into contact with the electrolyte, the electrolyte passes through these holes. The number, shape, and size (diameter, etc.) of the through-holes are not particularly limited, as long as the electrolyte can pass through or be held in the hollow part. For example, the through-holes may be micro-pores or large openings. Furthermore, if the shell has a porous structure, multiple minute spaces in the porous structure may connect to form through-holes that connect the external space outside the shell to the hollow part.

[0026] <Hollow Section> The hollow section is a cavity-like space clearly distinguishable from the shell section. The hollow section has the function of holding the electrolyte that flows in through the through-holes within the functional layer of the electrochemical element. Here, if the shell section has a porous structure, the hollow section has a size that is clearly distinguishable from the numerous minute spaces uniformly dispersed within the porous structure. For example, it is preferable that the hollow section has a diameter of three times or more the thickness of the shell section. The hollow section may also be filled with a gas such as air, or it may be in a vacuum or reduced pressure state.

[0027] A hollow organic particle may have one or more hollow sections, but it is preferable to have one hollow section in order to maintain a good balance between the porosity and fracture strength of the hollow organic particle. Here, if a hollow organic particle has two or more hollow sections, the partition separating adjacent hollow sections may be porous or dense, but it is preferable that it be dense.

[0028] The hollow portion of a hollow organic particle can be confirmed, for example, by SEM observation of the particle cross-section or by TEM observation of the particle itself.

[0029] <Volume-average particle diameter> The hollow organic particles of the present invention are required to have a volume-average particle diameter of 0.8 μm or more. By setting the volume-average particle diameter to 0.8 μm or more, the liquid retention capacity of the electrolyte can be sufficiently ensured, and the increase in the internal resistance of the electrochemical element can be suppressed. From the viewpoint of further suppressing the increase in the internal resistance of the electrochemical element, the volume-average particle diameter of the hollow organic particles is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. On the other hand, from the viewpoint of suppressing the reduction in the peel strength of the functional layer and the cycle characteristics of the electrochemical element, the volume-average particle diameter of the hollow organic particles is preferably 20 μm or less, and more preferably 10 μm or less. The volume-average particle diameter can be adjusted, for example, by changing the amount of reaction-promoting additive used in the preparation of the hollow organic particles described later.

[0030] <Porrosion> The porosity of the hollow organic particles of the present invention is preferably 40% or more, more preferably 50% or more, preferably 90% or less, and more preferably 80% or less. If the porosity is above the lower limit, the liquid retention capacity of the electrolyte can be sufficiently ensured, and the increase in the internal resistance of the electrochemical element can be further suppressed. If the porosity is below the upper limit, the fracture strength of the hollow organic particles is improved, and the cycle characteristics of the electrochemical element can be improved. The porosity can be adjusted, for example, by changing the composition and amount of the shell portion.

[0031] <Breaking Strength> The breaking strength of the hollow organic particles of the present invention is preferably 5 MPa or more, more preferably 10 MPa or more, more preferably 30 MPa or less, and more preferably 15 MPa or less. If the breaking strength is above the lower limit, the hollow organic particles for the functional layer of the electrochemical element can function well as a buffer, and the contact between the functional particles can be improved, further suppressing the increase in the internal resistance of the electrochemical element. If the breaking strength is below the upper limit, the binding strength can be improved. The breaking strength can be adjusted, for example, by changing the amount of crosslinkable monomer used in the production of the hollow organic particles (the degree of crosslinking of the polymer constituting the hollow organic particles).

[0032] <Glass Transition Temperature> The glass transition temperature of the polymer constituting the shell portion of the hollow organic particles of the present invention is preferably 50°C or higher, more preferably 75°C or higher, even more preferably 100°C or higher, even more preferably 150°C or higher, and preferably 400°C or lower, more preferably 350°C or lower, even more preferably 300°C or lower, and even more preferably 250°C or lower. If the glass transition temperature is above the lower limit, the increase in the internal resistance of the electrochemical element can be further suppressed. Also, if the glass transition temperature is below the upper limit, the binding strength can be improved. The glass transition temperature can be adjusted, for example, by changing the type and / or amount of monomer used in the production of the shell portion of the hollow organic particles.

[0033] <Composition> The above shell portion is not particularly limited, and polymers of any composition can be used. In particular, from the viewpoint of further suppressing the increase in the internal resistance of the electrochemical element, it is preferable that the hollow organic particles consist of a polymer containing at least one monomer unit selected from the group consisting of epoxy group-containing monomer units, crosslinkable monomer units other than epoxy group-containing monomer units, hydroxyl group-containing monomer units, and non-crosslinkable monomer units other than hydroxyl group-containing monomer units; it is more preferable that the polymer consists of at least one monomer unit selected from the group consisting of crosslinkable monomer units other than epoxy group-containing monomer units, hydroxyl group-containing monomer units, aromatic monovinyl monomer units, and conjugated diene monomer units; it is even more preferable that the polymer consists of a polymer containing crosslinkable monomer units other than epoxy group-containing monomer units, hydroxyl group-containing monomer units, and aromatic monovinyl monomer units; it is even more preferable that the polymer consists of a polymer containing crosslinkable monomer units other than epoxy group-containing monomer units, hydroxyl group-containing monomer units, and aromatic monovinyl monomer units. It is particularly preferable that the polymer consists of crosslinkable monomer units other than epoxy group-containing monomer units, and aromatic monovinyl monomer units.

[0034] [Epoxy Group-Containing Monomer Units] Examples of epoxy group-containing monomers that can form epoxy group-containing monomer units include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether, and glycidyl (2-butenyl) ether; and glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexenecarboxylic acid, and glycidyl ester of 4-methyl-3-cyclohexenecarboxylic acid. These may be used individually or in combination of two or more in any ratio.

[0035] The content of epoxy group-containing monomer units in the polymer is preferably 10% by mass or more, more preferably 20% by mass or more, and preferably 95% by mass or less, and more preferably 90% by mass or less, based on the total amount of monomer units as 100% by mass. If the content of epoxy group-containing monomer units in the polymer is above the lower limit, the liquid retention space can be expanded. Furthermore, if the content of epoxy group-containing monomer units in the polymer is below the upper limit, the binding strength can be improved.

[0036] [Crossable monomer units other than epoxy group-containing monomer units] Monomers that can form cross-linkable monomer units other than epoxy group-containing monomer units (cross-linkable monomers other than epoxy group-containing monomers) are not particularly limited and include polyfunctional monomers having two or more ethylenically unsaturated double bonds in one molecule. Examples of such polyfunctional monomers include divinyl compounds such as divinylbenzene, divinyldiphenyl, and divinylnaphthalene; difunctional (meth)acrylate compounds such as allyl (meth)acrylate, vinyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and pentaerythritol di(meth)acrylate; and trifunctional or more (meth)acrylate compounds such as trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol poly(meth)acrylate, and their ethoxylated derivatives. These may be used individually or in combination of two or more in any ratio. In particular, from the viewpoint of increasing fracture strength while suppressing an increase in the internal resistance of the electrochemical element, divinyl compounds, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tetra(meth)acrylate are preferred, divinylbenzene, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, and pentaerythritol tetraacrylate are more preferred, and divinylbenzene is even more preferred. In this invention, "(meth)acrylate" means acrylate and / or methacrylate.

[0037] The content of crosslinkable monomer units other than epoxy group-containing monomer units in the polymer is preferably 60% by mass or more, more preferably 70% by mass or more, and preferably 97% by mass or less, and more preferably 90% by mass or less, based on the total amount of monomer units as 100% by mass. If the content of crosslinkable monomer units other than epoxy group-containing monomer units in the polymer is above the lower limit, the fracture strength can be improved. Furthermore, if the content of crosslinkable monomer units other than epoxy group-containing monomer units in the polymer is below the upper limit, the binding strength can be improved.

[0038] [Total content ratio of epoxy group-containing monomer units and crosslinkable monomer units other than epoxy group-containing monomer units] The total content ratio of epoxy group-containing monomer units and crosslinkable monomer units other than epoxy group-containing monomer units in the polymer is preferably 60% by mass or more, more preferably 70% by mass or more, and preferably 97% by mass or less, and more preferably 90% by mass or less, based on the total amount of monomer units as 100% by mass.

[0039] [Hydroxyl group-containing monomer units] Hydroxyl group-containing monomers that can form hydroxyl group-containing monomer units include alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate (2-hydroxyethyl methacrylate), 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, di-2-hydroxypropyl itaconate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, and cyclohexanedimethanol mono(meth)acrylate; 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate; general formula: CH ２ =CR ａ -COO- (C ｑ H ２ｑ O) ｐ -H (where p is an integer from 2 to 9, q is an integer from 2 to 4, R ａ) represents a hydrogen atom or a methyl group. Esters of polyalkylene glycols represented by ) and (meth)acrylic acid; mono(meth)acrylic acid esters of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyl oxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyl oxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; mono(meth)aryl ethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, and (meth)allyl-6-hydroxyhexyl ether; diethylene glycol Examples include polyoxyalkylene glycol mono(meth)allyl ethers such as mono(meth)allyl ether and dipropylene glycol mono(meth)allyl ether; mono(meth)allyl ethers of halogen and hydroxy-substituted (poly)alkylene glycols such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether, and (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyhydric phenols such as eugenol and isoeugenol and their halogen-substituted derivatives; (meth)allyl thioethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl thioether and (meth)allyl-2-hydroxypropyl thioether; and amides having a hydroxyl group such as hydroxyethyl acrylamide and hydroxyethyl methacrylamide. These may be used individually or in combination of two or more in any ratio. In particular, 2-hydroxy-3-methacryloyloxypropyl acrylate is preferred from the viewpoint of further suppressing the increase in the internal resistance of the electrochemical element.In this invention, "(meth)allyl" means allyl and / or methallyl, "(meth)acryloyl" means acryloyl and / or methacryloyl, and "(meth)acrylic" means acrylic and / or methacrylic. In this invention, among hydroxyl group-containing monomers, those having epoxy groups or multiple ethylenically unsaturated double bonds are also considered hydroxyl group-containing monomers and are distinguished from epoxy group-containing monomers and other crosslinkable monomers.

[0040] The content of hydroxyl group-containing monomer units in the polymer is preferably 0.5% by mass or more, more preferably 10% by mass or more, preferably 30% by mass or less, and more preferably 28% by mass or less, based on the total amount of monomer units as 100% by mass. If the content of hydroxyl group-containing monomer units in the polymer is above the lower limit, the affinity for the electrolyte can be improved. Furthermore, if the content of hydroxyl group-containing monomer units in the polymer is below the upper limit, the stability in the slurry can be improved.

[0041] [Non-crosslinkable monomer units other than hydroxyl group-containing monomer units] Non-crosslinkable monomers that can form non-crosslinkable monomer units other than hydroxyl group-containing monomer units (hereinafter also simply referred to as "non-crosslinkable monomer units") are not particularly limited as long as they are non-crosslinkable monomer units that do not have hydroxyl groups, and include (meth)acrylate alkyl ester monomer units, acid group-containing monomer units, aromatic monovinyl monomer units, amino group-containing monomer units, thiol group-containing monomer units, monoolefin monomer units, isocyanate group-containing monomer units, conjugated diene monomer units, etc. These may be used individually or in combination of two or more types in any ratio.

[0042] The content of non-crosslinkable monomer units in the polymer is preferably 1% by mass or more, and preferably 25% by mass or less, based on the total amount of monomer units being 100% by mass. If the content of non-crosslinkable monomer units in the polymer is above the lower limit, the stability in the slurry can be improved. Furthermore, if the content of non-crosslinkable monomer units in the polymer is below the upper limit, the affinity for the electrolyte can be improved.

[0043] -(meth)acrylate alkyl ester monomer unit- Examples of (meth)acrylate alkyl ester monomers that can form (meth)acrylate alkyl ester monomer units include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate, etc. Examples of alkyl acrylates include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate, and other alkyl methacrylates. These may be used alone or in combination of two or more. Among these, at least one selected from butyl acrylate and methyl methacrylate is preferred.

[0044] The content of alkyl (meth)acrylate monomer units in the polymer is preferably 0.1% by mass or more, more preferably 10% by mass or more, preferably 80% by mass or less, and more preferably 70% by mass or less, when the total amount of repeating units contained in the polymer is taken as 100% by mass. If the content of alkyl (meth)acrylate monomer units in the polymer is above the lower limit, the electrolyte affinity can be improved. Furthermore, if the content of alkyl (meth)acrylate monomer units in the polymer is below the upper limit, the binding strength can be improved.

[0045] - Acid Group-Containing Monomers - Acid group-containing monomers that can form acid group-containing monomer units are not particularly limited, but examples include monomers having a carboxylic acid group, monomers having a sulfonic acid group, and monomers having a phosphate group. In this invention, acid group-containing monomers do not include hydroxyl group-containing monomers.

[0046] Examples of monomers having a carboxylic acid group include monocarboxylic acids and dicarboxylic acids. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of monomers having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, ethyl (meth)acrylate-2-sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-alyloxy-2-hydroxypropanesulfonic acid. Examples of monomers having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. These may be used individually or in combination of two or more in any ratio. In particular, from the viewpoint of further suppressing the increase in the internal resistance of the electrochemical element, monomers having a carboxylic acid are preferred, monocarboxylic acids are more preferred, and methacrylic acid is even more preferred.

[0047] The content of acid group-containing monomer units in the polymer is preferably 0.5% by mass or more, more preferably 1% by mass or more, preferably 25% by mass or less, and more preferably 20% by mass or less, based on the total amount of monomer units as 100% by mass. If the content of acid group-containing monomer units in the polymer is above the lower limit, the binding strength can be improved. Furthermore, if the content of acid group-containing monomer units in the polymer is below the upper limit, the electrolyte affinity can be improved.

[0048] - Aromatic Monovinyl Monomer Units - Examples of aromatic monovinyl monomers that can form aromatic monovinyl monomer units include styrene, vinyltoluene, α-methylstyrene, p-methylstyrene, ethyl vinylbenzene, ethyl vinyl biphenyl, and ethyl vinyl naphthalene. These may be used individually or in combination of two or more. Among these, styrene or ethyl vinylbenzene is preferred, and ethyl vinylbenzene is more preferred, from the viewpoint of further suppressing the increase in the internal resistance of the electrochemical element.

[0049] The proportion of aromatic monovinyl monomer units contained in the polymer is preferably 0.5% by mass or more, more preferably 1% by mass or more, and preferably 16% by mass or less, and more preferably 15% by mass or less, based on the total amount of monomer units as 100% by mass. If the proportion of aromatic monovinyl monomer units in the polymer is above the lower limit, the electrolyte affinity can be improved. Furthermore, if the content ratio of aromatic monovinyl monomer units in the polymer is below the upper limit, the cycle characteristics of the electrochemical element can be improved.

[0050] [Amino group-containing monomer units] Examples of amino group-containing monomers that can form amino group-containing monomer units include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, aminoethyl vinyl ether, and dimethylaminoethyl vinyl ether. These may be used individually or in combination of two or more in any ratio.

[0051] The proportion of amino group-containing monomer units contained in the polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total amount of monomer units being 100% by mass.

[0052] [Thiol group-containing monomer unit] The thiol group-containing monomer that can form a thiol group-containing monomer unit is not particularly limited, and examples include allyl mercaptan. The thiol group-containing monomer may be used alone, or two or more types may be used in any ratio.

[0053] The proportion of thiol group-containing monomer units contained in the polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total amount of monomer units being 100% by mass.

[0054] [Monoolefin Monomer Units] Monoolefin monomers that can form monoolefin monomer units are not particularly limited and include ethylene, propylene, butylene, vinylcyclohexane, norbornene, tricyclododecene, and 1,4-methano-1,4,4a,9a-tetrahydrofluorene. These may be used individually or in combination of two or more in any ratio.

[0055] The proportion of monoolefin monomer units contained in the polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total amount of monomer units being 100% by mass.

[0056] [Isocyanate group-containing monomer units] The isocyanate group-containing monomers that can form isocyanate group-containing monomer units are not particularly limited and include 2-isocyanatoethyl (meth)acrylate and 2-(2-methacryloyloxyethyloxy)ethyl isocyanate. These may be used individually or in combination of two or more in any ratio.

[0057] The proportion of isocyanate group-containing monomer units contained in the polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, and more preferably 10% by mass or less, based on the total amount of monomer units being 100% by mass.

[0058] [Conjugated diene monomer units] The conjugated diene monomers that can form conjugated diene monomer units are not particularly limited and include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. These may be used individually or in combination of two or more in any ratio. In this invention, conjugated diene monomer units are not included in the crosslinkable monomer units.

[0059] The proportion of conjugated diene monomer units contained in the polymer is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 70% by mass or less, and more preferably 60% by mass or less, based on the total amount of monomer units being 100% by mass.

[0060] <Method for preparing hollow organic particles> The hollow organic particles of the present invention are not particularly limited and can be prepared, for example, by the methods described in International Publication No. 2023 / 074651, International Publication No. 2022 / 092076, International Publication No. 2023 / 189800, and Japanese Patent Application Publication No. 2023-86486.

[0061] (Composition for Functional Layer of Electrochemical Element) The functional layer composition of the present invention is a composition containing the hollow organic particles of the present invention described above. In addition to the hollow organic particles described above, the functional layer composition of the present invention may also contain functional particles as particles that are blended to make the functional layer exhibit a desired function. Furthermore, the functional layer composition of the present invention may also contain at least one component selected from the group consisting of binders, solvents, and other components that are different from the hollow organic particles and functional particles described above. By using the functional layer composition of the present invention, a functional layer that can suppress the increase in the internal resistance of an electrochemical element can be formed.

[0062] <Hollow Organic Particles> As the hollow organic particles, the hollow organic particles of the present invention described above can be used. Here, when the functional layer composition of the present invention contains non-conductive particles (i.e., when the functional layer composition is a porous film layer used as a separator), the amount of hollow organic particles is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of non-conductive particles. When the functional layer composition contains non-conductive particles, if the amount of hollow organic particles in the functional layer composition is above the lower limit value above, the increase in the internal resistance of the electrochemical element equipped with the functional layer can be further suppressed. Furthermore, if the amount of hollow organic particles in the functional layer composition is below the upper limit value above, the binding strength can be improved.

[0063] Furthermore, when the functional layer composition does not contain non-conductive particles but contains an electrode active material (i.e., when the functional layer that can be formed by the functional layer composition is an electrode composite layer), it is preferable that the amount of hollow organic particles blended is 0.5 parts by mass or more, more preferably 1 part by mass or more, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of electrode active material. When the functional layer composition contains an electrode active material, if the amount of hollow organic particles blended in the functional layer composition is equal to or greater than the above lower limit, the increase in the internal resistance of the electrochemical element equipped with the functional layer can be further suppressed.

[0064] Furthermore, when the functional layer composition contains neither non-conductive particles nor an electrode active material and contains a binder, it is preferable that the blending amount of the hollow organic particles is 5% by mass or more and 10% by mass or less, where the total amount of the binder and the hollow organic particles is 100% by mass.

[0065] <Functional Particles> Examples of the functional particles optionally blended in the functional layer composition of the present invention include electrode active material particles when the functional layer is an electrode mixture layer, and non-conductive particles when the functional layer is a porous film layer.

[0066] [Electrode Active Material Particles] The electrode active material particles are particles formed of a substance that transfers electrons in an electrode of an electrochemical device. For example, when the electrochemical device is a lithium ion secondary battery, the electrode active material is not particularly limited, and particles formed of any of the following electrode active materials can be used.

[0067] -Positive Electrode Active Material- As the positive electrode active material blended in the positive electrode mixture layer of the positive electrode of a lithium ion secondary battery, for example, compounds containing a transition metal, such as transition metal oxides, transition metal sulfides, and composite metal oxides of lithium and a transition metal, can be used. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo. Specifically, the positive electrode active material is not particularly limited, and includes lithium-containing cobalt oxide (LiCoO ２ ), lithium manganate (LiMn ２ O ４ ), lithium-containing nickel oxide (LiNiO ２ ), lithium-containing composite oxides of Co-Ni-Mn, lithium-containing composite oxides of Ni-Mn-Al, lithium-containing composite oxides of Ni-Co-Al, olivine-type lithium iron phosphate (LiFePO ４ ), olivine-type lithium manganese phosphate (LiMnPO ４ ), Li １＋ｘ Mn ２－ｘ O ４ , which is a lithium-excess spinel compound represented by (0<X<2), Li[Ni ０．１７ Li０．２ Co ０．０７ Mn ０．５６ ]O ２ LiNi ０．５ Mn １．５ O ４ These are some examples. The positive electrode active material described above may be used individually or in combination of two or more types.

[0068] -Negative Electrode Active Materials- Examples of negative electrode active materials incorporated into the negative electrode composite layer of the negative electrode of a lithium-ion secondary battery include carbon-based negative electrode active materials, metal-based negative electrode active materials, and negative electrode active materials that combine these. Here, carbon-based negative electrode active materials refer to active materials with a carbon-based main skeleton that can be inserted (also called "doped") with lithium. Specifically, carbonaceous materials such as coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, pyrolysis vapor-grown carbon fibers, phenolic resin calcined bodies, polyacrylonitrile carbon fibers, pseudoisotropic carbon, furfuryl alcohol resin calcined bodies (PFA), and hard carbon, as well as graphite materials such as natural graphite and artificial graphite. Furthermore, a metallic anode active material is an active material containing a metal, which typically contains an element in its structure that allows for lithium insertion, and has a theoretical electrical capacity of 500 mAh / g or more per unit mass when lithium is inserted. Examples of metallic active materials include lithium metal, elemental metals that can form lithium alloys (e.g., Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, Sr, Zn, Ti, etc.), and their oxides, sulfides, nitrides, silicides, carbides, and phosphides. In addition, oxides such as lithium titanate can be mentioned. The above-mentioned anode active materials may be used individually or in combination of two or more types.

[0069] [Non-conductive particles] Non-conductive particles are not particularly limited and include known non-conductive particles used in electrochemical elements such as secondary batteries. Specifically, both inorganic and organic fine particles can be used as non-conductive particles, but inorganic fine particles are usually used. Among these, materials that are stable and electrochemically stable under the operating environment of electrochemical elements such as secondary batteries are preferred as materials for non-conductive particles. From this viewpoint, preferred examples of materials for non-conductive particles include aluminum oxide (alumina), hydrated aluminum oxide (boehmite), silicon oxide, magnesium oxide (magnesia), calcium oxide, titanium oxide (titania), and BaTiO2. ３ Examples include 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 also be subjected to elemental substitution, surface treatment, solid solution treatment, etc., as needed. When organic fine particles are used as nonconductive particles, it is preferable that their degree of swelling in the electrolyte is 1.2 times or less, and that they do not have a melting point or glass transition temperature below 250°C. The above-mentioned nonconductive particles may be used individually or in combination of two or more types. The above-mentioned organic fine particles are not usually hollow particles and do not fall under the category of hollow organic particles of the present invention.

[0070] <Binding Agent> The functional layer composition of the present invention may further contain a binding agent. When a functional layer is formed using a functional layer composition containing a binding agent in addition to the hollow organic particles described above, components such as hollow organic particles and functional particles are retained so as not to detach from the functional layer, and the adhesion between members via the functional layer is improved.

[0071] [Types of Binding Materials] The binding material is not particularly limited as long as it can be used within an electrochemical element. For example, a polymer obtained by polymerizing a monomer composition containing monomers capable of exhibiting binding properties (synthetic polymer, for example, an addition polymer obtained by addition polymerization) can be used as the binding material. Examples of such polymers include fluorine-based polymers such as polyvinylidene fluoride (polymers mainly containing fluorine-containing monomer units); aliphatic conjugated diene / aromatic vinyl copolymers such as styrene-butadiene copolymer (SBR) (polymers mainly containing aliphatic conjugated diene monomer units and aromatic vinyl monomer units); aliphatic conjugated diene / acrylonitrile copolymers such as butadiene-acrylonitrile copolymer (NBR); and vinyl alcohol polymers such as polyvinyl alcohol. These may be used individually or in combination of two or more in any ratio. Here, known monomers that can form the above-mentioned monomer units can be used. In this invention, the binder is not a hollow particle and does not fall under the category of hollow organic particles of this invention.

[0072] [Properties of the binder] When the binder is water-insoluble and exists in particulate form in a functional layer composition containing water as a solvent, it is preferable that the volume-average particle diameter of the binder is less than 300 nm. If the volume-average particle diameter of the binder is less than 300 nm, the increase in the internal resistance of the electrochemical element can be further suppressed, and the electrochemical properties of the electrochemical element equipped with the resulting functional layer can be improved. Here, "water-insoluble" means that when 0.5 g of the binder is dissolved in 100 g of water at 25°C, the insoluble content is 90% by mass or more. Furthermore, the volume-average particle diameter of the binder can be measured in the same manner as the method for measuring the volume-average particle diameter of hollow organic particles described above.

[0073] Furthermore, the glass transition temperature of the binder is preferably less than 50°C. If the glass transition temperature of the binder is below the above upper limit, the adhesion of the functional layer can be improved. The glass transition temperature of the binder can be adjusted, for example, by changing the type and proportion of monomers used in the preparation of the binder. The glass transition temperature of the binder can also be measured in the same manner as the method for measuring the glass transition temperature of hollow organic particles described above.

[0074] [Amount of ingredients] The amount of binder in the functional layer composition is not particularly limited, but it is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, preferably 80 parts by mass or less, and more preferably 70 parts by mass or less, per 100 parts by mass of hollow organic particles.

[0075] <Solvent> Examples of solvents include water and organic solvents. Examples of organic solvents include acetonitrile, N-methylpyrrolidone, acetylpyridine, cyclopentanone, N,N-dimethylacetamide, dimethylformamide, dimethyl sulfoxide, methylformamide, methyl ethyl ketone, furfural, and ethylenediamine. Among these, water is preferred. When the functional layer composition contains a solvent, the hollow parts of the hollow organic particles may be filled with the solvent.

[0076] <Other Ingredients> Other ingredients include known components such as thickeners, conductive materials, crosslinking agents, reinforcing agents, antioxidants, dispersants, rheological adjusters, and electrolyte additives that have the function of suppressing the decomposition of the electrolyte. These other ingredients may be present individually or in any proportion of two or more.

[0077] <Method for Preparing the Functional Layer Composition> The method for preparing the functional layer composition of the present invention is not particularly limited. For example, if the functional layer composition is an electrode composite layer composition, the functional layer composition can be prepared by mixing hollow organic particles, electrode active material particles, and a binder and / or other components used as needed in the presence of a solvent. If the functional layer composition is a porous film layer composition, the functional layer composition can be prepared by mixing hollow organic particles, non-conductive particles, and a binder and / or other components used as needed in the presence of a solvent. If the functional layer composition is an adhesive layer composition, the functional layer composition can be prepared by mixing hollow organic particles and a binder and / or other components used as needed in the presence of a solvent. The mixing method used when preparing the functional layer composition is not particularly limited, but mixing is performed using a stirrer or disperser that can be commonly used.

[0078] (Functional Layer for Electrochemical Elements) The functional layer of the present invention is a layer that performs functions such as electron transfer, reinforcement of components, and adhesion between components within an electrochemical element. Examples of functional layers include electrode composite layers that transfer electrons via electrochemical reactions, porous film layers that improve heat resistance and strength, and adhesive layers that improve adhesion. The functional layer of the present invention is formed from the above-described functional layer composition of the present invention. For example, it can be formed by applying the above-described functional layer composition to the surface of a suitable substrate to form a coating film, and then drying the formed coating film. That is, the functional layer of the present invention consists of the dried product of the above-described functional layer composition and usually contains at least hollow organic particles. Since each component contained in the functional layer is the same as that contained in the above-described functional layer composition, the preferred ratio of each component is the same as the preferred ratio of each component in the functional layer composition. Furthermore, if polymers such as hollow organic particles or binders have crosslinkable functional groups, they may be crosslinked during the drying of the functional layer composition or during heat treatment optionally performed after drying.

[0079] Furthermore, since the functional layer of the present invention is formed from the functional layer composition of the present invention, it is possible to suppress an increase in the internal resistance of an electrochemical element equipped with the functional layer.

[0080] <Substrate> There are no restrictions on the substrate to which the functional layer composition is applied. For example, a coating film of the functional layer composition may be formed on the surface of a release substrate, the coating film may be dried to form a functional layer, and the release substrate may be peeled off from the functional layer. In this way, the functional layer peeled off from the release substrate can be used as a self-supporting film to form components of an electrochemical element. However, from the viewpoint of improving the manufacturing efficiency of the component by omitting the step of peeling off the functional layer, it is preferable to use a current collector, separator substrate, or electrode substrate as the substrate. Specifically, when preparing an electrode composite layer, it is preferable to apply the functional layer composition onto a current collector as the substrate. Also, when preparing a porous film layer or an adhesive layer, it is preferable to apply the functional layer composition onto a separator substrate or electrode substrate.

[0081] [Current Collector] The current collector is made of a material that is electrically conductive and electrochemically durable. Specifically, the current collector can be made of, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, etc. Among these, copper foil is particularly preferred as the current collector for the negative electrode. Aluminum foil is particularly preferred as the current collector for the positive electrode. The above materials may be used individually or in combination of two or more materials in any ratio.

[0082] [Separator Substrate] The separator substrate is not particularly limited, but known separator substrates such as organic separator substrates can be used. Organic separator substrates are porous members made of organic materials. Examples of organic separator substrates include microporous membranes or nonwoven fabrics containing polyethylene, polyolefin resins such as polypropylene, and aromatic polyamide resins. Microporous membranes or nonwoven fabrics made of polyethylene are preferred due to their excellent strength.

[0083] [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 containing electrode active material particles and a binder is formed on the current collector described above. The electrode active material particles and binder contained in the electrode composite layer in the electrode substrate are not particularly limited, and the electrode active material particles and binder described above in the section "Functional Layer Composition for Electrochemical Element Functional Layer" can be used.

[0084] <Method for forming a functional layer> The following methods can be used to form a functional layer on a substrate such as a current collector, separator substrate, or electrode substrate as described above: 1) Applying the functional layer composition of the present invention to the surface of the substrate (in the case of an electrode substrate, the surface on the electrode composite layer side, the same applies hereinafter), and then drying it; 2) Immersing the substrate in the functional layer composition of the present invention and then drying it; and 3) Applying the functional layer composition of the present invention onto a release substrate, drying it to produce a functional layer, and transferring the obtained functional layer to the surface of the substrate. Among these, method 1) is particularly preferred because it allows for easy control of the thickness of the functional layer. Method 1) more specifically includes a step of applying the functional layer composition onto the substrate (application step) and a step of drying the functional layer composition applied onto the substrate to form a functional layer (drying step).

[0085] [Coating Process] The method for coating the above-mentioned functional layer composition onto the substrate is not particularly limited and known methods can be used. Specifically, coating methods such as the doctor blade method, dip method, reverse roll method, direct roll method, gravure method, extrusion method, and brush coating method can be used. In this case, the functional layer composition may be coated on only one side of the substrate or on both sides.

[0086] [Drying Process] The method for drying the functional layer composition on the substrate is not particularly limited and known methods can be used, such as drying with hot air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams. The drying conditions are not particularly limited, but the drying temperature is preferably 50 to 150°C and the drying time is preferably 1 to 30 minutes.

[0087] (Members equipped with a functional layer) Members equipped with the functional layer of the present invention (such as separators and electrodes) have the functional layer of the present invention described above, and may also be equipped with the functional layer of the present invention described above and components other than the substrate, as long as the effects of the present invention are not significantly impaired. Such components are not particularly limited and include electrode composite layers, porous film layers, and adhesive layers that do not fall under the functional layer of the present invention. Furthermore, the above members may be equipped with multiple types of functional layers of the present invention. For example, an electrode may be equipped with an electrode composite layer formed from the functional layer composition of the present invention on a current collector, and may be equipped with a porous film layer, an adhesive layer, and / or "other functional layers" formed from the functional layer composition of the present invention on the electrode composite layer. Also, for example, a separator may be equipped with a porous film layer formed from the functional layer composition of the present invention on a separator substrate, and may be equipped with an adhesive layer formed from the functional layer composition of the present invention on the porous film layer. Members equipped with the functional layer of the present invention can suppress an increase in the internal resistance of an electrochemical element equipped with the member.

[0088] (Electrochemical element) The electrochemical element of the present invention is not particularly limited to lithium-ion secondary batteries or electric double-layer capacitors, and is preferably a lithium-ion secondary battery. Furthermore, the electrochemical element of the present invention is equipped with the functional layer of the present invention. As a result, the increase in internal resistance of the electrochemical element of the present invention is suppressed.

[0089] In the following description, the present invention will be explained as an example in which the electrochemical element of the present invention is a lithium-ion secondary battery, but the present invention is not limited to the example below. A lithium-ion secondary battery as an example of the electrochemical element of the present invention comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode, negative electrode, and separator, preferably the negative electrode, comprises the functional layer of the present invention described above.

[0090] <Positive electrode, negative electrode, and separator> The positive electrode, negative electrode, and separator used in a lithium-ion secondary battery as an example of the electrochemical element of the present invention are battery components in which at least one of them is equipped with the functional layer of the present invention described above. Note that the positive electrode, negative electrode, and separator that are not equipped with the functional layer of the present invention are not particularly limited, and known positive electrodes, negative electrodes, and separators can be used.

[0091] <Electrolyte> Typically, an organic electrolyte is used as the electrolyte, which is obtained by dissolving a supporting electrolyte in an organic solvent. For example, lithium salts are used as the supporting electrolytes in lithium-ion secondary batteries. Examples of lithium salts include LiPF4. ６ LiAsF ６ LiBF ４ LiSbF ６ LiAlCl ４ LiClO ４ CF ３ SO ３ Li, C ４ F ９ SO ３ Li, CF ３ COOLi, (CF ３ CO) ２ NLi, (CF ３ SO ２ ) ２ NLi, (C ２ F ５ SO ２ Examples include NLi. Among them, LiPF is particularly soluble in solvents and exhibits a high degree of dissociation. ６ LiClO ４ CF ３ SO ３ Li is preferred. Note that one type of electrolyte may be used alone, or two or more types may be used in any ratio. 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.

[0092] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte, but suitable examples include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), and vinylene carbonate (VC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; and sulfur-containing compounds such as sulfolane and dimethyl sulfoxide. A mixture of these solvents may also be used. Among these, carbonates are preferred because they have a high dielectric constant and a wide stable potential range. Generally, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted by the type of solvent. The concentration of the electrolyte in the electrolyte can be adjusted as appropriate. In addition, known additives can be added to the electrolyte.

[0093] <Method for Manufacturing a Lithium-Ion Secondary Battery> A lithium-ion secondary battery, which is an example of the electrochemical element of the present invention, can be manufactured by, for example, stacking a positive electrode and a negative electrode with a separator in between, winding or folding them as needed according to the battery shape, placing them in a battery container, injecting an electrolyte into the battery container, and sealing it. At least one of the battery components, including the positive electrode, negative electrode, and separator, shall be equipped with the functional layer of the present invention described above. 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, for example, coin-shaped, button-shaped, sheet-shaped, cylindrical, rectangular, flat, etc.

[0094] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing quantities refer to mass unless otherwise specified. In addition, in polymers produced by copolymerizing multiple types of monomers, the proportion of monomer units formed by polymerization of a certain monomer in the polymer is usually equal to the ratio of that certain monomer to the total monomers used in the polymerization of the polymer (starting ratio), unless otherwise specified. Various measurements and evaluations in the examples and comparative examples were performed by the following methods.

[0095] <Confirmation of through-pores in hollow organic particles> 200 mg of hollow organic particles were placed in a 5 mL glass bottle at 25°C, then 4 mL of methyl ethyl ketone (MEK) was added and the bottle was sealed. The glass bottle was shaken 10 times by hand and then left at 25°C for 24 hours, and the proportion of precipitated hollow organic particles was determined. Specifically, the precipitated hollow organic particles in MEK were separated using a centrifuge, dried, and the mass of the precipitated hollow organic particles in MEK was measured. The proportion of precipitated hollow organic particles was then determined by calculating the ratio of the mass of the precipitated hollow organic particles in MEK to the total mass of the hollow organic particles. If the proportion of precipitated hollow organic particles was 5% or more, it was determined that the hollow organic particles had through-pores. <Volume-average particle diameter> The volume-average particle size of the hollow organic particles was measured using a particle size distribution analyzer (Beckman Coulter, product name: Multisizer 4e). The measurement conditions were: aperture diameter: 50 μm, dispersion medium: Isoton II (product name), concentration: 10%, number of particles measured: 100,000. Specifically, 0.2 g of a hollow organic particle sample was placed in a beaker, and an aqueous surfactant solution (Fujifilm Corporation, product name: Drywell) was added as a dispersant. Then, 2 ml of methyl ethyl ketone was added as a dispersion medium to wet the particles, and then 10 ml of methyl ethyl ketone was added and dispersed in an ultrasonic disperser for 1 minute before measurement was performed using the particle size distribution analyzer described above. The particle size D50 at which the cumulative volume calculated from the smallest diameter side became 50% of the obtained particle size distribution (volume basis) was defined as the "volume-average particle size". The volume-average particle size of the binder material of the comparative example was measured in the same manner. <Porosity> [Apparent density D１ [Measurement of] Apparent density D of hollow organic particles １ The following measurements were taken. First, the volume 100 cm³ ３ Approximately 30 cm in a volumetric flask ３ Hollow organic particles were packed into the volumetric flask, and the mass of the packed hollow organic particles was accurately weighed. Next, isopropanol was accurately filled to the mark into the volumetric flask filled with hollow organic particles or binder, taking care not to introduce air bubbles. The mass of isopropanol added to the volumetric flask was accurately weighed, and the apparent density D of the hollow organic particles or binder was calculated based on the following formula (I). １ (g / cm ３ The following equation (I) was calculated: Apparent density D １ = [Mass of hollow organic particles] / (100 - [Mass of isopropanol] ÷ [Specific gravity of isopropanol at the measurement temperature]) Apparent density D １ This corresponds to the specific gravity of the entire hollow organic particle, assuming that the hollow portion is considered part of the hollow organic particle. [True density D] ０ [Measurement of] Next, the true density D of hollow organic particles ０ The following measurements were taken: After pre-pulverizing the hollow organic particles, a volume of 100 cm³ was measured. ３ Approximately 10 g of crushed hollow organic particles were packed into a volumetric flask, and the mass of the packed crushed particles was accurately weighed. In the same manner as the measurement of apparent density described above, isopropanol was added to the volumetric flask, and the mass of isopropanol was accurately weighed. Based on the following formula (II), the true density D of the hollow organic particles was calculated. ０ (g / cm ３ The following equation (II) was calculated: True density D ０ = [Mass of the pulverized hollow organic particles] / (100 - [Mass of isopropanol] ÷ [Specific gravity of isopropanol at the measurement temperature]) True density D ０ This corresponds to the specific gravity of only the shell portion of the hollow organic particles. As is clear from the above measurement method, true density D ０ In calculating this, the hollow portion is not considered part of the hollow organic particle. [Porrosion (%)] And the apparent density D of the hollow organic particle １ and true density D ０The porosity (%) of the hollow organic particles was calculated using the following formula (III): Formula (III): Porosity (%) = 100 - (Apparent density D １ / True density D ０ ) × 100 The porosity of hollow organic particles can be rephrased as the proportion of the hollow portion that occupies in the specific gravity of the hollow organic particles. The porosity of the binder material of the comparative example was measured in the same manner. <Fracture Strength> The fracture strength of the hollow organic particles was measured as follows. As the microcompressive strength of the hollow organic particles, in accordance with JIS R1639-5, a microcompression tester (model: MCT-510) manufactured by Shimadzu Corporation was used to measure the compressive strength (MPa) when the particle diameter changed by 10% in the direction of load application, under the conditions of a measurement temperature of 150°C, a maximum test force of 2,000 mN, and a loading speed of 0.0466 mN / sec, and this was defined as the fracture strength. The fracture strength of the binder material of the comparative example was measured in the same manner. <Glass Transition Temperature> The glass transition temperature of the hollow organic particles (shell portion) was measured in accordance with JIS K7121, under the conditions of a measurement temperature of -100°C to 180°C and a heating rate of 5°C / min, using a differential scanning calorimetry analyzer (Nanotechnology Inc., DSC6220SII). The glass transition temperature of the binder in the comparative example was measured in the same manner. <Peel Strength> The negative electrodes prepared in the examples and comparative examples were cut into rectangles 100 mm long and 10 mm wide to make test specimens. These test specimens were placed with the surface of the negative electrode composite layer facing downwards, and cellophane tape was attached to the surface of the negative electrode composite layer. The cellophane tape used was the type specified in JIS Z1522. The cellophane tape was fixed to the test stand. Then, the stress was measured when one end of the current collector was pulled vertically upwards at a pulling speed of 50 mm / min to peel it off. This measurement was performed three times, the average value was calculated, and this average value was used as the peel strength and evaluated according to the following criteria: A: Peel strength of 5 N / m or more B: Peel strength of 1 N / m or more but less than 5 N / m C: Peel strength less than 1 N / m

[0096] <Internal Resistance of Lithium-Ion Secondary Batteries> To evaluate the internal resistance of the lithium-ion secondary batteries prepared in the examples and comparative examples, the IV resistance was measured as follows. A conditioning treatment was performed by charging at a charge rate of 0.1C (where C is a value expressed as rated capacity (mA) / 1 hour (h)) at a temperature of 25°C until the voltage reached 4.2V, then resting for 10 minutes, and finally discharging at a constant current (CC) at a discharge rate of 0.1C to 3.0V, repeating this operation three times. After that, under a -10°C atmosphere, the batteries were charged at 1C to 3.75V, and then charged for 20 seconds and discharged for 20 seconds at 0.5C, 1.0C, 1.5C, and 2.0C, centered around 3.75V. For each case, the battery voltage after 15 seconds on the charging side was plotted against the current value, and the slope was determined as the IV resistance (Ω). The obtained IV resistance values ​​(Ω) were evaluated according to the following criteria. Note that a smaller IV resistance value indicates lower internal resistance of the secondary battery. A: Less than 1.9Ω B: 1.9Ω or more and less than 2.1Ω C: 2.1Ω or more and less than 2.4Ω D: 2.4Ω or more

[0097] <Cycle Characteristics of Lithium-Ion Secondary Batteries> 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, constant current (CC) - constant voltage (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 charge and discharge at 0.2C was repeated three times. After that, under conditions of 25°C, the charge and discharge operation was performed 100 times at a charge / discharge rate of 1.0C with a cell voltage of 4.20-3.00V. In this process, the discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle was defined as X2. Using these discharge capacities X1 and X2, the rate of change in capacity, expressed as ΔC' = (X2 / X1) × 100 (%), was calculated and evaluated according to the following criteria. A larger value of this rate of change in capacity ΔC' indicates better cycle characteristics. A: ΔC' is 90% or more B: ΔC' is 60% or more but less than 90% C: ΔC' is less than 60%

[0098] (Example 1) <Preparation of Hollow Organic Particles> (1) Mixture Preparation Process First, the following materials were mixed to form the oil phase. DVB960 (trade name, manufactured by Nippon Steel Chemical & Material Co., Ltd., 96% divinylbenzene (crosslinkable monomer other than epoxy group-containing monomer), 4% ethylvinylbenzene (aromatic monovinyl monomer)) 38.7 parts t-Butyl peroxydiethyl acetate (oil-soluble polymerization initiator, manufactured by Kayaku Nurion Co., Ltd., trade name: Trigonox 27) 0.89 parts Rosin acid (softening point 150°C or higher, acid value: 150-160 mg KOH / g) 0.05 parts Hydrophobic solvent: heptane (solubility in water at 20°C: 2.2 mg / L) 61.3 parts

[0099] Next, in a stirring tank, an aqueous solution prepared by dissolving 19.59 parts magnesium chloride (water-soluble polyvalent metal salt) in 225 parts deionized water was gradually added under stirring to an aqueous solution prepared by dissolving 13.72 parts sodium hydroxide (alkali metal hydroxide salt) in 55 parts deionized water to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion (10 parts magnesium hydroxide), which was then used as the aqueous phase. The resulting aqueous phase and the oil phase were mixed to prepare a mixed solution.

[0100] (2) Suspension process Using an in-line emulsifier / disperser (manufactured by Eurotech Co., Ltd., product name: Cavitron), the rotor peripheral speed (peripheral speed at the outer edge of the rotor) was set to 40 m / s, and the mixture obtained in the above mixture preparation process was suspended to prepare a suspension in which droplets of the monomer composition containing heptane were dispersed in water.

[0101] (3) Polymerization process The suspension obtained in the suspension process above was heated to 80°C in a nitrogen atmosphere. After 1 hour had elapsed since reaching 80°C, 5 parts of methyl ethyl ketone (MEK) (solubility in water at 20°C: 275 g / L) were added to the suspension as a reaction accelerator, and the mixture was stirred for 24 hours under the temperature of 80°C to carry out the polymerization reaction. This polymerization reaction yielded a precursor composition, which is a slurry liquid in which precursor particles containing a hydrophobic solvent are dispersed in water.

[0102] (4) Washing and Solid-Liquid Separation Process The precursor composition obtained in the polymerization process was washed with dilute sulfuric acid (25°C, 10 minutes) to reduce the pH to 5.5 or less. Next, after separating the water by filtration, 200 parts of freshly deionized water were added to re-form a slurry, and the water washing treatment (washing, filtration, dewatering) was repeated several times at room temperature (25°C), and the solid was separated by filtration. The obtained solid was dried in a dryer at a temperature of 40°C to obtain precursor particles containing a hydrophobic solvent.

[0103] (5) Solvent Removal Process The precursor particles obtained in the solid-liquid separation process were heat-treated in a vacuum dryer at 200°C under vacuum conditions for 6 hours to remove the hydrophobic solvent contained within the particles and obtain hollow organic particles. Observation results from a scanning electron microscope and porosity values ​​confirmed that the obtained hollow organic particles were spherical and had hollow parts. Furthermore, the sedimentation rate was 10%, confirming that the hollow organic particles had through-pores.

[0104] <Preparation of slurry composition for negative electrode composite layer (composition for functional layer)> In a planetary mixer with a disperser, artificial graphite (tap density: 0.85 g / cm³) is used as the negative electrode active material. ３ A mixture was obtained by adding 100 parts of (capacity: 360 mAh / g), 1 part of carbon black (manufactured by TIMCAL, product name "Super C65") as a conductive material, and 1.2 parts (in terms of solid content) of a 2% aqueous solution of carboxymethylcellulose (manufactured by Daicel, product name "Daicel 2200") as a thickener. The obtained mixture was adjusted to a solid content of 60% with deionized water and then mixed at 25°C for 60 minutes. Next, the solid content was adjusted to 52% with deionized water and then mixed further at 25°C for 15 minutes to obtain a mixture. To the obtained mixture, 2.0 parts (in terms of solid content) of the hollow organic particles prepared above and deionized water were added and adjusted to a final solid content of 48%. After mixing for a further 10 minutes, a defoaming treatment was performed under reduced pressure to obtain a slurry composition for a negative electrode composite layer with good fluidity.

[0105] <Formation of the negative electrode> The obtained slurry composition for the negative electrode composite layer was coated onto a 15 μm thick copper foil, which serves as the current collector, using a comma coater at a speed of 1.2 m / min, until the basis weight after drying was 10.5 mg / cm². ２ The material was applied and dried. This drying was performed by transporting the copper foil at a speed of 1.2 m / min in a 120°C oven for 1 minute, and then in a 130°C oven for 1 minute. The resulting negative electrode base was rolled in a roll press to obtain a negative electrode composite layer with a density of 1.70 g / cm³. ３ A negative electrode for lithium-ion secondary batteries was obtained. The peel strength of the negative electrode for lithium-ion secondary batteries was then evaluated. The results are shown in Table 1.

[0106] <Formation of the positive electrode> LiCoO with a median diameter of 12 μm is used as the positive electrode active material. ２ 100 parts of [the material], 2 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., product name "HS-100") as a conductive material, 2 parts of polyvinylidene fluoride (manufactured by Kureha Corporation, product name "#7208") in terms of solid content as a binder, 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 obtain a slurry composition for the positive electrode composite layer. The obtained slurry composition for the positive electrode composite layer was coated onto a 20 μm thick aluminum foil current collector using a comma coater, with a basis weight of 23 mg / cm² after drying. ２ The material was coated and dried. This drying was performed by transporting aluminum foil at a speed of 0.5 m / min in a 60°C oven for 2 minutes. After that, it was heat-treated at 120°C for 2 minutes to obtain a cathode base. The cathode base was then rolled in a roll press to obtain a cathode composite layer with a density of 4.0 g / cm³. ３ A positive electrode for lithium-ion secondary batteries was obtained.

[0107] <Preparation of Separator> A single-layer polypropylene separator (manufactured by Cellguard, product name "Cellguard 2500") was prepared as the separator, which consists of a separator base material.

[0108] <Fabrication of Lithium-ion Secondary Battery> As described above, the pressed positive electrode for the lithium-ion secondary battery, the pressed negative electrode for the lithium-ion secondary battery, and a separator (a 20 μm thick microporous film made of polypropylene) were stacked in the order of separator / positive electrode / separator / negative electrode to obtain a laminate. Next, the laminate of electrodes and separators was wound around a core with a diameter of 20 mm to obtain a wound body comprising a positive electrode, separator, and negative electrode. Subsequently, the obtained wound body was compressed from one direction at a speed of 10 mm / second until it reached a thickness of 4.5 mm to obtain a flattened body. The obtained flattened body was elliptical in plan view, and its ratio of major axis to minor axis (major axis / minor axis) was 7.7. In addition, a non-aqueous electrolyte (LiPF4 at a concentration of 1.0 M) was used. ６A solution was prepared (a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 3 / 7 (mass ratio), to which 2% by volume of vinylene carbonate (VC) was further added as an additive). Next, the flattened body was placed in an aluminum laminate case together with the non-aqueous electrolyte. After connecting the negative electrode lead and positive electrode lead to the designated locations, the opening of the laminate case was sealed with heat to produce a laminate-type lithium-ion secondary battery as a non-aqueous secondary battery. The obtained secondary battery was a pouch type with dimensions of 35 mm wide x 48 mm high x 5 mm thick, and had a nominal capacity of 700 mAh. The internal resistance and cycle characteristics of this lithium-ion secondary battery were then evaluated. The results are shown in Table 1.

[0109] (Example 2) Hollow organic particles and lithium-ion secondary batteries were manufactured using the same procedure as in Example 1, except that the amount of MEK added as a reaction-accelerating additive in "(3) Polymerization step" was changed from 5 parts to 2 parts. Various measurements and evaluations were then performed. The results are shown in Table 1.

[0110] (Example 3) Hollow organic particles and lithium-ion secondary batteries were manufactured using the same procedure as in Example 1, except that in the "(1) Mixture Preparation Step" described above, the amount of magnesium chloride was changed from 19.59 parts to 7.83 parts, and the amount of sodium hydroxide was changed from 13.72 parts to 5.49 parts, so that the amount of magnesium hydroxide colloid dispersion was 4 parts in terms of magnesium hydroxide. Various measurements and evaluations were then performed. The results are shown in Table 1.

[0111] (Example 4) Hollow organic particles and lithium-ion secondary batteries were manufactured in the same procedure as in Example 1, except that steps (1) Mixture preparation step to (5) Solvent removal step were performed as described below, and various measurements and evaluations were carried out. The results are shown in Table 1. (1) Mixture preparation step First, the following materials were mixed to form an oil phase. 24 parts ethylene glycol dimethacrylate (crosslinkable monomer unit other than epoxy group-containing monomer) 20 parts pentaerythritol tetraacrylate (crosslinkable monomer other than epoxy group-containing monomer) 17 parts divinylbenzene (crosslinkable monomer other than epoxy group-containing monomer) 13 parts ethyl vinylbenzene (aromatic monovinyl monomer) 26 parts 2-hydroxy-3-methacryloyloxypropyl acrylate (hydroxyl group-containing monomer) 3 parts 2,2'-azobis(2,4-dimethylvaleronitrile) (oil-soluble polymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd., trade name: V-65) 0.007 parts rosinic acid (softening point 150°C or higher, acid value: 150-160 mg KOH / g) 100 parts hexane (hydrophobic solvent) Next, in a stirred tank, under room temperature conditions, an aqueous solution prepared by dissolving 17.1 parts magnesium chloride (water-soluble polyvalent metal salt) in 494 parts deionized water was gradually added under stirring to an aqueous solution prepared by dissolving 12.1 parts sodium hydroxide (alkali metal hydroxide) in 121 parts deionized water to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion (4 parts magnesium hydroxide), which became the aqueous phase. The resulting aqueous phase and oil phase were mixed to prepare a mixed solution.

[0112] (2) Suspension process The mixture obtained in the above mixture preparation process was suspended by stirring for 1 minute at a rotation speed of 4,000 rpm using a disperser (Primix Corporation, product name: Homomixer) to prepare a suspension in which droplets of monomer composition containing a hydrophobic solvent were dispersed in water.

[0113] (3) Polymerization step The suspension obtained in the suspension step above was heated in a nitrogen atmosphere from 40°C to 65°C over 30 minutes (heating rate: 50°C / h), and the polymerization reaction was carried out by stirring at a temperature of 65°C for 1 hour and 30 minutes to obtain a precursor composition containing precursor particles.

[0114] (4) Washing and Solid-Liquid Separation Process The precursor composition was washed with dilute sulfuric acid (25°C, 10 minutes) to reduce the pH to 5.5 or less. Then, after separating the water by filtration, 200 parts of freshly deionized water were added to re-form a slurry, and the water washing treatment (washing, filtration, dewatering) was repeated several times at room temperature (25°C), and the solid was separated by filtration to obtain the solid. The obtained solid was dried in a dryer at a temperature of 40°C to obtain precursor particles containing a hydrophobic solvent.

[0115] (5) Solvent Removal Process The precursor particles obtained in the solid-liquid separation process were heat-treated in a vacuum dryer at 200°C under a nitrogen atmosphere for 12 hours to remove the hydrophobic solvent contained within the particles and obtain the hollow organic particles of Example 4. The obtained hollow organic particles were confirmed to be spherical and to have a hollow portion based on the results of scanning electron microscopy observation and the value of the porosity. Furthermore, the settling rate was 10%, confirming that the hollow organic particles have through-pores.

[0116] (Example 5) Hollow organic particles and lithium-ion secondary batteries were manufactured in the same procedure as in Example 1, except that steps (1) Mixture preparation step to (5) Solvent removal step were performed as described below, according to the method corresponding to Manufacturing Example 3 in International Publication No. 2020 / 066704, and various measurements and evaluations were performed. The results are shown in Table 1. (1) Mixture preparation step First, the following materials were mixed to form an oil phase. 23.3 parts methacrylic acid (acid group-containing monomer) 22.2 parts divinylbenzene (crosslinkable monomer other than epoxy group-containing monomer) 15.6 parts ethylvinylbenzene (aromatic monovinyl monomer) 23.3 parts ethylene glycol dimethacrylate (crosslinkable monomer other than epoxy group-containing monomer) 15.6 parts trimethylolpropane triacrylate (crosslinkable monomer other than epoxy group-containing monomer) 3 parts 2,2'-azobis(2,4-dimethylvaleronitrile) (oil-soluble polymerization initiator) 100 parts hydrophobic solvent: cyclohexane

[0117] Next, 1.0 part of a surfactant was added to 800 parts of deionized water to prepare an aqueous solution, which was then used as the aqueous phase. The resulting aqueous phase and the oil phase were mixed to prepare a mixed solution.

[0118] (2) Suspension step The mixture obtained was stirred using an in-line emulsifier and disperser to obtain a suspension.

[0119] (3) Polymerization step The obtained suspension was subjected to a polymerization reaction by stirring under a nitrogen atmosphere at a temperature of 65°C for 4 hours. This polymerization reaction yielded a precursor composition, which is a slurry liquid in which precursor particles containing a hydrophobic solvent are dispersed in water.

[0120] (4) Washing and solid-liquid separation steps The obtained precursor composition was filtered to obtain a solid component, and the obtained solid component was dried in a dryer at a temperature of 40°C to obtain precursor particles containing a hydrophobic solvent.

[0121] (5) Solvent Removal Process Next, the precursor particles containing the hydrophobic solvent were heat-treated in a vacuum dryer at 200°C under vacuum conditions for 6 hours to remove the hydrophobic solvent contained within the particles and obtain hollow organic particles. Observation results from a scanning electron microscope and porosity values ​​confirmed that the obtained hollow organic particles were spherical and had hollow parts. Furthermore, the settling rate was 10%, confirming that the hollow organic particles had through-pores.

[0122] (Example 6) Hollow organic particles and lithium-ion secondary batteries were manufactured in the same procedure as in Example 1, except that steps (1) Mixture preparation step to (5) Solvent removal step were performed as described below, and various measurements and evaluations were carried out. The results are shown in Table 1. (1) Mixture preparation step First, the following materials were mixed to form the oil phase. DVB960 (trade name, manufactured by Nippon Steel Chemical & Material Co., Ltd., purity of divinylbenzene (crosslinkable monomer other than epoxy group-containing monomer): 96%, content of ethyl vinylbenzene (aromatic monovinyl monomer): 4%) 26.2 parts 2,2'-Azobis(4-methoxy-2,4-dimethylvaleronitrile) (oil-soluble polymerization initiator, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: V-70) 0.6 parts Rosin acid (manufactured by Arakawa Chemical Co., Ltd., trade name: Disproportionated Rosin Rondis R-CH, softening point 150°C or higher, acid value: 150-160 mg KOH / g) 0.002 parts Hydrophobic solvent: Hexane 73.4 parts

[0123] Next, in a stirred tank, under a temperature of 40°C, an aqueous solution prepared by dissolving 7.8 parts magnesium chloride (water-soluble polyvalent metal salt) in 225 parts deionized water was gradually added under stirring to an aqueous solution prepared by dissolving 5.5 parts sodium hydroxide (alkali metal hydroxide) in 55 parts deionized water. A dispersion of magnesium hydroxide colloid (a poorly water-soluble metal hydroxide colloid) was prepared, and stirring was stopped 40 minutes after addition to form the aqueous phase. The resulting aqueous phase and oil phase were mixed to prepare a mixed solution.

[0124] (2) Suspension process The mixture obtained in the above mixture preparation process was suspended by stirring for 1 minute at a rotation speed of 4,000 rpm using a disperser (Primix Corporation, product name: Homomixer) to prepare a suspension in which droplets of monomer composition containing a hydrophobic solvent were dispersed in water.

[0125] (3) Polymerization process The suspension obtained in the suspension process above was heated in a nitrogen atmosphere from 40°C to 65°C over 1 hour and 30 minutes, and then stirred for 4 hours under the temperature of 65°C to carry out the polymerization reaction. This polymerization reaction yielded a precursor composition, which is a slurry liquid in which precursor particles containing a hydrophobic solvent are dispersed in water.

[0126] (4) Washing and Solid-Liquid Separation Process The precursor composition obtained in the polymerization process was washed with dilute sulfuric acid (25°C, 10 minutes) to reduce the pH to 5.5 or less. Next, after separating the water by filtration, 200 parts of freshly deionized water were added to re-form a slurry, and the water washing treatment (washing, filtration, dewatering) was repeated several times at room temperature (25°C), and the solid was separated by filtration. The obtained solid was dried in a dryer at a temperature of 40°C to obtain precursor particles containing a hydrophobic solvent.

[0127] (5) Solvent Removal Process The precursor particles obtained in the solid-liquid separation process were heat-treated in a vacuum dryer at 200°C under vacuum conditions for 6 hours to remove the hydrophobic solvent contained within the particles and obtain hollow organic particles. The obtained hollow organic particles were confirmed to be spherical and have hollow parts based on observations using a scanning electron microscope and the porosity value. Furthermore, the settling rate was 10%, confirming that the hollow organic particles have through-pores.

[0128] (Example 7) Hollow organic particles and lithium-ion secondary batteries were manufactured in the same procedure as in Example 1, except that steps (1) Mixture preparation step to (5) Solvent removal step were performed as described below, according to the method corresponding to Manufacturing Example 3 in International Publication No. 2020 / 066704, and various measurements and evaluations were performed. The results are shown in Table 1. (1) Mixture preparation step First, the following materials were mixed to form an oil phase. 24 parts ethylene glycol dimethacrylate (crosslinkable monomer other than epoxy group-containing monomer) 20 parts pentaerythritol tetraacrylate (crosslinkable monomer other than epoxy group-containing monomer) 17 parts divinylbenzene (crosslinkable monomer other than epoxy group-containing monomer) 13 parts ethyl vinylbenzene (aromatic monovinyl monomer) 26 parts 2-hydroxy-3-methacryloyloxypropyl acrylate (hydroxyl group-containing monomer) 3 parts 2,2'-azobis(2,4-dimethylvaleronitrile) (oil-soluble polymerization initiator) 0.007 parts rosinic acid (softening point 150°C or higher, acid value: 150-160 mg KOH / g) 100 parts hydrophobic solvent: cyclohexane

[0129] Next, 1.0 part of a surfactant was added to 800 parts of deionized water to prepare an aqueous solution, which was then used as the aqueous phase. The resulting aqueous phase and the oil phase were mixed to prepare a mixed solution.

[0130] (2) Suspension step The mixture obtained was stirred using an in-line emulsifier and disperser to obtain a suspension.

[0131] (3) Polymerization step The obtained suspension was subjected to a polymerization reaction by stirring under a nitrogen atmosphere at a temperature of 65°C for 4 hours. This polymerization reaction yielded a precursor composition, which is a slurry liquid in which precursor particles containing a hydrophobic solvent are dispersed in water.

[0132] (4) Washing and solid-liquid separation steps The obtained precursor composition was filtered to obtain a solid component, and the obtained solid component was dried in a dryer at a temperature of 40°C to obtain precursor particles containing a hydrophobic solvent.

[0133] (5) Solvent Removal Process Next, the precursor particles containing the hydrophobic solvent were heat-treated in a vacuum dryer at 200°C under vacuum conditions for 6 hours to remove the hydrophobic solvent contained within the particles and obtain hollow organic particles. Observation results from a scanning electron microscope and porosity values ​​confirmed that the obtained hollow organic particles were spherical and had hollow parts. Furthermore, the settling rate was 10%, confirming that the hollow organic particles had through-pores.

[0134] (Comparative Example 1) A lithium-ion secondary battery was manufactured in the same manner as in Example 1, except that a polymer without hollow parts (particulate binder) produced by the following procedure was used instead of the hollow organic particles in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1. In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 62.5 parts of styrene, 1 part of 2-hydroxyethyl acrylate, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized water, and 0.5 parts of potassium persulfate as a polymerization initiator were added and stirred thoroughly, and 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 the particulate binder. A 5% aqueous sodium hydroxide solution was added to the mixture containing the above-mentioned particulate binder to adjust the pH to 8. After removing unreacted monomers by heated vacuum distillation, the mixture was cooled to below 30°C to obtain an aqueous dispersion containing the desired particulate binder.

[0135] (Comparative Example 2) A lithium-ion secondary battery was manufactured in the same manner as in Example 1, except that a polymer without hollow parts (particulate binder) produced by the following procedure was used instead of the hollow organic particles in Example 1, and various measurements and evaluations were performed. The results are shown in Table 1. 95 parts of butyl acrylate, 2 parts of acrylonitrile, 1 part of allyl methacrylate, 2 parts of methacrylic acid, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of deionized water, and 0.5 parts of potassium persulfate as a polymerization initiator were placed in a 5 MPa pressure vessel with a stirrer, and after thorough stirring, the mixture was heated to 50°C to start polymerization. When the polymerization conversion rate reached 96%, the mixture was cooled to stop the reaction and a mixture containing particulate binder was obtained. A 5% aqueous sodium hydroxide solution was added to the mixture containing the particulate binder to adjust the pH to 8, and after removing unreacted monomers by heated vacuum distillation, the mixture was cooled to below 30°C to obtain an aqueous dispersion containing the desired particulate binder.

[0136] (Comparative Example 3) Hollow organic particles and lithium-ion secondary batteries were manufactured using the same procedure as in Example 1, except that the amount of MEK added as a reaction-accelerating additive in "(3) Polymerization step" was changed from 5 parts to 1 part. Various measurements and evaluations were then performed. The results are shown in Table 1.

[0137] As shown in Table 1, in Examples 1 to 7, which use a functional layer containing hollow organic particles having a shell portion and a hollow portion surrounded by the shell portion, wherein the shell portion has at least one through-hole communicating with the hollow portion, and the volume average particle diameter is 0.8 μm or more, it can be seen that the increase in the internal resistance of lithium-ion secondary batteries can be suppressed.

[0138] According to the present invention, it is possible to provide hollow organic particles for an electrochemical element functional layer that can form a functional layer for an electrochemical element that can suppress an increase in the internal resistance of the electrochemical element. Furthermore, according to the present invention, it is possible to provide a composition for an electrochemical element functional layer that can form a functional layer for an electrochemical element that can suppress an increase in the internal resistance of the electrochemical element. Furthermore, according to the present invention, it is possible to provide a functional layer for an electrochemical element that can suppress an increase in the internal resistance of the electrochemical element. And according to the present invention, it is possible to provide an electrochemical element in which an increase in internal resistance is suppressed.

Claims

1. Hollow organic particles for an electrochemical element functional layer, having a shell portion and a hollow portion surrounded by the shell portion, wherein the shell portion has at least one through-hole communicating with the hollow portion, and the volume average particle diameter is 0.8 μm or more.

2. Hollow organic particles for an electrochemical element functional layer according to claim 1, wherein the volume-average particle diameter is 20 μm or less.

3. Hollow organic particles for an electrochemical element functional layer according to claim 1, wherein the porosity is 40% or more and 90% or less.

4. Hollow organic particles for an electrochemical element functional layer according to claim 1, wherein the breaking strength is 5 MPa or more.

5. The hollow organic particle for an electrochemical element functional layer according to claim 1, wherein the shell portion is made of a polymer having a glass transition temperature of 50°C or higher.

6. The hollow organic particle for an electrochemical element functional layer according to claim 1, wherein the shell portion is made of a polymer containing at least one monomer unit selected from the group consisting of epoxy group-containing monomer units, crosslinkable monomer units other than epoxy group-containing monomer units, hydroxyl group-containing monomer units, aromatic monovinyl monomer units, and conjugated diene monomer units.

7. A composition for an electrochemical element functional layer, comprising hollow organic particles for an electrochemical element functional layer as described in claim 1.

8. The composition for the functional layer of an electrochemical element according to claim 7, further comprising functional particles.

9. A functional layer for an electrochemical element formed using the electrochemical element functional layer composition according to claim 7 or 8.

10. An electrochemical element comprising the functional layer for an electrochemical element described in claim 9.

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