Laminate for electrochemical element and electrochemical element

Abstract

The purpose of the present invention is to provide a multilayer body for electrochemical elements, said multilayer body being able to be advantageously used as an element member that is excellent in terms of bondability at low temperatures and blocking resistance. A multilayer body according to the present invention is provided with a base material and a functional layer that contains heat-resistant fine particles and adhesive particles. The adhesive particles contain an adhesive polymer that contains an aromatic vinyl monomer unit and a wax that has a melting point of less than 95°C. In addition, if this multilayer body is viewed in plan from the functional layer side, the functional layer comprises a bonding region that is composed of the adhesive particles and a heat-resistant region that is composed of the heat-resistant fine particles, and the volume-average particle diameter of the adhesive particles is larger than the average height of the heat-resistant region in the layer stacking direction.

Description

[Technical Field]

[0001] The present invention relates to a laminate for an electrochemical device and an electrochemical device. [Background technology]

[0002] Electrochemical devices such as lithium ion secondary batteries, electric double layer capacitors, and lithium ion capacitors are small, lightweight, have high energy density, and are capable of repeated charging and discharging, and are therefore used in a wide range of applications. Electrochemical devices generally include multiple electrodes and element components such as separators that isolate the electrodes and prevent internal short circuits.

[0003] Here, laminates for electrochemical devices have been used as element components such as electrodes and separators, which are formed by laminating layers (functional layers) for exhibiting desired functions such as heat resistance and adhesiveness on a substrate. When forming the functional layers provided in such laminates, particles capable of exhibiting heat resistance (heat-resistant fine particles) and particles capable of exhibiting adhesiveness (adhesive particles) have been used in combination (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 034093 [Patent Document 2] International Publication No. 2018 / 034094 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, when manufacturing an electrochemical device, multiple element components such as electrodes and separators are stacked, arbitrarily wound, and then hot-pressed to produce a cell. However, when using element components made of the conventional laminate described above, shortening the hot-pressing time to improve cell production efficiency, etc., causes a problem in that the functional layer in the laminate located in the center of the cell, where heat is not sufficiently transferred, is difficult to exhibit sufficient adhesiveness. To address this problem, a method of ensuring low-temperature adhesiveness by lowering the glass transition temperature of adhesive particles in the functional layer is considered. However, according to the inventors' investigations, it has become clear that element components that have achieved low-temperature adhesiveness using this method have a problem in that the element components stick together (i.e., block) via the functional layer when stored or transported in a wound state.

[0006] That is, the above-mentioned conventional laminates have room for further improvement in terms of exhibiting a good balance of low-temperature adhesiveness and blocking resistance when used as element members.

[0007] Therefore, an object of the present invention is to provide a laminate for an electrochemical device that can be advantageously used as a device member having excellent low-temperature adhesion and blocking resistance, and an electrochemical device that includes the laminate for an electrochemical device as a device member. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to achieve the above object, and have found that, when producing a laminate having a functional layer on a substrate, by using adhesive particles made of a predetermined adhesive polymer and a wax having a melting point lower than a predetermined value and forming the functional layer on the substrate into a predetermined shape, the laminate can be used as a device component having excellent low-temperature adhesion and excellent blocking resistance, and have completed the present invention.

[0009] The present invention aims to advantageously solve the above-mentioned problems, and provides a laminate for an electrochemical device comprising a substrate and a functional layer containing heat-resistant fine particles and adhesive particles, wherein the adhesive particles contain an adhesive polymer containing aromatic vinyl monomer units and a wax having a melting point of less than 95°C, and when viewed from above from the functional layer side, the functional layer comprises an adhesive region made of the adhesive particles and a heat-resistant region made of the heat-resistant fine particles, and the volume-average particle diameter of the adhesive particles is greater than the average height in the stacking direction of the heat-resistant region. The above-mentioned laminate can be advantageously used as a device component having excellent low-temperature adhesion and blocking resistance. In the present invention, the phrase "containing a monomer unit" means that the polymer obtained using the monomer contains repeating units derived from the monomer. In the present invention, the "melting point" of the wax can be determined by measuring the melting point using a differential scanning calorimeter (DSC) under conditions of a temperature increase of 100°C / min and finding the maximum value of the resulting DSC curve. In the present invention, the "volume average particle size" of the adhesive particles contained in the functional layer can be measured using the method described in the examples. Furthermore, in the present invention, the "average height in the stacking direction" of the heat-resistant region can be measured using the method described in the examples.

[0010] In the laminate for an electrochemical device of the present invention, the adhesive particles preferably have a volume average particle diameter of 1.0 μm or more and 10.0 μm or less. If the volume average particle diameter of the adhesive particles is within the above range, the heat resistance of the device member made of the laminate can be increased, and the low-temperature adhesion and blocking resistance can be further improved.

[0011] In the laminate for electrochemical devices of the present invention, the ratio of the volume average particle diameter of the adhesive particles to the average height in the stacking direction of the heat-resistant region is preferably 1.1 to 10.0. If the ratio of the volume average particle diameter of the adhesive particles to the average height in the stacking direction of the heat-resistant region (volume average particle diameter of adhesive particles / average height in the stacking direction of the heat-resistant region) is within the above-mentioned range, the heat resistance of the device member made of the laminate can be increased, while the low-temperature adhesion and blocking resistance can be further improved.

[0012] In the laminate for an electrochemical device of the present invention, the adhesive particles preferably have a glass transition temperature of 10° C. or higher and 90° C. or lower. If the glass transition temperature of the polymer contained in the adhesive particles is within the above-mentioned range, the low-temperature adhesiveness and blocking resistance of the device member made of the laminate can be further improved. In the present invention, the "glass transition temperature" of the adhesive particles and the like can be measured using the method described in the Examples.

[0013] In the laminate for electrochemical devices of the present invention, the adhesive polymer preferably further contains a crosslinkable monomer unit. Use of an adhesive polymer containing a crosslinkable monomer unit in addition to an aromatic vinyl monomer unit can further improve the low-temperature adhesiveness of the device member made of the laminate.

[0014] In the laminate for an electrochemical device of the present invention, the heat-resistant fine particles are preferably inorganic fine particles. By using inorganic fine particles as the heat-resistant fine particles, the heat resistance of the device member made of the laminate can be improved.

[0015] In the laminate for an electrochemical device of the present invention, the wax is preferably an ester wax. Use of an ester wax as the wax can further improve the low-temperature adhesiveness of the device members made of the laminate.

[0016] In the laminate for an electrochemical device of the present invention, the melting point of the wax is preferably 40° C. or higher. Use of a wax with a melting point of 40° C. or higher can further improve the blocking resistance of the device member made of the laminate.

[0017] In addition, in the laminate for electrochemical devices of the present invention, the volume ratio of the content of the heat-resistant fine particles to the content of the adhesive particles in the functional layer is preferably from 55 / 45 to 95 / 5. If the volume ratio of the content of the heat-resistant fine particles to the content of the adhesive particles in the functional layer (heat-resistant fine particles / adhesive particles) is within the above-mentioned range, it is possible to further improve the low-temperature adhesion while increasing the heat resistance of the device component made of the laminate.

[0018] Furthermore, the present invention aims to advantageously solve the above-mentioned problems, and provides an electrochemical element comprising an electrode and a separator, wherein at least one of the electrode and the separator is formed using any one of the above-mentioned laminates for electrochemical elements. An electrochemical element comprising any one of the above-mentioned laminates as an element component has excellent element characteristics such as rate characteristics and cycle characteristics. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a laminate for an electrochemical device that can be advantageously used as a device component having excellent low-temperature adhesion and blocking resistance, and an electrochemical device including the laminate for an electrochemical device as a device component. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a plan view schematically showing an example of a laminate for an electrochemical device according to the present invention when viewed from the functional layer side. [Figure 2] 1 is a cross-sectional view schematically showing an example of a cross section in the stacking direction of a laminate for an electrochemical device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail. The laminate for an electrochemical device of the present invention can be used as element members such as separators and electrodes (positive and negative electrodes).The electrochemical device of the present invention includes the laminate for an electrochemical device of the present invention as an element member.

[0022] (Laminate for electrochemical devices) The laminate of the present invention includes a substrate and a functional layer formed on the substrate. The functional layer on the substrate includes, in plan view, at least an adhesive region made of adhesive particles and a heat-resistant region made of heat-resistant fine particles. The adhesive particles constituting the adhesive region have a volume-average particle diameter greater than the average height in the stacking direction of the heat-resistant region.

[0023] The laminate of the present invention having such a configuration can adhere well to the substrate via the functional layer, presumably because there are many places in the functional layer where the adhesive particles in the adhesive region protrude beyond the heat-resistant region. In addition, the adhesive polymer and / or wax derived from the adhesive particles melted by the heat press penetrates into the matrix of the heat-resistant fine particles that make up the heat-resistant region, presumably acting as an anchor (anchor effect is obtained), improving the low-temperature adhesion of the device component made up of the laminate. On the other hand, the heat-resistant region presumably prevents the adhesive polymer and / or wax derived from the adhesive particles melted by the heat press from spreading excessively in a direction parallel to the substrate surface, thereby ensuring a path for charge carriers such as lithium ions, improving device characteristics such as rate characteristics and cycle characteristics.

[0024] An example of the laminate of the present invention will be further described with reference to FIGS. 1 is a plan view schematically illustrating an example of a laminate 100 for an electrochemical device according to the present invention, as viewed from the functional layer side. In FIG. 1, a heat-resistant region 12 and a plurality of adhesive regions 11 surrounded by the heat-resistant region 12 are present on the surface of a functional layer 10 included in the laminate 100 for an electrochemical device. FIG. 2 is a cross-sectional view schematically illustrating an example of a cross section in the stacking direction of a laminate 100 for electrochemical devices according to the present invention. In FIG. 2, the laminate 100 for electrochemical devices is formed by stacking a functional layer 10 on a substrate 20, and the functional layer 10 has an adhesive region 11 and a heat-resistant region 12. The adhesive region 11 is composed of adhesive particles 11a, and the heat-resistant region 12 is composed of a plurality of heat-resistant fine particles 12a overlapping in the stacking direction (thickness direction). In FIG. 2, the particle diameter D of the adhesive particles (height from the substrate surface in the stacking direction) is larger than the height T of the heat-resistant region in the stacking direction. In the laminate of the present invention, the volume-average particle diameter of the adhesive particles is larger than the average height in the stacking direction of the heat-resistant region, and therefore, it is believed that there are many locations where the adhesive particles protrude, as shown in FIG. 2.

[0025] The laminate of the present invention is not limited to the examples shown in FIGS. 1 and 2. For example, in the laminate of the present invention, functional layers may be provided on both sides of the substrate. Here, when the laminate of the present invention has functional layers on both sides of the substrate, at least one of the functional layers may be a functional layer that satisfies predetermined properties. Furthermore, in the laminate of the present invention, the adhesive region of the functional layer may be composed of a single adhesive particle as shown in FIG. 2, or may be formed by a collection of multiple adhesive particles. Furthermore, in the laminate of the present invention, the adhesive region of the functional layer may be composed only of adhesive particles as shown in FIG. 2, or may be composed of adhesive particles and other components such as a binder described below. In addition, in the laminate of the present invention, the heat-resistant region of the functional layer may be composed only of heat-resistant fine particles as shown in FIG. 2, or may be composed of heat-resistant fine particles and other components such as a binder described below.

[0026] <Volume average particle size of adhesive particles> The volume average particle diameter of the adhesive particles is not particularly limited as long as it is greater than the average height in the stacking direction of the heat-resistant region, but is preferably 1.0 μm or more, more preferably 2.5 μm or more, even more preferably 5.0 μm or more, and particularly preferably 6.0 μm or more, and is preferably 10.0 μm or less, more preferably 9.0 μm or less, and even more preferably 8.0 μm or less. When the volume average particle diameter of the adhesive particles is 1.0 μm or more, it is presumed that the adhesive particles in the adhesive region protrude further than the heat-resistant region, which further improves the low-temperature adhesiveness of the element member made of the laminate. Furthermore, it is presumed that the larger volume average particle diameter of the adhesive particles allows the heat-resistant fine particles to be more densely packed in the heat-resistant region adjacent to the adhesive region, which improves the heat resistance of the element member made of the laminate. In addition, it is presumed that a gap is secured between the heat-resistant region and the adherend when adhering the element member having the functional layer to the adherend, which improves the electrolyte injectability of the electrochemical element. On the other hand, if the volume average particle diameter of the adhesive particles is 10.0 μm or less, the number of adhesive particles per unit volume of the functional layer (particle count) increases, which is presumably because the number of adhesion points increases when adhering an element member having the functional layer to an adherend, and the low-temperature adhesion of the element member can be further improved. In addition, the adhesive particles can be prevented from falling off, and a functional layer can be formed on the substrate in which adhesion areas made of adhesive particles are evenly distributed. The volume average particle size of the adhesive particles can be adjusted by changing the manufacturing conditions of the adhesive particles.

[0027] <Average height of heat-resistant area in the stacking direction> The average height of the heat-resistant region in the stacking direction is not particularly limited as long as it is smaller than the volume average particle diameter of the adhesive particles, but is preferably 0.5 μm or more, more preferably 0.8 μm or more, even more preferably 1.0 μm or more, preferably less than 5.0 μm, more preferably less than 4.0 μm, even more preferably less than 2.5 μm, and particularly preferably 2.0 μm or less. If the average height of the heat-resistant region in the stacking direction is 0.5 μm or more, the heat resistance of the element member including the functional layer can be sufficiently ensured, and if it is less than 5.0 μm, the ion diffusibility of the functional layer can be ensured, thereby improving the rate characteristics and cycle characteristics of the electrochemical element. The average height of the heat-resistant region in the stacking direction can be adjusted by changing the conditions for forming the functional layer (the content of heat-resistant microparticles in the functional layer composition used to form the functional layer, and the thickness of the coating obtained by supplying the functional layer composition onto the substrate).

[0028] <Volume average particle size of adhesive particles / Average height in the layering direction of the heat-resistant region> The ratio of the volume average particle diameter of the adhesive particles to the average height of the heat-resistant region in the stacking direction (volume average particle diameter of adhesive particles / average height of the heat-resistant region in the stacking direction) is preferably 1.1 or more, more preferably 1.2 or more, even more preferably 1.6 or more, and preferably 10.0 or less, more preferably 5.0 or less, even more preferably 4.5 or less, and particularly preferably 3.5 or less. If the ratio is 1.1 or more, it is presumed that this is because the adhesive particles in the adhesive region sufficiently protrude beyond the heat-resistant region, which further improves the low-temperature adhesiveness of the element member composed of the laminate. On the other hand, if the ratio is 10.0 or less, it is presumed that this is because the number of adhesive particles (particle number) per unit volume of the functional layer increases, thereby increasing the number of adhesive points when adhering the element member having the functional layer to the adherend, which further improves the low-temperature adhesiveness of the element member.

[0029] <Functional layer> The functional layer of the laminate of the present invention having the above-described structure contains heat-resistant fine particles and adhesive particles containing an adhesive polymer and wax. The functional layer may contain components (other components) other than the heat-resistant fine particles and adhesive particles (adhesive polymer and wax).

[0030] <<Heat-resistant fine particles>> Here, the heat-resistant fine particles contained in the functional layer are not particularly limited, and examples thereof include particles made of inorganic materials (i.e., inorganic fine particles) and particles made of organic materials (i.e., organic fine particles) that are stable and electrochemically stable in the environment in which the electrochemical element is used. As the heat-resistant fine particles, inorganic fine particles and organic fine particles may be used alone, or inorganic fine particles and organic fine particles may be used in combination.

[0031] [Inorganic fine particles] Examples of inorganic fine particles include inorganic oxide particles such as aluminum oxide (alumina, Al2O3), aluminum oxide hydrate (boehmite, AlOOH), gibbsite (Al(OH)3), silicon oxide, magnesium oxide (magnesia), magnesium hydroxide, calcium oxide, titanium oxide (titania), barium titanate (BaTiO3), ZrO, and alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalently bonded crystalline particles such as silicon and diamond; sparingly soluble ionic crystalline particles such as barium sulfate, calcium fluoride, and barium fluoride; and clay fine particles such as talc and montmorillonite. These particles may be subjected to element substitution, surface treatment, solid solution formation, etc., as necessary. The inorganic fine particles may be used singly or in combination of two or more types.

[0032] [Organic fine particles] The organic fine particles are fine particles made of a polymer that does not have adhesive properties, unlike the adhesive polymer contained in the adhesive particles described above. Examples of organic fine particles include various crosslinked polymer particles such as crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked products, polystyrene, polyimide, polyamide, polyamideimide, melamine resin, phenolic resin, and benzoguanamine-formaldehyde condensate, as well as heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide, as well as modified products and derivatives thereof. The organic fine particles may be used singly or in combination of two or more types. As described above, the organic fine particles are made of a polymer that does not have adhesive properties. Specifically, the glass transition temperature of the polymer that makes up the organic fine particles is preferably 90°C or higher, and more preferably 150°C or higher.

[0033] Among the above-mentioned heat-resistant fine particles, from the viewpoint of further improving the heat resistance of the element component, particles made of alumina (alumina particles), particles made of boehmite (boehmite particles), particles made of titania (titania particles), particles made of barium sulfate (barium sulfate particles), and organic fine particles having a glass transition temperature of 150°C or higher are preferred, and alumina particles, boehmite particles, titania particles, and barium sulfate particles are more preferred.

[0034] [Properties of heat-resistant particles] The heat-resistant fine particles preferably have a volume-average particle diameter of 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and preferably 1.0 μm or less, more preferably 0.9 μm or less, and even more preferably 0.8 μm or less. When the volume-average particle diameter of the heat-resistant fine particles is 0.1 μm or more, the heat-resistant fine particles are densely packed in the functional layer. This prevents a decrease in the ionic conductivity of the functional layer, allowing the electrochemical device to exhibit excellent device characteristics (especially rate characteristics). On the other hand, when the volume-average particle diameter of the heat-resistant fine particles is 1.0 μm or less, even when the functional layer is thinned, the device component comprising the laminate including the functional layer can fully exhibit excellent heat resistance. Therefore, the capacity of the electrochemical device can be increased while ensuring sufficient heat resistance of the device component.

[0035] <<Adhesive particles>> The adhesive particles are formed by the cooperation of at least an adhesive polymer and a wax to assume a particulate form. Here, in the adhesive particles, the adhesive polymer and the wax may exist separately, but it is preferable that they exist in a state where they are at least partially compatible (mixed). The adhesive particles may optionally contain components (optional components) other than the adhesive polymer and the wax.

[0036] [Adhesive polymer] The adhesive polymer contained in the adhesive particles contains at least an aromatic vinyl monomer unit, and may contain a monomer unit other than the aromatic vinyl monomer unit (another monomer unit).

[0037] -Aromatic vinyl monomer unit- When the adhesive polymer contains an aromatic vinyl monomer unit, the elasticity of the adhesive particles is improved, and the strength of the functional layer can be increased. Here, examples of aromatic vinyl monomers that can form aromatic vinyl monomer units are not particularly limited, and include, for example, styrene, α-methylstyrene, styrene sulfonic acid, butoxystyrene, vinylnaphthalene, etc. These may be used alone or in combination of two or more. Among these, styrene is preferred.

[0038] The content of the aromatic vinyl monomer units in the adhesive polymer is preferably 30% by mass or more, more preferably 60% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, when the total amount of all monomer units in the adhesive polymer is taken as 100% by mass. If the content of the aromatic vinyl monomer units is 30% by mass or more, the elasticity of the adhesive particles can be sufficiently improved, further increasing the strength of the functional layer. Therefore, the low-temperature adhesiveness of the device member comprising the laminate can be further improved. On the other hand, if the content of the aromatic vinyl monomer units is 90% by mass or less, the flexibility of the adhesive particles can be increased, further improving the low-temperature adhesiveness of the device member comprising the laminate. Furthermore, if the content of the aromatic vinyl monomer units is within the above-mentioned range, it is presumed that a good balance between the elasticity and flexibility of the adhesive particles is ensured, as described above. This further improves the low-temperature adhesiveness of the device member comprising the laminate, and allows the electrochemical device to exhibit excellent device characteristics (rate characteristics, cycle characteristics). In the present invention, the "content ratio of each monomer unit" contained in the polymer is 1 It can be measured using nuclear magnetic resonance (NMR) techniques such as H-NMR.

[0039] -Other monomer units- The other monomer units are not particularly limited, but preferred examples include crosslinkable monomer units and (meth)acrylic acid ester monomer units. In the present invention, "(meth)acrylic" means acrylic and / or methacrylic.

[0040] The crosslinkable monomer capable of forming the crosslinkable monomer unit is a monomer capable of forming a crosslinked structure during or after polymerization by heating or irradiation with energy rays. When the adhesive polymer contains the crosslinkable monomer unit, the elasticity of the adhesive particles can be improved, and as a result, the low-temperature adhesiveness of the element member made of the laminate can be further improved.

[0041] Examples of monomers capable of forming crosslinkable monomer units include polyfunctional monomers having two or more polymerization reactive groups. Examples of such polyfunctional monomers include divinyl compounds such as allyl methacrylate and divinylbenzene; di(meth)acrylic acid ester compounds such as diethylene glycol dimethacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, and 1,3-butylene glycol diacrylate; tri(meth)acrylic acid ester compounds such as trimethylolpropane trimethacrylate and trimethylolpropane triacrylate; and ethylenically unsaturated monomers containing epoxy groups such as allyl glycidyl ether and glycidyl methacrylate. These may be used alone or in combination of two or more. Among these, ethylene glycol dimethacrylate is preferred.

[0042] The content of the crosslinkable monomer units in the adhesive polymer is preferably 0.02% by mass or more, preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1% by mass or less, when the amount of all monomer units in the adhesive polymer is taken as 100% by mass. If the content of the crosslinkable monomer units is within the above range, the adhesive polymer contained in the adhesive polymer can be sufficiently prevented from eluting into the electrolyte solution. In addition, the elasticity of the adhesive particles can be improved, and as a result, the low-temperature adhesiveness of the element member made of the laminate can be further improved.

[0043] In addition, examples of (meth)acrylic acid ester monomers that can form (meth)acrylic acid ester monomer units include acrylates such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylate (n-butyl acrylate, t-butyl acrylate, etc.), pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate (2-ethylhexyl acrylate, etc.), nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate. and alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, butyl methacrylate (such as n-butyl methacrylate and t-butyl methacrylate), pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate (such as 2-ethylhexyl methacrylate), nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, and stearyl methacrylate. These (meth)acrylic acid ester monomers may be used alone or in combination of two or more. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate are preferred, and n-butyl acrylate and 2-ethylhexyl acrylate are more preferred.

[0044] The content of (meth)acrylic acid ester monomer units in the adhesive polymer is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 65% ​​by mass or less, more preferably 60% by mass or less, and even more preferably 35% by mass or less, when the total monomer units in the adhesive polymer is taken as 100% by mass. If the content of (meth)acrylic acid ester monomer units is 5% by mass or more, an excessive decrease in the glass transition temperature of the adhesive particles can be suppressed, and the blocking resistance of the element member made of the laminate can be further improved. On the other hand, if the content of (meth)acrylic acid ester monomer units is 65% by mass or less, the low-temperature adhesiveness of the element member made of the laminate can be further improved.

[0045] In addition to the above-mentioned crosslinkable monomer unit and (meth)acrylic acid ester monomer unit, other monomer units are not particularly limited and include monomer units described later in the section "Binder" (excluding those corresponding to any of aromatic vinyl monomer units, crosslinkable monomer units, and (meth)acrylic acid ester monomer units).

[0046] Furthermore, the content of monomer units other than the above-mentioned aromatic vinyl monomer units, crosslinkable monomer units, and (meth)acrylic acid ester monomer units in the adhesive polymer is preferably 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 7% by mass or less, and even more preferably 0% by mass or more and 5% by mass or less, when the total monomer units in the adhesive polymer is 100% by mass, from the viewpoint of ensuring the stability of the functional layer composition used to form the functional layer.

[0047] [wax] The wax contained in the adhesive particles and having a melting point of less than 95°C constitutes the adhesive particles together with the adhesive polymer described above. By using adhesive particles containing wax to form the functional layer of the laminate, it is possible to improve the low-temperature adhesion while ensuring the blocking resistance of the element member made of the laminate. The reason for this is unclear, but is presumed to be as follows. That is, when the element member made of the laminate is hot-pressed, the aforementioned anchor effect is obtained, and the element member exhibits excellent low-temperature adhesion, whereas wax is unlikely to exhibit its adhesive ability during storage, transportation, etc. at room temperature. Therefore, by forming a functional layer using adhesive particles containing wax with a melting point of less than 95°C, it is thought that the element member made of the laminate can achieve both excellent low-temperature adhesion and blocking resistance.

[0048] -Melting point- As mentioned above, the melting point of the wax must be less than 95°C, preferably 90°C or less, more preferably 70°C or less, even more preferably 60°C or less, preferably 40°C or more, and more preferably 44°C or more. If the melting point of the wax is 95°C or more, the low-temperature adhesiveness of the element member made of the laminate will decrease. On the other hand, if the melting point of the wax is 40°C or more, the blocking resistance of the element member made of the laminate can be further improved.

[0049] -kinds- The wax contained in the adhesive particles is not particularly limited as long as it has a melting point of less than 95°C, and vegetable waxes, animal waxes, petroleum waxes, synthetic waxes, and modified products thereof can be used.

[0050] Specific examples of vegetable waxes include candelilla wax, carnauba wax, rice wax, Japan wax, jojoba oil, and the like. A specific example of the animal wax is beeswax. Specific examples of petroleum waxes include paraffin wax, microcrystalline wax, and petrolatum wax. Synthetic waxes can be classified into Fischer-Tropsch waxes, polyolefin waxes, ester waxes, and the like.

[0051] Specific examples of polyolefin waxes include polyethylene wax, polypropylene wax, and polybutylene wax. As the ester wax, both monohydric alcohol fatty acid esters and polyhydric alcohol fatty acid esters can be used. Specific examples of monohydric alcohol fatty acid esters include behenyl stearate. Specific examples of polyhydric alcohol fatty acid esters include pentaerythritol esters such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, pentaerythritol tetrastearate, pentaerythritol tetralaurate, and pentaerythritol tetrabehenate; and dipentaerythritol esters such as dipentaerythritol hexamyristate, dipentaerythritol hexapalmitate, and dipentaerythritol hexalaurate.

[0052] The wax may be used singly or in combination of two or more. As the wax, ester wax and paraffin wax are preferred, and ester wax is more preferred, from the viewpoint that the wax has excellent compatibility with the monomer composition used to prepare the adhesive polymer, and therefore the content in the adhesive particles can be easily increased, thereby further improving the low-temperature adhesiveness of the element member made of the laminate.

[0053] Here, the content of the wax in the adhesive particles is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 6 parts by mass or more, particularly preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 12 parts by mass or less, per 100 parts by mass of the adhesive polymer. If the content of the wax in the adhesive particles is 1 part by mass or more per 100 parts by mass of the adhesive polymer, the low-temperature adhesiveness of the element member composed of the laminate can be further improved. On the other hand, if the content of the wax in the adhesive particles is 30 parts by mass or less per 100 parts by mass of the adhesive polymer, wax bleed-out can be sufficiently suppressed, the blocking resistance of the element member composed of the laminate can be further improved, and the rate characteristics and cycle characteristics of an electrochemical element including the element member can be improved.

[0054] The wax content in the functional layer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 6 parts by mass or more, particularly preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably 12 parts by mass or less, per 100 parts by mass of the adhesive polymer. If the wax content in the functional layer is 1 part by mass or more per 100 parts by mass of the adhesive polymer, the low-temperature adhesiveness of the element member comprising the laminate can be further improved. On the other hand, if the wax content in the functional layer is 30 parts by mass or less per 100 parts by mass of the adhesive polymer, wax bleed-out can be sufficiently suppressed, the blocking resistance of the element member comprising the laminate can be further improved, and the rate characteristics and cycle characteristics of an electrochemical device comprising the element member can be improved.

[0055] [Optional ingredients] The adhesive particles may optionally contain components other than the adhesive polymer and wax described above, as long as the desired effects of the present invention are obtained. Specific examples of optional components are not particularly limited, but for example, when an ester wax is used as the wax described above, a saturated fatty acid zinc salt can be mentioned as an optional component. Note that the saturated fatty acid zinc salt is a different component from the wax described above. By using the ester wax together with the saturated fatty acid zinc salt, the adhesive particles melted by heat pressing can be quickly solidified due to the increased solidification temperature, making it easier to handle the adhesive body after heat pressing.

[0056] Here, the saturated fatty acid zinc salt is preferably a zinc salt of a monovalent linear saturated fatty acid. If the saturated fatty acid zinc salt is a zinc salt of a monovalent linear saturated fatty acid, the above-mentioned desired effects of the saturated fatty acid zinc can be preferably obtained. The number of carbon atoms in the monovalent linear saturated fatty acid is preferably 14 or more, more preferably 16 or more, even more preferably 18 or more, and preferably 24 or less. If the number of carbon atoms in the monovalent linear saturated fatty acid is within the above range, the above-mentioned desired effects of the saturated fatty acid zinc can be preferably obtained. Specific examples of monovalent straight-chain saturated fatty acids include myristic acid (carbon number: 14), palmitic acid (carbon number: 16), stearic acid (carbon number: 18), arachidic acid (carbon number: 20), behenic acid (carbon number: 22), and lignoceric acid (carbon number: 24). The saturated fatty acid zinc salts may be used alone or in combination of two or more.

[0057] [Properties of adhesive particles] In addition to the above-mentioned volume average particle size, the adhesive particles preferably have the following properties.

[0058] - Glass transition temperature - The adhesive particles preferably have a glass transition temperature of 10° C. or higher, more preferably 30° C. or higher, and even more preferably 40° C. or higher, and preferably 90° C. or lower, and more preferably 80° C. or lower. If the adhesive particles have a glass transition temperature of 10° C. or higher, the blocking resistance of the element member made of the laminate can be further improved, and if the glass transition temperature is 90° C. or lower, the low-temperature adhesiveness of the element member can be further improved.

[0059] -Electrolyte swelling rate- The adhesive particles preferably have an electrolyte swelling ratio of 1.0 or more, more preferably 1.2 or more, and even more preferably 1.3 or more, and preferably 15 or less, more preferably 10 or less, and even more preferably 3 or less. When the electrolyte swelling ratio of the adhesive particles is 1.0 or more, the element component immersed in the electrolyte can be firmly adhered to the adherend via the functional layer. On the other hand, when the electrolyte swelling ratio of the adhesive particles is 15 or less, the resistance of the functional layer in the electrolyte is reduced, thereby improving the rate characteristics and cycle characteristics of the electrochemical element. Furthermore, when the electrolyte swelling ratio of the adhesive particles is 15 or less, the electrolyte injection property of the electrochemical element can be improved. In the present invention, the "electrolyte swelling degree" of the adhesive particles can be measured by the method described in the examples.

[0060] [Preparation of adhesive particles] The method for preparing the adhesive particles containing the adhesive polymer and wax described above is not particularly limited, and examples thereof include a method of suspension polymerizing a monomer composition containing a monomer group such as an aromatic vinyl monomer and wax, a method of emulsion polymerizing the monomer composition and then agglomerating it, and a method of polymerizing the monomer composition by any method and then pulverizing the obtained polymer. However, from the viewpoint of enabling low-cost production, a method of suspension polymerizing the monomer composition is preferred. Here, as an example, a method for preparing adhesive particles by suspension polymerization will be described.

[0061] - Preparation of Monomer Composition - First, a monomer group such as an aromatic vinyl monomer, wax, and other compounding ingredients added as needed are mixed to prepare a monomer composition. When using a saturated fatty acid zinc salt together with a wax (especially an ester wax), it is preferable to prepare a wax composition by premixing the saturated fatty acid zinc salt and the wax prior to the preparation of the monomer composition, and then use the wax composition to prepare the monomer composition. Such a wax composition can be prepared, for example, by heating and melting the ester wax and the saturated fatty acid zinc salt to homogeneously mix them, then cooling and solidifying them, and pulverizing and / or granulating them. Examples of other compounding agents include chain transfer agents, polymerization regulators, polymerization reaction retarders, reactive fluidizing agents, fillers, flame retardants, antioxidants, and colorants.

[0062] - Droplet formation - Next, the monomer composition is dispersed in water, a polymerization initiator is added, and then droplets of the monomer composition are formed. Here, the method for forming the droplets is not particularly limited, and for example, the droplets can be formed by shearing and stirring an aqueous medium containing the monomer composition using a disperser such as an emulsifying disperser. Here, examples of the polymerization initiator include oil-soluble polymerization initiators such as t-butylperoxy-2-ethylhexanoate, azobisisobutyronitrile, etc. The polymerization initiator may be added after the monomer composition is dispersed in water, or may be added to the monomer composition before it is dispersed in water. From the viewpoint of stabilizing the formed droplets of the monomer composition in water, it is preferable to add a dispersion stabilizer to water to form the droplets of the monomer composition. As the dispersion stabilizer, for example, metal hydroxides such as magnesium hydroxide, sodium dodecylbenzenesulfonate, etc. can be used.

[0063] -polymerization- After forming droplets of the monomer composition, the water containing the formed droplets is heated to initiate polymerization, thereby forming adhesive particles in the water. The polymerization reaction temperature is preferably 50°C or higher and 95°C or lower. The polymerization reaction time is preferably 1 hour or higher and 10 hours or lower, preferably 8 hours or lower, and more preferably 6 hours or lower.

[0064] -Washing, filtering, dehydration and drying- After the polymerization is completed, the water containing the adhesive particles is washed, filtered, and dried in accordance with a conventional method, thereby obtaining the adhesive particles.

[0065] [Ratio of heat-resistant particles to adhesive particles] Here, the content ratio of heat-resistant fine particles to adhesive particles in the functional layer is not particularly limited, but the volume ratio of the heat-resistant fine particles to the adhesive particle content (heat-resistant fine particles / adhesive particles) is preferably 55 / 45 or more, more preferably 60 / 40 or more, even more preferably 65 / 35 or more, preferably 95 / 5 or less, more preferably 80 / 20 or less, even more preferably 75 / 25 or less, and particularly preferably 70 / 30 or less. If the heat-resistant fine particles / adhesive particles (volume basis) value is 55 / 45 or more, the heat resistance of the element member consisting of the laminate can be improved, and if it is 95 / 5 or less, the low-temperature adhesion of the element member can be further improved.

[0066] Furthermore, the mass ratio of the heat-resistant microparticles to the adhesive particle content (heat-resistant microparticles / adhesive particles) is preferably 49 / 51 or more, more preferably 58 / 42 or more, even more preferably 64 / 36 or more, and preferably 99 / 1 or less, more preferably 94 / 6 or less, and even more preferably 91 / 9 or less. If the heat-resistant microparticles / adhesive particles (by mass) ratio is 49 / 51 or more, the heat resistance of the element member made of a laminate having a functional layer can be improved, and if it is 99 / 1 or less, the low-temperature adhesion of the element member can be further improved.

[0067] <<Other ingredients>> The functional layer provided in the laminate of the present invention can contain components other than the heat-resistant microparticles and adhesive particles described above, such as a binder, a water-soluble polymer, and a dispersant (other than the water-soluble polymer) such as sodium dodecylbenzenesulfonate. The other components may be used singly or in combination of two or more. Among these, binders and water-soluble polymers are preferred. The binder and the water-soluble polymer are made of a polymer different from the adhesive polymer contained in the adhesive particles and the polymer constituting the organic fine particles.

[0068] [Binding material] The binder is not particularly limited, and examples thereof include known polymers that are water-insoluble and dispersible in a dispersion medium such as water, such as conjugated diene polymers, acrylic polymers, and polyvinylidene fluoride (PVDF). One binder may be used alone, or two or more binders may be used in combination. Preferred binders are conjugated diene polymers and acrylic polymers, and more preferred are acrylic polymers. In the present invention, the polymer being "water-insoluble" means that when 0.5 g of the polymer is dissolved in 100 g of water at 25°C, the insoluble content is 90 mass % or more.

[0069] - Conjugated diene polymer - The conjugated diene polymer refers to a polymer containing conjugated diene monomer units derived from a conjugated diene monomer. Specific examples of the conjugated diene polymer include, but are not limited to, copolymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units, such as styrene-butadiene copolymer (SBR), butadiene rubber (BR), acrylic rubber (NBR) (copolymers containing acrylonitrile units and butadiene units), and hydrogenated products thereof.

[0070] - Acrylic polymer - The acrylic polymer refers to a polymer containing (meth)acrylic acid ester monomer units. The acrylic polymer preferably contains, in addition to the (meth)acrylic acid ester monomer units, at least one of crosslinkable monomer units and acid group-containing monomer units.

[0071] Examples of (meth)acrylic acid ester monomers capable of forming (meth)acrylic acid ester monomer units include those mentioned above in the "adhesive particles" section. These may be used alone or in combination of two or more. Among these, butyl acrylate is preferred. Furthermore, the content of (meth)acrylic acid ester monomer units in the binder (acrylic polymer) is preferably more than 65% by mass, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, when the total amount of all monomer units in the binder is 100% by mass, and is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0072] Examples of crosslinkable monomers capable of forming crosslinkable monomer units include those mentioned above in the "adhesive particles" section. These may be used alone or in combination of two or more. Among these, allyl methacrylate and allyl glycidyl ether are preferred. Furthermore, the content of the crosslinkable monomer units in the binder (acrylic polymer) is preferably 0.1% by mass or more, preferably 3.0% by mass or less, and more preferably 2.5% by mass or less, when the total amount of monomer units in the binder is taken as 100% by mass. If the content of the crosslinkable monomer units is 0.1% by mass or more, the rate characteristics and cycle characteristics of the electrochemical device can be improved, and if it is 3.0% by mass or less, the low-temperature adhesion of the device member made of the laminate can be further improved.

[0073] Examples of acid group-containing monomers that can form acid group-containing monomer units include monomers having a carboxylic acid group, monomers having a sulfonic acid group, monomers having a phosphoric acid group, and monomers having a hydroxyl group. Examples of the monomer having a carboxylic acid group include monocarboxylic acids and dicarboxylic acids. Examples of the monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of the dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, (meth)acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methylpropanesulfonic acid, and 3-allyloxy-2-hydroxypropanesulfonic acid. In the present invention, "(meth)allyl" means allyl and / or methallyl. Furthermore, examples of the monomer having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. In the present invention, "(meth)acryloyl" means acryloyl and / or methacryloyl. Examples of the monomer having a hydroxyl group include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. These acid group-containing monomers may be used alone or in combination of two or more. Among these, monomers having a carboxylic acid group are preferred, and methacrylic acid is more preferred.

[0074] Furthermore, the content of the acid group-containing monomer units in the binder (acrylic polymer) is preferably 0.1% by mass or more, preferably 3.0% by mass or less, and more preferably 2.5% by mass or less, when the total amount of all monomer units in the binder is 100% by mass.

[0075] The acrylic polymer used as the binder may contain monomer units other than the (meth)acrylic acid ester monomer units, crosslinkable monomer units, and acid group-containing monomer units described above. Examples of other monomers that may form the other monomer units contained in the acrylic polymer include aliphatic conjugated diene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene; aromatic vinyl monomers described in the "adhesive particles" section; nitrile group-containing monomers such as acrylonitrile and methacrylonitrile; olefin monomers such as ethylene and propylene; and halogen atoms such as vinyl chloride and vinylidene chloride. Other monomers include vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl benzoate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether; vinyl ketone monomers such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; and heterocycle-containing vinyl compound monomers such as N-vinylpyrrolidone, vinylpyridine, and vinylimidazole. Among these, acrylonitrile is preferred as the other monomer. These other monomers may be used singly or in any combination of two or more at any ratio. The content of the other monomer units in the acrylic polymer may be adjusted as appropriate. Here, the binder may contain aromatic vinyl monomer units, but the content of aromatic vinyl monomer units in the binder (particularly the acrylic polymer) is preferably less than 30% by mass, more preferably 20% by mass or less, even more preferably 10% by mass or less, particularly preferably 5% by mass or less, and most preferably 0% by mass (i.e., no aromatic vinyl monomer units are contained), when the total amount of all monomer units in the binder is taken as 100% by mass.

[0076] - Properties of binder - The structure of the binder in the functional layer is not particularly limited, but is preferably non-particulate, unlike the adhesive particles described above. Note that the binder in the functional layer composition used to form the functional layer may be particulate or non-particulate.

[0077] The binder preferably has a glass transition temperature of −100° C. or higher, more preferably −90° C. or higher, even more preferably −80° C. or higher, preferably lower than 30° C., more preferably lower than 20° C., even more preferably lower than 15° C., and particularly preferably lower than 10° C. If the binder has a glass transition temperature of −100° C. or higher, the binding ability and strength of the binder can be increased, and if the glass transition temperature is lower than 30° C., the flexibility of the functional layer containing the binder can be sufficiently ensured.

[0078] - Binder content - The content of the binder in the functional layer is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the heat-resistant fine particles. If the content of the binder in the functional layer is 0.1 parts by mass or more per 100 parts by mass of the heat-resistant fine particles, the heat-resistant fine particles present in the heat-resistant region can be sufficiently prevented from falling off the functional layer, while the low-temperature adhesion of the element member including the functional layer can be further improved. On the other hand, if the content of the binder in the functional layer is 20 parts by mass or less per 100 parts by mass of the heat-resistant fine particles, the rate characteristics and cycle characteristics of the electrochemical element including the element member made of the laminate can be improved.

[0079] -Method for preparing binder- The binder is not particularly limited, and can be prepared, for example, by polymerizing a monomer composition containing the above-mentioned monomers in an aqueous solvent such as water. Here, the proportion of each monomer in the total monomers in the monomer composition is usually the same as the proportion of each monomer unit in the binder. The polymerization method and polymerization reaction are not particularly limited, and known methods can be used.

[0080] [Water-soluble polymer] The water-soluble polymer can function as a dispersant that disperses components such as heat-resistant fine particles and adhesive particles well in the functional layer composition used to form the functional layer, and / or as a thickener that imparts an appropriate viscosity to the functional layer composition. If the water-soluble polymer functions as, for example, the dispersant described above, these components can be dispersed well in the functional layer composition to form a functional layer in which heat-resistant regions containing heat-resistant fine particles and adhesive regions containing adhesive particles are uniformly distributed, thereby improving the heat resistance of the device member including the functional layer and further improving the low-temperature adhesiveness of the device member. In the present invention, a polymer being "water-soluble" means that when 0.5 g of the polymer is dissolved in 100 g of water at 25°C, the insoluble content is less than 1.0 mass %.

[0081] Examples of the water-soluble polymer include carboxymethyl cellulose and its salts, polyacrylic acid, etc., but polyacrylic acid is preferred from the viewpoint of better dispersing components such as heat-resistant fine particles and adhesive particles and further improving the heat resistance and low-temperature adhesiveness of the element members.

[0082] The content of the water-soluble polymer in the functional layer is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and even more preferably 0.3 parts by mass or more, and preferably 1 part by mass or less, more preferably 0.9 parts by mass or less, and even more preferably 0.8 parts by mass or less, per 100 parts by mass of the heat-resistant fine particles. If the content of the water-soluble polymer in the functional layer is 0.1 parts by mass or more per 100 parts by mass of the heat-resistant fine particles, components such as the heat-resistant fine particles and adhesive particles are more effectively dispersed, further improving the heat resistance and low-temperature adhesiveness of the device components. On the other hand, if the content of the water-soluble polymer in the functional layer is 1 part by mass or less per 100 parts by mass of the heat-resistant fine particles, a decrease in the ionic conductivity of the functional layer is suppressed, and the rate characteristics and cycle characteristics of the electrochemical device can be sufficiently ensured.

[0083] The water-soluble polymer is not particularly limited and can be prepared by a known method.

[0084] <Base material> The substrate having the functional layer on at least one surface thereof may be appropriately selected depending on the type of element member in which the laminate of the present invention is used. For example, when the laminate of the present invention is used as a separator, a separator substrate is used as the substrate. For example, when the laminate of the present invention is used as an electrode, an electrode substrate is used as the substrate.

[0085] <<Separator substrate>> The separator substrate is not particularly limited, and examples thereof include known separator substrates such as organic separator substrates, which are porous members made of organic materials, and examples of organic separator substrates include microporous membranes or nonwoven fabrics containing polyolefin resins such as polyethylene, polypropylene, polybutene, and polyvinyl chloride, and aromatic polyamide resins. Among these, a microporous film made of a polyolefin resin is preferred from the viewpoint that the ratio of the electrode active material in the electrochemical device can be increased to increase the capacity per volume. The thickness of the separator substrate can be any thickness, preferably 5 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less, and even more preferably 5 μm or more and 18 μm or less.

[0086] <<Electrode base material>> The electrode substrates (positive electrode substrate and negative electrode substrate) are not particularly limited, but examples thereof include electrode substrates in which an electrode mixture layer is formed on a current collector. Here, the current collector, the electrode active materials (positive electrode active material, negative electrode active material) and binders for the electrode composite layer (binders for the positive electrode composite layer, binders for the negative electrode composite layer) in the electrode composite layer, and the method for forming the electrode composite layer on the current collector may be known, and for example, the method described in JP 2013-145763 A may be used.

[0087] <Method of manufacturing laminate> The method for producing the laminate of the present invention is not particularly limited, and for example, a method of forming a functional layer on a release sheet and transferring the functional layer onto a substrate can be used. However, from the viewpoint of eliminating the need for a transfer operation and improving production efficiency, it is preferable to produce the laminate through a step of supplying a functional layer composition containing at least heat-resistant fine particles, adhesive particles, and a dispersion medium onto a substrate (supplying step), and a step of drying the functional layer composition supplied onto the substrate (drying step).

[0088] <<Composition for functional layer>> As described above, the composition for the functional layer contains at least heat-resistant particles and adhesive particles in a dispersion medium, and optionally contains other components. The dispersion medium is not particularly limited, but water is preferably used. The method for preparing the composition for the functional layer is not particularly limited, and any known mixing or dispersing method can be used. Furthermore, when the laminate of the present invention is produced through the supplying step and the drying step as described above, the functional layer of the laminate is made of a dried product of the functional layer composition. Therefore, the components contained in the functional layer are those contained in the functional layer composition, and the preferred abundance ratios of the components in the functional layer composition are the same as the preferred abundance ratios of the components in the functional layer described above.

[0089] <<Supply process>> In the supplying step, the functional layer composition is supplied onto a substrate to form a coating of the functional layer composition on the substrate. The method for supplying the functional layer composition onto the substrate is not particularly limited, and the functional layer composition may be applied to the surface of the substrate, or the substrate may be immersed in the functional layer composition. Furthermore, it is preferable to apply the functional layer composition to the surface of the substrate, as this makes it easier to control the thickness of the functional layer (particularly the average height in the stacking direction of the heat-resistant region). The method for applying the composition for the functional layer to the surface of the substrate is not particularly limited, and examples thereof include the doctor blade method, reverse roll method, direct roll method, gravure coating method, bar coating method, extrusion method, and brush coating method. In the supplying step, a coating of the composition for a functional layer may be formed on only one surface of the substrate, or a coating of the composition for a functional layer may be formed on both surfaces of the substrate.

[0090] <<Drying process>> In the drying step, the coating of the functional layer composition formed on the substrate in the supplying step is dried to remove the dispersion medium, thereby forming a functional layer. The method for drying the coating of the composition for functional layer is not particularly limited and any known method can be used, such as drying with warm air, hot air, or low-humidity air, vacuum drying, or drying by irradiation with infrared rays or electron beams, etc. 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.

[0091] In addition, when manufacturing the laminate of the present invention, a supplying process and a drying process may be performed on one side of the substrate to form a functional layer, and then a supplying process and a drying process may be performed on the other side of the substrate to form a functional layer.

[0092] (electrochemical element) The electrochemical element of the present invention comprises an electrode and a separator, and is characterized in that at least one of the electrode and the separator comprises the laminate of the present invention described above. Since the electrochemical element of the present invention uses the laminate of the present invention described above as at least one of the electrode and the separator, the electrochemical element of the present invention has excellent element characteristics such as rate characteristics and cycle characteristics.

[0093] The electrochemical device of the present invention is not particularly limited, and may be, for example, a lithium ion secondary battery or an electric double layer capacitor, and is preferably a lithium ion secondary battery.

[0094] Hereinafter, a lithium ion secondary battery will be taken as an example of the electrochemical element of the present invention, and a case where the above-described laminate of the present invention is used as a separator of the lithium ion secondary battery will be described, but the electrochemical element of the present invention is not limited thereto.

[0095] <Positive and negative electrodes> As the positive electrode and negative electrode, electrodes made of the known electrode substrates (positive electrode substrate and negative electrode substrate) described above in the section "Substrate" can be used.

[0096] <Electrolyte> As the electrolyte, an organic electrolyte solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. For example, in lithium ion secondary batteries, a lithium salt is used as the supporting electrolyte. Examples of lithium salts include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, CF4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, and (C2F5SO2)NLi. Among these, LiPF6, LiClO4, and CF3SO3Li are preferred because they are easily soluble in solvents and exhibit a high degree of dissociation. One type of electrolyte may be used alone, or two or more types may be used in combination. Generally, the lithium ion conductivity tends to increase as the supporting electrolyte with a higher degree of dissociation is used, so the lithium ion conductivity can be adjusted by the type of supporting electrolyte.

[0097] The organic solvent used in the electrolyte is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in lithium ion secondary batteries, carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (ethyl methyl carbonate (EMC)), and vinylene carbonate; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; and the like are suitably used.

[0098] A mixture of these solvents may also be used. Among them, carbonates are preferred because of their high dielectric constant and 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 electrolytic solution can be adjusted as appropriate. Known additives may also be added to the electrolytic solution.

[0099] <Method of manufacturing an electrochemical element> The method for producing the electrochemical element of the present invention is not particularly limited. For example, the lithium ion secondary battery, which is an example of the electrochemical element of the present invention described above, can be produced by stacking a positive electrode and a negative electrode with a separator interposed therebetween, rolling or folding the stack as necessary, placing the stack in a battery container, injecting an electrolyte into the battery container, and sealing the container. At least one of the element components among the positive electrode, negative electrode, and separator is the laminate of the present invention. Furthermore, the battery container may contain an expanded metal, a fuse, an overcurrent prevention element such as a PTC element, a lead plate, or the like, as necessary, to prevent pressure buildup within the battery and overcharging and discharging. The shape of the battery may be any shape, such as a coin type, button type, sheet type, cylindrical type, rectangular type, or flat type. [Example]

[0100] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified. Furthermore, in a polymer produced by copolymerizing multiple types of monomers, the proportion of structural units formed by polymerizing a certain monomer in the polymer usually coincides with the ratio (feed ratio) of that certain monomer to all monomers used in the polymerization of the polymer, unless otherwise specified.

[0101] In the examples and comparative examples, the glass transition temperature, volume average particle diameter, degree of swelling in electrolyte, average height of the heat-resistant region in the stacking direction, ratio of the volume average particle diameter of the adhesive particles to the average height of the heat-resistant region in the stacking direction, ratio of the content of heat-resistant fine particles to the content of adhesive particles (volume ratio, mass ratio), low-temperature adhesion, blocking resistance, and heat resistance of the separator having a functional layer, and rate characteristics and cycle characteristics of the secondary battery were evaluated by the following methods.

[0102] <Glass transition temperature (Tg) of adhesive particles and binder> The adhesive particles and binder were used as measurement samples. 10 mg of the sample was weighed into an aluminum pan and measured using a differential scanning calorimetry (DSC) analyzer (SII NanoTechnology, Inc., EXSTAR DSC6220) under the conditions specified in JIS Z 8703. The measurement temperature range was -100°C to 200°C, with a heating rate of 10°C / min. The DSC curve was obtained under the conditions specified in JIS Z 8703. The glass transition temperature (°C) was determined by the intersection of the baseline just before the endothermic peak of the DSC curve, where the differential signal (DDSC) was 0.05 mW / min / mg or greater, and the tangent to the DSC curve at the first inflection point after the endothermic peak.

[0103] <Volume average particle size of binder> The volume-average particle size of the binder was measured by laser diffraction. Specifically, an aqueous dispersion containing the binder (adjusted to a solids concentration of 0.1% by mass) was used as a sample. The particle size distribution (volume basis) was measured using a laser diffraction particle size distribution analyzer (Beckman Coulter, Inc., "LS-230"), and the particle size D50 at which the cumulative volume calculated from the smallest diameter side reached 50% was defined as the volume-average particle size.

[0104] <Volume average particle size of heat-resistant fine particles> In the particle size distribution (volume basis) measured by laser diffraction, the particle size (D50) at which the cumulative volume calculated from the smallest diameter side becomes 50% was defined as the volume average particle size of the heat-resistant fine particles.

[0105] <Volume average particle size of adhesive particles in functional layer> The surface of the functional layer of the separator was observed by magnifying each adhesive particle using a field emission scanning electron microscope (FE-SEM, JEOL Ltd., "JSM-7800 Prime", detector: BED-C, acceleration voltage: 5 kV, magnification: 5000-10000 times). 200 adhesive particles were observed. The observed images of adhesive particles were binarized to determine the area of ​​the adhesive particles within the field of view. Specifically, image analysis software (Mitani Corporation, "WinROOF") was used to perform binarization with the emphasis conditions set to "brightness: -30" and "contrast: +70," a filter set to 7 × 7, and two thresholds (threshold 38). The surface of the functional layer was then viewed in plan for each of the 200 SEM images obtained, and the area of ​​the adhesive particles was determined. The adhesive particles were assumed to be perfect spheres, and the diameter of the adhesive particles was calculated from the area of ​​the adhesive particles. The volume of the 200 adhesive particles was calculated from the diameters of the adhesive particles, assuming that the adhesive particles were perfect spheres. The total volume of all adhesive particles was set to 100%, and the amount of adhesive particles present in each particle size range was expressed as a percentage. The particle diameter at which the amount of adhesive particles reached 50% was defined as the volume-average particle diameter of the adhesive particles in the functional layer.

[0106] <Electrolyte swelling rate> An aqueous dispersion containing adhesive particles was placed in a polytetrafluoroethylene dish and dried at 25°C for 48 hours to prepare a powder. Approximately 0.2 g of the obtained powder was pressed at 200°C and 5 MPa for 2 minutes to obtain a film. The obtained film was then cut into 1 cm squares to obtain test pieces. The mass W0 of this test piece was measured. The above test piece was immersed in an electrolyte solution for 72 hours at 60° C. Thereafter, the test piece was taken out of the electrolyte solution, the electrolyte solution on the surface of the test piece was wiped off, and the mass W1 of the test piece after the immersion test was measured. Using the measured masses W0 and W1, the degree of swelling in the electrolyte solution S (times) was calculated as S=W1 / W0. The electrolyte used was a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and vinylene carbonate (VC) (volume ratio: EC / DEC / VC = 68.5 / 30 / 1.5) with LiPF6 dissolved as a supporting electrolyte at a concentration of 1 mol / L.

[0107] <Average height of heat-resistant area in the stacking direction> The cross section of the separator with the functional layer was observed using the above-mentioned field emission scanning electron microscope (FE-SEM), and the height in the stacking direction of any five points in the heat-resistant region was measured from the obtained SEM image.The average of these measured values ​​was then calculated as the average height in the stacking direction of the heat-resistant region.

[0108] <Ratio of volume average particle diameter of adhesive particles to average height in stacking direction of heat-resistant region> From the values ​​obtained as described above, the volume average particle diameter / average height in the stacking direction was calculated.

[0109] <Ratio of heat-resistant fine particle content to adhesive particle content> The ratio (volume ratio, mass ratio) of the content of heat-resistant fine particles to the content of adhesive particles was calculated from the amounts of heat-resistant fine particles and adhesive particles charged when the composition for the functional layer was prepared. The density of alumina particles as heat-resistant fine particles was 4 g / cm. 3 It was calculated as:

[0110] <Low temperature adhesion> The positive electrode, negative electrode, and separator (with functional layers on both sides) prepared in the examples and comparative examples were each cut into a width of 10 mm and a length of 50 mm, and the positive electrode and separator were stacked and pressed using a roll press under conditions of a temperature of 50°C, a load of 8 kN / m, and a press speed of 30 m / min to obtain an integrated product in which the positive electrode and separator were integrated. The resulting integrated product was placed with the current collector side of the positive electrode facing downwards, and cellophane tape was attached to the surface of the positive electrode. The cellophane tape used was that specified in JIS Z1522. The cellophane tape was fixed to a horizontal test table. One end of the separator was then pulled vertically upward at a pulling rate of 50 mm / min, and the stress when peeled off was measured. The negative electrodes prepared in the examples and comparative examples were also subjected to the same operations as in the case of using the positive electrodes, and the stress was measured. The above-mentioned stress measurement was performed three times for each of the integrated positive electrode and separator and the integrated negative electrode and separator, for a total of six times, and the average stress value was calculated, and the obtained average value was used as the peel strength (N / m). The calculated peel strength was then used to evaluate the low-temperature adhesiveness of the separator with the functional layer according to the following criteria: A higher peel strength indicates that the separator as an element component can exhibit excellent low-temperature adhesiveness due to the functional layer. A: Peel strength 3N / m or more B: Peel strength 2N / m or more and less than 3N / m C: Peel strength 1N / m or more but less than 2N / m D: Peel strength less than 1N / m

[0111] <Blocking resistance> Two square pieces measuring 5 cm wide x 5 cm long were cut out from the prepared separator for evaluation (a separator substrate having a functional layer on one side). These two square pieces were stacked so that the functional layer sides faced each other. The two stacked separators were then heated at 40°C and 10 g / cm 2 A pressed specimen was obtained by placing the specimen under a pressure of 100 psi. The obtained pressed specimen was left for 24 hours. After leaving the specimen for 24 hours, the entire surface of one separator substrate side was fixed, and the other separator was pulled with a force of 0.3 N / m to observe whether it could be peeled off, and the blocking state was evaluated according to the following criteria. The less adhesion was observed, the better the blocking resistance. A: The square pieces are not glued together. B: The square pieces are adhered to each other but can be peeled off. C: The square pieces are bonded together and cannot be separated.

[0112] <Heat resistance> The separators prepared in the examples and comparative examples were cut into squares measuring 12 cm wide x 12 cm long, and a square measuring 10 cm on a side was drawn inside each resulting square to prepare a test piece. The test piece was then placed in a thermostatic chamber at 150°C and left for 1 hour, after which the change in the area of ​​the square drawn inside (= {(area of ​​square before leaving - area of ​​square after leaving) / area of ​​square before leaving} × 100%) was calculated as the thermal shrinkage rate and evaluated according to the following criteria. A smaller thermal shrinkage rate indicates that the separator with a functional layer has better heat resistance. A: Heat shrinkage rate is less than 3% B: Heat shrinkage rate is 3% or more and less than 5% C: Heat shrinkage rate is 5% or more and less than 10% D: Heat shrinkage rate is 10% or more

[0113] <Rate characteristics> The fabricated lithium-ion secondary battery was left standing for 24 hours in an environment of 25°C, and then charged and discharged at 4.35 V and 0.1 C, and discharged at 3.0 V and 0.1 C, in an environment of 25°C, to measure the initial capacity C0. Subsequently, the battery was charged and discharged at 4.35 V and 0.1 C, and discharged at 3.0 V and 2 C, in an environment of 25°C, to measure the capacity C1. The rate characteristics were evaluated by ΔC = (C0 - C1) / C0 × 100 (%), and a larger value indicates a secondary battery with better rate characteristics. A: ΔC is 90% or more B: ΔC is 85% or more and less than 90% C: ΔC is 80% or more and less than 85% D: ΔC is less than 80%

[0114] <Cycle characteristics> After injecting the electrolyte, the fabricated lithium-ion secondary battery was left standing at 25°C for 5 hours. Next, it was charged at 25°C at a constant current of 0.2C to a cell voltage of 3.65V, and then aged at 60°C for 12 hours. Then, it was discharged at 25°C at a constant current of 0.2C to a cell voltage of 3.00V. Then, it was subjected to CC-CV charging at a constant current of 0.2C (upper limit cell voltage 4.20V), and CC discharging at a constant current of 0.2C to 3.00V. This charge / discharge cycle at 0.2C was repeated three times. Thereafter, 100 cycles of charge and discharge were performed at a temperature of 25°C, a cell voltage of 4.20-3.00V, and a charge and discharge rate of 1.0 C. The discharge capacity of the first cycle was defined as X1, and the discharge capacity of the 100th cycle as X2. Then, the discharge capacity X1 and the discharge capacity X2 were used to calculate the capacity retention rate ΔC′=(X2 / X1)×100(%), and the capacity retention rate was evaluated according to the following criteria: A larger value of the capacity retention rate ΔC′ indicates that the secondary battery has better cycle characteristics. A: ΔC´ is 93% or more B: ΔC´ is 90% or more and less than 93% C: ΔC´ is less than 90%

[0115] Example 1 <Preparation of adhesive particles> <<Preparation of Ester Wax>> A 0.5 L four-neck flask equipped with a nitrogen inlet tube, a stirring blade, and a condenser was charged with 18 g (0.13 mol) of pentaerythritol and 104 g (0.52 mol) of lauric acid, and the mixture was reacted at 220°C for 10 hours under a nitrogen stream while distilling off the generated water. 46.5 g of toluene, 32 g of 2-propanol, and 19 g of a 10% aqueous potassium hydroxide solution containing 2.0 equivalents of potassium hydroxide as the acid value were added, and the mixture was stirred at 70°C for 30 minutes. After standing for 30 minutes, the aqueous layer was removed to obtain a crude product. Using 40 parts of ion-exchanged water per 100 parts of the crude product, the crude product was washed four times at 70°C to adjust the pH to 7. The solvent was distilled off from the resulting purified product under heating and reduced pressure conditions, and the product was filtered, solidified, and pulverized to obtain 140 g of pentaerythritol tetralaurate (melting point: 44°C) as an ester wax. <<Preparation of saturated fatty acid zinc salts>> A 3 L separable flask equipped with a stirring blade was charged with 306 g (0.90 mol) of behenic acid as a monovalent linear saturated fatty acid and 2500 g of water, and the temperature was raised to 90°C. Next, 75 g (0.90 mol) of 48% aqueous sodium hydroxide solution was added, and the mixture was stirred at 90°C for 1 hour. After that, 291 g (0.45 mol) of 25% aqueous zinc sulfate solution was added dropwise over 1 hour. After the dropwise addition was completed, the mixture was stirred for another 1 hour. To the resulting slurry, 1500 g of water was added and cooled to 65° C. Thereafter, the slurry was suction filtered, washed twice with 1000 g of water, and dried at 65° C. for 48 hours using a blower dryer to obtain zinc behenate as a saturated fatty acid zinc salt. <<Preparation of wax composition>> A 0.3 L separable flask equipped with a stirring blade and a nitrogen inlet tube was charged with 199.0 g of pentaerythritol tetralaurate as the ester wax and 1.0 g of the zinc behenate, and the mixture was stirred under a nitrogen stream at 150° C. for 1 hour. The mixture was then cooled, solidified, and pulverized to obtain a wax composition. <<Preparation of Monomer Composition>> 81.9 parts of styrene as an aromatic vinyl monomer, 18 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 parts of ethylene glycol dimethacrylate as a crosslinkable monomer were mixed together, and 10 parts of the wax composition calculated as the amount of ester wax was further mixed and dissolved to prepare a monomer composition. <<Preparation of colloidal dispersion containing dispersion stabilizer (metal hydroxide)>> A colloidal dispersion containing magnesium hydroxide as a dispersion stabilizer (metal hydroxide) was prepared by gradually adding, with stirring, an aqueous solution prepared by dissolving 5.6 parts of sodium hydroxide in 50 parts of ion-exchanged water (aqueous sodium hydroxide solution) to an aqueous solution prepared by dissolving 8.0 parts of magnesium chloride in 200 parts of ion-exchanged water (aqueous magnesium chloride solution). <<Suspension polymerization>> The above-mentioned monomer composition was added to the above-mentioned colloidal dispersion and further stirred, and then 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, product name "Perbutyl O") as a polymerization initiator was added to obtain a mixed solution. The obtained mixed solution was subjected to high-shear stirring at a rotation speed of 15,000 rpm for 1 minute using an in-line emulsifying disperser (manufactured by Pacific Machinery Works, product name "Cavitron") to form droplets of the monomer composition in the colloidal dispersion. The colloidal dispersion in which droplets of the monomer composition had been formed was placed in a reactor, heated to 90° C., and subjected to a polymerization reaction for 5 hours to obtain an aqueous dispersion containing adhesive particles. The degree of swelling in an electrolyte was measured using the aqueous dispersion containing the adhesive particles, and the results are shown in Table 1. <<Drying>> Further, while stirring the aqueous dispersion containing the adhesive particles, sulfuric acid was added dropwise at room temperature (25°C) and acid washing was performed until the pH reached 6.5 or less. Next, filtration and separation were performed, and 500 parts of ion-exchanged water was added to the obtained solid matter to re-slurry it, and the water washing treatment (washing, filtration, and dehydration) was repeated several times. Then, filtration and separation were performed, and the obtained solid matter was placed in a container of a dryer and dried at 40°C for 48 hours to obtain dried adhesive particles. The glass transition temperature of the resulting adhesive particles was measured, and the results are shown in Table 1.

[0116] <Preparation of binder> To a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate (manufactured by Kao Chemical Corporation, "EMAL (registered trademark) 2F") as an emulsifier, and 0.5 parts of ammonium persulfate as a polymerization initiator were supplied, the gas phase was replaced with nitrogen gas, and the temperature was raised to 60°C. Meanwhile, in another container, 50 parts of ion-exchanged water, 0.5 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 2 parts of methacrylic acid as an acid group-containing monomer, and 2 parts of acrylonitrile as a nitrile group-containing monomer, as well as 1 part of allyl methacrylate and 1 part of allyl glycidyl ether as crosslinkable monomers were mixed to prepare a monomer composition. The resulting monomer composition was continuously added to the above-mentioned reactor equipped with a stirrer over 4 hours to carry out polymerization. The reaction was carried out at 60°C during the addition. After the addition was completed, the mixture was stirred at 70°C for an additional 3 hours, and then the reaction was terminated, yielding an aqueous dispersion containing a particulate binder as an acrylic polymer. The resulting binder had a volume average particle diameter of 0.25 μm and a glass transition temperature of -40°C.

[0117] <Preparation of Functional Layer Composition> To 100 parts of alumina (Sumitomo Chemical Co., Ltd., "AKP3000", volume average particle diameter: 0.7 μm) as heat-resistant fine particles, 0.5 parts of polyacrylic acid as a water-soluble polymer was added, and ion-exchanged water was added so that the solid content concentration became 55%, and the mixture was mixed using a ball mill to obtain an alumina-containing slurry. In addition, 100 parts of the adhesive particles, 0.2 parts of sodium dodecylbenzenesulfonate ("Neopelex G-15" manufactured by Kao Chemical Corporation) as a dispersant, and ion-exchanged water were mixed to obtain an adhesive particle-containing mixed liquid with a solid content of 40%. The alumina-containing slurry and the adhesive particle-containing mixed solution were mixed so that the ratio of alumina to adhesive particles (alumina / adhesive particles) was 70 / 30 by volume (90 / 10 by mass). To the resulting mixed solution, 6 parts (solids equivalent) of the aqueous dispersion containing the binder per 100 parts of alumina, 1.5 parts of carboxymethyl cellulose as a water-soluble polymer (thickener), and ion-exchanged water were added to obtain a functional layer composition (solids concentration: 40%).

[0118] <Fabrication of separator with functional layer> A polyethylene microporous film (thickness: 12 μm) was prepared as a separator substrate. The functional layer composition obtained above was applied to one side of the prepared separator substrate using a bar coater method. The coating was dried at 50°C. The same procedure as above was then performed on the other side of the separator substrate, resulting in a separator with functional layers on both sides of the separator substrate. Each of the two functional layers of the obtained separator had an adhesive region made of adhesive particles and a heat-resistant region made of alumina as heat-resistant fine particles, and the average height of the heat-resistant region in the stacking direction was 2.0 μm. The volume-average particle diameter of the adhesive particles was 6.0 μm for each functional layer. The separator having functional layers on both sides was then evaluated for low-temperature adhesion and heat resistance. The results are shown in Table 1. Separately, the functional layer composition obtained above was applied to one side of a separator substrate (a polyethylene microporous membrane (thickness: 12 μm)) using a bar coater method, and the coating was dried at 50°C to obtain a separator with a functional layer on one side of the separator substrate. This separator with a functional layer on one side was used as an evaluation separator, and its blocking resistance was evaluated. The results are shown in Table 1.

[0119] <Preparation of positive electrode> A mixture of 100 parts of LiCoO2 (volume average particle diameter: 12 μm) as a positive electrode active material, 2 parts of acetylene black (HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, 2 parts of polyvinylidene fluoride (#7208, manufactured by Kureha Corporation) as a binder for the positive electrode composite layer in terms of solid content, and N-methylpyrrolidone as a solvent was mixed to a total solid content of 70%. These components were mixed using a planetary mixer to prepare a positive electrode slurry composition. The positive electrode slurry composition was applied to a 20 μm-thick aluminum foil current collector using a comma coater so that the dried film thickness was approximately 150 μm, and then dried. This drying was performed by transporting the aluminum foil at a speed of 0.5 m / min through an oven at 60°C for 2 minutes. The aluminum foil was then heat-treated at 120°C for 2 minutes to obtain a pre-press positive electrode blank. This pre-press positive electrode blank was rolled using a roll press to obtain a positive electrode having a positive electrode composite layer (thickness: 60 μm).

[0120] <Preparation of negative electrode> A 5 MPa pressure vessel equipped with a stirrer was charged with 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 parts of potassium persulfate as a polymerization initiator. After thorough stirring, the mixture was heated to 50 °C to initiate polymerization. When the polymerization conversion reached 96%, the reaction was stopped by cooling, yielding a mixture containing a binder (SBR) for the negative electrode composite layer. A 5% aqueous sodium hydroxide solution was added to the mixture containing the binder for the negative electrode composite layer, adjusting the pH to 8, and then the unreacted monomer was removed by heated vacuum distillation. The mixture was then cooled to below 30 °C to obtain an aqueous dispersion containing the desired binder for the negative electrode composite layer. 80 parts of artificial graphite (volume average particle diameter: 15.6 μm) as a negative electrode active material and 16 parts of silicon-based active material SiOx (volume average particle diameter: 4.9 μm) were blended, and 2.5 parts of a 2% aqueous solution of carboxymethylcellulose sodium salt (manufactured by Nippon Paper Industries Co., Ltd., "MAC350HC") as a viscosity modifier, equivalent to solids, and ion-exchanged water were mixed to adjust the solids concentration to 68%, and then further mixed at 25 ° C for 60 minutes. The solids concentration was further adjusted to 62% with ion-exchanged water, and then further mixed at 25 ° C for 15 minutes to obtain a mixed solution. 1.5 parts of the aqueous dispersion containing the above-mentioned binder for the negative electrode composite layer, equivalent to solids, and ion-exchanged water were added to this mixed solution, and the final solids concentration was adjusted to 52%, and then further mixed for 10 minutes to obtain a mixed solution. This mixed solution was degassed under reduced pressure to obtain a negative electrode slurry composition with good fluidity. The negative electrode slurry composition was applied to a 20 μm-thick copper foil current collector using a comma coater so that the dried film thickness was approximately 150 μm, and then dried. This drying was performed by transporting the copper foil at a speed of 0.5 m / min through an oven at 60°C for 2 minutes. The copper foil was then heat-treated at 120°C for 2 minutes to obtain a pre-press negative electrode blank. This pre-press negative electrode blank was rolled using a roll press to obtain a negative electrode having a negative electrode composite layer (thickness: 80 μm).

[0121] <Fabrication of lithium-ion secondary batteries> The positive electrode prepared as described above was cut into a 49 cm x 5 cm rectangle and placed with the surface on the positive electrode composite layer facing up. A separator (with functional layers on both sides) cut to 120 cm x 5.5 cm was placed on the positive electrode composite layer so that the positive electrode was located on one side of the separator in the longitudinal direction. Furthermore, the negative electrode prepared as described above was cut into a 50 cm x 5.2 cm rectangle and placed on the separator so that the surface on the negative electrode composite layer faced the separator and the negative electrode was located on the other side of the separator in the longitudinal direction. The resulting laminate was then wound around a wound body to obtain a wound body. This wound body was pressed at 50°C and 1 MPa to form a flat body, then wrapped in an aluminum packaging exterior as the battery exterior, and an electrolyte solution [solvent: ethylene carbonate / diethyl carbonate / vinylene carbonate (volume ratio) = 68.5 / 30 / 1.5, electrolyte: LiPF6 concentration 1 mol)] was injected so that no air remained. The opening of the aluminum packaging exterior was then heat-sealed at a temperature of 150°C to produce a wound-type lithium-ion secondary battery with a capacity of 800 mAh. The rate characteristics and cycle characteristics of the obtained lithium ion secondary battery were evaluated, and the results are shown in Table 1.

[0122] Examples 2 to 5 In preparing the adhesive particles, the amount of the wax composition (ester wax equivalent) was changed to 5 parts (Example 2), 15 parts (Example 3), 20 parts (Example 4), and 25 parts (Example 5), respectively. Except for this, adhesive particles, binders, functional layer compositions, separators, negative electrodes, positive electrodes, and lithium ion secondary batteries were obtained in the same manner as in Example 1. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0123] Example 6 When preparing the ester wax, behenic acid was used instead of lauric acid to obtain pentaerythritol tetrabehenate (melting point: 81°C) as the ester wax. Except for using this ester wax, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0124] Example 7 Except for using a monomer composition prepared as follows in preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. <Preparation of Monomer Composition> 82 parts of styrene as an aromatic vinyl monomer and 18 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer were mixed together, and 10 parts of a wax composition prepared in the same manner as in Example 1, converted into the amount of ester wax, was mixed and dissolved to prepare a monomer composition.

[0125] Example 8 Except for using a colloidal dispersion liquid prepared as follows in preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. <Preparation of colloidal dispersion containing dispersion stabilizer (metal hydroxide)> A colloidal dispersion containing magnesium hydroxide as a dispersion stabilizer (metal hydroxide) was prepared by gradually adding, with stirring, an aqueous solution prepared by dissolving 7.0 parts of sodium hydroxide in 50 parts of ion-exchanged water (aqueous sodium hydroxide solution) to an aqueous solution prepared by dissolving 10.0 parts of magnesium chloride in 200 parts of ion-exchanged water (aqueous magnesium chloride solution).

[0126] Example 9 Except for using a colloidal dispersion liquid prepared as follows in preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1. <Preparation of colloidal dispersion containing dispersion stabilizer (metal hydroxide)> A colloidal dispersion containing magnesium hydroxide as a dispersion stabilizer (metal hydroxide) was prepared by gradually adding, with stirring, an aqueous solution prepared by dissolving 4.2 parts of sodium hydroxide in 50 parts of ion-exchanged water (aqueous sodium hydroxide solution) to an aqueous solution prepared by dissolving 6.0 parts of magnesium chloride in 200 parts of ion-exchanged water (aqueous magnesium chloride solution).

[0127] Example 10 In preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1, except that 5 parts of paraffin wax (manufactured by Nippon Seiro Co., Ltd., product name "HNP-11") was used as the wax composition. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0128] (Examples 11 to 12) In preparing the functional layer composition, the alumina-containing slurry and the adhesive particle-containing mixed solution were mixed so that the mixing ratios of the alumina particles and the adhesive particles (alumina particles / adhesive particles) were 80 / 20 by volume (94 / 6 by mass) and 55 / 45 by volume (82 / 18 by mass), respectively. Adhesive particles, binder, functional layer composition, separator, negative electrode, positive electrode, and lithium-ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2.

[0129] Example 13 Except for using a monomer composition prepared as follows in preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2. <Preparation of Monomer Composition> 83.9 parts of styrene as an aromatic vinyl monomer, 16 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 parts of ethylene glycol dimethacrylate as a crosslinkable monomer were mixed together, and 10 parts of a wax composition prepared in the same manner as in Example 1 was mixed and dissolved in terms of the amount of ester wax to prepare a monomer composition.

[0130] Example 14 Except for using a monomer composition prepared as follows in preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2. <Preparation of Monomer Composition> 72.9 parts of styrene as an aromatic vinyl monomer, 27 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 parts of ethylene glycol dimethacrylate as a crosslinkable monomer were mixed together, and 10 parts of a wax composition prepared in the same manner as in Example 1 was mixed and dissolved in terms of the amount of ester wax to prepare a monomer composition.

[0131] Example 15 Except for using organic fine particles prepared as follows instead of alumina particles in preparing the functional layer composition, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2. <Preparation of organic fine particles (heat-resistant fine particles)> In a reactor A equipped with a stirrer, 0.20 parts of sodium dodecyl sulfate, 0.30 parts of ammonium persulfate, and 180 parts of ion-exchanged water were mixed to form a mixture, and the mixture was heated to 65° C. Meanwhile, in a separate vessel, 80.0 parts of n-butyl acrylate as a (meth)acrylic acid ester monomer, 10.0 parts of methacrylic acid as an acid group-containing monomer, 10.0 parts of acrylonitrile as a nitrile group-containing monomer, 0.8 parts of sodium dodecyl sulfate, and 40 parts of ion-exchanged water were mixed to prepare a monomer composition for seed particles. This seed particle monomer composition was continuously added to the above-mentioned reactor A over a period of 4 hours to carry out a polymerization reaction. The temperature inside the reactor was maintained at 65°C during the continuous addition of the seed particle monomer composition. After the continuous addition was completed, the polymerization reaction was continued for an additional 3 hours at 80°C. This resulted in an aqueous dispersion of seed particles. The volume average particle diameter of the seed particles was measured in the same manner as for the binder and was found to be 120 nm. Next, 20 parts of the aqueous dispersion of the seed particles (based on solids content) (16 parts n-butyl acrylate units, 2 parts methacrylic acid units, and 2 parts acrylonitrile units), 80 parts ethylene glycol dimethacrylate (Kyoeisha Chemical Co., Ltd., product name "Light Ester EG") as a crosslinking monomer, 0.8 parts sodium dodecylbenzenesulfonate, 3.2 parts t-butylperoxy-2-ethylhexanoate (NOF Corporation, product name "Perbutyl O") as a polymerization initiator, and 160 parts ion-exchanged water were added to a reactor equipped with a stirrer, and the mixture was stirred at 35°C for 12 hours, allowing the crosslinking monomer and polymerization initiator to be completely absorbed into the seed particles. The temperature inside the reactor was then maintained at 90°C, and a polymerization reaction (seed polymerization) was carried out for 5 hours. Next, steam was introduced to remove unreacted monomers and initiator decomposition products, obtaining an aqueous dispersion of organic fine particles. The glass transition temperature of the obtained organic fine particles was measured in the same manner as for the adhesive particles and binder, but no peak was observed within the measurement temperature range (-100°C to 200°C). This confirmed that the glass transition temperature of the organic fine particles was above 200°C.

[0132] Example 16 Adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1, except that zinc behenate, which is a zinc salt of saturated fatty acid, was not prepared and zinc behenate was not added to pentaerythritol tetralaurate as an ester wax when preparing the adhesive particles. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2.

[0133] (Comparative Example 1) Except for not using the wax composition when preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 2.

[0134] (Comparative Example 2) Except for using a monomer composition (not containing a wax composition) prepared as follows in preparing the adhesive particles, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2. <Preparation of Monomer Composition> A monomer composition was prepared by mixing 60.9 parts of styrene as an aromatic vinyl monomer, 39 parts of 2-ethylhexyl acrylate as a (meth)acrylic acid ester monomer, and 0.1 part of ethylene glycol dimethacrylate as a crosslinkable monomer.

[0135] (Comparative Example 3) In preparing the wax composition, adhesive particles, a binder, a functional layer composition, a separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were obtained in the same manner as in Example 1, except that polyethylene wax (melting point: 95°C, number average molecular weight: 7,300) was used instead of pentaerythritol tetralaurate as the ester wax. Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 2.

[0136] Comparative Example 4 Except for using a separator prepared as follows, a lithium ion secondary battery was obtained in the same manner as in Example 1. Various evaluations were then carried out in the same manner as in Example 1. The results are shown in Table 2. <Preparation of separator (with functional layer on both sides or one side)> To 100 parts of adhesive particles prepared in the same manner as in Example 1, 0.2 parts of sodium dodecylbenzenesulfonate ("Neopelex G-15" manufactured by Kao Chemical Corporation) as a dispersant and 6 parts (solids equivalent) of an aqueous dispersion containing a binder prepared in the same manner as in Example 1 were added, and ion-exchanged water was further added and mixed to a solids concentration of 40%, thereby obtaining a composition for a functional layer. A polyethylene microporous film (thickness: 12 μm) was prepared as a separator substrate. The functional layer composition obtained above was applied to one side of the prepared separator substrate in an amount of 0.3 g / m 2The coating was applied by a bar coater method so that the coating film was dried at 50°C. The same procedure as above was then carried out on the other side of the separator substrate, to obtain a separator having functional layers on both sides of the separator substrate. Separately, the functional layer composition obtained above was applied to one side of a separator substrate (a microporous polyethylene membrane (thickness: 12 μm)) using a bar coater method, and the coating was dried at 50°C to obtain a separator having a functional layer on one side of the separator substrate.

[0137] In addition, in Tables 1 and 2 shown below, "ST" indicates a styrene unit; "2EHA" indicates 2-ethylhexyl acrylate units, "EDMA" refers to ethylene glycol dimethacrylate units; "Acrylic" refers to an acrylic polymer; "PE" indicates a microporous membrane made of polyethylene; "Particle size" refers to the volume average particle size, "Swelling degree" indicates the swelling degree of the electrolyte, "Height of heat-resistant region" indicates the average height of the heat-resistant region in the stacking direction, "Organic" refers to organic particulates.

[0138] [Table 1]

[0139] [Table 2]

[0140] From Tables 1 and 2, it can be seen that the laminates of Examples 1 to 16 can be used favorably as separators excellent in low-temperature adhesion, blocking resistance, and heat resistance. It can also be seen that secondary batteries excellent in rate characteristics and cycle characteristics were obtained in Examples 1 to 16. On the other hand, in Comparative Example 1, in which the functional layer of the laminate was produced using adhesive particles that did not contain wax, it was found that the low-temperature adhesiveness of the separator made of the laminate was reduced. In addition, in Comparative Example 2, in which the functional layer of the laminate was prepared using adhesive particles that did not contain wax and had a low glass transition temperature, the low-temperature adhesion of the separator made of the laminate was ensured, but it was found that the blocking resistance of the separator was reduced. Furthermore, it can be seen that in Comparative Example 3, in which the functional layer of the laminate was produced using adhesive particles containing wax with a melting point of 95°C or higher, the low-temperature adhesiveness of the separator made of the laminate was reduced. Furthermore, in Comparative Example 4, in which the functional layer of the laminate was prepared using a functional layer composition that did not contain heat-resistant microparticles, it was found that the low-temperature adhesion and heat resistance of the separator made of the laminate, as well as the rate characteristics and cycle characteristics of the secondary battery, were reduced. [Industrial Applicability]

[0141] According to the present invention, it is possible to provide a laminate for an electrochemical device that can be advantageously used as a device component having excellent low-temperature adhesion and blocking resistance, and an electrochemical device including the laminate for an electrochemical device as a device component. [Explanation of symbols]

[0142] 100 laminate 10 Functional Layers 11 Adhesion area 11a Adhesive particles 12 Heat resistant area 12a Heat-resistant fine particles 20 Base material T Height of heat-resistant area in the stacking direction D Particle diameter of adhesive particles

Claims

1. A laminate for an electrochemical device comprising a functional layer containing heat-resistant fine particles and adhesive particles, and a substrate, The adhesive particles contain an adhesive polymer containing an aromatic vinyl monomer unit and a wax having a melting point of less than 95°C, When viewed from above from the functional layer side, the functional layer has an adhesive region made of the adhesive particles and a heat-resistant region made of the heat-resistant fine particles, the volume average particle diameter of the adhesive particles is larger than the average height in the stacking direction of the heat-resistant region, The adhesive particles have a glass transition temperature of 40°C or higher.

2. 2. The laminate for an electrochemical device according to claim 1, wherein the adhesive particles have a volume average particle size of 1.0 μm or more and 10.0 μm or less.

3. 3. The laminate for an electrochemical device according to claim 1, wherein a ratio of a volume average particle diameter of the adhesive particles to an average height in the stacking direction of the heat-resistant region is 1.1 or more and 10.0 or less.

4. 4. The laminate for an electrochemical device according to claim 1, wherein the adhesive particles have a glass transition temperature of 90° C. or lower.

5. 5. The laminate for an electrochemical device according to claim 1, wherein the adhesive polymer further contains a crosslinkable monomer unit.

6. 6. The laminate for an electrochemical device according to claim 1, wherein the heat-resistant fine particles are inorganic fine particles.

7. 7. The laminate for an electrochemical device according to claim 1, wherein the wax is an ester wax.

8. 8. The laminate for an electrochemical device according to claim 1, wherein the wax has a melting point of 40° C. or higher.

9. 9. The laminate for an electrochemical element according to claim 1, wherein the volume ratio of the content of the heat-resistant fine particles to the content of the adhesive particles in the functional layer is 55 / 45 or more and 95 / 5 or less.

10. An electrochemical element comprising an electrode and a separator, An electrochemical device, wherein at least one of the electrodes and the separator is formed using the laminate for an electrochemical device according to any one of claims 1 to 9.

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