Composition, undercoat layer, electrode, and lithium ion secondary battery

Abstract

A composition according to the present disclosure contains a conductive carbon material (A), an olefin resin (B), and an acrylic water-soluble polymer (C). The acrylic water-soluble polymer (C) has a structural unit derived from (meth) acrylamide and a structural unit derived from a vinyl monomer having a carboxyl group and / or a hydroxyl group. The content of structural units derived from (meth) acrylamide is 35-95 mass% with respect to the total amount of the acrylic water-soluble polymer (C). The content of a structural unit derived from a vinyl monomer having a carboxyl group and / or a hydroxyl group is 5-65 mass% with respect to the total amount of the acrylic water-soluble polymer (C).

Description

Technical Field

[0001] This disclosure relates to compositions, primers, electrodes, and lithium-ion secondary batteries. Background Technology

[0002] In recent years, lithium-ion rechargeable batteries have been widely used as power sources for electronic devices, electric vehicles, and energy storage. Especially recently, there has been a demand for high-capacity, high-output-power, and high-energy-density batteries suitable for use in hybrid vehicles and similar applications. Such lithium-ion rechargeable batteries offer the advantage of high energy density. On the other hand, due to the use of lithium metal and lithium ions, adequate safety measures are essential.

[0003] Patent Document 1 discloses a positive electrode for lithium-ion secondary batteries, which improves the safety of lithium-ion secondary batteries. The positive electrode disclosed in Patent Document 1 comprises a positive electrode current collector and a positive electrode additive material layer. The positive electrode additive material layer is laminated on at least one side of the positive electrode current collector. The positive electrode additive material layer has a positive electrode additive material layer and a base layer. The base layer is formed between the positive electrode current collector and the positive electrode additive material layer. The base layer comprises a conductive additive, a binder, and thermally expandable microcapsules. The thermally expandable microcapsules have a maximum volume expansion temperature of 70°C to 180°C.

[0004] In Patent Document 2, in order to suppress the rise in battery temperature when an internal short circuit occurs, a secondary battery is disclosed, which has an intermediate layer between the positive electrode current collector and the positive electrode additive material layer, the intermediate layer comprising a cured product of a curable resin having specific functional groups and a conductive material.

[0005] Patent Document 1: International Publication No. 2019 / 189866 Patent Document 2: International Publication No. 2018 / 198689 Summary of the Invention

[0006] The problem that the invention aims to solve We require lithium-ion secondary batteries with excellent safety, suppressed DC resistance during the initial charging and discharging phases, and suppressed DC resistance increases during long-term storage at high temperatures, exhibiting superior battery performance. Lithium-ion secondary batteries with suppressed DC resistance during the initial charging and discharging phase have superior output power compared to those without suppressed DC resistance. Furthermore, lithium-ion secondary batteries with suppressed DC resistance increases during long-term storage at high temperatures have superior lifespan compared to those without suppressed DC resistance increases.

[0007] One embodiment of this disclosure aims to solve the problem of providing a composition (preferably a composition for a base coat) and a base coating suitable for forming an electrode with excellent safety, low DC resistance during the initial charging and discharging phase, and suppression of the rise in DC resistance under high temperature conditions (especially after long-term storage).

[0008] Other embodiments of this disclosure aim to address the problem of providing electrodes and lithium-ion secondary batteries that exhibit high safety, suppress DC resistance at low levels during the initial charging and discharging phases, suppress the rise of DC resistance under high-temperature conditions (especially after long-term storage), and stably demonstrate excellent battery performance.

[0009] Methods for solving problems The specific methods used to solve the problem include the following.

[0010] <1> The composition contains a conductive carbon material (A), an olefin resin (B), and an acrylic water-soluble polymer (C). The aforementioned acrylic water-soluble polymer (C) has structural units derived from (meth)acrylamide and structural units derived from vinyl monomers having at least one of carboxyl and hydroxyl groups. The content of the structural units derived from (meth)acrylamide is 35% to 95% by mass relative to the total amount of the aforementioned acrylic water-soluble polymer (C). The content of the structural units derived from vinyl monomers having at least one of carboxyl and hydroxyl groups is 5% to 65% by mass relative to the total amount of the aforementioned acrylic water-soluble polymer (C).

[0011] <2> As mentioned above <1> The composition wherein the content of the aforementioned conductive carbon material (A) is 1% to 30% by mass relative to the total amount of the composition. The content of the aforementioned olefin resin (B) is 30% to 90% by mass relative to the total amount of the composition. The content of the aforementioned acrylic water-soluble polymer (C) is 1% to 20% by mass relative to the total amount of the composition.

[0012] <3> As mentioned above <1> or <2> The composition wherein the aforementioned olefin resin (B) comprises an ethylene resin or a propylene resin.

[0013] <4> As mentioned above <1> ~ <3> In any one of the compositions, the aforementioned olefin resin (B) has a particle size of 0.1 μm to 9.0 μm. The softening point of the aforementioned olefin resin (B) is above 70°C.

[0014] <5> As mentioned above <1> ~ <4> The composition of any one of the above-mentioned acrylic water-soluble polymers (C) has structural units derived from (meth)acrylamide, structural units derived from vinyl monomers having carboxyl groups, and structural units derived from vinyl monomers having hydroxyl groups.

[0015] <6> As mentioned above <1> ~ <5> The composition according to any one of the following methods, wherein the Tg of the aforementioned acrylic water-soluble polymer (C) is 150°C or higher.

[0016] <7> As mentioned above <1> ~ <6> The composition described in any one of the following statements further comprises an additive (D). The content of the aforementioned additive (D) is 1% to 50% by mass relative to the total amount of the composition.

[0017] <8> As mentioned above <7> The composition wherein the aforementioned additive (D) comprises carboxymethyl cellulose.

[0018] <9> As mentioned above <7> or <8> The composition wherein the aforementioned additive (D) comprises at least one of thermally expandable microcapsules having a maximum volume expansion temperature of 70°C to 180°C and an inorganic oxide filler.

[0019] <10> As mentioned above <1> ~ <9> The composition according to any one of the following methods, wherein the ratio of particle size distribution D99 to particle size distribution D10 (D99 / D10), as determined by laser diffraction scattering, is 35 or less.

[0020] <11> As mentioned above <1> ~ <10> The composition according to any one of the following methods, wherein the particle size distribution D99, as determined by laser diffraction scattering, is less than 20 μm.

[0021] <12> As mentioned above <1> ~ <11> The composition according to any one of the following methods, wherein the ratio of particle size distribution D99 to particle size distribution D50 (D99 / D50), as determined by laser diffraction scattering, is 20 or less.

[0022] <13> The base coating, comprising the aforementioned <1> ~ <12> The composition described in any one of the following statements.

[0023] <14> Electrode, which has a current collector, as mentioned above <13> The aforementioned base coating layer and binder material layer.

[0024] <15> As mentioned above <14> The electrode comprises, in sequence, the aforementioned current collector, the aforementioned base coating layer, and the aforementioned compound material layer.

[0025] <16> Lithium-ion secondary batteries, which have the aforementioned <14> or <15> The aforementioned electrode.

[0026] Invention Effects According to this disclosure, compositions (preferably compositions for primers) and primer coatings are available that are suitable for forming electrodes with excellent safety, low DC resistance during the initial charging and discharging phase, and suppressed rise in DC resistance under high temperature conditions (especially after long-term storage).

[0027] In addition, according to other embodiments of this disclosure, electrodes and lithium-ion secondary batteries can be provided that exhibit high safety, suppress DC resistance at low levels during the initial charging and discharging phases, suppress the rise of DC resistance under high temperature conditions (especially after long-term storage), and stably demonstrate excellent battery performance. Attached Figure Description

[0028] [ Figure 1 ] Figure 1 A simplified cross-sectional view of a laminated battery, which is an example of a lithium-ion secondary battery as described in this disclosure.

[0029] [ Figure 2 ] Figure 2 This is a simplified cross-sectional view of the positive electrode in a lithium-ion secondary battery according to one embodiment of this disclosure.

[0030] [ Figure 3 ] Figure 3 This is a simplified cross-sectional view of the negative electrode in a lithium-ion secondary battery according to one embodiment of this disclosure.

[0031] [ Figure 4 ] Figure 4 A simplified side view of an example of a three-roll mill. Detailed Implementation

[0032] The contents of this disclosure will now be described in detail. The description of the constituent elements described below is sometimes based on representative embodiments of this disclosure, but this disclosure is not limited to such embodiments.

[0033] In this disclosure, the numerical range indicated by "~" represents a range that includes the value preceding "~" as the lower limit and the value preceding "~" as the upper limit. Within the numerical ranges described in stages in this disclosure, the upper or lower limit value described in a particular numerical range can be replaced with the upper or lower limit value of other numerical ranges described in stages. Furthermore, within the numerical ranges described in this disclosure, the upper or lower limit value described in a particular numerical range can also be replaced with the values ​​shown in the embodiments.

[0034] In the description of groups (atomic groups) in this specification, the use of terms such as "substituted" and "unsubstituted" includes both unsubstituted and substituted groups (atomic groups). For example, the term "alkyl" includes not only unsubstituted alkyl groups (unsubstituted alkyl groups) but also substituted alkyl groups (substituted alkyl groups).

[0035] In this specification, “(meth)acrylate” means either or both of acrylate and methacrylate, “(meth)propylene-” means either or both of “propylene-” and “methpropylene-”, and “(meth)acryloyl” means either or both of acryloyl and methacryloyl.

[0036] In this specification, the term "process" includes not only independent processes, but also processes that can achieve the desired effect as long as they cannot be clearly distinguished from other processes.

[0037] The following is a detailed description of this public document.

[0038] (1) Composition The composition disclosed herein comprises a conductive carbon material (A), an olefinic resin (B), and an acrylic water-soluble polymer (C). The aforementioned acrylic water-soluble polymer (C) has structural units derived from (meth)acrylamide and structural units derived from vinyl monomers having at least one of a carboxyl group and a hydroxyl group. The content of the structural units derived from (meth)acrylamide is 35% to 95% by mass relative to the total amount of the aforementioned acrylic water-soluble polymer (C). The content of the structural units derived from vinyl monomers having at least one of a carboxyl group and a hydroxyl group is 5% to 65% by mass relative to the total amount of the aforementioned acrylic water-soluble polymer (C).

[0039] In this disclosure, the term "conductive carbon material" refers to a carbon material with a volume resistivity of less than 40 Ω·cm, preferably less than 3 Ω·cm, at 20°C.

[0040] In this disclosure, "olefin-based resin" refers to a resin containing structural units derived from olefins. More specifically, "olefin-based resin" includes homopolymers of olefins, copolymers of two or more olefins, or copolymers of olefins with other monomers.

[0041] In this disclosure, "acrylic water-soluble polymer" refers to a polymer comprising structural units derived from monomers having (meth)acryloyl groups (hereinafter also referred to as "(meth)acrylic monomers"). "Acrylic water-soluble polymer" includes homopolymers of (meth)acrylic monomers and copolymers of two or more (meth)acrylic monomers.

[0042] In this disclosure, "water-soluble polymer" means a polymer in which, after stirring and dissolving 1g of polymer in 100ml of water for 24 hours and filtering through a 300-mesh metal screen, the remaining solid content is less than 0.1%.

[0043] In this published text, “content” and “amount added” are considered to be substantially the same.

[0044] Because the composition of this disclosure has the above-described structure, it is possible to form an electrode with excellent safety, where the DC resistance is suppressed to a low level during the initial charging and discharging phase and the rise in DC resistance is suppressed under high-temperature conditions (especially after long-term storage). In other words, when the composition of this disclosure is applied to a secondary battery having electrodes, a lithium-ion secondary battery that achieves a balance between safety and battery performance (i.e., output power and lifespan) can be manufactured.

[0045] While the reasons for achieving the effects of this published text may not be clear, they can be inferred as follows.

[0046] The composition of this disclosure includes a water-dispersible olefin resin (B) that functions to melt at lower temperatures. This facilitates the application of a shut-off function during heating. The acrylic water-soluble polymer (C) contains (meth)acrylamide, which exhibits excellent heat resistance. Therefore, when the composition of this disclosure is used as a raw material for a base coating, the heat resistance, electrolyte resistance, and ion permeability of the base coating are improved in a well-balanced manner. Consequently, an electrode with excellent safety is obtained, where not only is the DC resistance suppressed to a low level during the initial charging and discharging phase, but the increase in DC resistance under high-temperature conditions (especially after long-term storage) is also significantly suppressed. As a result, when a lithium-ion secondary battery is manufactured using the composition of this disclosure, a balance between safety and battery performance (i.e., output power and lifespan) is achieved.

[0047] The composition of this disclosure is preferably used, for example, in components of electrodes in lithium-ion secondary batteries. More specifically, the composition of this disclosure is preferably used to form a base coating layer included in an electrode in a lithium-ion secondary battery having an electrode obtained by sequentially stacking a base coating layer and an additive material layer on at least one main surface of a current collector. More preferably, the composition of this disclosure is used to form a base coating layer included in a positive electrode in a lithium-ion secondary battery having a positive electrode obtained by sequentially stacking a base coating layer and an additive material layer on at least one main surface of a current collector.

[0048] In this disclosure, the term "current collector" refers to a sheet-like object used in a lithium-ion secondary battery to collect electrons generated by the active material and to supply electrons to the active material. The term "main face of the current collector" refers to the largest of the multiple sets of opposite faces.

[0049] (1.1) Conductive carbon materials (A) The composition of this disclosure contains a conductive carbon material (A). Therefore, the resistance of the composition of this disclosure is reduced.

[0050] Examples of conductive carbon materials (A) include, for example, graphite, carbon black, conductive carbon fibers, or fullerenes. Examples of graphite include, for example, synthetic graphite or natural graphite (e.g., flake graphite, block graphite, or amorphous graphite). Examples of conductive carbon fibers (A) include, for example, carbon nanotubes, carbon nanofibers, or carbon fibers. Conductive carbon materials (A) can be used alone or in combination of two or more.

[0051] The shape of the conductive carbon material (A) is not particularly limited, and it may also be in particulate form. When the conductive carbon material (A) is in particulate form, its particle size is not particularly limited. From the viewpoint of dispersing the conductive carbon material (A) among the particles contained in the undercoat layer and functioning as a conductive additive, the particle size of the conductive carbon material (A) is preferably 5 μm or less, more preferably 1 μm to 4 μm. In this case, the primary particle size of the conductive carbon material is preferably 0.5 μm or less, more preferably 0.1 μm to 0.4 μm.

[0052] The particle size of the conductive carbon material (A) is expressed as the particle size (particle size distribution D50, median particle size) in the volume-based particle size distribution measured using a particle size distribution measuring device based on laser diffraction scattering, representing the cumulative 50% volume percentage from the microparticle side.

[0053] Conductive carbon materials (A) are also commercially available. Commercially available carbon black products include, for example, "Super P" (manufactured by TIMCAL). Commercially available flake graphite products include "KS-6" (manufactured by TIMREX).

[0054] The content of conductive carbon material (A) is not particularly limited, but is preferably 1% to 30% by mass relative to the total amount of the composition. If the content of conductive carbon material (A) is within the above range, the composition of this disclosure has a large number of connection points between the conductive carbon materials (A), which can reduce the resistance of the composition at room temperature by utilizing the percolation effect. Furthermore, when the temperature of a lithium-ion secondary battery rises sharply, it becomes difficult to maintain contact between the conductive carbon materials (A), increasing the resistance of the undercoat. Therefore, the resulting lithium-ion secondary battery can perform a shut-off function. That is, the lithium-ion secondary battery has excellent safety. The shut-off function includes preventing the battery reaction of the lithium-ion secondary battery. The term "battery reaction" refers to the lithium-ion insertion and deintercalation reactions that occur between the positive and negative electrodes.

[0055] The higher the content of conductive carbon material (A), the better the battery performance of lithium-ion secondary batteries tends to be.

[0056] From the viewpoint of ensuring the shut-off function, the content of conductive carbon material (A) relative to the total amount of the composition is preferably 28% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. From the viewpoint of ensuring battery performance, the content of conductive carbon material (A) relative to the total amount of the composition is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more.

[0057] (1.2) Olefin resins (B) The composition disclosed herein contains an olefin-based resin (B). Therefore, when the composition of this disclosure is used as a raw material for a base coating, the lithium-ion secondary battery is less prone to thermal runaway, further improving the safety of the lithium-ion secondary battery.

[0058] The material of the olefin resin (B) is not particularly limited. From the viewpoint that the olefin resin (B) can more effectively perform its shut-off function (hereinafter referred to as "effective performance of the shut-off function") by melting in a lower temperature range during the rapid temperature rise of the lithium-ion secondary battery, the softening point of the olefin resin (B) is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 135°C or lower. From the viewpoint that the shape of the olefin resin (B) is maintained before and after the drying process performed during the manufacturing of the positive electrode (hereinafter referred to as "shape retention of the olefin resin (B) during the positive electrode drying process"), the softening point of the olefin resin (B) is preferably 70°C or higher, more preferably 90°C or higher, even more preferably 110°C or higher, and particularly preferably 120°C or higher. The softening point of the olefin resin (B) is preferably 70°C to 150°C.

[0059] The softening point of the olefin resin (B) was determined using JIS K2207 (ring and ball method).

[0060] Examples of olefin-based resins (B) include ethylene-based resins (e.g., polyethylene, ethylene-vinyl acetate copolymer (EVA), or polyethylene oxide), propylene-based resins (e.g., polypropylene), polyvinyl chloride, polyvinylidene chloride, polyvinylidene fluoride, polyamide, polystyrene, polyacrylonitrile, or poly(meth)acrylate. From the viewpoint of balancing effective shut-off function with maintaining the shape of the olefin-based resin during the positive electrode drying process, the olefin-based resin (B) preferably comprises an ethylene-based resin or a propylene-based resin.

[0061] The term "ethylene-based resin" refers to a resin in which ethylene is the main component, and "propylene-based resin" refers to a resin in which propylene is the main component. Here, "main component" refers to the component present in the largest quantity among the components contained in the resin. Examples of ethylene-based resins include homopolymers or copolymers of ethylene. Preferably, ethylene-based resins are copolymers of ethylene with at least one α-olefin. Examples of propylene-based resins include homopolymers or copolymers of propylene.

[0062] The olefin resin (B) preferably comprises a water-dispersible olefin resin. Therefore, when the composition of this disclosure is used as a raw material for the base coating, the lithium-ion secondary battery is less prone to thermal runaway, and the safety of the lithium-ion secondary battery is improved.

[0063] In this disclosure, the term "water-dispersible olefin resin" means an olefin resin that can be dispersed in water even without the addition of at least one of a surfactant and an organic solvent.

[0064] Examples of materials that can be used as water-dispersible olefin resins include polyethylene, polyethylene elastomers, ion-crosslinked polymers of polyolefins, or EVA.

[0065] The content of water-dispersible olefin resin is not particularly limited, but it is preferably 20% by mass or more, more preferably 50% by mass or more, or 100% by mass relative to the total amount of olefin resin (B).

[0066] As an olefin-based resin (B), commercially available products can be used.

[0067] Commercially available olefin-based resins (B) include the CHEMIPEARL (registered trademark) series (polyolefin aqueous dispersions) manufactured by Mitsui Chemicals Co., Ltd. Examples of products obtained by forming particulate aqueous dispersions of polyethylene or polypropylene include WP100, W100, W200, W300, W308, W310, W400, W401, W410, W4005, W500, WF640, W700, W800, W900, W950, P301W, or WH201.

[0068] The shape of the olefin resin (B) is not particularly limited, and it may also be in particulate form. When the olefin resin (B) is in particulate form, the particle size is not particularly limited. Regarding the particle size of the olefin resin (B), from the viewpoint of adjusting the particle size of the olefin resin in a manner that falls within the optimal film thickness range of the primer coating, the average primary particle size is preferably 9.0 μm or less, more preferably 4.0 μm or less, and even more preferably 2.0 μm or less. From the viewpoint of processability of the composition (e.g., a slurry for the primer coating), the particle size of the olefin resin (B) is preferably 0.1 μm or more, more preferably 0.5 μm or more. The particle size of the olefin resin (B) is preferably 0.1 μm to 9.0 μm. The smaller the particle size of the olefin resin (B), the more likely the olefin resin (B) is to aggregate.

[0069] The particle size of the olefin resin (B) is the average primary particle size value determined using the Coulter counting method.

[0070] Preferably, the olefin resin (B) has a particle size of 0.1 μm to 9.0 μm, and the softening point of the olefin resin (B) is 70°C or higher. Therefore, when the composition of this disclosure is used as a raw material for the base coating, the lithium-ion secondary battery is less prone to thermal runaway, and the safety of the lithium-ion secondary battery is further improved.

[0071] Olefin resins (B) can be used alone or in combination of two or more.

[0072] The content of olefin resin (B) is preferably 30% to 90% by mass relative to the total amount of the composition. If the content of olefin resin (B) is within the above range, good shut-off function can be ensured.

[0073] The higher the content of olefin resin (B), the better the safety of the lithium-ion secondary battery; however, there is a tendency for the battery performance to decrease. In other words, the safety and battery performance of a lithium-ion secondary battery are mutually restrictive. From this perspective, regarding the content of olefin resin (B), from the viewpoint of reducing the resistivity of the undercoat, it is preferably 80% by mass or less, more preferably 75% by mass or less, relative to the total amount of the composition. Furthermore, regarding the content of olefin resin (B), from the viewpoint of effectively utilizing the shut-off function, it is preferably 35% by mass or more, more preferably 40% by mass or more, further preferably 50% by mass or more, and particularly preferably 60% by mass or more, relative to the total amount of the composition.

[0074] (1.3) Acrylic water-soluble polymers (C) The compositions disclosed herein contain an acrylic water-soluble polymer (C).

[0075] The content of the acrylic water-soluble polymer (C) is not particularly limited, but is preferably 1% to 20% by mass relative to the total amount of the composition.

[0076] The content of the acrylic water-soluble polymer (C) is not particularly limited, but is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more, relative to the total amount of the composition. The content of the acrylic water-soluble polymer (C) is not particularly limited, but is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the total amount of the composition.

[0077] The acrylic water-soluble polymer (C) has structural units derived from (meth)acrylamide and structural units derived from a vinyl monomer having at least one of a carboxyl group and a hydroxyl group (hereinafter also referred to as "specific vinyl monomer"). The content of the structural units derived from (meth)acrylamide is 35% to 95% by mass relative to the total amount of the acrylic water-soluble polymer (C). The content of the structural units derived from the specific vinyl monomer is 5% to 65% by mass relative to the total amount of the acrylic water-soluble polymer (C).

[0078] The glass transition temperature (Tg) of the acrylic water-soluble polymer (C) is not particularly limited, but is preferably above 150°C. This results in superior heat resistance for the base coating.

[0079] The glass transition temperature (Tg) of the acrylic water-soluble polymer (C) is not particularly limited, but is preferably above 150°C and below 400°C.

[0080] From the viewpoint of obtaining a base coating with superior heat resistance, the glass transition temperature (Tg) of the acrylic water-soluble polymer (C) is more preferably 200°C or higher, more preferably 210°C or higher, particularly preferably 220°C or higher, even more preferably 230°C or higher, and even more preferably 240°C or higher. The glass transition temperature (Tg) of the water-soluble polymer is preferably 400°C or lower, more preferably 300°C or lower, and even more preferably 280°C or lower.

[0081] The method for determining the glass transition temperature (Tg) is the same as that described in the examples.

[0082] The content of structural units derived from (meth)acrylamide is 35% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more, relative to the total amount of the acrylic water-soluble polymer (C). From the viewpoint of obtaining a base coating with excellent heat resistance, the content of structural units derived from (meth)acrylamide is preferably 95% by mass or less, preferably 90% by mass or less, and more preferably 80% by mass or less, relative to the total amount of the acrylic water-soluble polymer (C).

[0083] The content of structural units derived from specific vinyl monomers is 5% by mass or more, preferably 10% by mass or more, and more preferably 20% by mass or more, relative to the total amount of the acrylic water-soluble polymer (C). From the viewpoint of obtaining a base coating with excellent heat resistance, the content of structural units derived from specific vinyl monomers is preferably 65% ​​by mass or less, preferably 40% by mass or less, and more preferably 30% by mass or less, relative to the total amount of the acrylic water-soluble polymer (C).

[0084] The aforementioned acrylic water-soluble polymer preferably has structural units derived from (meth)acrylamide, structural units derived from carboxyl-containing vinyl monomers (hereinafter also referred to as "carboxyl-containing vinyl monomers"), and structural units derived from hydroxyl-containing vinyl monomers (hereinafter also referred to as "hydroxyl-containing vinyl monomers"). As a result, the conductive carbon material (A) exhibits excellent adhesion to the olefin resin (B), and the adhesive force generated by the interaction between the acrylic polymers is improved.

[0085] In the case where the acrylic water-soluble polymer (C) has structural units from carboxyl-containing vinyl monomers and structural units from hydroxyl-containing vinyl monomers, the content of structural units from carboxyl-containing vinyl monomers is preferably within the following range.

[0086] The content of structural units from carboxyl-containing vinyl monomers is preferably 3% to 35% by mass relative to the total amount of acrylic water-soluble polymer (C).

[0087] The content of structural units derived from carboxyl-containing vinyl monomers is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, relative to the total amount of the acrylic water-soluble polymer (C). From the viewpoint of obtaining a base coating with excellent heat resistance, the content of structural units derived from carboxyl-containing vinyl monomers is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, relative to the total amount of the acrylic water-soluble polymer (C).

[0088] In the case where the acrylic water-soluble polymer (C) has structural units from carboxyl-containing vinyl monomers and structural units from hydroxyl-containing vinyl monomers, the content of structural units from hydroxyl-containing vinyl monomers is preferably within the following range.

[0089] The content of structural units from hydroxyl-containing vinyl monomers is preferably 2% to 30% by mass relative to the total amount of acrylic water-soluble polymer (C).

[0090] The content of structural units derived from hydroxyl-containing vinyl monomers is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 13% by mass or more, relative to the total amount of the acrylic water-soluble polymer (C). From the viewpoint of obtaining a base coating with excellent heat resistance, the content of structural units derived from hydroxyl-containing vinyl monomers is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, relative to the total amount of the acrylic water-soluble polymer (C).

[0091] (1.3.1) Raw materials for acrylic water-soluble polymer (C) Acrylic water-soluble polymer (C) is a polymer formed by polymerizing acrylic water-soluble polymer raw materials. The raw materials of acrylic water-soluble polymer (C) (hereinafter also referred to as "acrylic water-soluble polymer raw materials") contain (meth)acrylamide and specific vinyl monomers.

[0092] (1.3.1.1) (Methacrylamide) (Methacrylamide) can be either methacrylamide or acrylamide, or either methacrylamide or acrylamide. From the viewpoint of improving heat resistance, (meth)acrylamide is preferably methacrylamide.

[0093] The content of (meth)acrylamide is preferably 35% to 95% by mass relative to the total amount of acrylic water-soluble polymer raw materials.

[0094] The content of (meth)acrylamide is preferably 35% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and particularly preferably 75% by mass or more, relative to the total amount of the acrylic water-soluble polymer raw material. From the viewpoint of obtaining excellent heat resistance, the content of (meth)acrylamide is preferably 95% by mass or less, more preferably 90% by mass or less, and more preferably 80% by mass or less, relative to the total amount of the acrylic water-soluble polymer raw material.

[0095] (1.3.1.2) Specific vinyl monomers A specific vinyl monomer can copolymerize with (meth)acrylamide and has at least one of a carboxyl group and a hydroxyl group.

[0096] The specific vinyl monomer is selected from at least one of the groups consisting of carboxyl-containing vinyl monomers and hydroxyl-containing vinyl monomers. From the viewpoint of improving the adhesion between the conductive carbon material (A) and the olefin resin (B), and the improved adhesion resulting from the interaction between the adhesives, the specific vinyl monomer is preferably a carboxyl-containing vinyl monomer or a hydroxyl-containing vinyl monomer.

[0097] The content of a specific vinyl monomer is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, relative to the total amount of the acrylic water-soluble polymer raw material. The content of the specific vinyl monomer is preferably 65% ​​by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the total amount of the acrylic water-soluble polymer raw material.

[0098] (1.3.1.2.1) Carboxyl-containing vinyl monomers Examples of carboxyl-containing vinyl monomers include monocarboxylic acids, dicarboxylic acids, or their salts. Examples of monocarboxylic acids include (meth)acrylic acid. Examples of dicarboxylic acids include itaconic acid, maleic acid, fumaric acid, itaconic anhydride, maleic anhydride, or fumaric anhydride. These carboxyl-containing vinyl monomers can be used alone or in combination of two or more.

[0099] The carboxyl-containing vinyl monomer is preferably a monocarboxylic acid, more preferably (meth)acrylic acid, and even more preferably methacrylic acid.

[0100] The content of carboxyl-containing vinyl monomers is preferably 3% to 35% by mass relative to the total amount of acrylic water-soluble polymer raw materials.

[0101] The content of carboxyl-containing vinyl monomers is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 7% by mass or more, relative to the total amount of acrylic water-soluble polymer raw materials. The content of carboxyl-containing vinyl monomers is preferably 35% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, relative to the total amount of acrylic water-soluble polymer raw materials.

[0102] The content of carboxyl-containing vinyl monomers is preferably 20% to 95% by mass relative to the total amount of a specific vinyl monomer.

[0103] The content of carboxyl-containing vinyl monomers is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more, relative to the total amount of a specific vinyl monomer. The content of carboxyl-containing vinyl monomers is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less, relative to the total amount of a specific vinyl monomer.

[0104] (1.3.1.2.2) Hydroxyl-containing vinyl monomers Hydroxyl-containing vinyl monomers include vinyl monomers having hydroxyl groups but no carboxyl groups (hereinafter also referred to as "hydroxyl-containing vinyl monomers (C10)") and vinyl monomers having both hydroxyl and carboxyl groups (hereinafter also referred to as "hydroxyl-containing vinyl monomers (C20)").

[0105] Examples of hydroxyl-containing vinyl monomers (C10) include mono(meth)acrylates (C11), di(meth)acrylates (C12), and tri(meth)acrylates (C13).

[0106] Examples of mono(meth)acrylates (C11) having hydroxyl groups include, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, butanediol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, 2-(6-hydroxyhexanoyloxy)ethyl acrylate, glycerol mono(meth)acrylate, trimethylolpropane mono(meth)acrylate, or pentaerythritol mono(meth)acrylate.

[0107] Examples of di(meth)acrylates (C12) having hydroxyl groups include glycerol di(meth)acrylate, trimethylolpropane di(meth)acrylate, or pentaerythritol di(meth)acrylate.

[0108] Examples of tri(meth)acrylates (C13) having hydroxyl groups include pentaerythritol tri(meth)acrylate.

[0109] They can be used individually or in combination of two or more.

[0110] The hydroxyl-containing vinyl monomer (C10) is preferably a mono(meth)acrylate (C11) having hydroxyl groups, preferably at least one of 2-hydroxyethyl(meth)acrylate and 2-hydroxypropyl(meth)acrylate, and more preferably 2-hydroxyethyl(meth)acrylate.

[0111] The content of hydroxyl-containing vinyl monomers (C10) is preferably 2% to 30% by mass relative to the total amount of acrylic water-soluble polymer raw materials.

[0112] The content of hydroxyl-containing vinyl monomers (C10) is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 13% by mass or more, relative to the total amount of acrylic water-soluble polymer raw materials. The content of hydroxyl-containing vinyl monomers (C10) is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, relative to the total amount of acrylic water-soluble polymer raw materials.

[0113] The content of hydroxyl-containing vinyl monomers (C10) is preferably 5% to 80% by mass relative to the total amount of a specific vinyl monomer.

[0114] The content of hydroxyl-containing vinyl monomers (C10) is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, relative to the total amount of a specific vinyl monomer. The content of hydroxyl-containing vinyl monomers (C10) is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, relative to the total amount of a specific vinyl monomer.

[0115] Examples of hydroxyl-containing vinyl monomers (C20) include ricinoleic acid, lesquerolic acid, 15-hydroxylinoleic acid, auricolic acid, hydroxypalmitoic acid, or caffeic acid. They can be used alone or in combination of two or more.

[0116] (1.3.1.3) Water-soluble comonomers Acrylic water-soluble polymer raw materials may contain comonomers (hereinafter also referred to as "water-soluble comonomers") that can copolymerize with (meth)acrylamide and / or specific vinyl monomers.

[0117] Examples of water-soluble copolymerizable monomers include, for example, alkyl methacrylates (e.g., methyl methacrylate, or ethyl methacrylate), vinyl monomers containing functional groups (e.g., 2-aminoethyl methacrylate, glycidyl methacrylate, methacrylonitrile, allyl sulfonic acid, or 2-methacryloyloxyethyl phosphate), vinyl esters (e.g., vinyl acetate, or vinyl propionate), aromatic vinyl monomers (e.g., styrene, or α-methylstyrene), N-substituted unsaturated carboxylic acid amides (e.g., N-hydroxymethyl (meth)acrylamide), heterocyclic vinyl compounds (e.g., vinylpyrrolidone), vinylidene halide compounds (e.g., vinylidene chloride, or vinylidene fluoride), α-olefins (e.g., ethylene, or propylene), dienes (e.g., butadiene), or crosslinking vinyl monomers (e.g., methylenebis(meth)acrylamide, or divinylbenzene).

[0118] The content of the water-soluble comonomer is within a range that ensures the water solubility of the water-soluble polymer, for example, relative to the total amount of the acrylic water-soluble polymer raw material, for example, 37% by mass or less, preferably 15% by mass or less, and more than 0% by mass, especially preferably 0% by mass.

[0119] (1.3.1.4) Polymerization method for acrylic water-soluble polymer raw materials Acrylic water-soluble polymer raw materials can be polymerized using known methods to obtain water-soluble polymers. More specifically, for example, the acrylic water-soluble polymer raw materials and a polymerization initiator are added to water to polymerize the acrylic water-soluble polymer raw materials, and then the materials are matured as needed.

[0120] There are no particular restrictions on the polymerization initiator; any known polymerization initiator can be used. The polymerization temperature can range from 30℃ to 95℃. The polymerization time can range from 0.5 hours to 20 hours. The curing time can range from 0.5 hours to 6 hours.

[0121] (1.4) Additives (D) The compositions of this disclosure may include additives (D) as needed. Depending on the type of additive (D), various functions can be imparted to the compositions of this disclosure.

[0122] In this disclosure, “additive” refers to components other than conductive carbon materials (A), olefin resins (B), and acrylic water-soluble polymers (C).

[0123] Examples of additives (D) include thickening stabilizers, thermally expandable microcapsules (hereinafter also referred to as "thermally expandable microcapsules") with a maximum volume expansion temperature of 70°C to 180°C, inorganic oxide fillers, curable resin fillers, flake fillers, adhesive resins, synthetic rubber, and non-solid components.

[0124] The term "thermally expandable microcapsule" refers to particles having a shell formed of thermoplastic resin and a volatile expander encapsulated within the shell as a core component. More specifically, the thermally expandable microcapsule is preferably a microcapsule that softens, foams, and expands in volume when exposed to a temperature (e.g., 70°C to 160°C) just before thermal runaway caused by abnormal heating of a lithium-ion secondary battery begins, while in contact with the electrolyte (described later).

[0125] The term "maximum volume expansion temperature" refers to the temperature at which the expansion volume of the thermally expandable microcapsules is maximized when the volatile expanding agent encapsulated within the microcapsules vaporizes and the microcapsules begin to expand. Furthermore, the temperature at which the volatile expanding agent encapsulated within the microcapsules vaporizes and the microcapsules begin to expand is called the "volume expansion initiation temperature."

[0126] When additive (D) is present, the content of additive (D) is preferably 1% to 50% by mass relative to the total amount of the composition. If the content of additive (D) is within the above range, the shut-off function caused by the characteristics of additive (D) can be more effectively presented.

[0127] From the viewpoint of minimizing the impact of the ratio of conductive carbon material (A) and olefin resin (B), effectively maintaining the shut-off function, and preserving battery performance, the content of additive (D) relative to the total amount of the composition is preferably 40% by mass or less, more preferably 30% by mass or less. Furthermore, from the viewpoint of effectively maintaining the shut-off function, the content of additive (D) relative to the total amount of the composition is preferably 5% by mass or more, more preferably 10% by mass or more.

[0128] (1.4.1) Thickening and Stabilizing Agents The compositions disclosed herein may contain thickening and stabilizing agents. The compositions disclosed herein may also not contain thickening and stabilizing agents.

[0129] When the composition of this disclosure contains a thickening stabilizer and is used as a raw material for a primer coating, the particles can be stably dispersed during the adjustment of the primer coating slurry.

[0130] Examples of thickening and stabilizing agents include, for example, carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), methyl cellulose (MC), hydroxypropyl cellulose (HPC), polyethylene glycol (PEG), polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), polyacrylic acid (PAA), polycarboxylic acid ammonium salts, sugars such as lecithin, saponins and other glycosides, xanthan gum and other polysaccharides, sucrose polyether polyols, polyoxypropylene sorbitol ether, trimethylolpropane polyether polyol, pentaerythritol polyether polyol and other polyether polyols, oxidized starch, phosphate starch, casein, or various modified starches.

[0131] The content of the thickening stabilizer relative to the total amount of the composition is preferably 1% to 50% by mass. From the viewpoint of effectively performing the shut-off function and maintaining battery performance, the content of the thickening stabilizer relative to the total amount of the composition is preferably 15% by mass or less, more preferably 10% by mass or less. From the viewpoint of more effectively dispersing the microparticles in the primer slurry, the content of the thickening stabilizer relative to the total amount of the composition is preferably 1% by mass or more, more preferably 2% by mass or more.

[0132] CMC's commercially available products include "1130", "1140", "1240",

[1250] , "1260", "1330", "2200", and "DL100L" manufactured by Daicel Miraizu Co., Ltd.

[0133] (1.4.2) Thermally expandable microcapsules The compositions of this disclosure may contain thermally expandable microcapsules. The compositions of this disclosure may also not contain thermally expandable microcapsules.

[0134] When the composition of this disclosure contains thermally expandable microcapsules and the composition of this disclosure is used as a raw material for a base coating, the thermally expandable microcapsules expand in volume due to the abnormal heating of the lithium-ion secondary battery, effectively increasing the DC resistance of the electrode and improving the safety of the lithium-ion secondary battery.

[0135] The initial temperature of volume expansion of the thermally expandable microcapsules is preferably 100℃~180℃, more preferably 110℃~150℃, and even more preferably 120℃~130℃. The maximum volume expansion temperature of the thermally expandable microcapsules is preferably 100℃~180℃, more preferably 120~170℃, and even more preferably 145℃~155℃.

[0136] The thermoplastic resin constituting the outer shell preferably contains a (co)polymer comprising vinylidene chloride and a (co)polymer comprising (meth)acrylonitrile. This results in the thermoplastic resin constituting the outer shell exhibiting excellent electrolyte resistance, being thermoplastic, and possessing excellent gas barrier properties. From the viewpoint of electrolyte resistance, the thermoplastic resin constituting the outer shell is preferably a (co)polymer with (meth)acrylonitrile as the main component (51% by mass or more). In order to improve the foaming properties and heat resistance of the obtained thermally expandable microcapsules, the raw materials of the thermoplastic resin constituting the outer shell may include crosslinking monomers in addition to polymerizable monomers.

[0137] For volatile expanders, it is preferable to select a boiling point such that the maximum volume expansion temperature of the thermally expandable microcapsules is higher than the softening point of the olefin resin (B). More preferably, the boiling point is selected such that the initial volume expansion temperature of the thermally expandable microcapsules is equal to the softening point of the olefin resin (B). Therefore, when the temperature of the undercoating layer rises above the softening point of the olefin resin (B) due to the heat generated by the lithium-ion secondary battery, the DC resistance of the electrode increases efficiently. As a result, the safety of the lithium-ion secondary battery is further improved.

[0138] Examples of volatile expanding agents include, for example, low molecular weight hydrocarbons with a boiling point below 100°C, and non-flammable or flame-retardant compounds. Low molecular weight hydrocarbons with a boiling point below 100°C are preferred. Examples of low molecular weight hydrocarbons include, for example, propane, propylene, n-butane, isobutane, butene, isobutene, isopentane, neopentane, n-pentane, n-hexane, isohexane, heptane, or petroleum ether. Examples of non-flammable or flame-retardant compounds include, for example, halogenated hydrocarbons (e.g., chloromethane, dichloromethane, chlorofluoromethane, dichlorodifluoromethane, or chlorofluoromethane), or chlorofluorocarbons. One type of volatile expanding agent can be used alone, or two or more can be used in combination.

[0139] The particle size of the thermally expandable microcapsules is not particularly limited, but is preferably 1 μm to 40 μm, more preferably 3 μm to 30 μm, and even more preferably 5 μm to 25 μm.

[0140] The particle size of thermally expandable microcapsules is expressed as the particle size (D50, median particle size) of the cumulative 50% volume percentage of the particle size distribution measured using a particle size distribution measuring device based on laser diffraction scattering, measured using a device based on laser diffraction scattering.

[0141] The content of thermally expandable microcapsules is preferably 0% to 50% by mass relative to the total amount of the composition. From the viewpoint of minimizing the impact on the ratio of conductive carbon material (A) and olefin resin (B), and maintaining the shut-off function and battery performance, the content of thermally expandable microcapsules is preferably 50% by mass or less, more preferably 40% by mass or less, relative to the total amount of the composition. Furthermore, from the viewpoint of enhancing the shut-off function due to the thermal expansion of the thermally expandable microcapsules during abnormal heating, the content of thermally expandable microcapsules is preferably 5% by mass or more, more preferably 10% by mass or more, relative to the total amount of the composition.

[0142] As thermally expandable microcapsules, commercially available products can be used.

[0143] Commercially available products that utilize thermally expandable microcapsules include the "MATSUMOTOMICROSPHERE (registered trademark)" series manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd., the "EXPANCEL (registered trademark)" series manufactured by Akzo Nobel Co., Ltd., and the "ADVANCELL (registered trademark)" series manufactured by Sekisui Chemicals Co., Ltd.

[0144] (1.4.3) Inorganic oxide fillers The compositions of this disclosure may contain inorganic oxide fillers. The compositions of this disclosure may also not contain inorganic oxide fillers. When the compositions of this disclosure contain inorganic oxide fillers, the inorganic oxide fillers function as filler materials.

[0145] Increasing the content of inorganic oxide fillers helps improve the heat resistance of the positive electrode. Conversely, minimizing the content of inorganic oxide fillers allows them to form a base layer that adheres tightly to the positive electrode binder layer. This base layer melts during internal short circuits, contributing to improved safety. Furthermore, by selecting the type and properties of inorganic oxide fillers, it is possible to decompose the electrolyte and generate gas during battery overcharging.

[0146] Examples of inorganic oxide fillers include alumina (α-Al₂O₃, γ-Al₂O₃), aluminum hydroxide (Al(OH)₃), boehmite (AlOOH)), magnesium oxide (MgO), magnesium hydroxide (Mg(OH)₂), zirconium oxide (ZrO₂), titanium dioxide (TiO₂), silicon dioxide (SiO₂), silicon carbide (SiC), aluminum nitride (AlN), boron nitride (BN), mica, or graphite oxide (e.g., expanded graphite). One type of inorganic oxide filler can be used alone, or two or more can be used in combination. Alumina is preferably included among the inorganic oxide fillers.

[0147] The shape of the inorganic oxide filler is not particularly limited; for example, spherical, needle-shaped, ellipsoidal, plate-shaped, and scaly shapes are possible. The particle size of the inorganic oxide filler is not particularly limited, but is preferably 0.01 μm to 5 μm.

[0148] The particle size of inorganic oxide fillers is expressed as the particle size (D50, median particle size) of the cumulative 50% volume percentage of the particle size in the volume-based particle size distribution measured using a particle size distribution measuring device based on laser diffraction scattering.

[0149] The content of inorganic oxide filler is preferably 0% to 50% by mass relative to the total amount of the composition. From the viewpoint of minimizing the impact of the ratio of conductive carbon material (A) to olefin resin (B) and maintaining the shut-off function and battery performance, the content of inorganic oxide filler is preferably 40% by mass or less, more preferably 30% by mass or less, relative to the total amount of the composition. Furthermore, from the viewpoint of suppressing the flowability of the olefin resin (B) melting in the base coating at high temperatures and maintaining the shut-off function for a longer period, the content of inorganic oxide filler is preferably 5% by mass or more, more preferably 10% by mass or more, relative to the total amount of the composition.

[0150] (1.4.4) Adhesive resin The compositions disclosed herein may contain a binder resin as another component. Therefore, when the compositions of this disclosure are used as raw materials for a base coating, the binder resin can improve the physical properties of the base coating (e.g., electrolyte permeability, peel strength) and improve the battery performance of the lithium-ion secondary battery.

[0151] Examples of adhesive resins include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF copolymers, hydroxypropyl methylcellulose, polyvinyl alcohol, or cellulose diacetate. PVDF copolymers are copolymers of vinylidene fluoride with other monomers, such as PVDF-HFP (hexafluoropropylene) or PVDF-PEO (polyoxyethylene). From the viewpoint of reducing the resistance of the base coating, the adhesive resin preferably contains PVDF.

[0152] As an adhesive resin, commercially available products can be used.

[0153] Commercially available PVDF products include the KUREHA (registered trademark) KF polymer series manufactured by Kureha Corporation, such as "W#1100", "W#1300", "W#1700", "W#7200", or "W#7300".

[0154] The adhesive resin can be used alone or in combination of two or more types.

[0155] The binder resin content is preferably 1% to 20% by mass relative to the total amount of the composition. The sealing function depends on the balance between the binder resin content and the total content of the olefin resin (B) and the acrylic water-soluble polymer (C). It is believed that when the proportion of binder resin relative to the total amount of the composition is high, the proportions of olefin resin (B) and acrylic water-soluble polymer (C) relative to the total amount of the composition become low, thus reducing the sealing function. If the binder resin content is within the above range, a balance can be achieved between the processability of the composition (e.g., a primer slurry) and the assurance of the sealing function.

[0156] From the viewpoint of ensuring the shut-off function by utilizing the relationship between the content of olefin-based resin (B) and acrylic water-soluble polymer (C), the content of adhesive resin is preferably 15% by mass or less, more preferably 10% by mass or less, relative to the total amount of the composition. Furthermore, from the viewpoint of the processability of the composition (e.g., a primer coating slurry), the content of adhesive resin is preferably 2% by mass or more, more preferably 3% by mass or more, relative to the total amount of the composition.

[0157] (1.4.5) Synthetic rubber The compositions disclosed herein may contain synthetic rubber as other components. Therefore, when the compositions of this disclosure are used as raw materials for a primer, the adhesion between the primer and the current collector is improved, further reducing battery resistance.

[0158] Examples of synthetic rubbers include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, acrylonitrile-butadiene-styrene rubber, hydrogenated styrene-butadiene rubber (HSBR), butene rubber, polybutadiene, or polyisoprene rubber. From the viewpoint of low resistivity of the base coating, the synthetic rubber is preferably a rubber obtained by appropriately mixing an SBR emulsion or other water-dispersible binder, and more preferably includes SBR. One type of synthetic rubber may be used alone, or two or more types may be used in combination.

[0159] The shape of synthetic rubber is not particularly limited; it can also be in granular form.

[0160] As for synthetic rubber, commercially available products can be used. Examples of commercially available synthetic rubber include "TRD2001" (aqueous dispersion of styrene-butadiene rubber particles) manufactured by JSR Corporation.

[0161] (1.4.6) Non-solid components The compositions disclosed herein may contain non-solid components. Examples of non-solid components include various formulations from primer coating slurries (e.g., surfactants, dispersants, wetting agents, defoamers, etc.), water, etc.

[0162] Preferably, the composition of this disclosure further contains an additive (D) in an amount of 1% to 50% by mass relative to the total amount of the composition, and the additive (D) comprises carboxymethyl cellulose. This enables stable dispersion of microparticles in the primer slurry.

[0163] Preferably, the composition of this disclosure further contains an additive (D) in an amount of 1% to 50% by mass relative to the total amount of the composition. The additive (D) comprises at least one of thermally expandable microcapsules having a maximum volume expansion temperature of 70°C to 180°C and an inorganic oxide filler. This facilitates the activation of the olefinic resin (B)'s shut-off function.

[0164] Preferably, the composition of this disclosure further contains an additive (D) in an amount of 1% to 50% by mass relative to the total amount of the composition, wherein the additive (D) comprises alumina. This facilitates the activation of the olefinic resin (B)'s shut-off function.

[0165] (1.5) Physical properties of the composition Various physical properties of the compositions disclosed herein are described.

[0166] In the composition disclosed herein, from the viewpoint of forming an electrode with excellent safety, where the DC resistance is suppressed at a low level during the initial charging and discharging phase and the rise in DC resistance is suppressed under high temperature conditions, the ratio of particle size distribution D99 to particle size distribution D10 (D99 / D10), as measured by laser diffraction scattering, is preferably 35 or less.

[0167] The term "particle size distribution D99 determined by laser diffraction scattering" refers to the particle size that represents 99% of the cumulative volume from the microparticle side in a volume-based particle size distribution determined using a particle size distribution measuring device based on laser diffraction scattering. The method for determining D99 is the same as that described in the examples.

[0168] The term "particle size distribution D10 determined by laser diffraction scattering" refers to the particle size equivalent to 10% of the cumulative volume from the microparticle side in a volume-based particle size distribution determined using a particle size distribution measuring device based on laser diffraction scattering. The method for determining D10 is the same as that described in the examples.

[0169] A ratio (D99 / D10) of 35 or less indicates that the amount of aggregates in the composition is low (in other words, the amount of components dispersed in the composition is high). That is, the lower the ratio (D99 / D10), the less aggregates are present in the composition. The conductive carbon material (A) in the composition is uniformly dispersed, easily forming a uniform conductive path within the undercoat. This suppresses the increase in DC resistance during the initial charging and discharging phases of the battery, as well as the increase in DC resistance after long-term storage at high temperatures. Furthermore, the olefin resin (B) and the acrylic water-soluble polymer (C) in the composition are uniformly dispersed, thus facilitating efficient and effective shut-off. As a result, the composition of this disclosure can form an electrode with excellent safety, where the DC resistance during the initial charging and discharging phase is suppressed to a low level, and the increase in DC resistance at high temperatures is significantly suppressed. Therefore, a lithium-ion secondary battery with excellent battery performance can be obtained.

[0170] From the viewpoint of improving the safety and performance of lithium-ion secondary batteries, a ratio of (D99 / D10) of 3.0 to 30.0 is more preferred, 3.0 to 22.0 is even more preferred, and 3.0 to 15.0 is particularly preferred.

[0171] Methods for adjusting the ratio (D99 / D10) to the above range include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers (FILMIX), ultrasonic or high-pressure homogenizers, etc.

[0172] In the compositions disclosed herein, the particle size distribution D99, as determined by laser diffraction scattering, is preferably 20 μm or less. The smaller the agglomerates of the particles, the better the dispersibility of the materials contained in the composition. By setting D99 to 20 μm or less, the safety and battery performance of the lithium-ion secondary battery are easily improved compared to cases where D99 is greater than 20 μm. From the viewpoint of improving the safety and battery performance of the lithium-ion secondary battery, D99 of the composition is more preferably 2.0 μm to 20.0 μm, further preferably 2.0 μm to 15.0 μm, and particularly preferably 2.0 μm to 10.0 μm.

[0173] Examples of methods for adjusting the D99 of the composition to the above range include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers, ultrasonic or high-pressure homogenizers, etc.

[0174] Regarding the composition of this disclosure, the particle size distribution D10, as measured by laser diffraction scattering, is preferably 0.1 μm to 1.5 μm, more preferably 0.1 μm to 1.0 μm, and even more preferably 0.1 μm to 0.7 μm. Furthermore, from the viewpoint of dispersibility, the particle size distribution D10 is preferably 0.2 μm to 1.0 μm, more preferably 0.4 μm to 1.0 μm. If D10 is within the above range, the dispersibility of the materials contained in the composition is excellent, and compared to cases where D10 is not within the above range, it is easier to improve the safety and battery performance of the lithium-ion secondary battery.

[0175] Methods for adjusting D10 to the above range include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers, ultrasonic or high-pressure homogenizers, etc.

[0176] In the composition disclosed herein, the ratio (D99 / D50) of particle size distribution D99 to particle size distribution D50 (also simply "D50"), as determined by laser diffraction scattering, is preferably 20 or less. A ratio (D99 / D50) of 20 or less indicates that the size of agglomerates is suppressed relative to the median particle size of the particles in the composition. By making the ratio (D99 / D50) 20 or less, the composition exhibits excellent dispersibility. Consequently, compared to a ratio (D99 / D50) greater than 20, it is easier to improve the safety and battery performance of lithium-ion secondary batteries. From the viewpoint of improving the safety and battery performance of lithium-ion secondary batteries, a ratio (D99 / D50) of 2.0 to 16.0 is more preferred, further preferred to be 2.0 to 10.0, and particularly preferred to be 2.0 to 6.0.

[0177] The term "particle size distribution D50 determined by laser diffraction scattering" refers to the particle size that represents the cumulative 50% by volume, measured from the microparticle side, in a volume-based particle size distribution determined using a particle size distribution measuring device based on laser diffraction scattering. The method for determining D50 is the same as that described in the examples.

[0178] Methods for adjusting the ratio (D99 / D50) to the above range include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers, ultrasonic or high-pressure homogenizers, etc.

[0179] The particle size distribution D50 of the composition disclosed herein, as determined by laser diffraction scattering, is not particularly limited, but is preferably 0.5 μm to 5.0 μm, more preferably 0.5 μm to 3.0 μm, and even more preferably 0.5 μm to 2.0 μm. If D50 is within the above range, the composition exhibits excellent dispersibility, which easily improves the safety and performance of lithium-ion secondary batteries.

[0180] Methods for adjusting D50 to the above range include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers, ultrasonic or high-pressure homogenizers, etc.

[0181] With respect to the compositions of this disclosure, the particle size distribution D90 (also referred to as "D90") determined by laser diffraction scattering is preferably 1.0 μm to 10.0 μm, more preferably 1.0 μm to 7.0 μm, and even more preferably 1.0 μm to 4.0 μm. If D90 is within the above range, the composition exhibits excellent dispersibility, which easily improves the safety and battery performance of lithium-ion secondary batteries.

[0182] The term "particle size distribution D90 determined by laser diffraction scattering" refers to the particle size that represents 90% of the cumulative volume from the microparticle side in a volume-based particle size distribution determined using a particle size distribution measuring device based on laser diffraction scattering. The method for determining D90 is the same as that described in the examples.

[0183] Methods for adjusting D90 to the above range include kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers, ultrasonic or high-pressure homogenizers, etc.

[0184] (1.6) Preferred composition Regarding the content ratio of the conductive carbon material (A), olefin resin (B), and acrylic water-soluble polymer (C) mentioned above, from the viewpoint of effectively performing the shut-off function and maintaining battery performance, the following is preferred: the content of conductive carbon material (A) is 1% to 30% by mass relative to the total amount of the composition, the content of olefin resin (B) is 30% to 90% by mass relative to the total amount of the composition, and the content of acrylic water-soluble polymer (C) is 1% to 20% by mass relative to the total amount of the composition.

[0185] (1.6.1) Preferred composition (i) The composition disclosed herein preferably satisfies the following requirement (a1) in addition to the above-described structure. Therefore, the conductive carbon material (A) and the olefin resin (B) exhibit excellent adhesion, thus maintaining battery performance.

[0186] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (a1) and (a2). This improves the balance between effective shutdown function and maintenance of battery performance.

[0187] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (a1), (a2), and (a3). This improves the balance between effective shutdown function and maintenance of battery performance.

[0188] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (a1), (a2), (a3), and (a4). This improves the balance between maintaining the energy density of the lithium secondary battery and ensuring effective operation of the shutdown function and battery performance.

[0189] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (a1), (a2), (a3), (a4), and (a5). As a result, the electrode exhibits excellent high-temperature resistance, maintains the energy density of the lithium secondary battery, and improves the balance between effective shutdown function and battery performance maintenance.

[0190] The composition of this disclosure preferably satisfies, in addition to the above-described structure, the following requirements (a1), (a2), (a3), (a4), (a5), and (a6). Therefore, when the composition of this disclosure is applied to a lithium secondary battery having electrodes, a lithium-ion secondary battery with a superior balance between safety and battery performance (i.e., output power and lifespan) can be manufactured.

[0191] (1.6.1.1) Requirements (a1) to (a6) Requirement (a1): The content of structural units derived from (meth)acrylamide is 60% to 85% by mass relative to the total amount of the acrylic water-soluble polymer (C). Requirement (a2): The content of conductive carbon material (A) is 10% to 20% by mass relative to the total amount of the composition. Requirement (a3): The content of olefin resin (B) is 60% to 80% by mass relative to the total amount of the composition. Requirement (a4): The particle size of the olefin resin (B) is 1μm~3μm. Requirement (a5): The softening point of the olefin resin (B) is above 120°C. Requirement (a6): The compositions of this disclosure further contain additive (D), which comprises CMC. (1.6.2) Preferred composition (ii) The composition disclosed herein preferably satisfies the following requirement (b1) in addition to the above-described structure. Therefore, the conductive carbon material (A) and the olefin resin (B) exhibit excellent adhesion, thus maintaining battery performance.

[0192] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (b1) and (b2). This improves the balance between effective shutdown function and maintenance of battery performance.

[0193] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (b1), (b2), and (b3). This improves the balance between effective shutdown function and maintenance of battery performance.

[0194] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (b1), (b2), (b3), and (b4). This improves the balance between maintaining the energy density of the lithium secondary battery and ensuring effective operation of the shutdown function while maintaining battery performance.

[0195] The composition disclosed herein preferably satisfies, in addition to the above-described structure, the following requirements (b1), (b2), (b3), (b4), and (b5). As a result, the electrode exhibits excellent high-temperature resistance, maintains the energy density of the lithium secondary battery, and improves the balance between effective shutdown function and battery performance maintenance.

[0196] The composition of this disclosure preferably satisfies, in addition to the above-described structure, the following requirements (b1), (b2), (b3), (b4), (b5), and (b6). Therefore, when the composition of this disclosure is applied to a lithium secondary battery having electrodes, a lithium-ion secondary battery with particularly excellent balance between safety and battery performance (i.e., output power and lifespan) can be manufactured.

[0197] (1.6.2.1) Requirements (b1) to (b6) Requirement (b1): The content of structural units derived from (meth)acrylamide is 60% to 85% by mass relative to the total amount of the acrylic water-soluble polymer (C). Requirement (b2): The content of conductive carbon material (A) is 10% to 20% by mass relative to the total amount of the composition. Requirement (b3): ​​The content of olefin resin (B) is 70% to 80% by mass relative to the total amount of the composition. Requirement (b4): The particle size of the olefin resin (B) is 1μm~2μm. Requirement (b5): The softening point of the olefin resin (B) is above 120°C. Requirement (b6): The compositions of this disclosure further contain additive (D), which comprises CMC. (1.7) Method for manufacturing the composition The method for manufacturing the composition disclosed herein preferably includes a step of mixing a conductive carbon material (A), an olefinic resin (B), and an acrylic water-soluble polymer (C) to form a mixture (hereinafter also referred to as the "mixing step"), and a step of dispersing the mixture using a dispersing roller (hereinafter also referred to as the "dispersion step"). The mixing step and the dispersion step may be performed sequentially, and if performed sequentially, other steps (e.g., a step of kneading the mixture) may be performed between the mixing step and the dispersion step.

[0198] (1.7.1) Mixing process In the mixing process, conductive carbon material (A), olefin resin (B), and acrylic water-soluble polymer (C) are mixed to create a mixture. The mixing method is not particularly limited and any known method may be used.

[0199] The amounts of conductive carbon material (A), olefin resin (B), and acrylic water-soluble polymer (C) are the same as those described above as the content of conductive carbon material (A), olefin resin (B), and acrylic water-soluble polymer (C) in the compositions disclosed herein.

[0200] (1.7.2) Dispersion process In the dispersion process, a dispersion roller is used to disperse the mixture. This results in a composition in which the raw materials are further dispersed compared to the mixture before the dispersion process. Consequently, the resulting composition not only reduces the DC resistance during the initial charging and discharging phase when the electrode is incorporated into a secondary battery, but also effectively suppresses the increase in DC resistance at high temperatures compared to the case without the dispersion process.

[0201] The process of dispersing a mixture using a dispersing roller is also called "dispersion treatment". Alternatively, the mixture can be pre-mixed before dispersion treatment.

[0202] The dispersion method is not particularly limited, and methods using a mixing apparatus can be cited as examples. Examples of mixing apparatus include, for instance, kneaders, two-roll mills, three-roll mills, planetary mixers, ball mills, horizontal sand mills, vertical sand mills, ring bead mills, grinders, high-shear mixers, dispersers, thin-film spin mixers, ultrasonic or high-pressure homogenizers, etc. Among these, from the viewpoint of dispersing particles more uniformly in the mixture, a three-roll mill is preferred.

[0203] When using a mixing apparatus, methods of dispersing the mixture include batch dispersion, pass-through dispersion, and circulating dispersion. Two or more methods can be combined. "Batch dispersion" refers to a method of dispersing the mixture using only the mixing apparatus without piping. "Pass-through dispersion" refers to a method of dispersing the mixture by using a mixing system and passing it through the mixing apparatus. A mixing system includes a mixing apparatus, a first tank that supplies the mixture to the mixing apparatus via piping, and a second tank that receives the mixed mixture. "Circulating dispersion" refers to a method of dispersing the mixture by returning the mixed mixture from the second tank to the first tank while circulating it.

[0204] Reference Figure 4 The three-roll mill is described below. Figure 4 In the figures, reference numeral D1 indicates the rotation direction of the first roll 91 (hereinafter also referred to as the "feed roll 91"). Reference numeral D2 indicates the rotation direction of the second roll 92 (hereinafter also referred to as the "intermediate roll 92"). Reference numeral D3 indicates the rotation direction of the third roll 93 (hereinafter also referred to as the "finishing roll 93").

[0205] like Figure 4 As shown, the three-roll mill 90 includes a feed roll 91, an intermediate roll 92, a finishing roll 93, and blades 94. The feed roll 91 is separated from the intermediate roll 92 by a first interval L1 (see...). Figure 4 The intermediate roll 92 is separated from the finishing roll 93 by a second interval L2 (see...). Figure 4 The blade 94 is configured to contact the surface of the finishing roll 93.

[0206] Three-roll mill 90, such as Figure 4 As shown, a mixture 1110 is stored in the upper space formed by the feed roll 91 and the intermediate roll 92. The mixture 1110 adhering to the surface of the feed roll 91 is transferred to the surface of the intermediate roll 92. The mixture 1110 adhering to the surface of the intermediate roll 92 is transferred to the surface of the finishing roll 93. The mixture 1110 adhering to the surface of the finishing roll 93 is scraped off by a blade 94.

[0207] The feed roll 91, intermediate roll 92, and finishing roll 93 can each be any roll used in a known three-roll mill. The feed roll 91, intermediate roll 92, and finishing roll 93 each have approximately the same diameter. As for the blade 94, for example, a scraper can be used.

[0208] The rotational speeds of the feed roll 91, intermediate roll 92, and finishing roll 93 are not particularly limited and can be increased in the order of feed roll 91, intermediate roll 92, and finishing roll 93.

[0209] The rotational speed of the feed roll 91 is not particularly limited, but is preferably 5 rpm (revolutions per minute) to 84 rpm, more preferably 16 rpm to 56 rpm. The rotational speed of the intermediate roll 92 is not particularly limited, but is preferably 16 rpm to 240 rpm, more preferably 50 rpm to 160 rpm. The rotational speed of the finishing roll 93 is not particularly limited, but is preferably 50 rpm to 600 rpm, more preferably 150 rpm to 400 rpm.

[0210] From the viewpoint of uniformly dispersing the particles in the mixture, the ratio of the rotational speed of the intermediate roller 92 to the rotational speed of the feed roller 91 (rotational speed of the intermediate roller 92 / rotational speed of the feed roller 91) is preferably 2.0 to 4.0, more preferably 2.5 to 3.5.

[0211] From the viewpoint of uniformly dispersing the particles in the mixture, the ratio of the rotational speed of the finishing roll 93 to the rotational speed of the feed roll 91 (rotational speed of the finishing roll 93 / rotational speed of the feed roll 91) is preferably 5.0 to 12.0, more preferably 6.5 to 10.0.

[0212] The first interval L1 is not particularly limited, but from the viewpoint of uniformly dispersing the particles in the mixture, it is preferably 0 mm to 0.05 mm, and more preferably 0 mm to 0.02 mm.

[0213] The second interval L2 is not particularly limited, but from the viewpoint of uniformly dispersing the particles in the mixture, it is preferably 0 mm to 0.05 mm, and more preferably 0 mm to 0.02 mm.

[0214] The number of dispersion treatments (hereinafter also referred to as "number of treatments") can be one or more. Preferably, the number of treatments is three. When the number of treatments is three, compared to cases where the number of treatments is two or fewer or four or more, the conductive carbon material (A) and olefin resin (B) in the mixture are more easily and uniformly dispersed. As a result, a composition for producing a lithium-ion secondary battery in which the rise in DC resistance during the initial charging and discharging phase and under high-temperature conditions (especially after long-term storage) is more effectively suppressed can be obtained.

[0215] (2) Primer The base coat of this disclosure comprises the composition of this disclosure as described above. Regarding the composition of this disclosure, as described above, a description is therefore omitted here.

[0216] The thickness of the base coating is not particularly limited. From the viewpoint of further suppressing the DC resistance of the lithium-ion secondary battery under normal conditions, the thickness of the base coating is preferably 50 μm or less, more preferably 20 μm or less. From the viewpoint of further improving the DC resistance and more reliably exhibiting the shut-off function when the lithium-ion secondary battery is abnormally heated, the thickness of the base coating is preferably 0.1 μm or more, more preferably 0.2 μm or more.

[0217] The location where the base coating is formed is preferably at least a portion of at least one main surface of the positive electrode current collector, and can be appropriately selected according to the coating pattern of the positive electrode additive material layer (e.g., intermittent coating, or stripe coating, etc.).

[0218] (3) Electrode The electrode of this disclosure comprises a current collector, the primer layer of this disclosure as described above, and an adhesive material layer. The term "electrode" refers to at least one of the positive and negative electrodes of a lithium-ion secondary battery.

[0219] Because the electrodes of this disclosure have the above-described configuration, it is possible to manufacture lithium-ion secondary batteries with excellent safety and suppressed rise in DC resistance during the initial charging and discharging stages and under high-temperature conditions (especially after long-term storage).

[0220] The electrode of this disclosure preferably comprises a current collector, a base coating, and an additive material layer stacked sequentially. Therefore, the electrode of this disclosure increases the resistance between the current collector and the additive material layer when the lithium-ion secondary battery experiences a rapid temperature rise. This suppresses overheating of the lithium-ion secondary battery. Thus, the electrode of this disclosure improves the safety of the lithium-ion secondary battery. Furthermore, with respect to the electrode of this disclosure, even when the lithium-ion secondary battery is stored at high temperatures for extended periods, the increase in DC resistance within the lithium-ion secondary battery can be suppressed.

[0221] The electrode in this disclosure can be either a positive or a negative electrode. Preferably, the electrode in this disclosure is a positive electrode. When the electrode in this disclosure is a positive electrode, the resistance of the positive electrode increases, thereby enabling the resulting lithium-ion secondary battery to exhibit a good shut-off function.

[0222] (3.1) Positive electrode The positive electrode of this disclosure may have a current collector (hereinafter also referred to as "positive current collector"), a base coating, and an additive material layer (hereinafter also referred to as "positive additive material layer").

[0223] The positive electrode in this disclosure includes a first positive electrode configuration, a second positive electrode configuration, a third positive electrode configuration, and a fourth positive electrode configuration.

[0224] The first positive electrode configuration refers to the configuration obtained by sequentially layering a base coating and a positive electrode additive material layer on the two main surfaces of the current collector.

[0225] The second positive electrode configuration is a configuration obtained by sequentially layering a base coating and a positive electrode additive material layer on one main surface of the current collector, and layering a base coating on the other main surface of the current collector.

[0226] The third positive electrode configuration is a configuration obtained by sequentially stacking a base coating layer and a positive electrode additive material layer on one main surface of the current collector, and stacking a positive electrode additive material layer on the other main surface of the current collector.

[0227] The fourth positive electrode configuration refers to a configuration obtained by sequentially stacking a base coating layer and a positive electrode additive material layer on one main surface of the current collector, and not stacking the base coating layer and the positive electrode additive material layer on the other main surface of the current collector.

[0228] (3.1.1) Positive current collector Materials used as positive current collectors include, for example, aluminum, nickel, stainless steel (SUS), and copper. "Aluminum" includes pure aluminum or aluminum alloys.

[0229] (3.1.2) Primer coating Details regarding the primer coating and the composition forming it are as described above, and therefore are omitted here.

[0230] (3.1.3) Positive electrode mixture material layer The positive electrode mixture material layer contains positive electrode active substances and binders.

[0231] (3.1.3.1) Positive electrode active material As a positive electrode active material, any material that can absorb and release lithium ions is acceptable; there are no particular limitations, and it can be appropriately adjusted according to the intended use of the lithium-ion secondary battery.

[0232] Examples of positive electrode active materials include, for example, the first oxide and the second oxide.

[0233] The first oxide uses lithium (Li) and nickel (Ni) as its constituent metal elements.

[0234] The second oxide comprises at least one of Li, Ni, and a metallic element other than Li and Ni as a constitutive metallic element. Examples of metallic elements other than Li and Ni include transition metals and typical metallic elements. Preferably, the metallic element other than Li and Ni in the second oxide is included in a proportion equal to or less than that of Ni in terms of atomic number. The metallic element other than Li and Ni can be, for example, at least one selected from the group consisting of Co, Mn, Al, Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce. The positive electrode active material can be one element alone or two or more elements in combination.

[0235] The positive electrode active material preferably comprises a lithium-containing composite oxide (hereinafter sometimes referred to as "NCM") represented by the following formula (X). The lithium-containing composite oxide (X) has the following advantages: high energy density per unit volume and excellent thermal stability.

[0236] LiNi a Co b Mn c O2… Formula (X) In equation (X), a, b and c are each independently greater than 0 and less than 1, and the sum of a, b and c is 0.99~1.00.

[0237] As a specific example of NCM, LiNi can be cited. 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, etc.

[0238] The positive electrode active material may also contain a lithium-containing composite oxide (hereinafter sometimes referred to as "NCA") represented by the following formula (Y).

[0239] Li t Ni 1-x-y Co x Al y O2... formula (Y) In formula (Y), t is 0.95~1.15, x is 0~0.3, y is 0.01~0.2, and the sum of x and y is less than 0.5.

[0240] As a specific example of NCA, LiNi can be cited. 0.8 Co 0.15 Al 0.05 O2, etc.

[0241] The content of positive electrode active material is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and particularly preferably 70% by mass or more, relative to the total amount of positive electrode compound material layer.

[0242] The content of positive electrode active material is preferably 99.9% by mass or less, more preferably 99% by mass or less, relative to the total amount of positive electrode compound material layer.

[0243] (3.1.3.2) Adhesive Examples of adhesives include, for example, polyvinyl acetate, polymethyl methacrylate, nitrocellulose, fluoropolymers, or rubber particles.

[0244] Examples of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and vinylidene fluoride-hexafluoropropylene copolymer.

[0245] Examples of rubber particles include styrene-butadiene rubber particles and acrylonitrile rubber particles.

[0246] From the viewpoint of improving the oxidation resistance of the positive electrode binder material layer, the binder preferably contains a fluororesin. One type of binder may be used alone, or two or more may be used in combination.

[0247] From the perspective of balancing the physical properties of the positive electrode binder material layer (e.g., electrolyte permeability, peel strength, etc.) with battery performance, the binder content is preferably 0.1% to 4% by mass relative to the total amount of the positive electrode binder material layer.

[0248] (3.1.3.3) Conductive additives The positive electrode compound material layer may also contain conductive additives.

[0249] Known conductive additives can be used as conductive aids. Among known conductive additives, conductive carbon materials are preferred. Examples of conductive carbon materials include graphite, carbon black, conductive carbon fibers, or fullerenes. Examples of conductive carbon fibers include carbon nanotubes, carbon nanofibers, or carbon fibers. Examples of graphite include, for example, synthetic graphite or natural graphite. Examples of natural graphite include, for example, flake graphite, block graphite, or amorphous graphite. One conductive additive can be used alone or in combination of two or more. The conductive additive material can also be a commercially available product.

[0250] (3.1.3.4) Other components The positive electrode mixture material layer may also contain other components. Examples of other components include thickeners, surfactants, dispersants, wetting agents, and defoamers.

[0251] (3.2) Negative electrode The negative electrode of this disclosure includes a current collector (hereinafter also referred to as "negative electrode current collector") and an additive material layer (hereinafter also referred to as "negative electrode additive material layer"), and may also include a base coating layer.

[0252] The negative electrode in this disclosure may include a first negative electrode configuration, a second negative electrode configuration, a third negative electrode configuration, and a fourth negative electrode configuration.

[0253] The first negative electrode configuration refers to the configuration obtained by sequentially layering a base coating and a negative electrode additive material layer on the two main surfaces of the current collector.

[0254] The second negative electrode configuration is obtained by sequentially layering a base coating and a negative electrode additive material layer on one main surface of the current collector, and layering a base coating on the other main surface of the current collector.

[0255] The third negative electrode configuration is a configuration obtained by sequentially layering a base coating and a negative electrode mixture material layer on one main surface of the current collector, and layering a negative electrode mixture material layer on the other main surface of the current collector.

[0256] The fourth negative electrode configuration refers to a configuration obtained by sequentially layering a base coating and a negative electrode mixture material layer on one main surface of the current collector, and not layering the base coating and negative electrode mixture material layer on the other main surface of the current collector.

[0257] (3.2.1) Negative current collector Materials used as negative current collectors include, for example, copper, aluminum, nickel, stainless steel (SUS), or nickel-plated steel.

[0258] (3.2.2) Primer coating The primer coating is the same as the primer coating exemplified as the primer coating for the positive electrode.

[0259] (3.2.3) Negative electrode mixture material layer The negative electrode mixture material layer contains negative electrode active substances and binders.

[0260] (3.2.3.1) Negative electrode active material The negative electrode active material can be any material capable of absorbing and releasing lithium ions, without particular limitations. Preferably, the negative electrode active material is selected from at least one of the following groups: metallic lithium, lithium-containing alloys, metals or alloys capable of alloying with lithium, oxides capable of lithium ion doping and dedoping, transition metal nitrides capable of lithium ion doping and dedoping, and carbon materials capable of lithium ion doping and dedoping. Among these, the negative electrode active material is preferably a carbon material capable of lithium ion doping and dedoping (hereinafter referred to as "carbon material").

[0261] Examples of carbon materials include carbon black, activated carbon, graphite, and amorphous carbon. One type of carbon material can be used, or a mixture of two or more can be used. The morphology of the carbon material is not particularly limited; for example, it can be fibrous, spherical, or sheet-like. The particle size of the carbon material is not particularly limited, but is preferably 5 μm to 50 μm, more preferably 20 μm to 30 μm.

[0262] Examples of amorphous carbon materials include hard carbon, coke, mesophase carbon microspheres (MCMB) obtained by sintering at temperatures below 1500°C, and mesophase pitch carbon fibers (MCF).

[0263] Examples of graphite materials include natural graphite and synthetic graphite. Examples of synthetic graphite include graphitized MCMB and graphitized MCF. Graphite materials may also contain boron. Graphite materials may also be coated with metals or amorphous carbon. Examples of metals used as coatings for graphite materials include gold, platinum, silver, copper, or tin. Graphite materials may also be mixtures of amorphous carbon and graphite.

[0264] (3.2.3.2) Adhesive As a binder included in the negative electrode binder material layer, the same binder exemplified as that included in the positive electrode binder material layer can be cited.

[0265] The binder contained in the negative electrode binder layer can be the same as or different from the binder contained in the positive electrode binder layer.

[0266] The content of binder contained in the negative electrode binder material layer is not particularly limited and can be the same as the content of binder exemplified in the positive electrode binder material layer.

[0267] (3.2.3.3) Conductive additives The negative electrode binder material layer preferably contains a conductive additive. Examples of conductive additives include those that can be included in the positive electrode binder material layer.

[0268] (3.2.3.4) Other components The negative electrode mixture material layer may contain other components besides those mentioned above. Examples of such other components include thickeners, surfactants, dispersants, wetting agents, or defoamers.

[0269] In the electrodes of this disclosure, a current collector, a base coating, and a binder material layer are preferably stacked sequentially.

[0270] (4) Lithium-ion secondary battery The lithium-ion secondary battery disclosed herein has the electrodes described above.

[0271] Lithium-ion rechargeable batteries typically consist of an outer casing, electrodes (positive and negative electrodes), a separator, and an electrolyte. The outer casing houses the electrodes (positive and negative electrodes), the separator, and the non-aqueous electrolyte.

[0272] The following explanation uses the case where the positive and negative electrodes are the electrodes of this disclosure as an example.

[0273] (4.1) Outer packaging Examples of outer packaging include outer packaging containing a laminated film, and outer packaging consisting of a battery box and a battery box cover. The shape of the outer packaging is not particularly limited and can be appropriately selected based on the intended use of the lithium-ion secondary battery.

[0274] (4.2) Electrode As an electrode, it has a positive electrode and a negative electrode. The positive electrode can absorb and release lithium ions. The negative electrode can absorb and release lithium ions.

[0275] In the lithium-ion secondary battery of this disclosure, at least one of the positive electrode and the negative electrode is an electrode of this disclosure. If one of the positive electrode and the negative electrode of the lithium-ion secondary battery of this disclosure is an electrode of this disclosure, the other of the positive electrode and the negative electrode may be a known electrode used in lithium-ion secondary batteries.

[0276] (4.3) Diaphragm A separator separates the positive and negative electrodes. For example, a porous resin sheet can be used as a separator. The material of the porous resin sheet can be resin or a nonwoven fabric containing that resin. Examples of resins include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyester, cellulose, or polyamide. The separator is preferably a porous resin sheet with a single or multilayer structure. The porous resin sheet is primarily composed of one or more polyolefin resins. The separator thickness is preferably 5 μm to 30 μm. The separator is preferably disposed between the positive and negative electrodes.

[0277] (4.4) Non-aqueous electrolyte Non-aqueous electrolytes contain electrolytes and non-aqueous solvents.

[0278] (4.4.1) Electrolytes The electrolyte preferably contains at least one of a lithium salt containing fluorine (hereinafter also referred to as "fluorinated lithium salt") and a lithium salt not containing fluorine.

[0279] Examples of fluorinated lithium salts include inorganic acid anionic salts and organic acid anionic salts.

[0280] Examples of inorganic acid anionic salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), or lithium hexafluorotantalate (LiTaF6). Examples of organic acid anionic salts include lithium trifluoromethanesulfonate (LiCF3SO3). Among these, LiPF6 is particularly preferred as a fluorine-containing lithium salt. Examples of fluorine-free lithium salts include lithium perchlorate (LiClO4), lithium tetrachloroaluminate (LiAlCl4), or lithium decachlorodeborate (Li2B). 10 Cl 10 ).

[0281] When the electrolyte contains a fluorinated lithium salt, the proportion of the fluorinated lithium salt relative to the total amount of electrolyte is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass.

[0282] When the fluorinated lithium salt contains lithium hexafluorophosphate (LiPF6), the content of lithium hexafluorophosphate (LiPF6) is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of electrolyte.

[0283] When the non-aqueous electrolyte contains an electrolyte, the concentration of the electrolyte in the non-aqueous electrolyte is preferably 0.1 mol / L to 3 mol / L, more preferably 0.5 mol / L to 2 mol / L.

[0284] When the non-aqueous electrolyte contains lithium hexafluorophosphate (LiPF6), the concentration of lithium hexafluorophosphate (LiPF6) in the non-aqueous electrolyte is preferably 0.1 mol / L to 3 mol / L, more preferably 0.5 mol / L to 2 mol / L.

[0285] (4.4.2) Non-aqueous solvents Non-aqueous electrolytes typically contain non-aqueous solvents.

[0286] Examples of non-aqueous solvents include, for example, cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, fluorinated chain carbonates, aliphatic carboxylic acid esters, fluorinated aliphatic carboxylic acid esters, γ-lactones, fluorinated γ-lactones, cyclic ethers, fluorinated cyclic ethers, chain ethers, fluorinated chain ethers, nitriles, amides, lactams, nitromethane, nitrobenzene, sulfolane, trimethyl phosphate, dimethyl sulfoxide, or dimethyl sulfoxide phosphate. One non-aqueous solvent may be used alone or in combination of two or more.

[0287] Examples of cyclic carbonates include, for example, ethylene carbonate (EC), propylene carbonate (PC), or butyl carbonate (BC).

[0288] Examples of fluorinated cyclic carbonates include, for example, ethylene fluorocarbonate (FEC), ethylene difluorocarbonate (DFEC), or propylene trifluorocarbonate.

[0289] Examples of chain carbonates include, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or dipropyl carbonate (DPC).

[0290] Examples of fluorinated chain carbonates include, for instance, 2,2,2-trifluoroethyl methyl carbonate.

[0291] Examples of aliphatic carboxylic acid esters include, for example, methyl formate, methyl acetate, methyl propionate, methyl butyrate, methyl isobutyrate, methyl trimethylbutyrate, ethyl formate, ethyl acetate, ethyl propionate, ethyl butyrate, ethyl isobutyrate, or ethyl trimethylbutyrate.

[0292] Examples of fluorinated aliphatic carboxylic acid esters include, for example, methyl difluoroacetate, methyl 3,3,3-trifluoropropionate, ethyl difluoroacetate, or 2,2,2-trifluoroethyl acetate.

[0293] Examples of γ-lactones include, for example, γ-butyrolactone or γ-valerolactone.

[0294] Examples of cyclic ethers include, for example, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxacyclopentane, 4-methyl-1,3-dioxacyclopentane, 1,3-dioxacyclohexane, or 1,4-dioxacyclohexane.

[0295] Examples of chain ethers include, for example, 1,2-ethoxyethane (DEE), ethoxymethoxyethane (EME), diethyl ether, 1,2-dimethoxyethane, or 1,2-dibutoxyethane.

[0296] Examples of fluorinated chain ethers include HCF2CF2CH2OCF2CF2H, CF3CF2CH2OCF2CF2H, HCF2CF2CH2OCF2CFHCF3, CF3CF2CH2OCF2CFHCF3, and C6F. 13 OCH3, C6F 13 OC2H5, C8F 17 OCH3, C8F 17 OC2H5, CF3CFHCF2CH(CH3)OCF2CFHCF3, HCF2CF2OCH(C2H5)2, HCF2CF2OC4H9, HCF2CF2OCH2CH(C2H5)2, or HCF2CF2OCH2CH(CH3)2.

[0297] Examples of nitrile compounds include, for example, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, or 3-methoxypropionitrile.

[0298] Examples of amides include, for instance, N,N-dimethylformamide.

[0299] Examples of lactams include, for example, N-methylpyrrolidone, N-methyloxazolidinone, or N,N'-dimethylimidazolinone.

[0300] The non-aqueous solvent preferably comprises at least one selected from the group consisting of cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, and fluorinated chain carbonates. In this case, the total proportion of the cyclic carbonates, fluorinated cyclic carbonates, chain carbonates, and fluorinated chain carbonates relative to the total amount of the non-aqueous solvent is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass.

[0301] The non-aqueous solvent preferably includes at least one selected from the group consisting of cyclic carbonates and chain carbonates. In this case, the total proportion of cyclic carbonates and chain carbonates in the non-aqueous solvent is preferably 50% to 100% by mass, more preferably 60% to 100% by mass, and even more preferably 80% to 100% by mass, relative to the total amount of the non-aqueous solvent.

[0302] The content of non-aqueous solvent relative to the total amount of non-aqueous electrolyte is preferably 99% by mass or less, more preferably 97% by mass or less, and even more preferably 90% by mass or less. The content of non-aqueous solvent relative to the total amount of non-aqueous electrolyte is preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0303] From the viewpoint of further improving the dissociation property of the electrolyte and the mobility of ions, the intrinsic viscosity of the non-aqueous solvent is preferably below 10.0 mPa·s at 25°C.

[0304] (4.4.3) Electrolyte additives Non-aqueous solvents can contain electrolyte additives. This makes it difficult for side reactions, which are not part of the original battery reaction, to occur during the charge-discharge cycle of a lithium-ion secondary battery. The battery reaction refers to the reaction in which lithium ions are inserted into and out of the positive and negative electrodes. Side reactions include the reductive decomposition of the non-aqueous electrolyte caused by the negative electrode, the oxidative decomposition of the non-aqueous electrolyte caused by the positive electrode, and the dissolution of metal elements from the positive electrode active material.

[0305] There are no particular restrictions on the use of electrolyte additives; any known electrolyte additives may be used, for example, the additives described in Japanese Patent Application Publication No. 2019-153443 may be used.

[0306] (5) An example of a lithium-ion secondary battery Reference Figure 1 and Figure 2 An example of a lithium-ion secondary battery involved in the embodiments of this disclosure will be specifically described. Figure 1 This is a simplified cross-sectional view of the lithium-ion secondary battery 1 according to the embodiments of this disclosure. Figure 2 This is a simplified cross-sectional view of the positive electrode 11 in the lithium-ion secondary battery 1 according to the embodiments of this disclosure. Figure 3 This is a simplified cross-sectional view of the negative electrode 12 in the lithium-ion secondary battery 1 according to the embodiments of this disclosure.

[0307] The lithium-ion secondary battery 1 described in this disclosure is a stacked type. For example... Figure 1As shown, the lithium-ion secondary battery 1 includes a battery element 10, a positive electrode lead 21, a negative electrode lead 22, and an outer packaging body 30. The battery element 10 is sealed inside the outer packaging body 30. The outer packaging body 30 is formed of a laminated film. The positive electrode lead 21 and the negative electrode lead 22 are respectively mounted on the battery element 10. The positive electrode lead 21 and the negative electrode lead 22 extend from the inside of the outer packaging body 30 towards the outside and in opposite directions.

[0308] like Figure 1 As shown, the battery element 10 is composed of a positive electrode 11, a separator 13, and a negative electrode 12 stacked together.

[0309] like Figure 2 As shown, the positive electrode 11 is formed by forming a positive electrode additive material layer 11B on the two main surfaces of the positive electrode current collector 11A with a base coating. The positive electrode current collector 11A with a base coating is formed by forming a base coating 111 on the two main surfaces of the positive electrode current collector 110.

[0310] like Figure 3 As shown, the negative electrode 12 is formed by forming a negative electrode additive material layer 12B on the two main surfaces of the negative electrode current collector 12A with a base coating. The negative electrode current collector 12A with a base coating is formed by forming a base coating 121 on the two main surfaces of the negative electrode current collector 120.

[0311] like Figure 1 As shown, a positive electrode additive material layer 11B formed on one main surface of the positive electrode current collector 11A with a base coating on the positive electrode 11, and a negative electrode additive material layer 12B formed on one main surface of the negative electrode current collector 12A with a base coating on the negative electrode 12 adjacent to the positive electrode 11 are opposite each other through a separator 13.

[0312] A non-aqueous electrolyte is injected inside the outer packaging 30. The non-aqueous electrolyte permeates into the positive electrode flux layer 11B, the separator 13, and the negative electrode flux layer 12B. In the lithium-ion secondary battery 1, a single cell layer 14 is formed by adjacent positive electrode flux layer 11B, separator 13, and negative electrode flux layer 12B.

[0313] In this embodiment, the lithium-ion secondary battery 1 is a stacked type, but this disclosure is not limited to this; the lithium-ion secondary battery 1 can also be, for example, a wound type. A wound type is formed by overlapping and winding the positive electrode, separator, negative electrode, and separator in this order. Wound types include cylindrical and square types.

[0314] In this embodiment, such as Figure 1As shown, the positive lead 21 and the negative lead 22 protrude from the inside of the outer packaging 30 in opposite directions relative to the outer packaging 30, but this disclosure is not limited to this. For example, the positive lead and the negative lead may also protrude from the inside of the outer packaging 30 in the same direction relative to the outer packaging 30.

[0315] Example The embodiments described below will be described in detail with reference to the examples. It should be noted that this disclosure is not limited in any way by the descriptions in these embodiments.

[0316] [1] Preparation The products used in the examples and comparative examples are described below. The physical properties of each product are those in the product catalog.

[0317] [1.1] Conductive carbon materials (A) • Super-P: "Super-P" (conductive carbon black, solid content concentration: 100% by mass) manufactured by TIMCAL. • KS-6: TIMREX's "KS-6" (flake graphite, solid content concentration: 100% by mass) [1.2] Olefin resins (B) • W300: CHEMIPEARL (registered trademark) W300 manufactured by Mitsui Chemicals Co., Ltd. (aqueous dispersion of low molecular weight polyethylene, solid content concentration: 40% by mass, particle size (average primary particle size determined by Coulter counting method; the same below): 3.0 μm, softening point (ring and ball method): 132℃) • W700: "CHEMIPEARL (registered trademark) W700" manufactured by Mitsui Chemicals Co., Ltd. (aqueous dispersion of low molecular weight polyethylene, solid content concentration: 40% by mass, particle size: 1.0 μm, softening point (ring and ball method): 132°C) • W900: CHEMIPEARL (registered trademark) W900 (aqueous dispersion of low molecular weight polyethylene, solid content concentration: 40% by mass, particle size: 0.6 μm, softening point (ring and ball method): 132°C) manufactured by Mitsui Chemicals Co., Ltd. • W950: CHEMIPEARL (registered trademark) W950 manufactured by Mitsui Chemicals Co., Ltd. (aqueous dispersion of low molecular weight polyethylene, solid content concentration: 40% by mass, particle size: 0.6 μm, softening point (ring and ball method): 113°C) •WP100: CHEMIPEARL WP100 (a registered trademark) manufactured by Mitsui Chemicals Co., Ltd. (aqueous dispersion of low molecular weight polypropylene, solid content concentration: 40% by mass, particle size: 1.0 μm, softening point (ring and ball method): 148°C) [1.3] Acrylic water-soluble polymers (C) As acrylic water-soluble polymers (C), acrylic water-soluble polymers (C-1) to (C-5') are prepared as described below.

[0318] [1.3.1] Acrylic water-soluble polymer (C-1) 240.0 parts by weight of distilled water were added to a separable flask equipped with a stirrer and a reflux condenser. After purging with nitrogen, the temperature was raised to 70°C. Then, 0.6 parts by weight of ammonium persulfate were added, followed by the continuous addition of the following water-soluble monomer raw material over 3 hours. The mixture was maintained for another 3 hours, and the pH was adjusted to 9.0 using ammonia water to complete the polymerization. An appropriate amount of water was added to obtain an aqueous solution of the acrylic water-soluble polymer (C-1). The solid content of the aqueous solution of the acrylic water-soluble polymer (C-1) was 15.0%.

[0319] <Water-soluble monomer raw materials> 40.0 parts by weight of methacrylamide 50.0 parts by weight of methacrylic acid 10.0 parts by weight of 2-hydroxyethyl methacrylate 50.0 parts by weight of 25% ammonia solution 240.0 parts by weight of distilled water [1.3.1.2] Glass transition temperature (Tg) The glass transition temperature (Tg) of the acrylic water-soluble polymer (C-1) contained in the obtained aqueous solution was calculated using the FOX equation (1) below.

[0320] Equation (1): 1 / Tg = W1 / Tg1 + W2 / Tg2 + ... + Wn / Tgn In equation (1), Tg represents the glass transition temperature of the copolymer (unit: K), Tgi (i=1, 2, ..., n) represents the glass transition temperature of monomer i when forming a homopolymer (unit: K), and Wi (i=1, 2, ..., n) represents the mass fraction of monomer i in all monomers.

[0321] [1.3.2] Acrylic water-soluble polymers (C-2) ~ (C-5') The formulation was modified according to Table 1, except that the process was the same as in Example 1, to prepare aqueous solutions of acrylic water-soluble polymers (C-2) to (C-5'). The glass transition temperatures of the acrylic water-soluble polymers (C-2) to (C-5') were determined in the same manner as in Example 1.

[0322] In Table 1, “240 / 240” means that 240 parts by weight of distilled water were initially added to the flask, and then 240 parts by weight of distilled water were used during monomer dissolution.

[0323] [1.3.3] Comparative resins for acrylic water-soluble polymers (C) As a comparative resin for acrylic water-soluble polymer (C), the following resin is prepared.

[0324] • Polyacrylic acid: "POLYACRYLICACID" (aqueous solution of polyacrylic acid, solid content concentration: approximately 25% by mass) manufactured by FUJIFILM Wako Pure Chemical Corporation • Polyacrylamide: "POLYACRYLAMIDE" (aqueous solution of polyacrylamide, solid component concentration: approximately 10% by mass) manufactured by FUJIFILM Wako Pure Chemical Corporation [1.4] Additives (D) • CMC: "2200" (sodium carboxymethyl cellulose, solid content concentration: 100% by mass) manufactured by Daicel Miraizu Co., Ltd. • PVDF: “W#7200” (vinylidene fluoride resin, solid content concentration: 100% by mass) manufactured by Kureha Corporation •SBR: "TRD2001" (aqueous dispersion of styrene-butadiene rubber particles, solid content: 50% by mass) manufactured by JSR Corporation •MC: "MATSUMOTO MICROSPHERE (registered trademark) FN-100SS" (microcapsules, solid component concentration: 100% by mass, maximum volume expansion temperature: 145~155℃, volume expansion onset temperature: 120~130℃) manufactured by Matsumoto Oils & Fats Co., Ltd. Al2O3: “ALUMINUM OXIDE” manufactured by FUJIFILM Wako Pure Chemical Corporation (average particle size: 2 μm, solid content concentration: 100% by mass) The specific values ​​of proportions (including proportions), physical properties, parameters, etc. used in the following description can be replaced with the corresponding upper limit values ​​(defined in the form of "less than" or "less than") or lower limit values ​​(defined in the form of "more than" or "greater than") of the proportions (including proportions), physical properties, parameters, etc., described in the "Specific Embodiments" above. Furthermore, unless otherwise specified, "parts" and "%" in the following description are based on mass.

[0325] [2] Fabrication of a positive current collector with a base coating [2.1] Preparation of slurry for primer coating (Example 1) A 5L planetary disperser was used to prepare the slurry for the primer coating.

[0326] In the dispersion treatment of the slurry for the primer coating, a three-roll mill (AIMEX Corporation, BR-300HCVIII) was used.

[0327] Pre-stir 58 parts by weight of “Super-P” (A) for 5 minutes (Preparation step A).

[0328] 229.0 parts by mass of CMC aqueous solution (D) were added to the Super-P (A) powder and mixed for 20 minutes to obtain the first mixture (preparation step B). The CMC aqueous solution (D) was prepared by adding CMC (D) to distilled water in such a way that the content of CMC (D) was 1.6% by mass relative to the total amount of CMC aqueous solution (D).

[0329] The addition of 527.8 parts by mass of "CMC aqueous solution" (D) to the first mixture and mixing for 20 minutes was performed a total of 3 times to obtain the second mixture (preparation step C). The total amount of "CMC aqueous solution" (D) added to the first mixture was 1583.4 parts by mass.

[0330] Add 95.4 parts by mass of "acrylic water-soluble polymer (C-1)" (C) and 471.3 parts by mass of "W700" (B) to the second mixture, mix for 20 minutes, and then perform vacuum degassing for 30 minutes to obtain the third mixture (preparation step D).

[0331] use Figure 4The three-roll mill shown performs two dispersion treatments on the third mixture under the conditions of a roll gap of 10 μm and a roll speed of 300 rpm (gear ratio of 1:3:9) (preparation step E). Specifically, the rotation speed of the feed roll 91 is 33.3 rpm, the rotation speed of the intermediate roll 92 is 100 rpm, the rotation speed of the finishing roll 93 is 300 rpm, the first gap L1 is 10 μm, and the second gap L2 is 10 μm. A slurry (composition) for the base coating with a solid component concentration of 12.4% by mass is prepared in this manner (preparation step E).

[0332] (Examples 2-8, Example 11, Comparative Examples 1-5) As shown in Table 2, the materials and amounts added in each of the preparation steps A to D are changed. Otherwise, the preparation of the primer coating slurry (composition) is carried out in the same manner as in Example 1.

[0333] In Table 2, "WSP" represents acrylic water-soluble polymers. "PA" represents polyacrylic acid. "PAA" represents polyacrylamide.

[0334] (Example 9) A 5L planetary disperser was used to prepare the slurry for the primer coating.

[0335] In the dispersion treatment of the slurry for the primer coating, a three-roll mill (AIMEX Corporation, BR-300HCVIII) was used.

[0336] Mix 58 parts by mass of “Super-P” (A) and 87.0 parts by mass of “Al2O3” (D) for 10 minutes to obtain a mixture (preparation step A).

[0337] Add 550.0 parts by mass of “CMC aqueous solution” (D) to the mixture and mix further for 20 minutes to obtain the first mixture (preparation step B). “CMC aqueous solution” (D) is prepared by adding “CMC” (D) to distilled water in such a way that the content of “CMC” (D) is 1.0% by mass relative to the total amount of “CMC aqueous solution” (D).

[0338] The addition of 300.0 parts by mass of "CMC aqueous solution" (D) to the first mixture and mixing for 20 minutes was performed a total of 3 times to obtain the second mixture (preparation step C). The total amount of "CMC aqueous solution" (D) added to the first mixture was 900.0 parts by mass.

[0339] Add 95.4 parts by weight of "acrylic water-soluble polymer (C-3)" (C) and 290.0 parts by weight of "W700" (B) to the second mixture, mix for 20 minutes, and then perform vacuum degassing for 30 minutes to obtain the third mixture (preparation step D).

[0340] use Figure 4 The three-roll mill shown performs two dispersion treatments on the third mixture under the conditions of a roll gap of 10 μm and a roll speed of 300 rpm (gear ratio of 1:3:9) (preparation step E). Specifically, the rotation speed of the feed roll 91 is 33.3 rpm, the rotation speed of the intermediate roll 92 is 100 rpm, the rotation speed of the finishing roll 93 is 300 rpm, the first gap L1 is 10 μm, and the second gap L2 is 10 μm. A slurry (composition) for the base coating with a solid component concentration of 14.9% by mass is prepared in this manner (preparation step E).

[0341] (Example 10) As shown in Table 3, the materials added in preparation step A are changed, and the preparation of the primer coating slurry (composition) is carried out in the same manner as in Example 9.

[0342] In Table 3, "WSP" represents an acrylic water-soluble polymer.

[0343] [2.2] Application and drying of the primer layer A die coater was used in the application of the primer coating slurry.

[0344] The coating thickness after drying is 3 μm (coating weight is approximately 0.2 mg / cm²). 2 The method involves applying a base coating slurry to one main surface of an aluminum foil (20 μm thick, 200 mm wide, positive current collector) and drying it. Then, on the other main surface (uncoated side) of the aluminum foil, a base coating slurry is applied in the same manner to a thickness of 3 μm after drying and then dried. This yields an aluminum foil roll (positive current collector with a base coating) coated on both sides.

[0345] [3] Positive electrode production [3.1] Preparation of positive electrode mixture slurry A 5L planetary disperser was used in the preparation of the positive electrode mixture slurry.

[0346] The positive electrode active material will be "NCM523" (manufactured by Umicore, composition: LiNi). 0.5 Co 0.2 Mn 0.31520 parts by weight of O2, 30 parts by weight of "Super-P" (manufactured by TIMCAL Corporation, conductive carbon) as a conductive additive, and 30 parts by weight of "KS-6" (manufactured by TIMREX Corporation, flake graphite) as a conductive additive are mixed for 10 minutes to obtain a mixture for positive electrode.

[0347] Add 50 parts by mass of "NMP" to the positive electrode mixture and mix for 20 minutes to obtain the first positive electrode mixture.

[0348] 350 parts by mass of PVDF solution were added to the first cathode mixture and kneaded for 30 minutes. Then, 260 parts by mass of PVDF solution were added and kneaded for 15 minutes. Finally, 220 parts by mass of PVDF solution were added and kneaded for 15 minutes to obtain the second cathode mixture. The PVDF solution was prepared by adding PVDF to NMP at a PVDF content of 8% by mass relative to the total amount of PVDF solution.

[0349] To adjust the viscosity, 80 parts by weight of "NMP" were added to the mixture for the second positive electrode and mixed for 30 minutes, followed by vacuum degassing for 30 minutes.

[0350] A positive electrode slurry with a solid component concentration of 65% by mass was prepared in this manner.

[0351] [3.2] Application and drying A die-coating machine was used in the application of the positive electrode mixture slurry.

[0352] The mass of the positive electrode mixture material layer (the dried coating film) is 19.0 mg / cm³. 2 The positive electrode additive slurry was coated onto one main surface (i.e., the base coating) of a positive electrode current collector with a base coating layer (aluminum foil thickness: 20 μm, base coating layer thickness: 3 μm, width: 200 mm) and dried. Then, the mass of the positive electrode additive material layer (the dried coating film) was measured to be 19.0 mg / cm³. 2 In the same manner, the positive electrode slurry is applied to the other main surface (i.e., the base coating) of the positive electrode current collector with the base coating and then dried.

[0353] In a vacuum drying oven, the positive electrode rolls obtained in this manner, coated on both sides (coating amount totaling 38.0 mg / cm² on both sides), were dried at 130°C. 2 Dry for 12 hours.

[0354] [3.3] Pressurization A 35-ton press was used for pressurizing the positive electrode coil. The gap between the upper and lower rollers was adjusted to achieve a pressurization density of 2.9 ± 0.05 g / cm³. 3 The positive electrode is pressurized using a 35-ton pressurizer.

[0355] [3.4] Slicing The positive electrode roll is cut in a way that yields the area of ​​the positive electrode compound material layer (surface: 56mm×334mm, back: 56mm×408mm) and the area left blank for electrode tab welding, to obtain a positive electrode with a base coating layer laminated on aluminum foil.

[0356] [4] Negative electrode fabrication [4.1] Preparation of negative electrode mixture slurry A 5L planetary disperser was used in the preparation of the negative electrode mixture slurry.

[0357] 1050 parts by weight of "natural graphite" as the negative electrode active material and "Super-P" (conductive carbon with a BET specific surface area of ​​62 m²) as a conductive additive. 2 Mix 11 parts by mass (g) for 10 minutes to obtain a mixture for the negative electrode.

[0358] Add 450 parts by mass of “CMC aqueous solution” to the negative electrode mixture and mix for another 20 minutes to obtain the first negative electrode mixture.

[0359] Add 150 parts by mass of "CMC aqueous solution" to the first negative electrode mixture, mix for 30 minutes, add 293.5 parts by mass of "CMC aqueous solution" and mix for 30 minutes, add 450 parts by mass of water as solvent and mix for 15 minutes to obtain the second negative electrode mixture.

[0360] Add 45 parts by mass of “SBR aqueous solution” (manufactured by JSR Corporation, solid component concentration: 50% by mass) to the mixture for the second negative electrode, mix for 15 minutes, and then perform vacuum degassing for 10 minutes.

[0361] A negative electrode slurry with a solid component concentration of 45% by mass was prepared in this manner.

[0362] [4.2] Application and drying A die-coating machine was used in the application of the negative electrode mixture slurry.

[0363] The mass of the negative electrode mixture material layer (the dried coating film) is 11.0 mg / cm³. 2The negative electrode additive slurry was coated onto one main surface of a copper foil (10 μm thick, negative electrode current collector) and dried. Then, the same process was repeated on the opposite side (uncoated side), with the mass of the negative electrode additive layer (dried coating film) being 11.0 mg / cm³. 2 The negative electrode slurry was coated onto the other side of the copper foil and dried. The resulting double-coated negative electrode roll (coating weight totaling 22.0 mg / cm²) was then dried in a vacuum drying oven at 120°C. 2 Dry for 12 hours.

[0364] [4.3] Pressurization A small press was used for pressurizing the negative electrode winding. The gap between the upper and lower rollers was adjusted to achieve a pressurization density of 1.45 ± 0.05 g / cm³. 3 This method involves using a small pressurizer to pressurize the negative electrode coil.

[0365] [4.4] Slicing The negative electrode roll is cut to obtain the negative electrode by measuring the area of ​​the negative electrode mixture material layer (surface: 58mm×372mm, back: 58mm×431mm) and the area left blank for electrode tab welding.

[0366] [5] Fabrication of a wound battery (designed capacity of 1Ah) [5.1] Winding As a diaphragm, a porous membrane (60.5 mm × 450 mm) made of polyethylene with a porosity of 45% by volume and a thickness of 25 μm was used.

[0367] The negative electrode, separator, positive electrode with base coating, and separator obtained above are overlapped and wound together, and then pressurized for molding. Next, an aluminum tab is joined to the blank portion of the positive electrode with base coating using an ultrasonic bonding machine, and a nickel tab is joined to the blank portion of the negative electrode using the same ultrasonic bonding machine. The assembly is then clamped using a laminated film, and three sides are heat-sealed. This yields an outer packaging body with an opening (hereinafter referred to as "first outer packaging body").

[0368] [5.2] Injection of non-aqueous electrolyte Ethyl carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of EC:EMC:DMC = 3:3:4 to obtain a mixed solvent. In this mixed solvent, LiPF6 was dissolved to a concentration of 1.0 mol / L to prepare a non-aqueous electrolyte.

[0369] Before injecting the non-aqueous electrolyte, the first outer packaging body was subjected to reduced pressure drying using a vacuum dryer at 70°C for 12 hours. After injecting 4.7 ± 0.1 g of electrolyte into the first outer packaging body, the opening of the first outer packaging body was heated and sealed while vacuum suction was performed. Thus, a lithium-ion secondary battery precursor was obtained.

[0370] [5.3] Activation treatment The lithium-ion secondary battery precursor was kept at room temperature (25°C) for 24 hours. Then, the lithium-ion secondary battery precursor was charged with a constant current at 0.05C for 4 hours (0.05C-CC), followed by a 12-hour rest period. Next, it was charged with a constant current and constant voltage at 0.1C (0.1C-CCCV) to 4.2V, rested for 30 minutes, and then discharged with a constant current at 0.1C (0.1C-CC) to 2.8V. Further, the charge-discharge cycle (charging to 4.2V under 0.1C-CCCV conditions and discharging to 2.8V under 0.1C-CC conditions) was repeated 5 times. Then, the lithium-ion secondary battery precursor, having reached a fully charged state of 4.2V (SOC 100%), was stored at 25°C for 5 days. In this manner, wound-type batteries (lithium-ion secondary batteries) of Examples 1-11, Comparative Examples 1-5, and the Reference Example were obtained.

[0371] [6] Evaluation methods The particle size distribution of the base coating slurries prepared in Examples 1-11 and Comparative Examples 1-5 was measured as follows. The safety (heating), safety (stab damage) initial DCIR, and DCIR after high-temperature storage were evaluated for the wound batteries of Examples 1-11, Comparative Examples 1-5, and the reference example. The evaluation results are shown in Table 5.

[0372] [6.1] Particle size distribution 1.0 g of the primer coating slurry (hereinafter referred to as "sample") from Examples 1 to 11 and Comparative Examples 1 to 5, and 50 ml of water were placed in a 100 ml beaker. The sample fragments were broken up using a spatula, and the mixture was gently mixed using a dropper. Next, the sample was dispersed in water using a benchtop ultrasonic cleaner (Honda Electronics Co., Ltd., model W-113). The benchtop ultrasonic cleaner was set to an output power of 100 W and a kHz frequency for 60 seconds. Then, bubbles formed on the surface of the aqueous solution in the beaker were removed, and the volumetric particle size distribution of the sample was determined using a particle size distribution measuring device (MicrotracBEL Corp., MICROTRACMT3300EXII) via laser diffraction scattering. The volumetric particle size distribution values ​​D10, D50, D90, and D99 were determined using this measurement. The measurement results for D10, D50, D90, and D99 are shown in Table 5.

[0373] [6.2] Safety (Heating) For a wound battery (design capacity of 1Ah), the safety (heating) was evaluated by charging it to 4.2V at a constant current and constant voltage (0.1C-CCCV) at 0.1C in an environment of 25°C.

[0374] The battery cell for testing was placed in a thermostatic bath preheated to 50°C, and the AC resistance was measured at 1 kHz (amplitude 10 mV) while the bath was heated at a rate of 5°C / min. The battery cell temperature was recorded using a temperature measuring terminal located on the upper surface of the battery cell. The AC resistance was measured using a Solartron ModuLabXM ECS electrochemical measurement system.

[0375] Based on the measured resistance value, determine the initial temperature at which the resistance rises and the resistance change factor. The initial temperature at which the resistance rises is reached is calculated by taking the resistance value at 50°C as 1 and comparing it to the resistance value at 150°C.

[0376] Using the results of measurements of the initial temperature of resistance rise and the rate of change of resistance, a safety (heating) assessment is performed according to the following criteria. The acceptable safety (heating) rating is "A" or "B".

[0377] A: The starting temperature for the resistance increase is below 90℃, and the resistance change factor is more than 20 times.

[0378] B: The initial temperature of the resistance rise is above 90℃, and the resistance change factor is greater than 20 times. Or, the initial temperature of the resistance rise is below 90℃, and the resistance change factor is less than 20 times.

[0379] C: The starting temperature of the resistance rise is higher than 90℃, and the resistance change factor is less than 20 times.

[0380] [6.3] Forced internal short circuit test (pin test) For the wound battery (design capacity of 1Ah), under a temperature environment of 25℃, it was charged with constant current and constant voltage at 0.1C (0.1C-CCCV) to 4.2V, and then a nail puncture test was conducted (the diameter of the nail was 3mm, and the nail puncture speed was 1.0mm / second).

[0381] A 3mm diameter nail is inserted into the center of the wound battery cell at a speed of 1.0mm / s, short-circuiting the positive and negative terminals inside the battery container. The short-circuit behavior of the battery is then observed.

[0382] Multiple nail penetration tests (3 to 6 times) were conducted on the batteries at the same level. The total number of batteries tested was evaluated according to the following criteria. The acceptable evaluation for the nail penetration test is "A" and "B".

[0383] A: The proportion of batteries with an internal temperature higher than 300°C is less than 10% of the total number of batteries tested.

[0384] B: The proportion of batteries with an internal temperature higher than 300°C is greater than 10% and less than 60% of the total number of batteries tested.

[0385] C: The proportion of batteries with an internal temperature higher than 300°C is more than 60% of the total number of batteries tested.

[0386] [6.4] Initial DCIR Evaluation [6.4.1] Initial DCIR Measurement For a wound battery (design capacity of 1Ah), under a temperature environment of 25℃, it was charged with constant current and constant voltage at 0.1C (0.1C-CCCV) to 4.2V, and the initial DCIR was measured.

[0387] Perform a 10-second constant current discharge at 0.1C (0.1C-CC-10s), and a 10-second constant current charge at 0.1C (0.1C-CC-10s).

[0388] Next, a constant current discharge of 0.2C for 10 seconds (0.2C-CC-10s) was performed, followed by a constant current charge of 0.2C for 10 seconds (0.2C-CC-10s).

[0389] Next, a constant current discharge of 0.5C for 10 seconds (0.5C-CC-10s) was performed, followed by a constant current charge of 0.5C for 10 seconds (0.5C-CC-10s).

[0390] Next, a constant current discharge of 1.0C for 10 seconds (1.0C-CC-10s) was performed, followed by a constant current charge of 1.0C for 10 seconds (1.0C-CC-10s).

[0391] Next, a constant current discharge of 2.0C for 10 seconds (2.0C-CC-10s) was performed, followed by a constant current charge of 2.0C for 10 seconds (2.0-CC-10s).

[0392] The first DC resistance (DCIR) is determined based on the voltage drop (= voltage before discharge starts - voltage 10 seconds after discharge starts) and current values ​​(i.e., the current values ​​equivalent to discharge rates 0.1C to 2.0C) caused by the “CC10s discharge” at each discharge rate of 0.1C to 2.0C.

[0393] [6.4.2] Evaluation Method Based on the above measurements, the first relative value with the first DC resistance (DCIR) of the reference example (without a base coating) set to 100 is calculated, and an initial DCIR evaluation is performed according to the following criteria.

[0394] The first relative value of the first DC resistance is shown in Table 5. The acceptable ratings for the initial DCIR evaluation are "A" and "B".

[0395] A: The first relative value is below 100.

[0396] B: The first relative value is greater than 100 and less than 105.

[0397] C: The first relative value is greater than 105.

[0398] [6.5] DCIR evaluation after high-temperature storage [6.5.1] DCIR measurement after high-temperature storage For the fabricated wound battery (designed capacity of 1Ah), it was charged to 4.2V at a constant current and constant voltage of 0.1C (0.1C-CCCV) at 25°C, and then left to stand at 60°C for 28 days while charging. This method yielded the battery after high-temperature storage.

[0399] Perform the same DCIR evaluation process as the initial DCIR evaluation process described above to determine the second DC resistance (DCIR).

[0400] [6.5.2] Evaluation Method Based on the above measurements, the second relative value with the second DC resistance (DCIR) of the reference example (without a base coating) set to 100 was calculated, and the DCIR was evaluated after high-temperature storage according to the following criteria.

[0401] The second relative value of the second DC resistance is shown in Table 5. The acceptable ratings for DCIR evaluation after high-temperature storage are "A" and "B".

[0402] A: The second relative value is below 105.

[0403] B: The second relative value is greater than 105 and less than 110.

[0404] C: The second relative value is greater than 110.

[0405] [Table 4] [Table 5] In Tables 4 and 5, "MA" represents a structural unit derived from methacrylamide. "COOH" represents a structural unit derived from a vinyl monomer containing a carboxyl group. "OH" represents a structural unit derived from a vinyl monomer containing a hydroxyl group. "Initial temperature" refers to the temperature at which the resistance begins to rise. "Restoration factor" refers to the rate of change in resistance. "Initial" refers to the initial DCIR evaluation. "After high-temperature storage" refers to the DCIR evaluation after high-temperature storage. "PA" represents polyacrylic acid. "PAA" represents polyacrylamide.

[0406] The acrylic water-soluble polymers (C) of Comparative Examples 1 to 5 do not meet the following requirements: the content of structural units from (meth)acrylamide relative to the total amount of acrylic water-soluble polymer (C) is 35% to 95% by mass, and the content of structural units from vinyl monomers relative to the total amount of acrylic water-soluble polymer (C) is 5% to 65% to 70% by mass. Therefore, in Comparative Example 1, the DCIR evaluation result after high-temperature storage is "C". In Comparative Examples 2 and 4, the initial DCIR evaluation and the DCIR evaluation after high-temperature storage are both "C". In Comparative Example 3, the evaluation results for safety (heating), safety (spiking), initial DCIR evaluation, and DCIR evaluation after high-temperature storage are both "C". In Comparative Example 5, the evaluation results for safety (spiking), initial DCIR evaluation, and DCIR evaluation after high-temperature storage are both "C".

[0407] These results indicate that the compositions of Comparative Examples 1 to 5 are not suitable for forming electrodes with excellent safety, low DC resistance during the initial charging and discharging phase, and suppressed DC resistance rise under high temperature conditions (especially after long-term storage).

[0408] The compositions of Examples 1 to 11 contain a conductive carbon material (A), an olefin resin (B), and an acrylic water-soluble polymer (C). The acrylic water-soluble polymer (C) satisfies the following conditions: the content of structural units derived from (meth)acrylamide is 35% to 95% by mass relative to the total amount of the acrylic water-soluble polymer (C), and the content of structural units derived from vinyl monomers is 5% to 65% to 70% by mass relative to the total amount of the acrylic water-soluble polymer (C). Therefore, in Examples 1 to 11, the evaluation results for safety (heating), safety (puncture), initial DCIR evaluation, and DCIR evaluation after high-temperature storage are "A" or "C".

[0409] These results show that the compositions of Examples 1 to 11 are suitable for forming electrodes with excellent safety, low DC resistance during the initial charging and discharging phase, and suppressed DC resistance rise under high temperature conditions (especially after long-term storage).

[0410] The full disclosure of Japanese Patent Application 2023-052346, filed on March 28, 2023, is incorporated herein by reference.

[0411] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the extent that each document, patent application and technical standard is incorporated by reference to the extent that it is specifically and separately described.

Claims

1. A composition comprising a conductive carbon material (A), an olefinic resin (B), and an acrylic water-soluble polymer (C). The acrylic water-soluble polymer (C) has structural units derived from (meth)acrylamide and structural units derived from vinyl monomers having at least one of carboxyl and hydroxyl groups. The content of the structural units derived from (meth)acrylamide is 35% to 95% by mass relative to the total amount of the acrylic water-soluble polymer (C). The content of the structural units derived from vinyl monomers having at least one of carboxyl and hydroxyl groups is 5% to 65% by mass relative to the total amount of the acrylic water-soluble polymer (C).

2. The composition of claim 1, wherein, The conductive carbon material (A) comprises 1% to 30% by mass relative to the total amount of the composition. The content of the olefin resin (B) is 30% to 90% by mass relative to the total amount of the composition. The content of the acrylic water-soluble polymer (C) is 1% to 20% by mass relative to the total amount of the composition.

3. The composition of claim 1, wherein, The olefin resin (B) includes ethylene resin or propylene resin.

4. The composition of claim 1, wherein, The olefin resin (B) has a particle size of 0.1 μm to 9.0 μm. The softening point of the olefin resin (B) is above 70°C.

5. The composition of claim 1, wherein, The acrylic water-soluble polymer (C) has structural units derived from (meth)acrylamide, structural units derived from vinyl monomers having carboxyl groups, and structural units derived from vinyl monomers having hydroxyl groups.

6. The composition of claim 1, wherein, The Tg of the acrylic water-soluble polymer (C) is above 150°C.

7. The composition of claim 1, further comprising additive (D). The additive (D) is present in a content of 1% to 50% by mass relative to the total amount of the composition.

8. The composition of claim 7, wherein, The additive (D) contains carboxymethyl cellulose.

9. The composition of claim 7, wherein, The additive (D) comprises at least one of thermally expandable microcapsules having a maximum volume expansion temperature of 70°C to 180°C and an inorganic oxide filler.

10. The composition of claim 1, wherein, The ratio of particle size distribution D99 to particle size distribution D10 (D99 / D10), as determined by laser diffraction scattering, is less than 35.

11. The composition of claim 1, wherein, The particle size distribution D99, determined by laser diffraction scattering, is below 20 μm.

12. The composition of claim 1, wherein, The ratio of particle size distribution D99 to particle size distribution D50 (D99 / D50), as determined by laser diffraction scattering, is less than 20.

13. A base coating comprising the composition of any one of claims 1 to 12.

14. An electrode comprising a current collector, a base coating as described in claim 13, and a binder material layer.

15. The electrode as claimed in claim 14, wherein, The current collector, the base coating, and the compound material layer are stacked in sequence.

16. A lithium-ion secondary battery comprising the electrode as described in claim 14.

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