Binder composition for secondary battery electrode, electrode composition for secondary battery, secondary battery electrode, and secondary battery

Abstract

This binder composition for a secondary battery electrode contains a polymer component having a number average molecular weight (Mn) of 2,000 or more and an additive having a number average molecular weight (Mn) of less than 2,000 and satisfies all of the following (1) to (7). (1) The SP value (SPB) of the polymer component is 8-15 (cal / cm3)1 / 2. (2) The additive is a compound having an oxyethylene group and / or two hydroxyl groups. (3) The additive has neither a boiling point nor a thermal decomposition temperature in a temperature range of less than 200° C. (4) The glass transition temperature Tg2 (℃) of a mixture obtained by mixing the polymer component and the additive at a weight ratio of additive / polymer component = 10 / 90 is lower than the glass transition temperature Tg1 (℃) of the polymer component alone by 5℃ or more. (5) The weight ratio between the polymer component and the additive is additive / polymer component = 1 / 99-50 / 50. (6) The polymer component is at least one selected from the group consisting of starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl pyrrolidone, polytetrafluoroethylene, styrene-butadiene copolymer resins, and (meth) acrylic resins. (7) The HLB value of the additive is 9-12.5.

Description

Binder composition for secondary battery electrodes, electrode composition for secondary batteries, electrode for secondary batteries and secondary battery

[0001] This invention relates to a binder composition for secondary battery electrodes, an electrode composition for secondary batteries, an electrode for a secondary battery, and a secondary battery.

[0002] In recent years, in secondary batteries such as lithium-ion batteries and sodium-ion batteries, increasing the thickness of the electrode active material layer has been considered in order to increase the battery capacity. However, due to the demand for cost reduction, there is a tendency to increase the drying speed after coating the electrode active material layer (electrode composition). Therefore, when the coating thickness is increased to make the electrode active material layer thicker, problems such as insufficient drying or cracking of the electrode active material layer after drying occur.

[0003] To address these issues, improvements have been considered by increasing the amount of water-based binders (carboxymethylcellulose sodium salt, styrene-butadiene rubber). However, increasing the amount of water-based binders, which are insulators, increases the resistance within the electrodes, leading to a decrease in battery performance.

[0004] To address these issues, for example, Patent Document 1 proposes that the above problems can be improved by including a solvent with a boiling point of 200 to 300°C and a water solubility of 20 g / L or more in the negative electrode active material coating (negative electrode composition).

[0005] Patent No. 7011916

[0006] However, in the negative electrode active material coating described in Patent Document 1, evaporation and volatilization of the solvent tend to occur during the drying process, and the effect of improving electrode flexibility may not be sufficiently obtained. In such cases, problems such as a decrease in the yield of the battery manufacturing process and deterioration of cycle performance due to electrode cracking during charging and discharging occurred.

[0007] The present invention aims to solve the above problems and to provide a binder composition and electrode composition for secondary batteries that can manufacture electrodes with excellent flexibility and suppress the occurrence of electrode cracking during manufacturing and charging / discharging. The present invention also aims to provide a secondary battery and a method for manufacturing a secondary battery that improves the yield of the manufacturing process and is less prone to performance degradation due to electrode cracking during charging and discharging.

[0008] The binder composition for secondary battery electrodes of the present invention is a binder composition for secondary battery electrodes containing a polymer component having a number average molecular weight (Mn) of 2000 or more and an additive having a number average molecular weight (Mn) of less than 2000, and satisfies all of the following (1) to (7): (1) The SP value (SP) of the polymer component Ｂ ) is 8-15 (cal / cm³) ３ ) １／２ (2) The additive is a compound having an oxyethylene group and / or two hydroxyl groups; (3) The additive has neither a boiling point nor a thermal decomposition temperature in the temperature range below 200°C; (4) The glass transition temperature Tg of the mixture obtained by mixing the polymer component and the additive in a weight ratio of additive / polymer component = 10 / 90 ２ (°C) is the glass transition temperature Tg of the polymer component alone. １ (5) The temperature is 5°C or more lower than (°C); (6) The weight ratio of the polymer component to the additive is additive / polymer component = 1 / 99 to 50 / 50; (7) The polymer component is at least one selected from the group consisting of starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene copolymer resin and (meth)acrylic resin; (8) The HLB value of the additive is 9 to 12.5.

[0009] The electrode composition for secondary batteries of the present invention contains an electrode active material and the binder composition for secondary battery electrodes of the present invention.

[0010] The electrode for secondary batteries of the present invention is obtained by compression molding the electrode composition for secondary batteries of the present invention.

[0011] The secondary battery of the present invention is equipped with electrodes for a secondary battery of the present invention.

[0012] According to the present invention, it is possible to provide a binder composition for a secondary battery that can produce an electrode with excellent flexibility and suppress the occurrence of electrode cracking during production and charge / discharge. Further, according to the present invention, it is possible to provide a secondary battery and a method for manufacturing the secondary battery in which the production yield is improved and performance degradation due to electrode cracking during charge / discharge is unlikely to occur.

[0013] [Binder Composition for Secondary Battery Electrode] The binder composition for a secondary battery electrode of the present invention is a binder composition for a secondary battery electrode containing a polymer component having a number average molecular weight (Mn) of 2000 or more and an additive having a number average molecular weight (Mn) of less than 2000, and satisfies all of the following (1) to (7): (1) The SP value (SP Ｂ ) of the polymer component is 8 to 15 (cal / cm ３ ); (2) The additive is a compound having an oxyethylene group and / or two hydroxyl groups; (3) The additive does not have either a boiling point or a thermal decomposition temperature in a temperature range below 200 °C; (4) The glass transition temperature Tg ２ (°C) of a mixture obtained by mixing the polymer component and the additive at a weight ratio of additive / polymer component = 10 / 90 is 5 °C or more lower than the glass transition temperature Tg １ (°C) of the polymer component alone; (5) The weight ratio of the polymer component to the additive is additive / polymer component = 1 / 99 to 50 / 50; (6) The polymer component is at least one selected from the group consisting of starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene copolymer resin, and (meth)acrylic resin; (7) The HLB value of the additive is 9 to 12.5.

[0014] By using the binder composition for a secondary battery electrode of the present invention, an electrode for a secondary battery with excellent flexibility can be manufactured. Therefore, the occurrence of electrode cracking can be suppressed during the production of the electrode for a secondary battery and during the charge / discharge of the secondary battery using the same.

[0015] (Polymer Component) The polymer component is a high molecular weight compound having a number average molecular weight of 2000 or more.​​

[0016] The number-average molecular weight of the polymer component is preferably 3,000 or more and 1,000,000 or less.

[0017] The number-average molecular weight of polymer components can be measured by gel permeation chromatography (GPC) under the following conditions: Apparatus: "Waters Alliance 2695" [Waters Corporation] Column: "Guardcolumn Super H-L" (1 column), "TSKgel Super H2000, TSKgel Super H3000, TSKgel Super H4000 (all manufactured by Tosoh Corporation) linked together" Sample solution: 0.25 wt% tetrahydrofuran solution Solution injection volume: 10 μl Flow rate: 0.6 ml / min Measurement temperature: 40°C Detection device: Refractive index detector Reference material: Standard polyethylene glycol

[0018] As the polymer component, at least one selected from the group consisting of starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene copolymer resin, and (meth)acrylic resin can be used. Among these, styrene-butadiene copolymer resin and (meth)acrylic resin are preferred. Furthermore, styrene-butadiene copolymer resin and (meth)acrylic resin may be used in combination as the polymer component.

[0019] In this specification, "(meth)acrylic" means either or both acrylic and methacrylic, and the same applies to "(meth)acrylic acid," "(meth)acrylamide," "(meth)alkyl ester (meth)acrylate," etc. Furthermore, "(meth)acrylic resin" means a polymer mainly composed of acrylic monomers such as acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, various (meth)acrylic acid esters, hydroxyalkyl (meth)acrylates, and functional group-modified (meth)acrylic monomers (those having carboxyl groups, sulfonic acid groups, epoxy groups, amino groups, etc.), and optionally containing hydrophobic monomers, styrene-based, vinyl-based, and other copolymerizable monomers as copolymer components. The main component means a component that occupies 50% or more by weight of the polymer. Examples of "(meth)acrylic resins" include polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polyacrylamide (PAM), polymethacrylamide, acrylamide, copolymers composed of acrylic monomers and hydrophobic monomers, styrene-acrylic copolymers, vinyl-acrylic copolymers, crosslinked acrylic resins, and water-soluble or water-insoluble acrylic resins.

[0020] The number-average molecular weight of the styrene-butadiene copolymer resin is preferably 10,000 to 300,000.

[0021] The number-average molecular weight of the (meth)acrylic resin is preferably 5,000 to 100,000.

[0022] SP value of polymer component (SP Ｂ ) is 8-15 (cal / cm³) ３ ) １／２ That is the case.

[0023] In this invention, the SP value refers to the value calculated using the formula (28) on page 153 of the Fedors method (Polymer Engineering and Science, February, 1974, Vol. 14, No. 2, pp. 147-154), using the numerical values ​​(heat of vaporization and molar volume of atoms or functional groups at 25°C) described on page 152 (Table 5). Specifically, the SP value can be calculated by applying the numerical values ​​corresponding to the types of atoms and atomic groups in the molecular structure from the Δei and vi values ​​listed in Table 1 below, which are parameters of the Fedors method, to the following formula: SP value = (ΣΔei / Σvi) １／２ [In the formula, ΣΔe ｉ (Units are cal / mol) is the cohesive energy density (units are cal / mol), and ΣΔv ｉ This is molecular volume (unit is cm³). ３ It is (moles).

[0024]

[0025]

[0026] Furthermore, if the polymer component is a mixture of multiple compounds, the SP value of the mixture is calculated by taking the arithmetic mean of the SP values ​​of each compound based on their weight fractions.

[0027] (Additives) Additives are compounds with a number-average molecular weight of less than 2000. The number-average molecular weight of additives is preferably 70 to 1700, and more preferably 400 to 630. The number-average molecular weight of additives can be measured in the same way as the number-average molecular weight of polymer components.

[0028] The additive is a compound containing an oxyethylene group and / or two hydroxyl groups. The additive may also be a compound containing both an oxyethylene group and two hydroxyl groups. A compound containing an oxyethylene group is preferred as the additive.

[0029] Examples of compounds containing an oxyethylene group include oxyethylene adducts of linear or branched alkyl alcohols having 1 to 18 carbon atoms. The terminal end of the oxyethylene adduct may be a hydrocarbon group such as a methyl group or an ethyl group. It is preferable that the part of the compound containing an oxyethylene group other than the oxyethylene group does not contain aromatic functional groups.

[0030] Examples of linear alkyl alcohols having 1 to 18 carbon atoms include methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonanol, n-decanol, n-undecanol, n-dodecanol, n-tridecanol, n-tetradecanol, n-pentadecanol, n-hexadecanol, n-heptadecanol, and n-octadecanol. Among these, n-dodecanol and n-tetradecanol are preferred.

[0031] Examples of branched alkyl alcohols having 3 to 18 carbon atoms include isopropanol, isobutanol, isopentanol, isohexanol, isoheptanol, isooctanol, isononanol, isodecanol, isoundodecanol, isododecanol, isotridecanol, isotetradecanol, isopentadecanol, isohexadecanol, isoheptadecanol, and isooctadecanol. Among these, isodecanol is preferred.

[0032] The average number of moles of oxyethylene groups added is preferably 1 to 34, more preferably 3 to 14, and even more preferably 5 to 9.

[0033] When the linear alkyl alcohol having 1 to 18 carbon atoms is n-dodecanol, the average number of moles of oxyethylene groups added is preferably 5 to 9, and more preferably 8. As the additive, an EO adduct of n-dodecanol (average number of moles added: 5 to 9) is preferred, and an EO adduct of n-dodecanol (average number of moles added: 8.0 to 8.5) is more preferred.

[0034] When the branched alkyl alcohol having 3 to 18 carbon atoms is isodecanol, the average number of moles of oxyethylene groups added is preferably 5 to 9, and more preferably 7.0 to 7.1. The terminal end of the oxyethylene group may be a hydrogen atom, a methyl group, or an ethyl group. As the additive, isodecanol EO adducts (average number of moles added: 5 to 9) are preferred, isodecanol EO adducts (average number of moles added: 7.1) and isodecanol EO adducts with terminal methyl groups (average number of moles added: 7.0) are more preferred.

[0035] The additive may be a mixture of multiple compounds that differ only in the average number of oxyethylene groups added (hereinafter also referred to as the EO addition number). For example, the additive may be a 1:1 (weight ratio) mixture of a 5-mol EO adduct of a C1 alkyl alcohol (methanol) and a 7-mol EO adduct of a C1 alkyl alcohol (methanol). This additive is also called an EO adduct of a C1 alkyl alcohol (methanol) (average addition number 5.85).

[0036] The additive does not have a boiling point or thermal decomposition temperature in the temperature range below 200°C. The thermal decomposition temperature of the additive is the midpoint temperature measured in thermogravimetric analysis in accordance with JIS K 7120 (1987). The boiling point of the additive is the equilibrium reflux boiling point measured in accordance with JIS K 2233 (2024).

[0037] The additive is preferably an aqueous solution with a cloud point of less than 90°C. A cloud point below 90°C helps to suppress electrode cracking. Although the reason is unclear, it is believed that when the additive reaches its cloud point and precipitates during electrode drying, the slurry thickens. This suppresses the concentration of the additive on the electrode surface, allowing for the production of a uniform electrode and thus suppressing electrode cracking. The cloud point of the aqueous solution of the additive is more preferably 70°C or lower.

[0038] The cloud point is defined in JIS K 3211 "Surfactant Terminology" as "the temperature at which an aqueous solution of a surfactant begins to become cloudy when its temperature is increased," and is measured by the following method: After pouring a 1% by mass aqueous solution of the additive into a test tube to a height of approximately 40 mm, a thermometer is placed inside and the solution is heated while stirring well with the thermometer to a temperature approximately 2-3°C higher than the temperature at which clouding occurs, then cooled by air while stirring well again, and the temperature at which it becomes clear can be measured as the cloud point. Alternatively, if the aqueous solution is cloudy at room temperature, the solution can be cooled while stirring well until it becomes clear, then gradually heated again while stirring well to the temperature at which turbidity occurs, then gradually cooled while stirring again, and the temperature at which it becomes clear can be measured as the cloud point.

[0039] The HLB of the additive is 9 to 12.5. An HLB of 9 to 12.5 in the additive results in good water solubility and compatibility with polymer components.

[0040] HLB is a measure that indicates the balance between hydrophilicity and lipophilicity. A higher HLB value indicates higher inorganicity. For example, it is known as the value calculated by the Oda method described in "Introduction to Surfactants, 2007, published by Sanyo Chemical Industries, Ltd., authored by Takehiko Fujimoto, p. 212," and is not a value calculated by the Griffin method. The HLB value can be calculated from the ratio of the organic value to the inorganic value of an organic compound. HLB = 10 × inorganic value / organic value Here, the inorganic and organic values ​​in the above formula represent index values ​​that express organic and inorganic properties as proposed by Fujita et al., and can be calculated using the values ​​in the table described on page 213 of "Introduction to Surfactants."

[0041] SP value of additives (SP Ａ ) is preferably 8 to 15, and more preferably 8 to 12.

[0042] SP value of polymer component (SP Ｂ ) and the SP value of the additive (SP Ａ ) difference [SP Ａ - SP ＢThe absolute value of ] is preferably less than 2.0. When the absolute value of the difference in the above SP values ​​is less than 2.0, the compatibility between the polymer component and the additive is high, and the binder composition becomes particularly uniform, which can impart flexibility to the electrode and make electrode cracking less likely to occur during manufacturing or charging / discharging. When the absolute value of the difference in the above SP values ​​is 2.0 or more, the compatibility between the polymer component and the additive decreases, which may reduce the flexibility of the electrode.

[0043] (Combination of polymer component and additives) When the polymer component is a styrene-butadiene copolymer resin, preferred additives to combine it with include EO adducts of alkyl alcohols having 8 to 12 carbon atoms (average number of added moles is 5 to 9). When the polymer component is a (meth)acrylic acid resin, preferred additives to combine it with include EO adducts of alkyl alcohols having 8 to 12 carbon atoms (average number of added moles is 5 to 9).

[0044] (Glass transition temperature) The glass transition temperature Tg of a mixture obtained by mixing polymer components and additives in a weight ratio of additive / polymer component = 10 / 90. ２ However, the glass transition temperature Tg of the polymer component alone １ Tg is more than 5°C lower. ２ ga Tg １ If the temperature is 5°C or more lower than the glass transition temperature (Tg), it is thought that the additives can more easily penetrate between the polymer molecules, thus strengthening the effect of weakening the interactions between binder molecules. １ and the glass transition temperature Tg of the above mixture ２ All of these can be measured using the DSC (Differential Scanning Calorimetry) method.

[0045] When the polymer component is a styrene-butadiene copolymer resin, the glass transition temperature Tg of the binder composition for secondary battery electrodes of the present invention. ３ The glass transition temperature Tg of the binder composition for secondary battery electrodes is preferably between -38°C and +3.3°C. ３ This can be measured by the DSC method.

[0046] Glass transition temperature Tg of binder composition for secondary battery electrodes when styrene-butadiene copolymer resin is used as the polymer component. ３ This refers to the glass transition temperature Tg of the individual polymer components constituting the binder composition. １ It is preferable that the temperature be at least 5°C lower than that.

[0047] Furthermore, the glass transition temperature Tg of the binder composition for secondary battery electrodes when (meth)acrylic resin is used as the polymer component. ３ The temperature is preferably between 70°C and 110°C.

[0048] Glass transition temperature Tg of binder composition for secondary battery electrodes when styrene-butadiene copolymer resin is used as the polymer component. ３ This refers to the glass transition temperature Tg of the individual polymer components constituting the binder composition. １ It is preferable that the temperature be at least 5°C lower than that.

[0049] (Storage Modulus) The storage modulus (G') at 25°C was measured by forming a mixture of polymer components and additives in a weight ratio of additive / polymer component = 10 / 90 into a film with a thickness of 500 μm. ２５ ) and the storage modulus (G') at 130°C, measured by forming the above mixture into a film with a thickness of 500 μm. １３０ ) ratio [G' ２５ / G' １３０ It is preferable that the ratio of storage modulus is between 1.00 and 4.00. When the above ratio of storage modulus is between 1.00 and 4.00, the physical properties of the electrode, such as elasticity and flexibility, do not change easily when the electrode is cooled from the dry temperature to room temperature, and it is thought that this may suppress electrode cracking during drying. This effect is particularly noticeable when the above mixture is used, as there is no glass transition temperature between room temperature and the dry temperature (usually around 25 to 130°C). For example, the glass transition temperature Tg of the above mixture ２ If the temperature is 10°C or below, and the above ratio of storage moduli is 1.00 to 4.00, then electrode cracking when the electrode is cooled after drying can be suppressed. Conversely, the glass transition temperature Tg of the above mixture ２If the material is present between room temperature and the dry temperature, a change in physical properties occurs at the glass transition temperature, causing the storage modulus to change easily with temperature, and the above ratio will not be between 1.00 and 4.00. However, the fact that the above ratio of storage moduli does not satisfy 1.00 to 4.00 does not immediately mean that electrode cracking is likely to occur.

[0050] The storage modulus is measured by forming the above mixture into a 500 μm thick film and measuring the storage modulus at 25°C or 130°C during a heating process from 0 to 150°C with a frequency of 1 Hz and a shear strain of 0.1% using a dynamic viscoelasticity measuring device manufactured by Antonpaar.

[0051] When a styrene-butadiene copolymer resin is used as the polymer component, the storage modulus (G'') at 25°C was measured by forming the binder composition for secondary battery electrodes of the present invention into a film with a thickness of 500 μm. ２５ ) and the storage modulus (G'') at 130°C, measured by forming the binder composition for secondary battery electrodes of the present invention into a film with a thickness of 500 μm. １３０ ) ratio [G'' ２５ / G'' １３０ The value of ] is preferably between 2.00 and 8.00.

[0052] When (meth)acrylic resin is used as the polymer component, the storage modulus (G'') at 25°C was measured by forming the binder composition for secondary battery electrodes of the present invention into a film with a thickness of 500 μm. ２５ ) and the storage modulus (G'') at 130°C, measured by forming the binder composition for secondary battery electrodes of the present invention into a film with a thickness of 500 μm. １３０ ) ratio [G'' ２５ / G'' １３０ It is preferable that ] be 17.00 or higher.

[0053] The weight ratio of the polymer component to the additive in the binder composition for secondary battery electrodes of the present invention is additive / polymer component = 1 / 99 to 50 / 50. When the weight ratio of the polymer component to the additive (additive / polymer component) is within the above range, sufficient flexibility can be imparted to the electrode. If the weight ratio of the polymer component to the additive (additive / polymer component) is less than 1 / 99, in other words, if the weight of the additive is less than 1 part by weight per 100 parts by weight of the total polymer component and additive, the weight ratio of the additive is too low, and sufficient flexibility cannot be imparted to the binder composition for secondary battery electrodes. Also, if the weight ratio of the polymer component to the additive (additive / polymer component) is greater than 50 / 50, in other words, if the weight of the additive exceeds 50 parts by weight per 100 parts by weight of the total polymer component and additive, the weight ratio of the polymer component is too low, and sufficient strength of the electrode may not be ensured.

[0054] [Electrode Composition for Secondary Batteries] The electrode composition for secondary batteries of the present invention contains an electrode active material and the binder composition for secondary batteries of the present invention. Because the electrode composition for secondary batteries of the present invention contains the binder composition for secondary batteries of the present invention, it is possible to suppress the occurrence of electrode cracking during the manufacture of secondary battery electrodes and during the charging and discharging of secondary batteries using the same.

[0055] The electrode composition for secondary batteries of the present invention may be an electrode composition for lithium-ion batteries or an electrode composition for sodium-ion batteries. Furthermore, the electrode active material may be a negative electrode active material or a positive electrode active material.

[0056] The content of electrode active material in the electrode composition for secondary batteries is not particularly limited, but from the viewpoint of increasing electrode density and thus battery capacity, a high content of active material is preferable, and is preferably 90 to 95% by weight.

[0057] The content of the binder composition for secondary battery electrodes in the electrode composition for secondary batteries is not particularly limited, but it is preferably 0.1 to 10% by weight.

[0058] Examples of negative electrode active materials constituting the electrode composition for lithium-ion batteries include carbon-based materials [graphite (artificial graphite, natural graphite), non-graphitizable carbon (hard carbon), amorphous carbon, resin-fired bodies (e.g., phenolic resin and furan resin that have been fired and carbonized), cokes (e.g., pitch coke, needle coke and petroleum coke), and carbon fibers, etc.], silicon-based materials [silicon, silicon oxide (SiO₂)]. ｘ Examples include silicon-carbon composites (carbon particles coated with silicon and / or silicon carbide, silicon particles or silicon oxide particles coated with carbon and / or silicon carbide, and silicon carbide, etc.), silicon alloys (silicon-aluminum alloys, silicon-lithium alloys, silicon-nickel alloys, silicon-iron alloys, silicon-titanium alloys, silicon-manganese alloys, silicon-copper alloys, and silicon-tin alloys, etc.), conductive polymers (e.g., polyacetylene and polypyrrole), metals (tin, aluminum, zirconium, and titanium, etc.), metal oxides (titanium oxide and lithium-titanium oxide, etc.), metal alloys (e.g., lithium-tin alloys, lithium-aluminum alloys, and lithium-aluminum-manganese alloys, etc.), and mixtures of these with carbon-based materials.

[0059] Examples of positive electrode active materials constituting the electrode composition for lithium-ion batteries include composite oxides of lithium and transition metals {composite oxides of one type of transition metal (LiCoO) ２ LiNiO ２ LiAlMnO ４ LiMnO ２ and LiMn ２ O ４ (e.g., composite oxides containing two transition metal elements, such as LiFeMnO) ４ LiNi １－ｘ Co ｘ O ２ LiMn １－ｙ Co ｙ O ２ LiNi １／３ Co １／３ Al １／３ O ２ and LiNi ０．８ Co ０．１５ Al ０．０５ O ２), and composite oxides in which there are three or more transition metal elements [e.g., LiM ａ M' ｂ M'' ｃ O ２ (M, M', and M'' are different transition metal elements, respectively, and satisfy a + b + c = 1. For example, LiNi ０．８ Co ０．１ Mn ０．１ O ２ , LiNi １／３ Mn １／３ Co １／３ O ２ ), etc.], lithium-containing transition metal phosphates (e.g., LiFePO ４ , LiCoPO ４ , LiMnPO ４ and LiNiPO ４ ), transition metal oxides (e.g., MnO ２ and V ２ O ５ ), transition metal sulfides (e.g., MoS ２ and TiS ２ ), and conductive polymers (e.g., polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole), etc. may be mentioned, and two or more of them may be used in combination. Note that the lithium-containing transition metal phosphate may be one in which a part of the transition metal site is substituted with another transition metal.

[0060] As the negative electrode active material constituting the electrode composition for a sodium ion battery, carbon-based materials [non-graphitizable carbon (hard carbon), resin fired bodies (such as those obtained by firing and carbonizing phenol resins and furan resins, etc.), cokes (such as pitch coke, needle coke, and petroleum coke, etc.), and carbon fibers, etc.], silicon-based materials [silicon, silicon oxide (SiO x), silicon-carbon composites (carbon particles coated with silicon and / or silicon carbide on the surface, silicon particles or silicon oxide particles coated with carbon and / or silicon carbide on the surface, and silicon carbide, etc.), and silicon alloys (such as silicon-aluminum alloy, silicon-sodium alloy, silicon-nickel alloy, silicon-iron alloy, silicon-titanium alloy, silicon-manganese alloy, silicon-copper alloy, and silicon-tin alloy, etc.)], conductive polymers (such as polyacetylene and polypyrrole, etc.), metals (tin, aluminum, zirconium, and titanium, etc.), metal oxides (titanium oxides and sodium titanium oxides, etc.), metal alloys (such as sodium-tin alloy, sodium-aluminum alloy, and sodium-aluminum-manganese alloy, etc.), and mixtures of these with carbon-based materials, etc. can be mentioned. Among the above negative electrode active material particles, for those that do not contain sodium or sodium ions inside, a pre-doping treatment may be performed in advance to make a part or all of the negative electrode active material particles contain sodium or sodium ions. From the viewpoint of increasing the capacitance, as the negative electrode active material, it is preferably non-graphitizable carbon or a mixture of non-graphitizable carbon and a silicon-based material.

[0061] As the positive electrode active material constituting the electrode composition for a sodium ion battery, it is not particularly limited as long as it can be used in a sodium ion battery. Specifically, layered active materials, spinel-type active materials, oxoacid salt active materials, etc. can be mentioned. For example, NaFeO ２ , NaNiO ２ , NaCoO ２ , NaCrO ２ , NaMnO ２ , NaVO ２ , Na(Ni Ｘ Mn １－Ｘ )O ２ (0 < X < 1), Na(Fe Ｘ Mn １－Ｘ )O ２(0<X<1), NaVPO ４ F, Na ２ FePO ４ F, Na ３ V ２ (PO ４ ) ３ Examples include the following. Preferably, NaCoO ２ and NaCrO ２ That is the case.

[0062] In addition to the electrode active material and the binder composition for secondary batteries, the electrode composition for secondary batteries may also contain a thickening agent or the like.

[0063] Carboxymethylcellulose can be preferably used as a thickening agent. That is, the electrode composition for secondary batteries may further contain carboxymethylcellulose as a thickening agent.

[0064] The electrode composition for secondary batteries of the present invention can be obtained, for example, by mixing an electrode active material with the binder composition for secondary batteries of the present invention. Alternatively, the electrode composition for secondary batteries of the present invention can also be obtained by mixing an electrode active material with a polymer component constituting the binder composition for secondary batteries of the present invention and an additive constituting the binder composition for secondary batteries of the present invention.

[0065] [Electrodes for Secondary Batteries] The electrodes for secondary batteries of the present invention are obtained by compression molding the electrode composition for secondary batteries of the present invention. Because the electrodes for secondary batteries of the present invention are obtained by compression molding the electrode composition for secondary batteries of the present invention, the yield of the manufacturing process is high, and performance degradation due to electrode cracking during charging and discharging is less likely to occur in secondary batteries using the electrodes for secondary batteries of the present invention.

[0066] The compression molding conditions are preferably, for example, 1 to 50 MPa. Furthermore, the density of the electrode composition is preferably 1.0 to 3.5 g / cm³. ３ It is preferable to perform compression molding under conditions such as those described above. The thickness of the electrode composition for secondary batteries after compression molding is preferably 30 to 90 μm.

[0067] Examples of electrodes for secondary batteries include electrodes for lithium-ion batteries and electrodes for sodium-ion batteries.

[0068] The electrodes for secondary batteries may contain an electrolyte. Known electrolytes for secondary batteries can be used as the electrolyte.

[0069] As the solvent included in the electrolyte, non-aqueous solvents used in known electrolytes can be used, such as lactone compounds, cyclic or linear carbonate esters, linear carboxylic acid esters, cyclic or linear ethers, phosphate esters, nitrile compounds, amide compounds, sulfones, sulfolanes, and mixtures thereof.

[0070] Examples of lactone compounds include lactone compounds with five-membered rings (such as γ-butyrolactone and γ-valerolactone) and six-membered rings (such as δ-valerolactone).

[0071] Examples of cyclic carbonate esters include propylene carbonate (PC), ethylene carbonate (EC), and butylene carbonate (BC). Examples of linear carbonate esters include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, and di-n-propyl carbonate.

[0072] Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, and methyl propionate.

[0073] Examples of cyclic ethers include tetrahydrofuran, tetrahydropyran, 1,3-dioxolane, and 1,4-dioxane. Examples of linear ethers include dimethoxymethane and 1,2-dimethoxyethane.

[0074] Examples of phosphate esters include trimethyl phosphate, triethyl phosphate, ethyldimethyl phosphate, diethylmethyl phosphate, tripropyl phosphate, tributyl phosphate, tri(trifluoromethyl) phosphate, tri(trichloromethyl) phosphate, tri(trifluoroethyl) phosphate, 2-ethoxy-1,3,2-dioxaphosphoran-2-one, 2-trifluoroethoxy-1,3,2-dioxaphosphoran-2-one, and 2-methoxyethoxy-1,3,2-dioxaphosphoran-2-one.

[0075] Examples of nitrile compounds include acetonitrile. Examples of amide compounds include DMF. Examples of sulfones include dimethyl sulfone and diethyl sulfone.

[0076] These solvents may be used individually or in combination of two or more. Preferably, the mixed solvent is a mixture of ethylene carbonate and diethyl carbonate, a mixture of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate, or a mixture of ethylene carbonate and propylene carbonate.

[0077] As the electrolyte contained in the electrolyte solution, electrolytes used in known electrolyte solutions can be used. For example, lithium salts can be used in lithium-ion batteries, and sodium salts can be used in sodium-ion batteries.

[0078] LiPF is an example of a lithium salt. ６ LiBF ４ LiSbF ６ LiAsF ６ LiClO ４ and LiN (FSO ２ ) ２ Lithium salts of inorganic anions such as LiN(CF) ３ SO ２ ) ２ ,LiN(C ２ F ５ SO ２ ) ２ and LiC(CF ３ SO ２ ) ３Examples include lithium salts of organic anions such as LiPF. ６ Lithium hexafluoride phosphate, LiFSI (lithium bis(fluorosulfonyl)imide), and the like can be preferably used.

[0079] Examples of sodium salts include NaPF ６ NaBF ４ NaClO ４ and NaAsF ６ Inorganic sodium salts such as NaCF ３ SO ３ NaN(CF ３ SO ２ ) ２ NaN(C) ２ F ５ SO ２ ) ２ NaN(FSO) ２ ) ２ NaC(CF ３ SO ２ ) ３ Examples of organic sodium salts include the following. Of these, NaPF is preferred from the viewpoint of battery output and charge / discharge cycle characteristics. ６ That is the case.

[0080] The concentration of the electrolyte in the electrolyte solution is not particularly limited, but is preferably 0.3 to 5.0 mol / L, more preferably 0.5 to 2.0 mol / L, and even more preferably 0.8 to 1.5 mol / L.

[0081] [Secondary Battery] The secondary battery of the present invention is equipped with electrodes for secondary batteries of the present invention. Because the secondary battery of the present invention is equipped with electrodes for secondary batteries of the present invention, the yield in the manufacturing process is high and performance degradation due to electrode cracking during charging and discharging is less likely to occur.

[0082] Examples of rechargeable batteries include lithium-ion batteries and sodium-ion batteries.

[0083] This specification discloses the following:

[0084] (1) The present disclosure is a binder composition for secondary battery electrodes containing a polymer component having a number average molecular weight (Mn) of 2000 or more and an additive having a number average molecular weight (Mn) of less than 2000, and is a binder composition for secondary battery electrodes that satisfies all of the following (1) to (7). (1) The SP value (SP) of the polymer component Ｂ ) is 8-15 (cal / cm³) ３ ) １／２ (2) The additive is a compound having an oxyethylene group and / or two hydroxyl groups; (3) The additive has neither a boiling point nor a thermal decomposition temperature in the temperature range below 200°C; (4) The glass transition temperature Tg of the mixture obtained by mixing the polymer component and the additive in a weight ratio of additive / polymer component = 10 / 90 ２ (°C) is the glass transition temperature Tg of the polymer component alone. １ (5) The temperature is 5°C or more lower than (°C); (6) The weight ratio of the polymer component to the additive is additive / polymer component = 1 / 99 to 50 / 50; (7) The polymer component is at least one selected from the group consisting of starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene copolymer resin and (meth)acrylic resin; (8) The HLB value of the additive is 9 to 12.5.

[0085] This disclosure (2) relates to the SP value (SP) of the polymer component. Ｂ ) and the SP value of the additive (SP Ａ ) difference [SP Ａ - SP Ｂ The absolute value of ] is 2.0 (cal / cm²). ３ ) １／２ The binder composition for secondary battery electrodes described in this disclosure (1) is less than [amount missing].

[0086] Disclosure (3) is a binder composition for secondary battery electrodes according to Disclosure (1) or (2), wherein the cloud point of a 1% by weight aqueous solution of the additive is less than 90°C.

[0087] Disclosure (4) is a binder composition for secondary battery electrodes in any combination of any of Disclosures (1) to (3), wherein the additive is a compound having an oxyethylene group.

[0088] Disclosure (5) is a binder composition for secondary battery electrodes in any combination of any of Disclosures (1) to (4), wherein the polymer component is a styrene-butadiene copolymer resin or a (meth)acrylic resin.

[0089] (6) The storage modulus (G') at 25°C is measured by forming a mixture of the polymer component and the additive in a weight ratio of additive / polymer component = 10 / 90 into a film with a thickness of 500 μm. ２５ ) and the storage modulus (G') at 130°C, measured by forming the mixture into a film with a thickness of 500 μm. １３０ ) ratio [G' ２５ / G' １３０ This is a binder composition for secondary battery electrodes in any combination of any of the present disclosures (1) to (5), wherein [ ] is 1.00 to 4.00.

[0090] Disclosure (7) is an electrode composition for a secondary battery containing an electrode active material and a binder composition for a secondary battery electrode in any combination of any of Disclosures (1) to (6).

[0091] Disclosure (8) further relates to the secondary battery electrode composition according to Disclosure (7), comprising carboxymethylcellulose as a thickening agent.

[0092] The present disclosure (9) is an electrode for a secondary battery obtained by compression molding the electrode composition for a secondary battery described in the present disclosure (7) or (8).

[0093] Disclosure (10) is a secondary battery comprising the electrodes for a secondary battery described in Disclosure (9).

[0094] [Examples] The present invention will now be specifically described by examples, but the present invention is not limited to these examples unless it deviates from the spirit of the invention. Unless otherwise specified, parts refer to parts by weight.

[0095] (Preparation of Additives) The following additives were prepared: A1: EO adduct of isodecyl alcohol (average number of moles added: 7.1) A2: EO adduct of isodecyl alcohol with terminal methyl group (average number of moles added: 7.0) A5: EO adduct of C12 natural alcohol (average number of moles added: 8.3) A9: EO adduct of bisphenol A (average number of moles added: 1.0) A10: 1,3-butanediol A14: N-methylpyrrolidone A15: ethylene glycol A16: EO adduct of C15 synthetic alcohol (average number of moles added: 4.0) A17: EO adduct of C15 synthetic alcohol (average number of moles added: 12.0) A18: EO adduct of C18 fatty acid ester (average number of moles added: 14.0)

[0096]

[0097]

[0098] (Preparation of binder composition for secondary battery electrodes) (Examples 1, 2, 5, 8, 9, 10, Comparative Examples 2, 3, 7, 8, 41-43) Styrene-butadiene copolymer resin as polymer component (number average molecular weight: 200,000, SP Ｂ 8.30) An aqueous solution of the binder composition for secondary battery electrodes according to Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41-43 was prepared by adding an aqueous polymer solution containing 40% by weight of P1, additives A1, A2, A5, A9, A10, A16, A17, or A18 shown in Table 2 or Table 3, and deionized water, and stirring. At this time, the weight of the aqueous polymer solution and the weight of the additives were adjusted so that the total weight (solid content weight) of the additives and polymer components was 2.0 g, and the weight ratio of the additives and polymer components was the weight ratio shown in Table 4-1, and the weight of the deionized water was adjusted so that the total weight was 10 g.

[0099] (Molding of binder compositions for secondary battery electrodes) Next, the binder composition for secondary battery electrodes was poured into a PP tray (8.5 cm x 5.0 cm), dried on a hot plate at 80°C for 1 hour, and then dried under reduced pressure (>-90 kPa) for 1.5 hours to form the binder composition for secondary battery electrodes into a film, thereby obtaining film-like binder compositions for secondary battery electrodes B1, B2, B5, B8, B9, B10, B'2, B'3, B'7, B'8 and B'41 to B'43.

[0100] (Measurement of Breaking Strength) Tensile tests were performed on the obtained film-like binder compositions B1, B2, B5, B8, B9, B10, B'2, B'3, B'7, B'8 and B'41 to B'43 as test specimens, in accordance with ASTM D683 (Test Specimen Shape Type II). The breaking strength was measured as the point of maximum stress until the test specimen broke. The results are shown in Table 4-1. From the viewpoint of ensuring sufficient mechanical strength of the electrode, the above breaking strength should be 2.0 MPa or higher.

[0101] (Glass transition temperature Tg of individual polymer components) １ (Measurement) A polymer solution was prepared by adding a 40% by weight aqueous solution of polymer component P1 and 5.3 g of deionized water and stirring. The obtained polymer solution was poured into a PP tray (8.5 cm × 5.0 cm), dried on a hot plate at 80°C for 1 hour, then dried under reduced pressure (>-90 kPa) for 1.5 hours, and a portion was cut out to prepare a sample piece for measuring the glass transition temperature. Using the obtained sample piece, the glass transition temperature Tg was measured under the following conditions using the method specified in ASTM D3418-82 (DSC method). １ The temperature was measured to be 8.3°C. [Measurement conditions] (1) Heat from 30°C to 150°C at a rate of 20°C / min (2) Hold at 150°C for 10 minutes (3) Cool down to -80°C at a rate of 20°C / min (4) Hold at -80°C for 10 minutes (5) Heat up to 150°C at a rate of 20°C / min (6) Analyze the differential scanning calorimetry curve measured during the process of (5), and determine the position of the inflection point as the glass transition temperature Tg １ Let's assume that.

[0102] (Glass transition temperature Tg of polymer component / additive mixture) ２(Measurement of Tg) Parts of the obtained film-like binder compositions B1, B2, B5, B8, B9, B10, B'2, B'3, B'7, B'8 and B'41-B'43 were cut out to prepare sample pieces for measuring the glass transition temperature. Using the obtained sample pieces, Tg １ Under similar measurement conditions, the glass transition temperature Tg of a mixture with additive / polymer component = 10 / 90 was measured. ２ The following was measured. For binder compositions B1, B2, B5, B'2, B'3, B'41-B'43 for secondary battery electrodes, in which the weight ratio of additive / polymer component is 10 / 90, the glass transition temperature Tg of the above mixture was measured. ２ However, the glass transition temperature Tg of the binder composition ３ It is equal to. However, for secondary battery electrode binder compositions B8 to B10 and B'7 to B'8 in which the weight ratio of additive / polymer component is not 10 / 90, the glass transition temperature of the mixture is measured using secondary battery electrode binder composition B1, which is a binder composition in which the weight ratio of additive A1 / polymer component P1 is 10 / 90, as a sample piece. ２ The results are shown in Table 4-1.

[0103] Tg of binder compositions B8-B10 and B'7-B'8 for secondary battery electrodes where the weight ratio of additives / polymer components is not 10 / 90 ３ Regarding the Tg of a binder composition for secondary battery electrodes where the weight ratio of additives / polymer components is 10 / 90, ３ This is shown in Table 4-2.

[0104] (Storage modulus (G') ２５ ) and (G' １３０ (Measurement of viscoelasticity) Aqueous solutions of secondary battery electrode binder compositions B1, B2, B5, B8, B9, B10, B'2, B'3, B'7, B'8 and B'41-B'43 were formed into films with a thickness of 500 μm, and these were punched out to a diameter of Φ8 mm to obtain test pieces for viscoelasticity measurement. Using a dynamic viscoelasticity measuring device manufactured by Antonpaar, the storage modulus (G') at 25°C and 130°C was measured on the above test pieces for viscoelasticity measurement at a frequency of 1 Hz, a shear strain of 0.1%, and during a heating process from 0 to 150°C. ２５ ), (G' １３０) is measured, and the ratio of the storage modulus [G' ２５ / G' １３０ The ratio of storage modulus [G'] was determined. However, the ratio of storage modulus [G'] was determined for binder compositions B8 to B10 and B'7 to B'8 for secondary battery electrodes where the weight ratio of additive / polymer component is not 10 / 90. ２５ / G' １３０ For ], the ratio of storage modulus [G'] was measured using a secondary battery electrode binder composition B1, which is a secondary battery electrode binder composition in which the weight ratio of additive A1 / polymer component P1 is 10 / 90, as a test specimen. ２５ / G' １３０ The following was adopted. The results are shown in Table 4-1.

[0105] The ratio of storage moduli [G''] of binder compositions B8-B10 and B'7-B'8 for secondary battery electrodes where the weight ratio of additives / polymer components is not 10 / 90. ２５ / G'' １３０ Regarding ], the ratio of the storage modulus [G''] of a binder composition for secondary battery electrodes where the weight ratio of additives / polymer components is 10 / 90. ２５ / G'' １３０ This is shown in Table 4-2.

[0106] [Manufacturing of electrodes for lithium-ion batteries] 1.5 parts by weight of carboxymethylcellulose (CMC2260, manufactured by Daicel Corporation) as a thickening agent was dissolved in 48.5 parts of deionized water. 97.5 parts of artificial graphite (FNS-1, manufactured by Susshan China, D50: 15.3 μm), which is the electrode active material, were added, and the mixture was stirred three times at 2000 rpm for 2 minutes using a planetary stirring type mixing and kneading device {Awatori Rentaro [manufactured by Shinky Co., Ltd.]} to obtain a mixture. 3.0 parts of deionized water were added to this mixture and stirred at 2000 rpm for 2 minutes using Awatori Rentaro. Subsequently, 26 parts of deionized water were added and stirred at 2000 rpm for 2 minutes using Awatori Rentaro. Furthermore, five parts of 20% by weight aqueous solutions of secondary battery electrode binder compositions B1, B2, B5, B8, B9, B10, B'2, B'3, B'7, B'8, B'41-B'43 according to Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41-43 were added, and then the mixture was stirred at 1000 rpm for 1 minute using a foam stirring machine to prepare an electrode composition (negative electrode composition) slurry. The obtained electrode composition slurry was then applied to one side of a current collector (copper foil) in air using a wire bar, with an active material basis weight of 10.0-11.0 mg / cm². ２ The material was applied in such a manner, dried in a circulating air dryer at 130°C for 30 minutes, and then dried in a vacuum dryer at 100°C for 3 hours to obtain an electrode sheet in which an electrode layer (negative electrode layer) was formed on a current collector (copper foil). Finally, the obtained electrode sheet was pressed and compressed in a press machine until it reached a predetermined electrode density (electrode thickness) to obtain lithium-ion battery electrodes LE1, LE2, LE5, LE8, LE9, LE10, LE'2, LE'3, LE'7, LE'8, and LE'41 to LE'43 according to Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41 to 43.

[0107] (Confirmation of electrode cracking during drying) When drying the electrode composition slurry, the surface was visually inspected and evaluated for any cracks. The results are shown in Table 4-1.

[0108] (Bending Test) Electrodes LE1, LE2, LE5, LE8, LE9, LE10, LE'2, LE'3, LE'7, LE'8, and LE'41-LE'43 for lithium-ion batteries, according to Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41-43, were wrapped around a rod of a predetermined diameter with both ends fixed, and a 100g weight was then suspended from it. The diameter of the rod around which the electrodes were wrapped was gradually reduced, and the diameter of the rod at which cracks began to appear on the surface of the wrapped electrodes (crack initiation diameter) was confirmed. The results are shown in Table 4-1. Note that if the crack initiation diameter is 5 mm or less as a result of the bending test, the electrode can be said to have sufficient flexibility.

[0109] [Manufacturing of Lithium-ion Batteries] The lithium-ion battery electrodes LE1, LE2, LE5, LE8, LE9, LE10, LE'2, LE'3, LE'7, LE'8, and LE'41 to LE'43 according to Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41 to 43 were combined with a positive electrode and a separator, sealed in an aluminum laminate container, and an electrolyte was injected to obtain lithium-ion batteries LB1, LB2, LB5, LB8, LB9, LB10, LB'2, LB'3, LB'7, LB'8, and LB'41 to LB'43 according to Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41 to 43. The positive electrode consists of an aluminum foil (20 μm thick) which serves as the positive electrode current collector, with LiCoO2, the positive electrode active material, on its surface. ２ The positive electrode active material layer is 60 μm thick and contains 90% by weight of ethylene carbonate, 5% by weight of acetylene black as a conductive additive, and 5 parts by weight of PVdF as a binder. The separator is manufactured by Celgard (Celgard® 3501, 25 μm thick). The electrolyte is a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DC) in a volume ratio of EC:DC = 1:1, with LiFP as the electrolyte. ６ A solution prepared by dissolving the substance at a concentration of 1 mol / L was used.

[0110] (Charge-Discharge Test: Measurement of Initial Coulomb Efficiency) At 25°C, lithium-ion batteries LB1, LB2, LB5, LB8, LB9, LB10, LB'2, LB'3, LB'7, LB'8, LB'41-LB'43 were charged to 0.0V with a current of 0.05C using a constant current charging method (CC mode) with a charge-discharge measuring device "HJ-SD8" [manufactured by Hokuto Denko Co., Ltd.]. After a 10-minute pause, they were discharged to 1.5V with a current of 0.05C. The capacity charged at this time was defined as [Initial Charge Capacity (mAh)] and the capacity discharged as [Initial Discharge Capacity (mAh)]. The initial Coulomb efficiency was calculated using the following formula, and the first cycle evaluation was performed based on the evaluation criteria below. The results are shown in Table 4-1. [Initial Coulomb Efficiency (%)] = [Initial Discharge Capacity] ÷ [Initial Charge Capacity] × 100 [Evaluation Criteria] ◎: Initial Coulomb efficiency of 92.0% or higher ○: Initial Coulomb efficiency of 90.0% or higher, but less than 92.0% △+: Initial Coulomb efficiency of 87.0% or higher, but less than 90.0% △-: Initial Coulomb efficiency of 85.0% or higher, but less than 87.0% ×: Initial Coulomb efficiency of less than 85.0%

[0111] (Charge / Discharge Test: Evaluation of Cycle Characteristics) The negative electrode half-cells constituting LE1, LE2, LE5, LE8, LE9, LE10, LE'2, LE'3, LE'7, LE'8, LE'41-LE'43 for lithium-ion batteries in Examples 1, 2, 5, 8, 9, 10 and Comparative Examples 2, 3, 7, 8, 41-43 were charged to 0V with a current of 0.05C using a constant current charging method (also called CC mode), and after a 10-minute pause, were discharged to 1.5V with a current of 0.05C. The discharged capacity at this time was defined as [1 Cycle Discharge Capacity (mAh)]. The above test was repeated 50 times, and the discharged capacity at 50 cycles was defined as [50 Cycle Discharge Capacity (mAh)], and the capacity retention rate (%) at 50 cycles was obtained using the following formula. The results are shown in Table 4-1. Capacity retention rate (%) = 100 × [50-cycle discharge capacity (mAh)] / [1-cycle discharge capacity (mAh)] [Evaluation criteria] ◎: Capacity retention rate at 50 cycles is 90.5% or higher ○: Capacity retention rate at 50 cycles is 89.5% or higher and less than 90.5% △+: Capacity retention rate at 50 cycles is 88.5% or higher and less than 89.5% △-: Capacity retention rate at 50 cycles is 87.5% or higher and less than 88.5% ×: Capacity retention rate at 50 cycles is less than 87.5%

[0112]

[0113] The ratio of storage moduli [G''] of binder compositions B8-B10 and B'7-B'8 for secondary battery electrodes where the weight ratio of additives / polymer components is not 10 / 90. ２５ / G'' １３０ Regarding ], the ratio of the storage modulus [G''] of binder composition B1 for secondary battery electrodes, in which the weight ratio of additives / polymer components is 10 / 90. ２５ / G'' １３０ This is shown in Table 4-2.

[0114] The results in Table 4-1 show that the binder composition for secondary battery electrodes of the present invention can produce particularly flexible electrodes when the polymer component is a styrene-butadiene copolymer (SBR). It is believed that the use of flexible electrodes improves charge-discharge characteristics such as initial cycle characteristics, initial Coulomb efficiency, and cycle characteristics. Furthermore, the results from Examples 1, 9, 10, and Comparative Examples 7 and 8 confirm that the weight ratio of additives to polymer components does not necessarily have to be 10 / 90, but is acceptable within the range of 1 / 99 to 50 / 50. (Difference in glass transition temperature (Tg)) １ -Tg ２ For Comparative Examples 2, 3, 42, and 43, where the temperature was below 5°C, and for Comparative Examples 3, 41-43, where an additive outside the HLB value range of 9-12.5 was added, it was confirmed that cracks occurred during electrode drying and that the electrodes were prone to cracking during bending tests.

[0115]

[0116] Based on the results in Table 4-2, for binder compositions B1, B8, B9, and B10, where the additive / polymer component ratio is in the range of 1 / 99 to 50 / 50, the glass transition temperature Tg ３ Although the temperature range was within -38°C to +3.3°C, for binder compositions B'7 and B'8, where the additive / polymer component ratio was not within the range of 1 / 99 to 50 / 50, the glass transition temperature Tg was... ３ The temperature was either higher than +3.3°C or lower than -38°C. Furthermore, for binder compositions B1, B8, B9, and B10, where the additive / polymer component ratio was within the range of 1 / 99 to 50 / 50, the storage modulus ratio was within the range of 2.00 to 8.00. However, for binder compositions B'7 and B'8, where the additive / polymer component ratio was outside the range of 1 / 99 to 50 / 50, the storage modulus ratio was either less than 2.00 or greater than 8.00.

[0117] (Examples 13, 41, 42 and Comparative Examples 9, 11, 44, 45) (Production of binder composition for secondary battery electrodes) As a polymer component, polyacrylic acid (Mn: 5000, SP Ｂ:14.0) Except for using P2, aqueous solutions of the secondary battery electrode binder compositions according to Examples 13, 41, 42 and Comparative Examples 9, 11, 44, and 45 were prepared using the same procedure as in Example 1. The obtained aqueous solutions were molded into predetermined shapes, and secondary battery electrode binder compositions B13, B41, B42, B'9, B'11, B'44, and B'45 according to Examples 13, 41, 42 and Comparative Examples 9, 11, 44, and 45 were obtained using the same procedure as in Example 1, and the tensile strength and the glass transition temperature Tg of polymer component P2 alone were measured. １ , the glass transition temperature Tg of the polymer component / additive mixture ２ , the ratio of the storage modulus [G' ２５ / G' １３０ The glass transition temperature Tg of polymer component P2 alone was determined. The results are shown in Table 5-1. １ The temperature was 115°C. Furthermore, for secondary battery electrode binder compositions B41, B42, B'44, and B'45, where the weight ratio of additive / polymer component is not 10 / 90, the glass transition temperature of the mixture was measured using secondary battery electrode binder composition B13, which has a weight ratio of additive A1 / polymer component P2 of 10 / 90, as a sample. ２ Similarly, the ratio of storage moduli [G'] of binder compositions B41, B42, B'44 and B'45 for secondary battery electrodes, where the weight ratio of additives / polymer components is not 10 / 90. ２５ / G' １３０ For ], the ratio of storage modulus [G'] was measured using a secondary battery electrode binder composition B13, which is a secondary battery electrode binder composition in which the weight ratio of additive A10 / polymer component P2 is 10 / 90, as a test specimen. ２５ / G' １３０ [This was adopted.]

[0118] (Manufacturing of electrodes and lithium-ion batteries for lithium-ion batteries) Furthermore, using the obtained secondary battery electrode binder compositions B13, B41, B42, B'9, B'11, B'44, and B'45, lithium-ion battery electrodes LE13, LE41, LE42, LE'9, LE'11, LE'44, and LE'45 and lithium-ion batteries LB13, LB41, LB42, LB'9, LB'11, LB'44, and LB'45 were manufactured using the same procedure as in Example 1, and electrode cracking during drying, bending tests, initial Coulomb characteristics, and capacity retention rate at 50 cycles were measured. The results are shown in Table 5-1.

[0119]

[0120] Table 5-2 shows the storage modulus ratios [G''25 / G''130] for secondary battery electrode binder compositions B41, B42, B'44, and B'45, where the weight ratio of additives / polymer components is not 10 / 90, along with the storage modulus ratio [G''25 / G''130] for secondary battery electrode binder composition B13, where the weight ratio of additives / polymer components is 10 / 90.

[0121]

[0122] The results in Table 5-1 show that the binder composition for secondary battery electrodes of the present invention can produce electrodes with a certain degree of flexibility, even when the polymer component is polyacrylic acid (PAA). The results in Table 5-1 show that the flexibility of the electrodes is reduced compared to the case where the polymer component is SBR (Tables 4-1 and 4-2), but it was confirmed that flexibility can still be imparted to the electrodes by using the binder composition for secondary battery electrodes of the present invention. Furthermore, when an additive with an HLB value outside the range of 9 to 12.5 was added (Comparative Examples 9 and 11), or when the weight ratio of the polymer component to the additive was outside the range of 1 / 99 to 50 / 50 (Comparative Examples 44 and 45), cracking occurred during drying of the electrodes, and the electrodes became more prone to cracking during bending tests, similar to the case where the polymer component was styrene-butadiene copolymer (SBR).

[0123] Based on the results in Table 5-2, for binder compositions B13, B41, and B42, where the additive / polymer component ratio is in the range of 1 / 99 to 50 / 50, the glass transition temperature Tg ３ Although the glass transition temperature (Tg) was within the range of +70°C to +110°C, for binder compositions B'44 and B'45, where the additive / polymer component ratio was not within the range of 1 / 99 to 50 / 50, the glass transition temperature (Tg) was... ３ The temperature was either higher than +110°C or lower than +70°C. Furthermore, for binder compositions B1, B41, and B42, where the additive / polymer component ratio was within the range of 1 / 99 to 50 / 50, the storage modulus ratio was 17.00 or higher, but for binder composition B'45, where the additive / polymer component ratio was not within the range of 1 / 99 to 50 / 50, the storage modulus ratio was less than 17.00.

[0124] (Examples 19, 20, 23, 26-28, 31, Comparative Examples 15, 16, 20, 21, 46, 47, 22, 24) [Manufacturing of electrodes for sodium-ion batteries] The negative electrode active material was changed to hard carbon (Carbotron® PS(F), manufactured by Kureha Battery Materials Japan Co., Ltd., average particle size (d50): 20 μm), and the positive electrode active material was changed to NaCrO ２ Changed to NaPF ６Except for the change, the same procedure as in Examples 13, 41, 42 and Comparative Examples 9, 11, 43, 44 was used to manufacture the sodium ion battery electrodes SE19, SE20, SE23, SE26-SE28, SE31, SE'15, SE'16, SE'20, SE'21, SE'46, SE'47, SE'22, S related to Examples 19, 20, 23, 26-28, 31 and Comparative Examples 15, 16, 20, 21, 46, 47, 22, 24. Sodium-ion batteries SB19, SB20, SB23, SB26-SB28, SB31, SB'15, SB'16, SB'20, SB'21, SB'46, SB'47, SB'22, and SB'24 were obtained for E'24 and Examples 19, 20, 23, 26-28, 31, and Comparative Examples 15, 16, 20, 21, 46, 47, 22, and 24. Cracking during drying was confirmed, and bending tests and charge-discharge tests were performed. The results are shown in Tables 6 and 7. However, since there is a large difference in initial coulombic efficiency between lithium-ion batteries and sodium-ion batteries, the evaluation criteria for initial coulombic efficiency were changed as follows. [Evaluation Criteria (Sodium-ion Batteries)] ◎: Initial Coulomb efficiency of 87.0% or higher ○: Initial Coulomb efficiency of 85.0% or higher and less than 87.0% △+: Initial Coulomb efficiency of 82.0% or higher and less than 85.0% △-: Initial Coulomb efficiency of 80.0% or higher and less than 82.0% ×: Initial Coulomb efficiency of less than 80.0% Note that the evaluation criteria for cycle characteristics are the same as for lithium-ion batteries.

[0125]

[0126]

[0127] From the results in Tables 6 and 7, it was found that the sodium-ion battery electrodes according to Comparative Examples 15, 16, 46, 47, 22, and 24 underwent electrode cracking during drying, while the sodium-ion battery electrodes according to Examples 19, 20, 23, 26-28, and 31 were able to suppress electrode cracking during drying. From this, it was confirmed that the binder composition for secondary battery electrodes of the present invention can impart flexibility to sodium-ion battery electrodes. Furthermore, it was found that the sodium-ion battery electrodes according to Examples 19, 20, 23, 26-28, and 31 exhibited higher initial Coulomb efficiency and cycle characteristics compared to the sodium-ion battery electrodes according to Comparative Examples 15, 16, 20, 21, 46-47, 22, and 24.

[0128] The binder composition for secondary battery electrodes of the present invention is useful in methods for manufacturing secondary batteries such as lithium-ion batteries and sodium-ion batteries.

Claims

1. A binder composition for secondary battery electrodes containing a polymer component having a number average molecular weight (Mn) of 2000 or more and an additive having a number average molecular weight (Mn) of less than 2000, wherein the binder composition for secondary battery electrodes satisfies all of the following (1) to (7): (1) The SP value (SP) of the polymer component Ｂ ) is 8-15 (cal / cm³) ３ ) １／２ (2) The additive is a compound having an oxyethylene group and / or two hydroxyl groups; (3) The additive has neither a boiling point nor a thermal decomposition temperature in the temperature range below 200°C; (4) The glass transition temperature Tg of the mixture obtained by mixing the polymer component and the additive in a weight ratio of additive / polymer component = 10 / 90 ２ (°C) is the glass transition temperature Tg of the polymer component alone. １ (5) The temperature is 5°C or more lower than (°C); (6) The weight ratio of the polymer component to the additive is additive / polymer component = 1 / 99 to 50 / 50; (7) The polymer component is at least one selected from the group consisting of starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene copolymer resin and (meth)acrylic resin; (8) The HLB value of the additive is 9 to 12.

5.

2. The difference in the SP value (SP Ｂ ) of the polymer component and the SP value (SP Ａ ) of the additive [SP Ａ - SP Ｂ has an absolute value of less than 2.0 (cal / cm ３ ), and the binder composition for a secondary battery electrode according to claim 1. １／２ ​ 3. The binder composition for secondary battery electrodes according to claim 1, wherein the cloud point of a 1% by weight aqueous solution of the additive is less than 90°C.

4. The binder composition for secondary battery electrodes according to claim 1, wherein the additive is a compound having an oxyethylene group.

5. The binder composition for secondary battery electrodes according to claim 1, wherein the polymer component is a styrene-butadiene copolymer resin or a (meth)acrylic resin.

6. The storage modulus (G') at 25°C was measured by forming a mixture of the polymer component and the additive in a weight ratio of additive / polymer component = 10 / 90 into a film with a thickness of 500 μm. ２５ ) and the storage modulus (G') at 130°C, measured by forming the mixture into a film with a thickness of 500 μm. １３０ ) ratio [G' ２５ / G' １３０ A binder composition for secondary battery electrodes according to claim 1, wherein [ ] is 1.00 to 4.

00.

7. An electrode composition for a secondary battery containing an electrode active material and a binder composition for secondary battery electrodes according to any one of claims 1 to 6.

8. The electrode composition for a secondary battery according to claim 7, further comprising carboxymethylcellulose as a thickening agent.

9. An electrode for a secondary battery obtained by compression molding the electrode composition for a secondary battery described in claim 7.

10. A secondary battery comprising electrodes for a secondary battery as described in claim 9.

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