Electrode composition for secondary battery, electrode for secondary battery, and secondary battery

Abstract

To provide an electrode composition for a secondary battery that exhibits excellent uniformity and drying property of a slurry coating film, as well as superior durability of the battery under high-temperature conditions.SOLUTION: The present invention relates to an electrode composition for a secondary battery including an electrode active material, a binder resin, and a compound (A) which is an alkylene oxide adduct of a polyhydric alcohol. The average number of moles of added the alkylene oxide is 20 to 690, the alkylene oxide includes ethylene oxide, the saponification value of the compound (A) is less than 5, and the content of the compound (A) is 0.01 to 2.0% by weight based on the solid content weight of the electrode composition for a secondary battery.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrode composition for a secondary battery, an electrode for a secondary battery, and a secondary battery. [Background technology]

[0002] Secondary batteries such as lithium-ion batteries are being used in practical applications such as mobile phones, laptop computers, and other portable devices, as well as in hybrid and electric vehicles. To further popularize these devices, improvements in productivity and durability at high temperatures are required, and various technologies are being developed to address this need.

[0003] For example, in order to improve the productivity of electrodes, it is required to reduce the occurrence of coating errors in the electrode slurry and to shorten the drying time.

[0004] In order to solve such problems, Patent Document 1 discloses that an electrode slurry containing an electrode active material, a binder, and a solvent further contains carbonate esters. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-68280 Summary of the Invention [Problem to be solved by the invention]

[0006] The electrode slurry of Patent Document 1 was effective in improving the uniformity of the coating film, but this was not sufficient. Furthermore, the drying property of the coating film was not taken into consideration. Furthermore, there was a risk that the carbonate ester in the electrode slurry would hydrolyze, adversely affecting the durability of the secondary battery at high temperatures.

[0007] The present invention has been made to solve the above problems, and has an object to provide an electrode composition for a secondary battery which provides a slurry coating with excellent uniformity and drying properties, and which is excellent in durability at high temperatures in the battery. [Means for solving the problem]

[0008] The present inventors have made extensive studies and arrived at the present invention. The present invention relates to any of the following: An electrode composition for a secondary battery comprising an electrode active material, a binder resin, and a compound (A) which is an alkylene oxide adduct of a polyhydric alcohol, wherein the average number of moles of the alkylene oxide added is 20 to 690, the alkylene oxide contains ethylene oxide, the saponification value of the compound (A) is less than 5, and the content of the compound (A) is 0.01 to 2.0 wt % based on the solid content weight of the electrode composition for a secondary battery. A secondary battery electrode is obtained by compression molding the above secondary battery electrode composition. A secondary battery comprising the above secondary battery electrode. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electrode composition for a secondary battery which has excellent uniformity and drying properties of a slurry coating film, and excellent durability at high temperatures in the battery. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. The present invention relates to an electrode composition for a secondary battery, an electrode for a secondary battery, and a secondary battery. The electrode composition for a secondary battery of the present invention may be an electrode composition for a lithium ion battery or an electrode composition for a sodium ion battery. In this specification, when lithium ion batteries and sodium ion batteries are mentioned, these concepts also include lithium ion secondary batteries and sodium ion secondary batteries, respectively. Hereinafter, the "secondary battery electrode composition" will also be referred to as the "electrode composition."

[0011] [Electrode composition] The electrode composition for a secondary battery of the present invention is an electrode composition for a secondary battery containing an electrode active material, a binder resin, and a compound (A) which is an alkylene oxide adduct of a polyhydric alcohol, wherein the average number of moles of the alkylene oxide added is 20 to 690, the alkylene oxide contains ethylene oxide, the saponification value of the compound (A) is less than 5, and the content of the compound (A) is 0.01 to 2.0 wt % based on the solid content weight of the electrode composition for a secondary battery.

[0012] The electrode composition of the present invention may be an electrode composition for a positive electrode (also referred to as a positive electrode composition) or an electrode composition for a negative electrode (also referred to as a negative electrode composition). The electrode composition of the present invention itself does not contain an electrolyte solution, but as will be described later, an electrode layer for a secondary battery can be formed by adding an electrolyte solution to an electrode prepared using the electrode composition.

[0013] (electrode active material) The electrode active material may be a positive electrode active material or a negative electrode active material.

[0014] The positive electrode active material constituting the electrode composition for lithium ion batteries includes composite oxides of lithium and transition metals {composite oxides containing one type of transition metal (e.g., LiCoO2, LiNiO2, LiAlMnO4, LiMnO2, and LiMn2O4), composite oxides containing two types of transition metal elements (e.g., LiFeMnO4, LiNi 1-x Co x O2, LiMn 1-y Co y O2, LiNi 1 / 3 Co 1 / 3 Al 1 / 3 O2 and LiNi 0.8 Co 0.15 Al 0.05 O2) and composite oxides containing three or more transition metal elements [e.g., LiM a M' b M'' cO2 (where M, M', and M'' are different transition metal elements respectively, and a + b + c = 1. For example, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O2), etc.] etc.}, lithium-containing transition metal phosphates (such as LiFePO4, LiCoPO4, LiMnPO4, and LiNiPO4), transition metal oxides (such as MnO2 and V2O5), transition metal sulfides (such as MoS2 and TiS2), and conductive polymers (such as polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polyvinylcarbazole), etc. may be mentioned, and two or more kinds may be used in combination. In addition, the lithium-containing transition metal phosphate may be one in which a part of the transition metal site is substituted with another transition metal. When the electrode active material is a positive electrode active material, a composite oxide of lithium and a transition metal is preferable as the positive electrode active material.

[0015] The positive electrode active material constituting the electrode composition for a sodium ion battery 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, NaFeO2, NaNiO2, NaCoO2, NaCrO2, NaMnO2, NaVO2, Na(Ni X Mn 1-X )O2 (0 < X < 1), Na(Fe X Mn 1-X )O2 (0 < X < 1), NaVPO4F, Na2FePO4F, Na3V2(PO4)3, etc. can be mentioned. Preferably, they are NaCoO2 and NaCrO2.

[0016] Examples of the negative electrode active material constituting the electrode composition for lithium ion batteries include carbon-based materials [graphite (graphite, artificial graphite, natural graphite), non-graphitizable carbon (hard carbon), amorphous carbon, burned resins (e.g., phenolic resins, furan resins, etc., which are burned and carbonized), cokes (e.g., pitch coke, needle coke, petroleum coke, etc.), and carbon fibers], silicon-based materials [silicon, silicon oxide (SiO x ), silicon-carbon composites (carbon particles whose surfaces are coated with silicon and / or silicon carbide, silicon particles or silicon oxide particles whose surfaces are coated with carbon and / or silicon carbide, and silicon carbide, etc.) and silicon alloys (silicon-aluminum alloy, silicon-lithium alloy, silicon-nickel alloy, silicon-iron alloy, silicon-titanium alloy, silicon-manganese alloy, silicon-copper alloy, silicon-tin alloy, etc.), conductive polymers (for example, polyacetylene and polypyrrole), metals (tin, aluminum, zirconium, titanium, etc.), metal oxides (titanium oxide, lithium-titanium oxide, etc.) and metal alloys (for example, lithium-tin alloy, lithium-aluminum alloy, lithium-aluminum-manganese alloy, etc.), and mixtures of these with carbon-based materials, and two or more of these may be used in combination. When the electrode active material is a negative electrode active material, the negative electrode active material is preferably artificial graphite or natural graphite. When the negative electrode active material is graphite, the shape thereof is not particularly limited, and examples thereof include spherical graphite and scaly graphite.

[0017] As the negative electrode active material constituting the electrode composition for a sodium ion battery, the carbon-based material, silicon-based material, conductive polymer, metal, metal oxide, and metal alloy exemplified as the negative electrode active material constituting the electrode composition for a lithium ion battery can be used. However, among the materials exemplified above, the lithium-containing materials can be replaced with a material containing sodium, such as silicon-sodium alloy, sodium-titanium oxide, sodium-tin alloy, sodium-aluminum alloy, and sodium-aluminum-manganese alloy.

[0018] Among the particles of the negative electrode active material, those that do not contain lithium, lithium ions, sodium, or sodium ions inside may be subjected to a pre-doping treatment in which lithium, lithium ions, sodium, or sodium ions are contained in part or all of the particles of the negative electrode active material in advance.

[0019] From the viewpoint of increasing the electric capacity, the negative electrode active material is preferably non-graphitizable carbon or a mixture of non-graphitizable carbon and a silicon-based material.

[0020] The content of the electrode active material in the electrode composition is not particularly limited, but from the viewpoint of increasing the electrode density and thereby increasing the battery capacity, a high content of the electrode active material is preferable, and is preferably 78 to 97 wt % based on the solid content weight of the electrode composition, and more preferably 85 to 97 wt %.

[0021] (binder resin) The binder resin is a resin used in lithium ion batteries or sodium ion batteries, and examples thereof include starch, polyvinylidene fluoride, polyvinyl alcohol, polyvinylpyrrolidone, polytetrafluoroethylene, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyethylene, and polypropylene, and two or more types may be used in combination. When the electrode composition contains these substances, it is considered to contain a binder resin. In this specification, the binder resin is a substance that is distinguished from the compound (A).

[0022] Furthermore, many binder resins have a weight average molecular weight (Mw) of more than 50,000. The weight average molecular weight of the binder resin can be measured by gel permeation chromatography under the following conditions, for example. Apparatus: "Waters Alliance 2695" [Waters] Column: "Guardcolumn Super HL" (1 column), "TSKgel SuperH2000, TSKgel SuperH3000, TSKgel SuperH4000 (all manufactured by Tosoh Corporation) connected together" Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection volume: 10μl Flow rate: 0.6ml / min Measurement temperature: 40℃ Detector: Refractive index detector Reference material: Standard polyethylene glycol

[0023] The content of the binder resin is preferably 1 to 20% by weight based on the weight of the solid content of the electrode composition.

[0024] (Conductive additive) The electrode composition for a secondary battery of the present invention may contain a conductive additive, such as metals (aluminum, stainless steel (SUS), silver, gold, copper, titanium, etc.), carbon (graphite (flaky graphite (UP)), carbon black (acetylene black (AB), ketjen black, furnace black, channel black, thermal lamp black, etc.), carbon nanofibers (CNF), carbon nanotubes (CNT), etc.), and mixtures thereof, or two or more of these may be used in combination. The conductive additive is preferably acetylene black or carbon nanotubes. Carbon-based materials are used both as negative electrode active materials and as conductive additives, but in this application, those with a volume average particle diameter of 15 μm or more are considered to be negative electrode active materials, and those with a volume average particle diameter of less than 15 μm are considered to be conductive additives.

[0025] The content of the conductive assistant is preferably 1 to 6% by weight based on the weight of the solid content of the electrode composition.

[0026] (Compound (A)) The compound (A) is an alkylene oxide adduct of a polyhydric alcohol. Examples of polyhydric alcohols include alkylene glycols such as ethylene glycol, propylene glycol, and butylene glycol; trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, sorbitan, sorbitol, sucrose, mannitol, etc. The polyhydric alcohol is preferably at least one selected from the group consisting of ethylene glycol, propylene glycol, trimethylolpropane, glycerin, pentaerythritol, sorbitan, sorbitol, and sucrose, and more preferably at least one selected from the group consisting of ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitan, and sorbitol.

[0027] The alkylene oxide includes ethylene oxide, which provides excellent drying properties of the electrode composition slurry and excellent applicability to the electrode. The alkylene oxide may contain alkylene oxides other than ethylene oxide, such as propylene oxide and butylene oxide. In the present specification, alkylene oxide may be abbreviated as AO, ethylene oxide as EO, and propylene oxide as PO.

[0028] When the alkylene oxide is composed of a plurality of types of alkylene oxides, the addition may be in the form of random addition or block addition.

[0029] The alkylene oxide adduct of the polyhydric alcohol has an average number of added moles of alkylene oxide of 20 to 690. If the average number of added moles is less than 20, the dispersion stability, drying properties, and coatability to an electrode of the electrode composition slurry will be poor. If the average number of added moles exceeds 690, the dispersion stability and coatability to an electrode of the electrode composition slurry will be poor. The average number of moles of alkylene oxide added is preferably 40 to 690, since this provides better dispersion stability of the electrode composition slurry.

[0030] The molar ratio of ethylene oxide in the alkylene oxide is preferably 50% or more, more preferably 65% ​​or more, and even more preferably 70% or more, based on the total number of moles of alkylene oxide. When the ratio of EO is 50% or more, the dispersion stability of the electrode composition slurry is more excellent. The alkylene oxide may be ethylene oxide alone, that is, the molar ratio of ethylene oxide in the alkylene oxide may be 100% based on the total number of moles of alkylene oxide.

[0031] In the electrode composition of the present invention, the saponification value of the compound (A) is less than 5. If the saponification value is 5 or more, the dispersion stability when the electrode composition is made into a slurry and the applicability to an electrode are poor. The saponification value is a value measured according to JIS K0070 "Testing methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products."

[0032] The hydroxyl value of the compound (A) is preferably 3 to 120 KOH mg / g. When the hydroxyl value is within the above range, the dispersion stability of the electrode composition when made into a slurry and the applicability to the electrode are excellent. Furthermore, the dispersion stability of the electrode composition when made into a slurry and the high-temperature durability of the battery are also excellent, so the hydroxyl value of the compound (A) is more preferably 3 to 100 KOH mg / g. The hydroxyl value of the compound (A) is also preferably from 5 to 120 KOHmg / g, and more preferably from 5 to 100 KOHmg / g. The hydroxyl value of the compound (A) is a value measured by a method in accordance with JIS K1557-1:2007 "Testing methods for polyurethane raw material polyols."

[0033] The weight-average molecular weight of the compound (A) is preferably 800 to 37000. The weight-average molecular weight of the compound (A) is more preferably 3000 to 33000, because this improves the dispersion stability when the electrode composition is made into a slurry and the applicability to an electrode. The weight average molecular weight of the compound (A) can be measured by the same method as that for the weight average molecular weight of the binder resin. The larger the weight-average molecular weight of the compound (A), the better the dispersion stability when the electrode composition is made into a slurry. Furthermore, if the weight-average molecular weight of the compound (A) is similar, the straight-chain structure has a longer main chain length than the branched-chain structure, which increases molecular entanglement and improves dispersion stability when the electrode composition is made into a slurry.

[0034] The content of compound (A) is 0.01 to 2.0% by weight based on the solid content weight of the electrode composition for secondary batteries, and is preferably 0.6 to 1.3% by weight because this provides excellent dispersion stability to the slurry of the electrode composition. In addition, when the electrode composition for a secondary battery contains a conductive auxiliary, the content of the compound (A) is preferably 2 to 50% by weight based on the weight of the conductive auxiliary.

[0035] The compound (A) may contain one or more of the alkylene oxide adducts of the polyhydric alcohols.

[0036] [Method of manufacturing electrode composition for secondary battery] The electrode composition for a secondary battery of the present invention can be obtained by mixing the compound (A) with other components (electrode active material, binder resin, and, if necessary, components such as a conductive assistant). The compound (A) can also be obtained by carrying out an addition reaction of an alkylene oxide to a polyhydric alcohol by a known method.

[0037] The compound (A) contained in the electrode composition for secondary batteries of the present invention is an alkylene oxide adduct of a polyhydric alcohol, and therefore has multiple alkylene oxide chains per molecule. It is believed that compound (A) exhibits both hydrophobic and hydrophilic effects throughout the molecule, rather than being separated into hydrophobic and hydrophilic portions, due to the alkylene oxide chains at two or more locations on the starting polyhydric alcohol. The interaction between multiple portions of compound (A) and the electrolyte solvent facilitates compound (A)'s homogeneous mixing with the electrolyte solvent, presumably maintaining the viscosity and uniformity (dispersion state of the electrode active material and conductive additive) of the electrode composition slurry. Furthermore, this interaction acts like a crosslink within the coating, improving the applicability of the electrode composition slurry. On the other hand, compound (A) has an average added mole number of alkylene oxide of 20 to 690 and a relatively large molecular weight, so it is not easily adsorbed to the electrode active material and its interaction with the electrode active material is not too strong. Furthermore, this interaction is disrupted by an external stimulus such as drying, which promotes the evaporation of the solvent in the electrode composition slurry, resulting in excellent drying properties. Furthermore, since compound (A) is not easily hydrolyzed, secondary batteries using compound (A) have excellent durability at high temperatures.

[0038] [Electrode for secondary batteries] The secondary battery electrode of the present invention is produced by compression molding the secondary battery electrode composition of the present invention. The secondary battery electrode may be a lithium ion battery electrode or a sodium ion battery electrode. The method for compression molding the secondary battery electrode composition is not particularly limited, and methods such as roll pressing, pressing with a press, etc. can be used. The electrode density of the secondary battery electrode obtained by compression molding the secondary battery electrode composition is preferably 1.0 to 2.0 g / ml when the electrode is a negative electrode. When the electrode is a positive electrode, the content is preferably 3.0 to 4.0 g / ml in the case of a positive electrode for a lithium ion battery, and 2.5 to 3.5 g / ml in the case of a positive electrode for a sodium ion battery. The electrode density defined here means the density in a state where the electrolyte has not been permeated into the electrode composition for a secondary battery.

[0039] [Secondary battery] The secondary battery of the present invention comprises the secondary battery electrode of the present invention. In the secondary battery of the present invention, the electrolyte solution is sufficiently permeated into the secondary battery electrode of the present invention.

[0040] Examples of secondary batteries include lithium ion batteries and sodium ion batteries.

[0041] The secondary battery of the present invention is equipped with the secondary battery electrode of the present invention, and since the electrolyte solution is sufficiently permeated into the electrode, it has excellent charge / discharge efficiency (Coulomb efficiency) and direct current resistance (DCR).

[0042] Known materials can be used for the components of the secondary battery of the present invention other than the electrodes for the secondary battery. That is, known materials can be used as the materials for the current collector, the electrolyte, the separator, and the like. As the electrolyte, it is preferable to use a non-aqueous solvent such as ethylene carbonate, diethyl carbonate, or propylene carbonate. As the electrolyte contained in the electrolytic solution, electrolytes used in known electrolytic solutions can be used. For example, in the case of a lithium ion battery, a lithium salt can be used, and in the case of a sodium ion battery, a sodium salt can be used.

[0043] Examples of lithium salts include lithium salts of inorganic anions such as LiPF, LiBF, LiSbF, LiAsF, LiClO, and LiN(FSO), and lithium salts of organic anions such as LiN(CFSO), LiN(CFS0), and LiC(CFSO). Of these, LiPF (lithium hexafluorophosphate), LiFSI (lithium bis(fluorosulfonyl)imide), and the like are preferably used.

[0044] Examples of sodium salts include inorganic sodium salts such as NaPF6, NaBF4, NaClO4, and NaAsF6, and organic sodium salts such as NaCF3SO3, NaN(CF3SO2)2, NaN(C2F5SO2)2, NaN(FSO2)2, and NaC(CF3SO2)3. Of these, NaPF6 is preferred from the viewpoint of battery output and charge / discharge cycle characteristics.

[0045] The concentration of the electrolyte in the electrolytic 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.

[0046] In the secondary battery of the present invention, only the positive electrode may be composed of the secondary battery electrode of the present invention, only the negative electrode may be composed of the secondary battery electrode of the present invention, or both the positive electrode and the negative electrode may be composed of the secondary battery electrode of the present invention.

[0047] The secondary battery of the present invention can be used as a secondary battery for use in mobile phones, personal computers, hybrid vehicles, electric vehicles, stationary power sources, and the like.

[0048] The present specification discloses the following:

[0049] The present disclosure (1) is an electrode composition for a secondary battery containing an electrode active material, a binder resin, and a compound (A) that is an alkylene oxide adduct of a polyhydric alcohol, wherein the average number of moles of the alkylene oxide added is 20 to 690, the alkylene oxide contains ethylene oxide, the saponification value of the compound (A) is less than 5, and the content of the compound (A) is 0.01 to 2.0 wt % based on the solid content weight of the electrode composition for a secondary battery.

[0050] The present disclosure (2) is the electrode composition for a secondary battery according to the present disclosure (1), wherein the compound (A) has a hydroxyl value of 3 to 120 KOHmg / g.

[0051] The present disclosure (3) is the electrode composition for a secondary battery according to the present disclosure (1) or (2), in which the weight-average molecular weight of the compound (A) is 3,000 to 33,000.

[0052] The present disclosure (4) is an electrode composition for a secondary battery according to any one of the present disclosures (1) to (3), in which the molar ratio of ethylene oxide in the alkylene oxide is 70% or more based on the total number of moles of the alkylene oxide.

[0053] The present disclosure (5) is an electrode composition for a secondary battery according to any one of the present disclosures (1) to (4), wherein the polyhydric alcohol is at least one selected from the group consisting of ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitan, and sorbitol.

[0054] The present disclosure (6) is the electrode composition for a secondary battery according to any one of the present disclosures (1) to (5), further containing a conductive aid, wherein the content of the electrode active material is 78 to 97 wt % based on the solid content weight of the electrode composition for a secondary battery, the content of the binder resin is 1 to 20 wt % based on the solid content weight of the electrode composition for a secondary battery, and the content of the conductive aid is 1 to 6 wt % based on the solid content weight of the electrode composition for a secondary battery.

[0055] The present disclosure (7) is the electrode composition for a secondary battery according to the present disclosure (6), in which the content of the compound (A) is 2 to 50% by weight based on the weight of the conductive assistant.

[0056] The present disclosure (8) is an electrode for a secondary battery obtained by compression molding the electrode composition for a secondary battery according to any one of the present disclosures (1) to (7).

[0057] The present disclosure (9) is a secondary battery including the electrode for secondary batteries according to the present disclosure (8). [Example]

[0058] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples as long as they do not deviate from the gist of the present invention. Unless otherwise specified, parts mean parts by weight and % means % by weight.

[0059] (Preparation of Compounds (A) Nos. 1 to 18) The following Compounds (A) Nos. 1 to 18 were prepared. Table 1 shows the starting materials, the number of functional groups of the starting materials, the saponification value, the average number of moles of alkylene oxide (AO) added, the average number of moles of ethylene oxide (EO), the average number of moles of propylene oxide (PO) added, the molar ratio of ethylene oxide in alkylene oxide (EO / AO), the hydroxyl value, and the weight-average molecular weight (Mw) of Compounds (A) Nos. 1 to 18. (Compound (A) No. 1) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) and propylene oxide (PO) to propylene glycol was obtained as Compound (A) No. 1. The average number of moles of EO added was 272, and the average number of moles of PO added was 69. (Compound (A) No. 2, 13) Compounds (A) Nos. 2 and 13 were produced in the same manner as Compound (A) No. 1, except that the constitution of alkylene oxide (AO), the average number of moles of alkylene oxide (AO) added, the molar ratio of ethylene oxide (EO) in the alkylene oxide, and the molar ratio of propylene oxide (PO) in the alkylene oxide were changed as shown in Table 1.

[0060] (Compound (A) No. 3) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) and propylene oxide (PO) to glycerin was obtained as Compound (A) No. 3. The average number of moles of EO added was 324, and the average number of moles of PO added was 132.

[0061] (Compound (A) No. 4) After confirming the completion of the propylene oxide (PO) addition reaction to a polyhydric alcohol propylene oxide adduct produced by adding propylene glycol with PO, ethylene oxide (EO) was then added to the polyhydric alcohol alkylene oxide adduct, yielding Compound (A) No. 4. The average number of moles of EO added was 497, and the average number of moles of PO added was 103.

[0062] (Compound (A) No. 5, 14) Compounds (A) Nos. 5 and 14 were produced in the same manner as Compound (A) No. 4, except that the constitution of alkylene oxide (AO), the average number of moles of alkylene oxide (AO) added, the molar ratio of ethylene oxide (EO) in the alkylene oxide, and the molar ratio of propylene oxide (PO) in the alkylene oxide were changed as shown in Table 1. (Compound (A) No. 6) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) and propylene oxide (PO) to trimethylolpropane was obtained as Compound (A) No. 6. The average number of moles of EO added was 10, and the average number of moles of PO added was 68.

[0063] (Compound (A) No. 7) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) to ethylene glycol was obtained as Compound (A) No. 7. The average number of moles of EO added was 189. (Compound (A) No. 8-10, 16) Compounds (A) Nos. 8 to 10 and 16 were produced in the same manner as Compound (A) No. 7, except that the average number of moles of ethylene oxide (EO) added as alkylene oxide (AO) was changed as shown in Table 1.

[0064] (Compound (A) No. 11) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) to sorbitan was obtained as Compound (A) No. 11. The average number of moles of EO added was 690. (Compound (A) No. 12) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) to sorbitol was obtained as Compound (A) No. 12. The average number of moles of EO added was 20.

[0065] (Compound (A) No. 15) An autoclave was charged with 100 g of hydrogenated castor oil (weight-average molecular weight 940) and 0.3 g of potassium hydroxide, and then 94 g of ethylene oxide (EO) was reacted to obtain Compound (A) No. 15. The average number of moles of EO added in Compound (A) No. 15 was 40. (Compound (A) No. 17) An alkylene oxide adduct of a polyhydric alcohol produced by adding ethylene oxide (EO) to sorbitan was obtained as Compound (A) No. 17. The average number of moles of EO added was 500. (Compound (A) No. 18) An alkylene oxide adduct of a monohydric alcohol produced by adding ethylene oxide (EO) to 1-hexanol was obtained as Compound (A) No. 18. The average number of moles of EO added was 25.

[0066] [Table 1]

[0067] In Table 1, compounds (A) marked with an * are comparative examples outside the scope of the present invention.

[0068] (Preparation of positive electrode active material) The following positive electrode active materials were prepared. NCA:LiNi 0.8 Co0.15 Al 0.05 O2 ("HED NCA 7050", manufactured by BASF Toda Battery Materials LLC, volume average particle size (Dv50) 6.6 μm) NaCrO2: Sodium chromite (manufactured by Kojundo Chemical Laboratory)

[0069] (Preparation of negative electrode active material) The following negative electrode active materials were prepared. Graphite: Artificial graphite (FSN-1, manufactured by Shanshan in China, D50 particle size: 15.3 μm) HC: Hard carbon (Carbotron (registered trademark) PS (F), manufactured by Kureha Battery Materials Japan Co., Ltd., D50 particle size: 20 μm)

[0070] (Examples 1 to 10 and Comparative Examples 1 to 6: Preparation of Slurry of Positive Electrode Composition for Lithium Ion Batteries) Each compound (A) in the amount shown in Table 2 and 100.0 parts by weight of N-methyl-2-pyrrolidone (NMP) were stirred at 2000 rpm for 5 minutes using a planetary stirring mixer (Thinky Mixer, manufactured by THINKY CORPORATION). Next, polyvinylidene fluoride (PVDF, manufactured by Kishida Chemical Co., Ltd.) in the amount shown in Table 2 was added as a binder resin, and the mixture was stirred at 2000 rpm for 5 minutes using the Mixer.

[0071] Further, NCA was added as a positive electrode active material in an amount shown in Table 2, and acetylene black {AB: "Denka Black Li100", manufactured by Denka Co., Ltd., average primary particle size: 35 nm} and / or carbon nanotubes (CNT: "K-Nanos100P", manufactured by Kumho Corporation, outer diameter: 10 to 15 nm) as a conductive additive in an amount shown in Table 2. The mixture was then stirred at 2000 rpm for 4 minutes using a mixer to prepare a positive electrode composition slurry.

[0072] (Examples 11 to 21, Comparative Examples 7 to 11: Preparation of Slurry of Negative Electrode Composition for Lithium Ion Battery) Acetylene black (AB: "Denka Black Li100", manufactured by Denka Co., Ltd., average primary particle size: 35 nm) and / or carbon nanotubes (CNT: "K-Nanos100P", manufactured by Kumho Co., Ltd., outer diameter: 10-15 nm) in the amounts shown in Table 3 as a conductive additive, carboxymethyl cellulose (CMC) in the amounts shown in Table 3 as a binder resin, and 40.0 parts by weight of ion-exchanged water were mixed using a planetary stirring mixer kneader (Awatori Rentaro, manufactured by Thinky Corporation) at 2000 rpm for 5 minutes.

[0073] Next, styrene butadiene rubber (SBR) was added as a binder resin in the amount shown in Table 3, and the mixture was stirred for 5 minutes at 2000 rpm using a mixer. To the resulting dispersion, graphite in the amount shown in Table 3, each compound (A) in the amount shown in Table 3, and 60.0 parts by weight of ion-exchanged water were added as a negative electrode active material, and the mixture was stirred for 5 minutes at 2000 rpm using a mixer to prepare a negative electrode composition slurry.

[0074] (Examples 22 to 28, Comparative Examples 12 to 15: Preparation of Slurry of Positive Electrode Composition for Sodium Ion Batteries) Except for changing the positive electrode active material to NaCrO2 and adjusting the content of each component as shown in Table 4, slurries of positive electrode compositions were prepared in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 6.

[0075] (Examples 29 to 35, Comparative Examples 16 to 19: Preparation of Slurry of Negative Electrode Composition for Sodium Ion Battery) A negative electrode composition slurry was prepared in the same manner as in Examples 11 to 21 and Comparative Examples 7 to 11, except that the negative electrode active material was changed to hard carbon (HC) and the contents of each component were as shown in Table 5.

[0076] <Dispersion stability> The positive electrode composition slurry and the negative electrode composition slurry prepared above were each placed in a 100 ml screw tube and stored at room temperature for 24 hours, after which the weight of the sediment was measured. The dispersion stability was evaluated according to the following criteria, and the results are shown in Tables 2 to 5. ⊚: The weight of sediment is less than 5% by weight, and the dispersion stability is very good. Good: The weight of the sediment is 5% by weight or more and less than 10% by weight, and the dispersion stability is excellent. Δ: The weight of the sediment is 10% by weight or more and less than 30% by weight, and the dispersion stability is poor. ×: The weight of sediment is 30% by weight or more, and the dispersion stability is very poor.

[0077] <Applicability> The slurry of the positive electrode composition prepared above was applied to the surface of a current collector (10 cm × 15 cm, carbon-coated aluminum foil [product name "Carbon-Coated Aluminum Foil"], manufactured by Toyo Aluminum Co., Ltd.) so that the basis weight was 10 mg / cm. 2 The coating was applied to an area of ​​10 cm x 10 cm and a thickness of 40 ± 10 μm, and then heated to a temperature of 150°C to dry. The slurry of the negative electrode composition prepared above was applied to the surface of a current collector (10 cm x 15 cm, copper foil) so that the basis weight was 10 mg / cm 2 The coating was applied to an area of ​​10 cm x 10 cm and a thickness of 40 ± 10 μm, and then heated to a temperature of 150°C to dry. The coated area of ​​the current collector surface was observed using a one-shot shape measuring device (manufactured by Keyence). The entire coated surface was measured in 3D, and areas where the difference between the average value and the minimum value was 30 μm or more were considered to be defective areas. The evaluation criteria for coatability were set based on the area ratio of these defective areas, and evaluation was performed. The results are shown in Tables 2 to 5. ○: The coating area is 98% or more, and there is no cracking on the coated surface when it dries, showing excellent coating properties. △: Cracks occurred on the coated surface when drying, and the coated area was 95% or more but less than 98%, indicating slightly poor coatability. ×: Cracking occurred on the coated surface during drying, and the coated area was less than 95%, indicating poor coatability.

[0078] <Drying> The slurry of the positive electrode composition prepared above was applied to the surface of a current collector (10 cm × 15 cm, carbon-coated aluminum foil [product name "Carbon-Coated Aluminum Foil"], manufactured by Toyo Aluminum Co., Ltd.) at a rate of 10 mg / cm. 2 After application, the time until the applied surface dried at a temperature of 150°C was measured visually. The slurry of the negative electrode composition prepared above was applied to the surface of a current collector (10 cm x 15 cm, copper foil) in an amount of 10 mg / cm 2 After application, the time until the applied surface dried at a temperature of 150°C was measured visually. The drying property was evaluated according to the following criteria. The results are shown in Tables 2 to 5. Good: Drying time is 200 seconds or less, and drying is good. △: Drying time is more than 200 seconds and 300 seconds or less, and drying property is slightly poor. ×: The drying time was more than 300 seconds, and the waiting time was long, which hindered workability and resulted in poor drying properties.

[0079] (Making lithium-ion batteries) 1. Preparation of lithium ion batteries using the positive electrode compositions of Examples 1 to 10 and Comparative Examples 1 to 6 1.1 Preparation of positive electrodes for lithium ion batteries using the positive electrode compositions of Examples 1 to 10 and Comparative Examples 1 to 6 The slurries of the positive electrode compositions of Examples 1 to 10 and Comparative Examples 1 to 6 were applied to one side of a current collector {carbon-coated aluminum foil [product name "Carbon-Coated Aluminum Foil"], manufactured by Toyo Aluminum Co., Ltd.} using a wire bar in the atmosphere, pre-dried overnight in a draft, punched out to a size of 16 mm diameter, dried at 100°C for 2 hours, and pressed with a press to produce positive electrodes.

[0080] 1.2 Preparation of negative electrode for battery evaluation 90.9 parts by weight of artificial graphite (FSN-1, manufactured by Shanshan China Co., Ltd.) as the negative electrode active material, 5.1 parts by weight of AB as the conductive additive, and 2.0 parts by weight of SBR and 2.0 parts by weight of CMC as binders were mixed with NMP to obtain a mixed solution (solids concentration 10% by weight). The mixed solution was stirred at 2000 rpm for 1 minute using a planetary stirring mixer (Awatori Rentaro [manufactured by Thinky Corporation]) to prepare a slurry for the negative electrode active material layer. The obtained slurry was applied to one side of a current collector (copper foil) using a wire bar in the atmosphere, pre-dried overnight in a draft, and then punched out to a diameter of 16 mm, dried at 100°C for 2 hours, and pressed in a press to prepare a negative electrode for battery evaluation.

[0081] 1.3 Battery construction From the positive electrode side, a positive electrode using the positive electrode composition of Examples 1 to 10 and Comparative Examples 1 to 6, a separator (product name "#3501" manufactured by Celgard Inc.), and a negative electrode for battery evaluation were stacked in this order, electrolyte 1 was injected, and then the mixture was vacuum laminated to prevent oxygen from entering, thereby producing a lithium ion battery for use in charge / discharge tests. The electrolyte used was electrolyte 1 (EC / DEC=1 / 1 (volume ratio), LiPF61M). EC stands for ethylene carbonate, DEC stands for diethyl carbonate, and LiPF6 stands for lithium hexafluorophosphate.

[0082] 2. Preparation of Lithium-Ion Batteries Using Negative Electrode Compositions of Examples 11 to 21 and Comparative Examples 7 to 11 2.1 Preparation of negative electrodes for lithium ion batteries using negative electrode compositions of Examples 11 to 21 and Comparative Examples 7 to 11 The slurries of the negative electrode compositions obtained above in Examples 11 to 21 and Comparative Examples 7 to 11 were applied to one side of a current collector (copper foil) using a wire bar in the atmosphere, pre-dried overnight in a draft, and then punched out to a size of 16 mm in diameter. The resulting paste was further dried at 100°C under reduced pressure (1.3 kPa) for 2 hours, and pressed in a press to a target electrode density (electrode thickness) to produce negative electrodes.

[0083] 2.2 Preparation of positive electrode for battery evaluation A mixture (solid content: 10 wt%) was prepared by mixing 90 parts by weight of NCA as a positive electrode active material, 5.0 parts by weight of AB as a conductive additive, and 5.0 parts by weight of PVDF as a binder with NMP. The mixture was stirred at 2000 rpm for 1 minute using a planetary stirring mixer (Thinky Mixer, manufactured by THINKY CORPORATION) to prepare a slurry for the positive electrode active material layer. The obtained slurry was applied to one side of a current collector {carbon-coated aluminum foil [product name "Carbon-Coated Aluminum Foil"], manufactured by Toyo Aluminum Co., Ltd.} using a wire bar in the atmosphere, pre-dried overnight in a draft, and then punched out to a size of 16 mm diameter, dried at 100°C for 2 hours, and pressed in a press to prepare a positive electrode for battery evaluation.

[0084] 2.3 Battery construction Lithium ion batteries were fabricated in the same manner as in 1.3 above, except that negative electrodes using the negative electrode compositions of Examples 11 to 21 and Comparative Examples 7 to 11 and positive electrodes for battery evaluation fabricated in 2.2 above were used.

[0085] (Making sodium-ion batteries) 1. Preparation of sodium ion batteries using the positive electrode compositions of Examples 22 to 28 and Comparative Examples 12 to 15 1.1 Preparation of positive electrodes for sodium ion batteries using the positive electrode compositions of Examples 22 to 28 and Comparative Examples 12 to 15 The slurries of the positive electrode compositions of Examples 22 to 28 and Comparative Examples 12 to 15 were applied to one side of a current collector {carbon-coated aluminum foil [product name "Carbon-Coated Aluminum Foil"], manufactured by Toyo Aluminum Co., Ltd.} using a wire bar in the atmosphere, pre-dried overnight in a draft, punched out to a size of 16 mm diameter, dried at 100°C for 2 hours, and pressed with a press to produce positive electrodes.

[0086] 1.2 Preparation of negative electrode for battery evaluation A mixture (solids concentration 10 wt%) was obtained by mixing 90.9 parts by weight of hard carbon (Carbotron® PS(F), manufactured by Kureha Battery Materials Japan Co., Ltd.) as the negative electrode active material, 5.1 parts by weight of AB as the conductive additive, and 2.0 parts by weight of SBR and 2.0 parts by weight of CMC as binders with NMP. The mixture was stirred at 2000 rpm for 1 minute using a planetary stirring mixer (Awatori Rentaro [manufactured by Thinky Corporation]) to prepare a slurry for the negative electrode active material layer. The obtained slurry was applied to one side of a current collector (copper foil) using a wire bar in the atmosphere, pre-dried overnight in a draft, and then punched out to a diameter of 16 mm, dried at 100°C for 2 hours, and pressed in a press to prepare a negative electrode for battery evaluation.

[0087] 1.3 Battery construction Starting from the positive electrode side, a positive electrode using the positive electrode composition of Examples 22 to 28 and Comparative Examples 12 to 15, a separator [product name "#3501", manufactured by Celgard Inc.], and a negative electrode for battery evaluation were stacked in this order, electrolyte 2 was injected, and then the mixture was vacuum laminated to prevent oxygen from entering, thereby producing a sodium ion battery for use in charge / discharge tests. The electrolyte used was electrolyte 2 (EC / DEC=1 / 1 (volume ratio), NaPF61M). EC stands for ethylene carbonate, DEC stands for diethyl carbonate, and NaPF6 stands for sodium hexafluorophosphate.

[0088] 2. Preparation of sodium ion batteries using negative electrode compositions of Examples 29 to 35 and Comparative Examples 16 to 19 2.1 Preparation of negative electrodes for sodium ion batteries using negative electrode compositions of Examples 29 to 35 and Comparative Examples 16 to 19 The slurries of the negative electrode compositions obtained above in Examples 29 to 35 and Comparative Examples 16 to 19 were applied to one side of a current collector (copper foil) using a wire bar in the atmosphere, pre-dried overnight in a draft, and then punched out to a diameter of 16 mm, further dried at 100°C under reduced pressure (1.3 kPa) for 2 hours, and pressed in a press to a target electrode density (electrode thickness) to produce negative electrodes.

[0089] 2.2 Preparation of positive electrode for battery evaluation A mixture (solid content: 10 wt%) was prepared by mixing 290 parts by weight of NaCrO as a positive electrode active material, 5.0 parts by weight of AB as a conductive additive, and 5.0 parts by weight of PVDF as a binder with NMP. The mixture was stirred at 2000 rpm for 1 minute using a planetary stirring mixer (Thinky Mixer, manufactured by THINKY CORPORATION) to prepare a slurry for the positive electrode active material layer. The obtained slurry was applied to one side of a current collector {carbon-coated aluminum foil [product name "Carbon-Coated Aluminum Foil"], manufactured by Toyo Aluminum Co., Ltd.} using a wire bar in the atmosphere, pre-dried overnight in a draft, and then punched out to a size of 16 mm diameter, dried at 100°C for 2 hours, and pressed in a press to prepare a positive electrode for battery evaluation. 2.3 Battery construction Sodium ion batteries were fabricated in the same manner as in 1.3 above, except that negative electrodes using the negative electrode compositions of Examples 29 to 35 and Comparative Examples 16 to 19 and positive electrodes for battery evaluation fabricated in 2.2 above were used.

[0090] <Charge / discharge test: Measurement of initial coulombic efficiency> The initial performance of the lithium ion battery and sodium ion battery prepared above was evaluated at 25°C using a charge / discharge measuring device "HJ-SD8" (manufactured by Hokuto Denko Corporation) according to the following method. Using the constant current constant voltage charging method (also known as CCCV mode), the battery was charged to 0.0V at a current of 0.05C, and then maintained at 0.0V until the current reached 0.0025C. After a 10-minute break, the battery was discharged to 1.5V at a current of 0.05C. The charged capacity was defined as [initial charge capacity (mAh)], and the discharged capacity was defined as [initial discharge capacity (mAh)]. The initial coulombic efficiency was calculated using the following formula, and the results are shown in Tables 2 to 5. [Initial coulomb efficiency (%)] = [Initial discharge capacity] ÷ [Initial charge capacity] × 100

[0091] <First DCR> The DC resistance (initial DCR) at the first cycle was measured for the lithium-ion battery and sodium-ion battery fabricated above. The initial DCR was calculated from the voltage drop over 10 seconds from the start of discharge at the first cycle. The results are shown in Tables 2 to 5.

[0092] <Measurement of high-temperature durability of lithium-ion batteries> The lithium-ion battery fabricated above was evaluated using a charge / discharge measuring device "HJ-SD8" (manufactured by Hokuto Denko Corporation) at 70°C according to the following method. The lithium-ion battery was placed in a thermostatic chamber at 70°C for evaluation. The battery was charged to 4.2V at a current of 0.05C using a constant current / constant voltage charging method (also known as CCCV mode), and after a 10-minute break, it was discharged to 2.5V at a current of 0.05C. The above charge / discharge cycle was repeated 10 times, and the discharge capacity (%) at the 10th cycle relative to the discharge capacity at the 1st cycle was defined as the high-temperature durability (10 cycles). The results are shown in Tables 2 and 3.

[0093] <Measurement of high-temperature durability of sodium-ion batteries> The sodium-ion battery fabricated above was evaluated using a charge / discharge measuring device "HJ-SD8" (manufactured by Hokuto Denko Corporation) at 70°C according to the following method. The sodium-ion battery was placed in a thermostatic chamber at 70°C for evaluation. The battery was charged to 3.7 V at a current of 0.05 C using a constant current / constant voltage charging method (also known as CCCV mode), and after a 10-minute break, it was discharged to 2.5 V at a current of 0.05 C. The above charge / discharge cycle was repeated 10 times, and the discharge capacity (%) at the 10th cycle relative to the discharge capacity at the 1st cycle was defined as the high-temperature durability (10 cycles). The results are shown in Tables 4 and 5.

[0094] [Table 2]

[0095] [Table 3]

[0096] [Table 4]

[0097] [Table 5]

[0098] The electrode compositions for lithium ion batteries and the lithium ion batteries of Examples 1 to 21 were superior in uniformity and drying properties of the slurry coating film of the electrode composition, and also superior in durability of the battery at high temperatures, compared to the electrode compositions for lithium ion batteries and the lithium ion batteries of Comparative Examples 1 to 11. Similarly, the sodium ion battery electrode compositions and sodium ion batteries of Examples 22 to 35 were superior in uniformity and drying properties of the slurry coating film of the electrode composition, and also in durability of the battery at high temperatures, compared to the sodium ion battery electrode compositions and sodium ion batteries of Comparative Examples 12 to 19. Examples 1, 4 to 11, 13 to 16, and 18 to 20, which used electrode compositions containing Compound (A) Nos. 1 to 5, 7 to 9, and 11, exhibited excellent slurry dispersion stability in addition to the above effects. In particular, the electrode compositions of Examples 4, 6, 8, 16 and 18, which contained 1.0 wt % of Compound (A) No. 3, 5 or 7 based on the solid content weight of the electrode composition, exhibited particularly excellent dispersion stability of the slurry. Considering Examples 3 and 13, which used Compound (A) No. 6, the molar ratio of EO in AO was less than 50% based on the total number of moles of AO in Compound (A) No. 6, and the slurry of Example 3 had poor dispersion stability. On the other hand, the slurry of Example 13 had excellent dispersion stability. Since Example 13 is a negative electrode composition in which the solvent is water, it is believed that not only the molar ratio of EO in Compound (A) but also the molecular weight and hydroxyl value of Compound (A) contributed to the dispersion stability. The electrode composition of Example 21 uses Compound (A) No. 1 and has particularly excellent dispersion stability of the slurry, which is due to the absence of a conductive additive.

Claims

1. An electrode composition for a secondary battery, comprising an electrode active material, a binder resin, and a compound (A) which is an alkylene oxide adduct of a polyhydric alcohol, the average number of moles of alkylene oxide added is 20 to 690, the alkylene oxide comprises ethylene oxide; The saponification value of the compound (A) is less than 5, The content of the compound (A) is 0.01 to 2.0% by weight based on the solid content weight of the electrode composition for secondary batteries.

2. 2. The electrode composition for a secondary battery according to claim 1, wherein the compound (A) has a hydroxyl value of 3 to 120 KOHmg / g.

3. 3. The electrode composition for a secondary battery according to claim 1, wherein the compound (A) has a weight average molecular weight of 3,000 to 33,000.

4. 3. The electrode composition for a secondary battery according to claim 1, wherein the molar ratio of ethylene oxide in the alkylene oxide is 70% or more based on the total number of moles of the alkylene oxide.

5. 3. The electrode composition for a secondary battery according to claim 1, wherein the polyhydric alcohol is at least one selected from the group consisting of ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitan, and sorbitol.

6. Further, a conductive additive is contained, the content of the electrode active material is 78 to 97 wt % based on the solid content weight of the electrode composition for secondary batteries, the content of the binder resin is 1 to 20 wt % based on the solid content weight of the electrode composition for secondary batteries, 3. The electrode composition for a secondary battery according to claim 1, wherein the content of the conductive additive is 1 to 6% by weight based on the weight of the solid content of the electrode composition for a secondary battery.

7. 7. The electrode composition for a secondary battery according to claim 6, wherein the content of the compound (A) is 2 to 50% by weight based on the weight of the conductive additive.

8. 3. A secondary battery electrode obtained by compression molding the electrode composition for a secondary battery according to claim 1 or 2.

9. A secondary battery comprising the electrode for a secondary battery according to claim 8.

Images