Non-aqueous secondary battery electrode slurry, non-aqueous secondary battery electrode, and non-aqueous secondary battery

Abstract

Provided is a nonaqueous secondary battery electrode slurry which contains a binder polymer (A) having a first structural unit derived from an aromatic ethylenically unsaturated compound (a1), a cellulose derivative (B) having a second structural unit derived from an aromatic ethylenically unsaturated compound (a2), an electrode active material (C), and a liquid medium (D). The aromatic ethylenically unsaturated compound (a1) is a nonionic aromatic compound having one independent ethylenically unsaturated bond, the degree of etherification of the cellulose derivative (B) is from 0.50 to 1.0 (inclusive), the weight-average molecular weight of the cellulose derivative (B) is from 100,000 to 700,000 (inclusive), and at least a part of the cellulose derivative (B) is dissolved in the liquid medium (D).

Description

Technical Field

[0001] The present invention relates to a non-aqueous secondary battery electrode paste, a non-aqueous secondary battery electrode, and a non-aqueous secondary battery. Background Art

[0002] A non-aqueous secondary battery, for example, has a configuration including a positive electrode containing a metal oxide or the like as an active material, a negative electrode containing a carbon material such as graphite as an active material, and an electrolyte. The non-aqueous secondary battery is a secondary battery that charges and discharges by ions moving between the positive electrode and the negative electrode.

[0003] As a representative example of the non-aqueous secondary battery, a lithium ion secondary battery can be cited. From the viewpoints of miniaturization, weight reduction, etc., the non-aqueous secondary battery is used as a power source for notebook personal computers, mobile phones, power tools, electronic / communication devices, etc. In addition, recently, from the viewpoint of application to environmentally friendly vehicles, it is also used for electric vehicles and hybrid vehicle applications. Among them, high output power, high capacity, long life, etc. of the non-aqueous secondary battery are strongly required.

[0004] As an electrode of a non-aqueous secondary battery, a configuration in which an electrode active material layer is formed on a metal current collector is widely used. As the current collector, for example, a metal foil such as aluminum or copper is used. The electrode active material layer contains an electrode active material, a binder, and a conductive additive used as needed. The electrode active material is a substance capable of inserting and extracting ions that become charge carriers. The binder has a function of bonding between the active materials and a function of bonding the active material to the current collector.

[0005] In the manufacturing process of the electrode of the non-aqueous secondary battery, for example, a paste (electrode paste) in which an electrode binder and an electrode active material are dissolved or dispersed in water is coated on the surface of the current collector and dried to form an electrode active material layer on the current collector.

[0006] For example, Patent Document 1 describes a lithium ion secondary battery electrode paste obtained by using a lithium ion secondary battery electrode binder, an electrode active material, and carboxymethyl cellulose. It is also described that a lithium ion secondary battery electrode binder is obtained by emulsion polymerization of an ethylenically unsaturated monomer containing styrene, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated carboxylic acid, and an internal crosslinking agent.

[0007] In addition, Patent Document 2 describes a secondary battery electrode having an electrode layer containing at least one polymer selected from a styrene-butadiene copolymer and a copolymer obtained from a (meth)acrylate and an ethylenically unsaturated monomer having an acid component, and a specific nonionic surfactant.

[0008] Prior Art Documents

[0009] Patent Document

[0010] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-243464

[0011] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-239070

[0012] Non-Patent Document

[0013] Non-Patent Document 1: Y. Tezuka and Y. Tshuchiya, Carbohydr. Res. 291, 99-108 (1996) Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] For an electrode paste, it is required to be able to form an electrode active material layer having a high peel strength with respect to a current collector. In addition, for an electrode paste, it is required to reduce the resistance of an electrode manufactured using the same, that is, it is required to be able to manufacture a battery having a low internal resistance using the electrode paste.

[0016] In addition, in the process of coating an electrode paste on a current collector, the viscosity of the electrode paste affects the thickness of the electrode active material layer and the state of the surface of the electrode active material layer. In order to stabilize these qualities, it is possible to consider suppressing the change in viscosity with respect to the shear rate in the electrode paste.

[0017] On the other hand, in order to improve the dispersibility of the components in the electrode paste and to make the viscosity of the electrode paste suitable for coating, components such as a thickener are often added to the electrode paste. Therefore, the electrode paste tends to exhibit behavior as a non-Newtonian fluid. That is, the electrode paste has a tendency for the change in viscosity with respect to the shear rate to become large.

[0018] Therefore, an object of the present disclosure is to provide an electrode paste that can form an electrode active material layer having a high peel strength with respect to a current collector, can manufacture a battery having a low internal resistance, and has a small change in viscosity with respect to a change in shear rate. Another object of the present disclosure is to provide a non-aqueous secondary battery electrode having an electrode active material layer having a high peel strength with respect to a current collector and a non-aqueous secondary battery having a low internal resistance.

[0019] Means for Solving the Problems

[0020] The present disclosure includes the following embodiments.

[0021] [1] A non-aqueous secondary battery electrode paste, which contains a binder polymer (A), a cellulose derivative (B), an electrode active material (C), and a liquid medium (D). The above binder polymer (A) has a first structural unit derived from an aromatic ethylenically unsaturated compound (a1). The above aromatic ethylenically unsaturated compound (a1) is a non-ionic aromatic compound having one independent ethylenically unsaturated bond. The degree of etherification of the above cellulose derivative (B) is 0.50 or more and 1.0 or less, and the weight average molecular weight is 100,000 or more and 700,000 or less. At least a part of the above cellulose derivative (B) is dissolved in the above liquid medium (D).

[0022] [2] The non-aqueous secondary battery electrode paste according to [1], wherein the content of the above first structural unit in the above binder polymer (A) is 25% by mass or more and 65% by mass or less.

[0023] [3] The non-aqueous secondary battery electrode paste according to [1], wherein the above cellulose derivative (B) contains at least one selected from carboxymethyl cellulose and its salts.

[0024] [4] The non-aqueous secondary battery electrode paste according to [1], wherein the above binder polymer (A) further has a second structural unit derived from a non-ionic (meth)acrylate (a2). The above non-ionic (meth)acrylate (a2) is a non-ionic aliphatic compound having one (meth)acryloyl group and does not have an ethylenically unsaturated bond other than the (meth)acryloyl group.

[0025] [5] The non-aqueous secondary battery electrode paste according to [4], wherein the content of the above first structural unit in the above binder polymer (A) is 25% by mass or more and 65% by mass or less, and the content of the above second structural unit is 25% by mass or more and 70% by mass or less.

[0026] [6] The non-aqueous secondary battery electrode paste according to [4], wherein the above binder polymer (A) further has a third structural unit derived from an anionic unsaturated compound (a3). The above anionic unsaturated compound (a3) has an anionic functional group and one independent ethylenically unsaturated bond.

[0027] [7] The non-aqueous secondary battery electrode paste according to [6], wherein the content of the above first structural unit in the above binder polymer (A) is 25% by mass or more and 65% by mass or less, the content of the above second structural unit is 25% by mass or more and 70% by mass or less, and the content of the above third structural unit is 0.30% by mass or more and 15% by mass or less.

[0028] [8] The non-aqueous secondary battery electrode paste described in [6], wherein the binder polymer (A) further has a fifth structural unit derived from an internal crosslinking agent (a5) and a sixth structural unit derived from a surfactant (a6) having an ethylenic unsaturated bond. The internal crosslinking agent (a5) has a plurality of independent ethylenic unsaturated bonds, and the surfactant (a6) having an ethylenic unsaturated bond is a compound having one independent ethylenic unsaturated bond and functioning as a surfactant.

[0029] [9] The non-aqueous secondary battery electrode paste described in [8], wherein the content of the first structural unit in the binder polymer (A) is 25% by mass or more and 65% by mass or less, the content of the second structural unit is 25% by mass or more and 70% by mass or less, the content of the third structural unit is 0.30% by mass or more and 15% by mass or less, the content of the fifth structural unit is 0.010% by mass or more and 1.0% by mass or less, and the content of the sixth structural unit is 0.10% by mass or more and 5.0% by mass or less.

[0030]

[10] The non-aqueous secondary battery electrode paste described in [4], [6], or [8], wherein the binder polymer (A) further has a fourth structural unit derived from a conjugated diene compound (a4). The conjugated diene compound (a4) is a nonionic aliphatic compound having one conjugated diene structure and having no ethylenic unsaturated bond other than the conjugated diene structure.

[0031]

[11] The non-aqueous secondary battery electrode paste described in

[10] , wherein the content of the first structural unit in the binder polymer (A) is 25% by mass or more and 65% by mass or less, the content of the fourth structural unit is 15% by mass or more and 55% by mass or less, and the total content of the second structural unit and the fourth structural unit is 25% by mass or more and 70% by mass or less.

[0032]

[12] The non-aqueous secondary battery electrode paste described in [1], wherein the content of the binder polymer (A) is 0.50 parts by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the electrode active material (C), the content of the cellulose derivative (B) is 0.50 parts by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the electrode active material (C), and the content of the liquid medium (D) is 50 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the electrode active material (C).

[0033]

[13] A non-aqueous secondary battery electrode includes a current collector and an electrode active material layer formed on the current collector. The electrode active material layer contains a binder polymer (A), a cellulose derivative (B), and an electrode active material (C). The binder polymer (A) has a first structural unit derived from an aromatic ethylenically unsaturated compound (a1), and the aromatic ethylenically unsaturated compound (a1) is a non-ionic aromatic compound having one independent ethylenically unsaturated bond. The degree of etherification of the cellulose derivative (B) is 0.50 or more and 1.2 or less, and the weight-average molecular weight is 100,000 or more and 700,000 or less.

[0034]

[14] A non-aqueous secondary battery includes the non-aqueous secondary battery electrode described in

[13] .

[0035] Advantages of the Invention

[0036] According to the present disclosure, an electrode paste can be provided that can form an electrode active material layer with high peel strength relative to a current collector, can manufacture a battery with low internal resistance, and has small viscosity variation with respect to changes in shear rate. In addition, the present disclosure can provide a non-aqueous secondary battery electrode having an electrode active material layer with high peel strength relative to a current collector and a non-aqueous secondary battery with low internal resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a graph showing the relationship between the shear rate and viscosity of the electrode paste of one example and one comparative example of the present disclosure.

[0038] Figure 2 It is a graph showing the relationship between the shear rate and viscosity of the electrode paste of another example and another comparative example of the present disclosure. DETAILED DESCRIPTION

[0039] Hereinafter, as an embodiment of the present disclosure, a non-aqueous secondary battery electrode paste, a non-aqueous secondary battery electrode, and a non-aqueous secondary battery will be described. It should be noted that the present disclosure is not limited to the embodiments described below. In the following embodiments, the constituent elements (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present disclosure.

[0040] The term “(meth)acryloyl” is a general term for acryloyl and methacryloyl, and the term “(meth)acrylate” is a general term for acrylate and methacrylate.

[0041] The term “ethylenically unsaturated bond” refers to an ethylenically unsaturated bond having radical polymerizability unless otherwise specified.

[0042] In a polymer of a compound having an ethylenically unsaturated bond, for a structural unit derived from a compound having an ethylenically unsaturated bond, the chemical structure of the part other than the ethylenically unsaturated bond of the compound is the same as the chemical structure of the part other than the part corresponding to the ethylenically unsaturated bond of the structural unit in the polymer. For example, a structural unit derived from styrene has a structure of -CH2CH(C6H5(phenyl))- in the polymer.

[0043] It should be noted that in a structural unit having an ionic functional group, even when ion exchange is performed after the polymerization step, the structural unit is named based on the structure of the polymer. For example, when sodium acrylate is polymerized and the corresponding structural unit is changed to -CH2CH(COOH)- due to ion exchange, the structural unit is set as a structural unit derived from acrylic acid.

[0044] The so-called "plurality of independent ethylenically unsaturated bonds" refers to a plurality of ethylenically unsaturated bonds that do not form a conjugated diene with each other. That is, when two double bonds form a conjugated diene structure, the number of ethylenically unsaturated bonds contained in one conjugated diene structure is one.

[0045] The so-called "non-volatile component" is the component remaining after weighing 1 g of the mixture in an aluminum dish with a diameter of 5 cm and drying it at 105 °C for 1 hour while circulating air in a dryer under 1 atmospheric pressure (1013 hPa). Examples of the form of the mixture include a solution, a dispersion, a slurry, etc., but are not limited to them. The so-called "non-volatile component concentration" is the mass ratio (mass%) of the non-volatile component after drying under the above conditions to the mass (1 g) of the composition before drying.

[0046] In the numerical ranges described in stages in the present disclosure, the upper limit value or the lower limit value described in one numerical range can be replaced with the upper limit value or the lower limit value of another numerical range described in a different stage. In addition, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range can be replaced with the value shown in the synthesis example.

[0047] Each component in the present disclosure may include a plurality of conforming compounds. When there are a plurality of substances conforming to each component in the composition, the content rate or content of each component refers to the total content rate or content of the plurality of substances present in the composition unless otherwise specified.

[0048] Regarding the term "layer" in the present disclosure, when observing the region where the layer is present, it includes not only the case where it is formed throughout the entire region but also the case where it is formed only in a part of the region.

[0049] <1. Non-aqueous secondary battery electrode paste>

[0050] The non-aqueous secondary battery electrode paste of the present disclosure contains a binder polymer (A), a cellulose derivative (B), an electrode active material (C), and a liquid medium (D). The binder polymer (A) has a first structural unit derived from an aromatic ethylenically unsaturated compound (a1), and the aromatic ethylenically unsaturated compound (a1) is a nonionic aromatic compound having one independent ethylenic unsaturated bond. The degree of etherification of the cellulose derivative (B) is 0.50 or more and 1.2 or less, and the weight average molecular weight is 100,000 or more and 700,000 or less. The cellulose derivative (B) is dissolved in the liquid medium (D).

[0051] Hereinafter, the components of the binder polymer (A), the cellulose derivative (B), the electrode active material (C), and the liquid medium (D) will be described. The non-aqueous secondary battery electrode paste may contain other components such as a conductive additive in addition to these components.

[0052] It should be noted that hereinafter, the non-aqueous secondary battery electrode paste may sometimes be referred to as an electrode paste. The electrode paste is preferably used for manufacturing an electrode of a lithium ion secondary battery, and more preferably used for manufacturing a negative electrode of a lithium ion secondary battery.

[0053] 〔1-1. Binder polymer (A)〕

[0054] The binder polymer (A) has a first structural unit derived from an aromatic ethylenically unsaturated compound (a1). The binder polymer (A) may also be a copolymer having other structural units.

[0055] As other structural units, preferably selected are a second structural unit derived from a nonionic (meth)acrylate (a2), a third structural unit derived from an anionic unsaturated compound (a3), a fourth structural unit derived from a conjugated diene compound (a4), a fifth structural unit derived from an internal crosslinking agent (a5), and a sixth structural unit derived from a surfactant having an ethylenic unsaturated bond (hereinafter sometimes referred to as "polymerizable surfactant (a6)"), etc. In addition, the binder polymer (A) may have structural units other than the above structural units.

[0056] As a form of the binder polymer (A), it has a first structural unit, a second structural unit, a third structural unit, a fifth structural unit, and a sixth structural unit. As another form of the binder polymer (A), it has a first structural unit, a second structural unit, a third structural unit, a fourth structural unit, a fifth structural unit, and a sixth structural unit. As yet another form of the binder polymer (A), it has a first structural unit, a second structural unit, and a third structural unit. As yet another form of the binder polymer (A), it has a first structural unit, a second structural unit, and a third structural unit. As yet another form of the binder polymer (A), it has a first structural unit and a second structural unit. As yet another form of the binder polymer (A), it has a first structural unit, a second structural unit, and a fourth structural unit. It should be noted that the binder polymer (A) is not limited to the constitutions exemplified herein.

[0057] Details of (a1) to (a6) exemplified herein are described below. It should be noted that (a1) to (a5) are different from the polymerizable surfactant (a6) in terms of the function of having or not having surface activity.

[0058] A surfactant is a compound that can form micelles in water (having a critical micelle concentration).

[0059] [1-1-1. Aromatic ethylenically unsaturated compound (a1)]

[0060] In the present disclosure, the aromatic ethylenically unsaturated compound (a1) is a nonionic aromatic compound having one independent ethylenically unsaturated bond. The aromatic ethylenically unsaturated compound (a1) preferably has an aryl group, more preferably a phenyl group, but is not limited thereto. The ethylenically unsaturated bond preferably forms a vinyl group, but is not limited thereto. The aromatic ethylenically unsaturated compound (a1) may contain a single compound or two or more compounds.

[0061] Examples of the aromatic ethylenically unsaturated compound (a1) include styrene, tert-butylstyrene, p-methylstyrene, (meth)acrylic acid benzyl ester, etc. The aromatic ethylenically unsaturated compound (a1) preferably contains an aromatic vinyl compound, more preferably contains at least one compound selected from styrene and styrene derivatives, and further preferably contains styrene.

[0062] [1-1-2. Nonionic (meth)acrylate (a2)]

[0063] The nonionic (meth)acrylate (a2) is a nonionic aliphatic compound having one (meth)acryloyl group. The nonionic (meth)acrylate (a2) does not have an ethylenic unsaturated bond other than the (meth)acryloyl group. The nonionic (meth)acrylate (a2) may contain a single compound or two or more compounds.

[0064] The nonionic (meth)acrylate (a2) preferably contains an alkyl (meth)acrylate. Examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and the like.

[0065] The nonionic (meth)acrylate (a2) may also have a structure other than an alkyl group. The nonionic (meth)acrylate (a2) having a structure other than an alkyl group preferably has at least one selected from a hydroxyl group and a cyano group, and more preferably has a hydroxyl group. Examples of the nonionic (meth)acrylate (a2) having a hydroxyl group include hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, etc., but are not limited thereto.

[0066] [1-1-3. Anionic unsaturated compound (a3)]

[0067] The anionic unsaturated compound (a3) is a compound having an anionic functional group and one independent ethylenic unsaturated bond. Examples of the anionic functional group include a carboxyl group, a sulfo group, and a phosphoric acid group. The anionic functional group may also form a salt. The anionic unsaturated compound (a3) preferably contains a compound having at least one selected from a carboxyl group, a sulfo group, and their salts, and more preferably contains a compound having a carboxyl group. In addition, the anionic unsaturated compound (a3) is preferably formed of an aliphatic compound, but may also contain an aromatic compound.

[0068] The anionic unsaturated compound (a3) may contain a single compound or two or more compounds. The anionic unsaturated compound (a3) may also contain two or more compounds having different anionic functional groups. The anionic unsaturated compound (a3) may have one anionic functional group in one molecule or two or more anionic functional groups. The anionic unsaturated compound (a3) may also contain one or two or more compounds having a plurality of anionic functional groups.

[0069] The binder polymer (A) preferably contains at least one selected from the 31st structural unit and the 32nd structural unit, more preferably contains at least the 31st structural unit. The above 31st structural unit is derived from the first anionic unsaturated compound (a31) having an anionic functional group that has not formed a salt, and the above 32nd structural unit is derived from the second anionic unsaturated compound (a32) in which all anionic functional groups have formed a salt.

[0070] Examples of the first anionic unsaturated compound (a31) include unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid; unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid; half-esters of unsaturated dicarboxylic acids; and p-styrenesulfonic acid. Among them, the first anionic unsaturated compound (a31) preferably contains at least one selected from (meth)acrylic acid and itaconic acid, and more preferably contains (meth)acrylic acid.

[0071] Examples of the second anionic unsaturated compound (a32) include compounds in which all anionic functional groups in the first anionic unsaturated compound (a31) exemplified above have formed salts. The salt is not particularly limited, but is preferably at least one selected from alkali metal salts and ammonium salts, more preferably at least one selected from sodium salts, lithium salts, and ammonium salts, further preferably a sodium salt or an ammonium salt, and particularly preferably a sodium salt.

[0072] [1-1-4. Conjugated diene compound (a4)]

[0073] The conjugated diene compound (a4) is a nonionic aliphatic compound having one conjugated diene structure. The conjugated diene compound (a4) does not have an ethylenic unsaturated bond other than the conjugated diene structure. The conjugated diene compound (a4) may contain a single compound or two or more compounds. The conjugated diene compound (a4) preferably contains a compound having 10 or fewer carbon atoms, and more preferably contains a compound having 5 or fewer carbon atoms. The conjugated diene compound (a4) preferably contains a hydrocarbon.

[0074] Examples of the conjugated diene compound (a4) include 1,3-butadiene, isoprene, 1,3-pentadiene, 1,3-hexadiene, 1,3-heptadiene, 2,3-dimethylbutadiene, 2-chloro-1,3-butadiene, 3-methyl-1,3-pentadiene, isoprene (2-methyl-1,3-butadiene), etc., but are not limited to them. The conjugated diene compound (a4) preferably contains 1,3-butadiene.

[0075] [1-1-5. Internal crosslinking agent (a5)]

[0076] The internal crosslinking agent (a5) has multiple independent ethylenically unsaturated bonds. The internal crosslinking agent (a5) may contain a single compound or two or more compounds. The ethylenically unsaturated bonds contained in the internal crosslinking agent (a5) preferably form vinyl groups bonded to aryl groups or (meth)acryloyl groups, but are not limited thereto. The internal crosslinking agent (a5) more preferably contains vinyl groups bonded to aryl groups. The number of ethylenically unsaturated bonds contained in the internal crosslinking agent (a5) is preferably 2 to 4, more preferably 2 to 3, and further preferably 2.

[0077] The forms of the ethylenically unsaturated bonds contained in one molecule of the internal crosslinking agent (a5) may be included as a single type or two or more types. In addition, the internal crosslinking agent (a5) is preferably a nonionic compound.

[0078] Examples of the internal crosslinking agent (a5) include divinylbenzene, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, etc., but are not limited thereto.

[0079] [1-1-6. Polymerizable surfactant (a6)]

[0080] The polymerizable surfactant (a6) is a compound having one independent ethylenically unsaturated bond and functioning as a surfactant. The polymerizable surfactant (a6) is not particularly limited, but is preferably an anionic surfactant, and more preferably contains at least one selected from sulfonates and sulfates. The polymerizable surfactant (a6) may contain a single compound or two or more compounds. As the polymerizable surfactant (a6), it is preferably to contain at least any one of the compounds represented by the following chemical formulas (1) to (4), and more preferably contains the compound represented by the following chemical formula (2).

[0081] [Chemical formula 1]

[0082]

[0083] In formula (1), R 1 is preferably an alkyl group, and p is preferably an integer of 10 to 40. The carbon number of R 1 is more preferably 10 to 40, and R 1 is further preferably a straight-chain unsubstituted alkyl group having 10 to 40 carbon atoms.

[0084] [Chemical formula 2]

[0085]

[0086] In formula (2), R 2 is preferably an alkyl group, and q is preferably an integer of 10 to 12. R2 The carbon number of R is more preferably 10 to 40. 2 It is further preferably a straight-chain unsubstituted alkyl group having 10 to 40 carbon atoms.

[0087] [Chemical formula 3]

[0088]

[0089] In formula (3), R 3 is preferably an alkyl group, and M 1 is preferably NH4 or Na. The carbon number of R 3 is more preferably 10 to 40, and R 3 is further preferably a straight-chain unsubstituted alkyl group having 10 to 40 carbon atoms.

[0090] [Chemical formula 4]

[0091]

[0092] In formula (4), R 4 is preferably an alkyl group, and M 2 is more preferably NH4 or Na. The carbon number of R 4 is more preferably 10 to 40, and R 4 is further preferably a straight-chain unsubstituted alkyl group having 10 to 40 carbon atoms.

[0093] [1-1-7. Composition of Binder Polymer (A)]

[0094] The content rate of the first structural unit in the binder polymer (A) is preferably 25% by mass or more, more preferably 35% by mass or more, and further preferably 40% by mass or more.

[0095] The content rate of the first structural unit in the binder polymer (A) is preferably 65% by mass or less, more preferably 55% by mass or less, and further preferably 50% by mass or less.

[0096] When the binder polymer (A) contains the second structural unit, the content rate of the second structural unit in the binder polymer (A) is preferably 25% by mass or more, more preferably 35% by mass or more, and further preferably 40% by mass or more. However, when the binder polymer (A) contains the fourth structural unit, the content rate of the second structural unit is not necessarily preferably in this range.

[0097] When the binder polymer (A) contains the second structural unit, the content rate of the second structural unit in the binder polymer (A) is preferably 70% by mass or less, more preferably 60% by mass or less, and further preferably 50% by mass or less. However, when the binder polymer (A) contains the fourth structural unit, the content rate of the second structural unit is not necessarily preferably in this range.

[0098] When the binder polymer (A) contains the second structural unit, the content ratio of the first structural unit in the binder polymer (A) is preferably 25% by mass or more and 65% by mass or less, and the content ratio of the second structural unit is preferably 25% by mass or more and 70% by mass or less.

[0099] When the binder polymer (A) contains the second structural unit having a hydroxyl group, the content ratio of the second structural unit having a hydroxyl group in the binder polymer (A) is preferably 0.50% by mass or more, more preferably 1.0% by mass or more, and still more preferably 1.5% by mass or more.

[0100] When the binder polymer (A) contains the second structural unit having a hydroxyl group, the content ratio of the second structural unit having a hydroxyl group in the binder polymer (A) is preferably 5.0% by mass or less, more preferably 3.5% by mass or less, and still more preferably 2.5% by mass or less.

[0101] When the binder polymer (A) contains the third structural unit, the content ratio of the third structural unit in the binder polymer (A) is preferably 0.30% by mass or more, more preferably 0.80% by mass or more, and still more preferably 1.30% by mass or more.

[0102] When the binder polymer (A) contains the third structural unit, the content ratio of the third structural unit in the binder polymer (A) is preferably 15% by mass or less, more preferably 10% by mass or less, and still more preferably 8.0% by mass or less.

[0103] When the binder polymer (A) contains the second structural unit and the third structural unit, the content ratio of the first structural unit in the binder polymer (A) is preferably 25% by mass or more and 65% by mass or less, the content ratio of the second structural unit is preferably 25% by mass or more and 70% by mass or less, and the content ratio of the third structural unit is preferably 0.30% by mass or more and 15% by mass or less.

[0104] When the binder polymer (A) contains the 31st structural unit, the content ratio of the 31st structural unit in the binder polymer (A) is preferably 0.20% by mass or more, more preferably 0.50% by mass or more, and still more preferably 0.70% by mass or more.

[0105] When the binder polymer (A) contains the 31st structural unit, the content ratio of the 31st structural unit in the binder polymer (A) is preferably 10% by mass or less, more preferably 8.0% by mass or less, and still more preferably 6.5% by mass or less.

[0106] When the binder polymer (A) contains the 32nd structural unit, the content rate of the 32nd structural unit in the binder polymer (A) is preferably 0.10% by mass or more, more preferably 0.30% by mass or more, and further preferably 0.50% by mass or more.

[0107] When the binder polymer (A) contains the 32nd structural unit, the content rate of the 32nd structural unit in the binder polymer (A) is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and further preferably 1.0% by mass or less.

[0108] When the binder polymer (A) contains the 4th structural unit, the content rate of the 4th structural unit in the binder polymer (A) is preferably 15% by mass or more, more preferably 25% by mass or more, and further preferably 30% by mass or more.

[0109] When the binder polymer (A) contains the 4th structural unit, the content rate of the 4th structural unit in the binder polymer (A) is preferably 55% by mass or less, more preferably 45% by mass or less, and further preferably 35% by mass or less.

[0110] When the binder polymer (A) contains the 2nd structural unit and the 4th structural unit, the total content rate of the 2nd structural unit and the 4th structural unit in the binder polymer (A) is preferably 25% by mass or more, more preferably 35% by mass or more, and further preferably 45% by mass or more.

[0111] When the binder polymer (A) contains the 2nd structural unit and the 4th structural unit, the total content rate of the 2nd structural unit and the 4th structural unit in the binder polymer (A) is preferably 70% by mass or less, more preferably 63% by mass or less, and further preferably 58% by mass or less.

[0112] When the binder polymer (A) contains the 2nd structural unit and the 4th structural unit, the content rate of the 1st structural unit in the binder polymer (A) is preferably 25% by mass or more and 65% by mass or less, the content rate of the 4th structural unit is preferably 15% by mass or more and 55% by mass or less, and the total content rate of the 2nd structural unit and the 4th structural unit is preferably 25% by mass or more and 70% by mass or less.

[0113] When the binder polymer (A) contains the 5th structural unit, the content rate of the 5th structural unit in the binder polymer (A) is preferably 0.010% by mass or more, more preferably 0.030% by mass or more, and further preferably 0.040% by mass or more.

[0114] When the binder polymer (A) contains the fifth structural unit, the content rate of the fifth structural unit in the binder polymer (A) is preferably 1.0% by mass or less, more preferably 0.50% by mass or less, and still more preferably 0.10% by mass or less.

[0115] When the binder polymer (A) contains the sixth structural unit, the content rate of the sixth structural unit in the binder polymer (A) is preferably 0.10% by mass or more, more preferably 0.20% by mass or more, and still more preferably 0.30% by mass or more.

[0116] When the binder polymer (A) contains the sixth structural unit, the content rate of the sixth structural unit in the binder polymer (A) is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and still more preferably 2.0% by mass or less.

[0117] When the binder polymer (A) contains the second structural unit, the fifth structural unit, and the sixth structural unit, the content rate of the first structural unit is preferably 25% by mass or more and 65% by mass or less, the content rate of the second structural unit is preferably 25% by mass or more and 70% by mass or less, the content rate of the third structural unit is preferably 0.30% by mass or more and 15% by mass or less, the content rate of the fifth structural unit is preferably 0.010% by mass or more and 1.0% by mass or less, and the content rate of the above-mentioned sixth structural unit is preferably 0.10% by mass or more and 5.0% by mass or less.

[0118] [1-1-8. Glass transition temperature of the binder polymer (A)]

[0119] The glass transition temperature Tg of the binder polymer (A) is the peak temperature of the DDSC graph obtained as the temperature differential of DSC by performing DSC measurement (differential scanning calorimetry) at a heating rate of 10 °C / min in a nitrogen atmosphere using EXSTAR DSC / SS7020 manufactured by Hitachi High-Technologies Corporation.

[0120] The glass transition temperature Tg of the binder polymer (A) is preferably -30 °C or higher, more preferably -20 °C or higher, and still more preferably -10 °C or higher. This is to improve the cycle use characteristics of the non-aqueous secondary battery made using the binder polymer (A).

[0121] The glass transition temperature Tg of the binder polymer (A) is preferably 100 °C or lower, more preferably 50 °C or lower, and still more preferably 30 °C or lower. This is to improve the adhesion of the electrode active material layer containing the binder polymer (A) to the current collector foil.

[0122] [1-2. Cellulose derivative (B)]

[0123] The cellulose derivative (B) has a structure in which at least a part of the hydrogen atoms of the hydroxyl groups contained in cellulose is substituted, and it is easy to disperse the electrode active material (C) in the electrode paste. In the electrode paste of the present disclosure, at least a part of the cellulose derivative (B) is dissolved in the liquid medium (D) described later. In the electrode paste of the present disclosure, it is preferable that all of the cellulose derivative (B) contained is dissolved in the liquid medium (D), and a part may not be dissolved.

[0124] Examples of the cellulose derivative (B) include carboxymethyl cellulose (CMC), hydroxyethyl cellulose, hydroxypropyl cellulose, salts of CMC, etc. The cellulose derivative (B) may contain a single compound or two or more compounds. The cellulose derivative (B) preferably contains at least one selected from CMC and salts of CMC, and more preferably contains a salt of CMC. Examples of the salt of CMC include alkali metal salts of CMC, ammonium salts of CMC, etc., and alkali metal salts of CMC are preferred. As the alkali metal, Na, K or Li is preferred, and Na is more preferred.

[0125] The degree of etherification of the cellulose derivative (B) is 0.50 or more, preferably 0.55 or more, and more preferably 0.60 or more. This is to improve the dispersibility of the electrode active material (C) in the electrode paste.

[0126] The degree of etherification of the cellulose derivative (B) is 1.2 or less, preferably 1.0 or less, and more preferably 0.80 or less. This is to reduce the resistance of the electrode formed using the electrode paste. In addition, this is to improve the peeling strength of the electrode active material layer formed using the electrode paste with respect to the current collector.

[0127] Here, the degree of etherification of the cellulose derivative (B) is the number of etherified parts in each of the three hydroxyl groups contained in one structural unit of cellulose. The degree of etherification is the value measured by 13 13C NMR described in Non-Patent Document 1. At this time, in order to easily obtain the integral value of the signal, one or both of the etherified substituents and hydroxyl groups may be converted into another substituent as needed. When the cellulose derivative (B) is CMC or its salt, on the basis of methyl esterifying the carboxyl group or its salt of the etherified part and propionylating the hydroxyl group, the measurement based on 13 13C NMR is performed.

[0128] The weight average molecular weight of the cellulose derivative (B) is 100,000 or more, preferably 200,000 or more, and more preferably 300,000 or more. This is to increase the viscosity of the electrode paste and obtain good coatability.

[0129] The weight average molecular weight of the cellulose derivative (B) is 700,000 or less, preferably 500,000 or less, and more preferably 400,000 or less. This is to suppress an increase in the viscosity of the electrode slurry when the shear rate is low.

[0130] The weight average molecular weight of the cellulose derivative (B) is a pullulan-converted value measured by GPC. The specific measurement method will be described later in Examples.

[0131] 〔1-3. Electrode active material (C)〕

[0132] The electrode active material (C) is a material capable of intercalating / deintercalating ions such as lithium ions as charge carriers. The ions as charge carriers are preferably alkali metal ions, more preferably lithium ions, sodium ions, and potassium ions, and even more preferably lithium ions.

[0133] When the electrode is a negative electrode, the electrode active material, i.e., the negative electrode active material, preferably includes at least one of a carbon material, a silicon-containing material, and a titanium-containing material. As the carbon material used as the electrode active material, cokes such as petroleum coke, asphalt coke, coal coke, carbides of organic polymers, graphites such as artificial graphite and natural graphite can be cited. As silicon-containing materials, silicon compounds such as silicon simple substance and silicon oxide can be cited. As titanium-containing materials, lithium titanate and the like can be cited. These materials can be used alone, or two or more can be used in combination, or two or more can be used in a composite manner.

[0134] The negative electrode active material more preferably comprises at least one selected from a carbon material and a silicon-containing material, further preferably comprises a carbon material, further preferably comprises graphite, and particularly preferably comprises artificial graphite. This is to increase the effect of using the binder polymer (A) to improve the adhesion between the electrode active materials and between the electrode active materials and the collector.

[0135] When the electrode is a positive electrode, the electrode active material, i.e., the positive electrode active material, uses a material having a higher standard electrode potential than the negative electrode active material. As the positive electrode active material, lithium composite oxides containing nickel, such as Ni-Co-Mn lithium composite oxides, Ni-Mn-Al lithium composite oxides, Ni-Co-Al lithium composite oxides, lithium cobalt oxide (LiCoO2), spinel lithium manganese oxide (LiMn2O4), olivine lithium iron phosphate, TiS2, MnO2, MoO3, V2O5 and other chalcogenides can be cited. As the positive electrode active material, these substances can be used alone or in combination of two or more.

[0136] 〔1-4. Liquid medium (D)〕

[0137] The liquid medium (D) is a medium that remains in a liquid state in the range of 15°C or higher and 30°C or lower at 1 atmospheric pressure (1013 hPa), and has a boiling point of 250°C or lower at 1 atmospheric pressure. The liquid medium (D) can dissolve at least a part of the cellulose derivative (B) contained as an amount in the electrode paste described below. This is to increase the viscosity of the electrode paste to a level where the coating property becomes good.

[0138] The liquid medium (D) is preferably water, a hydrophilic solvent, or a combination thereof. Examples of the hydrophilic solvent include methanol, ethanol, isopropyl alcohol, N-methylpyrrolidone, etc. The liquid medium (D) more preferably contains water, and further preferably contains 95% by mass or more of water.

[0139] [[1-5. Content ratios of components in the electrode paste]]

[0140] In the electrode paste, the content of the binder polymer (A) relative to 100 parts by mass of the electrode active material (C) is preferably 0.50 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. This is to sufficiently bond between the electrode active materials (C) and between the electrode active material (C) and the current collector.

[0141] In the electrode paste, the content of the binder polymer (A) relative to 100 parts by mass of the electrode active material (C) is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and further preferably 3.0 parts by mass or less. This is to increase the content ratio of the electrode active material (C) in the electrode active material layer made using the electrode paste and to increase the capacity of the electrode.

[0142] In the electrode paste, the content of the cellulose derivative (B) relative to 100 parts by mass of the electrode active material (C) is preferably 0.50 part by mass or more, more preferably 1.0 part by mass or more, and further preferably 1.5 part by mass or more. This is to facilitate the dispersion of the electrode active material (C) in the electrode paste.

[0143] In the electrode paste, the content of the cellulose derivative (B) relative to 100 parts by mass of the electrode active material (C) is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and further preferably 3.0 parts by mass or less. This is to suppress an increase in the viscosity of the electrode paste beyond the necessary level. In addition, this is to increase the content ratio of the electrode active material (C) in the electrode active material layer made using the electrode paste and to increase the capacity of the electrode.

[0144] In the electrode paste, the content of the liquid medium (D) relative to 100 parts by mass of the electrode active material (C) is preferably 50 parts by mass or more, more preferably 75 parts by mass or more, and still more preferably 100 parts by mass or more. This is for facilitating the dispersion of the electrode active material (C) in the electrode paste and for improving the coatability of the electrode paste.

[0145] In the electrode paste, the content of the liquid medium (D) relative to 100 parts by mass of the electrode active material (C) is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, and still more preferably 150 parts by mass or less. This is for increasing the viscosity of the electrode paste to a level where the coatability becomes good and for shortening the drying time after coating the electrode paste.

[0146] In the electrode paste, the content of the binder polymer (A) relative to 100 parts by mass of the electrode active material (C) is preferably 0.50 part by mass or more and 6.0 parts by mass or less, the content of the cellulose derivative (B) relative to 100 parts by mass of the electrode active material (C) is preferably 0.50 part by mass or more and 6.0 parts by mass or less, and the content of the liquid medium (D) relative to 100 parts by mass of the electrode active material (C) is preferably 50 parts by mass or more and 300 parts by mass or less.

[0147] [1-6. Non-volatile component concentration of the electrode paste]

[0148] The non-volatile component concentration of the electrode paste is preferably 30% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. This is for increasing the concentration of the active components in the electrode paste so that a sufficient amount of the electrode active material layer can be formed with a smaller amount of the electrode paste. In addition, this is for increasing the viscosity of the electrode paste to a level where the coatability becomes good and for shortening the drying time after coating the electrode paste.

[0149] The non-volatile component concentration of the electrode paste is preferably 80% by mass or less, more preferably 70% by mass or less, and still more preferably 60% by mass or less. This is for facilitating the dispersion of the electrode active material (C) in the electrode paste and for improving the coatability of the electrode paste.

[0150] <2. Method for manufacturing a non-aqueous secondary battery electrode paste>

[0151] Hereinafter, an example of the method for manufacturing the electrode paste of the present disclosure will be described, however, the method for manufacturing the electrode paste is not limited to this example.

[0152] [2-1. Synthesis of the binder polymer (A)]

[0153] The binder polymer (A) can be obtained by polymerizing a compound having an ethylenically unsaturated bond as the monomer (a). As the monomer (a), an aromatic ethylenically unsaturated compound (a1) is included, and other ethylenically unsaturated compounds may be copolymerized as needed. Examples of other ethylenically unsaturated compounds include the above-mentioned compounds (a2) to (a6), etc., but are not limited to them.

[0154] As the polymerization method, for example, emulsion polymerization of the monomer (a) in an aqueous medium can be cited. As other components used in the synthesis of the binder polymer (A) based on emulsion polymerization, for example, a non-polymerizable surfactant, an alkaline substance, a radical polymerization initiator, etc. can be cited, but are not limited to them, and a chain transfer agent, etc. can also be used. Hereinafter, these components and the emulsion polymerization method that are necessary for synthesizing the binder polymer (A) or can be used as needed will be described. However, regarding the monomer (a), since it has been described above, the description will be omitted hereinafter.

[0155] [2-1-1. Aqueous Medium]

[0156] The aqueous medium used in emulsion polymerization is water, a hydrophilic solvent, or a mixture thereof. Examples of the hydrophilic solvent include methanol, ethanol, isopropanol, and N-methylpyrrolidone. From the viewpoint of polymerization stability, the aqueous medium is preferably water. It should be noted that as long as the polymerization stability is not impaired, a medium in which a hydrophilic solvent is added to water can also be used as the aqueous medium.

[0157] [2-1-2. Surfactant]

[0158] In the emulsion polymerization of the monomer (a), a non-polymerizable surfactant can improve the dispersion stability of at least one of the dispersion liquid (emulsion) during and after polymerization. As such a surfactant, an anionic surfactant and a non-ionic surfactant are preferably used.

[0159] Examples of the anionic surfactant include alkylbenzene sulfonate, alkyl sulfate, polyoxyethylene alkyl ether sulfate, and fatty acid salt.

[0160] Examples of the non-ionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polycyclic phenyl ether, polyoxyalkylene alkyl ether, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester.

[0161] The surfactant can be used alone or in combination of two or more.

[0162] [2-1-3. Alkaline Substance]

[0163] By adding an alkaline substance, it is possible to neutralize the acidic components contained in the monomer (a) and adjust the pH. By adjusting the pH, it is possible to improve the mechanical stability and chemical stability of at least one of the dispersion during emulsion polymerization and after emulsion polymerization.

[0164] The pH of the dispersion may be appropriately adjusted according to the specifications of the electrode, the conditions for preparing the slurry described later, etc. The pH of the dispersion is not limited, however, it is preferably 1.5 or more, more preferably 5.0 or more, and further preferably 6.0 or more at 23°C. The pH of the dispersion is not limited, however, it is preferably 10 or less, more preferably 9.0 or less. This is to suppress the sedimentation of the electrode active material (C) in the electrode slurry when adding the electrode active material.

[0165] Examples of the alkaline substance include ammonia, triethylamine, sodium hydroxide, lithium hydroxide, etc. These alkaline substances may be used alone or in combination of two or more.

[0166] [2-1-4. Radical polymerization initiator]

[0167] The radical polymerization initiator used in emulsion polymerization is not particularly limited. For example, it may include persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide; azo compounds; and organic peroxides such as tert-butyl hydroperoxide, tert-butyl perbenzoate, and cumene hydroperoxide. Among them, persulfates and organic peroxides are preferred. In emulsion polymerization, a radical polymerization initiator may also be used in combination with a reducing agent such as sodium bisulfite, Rongalite, and ascorbic acid for redox polymerization.

[0168] The addition amount of the radical polymerization initiator is preferably 0.10 parts by mass or more, more preferably 0.20 parts by mass or more, based on 100 parts by mass of the monomer (a). This is to improve the conversion rate of the polymerization of the monomer (a). The addition amount of the radical polymerization initiator is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, based on 100 parts by mass of the monomer (a). This is to increase the molecular weight of the binder polymer (A) and reduce the swelling rate of the electrode active material layer prepared using the electrode slurry in the electrolyte.

[0169] [2-1-5. Emulsion polymerization method]

[0170] As the emulsion polymerization method, for example, a method of performing emulsion polymerization while continuously supplying each component used in the emulsion polymerization can be cited. The temperature of the emulsion polymerization is not particularly limited. For example, it is preferably 30 °C or higher, more preferably 50 °C or higher, and further preferably 55 °C or higher. The temperature of the emulsion polymerization is not particularly limited. For example, it is preferably 90 °C or lower, more preferably 85 °C or lower, and further preferably 80 °C or lower. The emulsion polymerization is preferably carried out with stirring. In addition, it is preferable to continuously supply the monomer (a) and the radical polymerization initiator into the reaction vessel. This is to make the radical polymerization initiator exist more uniformly in the reaction solution.

[0171] [2-2. Mixing of Each Component (Manufacture of Electrode Paste)]

[0172] A method of mixing a cellulose derivative (B), an electrode active material (C), an optional liquid medium (D) (the aqueous medium used in the above polymerization may be directly used as the liquid medium (D)), and other optional components in the dispersion of the binder polymer (A) (hereinafter sometimes referred to as the binder composition) obtained by the above process can be cited, but it is not limited thereto. The order of the added components is not particularly limited as long as it is appropriately determined. As the mixing method, a method using a mixing device such as a stirring type, a rotary type, or an oscillating type can be cited.

[0173] [2-3. Viscosity of Electrode Paste]

[0174] The viscosity "η -1 " of the electrode paste of the present disclosure at a shear rate of 100 s 100 and the viscosity η -1 at a shear rate of 0.10 s 0.10 The ratio (η 100 / η 0.10 ) is preferably 0.30 or higher, more preferably 0.40 or higher, and further preferably 0.50 or higher. In addition, the ratio (η 100 / η 0.10 ) is preferably 0.90 or lower, more preferably 0.80 or lower, and further preferably 0.70 or lower.

[0175] Regarding the viscosity when changing the shear rate of the electrode paste, using a viscosity-viscoelasticity measuring device (for example, manufactured by HAAKE, RS6000) and a cone plate, at a measurement temperature of 25 °C, from 0.010 s -1 to 1000 s -1 The shear rate is increased by 27% every minute while measuring. A cone plate with a diameter of 35 mm and an angle of 2° is used.

[0176] <3. Non-aqueous Secondary Battery Electrode>

[0177] The non-aqueous secondary battery electrode of the present disclosure (hereinafter sometimes referred to as "electrode") includes a current collector and an electrode active material layer formed on the current collector. As the shape of the electrode, for example, a laminate and a wound body can be cited, but there is no particular limitation. In addition, the formation range of the electrode active material layer on the current collector is not particularly limited, and it can be formed on the entire surface of the current collector or on a part of the surface of the current collector. When the current collector is in the shape of a plate, foil, etc., the electrode active material layer can be formed on both sides of the current collector or only on one side.

[0178] [3-1. Current Collector]

[0179] The current collector is preferably a metal sheet having a thickness of 0.001 mm or more and 0.5 mm or less. As the metal, iron, copper, aluminum, nickel, stainless steel, etc. can be cited. When the non-aqueous secondary battery electrode is the negative electrode of a lithium-ion secondary battery, the current collector is preferably a copper foil.

[0180] [3-2. Electrode Active Material Layer]

[0181] The electrode active material layer of the present disclosure contains a binder polymer (A), a cellulose derivative (B), and an electrode active material (C). The components cited here are as described above. The electrode active material layer may also contain a conductive aid, etc. as other components.

[0182] [3-3. Method for Manufacturing Electrode]

[0183] As a method for manufacturing the electrode, for example, it can be manufactured by coating an electrode paste on a current collector, drying it to form an electrode active material layer, and then cutting it into an appropriate size.

[0184] As a method for coating the electrode paste on the current collector, there is no particular limitation. For example, a reverse roll method, a direct roll method, a doctor blade method, a knife coating method, an extrusion method, a curtain coating method, an intaglio method, a bar coating method, an impregnation method, and an extrusion method can be cited. Among these coating methods, considering various physical properties such as the viscosity of the electrode paste and the drying property, it is preferable to use the doctor blade method, the knife coating method, or the extrusion method. This is to obtain an electrode active material layer with a smooth surface and small fluctuations in thickness.

[0185] The electrode paste can be coated on only one side of the current collector or on both sides. When the electrode paste is coated on both sides of the current collector, it can be coated one side at a time or both sides can be coated at once. In addition, the electrode paste can be continuously coated on the current collector or intermittently coated. The coating amount of the electrode paste can be appropriately determined according to the design capacity of the battery, the composition of the electrode paste, etc. Although the coating amount of the electrode paste also depends on the properties of the electrode paste, it is preferably 15 mg / cm 2The following (in the case of coating both sides, it is the coating amount per side). This is to be able to suppress the generation of cracks on the electrode surface during the drying process of the electrode paste.

[0186] The electrode paste coated on the current collector is dried, thereby forming an electrode active material layer on the current collector. The drying method of the electrode paste is not particularly limited. For example, hot air, reduced pressure or vacuum environment, (far) infrared rays, and low-temperature air can be used alone or in combination. The drying temperature and drying time of the electrode paste can be appropriately adjusted according to the concentration of non-volatile components in the electrode paste, the coating amount on the current collector, etc. The drying temperature is preferably 40 °C or higher and 350 °C or lower, and more preferably 60 °C or higher and 100 °C or lower from the viewpoint of productivity. The drying time is preferably 1 minute or longer and 30 minutes or shorter.

[0187] The electrode sheet having an electrode active material layer formed on the current collector can be cut to be made into a size and shape suitable for the electrode. The cutting method of the electrode sheet is not particularly limited, and a slitter, a laser, wire cutting, a cutting machine, a Thomson knife, etc. can be used.

[0188] Before or after cutting the electrode sheet, the electrode sheet can be pressed as needed. By pressing, the electrode active material is more firmly adhered to the current collector, and in addition, the non-aqueous battery can be miniaturized by thinning the electrode. As the pressing method, a general method can be used, and a die pressing method or a roll pressing method is particularly preferably used. In the case of the die pressing method, the pressing pressure is not particularly limited, and it is preferably set to 0.5 t / cm 2 or more and 5 t / cm 2 or less. In the case of the roll pressing method, the line pressure is not particularly limited, and it is preferably set to 0.5 t / cm or more and 5 t / cm or less. This is to suppress the insertion and detachment capacity reduction of charge carriers such as lithium ions into the electrode active material while obtaining the above effects brought about by pressing.

[0189] 〔3-4. Peel strength of the electrode〕

[0190] The peel strength of the negative electrode active material layer relative to the current collector is preferably 15 mN / mm or more, more preferably 18 mN / mm or more, and further preferably 20 mN / mm or more.

[0191] The higher the peel strength of the negative electrode active material layer relative to the current collector, the better, and the upper limit is not particularly limited, but it can be 25 mN / mm or less.

[0192] The peel strength of the negative electrode active material layer relative to the current collector is measured by the method described in the examples.

[0193] 〔3-5. Electrode resistance〕

[0194] The resistance of the negative electrode active material layer is preferably 350 mΩ·cm 2 More preferably, it is 300 mΩ·cm or less 2 Further preferably, it is 255 mΩ·cm or less 2 Further preferably, it is 235 mΩ·cm or less 2 or less. The lower the resistance of the negative electrode active material layer, the better, and the lower limit is not particularly limited, but it can be 150 mΩ·cm 2 or more.

[0195] The interfacial resistance between the negative electrode active material layer and the current collector is preferably 100 mΩ·cm 2 More preferably, it is 88 mΩ·cm or less 2 Further preferably, it is 73 mΩ·cm or less 2 or less. The lower the interfacial resistance between the negative electrode active material layer and the current collector, the better, and the lower limit is not particularly limited, but it can be 30 mΩ·cm 2 or more.

[0196] The resistance of the negative electrode active material layer and the interfacial resistance between the negative electrode active material layer and the current collector are measured using an electrode resistance measuring machine (for example, manufactured by HIOKI E.E. CORPORATION, electrode resistance measuring system XF057).

[0197] <4. Non-aqueous secondary battery>

[0198] The non-aqueous secondary battery of the present disclosure includes the non-aqueous secondary battery electrode of the present disclosure.

[0199] As a preferred example of the non-aqueous secondary battery of the present disclosure, a lithium-ion secondary battery will be described, but the battery configuration is not limited to the examples described herein. The non-aqueous secondary battery of the present disclosure houses components such as a positive electrode, a negative electrode, an electrolyte, and a separator as needed in an outer package, and one or both of the positive electrode and the negative electrode use the above-described electrode. In the non-aqueous secondary battery of the present disclosure, at least one of the positive electrode and the negative electrode contains a binder polymer (A), and preferably at least the negative electrode contains a binder polymer (A).

[0200] 〔4-1. Electrolyte〕

[0201] A non-aqueous liquid having ion conductivity is used as the electrolyte. As the electrolyte, a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, etc. can be cited, but the former is preferred. This is to obtain a non-aqueous battery with low manufacturing cost and low internal resistance.

[0202] An alkali metal salt can be used as the electrolyte, which can be appropriately selected according to the type of the electrode active material, etc. As the electrolyte, LiClO4, LiBF6, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiB 10 Cl 10 , LiAlCl4, LiCl, LiBr, LiB(C2H5)4, CF3SO3Li, CH3SO3Li, LiCF3SO3, LiC4F9SO3, Li(CF3SO2)2N, lithium aliphatic carboxylate, etc. In addition, other alkali metal salts can also be used as the electrolyte.

[0203] The organic solvent for dissolving the electrolyte is not particularly limited. For example, carbonate compounds such as ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), dimethyl carbonate (DMC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC); nitrile compounds such as acetonitrile; and carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate. These organic solvents can be used alone or in combination of two or more. Among them, it is preferable to use a solvent obtained by combining linear carbonate solvents as the organic solvent. As the linear carbonate solvents, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, etc. can be cited.

[0204] [4-2. Outer packaging body]

[0205] A laminate of an aluminum foil and a resin film, etc. can be appropriately used as the outer packaging body, but it is not limited thereto. The shapes of the battery can be coin type, button type, sheet type, cylindrical type, square type, flat type, etc., and there is no particular limitation.

[0206] Examples

[0207] Hereinafter, the present embodiment will be described in more detail by using examples. However, the present embodiment is not limited to the examples described below. In the following examples, as an example of the electrode paste, a negative electrode paste of a lithium ion battery is produced. It should be noted that the water used in the following examples and comparative examples is ion-exchanged water unless otherwise specified.

[0208] <1. Binder polymer (A)>

[0209] [1-1. Synthesis example 1]

[0210] The monomers (a) of the type and in the amounts shown in Synthesis Example 1 of Table 1 were mixed with 200 parts by mass of water and emulsified to prepare a monomer emulsion. AQUALON KH10 used as the polymerizable surfactant (a6) is ammonium polyoxyethylene-1-(allyloxymethyl)alkyl ether sulfate manufactured by Daiichi Kogyo Seiyaku Co., Ltd., and is a compound represented by the above formula (2).

[0211] Then, the polymerization initiators of the type and in the amounts shown in Synthesis Example 1 of Table 1 were respectively dissolved in 50 parts by mass of water to prepare an aqueous polymerization initiator solution.

[0212] [Table 1]

[0213]

[0214] 150 parts by mass of water was added to a separable flask equipped with a condenser, a thermometer, a stirrer, and a dropping funnel, and the temperature was raised to 75°C. To this separable flask, the above monomer emulsion and the aqueous polymerization initiator solution were continuously fed while stirring at 75°C for 3 hours respectively, and emulsion polymerization was carried out to obtain an emulsion. The obtained emulsion was cooled to room temperature (25°C). To the cooled emulsion, 17 parts by mass of 25% by mass ammonia water (basic substance in Table 1: 4.25 parts by mass of ammonia, 12.75 parts by mass of water) and 130 parts by mass of water were added. It should be noted that Rongalite SFS used as the polymerization initiator is manufactured by Sumitomo Seika Chemicals Co., Ltd.

[0215] By this process, the binder composition of Synthesis Example 1 was obtained as an emulsion containing the binder polymer (A1).

[0216] [1-2. Synthesis Example 2]

[0217] The monomers (a) of the type and in the amounts shown in Synthesis Example 2 of Table 1 were mixed with 200 parts by mass of water and emulsified to prepare a monomer emulsion.

[0218] Then, the radical polymerization initiators of the type and in the amounts shown in Synthesis Example 2 of Table 1 were dissolved in 50 parts by mass of water to prepare an aqueous polymerization initiator solution.

[0219] 200 parts by mass of water was added to a 5 MPa pressure-resistant container equipped with a stirrer, and the temperature was raised to 60°C under an internal pressure of 1.0 MPa in the container. The above monomer emulsion and the aqueous solution in which the radical polymerization initiator was dissolved were respectively charged into the pressure-resistant container at one time, and stirred at 60°C for 8 hours, whereby emulsion polymerization was carried out to obtain an emulsion. The obtained emulsion was cooled to room temperature (25°C). To the cooled emulsion, 5.3 parts by mass of 25% by mass ammonia water (basic substance in Table 1: 1.325 parts by mass of ammonia, 3.975 parts by mass of water) and 130 parts by mass of water were added.

[0220] Using this process, as an emulsion containing the binder polymer (A2), an emulsion of Synthetic Example 2 containing dispersed particles containing the binder polymer and an aqueous medium was obtained.

[0221] [1-3. Measurement of non-volatile content concentration]

[0222] 1 g of each of the emulsions obtained in Synthetic Example 1 and Synthetic Example 2 was weighed in an aluminum dish with a diameter of 5 cm, and dried at 105 °C for 1 hour while circulating air in a dryer under 1 atmospheric pressure (1013 hPa). Then, the mass of the remaining components was measured, and the non-volatile content concentration (mass %) was determined. The measured values of the non-volatile content concentrations of the emulsions obtained in Synthetic Example 1 and Synthetic Example 2 are shown in Table 1.

[0223] [1-4. Measurement of glass transition temperature]

[0224] 1 g of each of the emulsions obtained in Synthetic Example 1 and Synthetic Example 2 was dried at 105 °C for 1 hour while circulating air in a dryer under 1 atmospheric pressure (1013 hPa). Then, the remaining components were taken out and filled in a sample pan, and DSC measurement was performed. The DSC measurement was carried out using EXSTAR DSC / SS7020 manufactured by Hitachi High-Technologies Corporation at a heating rate of 10 °C / minute in a nitrogen atmosphere. For each synthetic example, the peak temperature of the DDSC curve obtained by differentiating the temperature of the DSC was set as the glass transition temperature (°C) of the binder polymer (A1) or the binder polymer (A2). The measured values of the glass transition temperatures of the binder polymer (A1) and the binder polymer (A2) are shown in Table 1.

[0225] <2. Negative electrode paste>

[0226] [2-1. Preparation of negative electrode paste]

[0227] In each of the examples and comparative examples, for the binder polymer (A), the cellulose derivative (B), and the electrode active material (C) (negative electrode active material), the types shown in Table 2 were used and mixed with water as the liquid medium (D) so as to be in the amounts shown in Table 2, to prepare a negative electrode paste. It should be noted that the amount of water added in this process was adjusted so that the total amount including the water contained in the above emulsion was the amount shown in Table 2.

[0228] For the binder polymer (A), the binder polymer (A1) synthesized in Synthetic Example 1 and the binder polymer (A2) synthesized in Synthetic Example 2 were used.

[0229] [Table 2]

[0230]

[0231] The following sodium carboxymethyl cellulose (CMC-Na) is used as the cellulose derivative (B).

[0232] CMC1130: manufactured by Daicel Corporation, degree of etherification 0.70, weight-average molecular weight 300,000

[0233] CMC1240: manufactured by Daicel Corporation, degree of etherification 0.90, weight-average molecular weight 380,000

[0234] CMC2200: manufactured by Daicel Corporation, degree of etherification 0.90, weight-average molecular weight 1,000,000

[0235] CMC1380: manufactured by Daicel Corporation, degree of etherification 1.3, weight-average molecular weight 1,110,000

[0236] The degree of etherification of CMC-Na is a value measured by the method described in Non-Patent Document 1, and the sample used in the measurement is obtained by the method described below.

[0237] 5.0 g of CMC-Na, 100 mL of Me2SO (dimethyl sulfoxide), and 20.0 mL of dimethyl sulfate are added to a 300 mL round-bottom flask, and the mixture is heated at 45 °C for 24 hours. Thereafter, the mixture is poured into methanol containing 0.1 vol% of HCl to separate the reaction product, and the product is dried under vacuum. Methylated CMC (MCMC) is obtained by this process.

[0238] In a 100 mL round-bottom flask, 1.0 g of the obtained MCMC, 5.0 mL of propionic anhydride, 50 mL of pyridine, and 0.20 g of 4-(dimethylamino)pyridine are dissolved in 50 mL of dimethylacetamide containing 6 mass% of LiCl. The mixture is heated at 100 °C for 6 hours. Thereafter, the mixture is poured into 2 L of water to separate the product, and the product is dried under vacuum. Propionylated MCMC (PMCMC) is obtained by this process.

[0239] The obtained PMCMC is subjected to 13 13C NMR measurement.

[0240] Solvent: dimethyl sulfoxide-d6

[0241] Solution temperature: 100 °C

[0242] Measuring device: JNM-EX400 (100 MHz) manufactured by JEOL Ltd.

[0243] Probe: 5 mm diameter C-H double probe

[0244] Measurement mode: Quantitative mode

[0245] Measurement method: non-NOE gated decoupling technique

[0246] Repetition time (pulse repetition time): 30 seconds

[0247] Number of accumulations: 2000 times

[0248] Based on the data obtained by 13 13C NMR measurement, the ratio value I1 / I2 of the cumulative value (total value of 3 peaks) I1 of the peaks corresponding to the C=O of the propionyl group appearing at 175.7 ppm, 176.2 ppm, and 176.7 ppm to the cumulative value (total value of 2 peaks) I2 of the peaks appearing at 103.0 ppm and 104.5 ppm is calculated. This ratio value I1 / I2 is the number of unsubstituted hydroxyl groups in each structural unit of the cellulose derivative. Therefore, (3 - I1 / I2) is the number of substituted (converted to ether bonds) hydroxyl groups in each structural unit, and this value is the degree of etherification.

[0249] The weight-average molecular weight of CMC-Na is the amylopectin conversion value measured by GPC, and the measurement is carried out using the following apparatus and conditions.

[0250] GPC apparatus: GPC-101 (manufactured by RESONAC Co., Ltd.)

[0251] Solvent: 0.1 M aqueous NaNO3 solution

[0252] Sample column: Shodex Column Ohpak SB-806 HQ (8.0 mm I.D. x 300 mm) × 2

[0253] Reference column: Shodex Column Ohpak SB-800 RL (8.0 mm I.D. x 300 mm) × 2

[0254] Column temperature: 40 °C

[0255] Sample concentration: 0.1 mass%

[0256] Detector: RI-71S (manufactured by Shimadzu Corporation)

[0257] Flow rate: 1 ml / min

[0258] Molecular weight standard: amylopectin (P-5, P-10, P-20, P-50, P-100, P-200, P-400, P-800, P-1300, P-2500 (manufactured by RESONAC Co., Ltd.))

[0259] In any of the examples and comparative examples, artificial graphite (G49, manufactured by Jiangxi Zichen Technology Co., Ltd.) was used as the electrode active material (C).

[0260] [2-2. Various measurements of the negative electrode paste]

[0261] [2-2-1. Concentration of non-volatile components in the negative electrode paste]

[0262] 1 g of the mixture of the negative electrode pastes obtained in each of the examples and comparative examples was weighed in an aluminum dish with a diameter of 5 cm, and dried at 130 °C for 1 hour while circulating air in a dryer under 1 atmospheric pressure (1013 hPa). Then, the mass of the remaining components was measured, and the non-volatile component concentration (mass%) was determined. The non-volatile component concentrations of the electrode pastes prepared in each of the examples and comparative examples are shown in Table 2.

[0263] [2-2-2. Viscosity of the negative electrode paste]

[0264] Using a viscosity-viscoelasticity measuring device RS6000 and a cone plate manufactured by HAAKE, the viscosity of the paste was measured with the measurement temperature set at 25 °C. The cone plate had a diameter of 35 mm and an angle of 2°, and the viscosity was measured while increasing the shear rate by 27% every 1 minute from 0.010 s -1 to 1000 s -1 (i.e., the shear rate becomes an exponential function of time).

[0265] As an example of the measurement results, Figure 1 shows the relationship between the shear rate and viscosity of the electrode pastes of Example 1 and Comparative Example 1. In addition, Figure 2 shows the relationship between the shear rate and viscosity of the electrode pastes of Example 3 and Comparative Example 3. It can be seen that the viscosity of the electrode paste of Example 1 is stable even when the shear rate changes compared to the electrode paste of Comparative Example 1. In addition, it can be seen that the viscosity of the electrode paste of Example 3 is stable even when the shear rate changes compared to the electrode paste of Comparative Example 3.

[0266] The viscosities "η -1 " and "η -1 " at the shear rates of 0.10 s 0.10 and 100 s 100 of the electrode pastes prepared in each of the examples and comparative examples are shown in Table 2.

[0267] <3. Negative electrode>

[0268] 〔3-1. Fabrication of Negative Electrode〕

[0269] On both sides of a copper foil (negative electrode current collector) with a thickness of 10 μm, a negative electrode paste is coated using the direct roll method. The coating amount of the negative electrode paste onto the negative electrode current collector is adjusted such that the thickness after the subsequent rolling process is 170 μm on each side.

[0270] The negative electrode paste coated on the negative electrode current collector is dried at 90 °C for 10 minutes and pressed using a rolling press (manufactured by Thank-Metal Co., Ltd., pressing load 8 t, roll width 7 cm) to obtain a negative electrode sheet having a negative electrode active material layer formed on the current collector. The obtained negative electrode sheet is cut into 52 mm × 42 mm and a conductive terminal is attached to fabricate a negative electrode.

[0271] 〔3-2. Various Measurements of Negative Electrode〕

[0272] [3-2-1. Measurement of Peel Strength of Negative Electrode Active Material Layer]

[0273] The peel strength of the negative electrode active material layer with respect to the current collector is measured as follows. The pressed negative electrode sheet in the above negative electrode fabrication process is cut into a size of 25 mm × 100 mm as a test piece. The negative electrode active material layer on the test piece and a SUS plate with a width of 50 mm and a length of 200 mm are adhered using a double-sided tape (NITTOTAPE (registered trademark) No. 5, manufactured by Nitto Denko Corporation) such that the center of the test piece coincides with the center of the SUS plate. It should be noted that the double-sided tape is adhered so as to cover the entire range of the test piece.

[0274] After the test piece and the SUS plate are placed in the adhered state for 10 minutes, the negative electrode active material layer is peeled 20 mm along the length direction from one end of the test piece, the test piece on the copper foil side is folded 180°, and this part (the copper foil side of the part of the test piece from which the negative electrode active material layer has been peeled) is clamped by the upper chuck of the testing machine. Subsequently, one end of the SUS plate from which the negative electrode active material layer has been peeled is clamped by the lower chuck. In this state, the copper foil is peeled from the test piece at a speed of 100 ± 10 mm / min to obtain a graph of peel length (mm) - peel force (mN). The average value (mN) of the peel force when the peel length is 10 mm to 45 mm is calculated from the obtained graph, and the obtained value is divided by the width 25 mm of the test piece, and the resulting value is set as the peel strength (mN / mm) of the negative electrode active material layer. It should be noted that in any of the examples and comparative examples, no peeling occurred between the double-sided tape and the SUS plate and no interfacial peeling occurred between the double-sided tape and the negative electrode active material layer during the test.

[0275] [3-2-2. Measurement of Resistance]

[0276] Using the electrode resistance measurement system XF057 manufactured by Hioki Electric Co., Ltd., the resistance of the negative electrode active material layer (mΩ·cm 2 ), and the interfacial resistance between the negative electrode active material layer and the current collector (mΩ·cm 2 ) were measured.

[0277] <4. Lithium-ion secondary battery>

[0278] [4-1. Fabrication of battery]

[0279] Lithium-ion secondary batteries were fabricated using the negative electrodes of the respective examples and comparative examples. It should be noted that, in the following description, the fabrication of the negative electrode was as described above.

[0280] 94 parts by mass of LiNi 0.6 Mn 0.2 Co 0.2 O2, 3 parts by mass of acetylene black as a conductive additive, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed. 50 parts by mass of N-methylpyrrolidone was added to the resulting mixture and further mixed to prepare a positive electrode paste.

[0281] The positive electrode paste was coated on both sides of an aluminum foil (positive electrode current collector) with a thickness of 15 μm by the direct roll method. The coating amount of the positive electrode paste on the positive electrode current collector was adjusted so that the thickness after the subsequent rolling process was 125 μm on each side.

[0282] The positive electrode paste coated on the positive electrode current collector was dried at 120°C for 5 minutes and pressed using a roll press (manufactured by Thank-Metal Co., Ltd., pressing load 5 t, roll width 7 cm) to obtain a positive electrode sheet having a positive electrode active material layer formed on the current collector. The obtained positive electrode sheet was cut into 50 mm × 40 mm and a conductive terminal was attached to fabricate a positive electrode.

[0283] A separator made of a polyolefin-based porous film (made of polyethylene, 25 μm) was interposed between the positive electrode and the negative electrode, and the positive electrode active material layer and the negative electrode active material layer were accommodated in an aluminum laminated outer package (battery pack) so as to face each other. An electrolytic solution was injected into the outer package and vacuum-infiltrated, and then packaged using a vacuum heat sealer to fabricate a lithium-ion secondary battery for evaluation. Regarding the electrolytic solution, LiPF6 was dissolved at 1.0 mol / L in a mixed solvent of ethylene carbonate (EC) / ethyl methyl carbonate (EMC) / diethyl carbonate (DEC) = 30 / 50 / 20 (volume ratio), and 1 part by mass of vinylene carbonate was mixed in 99 parts by mass of the resulting solution.

[0284] [4-2. Measurement of cycle capacity retention rate of battery]

[0285] Regarding the cycle capacity retention rate of the batteries of each example and each comparative example at high temperature, the following steps (i) to (iv) were repeated in this order under the condition of 45°C. Here, one series of operations of (i) to (iv) was defined as one cycle.

[0286] (i) Charge at a current of 1C until the voltage reaches 4.2V (constant current (CC) charging).

[0287] (ii) Charge at a voltage of 4.2V until the current reaches 0.05C (constant voltage (CV) charging).

[0288] (iii) Stand still for 15 minutes.

[0289] (iv) Discharge at a current of 1C until the voltage reaches 2.75V (constant current (CC) discharging).

[0290] The time integral value of the current in steps (i) and (ii) was defined as the charge capacity, and the time integral value of the current in step (iv) was defined as the discharge capacity. The discharge capacity of the first cycle and the discharge capacity of the 500th cycle were measured. 100×(discharge capacity of the 500th cycle) / (discharge capacity of the first cycle) [%] was calculated as the cycle capacity retention rate of the battery at high temperature. The cycle capacity retention rates (500 cycles) of the batteries of each example and each comparative example are shown in Table 2.

[0291] <5. Evaluation results>

[0292] The electrode pastes of Examples 1 to 4 all contained a binder polymer (A), a cellulose derivative (B), an electrode active material (C), and a liquid medium (D). The binder polymer (A) in the electrode pastes of Examples 1 to 4 had a first structural unit derived from an aromatic vinyl unsaturated compound (a1) which was a non-ionic aromatic compound having one independent ethylenic unsaturated bond. The degree of etherification of the cellulose derivative (B) in the electrode pastes of Examples 1 to 4 was 0.50 or more and 1.0 or less, and the weight average molecular weight was 100,000 or more and 700,000 or less. In addition, all the cellulose derivatives (B) were dissolved in the liquid medium (D).

[0293] The change in viscosity Δη 100 / Δη 0.10 of the electrode pastes of Examples 1 to 4 caused by the change in shear rate was small. The electrode active material layers formed on the electrodes made using the electrode pastes of Examples 1 to 4 had a high peel strength relative to the current collector. In addition, in the electrodes made using the electrode pastes of Examples 1 to 4, the interfacial resistance between the electrode active material and the current collector and the resistance within the negative electrode active material layer were low, and the internal resistance of the battery equipped with this electrode became low.

[0294] In Comparative Examples 1 to 4 where the cellulose derivative (B) has a high molecular weight, the viscosity significantly increases when the shear rate is low. In the electrodes fabricated using the electrode pastes of Comparative Examples 1 to 4, the peel strength of the electrode active material layer relative to the current collector is low. Further, in the electrodes fabricated using the electrode pastes of Comparative Examples 1 to 4, the interfacial resistance between the electrode active material and the current collector and the resistance within the negative electrode active material layer are high, and the internal resistance of the battery equipped with such an electrode becomes high.

[0295] From the above, it can be seen that for a non-aqueous secondary battery electrode paste containing a binder polymer (A), a cellulose derivative (B), an electrode active material (C), and a liquid medium (D), the binder polymer (A) has a first structural unit derived from an aromatic ethylenically unsaturated compound (a1), the aromatic ethylenically unsaturated compound (a1) is a non-ionic aromatic compound having one independent ethylenic unsaturated bond, the degree of etherification of the cellulose derivative (B) is 0.50 or more and 1.2 or less, and the weight average molecular weight is 100,000 or more and 700,000 or less, and the cellulose derivative (B) is dissolved in the liquid medium (D), the change in viscosity with respect to the change in shear rate is small, an electrode active material layer with a high peel strength relative to the current collector can be formed, and a battery with a low internal resistance can be manufactured.

[0296] In addition, the battery equipped with the electrode fabricated using the electrode paste of Examples 1 to 4 has an excellent cycle capacity retention rate (500 cycles) compared to the battery equipped with the electrode fabricated using the electrode paste of Comparative Examples 1 to 4.

[0297] The entire disclosure of Japanese Patent Application No. 2022-202794 is incorporated herein by reference.

[0298] All documents, patent applications, and technical standards of the present disclosure are incorporated herein by reference to the same extent as if each document, patent application, and technical standard were specifically and individually recited as being incorporated by reference.

Claims

1. A non-aqueous secondary battery electrode paste, which contains a binder polymer A, a cellulose derivative B, an electrode active material C, and a liquid medium D, The binder polymer A has a first structural unit derived from an aromatic ethylenically unsaturated compound a1, and the aromatic ethylenically unsaturated compound a1 is a non-ionic aromatic compound having one independent ethylenically unsaturated bond, The degree of etherification of the cellulose derivative B is 0.50 or more and 1.2 or less, and the weight average molecular weight is 100,000 or more and 700,000 or less, At least a part of the cellulose derivative B is dissolved in the liquid medium D.

2. The non-aqueous secondary battery electrode paste according to claim 1, wherein, The content of the first structural unit in the binder polymer A is 25% by mass or more and 65% by mass or less.

3. The non-aqueous secondary battery electrode paste according to claim 1, wherein, The cellulose derivative B contains at least one selected from carboxymethyl cellulose and its salts.

4. The non-aqueous secondary battery electrode paste according to claim 1, wherein, The binder polymer A further has a second structural unit derived from a non-ionic (meth)acrylate a2, and the non-ionic (meth)acrylate a2 is a non-ionic aliphatic compound having one (meth)acryloyl group and not having an ethylenically unsaturated bond other than the (meth)acryloyl group.

5. The non-aqueous secondary battery electrode paste according to claim 4, wherein, The content of the first structural unit in the binder polymer A is 25% by mass or more and 65% by mass or less, and the content of the second structural unit is 25% by mass or more and 70% by mass or less.

6. The non-aqueous secondary battery electrode paste according to claim 4, wherein, The binder polymer A further has a third structural unit derived from an anionic unsaturated compound a3, and the anionic unsaturated compound a3 has an anionic functional group and one independent ethylenically unsaturated bond.

7. The non-aqueous secondary battery electrode paste according to claim 6, wherein, The content of the first structural unit in the binder polymer A is 25% by mass or more and 65% by mass or less, the content of the second structural unit is 25% by mass or more and 70% by mass or less, and the content of the third structural unit is 0.30% by mass or more and 15% by mass or less.

8. The non-aqueous secondary battery electrode paste according to claim 6, wherein, The binder polymer A further has a fifth structural unit derived from an internal crosslinking agent a5 and a sixth structural unit derived from a surfactant a6 having an ethylenically unsaturated bond, The internal crosslinking agent a5 has a plurality of independent ethylenically unsaturated bonds, The surfactant a6 having an ethylenically unsaturated bond is a compound having one independent ethylenically unsaturated bond and acting as a surfactant.

9. The non-aqueous secondary battery electrode paste according to claim 8, wherein, The content rate of the first structural unit in the binder polymer A is 25% by mass or more and 65% by mass or less, the content rate of the second structural unit is 25% by mass or more and 70% by mass or less, the content rate of the third structural unit is 0.30% by mass or more and 15% by mass or less, the content rate of the fifth structural unit is 0.010% by mass or more and 1.0% by mass or less, and the content rate of the sixth structural unit is 0.10% by mass or more and 5.0% by mass or less.

10. The non-aqueous secondary battery electrode paste according to claim 4, 6 or 8, wherein the binder polymer A further has a fourth structural unit derived from a conjugated diene compound a4, the conjugated diene compound a4 is a nonionic aliphatic compound having one conjugated diene structure and having no ethylenic unsaturated bond other than the conjugated diene structure.

11. The non-aqueous secondary battery electrode paste according to claim 10, wherein the content rate of the first structural unit in the binder polymer A is 25% by mass or more and 65% by mass or less, the content rate of the fourth structural unit is 15% by mass or more and 55% by mass or less, and the total content rate of the second structural unit and the fourth structural unit is 25% by mass or more and 70% by mass or less.

12. The non-aqueous secondary battery electrode paste according to claim 1, wherein the content of the binder polymer A is 0.50 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the electrode active material C, the content of the cellulose derivative B is 0.50 part by mass or more and 6.0 parts by mass or less with respect to 100 parts by mass of the electrode active material C, the content of the liquid medium D is 50 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the electrode active material C.

13. A non-aqueous secondary battery electrode comprising a current collector and an electrode active material layer formed on the current collector, wherein the electrode active material layer contains a binder polymer A, a cellulose derivative B and an electrode active material C, the binder polymer A has a first structural unit derived from an aromatic ethylenically unsaturated compound a1, and the aromatic ethylenically unsaturated compound a1 is a nonionic aromatic compound having one independent ethylenic unsaturated bond, the degree of etherification of the cellulose derivative B is 0.50 or more and 1.2 or less, and the weight average molecular weight is 100,000 or more and 700,000 or less.

14. A non-aqueous secondary battery comprising the non-aqueous secondary battery electrode according to claim 13.

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