JP2019160651A - Binder composition, electrode mixture raw material, electrode mixture, electrode, nonaqueous electrolyte secondary battery, and manufacturing method of electrode mixture - Google Patents

Abstract

To provide a binder composition having both high adhesive strength and good slurry characteristics.SOLUTION: A binder composition according to the present invention contains a vinylidene fluoride polymer containing a first structural unit derived from vinylidene fluoride and a second structural unit derived from a compound represented by the following formula (1). [In the formula (1), R, R, and Rare each independently a hydrogen atom, a chlorine atom or an alkyl group having 1 to 5 carbon atoms, and X is {(CH)O}is an atomic group having a molecular weight of 600 or less, and here, n is 2 to 6 and m is 2 to 6.]SELECTED DRAWING: None

Description

  The present invention relates to a binder composition used in the production of a non-aqueous electrolyte secondary battery, particularly a lithium ion secondary battery, and an electrode mixture raw material, an electrode mixture, an electrode, a non-aqueous electrolyte secondary battery and an electrode using the same The present invention relates to a method for producing a mixture.

  In recent years, the development of electronic technology has been remarkable, and high functionality of small portable devices has been advanced. For this reason, power sources used for these are required to be smaller and lighter, that is, to have higher energy density. As a battery having a high energy density, a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery or the like is widely used.

  Nonaqueous electrolyte secondary batteries are also used in hybrid vehicles combining secondary batteries and engines, and electric vehicles powered by secondary batteries, from the viewpoint of global environmental problems and energy saving. Applications are expanding.

  An electrode for a nonaqueous electrolyte secondary battery has a structure having a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer is generally formed by applying an electrode mixture containing an electrode active material and a binder composition onto a current collector in a slurry state in which the electrode mixture is dispersed in an appropriate solvent, and volatilizing the solvent. As the binder resin (binder) in the binder composition, a vinylidene fluoride polymer mainly containing repeating units derived from vinylidene fluoride (VDF) is mainly used.

  In recent years, improvement in the adhesive strength of binder resin has been demanded. For example, in Patent Document 1, a vinylidene fluoride polymer containing a structural unit derived from a (meth) acrylic monomer having a hydroxy group is used as a binder resin. It is disclosed. Patent Document 2 discloses that a vinylidene fluoride polymer containing acryloxyethyl succinic acid (AES) terminated with a carboxyl group is used as a binder resin.

Special Table 2010-525124 (released July 22, 2010) WO2012 / 090876 (released July 5, 2012)

  However, the binder resin using the vinylidene fluoride polymer disclosed in Patent Documents 1 and 2 tends to increase the viscosity of the slurry, which may cause problems in handling properties during battery production.

  This invention is made | formed in view of the above-mentioned problem, The objective is to provide the binder composition in which high adhesive force and favorable slurry characteristics were compatible.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a vinylidene fluoride polymer having a specific glycol skeleton as a binder resin. The present invention has been completed. The present invention can be described as follows.

  The binder composition according to the present invention is a binder composition used for binding an electrode active material to a current collector in order to solve the above problems, and the binder composition is derived from vinylidene fluoride. A first structural unit and the following formula (1)

[In the formula _{(1), R 1, R} 2, R 3 each independently represent a hydrogen atom, a chlorine atom or an alkyl group having 1 to 5 carbon atoms, X is a _{{(CH 2) n O}} m And an atomic group having a molecular weight of 600 or less, where n is 2 to 6 and m is 2 to 6. ]
The vinylidene fluoride polymer containing the 2nd structural unit derived from the compound represented by these is contained.

  Moreover, the electrode mixture raw material which concerns on this invention contains the above-mentioned binder composition and the conductive support agent which consists of carbon materials, The oxygen content of the said conductive support agent is less than 5 mass%, The said conductive support agent In an electrode mixture raw material containing 0.5 to 50.0% by mass (provided that the total of the conductive assistant, the non-aqueous solvent, and the vinylidene fluoride polymer is 100% by mass) is there.

  Moreover, the electrode mixture which concerns on this invention is an electrode mixture containing the above-mentioned electrode mixture raw material and an electrode active material.

  Moreover, the electrode which concerns on this invention is an electrode provided with the mixture layer formed from the above-mentioned electrode mixture on a collector.

  Moreover, the nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including the above-described electrode.

  Moreover, the manufacturing method of the electrode mixture which concerns on this invention is a process which prepares the electrode mixture raw material containing the above-mentioned binder composition, a conductive support agent, and a nonaqueous solvent, and is polar to the said electrode mixture raw material. It includes a step of preparing an electrode mixture by adding a group-containing vinylidene fluoride polymer.

  The present invention has an effect that it is possible to provide a binder composition having both high adhesive strength and good slurry characteristics.

  Next, the present invention will be specifically described.

[Vinylidene fluoride polymer]
The vinylidene fluoride polymer according to the present embodiment is obtained by polymerizing vinylidene fluoride and a compound represented by the following formula (1).

[In the formula _{(1), R 1, R} 2, R 3 each independently represent a hydrogen atom, a chlorine atom or an alkyl group having 1 to 5 carbon atoms, X is a _{{(CH 2) n O}} m And an atomic group having a molecular weight of 600 or less, where n is 2 to 6 and m is 2 to 6. ]
The vinylidene fluoride polymer according to the present embodiment is a polymer having a first structural unit derived from vinylidene fluoride and a second structural unit derived from the compound represented by the formula (1).

In the compound represented by the formula (1), the atomic group forming X has a glycol skeleton structure composed of {(CH ₂ ) _n O} _m . The molecular weight of this atomic group is 600 or less, more preferably 400 or less, and even more preferably 150 or less.

In the compound represented by the formula (1), the atomic group forming X is an ethylene glycol skeleton [—C ₂ H ₄ O—] in which n is 2, or a propylene glycol skeleton in which n is 3. It is more preferable to have [—C ₃ H ₆ O—].

In Formula (1), R ₁ , R ₂ , and R ₃ are each independently a hydrogen atom, a chlorine atom, or an alkyl group having 1 to 5 carbon atoms, but from the viewpoint of polymerization reactivity, hydrogen or 1 carbon atom. ~ 3 alkyl groups are more preferred and hydrogen is particularly preferred.

  The compound represented by the formula (1) is more preferably a polyethylene glycol monoacrylate represented by the following formula (2) or a polypropylene glycol monoacrylate represented by the following formula (3). Of these, polyethylene glycol monoacrylate is particularly preferred.

  The arrangement of the constituent units constituting the vinylidene fluoride polymer may be any of a random copolymer, a block copolymer, and a graft copolymer.

  In addition, the vinylidene fluoride polymer according to the present embodiment includes, in addition to the first structural unit derived from vinylidene fluoride and the second structural unit derived from the compound represented by formula (1), yet another monomer. It is good also as a ternary or more polymer containing the structural unit derived from. Examples of such monomers include halogenated alkyl vinyl compounds, hydrocarbonated monomers, dimethacrylic acid (poly) alkylene glycol esters, diacrylic acid (poly) alkylene glycol esters, and polyvinylbenzene.

  Examples of the halogenated alkyl vinyl compound include a fluorinated alkyl vinyl compound. Specifically, for example, hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), trifluoroethylene (TFE), tetrafluoroethylene. , Hexafluoroethylene, and fluoroalkyl vinyl ether.

  Moreover, as another monomer, a polar group containing compound may be sufficient. As a polar group containing compound, the compound containing a carboxyl group, an epoxy group, or a sulfonic acid group etc. is mentioned, for example, It is preferable that it is a compound containing a carboxyl group especially. Specific examples include acrylic acid, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, acryloyloxyethyl acrylic acid, acryloyloxypropyl succinic acid, and the like. In addition, the said other monomer may be used individually by 1 type, and may use 2 or more types.

  The vinylidene fluoride polymer according to the present embodiment has a total of 100 mol% of the first structural unit derived from vinylidene fluoride and the second structural unit derived from the compound represented by the formula (1). In addition, the second structural unit is preferably included in the range of 0.01 to 10 mol%, more preferably in the range of 0.05 to 5 mol%, and in the range of 0.1 to 3 mol%. It is particularly preferable to include it.

  Further, in the case where the vinylidene fluoride polymer includes structural units derived from other monomers in addition to the first and second structural units, when the total of all the structural units is 100 mol%, The content of structural units derived from other monomers is preferably in the range of 0.01 to 10 mol%, for example. When the content of structural units derived from other monomers is more than 10 mol%, properties such as chemical resistance inherent in the fluororesin may be impaired.

  As a preferred embodiment of the present invention, the vinylidene fluoride polymer is a binary weight composed of a first structural unit derived from vinylidene fluoride and a second structural unit derived from the compound represented by the formula (1). It is a coalescence.

The abundance of each structural unit can be determined by ¹ H NMR or ¹⁹ F NMR.

  The inherent viscosity of the vinylidene fluoride polymer according to this embodiment (the logarithmic viscosity at 30 ° C. of a solution obtained by dissolving 4 g of resin in 1 liter of N, N-dimethylformamide) is 0.1 to 5.0 dL / g. It is preferable that it is 0.3 to 3.5 dL / g. If it is a viscosity within the said range, it can be conveniently used for the electrode mixture for nonaqueous electrolyte secondary batteries.

  It does not specifically limit as a method to manufacture the vinylidene fluoride polymer which concerns on this embodiment, Conventionally well-known methods, such as suspension polymerization, emulsion polymerization, and solution polymerization, can be mentioned. Among these, from the viewpoint of easiness of post-treatment and the like, the polymerization method is preferably aqueous suspension polymerization or emulsion polymerization, and more preferably aqueous suspension polymerization.

  As a suspending agent in suspension polymerization using water as a dispersion medium, methyl cellulose, methoxylated methyl cellulose, propoxylated methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, gelatin and the like can be used.

  In addition, as polymerization initiators, diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (perfluoroacyl) peroxide Oxide, t-butylperoxypivalate, etc. can be used.

  In addition, the degree of polymerization of the resulting polymer is adjusted by adding a chain transfer agent such as ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, and carbon tetrachloride. It is also possible.

[Binder composition]
The binder composition according to this embodiment contains the vinylidene fluoride polymer and a solvent. As the vinylidene fluoride polymer, the above-mentioned vinylidene fluoride polymer obtained by polymerizing vinylidene fluoride and the compound represented by the formula (1) may be used alone or in combination of two or more kinds. Also good.

  The binder composition according to this embodiment may further contain another polymer as long as the desired effect is not inhibited. Moreover, in the binder composition which concerns on this embodiment, unless the desired effect is inhibited, various additives may be included.

  By adding a conductive additive to the binder composition according to the present embodiment, an electrode mixture material described later can be obtained. Moreover, the electrode mixture mentioned later can be obtained by adding an electrode active material to this electrode mixture raw material. In addition, when adding a conductive support agent and / or an electrode active material to a binder composition, you may add these to a binder composition as it is. Or you may add a conductive support agent and / or an electrode active material to a solvent, and what was stirred and mixed may be added to a binder composition.

(solvent)
The solvent used in the binder composition in the present embodiment is not particularly limited as long as it is a solvent that can dissolve the vinylidene fluoride polymer, and may be a non-aqueous solvent or an aqueous solvent. Specifically, N-methyl-2-pyrrolidone (NMP), water, dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, hexamethylphosphoamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate , Trimethyl phosphate, acetone, methyl ethyl ketone, and tetrahydrofuran. These solvents may be used alone or as a mixed solvent in which two or more kinds are mixed. The solvent used in the binder composition is preferably a non-aqueous solvent, among which nitrogen-containing organic solvents such as N-methyl-2-pyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide are preferred, and N- Methyl-2-pyrrolidone is more preferred.

  In the binder composition, when the vinylidene fluoride polymer is 100 parts by mass, the amount of the solvent is preferably 400 to 10000 parts by mass, and more preferably 600 to 5000 parts by mass. Within the range of the amount of the solvent described above, the solution viscosity is moderate and the handling property is excellent.

(Other polymers)
In addition to the above-mentioned vinylidene fluoride polymer obtained by polymerizing vinylidene fluoride and the compound represented by the formula (1), the binder composition in the present embodiment is within a range that does not impair the effects of the present invention. Other polymers may be included.

  Examples of such other polymers include vinylidene fluoride homopolymers, vinylidene fluoride polymers not containing a structural unit derived from the compound represented by formula (1), and polar group-containing vinylidene fluoride polymers. Can be mentioned. More specifically, a VDF / APS copolymer containing a structural unit derived from mono (acryloxypropyl) succinate (APS) and a VDF / HFP copolymer containing a structural unit derived from hexafluoropropylene (HFP) And a VDF / AA copolymer containing a structural unit derived from acrylic acid (AA), a VDF / HFP / APS copolymer, and the like.

  When the binder composition contains the other polymer, the amount of the vinylidene fluoride polymer is preferably 1 part by mass or more, for example, 1 to 50 parts by mass when the other polymer is 100 parts by mass. is there.

(Other components of binder composition)
The binder composition in this embodiment may contain components other than the above-described components. Examples of other components include a dispersant such as polyvinylpyrrolidone.

[Electrode material mixture]
The electrode mixture raw material according to the present embodiment contains the binder composition and a conductive additive. By mixing the electrode mixture raw material and the electrode active material, an electrode mixture described later can be easily prepared. The electrode mixture raw material is in the form of a paste or slurry, and can be adjusted to a desired viscosity by adjusting the amount of the solvent.

(Conductive aid)
The conductive additive is added for the purpose of improving the conductivity of the electrode mixture layer when using an active material having a low electron conductivity such as LiCoO ₂ .

  Examples of the conductive assistant used in the present embodiment include a conductive assistant made of a carbon material. Such a conductive auxiliary agent is not particularly limited as long as it is made of a conductive carbon material. For example, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber, etc.), graphite fine powder, and graphite Carbon materials such as fibers can be used alone or in combination of two or more.

  The oxygen content of the conductive additive made of a carbon material is preferably less than 5% by mass, more preferably 2% by mass or less, and even more preferably 1% by mass or less. When the oxygen content of the conductive additive is 5% by mass or more, the viscosity of the electrode mixture becomes high, resulting in a problem that the handling property of the electrode mixture is deteriorated.

  Here, the oxygen content of the conductive auxiliary means the amount of oxygen in the compound, that is, the oxygen bonded to the carbon material in the carbon material constituting the conductive auxiliary, and is a value measured by elemental analysis. It is. More specifically, the oxygen content of the conductive assistant is the mass of hydrogen (H), carbon (C) and nitrogen (N) in the sample obtained by elemental analysis using a CHN analyzer (Parkin-elmer 2400II). From the ratio, it is calculated by the following formula.

Oxygen content (% by mass) = 100 (%) − (C (%) + H (%) + N (%))
The amount of the conductive auxiliary in the electrode mixture raw material is preferably 0.5 to 50.0% by mass when the total of the conductive auxiliary, the non-aqueous solvent and the vinylidene fluoride polymer is 100% by mass, It is more preferably 1 to 30% by mass, and further preferably 5 to 20% by mass.

[Electrode mixture]
The electrode mixture according to the present embodiment contains the binder composition, a conductive additive and an electrode active material. An electrode can be produced by applying this electrode mixture on a current collector to form an electrode mixture layer. The electrode mixture is in the form of a slurry, and can be adjusted to a desired viscosity by adjusting the amount of a solvent such as a binder composition.

  The electrode mixture can be used as an electrode mixture for a positive electrode or an electrode mixture for a negative electrode by changing the type of the electrode active material according to the type of the current collector to be applied. Since vinylidene fluoride polymers generally have excellent oxidation resistance, the electrode mixture in this embodiment is a positive electrode active material, that is, a positive electrode using a positive electrode active material (positive electrode material). It can be suitably used as an electrode mixture.

  Since the electrode mixture according to the present embodiment includes the binder composition containing the vinylidene fluoride polymer, an electrode obtained by applying and drying the electrode mixture on the current collector is the current collector and Excellent adhesion to the mixture layer.

(Electrode active material)
As described above, the electrode active material used in the electrode mixture in the present embodiment is an electrode active material for a negative electrode, that is, a negative electrode, when the electrode mixture according to the present embodiment is used as an electrode mixture for a negative electrode. An active material may be used. When the electrode mixture according to this embodiment is used as a positive electrode mixture, a positive electrode active material, that is, a positive electrode active material may be used.

Examples of the positive electrode active material include a lithium-based positive electrode active material containing lithium. Examples of the lithium-based positive electrode active material include a composite metal chalcogen compound represented by a general formula LiMY ₂ such as LiCoO ₂ and LiCo _x Ni _1-x O ₂ (0 ≦ x <1), or a composite metal oxide, LiMn ₂ O _And composite metal oxides having a spinel structure such as ₄ and olivine type lithium compounds such as LiFePO ₄ . Here, M is at least one of transition metals such as Co, Ni, Fe, Mn, Cr and V or Al, and Y is a chalcogen element such as O and S.

  As the negative electrode active material, conventionally known materials including carbon-based materials such as graphite can be used.

  In the electrode mixture according to the present embodiment, the vinylidene fluoride polymer is preferably 0.5 to 15 parts by mass per 100 parts by mass in total of the vinylidene fluoride polymer and the electrode active material, and 1 to 10 parts by mass. The electrode active material is preferably 85 to 99.5 parts by mass, and more preferably 90 to 99 parts by mass.

  When each component is contained within the above range, it is possible to produce the electrode with high productivity using the electrode mixture according to the present embodiment. When the electrode is produced, the mixture layer and the current collector Shows high adhesiveness (peel strength).

  As a method for producing the electrode mixture according to the present embodiment, the binder composition or the electrode mixture raw material and the electrode active material may be mixed so as to form a uniform slurry. The order of mixing is not particularly limited. For example, the electrode active material may be added as it is to the binder composition or the electrode mixture raw material. Alternatively, a vinylidene fluoride polymer is dissolved in a part of a solvent to obtain a binder solution, and an electrode active material, a conductive auxiliary agent and the remaining solvent are added to the binder solution, and the mixture is stirred and mixed to obtain an electrode mixture. be able to.

〔electrode〕
The electrode according to the present embodiment can be obtained by applying and drying the electrode mixture on a current collector. The electrode according to the present embodiment includes a current collector and a layer formed from an electrode mixture. In addition, when a negative electrode mixture is used as the electrode mixture, a negative electrode is obtained, and when a positive electrode mixture is used as the electrode mixture, a positive electrode is obtained.

  In addition, in this invention, the layer formed from an electrode mixture formed by apply | coating and drying an electrode mixture to a collector is described as a mixture layer.

  The current collector used in the present invention includes, for example, copper in order to obtain a negative electrode, and examples of the shape thereof include a metal foil and a metal net. In order to obtain a negative electrode, it is preferable to use a copper foil as the current collector.

  The current collector used in the present invention includes, for example, aluminum in order to obtain a positive electrode, and examples of the shape thereof include a metal foil and a metal net. In order to obtain a positive electrode, it is preferable to use an aluminum foil as the current collector.

  The thickness of the current collector is usually 5 to 100 μm, preferably 5 to 20 μm.

The thickness of the mixture layer is usually 20 to 250 μm, preferably 20 to 150 μm. Moreover, the fabric weight of a mixture layer is 20-700 g / m < ² > normally, Preferably it is 30-500 g / m < ² >.

  When manufacturing the electrode which concerns on this embodiment, an electrode mixture is apply | coated to at least one surface of an electrical power collector, Preferably it is both surfaces. The method for coating is not particularly limited, and examples thereof include a method using a bar coater, a die coater, or a comma coater.

  Moreover, as drying performed after apply | coating, it is normally performed for 1 to 300 minutes at the temperature of 50-150 degreeC. Moreover, the pressure at the time of drying is not particularly limited, but it is usually carried out under atmospheric pressure or reduced pressure.

  Further, heat treatment may be performed after drying. When performing heat processing, it is normally performed for 1 to 300 minutes at the temperature of 100-250 degreeC. In addition, although the temperature of heat processing overlaps with the said drying, these processes may be a separate process and the process performed continuously.

  Further, press processing may be performed. When performing a press process, it is normally performed at 1-200 MPa-G. It is preferable to perform the press treatment because the electrode density can be improved.

  When the electrode mixture is applied to one surface of the current collector, the electrode layer structure is a two-layer structure of the mixture layer / current collector, and the electrode mixture is applied to both surfaces of the current collector. Has a three-layer structure of a mixture layer / current collector / mixture layer.

  In the electrode according to the present embodiment, since the current collector and the mixture layer exhibit high adhesiveness (peeling strength) by using the electrode mixture, the electrode cracks in processes such as pressing, slitting, and winding. And peeling are less likely to occur, leading to improved productivity.

[Nonaqueous electrolyte secondary battery]
The nonaqueous electrolyte secondary battery according to this embodiment includes the electrode.

  The nonaqueous electrolyte secondary battery according to the present embodiment is not particularly limited except that the electrode is provided. As the nonaqueous electrolyte secondary battery, the electrode, preferably the positive electrode, is used, and conventionally known members can be used for members other than the electrode, such as a separator.

[Summary]
The binder composition according to the present invention is a binder composition used for binding an electrode active material to a current collector, the binder composition comprising a first structural unit derived from vinylidene fluoride, Following formula (1)

[In the formula _{(1), R 1, R} 2, R 3 each independently represent a hydrogen atom, a chlorine atom or an alkyl group having 1 to 5 carbon atoms, X is a _{{(CH 2) n O}} m And an atomic group having a molecular weight of 600 or less, where n is 2 to 6 and m is 2 to 6. ]
The vinylidene fluoride polymer containing the 2nd structural unit derived from the compound represented by these is contained.

  In the binder composition according to the present invention, the vinylidene fluoride polymer contains 0.01 to 10 mol% of the second structural unit (provided that the first structural unit and the second structural unit are included). In the range of 100 mol%).

  In the binder composition according to the present invention, the inherent viscosity of the vinylidene fluoride polymer is preferably 0.1 to 5.0 dL / g.

  Moreover, it is preferable that the binder composition concerning this invention further contains a non-aqueous solvent.

  The electrode mixture raw material according to the present invention includes the binder composition described above and a conductive auxiliary composed of a carbon material, and the oxygen content of the conductive auxiliary is less than 5% by mass. 0.5 to 50.0% by mass (provided that the total of the conductive assistant, the non-aqueous solvent, and the vinylidene fluoride polymer is 100% by mass).

  The electrode mixture which concerns on this invention is an electrode mixture containing the above-mentioned electrode mixture raw material and an electrode active material.

  The electrode which concerns on this invention is an electrode provided with the mixture layer formed from the above-mentioned electrode mixture on a collector.

  The nonaqueous electrolyte secondary battery according to the present invention is a nonaqueous electrolyte secondary battery including the above-described electrode.

  The method for producing an electrode mixture according to the present invention includes a step of preparing an electrode mixture material containing the binder composition, a conductive additive, and a nonaqueous solvent, and a polar group in the electrode mixture material. And a step of preparing an electrode mixture by adding a vinylidene fluoride polymer.

  Examples will be shown below, and the embodiments of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention.

  As will be described later, an electrode mixture was produced using various binder compositions according to the present invention, and an evaluation test for peel strength and slurry viscosity was performed using the mixture.

  In addition, “inherent viscosity” in the present specification is a value measured by the following method.

(Inherent viscosity ηi)
In order to calculate the inherent viscosity ηi, a vinylidene fluoride polymer solution is prepared by dissolving 80 mg of vinylidene fluoride polymer in 20 mL of N, N-dimethylformamide. The viscosity η of the solution is measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C. The inherent viscosity ηi is obtained by the following formula using the viscosity η.
ηi = (1 / C) · ln (η / η0)
In the above formula, η0 is the viscosity of N, N-dimethylformamide as a solvent, and C is 0.4 g / dL.

[Example 1]
As a monomer A, 60 g of polyvinylidene fluoride (PVDF) was placed in a polyethylene bag (Lami Zip (registered trademark), manufactured by Nippon Production Co., Ltd.), and the inside of the bag was purged with nitrogen. Thereafter, the bag entrance was heat sealed and sealed.

  Next, the bag sealed with the PVDF was irradiated with an electron beam so that the absorbed dose of PVDF was 30 kGy, thereby producing an electron beam irradiated PVDF.

  Thereafter, 2.9 g of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2) represented by the formula (2), 36.3 g of ion-exchanged water, and 13 g of isopropyl alcohol are added as monomer B to a 300 ml sample bottle. 30 g of electron beam irradiated PVDF (1) was added thereto and mixed with stirring at 25 ° C. for 3 hours.

  The stirred reaction mixture was taken out and transferred to Nutsche attached to a suction filter bottle. The reaction product was washed and filtered in Nutsche using ion-exchanged water to remove unreacted EGMA and EGMA homopolymer. Thereafter, the reaction product was washed and filtered in Nutsche using ethanol. Then, it dried at 75 degreeC for 5 hours, and obtained the polymer (VDF / EGMA polymer) of vinylidene fluoride (VDF) and polyethyleneglycol monoacrylate (EGMA).

The resulting VDF / EGMA polymer, from the ¹ H NMR spectrum obtained by ¹ H NMR measurement of the following conditions to measure the EGMA introduction amount of the polymer.

Apparatus: Bruker AVANCE AC 400FT NMR spectrum meter Measurement conditions Frequency: 400 MHz
Measuring solvent: DMSO-d ₆
Measurement temperature: 25 ° C
The amount of the first structural unit derived from the vinylidene fluoride of the polymer and the amount of the second structural unit derived from the EGMA were adjusted to 4.00 to 4.20 ppm mainly derived from EGMA in the ¹ H NMR spectrum. Calculation was based on the observed signal and the integrated intensity of the signal observed mainly at 2.24 ppm and 2.87 ppm derived from vinylidene fluoride.

  In the obtained VDF / EGMA polymer, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 99.68 mol%, and the amount of the second structural unit derived from EGMA (EGMA Amount) was 0.32 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / EGMA polymer, the inherent viscosity was 1.5 dL / g.

  1 g of the VDF / EGMA polymer obtained above and 9 g of N-methyl-2pyrrolidone (NMP) were mixed to prepare a 10% by mass solution of the VDF / EGMA polymer.

Lithium-nickel-cobalt-manganese composite oxide (NCM523; Li _1.00 Ni _0.50 Mn _0.20 Co _0.20 O ₂ , average particle size 11 μm) as an electrode active material and 10.0 g as a conductive additive Carbon black (SP; Super-P (registered trademark) manufactured by Timcal Japan, average particle size 40 nm, specific surface area 60 m ² / g, oxygen content 0.3 mass%) 0.1 g was mixed, and NMP 1.1 g was mixed there. Then, 2.0 g of a 10% by mass solution of VDF / EGMA polymer was added and mixed to prepare a slurry-like positive electrode mixture.

The obtained positive electrode mixture was coated on a 15 μm thick Al foil with a bar coater and dried at 110 ° C. for 30 minutes to produce a single-side coated electrode (positive electrode) having a single-sided weight of 200 g / m ² .

A single-side coated electrode (positive electrode) having a weight per side of 200 g / m ² is cut into a length of 100 mm and a width of 20 mm, and a tensile tester (“STA-1150 UNIVERSAL TESTING MACHINE” manufactured by ORIENTEC Co., Ltd.) according to JIS K6854-1. ), A 90 ° peel test was conducted at a head speed of 10 mm / min, and the peel strength (positive electrode) was measured, and found to be 8.2 gf / mm.

The slurry viscosity of the positive electrode mixture was measured at 25 ° C. and a shear rate of 2 s ⁻¹ using an E-type viscometer. The slurry viscosity was measured by waiting 60 seconds after the slurry was charged into the measuring apparatus and then rotating the rotor. Moreover, the maximum value of the viscosity within 100 seconds from the start of rotation of the rotor was defined as the slurry viscosity. The slurry viscosity of the positive electrode mixture thus measured was 4750 mPa · s.

[Example 2]
A VDF / EGMA polymer was obtained in the same manner as in Example 1 except that the addition amount of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2) represented by the formula (2) was changed to 0.57 g. It was.

  About the obtained VDF / EGMA polymer, when the amount of EGMA introduced into the polymer was measured in the same manner as in Example 1, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 99. The amount of the second structural unit derived from EGMA (EGMA amount) was 0.13 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / EGMA polymer, the inherent viscosity was 1.5 dL / g.

  Using the obtained VDF / EGMA polymer, a binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1, and the peel strength (positive electrode) was measured. It was 4 gf / mm. The slurry viscosity was 4625 mPa · s.

[Example 3]
As monomer B, polyethylene glycol monoacrylate (EGMA, n = 2, m = 4) was used instead of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2), and the addition amount was 0.52 g. A VDF / EGMA polymer was obtained in the same manner as in Example 1 except that.

  About the obtained VDF / EGMA polymer, when the amount of EGMA introduced into the polymer was measured in the same manner as in Example 1, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 99. The amount of the second structural unit derived from EGMA (EGMA amount) was 0.46 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / EGMA polymer, the inherent viscosity was 1.5 dL / g.

  Using the obtained VDF / EGMA polymer, a binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1, and the peel strength (positive electrode) was measured. 0.7 gf / mm. The slurry viscosity was 4270 mPa · s.

[Example 4]
A binder composition, a positive electrode mixture, and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1 except that carbon nanotubes (CNT; oxygen content 2.0 mass%) were used as the conductive assistant. The peel strength (positive electrode) was measured and found to be 0.8 gf / mm. The slurry viscosity was 17600 mPa · s.

[Example 5]
In an autoclave having an internal volume of 2 liters, 1096 g of ion-exchanged water, 0.2 g of Metroles (registered trademark) 90SH-100 (manufactured by Shin-Etsu Chemical Co., Ltd.), 2.2 g of a 50 mass% diisopropyl peroxydicarbonate-fluorocarbon 225 cb solution, Each amount of 426 g of vinylidene chloride (monomer A) and an initial addition amount of 0.2 g of acryloyloxypropyl succinic acid (APS, monomer B) was charged, and the temperature was raised to 26 ° C. over 1 hour. Thereafter, the temperature was maintained at 26 ° C., and a 6 mass% acryloyloxypropyl succinic acid aqueous solution was gradually added at a rate of 0.5 g / min. The resulting polymer slurry was dehydrated and dried to obtain a vinylidene fluoride copolymer containing a polar group (VDF / APS copolymer, polymer A). A total of 4.0 g of acryloyloxypropyl succinic acid was added, including the amount added initially.

  Using this VDF / APS copolymer (polymer A) and the VDF / EGMA polymer (polymer B) obtained in Example 1, VDF / APS copolymer: VDF / EGMA polymer = 9: 1. To obtain a blend polymer. The inherent viscosity of this blend polymer was 1.5 dL / g.

  0.6 g of the blend polymer obtained above and 9.4 g of N-methyl-2pyrrolidone (NMP) were mixed to prepare a 6% by mass solution of a blend binder. A positive electrode mixture and a single-side coated electrode (positive electrode) were produced in the same manner as in Example 1 except that this blend binder 6 mass% solution was used, and the peel strength (positive electrode) was measured to find 1.1 gf / mm. The slurry viscosity was 140013 mPa · s.

[Example 6]
In an autoclave with an internal volume of 2 liters, 1280 g of ion-exchanged water, 0.4 g of Metroles (registered trademark) 90SH-100 (manufactured by Shin-Etsu Chemical Co., Ltd.), 1.7 g of a 50 mass% diisopropyl peroxydicarbonate-fluorocarbon 225 cb solution and Each amount of vinylidene chloride (monomer A) 400 g was charged and heated to 45 ° C. over 1 hour. Thereafter, the temperature was maintained at 45 ° C., and 0.02 mass% polyethylene glycol monoacrylate (EGMA, n = 2, m = 2, monomer B) was gradually added at a rate of 0.5 g / min. The obtained polymer slurry was dehydrated and dried to obtain a vinylidene fluoride polymer (VDF / EGMA polymer, polymer B) containing a polar group. Polyethylene glycol monoacrylate (EGMA, n = 2, m = 2) was added in a total amount of 4.0 g including the amount added initially.

  About the obtained VDF / EGMA polymer, when the amount of EGMA introduced into the polymer was measured in the same manner as in Example 1, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 99. The amount of the second structural unit derived from EGMA (EGMA amount) was 0.24 mol%.

  Using this VDF / EGMA polymer (Polymer B) and the VDF / APS copolymer (Polymer A) obtained in Example 5, VDF / APS copolymer: VDF / EGMA polymer = 9: 1. To obtain a blend polymer. The inherent viscosity of this blend polymer was 1.5 dL / g.

  A positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 5 except that the blend polymer obtained above was used, and the peel strength (positive electrode) was measured, and 1.0 gf / mm was measured. Met. The slurry viscosity was 152525 mPa · s.

[Example 7]
1 g of VDF / EGMA polymer used in Example 6 and 9 g of N-methyl-2pyrrolidone (NMP) were mixed to prepare a 10% by mass solution of VDF / EGMA polymer.

  1 g of the above VDF / EGMA polymer solution, 0.1 g of carbon nanotubes (CNT; oxygen content 2.0 mass%) used in Example 4 as a conductive auxiliary agent, and 2 g of NMP were mixed, and an electrode mixture raw material was used. Obtained.

  Using the electrode mixture raw material, the slurry viscosity of the electrode mixture raw material was measured in the same manner as in the positive electrode mixture of Example 1, and was 11519 mPa · s.

[Comparative Example 1]
Instead of the VDF / EGMA polymer, the binder composition and the positive electrode composite were prepared in the same manner as in Example 1, except that the polyvinylidene fluoride (PVDF, inherent viscosity 1.7 dL / g) used in Example 1 was used as it was. An agent and a single-side coated electrode (positive electrode) were prepared. The peel strength (positive electrode) of the obtained positive electrode mixture was measured and found to be 3.4 gf / mm. The slurry viscosity was 4750 mPa · s.

[Comparative Example 2]
Example except that 4-hydroxybutyl acrylate (HBA) was used as the monomer B instead of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2) and the addition amount was 2.86 g. In the same manner as in Example 1, a VDF / HBA polymer was obtained.

About the obtained VDF / HBA polymer, the amount of HBA introduced into the polymer was measured by ¹ H NMR measurement under the same conditions as in Example 1.

The amount of the first structural unit derived from the vinylidene fluoride of the polymer and the amount of the second structural unit derived from HBA are signals observed at 4.00 ppm mainly derived from HBA in the ¹ H NMR spectrum. And based on the integrated intensity of signals observed mainly at 2.24 ppm and 2.87 ppm derived from vinylidene fluoride.

  In the obtained VDF / HBA polymer, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 99.46 mol%, and the amount of the second structural unit derived from HBA (HBA Amount) was 0.54 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / HBA polymer, the inherent viscosity was 1.5 dL / g.

  Using the obtained VDF / HBA polymer, a binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1, and the peel strength (positive electrode) was measured. It was 2 gf / mm. The slurry viscosity was 4000 mPa · s.

[Comparative Example 3]
As monomer B, acrylic acid (AA) was used instead of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2), and the addition amount was 0.57 g. Thus, a VDF / AA polymer was obtained.

  About the obtained VDF / AA polymer, the quantity (AA quantity) of the 2nd structural unit derived from AA was calculated | required by neutralization titration using 0.03 mol / L sodium hydroxide aqueous solution. More specifically, a solution to be titrated was prepared by dissolving 0.3 g of a polymer in 9.7 g of acetone at about 80 ° C. and then adding 3 g of pure water. As an indicator, phenolphthalein was used, and neutralization titration was performed using a 0.03 mol / L aqueous sodium hydroxide solution at room temperature.

  Furthermore, the amount of the first structural unit derived from vinylidene fluoride was calculated from the relationship between the amount of AA determined by neutralization titration and the total amount of polymer used for neutralization titration.

  In the obtained VDF / AA polymer, the amount of the first structural unit derived from vinylidene fluoride (the amount of VDF) was 99.70 mol%, and the amount of the second structural unit derived from AA (AA Amount) was 0.30 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / AA polymer, the inherent viscosity was 1.5 dL / g.

  Using the obtained VDF / AA polymer, a binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1, and the peel strength (positive electrode) was measured. 0.8 gf / mm. The slurry viscosity was 8125 mPa · s.

[Comparative Example 4]
A binder composition, a positive electrode mixture, and a single-side coated electrode (positive electrode) were used in the same manner as in Example 4 except that the VDF / AA polymer obtained in Comparative Example 3 was used instead of the VDF / EGMA polymer. The peel strength (positive electrode) was measured and found to be 0.6 gf / mm. The slurry viscosity was 26800 mPa · s.

[Comparative Example 5]
As monomer B, instead of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2), mono (acryloxypropyl) succinate (APS) was used, and the addition amount was 0.57 g. In the same manner as in Example 1, a VDF / APS polymer was obtained.

About the obtained VDF / APS polymer, the amount of APS introduced into the polymer was measured by ¹ H NMR measurement under the same conditions as in Example 1.

The amount of the first structural unit derived from the vinylidene fluoride of the polymer and the amount of the second structural unit derived from APS are signals observed at 4.18 ppm mainly derived from APS in the ¹ H NMR spectrum. And based on the integrated intensity of signals observed mainly at 2.24 ppm and 2.87 ppm derived from vinylidene fluoride.

  In the obtained VDF / APS polymer, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 99.67 mol%, and the amount of the second structural unit derived from APS (APS Amount) was 0.33 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / APS polymer, the inherent viscosity was 1.5 dL / g.

  Using the obtained VDF / APS polymer, a binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1, and the peel strength (positive electrode) was measured. 0.9 gf / mm. The slurry viscosity was 6000 mPa · s.

[Comparative Example 6]
A mixture of polyvinylidene fluoride (PVDF) and EGMA (slurry added) used in Example 1 instead of VDF / EGMA polymer (mass ratio PVDF / EGMA = 1 / 0.008, inherent viscosity 1.5 dL / g) A binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were produced in the same manner as in Example 1 except that was used. The peel strength (positive electrode) of the obtained positive electrode mixture was measured and found to be 4.4 gf / mm.

[Comparative Example 7]
As monomer B, 2- (2-ethoxyethoxy) ethyl acrylate (EEEA) was used instead of polyethylene glycol monoacrylate (EGMA, n = 2, m = 2), and the addition amount was 2.9 g. Except for the above, a VDF / EEEA polymer was obtained in the same manner as in Example 1.

About the obtained VDF / EEEA polymer, the amount of EEEA introduced into the polymer was measured by ¹ H NMR measurement under the same conditions as in Example 1.

The amount of the first structural unit derived from the vinylidene fluoride of the polymer and the amount of the second structural unit derived from EEEA are signals observed at 4.11 ppm mainly derived from EEEA in the ¹ H NMR spectrum. And based on the integrated intensity of signals observed mainly at 2.24 ppm and 2.87 ppm derived from vinylidene fluoride.

  In the obtained VDF / EEEA polymer, the amount of the first structural unit derived from vinylidene fluoride (VDF amount) was 98.30 mol%, and the amount of the second structural unit derived from EEEA (EEEA Amount) was 1.70 mol%. Moreover, when the inherent viscosity was measured about the obtained VDF / EEEA polymer, the inherent viscosity was 1.5 dL / g.

  Using the obtained VDF / EEEA polymer, a binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1, and the peel strength (positive electrode) was measured. 0.9 gf / mm.

[Comparative Example 8]
Instead of VDF / EGMA polymer, a mixture of polyvinylidene fluoride (PVDF) used in Example 1 and polyethylene glycol (PEG, average molecular weight 1500) (mass ratio PVDF / PEG = 1 / 0.075, inherent viscosity) A binder composition, a positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1 except that 1.5 dL / g) was used. The peel strength (positive electrode) of the obtained positive electrode mixture was measured and found to be 3.0 gf / mm.

[Comparative Example 9]
In an autoclave having an internal volume of 2 liters, 900 g of ion-exchanged water, 0.4 g of hydroxypropylmethylcellulose, 6 g of butyl peroxypivalate, 396 g of vinylidene fluoride (monomer A), and an initial amount of 0.8 g of acrylic acid (monomer B) were added. Each amount was charged and heated to 50 ° C. A 1% by mass aqueous acrylic acid solution containing acrylic acid was continuously supplied to the reaction vessel under the condition that the pressure was kept constant during the polymerization. The obtained polymer slurry was dehydrated and dried to obtain a vinylidene fluoride copolymer containing a polar group (VDF / AA copolymer, polymer B). A total of 4.0 g of acrylic acid was added, including the amount added initially.

  Using this VDF / AA copolymer (Polymer B) and the VDF / APS copolymer (Polymer A) obtained in Example 5, VDF / APS copolymer: VDF / AA copolymer = 9: Blending was performed to obtain a blend polymer. The inherent viscosity of this blend polymer was 1.5 dL / g.

  0.6 g of the blend polymer obtained above and 9.4 g of N-methyl-2pyrrolidone (NMP) were mixed to prepare a 6% by mass solution of a blend binder. A positive electrode mixture and a single-side coated electrode (positive electrode) were prepared in the same manner as in Example 1 except that this blend binder 6 mass% solution was used, and the peel strength (positive electrode) was measured. mm. The slurry viscosity was 177350 mPa · s.

[Comparative Example 10]
1 g of the VDF / AA copolymer used in Comparative Example 9 and 9 g of N-methyl-2pyrrolidone (NMP) were mixed to prepare a 10% by mass solution of the VDF / AA copolymer.

  1 g of the above VDF / AA copolymer solution, 0.1 g of carbon nanotubes (CNT; oxygen content 2.0 mass%) used in Example 4 as a conductive assistant, and 2 g of NMP were mixed, and an electrode mixture raw material Got.

  When the slurry viscosity of the electrode mixture raw material was measured in the same manner as in the positive electrode mixture of Example 1, using the electrode mixture raw material, it was 42699 mPa · s.

  The results of Examples 1 to 7 and Comparative Examples 1 to 10 are shown in Tables 1, 2, and 3 below.

  As shown in Table 1, Examples 1 to 3 showed high peel strength and low slurry viscosity.

  In contrast, Comparative Example 1 using PVDF as the binder resin in the binder composition showed a low slurry viscosity but a low peel strength. The same applies to Comparative Example 2 in which a VDF / HBA polymer is used as a binder resin, and the peel strength is inferior to Examples 1-3.

  Although the comparative example 3 using a VDF / AA polymer as a binder resin shows a good peel strength, the slurry viscosity is high and the slurry characteristics are inferior to those of Examples 1 to 3.

  Further, in Example 4 using the polymer of the present invention as the binder resin, the peel strength was increased and the slurry viscosity was reduced as compared with Comparative Example 4 using the VDF / AA polymer.

  Further, Comparative Example 5 using a VDF / APS polymer as a binder resin, Comparative Example 6 using a mixture of PVDF and EGMA, Comparative Example 7 using a VDF / EEEA polymer, and Comparative Example using a mixture of PVDF and PEG All 8 were inferior to the examples in either or both of peel strength and slurry properties.

  Moreover, as shown in Table 2, Examples 5-6 which blended VDF / EGMA polymer and VDF / APS copolymer showed high peeling strength and low slurry viscosity.

  On the other hand, Comparative Example 9 in which a VDF / AA copolymer and a VDF / APS copolymer were blended did not contain a VDF / EGMA polymer, and thus had a high slurry viscosity.

  In addition, as shown in Table 3, Example 7 which is an electrode mixture raw material composed of a conductive additive, an organic solvent, and a VDF / EGMA polymer is different from the VDF / EGMA polymer. The slurry viscosity was significantly lower than that of Comparative Example 10 including coalescence.

  The present invention can be used as a binder composition used for binding a current collector and an electrode active material in a non-aqueous electrolyte secondary battery.

Claims (9)

A binder composition used for binding an electrode active material to a current collector,
The binder composition contains a vinylidene fluoride polymer containing a first structural unit derived from vinylidene fluoride and a second structural unit derived from a compound represented by the following formula (1). object.

[In the formula _{(1), R 1, R} 2, R 3 each independently represent a hydrogen atom, a chlorine atom or an alkyl group having 1 to 5 carbon atoms, X is a _{{(CH 2) n O}} m And an atomic group having a molecular weight of 600 or less, where n is 2 to 6 and m is 2 to 6. ]   The vinylidene fluoride polymer contains 0.01 to 10 mol% of the second structural unit (provided that the total of the first structural unit and the second structural unit is 100 mol%). The binder composition according to claim 1, comprising a range.   The binder composition according to claim 1 or 2, wherein the inherent viscosity of the vinylidene fluoride polymer is 0.1 to 5.0 dL / g.   The binder composition according to any one of claims 1 to 3, further comprising a non-aqueous solvent. The binder composition according to claim 4 and a conductive auxiliary agent made of a carbon material,
The oxygen content of the conductive assistant is less than 5% by mass,
The conductive auxiliary agent is included in a range of 0.5 to 50.0% by mass (however, the total of the conductive auxiliary agent, the non-aqueous solvent, and the vinylidene fluoride polymer is 100% by mass), Electrode material mixture.   An electrode mixture comprising the electrode mixture material according to claim 5 and an electrode active material.   The electrode which equips a collector with the mixture layer formed from the electrode mixture of Claim 6.   A nonaqueous electrolyte secondary battery comprising the electrode according to claim 7. A method for producing an electrode mixture,
The process of preparing the electrode mixture raw material containing the binder composition of any one of Claim 1 to 3, a conductive support agent, and a nonaqueous solvent, and polar group containing fluorination in the said electrode mixture raw material The manufacturing method of the electrode mixture characterized by including the process of adding a vinylidene polymer and preparing an electrode mixture.