JP6244673B2 - Binder for positive electrode of electricity storage device - Google Patents

Description

  The present invention relates to an electrode binder used for an electrode of an electricity storage device.

  Lithium ion secondary batteries have high energy density and high capacity, and are therefore widely used as driving power sources for mobile information terminals. In recent years, use in industrial applications, such as mounting on electric / hybrid vehicles that require large capacity, is also becoming widespread. Therefore, studies have been made to further increase the capacity and performance.

  Lithium ion secondary batteries have a higher charge / discharge voltage than conventional secondary batteries such as nickel hydride secondary batteries, nickel cadmium secondary batteries, and lead secondary batteries. The electrode is exposed to a high potential. As a result, voltage resistance, that is, oxidation resistance and reduction resistance are required for a binder or the like which is an electrode material constituting the positive and negative electrodes.

  Styrene butadiene rubber and polyvinylidene fluoride are known as binders currently used for electrodes of lithium ion secondary batteries. However, these materials have problems such as high cost, insufficient binding properties, and insufficient voltage resistance.

  Therefore, Patent Document 1 proposes an electrode mixture binder containing an aromatic polyamide and an amine solvent for the purpose of providing a binder having high electrochemical stability. As a polyamide-based electrode binder, the present applicant also first includes a polyamic acid containing a tetracarboxylic acid component and a diamine component, a carboxylic acid compound having two pairs of carboxyl groups in the molecule or an esterified product thereof, and a solvent. The binder resin precursor solution composition for electrodes containing was proposed (refer patent document 2).

JP 2012-142244 A International Publication No. 2010/113991 Pamphlet

  However, the characteristics required for the lithium ion secondary battery are increasing, and a binder having higher withstand voltage than that of the binder used so far is required. Accordingly, an object of the present invention is to provide a binder for an electrode whose performance is further improved as compared with the conventional techniques described above.

  As a result of intensive studies to solve the above problems, the present inventors have found that it is effective to use an oxalic acid compound as a unit derived from a dicarboxylic acid in a binder containing a polyamide-based resin.

  The present invention has been made on the basis of the above knowledge, and includes the polyamide resin comprising a dicarboxylic acid component and a diamine component, and providing the binder for an electrode of an electricity storage device, wherein the dicarboxylic acid component is oxalic acid. Is a solution.

  According to the present invention, an electrode binder having high voltage resistance is provided. Therefore, the battery using the binder of the present invention has good cycle characteristics and a long life.

FIG. 1 is a diagram showing the measurement results of linear sweep voltammetry measured for the electrode obtained in Example 1. FIG. FIG. 1 is a view showing the measurement result (5th cycle) of cyclic voltammetry measured for the electrode obtained in Example 1. FIG.

  The binder of this invention is used for the electrode of an electrical storage device. Representative examples of the electricity storage device include a secondary battery and an electric double layer capacitor, but are not limited thereto. In any form of the electricity storage device, the electrode is formed by applying an electrode mixture containing at least the binder of the present invention and a conductive additive to the surface of the current collector. The binder of the present invention is used to bind a conductive additive and hold it on the surface of the current collector. When the electricity storage device is a secondary battery, the electrode mixture includes the active material in addition to the binder of the present invention and the conductive additive.

  When the electricity storage device is a secondary battery, the binder of the present invention is advantageously used for an electrode of a nonaqueous electrolyte secondary battery. For example, it is advantageous to be used for an electrode of a lithium ion secondary battery. The nonaqueous electrolyte secondary battery has a higher battery voltage than the aqueous electrolyte secondary battery, and the binder of the present invention has a high voltage resistance as described later. Therefore, the nonaqueous electrolyte secondary battery is used as an electrode for the nonaqueous electrolyte secondary battery. This is because it is difficult to deteriorate.

  The binder of the present invention has a basic structure of polyamide. Polyamide is generally composed of a dicarboxylic acid component and a diamine component, and the binder of the present invention has one of the characteristics of the dicarboxylic acid component. Specifically, the binder of the present invention uses oxalic acid as a dicarboxylic acid component in the basic structure of polyamide. That is, a unit derived from an oxalic acid compound is used as a unit derived from a dicarboxylic acid. An amide bond in which the dicarboxylic acid component is succinic acid is generally called an oxamide bond. Therefore, it can be said that the binder of this invention contains the polyamide containing an oxamide bond unit. As a result of the examination by the present inventors, it was found that the binder of the present invention unexpectedly shows a high voltage resistance due to containing the oxamide bond unit.

  Succinic acid, which is a dicarboxylic acid component used as a raw material for the polyamide used in the binder of the present invention, is a compound that provides an oxamide bond unit to the binder. As a raw material for introducing oxalic acid into the main chain skeleton of polyamide, a compound derived from oxalic acid such as oxalic acid and / or oxalic acid diester (hereinafter also referred to as “oxalic acid compound”) is used. The oxalic acid compound only needs to have reactivity with an amino group. When producing polyamides at a high polymerization temperature, succinic acid may be thermally decomposed when oxalic acid itself is used as a raw material. Therefore, the oxalic acid compound produced at a high polymerization temperature was derived from oxalic acid. Compounds are preferred.

  As the compound derived from oxalic acid, oxalic acid diester is preferable from the viewpoint of suppressing side reactions in the polycondensation reaction. Succinic acid diesters include oxalic acid diesters of aliphatic monohydric alcohols, oxalic acid diesters of alicyclic alcohols, and oxalic acid diesters of aromatic alcohols.

Examples of oxalic acid diesters of aliphatic monohydric alcohols include dimethyl oxalate, diethyl oxalate, di-n- (or i-) propyl oxalate, di-n- (or i-, or t-) butyl oxalate, An oxalic acid diester of an aliphatic monohydric alcohol having 3 or more carbon atoms is preferable, di-n-butyl oxalate, di-butyl oxalate and / or di-t-butyl oxalate is more preferable, and di-n-butyl oxalate is still more preferable. The two alcohol residues in the succinic acid diester may be the same or different.
Examples of oxalic acid diesters of alicyclic alcohols include dicyclohexyl oxalate.
Examples of oxalic acid diesters of aromatic alcohols include diphenyl oxalate.
The oxalic acid diester is preferably at least one selected from the group consisting of an oxalic acid diester of an aliphatic monohydric alcohol having more than 3 carbon atoms, an oxalic acid diester of an alicyclic alcohol, and an oxalic acid diester of an aromatic alcohol. n-Butyl, di-i-butyl oxalate and / or di-t-butyl oxalate are more preferred, and di-n-butyl oxalate is still more preferred.

  These oxalic acid compounds can be added alone or in combination of two or more at the time of producing the polyamide resin.

Examples of raw materials for dicarboxylic acid components other than oxalic acid compounds include dicarboxylic acids other than oxalic acid compounds, diamines, lactams, aminocarboxylic acids, and the like.
Examples of dicarboxylic acids other than oxalic acid compounds include aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, aromatic dicarboxylic acids, and compounds derived therefrom.
Aliphatic dicarboxylic acids include malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, 3,3-diethylsuccinic acid. Examples include acids, azelaic acid, sebacic acid, and suberic acid.
Examples of the alicyclic dicarboxylic acid include 1,3-cyclopentane dicarboxylic acid and 1,4-cyclohexane dicarboxylic acid.
Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3 -Phenylenedioxydiacetic acid, dibenzoic acid, 4,4'-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid Can be mentioned.
Dicarboxylic acids other than these succinic acid compounds can be added alone or in combination of two or more when the polyamide resin is produced.
Furthermore, polycarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid can be used within the range where melt molding is possible regardless of the presence or absence of dicarboxylic acids other than oxalic acid compounds.

  The oxalic acid compound is preferably 50 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, from the viewpoint of water absorption of the obtained polymer in all dicarboxylic acids used in the polyamide resin. Still more preferably, it is 95 mol% or more, Most preferably, it is 99 mol% or more. When the proportion of the oxalic acid compound is large, the water absorption tends to be low.

  The oxalic acid compound is preferably 10 mol% or more, more preferably 30 mol% or more, and still more preferably 49 mol%, from the viewpoint of water absorption of the obtained polymer in all raw materials used for the polyamide resin. That's it.

  In the polyamide used for the binder of the present invention, other dicarboxylic acid components other than the oxalic acid compound can be used as long as the effects of the present invention are not impaired. As such other dicarboxylic acid components, for example, aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, aromatic dicarboxylic acid and the like can be used alone or in combination.

Aliphatic dicarboxylic acids include malonic acid, dimethylmalonic acid, succinic acid, glutaric acid, adipic acid, 2-methyladipic acid, trimethyladipic acid, pimelic acid, 2,2-dimethylglutaric acid, 3,3-diethylsuccinic acid. Examples include acids, azelaic acid, sebacic acid, and suberic acid.
Examples of the alicyclic dicarboxylic acid include 1,3-cyclopentane dicarboxylic acid and 1,4-cyclohexane dicarboxylic acid.
Aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,4-phenylenedioxydiacetic acid, 1,3 -Phenylenedioxydiacetic acid, dibenzoic acid, 4,4'-oxydibenzoic acid, diphenylmethane-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, etc. Is mentioned.
In addition to the other dicarboxylic acid components described above, polyvalent carboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid can also be used as long as melt molding is possible.

  When other dicarboxylic acid components are used, the proportion is preferably 25 mol% or less, more preferably 15 mol% or less, still more preferably 10 mol% or less, still more preferably 5 mol% or less, based on the oxalic acid compound. 0 mol% (that is, the dicarboxylic acid component consists only of oxalic acid) is particularly preferred. The molar ratio of the other dicarboxylic acid component to the oxalic acid compound also means the molar ratio of the unit derived from the compound A and the unit derived from the other dicarboxylic acid component in the polyamide resin.

  As the diamine component used together with the dicarboxylic acid component described above, those that can react with the dicarboxylic acid component to form an oxamide bond are used. As such a diamine component, for example, a diamine having the structure of the following formula (1) (hereinafter also referred to as “diamine A”) can be used.

R ₁ and R ₂ in the formula (1) are preferably, for example, a hydrocarbon chain having 1 to 3 carbon atoms, and more preferably a hydrocarbon chain having 1 to 2 carbon atoms. The carbon number of the hydrocarbon chain in R ₁ and R ₂ may be the same or different. From the viewpoint of improving the voltage resistance of the binder, bisaminomethylcyclohexane in which R ₁ and R _{2 in} formula (1) are both methylene groups is preferable. Among bisaminomethylcyclohexane, 1,3-bisaminomethylcyclohexane and 1,4-bisaminomethylcyclohexane are more preferable, and 1,3-bisaminomethylcyclohexane is more preferable. These diamine A can be used individually by 1 type or in combination of 2 or more types.

  As another diamine component used by this invention, the diamine (henceforth "diamine B") which has the structure of the following formula | equation (2) is mentioned, for example.

R ₃ and R ₄ in the formula (2) are preferably, for example, a hydrocarbon chain having 1 to 4 carbon atoms, and more preferably a hydrocarbon chain having 1 to 2 carbon atoms. The carbon number of the hydrocarbon chain in R ₃ and R ₄ may be the same or different. From the viewpoint of improving the voltage resistance of the binder, examples of the diamine B include p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, m-xylylenediamine, 4,4′-diaminodiphenylmethane, 4,4. '-Diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, and the like can be used. From the viewpoint of further improving the voltage resistance of the binder, it is preferable to use p-xylylenediamine or m-xylylenediamine as the diamine B, and it is more preferable to use m-xylylenediamine. Diamine B can be used singly or in combination of two or more.

  Still another diamine component used in the present invention includes, for example, an aliphatic alkylene diamine which is a diamine having the structure of the following formula (3) (hereinafter also referred to as “diamine C”).

R ₅ in the formula (3) is a divalent aliphatic hydrocarbon chain composed of a straight chain or a branched chain. R ₅ preferably has 4 to 12 carbon atoms, more preferably 5 to 10 carbon atoms.

When R ₅ in the formula (3) is a straight chain, the diamine C includes 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,7-heptanediamine, 1,8-octanediamine, 1 , 9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, 1,12-dodecanediamine and the like are preferably used.

When R ₅ in the formula (3) is a branched chain, examples of the diamine C include 1-butyl-1,2-ethanediamine, 1,1-dimethyl-1,4-butanediamine, 1-ethyl-1, 4-butanediamine, 1,2-dimethyl-1,4-butanediamine, 1,3-dimethyl-1,4-butanediamine, 1,4-dimethyl-1,4-butanediamine, 2,3-dimethyl- 1,4-butanediamine, 2-methyl-1,5-pentanediamine, 3-methyl-1,5-pentanediamine, 2,5-dimethyl-1,6-hexanediamine, 2,4-dimethyl-1, 6-hexanediamine, 3,3-dimethyl-1,6-hexanediamine, 2,2-dimethyl-1,6-hexanediamine, 2,2,4-trimethyl-1,6-hexanediamine, 2,4, 4-trimethyl-1 , 6-hexanediamine, 2,4-diethyl-1,6-hexanediamine, 2,2-dimethyl-1,7-heptanediamine, 2,3-dimethyl-1,7-heptanediamine, 2,4-dimethyl -1,7-heptanediamine, 2,5-dimethyl-1,7-heptanediamine, 2-methyl-1,8-octanediamine, 3-methyl-1,8-octanediamine, 4-methyl-1,8 -Octanediamine, 1,3-dimethyl-1,8-octanediamine, 1,4-dimethyl-1,8-octanediamine, 2,4-dimethyl-1,8-octanediamine, 3,4-dimethyl-1 , 8-octanediamine, 4,5-dimethyl-1,8-octanediamine, 2,2-dimethyl-1,8-octanediamine, 3,3-methyl-1,8-octanediamine, 4, 4-dimethyl-1,8-octane diamine, it is preferred to use 5-methyl-1,9-nonanediamine or the like.

  The various diamines C can be used alone or in combination of two or more.

  Among the various diamines C, 1,5-pentanediamine, 1,6-hexamethylenediamine, 1,8-octanediamine, and 2-methyl-1,8-octanediamine are highly resistant to voltage. 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine are preferable. In particular, 1,6-hexamethinediamine, 1,9-nonanediamine, 2-methyl-1,8-octanediamine, or 1,12-dodecanediamine is preferable.

  In the present invention, the various diamine components described above, that is, diamines A, B, and C can be used in any combination. By doing in this way, it becomes possible to improve the withstand voltage property of a binder further. For example, a combination of diamine A and diamine C can be used as the diamine component (hereinafter also referred to as “combination 1”). Alternatively, a combination of diamine B and diamine C can be used as the diamine component (hereinafter also referred to as “combination 2”). Furthermore, as the diamine component, two or more diamine components C having different structures can be used (hereinafter also referred to as “combination 3”).

  When the combination 1 is employed, the molar ratio of the diamine A and the diamine C is expressed as diamine A: diamine C in terms of mol% from the viewpoint of improving voltage resistance, and is 97: 3 to 50:50. It is preferable that it is 95: 5-55: 45, it is still more preferable that it is 90: 10-55: 45, and it is still more preferable that it is 85: 15-60: 40. In the following description, the molar ratio of diamine A and diamine C also means the molar ratio of units derived from diamine A and units derived from diamine C in the polyamide.

  When the combination 1 is employed, 1,3-bisaminomethylcyclohexane or 1,4-bisaminomethylcyclohexane is used as the diamine A, and 1,6-hexamethylenediamine is used as the diamine C. preferable.

  When the combination 2 is adopted, the molar ratio of the diamine B and the diamine C is expressed as diamine B: diamine C in terms of mol% from the viewpoint of improving the voltage resistance, and is 95: 5 to 5:95. It is preferably 80:20 to 20:80, more preferably 70:30 to 30:70, and still more preferably 60:40 to 40:60. In the following description, the molar ratio of diamine B and diamine C also means the molar ratio of units derived from diamine B and units derived from diamine C in the polyamide.

  When the combination 2 is employed, m-xylylenediamine or p-xylylenediamine is used as the diamine B, and 1,10-dodecanediamine or 1,12-dodecanediamine is used as the diamine C. preferable.

  When the combination 3 is adopted, the molar ratio between the first diamine C and the second diamine C is a molar ratio from the viewpoint of improving the voltage resistance, and the first diamine C: second diamine. In terms of C, it is preferably 99: 1 to 6:94, more preferably 95: 5 to 6:94, still more preferably 90:10 to 60:40, and 90:10 Even more preferably, it is 70:30. In the following description, the molar ratio of the first diamine C and the second diamine C also means the molar ratio of the unit derived from diamine B and the unit derived from diamine C in the polyamide.

  When the combination 3 is employed, it is preferable to use 1,9-nonanediamine as the first diamine C and 2-methyl-1,8-octanediamine as the second diamine C.

  The polyamide contained in the binder of the present invention preferably has an appropriate molecular weight from the viewpoint of enhancing its binding properties. When the molecular weight is expressed in terms of relative viscosity ηr, the relative viscosity ηr is preferably 1.6 to 6.0, and more preferably 1.6 to 4.5. A method for measuring the relative viscosity ηr will be described in detail in Examples described later.

  The polyamide contained in the binder of the present invention can be produced using any method known as a method for producing polyamide. From the viewpoint of high molecular weight and productivity, it is preferable to obtain a diamine and oxalic acid diester by polycondensation reaction batchwise or continuously. Specifically, it is more preferable to perform (i) pre-polycondensation step and (ii) post-polycondensation step shown in the following operations in this order.

(I) Pre-polycondensation step: First, the inside of the reactor is purged with nitrogen, and then, for example, oxalic acid diester is mixed as a diamine and oxalic acid source component. When mixing, a solvent in which both the diamine and the oxalic acid source component are soluble may be used. As a solvent in which both the diamine component and the oxalic acid source component are soluble, for example, toluene, xylene, trichlorobenzene, phenol, trifluoroethanol and the like can be used. In particular, toluene can be preferably used. For example, after heating the toluene solution which melt | dissolved diamine to 50 degreeC, oxalic acid source components, such as a oxalic acid diester, are added with respect to this. At this time, the charging ratio of the oxalic acid source component such as oxalic acid diester and the diamine is 0.8 to 1.5 (molar ratio), preferably 0.91 from the viewpoint of increasing the molecular weight. To 1.1 (molar ratio), more preferably 0.99 to 1.01 (molar ratio).

  The temperature in the reactor charged in this way is increased under normal pressure while stirring and / or nitrogen bubbling. The reaction temperature is preferably controlled so that the final temperature reaches 80 to 150 ° C, particularly 100 to 140 ° C. The reaction time at the final temperature reached is preferably 3 to 6 hours.

(Ii) Post-polycondensation step: In order to further increase the molecular weight, the polymer produced in the pre-polycondensation step is gradually heated in the reactor under normal pressure. In the temperature raising process, the final reached temperature of the pre-polycondensation step, that is, preferably from 80 to 150 ° C, is finally preferably 265 ° C to 350 ° C, more preferably 265 ° C to 345 ° C, and further preferably 270 ° C. The temperature is made 340 ° C. or lower, more preferably 270 ° C. or higher and 335 ° C. or lower. It is preferable to carry out the reaction while keeping the temperature rising time preferably 1 to 8 hours, more preferably 2 to 6 hours. Furthermore, in the post-polymerization step, polymerization can be performed under reduced pressure as necessary. The preferable final ultimate pressure in the case of performing the vacuum polymerization is less than 0.1 MPa to 13.3 Pa.

  The polyamide thus obtained can be used alone or in combination with other components to form an electrode binder. The electrode binder is mixed with, for example, active material particles and conductive auxiliary particles to form an electrode mixture. An active material layer is formed by applying this mixture to the surface of the current collector. You may make this electrode mixture contain binders other than the polyamide mentioned above as needed. Examples of such a binder include various polyamides such as aromatic polyamide, aliphatic polyamide, and alicyclic polyamide.

  Various materials can be used as the active material contained in the electrode mixture depending on the type of the secondary battery. For example, in the case of a lithium secondary battery, a lithium transition metal composite oxide such as lithium cobaltate can be used as the positive electrode active material. As the negative electrode active material, graphite, silicon, olivine iron, or the like can be used. As the conductive assistant, for example, acetylene black can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples.

  Prior to the description of Examples and Comparative Examples, the production of polyamide used in the Examples will be described with reference to Production Examples 1 to 4.

[Production Example 1]
(I) Pre-polycondensation step: The inside of a separable flask having a stirrer, a reflux condenser, a nitrogen inlet tube, and a raw material inlet and having an internal volume of 500 mL was replaced with nitrogen gas having a purity of 99.9999%. . Next, 200 mL of dehydrated toluene, 12.6565 g (0.0890 mol) of 1,3-bisaminomethylcyclohexane (BAMC), 6.8907 g (0.0593 mol) of 1,6-hexanediamine (HMDA) were added to this separable flask. ), And 29.9985 g (0.1483 mol) of dibutyl oxalate. This separable flask was placed in an oil bath, heated to 130 ° C., and reacted for 5 hours under reflux. Note that all operations from preparation of raw materials to completion of the reaction were performed under a nitrogen stream of 50 mL / min.

(Ii) Post-polycondensation step: The prepolymer obtained by the above operation was charged into a glass reaction tube having a diameter of about 35 mmφ equipped with a stirrer, an air cooling tube, and a nitrogen introduction tube, and the inside of the reaction tube was 13.3 Pa or less. The operation of keeping under reduced pressure and then introducing nitrogen gas to normal pressure was repeated 5 times. Then, it moved to the salt bath kept at 210 degreeC under 50 mL / min nitrogen stream, and temperature rising was started immediately. After the temperature of the salt bath was 280 ° C. over 1 hour, the inside of the container was depressurized to about 66.5 Pa and further reacted for 2 hours. Subsequently, after introducing nitrogen gas to a normal pressure, it was taken out from the salt bath and cooled to room temperature under a nitrogen stream of 50 mL / min to obtain polyamide (BAMC / HMDA = 60/40).

[Production Example 2]
(I) Pre-polycondensation step: The inside of a 1 L separable flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and raw material inlet is replaced with nitrogen gas having a purity of 99.9999% for dehydration. 500 mL of toluene was added, 0.0246 g of benzenephosphinic acid was added as a catalyst and dissolved, then 43.2498 g (0.2510 mol) of 1,10-decanediamine (DMDA) and 34.2355 g of m-xylylenediamine (MXDA). (0.2514 mol) was charged. After this separable flask was placed in an oil bath and heated to 50 ° C., 101.6145 g (0.5024 mol) of dibutyl oxalate was charged. Next, the temperature of the oil bath was raised to 130 ° C., and the reaction was carried out for 5 hours under reflux. Note that all operations from preparation of raw materials to completion of the reaction were performed under a nitrogen stream of 50 mL / min. After the contents were cooled, the solvent was distilled off by filtration and vacuum drying to obtain a prepolymer.
(Ii) Post-polycondensation step: The prepolymer obtained by the above operation is charged into a 300 mL separable flask equipped with a stirrer, an air cooling tube, and a nitrogen introduction tube, and the pressure inside the reaction tube is reduced to 13.3 Pa or less. Then, the operation of introducing nitrogen gas to normal pressure was repeated five times, and then the mixture was transferred to a salt bath maintained at 190 ° C. under a nitrogen stream of 50 mL / min, and the temperature was immediately raised. After the temperature of the salt bath was adjusted to 250 ° C. over 1 hour, the inside of the container was depressurized to 77 Pa and further reacted for 2.5 hours in the solid state. The polyamide (MXDA / HMDA = 50/50) was obtained by removing from the salt bath and cooling to room temperature under a nitrogen stream of 50 mL / min.

[Production Example 3]
(I) Pre-polycondensation step: The inside of a 1 L separable flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, and raw material inlet is replaced with nitrogen gas having a purity of 99.9999% for dehydration. 500 ml of used toluene, 68.3091 g (0.4316 mol) of 1,9-nonanediamine (NMDA), and 12.0545 g (0.0762 mol) of 2-methyl-1,8-octanediamine (MODA) were charged. This separable flask was placed in an oil bath and heated to 50 ° C., and then 102.1195 g (0.5053 mol) of dibutyl oxalate was charged. Next, the temperature of the oil bath was raised to 130 ° C., and the reaction was carried out for 5 hours under reflux. Note that all operations from preparation of raw materials to completion of the reaction were performed under a nitrogen stream of 50 mL / min. After the contents were cooled, the solvent was distilled off by filtration and vacuum drying to obtain a prepolymer.
(Ii) Post-polycondensation step: The prepolymer obtained by the above operation is charged into a glass reaction tube having a diameter of about 35 mmφ equipped with a stirrer, an air cooling tube, and a nitrogen introduction tube, and the pressure inside the reaction tube is reduced to 13.3 Pa or less. Then, the operation of introducing nitrogen gas to normal pressure was repeated 5 times, and then the mixture was transferred to a salt bath maintained at 210 ° C. under a nitrogen stream of 50 mL / min, and the temperature was immediately raised. The salt bath temperature was 260 ° C. over 1 hour, and the reaction was further continued for 2 hours. The polyamide (NMDA / MODA = 85/15) was obtained by removing from the salt bath and cooling to room temperature under a nitrogen stream of 50 mL / min.

[Production Example 4]
(I) Pre-polycondensation step: A 500 mL round bottom flask (equipped with a dropping funnel and a reflux condenser) is placed in an oil bath, and 200 mL of dehydrated toluene and 20.037 g of 1,12-dodecanediamine (DDDA) are added, Under a nitrogen stream, the oil bath set temperature was 50 ° C., and the contents were stirred with a magnetic stirrer until the contents became a homogeneous solution. Next, 20.225 g of dibutyl oxalate was poured into the flask from the dropping funnel, and then the oil bath was set at 120 ° C. and refluxed for 5 hours under a nitrogen stream. After completion of the reaction, toluene and produced butanol were distilled off, and the flask was heated and vacuum dried at 80 ° C. overnight to obtain 25.4 g of a prepolymer.

(Ii) Post-polycondensation step: 13.92 g of the prepolymer obtained by the above operation was charged into a glass reaction tube (equipped with an air-cooled tube, a nitrogen introduction tube, and a mechanical stirrer) having a diameter of about 30 mmφ, and the inside was filled with nitrogen. Replaced. Next, the reaction tube was placed in a 170 ° C. salt bath, and the temperature was raised from 170 ° C. to 250 ° C. over 1 hour. Then, pressure reduction was started at 250 ° C., and the reaction was continued for 2 hours while gradually increasing the degree of vacuum. To obtain poly (dodecamethyleneoxamide). The final ultimate pressure was 0.07 mmHg (9.3 Pa). During the reaction, stirring was performed at 30 rpm.

[Measurement of relative viscosity ηr of the obtained polyamide]
The relative viscosity ηr of the polyamide obtained in each production example was measured. The relative viscosity ηr was measured at 25 ° C. using an Ostwald viscometer using a 96 wt% polyamide sulfuric acid solution (concentration: 1.0 g / dl). The measurement results are shown in Table 1 below.

[Examples 1 to 4]
The polyamide obtained in each production example was used as a binder. VGCF-H as a conductive auxiliary agent was mixed with the hexafluoroisopropanol solution of polyamide obtained in each production example so that the mass ratio of binder: VGCF-H was 3: 7 to prepare an electrode mixture slurry. . This electrode mixture slurry was applied to one surface of a circular current collector made of aluminum foil and having a diameter of 16 mm, and then dried. The coating amount was about 1 mg and the coating thickness was about 20 μm. In this way, an electrode was obtained.

[Comparative Example 1]
In Example 1, an electrode was obtained in the same manner as in Example 1 except that polyvinylidene fluoride was used instead of polyamide.

[Evaluation]
The electrodes obtained in the examples and comparative examples were subjected to electrochemical measurements to evaluate the voltage resistance of the binder. With respect to the evaluation of the withstand voltage, measurement using linear sweep voltammetry (LSV) was performed on the positive electrode side, and measurement using cyclic voltammetry (CV) was performed on the negative electrode side. In any measurement, a potentiostat was used, and the electrodes obtained in Examples and Comparative Examples were used as working electrodes. Metallic lithium was used for the reference electrode and the counter electrode. LiPF ₆ was used as the supporting salt, and a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7 was used as the non-aqueous solvent. The concentration of the supporting salt was 1 mol / L.

  In the measurement of LSV, the start potential was set to 3.2V, and the end potential was set to 4.2V. The scanning speed of the potential was 0.89 mV / sec. In the measurement of CV, the starting potential was set to 3.2V, and the folding potential was set to 0.1V. The scanning speed of the potential was 0.89 mV / sec. The results of LSV measured for the electrodes obtained in Example 1 and Comparative Example 1 are shown in FIG. Moreover, the result of CV measured about the electrode obtained in Example 3 and Comparative Example 1 is shown in FIG. Furthermore, the current density at 4.5 V in LSV measured for the electrodes obtained in each Example and Comparative Example is shown in Table 1 below. Furthermore, Table 1 also shows the current density at 0.5 V in the fifth cycle in the CV measured for the electrodes obtained in each Example and Comparative Example. 1 and 2 and the current density shown in Table 1 are obtained by standardizing the actually measured current density to the thickness of the electrode layer applied to the electrode to 20 μm.

  As is clear from the results shown in Table 1, the electrode obtained in each example has the same or less reduction current value and oxidation current value than the electrode obtained in the comparative example. It can be seen that the voltage is high. In particular, it can be seen that the binder used in Example 1 has high withstand voltage when used as a positive electrode, and the binder used in Example 3 has high withstand voltage when used in a negative electrode.

Claims (11)

Contains a polyamide resin comprising a dicarboxylic acid component and the diamine component, the dicarboxylic acid component Ri oxalic der, as the diamine component, with a diamine having the structure of any of to the following formula (1) to (3) , Binder for positive electrode of electricity storage device.

The positive electrode binder according to claim 1 , wherein the diamine component having the structure of the formula (2) is m-xylylenediamine. Formula (3) diamine component 1,6 methine diamine having the structure of, 1,9, claim 1 is 2-methyl-1,8-octane diamine or 1,12-dodecane diamine The positive electrode binder. 2. The positive electrode binder according to claim 1 , wherein a diamine having the structure of the formula (1) and a diamine having the structure of (3) are used as the diamine component. 2. The positive electrode binder according to claim 1 , wherein a diamine having the structure of the formula (2) and a diamine having the structure of (3) are used as the diamine component. As the diamine component, the positive electrode binder according to claim 1 with a diamine having a structure of two or more of the above formula (3) is a different structure from each other. The positive electrode binder according to claim 6 , wherein 1,9-nonamethylenediamine and 2-methyl-1,8-octamethylenediamine are used as the diamine component. The binder for positive electrodes as described in any one of Claim 1 thru | or 7 used for a nonaqueous electrolyte secondary battery. , The positive electrode mixture of the electric storage device including a positive electrode binder and conductive aid according to any one of claims 1 to 8. The positive electrode of the electric storage device having a positive electrode binder according to any one of claims 1 to 8. An electricity storage device comprising the positive electrode according to claim 10 .

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