CARBON NANOTUBE DISPERSION COMPOSITION, MIXTURE SLURRY, ELECTRODE FILM, AND SECONDARY BATTERY

Abstract

A carbon nanotube dispersion composition includes carbon nanotubes (A), a dispersant (B), and a solvent (C). A particle diameter D.sub.50 at a cumulative volume of 50% according to laser diffraction particle size distribution measurement is 0.3 to 7 m, and (1) and (2) below are satisfied. (1) The dispersant (B) is a polymer that has a weight average molecular weight of 5,000 or more and 360,000 or less and includes a carboxyl group-containing structural unit derived from at least one of (meth)acrylic acid and (meth)acrylate having a carboxyl group. (2) When the particle diameter D.sub.50 at a cumulative volume of 50% according to laser diffraction particle size distribution measurement of the carbon nanotube dispersion composition is X [m], and a pH is Y, X and Y satisfy (Formula a) and (Formula b) below:

[00001]$\begin{array}{cc}Y-0.149X+4\text{.545}& \left(\mathrm{Formula}a\right)\end{array}$$\begin{array}{cc}Y-0.134X+5.140.& \left(\mathrm{Formula}b\right)\end{array}$

Claims

1. A carbon nanotube dispersion composition comprising carbon nanotubes (A), a dispersant (B), and a solvent (C), wherein a particle diameter D.sub.50 at a cumulative volume of 50% according to laser diffraction particle size distribution measurement is 0.3 to 7 m, and the carbon nanotube dispersion composition satisfies (1) and (2) below: (1) the dispersant (B) is a polymer that has a weight average molecular weight of 5,000 or more and 360,000 or less and comprises a carboxyl group-containing structural unit derived from at least one of (meth)acrylic acid and (meth)acrylate having a carboxyl group, wherein a content ratio of the carboxyl group-containing structural unit is 80 mass % or more based on a mass of the polymer; and (2) in a case where the particle diameter D.sub.50 at a cumulative volume of 50% according to laser diffraction particle size distribution measurement of the carbon nanotube dispersion composition is X [m], and a pH is Y, X and Y satisfy (Formula a) and (Formula b) below: $\begin{array}{cc}Y-0.149X+4\text{.545}& \left(\mathrm{Formula}a\right)\end{array}$ $\begin{array}{cc}Y-0.134X+5.140.& \left(\mathrm{Formula}b\right)\end{array}$

2. The carbon nanotube dispersion composition according to claim 1, further comprising a basic compound (D).

3. The carbon nanotube dispersion composition according to claim 1, wherein a phase angle at 1 Hz at 25 C. according to dynamic viscoelasticity measurement is 3 or more and less than 60.

4. The carbon nanotube dispersion composition according to claim 1, wherein a complex modulus at 1 Hz at 25 C. according to dynamic viscoelasticity measurement is 5 Pa or more and less than 300 Pa.

5. The carbon nanotube dispersion composition according to claim 1, wherein a content of the dispersant (B) is 15 to 160 parts by mass with respect to 100 parts by mass of the carbon nanotubes (A).

6. The carbon nanotube dispersion composition according to claim 1, wherein a content of the dispersant (B) is 15 to 90 parts by mass with respect to 100 parts by mass of the carbon nanotubes (A).

7. The carbon nanotube dispersion composition according to claim 1, wherein a BET specific surface area according to nitrogen adsorption measurement of the carbon nanotubes (A) is 100 m.sup.2/g or more and 1200 m.sup.2/g or less.

8. The carbon nanotube dispersion composition according to claim 1, wherein the carboxyl group-containing structural unit is a structural unit derived from (meth)acrylic acid.

9. A mixture slurry comprising the carbon nanotube dispersion composition according to claim 1 and an active material.

10. An electrode film formed from the mixture slurry according to claim 9.

11. A secondary battery comprising a positive electrode and a negative electrode, wherein at least one of the positive electrode and the negative electrode comprises the electrode film according to claim 10.

Description

EXAMPLES

[0239] The present invention will be described more specifically below with reference to Examples. The present invention is not limited to the following Examples as long as it does not exceed the gist thereof. Unless otherwise specified, parts refers to parts by mass, and % refers to mass %.

<Average Outer Diameter of Carbon Nanotubes>

[0240] Measurement method: carbon nanotubes were dispersed in toluene using an ultrasonic homogenizer, and then the carbon nanotubes placed and dried on a collodion film were observed and imaged using a transmission electron microscope (TEM). Next, 100 carbon nanotubes were randomly selected in the observed image, and their respective outer diameters were measured. Then, an average outer diameter (nm) of the raw material carbon nanotubes was calculated as the number average of the outer diameters.

<Specific Surface Area Measurement of Carbon Nanotubes>

[0241] 0.03 g of CNT was weighed using an electronic balance (MSA225S100DI manufactured by Sartorius), and then dried at 110 C. for 15 minutes while degassing. Afterward, a BET specific surface area of the CNT was measured using a fully automatic specific surface area measurement apparatus (HM-model1208 manufactured by MOUNTECH).

[0242] Details of the materials used in the present Examples and Comparative Examples are as follows:

<Carbon Nanotubes (A)>

[0243] TUBALL: Single-wall carbon nanotubes (produced by OCSiAl, average outer diameter 1.6 nm, specific surface area 980 m.sup.2/g) [0244] 10B: JENOTUBE10B (produced by JEIO, multi-wall CNT, average outer diameter 10 nm, specific surface area 233 m.sup.2/g) [0245] 6A: JENOTUBE6A (produced by JEIO, multi-wall CNT, average outer diameter 6 nm, specific surface area 680 m.sup.2/g) [0246] TNSAR: Single-wall carbon nanotubes (produced by Timesnano, average outer diameter 1.5 nm, specific surface area 950 m.sup.2/g) [0247] BT1001M: (produced by LGC, multi-wall CNT, average outer diameter 10 nm, specific surface area 260 m.sup.2/g)

<Basic Compound (D)>

[0248] D-1: Na.sub.2CO.sub.3 (sodium carbonate, produced by Tokyo Chemical Industry Co., Ltd., purity >99.0%) [0249] D-2: NaOH (sodium hydroxide, produced by Tokyo Chemical Industry Co., Ltd., purity >98.0%, granular) [0250] D-3: KOH (potassium hydroxide, produced by Tokyo Chemical Industry Co., Ltd., purity >86.0%) [0251] D-4: CH3COONa (sodium acetate, produced by Tokyo Chemical Industry Co., Ltd., purity >98.5%) [0252] D-5: K2CO.sub.3 (potassium carbonate, produced by Tokyo Chemical Industry Co., Ltd., purity >99.0%) [0253] D-6: BtONa (sodium t-butoxide, produced by Tokyo Chemical Industry Co., Ltd., purity >98.0%)

<Production of Dispersant (B) and the Like>

(Dispersant (B-1))

[0254] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 100 parts of acrylic acid, 0.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A 4-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-1)).

(Dispersant (B-2))

[0255] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 95 parts of acrylic acid, 5 parts of acrylonitrile, 2.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A 4-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotation using a disper, and the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-2)).

(Dispersant (B-3))

[0256] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 95 parts of acrylic acid, 5 parts of 2-hydroxyethyl acrylate, 0.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A 4-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, and the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-3)).

(Dispersant (B-4))

[0257] A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was loaded with 100 parts of methanol, 0.1 parts of diethanolamine, and 5 parts of sodium hypophosphite, and was replaced with nitrogen gas. Inside of the reaction vessel was heated to 70 C., and 90 parts of acrylic acid and 10 parts of N-vinyl-2-pyrrolidone were added dropwise over a period of 2 hours. Subsequently, an initiator aqueous solution composed of 2 parts of 2,2-azobis-2-amidinopropane dihydrochloride (produced by Fujifilm Wako Pure Chemical Corporation: V-50) and 18 parts of ion-exchanged water was added dropwise over a period of 1.5 hours. After completing the dropwise addition, reaction was allowed to occur for 3.5 hours. Then, an aqueous solution composed of 0.1 parts of V-50 and 0.9 parts of ion-exchanged water was added. After an additional 30 minutes, an aqueous solution composed of 0.1 parts of V-50 and 0.9 parts of ion-exchanged water was added again.

[0258] After 4.5 hours from start of polymerization, it was confirmed that the conversion rate reached 95%, and 0.5 parts of 10% malonic acid aqueous solution was added as a pH adjusting agent to obtain an aqueous dispersion of the polymer. Subsequently, it was filtered by filtering under reduced pressure and washed with methanol, and the solvent was completely removed by drying under reduced pressure to obtain a polymer (dispersant (B-4)).

(Dispersant (B-5))

[0259] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 100 parts of methacrylic acid, 0.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-5)).

(Dispersant (B-6))

[0260] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 90 parts of acrylic acid, 5 parts of acrylonitrile, 5 parts of 2-hydroxyethyl acrylate, 2.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-6)).

(Dispersant (B-7))

[0261] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 95 parts of acrylic acid, 5 parts of methyl acrylate, 0.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-7)).

(Dispersant (B-8))

[0262] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 100 parts of acrylic acid, 6.9 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 250 parts of methyl ethyl ketone and 250 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-8)).

(Dispersant (B-9))

[0263] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 100 parts of acrylic acid, 1.25 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 250 parts of methyl ethyl ketone and 250 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-9)).

(Dispersant (B-10))

[0264] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 80 parts of acrylic acid, 20 parts of acrylamide, 0.55 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-10)).

(Dispersant (B-1))

[0265] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 70 parts of acrylic acid, 30 parts of acrylonitrile, 2.8 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 500 parts of methyl ethyl ketone and 500 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-1)).

(Dispersant (B-2))

[0266] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 100 parts of acrylic acid, 9.3 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 250 parts of methyl ethyl ketone and 250 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-2)).

(Dispersant (B-3))

[0267] To a reaction vessel equipped with a thermometer, a condenser, and a stirrer, 137 parts of ion-exchanged water, 100 parts of acrylic acid, 0.03 parts of 3-mercapto-1,2-propanediol, and 0.5 parts of V-50 (produced by Fujifilm Wako Pure Chemical Corporation) as a polymerization initiator were added, heated to 70 C., and stirred for 300 minutes (5 hours) at a temperature of 70 C. Cooling was performed when the conversion rate became 90% or more, and the reaction was ended. Subsequently, unreacted raw materials were reduced by heated vacuum distillation to obtain an aqueous solution of the polymer. A four-neck separable flask was loaded with 250 parts of methyl ethyl ketone and 250 parts of methanol, and upon 1,000 rotations using a disper, the aqueous solution of the polymer was added dropwise over a period of 1 hour. The resulting white precipitate was filtered out and dried under reduced pressure to obtain a polymer (dispersant (B-3)).

[0268] The molecular weight of the dispersant (B) was measured using gel permeation chromatography (GPC) equipped with an RI detector and a UV detector (210 nm), specifically as follows. [0269] Apparatus: HLC-8320GPC (manufactured by Tosoh Corporation) [0270] Separation columns: The following were disposed in series sequentially. [0271] TSKgel Guardcolumn PWXL (6.0 mm I.D.4 cm) [0272] Two columns of TSKgel GMPXL (7.8 mm I.D.30 cm) [0273] Column temperature: 40 C. [0274] Eluent: 0.2 M phosphate buffer solution (pH 7.0) [0275] Flow rate: 1.0 mL/min

[0276] The sample was prepared at a concentration of 0.1 mass % in a mixed solution composed of the above eluent, and 0.1 mL was injected. The molecular weight was determined as a converted value using standard PEO/PEG (Agilent Technologies).

TABLE-US-00001 TABLE 1 Content ratio of each structural unit in polymer [mass %] Weight Structural Structural Structural average Structural Structural unit 3 Structural unit 5 unit 6 Structural molecular unit 1 unit 2 (Hydroxyl unit 4 (Nitrile (Ester unit 7 weight (Carboxyl group) group) (Heterocycle) group) group) (Amide) Mw Dispersant 100 69,000 (B-1) Dispersant 95 5 68,000 (B-2) Dispersant 95 5 69,000 (B-3) Dispersant 90 10 69,000 (B-4) Dispersant 100 70,000 (B-5) Dispersant 90 5 5 68,000 (B-6) Dispersant 95 5 68,000 (B-7) Dispersant 100 8,000 (B-8) Dispersant 100 50,000 (B-9) Dispersant 80 20 100,000 (B-10) Dispersant 70 30 69,000 (B-1) Dispersant 100 4,500 (B-2) Dispersant 100 380,000 (B-3)

<Preparation of Dispersion Composition>

Example 1-1

[0277] According to the materials and compositions shown in Table 2, the materials were added sequentially, and the CNT dispersion composition was prepared according to the following method.

[0278] 1960.8 parts of ion-exchanged water, 18 parts of the dispersant (B-1), and 1.2 parts of the basic compound (D) were added to a stainless steel vessel and stirred with a disper until uniform.

[0279] Subsequently, 20 parts of CNT (TUBALL) were added while stirring with a disper, a square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch-type dispersion was performed at a speed of 8,000 rpm until the entirety became uniform and the dispersion particle size became 250 m or less as measured by a grind gauge. At this time, the dispersion particle size confirmed by the grind gauge was 180 m.

[0280] Subsequently, the dispersion liquid was supplied from the stainless steel vessel via piping to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine), and a pass-type dispersion treatment was performed until the particle diameter D.sub.50 became 0.3 to 7 m. After 50 passes, the particle diameter D.sub.50 was 1.5 m.

[0281] The dispersion treatment was performed using a single nozzle chamber at a nozzle diameter of 0.20 mm and a pressure of 150 MPa, and a carbon nanotube dispersion composition 1 was obtained, containing 1.0 mass % of TUBALL as the carbon nanotubes (A), 0.90 mass % of the dispersant (B-1) as the dispersant (B), and 0.06 mass % of the basic compound (D-1) (Na.sub.2CO.sub.3) as the basic compound (D).

Examples 1-2 to 1-28, 1-31 to 1-33, Comparative Examples 1-1 to 1-5

[0282] According to the materials and the compositions shown in Table 2, a pass-type dispersion treatment was performed in the same manner as in Example 1-1 until the particle diameter D.sub.50 became 0.3 to 7 m, and each dispersion composition (dispersion compositions 2 to 28, 31 to 33, comparative dispersion compositions 1 to 5) was obtained.

[0283] Regarding the dispersion conditions, in the case where the particle diameter D.sub.50 was 7 m or more at a time point upon performing 20 passes of the pass-type dispersion treatment, an additional 2 passes of the pass-type dispersion treatment were performed, measurement was performed again, this was repeated until the particle diameter D.sub.50 became 7 m or less, and the number of passes was controlled to adjust the particle diameter D.sub.50 to be 0.3 to 7 m.

Example 1-29

[0284] According to the compositions shown in Table 2, the dispersant (B-1), the basic compound (D-1), and ion-exchanged water were loaded in a glass bottle (M-225, manufactured by Hakuyo Glass Co., Ltd.), and sufficiently mixed and dissolved, or mixed. Then, CNT was added and, with zirconia beads (bead diameter 0.5 mm ) as media, dispersed for a total of 8 hours using a paint conditioner while cooling the glass bottle every 2 hours, to obtain a carbon nanotube dispersion composition 29. The particle diameter D.sub.50 was 3.8 m.

Example 1-30

[0285] According to the compositions shown in Table 2, the dispersant (B-1), the conductive material, and a small amount of ion-exchanged water were loaded in a Labo Plastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd.) and dispersed for 3 hours. Then, the mixture was transferred to a stainless steel container, and the remaining ion-exchanged water and basic compound (D-1) were added. A square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch-type dispersion was performed at a speed of 8,000 rpm until the entirety became uniform and the dispersion particle size measured by a grind gauge became 250 m or less, to obtain a carbon nanotube dispersion composition 30. At this time, the dispersion particle size confirmed by the grind gauge was 80 m, and the particle diameter D.sub.50 was 6.0 m.

Examples 1-34 to 1-36

[0286] According to the compositions shown in Table 2, carbon nanotube dispersion compositions 34 to 36 were obtained according to the same method as in Example 1-1.

<Measurement and Evaluation of Physical Properties of Dispersion Compositions>

[0287] Physical property measurement of the dispersion compositions and evaluation of storage stability were performed according to the following methods. The results are shown in Table 2.

(Method of Measuring Particle Diameter D.SUB.50 .of Dispersion Compositions)

[0288] The particle diameter D.sub.50 at a cumulative volume of 50% was measured using a laser diffraction particle size distribution analyzer (Partical LA-960V2, manufactured by HORIBA).

[0289] The circulation/ultrasonic operating conditions were set as follows: circulation speed: 3, ultrasonic intensity: 7, ultrasonic time: 1 minute, stirring speed: 1, stirring mode: continuous. In addition, during degassing, ultrasonic operation was performed with an ultrasonic intensity of 7 and an ultrasonic time of 5 seconds. The particle refractive index of the carbon-based conductive material was set to 1.9, and the shape was set to non-spherical. The refractive index of the solvent was set to 1.333. During measurement, the concentration of the CNT dispersion composition was diluted such that the value of the transmittance was in the range of 50 to 85%. The particle size criterion was set to volume.

(Method of Measuring pH of Dispersion Compositions)

[0290] The sample for pH measurement was measured using a benchtop PH meter (SevenCompact S200 Expert Pro, manufactured by Mettler Toledo) at a temperature of 25 C.

(Complex Modulus and Phase Angle of Dispersion Compositions)

[0291] The complex modulus and the phase angle of the dispersion compositions were determined by performing dynamic viscoelasticity measurement using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific Inc.) with a 35 mm diameter, 2 cone at 25 C. and a frequency of 1 Hz, in the strain rate range of 0.01% to 5%.

[0292] The complex modulus is preferably 5 Pa or more and less than 300 Pa, and more preferably 10 Pa or more or less than 60 Pa.

[0293] The phase angle is preferably 3 or more and less than 60, and more preferably 10 or more.

[0294] The lower the complex modulus of the dispersion composition is, and the closer the phase angle of the dispersion composition is to 90, the better the fluidity. [0295] Evaluation criteria for complex modulus [0296] 1:300 Pa or more or less than 5 Pa [0297] 2:60 Pa or more and less than 300 Pa [0298] 3:10 Pa or more and less than 60 Pa [0299] 4:5 Pa or more and less than 10 Pa [0300] Evaluation criteria for phase angle [0301] 1:10 or more and less than 60 [0302] 2:3 or more and less than 10 [0303] 3: Less than 3

(Method of Evaluating Storage Stability of Dispersion Compositions)

[0304] Evaluation of storage stability was performed by determining presence/absence of fluidity after leaving standing and storing the dispersion composition at 40 C. The determination method was as follows. The complex modulus was evaluated by performing dynamic viscoelasticity measurement using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific Inc.) with a 35 mm diameter, 2 cone at 25 C. and a frequency of 1 Hz, in the strain rate range of 0.01% to 5%. With evaluation criteria to , practical use is possible.

Evaluation Criteria

[0305] : Less than 300 Pa even after 1 month (excellent) [0306] : Reaching 300 Pa after 1 month (good) [0307] : Reaching 300 Pa after 1 week (acceptable) [0308] x: Reaching 300 Pa after 1 day

TABLE-US-00002 TABLE 2-1 CNT (A) Dispersant (B), etc. Content Content Dispersion composition Type ratio (%) Type ratio (%) Example 1-1 Dispersion composition 1 TUBALL 1.0 B-1 0.90 Example 1-2 Dispersion composition 2 TUBALL 1.0 B-1 0.90 Example 1-3 Dispersion composition 3 TUBALL 1.0 B-1 0.90 Example 1-4 Dispersion composition 4 TUBALL 1.0 B-1 0.90 Example 1-5 Dispersion composition 5 TUBALL 1.0 B-1 0.90 Example 1-6 Dispersion composition 6 TUBALL 1.0 B-1 0.90 Example 1-7 Dispersion composition 7 TUBALL 1.0 B-1 0.90 Example 1-8 Dispersion composition 8 10B 2.5 B-1 1.00 Example 1-9 Dispersion composition 9 10B 2.5 B-1 1.00 Example 1-10 Dispersion composition 10 10B 2.5 B-1 1.00 Example 1-11 Dispersion composition 11 10B 2.5 B-1 1.00 Example 1-12 Dispersion composition 12 6A 1.2 B-1 0.75 Example 1-13 Dispersion composition 13 6A 1.2 B-1 0.75 Example 1-14 Dispersion composition 14 6A 1.2 B-1 0.75 Example 1-15 Dispersion composition 15 6A 1.2 B-1 0.75 Example 1-16 Dispersion composition 16 TNSAR 1.0 B-1 0.90 Example 1-17 Dispersion composition 17 BT1001M 2.5 B-1 1.00 Example 1-18 Dispersion composition 18 TUBALL 1.0 B-2 0.90 Example 1-19 Dispersion composition 19 TUBALL 1.0 B-3 0.90 Example 1-20 Dispersion composition 20 TUBALL 1.0 B-4 0.90 Dispersant Basic compound Basic compound (D) Water amount/CNT amount/ Content Content 100 parts by dispersant 100 Type ratio (%) ratio (%) mass parts by mass Example 1-1 D-1 0.06 98.04 90 7 Example 1-2 D-1 0.12 97.98 90 13 Example 1-3 D-1 0.06 98.04 90 7 Example 1-4 D-1 0.12 97.98 90 13 Example 1-5 D-1 0.16 97.94 90 18 Example 1-6 D-1 0.11 97.99 90 12 Example 1-7 D-1 0.18 97.92 90 20 Example 1-8 D-1 0.07 96.43 40 7 Example 1-9 D-1 0.13 96.37 40 13 Example 1-10 D-1 0.13 96.37 40 13 Example 1-11 D-1 0.21 96.29 40 21 Example 1-12 D-1 0.04 98.01 63 5 Example 1-13 D-1 0.11 97.94 63 15 Example 1-14 D-1 0.05 98.00 63 7 Example 1-15 D-1 0.12 97.93 63 16 Example 1-16 D-1 0.12 97.98 90 13 Example 1-17 D-1 0.12 96.38 40 12 Example 1-18 D-1 0.11 97.99 90 12 Example 1-19 D-1 0.11 97.99 90 12 Example 1-20 D-1 0.11 97.99 90 12 CNT (A) Dispersant (B), etc. Content Content Dispersion composition Type ratio (%) Type ratio (%) Example 1-21 Dispersion composition 21 TUBALL 1.0 B-5 0.90 Example 1-22 Dispersion composition 22 TUBALL 1.0 B-6 0.90 Example 1-23 Dispersion composition 23 TUBALL 1.0 B-7 0.90 Example 1-24 Dispersion composition 24 TUBALL 1.0 B-1 0.90 Example 1-25 Dispersion composition 25 TUBALL 1.0 B-1 0.90 Example 1-26 Dispersion composition 26 TUBALL 1.0 B-1 0.90 Example 1-27 Dispersion composition 27 TUBALL 1.0 B-1 0.90 Example 1-28 Dispersion composition 28 TUBALL 1.0 B-1 0.90 Example 1-29 Dispersion composition 29 TUBALL 1.0 B-1 0.90 Example 1-30 Dispersion composition 30 TUBALL 1.0 B-1 0.90 Example 1-31 Dispersion composition 31 TUBALL 1.0 B-1 0.90 Example 1-32 Dispersion composition 32 TUBALL 1.0 B-1 0.90 Example 1-33 Dispersion composition 33 TUBALL 1.0 B-1 0.90 Example 1-34 Dispersion composition 34 TUBALL 1.0 B-8 0.90 Example 1-35 Dispersion composition 35 TUBALL 1.0 B-9 0.90 Example 1-36 Dispersion composition 36 TUBALL 1.0 B-10 0.90 Comparative Comparative dispersion TUBALL 1.0 B-1 0.90 Example 1-1 composition 1 Comparative Comparative dispersion TUBALL 1.0 B-1 0.90 Example 1-2 composition 2 Comparative Comparative dispersion TUBALL 1.0 B-1 0.90 Example 1-3 composition 3 Comparative Comparative dispersion TUBALL 1.0 B-2 0.90 Example 1-4 composition 4 Comparative Comparative dispersion TUBALL 1.0 B-3 0.90 Example 1-5 composition 5 Dispersant Basic compound Basic compound (D) Water amount/CNT amount/ Content Content 100 parts by dispersant 100 Type ratio (%) ratio (%) mass parts by mass Example 1-21 D-1 0.12 97.98 90 13 Example 1-22 D-1 0.10 98.00 90 11 Example 1-23 D-1 0.07 98.03 90 8 Example 1-24 D-2 0.08 98.02 90 9 Example 1-25 D-3 0.08 98.02 90 9 Example 1-26 D-4 0.35 97.75 90 39 Example 1-27 D-5 0.13 97.97 90 14 Example 1-28 D-6 0.28 97.82 90 31 Example 1-29 D-1 0.05 98.05 90 6 Example 1-30 D-1 0.04 98.06 90 4 Example 1-31 D-1 0.05 98.05 90 6 Example 1-32 D-1 0.04 98.06 90 4 Example 1-33 D-2 0.03 98.07 90 3 Example 1-34 D-1 0.11 97.99 90 12 Example 1-35 D-1 0.11 97.99 90 12 Example 1-36 D-1 0.11 97.99 90 12 Comparative 98.10 90 Example 1-1 Comparative D-1 0.24 98.07 90 3 Example 1-2 Comparative D-1 0.04 98.10 90 4 Example 1-3 Comparative D-1 0.06 98.10 90 7 Example 1-4 Comparative D-1 0.06 98.10 90 7 Example 1-5

TABLE-US-00003 TABLE 2-2 Particle Value Value Complex diameter D.sub.50 pH of 0.149X + of 0.134X + modulus Phase angle Storage X Y 4.545 5.140 Evaluation Evaluation stability Example 1-1 1.5 4.4 4.32 4.94 2 1 Example 1-2 1.6 4.7 4.31 4.93 2 1 Example 1-3 0.8 4.5 4.43 5.03 3 1 Example 1-4 0.8 4.7 4.43 5.03 3 1 Example 1-5 0.8 4.9 4.43 5.03 3 1 Example 1-6 0.5 4.6 4.47 5.07 3 1 Example 1-7 0.5 5.0 4.47 5.07 3 1 Example 1-8 1.2 4.4 4.37 4.98 3 1 Example 1-9 1.2 4.7 4.37 4.98 3 1 Example 1-10 0.4 4.7 4.49 5.09 3 1 Example 1-11 0.4 5.0 4.49 5.09 3 1 Example 1-12 1.3 4.4 4.35 4.97 3 1 Example 1-13 1.3 4.8 4.35 4.97 3 1 Example 1-14 0.7 4.5 4.44 5.05 3 1 Example 1-15 0.7 4.9 4.44 5.05 3 1 Example 1-16 0.8 4.7 4.43 5.03 2 1 Example 1-17 0.9 4.6 4.41 5.02 3 1 Example 1-18 0.8 4.7 4.43 5.03 3 1 Example 1-19 0.8 4.7 4.43 5.03 3 1 Example 1-20 0.8 4.7 4.43 5.03 3 1 Particle Value Value Complex diameter D.sub.50 pH of 0.149X + of 0.134X + modulus Phase angle Storage X Y 4.545 5.140 Evaluation Evaluation stability Example 1-21 0.8 4.7 4.43 5.03 3 1 Example 1-22 0.9 4.8 4.41 5.02 3 1 Example 1-23 0.9 4.7 4.41 5.02 2 2 Example 1-24 0.8 4.7 4.43 5.03 3 1 Example 1-25 0.8 4.7 4.43 5.03 3 1 Example 1-26 0.8 4.7 4.43 5.03 2 1 Example 1-27 0.8 4.7 4.43 5.03 3 1 Example 1-28 0.8 4.7 4.43 5.03 2 1 Example 1-29 3.8 4.3 3.98 4.63 2 2 Example 1-30 6.0 3.8 3.65 4.33 3 1 Example 1-31 4.1 4.1 3.93 4.59 3 1 Example 1-32 5.5 4.0 3.72 4.40 3 1 Example 1-33 5.8 3.9 3.68 4.36 3 1 Example 1-34 0.4 4.5 4.49 5.19 2 2 Example 1-35 1.7 4.6 4.29 5.37 3 1 Example 1-36 1.8 5.2 4.28 5.38 2 1 Comparative 1.3 3.1 4.35 4.97 1 3 X Example 1-1 Comparative 1.4 8.8 4.34 4.95 1 3 X Example 1-2 Comparative 1.8 4.4 4.28 4.90 1 3 X Example 1-3 Comparative 4.5 4.3 3.87 4.54 1 3 X Example 1-4 Comparative 4.2 4.4 3.92 4.58 1 3 X Example 1-5

<Preparation and Evaluation of Secondary Battery>

<Preparation of Negative Electrode Mixture Slurry and Negative Electrode>

Example 2-1

[0309] A dispersion composition (dispersion composition 1), a thickener, and water were added to a plastic container, and then stirred for 30 seconds at 2,000 rpm using a rotation-revolution mixer (THINKY MIXER manufactured by Thinky Corporation, ARE-310). Subsequently, artificial graphite and silicon (artificial graphite: silicon=9:1 (mass ratio)) were added as negative electrode active materials, and stirred for 150 seconds at 2,000 rpm using the rotation-revolution mixer. Furthermore, thereafter, SBR (styrene-butadiene rubber) was added and stirred for 30 seconds at 2,000 rpm using the rotation-revolution mixer to obtain a negative electrode mixture slurry.

[0310] The active materials, the CNT, the dispersant, the thickener, and the SBR in the negative electrode mixture slurry were blended to the blending amounts (mass %) in Table 3 when the total thereof was 100 mass %, and the amount of water was adjusted such that the non-volatile content of the negative electrode mixture slurry became 45%. The blending amount in Table 3 represents the net content ratio (non-volatile content mass %) of each component in the negative electrode mixture slurry.

[0311] The obtained negative electrode mixture slurry was coated on a 20 m thick copper foil using an applicator, and then the coated film was dried in an electric oven at 120 C.5 C. for 25 minutes to prepare an electrode film. Subsequently, the electrode film was subjected to a rolling treatment using a roll press (3t hydraulic roll press manufactured by THANK METAL) to obtain a negative electrode (negative electrode 1). The basis weight per unit area of the mixture layer was 10 mg/cm.sup.2, and the density of the mixture layer after the rolling treatment was 1.6 g/cm.sup.3.

[0312] The raw materials mentioned above are as follows. [0313] Artificial graphite: CGB-20 (produced by Nippon Graphite Industries, Ltd.), non-volatile content 100% [0314] Silicon: Silicon monoxide (produced by Osaka Titanium Technologies Co., Ltd., SILICON MONOOXIDE SiO 1.3C 5 m, non-volatile content 100%) [0315] Thickener: CMC (carboxymethyl cellulose, #1190 (produced by Daicel FineChem Ltd.), non-volatile content 100%) [0316] Binder: SBR (styrene-butadiene rubber, TRD2001 (produced by JSR Corporation), non-volatile content 48%)

Examples 2-2 to 2-36

[0317] The dispersion composition was changed to each dispersion composition (dispersion compositions 2 to 36) shown in Table 3, and the composition ratio was changed as shown in Table 3. Except for the above, negative electrode mixture slurries were produced in the same manner as in Example 2-1, and negative electrodes 2 to 36 were obtained in the same manner.

Comparative Examples 2-1 to 2-5

[0318] The dispersion composition was changed to each dispersion composition (comparative dispersion compositions 1 to 5) shown in Table 3. Except for the above, comparative negative electrode mixture slurries were produced in the same manner as in Example 2-1, and comparative negative electrodes 1 to 5 were obtained in the same manner.

Reference Example 2-1: Preparation of Standard Negative Electrode

[0319] To a plastic container of a capacity 150 ml, 0.5 mass % of acetylene black (DENKA BLACK (registered trademark) HS-100, produced by Denka Company Limited), 1 mass % of MAC500LC (carboxymethyl cellulose sodium salt, Sunrose special type MAC500LC, produced by Nippon Paper Industries Co., Ltd., non-volatile content 100%), and 98.4 mass % of water were added, and then stirred for 30 seconds at 2,000 rpm using a rotation-revolution mixer (THINKY MIXER manufactured by Thinky Corporation, ARE-310). Furthermore, 97 mass % of artificial graphite (CGB-20, produced by Nippon Graphite Industries, Ltd.) was added as an active material, and stirred for 150 seconds at 2,000 rpm using the rotation-revolution mixer (THINKY MIXER manufactured by Thinky Corporation, ARE-310). Subsequently, 3.1 mass % of SBR (styrene-butadiene rubber, TRD2001, non-volatile content 48%, produced by JSR Corporation) was added, and stirred for 30 seconds at 2,000 rpm using the rotation-revolution mixer (THINKY MIXER manufactured by Thinky Corporation, ARE-310) to obtain a standard negative electrode mixture slurry. The non-volatile content of the standard negative electrode mixture slurry was 50 mass %.

[0320] The above standard negative electrode mixture slurry was coated onto a 20 m thick copper foil serving as a current collector using an applicator, and then dried in an electric oven at 80 C.5 C. for 25 minutes to adjust the basis weight per unit area of the electrode to 10 mg/cm.sup.2. Furthermore, a rolling treatment was performed using a roll press (3t hydraulic roll press manufactured by THANK METAL) to prepare a standard negative electrode with a density of the electrode mixture layer being 1.6 g/cm.sup.3.

TABLE-US-00004 TABLE 3 Dispersion composition Active Thickener Binder CNT (A) Dispersant material CMC SBR Non- Non- Non- Non- Non- volatile volatile volatile volatile volatile content content content content content Negative electrode Type mass % mass % mass % mass % mass % Example 2-1 Negative electrode 1 Dispersion composition 1 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-2 Negative electrode 2 Dispersion composition 2 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-3 Negative electrode 3 Dispersion composition 3 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-4 Negative electrode 4 Dispersion composition 4 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-5 Negative electrode 5 Dispersion composition 5 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-6 Negative electrode 6 Dispersion composition 6 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-7 Negative electrode 7 Dispersion composition 7 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-8 Negative electrode 8 Dispersion composition 8 JENOTUBE10B 0.50 0.20 96.8 1.0 1.5 Example 2-9 Negative electrode 9 Dispersion composition 9 JENOTUBE10B 0.50 0.20 96.8 1.0 1.5 Example 2-10 Negative electrode 10 Dispersion composition 10 JENOTUBE10B 0.50 0.20 96.8 1.0 1.5 Example 2-11 Negative electrode 11 Dispersion composition 11 JENOTUBE10B 0.50 0.20 96.8 1.0 1.5 Example 2-12 Negative electrode 12 Dispersion composition 12 JENOTUBE6A 0.30 0.19 97.0 1.0 1.5 Example 2-13 Negative electrode 13 Dispersion composition 13 JENOTUBE6A 0.30 0.19 97.0 1.0 1.5 Example 2-14 Negative electrode 14 Dispersion composition 14 JENOTUBE6A 0.30 0.19 97.0 1.0 1.5 Example 2-15 Negative electrode 15 Dispersion composition 15 JENOTUBE6A 0.30 0.19 97.0 1.0 1.5 Example 2-16 Negative electrode 16 Dispersion composition 16 TNSAR 0.10 0.09 97.3 1.0 1.5 Example 2-17 Negative electrode 17 Dispersion composition 17 BT1001M 0.50 0.20 96.8 1.0 1.5 Example 2-18 Negative electrode 18 Dispersion composition 18 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-19 Negative electrode 19 Dispersion composition 19 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-20 Negative electrode 20 Dispersion composition 20 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-21 Negative electrode 21 Dispersion composition 21 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-22 Negative electrode 22 Dispersion composition 22 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-23 Negative electrode 23 Dispersion composition 23 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-24 Negative electrode 24 Dispersion composition 24 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-25 Negative electrode 25 Dispersion composition 25 TUBALL 0.1 0.09 97.3 1.0 1.5 Example 2-26 Negative electrode 26 Dispersion composition 26 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-27 Negative electrode 27 Dispersion composition 27 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-28 Negative electrode 28 Dispersion composition 28 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-29 Negative electrode 29 Dispersion composition 29 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-30 Negative electrode 30 Dispersion composition 30 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-31 Negative electrode 31 Dispersion composition 31 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-32 Negative electrode 32 Dispersion composition 32 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-33 Negative electrode 33 Dispersion composition 33 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-34 Negative electrode 34 Dispersion composition 34 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-35 Negative electrode 35 Dispersion composition 35 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-36 Negative electrode 36 Dispersion composition 36 TUBALL 0.10 0.09 97.3 1.0 1.5 Comparative Comparative negative Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-1 electrode 1 composition 1 Comparative Comparative negative Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-2 electrode 2 composition 2 Comparative Comparative negative Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-3 electrode 3 composition 3 Comparative Comparative negative Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-4 electrode 4 composition 4 Comparative Comparative negative Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 2-5 electrode 5 composition 5

<Preparation of Positive Electrode Mixture Slurry and Positive Electrode>

Example 3-1

[0321] A dispersion composition (dispersion composition 1), a thickener, and water were added to a plastic container, and then stirred for 30 seconds at 2,000 rpm using a rotation-revolution mixer (THINKY MIXER manufactured by Thinky Corporation, ARE-310). Subsequently, LFP was added as a positive electrode active material and stirred for 150 seconds at 2,000 rpm using the rotation-revolution mixer (THINK Y MIXER manufactured by Thinky Corporation, ARE-310). Furthermore, thereafter, PTFE was added as a binder, and stirred for 30 seconds at 2,000 rpm using the rotation-revolution mixer (THINK Y MIXER manufactured by Thinky Corporation, ARE-310) to obtain a positive electrode mixture slurry.

[0322] The active material, the CNT, the dispersant, the thickener, and the binder (PTFE) in the positive electrode mixture slurry were blended to the blending amounts (mass %) shown in Table 4 when the total of the non-volatile contents thereof were 100 mass %, and the amount of water was adjusted such that the non-volatile contents of the positive electrode mixture slurry became 65%. The blending amount in Table 4 represents the net content ratio (non-volatile content mass %) of each component in the positive electrode mixture slurry.

[0323] The positive electrode mixture slurry was coated onto a 20 m thick aluminum foil using an applicator, and then dried in an electric oven at 120 C.5 C. for 25 minutes to prepare an electrode film. Subsequently, the electrode film was subjected to a rolling treatment using a roll press (3t hydraulic roll press manufactured by THANK METAL) to obtain a positive electrode (positive electrode 1). The basis weight per unit area of the mixture layer was 20 mg/cm.sup.2, and the density of the mixture layer after the rolling treatment was 2.1 g/cc.

[0324] The raw materials mentioned above are as follows. [0325] LFP: Lithium iron phosphate HED (registered trademark) LFP-400 (produced by BASF, non-volatile content 100%) [0326] Binder: PTFE (polytetrafluoroethylene, Polyflon PTFE D-210C (produced by Daikin Industries, Ltd., non-volatile content 60%) [0327] Thickener: CMC (carboxymethyl cellulose #1190 (produced by Daicel FineChem Ltd., non-volatile content 100%)

Examples 3-2 to 3-36

[0328] The conductive material dispersion was changed to each dispersion composition (dispersion compositions 2 to 36) shown in Table 4. Except for the above, positive electrodes 2 to 36 were obtained by the same method as in Example 3-1.

Comparative Examples 3-1 to 3-5

[0329] The conductive material dispersion was changed to each dispersion composition (comparative dispersion compositions 1 to 5) shown in Table 4. Except for the above, comparative positive electrodes 1 to 5 were obtained by the same method as in Example 3-1.

Reference Example 3-1: Preparation of Standard Positive Electrode

[0330] 92 mass % of LFP (HED (registered trademark) LFP-400, produced by BASF, non-volatile content 100%) as a positive electrode active material, 4 mass % of acetylene black (DENKA BLACK (registered trademark) HS-100, produced by Denka Company Limited, non-volatile content 100%), and 1.6 mass % of a thickener (carboxymethyl cellulose #1190, produced by Daicel FineChem Ltd., non-volatile content 100%) were added to a plastic container and then mixed using a spatula until uniform. Subsequently, 20.5 mass % of water was added, and stirred for 30 seconds at 2,000 rpm using a rotation-revolution mixer (THINKY MIXER manufactured by Thinky Corporation, ARE-310). Then, the mixture in the plastic container was mixed with a spatula until uniform, and 4 mass % of PTFE (produced by Daikin Industries, Ltd., non-volatile content 60 mass %) was added and stirred for 30 seconds at 2,000 rpm using the rotation-revolution mixer. Furthermore, thereafter, 11.2 mass % of water was added and stirred for 30 seconds at 2,000 rpm using the rotation-revolution mixer. Finally, the mixture was stirred for 10 minutes at 3,000 rpm using a high-speed stirrer to obtain a standard positive electrode mixture slurry.

[0331] The standard positive electrode mixture slurry was coated onto a 20 m thick aluminum foil using an applicator, and then dried in an electric oven at 120 C.5 C. for 25 minutes to prepare an electrode film. Subsequently, the electrode film was subjected to a rolling treatment using a roll press (3t hydraulic roll press manufactured by THANK METAL) to obtain a standard positive electrode. The basis weight per unit area of the electrode mixture layer was 20 mg/cm.sup.2, and the density of the electrode mixture layer after the rolling treatment was 2.1 g/cc.

TABLE-US-00005 TABLE 4 Dispersion composition Active Thickener Binder CNT (A) Dispersant material CMC PTFE Non- Non- Non- Non- Non- volatile volatile volatile volatile volatile content content content content content Negative electrode Type mass % mass % mass % mass % mass % Example 3-1 Positive electrode 1 Dispersion composition 1 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-2 Positive electrode 2 Dispersion composition 2 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-3 Positive electrode 3 Dispersion composition 3 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-4 Positive electrode 4 Dispersion composition 4 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-5 Positive electrode 5 Dispersion composition 5 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-6 Positive electrode 6 Dispersion composition 6 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-7 Positive electrode 7 Dispersion composition 7 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-8 Positive electrode 8 Dispersion composition 8 JENOTUBE10B 0.10 0.04 97.4 1.0 1.5 Example 3-9 Positive electrode 9 Dispersion composition 9 JENOTUBE10B 0.10 0.04 97.4 1.0 1.5 Example 3-10 Positive electrode 10 Dispersion composition 10 JENOTUBE10B 0.10 0.04 97.4 1.0 1.5 Example 3-11 Positive electrode 11 Dispersion composition 11 JENOTUBE10B 0.10 0.04 97.4 1.0 1.5 Example 3-12 Positive electrode 12 Dispersion composition 12 JENOTUBE6A 0.10 0.06 97.3 1.0 1.5 Example 3-13 Positive electrode 13 Dispersion composition 13 JENOTUBE6A 0.10 0.06 97.3 1.0 1.5 Example 3-14 Positive electrode 14 Dispersion composition 14 JENOTUBE6A 0.10 0.06 97.3 1.0 1.5 Example 3-15 Positive electrode 15 Dispersion composition 15 JENOTUBE6A 0.10 0.06 97.3 1.0 1.5 Example 3-16 Positive electrode 16 Dispersion composition 16 TNSAR 0.10 0.09 97.3 1.0 1.5 Example 3-17 Positive electrode 17 Dispersion composition 17 BT1001M 0.10 0.04 97.4 1.0 1.5 Example 3-18 Positive electrode 18 Dispersion composition 18 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-19 Positive electrode 19 Dispersion composition 19 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-20 Positive electrode 20 Dispersion composition 20 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-21 Positive electrode 21 Dispersion composition 21 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-22 Positive electrode 22 Dispersion composition 22 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-23 Positive electrode 23 Dispersion composition 23 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-24 Positive electrode 24 Dispersion composition 24 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-25 Positive electrode 25 Dispersion composition 25 TUBALL 2.0 1.80 93.7 1.0 1.5 Example 3-26 Positive electrode 26 Dispersion composition 26 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-27 Positive electrode 27 Dispersion composition 27 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-28 Positive electrode 28 Dispersion composition 28 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-29 Positive electrode 29 Dispersion composition 29 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-30 Positive electrode 30 Dispersion composition 30 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-31 Positive electrode 31 Dispersion composition 31 TUBALL 0.50 0.45 96.6 1.0 1.5 Example 3-32 Positive electrode 32 Dispersion composition 32 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-33 Positive electrode 33 Dispersion composition 33 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-34 Positive electrode 34 Dispersion composition 34 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-35 Positive electrode 35 Dispersion composition 35 TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-36 Positive electrode 36 Dispersion composition 36 TUBALL 0.10 0.09 97.3 1.0 1.5 Comparative Comparative positive Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-1 electrode 1 composition 1 Comparative Comparative positive Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-2 electrode 2 composition 2 Comparative Comparative positive Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-3 electrode 3 composition 3 Comparative Comparative positive Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-4 electrode 4 composition 4 Comparative Comparative positive Comparative dispersion TUBALL 0.10 0.09 97.3 1.0 1.5 Example 3-5 electrode 5 composition 5

(Preparation of Secondary Battery)

[0332] Using the standard positive electrode and the negative electrode or the comparative negative electrode described in Table 5, or using the positive electrode or the comparative positive electrode and the standard negative electrode described in Table 6, which were punched out to 50 mm45 mm and 45 mm40 mm, respectively, the punched positive electrode and negative electrode, with a separator (porous polypropylene film) inserted therebetween, were inserted into an aluminum laminate bag and dried in an electric oven at 70 C. for 1 hour. Subsequently, in a glove box filled with argon gas, 2 mL of an electrolyte (non-aqueous electrolyte obtained by mixing ethylene carbonate, dimethyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1 to prepare a mixed solvent, further, adding 1 mass % of vinylene carbonate as an additive with respect to 100 mass % of the mixed solvent, and then dissolving LiPF.sub.6 at a concentration of 1 M) was injected, and the aluminum laminate bag was then sealed to prepare each secondary battery.

<Evaluation of Secondary Battery>

[0333] The obtained secondary batteries were evaluated according to the following method. The results are shown in Table 5 and Table 6.

(Rate Characteristic Evaluation Method for Secondary Battery)

[0334] The evaluation was performed in the same manner as described in paragraph 0178 of Japanese Patent No. 7107413. With the evaluation criteria to , practical use is possible.

Evaluation Criteria for Rate Characteristics

[0335] : 90% or higher (excellent) [0336] : 85% or higher and less than 90% (good) [0337] : 80% or higher and less than 85% (acceptable) [0338] x: Less than 80%

(Cycle Characteristics Evaluation Method for Secondary Battery)

[0339] The evaluation was performed in the same manner as described in paragraph 0179 of Japanese Patent No. 7107413. With the evaluation criteria being to , practical use is possible.

Evaluation Criteria for Cycle Characteristics

[0340] : 90% or higher (excellent) [0341] : 80% or higher and less than 90% (good) [0342] : 70% or higher and less than 80% (acceptable) [0343] x: Less than 70%

TABLE-US-00006 TABLE 5 Rate Cycle Negative electrode Positive electrode characteristics characteristics Example 5-1 Negative electrode 1 Standard positive electrode Example 5-2 Negative electrode 2 Standard positive electrode Example 5-3 Negative electrode 3 Standard positive electrode Example 5-4 Negative electrode 4 Standard positive electrode Example 5-5 Negative electrode 5 Standard positive electrode Example 5-6 Negative electrode 6 Standard positive electrode Example 5-7 Negative electrode 7 Standard positive electrode Example 5-8 Negative electrode 8 Standard positive electrode Example 5-9 Negative electrode 9 Standard positive electrode Example 5-10 Negative electrode 10 Standard positive electrode Example 5-11 Negative electrode 11 Standard positive electrode Example 5-12 Negative electrode 12 Standard positive electrode Example 5-13 Negative electrode 13 Standard positive electrode Example 5-14 Negative electrode 14 Standard positive electrode Example 5-15 Negative electrode 15 Standard positive electrode Example 5-16 Negative electrode 16 Standard positive electrode Example 5-17 Negative electrode 17 Standard positive electrode Example 5-18 Negative electrode 18 Standard positive electrode Example 5-19 Negative electrode 19 Standard positive electrode Example 5-20 Negative electrode 20 Standard positive electrode Example 5-21 Negative electrode 21 Standard positive electrode Example 5-22 Negative electrode 22 Standard positive electrode Example 5-23 Negative electrode 23 Standard positive electrode Example 5-24 Negative electrode 24 Standard positive electrode Example 5-25 Negative electrode 25 Standard positive electrode Example 5-26 Negative electrode 26 Standard positive electrode Example 5-27 Negative electrode 27 Standard positive electrode Example 5-28 Negative electrode 28 Standard positive electrode Example 5-29 Negative electrode 29 Standard positive electrode Example 5-30 Negative electrode 30 Standard positive electrode Example 5-31 Negative electrode 31 Standard positive electrode Example 5-32 Negative electrode 32 Standard positive electrode Example 5-33 Negative electrode 33 Standard positive electrode Example 5-34 Negative electrode 34 Standard positive electrode Example 5-35 Negative electrode 35 Standard positive electrode Example 5-36 Negative electrode 36 Standard positive electrode Comparative Comparative Standard positive electrode X Example 5-1 negative electrode 1 Comparative Comparative Standard positive electrode X Example 5-2 negative electrode 2 Comparative Comparative Standard positive electrode X Example 5-3 negative electrode 3 Comparative Comparative Standard positive electrode X Example 5-4 negative electrode 4 Comparative Comparative Standard positive electrode X Example 5-5 negative electrode 5

TABLE-US-00007 TABLE 6 Rate Cycle Negative electrode Positive electrode characteristics characteristics Example 6-1 Standard negative electrode Positive electrode 1 Example 6-2 Standard negative electrode Positive electrode 2 Example 6-3 Standard negative electrode Positive electrode 3 Example 6-4 Standard negative electrode Positive electrode 4 Example 6-5 Standard negative electrode Positive electrode 5 Example 6-6 Standard negative electrode Positive electrode 6 Example 6-7 Standard negative electrode Positive electrode 7 Example 6-8 Standard negative electrode Positive electrode 8 Example 6-9 Standard negative electrode Positive electrode 9 Example 6-10 Standard negative electrode Positive electrode 10 Example 6-11 Standard negative electrode Positive electrode 11 Example 6-12 Standard negative electrode Positive electrode 12 Example 6-13 Standard negative electrode Positive electrode 13 Example 6-14 Standard negative electrode Positive electrode 14 Example 6-15 Standard negative electrode Positive electrode 15 Example 6-16 Standard negative electrode Positive electrode 16 Example 6-17 Standard negative electrode Positive electrode 17 Example 6-18 Standard negative electrode Positive electrode 18 Example 6-19 Standard negative electrode Positive electrode 19 Example 6-20 Standard negative electrode Positive electrode 20 Example 6-21 Standard negative electrode Positive electrode 21 Example 6-22 Standard negative electrode Positive electrode 22 Example 6-23 Standard negative electrode Positive electrode 23 Example 6-24 Standard negative electrode Positive electrode 24 Example 6-25 Standard negative electrode Positive electrode 25 Example 6-26 Standard negative electrode Positive electrode 26 Example 6-27 Standard negative electrode Positive electrode 27 Example 6-28 Standard negative electrode Positive electrode 28 Example 6-29 Standard negative electrode Positive electrode 29 Example 6-30 Standard negative electrode Positive electrode 30 Example 6-31 Standard negative electrode Positive electrode 31 Example 6-32 Standard negative electrode Positive electrode 32 Example 6-33 Standard negative electrode Positive electrode 33 Example 6-34 Standard negative electrode Positive electrode 34 Example 6-35 Standard negative electrode Positive electrode 35 Example 6-36 Standard negative electrode Positive electrode 36 Comparative Standard negative electrode Comparative X Example 6-1 positive electrode 1 Comparative Standard negative electrode Comparative X Example 6-2 positive electrode 2 Comparative Standard negative electrode Comparative X Example 6-3 positive electrode 3 Comparative Standard negative electrode Comparative X Example 6-4 positive electrode 4 Comparative Standard negative electrode Comparative X Example 6-5 positive electrode 5

[0344] As can be learned from Tables 2, 5, and 6, it has been confirmed that a dispersion composition that includes a polymer containing 80 mass % or more of a carboxyl group-containing structural unit and a basic compound, and is adjusted to an appropriate pH with respect to a particle diameter D.sub.50, can achieve fluidity, storage stability, and battery performance.

[0345] When adjusting the particle diameter D.sub.50 of the carbon nanotube dispersion composition to 0.3 to 7.0 m, dispersion using a dispersant (B) which is a polymer having a weight average molecular weight of 5,000 or more and 360,000 or less and including a carboxyl group-containing structural unit could be applied by adjusting the pH, regardless of the type of the carbon nanotubes or the type of the basic compound.

[0346] As in the comparative examples, in the case where the pH was low or in the case where a polymer with a low content ratio of the carboxyl group-containing structural unit was used, fluidity was poor due to insufficient electric repulsive force of the carboxyl groups. In the case where the pH was high, the affinity between the polymer and the carbon nanotubes decreased, and thickening due to aggregation of the carbon nanotubes occurred. In the case where the dispersant was a polymer with a small molecular weight, steric repulsive force was insufficient, and fluidity was poor. In the case of a polymer with a large molecular weight, thickening occurred due to the viscosity of the polymer itself.

[0347] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above. Various modifications understandable by those skilled in the art may be made to the configurations and details of the present invention within the scope of the invention.