JP2017182962A - Slurry composition superior in viscosity for lithium ion secondary battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slurry composition for a lithium ion secondary battery electrode, which is superior in viscosity and suitability to coating.SOLUTION: A slurry composition for a lithium ion secondary battery electrode comprises an active material, a conducting agent, a binder, and a solvent. The conducting agent is carbon black of which the crystallization rate calculated from a crystal layer thickness Lc and an average primary particle diameter is 60% or more. In the slurry composition, blend ratios of the solid contents are as follows: 80-99.8 mass% for the active material; 0.1-10 mass% for the conducting agent; and 0.1-10 mass% for the binder. The slurry composition is 50-70 mass% in solid content concentration, and 10 Pa s or less in viscosity at a shear rate of 1 s. With the slurry composition, viscosities ηand ηfor arbitrary shear rates γand γ(γ<γ) satisfy η>ηin a range of the shear rate of 0.01-100 s.SELECTED DRAWING: Figure 1

Description

The present invention relates to a slurry composition for a lithium ion secondary battery electrode excellent in viscosity characteristics and coatability, and a lithium ion secondary battery using the same.

Lithium ion secondary batteries are widely used as power sources for small electronic devices such as smartphones and tablet computers. Generally, a lithium ion secondary battery includes an electrolyte solution including an electrode, a separator, and an electrolyte. An electrode is manufactured by coating and drying an electrode slurry in which an active material, a conductive agent, a binder, and the like are dispersed in a solvent on a metal plate for a current collector to form a composite layer.

The role of the conductive agent is to impart conductivity to an active material having low conductivity, and to prevent the conductivity from being impaired due to repeated expansion and contraction of the active material during charging and discharging. Therefore, if the dispersion state of the active material and the conductive agent is poor in the electrode, a portion with poor conductivity appears locally, the active material is not effectively used, the discharge capacity is reduced, and the battery characteristics are reduced. Become. That is, the battery characteristics are not only the material characteristics such as the chemical composition of the active material and the conductivity of the conductive agent, but also the structural characteristics such as the compounding ratio and mixing / dispersing state of the material in the composite material layer, the density of the composite material layer, and the porosity. It is necessary to optimize them. Moreover, in order to continue producing electrodes stably while maintaining the structure of the composite layer in an optimum state, it is necessary to reduce the unevenness of the electrode slurry coating and the dispersion of the composite layer thickness to the utmost.

The specific surface area of the conductive agent that is conventionally used is about 40~70m ² / g, much higher than the specific surface area of the cathode active material (0.2~1.0m ² / g). For example, when 92% by mass of the positive electrode active material having a specific surface area of 0.7 m ² / g and 8% by mass of the conductive agent having a specific surface area of 65 m ² / g are mixed, the ratio of the surface area occupied by the conductive agent reaches 89%. Thus, it can be seen that the properties of the conductive agent are dominant in the coatability of the electrode slurry.

In recent years, further increase in capacity of lithium ion secondary batteries has been demanded, and the blending ratio of the active material in the composite layer is increasing, and conversely, the blending ratio of the conductive agent and the binder tends to decrease. When the blending ratio of the conductive agent decreases, it becomes difficult to form a conductive path in the electrode, and the battery characteristics deteriorate. Therefore, studies have been made to maintain the conductive path by using a conductive agent having a small particle diameter. However, as the particle size is reduced, the specific surface area and liquid absorption are increased, and the viscosity of the electrode slurry is remarkably increased, so that uniform dispersion becomes difficult. In addition, there is a problem that unevenness is likely to occur during coating, and high-performance electrodes cannot be stably produced.

Therefore, for the purpose of uniformly dispersing the electrode slurry, Patent Document 1 studies an attempt to disperse the conductive agent using a high-pressure jet mill. However, according to this method, processing by a special apparatus is necessary, and since the structure is miniaturized to submicron order, there is a problem that the fine structure of the conductive agent is changed and the conductivity is lowered. In Patent Document 2, studies have been made to control the aggregation state of a solid material composed of an active material and a binder. However, the aggregation state of the conductive agent is not controlled, and the target is used when a conductive agent having a small particle size is used. It was difficult to achieve the electrode slurry characteristics. Further, in Patent Document 3, it is considered to prepare a conductive agent slurry having a wide particle size distribution in advance, but since the fine structure of the conductive agent is processed under the condition that the fine structure is not crushed, The particle size distribution of the conductive agent having a diameter could not be controlled.

JP 2004-289696 A Japanese Patent No. 5500395 Japanese Patent No. 5561559

The objective of this invention is providing the slurry composition for lithium ion secondary battery electrodes excellent in the viscosity characteristic and coating property.

The present invention employs the following means in order to solve the above problems.
(1) An active material, a conductive agent, a binder, and a solvent, wherein the conductive agent is carbon black having a crystallization rate calculated from the crystal layer thickness Lc and the average primary particle diameter of 60% or more. A slurry composition for a secondary battery electrode.
(2) The solid content is 80 to 99.8% by mass of the active material, 0.1 to 10% by mass of the conductive agent, 0.1 to 10% by mass of the binder, and the solid content concentration is 50 to 70% by mass, The viscosity at a shear rate of 1 s ⁻¹ is 10 Pa · s or less, and the viscosity η ₁ , η ₂ for any shear rate γ ₁ , γ ₂ (γ ₁ <γ ₂ ) in the range of a shear rate of 0.01 to 100 s ^−1. Satisfying η ₁ > η _2. The slurry composition according to the above (1).
(3) A lithium ion secondary battery using the slurry composition according to (1) or (2).

Since the slurry composition for a lithium ion secondary battery electrode of the present invention is excellent in viscosity characteristics and coatability, a high performance lithium ion secondary battery can be provided with high productivity.

Example of electrode slurry viscosity in the range of shear rate 0.01-100 s ⁻¹

The slurry composition for a lithium ion secondary battery electrode of the present invention includes an active material, a conductive agent, a binder, and a solvent. Depending on the purpose, additives such as a dispersant and a flame retardant can also be contained.

The conductive agent used in the slurry composition for a lithium ion secondary battery electrode of the present invention is carbon black having a crystallization rate calculated from the crystal layer thickness Lc and the average primary particle diameter of 60% or more. Here, the crystallization rate is a volume ratio of the surface crystal layer to the average primary particle diameter of carbon black, and can be obtained by the formula (1).

ここでｄはカーボンブラックの平均一次粒子径、Ｌｃは結晶層厚みである。

Here, d is the average primary particle diameter of carbon black, and Lc is the crystal layer thickness.

As a result of intensive studies to improve the viscosity characteristics and coating properties of the slurry composition for lithium ion secondary battery electrodes, the present inventor has found that the crystallization ratio of carbon black, which is a conductive agent, greatly affects these characteristics. I found out. That is, when the crystallization rate of carbon black is 60% or more, a uniformly dispersed electrode slurry can be prepared without giving strong shearing that causes destruction of the microstructure of the carbon black. The characteristics of the ion secondary battery can be greatly improved. Although the detailed mechanism is unknown, it is considered that some change occurred in the wettability with the solvent due to the high crystallinity on the surface of the carbon black particles. When the crystallization rate of carbon black is less than 60%, this effect is not exhibited, and it is difficult to uniformly disperse the electrode slurry, unevenness is likely to occur during coating, and high-performance electrodes cannot be stably produced.

The crystal layer thickness Lc of carbon black used as a conductive agent in the slurry composition for a lithium ion secondary battery electrode of the present invention can be determined by X-ray diffraction. Specifically, X-ray diffraction is performed using CuKα rays under the conditions of a measurement range 2θ = 10 to 40 ° and a slit width of 0.5 °. Using the obtained (002) plane diffraction line, the crystallite size Lc can be obtained by the Scherrer equation: Lc (Å) = (K × λ) / (β × cos θ). Here, K is a form factor constant of 0.9, λ is an X-ray wavelength of 1.54 mm, θ is an angle indicating a maximum value in the (002) diffraction line absorption band, and β is a half-value width in the (002) diffraction line absorption band. (Radians). The crystal layer thickness Lc of carbon black can be adjusted by the synthesis temperature of carbon black. It can also be adjusted by heat-treating the synthesized carbon black in an inert atmosphere.

The average primary particle size of carbon black used as a conductive agent in the slurry composition for a lithium ion secondary battery electrode of the present invention is preferably 17 nm or more and less than 50 nm, more preferably 36 nm or less, and 27 nm or less. More preferably it is. Since carbon black used in conventional electrode slurries has a crystallization rate of less than 60%, it is difficult to form a slurry when the average primary particle size is 27 nm or less. On the other hand, since the carbon black used in the present invention has a crystallization rate of 60% or more, it can be slurried even if the average primary particle size is 27 nm or less. Thus, by using carbon black having a small particle diameter, high conductivity can be exhibited even if the compounding ratio in the composite layer is low. On the other hand, when the average primary particle size is less than 17 nm, the specific surface area is greatly increased, and the amount of the conductive agent adsorbing the solvent or binder is increased, so that the electrode slurry is thickened, and a uniform mixture layer is formed. It becomes difficult to form. The average primary particle diameter of carbon black can be obtained by measuring the primary particle diameter of 100 carbon blacks from a 50,000-fold image obtained by a transmission electron microscope (TEM) and calculating the average value. The primary particles of carbon black have a small aspect ratio and a shape close to a true sphere, but are not perfect spheres. Therefore, the largest of the line segments connecting the two outer peripheral points of the primary particles in the TEM image is the primary particle diameter of carbon black. It is generally known that the primary particle size of carbon black is greatly influenced by the temperature of the synthesis reaction field, and the primary particle size decreases as the temperature increases.

The specific surface area of carbon black used as a conductive agent in the slurry composition for a lithium ion secondary battery electrode of the present invention is preferably 40 m ² / g or more and less than 300 m ² / g. This is characterized in that it is higher than the specific surface area of carbon black conventionally used for conductive agents. When the specific surface area is 40 m ² / g or more, the number of contact points with the active material in the composite layer increases, and the conductivity can be improved. When the specific surface area is 300 m ² / g or more, the amount of the conductive agent adsorbing the solvent or the binder increases, so that the electrode slurry is thickened and it is difficult to form a uniform mixture layer. Furthermore, since the carbon black of the present invention is a carbon black having very few surface irregularities or pores or hydrophilic surface functional groups, it is difficult to disperse in the electrode slurry when the specific surface area is 300 m ² / g or more. It becomes. On the other hand, in carbon black having a high specific surface area exceeding 300 m ² / g, when a large amount of hydrophilic surface functional groups are provided, high dispersion in the electrode slurry may be possible. The specific surface area can be measured by the BET method according to JIS K6217-2. The specific surface area of carbon black can be increased by reducing the primary particle size, making it hollow, making the particle surface porous, etc., and does not necessarily depend only on the primary particle size.

The method for producing carbon black according to the present invention is not particularly limited. For example, a raw material gas such as a hydrocarbon is supplied from a nozzle installed at the top of the reactor and is subjected to a pyrolysis reaction and / or a partial combustion reaction. Carbon black can be produced and collected from a bag filter directly connected to the bottom of the reactor. The raw material gas to be used is not particularly limited, and gaseous hydrocarbons such as acetylene, methane, ethane, propane, ethylene, propylene, and butadiene, and oils such as toluene, benzene, xylene, gasoline, kerosene, light oil, and heavy oil Gasified hydrocarbons can be used. A plurality of these can also be mixed and used. Among them, it is preferable to use acetylene gas with few impurities. Since the temperature in the reaction furnace increases due to the decomposition heat of the acetylene gas, carbon black having a small particle size and a large crystal layer thickness Lc can be obtained.

The solid content blending ratio of the slurry composition for a lithium ion secondary battery electrode of the present invention is 80 to 99.8% by mass of the active material, 0.1 to 10% by mass of the conductive agent, and 0.1 to 10% by mass of the binder. Is preferred. By using carbon black, which has a high crystallization rate, as a conductive agent and using the above-mentioned solid content, it is possible to increase the mixing ratio of the active material in the composite layer without impairing the coating property and conductivity of the electrode slurry. The capacity of the lithium ion secondary battery can be increased. In addition, by using carbon black having a high crystallization ratio and a small particle size, the conductivity can be improved even with the same solid content, and high output of the lithium ion secondary battery can be achieved.
Moreover, it is preferable that solid content concentration of the slurry composition for lithium ion secondary battery electrodes of this invention is 50-70 mass%. When the solid content concentration exceeds 70% by mass, strong shearing is applied when the electrode slurry is kneaded, so that the primary aggregation of the conductive agent is destroyed and the conductivity is lowered. In addition, cracks are likely to occur in the drying process. On the other hand, if the solid content concentration is less than 50% by mass, the drying process after coating takes time, and the productivity is lowered.

The slurry composition for lithium ion secondary battery electrodes of the present invention preferably has a viscosity at a shear rate of 1 s ⁻¹ of 10 Pa · s or less. The electrode slurry coating method on the current collector includes a doctor blade method, a roll coater method, a die coater method, etc., and the coating speed is generally about 10 to 50 m / min. If the viscosity at a shear rate of 1 s ⁻¹ corresponding to this region is 10 Pa · s or less, uniform coating is possible. The viscosity at a shear rate of 1 s ⁻¹ is preferably 1 Pa · s or higher. If it is less than 1 Pa · s, the active material tends to settle after coating, and the structure of the composite layer may be biased. The viscosity of the electrode slurry can be measured by a rheometer. The viscosity in the present invention is the viscosity at a measurement temperature of 25 ° C. The viscosity of the electrode slurry can be adjusted by changing the blending ratio of solids such as active material, conductive agent, binder, solid content concentration, dispersion conditions, addition of dispersant, crystallization rate of carbon black as a conductive agent, etc. .

The slurry composition for a lithium ion secondary battery electrode of the present invention has viscosities η ₁ and η _{2 with} respect to arbitrary shear rates γ ₁ and γ ₂ (γ ₁ <γ ₂ ) in the range of shear rates of 0.01 to 100 s ^−1. Is preferably η ₁ > η ₂ . Usually, the viscosity of the electrode slurry tends to monotonously decrease with increasing shear rate. Therefore, if η ₁ > η ₂ , the flow characteristics do not change even if the shear rate applied during coating changes, and stable coating is possible. When η ₁ ≦ η ₂ , since the viscosity increases when the shear rate is increased or the viscosity decreases when the shear rate is decreased, stable coating is difficult. Although the detailed mechanism is unknown, it is considered that the flow characteristics were improved because the crystallinity on the surface of the carbon black particles was increased, which caused some change in the wettability with the solvent. When the crystallization rate of carbon black is less than 60%, η ₁ ≦ η ₂ is exhibited due to a phenomenon such as poor wettability with a solvent and aggregation of particles, and uniform dispersion of the electrode slurry becomes difficult. Unevenness is likely to occur during coating, and high-performance electrodes cannot be stably produced.

Although the active material used for the slurry composition for lithium ion secondary battery electrodes of the present invention is not particularly limited, lithium cobaltate or nickel / manganese / lithium cobaltate is preferable. Moreover, it is preferable that the average particle diameter of an active material is 1-20 micrometers. When the thickness is less than 1 μm, the electrode slurry is thickened, and when it exceeds 20 μm, it is difficult to produce a smooth electrode.

The binder used in the lithium ion secondary battery electrode slurry composition of the present invention is not particularly limited, for example, polyethylene, nitrile rubber, polybutadiene, butyl rubber, polystyrene, styrene-butadiene rubber, polysulfide rubber, nitrocellulose, Cetylmethylcellulose, polyvinyl alcohol, tetrafluoroethylene resin, polyvinylidene fluoride, polychlorochloroprene, and the like can be used. Moreover, what melt | dissolved these in the solvent previously can also be used.

The solvent used for the slurry composition for lithium ion secondary battery electrodes of the present invention is not particularly limited, and for example, N-methylpyrrolidone, ethanol, ethyl acetate, or the like can be used.

The kneading method at the time of preparing the slurry composition for the lithium ion secondary battery electrode of the present invention is not particularly limited, and for example, a general apparatus such as a mixer, a kneader, a disperser, a mill, a rotation and revolution type rotating apparatus is used. can do.

The lithium ion secondary battery of the present invention can be produced, for example, by applying the electrode slurry of the present invention to a current collector made of a metal foil, and then drying and depositing the current collector. A secondary battery can be manufactured by immersing the electrolytic solution in an electrode group formed by laminating or winding a positive electrode and a negative electrode through a separator. Since the electrode slurry of the present invention has excellent coating properties while containing a conductive agent having a small particle size and a high specific surface area, it can exhibit excellent battery characteristics.

The current collector is not particularly limited, and a metal foil of gold, silver, copper, platinum, aluminum, iron, nickel, chromium, manganese, lead, tungsten, titanium, or an alloy containing these as a main component is used. Is done. It is preferable to use aluminum for the positive electrode and copper for the negative electrode.

The electrolytic solution is not particularly limited, and a nonaqueous electrolytic solution containing lithium salt or an ion conductive polymer can be used. Examples of the nonaqueous solvent for the nonaqueous electrolyte in the nonaqueous electrolytic solution containing a lithium salt include ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and methyl ethyl carbonate. Examples of the lithium salt that can be dissolved in the non-aqueous solvent include lithium hexafluorophosphate, lithium borotetrafluoride, and lithium trifluoromethanesulfonate.

The separator is not particularly limited, and synthetic resins such as polyethylene and polypropylene can be used. It is preferable to use a porous film because the electrolyte retainability is good.

Hereinafter, the present invention will be described in detail by way of examples. However, the scope of the present invention is not limited to the following examples.

Example 1
Atomylene gas 12m ³ / h, oxygen gas 9m ³ / h, hydrogen gas 0.5m ³ / h sprayed from a nozzle installed at the top of a carbon black reactor (furnace length 5m, furnace diameter 0.5m) Then, carbon black was produced by utilizing thermal decomposition and combustion reaction of acetylene gas. This carbon black was heat-treated at 1700 ° C. for 1 hour in a nitrogen atmosphere. The obtained carbon black was measured for the following physical properties. The evaluation results are shown in Table 1.
(1) Crystal layer thickness Lc: Using an X-ray diffractometer (“D8ADVANCE” manufactured by Brucker), X-ray diffraction is performed using CuKα rays in a measurement range of 2θ = 10 to 40 ° and a slit width of 0.5 °. It was. For calibration of the measurement angle, silicon for X-ray standard (metal silicon manufactured by Mitsuwa Chemicals) was used. Using the diffraction line of the (002) plane obtained, the crystal layer thickness Lc was determined by Scherrer's formula: Lc (Å) = (K × λ) / (β × cos θ). Here, K is a form factor constant of 0.9, λ is an X-ray wavelength of 1.54 mm, θ is an angle indicating a maximum value in the (002) diffraction line absorption band, and β is a half-value width in the (002) diffraction line absorption band. (Radians).
(2) Average primary particle diameter: 100 primary particle diameters of carbon black were measured from a 50,000 times image of a transmission electron microscope (TEM), and an average value was calculated.
(3) Crystallization rate: The volume ratio of the surface crystal layer to the average primary particle diameter of carbon black, which can be determined by the following equation.
(4) Specific surface area: Measured according to JIS K 6217-2.

ここでｄはカーボンブラックの平均一次粒子径、Ｌｃは結晶層厚みである。

Here, d is the average primary particle diameter of carbon black, and Lc is the crystal layer thickness.

4 parts by mass of the obtained carbon black and LiNi _1/3 Mn _1/3 Co _1/3 O ₂ (“CELLSEED NMC Ni: Mn: Co = 1: 1: 1” manufactured by Nippon Chemical Industry Co., Ltd.) 92 mass 4 parts by weight of polyvinylidene fluoride (“Kureha KF Polymer W # 1100” manufactured by Kureha Co., Ltd.) as a binder and 67 parts by mass of N-methylpyrrolidone (manufactured by Aldrich) as a solvent, NBK-1 ") was kneaded for 15 minutes under the condition of a rotational speed of 1000 rpm to produce an electrode slurry having a solid content concentration of 60% by mass. The viscosity of this electrode slurry at 25 ° C. was evaluated with a viscoelasticity measuring device (“MCR102” manufactured by Anton Paar, φ30 mm, cone plate with an angle of 3 °, gap 1 mm). The shear rate was measured by changing from 0.01 to 100 s ⁻¹ . Table 1 shows the relationship between the viscosity η ₁ and η ₂ with respect to the viscosity at a shear rate of 1 s ⁻¹ and arbitrary shear rates γ ₁ and γ ₂ (γ ₁ <γ ₂ ).
Further, the degree of dispersion of the electrode slurry was evaluated by a particle gauge method according to JIS K5600-2-5. Specifically, 0.5 ml of electrode slurry was dropped on a particle gauge table, and was thinly stretched into a gauge groove with a scraper, and the particle size of the largest particle observed on the gauge was measured. Measurement was performed three times, and the average value was taken as the measured value. The evaluation results are shown in Table 1.

The obtained electrode slurry was coated on an aluminum foil (current collector) having a thickness of 20 μm using a coating machine (“MINI-COATER MODEL: MC10” manufactured by Hosen Co., Ltd.), and the dried one was pressed. The positive electrode was produced by cutting. The electrode plate resistance of this positive electrode was evaluated by the AC impedance method. Specifically, the positive electrode is set in a SUS tripolar cell, and an impedance analyzer (“electrochemical measurement system 12608W type” manufactured by Toyo Technica Co., Ltd., electrode area 1.54 cm ² , sweep frequency 1 MHz → 1 Hz, applied voltage 10 mV) The AC resistance of the electrode was measured at a measurement temperature of 20 degrees. The evaluation results are shown in Table 1.

Metallic lithium (manufactured by Honjo Metal Co., Ltd.) was used as the counter electrode with respect to the positive electrode, and a polyolefin cell non-woven fabric was used as a separator to electrically isolate them to produce a coin cell (CR-2032 type). In the electrolyte solution, 1 mol / L of lithium hexafluorophosphate (manufactured by Stella Chemifa) is dissolved in a solution in which ethylene carbonate (manufactured by Aldrich) / dimethyl carbonate (manufactured by Aldrich) is mixed at a volume ratio of 1/1. Was used. As a battery discharge test, first, constant current / constant voltage charging was performed at a current density of 0.7 mA / cm ² and an upper limit voltage of 5.0 V, and then a current density of 0.7 mA / cm ² and a lower limit voltage of 3.0 V were performed. The discharge capacity when performing constant current discharge was measured, and the capacity density (mAh / g) divided by the amount of the positive electrode active material was taken as the initial capacity, and this capacity (mAh) was determined as a current value that can be charged and discharged in 1 hour. “1C”. Then, as an evaluation of the output characteristics, after performing constant current / constant voltage charging with a current of 0.2 C and an upper limit voltage of 5.0 V, a constant current discharge was performed with a current of 3 C and a lower limit voltage of 3.0 V. The value (mAh / g) obtained by dividing the discharge capacity by the amount of the positive electrode active material was calculated as the 3C discharge capacity. The evaluation results are shown in Table 1.

Comparative Example 1
An electrode slurry was obtained in the same manner as in Example 1 except that carbon black was not heat-treated at 1700 ° C. for 1 hour in a nitrogen atmosphere. Since the viscosity of the electrode slurry was high, coating could not be performed. The evaluation results are shown in Table 1.

Example 2 and Comparative Example 2
An electrode slurry was obtained in the same manner as in Example 1 except that the heat treatment temperature was changed to 1900 ° C. and 1600 ° C., and the crystal layer thickness Lc of carbon black was changed as shown in Table 1. The evaluation results are shown in Table 1.

Examples 3-6
Except that the blending amount of the solvent was changed to 108 parts by mass, 100 parts by mass, 43 parts by mass, 39 parts by mass, and the solid content concentration of the electrode slurry was changed as shown in Table 1, it was the same as Example 1. An electrode slurry was obtained. The evaluation results are shown in Table 1.

Example 7
An electrode slurry was obtained in the same manner as in Example 1 except that the electrode slurry dispersion condition in the defoaming kneader was changed to kneading for 10 minutes at 800 rpm. The evaluation results are shown in Table 1.

Example 8
An electrode slurry was obtained in the same manner as in Example 1 except that the mixing ratio in the mixture layer was changed to 94 parts by mass of the active material, 2 parts by mass of carbon black, and 4 parts by mass of the binder. The evaluation results are shown in Table 1.

Example 9
Commercially available carbon black ("Denka Black powder" manufactured by Denka) was used as the conductive agent by heating at 1700 ° C for 1 hour in a nitrogen atmosphere, and the mixing ratio in the mixture layer was 88 parts by mass of active material, carbon black An electrode slurry was obtained in the same manner as in Example 1 except that the content was changed to 7 parts by mass and 5 parts by mass of the binder. The evaluation results are shown in Table 1.

Example 10
Commercially available carbon black ("Denka Black HS-100" manufactured by Denka) was used as the conductive agent by heating at 1700 ° C for 1 hour in a nitrogen atmosphere. The compounding ratio in the composite layer was 82 parts by mass of carbon, carbon An electrode slurry was obtained in the same manner as in Example 1 except that the amount was changed to 10 parts by mass of black and 8 parts by mass of binder. The evaluation results are shown in Table 1.

Example 11
An electrode slurry was obtained in the same manner as in Example 1 except that a commercially available carbon black (“Denka Black FX-35” manufactured by Denka Co., Ltd.) was used which was heat-treated at 1700 ° C. for 1 hour in a nitrogen atmosphere. . The evaluation results are shown in Table 1.

Comparative Example 3
An electrode slurry was obtained in the same manner as in Example 9 except that carbon black was not heat-treated at 1700 ° C. for 1 hour in a nitrogen atmosphere. The evaluation results are shown in Table 1.

ここでｄはカーボンブラックの平均一次粒子径、Ｌｃは結晶層厚みである。

Here, d is the average primary particle diameter of carbon black, and Lc is the crystal layer thickness.

From the evaluation results of Table 1, the slurry composition for lithium ion secondary battery electrodes of the present invention uses carbon black having a crystallization rate calculated from the crystal layer thickness Lc and the average primary particle diameter of 60% or more as a conductive agent. Therefore, it has excellent viscosity characteristics and coatability. Therefore, a high-performance lithium ion secondary battery can be provided with high productivity.

The slurry composition for lithium ion secondary battery electrodes of the present invention can be used as an electrode for lithium ion secondary batteries.

Claims (3)

An active material, a conductive agent, a binder, and a solvent are included, and the conductive agent is carbon black having a crystallization rate calculated by the formula (1) from the crystal layer thickness Lc and the average primary particle diameter d of 60% or more. A slurry composition for a lithium ion secondary battery electrode.

The solid content is 80 to 99.8% by mass of the active material, the conductive agent is 0.1 to 10% by mass, the binder is 0.1 to 10% by mass, the solid content is 50 to 70% by mass, and the shear rate is 1 s. ^The viscosity η ₁ and η ₂ for any shear rate γ ₁ and γ ₂ (γ ₁ <γ ₂ ) in the range of shear rate 0.01 to 100 s ⁻¹ is η _1. The slurry composition of claim 1, satisfying> η ₂ . A lithium ion secondary battery using the slurry composition according to claim 1.

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