KR102493033B1 - Carbon black for battery, mixed powder, coating liquid for battery, electrode for battery, and battery - Google Patents

Abstract

The present invention provides carbon black for batteries having excellent conductivity and dispersibility. The battery carbon black of the present invention has a number average primary particle diameter of 20 nm or more and 40 nm or less, a ratio of DBP absorption to compressed DBP absorption of 2.2 or less, and a compressed DBP absorption of 100 mL/100 g or more and 200 mL/100 g or less.

Description

Carbon black for batteries, mixed powder, coating solution for batteries, electrodes for batteries and batteries

The present invention relates to carbon black for batteries, a mixed powder, a coating solution for batteries, electrodes for batteries, and batteries.

A lithium ion secondary battery in which a negative electrode is formed using a material capable of intercalating and releasing lithium ions can suppress the precipitation of dendrites compared to a lithium battery in which a negative electrode is formed using metal lithium. Therefore, it has the advantage of being able to provide a high-capacity, high-energy-density battery with improved safety by preventing battery short circuit.

In recent years, further improvement of the energy density of this lithium ion secondary battery has been requested. For this reason, it is requested|required to reduce the content of the electrically conductive agent in an electrode mixture. For example, in commercial batteries such as digital devices, the content of the conductive agent in the positive electrode composite is typically 2% by mass or less, and preferably 1% by mass or less.

From these circumstances, carbon black as a conductive agent is required to exhibit sufficient electron conductivity even in a small amount of addition.

For example, in Patent Document 1, as carbon black for non-aqueous secondary batteries having excellent conductivity and dispersibility, carbon black having BET specific surface area, DBP absorption amount, electrical resistivity, sulfur content, and volatile component content within predetermined ranges, respectively. has been initiated.

On the other hand, in electrode composite materials, it is required that the blended materials are uniformly dispersed from the viewpoint of improving the performance of lithium ion secondary batteries.

For example, Patent Literature 2 discloses a method for producing a positive electrode mixture characterized by performing two-step kneading of solidification kneading and dilute dispersion.

Japanese Unexamined Patent Publication No. 2012-221684 Japanese Unexamined Patent Publication No. 2012-59466

As a common structure, carbon black has a structure in which primary particles close to spherical shapes are connected to each other in a bead shape, and such a structure is called a structure. In general, the smaller the primary particle diameter is, the more electrical contacts are present in the same mass of conductive agent, and the electronic conductivity is improved. In addition, the longer the structure is connected, the greater the distance at which electrons can be conducted without contact resistance, and thus the electron conductivity is improved.

The length of the structure is generally evaluated indirectly using the DBP absorption amount measured based on JIS K6217-4, and the larger the DBP absorption amount, the longer the structure and the better the conductivity.

On the other hand, carbon black having a small primary particle diameter and a long structure has excellent conductivity, but has an aspect of being difficult to disintegrate and easy to aggregate because the interaction between the particles is large. Therefore, in general, when manufacturing an electrode, a method of applying a coating solution in which an active material, a conductive agent, and a binder are dispersed in water or an organic solvent is applied to a metal foil, but carbon black having a small primary particle diameter and a long structure is used as a conductive agent. When used, it is easy to cause problems such as condensation of the conductive agent remaining in the coating solution, resulting in irregularities on the electrode, or coating failure due to excessively high viscosity of the coating solution.

In view of the above problems and circumstances, an object of the present invention is to provide carbon black for batteries excellent in conductivity and dispersibility. In addition, a battery coating solution with excellent dispersibility produced using this battery carbon black and a mixed powder as one form of material for producing the same, as well as a battery electrode with low resistance produced using the same and a battery with excellent high output characteristics are provided. aims to do

That is, the present invention employs the following means in order to solve the above problems.

(1) A battery carbon black having a number average primary particle diameter of 20 nm or more and 40 nm or less, a ratio of DBP absorption to compressed DBP absorption of 2.2 or less, and a compressed DBP absorption of 100 mL/100 g or more and 200 mL/100 g or less.

(2) The battery carbon black according to (1), which is acetylene black.

(3) A battery coating solution containing an active material, a polymeric binder, and the carbon black for batteries according to (1) or (2).

(4) The battery coating solution according to (3), further comprising a polymeric dispersant.

(5) The battery coating solution according to (4), wherein the polymeric dispersant contains at least one selected from the group consisting of polyvinylpyrrolidone and copolymers having vinylpyrrolidone units.

(6) The battery coating solution according to (4) or (5), wherein the content of the polymer dispersant is 0.05 mg or more and 0.5 mg or less per 1 m 2 based on the total surface area of the carbon black.

(7) at least one selected from the group consisting of a polymeric dispersant and the battery carbon black according to (1) or (2), wherein the polymeric dispersant is polyvinylpyrrolidone and a copolymer having vinylpyrrolidone units; Mixed powder, containing species.

(8) The mixed powder according to (7), wherein the content of the polymer dispersant is 0.05 mg or more and 0.5 mg or less per 1 m 2 with respect to the total surface area of the carbon black.

(9) A battery coating solution comprising the mixed powder according to (7) or (8), an active material, and a polymeric binder.

(10) A battery electrode comprising a metal foil and a coating film containing the battery carbon black according to (1) or (2) formed on the metal foil.

(11) The battery electrode according to (10), wherein the coating film further contains an active material and a polymeric binder.

(12) The battery electrode according to (10) or (11), wherein the coating film further contains a polymer dispersant.

(13) The battery electrode according to (12), wherein the polymeric dispersant contains at least one selected from the group consisting of polyvinylpyrrolidone and copolymers having vinylpyrrolidone units.

(14) The battery electrode according to (12) or (13), wherein the content of the polymer dispersant in the coating film is 0.05 mg or more and 0.5 mg or less per 1 m 2 with respect to the total surface area of the carbon black.

(15) A battery comprising the battery electrode according to any one of (10) to (14).

(16) a step of applying the battery coating liquid according to any one of (3) to (6) and (9) onto a metal foil, and obtaining a battery electrode having a coating film formed of the metal foil and the battery coating liquid; , A method for manufacturing an electrode for a battery.

As a result of intensive research, the present inventors have found that carbon black for batteries having a ratio of DBP absorption to compressed DBP absorption in a specific range is excellent in dispersibility, and by optimizing the value of the primary particle diameter and compressed DBP absorption, high conductivity and high conductivity are achieved. It was found that acidity is compatible. In addition, it was found that the dispersibility is further improved by using an appropriate polymeric dispersant in combination. Electrodes for batteries manufactured using these materials have low resistance, and the batteries are characterized by excellent high-output characteristics.

1 is a transmission electron micrograph of carbon black for a battery of Example 4.
2 is a transmission electron micrograph of acetylene black of Comparative Example 1.

Hereinafter, one embodiment of the present invention will be described in detail. The battery carbon black of the present embodiment has a number average primary particle diameter of 20 nm or more and 40 nm or less, a ratio of DBP absorption to compressed DBP absorption of 2.2 or less, and a compressed DBP absorption of 100 mL/100 g or more and 200 mL/100 g or less. It is a carbon black for a battery to be. Further, the ratio of the DBP absorption amount to the compressed DBP absorption amount means a value obtained by dividing the DBP absorption amount by the compressed DBP absorption amount (DBP absorption amount/compressed DBP absorption amount).

The carbon black in this embodiment is selected from acetylene black, furnace black, channel black, and the like, similarly to carbon black as a general conductive agent for batteries. Among them, acetylene black having excellent crystallinity and purity is more preferable.

The number average primary particle diameter of the carbon black for batteries in this embodiment is 20 nm or more and 40 nm or less. By setting the number average primary particle diameter to 20 nm or more, the interaction between particles is suppressed and dispersibility is obtained. In addition, by setting the number average primary particle diameter to 40 nm or less, more electrical contacts exist in the conductive agent of the same mass, and good electronic conductivity is obtained.

The DBP absorption amount of the carbon black for batteries in this embodiment is a value measured based on JIS K6217-4. In addition, the compressed DBP absorption amount is a value measured by the same method as the DBP absorption amount with respect to a compressed sample manufactured in accordance with JIS K6217-4 Annex A.

The ratio of the DBP absorption amount to the compressed DBP absorption amount of the battery carbon black in the present embodiment is 2.2 or less. A larger value of the DBP absorption amount than the compressed DBP absorption amount means that the amount of agglomerated particles destroyed when preparing the compressed sample is large, and greater energy is required to break them down. Therefore, by setting the ratio of the DBP absorption amount to the compressed DBP absorption amount to 2.2 or less, the energy required to disintegrate the agglomerated particles is suppressed, and the dispersibility becomes good.

The compressed DBP absorption amount of the battery carbon black in the present embodiment is 100 mL/100 g or more and 200 mL/100 g or less, and more preferably 110 mL/100 g or more and 140 mL/100 g or less. By setting the compressed DBP absorption amount to 100 mL/100 g or more, the structure when used as a conductive agent has a sufficient length, and good conductivity is obtained. Moreover, by setting it as 200mL/100g or less, aggregation by entanglement of structures is suppressed and dispersibility becomes favorable.

When producing an electrode using the battery carbon black of the present embodiment, the battery carbon black can be dispersed in a medium together with an active material and a polymer binder and used as a battery coating solution. As the active material, a composite oxide having a layered halite structure such as lithium cobaltate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, or the like for the positive electrode, or a spinel structure such as lithium manganate or lithium nickel manganate can be used as the active material. and complex oxides having an olivine-type structure, such as lithium iron phosphate, lithium manganese phosphate, and lithium iron manganese phosphate. Examples of the active material for the negative electrode include carbon-based materials such as artificial graphite, natural graphite, soft carbon and hard carbon, metal-based materials alloyed with alkali metals such as silicon and tin, and metal composite oxides such as lithium titanate. there is. Examples of the polymer binder include polymers such as polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene copolymer, polyvinyl alcohol, acrylonitrile-butadiene copolymer, and carboxylic acid-modified (meth)acrylic acid ester copolymer. can Among these, polyvinylidene fluoride is preferable in terms of oxidation resistance when used for a positive electrode, and polyvinylidene fluoride or a styrene-butadiene copolymer is preferable in terms of adhesive strength when used for a negative electrode.

Examples of the dispersion medium of the coating liquid for electrodes include water, N-methylpyrrolidone, cyclohexane, methyl ethyl ketone, and methyl isobutyl ketone. When polyvinylidene fluoride is used as the polymeric binder, N-methylpyrrolidone is preferable in terms of solubility, and when a styrene-butadiene copolymer is used, water is preferable.

The coating liquid for electrodes may further contain a polymer dispersing agent. As the polymer dispersant, polyvinylpyrrolidone, a copolymer having a vinylpyrrolidone unit, polyvinylimidazole, polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, carboxymethylcellulose, acetylcellulose, and carboxylic acid modified ( It is preferable to use at least one or more selected from meth)acrylic acid ester copolymers and the like. Among them, it is more preferable to include at least one or more selected from polyvinylpyrrolidone and copolymers having vinylpyrrolidone units (also referred to as copolymers containing polyvinylpyrrolidone). Among these, polyvinylpyrrolidone is preferable. By including the polymer dispersant, the dispersibility of the carbon black for batteries is further improved.

The content of the polymer dispersant is preferably 0.05 mg or more and 0.5 mg or less, and more preferably 0.2 mg or more and 0.5 mg or less per 1 m 2 based on the total surface area of the battery carbon black. By setting it as 0.05 mg or more, the polymer dispersant exhibits a sufficient dispersing effect, and the dispersibility of the battery carbon black is further improved. Moreover, by setting it as 0.5 mg or less, the effect which an excessive polymer dispersant coats the surface of an active material, and obstructs a charge transfer reaction is suppressed, and high resistance of a battery is suppressed.

As one of the forms for obtaining the coating solution for an electrode including the polymer dispersant, it may be provided in the form of a mixed powder in which the battery carbon black and the polymer dispersant are mixed in advance. In the form of a mixed powder, it becomes possible for a battery manufacturer to obtain a coating solution for an electrode containing the polymer dispersant simply by applying the conventional process without using the polymer dispersant as it is.

As a mixing device for producing the electrode coating liquid, a mixer such as a grinder, universal mixer, Henschel mixer or ribbon blender, or a medium agitation type mixer such as a bead mill, vibration mill or ball mill can be used. In addition, it is preferable to perform vacuum degassing in the stage before coating in order to ensure smoothness by preventing the occurrence of defects in the coating film of the prepared coating solution for electrodes. If bubbles exist in the coating solution, when it is applied to the electrode, defects occur in the coating film, which causes loss of smoothness.

In addition, the battery coating solution may contain components other than battery carbon black, an active material, a polymer binder, and a polymer dispersant within a range that does not impair the effects of the present invention. For example, for the purpose of further improving conductivity, carbon nanotubes, carbon nanofibers, graphite, graphene, carbon fibers, elemental carbon, glassy carbon, metal particles and the like may be included in addition to carbon black for batteries.

As a method for producing the mixed powder, a method of dry mixing or wet mixing using a solvent such as water is exemplified. As the mixing device, mixers such as a V-type mixer, a high-speed stirring mixer, a universal mixer, a flash blender, or a tumbler mixer can be used.

In the above, a preferred embodiment of the carbon black for a battery according to the present invention has been described, but the present invention is not limited thereto.

For example, the present invention may also relate to a coating solution for batteries containing the carbon black for batteries. In one embodiment of the present invention, the battery coating solution may contain the battery carbon black and the dispersion medium. Moreover, the coating liquid for batteries may further contain the said active material. In addition, the battery coating solution may further contain the above-mentioned polymeric binder. Moreover, the coating liquid for batteries may further contain the said polymeric dispersing agent.

This invention may also relate to the mixed powder containing the said battery carbon black and the said polymer dispersing agent.

The present invention may also relate to a battery electrode comprising a metal foil and a coating film containing the carbon black for a battery formed on the metal foil. In one embodiment of the present invention, the coating film may be formed from the coating solution for a battery. The coating film is formed, for example, by applying and drying the coating solution for a battery. The coating film may further contain the active material. Moreover, the said coating film may further contain the said polymeric binder. Moreover, the said coating film may further contain the said polymer dispersing agent.

The method of applying the battery coating solution may be, for example, a slot die method, a lip method, a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. Among them, the slot die method, the granulation method, and the reverse roll method are preferable.

The application method of the coating solution for batteries may be selected according to the physical properties and dryness of the coating solution for batteries. In this way, a good surface state of the coating layer can be obtained. Application of the battery coating solution to the metal foil may be applied to one side or both sides, and in the case of both sides, one side may be sequentially applied or both sides may be coated simultaneously. In addition, application|coating may be continuous, intermittent, or a stripe may be sufficient as it. What is necessary is just to determine suitably the coating thickness, length, and width of the battery coating liquid according to the size of the battery to be applied. For example, the coating thickness of the battery coating solution, that is, the thickness of the coating film can be in the range of 10 μm to 500 μm.

The drying method of the battery coating solution is not particularly limited, and for example, a drying method by hot air, vacuum, infrared rays, far-infrared rays, electron beams, low-temperature air or the like can be used alone or in combination.

When using a metal foil as a positive electrode, aluminum foil etc. may be sufficient as it, for example. In addition, when using a metal foil as a negative electrode, copper foil etc. may be sufficient as it, for example. Although the shape of the metal foil is not particularly limited, it is preferable that the thickness is 5 to 30 µm from the point of facilitating workability.

You may press an electrode as needed. As the press method, a generally employed method can be used, but a mold press method or a calender press method (cold or hot roll) is particularly preferred. The press pressure in the calender press method is not particularly limited, but is preferably 0.02 to 3 ton/cm.

This invention may also relate to the battery provided with the said battery electrode. In one embodiment, the battery may be a lithium ion secondary battery, a nickel hydride secondary battery, or an electric double layer capacitor.

The present invention may also relate to a method for manufacturing a battery electrode. In one embodiment, the manufacturing method of a battery electrode may include the process of applying the said battery coating liquid on metal foil, and obtaining the battery electrode provided with the coating film formed from the said metal foil and the said battery coating liquid.

The present invention may also relate to the use of the carbon black as a carbon black for a battery. The present invention may also relate to the use of the carbon black for producing a coating solution for a battery. The invention may also relate to the use of the carbon black for the production of batteries.

Example

Hereinafter, one embodiment of the carbon black for a battery according to the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples unless the gist thereof is exceeded.

<Example 1>

(carbon black for batteries)

As carbon black for batteries, furnace black (manufactured by Timcal Graphite And Carbon Co., Ltd.) having a number average primary particle diameter of 40 nm, a DBP absorption of 234 mL/100 g, and a compressed DBP absorption of 115 mL/100 g was used. In addition, the DBP absorption amount and compressed DBP absorption amount were measured by the following method.

[DBP absorption amount]

The DBP absorption amount was measured by a method conforming to JIS K6217-4, and the compressed DBP absorption amount was measured by the same measurement method as the DBP absorption amount for a compressed sample produced by a method conforming to JIS K6217-4 Annex A.

[Number Average Primary Particle Diameter]

For the number average primary particle diameter, five images at 100,000 magnification were photographed using a transmission electron microscope JEM-2000FX (manufactured by Nippon Electronics Co., Ltd.), and introduced into image analysis software (manufactured by Nireco, "Luzex AP"). The number average primary particle diameter was obtained for 200 or more extracted primary particles, and their arithmetic average value was calculated.

(Production of coating solution for batteries)

5 parts by mass of furnace black, 90 parts by mass of lithium iron phosphate (manufactured by Aleees) as an active material, and a polyvinylidene fluoride solution (manufactured by Kureha Chemical Co., Ltd., "KF Polymer (1120)") as a polymer binder Dissolve By mass, 5 parts by mass and N-methylpyrrolidone (manufactured by Kishida Chemical Co., Ltd.) were further added as a dispersion medium, and mixed using a rotating revolution type mixer (manufactured by Shinki Co., Ltd., Awatori Rentaro ARV-310) to obtain a coating solution got it This coating solution was applied to an aluminum foil having a thickness of 20 μm using a Baker-style applicator, dried, and then pressed and cut to obtain a positive electrode for a lithium secondary battery.

[Evaluation of dispersibility (coating solution for electrode)]

The dispersibility of the coating liquid for electrodes was evaluated by a method using a particle size meter described in JIS K5600-2-5. Specifically, the coating solution was applied using a scraper, and linear marks extending 10 mm or more continuously on the sample surface were measured, and graduations were measured at locations where three or more lines were arranged with respect to one groove. Dispersibility means better dispersibility, so that a numerical value is low.

[Evaluation of dispersibility (electrode appearance)]

The dispersibility of the battery carbon black was judged by the external appearance of the positive electrode for lithium secondary batteries. Specifically, five electrodes of 100 mm square were produced and evaluated according to the following scale.

Excellent: No stripe-like coating traces and agglomerates were observed on the electrode surface in all five sheets.

Good: Streaked coating traces or aggregated lumps of less than 1 mm were observed on one or more electrode surfaces.

Defect: Aggregates of 1 mm or more were observed on one or more electrode surfaces.

[Evaluation of electrode resistance]

A positive electrode for lithium secondary batteries was cut into a disc shape with a diameter of 14 mm, and the front and back sides were sandwiched by SUS304 flat electrodes, using an electrochemical measurement system (function generator 1260 and potentiometer galvanostat 1287, manufactured by Solartron). As a result of measuring the resistance to a 1Hz alternating current between both electrodes, it was 26Ω.

(Production of lithium ion secondary battery)

Using the positive electrode for lithium secondary batteries as a positive electrode, a lithium ion secondary battery was produced as follows.

A CR-2032 coin cell was obtained by using the positive electrode for a lithium secondary battery as a positive electrode, metal lithium (manufactured by Honjo Kinzoku Co., Ltd.) as a negative electrode, and using an olefin fiber nonwoven fabric as a separator to electrically isolate them. In the electrolyte, lithium hexafluorophosphate (LiPF6, manufactured by Stella Chemifa) was mixed in a solution of EC (ethylene carbonate, manufactured by Aldrich) and MEC (methylethyl carbonate, manufactured by Aldrich) at a volume ratio of 1:2. 1 mol/L of was used.

[Evaluation of Lithium Ion Secondary Battery]

About the lithium ion secondary battery produced above, it evaluated as follows.

[Initial capacity]

First, constant current/constant voltage charging was performed at a current density of 0.7 mA/cm 2 and an upper limit voltage of 4.0 V, and then discharge capacity was measured when constant current discharge was performed at a current density of 0.7 mA/cm 2 and a lower limit voltage of 2.0 V. The capacity density (mAh/g) divided by the amount of active material was calculated. The current value capable of charging and discharging this capacity (mAh) in 1 hour was defined as "1C". Subsequently, constant current/constant voltage charging was performed with a current of 0.2 C and an upper limit voltage of 4.0 V, and constant current discharge was further performed with a current of 0.2 C and a lower limit voltage of 2.0 V. Repeated 5 times, the fifth constant current discharge The value (mAh/g) obtained by dividing the discharge capacity at the time by the amount of the positive electrode active material was calculated as the initial capacity. The initial capacity of the cell of this example was 159 mAh/g.

[5C discharge capacity]

As an evaluation of high output characteristics, constant current/constant voltage charging was performed with a current of 0.2 C and an upper limit voltage of 4.0 V, and then constant current discharge was performed with a current of 5 C and a lower limit voltage of 2.0 V. When the value (mAh/g) divided by the amount was calculated as a 5C discharge capacity, it was 75 mAh/g.

<Examples 2 to 4>

Except for changing the furnace black of Example 1 to acetylene black (SB50L, FX35, AB powder phase manufactured by Denki Chemical Industry Co., Ltd.) having the number average primary particle diameter, DBP absorption amount, and compressed DBP absorption amount shown in Table 1, A coating solution for a battery, an electrode, and a secondary battery were produced in the same manner as in Example 1, and each evaluation was performed. The results are shown in Table 1. Further, when the carbon black for batteries in Example 4 was observed by a transmission electron microscope, a transmission electron microscope picture shown in FIG. 1 was obtained.

<Examples 5 to 9>

The furnace black of Example 1 was changed to acetylene black (SB50L manufactured by Denki Chemical Industry Co., Ltd.) having a number average primary particle diameter of 37 nm, a DBP absorption of 218 mL/100 g, and a compressed DBP absorption of 111 mL/100 g, and polyvinyl film as a polymer dispersant Rolidone (manufactured by Junsei Chemical Co., Ltd., PVP K-30) was further added in an amount shown in Table 2, and a coating solution for a battery, an electrode, and a secondary battery were prepared in the same manner as in Example 1, and each evaluation was performed. However, the total surface area of acetylene black was obtained by multiplying the total mass of acetylene black by the BET specific surface area measured using a nitrogen adsorption specific surface area meter (Macsorb 1201, manufactured by Mountec Co., Ltd.). The results are shown in Table 2.

<Example 10>

(Preparation of mixed powder)

Acetylene black (SB50L, manufactured by Denki Chemical Industry Co., Ltd.) and polyvinylpyrrolidone (PVP K-30, manufactured by Junsei Chemical Co., Ltd.) with a number average primary particle diameter of 37 nm, a DBP absorption of 218 mL/100 g, and a compressed DBP absorption of 111 mL/100 g were mixed. , The content of polyvinylpyrrolidone per 1 m of the surface area of acetylene black was mixed at a ratio of 0.17 mg using a V-type mixer (Dalton, VM-10) to obtain a mixed powder.

Except for changing the furnace black of Example 1 to the above mixed powder, a coating solution for a battery, an electrode, and a secondary battery were prepared in the same manner as in Example 1, and each evaluation was performed. The results are shown in Table 2.

<Comparative Example 1>

Furnace black of Example 1 was furnace black (manufactured by Timcal Graphite And Carbon Co., Ltd.) or acetylene black (manufactured by Denki Chemical Industry Co., Ltd.) having the number average primary particle diameter, DBP absorption amount, and compressed DBP absorption amount shown in Table 3 A battery coating solution, an electrode, and a secondary battery were produced in the same manner as in Example 1 except for changing, and each evaluation was performed. In the case of using the battery coating solution used in Comparative Example 1, the dispersibility was poor, and the electrode plate resistance also showed a high value. Also in battery evaluation, the 5C discharge capacity was below the measurement limit. The results are shown in Table 3. Furthermore, when the acetylene black of Comparative Example 1 was observed by a transmission electron microscope, a transmission electron microscope picture shown in FIG. 2 was obtained.

<Comparative Example 2>

Acetylene black having a number average primary particle size of 48 nm was used as carbon black, and a coating solution for a battery, an electrode, and a secondary battery were prepared in the same manner as in Example 1, and each evaluation was performed. The battery coating liquid used in Comparative Example 2 had excellent dispersibility, but exhibited a high electrode resistance. Also in battery evaluation, the 5C discharge capacity was below the measurement limit. The results are shown in Table 3.

<Comparative Example 3>

Using furnace black having a DBP absorption of 254 ml/100 g as carbon black, a coating solution for a battery, an electrode, and a secondary battery were prepared in the same manner as in Example 1, and each evaluation was performed. The battery coating solution used in Comparative Example 3 had excellent dispersibility, but exhibited a high electrode resistance. Also in battery evaluation, the 5C discharge capacity was lower than that of the examples of the present invention. The results are shown in Table 3.

From the results of Tables 1, 2 and 3, it was found that the battery carbon blacks of the examples of the present invention were excellent in conductivity and dispersibility, the electrodes produced using them had low resistance, and the batteries had excellent high output characteristics. Moreover, it was found that the same effect can be obtained also by providing in the form of a mixed powder.

In addition, the positive electrode, the negative electrode, and the lithium ion secondary battery using various active materials other than the present example also gave good evaluation results regardless of the type of active material or polymer dispersant.

The battery carbon black of the present invention is excellent in conductivity and dispersibility, and by using the carbon black, an electrode with low resistance and a battery excellent in high output characteristics can be obtained. In addition, by providing in the form of a mixed powder, the battery manufacturer can obtain the above effects without changing the conventional process.

Claims (16)

active material,
A polymeric binder;
Carbon black having a number average primary particle diameter of 20 nm or more and 40 nm or less, a ratio of DBP absorption to compressed DBP absorption of 2.2 or less, and a compressed DBP absorption of 100 mL / 100 g or more and 200 mL / 100 g or less;
polymeric dispersant
including,
The coating solution for a battery, wherein the content of the polymer dispersant is 0.05 mg or more and 0.5 mg or less per 1 m 2 with respect to the total surface area of the carbon black. The coating solution for a battery according to claim 1, wherein the carbon black is acetylene black. The coating solution for a battery according to claim 1, wherein the polymer dispersant contains at least one selected from the group consisting of polyvinylpyrrolidone and copolymers having vinylpyrrolidone units. metal foil,
A coating film formed on the metal foil
to provide,
The coating film has a number average primary particle diameter of 20 nm or more and 40 nm or less, a ratio of DBP absorption to compressed DBP absorption of 2.2 or less, and a carbon black having a compressed DBP absorption of 100 mL / 100 g or more and 200 mL / 100 g or less, and a polymer dispersant include,
The battery electrode, wherein the content of the polymer dispersant in the coating film is 0.05 mg or more and 0.5 mg or less per 1 m 2 with respect to the total surface area of the carbon black. The battery electrode according to claim 4, wherein the coating film further comprises an active material and a polymeric binder. The battery electrode according to claim 4, wherein the polymer dispersant contains at least one selected from the group consisting of polyvinylpyrrolidone and copolymers having vinylpyrrolidone units. A battery comprising the battery electrode according to any one of claims 4 to 6. A method for producing a battery electrode including a step of applying the coating liquid for a battery according to any one of claims 1 to 3 onto a metal foil and obtaining a battery electrode having a coating film formed from the metal foil and the coating liquid for a battery. delete delete delete delete delete delete delete delete

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