KR20160029715A - Carbon black dispersion - Google Patents

Abstract

The present invention relates to a carbon black dispersing liquid comprising: carbon black; a dispersed medium; and a polyvinyl butyral resin having weight average molecular weight of greater than five, to a producing method thereof, to electrode slurry and an producing method of an electrode using the carbon black dispersing liquid, and to an electrode produced by using the carbon black dispersing liquid, and a secondary battery. The carbon black dispersion has good dispersibility and storage stability.

Description

Carbon Black Dispersion {CARBON BLACK DISPERSION}

The present invention relates to a carbon black dispersion. The present invention also relates to a method for producing the above dispersion, a method for producing an electrode slurry and an electrode using the dispersion, an electrode manufactured by the method, and a battery including the same.

Carbon black is used as a material for coloring, shielding, or conducting in various technical fields, and it has become important to finely disperse carbon black in a solvent in order to satisfy requirements required for various applications.

On the other hand, there is a growing demand for mounting a small, lightweight, yet large-capacity battery in electronic devices. In addition, performance improvement of large secondary batteries for automobiles has been continuously required. In response to such a demand, development of a secondary battery has been actively carried out. Generally, an electrode of a secondary battery is formed by applying a slurry containing an electrode active material, a binder resin, and a conductive material to a surface of a current collector. At this time, carbon black may be added as a conductive material.

Since carbon black has a large specific surface area, the cohesive force is strong and it is difficult to uniformly disperse in the slurry for electrode formation. When the dispersibility of carbon black is inadequate, a uniform conductive network can not be formed. Therefore, not only the internal resistance of the electrode can be sufficiently reduced, but also resistance distribution is generated inside the electrode due to partial agglomeration. So that partial heating or deterioration may occur. When charging and discharging are repeated, the interfacial adhesion between the current collector and the electrode layer or between the active material and the carbon black is deteriorated, and battery performance may be deteriorated. When the dispersibility of the carbon black is insufficient, The deterioration of the interfacial adhesion can be further exacerbated.

For dispersing carbon black, various additives, for example, dispersants such as surfactants and pigment dispersion resins have been tried. However, the method using a surfactant is advantageous for dispersion in an aqueous system, but is unsuitable for dispersion in an organic solvent. There is a problem that the carbon black easily re-agglomerates and the stability with time is lowered even when the pigment dispersion resin is used. In addition, when the amount of the surfactant or the pigment dispersion resin is decreased when the electrode of the battery is manufactured, sufficient dispersibility can not be obtained. When the addition amount of the surfactant or the pigment dispersion resin is increased to obtain sufficient dispersibility, The content may be reduced and the battery capacity may be lowered.

There has been attempted a method of introducing an acidic functional group into the surface of a particle by oxidation treatment of carbon black in a gas phase or a liquid phase. However, in gas phase oxidation such as plasma or ozone treatment, there are problems such as low treatment efficiency, In the treatment, a strong acid such as acetic acid or hydrogen peroxide is used, and therefore there is a problem in work safety and the like.

Further, in order to improve the dispersibility of carbon black, a method of adding a vinyl pyrrolidone type resin has been attempted. However, due to the hygroscopicity of the vinyl pyrrolidone resin, water may easily be contained in the electrode slurry and the electrode coat film, and the active material may be deteriorated.

Japanese Patent Application Laid-Open No. 7-268268

One embodiment of the present invention provides a carbon black dispersion having improved dispersibility and improved adhesion to the current collector at the time of electrode production. Other embodiments of the present disclosure relate to a method for producing the carbon black dispersion, a method for producing an electrode slurry and an electrode using the carbon black dispersion, an electrode manufactured by the method, and a battery including the same.

One embodiment of the application is carbon black; Dispersion media; And a polyvinyl butyral resin having a weight average molecular weight of more than 50,000.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 150,000 or more.

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is at least 15% by weight.

According to another embodiment of the present application, the carbon black dispersion comprises a first polyvinyl butyral resin having a weight average molecular weight of more than 50,000; And a second polyvinyl butyral resin having a weight average molecular weight smaller than that of the first polyvinyl butyral resin. Here, the second polyvinyl butyral resin may have a weight average molecular weight of 50,000 or less as long as the weight average molecular weight is smaller than that of the first polyvinyl butyral resin, but may be 50,000 or less.

According to another embodiment of the present application, the carbon black dispersion contains a carbon black composite into which the polyvinyl butyral resin is introduced on the surface of the carbon black.

According to another embodiment of the present application, the dispersion particle diameter (D ₅₀ ) of the carbon black in the dispersion is 0.03 to 3 μm, preferably 0.5 to 2 μm, for example, 0.5 to 1.5 μm. Here, the dispersed particle diameter of the carbon black means the particle diameter of the secondary particle formed by aggregating the primary particles of the carbon black. Such a dispersed particle size can be measured by a laser diffraction particle size analysis method.

Another embodiment of the present application provides a process for producing a carbon black dispersion comprising mixing carbon black, a dispersion medium and the above-mentioned polyvinyl butyral resin. For example, the carbon black dispersion may be prepared by adding carbon black to a dispersion medium in which a polyvinyl butyral resin is dissolved, or adding a carbon black to a dispersion medium and then dissolving the polyvinyl butyral resin, or adding carbon black and polyvinyl butyral And then adding and mixing the resins together.

 Another embodiment of the present application provides a method for producing an electrode slurry comprising mixing the carbon black dispersion, an electrode active material and a binder resin.

Another embodiment of the present application relates to a method for producing an electrode slurry, comprising: preparing an electrode slurry by mixing the carbon black dispersion, an electrode active material and a binder resin; And forming an electrode using the electrode slurry.

Another embodiment of the present application provides an electrode slurry comprising the carbon black dispersion, the electrode active material, and the binder resin.

Another embodiment of the present application provides an electrode manufactured using the electrode slurry including the carbon black dispersion, the electrode active material, and the binder resin, and a secondary battery including the electrode. The fact that the electrode is manufactured using the electrode slurry means that the electrode slurry, the dried product thereof, or a cured product thereof.

According to the embodiments described herein, a polyvinyl butyral resin comprising a hydroxyl group as a polar group and a butyral group as a nonpolar group can be used having a specific molecular weight range, whereby carbon black having different polarities and a dispersion medium such as NMP are mixed with each other . Further, by using the above-mentioned polyvinyl butyral resin, it is possible to solve the problem that the adhesive force of the electrode, which is caused by not dispersing the conductive material, is low. Accordingly, the carbon black dispersion according to the embodiments of the present invention is not only excellent in dispersibility and storage stability, but also can improve the adhesion of the electrode to the current collector when it is added to the electrode slurry as a conductive material.

Hereinafter, the embodiments will be described in detail.

The carbon black dispersion according to the above-described embodiment includes carbon black; Dispersion media; And a polyvinyl butyral resin having a weight average molecular weight of more than 50,000. When the weight average molecular weight of the polyvinyl butyral resin is large, the adhesion to the current collector can be improved when the electrode is manufactured later than when the low molecular weight polyvinyl butyral resin is used in the same amount.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 150,000 or more.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 200,000 or more.

According to another embodiment of the present application, the weight average molecular weight of the polyvinyl butyral resin is 350,000 or less.

The weight average molecular weight of the polyvinyl butyral resin is measured using GPC (Gel Permeation Chromatography) under the following conditions. In the molecular weight measurement, DMF is used as a solvent. In the dispersion state, the molecular weight of the supernatant can be measured by centrifugation. In the electrode and the cell state, the electrode can be scratched and the molecular weight can be measured by extracting the polyvinyl butyral resin using THF.

- Column: Polar Gel M + L

Solvent: DMF (0.45 μm filtered) containing 0.05 M LiBr salt,

- Flow rate: 1.0 ml / min

- Injection volume: 100 μL (0.45 μm filtered)

- Measurement time: 30 min

- Detection device: Waters RI detector

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is at least 15% by weight.

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is 20% by weight or more.

According to another embodiment of the present application, the content of the repeating unit containing a hydroxyl group in the polyvinyl butyral resin is 35% by weight or less.

When the hydroxyl group content of the polyvinyl butyral resin is high, the mixing energy of the carbon black dispersion is increased and the stability of the battery state can be improved. The content of the hydroxyl group-containing repeating unit of the polyvinyl butyral resin can be measured by NMR. Generally, polyvinyl butyral resins are prepared in water, and when the hydroxyl content is high, the polyvinyl butyral resin melts in water and blocks the process line. As a result, smooth production was difficult, and polyvinyl butyral resin having a high content of a hydroxyl group-containing repeating unit was hardly mass-produced. However, in the present invention, it has been found that when the content of the repeating unit containing a hydroxyl group is as high as described above, it can be usefully used for a carbon black dispersion.

The content of the acetyl group-containing repeating unit in the polyvinyl butyral resin is 5% by weight or less. When the acetal group is present in the polyvinyl butyral resin, dispersion can be inhibited due to viscosity increase. Therefore, the acetal group-containing repeating unit is preferably 5 wt% or less and as small as possible. The acetal group-containing repeating unit can be measured through NMR.

According to another embodiment of the present application, the carbon black dispersion comprises a first polyvinyl butyral resin having a weight average molecular weight of more than 50,000; And a second polyvinyl butyral resin having a weight average molecular weight smaller than that of the first polyvinyl butyral resin. When two or more polyvinyl butyral resins having different molecular weights are used as described above, the PDI can be broadened, for example, from 4 to 7. As a result, it is possible to improve the dispersibility by the low molecular weight resin and to improve the adhesion by the high molecular weight resin. PDI can also be measured using Gel Permeation Chromatography (GPC). After the weight average molecular weight (Mw) and the number average molecular weight (Mn) are determined by the above method, the molecular weight distribution (PDI) can be calculated from the weight average molecular weight / number average molecular weight (Mw / Mn).

Here, the second polyvinyl butyral resin may have a weight average molecular weight of 50,000 or less as long as the weight average molecular weight is smaller than that of the first polyvinyl butyral resin, but may be 50,000 or less. When a polyvinyl butyral resin having a weight average molecular weight of 50,000 or less is used, the dispersibility of carbon black can be improved by lowering the viscosity, and flexibility of the material can be improved by using a polyvinyl butyral resin having a weight average molecular weight of more than 50,000 Can be increased. Specifically, in the process of dispersing the carbon black, the polyvinyl butyral resin having a low molecular weight is first dispersed using a bead mill or a dispersing machine to decrease the viscosity of the carbon black dispersion by the polyvinyl butyral resin having a low molecular weight And an effect of improving dispersibility can be exhibited. Subsequently, the polyvinyl butyral resin having a high molecular weight is mixed by using a mixer, whereby the flexibility of the battery can be improved by the polyvinyl butyral resin having a high molecular weight.

According to one example, as the second polyvinyl butyral resin, a polyvinyl butyral resin having a weight average molecular weight of from 1 to 50,000 can be used. When the weight average molecular weight of the second resin is 1,000 or more, it is possible to prevent the deterioration of the final physical properties (flexibility reduction and the like). When the weight average molecular weight is 50,000 or less, the viscosity can be prevented from increasing and the dispersibility can be improved.

According to one example, as the polyvinyl butyral resin, a resin containing a butyral-containing unit represented by the following formula (1), an acetyl group-containing unit represented by the following formula (2) and a hydroxyl group containing unit represented by the following formula (3) may be used.

[Chemical Formula 1]

In Formula 1, R is an alkyl group having 1 to 20 carbon atoms. The R may be an alkyl group having 1 to 5 carbon atoms, specifically an alkyl group having 1 to 3 carbon atoms.

(2)

(3)

As the polyvinyl butyral resin, various commercially available products and synthetic products may be used alone or in combination of two or more kinds as long as the content of the repeating units and the weight average molecular weight are satisfied. The hydroxyl group may be adjusted by a chemical modification method such as acylation or urethanization.

According to another embodiment of the present application, various commercially available carbon blacks such as furnace black, channel black, thermal black, acetylene black, and Ketjen black can be used. Hollow carbon black and the like can also be used.

The primary particle diameter of the carbon black may be 1 to 50 nm. Here, the particle diameter of the primary particles means the particle diameter of the carbon black particles not aggregated and can be measured by an electron microscope such as SEM or TEM.

According to one example, the specific surface area of the carbon black may be from 30 m ² / g to 1,500 m ² / g, for example from 30 m ² / g to 350 m ² / g. The specific surface area of carbon black can be measured by using BET (Brunauer-Emmett-Tellery). Specifically, the amount of adsorbed nitrogen gas is measured by adsorbing nitrogen gas (N ₂ ) The surface area can be obtained.

The carbon black may be surface treated as required in the art. The impurities can be removed by surface treatment with, for example, acetylene gas.

According to one embodiment of the present application, the dispersion medium may be an organic solvent containing one or two or more hetero atoms selected from the group consisting of nitrogen atoms (N) and oxygen atoms (O) having a non-covalent electron pair.

Specifically, the dispersion medium may be an amide-based polar organic solvent such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc) or N-methylpyrrolidone (NMP); Propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl -2-propanol (tert-butanol), pentanol, hexanol, heptanol or octanol; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; Polyhydric alcohols such as glycerin, trimethylol propane, pentaerythritol, or sorbitol; Ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol Glycol ethers such as monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, and tetraethylene glycol monobutyl ether; Ketones such as acetone, methyl ethyl ketone, methyl propyl ketone, or cyclopentanone; And esters such as ethyl acetate,? -Butyllactone, and? -Propiolactone. Any one or a mixture of two or more of them may be used.

In particular, N-methyl-2-pyrrolidone is an organic compound having a five-membered ring structure including a lactam structure, and belongs to an aprotic polar solvent such as dimethylformamide, dimethylacetamide, dimethylsulfoxide and the like. In order to have high solubility, it is used as a solvent for various materials especially in the field of polymer chemistry. Therefore, it is preferable to use N-methyl-2-pyrrolidone.

The content of the carbon black, the dispersion medium and the polyvinyl butyral resin may be appropriately determined depending on the use of the dispersion.

According to one embodiment, the polyvinyl butyral resin may vary depending on the specific surface area (BET) of the carbon black for uniform dispersion of the carbon black in the dispersion. For example, the polyvinyl butyral resin may be contained in an amount of 1 to 100 parts by weight, for example, 1 to 50 parts by weight based on 100 parts by weight of carbon black. More specifically, the polyvinyl butyral resin may be used in an amount of 5 to 40 parts by weight, for example 5 to 30 parts by weight, based on 100 parts by weight of carbon black. When the content of the polyvinyl butyral resin is within the above range, the uniform dispersibility of the carbon black in the dispersion can be improved. Even when an excess amount of the polyvinyl butyral resin is added in excess of the above range, the effect of improving the dispersibility is not greatly increased.

According to one embodiment, the dispersion medium in the carbon black dispersion may be contained in an amount of 50 to 99 wt%, and the carbon black may vary depending on the specific surface area, but may be contained, for example, in an amount of 1 to 50 wt%, for example, 10 to 25 wt%. In this range, the carbon black can be uniformly dispersed in the solvent.

According to another embodiment of the present application, the dispersed particle diameter (D ₅₀ ) of the carbon black in the dispersion is 0.03 to 3 μm. The dispersed particle diameter of the carbon black is preferably 0.03 to 2 μm, more preferably 0.05 to 1 μm, and more preferably 0.1 to 1 μm, more preferably 0.05 to 0.5 μm. Compositions having a dispersed particle size of carbon black of less than 0.03 m may be difficult to produce. In addition, a composition in which the dispersion diameter of carbon black exceeds 3 占 퐉 may cause film defects or poor storage stability when coated. When the dispersed particle diameter of the carbon black is within the above range, the carbon black dispersion can exhibit more excellent electrical, thermal and mechanical characteristics due to the uniform dispersion of the carbon black, and the workability can be improved by maintaining the low viscosity, Is possible. The dispersed particle diameter referred to herein is the particle diameter (D ₅₀ ) of 50% in the volume particle size distribution when the volume ratio of the particles is integrated from the minute particle diameter. The dispersed particle size of the carbon black can be measured using a laser diffraction particle size analysis method, for example, with a Mastersizer 3000 from Yarosha.

According to another embodiment of the present application, the viscosity of the carbon black dispersion may be 1-30 Pa.s, more preferably 5-15 Pa.s. The viscosity of the dispersion can be measured with a Haake rheometer, specifically at Shear viscosity of 1.2 / s.

The carbon black dispersion according to the above-described embodiment can be produced by a manufacturing method comprising mixing carbon black, a dispersion medium and the above-mentioned polyvinyl butyral resin. For example, the carbon black dispersion may be prepared by adding carbon black to a dispersion medium in which a polyvinyl butyral resin is dissolved, or adding a carbon black to a dispersion medium and then dissolving the polyvinyl butyral resin, or adding carbon black and polyvinyl butyral And then adding and mixing the resins together. In order to obtain a desired dispersed particle diameter, a milling method such as a ball mill, a bead mill or a basket mill or a homogenizer, a bead mill, a roll mill, a basket A dispersion process may be used using a mill, an impact mill, a universal stirrer, a clear mixer or a TK mixer.

According to one example, mixing carbon black and a dispersion medium to prepare a carbon black slurry (step 1); And mixing the carbon black slurry with a polyvinyl butyral resin having a weight average molecular weight of more than 50,000 (step 2).

Each step will be described in detail below.

Step 1 for producing the carbon black dispersion is a step of mixing a carbon black and a dispersion medium to prepare a carbon black slurry. At this time, the types and amounts of the carbon black and the dispersion medium are the same as those described above.

The mixing of the carbon black and the dispersion medium is carried out using a mixing apparatus such as a conventional mixing method, specifically, a homogenizer, a bead mill, a ball mill, a basket mill, an agitation mill, a universal stirrer, a clear mixer or a TK mixer .

In mixing the carbon black and the dispersion medium, a cavitation dispersion treatment may be carried out in order to enhance the mixing property of the carbon black and the dispersion medium or the dispersibility of the carbon black in the dispersion medium. The cavitation dispersion treatment is a dispersion treatment method using shock waves generated by rupture of vacuum bubbles formed in water when high energy is applied to a liquid, and can be dispersed without impairing the characteristics of the carbon black by the above method. Specifically, the cavitation dispersion treatment may be performed by ultrasonic wave, jet mill, or shear dispersion treatment.

The dispersion treatment process may be suitably performed depending on the amount of carbon black and the kind of dispersant.

Specifically, when the ultrasonic treatment is performed, the frequency is in the range of 10 kHz to 150 kHz, the amplitude is in the range of 5 to 100 탆, and the irradiation time may be 1 to 300 min. As the ultrasonic wave generating device for performing the ultrasonic wave processing process, for example, an ultrasonic homogenizer may be used. Further, when performing the jet mill treatment, the pressure may be 20 MPa to 250 MPa, and may be performed a plurality of times, more specifically, two or more times. As the jet mill dispersing apparatus, a high pressure wet jet mill or the like can be used.

The temperature during the cavitation dispersion treatment step is not particularly limited, but may be performed at a temperature at which there is no fear of viscosity change of the dispersion due to evaporation of the dispersion medium. Specifically at a temperature of 50 DEG C or less, more specifically 15 to 50 DEG C. [

Step 2 for producing a carbon black dispersion according to an embodiment of the present invention is a step of mixing the polyvinyl butyral resin with the carbon black slurry prepared in step 1 above. At this time, the kind and amount of the polyvinyl butyral resin are the same as those described above.

The mixing step may be performed by a conventional mixing or dispersing method, and specifically concretely, a milling (milling) process such as a ball mill, a bead mill, a basket mill, ) Method, or a homogenizer, a bead mill, a roll mill, a basket mill, an impact mill, a universal stirrer, a clear mixer or a TK mixer. More specifically, it can be performed by a milling method using a bead mill. At this time, the size of the bead mill may be suitably determined according to the kind and amount of the carbon black and the kind of the polyvinyl butyral resin, and specifically, the diameter of the bead mill may be 0.5 to 2 mm.

According to the above-described production method, a dispersion in which carbon black is uniformly dispersed in a dispersion medium can be produced.

Another embodiment of the present application provides a method for producing an electrode slurry comprising mixing the carbon black dispersion, an electrode active material and a binder resin.

Another embodiment of the present application relates to a method for producing an electrode slurry, comprising: preparing an electrode slurry by mixing the carbon black dispersion, an electrode active material and a binder resin; And forming an electrode using the electrode slurry.

The electrode slurry and the method for producing the electrode and the material such as the electrode active material, the binder resin, and the like can be used as those known in the art. For example, PVDF or the like may be used as the binder resin. The binder resin such as PVDF in the electrode slurry is used for bonding the metal thin film and the electrode active material, while the polyvinyl butyral resin in the above-mentioned carbon black dispersion is for dispersing the carbon black before it is mixed with the electrode active material. The binder resin in the electrode slurry to which the electrode active material is already added can not disperse the carbon black, so that the binder resin in the electrode slurry and the polyvinyl butyral resin in the carbon black dispersion are distinguished.

The step of forming the electrode may be performed by applying the slurry to the current collector and drying or curing the slurry as necessary.

Another embodiment of the present application provides an electrode slurry comprising the carbon black dispersion, the electrode active material, and the binder resin.

Another embodiment of the present application provides an electrode manufactured using the electrode slurry including the carbon black dispersion, the electrode active material, and the binder resin, and a secondary battery including the electrode. The fact that the electrode is manufactured using the electrode slurry means that the electrode slurry, the dried product thereof, or a cured product thereof.

The secondary battery includes an anode, a cathode, and an electrolyte, and at least one of an anode and a cathode may be manufactured by an electrode slurry including the carbon black dispersion. The battery may further include a separator provided between the anode and the cathode, if necessary.

The secondary battery may be a lithium ion secondary battery.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Example  1 to 8 and Comparative Example  1 and 2

15% by weight (based on carbon black dispersion) of carbon black (Denka's FX-35, primary particle diameter 23 nm, specific surface area BET 135 m ² / g) was added to 500 g of N-methylpyrrolidone (NMP) Of polyvinyl butyral was dispersed so as to be 1.5 wt% (based on carbon black dispersion). At this time, a beads mill was used. At this time, the dispersion target had a particle size (D50) of 1 micrometer. The dispersed particle diameter and viscosity of the carbon black dispersion thus prepared were measured and shown in Table 2 below.

Then, an electrode slurry was prepared using the carbon black dispersion prepared above. To prepare 100 parts by weight of the solid content of the electrode slurry, 97.35 parts by weight of the carbon black dispersion, Li-Ni-Mn-based positive electrode active material, and 1 part by weight of PVdF binder were mixed. At this time, the carbon black and the polyvinyl butyral resin in the carbon black dispersant were respectively contained in an amount of 1.5 parts by weight and 0.15 parts by weight based on 100 parts by weight of the solid content of the electrode slurry. Subsequently, the electrode slurry was coated on the aluminum current collector and rolled by a roll press to produce a positive electrode plate (compound density of 3.3 g / cc).

On the other hand, an anode slurry containing 97.3 parts by weight of an anode active material, 0.7 parts by weight of a conductive material, 1 part by weight of a thickener (CMC) and 1 part by weight of a binder (SBR) was applied to a copper collector, g / cc. < / RTI >

A mono cell was prepared using the positive electrode and the negative electrode to which the carbon black dispersion prepared above was applied. Specifically, a polyethylene separator was inserted between the negative electrode plate and the positive electrode plate, inserted into a battery case, and then an electrolyte was injected to assemble the battery. At this time, a mixed solution of ethylene carbonate, ethyl methyl carbonate and diethyl carbonate (1/2/1 by volume) in which 1.0 M LiPF ₆ was dissolved was used as an electrolyte solution.

Adhesive strength measurement

For the measurement of the adhesive strength, the anode plate (before the preparation of the battery) was cut to the same size of 15 mm × 150 mm and fixed on a slide glass. Then, the anode plate was peeled off from the collector to measure a 180 degree peel strength. The evaluation was made by measuring the peel strengths of 5 or more and calculating the average value. The results of adhesion measurement are shown in Table 2 below.

Monocell evaluation

The battery prepared above was charged and discharged at a temperature of 1.0 C / 1.0 C three times, and the SOC was set based on the final discharge capacity. A 10-second resistance was measured by applying a discharge pulse from SOC50 to 6.5C.

The polyvinyl butyral resin constituent unit (wt%) Molecular weight (DMF) PVB PVAc PVA Mn Mw PDI Example 1 68.3 0.9 30.8 72K 273K 3.80 Example 2 75.0 1.2 23.8 102K 348K 3.20 Example 3 74.1 2.3 23.6 44K 160K 3.60 Example 4 72 2.5 25.5 19K 57K 2.70 Comparative Example 1 - - - - - - Comparative Example 2 78.0 2.5 19.5 14K 37K 2.65 Example 5 85.0 2.5 12.5 30K 99K 3.30 Example 6 80.7 2.1 17.3 56K 177K 3.40 Example 7 * 73.5 1.8 24.7 30K 190K 6.34 Example 7 (1) * 72 2.5 25.5 19K 57K 2.70 Example 7 (2) * 75 1.2 23.8 102K 348K 3.20 Example 8 ** 74.6 1.8 23.7 54K 250K 4.43 Example 8 (1) ** 74.1 2.3 23.6 44K 160K 3.60 Example 8 (2) ** 75.0 1.2 23.8 102K 348K 3.20 * The content and the molecular weight of the constituent unit in Example 7 were such that when the polyvinyl butyral resin of Example 7 (1) and the polyvinyl butyral resin of Example 7 (2) were used together, .
** The content and the molecular weight of the constituent unit in Example 8 were such that when the polyvinyl butyral resin of Example 8 (1) and the polyvinyl butyral resin of Example 8 (2) were used together, the entirety of the carbon black dispersion It is a standard value.

Carbon black dispersion electrode
Adhesion
(gf / 10 mm) 6.5 C, 25 Discharge SOC50 DC-IR (ohm) Particle size (D10) Granularity
(D50) Granularity
(D90) Viscosity (Pa.s, @ 1.2 / s) Example 1 0.30 0.92 3.62 9.6 77 1.147 Example 2 0.33 1.01 3.68 11.3 80 1.177 Example 3 0.34 1.08 3.68 8.7 40 1.133 Example 4 0.29 0.90 3.48 8.3 36 1.138 Comparative Example 1 No dispersion wetting Comparative Example 2 0.34 0.99 3.29 7.8 14 1.292 Example 5 0.36 0.96 3.33 8.2 30 1.193 Example 6 0.34 0.99 3.48 8.6 35 1.183 Example 7 0.30 0.96 3.91 9.1 60 1.149 Example 8 0.32 0.94 3.57 9.5 64 1.145

As shown in Table 2, carbon black was not dispersed in Comparative Example 1, and electrode adhesion was significantly improved in Examples in comparison with Comparative Example 2. Particularly, when a polyvinyl butyral resin having a hydroxyl group-containing PVA content of 20% by weight or more was used, it was confirmed that the electrode adhesion property was even better.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And falls within the scope of the invention.

Claims (14)

Carbon black; Dispersion media; And a polyvinyl butyral resin having a weight average molecular weight of more than 50,000. The carbon black dispersion according to claim 1, wherein the polyvinyl butyral resin has a weight average molecular weight of 150,000 or more. The carbon black dispersion according to claim 1, wherein the polyvinyl butyral resin has a weight average molecular weight of 200,000 or more. The carbon black dispersion according to claim 1, wherein the content of the hydroxyl group-containing repeating unit in the polyvinyl butyral resin is 15% by weight or more. The carbon black dispersion according to claim 1, wherein the content of the hydroxyl group-containing repeating unit in the polyvinyl butyral resin is 20% by weight or more. The carbon black dispersion according to claim 1, wherein the viscosity of the carbon black dispersion is 1-30 Pa.s. The method of claim 1, wherein the carbon black dispersion comprises a first polyvinyl butyral resin having a weight average molecular weight of greater than 50,000; And a second polyvinyl butyral resin having a weight average molecular weight smaller than that of said first polyvinyl butyral resin. The carbon black dispersion according to claim 1, wherein the dispersed particle diameter (D ₅₀ ) of the carbon black in the dispersion is 0.03 to 3 μm. A process for producing a carbon black dispersion according to any one of claims 1 to 8, which comprises mixing carbon black, a dispersion medium, and a polyvinyl butyral resin having a weight average molecular weight of more than 50,000. A method for producing an electrode slurry, which comprises mixing a carbon black dispersion, an electrode active material and a binder resin according to any one of claims 1 to 8. Preparing an electrode slurry by mixing the carbon black dispersion, the electrode active material and the binder resin according to any one of claims 1 to 8; And forming an electrode using the electrode slurry. An electrode slurry comprising the carbon black dispersion liquid according to any one of claims 1 to 8, an electrode active material, and a binder resin. An electrode produced by using an electrode slurry comprising the carbon black dispersion liquid according to any one of claims 1 to 8, an electrode active material, and a binder resin. A secondary battery comprising an electrode according to claim 13.