KR101639206B1 - A method of preparing an anode slurry composition comprising a dispersed mixture of conductive additive covered lto and graphite - Google Patents

Abstract

The present invention relates to a method for producing an anode active material slurry composition in which LTO is uniformly dispersed and mixed in graphite. The slurry composition according to the present invention has the effect that the LTO particles are uniformly dispersed in the negative electrode active material slurry containing graphite.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode slurry composition containing a dispersion mixture of LTO and graphite coated with a conductive material,

The present invention relates to a method for producing a negative electrode slurry composition for a secondary battery. More particularly, the present invention relates to a negative electrode slurry composition in which LTO is uniformly dispersed and mixed in graphite.

Lithium secondary batteries are increasingly used in small electronic devices for electric vehicles and electric power storage, and there is a growing demand for cathode materials for secondary batteries having high stability, long life, high energy density and high output characteristics. Particularly, the improvement of the low temperature output characteristic of the lithium secondary battery is mainly attempted by improving the electrolyte and the cathode material. Recently, a method of improving the low temperature power by changing the active material such as adoption of amorphous carbon as the negative electrode active material has been considered. However, if the active material is changed, there is a problem that the available cell voltage range is changed or the profile pattern is changed, resulting in a decrease in the high temperature characteristics and the capacity of the battery.

Lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) is generally used as an electrode material for a lithium battery. Mixing LTO with an anode material increases the conductivity of the cathode electrode, thereby lowering the charge transfer resistance of the battery. The effect of improving the room temperature and low temperature output is exhibited.

Conventionally, when a negative electrode material is prepared by mixing LTO with a carbon-based material, a method of simultaneously injecting graphite and LTO into a dispersion medium is used, or a large amount of graphite is added to a dilute dispersion medium in which LTO is dispersed. However, when such a method is used, it is difficult to produce a homogeneous mixture in the preparation of the negative electrode slurry composition because LTO acts strongly in the intergranular aggregation phenomenon.

It is an object of the present invention to provide a method of manufacturing an electrode having high dispersibility of LTO by preventing aggregation of LTO when preparing a slurry composition for negative electrode comprising LTO and graphite. Other objects and advantages of the present invention will become apparent from the following description. It is also to be easily understood that the objects and advantages of the present invention can be realized by the means or method described in the claims, and the combination thereof.

The present invention is to solve the above problems, and provides a novel method for producing a negative electrode active material slurry. The method includes the steps of injecting a conductive material into an aqueous medium to produce a first mixture (S10), adding lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) to the first mixture, Preparing a second mixture comprising composite particles at least partially coated with LTO (S20), further adding an aqueous medium to the second mixture to prepare a third mixture (S30), adding graphite And a step (S40) of preparing a fourth mixture in which the composite particles obtained in the step (S20) are uniformly dispersed in the graphite.

Here, in the step (S10), the content of the conductive material in the first mixture is controlled to 5 wt% to 15 wt% or less based on 100 wt% of the aqueous medium.

Here, the step (S20) may be such that the content of the composite particles in the second mixture is controlled to 40% by weight to 60% by weight based on 100% by weight of the aqueous medium.

Here, the step (S30) may be such that the content of the composite particles in the third mixture is controlled to 5 wt% to 15 wt% or less based on 100 wt% of the aqueous medium.

In the step (S40), the content of the composite particles and the graphite in the fourth mixture is adjusted to 50 to 80% by weight based on 100% by weight of the aqueous medium.

Here, the aqueous medium of each of the steps (S10) and (S30) includes 0.1 to 5% by weight of the polymeric binder resin relative to 100% by weight of the aqueous medium.

Wherein the fifth mixture is prepared by further adding an aqueous medium to the fourth mixture so that the content of the composite particles and the graphite in the fifth mixture is controlled to 50% by weight or less based on 100% by weight of the aqueous medium As shown in FIG.

The method of manufacturing a slurry composition for a negative electrode according to the present invention has an effect that LTO particles are uniformly dispersed in a carbon material such as graphite and a slurry composition of an anode active material.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. On the other hand, the shape, size, scale or ratio of the elements in the drawings incorporated herein can be exaggerated to emphasize a clearer description.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart showing a time-series method for producing the slurry composition of the present invention. FIG.
2 is a schematic view schematically showing a state in which LTO particles are dispersed around graphite in a negative electrode active material slurry in the electrode manufacturing method according to the present invention.
3 is an SEM photograph showing graphite and LTO particles dispersed in a negative electrode prepared by the method according to the present invention.
4 is an SEM photograph showing a state in which graphite and LTO particles are dispersed in a negative electrode prepared by the method according to Comparative Example 1. Fig.
5 is an SEM photograph showing a state in which graphite and LTO particles are dispersed in a negative electrode prepared by the method according to Comparative Example 2. Fig.

The terms or words used in the present specification and claims should not be construed to be limited to ordinary or dictionary terms and the inventor shall properly define the concept of the term in order to best explain its invention The present invention should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

As described above, the lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) has a high conductivity and a high specific surface area, so that the charge transfer resistance is low at room temperature and low temperature, . In addition, LTO has stability and excellent low-temperature characteristics, and since it is a three-dimensional oxide, its volume expansion is very small and has excellent cycle life. According to this feature, when LTO is mixed with the anode material, the conductivity of the anode electrode is increased to lower the charge transfer resistance of the battery, thereby improving the room temperature and low temperature output. However, LTO has a drawback that it is difficult to produce a homogeneous mixture in the production of the negative electrode slurry composition due to strong intergranular aggregation phenomenon.

In order to solve the above technical problems, the present invention provides a method of manufacturing an anode slurry composition in which LTO forms a uniformly dispersed phase with a carbon material in an anode material comprising LTO and a carbon material. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a process flow chart showing each step of the method for producing the slurry composition of the present invention in a time-wise manner. Hereinafter, the method for producing the slurry composition of the present invention will be described in detail with reference to Fig.

The method for preparing a slurry composition according to the present invention comprises the steps of: (S10) preparing a first mixture by injecting a conductive material into an aqueous medium; Introducing lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) into the first mixture (S20); Further adding an aqueous medium to the second mixture to produce a third mixture (S30); And adding a carbon material to the third mixture to produce a fourth mixture (S40).

In the present specification, the aqueous medium means a dispersion medium for dispersing a solid solute such as a conductive material, LTO, and a carbon material contained in the slurry composition of the present invention. The aqueous medium is not particularly limited, but is an aqueous solvent such as water. The aqueous medium may further include a polymer binder resin in a range of 0.1 wt% to 5 wt%, preferably 0.1 wt% to 2 wt%, based on 100 wt% of the solvent. The polymeric binder resin serves to bind the particles and / or bind the electrode material and the current collector in the slurry composition and to control the viscosity. The polymeric binder resin is preferably a water-soluble polymer resin. Non-limiting examples of the water-soluble polymer resin include carboxymethylcellulose, vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, Polymethylmethacrylate, styrene butadiene rubber (SBR), but are not limited thereto. In one specific embodiment of the present invention, the polymer resin may be used alone or in combination of two or more.

When the aqueous medium is prepared as described above, a conductive material is injected into the aqueous medium to prepare the first mixture. The first mixture is adjusted so that the content of the conductive material in 100 wt% of the aqueous medium is 5 wt% to 20 wt%, preferably 5 wt% to 15 wt%.

The conductive material is added to control the surface energy of the LTO to a level similar to that of the carbon material used as the active material, in addition to improving the conductivity of the active material. Accordingly, in one specific embodiment of the present invention, it is preferable to use a carbon material as the conductive material. Non-limiting examples of the carbon material include low-crystalline carbon and high-crystalline carbon, all of which are usable. Examples of low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, graphite, carbon nanotubes, pyrolytic carbon, , Mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum and coal tar pitch derived cokes. But the present invention is not limited thereto.

The conductive material has an average particle diameter of 1 nm to 100 nm, preferably 15 nm to 50 nm, more preferably 20 nm to 40 nm. The conductive material covers the surface of the LTO particles in a later step, thereby offsetting the difference in surface energy between the LTO and the carbonaceous anode active material, thereby allowing the two materials to be uniformly mixed. Therefore, it is preferable that the conductive material particles are prepared in the above-mentioned range so as to be attached to the LTO particles to cover the surface.

Next, lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) is added to the first mixture to prepare a second mixture (S20). According to a specific embodiment of the present invention, the amount of the LTO is adjusted such that the content of the conductive material particles and the solid content as the LTO particles in the second mixture is controlled to 40% by weight to 60% by weight based on 100% by weight of the aqueous medium. When the concentration is less than the above-mentioned range, the density of the solid content in the aqueous medium is low and the adhesion between the conductive material particles and the LTO particles is lowered, and the conductive material particles do not effectively cover the LTO particles. When the concentration exceeds the above range (effect of LTO dispersion), no effect is obtained.

After LTO charging, the second mixture can be agitated (weakly) agitated using mechanical or electromagnetic means until the conductive material and LTO particles are evenly dispersed in the aqueous medium.

The LTO has an average particle diameter of 0.3 탆 to 10 탆, preferably 0.5 탆 to 3 탆, more preferably 1 탆 to 2 탆.

On the other hand, at this stage, at least a part of the surface of the LTO particles is covered with the conductive material added in the above-mentioned step. By coating the LTO particles with the conductive material of the carbon material, the surface energy of the LTO particles becomes similar to the surface energy of the graphite and the carbon material, which are cathode materials to be mixed at a later stage, so that the two materials can be easily mixed.

Hereinafter, LTO particles coated with a conductive material particle are referred to herein as a conductive material / LTO composite particle or composite particle for convenience of description.

Next, an aqueous medium is further added to the second mixture to prepare a third mixture (S30). The content of the composite particles in the third mixture is 5 wt% to 15 wt% or less based on 100 wt% of the aqueous medium. The second mixture has a content of the composite particles of at most 60% by weight, and when the solid content is further added in this state, the solid components contained in the mixture are not easily mixed. Therefore, in the step to be described later, the aqueous medium is further added to the second mixture before the cathode material is put in, and the concentration is appropriately lowered within the above-mentioned range of the concentration of the mixture.

Next, a carbon material is further added to the third mixture to produce a fourth mixture (S40). The amount of the carbon material to be added is adjusted so that the electrochemical device in which the negative electrode slurry composition according to the present invention is to be used exhibits an electric capacity suited for its use or intended use.

The carbon material is added to be used as a negative electrode active material in the negative electrode slurry composition of the present invention. As the carbon material, both low-crystalline carbon and high-crystalline carbon may be used. Examples of low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, graphite, carbon nanotubes, pyrolytic carbon, High temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes It is representative. According to a preferred embodiment of the present invention, the carbon material is graphite.

According to one embodiment of the present invention, the carbon material is at least one selected from the group consisting of Si, Sn, Li, Mg, Al, Ca, Ce, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, (Me) and / or two or more metals (Me) which are at least one selected from the group consisting of Pd, Ag, Cd, In, Sb, Pt, Au, Hg, Pb and Bi It can be done. In one example, the composite is coated with a carbon material at least about 50%, preferably at least about 70% of the surface of the composite. When the surface of the composite is coated with a carbon material, the surface energy of the composite becomes similar to that of the carbon material, so that the dispersion of the LTO can be more effectively achieved.

The carbon material preferably has a specific surface area of 10 m ² / g or less. If the specific surface area of the carbon material is more than 10 m ² / g, the initial efficiency of the cathode may be lowered. In the present invention, the lower limit of the specific surface area of the carbon material is not particularly limited. The preferred lower limit is 2 m < ² > / g, but this is merely an example, and not limited thereto.

The carbon material may have a particle diameter of 5 占 퐉 to 50 占 퐉, preferably 5 占 퐉 to 30 占 퐉, and more preferably 5 占 퐉 to 20 占 퐉. If the average particle diameter of the carbon material is less than 5 mu m, the initial efficiency of the cathode may be reduced due to the fine powder of carbon material. If the average particle diameter is more than 50 mu m, the processability of the anode slurry may be decreased and scratches may be increased.

According to a specific embodiment of the present invention, the content of the composite particles and the carbon material in the mixture is 50% by weight to 80% by weight based on 100% by weight of the aqueous medium. This concentration is suitably controlled by further introduction of the aqueous medium at a later stage. According to one specific embodiment of the present invention, the concentration of the slurry composition is finally adjusted to about 50%.

According to a specific embodiment of the present invention, the negative electrode slurry composition may contain carbon black, acetylene black, ketjen black, carbon fiber, polyacetylene, polyaniline, polypyrrole, polythiophene and polysulfuronitrile, , Palladium, and nickel, may be further included. The negative electrode slurry composition of the present invention may further contain additives such as a stabilizer, a flame retardant, a lubricant, an antioxidant, a plasticizer, a dispersant, and an antistatic agent within an allowable range.

According to another aspect of the present invention, an electrochemical device using the negative electrode slurry composition according to the present invention can be manufactured. The electrochemical device of the present invention includes all devices that perform an electrochemical reaction. Examples of the electrochemical device include capacitors such as all types of primary cells, secondary cells, fuel cells, solar cells, and super capacitors. Particularly, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery is preferable among the above secondary batteries.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention may be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

21.255 g of distilled water and 0.255 g of carboxymethylcellulose were mixed to prepare an aqueous medium. Next, 0.255 g of a conductive material (SuperC-65) was added to 2.151 g of the aqueous medium and mixed by stirring. At this time, the concentration of solid content in the aqueous medium was 11.79%. Next, LTO (T-30 D2) 1.731 was added with stirring. At this time, the solid content in the aqueous medium was 48.67%. Next, 12.262 g of the aqueous medium was added thereto to adjust the solid content to 13.18%. Next, 23 g of graphite (AGM-01) was added and mixed by stirring. At that time, the solid content was 63.86 g. The aqueous medium 7.099, distilled water 4.779 g and BA35 1.405 as a thickener were added to adjust the final negative electrode slurry composition to 49%. The slurry composition was applied to an aluminum foil and dried by heating to prepare a negative electrode.

3 is a SEM photograph of a negative electrode made of the negative electrode slurry composition of the embodiment of the present invention. From this, it was confirmed that the LTO particles were uniformly dispersed and distributed among the graphite particles without aggregation.

Comparative Example  One

21.008 g of distilled water and 0.255 g of carboxymethylcellulose were mixed to prepare an aqueous medium. Next, 0.255 g of the conductive material (SuperC-65) was added to 14.183 g of the aqueous medium and mixed by stirring. At this time, the solid content in the aqueous medium was 2.95%. Next, 2.444 g of LTO (T-30 D2) and 22 g of graphite (AGM-01) were simultaneously introduced and stirred. At this time, the solid content in the aqueous medium was 63.96%. Next, 7.091 g of the aqueous medium was added thereto to adjust the solid content to 54.29%. After that, 8.791 of distilled water and 1.392 g of BA35 as a thickener were further added to adjust the concentration of the final negative electrode slurry composition to 45.46%. The slurry composition was applied to an aluminum foil and dried by heating to prepare a negative electrode.

4 is an SEM photograph of a negative electrode made of the negative electrode slurry composition of Comparative Example 1. Fig. According to this, it was confirmed that LTO particles were aggregated and distributed among the graphite particles.

Comparative Example  2

21.008 g of distilled water and 0.255 g of carboxymethylcellulose were mixed to prepare an aqueous medium. Next, 0.255 g of conductive material (SuperC-65) and 2.444 g of LTO (T-30 D2) were added and 14.183 g of the aqueous medium was added to adjust the solid content to 17.00% in the aqueous medium. Next, 22 g of graphite (AGM-01) was added thereto, followed by stirring and mixing. At that time, the solid content was 63.96 g. 7.081 g of the aqueous medium, 4.724 g of distilled water and BA35 1.392 as a thickener were added to adjust the concentration of the final negative electrode slurry composition to 49%. The slurry composition was applied to an aluminum foil and dried by heating to prepare a negative electrode.

5 is a SEM photograph of a negative electrode made of the negative electrode slurry composition of Comparative Example 2. Fig. According to this, it was confirmed that LTO particles were aggregated and distributed among the graphite particles.

Claims (7)

In the production of a negative electrode active material slurry for a secondary battery,
(S10) adding a conductive material to an aqueous medium to prepare a first mixture;
(S20) a step of adding a lithium titanium oxide (Li ₄ Ti ₅ O ₁₂ , LTO) to the first mixture to prepare a second mixture including the composite particles in which the conductive material particles at least partially cover the LTO ;
(S30) further adding an aqueous medium to the second mixture to prepare a third mixture;
(S40) adding graphite to the third mixture to produce a fourth mixture in which the composite particles obtained in the step (S20) are uniformly dispersed in the graphite;
Wherein the negative electrode active material slurry has an average particle diameter of not more than 100 nm.
The method according to claim 1,
Wherein the conductive material in the first mixture is adjusted to 5 wt% to 15 wt% based on 100 wt% of the aqueous medium.
The method according to claim 1,
Wherein the mixing of the composite particles in the second mixture is controlled to 40 wt% to 60 wt% based on 100 wt% of the aqueous medium.
The method according to claim 1,
Wherein the step (S30) is such that the content of the composite particles in the third mixture is controlled to 5 wt% to 15 wt% or less based on 100 wt% of the aqueous medium.
The method according to claim 1,
Wherein the content of the composite particles and the graphite in the fourth mixture is adjusted to 50 to 80% by weight based on 100% by weight of the aqueous medium.
The method according to claim 1,
Wherein the aqueous medium of each of the steps (S10) and (S30) comprises 0.1 to 5% by weight of the polymeric binder resin relative to 100% by weight of the aqueous medium.
The method according to claim 1,
(S50) adding an aqueous medium to the fourth mixture to prepare a fifth mixture, and adjusting the content of the composite particles and the graphite in the fifth mixture to 50% by weight or less based on 100% by weight of the aqueous medium Wherein the negative electrode active material slurry further comprises a negative electrode active material.

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