KR100580111B1 - Method of preparing anode material for lithium ion battery - Google Patents

Abstract

The present invention relates to a method for producing a negative electrode material for a lithium ion battery, to produce a carbon material in which any one of cobalt, chromium, iron or titanium is uniformly distributed on the surface.

To this end, the present invention provides a solution in which an organic metal compound containing cobalt, chromium, iron or titanium as an amorphous carbon is dissolved in an organic solvent in uniformly coating amorphous carbon on the surface of graphite in a method of manufacturing a negative electrode material for a lithium ion battery. Carbon material by a process of coating a solution containing a solution of an amorphous carbon coating material in an organic solvent on a surface of graphite powder having a thickness of 1 to 30 µm, drying and carbonizing at a temperature of 500 to 2500 ° C. under an inert atmosphere. The lithium ion battery using the carbon material according to the present invention as a negative electrode material by providing a manufacturing method of the present invention has excellent cycle characteristics because the conductivity is improved by uniformly distributing cobalt, chromium, iron or titanium in carbonaceous material, and also charge and discharge It has the effect of increasing the dose.

Lithium ion battery, negative electrode material, carbon material, pitch, organometallic compound

Description

Method for preparing carbon material for lithium ion battery anode material {Method of preparing anode material for lithium ion battery}

The present invention relates to a method for manufacturing a negative electrode material for a lithium ion battery, and more particularly, lithium ion 2 which can be obtained by coating with a pitch dispersed with an organometallic compound containing cobalt, chromium, iron or titanium on the surface of graphite. A method for producing a carbon material used as a negative electrode material for a secondary battery.

Generally, it can be said that it is ideal to use lithium metal having high electromotive force and high energy density as a negative electrode active material of a lithium ion secondary battery.

However, as lithium metal is repeatedly charged and discharged in lithium secondary batteries, the dissolution and precipitation of lithium metal are repeated, resulting in precipitation of lithium in the dendrite (dendrite), resulting in a decrease in charging and discharging efficiency. I have a problem that is difficult to do.

In order to solve this problem, it is proposed to use a carbon material instead of lithium as a negative electrode active material, examples of which are Japanese Patent Laid-Open Nos. 63-114056, 62-268056, 2-82466, and 2-79153. Hoi, Hei 4-359862, Hei 5-101818, Hei 7-105936, Hei 7-169458, etc. are mentioned.

Carbon materials have the advantage of longer life due to higher safety and less deterioration due to charging and discharging, since lithium ions are intercalated between crystal lattice layers and lithium ions are easily released by the discharge reaction.

Carbon materials that can be used as anode materials for lithium ion batteries can be classified into graphite and amorphous carbon materials, and graphite based natural graphite, artificial graphite, graphitized mesocarbon microbeads and mesophase pitch carbon fibers And graphite whiskers. Examples of the amorphous carbon material include various types of coke, mesocarbon microbeads, mesophase pitch-based carbon fibers, vapor-grown carbon fibers, polyacrylonitrile-based carbon fibers, and thermosetting resin carbides. Can be mentioned.

Among them, when the graphite-based carbon material is used as the electrode material, it has the advantages of excellent potential flatness and low potential, but has a limit of discharge capacity.

On the other hand, amorphous carbon material has a relatively poor potential flatness, which makes it difficult to manufacture a large capacity battery, but has an advantage of large discharge capacity and easy control of shape and physical properties.

Therefore, a method of compensating for the shortcomings of the negative electrode material produced by only one type by mixing two or more carbon materials to produce the negative electrode material has been proposed.

For example, Japanese Patent Application Laid-Open No. Hei 8-222206, Hei 7-326343 and the like can be cited, but the above method by simple mixing has a problem that it is difficult to obtain uniform characteristics.

As a method for compensating for this, Korean Patent Registration No. 345295 proposes to carbonize a mixed solution made by dissolving a carbonaceous raw material in an organic solvent on the surface of graphite powder, but carbonizes it as a method for further functionalizing it. Patent Application No. 2003-0096008 proposed by them discloses a method of manufacturing a carbon material for a lithium ion battery negative electrode material in which amorphous carbon in which silver or copper is dispersed on a surface is uniformly coated on the surface of graphite to improve properties.

However, the method according to the patent application 2003-0096008 by the present inventors uses a precious metal-based raw material such as silver, so that economical manufacturing is difficult.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an economical manufacturing method that does not use precious metals such as silver in the negative electrode material for lithium-ion batteries, while containing inexpensive elements while exhibiting the same level or more. The purpose of the present invention is to provide a variety of raw materials, and to provide a manufacturing method for achieving higher capacity and improved cycle characteristics.

In order to achieve the above object, the present invention provides an organic metal compound solution prepared by dissolving an organometallic compound containing at least one of cobalt, chromium, iron or titanium in a first organic solvent and an amorphous carbon coating material. A mixing step of mixing the amorphous carbon coating material stock solution prepared by dissolving in an organic solvent; A coating step of coating the mixed solution obtained in the mixing step on the surface of the graphite powder; A drying step of removing the organic solvent by drying the graphite powder coated in the coating step; And a carbonization step of carbonizing the graphite powder dried in the drying step at a temperature of 500 to 2500 ° C. under an inert atmosphere.

Preferably, the organometallic compound in the case of cobalt containing Co (C ₅ H ₇ O ₂ ) ₃ , the organic metal compound in the case of chromium containing Cr (C ₅ H ₇ O ₂ ) ₃ , iron The organometallic compound may be Fe (C ₅ H ₇ O ₂ ) ₃ , and Ti (C ₁₆ H ₃₆ O ₄ ) may be used as the organometallic compound when titanium is contained. The content of cobalt, chromium, iron or titanium is preferably 0.001 to 30% by weight based on the coated amorphous carbon cladding raw material portion.

In addition, as an amorphous carbon coating material, organic materials having a carbon yield of 5% by weight or more, such as tar, pitch, phenol resin, furan resin, and furfuryl alcohol, may be preferably used.

Hereinafter, the present invention will be described in more detail.

The present invention is directed to a method for producing a carbon material used as an electrode of a lithium ion battery, and the manufacturing method first includes an organometallic compound containing cobalt, chromium, iron or titanium in a first mixing process. The organometallic compound solution prepared by dissolving in an organic solvent and the amorphous carbon cladding material solution prepared by dissolving the amorphous carbon cladding material in a second organic solvent are mixed.

Organometallic compounds containing at least one of cobalt, chromium, iron or titanium include Co (C ₅ H ₇ O ₂ ) ₃ , Cr (C ₅ H ₇ O ₂ ) ₃ , Fe (C ₅ H ₇ O ₂ ) ₃ , Ti (C ₁₆ H ₃₆ O ₄ ) may be used, but the type is not limited as long as it can be dissolved in the first organic solvent.

As the first organic solvent, any organic solvent can be used as long as it can dissolve such organometallic compounds such as acetone, pyridine, tetrahydrofuran, toluene, benzene and quinoline.

As the second organic solvent, it is preferable to use the same organic solvent as the first organic solvent as long as it can dissolve the amorphous carbon cladding material, because it is easy to uniformly mix the two solutions. Can be used

On the other hand, the content of any one of cobalt, chromium, iron or titanium contained in the organometallic compound is 0.001 to 30% by weight based on only the cobalt, chromium, iron or titanium components relative to the coated amorphous carbon coating material. In the case of using an amount of 0.001% by weight or less, the effect of improving the performance is small with respect to the complexity of the process, and when an amount of 30% by weight or more is used, the carbonaceous portion is small, so that the charge and discharge capacity of the battery is not preferable.

Next, in the coating step of the second step, the mixed solution obtained in the mixing step is coated on the surface of the graphite powder having a diameter of 1 to 30 μm. As an amorphous carbon coating material used to coat the surface of the graphite powder, tar , Pitch, phenol resin, furan resin, and furfuryl alcohol, such as organic matter having a carbon yield of 5% by weight or more, and can be used as long as it is dissolved in various organic solvents.

The mixing ratio of the organic solvent and the carbonaceous raw material is appropriately blended so that the surface can be sufficiently coated according to the solubility and the addition amount according to the type of organic solvent and the amorphous carbon coating material used.

In addition, the graphite powder used in the present invention can be used both artificial graphite and natural graphite, but if the purity is low, the performance is reduced, so that the fixed carbon content is more than 90% by weight and the ash content is preferably 5% by weight or less.

In addition, as mentioned above, the particle size of the graphite powder is preferably 1 to 30 μm in diameter. If the diameter is 1 μm or less, irreversibility is reduced during charging and discharging. This is because the workability is poor.

The mixing of the organic solvent and the amorphous carbon coating material may be carried out using a conventional mixer. Preferably, the graphite powder is mixed in the mixed solution of the organic metal compound solution and the solution of the amorphous carbon coating material in a slurry state.

In the drying step of the third step, the graphite powder coated in the coating step of the second step is dried to remove the organic solvent.

In this drying process, the graphite powder mixed in the slurry state may be filtered or distilled under reduced pressure in a conventional manner to remove the organic solvent, and the organic solvent recovered and removed may be reused or 300 to prevent oxidation. The organic solvent may be removed by drying at a temperature not higher than ℃.

In the fourth carbonization step, the graphite powder dried in the third drying step is carbonized at an inert atmosphere at a temperature of 500 to 2500 ° C.

When the graphite powder coated with the amorphous carbon coating material is carbonized during the carbonization process, an amorphous carbon coating layer is formed on the surface of the graphite powder, and the carbonization temperature at this time is 500 to 2500 ° C, and the carbonization temperature is If the temperature is less than 500 ° C, the crystal structure of carbon is not sufficiently developed and the conductivity is low. Since the graphitization proceeds at 2500 ° C or more, the characteristics of amorphous carbon are lost. Also, depending on the type of metal to be dispersed, the metal component vaporizes. Because it is removed, the effect of adding metal is lost.

Therefore, depending on the type of metal, heat treatment above the vaporization temperature should be avoided.

Hereinafter, preferred examples are provided to aid in understanding the present invention, but the following examples are provided only for better understanding of the present invention, and the present invention is not limited to the following examples.

<Example 1>

A petroleum isotropic pitch at a softening point of 258 ° C. was added to tetrahydrofuran and completely dissolved at room temperature to prepare a pitch solution.

Cobalt-containing organometallic compound solution was prepared by adding 0.5 atomic% of Co (C ₅ H ₇ O ₂ ) ₃ to tetrahydrofuran and completely dissolving at room temperature in terms of pitch.

The pitch solution and the cobalt-containing organometallic compound solution were stirred and mixed at room temperature for 1 hour. At this time, 100 g of graphite powder was added to the pitch and the organometallic compound mixed solution based on a weight of 7 g of the pitch.

Subsequently, tetrahydrofuran was evaporated by heating to 100 ° C. while mixing with a stirrer in the form of a screw to prepare a graphite powder coated with a cobalt dispersion pitch.

The coated graphite powder was carbonized at 1900 ° C. for 1 hour in an inert atmosphere to prepare a graphite powder in which amorphous carbon in which cobalt was uniformly dispersed was formed.

The electrical conductivity measured while applying the pressure of 10 kg / cm ² to the graphite powder was 0.20 Ω / cm, and the charge and discharge characteristics of the graphite powder were evaluated. As a result, the second charge / discharge capacity showed a value of 359 mAh / g.

Comparative Example 1

A petroleum isotropic pitch at a softening point of 258 ° C. was added to tetrahydrofuran and completely dissolved at room temperature to prepare a pitch solution.

Pitch-coated graphite powder was prepared by adding 100 g of graphite powder to the pitch solution based on the weight of 7 g of the pitch, followed by heating to 100 ° C. while mixing with a screw-type stirrer to evaporate tetrahydrofuran.

The coated graphite powder was carbonized at 1900 ° C. for 1 hour in an inert atmosphere to prepare graphite powder in which amorphous carbon was externally formed.

The electrical conductivity measured while applying the pressure of 10 kg / cm ² to the graphite powder was 0.24 Ω / cm, and the charge and discharge characteristics were evaluated as the negative electrode material of the lithium ion battery. As a result, the second charge / discharge capacity showed a value of 322 mAh / g.

<Example 2>

A petroleum isotropic pitch at a softening point of 258 ° C. was added to tetrahydrofuran and completely dissolved at room temperature to prepare a pitch solution.

Cr (C ₅ H ₇ O ₂ ) ₃ was added to tetrahydrofuran and dissolved completely at room temperature to prepare a chromium-containing organometallic compound solution.

The pitch solution and the chromium-containing organometallic compound solution were mixed and stirred at room temperature for 1 hour, and 100 g of graphite powder was added to the pitch and organometallic compound mixed solution based on the weight of 7 g of the pitch, and then mixed with a screw-type stirrer. Tetrahydrofuran was evaporated by heating to 100 ° C. while preparing a pitch-coated graphite powder in which chromium was dispersed.

The coated graphite powder was carbonized at 1900 ° C. for 1 hour in an inert atmosphere to prepare graphite powder in which amorphous carbon in which chromium was uniformly dispersed was formed.

The electrical conductivity measured while applying the pressure of 10 kg / cm ² to the graphite powder was 0.18 Ω / cm, and the charge and discharge characteristics of the graphite powder were evaluated. As a result, the second charge / discharge capacity showed a value of 335 mAh / g.

<Example 3>

A petroleum isotropic pitch at a softening point of 258 ° C. was added to tetrahydrofuran and completely dissolved at room temperature to prepare a pitch solution.

An iron-containing organometallic compound solution was prepared by adding only 0.5 atomic% of Fe (C ₅ H ₇ O ₂ ) ₃ to tetrahydrofuran and completely dissolving at room temperature.

The pitch solution and the iron-containing organometallic compound solution were mixed and stirred at room temperature for 1 hour, and 100 g of graphite powder was added to the pitch and the organometallic compound mixed solution based on the weight of 7 g of the pitch and then mixed with a screw-type stirrer. While heating to 100 ℃ while evaporating tetrahydrofuran to produce a pitch-coated graphite powder in which iron is dispersed.

The coated graphite powder was carbonized at 1900 ° C. for 1 hour in an inert atmosphere to prepare graphite powder in which amorphous carbon in which iron was uniformly dispersed was formed.

The electrical conductivity measured while applying the pressure of 10 kg / cm ² to the graphite powder was 0.23 Ω / cm, and the charge and discharge characteristics were evaluated as the negative electrode material of the lithium ion battery. As a result, the second charge / discharge capacity showed a value of 342 mAh / g.

<Example 4>

A petroleum isotropic pitch at a softening point of 258 ° C. was added to tetrahydrofuran and completely dissolved at room temperature to prepare a pitch solution.

A Ti-containing organometallic compound solution was prepared by adding 0.5 atomic% Ti (C ₁₆ H ₃₆ O ₄ ) to tetrahydrofuran and completely dissolving at room temperature.

The pitch solution and the titanium-containing organometallic compound solution were mixed and stirred at room temperature for 1 hour, and 100 g of graphite powder was added to the pitch and the organometallic compound mixed solution based on the weight of 7 g of the pitch and then mixed with a screw-type stirrer. While heating to 100 ℃ while evaporating tetrahydrofuran to produce a pitch-coated graphite powder in which titanium is dispersed.

The coated graphite powder was carbonized at 1900 ° C. for 1 hour in an inert atmosphere to prepare graphite powder in which amorphous carbon in which titanium was uniformly dispersed was formed.

The electrical conductivity measured while applying this graphite powder at a pressure of 10 kg / cm ² was 0.12 Ω / cm, and the charge and discharge characteristics were evaluated as the negative electrode material of the lithium ion battery. As a result, the second charge / discharge capacity showed a value of 328mAh / g.

In consideration of the above embodiments, it can be seen that various electrical conductivity and charge / discharge capacities are shown according to the type of metal to be added, and when added to an organometallic compound solution, it is relatively inexpensive compared to expensive metal elements such as silver. Among the metal elements of, cobalt, chromium, iron, and titanium were found to exhibit good electrical conductivity and charge / discharge capacity. The use of these metal elements also improved the high capacity and cycle characteristics of the present invention.

As described above, preferred embodiments of the present invention have been described in detail, but those skilled in the art will be able to modify the present invention without departing from the spirit and scope of the present invention. It will be appreciated that the present invention may be modified or implemented, and the true technical protection scope of the present invention should be defined by the claims.

According to the present invention, the carbonaceous material for lithium battery negative electrode material in which the graphite-based and amorphous carbon materials are mixed by coating and carbonizing an amorphous carbon coating material containing any one of cobalt, chromium, iron or titanium on the surface of the graphite powder. By improving the conductivity, there is an effect that can produce a product that improves the characteristics of the battery.

In addition, since these materials are inexpensive elements compared to expensive elements such as silver, there is an effect of manufacturing a carbon material for a lithium battery negative electrode material which is cheaper and has improved characteristics.

Claims (5)

Amorphous carbon coating material prepared by dissolving an organometallic compound solution prepared by dissolving an organometallic compound containing at least one of cobalt, chromium, iron, or titanium in a first organic solvent and an amorphous carbon coating material in a second organic solvent. A mixing process of mixing the solutions; A coating step of coating the mixed solution obtained in the mixing step on the surface of the graphite powder; A drying step of removing the organic solvent by drying the graphite powder coated in the coating step; And And carbonizing the graphite powder dried in the drying step at a temperature of 500 to 2500 ° C. under an inert atmosphere. The method of claim 1, A particle size of the graphite powder is 1 ~ 30㎛ the manufacturing method of the carbon material for lithium ion battery negative electrode material. The method of claim 1, The cobalt-containing Co as the organometallic compound _{(C 5 H 7 O 2)} 3, said chromium containing Cr as the organometallic compound _{(C 5 H 7 O 2)} 3, as the iron-containing organic metal compounds Fe (C ₅ H ₇ O ₂ ) _{3, A} method of producing a carbon material for lithium ion battery negative electrode material, characterized in that at least one of Ti (C ₁₆ H ₃₆ O ₄ ) is used as the titanium-containing organometallic compound. The method of claim 1, The content of any one of the cobalt, chromium, iron or titanium is 0.001 to 30% by weight based on the coated amorphous carbon coating material portion, characterized in that the carbon material for lithium ion battery negative electrode material. The method of claim 1, The amorphous carbon cladding material is any one of tar, pitch, phenol resin, furan resin, and furfuryl alcohol having a carbon yield of 5% by weight or more.