Method for producing materials for graphitic carbon coated graphite electrodes

Abstract

The present disclosure provides a method (200) for producing a graphite-based material for an electrode. The method (200) includes forming a block material comprising graphite into a feedstock block. Coating the feedstock block with a second material, the second material comprising carbon. Heating the coated feedstock block to allow graphitization of the coated feedstock block to produce a carbon-coated graphite-based material. Heating the coated feedstock block to a temperature greater than about 2600°C to remove impurities. Such a process results in graphite powder having a high purity content greater than about 99.95%. The present disclosure further provides an electrode made from the graphite-based material.

Description

[Technical Field]

[0001] The present disclosure relates generally to anodes for lithium-ion batteries. In particular, the present disclosure relates to a means for producing high-quality graphitic carbon-coated anodes for lithium-ion batteries. [Background technology]

[0002] The background discussion includes information that may be useful in understanding the present invention. No admission is made that any of the information provided herein is prior art or relevant to the present invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Typically, the negative electrode in a lithium-ion battery is a graphite electrode. Traditionally, graphite electrodes are made from synthetic graphite or natural graphite flakes, which are crushed and molded, purified by acid washing / treatment, coated with carbon, and heat-treated at high temperatures of approximately 1000-1200°C. High purities of over 99.9% can be achieved with graphite powder, but the processes used can require additional equipment and resources. For example, acid washing, filtering, and drying facilities require large amounts of water, as well as wastewater treatment plants. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a method for producing a graphite-based material for producing electrodes.

[0005] Another object of the present invention is to provide a method for producing high purity graphite-based materials for electrodes.

[0006] Another object of the present invention is to provide a method for producing high purity graphite-based materials by eliminating chemical refining processes, making the process environmentally friendly.

[0007] Another object of the present invention is to provide a method for producing graphite-based materials for electrodes having high tap density. [Means for solving the problem]

[0008] The present disclosure relates generally to anodes for lithium-ion batteries. In particular, the present disclosure relates to a means for producing high-quality graphitic carbon-coated anodes for lithium-ion batteries.

[0009] In one embodiment, the present disclosure provides a method for producing a graphite-based material for an electrode. The method includes crushing a block of material containing graphite flakes and forming it into spherical graphite powder. The method further includes coating the raw material block with a second material, the second material being a carbon source such as coal tar pitch, petroleum tar pitch, and / or a polymer-based material. The method further includes heating the carbon source-coated graphite powder to allow carbonization, followed by graphitization of the coated carbon source on the graphite particles to produce a graphitic carbon-coated graphite-based material.

[0010] In some embodiments, the block material comprises natural graphite flakes.

[0011] In some embodiments, the block of material is formed using either or a combination of milling and spherical milling operations.

[0012] In some embodiments, the second material comprises pitch and / or a polymeric material.

[0013] In some embodiments, the coated feedstock powder is heated to a temperature between about 2500°C and 3000°C.

[0014] In some embodiments, the carbon-coated graphite-based material produced has a tap density of from about 1.1 grams per cubic centimeter (g / cc) to about 1.25 g / cc.

[0015] In some embodiments, the carbon-coated graphite-based material produced has a capacity of about 360 milliamp-hours per gram (mAh / g) to about 370 mAh / g.

[0016] In some embodiments, the carbon-coated graphite-based material produced has a purity greater than about 99.95%.

[0017] In another aspect, the present disclosure provides an electrode made from a graphite-based material. The graphite-based material is produced by forming a block material including graphite into a feedstock block. The graphite-based material is further produced by coating the feedstock block with a second material, the second material including carbon. The graphite-based material is further produced by heating the coated feedstock block, allowing graphitization of the coated feedstock block to produce a carbon-coated graphite-based material.

[0018] In some embodiments, the electrodes have an efficiency of about 92% to about 95%.

[0019] Various objects, features, aspects and advantages of the present subject matter will become more apparent from the following detailed description of preferred embodiments, taken in conjunction with the accompanying drawings in which like numerals represent like elements. [Brief explanation of the drawings]

[0020] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure.

[0021] [Figure 1] 1 shows a schematic flow diagram of a conventional process for producing materials for making graphite electrodes.

[0022] [Figure 2]FIG. 1 shows a schematic flow diagram of a method for producing a graphite-based material for an electrode, according to one embodiment of the present disclosure.

[0023] [Figure 3] FIG. 1 shows an exemplary schematic flow diagram of a process for producing a material for producing graphite electrodes.

[0024] [Figure 4] 1 shows Raman spectra of graphitic carbon coated graphite made according to our process and amorphous carbon coated graphite by a conventional process. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following is a detailed description of embodiments of the present disclosure, as illustrated in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail provided is not intended to limit the possible variations of the embodiments; rather, the intent is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure, as defined by the appended claims.

[0026] FIG. 1 shows a schematic flow diagram of a conventional process 100 for producing materials for producing graphite electrodes. The conventional process 100 includes an acid treatment step to improve the purity of the graphite. Graphite electrodes are made by crushing and shaping natural graphite powder. Milling techniques, such as milling and spherical milling, may be used. The crushed graphite powder is treated with acid to leach out impurities. The acid wash may include any or a combination of organic and inorganic acids, such as, but not limited to, hydrofluoric acid (HF), hydrochloric acid (HCl), sulfuric acid (H2SO4), and nitric acid (HNO3). The treated graphite powder is then coated with a carbon source. The carbon source may be in the form of pitch coated on the graphite powder. The pitch-coated graphite powder is then heat-treated to approximately 1200°C, resulting in carbonization of the carbon-source-coated graphite powder. The resulting electrode is an amorphous carbon-coated natural graphite powder. The purity of the resulting electrode material may be greater than about 99.95%.

[0027] However, process 100 requires large amounts of acid and water and may require additional wastewater treatment plants to effectively remove traces of acid before discharging the water. The required resources make the process expensive and cumbersome. Furthermore, the use of strong acids can pose environmental hazards.

[0028] Therefore, there may be a need for a means of producing or manufacturing graphite electrodes that does not require large amounts of acid and water.

[0029] JP3534391 and US5344726 disclose a process for coating amorphous carbon on the surface of spherically processed crystalline graphite, in which a hydrocarbon precursor such as propane, methane, acetylene, or benzene is pyrolytically deposited on the heated surface of the graphite to produce an active negative electrode material in which the core crystalline carbon is coated with a thin layer of amorphous carbon.

[0030] JP3193342 and KR101091547 disclose carbon precursors such as coal tar pitch, formaldehyde-based resins, heat-treated pitch, vinyl-based resins, and nitrogen- and sulfur-containing heterocyclic compounds. In this case, the graphite-pitch mixer dispersion has a pitch content of 1 to 10 parts by weight based on 100 parts by weight of graphite. The resulting pitch-coated graphite has a fixed carbon ratio of the carbon coating layer of 0.5 to 5 by weight relative to the graphite.

[0031] JP2005515957 and US9096473 provide a means for producing an artificial graphite active negative electrode from coke coated with petroleum pitch through a liquid medium.

[0032] US6596437 provides a chemical combinatorial route to obtain coated active materials. This process involves the use of non-aqueous or organic solvents to prepare an amorphous carbon precursor as a coating material. This process requires the use and evaporation of a large amount of organic solvent, making the manufacturing process cumbersome. Furthermore, the use of organic solvents in mass production can limit environmental issues such as solvent recovery.

[0033] As a result, it would be advantageous to provide a process for dry carbon coating that does not involve significant amounts of harmful solvents. The present disclosure provides a process for producing a material for making graphite electrodes. In this process, natural graphite powder is crushed and formed, coated with pitch, and then carbonized / graphitized at very high temperatures, above about 2600°C, to remove impurities and convert the pitch on the graphite into graphitic carbon on the graphite particles. Such a process results in graphite powder with a high purity content. In some cases, the purity content from such a process may be 99.95% or higher.

[0034] 2 shows a schematic flow diagram of a method for producing a graphite-based material for an electrode according to one embodiment of the present disclosure. In step 202, method 200 includes forming a block material including graphite into a feedstock block. In step 204, method 200 includes coating the feedstock block with a second material, the second material including carbon. In step 206, method 200 includes heating the coated feedstock block to allow graphitization of the coated feedstock block to produce a carbon-coated graphite-based material.

[0035] In some embodiments, the block material comprises natural graphite flakes.

[0036] In some embodiments, the block of material is formed using either or a combination of milling and spherical milling operations.

[0037] In some embodiments, the second material comprises pitch.

[0038] In some embodiments, the coated feedstock block is heated to a temperature between about 2500°C and 3000°C.

[0039] In some embodiments, the carbon-coated graphite-based material produced has a tap density of from about 1.1 grams per cubic centimeter (g / cc) to about 1.25 g / cc.

[0040] In some embodiments, the carbon-coated graphite-based material produced has a capacity of about 360 milliamp-hours per gram (mAh / g) to about 370 mAh / g.

[0041] In some embodiments, the carbon-coated graphite-based material produced has a purity greater than about 99.95%.

[0042] FIG. 3 shows an exemplary schematic flow diagram of a process 300 for producing a material for manufacturing graphite electrodes. The process 300 may include shaping and milling natural graphite flakes. Milling techniques, such as milling and spherical milling, may be used. The crushed graphite powder may then be coated with pitch, where the pitch may serve as a carbon source. The pitch-coated graphite flakes are then heat-treated to a temperature of approximately 2600°C to graphitize the coated graphite flakes. The resulting material is graphitic carbon-coated natural graphite. The resulting material may have a purity greater than approximately 99.95%.

[0043] Additionally, Process 300 provided additional benefits. The resulting material has a high tap density, which can aid in easy dispersion and coating in the electrode manufacturing process. Furthermore, Process 300 does not require the use of strong acids for the purification of graphite. Therefore, there may be no requirement for a wastewater treatment plant. Furthermore, Process 200 also results in water savings.

[0044] In process 300, the graphite powder is heated to such a high temperature that impurities trapped within the pores of the material also evaporate due to the heat, thus resulting in a material with higher purity.

[0045] Table 1 below provides an exemplary comparison of the properties of different samples of material used to make graphite electrodes, where Sample 1 may be material obtained from conventional process 100 of FIG. 1. Samples 2 and 3 may be obtained from process 300. Sample 4 may be similar to Samples 2 and 3, but with an additional coating of pitch followed by an additional step of carbonization. Each of the samples has an average grain size (D50) of about 10 micrometers. [Table 1]

[0046] Figure 4 shows the laser Raman spectroscopy of (Sample 3) graphitic carbon coated graphite powder and (Sample 4) amorphous carbon coated graphite powder. Laser Raman spectroscopy is a sensitive technique for distinguishing the surface structural fingerprints of different graphite materials, primarily with respect to the disorder and degree of graphitization. Raman spectra were recorded from the surface of the graphite and amorphous carbon coated graphite anode materials and are shown in Figure 4. The primary G band is located at 1577 cm for both the graphitic carbon coated graphite anode material and the amorphous carbon coated graphite anode material. -1 and sp representing the ordered structure of the graphite plane. 2 E in carbon domains 2g Higher G-band intensity and full width at half maximum (FWHM) G ) corresponds to the degree of graphitization of the carbon material. As shown in Figure 4, the graphitic carbon coated graphite powder sample (Sample 3) has a higher FWHM G (23cm -1 ) compared to Sample 4 with an amorphous carbon coated specimen, indicating a minimal in-plane defect concentration and a high level of graphitization. G (51cm -1 ) values ​​showed a sharp and intense G band.

[0047] The integral ratio of ID / IG intensity relates to the degree of in-plane defects in the carbon material. Sample 3 exhibits a lower D band intensity and a lower I D / I G is 0.07, which indicates that the graphite surface is coated with highly ordered graphitic carbon. D / I G This indicates that the surface of the graphite is coated with amorphous carbon.

[0048] In another aspect, the present disclosure provides an electrode made from a graphite-based material. The graphite-based material is produced by crushing a flaky material comprising graphite flakes and forming it into spherical graphite powder. The spherical graphite powder is further produced by coating a feedstock block with a second material, the second material comprising pitch. The graphite-based material is further produced by heating the pitch-coated feedstock graphite powder to allow graphitization of the coated feedstock block, producing a graphitic carbon-coated graphite-based material.

[0049] In some embodiments, the electrodes have an efficiency of about 92% to about 95%.

[0050] It will be apparent to those skilled in the art that many additional modifications beyond those already described are possible without departing from the concept of the present invention. Accordingly, the subject matter of the present invention should not be limited except in the spirit of the appended claims. In interpreting this disclosure, all terms should be interpreted in the broadest manner consistent with the context. In particular, the terms "comprises" and "comprising" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that a referenced element, component, or step may be present, utilized, or combined with other elements, components, or steps not explicitly referenced. When a claim of the specification refers to at least one selected from the group consisting of A, B, C, ..., and N, the text should be interpreted as requiring only one element from the group, not A+N, or B+N, etc. The foregoing description of specific embodiments fully reveals the general nature of the embodiments herein, so that other embodiments may readily modify and / or adapt such specific embodiments by applying current knowledge without departing from the general concept; therefore, such adaptations and modifications should be understood and are intended to be within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phrases or terminology used herein are for purposes of description and not of limitation. Thus, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.

[0051] While the foregoing describes various embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the embodiments, versions, or examples described, which, when combined with information and knowledge available to those skilled in the art, are included to enable those skilled in the art to make and use the invention. Advantages of the invention

[0052] The present invention provides a method for producing a graphite-based material for producing electrodes for use in secondary batteries.

[0053] The present invention provides a method for producing high purity graphite-based materials for electrodes used in secondary batteries.

[0054] The present invention provides an environmentally friendly method for producing high purity graphite-based materials for electrodes.

[0055] The present invention provides a method for producing graphite-based materials for electrodes having high tap density.

Claims

1. A method (200) for producing a graphite-based material for an electrode, comprising: A step of forming a flaky material made of graphite into spherical graphite powder; coating spherical graphite powder with a second material, the second material comprising pitch, and heating the pitch-coated material to allow graphitization of the coated feedstock to produce a graphitic carbon-coated graphite-based material (200).

2. The method (200) of claim 1, wherein the flaky material comprises natural graphite flakes.

3. The method (200) of claim 1, wherein the block of material is formed using one or a combination of milling and spherical milling processes.

4. The method (200) of claim 1, wherein the coated feedstock block is heated to a temperature of about 2500°C to 3000°C.

5. The method (200) of claim 1, wherein the produced carbon-coated graphite-based material has a tap density of about 1.1 grams per cubic centimeter (g / cc) to about 1.25 g / cc.

6. 10. The method of claim 1, wherein the produced carbon-coated graphite-based material has a capacity of about 360 milliamp-hours per gram (mAh / g) to about 370 mAh / g.

7. 10. The method (200) of claim 1, wherein the produced carbon-coated graphite-based material has a purity greater than about 99.95%.

8. 10. The method (200) of claim 1, wherein the graphitic carbon coated graphite material exhibits an ID / IG ratio lower than 0.

07.

9. An electrode made from a graphite-based material, the graphite-based material comprising: a step of forming a block material made of graphite into a raw material block; coating the raw material block with a second material, the second material comprising pitch; and 1. An electrode produced by the process of heating a pitch-coated stock block to allow graphitization of the coated stock block, producing a carbon-coated graphite-based material.

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