Method for preparing ultra-high-purity graphite powder through gradient purification and ultra-high-purity graphite powder

Abstract

The invention provides a method for preparing ultra-high-purity graphite powder through gradient purification and the ultra-high-purity graphite powder. The method comprises the following steps: mixing graphite with a mixed acid solution, and carrying out chemical purification reaction to obtain slurry; carrying out solid-liquid separation treatment on the slurry to obtain a solid which is a primary intermediate material; contacting the primary intermediate material with halogen-containing gas to carry out halogenation reaction, and carrying out ultrasonic cleaning on the obtained product to obtain a secondary intermediate material; performing high-temperature purification reaction on the secondary intermediate material to obtain ultra-high-purity graphite powder; wherein the mass ratio of the graphite to the mixed acid liquor is 1: 1-1: 3; the temperature of the halogenation reaction is 500 to 1000 DEG C, and the time of the halogenation reaction is 120 to 360 minutes; the temperature of the high-temperature purification reaction is 2800 to 3000 DEG C, and the time of the high-temperature purification reaction is 240 to 480 minutes. The preparation of the ultra-high-purity graphite powder can be realized through a gradient purification method without a large amount of water washing and a relatively high halogenation temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of high-purity graphite preparation, and particularly relates to a method for preparing ultra-high-purity graphite powder through stepwise purification and the ultra-high-purity graphite powder. Background Art

[0002] Graphite is widely used in many fields due to its excellent electrical and thermal conductivity, high temperature resistance, and chemical stability. With the rapid development of science and technology, especially in high-tech industries such as semiconductors, photovoltaics, aerospace, and nuclear energy, more stringent requirements have been placed on the purity of graphite. Traditional graphite purification methods have problems such as low purification efficiency, severe environmental pollution, and high equipment requirements. Among them, chemical purification requires a large amount of water washing, which produces a large amount of wastewater, puts great pressure on the environment, and the purity can only reach below 99.99%. At the same time, the impurity vaporization temperature of high-temperature halogen purification is too high, and halogen gas seriously corrodes equipment at high temperatures. The equipment is expensive, energy consumption is high, and the cost is high, making large-scale production difficult.

[0003] Therefore, there is an urgent need to develop new and efficient ultra-high purity graphite powder preparation technologies to break through the limitations of existing technologies and meet the growing demand for ultra-high purity graphite powder in various fields. Summary of the Invention

[0004] To solve the above technical problems, the present invention aims to provide a method for preparing ultra-high-purity graphite powder by cascade purification and ultra-high-purity graphite powder. The cascade purification method can achieve the preparation of ultra-high-purity graphite powder without requiring extensive water washing or high halogenation temperatures.

[0005] To achieve the above object, the present invention provides a method for preparing ultra-high purity graphite powder by cascade purification, wherein the method comprises:

[0006] S1: mixing graphite with mixed acid solution to perform chemical purification reaction to obtain slurry; performing solid-liquid separation on the slurry to obtain a solid as a primary intermediate material;

[0007] S2: contacting the primary intermediate material with a halogen-containing gas to carry out a halogenation reaction, and ultrasonically cleaning the obtained product to obtain a secondary intermediate material;

[0008] S3: subjecting the secondary intermediate material to a high-temperature purification reaction to obtain ultra-high-purity graphite powder;

[0009] The mass ratio of the graphite to the mixed acid solution is 1:1 to 1:3; the temperature of the halogenation reaction is 500-1000°C, and the time of the halogenation reaction is 120-360 minutes; the temperature of the high-temperature purification reaction is 2800-3000°C, and the time of the high-temperature purification reaction is 240-480 minutes.

[0010] In some specific embodiments, the halogenation reaction temperature is preferably 600-900°C, and the halogenation reaction time is 150-300 minutes; more preferably, the halogenation reaction temperature is 800-900°C, and the halogenation reaction time is 200-280 minutes. In the present invention, a higher halogenation reaction temperature is not required to ensure the vaporization and removal of all impurities. The halogenation stage only requires the graphite to complete the halogenation reaction and vaporize and remove a small portion of impurities, while the majority of impurities will be converted into metal halides, which will be removed by dissolution in the subsequent ultrasonic cleaning step, thereby saving energy consumption and cost.

[0011] According to a specific embodiment of the present invention, preferably, the concentration of hydrogen ions in the mixed acid solution is 10-30 mol / L.

[0012] According to a specific embodiment of the present invention, preferably, the mixed acid solution includes a combination of two or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid.

[0013] According to a specific embodiment of the present invention, preferably, the graphite is flake graphite with a carbon content greater than 90%.

[0014] According to a specific embodiment of the present invention, preferably, during the halogenation reaction, the flow rate of the halogen-containing gas is 80-120 L / h, more preferably 95-105 L / h.

[0015] According to a specific embodiment of the present invention, preferably, the halogen-containing gas includes one or a combination of two or more of Cl2, HCl, F2, HF, and Freon.

[0016] According to a specific embodiment of the present invention, preferably, the temperature of the chemical purification reaction is 50-80°C, and the chemical purification reaction time is 60-240 minutes. More preferably, the temperature of the chemical purification reaction is 50-65°C, and the chemical purification reaction time is 120-180 minutes.

[0017] According to a specific embodiment of the present invention, preferably, the vacuum degree of the high-temperature purification reaction is ≤ 0.5 Pa. More preferably, the temperature of the high-temperature purification reaction is 2900-2950° C., and the time of the high-temperature purification reaction is 300-360 min.

[0018] In the present invention, in the chemical purification stage, impurities are mainly removed from elements such as silicon, aluminum, sodium, and potassium, and a certain impurity removal effect is also achieved on other elements; in the halogenation reaction stage, impurities are mainly removed from elements such as boron, vanadium, and tungsten, and a certain impurity removal effect is also achieved on other elements; in the high-temperature purification stage, impurities are mainly removed from non-metallic impurities such as N, P, and S, and a certain impurity removal effect is also achieved on other elements.

[0019] According to a specific embodiment of the present invention, the pH value of the primary intermediate material is preferably less than 3; the purity of the primary intermediate material is 99.9%-99.99%, and the moisture content is less than 0.2%. The pH of the primary intermediate material is determined according to the "pH Determination Method" in Appendix C of GB / T24533-2019.

[0020] According to a specific embodiment of the present invention, preferably, the purity of the secondary intermediate material is 99.99% to 99.999%, and the moisture content is less than 0.2%.

[0021] In some specific embodiments, the solid-liquid separation treatment preferably includes centrifugal dehydration and flash drying; wherein the centrifugal dehydration is performed only once, eliminating the need for extensive water washing. More preferably, the flash drying temperature is 180-200°C. In the present invention, the primary intermediate material obtained after the flash drying treatment remains acidic and can be further contacted with an acidic halogen-containing gas for halogenation without the need for water washing to neutrality. This allows the residual acid and some impurities on the graphite to be vaporized and discharged during the halogenation reaction, avoiding the generation of large amounts of wastewater.

[0022] In some specific embodiments, preferably, in step S2, the ultrasonic cleaning process is carried out in ultrapure water, so that the halide generated during the halogenation reaction is dissolved in the ultrapure water, and the resistivity of the ultrapure water is greater than 18 MΩ / cm; more preferably, in step S2, the ultrasonic cleaning further includes the steps of centrifugal dehydration and drying.

[0023] In some specific embodiments, preferably, the power density of the ultrasonic cleaning is 20-40 W / L, and the time of the ultrasonic cleaning is 120-240 min.

[0024] The present invention provides ultra-high purity graphite powder, which is prepared by the above method.

[0025] According to a specific embodiment of the present invention, preferably, the purity of the ultra-high purity graphite powder is greater than 99.999% and the ash content is less than 10 ppm.

[0026] According to a specific embodiment of the present invention, preferably, the purity of the ultra-high purity graphite powder is above 99.9999%, and the content of element B in the ash is less than 0.01 ppm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) Conventional halogenation reactions in the prior art require the removal of impurities at high temperatures, so the impurity removal temperature needs to be increased to above 1500°C. In contrast, the method for preparing ultra-high-purity graphite powder through stepwise purification provided by the present invention directly performs a halogenation reaction on the intermediate material after chemical purification after drying, without the need for water washing to neutrality; further, the metal halide impurities are dissolved in water by ultrasonic cleaning. Therefore, the present invention divides "halogenation" and "impurity removal" into two stages, replacing pure "gasification impurity removal" with "dissolution impurity removal", so that the halogenation temperature can be controlled below 1000°C, thereby significantly reducing the impurity removal temperature of the halogenation reaction, reducing the energy consumption of the halogenation reaction and the requirements for halogenation equipment; at the same time, by utilizing the characteristics that both chemical purification and halogenation reactions are in an acidic environment, water washing and waste acid liquid discharge can be reduced, thereby reducing environmental pollution.

[0029] (2) The method for preparing ultra-high purity graphite powder by cascade purification provided by the present invention can reduce the discharge temperature of impurities at high temperatures by adopting high vacuum purification in the high-temperature purification stage, thereby reducing the content of non-metallic elements such as N, P, and S.

[0030] (3) The present invention adopts a chemical-halogenation-high vacuum and high temperature step-by-step purification method to eliminate different impurity elements in stages according to the characteristics of the impurities: in the chemical purification stage, the main impurities are removed to make the overall purity of the graphite reach more than 99.9%; in the halogenation reaction stage, the metal impurities are removed; in the high vacuum and high temperature purification stage, the trace non-metallic impurities are removed, and the purity of the graphite is gradually increased to more than 99.999%, or even more than 99.9999%; thereby greatly reducing the production cost of ultra-high purity graphite and the stringent requirements for purification equipment, realizing large-scale production, and achieving the highest level of purity in the industry at the most optimized cost. DETAILED DESCRIPTION

[0031] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0032] Example 1:

[0033] This embodiment provides a method for preparing ultra-high purity graphite powder by step-by-step purification, and the specific process is as follows:

[0034] S1: Flake graphite with a carbon content of 95.2% and a mixed acid solution of hydrochloric acid, nitric acid, and hydrofluoric acid are placed in a reactor and mixed uniformly for chemical purification reaction. After the reaction is completed, the resulting slurry is discharged; the slurry is centrifuged and dehydrated, and flash dried at 200°C to obtain a primary intermediate material; the purity of the primary intermediate material obtained by conventional calcination method is tested to be 99.94%, and the pH value of the primary intermediate material is 1.8 and the water content is 0.05% as described in Appendix C of GB / T 24533-2019;

[0035] The mass ratio of the graphite to the mixed acid solution is 1:1.5, the concentration of hydrogen ions in the mixed acid solution is 15 mol / L, and the volume ratio of hydrochloric acid, nitric acid, and hydrofluoric acid is 3:1:1. The temperature of the chemical purification reaction is 65° C., and the reaction time is 120 min.

[0036] S2: The acidic primary intermediate material is subjected to a halogenation reaction in a high-temperature furnace filled with Freon gas. After the reaction, the product of the halogenation reaction is placed in an ultrasonic cleaning device and ultrasonically cleaned with ultrapure water (resistivity of 18.2 MΩ / cm) to dissolve the halide generated during the halogenation reaction in the ultrapure water. The product is then centrifuged to remove impurities and then dried to obtain a secondary intermediate material. The purity of the secondary intermediate material obtained by conventional calcination method is 99.998%, and the moisture content is 0.04%;

[0037] The halogenation reaction temperature is 800°C, the flow rate of Freon gas is 100 L / h, and the halogenation reaction time is 240 min; the power density of ultrasonic cleaning is 25 W / L, and the ultrasonic cleaning time is 150 min;

[0038] S3: The secondary intermediate material is subjected to high-temperature purification under high vacuum conditions. The high-temperature purification temperature is 2950°C, the vacuum degree is 0.5 Pa, and the high-temperature purification time is 360 minutes to obtain an ultra-high purity graphite powder product.

[0039] The test results of glow discharge mass spectrometry (GD-MS) of the ultra-high purity graphite powder prepared in this example are shown in Table 1.

[0040] Table 1. Element content test results

[0041] element Content / ppm element Content / ppm element Content / ppm element Content / ppm Li <0.01 Be <0.01 B <0.01 C matrix N - O - Na ＜0.05 Mg ＜0.05 Al 0.02 Si 0.15 P ＜0.1 S 0.05 Cl 0.11 K ＜0.05 Ca ＜0.05 Sc <0.01 Ti <0.01 V <0.01 Cr <0.1 Mn <0.01 Fe <0.01 Co <0.01 Ni <0.01 Cu <0.05 Zn ＜0.05 Ga <0.01 Ge <0.05 As <0.05 Se <0.05 Br <0.05 Rb <0.05 Sr <0.05 Y <0.05 Zr <0.05 Nb <0.05 Mo <0.05 Ru <0.05 Rh <0.01 Pd <0.05 Ag <0.05 Cd <0.05 In <0.05 Sn <0.05 Sb <0.05 Te <0.05 I <0.05 Cs <0.05 Ba <0.05 La <0.05 Ce <0.05 Pr <0.05 Nd <0.05 Sm <0.05 Eu <0.05 Gd <0.05 Tb <0.05 Dy <0.05 Ho <0.05 Er <0.05 Tm <0.05 Tb <0.05 Lu <0.05 Hf <0.05 Ta <5 W <0.05 Re <0.01 Os <0.01 Ir <0.01 Pt <0.01 Au <0.1 Hg <0.1 Tl <0.05 Pb <0.05 Bi <0.05 Th <0.01 U <0.01

[0042] After testing, the purity of the ultra-high purity graphite powder is 99.99996%, the ash content is 0.00004%, and the B element content in the ash is less than 0.01ppm.

[0043] Example 2:

[0044] This embodiment provides a method for preparing ultra-high purity graphite powder by step-by-step purification, and the specific process is as follows:

[0045] S1: Flake graphite with a carbon content of 95.4% and a mixed acid solution of hydrochloric acid, nitric acid, and hydrofluoric acid are placed in a reactor and mixed uniformly for chemical purification reaction. After the reaction is completed, the obtained slurry is discharged; the slurry is centrifuged and dehydrated, and flash dried at 180°C to obtain a primary intermediate material; the purity of the obtained primary intermediate material is tested by a conventional calcination method to be 99.92%. According to the record in Appendix C of GB / T 24533-2019, the pH value of the primary intermediate material is 1.7 and the water content is 0.04%;

[0046] The mass ratio of the graphite to the mixed acid solution is 1:2, the concentration of hydrogen ions in the mixed acid solution is 18 mol / L, and the volume ratio of hydrochloric acid, nitric acid, and hydrofluoric acid is 4:1:1; the temperature of the chemical purification reaction is 50° C., and the reaction time is 180 min;

[0047] S2: The acidic primary intermediate material is subjected to a halogenation reaction in a high-temperature furnace with chlorine gas. After the reaction, the product of the halogenation reaction is placed in an ultrasonic cleaning device and ultrasonically cleaned with ultrapure water (resistivity of 18.1 MΩ / cm) to dissolve the halide generated during the halogenation reaction in the ultrapure water. The product is centrifuged to remove impurities and then dried to obtain a secondary intermediate material. The purity of the secondary intermediate material obtained by conventional calcination method is 99.997%, and the moisture content is 0.04%;

[0048] The halogenation reaction temperature is 900° C., the chlorine gas flow rate is 100 L / h, and the halogenation reaction time is 240 min. The ultrasonic cleaning power density is 28 W / L, and the ultrasonic cleaning time is 180 min.

[0049] S3: The secondary intermediate material is subjected to high-temperature purification under high vacuum conditions, with the high-temperature purification temperature being 2900°C, the vacuum degree being 0.5 Pa, and the high-temperature purification time being 300 minutes to obtain an ultra-high-purity graphite powder product.

[0050] The ultra-high purity graphite powder prepared in this example was subjected to GD-MS testing. The test showed that the purity of the ultra-high purity graphite powder was 99.99995%, the ash content was 0.00005%, and the B element content in the ash was less than 0.01 ppm.

[0051] Example 3:

[0052] This embodiment provides a method for preparing graphite powder, which is carried out by referring to the steps in Example 1, except that: in step S2, the halogenation reaction temperature is 550°C;

[0053] The remaining steps and parameters remain unchanged to obtain an ultra-high purity graphite powder product.

[0054] The ultra-high purity graphite powder prepared in this example was subjected to GD-MS testing. The test showed that the purity of the ultra-high purity graphite powder was 99.99991%, the ash content was 0.00009%, and the B element content in the ash was less than 0.01 ppm.

[0055] Example 4:

[0056] This embodiment provides a method for preparing graphite powder, which is carried out according to the steps in Example 2, except that: in step S3, the high-temperature purification temperature is 2800°C, the vacuum degree is 0.2 Pa, and the high-temperature purification time is 420 minutes;

[0057] The remaining steps and parameters remain unchanged to obtain an ultra-high purity graphite powder product.

[0058] The ultra-high purity graphite powder prepared in this example was subjected to GD-MS testing. The test showed that the purity of the ultra-high purity graphite powder was 99.99994%, the ash content was 0.00006%, and the B element content in the ash was less than 0.01 ppm.

[0059] Comparative Example 1:

[0060] This comparative example provides a method for preparing graphite powder, which is carried out by referring to the steps in Example 1, except that: in step S3, no ultrasonic cleaning step is performed after the halogenation reaction is completed;

[0061] The remaining steps and parameters remain unchanged to obtain the graphite powder product.

[0062] The graphite powder prepared in this comparative example was subjected to a GD-MS test. The test showed that the purity of the graphite powder was 99.998%, the ash content was 0.002%, and the B element content in the ash was 0.07 ppm.

[0063] It can be seen from this that in this comparative example, the impurities cannot be fully removed without performing the ultrasonic cleaning step, resulting in a decrease in the purity of the obtained graphite powder.

[0064] Comparative Example 2:

[0065] This comparative example provides a method for preparing graphite powder, and the specific process is as follows:

[0066] (1) Flake graphite with a carbon content of 95.4% and a mixed acid solution of hydrochloric acid, nitric acid and hydrofluoric acid are put into a reactor and mixed evenly to perform a chemical purification reaction, and the slurry is discharged after the reaction is completed;

[0067] The temperature of the chemical purification reaction is 50° C., and the reaction time is 180 min. The mass ratio of the graphite to the mixed acid solution is 1:1.5, the concentration of hydrogen ions in the mixed acid solution is 15 mol / L, and the volume ratio of hydrochloric acid, nitric acid, and hydrofluoric acid is 3:1:1.

[0068] (2) centrifugally dewatering the slurry and washing it with water multiple times, washing it with water until it is neutral, and then flash drying it at 200° C. to obtain a primary intermediate material; wherein the primary intermediate material has a purity of 99.92% and a water content of 0.04%;

[0069] (3) The obtained primary intermediate material is subjected to high-temperature purification under vacuum conditions, with the purification temperature being 2900° C., the vacuum degree being 0.5 Pa, and the purification time being 300 min to obtain a graphite powder product.

[0070] The graphite powder prepared in this comparative example was subjected to a GD-MS test. The test showed that the purity of the graphite powder was 99.996%, the ash content was 0.004%, and the B element content in the ash was 0.13 ppm.

[0071] It can be seen from this that the graphite powder prepared in this comparative example without the stepwise purification method cannot achieve a higher purity and requires a large amount of water for washing.

[0072] Comparative Example 3:

[0073] This comparative example provides a method for preparing graphite powder, which is carried out according to the steps in Example 1, except that: in step S2, the halogenation reaction is carried out at a higher temperature, the halogenation reaction temperature is 1200° C., the halogenation reaction time is 240 min, and ultrasonic cleaning is not performed after halogenation;

[0074] The remaining steps and parameters remain unchanged to obtain the graphite powder product.

[0075] The graphite powder prepared in this comparative example was subjected to a GD-MS test. The test showed that the purity of the graphite powder was 99.998%, the ash content was 0.002%, and the B element content in the ash was 0.04 ppm.

[0076] It can be seen from this that the method of carrying out the halogenation reaction at a relatively high temperature to simultaneously achieve impurity removal in this comparative example has a relatively high energy consumption, and the purity of the prepared graphite powder is not as good as that of Example 1-2.

[0077] Comparative Example 4:

[0078] This comparative example provides a method for preparing graphite powder, which is carried out according to the steps in Example 1, except that: the primary intermediate material obtained in step S1 is centrifugally dehydrated and washed with water multiple times, and then subjected to a halogenation reaction in step S2 after washing to neutrality, the halogenation reaction temperature is 900° C., the halogenation reaction time is 360 min, and ultrasonic cleaning is not performed after the halogenation is completed;

[0079] The remaining steps and parameters remain unchanged to obtain the graphite powder product.

[0080] The graphite powder prepared in this comparative example was subjected to a GD-MS test. The test showed that the purity of the graphite powder was 99.996%, the ash content was 0.004%, and the B element content in the ash was 0.05 ppm.

[0081] It can be seen that compared with Examples 1-2, after the ultrasonic cleaning step after the halogenation reaction was replaced with multiple water washing steps before the halogenation reaction, the impurity removal effect decreased in this comparative example.

[0082] Comparative Example 5:

[0083] This comparative example provides a method for preparing graphite powder, which is carried out according to the steps in Example 1, except that: during the high-temperature purification in step S3, no vacuum operation is performed;

[0084] The remaining steps and parameters remain unchanged to obtain the graphite powder product.

[0085] The graphite powder prepared in this comparative example was subjected to a GD-MS test. The test showed that the purity of the graphite powder was 99.9997%, the ash content was 0.0003%, and the B element content in the ash was 0.02 ppm.

[0086] It can be seen from this that when high vacuum conditions are not adopted, the impurity discharge temperature at high temperature cannot be reduced, and the impurity removal effect is reduced.

[0087] Comparative Example 6:

[0088] This comparative example provides a method for preparing graphite powder, which is carried out according to the steps in Example 1, except that the conditions of the high-temperature purification reaction in step S3 are changed to 2750°C and the high-temperature purification time is 360 minutes.

[0089] The remaining steps and parameters remain unchanged to obtain the graphite powder product.

[0090] The graphite powder prepared in this comparative example was subjected to a GD-MS test. The test showed that the purity of the graphite powder was 99.9998%, the ash content was 0.0002%, and the B element content in the ash was less than 0.01 ppm.

[0091] It can be seen from this that when the reaction temperature of the high-temperature purification is not within the specified range of this application, the prepared graphite powder cannot achieve a higher purity.

Claims

1. A method for preparing ultra-high purity graphite powder by stepwise purification, wherein: The method includes: S1: mixing graphite with mixed acid solution to perform chemical purification reaction to obtain slurry; performing solid-liquid separation on the slurry to obtain a solid as a primary intermediate material; S2: contacting the primary intermediate material with a halogen-containing gas to carry out a halogenation reaction, and ultrasonically cleaning the obtained product to obtain a secondary intermediate material; S3: subjecting the secondary intermediate material to a high-temperature purification reaction to obtain ultra-high-purity graphite powder; Wherein, the mass ratio of the graphite to the mixed acid solution is 1:1 to 1:3; The halogenation reaction temperature is 500-1000°C, and the halogenation reaction time is 120-360min; The temperature of the high-temperature purification reaction is 2800-3000° C., and the time of the high-temperature purification reaction is 240-480 minutes.

2. The method according to claim 1, wherein The concentration of hydrogen ions in the mixed acid solution is 10-30 mol / L; Preferably, the mixed acid solution includes a combination of two or more of hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid.

3. The method according to claim 1, wherein The graphite is flake graphite with a carbon content greater than 90%.

4. The method according to claim 1, wherein During the halogenation reaction, the flow rate of the halogen-containing gas is 80-120 L / h; Preferably, the halogen-containing gas includes one or a combination of two or more of Cl2, HCl, F2, HF, and Freon.

5. The method according to claim 1, wherein The temperature of the chemical purification reaction is 50-80° C., and the time of the chemical purification reaction is 60-240 minutes.

6. The method according to claim 1, wherein The vacuum degree of the high-temperature purification reaction is ≤0.5Pa.

7. The method according to claim 1, wherein The pH value of the primary intermediate material is less than 3; the purity of the primary intermediate material is 99.9%-99.99%, and the moisture content is less than 0.2%.

8. The method according to claim 1, wherein The purity of the secondary intermediate material is 99.99% to 99.999%, and the moisture content is less than 0.2%.

9. Ultra-high purity graphite powder prepared by the method according to any one of claims 1 to 8.

10. The ultra-high purity graphite powder according to claim 9, wherein The purity of the ultra-high purity graphite powder is greater than 99.999% and the ash content is less than 10ppm; Preferably, the purity of the ultra-high purity graphite powder is above 99.9999%, and the content of element B in the ash is less than 0.01 ppm.