Method for manufacturing purified graphite

Abstract

A two-stage method for producing purified graphite is described. The first stage of the method includes applying a graphite material to a caustic bake (14) and using water to remove any residual caustic agent (16, 18). The graphite material is then subjected to a primary acid wash (20). The acid-washed graphite material is then neutralized and washed (22, 24) to yield an intermediate purified graphite product (28). In the second stage, the intermediate purified graphite product is subjected to a low-temperature caustic leaching (34). Any caustic agent remaining in the intermediate purified graphite product is removed using water (35, 36, 38), and the intermediate purified graphite product is subjected to a secondary acid wash (40). Finally, the intermediate purified graphite product is neutralized and washed (42, 44, 45) to yield a final purified graphite product (46) with a purity of 99.95% or higher.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing refined graphite, and in particular, but not exclusively, to such a method for manufacturing battery-grade spherical refined graphite (SPG). Background Technology

[0002] Spherical graphite is manufactured from flake graphite concentrate, where the flakes must be rounded to produce spherical graphite particles. Because spherical graphite can spread thinly and uniformly during the manufacturing process, it is used as an anode material for lithium-ion batteries. Spherical refined graphite (SPG) is sold as either coated or uncoated products. Uncoated SPG is produced by pulverizing, rounding, and refining flake graphite. Most uncoated natural SPG is currently manufactured in China due to low labor costs and lax environmental regulations. The pulverized and rounded graphite is chemically refined to 94% to 99.95% C using strong hydrofluoric acid and other acids. Impurities have a detrimental effect on battery performance.

[0003] Apart from environmental issues, hydrofluoric acid, typically used in the purification processes of prior art, is also highly toxic and dangerous to use. Therefore, significant efforts are being made to find more cost-effective, non-toxic, and environmentally sustainable processes for the purification of spherical graphite.

[0004] With the widespread use of lithium-ion batteries, there is now a significant market for recycling this type of battery. In a typical advanced technology recycling plant, lithium-ion batteries are first separated for plastic, aluminum, and copper components and sent to a dedicated recycling process to ensure they are safe for further processing. After this process, the remaining components of the battery are chemical and mineral components. "Black mass" is the residue left over from conventional wet smelting processes used to recover valuable metals. Black mass typically consists of a mixture of carbon, lithium, manganese, cobalt, and nickel in varying proportions, including anode materials composed of natural battery graphite, synthetic graphite, and silicon. Since graphite accounts for nearly 50% of the mass of a typical lithium-ion battery, there is a significant advantage in being able to purify the black mass material to recover high-purity graphite. The problem to be solved

[0005] The present invention was developed for the purpose of providing a cost-effective and environmentally sustainable method for producing refined graphite with a carbon content of 99.9% or more. Although the present invention has been described particularly in relation to the production of battery-grade SPG, it will be understood that the method for producing refined graphite can also have broader applications.

[0006] References to prior art in this specification are provided for illustrative purposes only and should not be construed as an acknowledgment that such prior art is part of the general knowledge of the world in Australia or other regions. means of solving the problem

[0007] According to one aspect of the present invention, a method for producing purified graphite comprising the following steps is provided. :

[0008] Step of applying graphite material to sodium hydroxide (NaOH) bake;

[0009] Step of releasing any residual NaOH using water;

[0010] Step of applying graphite material to primary acid washing;

[0011] A step of neutralizing and washing acid-washed graphite material to produce (delivering) an intermediate purified graphite product;

[0012] Step of applying the intermediate purified graphite product to NaOH leaching;

[0013] A step of releasing any residual NaOH from the intermediate purified graphite product using water;

[0014] Step of applying the intermediate purified graphite product to acid washing; and

[0015] A step of neutralizing and washing the intermediate purified graphite product to produce a final purified graphite product.

[0016] Preferably, the step of applying the graphite material to the NaOH bake comprises mixing the graphite material with liquid NaOH (50%) and heating the mixture in a furnace. Typically, the mixture is heated to a temperature of 450°C to 550°C. Advantageously, the mixture is heated for approximately 25 to 45 minutes. Preferably, the mixture is heated to 500°C for 30 minutes.

[0017] Preferably, the step of releasing any residual NaOH involves immersing the material in hot water. Preferably, after the step of releasing any residual NaOH, the material is washed and filtered. Typically, the material is washed and filtered in a neutral washing step using 2.0 to 7.0 parts of H2O at ambient temperature for about 5 to 10 minutes.

[0018] Preferably, the step of applying the material to a primary acid wash comprises washing the material with a diluted acid mixture containing water and H2SO4. Typically, the diluted acid mixture contains 2.0 to 5.0 parts H2O and 0.15 to 0.25 parts H2SO4 96%. Advantageously, the diluted acid mixture contains 4.0 parts H2O and 0.17 parts H2SO4 96%. Preferably, the primary acid wash is performed at an elevated temperature in the range of approximately 70°C to 90°C to increase reactivity. Typically, the primary acid wash is performed at an elevated temperature of 80°C for about 25 to 45 minutes.

[0019] Preferably, the step of neutralizing and washing the acid-washed graphite material comprises filtering the material at ambient temperature and performing a final wash with water at elevated temperature, respectively. Typically, the final wash with water is performed at 85°C for 30 minutes using 20 parts H2O. Preferably, the step of neutralizing and washing the material comprises washing the acid-washed graphite material in 3 to 7 parts H2O for 3 to 7 minutes while stirring at ambient temperature.

[0020] Preferably, the step of applying the intermediate purified graphite product to NaOH leaching comprises immersing the intermediate purified graphite product in 0.1 to 0.3 parts NaOH (50%) and 2.0 to 4.0 parts H2O at a low temperature. Typically, NaOH leaching takes place at a temperature in the range of 72°C to 88°C. Preferably, the residence time for NaOH leaching is about 1.5 to 2.5 hours.

[0021] Preferably, the intermediate purified graphite product is neutralized and washed before being applied to the acid washing step.

[0022] Advantageously, the only reagents used are NaOH in the NaOH bake and NaOH leaching steps, and H2SO4 in the acid washing step.

[0023] Preferably, the intermediate purified graphite product is finally washed in a water bath and neutralized with water after the acid washing step.

[0024] Preferably, the acid washing of the intermediate purified graphite product is performed with a diluted acid mixture comprising 2.0 to 4.0 parts H2O and 0.01 to 0.04 parts H2SO496%. Typically, the diluted acid mixture comprises 2.5 parts H2O and 0.03 parts H2SO496%, and the acid washing is performed at an elevated temperature in the range of approximately 77°C to 93°C to increase reactivity. Preferably, the acid washing is performed at an elevated temperature of 80°C for approximately 35 minutes.

[0025] By incorporating a second stage NaOH leaching step with low chemical consumption, the carbon content of the final purified graphite product can be increased to 99.98%.

[0026] Throughout the specification, unless the context otherwise requires, the word “comprise” or variations such as “comprises” or “comprising” will be understood to mean the inclusion of a specified integer or group of integers, but not the exclusion of another integer or group of integers. Likewise, the word “preferably” or variations such as “preferred” will be understood to mean that a specified integer or group of integers is preferred but not essential to the operation of the invention. Brief explanation of the drawing

[0027] The characteristics of the present invention will be better understood from the following detailed description of several specific embodiments of a method for producing refined graphite given merely as examples with reference to the accompanying drawings, wherein: FIG. 1 illustrates a typical manufacturing process for producing refined graphite; FIG. 2 is a process flow diagram illustrating a first embodiment of a method for producing purified spherical graphite according to the present invention; FIG. 3 is a process flow diagram illustrating a second embodiment of a method for manufacturing purified spherical graphite according to the present invention. Specific details for implementing the invention

[0028] The manufacturing process of purified spherical graphite (SPG) includes the steps of pulverizing, rounding, homogenizing, and purifying flake graphite, as illustrated in FIG. 1. Purification is traditionally carried out by chemical purification, followed by dehydration, drying, sorting, and packaging of the finished SPG product.

[0029] As illustrated in FIG. 2, a first embodiment of the method (10) for producing purified graphite according to the present invention comprises the step of applying a spherical graphite material (12) to a caustic bake as shown in step (14). The starting material (12) is typically 1 part SPG to 20 parts of unrefined spherical graphite material. Preferably, the step of applying the spherical graphite material to the caustic bake comprises mixing the spherical graphite material with liquid NaOH (50%) and heating the mixture in a furnace or kiln. Typically, the mixture contains 0.3 parts water and 0.66 parts NaOH. Preferably, the mixture is heated to a temperature of 400°C to 550°C for approximately 25 to 45 minutes. The weight of the material was checked before and after heat treatment at different temperatures. As a result, it was found that the graphite does not burn at a process temperature of 500°C if the dwelling time does not exceed about 40 minutes. More preferably, the mixture is heated to 500°C for 30 minutes. After caustic baking, the material has a solid consistency (H2O evaporates from NaOH).

[0030] The method further comprises a step of releasing any residual caustic agent using water in step (16). Preferably, the step of releasing any residual caustic agent comprises immersing the solid material in water and dissolving any residual caustic agent for about 10 to 45 minutes. Typically, this is performed in hot water, for example, water heated to 40°C to 85°C. Typically, 1 part of spherical graphite material is immersed in 3 to 20 parts of H2O. In this embodiment, 1 part of spherical graphite material is immersed in 17 parts of H2O at about 85°C for 30 minutes.

[0031] Preferably, after the step of releasing any residual caustic agent, the material is washed and filtered in step (18). Typically, this is done at ambient temperature for about 30 minutes using 10 parts H2O.

[0032] The above method further comprises the step of applying the material to acid washing in step (20). Typically, the step of applying the material to acid washing comprises washing the material with a diluted acid mixture containing water and H2SO4. Typically, the diluted acid mixture contains 4 parts H2O and 0.17 parts H2SO4. Preferably, the acid washing is performed at an elevated temperature in the range of approximately 77°C to 93°C to increase reactivity. More preferably, the acid washing is performed at an elevated temperature of 85°C. Typically, the material is applied to acid washing for about 30 minutes.

[0033] The above method further comprises a step (22) of filtering the material and a step (24) of final washing to yield an intermediate spherical purified graphite (SPG) product (28). Preferably, the steps of filtering and washing the material include filtering the material at ambient temperature and washing it with water at elevated temperature, respectively. Typically, the final washing with water is performed at 85°C for 30 minutes using 20 parts H2O.

[0034] Advantageously, this process yields an intermediate spherical purified graphite (SPG) product having a final purity of 99.96%C at step (28).

[0035] The method of FIG. 2 further comprises a second stage, beginning with step (34) of applying the intermediate SPG product (28) to caustic leaching. Preferably, the caustic leaching step (34) comprises immersing the intermediate SPG product (28) in 0.2 parts NaOH (50%) and 4 parts H2O. Preferably, the caustic leaching step (34) is performed for about 1.5 to 2.5 hours at a relatively low temperature in the range of about 77°C to 93°C. More preferably, the caustic leaching step is performed for about 120 minutes at 80°C.

[0036] The above method further includes a step of releasing any residual caustic agent using water in step (36). Preferably, the step of releasing any residual caustic agent includes immersing the material in H2O at ambient temperature for about 30 minutes.

[0037] Preferably, after the step of releasing any residual caustic agent, the material is washed and filtered in step (38). Preferably, in step (38), neutral washing is performed at ambient temperature for about 30 minutes using 10 parts H2O.

[0038] The method further comprises the step of applying the intermediate SPG product to a secondary acid wash in step (40). Typically, the step of applying the material to the secondary acid wash comprises washing the material with a diluted acid mixture containing water and H2SO4, wherein a very low concentration of H2SO4 is sufficient (preferably 0.01 to 0.04 parts H2SO4 and 4 parts water). Typically, the diluted acid mixture contains 4 parts H2O and 0.03 parts H2SO4. Preferably, the secondary acid wash is performed at an elevated temperature in the range of approximately 77°C to 93°C to increase reactivity. More preferably, the secondary acid wash is performed at an elevated temperature of 85°C for approximately 35 minutes.

[0039] The above method further comprises the step of filtering the intermediate SPG product in step (42), and finally washing and neutralizing with water in step (44) to yield the final SPG product in step (46). Preferably, the steps of filtering and washing the material each comprise filtering the material at ambient temperature and washing it with water at elevated temperature. Typically, the final washing with water is performed at 85°C for 30 minutes using 10 parts H2O.

[0040] By incorporating a second stage caustic leaching step with low chemical consumption, the carbon content of the final SPG product in step (46) can be increased to 99.98%.

[0041] Test work

[0042] The parameters listed in Table 1 are for a first embodiment of the method (30) for purifying SPG exemplified in FIG. 2.

[0043] The method of FIG. 2 consists of two parts, and therefore the parameter table of Table 1 is shown in two parts. Part 1 corresponds to the first stage of the method of FIG. 2. Part 2 corresponds to the second stage of the method of FIG. 2, which includes caustic leaching.

[0044] [Table 1]

[0045] Desirable parameters for the method (30) of FIG. 2

[0046]

[0047] FIG. 3 illustrates a second embodiment of a method (50) for producing purified spherical graphite. This second embodiment of the method of the present invention is similar in many respects to the method of FIG. 2, and thus similar reference numbers will be used to identify essentially identical method steps, which will not be described again in detail. As with the method (30) of FIG. 2, this is also a two-stage process, but has less chemical consumption and lower water consumption.

[0048] As in the first embodiment, the second embodiment of the method (50) of FIG. 3 begins with 1 part of unrefined SPG graphite in step (12). This is followed by a mixing step (13) comprising mixing the graphite with NaOH. Preferably, the mixture comprises 0.5 to 0.7 parts of NaOH and 0.2 to 0.4 parts of tap water. More preferably, the mixture comprises 0.3 parts of (tap) water and 0.66 parts of NaOH. The method (50) also comprises a step (14) of applying the spherical graphite material to a caustic bake, wherein the mixture of the spherical graphite material and NaOH is heated to a temperature of 400°C to 550°C for approximately 25 to 45 minutes. More preferably, in the caustic bake step (14), the mixture is heated to 500°C for approximately 30 minutes.

[0049] The caustic bake step (14) is followed by a caustic agent release step (16) in which any residual caustic agent is dissolved in a water bath to cool and release impurities soluble in water. Preferably, in this embodiment, the caustic agent release step (16) comprises immersing the solid material in water and dissolving any residual caustic agent for about 5 to 15 minutes. Typically, this is performed in hot water, for example, water heated to 35°C to 45°C. Typically, 1 part of the spherical graphite material is immersed in 2 to 5 parts of H2O. In this embodiment, 1 part of the spherical graphite material is immersed in 3.3 parts of H2O at about 40°C for 10 minutes.

[0050] Preferably, after the caustic agent release step (16), the material is washed and filtered in the washing neutral step (18). Typically, this is performed at ambient temperature for about 5 to 10 minutes using 2.0 to 7 parts H2O. In the example illustrated, the washing neutral step (18) is performed at ambient temperature for about 5 minutes using 2.3 parts H2O. After 10 minutes, the slurry is filtered until the pH value becomes neutral. After the caustic bake, the material has a solid roughness and is then subjected to a primary acid wash in step (20). The filter cake material is placed in a stirred reactor filled with diluted acid while wet. Gentle stirring supports the process of dissolving impurities. The primary acid wash is preferably performed at elevated temperature with a mixture of 2.0 to 5.0 parts H2O and 0.15 to 0.25 parts H2SO496%. Preferably, the filter cake material is maintained in a stirred reactor for 25 to 45 minutes, and the temperature is maintained at 70°C to 90°C. More preferably, the first acid washing step (20) is performed at 80°C for 35 minutes with 4.0 parts H2O and 0.17 parts H2SO496%.

[0051] In step (22), the washing neutralization of the material is used to separate the acid and dissolved impurities. The washing neutralization step (22) preferably involves washing the acid-washed graphite material in 3 to 7 parts H2O for 3 to 7 minutes while stirring at ambient temperature. Typically, the washing neutralization step (22) involves washing the acid-washed graphite material in 5 parts H2O for 5 minutes while stirring at ambient temperature. Afterward, the material is applied to a water bath having 2 to 8 parts H2O for 20 to 40 minutes at ambient temperature to further remove impurities in step (24). Preferably, the water bath (24) is performed with 7 parts H2O for 40 minutes at ambient temperature. The washing neutralization step (22) must be repeated until the pulp becomes pH neutral. The final result of this first stage of the method (50) is to yield an intermediate spherical purified graphite (SPG) product (28) having a purity of 99.4%C to 99.9%C.

[0052] The first stage of the method (50) is basically the same as in the first embodiment (method (30) of FIG. 2), except that an additional mixing step (13) is introduced before the caustic bake in this case. The first stage is performed with tap water, and the second stage is performed with deionized water.

[0053] In the second stage, the method (50) of FIG. 3 further comprises the step of applying the intermediate SPG product (28) to caustic leaching in step (34). Preferably, the caustic leaching step (34) comprises immersing the intermediate SPG product (28) in 0.1 to 0.3 parts NaOH (50%) and 2.0 to 4.0 parts H2O. More preferably, the caustic leaching step (34) comprises immersing the intermediate SPG product (28) in 0.2 parts NaOH (50%) and 2.5 parts H2O. Preferably, the caustic leaching step (34) is performed for about 1.5 to 2.5 hours at a relatively low temperature in the range of approximately 77°C to 93°C. More preferably, the caustic leaching step is performed for about 120 minutes at 80°C. Although the concentration of NaOH is low, it is sufficient to remove small amounts of impurities remaining in the graphite. This process will likely be supported by a liquid phase that enables better mobility of Na+ ions. Due to the lower temperature, the reactivity is slower; therefore, a reaction time of 2 hours was identified as an appropriate duration.

[0054] After caustic leaching, the caustic water containing dissolved impurities needs to be neutralized by washing and filtration in step (35). The washing and neutralization step (35) preferably involves washing the leached graphite material in 3 to 7 parts H2O for 3 to 7 minutes while stirring at ambient temperature. Typically, the washing and neutralization step (35) involves washing the acid-washed graphite material in 5 parts deionized H2O for 5 minutes while stirring at ambient temperature. Then, in step (36), to further remove impurities, the material is applied to a water bath having 2 to 8 parts H2O for 20 to 40 minutes at an elevated temperature. Preferably, the water bath (36) is performed with 3.5 parts H2O for 30 minutes at 80°C. The water bath (36) supports the dissolution of impurities that dissolve more slowly and the release of any residual caustic agent. The washing neutralization step may need to be repeated until the pulp becomes pH neutral (see additional washing neutralization step (38)).

[0055] The method (50) further comprises the step of applying the intermediate SPG product from step (40) to a secondary acid wash. Typically, the secondary acid wash step (40) comprises washing the material with a diluted acid mixture containing water and H2SO4, where a very low concentration of H2SO4 is sufficient. The filter cake is placed in a stirred reactor filled with the diluted acid while wet. The acid concentration is very low because the amount of impurities to be dissolved is very small. Stirring supports the process of dissolving the impurities. Preferably, the diluted acid mixture contains 2.0 to 4.0 parts H2O and 0.01 to 0.04 parts H2SO496%. Typically, the diluted acid mixture contains 2.5 parts H2O and 0.03 parts H2SO496%. Preferably, the secondary acid wash is performed at an elevated temperature in the range of approximately 77°C to 93°C to increase reactivity. More preferably, the secondary acid wash is performed at an elevated temperature of 85°C for about 35 minutes.

[0056] The method (50) further comprises additional steps of washing and neutralizing the intermediate SPG product in step (42), and finally washing and neutralizing with water in steps (44 and 45) to yield a final SPG product with a purity of 99.95% or higher in step (46). Preferably, the steps of neutralizing and washing the material include a washing and neutralizing step (42) of the material at ambient temperature and a water bath (44) at elevated temperature, respectively. The washing and neutralizing step (42) preferably comprises washing the graphite material in 3 to 10 parts H2O at ambient temperature with stirring 3 x 10 / 3 every minute. Typically, the washing and neutralizing step (42) comprises washing the acid-washed graphite material in 3.5 parts H2O for 5 minutes with stirring at ambient temperature. Afterward, the material is applied to another water bath (44) having 2 to 10 parts H2O at elevated temperature for 20 to 40 minutes to further remove impurities. Preferably, the water bath (42) is performed at 80°C for 30 minutes with 3.5 parts H2O.

[0057] An additional washing neutralization step (45) may be required until the graphite material becomes pH neutral. The washing neutralization step (45) preferably includes washing the graphite material in 3 to 10 parts H2O with stirring every 5 minutes at ambient temperature.

[0058] Final filtration is also a dehydration step before placing the graphite into the dryer. The recommended temperature for drying is relatively low (150°C or lower) to prevent particle damage that may occur if high temperatures are applied.

[0059] The second stage of this method (50) is basically the same as the first method (30), except that additional washing neutralization steps (35, 42 and 45) are introduced.

[0060] While the embodiments described above describe a method for refining graphite using refined spherical graphite (SPG) as a starting material, the same chemical refining process can also be used to use flake graphite as a starting material or to refine black mass, which is a residue generated from the recycling of lithium-ion batteries. Black mass is a residue remaining from conventional wet smelting processes that recover useful metals. The refining process increases the grade from 30-50% carbon to +99% carbon for reuse in the graphite market.

[0061] Since preferred embodiments of a method for purifying SPG have been described in detail, it will be apparent that the described embodiments provide numerous advantages over the prior art, including the following:

[0062] (i) The method is relatively simple using standard industrial process steps, but can achieve a purity of 99.95% or higher.

[0063] (ii) The amount of caustic agent and acid used in the purification process is significantly reduced compared to the prior art method, and the process time is also shortened.

[0064] (iii) The chemicals used in the method are more environmentally sustainable than those in the prior art method and do not harm the spherical graphite product.

[0065] It will be apparent to those skilled in the art that, in addition to the embodiments described above, various modifications and improvements can be made to said embodiments without departing from the basic concept of the invention. For example, the method may involve a multi-stage and multi-parameter process (temperature, residence time, concentrations of acid and caustic agent, volume of wash water, etc.), and thus sophisticated optimization will undoubtedly lead to further improvements in purity and cost reduction. Furthermore, although the process is described as applying unrefined SPG, it is not limited to spherical graphite and may be applied using other types of flake graphite as precursor materials, such as flake graphite concentrates or selected fractions of by-products from spherical graphite production. Accordingly, it will be recognized that the scope of the invention is not limited to the specific embodiments described.

Claims

Claim 1 A method for producing purified graphite, comprising the steps of: applying a graphite material to a sodium hydroxide (NaOH) bake; releasing residual NaOH using water; applying the graphite material to a primary acid wash; neutralizing and washing the acid-washed graphite material to deliver an intermediate purified graphite product; applying the intermediate purified graphite product to an NaOH leach at 72°C to 93°C; releasing residual NaOH from the intermediate purified graphite product using water; applying the intermediate purified graphite product to an acid wash; and neutralizing and washing the intermediate purified graphite product to deliver a final purified graphite product. Claim 2 A method for producing purified graphite according to claim 1, wherein NaOH leaching occurs at a temperature in the range of 77°C to 93°C. Claim 3 A method for producing purified graphite according to claim 1, wherein the step of applying the graphite material to the NaOH bake comprises mixing the graphite material with liquid NaOH (50 wt%) and heating the mixture in a furnace. Claim 4 A method for manufacturing purified graphite according to paragraph 3, wherein the mixture is heated to a temperature of 450°C to 550°C. Claim 5 A method for producing purified graphite according to claim 4, wherein the mixture is heated for 25 to 45 minutes. Claim 6 A method for producing purified graphite according to claim 5, wherein the mixture is heated to 500°C for 30 minutes. Claim 7 A method for producing purified graphite according to claim 1, wherein the step of releasing residual NaOH comprises immersing the graphite material in hot water. Claim 8 A method for producing purified graphite according to claim 1, wherein, after the step of releasing the residual NaOH, the graphite material is washed and filtered. Claim 9 A method for producing purified graphite according to claim 8, wherein the above material is washed and filtered for 5 to 10 minutes at ambient temperature using 2.0 to 7.0 parts by weight of H2O. Claim 10 A method for producing purified graphite according to claim 1, wherein the step of applying the graphite material to a primary acid wash comprises washing the graphite material with a diluted acid mixture containing water and H2SO4. Claim 11 A method for producing purified graphite according to claim 10, wherein the diluted acid mixture comprises 2.0 to 5.0 parts by weight of H2O and 0.15 to 0.25 parts by weight of 96% by weight of H2SO4. Claim 12 A method for producing purified graphite according to claim 11, wherein the diluted acid mixture comprises 4.0 parts by weight of H2O and 0.17 parts by weight of 96% by weight of H2SO4. Claim 13 A method for producing purified graphite according to claim 10, wherein the first acid washing is performed at a temperature in the range of 70°C to 90°C to increase reactivity. Claim 14 A method for manufacturing purified graphite according to claim 13, wherein the first acid washing is performed for 25 to 45 minutes at a temperature of 80°C. Claim 15 A method for manufacturing purified graphite according to claim 1, wherein the steps of neutralizing and washing the acid-washed graphite material each include filtering the material at ambient temperature and finally washing it with water at elevated temperature. Claim 16 A method for producing purified graphite according to claim 15, wherein the final washing using the above water takes place at 85°C for 30 minutes using 20 parts by weight of H2O. Claim 17 A method for producing purified graphite according to claim 1, wherein the step of neutralizing and washing the material comprises washing the acid-washed graphite material in 3 to 7 parts by weight of H2O for 3 to 7 minutes while stirring at ambient temperature. Claim 18 A method for producing purified graphite according to claim 1, wherein the step of applying the intermediate purified graphite product to NaOH leaching comprises immersing the intermediate purified graphite product in 0.1 to 0.3 parts by weight of NaOH (50 wt%) and 2.0 to 4.0 parts by weight of H2O. Claim 19 A method for producing purified graphite according to claim 1, wherein the residence time of the NaOH leaching is 1.5 to 2.5 hours. Claim 20 A method for producing purified graphite according to claim 1, wherein the intermediate purified graphite product is neutralized and washed before being applied to an acid washing step. Claim 21 A method for producing purified graphite according to claim 20, wherein the only reagent used is NaOH in the NaOH bake and NaOH leaching steps and H2SO4 in the acid washing step. Claim 22 A method for producing purified graphite according to claim 21, wherein the intermediate purified graphite product is finally washed in a water bath and neutralized with water after an acid washing step. Claim 23 A method for producing purified graphite according to claim 1, wherein the acid washing of the intermediate purified graphite product is performed with a diluted acid mixture comprising 2.0 to 4.0 parts by weight of H2O and 0.01 to 0.04 parts by weight of 96% by weight of H2SO4. Claim 24 A method for producing purified graphite according to claim 23, wherein the diluted acid mixture comprises 2.5 parts by weight of H2O and 0.03 parts by weight of 96% by weight of H2SO4, and the acid washing is performed at an elevated temperature in the range of 77°C to 93°C to increase reactivity. Claim 25 A method for manufacturing purified graphite according to claim 24, wherein the acid washing is performed for 35 minutes at a temperature of 80°C.

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