Battery-grade carbon material and green purification method thereof

Abstract

The invention belongs to the technical field of preparation of battery-grade carbon materials, and discloses a battery-grade carbon material and a green purification method thereof.The method comprises the steps that a to-be-purified carbon material is subjected to deliming treatment through a citric acid deliming agent, then washing and separating are conducted, and a pre-deliming treatment carbon material is obtained; wherein the citric acid deliming agent is prepared from the following components in percentage by mass: 5 to 15 percent of citric acid, 0.1 to 0.5 percent of rhamnolipid and the balance of water; carrying out deliming treatment on the carbon material subjected to pre-deliming treatment by using an ionic liquid deliming agent, and then washing, separating and drying to obtain a battery-grade carbon material; wherein 1-butyl-3-methylimidazolium hydrogen sulfate is adopted as the ionic liquid. The biological acid and the ionic liquid are used as the deashing detergent, so that the use of conventional strong acid and strong alkali is avoided, and the manufacturing cost of equipment and the environmental protection cost can be effectively reduced; meanwhile, valuable substances in the detergent and the ash are recycled, so that recycling of the ash and regeneration of the detergent are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing battery-grade carbon materials, and particularly relates to a battery-grade carbon material and a green purification method thereof. Background Art

[0002] Due to the large-scale grid connection of renewable energy for power generation, the demand for power grid frequency modulation and peak shaving is increasing day by day. As an important part of the battery, the market demand for carbon materials, including conductive carbon black, artificial graphite, supercapacitor carbon, etc., has exploded. However, most carbon materials have a certain amount of ash in their precursors (biomass, minerals), and they cannot meet the battery-grade purity requirements without purification treatment. Therefore, the purification of such carbon materials is a technical problem with a wide range of impacts. Currently, the main purification methods of carbon materials are as follows:

[0003] 1. Acid-base washing method

[0004] The current mainstream method. By using a strong base (such as NaOH) to remove acidic impurities such as silicates, and then using a strong acid (such as HCl, HNO3) to dissolve metal oxide impurities, the purity of artificial graphite can be increased to 99.5%. However, it is necessary to be equipped with wastewater treatment facilities, and there is an environmental risk in the acid mist emission. It is also possible to directly use hydrofluoric acid for washing, but the operation of hydrofluoric acid is extremely dangerous, highly toxic, and the waste liquid is extremely difficult to treat.

[0005] 2. High-temperature roasting method

[0006] Vaporize impurities at 2700 - 3000 °C, which is suitable for refining high-purity (≥99.5%) materials. However, when the loading capacity of equipment such as Acheson furnaces is large, the temperature uniformity is poor, and the energy consumption is extremely high (more than 15,000 kWh of electricity is consumed per ton of product).

[0007] 3. Halogen gas-assisted purification

[0008] React with halogen gases (such as Cl2, CF4) at a high temperature of 1000 °C to oxidize metal impurities, and the purity can reach more than 99.5%. However, halogen gases are highly toxic, and strict sealing and tail gas treatment systems are required; moreover, the cost of high-temperature reactions is very high.

[0009] In summary, the current purification of battery-grade carbon materials relies on strong acids, strong bases, and highly toxic media, and the energy consumption problems of some processes are also very serious; in addition, a large amount of wastewater and waste gas are extremely difficult to treat, which is neither green nor economical. There is an urgent need to develop a green purification method that does not rely on hazardous chemicals and is recyclable. Summary of the Invention

[0010] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a battery-grade carbon material and a green purification method thereof, and the conditions for purifying the battery-grade carbon material in the present invention are relatively mild and environmentally friendly.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] A green purification method for battery-grade carbon materials includes the following processes:

[0013] The carbon material to be purified is subjected to deashing treatment with a citric acid deashing agent, followed by washing and separation to obtain a pre-deashed carbon material; wherein, graded by mass fraction, the citric acid deashing agent contains: 5% - 15% citric acid, 0.1% - 0.5% rhamnolipid, and the balance is water;

[0014] The pre-deashed carbon material is subjected to deashing treatment with an ionic liquid deashing agent, followed by washing, separation, and drying to obtain battery-grade carbon materials; wherein, the ionic liquid used is 1-butyl-3-methylimidazolium hydrogen sulfate.

[0015] Preferably, when the carbon material to be purified is subjected to deashing treatment with the citric acid deashing agent, the dosage ratio of the carbon material to be purified to the citric acid deashing agent is 25 - 50 mg / mL.

[0016] Preferably, when the carbon material to be purified is subjected to deashing treatment with the citric acid deashing agent, the carbon material to be purified and the citric acid deashing agent are mixed and stirred, and the deashing treatment is carried out at 60 - 90 °C.

[0017] Preferably, when the carbon material to be purified is subjected to deashing treatment with the citric acid deashing agent, the stirring speed is 200 - 400 rpm, and the treatment time is 1 - 3 hours.

[0018] Preferably, when the pre-deashed carbon material is subjected to deashing treatment with the ionic liquid deashing agent, the dosage ratio of the pre-deashed carbon material to the ionic liquid is 25 - 50 mg / mL.

[0019] Preferably, when the pre-deashed carbon material is subjected to deashing treatment with the ionic liquid deashing agent, the pre-deashed carbon material and the ionic liquid are mixed and stirred, and the deashing treatment is carried out at 60 - 90 °C.

[0020] Preferably, when the pre-deashed carbon material is subjected to deashing treatment with the ionic liquid deashing agent, the stirring speed is 200 - 400 rpm, and the treatment time is 1 - 3 hours.

[0021] Preferably, after the carbon material to be purified is subjected to deashing treatment, washing, and separation with the citric acid deashing agent, a primary waste liquid is obtained. The primary waste liquid is subjected to alkali addition treatment to form a hydroxide precipitate, followed by filtration to obtain a secondary waste liquid and a hydroxide precipitate. The obtained hydroxide precipitate is calcined to obtain a metal oxide; the secondary waste liquid is subjected to electrodialysis treatment to obtain a citric acid-metal complex with a molecular weight > 200 Da and regenerated citric acid, and the regenerated citric acid is concentrated to the concentration required for the citric acid deashing agent;

[0022] After subjecting the pre - deashing treated carbon material to deashing treatment with an ionic liquid deashing agent, washing, and separation, tertiary waste liquid is obtained; the tertiary waste liquid is acid - treated and separated to obtain silica gel and quaternary waste liquid; the quaternary waste liquid is subjected to electrodialysis treatment to separate out the ionic liquid deashing agent.

[0023] Preferably, the base is an aqueous sodium hydroxide solution with a concentration of 0.1 - 0.5 mol / L, the acid is hydrochloric acid with a concentration of 0.1 - 0.5 mol / L, and when the tertiary waste liquid is acid - treated, the pH is adjusted to 2 - 3.

[0024] The present invention also provides a battery - grade carbon material obtained by the green purification method as described above.

[0025] The present invention has the following beneficial effects:

[0026] The green purification method of the battery - grade carbon material of the present invention uses bio - acid and ionic liquid as deashing detergents. Among them, citric acid, as a bio - based weak acid, has the advantages of high efficiency and environmental protection in removing ash (especially metal oxides). Principle: Citric acid can release hydrogen ions to directly dissolve metal oxides to form metal cations; the metal cations then form stable complexes with citrate ions to achieve the removal of metal oxides. Using the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogen sulfate ([BMIM][HSO4]), silicates can be dissolved. Therefore, the present invention can remove metal oxide ash and non - metal oxide ash in the carbon material to be purified to the greatest extent, and has a good deashing effect. And the present invention uses bio - acid citric acid and ionic liquid as deashing detergents, avoiding the use of conventional strong acids and strong bases, which can effectively reduce the manufacturing cost of equipment and environmental protection cost; at the same time, valuable substances in the detergent and ash are recovered, realizing the reuse of ash and the regeneration of the detergent. It meets the requirements of circular economy and green economy and is expected to completely replace the traditional acid - base washing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Process flow chart of the green purification method of the battery - grade carbon material of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components described and shown in the accompanying drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0029] The present invention innovatively uses citric acid and ionic liquid as deashing detergents and designs a complete regeneration scheme for the detergents. Specifically, the green purification method for battery-grade carbon materials of the present invention includes the following steps:

[0030] Step 1. Removing metal oxide ash:

[0031] Step 1.1: Mix citric acid, rhamnolipid, and pure water evenly by stirring to obtain a citric acid deashing agent; classified by mass fraction, the citric acid deashing agent contains: 5% - 15% citric acid, 0.1% - 0.5% rhamnolipid, and the balance is water;

[0032] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 25 - 50 mg / mL, and stir at a stirring rate of 200 - 400 rpm at 60 - 90 °C for 1 - 3 hours for deashing treatment, then wash and separate to obtain a pre-deashed carbon material and a primary waste liquid. Then, add a 0.1 - 0.5 mol / L sodium hydroxide aqueous solution to the primary waste liquid to precipitate metal cations to form hydroxide precipitates, then filter to obtain a secondary waste liquid and metal hydroxide precipitates. Calcinate the obtained hydroxide precipitates to obtain metal oxides; subject the secondary waste liquid to electrodialysis treatment through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid, and concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent for use in the process of preparing the citric acid deashing agent in Step 1.1;

[0033] Step 2. Removing non-metal oxide ash:

[0034] Mix the pre - deashing treated carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogen sulfate at a dosage ratio of 25 - 50 mg / mL, and stir at a stirring rate of 200 - 400 rpm at 60 - 90 °C for 1 - 3 hours for deashing treatment. Then wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.1 - 0.5 mol / L hydrochloric acid to the tertiary waste liquid to adjust the pH of the tertiary waste liquid to 2 - 3 to form silica gel precipitate, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate out the ionic liquid deashing agent; after drying, the silica gel can be used as an adsorbent or ceramic raw material.

[0035] All the following examples are based on carbon powder with an initial ash content of 8% and a specific surface area of 200 m 2 / g, which is sieved through a 300 - mesh screen after ball - milling.

[0036] Example 1

[0037] The green purification method of the battery - grade carbon material in this example includes the following steps:

[0038] Step 1. Remove metal oxide ash:

[0039] Step 1.1: Mix citric acid, rhamnolipid and pure water and stir evenly to obtain a citric acid deashing agent; classified by mass fraction, the citric acid deashing agent contains: 10% citric acid, 0.3% rhamnolipid, and the balance is water;

[0040] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 30 mg / mL, and stir at a stirring rate of 300 rpm at 80 °C for 2 hours for deashing treatment. Then wash and separate to obtain pre - deashing treated carbon material and primary waste liquid. Then add 0.5 mol / L sodium hydroxide aqueous solution to the primary waste liquid for metal cation precipitation to form hydroxide precipitate. Then filter to obtain secondary waste liquid and metal hydroxide precipitate. Calcinate the obtained metal hydroxide precipitate to obtain metal oxide; perform electrodialysis treatment on the secondary waste liquid through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid. Concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent and use it for the process of preparing the citric acid deashing agent in Step 1.1;

[0041] Step 2. Remove non - metal oxide ash:

[0042] Mix the pre - deashed carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogen sulfate at a dosage ratio of 30 mg / mL, and stir at a stirring rate of 300 rpm at 80 °C for 2 hours for deashing treatment. Then, wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.3 mol / L hydrochloric acid to the tertiary waste liquid, adjust the pH of the tertiary waste liquid to 3 to form silica gel precipitate, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate out the ionic liquid deashing agent; the silica gel can be used as an adsorbent after drying.

[0043] Characterization tests were carried out on the purified carbon material obtained in this example. The results showed that the ash content was 2.3%, and the specific surface area was 200 m 2 / g. The ash content decreased significantly, and the specific surface area did not decrease significantly, indicating that the deashing process did not affect the original pore structure of the material.

[0044] Example 2

[0045] The green purification method of the battery - grade carbon material in this example includes the following steps:

[0046] Step 1. Remove metal oxide ash:

[0047] Step 1.1: Mix citric acid, rhamnolipid and pure water and stir evenly to obtain a citric acid deashing agent; by mass - fraction grading, the citric acid deashing agent contains: 15% citric acid, 0.5% rhamnolipid, and the balance is water;

[0048] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 35 mg / mL, and stir at a stirring rate of 400 rpm at 90 °C for 1 hour for deashing treatment. Then, wash and separate to obtain pre - deashed carbon material and primary waste liquid. Then, add 0.4 mol / L sodium hydroxide aqueous solution to the primary waste liquid for metal cation precipitation to form hydroxide precipitate, and then filter to obtain secondary waste liquid and metal hydroxide precipitate. Calcinate the obtained metal hydroxide precipitate to obtain metal oxide; perform electrodialysis treatment on the secondary waste liquid through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid, and concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent for the process of preparing the citric acid deashing agent in Step 1.1;

[0049] Step 2. Remove non - metal oxide ash:

[0050] Mix the pre - deashed carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogen sulfate at a dosage ratio of 35 mg / mL, and stir at a stirring rate of 400 rpm at 60 °C for 1 hour for deashing treatment. Then, wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.1 - 0.5 mol / L hydrochloric acid to the tertiary waste liquid, adjust the pH of the tertiary waste liquid to 3 to form silica gel precipitation, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate the ionic liquid deashing agent; after drying, the silica gel can be used as an adsorbent or ceramic raw material.

[0051] Characterization tests were carried out on the purified carbon material obtained in this example. The results showed that the ash content was 1.5%, and the specific surface area was 210 m 2 / g. The ash content was significantly reduced, and the specific surface area increased somewhat, indicating that the purification method of the present invention also improved the original pore structure.

[0052] Example 3

[0053] The green purification method of the battery - grade carbon material in this example includes the following steps:

[0054] Step 1. Remove metal oxide ash:

[0055] Step 1.1: Mix citric acid, rhamnolipid, and pure water and stir evenly to obtain a citric acid deashing agent; classified by mass fraction, the citric acid deashing agent contains: 13% citric acid, 0.4% rhamnolipid, and the balance is water;

[0056] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 40 mg / mL, and stir at a stirring rate of 350 rpm at 85 °C for 1.5 hours for deashing treatment. Then, wash and separate to obtain pre - deashed carbon material and primary waste liquid. Then, add 0.3 mol / L sodium hydroxide aqueous solution to the primary waste liquid for metal cation precipitation to form hydroxide precipitation. Then, filter to obtain secondary waste liquid and metal hydroxide precipitation. Calcinate the obtained metal hydroxide precipitation to obtain metal oxide; perform electrodialysis treatment on the secondary waste liquid through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid. Concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent for the process of preparing the citric acid deashing agent in Step 1.1;

[0057] Step 2. Remove non - metal oxide ash:

[0058] Mix the pre - deashing treated carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogen sulfate at a dosage ratio of 40 mg / mL, and stir at a stirring rate of 350 rpm at 65 °C for 1.5 hours for deashing treatment. Then, wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.1 - 0.5 mol / L hydrochloric acid to the tertiary waste liquid, adjust the pH of the tertiary waste liquid to 2.5 to form silica gel precipitation, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate the ionic liquid deashing agent; after drying, the silica gel can be used as an adsorbent or ceramic raw material.

[0059] Characterization tests were carried out on the purified carbon material obtained in this example. The results showed that the ash content was 1.9%, and the specific surface area was 200 m 2 / g. The ash content decreased significantly, and the specific surface area did not decrease significantly, indicating that the deashing process did not affect the original pore structure of the material.

[0060] Example 4

[0061] The green purification method of the battery - grade carbon material in this example includes the following steps:

[0062] Step 1. Remove metal oxide ash:

[0063] Step 1.1: Mix citric acid, rhamnolipid, and pure water and stir evenly to obtain a citric acid deashing agent; classified by mass fraction, the citric acid deashing agent contains: 8% citric acid, 0.2% rhamnolipid, and the balance is water;

[0064] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 45 mg / mL, and stir at a stirring rate of 250 rpm at 60 - 90 °C for 2.5 hours for deashing treatment. Then, wash and separate to obtain pre - deashing treated carbon material and primary waste liquid. Then, add 0.2 mol / L sodium hydroxide aqueous solution to the primary waste liquid for metal cation precipitation to form hydroxide precipitation, and then filter to obtain secondary waste liquid and metal hydroxide precipitation. Calcinate the obtained metal hydroxide precipitation to obtain metal oxide; perform electrodialysis treatment on the secondary waste liquid through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid. Concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent for the process of preparing the citric acid deashing agent in Step 1.1;

[0065] Step 2. Remove non - metal oxide ash:

[0066] Mix the pre - deashed carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogensulfate at a dosage ratio of 45 mg / mL, and stir at a stirring rate of 300 rpm at 70 °C for 3 hours for deashing treatment. Then, wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.1 - 0.5 mol / L hydrochloric acid to the tertiary waste liquid, adjust the pH of the tertiary waste liquid to 2 to form silica gel precipitate, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate out the ionic liquid deashing agent; after drying the silica gel, it can be used as an adsorbent or ceramic raw material.

[0067] Characterization tests were carried out on the purified carbon material obtained in this example. The results showed that the ash content was 2.6%, and the specific surface area was 200 m 2 / g. The ash content decreased significantly, and the specific surface area did not decrease significantly, indicating that the deashing process did not affect the original pore structure of the material.

[0068] Example 5

[0069] The green purification method of the battery - grade carbon material in this example includes the following steps:

[0070] Step 1. Remove metal oxide ash:

[0071] Step 1.1: Mix citric acid, rhamnolipid, and pure water and stir evenly to obtain a citric acid deashing agent; classified by mass fraction, the citric acid deashing agent contains: 6% citric acid, 0.1% rhamnolipid, and the balance is water;

[0072] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 50 mg / mL, and stir at a stirring rate of 200 rpm at 70 °C for 3 hours for deashing treatment. Then, wash and separate to obtain pre - deashed carbon material and primary waste liquid. Then, add 0.1 mol / L sodium hydroxide aqueous solution to the primary waste liquid to precipitate metal cations to form hydroxide precipitate. Then, filter to obtain secondary waste liquid and metal hydroxide precipitate. Calcinate the obtained metal hydroxide precipitate to obtain metal oxide; perform electrodialysis treatment on the secondary waste liquid through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid. Concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent and use it in the process of preparing the citric acid deashing agent in Step 1.1;

[0073] Step 2. Remove non - metal oxide ash:

[0074] Mix the pre - deashed carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogensulfate at a dosage ratio of 50 mg / mL, and stir at a stirring rate of 250 rpm at 75 °C for 2.5 hours for deashing treatment. Then, wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.1 - 0.5 mol / L hydrochloric acid to the tertiary waste liquid, adjust the pH of the tertiary waste liquid to 2 to form silica gel precipitation, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate the ionic liquid deashing agent; after drying, the silica gel can be used as an adsorbent or ceramic raw material.

[0075] Characterization tests were carried out on the purified carbon material obtained in this example. The results showed that the ash content was 2.9%, and the specific surface area was 200 m 2 / g. The ash content was significantly reduced, and the specific surface area did not decrease significantly, indicating that the deashing process did not affect the original pore structure of the material.

[0076] Example 6

[0077] The green purification method of the battery - grade carbon material in this example includes the following steps:

[0078] Step 1. Remove metal oxide ash:

[0079] Step 1.1: Mix citric acid, rhamnolipid, and pure water and stir evenly to obtain a citric acid deashing agent; classified by mass fraction, the citric acid deashing agent contains: 5% citric acid, 0.3% rhamnolipid, and the balance is water;

[0080] Step 1.2: Mix the carbon material to be purified with the citric acid deashing agent at a dosage ratio of 25 mg / mL, and stir at a stirring rate of 300 rpm at 60 °C for 3 hours for deashing treatment. Then, wash and separate to obtain pre - deashed carbon material and primary waste liquid. Then, add 0.3 mol / L sodium hydroxide aqueous solution to the primary waste liquid for metal cation precipitation to form hydroxide precipitation. Then, filter to obtain secondary waste liquid and metal hydroxide precipitation. Calcinate the obtained metal hydroxide precipitation to obtain metal oxide; perform electrodialysis treatment on the secondary waste liquid through a nanofiltration - electrodialysis combined device to obtain a citric acid - metal complex with a molecular weight > 200 Da and regenerated citric acid. Concentrate the regenerated citric acid to the concentration required for the citric acid deashing agent and use it in the process of preparing the citric acid deashing agent in Step 1.1;

[0081] Step 2. Remove non - metal oxide ash:

[0082] Mix the pre - deashing treated carbon material with the ionic liquid 1 - butyl - 3 - methylimidazolium hydrogen sulfate at a dosage ratio of 25 mg / mL, and stir at a stirring rate of 200 rpm at 90 °C for 3 hours for deashing treatment. Then wash and separate to obtain battery - grade carbon material and tertiary waste liquid; dry the battery - grade carbon material; add 0.1 - 0.5 mol / L hydrochloric acid to the tertiary waste liquid to adjust the pH of the tertiary waste liquid to 2.5 to generate silica gel precipitation, and then separate to obtain silica gel and quaternary waste liquid; perform electrodialysis treatment on the quaternary waste liquid through a nanofiltration - electrodialysis combined device to separate out the ionic liquid deashing agent; after drying, the silica gel can be used as an adsorbent or ceramic raw material.

[0083] Characterize and test the purified carbon material obtained in this example. The results show that the ash content is 3.1%, and the specific surface area is 200 m 2 / g. The ash content is significantly reduced, and the specific surface area has no obvious decrease, indicating that the deashing process does not affect the original pore structure of the material.

[0084] In summary, the present invention uses bio - acid and ionic liquid as deashing detergents, avoiding the use of conventional strong acids and strong bases, which can effectively reduce the manufacturing cost of equipment and environmental protection cost; at the same time, recycle valuable substances in the detergent and ash, realizing the reuse of ash and the regeneration of detergent. It meets the requirements of circular economy and green economy and is expected to completely replace the traditional acid - base washing process. Therefore, the present invention well solves the problems that the purification of current battery - grade carbon materials depends on strong acids, strong bases, and highly toxic media, resulting in extremely high requirements for equipment materials, sealing, etc., high equipment investment, and serious energy consumption problems in some processes; in addition, it also solves the problems that a large amount of waste water and waste gas generated by the existing technology are extremely difficult to treat, which is neither green nor economical.

[0085] Obviously, the described embodiments are only partial embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0086] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement without departing from the spirit and scope of the present invention shall be covered by the scope of the present invention.

Claims

1. A green purification method for battery-grade carbon materials, characterized in that: The process includes the following: The carbon material to be purified is deashed with a citric acid deashing agent, and then washed and separated to obtain a pre-deashed carbon material; wherein, the citric acid deashing agent contains, by mass fraction, 5% to 15% citric acid, 0.1% to 0.5% rhamnolipid, and the remainder is water; The pre-deashing carbon material is deashed with an ionic liquid deashing agent, and then washed, separated and dried to obtain a battery-grade carbon material; wherein the ionic liquid is 1-butyl-3-methylimidazole hydrogen sulfate.

2. A green purification method for battery-grade carbon materials according to claim 1, characterized in that: When the carbon material to be purified is deashed with a citric acid deashing agent, the usage ratio of the carbon material to be purified to the citric acid deashing agent is 25-50 mg / mL.

3. A green purification method for battery-grade carbon materials according to claim 1, characterized in that: When the carbon material to be purified is deashed with a citric acid deashing agent, the carbon material to be purified and the citric acid deashing agent are mixed and stirred, and the deashing is performed at 60-90°C.

4. A green purification method for battery-grade carbon materials according to claim 3, characterized in that: When the carbon material to be purified is deashed using a citric acid deashing agent, the stirring speed is 200-400 rpm and the treatment time is 1-3 hours.

5. The green purification method of battery-grade carbon materials according to claim 1, characterized in that: When the pre-deashed carbon material is deashed with an ionic liquid deashing agent, the dosage ratio of the pre-deashed carbon material to the ionic liquid is 25-50 mg / mL.

6. The green purification method of battery-grade carbon materials according to claim 1, characterized in that: When the pre-deashed carbon material is deashed with the ionic liquid deashing agent, the pre-deashed carbon material and the ionic liquid are mixed and stirred and deashed at 60-90°C.

7. A green purification method for battery-grade carbon materials according to claim 6, characterized in that: When the pre-deashing carbon material is deashed with the ionic liquid deashing agent, the stirring speed is 200-400 rpm and the treatment time is 1-3 hours.

8. A green purification method for battery-grade carbon materials according to any one of claims 1 to 7, characterized in that: The carbon material to be purified is deashed, washed and separated with a citric acid deashing agent to obtain a primary waste liquid, the primary waste liquid is treated with alkali to generate a hydroxide precipitate, and then filtered to obtain a secondary waste liquid and a hydroxide precipitate, and the obtained hydroxide precipitate is calcined to obtain a metal oxide; the secondary waste liquid is subjected to electrodialysis treatment to obtain a citric acid-metal complex with a molecular weight>200Da and regenerated citric acid, and the regenerated citric acid is concentrated to the concentration required by the citric acid deashing agent; The pre-deashing carbon material is deashed, washed and separated with an ionic liquid deashing agent to obtain a tertiary waste liquid; the tertiary waste liquid is treated with acid and separated to obtain silica gel and a quaternary waste liquid; the quaternary waste liquid is subjected to electrodialysis to separate the ionic liquid deashing agent.

9. A green purification method for battery-grade carbon materials according to claim 8, characterized in that: The alkali is 0.1-0.5 mol / L sodium hydroxide aqueous solution, and the acid is 0.1-0.5 mol / L hydrochloric acid. When the tertiary waste liquid is treated with acid, the pH is adjusted to 2-3.

10. A battery-grade carbon material obtained by the green purification method according to any one of claims 1 to 9.

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