Method for preparing graphene from graphite leaching residue of waste lithium ion battery

Abstract

The application provides a method for preparing graphene from graphite leaching residue of waste lithium ion batteries, comprising the following steps: obtaining graphite leaching residue by acid leaching of black powder recovered from waste lithium ion batteries; dispersing the graphite leaching residue in an electrolyte, and sequentially performing first electrolysis and second electrolysis; the voltage of the first electrolysis is lower than that of the second electrolysis; taking the upper electrolyte, and performing centrifugal treatment to obtain upper suspension and filter residue; diluting the upper suspension, and performing hydrothermal reaction; and separating and drying the reaction product to obtain reduced graphene oxide. The method has the advantages of simple process, environmental friendliness, low cost, high product added value, high-value recovery of graphite leaching residue, preparation of high-quality reduced graphene oxide without additional addition of oxidizing agents, and excellent application prospect.

Description

Technical Field

[0001] This invention belongs to the field of recycling of retired lithium batteries and resource utilization of solid waste, specifically involving a method for preparing graphene from graphite leaching residue of waste lithium-ion batteries. Background Technology

[0002] The rapid development of the lithium-ion battery industry in recent years has led to an explosive growth in the number of retired lithium-ion batteries. These batteries contain valuable metals such as lithium, nickel, cobalt, and manganese, making them important secondary resources. Without effective recycling, this will result in enormous resource waste, and if harmful components such as organic electrolytes are not treated, it will cause significant environmental pollution. Currently, there are well-established industrial recycling lines for recovering battery cathodes. However, compared to the cathode materials rich in valuable metals, the recycling of anode graphite has been largely neglected. Waste anode graphite contains various metallic and non-metallic impurities, and after thousands of charge-discharge cycles, its structure is severely damaged, making repair and regeneration extremely difficult. Developing it into other functional materials may be a better option.

[0003] Graphene, due to its unique sp... 2 Hybrid structures and excellent physicochemical properties have attracted widespread attention as advantageous new materials in materials science, electronics, and biology. Patent CN115285983 B uses the Hummers method to prepare graphene oxide from waste graphite. While this method can produce graphene oxide, it requires a strong oxidant like potassium permanganate, and the process is complex and lengthy. Patent CN 114291812 A uses a system of concentrated sulfuric acid, nitric acid, and potassium chlorate to prepare graphene from graphite. This method requires a protective atmosphere and also produces NO. x The process involves the release of toxic gases and poses both danger and serious environmental pollution. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a method for preparing graphene from graphite leaching residue of waste lithium-ion batteries. This method has the advantages of simple process, low actual consumption, low processing cost, environmental friendliness, and high product added value.

[0005] To achieve the above objectives, the present invention proposes the following technical solution:

[0006] A method for preparing graphene from graphite leaching residue of waste lithium-ion batteries includes:

[0007] (1) The black powder recovered from waste lithium-ion batteries is acid-leached to obtain graphite leaching residue;

[0008] (2) Disperse the graphite leaching residue in the electrolyte and perform the first electrolysis and the second electrolysis in sequence; the voltage of the first electrolysis is lower than the voltage of the second electrolysis;

[0009] (3) Take the upper electrolyte, centrifuge to obtain the upper suspension and filter residue, dilute the upper suspension and carry out hydrothermal reaction, and the resulting reaction product is separated and dried to obtain reduced graphene oxide.

[0010] Preferably, in step (2), the voltage of the first electrolysis is less than 1V, more preferably 0.3~0.7V; and the time of the first electrolysis is 0.5~24h, more preferably 2~6h.

[0011] Preferably, in step (2), the voltage of the second electrolysis is 1~10V, more preferably 2~4V; and the time of the second electrolysis is 0.5~24h, more preferably 1~4h.

[0012] Preferably, the electrolyte in the electrolyte solution is one or more of sulfuric acid, sulfate, nitrate, and chloride; and the concentration of the electrolyte in the electrolyte solution is 1~5 mol / L.

[0013] Preferably, in step (3), the temperature of the hydrothermal reaction is 90~150℃ and the time of the hydrothermal reaction is 1~12h.

[0014] Preferably, in step (3), the filter residue is returned to step (2) for further electrolysis.

[0015] As a preferred embodiment, the method further includes: after electrolyzing 5 to 10 batches of graphite leaching residue with the electrolyte, filtering the electrolyte, adding alkali to the filtrate to adjust the pH, precipitating, and separating the solid and liquid to obtain liquid and solid.

[0016] Preferably, the liquid obtained from solid-liquid separation is returned to the electrolysis process as an electrolyte, and the obtained solid is used to extract metals.

[0017] Preferably, the solid-liquid ratio of the upper suspension after dilution is 1~5 mg / mL.

[0018] Preferably, in step (2), the second electrolysis process involves ultrasonic treatment of the electrolysis system.

[0019] Compared with the prior art, one or more of the above-mentioned technical solutions can achieve at least one of the following beneficial effects:

[0020] (1) The process is simple, environmentally friendly, low cost, and high added value of the product. The preparation of reduced graphene oxide can be achieved without the need to add an additional oxidant, thus avoiding the use of potassium permanganate in the traditional graphene oxide preparation process.

[0021] (2) The purification and recovery of valuable metals in graphite leaching residue can also be achieved simultaneously during the electrolysis process.

[0022] (3) The electrolysis system is simple and safe, and the electrolyte can be recycled, which can effectively solve the problems of difficult and costly treatment of graphite leaching residue; the prepared reduced graphene oxide is of high quality and has 1 to 3 layers of graphite. Detailed Implementation

[0023] In the process of recycling and processing graphite leaching residue from waste lithium-ion batteries, the applicant discovered that when graphite leaching residue is used as raw material to prepare graphene products by electrolysis followed by hydrothermal treatment, the difficulty is significantly reduced compared to primary graphite materials. Based on this important discovery, the applicant was able to prepare graphene products from negative electrode graphite waste, thereby realizing the high-value utilization of graphite leaching residue from waste lithium-ion batteries, and thus completing this invention.

[0024] Some embodiments of the present invention provide a method for preparing graphene from graphite leaching residue of waste lithium-ion batteries, comprising:

[0025] (1) The black powder recovered from waste lithium-ion batteries is acid-leached to obtain graphite leaching residue;

[0026] (2) Disperse the graphite leaching residue in the electrolyte and perform the first electrolysis and the second electrolysis in sequence; the voltage of the first electrolysis is lower than the voltage of the second electrolysis;

[0027] (3) Take the upper electrolyte, centrifuge to obtain the upper suspension and filter residue, dilute the upper suspension and carry out hydrothermal reaction, and the resulting reaction product is separated and dried to obtain reduced graphene oxide.

[0028] In some preferred embodiments, in step (2), the voltage of the first electrolysis is less than 1V, more preferably 0.3~0.7V; the time of the first electrolysis is 0.5~24h, more preferably 2~6h.

[0029] In a partially preferred embodiment, in step (2), the voltage of the second electrolysis is 1~10V, more preferably 2~4V; the time of the second electrolysis is 0.5~24h, more preferably 1~4h.

[0030] In some preferred embodiments, the electrolyte in the electrolyte solution is one or more of sulfuric acid, sulfate, nitrate, and chloride; the concentration of the electrolyte in the electrolyte solution is 1~5 mol / L.

[0031] In some preferred embodiments, in step (3), the temperature of the hydrothermal reaction is 90~150℃; and the time of the hydrothermal reaction is 1~12h.

[0032] In some preferred embodiments, in step (3), the filter residue is returned to step (2) for further electrolysis.

[0033] In some preferred embodiments, the method further includes: after electrolyzing 5 to 10 batches of graphite leaching residue with the electrolyte, filtering the electrolyte to separate the carbon residue, adding alkali to the filtrate to adjust the pH, precipitating, and separating the solid and liquid to obtain a liquid and a metal hydroxide solid. The obtained liquid can be returned to be used as electrolyte, and the solid can be used to recover metals.

[0034] In some preferred embodiments, the solid-liquid ratio of the upper suspension after dilution is 1~5 mg / mL.

[0035] In a partially preferred embodiment, in step (2), the second electrolysis process involves ultrasonic treatment of the electrolysis system. The parameters used in the ultrasonic treatment, such as the power, can be conventional parameters in the art, as long as they can promote the homogeneity of the system.

[0036] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0039] Example 1

[0040] A method for preparing graphene from graphite leaching residue of waste lithium-ion batteries includes:

[0041] (1) Black powder is obtained from waste lithium-ion batteries after pretreatment and sorting. The black powder is then acid-leached to obtain graphite leaching residue.

[0042] (2) The graphite leaching residue was dispersed in a 5 mol / L sodium sulfate solution and electrolyzed using a platinum electrode as the electrolysis electrode. The electrolysis was carried out first at a voltage of 0.5V for 4 hours, and then continued at a voltage of 3V for 0.5 hours. The entire electrolysis process was treated with ultrasound.

[0043] (3) Take the upper electrolyte and centrifuge it at a speed of 10,000 rpm. Centrifuge to obtain the upper suspension and filter residue. Dilute the upper suspension by a dilution ratio of 1:10 to obtain a suspension with a solid-liquid ratio of 2 mg / mL. Perform hydrothermal reaction at 120℃ for 12 h. After hydrothermal reaction, centrifuge and freeze dry to obtain the reduced graphene oxide product. Return the filter residue to step (2) for further electrolytic recovery.

[0044] The resulting reduced graphene oxide product has a 1-3 layer graphite structure.

[0045] Example 2

[0046] The only difference between this embodiment and embodiment 1 is that the electrolysis voltage and time are different in step (2), specifically including: first electrolysis with an electrolysis voltage of 0.3V for 6 hours, and then electrolysis with a voltage of 2V for 4 hours.

[0047] The resulting reduced graphene oxide has a 1-3 layer graphite structure.

[0048] Example 3

[0049] The only difference between this embodiment and embodiment 1 is that the electrolysis voltage and time are different in step (2), specifically including: first electrolysis at an electrolysis voltage of 0.7V for 2 hours, and then electrolysis at a voltage of 4V for 1 hour.

[0050] The resulting reduced graphene oxide has a 1-3 layer graphite structure.

[0051] Example 4

[0052] The only difference between this embodiment and embodiment 1 is that, in step (2), ultrasonic treatment is not performed during the electrolysis process.

[0053] The final reduced graphene oxide had 5 to 10 graphite layers, indicating that ultrasound is more effective in placing fewer graphene oxide layers within the upper electrolyte layer.

[0054] Comparative Example 1

[0055] The only difference between this comparative example and Example 1 is that in step (2), only one electrolysis step is performed. Specifically, the graphite leaching residue is dispersed in a 5 mol / L sodium sulfate solution, and electrolysis is performed using a platinum electrode as the electrolysis electrode. Electrolysis is carried out at a voltage of 3V for 4.5 hours. The entire electrolysis process is treated with ultrasound.

[0056] Experimental results showed that the amount of reduced graphene oxide prepared was significantly reduced, i.e., the yield was lower, and the thickness of the obtained reduced graphene oxide increased, i.e., the number of graphite layers increased. Analysis suggests this may be because omitting the first electrolysis step resulted in poor exfoliation performance during the exfoliation process.

[0057] Comparative Example 2

[0058] The only difference between this comparative example and Example 1 is the electrolytic raw material; artificial primary graphite products are used directly as the raw material. Specifically:

[0059] (1) The graphite product was dispersed in a 5 mol / L sodium sulfate solution and electrolyzed using a platinum electrode as the electrolysis electrode. The electrolysis was first carried out at a voltage of 0.5 V for 4 h, and then continued at a voltage of 3 V for 0.5 h. The entire electrolysis process was treated with ultrasound.

[0060] (2) Take the upper electrolyte and centrifuge it at a speed of 10,000 rpm. Centrifuge to obtain the upper suspension and filter residue. Dilute the upper suspension to obtain a suspension with a solid-liquid ratio of 2 mg / mL. Perform hydrothermal reaction at 120℃ for 12 h. After hydrothermal reaction, centrifuge and freeze dry to obtain graphene product. Return the filter residue to step (1) for further electrolytic recovery.

[0061] Experimental results show that the amount of reduced graphene oxide prepared was significantly reduced, i.e., the yield was lower, and the number of graphite layers in the obtained reduced graphene oxide increased. This indicates that preparing reduced graphene oxide from artificial primary graphite products is more difficult than preparing reduced graphene oxide from graphite leaching residue.

[0062] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing graphene from graphite leaching residue of waste lithium-ion batteries, characterized in that, include: (1) The black powder recovered from waste lithium-ion batteries is acid-leached to obtain graphite leaching residue; (2) The graphite leaching residue is dispersed in the electrolyte, and the first electrolysis and the second electrolysis are carried out in sequence; the voltage of the first electrolysis is lower than the voltage of the second electrolysis; the voltage of the first electrolysis is less than 1V, and the time of the first electrolysis is 0.5~24h; the voltage of the second electrolysis is 1~10V, and the time of the second electrolysis is 0.5~24h; the electrolysis system is ultrasonically treated during the second electrolysis process; (3) Take the upper electrolyte, centrifuge to obtain the upper suspension and filter residue, dilute the upper suspension and carry out hydrothermal reaction, and the resulting reaction product is separated and dried to obtain reduced graphene oxide.

2. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in claim 1, characterized in that, In step (2), the voltage of the first electrolysis is 0.3~0.7V, and the electrolysis time is 2~6h.

3. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in claim 1, characterized in that, In step (2), the voltage of the second electrolysis is 2~4V, and the electrolysis time is 1~4h.

4. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in any one of claims 1 to 3, characterized in that, The electrolyte in the electrolyte solution is one or more of sulfuric acid, sulfate, nitrate, and chloride; the concentration of the electrolyte in the electrolyte solution is 1~5 mol / L.

5. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in any one of claims 1 to 3, characterized in that, In step (3), the temperature of the hydrothermal reaction is 90~150℃; the time of the hydrothermal reaction is 1~12h.

6. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in any one of claims 1 to 3, characterized in that, In step (3), the filter residue is returned to step (2) for further electrolysis.

7. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in any one of claims 1 to 3, characterized in that, Also includes: After electrolyzing 5 to 10 batches of graphite leaching residue with the electrolyte, the electrolyte is filtered, alkali is added to the filtrate to adjust the pH, precipitation occurs, and solid-liquid separation is performed to obtain liquid and solid. The liquid obtained from solid-liquid separation is returned to the electrolysis process as electrolyte, while the solid obtained is used to extract metals.

8. The method for preparing graphene from graphite leaching residue of waste lithium-ion batteries as described in any one of claims 1 to 3, characterized in that, The upper suspension has a solid-liquid ratio of 1~5 mg / mL after dilution.