Method and system for preparing porous carbon from battery carbon residue

Abstract

The embodiment of the application provides a method and system for preparing porous carbon from battery carbon residue. The method for preparing porous carbon from battery carbon residue comprises the following steps: S1: mixing battery carbon residue and a chemical activator to form a precursor, and performing activation treatment on the precursor to obtain sintered carbon residue; and S2: performing leaching treatment on the sintered carbon residue by using a leaching solution to obtain a solid-liquid mixture, and separating the solid-liquid mixture to obtain porous carbon. The method can efficiently, at low cost and in an environmentally friendly manner, utilize waste lithium ion battery carbon residue as a resource. The system for implementing the method has a simple structure and is suitable for wide application and promotion.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a method and system for preparing porous carbon from battery carbon slag. Background Technology

[0002] With the rapid development of the global new energy industry, lithium-ion batteries, due to their advantages such as high energy density and long cycle life, have been widely used in consumer electronics (such as mobile phones and laptops), electric vehicles (such as new energy vehicles), and energy storage systems (such as grid-scale energy storage devices). Industry forecasts predict that the total amount of retired lithium-ion batteries globally will exceed 11 million tons by 2030. In the composition of lithium-ion batteries, the negative electrode material (usually graphite) accounts for 15%-20% of the total battery mass, and its resource utilization is of great significance for alleviating graphite resource shortages and reducing battery production costs.

[0003] However, current recycling technologies for retired batteries mainly focus on extracting valuable metals (such as lithium, cobalt, and nickel) from the cathode material, while lacking effective methods for treating the graphite-rich carbon slag in the anode material. If this carbon slag is simply piled up, landfilled, or incinerated, it not only wastes high-quality graphite resources but also causes environmental risks such as heavy metal pollution and dioxin emissions.

[0004] Therefore, developing an efficient and low-cost technology for the resource utilization of spent lithium-ion battery carbon residue is a key link in realizing a closed-loop cycle of the battery industry chain and green and low-carbon development. Summary of the Invention

[0005] This application provides a method for preparing porous carbon from battery carbon slag. This method enables efficient, low-cost, and environmentally friendly resource utilization of waste lithium-ion battery carbon slag. The system structure for implementing this method is simple and suitable for widespread application.

[0006] This application provides a method for preparing porous carbon from battery carbon slag, comprising:

[0007] S1: Battery carbon slag is mixed with a chemical activator to form a precursor, and the precursor is activated to obtain sintered carbon slag.

[0008] S2: The sintered carbon slag is leached with a leachate to obtain a solid-liquid mixture, and the solid-liquid mixture is separated to obtain porous carbon.

[0009] As described above, S1 further includes pretreatment of the battery carbon residue, the pretreatment including crushing and screening the battery carbon residue to make the particle size of the battery carbon residue ≤150μm.

[0010] In the method described above, the battery carbon residue contains 70-90% fixed carbon, 5-10% volatile matter, and 5-15% ash by mass.

[0011] The method described above, wherein the chemical activator comprises at least one selected from sodium hydroxide, potassium hydroxide, zinc chloride, and phosphoric acid; and / or,

[0012] The mass ratio of the battery carbon residue to the chemical activator is 1:(0.1-10).

[0013] The method described above, wherein the activation process includes:

[0014] The precursor is heated from room temperature to T1 at a heating rate of 1-10℃ / min for low-temperature pretreatment for 0.5-1h, where 200℃≤T1≤400℃;

[0015] Then, the temperature is increased to T2 at a heating rate of 1-10℃ / min for high-temperature activation for 1-4 hours to obtain the sintered carbon slag, where 400℃ < T2 ≤ 900℃.

[0016] The method described above, wherein the leachate comprises at least one of water, dilute hydrochloric acid solution, and dilute alkaline solution; and / or,

[0017] In the leaching process, the liquid-to-solid ratio of the leachate to the sintered carbon slag is (10-50):1, the time is 0.5-3 hours, and the temperature is 40-80℃.

[0018] The method described above, wherein the leaching treatment includes ultrasonic-assisted leaching treatment, with an ultrasonic frequency of 20-60Hz and a power of 100-1000W.

[0019] The method described above further includes post-treatment of the porous carbon, the post-treatment including washing the porous carbon;

[0020] The detergent used in the washing process includes at least one of water, dilute hydrochloric acid solution, and dilute alkali solution, and the pH of the washing solution obtained after the washing process is 6-7.

[0021] The method described above further includes drying the washed porous carbon at a temperature of 60-80°C.

[0022] This application also provides a system for implementing the method for preparing porous carbon from battery carbon residue as described above, wherein the system includes: an activation unit and a leaching unit;

[0023] The activation unit includes a battery carbon slag inlet, a chemical activator inlet, and a sintered carbon slag outlet; the leaching unit includes a sintered carbon slag inlet and a leachate inlet.

[0024] The sintered slag outlet is connected to the sintered slag inlet.

[0025] The method for preparing porous carbon from battery carbon slag provided in this application includes activating the battery carbon slag and leaching it to obtain porous carbon. This method solves the four major problems of "resource waste, inefficient process, low product value, and environmental risk" faced in the disposal of waste lithium battery anode carbon slag. It can transform the environmental burden into high-performance functional materials with broad market prospects and provides technical support for realizing a green closed-loop cycle of the entire battery industry chain. Attached Figure Description

[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0027] Figure 1 This is a process flow diagram for preparing porous carbon from battery carbon residue in some embodiments of this application;

[0028] Figure 2 This is a SEM image of the pretreated battery carbon residue in Example 1 of this application;

[0029] Figure 3 Here is a SEM image of the porous carbon in Example 1 of this application;

[0030] Figure 4 The images show the XRD patterns of the pretreated battery carbon residue and porous carbon in Example 1 of this application.

[0031] Figure 5 This is a SEM image of the porous carbon in Example 3 of this application. Detailed Implementation

[0032] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0033] Current recycling technologies for retired lithium-ion batteries primarily focus on extracting valuable metals from the cathode material. Through processes such as crushing, screening, and hydrometallurgical methods (e.g., acid leaching, solvent extraction), metals like cobalt, nickel, and lithium can be separated and recovered. However, the anode carbon slag (containing graphite) generated during this process is often considered a low-value byproduct and is not fully recycled. Existing technologies for treating anode carbon slag are relatively crude, mainly involving simple stockpiling, landfilling, or direct incineration. These methods not only result in a serious waste of graphite resources but also pose environmental pollution risks due to residual metallic impurities (such as aluminum, copper, and iron) and harmful substances (such as electrolyte residue) in the carbon slag.

[0034] While some studies have attempted to recover graphite from battery slag using physical or chemical methods, these methods suffer from several drawbacks: complex processes requiring multiple pretreatment steps (such as acid washing and alkali washing) to remove impurities, which are cumbersome and energy-intensive; low product added value, as the recovered graphite is typically low-purity particles, making it difficult to meet the demands of high-end applications (such as high-performance electrode materials and adsorbent materials); and environmental risks, as chemical treatment may generate wastewater containing heavy metals or harmful gases, requiring additional treatment to avoid secondary pollution. This application innovatively integrates activation treatment and impurity removal into a single process step, combined with leaching treatment, enabling simultaneous and efficient removal of metal impurities from battery slag and in-situ construction of porous carbon structures. This significantly improves resource recovery efficiency, product added value, and environmental friendliness.

[0035] Figure 1 This is a process flow diagram for preparing porous carbon from battery carbon residue in some embodiments of this application. For example... Figure 1 As shown, this application provides a method for preparing porous carbon from battery carbon slag, comprising:

[0036] S1: Mix battery carbon slag with a chemical activator to form a precursor, and then activate the precursor to obtain sintered carbon slag.

[0037] S2: Use a leaching solution to leach the sintered carbon slag to obtain a solid-liquid mixture, and separate the solid-liquid mixture to obtain porous carbon.

[0038] Specifically, in the activation process, the chemical activator has a dual function. On the one hand, it can react with various metallic impurities (such as Fe, Al, Cu, Ni, Co, etc.) present in the battery carbon slag to generate stable crystalline or insoluble salts. These salts can be efficiently dissolved in the subsequent leaching process, thereby achieving deep separation and removal of metallic impurities. On the other hand, the chemical activator erodes the carbon skeleton through esterification, cross-linking, and other reactions, and releases volatile gases such as H2O, CO, and CO2 during the activation process, thereby constructing a multi-level pore structure with a wide pore size distribution within the carbon matrix, resulting in porous carbon.

[0039] The method for preparing porous carbon from battery carbon residue of the present invention has a simple and efficient process flow, and the prepared porous carbon material has a high specific surface area (up to 500 m²). 2 The method of this invention (with a purity of 99% or higher) has promising prospects for industrial application. Furthermore, it can obtain porous carbon materials with a purity of up to 99%, achieving efficient removal of impurities from battery carbon slag. Simultaneously, the integrated activation and sintering with the chemical activator simultaneously achieves "metal impurity fixation and transformation" and "carbon skeleton pore construction" in one step, significantly simplifying the process and reducing energy consumption and material costs. The chemical activator of this invention can introduce other functional groups during the activation process, enriching the surface of the obtained porous carbon with acidic sites and hydrophilic groups, significantly improving its adsorption performance and interfacial activity in catalytic and electrochemical applications, eliminating the need for subsequent surface modification steps. This invention directly transforms low-value carbon slag generated during the recycling of waste lithium-ion batteries into high-value-added porous carbon materials, providing a promising path for the resource utilization of graphite, and possessing significant environmental and economic benefits.

[0040] In some embodiments of the present invention, the battery carbon residue is further pretreated before S1. The pretreatment includes crushing and screening the battery carbon residue so that the particle size of the battery carbon residue is ≤150μm, which can promote the activation treatment and subsequent leaching treatment, improve the generation efficiency of porous carbon and improve the purity of porous carbon.

[0041] In some embodiments, the battery carbon residue can be dried, crushed and screened to obtain battery carbon residue with a particle size ≤150μm.

[0042] This invention does not specifically limit the type of battery carbon residue, and can use carbon residue from commonly used waste batteries in the field. For example, battery carbon residue can be derived from graphite residue from waste lithium-ion batteries (lithium iron phosphate batteries or ternary lithium-ion batteries with graphite as the negative electrode) after crushing and wet extraction of valuable metals.

[0043] In some embodiments of the present invention, the battery carbon slag contains 70-90% fixed carbon, 5-10% volatile matter, and 5-15% ash. The ash contains one or more of Al, Na, Ni, Co, Mn, Si, Cu, Ca, Mg, Li, and Fe. This battery carbon slag can more efficiently prepare porous carbon materials with higher purity.

[0044] This invention does not specifically limit the chemical activator and can use any chemical activator commonly used in the art. In some embodiments of this invention, the chemical activator may include at least one of sodium hydroxide, potassium hydroxide, zinc chloride, and phosphoric acid. In particular, when the chemical activator includes phosphoric acid, H3PO4 is thoroughly mixed with battery carbon slag before activation treatment. During the activation treatment, H3PO4 plays a dual role: on the one hand, it reacts with various metallic impurities (such as Fe, Al, Cu, Ni, Co, etc.) present in the battery carbon slag to generate stable crystalline or insoluble phosphates (such as FePO4, AlPO4, etc.). These phosphates can be efficiently dissolved in the subsequent chemical leaching process, thereby achieving deep separation and removal of metallic impurities. On the other hand, as a chemical activator, H3PO4 erodes the carbon skeleton through esterification, cross-linking, and other reactions, and releases volatile gases such as H2O, CO, and CO2 during pyrolysis, thereby constructing a multi-level pore structure with a wide pore size distribution within the carbon matrix. During the activation process, H3PO4 can introduce phosphorus and oxygen functional groups, making the surface of the resulting porous carbon rich in acidic sites and hydrophilic groups, which significantly improves its adsorption performance and interfacial activity in catalysis and electrochemical applications, eliminating the need for subsequent surface modification steps.

[0045] In some embodiments of the present invention, when the mass ratio of battery carbon residue to chemical activator is 1:(0.1-10), the chemical activator and battery carbon residue can react more fully, remove impurities from the battery carbon residue more efficiently, and form a richer pore structure in the battery carbon residue. Further, the mass ratio of battery carbon residue to chemical activator is 1:(1-5).

[0046] In some embodiments of the present invention, the activation treatment includes: heating the precursor from room temperature to T1 at a heating rate of 1-10℃ / min, and performing a low-temperature pretreatment for 0.5-1h, where 200℃≤T1≤400℃;

[0047] Then, the temperature is increased to T2 at a rate of 1-10℃ / min for high-temperature activation for 1-4 hours to obtain sintered carbon slag, where 400℃ < T2 ≤ 900℃.

[0048] The low-temperature section (T1) mainly removes volatiles and initially activates the carbon skeleton, while the high-temperature section (T2) forms multi-level channels through the etching effect of the activator.

[0049] Furthermore, high-temperature activation also includes: heating to 400-800℃ at a heating rate of 1-10℃ / min, holding at that temperature for 1-3 hours, and then cooling to room temperature at a rate of 1-10℃ / min to obtain sintered carbon slag. When the activation temperature is controlled at 600-800℃, the amount of insoluble salt formation and pore formation efficiency reach the optimal balance, at which point the specific surface area of ​​the product can reach a peak of 500-600 m² / g.

[0050] The present invention does not particularly limit the leachate and can use any leachate commonly used in the art. Exemplarily, the leachate includes at least one of water, dilute hydrochloric acid solution, and dilute alkaline solution.

[0051] In some embodiments of the present invention, during the leaching process, when the liquid-solid ratio of the leachate to the sintered carbon slag is (10-50):1, the time is 0.5-3h, and the temperature is 40-80℃, the insoluble salt obtained from the activation treatment can be leached efficiently while saving energy, resulting in porous carbon materials with higher purity.

[0052] In some embodiments of the present invention, the leaching treatment includes ultrasonic-assisted leaching treatment. When the ultrasonic frequency is 20-60Hz and the power is 100-1000W, ultrasonic-assisted leaching treatment can accelerate the dissolution and diffusion of impurities such as insoluble salts and improve the efficiency of leaching treatment.

[0053] In some embodiments of the present invention, the porous carbon is further subjected to post-treatment, which includes washing the porous carbon.

[0054] The detergent used in the washing process includes at least one of water, dilute hydrochloric acid solution, and dilute alkali solution. When the pH of the washing solution obtained after the washing process is 6-7, it can effectively remove residual activators and further improve the purity of porous carbon.

[0055] In some embodiments of the present invention, the post-processing further includes drying the washed porous carbon at a temperature of 60-80°C to obtain porous carbon material with higher purity.

[0056] This application provides a method for the resource utilization of carbon slag from waste lithium-ion batteries. Through the synergistic effect of gradient temperature activation and ultrasonic-assisted leaching, it not only solves the technical bottleneck of removing metal impurities from the carbon slag but also achieves efficient preparation of porous carbon materials in a one-step process. In this embodiment, when H3PO4 is selected as the activator, it reacts with metal impurities at high temperatures to generate soluble phosphates (such as AlPO4 and FePO4), while simultaneously forming pores in the carbon framework through a dehydration reaction. The reaction mechanism is as follows: H3PO4 first reacts with metal oxides to generate metal phosphates, and then releases gas through a dehydration reaction (H3PO4→P2O5+H2O), forming channels in the carbon matrix. Activation at a specific temperature also protects the pore structure of the porous carbon, ensuring its specific surface area. Furthermore, ultrasonic-assisted leaching at specific frequencies and power improves leaching efficiency because the microjets generated by ultrasonic cavitation can disrupt the boundary layer on the carbon slag surface, accelerating impurity dissolution. By optimizing parameters (such as activation temperature and the amount of chemical activator added), more carbon in battery carbon residue can be converted into high-purity porous carbon, reducing ash content and obtaining porous carbon with rich pore size distribution, which is suitable for applications such as adsorption, catalysis and supercapacitors.

[0057] The present invention also provides a system for carrying out the above-described method for preparing porous carbon from battery carbon residue, comprising: an activation unit and a leaching unit;

[0058] The activation unit includes a battery carbon slag inlet, a chemical activator inlet, and a sintered carbon slag outlet; the leaching unit includes a sintered carbon slag inlet and a leachate inlet.

[0059] The sintered slag outlet is connected to the sintered slag inlet.

[0060] Specifically, the chemical activator enters the activation unit through the chemical activator inlet, and the battery carbon slag enters the activation unit through the battery carbon slag inlet. In the activation unit, the chemical activator and the battery carbon slag are mixed and activated to obtain sintered carbon slag. The sintered carbon slag is output through the outlet of the activation unit and enters the leaching unit through the inlet of the leaching unit. The leachate enters the leaching unit through the inlet of the leaching unit. In the leaching unit, the leachate leaches the sintered carbon slag to obtain a solid-liquid mixture including porous carbon.

[0061] The system structure of this invention is simple and suitable for widespread application.

[0062] The present invention will be further described below with reference to specific embodiments.

[0063] Example 1

[0064] The method for preparing porous carbon from battery carbon residue in this embodiment includes:

[0065] 50g of waste lithium-ion battery carbon residue from a battery recycling company was collected, containing 84.62 wt.% fixed carbon, 7.32 wt.% volatile matter, and 8.06 wt.% ash. The residue was dried at 105℃, crushed, and sieved to collect particles smaller than 150μm for later use. The scanning electron microscope (SEM) observation results are as follows: Figure 2 As shown, a large number of impurities are attached to the surface of the battery carbon residue (graphite particles).

[0066] Weigh 2g of battery carbon slag and mix it with 85wt% H3PO4 aqueous solution at a mass ratio of 1:3. Stir until homogeneous to form a slurry, and dry to obtain a precursor. Place the precursor in a tube furnace and, under argon atmosphere protection, first heat to 300℃ at 5℃ / min and hold for 30min, then heat to 600℃ at 5℃ / min and hold for 2h to complete the activation treatment. After cooling, sintered carbon slag is obtained.

[0067] Sintered carbon slag was mixed with 1 mol / L NaOH solution at a liquid-to-solid ratio of 20:1 (mL / g) and leached for 1 h under ultrasonic conditions at a frequency of 40 kHz and a power of 300 W. Then, it was placed in a constant temperature water bath at 60 ℃ and stirred for another 2 h to remove residual phosphoric acid and some ash, resulting in a solid-liquid mixture.

[0068] The solid-liquid mixture was separated by filtration. The obtained solid was repeatedly washed with deionized water until the pH of the washing solution stabilized at 6-7. The washed material was then dried in an 80℃ drying oven for 10 hours. Finally, the dried material was gently ground to obtain a uniform porous carbon material.

[0069] Its observation effect under scanning electron microscopy is as follows Figure 3 As shown, the porous carbon material obtained in this embodiment contains almost no impurities (the impurities remaining in the battery carbon slag are effectively removed), and a well-developed porous structure is successfully constructed. Its XRD test analysis results are as follows: Figure 4 As shown, from Figure 4 As can be seen, compared with the pretreated battery carbon slag (fine carbon slag), most of the characteristic diffraction peaks corresponding to impurities in the porous carbon material of this embodiment disappeared, confirming that the method of the present invention has a significant effect on removing impurities.

[0070] The graphite purity of the porous carbon material was determined to be 99.07% according to the graphite chemical analysis method (GB / T-2023). Simultaneously, the specific surface area of ​​the porous carbon material in this embodiment was measured using a fully automated specific surface area and porosity analyzer (model ASAP2020HD88) from Micron Instruments, and the result was 506.83 m². 2 / g.

[0071] Example 2

[0072] The method for preparing porous carbon from battery carbon residue in this embodiment includes:

[0073] 50g of waste lithium-ion battery carbon residue generated by a domestic battery recycling company was taken, with a fixed carbon content of 84.62wt.%, volatile matter of 7.32wt.%, and ash content of 8.06wt.%. The carbon residue was dried at 105℃, crushed with a crusher, and sieved to collect battery carbon residue with a particle size of less than 150μm for later use.

[0074] Weigh 2g of battery carbon slag and mix it with KOH at a mass ratio of 1:3, then grind it evenly. Place it in a tube furnace and, under the protection of an argon atmosphere, first heat it to 300℃ at a rate of 5℃ / min and hold it for 30min, then heat it to 800℃ at a rate of 5℃ / min and hold it at this temperature for 2h to complete the segmented activation calcination process. After cooling, sintered carbon slag is obtained.

[0075] Sintered carbon slag was mixed with 1.5 mol / L hydrochloric acid solution at a liquid-to-solid ratio of 20:1 (mL / g) and leached for 1 h under ultrasonic conditions at a frequency of 40 kHz and a power of 300 W. Then, it was placed in an 80 ℃ constant temperature water bath and stirred for 2 h to remove residual KOH and some ash, resulting in a solid-liquid mixture.

[0076] The solid-liquid mixture was separated by filtration. The obtained solid was repeatedly washed with deionized water until the pH of the washing solution stabilized at 6-7. The washed material was then dried in an 80℃ drying oven for 10 hours. Finally, the dried material was gently ground to obtain a uniform porous carbon material.

[0077] The graphite purity of the porous carbon material was measured to be 97.28% according to the graphite chemical analysis method (GB / T-2023). Simultaneously, the specific surface area of ​​the porous carbon material in this embodiment was measured using a fully automated specific surface area and porosity analyzer (model ASAP2020HD88) from Micron Instruments, and the result was 463.21 m². 2 / g.

[0078] Example 3

[0079] The method for preparing porous carbon from battery carbon residue in this embodiment includes:

[0080] 50g of waste lithium-ion battery carbon residue generated by a domestic battery recycling company was taken, with a fixed carbon content of 84.62wt.%, volatile matter of 7.32wt.%, and ash content of 8.06wt.%. The carbon residue was dried at 105℃, crushed with a crusher, and sieved to collect battery residue with a particle size of less than 150μm for later use.

[0081] Weigh 2g of battery carbon residue and mix it with NaOH at a mass ratio of 1:3, then grind it evenly. Place it in a tube furnace and, under an argon atmosphere, first raise the temperature to 300℃ at a rate of 5℃ / min and hold for 30min, then raise the temperature to 800℃ at a rate of 5℃ / min and hold at this temperature for 2h to complete the segmented activation calcination process. After cooling, sintered carbon residue is obtained. Mix the sintered carbon residue with 1mol / L hydrochloric acid solution at a liquid-to-solid ratio of 20:1 (mL / g) and leach it under ultrasonic conditions at a frequency of 40kHz and a power of 300W for 1h. Then, place it in an 80℃ constant temperature water bath and stir for 2h to remove residual NaOH and some ash, obtaining a solid-liquid mixture.

[0082] The solid-liquid mixture was separated by filtration. The obtained solid was repeatedly washed with deionized water until the pH of the washing solution stabilized at 6-7. The washed material was then dried in an 80℃ drying oven for 10 hours. Finally, the dried material was gently ground to obtain a uniform porous carbon material.

[0083] Its observation effect under scanning electron microscopy is as follows Figure 5 As shown, most of the impurities on the surface of the graphite particles are effectively removed.

[0084] The graphite purity of the porous carbon material was determined to be 98.28% according to the graphite chemical analysis method (GB / T-2023). Simultaneously, the specific surface area of ​​the porous carbon material in this embodiment was measured using a fully automated specific surface area and porosity analyzer (model ASAP2020HD88) from Micron Instruments, and the result was 112.53 m². 2 / g.

[0085] Example 4

[0086] The method for preparing porous carbon from battery carbon residue in this embodiment includes:

[0087] 50g of waste lithium-ion battery carbon residue generated by a domestic battery recycling company was taken, with a fixed carbon content of 84.62wt.%, volatile matter of 7.32wt.%, and ash content of 8.06wt.%. The carbon residue was dried at 105℃, crushed with a crusher, and sieved to collect battery carbon residue with a particle size of less than 150μm for later use.

[0088] Weigh 2g of battery carbon slag and mix it with ZnCl2 at a mass ratio of 1:4, then grind it evenly. Place it in a tube furnace and, under an argon atmosphere, first raise the temperature to 300℃ at a rate of 5℃ / min and hold for 30min, then raise the temperature to 800℃ at a rate of 5℃ / min and hold at this temperature for 2h to complete the segmented activation calcination process. After cooling, sintered carbon slag is obtained. Mix the sintered carbon slag with a 1mol / L dilute hydrochloric acid solution at a liquid-to-solid mass ratio of 20:1 (mL / g), and leach it under ultrasonic conditions at a frequency of 40kHz and a power of 300W for 1h. Then, place it in a 60℃ constant temperature water bath and stir for 2h to remove residual ZnCl2 and some ash, obtaining a solid-liquid mixture.

[0089] The solid-liquid mixture was separated by filtration. The obtained solid was repeatedly washed with deionized water until the pH of the washing solution stabilized at 6-7. The washed material was then dried in an 80℃ drying oven for 10 hours. Finally, the dried material was gently ground to obtain a uniform porous carbon material.

[0090] The graphite purity of the porous carbon material was determined to be 87.36% according to the graphite chemical analysis method (GB / T-2023). Simultaneously, the specific surface area of ​​the porous carbon material in this embodiment was measured using a fully automated specific surface area and porosity analyzer (model ASAP2020HD88) from Micron Instruments, and the result was 142.96 m². 2 / g.

[0091] Examples 5-8

[0092] The methods for preparing porous carbon from battery carbon residue in Examples 5-8 are basically the same as those in Example 1, except that:

[0093] 2g of battery carbon residue was weighed and mixed with 85% H3PO4 at mass ratios of 1:1, 1:2, 1:4, and 1:5 to form a uniform slurry, which was then dried to obtain the precursor.

[0094] The obtained porous carbon material was tested according to the graphite chemical analysis method (GB / T-2023) and a fully automated specific surface area and pore size analyzer. The carbon content and specific surface area results are shown in Table 1.

[0095] Table 1

[0096]

[0097] As shown in the table above, by optimizing the amount of chemical activator, impurities can be converted into phosphates more fully, improving the purity of porous carbon, forming a rich pore structure, increasing the specific surface area, and ensuring the stability of the pore structure. At the same time, the appropriate amount of chemical activator results in a lower load on subsequent post-treatment.

[0098] Examples 9-12

[0099] The methods for preparing porous carbon from battery carbon residue in Examples 9-12 are basically the same as those in Example 1, except that:

[0100] During the activation process, under the protection of an argon atmosphere, the temperature is first raised to 300℃ at a rate of 5℃ / min and held for 30min. Then, the temperature is raised to 400℃, 500℃, 700℃, and 800℃ respectively, and held at these temperatures for 2h to complete the activation process.

[0101] The obtained porous carbon material was tested according to the graphite chemical analysis method (GB / T-2023) and a fully automated specific surface area and pore size analyzer. The measured carbon content and specific surface area results are shown in Table 2.

[0102] Table 2

[0103]

[0104] As shown in Table 2, further optimization of the high-temperature section temperature of the activation treatment can improve the removal efficiency of metal impurities, increase the purity of porous carbon, and form a rich pore structure to ensure the specific surface area of ​​porous carbon; at the same time, it can reduce the difficulty of post-processing.

[0105] Examples 13-16

[0106] The methods for preparing porous carbon from battery carbon residue in Examples 13-16 are basically the same as those in Example 1, except that:

[0107] During the activation process, under the protection of an argon atmosphere, the temperature is first raised to 300℃ at a rate of 5℃ / min and held for 30min. Then, the temperature is raised to 600℃ at a rate of 5℃ / min and held at this temperature for 1h, 1.5h, 2.5h and 3h respectively to complete the segmented activation process. After cooling, sintered carbon slag is obtained.

[0108] The obtained porous carbon material was tested according to the graphite chemical analysis method (GB / T-2023) and a fully automated specific surface area and pore size analyzer. The carbon content and specific surface area results are shown in Table 3.

[0109] Table 3

[0110]

[0111] As shown in the table above, by selecting the appropriate time for the high-temperature activation process, impurities in the battery carbon residue can be more fully converted, reducing the ash content in the porous carbon, increasing the purity of the porous carbon, forming a rich pore structure, and increasing the specific surface area of ​​the porous carbon.

[0112] Example 17

[0113] The method for preparing porous carbon from battery carbon residue in this embodiment is basically the same as that in Example 1, except that deionized water is used instead of 1 mol / L sodium hydroxide solution during the leaching treatment. According to the graphite chemical analysis method (GB / T-2023), the graphite purity of the porous carbon material was measured to be 89.16%.

[0114] Examples 18-23

[0115] The methods for preparing porous carbon from battery carbon residue in Examples 18-23 are basically the same as those in Example 1, except that the leaching temperature is 40℃ and 80℃, and the water immersion time is 1h and 3h, respectively.

[0116] The obtained porous carbon material was tested according to the graphite chemical analysis method (GB / T-2023), and the carbon content was measured as shown in Table 4:

[0117] Table 4

[0118]

[0119] As can be seen from Table 4, increasing the leaching temperature can improve the purity of porous carbon materials, and extending the leaching time can also improve the purity of porous carbon materials.

[0120] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing porous carbon from battery carbon slag, characterized in that, include: S1: Battery carbon slag is mixed with a chemical activator to form a precursor, and the precursor is activated to obtain sintered carbon slag. S2: The sintered carbon slag is leached with a leachate to obtain a solid-liquid mixture, and the solid-liquid mixture is separated to obtain porous carbon.

2. The method according to claim 1, characterized in that, S1 includes pretreatment of the battery carbon residue, which includes crushing and screening the battery carbon residue to make the particle size of the battery carbon residue ≤150μm.

3. The method according to claim 1 or 2, characterized in that, The battery carbon residue contains 70-90% fixed carbon, 5-10% volatile matter, and 5-15% ash.

4. The method according to any one of claims 1-3, characterized in that, The chemical activator includes at least one of sodium hydroxide, potassium hydroxide, zinc chloride, and phosphoric acid; and / or, The mass ratio of the battery carbon residue to the chemical activator is 1:(0.1-10).

5. The method according to any one of claims 1-4, characterized in that, The activation process includes: The precursor is heated from room temperature to T1 at a heating rate of 1-10℃ / min for low-temperature pretreatment for 0.5-1h, where 200℃≤T1≤400℃; Then, the temperature is increased to T2 at a heating rate of 1-10℃ / min for high-temperature activation for 1-4 hours to obtain the sintered carbon slag, where 400℃ < T2 ≤ 900℃.

6. The method according to any one of claims 1-5, characterized in that, The leachate comprises at least one of water, dilute hydrochloric acid solution, and dilute alkaline solution; and / or, In the leaching process, the liquid-to-solid ratio of the leachate to the sintered carbon slag is (10-50):1, the time is 0.5-3 hours, and the temperature is 40-80℃.

7. The method according to any one of claims 1-6, characterized in that, The leaching treatment includes ultrasonic-assisted leaching treatment, with an ultrasonic frequency of 20-60Hz and a power of 100-1000W.

8. The method according to any one of claims 1-7, characterized in that, It also includes post-treatment of the porous carbon, the post-treatment including washing the porous carbon; The detergent used in the washing process includes at least one of water, dilute hydrochloric acid solution, and dilute alkali solution, and the pH of the washing solution obtained after the washing process is 6-7.

9. The method according to claim 8, characterized in that, The post-processing further includes drying the washed porous carbon at a temperature of 60-80°C.

10. A system for implementing the method for preparing porous carbon from battery carbon slag according to any one of claims 1-9, characterized in that, include: Activation unit and leaching unit; The activation unit includes a battery carbon residue inlet, a chemical activator inlet, and a precursor outlet; the leaching unit includes a precursor inlet and a leachate inlet. The precursor outlet is connected to the precursor inlet.

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