A method for preparing graphene aerogel by a multistage intercalation-supercritical drying method

Abstract

The application discloses a kind of multistage intercalation-supercritical drying method preparation graphene aerogel method, belong to new energy material recycling and nanomaterial preparation technical field.The method includes: the waste lithium battery is handled, and graphite residue is obtained;Graphite residue is soaked in KNO3 solution and FeCl3 solution, instantaneously expands under inert atmosphere, obtains pre-peeling graphite, and then is oxidized, and obtains graphene oxide suspension, adds sodium lignosulfonate, carries out hydrothermal reaction, obtains reduced graphene;Reduced graphene dispersion liquid is placed in supercritical CO2 And dry processing can be carried out.The graphite negative pole in waste lithium battery is used as raw material in the application, combined with multistage intercalation stripping process and supercritical drying technology, the stripping efficiency of graphene and the structural stability of aerogel are significantly improved.The product obtained has high specific surface area, excellent electrical conductivity and mechanical strength, and can be applied in supercapacitor, catalytic carrier and other fields.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling technology, specifically to a method for preparing graphene aerogel using a multi-stage intercalation-supercritical drying method. Background Technology

[0002] Graphene aerogels, due to their lightweight, high conductivity, and porous structure, have broad application prospects in energy storage, environmental remediation, and other fields. However, traditional preparation methods typically rely on high-purity graphite raw materials, resulting in high costs and complex processes. Furthermore, traditional freeze-drying or atmospheric pressure drying can easily lead to aerogel structure collapse. On the other hand, waste lithium batteries are rich in graphite anode materials, and direct disposal or inefficient recycling can easily lead to resource waste and environmental pollution. Current technologies for extracting graphene from waste lithium batteries mostly employ single intercalation or strong acid oxidation methods, which suffer from low exfoliation efficiency, numerous product defects, and difficulty in maintaining the intact porous structure of the aerogel during subsequent drying. Therefore, developing a method for preparing graphene aerogels using waste lithium batteries as raw materials that combines efficient exfoliation with controllable structure is of great significance. Summary of the Invention

[0003] This invention addresses the problems of low exfoliation efficiency and numerous product defects in existing processes for extracting graphene from spent lithium batteries. The aim is to propose a method for preparing graphene aerogels based on a multi-stage intercalation-supercritical drying method using recycled spent lithium batteries. This method significantly improves graphite exfoliation efficiency through the synergistic effect of multi-stage intercalation and instantaneous high-temperature expansion. Simultaneously, the use of sodium lignosulfonate and supercritical CO2 drying technology enables graphene reduction and three-dimensional network construction, preventing structural collapse and providing a new approach for the high-value utilization of spent lithium batteries.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0005] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0006] Waste lithium batteries are processed to obtain graphite slag;

[0007] Graphite slag was soaked in KNO3 solution and FeCl3 solution, and then expanded instantaneously under an inert atmosphere to obtain pre-exfoliated graphite;

[0008] Pre-exfoliated graphite is oxidized to obtain a graphene oxide suspension;

[0009] Sodium lignosulfonate was added to a suspension of graphene oxide and a hydrothermal reaction was carried out to obtain reduced graphene.

[0010] The reduced graphene dispersion was dried in supercritical CO2 to obtain a three-dimensional porous graphene aerogel.

[0011] Furthermore, the waste lithium batteries are processed to obtain graphite slag, including the following steps:

[0012] Waste lithium batteries are discharged, crushed, magnetically separated, and pulverized and screened to obtain crushed material with a particle size of less than 0.8 mm.

[0013] The obtained crushed material was calcined under a nitrogen / argon atmosphere to obtain battery powder.

[0014] The battery powder was leached in an acid solution to obtain graphite residue.

[0015] Furthermore, the calcination temperature is 400-600℃, the calcination time is 1-3h, and the heating rate is 3-6℃ / min;

[0016] The leaching temperature is 80-90℃, the leaching time is 3-4h, and the solid-liquid ratio is 20-30g / L.

[0017] Furthermore, the soaking time is 30-60 min; the concentration of KNO3 solution is 0.5-1.5 mol / L, the concentration of FeCl3 solution is 0.2-0.8 mol / L, and the molar ratio of KNO3 to FeCl3 is 1:0.5-1:1.

[0018] Furthermore, the instantaneous expansion temperature is 800-1000℃, and the instantaneous expansion holding time is 5-10 min; the temperature is increased to 800-1000℃ at a heating rate of 10-20℃ / min.

[0019] Furthermore, the specific process of oxidizing the pre-exfoliated graphite is as follows: after combining the pre-exfoliated graphite with sulfuric acid, potassium permanganate is added, the oxidation reaction is carried out, followed by dilution and ultrasonication to obtain a graphene oxide suspension.

[0020] Furthermore, the mass ratio of pre-stripped graphite to sulfuric acid is 1:3-5, the sulfuric acid mass concentration is 95-98%, and the mass ratio of potassium permanganate to graphite is 0.5-2:1.

[0021] The oxidation reaction is carried out at a temperature of 30-50℃ for 2-4 hours; the ultrasonic power is 300-500W for 1-2 hours.

[0022] Furthermore, the mass ratio of graphene to sodium lignosulfonate is 1:0.1-0.3.

[0023] Furthermore, the hydrothermal reaction temperature is 180-220℃, and the time is 6-12h; after the hydrothermal reaction, the sample is washed with 0.1-0.5mol / L sodium hydroxide solution until the pH is neutral.

[0024] Furthermore, the drying process involves a pressure of 8-10 MPa, a temperature of 40-50℃, and a processing time of 4-8 hours.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention utilizes graphite slag from waste lithium batteries as raw material and achieves efficient and low-cost preparation of high-performance graphene aerogels through the integrated innovation of multi-level intercalation synergistic expansion, biomass-enhanced self-assembly, and supercritical drying technologies. By leveraging the synergistic effect of KNO3 and FeCl3 dual intercalating agents and enabling instantaneous expansion, controllable expansion of the graphite interlayer spacing is achieved, significantly improving exfoliation efficiency. Combined with oxidation and sodium lignosulfonate-assisted hydrothermal self-assembly, an enhanced graphene framework with a three-dimensional porous network is constructed. Finally, supercritical CO2 drying is used to remarkably preserve the microporous structure, resulting in an aerogel with both high conductivity (>100 S / m) and ultra-low density (3-10 mg / cm³). 3 It possesses excellent mechanical resilience (90% compression deformation recovery rate > 95%), shortens the production cycle by 30% and reduces costs by 40% compared to traditional processes, and simultaneously achieves full-scale high-value utilization of waste battery graphite resources. It has significant technological advancements and environmental and economic benefits in the fields of new energy material recycling and functional material preparation.

[0027] Furthermore, the waste lithium batteries are subjected to inert atmosphere calcination and gradient acid leaching processes (80-90℃, solid-liquid ratio 20-30g / L) to precisely remove the binder and metal impurities on the graphite surface, thereby increasing the purity of the raw materials to over 90%. Attached Figure Description

[0028] Figure 1 Here is a SEM image of the regenerated graphene aerogel from Example 1;

[0029] Figure 2 Raman blotting of the regenerated graphene aerogel in Example 1;

[0030] Figure 3 This is a SEM image of the regenerated graphene aerogel in Comparative Example 1. Detailed Implementation

[0031] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0032] The present invention discloses a method for preparing graphene aerogel by a multi-stage intercalation-supercritical drying method, comprising the following steps:

[0033] (1) Discharge, crush, magnetically separate and pulverize the waste lithium batteries to obtain crushed material with a particle size of less than 0.8 mm. Place the obtained crushed material in a tube furnace and calcine it under a nitrogen / argon atmosphere. The calcination temperature is 400-600℃, the calcination time is 1-3 h, and the heating rate is set to 3-6℃ / min to remove organic binders and electrolyte to obtain battery powder.

[0034] (2) The calcined battery powder is placed in a 30% nitric acid solution, the leaching temperature is 80-90℃, the leaching time is 3-4h, the solid-liquid ratio is 20-30g / L, and the purified graphite residue is obtained after filtration and drying.

[0035] (3) The separated graphite slag is immersed in KNO3 solution and FeCl3 solution in sequence, with each stage of immersion time being 30-60 min. Then, it undergoes instantaneous thermal expansion under an inert atmosphere to obtain pre-exfoliated graphite.

[0036] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (mass concentration 95-98%) at a certain mass ratio, potassium permanganate is added and reacted at 30-50℃ for 2-4 hours. After dilution with deionized water, ultrasonic treatment (power 300-500W) is performed for 1-2 hours to obtain graphene oxide suspension.

[0037] (5) Add sodium lignosulfonate to the graphene oxide suspension and perform a hydrothermal reaction at 180-220℃ for 6-12 hours. After centrifugation, reduce graphene is obtained.

[0038] (6) The reduced graphene dispersion was placed in a supercritical CO2 device, and three-dimensional porous graphene aerogel was obtained by controlling the pressure, temperature and processing time.

[0039] In step (3), the concentration of KNO3 solution is 0.5-1.5 mol / L, the concentration of FeCl3 solution is 0.2-0.8 mol / L, and the molar ratio of KNO3 to FeCl3 is 1:0.5-1:1.

[0040] In step (3), the temperature is increased to 800-1000℃ at a rate of 10-20℃ / min for instantaneous thermal expansion, and the thermal expansion holding time is 5-10min.

[0041] In step (4), the mass ratio of stripped graphite to concentrated sulfuric acid is 1:3-5, and the mass ratio of potassium permanganate to graphite is 0.5-2:1;

[0042] In step (5), the mass ratio of graphene to sodium lignosulfonate is 1:0.1-0.3.

[0043] In step (5), after the hydrothermal reaction, the sample needs to be washed with a 0.1-0.5 mol / L sodium hydroxide solution until the pH is neutral.

[0044] In step (6), the pressure is controlled at 8-10 MPa, the temperature at 40-50℃, and the treatment time is 4-8 hours.

[0045] The following are specific examples.

[0046] Example 1

[0047] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0048] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 400℃, the calcination time is 3h, and the heating rate is set to 3℃ / min to remove organic binder and electrolyte.

[0049] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 80℃, the leaching time was 3.5h, the solid-liquid ratio was 20g / L, and the purified graphite residue was obtained after filtration and drying.

[0050] (3) The separated graphite slag was successively immersed in 0.5 mol / L KNO3 and 0.3 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.5. The immersion time for each stage was 30 min. Then, the temperature was raised to 900℃ at 10℃ / min and held for 5 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0051] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:3, potassium permanganate was added. The mass ratio of potassium permanganate to graphite was 2:1. The mixture was reacted at 30°C for 2 hours. After dilution with deionized water, the mixture was ultrasonically treated (power 500W) for 1 hour to obtain graphene oxide suspension.

[0052] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 180℃ for 12h. After the reaction, the graphene was washed with 0.2mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0053] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 8 MPa and 40 °C for 5 h to obtain a three-dimensional porous graphene aerogel.

[0054] In Example 1, the graphene exfoliation yield was 99-95%.

[0055] The three-dimensional porous graphene aerogel in Example 1 has a porosity of 95-97%, a conductivity of 135-150 S / m, a compression resilience of 97-98%, and a density of 3-5 mg / cm³. 3 Specific surface area is 310-460 m² 2 / g.

[0056] See Figure 1 As can be seen, graphene aerogel exhibits a three-dimensional porous network structure with interwoven layers. This structure endows it with a large specific surface area, which is beneficial for the adsorption and diffusion of gases and liquids, while also giving the material good flexibility and a certain degree of mechanical strength.

[0057] See Figure 2 As can be seen in the figure, peaks D, G, and 2D appear. The higher intensity of peak G indicates that the carbon atoms in the graphene aerogel have good sp0 properties. 2 Hybrid structure, high crystallinity. D / I G The ratio is 0.146, which is relatively low, indicating a low degree of material defect. 2D / I G The ratio is 0.465. Based on the characteristics of each peak, it can be inferred that the graphene aerogel has a small number of layers and may be an aerogel structure composed of few or single-layer graphene.

[0058] comprehensive Figure 1 and Figure 2 Analysis shows that this graphene aerogel has the structural characteristics of high crystallinity, few defects, and possibly few layers, while also possessing a three-dimensional porous macroscopic structure, which may have good application potential in the fields of adsorption, catalysis, and energy storage.

[0059] Example 2

[0060] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0061] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 500℃, the calcination time is 3h, and the heating rate is set to 5℃ / min to remove organic binder and electrolyte.

[0062] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 80℃, the leaching time was 4h, the solid-liquid ratio was 20g / L, and the purified graphite residue was obtained after filtration and drying.

[0063] (3) The separated graphite slag was successively immersed in 0.8 mol / L KNO3 and 0.4 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.6. The immersion time for each stage was 30 min. Then, the temperature was raised to 800℃ at 10℃ / min and held for 5 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0064] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:3, potassium permanganate was added. The mass ratio of potassium permanganate to graphite was 1.5:1. The mixture was reacted at 30°C for 2 hours. After dilution with deionized water, the mixture was ultrasonically treated (power 500W) for 1 hour to obtain graphene oxide suspension.

[0065] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 180℃ for 12h. After the reaction, the graphene was washed with 0.1mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0066] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 10 MPa and 40 °C for 5 h to obtain a three-dimensional porous graphene aerogel.

[0067] Example 3

[0068] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0069] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 600℃, the calcination time is 2h, and the heating rate is set to 5℃ / min to remove organic binder and electrolyte.

[0070] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 80℃, the leaching time was 4h, the solid-liquid ratio was 30g / L, and the purified graphite residue was obtained after filtration and drying.

[0071] (3) The separated graphite slag was successively immersed in 1 mol / L KNO3 and 0.4 mol / L FeCl3 solution, with a molar ratio of KNO3 to FeCl3 of 1:0.8. The immersion time for each stage was 40 min. Then, the temperature was raised to 800℃ at 15℃ / min and held for 5 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0072] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:3, potassium permanganate was added. The mass ratio of potassium permanganate to graphite was 1:1. The mixture was reacted at 40℃ for 4 hours. After dilution with deionized water, it was ultrasonically treated (power 500W) for 1.5 hours to obtain graphene oxide suspension.

[0073] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 200℃ for 10h. After the reaction, the graphene was washed with 0.2mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0074] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 10 MPa and 40 °C for 5 h to obtain a three-dimensional porous graphene aerogel.

[0075] Example 4

[0076] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0077] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 1h, and the heating rate is set to 5℃ / min to remove organic binder and electrolyte.

[0078] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 85℃, the leaching time was 3.5h, the solid-liquid ratio was 25g / L, and the purified graphite residue was obtained after filtration and drying.

[0079] (3) The separated graphite slag was successively immersed in 1.5 mol / L KNO3 and 0.5 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:1. The immersion time for each stage was 60 min. Then, the temperature was raised to 800℃ at 15℃ / min and held for 5 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0080] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:4, potassium permanganate was added. The mass ratio of potassium permanganate to graphite was 1:1. The mixture was reacted at 40℃ for 4 hours. After dilution with deionized water, it was ultrasonically treated (power 500W) for 1.5 hours to obtain graphene oxide suspension.

[0081] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 200℃ for 8 hours. After the reaction, the graphene was washed with 0.5mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0082] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 10 MPa and 40 °C for 5 h to obtain a three-dimensional porous graphene aerogel.

[0083] Example 5

[0084] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0085] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 1h, and the heating rate is set to 5℃ / min to remove organic binder and electrolyte.

[0086] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 85℃, the leaching time was 3.5h, the solid-liquid ratio was 25g / L, and the purified graphite residue was obtained after filtration and drying.

[0087] (3) The separated graphite slag was successively immersed in 1.5 mol / L KNO3 and 0.5 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.5. The immersion time for each stage was 60 min. Then, the temperature was raised to 1000℃ at 20℃ / min and held for 5 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0088] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:4, potassium permanganate is added. The mass ratio of potassium permanganate to graphite is 1:1. The mixture is reacted at 30℃ for 3 hours. After dilution with deionized water, it is ultrasonically treated (power 500W) for 2 hours to obtain graphene oxide suspension.

[0089] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 220℃ for 6 hours. After the reaction, the graphene was washed with 0.5 mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0090] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 9 MPa and 50 °C for 6 h to obtain a three-dimensional porous graphene aerogel.

[0091] Example 5

[0092] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0093] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 1h, and the heating rate is set to 5℃ / min to remove organic binder and electrolyte.

[0094] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 90℃, the leaching time was 3h, the solid-liquid ratio was 30g / L, and the purified graphite residue was obtained after filtration and drying.

[0095] (3) The separated graphite slag was successively immersed in 1.2 mol / L KNO3 and 0.6 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.5. The immersion time for each stage was 50 min. Then, the temperature was raised to 1000℃ at 20℃ / min and held for 5 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0096] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:5, potassium permanganate was added. The mass ratio of potassium permanganate to graphite was 0.5:1. The mixture was reacted at 30℃ for 3 hours. After dilution with deionized water, it was ultrasonically treated (power 500W) for 1 hour to obtain graphene oxide suspension.

[0097] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 220℃ for 6 hours. After the reaction, the graphene was washed with 0.5 mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0098] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 9 MPa and 40 °C for 6 h to obtain a three-dimensional porous graphene aerogel.

[0099] Example 6

[0100] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0101] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 1h, and the heating rate is set to 5℃ / min to remove organic binder and electrolyte.

[0102] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 90℃, the leaching time was 3h, the solid-liquid ratio was 30g / L, and the purified graphite residue was obtained after filtration and drying.

[0103] (3) The separated graphite slag was successively immersed in 1 mol / L KNO3 and 0.3 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.5. The immersion time for each stage was 50 min. Then, the temperature was raised to 800℃ at 15℃ / min and kept for 10 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0104] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:5, potassium permanganate is added. The mass ratio of potassium permanganate to graphite is 1.5:1. The mixture is reacted at 40℃ for 5 hours. After dilution with deionized water, it is ultrasonically treated (power 500W) for 1 hour to obtain graphene oxide suspension.

[0105] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.3. The reaction was carried out hydrothermally at 200℃ for 12h. After the reaction, the graphene was washed with 0.25mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0106] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 8 MPa and 50 °C for 8 h to obtain a three-dimensional porous graphene aerogel.

[0107] Example 7

[0108] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0109] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into the machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 450℃, the calcination time is 1.5h, and the heating rate is set to 6℃ / min to remove organic binder and electrolyte.

[0110] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 85℃, the leaching time was 3h, the solid-liquid ratio was 20g / L, and the purified graphite residue was obtained after filtration and drying.

[0111] (3) The separated graphite slag was successively immersed in 0.6 mol / L KNO3 and 0.2 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.7. The immersion time for each stage was 45 min. Then, the temperature was raised to 850℃ at 15℃ / min and held for 8 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0112] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:4, potassium permanganate was added. The mass ratio of potassium permanganate to graphite was 1:1. The mixture was reacted at 50°C for 2 hours. After dilution with deionized water, the mixture was ultrasonically treated (power 500W) for 1 hour to obtain graphene oxide suspension.

[0113] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.2. The reaction was carried out hydrothermally at 190℃ for 8 hours. After the reaction, the graphene was washed with 0.1mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0114] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 8 MPa and 45 °C for 4 h to obtain a three-dimensional porous graphene aerogel.

[0115] Example 8

[0116] A method for preparing graphene aerogels via multi-level intercalation-supercritical drying includes the following steps:

[0117] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 2h, and the heating rate is set to 4℃ / min to remove organic binder and electrolyte.

[0118] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 90℃, the leaching time was 4h, the solid-liquid ratio was 30g / L, and the purified graphite residue was obtained after filtration and drying.

[0119] (3) The separated graphite slag was successively immersed in 1.3 mol / L KNO3 and 0.8 mol / L FeCl3 solutions, with a molar ratio of KNO3 to FeCl3 of 1:0.9. The immersion time for each stage was 55 min. Then, the temperature was raised to 950℃ at 20℃ / min and held for 6 min under Ar2 atmosphere to obtain pre-exfoliated graphite.

[0120] (4) After mixing pre-exfoliated graphite with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:5, potassium permanganate is added, the mass ratio of potassium permanganate to graphite is 2:1, and the reaction is carried out at 35℃ for 3h. After dilution with deionized water, the mixture is ultrasonically treated (power 500W) for 1h to obtain graphene oxide suspension.

[0121] (5) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 200℃ for 10h. After the reaction, the graphene was washed with 0.2mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0122] (6) The reduced graphene dispersion was placed in a supercritical CO2 device and treated at 10 MPa and 40 °C for 7 h to obtain a three-dimensional porous graphene aerogel.

[0123] Comparative Example 1

[0124] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 2h, and the heating rate is set to 4℃ / min to remove organic binder and electrolyte.

[0125] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 90℃, the leaching time was 4h, the solid-liquid ratio was 30g / L, and the purified graphite residue was obtained after filtration and drying.

[0126] (3) After separating the graphite slag, mix it with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:5, add potassium permanganate, the mass ratio of potassium permanganate to graphite is 2:1, react at 35℃ for 3h, dilute with deionized water and ultrasonically treat (power 500W) for 1h to obtain graphene oxide suspension.

[0127] (4) Sodium lignosulfonate was added to the graphene oxide suspension. The mass ratio of graphene to sodium lignosulfonate was 1:0.1. The reaction was carried out hydrothermally at 200℃ for 10h. After the reaction, the graphene was washed with 0.2mol / L NaOH solution until the pH was neutral. After centrifugation, the reduced graphene was obtained.

[0128] (5) Reduced graphene was freeze-dried to obtain graphene aerogel.

[0129] See Figure 3 As can be seen, the graphene aerogels without KNO3 and FeCl3 solutions for solution intercalation and supercritical CO2 drying exhibit irregular blocky and sheet-like structures, indicating that they were not effectively exfoliated. Simultaneously, the bright areas suggest that the graphene aerogels obtained by this method have relatively poor electrical conductivity.

[0130] Comparative Example 2

[0131] (1) Discharge the waste lithium battery to 1.5V in a 1mol / L NaCl solution, take it out, wipe it dry, and put it into a machine for crushing, magnetic separation and crushing and sieving to obtain crushed material with a particle size of less than 0.8mm. Place the obtained crushed material in a tube furnace and calcine it under N2 atmosphere. The calcination temperature is 550℃, the calcination time is 2h, and the heating rate is set to 4℃ / min to remove organic binder and electrolyte.

[0132] (2) The calcined battery powder was placed in a 30% nitric acid solution, the leaching temperature was 90℃, the leaching time was 4h, the solid-liquid ratio was 30g / L, and the purified graphite residue was obtained after filtration and drying.

[0133] (3) After separating the graphite slag, mix it with concentrated sulfuric acid (concentration 95-98%) at a mass ratio of 1:2, add potassium permanganate, the mass ratio of potassium permanganate to graphite is 3:1, react at 35℃ for 3h, dilute with deionized water and ultrasonically treat (power 500W) for 1h to obtain graphene oxide suspension.

[0134] (4) Add ethylenediamine to the graphene oxide suspension, with a mass ratio of graphene to ethylenediamine of 1:0.5. Perform hydrothermal reaction at 200℃ for 10h. After the reaction, wash with 0.2mol / L NaOH solution until pH is neutral. After centrifugation, obtain reduced graphene.

[0135] (5) Reduced graphene was freeze-dried to obtain graphene aerogel.

[0136] Table 1 Key performance parameters of graphene aerogels prepared in each embodiment and comparative example.

[0137]

[0138] As shown in Table 1, the graphene aerogel in Comparative Example 1, which did not use KNO3 and FeCl3 solutions for solution intercalation and supercritical CO2 drying, exhibited irregular blocky and sheet-like structures, making effective exfoliation impossible. In Comparative Example 2, although ethylenediamine was used to generate graphene aerogel, its overall performance was far inferior to sodium lignosulfonate, especially in terms of conductivity, which is crucial for its subsequent application in electronic devices.

[0139] This invention uses spent lithium-ion batteries as raw materials. Graphite slag is obtained through pretreatment steps including discharge, crushing, and calcination purification. Then, a three-dimensional porous graphene aerogel is prepared by sequentially employing nitrate / metal salt multi-level intercalation, chemical oxidation exfoliation, and hydrothermal reduction combined with supercritical CO2 drying technology. Its innovation lies in utilizing the graphite anode from spent lithium-ion batteries as raw material, and combining multi-level intercalation exfoliation with supercritical drying technology, significantly improving the graphene exfoliation efficiency and the structural stability of the aerogel. The resulting product possesses high specific surface area, excellent conductivity, and mechanical strength, and can be applied in fields such as supercapacitors and catalyst supports. This invention achieves resource recycling, and the process is environmentally friendly and low-cost.

[0140] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0141] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

Claims

1. A method for preparing graphene aerogel using a multi-stage intercalation-supercritical drying method, characterized in that, Includes the following steps: Waste lithium batteries are processed to obtain graphite slag; Graphite slag was soaked in KNO3 solution and FeCl3 solution, and then expanded instantaneously under an inert atmosphere to obtain pre-exfoliated graphite; Pre-exfoliated graphite is oxidized to obtain a graphene oxide suspension; Sodium lignosulfonate was added to a suspension of graphene oxide and a hydrothermal reaction was carried out to obtain reduced graphene. The reduced graphene dispersion was dried in supercritical CO2 to obtain a three-dimensional porous graphene aerogel.

2. The method for preparing graphene aerogel using the multi-stage intercalation-supercritical drying method according to claim 1, characterized in that, The process of processing waste lithium batteries to obtain graphite slag includes the following steps: Waste lithium batteries are discharged, crushed, magnetically separated, and pulverized and screened to obtain crushed material with a particle size of less than 0.8 mm. The obtained crushed material was calcined under a nitrogen / argon atmosphere to obtain battery powder. The battery powder was leached in an acid solution to obtain graphite residue.

3. The method for preparing graphene aerogel using the multi-stage intercalation-supercritical drying method according to claim 2, characterized in that, The calcination temperature is 400-600℃, the calcination time is 1-3 h, and the heating rate is 3-6℃ / min; The leaching temperature is 80-90℃, the leaching time is 3-4 h, and the solid-liquid ratio is 20-30 g / L.

4. The method for preparing graphene aerogel using the multi-stage intercalation-supercritical drying method according to claim 1, characterized in that, The soaking time is 30-60 min; the concentration of KNO3 solution is 0.5-1.5 mol / L, the concentration of FeCl3 solution is 0.2-0.8 mol / L, and the molar ratio of KNO3 to FeCl3 is 1:0.5-1:

1.

5. The method for preparing graphene aerogel using the multi-stage intercalation-supercritical drying method according to claim 1, characterized in that, The instantaneous expansion temperature is 800-1000℃, and the holding time for instantaneous expansion is 5-10 min; the temperature is increased to 800-1000℃ at a heating rate of 10-20℃ / min.

6. The method for preparing graphene aerogel using the multi-stage intercalation-supercritical drying method according to claim 1, characterized in that, The specific process of oxidizing pre-exfoliated graphite is as follows: after mixing pre-exfoliated graphite with sulfuric acid, potassium permanganate is added, the oxidation reaction is carried out, followed by dilution and ultrasonication to obtain a graphene oxide suspension.

7. The method for preparing graphene aerogel using the multi-stage intercalation-supercritical drying method according to claim 6, characterized in that, The mass ratio of pre-stripped graphite to sulfuric acid is 1:3-5, the sulfuric acid concentration is 95-98%, and the mass ratio of potassium permanganate to graphite is 0.5-2:

1. The oxidation reaction is carried out at a temperature of 30-50℃ for 2-4 hours; the ultrasonic power is 300-500 W for 1-2 hours.

8. The method for preparing graphene aerogel by multi-stage intercalation-supercritical drying according to claim 1, characterized in that, The mass ratio of graphene oxide to sodium lignosulfonate is 1:0.1-0.

3.

9. The method for preparing graphene aerogel by multi-stage intercalation-supercritical drying according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 180-220℃ for 6-12 hours.

10. The method for preparing graphene aerogel by multi-stage intercalation-supercritical drying according to claim 1, characterized in that, The drying process is carried out at a pressure of 8-10 MPa, a temperature of 40-50℃, and a processing time of 4-8 h.

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