A method for processing battery negative electrode recycled graphite and a prepared graphene slurry

Abstract

The application relates to the field of graphene, and specifically discloses a treatment method of battery negative electrode recycling graphite and prepared graphene slurry. The treatment method of battery negative electrode recycling graphite comprises the following steps: recycling graphite is added into an acid washing liquid for acid washing treatment, then water washing and drying are carried out, and acid washing graphite is obtained; the acid washing graphite is mixed with a repairing agent, then heating treatment is carried out under an inert atmosphere, and a graphite mixture is obtained. The preparation of the graphene slurry comprises the following steps: the graphite mixture, an auxiliary component and a solvent are mixed, and the graphene slurry is prepared after homogenization and dispersion. According to the application, the recycling graphite is impurity-removed and interlayer-weakened through acid washing treatment, then the thickness and interlayer binding force of the recycling graphite are reduced through heating treatment, a repairing agent is introduced to provide a carbon source in the heating process, the defects of the recycling graphite are reduced, finally, the recycling graphite is liquid-phase exfoliated by using a solvent to prepare the graphene slurry, and recycling graphite is reused to prepare high-value-added graphene slurry.

Description

Technical Field

[0001] This application relates to the field of graphite, and more specifically, to a method for recovering graphite from a battery negative electrode and the resulting graphene slurry. Background Technology

[0002] With the widespread use of electricity in society, the annual consumption of batteries is substantial. Among them, lithium-ion batteries are widely used in electric vehicles, 3C products, energy storage batteries, and other fields. In recent years, with the promotion of national new energy vehicle policies, lithium-ion batteries have developed rapidly.

[0003] Driven by the increasing use of lithium-ion batteries, recycling them is an inevitable trend based on environmental protection principles. Currently, lithium-ion battery recycling technologies mainly focus on recovering metallic elements such as nickel, cobalt, manganese, aluminum, copper, and lithium from the batteries, but research on the recycling of graphite materials in the negative electrode of lithium batteries is relatively limited.

[0004] Graphene is a novel material with a single-layer sheet structure composed of carbon atoms. It is a two-dimensional material, only one atom thick, consisting of a hexagonal honeycomb lattice formed by carbon atoms with sp2 hybrid orbitals. It is widely used in energy storage materials, environmental engineering, and sensitive sensing, and is known as "black gold" or "the king of new materials." Its potential applications are broad, making it a focus of attention and research in the new energy field. When negative electrode graphite is in prolonged contact with a lithium-containing SEM film, due to a reversible reaction, some lithium ions are continuously embedded and fixed into the graphite microstructure. This causes lithium ions to accumulate in the negative electrode graphite in the form of lithium salts. Therefore, long-term use of lithium batteries leads to a large number of lithium ions being embedded and fixed in the graphite microstructure. This structure results in a relatively loose negative electrode graphite layer structure, making it easy to peel off and facilitating graphite recycling.

[0005] Currently, patent CN111416170 proposes a method for preparing graphene from recycled graphite in lithium batteries. The preparation process includes purifying carbon powder with concentrated sulfuric acid, modifying the surface of the purified carbon powder, and reducing the modified carbon powder. The carbon powder purification step requires purification under high temperature and pressure conditions. The carbon powder surface modification step requires ice bath and constant temperature water bath, and uses a large amount of sulfuric acid, potassium permanganate, hydrochloric acid, hydrogen peroxide, sodium nitrate, and other components. The reduction step of the modified carbon powder requires treatment under high temperature conditions containing hydrogen. The inventor believes that the above process for preparing graphene is cumbersome, consumes a large amount of raw materials, has difficult-to-control conditions, and has low preparation efficiency.

[0006] Patent CN111883869 proposes a method for recovering lithium from graphite anodes of spent power batteries and preparing graphene. This method uses water vapor to oxidize and etch graphite, followed by the Hummers process to prepare porous graphene oxide. However, the inventors believe that introducing water vapor and decomposing it at high temperatures poses operational safety issues. Furthermore, the high-temperature oxidation process is intense and difficult to control, potentially leading to defects such as graphene structural damage and atomic deficiencies. Additionally, the Hummers process can introduce heteroatoms due to the strong oxidant and generate large amounts of waste acid.

[0007] Therefore, the technology for recovering graphite from negative electrodes has been difficult to implement in the graphite field, and the further application of the recovered graphite is even more difficult to develop. Summary of the Invention

[0008] To improve the complex process of recovering graphite from negative electrodes, this application provides a method for processing graphite recovered from battery negative electrodes and the resulting graphene slurry.

[0009] In a first aspect, this application provides a method for processing graphite recovered from a battery negative electrode, employing the following technical solution: A method for processing graphite recovered from a battery negative electrode includes the following steps:

[0010] Pickling treatment: Take the recovered graphite, add it to the pickling solution for pickling treatment, then wash with water and dry to obtain pickled graphite; Heat treatment: Mix the pickled graphite with the repair agent, and then heat it under an inert atmosphere to obtain a graphite mixture.

[0011] The above-described graphite recycling process described in this application is simple to operate, easy to control, highly efficient, and involves minimal addition of acidic components, thus reducing the environmental impact of acidic components and ensuring operational safety.

[0012] In the pickling process, the pickling solution is first used at room temperature to remove impurities from the polarity of the recycled graphite and weaken the interlayer bonding of the graphite. Then, the pickled graphite is mixed with a repair agent, and heat treatment is used to further reduce the thickness and interlayer bonding of the recycled graphite. The introduced repair agent is preferably a cycloalkane powder and / or a polycyclic aromatic hydrocarbon powder with a boiling point greater than 200℃. During the heat treatment, it provides a carbon source through cracking. Since the pickled graphite contains oxygen, it will consume carbon atoms of the graphite and generate carbon dioxide during the heat treatment. Therefore, the carbon source provided by the repair agent can react with oxygen in the heating environment, reducing the carbon atom consumption problem caused by carbon atom loss. At the same time, the carbon source provided by the repair agent can replenish the missing carbon atom positions on the graphite surface in the heating environment, thereby reducing the defects generated in the recycled graphite during the heat treatment process. This allows for the further preparation of downstream products, realizing the reuse of recycled graphite in battery negative electrodes.

[0013] Preferably, the recycled graphite is graphite flakes with a diameter D50 of 5-150 μm; and the resulting graphite mixture, after testing, has a BET specific surface area of ​​2-100 m². 2 / g, bulk density is 0.0025g / cm³ 3 -0.1g / cm 3 ,

[0014] Preferably, the repair agent is a cycloalkane powder and / or a polycyclic aromatic hydrocarbon powder with a boiling point greater than 200°C.

[0015] By using the above-mentioned repair agents, rapid and stable pyrolysis can be achieved during heat treatment to provide a carbon source. Cycloalkanes such as dodecane, hexadecane, and cyclohexane can be selected, while polycyclic aromatic hydrocarbons such as phenanthrene, anthracene, and naphthalene can be selected.

[0016] Preferably, in the pickling process, the weight ratio of the recovered graphite to the pickling solution is 1:3-15.

[0017] By controlling the weight ratio of recycled graphite to pickling solution, the pickling solution can fully purify and remove impurities from the recycled graphite, and weaken the interlayer structure within the recycled graphite. This allows the carbon source provided by the repair agent to replenish the missing carbon atoms on the graphite surface during subsequent heat treatment, reducing defects in the resulting graphite mixture. Furthermore, the pickling process in this application involves pickling the recycled graphite at room temperature, eliminating the need for high-temperature and high-pressure purification, making the operation simple and safe.

[0018] Preferably, the pickling solution is composed of an oxidizing agent and a sulfuric acid solution with a mass fraction of 70-98% in a weight ratio of 1:10-50, wherein the oxidizing agent is at least one of potassium permanganate, hydrogen peroxide, ammonium nitrate and acetic acid.

[0019] By using the above-mentioned pickling solution composition, impurities in the recycled graphite can be fully removed, reducing the defects caused by the introduction of heteroatoms into the graphite structure during subsequent heat treatment. At the same time, the pickling solution can weaken the interlayer of graphite during the pickling process, allowing the carbon source to replenish the missing carbon atoms on the graphite surface during heat treatment, reducing the graphite deficiency problem and realizing the reuse of recycled graphite in battery negative electrodes.

[0020] Preferably, in the heat treatment, the weight ratio of pickled graphite to repair agent is 100:1-8; the pickled graphite and repair agent are mixed at a speed of 10-25 rpm for 15-30 min.

[0021] By controlling the mixing weight ratio of acid-washed graphite and the repair agent, the repair agent is decomposed during heat treatment to provide a carbon source and is fully dispersed between the graphite layers. Simultaneously, controlling the mixing conditions ensures thorough mixing, allowing the uniformly dispersed carbon source to react with oxygen first during subsequent heat treatment. This reduces the carbon atom loss caused by the reaction between carbon atoms and oxygen within the graphite layers. The uniformly dispersed carbon source then replenishes the missing carbon atoms on the graphite surface, improving the defects in the recycled graphite. This allows for the further preparation of downstream products, enabling the reuse of recycled graphite in battery anodes. The mixing process of acid-washed graphite and the repair agent preferably employs a dual-motion dry powder mixer, with the barrel rotating at 11-25 rpm and the blades rotating at 22-50 rpm.

[0022] Preferably, in the heat treatment, the inert atmosphere is an argon atmosphere or a nitrogen atmosphere, the heat treatment temperature is 800-1000℃, and the heat treatment time is 30-300s.

[0023] By controlling the inert atmosphere, temperature, and time of the heating treatment, the thickness and interlayer bonding force of the recycled graphite can be reduced. At the same time, the repair agent can be fully decomposed and provide a carbon source to the graphite interlayer. The carbon source reacts with oxygen to reduce the loss of carbon atoms between graphite layers, or the carbon source replenishes the missing carbon atoms on the graphite surface, thereby improving the defect problem of recycled graphite and increasing the utilization rate of recycled graphite in battery negative electrodes.

[0024] Secondly, this application provides a graphene slurry, which adopts the following technical solution:

[0025] A graphene slurry is prepared by dispersing a graphite mixture, additives and solvent, wherein the amount of graphite mixture is 0.1-20% by weight, the amount of solvent is 77.5-99% by weight, and the amount of additives is 10-50% by weight of graphite.

[0026] By controlling the amounts of graphite mixture, solvent, and additives, the graphite mixture can be uniformly dispersed in the solvent system, thereby obtaining a graphene slurry with stable quality during the dispersion process. Preferably, the graphene slurry can be prepared by physical-mechanical liquid-phase exfoliation.

[0027] Preferably, the additive is composed of a dispersant, an antifoaming agent, and a viscosity modifier mixed in a weight ratio of 10-30:1-5:1; the solvent is NMP, DBE, DMF, ethanol, or water.

[0028] By using the above-mentioned specific weight ratio of dispersant, defoamer and viscosity modifier, the dispersibility of graphite mixture in solvent can be improved, the fine bubbles that appear during the dispersion process can be reduced and suppressed, and the resulting graphene slurry system has good dispersibility and wide application. The above-mentioned solvent can disperse the graphite mixture evenly, and at the same time, under the mechanical shear force of dispersion, the graphite layers are peeled off to obtain graphene.

[0029] The dispersant mentioned above can be at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium hydroxymethyl cellulose, alkali lignin, sodium citrate, sodium lignin sulfonate, Tween, and polyethylene glycol, which can improve the mixing and dispersibility of graphite mixtures and solvents. After mechanical exfoliation and dispersion treatment, the graphene slurry obtained has good dispersibility.

[0030] The defoamer mentioned above can be at least one of BYK055, BYK116, BYK306, and BYK463, which can reduce or suppress fine foam that appears during the dispersion process.

[0031] The viscosity modifier mentioned above can be at least one of Gaotai 2025, Haiming 299, and Gaotai 6050, which can adjust the viscosity of the system so that the obtained graphene slurry has good processing performance and a wide range of applications.

[0032] Preferably, the graphene slurry contains graphene flakes with a diameter of 1-10 μm. By using the specific amounts and types of dispersants, defoamers, viscosity modifiers and solvents mentioned above, the graphene can be mechanically exfoliated and dispersed uniformly and stably to obtain a graphene slurry with a flake diameter of 1-10 μm, making the graphene slurry within this flake diameter range easy to process and apply to downstream fields.

[0033] Thirdly, this application provides a method for preparing graphene slurry, which adopts the following technical solution:

[0034] A method for preparing graphene slurry includes the following steps: homogenizing a graphite mixture and additives in a solvent under a pressure of 500-1500 bar, preferably for a homogenization time of 1-3 h, to obtain graphene slurry;

[0035] The graphite mixture is the graphite mixture obtained by the method for recovering graphite from the negative electrode of the battery described in the first aspect above.

[0036] Currently, in the related technologies for preparing graphene, strong oxidizing agents (concentrated sulfuric acid, potassium permanganate, hydrogen peroxide, etc.) are often used to treat graphite. Under the action of strong oxidizing agents, graphite sheets are peeled off, acquiring oxygen-containing functional groups. These functional groups are then eliminated through thermal reduction or reducing agent treatment, thus achieving the purpose of preparing graphene. However, the inventors believe that the introduced oxygen atoms are difficult to completely remove during the subsequent reduction process. Whether through thermal reduction or the use of reducing agents, the final graphene will contain a certain amount of residual oxygen. Moreover, after reduction treatment, the defects in graphene actually increase. This is because removing oxygen atoms also removes carbon atoms, forming pores and causing intrinsic defects in graphene.

[0037] Therefore, this application first uses an acid washing solution to remove impurities from the recycled graphite, while simultaneously weakening the interlayer bonding of the graphite. After water washing, heat treatment further reduces the thickness and interlayer bonding of the recycled graphite. During the heat treatment, the repair agent is decomposed to provide a carbon source. This carbon source reacts with oxygen to reduce the loss of carbon atoms between graphite layers, or replenishes the missing carbon atoms on the graphite surface, thus improving the defects in the recycled graphite and resulting in a graphene slurry with fewer defects. Then, the graphite is dispersed in a solvent, and a homogeneous dispersion method is used for liquid-phase exfoliation to prepare graphene. The resulting graphene sheets have a diameter of 1-10 μm and a thickness of 0.35-4 nm, with an IG / ID ratio >5 as measured by Raman spectroscopy. This enables the reuse of recycled graphite from lithium-ion battery anodes to prepare high-value-added graphene slurry. Furthermore, the introduction of strong oxidants during graphene preparation reduces the difficulty in removing introduced oxygen atoms, thus minimizing residual oxygen in the graphene and reducing defects such as pores and missing carbon atoms.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. In the method for processing recycled graphite in this application, after removing impurities and weakening the interlayer by acid washing, the thickness and interlayer bonding of the recycled graphite are reduced by heat treatment. At the same time, a repair agent is introduced to provide carbon source to the graphite interlayer during the heating process. The provided carbon source reacts with oxygen to reduce the loss of carbon atoms in the graphite interlayer, or the carbon source is added to the carbon atom missing positions on the graphite surface to improve the defects that may occur in the recycled graphite during heat treatment.

[0040] 2. In the graphene slurry of this application, a solvent is used to disperse a graphite mixture, and during the dispersion process, the mixture is liquid-phase exfoliated to prepare graphene. No strong oxidant is introduced during the graphene preparation process, which reduces the presence of residual oxygen in the graphene due to the difficulty in removing the introduced oxygen atoms, and reduces defects such as pores and missing carbon atoms in the graphene. Attached Figure Description

[0041] Figure 1This is a 500x SEM image of the graphite recovered in this application;

[0042] Figure 2 This is a 10,000x SEM image of the graphene prepared in Example 1 of this application;

[0043] Figure 3 This is the AFM image of the graphene prepared in Example 1 of this application;

[0044] Figure 4 This is the AFM detection spectrum of graphene obtained in Example 1 of this application;

[0045] Figure 5 This is the Raman spectrum of graphene obtained in Example 1 of this application;

[0046] Figure 6 This is a 10,000x SEM image of the graphene obtained in Example 2 of this application;

[0047] Figure 7 Here is the AFM image of the graphene prepared in Example 2 of this application;

[0048] Figure 8 This is the AFM detection spectrum of graphene obtained in Example 2 of this application;

[0049] Figure 9 This is the Raman spectrum of graphene obtained in Example 2 of this application;

[0050] Figure 10 This is a 10,000x SEM image of the graphene obtained in Example 3 of this application;

[0051] Figure 11 This is the AFM image of the graphene prepared in Example 3 of this application;

[0052] Figure 12 This is the AFM detection spectrum of graphene obtained in Example 3 of this application;

[0053] Figure 13 This is the Raman spectrum of graphene obtained in Example 3 of this application;

[0054] Figure 14 This is a 20,000x SEM image of the graphene prepared in Comparative Example 1 of this application;

[0055] Figure 15 This is the AFM image of the graphene prepared in Comparative Example 1 of this application;

[0056] Figure 16 This is the AFM detection spectrum of the graphene prepared in Comparative Example 1 of this application;

[0057] Figure 17This is the Raman spectrum of the graphene prepared in Comparative Example 1 of this application;

[0058] Figure 18 This is a 10,000x SEM image of the graphene prepared in Comparative Example 2 of this application.

[0059] Figure 19 This is the AFM image of the graphene prepared in Comparative Example 2 of this application;

[0060] Figure 20 This is the AFM detection spectrum of the graphene prepared in Comparative Example 2 of this application;

[0061] Figure 21 This is the Raman spectrum of the graphene prepared in Comparative Example 2 of this application. Detailed Implementation

[0062] The following is in conjunction with the appendix Figure 1-21 The present application will be further described in detail with reference to the embodiments.

[0063] Example of preparation of graphite mixture

[0064] Preparation Example 1

[0065] The preparation of graphite mixtures includes the following steps:

[0066] 92 kg of sulfuric acid with a mass fraction of 75% and 8 kg of hydrogen peroxide with a mass fraction of 30% were mixed evenly to obtain a mixed pickling solution.

[0067] Take 20 kg of recycled graphite powder with a diameter D50 of 80 μm, pickle the recycled graphite powder with mixed pickling solution at room temperature for 40 min, then wash the pickled recycled graphite powder with water until the pH value is 5-7, filter the recycled graphite powder, and dry it at 50℃ for 5 h to obtain pickled graphite powder.

[0068] The dried pickled graphite powder was mixed with 1.5 kg of naphthalene powder. In this embodiment, a dual-motion dry powder mixer was used for powder mixing. The mixing process was carried out with a barrel speed of 20 rpm, a blade speed of 30 rpm, and a mixing time of 15 min to obtain a graphite mesophase mixture.

[0069] A graphite mesophase mixture was heated at 880°C for 150 s under an argon atmosphere to obtain a graphite mixture with a BET specific surface area of ​​20 m². 2 / g, bulk density is 0.02g / cm³ 3 .

[0070] Preparation Example 2

[0071] The preparation of graphite mixtures includes the following steps:

[0072] 115.2 kg of 90% sulfuric acid, 3 kg of potassium permanganate, and 2.4 kg of ammonium nitrate were mixed evenly to obtain a mixed pickling solution.

[0073] Take 20 kg of recycled graphite powder with a diameter D50 of 40 μm, pickle the recycled graphite powder with mixed pickling solution at room temperature for 35 min, then wash the pickled recycled graphite powder with water until the pH value is 5-7, filter the recycled graphite powder, and dry it at 45℃ for 3 h to obtain pickled graphite powder.

[0074] The dried pickled graphite powder was mixed with 0.4 kg of anthracene powder. In this embodiment, a dual-motion dry powder mixer was used for powder mixing. The mixing process was carried out with a barrel speed of 25 rpm, a blade speed of 45 rpm, and a mixing time of 15 min to obtain a graphite mesophase mixture.

[0075] A graphite mesophase mixture was heated at 950°C for 35 seconds under an argon atmosphere to obtain a graphite mixture with a BET specific surface area of ​​35 m². 2 / g, bulk density is 0.003g / cm³ 3 .

[0076] Preparation Example 3

[0077] The preparation of graphite mixtures includes the following steps:

[0078] 54.55 kg of 98% sulfuric acid, 2.2 kg of potassium permanganate, and 3.25 kg of acetic acid were mixed evenly to obtain a mixed pickling solution.

[0079] Take 20 kg of recycled graphite powder with a diameter D50 of 25 μm, pickle the recycled graphite powder with a mixed pickling solution at room temperature for 35 min, then wash the pickled recycled graphite powder with water until the pH value is 5-7, filter the recycled graphite powder, and dry it at 55℃ for 1.5 h to obtain pickled graphite powder.

[0080] The dried pickled graphite powder was mixed with 0.4 kg of phenanthrene powder and 0.6 kg of dodecane powder. In this embodiment, a dual-motion dry powder mixer was used for powder mixing. The mixing process was carried out with a barrel speed of 15 rpm, a blade speed of 35 rpm, and a mixing time of 15 min to obtain a graphite mesophase mixture.

[0081] A graphite mesophase mixture was heated at 830°C for 280 s under an argon atmosphere to obtain a graphite mixture with a BET specific surface area of ​​28 m². 2 / g, bulk density is 0.006g / cm³ 3 .

[0082] Preparation of Comparative Example 1

[0083] The preparation of graphite-treated materials includes the following steps:

[0084] 54.55 kg of 98% sulfuric acid, 2.2 kg of potassium permanganate, and 3.25 kg of acetic acid were mixed evenly to obtain a mixed pickling solution.

[0085] Take 20 kg of recycled graphite powder with a diameter D50 of 25 μm, pickle the recycled graphite powder with a mixed pickling solution at room temperature for 35 min, then wash the pickled recycled graphite powder with water until the pH value is 5-7, filter the recycled graphite powder, and dry it at 55℃ for 1.5 h to obtain pickled graphite powder.

[0086] Under an argon atmosphere, dried pickled graphite powder was heated at 830°C for 280 seconds to obtain a graphite-treated material with a BET specific surface area of ​​25 m². 2 / g, bulk density is 0.005g / cm³ 3 .

[0087] Example

[0088] Example 1

[0089] The preparation of graphene slurry includes the following steps:

[0090] 130g of the graphite mixture prepared in Example 1, 824.5g of deionized water, 28.4g of sodium dodecylbenzenesulfonate, 14.2g of BYK055 defoamer, and 2.8g of Gaotai 2025 viscosity modifier were added to a homogenizer for mixing and dispersion. The homogenizer was set at a dispersion pressure of 800 bar and the mixture was dispersed for 1 hour to obtain a graphene slurry.

[0091] (Detection 1) SEM Detection: The graphene in the original recycled graphite and the graphene slurry prepared in Example 1 was subjected to SEM detection. See [link to relevant documentation]. Figure 1 The image shows a SEM image of the recovered graphite at 500x magnification. Figure 2 This is a SEM image of the graphene prepared in Example 1 at a magnification of 10,000x. Figure 2 It can be seen that the graphene prepared in this embodiment has a relatively complete morphology and few defects.

[0092] (Test 2) AFM Detection: The graphene in the prepared graphene slurry was subjected to AFM detection. See [link to relevant documentation]. Figure 3-4 The graphene in the graphene slurry prepared in Example 1 was detected, specifically targeting... Figure 3The graphene in the upper right corner was tested for sheet diameter and thickness. The sheet diameter was measured to be 6.8 μm and the thickness to be 2.66 nm. The number of layers is relatively thin. Other test results are shown in Table 1 below:

[0093] Table 1. AFM detection data of graphene in the graphene slurry prepared in Example 1.

[0094]

[0095] In Table 1 above, the height [red] refers to the corresponding Figure 3 The arrow to the left of graphene in the upper right corner corresponds to... Figure 4 The left arrow in the image appears as a red arrow in the detection spectrum, and is therefore defined as "high [red]"; similarly, "high [blue]" refers to the corresponding... Figure 3 The arrow to the right of graphene in the upper right corner corresponds to... Figure 4 The right arrow in the image appears as a blue arrow in the detection spectrum, and is therefore defined as: "height [blue]".

[0096] (Detection 3) Raman spectroscopy detection: See [link] Figure 5 The graphene was subjected to Raman spectroscopy, and the IG / ID ratio was found to be 9.35. The higher the IG / ID value, the better the quality of the graphene prepared in this embodiment.

[0097] Example 2

[0098] The preparation of graphene slurry includes the following steps:

[0099] 60g of the graphite mixture obtained in Preparation Example 2, 913g of deionized water, 24.5g of sodium hydroxymethyl cellulose, 1.6g of BYK116 defoamer, and 0.8g of Hemings 299 viscosity modifier were added to a homogenizer for mixing and dispersion. The homogenizer was set at a dispersion pressure of 900 bar and the mixture was dispersed for 1 hour to obtain a graphene slurry.

[0100] (Test 1) SEM test: The graphene in the graphene slurry prepared in this embodiment was tested by SEM. Figure 6 This is a SEM image of the graphene prepared in Example 2 at a magnification of 10,000x. Figure 6 It can be seen that the graphene prepared in this embodiment has a relatively complete morphology and few defects.

[0101] (Test 2) AFM Detection: The graphene in the prepared graphene slurry was subjected to AFM detection. See [link to relevant documentation]. Figure 7-8 ,against Figure 7 The graphene in the upper left corner was tested for sheet diameter and thickness. The sheet diameter was measured to be 1.3 μm and the thickness to be 1.40 nm, indicating a relatively thin layer thickness. Other test results are shown in Table 2 below.

[0102] Table 2. AFM detection data of graphene in the graphene slurry prepared in Example 2.

[0103]

[0104] In Table 2 above, the height [red] refers to the corresponding Figure 7 The arrow to the left of graphene in the upper left corner corresponds to... Figure 8 The left arrow in the image appears as a red arrow in the detection spectrum, and is therefore defined as "high [red]"; similarly, "high [blue]" refers to the corresponding... Figure 7 The arrow to the right of graphene in the upper left corner corresponds to... Figure 8 The right arrow in the image appears as a blue arrow in the detection spectrum, and is therefore defined as: "height [blue]".

[0105] (Detection 3) Raman spectroscopy detection: See [link] Figure 9 The graphene was subjected to Raman spectroscopy, and the IG / ID ratio was measured to be 5.79.

[0106] Example 3

[0107] The preparation of graphene slurry includes the following steps:

[0108] 80g of the graphene mixture prepared in Example 3, 888g of deionized water, 29.1g of sodium dodecyl sulfate, 1.5g of BYK116 defoamer, and 1.5g of Gaotai 6050 viscosity modifier were added to a homogenizer for mixing and dispersion. The homogenizer was set at a dispersion pressure of 700 bar and the mixture was dispersed for 1.5 hours to obtain a graphene slurry.

[0109] (Test 1) SEM test: The graphene in the original recycled graphite and the graphene slurry prepared in Example 3 of this study was tested by SEM. Figure 10 This is a SEM image of the graphene prepared in Example 3 at a magnification of 10,000x. Figure 10 It can be seen that the graphene prepared in this embodiment has a relatively complete morphology and few defects.

[0110] (Test 2) AFM Detection: The graphene in the prepared graphene slurry was subjected to AFM detection. See [link to relevant documentation]. Figure 11-12 The graphene in the graphene slurry prepared in Example 3 was detected, specifically targeting... Figure 11 The graphene in the lower left corner was tested for sheet diameter and thickness. The sheet diameter was measured to be 2.5 μm and the thickness to be 1.49 nm. The number of layers is relatively thin. Other test results are shown in Table 3 below:

[0111] Table 3. AFM detection data of graphene in the graphene slurry prepared in Example 3.

[0112]

[0113] In Table 3 above, the height [red] refers to the corresponding Figure 11 The arrow to the left of graphene in the lower left corner corresponds to... Figure 12 The left arrow in the image appears as a red arrow in the detection spectrum, and is therefore defined as "high [red]"; similarly, "high [blue]" refers to the corresponding... Figure 11 The arrow to the right of graphene in the lower left corner corresponds to... Figure 12 The right arrow in the image appears as a blue arrow in the detection spectrum, and is therefore defined as: "height [blue]".

[0114] (Detection 3) Raman spectroscopy detection: See [link] Figure 13 The graphene was subjected to Raman spectroscopy, and the IG / ID ratio was measured to be 6.39. The higher the IG / ID value, the better the quality of the graphene prepared in this embodiment.

[0115] Comparative Example

[0116] Comparative Example 1

[0117] The preparation of graphene slurry includes the following steps:

[0118] 80g of the graphene mixture prepared in Comparative Example 1, 888g of deionized water, 29.1g of sodium dodecyl sulfate, 1.5g of BYK116 defoamer, and 1.5g of Gaotai 6050 viscosity modifier were added to a homogenizer for mixing and dispersion. The homogenizer was set at a dispersion pressure of 700 bar and the mixture was dispersed for 1.5 hours to obtain the graphene slurry.

[0119] (Test 1) SEM detection: The graphene in the graphene slurry prepared in Comparative Example 1 was detected by SEM. Figure 14 This is a SEM image of the graphene prepared in Comparative Example 1 at a magnification of 20,000x. Figure 14 It can be seen that the graphene prepared in Comparative Example 1 has a relatively complete morphology.

[0120] (Test 2) AFM Detection: The graphene in the prepared graphene slurry was subjected to AFM detection. See [link to relevant documentation]. Figure 15-16 To detect the graphene in the graphene slurry prepared in Comparative Example 1, specifically targeting... Figure 15 The graphene on the right side of the middle section underwent tests for sheet diameter and thickness, with a measured sheet diameter of 2.4 μm and a thickness of 1.68 nm. Other test results are shown in Table 4 below.

[0121] Table 4. AFM detection data of graphene in the graphene slurry prepared in Comparative Example 1.

[0122]

[0123] In Table 4 above, the height [red] refers to the corresponding Figure 15 The arrow to the right of graphene corresponds to... Figure 16The right-hand arrow in the image appears as a red arrow in the detection spectrum, and is therefore defined as "high [red]"; similarly, "high [blue]" refers to the corresponding... Figure 15 The arrow to the left of graphene on the right corresponds to... Figure 16 The left arrow in the image appears as a blue arrow in the detection spectrum, and is therefore defined as: "height [blue]".

[0124] (Detection 3) Raman spectroscopy detection: See [link] Figure 17 Raman spectroscopy revealed that the graphene had an IG / ID ratio of 1.16, which was relatively low, indicating that the quality of the obtained graphene was lower than that of Example 3.

[0125] Comparative Example 2

[0126] The preparation of graphene slurry includes the following steps:

[0127] Take 80g of recycled graphite powder with a diameter D50 of 25μm, its BET is 3.62m. 2 / g, with a bulk density of 0.675g / cm³. 3 Then, 80 kg of the recovered graphite powder, 888 g of deionized water, 29.1 g of sodium dodecyl sulfate, 1.5 g of BYK116 defoamer, and 1.5 g of Gaotai 6050 viscosity modifier were added to a homogenizer for mixing and dispersion. The homogenizer was set at a dispersion pressure of 700 bar and the dispersion was carried out for 1.5 h to obtain graphene slurry.

[0128] (Test 1) SEM detection: The graphene in the graphene slurry prepared in Comparative Example 2 was detected by SEM. Figure 18 This is a SEM image of the graphene prepared in Comparative Example 2 at a magnification of 10,000x. Figure 18 It can be seen that the graphene prepared in Comparative Example 2 has a relatively disordered morphology and contains a lot of complex substances.

[0129] (Test 2) AFM Detection: The graphene in the prepared graphene slurry was subjected to AFM detection. See [link to relevant documentation]. Figures 19-20 To detect the graphene in the graphene slurry prepared in Comparative Example 2, specifically targeting... Figure 19 The graphene in the middle and lower part was tested for sheet diameter and thickness. The sheet diameter was measured to be 6.4 μm and the thickness to be 13.53 nm. Other test results are shown in Table 5 below:

[0130] Table 5. AFM detection data of graphene in the graphene slurry prepared in Comparative Example 2.

[0131]

[0132] In Table 5 above, the height [red] refers to the corresponding Figure 19 The left arrow of the graphene in the lower middle part corresponds to... Figure 20The left arrow in the image appears as a red arrow in the detection spectrum, and is therefore defined as "high [red]"; similarly, "high [blue]" refers to the corresponding... Figure 19 The arrow to the right of the graphene in the lower middle part corresponds to... Figure 20 The right arrow in the image appears as a blue arrow in the detection spectrum, and is therefore defined as: "height [blue]".

[0133] (Detection 3) Raman spectroscopy detection: See [link] Figure 21 Raman spectroscopy of graphene yielded an IG / ID ratio of 10.32, which is relatively high.

[0134] As can be seen from the detection results of Examples 1-3 above, the higher the IG / ID ratio in Raman spectroscopy, the better the quality of the obtained graphene. The graphene slurry prepared by the graphite recycling method of this application has fewer graphene defects and better quality. The thickness of the graphene is 0.35-4nm, and the thickness of one layer of graphene is 0.35nm. The graphene obtained by this application has a thinner number of layers, excellent thermal and electrical conductivity, and a wide range of applications.

[0135] The graphene IG / ID value of Comparative Example 1 was only 1.16, which was significantly lower than the graphene IG / ID value obtained in this application. This indicates that the graphene introduced in this application during the heat treatment process can be thermally decomposed to provide a carbon source to the graphite interlayer. The provided carbon source reacts with oxygen to reduce the loss of carbon atoms between graphite layers, or the carbon source replenishes the missing carbon atom sites on the graphite surface, thereby improving the defects that may occur in the heat treatment of recycled graphite, so that the obtained graphene has a complete morphology, better quality, and fewer defects.

[0136] The graphene prepared in Comparative Example 2 had a higher surface roughness, larger sheet diameter, greater thickness, and more disordered morphology. This indicates that the present application can remove impurities and weaken interlayers of recycled graphite through acid washing, and reduce the thickness and interlayer bonding force of recycled graphite through heating treatment. Furthermore, the carbon source provided by the cracking of the repair agent during the heating process reacts with oxygen to reduce the loss of carbon atoms between graphite layers and replenish the carbon source to the missing carbon atom positions on the graphite surface. This results in the graphene obtained after homogeneous dispersion and exfoliation treatment having a complete morphology without disordered morphology.

[0137] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for recovering graphite from battery negative electrodes, characterized in that: Includes the following steps: Pickling treatment: Take the recycled graphite, add it to the pickling solution for pickling treatment, then wash with water and dry to obtain pickled graphite; Heat treatment: Acid-washed graphite is mixed with a repair agent and then heated under an inert atmosphere to obtain a graphite mixture; The repair agent is a polycyclic aromatic hydrocarbon powder with a boiling point greater than 200℃; The heat treatment temperature is 800-1000℃, and the heat treatment time is 30-300s.

2. The method for recovering graphite from a battery negative electrode according to claim 1, characterized in that: In the pickling process, the weight ratio of recovered graphite to pickling solution is 1:3-15.

3. The method for recovering graphite from a battery negative electrode according to claim 2, characterized in that: In the pickling process, the pickling temperature is room temperature and the pickling time is 20-60 minutes.

4. A method for processing graphite recovered from a battery negative electrode according to any one of claims 1-3, characterized in that: The pickling solution is composed of an oxidizing agent and a sulfuric acid solution with a mass fraction of 70-98% at a weight ratio of 1:10-50. The oxidizing agent is at least one of potassium permanganate, hydrogen peroxide, and ammonium nitrate.

5. The method for processing graphite recovered from the negative electrode of a battery according to claim 1, characterized in that: In the heat treatment, the weight ratio of pickled graphite to repair agent is 100:1-8.

6. A graphene slurry, characterized in that: It is prepared by dispersing a graphite mixture, additives and solvent. By weight percentage, the amount of graphite mixture is 0.1-20%, the amount of solvent is 77.5-99%, and the amount of additives is 10-50% of the amount of graphite. The graphite mixture is the graphite mixture obtained by the method for recovering graphite from the negative electrode of the battery according to any one of claims 1-5; The additive is composed of a mixture of dispersant, defoamer and viscosity modifier in a weight ratio of 10-30:1-5:

1.

7. The graphene slurry according to claim 6, characterized in that: In the graphene slurry, the graphene flakes have a diameter of 1-10 μm.

8. A method for preparing a graphene slurry, characterized in that: The method includes the following steps: homogenizing the additive and the graphite mixture obtained by the treatment method according to any one of claims 1-5 in a solvent under a pressure of 500-1500 bar to obtain a graphene slurry.

Images