Treatment method for recovering high-purity graphite from black powder leaching residues

Abstract

The invention provides a treatment method for recovering high-purity graphite from black powder leaching residues. The treatment method comprises the following steps: removing impurity elements in graphite from the black powder leaching residues in a Joule heat flash evaporation manner; the black powder leaching residues obtained after impurity removal are put into a ball mill, liquid phenolic resin is added, full mixing is conducted, and ball milling is conducted; and putting the ball-milled mixture into flash evaporation Joule thermal equipment, and carbonizing and graphitizing the phenolic resin to obtain regenerated graphite. According to the method, the temperature of the black powder leaching residues can be increased within an extremely short time, metal impurities in the black powder leaching residues are gasified, and impurities in graphite are removed. Phenolic resin is used for carbonization and graphitization, generated disordered carbon can fill up particle cracks in waste graphite and internal lattice defects, a conductive network among graphite particles is established, a compact carbon layer is formed on the surface of graphite, and graphite structure transformation can also be induced in the step. The regenerated graphite obtained by the method is similar to commercial graphite in capacity and good in cycling stability.

Description

Technical Field

[0001] This invention relates to the field of resource recycling technology for waste lithium-ion batteries, and in particular to a method for recovering high-purity graphite from black powder leaching residue. Background Technology

[0002] The main component of the black powder leaching residue in the wet recycling process of lithium batteries is graphite. However, graphite is mixed with various impurities from the multiple processing steps in the wet recycling process of lithium batteries, resulting in the presence of elements such as fluorine, aluminum, lithium, cobalt, iron, nickel and manganese in graphite. These impurities affect the performance of graphite, preventing it from being utilized at a high value.

[0003] Among related technologies, graphite pyrometallurgical recycling can be used, but it can only remove organic components, and the removal rate of metallic impurities is not ideal. Furthermore, regenerating graphite requires ultra-high temperature treatment, resulting in high energy consumption and high metallic impurity content, leading to low-quality recycled graphite that is difficult to utilize at high value and has low economic value. On the other hand, using methods such as acid washing to remove impurities will generate large amounts of acid and alkaline wastewater, causing environmental pollution and increasing treatment costs. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention provide a method for recovering high-purity graphite from black powder leaching residue, which can remove impurity elements from graphite, improve the crystal structure and cycle stability of graphite, and obtain high-quality recycled graphite.

[0005] One embodiment of the present invention provides a method for recovering high-purity graphite from black powder leaching residue, comprising the following steps: S1. Remove impurity elements from graphite by flash evaporation and Joule heating of the black powder leaching residue; S2. Place the impurity-removed black powder leaching residue into a ball mill, add liquid phenolic resin, mix thoroughly, and then ball mill. S3. The ball-milled mixture is placed in a flash joule heating device to carbonize and graphitize the phenolic resin, thereby obtaining recycled graphite.

[0006] In some embodiments, in step S1, the temperature of the flash Joule heating is 2700-2900 K.

[0007] In some embodiments, the ball milling time in step S2 is 10-14 hours.

[0008] In some embodiments, in step S3, the temperature of the flash joule heating is 2500-3000 K.

[0009] In some embodiments, in step S1, the heat of the impurity vapor discharged from the black powder leaching residue during flash joule heating is recovered and used to heat the equipment that needs to be heated.

[0010] In some embodiments, in step S3, the heat of the mixture of pyrolysis gas and impurity vapor discharged during the carbonization and graphitization of phenolic resin is recovered and used to heat the equipment that needs to be heated.

[0011] In some embodiments, in step S3, the pyrolysis gas and impurity vapor in the heat-exchanged mixed gas are separated and collected separately.

[0012] Another embodiment of the present invention provides a method for preparing recycled graphite by means of the above-described treatment method for recovering high-purity graphite from black powder leaching residue. Attached Figure Description

[0013] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings. in: Figure 1 This is a flowchart of a method for recovering high-purity graphite from black powder leaching residue in an embodiment of the present invention. Detailed Implementation

[0014] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0015] The following describes a method for recovering high-purity graphite from black powder leaching residue according to an embodiment of the present invention, with reference to the accompanying drawings.

[0016] like Figure 1 As shown, one embodiment of the present invention proposes a method for recovering high-purity graphite from black powder leaching residue, comprising the following steps: S1. Remove impurity elements from graphite by flash evaporation and Joule heating of the black powder leaching residue; S2. Place the impurity-removed black powder leaching residue into a ball mill, add liquid phenolic resin, mix thoroughly, and then ball mill. S3. The ball-milled mixture is placed in a flash joule heating device to carbonize and graphitize the phenolic resin, thereby obtaining recycled graphite.

[0017] This invention removes impurity elements from graphite by using flash joule heating, which can heat the black powder leaching residue in a very short time, vaporize the metallic impurities in the black powder leaching residue, and remove impurities from graphite.

[0018] Even after impurities are removed from graphite through flash Joule heating, some lattice defects still remain. In this embodiment of the invention, the black powder leaching residue after impurity removal is placed in a ball mill, and liquid phenolic resin is added and thoroughly mixed before ball milling. This facilitates subsequent repair of the graphite structure and ensures the uniformity of the material reaction. The ball-milled mixture is then placed in a flash Joule heating device, causing the phenolic resin to carbonize and graphite. The resulting disordered carbon fills the particle cracks and internal lattice defects in the waste graphite, establishing a conductive network between graphite particles and forming a dense carbon layer on the graphite surface. This step also induces graphite structural transformation. The recycled graphite obtained using the method of this embodiment has a capacity similar to commercial graphite and good cycle stability. The method of this embodiment has a short heating time, low energy consumption, and does not require acid or alkali reagents, thus avoiding wastewater generation at the source, and has significant industrial application and market prospects.

[0019] In some embodiments, the flash Joule heating temperature in step S1 is 2700-2900 K. At this temperature, most impurities can be completely removed, the impurity content in the graphite meets the requirements for battery-grade graphite, and the structure and properties of the graphite are improved to some extent.

[0020] In some embodiments, the ball milling time in step S2 is 10-14 hours, preferably 12 hours.

[0021] In some embodiments, in step S3, the temperature of the flash joule heating is 2500-3000 K.

[0022] In some embodiments, in step S1, the heat of the impurity vapor discharged from the black powder leaching residue during flash joule heating is recovered and used to heat the equipment that needs to be heated.

[0023] In some embodiments, in step S3, the heat of the mixture of pyrolysis gas and impurity vapor discharged during the carbonization and graphitization of phenolic resin is recovered and used to heat the equipment that needs to be heated.

[0024] In some embodiments, in step S3, the pyrolysis gas and impurity vapor in the heat-exchanged mixed gas are separated and collected separately.

[0025] Furthermore, separation can be achieved by adjusting the temperature and pressure, taking advantage of the difference in liquefaction points between pyrolysis gas and impurity vapor.

[0026] Another embodiment of the present invention provides a method for preparing recycled graphite by means of the above-described treatment method for recovering high-purity graphite from black powder leaching residue.

[0027] The recycled graphite obtained using the method of this invention has a similar capacity to commercial graphite and good cycle stability.

[0028] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0029] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for recovering high-purity graphite from black powder leaching residue, characterized in that, Includes the following steps: S1. Remove impurity elements from graphite by flash evaporation and Joule heating of the black powder leaching residue; S2. Place the impurity-removed black powder leaching residue into a ball mill, add liquid phenolic resin, mix thoroughly, and then ball mill. S3. The ball-milled mixture is placed in a flash joule heating device to carbonize and graphitize the phenolic resin, thereby obtaining recycled graphite.

2. The method for recovering high-purity graphite from black powder leaching residue according to claim 1, characterized in that, In step S1, the flash Joule heating temperature is 2700-2900 K.

3. The method for recovering high-purity graphite from black powder leaching residue according to claim 1, characterized in that, In step S2, the ball milling time is 10-14 hours.

4. The method for recovering high-purity graphite from black powder leaching residue according to claim 1, characterized in that, In step S3, the flash joule heating temperature is 2500-3000 K.

5. The method for recovering high-purity graphite from black powder leaching residue according to claim 1, characterized in that, In step S1, the heat of the impurity steam discharged during the flash joule heating process of the black powder leaching residue is recovered and used to heat the equipment that needs to be heated.

6. The method for recovering high-purity graphite from black powder leaching residue according to claim 1, characterized in that, In step S3, the heat from the mixture of pyrolysis gas and impurity vapor emitted during the carbonization and graphitization of phenolic resin is recovered and used to heat the equipment that needs to be heated.

7. The method for recovering high-purity graphite from black powder leaching residue according to claim 6, characterized in that, In step S3, the pyrolysis gas and impurity vapor in the heat-exchanged mixed gas are separated and collected separately.

8. A recycled graphite prepared by the processing method for recovering high-purity graphite from black powder leaching residue as described in any one of claims 1-7.

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