A method for repairing and regenerating waste negative electrode graphite, a repairing material thereof and application thereof

Abstract

The application discloses a kind of waste negative graphite's repair regeneration method and its repair material and application.A kind of waste negative graphite's repair regeneration method, including the following steps: waste negative graphite is carried out acid cleaning in the concentration of 0.5~3.0 M hydrochloric acid, impurity is removed, and drying is obtained purified graphite, subsequently it is placed in low temperature plasma reaction device.After being pumped and replaced by ammonia to construct oxygen-free environment, plasma treatment is carried out under 10~100 Pa pressure and 100~400 W power for 5~50 min, and the repair material is obtained.The application adopts solvent-free plasma gas phase dry method, by the physical sputtering and chemical action of high-energy particle, not only can high-efficiency remove residual impurities on graphite surface, but also can realize in-situ lattice reconstruction and heteroatom doping.The method is simple in process, low in energy consumption, short in repair time.The prepared regenerated graphite is used as lithium ion battery negative electrode, and exhibits excellent reversible specific capacity and cycle stability.

Description

Technical Field

[0001] This invention relates to the field of power lithium-ion battery recycling technology, specifically to a method for repairing and regenerating waste negative electrode graphite, as well as its repair materials and applications. Background Technology

[0002] Lithium-ion batteries (LIBs) are widely recognized as the core energy storage technology for portable electronic devices and electric vehicles (EVs). However, due to their typically short service life of only 3–10 years, a continuous stream of used lithium-ion batteries is generated, making the efficient recycling and reuse of these materials a key issue for the sustainable development of the battery industry. Among these, the recycling of used negative electrode graphite is particularly important. On the one hand, as a critical strategic resource, the recycling of graphite helps alleviate the pressure of the gradual depletion of natural graphite resources; on the other hand, it can significantly reduce the high energy consumption and carbon emissions associated with traditional ore mining and refining processes.

[0003] However, current technologies for the regeneration and repair of waste negative electrode graphite still face significant bottlenecks, making it difficult to achieve an effective balance between structural restoration and green, low-carbon practices. Processes such as wet recycling primarily rely on acid / alkali leaching to remove metallic impurities from the graphite surface. For example, leaching with nitric acid and ethanol has been proven to significantly improve the storage performance of lithium-ion batteries at a current density of 0.05 A·g. −1 It can achieve 305.49 mAh·g −1The specific capacity of the graphite anode is superior to that of untreated graphite, as shown in the following reference: XU YJ, SONG XH, CHANG Q, et al. The regeneration of graphite anode from spent lithium-ion batteries by washing with a nitricacid / ethanol solution[J]. New Carbon Materials, 2022, 37(5): 1011-1020. Although this method is relatively simple to operate, its scope of action is mostly limited to the physicochemical purification of the surface, and it is difficult to completely remove the dense and stable solid electrolyte interface (SEI) film formed on the surface of aged graphite. In addition, the wet process lacks the ability to deeply control the material structure and cannot effectively repair the bulk lattice defects of graphite caused by volume expansion and stress accumulation during long-term charge-discharge cycles. As a result, the recovery of the electrochemical kinetic performance of the regenerated graphite is limited, which is difficult to meet the remanufacturing requirements of high-end battery anodes. In order to achieve more thorough structural reconstruction and performance recovery, it is usually necessary to perform high-temperature heat treatment on the waste graphite to improve the degree of graphitization. Waste graphite was placed in a tube furnace at 1300 °C and carbonized in a continuously flowing Ar gas atmosphere for 2 h. The resulting reclaimed graphite exhibited a discharge specific capacity of 444 mAh g⁻¹ during the first cycle at 0.1 C rate. −1 See the following reference: SEN A, KUMAR K, KUMAR S, et al. Reviving Graphite Anode from Spent Li-Ion Batteries via Acid Leaching and Carbonization Methodology[J]. ACSSustainable Resource Management, 2025, 2(4): 642-650. Although this method can significantly improve the crystallinity of graphite, it has extremely high energy consumption, stringent requirements for equipment conditions, and may also bring significant secondary pollution and carbon emission problems, thereby greatly increasing the overall recycling cost and weakening its environmentally friendly advantages.

[0004] Therefore, given these limitations, there is an urgent need to develop a green, energy-saving, and sustainable method and application for the direct regeneration of waste negative electrode graphite through plasma treatment, so as to achieve efficient repair and green closed-loop recycling of waste negative electrode graphite. Summary of the Invention

[0005] The purpose of this invention is to provide a method and application for the direct regeneration of waste anode graphite through plasma treatment. This invention employs a solvent-free plasma gas-phase coherent process. Through the physical sputtering and chemical action of high-energy particles, it not only efficiently removes residual impurities from the graphite surface but also achieves in-situ lattice reconstruction and heteroatom doping. This method is simple, energy-efficient, and has a short remediation time. The resulting regenerated graphite, when used as an anode in lithium-ion batteries, exhibits excellent reversible specific capacity and cycle stability, providing a green and efficient closed-loop pathway for the recycling of waste graphite.

[0006] The objective of this invention is achieved as follows: A method for directly regenerating waste negative electrode graphite through plasma treatment includes the following steps: S1. Place the waste negative electrode graphite in hydrochloric acid for acid washing to remove impurities, then wash with deionized water until neutral, and transfer to a drying oven to dry to obtain purified graphite. S2. The purified graphite obtained in S1 is evenly spread in a ceramic boat and then transferred to a low-temperature plasma reactor. After vacuuming and replacing with working gas to create an oxygen-free environment, working gas is introduced for plasma treatment to obtain the repair material.

[0007] In step S1, the concentration of hydrochloric acid is 0.5~3.0 mol / L, and the pickling time is 2 hours.

[0008] In S1, the temperature of the drying oven is 58-62 ℃, and the drying time is 11-13 hours.

[0009] In S2, the working gas is at least one of NH3 and N2.

[0010] In S2, the reaction pressure of the plasma treatment is 10~100 Pa.

[0011] In S2, the power of the plasma reaction device is 100~400 W.

[0012] In S2, the plasma treatment time is 5 min to 50 min.

[0013] The repair material is obtained from a repair and regeneration method for waste negative electrode graphite.

[0014] A repair and regeneration method for waste negative electrode graphite yields a repair material that is used in battery manufacturing.

[0015] The beneficial effects of this invention are: 1. This invention uses plasma engineering technology as a rapid and highly controllable gas phase solution, which effectively overcomes the defects of solid and liquid modification methods.

[0016] 2. Unlike traditional regeneration methods, this invention uses an electromagnetic field to excite a gas source into plasma, generating high-energy electrons, ions, and free radicals. On one hand, these particles effectively remove residual surface impurities through sputtering; on the other hand, the plasma can penetrate the graphite microporous network and interact with the graphite surface, achieving in-situ lattice reconstruction and nitrogen atom doping.

[0017] 3. As a solvent-free dry process, the plasma treatment technology of this invention significantly shortens the remediation time of waste graphite and reduces energy consumption, which is in full compliance with the principles of green closed-loop chemistry. Attached Figure Description

[0018] Figure 1 The XRD patterns of the repair materials prepared in Examples 1-3 and Comparative Example 1 are shown below. Figure 2 The Raman spectra of the repair materials prepared in Examples 1-3 and Comparative Example 1 are shown below. Figure 3 The images shown are scanning electron microscope (SEM) images of the repair materials prepared in Examples 1-3 and Comparative Example 1 of the present invention. Figure 4 The cycle performance diagrams are for the repair materials prepared in Examples 1-3 of the present invention and the coin half-cell prepared in Comparative Example 1. Figure 5 The rate performance diagrams are for button half-cells made from the repair materials prepared in Examples 1-3 of this invention. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. Example 1

[0020] First, the raw waste negative electrode graphite was acid-washed with 1 mol / L hydrochloric acid for 2 hours to remove impurities, then washed with deionized water until neutral, and dried in a 60 ℃ drying oven for 12 hours to obtain purified graphite. The purified graphite was evenly spread into a thin layer in a ceramic boat and placed inside the radio frequency coil of a low-temperature plasma reaction device. Under the conditions of a chamber pressure of 60 Pa and a discharge power of 300 W, ammonia plasma was excited to repair the purified graphite. After 10 min of treatment, the repaired material was obtained, denoted as N-Gr-10. Example 2

[0021] First, the raw waste negative electrode graphite was acid-washed with 1 mol / L hydrochloric acid for 2 hours to remove impurities, then washed with deionized water until neutral, and dried in a 60 ℃ drying oven for 12 hours to obtain purified graphite. The purified graphite was evenly spread into a thin layer in a ceramic boat and placed inside the radio frequency coil of a low-temperature plasma reaction device. Under the conditions of a chamber pressure of 60 Pa and a discharge power of 300 W, ammonia plasma was excited to repair the purified graphite. After 20 min of treatment, the repaired material was obtained, denoted as N-Gr-20. Example 3

[0022] First, the raw waste negative electrode graphite was acid-washed with 1 mol / L hydrochloric acid for 2 hours to remove impurities, then washed with deionized water until neutral, and dried in a 60 ℃ drying oven for 12 hours to obtain purified graphite. The purified graphite was evenly spread into a thin layer in a ceramic boat and placed inside the radio frequency coil of a low-temperature plasma reaction device. Under the conditions of a chamber pressure of 60 Pa and a discharge power of 300 W, ammonia plasma was excited to repair the purified graphite. After 30 min of treatment, the repaired material was obtained, denoted as N-Gr-30.

[0023] Comparative Example 1 This comparative example directly provides a waste negative electrode graphite, denoted as SG.

[0024] The repair materials prepared in Examples 1-3 and Comparative Example 1 were characterized as follows: according to Figure 1 It can be seen that all samples exhibit characteristic diffraction peaks corresponding to the (100), (101), and (004) crystal planes of graphite, while a significant (002) peak exists at approximately 26.3°. Further reference... Figure 1 As can be seen from the magnified image of the (002) characteristic peak of Comparative Example 1 (SG), this peak broadens and shifts to a lower angle (approximately 26.2°), indicating that the interlayer spacing has irreversibly expanded after long-term cycling, resulting in lattice damage. In contrast, after ammonia plasma treatment according to the present invention, the (002) peak of the regenerated samples of Examples 1-3 gradually shifts to a higher angle. In particular, the peak shift of the repaired sample of Example 2 (N-Gr-20) is approximately 26.5°, the full width at half maximum (FWHM) is significantly reduced, and it exhibits the highest peak intensity. This structural transformation indicates that the high-energy plasma treatment of the present invention can effectively promote carbon atom rearrangement, thereby repairing the damaged graphite lattice. The test results demonstrate that the process conditions of Example 2 exhibit the best structural repair effect, significantly better than Comparative Example 1.

[0025] according to Figure 2 It can be seen that Comparative Example 1 (SG) exhibits a high value of 0.39. I D / I G The values ​​confirmed the presence of amorphous organic impurities in the severely fractured graphite surface and the residual degraded SEI film. After ammonia plasma treatment, the values ​​of Examples 1-3... I D / I G The values ​​all showed a downward trend, with the N-Gr-20 sample reaching a minimum of 0.05. This not only proves that it can effectively remove amorphous residues on the surface, but also achieves efficient repair of defects and cracks on the graphite surface, significantly improving the crystallinity and structural integrity of recycled graphite.

[0026] according to Figure 3 As can be observed, Comparative Example 1 (SG) exhibits a large number of graphite fragments and is covered with irregular amorphous aggregates. These impurities mainly originate from the irreversible accumulation of dead lithium and residual SEI components. After ammonia plasma treatment, these structural defects are gradually eliminated. For the Example 1 (N-Gr-10) sample, its surface has become relatively smooth; while for the Example 2 (N-Gr-20) sample, the impurity layer on its surface has been completely removed, exposing a well-defined, highly clean, and intact graphite substrate.

[0027] according to Figure 4 It can be seen that Comparative Example 1 (SG) suffers from severe capacity decay, with its capacity dropping to approximately 150 mAh g after 100 cycles at a current density of 0.5 C. −1 In contrast, the electrochemical performance of the samples from Examples 1-3 treated with the present invention was significantly improved. In particular, Example 2 (N-Gr-20) exhibited a high electrochemical performance of 412 mAh g⁻¹. −1 The reversible specific capacity remained stable and showed no significant decay after 100 cycles, exceeding the theoretical value of graphite (372 mAh g). −1 This fully demonstrates that the graphite repaired and regenerated by this invention has excellent practical application value.

[0028] according to Figure 5 It can be seen that the N-Gr-20 anode maintains approximately 430, 413, 359, and 296 mAh g⁻¹ at 0.5 C, 1 C, 2 C, and 3 C rates, respectively. −1 The specific capacity is stable and reversible. When the rate is restored to 0.5 C, its specific capacity rapidly recovers to 433 mAh g⁻¹. −1 This indicates that the repair material prepared by the present invention has excellent structural stability and electrochemical reversibility, and can meet the requirements of high-rate charge and discharge.

[0029] In summary, Example 2 (N-Gr-20) prepared using the parameters of this invention exhibits the best structural repair effect and lithium storage performance, significantly superior to the untreated Comparative Example 1. This invention provides a green, simple, and efficient repair and regeneration technology pathway for the closed-loop recycling of waste negative electrode graphite.

Claims

1. A method for repairing and regenerating waste negative electrode graphite, characterized in that, Includes the following steps: S1. Place the waste negative electrode graphite in hydrochloric acid for acid washing to remove impurities, then wash with deionized water until neutral, and transfer to a drying oven to dry to obtain purified graphite. S2. The purified graphite obtained in S1 is evenly spread in a ceramic boat and then transferred to a low-temperature plasma reactor. After vacuuming and replacing with working gas to create an oxygen-free environment, working gas is introduced for plasma treatment to obtain the repair material.

2. The method for repairing and regenerating waste negative electrode graphite according to claim 1, characterized in that, In step S1, the concentration of hydrochloric acid is 0.5~3.0 mol / L, and the pickling time is 2 hours.

3. The method for repairing and regenerating waste negative electrode graphite according to claim 1, characterized in that, In S1, the temperature of the drying oven is 58-62 ℃, and the drying time is 11-13 hours.

4. The method for repairing and regenerating waste negative electrode graphite according to claim 1, characterized in that, In S2, the working gas is at least one of NH3 and N2.

5. The method for repairing and regenerating waste negative electrode graphite according to claim 1, characterized in that, In S2, the reaction pressure of the plasma treatment is 10~100 Pa.

6. The method for repairing and regenerating waste negative electrode graphite according to claim 1, characterized in that, In S2, the power of the plasma reaction device is 100~400 W.

7. The method for repairing and regenerating waste negative electrode graphite according to claim 1, characterized in that, In S2, the plasma treatment time is 5 min to 50 min.

8. A repair material obtained by the repair and regeneration method of waste negative electrode graphite according to any one of claims 1-7.

9. The repair material obtained by the repair and regeneration method of waste negative electrode graphite as described in any one of claims 1-7 is used in the preparation of batteries.

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