Method for rapidly preparing high-performance negative electrode material by using photovoltaic waste graphite and application

Abstract

The present application relates to the technical field of secondary resource recycling, and particularly relates to a method for rapidly preparing high-performance negative electrode material by using photovoltaic waste graphite and application, wherein the waste graphite of the preparation method is derived from waste hot field graphite in the process of drawing crystalline silicon in the photovoltaic industry, the particle size of the waste graphite is controlled through crushing, ball milling and screening, harmful impurities in the waste graphite are removed by acid washing, then the purified waste graphite is placed in an electrothermal impact device, and high-performance graphite negative electrode material is rapidly prepared from the waste graphite under two-stage pulse heating by controlling the pressure and size of compression molding, the synthesis atmosphere, voltage, temperature and time of the electrothermal high-temperature pulse process, and the like. The graphite negative electrode material with uniform particle size and high graphitization degree can be prepared, and when the graphite negative electrode material is used as a negative electrode of a lithium ion battery, high specific capacity and excellent long cycle stability are exhibited.

Description

Technical Field

[0001] This invention relates to the field of secondary resource recycling technology, specifically to a method and application for rapidly preparing high-performance anode materials using photovoltaic waste graphite. Background Technology

[0002] In recent years, the photovoltaic industry has become one of the important areas of global energy transition. Silicon material, as the core raw material of the photovoltaic industry chain, is limited in quality by the thermal field system. Common thermal field raw materials are mainly special graphite. As a high-purity graphite, it has advantages such as high density, high strength, and isotropy. However, due to the inherent working characteristics of the thermal field system, it undergoes crystallization, deformation, and cracking during the melting of crystalline silicon, making it unrecyclable. With the development of the photovoltaic industry, the consumption and waste of photovoltaic graphite have increased rapidly. Given that photovoltaic waste graphite has advantages such as low impurity content and good crystallinity, and that the initial preparation process is relatively complex and the production cost is relatively high, the recycling and reuse of photovoltaic waste graphite has certain economic value.

[0003] Currently, the recycling of photovoltaic waste graphite mainly focuses on dumping and incineration, which inevitably causes environmental pollution and resource waste. Traditional graphite recycling mainly focuses on wet recycling and pyrometallurgical recycling, but these methods have many drawbacks in practical applications. CN112645320A discloses a method for preparing low-cost anode materials by recycling graphite crucibles. This method first performs acid washing to remove impurities, and then achieves regeneration through granulation, mixing, and demagnetization. This method has a long experimental process, requires the use of a large amount of acid and alkali reagents, and causes secondary pollution. CN112768690A discloses a method for preparing lithium-ion battery anode materials by recycling waste graphite crucibles. This method requires multiple high-temperature heat treatments, which are cumbersome, energy-intensive, and not conducive to the green recycling of solid waste.

[0004] In summary, there is an urgent need for a simple, low-energy, and environmentally friendly method to directly regenerate photovoltaic waste graphite. Thermal shock, as a highly efficient heating method, can raise the temperature to over 3000℃ within one second, far exceeding that of commonly used muffle furnaces, and has become an important means of preparing graphene, high-entropy alloys, and recycling solid waste. Summary of the Invention

[0005] The purpose of this invention is to provide a method for rapidly preparing high-performance anode materials using photovoltaic waste graphite. The preparation method involves first reducing the particle size of the waste graphite through crushing, ball milling, and sieving; then removing harmful impurities from the waste graphite using acid washing; and finally placing the purified waste graphite in an electrothermal shock device. By controlling the compression molding pressure and size, and the synthesis atmosphere, temperature, time, and voltage of the electrothermal high-temperature pulse process, rapid regeneration of waste graphite is achieved under two-stage pulse regulation. When applied to lithium-ion battery anodes, it exhibits high specific capacity and excellent long-cycle stability. This preparation method has the advantages of short process, high efficiency, and low energy consumption, enabling secondary value-added reuse of existing waste resources.

[0006] A method for rapidly preparing high-performance anode materials using photovoltaic waste graphite includes the following steps:

[0007] S1: Prepare photovoltaic waste graphite with a particle size of 5-75 μm;

[0008] S2: Use acid washing to remove impurities contained in photovoltaic waste graphite;

[0009] S3: The purified waste graphite is placed in an electrothermal shock device. By controlling the compression molding pressure and size, the synthesis atmosphere, voltage, temperature and time of the electrothermal high-temperature pulse process, rapid heat treatment is carried out to achieve efficient regeneration of photovoltaic waste graphite.

[0010] Furthermore, the photovoltaic waste graphite includes one or more of the following: graphite crucible, graphite electrode, heater, insulation cylinder, flow guide cylinder, electrode nut, and plate.

[0011] Furthermore, in step S1, the photovoltaic waste graphite is pre-crushed, ball-milled, and sieved to achieve a target particle size of 5–75 μm; the ball milling speed is 300–2000 r / min; and the time is 5–18 h.

[0012] Furthermore, the acid washing in step S2 is carried out in one or more of HCl, H2SO4, HF, and HNO3; the acid washing concentration is 0.5–5 mol / L; and the time is 0.5–4 h.

[0013] Furthermore, in step S3, the pressure and size of the compression molding are controlled to adjust the system resistance to 0.5-5Ω; the synthesis atmosphere is one of vacuum, argon, nitrogen, and helium.

[0014] Furthermore, the electro-induced high-temperature pulse process in step S3 adopts a two-stage voltage control mode; the first stage pulse voltage is 20-100V, and the second stage pulse voltage is 100-200V; the peak temperature after the first high-temperature pulse is approximately 500-1000℃, and the peak temperature after the second high-temperature pulse is 1000-3500℃; the first stage pulse time is 0.1-0.5s, the second stage pulse time is 0.2-1.0s, and the total pulse time is 0.3-1.5s.

[0015] Furthermore, the electro-induced high-temperature pulse process in step S3 is performed once or multiple times.

[0016] On the other hand, this invention proposes the application of the above method in the second-level recycling and regeneration of photovoltaic waste graphite.

[0017] The beneficial effects of this invention are:

[0018] 1. The preparation method described in this invention employs a two-stage pulse heating process. The first stage, a low-pressure pulse, removes volatiles, while the second stage, a high-pressure pulse, enables rapid high-temperature regeneration of waste graphite. This segmented pulse heating reduces mass loss during the regeneration process and avoids damage to the equipment.

[0019] 2. The preparation method described in this invention realizes direct regeneration of photovoltaic waste graphite in seconds, which has the advantages of short process, high efficiency and no pollution. It effectively realizes the green and high-value recycling of solid waste and avoids the problems of secondary pollution, high energy consumption and high cost in the traditional recycling process.

[0020] 3. The preparation method described in this invention achieves a rapid transformation to an ordered crystal structure, and the recycled graphite possesses advantages such as uniform particle size and high graphitization degree. When applied to lithium-ion battery anode materials, it exhibits superior electrochemical performance compared to commercial graphite, retaining a specific capacity of 413 mAh / g after 100 cycles at a current density of 0.5C.

[0021] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a temperature-time diagram of the thermal shock process in Embodiments 1-4 of the present invention.

[0024] Figure 2This is a SEM image of the regenerated graphite material after thermal shock in Embodiment 1 of the present invention.

[0025] Figure 3 This is a SEM image of the regenerated graphite material after thermal shock in Embodiment 2 of the present invention.

[0026] Figure 4 This is a SEM image of the regenerated graphite material after thermal shock in Embodiment 3 of the present invention.

[0027] Figure 5 This is a SEM image of the regenerated graphite material after thermal shock in Example 4 of the present invention.

[0028] Figure 6 This is the XRD pattern of the regenerated graphite material after thermal shock in Embodiment 1 of the present invention.

[0029] Figure 7 This is the Raman spectrum of the regenerated graphite material after thermal shock in Example 1 of the present invention.

[0030] Figure 8 This is a charge-discharge cycle performance diagram of the regenerated graphite material after thermal shock in Embodiment 1 of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] This embodiment describes a method for rapidly preparing high-performance anode materials using photovoltaic waste graphite, comprising the following steps:

[0034] S1: Photovoltaic waste graphite is crushed, ball-milled, and sieved to prepare photovoltaic waste graphite with a particle size of 5-75μm;

[0035] S2: The photovoltaic waste graphite described in step S1 is acid-washed and impurities are removed in a 1 mol / L HCl solution, then washed with water and dried for later use;

[0036] S3: The purified waste graphite described in step S2 is placed in an electrothermal shock device. The system resistance is adjusted to 2Ω by controlling the compression molding pressure and size. Under vacuum conditions, the voltage of the first pulse of the electrothermal high-temperature pulse process is adjusted to 50V, and the voltage of the second pulse is controlled to 200V. The peak temperature after the first high-temperature pulse is about 800℃, and the peak temperature after the second high-temperature pulse is 3500℃. The pulse duration is 0.2s and 0.5s, with a total pulse duration of 0.7s. Rapid heating and cooling treatment is performed to achieve efficient regeneration of photovoltaic waste graphite.

[0037] Example 2

[0038] This embodiment describes a method for rapidly preparing high-performance anode materials using photovoltaic waste graphite, comprising the following steps:

[0039] S1: Photovoltaic waste graphite is crushed, ball-milled, and sieved to prepare photovoltaic waste graphite with a particle size of 5-75μm;

[0040] S2: The photovoltaic waste graphite described in step S1 is acid-washed and impurities are removed in a 1 mol / L HCl solution, then washed with water and dried for later use;

[0041] S3: The purified waste graphite described in step S2 is placed in an electrothermal shock device. The system resistance is adjusted to 2Ω by controlling the compression molding pressure and size. Under vacuum conditions, the voltage of the first pulse of the electrothermal high-temperature pulse process is adjusted to 50V, and the voltage of the second pulse is controlled to 180V. The peak temperature after the first high-temperature pulse is about 800℃, and the peak temperature after the second high-temperature pulse is 2000℃. The pulse duration is 0.2s and 0.5s, and the total pulse duration is 0.7s. Rapid heating and cooling treatment is performed to achieve efficient regeneration of photovoltaic waste graphite.

[0042] Example 3

[0043] This embodiment describes a method for rapidly preparing high-performance anode materials using photovoltaic waste graphite, comprising the following steps:

[0044] S1: Photovoltaic waste graphite is crushed, ball-milled, and sieved to prepare photovoltaic waste graphite with a particle size of 5-75μm;

[0045] S2: The photovoltaic waste graphite described in step S1 is acid-washed and impurities are removed in a 1 mol / L HCl solution, then washed with water and dried for later use;

[0046] S3: The purified waste graphite described in step S2 is placed in an electrothermal shock device. The system resistance is adjusted to 2Ω by controlling the compression molding pressure and size. Under vacuum conditions, the voltage of the first pulse of the electrothermal high-temperature pulse process is adjusted to 50V, and the voltage of the second pulse is controlled to 150V. The peak temperature after the first high-temperature pulse is about 800℃, and the peak temperature after the second high-temperature pulse is 1500℃. The pulse duration is 0.2s and 0.5s, and the total pulse duration is 0.7s. Rapid heating and cooling treatment is performed to achieve efficient regeneration of photovoltaic waste graphite.

[0047] Example 4

[0048] This embodiment describes a method for rapidly preparing high-performance anode materials using photovoltaic waste graphite, comprising the following steps:

[0049] S1: Photovoltaic waste graphite is crushed, ball-milled, and sieved to prepare photovoltaic waste graphite with a particle size of 5-75μm;

[0050] S2: The photovoltaic waste graphite described in step S1 is acid-washed and impurities are removed in a 1 mol / L HCl solution, then washed with water and dried for later use;

[0051] S3: The purified waste graphite described in step S2 is placed in an electrothermal shock device. The system resistance is adjusted to 2Ω by controlling the compression molding pressure and size. Under vacuum conditions, the voltage of the first pulse of the electrothermal high-temperature pulse process is adjusted to 50V, and the voltage of the second pulse is controlled to 100V. The peak temperature after the first high-temperature pulse is about 800℃, and the peak temperature after the second high-temperature pulse is 1000℃. The pulse duration is 0.2s and 0.5s, and the total pulse duration is 0.7s. Rapid heating and cooling treatment is performed to achieve efficient regeneration of photovoltaic waste graphite.

[0052] The performance of photovoltaic waste graphite before and after regeneration, as well as commercial graphite, was evaluated in the examples. Electrodes were prepared by homogenizing graphite, Super-P, and PVDF in an 8:1:1 ratio. Lithium metal sheets were used as the counter electrode, and 1 mol / L LiPF6 (EC:EMC:DMC = 1:1:1) was used as the electrolyte. Electrochemical performance tests were conducted, and the results are shown in the table below:

[0053]

[0054]

[0055] As shown in the table above, by comparing the performance of commercial graphite, waste graphite and the recycled graphite prepared by this invention, it can be seen that the recycled graphite prepared by this invention has an ID / IG value similar to that of commercial graphite, indicating that it has a high degree of graphitization, and shows superior discharge specific capacity and cycle stability compared to commercial graphite.

[0056] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for rapidly preparing high-performance anode materials using photovoltaic waste graphite, characterized in that, Includes the following steps: S1. Prepare photovoltaic waste graphite with a particle size of 5~75μm; S2. Use acid washing to remove impurities contained in photovoltaic waste graphite; S3. The purified waste graphite is placed in an electrothermal shock device. By controlling the compression molding pressure and size, the synthesis atmosphere, voltage, temperature and time of the electrothermal high-temperature pulse process, rapid heat treatment is carried out to achieve efficient regeneration of photovoltaic waste graphite. In step S1, the photovoltaic waste graphite is pre-crushed, ball-milled, and sieved to achieve a target particle size of 5-75 μm; the ball milling speed is 300-2000 r / min; and the time is 5-18 h. The electrothermal high-temperature pulse process in step S3 adopts a two-stage voltage control mode; the first stage pulse voltage is 20-100V, and the second stage pulse voltage is 100-200V. The peak temperature after the first high-temperature pulse is 500-1000℃, and the peak temperature after the second high-temperature pulse is 1000-3500℃; the pulse duration of the first pulse is 0.1-0.5s, the pulse duration of the second pulse is 0.2-1.0s, and the total pulse duration is 0.3-1.5s. In step S3, the pressure and size of the compression molding are controlled to adjust the system resistance to 0.5-5Ω.

2. The method for rapidly preparing high-performance anode materials using photovoltaic waste graphite as described in claim 1, characterized in that: The photovoltaic waste graphite includes one or more of the following: graphite crucible, graphite electrode, heater, insulation cylinder, flow guide cylinder, electrode nut, and plate.

3. The method for rapidly preparing high-performance anode materials using photovoltaic waste graphite as described in claim 1, characterized in that: The acid washing step S2 is carried out in one or more of HCl, H2SO4, HF, and HNO3; the acid washing concentration is 0.5-5 mol / L; and the time is 0.5-4 h.

4. The method for rapidly preparing high-performance anode materials using photovoltaic waste graphite as described in claim 1, characterized in that: The synthesis atmosphere is one of vacuum, argon, nitrogen, or helium.

5. The method for rapidly preparing high-performance anode materials using photovoltaic waste graphite as described in claim 1, characterized in that: The electrothermal high-temperature pulse process in step S3 is performed once or multiple times.

6. The application of the method as described in any one of claims 1-5 in the second-level recycling and regeneration of photovoltaic waste graphite.

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