Asphalt shear-coated graphite negative electrode based on waste graphite and preparation method of asphalt shear-coated graphite negative electrode

Abstract

The invention particularly relates to an asphalt shear coated graphite negative electrode based on waste graphite and a preparation method of the asphalt shear coated graphite negative electrode. According to the technical scheme, asphalt is placed in a reaction kettle, waste graphite is added at the temperature of 250-350 DEG C, the adding amount of the waste graphite is 10-50 wt% of the asphalt, mechanical stirring is conducted for 1-5 h, and a mixture is obtained; placing the mixture in a tubular furnace, heating to 800-1200 DEG C at a speed of 20-25 DEG C / min in a protective atmosphere, preserving heat for 2-3 hours, cooling to room temperature along with the furnace, and grinding to obtain a ground material; and placing the ground material in a hydrochloric acid solution according to a solid-to-liquid ratio of 40-60Kg / m < 3 >, treating for 2-3h at 100-120 DEG C by a hydrothermal method, washing with deionized water, filtering, and drying to obtain the asphalt shear coated graphite negative electrode based on the waste graphite. The method has the characteristic of low energy consumption, and the prepared asphalt shear coated graphite negative electrode based on the waste graphite is high in specific capacity and easy to industrialize.

Description

Technical Field

[0001] The present invention belongs to the technical field of graphite negative electrode materials, and specifically relates to a graphite negative electrode sheared and coated with asphalt based on waste graphite and a preparation method thereof. Background Art

[0002] Commercial lithium-ion batteries require one kilogram of graphite for every kilowatt-hour of battery capacity. The production of battery-grade graphite is a complex process. Natural graphite is primarily found in associated graphite deposits, and its production involves four key steps: mining, beneficiation, purification, and processing. The mining of natural graphite not only significantly impacts the environment (including vegetation, air, and water pollution), but also poses health risks to workers involved (such as pneumoconiosis). To meet the requirements for battery-grade graphite, acid leaching, alkaline roasting, and inert atmosphere heat treatment are required, further exacerbating environmental pollution. The production of synthetic graphite, on the other hand, generates significant carbon emissions and energy consumption. The process involves calcining and mixing petroleum coke, needle coke, and asphalt at a specific temperature, followed by crushing, grading, and finally high-temperature graphitization (typically 2500°C). Research indicates that greenhouse gas emissions and energy consumption during the graphitization stage are 13.8 kgCO₂-eq / kg and 45.9 MJ / kg, respectively. This contributes to the current high price of battery-grade graphite, which accounts for nearly 10% of the total cost of lithium batteries. Therefore, the recycling of waste graphite has attracted the attention of those skilled in the art.

[0003] Currently, high-temperature calcination repair has become a common method for graphite recycling because of its simple operation. For example, the patented technology "A Recycling Process for Waste Graphite Negative Electrode Sheets of Lithium-ion Batteries" (CN119481402A) uses a temperature of 2500-3500°C to calcine and repair waste graphite. However, high-temperature treatment will produce a large amount of carbon emissions and energy consumption, which is not conducive to industrialization.

[0004] Asphalt is a byproduct of the petroleum industry and is inexpensive. As a soft carbon precursor, asphalt has a large interlayer spacing after carbonization and is often used to coat the surface of graphite negative electrodes, which can effectively improve the rate performance of graphite negative electrodes. For example: The patented technology of "A method for coating graphite and asphalt-coated graphite" (CN119581519A) uses asphalt with a coating agent to coat micron-sized graphite, and washes it with a detergent to remove excess coating agent. Although the rate performance of the prepared asphalt-coated graphite negative electrode is improved, the specific capacity is not improved compared to commercial graphite.

[0005] The patented technology of "coating asphalt solid phase composition, modified asphalt-coated natural graphite negative electrode material and its preparation and lithium-ion battery" (CN119320567A) uses coating asphalt and modification additives to coat and modify natural graphite. Although the specific capacity of the prepared asphalt-coated graphite can reach 372mAh / g, the specific capacity is still relatively low and difficult to apply in practice.

[0006] The patented technology "A method for preparing high-performance graphite negative electrode coated asphalt" (CN117417642A) adds a cross-linking link during the preparation of asphalt and introduces graphene oxide during the coating process to improve the coating stability of the asphalt. However, the prepared asphalt-coated graphite has a specific capacity of only 340.7mAh / g, making it difficult to industrialize.

[0007] In summary, the existing technology not only has the problem of high energy consumption, but also the asphalt-coated graphite negative electrode has the problem of low capacity and is difficult to industrialize. Summary of the Invention

[0008] The present invention aims to overcome the defects of the prior art and aims to provide a method for preparing a asphalt shear-coated graphite negative electrode based on waste graphite with low energy consumption. The asphalt shear-coated graphite negative electrode based on waste graphite prepared by this method has a high specific capacity and is easy to industrialize.

[0009] To achieve the above object, the technical solution adopted by the present invention is: Asphalt is placed in a reactor, and waste graphite is added at 250-350° C., wherein the amount of the waste graphite added is 10-50 wt % of the asphalt. The mixture is mechanically stirred for 1-5 hours to obtain a mixture.

[0010] The mixture is placed in a tube furnace, heated to 800-1200°C at a rate of 20-25°C / min in a protective atmosphere, kept warm for 2-3 hours, cooled to room temperature with the furnace, and ground to obtain a mill base. Then, the solid-liquid ratio is 40-60 kg / m 3 The ground material is placed in a hydrochloric acid solution, treated hydrothermally at 100-120° C. for 2-3 hours, then washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0011] The asphalt ash content is ≤5%, and the softening point is ≤200°C.

[0012] The waste graphite comes from discarded lithium-ion battery negative electrode graphite, and the C content of the waste graphite is greater than 90wt%.

[0013] The rotation speed of the mechanical stirring is 800-1200 rpm.

[0014] The concentration of the hydrochloric acid solution is 1-1.5 mol / L.

[0015] The number of times of washing is 3 to 5.

[0016] The drying temperature is 60-100° C., and the drying time is 10-12 hours.

[0017] The protective atmosphere is Ar or N2.

[0018] The filtration is carried out using a vacuum filter.

[0019] Due to the adoption of the above technical solution, the present invention has the following positive effects and outstanding features compared with the prior art: The present invention uses a large proportion of asphalt, which can provide more lithium insertion and extraction channels; and the waste graphite used is sheared into graphene, which does not require high-temperature repair and only requires carbonizing the asphalt at a lower temperature. Therefore, the energy consumption is low, the production cost is low, and it is easy to industrialize.

[0020] The waste graphite used in the present invention continuously embeds and extracts lithium ions during long-term service, resulting in the waste graphite having characteristics such as increased interlayer spacing, weakened interlayer van der Waals forces, and surface structural damage and defects, making it easier to peel and disperse than ordinary graphite. Furthermore, in the early stages of the cycle, an SEI film forms on the surface of the waste graphite negative electrode. Its main components are various organic and inorganic lithium salts. After carbonization, it forms a rich functional group on the surface of the waste graphite, which is conducive to asphalt coating. Therefore, under high-speed stirring, asphalt can easily shear and coat the waste graphite, and the graphene sheared from the waste graphite can provide a large amount of lithium storage capacity. The prepared asphalt-sheathed graphite negative electrode based on waste graphite has a specific capacity of 400.3 to 435.2 mAh / g, which has a higher specific capacity.

[0021] Therefore, the present invention not only has the characteristics of low energy consumption, but also the prepared asphalt shear-coated graphite negative electrode based on waste graphite has high specific capacity and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a TEM image of a graphite negative electrode sheared and coated with asphalt based on waste graphite prepared by the present invention; Figure 2 for Figure 1 Rate performance diagram of the product shown; Figure 3 for Figure 1 Cycling performance graph of the product shown. DETAILED DESCRIPTION

[0023] A graphite negative electrode coated with asphalt based on waste graphite and its preparation method. The preparation method described in this specific embodiment is: Asphalt is placed in a reactor, and waste graphite is added at 250-350° C., wherein the amount of the waste graphite added is 10-50 wt % of the asphalt. The mixture is mechanically stirred for 1-5 hours to obtain a mixture.

[0024] The mixture is placed in a tube furnace, heated to 800-1200°C at a rate of 20-25°C / min in a protective atmosphere, kept warm for 2-3 hours, cooled to room temperature with the furnace, and ground to obtain a mill base. Then, the solid-liquid ratio is 40-60 kg / m 3 The ground material is placed in a hydrochloric acid solution, treated hydrothermally at 100-120° C. for 2-3 hours, then washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0025] The C content of the waste graphite is greater than 90 wt %.

[0026] The rotation speed of the mechanical stirring is 800-1200 rpm.

[0027] The concentration of the hydrochloric acid solution is 1-1.5 mol / L.

[0028] The number of times of washing is 3 to 5.

[0029] The drying temperature is 60-100° C., and the drying time is 10-12 hours.

[0030] The protective atmosphere is Ar or N2.

[0031] In this specific implementation mode: The asphalt ash content is ≤5%, and the softening point is ≤200°C.

[0032] The waste graphite comes from the negative electrode graphite of discarded lithium-ion batteries.

[0033] The filtration is carried out using a vacuum filter.

[0034] The details will not be described in detail in the embodiments.

[0035] Example 1 A graphite negative electrode coated with asphalt based on waste graphite and its preparation method. The preparation method described in this embodiment is: Asphalt was placed in a reactor, and waste graphite was added at 250° C., wherein the amount of the waste graphite added was 10 wt % of the asphalt. The mixture was mechanically stirred for 2 h to obtain a mixture.

[0036] The mixture was placed in a tube furnace, heated to 800°C at a rate of 20°C / min in a protective atmosphere, kept warm for 2 hours, cooled to room temperature with the furnace, and ground to obtain a ground material. 3The ground material was placed in a hydrochloric acid solution, treated hydrothermally at 100° C. for 2 h, washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0037] The C content of the waste graphite is 91 wt %.

[0038] The rotation speed of the mechanical stirring is 800 rpm.

[0039] The concentration of the hydrochloric acid solution is 1 mol / L.

[0040] The number of washings was 3.

[0041] The drying temperature is 60° C. and the drying time is 10 h.

[0042] The protective atmosphere is N2.

[0043] The specific capacity of the asphalt shear-coated graphite negative electrode based on waste graphite prepared in this embodiment is 427.9 mAh / g.

[0044] Example 2 A graphite negative electrode coated with asphalt based on waste graphite and its preparation method. The preparation method described in this embodiment is: Asphalt was placed in a reaction kettle, and waste graphite was added at 275° C., wherein the amount of the waste graphite added was 20 wt % of the asphalt. The mixture was mechanically stirred for 3 h to obtain a mixture.

[0045] The mixture was placed in a tube furnace, heated to 900°C at a rate of 21°C / min in a protective atmosphere, kept at this temperature for 2.2 hours, cooled to room temperature with the furnace, and ground to obtain a mill base. Then, the solid-liquid ratio was 45 kg / m 3 The ground material was placed in a hydrochloric acid solution, treated hydrothermally at 105° C. for 2.2 h, washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0046] The C content of the waste graphite is 92 wt %.

[0047] The rotation speed of the mechanical stirring is 900 rpm.

[0048] The concentration of the hydrochloric acid solution is 1.1 mol / L.

[0049] The number of washings was 3.

[0050] The drying temperature is 70° C. and the drying time is 10 h.

[0051] The protective atmosphere is N2.

[0052] The specific capacity of the asphalt shear-coated graphite negative electrode based on waste graphite prepared in this embodiment is 435.2 mAh / g.

[0053] Example 3 A graphite negative electrode coated with asphalt based on waste graphite and its preparation method. The preparation method described in this embodiment is: Asphalt was placed in a reactor, and waste graphite was added at 300° C., wherein the amount of the waste graphite added was 30 wt % of the asphalt. The mixture was mechanically stirred for 1 hour to obtain a mixture.

[0054] The mixture was placed in a tube furnace, heated to 1000°C at a rate of 22°C / min in a protective atmosphere, kept at this temperature for 2.4 hours, cooled to room temperature with the furnace, and ground to obtain a mill base. Then, the solid-liquid ratio was 50 kg / m 3 The ground material was placed in a hydrochloric acid solution, treated hydrothermally at 110° C. for 2.4 h, washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0055] The C content of the waste graphite is 94 wt %.

[0056] The rotation speed of the mechanical stirring is 1000 rpm.

[0057] The concentration of the hydrochloric acid solution is 1.2 mol / L.

[0058] The number of washings was 4.

[0059] The drying temperature is 80° C. and the drying time is 11 h.

[0060] The protective atmosphere is Ar.

[0061] The specific capacity of the asphalt shear-coated graphite negative electrode based on waste graphite prepared in this embodiment is 417.2 mAh / g.

[0062] Example 4 A graphite negative electrode coated with asphalt based on waste graphite and its preparation method. The preparation method described in this embodiment is: Asphalt was placed in a reactor, and waste graphite was added at 325° C., wherein the amount of the waste graphite added was 40 wt % of the asphalt. The mixture was mechanically stirred for 4 h to obtain a mixture.

[0063] The mixture was placed in a tube furnace, heated to 1100°C at a rate of 23°C / min in a protective atmosphere, kept warm for 2.6 hours, cooled to room temperature with the furnace, and ground to obtain a mill base. Then, the solid-liquid ratio was 55 kg / m 3The ground material was placed in a hydrochloric acid solution, treated hydrothermally at 115° C. for 2.6 h, washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0064] The C content of the waste graphite is 96 wt %.

[0065] The rotation speed of the mechanical stirring is 1100 rpm.

[0066] The concentration of the hydrochloric acid solution is 1.3 mol / L.

[0067] The number of washings was 4.

[0068] The drying temperature is 90° C. and the drying time is 11 h.

[0069] The protective atmosphere is Ar.

[0070] The specific capacity of the asphalt shear-coated graphite negative electrode based on waste graphite prepared in this embodiment is 408.1 mAh / g.

[0071] Example 5 A graphite negative electrode coated with asphalt based on waste graphite and its preparation method. The preparation method described in this embodiment is: Asphalt was placed in a reaction kettle, and waste graphite was added at 350° C., wherein the amount of the waste graphite added was 50 wt % of the asphalt. The mixture was mechanically stirred for 5 h to obtain a mixture.

[0072] The mixture was placed in a tube furnace, heated to 1200°C at a rate of 25°C / min in a protective atmosphere, kept warm for 3 hours, cooled to room temperature with the furnace, and ground to obtain a ground material. 3 The ground material was placed in a hydrochloric acid solution, treated hydrothermally at 120° C. for 3 h, washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

[0073] The C content of the waste graphite is 98 wt %.

[0074] The rotation speed of the mechanical stirring is 1200 rpm.

[0075] The concentration of the hydrochloric acid solution is 1.5 mol / L.

[0076] The number of washings was 5.

[0077] The drying temperature is 100° C. and the drying time is 12 hours.

[0078] The protective atmosphere is Ar.

[0079] The specific capacity of the asphalt shear-coated graphite negative electrode based on waste graphite prepared in this embodiment is 400.3 mAh / g.

[0080] Compared with the prior art, this embodiment has the following positive effects and outstanding features: The asphalt used in this specific embodiment has a large proportion, which can provide more lithium insertion and extraction channels; and the waste graphite used is sheared into graphene, which does not require high-temperature repair and only requires carbonization of the asphalt at a lower temperature, so the energy consumption is low, the production cost is low and it is easy to industrialize.

[0081] The waste graphite used in this specific embodiment is constantly embedded / de-inserted with lithium ions during long-term service, resulting in the waste graphite having characteristics such as enlarged interlayer spacing, weakened interlayer van der Waals forces, and surface structural damage and defects, making it easier to peel and disperse than ordinary graphite. In addition, in the early stage of the cycle, an SEI film will be generated on the surface of the waste graphite negative electrode, the main components of which are various organic and inorganic lithium salts. After carbonization, rich functional groups will be formed on the surface of the waste graphite, which is conducive to the coating of asphalt. Therefore, under high-speed stirring, asphalt can easily shear and coat the waste graphite, and the graphene sheared from the waste graphite can provide a large amount of lithium storage capacity. The prepared asphalt sheared and coated graphite negative electrode based on waste graphite is shown in the accompanying figure: Figure 1 TEM image of a graphite negative electrode sheared and coated with asphalt based on waste graphite prepared in Example 1; Figure 2 for Figure 1 Rate performance diagram of the product shown; Figure 3 for Figure 1 The cycle performance diagram of the product shown. Figure 1 It can be seen that the waste graphite was successfully cut into thin sheets and the asphalt was evenly coated on its surface; Figure 2 It can be seen that the product has a first-cycle charge capacity of up to 435.2 mAh / g at a rate of 0.1 A / g, and can still recover its initial capacity after cycling at a high rate, indicating that it has good rate performance. Figure 3 As can be seen, after 1000 cycles at a rate of 0.5 A / g, 96% of the specific capacity was retained, indicating good cycling stability. The pitch-coated graphite anode prepared in this embodiment, based on waste graphite, exhibited a higher specific capacity of 400.3 to 435.2 mAh / g.

[0082] Therefore, this specific embodiment not only has the characteristics of low energy consumption, but also the prepared asphalt shear-coated graphite negative electrode based on waste graphite has high specific capacity and is easy to industrialize.

Claims

1. A method for preparing a graphite negative electrode by asphalt shear coating based on waste graphite, characterized in that: Put asphalt in a reactor, add waste graphite at 250-350° C., wherein the amount of waste graphite added is 10-50 wt % of the asphalt, and mechanically stir for 1-5 hours to obtain a mixture; The mixture is placed in a tube furnace, heated to 800-1200°C at a rate of 20-25°C / min in a protective atmosphere, kept warm for 2-3 hours, cooled to room temperature with the furnace, and ground to obtain a grinding material; then, the solid-liquid ratio is 40-60 kg / m 3 The ground material is placed in a hydrochloric acid solution, treated hydrothermally at 100-120° C. for 2-3 hours, then washed with deionized water, filtered, and dried to obtain a asphalt shear-coated graphite negative electrode based on waste graphite.

2. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The asphalt ash content is ≤5%, and the softening point is ≤200°C.

3. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The waste graphite comes from discarded lithium-ion battery negative electrode graphite, and the C content of the waste graphite is greater than 90wt%.

4. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The rotation speed of the mechanical stirring is 800-1200 rpm.

5. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The concentration of the hydrochloric acid solution is 1-1.5 mol / L.

6. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The number of times of washing is 3 to 5.

7. The method for preparing a graphite negative electrode by shearing with asphalt coating based on waste graphite according to claim 1, characterized in that: The drying temperature is 60-100° C., and the drying time is 10-12 hours.

8. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The protective atmosphere is Ar or N2.

9. The method for preparing a graphite negative electrode by asphalt shearing coating based on waste graphite according to claim 1, characterized in that: The filtration is carried out using a vacuum filter.

10. A graphite negative electrode based on asphalt shear coating of waste graphite, characterized in that: The asphalt sheared coated graphite negative electrode based on waste graphite is a asphalt sheared coated graphite negative electrode based on waste graphite prepared by the preparation method of the asphalt sheared coated graphite negative electrode based on waste graphite according to any one of claims 1 to 9.

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