Regenerated graphite negative electrode material as well as preparation method and application thereof

Abstract

The invention provides a regenerated graphite negative electrode material and a preparation method and application thereof, and belongs to the field of regenerated graphite negative electrode materials. The preparation method of the regenerated graphite negative electrode material provided by the invention comprises the following steps: mixing a negative electrode active substance in a waste battery with an acid solution, carrying out acid leaching, and then carrying out first filtration to respectively obtain an acid leaching solution containing copper ions and waste graphite; mixing the copper ion-containing pickle liquor with alkali liquor, carrying out precipitation reaction, and then sequentially carrying out second filtering and drying to obtain copper oxide; mixing the waste graphite, the copper oxide and asphalt, and sequentially calcining and pickling to obtain a regenerated graphite negative electrode material; the mass ratio of the waste graphite to the copper oxide to the asphalt is 100: (8-12): (5-15). The regenerated graphite negative electrode material prepared by the preparation method provided by the invention has good specific capacity and cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of regenerated graphite negative electrode material, and particularly relates to a regenerated graphite negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries have become the mainstream technology in the current energy storage field due to their high energy density, and are widely used in electric vehicles and electronic devices. Graphite is still the preferred negative electrode material of commercial lithium ion batteries due to its cost-effectiveness, cycle stability, high specific capacity and low working potential, accounting for about 15% to 21% of the total mass of the battery. However, the typical service life of lithium ion batteries is only 5 to 8 years, and with the rapid increase in the number of retired batteries, the waste graphite in the retired batteries is mostly incinerated at the present stage, which not only has low economic returns, but also causes significant carbon emissions.

[0003] The traditional recycling process of waste graphite includes removing metal impurities by acid leaching and repairing graphite structure by heat annealing, but the performance of the regenerated graphite obtained by the traditional regeneration is generally inferior to that of the commercial negative electrode graphite, and a large amount of acidic wastewater is generated in the acid leaching process. The acidic wastewater has a high copper content, and the traditional neutralization and precipitation method produces copper hydroxide sludge with low purity and poor performance, which has limited economic value and is mostly discarded as waste, causing environmental pollution. SUMMARY

[0004] The present application provides a regenerated graphite negative electrode material and a preparation method and application thereof. The regenerated graphite negative electrode material prepared by the preparation method provided by the present application not only effectively utilizes the copper ions in the acid leaching wastewater, but also has good specific capacity and cycle stability.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions: The present application provides a preparation method of a regenerated graphite negative electrode material, comprising the following steps: After mixing the negative electrode active material in the waste battery with an acid solution for acid leaching and first filtering, an acid leaching solution containing copper ions and waste graphite are obtained; After mixing the acid leaching solution containing copper ions with an alkali solution for a precipitation reaction, and then sequentially performing second filtering and drying, copper oxide is obtained; After mixing the waste graphite, the copper oxide and pitch, calcination and acid pickling are sequentially performed to obtain the regenerated graphite negative electrode material; the mass ratio of the waste graphite, the copper oxide and the pitch is 100: (8-12): (5-15).

[0006] Preferably, the acid in the acid solution is hydrochloric acid or sulfuric acid; The concentration of the acid solution is 0.8-1.2 mol / L.

[0007] Preferably, the acid solution contains 0.8 to 1.2 wt% hydrogen peroxide.

[0008] Preferably, the acid leaching temperature is 60~80℃ and the acid leaching time is 2~4h.

[0009] Preferably, the pH of the precipitation reaction is 6.6 to 7.

[0010] Preferably, the drying temperature is 100~350℃ and the drying time is 1~3h.

[0011] Preferably, the calcination temperature is 800~1000℃ and the calcination time is 2~4h.

[0012] Preferably, the pickling solution used for pickling is a hydrochloric acid solution; the concentration of the hydrochloric acid solution is 0.8~1.2 mol / L.

[0013] The present invention also provides a recycled graphite anode material prepared by the preparation method described in the above technical solution.

[0014] This invention also provides the application of the recycled graphite anode material described in the above technical solution in lithium-ion batteries.

[0015] This invention provides a method for preparing recycled graphite anode material, comprising the following steps: mixing the anode active material from waste batteries with an acid solution for acid leaching, followed by a first filtration to obtain an acid leaching solution containing copper ions and waste graphite; mixing the acid leaching solution containing copper ions with an alkaline solution for a precipitation reaction, followed by a second filtration and drying to obtain copper oxide; mixing the waste graphite, copper oxide, and asphalt, followed by calcination and acid washing to obtain the recycled graphite anode material; the mass ratio of waste graphite, copper oxide, and asphalt is 100:(8~12):(5~15). This invention utilizes an acid leaching solution containing copper ions to prepare copper oxide, and then mixes the copper oxide with waste graphite and asphalt for calcination. By limiting the mass ratio of waste graphite, copper oxide, and asphalt, copper oxide can catalyze the waste graphite, improving the specific capacity and cycle stability of the recycled graphite anode material. Acid washing of the calcined product removes copper oxide, forming a fast channel in the recycled graphite, which is beneficial for lithium ion transport, further improving the specific capacity and cycle stability of the recycled graphite anode material. The results of the examples show that the half-cell prepared from the recycled graphite anode material prepared by the preparation method provided by the present invention can achieve a specific capacity of 351 mAh / g at a 0.5C rate, and the capacity retention rate can reach 78% after 300 cycles, exhibiting good specific capacity and cycle stability. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation process of recycled graphite anode materials in the embodiments and comparative examples of the present invention. Figure 2 The images show the XRD patterns of waste graphite (SG), recycled graphite anode material (RG) in Example 1 of the present invention, and recycled graphite anode material (CG) in Comparative Example 1. Figure 3 The images show the Raman spectra of waste graphite (SG), recycled graphite anode material (RG) in Example 1 of the present invention, and recycled graphite anode material (CG) in Comparative Example 1. Figure 4 This is a SEM image of the recycled graphite anode material (CG) in Comparative Example 1 of the present invention; Figure 5 This is a TEM image of the recycled graphite anode material (CG) in Comparative Example 1 of the present invention; Figure 6 Here is a SEM image of waste graphite (SG) in Embodiment 1 of the present invention; Figure 7 This is a TEM image of waste graphite (SG) in Embodiment 1 of the present invention; Figure 8 This is a SEM image of the recycled graphite anode material (RG) in Example 1 of the present invention; Figure 9 This is a TEM image of the recycled graphite anode material (RG) in Example 1 of the present invention; Figure 10 A photograph of the carbonized asphalt material prepared in Comparative Example 5 of this invention; Figure 11 This is a 500x magnified SEM image of the carbonized asphalt material prepared in Comparative Example 5 of this invention. Figure 12 This is a 5000x magnified SEM image of the carbonized asphalt material prepared in Comparative Example 5 of this invention. Figure 13 A photograph of the graphite anode material prepared in Comparative Example 6 of this invention; Figure 14 This is a 500x magnified SEM image of the graphite anode material prepared in Comparative Example 6 of this invention. Figure 15 This is a 5000x magnified SEM image of the graphite anode material prepared in Comparative Example 6 of this invention. Figure 16 Cycle performance diagrams of batteries prepared in Application Example 1 and Comparative Application Example 1 of the present invention; Figure 17 The rate performance diagrams are for batteries prepared in Application Example 1 and Comparative Application Example 1 of the present invention. Figure 18 The cycling performance diagrams are for batteries prepared in Application Example 1 and Comparative Application Examples 2-3 of this invention. Figure 19 The rate performance diagrams are for batteries prepared in Application Example 1 and Comparative Application Examples 2-3 of this invention. Figure 20 The cycle performance diagrams are for batteries prepared in Application Example 1, Comparative Application Example 1, and Comparative Application Example 4 of the present invention. Figure 21 The rate performance diagrams are for batteries prepared in Application Example 1, Comparative Application Example 1, and Comparative Application Example 4 of the present invention. Figure 22 Cycle performance graphs of batteries prepared in Comparative Application Example 5 and Comparative Application Example 6 of the present invention; Figure 23 The rate performance diagrams are for the batteries prepared in Comparative Application Example 5 and Comparative Application Example 6 of the present invention. Detailed Implementation

[0017] This invention provides a method for preparing recycled graphite anode material, comprising the following steps: The negative electrode active material in the waste battery is mixed with an acid solution, then acid leaching is carried out and filtered to obtain an acid leaching solution containing copper ions and waste graphite, respectively. The copper-containing acid leaching solution and alkaline solution are mixed to carry out a precipitation reaction, and then filtered and dried in sequence to obtain copper oxide. The waste graphite, copper oxide, and asphalt are mixed and then calcined and acid-washed in sequence to obtain recycled graphite anode material.

[0018] This invention involves mixing the negative electrode active material from waste batteries with an acid solution, followed by acid leaching and filtration to obtain an acid leaching solution containing copper ions and waste graphite, respectively.

[0019] As one embodiment of the present invention, the negative electrode active material in the waste battery can be obtained by discharging the waste battery in a 1 mol / L NaCl solution for 24 hours, then disassembling and removing the negative electrode sheet, separating the copper foil and active material in the negative electrode sheet to obtain the negative electrode active material in the waste battery.

[0020] In one embodiment of the present invention, the acid in the acid solution can be hydrochloric acid or sulfuric acid; the concentration of the acid solution can be 0.8~1.2 mol / L; and the acid solution can contain 0.8~1.2 wt% hydrogen peroxide.

[0021] In one embodiment of the present invention, the mass ratio of the negative electrode active material in the waste battery to the volume of the acid solution can be 1 kg: (2.5~3.5) L or 1 kg: 3 L. By limiting the type and concentration of the acid solution and the ratio of the negative electrode active material to the acid solution within the above ranges, the present invention can fully leach out the copper element and other metallic impurities contained in the negative electrode active material of the waste battery, resulting in higher purity of the obtained waste graphite.

[0022] In one embodiment of the present invention, the acid leaching can be carried out under stirring conditions; the acid leaching temperature can be 60~80℃ or 70℃; the acid leaching time can be 2~4h or 3h. The present invention does not specifically limit the stirring speed, as long as it is sufficient to rotate the mixture. Limiting the acid leaching temperature and time to the above-mentioned ranges allows for the thorough leaching of metal ions (mainly copper ions) from the negative electrode active material in waste batteries.

[0023] The present invention does not have any special limitations on the operation of the first filtration; solid-liquid separation can be achieved by using filtration operations commonly used by those skilled in the art.

[0024] In one embodiment of the present invention, after filtration, the solid product obtained by filtration can be washed and dried in sequence.

[0025] In one embodiment of the present invention, the washing agent can be deionized water; the washing can be performed three times. The present invention removes acidic solution from the filtered solid through washing.

[0026] This invention does not impose any special limitations on the drying parameters after washing; drying parameters commonly used by those skilled in the art can be employed to dry the moisture. In an embodiment of this invention, the drying temperature after washing is 60°C.

[0027] After obtaining the copper-containing acid leaching solution, the present invention mixes the copper-containing acid leaching solution and alkaline solution to carry out a precipitation reaction, and then performs a second filtration and drying to obtain copper oxide.

[0028] In one embodiment of the present invention, the alkaline solution may be a sodium hydroxide solution. The present invention does not impose a particular limitation on the concentration of the alkaline solution; any alkaline solution concentration that can be adjusted for pH, commonly used by those skilled in the art, may be employed.

[0029] The present invention does not have a special limitation on the addition ratio of the copper-containing acid leaching solution and the alkaline solution, as long as the pH of the mixture can be adjusted to the pH value required for the precipitation reaction.

[0030] In one embodiment of the present invention, the pH of the precipitation reaction can be 6.6-7, or 6.68-6.8. Limiting the pH of the precipitation reaction to the above range ensures the complete progress of the precipitation reaction.

[0031] The present invention does not have any special limitations on the operation of the second filtration; solid-liquid separation can be achieved by using filtration operations commonly used by those skilled in the art.

[0032] In one embodiment of the present invention, the drying temperature can be 100~350℃, 150~300℃, or 250~300℃; the drying time can be 1~3h, 1~2.5h, or 1~1.5h. By limiting the drying temperature and time to the above ranges, the present invention ensures the yield of copper oxide.

[0033] In one embodiment of the present invention, after the drying process is completed, the dried product can be ball-milled to obtain copper oxide.

[0034] In one embodiment of the present invention, the ball mill rotation speed can be 350~450 rpm or 400 rpm; the ball milling time can be 2~12 h, 4~10 h, or 6~8 h. Limiting the ball mill rotation speed and time to the above ranges allows for better catalysis of subsequent waste graphite.

[0035] After obtaining waste graphite and copper oxide, the present invention mixes the waste graphite, copper oxide and asphalt and then calcines and pickles them sequentially to obtain recycled graphite anode material.

[0036] In this invention, the mass ratio of waste graphite, copper oxide, and asphalt is 100:(8~12):(5~15), preferably 100:(9~11):(8~12), and more preferably 100:10:10. Limiting the mass ratio of waste graphite, copper oxide, and asphalt to the above range ensures sufficient modification of the waste graphite.

[0037] In an embodiment of the present invention, the asphalt was purchased from Zigong Dongxin Electric Carbon Co., Ltd.

[0038] In one embodiment of the present invention, the mixing of waste graphite, copper oxide, and asphalt can be performed by ball milling; the rotation speed of the ball mill can be 200~400 rpm or 300 rpm; the ball milling time can be 1.5~2.5 h or 2 h. Limiting the mixing parameters to the above range ensures that the waste graphite, copper oxide, and asphalt are mixed uniformly.

[0039] In one embodiment of the present invention, the calcination can be carried out under an inert atmosphere, which can be argon; the calcination temperature can be 800~1000℃, 850~950℃, or 900℃; the calcination time can be 2~4h, 2.5~3.5h, or 3h. By limiting the calcination temperature and time to the above ranges, the present invention ensures the decomposition and carbonization of asphalt, forming a graphite-like layer on the waste graphite.

[0040] As one embodiment of the present invention, after calcination, the calcined product can be acid washed.

[0041] In one embodiment of the present invention, the pickling solution used for pickling has the same composition as the acid solution described above, and will not be repeated here.

[0042] In one embodiment of the present invention, the mass ratio of the calcined product to the volume of the pickling solution can be 1 kg: (2.5~3.5) L or 1 kg: 3 L. By limiting the type and concentration of the pickling solution used for pickling and the ratio to the calcined product to the above range, the present invention can better remove copper oxide from the calcined product, thereby forming a fast channel in the recycled graphite, which is beneficial for lithium ion transport and further improves the specific capacity and cycle stability of the recycled graphite anode material.

[0043] As one embodiment of the present invention, after pickling, the pickling product can be washed and dried to obtain a recycled graphite anode material.

[0044] In one embodiment of the present invention, the detergent used to wash the acid-washed product can be deionized water; the washing can be performed three times. The present invention removes the acid solution from the acid-washed product through washing.

[0045] The drying temperature after washing the acid-washed product can be 60-80℃, or even 70℃. The drying time is not particularly limited; drying parameters commonly used by those skilled in the art can be employed to dry the moisture.

[0046] This invention utilizes an acid leaching solution containing copper ions to prepare copper oxide, which is then mixed with waste graphite and asphalt and calcined. By limiting the mass ratio of waste graphite, copper oxide, and asphalt, copper oxide can catalyze the waste graphite, thereby improving the specific capacity and cycle stability of the recycled graphite anode material. By acid washing the calcined product, copper oxide can be removed, forming a fast channel in the recycled graphite, which is beneficial for lithium ion transport and further improves the specific capacity and cycle stability of the recycled graphite anode material.

[0047] The present invention also provides a recycled graphite anode material prepared by the preparation method described in the above technical solution.

[0048] This invention also provides the application of the recycled graphite anode material described in the above technical solution in lithium-ion batteries.

[0049] In the embodiments and comparative examples of the present invention, the preparation process of the recycled graphite anode material is as follows: Figure 1 As shown: from Figure 1As can be seen from the examples, waste graphite (SG) is mixed with copper oxide and asphalt and calcined at 800°C, then acid-washed to obtain recycled graphite anode material (RG). The surface of the recycled graphite anode material has a graphite-like layer, and after acid washing, it forms a fast channel, which is conducive to the transport of lithium ions. In the comparative example, waste graphite (SG) is mixed with asphalt and calcined at 800°C to obtain recycled graphite anode material (CG). The surface of the recycled graphite anode material (CG) has a graphite-like layer, but no fast channel is formed.

[0050] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0051] Example 1 A method for preparing a recycled graphite anode material comprises the following steps: Waste batteries were discharged in a 1 mol / L NaCl solution for 24 hours, then the negative electrode was removed and the copper foil and active material in the negative electrode were separated to obtain the negative electrode active material from the waste batteries. The negative electrode active material from the waste batteries was mixed with an acid solution (a 1 mol / L hydrochloric acid solution containing 1 wt% hydrogen peroxide) (the mass ratio of the negative electrode active material from the waste batteries to the volume of the acid solution was 1 kg: 3 L). Under stirring conditions, the mixture was acid-leached at 80°C for 2 hours and then filtered. The liquid product obtained by filtration was an acid leaching solution containing copper ions. The solid product obtained by filtration was washed three times with deionized water and then dried at 60°C for 4 hours to obtain waste graphite (denoted as SG). The copper-containing acid leaching solution and alkaline solution (5 mol / L sodium hydroxide solution) were mixed, and the pH of the mixture was adjusted to 6.68. After precipitation reaction for 5 min, the mixture was filtered sequentially. The solid product obtained by filtration was washed three times with deionized water, dried at 300℃ for 1 h, and then ball-milled at 400 rpm for 4 h to obtain copper oxide. The waste graphite, copper oxide, and asphalt were mixed at a mass ratio of 100:10:10 (copper oxide content was 10% of the mass of waste graphite) and ball-milled at 400 rpm for 2 hours. The mixture was then calcined at 800℃ for 2 hours. The calcined product was then acid-washed (using a 1 mol / L hydrochloric acid solution containing 1 wt% hydrogen peroxide, with a mass ratio of calcined product to acid solution volume of 1 kg: 3 L). After washing three times with deionized water, the mixture was dried at 60℃ for 6 hours to obtain the recycled graphite anode material (denoted as RG).

[0052] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the preparation step of copper oxide and the addition of copper oxide are omitted. Otherwise, they are the same as in Example 1, and the resulting recycled graphite anode material is denoted as CG.

[0053] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the mass ratio of the waste graphite, copper oxide and asphalt is 100:5:10 (the copper oxide content is 5% of the mass of the waste graphite), and the rest is the same as Example 1.

[0054] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the mass ratio of the waste graphite, copper oxide and asphalt is 100:20:10 (the copper oxide content is 20% of the mass of the waste graphite), and the rest is the same as Example 1.

[0055] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that acid washing was not performed and the operation after acid washing was the same as in Example 1. The resulting recycled graphite anode material (denoted as BRG) was obtained.

[0056] The copper oxide content of the recycled graphite anode material (BRG) in Comparative Example 4 was calculated by theoretical calculation (based on the mass of the amount added). The copper oxide content in the recycled graphite anode material in Comparative Example 4 was 7%.

[0057] Comparative Example 5 The asphalt was calcined at 800℃ for 2 hours to obtain carbonized asphalt material (denoted as CB).

[0058] Comparative Example 6 A method for preparing a graphite anode material comprises the following steps: The waste batteries were discharged in a 1 mol / L NaCl solution for 24 hours, and then the negative electrode was removed. The copper foil and active material in the negative electrode were separated to obtain the negative electrode active material from the waste batteries. The negative electrode active material from the waste batteries was mixed with an acid solution (a 1 mol / L hydrochloric acid solution containing 1 wt% hydrogen peroxide) (the mass ratio of the negative electrode active material from the waste batteries to the volume of the acid solution was 1 kg: 3 L). Under stirring conditions, the mixture was acid-leached at 80°C for 2 hours and then filtered. The liquid product obtained by filtration was an acid leaching solution containing copper ions. The copper-containing acid leaching solution and alkaline solution (5 mol / L sodium hydroxide solution) were mixed, and the pH of the mixture was adjusted to 6.68. After precipitation reaction for 5 min, the mixture was filtered sequentially. The solid product obtained by filtration was washed three times with deionized water, dried at 300℃ for 1 h, and then ball-milled at 400 rpm for 4 h to obtain copper oxide. The copper oxide and pitch were mixed at a mass ratio of 10:10 and ball-milled at 200-400 rpm for 2 hours, and then calcined at 800℃ for 2 hours to obtain the graphite anode material (denoted as CCB).

[0059] Phase and composition analysis of the regenerated graphite anode materials obtained in Example 1 and Comparative Example 1 was performed using X-ray diffraction with Cu Kα radiation; the complex and chemical state were analyzed using Raman spectroscopy; and the microstructure and structure of the samples were observed using high-resolution transmission electron microscopy and field emission scanning electron microscopy.

[0060] The XRD patterns of waste graphite (SG), recycled graphite anode material (RG), and recycled graphite anode material (CG) in Example 1 are shown below. Figure 2 As shown, the Raman spectrum is as follows Figure 3 As shown.

[0061] from Figure 2 and Figure 3 As can be seen, all three materials exhibit characteristic diffraction peaks of a hexagonal graphite structure; Raman spectroscopy was used to characterize the microstructure of the materials, and the results showed that the peaks at 1312 and 1538 cm⁻¹ were positive. -1 There are obvious D and G peaks. The calculated ID / IG values ​​of RG, CG, and SG are 0.63, 1.05, and 0.73, respectively. In Comparative Example 1, CG is 1.05, and its defect increase is due to the presence of amorphous carbon on the surface, while in the example, RG is 0.63, and the ID / IG value decreases due to the catalysis of copper oxide.

[0062] SEM image of the recycled graphite anode material (CG) in Comparative Example 1 is shown below. Figure 4 As shown, the TEM image is as follows Figure 5 As shown; the SEM image of waste graphite (SG) in Example 1 is shown below. Figure 6 As shown, the TEM image is as follows Figure 7 As shown; the SEM image of the recycled graphite anode material (RG) in Example 1 is shown below. Figure 8 As shown, the TEM image is as follows Figure 9 As shown.

[0063] from Figures 4-9It can be seen that the SG sample surface exhibits obvious cracks, residual binder, and a large number of carbon black agglomerates; in contrast, CG and RG both show smoother surfaces and effectively restored structural integrity. Corresponding TEM images further reveal widespread cracking within SG. Comparative analysis shows that the CG surface is covered with a 4-5 nm amorphous carbon layer, while RG has a more ordered graphite-like carbon layer with a thickness of 3-4 nm. The interlayer spacing of SG is 0.343 nm (close to the theoretical value), and its slight expansion is attributed to lithium-ion intercalation during electrochemical cycling; the outer amorphous carbon region of CG exhibits a larger interlayer spacing of 0.424 nm, while RG shows a graphite-like structural interlayer spacing of 0.357 nm.

[0064] The materials prepared in Comparative Examples 5 and 6 were observed using a camera and a field emission scanning electron microscope. A photograph of the carbonized pitch material prepared in Comparative Example 5 is shown below. Figure 10 As shown, a 500x magnified SEM image of the carbonized asphalt material prepared in Comparative Example 5 is shown below. Figure 11 As shown, the SEM image magnified 5000 times is as follows: Figure 12 As shown; a photograph of the graphite anode material prepared in Comparative Example 6 is shown. Figure 13 As shown, a 500x magnified SEM image of the graphite anode material prepared in Comparative Example 6 is shown below. Figure 14 As shown, the SEM image magnified 5000 times is as follows: Figure 15 As shown.

[0065] from Figures 10-15 It can be seen that the sample of asphalt directly burned in Comparative Example 5 is in a fluffy state, and CB appears to be flaky when observed by SEM; while the CCB prepared in Comparative Example 6 is dense and has a large number of small pores inside.

[0066] Application Example 1 The recycled graphite anode material prepared in Example 1, carbon black, and carboxymethyl cellulose (CMC) (mass ratio 80:10:10) were first ground for half an hour, then deionized water was added for further grinding to form a uniform slurry. The slurry was then coated onto copper foil and dried at 80°C for 20 minutes before being stored in a vacuum drying oven. Finally, the dried graphite electrode was cut into a disc with a diameter of 12 mm to prepare the final anode electrode. A 2032 type coin cell (half cell) was assembled in a glove box. The cathode was lithium metal, the separator was Celgard 2400 film, and the electrolyte was prepared by dissolving 1M LiPF6 and fluorocarbonate (FEC) (10 Vol.%) in a mixture of ethylene carbonate and diethyl carbonate (DEC) at a volume ratio of 1:1.

[0067] Comparative Application Example 1 The only difference between Comparative Example 1 and Application Example 1 is that the recycled graphite anode material prepared in Comparative Example 1 is used; otherwise, they are the same as in Application Example 1.

[0068] Comparative Application Example 2 The only difference between Comparative Example 2 and Comparative Example 1 is that Comparative Example 2 uses the recycled graphite anode material prepared in Comparative Example 2; otherwise, they are the same as in Comparative Example 1.

[0069] Comparative Application Example 3 The only difference between Comparative Example 3 and Comparative Example 1 is that Comparative Example 3 uses the recycled graphite anode material prepared in Comparative Example 3; otherwise, they are the same as in Comparative Example 1.

[0070] Comparative Application Example 4 The only difference between Comparative Example 4 and Comparative Example 1 is that Comparative Example 4 uses recycled graphite anode material prepared in Comparative Example 4; otherwise, they are the same as in Comparative Example 1.

[0071] Comparative Application Example 5 The only difference between Comparative Example 5 and Comparative Example 1 is that the carbonized asphalt material prepared in Comparative Example 5 is used; otherwise, they are the same as in Comparative Example 1.

[0072] Comparative Application Example 6 The only difference between Comparative Example 6 and Comparative Example 1 is that the graphite anode material prepared in Comparative Example 6 is used; otherwise, they are the same as in Comparative Example 1.

[0073] The electrochemical performance of the batteries obtained using the Xinwei test cabinet corresponding to Case 1 and Comparative Application Examples 1-6 was tested.

[0074] The cycle performance graphs of the batteries prepared in Application Example 1 and Comparative Application Example 1 are shown below. Figure 16 As shown, from Figure 16 It can be seen that after three activation cycles at 0.05C, the cycling performance of RG, CG, and SG half-cells at a 0.5C rate (nominal specific capacity of 372 mAh / g at 1C) shows that RG and CG achieve full activation after approximately 25 cycles, while SG requires approximately 50 cycles. The capacities of RG, CG, and SG after full activation are 351, 323, and 295 mAh / g, respectively, with initial coulombic efficiencies of 88.0%, 87.6%, and 87.0%, respectively. After 300 cycles, the capacities retained by RG, CG, and SG are 274, 214, and 158 mAh / g, respectively, corresponding to capacity retention rates of 78%, 66%, and 53%. This confirms that the surface structure of the regenerated graphite anode material prepared in Example 1 can effectively improve cycle stability.

[0075] The rate performance graphs of the batteries prepared in Application Example 1 and Comparative Application Example 1 are shown below. Figure 17 As shown, from Figure 17As can be seen, with step current densities of 0.1C, 0.2C, 0.5C, 1C, 2C, and 0.1C, the capacities of RG, CG, and SG at 0.1C are approximately 357, 331, and 341 mAh / g, respectively; while when the current increases to 2C, the capacities decrease to 229, 148, and 76 mAh / g, respectively, with capacity retention rates of 64%, 44.7%, and 22% relative to 0.1C. These results verify that the graphite-like coating layer generated by copper oxide catalysis in Example 1, and that the rapid channel formation after acid washing, can significantly improve the electrochemical performance of regenerated graphite.

[0076] The cycle performance graphs of the batteries prepared in Application Example 1 and Comparative Application Examples 2-3 are shown below. Figure 18 As shown, the rate performance diagram is as follows: Figure 19 As shown, Figure 18 and Figure 19 These tests are conducted in the early stages of battery fabrication, when the battery capacity is relatively small. Figure 18 and Figure 19 It can be seen that when the amount of copper oxide increases from 5% to 10% of the mass of waste graphite, the battery performance is significantly improved; however, when the amount of copper oxide reaches 20%, the cycle stability and rate performance will significantly decline. The results confirm that when the amount of copper oxide in Example 1 is 10% of the mass of waste graphite, it can better catalyze the waste graphite and obtain a recycled graphite anode material with better performance.

[0077] The cycle performance graphs of the batteries prepared in Application Example 1, Comparative Application Example 1, and Comparative Application Example 4 are shown below. Figure 20 As shown, the rate performance diagram is as follows: Figure 21 As shown, from Figure 20 and 21 It can be seen that the copper oxide content in the recycled graphite anode material of Comparative Example 4 is 7%, and its theoretical capacity should be about 93% of that of Example 1 (RG). Experimental data show that the capacities of RG and BRG at 0.1C are 357 and 328 mAh / g, respectively, with BRG reaching 92% of the capacity of RG, which is highly consistent with the theoretical prediction. Furthermore, BRG exhibits significantly better cycle stability than CG, and their rate performance is comparable. This demonstrates that the high rate performance of the obtained RG material is greatly improved after acid washing, which is attributed to the tiny surface pores formed during the copper removal process.

[0078] The cycle performance graphs of the batteries prepared in Comparative Application Example 5 and Comparative Application Example 6 are shown in the figure. Figure 22 As shown, the rate performance diagram is as follows: Figure 23 As shown, from Figure 22 and 23 It can be seen that the cycle life and energy efficiency of copper oxide-catalyzed asphalt are significantly better than those of uncatalyzed asphalt, indicating that the electrochemical energy storage of copper oxide-catalyzed asphalt is significantly improved.

[0079] The half-cell prepared from the recycled graphite anode material prepared by the method provided by this invention can achieve a specific capacity of 351 mAh / g at a 0.5C rate, and the capacity retention rate can reach 78% after 300 cycles, exhibiting good specific capacity and cycle stability.

[0080] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a recycled graphite anode material, comprising the following steps: The negative electrode active material in the waste battery is mixed with an acid solution and then subjected to acid leaching followed by a first filtration to obtain an acid leaching solution containing copper ions and waste graphite, respectively. After mixing the copper-containing acid leaching solution and alkaline solution to carry out a precipitation reaction, the solution is then subjected to a second filtration and drying to obtain copper oxide. The waste graphite, copper oxide and asphalt are mixed and then calcined and acid-washed in sequence to obtain recycled graphite anode material; the mass ratio of the waste graphite, copper oxide and asphalt is 100:(8~12):(5~15).

2. The preparation method according to claim 1, characterized in that, The acid in the acid solution is hydrochloric acid or sulfuric acid; The concentration of the acid solution is 0.8~1.2 mol / L.

3. The preparation method according to claim 2, characterized in that, The acid solution contains 0.8 to 1.2 wt% hydrogen peroxide.

4. The preparation method according to claim 1, characterized in that, The acid leaching temperature is 60~80℃, and the acid leaching time is 2~4h.

5. The preparation method according to claim 1, characterized in that, The pH of the precipitation reaction is 6.6-7.

6. The preparation method according to claim 1, characterized in that, The drying temperature is 100~350℃, and the drying time is 1~3h.

7. The preparation method according to claim 1, characterized in that, The calcination temperature is 800~1000℃, and the calcination time is 2~4h.

8. The preparation method according to claim 1, characterized in that, The pickling solution used is a hydrochloric acid solution; the concentration of the hydrochloric acid solution is 0.8~1.2 mol / L.

9. The recycled graphite anode material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the recycled graphite anode material according to claim 9 in lithium-ion batteries.

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