Separation method and separation apparatus for electrode material

Abstract

The embodiment of the application provides a separation method and a separation device of an electrode material. The separation method of the electrode material comprises the following steps: S1, performing oxygen-containing roasting treatment on electrode material to be separated which at least comprises graphite and lithium iron phosphate, to obtain intermediate electrode material; S2, performing flotation separation on the intermediate electrode material, to obtain graphite and positive electrode precursor tailings; and S3, mixing the positive electrode precursor tailings with a lithium source and a carbon source to obtain a mixed system, and performing anaerobic calcination treatment on the mixed system, to obtain lithium iron phosphate. The separation method can efficiently, at low cost and in an environmentally friendly manner, separate the positive electrode material and the negative electrode material in a waste lithium iron phosphate battery.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a method and apparatus for separating electrode materials. Background Technology

[0002] With the rapid development of the global new energy vehicle and energy storage industries, lithium iron phosphate (LFP) batteries have become the mainstream technology for power and energy storage batteries due to their advantages such as high safety, long cycle life, and low cost. According to industry data, the installed capacity of LFP batteries has remained stable at over 60% for a long time, and a large-scale retirement wave is expected in the future. However, the lithium iron phosphate cathode material, graphite anode material, and valuable metals such as lithium, cobalt, and nickel contained in retired batteries will lead to resource waste and environmental pollution if not effectively recycled. Therefore, developing an efficient, low-cost, and environmentally friendly method for recycling spent LFP batteries has become a core demand in the battery recycling field. Summary of the Invention

[0003] This application provides a method for separating electrode materials. This method can efficiently, cost-effectively, and environmentally friendly separate the positive and negative electrode materials from spent lithium iron phosphate batteries. The separation system used to implement this method has a simple structure and is suitable for widespread application.

[0004] This application provides a method for separating electrode materials, comprising:

[0005] S1: The electrode material to be separated, which includes at least graphite and lithium iron phosphate, is subjected to aerobic calcination to obtain the intermediate electrode material.

[0006] S2: The intermediate electrode material is separated by flotation to obtain graphite and positive electrode precursor tailings;

[0007] S3: The positive electrode precursor tailings are mixed with lithium source and carbon source to obtain a mixed system, and the mixed system is subjected to anaerobic calcination to obtain lithium iron phosphate.

[0008] In the separation method described above, the electrode material to be separated is obtained by crushing and sorting the positive and negative electrode sheets in the battery.

[0009] In the separation method described above, the temperature during the aerobic roasting treatment is 400-550℃ and the time is 30-75min.

[0010] The separation method described above, wherein the flotation separation includes adding a collector and a frother for flotation separation, and the flotation separation includes at least one roughing treatment and at least one scavenging treatment;

[0011] The amount of collector added in the roughing process is greater than the amount of collector added in the scavenging process, and the amount of frother added in the roughing process is greater than the amount of frother added in the scavenging process.

[0012] In the separation method described above, in the coarse selection process, the amount of collector added accounts for 100 g / t to 300 g / t of the mass of the intermediate electrode material, and the amount of foaming agent added accounts for 50 g / t to 150 g / t of the mass of the intermediate electrode material.

[0013] In the separation method described above, during the scavenging process, the amount of collector added accounts for 5 g / t to 50 g / t of the mass of the intermediate electrode material, and the amount of foaming agent added accounts for 0 g / t to 20 g / t of the mass of the intermediate electrode material.

[0014] In the separation method described above, the molar ratio of P, Fe, and Li in the mixed system is 1:1:(1.02-1.07).

[0015] In the separation method described above, the mass percentage of carbon in the mixed system is 1.5-5%.

[0016] In the separation method described above, the temperature during the anaerobic calcination treatment is 650-770℃ and the time is 10-20h.

[0017] The present invention also provides a separation system for implementing the electrode material separation method described above, wherein the system includes an aerobic calcination unit, a flotation separation unit, and an oxygen-free calcination unit;

[0018] The aerobic roasting unit has an inlet for the electrode material to be separated and an outlet for the intermediate electrode material; the flotation separation unit has an inlet for the intermediate electrode material, an outlet for graphite and an outlet for the positive electrode precursor tailings; and the anaerobic calcination unit has an inlet for the positive electrode precursor tailings, an inlet for the lithium source and an inlet for the carbon source.

[0019] The intermediate electrode material outlet is connected to the intermediate electrode material inlet, and the positive electrode precursor tailings outlet is connected to the positive electrode precursor tailings inlet.

[0020] The electrode material separation method provided in this application includes, in sequence, aerobic roasting, flotation separation, and anaerobic calcination of the electrode material to be separated. This method can separate the positive electrode material from the negative electrode material to be separated, and obtain positive electrode material and negative electrode material with high purity. This separation method is simple to operate and is suitable for widespread application. Attached Figure Description

[0021] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0022] Figure 1 This is a flowchart illustrating the separation process of electrode materials in some embodiments of the present invention;

[0023] Figure 2 The graph shows the flotation separation results of n-dodecane in Experimental Example 1;

[0024] Figure 3 The flotation separation structure diagram of 2-octanol in Experimental Example 1;

[0025] Figure 4 The flotation separation results for different CMC dosages in Experiment Example 2 are shown in the figure.

[0026] Figure 5 The graph shows the flotation separation results at different temperatures in Experiment Example 3;

[0027] Figure 6 The flotation separation results at different times in Experiment Example 3 are shown in the figure.

[0028] Figure 7 The contact angle diagrams are for the positive and negative electrode powders in Experiment Example 4.

[0029] Figure 8 The circuit performance graph of the battery in Experiment Example 6 is shown.

[0030] Figure 9 The rate performance graph is for the battery in Test Example 6. Detailed Implementation

[0031] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0032] Currently, recycling technologies for lithium iron phosphate batteries are mainly divided into physical, chemical, and biological methods. Among them, flotation is widely used for separating positive and negative electrode materials of lithium-ion batteries due to its simple operation and low cost. The core principle of flotation is to achieve separation by utilizing the difference in surface wettability (contact angle difference) of materials: highly hydrophilic materials (such as iron oxide) do not easily adhere to air bubbles and sink to the bottom of the tank, while highly hydrophobic materials (such as graphite) easily adhere to air bubbles and float to the surface to form a concentrate. However, existing flotation technologies face significant challenges when processing lithium iron phosphate (LiFePO4) batteries: LiFePO4 cathode material itself has a certain degree of hydrophilicity, while graphite anode material is highly hydrophobic, but the difference in their contact angles is limited (usually less than 30°), resulting in poor flotation selectivity. To enhance separation, existing technologies require the addition of inhibitors (such as sodium carboxymethyl cellulose, CMC) to suppress the flotation behavior of LiFePO4, while also increasing the dosage of collectors (such as n-dodecane) and frothers (such as 2-octanol), with reagent costs accounting for more than 30% of the overall process cost. Traditional flotation processes cannot completely remove binders (such as PVDF) and electrolyte residues from the electrode material surface, leading to a decrease in the electrochemical performance of the separated electrode material. This application achieves efficient separation of LiFePO4 and graphite, as well as the regeneration of LiFePO4 material, by controlling the hydrophilicity of the electrode material surface through aerobic calcination pretreatment, combined with flotation separation and anaerobic calcination treatment.

[0033] Figure 1 This is a flowchart illustrating the separation process of electrode materials in some embodiments of the present invention. For example... Figure 1 As shown, the present invention provides a method for separating electrode materials, comprising:

[0034] S1: The electrode material to be separated (waste lithium iron phosphate black powder), which includes at least graphite and lithium iron phosphate, is subjected to aerobic roasting to obtain intermediate electrode material (roasted black powder).

[0035] S2: The intermediate electrode material is separated by flotation to obtain graphite (concentrate) and positive electrode precursor tailings (tailings).

[0036] S3: Mix the positive electrode precursor tailings with lithium source and carbon source to obtain a mixed system. Perform anaerobic calcination on the mixed system to obtain lithium iron phosphate (regenerated lithium iron phosphate powder).

[0037] Specifically, the separation method includes: S1: Aerobic roasting is performed on the electrode material to be separated, which includes at least graphite and lithium iron phosphate. On the one hand, this removes the binder and electrolyte residue on the surface of the electrode material to be separated, restoring its intrinsic surface properties; on the other hand, it oxidizes the lithium iron phosphate in the electrode material to be separated into the more hydrophilic Li3Fe2(PO4)3 and Fe2O3, thereby increasing its wettability difference with graphite, and obtaining the intermediate electrode material; S2: The intermediate electrode material is separated by flotation to obtain graphite and positive electrode precursor tailings including Li3Fe2(PO4)3 and Fe2O3; S3: ... The cathode precursor tailings are mixed with lithium source and carbon source to obtain a mixed system. The mixed system is then subjected to anaerobic calcination. During the anaerobic calcination, the lithium source, carbon source and cathode precursor tailings undergo a high-temperature solid-state reaction. The lithium source is used to lithiate Li3Fe2(PO4)3 and Fe2O3 in the cathode precursor tailings, and the carbon source is used to promote the reduction of Li3Fe2(PO4)3 and Fe2O3 in the cathode precursor tailings. This results in the crystallization of the cathode precursor tailings to form lithium iron phosphate. At the same time, the carbon source can also form a carbon coating layer on the surface of lithium iron phosphate, further enhancing the stability and conductivity of lithium iron phosphate and improving the electrochemical performance of the battery.

[0038] The electrode material separation method of the present invention can effectively separate graphite anode and lithium iron phosphate cathode by flotation. It can significantly reduce the amount of collector and foaming agent without the use of inhibitors, and provides a feasible path for the green and low-cost recycling of retired lithium iron phosphate batteries.

[0039] In this invention, aerobic roasting can be performed in a muffle furnace, specifically including: heating the electrode material to be separated, which includes at least graphite and lithium iron phosphate, to a predetermined temperature in an air atmosphere and holding it at that temperature for a certain period of time for aerobic roasting.

[0040] The oxygen-free calcination process can be carried out in a tube furnace, and the calcination atmosphere for the oxygen-free calcination process can be nitrogen.

[0041] The present invention does not impose any particular limitation on the carbon source, which can be any carbon-containing compound commonly used in the art. For example, the carbon source can be at least one of glucose, sucrose and pitch.

[0042] In some embodiments of the present invention, the electrode materials to be separated are obtained by crushing and sorting the positive and negative electrode plates in the battery. The battery can be a spent lithium iron phosphate battery (retired lithium iron phosphate battery).

[0043] In some embodiments of the present invention, the aerobic calcination treatment is carried out at a temperature of 400-550°C for 30-75 minutes. This temperature range is selected based on thermodynamic calculations and experimental verification, enabling more effective decomposition of organic binders (such as PVDF) and electrolyte residues (such as LiPF6), while simultaneously oxidizing lithium iron phosphate (LiFePO4) to Li3Fe2(PO4)3 and Fe2O3. The resulting Li3Fe2(PO4)3 and Fe2O3 exhibit higher hydrophilicity (contact angle reduced by approximately 30°), while graphite remains hydrophobic, thereby significantly amplifying the difference in wettability between the two.

[0044] In some embodiments of the present invention, flotation separation includes adding a collector and a frother for flotation separation, and flotation separation includes at least one roughing process and at least one scavenging process.

[0045] The amount of collector added in the roughing process is greater than that in the scavenging process, and the amount of frother added in the roughing process is greater than that in the scavenging process.

[0046] In this invention, the number of coarse selection and sweeping processes can be adjusted according to actual needs. In some embodiments, the coarse selection process can be performed twice, the sweeping process can be performed twice, and the coarse selection and sweeping processes can be performed alternately.

[0047] In other embodiments, the roughing process can be performed once, and the scavenging process can be performed twice. The flotation separation can sequentially include a roughing process, a first scavenging process, and a second scavenging process. Specifically, as shown... Figure 1 As shown, the flotation separation includes roughing the intermediate electrode material to separate the graphite (concentrate) from the cathode precursor tailings (tailings); then, the cathode precursor tailings undergo a first scavenging process to further separate the graphite from the cathode precursor tailings, resulting in scavenged concentrate 1 (graphite) and scavenged tailings 1 (high-purity cathode precursor tailings); next, scavenged tailings 1 undergo a second scavenging process to further separate the graphite from the scavenged tailings 1, resulting in scavenged concentrate 2 (graphite) and scavenged tailings 2 (high-purity cathode precursor tailings).

[0048] This invention improves the efficiency of flotation separation by including roughing and scavenging processes, thereby efficiently obtaining high-purity cathode precursor tailings and minimizing the use of reagents (frothers and collectors).

[0049] Furthermore, in the roughing process, when the amount of collector added is 100g / t to 300g / t of the mass of the intermediate electrode material, and the amount of frother added is 50g / t to 150g / t of the mass of the intermediate electrode material, the effect of the roughing process can be improved, thereby obtaining high-purity cathode precursor tailings.

[0050] Furthermore, in the scavenging process, when the amount of collector added is 5 g / t to 50 g / t of the intermediate electrode material and the amount of frother added is 0 g / t to 20 g / t of the intermediate electrode material, the effect of the scavenging process can be improved, thereby obtaining high-purity cathode precursor tailings.

[0051] The present invention does not specifically limit the collector, and it can be a collector commonly used in the art. For example, the collector can include at least one of kerosene and diesel oil. The present invention does not specifically limit the foaming agent, and it can be a foaming agent commonly used in the art. For example, the foaming agent can include at least one of methyl isobutyl methanol and sodium dodecyl sulfate.

[0052] In some embodiments of the present invention, when the molar ratio of P, Fe, and Li in the mixed system is 1:1:(1.02-1.07), lithium is in excess, which can fully lithilate the positive electrode precursor tailings to obtain lithium iron phosphate.

[0053] In some embodiments of the present invention, when the mass percentage of carbon in the mixed system is 1.5-5%, Li3Fe2(PO4)3 and Fe2O3 in the positive electrode precursor tailings can be more fully reduced to obtain lithium iron phosphate, and a carbon coating layer of suitable thickness can be formed on the surface of lithium iron phosphate, thereby obtaining lithium iron phosphate with excellent capacity, conductivity and stability.

[0054] This invention also allows for the selection of the temperature and time for anaerobic calcination to further improve the efficiency of the anaerobic calcination process and obtain lithium iron phosphate with excellent electrochemical performance. In this invention, the temperature for anaerobic calcination can be determined based on DCS curves. In some embodiments of this invention, during anaerobic calcination, a temperature of 650-770℃ and a time of 10-20h correspond to the reduction peak of Li3Fe2(PO4)3 and the crystallization peak of LiFePO4. When using the above-mentioned temperature and time for anaerobic calcination, the tailings of the cathode precursor can be reduced more fully while saving energy, thereby improving the yield of lithium iron phosphate.

[0055] The present invention also provides a separation system for implementing the above-described separation method for electrode materials, comprising: an aerobic roasting unit, a flotation separation unit, and an oxygen-free calcination unit;

[0056] The aerobic roasting unit has an inlet for the electrode material to be separated and an outlet for the intermediate electrode material; the flotation separation unit has an inlet for the intermediate electrode material, an outlet for graphite and an outlet for the positive electrode precursor tailings; and the anaerobic calcination unit has an inlet for the positive electrode precursor tailings, an inlet for the lithium source and an inlet for the carbon source.

[0057] The intermediate electrode material outlet is connected to the intermediate electrode material inlet, and the positive electrode precursor tailings outlet is connected to the positive electrode precursor tailings inlet.

[0058] Specifically, the electrode material to be separated enters the aerobic roasting unit through the electrode material inlet. In the aerobic roasting unit, the binder and electrolyte in the electrode material are removed, and the lithium iron phosphate in the electrode material is oxidized to the more hydrophilic Li3Fe2(PO4)3 and Fe2O3, thus obtaining the intermediate electrode material. The intermediate electrode material is output from the intermediate electrode material outlet of the aerobic roasting unit and enters the flotation separation unit through the intermediate electrode material inlet. In the flotation separation unit, the intermediate electrode material is separated to obtain graphite and... The precursor tailings and graphite are output from the graphite outlet of the flotation separation unit, and the cathode precursor tailings are output from the cathode precursor tailings outlet of the flotation separation unit. The cathode precursor tailings enter the anaerobic calcination unit through the cathode precursor tailings inlet. The lithium source and carbon source enter the anaerobic calcination unit through the lithium source inlet. In the anaerobic calcination unit, the lithium source, carbon source, and cathode precursor tailings undergo lithiation reduction to obtain lithium iron phosphate. At the same time, the carbon source can form a carbon coating layer to coat at least part of the surface of the lithium iron phosphate.

[0059] The separation system of the present invention has a simple structure and is suitable for widespread application.

[0060] The present invention will be further described below with reference to specific embodiments.

[0061] Experimental Example 1

[0062] This experimental example is used to investigate the effect of aerobic roasting on flotation separation, specifically including:

[0063] Example: The crushed and sorted electrode material to be separated is placed in a muffle furnace for aerobic roasting treatment. The aerobic roasting treatment temperature is 500℃ and the time is 30 minutes to obtain intermediate electrode material.

[0064] Subsequently, flotation separation was performed using an XFD-1.5L flotation machine. 60g of intermediate electrode material was weighed and placed in a 1.5L flotation cell. After adjusting the slurry for 3 minutes, n-dodecane (stirred for 2 minutes) and sec-octanol (stirred for 1 minute) were added sequentially, and flotation separation began. The skimming time was 3 minutes, yielding cathode precursor tailings. The dosages of n-dodecane were 100 g / t, 150 g / t, 200 g / t, 250 g / t, and 300 g / t, and the dosages of sec-octanol were 50 g / t, 75 g / t, 100 g / t, 125 g / t, and 150 g / t. The roasting grade and recovery rate (roasting recovery rate) of the cathode precursor tailings under aerobic roasting were calculated for different dosages of n-dodecane and sec-octanol. Specifically, this includes: determining the Fe content in the cathode precursor tailings using ICP-OES, and further calculating the mass of the cathode precursor in the tailings based on the Fe content. The grade is calculated using Equation 1, and the recovery rate is calculated using Equation 2.

[0065] Formula 1

[0066] In Equation 1, α1 represents the grade of the positive electrode precursor tailings, %; m 前驱体 M represents the mass of the positive electrode precursor (calculated from the Fe element content), in g; 尾矿 The mass of the positive electrode precursor tailings is expressed in g.

[0067] Formula 2

[0068] In Equation 2, ε is the recovery rate of the cathode precursor tailings, %; α1 is the grade of the cathode precursor tailings, %; M1 is the mass of the cathode precursor tailings, %; α0 is the grade of the electrode material to be separated (mass percentage of cathode precursor in the electrode material to be separated), %; M0 is the total mass of the electrode material to be separated, %.

[0069] Comparative example: The crushed and sorted electrode material to be separated was placed in a tube furnace for pyrolysis treatment. The atmosphere of the pyrolysis treatment was nitrogen, the temperature of the pyrolysis treatment was 500℃, and the time was 30 minutes to obtain the intermediate electrode material.

[0070] Subsequently, flotation separation was performed using an XFD-1.5L flotation machine. 60g of intermediate electrode material was weighed and placed in a 1.5L flotation cell. After adjusting the slurry for 3 minutes, n-dodecane (stirred for 2 minutes) and 2-octanol (stirred for 1 minute) were added sequentially, and flotation separation began. The skimming time was 3 minutes, yielding cathode precursor tailings. The dosages of n-dodecane were 100 g / t, 150 g / t, 200 g / t, 250 g / t, and 300 g / t, and the dosages of 2-octanol were 50 g / t, 75 g / t, 100 g / t, 125 g / t, and 150 g / t. The pyrolysis grade and the recovery rate (pyrolysis recovery rate) of the cathode precursor tailings were calculated for different dosages of n-dodecane and 2-octanol.

[0071] Figure 2 The graph shows the flotation separation results of n-dodecane in Experimental Example 1; Figure 3 This is the flotation separation structure diagram of 2-octanol from Experimental Example 1. From... Figure 2 and Figure 3 It can be seen that, under different dosages of n-dodecane and 2-octanol, the flotation separation effect of the examples is better than that of the comparative example. Furthermore, while achieving similar grades and recoveries, the reagent dosage required for the examples is lower than that for the comparative example. This indicates that aerobic roasting not only helps improve the recovery effect of flotation separation but also reduces reagent consumption.

[0072] Experimental Example 2

[0073] This experimental example is used to investigate the effect of aerobic roasting on flotation separation, specifically including:

[0074] Example: The crushed and sorted electrode material to be separated is placed in a muffle furnace for aerobic roasting treatment. The aerobic roasting treatment temperature is 500℃ and the time is 30 minutes to obtain intermediate electrode material.

[0075] Subsequently, flotation separation was performed using an XFD-1.5L flotation machine. 60g of intermediate electrode material was weighed and placed in a 1.5L flotation cell. The slurry was first prepared for 3 minutes, then sodium carboxymethyl cellulose (CMC) inhibitor was added and stirred for 2 minutes, followed by n-dodecane and stirring for 2 minutes. Finally, 2-octanol was added and stirred for 1 minute before flotation separation began. The skimming time was set to 3 minutes, yielding cathode precursor tailings. The slurry concentration was 40 g / L, the n-dodecane dosage was 300 g / t, and the 2-octanol dosage was 150 g / t. The effect of CMC dosage (0, 100, 200, 300, 400, 500 g / t) on the flotation separation effect was investigated. The roasting grade and the recovery rate (roasting recovery rate) of the cathode precursor tailings under aerobic roasting treatment were calculated for different CMC dosages.

[0076] Comparative example: The crushed and sorted electrode material to be separated was placed in a tube furnace for pyrolysis treatment. The atmosphere of the pyrolysis treatment was nitrogen, the temperature of the pyrolysis treatment was 500℃, and the time was 30 minutes to obtain the intermediate electrode material.

[0077] Subsequently, flotation separation was performed using an XFD-1.5L flotation machine. 60g of intermediate electrode material was weighed and placed in a 1.5L flotation cell. The slurry was first prepared for 3 minutes, then sodium carboxymethyl cellulose (CMC) inhibitor was added and stirred for 2 minutes, followed by n-dodecane and stirring for 2 minutes. Finally, 2-octanol was added and stirred for 1 minute before flotation separation began. The skimming time was set to 3 minutes, yielding cathode precursor tailings. The slurry concentration was 40 g / L, the n-dodecane dosage was 300 g / t, and the 2-octanol dosage was 150 g / t. The effect of CMC dosage (0, 100, 200, 300, 400, 500 g / t) on the flotation separation effect was investigated. The pyrolysis grade and the recovery rate (pyrolysis recovery rate) of the cathode precursor tailings were calculated for different CMC dosages.

[0078] Figure 4 The graph shows the flotation separation results for different CMC dosages in Experiment Example 2. Figure 4 As shown, under different CMC dosage conditions, the calcination grade and calcination recovery rate of the embodiment were higher than those of the comparative example. Furthermore, the addition of CMC had a limited effect on improving the recovery effect of the embodiment, indicating that it already possessed good floatability; while in the comparative example, the grade and recovery rate of lithium iron phosphate significantly increased after the addition of CMC, demonstrating that the inhibitor had a significant effect on improving the selectivity of the flotation separation in the comparative example.

[0079] Experimental Example 3

[0080] This experimental example is used to investigate the effect of aerobic roasting on flotation separation, specifically including:

[0081] Example: The crushed and sorted electrode materials to be separated were placed in a muffle furnace for aerobic calcination treatment. The aerobic calcination treatment temperatures were 350, 400, 450, 500, and 550°C, and the time was 30 minutes to obtain intermediate electrode materials; the aerobic calcination treatment temperature was 500°C, and the time was 15, 30, 45, 60, and 75 minutes respectively.

[0082] Subsequently, flotation separation was performed using an XFD-1.5L flotation machine. 60g of intermediate electrode material was weighed and placed in a 1.5L flotation cell. The pulp was first prepared for 3 minutes, then n-dodecane was added and stirred for 2 minutes, followed by 2-octanol and stirring for 1 minute. Flotation then commenced, with a skimming time of 3 minutes, a pulp concentration of 40 g / L, a n-dodecane dosage of 300 g / t, and a 2-octanol dosage of 150 g / t, yielding cathode precursor tailings. The roasting grade and the recovery rate of the cathode precursor tailings (roasting recovery rate) under different temperatures and times were calculated.

[0083] Comparative Example: The crushed and sorted electrode materials to be separated were placed in a tube furnace for pyrolysis treatment. The atmosphere for pyrolysis treatment was nitrogen. The pyrolysis treatment temperatures were 350, 400, 450, 500, and 550℃, and the time was 30 minutes to obtain intermediate electrode materials. The pyrolysis treatment temperature was 500℃, and the time was 15, 30, 45, 60, and 75 minutes, respectively.

[0084] Subsequently, flotation separation was performed using an XFD-1.5L flotation machine. 60g of intermediate electrode material was weighed and placed in a 1.5L flotation cell. The pulp was first prepared for 3 minutes, then n-dodecane was added and stirred for 2 minutes, followed by 2-octanol and stirring for 1 minute. Flotation then commenced, with a skimming time of 3 minutes, a pulp concentration of 40 g / L, a n-dodecane dosage of 300 g / t, and a 2-octanol dosage of 150 g / t, yielding cathode precursor tailings. The pyrolysis grade and the recovery rate (pyrolysis recovery rate) of the cathode precursor tailings were calculated at different temperatures and times.

[0085] Figure 5 The graph shows the flotation separation results at different temperatures in Experiment Example 3; Figure 6 The graph shows the flotation separation results at different times in Experiment Example 3. Figure 5 as well as Figure 6 It can be seen that, under all temperature and time conditions, the flotation separation effect of aerobic roasting is better than that of pyrolysis. Furthermore, experimental results show that the flotation separation effect is even better when the temperature of aerobic roasting is 400-550℃ and the time is 30-75 min.

[0086] Test Example 4

[0087] This experimental example was used to investigate the effect of aerobic roasting on the contact angle of lithium iron phosphate and graphite, specifically including:

[0088] The positive and negative electrode sheets of lithium iron phosphate batteries were obtained separately. The positive electrode sheets were crushed and sorted to obtain lithium iron phosphate positive electrode powder, and the negative electrode sheets were crushed and sorted to obtain graphite negative electrode powder.

[0089] Example: Lithium iron phosphate cathode powder was placed in a muffle furnace for aerobic calcination at a temperature of 500°C for 30 minutes to obtain calcined cathode powder; graphite anode powder was placed in a muffle furnace for aerobic calcination at a temperature of 500°C for 30 minutes to obtain calcined anode powder.

[0090] Comparative Example: Lithium iron phosphate cathode powder was pyrolyzed in a tube furnace at a temperature of 500°C for 30 minutes to obtain pyrolyzed cathode powder; graphite anode powder was pyrolyzed in a tube furnace at a temperature of 500°C for 30 minutes to obtain pyrolyzed anode powder.

[0091] The contact angles of calcined positive electrode powder, calcined negative electrode powder, pyrolytic positive electrode powder, and pyrolytic negative electrode powder were tested using a JC2000D1 contact angle measurement system. The results are as follows: Figure 7 As shown. From Figure 7 The results show that the contact angle of the positive electrode powder after aerobic roasting is 20°, while that after pyrolysis is 50°, indicating that aerobic roasting enhances the hydrophilicity of the positive electrode powder. The contact angles of the negative electrode powder after aerobic roasting and pyrolysis are similar, indicating similar hydrophobicity. Overall, the difference in contact angles between the positive and negative electrode powders after aerobic roasting is greater than that after pyrolysis.

[0092] Experimental Example 5

[0093] This experimental example is used to investigate the impact of flotation separation processes, specifically including:

[0094] The intermediate electrolytic material was obtained by calcining at 500℃ for 45 min in a muffle furnace. Then, according to... Figure 1 The flotation separation process is shown below: an XFD-1.5L flotation machine is used, with a pulp concentration of 40 g / L, a dodecane dosage of 300 g / t, and a 2-octanol dosage of 150 g / t. After roughing, tailings are obtained. These tailings undergo a first scavenging treatment to obtain scavenged tailings 1, followed by a second scavenging treatment to obtain scavenged tailings 2. The grades and recoveries of the roughing, first scavenging, and second scavenging treatments are calculated, and the results are shown in Table 1.

[0095] Table 1

[0096]

[0097] As can be seen from Table 1, the grade of the final scavenged tailings 2 is 98.54%, which can be used as a precursor for cathode materials in lithium iron phosphate regeneration.

[0098] Experimental Example 6

[0099] This experimental example is used to verify the electrochemical performance of regenerated lithium iron phosphate:

[0100] 50 g of scavenged tailings 2 obtained from Example 5 was weighed and uniformly mixed with 0.5 g of lithium carbonate and 1.5 g of glucose to obtain a mixture system. This mixture system was placed in a corundum ceramic boat and calcined in a tube furnace under a nitrogen atmosphere. The calcination program was set as follows: the temperature was increased to 700°C at a rate of 10°C / min, and then maintained at this temperature for 10 hours. After calcination, the furnace was cooled to room temperature to obtain regenerated lithium iron phosphate.

[0101] The aforementioned lithium iron phosphate was used as the active material and thoroughly mixed with PVDF and acetylene black in an N-methylpyrrolidone (NMP) solvent at a mass ratio of 8:1:1 to prepare a homogeneous slurry. Subsequently, the slurry was uniformly coated onto an aluminum foil current collector using a coater, and after vacuum drying at 120°C for 12 hours, it was cut into positive electrode sheets. Using this positive electrode sheet as the working electrode, a lithium metal sheet as the counter / reference electrode, a Celgard 2400 microporous membrane as the separator, and a 1 M LiPF6 EC / DEC (volume ratio 1:1) solution as the electrolyte, a CR2032 coin cell was assembled in an argon-protected glove box. Finally, the electrochemical performance of the assembled half-cell was tested.

[0102] Cyclic performance test: (1) Let the button battery rest for 6 hours; (2) Activate for 2 cycles; (3) Charge to 4.2 V with 1 C constant current and constant voltage; (4) Let stand for 5 minutes; (5) Discharge to 2.5 V with 1 C constant current.

[0103] Rate performance test: (1) Let the button battery rest for 6 hours; (2) Charge it to 4.2 V with constant current and constant voltage at a certain rate; (3) Let it stand for 5 minutes; (4) Discharge it to the cutoff voltage of 2.5 V with constant current at the corresponding rate. Repeat each charge and discharge rate 5 times.

[0104] Figure 8 The circuit performance graph of the battery in Experiment Example 6 is shown. Figure 9 This is a rate performance graph for the battery in Test Example 6. From... Figure 8 As can be seen, the cycle test results at 1C rate show that after 50 cycles, the battery retains 93.82% of its capacity, demonstrating excellent cycle performance. Figure 9 It can be seen that when the rate is reduced from 10 C to 0.1 C, the discharge specific capacity reaches 153.42 mAh / g, which shows excellent rate performance.

[0105] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for separating electrode materials, characterized in that, include: S1: The electrode material to be separated, which includes at least graphite and lithium iron phosphate, is subjected to aerobic calcination to obtain the intermediate electrode material. S2: The intermediate electrode material is separated by flotation to obtain graphite and positive electrode precursor tailings; S3: The positive electrode precursor tailings are mixed with lithium source and carbon source to obtain a mixed system, and the mixed system is subjected to anaerobic calcination to obtain lithium iron phosphate.

2. The separation method according to claim 1, characterized in that, The electrode materials to be separated are obtained by crushing and sorting the positive and negative electrode plates in the battery.

3. The separation method according to claim 1 or 2, characterized in that, In the aerobic roasting process, the temperature is 400-550℃ and the time is 30-75min.

4. The separation method according to any one of claims 1-3, characterized in that, The flotation separation includes adding a collector and a frother for flotation separation, and the flotation separation includes at least one roughing treatment and at least one scavenging treatment. The amount of collector added in the roughing process is greater than the amount of collector added in the scavenging process, and the amount of frother added in the roughing process is greater than the amount of frother added in the scavenging process.

5. The separation method according to claim 4, characterized in that, In the roughing process, the amount of collector added accounts for 100g / t to 300g / t of the mass of the intermediate electrode material, and the amount of foaming agent added accounts for 50g / t to 150g / t of the mass of the intermediate electrode material.

6. The separation method according to claim 4 or 5, characterized in that, In the scavenging process, the amount of collector added accounts for 5 g / t to 50 g / t of the mass of the intermediate electrode material, and the amount of foaming agent added accounts for 0 g / t to 20 g / t of the mass of the intermediate electrode material.

7. The separation method according to any one of claims 1-6, characterized in that, In the mixed system, the molar ratio of P, Fe, and Li is 1:1:(1.02-1.07).

8. The separation method according to any one of claims 1-7, characterized in that, In the mixed system, the mass percentage of carbon is 1.5-5%.

9. The separation method according to any one of claims 1-8, characterized in that, In the aforementioned oxygen-free calcination treatment, the temperature is 650-770℃ and the time is 10-20h.

10. A separation system for implementing the separation method of electrode materials according to any one of claims 1-9, characterized in that, It includes an aerobic roasting unit, a flotation separation unit, and an anaerobic calcination unit; The aerobic roasting unit has an inlet for the electrode material to be separated and an outlet for the intermediate electrode material; the flotation separation unit has an inlet for the intermediate electrode material, an outlet for graphite and an outlet for the positive electrode precursor tailings; and the anaerobic calcination unit has an inlet for the positive electrode precursor tailings, an inlet for the lithium source and an inlet for the carbon source. The intermediate electrode material outlet is connected to the intermediate electrode material inlet, and the positive electrode precursor tailings outlet is connected to the positive electrode precursor tailings inlet.

Images