A positive electrode black powder and a method for recovering the same

Abstract

This application provides a cathode black powder and a method for its recovery. The cathode black powder of this application comprises a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. This application improves the efficiency of wet lithium leaching recovery by controlling the ratio of the peak intensity of the 311 characteristic diffraction peak to the peak intensity of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder within a certain range, which helps simplify subsequent recovery processes and reduce recovery costs.

Description

Technical Field

[0001] This application relates to the field of secondary battery recycling technology, and in particular to a positive electrode black powder and its recycling method. Background Technology

[0002] With the large-scale application of lithium batteries in new energy vehicles and energy storage, the number of retired and scrapped lithium batteries is growing rapidly. The harmless treatment and resource utilization of lithium batteries can effectively avoid environmental pollution and resource waste, while also offering significant economic benefits. In the dismantling and recycling process of retired lithium batteries, achieving efficient separation of cathode black powder and aluminum foil to obtain cathode black powder with high dispersibility and low impurity content is a key step in improving the recovery rate of lithium iron phosphate materials. Summary of the Invention

[0003] The purpose of this application is to provide a cathode black powder and a method for its recycling, so as to improve the efficiency of wet recycling of leached lithium, simplify subsequent recycling processes, and reduce recycling costs.

[0004] To achieve the above objectives, a first aspect of this application provides a cathode black powder, the cathode black powder comprising a lithium phosphate having an olivine structure, the cathode black powder satisfying: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

[0005] As an embodiment of this application, the cathode black powder satisfies: 0.22°≤F(311)≤0.31°, where F(311) is the half-peak width of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

[0006] As an embodiment of this application, the positive electrode black powder satisfies: 0.15°≤F (200) ≤0.4°, where F (200) The full width at half maximum (FWHM) of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

[0007] As an embodiment of this application, the height H2 of the characteristic peak with the largest particle size and the height H1 of the characteristic peak with the highest volume percentage in the particle size distribution diagram of the positive electrode black powder satisfy: 0.12≤H2 / (H1+H2)≤0.23.

[0008] As an embodiment of this application, the positive electrode black powder contains impurity elements, the impurity elements include Al elements, and the content of the Al elements is A, which satisfies: A≤2.5wt%.

[0009] As an embodiment of this application, the positive electrode black powder contains impurity elements, which include at least one of Al, Cu, Mg, B, Ca, W, Cr, Zr, Ti, La, and V, and the total content of the impurity elements is C, satisfying: C≤3wt%.

[0010] As an embodiment of this application, the specific surface area B of the positive electrode black powder satisfies: 3.3m². 2 / g≤B≤7m 2 / g.

[0011] As an embodiment of this application, the powder conductivity K of the 20KN positive electrode black powder satisfies: 0.05S / cm≤K≤0.35S / cm.

[0012] As an embodiment of this application, the tap density TD of the cathode black powder satisfies: TD ≤ 1.12 g / cm³ 3 .

[0013] A second aspect of this application provides a method for recovering cathode black powder, comprising the following steps:

[0014] S1. Discharge and disassemble retired lithium-ion batteries to obtain positive electrode plates;

[0015] S2. Place the positive electrode sheet into a laser cleaning machine and clean each surface of the positive electrode sheet for 0.75h to 4h under the conditions of laser wavelength of 405nm~976nm and cleaning power of 100W~1000W. Then, sieve to obtain positive electrode black powder.

[0016] The cathode black powder contains a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

[0017] Compared with the prior art, the beneficial effects of this application are:

[0018] The cathode black powder described in this application comprises a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200)The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. This application improves the efficiency of wet lithium leaching recovery by controlling the ratio of the peak intensity of the 311 characteristic diffraction peak to the peak intensity of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder within a certain range, which helps simplify subsequent recovery processes and reduce recovery costs. Attached Figure Description

[0019] Figure 1 The X-ray diffraction pattern of the cathode black powder prepared in Example 1;

[0020] Figure 2 This is a particle size distribution diagram of the positive electrode black powder prepared in Example 1. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0023] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0024] Unless otherwise specified, all reagents or instruments used in this application are commercially available products.

[0025] The cathode black powder is mainly a mixture of cathode active material, conductive agent and binder decomposition products. The impurity elements mainly come from the doping and coating elements in the cathode active material, the side reaction products at the cathode / electrolyte interface and the damaged aluminum foil, etc.

[0026] This application provides a cathode black powder, which is obtained by laser cleaning a cathode electrode sheet. The cathode black powder of this application comprises a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I(200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

[0027] The inventors of this application have discovered that the ratio of the peak intensity of the 311 characteristic diffraction peak to the peak intensity of the 200 characteristic diffraction peak in the X-ray diffraction pattern of cathode black powder can reflect the content of aluminum impurities to a certain extent. By controlling the ratio within the range of this application, the leaching efficiency can be improved, which is beneficial to simplifying the subsequent recycling process and reducing the recycling cost. The method for obtaining the X-ray diffraction pattern of cathode black powder in this application is as follows: The sample to be tested is ground into powder for 15 minutes and pressed into a uniform thin sheet. Then, the sample is loaded onto the sample stage of the X-ray diffractometer, and the X-ray diffractometer is started to obtain the corresponding X-ray diffraction pattern. The parameters of the X-ray diffractometer are as follows: target material: Cu target; X-ray wavelength: 1.5406; scanning mode: continuous scanning; start angle & end angle: 10°~90°; scanning speed: 10° / min; step size: 0.01°.

[0028] In some embodiments, the positive electrode black powder satisfies: 2≤I (311) / I (200) ≤3.7.

[0029] In some embodiments, the positive electrode black powder satisfies: 0.22° ≤ F (311) ≤0.31°, where F (311) The full width at half maximum (FWHM) of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder is given. For example, the FWHM of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder can be 0.22°, 0.24°, 0.26°, 0.28°, 0.31°, or a value within the range formed by any two of the above points.

[0030] In some embodiments, the positive electrode black powder satisfies: 0.15° ≤ F (200) ≤0.4°, where F (200) The full width at half maximum (FWHM) of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder is given. For example, the FWHM of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder can be 0.15°, 0.2°, 0.25°, 0.3°, 0.35°, 0.4°, or a value within the range formed by any two of the above points.

[0031] In this application, F (311) and F (200) Within the above range, it is beneficial to improve leaching efficiency.

[0032] In some embodiments, the particle size distribution diagram of the cathode black powder contains at least two characteristic peaks, and at least one characteristic peak is greater than 20 μm. The height H2 of the characteristic peak with the largest particle size and the height H1 of the characteristic peak with the highest volume percentage in the particle size distribution diagram of the cathode black powder satisfy the following condition: 0.12 ≤ H2 / (H1+H2) ≤ 0.23. For example, H2 / (H1+H2) can be 0.12, 0.15, 0.18, 0.2, 0.23, or a value within the range formed by any two of the above points. When H2 and H1 satisfy the above relationship, the content of large aluminum foil particles mixed in during the laser cleaning process is relatively small in the cathode black powder and can be separated through subsequent sieving processes. This effectively controls the Al impurity content and simplifies the subsequent recycling process, reducing recycling costs.

[0033] In some embodiments, the cathode black powder contains impurity elements, including Al, and the content of Al is A, satisfying the condition: A ≤ 2.5 wt%. For example, the Al content A in the cathode black powder can be 0.1 wt%, 0.5 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, 2 wt%, 2.5 wt%, or a value within a range consisting of any two of the above points. In some embodiments, the Al content is A, satisfying the condition: 0.5 wt% ≤ A ≤ 2.5 wt%. The Al content in the cathode black powder being within the above range indicates that the recycling process effectively strips the cathode coating from the aluminum foil, significantly reducing the Al impurity content in the cathode black powder, which is beneficial for simplifying subsequent recycling processes and reducing recycling costs.

[0034] In some embodiments, the cathode black powder contains impurity elements, which include at least one of Al, Cu, Mg, B, Ca, W, Cr, Zr, Ti, La, and V.

[0035] In some embodiments, the total content of the impurity elements is C, satisfying: C ≤ 3 wt%. For example, the total content of the impurity elements C can be 0.7 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, or a value within a range consisting of any two of the above. In some embodiments, the total content of the impurity elements is C, satisfying: 0.7 wt% ≤ C ≤ 3 wt%. Having the total content of impurity elements C within the above range effectively reduces the process costs of chemical impurity removal and wastewater treatment in the subsequent recovery of cathode black powder, thereby reducing recovery costs.

[0036] In some embodiments, the specific surface area B of the positive electrode black powder satisfies: 3.3 m² / g. 2 / g≤B≤7m 2 / g. For example, the specific surface area B of the cathode black powder can be 3.3m². 2 / g、4m 2 / g, 4.5m 2 / g、5m 2 / g, 5.5m 2 / g、6m 2 / g, 6.5m 2 / g、7m 2 / g or a value within the range defined by any two of the above points. A specific surface area of ​​the cathode black powder within the above range is beneficial for the leaching and recovery of Fe and Li elements in the subsequent wet recovery process.

[0037] In some embodiments, the powder conductivity K of the 20KN cathode black powder satisfies: 0.05 S / cm ≤ K ≤ 0.35 S / cm. For example, the powder conductivity K of the 20KN cathode black powder can be 0.05 S / cm, 0.08 S / cm, 0.1 S / cm, 0.15 S / cm, 0.2 S / cm, 0.25 S / cm, 0.3 S / cm, 0.35 S / cm, or a value within a range consisting of any two of the above points. A powder conductivity of the cathode black powder within the above range is beneficial for improving the subsequent recovery rate of Fe and Li elements.

[0038] In some embodiments, the tap density TD of the cathode black powder satisfies: TD ≤ 1.12 g / cm³ 3 For example, the tap density (TD) of the cathode black powder can be 0.5 g / cm³. 3 0.6g / cm 3 0.7g / cm 3 0.8g / cm 3 0.9g / cm 3 1g / cm 3 1.12 g / cm 3 Or a value within the range formed by any two of the above points. In some embodiments, the tap density TD of the positive electrode black powder satisfies: 0.9 ≤ TD ≤ 1.12 g / cm³ 3 The tap density of the cathode black powder is within the above range, which is beneficial to improving the recovery rate of Fe and Li elements.

[0039] Embodiments of this application also provide a method for recovering cathode black powder, comprising the following steps:

[0040] S1. Discharge and disassemble retired lithium-ion batteries to obtain positive electrode plates;

[0041] S2. Place the positive electrode sheet into a laser cleaning machine and clean each surface of the positive electrode sheet for 0.75h to 4h under the conditions of laser wavelength of 405nm~976nm and cleaning power of 100W~1000W. Then, sieve to obtain positive electrode black powder.

[0042] The cathode black powder contains a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

[0043] The cathode black powder recovery method provided in this application employs laser cleaning. Laser cleaning removes the cathode black powder from the surface of the current collector aluminum foil through vaporization, shock waves, and thermoelastic forces. The cathode black powder recovery rate is high, and its dispersibility is good, significantly improving the efficiency of subsequent wet leaching. Furthermore, the laser cleaning process requires no cleaning medium, greatly reducing damage to the aluminum foil and effectively lowering the aluminum impurity content in the cathode black powder.

[0044] In some embodiments, the laser wavelength is 520 nm to 976 nm. For example, the laser wavelength can be 520 nm, 635 nm, 755 nm, 808 nm, 915 nm, 940 nm, 976 nm, or a value within the range formed by any two of the above points. A laser wavelength within the above range can further improve the quality of the recovered cathode black powder, thereby improving the efficiency of wet leaching lithium recovery.

[0045] In some embodiments, the cleaning power is 100W to 600W. For example, the cleaning power can be 100W, 200W, 300W, 400W, 500W, 600W, or a value within the range of any two of the above. Laser cleaning power within the above range can further improve the quality of the recovered cathode black powder, thereby improving the efficiency of wet leaching lithium recovery.

[0046] The following are specific embodiments of this application, and the technical solutions of this application are further described in conjunction with the embodiments. However, this application is not limited to these embodiments. Unless otherwise specified, the reagents, methods, and equipment used in this application are all conventional reagents, methods, and equipment in this technical field.

[0047] Example 1

[0048] Example 1 provides a method for recovering cathode black powder, comprising the following steps:

[0049] (1) After the retired lithium iron phosphate batteries are fully discharged using a discharge device, they are automatically disassembled to obtain positive electrode plates, negative electrode plates and separators respectively.

[0050] (2) The above positive electrode sheet was placed in a laser cleaning machine and cleaned for 0.75 hours on each side under the conditions of laser wavelength 976nm and cleaning power 100W to obtain a mixture of black powder and aluminum foil.

[0051] (3) Add the mixture obtained in step 2 to a vibrating screen with a screen size of 0.1 mm and a screening time of 0.5 h to obtain positive electrode black powder.

[0052] The difference between Examples 2-8 and Example 1 lies in the laser cleaning power, as detailed in Table 1.

[0053] The difference between Examples 9-16 and Example 1 lies in the different laser cleaning wavelengths, as detailed in Table 1.

[0054] The difference between Examples 17-24 and Example 1 lies in the laser cleaning time, as detailed in Table 1.

[0055] The difference between Comparative Example 1 and Example 1 is that the laser cleaning power is 1500W.

[0056] The difference between Comparative Example 2 and Example 1 is that the laser cleaning wavelength is 248nm.

[0057] The difference between Comparative Example 3 and Example 1 is that the laser cleaning time is 10 hours.

[0058] The physical properties of the cathode black powder in Examples 1-24 and Comparative Examples 1-3 are shown in Table 1. The XRD pattern of the cathode black powder obtained in Example 1 is shown below. Figure 1 As shown in the figure, the particle size distribution diagram is as follows: Figure 2 As shown, the test spectra of other embodiments are similar and will not be listed one by one. The results are detailed in Table 1.

[0059] Table 1

[0060]

[0061]

[0062] Table 1 (continued)

[0063]

[0064]

[0065] The black powder obtained in the examples and comparative examples was subjected to wet recovery. The wet recovery process for lithium is as follows:

[0066] The cathode black powder was separated into impurities (Al) by alkali dissolution with 32% liquid alkali and filtration, resulting in a NaAlO2 solution and a filter residue containing lithium phosphate. The filter residue was then subjected to acid leaching with 98% sulfuric acid and filtration to obtain a filtrate containing lithium iron phosphate. Finally, the pH of the lithium iron phosphate filtrate was adjusted and leached with sodium carbonate to obtain a lithium precipitate. The efficiency results of this wet lithium recovery process are shown in Table 2.

[0067] Table 2

[0068]

[0069]

[0070] Comparing Examples 1-24 and Comparative Examples 1-3, it can be seen that by controlling the ratio of the peak intensity of the 311 characteristic diffraction peak to the peak intensity of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder within a certain range, the efficiency of wet recovery of leached lithium is improved.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit the scope of protection of this application. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the substance and scope of the technical solutions of this application.

Claims

1. A positive electrode black powder, characterized in that, The cathode black powder contains a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder; The height H2 of the characteristic peak with the largest particle size and the height H1 of the characteristic peak with the highest volume percentage in the particle size distribution diagram of the positive electrode black powder satisfy the following: 0.12≤H2 / (H1+H2)≤0.23; The positive electrode black powder contains impurity elements, the impurity elements include Al, and the content of Al is A, which satisfies: A≤2.5wt%.

2. The positive electrode black powder according to claim 1, characterized in that, The positive electrode black powder satisfies: 0.22°≤F (311) ≤0.31°, where F (311) The full width at half maximum (FWHM) of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

3. The positive electrode black powder according to claim 1, characterized in that, The positive electrode black powder satisfies: 0.15° ≤ F (200) ≤0.4°, where F (200) The full width at half maximum (FWHM) of the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

4. The positive electrode black powder according to claim 1, characterized in that, The cathode black powder contains impurity elements, which include at least one of Al, Cu, Mg, B, Ca, W, Cr, Zr, Ti, La, and V. The total content of the impurity elements is C, which satisfies the condition: C≤3wt%.

5. The positive electrode black powder according to claim 1, characterized in that, The specific surface area B of the cathode black powder satisfies: 3.3m² 2 / g≤B≤7m 2 / g.

6. The positive electrode black powder according to claim 1, characterized in that, The powder conductivity K of the 20KN positive electrode black powder satisfies: 0.05S / cm≤K≤0.35S / cm.

7. The positive electrode black powder according to claim 1, characterized in that, The tap density TD of the positive electrode black powder satisfies: TD≤1.12g / cm³.

8. A method for recovering cathode black powder, characterized in that, Includes the following steps: S1. Discharge and disassemble retired lithium-ion batteries to obtain positive electrode plates; S2. Place the positive electrode sheet into a laser cleaning machine and clean each surface of the positive electrode sheet for 0.75h to 4h under the conditions of laser wavelength of 405nm~976nm and cleaning power of 100W~1000W. Then, sieve to obtain positive electrode black powder. The cathode black powder is used to recover leached lithium; The cathode black powder contains a lithium phosphate with an olivine structure, and the cathode black powder satisfies: I (311) / I (200) ≥2, where I (311) I represents the peak intensity of the 311 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder. (200) The peak intensity is the 200 characteristic diffraction peak in the X-ray diffraction pattern of the cathode black powder.

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