Method for repairing and regenerating waste ternary positive electrode material

Abstract

The application provides a repairing and regenerating method of waste ternary positive electrode material, which comprises the following steps: mixing the waste ternary positive electrode material with a doping source solution, performing a solvothermal treatment, performing solid-liquid separation and drying to obtain a pretreated material; the doping source solution comprises a phosphorus source and a fluorine source, and the phosphorus source is an organic phosphorus source; sintering the pretreated material to obtain a pre-doped material; mixing a lithium source with the pre-doped material and performing calcination to obtain a repaired ternary positive electrode material. The repairing and regenerating method can improve the lithium supplement effect and the surface stability of the waste ternary positive electrode material through the composite doping of phosphate ions and fluorine ions, so that the electrochemical performance of the repaired ternary positive electrode material is improved.

Description

Technical Field

[0001] This invention belongs to the field of waste battery resource recycling technology, and relates to a method for repairing and regenerating waste ternary cathode materials. Background Technology

[0002] With the development of the new energy electric vehicle industry, the consumption of lithium-ion batteries has experienced explosive growth, leading to a year-on-year increase in the number of retired batteries. If these used lithium-ion batteries are not recycled and processed, the heavy metals, electrolytes, and decomposition products they contain will pollute the environment and result in a huge waste of valuable resources. Therefore, developing efficient and environmentally friendly used lithium-ion battery recycling technologies is of great significance for achieving resource recycling, environmental protection, and sustainable industrial development.

[0003] The main methods for recycling spent lithium-ion battery cathode materials are hydrometallurgy and pyrometallurgy. In comparison, direct repair and regeneration of spent cathode materials can significantly reduce recycling costs and minimize secondary pollution during the recycling process. Although traditional recycling processes can replenish lithium through molten salt methods to obtain repaired cathode materials, these methods have poor lithium replenishment effects and cannot achieve satisfactory performance restoration.

[0004] Based on the above research, there is a need to provide a method for repairing and regenerating waste ternary cathode materials with excellent repair and regeneration effects. Summary of the Invention

[0005] The purpose of this invention is to provide a method for repairing and regenerating waste ternary cathode materials. The repair and regeneration method improves the lithium replenishment effect and enhances the surface stability of waste ternary cathode materials through the composite doping of phosphate and fluorine ions, thereby improving the electrochemical performance of the repaired ternary cathode materials.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for repairing and regenerating waste ternary cathode materials, the method comprising the following steps:

[0008] (1) The waste ternary cathode material is mixed with the doped source solution, subjected to solvothermal treatment, solid-liquid separation and drying to obtain the pretreated material;

[0009] The doping source solution includes a phosphorus source and a fluorine source, wherein the phosphorus source is an organic phosphorus source;

[0010] (2) Sinter the pretreated material described in step (1) to obtain a pre-doped material;

[0011] (3) Mix and calcine the lithium source and the pre-doped material described in step (2) to obtain the repaired ternary cathode material.

[0012] This invention first pre-dops the surface of waste ternary cathode materials using an organophosphorus source and a fluorine source. The organophosphorus source contains phosphonic acid groups, which can coordinate and chelate with residual alkali or transition metals on the surface of the waste ternary cathode material, forming a uniform organic-inorganic hybrid interface layer and improving the surface stability of the waste ternary cathode material. After sintering, the phosphonic acid groups can be converted in situ into uniformly distributed phosphate groups that can enter the crystal lattice. The doping of phosphate anions has an attractive effect on lithium ions, thereby improving the subsequent lithium replenishment effect. Furthermore, the doping source solution of this invention also contains a fluorine source, which can co-dopade with phosphate ions on the surface of the waste cathode material, constructing a composite anion doped layer with strong electronegativity. Due to the extremely strong electronegativity of fluorine, a stronger negative electric field region can be formed, generating a stronger electrostatic attraction for positively charged lithium ions, thereby further improving the subsequent lithium replenishment effect and enhancing the electrochemical performance of the repaired ternary cathode material.

[0013] Preferably, the organophosphorus source in step (1) includes phytic acid and / or aminotrimethylenephosphonic acid.

[0014] The specific organophosphorus source preferably used in this invention contains a large number of phosphonic acid groups. Since phosphonic acid groups can be chemically bonded to metal ions, and the organophosphorus source also contains carbon, carbon doping can also be achieved, further improving the electrochemical performance of the material. Therefore, compared with using inorganic phosphorus sources for doping, this invention can improve the uniformity and stability of phosphate doping, and can also achieve carbon doping.

[0015] Preferably, in the doping source solution described in step (1), the mass of the phosphorus source is 1wt%-3wt% of the mass of the waste ternary cathode material, for example, it can be 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] The amount of phosphorus source added in this invention should not be too much, otherwise it will hinder the diffusion rate of lithium ions, reduce the material capacity, and also reduce the uniformity of phosphate doping. At the same time, if the amount of phosphorus source added is too little, the effect of the phosphorus source will be reduced.

[0017] Preferably, in the doping source solution described in step (1), the mass of the fluorine source is 2wt%-5wt% of the mass of the waste ternary cathode material. For example, it can be 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, or 5wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] When the amount of fluorine source added in this invention is too large, it will block the ion channels, reduce the lithium ion diffusion rate, affect the lithium replenishment effect, and may also cause lattice distortion, reducing the stability of the material; however, if the amount of fluorine source added is too small, the lithium replenishment effect will decrease, affecting the performance of the repaired ternary cathode material.

[0019] Preferably, the fluorine source in step (1) includes LiF and / or NH4F.

[0020] Preferably, in the doping source solution described in step (1), the total concentration of phosphorus source and fluorine source is 1g / L-5g / L, for example, it can be 1g / L, 2g / L, 3g / L, 4g / L or 5g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the solvent in the doped source solution in step (1) includes ethanol and water.

[0022] Preferably, the volume ratio of ethanol to water is 1:(0.5-1.5), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2 or 1:1.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] Preferably, the temperature of the solvent heat treatment in step (1) is 100℃-150℃, for example, it can be 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the solvent heat treatment time in step (1) is 1h-3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the waste ternary cathode material in step (1) is ball-milled and sieved before being mixed with the doping source solution.

[0026] Preferably, the sintering temperature in step (2) is 600℃-800℃, for example, it can be 600℃, 650℃, 700℃, 750℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the sintering time in step (2) is 2h-4h, for example, it can be 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the heating rate of the sintering in step (2) is 1℃ / min-5℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the sintering atmosphere in step (2) includes nitrogen and / or an inert gas.

[0030] Preferably, the roasting temperature in step (3) is 750℃-800℃, for example, 750℃, 760℃, 770℃, 780℃, 790℃ or 800℃, and the time is 6h-10h, for example, 6h, 7h, 8h, 9h or 10h, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the heating rate of the roasting in step (3) is 1℃ / min-5℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the roasting atmosphere in step (3) includes nitrogen and / or an inert gas.

[0033] Preferably, the lithium salt in step (3) includes lithium hydroxide and / or lithium nitrate.

[0034] The amount of lithium salt added in this invention is determined based on the amount of lithium missing in the waste ternary cathode material after testing.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The method for repairing and regenerating waste ternary cathode materials described in this invention first pre-dops the surface of the waste ternary cathode materials using an organophosphorus source and a fluorine source. The organophosphorus source contains phosphonic acid groups, which can coordinate and chelate with residual alkali or transition metals on the surface of the waste ternary cathode materials to form a uniform organic-inorganic hybrid interface layer, improving the surface stability of the waste ternary cathode materials. After sintering, the phosphonic acid groups can be converted in situ into uniformly distributed phosphate groups that can enter the crystal lattice. The doping of phosphate anions has an attractive effect on lithium ions, thereby improving the subsequent lithium replenishment effect. Furthermore, the doping source solution of this invention also contains a fluorine source, which can co-dopade with phosphate ions on the surface of the waste cathode materials to construct a composite anion doped layer with strong electronegativity. Due to the extremely strong electronegativity of fluorine, a stronger negative electric field region can be formed, generating a stronger electrostatic attraction for positively charged lithium ions, thereby further improving the subsequent lithium replenishment effect and enhancing the electrochemical performance of the repaired ternary cathode materials. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0038] The waste ternary cathode material used in the following examples and comparative examples is waste NCM523 ternary cathode powder, with a metal element molar ratio of Ni:Co:Mn=0.5:0.2:0.3, including the following by mass percentage: Ni 29.2wt%, Co 12.4wt%, Mn 15.0wt%, Li 6.5wt%, impurities Al 1.2wt%, C 2.8wt%, and balance oxygen.

[0039] Example 1

[0040] This embodiment provides a method for repairing and regenerating waste ternary cathode materials, the method comprising the following steps:

[0041] (1) The waste ternary cathode material is first ball-milled and sieved, then ultrasonically mixed with the doping source solution, and then solvothermal treated at 120°C for 2 hours. After cooling, solid-liquid separation and drying are performed to obtain the pretreated material.

[0042] The doping source solution includes a phosphorus source, a fluorine source, and a solvent, wherein the total concentration of the phosphorus source and the fluorine source is 3 g / L, the phosphorus source is phytic acid, the fluorine source is NH4F, and the solvent is ethanol and water in a volume ratio of 1:1.

[0043] The mass of the phosphorus source is 2 wt% of the mass of the waste ternary cathode material, and the mass of the fluorine source is 4 wt% of the mass of the waste ternary cathode material.

[0044] (2) The pretreated material described in step (1) is heated to 700°C for 3 hours under a nitrogen atmosphere at a heating rate of 3°C / min to obtain a pre-doped material;

[0045] (3) Mix lithium hydroxide and the pre-doped material described in step (2), and then calcine it at 780°C for 8 hours under an argon atmosphere at a heating rate of 3°C / min to obtain the repaired ternary cathode material.

[0046] Example 2

[0047] This embodiment provides a method for repairing and regenerating waste ternary cathode materials, the method comprising the following steps:

[0048] (1) The waste ternary cathode material is first ball-milled and sieved, then ultrasonically mixed with the doping source solution, and then solvothermal treated at 100°C for 3 hours. After cooling, solid-liquid separation and drying are performed to obtain the pretreated material.

[0049] The doping source solution includes a phosphorus source, a fluorine source, and a solvent, wherein the total concentration of the phosphorus source and the fluorine source is 5 g / L, the phosphorus source is aminotrimethylenephosphonic acid, the fluorine source is NH4F, and the solvent is ethanol and water in a volume ratio of 1:0.5.

[0050] The mass of the phosphorus source is 3 wt% of the mass of the waste ternary cathode material, and the mass of the fluorine source is 2 wt% of the mass of the waste ternary cathode material.

[0051] (2) The pretreated material described in step (1) is heated to 800°C for 2 hours under a nitrogen atmosphere at a heating rate of 5°C / min to obtain a pre-doped material;

[0052] (3) Mix lithium hydroxide and the pre-doped material described in step (2), and then calcine it at 750°C for 10 hours under an argon atmosphere at a heating rate of 1°C / min to obtain the repaired ternary cathode material.

[0053] Example 3

[0054] This embodiment provides a method for repairing and regenerating waste ternary cathode materials, the method comprising the following steps:

[0055] (1) The waste ternary cathode material is first ball-milled and sieved, then ultrasonically mixed with the doping source solution, and then solvothermal treated at 150°C for 1 hour. After cooling, solid-liquid separation and drying are performed to obtain the pretreated material.

[0056] The doping source solution includes a phosphorus source, a fluorine source, and a solvent, wherein the total concentration of the phosphorus source and the fluorine source is 1 g / L, the phosphorus source is phytic acid, the fluorine source is LiF, and the solvent is ethanol and water in a volume ratio of 1:1.

[0057] The mass of the phosphorus source is 1 wt% of the mass of the waste ternary cathode material, and the mass of the fluorine source is 5 wt% of the mass of the waste ternary cathode material.

[0058] (2) The pretreated material described in step (1) is heated to 600°C for 4 hours under a nitrogen atmosphere at a heating rate of 1°C / min to obtain a pre-doped material;

[0059] (3) Mix lithium hydroxide and the pre-doped material described in step (2), and then calcine it at 800°C for 6 hours under an argon atmosphere at a heating rate of 5°C / min to obtain the repaired ternary cathode material.

[0060] Example 4

[0061] This embodiment provides a method for repairing and regenerating waste ternary cathode materials. Except for step (1), where the mass of the phosphorus source is 0.5 wt% of the mass of the waste ternary cathode material, the repair and regeneration method is the same as in embodiment 1.

[0062] Example 5

[0063] This embodiment provides a method for repairing and regenerating waste ternary cathode materials. Except for step (1), where the mass of the phosphorus source is 5 wt% of the mass of the waste ternary cathode material, the repair and regeneration method is the same as in embodiment 1.

[0064] Example 6

[0065] This embodiment provides a method for repairing and regenerating waste ternary cathode materials. Except for step (1), where the mass of the fluorine source is 1 wt% of the mass of the waste ternary cathode material, the repair and regeneration method is the same as in embodiment 1.

[0066] Example 7

[0067] This embodiment provides a method for repairing and regenerating waste ternary cathode materials. Except for step (1), where the mass of the fluorine source is 8 wt% of the mass of the waste ternary cathode material, the repair and regeneration method is the same as in embodiment 1.

[0068] Comparative Example 1

[0069] This comparative example provides a method for repairing and regenerating waste ternary cathode materials. Except for step (1), which is skipped and the waste ternary cathode materials are directly subjected to steps (2) and (3), the repair and regeneration method is the same as that in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a method for repairing and regenerating waste ternary cathode materials. Except for the fact that the doping source solution in step (1) does not contain a fluorine source, the repair and regeneration method is the same as that in Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a method for repairing and regenerating waste ternary cathode materials. Except for the fact that the doping source solution in step (1) does not contain a phosphorus source, the repair and regeneration method is the same as that in Example 1.

[0074] Comparative Example 4

[0075] This comparative example provides a method for repairing and regenerating waste ternary cathode materials. Except for the phosphorus source being ammonium dihydrogen phosphate in the doping source solution in step (1), the repair and regeneration method is the same as in Example 1.

[0076] The repaired ternary cathode materials obtained in the above examples and comparative examples were used to prepare batteries. The battery preparation process and performance testing are as follows:

[0077] 1) Battery manufacturing

[0078] The repaired ternary cathode materials obtained in the above examples and comparative examples were mixed with conductive carbon black (SP) and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1, respectively. N-methylpyrrolidone (NMP) solvent was added and stirred to form a uniform slurry. The slurry was uniformly coated on the surface of an aluminum foil current collector and dried under vacuum at 90°C for 15 hours. After removal, the cathode sheet was obtained by rolling and stamping. The cathode sheet was used as the cathode, lithium metal sheet as the anode, and polypropylene microporous membrane as the separator. 1 mol / L LiPF6+EC / DMC / EMC (the volume ratio of EC, DMC, and EMC was 1:1:1) was used as the electrolyte. The CR2032 stainless steel button cell was assembled in a glove box filled with argon gas and with a water and oxygen content of less than 0.1 ppm. After standing for 12 hours, its charge and discharge performance was tested.

[0079] 2) Performance Testing

[0080] Performance tests were performed on the batteries provided in the examples and comparative examples, including capacity, cycle life, and high-temperature storage performance tests:

[0081] Initial capacity and initial coulombic efficiency: The test temperature was 25℃, the voltage range was 3.0-4.4V, and the coin cell was charged and discharged once at 0.1C to test the initial discharge specific capacity and initial coulombic efficiency of the material.

[0082] Room temperature cycling performance: The test temperature is 25℃, the voltage range is 3.0-4.5V, the coin cell is activated by charging and discharging twice at 0.2C, and then charged and discharged 50 times at 1C to obtain the 50-cycle capacity retention rate of the material.

[0083] The test results are shown in Table 1 below:

[0084] Table 1

[0085]

[0086] As can be seen from Table 1 above:

[0087] As shown in Example 1 and Comparative Example 1, the present invention, through the composite doping of phosphate and fluoride ions, can not only improve the lithium replenishment effect but also enhance the material stability and electrochemical performance. As shown in Example 1 and Comparative Example 2, the doping of fluoride ions can construct a composite anion doped layer with strong electronegativity, further improving the lithium replenishment effect and thus further enhancing the electrochemical performance of the repaired ternary cathode material. As shown in Example 1 and Comparative Example 3, the doping of phosphate anions in the present invention has an attractive effect on lithium ions, thereby improving the subsequent lithium replenishment effect and material stability. As shown in Example 1 and Comparative Example 4, compared with inorganic phosphorus sources, the present invention uses organic phosphorus sources, which can improve the uniformity and stability of phosphate doping and can also achieve carbon doping, thereby further enhancing the electrochemical performance of the battery. As shown in Example 1 and Examples 4-7, the amount of phosphorus source and fluoride source added in the present invention will affect their respective effects, and it is preferred to add them within a specific range.

[0088] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for repairing and regenerating waste ternary cathode materials, characterized in that, The repair and regeneration method includes the following steps: (1) The waste ternary cathode material is mixed with the doped source solution, subjected to solvothermal treatment, solid-liquid separation and drying to obtain the pretreated material; The doping source solution includes a phosphorus source and a fluorine source, wherein the phosphorus source is an organic phosphorus source; (2) Sinter the pretreated material described in step (1) to obtain a pre-doped material; (3) Mix and calcine the lithium source and the pre-doped material described in step (2) to obtain the repaired ternary cathode material.

2. The repair and regeneration method according to claim 1, characterized in that, The organophosphorus source in step (1) includes phytic acid and / or aminotrimethylenephosphonic acid; Preferably, in the doping source solution described in step (1), the mass of the phosphorus source is 1wt%-3wt% of the mass of the waste ternary cathode material.

3. The repair and regeneration method according to claim 1 or 2, characterized in that, In step (1), the mass of the fluorine source in the doping source solution is 2wt%-5wt% of the mass of the waste ternary cathode material. Preferably, the fluorine source in step (1) includes LiF and / or NH4F.

4. The repair and regeneration method according to claim 1 or 2, characterized in that, In step (1), the total concentration of phosphorus and fluorine sources in the doping source solution is 1 g / L-5 g / L; Preferably, the solvent in the doped source solution in step (1) includes ethanol and water; Preferably, the volume ratio of ethanol to water is 1:(0.5-1.5).

5. The repair and regeneration method according to claim 1 or 2, characterized in that, The temperature of the solvent heat treatment in step (1) is 100℃-150℃; Preferably, the solvent heat treatment time in step (1) is 1h-3h.

6. The repair and regeneration method according to claim 1 or 2, characterized in that, Before mixing the waste ternary cathode material with the doping source solution in step (1), it is first ball-milled and sieved.

7. The repair and regeneration method according to claim 1 or 2, characterized in that, The sintering temperature in step (2) is 600℃-800℃; Preferably, the sintering time in step (2) is 2h-4h.

8. The repair and regeneration method according to claim 1 or 2, characterized in that, The heating rate for sintering in step (2) is 1℃ / min-5℃ / min; Preferably, the sintering atmosphere in step (2) includes nitrogen and / or an inert gas.

9. The repair and regeneration method according to claim 1 or 2, characterized in that, The roasting temperature in step (3) is 750℃-800℃, and the time is 6h-10h; Preferably, the heating rate of the calcination in step (3) is 1℃ / min-5℃ / min; Preferably, the roasting atmosphere in step (3) includes nitrogen and / or an inert gas.

10. The repair and regeneration method according to claim 1 or 2, characterized in that, The lithium salt in step (3) includes lithium hydroxide and / or lithium nitrate.

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