Repairing and regenerating method of decommissioned sodium ion battery layered oxide positive electrode material

Abstract

The invention provides a method for repairing and regenerating a layered oxide positive electrode material of a retired sodium-ion battery, and belongs to the technical field of sodium-ion battery recovery, the method comprises the following steps: separating waste layered oxide powder through a heat treatment mode; the method comprises the following steps: mixing and grinding waste layered oxide powder and a regenerant (a sodium supplementing agent and a potassium doping agent) according to a certain proportion; and through solid-phase sintering, uniform and rapid sodium supplement and potassium doping are realized at the same time, and the completely repaired layered oxide positive electrode material is obtained. According to the method, direct repair and regeneration are realized through the steps, and the obtained material is excellent in electrochemical performance and still shows high specific capacity especially under high current density. The repair and regeneration method is simple in process and high in efficiency, not only reduces the harm of the retired sodium ion battery to the environment, but also provides an effective solution for the application of the layered oxide under high magnification.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling of retired sodium-ion batteries, and specifically to a recycling, repair and regeneration technology for waste layered oxide cathode materials. Background Art

[0002] Due to the rich sodium resources and low cost, sodium-ion batteries, as an effective supplement to lithium-ion batteries, have broad application prospects in low-speed electric vehicles and large-scale energy storage power stations. At present, many enterprises have started the production and application of sodium-ion batteries. Like lithium-ion batteries, sodium-ion batteries also have a certain service life. Waste sodium-ion batteries contain a large amount of valuable substances, such as metal elements manganese, nickel, cobalt, etc. If there is no reasonable treatment method, it will cause serious pollution to the environment. Therefore, recycling them can not only prevent environmental damage, but also recycle the valuable substances in them.

[0003] Layered oxide cathodes have been gradually commercially produced due to their high energy density and excellent cycle performance. However, after multiple cycles, the material structure undergoes phase transformation, component loss, surface contains degraded impurity phases and residual alkali, etc. Therefore, in order to achieve the efficient resource utilization of layered oxide cathode materials, it is necessary to electrochemically repair the failed layered oxide cathode materials so that they can be reapplied to sodium-ion batteries. Commonly used direct regeneration methods include solid-phase sintering method, hydrothermal method, molten salt method, etc. Although these methods can realize the sodium supplementation and regeneration of waste layered oxide materials, the performance of the regenerated materials cannot meet the requirements of the increasingly developing electric vehicle field for high energy density and fast charging. Therefore, during the process of sodium supplementation using the direct regeneration method, simultaneously carrying out component regulation to improve the electrochemical performance of the repaired and regenerated materials is a research direction worthy of exploration at present. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for repairing and regenerating a layered oxide cathode material of a retired sodium-ion battery, including the following steps:

[0005] S1. Separating the aluminum foil and the active material from the waste layered oxide cathode sheet by heat treatment to obtain waste layered oxide powder;

[0006] S2. Measuring the molar ratio of sodium element in the waste layered oxide powder and calculating the sodium ion deficiency amount according to the theoretical stoichiometric ratio;

[0007] S3. Adding a regenerant to the waste layered oxide powder according to the calculated sodium ion deficiency amount, mixing and grinding to obtain a precursor, and the regenerant is a mixture of a sodium supplement agent and a potassium doping agent;

[0008] S4. Calcinate the precursor at a high temperature, and after cooling, a repaired and complete layered oxide cathode material is obtained.

[0009] In the present invention, a mixture of a sodium supplement agent and a potassium doping agent is used as a regenerant. Compared with a single sodium supplement agent, adding a potassium doping agent and a sodium supplement agent can form a eutectic mixture, improve the fluidity of the molten salt, and make the reactants contact more evenly. At the same time, when potassium is doped into the structure of the waste layered oxide, the layer spacing will be enlarged, which is beneficial to the supplement of sodium ions and improves the regeneration efficiency.

[0010] Further, the structural general formula of the layered oxide cathode material is: Na x TMO 2 , 0.6 ≤ x ≤ 1, and TM is one or more of Fe, Mn, Ni, Cu, Co, Ti, V, and Cr.

[0011] Further, in step S1, the heat treatment temperature is 350 - 600 °C, and the heat treatment time is 1 - 5 hours.

[0012] Further, in step S3, the sodium supplement agent is one of sodium hydroxide, sodium nitrate, and sodium carbonate, and the potassium doping agent is one of potassium hydroxide, potassium nitrate, and potassium carbonate.

[0013] Further, the regenerant in step S3 is selected from any one of the following combinations: sodium hydroxide and potassium hydroxide, sodium nitrate and potassium nitrate, and sodium carbonate and potassium carbonate.

[0014] Further, in step S3, the molar amount of potassium ions in the regenerant accounts for 0.5% - 5% of the waste layered oxide powder, and the ratio of the total molar amount of sodium and potassium ions in the regenerant to the sodium ion deficiency amount is 1 - 1.05:1.

[0015] Further, in step S4, the calcination temperature is 850 - 1000 °C, and the calcination time is 6 - 15 hours.

[0016] Compared with the prior art, the positive and progressive effects of the present invention are as follows:

[0017] (1) A method for repairing and regenerating a layered oxide cathode material of a retired sodium-ion battery provided by the present invention. The repair method recovers and directly regenerates the waste layered oxide cathode material without destroying its structure. On the one hand, the sodium supplement agent and potassium doping agent in the regenerant can form a eutectic mixed salt, which is beneficial to the uniform mixing and mass transfer of reactants to a certain extent, making the surface degradation phase reaction more complete. On the other hand, sodium supplementation and potassium doping are carried out simultaneously under high-temperature calcination conditions to optimize the composition, structure, and electrochemical performance of the material. Potassium ions occupy the sodium layer vacancies, expanding the layer spacing, which is beneficial to the migration and supplementation of sodium ions, enhancing the reaction kinetics and promoting the regeneration efficiency. In addition, the introduction of potassium improves the kinetics of sodium ion deintercalation of the regenerated material, enhances the rate performance, and potassium acts as a structural pillar to inhibit the structural phase change during charge and discharge, improving the cycle stability.

[0018] (2) By accurately measuring and supplementing the missing sodium ions, the repair and regeneration method can effectively restore the performance of the failed layered oxide cathode material of the sodium-ion battery and avoid the formation of surface residual alkali. Moreover, the repair and regeneration method is applicable to a variety of layered oxide materials, with wide applicability.

[0019] (3) This repair and regeneration method adopts a solid-phase sintering method with a simple process, and no toxic organic reagents are added during the process, which is green, environmentally friendly, and economical.

[0020] (4) A method for repairing and regenerating a layered oxide cathode material of a retired sodium-ion battery provided by the present invention. Applying the repair and regeneration method, the structure of the waste layered oxide is repaired completely, and it has a high specific capacity at a high current density, and the rate performance and cycle performance are improved. Description of the Drawings

[0021] Figure 1 It is an XRD comparison diagram of the R-NFM-K-1% material in Example 1 of the present invention, the R-NFM material in Comparative Example 1, and the S-NFM material in Comparative Example 3;

[0022] Figure 2 It is a rate performance comparison diagram of the R-NFM-K-1% material in Example 1 of the present invention, the R-NFM material in Comparative Example 1, and the S-NFM material in Comparative Example 3;

[0023] Figure 3 It is a SEM morphology diagram of the S-NFM material in Comparative Example 3 of the present invention;

[0024] Figure 4 It is a SEM morphology diagram of the R-NFM-K-2% material in Example 2 of the present invention;

[0025] Figure 5 It is an EDS distribution diagram of potassium element of the R-NFM-K-2% material in Example 2 of the present invention. Detailed implementation manners

[0026] The technical solutions in the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Example 1

[0028] (1) Place the waste layered oxide cathode sheet in a muffle furnace and heat-treat it at 500 °C for 2 hours to separate the aluminum foil and the active material, obtaining waste Na x Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 powder (0.5 ≤ x < 1), marked as S-NFM.

[0029] (2) Analyze and determine the molar ratio of sodium element in the S-NFM material, and calculate the amount of sodium ion deficiency;

[0030] (3) Use a regenerant which is a mixed salt of sodium hydroxide and potassium hydroxide. The molar amount of potassium ions in the regenerant is 1% of that of S-NFM. The regenerant is added in a ratio of 1:1 of the total molar amount of sodium and potassium ions to the amount of sodium ion deficiency in S-NFM, and mixed and ground to obtain a precursor.

[0031] (4) Calcinate the obtained precursor at 900 °C for 12 h, and after cooling, obtain a repaired and complete layered oxide cathode material Na 0.99 K 0.01 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 , marked as R-NFM-K-1%.

[0032] Perform XRD test on the repaired and regenerated material R-NFM-K-1% obtained in Example 1. As can be seen from the appendix Figure 1 It can be seen that R-NFM-K-1% is restored to the O3 layered phase, with the space group R-3m, and there is basically no NiO impurity phase, and the diffraction peaks are strong and sharp, and the full width at half maximum is narrow, indicating good crystallinity of the crystal. Perform rate performance test on the obtained repaired and regenerated material R-NFM-K-1%. As can be seen from the appendix Figure 2 It can be seen that the specific capacity reaches 86 mAh / g at a high current density of 5C.

[0033] Example 2

[0034] Steps (1) and (2) of this example are the same as those of Example 1. Steps (3) and (4) are specifically as follows:

[0035] The regenerant used is a mixed salt of sodium nitrate and potassium nitrate. The molar amount of potassium ions in the regenerant is 2% of S-NFM. The regenerant is added in a ratio of the total molar amount of sodium and potassium ions to the sodium ion deficiency in S-NFM of 1.03:1, and mixed and ground to obtain a precursor; the obtained precursor is calcined at 900 °C for 15 h and cooled to obtain a repaired and complete layered oxide cathode material Na 0.98 K 0.02 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 , labeled as R-NFM-K-2%.

[0036] Perform SEM characterization of the morphology and EDS characterization of potassium element on the repaired and regenerated material R-NFM-K-2% obtained in Example 2. From Attachment Figure 4 and Attachment Figure 5 It can be seen that the particles are repaired completely and the potassium element is evenly distributed, proving that potassium is successfully doped into the waste layered oxide cathode material.

[0037] Example 3

[0038] Steps (1) and (2) of this example are the same as those of Example 1. Steps (3) and (4) are specifically as follows:

[0039] The regenerant used is a mixed salt of sodium carbonate and potassium carbonate. The molar amount of potassium ions in the regenerant is 3% of S-NFM. The regenerant is added in a ratio of the total molar amount of sodium and potassium ions to the sodium deficiency in S-NFM of 1.05:1, and mixed and ground to obtain a precursor; the obtained precursor is calcined at 950 °C for 12 h and cooled to obtain a repaired and complete layered oxide cathode material Na 0.97 K 0.03 Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 , labeled as R-NFM-K-3%.

[0040] Example 4

[0041] (1) Place the waste layered oxide cathode sheet in a muffle furnace and heat-treat it at 450 °C for 3 hours to separate the aluminum foil and the active material, and obtain waste Na x Cu 0.22 Fe 0.30 Mn 0.48 O 2 powder (0.5 ≤ x < 0.9), labeled as S-CFM.

[0042] (2) Analyze and determine the molar ratio of sodium element in the S-CFM material, and calculate the amount of sodium ion deficiency;

[0043] (3) Use a regenerant which is a mixed salt of sodium hydroxide and potassium hydroxide. The molar amount of potassium ion in the regenerant is 0.5% of that of S-CFM. The regenerant is added in a ratio of 1:1 of the total molar amount of sodium and potassium ions to the amount of sodium ion deficiency in S-CFM, and mixed and ground to obtain a precursor;

[0044] (4) Calcinate the obtained precursor at 900 °C for 12 h, and cool to obtain a repaired and complete layered oxide cathode material Na 0.895 K 0.005 Cu 0.22 Fe 0.30 Mn 0.48 O 2 , marked as R-CFM-K-0.5%.

[0045] Example 5

[0046] Steps (1) and (2) of this example are the same as those of Example 4. Steps (3) and (4) are specifically as follows:

[0047] Use a regenerant which is a mixed salt of sodium nitrate and potassium nitrate. The molar amount of potassium ion in the regenerant is 1% of that of the waste S-CFM. The regenerant is added in a ratio of 1.03:1 of the total molar amount of sodium and potassium ions to the amount of sodium ion deficiency in S-CFM, and mixed and ground to obtain a precursor; Calcinate the obtained precursor at 950 °C for 12 h, and cool to obtain a repaired and complete layered oxide cathode material Na 0.89 K 0.01 Cu 0.22 Fe 0.30 Mn 0.48 O 2 , marked as R-CFM-K-1%.

[0048] Example 6

[0049] Steps (1) and (2) of this example are the same as those of Example 4. Steps (3) and (4) are specifically as follows:

[0050] Use a regenerant which is a mixed salt of sodium carbonate and potassium carbonate. The molar amount of potassium ion in the regenerant is 2% of that of S-CFM. The regenerant is added in a ratio of 1.05:1 of the total molar amount of potassium ion to the amount of sodium ion deficiency in S-CFM, and mixed and ground to obtain a precursor.

[0051] Calcinate the obtained precursor at 950 °C for 15 h, and cool to obtain a repaired and complete layered oxide cathode material Na 0.88 K 0.02 Cu 0.22Fe 0.30 Mn 0.48 O 2 , labeled as R-CFM-K-2%.

[0052] Comparative Example 1

[0053] Steps (1) and (2) of this example are the same as those of Example 1. Steps (3) and (4) are specifically as follows:

[0054] Using a single sodium hydroxide salt as the regenerant, the regenerant is added in a ratio of 1:1 of the molar amount of sodium ions to the sodium ion deficiency in S-NFM, and mixed and ground to obtain a precursor; the obtained precursor is calcined at 900 °C for 12 h and cooled to obtain the repaired layered oxide cathode material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 , labeled as R-NFM.

[0055] Comparative Example 2

[0056] Steps (1) and (2) of this example are the same as those of Example 4. Steps (3) and (4) are specifically as follows:

[0057] Using a single sodium hydroxide salt as the regenerant, the regenerant is added in a ratio of 1:1 of the molar amount of sodium ions to the sodium ion deficiency in S-CFM, and mixed and ground to obtain a precursor; the obtained precursor is calcined at 900 °C for 12 h and cooled to obtain the repaired layered oxide cathode material Na 0.9 Cu 0.22 Fe 0.30 Mn 0.48 O 2 , labeled as R-CFM.

[0058] Comparative Example 3

[0059] This comparative example is the waste Na x Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O 2 powder obtained after being treated in step (1) of Example 1, labeled as S-NFM.

[0060] SEM morphological characterization analysis was performed on the S-NFM material separated in Comparative Example 3. As can be seen from the appendix Figure 3 the particles are broken and there are cracks.

[0061] The layered oxide cathode materials in the above Examples 1-6 and Comparative Examples 1-3 were assembled into sodium-ion batteries for testing. The cathode material, binder polyvinylidene fluoride (PVDF), and conductive agent carbon black (Super P) were mixed at a mass ratio of 8:1:1, and N-methylpyrrolidone was used as a solvent to prepare a cathode slurry. The cathode slurry was coated on an aluminum foil and dried in a vacuum oven at 120 °C for 12 hours, and then punched into a cathode sheet with a diameter of 14 mm using a punching machine. A CR2032 type button battery case was used, the cathode sheet was the above cathode material, a sodium sheet was used as the anode, a glass fiber was used as the separator, and 1M NaPF6 / EC:DMC = 1:1, 5% FEC was used as the electrolyte to assemble a button battery in a glove box. The constant current charge-discharge mode was used, the voltage range was 2-4V, the current magnitude in the first three cycles was 0.1C, and the long cycle was 1C. The specific test results are shown in Table 1 below.

[0062] Table 1 Performance test results of the layered oxide cathode materials in Examples 1-6 and Comparative Examples 1-3

[0063]

[0064] The test results based on the above Examples 1-6 and Comparative Examples 1-3 show that the present invention realizes the repair and regeneration of waste layered oxide cathode materials, the structure is repaired completely, there is no impurity phase, and the electrochemical performance is significantly improved, especially the rate performance is more excellent. The repair and regeneration process is simple and scalable, which has reference significance for the recycling and regeneration of retired sodium-ion batteries.

[0065] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention shall be covered by the protection scope of the present invention.

Claims

1. A method for repairing and regenerating layered oxide positive electrode materials of retired sodium ion batteries, characterized in that: The following steps are involved: S1. Separating aluminum foil and active material from waste layered oxide positive electrode sheets by heat treatment to obtain waste layered oxide powder; S2. Determine the molar ratio of sodium element in the waste layered oxide powder, and calculate the missing amount of sodium ions according to the theoretical stoichiometric ratio; S3, according to the calculated missing amount of sodium ions, adding a regeneration agent to the waste layered oxide powder, mixing and grinding, to obtain a precursor; the regeneration agent is a mixture of a sodium supplement and a potassium doping agent; S4, calcining the precursor at a high temperature, and obtaining a completely repaired layered oxide positive electrode material after cooling.

2. The method for repairing and regenerating a retired sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that: The general structural formula of the layered oxide positive electrode material is: Na x TMO2, 0.6≤x≤1, TM is one or more of Fe, Mn, Ni, Cu, Co, Ti, V, Cr.

3. The method for repairing and regenerating a retired sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that: The heat treatment temperature in step S1 is 350-600° C., and the heat treatment time is 1 to 5 hours.

4. The method for repairing and regenerating a retired sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that: In step S3, the sodium supplement is one of sodium hydroxide, sodium nitrate and sodium carbonate, and the potassium dopant is one of potassium hydroxide, potassium nitrate and potassium carbonate.

5. The method for repairing and regenerating a retired sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that: The regeneration agent in step S3 is selected from the following combination: any one of sodium hydroxide and potassium hydroxide, sodium nitrate and potassium nitrate, sodium carbonate and potassium carbonate.

6. The method for repairing and regenerating a retired sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that: The molar amount of potassium ions in the regeneration agent in step S3 accounts for 0.5% to 5% of the waste layered oxide powder, and the ratio of the total molar amount of sodium and potassium ions in the regeneration agent to the missing amount of sodium ions is 1 to 1.05:

1.

7. The method for repairing and regenerating a retired sodium ion battery layered oxide positive electrode material according to claim 1, characterized in that: The calcination temperature in step S4 is 850-1000° C., and the calcination time is 6-15 hours.

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