A processing method for recovering performance of a layered oxide positive electrode material

Abstract

The application belongs to the technical field of battery materials, and particularly relates to a treatment method for restoring the performance of a layered oxide positive electrode material. The application provides a treatment method for restoring the performance of a layered oxide positive electrode material, which comprises the following steps: testing residual alkali of the layered oxide positive electrode material; measuring the residual alkali < 4.0 wt%, and then firing the layered oxide positive electrode material at 850-900 DEG C; obtaining the repaired layered oxide positive electrode material; measuring the residual alkali >= 4.0 wt%, mixing the layered oxide positive electrode material with a reducing agent, first sintering, second sintering, and then obtaining the repaired layered oxide positive electrode material; the temperature of the first sintering is 400-500 DEG C; and the temperature of the second sintering is 850-900 DEG C. The treatment method provided by the application restores the layered oxide positive electrode material, improves the processing performance of the material, and is easy to be industrialized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to a treatment method for restoring the performance of a layered oxide positive electrode material. BACKGROUND

[0002] Sodium-ion batteries and lithium-ion batteries have similar working principles, and energy storage and release are realized by reversible intercalation and deintercalation of sodium or lithium ions between positive and negative electrodes. Transition metal oxide systems (layered oxides) are widely used in lithium-ion batteries and sodium-ion batteries due to their high capacity and high rate performance characteristics, but the storage stage after preparation of the positive electrode material and the positive electrode material processing process (such as crushing, sieving, and demagnetization) make the layered oxide positive electrode material easy to contact with air, and then react with H2O and CO2 in the air, resulting in problems such as capacity and rate performance decline, which limits the normal use of the material. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to overcome the defects that the layered oxide as a positive electrode material is easy to react with H2O and CO2 in the air, resulting in capacity and rate performance decline, so as to provide a treatment method for restoring the performance of a layered oxide positive electrode material.

[0004] To this end, the present application provides the following technical solutions.

[0005] The present application provides a treatment method for restoring the performance of a layered oxide positive electrode material, comprising the following steps:

[0006] Testing the residual alkali of the layered oxide positive electrode material;

[0007] When the measured residual alkali is less than 4.0wt%, the layered oxide positive electrode material is resintered to obtain a repaired layered oxide positive electrode material;

[0008] When the measured residual alkali is greater than or equal to 4.0wt%, the layered oxide positive electrode material is mixed with a reducing agent, first sintered, and then second sintered to obtain a repaired layered oxide positive electrode material;

[0009] The first sintering temperature is 400-500 DEG C, and the second sintering temperature is 850-900 DEG C.

[0010] The residual alkali is tested by a conventional testing method in the art, and the present application does not make any specific limitation;

[0011] In an alternative embodiment, the mass ratio of the layered oxide positive electrode material to the reducing agent is (10-200):(1-2);

[0012] In an alternative embodiment, the reducing agent comprises carbon black.

[0013] In an alternative embodiment, the reducing agent further comprises polyvinylpyrrolidone;

[0014] Preferably, the reducing agent is a mixture of carbon black and polyvinylpyrrolidone;

[0015] In an alternative embodiment, the first sintering is performed under a compressed air atmosphere.

[0016] The compressed air atmosphere has a lower content of moisture and carbon dioxide than an air atmosphere.

[0017] In an alternative embodiment, the mass ratio of the carbon black to the polyvinylpyrrolidone is (0.9-1.1):(0.9-1.1);

[0018] In an alternative embodiment, the flow rate of the compressed air atmosphere is 3-5 m 3 / h;

[0019] In an alternative embodiment, the first sintering has a time of 4-8 h;

[0020] In an alternative embodiment, the first sintering has a heating rate of 5-10 °C / min.

[0021] In an alternative embodiment, the second sintering is performed under a compressed air atmosphere.

[0022] In an alternative embodiment, the flow rate of the compressed air atmosphere is 3-5 m 3 / h;

[0023] In an alternative embodiment, the second sintering has a time of 8-12 h;

[0024] In an alternative embodiment, the second sintering has a heating rate of 5-10 °C / min.

[0025] In an alternative embodiment, the layered oxide cathode material comprises a sodium-ion battery layered oxide cathode material.

[0026] Preferably, the sodium-ion battery layered oxide cathode material comprises an O3-type layered oxide cathode material.

[0027] The layered oxide cathode material is optionally a layered oxide cathode material powder.

[0028] In an alternative embodiment, the re-sintering has a time of 8-12 h.

[0029] In an alternative embodiment, the re-sintering has a heating rate of 5-10 °C / min.

[0030] The technical scheme of the present application has the following advantages:

[0031] 1. The processing method for restoring the performance of layered oxide positive electrode material provided by the present application comprises the following steps: testing the residual alkali of the layered oxide positive electrode material; if the residual alkali is less than 4.0wt%, the layered oxide positive electrode material is fired at 850-900℃; if the residual alkali is greater than or equal to 4.0wt%, the layered oxide positive electrode material is mixed with a reducing agent, first sintered, and second sintered to obtain the repaired layered oxide positive electrode material; the first sintering temperature is 400-500℃; and the second sintering temperature is 850-900℃. The processing method provided by the present application restores the layered oxide positive electrode material, improves the processing performance of the material, and facilitates industrialization.

[0032] The layered oxide positive electrode material is prone to react with H2O and CO2 in the air, which affects the electrical performance of the material. When the positive electrode material is in short-term contact with the air, the reactants are mostly in the form of Na2CO3 remaining on the surface of the positive electrode, and the material substrate is basically unchanged. When the positive electrode material is in long-term contact with the air, in addition to Na2CO3 remaining on the surface of the positive electrode, there are also some transition metal oxides on the surface layer of the substrate. The longer the contact time, the greater the adverse effects.

[0033] When the residual alkali is less than 4.0wt%, it indicates that the positive electrode material is in short-term contact with the air. The layered oxide positive electrode material is fired at 850-900℃ for 8h. The residual alkali on the surface of the substrate is less than 4.0wt%, Na2CO3 reacts with the substrate during the firing, and Na atoms are re-migrated into the layered oxygen structure.

[0034] When the residual alkali is greater than 4.0wt%, it indicates that the positive electrode material is in long-term contact with the air. Too many Na atoms are precipitated, and transition metal oxides appear on the surface of the positive electrode material substrate. Two sintering processes of the positive electrode material and the reducing agent can effectively remove the adverse effects and restore the electrical performance of the layered oxide positive electrode material. The first sintering process is performed at 400-500℃, which promotes the reduction of transition metal oxides and reduces the diffusion energy required for transition metal oxides to return to the substrate lattice. The second sintering process is further performed at 850-900℃, and the residual Na2CO3 on the surface of the substrate reacts with the substrate, and Na atoms are re-migrated into the layered oxygen structure of the layered oxide positive electrode material.

[0035] 2. The application provides a treatment method for restoring the performance of a layered oxide positive electrode material, wherein the reducing agent is preferably a mixture of carbon black and polyvinylpyrrolidone, the carbon black plays a reducing role, the polyvinylpyrrolidone acts as a reaction activator to promote the reduction of the transition metal oxide, and the mixture of the two can further improve the performance of the layered oxide positive electrode material after the treatment method. DETAILED DESCRIPTION

[0036] The following examples are provided to better further understand the application and are not limited to the best mode, and do not constitute a limitation on the content and scope of protection of the application. Any person who obtains the same or similar products under the inspiration of the application or by combining the application with other prior art features falls within the scope of protection of the application.

[0037] If the specific experimental steps or conditions are not indicated in the examples, the operations or conditions can be performed according to the conventional experimental steps described in the literature in the field. If the reagents or instruments used are not indicated by the manufacturer, they are conventional reagent products that can be obtained by purchase.

[0038] The compressed air atmosphere used in the following examples is an atmosphere free of moisture and carbon dioxide.

[0039] The application provides a treatment method for restoring the performance of a layered oxide positive electrode material, comprising the following steps:

[0040] The residual alkali of the layered oxide positive electrode material with degraded performance after use is tested;

[0041] When the residual alkali is less than 4.0 wt%, the layered oxide positive electrode material is resintered at 850-900°C for 8-12h under a compressed air atmosphere (3-5m 3 / h), to obtain a repaired layered oxide positive electrode material;

[0042] When the residual alkali is greater than or equal to 4.0 wt%, the layered oxide positive electrode material is mixed with a reducing agent, first sintered at 400-500°C for 4-8h, and second sintered at 850-900°C for 8-12h under a compressed air atmosphere (3-5m 3 / h), to obtain a repaired layered oxide positive electrode material.

[0043] Example 1

[0044] The application provides a preparation method of an O3-type layered oxide positive electrode material, comprising the following steps:

[0045] (1) 5kg of Ni0.33 Fe 0.33 Mn 0.33 (OH)2and 2.99kg sodium carbonate were mixed with a high-speed mixer, sintered at 980℃ for 12h under air atmosphere (5m 3 / h) and crushed to obtain O3-type layered oxide positive electrode material.

[0046] (2) 5kg of the first sintered material and 50g of CaCO3 were mixed in a high-speed mixer, sintered at 800℃ for 12h under air atmosphere (5m 3 / h) at a temperature increasing rate of 8℃ / min, and crushed to obtain O3-type layered oxide positive electrode material.

[0047] The embodiment also provides a treatment method for restoring the performance of layered oxide positive electrode material, comprising the following steps:

[0048] 1kg of O3-type layered oxide positive electrode material was placed in an environment with air humidity of 40% for 6 days, and the residual alkali was measured to be 3.65wt%. The O3-type layered oxide positive electrode material was resintered at 850℃ for 8h under compressed air atmosphere (5m 3 / h) to obtain layered oxide positive electrode material with restored performance.

[0049] Example 2

[0050] The embodiment provides a treatment method for restoring the performance of layered oxide positive electrode material, comprising the following steps:

[0051] 1kg of O3-type layered oxide positive electrode material prepared according to the preparation method of Example 1 was placed in an environment with air humidity of 40% for 10 days, and the residual alkali was measured to be 4.89wt%. 1kg of the exposed O3-type layered oxide positive electrode material, 2.5g of carbon black and 2.5g of polyvinylpyrrolidone were mixed, and the mixture was sintered at 400℃ for 6h and then at 850℃ for 8h under compressed air atmosphere (5m 3 / h) at a temperature increasing rate of 8℃ / min to obtain layered oxide positive electrode material with restored performance.

[0052] Example 3

[0053] The embodiment provides a treatment method for restoring the performance of layered oxide positive electrode material, comprising the following steps:

[0054] 500g of O3-type layered oxide positive electrode material prepared according to the preparation method of Example 1 was placed in an environment with air humidity of 40% for 20 days, and the residual alkali was measured to be about 6.0wt%. 500g of the exposed O3-type layered oxide positive electrode material, 25g of carbon black and 25g of polyvinylpyrrolidone were mixed, and the mixture was sintered at 400℃ for 6h and then at 850℃ for 8h under compressed air atmosphere (3m 3 / h) and then sintered at 500°C for 8h at a heating rate of 5°C / min and then sintered at 900°C for 12h at a heating rate of 5°C / min to obtain the layered oxide cathode material with recovered performance.

[0055] Example 4

[0056] The present example provides a treatment method for recovering performance of a layered oxide cathode material, comprising the following steps:

[0057] 500g of the O3-type layered oxide cathode material prepared according to the preparation method of Example 1 was placed in an environment with an air humidity of 40% for 20 days, and the residual alkali was measured to be about 6.0wt%. 500g of the exposed O3-type layered oxide cathode material, 5g of carbon black and 5g of polyvinylpyrrolidone were mixed, and the mixture was sintered at 850°C for 8h under a compressed air atmosphere (5m 3 / h) and then sintered at 500°C for 8h at a heating rate of 5°C / min and then sintered at 900°C for 12h at a heating rate of 5°C / min to obtain the layered oxide cathode material with recovered performance.

[0058] Comparative Example 1

[0059] The present comparative example provides an O3-type layered oxide cathode material without recovered performance, comprising the following steps:

[0060] 1kg of the O3-type layered oxide cathode material prepared according to the preparation method of Example 1 was placed in an environment with an air humidity of 40% for 10 days, and the residual alkali was measured to be 4.89wt%. The 1kg of the exposed O3-type layered oxide cathode material, 2.5g of carbon black and 2.5g of polyvinylpyrrolidone were mixed, and the mixture was sintered at 850°C for 8h under a compressed air atmosphere (5m 3 / h) and then sintered at 500°C for 8h at a heating rate of 5°C / min and then sintered at 900°C for 12h at a heating rate of 5°C / min to obtain the layered oxide cathode material with recovered performance.

[0061] Comparative Example 2

[0062] The present comparative example provides an O3-type layered oxide cathode material without recovered performance, comprising the following steps:

[0063] 1kg of the O3-type layered oxide cathode material prepared according to the preparation method of Example 1 was placed in an environment with an air humidity of 40% for 10 days, and the residual alkali was measured to be 4.89wt%. The 1kg of the exposed O3-type layered oxide cathode material, 2.5g of carbon black and 2.5g of polyvinylpyrrolidone were mixed, and the mixture was sintered at 850°C for 8h under a compressed air atmosphere (5m 3 / h) and then sintered at 500°C for 8h at a heating rate of 5°C / min and then sintered at 900°C for 12h at a heating rate of 5°C / min to obtain the layered oxide cathode material with recovered performance.

[0064] Test Example

[0065] The O3-type layered oxide positive electrode material prepared in Example 1 was used as Comparative Experiment 1, and the O3-type layered oxide positive electrode material after being treated for 6 days in Example 1 was used as Comparative Experiment 2. The O3-type layered oxide positive electrode material after being placed for 10 days in Example 2 was used as Comparative Experiment 3.

[0066] The positive electrode materials of the examples and comparative examples were subjected to performance testing. The positive electrode materials were mixed with ethyne carbon black and PVDF at a mass ratio of 80:10:10, 1-methyl-2-pyrrolidone was added, and the mixture was ball milled for 1 h to form a slurry. The slurry was uniformly coated on an aluminum sheet, dried, and pressed into a positive electrode sheet. A metal sodium sheet was used as a negative electrode, a 1 mol / L NaClO4 PC solution was used as an electrolyte, and a 2032 button cell was assembled. The performance was tested by a Land test system.

[0067] Specifically as follows:

[0068] (1) 0.1C charge specific capacity detection method: at room temperature, within a cutoff voltage of 2.0-4.5 V, 0.1C charging once, and the results are shown in Table 1.

[0069] (2) 0.1C discharge specific capacity detection method: at room temperature, within a cutoff voltage of 2.0-4.5 V, 0.1C discharging once; and the results are shown in Table 1.

[0070] (3) Initial efficiency detection method: calculated according to the following formula,

[0071] Initial efficiency = 0.1C discharge specific capacity / 0.1C charge specific capacity x 100%;

[0072] (4) Rate performance detection method: at room temperature, within a cutoff voltage of 2.0-4.5 V, 1C charging once and 1C discharging once; calculated according to the following formula, and the results are shown in Table 1.

[0073] Rate performance = 1C discharge capacity / 0.1C discharge capacity x 100%;

[0074] (5) Cycle performance detection method: at room temperature, within a cutoff voltage of 2.0-4.5 V, 1C charging once and 1C discharging once, and cycled for 50 times; and the results are shown in Table 1. The cycle performance calculation formula is as follows:

[0075] Cycle performance = 100% x 50 th discharge specific capacity / 1 st discharge specific capacity

[0076] (6) Residual alkali detection method: residual alkali is detected by a potential titrator, 5 g of the positive electrode material is taken to prepare a solution in 100 ml of water, an acidic solution is used as a titrant to neutralize the alkaline substances in the positive electrode material, and the potential change is recorded at the same time, when the potential change reaches a preset end potential, the titration is ended. The residual alkali content in the positive electrode material is calculated by calculating the volume of the titrant consumed in the titration process, and the results are shown in Table 1.

[0077] Table 1 Test results of examples and comparative examples

[0078]

[0079] As can be seen from Table 1, the layered oxide positive electrode material treated by the treatment method for recovering the performance of the layered oxide positive electrode material provided by the application has low residual alkali, high specific capacity, high initial efficiency, good rate performance and good cycle performance after being made into a battery again;

[0080] As can be seen from the comparison of the examples and the comparative examples, the performance of the layered oxide positive electrode material treated by the application is similar to that of the layered oxide positive electrode material just prepared, which shows that the application can effectively recover the performance of the layered oxide positive electrode material with deteriorated performance and achieve recycling. The specific capacity, rate performance and cycle performance of the layered oxide positive electrode material with too high residual alkali without treatment are significantly reduced; the treatment method for recovering the performance of the layered oxide positive electrode material in the prior art can reduce part of the residual alkali and recover part of the performance, but the specific capacity, rate performance and cycle performance are still poorer than those of the positive electrode material just prepared.

[0081] Obviously, the above examples are merely examples for clearly illustrating but not limiting the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the application.

Claims

1. A method for restoring the performance of layered oxide cathode materials, characterized in that, Includes the following steps: Test residual alkali in layered oxide cathode materials; The residual alkali was measured to be <4.0wt%. The layered oxide cathode material was refracted at 850-900℃ to obtain the repaired layered oxide cathode material. The residual alkali was measured to be ≥4.0wt%. The layered oxide cathode material and the reducing agent were mixed, and the mixture was sintered for the first time and then for the second time to obtain the repaired layered oxide cathode material. The first sintering temperature is 400-500℃; the second sintering temperature is 850-900℃.

2. The processing method according to claim 1, characterized in that, The mass ratio of the layered oxide cathode material to the reducing agent is (10-200):(1-2); and / or, The reducing agent includes carbon black.

3. The processing method according to claim 2, characterized in that, The reducing agent also includes polyvinylpyrrolidone; and / or, The first sintering was carried out under a compressed air atmosphere.

4. The processing method according to claim 3, characterized in that, The mass ratio of the carbon black to the polyvinylpyrrolidone is (0.9-1.1):(0.9-1.1); and / or, The flow rate of the compressed air atmosphere is 3-5 m³ / h. 3 / h; and / or, The first sintering time is 4-8 hours; and / or, The heating rate for the first sintering is 5-10℃ / min.

5. The processing method according to any one of claims 1-4, characterized in that, The second sintering is carried out under a compressed air atmosphere.

6. The processing method according to claim 5, characterized in that, The flow rate of the compressed air atmosphere is 3-5 m³ / h. 3 / h; and / or, The second sintering time is 8-12 hours; and / or, The heating rate for the second sintering is 5-10℃ / min.

7. The processing method according to claim 6, characterized in that, The layered oxide cathode material includes sodium-ion battery layered oxide cathode materials.

8. The processing method according to claim 7, characterized in that, The sodium-ion battery layered oxide cathode material includes O3-type layered oxide cathode material.

9. The processing method according to claim 8, characterized in that, The reheating time is 8-12 hours.

10. The processing method according to claim 9, characterized in that, The heating rate during the reheating process is 5-10℃ / min.

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