Sodium ion positive electrode material and failure rerepair method thereof

Abstract

The invention discloses a sodium ion positive electrode material and a failure re-repairing method thereof.The failure re-repairing method of the sodium ion positive electrode material is used for re-repairing the sodium ion positive electrode material which fails due to exposure to a wet environment and comprises the following steps that S1, the failed sodium ion positive electrode material is washed with absolute ethyl alcohol and then subjected to vacuum drying, and the sodium ion positive electrode material is obtained; the pretreated layered oxygen positive electrode material is obtained; s2, preparing a repairing solvent, wherein the repairing solvent is prepared by dissolving hydrochloric acid modified polyaniline and multi-walled carbon nanotubes in N-methyl pyrrolidone; s3, dissolving the layered oxygen positive electrode material in a repairing solvent, and stirring to obtain a sodium ion positive electrode material to be dried; and S4, carrying out vacuum drying on the sodium ion positive electrode material to be dried, and cooling to obtain the repaired layered oxide positive electrode material. The method can effectively remove moisture and impurities on the surface of the failed material, recover the basic performance, and improve the stability of the repaired material structure, the specific capacity of current discharge and the cycle performance of the material.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and in particular relates to a sodium ion positive electrode material and a failure repair method thereof. Background Art

[0002] With the vigorous development of new energy vehicles and electrochemical energy storage industries, the demand for lithium mineral resources has increased dramatically, and the sustainable supply of lithium resources is at risk. Therefore, sodium-ion batteries are expected to complement and effectively replace lithium-ion batteries with their advantages of abundant sodium resources, low prices, and environmental friendliness. Sodium-ion batteries can be divided into different systems, such as layered oxide systems, Prussian blue compound systems, tunnel oxide systems, and polyanion systems, according to the different positive electrode materials. Layered transition metal oxide systems (Na x TMO2 (TMO2) is currently the most promising cathode material for sodium-ion batteries due to its high energy density and excellent rate performance. However, in the Pearl River Delta region, high humidity makes battery production more difficult to control. Improper storage of cathode materials, such as prolonged exposure to air and high humidity during trial production, can cause them to absorb moisture, altering their surface composition and structure, leading to failure.

[0003] Therefore, there is an urgent need to design a sodium ion positive electrode material and a failure repair method thereof to solve the above problems. Summary of the Invention

[0004] In order to solve the technical problem mentioned in the background technology that the sodium ion positive electrode material is exposed to air and high humidity environment for too long during the trial production process, which will cause the material to absorb moisture and the surface composition and structure to change, a sodium ion positive electrode material and a method for repairing its failure are provided.

[0005] To achieve the above objectives, the specific technical solutions of the sodium ion positive electrode material and the failure repair method thereof of the present invention are as follows: A method for repairing a failed sodium ion cathode material, for repairing a failed sodium ion cathode material due to exposure to a humid environment, comprising the following steps: S1. Washing the spent sodium ion cathode material with anhydrous ethanol and then vacuum drying it to obtain a pretreated layered oxygen cathode material; S2, preparing a repair solvent, wherein the repair solvent is prepared by dissolving hydrochloric acid-modified polyaniline and multi-walled carbon nanotubes in N-methylpyrrolidone; S3, dissolving the layered oxygen cathode material in a repair solvent and stirring to obtain a sodium ion cathode material to be dried; S4. The sodium ion positive electrode material to be dried is vacuum dried and cooled to obtain a repaired layered oxide positive electrode material.

[0006] Furthermore, after step S4, the following steps are further included: The repaired layered oxide positive electrode material is washed with N-methylpyrrolidone, and then vacuum dried and cooled.

[0007] Furthermore, the mass ratio of N-methylpyrrolidone to the repaired layered oxide positive electrode material is 1-10:1.

[0008] Furthermore, the vacuum drying temperature is set to 100°C-150°C.

[0009] Furthermore, in step S1, The mass ratio of the spent sodium ion positive electrode material to anhydrous ethanol washing is 1:1-10.

[0010] Furthermore, in step S2, The mass ratio of hydrochloric acid modified polyaniline to multi-walled carbon nanotubes is 0.1-10:1, and the mass ratio of the mixture of the two to the layered oxide is 0.01-1:1.

[0011] Furthermore, the mass ratio of hydrochloric acid modified polyaniline, multi-walled carbon nanotubes and N-methylpyrrolidone is 1-2:5-10:20.

[0012] Furthermore, in step S3, After dissolving the layered oxygen cathode material in the repair solvent, ultrasonic stirring is used, and the stirring time is set to 20min-40min.

[0013] Furthermore, the ultrasonic stirring speed is 200 r / min-800 r / min.

[0014] A sodium ion positive electrode material can be repaired after failure using the above-mentioned sodium ion positive electrode material failure repair method.

[0015] The method for repairing failed sodium ion positive electrode materials of the present invention has the following advantages: through anhydrous ethanol washing and vacuum drying pretreatment, moisture and impurities on the surface of the failed material are effectively removed, and the basic properties of the material are restored; the weak acid property of hydrochloric acid-modified polyaniline is utilized to effectively neutralize residual alkali such as NaOH and NaCO3 on the surface of the sodium ion positive electrode material, thereby avoiding the problem of aggravated side reactions after the material is subsequently manufactured into a battery, and improving the stability of the repaired material structure; and the excellent electrical conductivity of hydrochloric acid-modified polyaniline and carbon nanotubes is further utilized to provide the surface of the repaired material with a coating protective layer, thereby increasing the specific capacity of large current discharge, reducing the corrosion of the electrode material by the electrolyte during the charge and discharge cycle process after the battery is manufactured into a battery cell, and improving the cycle performance of the material.

[0016] The sodium ion positive electrode material of the present invention has the following advantages: the sodium ion positive electrode material can not only restore its own electrochemical properties through the above method, but also improve the specific capacity of large current discharge and the cycle performance of the material. Moreover, the electrochemical performance of the repaired material is very close to that of the newly prepared sodium layered oxide positive electrode material of the same model, and the specific capacity of large current discharge and the cycle performance of the material are further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention is a flow chart of the method for repairing failed sodium ion positive electrode materials. DETAILED DESCRIPTION

[0018] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0019] Those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not other features, the combination of features from different embodiments is intended to be within the scope of the present invention and to form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0020] Please refer to the attached Figure 1 The present invention describes a sodium ion positive electrode material and a method for repairing a failed electrode.

[0021] This embodiment provides a method for repairing a failed sodium ion cathode material, which is used to repair a failed sodium ion cathode material due to exposure to a humid environment. Figure 1 Flowchart of the method for repairing failed sodium ion cathode materials according to this embodiment. Figure 1 As shown, the method includes the following steps: S1. Washing the spent sodium ion cathode material with anhydrous ethanol and then vacuum drying it to obtain a pretreated layered oxygen cathode material; S2, preparing a repair solvent, wherein the repair solvent is prepared by dissolving hydrochloric acid-modified polyaniline and multi-walled carbon nanotubes in N-methylpyrrolidone; S3, dissolving the layered oxygen cathode material in a repair solvent and stirring to obtain a sodium ion cathode material to be dried; S4. The sodium ion positive electrode material to be dried is vacuum dried and cooled to obtain a repaired layered oxide positive electrode material.

[0022] Through anhydrous ethanol washing and vacuum drying pretreatment, the moisture and impurities on the surface of the failed material are effectively removed, and the basic properties of the material are restored. The weak acid properties of hydrochloric acid-modified polyaniline are used to effectively neutralize the residual alkali such as NaOH and NaCO3 on the surface of the sodium ion positive electrode material, avoiding the problem of aggravated side reactions after the material is subsequently made into a battery, and improving the stability of the repaired material structure. The excellent conductivity of hydrochloric acid-modified polyaniline and carbon nanotubes is then used to give the surface of the repaired material a coating protective layer, which can improve the specific capacity of large current discharge, and can reduce the erosion of the electrode material by the electrolyte during the charge and discharge cycle process after it is made into a battery cell, thereby improving the cycle performance of the material.

[0023] Furthermore, the sodium ion layered oxide of this embodiment includes a molecular formula of Na x TMO2, wherein it is understood that TM is some common transition metal elements, including one or more of Cu, Ni, Mg, Ti, Zn, Fe, and Mn; Furthermore, after step S4, the following steps are further included: The repaired layered oxide positive electrode material is washed with N-methylpyrrolidone, and then vacuum dried and cooled.

[0024] The repaired layered oxide is then washed with N-methylpyrrolidone to evenly disperse the repair components and ensure the consistency of the repair effect.

[0025] Specifically, in actual application, workers can ensure the stability and repeatability of the repair process by optimizing the process parameters of each step (such as mass ratio, temperature, stirring speed, etc.): Specifically, the mass ratio of N-methylpyrrolidone to the repaired layered oxide positive electrode material is 1-10:1. An N-methylpyrrolidone washing step is added after step S4 to further remove residual repair solvent and impurities and improve the purity of the repaired material. The mass ratio of N-methylpyrrolidone to the repaired material is 1-10:1, ensuring a good washing effect while avoiding excessive waste of solvent.

[0026] Specifically, the vacuum drying temperature is set to 100°C-150°C, which can effectively remove the solvent and avoid thermal decomposition of the material.

[0027] Specifically, in step S1, the spent sodium ion positive electrode material is washed with anhydrous ethanol in a mass ratio of 1:1-10, thereby ensuring sufficient washing without wasting solvent.

[0028] Furthermore, in step S2, The mass ratio of hydrochloric acid modified polyaniline to multi-walled carbon nanotubes is 0.1-10:1, and the mass ratio of the mixture of the two to the layered oxide is 0.01-1:1.

[0029] Furthermore, the mass ratio of hydrochloric acid modified polyaniline, multi-walled carbon nanotubes and N-methylpyrrolidone is 1-2:5-10:20.

[0030] In some embodiments, 5 g of hydrochloric acid-modified polyaniline and 25 g of multi-walled carbon nanotubes were dissolved in 100 g of N-methylpyrrolidone to obtain a mixed solvent. It is understood that the mass ratio of hydrochloric acid-modified polyaniline, multi-walled carbon nanotubes and N-methylpyrrolidone can be appropriately adjusted according to the above ratio and is not specifically limited here. Furthermore, in step S3, After dissolving the layered oxide cathode material in the repair solvent, ultrasonic stirring is used for 20-40 minutes. Ultrasonic stirring can break up material agglomerates, promote the uniform distribution of the repair components on the material surface, and enhance the repair effect.

[0031] Specifically, the ultrasonic stirring speed is 200 r / min-800 r / min. Ultrasonic stirring (200-800 r / min, 20-40 minutes) is used to ensure full contact and uniform mixing of the repair solvent and the material.

[0032] Optionally, in some embodiments, the ultrasonic stirring duration is 30 min and the speed is set to 400 r / min.

[0033] This embodiment also provides a sodium ion positive electrode material, which can be repaired after failure using the above-mentioned sodium ion positive electrode material failure repair method.

[0034] The above method can not only restore the electrochemical properties of the sodium ion positive electrode material, but also improve the specific capacity of large current discharge and the cycle performance of the material. Moreover, the electrochemical performance of the repaired material is very close to that of the newly prepared sodium-ion layered oxide positive electrode material of the same model, and the specific capacity of large current discharge and the cycle performance of the material are further improved.

[0035] Furthermore, in order to prove that the repaired sodium ion positive electrode material not only improves the specific capacity but also its cycle performance, several embodiments are set up below to further verify: Example 1: S1, 100g of NaNi layered oxide cathode material for sodium ion battery after exposure to a non-dehumidified environment for 3 days 1 / 3 Fe 1 / 3 Mn 1 / 3O2 was washed with 400 g of 99.9% anhydrous ethanol and then vacuum dried at 120°C for 1 day to obtain a pretreated layered oxygen cathode material.

[0036] S2. Dissolve 5 g of hydrochloric acid-modified polyaniline and 25 g of multi-walled carbon nanotubes in 100 g of N-methylpyrrolidone to obtain a mixed solvent.

[0037] S3. Dissolve the layered oxygen cathode material obtained in step S1 in the solvent obtained in S2, and stir ultrasonically for 30 minutes at a speed of 400 r / min.

[0038] S4. The solution obtained in S3 was vacuum dried at 140° C., cooled, washed with 400 g of N-methylpyrrolidone, and then vacuum dried at 140° C. and cooled to obtain a repaired positive electrode material, which was used as the positive electrode material for a sodium ion battery.

[0039] Example 2: The basic conditions are the same as those of Example 1, except that the amount of hydrochloric acid-modified polyaniline added is 10 g.

[0040] Example 3: The basic conditions are the same as those in Example 1, except that the amount of multi-walled carbon nanotubes added is 50 g.

[0041] Example 4: The basic conditions are the same as those in Example 1, except that the amount of hydrochloric acid-modified polyaniline added is 10 g, and the amount of multi-walled carbon nanotubes added is 50 g.

[0042] Example 5: The basic conditions are the same as those in Example 1, except that the stirring speed in step S3 is 200 r / min.

[0043] Example 6: The basic conditions are the same as those in Example 1, except that the stirring speed in step S3 is 600 r / min.

[0044] Several comparative examples were set up as control experiments for this method to further verify the advanced nature of this method: Comparative Example 1: 100g of NaNi2O3 layered oxide cathode material for sodium ion battery was exposed to a non-dehumidified environment for 3 days. 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was washed with 400g of 99.9% anhydrous ethanol and then vacuum dried at 120°C for 1 day to obtain a layered oxide positive electrode material and used as the positive electrode material for sodium ion batteries.

[0045] Comparative Example 2: 100 g of the layered oxide material was exposed to a non-dehumidified environment for 3 days, and the failed layered oxide material was directly used as the positive electrode material of the sodium ion battery.

[0046] Comparative Example 3: The unfailed layered oxide material is directly used as the positive electrode material of the sodium ion battery.

[0047] According to the above embodiments and comparative examples, comparative experiments were carried out. In comparative experiment 1, the materials obtained from the above embodiments 1-6 and comparative examples 1-3 were characterized in terms of moisture, specific surface area (BET), and particle size. The characterization results are shown in Table 1. In comparative experiment 2, the materials obtained from the above embodiments 1-6 and comparative examples 1-3 were used to prepare positive electrodes, and sodium sheets were used as negative electrodes to obtain button batteries. The discharge capacity was tested at current densities of 12.5 mA / g (0.1C), 125 mA / g (1C), and 375 mA / g (3C). A room temperature cycle test was carried out for 50 cycles at a current density of 12.5 mA / g (0.1C). The test results are shown in Table 2.

[0048] It should be noted that the above-mentioned normal temperature cycle test refers to charging at room temperature with a constant current and constant voltage of 0.1C; leaving it for 10 minutes; discharging at a constant current of 0.5C, leaving it for 10 minutes; and continuously cycling the charge and discharge steps. As shown in Table 1, the positive electrode materials of Comparative Examples 1 and 2 contained high moisture content, while the moisture content of the materials of Examples 1-6 was reduced, only slightly higher than that of the intact material of Comparative Example 3. This demonstrates that the present invention effectively repaired the failed materials. Furthermore, the specific surface area and particle size of the repaired layered oxygen positive electrode materials of Examples 1-6 were similar to those of the original, intact material of Comparative Example 3, indicating no impact on battery performance. As can be seen from Table 2, the positive electrode battery material of Comparative Example 2 that has failed has a low discharge specific capacity and can be maintained for less than 100 cycles at room temperature. The positive electrode battery material of Comparative Example 1 that has only been washed with anhydrous ethanol has a 0.1C specific capacity of 80.5 mAh / g and a capacity retention rate of 74.7% after 50 cycles at room temperature. The 0.1C discharge specific capacity and 1C discharge specific capacity of Examples 1-6 using the above-mentioned repair method are close to those of Comparative Example 3 that has not failed, and the 3C discharge specific capacity and the capacity retention rate after 100 cycles are higher than those of the material in Comparative Example 3, further indicating that the repaired sodium-layered oxide positive electrode material has restored its own electrochemical properties and improved the specific capacity of large current discharge and the cycle performance of the material.

[0049] In summary, this method for repairing failed layered oxide cathode materials for sodium-ion batteries is simple, efficient, and reproducible. The electrochemical performance of the repaired material closely matches that of newly prepared, similar-model sodium-ion battery layered oxide cathode materials, further enhancing the high-current discharge capacity and cycling performance of the material.

[0050] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for repairing a failed sodium ion cathode material, which is used to repair a failed sodium ion cathode material due to exposure to a humid environment, characterized in that: The following steps are involved: S1. Washing the spent sodium ion cathode material with anhydrous ethanol and then vacuum drying it to obtain a pretreated layered oxygen cathode material; S2, preparing a repair solvent, wherein the repair solvent is prepared by dissolving hydrochloric acid-modified polyaniline and multi-walled carbon nanotubes in N-methylpyrrolidone; S3, dissolving the layered oxygen cathode material in a repair solvent and stirring to obtain a sodium ion cathode material to be dried; S4. The sodium ion positive electrode material to be dried is vacuum dried and cooled to obtain a repaired layered oxide positive electrode material.

2. The method for repairing failed sodium ion cathode materials according to claim 1, characterized in that: After step S4, the following steps are further included: The repaired layered oxide positive electrode material is washed with N-methylpyrrolidone, and then vacuum dried and cooled.

3. The method for repairing failed sodium ion cathode materials according to claim 2, characterized in that: The mass ratio of N-methylpyrrolidone to the repaired layered oxide positive electrode material is 1-10:

1.

4. The method for repairing a failed sodium ion cathode material according to any one of claims 1 to 3, characterized in that: The vacuum drying temperature is set at 100°C-150°C.

5. The method for repairing failed sodium ion cathode materials according to claim 1, characterized in that: In step S1, The mass ratio of the spent sodium ion positive electrode material to anhydrous ethanol washing is 1:1-10.

6. The method for repairing failed sodium ion cathode materials according to claim 1, characterized in that: In step S2, The mass ratio of hydrochloric acid modified polyaniline to multi-walled carbon nanotubes is 0.1-10:1, and the mass ratio of the mixture of the two to the layered oxide is 0.01-1:

1.

7. The method for repairing a failed sodium ion cathode material according to any one of claims 1 or 6, characterized in that: The mass ratio of hydrochloric acid modified polyaniline, multi-walled carbon nanotubes and N-methylpyrrolidone is 1-2:5-10:

20.

8. The method for repairing failed sodium ion cathode materials according to claim 1, characterized in that: In step S3, After dissolving the layered oxygen cathode material in the repair solvent, ultrasonic stirring is used, and the stirring time is set to 20min-40min.

9. The method for repairing a failed sodium ion cathode material according to claim 8, wherein: The ultrasonic stirring speed is 200r / min-800r / min.

10. A sodium ion positive electrode material, characterized in that After failure, the sodium ion positive electrode material can be repaired using the sodium ion positive electrode material failure repair method as described in any one of claims 1 to 9.

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