MOF-derived carbon nanotube-coated sodium-ion battery cathode material and preparation method thereof

Abstract

The application discloses a MOFs derived carbon nanotube coated sodium ion battery positive electrode material and a preparation method thereof, which comprises the following steps: providing uniform growth sites on the surface of a sodium ion battery positive electrode material, uniformly coating MOFs materials, and finally catalyzing metal ions in the MOFs materials through high temperature to promote the growth of carbon nanotubes, so as to form a protective layer with a dense carbon nanotube structure on the surface of the material. The coating mode of the application realizes the integrity, uniformity and stability of the surface material loading, so that the material has high specific capacity performance and good cycle performance.

Description

Technical Field

[0001] The present invention relates to the field of sodium-ion batteries, and particularly to a MOFs-derived carbon nanotube-coated sodium-ion battery cathode material and a preparation method thereof. Background Art

[0002] Considering the social demand for renewable energy and reliable energy storage devices, rechargeable lithium-ion batteries (LIBs) have been widely used in portable electronics and electric vehicles. However, the global lithium resources are unevenly distributed and extremely limited in reserves, making sustainable mining impossible, and at the same time causing soaring prices of downstream lithium-containing materials. In contrast, sodium resources have significant advantages in terms of abundance, wide distribution, and low cost; and sodium-ion batteries (SIBs) have a similar charge and discharge mechanism to lithium-ion batteries, and have economic sustainability and safety, and are considered to be the most promising next-generation batteries. As a key component that determines the energy output and cost of sodium-ion batteries, the cathode material plays a crucial role in the electrochemical performance and safety of sodium-ion batteries, so it has received increasing attention, but its actual production is still a challenge. Layered transition metal oxide cathodes (NaxTMO2, where 0.67 < x < 1; TM = Fe, Mn, Ni, Cu or a combination thereof) have broad prospects due to their large theoretical capacity and low cost and have attracted extensive attention. However, due to factors such as low electronic conductivity, poor cycle stability, and high residual alkali, it affects the electrochemical performance of the cathode material and limits its further application. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a MOFs-derived carbon nanotube-coated sodium-ion battery cathode material and a preparation method thereof. First, uniform growth sites are provided on the surface of the sodium-ion battery cathode material, then the MOFs material is uniformly coated, and finally, the metal ions in the MOFs material are catalytically heated at high temperature to promote the growth of carbon nanotubes, thereby forming a protective layer with a dense carbon nanotube structure on the surface of the material. The coating method of the present invention realizes the integrity, uniformity, and stability of the surface material loading, and further improves the specific capacity and cycle performance of the material.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] First, a preparation method of a MOFs-derived carbon nanotube-coated sodium-ion battery cathode material, characterized by comprising the following steps:

[0006] (1) Dissolve a nitrogen-containing organic compound in a solution to form a coating solution;

[0007] (2) Add the sodium-ion battery cathode material to the coating solution, stir at 300 - 800 r / min for 0.5 h - 8 h, filter, wash, and dry to obtain a coated material;

[0008] (3) Dissolve the organic acid in the solution to obtain an organic acid solution;

[0009] (4) Disperse the metal salt in the solution to form a metal salt dispersion;

[0010] (5) Place the coated material in a reactor, add organic acid solution and metal salt dispersion in sequence, stir at 300-800 r / min for 10-60 min at 30℃-100℃, filter, wash and dry to obtain coated precursor cathode material;

[0011] (6) The precursor cathode material is placed in a rotary furnace under a nitrogen atmosphere and heated to 650-1000°C at a heating rate of 1-5°C / min. The temperature is held for 1-4 hours and then cooled to room temperature to obtain MOFs-derived carbon nanotube-coated sodium-ion battery cathode material.

[0012] Furthermore, the solution comprises one or more of methanol, ethanol, propanol, isopropanol, acetone, dimethylformamide, and dimethylacetamide.

[0013] Further, in step (1), the nitrogen-containing organic compound is one or more of urea, dopamine, polyacrylonitrile, melamine, pyridine, triethylamine, ethyleneimine, pyrrole, and biuret.

[0014] Further, in step (2), the sodium-ion battery cathode material is specifically a layered metal oxide cathode material with the chemical formula Na. a TM b O2; where TM is one or more elements selected from Li, Ni, Mg, Cu, Mn, Zn, Co, Ca, Ba, Sr, Al, B, Cr, Zr, Ti, Sn, V, Mo, Ru, Nb, and Sb; a satisfies: 0.5 < a < 1.5; a and b satisfy charge balance; chemical formula Na a TM b In O2, the transition metal elements satisfy charge balance; when 0.5 < a < 0.8, it indicates that the layered cathode material has a P2 phase structure; when 0.8 < a < 1.5, it indicates that the layered cathode material has an O3 phase structure.

[0015] Furthermore, in step (2), the particle size of the sodium-ion battery cathode material is 2μm to 20μm.

[0016] Further, in step (2), the mass ratio of the sodium-ion battery cathode material, nitrogen-containing organic molecules, and solvent is 1:(0.005~0.4):(1~10), and the thickness of the coating layer in the coating material is 4~35nm.

[0017] Further, in step (3), the concentration of the organic acid in the organic acid solution is 10-20 wt%, and the organic acid is one or more of 2,5-dihydroxyterephthalic acid, 5-hydroxyisophthalic acid, pyromellitic acid, 1,2,4,5-benzenetetracarboxylic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, and 2-aminoterephthalic acid.

[0018] Further, in step (4), the concentration of the metal salt in the metal salt dispersion is 15-20 wt%, and the metal salt is one or more of cobalt acetate, cobalt nitrate, cobalt sulfate, nickel acetate, nickel nitrate, nickel sulfate, ferric nitrate, ferrocene, and ferric sulfate.

[0019] Further, in step (5), the mass ratio of the coating material, the metal salt dispersion, and the organic acid solution is 100:15-30:15-25.

[0020] Secondly, this invention provides a MOFs-derived carbon nanotube-coated sodium-ion battery cathode material, which is prepared by the above-mentioned preparation method.

[0021] Thirdly, the MOFs-derived carbon nanotube-coated sodium-ion battery cathode material provided by this invention is applied to sodium-ion batteries.

[0022] The beneficial effects of this invention are:

[0023] This invention first provides uniform growth sites on the surface of the sodium-ion battery cathode material, then uniformly coats it with MOFs (Metal-Oxide-Factory) materials, and finally catalyzes the growth of carbon nanotubes by high-temperature catalysis of metal ions in the MOFs material. This forms a protective layer with a dense carbon nanotube structure on the material surface. On the one hand, this reduces the contact area of ​​the internal layered transition metal oxides exposed to the electrolyte, thus overcoming the instability problem caused by interfacial side reactions. On the other hand, the carbon nanotubes on the surface provide an excellent and rapid electron / ion pathway for the cathode material, improving the material's reactivity and conductivity. This coating method eliminates the need for conductive agents in the subsequent slurry preparation, improves space utilization, and achieves the integrity, uniformity, and stability of the surface material loading, thereby improving the material's specific capacity and cycle performance. Attached Figure Description

[0024] Figure 1 The sodium-ion battery cathode material prepared in Example 1 underwent its first charge and discharge cycle.

[0025] Figure 2 The sodium-ion battery cathode material prepared in Comparative Example 1 was charged and discharged for the first time.

[0026] Figure 3 The schematic diagram of the preparation principle of the MOFs-derived carbon nanotube-coated sodium-ion battery cathode material of this invention. Detailed Implementation

[0027] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0028] Example 1

[0029] Mix 50g of urea powder and 200g of methanol solution to form a coating solution; add 500g of sodium-ion battery layered cathode material Na... 0.9 Ni 0.4 Fe 0.2 Mn 0.4 O2 was added to the coating solution, stirred at 500 rpm for 40 min, filtered, washed three times with methanol, and dried at 100℃ for 8 h to obtain the coated material.

[0030] 20g of 1,3,5-benzenetricarboxylic acid was mixed with 100g of N,N-dimethylformamide to form a 1,3,5-benzenetricarboxylic acid solution; 25g of nickel acetate was uniformly dispersed in 100g of N,N-dimethylformamide to obtain a nickel acetate dispersion.

[0031] 490g of the coating material, 120g of 1,3,5-benzenetricarboxylic acid solution and 125g of nickel acetate dispersion were added sequentially to a reaction vessel. The mixture was stirred at 500r / min for 40min at 50℃, filtered, washed three times with methanol, and dried at 100℃ for 8h to obtain the coated precursor cathode material.

[0032] The precursor cathode material was placed in a rotary furnace under a nitrogen atmosphere. The nitrogen flow rate was 400 μL / min, and the temperature was increased to 900℃ at a heating rate of 2℃ / min. The temperature was then held for 2 hours and cooled to room temperature to obtain MOFs-derived carbon nanotube-coated sodium-ion battery cathode material.

[0033] Example 2

[0034] The difference between this embodiment and Embodiment 1 is that the metal salt is cobalt acetate.

[0035] Example 3

[0036] The difference between this embodiment and Example 1 is that the nitrogen-containing organic compound is pyrrole.

[0037] Example 4

[0038] The difference between this embodiment and Embodiment 1 is that the rotary kiln temperature is 950°C and maintained at that temperature for 1 hour.

[0039] Example 5

[0040] The difference between this embodiment and Embodiment 1 is that,

[0041] The metal salt is ferrocene;

[0042] The precursor cathode material was placed in a rotary furnace under a nitrogen atmosphere. The nitrogen flow rate was 400 μL / min, and the temperature was increased to 1000℃ at a heating rate of 2℃ / min. The temperature was held for 1 hour and then cooled to room temperature to obtain MOFs-derived carbon nanotube-coated sodium-ion battery cathode material.

[0043] Comparative Example 1

[0044] The difference between this embodiment and Example 1 is that there is no nitrogen-containing organic molecule coating step, while the remaining operating parameters and steps are exactly the same as in Example 1.

[0045] 20g of 1,3,5-benzenetricarboxylic acid was mixed with 100g of N,N-dimethylformamide to form a 1,3,5-benzenetricarboxylic acid solution; 25g of nickel acetate was uniformly dispersed in 100g of N,N-dimethylformamide to obtain a nickel acetate dispersion.

[0046] 500g of sodium-ion battery layered cathode material Na 0.9 Ni 0.4 Fe 0.2 Mn 0.4 O2, 120g of 1,3,5-benzenetricarboxylic acid solution and 125g of nickel acetate solution were added sequentially to the reactor. The mixture was stirred at 500r / min for 40min at 50℃. After filtration and washing with methanol three times, the mixture was dried and dried at 100℃ for 8h to obtain the coated precursor cathode material.

[0047] The precursor cathode material was placed in a rotary furnace under a nitrogen atmosphere. The nitrogen flow rate was 400 μL / min, and the temperature was increased to 900°C at a heating rate of 2°C / min. The temperature was then held for 2 hours and cooled to room temperature to obtain MOFs-derived carbon nanotube-coated sodium-ion battery cathode material.

[0048] Comparative Example 2

[0049] The difference between this embodiment and embodiment 1 is that the rotary kiln processing step is not performed, while the remaining operating parameters and steps are exactly the same as in embodiment 1.

[0050] Mix 50g of urea powder and 200g of methanol solution to form a coating solution; add 500g of sodium-ion battery layered cathode material Na... 0.9 Ni 0.4 Fe 0.2 Mn 0.4O2 was added to the coating solution, stirred at 500 rpm for 40 min, filtered, washed three times with methanol, and dried at 100℃ for 8 h to obtain the coated material.

[0051] 20g of 1,3,5-benzenetricarboxylic acid and 100g of N,N-dimethylformamide were mixed evenly to form a 1,3,5-benzenetricarboxylic acid solution; 25g of nickel acetate and 100g of N,N-dimethylformamide were mixed evenly to obtain a nickel acetate solution.

[0052] 490g of coating material, 120g of 1,3,5-benzenetricarboxylic acid solution and 125g of nickel acetate solution were added sequentially to a reaction vessel. The mixture was stirred at 500r / min for 40min at 50℃. After filtration and washing with methanol three times, the mixture was dried at 100℃ for 8h to obtain the coated sodium-ion battery cathode material.

[0053] Sodium-ion battery cathode materials obtained in Examples 1-5 and Comparative Examples 1-2 and Na 0.9 Ni 0.4 Fe 0.2 Mn 0.4 The O2 cathode material underwent the following tests, and the test results are shown in Tables 1 and 2:

[0054] 1. pH value test

[0055] Weigh out 2g of the sodium-ion battery cathode material obtained in Examples 1-5 and Comparative Examples 1-2, and Na 0.9 Ni 0.4 Fe 0.2 Mn 0.4 O2 cathode material was added to 30 mL of deionized water, sealed with plastic wrap, and placed on a magnetic stirrer and stirred for 30 minutes. The pH value of the prepared sample was then measured using a pH meter.

[0056] 2. Sodium hydroxide (NaOH) content test

[0057] Weigh out 2g of the sodium-ion battery cathode material obtained in Examples 1-5 and Comparative Examples 1-3, and Na... 0.9 Ni 0.4 Fe 0.2 Mn 0.4 For the O2 cathode material, 30 mL of deionized water was added and the mixture was stirred on a magnetic stirrer for 30 minutes. The filtrate was then obtained by vacuum filtration using a Buchner funnel and the content of sodium hydroxide (NaOH) in the residual alkali on the surface of the layered cathode material was tested using a potentiometric titrator.

[0058] 3. Electrochemical performance testing

[0059] The sodium-ion battery cathode materials obtained in Examples 1-5 and Comparative Examples 1-2 and Na 0.9 Ni0.4 Fe 0.2 Mn 0.4 A coin cell was assembled using O2 as the positive electrode, sodium metal sheet as the negative electrode, glass fiber as the separator, and 1 mol / L NaClO4 (PC + 5% FEC) as the electrolyte. Charge-discharge tests were conducted at a current density of 0.1C within a voltage range of 2.0–4.0 V.

[0060] The 150-cycle cycle retention rate was tested under the following conditions: The sodium-ion battery was first formed, then charged at 40°C with a constant current of 0.01C to 3.5V, followed by a constant current charge of 0.2C to 4.0V, then charged at a constant voltage of 0.05C. After resting for 10 minutes, it was discharged at 30±0.5°C with a discharge rate of 0.1C to 2.0V. The 150-cycle capacity retention rate was calculated using the following formula:

[0061] 150-cycle capacity retention = discharge capacity after 150 cycles / initial discharge capacity × 100%.

[0062] Table 1

[0063]

[0064] As can be seen from Table 1, the sodium-ion battery cathode material in the embodiments, after being coated with MOFs-derived carbon nanotubes, is beneficial to the improvement of the material's performance, which is reflected in the decrease of pH, higher cathode material capacity, and better cycle performance.

[0065] Based on the disclosure in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for preparing a MOFs-derived carbon nanotube-coated sodium-ion battery cathode material, characterized in that: Includes the following steps: (1) Dissolve nitrogen-containing organic compounds in a solution to form a coating solution; The nitrogen-containing organic compound is one or more of urea, dopamine, polyacrylonitrile, melamine, pyridine, triethylamine, ethyleneimine, pyrrole, and biuret. (2) Add the sodium-ion battery cathode material to the coating solution, stir at 300-800 r / min for 0.5-8 h, filter, wash and dry to obtain the coating material; The sodium-ion battery cathode material is a layered metal oxide cathode material with the chemical formula Na. a TM b O2; where TM is one or more elements selected from Li, Ni, Mg, Cu, Mn, Zn, Co, Ca, Ba, Sr, Al, B, Cr, Zr, Ti, Sn, V, Mo, Ru, Nb, and Sb; a satisfies: 0.5 < a < 1.5; (3) Dissolve the organic acid in the solution to obtain an organic acid solution; (4) Disperse the metal salt in the solution to form a metal salt dispersion; (5) Place the coated material in a reactor, add organic acid solution and metal salt dispersion in sequence, stir at 30℃~100℃ and 300~800r / min for 10~60min, filter, wash and dry to obtain coated precursor cathode material; (6) The precursor cathode material is placed in a rotary furnace under a nitrogen atmosphere and heated to 650-1000°C at a heating rate of 1-5°C / min. The temperature is held for 1-4 hours and then cooled to room temperature to obtain MOFs-derived carbon nanotube-coated sodium-ion battery cathode material.

2. The method for preparing MOFs-derived carbon nanotube-coated sodium-ion battery cathode material according to claim 1, characterized in that: The solution includes one or more of methanol, ethanol, propanol, isopropanol, acetone, dimethylformamide, and dimethylacetamide.

3. The method for preparing MOFs-derived carbon nanotube-coated sodium-ion battery cathode material according to claim 1, characterized in that: In step (2), the particle size of the sodium-ion battery cathode material is 2μm to 20μm.

4. The method for preparing MOFs-derived carbon nanotube-coated sodium-ion battery cathode material according to claim 1, characterized in that: In step (2), the mass ratio of the sodium-ion battery cathode material, nitrogen-containing organic molecules, and solvent is 1:(0.005~0.4):(1~10), and the thickness of the coating layer in the coating material is 4~35nm.

5. The method for preparing MOFs-derived carbon nanotube-coated sodium-ion battery cathode material according to claim 1, characterized in that: In step (3), the concentration of the organic acid in the organic acid solution is 10-20 wt%, and the organic acid is one or more of 2,5-dihydroxyterephthalic acid, 5-hydroxyisophthalic acid, pyromellitic acid, 1,2,4,5-benzenetetracarboxylic acid, 2,2'-bipyridine-5,5'-dicarboxylic acid, and 2-aminoterephthalic acid.

6. The method for preparing MOFs-derived carbon nanotube-coated sodium-ion battery cathode material according to claim 1, characterized in that: In step (4), the concentration of the metal salt in the metal salt dispersion is 15-20 wt%, and the metal salt is one or more of cobalt acetate, cobalt nitrate, cobalt sulfate, nickel acetate, nickel nitrate, nickel sulfate, ferric nitrate, ferrocene, and ferric sulfate.

7. The method for preparing MOFs-derived carbon nanotube-coated sodium-ion battery cathode material according to claim 1, characterized in that: In step (5), the mass ratio of the coating material, the metal salt dispersion, and the organic acid solution is 100: 15-30: 15-25.

8. A MOF-derived carbon nanotube-coated cathode material for sodium-ion batteries, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 7.

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