CN115172724A - Sodium ferrous sulfate/carbon nano tube composite positive electrode material, preparation method and sodium ion battery - Google Patents

Abstract

The invention discloses a sodium ferrous sulfate/carbon nano tube composite anode material, a preparation method and a sodium ion battery, wherein the preparation method comprises the following steps: dispersing carbon nanotubes in deionized water, and performing ultrasonic treatment to form uniform carbon nanotube dispersion liquid; adding ferrous sulfate heptahydrate, anhydrous sodium sulfate and an antioxidant into deionized water, stirring uniformly, mixing with the carbon nano tube dispersion liquid, and performing ultrasonic treatment to obtain a mixed solution; and then carrying out spray drying treatment on the mixed solution to obtain a precursor, uniformly grinding the precursor, and then carrying out secondary calcination in an inert gas atmosphere to obtain the sodium ferrous sulfate/carbon nanotube composite cathode material. The sodium ferrous sulfate/carbon nano tube composite cathode material provided by the invention has excellent sodium storage capacity, excellent charge-discharge cycle stability and good rate performance, is simple in synthesis method, low in cost, convenient for industrial control and wide in market application prospect.

Description

Sodium ferrous sulfate/carbon nanotube composite cathode material, preparation method and sodium ion battery

technical field

The invention relates to the field of positive electrode materials for sodium ion batteries, in particular to a sodium ferrous sulfate/carbon nanotube composite positive electrode material, a preparation method and a sodium ion battery.

Background technique

As early as the 1970s, the research on sodium-ion batteries has been started, and the research on sodium-ion batteries is relatively slow due to the lack of suitable anodes. It was not until 2000 that it was discovered that hard carbon can be used as a negative electrode material for sodium electricity, which has almost the same reversible capacity as the graphite negative electrode of lithium ion battery, and this discovery has promoted the development of sodium ion battery. Since then, the scarcity of lithium resources has greatly restricted the development of fields such as electric vehicles and energy storage. Therefore, the development and search for a new energy storage system that can replace lithium is a hot spot that everyone pays attention to. Na-ion batteries have the advantages of abundant resources, low cost, wide distribution, and similar working principles to lithium-ion batteries, which have attracted people's attention and provide a new option for electrochemical energy storage. Research on sodium-ion batteries. In recent years, with the rapid development of mobile smart terminal equipment, especially flexible wearable devices, implantable medical devices, and wireless communication equipment, people have put forward higher requirements for energy storage batteries. Compared with the existing lithium-ion battery system, sodium-ion battery has more potential in large-scale energy storage, so its application prospect is very broad.

As a vital functional component of Na-ion batteries, Na-ion cathode materials play a key role in improving the performance of Na-ion batteries. The current mainstream cathode materials include transition metal oxides, polyanion compounds, organic cathode materials, and Prussian blue analogs. Among them, Na ₂ Fe(SO ₄ ) ₂ is considered to be one of the most promising cathode materials for large-scale applications in Na-ion batteries due to its high average voltage, high specific capacity, and ease of synthesis. However, due to its own electronic insulation, it affects the high-rate charge-discharge performance of the material, and its poor cycle stability limits its development and application.

Now, sulfate-based electrode materials have been used, because pure Na ₂ Fe(SO ₄ ) ₂ materials are not easy to prepare, and have low electronic conductivity and poor kinetic performance. Using spray drying method, Na ₂ Fe(SO ₄ ) ₂ /CNTs composites with higher specific capacity and better cycle stability were obtained by compounding with carbon nanotubes with good conductivity and ductility. chemical properties. It has good rate and cycle performance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems of the high-rate charge-discharge performance, poor cycle stability, low electronic conductivity and poor kinetic performance of the existing sodium-ion battery positive electrode material due to its own electronic insulation. A sodium ferrous sulfate/carbon nanotube composite positive electrode material, a preparation method and a sodium ion battery are proposed; the chemical formula of the positive electrode material for the sodium ion battery of the present invention is Na ₂ Fe(SO ₄ ) ₂ /CNTs. The particle size of the sodium ferrous sulfate/carbon nanotube composite cathode material particles is 2-10 μm. Due to the modification of doped carbon nanotubes, the hollow spherical structure does not collapse a lot when the composite is sintered.

In the composite cathode material of the structure provided by the present invention, Na ₂ Fe(SO ₄ ) ₂ is closely combined with carbon nanotubes, and carbon nanotubes form a good coating on Na ₂ Fe(SO ₄ ) ₂ , and the rate performance of the material is high. Has been greatly optimized.

The object of the present invention can be achieved through the following technical solutions: the preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material, the method comprises the following steps:

(1) disperse carbon nanotubes in deionized water, and ultrasonically treat for 30-90min;

(2) adding a certain proportion of ferrous sulfate heptahydrate, anhydrous sodium sulfate and antioxidant into deionized water, after stirring for 1-6h, mixing with the solution in step (1), and ultrasonically treating for 30-90min to obtain a mixed solution-1 ;

(3) spray-drying the mixed solution obtained in step (2) to obtain a precursor, grind the precursor for 5-10 min, and after the grinding is uniform, go through the first calcination and the second calcination in an inert gas atmosphere , to obtain sodium ferrous sulfate/carbon nanotube composite cathode material;

As a preferred embodiment of the present invention, the mass ratio of water and carbon nanotubes in step (1) is 800: (100-400);

As a preferred embodiment of the present invention, in step (2), the antioxidant is one or more of ascorbic acid, erythorbic acid, sodium erythorbate, tea polyphenols, and hydroquinone;

As a preferred embodiment of the present invention, in step (2), the molar ratio of ferrous sulfate heptahydrate, anhydrous sodium sulfate, antioxidant and deionized water is (1-2):(1-2):(0.0001 -0.001): 500, the mass fraction of carbon nanotubes in step (2) mixed solution one is 10-30% wt;

As a preferred embodiment of the present invention, in step (3), the inlet temperature of the spray drying is 120-190°C, the outlet temperature is 70-90°C, and the feeding rate is 200-800ml/h;

As a preferred embodiment of the present invention, in step (3), a crucible or a porcelain boat can be used for calcination, and the inert gas is nitrogen, argon or a mixture of hydrogen and argon;

As a preferred embodiment of the present invention, in step (3), the first calcination is heated to 110-200°C at a heating rate of 0.5-5°C/min, and the temperature is kept constant for 1-3h;

As a preferred embodiment of the present invention, in the second step calcination in step (3), the temperature is raised to 340-400°C at a heating rate of 0.5-5°C/min, and the temperature is kept constant for 12-36 hours.

The sodium ferrous sulfate/carbon nanotube composite positive electrode material includes a positive electrode sheet, the positive electrode sheet is prepared from a positive electrode material, a conductive additive, a binder and a solvent, and the positive electrode material is the above-prepared sodium ferrous sulfate/carbon nanometer Tube composite cathode material.

A sodium ion battery is composed of a positive electrode, a diaphragm, an electrolyte and a negative electrode metal sodium, and the positive electrode is the positive electrode sheet of the sodium ion battery described in the above technical solution.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention provides a sodium ferrous sulfate/carbon nanotube positive electrode material, its preparation method and application. After dissolving ferrous sulfate heptahydrate, anhydrous sodium sulfate and ascorbic acid in deionized water to form a mixed solution, adding The carbon nanotube dispersion solution is spray-dried to obtain a precursor, and the precursor is calcined twice in an inert gas atmosphere to obtain a sodium ferrous sulfate/carbon nanotube positive electrode material.

2. The carbon nanotubes of the present invention have good electrical conductivity. After being compounded with sodium ferrous sulfate, the conductivity of the sodium ferrous sulfate/carbon nanotube positive electrode material is greatly improved, including sodium ferrous sulfate/carbon nanotube materials. The rechargeable sodium (ion) battery exhibits high discharge specific capacity and good cycle performance.

3. The synthesis method of the invention is simple, low in cost, convenient for industrial control, and has broad market application prospects.

Description of drawings

In order to facilitate the understanding of those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

Fig. 1 is the X-ray diffraction pattern of the sodium ferrous sulfate/carbon nanotube composite material prepared in Example 1;

Fig. 2 is the scanning electron microscope (SEM) picture of the sodium ferrous sulfate/carbon nanotube composite material prepared in Example 1;

Fig. 3 is the sodium battery rate performance diagram of the sodium ferrous sulfate/carbon nanotube composite material prepared in Example 2;

Fig. 4 is the charge-discharge curve diagram of the sodium ferrous sulfate/carbon nanotube composite material prepared in Example 2 at 0.2C;

Fig. 5 is the charge-discharge curve diagram of the sodium ferrous sulfate/carbon nanotube composite prepared in Example 3 at 0.2C;

Fig. 6 is the charge-discharge curve diagram of the sodium ferrous sulfate/carbon nanotube composite material prepared in Example 3 at 0.5C;

7 is a charge-discharge curve diagram of the sodium ferrous sulfate/carbon nanotube composite prepared in Example 3 at 1C;

8 is a charge-discharge curve diagram of the sodium ferrous sulfate/carbon nanotube composite prepared in Example 3 at 0.1C.

Detailed ways

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

Example 1:

This embodiment includes the following steps:

Preparation of sodium ferrous sulfate/carbon nanotube composite cathode material:

(1) Disperse 2g of carbon nanotubes into 100mL of deionized water, and under the action of ultrasonic waves, ultrasonicate for 40min to form a stable carbon nanotube dispersion liquid A;

(2) 10g of ferrous sulfate heptahydrate, 5g of anhydrous sodium sulfate, 0.1g of ascorbic acid were dissolved in 100ml of deionized water, and stirred for 5h to prepare salt solution B;

(3) mixing dispersion liquid A and salt solution B, ultrasonic 60min to obtain mixed solution C;

(4) the mixed solution C is spray-dried by a spray dryer, the inlet temperature is set to 160 °C, the outlet temperature is 70 °C, the solution is kept in a stirring state, and the feeding speed is set to be 400ml/h to obtain the precursor material;

(5) Grind the precursor material for 5 minutes, transfer the material to a porcelain boat, place it in an argon atmosphere tube furnace, raise the temperature to 130°C at a heating rate of 2°C/min, keep it for 2 hours, and then heat it at 1°C/min. The heating rate of min was heated to 130 °C, and calcined for 24 h to obtain sodium ferrous sulfate/carbon nanotube composite cathode material;

Preparation of sodium ion battery: The sodium ferrous sulfate/carbon nanotube composite material, SuperP, and PVDF were dispersed and stirred at a high speed at a mass ratio of 7:2:1 for 2 hours to prepare a conductive slurry;

Figure 1 shows the XRD pattern of the target product obtained in Example 1 and the standard card PDF#21-1360 of Na2Fe(SO4)2. It can be seen from the figure that the main component of the material is Na2Fe(SO4)2, and the crystallinity is good.

Figure 2 shows the SEM picture of the target product obtained in Example 1, and it can be seen from the figure that the target product is mainly composed of hollow spherical particles.

Example 2:

This embodiment includes the following steps:

(1) Disperse 3g of carbon nanotubes into 100mL of deionized water, and under the action of ultrasonic waves, ultrasonicate for 40 minutes to form a stable carbon nanotube dispersion liquid A;

(2) 10g of ferrous sulfate heptahydrate, 5g of anhydrous sodium sulfate, 0.1g of ascorbic acid were dissolved in 100ml of deionized water, and stirred for 5h to prepare salt solution B;

(3) mixing dispersion liquid A and salt solution B, ultrasonic 60min to obtain mixed solution C;

(4) the mixed solution C is spray-dried by a spray dryer, the inlet temperature is set to 160 °C, the outlet temperature is 70 °C, the solution is kept in a stirring state, and the feeding speed is set to 400ml/h to obtain the precursor material;

(5) Grind the precursor material for 5 minutes, transfer the material to a porcelain boat, place it in an argon atmosphere tube furnace, raise the temperature to 130°C at a heating rate of 2°C/min, keep it for 2 hours, and then heat it at 1°C/min. The temperature was increased to 130 °C at a heating rate of min, and calcined for 24 h to obtain a sodium ferrous sulfate/carbon nanotube composite cathode material.

Preparation of sodium ion battery: The sodium ferrous sulfate/carbon nanotube composite material, SuperP, and PVDF were dispersed and stirred at a high speed at a mass ratio of 7:2:1 for 2 hours to prepare a conductive slurry.

Figure 3 shows the battery rate performance diagram of the target product obtained in Example 2. The rates were tested in sequence at 0.1C, 0.2C, 0.5C, 1C, 2C, and 0.1C, and the discharge capacity at 0.1C was 74mAh. g ^-1 , the discharge capacity at 0.2C is 71mAh g ^-1 , the discharge capacity at 0.5C is 67mAh g ^-1 , the discharge capacity at 1C is 64mAh g ^-1 , the discharge capacity at 2C is 59mAh g-1 g ^-1 , the discharge capacity when returned to 0.1C is 74mAh g ^-1 , with good stability.

Figure 4 shows the long-term charge-discharge cycle diagram of the battery of the target product obtained in Example 2 at 0.2C, the cycle number is 100 cycles, the discharge capacity at 0.2C is 71mAh g ^-1 , the Coulomb efficiency is 98%, and the Good stability.

Example 3:

This embodiment includes the following steps:

(1) Disperse 2g of carbon nanotubes into 100mL of deionized water, and under the action of ultrasonic waves, ultrasonicate for 40min to form a stable carbon nanotube dispersion liquid A;

(2) 10g of ferrous sulfate heptahydrate, 5g of anhydrous sodium sulfate, 0.1g of ascorbic acid were dissolved in 100ml of deionized water, and stirred for 5h to prepare salt solution B;

(3) mixing dispersion liquid A and salt solution B, ultrasonic 60min to obtain mixed solution C;

(4) the mixed solution C is spray-dried by a spray dryer, the inlet temperature is set to 170°C, the outlet temperature is 60°C, the solution is kept in a stirring state, and the feeding speed is set to 400ml/h to obtain the precursor material;

(5) Grind the precursor material for 5 minutes, transfer the material to a porcelain boat, place it in an argon atmosphere tube furnace, raise the temperature to 130°C at a heating rate of 2°C/min, keep it for 2 hours, and then heat it at 1°C/min. The temperature was increased to 130 °C at a heating rate of min, and calcined for 24 h to obtain a sodium ferrous sulfate/carbon nanotube composite cathode material.

Preparation of sodium ion battery: The sodium ferrous sulfate/carbon nanotube composite material, SuperP, and PVDF were dispersed and stirred at a high speed at a mass ratio of 7:2:1 for 2 hours to prepare a conductive slurry.

Figures 5, 6, 7, and 8 show the capacity-voltage curves of the target product battery obtained in Example 3 at different rates of 0.2C, 0.5C, 1C, and 0.1C, respectively.

The above-disclosed preferred embodiments of the present invention are provided only to help illustrate the present invention. The preferred embodiments do not describe all the details and do not limit the invention to specific embodiments only. Obviously, many modifications and variations are possible in light of the contents of this specification. These embodiments are selected and described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is to be limited only by the claims and their full scope and equivalents.

Claims (10)

1. the preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material, is characterized in that, the method comprises the following steps: Step 1: Disperse certain carbon nanotubes in deionized water to form a uniform dispersion under ultrasonic treatment; Step 2: add a certain proportion of ferrous sulfate heptahydrate, anhydrous sodium sulfate and antioxidant into deionized water, stir for 1-6h, mix with the dispersion in step 1, and ultrasonically treat for 30-90min to obtain mixed solution 1; Step 3: The mixed solution 1 obtained in step 2 is spray-dried to obtain a precursor, and the precursor is ground for 5-10 minutes. After the grinding is uniform, the first calcination and the second calcination are carried out in an inert gas atmosphere to obtain Sodium ferrous sulfate/carbon nanotube composite cathode material. 2. The preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1, wherein the mass ratio of water and carbon nanotubes in the step 1 is 800:(100-400). 3. the preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1, is characterized in that, in described step 2, antioxidant is ascorbic acid, erythorbic acid, sodium erythorbate, tea polyphenol, para One or more of the diphenols. 4. the preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1, is characterized in that, in described step 2, heptahydrate ferrous sulfate, anhydrous sodium sulfate, antioxidant and deionized water The molar ratio is (1-2): (1-2): (0.0001-0.001): 500; the mass fraction of carbon nanotubes in mixed solution one is 10-30% wt. 5. the preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1, is characterized in that, in described step 3, the inlet temperature of spray drying is 120-190 ℃, and the outlet temperature is 70-90 ℃ , the feed rate is 200-800ml/h. 6 . The method for preparing a sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1 , wherein the inert gas is nitrogen, argon or a hydrogen-argon mixture. 7 . 7. The preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1, wherein the first calcination is heated to 110-200 ℃ with a heating rate of 0.5-5 ℃/min , constant temperature 1-3h. 8. The preparation method of sodium ferrous sulfate/carbon nanotube composite positive electrode material according to claim 1, characterized in that, the first calcination is heated to 340-400 ℃ with a heating rate of 0.5-5 ℃/min , constant temperature 12-36h. 9. Sodium ferrous sulfate/carbon nanotube composite positive electrode material, characterized in that, the chemical formula of the composite positive electrode material is Na ₂ Fe(SO ₄ ) ₂ /CNTs, which is described in any one of claims 1-8 The preparation method of sodium ferrous sulfate/carbon nanotube composite cathode material is prepared. 10. A sodium-ion battery, comprising positive electrode sheet, diaphragm, electrolyte and negative metal sodium; it is characterized in that, described positive electrode sheet is made of sodium ferrous sulfate/carbon nanometer according to any one of claims 1-8 The preparation method of tube composite positive electrode material is prepared from the composite positive electrode material, conductive additive, binder and solvent prepared.

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