Composite flexible electrode material and preparation method thereof

Abstract

The invention belongs to the field of electrochemistry, and particularly relates to a composite flexible electrode material and a preparation method thereof.The preparation method comprises the steps that a carbon nano tube is subjected to sulfonic acid modification, sulfur-containing groups are added to the surface of the carbon nano tube, and a sulfur-containing carbon nano tube is obtained; then carrying out manganese modification by using potassium permanganate to obtain a modified carbon nanotube; mixing a copper salt and a manganese salt to prepare a manganese-based oxide; carrying out acid treatment on the manganese-based oxide to obtain an acidified oxide; mixing the acidified oxide with the modified carbon nanotube, adding dilute ammonia water for full reaction, and then performing heat treatment; and the composite flexible electrode material is obtained after film formation. The composite flexible electrode material is good in flexibility, high in specific capacity and good in cycling stability.

Description

Technical Field

[0001] The present invention belongs to the field of electrochemistry, and particularly relates to a composite flexible electrode material and a preparation method thereof. Background Art

[0002] The iterative update of wearable electronic products has promoted the rapid development of flexible energy storage devices. Among them, flexible supercapacitors and flexible aqueous zinc-ion batteries have broad application prospects in the energy storage of wearable electronic products. Aqueous zinc-ion batteries (ZIBs) store energy in the form of multivalent state changes in aqueous electrolytes, and have the characteristics of large energy density, high safety, simple manufacturing, and low cost. They are a type of high-performance rechargeable battery that has been studied extensively in the past decade. However, for high-energy-density flexible energy storage devices, preparing flexible electrode materials with high capacity and long working life is the key to manufacturing flexible energy storage and conversion devices. At present, there are still some challenges in preparing flexible electrode materials with high capacity and excellent electrochemical performance, such as low loading of active materials, slow ion diffusion caused by material accumulation, and complex and harsh conditions for preparing flexible electrodes, which severely limit the practical development of flexible electrodes. Composite with flexible conductive substrate materials such as carbon nanotubes and graphene can enhance conductivity, improve the flexibility and cycle stability of the battery. However, there are strong van der Waals forces between carbon nanotubes, and they have a high aspect ratio, resulting in easy agglomeration or entanglement of carbon nanotubes, increasing the difficulty of dispersion and affecting their electrochemical performance. Summary of the Invention

[0003] To solve the problems of low loading of active materials, easy agglomeration of carbon nanotube conductive substrates, and easy material accumulation in the prior art, the present invention mainly provides a composite flexible electrode material with good dispersibility, uniform dispersion of carbon nanotubes and manganese dioxide, and high loading. The technical solution is as follows: A preparation method of a composite flexible electrode material, comprising the following steps: sulfonic acid modification of carbon nanotubes to increase sulfur-containing groups on their surfaces to obtain sulfur-containing carbon nanotubes; then manganese modification using potassium permanganate to obtain modified carbon nanotubes; mixing copper salts and manganese salts to prepare manganese-based oxides; acid treatment of the manganese-based oxides to obtain acidified oxides; mixing the acidified oxides and the modified carbon nanotubes, reacting with dilute ammonia water, and then heat treatment; after film formation, a composite flexible electrode material is obtained.

[0004] Further, the mass ratio of potassium permanganate to sulfur-containing carbon nanotubes is 1:2 - 6; the mass ratio of acidified oxides to modified carbon nanotubes is 0.2 - 1:1.

[0005] Further, the copper salts and manganese salts are one or more of acetates, oxalates, and formates; the molar ratio of copper salts to manganese salts is 1:3 - 6.

[0006] Further, it includes the following steps: a. Prepare sulfur-containing carbon nanotubes; configure a potassium permanganate solution, then add the sulfur-containing carbon nanotubes to the potassium permanganate solution, react at 30-55 °C for 1-2 h, separate and collect the precipitate, wash and dry it to obtain modified carbon nanotubes; b. Mix copper salt and manganese salt to prepare manganese-based oxide; disperse the manganese-based oxide in a dilute hydrochloric acid solution, then soak for 2-6 h, collect the precipitate, and wash it with dilute hydrochloric acid multiple times to obtain acidified oxide; c. Grind the acidified oxide and the modified carbon nanotubes and place them in water, mix and disperse, stir at a low speed for 0.5-2 h; dropwise add dilute ammonia water to adjust the system to neutral, continue to stir at a low speed for 0.5-1 h, then heat up to the system boiling slightly, keep it for 20-40 min, add a binder during the boiling process, stop heating, mix evenly, and then form a film physically to obtain a composite flexible electrode material.

[0007] Further, disperse the carbon nanotubes in dichloromethane, then add chlorosulfonic acid, stir and react at 0-10 °C for 1.5-2.5 h, then stir at room temperature until the system reaches room temperature, and continue to stir for 0.5-1 h; separate and collect the precipitate, wash and dry it to obtain sulfur-containing carbon nanotubes.

[0008] Further, the mass ratio of the carbon nanotubes to chlorosulfonic acid is 1:0.2-1.

[0009] Further, place copper salt, manganese salt and potassium nitrate in water, slowly dropwise add ammonia water until the system is clear, mix and evaporate to dryness, then calcine at 700-850 °C for 8-16 h to obtain manganese-based oxide.

[0010] Further, the molar ratio of the manganese salt to potassium nitrate is 1:0.5-1.2.

[0011] Further, the speed of the low-speed stirring in step c is 100-200 rpm; the binder in step c is polyvinylidene fluoride or carboxymethyl cellulose.

[0012] A composite flexible electrode material prepared by the above method.

[0013] Adopting the above scheme, the method of the present invention has the following advantages: 1. The carbon nanotubes and the active material of the composite flexible electrode of the present invention have good dispersibility. The manganese-based oxide active material is nanoscale, with uniform size, high specific surface area, many active sites, and is tightly connected with the carbon nanotubes, and has good electrochemical performance.

[0014] 2. In the present invention, manganese dioxide is directly generated on carbon nanotubes by potassium permanganate, which can not only improve the conductivity of the material, but also protect manganese dioxide, alleviate the direct contact between the electrolyte and the active material, and provide manganese dioxide materials with various exposure degrees by the manganese-based oxide, thereby improving the cycle stability of the electrode.

[0015] 3. In the present invention, sulfonic acid groups are introduced onto the carbon nanotubes to increase the hydrophilicity of the carbon nanotubes, thereby improving their dispersibility and adsorption in the reaction system, increasing pores, improving the binding stability between the carbon nanotubes and the active material, and the multiple lone pairs of electrons of sulfur atoms make their introduction conducive to improving the conductivity and capacity of the material.

[0016] 4. The sulfonic acid groups introduced onto the carbon nanotubes of the present invention produce complexation and electrostatic interactions with partially ionized copper ions in the manganese-based oxide under the action of ammonia water, forming an electrostatic attraction with the manganese-based oxide, thereby promoting the dispersion and combination of the carbon nanotubes and the manganese-based oxide and reducing the agglomeration of raw materials.

[0017] 5. The present invention uses easily removable ammonia water to react with the acidified manganese-based oxide, reacts with the hydrogen ions in the manganese-based oxide, and then removes ammonia by heat treatment to promote the particle refinement of the manganese-based oxide and improve the specific surface area and active sites of the manganese-based oxide.

[0018] 6. Copper is doped into the manganese-based oxide in the present invention. Part of the copper is removed from the structure under the action of ammonia water and sulfonic acid, promoting the nanosizing of the manganese-based oxide, while the copper atoms remaining in the structure can increase the number of active sites, improve the ion transfer / electron transfer efficiency, reduce the energy band of manganese dioxide, enhance the conductivity, and improve the capacitance performance of the material.

[0019] 7. The preparation method of the present invention is simple, the raw materials are easy to obtain, and the active substances in the prepared cathode material have good dispersibility, good flexibility, high specific capacity, and good cycle performance. Description of the Drawings

[0020] Figure 1 is the scanning electron microscope image of Example 1; Figure 2 is the specific capacity curve of the long-cycle charge and discharge of the battery prepared from the electrode material of Example 1 at a current density of 2 A·g -1 current density; Figure 3 is the specific capacity curve of the long-cycle charge and discharge of the battery prepared from the electrode material of Example 2 at a current density of 2 A·g -1 current density; Figure 4 is the specific capacity curve of the long-cycle charge and discharge of the battery prepared from the electrode material of Comparative Example 1 at a current density of 2 A·g -1 current density; Figure 5 is the specific capacity curve of the battery prepared with the electrode material of Comparative Example 2 during long - cycle charge - discharge at a current density of 2 A·g -1 current density. Detailed implementation manners

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0022] Example 1: (1) 1 g of carbon nanotubes was fully dispersed in dichloromethane, then 0.6 g of chlorosulfonic acid was added, and the mixture was stirred at 5 °C for 2 h, then stirred at room temperature until the system reached room temperature, and continued to stir for 1 h; the precipitate was separated and collected, washed thoroughly and dried to obtain sulfur - containing carbon nanotubes; 250 mg of potassium permanganate was used to prepare a potassium permanganate solution, and then 1 g of sulfur - containing carbon nanotubes was added to the potassium permanganate solution, and the reaction was carried out at 45 °C for 1.5 h, the precipitate was separated and collected, washed thoroughly and dried to obtain modified carbon nanotubes; (2) 0.5 g of copper oxalate, 2 g of manganese oxalate and 1.2 g of potassium nitrate were placed in water, and ammonia water was slowly added dropwise until the system was clear, and after thorough mixing, it was evaporated to dryness; then it was calcined at 750 °C for 12 h to obtain a manganese - based oxide; the manganese - based oxide was fully dispersed in a 0.5 mol / L dilute hydrochloric acid solution, then soaked for 4 h, the precipitate was collected, and after being washed with dilute hydrochloric acid multiple times, an acidified oxide was obtained; (3) 0.6 g of the acidified oxide was ground and placed in water with 1 g of modified carbon nanotubes, and they were thoroughly mixed and dispersed, and stirred at a speed of 150 rpm for 1 h; dilute ammonia water was added dropwise to adjust the system to neutrality, and continued to stir for 0.5 - 1 h, then the temperature was raised to make the system slightly boiling, and maintained for 30 min; during the boiling process, 20 mL of 10% (w / w) polyvinylidene fluoride solution was added, and after adding, the heating was stopped and mixed evenly to obtain a mixed solution; (4) A 40 cm 2 dust - free filter cloth was placed in the funnel, ensuring that it completely fit the funnel wall without bubbles. Slowly pour 50 mL of the mixed solution into the funnel, turn on the pump for suction filtration, filter the mixed solution onto the dust - free filter cloth, and after drying, the formed film was removed from the dust - free filter cloth to obtain a composite flexible electrode material.

[0023] The obtained sample was characterized, and the scanning electron microscope photograph as Figure 1 shown was obtained. It can be seen from the figure that the active particles are evenly distributed among the carbon nanotubes, and the particle size is extremely small, all being nanoparticles.

[0024] The obtained electrode material has excellent flexibility and can be bent well, even folded in half.

[0025] Example 2: (1) 1 g of carbon nanotubes was fully dispersed in dichloromethane, then 0.6 g of chlorosulfonic acid was added, and the mixture was stirred at 5 °C for 2 h, then stirred at room temperature until the system reached room temperature, and continued to stir for 1 h; the precipitate was separated and collected, washed thoroughly and dried to obtain sulfur-containing carbon nanotubes; 170 mg of potassium permanganate was taken to prepare a potassium permanganate solution, then 1 g of sulfur-containing carbon nanotubes was added to the potassium permanganate solution, and the reaction was carried out at 45 °C for 1.5 h, the precipitate was separated and collected, washed thoroughly and dried to obtain modified carbon nanotubes; (2) 0.5 g of copper oxalate and 2 g of manganese oxalate were placed in water with 1.2 g of potassium nitrate, and ammonia water was slowly added dropwise until the system was clear, and after thorough mixing, it was evaporated to dryness; then it was calcined at 800 °C for 8 h to obtain a manganese-based oxide; the manganese-based oxide was fully dispersed in a 0.5 mol / L dilute hydrochloric acid solution, then soaked for 2 h, the precipitate was collected, and after washing with dilute hydrochloric acid multiple times, an acidified oxide was obtained; (3) 0.6 g of the acidified oxide was ground and placed in water with 0.6 g of modified carbon nanotubes, and after thorough mixing and dispersion, it was stirred at a speed of 150 rpm for 1 h; dilute ammonia water was added dropwise to adjust the system to neutral, and continued to stir for 0.5 - 1 h, then the temperature was raised to the system's gentle boil and maintained for 30 min; during the boiling process, 20 mL of a 10% (w / w) polyvinylidene fluoride solution was added, and after adding, heating was stopped and mixed evenly to obtain a mixed solution; (4) Cut a 40 cm 2 dust-free filter cloth was placed in the funnel, ensuring that it completely adhered to the funnel wall without air bubbles, and 50 mL of the mixed solution was slowly poured into the funnel, the pump was turned on for suction filtration, the mixed solution was filtered onto the dust-free filter cloth, and after drying, the formed film was removed from the dust-free filter cloth to obtain a composite flexible electrode material.

[0026] Example 3: (1) 1 g of carbon nanotubes was fully dispersed in dichloromethane, then 0.6 g of chlorosulfonic acid was added, and the mixture was stirred at 5 °C for 2 h, then stirred at room temperature until the system reached room temperature, and continued to stir for 1 h; the precipitate was separated and collected, washed thoroughly and dried to obtain sulfur-containing carbon nanotubes; 450 mg of potassium permanganate was taken to prepare a potassium permanganate solution, then 1 g of sulfur-containing carbon nanotubes was added to the potassium permanganate solution, and the reaction was carried out at 55 °C for 1 h, the precipitate was separated and collected, washed thoroughly and dried to obtain modified carbon nanotubes; (2) 0.5 g of copper oxalate and 2 g of manganese oxalate were placed in water with 1.2 g of potassium nitrate, and ammonia water was slowly added dropwise until the system was clear, and after thorough mixing, it was evaporated to dryness; then it was calcined at 750 °C for 12 h to obtain a manganese-based oxide; the manganese-based oxide was fully dispersed in a 0.5 mol / L dilute hydrochloric acid solution, then soaked for 6 h, the precipitate was collected, and after washing with dilute hydrochloric acid multiple times, an acidified oxide was obtained; (3) Grind 0.6 g of the acidified oxide and place it in water with 1.5 g of the modified carbon nanotubes, mix and disperse them thoroughly, and stir at 150 rpm for 1 h; add dilute ammonia water to adjust the system to neutrality, continue stirring for 0.5-1 h, and then heat the system to a slight boil and maintain it for 30 min; add 20 mL of 10% (w / w) polyvinylidene fluoride solution during the boiling process, stop heating after adding, and mix well to obtain a mixed solution; (4) Cut 40 cm 2 Place the dust-free filter cloth in the funnel, making sure it fits the funnel wall completely without bubbles, slowly pour 50 mL of the mixed solution into the funnel, turn on the pump to filter, filter the mixed solution onto the dust-free filter cloth, and remove the formed film from the dust-free filter cloth after drying to obtain a composite flexible electrode material.

[0027] Comparative Example 1: The difference from Example 1 is: (1) Disperse 1 g of carbon nanotubes in dichloromethane, then add 0.6 g of chlorosulfonic acid, stir and react at 5°C for 2 h, then stir at room temperature until the system reaches room temperature, and continue stirring for 1 h; separate and collect the precipitate, wash it thoroughly and dry it to obtain modified carbon nanotubes.

[0028] Comparative Example 2: The difference from Example 1 is: (1) Take 250 mg of potassium permanganate to prepare a potassium permanganate solution, then add 1 g of carbon nanotubes to the potassium permanganate solution, react at 30-55°C for 1-2 h, separate and collect the precipitate, wash it thoroughly and dry it to obtain modified carbon nanotubes.

[0029] Comparative Example 3: The difference from Example 1 is: (2) 0.5 g of copper oxalate, 2 g of manganese oxalate and 1.2 g of potassium nitrate were placed in water, and aqueous ammonia was slowly added until the system was clear. After thorough mixing, the mixture was evaporated to dryness. The mixture was then calcined at 750 °C for 12 h to obtain a manganese-based oxide. (3) Grind 0.6 g of manganese-based oxide and place it in water with 1 g of modified carbon nanotubes, mix and disperse them thoroughly, and stir at 100-200 rpm for 0.5-2 h. Then, heat the system until it is slightly boiling, add 20 mL of 10% (w / w) polyvinylidene fluoride solution, stop heating after adding, and mix well to obtain a mixed solution.

[0030] The active substance of the composite flexible electrode material prepared in Comparative Example 3 has poor affinity with the modified carbon nanotubes, low dispersion, and relatively large particles of manganese-based oxide, which are only micron particles.

[0031] Electrochemical performance test: Using the flexible cathode materials prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 as the cathode, a zinc sheet as the anode, 1M aqueous zinc sulfate solution as the electrolyte, and a glass fiber separator as the separator, a button-type zinc-ion battery was assembled. The button-type zinc-ion battery was tested for the specific capacity of long-cycle charge and discharge at a current density of 2 A / g in the voltage range of 1.0 - 1.8 V for 300 cycles to evaluate the electrochemical performance of the electrode materials of the present invention. The test results are as Figures 2 to 5 shown.

[0032] It can be Figure 2 seen that at high current, the initial discharge specific capacity of the electrode material of Example 1 of the present invention is about 80 mAh / g. At 300 cycles, the discharge specific capacity exceeds 100 mAh / g, higher than the initial value. After 400 cycles, it can still maintain a specific capacity of nearly 80 mAh / g, with a high capacity retention rate, indicating that the electrode material prepared by the present invention has excellent cycle performance. Although there is a relatively obvious decline after 300 cycles, and during the cycling process, the highest discharge specific capacity can reach 200 mAh / g, indicating that the electrode material of the present invention has many active sites and good capacity potential.

[0033] The amount of potassium permanganate added in Example 2 is less, and the content of modified carbon nanotubes is also reduced. The cycle test results of Example 2 are as Figure 3 shown. Comparing Figure 2 and Figure 3 it can be seen that the initial discharge specific capacity of Comparative Example 1 exceeds 100 mAh / g, but it can only reach about 80 mAh / g after 300 cycles, and the capacity retention ability is inferior to that of Example 1.

[0034] The cycle test results of Comparative Example 1 without directly generating manganese dioxide on the carbon nanotubes are as Figure 4 shown. It can be seen from the figure that after 200 cycles, the specific capacity of the sample shows a cliff-like decline, indicating that directly generating manganese dioxide on the carbon nanotubes has an obvious impact on the cycle stability of the battery and the capacity retention ability in the later stage of cycling.

[0035] The cycle test results of Comparative Example 2 without sulfonic acid modification are as Figure 5 shown. It can be seen from the figure that the Coulomb efficiency of the sample in Comparative Example 2 fluctuates greatly, and the Coulomb efficiency is low, with a large charge and discharge energy loss and a low charge transfer efficiency, and the activity of the electrode material decreases rapidly, indicating that the step of sulfonic acid modification is beneficial to promoting the full contact between carbon nanotubes and manganese-based oxides, reducing the accumulation of materials, and has an obvious improvement effect on the performance of the electrode material.

[0036] Those skilled in the art can make various corresponding changes and deformations according to the technical solutions and concepts described above, and all such changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a composite flexible electrode material, characterized in that, It includes the following steps: Sulfonate-modify the carbon nanotubes to increase sulfur-containing groups on their surfaces, obtaining sulfur-containing carbon nanotubes; then use potassium permanganate for manganese modification to obtain modified carbon nanotubes; Mix copper salts and manganese salts to prepare manganese-based oxides; subject the manganese-based oxides to acid treatment to obtain acidified oxides; mix the acidified oxides with the modified carbon nanotubes, add dilute ammonia water to react, and then perform heat treatment; after film formation, a composite flexible electrode material is obtained.

2. The preparation method of the composite flexible electrode material according to claim 1, wherein The mass ratio of the potassium permanganate to the sulfur-containing carbon nanotubes is 1:2 - 6; the mass ratio of the acidified oxides to the modified carbon nanotubes is 0.2 - 1:

1.

3. The preparation method of the composite flexible electrode material according to claim 1, wherein The copper salts and manganese salts are one or several of acetate, oxalate, formate; the molar ratio of the copper salts to the manganese salts is 1:3 - 6.

4. The preparation method of the composite flexible electrode material according to claim 3, characterized in that, It includes the following steps: a. Prepare sulfur-containing carbon nanotubes; Prepare a potassium permanganate solution, then add the sulfur-containing carbon nanotubes to the potassium permanganate solution, react at 30 - 55 °C for 1 - 2 h, separate and collect the precipitate, wash and dry it to obtain modified carbon nanotubes; b. Mix copper salts and manganese salts to prepare manganese-based oxides; disperse the manganese-based oxides in a dilute hydrochloric acid solution, then soak for 2 - 6 h, collect the precipitate, and wash it with dilute hydrochloric acid multiple times to obtain acidified oxides; c. Grind the acidified oxides and mix them with the modified carbon nanotubes in water, disperse and mix, stir at a low speed for 0.5 - 2 h; add dilute ammonia water to adjust the system to neutral, continue to stir at a low speed for 0.5 - 1 h, then raise the temperature to the system's gentle boil, maintain for 20 - 40 min, add a binder during the boiling process, stop heating, mix evenly, and then form a film physically to obtain a composite flexible electrode material.

5. The preparation method of the composite flexible electrode material according to claim 1 or 4, characterized in that, Disperse the carbon nanotubes in dichloromethane, then add chlorosulfonic acid, stir and react at 0 - 10 °C for 1.5 - 2.5 h, then stir at room temperature until the system reaches room temperature, continue to stir for 0.5 - 1 h; separate and collect the precipitate, wash and dry it to obtain sulfur-containing carbon nanotubes.

6. The preparation method of the composite flexible electrode material according to claim 5, characterized in that, The mass ratio of the carbon nanotubes to the chlorosulfonic acid is 1:0.2 - 1.

7. The preparation method of the composite flexible electrode material according to claim 4, characterized in that, Put the copper salts, manganese salts and potassium nitrate in water, add ammonia water dropwise until the system is clear, mix and evaporate to dryness, and then calcine at 700 - 850 °C for 8 - 16 h to prepare manganese-based oxides.

8. The preparation method of the composite flexible electrode material according to claim 7, characterized in that, The molar ratio of the manganese salts to the potassium nitrate is 1:0.5 - 1.

2.

9. The preparation method of the composite flexible electrode material according to claim 8, wherein The speed of the low-speed stirring in step c is 100 - 200 rpm; the binder in step c is polyvinylidene fluoride or carboxymethyl cellulose.

10. A composite flexible electrode material prepared by the method according to claim 1.

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