Preparation process of nickel cobaltate carbon aerogel electrode material

Abstract

The invention relates to the technical field of supercapacitors, and discloses a preparation process of a nickel cobaltate carbon aerogel electrode material, which comprises the following steps: adding cobalt nitrate, nickel nitrate and modified phenolic aerogel into water, stirring for adsorption, then adding urea and ethylene glycol, reacting, and finally calcining at high temperature to obtain the nickel cobaltate carbon aerogel electrode material. After the nickel cobaltate particles are coated with the carbon aerogel, the nickel cobaltate particles are not prone to volume expansion and deformation in the charging and discharging process, good structural stability can be kept, the phenomena of pulverization, falling and the like of the active electrode material are inhibited, the electrode material still has high specific capacitance after multiple times of circulation, and the specific capacitance of the electrode material is improved. And excellent cycling stability is shown. The modified phenolic aerogel disclosed by the invention contains a thiazole structure, and nitrogen-sulfur co-doped carbon aerogel is formed during high-temperature calcination, so that the electrochemical performance and the specific capacitance of a carbon aerogel electrode material are favorably improved.

Description

Technical Field

[0001] The invention relates to the technical field of supercapacitors, and in particular to a preparation process of a nickel cobaltate carbon aerogel electrode material. Background Art

[0002] In recent years, the development of new electrochemical energy storage devices has been a research hotspot. Among them, supercapacitors have higher power density, energy density, charge and discharge speed and cycle life compared to traditional capacitors, and are a very promising energy storage device.

[0003] Nickel cobalt oxide is a metal composite oxide with mixed valence and multiple active centers, which can produce higher pseudocapacitance and has been widely studied and applied in supercapacitor electrode materials. However, nickel cobalt oxide is prone to volume expansion during long-term charging and discharging, resulting in poor structural stability of the electrode material, and prone to powdering and active material shedding. This leads to poor cycle stability of the electrode material.

[0004] Carbon aerogel has the advantages of large pore volume and high conductivity. It can be compounded with transition metal oxides to make electrode active materials and is widely used in electrode materials such as supercapacitors. Common carbon aerogel precursors include phenolic aerogel, sodium alginate aerogel, cellulose aerogel, etc. Introducing heteroatoms such as nitrogen, phosphorus, and sulfur into the carbon aerogel matrix can improve its wettability, conductivity, and pseudocapacitance effect. Summary of the invention

[0005] Technical problem to be solved: The present invention provides a nickel cobalt oxide carbon aerogel electrode material with high specific capacitance and cycle stability and a preparation process.

[0006] Technical solution: A preparation process of nickel cobalt oxide carbon aerogel electrode material, comprising the following steps: Step A, add resorcinol, 5-(imino-6-hydroxybenzothiazole)resorcinol and water into a reaction container, stir, add formaldehyde aqueous solution and sodium carbonate, seal the reaction container, react at 40-50° C. for 24-36 hours, then react at 80-90° C. for 72-84 hours, place the generated gel product in acetone for 48 hours, change the acetone every 12 hours, filter and dry to obtain modified phenolic aerogel.

[0007] Step B, add water, cobalt nitrate and nickel nitrate into a container, add modified phenolic aerogel after stirring, stir and adsorb at 20-35°C for 3-6h, then add urea and ethylene glycol, pour the solution into a hydrothermal reactor, react at 110-125°C for 12-18h, filter and wash with water and ethanol in turn, dry and place the product in a resistance furnace for calcination to obtain nickel cobaltate carbon aerogel electrode material.

[0008] Among them, in step A, the ratio of resorcinol, 5-(imino-6-hydroxybenzothiazole)resorcinol, formaldehyde and sodium carbonate is (0.6-0.8) mol: (0.2-0.4) mol: (4.2-5.4) mol: (0.003-0.005) mol.

[0009] Wherein, the ratio of cobalt nitrate, nickel nitrate, modified phenolic aldehyde aerosol and urea in step B is (30-60mmol): (15-30)mmol: (90-220)mmol: 1g.

[0010] In step B, the calcination is first carried out in an air atmosphere, the temperature is raised to 240-280° C., and the calcination is carried out for 4-7 hours; then in a nitrogen atmosphere, the temperature is raised to 950-1100° C., and the calcination is carried out for 4-6 hours.

[0011] Among them, the preparation method of 5-(imino-6-hydroxybenzothiazole)resorcinol is as follows: add ethanol, 2-amino-6-hydroxybenzothiazole and 3,5-dihydroxybenzaldehyde in a ratio of 1 mol: (1-1.1) mol into a reaction container, heat to 70-80°C, condense and reflux for 5-8h, heat and evaporate until a precipitate is precipitated, filter after cooling, wash the filter cake with petroleum ether, and then recrystallize in ethanol to obtain 5-(imino-6-hydroxybenzothiazole)resorcinol. The preparation reaction formula is as follows: .

[0012] (III) Technical effect: The present invention utilizes 5-(imino-6-hydroxybenzothiazole)resorcinol as a functional monomer to replace part of resorcinol and undergoes a condensation reaction with formaldehyde. 5-(imino-6-hydroxybenzothiazole)resorcinol contains both phenol and resorcinol structures, and has more ortho-position polymerization sites of the phenolic hydroxyl group. It undergoes cross-linking and condensation reaction with formaldehyde to form a modified phenolic aerogel with a three-dimensional porous network structure. After carbonization, the pores are more abundant and the specific surface area is larger.

[0013] The modified phenolic aerogel of the present invention contains a Schiff base thiazole structure, which can interact with cobalt and nickel ions in a coordination manner, so that the cobalt and nickel ions are uniformly adsorbed into the phenolic aerogel matrix. After a hydrothermal reaction, a nickel cobaltate precursor is uniformly dispersed in the aerogel matrix. After high-temperature calcination, the generated nickel cobaltate particles are uniformly dispersed in the carbon aerogel matrix, which reduces the agglomeration of the nickel cobaltate particles, is conducive to increasing electrochemical chemical sites, and exhibits a higher pseudocapacitance effect and specific capacitance.

[0014] After the nickel cobalt oxide particles of the present invention are coated with carbon aerogel, the nickel cobalt oxide particles are not prone to volume expansion and deformation during charge and discharge, and can maintain good structural stability, inhibiting the occurrence of pulverization and shedding of active electrode materials. After multiple cycles, the electrode material still has a high specific capacitance and exhibits excellent cycle stability.

[0015] The carbon aerogel of the present invention has large pore volume and specific surface area, which is beneficial to the contact between the electrode material and the electrolyte and promotes the transmission of ions and electrons. The modified phenolic aerogel contains a thiazole structure. When calcined at high temperature, nitrogen-sulfur co-doped carbon aerogel is formed to generate active structures such as pyridine nitrogen and thiophene, which can provide additional pseudocapacitive effect and charge storage capacity, and is beneficial to improving the electrochemical performance and specific capacitance of the carbon aerogel electrode material. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present disclosure clearer, the technical solution of the present disclosure will be clearly and completely described in combination with the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be arbitrarily combined with each other without conflict.

[0017] Embodiment 1: (1) Add 60 mL of ethanol, 40 mmol of 2-amino-6-hydroxybenzothiazole, and 40 mmol of 3,5-dihydroxybenzaldehyde into a reaction container, heat to 80°C, condense and reflux for 5 h, heat and evaporate until a precipitate is precipitated, cool and filter, wash the filter cake with petroleum ether, and then recrystallize in ethanol to obtain 5-(imino-6-hydroxybenzothiazole)resorcinol.

[0018] (2) Add 40 mmol of resorcinol, 10 mmol of 5-(imino-6-hydroxybenzothiazole)resorcinol, 40 mL of water, an aqueous solution containing 240 mmol of formaldehyde (mass fraction 37%), and 0.22 mmol of sodium carbonate into a reaction container, seal the reaction container, react at 50 °C for 24 h, and then react at 80 °C for 72 h. Place the generated gel product in acetone for 48 h, replace the acetone every 12 h, filter and dry to obtain a modified phenolic aerogel.

[0019] (3) Add 150 mL of water, 30 mmol of cobalt nitrate, and 15 mmol of nickel nitrate into a container, stir, then add 1 g of modified phenolic aerogel, stir and adsorb at 20 °C for 4 h, then add 90 mmol of urea and 40 mL of ethylene glycol, pour the solution into a hydrothermal reactor, react at 125 °C for 18 h, filter, wash with water and ethanol in turn, dry, place the product in a resistance furnace, first heat to 250 °C in an air atmosphere, calcine for 7 h, then heat to 950 °C in a nitrogen atmosphere, calcine for 6 h, to obtain nickel cobalt oxide carbon aerogel electrode material.

[0020] Embodiment 2: (1) Add 80 mL of ethanol, 40 mmol of 2-amino-6-hydroxybenzothiazole, and 44 mmol of 3,5-dihydroxybenzaldehyde into a reaction container, heat to 70°C, condense and reflux for 8 h, heat and evaporate until a precipitate is precipitated, cool and filter, wash the filter cake with petroleum ether, and then recrystallize in ethanol to obtain 5-(imino-6-hydroxybenzothiazole)resorcinol.

[0021] (2) Add 35 mmol of resorcinol, 15 mmol of 5-(imino-6-hydroxybenzothiazole)resorcinol, 40 mL of water, an aqueous solution containing 210 mmol of formaldehyde (mass fraction 37%), and 0.15 mmol of sodium carbonate into a reaction container, seal the reaction container, react at 40 °C for 36 h, and then react at 90 °C for 72 h. Place the generated gel product in acetone for 48 h, replace the acetone every 12 h, filter and dry to obtain a modified phenolic aerogel.

[0022] (3) Add 200 mL of water, 40 mmol of cobalt nitrate, and 20 mmol of nickel nitrate into a container, stir, then add 1 g of modified phenolic aerogel, stir and adsorb at 35 °C for 3 h, then add 130 mmol of urea and 60 mL of ethylene glycol, pour the solution into a hydrothermal reactor, react at 110 °C for 18 h, filter, wash with water and ethanol in turn, dry, place the product in a resistance furnace, first heat to 240 °C in an air atmosphere, calcine for 7 h, then heat to 1100 °C in a nitrogen atmosphere, calcine for 4 h, to obtain nickel cobalt oxide carbon aerogel electrode material.

[0023] Embodiment 3: (1) Add 60 mL of ethanol, 40 mmol of 2-amino-6-hydroxybenzothiazole, and 40 mmol of 3,5-dihydroxybenzaldehyde into a reaction container, raise the temperature to 75°C, condense and reflux for 8 h, heat and evaporate until a precipitate is precipitated, cool and filter, wash the filter cake with petroleum ether, and then recrystallize in ethanol to obtain 5-(imino-6-hydroxybenzothiazole)resorcinol.

[0024] (2) Add 30 mmol of resorcinol, 20 mmol of 5-(imino-6-hydroxybenzothiazole)resorcinol, 30 mL of water, an aqueous solution containing 270 mmol of formaldehyde (mass fraction 37%), and 0.25 mmol of sodium carbonate into a reaction container, seal the reaction container, react at 50 °C for 24 h, and then react at 80 °C for 84 h. Place the generated gel product in acetone for 48 h, replace the acetone every 12 h, filter and dry to obtain a modified phenolic aerogel.

[0025] (3) Add 200 mL of water, 50 mmol of cobalt nitrate, and 25 mmol of nickel nitrate into a container, stir, then add 1 g of modified phenolic aerogel, stir and adsorb at 25 °C for 5 h, then add 170 mmol of urea and 70 mL of ethylene glycol, pour the solution into a hydrothermal reactor, react at 120 °C for 18 h, filter, wash with water and ethanol in turn, dry, place the product in a resistance furnace, first heat to 280 °C in an air atmosphere, calcine for 4 h, then heat to 1000 °C in a nitrogen atmosphere, calcine for 4 h, to obtain nickel cobalt oxide carbon aerogel electrode material.

[0026] Embodiment 4: (1) Add 200 mL of water, 60 mmol of cobalt nitrate, and 30 mmol of nickel nitrate into a container, stir, then add 1 g of modified phenolic aerogel (prepared in Example 1), stir and adsorb at 25 ° C for 6 h, then add 220 mmol of urea and 70 mL of ethylene glycol, pour the solution into a hydrothermal reactor, react at 120 ° C for 18 h, filter, wash with water and ethanol in turn, dry, place the product in a resistance furnace, first heat to 250 ° C in an air atmosphere, calcine for 6 h, then heat to 1000 ° C in a nitrogen atmosphere, calcine for 4 h, to obtain a nickel cobalt oxide carbon aerogel electrode material.

[0027] Comparative Example 1: (1) Add 50 mmol of resorcinol, 40 mL of water, an aqueous solution containing 240 mmol of formaldehyde (mass fraction 37%), and 0.22 mmol of sodium carbonate into a reaction container, seal the reaction container, react at 50 °C for 24 h, and then react at 80 °C for 72 h. Place the generated gel product in acetone for 48 h, replace the acetone every 12 h, filter and dry to obtain phenolic aerogel.

[0028] (2) Add 150 mL of water, 30 mmol of cobalt nitrate, and 15 mmol of nickel nitrate into a container, stir, then add 1 g of phenolic aerogel, stir and adsorb at 20 °C for 4 h, then add 90 mmol of urea and 40 mL of ethylene glycol, pour the solution into a hydrothermal reactor, react at 125 °C for 18 h, filter, wash with water and ethanol in turn, dry, place the product in a resistance furnace, first heat to 250 °C in an air atmosphere, calcine for 7 h, then heat to 950 °C in a nitrogen atmosphere, calcine for 6 h, to obtain nickel cobalt oxide carbon aerogel electrode material.

[0029] Comparative Example 2 (1) Add 60 mL of ethanol and 40 mmol of 2-aminobenzothiazole ( ), 40mmol3,5-dihydroxybenzaldehyde, heated to 80℃, condensed and refluxed for 5h, heated and evaporated until a precipitate was precipitated, filtered after cooling, the filter cake was washed with petroleum ether, and then recrystallized in ethanol to obtain 5-(iminobenzothiazole)resorcinol. The structural formula is .

[0030] (2) Add 40 mmol of resorcinol, 10 mmol of 5-(iminobenzothiazole)resorcinol, 40 mL of water, an aqueous solution containing 240 mmol of formaldehyde (mass fraction 37%), and 0.22 mmol of sodium carbonate into a reaction container, seal the reaction container, react at 50 °C for 24 h, and then react at 80 °C for 72 h. Place the generated gel product in acetone for 48 h, replace the acetone every 12 h, filter and dry to obtain a modified phenolic aerogel.

[0031] (3) Add 150 mL of water, 30 mmol of cobalt nitrate, and 15 mmol of nickel nitrate into a container, stir, then add 1 g of modified phenolic aerogel, stir and adsorb at 20 °C for 4 h, then add 90 mmol of urea and 40 mL of ethylene glycol, pour the solution into a hydrothermal reactor, react at 125 °C for 18 h, filter, wash with water and ethanol in turn, dry, place the product in a resistance furnace, first heat to 250 °C in an air atmosphere, calcine for 7 h, then heat to 950 °C in a nitrogen atmosphere, calcine for 6 h, to obtain nickel cobalt oxide carbon aerogel electrode material.

[0032] The pore volume and specific surface area of ​​the nickel cobalt oxide carbon aerogel electrode material were determined by a specific surface and porosity analyzer using a nitrogen adsorption-desorption method. The electrode material was vacuum degassed at 150°C for 12 h before the test.

[0033] Table 1 Pore volume and specific surface area test Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Pore ​​volume (cm3 / g) 0.536 0.720 0.685 0.514 0.363 0.397 Specific surface area (m2 / g) 706.9 920.2 852.0 670.8 476.5 517.6 The nickel cobalt oxide carbon aerogel electrode material, conductive carbon black and polytetrafluoroethylene were added to ethanol in a mass ratio of 8:1:1, stirred and mixed, and then the slurry was coated on the surface of nickel foam, dried and pressed into sheets to make a working electrode, with Ag / AgCl electrode as the reference electrode, platinum electrode as the counter electrode, and 1 mol / L potassium hydroxide solution as the electrolyte. Cyclic voltammetry and charge-discharge tests were performed on an electrochemical workstation using a three-electrode system. The current density during the test was 1-10 A / g.

[0034] Table 2 Specific capacitance test at current density of 1 A / g Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Specific capacitance (F / g) 927.6 1160.8 1372.1 1459.2 659.2 845.4 Specific capacitance after 500 cycles (F / g) 844.5 1077.3 1223.0 1260.6 527.7 745.9 Retention rate (%) 91.04 92.81 89.13 86.39 80.04 88.23 Table 3 Specific capacitance test at current density of 10 A / g Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Specific capacitance (F / g) 623.7 763.3 901.3 942.6 414.6 547.1 Specific capacitance after 500 cycles (F / g) 568.3 703.0 798.9 814.8 325.5 478.0 Retention rate (%) 91.12 92.10 88.64 86.44 78.51 87.37 After testing, the nickel cobalt oxide carbon aerogel electrode material prepared in each embodiment has a higher pore volume and specific surface area. This is because the use of 5-(imino-6-hydroxybenzothiazole) resorcinol ( ) as a functional monomer, replacing part of resorcinol and formaldehyde for polycondensation reaction, 5-(imino-6-hydroxybenzothiazole)resorcinol also contains phenol ( ) and resorcinol structure ( ), the ortho-position polymerization sites of phenolic hydroxyl groups are more, and they are cross-linked and condensed with formaldehyde to form a modified phenolic aerogel with a three-dimensional porous network structure. After carbonization, the pores are more abundant and the specific surface area is large. In addition, the modified phenolic aerogel contains Schiff base thiazole structure, which can interact with cobalt and nickel ions in coordination, so that cobalt and nickel ions are uniformly adsorbed into the phenolic aerogel matrix. After the hydrothermal reaction, the nickel cobaltate precursor is uniformly dispersed in the aerogel matrix. After high-temperature calcination, the generated nickel cobaltate particles are uniformly dispersed in the carbon aerogel matrix, which reduces the agglomeration of nickel cobaltate particles, is conducive to increasing electrochemical chemical sites, and exhibits a higher pseudocapacitance effect and specific capacitance. At the same time, after the nickel cobaltate particles are coated with carbon aerogel, the nickel cobaltate particles are not easy to expand and deform in volume during charging and discharging, and can maintain good structural stability, inhibiting the pulverization and shedding of active electrode materials. After multiple cycles, the electrode material still has a high specific capacitance and exhibits excellent cycle stability. The large pore volume and specific surface area of ​​carbon aerogel are beneficial to the contact between electrode materials and electrolytes, and promote the transmission of ions and electrons. In addition, the modified phenolic aerogel contains a thiazole structure. When calcined at high temperature, nitrogen-sulfur co-doped carbon aerogel is formed, generating active structures such as pyridine nitrogen and thiophene, which can provide additional pseudocapacitive effects and charge storage capacity, which is beneficial to improving the electrochemical properties and specific capacitance of carbon aerogel electrode materials.

[0035] Compared with Example 1, Comparative Example 1 does not add 5-(imino-6-hydroxybenzothiazole)resorcinol, the phenolic hydroxyl group of resorcinol has fewer ortho-position polymerization sites, and it is difficult to form a good three-dimensional porous network structure after condensation with formaldehyde to generate phenolic aerogel. The pore volume and specific surface area of ​​the carbon aerogel electrode material after carbonization are small, and the phenolic aerogel does not contain Schiff base thiazole groups, and cannot interact with cobalt and nickel ions, making it difficult to uniformly adsorb cobalt and nickel ions into the phenolic aerogel matrix. The generated nickel cobaltate particles are not uniformly dispersed in the carbon aerogel matrix, which makes the nickel cobaltate particles easy to agglomerate, reducing the pore volume and specific surface area of ​​the carbon aerogel, and due to the agglomeration of the nickel cobaltate particles, the electrochemical chemical sites of the electrode material are reduced, the pseudocapacitance effect and specific capacitance are low, and the cycle stability is poor.

[0036] Compared with Example 1, Comparative Example 2 uses 5-(iminobenzothiazole)resorcinol ( ) undergoes a condensation reaction with resorcinol and formaldehyde. It only contains a resorcinol structure but no phenol structure. The ortho-position polymerization sites of the phenolic hydroxyl group are relatively few. It is difficult for the phenolic aerogel generated after condensation with formaldehyde to form a good three-dimensional porous network structure. After carbonization, the pore volume and specific surface area of ​​the carbon aerogel electrode material are relatively small, and the specific capacitance of the electrode material is smaller than that of Example 1.

Claims

1. A process for preparing a nickel cobalt oxide carbon aerogel electrode material, characterized in that: The preparation process comprises the following steps: Step A, adding resorcinol, 5-(imino-6-hydroxybenzothiazole)resorcinol and water into a reaction container, stirring and then adding formaldehyde aqueous solution and sodium carbonate, sealing the reaction container, placing the gel product in acetone after the reaction, filtering and drying to obtain a modified phenolic aerogel; Step B, add water, cobalt nitrate and nickel nitrate into a container, stir and then add modified phenolic aerogel, stir for adsorption, then add urea and ethylene glycol, pour the solution into a hydrothermal reactor for reaction, filter and wash, dry and place the product in a resistance furnace for calcination to obtain nickel cobaltate carbon aerogel electrode material.

2. The preparation process of the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: In the step A, the ratio of resorcinol, 5-(imino-6-hydroxybenzothiazole)resorcinol, formaldehyde and sodium carbonate is (0.6-0.8) mol: (0.2-0.4) mol: (4.2-5.4) mol: (0.003-0.005) mol.

3. The preparation process of the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: In step A, the reaction is first carried out at 40-50° C. for 24-36 h, and then at 80-90° C. for 72-84 h.

4. The process for preparing the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: The adsorption in step B is carried out at 20-35° C. for 3-6 hours.

5. The process for preparing the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: In the step B, the ratio of cobalt nitrate, nickel nitrate, modified phenolic aldehyde aerosol and urea is (30-60 mmol): (15-30) mmol: (90-220) mmol: 1 g.

6. The process for preparing the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: The reaction in step B is carried out at 110-125° C. for 12-18 hours.

7. The process for preparing the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: In the step B, the calcination is first carried out in an air atmosphere, the temperature is raised to 240-280° C., and the calcination is carried out for 4-7 hours; then, the temperature is raised to 950-1100° C., and the calcination is carried out for 4-6 hours in a nitrogen atmosphere.

8. The process for preparing the nickel cobalt oxide carbon aerogel electrode material according to claim 1, characterized in that: The preparation method of 5-(imino-6-hydroxybenzothiazole)resorcinol is as follows: ethanol, 2-amino-6-hydroxybenzothiazole and 3,5-dihydroxybenzaldehyde are added into a reaction container, the temperature is raised to 70-80° C., condensation reflux reaction is performed for 5-8 hours, heating and evaporation are performed until a precipitate is precipitated, filtering is performed after cooling, the filter cake is washed with petroleum ether, and then recrystallization is performed in ethanol to obtain 5-(imino-6-hydroxybenzothiazole)resorcinol.

9. The process for preparing the nickel cobalt oxide carbon aerogel electrode material according to claim 7, characterized in that: The ratio of the 2-amino-6-hydroxybenzothiazole to 3,5-dihydroxybenzaldehyde is 1 mol: (1-1.1) mol.