Preparation method and application of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres

Abstract

A preparation method of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres. The method solves the problems of complex preparation method of the existing phenolic resin microspheres and carbon spheres, small specific surface area of the prepared phenolic resin microspheres, large particle size, and poor porosity. The method comprises the following steps: the preparation method uses lignin, phenol, copper sulfate, iron sulfate and formaldehyde as raw materials, and inorganic alkali as catalyst, and Cu-Fe-S co-doped lignin modified phenolic resin microspheres are prepared by suspension polymerization, and then Cu-Fe-S co-doped porous carbon spheres are obtained through carbonization; the Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres are used for preparing supercapacitors as negative electrode materials. The preparation method has simple process and low cost; the prepared phenolic resin microspheres have large specific surface area, small particle size and developed porosity, and are applied to supercapacitors as negative electrode materials, so that the cycle life, power density and energy density of the supercapacitors can be improved.

Description

Technical fields:

[0001] This invention relates to the field of carbon materials technology, and in particular to a method for preparing Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres and their application. Background technology:

[0002] Porous carbon materials have attracted widespread attention in recent years due to their unique physical and chemical properties. These materials possess abundant pore structures and a large surface area, enabling them to exhibit excellent performance in numerous fields. Particularly in the field of supercapacitors, the application of porous carbon materials has garnered significant attention. Supercapacitors, as a novel type of energy storage device, offer advantages such as high power density, rapid charge and discharge, and long cycle life. The application of porous carbon materials in supercapacitors can greatly enhance their electrochemical performance.

[0003] Doping carbon materials can optimize their pore size, structure, conductivity, and surface properties, significantly impacting the electrochemical performance of supercapacitors. Doping with heteroatoms and metal atoms can modulate the wettability of carbon materials, improve the conductivity of active materials, and enhance the capacitance potential of supercapacitors. Current research has shown positive results using metal elements such as Cu and Fe to modify the structure of carbon materials, as well as by doping with heteroatoms. Therefore, co-doping with metal elements and heteroatoms for the modification of carbon materials holds great potential and has a promising future in supercapacitor applications.

[0004] Existing technologies for producing phenolic resins are complex, resulting in large sphere diameters, small specific surface areas, and small porosity. Furthermore, existing technologies have demonstrated that porous carbon materials, when used as anode materials in supercapacitors, can enhance electrochemical performance to achieve 550 F·g. -1 The theoretical electrochemical specific capacitance is the upper limit of the specific capacitance of carbon materials. In order to solve these problems, a new method for preparing phenolic resin microspheres and their carbon spheres is provided. Summary of the Invention:

[0005] This invention addresses the problems of complex preparation methods for existing phenolic resin microspheres and their carbon spheres, resulting in microspheres with small specific surface area, large diameter, and underdeveloped pores. It provides a method for preparing Cu-Fe-S co-doped lignin-based phenolic resin carbon spheres. This method is simple and low-cost; the prepared phenolic resin microspheres have a large specific surface area, small diameter, and well-developed pores. When used as a negative electrode material in supercapacitors, it can improve the cycle life, power density, and energy density of supercapacitors. This invention also provides an application of Cu-Fe-S co-doped lignin-based phenolic resin carbon spheres.

[0006] The present invention solves its problems through the following technical solution: the preparation method of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres uses lignin, phenol, copper sulfate, ferric sulfate and formaldehyde as raw materials, inorganic base as catalyst, and suspension polymerization to prepare Cu-Fe-S co-doped lignin-modified phenolic resin microspheres, which are then carbonized to obtain Cu-Fe-S co-doped porous carbon spheres.

[0007] Furthermore, the specific steps include:

[0008] Step A: Phenol, formaldehyde, and lignin are added to the reaction apparatus, with an inorganic base as a catalyst. The mixture is stirred and heated to 40–60°C. After adding a dispersant, the mixture is stirred for 30 minutes and then heated to 95–100°C for 8 hours. Copper sulfate and ferric sulfate are added, and the mixture is stirred for 3–5 hours. After stirring for another 3 hours, a curing agent is added, and the mixture is washed 3–5 times. The Cu-Fe-S co-doped lignin-based phenolic resin microspheres are separated by filtration. The microspheres are then washed with deionized water 3–5 times, filtered, and dried. The resulting solid powder is the Cu-Fe-S co-doped lignin-based heterophenolic resin microsphere.

[0009] Step B: The Cu-Fe-S co-doped lignin-based phenolic resin microspheres prepared in Step A are placed in a tube furnace filled with nitrogen for carbonization to obtain Cu-Fe-S co-doped porous carbon spheres.

[0010] Furthermore, the copper sulfate and ferric sulfate provide the S source for the Cu-Fe-S co-doped lignin-based phenolic resin microspheres; the copper sulfate provides the Cu source for the Cu-Fe-S co-doped lignin-based phenolic resin microspheres; and the ferric sulfate provides the Fe source for the Cu-Fe-S co-doped lignin-based phenolic resin microspheres.

[0011] Furthermore, the amount of lignin used is 50% to 90% of the sum of the mass of lignin and phenol.

[0012] Furthermore, the dispersant is one or more of polyethylene glycol or polyvinyl alcohol; the inorganic alkali is any one of ammonia, sodium hydroxide, potassium hydroxide, and calcium hydroxide; the curing agent is at least one of hexamethylenetetramine, m-phenylenediamine, and ethylenediamine; after adding the dispersant, stir for 30 min; add the curing agent, continue stirring for 3 h, and wash 3 to 5 times; filter to separate Cu-Fe-S co-doped lignin-based phenolic resin microspheres, and wash with deionized water repeatedly 3 to 5 times.

[0013] Furthermore, copper, iron, and sulfur elements are incorporated into lignin-based phenolic resins via suspension polymerization.

[0014] The formaldehyde and phenol molar ratio is 1:3. Lignin accounts for 19.08% to 34.35% of the total mass; phenol accounts for 3.82% to 19.08% of the total mass; formaldehyde accounts for 36.57% of the total mass; dispersant accounts for 8.10% of the total mass; catalyst accounts for 1.62% of the total mass; curing agent accounts for 6.48% of the total mass; copper sulfate accounts for 0% to 2.59% of the total mass; and ferric sulfate accounts for 0% to 6.48% of the total mass.

[0015] Furthermore, the carbonization temperature in step B is 700–1000℃; the carbonization time is 30–120 min; and the carbonization heating rate is 1–10℃ / min.

[0016] The reaction apparatus for step A is equipped with a mechanical stirrer, a condenser, and a temperature detection device.

[0017] In step A, phenol, formaldehyde, and lignin are added to the reaction apparatus, with an inorganic base as a catalyst. The mixture is stirred and heated to 45°C.

[0018] The present invention also provides an application of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres prepared according to the preparation method as negative electrode materials in supercapacitors.

[0019] Furthermore, the specific steps of the electrode preparation method are as follows: Take 0.15-0.25g of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres, then weigh carbon black and polytetrafluoroethylene in a mass ratio of 8:1:1. Mix the three and add 10-15mL of anhydrous ethanol to form a suspension. After ultrasonic dispersion for 30min, take it out and place it in an oven to dry for 60min until the mixture becomes viscous. Take 0.1-0.2g of the mixture and coat it on a 1cm... 2 The electrode is obtained by drying on a square nickel foam for 12 hours.

[0020] Compared with the above-mentioned background technology, the present invention has the following beneficial effects:

[0021] 1. Using lignin to replace phenol as a raw material results in relatively mild reaction conditions, simple operation, and no other wastewater discharge, making it an environmentally friendly process route.

[0022] 2. The reaction yield is high, saving costs.

[0023] 3. Copper sulfate and ferric sulfate provide sulfur, iron, and copper sources for Cu-Fe-S co-doped phenolic resin microspheres, respectively. The resulting Cu-Fe-S co-doped carbon composite material, as an electrode material, exhibits excellent stability and good electrochemical performance.

[0024] 4. The prepared carbon spheres have well-developed pores, a large specific surface area, and good mechanical strength. The small-particle-size Cu-Fe-S co-doped phenolic resin-based carbon spheres are used as electrode materials in the electrochemical field. Specifically, carbon spheres with a diameter of approximately 0–10 μm can be used in electrochemical applications. Supercapacitors made using Cu-Fe-S co-doped carbon spheres with a diameter of approximately 0–10 μm exhibit excellent electrochemical performance, with a specific capacitance exceeding 1500 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate reaches over 95%. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of Cu-Fe-S co-doped phenolic resin-based porous carbon spheres according to an embodiment of the present invention;

[0026] Figure 2 This is a transmission electron microscope (TEM) image of Cu-Fe-S co-doped phenolic resin-based porous carbon spheres according to an embodiment of the present invention.

[0027] Figure 3 Thermogravimetric analysis diagram of Cu-Fe-S co-doped phenolic resin-based porous carbon spheres in an embodiment of the present invention;

[0028] Figure 4 The constant current charge-discharge diagrams at different current densities are shown for the Cu-Fe-S co-doped phenolic resin-based porous carbon sphere active material used as the negative electrode material of a supercapacitor in this embodiment of the invention. Detailed implementation method:

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0031] This invention is not limited to the specific embodiments listed below. Those skilled in the art can implement this invention using various other specific embodiments based on the content disclosed herein. Any modifications or alterations made to the design structure and concept of this invention fall within the protection scope of this invention. It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0032] This invention provides a method for preparing Cu-Fe-S co-doped phenolic resin-based carbon spheres, the specific steps of which are as follows:

[0033] Step A: In a reaction apparatus equipped with a mechanical stirrer, condenser, and temperature detection device, lignin, phenol, and formaldehyde are added, with an inorganic base as a catalyst. The mixture is stirred and heated to 40–60°C, preferably 45°C. After adding a dispersant, the mixture is stirred for 30 minutes and then heated to 85–90°C for 8 hours. Copper sulfate and ferric sulfate are added, and the mixture is stirred for 3–5 hours. Then, a curing agent is added, and the mixture is stirred for another 3 hours. The mixture is washed 3–5 times, and Cu-Fe-S co-doped phenolic resin microspheres are separated by filtration. The microspheres are then washed with deionized water 3–5 times, filtered again, and dried. The resulting solid powder is the Cu-Fe-S co-doped phenolic resin microsphere.

[0034] Step B: The Cu-Fe-S co-doped phenolic resin microspheres prepared in Step A are placed in a tube furnace filled with nitrogen for carbonization to obtain Cu-Fe-S co-doped phenolic resin-based porous carbon spheres. The carbonization temperature is 700–1000℃; the carbonization time is 30–120 min; and the carbonization heating rate is 1–10℃ / min.

[0035] Step C: The active material obtained in Step B is mixed with carbon black and polytetrafluoroethylene in an appropriate amount of anhydrous ethanol to form a uniform suspension. After ultrasonic dispersion for 30 minutes, the mixture is removed and placed in an oven to dry until it becomes viscous. The active material is then coated onto nickel foam as an electrode material. An electrolyte is prepared, and electrochemical tests are performed: cyclic voltammetry, constant current charge-discharge testing, impedance testing, and cycle life testing. A three-electrode system is used for the electrochemical tests. The electrolyte is a 3M KOH solution, the reference electrode is a calomel electrode, and the counter electrode is a platinum electrode. The cyclic voltammetry scan rates are 0.05 V / s, 0.075 V / s, 0.25 V / s, 0.1 V / s, and 0.5 V / s, respectively. The constant current charge-discharge test current densities are 1 A·g⁻¹. -1 2A·g -1 5A·g -1 8A·g -1 10A·g -1 .

[0036] The method of the present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention.

[0037] Example 1:

[0038] In a 500ml four-necked flask, 150g of deionized water, 16.485g of lignin, 7.065g of phenol, and 22.55g of formaldehyde were added. 1g of ammonia was added as a catalyst. The mixture was heated to 45℃, and 5g of polyvinyl alcohol was added. Heating and stirring continued until the temperature reached 85℃. The mixture was stirred at this temperature for 15 hours while maintaining a constant stirring speed. 1.596g of copper sulfate and 3.999g of ferric sulfate were added, and the reaction was continued at this temperature for 4 hours. 4g of HMTA was added, and stirring was continued for 3 hours to terminate the reaction. The mixture was allowed to cool to room temperature before being discharged. The product was washed three times with deionized water, and the supernatant was filtered after it became clear. The supernatant was dried at 60℃ for 6 hours to obtain Cu-Fe-S co-doped phenolic resin microspheres.

[0039] Particle size analysis of the microspheres revealed that the Cu-Fe-S co-doped phenolic resin microspheres had a particle size of approximately 150 nm, as shown in the scanning electron microscope image below. Figure 1 As shown ( Figure 1 The scale bar is 200 nm.

[0040] 10g of Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. The pre-carbonized microspheres were then placed in a tube furnace under nitrogen protection. The carbonization heating rate was 2℃ / min, the carbonization temperature was 850℃, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed, yielding Cu-Fe-S co-doped porous carbon spheres. The specific surface area was measured to be 2800 m². 2 / g, such as Figure 2 As shown ( Figure 2 The scale bar is 200 nm. Its electrochemical performance was measured, and its specific capacitance reached 1280 F / g. Its cyclic voltammetry curve is shown below. Figure 3 As shown, after 5000 constant current charge-discharge cycles, the capacitance retention rate is 96.2%, and the constant current charge-discharge curve is as follows. Figure 4 As shown.

[0041] Example 2:

[0042] Based on Example 1, the carbonization heating rate was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was set to 1℃ / min, the carbonization temperature to 850℃, and the carbonization time to 120min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 3000 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 800 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 91.0%.

[0043] Example 3:

[0044] Based on Example 1, the carbonization heating rate was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was set to 5℃ / min, the carbonization temperature to 850℃, and the carbonization time to 120min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 2000 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 1000 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 95.0%.

[0045] Example 4:

[0046] Based on Example 1, the carbonization heating rate was changed. 10g of Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 8℃ / min, the carbonization temperature was 850℃, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The specific surface area was measured to be 1500 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 650 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 91.0%.

[0047] Example 5:

[0048] Based on Example 1, the carbonization heating rate was changed. 10g of Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 10℃ / min, the carbonization temperature was 850℃, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The specific surface area was measured to be 800m². 2 The electrochemical performance was measured, and its specific capacitance value reached 280 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 85.0%.

[0049] Example 6:

[0050] Based on Example 1, the carbonization temperature was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The carbonization temperature was set to 700℃, the heating rate was 2℃ / min, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 1000 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 400 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 93.0%.

[0051] Example 7:

[0052] Based on Example 1, the carbonization temperature was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The carbonization temperature was set to 800℃, the heating rate was 2℃ / min, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 1300 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 600 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 94.5%.

[0053] Example 8:

[0054] Based on Example 1, the carbonization temperature was changed. 10g of Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The carbonization temperature was set to 900℃, the heating rate was 2℃ / min, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 1800 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 1000 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 96.5%.

[0055] Example 9:

[0056] Based on Example 1, the carbonization temperature was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The carbonization temperature was set to 1000℃, the heating rate was 2℃ / min, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 1500 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 600 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 87.0%.

[0057] Example 10:

[0058] Based on Example 1, the carbonization time was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2℃ / min, the carbonization temperature was 850℃, and the carbonization time was 30min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 450m². 2 The electrochemical performance was measured, and its specific capacitance value reached 350 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 83.5%.

[0059] Example 11:

[0060] Based on Example 1, the carbonization time was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2℃ / min, the carbonization temperature was 850℃, and the carbonization time was 60min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 800m². 2 The electrochemical performance was measured, and its specific capacitance value reached 640 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 87.5%.

[0061] Example 12:

[0062] Based on Example 1, the carbonization time was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2℃ / min, the carbonization temperature was 850℃, and the carbonization time was 90min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 1500 m².2 The electrochemical performance was measured, and its specific capacitance value reached 880 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 92.0%.

[0063] Example 13:

[0064] Based on Example 1, the carbonization time was changed. 10g of the Cu-Fe-S co-doped phenolic resin microspheres from Example 1 were weighed and pre-carbonized. The pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2℃ / min, the carbonization temperature was 850℃, and the carbonization time was 150min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 2000 m². 2 The electrochemical performance was measured, and its specific capacitance value reached 600 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 84.0%.

[0065] Example 14:

[0066] Based on Example 1, the amount of lignin was varied. Using a particle size analyzer, it was found that when the mass of lignin was 11.775 g, which is 50% of the sum of the masses of lignin and phenol, the microsphere diameter was approximately 300 nm. The obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. The specific surface area of ​​the product after cooling was measured to be 2000 m². 2 / g, its electrochemical performance was measured. When the current density was 1A / g, its specific capacitance value reached 900F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 95.5%.

[0067] Example 15:

[0068] Based on Example 1, the amount of lignin was varied. Using a particle size analyzer, it was found that when the mass of lignin was 14.13 g, which is 60% of the sum of the masses of lignin and phenol, the microsphere diameter was approximately 200 nm. The obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. After the tube furnace cooled, the product was removed, and its specific surface area was measured to be 2500 m². 2 / g, its electrochemical performance was measured. When the current density was 1A / g, its specific capacitance value reached 1100F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 96.0%.

[0069] Example 16:

[0070] Based on Example 1, the amount of lignin was varied. Using a particle size analyzer, it was found that when the mass of lignin was 18.84 g, which is 80% of the sum of the masses of lignin and phenol, the microsphere diameter was approximately 120 nm. The obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. After the tube furnace cooled, the product was removed, and its specific surface area was measured to be 3000 m². 2 / g, its electrochemical performance was measured. When the current density was 1A / g, its specific capacitance value reached 1050F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 93.2%.

[0071] Example 17:

[0072] Based on Example 1, the amount of lignin was varied. Using a particle size analyzer, it was found that when the mass of lignin was 21.195 g, which is 90% of the sum of the masses of lignin and phenol, the microsphere diameter was approximately 100 nm. The obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. The specific surface area of ​​the product after cooling was measured to be 3300 m². 2 / g, its electrochemical performance was measured. When the current density was 1A / g, its specific capacitance value reached 800F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 90.8%.

[0073] Example 18:

[0074] Based on Example 1, the amounts of copper sulfate and ferric sulfate were varied. Using a particle size analyzer, it was found that when the copper sulfate content was 31.9 g and the ferric sulfate content was 8.0 g, the resulting Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. The product was then removed after the tube furnace cooled, and its specific surface area was measured to be 2000 m². 2 The electrochemical performance was measured, and its specific capacitance was found to be 450 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 85.0%.

[0075] Comparative Example 1:

[0076] Based on Example 1, the amounts of copper sulfate and ferric sulfate were varied. Using a particle size analyzer, it was found that the amount of copper sulfate and ferric sulfate added was unnecessary. The obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2℃ / min, the carbonization temperature was 850℃, and the carbonization time was 120min. After the tube furnace cooled, the sample was removed. The specific surface area was measured to be 500m². 2 / g, its electrochemical performance was measured, and its specific capacitance value reached 600F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 88.0%.

[0077] Comparative Example 2:

[0078] Based on Example 1, the amounts of copper sulfate and ferric sulfate were varied. Using a particle size analyzer, it was found that when the amount of copper sulfate was 0 g and the amount of ferric sulfate was 3.999 g, the obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-Fe-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. After the tube furnace cooled, the product was removed, and its specific surface area was measured to be 1200 m². 2 The specific capacitance was measured to be 750 F / g, and after 5000 constant current charge-discharge cycles, the capacitance retention rate was 90.0%.

[0079] Comparative Example 3:

[0080] Based on Example 1, the amounts of copper sulfate and ferric sulfate were varied. Using a particle size analyzer, it was found that when the amount of copper sulfate was 1.596 g and the amount of ferric sulfate was 0 g, the obtained Cu-Fe-S co-doped phenolic resin microspheres were pre-carbonized. 10 g of the pre-carbonized Cu-S co-doped phenolic resin microspheres were placed in a tube furnace under nitrogen protection. The heating rate was 2 °C / min, the carbonization temperature was 850 °C, and the carbonization time was 120 min. After the tube furnace cooled, the sample was removed. After the tube furnace cooled, the product was removed, and its specific surface area was measured to be 1500 m². 2 The electrochemical performance was measured, and its specific capacitance was found to be 800 F / g. After 5000 constant current charge-discharge cycles, the capacitance retention rate was 92.5%.

Claims

1. A method for preparing Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres, characterized in that: The preparation method uses lignin, phenol, copper sulfate, ferric sulfate and formaldehyde as raw materials, inorganic base as catalyst, and suspension polymerization to prepare Cu-Fe-S co-doped lignin-modified phenolic resin microspheres, which are then carbonized to obtain Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres. Specifically, the following steps are included: Step A: Add phenol, formaldehyde, and lignin to the reaction apparatus, using an inorganic base as a catalyst, stir, and heat to 40-60°C. o C. After adding the dispersant, stir and continue heating to 95-100°C. o After reacting at C for 8 hours, copper sulfate and ferric sulfate were added, and after stirring, a curing agent was added. Stirring continued, and the mixture was washed and filtered to separate Cu-Fe-S co-doped lignin-based phenolic resin microspheres. The microspheres were then repeatedly washed with deionized water, filtered, and dried to obtain the solid powder, which is the Cu-Fe-S co-doped lignin-based phenolic resin microsphere. Step B: The Cu-Fe-S co-doped lignin-based phenolic resin microspheres prepared in Step A are placed in a tube furnace filled with nitrogen for carbonization to obtain Cu-Fe-S co-doped lignin-based phenolic resin carbon spheres.

2. The preparation method according to claim 1, characterized in that, The copper sulfate and ferric sulfate provide the S source for the Cu-Fe-S co-doped lignin-based phenolic resin microspheres; the copper sulfate provides the Cu source for the Cu-Fe-S co-doped lignin-based phenolic resin microspheres; and the ferric sulfate provides the Fe source for the Cu-Fe-S co-doped lignin-based phenolic resin microspheres.

3. The preparation method according to claim 1, characterized in that, The amount of lignin used is 50% to 90% of the sum of the mass of lignin and phenol.

4. The preparation method according to claim 1, characterized in that, The dispersant is one or more of polyethylene glycol or polyvinyl alcohol; the inorganic alkali is any one of ammonia, sodium hydroxide, potassium hydroxide, and calcium hydroxide; the curing agent is at least one of hexamethylenetetramine, m-phenylenediamine, and ethylenediamine; after adding the dispersant, stir for 30 min; add the curing agent, continue stirring for 3 h, and wash 3 to 5 times; filter to separate Cu-Fe-S co-doped lignin-based phenolic resin microspheres, and wash with deionized water 3 to 5 times.

5. The preparation method according to claim 1, characterized in that... Copper, iron and sulfur elements are incorporated into lignin-based phenolic resin through suspension polymerization. The formaldehyde and phenol molar ratio is 1:

3. The lignin accounts for 19.08% to 34.35% of the total mass; phenol accounts for 3.82% to 19.08% of the total mass; formaldehyde accounts for 36.57% of the total mass; dispersant accounts for 8.10% of the total mass; catalyst accounts for 1.62% of the total mass; curing agent accounts for 6.48% of the total mass; copper sulfate accounts for 0% to 2.59% of the total mass; and ferric sulfate accounts for 0% to 6.48% of the total mass.

6. The preparation method according to claim 1, characterized in that, The carbonization temperature in step B is 700-1000°C; the carbonization time is 30-120 min; and the carbonization heating rate is 1-10°C / min. The reaction apparatus for step A is equipped with a mechanical stirrer, a condenser, and a temperature detection device. In step A, phenol, formaldehyde, and lignin are added to the reaction apparatus, with an inorganic base as a catalyst. The mixture is stirred and heated to 45°C. o C.

7. A Cu-Fe-S co-doped lignin-based phenolic resin-based carbon sphere prepared by the preparation method according to claim 1.

8. The application of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres according to claim 7 in the preparation of anode materials for supercapacitors.

9. The application according to claim 8, characterized in that, The specific steps for preparing the electrode are as follows: Take 0.15~0.25 g of Cu-Fe-S co-doped lignin-based phenolic resin-based carbon spheres. Then, weigh the carbon spheres, carbon black, and polytetrafluoroethylene (PTFE) in a mass ratio of 8:1:

1. Mix the three components and add 10~15 mL of anhydrous ethanol to form a suspension. After ultrasonic dispersion for 30 min, remove the suspension and place it in an oven to dry for 60 min until the mixture becomes viscous. Take 0.1~0.2 g of the mixture and coat it onto a 1 cm thick surface. 2 The electrode was obtained by drying on a square nickel foam for 12 hours.

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