Preparation method of supercapacitor electrode material

Abstract

The invention discloses a preparation method of a supercapacitor electrode material, and the method comprises the steps: cleaning forestry waste with deionized water, drying the forestry waste, crushing the forestry waste until the particle size does not exceed 3mm, mixing the dried and crushed forestry waste with dry bean dregs, adding a certain mass of deionized water, putting the mixture into a reaction kettle, and carrying out hydrothermal carbonization reaction, and after the reaction is finished, naturally cooling to room temperature, filtering to obtain a solid product, soaking with benzyl alcohol, washing with deionized water, drying, grinding the obtained carbon-based precursor for 60 minutes, putting into a vacuum chamber of a plasma generator, introducing nitrogen, heating to a certain temperature, keeping the temperature for a certain time, and exciting nitrogen plasma to activate through microwaves to obtain the target carbon electrode material. The target carbon electrode material is used as a supercapacitor electrode material. The preparation process is simple and convenient, low in cost, easy to repeat and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the field of biomass energy material preparation, and specifically relates to a method for preparing a supercapacitor electrode material. Background Art

[0002] With the in-depth development and utilization of renewable energy, the effective storage of energy has become crucial. Supercapacitors are considered to be one of the most promising energy storage systems at present because of their advantages such as high power density, fast charging and discharging process, and good safety and stability. They can be used in portable electronic devices, backup energy systems, and military fields. At the same time, supercapacitors are also mixed with lithium-ion batteries or fuel cells in hybrid vehicles, as well as some large-scale power and energy systems.

[0003] The performance of supercapacitors depends largely on the electrode materials and structures. Carbon materials are preferred for suitable electrode materials due to their wide availability, good conductivity and electrochemical properties. However, if carbon nanomaterials such as carbon nanotubes or graphite are used as electrode materials, they will be expensive and the synthesis process may also cause environmental pollution. Carbon-rich biochar materials are derived from cheap and readily available biomass and can be obtained by pyrolysis or hydrothermal methods. They have been shown to have the potential to be used as supercapacitor electrode materials. In order to improve the electrochemical properties of biochar, its surface structure is often modified by heteroatom (N, O, B, S or P) doping, and the pore structure is often adjusted by physical or chemical methods.

[0004] In my country, camphor is mainly distributed in the area south of the Yangtze River. Due to its wide range of soil requirements and its evergreen characteristics, it is an excellent tree species for greening, gardening, windbreak and soundproofing forests. Pruning it will produce a large number of discarded branches and leaves. Its rational use is of great significance to improving resource utilization and ecological environment. In addition, camphor trees contain terpenes, phenols, sugars and other substances, especially linalool and camphor lactones, which can be converted into excellent carbon-rich materials using hydrothermal method. Bean dregs are the main by-products in the processing of soy products. When 1kg of soybeans are processed into soy milk or tofu, about 1.1kg of fresh bean dregs will be produced. According to statistics, the annual output of bean dregs in my country has reached more than 20 million tons in recent years. The traditional way of utilization in my country is to use it as feed and fertilizer, or to develop it as food, but various utilization methods are constrained by the high water content and difficult storage of bean dregs, so its utilization rate is only about 5~20%, causing serious environmental pollution and waste of resources. Taking into full account the composition characteristics of soybean dregs, matching appropriate processing technologies, stimulating the synergistic effects between material components, and converting them into high-value products are the development trends of modern green chemistry. In particular, soybean dregs contain a large amount of crude protein, which is expected to become a good raw material for preparing nitrogen in-situ doped carbon. The present invention utilizes the special components in camphor and the nitrogen-rich characteristics of soybean dregs, and combines hydrothermal carbonization technology to utilize the high reactivity and diffusivity of water in subcritical or supercritical conditions, so that high-moisture content macromolecular organic matter undergoes decarboxylation, polymerization and aromatization reactions under relatively mild conditions, and is converted into high-value-added carbon materials, thereby realizing the heteroatom doping adjustment on the surface of biocarbon materials, and green economy.

[0005] In addition, for the development of the pore structure of biocarbon materials, most of the current physical and chemical activation methods use high temperatures or use alkali, acid or salt activators, which are costly, difficult to recycle the activators, and easy to cause pollution. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a supercapacitor electrode material, which uses plasma activation technology to adjust the pores of carbon materials at low temperature, in a short time, and without using any chemicals, and combines camphor and bean dregs copolymerization with plasma low-temperature activation to obtain excellent electrode materials with broad application prospects. The above method has a simple preparation process, low cost, easy to repeat, and is green and environmentally friendly.

[0007] A method for preparing a supercapacitor electrode material comprises the following steps: Step A: Take forestry waste, wash it with deionized water, dry it, and crush it to a particle size of less than 3 mm; Step B: Mix the dried and crushed forestry waste obtained in step A with dry bean dregs, add deionized water, place in a reactor, turn on a magnetic stirring device, rotate at 1000 r / min, heat to 250-320° C. at a rate of 10° C. / min, react for 10-15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak in benzyl alcohol for 24 hours, wash with deionized water and dry to obtain a carbon-based precursor; Step C: Grind the carbon-based precursor obtained in step B for 60 minutes, place it in a plasma vacuum chamber, introduce nitrogen, heat and keep it warm for a certain period of time, and generate nitrogen plasma activation through microwave source excitation to obtain the target carbon electrode material, which is used as a supercapacitor electrode material.

[0008] Furthermore, the forestry waste in step A is one or a combination of camphor tree branches, leaves, and sawdust.

[0009] Furthermore, the dry bean dregs in step B are one or a combination of soybean dregs, black bean dregs, and mung bean dregs.

[0010] Furthermore, the mass ratio of the dried and crushed forestry waste to the dry bean dregs and deionized water in step B is 1:1:16 to 3:1:40.

[0011] Furthermore, the drying in step A and step B is vacuum drying at a vacuum degree of 20000 Pa and a temperature of 80° C., and the drying time is 18 hours.

[0012] Furthermore, the nitrogen gas flow in step C is controlled by a needle valve to maintain the discharge pressure at 20Pa.

[0013] Furthermore, the heating temperature in step C is 120-140° C., and the heating time is 5-10 minutes.

[0014] Furthermore, the microwave source excitation frequency in step C is 2450 MHz and the power is 300 W. Beneficial Effects

[0015] 1. The present invention uses camphor tree waste as a carbon material precursor, which has a wide source, low cost, and is rich in terpenes and phenols. Using it as a raw material to prepare biochar is beneficial for copolymerization with the bean dregs selected by the present invention to form a carbon skeleton containing rich active functional groups.

[0016] 2. The present invention uses bean dregs as a nitrogen source, which can not only provide a partial carbon source, but also promote the in-situ doping of nitrogen on the surface of the carbon material, improve the electrochemical properties of the carbon electrode material, and enhance its interaction with the electrolyte when used as an electrode.

[0017] 3. The present invention uses nitrogen plasma to adjust the pore structure of the carbon-based electrode material precursor, which is low-temperature, energy-saving, rapid and pollution-free, and can effectively improve the microporous structure of the carbon-based material precursor and increase the specific pore volume.

[0018] 4. In the process of preparing carbon-based electrode materials, the present invention makes full use of the cross-linking interaction of the raw material components under hydrothermal conditions, organically combines nitrogen plasma to adjust the microporous structure, and the prepared electrode material has a capacitance increased by more than 50% compared with the carbon electrode material activated by alkali using a single camphor tree raw material.

[0019] 5. The electrode material prepared by the present invention realizes in-situ nitrogen doping, has rich pores, and retains a carbon skeleton containing rich active functional groups. It uses nitrogen plasma activation to provide a high pseudocapacitive specific capacity, improves the ion permeability and conductivity of the material, and enables it to have a large specific pore volume and excellent electrical properties. DETAILED DESCRIPTION

[0020] The present invention is further explained and illustrated below in conjunction with various embodiments.

[0021] A method for preparing a supercapacitor electrode material of the present invention comprises the following steps: Step A: Take forestry waste, clean it with deionized water, dry it, and crush it to a particle size of less than 3 mm; the forestry waste is one or a combination of camphor tree branches, leaves, and sawdust; the drying conditions are: vacuum degree 20000Pa, vacuum drying temperature 80°C, and drying time 18 hours.

[0022] Step B: Mix the dried and crushed forestry waste obtained in step A with dry bean dregs, add deionized water, place in a reactor, turn on the magnetic stirring device, rotate at 1000 r / min, heat to 250-320° C. at a rate of 10° C. / min, react for 10-15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak in benzyl alcohol for 24 hours, wash with deionized water and dry to obtain a carbon-based precursor.

[0023] The mass ratio of the dried and crushed forestry waste to dry bean dregs and deionized water is 1:1:16~3:1:40; the dry bean dregs are one or a combination of soybean dregs, black bean dregs and mung bean dregs; the drying conditions are: vacuum degree of 20000Pa, vacuum drying temperature of 80°C, and drying time of 18 hours.

[0024] Step C: Grind the carbon-based precursor obtained in step B for 60 minutes, place it in a plasma vacuum chamber, introduce nitrogen, heat and keep it warm for a certain period of time, and generate nitrogen plasma activation through microwave source excitation to obtain the target carbon electrode material, which is used as a supercapacitor electrode material.

[0025] The nitrogen gas flow rate is controlled by a needle valve to maintain the discharge pressure at 20Pa; the heating temperature is 120~140℃, and the insulation time is 5~10min; the microwave source excitation frequency is 2450MHz, and the power is 300W.

[0026] In order to better understand the present invention, the present invention is further described in detail below through examples. Embodiment 1

[0027] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 10g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 160g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 250℃ at a rate of 10℃ / min. React for 10 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 120℃, and keep it warm for 5min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W to obtain the target carbon electrode material.

[0028] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 201.2 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 187.1 F / g. Embodiment 2

[0029] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 10g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 160g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 320℃ at a rate of 10℃ / min. React for 15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 120℃, and keep it warm for 5min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W to obtain the target carbon electrode material.

[0030] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 221.5 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 207.1 F / g. Embodiment 3

[0031] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 10g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 160g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 250℃ at a rate of 10℃ / min. React for 10 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 140℃, and keep it warm for 10min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W, to obtain the target carbon electrode material.

[0032] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 217.6 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 191.2 F / g. Embodiment 4

[0033] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 10g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 160g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 320℃ at a rate of 10℃ / min. React for 15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 140℃, and keep it warm for 10min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W, to obtain the target carbon electrode material.

[0034] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 240.2 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 227.2 F / g. Embodiment 5

[0035] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 30g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 400g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 320℃ at a rate of 10℃ / min. React for 15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 140℃, and keep it warm for 10min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W, to obtain the target carbon electrode material.

[0036] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 230.7 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 216.8 F / g. Embodiment 6

[0037] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 30g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 400g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 250℃ at a rate of 10℃ / min. React for 15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 140℃, and keep it warm for 10min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W, to obtain the target carbon electrode material.

[0038] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 210.6 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 195.8 F / g. Embodiment 7

[0039] Take camphor tree branches, clean them with deionized water, dry them, and crush them to a particle size of no more than 3mm; mix 30g of the dried and crushed branches with 10g of dry bean dregs (one or more of soybean dregs, black bean dregs, and mung bean dregs), add 400g of deionized water, place them in a reactor, turn on the magnetic stirring device, the speed is 1000r / min, and the temperature is increased to 290℃ at a rate of 10℃ / min. React for 12 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak it in benzyl alcohol for 24 hours, wash it with deionized water and dry it to obtain a carbon-based precursor. Grind the obtained carbon-based precursor for 60min, place it in a quartz tube vacuum chamber, pass nitrogen, control it through a needle valve, maintain the discharge pressure at 20Pa, heat it to 130℃, and keep it warm for 7min, excite nitrogen plasma activation through a microwave source, the excitation frequency is 2450MHz, and the power is 300W to obtain the target carbon electrode material.

[0040] Cyclic voltammetry tests show that at a current density of 1 A / g, the specific capacitance is 219.8 F / g, and after 1000 cycles of charge and discharge, the mass specific capacitance can still be maintained at 206.6 F / g.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a supercapacitor electrode material, characterized in that: The following steps are involved: Step A: Take forestry waste, wash it with deionized water, dry it, and crush it to a particle size of less than 3 mm; Step B: Mix the dried and crushed forestry waste obtained in step A with dry bean dregs, add deionized water, place in a reactor, turn on a magnetic stirring device, rotate at 1000 r / min, heat to 250-320° C. at a rate of 10° C. / min, react for 10-15 hours, cool naturally to room temperature after the reaction, filter to obtain a solid product, soak in benzyl alcohol for 24 hours, wash with deionized water and dry to obtain a carbon-based precursor; Step C: Grind the carbon-based precursor obtained in step B for 60 minutes, place it in a plasma vacuum chamber, introduce nitrogen, heat and keep it warm for a certain period of time, and generate nitrogen plasma activation through microwave source excitation to obtain the target carbon electrode material, which is used as a supercapacitor electrode material.

2. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that: The forestry waste in step A is one or a combination of camphor tree branches, leaves, and wood chips.

3. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that: The dry bean dregs in step B are one or a combination of soybean dregs, black bean dregs, and mung bean dregs.

4. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that: The mass ratio of the dried and crushed forestry waste to the dry bean dregs and deionized water in the step B is 1:1:16 to 3:1:

40.

5. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that The drying in step A and step B is vacuum drying at a vacuum degree of 20000 Pa and a temperature of 80° C., and the drying time is 18 hours.

6. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that The nitrogen gas flow rate in step C is controlled by a needle valve to maintain the discharge pressure at 20Pa.

7. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that The heating temperature in step C is 120-140° C. and the temperature is kept for 5-10 minutes.

8. The method for preparing a supercapacitor electrode material according to claim 1, characterized in that The microwave source in step C has an excitation frequency of 2450 MHz and a power of 300 W.