Carbon production device and method based on coupling of low-pressure arc and paramagnetic resonance

Abstract

The application discloses a carbon preparation device and method based on low-voltage arc and paramagnetic resonance coupling. The device comprises a low-voltage discharge chamber, an electrode assembly, a vacuum pump, a static magnetic field generating coil and a microwave generator. The method is as follows: carbon precursors are fed into the low-voltage discharge chamber, electrode plate one and electrode plate two initiate low-voltage arc discharge to generate a uniform thermal field, which induces carbon precursors to generate carbon center free radicals with unpaired electrons; the arc uniformly wraps the carbon precursor particle flow in a low-pressure environment; the static magnetic field generated by the static magnetic field generating coil and the microwave frequency emitted by the microwave generator are adjusted to make the target defect center produce paramagnetic resonance, guiding the reconstruction of the carbon precursor pore structure or interlayer structure. The application can be used for preparing capacitor carbon for supercapacitors and negative electrode hard carbon for sodium ion or lithium ion batteries, and solves the problems of uneven energy distribution, high risk of local ablation of carbon skeleton, and difficulty in directional regulation of pore structure and interlayer structure in the existing carbon preparation mode.

Description

Technical Field

[0001] This invention relates to the field of directional control of the microstructure of carbon precursors and cross-application of plasma technology. Specifically, it relates to a carbon-making device and method that superimposes a controlled static magnetic field and a high-frequency alternating electromagnetic field in a low-pressure electric arc thermal field and uses electron paramagnetic resonance conditions to couple and control the defect centers of carbon precursors. This device can be used to prepare capacitor carbon for supercapacitors and hard carbon for negative electrodes of sodium-ion or lithium-ion batteries. Background Technology

[0002] Capacitor carbon and anode hard carbon are important materials in electrochemical energy storage systems. Capacitor carbon typically requires a high specific surface area, a reasonable micropore / mesopore distribution, and good pore connectivity; anode hard carbon typically requires a disordered carbon structure, relatively enlarged graphite microcrystal interlayer spacing, and suitable open and closed pore structures to improve energy storage processes such as ion adsorption, intercalation, or intrapore sodium storage.

[0003] Existing preparation methods mainly include high-temperature pyrolysis, physical activation, chemical activation, and plasma modification. High-temperature pyrolysis and physical activation processes typically have high energy consumption and narrow windows for controlling pore structure and interlayer structure. Although chemical activation with strong acids, strong bases, or salts can improve the degree of pore development, it may lead to problems such as complex post-processing, equipment corrosion, and high environmental burden.

[0004] Low-voltage electric arcs can, to some extent, expand the plasma interaction area and reduce the risk of localized overheating, thus facilitating the formation of a relatively uniform heat treatment environment. However, a single low-voltage electric arc primarily provides the overall thermal field, with limited ability to selectively control different free radicals, edge defects, and unpaired electrons near dangling bonds in the carbon precursor. Therefore, a carbon production method that can couple a macroscopically uniform thermal field with localized energy at defect centers is still needed.

[0005] Electron paramagnetic resonance (EPR) signals can characterize parameters such as the Landé g-factor, linewidth, and lineshape of species containing unpaired electrons. For carbon precursors, different Landé g-factor ranges correspond to unpaired electrons in different chemical environments, such as carbon central radicals and mobile electron signals from defects associated with aromatic or graphitic structures. Therefore, by controlling the magnetic induction intensity of the static magnetic field and the frequency of the high-frequency alternating electromagnetic field to satisfy the resonance conditions of specific defect centers, it is hoped that the controllability of the local structural evolution during the heat treatment of carbon precursors can be improved. Summary of the Invention

[0006] The present invention aims to provide a carbon production method and apparatus based on low-voltage electric arc and paramagnetic resonance coupling, so as to solve the problems of uneven energy distribution, high risk of local ablation of carbon skeleton, and difficulty in directional control of pore structure and interlayer structure in existing carbon production methods.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention relates to a charcoal-making device based on low-voltage electric arc and paramagnetic resonance coupling, comprising a low-voltage discharge chamber, an electrode assembly, a vacuum pump, a static magnetic field generating coil, and a microwave generator. The electrode assembly is placed inside the low-voltage discharge chamber and includes two electrode plates, a first electrode plate and a second electrode plate, arranged parallel to each other and fixed on both sides of the chamber. Electrode plates a first electrode plate and a second electrode plate are connected to a pulse power supply. The inlet of the vacuum pump is connected to the outlet of the side of the low-voltage discharge chamber. Two static magnetic field generating coils are symmetrically arranged outside the low-voltage discharge chamber and are both powered by a DC power supply. The transmitting end of the microwave generator is connected to a hollow tube, which passes through the static magnetic field generating coil near electrode plate a second electrode plate, enters the low-voltage discharge chamber, and passes through electrode plate a second electrode plate.

[0009] Preferably, a feed hopper is fixed at the feed inlet at the top of the low-pressure discharge chamber and a vacuum valve is provided.

[0010] Preferably, a collection box is provided at the discharge port at the bottom of the low-pressure discharge chamber.

[0011] Preferably, the pulse power supply, DC power supply, and microwave generator are all controlled by a controller.

[0012] This invention relates to a carbon-making method based on low-voltage electric arc and paramagnetic resonance coupling, as detailed below:

[0013] The carbon precursor is fed into a low-pressure discharge chamber. Inside the chamber, electrode plates one and two, under the influence of a pulsed power supply, induce a low-pressure arc discharge, generating a uniform thermal field that induces the carbon precursor to produce carbon-centric free radicals with unpaired electrons. A vacuum pump maintains the low-pressure environment of the discharge chamber at 50–500 Pa, ensuring the arc uniformly envelops the carbon precursor particle flow. Two static magnetic field generating coils, powered by a DC power supply, generate a static magnetic field, causing Zeeman splitting of the electronic energy levels within the carbon precursor. Microwaves emitted by a microwave generator are transmitted through a hollow tube between electrode plates one and two, generating a high-frequency alternating electromagnetic field. The magnetic induction intensity B of the static magnetic field and the frequency of the microwaves emitted by the microwave generator are adjusted. This causes the magnetic induction intensity B and microwave frequency to... Landes and the target defect center The factor satisfies the paramagnetic resonance condition, thereby causing the target defect center to generate paramagnetic resonance and guiding the reconstruction of the bulk pore structure or interlayer structure of the carbon precursor.

[0014] Preferably, the paramagnetic resonance condition follows the Zeeman split resonance energy matching model:

[0015]

[0016] In the formula, Let be Planck's constant. The microwave frequency emitted by the microwave generator. Landes, as the target defect center for carbon precursors factor, For Bohr magneton, The magnetic flux density of the static magnetic field is denoted as .

[0017] More preferably, during the preparation of capacitor carbon, the vacuum degree of the low-pressure discharge chamber is maintained at 100–500 Pa, the temperature is maintained at 800–1000°C, and the target defect is an oxygen- or nitrogen-containing defect. (Landesch) The factor ranges from 2.0027 to 2.0040.

[0018] More preferably, the Landes The factor ranges from 2.0030 to 2.0040.

[0019] More preferably, the paramagnetic resonance coupling of carbon center radicals near oxygen- or nitrogen-containing defects promotes the activation, breakage, and removal of C–O–C oxygen-containing bridges and adjacent oxygen-containing functional groups, thereby promoting micropore expansion, mesopore formation, and improved pore connectivity.

[0020] More preferably, during the preparation of the negative electrode hard carbon, the vacuum degree of the low-pressure discharge chamber is maintained at 50–200 Pa, and the temperature is maintained at 1000–1400°C. The target defects are the edges of aromatic plates, the surface of open micropores, vacancies, and oxygen / nitrogen terminating dangling bond defects. With a factor of 2.0024 to 2.0030, the paramagnetic resonance coupling of the carbon center free radicals near these defects enhances the energy absorption and structural perturbation of the local defect sites, suppresses the tendency of excessively ordered stacking of graphite sheets, and makes the interlayer spacing d002 of the graphite microcrystals of the obtained negative electrode hard carbon greater than 0.37 nm.

[0021] The present invention has the following beneficial effects:

[0022] 1. This invention combines the macroscopic uniform thermal field of a low-voltage electric arc with a paramagnetic resonance coupled field composed of a static magnetic field and a high-frequency alternating electromagnetic field under paramagnetic resonance conditions. This can solve the problem of large randomness in structural evolution in single thermal field treatment and improve the directionality of carbon precursor pore structure and interlayer structure control.

[0023] 2. In the preparation of capacitive carbon, this invention promotes the activation and removal of oxygen- and nitrogen-containing bridges and functional groups by matching the Landes g factor of free radicals near carbon centers with oxygen / nitrogen defects. This is beneficial for the formation of a hierarchical pore structure in which micropores and mesopores coexist, thereby improving adsorption performance and electrochemical ion transport performance.

[0024] 3. In the preparation of anode hard carbon, this invention suppresses the excessive ordering trend during high-temperature processing by matching the Landes g factor of free radicals at the edges of aromatic sheets, the surface of open micropores, vacancies and dangling bonds of carbon centers. This is beneficial to obtaining a larger interlayer spacing d002 and a stable disordered layer structure, thereby improving the reversible storage capacity of sodium ions or lithium ions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the carbon-making device based on low-voltage electric arc and paramagnetic resonance coupling of the present invention. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] like Figure 1As shown, the charcoal-making device based on low-voltage electric arc and paramagnetic resonance coupling includes a feed hopper 1, a vacuum valve 7, a low-voltage discharge chamber, an electrode assembly, a vacuum pump, a static magnetic field generating coil 4, and a microwave generator 9. The feed hopper 1 is fixed at the feed inlet at the top of the low-voltage discharge chamber, and a vacuum valve 7 is provided at the feed inlet of the low-voltage discharge chamber. Carbon precursors (such as biomass-based pre-carbonized materials) enter the low-voltage discharge chamber continuously or intermittently through the feed hopper 1 and are dispersed in the reaction zone. The electrode assembly is placed in the low-voltage discharge chamber and includes electrode plate 2 and electrode plate 3 fixed parallel to both sides of the low-voltage discharge chamber. Electrode plate 2 and electrode plate 3 are connected to a pulse power supply 8 to initiate a low-voltage (50-180V) electric arc discharge, generating a uniform thermal field that excites the chemical bonds in the carbon precursor particles to a high-energy state, producing carbon-centered free radicals with unpaired electrons. The vacuum pump's inlet is connected to the outlet on the side of the low-pressure discharge chamber. The vacuum pump continuously pumps air to maintain a low-pressure state and promptly removes impurity gases (such as CO, CO2, and H2O) removed during the reconstruction process, maintaining a low-pressure environment of 50–500 Pa in the low-pressure discharge chamber. This low-pressure environment is crucial for transforming the arc from a "linear" to a "dispersed surface," ensuring uniform encapsulation of the particle flow. Two static magnetic field generating coils 4 are symmetrically arranged outside the low-pressure discharge chamber, both powered by a DC power supply 10, providing a stable static magnetic field 12. This causes Zeeman splitting of the electronic energy levels inside the carbon precursor, providing the necessary physical conditions for paramagnetic resonance. The transmitting end of microwave generator 9 is connected to hollow tube 5. Hollow tube 5 passes through the static magnetic field generating coil 4 near electrode plate 2 3 and enters the low-voltage discharge chamber. After passing through electrode plate 2 3, the high-frequency (e.g., 9.4 GHz) microwaves emitted by microwave generator 9 are transmitted between electrode plate 1 2 and electrode plate 2 3 via hollow tube 5, generating a high-frequency alternating electromagnetic field 13. The microwave frequency can be X-band, Q-band, or other frequency bands selected according to the Landé g factor. The pulse power supply, DC power supply, and microwave generator 9 are all controlled by controller 11. The controller can adjust the pulse frequency of the pulse power supply, adjust the current of the DC power supply to provide static magnetic fields with different magnetic induction intensities B, and adjust the microwave frequency of microwave generator 9 to induce paramagnetic resonance at the target defect center. During this process, the defect generates carbon center free radicals with unpaired electrons. The target defect center is the carbon center free radical near the target defect.

[0028] In a preferred embodiment, a collection box 6 is provided at the outlet at the bottom of the low-pressure discharge chamber to collect the carbon precursor after the low-pressure electric arc and paramagnetic resonance coupling treatment.

[0029] The carbon production method based on low-voltage electric arc and paramagnetic resonance coupling is as follows:

[0030] The feed hopper continuously feeds the carbon precursor into the low-pressure discharge chamber. Inside the chamber, electrode plates 2 and 3, under the action of pulse power supply 8, induce a low-pressure arc discharge, generating a uniform thermal field that induces the carbon precursor to produce carbon-centered free radicals with unpaired electrons. A vacuum pump maintains the low-pressure environment in the discharge chamber at 50–500 Pa, causing the arc to form a "dispersed surface" that uniformly envelops the carbon precursor particle flow. Two static magnetic field generating coils 4, under the action of DC power supply 10, generate a static magnetic field 12, causing Zeeman splitting of the electronic energy levels within the carbon precursor. Microwaves emitted by microwave generator 9 are transmitted through hollow tube 5 between electrode plates 2 and 3, generating a high-frequency alternating electromagnetic field 13. This superimposes the controlled static magnetic field and the high-frequency alternating electromagnetic field in the reaction zone between electrode plates 2 and 3. The magnetic induction intensity B of the static magnetic field and the microwave frequency emitted by microwave generator 9 are adjusted. (Also the frequency of the high-frequency alternating electromagnetic field), causing the magnetic induction intensity B and microwave frequency to... Landes and the target defect center The factors satisfy the paramagnetic resonance condition, thereby coupling electromagnetic energy to the target defect center, causing the target defect center to generate paramagnetic resonance, and guiding the reconstruction of the carbon precursor pore (micropore / mesopore) structure or interlayer structure.

[0031] Among them, the paramagnetic resonance condition follows the Zeemansplitting resonance energy matching model:

[0032]

[0033] In the formula, Let be Planck's constant. The microwave frequency emitted by microwave generator 9. Landes, as the target defect center for carbon precursors factor, For Bohr magneton, The magnetic flux density of the static magnetic field is denoted as .

[0034] During the preparation of capacitor carbon, the vacuum degree of the low-pressure discharge chamber is maintained at 100–500 Pa, and the temperature is maintained at 800–1000°C. The target defect is preferably an oxygen- or nitrogen-containing defect, and the Landé clairvoyance of the defect center is the target defect. The factor is 2.0027–2.0040, preferably 2.0030–2.0040, and is used to match carbon center radicals near oxygen- or nitrogen-containing defects. Paramagnetic resonance coupling of carbon center radicals near oxygen- or nitrogen-containing defects promotes the activation, breakage, and removal of C–O–C oxygen-containing bridges and adjacent oxygen-containing functional groups, thereby promoting micropore expansion, mesopore formation, and improved pore connectivity.

[0035] During the preparation of the anode hard carbon, the vacuum degree of the low-pressure discharge chamber is maintained at 50–200 Pa, and the temperature is maintained at 1000–1400°C. Target defects are preferably the edges of aromatic lamellars, open (not closed) micropore surfaces, vacancies, and oxygen / nitrogen terminating dangling bond defects. The Landes crystallization at the center of this defect... The factor ranges from 2.0024 to 2.0030. The paramagnetic resonance coupling of the carbon center free radicals near these defects enhances the energy absorption and structural perturbation of the local defect sites, suppressing the tendency of excessively ordered stacking of graphite sheets. This is beneficial for obtaining a larger interlayer spacing and a stable disordered layer structure, resulting in a graphite microcrystal interlayer spacing d002 greater than 0.37 nm in the obtained negative electrode hard carbon.

[0036] Example 1: Control of Carbon Pore Structure in Capacitors

[0037] Use biomass-based pre-carbonized feed from the same batch that has been pre-carbonized at 600°C as raw material, such as coconut shell-based pre-carbonized feed.

[0038] The control group was treated with a low-voltage electric arc at 900°C in a 400Pa environment. This process mainly relied on overall thermal action to open the pores and partially enlarge them, and the product pore size distribution was still mainly micropores.

[0039] The experimental group also used a 900°C thermal field provided by a low-voltage electric arc at a 400 Pa environment, but superimposed a paramagnetic resonance coupling field composed of a static magnetic field and a high-frequency alternating electromagnetic field. The preferred parameters were g = 2.0035, ν = 9.0 GHz, and B = 0.321 T. This g value is located in the radical response range of carbon centers near oxygen-containing defects. Preparing capacitive carbon under these preferred parameters, which meet the paramagnetic resonance conditions, can promote the activation and removal of oxygen-containing defects and C–O–C oxygen-containing bridges, causing some micropores to expand into mesopores and improving pore connectivity.

[0040] Table 1 shows a comparison of the performance indicators of the capacitor carbon prepared in the control group and the experimental group.

[0041] Table 1

[0042] Performance indicators control group experimental group Results Explanation methylene blue adsorption value 145mg / g 235mg / g The increased methylene blue adsorption value indicates an increase in mesoporous contribution and pore connectivity, which can be attributed to the synergistic effect of oxygen-containing defect activation, removal, and pore structure rearrangement. Iodine adsorption value 1180mg / g 1350mg / g An increase in iodine adsorption value indicates that the total adsorption sites and microporous structure remain at a high level.

[0043] Example 2: Regulation of interlayer structure of hard carbon in negative electrode

[0044] A lignin-based hard carbon precursor was selected and processed under a vacuum of 150 Pa.

[0045] The control group was treated with a low-voltage electric arc to provide a 1300°C thermal field. Due to the lack of local resonant coupling regulation, the carbon layer underwent localized ordering under the drive of high-temperature thermodynamics, and the interlayer spacing showed a tendency to shrink.

[0046] The experimental group also used a low-voltage electric arc to provide a 1300°C thermal field, but superimposed a paramagnetic resonance coupling field composed of a static magnetic field and a high-frequency alternating electromagnetic field. This field was optimally matched to the carbon center free radicals at the edges of aromatic lamellars, the surfaces of open micropores, vacancies, and oxygen / nitrogen-terminated dangling bond defects, with a Landé g-factor of 2.0024–2.0030. If a Q-band microwave frequency is used, [the value is missing from the original text]. For a frequency of 35 GHz, the corresponding B is in the range of 1.248–1.249 T. In this embodiment, B = 1.248 T is chosen. Preparing hard carbon anodes under these parameters, which meet the paramagnetic resonance conditions, can enhance the structural perturbation of local defect sites and reduce the tendency for excessively ordered stacking of layers at high temperatures, thereby helping to maintain a larger interlayer spacing d002.

[0047] Table 2 shows a comparison of the performance indicators of the negative electrode hard carbon prepared in the control group and the experimental group.

[0048] Table 2

[0049] Performance indicators control group experimental group Results Explanation Interlayer spacing d002 0.362nm 0.386nm The increased interlayer spacing in the experimental group indicates that resonant coupling helps suppress excessively ordered stacking and maintain a disordered layer structure. First reversible capacity 265mAh / g 335mAh / g Synergistic regulation of interlayer spacing, defect sites, and pore structure is beneficial to improving the reversible storage capacity of sodium ions.

Claims

1. A charcoal-making device based on low-voltage electric arc and paramagnetic resonance coupling, comprising a low-voltage discharge chamber and an electrode assembly, characterized in that: It also includes a vacuum pump, a static magnetic field generating coil, and a microwave generator; the electrode assembly is placed in the low-pressure discharge chamber, including electrode plate one and electrode plate two arranged in parallel and fixed on both sides of the low-pressure discharge chamber, and electrode plate one and electrode plate two are connected to a pulse power supply; the air inlet of the vacuum pump is connected to the air outlet on the side of the low-pressure discharge chamber; the two static magnetic field generating coils are symmetrically arranged outside the low-pressure discharge chamber and are both powered by a DC power supply; the transmitting end of the microwave generator is connected to a hollow tube, which passes through the static magnetic field generating coil near electrode plate two, and enters the low-pressure discharge chamber, passing through electrode plate two.

2. The charcoal-making device based on low-voltage electric arc and paramagnetic resonance coupling according to claim 1, characterized in that: The feed hopper is fixed at the feed inlet at the top of the low-pressure discharge chamber and is equipped with a vacuum valve.

3. The charcoal-making device based on low-voltage electric arc and paramagnetic resonance coupling according to claim 1, characterized in that: A collection box is installed at the discharge port at the bottom of the low-pressure discharge chamber.

4. The charcoal-making apparatus based on low-voltage electric arc and paramagnetic resonance coupling according to claim 1, 2 or 3, characterized in that: The pulse power supply, DC power supply, and microwave generator are all controlled by a controller.

5. A carbon production method based on low-voltage electric arc and paramagnetic resonance coupling, characterized in that: The carbon precursor is fed into a low-pressure discharge chamber. Under the action of a pulse power supply, electrode plate one and electrode plate two in the low-pressure discharge chamber trigger a low-pressure arc discharge, generating a uniform thermal field and inducing the carbon precursor to generate carbon-centered free radicals with unpaired electrons. The vacuum pump maintains the low-pressure environment of 50 to 500 Pa in the low-pressure discharge chamber, so that the arc uniformly wraps the carbon precursor particle flow. Two static magnetic field generating coils, under the action of a DC power supply, generate a static magnetic field, causing Zeeman splitting of the electronic energy levels inside the carbon precursor; microwaves emitted by the microwave generator are transmitted through a hollow tube between electrode plate one and electrode plate two, generating a high-frequency alternating electromagnetic field; the magnetic induction intensity B of the static magnetic field and the microwave frequency emitted by the microwave generator are adjusted. This causes the magnetic induction intensity B and microwave frequency to... Landes and the target defect center The factor satisfies the paramagnetic resonance condition, thereby causing the target defect center to generate paramagnetic resonance and guiding the reconstruction of the bulk pore structure or interlayer structure of the carbon precursor.

6. The carbon production method based on low-voltage electric arc and paramagnetic resonance coupling according to claim 5, characterized in that: The paramagnetic resonance condition follows the Zeeman split resonance energy matching model: In the formula, is Planck's constant. The microwave frequency emitted by the microwave generator. Landes, as the target defect center for carbon precursors factor, For Bohr magneton, The magnetic flux density of the static magnetic field is denoted as .

7. The carbon production method based on low-voltage electric arc and paramagnetic resonance coupling according to claim 6, characterized in that: During the preparation of capacitor carbon, the vacuum degree of the low-pressure discharge chamber is maintained at 100–500 Pa, and the temperature is maintained at 800–1000°C. The target defects are oxygen-containing or nitrogen-containing defects. (Landesch) The factor ranges from 2.0027 to 2.0040.

8. The carbon production method based on low-voltage electric arc and paramagnetic resonance coupling according to claim 7, characterized in that: Landes The factor ranges from 2.0030 to 2.0040.

9. The carbon production method based on low-voltage electric arc and paramagnetic resonance coupling according to claim 7, characterized in that: Paramagnetic resonance coupling of carbon center free radicals near oxygen- or nitrogen-containing defects promotes the activation, breakage, and removal of C–O–C oxygen-containing bridges and adjacent oxygen-containing functional groups, thereby promoting micropore expansion, mesopore formation, and improved pore connectivity.

10. The carbon production method based on low-voltage electric arc and paramagnetic resonance coupling according to claim 6, characterized in that: During the preparation of the negative electrode hard carbon, the vacuum degree of the low-pressure discharge chamber is maintained at 50–200 Pa, and the temperature is maintained at 1000–1400°C. The target defects are the edges of aromatic plates, the surface of open micropores, vacancies, and oxygen / nitrogen terminating dangling bond defects. (Landesch) With a factor of 2.0024 to 2.0030, the paramagnetic resonance coupling of the carbon center free radicals near these defects enhances the energy absorption and structural perturbation of the local defect sites, suppresses the tendency of excessively ordered stacking of graphite sheets, and makes the interlayer spacing d002 of the graphite microcrystals of the obtained negative electrode hard carbon greater than 0.37 nm.

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