High-energy density capacitor and preparation method thereof

Abstract

The invention relates to the technical field of capacitors, and discloses a high-energy-density capacitor which is characterized in that a positive electrode is composed of a composite active material, a conductive agent and a binder, the composite active material comprises a mixture of nitrogen-sulfur co-doped carbon foam magnetic microspheres and iron sesquioxide nanodot at nitrogen-doped graphene, and the conductive agent is a mixture of nitrogen-sulfur co-doped carbon foam magnetic microspheres and iron sesquioxide nanodot at nitrogen-doped graphene. The preparation method of the nitrogen-sulfur co-doped carbon foam magnetic microspheres comprises the following steps: by taking polyacrylonitrile as a carbon source, thiourea as a sulfur source and ferric nitrate as an iron source, carrying out hydrothermal reaction and then carrying out carbonization treatment at 800-1000 DEG C for 2-4 hours; the energy density of the high-energy-density capacitor can reach 700-800 Wh / kg, the power density is larger than or equal to 10 kW / kg, compared with a traditional super capacitor, the high-energy-density capacitor has the advantages that the energy density is remarkably improved, and the application requirements of the fields with high requirements for energy and power such as electric automobiles and intelligent power grids can be met.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and specifically relates to a high energy density capacitor based on a composite electrode and a hierarchical pore structure and a preparation method thereof, which is applicable to electric vehicles, smart grids and portable electronic devices. Background Art

[0002] With the rapid development of technology, capacitors have been widely used in many fields such as modern electronic devices, electric vehicles and smart grids. However, there are some problems that need to be solved urgently in the performance of current traditional supercapacitors. For example, their energy density is generally low, usually lower than 50 Wh / kg, which severely limits their application in some scenarios with high energy requirements. At the same time, the problems of insufficient active sites of electrode materials and low migration rate of electrolyte ions also restrict the improvement of the overall performance of capacitors.

[0003] Many researchers and enterprises are committed to solving these problems. For example, Patent CN119274786A proposes to use nitrogen and sulfur functionalized carbon foam materials to improve the performance of capacitors. However, it is found in actual applications that its cycle life is still insufficient, and the number of cycles is less than 3000 times, which is difficult to meet the requirements of long-term stable use. In addition, the literature "Triazine-containing covalent organic polymer-derived grid-like multilocular spheres" (Adv. Mater. 2025) reports a new material system. Although there is a breakthrough in energy density, achieving an energy density of 675 Wh / kg, the preparation process of this material is complex, involving multi-step high-precision operations, and the cost is high, which is not conducive to large-scale industrial production and practical applications. Summary of the Invention

[0004] (I) Technical Problems to be Solved The present invention aims to provide a high energy density capacitor and a preparation method thereof to solve the problems of low energy density, short cycle life, complex preparation process and high cost of capacitors in the prior art.

[0005] (II) Technical Solutions Innovation of Electrode Materials: The positive electrode uses a nitrogen and sulfur co-doped carbon foam magnetic microsphere and iron oxide nanodot composite. Through the hydrothermal carbonization method of thiourea, the reaction conditions are precisely controlled to significantly increase the specific surface area of the carbon foam magnetic microsphere, reaching ≥2000 m² / g, and effectively enhancing the pseudocapacitance effect. Among them, the preparation method of the nitrogen and sulfur co-doped carbon foam magnetic microsphere is as follows: Polyacrylonitrile is used as the carbon source, which has abundant carbon atoms and provides sufficient carbon elements for the subsequent formation of carbon foam; thiourea is used as the sulfur source, which can uniformly dope sulfur elements into the carbon material during the hydrothermal reaction. The doping of sulfur elements can not only adjust the electronic structure of the carbon material but also increase its active sites; ferric nitrate is used as the iron source, and after hydrothermal reaction and carbonization treatment, the carbonization temperature is strictly controlled at 800 - 1000 °C for 2 - 4 hours. Under these conditions, iron elements can be evenly distributed in the carbon foam magnetic microsphere to form a magnetic microsphere structure, which is conducive to improving the conductivity of the electrode and the utilization rate of active substances.

[0006] The negative electrode selects a honeycomb-like multi-cavity nanosphere covalent triazine porous polymer (GS-TCOP) material. Its unique honeycomb-like multi-cavity structure greatly increases the specific surface area of the electrode, accelerates the diffusion rate of ions in the electrode material, and can effectively buffer the volume expansion of active substances during charge and discharge, thereby improving the stability and cycle life of the electrode. The specific capacitance of this material in the KI-H2SO4 mixed electrolyte is ≥8000 Fg⁻¹, and the energy density is ≥600 Whkg⁻¹, showing excellent electrochemical performance.

[0007] Structural design: The dielectric layer uses an arrayed aluminum oxide / silicon nitride composite film with a thickness precisely controlled at 50 - 200 nm. Through atomic layer deposition (ALD) technology, the uniformity and density of the film are ensured. This arrayed dielectric layer structure not only has a high dielectric constant (ε≥15) and can effectively store charges but also has excellent voltage resistance, with a breakdown field strength ≥50 MV / m, ensuring the stable operation of the capacitor at high voltages.

[0008] The encapsulation housing (50) incorporates a cloud controller (51) and a voltage detection module (52). The cloud controller is connected to external devices through a wireless communication module (ZigBee or NB-IoT), enabling real-time remote monitoring of the charge and discharge status of the capacitor, and being able to optimize the charge and discharge strategy based on the monitoring data and give early warnings of faults, greatly improving the safety and reliability of the capacitor in actual use.

[0009] Optimization of the preparation process: The positive and negative electrode slurries are mixed using airflow pulverization technology, and the particle size distribution D50≤5 μm is strictly controlled to ensure the uniformity and consistency of the electrode material particles, which is conducive to improving the conductivity of the electrode and the utilization rate of active substances.

[0010] The electrolyte is injected by the vacuum impregnation method. The vacuum degree is strictly controlled at ≤10⁻³ Pa, and the impregnation time is ≥24 hours, ensuring that the electrolyte can be fully filled into the pores of the electrode material, improving the internal resistance uniformity and cycle stability of the capacitor.

[0011] (III) Beneficial effects The energy density of this high-energy density capacitor can reach 700 - 800 Wh / kg, and the power density is ≥10 kW / kg, showing a significant improvement compared to traditional supercapacitors, and can meet the application requirements of fields with high energy and power requirements such as electric vehicles and smart grids.

[0012] The cycle life exceeds 10,000 times (capacity retention rate ≥90%), greatly extending the service life of the capacitor, reducing the use cost, and improving its competitiveness in practical applications.

[0013] It supports operation in a wide temperature range from -40°C to 85°C, has excellent environmental adaptability, and can operate stably under harsh environmental conditions, broadening its application range. Brief description of the drawings

[0014] Figure 1 It is a schematic diagram of the process of the present invention; Detailed implementation manners

[0015] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Detailed implementation manners

[0016] Example 1 Please refer to Figure 1 , Preparation of the positive electrode: Mix nitrogen-sulfur co-doped carbon foam magnetic microspheres (prepared according to the above preparation method) and iron oxide nanodots@nitrogen-doped graphene in a mass ratio of 3:1, and then add an appropriate amount of PVDF binder. The three are fully mixed by the air flow pulverization technology to ensure that the particle size distribution D50 ≤ 5 μm. Then the mixed slurry is coated on the aluminum foil current collector and dried in a vacuum drying oven at 120°C for 12 hours to completely remove the solvent and moisture. Finally, it is pressed at a pressure of 10 MPa to form a positive electrode sheet with stable performance.

[0017] Negative electrode preparation: Take GS-TCOP material, mix it with acetylene black and PTFE in a ratio of 7:2:1, and also use the air flow pulverization technology to mix evenly. The particle size distribution D50 ≤ 5μm. Coat the mixed slurry on the copper foil current collector, and cure it at a temperature of 120°C for 6 hours in an argon atmosphere to ensure good bonding between the negative electrode material and the current collector, and form a negative electrode sheet with excellent performance.

[0018] Dielectric layer deposition: Use atomic layer deposition (ALD) technology to alternately deposit alumina and silicon nitride thin films on the surface of the positive electrode. The total number of cycles is 200 times. The deposition temperature is strictly controlled at 200 - 250°C, and the thickness of a single cycle is 0.1nm. By precisely controlling the deposition parameters, ensure that the thickness of the dielectric layer is uniform and dense. Finally, obtain an alumina / silicon nitride composite thin film with a thickness of 150nm, and its dielectric constant ≥ 15, which can effectively store charges and improve the insulation performance of the capacitor.

[0019] Assembly and encapsulation: In a glove box filled with argon, stack and assemble the prepared positive electrode sheet, dielectric layer and negative electrode sheet, and then inject a mixed electrolyte of potassium hydroxide and sulfuric acid (KOH concentration is 6mol / L, H2SO4 concentration is 1mol / L). Use the vacuum impregnation method to ensure that the electrolyte fully fills the pores of the electrode material. The vacuum degree ≤ 10⁻³Pa, and the impregnation time ≥ 24 hours. Finally, use laser welding technology to encapsulate the shell to ensure the airtightness and stability of the encapsulation, and integrate the voltage detection module to complete the assembly of the capacitor.

[0020] Performance test: Conduct performance tests on the assembled capacitor, and conduct charge and discharge tests in the voltage range of 0 - 2.7V. The test results show that its energy density is 765Wh / kg. After 5000 cycles of charge and discharge, the capacity retention rate is still as high as 93%, showing excellent electrochemical performance and cycle stability.

[0021] Example 2 Positive electrode preparation: The same as in Example 1.

[0022] Negative electrode preparation: The same as in Example 1.

[0023] Dielectric layer deposition: Use atomic layer deposition (ALD) technology to alternately deposit alumina and silicon nitride thin films on the surface of the positive electrode. The total number of cycles is 100 times, and other parameters are the same as in Example 1. Finally, obtain an alumina / silicon nitride composite thin film with a thickness of 75nm.

[0024] Assembly and encapsulation: The same as in Example 1.

[0025] Performance Test: Under the same test conditions, the energy density of this capacitor is 720 Wh / kg, and the breakdown voltage is increased to 3.0 V, indicating that the adjustment of the dielectric layer thickness has a significant impact on its performance. In practical applications, an appropriate dielectric layer thickness can be selected according to specific requirements.

[0026] Example 3 Positive Electrode Preparation: The same as in Example 1.

[0027] Negative Electrode Preparation: The same as in Example 1.

[0028] Dielectric Layer Deposition: Using atomic layer deposition (ALD) technology, alumina and silicon nitride thin films are alternately deposited on the surface of the positive electrode. The total number of cycles is 150 times, and other parameters are the same as in Example 1, obtaining a composite thin film with a thickness of 112.5 nm.

[0029] Assembly and Encapsulation: The same as in Example 1.

[0030] Performance Test: The test results show that the energy density of this capacitor is 740 Wh / kg, and after 8000 cycles, the capacity retention rate is 92%, further verifying the stability of this preparation process and the excellent performance of the capacitor.

[0031] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high energy density capacitor, characterized in that: The positive electrode is composed of a composite active material, a conductive agent, and a binder. The composite active material contains a mixture of nitrogen and sulfur co-doped carbon foam magnetic microspheres and iron oxide nanoparticles @ nitrogen-doped graphene. The preparation method of the nitrogen and sulfur co-doped carbon foam magnetic microspheres includes: using polyacrylonitrile as the carbon source, thiourea as the sulfur source, and ferric nitrate as the iron source, followed by hydrothermal reaction and carbonization treatment. The carbonization temperature is 800 - 1000 °C, and the time is 2 - 4 hours. The mass ratio of the nitrogen and sulfur co-doped carbon foam magnetic microspheres to the iron oxide nanoparticles in the positive electrode active material is 3:1, and the loading amount of nitrogen-doped graphene is 10% - 15% of the total mass.

2. The negative electrode uses a honeycomb-like multi-cavity nanosphere covalent triazine porous polymer (GS-TCOP) material. The specific capacitance of the GS-TCOP material in the KI-H2SO4 mixed electrolyte is ≥8000 Fg⁻¹, and the energy density is ≥600 Whkg⁻¹.

3. The dielectric layer is an arrayed aluminum oxide / silicon nitride composite film with a thickness of 50 - 200 nm. The arrayed arrangement is a hexagonal honeycomb structure, the diameter of a single pore is 10 - 50 nm, and the porosity is ≥80%.

4. The electrolyte uses a mixed electrolyte of potassium hydroxide and sulfuric acid, where the concentration of KOH is 6 mol / L and the concentration of H2SO4 is 1 mol / L.

5. The encapsulation housing contains a cloud controller and a voltage detection module, which are used to monitor the charge and discharge status of the capacitor in real time and upload it to the cloud platform. The cloud controller is connected to external devices through a wireless communication module (ZigBee or NB-IoT) to realize remote charge and discharge strategy optimization and fault warning.

6. The high energy density capacitor according to claim 1, wherein: The specific surface area of the nitrogen and sulfur co-doped carbon foam magnetic microspheres is ≥2000 m² / g, with excellent electrical conductivity and active material utilization rate.

7. A high energy density capacitor according to claim 1, characterized in that: The pore size distribution of the honeycomb-like multi-cavity structure of the GS-TCOP material is 5 - 50 nm, and the specific surface area is ≥3000 m² / g, which can effectively accelerate ion diffusion and buffer volume expansion.

8. A high energy density capacitor according to claim 1, characterized in that: The dielectric constant of the aluminum oxide / silicon nitride composite film of the dielectric layer is ≥15, and the breakdown field strength is ≥50 MV / m, with excellent insulation performance and voltage resistance performance.

9. A high energy density capacitor according to claim 1, characterized in that: The conductivity of the mixed electrolyte of potassium hydroxide and sulfuric acid of the electrolyte is ≥2 S / cm, which can effectively improve the ion migration rate.

10. A high energy density capacitor according to claim 1, characterized in that: The cloud controller of the encapsulation housing can realize real-time monitoring of the charge and discharge status of the capacitor, optimize the charge and discharge strategy according to the monitoring data, give early warning of faults, and improve the safety and reliability of the capacitor.

11. A method for preparing a high energy density capacitor according to any one of claims 1-6, characterized in that, It includes the following steps: S1. Preparation of the positive electrode: Mix the composite active material, conductive carbon (SuperP), and PVDF binder in a mass ratio of 8:1:1, mix evenly by air jet milling technology, with a particle size distribution D50 ≤ 5 μm, coat it on an aluminum foil current collector, dry at 120 °C for 12 hours, and then press at 10 MPa. S2. Preparation of the negative electrode: Mix the GS-TCOP material, acetylene black, and PTFE in a ratio of 7:2:1, mix evenly by air jet milling technology, with a particle size distribution D50 ≤ 5 μm, coat it on a copper foil current collector, and cure at 120 °C for 6 hours in an argon atmosphere. S3. Dielectric layer deposition: Using atomic layer deposition (ALD) technology, alumina and silicon nitride thin films are alternately deposited on the positive electrode surface. The total number of cycles is 100 - 200 times, the deposition temperature is 200 - 250 °C, and the thickness per single cycle is 0.1 nm; S4. Assembly and encapsulation: After stacking the positive electrode, dielectric layer, and negative electrode, electrolyte is injected. Using the vacuum impregnation method, the vacuum degree is ≤10⁻³ Pa, the impregnation time is ≥24 hours, and then the housing is encapsulated by laser welding and a voltage detection module is integrated.

12. The preparation method according to claim 7, characterized in that, During the preparation process of the positive electrode, the mixing time of the composite active material is 1 - 2 hours to ensure that the materials are fully and evenly mixed.

13. The preparation method according to claim 7, wherein, During the preparation process of the negative electrode, the curing time is 6 - 8 hours to ensure good bonding between the materials and the current collector.

14. The preparation method according to claim 7, wherein During the dielectric layer deposition process, the deposition rate of the ALD technology is 0.1 - 0.2 nm / cycle to ensure uniform deposition of the thin film.

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