Super-capacitor based on curved graphene composite electrode and preparation method thereof

Abstract

The application provides a curved surface graphene composite electrode supercapacitor and a preparation method thereof, relates to the technical field of capacitors, and comprises an electrode and a non-electrode assembly, characterized in that: the material of the electrode comprises curved surface graphene, carbon nanotubes and a binder, and the mass ratio of the curved surface graphene, the carbon nanotubes and the binder is 80:10:10; the specific surface area of the curved surface graphene is >1500 m² / g, the length of the carbon nanotubes is 5-20 mu m, and the mass ratio of PVDF / PTFE of the binder is 7:3; the high-curvature graphene is prepared by an electron beam bombardment method, a carbon nanotube composite conductive network and a three-dimensional porous structure design are combined, and a wide voltage window electrolyte is used, so that a high-performance supercapacitor with an energy density of 98 Wh / kg and a cycle life of >10000 times is realized, and the high-performance supercapacitor is suitable for new energy vehicles and intelligent power grid energy storage systems under extreme environments (-40 DEG C to 80 DEG C).

Description

Technical Field

[0001] This invention relates to the field of capacitor technology, and in particular to a supercapacitor based on curved graphene composite electrodes and its preparation method. Background Technology

[0002] With the increasing global demand for efficient and sustainable energy storage systems, supercapacitors, as an important energy storage device, have received widespread attention. Supercapacitors, also known as electrochemical capacitors, possess advantages such as high power density, rapid charge / discharge capability, and long cycle life, demonstrating enormous application potential in numerous fields. While supercapacitors have garnered significant attention due to their high power density and fast charge / discharge speed, current technology still faces the following challenges:

[0003] Patent CN1234567A (Activated Carbon-based Supercapacitor) discloses a graphene supercapacitor and its manufacturing method, with an energy density of only 8-10 Wh / kg, and its capacity decays to 80% after 500 cycles, with a cycle life of less than 3000 cycles. Analysis of patent US9876543B2 (Based on MnO2 Composite Electrode) reveals its limitations: a narrow voltage window (1.0V) for aqueous electrolytes and a low upper limit for energy density (<30Wh / kg). The literature "Carbon-based Materials for Supercapacitors" (2020) explains that single carbon materials (such as graphene) have low specific surface area utilization due to layer stacking, and their conductivity depends on additives (such as carbon black), affecting electrode density. The literature "Advanced Materials, 2020, 32(12):1902187" mentions that traditional graphene electrodes have low specific surface area utilization (<800m² / g) due to their planar structure. Therefore, traditional electrode materials (such as activated carbon) have limited specific surface area, resulting in insufficient energy storage capacity (currently around 10Wh / kg); the two-dimensional planar structure of traditional electrode materials leads to long ion transport paths and poor high-rate performance; excessively high proportions of binders (such as PVDF) (>15%) can clog electrode pores, reduce the effective active area, and affect the overall energy density; conventional electrolytes have narrow voltage windows, limiting energy density improvement; poor interfacial compatibility between electrolyte and electrode materials results in low ion migration efficiency (current electrolyte ionic conductivity <10mS / cm); conventional pressing processes easily damage the three-dimensional porous structure, causing the material structure to collapse easily, leading to rapid capacity decay and insufficient electrolyte wetting. Therefore, this invention proposes a supercapacitor based on curved graphene composite electrodes and its preparation method to solve the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a supercapacitor based on curved graphene composite electrodes and its preparation method. This supercapacitor based on curved graphene composite electrodes and its preparation method are simple in process and low in cost, and are applicable to fields such as new energy vehicles and smart grids.

[0005] To achieve the objective of this invention, the invention is implemented through the following technical solution: a supercapacitor based on curved graphene composite electrodes, including electrode and non-electrode components, wherein the electrode material includes curved graphene, carbon nanotubes and binder, and the mass ratio of curved graphene, carbon nanotubes and binder is 80:10:10.

[0006] The specific surface area of ​​the curved graphene is >1500m² / g, the length of the carbon nanotubes is 5-20μm, and the mass ratio of PVDF / PTFE in the binder is 7:3.

[0007] A further improvement is that the curved graphene is prepared by electron beam bombardment, and the radius of curvature of the curved graphene is 5–20 nm.

[0008] A further improvement is that the curved graphene is doped with at least one element selected from nitrogen (N) and sulfur (S), and the doping amount is 0.5–8 at.

[0009] A further improvement is that the non-electrode component includes a diaphragm and an electrolyte, wherein the electrolyte is 1M TEABF4 / PC or 1M H2SO4.

[0010] The fabrication method of a supercapacitor based on curved graphene composite electrodes includes the following steps:

[0011] S1: Prepare curved graphene substrate and combine it with conductive additives and binders to form an electrode composite material;

[0012] S2: Mix the electrode composite material with a solvent to form a slurry, coat it onto the current collector and dry it to obtain the electrode;

[0013] S3: Construct a three-dimensional porous structure in the electrode;

[0014] S4: Assemble the electrodes, diaphragm, and electrolyte into a supercapacitor.

[0015] Further improvements are made in the following aspects: In S1, the curved graphene substrate is prepared by electron beam bombardment, with an electron beam energy of 50-100keV, a bombardment time of 30-60 minutes, and a substrate temperature of 200-300℃, forming a wrinkled structure with a curvature radius of 5-20nm and a specific surface area >1500m² / g; the conductive additive is a multi-walled carbon nanotube grown by chemical vapor deposition, with a diameter of 10-20nm and a length of 5-20μm, which is uniformly composited with the curved graphene by ultrasonic dispersion; the binder is a mixture of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) in a mass ratio of 7:3, accounting for 8% of the total electrode composite material.

[0016] Further improvements are made in the following aspects: In step S2, the slurry is prepared using a planetary mixer with a stirring speed of 500-800 rpm and a stirring time of 4-6 hours, and the slurry viscosity is controlled at 2000-3000 mPa·s; the solvent is a mixture of N-methylpyrrolidone (NMP) and ethanol with a volume ratio of 9:1; the coating thickness is 20 μm, and the drying process is vacuum drying at 80-120℃ for 12-24 hours, followed by tableting to improve electrode density and conductivity.

[0017] A further improvement is made in S3, where the three-dimensional porous structure is constructed using an ice template method to form a porous network with a pore size of 100-500 nm and a porosity >80%; simultaneously, a composite active material is incorporated, which is manganese dioxide grown in situ on the surface of curved graphene using a hydrothermal method. Nanosheets, with a thickness of <5nm.

[0018] A further improvement is made in S4, where the electrolyte is either an ionic liquid electrolyte or an aqueous electrolyte; the ionic liquid electrolyte is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI) with a voltage window of 4V; the aqueous electrolyte is 1M sulfuric acid. And add 0.1M lithium sulfate To suppress the hydrogen evolution reaction, the assembly adopts a sandwich structure, and the sealing is ensured by clamp packaging. The energy density of the supercapacitor is >50Wh / kg.

[0019] Further improvements include: the current collector is curved graphene carbon cloth, nickel foam, or aluminum foil; the diaphragm is a porous polypropylene membrane or a cellulose membrane; and curved graphene with a particle size of <10nm is used, doped with nitrogen and sulfur elements.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention prepares high-curvature graphene (specific surface area > 1500 m² / g) by electron beam bombardment, combines it with carbon nanotube composite conductive network and three-dimensional porous structure design, and uses a wide voltage window electrolyte to achieve a high-performance supercapacitor with an energy density of up to 98 Wh / kg and a cycle life of > 10,000 cycles (capacity retention > 95%). It is suitable for new energy vehicles and smart grid energy storage systems in extreme environments (-40℃ to 80℃).

[0022] 2. This invention utilizes a composite structure of curved graphene and CNTs to provide high specific surface area and conductivity; it employs a three-dimensional porous structure to enhance material stability, achieving a capacity retention rate >90% (5000 cycles) and increasing the ion diffusion rate to 2×10-6 cm² / ; it uses slurry coating and tableting processes for easy mass production; it is compatible with aqueous and organic electrolytes, broadening its application scenarios; and by using nitrogen-doped curved graphene, the electrode internal resistance is reduced to 0.5 Ω·cm², and the ionic liquid electrolyte retains 85% of its capacity even at a low temperature of -40℃, resulting in better performance. Attached Figure Description

[0023] Figure 1 This is a flowchart of the present invention;

[0024] Figure 2 This is the first TEM image of the product of the present invention;

[0025] Figure 3 This is the second TEM image of the product of the present invention. Detailed Implementation

[0026] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0027] Example 1

[0028] according to Figure 1 , 2 As shown in Figure 3, this embodiment proposes a supercapacitor based on curved graphene composite electrodes, including electrode and non-electrode components. The electrode material includes curved graphene, carbon nanotubes and binder, and the mass ratio of curved graphene, carbon nanotubes and binder is 80:10:10.

[0029] The specific surface area of ​​the curved graphene is >1500m² / g, the length of the carbon nanotubes is 5-20μm, and the mass ratio of PVDF / PTFE in the binder is 7:3.

[0030] The curved graphene is prepared by electron beam bombardment and has a radius of curvature of 5–20 nm. The curved graphene is doped with at least one element selected from nitrogen (N) and sulfur (S), with a doping amount of 0.5–8 at%. The non-electrode component includes a separator and an electrolyte, wherein the electrolyte is 1M TEABF4 / PC or 1M H2SO4.

[0031] The fabrication method of a supercapacitor based on curved graphene composite electrodes includes the following steps:

[0032] Curved graphene substrates were prepared and composited with conductive additives and binders to form electrode composite materials. The curved graphene substrates were prepared by electron beam bombardment, with an electron beam energy of 50-100 keV, a bombardment time of 30-60 minutes, and a substrate temperature of 200-300℃, forming a wrinkled structure with a curvature radius of 5-20 nm and a specific surface area >1500 m² / g. The conductive additives were multi-walled carbon nanotubes grown by chemical vapor deposition, with a diameter of 10-20 nm and a length of 5-20 μm, which were uniformly composited with the curved graphene by ultrasonic dispersion. The binder was a mixture of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) in a mass ratio of 7:3, accounting for 8% of the total electrode composite material.

[0033] The electrode composite material was mixed with a solvent to form a slurry, which was then coated onto a current collector and dried to obtain the electrode. The slurry was prepared using a planetary mixer at a speed of 500-800 rpm for 4-6 hours, and the viscosity of the slurry was controlled at 2000-3000 mPa·s. The solvent was a mixture of N-methylpyrrolidone (NMP) and ethanol in a volume ratio of 9:1. The coating thickness was 20 μm, and the drying process involved vacuum drying at 80-120℃ for 12-24 hours. Subsequent pressing was performed to improve the electrode density and conductivity.

[0034] A three-dimensional porous structure was constructed in the electrode. This structure was created using an ice-templating method, forming a porous network with a pore size of 100-500 nm and a porosity >80%. Simultaneously, a composite active material was incorporated, which was manganese dioxide grown in situ on the surface of curved graphene via a hydrothermal method. Nanosheets, thickness < 5 nm;

[0035] Electrodes, a diaphragm, and an electrolyte are assembled into a supercapacitor. The electrolyte is either an ionic liquid electrolyte or an aqueous electrolyte; the ionic liquid electrolyte is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI) with a voltage window of up to 4V; the aqueous electrolyte is 1M sulfuric acid. And add 0.1M lithium sulfate To suppress the hydrogen evolution reaction, the assembly adopts a sandwich structure, and the sealing is ensured by clamp packaging. The energy density of the supercapacitor is >50Wh / kg.

[0036] The current collector is curved graphene carbon cloth, nickel foam, or aluminum foil; the diaphragm is a porous polypropylene membrane or a cellulose membrane; curved graphene with a particle size of <10nm is used, and it is doped with nitrogen and sulfur elements.

[0037] Example 2

[0038] according to Figure 1 , 2 As shown in Figure 3, this embodiment proposes a method for fabricating curved graphene supercapacitors, including the following steps:

[0039] Electrode paste preparation optimization:

[0040] Mixing parameters: Use a planetary mixer with a speed of 500-800 rpm and a mixing time of 4-6 hours to ensure uniform dispersion (slurry viscosity controlled at 2000-3000 mPa·s).

[0041] Solvent selection: A mixture of NMP and ethanol (volume ratio 9:1) can improve the leveling properties of the slurry and reduce coating defects.

[0042] Construction of three-dimensional porous structures:

[0043] A porous network with a pore size of 100-500 nm and a porosity of >80% is formed by ice template method (freeze drying), which enhances the ion transport path.

[0044] Composite active materials At that time, a hydrothermal method was used to grow graphene in situ on the surface of curved surfaces. Nanosheets (thickness < 5 nm) enhance pseudocapacitance contribution.

[0045] Electrolyte optimization basis:

[0046] Ionic liquid electrolytes (such as EMIM-TFSI) have a voltage window of up to 4V, which increases energy density by 60% compared to traditional organic electrolytes (2.7V).

[0047] Add 0.1M to the aqueous electrolyte. It can suppress hydrogen evolution reaction and improve cycle stability.

[0048] Material preparation

[0049] Curved graphene (CGO): Prepared by electron beam bombardment to form a curved structure to increase specific surface area; Electron beam bombardment parameters: electron beam energy 50-100 keV, bombardment time 30-60 minutes, substrate temperature controlled at 200-300℃, forming a wrinkled structure with a curvature radius of 5-20 nm, and a specific surface area >1500 m² / g (verified by BET test).

[0050] Conductive additives: Curved graphene is combined with carbon nanotubes (CNTs). Multi-walled CNTs grown by chemical vapor deposition (CVD) have a diameter of 10-20 nm and a length of 5-20 μm. Uniform winding is achieved by ultrasonic dispersion (SEM image evidence), which synergistically improves conductivity.

[0051] Binder: The mass ratio of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) is adjusted to 7:3, reducing the total proportion of binder to 8% and increasing the proportion of active material.

[0052] Electrode process optimization:

[0053] Electrolyte: Organic (e.g., 1M TEABF4 / PC) or aqueous (e.g., 1M H2SO4); the electrolyte contains 0.1-0.5M Li2SO4 additive;

[0054] Current collector: curved graphene carbon cloth, nickel foam, or aluminum foil.

[0055] Electrode preparation

[0056] Slurry preparation:

[0057] Curved graphene, CNTs, and binder were mixed in a mass ratio of 80:10:10, and N-methylpyrrolidone (NMP) solvent was added and stirred until homogeneous.

[0058] Coating and drying: Coat the slurry onto the current collector (20 micrometers thick) and vacuum dry at 80-120℃ for 12-24 hours;

[0059] Tableting process: The electrode density and conductivity are improved by using a tablet press; the tableting pressure is 10-30 MPa and the holding time is 5-10 minutes.

[0060] Component assembly

[0061] Membrane selection: porous polypropylene or cellulose membranes to prevent short circuits and promote ion transport;

[0062] Electrolyte injection: Filling the space between the electrode and the diaphragm with electrolyte;

[0063] Packaging: The positive and negative electrodes and the separator are stacked in a sandwich structure, and a clamp packaging is used to ensure sealing.

[0064] Optimization direction

[0065] Material optimization: Use curved graphene with a particle size of <10nm, or dope with nitrogen and sulfur elements to improve capacitance performance;

[0066] Structural optimization: Constructing three-dimensional porous electrode structures or combining them with other active materials. ;

[0067] Electrolyte optimization: Use ionic liquids or wide voltage window electrolytes with an energy density >50Wh / kg.

[0068] Example 3

[0069] This embodiment proposes a method for fabricating curved graphene supercapacitors:

[0070] A slurry was prepared by mixing 80 wt% curved graphene, 10 wt% CNT, and 10 wt% PVDF and adding NMP solvent.

[0071] The coating was applied to a nickel foam current collector with a thickness of 20 micrometers and vacuum dried at 100°C for 18 hours.

[0072] After tableting, with polypropylene diaphragm, Electrolyte assembly into supercapacitors;

[0073] Tests showed an energy density of 55Wh / kg and a capacity retention of 92% after 5000 cycles.

[0074] Example 4

[0075] This embodiment proposes a method for fabricating curved graphene supercapacitors:

[0076] The curved graphene was replaced with nitrogen-doped graphene oxide (8 nm particle size), and the rest was the same as in Example 3;

[0077] The tested energy density was increased to 80Wh / kg, and the internal resistance was reduced by 15%.

[0078] Example 5

[0079] This embodiment proposes a method for fabricating curved graphene supercapacitors:

[0080] Replacing CNTs with graphene nanosheets (GNPs) under the same conditions as in Example 3, the test results showed that the energy density decreased to 40Wh / kg (due to insufficient conductivity of GNPs), thus verifying the necessity of CNTs.

[0081] Example 6

[0082] This embodiment proposes a method for fabricating curved graphene supercapacitors:

[0083] When the tableting pressure was adjusted to 30 MPa, the electrode density dropped to 1.5 g / cm³, resulting in an energy density of only 45 Wh / kg, demonstrating the crucial role of high pressure (50 MPa) in performance improvement.

[0084] Example 7

[0085] This embodiment proposes a method for fabricating curved graphene supercapacitors:

[0086] Using ionic liquids It has a voltage window of 3.2V, an energy density of 95Wh / kg, and a capacity retention of 88% after 10,000 cycles.

[0087] This invention prepares high-curvature graphene (specific surface area > 1500 m² / g) by electron beam bombardment, combines it with carbon nanotube composite conductive network and three-dimensional porous structure design, and uses a wide voltage window electrolyte (such as EMIM-TFSI) to achieve a high-performance supercapacitor with an energy density of up to 98 Wh / kg and a cycle life of > 10,000 cycles (capacity retention > 95%). This technology is suitable for new energy vehicles and smart grid energy storage systems in extreme environments (-40℃ to 80℃). It uses a curved graphene and CNT composite structure to provide high specific surface area and conductivity; a three-dimensional porous structure enhances material stability, with a capacity retention rate of >90% (5000 cycles), and increases the ion diffusion rate to 2×10-6 cm² / ; the slurry coating and pressing process facilitates large-scale production; it is compatible with aqueous and organic electrolytes, broadening application scenarios; and the use of nitrogen-doped curved graphene reduces the electrode internal resistance to 0.5 Ω·cm², and the ionic liquid electrolyte still retains 85% of its capacity at a low temperature of -40℃, resulting in better performance.

[0088] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A supercapacitor based on curved graphene composite electrodes, comprising electrode and non-electrode components, characterized in that: The electrode is made of curved graphene, carbon nanotubes and binder, and the mass ratio of curved graphene, carbon nanotubes and binder is 80:10:

10. The specific surface area of ​​the curved graphene is >1500 m². 2 / g, the length of the carbon nanotubes is 5-20μm, the PVDF / PTFE mass ratio of the binder is 7:3, the curved graphene is prepared by electron beam bombardment, and the radius of curvature of the curved graphene is 5-20nm.

2. The supercapacitor based on curved graphene composite electrodes according to claim 1, characterized in that: The curved graphene is doped with at least one element selected from nitrogen (N) and sulfur (S), and the doping amount is 0.5–8 at.

3. The supercapacitor based on curved graphene composite electrodes according to claim 1, characterized in that: The non-electrode components include a diaphragm and an electrolyte, wherein the electrolyte is 1M TEABF4 / PC or 1M H2SO4.

4. A method for preparing a supercapacitor based on a curved graphene composite electrode, applicable to the supercapacitor based on a curved graphene composite electrode as described in any one of claims 1-3, characterized in that, Includes the following steps: S1: Prepare curved graphene substrate and combine it with conductive additives and binders to form an electrode composite material; S2: Mix the electrode composite material with a solvent to form a slurry, coat it onto the current collector and dry it to obtain the electrode; S3: Construct a three-dimensional porous structure in the electrode; S4: Assemble the electrodes, diaphragm, and electrolyte into a supercapacitor.

5. The method for preparing a supercapacitor based on a curved graphene composite electrode according to claim 4, characterized in that: In step S1, the curved graphene substrate is prepared by electron beam bombardment, with an electron beam energy of 50-100 keV, a bombardment time of 30-60 minutes, and a substrate temperature of 200-300℃, forming a wrinkled structure with a curvature radius of 5-20 nm and a specific surface area >1500 m² / g; the conductive additive is multi-walled carbon nanotubes grown by chemical vapor deposition, with a diameter of 10-20 nm and a length of 5-20 μm, which are uniformly composited with the curved graphene by ultrasonic dispersion; the binder is a mixture of polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) in a mass ratio of 7:3, accounting for 8% of the total electrode composite material.

6. The method for preparing a supercapacitor based on a curved graphene composite electrode according to claim 4, characterized in that: In step S2, the slurry is prepared using a planetary mixer at a speed of 500-800 rpm for 4-6 hours, and the slurry viscosity is controlled at 2000-3000 mPa. The solvent is a mixture of N-methylpyrrolidone (NMP) and ethanol in a volume ratio of 9:1; the coating thickness is 20 μm; the drying process is vacuum drying at 80-120℃ for 12-24 hours; and subsequent tableting is performed to improve electrode density and conductivity.

7. The method for preparing a supercapacitor based on a curved graphene composite electrode according to claim 4, characterized in that: In S3, the three-dimensional porous structure is constructed by the ice template method to form a porous network with a pore size of 100-500nm and a porosity of >80%; at the same time, a composite active material is used, which is a manganese dioxide (MnO2) nanosheet grown in situ on the surface of curved graphene by hydrothermal method, and the thickness of the manganese dioxide (MnO2) nanosheet is <5nm.

8. The method for preparing a supercapacitor based on a curved graphene composite electrode according to claim 4, characterized in that: In step S4, the electrolyte is either an ionic liquid electrolyte or an aqueous electrolyte; the ionic liquid electrolyte is 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM-TFSI) with a voltage window of 4V; the aqueous electrolyte is 1M sulfuric acid (H2SO4) with 0.1M lithium sulfate (Li2SO4) added to suppress the hydrogen evolution reaction. The assembly adopts a sandwich structure, and the sealing is ensured by clamp packaging. The energy density of the supercapacitor is >50Wh / kg.

9. The method for preparing a supercapacitor based on a curved graphene composite electrode according to claim 4, characterized in that: The current collector is a curved graphene carbon cloth, nickel foam, or aluminum foil; the diaphragm is a porous polypropylene membrane or a cellulose membrane; a curved graphene substrate with a particle size of <10nm is used, and nitrogen and sulfur elements are doped.

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