Hybrid capacitor negative electrode and preparation method and application thereof

Abstract

The invention belongs to the technical field of energy storage, and particularly relates to a hybrid capacitor negative electrode and a preparation method and application thereof. A hybrid capacitor negative electrode comprises a conductive current collector and an active material layer coated on the conductive current collector. The active material layer is prepared from the following raw material components in percentage by mass: 83.0 wt%-91.30 wt% of graphite; 0.009 wt% to 1.74 wt% of fluorinated graphdiyne; 0.070 wt% to 7.98 wt% of conductive carbon black; 0.017 wt% to 1.71 wt% of graphene; 0.027 wt% to 3.23 wt% of sodium carboxymethyl cellulose; and 0.036 wt%-3.61 wt% of styrene butadiene rubber.

Description

Technical Field

[0001] This invention belongs to the field of energy storage technology, and particularly relates to a hybrid capacitor negative electrode, its preparation method, and its application. Background Technology

[0002] Energy storage technology, especially lithium-ion battery technology, is a core pillar of modern electronics and new energy industries. Its continuous performance breakthroughs are crucial for the development of consumer electronics, electric vehicles, and large-scale grid energy storage. Among the four key materials for lithium-ion batteries, the anode material directly determines core indicators such as the battery's initial coulombic efficiency, cycle stability, and safety performance. Currently, graphite materials, with their stable layered structure, theoretical specific capacity of up to 372 mAh / g, excellent conductivity, mature production processes, and cost advantages, have become the most widely used and technologically mature mainstream choice for commercial lithium-ion battery anode materials, occupying an absolute dominant position in the market.

[0003] However, as downstream applications place increasingly stringent demands on battery energy density, power density, cycle life, and safety, the inherent limitations of traditional graphite anode materials are becoming increasingly apparent. For example, under rapid charge-discharge (high rate) conditions, the capacity of graphite anodes decays rapidly, resulting in poor kinetic performance. Simultaneously, during long-term cycling, continuous side reactions occur between the electrolyte and the graphite anode surface, leading to repeated rupture and regeneration of the unstable solid electrolyte interphase (SEI) film. This not only continuously consumes limited active lithium ions, causing irreversible capacity decay, but may also induce lithium dendrite growth, posing serious safety hazards. To overcome these performance limitations, modifying graphite materials has become a research hotspot in the industry. Among these methods, doping with fluorine, an element with strong electronegativity, is widely recognized as a highly promising technological path. Both theory and practice have shown that the introduction of fluorine helps form a lithium fluoride (LiF)-rich SEI film on the graphite surface. This film possesses higher mechanical strength and chemical stability, effectively suppressing side reactions and improving cycle performance and safety.

[0004] Despite the promising application prospects of fluorine doping modification, a series of technical challenges remain in current practices. These challenges include how to efficiently, controllably, and cost-effectively introduce fluorine uniformly into anode materials and ensure good compatibility with existing electrode fabrication systems. First, existing fluorination processes often suffer from uneven doping, leading to variations in electrochemical performance across different regions of the anode sheet. This prevents the full realization of the modification advantages of fluorine, resulting in limited overall performance improvement. Second, directly introducing fluorine-containing substances as additives into traditional anode slurry systems can easily cause problems such as uneven dispersion, agglomeration, and abnormal viscosity due to interfacial compatibility issues. This directly affects the quality of subsequent coating processes, leading to defects in the final anode sheet, such as cracking, powdering, and uneven distribution of active materials, severely damaging the structural stability and electrochemical performance of the electrode. Therefore, there is an urgent need in this field for a new technical solution that not only achieves the uniform and stable presence of fluorine in a graphite matrix but also ensures the uniformity and stability of the entire anode slurry system. This would enable the large-scale fabrication of high-rate, long-life hybrid capacitor anodes with complete structure and excellent performance. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned shortcomings by providing a hybrid capacitor negative electrode, its preparation method, and its application. By organically combining an active material with fluorinated graphdiyne, and through parameter configuration and process optimization, a high-performance graphite-doped fluorine hybrid capacitor negative electrode is produced using methods such as slurry mixing and coating. This enables the use of fluorinated carbon-based materials as dopants to effectively improve the rate capability and long cycle life of the hybrid capacitor negative electrode.

[0006] Technicians should be aware that the performance limitations of hybrid battery capacitors primarily lie in the negative electrode. While traditional negative electrode materials such as graphite possess some lithium storage capacity, their kinetic performance during high-rate charge / discharge processes and the resulting decrease in cycle life hinder improvements in overall device power density and long-term stability. Conversely, materials like activated carbon, despite their good power characteristics, suffer from insufficient specific capacity, directly impacting the device's energy density. Therefore, the research and development approach focuses on overcoming the limitations of traditional single materials and exploring composite material systems to discover a negative electrode solution that can simultaneously meet the demands of high-rate charging and long-cycle operation.

[0007] Against this backdrop, graphdiyne-based carbon materials, in particular, have attracted significant attention due to their excellent lithium storage capacity (experimental storage capacity as high as 2084.1 mAh / g) and the dual advantages of possessing both battery energy storage and capacitance characteristics. Graphdiyne's unique two-dimensional porous structure, abundant sp-hybridized carbon atoms, and the resulting fast ion / electron transport channels and abundant active sites theoretically enable it to not only provide lithium storage capacity far exceeding that of traditional graphite but also potentially possess excellent rate performance and cycle stability. This discovery forms the core idea of ​​this application—introducing graphdiyne as a highly promising anode active material into hybrid battery capacitors.

[0008] Firstly, a hybrid capacitor negative electrode employs the following technical solution:

[0009] A hybrid capacitor negative electrode includes a conductive current collector and an active material layer coated on the conductive current collector; the raw material layer comprises, by mass fraction, the following components:

[0010] Graphite: 83.0 wt% to 91.30 wt%;

[0011] Fluorinated graphyne: 0.009 wt%–1.74 wt%;

[0012] Conductive carbon black: 0.070wt%~7.98wt%;

[0013] Graphene: 0.017wt%~1.71wt%;

[0014] Sodium carboxymethyl cellulose: 0.027 wt% to 3.23 wt%;

[0015] Styrene-butadiene rubber: 0.036wt%~3.61wt%.

[0016] Furthermore, the raw materials for the active material layer, by mass fraction, include the following components:

[0017] Graphite: 90.387 wt%;

[0018] Fluorinated graphyne: 0.913 wt%;

[0019] Conductive carbon black: 4.20 wt%;

[0020] Graphene: 0.90 wt%;

[0021] Sodium carboxymethyl cellulose: 1.70 wt%;

[0022] Styrene-butadiene rubber: 1.90 wt%.

[0023] Furthermore, the thickness of the active material layer is 50 μm to 75 μm.

[0024] Secondly, a method for preparing the negative electrode of a hybrid capacitor adopts the following technical solution:

[0025] A method for preparing the negative electrode of a hybrid capacitor includes the following steps:

[0026] Step (1): Sodium carboxymethyl cellulose is dissolved in deionized water and stirred by a first multi-stage variable speed to form a uniform and stable binder solution;

[0027] Step (2): Add conductive carbon black and graphene to the binder solution obtained in step (1) and perform a second multi-stage variable speed stirring to form a conductive slurry with a uniformly dispersed conductive network.

[0028] Step (3): Graphite and fluorinated graphylene are added to the conductive slurry obtained in step (2), and the materials are fully mixed and doped with fluorine by a third multi-stage variable speed stirring to form a mixed slurry.

[0029] Step (4): Add styrene-butadiene rubber to the mixed slurry obtained in step (3) and perform a fourth multi-stage variable speed stirring to obtain a negative electrode slurry. Coat the negative electrode slurry evenly on the conductive current collector, and after drying and cutting, obtain the negative electrode of the mixed capacitor.

[0030] Further, in step (1), the first multi-stage variable speed stirring process includes: a low-speed wetting stage of 100r / min to 150r / min for 5min to 8min, a medium-speed dispersion stage of 300r / min to 350r / min for 5min to 8min, and a high-speed homogenization stage of 600r / min to 650r / min for 300min to 360min.

[0031] Further, in step (2), the second multi-stage variable speed stirring process includes: a low-speed wetting stage of 100r / min to 150r / min for 5min to 8min, a medium-speed dispersion stage of 300r / min to 350r / min for 5min to 8min, and a high-speed homogenization stage of 600r / min to 650r / min for 180min to 240min.

[0032] Further, in step (3), the third multi-stage variable speed stirring process includes: a low-speed wetting stage of 100r / min to 150r / min for 5min to 8min, a medium-speed dispersion stage of 300r / min to 350r / min for 5min to 8min, a high-speed homogenization stage of 600r / min to 650r / min for 840min to 900min, and an ultra-high-speed stage of 1200r / min to 1300r / min for 60min to 90min.

[0033] Further, in step (4), the fourth multi-stage variable speed stirring process includes: a high-speed homogenization stage of 600r / min to 650r / min for 60min to 90min, and a defoaming stage of 20r / min to 30r / min for 60min to 90min.

[0034] Further, in step (4), the drying process includes drying at a temperature of 60℃ to 80℃ for 24h to 26h.

[0035] Thirdly, an application of the negative electrode of a hybrid capacitor employs the following technical solution:

[0036] An application of the above-described hybrid capacitor negative electrode in the fabrication of energy storage devices.

[0037] The beneficial effects of this invention are:

[0038] This invention provides a fluorine-doped graphite hybrid capacitor anode. By introducing fluorinated graphylene as the core dopant and organically combining it with graphite, a composite conductive agent, and a composite binder, it successfully solves the technical problems of uneven doping and limited performance improvement in traditional fluorine modification processes. The uniform distribution of fluorinated graphylene not only significantly improves the overall conductivity and mechanical properties of the electrode, but more importantly, it induces the formation of a dense and stable SEI film rich in lithium fluoride on the electrode surface. This high-quality SEI film effectively suppresses side reactions and structural damage during cycling, thus enabling the anode of this invention to exhibit superior performance compared to unmodified graphite anodes in terms of coulombic efficiency, rate performance (high current charge / discharge capability), and cycle life.

[0039] This invention provides a method for preparing a hybrid capacitor negative electrode. By controlling the order of addition of each material (binder, conductive agent, and active material) and the stirring parameters (speed and time), the method ensures that the slurry maintains high uniformity and stability from the initial wetting and dispersion to the final mixing and doping, effectively avoiding agglomeration. This method not only guarantees uniform fluorine doping but also features a simple process, mild conditions, good repeatability, and full compatibility with existing lithium battery production lines. It overcomes the bottlenecks of existing fluorine modification technologies, such as complex processes, high costs, and difficulty in industrialization, providing a practical and feasible technical approach for the large-scale production of high-performance fluorine-doped negative electrodes.

[0040] The hybrid capacitor negative electrode provided by this invention, when applied to energy storage devices such as hybrid capacitors or lithium-ion batteries, can directly translate its material-level performance advantages into improved overall performance of the end device. Due to the excellent kinetic performance and cycle stability of this negative electrode, the assembled battery device exhibits stronger high-current charge / discharge capabilities, longer lifespan, and lower capacity decay rate. This effectively meets the urgent needs of downstream applications such as electric vehicles and high-end consumer electronics for batteries that are "faster to charge, longer to use, and safer," resulting in significant economic benefits and broad market application prospects. Attached Figure Description

[0041] Figure 1 This is a scanning electron microscope image of the active material layer of the negative electrode prepared in Example 1 of the present invention.

[0042] Figure 2 This is an energy dispersive spectroscopy (EDS) scanning electron microscope (SEM) image of the active material layer of the negative electrode prepared in Example 1 of the present invention.

[0043] Figure 3 This is a comparison of the active material layer and the graphite Raman spectrum of the negative electrode prepared in Example 1 of the present invention.

[0044] Figure 4 This is a comparison diagram of the active material layer of the negative electrode prepared in Example 1 of the present invention and the XPS total spectrum of graphite.

[0045] Figure 5 The image shows the XPS C 1s spectrum of the active material layer of the negative electrode prepared in Example 1 of this invention.

[0046] Figure 6 This is a ratio comparison diagram of the active material layer of the negative electrode prepared in Example 1 of the present invention and graphite only.

[0047] Figure 7 This is a comparison cycle diagram of the active material layer of the negative electrode prepared in Example 1 of the present invention and graphite only. Detailed Implementation

[0048] The following detailed description, in conjunction with embodiments, provides a further specific account of the hybrid capacitor negative electrode, its preparation method, and its application according to the present invention. For the sake of simplicity, this document cannot exhaustively list all alternative technical features and embodiments included in the present invention. Therefore, those skilled in the art should understand that any technical feature and embodiment within this embodiment does not limit the scope of protection of the present invention. The scope of protection includes all alternative technical features and embodiments adopted by those skilled in the art without inventive effort. Specifically, any embodiment obtained by replacing any technical feature in the present invention or by combining any two or more technical features provided by the present invention should be within the scope of protection of the present invention. Where specific techniques and conditions are not specified in the embodiments, they are performed according to the techniques and conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0049] Example

[0050] Example 1

[0051] Example 1 provides a hybrid capacitor negative electrode, comprising a copper foil and an active material layer with a thickness of 75 μm coated on the copper foil; wherein the raw material of the active material layer comprises the following components:

[0052] Graphite 90.387g, fluorinated graphdiyne 0.913g, conductive carbon black 4.200g, graphene 0.900g, sodium hydroxymethyl cellulose 1.700g and styrene-butadiene rubber 1.900g.

[0053] Example 1 also provides a method for preparing the negative electrode of a hybrid capacitor, comprising the following steps:

[0054] Add sodium carboxymethyl cellulose, 25 mL of water, and a magnetic stir bar to a beaker, then place it on a magnetic stirrer and stir at 100 rpm for 5 minutes. Then stir at 300 rpm for 5 minutes, and then at 600 rpm for 300 minutes. After stirring, add conductive carbon black and graphene to the beaker and stir at 100 rpm for 5 minutes, then at 300 rpm for 5 minutes. After the previous step, stir at 600 rpm for 180 minutes. After stirring, add graphite, trifluorographyne, and 100 mL of water, and stir at 100 rpm, 300 rpm, and 600 rpm for 5 minutes, 5 minutes, and 840 minutes respectively. Then increase the speed to 1200 rpm and stir for 60 minutes. After stirring, add styrene-butadiene rubber and stir at 600 rpm for 60 minutes. Finally, stir at 20 rpm for 60 minutes to remove bubbles.

[0055] Cut a rectangular copper foil, wipe the glass surface of the coating machine clean and spray it with alcohol, lay the copper foil flat on the coating machine, and then evenly coat the copper foil surface with the uniformly stirred slurry through the coating machine. After coating, transfer the copper foil to a vacuum drying oven and dry it at 60°C for 26 hours. Then, use a cutter with a diameter of 12mm to cut the copper foil into circular electrode sheets through a cutting machine to obtain the negative electrode of the hybrid capacitor.

[0056] The scanning electron microscope (SEM) energy dispersive spectroscopy (EDS) image of the active material layer of the hybrid capacitor negative electrode prepared in Example 1 is shown below. Figure 2 As shown, the presence of fluorine can be clearly detected by energy dispersive spectroscopy, further proving that fluorine has been successfully doped into graphite materials.

[0057] The Raman spectrum of the active material layer of the negative electrode prepared in Example 1 is as follows: Figure 3 As shown. Compared with graphite, the fluorine-doped graphite sample exhibits a significant change in Raman spectroscopy: the G peak of the active material layer is located at 1578 cm⁻¹. -1 Compared to the G peak of graphite (1573 cm⁻¹) -1 It shifted 5cm towards higher wavenumbers. -1 This shift reflects the presence of sp in graphite after fluorination. 2 The vibrational modes of hybrid carbon atoms have changed, while the D peak of graphite at 1344 cm⁻¹... -1 Transformed to fluorine-doped graphite at 1342 cm⁻¹ -1 This reflects that after successful doping, the material developed more local defects, and finally the G' peak at 2715 cm⁻¹ was not as high as in the undoped material. -1 Become doped 2700cm -1 This reflects that fluorine doping increases the interlayer spacing of graphite, weakens the interlayer van der Waals forces, and causes the peak to shift towards lower wavenumbers.

[0058] The XPS total spectrum of the active material layer of the negative electrode prepared in Example 1 is shown below. Figure 4 As shown, compared with graphite, the active material layer sample, while retaining the original characteristic peaks of C and O elements, showed a distinct F1s characteristic peak near the binding energy of 688 eV. This newly appearing F element characteristic peak clearly confirms that fluorine atoms were successfully introduced into the graphite structure, proving the successful realization of elemental doping.

[0059] The XPS C1s spectrum of the active material layer of the negative electrode prepared in Example 1 is shown below. Figure 5 As shown, in addition to displaying the characteristic peaks of the most basic C–C and C–O chemical bonds, obvious C–F characteristic peaks also appeared in the high binding energy region. This result further proves that fluorine has been successfully doped into the graphite structure, providing strong spectroscopic evidence for the effectiveness of the fluorination reaction.

[0060] The rate performance of the negative electrode prepared in Example 1 is as follows: Figure 6 As shown, the Figure 6 The electrochemical performance of the active material layer and the undoped sample was compared under different rate conditions. It is evident that the active material layer sample provided in Example 1 exhibits superior capacity retention and rate performance compared to graphite at different rate conditions, fully demonstrating the significant advantages of this invention in improving the rate performance of materials.

[0061] The button cell with the negative electrode prepared in Example 1 still maintained a capacity of 350 mAh / g after 180 cycles at a current density of 0.3C, and the coulombic efficiency remained at 100%. Figure 7 As shown, compared to graphite button batteries, it exhibits superior capacity retention and extremely low capacity decay, further verifying the significant advantages of fluorine-doped graphite materials in improving battery cycle stability and overall performance, and fully demonstrating the superiority of this invention.

[0062] Example 2

[0063] Example 2 provides a hybrid capacitor negative electrode, comprising a copper foil and an active material layer with a thickness of 50 μm coated on the copper foil; wherein the raw material of the active material layer comprises the following components:

[0064] 83.000g of graphite, 0.009g of fluorinated graphdiyne, 0.070g of conductive carbon black, 0.017g of graphene, 0.027g of sodium hydroxymethyl cellulose and 0.036g of styrene-butadiene rubber.

[0065] Example 2 also provides a method for preparing the negative electrode of a hybrid capacitor, comprising the following steps:

[0066] Add sodium carboxymethyl cellulose, 25 mL of water, and a magnetic stir bar to a beaker, then place it on a magnetic stirrer and stir at 100 rpm for 5 minutes. Then stir at 300 rpm for 5 minutes, and then at 600 rpm for 300 minutes. After stirring, add conductive carbon black and graphene to the beaker and stir at 100 rpm for 5 minutes, then at 300 rpm for 5 minutes. After the previous step, stir at 600 rpm for 180 minutes. After stirring, add graphite, trifluorographyne, and 100 mL of water, and stir at 100 rpm, 300 rpm, and 600 rpm for 5 minutes, 5 minutes, and 840 minutes respectively. Then increase the speed to 1200 rpm and stir for 60 minutes. After stirring, add styrene-butadiene rubber and stir at 600 rpm for 60 minutes. Finally, stir at 20 rpm for 60 minutes to remove bubbles.

[0067] Cut a rectangular copper foil, wipe the glass surface of the coating machine clean and spray it with alcohol, lay the copper foil flat on the coating machine, and then evenly coat the copper foil surface with the uniformly stirred slurry through the coating machine. After coating, transfer the copper foil to a vacuum drying oven and dry it at 60°C for 24 hours. Then, use a cutter with a diameter of 10mm to cut the copper foil into circular electrode sheets through a cutting machine to obtain the negative electrode of the hybrid capacitor.

[0068] Example 3

[0069] Example 3 provides a hybrid capacitor negative electrode, comprising a copper foil and an active material layer with a thickness of 75 μm coated on the copper foil; wherein the raw material of the active material layer comprises the following components:

[0070] Graphite 91.300g, fluorinated graphdiyne 1.740g, conductive carbon black 7.980g, graphene 1.710g, sodium hydroxymethyl cellulose 3.230g and styrene-butadiene rubber 3.610g.

[0071] Example 3 also provides a method for preparing the negative electrode of a hybrid capacitor, comprising the following steps:

[0072] Add sodium carboxymethyl cellulose, 25 mL of water, and a magnetic stir bar to a beaker, then place it on a magnetic stirrer and stir at 150 rpm for 8 minutes. Then stir at 350 rpm for 8 minutes, and then at 650 rpm for 360 minutes. After stirring, add conductive carbon black and graphene to the beaker and stir at 150 rpm for 8 minutes, then at 350 rpm for 8 minutes. After the previous step, stir at 650 rpm for 240 minutes. After stirring, add graphite, trifluorographyne, and 100 mL of water, and stir at 150 rpm, 350 rpm, and 650 rpm for 8 minutes, 8 minutes, and 900 minutes respectively. Then increase the speed to 1300 rpm and stir for 90 minutes. After stirring, add styrene-butadiene rubber and stir at 650 rpm for 90 minutes. Finally, stir at 30 rpm for 90 minutes to remove bubbles.

[0073] Cut a rectangular copper foil, wipe the glass surface of the coating machine clean and spray it with alcohol, lay the copper foil flat on the coating machine, and then evenly coat the copper foil surface with the uniformly stirred slurry through the coating machine. After coating, transfer the copper foil to a vacuum drying oven and dry it at 80°C for 26 hours. Then, use a cutter with a diameter of 15mm to cut the copper foil into circular electrode sheets through a cutting machine to obtain the negative electrode of the hybrid capacitor.

[0074] Example 4

[0075] Example 4 provides a hybrid capacitor negative electrode, comprising a copper foil and an active material layer with a thickness of 60 μm coated on the copper foil; wherein the raw material of the active material layer comprises the following components:

[0076] 85.000g of graphite, 1.000g of fluorinated graphdiyne, 6.000g of conductive carbon black, 1.200g of graphene, 2.500g of sodium hydroxymethyl cellulose and 2.800g of styrene-butadiene rubber.

[0077] Example 4 also provides a method for preparing the negative electrode of a hybrid capacitor, comprising the following steps:

[0078] Add sodium carboxymethyl cellulose, 25 mL of water, and a magnetic stir bar to a beaker, then place it on a magnetic stirrer and stir at 120 rpm for 6 minutes. Then stir at 320 rpm for 6 minutes, and then at 620 rpm for 330 minutes. After stirring, add conductive carbon black and graphene to the beaker and stir at 120 rpm for 6 minutes, then at 320 rpm for 6 minutes. After the previous step, stir at 620 rpm for 200 minutes. After stirring, add graphite, trifluorographyne, and 100 mL of water, and stir at 120 rpm, 320 rpm, and 620 rpm for 6 minutes, 6 minutes, and 870 minutes respectively. Then increase the speed to 1250 rpm and stir for 75 minutes. After stirring, add styrene-butadiene rubber and stir at 620 rpm for 75 minutes. Finally, stir at 25 rpm for 75 minutes to remove bubbles.

[0079] Cut a rectangular copper foil, wipe the glass surface of the coating machine clean and spray it with alcohol, lay the copper foil flat on the coating machine, and then evenly coat the copper foil surface with the uniformly stirred slurry through the coating machine. After coating, transfer the copper foil to a vacuum drying oven and dry it at 70°C for 25 hours. Then, use a cutter with a diameter of 12mm to cut the copper foil into circular electrode sheets through a cutting machine to obtain the negative electrode of the hybrid capacitor.

[0080] Example 5

[0081] Example 5 provides a hybrid capacitor negative electrode, comprising a copper foil and an active material layer with a thickness of 65 μm coated on the copper foil; wherein the raw material of the active material layer comprises the following components:

[0082] 88.000g of graphite, 0.100g of fluorinated graphdiyne, 2.000g of conductive carbon black, 0.500g of graphene, 1.000g of sodium hydroxymethyl cellulose and 1.200g of styrene-butadiene rubber.

[0083] Example 5 also provides a method for preparing the negative electrode of a hybrid capacitor, comprising the following steps:

[0084] Add sodium carboxymethyl cellulose, 25 mL of water, and a magnetic stir bar to a beaker, then place it on a magnetic stirrer and stir at 130 rpm for 7 minutes. Then stir at 330 rpm for 7 minutes, and then at 630 rpm for 350 minutes. After stirring, add conductive carbon black and graphene to the beaker and stir at 130 rpm for 7 minutes, then at 330 rpm for 7 minutes. After the previous step, stir at 630 rpm for 220 minutes. After stirring, add graphite, trifluorographyne, and 100 mL of water, and stir at 130 rpm, 330 rpm, and 630 rpm for 7 minutes, 7 minutes, and 880 minutes respectively. Then increase the speed to 1280 rpm and stir for 80 minutes. After stirring, add styrene-butadiene rubber and stir at 630 rpm for 80 minutes. Finally, stir at 28 rpm for 80 minutes to remove bubbles.

[0085] Cut a rectangular copper foil, wipe the glass surface of the coating machine clean and spray it with alcohol, lay the copper foil flat on the coating machine, and then evenly coat the copper foil surface with the uniformly stirred slurry through the coating machine. After coating, transfer the copper foil to a vacuum drying oven and dry it at 75°C for 24 hours. Then, use a cutter with a diameter of 12mm to cut the copper foil into circular electrode sheets through a cutting machine to obtain the negative electrode of the hybrid capacitor.

[0086] Example 6

[0087] Example 6 provides a hybrid capacitor negative electrode, comprising a copper foil and an active material layer with a thickness of 55 μm coated on the copper foil; wherein the raw material of the active material layer comprises the following components:

[0088] 83.000g of graphite, 1.740g of fluorinated graphdiyne, 7.980g of conductive carbon black, 0.017g of graphene, 3.230g of sodium hydroxymethyl cellulose and 0.036g of styrene-butadiene rubber.

[0089] Example 6 also provides a method for preparing the negative electrode of a hybrid capacitor, comprising the following steps:

[0090] Add sodium carboxymethyl cellulose, 25 mL of water, and a magnetic stir bar to a beaker, then place it on a magnetic stirrer and stir at 150 rpm for 5 minutes. Then stir at 300 rpm for 8 minutes, and then stir at 650 rpm for 300 minutes. After stirring, add conductive carbon black and graphene to the beaker and stir at 100 rpm for 8 minutes, then stir at 350 rpm for 5 minutes. After the previous step, stir at 600 rpm for 240 minutes. After stirring, add graphite, trifluorographyne, and 100 mL of water, and stir at 150 rpm, 300 rpm, and 650 rpm for 5 minutes, 8 minutes, and 900 minutes respectively. Then increase the speed to 1200 rpm and stir for 90 minutes. After stirring, add styrene-butadiene rubber and stir at 650 rpm for 60 minutes. Finally, stir at 30 rpm for 90 minutes to remove bubbles.

[0091] Cut a rectangular piece of copper foil, wipe the glass surface of the coating machine clean and spray it with alcohol, lay the copper foil flat on the coating machine, and then evenly coat the copper foil surface with the uniformly stirred slurry through the coating machine. After coating, transfer the copper foil to a vacuum drying oven and dry it at 80°C for 24 hours. Then, use a cutter with a diameter of 12mm to cut the copper foil into circular electrode sheets through a cutting machine to obtain the negative electrode of the hybrid capacitor.

[0092] Comparative Example 1

[0093] Comparative Example 1 used the exact same raw material composition and preparation method as Example 1, except that 0.913 g of fluorinated graphynylene was replaced with an equal mass of graphite. That is, the raw materials for the active material layer included: 91.300 g of graphite, 4.200 g of conductive carbon black, 0.900 g of graphene, 1.700 g of sodium carboxymethyl cellulose, and 1.900 g of styrene-butadiene rubber. The preparation method, coating thickness, and post-treatment procedures were completely consistent with Example 1.

[0094] Comparative Example 2

[0095] Comparative Example 2 used the exact same raw material composition and preparation method as Example 1, except that 0.900g of graphene was replaced with an equal mass of conductive carbon black. Specifically, the raw materials for the active material layer included: 90.387g of graphite, 0.913g of fluorinated graphdiyne, 5.100g of conductive carbon black, 1.700g of sodium carboxymethyl cellulose, and 1.900g of styrene-butadiene rubber. The preparation method, coating thickness, and post-treatment procedures were completely identical to those in Example 1.

[0096] Comparative Example 3

[0097] Comparative Example 3 used the exact same raw material composition and preparation method as Example 1, except that 4.200g of conductive carbon black was replaced with an equal mass of graphene. That is, the raw materials for the active material layer included: 90.387g of graphite, 0.913g of fluorinated graphdiyne, 5.100g of graphene, 1.700g of sodium carboxymethyl cellulose, and 1.900g of styrene-butadiene rubber. The preparation method, coating thickness, and post-treatment procedures were completely consistent with Example 1.

[0098] Comparative Example 4

[0099] Comparative Example 4 used the exact same raw material components and amounts as Example 1. The difference was in the preparation method: all dry powder raw materials (graphite, fluorinated graphdiyne, conductive carbon black, graphene, sodium hydroxymethyl cellulose, styrene-butadiene rubber) and 125 mL of water were added to a beaker at once, and then stirred directly at a high speed of 600 r / min. The total stirring time was the same as the cumulative stirring time in Example 1. Finally, defoaming treatment was performed.

[0100] Comparative Example 5

[0101] Comparative Example 5 used the exact same raw material composition and dosage as Example 1, and the stirring parameters and time were also exactly the same. The only difference was that the order of steps (2) and (3) was reversed. That is, after the CMC was completely dissolved, graphite and fluorinated graphylene were added first and stirred, and then conductive carbon black and graphene were added and stirred.

[0102] Comparative Example 6

[0103] Comparative Example 6 used the exact same raw material components and amounts as Example 1. The difference lay in the preparation method: after each feeding step, the low-speed and medium-speed stirring stages were omitted, and high-speed stirring at 600 r / min was used directly. For example, after adding CMC, stirring was performed directly at 600 r / min for 300 min; after adding the conductive agent, stirring was performed directly at 600 r / min for 180 min, and so on. The total stirring time remained the same as in Example 1.

[0104] Comparative Example 7

[0105] Comparative Example 7 used the exact same raw material components and amounts as Example 1. The difference was in the preparation method: all stirring steps were carried out at a constant medium speed of 300 r / min, and the total stirring time was the same as the cumulative stirring time of Example 1.

[0106] Comparative Example 8

[0107] Comparative Example 8 used the exact same raw material composition and preparation method as Example 1. The only difference was that in step (3), the high-speed stirring time at 600 r / min was significantly shortened from 840 min to the conventional 120 min. All other steps were completely consistent with Example 1.

[0108] Comparative Example 9

[0109] Comparative Example 9 used the exact same raw material composition and preparation method as Example 1. The only difference was that, at the end of step (3), the ultra-high-speed intensification step of stirring at 1200 r / min for 60 min was omitted, and after completing 840 min of stirring at 600 r / min, it directly proceeded to step (4).

[0110] Comparative Example 10

[0111] Comparative Example 10 used the exact same raw material composition and preparation method as Example 1. The only difference was that in step (4), after adding styrene-butadiene rubber and stirring at 600 r / min for 60 min, the low-speed defoaming process of stirring at 20 r / min for 60 min was omitted, and coating was carried out directly.

[0112] Performance testing

[0113] 1. Assembly of button batteries

[0114] The hybrid capacitor negative electrode (as working electrode), lithium metal sheet (as counter electrode and reference electrode), and polypropylene microporous membrane (as separator) prepared in Example 1 and Comparative Examples 1-10 were assembled into CR2032 type button batteries in a glove box filled with high-purity argon gas (water and oxygen content both <0.1ppm). The electrolyte used was 1M lithium hexafluorophosphate (LiPF6) dissolved in a mixed solvent of ethylene carbonate, diethyl carbonate, and ethyl carbonate (volume ratio 1:1:1).

[0115] 2. Determination of electrochemical performance

[0116] The electrochemical performance of assembled button cells was tested at room temperature using the Xinwei Battery Testing System, including cycle performance testing and rate performance testing.

[0117] (1) Ratio performance test:

[0118] To evaluate the charge-discharge capability of the negative electrode at high current densities, the battery was tested at different rates. The test procedure was set as follows: first, activation was performed for three cycles at a current density of 0.1C, followed by constant current charge-discharge tests at rates of 0.2C, 0.5C, 1C, and 2C, with five cycles at each rate. The voltage window was uniformly set to 0.005-3.0V (relative to Li / Li). +The 2C capacity retention rate recorded in this application refers to the ratio of the discharge specific capacity stabilized at 2C rate to the discharge specific capacity stabilized at 0.1C rate. This process ensures that the different samples of the examples and comparative examples are evaluated under consistent conditions, allowing for comparable rate performance assessments. Figure 6 This is the rate performance diagram of the negative electrode prepared in Example 1.

[0119] (2) Long-cycle performance test:

[0120] To evaluate the long-term stability of the negative electrode, the battery underwent a long-term charge-discharge cycle test at a constant current density of 0.3C, totaling 200 cycles. The voltage window was also set at 0.005–3.0V. Before testing, all batteries were allowed to stand for 30 minutes to ensure that the electrolyte fully wetted the electrodes. The "200-cycle capacity retention rate" recorded in this application refers to the ratio of the discharge specific capacity after 200 cycles to the initial discharge specific capacity. Figure 7 This is the long-cycle performance curve of the negative electrode prepared in Example 1.

[0121] The hybrid capacitor negative electrodes prepared in Example 1 and Comparative Examples 1-10 were assembled into button cells and tested according to the above performance test methods. The key data of their cycle performance and rate performance are summarized in Table 1.

[0122] Table 1 Performance comparison of Example 1 and Comparative Examples 1-10

[0123]

[0124]

[0125] Comparative Example 1 showed a cycle capacity retention of only 60% and a 2C rate capacity retention of only 50%. This contrasts sharply with the 100% and 80% retention of Example 1. The results indicate that fluorinated graphdiyne is a core component for forming a stable SEI film, suppressing side reactions, and improving cycle stability and kinetic performance. Without this component, the anode performance deteriorates sharply.

[0126] Comparative Examples 2 and 3: Comparative Example 2 (without graphene): Its 2C rate capacity retention rate plummeted to 40%. Comparative Example 3 (without conductive carbon black): Its 2C rate capacity retention rate also dropped to 60%. The results of both comparative examples are far worse than the 80% of Example 1. This fully demonstrates that the "point-surface combined" three-dimensional conductive network constructed by conductive carbon black (dot-like) and graphene (sheet-like) has a synergistic effect of 1+1>2. The absence of either one prevents the formation of the most efficient electron transport channel, thus severely impacting rate performance.

[0127] Comparative Example 4 exhibited low cycle capacity retention and 2C rate capacity retention, at only 50% and 30%, respectively. This is because the "one-step feeding" method resulted in ineffective dissolution of the binder, severe powder agglomeration, and extremely poor slurry quality, making it impossible to form a structurally complete electrode coating. This demonstrates the necessity of the step-by-step feeding process employed in this invention.

[0128] Comparative Example 5 exhibited a cycle capacity retention of 85% and a 2C rate capacity retention of 60%. While its performance was acceptable, it was significantly inferior to Example 1. This demonstrates that the specific order of "building the conductive network first, then adding the main active material" is crucial for ensuring uniform coating of the conductive agent, forming a highly efficient conductive network, and thus achieving optimal performance.

[0129] Comparative Example 6 showed a reduction in cycle capacity retention to 70% and a 2C rate capacity retention to 55%. This was because the excessively high shear force in the initial stage damaged the CMC polymer chains, weakening the bonding effect and leading to a decrease in electrode structural stability.

[0130] Comparative Example 7 exhibited a cycle capacity retention of 80%, but its 2C rate capacity retention was only 50%. This indicates that the shear force from medium-speed stirring was insufficient to fully disperse the conductive agent and achieve efficient fluorine doping, severely impacting the electrode's kinetic performance.

[0131] Comparative Example 8 showed a reduction in cycle capacity retention and 2C rate capacity retention to 75% and 40%, respectively. This significant difference from Example 1 demonstrates that continuous high-shear stirring for up to 840 minutes is a crucial step in ensuring the fluorine doping reaction proceeds fully and achieving deep material modification.

[0132] Comparative Example 9 showed a reduced cycle capacity retention of 70% and a 2C rate capacity retention of 45%. This demonstrates that the final ultra-high-speed strengthening step has an indispensable gain effect in achieving the ultimate uniform dispersion of materials and maximizing performance.

[0133] Comparative Example 10 showed that its cycle capacity retention and 2C rate capacity retention decreased to 60% and 40%, respectively. This indicates that residual bubbles in the slurry severely damaged the structural integrity and performance of the final electrode, demonstrating the necessity of a low-speed defoaming process.

[0134] In this study, many factors affected electrochemical performance, but three were the most critical overall. First, stirring time is paramount: insufficient stirring at each stage leads to uneven mixing of active materials, binders, conductive agents, and thickeners. This can result in decreased capacity and rate performance, or even poor bonding between the coating and current collector, rendering the battery virtually ineffective. Second, the order of material addition must be standardized: adding all materials at once instead of sequentially can easily cause agglomeration and phase separation, ultimately leading to battery failure. Third, the drying process must strictly adhere to vacuum drying: residual solvent or moisture on the electrodes can cause active materials to detach; oxidation further weakens capacity and cycle stability.

[0135] Therefore, thorough and phased mixing ensures uniformity and adhesion; a strict order of feeding avoids agglomeration and phase separation; and standardized vacuum drying prevents moisture absorption and oxidation. These three factors together determine the coating quality and interfacial stability, which are the foundation for obtaining repeatable, high-performance electrochemical performance.

[0136] For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, but obvious variations or modifications derived therefrom are still within the scope of protection of the claims of this invention.

Claims

1. A negative electrode of a hybrid capacitor, characterized in that, It includes a conductive current collector and an active material layer coated on the conductive current collector; the raw materials of the active material layer, by mass fraction, include the following components: Graphite: 83.0 wt% to 91.30 wt%; Fluorinated graphyne: 0.009 wt%–1.74 wt%; Conductive carbon black: 0.070wt%~7.98wt%; Graphene: 0.017wt%~1.71wt%; Sodium carboxymethyl cellulose: 0.027 wt% to 3.23 wt%; Styrene-butadiene rubber: 0.036wt%~3.61wt%.

2. The negative electrode of the hybrid capacitor according to claim 1, characterized in that, The raw materials for the active material layer, by mass fraction, include the following components: Graphite: 90.387 wt%; Fluorinated graphyne: 0.913 wt%; Conductive carbon black: 4.20 wt%; Graphene: 0.90 wt%; Sodium carboxymethyl cellulose: 1.70 wt%; Styrene-butadiene rubber: 1.90 wt%.

3. The negative electrode of the hybrid capacitor according to claim 1, characterized in that, The thickness of the active material layer is 50 μm to 75 μm.

4. A method for preparing the negative electrode of a hybrid capacitor as described in claim 1, characterized in that, Includes the following steps: Step (1): Sodium carboxymethyl cellulose is dissolved in deionized water and stirred by a first multi-stage variable speed to form a uniform and stable binder solution; Step (2): Add conductive carbon black and graphene to the binder solution obtained in step (1) and perform a second multi-stage variable speed stirring to form a conductive slurry with a uniformly dispersed conductive network. Step (3): Graphite and fluorinated graphylene are added to the conductive slurry obtained in step (2), and the materials are fully mixed and doped with fluorine by a third multi-stage variable speed stirring to form a mixed slurry. Step (4): Add styrene-butadiene rubber to the mixed slurry obtained in step (3) and perform a fourth multi-stage variable speed stirring to obtain a negative electrode slurry. Coat the negative electrode slurry evenly on the conductive current collector, and after drying and cutting, obtain the negative electrode of the mixed capacitor.

5. The preparation method according to claim 4, characterized in that, In step (1), the first multi-stage variable speed stirring process includes: a low-speed wetting stage of 100r / min to 150r / min for 5min to 8min, a medium-speed dispersion stage of 300r / min to 350r / min for 5min to 8min, and a high-speed homogenization stage of 600r / min to 650r / min for 300min to 360min.

6. The preparation method according to claim 4, characterized in that, In step (2), the second multi-stage variable speed stirring process includes: a low-speed wetting stage of 100r / min to 150r / min for 5min to 8min, a medium-speed dispersion stage of 300r / min to 350r / min for 5min to 8min, and a high-speed homogenization stage of 600r / min to 650r / min for 180min to 240min.

7. The preparation method according to claim 4, characterized in that, In step (3), the third multi-stage variable speed stirring process includes: a low-speed wetting stage of 100r / min to 150r / min for 5min to 8min, a medium-speed dispersion stage of 300r / min to 350r / min for 5min to 8min, a high-speed homogenization stage of 600r / min to 650r / min for 840min to 900min, and an ultra-high-speed stage of 1200r / min to 1300r / min for 60min to 90min.

8. The preparation method according to claim 4, characterized in that, In step (4), the fourth multi-stage variable speed stirring process includes: a high-speed homogenization stage of 600 r / min to 650 r / min for 60 min to 90 min, and a defoaming stage of 20 r / min to 30 r / min for 60 min to 90 min.

9. The preparation method according to claim 4, characterized in that, In step (4), the drying process includes drying at a temperature of 60℃ to 80℃ for 24h to 26h.

10. The use of a hybrid capacitor negative electrode as described in any one of claims 1 to 3 in the fabrication of an energy storage device.

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