Electrochemical device of single-walled carbon nanotube graphene composite conductive agent based on wisteria structure

Abstract

The invention provides an electrochemical device of a single-walled carbon nanotube graphene composite conductive agent based on a wisteria structure. The electrochemical device comprises a battery cell and a shell, the battery cell is arranged in the shell and comprises a positive plate, a negative plate and a diaphragm; the diaphragm is arranged between the positive plate and the negative plate, the slurry comprises an active substance, an adhesive, a composite conductive agent of single-walled carbon nanotube graphene with a wisteria structure and an organic solvent, and the composite conductive agent of the single-walled carbon nanotube graphene with the wisteria structure comprises a single-walled carbon nanotube winding vine strip and a plurality of petal-shaped graphene, each petal-shaped graphene grows in situ along the defect part of the peripheral wall of the single-walled carbon nanotube winding vine strip. According to the electrochemical device, the added single-walled carbon nanotube graphene composite conductive agent with a wisteria structure not only reduces the dispersion difficulty of the prepared slurry, but also reduces the interface electrical impedance of the conductive agent, and is beneficial to the preparation of a three-dimensional conductive network with a continuous conductive network and a stable structure.

Description

Technical Field

[0001] This disclosure relates to the field of electrochemical device technology, and in particular to an electrochemical device based on a single-walled carbon nanotube-graphene composite conductive agent with a wisteria flower structure. Background Technology

[0002] A lithium-ion battery is an electrochemical energy storage device that stores and releases energy through the migration of lithium ions in the active material layer between the positive and negative electrodes. The fabrication of the positive and negative electrodes for lithium-ion batteries typically involves first mixing active materials, conductive agents, and organic solvents to obtain a slurry, then coating the slurry onto a current collector and drying it. Single-walled carbon nanotubes (SUVs) are a common conductive agent. Due to their high aspect ratio and high axial thermal conductivity, SUVs exhibit irreplaceable advantages in the field of lithium-ion batteries.

[0003] Chemical vapor deposition (CVD) is a common method for preparing single-walled carbon nanotubes (SUVs). However, during the preparation of SUVs, the newly formed SUVs are extremely small in size and have a high specific surface area. As a result, they are easily attracted and entangled by van der Waals forces, spontaneously aggregating into "coarse bundles" with diameters as high as 10-20 nm. These coarse bundles of SUVs increase the difficulty of dispersing the lithium-ion battery slurry, making it impossible to prepare a uniformly dispersed slurry, which in turn affects the effective performance of the conductivity of the SUVs.

[0004] In addition, many researchers are currently incorporating graphene to improve the conductivity of lithium batteries. However, when single-walled carbon nanotubes and graphene are physically mixed, the high surface energy of the single-walled carbon nanotubes makes them prone to entanglement and aggregation, while the graphene sheets tend to stack. This results in problems such as poor dispersion, high interfacial electrical impedance, insufficient continuity of the conductive network, and poor stability. Summary of the Invention

[0005] The purpose of this disclosure is to overcome the shortcomings of the prior art and provide an electrochemical device based on a wisteria flower-structured single-walled carbon nanotube-graphene composite conductive agent that not only reduces the difficulty of dispersing the slurry but also reduces the interfacial resistance of the conductive agent, which is beneficial for preparing a continuous and structurally stable three-dimensional conductive network.

[0006] The purpose of this disclosure is achieved through the following technical solution: An electrochemical device based on a wisteria flower-structured single-walled carbon nanotube-graphene composite conductive agent includes a battery cell and a housing; the battery cell is disposed within the housing, and the battery cell includes a positive electrode, a negative electrode, and a separator; the separator is disposed between the positive electrode and the negative electrode. The positive electrode and / or the negative electrode are coated with a slurry, the slurry comprising an active material, a binder, a composite conductive agent of single-walled carbon nanotube graphene with a wisteria flower structure, and an organic solvent; the composite conductive agent of single-walled carbon nanotube graphene with a wisteria flower structure comprises single-walled carbon nanotube vines and multiple petal-shaped graphenes, each of the petal-shaped graphenes growing in situ along the defects of the outer peripheral wall of the single-walled carbon nanotube vines.

[0007] In one embodiment, the method for preparing the composite conductive agent of single-walled carbon nanotube graphene with the wisteria flower structure includes the following steps: The precursor reaction solution is introduced into the central region of the reaction apparatus; A gaseous reducing agent is introduced into the central region of the reaction apparatus, and a mixture of carbon source and inert gas is introduced into the peripheral region of the reaction apparatus to react and obtain powder; wherein the flow rate of the mixed gas is less than the flow rate of the gaseous reducing agent. The powder was purified by acid washing to obtain a composite conductive agent of single-walled carbon nanotube graphene with the wisteria flower structure.

[0008] In one embodiment, the flow rate of the mixed gas is 2 L / min-30 L / min; and / or, The flow rate of the gaseous reducing agent is 2 L / min to 50 L / min.

[0009] In one embodiment, during the step of introducing the precursor reaction solution into the central region of the reaction apparatus, the inlet flow rate is 0.2 mL / min to 20 mL / min.

[0010] In one embodiment, when a gaseous reducing agent is introduced into the middle region of the reaction device and a mixture of carbon source and inert gas is introduced into the outer region of the reaction device for reaction, the temperature of the front reaction zone is controlled at 500℃-1000℃, the temperature of the middle reaction zone is controlled at 900℃-1300℃, and the temperature of the rear reaction zone is controlled at 900℃-1300℃.

[0011] In one embodiment, the mixing ratio of the carbon source and the inert gas is (100-500):1.

[0012] In one embodiment, the precursor reaction solution is obtained by mixing a transition metal compound and a carbon-containing organic solvent.

[0013] In one embodiment, the concentration of the precursor reaction solution is 0.01 g / mL to 0.05 g / mL.

[0014] In one embodiment, the gaseous reducing agent includes at least one selected from hydrogen, carbon monoxide, and ammonia; and / or, The inert protective gas includes at least one of argon, nitrogen, and helium.

[0015] In one embodiment, the amount of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure used accounts for 0.5%-1.0% of the mass percentage of the slurry.

[0016] Compared with the prior art, this disclosure has at least the following advantages: Since the composite conductive agent of single-walled carbon nanotube graphene with the wisteria flower structure includes single-walled carbon nanotubes wrapped around a vine and multiple petal-shaped graphenes, each petal-shaped graphene grows in situ along the defects of the outer peripheral wall of the single-walled carbon nanotubes wrapped around the vine. This effectively reduces the growth flow rate and nucleation density of single-walled carbon nanotubes on the outer peripheral wall of the vine, thus blocking the probability of newly generated single-walled carbon nanotubes spontaneously agglomerating into bundles. This results in the outer peripheral wall of the vine being dominated by the formation of petal-shaped graphenes, allowing the multiple petal-shaped graphenes to physically separate the wrapped single-walled carbon nanotubes, preventing the vine from re-agglomerating due to van der Waals forces. Simultaneously, it avoids the self-stacking of the petal-shaped graphenes, significantly improving the dispersibility of the composite conductive agent of single-walled carbon nanotube graphene, which is beneficial for preparing a composite conductive agent. The uniform dispersion of the slurry reduces the difficulty of dispersing the slurry in lithium battery manufacturing, thereby ensuring the effective conductivity of the single-walled carbon nanotube-graphene composite conductive agent with wisteria flower structure. On the other hand, since the petal-shaped graphene grows and attaches directly to the surface defects of the single-walled carbon nanotube winding vine through chemical covalent bonding (such as C-C bonds) or interfacial adsorption (strong chemical bonding formed by the lone pair electrons of the single-walled carbon nanotube and the empty orbitals of the graphene), it effectively reduces the surface defects of the single-walled carbon nanotube winding vine. This not only reduces the gap between the single-walled carbon nanotube winding vine and the petal-shaped graphene interface, thereby reducing the interfacial impedance of the single-walled carbon nanotube winding vine and the petal-shaped graphene, but also improves the stability and conductivity of the connection between the single-walled carbon nanotube winding vine and the petal-shaped graphene. This is beneficial for preparing a three-dimensional conductive network with low interfacial impedance, continuous conductive network and stable structure. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1This is a flowchart of an electrochemical device for a single-walled carbon nanotube-graphene composite conductive agent based on a wisteria flower structure, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a reaction apparatus according to an embodiment of the present invention from one direction; Figure 3 This is an electron microscope image of the wisteria flower structure single-walled carbon nanotube-graphene composite conductive agent of Example 1 of the present invention. Figure 3A for Figure 3 A high-magnification electron microscope image of a single-walled carbon nanotube-graphene composite conductive agent with a wisteria flower structure. Figure 4 This is the Raman spectrum graphitization characteristic peak diagram of the wisteria flower structure single-walled carbon nanotube graphene composite conductive agent of Example 1 of the present invention. Figure 5 This is an electron microscope image of the wisteria flower structure single-walled carbon nanotube-graphene composite conductive agent of Comparative Example 4 of the present invention. Figure 6 This is a comparison chart of experimental data on the rate capability of Examples 1-5 and Comparative Examples 1-4 of the present invention; Figure 7 This is a comparison chart of experimental data on electrical impedance in Examples 1-5 and Comparative Examples 1-4 of the present invention. Detailed Implementation

[0019] To facilitate understanding of this disclosure, a more complete description will be given below with reference to the accompanying drawings, which illustrate preferred embodiments of the present disclosure. However, this disclosure can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0020] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this disclosure. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0022] Please see Figure 1 To better understand the technical solutions and beneficial effects of this disclosure, the following detailed description is provided in conjunction with specific embodiments. An electrochemical device based on a wisteria-structured single-walled carbon nanotube-graphene composite conductive agent, according to one embodiment, includes a battery cell and a housing. The battery cell is disposed within the housing and includes a positive electrode, a negative electrode, and a separator. The separator is disposed between the positive electrode and the negative electrode. The positive electrode and / or the negative electrode are coated with a slurry, which includes an active material, a binder, a wisteria-structured single-walled carbon nanotube-graphene composite conductive agent, and an organic solvent. The wisteria-structured single-walled carbon nanotube-graphene composite conductive agent includes single-walled carbon nanotubes wrapped around a vine and multiple petal-shaped graphenes. Each petal-shaped graphene is grown in situ along a defect on the outer peripheral wall of the single-walled carbon nanotube-wrapped vine.

[0023] It should be noted that currently, traditional graphene and single-walled carbon nanotubes are generally physical mixtures of monomers. When the two are physically mixed, the connection between the surface defects of single-walled carbon nanotubes and graphene is mainly through van der Waals forces and non-covalent weak interactions of π-π stacking, without chemical bonding. This results in a large interfacial gap, leading to high interfacial electrical impedance, insufficient continuity of the conductive network, and poor stability.

[0024] Therefore, in this disclosure, by controlling the conditions of chemical vapor deposition, multiple petal-shaped graphenes are grown in situ along the defects on the outer peripheral wall of the single-walled carbon nanotube winding vine. The petal-shaped graphenes grow and attach directly to the surface defects of the single-walled carbon nanotube winding vine through chemical covalent bonding (such as C-C bonds) or interfacial adsorption (strong chemical bonding formed by the lone pair electrons of the single-walled carbon nanotube and the empty orbitals of the graphene), effectively repairing the surface defects of the single-walled carbon nanotube winding vine. This not only reduces the gap between the single-walled carbon nanotube winding vine and the petal-shaped graphene interface, thereby effectively reducing the interfacial impedance between the single-walled carbon nanotube winding vine and the petal-shaped graphene, but also improves the stability and conductivity of the connection between the single-walled carbon nanotube winding vine and the petal-shaped graphene. This is beneficial for preparing a three-dimensional conductive network with low interfacial impedance, continuous conductive network and stable structure.

[0025] Furthermore, since each of the petal-shaped graphenes grows in situ at the defects on the outer peripheral wall of the single-walled carbon nanotube-entwined vine, details can be found in [reference needed]. Figure 3 , Figure 3A and Figure 4This method effectively reduces the growth rate and nucleation density of single-walled carbon nanotubes (SUVs) on the outer wall of the vine-like structure, thereby blocking the spontaneous aggregation of newly formed SUVs on the outer wall. This results in the formation of petal-shaped graphene on the outer wall, allowing multiple petal-shaped graphenes to physically separate the vine-like structure and prevent re-aggregation due to van der Waals forces. Simultaneously, it avoids the stacking of petal-shaped graphenes, significantly improving the dispersibility of the SUV-graphene composite conductive agent. This reduces the dispersion difficulty of lithium battery slurry preparation, facilitating the preparation of a uniformly dispersed slurry and ensuring the effective conductivity of the wisteria-structured SUV-graphene composite conductive agent.

[0026] Furthermore, since the composite conductive agent of wisteria flower-structured single-walled carbon nanotube graphene has the characteristics of good dispersibility, low interfacial resistance, continuous conductive network and stable three-dimensional conductive network, it can be ensured that a high energy density electrochemical device can be prepared using a small amount of wisteria flower-structured single-walled carbon nanotube graphene composite conductive agent.

[0027] It is worth mentioning that the higher the degree of graphitization of the composite conductive agent of wisteria flower-structured single-walled carbon nanotubes and graphene, the better its conductivity. Figure 4 As shown, the G peak is sharp and the D peak is not obvious, indicating that the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure has a high degree of graphitization and good conductivity, which is conducive to the preparation of a three-dimensional conductive network with continuous conductive network, stable structure and high conductivity.

[0028] Specifically, in one embodiment, the amount of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure used accounts for 0.5%-1.0% of the mass percentage of the slurry.

[0029] It is understandable that the composite conductive agent of single-walled carbon nanotubes and graphene with wisteria flower structure is first mixed with NMP at a ratio of 1:99 to obtain the conductive composite dispersion SWCNT-GN of NMP system. Then, a slurry is prepared by mixing the active material, binder and conductive composite dispersion SWCNT-GN at a ratio of (89-89.5):10:(0.5-1.0) to ensure that a high energy density electrochemical device can be prepared using a small amount of single-walled carbon nanotube and graphene composite conductive agent with wisteria flower structure.

[0030] In one embodiment, the adhesive is PVDF.

[0031] In one embodiment, the slurry was prepared by mixing the active material, binder, and conductive composite dispersion SWCNT-GN in a ratio of 89:10:1.0.

[0032] It should be noted that some composite conductive agents combining single-walled carbon nanotubes and graphene are also available on the market, such as the graphene-carbon nanotube three-dimensional structure composite material in patent CN 105000542 A. However, this requires the assistance of an ultrasonic device to uniformly disperse the graphene in a liquid carbon source, and then obtain it through chemical vapor deposition. This method suffers from problems such as uneven graphene dispersion, complex processes, weak interfacial bonding, and high costs.

[0033] Therefore, in this disclosure, a wisteria-structured single-walled carbon nanotube-graphene composite conductive agent is generated in one step by fully utilizing the conditions of a mixed gas of single-walled carbon nanotube precursor reaction liquid, gaseous reducing agent, carbon source, and inert gas, and a catalyst. This eliminates the need for ultrasonic dispersion and mixing, simplifying the operation and eliminating the need for graphene addition. It achieves the one-step generation of single-walled carbon nanotubes winding around vines and multiple petal-shaped graphenes, effectively reducing preparation costs. It also improves the self-dispersion of petal-shaped graphene and single-walled carbon nanotube winding vines, reduces the interfacial gap between petal-shaped graphene and single-walled carbon nanotube winding vines, thereby lowering the interfacial impedance between them and improving the stability of their connection. This facilitates the preparation of a wisteria-structured single-walled carbon nanotube-graphene composite conductive agent with good dispersibility, low interfacial impedance, continuous conductive network, and stable three-dimensional conductive network.

[0034] In one embodiment, when the catalyst concentration is low and the gaseous reducing agent concentration is high, the precursor reaction liquid mainly forms single-walled carbon nanotubes; when the catalyst concentration is high and the mixed gas concentration of carbon source and inert gas is high, it mainly forms graphene, so as to achieve the one-step generation of wisteria flower structure single-walled carbon nanotube graphene composite conductive agent.

[0035] In one embodiment, a wisteria-shaped single-walled carbon nanotube-graphene composite conductive agent is generated in one step using a reaction apparatus.

[0036] In one embodiment, such as Figure 2As shown, the reaction device includes a reaction vessel. From the center outwards, the end of the reaction vessel is sequentially divided into a central region, an intermediate region, and an outer region. The central region has atomizing pinholes for introducing the precursor reaction liquid. The intermediate region has multiple reducing pores for introducing a gaseous reducing agent. The outer region has multiple air inlets for introducing a mixture of carbon source and inert gas. This achieves a partitioned arrangement of the precursor reaction liquid, gaseous reducing agent, and the mixture of carbon source and inert gas, allowing the precursor reaction liquid to gradually diffuse from the central region to the periphery of the reaction device to create a gradient difference. This facilitates the formation of a partitioned arrangement where the intermediate region serves as the core area for single-walled carbon nanotube growth, and the outer region serves as the core area for graphene growth. This allows multiple petal-shaped graphene particles to grow in situ along the defects on the outer wall of the single-walled carbon nanotube vine.

[0037] In one embodiment, the reaction vessel is sequentially formed with a front reaction zone, a middle reaction zone, and a rear reaction zone along its length to meet the growth requirements of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure at different stages.

[0038] In one embodiment, the method for preparing a composite conductive agent of wisteria flower-structured single-walled carbon nanotube graphene via a reaction apparatus includes some or all of the following steps: S101. The precursor reaction solution is introduced into the central area of ​​the reaction device, so that the precursor reaction solution gradually diffuses from the central area of ​​the reaction device to the periphery of the reaction device to form a gradient difference. This ensures that the concentration of gas reducing agent in the central area near the center is high, which is mainly for the generation of single-walled carbon nanotubes, while the concentration of the mixed gas of carbon source and inert gas in the peripheral area far from the center is high, which is mainly for the generation of graphene. This is conducive to the partitioning of the core area for single-walled carbon nanotube growth and the core area for graphene growth, so that multiple petal-shaped graphenes can grow in situ along the defects of the outer wall of the single-walled carbon nanotube vine.

[0039] In one embodiment, the precursor reaction liquid enters the central region of the reaction device through atomizing pinholes in the central region.

[0040] Specifically, in one embodiment, in the step of introducing the precursor reaction solution into the central region of the reaction device, the inlet flow rate is 0.2 mL / min-20 mL / min to ensure that the inlet flow rate of the precursor reaction solution is suitable. This is beneficial for the precursor reaction solution to gradually diffuse from the central region of the reaction device to the periphery of the reaction device to form a suitable gradient difference. That is, to ensure that the precursor reaction solution has a suitable gradient difference in the front reaction zone, middle reaction zone and rear reaction zone of the reaction device, thereby facilitating the formation of different growth core regions for single-walled carbon nanotubes and graphene.

[0041] In one embodiment, the precursor reaction solution is obtained by mixing a transition metal compound and a carbon-containing organic solvent. Specifically, the transition metal compound includes at least one selected from ferrocene, cobalt dicene, nickel dicene, and platinum dicene.

[0042] In one embodiment, the carbon-containing organic solvent includes at least one of ethanol, toluene, n-hexane, and cyclohexane.

[0043] In one embodiment, the concentration of the precursor reaction solution is 0.01 g / mL to 0.05 g / mL.

[0044] S102. A gaseous reducing agent is introduced into the middle region of the reaction device, and a mixture of carbon source and inert gas is introduced into the outer region of the reaction device to react and obtain powder.

[0045] It is understandable that, due to its proximity to the central region, the intermediate region contains multiple reducing vents, allowing the gaseous reducing agent introduced through these vents to diffuse and contact effectively with the precursor reaction liquid, thus ensuring a high concentration of reducing agent in the intermediate region. Conversely, because the peripheral region is located far from the central region, it contains multiple air inlets. This means that the mixture of carbon source and inert gas introduced through these inlets is located in the peripheral region, far from the central region, resulting in a slower mixing rate between the carbon source and inert gas mixture and the precursor reaction liquid in the central region. This ensures that the precursor reaction liquid is in a relatively stable state when entering the initial reaction zone of the reaction apparatus. In the region enriched with gaseous reducing agents, single-walled carbon nanotubes (SUVs) grow by interacting with the carbon source, forming the core region for SUV growth and generating SUV vines. Furthermore, this effectively reduces the growth rate and nucleation density of SUVs in the peripheral region, thereby blocking the spontaneous aggregation of newly generated SUVs on the outer wall of the SUV vines. This results in the outer wall of the SUV vines primarily producing petal-shaped graphene, which physically separates the entangled SUVs, preventing them from re-aggregating due to van der Waals forces.

[0046] When the single-walled carbon nanotubes (SHU) wrapped vine slowly enter the later reaction zone under the impetus of the mixed gas and gaseous reducing agent, the mixed gas and gaseous reducing agent are already uniformly mixed. This allows the carbon source in the mixed gas to decompose into a secondary carbon source under high temperature conditions. The secondary carbon source then deposits on the defects on the surface of the SHU wrapped vine and precipitates in different directions to form petal-shaped graphene. This achieves in-situ growth of the petal-shaped graphene along the defects on the outer peripheral wall of the SHU wrapped vine, effectively repairing the defects on the outer peripheral wall of the SHU wrapped vine. This effectively reduces the surface defects of the composite conductive agent of the wisteria-shaped SHU graphene and effectively reduces the interfacial gap between the petal-shaped graphene and the SHU wrapped vine, which is beneficial for the preparation of... A composite conductive agent of single-walled carbon nanotube graphene with a wisteria flower structure was obtained, possessing good dispersibility, low interfacial impedance, continuous and stable three-dimensional conductive network. Furthermore, a one-step generation of single-walled carbon nanotubes entwined with vines and multiple petal-shaped graphenes was achieved, effectively reducing preparation costs. The grown petal-shaped graphenes also physically separate the entwined single-walled carbon nanotubes from the vines, preventing the vines from re-aggregating due to van der Waals forces. Simultaneously, the self-stacking of the petal-shaped graphenes was avoided, significantly improving the dispersibility of the composite conductive agent. This reduces the dispersion difficulty in lithium battery slurry preparation, facilitating the preparation of uniformly dispersed slurries, and thus ensuring the effective performance of the conductivity of the wisteria flower structure single-walled carbon nanotube graphene composite conductive agent.

[0047] In one embodiment, each of the reduction pores is uniformly distributed along the circumference of the atomizing pinhole to achieve a uniform distribution of each reduction pore.

[0048] In one embodiment, each air inlet is evenly distributed along the circumference of the atomizing pinhole to achieve uniform distribution of each air inlet.

[0049] It should be noted that although controlling the partitioning of the mixed gas of precursor reaction liquid, gaseous reducing agent, carbon source and inert gas can, to some extent, achieve the partitioning of the core region for single-walled carbon nanotube growth and the core region for graphene growth, the gaseous reducing agent will be gradually consumed as the reaction continues. This will cause the concentration of the gaseous reducing agent in the front reaction zone to gradually decrease, tending to grow graphene. At this time, the graphene generated is prone to uneven thickness and low graphitization due to insufficient carbon source pyrolysis. This will affect the content of single-walled carbon nanotubes generated, thus affecting the purity and structural strength of the single-walled carbon nanotube vine, and consequently affecting the conductivity of the composite conductive agent of single-walled carbon nanotube graphene in wisteria flower structure.

[0050] Therefore, in this disclosure, by controlling the flow rate of the mixed gas to be less than the flow rate of the gaseous reducing agent, the concentration of the gaseous reducing agent is ensured to be high throughout the entire process in the front reaction zone of the reaction device, which tends to grow single-walled carbon nanotubes. This reduces the probability of generating graphene with uneven thickness and low graphitization degree in the front reaction zone, which is beneficial to generating single-walled carbon nanotubes with high purity and high structural strength that entwine the vines. This ensures the generation of a composite conductive agent with a wisteria flower structure of single-walled carbon nanotube graphene that has good dispersibility, low interfacial resistance, continuous and stable conductive network, and high graphitization degree.

[0051] It should be noted that if the flow rate of the mixed gas differs significantly from that of the gaseous reducing agent, good mixing between the two cannot be guaranteed upon entering the later reaction zone. This results in insufficient carbon source for the growth of petal-shaped graphene, leading to the shriveling of the generated petal-shaped graphene. For details, please refer to [link to relevant documentation]. Figure 5 Electron micrograph of the composite conductive agent of single-walled carbon nanotubes and graphene in the wisteria flower structure of Comparative Example 5; If the flow rate of the mixed gas and the flow rate of the gas reducing agent are small, it is not conducive to the formation of a good gradient difference between the middle and outer regions of the gas reducing agent in the front reaction zone, thus affecting the purity and structural strength of the single-walled carbon nanotubes winding around the vine.

[0052] Therefore, in one embodiment, the flow rate ratio of the mixed gas to the gas reducing agent is 1:(1.5-25) to control the flow rate difference between the mixed gas and the gas reducing agent to be suitable. This facilitates the formation of a good gradient difference between the gas reducing agent in the middle and outer regions of the front-end reaction zone, effectively ensuring a high concentration of the gas reducing agent in the precursor reaction liquid throughout the entire process in the front-end reaction zone. This promotes the growth of single-walled carbon nanotubes and is beneficial for generating high-purity, high-strength single-walled carbon nanotube vine-like structures. Simultaneously, it ensures that the mixed gas and gas reducing agent do not prematurely grow unevenly thick, low-graphitized graphene in the middle reaction zone, thus providing sufficient carbon source for the generation of petal-shaped graphene in the later reaction zone. This is beneficial for generating highly saturated petal-shaped graphene. For details, please refer to [link to relevant documentation]. Figure 3 and Figure 3A The electron microscope image of the single-walled carbon nanotube graphene composite conductive agent with wisteria flower structure in Example 1 is shown, which is beneficial for preparing a three-dimensional conductive network of single-walled carbon nanotube graphene with wisteria flower structure that has high saturation, good dispersibility, low interfacial resistance, continuous conductive network and stable structure.

[0053] In a preferred embodiment, the flow rate ratio of the mixed gas to the flow rate of the gaseous reducing agent is 1:(1.5-5.0).

[0054] In one embodiment, the flow rate of the mixed gas is 2 L / min-30 L / min, especially in conjunction with the flow rate of the gaseous reducing agent being 2 L / min-50 L / min. The ratio of the flow rate of the mixed gas to the flow rate of the gaseous reducing agent is 1:(1.5-25) to ensure that the precursor reaction solution tends to grow single-walled carbon nanotube vines in the front reaction zone and petal-shaped graphene in the back reaction zone.

[0055] In one embodiment, the mixing ratio of the carbon source and the inert gas is (100-500):1.

[0056] In one embodiment, the gaseous reducing agent includes at least one of hydrogen, carbon monoxide, and ammonia.

[0057] In one embodiment, the inert protective gas includes at least one of argon, nitrogen, and helium.

[0058] In one embodiment, the carbon source includes at least one of methane and acetylene, and ethylene.

[0059] In one embodiment, the precursor reaction liquid, gaseous reducing agent, and mixture of carbon source and inert gas are continuously introduced to ensure the reaction proceeds fully.

[0060] In one embodiment, the distance between the atomizing pinhole and the reducing gas hole is 1cm-5cm; the distance between the reducing gas hole and the air inlet is 5cm-10cm, to ensure that the distribution of the atomizing pinhole, reducing gas hole and air inlet is more suitable. In particular, when combined with the use of the flow rate of the mixed gas being 2L / min-30 L / min, the flow rate of the gaseous reducing agent being 2L / min-50 L / min, and the inlet flow rate of the precursor reaction liquid being 0.2 mL / min-20 mL / min, it can be effectively ensured that the precursor reaction liquid mainly generates single-walled carbon nanotubes in the front reaction zone of the reaction device, while the rear reaction zone mainly generates graphene.

[0061] In one embodiment, the pore size of the atomizing pinhole is 1μm-500μm.

[0062] In one embodiment, the pore size of the reducing pores is 4cm-12cm.

[0063] In one embodiment, the diameter of the air inlet is 4cm-12cm.

[0064] It should be noted that although by reasonably controlling the flow rate ratio of the mixed gas to the gas reducing agent, and by partitioning the mixed gas and the gas reducing agent, different growth environments for single-walled carbon nanotube-entwined vines and petal-shaped graphene can be constructed to a certain extent, the growth of single-walled carbon nanotubes depends on the one-dimensional winding of the catalyst, while the growth of graphene depends on the two-dimensional spreading of the substrate surface. This results in a significant difference in the growth mechanisms of single-walled carbon nanotubes and graphene, leading to the problem that petal-shaped graphene and single-walled carbon nanotube-entwined vines are prone to large gaps at the bonding interface during the growth process, making it difficult to achieve comprehensive repair of defects.

[0065] Therefore, in this disclosure, when a gaseous reducing agent is introduced into the middle region of the reaction device and a mixture of carbon source and inert gas is introduced into the peripheral region of the reaction device for reaction, the temperature of the front reaction zone is controlled to be 500℃-1000℃, the temperature of the middle reaction zone is 900℃-1300℃, and the temperature of the rear reaction zone is 900℃-1300℃.

[0066] It is understandable that by setting the temperature of the intermediate reaction zone to 900℃-1300℃, which is significantly higher than the traditional growth environment of single-walled carbon nanotubes (700℃-900℃), the temperature of the intermediate reaction zone is ensured to be no lower than that of the later reaction zone. This allows for the simultaneous activation of the dual growth system of single-walled carbon nanotubes and graphene. The increased surface defect energy of the single-walled carbon nanotube vines generated in the intermediate reaction zone at high temperatures allows for adjustment of the one-dimensional winding degree of the vines, thus providing a better growth environment for the two-dimensional spreading of graphene. Furthermore, the increased surface defect area of ​​the single-walled carbon nanotube vines at high temperatures promotes the uniformity and completeness of the carbon source. Surface deposition and attachment growth allows for the formation of a relatively dense substrate layer at surface defects of the single-walled carbon nanotube (SUV) vines. This effectively reduces the large gaps at the interface between the petal-shaped graphene and the SUV vines during growth, and also achieves more comprehensive repair of surface defects. As the mixed gas and gaseous reducing agent continue to diffuse and mix, the homogeneously mixed gas and reducing agent provide sufficient carbon source for the subsequent reaction zone when the SUV vines enter. This sufficient carbon source enables the rapid and uniform growth of highly saturated petal-shaped graphene on the already formed substrate layer. Figure 3A As shown, this allows petal-shaped graphene to grow fully and uniformly along the surface defects of the single-walled carbon nanotubes that wrap around the vine, which is beneficial for preparing a composite conductive agent with a wisteria flower structure of single-walled carbon nanotube graphene, characterized by high saturation, uniform thickness, good dispersibility, low interfacial impedance, continuous conductive network, and stable structure.

[0067] It is also understandable that the temperature of the front reaction zone is 500℃-1000℃, which is conducive to the construction of a core region that tends to generate single-walled carbon nanotubes and vine-like tendrils, while the temperature of the back reaction zone is 900℃-1300℃, which is conducive to the construction of a core region that tends to generate petal-shaped graphene.

[0068] In one embodiment, the length of the front reaction zone is 30cm-40cm, the length of the middle reaction zone is 30cm-40cm, and the length of the rear reaction zone is 30cm-40cm. In particular, with the use of a mixed gas flow rate of 2L / min-30L / min, a gaseous reducing agent flow rate of 2L / min-50L / min, and a flow rate ratio of the mixed gas to the gaseous reducing agent of 1:(1.5-5.0), it is ensured that the precursor reaction liquid tends to grow high-purity, structurally stable single-walled carbon nanotube vines in the front reaction zone of the reaction device, the middle reaction zone is a dual growth activation zone of single-walled carbon nanotubes and graphene, and the rear reaction zone tends to grow petal-shaped graphene with uniform thickness and small interfacial gaps.

[0069] In a preferred embodiment, the lengths of the front reaction region, the middle reaction region, and the rear reaction region are all equal. Specifically, the lengths of the front reaction region, the middle reaction region, and the rear reaction region are all 35 cm.

[0070] S103. The powder is acid-washed and purified to effectively remove impurities such as metal catalysts and amorphous carbon, to obtain a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure.

[0071] The preparation method of the aforementioned wisteria-shaped single-walled carbon nanotube-graphene composite conductive agent involves first introducing the precursor reaction solution into the central region of the reaction apparatus. Then, a gaseous reducing agent is introduced into the central region of the apparatus, while a mixture of carbon source and inert gas is introduced into the peripheral region. Simultaneously, the flow rate of the mixed gas is lower than that of the gaseous reducing agent. This allows the precursor reaction solution to tend to grow high-purity, structurally stable single-walled carbon nanotubes into vine-like strands in the front reaction zone, a dual-growth activation zone for single-walled carbon nanotubes and graphene in the middle reaction zone, and a tendency to grow petal-shaped graphene with uniform thickness and small interfacial gaps in the rear reaction zone. Thus, ultrasonic treatment is unnecessary. The method involves simple dispersion and mixing, eliminating the need for additional graphene addition and effectively reducing preparation costs. It achieves one-step generation of single-walled carbon nanotube (SCH) vine-like strands and multiple petal-shaped graphenes, while also improving the self-dispersion of the petal-shaped graphene and the SCH vine-like strands. Furthermore, it reduces the interfacial gap between the petal-shaped graphene and the SCH vine-like strands, thereby lowering the interfacial impedance and improving the stability of the connection between them. This facilitates the preparation of a composite conductive agent with a wisteria flower structure containing single-walled carbon nanotube graphene, exhibiting good dispersibility, low interfacial impedance, continuous conductive network, and structural stability.

[0072] This disclosure also provides a method for preparing a slurry. First, a composite conductive agent consisting of single-walled carbon nanotubes with a wisteria flower structure and graphene, along with an organic solvent, is dispersed and mixed using a homogenizer to obtain a conductive composite dispersion. Then, the conductive composite dispersion, active material, and PVDF are mixed, and an organic solvent is added to adjust the consistency. Following this, a degassing treatment is performed to obtain a slurry with a viscosity of 4000 cP-8000 cP for later use. It is worth noting that the slurry with a viscosity of 4000 cP-8000 cP solves the core problems of easy sedimentation at low viscosity and difficulty in leveling at high viscosity, ultimately achieving a coating effect with a smooth surface, uniform thickness, and consistent performance on the electrode, thus ensuring better quality of the resulting coating.

[0073] In one embodiment, the active material, PVDF, and conductive composite dispersion are mixed in a ratio of (89-89.5):10:(0.5-1.0) to help obtain an electrochemical device with high energy density.

[0074] In a preferred embodiment, the active material, PVDF, and conductive composite dispersion are in a ratio of (89-89.2):10:(0.5-0.8) to ensure that a highly conductive electrochemical device can be prepared using a small amount of the composite conductive agent of wisteria-structured single-walled carbon nanotube graphene.

[0075] In a preferred embodiment, the active material, PVDF, and conductive composite dispersion are in a ratio of 89:10:1.0.

[0076] In one embodiment, the prepared slurry is coated onto a current collector with a thickness of 10μm-30μm using a coating machine, and the coating thickness is controlled to be 100μm-300μm. Then, it is dried to form an active layer on the current collector.

[0077] In one embodiment, the current collector is an aluminum foil.

[0078] In one embodiment, the drying temperature is 70°C-90°C and the drying time is 1h-4h.

[0079] In one embodiment, a composite conductive agent of single-walled carbon nanotube graphene with a wisteria flower structure is used in a positive electrode slurry.

[0080] Compared with the prior art, this disclosure has at least the following advantages: Since the composite conductive agent of single-walled carbon nanotube graphene with the wisteria flower structure includes single-walled carbon nanotubes wrapped around a vine and multiple petal-shaped graphenes, each petal-shaped graphene grows in situ along the defects of the outer peripheral wall of the single-walled carbon nanotubes wrapped around the vine. This effectively reduces the growth flow rate and nucleation density of single-walled carbon nanotubes on the outer peripheral wall of the vine, thus blocking the probability of newly generated single-walled carbon nanotubes spontaneously agglomerating into bundles. This results in the outer peripheral wall of the vine being dominated by the formation of petal-shaped graphenes, allowing the multiple petal-shaped graphenes to physically separate the wrapped single-walled carbon nanotubes, preventing the vine from re-agglomerating due to van der Waals forces. Simultaneously, it avoids the self-stacking of the petal-shaped graphenes, significantly improving the dispersibility of the composite conductive agent of single-walled carbon nanotube graphene, which is beneficial for preparing a composite conductive agent. The uniform dispersion of the slurry reduces the difficulty of dispersing the slurry in lithium battery manufacturing, thereby ensuring the effective conductivity of the single-walled carbon nanotube-graphene composite conductive agent with wisteria flower structure. On the other hand, since the petal-shaped graphene grows and attaches directly to the surface defects of the single-walled carbon nanotube winding vine through chemical covalent bonding (such as C-C bonds) or interfacial adsorption (strong chemical bonding formed by the lone pair electrons of the single-walled carbon nanotube and the empty orbitals of the graphene), it effectively reduces the surface defects of the single-walled carbon nanotube winding vine. This not only reduces the gap between the single-walled carbon nanotube winding vine and the petal-shaped graphene interface, thereby reducing the interfacial impedance of the single-walled carbon nanotube winding vine and the petal-shaped graphene, but also improves the stability and conductivity of the connection between the single-walled carbon nanotube winding vine and the petal-shaped graphene. This is beneficial for preparing a three-dimensional conductive network with low interfacial impedance, continuous conductive network and stable structure.

[0081] The following are some specific examples. When %, it refers to a percentage by weight. It should be noted that the following examples do not exhaustively list all possible scenarios, and unless otherwise specified, the materials used in the examples are commercially available.

[0082] Example 1: (1) Prepare a precursor reaction solution with a concentration of 0.02 g / ml by mixing ferrocene with n-hexane; (2) The precursor reaction solution is fed into the atomizing needle hole (pore diameter 200μm) of the reaction device at a flow rate of 6 mL / min. The temperature of the front section of the reaction device is 800℃ and the length of the front section reaction zone is 35cm. The temperature of the middle and rear sections reaction zones is 1250℃ and the length of the middle section reaction zone is 35cm and the length of the rear section reaction zone is 35cm. (3) Hydrogen gas is fed into the reduction port (orifice diameter 8 cm) of the reaction apparatus at a flow rate of 5 L / min, and a mixture of argon and methane gas (methane to argon ratio of 200:1) is fed into the inlet port (orifice diameter 12 cm) of the reaction apparatus at a flow rate of 2 L / min. The distance between the atomizing pinhole and the reduction port is 3 cm; the distance between the reduction port and the inlet port is 6 cm; the flow rate ratio of the mixed gas to the hydrogen gas is 1:2.5, and powder is obtained. (4) The prepared powder was acid washed and purified to obtain a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure (SWCNT-GN). (5) After dispersing the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent by homogenizer, the mass ratio of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent is 1:99, and the conductive composite dispersion of NMP system SWCNT-GN is obtained. (6) Using lithium iron phosphate (LFP) as the positive electrode active material, LFP, PVDF and conductive composite dispersion SWCNT-GN are mixed in a mass ratio of 89:10:1, and NMP solvent is added to adjust the slurry. The mixed slurry is degassed using a degassing machine to prepare a slurry with a viscosity of 4750 cP. The prepared slurry is coated on an aluminum foil with a thickness of 20 μm and a coating thickness of 200 μm. The flow rate of the coating machine is set to 6 to obtain the positive electrode sheet. (7) Place the positive electrode sheet in a vacuum drying oven and dry it at 80°C for 1 hour for later use; (8) The positive electrode sheet from step (7) is made into a button cell to obtain an electrochemical device, and then the impedance value and rate performance (0.1C, 0.2C, 0.5C, 1C, 2C) are tested.

[0083] Example 2: (1) Prepare a precursor reaction solution with a concentration of 0.01 g / ml by mixing cobalt thiophene with ethanol; (2) The precursor reaction solution is fed into the atomizing needle hole (1 μm diameter) of the reaction device at a flow rate of 15 mL / min. The temperature of the front section of the reaction device is 500℃ and the length of the front reaction zone is 30 cm. The temperature of the middle and rear reaction zones is 900℃ and the length of the middle reaction zone is 30 cm. The length of the rear reaction zone is 30 cm. (3) Hydrogen gas is fed into the reduction port (orifice diameter 4 cm) of the reaction device at a flow rate of 1 L / min, and a mixture of argon and methane gas (methane to argon ratio of 100:1) is fed into the inlet port (orifice diameter 8 cm) of the reaction device at a flow rate of 2 L / min. The distance between the atomizing pinhole and the reduction port is 1 cm; the distance between the reduction port and the inlet port is 5 cm; the flow rate ratio of the mixed gas to the hydrogen gas is 1:0.5, and powder is obtained. (4) The prepared powder was acid washed and purified to obtain a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure (SWCNT-GN). (5) After dispersing the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent by homogenizer, the mass ratio of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent is 1:99, and the conductive composite dispersion of NMP system SWCNT-GN is obtained. (6) Using lithium iron phosphate (LFP) as the positive electrode active material, LFP, PVDF and conductive composite dispersion SWCNT-GN are mixed in a mass ratio of 89:10:1, and NMP solvent is added to adjust the slurry. The mixed slurry is degassed using a degassing machine to prepare a slurry with a viscosity of 4700 cP. The prepared slurry is coated on an aluminum foil with a thickness of 20 μm and a coating thickness of 200 μm. The flow rate of the coating machine is set to 6 to obtain the positive electrode sheet. (7) Place the positive electrode sheet in a vacuum drying oven overnight at 70°C for 4 hours for later use; (8) The positive electrode sheet from step (7) is made into a button cell to obtain an electrochemical device, and then the impedance value and rate performance (0.1C, 0.2C, 0.5C, 1C, 2C) are tested.

[0084] Example 3: (1) Prepare a precursor reaction solution with nickel dicema and toluene at a concentration of 0.03 g / ml; (2) The precursor reaction solution is fed into the atomizing needle hole (500 μm) of the reaction device at a flow rate of 0.2 mL / min. The temperature of the front section of the reaction device is 600℃ and the length of the front reaction zone is 40 cm. The temperature of the middle and rear reaction zones is 1000℃ and the length of the middle reaction zone is 40 cm. The length of the rear reaction zone is 40 cm. (3) Ammonia gas is fed into the reduction port (6 cm in diameter) of the reaction device at a flow rate of 50 L / min, and argon and methane mixed gas (methane to argon ratio of 500:1) is fed into the inlet port (10 cm in diameter) of the reaction device at a flow rate of 2 L / min. The distance between the atomizing pinhole and the reduction port is 5 cm; the distance between the reduction port and the inlet port is 10 cm; the flow rate ratio of the mixed gas to the hydrogen gas is 1:25, and powder is obtained. (4) The prepared powder was acid washed and purified to obtain a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure (SWCNT-GN). (5) After dispersing the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent by homogenizer, the mass ratio of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent is 1:99, and the conductive composite dispersion of NMP system SWCNT-GN is obtained. (6) Using lithium iron phosphate (LFP) as the positive electrode active material, LFP, PVDF and conductive composite dispersion SWCNT-GN are mixed in a mass ratio of 89:10:1, and NMP solvent is added to adjust the slurry. The mixed slurry is then mixed using a degassing machine to prepare a slurry with a viscosity of 4680 cP. The prepared slurry is then coated onto an aluminum foil with a thickness of 20 μm and a coating thickness of 200 μm. The flow rate of the coating machine is set to 6 to obtain the positive electrode sheet. (7) Place the positive electrode sheet in a vacuum drying oven overnight at 80°C for 3 hours for later use; (8) The positive electrode sheet from step (7) is made into a button cell to obtain an electrochemical device, and then the impedance value and rate performance (0.1C, 0.2C, 0.5C, 1C, 2C) are tested.

[0085] Example 4: (1) Prepare a precursor reaction solution with a concentration of 0.03 g / ml by mixing platinum thiocene with cyclohexane; (2) The precursor reaction solution is fed into the atomizing needle hole (100 μm diameter) of the reaction device at a flow rate of 10 mL / min. The temperature of the front section of the reaction device is 900℃ and the length of the front reaction zone is 38 cm. The temperature of the middle and rear reaction zones is 1200℃ and the length of the middle reaction zone is 38 cm. The length of the rear reaction zone is 38 cm. (3) Hydrogen gas is fed into the reduction port (10 cm in diameter) of the reaction device at a flow rate of 10 L / min, and nitrogen and methane mixed gas (methane to nitrogen ratio of 300:1) is fed into the inlet port (12 cm in diameter) of the reaction device at a flow rate of 2 L / min. The distance between the atomizing pinhole and the reduction port is 4 cm; the distance between the reduction port and the inlet port is 8 cm; the flow rate ratio of the mixed gas to the hydrogen gas is 1:5.0, and powder is obtained. (4) The prepared powder was acid washed and purified to obtain a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure (SWCNT-GN). (5) After dispersing the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent by homogenizer, the mass ratio of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent is 1:99, and the conductive composite dispersion of NMP system SWCNT-GN is obtained. (6) Using lithium iron phosphate (LFP) as the positive electrode active material, LFP, PVDF and conductive composite dispersion SWCNT-GN are mixed in a mass ratio of 89:10:1, and NMP solvent is added to adjust the slurry. The mixed slurry is then mixed using a degassing machine to prepare a slurry with a viscosity of 4600 cP. The prepared slurry is then coated onto an aluminum foil with a thickness of 20 μm and a coating thickness of 200 μm. The flow rate of the coating machine is set to 6 to obtain the positive electrode sheet. (7) Place the positive electrode sheet in a vacuum drying oven overnight at 85°C for 2 hours for later use; (8) The positive electrode sheet from step (7) is made into a button cell to obtain an electrochemical device, and then the impedance value and rate performance (0.1C, 0.2C, 0.5C, 1C, 2C) are tested.

[0086] Example 5: (1) Prepare a precursor reaction solution with a concentration of 0.05 g / ml by mixing ferrocene and n-hexane; (2) The precursor reaction solution is fed into the atomizing needle hole (pore diameter 250μm) of the reaction device at a flow rate of 20 mL / min. The temperature of the front section of the reaction device is 1000℃ and the length of the front section reaction zone is 36cm. The temperature of the middle and rear sections reaction zones is 1300℃ and the length of the middle section reaction zone is 36cm. The length of the rear section reaction zone is 36cm. (3) Hydrogen gas is fed into the reduction port (12 cm in diameter) of the reaction device at a flow rate of 6 L / min, and a mixture of helium and ethylene gas (methane to helium ratio of 500:1) is fed into the inlet port (12 cm in diameter) of the reaction device at a flow rate of 2 L / min. The distance between the atomizing pinhole and the reduction port is 4 cm; the distance between the reduction port and the inlet port is 8 cm; the flow rate ratio of the mixed gas to the hydrogen gas is 1:3, and powder is obtained. (4) The prepared powder was acid washed and purified to obtain a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure (SWCNT-GN). (5) After dispersing the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent by homogenizer, the mass ratio of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure and NMP solvent is 1:99, and the conductive composite dispersion of NMP system SWCNT-GN is obtained. (6) Using lithium iron phosphate (LFP) as the positive electrode active material, LFP, PVDF and conductive composite dispersion SWCNT-GN are mixed in a mass ratio of 89:10:1, and NMP solvent is added to adjust the slurry. The mixed slurry is then mixed using a degassing machine to prepare a slurry with a viscosity of 4700 cP. The prepared slurry is coated onto an aluminum foil with a thickness of 20 μm and a coating thickness of 200 μm. The flow rate of the coating machine is set to 6 to obtain the positive electrode sheet. (7) Place the positive electrode sheet in a vacuum drying oven overnight at 90°C for 1.5 hours for later use; (8) The positive electrode sheet from step (7) is made into a button cell to obtain an electrochemical device, and then the impedance value and rate performance (0.1C, 0.2C, 0.5C, 1C, 2C) are tested.

[0087] Comparative Example 1: The difference from Example 1 is that steps (1)-(4) are omitted, and the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure in step (5) is directly replaced with commercially available SP conductive agent (traditional single-walled carbon nanotube), while the rest remain unchanged.

[0088] Comparative Example 2: The difference from Example 1 is that steps (1)-(4) are omitted, and the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure in step (5) is directly replaced with commercially available 0.5% SP + 0.5% CNTs mixed conductive agent, while the rest remain unchanged.

[0089] Comparative Example 3 The difference from Example 1 is that the temperature of the middle reaction zone in step (2) is directly replaced by 900℃ (the middle growth temperature of traditional single-walled carbon nanotubes), while the rest remain unchanged.

[0090] Comparative Example 4 The difference from Example 1 is that the temperature of the later reaction zone in step (2) is directly replaced with 900°C instead of 1250°C, while the rest remains unchanged.

[0091] The dispersion performance of the slurries from steps (6) of Examples 1-5 and Comparative Examples 1-4 was tested, and the experimental data in Table 1 were obtained: Table 1 Dispersion performance project Visual inspection Viscosity (mPa·s) Observe after standing for 7 days Example 1 There are no obvious particles, and the coated surface is smooth. 4750 No settlement Example 2 There are no obvious particles, and the coated surface is smooth. 4700 No settlement Example 3 There are no obvious particles, and the coated surface is smooth. 4680 No settlement Example 4 There are no obvious particles, and the coated surface is smooth. 4600 No settlement Example 5 There are no obvious particles, and the coated surface is smooth. 4700 No settlement Comparative Example 1 There are no obvious particles, and the surface of the coated layer is slightly rough. 4130 slight settlement Comparative Example 2 There are no obvious particles, and the surface of the coated layer is slightly rough. 4150 Slight sedimentation Comparative Example 3 There are no obvious particles, and the surface of the coated layer is slightly rough. 4310 slight settlement Comparative Example 4 There are no obvious particles, and the surface of the coated layer is slightly rough. 4390 slight settlement As can be seen from Table 1, Examples 1-5 and Comparative Examples 1-4, under the same ratio and mixing conditions of LFP, PVDF, and conductive composite dispersion SWCNT-GN, the viscosity of the slurry in Examples 1-5 is significantly higher than that in Comparative Examples 1-4. This proves that the conductive composite dispersion SWCNT-GN in Examples 1-5 has better dispersibility, and no sedimentation was observed after standing for 7 days. This indicates that the dispersion performance of the single-walled carbon nanotube graphene composite conductive agent with wisteria flower structure used in Examples 1-5 is significantly better than that in Comparative Examples 1-4.

[0092] The rate performance and resistance of the electrochemical devices in Examples 1-5 and Comparative Examples 1-4 were tested respectively to obtain... Figure 6 and Figure 7 Comparison chart of experimental data: from Figure 6 and Figure 7It can be seen that, due to the partitioning of the reaction apparatus in Examples 1-5, and by reasonably controlling the flow rate of the precursor reaction liquid (0.2 mL / min-20 mL / min), the concentration of the precursor reaction liquid (0.01 g / mL-0.05 g / mL), the flow rate of the gaseous reducing agent (2 L / min-50 L / min), and the flow rate of the mixed gas (2 L / min-30 L / min), the results are as follows: The flow rate was controlled by adjusting the flow rate of the mixed gas to the flow rate of the reducing agent to a ratio of 1:(1.5-5.0), and the intermediate reaction temperature was equal to the final reaction temperature. This ensured that the precursor reaction solution tended to grow high-purity, structurally stable single-walled carbon nanotubes (SHU) into vine-like strands in the front reaction zone of the reaction apparatus. The middle reaction zone achieved dual growth activation of SHU and graphene, while the final reaction zone tended to grow petal-shaped graphene with uniform thickness and small interfacial gaps. This facilitated the preparation of a composite conductive agent with a wisteria-like structure of SHU and graphene, characterized by good dispersibility, low interfacial impedance, continuous conductive network, and structural stability. This ensured that a high-conductivity electrochemical device could be prepared using a smaller amount of the wisteria-like structure SHU composite conductive agent, resulting in significantly better overall performance than Comparative Examples 1-4. Among these, Example 1 exhibited the best overall performance.

[0093] Furthermore, when the flow rate of the mixed gas is in the ratio of 1:(1.5-5.0) to the flow rate of the gas reducing agent, the overall performance of Examples 1, 4 and 5 is significantly better than that of Examples 2 and 3.

[0094] Furthermore, when the intermediate reaction temperature is equal to the subsequent reaction temperature, the overall performance of Example 1 is significantly better than that of Comparative Examples 3-4.

[0095] The embodiments described above are merely illustrative of several implementations of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the disclosed patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. An electrochemical device based on a single-walled carbon nanotube-graphene composite conductive agent with a wisteria flower structure, comprising a battery cell and a housing; the battery cell is disposed within the housing, the battery cell comprising a positive electrode, a negative electrode, and a separator; the separator is disposed between the positive electrode and the negative electrode, the positive electrode and / or the negative electrode being coated with a slurry, characterized in that, The slurry includes active substances, binders, a composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure, and an organic solvent. The composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure includes single-walled carbon nanotubes wrapped around vines and multiple petal-shaped graphenes. Each of the petal-shaped graphenes grows in situ along the defects of the outer peripheral wall of the single-walled carbon nanotubes wrapped around vines.

2. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 1, characterized in that, The preparation method of the composite conductive agent of single-walled carbon nanotube graphene with wisteria flower structure includes the following steps: The precursor reaction solution is introduced into the central region of the reaction apparatus; A gaseous reducing agent is introduced into the central region of the reaction apparatus, and a mixture of carbon source and inert gas is introduced into the peripheral region of the reaction apparatus to react and obtain powder; wherein the flow rate of the mixed gas is less than the flow rate of the gaseous reducing agent. The powder was purified by acid washing to obtain a composite conductive agent of single-walled carbon nanotube graphene with the wisteria flower structure.

3. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 2, characterized in that, The flow rate of the mixed gas is 2 L / min-30 L / min; and / or, The flow rate of the gaseous reducing agent is 2 L / min to 50 L / min.

4. The electrochemical device based on a wisteria flower-structured single-walled carbon nanotube-graphene composite conductive agent according to claim 2, characterized in that, In the step of introducing the precursor reaction solution into the central region of the reaction apparatus, the inlet flow rate is 0.2 mL / min-20 mL / min.

5. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 2, characterized in that, When a gaseous reducing agent is introduced into the middle region of the reaction device, and a mixture of carbon source and inert gas is introduced into the outer region of the reaction device for reaction, the temperature of the front reaction zone is controlled at 500℃-1000℃, the temperature of the middle reaction zone is controlled at 900℃-1300℃, and the temperature of the rear reaction zone is controlled at 900℃-1300℃.

6. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 2, characterized in that, The mixing ratio of the carbon source and the inert gas is (100-500):

1.

7. The electrochemical device based on a wisteria flower-structured single-walled carbon nanotube-graphene composite conductive agent according to claim 2, characterized in that, The precursor reaction solution is obtained by mixing a transition metal compound and a carbon-containing organic solvent.

8. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 2, characterized in that, The concentration of the precursor reaction solution is 0.01 g / mL to 0.05 g / mL.

9. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 2, characterized in that, The gaseous reducing agent includes at least one of hydrogen, carbon monoxide, and ammonia; and / or, The inert protective gas includes at least one of argon, nitrogen, and helium.

10. The electrochemical device based on the wisteria flower structure and graphene composite conductive agent according to claim 1, characterized in that, The amount of the composite conductive agent, consisting of single-walled carbon nanotubes and graphene with a wisteria flower structure, used accounts for 0.5%-1.0% of the mass percentage of the slurry.

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