A composite conductive paste with a point-line-surface structure and its preparation method

Abstract

This invention discloses a composite conductive paste with a point-line-surface structure and its preparation method, belonging to the field of conductive paste technology. The conductive paste comprises a composite conductive agent, a dispersing agent, and N-methylpyrrolidone. The composite conductive agent includes zero-dimensional carbon black-based conductive agents, one-dimensional carbon nanotube conductive agents, and two-dimensional graphene conductive agents. In the composite conductive agent, the mass percentage of zero-dimensional carbon black-based conductive agents is 5%~20%, the mass percentage of one-dimensional carbon nanotube conductive agents is 10%~30%, and the mass percentage of two-dimensional graphene conductive agents is 50%~80%. This invention constructs a "point-line-surface" synergistic conductive structure by using a composite conductive agent system of zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional graphene in a certain proportion, solving the problems of high contact resistance, easy breakage of conductive networks, and high addition amount crowding out the proportion of active material in single-dimensional conductive agents.

Description

Technical Field

[0001] This invention belongs to the field of conductive paste and its preparation technology, and particularly relates to a composite conductive paste with a point-line-surface structure and its preparation method. Background Technology

[0002] With the increasing demands for energy density, power density, and cycle life of lithium-ion batteries from new energy vehicles and energy storage systems, the performance of conductive agents, as a crucial component of electrodes, directly determines the electron transport efficiency and utilization rate of active materials within the electrode. An ideal conductive agent should construct a highly efficient and complete three-dimensional conductive network within the electrode to minimize internal resistance, improve rate performance, and enhance cycle stability.

[0003] Currently, conductive agents used in lithium-ion batteries mainly fall into the following categories: 1. Zero-dimensional (0D) carbon black conductive agents, represented by SuperP, SuperC65, acetylene black, and Ketjen black. These conductive agents are inexpensive and have a moderate specific surface area, forming conductive paths through point contact. However, their main limitations are: relatively high point-to-point contact resistance, and the tendency for the conductive network to break due to electrode volume expansion and contraction during cycling. When used alone, they require a relatively high addition amount (typically 3%–5%), limiting the improvement of energy density. 2. One-dimensional (1D) carbon nanotube (CNT) conductive agents, including single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). Carbon nanotubes possess excellent axial conductivity (conductivity up to 10⁻⁶). 5 ~10 6 With a high aspect ratio (typically >1000), it can achieve "line connection" across the gaps between active particles. However, its main problems are: (1) Carbon nanotubes are easily entangled and agglomerated due to strong van der Waals forces, and it is difficult to untangle and distribute them evenly under conventional dispersion conditions; (2) The contact between carbon nanotubes and active materials is line-point contact, and the contact area is limited; (3) When used alone, the number of overlapping points between carbon nanotubes is insufficient, making it difficult to form a continuous conductive network that runs through the entire electrode thickness. III. Two-dimensional (2D) graphene conductive agent has a very large theoretical specific surface area (2630m² / g) and extremely high intrinsic conductivity. The two-dimensional sheet structure of graphene can form a large area contact between the surface or the point with the electrode active material, effectively reducing the interfacial contact resistance. However, the graphene sheets are very prone to face-to-face π-π stacking and agglomeration, and when graphene is used alone, the contact between the sheets is a transition from two-dimensional surface contact to one-dimensional line contact. If the dispersion is not proper, the flat stacking of the sheets will hinder ion transport.

[0004] In recent years, researchers have attempted to physically mix the above three types of conductive agents in order to achieve a synergistic conductive effect. However, the existing technology has the following prominent defects: (1) The dispersion behavior of materials of different dimensions is very different: carbon black is easy to disperse but easy to agglomerate, carbon nanotubes require high-intensity shear untangling, and graphene requires gentle dispersion to prevent structural damage. When the three are placed in the same system, the single dispersion process cannot take into account the dispersion requirements of various materials, resulting in uneven distribution of each group in the slurry, and even selective agglomeration and phase separation. (2) Lack of the ability to construct an ordered structure of "point-line-surface": the existing mixing methods are mostly simple mechanical stirring and mixing, which cannot achieve the ordered self-assembly arrangement of the three-dimensional materials at the mesoscale. There are a large number of "conductive islands" and "breakpoints" in the conductive network, and the synergistic effect is not fully utilized. (3) Poor compatibility with different graphene raw materials: As mentioned above, the physicochemical properties of the three types of graphene are significantly different: flash Joule heating (many defects, large specific surface area), mechanical exfoliation (inert surface, intact structure) and carbon atom rearrangement in pyrolysis furnace (medium defects). When these three types of graphene are combined with carbon black and carbon nanotubes, the existing dispersion system cannot simultaneously adapt to the three types of graphene, which greatly limits the flexibility of raw material sources. Summary of the Invention

[0005] Based on the technical problems existing in the prior art, the present invention provides a composite conductive paste with a point-line-surface structure and its preparation method.

[0006] According to a first aspect of the technical solution of the present invention, a composite conductive paste having a point-line-surface structure is provided, comprising a composite conductive agent, a dispersing agent and N-methylpyrrolidone; The composite conductive agent includes zero-dimensional carbon black conductive agents, one-dimensional carbon nanotube conductive agents, and two-dimensional graphene conductive agents. In the composite conductive agent, the mass percentage of the zero-dimensional carbon black conductive agent is 5% to 20%, the mass percentage of the one-dimensional carbon nanotube conductive agent is 10% to 30%, and the mass percentage of the two-dimensional graphene conductive agent is 50% to 80%.

[0007] A further improvement of the present invention is that the zero-dimensional carbon black conductive agent includes super P conductive carbon black, super C65 conductive carbon black and acetylene black; The one-dimensional carbon nanotube conductive agent includes single-arm carbon nanotubes and multi-arm carbon nanotubes. The two-dimensional graphene conductive agent includes rotary-cut graphene, flash-electrode Joule-processed graphene, and molecular template-processed graphene.

[0008] A further improvement of the present invention is that the particle size of the carbon black in the zero-dimensional carbon black conductive agent is 30nm~50nm; The diameter of the carbon nanotubes in the one-dimensional carbon nanotube conductive agent is 5nm~20nm, and the aspect ratio is >1000. The graphene sheet diameter in the two-dimensional graphene conductive agent is 500 nm to 5 µm.

[0009] A further improvement of the present invention is that the specific surface area of ​​the composite conductive agent is 15m². 2 / g, the compacted density of the composite conductive agent is 1.5 g / cm³. 3 ~2.2g / cm 3 The conductivity of the composite conductive agent is 100S / cm~150S / cm.

[0010] A further improvement of the present invention is that the dispersing agent comprises polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, decaamine, cyclohexanediamine, sodium dodecyl sulfate, and dopamine hydrochloride.

[0011] A further improvement of the present invention is that the mass ratio of the following components is (2-5): (1-3): (0.5-2): (0.5-2): (1-3): (0.5-1.5).

[0012] A further improvement of the present invention is that the mass percentage of the dispersing agent in the conductive slurry is 0.3% to 1%.

[0013] A further improvement of the present invention is that the solid content of the composite conductive agent is 5%.

[0014] According to a second aspect of the technical solution of the present invention, a method for preparing a composite conductive paste having a point-line-surface structure is provided, for preparing the above-mentioned composite conductive paste having a point-line-surface structure, comprising the following steps: Step S1: Disperse the composite conductive agent in N-methylpyrrolidone, and add a dispersing agent to mix and form a preliminary slurry.

[0015] Step S2: The initial mixed slurry is dispersed using a high-speed mixer to obtain a pre-dispersed slurry; Step S3: Inject the pre-dispersed slurry into a sand mill and grind the pre-dispersed slurry to obtain the target slurry; A further improvement of the present invention is that, in step S2, the stirring speed of the high-speed mixer is 1000 rpm / min to 3000 rpm / min, and the stirring time is 30 min to 120 min. In step S3, the grinding pressure of the grinding machine is 0.4MPa~0.6MPa, and the grinding time is 60min~120min.

[0016] Compared with the prior art, the above-mentioned technical solution of the composite conductive paste with point-line-surface structure and its preparation method of the present invention has the following beneficial technical effects: 1. This invention utilizes a composite conductive agent system composed of zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional graphene in a specific ratio to construct a "point-line-surface" synergistic conductive structure. This solves the problems of high contact resistance, easy breakage of conductive networks, and high addition amount that crowds out the proportion of active material in single-dimensional conductive agents. It can form a three-dimensional conductive network that runs through the electrode, effectively reducing the internal resistance of the electrode, improving the rate performance and cycle stability of the battery, while reducing the total amount of conductive agent added, thus helping to improve the energy density of the battery.

[0017] 2. This invention solves the problem of limited raw material sources and applicable scenarios for composite conductive pastes by incorporating a variety of commercially mature raw material selections into conductive agents of various dimensions, covering different types of carbon black, carbon nanotubes and graphene prepared by various processes. It can flexibly match raw materials according to the performance requirements and cost requirements of different battery systems, and is compatible with graphene of three types of processes, which greatly expands the application scope of the paste and the selection space of raw materials.

[0018] 3. This invention solves the problems of poor size matching, low overlapping efficiency, and difficulty in forming an ordered conductive structure by precisely limiting the parameter ranges of zero-dimensional carbon black particle size, one-dimensional carbon nanotube diameter and aspect ratio, and two-dimensional graphene sheet diameter. It ensures that carbon black can fill the gaps between particles, carbon nanotubes can cross contact points, and graphene can form large-area surface contacts, achieving efficient and orderly overlapping of "point-line-surface" and strengthening the continuity and stability of the conductive network.

[0019] 4. This invention solves the problems of excessively high specific surface area of ​​the conductive agent leading to a surge in binder usage and low compaction density limiting energy density improvement by regulating the specific surface area, compaction density, and conductivity of the composite conductive agent within a reasonable range. It maintains a moderate specific surface area while ensuring high conductivity, reduces binder consumption, and increases electrode compaction density, thereby achieving a balanced optimization of conductivity and energy density.

[0020] 5. This invention solves the problem that a single dispersant cannot simultaneously adapt to three types of carbon materials with different surface properties by using a composite dispersant with six functional components. Each component can adsorb conductive materials of the corresponding dimension in a differentiated manner, realizing the stable co-dispersion of zero-dimensional carbon black, one-dimensional carbon nanotubes and two-dimensional graphene in the same system, effectively avoiding selective agglomeration and phase separation, and significantly improving the uniformity of slurry dispersion.

[0021] 6. By limiting the mass ratio range of the six dispersing functional components, this invention solves the problem of insufficient dispersion ability and inability to induce orderly assembly caused by the imbalance of the dispersant group distribution ratio. It maximizes the functional synergy of each component, accurately realizes the differentiated surface modification of carbon materials of different dimensions, and can induce the conductive agent to form a hierarchical conductive structure in an orderly self-assembly during the dispersion process, thereby simultaneously enhancing the dispersion stability of the slurry and the construction efficiency of the conductive network.

[0022] 7. This invention solves the problems of poor dispersion and easy stratification of the slurry when the amount of dispersant added is too low, and damage to the electrochemical performance of the electrode when the amount of dispersant added is too high, by controlling the amount of dispersant added to the range of 0.3% to 1% of the total mass of the slurry. Only a low amount of dispersant is needed to achieve long-term storage without stratification of the slurry for more than 180 days, while avoiding the negative impact of excessive dispersant on the battery internal resistance and cycle life, thus balancing the dispersion effect and electrochemical performance.

[0023] 8. This invention solves the problems of excessively high slurry viscosity, difficulty in dispersing shear, and easy formation of agglomeration dead zones caused by excessively high solid content, and low production efficiency and high solvent consumption caused by excessively low solid content, by setting the solid content of the composite conductive agent to 5%. It is suitable for high-speed stirring and sand milling processes, ensuring uniform shear force during dispersion, achieving full untangling and uniform dispersion of the conductive agent, and taking into account both processing feasibility and production efficiency.

[0024] 9. This invention solves the problem that a single dispersion process cannot meet the dispersion requirements of carbon materials of different dimensions by adopting a stepwise preparation process of premixing ingredients, high-speed stirring and pre-dispersion, and sand milling and circulating grinding. First, the raw materials are wetted by mixing, then preliminary dispersion is achieved by high-speed stirring, and finally, controllable shear force is provided by sand milling to complete the full unentanglement and orderly assembly of the conductive agent, and finally form a structurally stable "point-line-surface" three-dimensional conductive network.

[0025] 10. This invention solves the problem of carbon material structural damage, insufficient dispersion or over-grinding caused by improper process parameters by limiting the speed and duration of high-speed stirring and the grinding pressure and duration of sand milling. While effectively untangling carbon nanotubes and peeling off graphene agglomerates, it avoids damaging the intrinsic structure of carbon materials, ensuring the original conductivity of the conductive agent, and can stably prepare high-quality composite conductive slurry with uniform dispersion and complete structure. Attached Figure Description

[0026] The accompanying drawings are provided to better understand the invention and are not intended to unduly limit the scope of the invention. Wherein: Figure 1 SEM and TEM images of the conductive carbon black SuperC65 of the present invention; Figure 2 These are SEM and TEM images of the multi-walled carbon nanotubes of the present invention. Figure 3 SEM and TEM images of mechanically exfoliated graphene; Figure 4 SEM and TEM images of flash-electrode Joule graphene; Figure 5 SEM and TEM images of graphene obtained using the molecular template method; Figure 6 This is a Laman characterization diagram of the composite conductive agent of the present invention; Figure 7 This is a BET characterization diagram of the composite conductive agent of the present invention; Figure 8 The image shows the AFM characterization of the composite conductive agent of the present invention. Figure 9 These are SEM and TEM images of the composite conductive agent of the present invention; Figure 10 The compaction resistance test diagram of the composite conductive agent of the present invention is shown. Detailed Implementation The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0027] This invention discloses a composite conductive slurry with a point-line-surface structure and its preparation method, belonging to the field of conductive slurry technology. The conductive slurry comprises a composite conductive agent, a dispersing agent, and N-methylpyrrolidone. The composite conductive agent includes zero-dimensional carbon black-based conductive agents, one-dimensional carbon nanotube conductive agents, and two-dimensional graphene conductive agents. In the composite conductive agent, the mass percentage of the zero-dimensional carbon black-based conductive agent is 5%~20%, the mass percentage of the one-dimensional carbon nanotube conductive agent is 10%~30%, and the mass percentage of the two-dimensional graphene conductive agent is 50%~80%. This invention constructs a "point-line-surface" synergistic conductive structure by using a composite conductive agent system of zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional graphene in a certain proportion. This solves the problems of high contact resistance, easy breakage of conductive networks, and high addition amount crowding out the proportion of active material in single-dimensional conductive agents. It can form a three-dimensional conductive network that runs through the electrode, effectively reducing the internal resistance of the electrode, improving the rate performance and cycle stability of the battery, while reducing the total amount of conductive agent added, thus helping to improve the energy density of the battery.

[0028] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0029] Example 1 This embodiment provides a composite conductive paste with a point-line-surface structure, comprising a composite conductive agent, a dispersing agent, and N-methylpyrrolidone; the composite conductive agent includes zero-dimensional carbon black conductive agents, one-dimensional carbon nanotube conductive agents, and two-dimensional graphene conductive agents; in the composite conductive agent, the mass percentage of the zero-dimensional carbon black conductive agent is 5%~20%, the mass percentage of the one-dimensional carbon nanotube conductive agent is 10%~30%, and the mass percentage of the two-dimensional graphene conductive agent is 50%~80%. Zero-dimensional carbon black conductive agents, as point structural units in the conductive network, can fill the gaps between conductive components and active material particles, increasing the number of conductive contact sites. One-dimensional carbon nanotube conductive agents, as line structural units, can cross particle gaps to form long-range conductive paths, connecting discrete conductive points. Two-dimensional graphene conductive agents, as surface structural units, can form large-area contacts with active materials, constructing the main framework of the conductive network. When the three are compounded in the above proportions, a three-dimensional synergistic conductive mechanism can be formed through geometric complementarity, effectively solving the problems of high contact resistance, easy breakage of conductive networks, and high addition amount of single-dimensional conductive agents. A complete through-type conductive network can be constructed with a lower total addition amount, reducing the crowding out of the active material by the conductive agent and improving the electrode energy density.

[0030] Specifically, the zero-dimensional carbon black conductive agents include super P conductive carbon black, super C65 conductive carbon black, and acetylene black; the one-dimensional carbon nanotube conductive agents include single-arm carbon nanotubes and multi-arm carbon nanotubes; and the two-dimensional graphene conductive agents include rotary-cut graphene, flash-electrode Joule-processed graphene, and molecular template-processed graphene. Super P conductive carbon black boasts excellent conductivity and moderate cost, while Super C65 conductive carbon black exhibits extremely low impurity content and higher purity. Acetylene black features mature technology and good economic efficiency, allowing for flexible selection and combination based on battery performance and cost requirements. Single-arm carbon nanotubes offer higher intrinsic conductivity and superior electrical performance, while multi-arm carbon nanotubes offer better mechanical properties and lower production costs, making them suitable for electrode systems with varying rate and cycle performance requirements. Rotary-cut graphene has a complete structure and fewer defects, while flash-electrode Joule graphene has a large specific surface area and abundant edge active sites. Molecular template-based graphene has controllable layer count and uniform sheet size distribution. The dispersing agents described above exhibit good dispersibility for graphene produced by the three different processes, ensuring the dispersion stability and conductivity of the slurry under different raw material systems and significantly expanding the flexibility of raw material sources.

[0031] Specifically, the carbon black in the zero-dimensional carbon black conductive agent has a particle size of 30nm~50nm; the carbon nanotubes in the one-dimensional carbon nanotube conductive agent have a diameter of 5nm~20nm and an aspect ratio >1000; and the graphene in the two-dimensional graphene conductive agent has a sheet diameter of 500nm~5µm. The aforementioned size parameters enable scale matching of the three types of conductive components. Carbon black particles of 30nm to 50nm can be embedded in the tiny gaps formed by the overlap of carbon nanotubes and graphene sheets, eliminating conductive islands and supplementing conductive contact points. Carbon nanotubes with a diameter of 5nm to 20nm and an aspect ratio greater than 1000 can form bridging conductive paths between active particles, reducing resistance loss caused by point-to-point contact and constructing long-range conductive pathways. Graphene sheets with a diameter of 500nm to 5µm can form large-area surface contact with active material particles, effectively reducing interfacial contact resistance. The sizes of the three components are mutually compatible, and they can spontaneously form an ordered hierarchical overlap structure during the dispersion process, ensuring the continuity and integrity of the "point-line-surface" conductive network.

[0032] Specifically, the composite conductive agent has a specific surface area of ​​15 m² / g to 300 m² / g, a compaction density of 1.5 g / cm³ to 2.2 g / cm³, and a conductivity of 100 S / cm to 150 S / cm. This moderate specific surface area range avoids a significant increase in binder adsorption due to excessively high surface areas, ensuring electrode bonding strength while reducing binder usage and preventing binder from crowding out the active material. The compaction density of 1.5 g / cm³ to 2.2 g / cm³ is suitable for electrode rolling processes, improving the volumetric energy density of the electrode and meeting the design requirements of high-energy-density batteries. The conductivity of 100 S / cm to 150 S / cm ensures rapid electron transport within the electrode, effectively reducing the ohmic internal resistance of the electrode, improving the battery's rate charge / discharge performance and structural stability during cycling, ultimately achieving synergistic optimization of conductivity, processing performance, and energy density.

[0033] Specifically, the dispersing agents include polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, decaamine, cyclohexanediamine, sodium dodecyl sulfate, and dopamine hydrochloride. Polyvinylpyrrolidone, as a nonionic polymeric dispersant, has its pyrrolidone ring adsorbed onto the surface of carbon nanotubes, effectively inhibiting entanglement and aggregation between carbon nanotubes due to the steric hindrance effect generated by its long molecular chain. Hexadecyltrimethylammonium bromide, as a cationic surfactant, has its long-chain alkyl hydrophobic ends adsorbed onto the carbon black surface through hydrophobic interactions, while its hydrophilic quaternary ammonium salt head groups face the solvent, preventing secondary aggregation of carbon black particles through electrostatic repulsion. Decaamine and cyclohexanediamine are amino-containing small molecule compounds; their amino groups can form hydrogen bonds or electrostatic interactions with oxygen-containing functional groups such as carboxyl and hydroxyl groups at the edge of graphene. To achieve anchoring and bonding with graphene sheets, stabilizing the graphene sheet structure; sodium dodecyl sulfate, as an anionic surfactant, can adsorb onto the surface of various carbon materials to provide electrostatic repulsion stabilization, while forming a complex system with hexadecyltrimethylammonium bromide to regulate the system's charge state and promote orderly contact between materials of different dimensions; the catechol groups of dopamine hydrochloride can undergo a weak oxidative self-polymerization reaction on the surface of carbon materials to form a polydopamine thin layer, which produces a universal adhesion and anchoring effect on the surface of various carbon materials, acting as a molecular bridge to connect carbon materials of different dimensions and strengthening the interfacial bonding between carbon black, carbon nanotubes, and graphene.

[0034] Specifically, the mass ratio of polyvinylpyrrolidone: hexadecyltrimethylammonium bromide: decaamine: cyclohexanediamine: sodium dodecyl sulfate: dopamine hydrochloride is (2-5): (1-3): (0.5-2): (0.5-2): (1-3): (0.5-1.5). Within this mass ratio range, the six functional components can maximize synergistic effects, precisely matching the differences in surface properties of three different types of carbon materials, achieving differentiated surface modification and adsorption stabilization of zero-dimensional carbon black, one-dimensional carbon nanotubes, and two-dimensional graphene. This ratio can guide zero-dimensional carbon black to preferentially adsorb onto the surface of one-dimensional carbon nanotubes during the sand milling and dispersion process, forming beaded structural units, which then overlap with two-dimensional graphene sheets in a three-dimensional manner, spontaneously forming hierarchical and ordered "point-line-surface" conductive structural units. The ratio range can flexibly adapt to carbon raw materials with different specific surface areas and different defect degrees, avoiding the decline in the dispersion effect of other materials due to the excessive proportion of a single component, and ensuring stable co-dispersion and ordered structural construction under different raw material systems.

[0035] Specifically, the dispersant in the conductive slurry comprises 0.3% to 1% by mass. This addition range ensures excellent dispersion stability while avoiding the negative impact of excessive residual dispersant on the electrochemical performance of the electrode. An addition of more than 0.3% can effectively modify the surface of three types of carbon materials with vastly different surface properties, preventing the composite conductive slurry from exhibiting stratification, sedimentation, or agglomeration even after long-term storage exceeding 180 days. An addition of less than 1% will not leave excessive non-conductive components in the electrode, thus avoiding increased internal resistance or reduced cycle life. The preferred addition is 0.5%, which achieves excellent dispersion and structure induction effects, combining good economy and performance without adversely affecting the electrochemical performance of the battery.

[0036] Specifically, the solid content of the composite conductive agent is 5%. A solid content of 5% allows the slurry to maintain suitable viscosity and fluidity, making it suitable for high-speed stirring pre-dispersion and sand milling cyclic grinding processes. This ensures that shear force can be uniformly transferred to various conductive components during dispersion, achieving uniform dispersion of carbon black, full unentanglement of carbon nanotubes, and effective exfoliation of graphene sheets. It avoids shear dead zones and agglomeration residues caused by excessively high viscosity, and also avoids excessive solvent consumption and low production efficiency caused by excessively low solid content. The composite conductive slurry prepared at this solid content has good compatibility and can be directly mixed with active materials, binders, and other components to formulate electrode slurries, making it suitable for existing lithium battery electrode preparation processes.

[0037] Specifically, the polyvinylpyrrolidone in the dispersion reagent has a weight-average molecular weight of 10,000 to 60,000. The dispersion reagent is a homogeneous, transparent liquid solution.

[0038] Preferably, the mass ratio of polyvinylpyrrolidone: hexadecyltrimethylammonium bromide: decaamine: cyclohexanediamine: sodium dodecyl sulfate: dopamine hydrochloride is 3:2:1:1:2:1.

[0039] Preferably, the dispersing agent accounts for 0.5% of the mass of the conductive slurry.

[0040] Example 2 This embodiment provides a method for preparing a composite conductive paste with a point-line-surface structure, which employs mechanical exfoliation of graphene and includes the following steps: 1) Using mechanically exfoliated graphene, multi-walled carbon nanotubes, and conductive carbon black SuperC65 as conductive agents, they were dispersed in N-methylpyrrolidone at a ratio of 7:2:1 to prepare a composite conductive slurry with a solid content of 5%, and 0.5% dispersing agent was added. The morphology and structure of each conductive agent are as follows: Figure 1-3 As shown.

[0041] 2) Disperse a composite conductive agent with a solid content of 5% and a dispersing agent of 0.5% in N-methylpyrrolidone (NMP), and disperse the slurry in a high-speed mixer for 60 min at a stirring speed of 2000 rpm / min. 3) The conductive slurry prepared in step 2) is injected into a sand mill by starting a diaphragm pump to circulate and grind the slurry. The grinding pressure is less than 0.5 MPa and the pump working pressure is 0.3 MPa. After grinding for 30 minutes, a 5% solid content 0D conductive carbon black SuperC65-1D multi-walled carbon nanotube-2D mechanically exfoliated graphene “point-line-surface” structure composite conductive slurry is obtained.

[0042] The conductive paste prepared in this embodiment exhibits extremely long dispersion stability, and the paste does not show stratification even after long-term storage (180 days). Figure 6 As shown, the Raman spectrum of the carbon black SuperC65-multi-arm carbon nanotube-mechanically exfoliated graphene conductive paste with a "point-line-plane" structure is as follows: the D peak is located at 1350 cm⁻¹, representing defects and disorder in the graphene structure, while the G peak is located at 1580 cm⁻¹, representing the ordered in-plane vibrations of the sp² hybrid bonds of carbon atoms in the graphene. It can be seen that ID / IG = 0.31, which means that the graphene in this composite structure has a two-dimensional characteristic structure with a relatively small number of layers, approximately 4. Simultaneously, atomic force microscopy analysis shows that the thickness of this "point-line-plane" structure is approximately 2 nm, which basically confirms the structure of the Raman spectrum. Figure 8 As shown. Figure 7 The specific surface area analysis of the composite conductive agent with the "point-line-surface" structure shown indicates that the nanoparticles have a relatively moderate specific surface area of ​​approximately 32.6 m². 2 / g, which is beneficial for constructing a conductive transport network and reducing the amount of binder. SEM and TEM images clearly show that the nanoparticles in the composite conductive slurry prepared by dispersion and sand milling exhibit obvious "point-line-surface" structural characteristics, which is conducive to the construction of a three-dimensional conductive network. Figure 9 Through compaction resistance analysis () Figure 10 This composite conductive agent with a "point-line-surface" structure exhibits excellent conductivity; under a pressure of 20 MPa, its compaction resistance is only 35 mΩ. ·cm.

[0043] In summary, this "point-line-surface" composite conductive paste achieves an excellent balance among structural stability, electronic conductivity, processing adaptability, and long-term storage performance through the geometric complementarity of multidimensional carbon materials and a suitable specific surface area design. This strategy provides a conductive network solution with great engineering potential for improving the rate performance and optimizing the energy density of high-performance lithium iron phosphate (LFP) and high-nickel ternary (NCM) systems.

[0044] Example 3 This embodiment provides a method for preparing a composite conductive paste with a point-line-surface structure, using flash-electrode Joule-thermal graphene instead of mechanically exfoliated graphene as the "surface" structural unit of the two-dimensional (2D) conductive component. Flash-electrode Joule-thermal graphene possesses a small nanosheet structure and a grape-bundle aggregate structure, such as... Figure 5 As shown, its abundant edge active sites facilitate anchoring with the composite dispersing agent, but also place higher demands on the dispersion process. The process includes the following steps: (1) Flash-evaporized Joule-thermal graphene, multi-walled carbon nanotubes (and conductive carbon black SuperC65 as conductive agents) were dispersed in NMP at a mass ratio of graphene:carbon nanotubes:carbon black = 6:3:1 to prepare a composite conductive slurry with a solid content of 5%. 0.6% of the total mass of the slurry was added to the composite dispersant FS530 (slightly increased from 0.5% in Example 1 to meet the dispersion challenge brought by the higher specific surface area of ​​flash-evaporized Joule-thermal graphene).

[0045] (2) Disperse the composite conductive agent with a solid content of 5% and the composite dispersant FS530 with 0.6% in NMP. Use a high-speed mixer to pre-disperse the slurry for 90 min (extending the pre-dispersion time helps the initial wetting of high specific surface area graphene) and 2000 rpm.

[0046] (3) The conductive slurry prepared in step (2) was injected into a sand mill using a pneumatic diaphragm pump, and the slurry was circulated and ground repeatedly. The grinding pressure was less than 0.5 MPa, and the pump working pressure was 0.3 MPa. Considering that flash Joule-thermal graphene has many defects and relatively low structural stability, in order to prevent excessive grinding from causing further breakage or disorder of the graphene sheets, the grinding time was adjusted to 360 min (a significant improvement compared to Example 1). After grinding, a "point-line-surface" structure composite conductive slurry of 0D conductive carbon black Super C65-1D multi-walled carbon nanotube-2D flash Joule-thermal graphene with a solid content of 5% was obtained.

[0047] Example 4 This embodiment provides a method for preparing a composite conductive paste with a point-line-surface structure, using molecular template-based graphene instead of mechanically exfoliated graphene as the "surface" structural unit of the two-dimensional (2D) conductive component. This type of graphene is prepared by controlling the rearrangement and crystallization of carbon atoms under template induction in a high-temperature pyrolysis furnace. It features controllable layer number (typically 3-10 layers), uniform sheet size distribution, and moderate surface chemical activity, combining good conductivity with relatively economical production costs, making it a graphene material with great industrial application potential. The method includes the following steps: (1) Using molecular template method graphene (specific surface area >300 m² / g, number of layers about 5~8), multi-walled carbon nanotubes and conductive carbon black SuperC65 as conductive agents, the graphene: carbon nanotubes: carbon black = 5:3:2 were dispersed in NMP to prepare a composite conductive slurry with a solid content of 5%. At the same time, 0.5% of the total mass of the slurry was added to the composite dispersant FS530 (consistent with Example 1, this amount is sufficient for pyrolysis furnace graphene with medium specific surface area).

[0048] (2) Disperse the above-mentioned composite conductive agent with a solid content of 5% and FS530 dispersant in NMP, and pre-disperse the slurry using a high-speed mixer for 60 min and 2000 rpm.

[0049] (3) The conductive slurry prepared in step 2) is injected into a sand mill using a pneumatic diaphragm pump for cyclic grinding. The grinding pressure is less than 0.5 MPa, and the pump working pressure is 0.3 MPa. The molecular template method for graphene has mechanical strength between that of mechanical exfoliation and flash Joule heating, and a grinding time of 60 min can be used to balance good dispersion and structural protection.

[0050] Example 5 This embodiment provides a method for preparing a composite conductive paste with a point-line-surface structure, used to prepare the composite conductive paste with a point-line-surface structure as described in any one of claims 1-9, characterized by comprising the following steps: Step S1: Disperse the composite conductive agent in N-methylpyrrolidone, and add a dispersing agent to mix and form a preliminary slurry.

[0051] Step S2: The initial mixed slurry is dispersed using a high-speed mixer to obtain a pre-dispersed slurry; Step S3: Inject the pre-dispersed slurry into a sand mill and grind the pre-dispersed slurry to obtain the target slurry; Specifically, in step S2, the mixing speed of the high-speed mixer is 1000 rpm / min to 3000 rpm / min, and the mixing time is 30 min to 120 min; In step S3, the grinding pressure of the grinding machine is 0.4MPa~0.6MPa, and the grinding time is 60min~120min.

[0052] Example 6 This embodiment provides a method for preparing the dispersant reagent in Example 1, which is formulated from the following components in the following mass ratio: Polyvinylpyrrolidone (PVP, Mw=30000): cetyltrimethylammonium bromide (CTAB): decaamine: cyclohexanediamine: sodium dodecyl sulfate (SDS): dopamine hydrochloride = 3:2:1:1:2:1.

[0053] Preparation method: Weigh each component according to the above mass ratio, add them sequentially to deionized water at room temperature, stir at 300-500 rpm for 30-60 minutes until completely dissolved to form a homogeneous and transparent solution, thus obtaining the composite dispersion reagent FS530.

[0054] Example 7 This embodiment provides a method for preparing the dispersant reagent in Example 1, which is formulated from the following components in the following mass ratio: Polyvinylpyrrolidone (PVP, Mw=10000): cetyltrimethylammonium bromide (CTAB): decaamine: cyclohexanediamine: sodium dodecyl sulfate (SDS): dopamine hydrochloride = 2:1:0.5:0.5:1:0.5.

[0055] The preparation method is the same as in Example 1.

[0056] Example 8 This embodiment provides a method for preparing the dispersant reagent in Example 1, which is formulated from the following components in the following mass ratio: Polyvinylpyrrolidone (PVP, Mw=60000): cetyltrimethylammonium bromide (CTAB): decaamine: cyclohexanediamine: sodium dodecyl sulfate (SDS): dopamine hydrochloride = 5:3:2:2:3:1.5.

[0057] The preparation method is the same as in Example 1.

[0058] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0059] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A composite conductive paste having a point-line-surface structure, characterized in that, It contains a composite conductive agent, a dispersing agent, and N-methylpyrrolidone; The composite conductive agent includes zero-dimensional carbon black conductive agents, one-dimensional carbon nanotube conductive agents, and two-dimensional graphene conductive agents. In the composite conductive agent, the mass percentage of the zero-dimensional carbon black conductive agent is 5% to 20%, the mass percentage of the one-dimensional carbon nanotube conductive agent is 10% to 30%, and the mass percentage of the two-dimensional graphene conductive agent is 50% to 80%.

2. The composite conductive paste with a point-line-surface structure according to claim 1, characterized in that, The zero-dimensional carbon black conductive agents include super P conductive carbon black, super C65 conductive carbon black and acetylene black. The one-dimensional carbon nanotube conductive agent includes single-arm carbon nanotubes and multi-arm carbon nanotubes. The two-dimensional graphene conductive agent includes rotary-cut graphene, flash-electrode Joule-processed graphene, and molecular template-processed graphene.

3. The composite conductive paste with a point-line-surface structure according to claim 1, characterized in that, The carbon black in the zero-dimensional carbon black conductive agent has a particle size of 30nm~50nm. The diameter of the carbon nanotubes in the one-dimensional carbon nanotube conductive agent is 5nm~20nm, and the aspect ratio is >1000. The graphene sheet diameter in the two-dimensional graphene conductive agent is 500 nm to 5 µm.

4. The composite conductive paste with a point-line-surface structure according to claim 1, characterized in that, The specific surface area of ​​the composite conductive agent is 15m². 2 / g, the compacted density of the composite conductive agent is 1.5 g / cm³. 3 ~2.2g / cm 3 The conductivity of the composite conductive agent is 100S / cm~150S / cm.

5. A composite conductive paste with a point-line-surface structure according to claim 1, characterized in that, The dispersing agents include polyvinylpyrrolidone, hexadecyltrimethylammonium bromide, decaamine, cyclohexanediamine, sodium dodecyl sulfate, and dopamine hydrochloride.

6. A composite conductive paste with a point-line-surface structure according to claim 5, characterized in that, The mass ratio of the following components is (2-5): (1-3): (0.5-2): (0.5-2): (1-3): (0.5-1.5).

7. A composite conductive paste with a point-line-surface structure according to claim 1, characterized in that, The dispersing agent accounts for 0.3% to 1% of the mass of the conductive slurry.

8. A composite conductive paste with a point-line-surface structure according to claim 1, characterized in that, The solid content of the composite conductive agent is 5%.

9. A method for preparing a composite conductive paste with a point-line-surface structure, used to prepare the composite conductive paste with a point-line-surface structure according to any one of claims 1-9, characterized in that, Includes the following steps: Step S1: Disperse the composite conductive agent in N-methylpyrrolidone, and simultaneously add a dispersing agent to mix and form a preliminary slurry; Step S2: The initial mixed slurry is dispersed using a high-speed mixer to obtain a pre-dispersed slurry; Step S3: Inject the pre-dispersed slurry into a sand mill and grind the pre-dispersed slurry to obtain the target slurry.

10. The method for preparing a composite conductive paste with a point-line-surface structure according to claim 9, characterized in that, In step S2, the mixing speed of the high-speed mixer is 1000 rpm / min to 3000 rpm / min, and the mixing time is 30 min to 120 min. In step S3, the grinding pressure of the grinding machine is 0.4MPa~0.6MPa, and the grinding time is 60min~120min.

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