Organic system carbon nanotube conductive paste and preparation method thereof

Abstract

The invention relates to the technical field of conductive paste preparation, and provides an organic system carbon nanotube conductive paste and a preparation method thereof, the paste adopts a binary organic solvent system and is composed of butyl carbitol and DMF, and efficient deagglomeration and uniform dispersion of carbon nanotubes can be realized without adding a dispersant. The preparation method comprises the steps that DMF and butyl carbitol are premixed, carbon nanotube powder is added for premixing, and finally the conductive paste is obtained through sanding. According to the method, the uniform dispersion and high stability of the slurry are ensured by accurately controlling the solvent proportion, premixing parameters and sanding conditions. The invention breaks through the technical bottleneck that the conductivity is restricted by the traditional dispersant, simplifies the process flow, reduces the production cost, and improves the energy density and fast charge efficiency of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of carbon nanotube conductive pastes, and specifically relates to an organic system carbon nanotube conductive paste and a preparation method thereof. Background Art

[0002] As one of the most core components of power batteries and electrochemical energy storage, lithium batteries have entered a golden development period. Conductive agents have a great impact on the safety, cycle performance and fast charging performance of lithium batteries, and are key materials in the lithium battery industry chain. Carbon nanotubes are new carbon materials with excellent performance. Carbon nanotube conductive paste is an important component of the conductive agent for the positive or negative electrode of lithium batteries, and has an important impact on the performance of lithium batteries.

[0003] For carbon nanotube conductive paste, dispersibility, stability and conductivity are three important performance indicators. Dispersibility refers to the degree of uniform distribution of carbon nanotubes in a solvent without agglomeration. When carbon nanotubes are uniformly dispersed, a continuous conductive network can be formed to ensure efficient electron transmission. If the dispersibility of the carbon nanotube conductive paste is poor, on the one hand, the agglomerated particles will increase the viscosity of the paste, affecting the coating uniformity and resulting in uneven thickness of the electrode sheet, which will in turn affect the battery capacity and cycle life. On the other hand, the paste with insufficient dispersibility is prone to form "dead zones" in the positive electrode of the battery, reducing the utilization rate of active materials and affecting the rate performance and energy density.

[0004] Stability refers to the ability of the paste to maintain a uniformly dispersed state during storage or use, which is manifested as viscosity change and sedimentation degree. The paste with poor stability will sediment after standing and needs to be stirred again, increasing the production complexity; due to the instability of the paste, the viscosity fluctuates greatly, resulting in the layering of the paste, causing differences in the local composition of the electrode sheet, leading to uneven current distribution in the battery and accelerating capacity decay. In addition, the unstable paste needs to be frequently detected and adjusted, increasing the time and material costs.

[0005] Conductivity refers to the ability of the paste to form a low-resistance conductive network in the battery, which directly affects the internal resistance and efficiency of the battery. The paste with poor conductivity will increase the internal resistance of the battery, resulting in heat energy loss, reduced charging speed and shortened cycle life. High conductivity supports large current charge and discharge, improving the fast charging ability. Low resistivity reduces ohmic polarization, improves the energy conversion efficiency of the battery, and increases the capacity retention rate.

[0006] In the prior art, most carbon nanotube conductive pastes use dispersants during the preparation process to improve dispersibility and stability. For example, the method for preparing a carbon nanotube dispersion in Chinese Patent No. CN111094180B discloses that the dispersant is one or more selected from styrene butene rubber (SBR), carboxymethyl cellulose (CMC), hydrogenated acrylonitrile butadiene rubber (H-NBR), polyvinylpyrrolidone (PVP) and polyvinyl butyral (PVB).

[0007] Multiple studies have found that dispersants (such as PVP, PVB) form physical adsorption or hydrogen bonding with the surface of carbon nanotubes through polar groups (such as amide groups, hydroxyl groups), weakening the van der Waals forces between tubes and promoting dispersion. However, after non-conductive polymers of this kind coat carbon nanotubes, they will hinder the direct transfer of electrons between tubes. For example, the pyrrolidone ring of PVP is adsorbed on the surface of carbon tubes through π-π stacking, but its insulating main chain covers the conductive channels, resulting in an increase in the interfacial contact resistance and a decrease in the overall conductivity.

[0008] Some studies have found that dispersants are likely to remain in the carbon tube network after the slurry dries, forming an insulating barrier. Taking SBR as an example, its rubber elastomer forms a continuous phase in the electrode, blocking the conductive path between carbon tubes and active materials, resulting in an increase in the resistivity of the electrode sheet. Some studies have shown that the resistivity of the electrode with 5% SBR added is more than twice that of the system without dispersant. In addition, the residual sodium ions of CMC may trigger side reactions in the electrolyte, further deteriorating the conductive stability of the electrochemical interface. There are also studies that have found that dispersants such as H-NBR rely on highly polar solvents (such as NMP) to achieve dispersion, but such solvents are difficult to completely volatilize during battery cycling, and the residues increase the ionic migration impedance in the pores of the electrode. By comparison, it is found that the carbon tube slurry dispersed with PVB is uniformly dispersed in the NMP system, but the solvent residue after the electrode sheet dries causes a 15% increase in the lithium ion diffusion impedance.

[0009] Based on the above background, a binary co-solvent system of DMF + butyl carbitol is designed. By utilizing the polarity and structural characteristics of the solvent molecules themselves, the planar amide group of DMF is oriented to adsorb carbon tubes, and the high polarity of butyl carbitol inhibits re-aggregation, achieving the deagglomeration of carbon tubes without dispersants, eliminating the interference of the insulating layer on the conductive path, solving the industry pain point of being difficult to balance conductivity and dispersibility, and forming multiple gains in process simplification, cost control, and battery performance breakthrough, which is of great significance. Summary of the Invention

[0010] To solve the problems existing in the background technology, the present invention provides a binary organic solvent, which is composed of a main solvent and a co-solvent, wherein:

[0011] The main solvent is: butyl carbitol solvent;

[0012] The co-solvent is: DMF solvent, that is, N,N-dimethylformamide solvent.

[0013] The present invention also provides the application of the binary organic solvent in the preparation of carbon nanotube conductive slurry.

[0014] A preparation method of an organic system carbon nanotube conductive slurry is carried out according to the following steps:

[0015] S1. Binary solvent premixing: Accurately weigh 100 - 200 parts by weight of DMF solvent and 150 - 400 parts by weight of butyl carbitol solvent and put them into a premixer for premixing to obtain a premixed solution;

[0016] S2. Carbon nanotube premixing: Put 10 - 30 parts of carbon nanotube powder into the above-mentioned premixed solution to obtain a premixed material;

[0017] S3. Fine grinding: Grind the premixed material obtained in step S2 to obtain the carbon nanotube conductive paste.

[0018] In a preferred embodiment, in step S1, the rotation speed of the premixer is 1000 rmp, the flow rate is 500 L / min, and the premixing time is 10 - 30 min;

[0019] In a preferred embodiment, in step S2, the rotation speed of the premixer is 1000 rmp, the flow rate is 300 L / min, and the premixing time is 20 - 60 min.

[0020] In a preferred embodiment, in step S3, the grinding process is carried out using a sand mill at a rotation speed of 700 rpm for 1 - 3 h.

[0021] The beneficial effects achieved by the present invention are as follows:

[0022] In the preparation of traditional carbon nanotube conductive paste, although the introduction of a dispersant can improve the dispersibility, its insulating properties will significantly hinder the electron transport of the conductive network, resulting in an increase in the resistivity of the battery system. The present invention innovatively designs a binary organic solvent synergistic system, including a composite solvent of DMF and butyl carbitol, which can achieve efficient deagglomeration and uniform dispersion of carbon nanotubes without introducing any dispersant. In this solvent combination, the planar amide group of DMF is adsorbed on the surface of the carbon nanotubes by π-π interaction to weaken the van der Waals force, while the high-polarity solvent environment of butyl carbitol inhibits the secondary aggregation of particles. The synergistic effect of the two improves the dispersibility (no visible aggregates under the microscope) and stability (viscosity change rate < 25% in 15 days) of the paste, while avoiding the shielding effect of insulating molecules on the conductive path, reducing the resistivity of the electrode sheet to 32.4 Ω·cm (a 44.6% decrease compared to the PVP-containing system). The present invention not only simplifies the process flow, but also breaks through the technical bottleneck of the dispersant restricting the conductive performance, which has important value for the development of lithium battery electrode materials with high energy density and long cycle life. Experiments show that the resistivity of the paste is as low as 32.4 Ω·cm, a 43.5% decrease compared to the dispersant-containing system, and the viscosity change rate after standing for 15 days is only 24.1%, with better stability than the traditional scheme. The preparation process accurately controls the solvent ratio (DMF ≥ 25%, butyl carbitol ≥ 50%), premixing parameters (rotation speed of 1000 rpm, gradient flow rate) and sanding conditions (grinding at 700 rpm for 1 - 3 hours), which not only ensures the dispersion uniformity, but also simplifies the production process and shortens the production cycle.

[0023] The DMF and butyl carbitol composite solvent system designed in the present invention avoids the use of dispersants such as PVP, eliminates the interference of the insulating coating layer on the electrode conductive network, and at the same time reduces the emission of pyrolysis waste gas, meeting the requirements of green manufacturing. The slurry solvent is easy to volatilize and has less residue, reducing the ionic migration impedance. This characteristic makes it more suitable for the requirements of high-energy density batteries. Especially in the fast charging scenario, it can reduce ohmic polarization and extend the cycle life. The present invention breaks through the restriction of dispersants on the conductivity performance and provides a new path for the upgrade of lithium battery conductive agents. Its characteristics of low resistance and high stability can significantly improve the battery energy density and fast charging efficiency, and are applicable to fields such as power batteries and energy storage systems. Description of the Drawings

[0024] Figure 1 It is a flow chart of the preparation method of the organic system carbon nanotube conductive slurry.

[0025] Figure 2 Showing the physical state of the slurry (DMF + butyl carbitol) in Example 1 after standing for 15 days.

[0026] Figure 3 Showing the layering phenomenon of the slurry (single DMF solvent) in Comparative Example 1 after standing for 15 days.

[0027] Figure 4 Showing the physical state of the slurry (single butyl carbitol) in Comparative Example 2 after standing for 15 days.

[0028] Figure 5 Showing the physical state of the slurry (DMF + butanol + PVP) in Comparative Example 3 after standing for 15 days.

[0029] Figure 6 Showing the optical microscope image of the slurry in Example 1, presenting the uniform dispersion state of carbon nanotubes.

[0030] Figure 7 Showing the optical microscope image of the slurry in Comparative Example 1, presenting the dispersion state of carbon nanotubes.

[0031] Figure 8 Showing the optical microscope image of the slurry in Comparative Example 2, presenting the aggregation phenomenon of carbon nanotubes.

[0032] Figure 9 Showing the optical microscope image of the slurry in Comparative Example 3, presenting the uniform dispersion state of carbon nanotubes. Detailed Embodiments

[0033] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the accompanying drawings of the present invention. In addition, the forms of each structure described in the following embodiments are merely examples, and the present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0034] The present invention provides a binary organic solvent, which is composed of a main solvent and a co-solvent. Among them, the main solvent is: butyl carbitol solvent; the co-solvent is: DMF solvent, that is, N,N-dimethylformamide solvent.

[0035] Butyl carbitol (chemical name: diethylene glycol monobutyl ether, English name: Diethylene glycol monobutylether) is a bifunctional organic compound containing an ether bond and a hydroxyl group, chemical formula: C8H 18 O3, molecular weight: 162.23 g / mol, structural formula: C4H9-O-CH2-CH2-O-CH2-CH2-OH or abbreviated as HO(CH2)2O(CH2)2OC4H9.

[0036] The molecular structure of butyl carbitol contains three key parts:

[0037] Butyl group (C4H9-), located at one end of the molecule, is a hydrophobic alkyl chain, usually a straight-chain structure (n-butyl), providing compatibility with non-polar substances (such as oils, resins), and enhancing the dissolution ability of the solvent for organic substances.

[0038] Ethoxy chain (-O-CH2-CH2-O-CH2-CH2-), containing two ethoxy units (-O-CH2-CH2-), connected by an ether bond (-O-), forming a flexible chain segment. The polarity of the ether bond enables it to be miscible with polar solvents such as water and alcohols, and at the same time provides a steric hindrance effect between molecules.

[0039] Hydroxyl group (-OH), located at the other end of the molecule, is a hydrophilic group, endowing the compound with partial water solubility.

[0040] The planar amide group (-N(C=O)-) in the DMF molecule has a conjugated electron structure and can be adsorbed on the surface of carbon nanotubes (CNT) by π-π stacking. This force (about 0.5 - 1.5 kJ / mol) effectively weakens the van der Waals force between carbon tubes (about 0.3 - 0.5 nN / tube), prompting the carbon nanotube bundles to dissociate into single or small bundle structures.

[0041] Polar solvation effect: The high polarity of DMF (dielectric constant ε≈37) forms a strong solvation layer, enhancing the affinity between carbon nanotubes and the solvent through dipole-dipole interactions (electrostatic attraction between polar molecules and the charged defects on the surface of carbon nanotubes), and reducing the tendency of aggregation.

[0042] The molecular structure of butyl carbitol contains a flexible ethoxy chain (-O-CH2-CH2-O-), and its chain length (about 0.8 nm) can form a physical barrier to prevent the carbon nanotubes after dissociation from approaching and aggregating again due to Brownian motion.

[0043] The butyl end (hydrophobic) and the ethoxy / hydroxy end (hydrophilic) of butyl carbitol form an amphiphilic structure. The hydrophobic part adsorbs on the non-polar region of the carbon nanotube surface, and the hydrophilic part extends outward to form a stable solvation layer (thickness about 1 - 2 nm), dynamically inhibiting the re-aggregation of carbon nanotubes. Although the dielectric constant of butyl carbitol (ε≈12) is lower than that of DMF, its polarity can still maintain the polarity gradient of the solvent system, synergistically with DMF to enhance the solvation shielding effect of the charges on the carbon nanotube surface.

[0044] In the dispersion stage, DMF is rapidly adsorbed on the surface of carbon nanotubes, breaking the van der Waals forces between tubes through π-π interactions to achieve primary dispersion; in the stabilization stage, the long-chain structure of butyl carbitol fills the gaps between carbon nanotubes, locking the dispersed state through steric hindrance and the solvation layer. The high polarity of DMF and the medium polarity of butyl carbitol form a gradient polarity field, optimizing the wettability of the carbon nanotube surface and reducing the interfacial energy (from about 50 mN / m in pure DMF to 35 mN / m in the mixed system), promoting the uniform dispersion of carbon nanotubes. The hydroxyl group (-OH) of butyl carbitol forms an intermolecular hydrogen bond with the amide group of DMF (bond energy about 5 - 25 kJ / mol), enhancing the interaction between solvent molecules, constructing a stable solvent network, and further inhibiting the sedimentation of carbon nanotubes.

[0045] The preparation method of the carbon nanotube conductive agent of the present invention includes the following steps:

[0046] Binary solvent premixing (S1): Put 100 - 200 parts of DMF and 150 - 400 parts of butyl carbitol into a premixer in proportion, and premix for 10 - 30 minutes under the conditions of a rotation speed of 1000 rpm and a flow rate of 500 L / min to ensure that the two solvent molecules are fully miscible and form a homogeneous phase. The solvent ratio at this stage directly affects the subsequent dispersion effect, and the proportion of DMF needs to be ≥25% to activate the π-π adsorption effect.

[0047] Carbon nanotube premixing (S2): Add 10 - 30 parts of carbon nanotube powder to the premixed solution, and premix for 20 - 60 minutes at a rotation speed of 1000 rpm and a flow rate of 300 L / min to preliminarily wet and disperse the carbon nanotubes. The flow rate is reduced to 300 L / min at this stage to enhance the shear force and avoid local accumulation of carbon nanotubes due to turbulence.

[0048] Fine grinding (S3): Grind for 1 - 3 hours at a speed of 700 rpm using a sand mill. Further dissociate the carbon nanotube bundles through the mechanical collision of zirconium beads (particle size 0.3 mm) to finally obtain a slurry with a particle size D50 ≤ 200 nm. A grinding time > 1 h can ensure uniform dispersion, while a speed > 600 rpm can break through the van der Waals binding energy of about 0.3 nN between carbon nanotubes.

[0049] Example 1: Binary solvent (DMF + butyl carbitol) synergistic dispersion, specific scheme is as follows: Solvent premixing; Solvent composition: 100 parts of DMF + 200 parts of butyl carbitol; Premixing parameters: speed 1000 rpm, flow rate 500 L / min, premixing time 30 min;

[0050] Carbon nanotube premixing; Carbon nanotube addition amount: 10 parts; Premixing parameters: speed 1000 rpm, flow rate 300 L / min, premixing time 60 min;

[0051] Fine grinding process; Sand grinding time: 2 hours; Sand grinding speed: 700 rpm.

[0052] Experimental detection method:

[0053] I. Viscosity detection method

[0054] Testing equipment:

[0055] Viscosity meter model: NDJ - 1B rotational viscometer.

[0056] Testing principle: Calculate the viscosity value by measuring the resistance (torque) of the slurry under the action of a rotating rotor.

[0057] Testing steps are as follows:

[0058] Initial viscosity test: Directly sample the prepared carbon nanotube conductive slurry and measure its initial viscosity using an NDJ - 1B viscometer.

[0059] Viscosity test after standing: Let the slurry sample stand for 15 days, observe the sedimentation situation, and then measure the viscosity after standing again using the same viscometer.

[0060] Parameter settings: Temperature, rotor model, or speed are not clearly mentioned, but according to the normal operation of the equipment, standard test conditions (such as a constant temperature environment of 25°C and a specific rotor speed) may be adopted.

[0061] Data processing process is as follows: Record the initial viscosity and the viscosity value after standing for 15 days, and calculate the viscosity change rate (as shown in the "Viscosity change" column in the table). By comparing the viscosity changes of different examples and comparative examples, evaluate the stability of the slurry (the smaller the viscosity change, the better the stability).

[0062] II. Conductivity detection test;

[0063] Testing equipment:

[0064] Model of resistivity tester: RTS-8 four-probe resistivity tester.

[0065] Testing principle: The four-probe method measures the surface resistance of the electrode sheet and calculates the resistivity by combining geometric parameters, reducing the influence of contact resistance on the results.

[0066] Electrode sheet preparation process: Slurry mixing formula: Nickel cobalt manganese ternary cathode material: SP: Conductive slurry: PVDF = 95:1:1.5:2.5, solid content is 65%. Stirring conditions: Stir at 2000 rpm for 10 minutes to ensure uniform mixing of the slurry.

[0067] Coating process: Coat the slurry on the PI film, coating thickness is 200 μm. Drying treatment: Dry in an oven at 130 °C for 1 hour to remove the solvent and form the electrode sheet.

[0068] Resistivity testing steps:

[0069] Place the dried electrode sheet in the RTS-8 tester and directly measure the resistivity of the electrode sheet by the four-probe method. Record the resistivity data of different examples and comparative examples (as shown in the "Resistivity (Ω·cm)" column in the table).

[0070] Experimental results:

[0071] Table 1, Detection data of viscosity and electrode sheet resistivity in Example 1

[0072] Test Index Initial Value After Standing for 15 Days Change Rate Viscosity (cp) 3320 4120 24.10％ Polar Plate Resistivity (Ω·cm) 32.4 - -

[0073] III. Detection of dispersibility and stability;

[0074] Observation method 1: Observe the sedimentation and stratification phenomenon of the slurry after standing for 15 days (as shown in the attachment Figure 2 - Figure 5 ).

[0075] Observation method 2: Observation with an optical microscope; Equipment model: ZEISS Smartzoom5 optical microscope.

[0076] Steps: Dilute the slurry 10 times and drop it on a glass slide to observe the dispersion state (aggregation degree) of carbon nanotubes.

[0077] Experimental results:

[0078] Sedimentation observation: No sedimentation after standing for 15 days ( Figure 2 ).

[0079] Optical microscope test: Uniform dispersion, no obvious aggregation ( Figure 6 ).

[0080] Comparative Example 1: Single solvent (only DMF); Experimental conditions:

[0081] Solvent composition: 300 parts of DMF (without butyl carbitol); Other conditions are the same as in Example 1.

[0082] The experimental detection method is the same as in Example 1.

[0083] Experimental results:

[0084] Table 2, Detection data of viscosity and pole piece resistivity of Comparative Example 1

[0085] Test Index Initial Value After Standing for 15 Days Change Rate Viscosity (cp) 3520 5430 54.30％ Polar Plate Resistivity (Ω·cm) 42.9 - -

[0086] Dispersibility and stability results: Sedimentation observation: The slurry has poor stability and obvious stratification after standing ( Figure 3 ). Optical microscope test: Good dispersibility, but insufficient stability ( Figure 7 ).

[0087] Comparative Example 2: Single solvent (only butyl carbitol); Experimental conditions: Solvent composition: 300 parts of butyl carbitol (without DMF), and other conditions are the same as in Example 1.

[0088] Experimental results:

[0089] Table 3, Detection data of viscosity and pole piece resistivity of Comparative Example 2

[0090] Test Index Initial Value After Standing for 15 Days Change Rate Viscosity (cp) 3250 4220 29.80％ Polar Plate Resistivity (Ω·cm) 44.6 - -

[0091] Dispersibility and stability test results: Sedimentation observation: Good stability, but poor dispersibility ( Figure 4 ). Optical microscope test: Obvious aggregation of carbon nanotubes ( Figure 8 ).

[0092] Comparative Example 3: Binary solvent + dispersant (DMF + butanol + PVP); Experimental conditions:

[0093] This comparative example refers to the components used in the method for preparing a carbon nanotube dispersion in the Chinese patent with the publication number CN111094180B. 150 parts of butanol + 150 parts of DMF (total solvent 300 parts, the same as the total amount in Example 1) are added in the preparation step S1, and 10 parts of carbon nanotubes + 3 parts of PVP (PVP is 30% of the weight of the carbon tubes) are added in the step S2. Other steps are the same as in Example 1.

[0094] Experimental results:

[0095] Table 4, Detection data of viscosity and pole piece resistivity of Comparative Example 3

[0096] Test Index Initial Value After Standing for 15 Days Change Rate Viscosity (cp) 2950 3860 30.80％ Polar Plate Resistivity (Ω·cm) 57.3 - -

[0097] Dispersion and stability test results: Sedimentation observation: The stability is similar to that of Example 1 ( Figure 5 ). Optical microscope test: The dispersion is comparable to that of Example 1 ( Figure 9 ).

[0098] Table 5. Summary of experimental results

[0099]

[0100]

[0101] DMF and butyl carbitol work synergistically. The planar amide group in the DMF molecule binds to the surface of carbon nanotubes through π-π interaction, effectively weakening the van der Waals force between carbon tubes and achieving primary dispersion. The ethoxy chain segment (-CH2CH2O-) of butyl carbitol forms a highly polar solvent environment (dielectric constant ε≈12), and inhibits the secondary aggregation of carbon tubes through steric hindrance effect, compensating for the stability defect when DMF is used alone.

[0102] Table 6. Analysis data of the synergistic effect of DMF and butyl carbitol

[0103] Group Dispersion (Microscope) Viscosity Change Rate (15 Days) Resistivity (Ω·cm) Example 1 Uniform and No Aggregation 24.1％ 32.4 Comparative Example 1 (DMF) Good Dispersion 54.3％ 42.9 Comparative Example 2 (Butyl) Significant Aggregation 29.8％ 44.6

[0104] When DMF is used alone, the dispersion is good but the stability is poor (viscosity change rate 54.3%). When butyl carbitol is used alone, the stability is better but the dispersion fails. The binary system improves both the dispersion and viscosity stability, proving that the synergistic effect breaks through the performance bottleneck of single solvents.

[0105] The traditional PVP dispersant (Comparative Example 3) forms an insulating coating layer on the surface of carbon tubes, resulting in an increase in resistivity to 57.3 Ω·cm (76.8% higher than that of Example 1).

[0106] The dispersant-free system (Example 1) reduces the resistivity to 32.4 Ω·cm, reaching the leading level of similar technologies.

[0107] Omitting the dispersant addition step (Comparative Example 3 requires precise control of the 1:3 ratio of PVP to carbon tubes) shortens the production cycle by 20% (from 5 steps to 3 steps); the market price of PVP is about 50 / kg, and calculated according to the addition amount of Comparative Example 3, the cost per ton of slurry is saved by 1500; avoiding the generation of nitrogen-containing waste gas due to the pyrolysis of PVP (decomposition rate >80% at 300°C).

[0108] Table 7. Comparison table of key performance indicators of Example 3 and Example 1

[0109] Index Example 1 Comparative Example 3 (Containing PVP) Improvement Range Initial Viscosity (cp) 3320 2950 +12.5％ Resistivity (Ω·cm) 32.4 57.3 -43.5％ Slurry Sedimentation Time (Days) >15 >15 Equal <![CDATA[The compaction density of the electrode sheet (g / cm 3 )]]> 3.72 3.65 +1.9％

[0110] As can be seen from Table 7, compared with Example 3, Example 1 shows a significant decrease in resistivity (43.5%) and an increase in compaction density, proving that this system is more suitable for the manufacture of high energy density batteries.

[0111] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A binary organic solvent, characterized in that, It is composed of a main solvent and a co-solvent, where: The main solvent is: butyl carbitol solvent; The co-solvent is: DMF solvent, namely N,N-dimethylformamide solvent.

2. The application of the binary organic solvent according to claim 1 in the preparation of carbon nanotube conductive paste.

3. A preparation method of an organic system carbon nanotube conductive paste, characterized in that, It uses the binary organic solvent according to claim 1 and proceeds according to the following steps: S1. Premixing of binary solvents: Put 100-200 parts by weight of accurately weighed DMF solvent and 150-400 parts by weight of butyl carbitol solvent into a premixer for premixing to obtain a premixed liquid; S2. Premixing of carbon nanotubes: Put 10-30 parts of carbon nanotube powder into the above premixed liquid to obtain a premixed product; S3. Fine grinding: Grind the premixed product obtained in step S2 to obtain the carbon nanotube conductive paste.

4. The preparation method of the organic system carbon nanotube conductive paste according to claim 3, wherein, In step S1, the rotation speed of the premixer is 1000 rmp, the flow rate is 500 L / min, and the premixing time is 10-30 min.

5. The preparation method of the organic system carbon nanotube conductive paste according to claim 3, characterized in that, In step S2, the rotation speed of the premixer is 1000 rmp, the flow rate is 300 L / min, and the premixing time is 20-60 min.

6. The preparation method of the organic system carbon nanotube conductive paste according to claim 3, characterized in that, In step S3, the grinding process is carried out using a sand mill at a rotation speed of 700 rpm for 1-3 h.

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