Composition of electrically conductive carbon allotropes dispersed in an organic fluid

Abstract

The present application provides a composition of electrically conductive carbon allotropes dispersed in an organic fluid. The composition comprises: electrically conductive carbon allotropes; hydrogenated nitrile rubber; an organic fluid for dispersing the electrically conductive carbon allotropes and the hydrogenated nitrile rubber; wherein the average curvature of the electrically conductive carbon allotropes is 1°-20°, the average curvature being determined from the average diameter of the electrically conductive carbon allotropes, and the BET surface area of the electrically conductive carbon allotropes is 200 to 1400 m 2 / g; wherein the amount of hydrogenated nitrile rubber is 10wt%-300wt% relative to the weight of the electrically conductive carbon allotropes; and wherein the contour length of the hydrogenated nitrile rubber is below 1400nm. The composition of the present application significantly improves the concentration and dispersibility of the electrically conductive carbon allotropes in the organic fluid by precisely matching the contour length of the HNBR and the average curvature of the electrically conductive carbon allotropes, enables the viscosity of the electrically conductive carbon allotrope dispersion to be maintained at an acceptable level, and enables the storage stability of the dispersion to be good.

Description

Technical Field

[0001] This invention relates to the field of battery electrodes, and more specifically to compositions in which conductive carbon allotropes are dispersed in organic fluids. Background Technology

[0002] Currently, conductive carbon allotropes, especially carbon nanotubes (CNTs), are widely used as important conductive materials in fields such as secondary batteries, printed conductive wires, electromagnetic interference shielding, and sensors.

[0003] Conductive carbon allotropes should be present in high concentrations in organic fluids for ease of use without requiring excessive solvent. The dispersion of conductive carbon allotropes in organic fluids should have sufficiently low viscosity for easy pumping. Furthermore, the dispersion of conductive carbon allotropes in organic fluids should exhibit good storage stability. Therefore, the dispersibility of conductive carbon allotropes in organic fluids is crucial to their application.

[0004] Currently, there are some methods in the literature for using hydrogenated nitrile butadiene rubber (HNBR) as a dispersing agent to disperse conductive carbon allotropes, but there is a lack of specific data on the HNBR dispersing agents required for different types of carbon nanotubes, which means that technicians can only determine the optimal amount of dispersing agent to use through experiments.

[0005] Therefore, there is a need to find a better method for selecting HNBR dispersants for the dispersion of conductive carbon allotropes in order to improve the concentration and dispersibility of the conductive carbon allotropes dispersion, keep the viscosity of the dispersion at an acceptable level, and ensure good storage stability of the dispersion. Summary of the Invention

[0006] The main objective of this invention is to provide a composition in which conductive carbon allotropes are dispersed in an organic fluid, thereby solving the problems of low concentration, poor dispersibility, high viscosity and poor storage stability of conductive carbon allotropes in the prior art.

[0007] To achieve the above objectives, according to one aspect of the present invention, a composition in which a conductive carbon allotrope is dispersed in an organic fluid is provided, the composition comprising: a conductive carbon allotrope; hydrogenated nitrile butadiene rubber; and an organic fluid for dispersing the conductive carbon allotrope and the hydrogenated nitrile butadiene rubber; wherein the average curvature of the conductive carbon allotrope is 1°-20°, the average curvature being determined by the average diameter of the conductive carbon allotrope, and the BET surface area of ​​the conductive carbon allotrope is 200 to 1400 m². 2 / g; wherein, relative to the weight of the conductive carbon allotrope, the amount of hydrogenated nitrile butadiene rubber is 10wt%-300wt%; and wherein, the profile length of the hydrogenated nitrile butadiene rubber is less than 1400nm.

[0008] Furthermore, in the above composition, when the average curvature of the conductive carbon allotrope is greater than 4... o When the angle is ≤20°, the profile length of the hydrogenated nitrile butadiene rubber is 20 nm to 1000 nm, and the amount of hydrogenated nitrile butadiene rubber relative to the weight of the conductive carbon allotrope is greater than 50 wt% and ≤300 wt%.

[0009] Furthermore, in the above composition, when the average curvature of the conductive carbon allotrope is greater than 10... o When the angle is ≤20°, the profile length of the hydrogenated nitrile butadiene rubber is 20 nm to 400 nm, and the amount of hydrogenated nitrile butadiene rubber relative to the weight of the conductive carbon allotrope is greater than 100 wt% and ≤300 wt%.

[0010] Furthermore, in the above composition, the hydrogenated nitrile rubber has a density of less than 4.5 MPa in the hydrogenated nitrile rubber / carbon nanotube system. 1 / 2 The Ra value.

[0011] Furthermore, in the above composition, the hydrogenated nitrile butadiene rubber has a density of less than 4.0 MPa in the hydrogenated nitrile butadiene rubber / carbon nanotube system. 1 / 2 The Ra value.

[0012] Furthermore, in the above composition, the residual double bond content of the hydrogenated nitrile rubber is less than 10%.

[0013] Furthermore, in the above composition, based on the weight of the hydrogenated nitrile butadiene rubber, the acrylonitrile content of the hydrogenated nitrile butadiene rubber is 20 wt% to 50 wt%.

[0014] Furthermore, in the above composition, the conductive carbon allotrope is a multi-walled nanotube, a single-walled nanotube, an oligo-walled nanotube, graphene, or carbon black.

[0015] Furthermore, in the above composition, the profile length of the hydrogenated nitrile rubber is 30-1300 nm.

[0016] Further, in the above composition, the organic fluid is selected from dimethylformamide, diethylformamide, dimethylacetamide, N-methylpyrrolidone, cyclohexylpyrrolidone, dimethylacrylurea, γ-butyrolactone, γ-valerolactone, ε-propiolactone, cyclic carbonate, dimethyl sulfoxide, tetramethylurea, or triethyl phosphate.

[0017] The composition of this application significantly improves the concentration and dispersibility of conductive carbon allotropes in organic fluids by precisely matching the profile length of HNBR and the average curvature of conductive carbon allotropes, enabling the viscosity of the conductive carbon allotrope dispersion to be maintained at an acceptable level and ensuring good storage stability of the dispersion. Attached Figure Description

[0018] Figure 1 The following are shown: A - Rheological curve of Ketjen black dispersed with HNBR 34-1434; B - Solid sample; C - Viscosity data curves of 5 wt% Ketjen black dispersed with different amounts of HNBR 34-1434.

[0019] Figure 2 The following data are shown: A - Rheological curves of 6 wt% Ketjenblack and HNBR 34-300 with 40 wt% to 80 wt% Ketjenblack; B - Comparative data of different types of HNBR and Ketjenblack with different concentrations and amounts.

[0020] Figure 3 Rheological profiles of 1 wt% HNBR 34-1434 with different concentrations (5 wt% to 20 wt%) of graphene are shown.

[0021] Figure 4 The Brookfield viscosity profiles of Super P HNBR dispersed carbon black of different types and dosages are shown. "None" indicates that no HNBR was used, and the numbers in the figure indicate the dosage.

[0022] Figure 5 Rheological curves of 25% carbon black Super P dispersed with different amounts of HNBR34-1434 are shown.

[0023] Figure 6 Rheological curves of 25% carbon black Super P dispersed in different amounts of HNBR34-72 are shown.

[0024] Figure 7 The viscosities of different HNBR dosages are shown: HNBR 34-1686 (left), HNNR 34-1434 (right).

[0025] Figure 8 The viscosities of different HNBR dosages are shown: HNBR 34-1065 (left), HNNR 34-72 (right).

[0026] Figure 9 The viscosity is shown for different amounts of HNBR 34-34.

[0027] Figure 10 The following are examples of 1 wt% HNBR sand-milled dispersion of 4 wt% mw CNT: HNBR 34-1434 (left) and HNBR 34-300 (right).

[0028] Figure 11 Rheological profiles of 5 wt% small mw CNTs dispersed in 1 wt% HNBR 34-1065 and HNBR 34-300 are shown.

[0029] Figure 12 Rheological profiles of 0.5 wt% swCNT dispersed in HNBR 34-1434 and HNBR 34-72 are shown.

[0030] Figure 13 The rheological curves of swCNT dispersion are shown, where the amount of swCNT is 0.625 wt% and the amount of HNBR is 1.25 wt%.

[0031] Figure 14 The rheological curves of swCNT dispersion are shown, where the amount of swCNT is 0.75 wt% and the amount of HNBR is 1.5 wt%.

[0032] Figure 15 The rheological curves of swCNT dispersion are shown, where the amount of swCNT used is shown in the figure, and the amount of HNBR34-72 used is twice that of nanotubes.

[0033] Figure 16 The rheological curves of swCNT dispersion are shown, where the amount of swCNT used is shown in the figure, and the amount of HNBR34-1434 used is twice that of nanotubes.

[0034] Figure 17 The effect of NMP dilution on cathode slurry is shown, depending on the amount of swCNTs used and the concentration of the slurry. The concentration of swCNTs in the slurry is given in the figure.

[0035] Figure 18 The rheological profile of a 1 wt% fw CNT dispersion is shown, and the profile length and dosage of HNBR are given in the figure.

[0036] Figure 19 Rheological profiles of 1 wt% fwCNT and 1 wt% HNBR (profile lengths of 34 and 434 nm) are shown.

[0037] Figure 20 It was shown at 25s -1 Effect of HNBR profile length on fwCNT viscosity (1wt%) at shear rate.

[0038] Figure 21 A schematic diagram of the interaction between small mwCNTs and HNBRs with larger profile lengths is shown.

[0039] Figure 22 A schematic diagram of the interaction between fwCNT and short profile length HNBR is shown. Detailed Implementation

[0040] It should be noted that, unless otherwise specified, the various embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments. The following embodiments are merely exemplary and are not intended to limit the scope of protection of the present invention.

[0041] As explained in the background section, although there are some existing methods for using hydrogenated nitrile butadiene rubber (HNBR) as a dispersing agent to disperse conductive carbon allotropes, there is a lack of specific data on the HNBR dispersing agents required for different types of carbon nanotubes, which means that technicians can only determine the optimal amount of dispersing agent to use through experiments.

[0042] The inventors have observed that conductive carbon allotropes with higher curvature are more difficult to disperse. In the dispersion, the dispersing agent HNBR adsorbs onto the surface of the conductive carbon allotropes to prevent their aggregation. Furthermore, difficult-to-disperse conductive carbon allotropes require more dispersing agent, but large amounts of HNBR lead to higher viscosity, making dispersion exceptionally difficult.

[0043] The inventors, through studying the interaction between conductive carbon allotropes and various HNBR dispersants during the dispersion process in organic fluids, surprisingly discovered that manipulating the profile length of the HNBR dispersant can solve the above problems. Profile length is an important parameter that determines how the dispersant adsorbs or even becomes entangled on the conductive carbon allotropes. Generally, HNBR dispersants with shorter profile lengths adapt more easily to the highly curved surfaces of conductive carbon allotropes; therefore, HNBRs with smaller profile lengths are advantageous.

[0044] Therefore, to address the problems in the prior art, a typical embodiment of the present invention provides a composition in which a conductive carbon allotrope is dispersed in an organic fluid. The composition comprises: a conductive carbon allotrope; hydrogenated nitrile butadiene rubber; and an organic fluid for dispersing the conductive carbon allotrope and the hydrogenated nitrile butadiene rubber. The conductive carbon allotrope has an average curvature of 1°-20°, the average curvature being determined by the average diameter of the conductive carbon allotrope, and the BET surface area of ​​the conductive carbon allotrope is 200 to 1400 m². 2 / g; wherein, relative to the weight of the conductive carbon allotrope, the amount of hydrogenated nitrile butadiene rubber is 10wt%-300wt%; and wherein, the profile length of the hydrogenated nitrile butadiene rubber is less than 1400nm.

[0045] Preferably, the average curvature of the conductive carbon allotrope is 4°-20°. For example, the average curvature of the conductive carbon allotrope can be 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, 15°, 16°, 17°, 18°, 19° or 20°.

[0046] Preferably, the profile length of the hydrogenated nitrile rubber is 20-1400 nm, for example, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, 220 nm, 250 nm, 280 nm, 300 nm, 320 nm, 350 nm, 380 nm, 400 nm, 420 nm, 450 nm, 480 nm, 500 nm, 520 nm, 550 nm, 580 nm, 600 nm, 620 nm, 650 nm, 680 nm, 700 nm, 720 nm, 750 nm, 780 nm, 800 nm, 820 nm, 850 nm, 880 nm, 900 nm, 920 nm, 950 nm, 980 nm, 1000 nm, 1100 nm, 1200 nm, 1300 nm or 1400 nm.

[0047] The composition of this application significantly improves the concentration and dispersibility of conductive carbon allotropes in organic fluids by precisely matching the profile length of HNBR and the average curvature of conductive carbon allotropes, enabling the viscosity of the conductive carbon allotrope dispersion to be maintained at an acceptable level and ensuring good storage stability of the dispersion.

[0048] In some embodiments of the present invention, in the composition of the present invention, when the average curvature of the conductive carbon allotrope is greater than 4... o Furthermore, at ≤20°, the profile length of the hydrogenated nitrile butadiene rubber (HNBR) is 20 nm to 1000 nm, and the amount of HNBR relative to the weight of the conductive carbon allotrope is greater than 50 wt% and ≤300 wt%. This composition, by further precisely matching the profile length of the HNBR and the average curvature of the conductive carbon allotrope, shortens the dispersion process time, further reduces the viscosity of the conductive carbon allotrope dispersion, and ensures good storage stability of the dispersion.

[0049] In some embodiments of the present invention, in the composition of the present invention, when the average curvature of the conductive carbon allotrope is greater than 10... oFurthermore, at ≤20°, the profile length of the hydrogenated nitrile butadiene rubber (HNBR) is 20 nm to 400 nm, and the amount of HNBR relative to the weight of the conductive carbon allotrope is greater than 100 wt% and ≤300 wt%. This composition, by further precisely matching the profile length of the HNBR and the average curvature of the conductive carbon allotrope, significantly improves the concentration and dispersibility of the conductive carbon allotrope in organic fluids, further enabling the viscosity of the conductive carbon allotrope dispersion to be maintained at an acceptable level, and ensuring good storage stability of the dispersion.

[0050] In some embodiments of the present invention, in the compositions of the present invention, the hydrogenated nitrile butadiene rubber has a content of less than 4.5 MPa in the hydrogenated nitrile butadiene rubber / carbon nanotube system. 1 / 2 The Ra value. Matching this parameter can further enhance the interaction between hydrogenated nitrile rubber and carbon allotropes, thereby better dispersing the conductive carbon allotropes in the organic fluid, further increasing the concentration of conductive carbon allotropes in the organic fluid, and further reducing the viscosity of the conductive carbon allotrope dispersion.

[0051] Specifically, in the compositions of the present invention, the hydrogenated nitrile butadiene rubber has a content of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, or 4.5 MPa in the hydrogenated nitrile butadiene rubber / carbon nanotube system. 1 / 2 The Ra value.

[0052] In some embodiments of the present invention, in the compositions of the present invention, the hydrogenated nitrile butadiene rubber has a content of less than 4.0 MPa in the hydrogenated nitrile butadiene rubber / carbon nanotube system. 1 / 2 The Ra value. Matching this parameter can further enhance the interaction between hydrogenated nitrile rubber and carbon allotropes, thereby better dispersing the conductive carbon allotropes in the organic fluid, further increasing the concentration of conductive carbon allotropes in the organic fluid, and further reducing the viscosity of the conductive carbon allotrope dispersion.

[0053] Preferably, in the composition of the present invention, the hydrogenated nitrile rubber has a molecular weight of 3.0-4.0 MPa in the hydrogenated nitrile rubber / carbon nanotube system. 1 / 2 The Ra value.

[0054] In some embodiments of the present invention, the residual double bond content of hydrogenated nitrile butadiene rubber (HNBR) in the composition of the present invention is less than 10%, preferably less than 5%, and more preferably less than 2%. By controlling the residual double bond content of HNBR, its bonding force with conductive carbon allotropes can be further enhanced, thereby providing a more stable electrode material in energy storage devices such as supercapacitors and lithium-ion batteries, and further improving energy density and cycle stability.

[0055] Specifically, in the composition of the present invention, the residual double bond content of the hydrogenated nitrile rubber can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%.

[0056] In some embodiments of the present invention, in the compositions of the present invention, the acrylonitrile content of the hydrogenated nitrile butadiene rubber is 20 wt% to 50 wt%, preferably 25 wt% to 45 wt%, and more preferably 30 wt% to 40 wt%, based on the weight of the hydrogenated nitrile butadiene rubber. Controlling the acrylonitrile content further enables it to exhibit better compatibility and stability in various organic fluids, thereby providing a more stable electrode material and ensuring high electrochemical stability.

[0057] Specifically, based on the weight of the hydrogenated nitrile butadiene rubber, the acrylonitrile content of the hydrogenated nitrile butadiene rubber can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%.

[0058] In some embodiments of the present invention, the profile length of the hydrogenated nitrile butadiene rubber in the compositions of the present invention is 30-1300 nm. Hydrogenated nitrile butadiene rubber having this profile length range can further shorten the dispersion process time and further reduce viscosity.

[0059] In some embodiments of the present invention, the organic fluid in the compositions of the present invention is selected from dimethylformamide, diethylformamide, dimethylacetamide, N-methylpyrrolidone, cyclohexylpyrrolidone, dimethylacrylurea, γ-butyrolactone, γ-valerolactone, ε-propiolactone, cyclic carbonates, dimethyl sulfoxide, tetramethylurea, or triethyl phosphate. The organic fluid is not limited thereto, and those skilled in the art can select a suitable organic fluid according to actual needs.

[0060] Conductive carbon allotropes

[0061] Among many conductive carbon allotropes, this invention relates to conductive carbon allotropes with conductivity higher than that of semiconductors. For example, conductive carbon allotropes can be multi-walled nanotubes (mwCNTs), single-walled nanotubes (swCNTs), oligo-walled nanotubes (fwCNTs), graphene, or carbon black, etc.

[0062] Methods for calculating surface curvature

[0063] The surface curvature is related to the diameter of the conductive carbon allotrope. The diameter of the conductive carbon allotrope in this invention refers to the average diameter of a circle based on the center position of a carbon atom. The surface curvature β = 2π / n, where n is the number of sides / number of carbon atoms, and n = diameter d of the conductive carbon allotrope / average bond length (2.46 Å = 0.246 nm), with the diameter d measured by transmission electron microscopy (TEM).

[0064] HNBR dispersant

[0065] Hydrogenated nitrile butadiene rubber (NBR) comprises α,β-unsaturated nitrile-derived structural units. The content of α,β-unsaturated nitrile-derived structural units, such as acrylonitrile, in the hydrogenated NBR can range from 20-50 wt% of the total weight of the NBR, more preferably 25-45 wt%, and most preferably 30-40 wt%. The hydrogenated NBR may also comprise at least one of conjugated diene-derived structural units and hydrogenated conjugated diene-derived structural units, or any combination thereof. The type of conjugated diene is not particularly limited, but butadiene, isoprene, 2,3-dimethylbutadiene, pentadiene, and mixtures thereof are particularly preferred. The number of conjugated diene-derived structural units is limited to a residual double bond (RDB) content of less than 10%, preferably less than 5%, more preferably less than 2%, to ensure high electrochemical stability. The RDB content can be calculated as 100% minus the degree of hydrogenation (%). In the hydrogenation process of NBR known in the art, the degree of hydrogenation can be observed by FT-IR.

[0066] Hydrogenated nitrile butadiene rubber may include one or any combination of copolymerizable comonomers. Comonomers may be aromatic vinyl monomers, α,β-unsaturated carboxylic acids and their corresponding esters, α,β-unsaturated dicarboxylic acids and their esters.

[0067] The hydrogenated nitrile butadiene rubber (HNBR) of the present invention can be manufactured according to methods known in the art, such as EP-B-1394190, EP-A-1801126, EP-B-1825913, EP-B-18 26220, EP-B / 1894946, and EP-B-2027919, the teachings of which are incorporated herein by reference. The manufacture of short profile length HNBR requires a metathesis-based molecular weight degradation step of the NBR prior to hydrogenation. Suitable production methods are known, for example, EP 2418225, EP1426407A, EP 2289622, and EP2289623. Those skilled in the art can readily select suitable olefins as cross-metathesis partners with the nitrile copolymer, suitable metathesis catalysts, and their amounts to obtain copolymers with the desired profile length. Hydrogenation can be carried out using various techniques known in the art, without significant change in profile length before and after hydrogenation.

[0068] Ra value of HNBR

[0069] The suitable composition of HNBR can be determined by its interaction with conductive carbon allotropes. In a simple way, the Hansen solubility parameter (HSP) of HNBR can be compared with the HSP set of typical carbon nanotube materials. For two sets of HSPs, one for polymeric HNBR and the other for carbon nanotube materials, the distance between them is given by the Ra value, a quantitative indicator used to describe the distance between solubility parameters, typically representing the distance between the solubility of a chemical substance in a solvent. A higher Ra value indicates a larger difference between solubility parameters, while a lower Ra value indicates a smaller difference between solubility parameters. Ra is calculated as follows:

[0070] Ra=[4(δ D C -δ D p ) 2 +(δ P C -δ P p ) 2 +(δ H C -δ H p ) 2 ] 1 / 2 , where δ D δ P、 δ H These are HSPs used to disperse (van der Waals) interactions (D), polar interactions (P), and hydrogen bonds (H), respectively. C represents carbon nanotubes, and P represents polymers.

[0071] If the Ra value is small, the polymer tends to adsorb well on the carbon nanotube surface, thereby stabilizing the surface and preventing re-aggregation. The reference HSP for carbon nanotubes is obtained from Detriche et al. (S. Detriche, JB Nagy, Z. Mekhalif, J. Delhalle, Surface State of Carbon Nanotube and Hansen Solubility Parameters, J. Nanoscience Nanotechnology, 9(2009) p 6015-6025), which gives a value of 17.7 MPa. 1 / 2 6.2MPa 1 / 2 and 4.2MPa 1 / 2 δ D δ P and δ H This type of CNT has a diameter of 9.5 nm and a thickness of 250-300 μm. 2 / g of BET area represents a small-diameter mwCNT with a high surface area.

[0072] The HSP of HNBRs with a specific monomer composition can be estimated using the group contribution method in the HSPiP software (available at www.hansen-solution.com).

[0073] This invention uses the Hansen solubility parameter manual and the HSP software package to determine the HSP of polymer dispersants using a three-group contribution method: δ D δ P and δ H First, the weight composition (%) of the polymer HNBR is calculated as the mole fraction of acrylonitrile and hydrogenated butadiene units, assuming a random distribution. Then, structural information can be used to calculate the HSP according to "CM Hansen, Hansen solubilityParameters-A User's handbook, Boca Raton, Florida, USA, CRC Press LLC, 2007. Table 1.1 in Pages 10-11, Table 3.III.1 and Table 3.III.2 in Pages 70-73". Alternatively, the HSPiP software allows structural input.

[0074] The HSP of the polymer HNBR was calculated using the group contribution method from Hoftyzer and Krevelen, Hoy, and Beerbower, as available in the user manual, and the obtained values ​​were then averaged. The Ra value was set to be less than 4.5 MPa relative to the CNT reference HSP. 1 / 2 More preferably less than 4MPa 1 / 2 HNBR is a suitable dispersant.

[0075] HNBR profile length

[0076] Chain length is crucial for the interaction and adsorption of HNBR on conductive carbon materials. Weight-average molecular weight (MA) and number-average molecular weight (NMR) are determined by analyzing polymer chain lengths relative to polystyrene standards of known molecular weights using gel permeation chromatography (GPC). In this invention, MA is used because it clearly reflects the polymer's viscosity in organic solvents. The molar composition is then determined based on the known monomer unit content, giving the number of monomer units per chain. Chain length, here the profile length, is determined using the standard cc length of 0.154 nm for sp3 hybridized carbon atoms. The acrylonitrile monomer unit has a length of 2 cc, the hydrogenated 1,2-butadiene unit has a length of 2 cc, and the hydrogenated 1,4-butadiene unit has a length of 4 cc. The main chain is considered saturated with a minimum bond angle of 109°. o The contour length L = N dCC*sin(109) o / 2), where dCC is the standard CC length (0.154nm), and N is the number of monomer units calculated for each monomer type.

[0077] In dilute solutions, polymers form with a Flory radius R. F The entangled structure. Depending on the solvation capability of the solvent (here, the dispersion medium), this radius is proportional to the profile length in a specific way; that is, for a good solvent, R... F ≈L 3 / 5 For the ideal condition θ, then R F ≈L 1 / 2 In LiB applications, NMP and other polar fluids are primarily used, and these are good solvents for dispersing agents in HNBR polymers. After dissolving in a good solvent, the profile length typically increases, which usually leads to an increase in viscosity. Therefore, an appropriate profile length is crucial for viscosity control and dispersion stability.

[0078] Organic fluids

[0079] The organic fluid used as the dispersion medium can be an amide-based organic solvent, such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), or N-methylpyrrolidone (NMP), cyclohexylpyrrolidone, and dimethylacrylurea. Cycloamides are preferred. The solvent can be selected based on the proximity of the solvent's HSP to the conductive carbon allotrope to be dispersed, as described in the aforementioned paper by Detriche et al.

[0080] Another suitable class of solvents are cyclic esters and cyclic carbonates. These include γ-butyrolactone, γ-valerolactone, or ε-propiolactone. Other polar solvents can also be used, such as dimethyl sulfoxide, tetramethylurea, and triethyl phosphate. These solvents can be used as alternatives to NMP because they are less toxic.

[0081] The organic fluid needs to be able to dissolve the required HNBR. Preferably, the organic fluid is the same solvent used for the cathode slurry to keep the manufacturing process simple. Therefore, other requirements for the organic fluid are mainly influenced by the process requirements of the cathode slurry, such as the ability to solvate polymers like polyvinylidene fluoride, a sufficiently high flash point to reduce the risk of explosion, and a not-too-high boiling point to facilitate cathode drying.

[0082] Method for preparing compositions in which conductive carbon allotropes are dispersed in organic fluids

[0083] The dispersion of conductive carbon allotropes in organic fluids containing HNBR dispersant requires the application of sufficiently high shear forces using methods known in the art, such as homogenizers, ball mills, sand mills, bead mills, high-pressure sputtering with nozzles of various geometries, and ultrasonication. These methods can be combined, for example, by first applying a device with lower shear forces to obtain a pre-dispersion, and then using a mechanical device with higher shear forces for dispersion.

[0084] Typically, a solution of HNBR dispersant is first prepared in an organic fluid, followed by the addition of conductive carbon allotropes, and then appropriate mixing steps are performed to obtain a pre-dispersion. A high-shear mixer is then used to prepare a finer dispersion or slurry. Various mixing devices, as described above, can be used to achieve dispersion. For small-scale laboratory experiments, a one-step method can be employed, such as ball milling the HNBR solution in an organic fluid together with the conductive carbon allotropes. For industrial-scale production, since the high-shear mixer requires the addition of a flowable material, i.e., a pre-dispersion, it is preferable to first prepare a flowable pre-dispersion of the conductive carbon allotropes to allow the material to enter the high-shear mixer, such as a sand mill or high-pressure nozzle. There are no specific limitations on the mixing method, provided the shear force is strong enough and applied for a sufficiently long time; for example, a type of shear mixer such as a ball mill, bead mill, or sand mill can be used. High-shear mixing can also be achieved using other techniques, such as high-pressure sputtering using a nozzle, which pressurizes the dispersion through a small orifice that generates high shear force. These nozzles can be arranged in parallel and can have specific geometries, allowing the accelerated, dispersed streams to collide with each other, thus increasing very strong shear forces. The dispersion can also be pressurized through a narrow annular gap instead of an orifice; after exiting the gap, the accelerated dispersion may impact an impactor, such as a Gaulin homogenizer. For technically sound dispersion, mixing equipment can also be connected in series to improve dispersion quality. In most cases, mixing equipment allows the dispersion to be recirculated after each dispersion step, allowing multiple dispersions to be achieved using the same machine. HNBR dispersing aids are crucial for producing good dispersions; in the absence of sufficient dispersing aids, conductive carbon allotropes may be mechanically degraded. For example, excessively long shearing times on carbon nanotubes can cause them to break, reducing their conductivity in the final application.

[0085] Example

[0086] Material

[0087] HNBR dispersant

[0088] 3406: HNBR, with an RDB content of less than 0.9%, acrylonitrile content of 34 wt%, butene content (from hydrogenated vinyl) of 15.2 wt%, and a profile length of 1686 nm (abbreviated as 34-1686). Ra values ​​based on HSP are 18.32, 7.26, and 3.34 δ. D δ P and δ H The calculated value is 3.07 MPa. 1 / 2 This material is a commercial product of Arlanxeo.

[0089] AT 3404: HNBR, with an RDB content of less than 0.9%, acrylonitrile content of 34%, butene content (from hydrogenated vinyl) of 15.2%, and a profile length of 1434 nm, abbreviated as 34-1434. It has the same characteristics as... 3406 has the same composition and therefore the same Ra value. This material is a commercial product of Arlanxeo.

[0090] The experimental HNBR 3402: HNBR, with an RDB content of less than 0.9%, an acrylonitrile content of 34%, a butene content (from hydrogenated vinyl) of 15.2%, and a profile length of 1065 nm (abbreviated as 34-1065). It has the same characteristics as... 3406 has the same composition and therefore the same Ra value. This sample was tested in a twin-screw extruder (Leistritz extruder, model ZSE27MAX-480, L / D ratio 48, with 11 zones, screw diameter 28.7 mm, temperature set at 280°C). AT3404 was prepared by mechanical shearing.

[0091] HNBR 3400, experimental sample 34-300: HNBR with RDB content less than 0.9%, acrylonitrile content 34%, butene content (from hydrogenated vinyl) 15.2%, profile length 300 nm, abbreviated as 34-300. It has the same characteristics as... 3406 has the same composition and therefore the same Ra value. This sample was prepared by NBR metathesis and subsequent hydrogenation as described in EP2289623, in which a suitable metathesis catalyst and an appropriate amount of 1-hexene were used for metathesis as an olefin.

[0092] HNBR 3400, Experimental Sample 34-72: HNBR with RDB content less than 0.9%, acrylonitrile content 34%, butene content (from hydrogenated vinyl) 15.2%, profile length 72 nm, abbreviated as 34-72. It has the same characteristics as... 3406 has the same composition and therefore the same Ra value. The preparation of this sample is similar to that of experimental samples 34-300, where the amounts of catalyst and olefin are suitable to achieve the desired profile length.

[0093] HNBR 3400, experimental sample 34-34: HNBR with RDB content less than 0.9%, acrylonitrile content 34%, butene content (from hydrogenated vinyl) 15.2%, and profile length 34 nm, abbreviated as 34-34. It has the same characteristics as... 3406 has the same composition and therefore the same Ra value. The preparation of this sample is similar to that of HNBR 34-300, where the amounts of catalyst and olefin are suitable to achieve the desired profile length.

[0094] HNBR 3400, Experimental Sample 34-434: HNBR with RDB content less than 0.9%, acrylonitrile content 34%, butene content (from hydrogenated vinyl) 15.2%, and profile length 434 nm, abbreviated as 34-434. It has the same characteristics as... 3406 has the same composition and therefore the same Ra value. The preparation of this sample is similar to that of HNBR 34-300, where the amounts of catalyst and olefin are suitable to achieve the desired profile length.

[0095] 5008: HNBR, with an RDB content of less than 0.9%, an acrylonitrile content of 49%, a butene content (from hydrogenated vinyl) of 12%, and a profile length of 1033 nm (abbreviated as 49-1033). The Ra value was determined to be 4.73 MPa. 1 / 2 This material is a commercial product of Arlanxeo.

[0096] 4307:HNBR, with an RDB content of less than 0.9%, an acrylonitrile content of 43%, a butene content (from hydrogenated vinyl) of 13%, and a profile length of 1242 nm, abbreviated as 43-1242. Its Ra value is determined to be 3.77 MPa. 1 / 2 This material is a commercial product of Arlanxeo.

[0097] AT 3904:HNBR, RDB content less than 0.9%, acrylonitrile content 39%, butene content (from hydrogenated vinyl) 13%, profile length 1267 nm, abbreviated as 39-1267. Ra value measured at 3.33 MPa. 1 / 2 This material is a commercial product of Arlanxeo.

[0098] Conductive carbon allotropes with low or zero curvature

[0099] Carbon black Super P: supplied by Imerys, surface area 62m² 2 / g. Electron micrographs (RM. Gnanamuthu, CWLee / Materials Chemistry and Physics 130(2011)831–834) show a large principal particle size (50 nm) and an estimated mean curvature much lower than 1. o .

[0100] Graphene: Conductive graphene SE1232 supplied by Changzhou Sixth Element Chemical Co., Ltd., China. Electron micrographs of the dried coating show that the layered flakes have an average of 5 loosely connected layers, with a length or width of 10 μm and a surface area of ​​305 m². 2 / g (supplier information). Although individual sheets are typically curved and wavy, the average curvature is quite small and therefore considered to be 0.

[0101] Conductive carbon allotropes with moderate curvature

[0102] mwCNT: Entangled multi-walled CNT GT-200 obtained from Shandong Dazhan Nanomaterials Co., Ltd. using GT-200, and analyzed by electron microscopy, with an estimated average diameter of 15 nm and a surface area of ​​approximately 200 m². 2 / g, curvature approximately 1.9 o .

[0103] Ketjen Black (KB) ECP-600JD: Supplied by Nouryon, primary particle size estimated at approximately 34nm (supplier information). BET surface area is 1270m². 2 / g (supplier information). Electron micrographs show graphitized carbon layers with irregular curvature, where individual segments resemble circular cuts ranging from 5 to 7 nm, with an estimated curvature of 1.5. o The porosity is 80%, which indicates the presence of a large area of ​​curved surface.

[0104] Small-diameter mwCNTs: mwCNT CR3000 obtained from Superray, based on electron microscope images from the supplier, with an average diameter of 11 nm and a BET surface area of ​​285 m². 2 / g, curvature 2.6 o .

[0105] Conductive carbon allotropes with high curvature

[0106] swCNT: Tuball provided by OCSiAl TM Electron microscopy determined that the average diameter was 1.7 nm, the average length was estimated to be 20 μm, and the BET surface area was >500 m². 2 / g(MRPredtechenskiy et al. Carbon Trends 8(2022)100175). The curvature is estimated to be 17. o .

[0107] fwCNT: Oligowalled carbon nanotubes obtained from the market were characterized by TEM analysis of the diluted dispersion. The results showed that the average diameter of the carbon nanotubes with three walls was 7 nm, and the estimated curvature was 4. o In the paper by Chen et al. (New J. Chem., 2022, 46, 18724), double-walled CNTs have a diameter of 670 μm. 2 The BET surface area of ​​ / g allows the fwCNT samples used in this invention to have a surface area of ​​400-500 m² / g.2 / g of BET surface area.

[0108] Dispersion test

[0109] In Method A, a conductive carbon allotrope and HNBR dissolved in NMP were placed together in a Retsch single-ball mill to form a mixture. This mixture was then ball-milled at 28 Hz for 30 minutes (6 minutes per mill, followed by cooling to room temperature (RT) before the next 6-minute milling cycle, for a total of 5 cycles) to form a dispersion. The dispersion was then coated onto a PET film using a gauge bar coater with a 250 μm gap and dried. The rheological properties of the dispersion were determined by measuring at RT from 1 to 1000 s⁻¹. -1 The shear scan was used for measurement.

[0110] When the dispersion can be coated into dark, continuous ink flakes using a gauge bar coater with 250 μm and 350 μm gaps, and simultaneously within 100 s... -1 A good quality coating can be obtained when the viscosity is between 1 and 5 Pa·s.

[0111] In Method B, the conductive carbon allotrope dissolved in NMP and HNBR are pre-dispersed in a high-speed mixer (6000 rpm, 30 min), ground in a sand mill (2500 rpm), and samples are taken at regular time intervals.

[0112] Experimental Series 1

[0113] Using method A, disperse Ketjen black to a concentration between 5 wt% and 8 wt% using HNBR 34-1434 dissolved in NMP at a concentration of 2 wt% to 4 wt%. 20 wt% and 10 wt% Ketjen black remain completely solid (see [link to method A]). Figure 1 -B). At 6.5 wt% and 8 wt% Ketjenblack dosages, the dispersions were solid and uncoatable. At a Ketjenblack content of 5 wt%, good dispersions were obtained with HNBR 34-1434 contents of 2 wt%, 3 wt%, and 4 wt% (see [link to relevant documentation]). Figure 1 Therefore, the weight ratio of HNBR to Ketjenblack can be 0.6. The Ketjenblack content can be further optimized between 5 wt% and 6.5 wt%.

[0114] Next, 6 wt% Ketjen Black was dispersed, but the viscosity of HNBR 34-1434 was too high (see [link]). Figure 1 -A). Then, HNBR 34-300 was tried, yielding a good dispersion in which the optimal HNBR 34-300 content relative to Ketjen Black was 60 wt% (see [link]). Figure 2 ).

[0115] Therefore, due to the high curvature and extremely high surface area of ​​Ketjenblack, HNBR with an appropriate dosage and a shorter profile length is preferred.

[0116] Test Series 2 (Comparative Example)

[0117] Using method A, disperse graphene SE1232 at a concentration of 5 wt% to 20 wt%, while simultaneously adding 1 wt% HNBR34-1434. At 20 wt% graphene, only solid blends are obtained. The optimal slurry is obtained when the graphene concentration is 15 wt% and the HNBR 34-1434 concentration is 1 wt% (HNBR 34-1434 to graphene weight ratio is 0.067). Because graphene has virtually no curvature and is already very wrinkled, it does not easily re-aggregate, thus allowing the use of relatively low concentrations of HNBR with higher profile lengths to maintain good dispersion. Therefore, for sheet-like carbon materials, low molecular weight HNBR is not required for dispersion. Figure 3 Rheological curves of 1 wt% HNBR 34-1434 with different concentrations (5 wt% to 20 wt%) of graphene are shown. It can be seen that the lower graphene concentration yields a dispersion with very low viscosity, which cannot be coated.

[0118] Test Series 3 (Comparative Example)

[0119] Method A was used to disperse carbon black Super P at higher concentrations. The viscosity of the dispersion was measured using a Brookfield LVDV-II+Pro viscometer, characterizing the viscosity at low shear rates, and viscosity data were obtained for carbon black Super P concentrations from 5 wt% to 30 wt% and for different types and concentrations of HNBR dispersants.

[0120] like Figure 4 As shown, Super P can be dispersed at a concentration of 5 wt% (data points are marked "None") without any dispersing aids, but not at higher concentrations. Viscosities slightly above 10,000 cps are acceptable. The data indicate that HNBR can prepare dispersions with very high carbon black concentrations. Furthermore, higher HNBR dosages tend to result in viscosity higher than necessary. HNBR 34-72 can disperse Super C to a concentration of 20 wt% while maintaining a low viscosity. If the HNBR concentration is optimized to values ​​greater than 5 wt% or 6 wt%, a carbon black concentration of 25 wt% can be achieved.

[0121] Further testing using the same method A, but with HNBR 34-1434 at a carbon black concentration of 25 wt%, showed minimum viscosity at 1 wt% HNBR. Higher dosages resulted in increased viscosity but improved shear stability to 1000 s.-1 However, as high as 300 s-1 Its stability is considered acceptable (see [reference]). Figure 5 ).

[0122] When using HNBR 34-72, low-viscosity dispersions can be prepared with dosages between 2wt% and 4wt%, but concentrations exceeding 150s... -1 Poor stability can be observed at certain shear rates. This indicates that both HNBR dispersants can produce highly concentrated dispersions, but the shorter profile length of HNBR leads to poorer shear stability (see [link to dispersant description]). Figure 6 ).

[0123] Therefore, carbon black with a low specific surface area and virtually no actual curvature can preferably be dispersed in HNBR with a profile length greater than 1000 nm.

[0124] Experimental Series 4

[0125] Dispersing at a concentration of 5 wt% using method A yielded a considerably small 1.9%. o Curvature-entangled mwCNT (GT-200). Several HNBRs were used as polymer dispersants, with HNBR dosages varying between 0.5 wt% and 4 wt%. Flow curves were plotted, and viscosities at different shear rates were recorded.

[0126] Optimal coating behavior and minimum dispersion viscosity were observed when the HNBR dosage was 1 wt% and the HNBR / mwCNT weight ratio was 0.2. Lower dosages resulted in dispersions that could not be coated and exhibited quasi-elastic solid behavior. At higher dosages exceeding 1 wt%, the viscosity increased again, but the dispersion remained coatable. If the HNBR dosage was too low, the mwCNT coils tended to re-aggregate, resulting in a gel material. At high HNBR dosages, polymer molecules were adsorbed onto the mwCNT coils and tended to swell, which increased the dispersion viscosity but did not lead to agglomeration (see [link to HNBR dosage]). Figure 7-9 ).

[0127] Experiments were conducted with different profile lengths and different HNBRs. The optimal HNBR / mwCNT weight ratio was found to be 0.2 when the profile length reached 1020 nm. Short profile length HNBRs 34-72 at an HNBR / CNT weight ratio of 0.2 exhibited similar viscosities, but surprisingly, higher HNBR dosages resulted in lower dispersion viscosities, despite more polymer being adsorbed onto the nanotube clusters. In this manner, HNBR-modified nanotubes may require smaller volumetric volumes in the liquid. It can be inferred that the adsorption of HNBR becomes increasingly tighter, with fewer polymer rings and chains extending into the liquid volume. Therefore, it can be concluded that for carbon allotropes requiring greater adsorption due to their surface properties, HNBRs with shorter profile lengths may be highly advantageous. Industrial users have a strong need for low-viscosity mwCNT dispersions. The mwCNT concentration can also be further increased if short profile length HNBRs are used.

[0128] Using method B, 4 wt% mwCNT was dispersed with 1 wt% HNBR 34-1434, and the viscosity was tracked over milling time. For comparison, the test was repeated using HNBR 34-300. In both cases, the viscosity minimum was reached after 1 hour of milling. At the same milling time, the dispersion of HNBR 34-300 exhibited lower viscosity, particularly at lower shear rates. However, HNBR with shorter profile lengths showed higher viscosity peaks at the start of the milling test (see [link to method B]). Figure 10 ).

[0129] Therefore, for the dispersion of small curvature CNTs with only a small amount of polymer dispersing aid, the preferred profile length of HNBR is at least 1000 nm.

[0130] Experimental Series 5

[0131] Entangled mwCNTs (GT-200) were dispersed at a concentration of 5 wt% using method A. Several different molecular structures of HNBR were used as polymer dispersants at a concentration of 1 wt%, while the dosage of mwCNTs was 1 wt%. HNBR 49-1033 yielded a coatable, high-viscosity paste. HNBR 43-1242 had higher viscosity but remained coatable. The polymers had different compositions due to variations in their nitrile content. The profile length of HNBR 49-1033 was slightly less than that of 34-1434; however, its Ra value relative to CNTs was 4.73 MPa. 1 / 2 This is too high for pure carbon nanotubes. The Ra value of HNBR 43-1242 is 3.77 MPa. 1 / 2 It is a dispersant with an acceptable Ra value.

[0132] Therefore, for high-purity carbon nanotubes with a carbon content >99wt%, the preferred HNBR dispersant should have an Ra value of 4.5MPa. 1 / 2 Or lower.

[0133] Experimental Series 6

[0134] Using method A, small-diameter mwCNTs with a curvature of 2.6° (mwCNT CR3000) were dispersed using HNBR 34-300 and HNBR 34-1065. The concentration of mwCNTs in NMP was 5 wt%, and the concentration of HNBR was 1 wt%. The small diameter of the mwCNTs made them more difficult to disperse. To obtain a 5 wt% concentration of mwCNTs, a 1 wt% concentration of HNBR was required, necessitating the selection of an HNBR with a smaller profile length. Clearly, a profile length of 1065 nm was insufficient to obtain a low-viscosity paste. HNBR 34-300 with a profile length of 300 nm was well-suited as a dispersant. Smaller diameter CNTs obviously require dispersants with smaller profile lengths (see [link to dispersant description]). Figure 11 ).

[0135] Experimental Series 7

[0136] By using method A, swCNTs (Tuball) with a high curvature of 17° are dispersed. TM The concentration of HNBR was between 0.5 and 1.125 wt%, with 1 to 2.25 wt% added, and the profile length ranged from 72 to 1434 nm.

[0137] First, swCNTs were dispersed to a concentration of 0.5 wt% using 1 wt%–2 wt% HNBR 34-1434 and HNBR 34-72, yielding a dispersion with low viscosity. Dispersions at higher concentrations of swCNTs are also possible. HNBR with a shorter profile length exhibits lower viscosity. Furthermore, only a 1 wt% dosage of HNBR with a shorter profile length is required to prepare a dispersion with an HNBR / CNT weight ratio of 2. When the swCNT concentration is maintained at 0.5 wt%, the HNBR dosage can be varied between 1 wt% and 2 wt% to obtain dispersions with good dispersion viscosity. HNBR 34-72 with a shorter profile length provides lower viscosity and exhibits better storage stability (see [link to product description]). Figure 12 ).

[0138] When the concentration of swCNT was increased to 0.625 wt% and 0.75 wt% using two different HNBR samples, good dispersions could be prepared while maintaining an HNBR / CNT weight ratio of 2. However, the viscosity of HNBR with a shorter profile length was lower (see [link to relevant documentation]). Figure 13-14 ).

[0139] Dispersing higher concentrations of swCNTs becomes more difficult because the CNT coils occupy a larger volume of the available dispersion medium, NMP. A fixed HNBR dosage of 2 by weight means that the amount of HNBR is twice the amount of swCNTs. Results showed that the dispersion prepared with HNBR 34-1434 containing 1 wt% swCNTs had too high a viscosity; however, a storage-stable, low-viscosity dispersion was obtained with HNBR 34-72 (see [link to product description]). Figure 15 The dosage of HNBR 34-72 with a short profile length could be further optimized, but this seems unlikely for HNBR 34-1434. The comparative example cited in EP 3926710 did not even achieve complete dispersion at a swCNT concentration of 0.4 wt% because the HNBR profile length was too large, estimated at 1800 nm.

[0140] When HNBR 34-1434 was used in dispersions of 0.875 wt% and 1 wt% swCNT, the viscosity was higher compared to HNBR dispersion aids with shorter profile lengths (see [link]). Figure 15-16 The sharp increase in viscosity indicates that the dispersion sample is no longer storage-stable at 1.125 wt% swCNT. This suggests re-aggregation of swCNT coils or a significant increase in size. Regardless of the molecular causes of the instability of dispersions of high-curvature CNTs with small diameters, HNBRs with short profile lengths are preferred.

[0141] Short-profile HNBRs can adhere well to swCNTs to prevent aggregation, such as Figure 15 As shown. Without theoretical constraints, it's conceivable that shorter HNBRs would produce fewer long chains and rings, resulting in less CNT coil expansion; therefore, even at high swCNT concentrations, the viscosity remains low. This high-concentration, low-viscosity CNT dispersant is an ideal dispersion for practical applications because it allows use in cathode slurries without excessive dilution from added NMP. If the amount of solvent can be reduced, it will also be more advantageous for the application of conductive coatings (see...). Figure 17 ).

[0142] Experimental Series 8

[0143] Using method A, fwCNTs with a curvature of 4° were dispersed to a concentration of 1 wt% CNTs using 1 wt% and 2 wt% HNBR 34-1434. Then, further dispersion was performed using 1 wt% and 2 wt% HNBR 34-300.

[0144] All dispersions were coated onto PET film using a 250μ gauge. The dried dispersions had low resistivity, making them suitable for conductor and flexible electrode applications.

[0145] The dispersion prepared with HNBR 34-1434 exhibited higher viscosity. After 6 days of storage, the viscosity increased slightly again. The viscosity of the dispersion containing 2 wt% HNBR 34-1434 increased further and also increased slightly with storage (see [link to product description]). Figure 18 ).

[0146] When using HNBR 34-300, low-viscosity dispersions are obtained. Importantly, only 1 wt% of the dispersant is required, and the viscosity does not increase with higher HNBR dosages. Furthermore, there is no storage dependence on viscosity. Since the viscosity in these experiments remains low, dispersions of higher concentrations of CNTs can be achieved, and the HNBR dosage can still be slightly reduced (see [link to relevant documentation]). Figure 18 ).

[0147] However, compared to mwCNTs with smaller curved surfaces, fwCNTs with relatively high curvature require an HNBR / CNT weight ratio of 1 or lower to achieve good dispersion.

[0148] Figure 19 Rheological profiles of fwCNT dispersion using HNBR with short profile lengths are shown. HNBR 34-434 is well-suited for fwCNT dispersion. Furthermore, stable dispersion can be achieved even with very short profile lengths of HNBR 34-34. Detailed data comparisons show that HNBR 34-34 exhibits the lowest viscosity flow profiles at lower shear rates, suggesting the possible existence of an optimal profile length. While a profile length of 34 nm can still be assumed to be suitable, the inventors believe that the profile length should not be less than 20 nm to allow for the modification of fwCNT steric stability using HNBR with these short profile lengths.

[0149] Typically, carbon allotropes with high curvature require higher amounts of HNBR dispersants to avoid agglomeration. Simultaneously, due to their high aspect ratio, these carbon allotropes tend to occupy a higher volume fraction. High doses of HNBR further increase the coil size of the carbon nanotubes, resulting in excessively high dispersion viscosity. Surprisingly, shorter profile length HNBR dispersants avoid the high viscosity problem, although they may not provide as much steric stability. Shorter profile length HNBR can more easily and tightly wrap around relatively thin carbon nanotubes, resulting in good stearic acid stability (see [link to article]). Figure 20 ).

[0150] The prepared CNT dispersion samples were analyzed by electron microscopy after further dilution in NMP, casting on a grid, and drying. Figure 21A small mw CNT is shown. The sample preparation yielded a layer formed by several CNT coils. One coil is outlined in the figure. HNBR 34-1434 was used as a dispersant and is not visible here due to lack of contrast. However, for illustration, the long polymer chains are plotted below, some of which are stretched and adsorbed onto the CNTs, while the majority of the polymer is considered to extend into the liquid in the dispersed state. These rings provide steric stability to the CNT coils, preventing re-agglomeration. It is thought that longer HNBR chains or more HNBR polymer coils adsorbed onto the CNTs would extend the combined CNT-polymer coils, thus requiring a larger fluid volume. This would increase the viscosity of the dispersion.

[0151] Figure 22 The fwCNTs shown are much thinner and dispersed per weight into more CNT coils. Due to the higher curvature of these CNTs, HNBR will adsorb onto the CNTs into a more compact adsorbed complex. In this case, the HNBR polymer chains are drawn with a coarse profile length of only 250 nm. HNBR effectively prevents re-agglomeration of the highly curved and therefore very active CNT surface, and due to the shorter profile length, the polymer can more easily fit into the CNT coils. HNBR will enter the free fluid volume to a lesser extent while still providing the necessary steric stability, this time over a smaller distance. In this way, the shorter profile length of HNBR provides excellent dispersion performance while avoiding the viscosity increase caused by CNT coil expansion. Table 1 below summarizes the above experiments.

[0152] Table 1

[0153]

[0154] Based on the described experiments, swCNTs with small diameters of less than 2 nm and thus high surface curvature of at least 1.1% can be dispersed at low viscosity and excellent processability, provided that a small profile length HNBR, such as 72 nm, is used. Those skilled in the art can explore even smaller profile length HNBRs to achieve higher CNT concentrations.

[0155] fwCNTs can be dispersed in HNBR with a profile length of approximately 300 nm at concentrations above 1 wt%, most likely at least up to 1.5 wt%. Those skilled in the art can further optimize the process using the same or similar HNBR with dosage variations to achieve the desired higher fwCNT concentrations and lower viscosity.

[0156] Compared to HNBR with a larger profile length, carbon nanotubes with a smaller diameter of approximately 11 nm can be dispersed with 1 wt% of HNBR with a profile length of 300 nm to a concentration of at least 5 wt% and with lower viscosity. Those skilled in the art can even optimize the profile length of the HNBR to a slightly lower length, thereby further increasing the concentration of CNTs in the dispersion.

[0157] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A composition comprising a conductive carbon allotrope dispersed in an organic fluid, characterized in that, The composition comprises: Conductive carbon allotropes; Hydrogenated nitrile butadiene rubber; An organic fluid is used to disperse the conductive carbon allotrope and the hydrogenated nitrile rubber. The conductive carbon allotrope has an average curvature of 1°-20°, which is determined by the average diameter of the conductive carbon allotrope, and the BET surface area of ​​the conductive carbon allotrope is 200 to 1400 m². 2 / g; The amount of hydrogenated nitrile rubber is 10 wt% to 300 wt% relative to the weight of the conductive carbon allotrope; and The profile length of the hydrogenated nitrile rubber is less than 1400 nm.

2. The composition according to claim 1, characterized in that, When the average curvature of the conductive carbon allotrope is greater than 4° and ≤20°, the profile length of the hydrogenated nitrile butadiene rubber is 20 nm to 1000 nm, and the amount of the hydrogenated nitrile butadiene rubber relative to the weight of the conductive carbon allotrope is greater than 50 wt% and ≤300 wt%.

3. The composition according to claim 1, characterized in that, When the average curvature of the conductive carbon allotrope is greater than 10° and ≤20°, the profile length of the hydrogenated nitrile butadiene rubber is 20 nm to 400 nm, and the amount of the hydrogenated nitrile butadiene rubber relative to the weight of the conductive carbon allotrope is greater than 100 wt% and ≤300 wt%.

4. The composition according to any one of claims 1-3, characterized in that, The hydrogenated nitrile butadiene rubber has a density of less than 4.5 MPa in the hydrogenated nitrile butadiene rubber / carbon nanotube system. 1 / 2 The Ra value.

5. The composition according to any one of claims 1-3, characterized in that, The hydrogenated nitrile butadiene rubber has a density of less than 4.0 MPa in the hydrogenated nitrile butadiene rubber / carbon nanotube system. 1 / 2 The Ra value.

6. The composition according to any one of claims 1-3, characterized in that, The residual double bond content of the hydrogenated nitrile butadiene rubber is less than 10%.

7. The composition according to any one of claims 1-3, characterized in that, Based on the weight of the hydrogenated nitrile butadiene rubber, the acrylonitrile content of the hydrogenated nitrile butadiene rubber is from 20 wt% to 50 wt%.

8. The composition according to claim 1, characterized in that, The conductive carbon allotrope is a multi-walled nanotube, a single-walled nanotube, an oligo-walled nanotube, graphene, or carbon black.

9. The composition according to claim 1, characterized in that, The profile length of the hydrogenated nitrile butadiene rubber is 30-1300 nm.

10. The composition according to any one of claims 1-3, characterized in that, The organic fluid is selected from dimethylformamide, diethylformamide, dimethylacetamide, N-methylpyrrolidone, cyclohexylpyrrolidone, dimethylacrylurea, γ-butyrolactone, γ-valerolactone, ε-propiolactone, cyclic carbonate, dimethyl sulfoxide, tetramethylurea, or triethyl phosphate.

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