Preparation method of carbon composite fluid without polymer binder

Abstract

The invention provides a preparation method of a carbon composite current collector without a macromolecular adhesive. The method ingeniously utilizes charge transfer and pi-pi interaction between the conductive carbon material and the auxiliary agent to realize infiltration of the conductive carbon material, and assists uniform mixing of the conductive carbon material to finally form the paste slurry. And after the pasty slurry is pressed and washed, the carbon composite current collector with uniform thickness and good conductivity is constructed on the surface of a substrate. In the carbon film, the carbon nanotubes with the one-dimensional structure construct a conductive network, the graphite powder or graphene with the two-dimensional structure plays a role in bonding the carbon tubes under high voltage by utilizing the flexibility of the graphite powder or graphene and through pi-pi interaction, the contact resistance between the carbon tubes is reduced, and the mechanical property of the composite current collector is enhanced. The preparation method is simple in process and low in cost, the prepared carbon composite current collector is outstanding in chloride ion corrosion resistance, and powerful guarantee is provided for performance improvement and long-term stable operation of a chloride ion-containing water system energy storage device.

Description

Technical Field

[0001] This invention belongs to the field of current collector preparation technology for chloride ion-containing aqueous energy storage devices, specifically relating to a method for preparing a corrosion-resistant carbon composite current collector without polymer binders. Background Technology

[0002] With the increasing depletion of non-renewable resources, the demand for green, sustainable, and cost-effective energy storage technologies is becoming increasingly urgent. Aquatic energy storage technologies stand out due to their safety, environmental friendliness, high efficiency, and economic viability. Seawater electrolytes, in particular, are expected to become a key technology in future renewable energy grids due to their abundant resources, low cost, and environmental friendliness, effectively addressing the intermittency of renewable energy sources. However, the high concentration of chloride ions in seawater poses a challenge to battery materials. In chloride-containing aqueous electrolyte environments, the corrosion resistance of current collectors during charge and discharge becomes particularly critical. Furthermore, aquatic energy storage technologies are also applied in water treatment, such as in capacitive deionization and electrodialysis processes, where current collectors also face the challenge of corrosion resistance.

[0003] Currently, commercially available electrode current collectors mostly use carbon-coated aluminum or copper foil (CN202521714677.1). However, these metal foils are prone to corrosion during long-term cycling in batteries and capacitors, leading to structural failure and affecting cycle stability. Aqueous energy storage devices commonly use titanium foil, titanium mesh, or porous titanium plates as current collectors (CN120545354A, CN120511288A). However, in chloride ion-containing environments, titanium foil has a narrow stable operating voltage range (-0.49 V-0.91 V vs SHE), and is easily corroded by chloride ions under overpressure. Although graphite paper is a commonly used current collector for aqueous chloride ion energy storage devices (CN120674626A, CN118270827A), its small specific surface area and impermeability limit the miniaturization and performance improvement of energy storage devices.

[0004] Therefore, developing a full-carbon composite current collector that combines excellent conductivity and resistance to chloride ion corrosion is of great significance for the preparation of high-performance, well-cycle-stable chloride-containing aqueous energy storage devices. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing a carbon composite current collector without polymer binders. The technical solution adopted is as follows: In a first aspect, the present invention provides a method for preparing a carbon composite current collector without polymer binders, comprising the following steps: (1) Graphite powder and carbon nanotubes are mixed at a mass ratio of 0.1:1–10:1 and fully mixed in a mill to obtain solid powder.

[0006] (2) Add additives to the solid powder of step (1) at 5%-50% of the powder mass, mix thoroughly in a machine to obtain a paste-like slurry of graphite powder and carbon nanotubes; (3) The paste from step (2) is applied to the surface of the substrate to form a conductive graphite powder / carbon nanotube film; (4) The film from step (3) is pressed in segments at 2–50 MPa and 80–180 ℃. The additives are extruded by adjusting the process parameters, so that the graphite powder, carbon nanotubes, and carbon nanotubes and graphite powder are tightly bonded to form a stable π-π interaction. (5) The composite current collector is obtained by washing, drying or vacuum heating to remove residual additives according to the properties of the additives added in step (2).

[0007] Preferably, the carbon nanotubes in step (1) are one or a mixture of several of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, and the purity is required to be ≥90 wt%.

[0008] Preferably, the graphite powder in step (1) is 1500-15000 mesh screened graphite powder, or a mixture of two or more different mesh sizes in the 1500-15000 mesh range. The graphite powder is connected and anchored to the carbon nanotubes through π-π stacking and van der Waals forces. Graphene, as a special case of sp2 hybrid carbon atom layer stacking less than 10 layers, belongs to one type of graphite powder.

[0009] In this invention, the thorough mixing of graphite powder and carbon nanotubes in step (1) is the guarantee of the film-forming properties, uniformity and stability of the conductive carbon film.

[0010] Preferably, the auxiliary agent in step (2) is one or a mixture of several of the following: methylphenol, methoxyphenol, decaoxyphenol, cashew phenol, cashew diol, methyl anisole, 1,3-dimethyl-2-imidazolinone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, cyclohexyl-2-pyrrolidone, o-dichlorobenzene, 2-ethylnaphthalene, benzothiophene-2-ethyl acetate, and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and the amount of auxiliary agent added is 5%–50% of the mass ratio of the solid powder.

[0011] In this invention, the additives added in step (2) are mainly adsorbed onto the surface of carbon materials through π–π interactions or dipole–π interactions, playing a role in lubrication and connecting carbon materials to achieve the preparation of paste slurry.

[0012] Preferably, the segmented pressing in step (4) achieves additive extrusion, graphite powder / carbon nanotube film formation, and regulates carbon film thickness and releases internal stress of carbon film by independently controlling the pressure (2-50 MPa), time (2-300 s) and temperature (30-180 ℃) of each segment.

[0013] More preferably, the segmented pressing in step (4) includes at least one of the following pressing methods: rolling pressure of 2 MPa, rolling ambient temperature of 120 ℃, and rolling speed of 10 cm / min; rolling pressure increased to 5 MPa, rolling ambient temperature of 120 ℃, and rolling speed of 30 cm / min; and rolling pressure increased to 20 MPa, rolling ambient temperature of 120 ℃, and rolling speed of 30 cm / min.

[0014] Preferably, the composite current collector carbon film obtained after hot pressing in step (4) has a thickness of 2–200 μm and a density of 2–20 g / m³. 2 Sheet resistance ≤100 Ω / □.

[0015] Secondly, the present invention provides a carbon composite current collector without polymer binder obtained by the preparation method of the first aspect.

[0016] Thirdly, the present invention provides the application of the carbon composite current collector without polymer binder described above in chloride ion-containing aqueous batteries, supercapacitors, flexible energy storage devices, or electrodialysis and capacitive deionization.

[0017] Compared with the prior art, the beneficial effects of this application include: The composite current collector prepared in this application exhibits excellent water resistance, effectively solving the problem of poor corrosion resistance of traditional current collectors in aqueous electrolyte environments containing chloride ions. In terms of the preparation process, the solid component in the slurry accounts for more than 50%, which not only reduces the amount of additives used, making them easier to recycle, but also controls the solvent consumption to below 10%. No polymer binders are used in the entire process, and there is no issue of metal deposition, making it highly compatible with existing coating production lines. The final current collector has low sheet resistance (≤100 Ω / □), good flexibility (bendable), and after 1000 cycles of testing, the resistance change rate is strictly controlled within 10%, demonstrating excellent stability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0019] Figure 1 This is a flowchart of the preparation method of the composite current collector in this application; Figure 2 This is a schematic diagram of the composite current collector of this application; Figure 3 Here are physical images and scanning electron microscope images of the composite current collector prepared in Example 1 of this application; Figure 4 The results are from the voltammetric cycle test in a 5 M sodium chloride aqueous solution used in this application. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through embodiments.

[0021] It should be noted that, in the following embodiments of the present invention, unless otherwise specified, the parts and percentages are all by mass.

[0022] "Parts by mass" is a unit of measurement that expresses the proportional relationship between the masses of components. One part can represent any mass value, such as 1 gram or 2.689 grams. If component A has a parts by mass and component B has b parts by mass, then the mass ratio of A to B is a:b. Note that the total number of parts by mass is not limited to 100 parts, unlike percentages.

[0023] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0024] When equivalents, concentrations, or other parameters are expressed as ranges, all ranges consisting of upper and lower limits are included, whether or not they are listed separately. For example, the range "2-50 MPa" should be understood to include sub-ranges such as "2-5 MPa", "2-10 MPa", "2-20 MPa", and "5-30 MPa". Numerical ranges by default include the endpoints and all integers and fractions within them, unless otherwise specified. Example 1

[0025] A method for preparing a carbon composite current collector without polymer binder, referenced Figure 1 and Figure 2 ,include: (1) Weigh 5 parts of multi-walled carbon nanotubes, 1 part of high-purity conductive graphite powder of 2000 mesh, 3 parts of 8000 mesh, and 1 part of 15000 mesh, and process them in a planetary ball mill for 12 hours to achieve full mixing of conductive graphite powder and multi-walled carbon nanotubes.

[0026] (2) Transfer the mixed powder to a vacuum kneader, add 2 parts of m-methoxyphenol and mix, and extrude the mixture through a screw to obtain a uniform paste.

[0027] (3) The slurry is pressed onto the surface of a 300 μm thick filter paper using a roller press. The roller pressure is 2 MPa, the roller pressing ambient temperature is 120℃, the roller pressing speed is 10 cm / min, and the carbon film thickness between the rollers is 500 μm. The roller pressing pressure of the composite membrane is increased to 5 MPa, the roller pressing ambient temperature is 120 ℃, the roller pressing speed is 30 cm / min, and the carbon film thickness between the rollers is 450 μm. The roller pressing pressure of the composite membrane is increased to 20 MPa, the roller pressing ambient temperature is 120 ℃, the roller pressing speed is 30 cm / min, and the carbon film thickness between the rollers is 400 μm.

[0028] (4) The residual m-methoxyphenol was removed by immersion in ethanol and dried at 60 degrees Celsius to form the composite current collector. The surface resistivity was 7.6 ± 2.72 Ω / □, and the residual m-methoxyphenol was <0.5%. The physical image and scanning electron microscope image of the composite current collector prepared in this example are attached. Figure 3 As shown. After 1000 voltammetric cycles in a 5 M sodium chloride aqueous solution, no significant redox peak was observed within the water electrolysis voltage window, and the current decrease was less than 10%. Figure 4 ). Example 2

[0029] The difference between Example 2 and Example 1 is that the auxiliary agent m-methoxyphenol in step (2) is replaced with a mixture of m-cresol and ethanol at a mass ratio of 3:1. The rest is the same as in Example 1. Example 3

[0030] The difference between Example 3 and Example 1 is that the auxiliary agent m-methoxyphenol in step (2) is replaced with a mixture of decoxyphenol / anisole at a mass ratio of 1:1, while the rest is the same as in Example 1. Example 4

[0031] The difference between Example 4 and Example 1 is that the auxiliary agent m-methoxyphenol in step (2) is replaced with a mixture of cashew phenol / o-dichlorobenzene at a mass ratio of 2:1, while the rest is the same as in Example 1. Example 5

[0032] The difference between Example 5 and Example 1 is that the 2 parts of m-methoxyphenol in step (2) are replaced with 3 parts of 1,3-dimethyl-2-imidazolinone, and the rest is the same as in Example 1. Example 6

[0033] The difference between Example 6 and Example 1 is that the 2 parts of m-methoxyphenol in step (2) are replaced with 5 parts of N-methyl-2-pyrrolidone, and the rest is the same as in Example 1. Example 7

[0034] The difference between Example 7 and Example 1 is that the 2 parts of m-methoxyphenol in step (2) are replaced with 3 parts of N,N-dimethylformamide or cyclohexyl-2-pyrrolidone, and the rest is the same as in Example 1. Example 8

[0035] The difference between Example 8 and Example 1 is that the 2 parts of m-methoxyphenol in step (2) are replaced with 2 parts of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, and the rest is the same as in Example 1. Example 9

[0036] The difference between Example 9 and Example 1 is that the multi-walled carbon nanotubes in step (1) are replaced with single-walled carbon nanotubes, while the rest is the same as in Example 1. Example 10

[0037] The difference between Example 10 and Example 1 is that the 1 part of 2000 mesh, 3 parts of 8000 mesh and 1 part of 15000 mesh high-purity conductive graphite powder in step (1) is replaced with 5 parts of graphene powder, and the rest is the same as in Example 1. Example 11

[0038] The difference between Example 11 and Example 1 is that the 1 part of 2000 mesh, 3 parts of 8000 mesh and 1 part of 15000 mesh high-purity conductive graphite powder in step (1) is replaced with 5 parts of 8000 mesh graphite powder, and the rest is the same as in Example 1. Example 12

[0039] The difference between Example 12 and Example 1 is that the rolling equipment in step (3) is replaced with a hot pressing equipment, while the rest is the same as in Example 1. Example 13

[0040] The difference between Example 13 and Example 1 is that the final rolling pressure of the rolling equipment in step (3) is changed to 10MPa, while the rest is the same as in Example 1. Example 14

[0041] The difference between Example 14 and Example 1 is that the 300 μm thick filter paper in step (3) is replaced with a 300 μm thick polyimide membrane treated with potassium hydroxide, and the rest is the same as in Example 1. Example 15

[0042] The difference between Example 15 and Example 1 is that the 300 μm thick filter paper in step (3) is replaced with a 300 μm thick plasma-activated polyethylene terephthalate film, and the hot pressing temperature is reduced to 50 °C. The rest is the same as in Example 1.

[0043] The composite current collectors of Examples 1-13 were tested using the following specific test methods: Shear resistance of membrane surface (four-probe method): At least 5 measurements at different locations are required, the average value is taken, and the standard deviation (uniformity) is reported. Flexibility: Refer to GB / T 6742 - Coating film bending test (cylindrical shaft). Shaft diameter 32 mm.

[0044] Electrolyte resistance: The sample was placed parallel to the graphite plate by 1 mm and immersed in a 5 M sodium chloride aqueous solution at room temperature. A voltammetric cycle test was performed at 100 mV / s, -1.4 V to 1.4 V. Stability was determined by monitoring the redox peak.

[0045] Water resistance: Immerse the sample completely in deionized water at 40±5 ℃ for 72 hours, remove it, dry the surface moisture, observe whether there are any phenomena such as blistering, discoloration, or peeling, and record them. Interlayer adhesion (cross-cut test): Using a utility knife blade, cut 10 × 10 squares at 1 mm intervals on the coating surface, cutting down to the substrate. After removing debris, press 3M tape onto the square area, hold for 60 seconds, and then quickly peel off the tape at a 180° angle to observe the coating peeling off in the square area.

[0046] The test results of Examples 1-13 are shown in Table 1 below.

[0047] Table 1. Comparison of test results for composite current collectors in Examples 1-13 Shear resistance Ω / □ flexibility 5 M NaCl corrosion Water resistance Interlayer adhesion Example 1 7.6±2.72 10 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by less than 10%. 72 h intact 40% non-peeling Example 2 5.2±2.82 10 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by less than 10%. 72 h intact 40% non-peeling Example 3 25.5±7.02 10 times without cracks No redox peak was observed after 1000 cycles, and the current decrease was <5%. 72 h intact 30% non-peeling Example 4 29.7±5.02 6 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by less than 20%. 72 h intact 10% non-peeling Example 5 14.2±5.58 No cracks 8 times No redox peak was observed after 1000 cycles, and the current decreased by less than 20%. 72 h intact 40% non-peeling Example 6 3.8±1.44 10 times without cracks No redox peak was observed after 1000 cycles, and the current decrease was <5%. 72 h intact 40% non-peeling Example 7 5.8±2.35 10 times without cracks No redox peak was observed after 1000 cycles, and the current decrease was <5%. 72 h intact 40% non-peeling Example 8 19.7±5.35 6 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by 20%. 72 h intact 30% non-peeling Example 9 5.5±2.07 10 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by 5%. 72 h intact 50% non-peeling Example 10 12.2±6.07 No cracks 8 times No redox peak was observed after 1000 cycles, and the current decreased by 10%. 72 h intact 30% non-peeling Example 11 18.8±5.83 No cracks 8 times No redox peak was observed after 1000 cycles, and the current decreased by 20%. 72 h intact 20% non-peeling Example 12 6.2±3.64 No cracks 8 times No redox peak was observed after 1000 cycles, and the current decreased by 10%. 72 h intact 50% non-peeling Example 13 36.2±5.64 No cracks 8 times No redox peak was observed after 1000 cycles, and the current decreased by 10%. 72 h intact 20% non-peeling Example 14 16.2±6.24 10 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by 10%. 48 h intact 10% non-peeling Example 15 10.2±5.75 4 times without cracks No redox peak was observed after 1000 cycles, and the current decreased by 50%. 12 hours intact 5% Non-peeling As can be seen from Table 1, compared with Example 1, Examples 4, 5, 8, and 11 have larger contact resistance values. This is related to the interaction strength between the additives and the carbon material surface. The interaction between the latex and the material results in poor wettability, which in turn leads to poor uniformity of slurry dispersion and increased contact resistance.

[0048] Compared with Example 1, Example 13 has a larger contact resistance, which is due to the lower pressing pressure and the removal of solvent, resulting in higher contact resistance.

[0049] Examples 1-15 showed very low interlayer adhesion due to the lack of polymeric binder, but this did not affect the stability during cyclic testing. Compared to Example 1, Examples 14 and 15 showed poorer interlayer adhesion because the polymeric membrane surface was smoother than the filter paper, reducing the adhesion of the carbon membrane. Further surface treatment is needed to improve adhesion.

[0050] The embodiments 1-15 described above are only used to illustrate the technical solutions of this application and are not intended to limit them. Those skilled in the art can make appropriate modifications to these embodiments or equivalent substitutions for technical features based on an understanding of the core essence of this application, and such modifications still fall within the protection scope of this application. Furthermore, it should be clarified that the content mentioned in the background section is only used to enhance the understanding of the technical background of this application and should not be regarded as a default endorsement or implication of the prior art.

[0051] It should be further noted that the above embodiments are merely for understanding the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. The embodiments may differ in their feature composition, but this does not preclude the combination of technical features from different embodiments to form new implementation schemes. Any embodiment covered by the claims can be freely combined with other embodiments. In short, as long as it does not deviate from the core technology and innovative concept of this application, any reasonable deduction and extension based on this application is protected.

Claims

1. A method for producing a binderless carbon composite current collector, characterized by, Comprising the following steps: (1) mixing graphite powder and carbon nanotubes in a mass ratio of 0.1:1-10:1, achieving sufficient mixing in a mill to obtain a solid powder; (2) adding an additive to the solid powder of step (1) in an amount of 5%-50% of the mass of the powder, achieving sufficient mixing in a machine to obtain a graphite powder and carbon nanotube paste slurry; (3) coating the paste slurry of step (2) on the surface of a substrate to form a conductive graphite powder / carbon nanotube film; (4) segmentally pressing the film of step (3) at 2-50 MPa, 80-180 ℃, adjusting the process parameters to achieve extrusion of the additive, and allowing the graphite powder, carbon nanotubes, and carbon nanotubes and graphite powder to tightly bind to form stable π-π interactions; (5) washing, drying, or vacuum heating to remove residual additives according to the properties of the additive added in step (2) to obtain the composite current collector.

2. The method of claim 1, wherein: The carbon nanotubes of step (1) are one or a mixture of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, with a purity of ≥90 wt%.

3. The method of claim 1, wherein: The graphite powder of step (1) is 1500 mesh-15000 mesh sieved graphite powder, or a mixture of two or more different mesh sizes in the range of 1500 mesh-15000 mesh, which achieves connection and anchoring of the graphite powder and carbon nanotubes through π-π stacking and van der Waals forces; the graphite powder includes graphene with sp2 hybridized carbon atom layers stacked in less than 10 layers.

4. The method of claim 1, wherein: The additive of step (2) is one or a mixture of several of methylphenol, methoxyphenol, decyloxyphenol, cardanol, cardol, methyl anisole, 1,3-dimethyl-2-imidazolinone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, cyclohexyl-2-pyrrolidone, o-dichlorobenzene, 2-ethylnaphthalene, benzothiophene-2-ethyl acetate, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and the additive is added in an amount of 5%-50% of the mass of the solid powder; the additive is adsorbed on the surface of the carbon material through π-π interactions or dipole-π interactions.

5. The method of claim 1, wherein: The segmental pressing of step (4) independently controls the pressure of each segment to be 2-50 MPa, the time to be 2-300 s, the speed to be 10-30 cm / min, and the temperature to be 30-180 ℃, to achieve extrusion of the additive, formation of a graphite powder / carbon nanotube film, and regulation of the thickness of the carbon film and release of internal stress in the carbon film.

6. The method of claim 5, wherein: The segmental pressing at least includes one of the following pressing methods: roller pressing at a pressure of 2 MPa, a roller pressing ambient temperature of 120 ℃, and a roller pressing speed of 10 cm / min; roller pressing at a pressure of 5 MPa, a roller pressing ambient temperature of 120 ℃, and a roller pressing speed of 30 cm / min; and roller pressing at a pressure of 20 MPa, a roller pressing ambient temperature of 120 ℃, and a roller pressing speed of 30 cm / min.

7. The method of claim 1, wherein: Step (4) The composite current collector carbon film thickness after hot pressing is 2-200 μm, density is 2-20 g / m 2 , and sheet resistance is ≤ 100 Ω / □.

8. A carbon composite current collector without polymeric binder, characterized by: Obtained by the preparation method of any one of claims 1-7.

9. Use of the polymer binder-free carbon composite current collector of claim 8 in a chlorine ion-containing aqueous battery or supercapacitor or flexible energy storage device or electrodialysis, capacitive deionization.

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