Process for producing an electrically conductive conductor run having at least one carbon conductor

Abstract

The present invention relates to a process for producing an electrically conductive conductor run (1) comprising at least one carbon conductor (3), comprising the steps of: a) producing or providing a conductor run (1) as intermediate product comprising at least one carbon conductor (3) comprising, in particular, graphite, pyrolytic graphite, graphene, graphyne and / or carbon nanotubes, b) dissolving at least one intercalation material (2) in a solvent (5), where the intercalation material (2) is suitable for intercalation into the material of the at least one carbon conductor (3) of the conductor run (1), c) placing the conductor run (1) into the solvent (5) containing the dissolved intercalation material (2) for a predefined period of time and at a particular temperature for induction of intercalation, in which atoms or molecules of the intercalation material (2) are intercalated in the material of the respective carbon conductor (3), especially adsorbed onto a carbon structure form of the carbon conductor (3), especially in an intermediate region (4) between the layers of a multilayer carbon structure form, and d) sequentially repeatedly performing steps b) and c) for different intercalation materials (2) and solvents (5) in order to sequentially intercalate different intercalation materials (2) into the material of the carbon conductor (3) of the conductor run (1).

Description

[0001] Description

[0002] title

[0003] Method for producing an electrically conductive conductor strand with at least one carbon conductor

[0004] State of the art

[0005] The present invention relates to a method for producing an electrically conductive conductor strand comprising at least one carbon conductor.

[0006] Carbon conductors are known from the prior art. For example, the prior art includes electrical conductors made of graphite, pyrolytic graphite, carbon nanotubes, or graphene. DE102020206563 A1 describes the production of an electrical graphene conductor. EP1404908B1 discloses that carbon nanotubes (CNTs) can be dispersed in superacids, thus enabling the production of continuous fibers made of carbon nanotubes. Such electrical conductors are used, for example, in electric motors, as described in WO 2018 / 233897 A1 or WO 2018 / 158003 A1.

[0007] To increase the electrical conductivity of the carbon conductor, it is known to dope the carbon conductor. For example,

[0008] DE 10 2019 220 177 A1 discloses that graphene can be doped with intrinsically doped graphene. WO 2021 / 004692 A1 shows how graphene can be doped with transition metal oxides to increase its electrical conductivity. EP 0 081 004 B1 shows that the electrical conductivity of graphite can be increased by doping with BF3, SiFz1, HfFz1, TiFz1, ZrFz1, PF5, NbFs, TaFs, AsFs, or SbFs.

[0009] From CN 106 744 888 A, it is known to produce graphene in a graphene dispersion by adding aluminum fluoride and amines. From Nakajima, T., Kawaguchi, M., & Watanabe, N. (1981). Ternary intercalation compound of graphite with aluminum fluoride and fluorine. Zeitschrift für Naturforschung B, 36(11), 1419-1423, it is also known that aluminum fluoride intercalates into graphite when equimolar fluorine is present in the gas phase and at sufficiently high temperatures. The disadvantage is that intercalation requires high temperatures, which means that the fluorine fluorinates the graphite as early as 300°C, thus impairing its electrical conductivity.

[0010] EP 0 212 940 A1 shows that metal chlorides are particularly well suited for intercalation doping if they have a low sublimation or boiling point. Therefore, EP0212940 uses aluminum chloride, which has a low sublimation point of 180°C, to intercalate other metal chlorides with a higher sublimation or boiling point into the graphite more quickly and at lower temperatures.

[0011] Another disadvantage of the current state of the art is that, as shown by Matsumoto et al. (Matsumoto, K., Minori, D., Takagi, K., & Hagiwara, R. (2014), Expansion of tetrachloroaluminate-graphite intercalation compound by reaction with anhydrous hydrogen fluoride. Carbon, 67, 434-439), fluorination of graphite intercalated with metal chloride with anhydrous hydrofluoric acid (HF) leads to the formation of gases in the graphite, causing the graphite to expand. This would also lead to the expansion and thus destruction of the conductors.

[0012] Another possibility for doping is shown in WO 2021 / 128495 A1 .

[0013] Disclosure of the invention

[0014] The invention allows intercalation of intercalating substances, particularly metal fluorides, into carbon conductors, particularly graphene films or graphite films, without the use of fluorine gas, solely through liquid-phase intercalation. The interaction with the also intercalated solvent can result in a further increase in electrical conductivity.

[0015] The process is used to produce an electrically conductive conductor strand.

[0016] The conductor strand comprises at least one carbon conductor. The method comprises the steps explained below. First, a first step a) is carried out to produce or provide a conductor strand as an intermediate product comprising at least one carbon conductor. The carbon conductor comprises, in particular, graphite, pyrolytic graphite, graphene, graphyne, and / or carbon nanotubes.

[0017] A second step b) is then carried out to dissolve at least one intercalation substance in a solvent. The intercalation substance is suitable for intercalation into the material of the at least one carbon conductor of the conductor strand. The solvent is suitable for dissolving the intercalation substance. Thus, a solution is created in which the intercalation substance is dissolved.

[0018] Finally, the third step (c) involves immersing the conductor strand in the solvent containing the dissolved intercalation substance for a predefined period of time at a specific temperature. The temperature is preferably a temperature greater than 0°C and less than the boiling point of the solvent. This initiates an intercalation process in which atoms or molecules of the intercalation substance are incorporated into the material of the respective carbon conductor. In particular, the intercalation substance attaches to a carbon structural form of the carbon conductor, preferably in an intermediate region between the layers of a multilayer carbon structural form.

[0019] The process enables an increase in the electrical conductivity of carbon conductors, such as graphene or graphite conductors, through liquid-phase intercalation of intercalating agents, which are very strong Lewis acids. For this purpose, the intercalating agent is dissolved in a suitable solvent. If the film is immersed in this solution and stored for a defined period of time at a defined temperature, at least a portion of the intercalating agent and, if applicable, the solvent, intercalates from the solution.

[0020] The advantage over the known method lies in the fact that many intercalation substances, such as metal halides, which, due to their pronounced Lewis acidity, can increase the electrical conductivity of carbon conductors, especially graphene and graphite films, to values ​​of more than 50 MS / m after intercalative doping, can only be intercalated using this process. Furthermore, the process makes it possible to intercalate such intercalation substances without damaging the carbon conductor, especially the graphene or graphite conductor.

[0021] It is intended that a sequential intercalation of different intercalation substances takes place. For this purpose, the second step b) and the third step c) are carried out sequentially for different intercalation substances and solvents. In this way, different intercalation substances are sequentially intercalated into the carbon conductor material of the conductor strand. The sequential intercalations are carried out, in particular, from different solvents. The intercalation causes the intercalant to not be evenly distributed in the interlayer spaces between the graphene layers. Rather, there is a regular distance between the interlayer spaces filled with intercalant and the empty interlayer spaces. If only every second interlayer space is occupied, this corresponds to level 2, and if only every third interlayer space is occupied, this corresponds to level 3.The individual intercalations preferably occur up to the same stage or up to compatible stages. For example, the sequential intercalation of different metal fluorides is possible. This means that a first metal fluoride is intercalated at a specific stage, followed by another metal fluoride at the same stage or at a stage compatible with the previous occupancy state of the intermediate region. This preferably exploits the fact that the metal fluorides used do not dissolve in the same solvent, so that first one metal fluoride is intercalated from one solvent and then the other metal fluoride from the other solvent.

[0022] Sequential intercalation enables higher electrical conductivities because advantageous properties can be combined without mutual interaction, as would occur with co-intercalation. For example, a metal fluoride that improves the interlayer conductivity between the carbon layers and a metal fluoride that improves the in-plane electrical conductivity can be spatially separated from each other in the carbon conductor, especially graphene or graphite conductors.

[0023] The subclaims describe preferred developments of the invention. The intercalation substance is preferably a metal fluoride. Metal fluorides exhibit high Lewis acidity and are advantageous in terms of high electrical conductivities. The intercalation substance is particularly preferably a pentafluoride, in particular BiFs or NbFs or TaFs, or a tetrafluoride, in particular SnF4 or VF4 or ZrF4 or TiF4 or NbF4.

[0024] In a preferred embodiment, the solvent comprises a superacid. This is particularly fluorosulfonic acid or trifluoromethanesulfonic acid. This leads to dissolution of the intercalation substance.

[0025] In a further preferred embodiment, the solvent comprises an organic solvent. This is, in particular, acetonitrile. Organic solvents also allow dissolution of the intercalation agent.

[0026] An oxidizing agent is preferably added to the organic solvent. This accelerates the intercalation process. The oxidizing agent is typically xenon difluoride or trichloroisocyanuric acid.

[0027] In a further preferred embodiment, the solvent comprises a mineral acid. The mineral acid is, in particular, nitric acid. Mineral acid also dissolves the intercalation substance.

[0028] Intercalation preferably occurs exclusively from the liquid phase. Therefore, the use of fluorine gas or similar is not necessary. This minimizes the risk of damage to the conductor strand. Intercalation from the gas phase is preferably avoided. Nevertheless, high electrical conductivities of the conductor strand are achieved through intercalation.

[0029] In the second step b), the intercalant is completely dissolved. Thus, the entire intercalant is present in solution. Since intercalation occurs primarily from the liquid phase, a sufficient amount or concentration of the intercalant is present to achieve optimal intercalation.

[0030] Preferably, in the third step c), the conductor strand is completely covered by a liquid film of the solvent containing the dissolved intercalation substance. Thus, optimal intercalation is achieved. In particular, intercalation can occur from all sides of the conductor strand, ensuring uniform deposition of the intercalation substance in the intermediate regions.

[0031] Short description of the drawings

[0032] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing:

[0033] Figure 1 is a schematic representation of a conductor strand that can be produced using a method according to an embodiment of the invention,

[0034] Figure 2 shows a schematic cross section through the conductor strand from

[0035] Figure 1 , which is in a solvent with dissolved intercalant, and

[0036] Figure 3 is a schematic representation of the intercalation during a

[0037] Heat treatment within the scope of the method according to an embodiment of the invention.

[0038] Embodiments of the invention

[0039] Preferably, all identical components, elements and / or units in all figures are provided with the same reference numerals.

[0040] To carry out the method according to the invention, at least one conductor strand 1 is provided or produced as an intermediate product in a first step. This conductor strand 1 is a conductor composite, for example a yarn, which is composed, for example, of a plurality of carbon conductors 3, wherein the carbon conductor 3 can each be a conductor film, a filament, or a fiber. Alternatively, the carbon conductors 3 can also be yarns or conductor composites with a smaller diameter than the conductor strand 1. The carbon conductors 3 are made of a carbon material such as graphite, pyrolytic graphite, graphene, graphine, and / or carbon nanotubes, or of compounds based thereon, for example graphene oxide. Figure 1 schematically shows such a conductor strand 1, which has at least one carbon conductor 3.

[0041] In a second step of the method, at least one intercalation substance 2 is dissolved in a solvent 5. The intercalation substance 2 is selected such that it is suitable for intercalation into the material of the at least one carbon conductor 3 of the conductor strand 1.

[0042] In a third step, the conductor strand 1 is immersed in the solvent 5 containing the dissolved intercalation substance 2. This is shown schematically in Figure 2. The immersion takes place for a predefined period of time to initiate an intercalation 100, during which atoms or molecules of the intercalation substance 2 are incorporated into the material of the respective carbon conductor 3, for example, they are deposited onto a carbon structural form of the carbon conductor 3, e.g., in the intermediate region 4 between the layers of a multilayer carbon structural form. The intercalation 100 takes place at a process temperature above 0°C and below the boiling temperature of the solvent 5.

[0043] Figure 3 schematically shows a basic process of intercalation 100, showing, by way of example, how the intercalation substance 2 intercalates into intermediate layers 4 of the carbon material, formed in the example from graphene, of the at least one carbon conductor 3 of the conductor strand 1. Figure 3 shows various stages of intercalation 100, in which different amounts of the intercalation substance 2 are intercalated into the carbon material of the carbon conductor 3.

[0044] Various embodiments are provided for the intercalation substances 2 and the solvent 5, which are described below as three different examples. According to the invention, the intercalation substances 2 can be a metal fluoride, in particular a pentafluoride such as, for example, BiFs or NbFs or TaFs, or a tetrafluoride such as, for example, SnF4 or VF4 or ZrF4 or TiF4 or NbF4. The solvent 5 used can, in particular, be a superacid such as, for example, fluorosulfonic acid or trifluoromethanesulfonic acid. It can also be an organic solvent such as, for example, acetonitrile. An oxidizing agent such as, for example, xenon difluoride or trichloroisocyanuric acid is preferably added to the organic solvent. Furthermore, the solvent 5 can be a mineral acid such as, for example, nitric acid.

[0045] Example 1 :

[0046] 150 mg of BiFs as intercalant 2 are weighed into 4 ml of fluorosulfonic acid as solvent 5 in a glove box. After 24 hours, the BiFs has completely dissolved. A graphite film measuring 50 x 50 mm is placed into this solution, forming the conductor strand 1. 2 with a film thickness of 25 pm, so that the liquid level is above the graphite film. Intercalation 100 occurs, in which the BiFs from the solution is incorporated into the material of the graphite film. After 72 hours, the graphite film is removed from the solution and blotted with a paper towel to absorb the excess solution.

[0047] Example 2:

[0048] 170 mg of TiF4 as intercalant 2 and 80 mg of XeF2 as oxidant are weighed into 5 ml of acetonitrile in a glove box. After 72 h, the fluorides, i.e., intercalant 2 and the oxidant, have completely dissolved. A 50 x 50 mm graphite film, forming conductor strand 1, is placed into this solution. 2 with a film thickness of 25 pm, so that the liquid level is above the graphite film. Intercalation occurs, in which the TiF4 from the solution is incorporated into the material of the graphite film. This intercalation is accelerated by the oxidizing agent. After 48 hours, the film is removed from the solution and blotted with a paper towel to absorb the excess solution.

[0049] Example 3:

[0050] A sequential intercalation 100 of two different intercalation substances 2 is carried out. For this purpose, the fluorides such as TiF4 and NbF5 are used as intercalation substances 2 as follows. First, 65 mg of TiF4 as the first intercalation substance 2 and 80 mg of XeF2 as the oxidizing agent are weighed into 5 ml of acetonitrile as the solvent 5 in a glove box. After 72 hours, the fluorides, i.e. the first intercalation substance 2 and the oxidizing agent, have completely dissolved. A graphite film of 50 x 50 mm in size, forming the conductor strand 1, is placed in this solution. 2 with a film thickness of 25 pm, so that the liquid level is above the graphite film. After 48 hours, the film is removed from the solution and blotted with a paper towel to remove the excess solution. The graphite film is thus intercalated with TiF4 in stage 4.

[0051] Next, 75 mg of NbFs as the second intercalant 2 is weighed into a glove box in 5 ml of fluorosulfonic acid as solvent 5. After 24 hours, the NbFs has completely dissolved. The 50 x 50 mm graphite film, which has already been intercalated with TiF4 in stage 4, is placed into this solution. 2 and a film thickness of 25 pm, so that the liquid level is above the graphite film. After 72 hours, the film is removed from the solution and blotted with a paper towel to absorb the excess solution. This results in a graphite film sequentially intercalated with two different fluorides.

Claims

Claims 1 . Method for producing an electrically conductive conductor strand (1) comprising at least one carbon conductor (3), comprising the steps of: a) producing or providing a conductor strand (1) as Intermediate product comprising at least one carbon conductor (3), which in particular comprises graphite, pyrolytic graphite, graphene, graphine and / or carbon nanotubes, b) dissolving at least one intercalation substance (2) in a solvent (5), wherein the intercalation substance (2) is suitable for intercalation into the material of the at least one carbon conductor (3) of the conductor strand (1), c) placing the conductor strand (1) in the solvent (5) with the dissolved intercalation substance (2) for a predefined period of time and at a specific temperature to initiate an intercalation (100), in which atoms or molecules of the intercalation substance (2) are incorporated in the material of the respective carbon conductor (3), in particular are deposited on a carbon structural form of the carbon conductor (3), in particular in an intermediate region (4) between the layers of a multi-layer carbon structural form,and d) sequentially repeating steps b) and c) for different intercalation substances (2) and solvents (5) in order to sequentially intercalate different intercalation substances (2) into the material of the carbon conductor (3) of the conductor strand (1).

2. Method according to one of the preceding claims, characterized in that the intercalation substance (2) is a metal fluoride, in particular a pentafluoride, preferably BiFs or NbFs or TaFs, or a tetrafluoride, preferably SnF4 or VF4 or ZrF4 or TiF4 or NbF4.

3. Method according to one of the preceding claims, characterized in that the solvent (5) comprises a superacid, in particular fluorosulfonic acid or trifluoromethanesulfonic acid.

4. Method according to one of the preceding claims, characterized in that the solvent (5) comprises an organic solvent, in particular acetonitrile.

5. The method according to claim 4, characterized in that an oxidizing agent, in particular xenon difluoride or trichloroisocyanuric acid, is added to the organic solvent (5).

6. Method according to one of the preceding claims, characterized in that the solvent (5) comprises a mineral acid, in particular nitric acid.

7. Method according to one of the preceding claims, characterized in that the intercalation (100) takes place exclusively from the liquid phase.

8. Method according to one of the preceding claims, characterized in that in step b) the intercalation substance (2) is completely dissolved.

9. Method according to one of the preceding claims, characterized in that in step c) the conductor strand (1) is completely covered by a liquid film of the solvent (5) with the dissolved intercalation substance (2).

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