WO2012013680A1 - Electrically conductive pastes having increased charge storage capacity, comprising graphite layers and layers of laminar silicates or laminar double hydroxides, and electrical capacitors produced by means of said pastes - Google Patents

Electrically conductive pastes having increased charge storage capacity, comprising graphite layers and layers of laminar silicates or laminar double hydroxides, and electrical capacitors produced by means of said pastes Download PDF

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WO2012013680A1
WO2012013680A1 PCT/EP2011/062835 EP2011062835W WO2012013680A1 WO 2012013680 A1 WO2012013680 A1 WO 2012013680A1 EP 2011062835 W EP2011062835 W EP 2011062835W WO 2012013680 A1 WO2012013680 A1 WO 2012013680A1
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electrically conductive
layers
pastes
paste according
composite material
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PCT/EP2011/062835
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German (de)
French (fr)
Inventor
Giulio Lolli
Leslaw Mleczko
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Bayer Technology Services Gmbh
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Publication of WO2012013680A1 publication Critical patent/WO2012013680A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/14—Conductive material dispersed in non-conductive inorganic material
    • H01B1/18—Conductive material dispersed in non-conductive inorganic material the conductive material comprising carbon-silicon compounds, carbon or silicon
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L33/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides or nitriles thereof; Compositions of derivatives of such polymers
    • C08L33/18—Homopolymers or copolymers of nitriles
    • C08L33/20—Homopolymers or copolymers of acrylonitrile
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/36—Nanostructures, e.g. nanofibres, nanotubes or fullerenes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein

Definitions

  • Electrically conductive pastes with increased charge storage capacity comprising graphene layers and layers of phyllosilicates or layered double hydroxides, as well as electrical capacitors produced with these pastes
  • the present invention relates to electrically conductive pastes having an increased ability to store electrical charge.
  • the pastes for this purpose comprise a composite material of graphene layers and layers of sheet silicates or layered double hydroxides.
  • the present invention relates to electrical capacitors made using the aforementioned pastes,
  • Graphenes are two-dimensional Kohienstoffkristalle, which are constructed analogous to individual graphite layers.
  • the carbon atoms are arranged in a hexagonal honeycomb structure. This arrangement results from the hybridization ("melting") of the 2s, 2px, and 2py orbitals of the participating carbon atoms to so-called sp l hybrid orbitals
  • Graphene has metallic and nonmetallic properties, and metallic properties of graphene are the good electrical and thennical conductivity.
  • the non-metallic properties provide high thermal stability, chemical inertness and lubricity of these compounds, and one way to make these properties available to engineering applications is to incorporate graphene into composite materials.
  • US2007 / 0158618A 1 describes the preparation of graphene nanocomposites by exfoliation of graphite and reduction of the resulting material with a ball mill and subsequent mixing of these graphene layers with polymers.
  • US2007 / 0092716A1 describes the preparation of a graphene composite material in which nano-sheet layers are mixed together with polymeric material and extruded in the form of fibers, for example.
  • a disadvantage of the known methods for the production of graphene composite materials is in particular the difficulty of being able to precisely adjust the thickness of the graphene layers in the composite material and to integrate graphene layers having a thickness of well below 20 nm.
  • graphene layers of such a small thickness are advantageous since they have a high specific surface area in comparison with graphite, but at the same time have a two-dimensionally ordered structure, such as graphite, which allow a fast and spatially directed movement of ions in this structure, which is useful for electrical applications high importance.
  • Graphene layers with a thickness of well below 20 nm in connection with their use in a composite material, have the advantage over graphene layers with a thickness of around 20 nm or more that the percolation threshold (substance concentration at which it directly leads to a reduction of the electrical resistance within the composite material comes) is significantly reduced.
  • the percolation threshold is less than 0.1% by weight.
  • graphene layers having a thickness of about 20 nm have been described as having percolation thresholds of 3-5% by weight [Stankovich et al. Nature, Vol. 442, July 2006].
  • graphene composite materials are present in a composite with polymer materials.
  • Polymeric materials as described in the above prior art documents are nonporous and thus do not permit movement of ions therein, so that such composite materials are little or no suitable for electrical applications and especially for charge storage.
  • Materials which appear more suitable in combination with the aforementioned graphene layers are the fillers known per se, such as layered silicates or layered double hydroxides, which in themselves have no electrical or thermal conductivity, but are available in ordered and high porosity.
  • US Pat. No. 4,921,681 describes a composite with montmorillonite (a layered silicate) and partially carbonated polyacrylonitrile as an intermediate for the production of highly oriented pyroiytic graphite (HOPG). (Grapheniagen).
  • Example 1 is carbonated for 3 hours at 700 ° C.
  • such an intermediate has a relative nitrogen content of at least 20% relative to the molecular weight of polyacrylonitrile.
  • the relative nitrogen content of polyacrylonitrile ie the starting material
  • such composite materials are not as well suited for the aforementioned inventive purposes of producing a paste having increased charge storage capability because the composite material of graphene sheets and sheets of sheet silicates or layered double hydroxides used has a relative nitrogen content of less than 20% based on the molecular weight of polyacrylonitrile should make.
  • this proportion of nitrogen content determines the thickness and spatial structure of the resulting graphene layers of the composite material.
  • That of US 4,921,681 has a HOPG structure with a significantly increased layer thickness compared to the above-mentioned desired thickness of 20 nm.
  • a suitable composite material, as well as a method for its production, is disclosed in the German patent application DE 10 2009 049 379.4.
  • Such a capacitor is described, for example, in US Pat. No. 3,652,902, in which the condenser there is composed of alternating layers of activated carbon and layers of a highly porous, non-conductive material which has been filled with a conductive, liquid material.
  • the activated carbon has a high specific surface area, activated carbon has an amorphous structure and thus leads to the fact that the charges possibly stored in their pores can only slowly permeate out of the activated carbon when the previously applied voltage is switched off.
  • the capacity of such a capacitor is severely limited in the case of rapid charge / discharge cycles because those processes can only proceed slowly.
  • An alternative capacitor is described in US 5,621,607, wherein the conductive layers of a composite material made of metal, especially aluminum, and carbon. The use of this composite material is intended in particular to allow a lightweight design of the capacitor. Otherwise, the capacitor according to US 5,621,607 again comprises an electrolyte between the layers of the aforementioned composite material.
  • an electrically conductive paste with increased charge storage capacity which is characterized in that it comprises a) between 3 and 25% by weight of a composite of i) phyllosilicate or layered double hydroxides and ii) polyacrylonitrile at least partially decomposed to graphene layers with a relative nitrogen content of less than 20% relative to the relative molecular mass of polyacrylonitrile, b) between 1 and 10% by weight at least an electrically conductive additive, and c) comprises an electrolyte solution.
  • Such a composite material has graphene layers with a thickness of significantly less than 20 nm and combines the advantages of such graphene layers (mechanical and electrical conductivity) with the advantageous properties of sheet silicates or layered double hydroxides (insulation and filler functionality) in a material.
  • Such composites also offer the advantage that the nature of the material is similar to that of phyllosilicates or layered hydroxides, meaning that these composites can also be used for known processes and methods in which phyllosilicates or layered double hydroxides are already used as starting materials.
  • the phyllosilicates usable in the paste according to the invention are the silicate structures known from the prior art with two-dimensional layers of SiQ 4 tetrahedra (also referred to as foliar or phyllosilicates),
  • Suitable phyllosilicates are bentonite, talc, pyrophyllite, mica, serpentine, kaoiinite or mixtures thereof.
  • the layer silicates can be modified by known methods to change the layer spacing. For this purpose, for example, between the layers, ammonium compounds which have at least one acid group are intercalated (see DE10351268A1).
  • the storage takes place by exchanging the cations contained in the layer lattice of the silicates by the ammonium compounds with at least one acid group and generally leads to a widening of the layer spacing.
  • Phyllosilicates, or the phyllosilicates modified by the process described above preferably have a layer spacing of 0.5 to 2.5 nm and more preferably of 0.7 to 1.5 nm.
  • Under Schichtdoppelhydroxiden refers to compounds within the scope of the present invention, the [under the general formula M 'i. x N J + x (OH) 2 ] [A n ⁇ ] x / n x y H 2 O, where M + is a divalent alkaline earth or transition metal ion such as Mg + , Ni 2+ , Cu 2 t or Zn 2+ , N 3+ is a trivalent main group or transition metal ion such as Al 3 * , Cr ' + , Fe 3 * or Ga 3+ , A n ⁇ an anion such as N0 3 " , C0 3 2 ⁇ , Cl ⁇ or S0 4 2" , x is a rational number between 0 and 1, and y is a positive number, including 0.
  • M + is a divalent alkaline earth or transition metal ion such as Mg + , Ni 2+ , Cu 2 t or Zn 2+
  • N 3+ is a trivalent main
  • layered double hydroxides also includes the oxides of these compounds.
  • Natural and synthetic hydrotalcites and compounds having a hydrotaicit-like structure are preferably used as layered double hydroxides.
  • the preparation of the hydrotalcites or of the compounds having a hydrotalcite-like structure it is possible in principle to use any process familiar to the person skilled in the art (see, for example, Handbook of Clav Science, F. Bergaya, BKG Theng and G. Lagaly, Developments in Clay Science, Vol. 1, Chapter 13.1 and Layered Double Hydroxides, C. Forano, T. Hibino, F. Leroux, C. Taviot-Gueho, Handbook of Clay Science, 2006).
  • hydrotalcites of the general (nominal) formula 2 ⁇ 2 + M 2 3 ⁇ (OH) 4X 44 ⁇ A 2 / r , n ⁇ ⁇ zH 2 O where M 2x 2+ is a divalent metal selected from is the group of Mg, Zn, Cu, Ni, Co, Mn, Ca and / or Fe and M 2 ' 1 is a trivalent metal selected from the group of Al, Fe, Co, Mn, La, Ce and / or Cr , "X" is a number from 0.5 to 10 at intervals of 0.5, A is an interstitial anion, "n” is the charge of the interstitial anion, which may be up to 8 and usually up to 4, and "z” is one natural number of 1 to 6, preferably 2 to 4 is used.
  • M 2x 2+ is a divalent metal selected from is the group of Mg, Zn, Cu, Ni, Co, Mn, Ca and / or Fe
  • M 2 ' 1 is a trivalent metal selected from the group
  • Suitable interstitial anions are usually organic anions such as alkoxides, alkyl ether sulfates, aromatic ether sulfates and / or glycol ether sulfates or inorganic anions such as carbonates, bicarbonates, nitrates, chlorides, sulfates, B (OH) 4 " and / or polyoxometallates such as Mo 7 O 2 4 b " or V ] 0 O 2 g 6" .
  • organic anions such as alkoxides, alkyl ether sulfates, aromatic ether sulfates and / or glycol ether sulfates or inorganic anions such as carbonates, bicarbonates, nitrates, chlorides, sulfates, B (OH) 4 " and / or polyoxometallates such as Mo 7 O 2 4 b " or V ] 0 O 2 g 6" .
  • Preferred interstitial anions are C0 3 2 " and N0 3 " .
  • the corresponding metal oxide which can be obtained by calcining and can be present in the composite material of the paste according to the invention, has the general formula M 2x 2+ ⁇ 2 3+ (0) (4 ⁇ 4) / 2, where M is 2x 2+ , M 2 3 + and "x" have the same meaning as described above.
  • composite materials with Schichtdoppeihvdroxiden are preferably used.
  • composite materials with hydrotalcites which have a layer spacing of 0.5 to 2.5 nm and preferably of 0.7 to 1.5 nm.
  • the layer spacing can be artificially increased as in the layer silicates by using suitable intercalating agents.
  • anions such as, for example, 3-aminobenzenesulfonic acid, 4-toluenesulfonic acid monohydrate, 4-hydroxybenzenesulfonic acid, dodecylsulfonic acid and terephthalic acid are suitable for this purpose.
  • Other anions are familiar to the person skilled in the art.
  • the anions are used exclusively for modifying the layers of the layered double hydroxides. They decompose during the manufacturing process of the composite materials in the thermal treatment.
  • Particularly suitable hydrotalcites are marketed by the company Sasol Deutschland GmbH under the brand name Pural.
  • the layers of the layered silicate or the layered double hydroxides mainly contain graphene layers which are formed by polymerization and calcination of acrylonitrile during the production process of the composite material.
  • HOPG highly oriented pyrolytic graphite
  • This intermediate has a relative nitrogen content of at least 20% relative to the molecular weight of polyacrylonitrile.
  • the relative nitrogen content of polvacrylonitrile i.e., the starting material) is 26%.
  • the composite material used in the paste of the invention differs in that the relative nitrogen content is less than 20%, preferably less than 15%, more preferably equal to or less than 10%, even more preferably equal to or less than 5%, and even more preferably equal to or less than 3% based on the molecular weight of polyacrylonitrile.
  • the composite material used in the paste according to the invention in this case has no HOPG structure, but rather has a graphene sheet structure with a layer thickness of 0.5 to 2.5 nm.
  • the calculation of the nitrogen mass fraction can be carried out by the known and established standard method ICP-MS (mass spectrometry with inductively coupled plasma), for example, by a DIN ISO 17025 certified analytical laboratory.
  • the relative proportion by weight of nitrogen relative to the molecular weight of polyacrylonitrile can be 20% or even more than 20%.
  • the above preferred values for the relative proportions by weight of nitrogen are also preferred in this case.
  • the reduction of the relative nitrogen content in the composite material of the paste according to the invention is achieved by correspondingly increasing the calcining temperature. For example, to obtain a nitrogen content of equal to or less than 10%, calcination at 1000 ° C. for at least 40 minutes, preferably at least 90 minutes and more preferably at least two hours in a conventional heating furnace is necessary (taking into account the maximum loading capacity of the stove)
  • polyacrylonitrile at least partially decomposed into graphene layers describes the carbonization of polyacrylonitrile to graphene layers by the above described calcination step partially decomposed polyacrylonitrile in the composite.
  • the temperature has a direct influence on the carbon - nitrogen ratio.
  • the thermal treatment must be carried out for a certain period of time, so that as far as possible all compounds to be removed can be passed via diffusion to the outside (outside the composite material) and the compounds within the composite material can rearrange to an equilibrium state.
  • At least for a period of 10 minutes preferably at least 40 minutes and more preferably at least 90 minutes must be calcined in a conventional heating oven or at least 5 minutes and more preferably at least 45 minutes in a microwave oven.
  • the decomposition process of polyacrylonitrile to graphene layers is known.
  • Degradation products which are formed by the decomposition of polyacrylonitrile are, for example, ikN 2 , MI and HCN.
  • a preferred embodiment of the invention relates to a paste with a composite material in which the polyacrylonitrile has decomposed to 95%, preferably 98%, more preferably 99% and most preferably completely to graphene layers.
  • the calcination step is preferably carried out under an inert atmosphere (argon or nitrogen and preferably Ar) and at atmospheric pressure.
  • the term "calcination” is generally understood to mean a thermal treatment step, ie heating of a material with the aim of decomposing it
  • the material which is to be decomposed into graphene layers is polyacrylonitrile according to the invention.
  • graphene layer is understood to mean two-dimensional carbon crystals which are constructed analogously to individual graphite layers and whose carbon atoms are arranged in a hexagonal honeycomb structure with the formation of sp 2 hybrid orbitals.
  • a single graphene layer has a layer thickness of 0.335 nm.
  • a layer spacing of the layered silicates or layered double hydroxides of preferably 0.5 to 2.5 nm 1 to 7 graphene layers can therefore be located within a single layer.
  • the paste according to the invention in preferred embodiments between 5 and 25% by weight, particularly preferably between 5 and 10 wt .-%, most preferably between 5 and 7 wt .- " ⁇ > of the composite material.
  • the limitation of the inventive proportion of Verbundmateriai in the paste down is advantageous because from this amount of the composite material in the paste according to the invention, its advantageous charge storage ability in the paste emerges particularly noticeable.
  • the limitation upwards is advantageous because it has surprisingly been found that an increase up to that point is still advantageous compared to the previously known state of the art, but beyond that the advantageousness decreases again.
  • the electrolytic solution present in the paste in accordance with the invention is any or all of the liquid or mixture of substances which under ambient conditions (1013 hPa, 23 ° C) comprises ions.
  • the electrolyte solution is intended to ensure and / or improve the electrical conduction in the paste.
  • electrolyte solutions are, for example, aqueous solutions of salts, acids or bases.
  • aqueous solutions of salts, acids or bases are, for example, solutions of alkali metal and / or alkaline earth metal hydroxides, alkali metal and / or alkaline earth metal halides and halogenated hydrogen, etc., in water.
  • a so-called ionic liquid can also be used as electrolyte solution. Ionic liquids are generally known to the person skilled in the art and are comprehensively described, for example, in WO 2005/016483 A1.
  • the paste according to the invention also comprises between 1 and 10% by weight of at least one electrically conductive additive.
  • this additive also serves, for example, to change the viscosity and / or other physical properties of the paste.
  • the at least one additive is present in the paste according to the invention preferably in a proportion of 2 to 8 wt .-%, more preferably, in a proportion of 5 to 7 wt .-% before.
  • the additives can also further improve their charge storage capability. However, this is not essential to the present invention. Even without the abovementioned additives, the paste according to the invention is already characterized by a charge storage capacity that is considerably greater than those of prior art materials.
  • the presence of the electrically conductive additives only leads to the full utilization of the charge storage potential of the composite materials contained in the paste according to the invention, as they transport the charges to be stored correspondingly faster to the storage location.
  • additives are those Selected from the list consisting of activated carbon, carbon nanotubes (the person skilled in the art also known under the name carbon nanofibers or other names), metal nanofibers or metal nanowires as the skilled person generally knows electrically conductive polymers.
  • a particularly preferred aggregate are carbon nanotubes (both so-called “single-walled carbon nanotubes”, as well as so-called “multi-walled carbon nanotubes”). These are particularly advantageous because they make a significant contribution to the electrical conductivity of the same in addition to a significant increase in the viscosity of the paste. In addition, pastes according to the invention with the additive carbon nanotube also show a still further improved charge storage capability.
  • a proportion of the composite material in the upper region of the inventive 5 to 25 wt .-% can be dispensed with the addition of an aggregate to increase the viscosity.
  • the paste of the invention is particularly advantageous because it has surprisingly been found that it combines a number of positive properties in itself, which makes them particularly suitable for use in the production of electrical capacitors.
  • the electrolyte Due to the high porosity of the individual materials of the composite material, on the one hand, the electrolyte is absorbed by the capillary forces into the voids of the composite material and remains there without further precautionary measures. This is especially advantageous, for example, when corrosive electrolytes are to be used.
  • the paste according to the invention which then comprises the composite material soaked in electrolyte, upon application of a voltage to a concentration (depending on the polarization of the voltage) of charges of the same name on the surfaces of the graphene layers of the composite material, since these interspersed between the respective layered silicates or layered double hydroxides are polarized relative to the surrounding electrolyte. This also results in the particularly high charge storage capacity of the paste according to the invention.
  • Another advantage of the paste according to the invention is that it can deliver the aforementioned stored charges again very quickly when the voltage is removed, which leads to the predestined use for the production of a capacitor.
  • both materials layered silicates or layered double hydroxides
  • graphene layers have a high specific surface area and porosity, so that the charge mobility is very high, and secondly and essentially different from prior art composite materials, the voids of the materials (porosity) are characterized by a low tortuosity, so that not only the theoretical specific surface is very high, but also the readily available specific surface area is similarly high.
  • Low tortuosity in the context of the present invention, refers in particular to the property of the materials that they have spatially ordered pores which, in particular, are largely accessible from the outer surface of the materials (no "dead spaces").
  • the small thickness of the graphene layers in the composite material of the paste according to the invention means that rapid transport of the stored charges to the outside can take place.
  • the paste according to the invention is therefore particularly suitable as a material for the production of electrodes of a capacitor, especially as it can also be used in a particularly extensive manner as a paste, since it is particularly variable with regard to the shaping of the electrodes of a condenser.
  • a further subject of the present invention is accordingly a capacitor comprising two electrodes of the paste according to the invention and a dielectric located between these two electrodes.
  • the dielectric may be any substance whose dielectric constant is greater than that of the paste.
  • the electrolyte solution as described above may be the dielectric.
  • the dielectric is at the same time a means which prevents the physical contact between the two electrodes from the paste according to the invention.
  • the dielectric comprises a porous membrane.
  • the dielectric is a porous membrane whose pore volume is filled with an electrolyte solution.
  • Fig. 1 shows the schematic structure of a capacitor according to the invention, as it was also used as a test system for Example 6.
  • each denotes a nickel sheet
  • each a Teflon disk with a central hole, as described in more detail in Example 4 and 5, (3) a membrane for separating the two capacitor surfaces (4).
  • FIG. 2 shows the specific capacitance (F s ) in farads per gram of carbon [F / gc] per electrode of the capacitor, plotted against the sampling rate (A) of the cyclic voltammetry in millivolts per second [mV / s].
  • a sampling rate of 250 mV / s corresponds to a complete charging and discharging cycle of a capacitor within four seconds
  • a sampling rate of 100 mV / s to a complete charging and discharging cycle of a capacitor within ten seconds
  • FIG. 3 shows a transmission electron micrograph of the composite material present in the paste according to the invention. Shown are also the dimensions of the two graphene layers (A, C) and the interposed layer of a layered silicate or layered double hydroxide (B). The dimensions are A ⁇ 3.9 nm, B ⁇ 4.8 nm and C ⁇ 2.9 ran.
  • hydrotalcite material plural MG 63 ABSA with a layer spacing of 1.7 nm from Sasol Deutschland GmbH were dried in an oven at 70 ° C. in order to reduce excess moisture.
  • This hydrotalcite material by weight has a nominal chemical composition on 63.% MgO and 37 wt.% A1 2 0 3, packaged in a layered structure with 0.7 nm spacing between the individual layers.
  • meta-aminobenzenesulfonic acid was added during the preparation of the hydrotalcite.
  • This powder was then placed in a sealable container and heated in an oven for 3 hours at 70 ° C.
  • the polymerization initiator degraded during the process. Due to the polymerization, the color of the material changed from white to a pale yellow. Thereafter, the furnace temperature was raised to 300 ° C. During this step, the polyacrylonitrile was crosslinked.
  • the resulting polyacrylonitrile / hydrotalcite composite was dark brown.
  • the polyacrylonitrile was then carbonized in a quartz oven at 1000 ° C under argon flow. The material was left at these temperatures for two hours. This resulted in a verb ndmaterial of graphene layers and hydrotalcite, which appeared dark gray due to its carbon content.
  • Example 2 Preparation of a first paste according to the invention
  • the paste according to the invention was prepared by mixing the composite material from Example 1 (composition ca, 13.9% C 1.9% N 84.2% MgA10 x , with about 200 mg BET surface area) with an electrolyte (20% KOH solution in water) and carbon nanotubes ( Bayer Material Science, type Baytubes® C150P) was mixed as an aggregate.
  • the mixture was composed of 1 g of Verbundmateriais according to Example 1, 600 mg of carbon nanotubes as an aggregate and 8.4 g of a 20% aqueous KOH solution together. The mixture was sonicated for better dispersion of the solids in the KOH solution. A dark, highly viscous paste was obtained.
  • Example 3 Preparation of a Second Paste According to the Invention The procedure was analogous to Example 2, with the sole difference that now not 1 g of the composite material and 8.4 g of a 20% aqueous KOH solution were used, but only 600 mg of the Composite material and 8.8 g of a 20% aqueous KOH solution were used.
  • Examples 4 and 5 Producing Capacitors According to the Invention
  • the paste of Examples 2 and 3 was applied to a flat nickel metal electrode of 7 ⁇ 7 cm and 3 mm thickness by applying to the abovementioned nickel metal electrode a Teflon disc (also 7 ⁇ 7 cm) having a thickness of 1 mm was placed with a center hole of diameter 16 mm, in the middle of the aforementioned hole, the aforementioned paste was introduced and coated with a doctor blade over the Teflon disk to remove excess paste. This resulted in an electrode of 16 mm diameter paste electrically contacted via the nickel metal electrode. The volume of the paste was thus about 0.2 cm 3 each.
  • the electrode had a carbon content of about 10 mg / cm 2 .
  • Example 5 The capacitor prepared from the paste according to Example 2 is hereinafter Example 5, while that made from the paste according to Example 3, hereinafter Example 4 forms. In the manner described above, a second electrode was also prepared.
  • the two electrodes produced in this way were each sedimented on one side onto a glass fiber membrane (# 13400-42, 42 mm diameter, Sartorius AG, Göttingen) as a porous separating layer.
  • the glass fiber membrane was previously impregnated with the KOH solution, which was also used in the course of the preparation of the paste according to Example 2.
  • the function of the fiberglass membrane was merely to space the electrodes.
  • the actual dielectric was the aforementioned KOH solution.
  • FIG. 1 A schematic view of the capacitor structure is shown in FIG. 1.
  • a paste was prepared analogously to Example 2, with the only difference that of 1 g of composite material according to Example 1 now 1 g of carbon black from Norit type RB4 was used.
  • a paste was prepared analogously to Example 2, with the only difference being that 1 g of compound according to Example 1 now contains 0.1 g of exfoliated graphene (from Angstron Materials LLC, Nano Graphene Platelets (NGPs), type: N008-100 ) has been used.
  • exfoliated graphene from Angstron Materials LLC, Nano Graphene Platelets (NGPs), type: N008-100 ) has been used.
  • a paste was prepared analogously to Example 2, with the only difference that 1 g of carbon nanotubes from Bayer Material Science Baytubes® C 150P from 1 g of composite material was used.
  • Comparative Example 4 thus corresponds to a capacitor prepared with the paste according to Comparative Example 1
  • Comparative Example 5 thus corresponds to a capacitor prepared with the paste according to Comparative Example 2
  • Comparative Example 6 thus corresponds to a capacitor prepared with the paste according to Comparative Example 3.
  • Example 6 Capacity of the capacitors
  • the capacitor according to Examples 4 and 5, and the capacitors according to Comparative Examples 4-6 were examined by cyclic voltammetry (from 0 to 1 V). In addition, their cyclic discharge capacity was determined as part of these cyclic voltammetric tests to determine their effective capacity. Cyclic voltammetry was performed at sampling rates of 250 mV / s to 2 mV / s. The sampling rate of 250 mV / s was equivalent to a full charge / discharge cycle in four (4) seconds, simulating very demanding working conditions.
  • High and low sampling rate measurements allowed the determination of the effect of porosity and mass transfer limitations on capacitance.
  • An ideal system would have a constant capacity at each sampling rate, while high tortuosity microporous systems would have a significant decrease in capacity at high sampling rates.
  • the absolute capacity of the system at ideal (very slow) sampling rates would be the higher the higher the specific surface area of the electrode system.

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Abstract

The invention relates to electrically conductive pastes having an increased capacity for storing electrical charge. Said pastes comprise for said purpose a composite material made of graphite layers and layers of laminar silicates or laminar double hydroxides. The invention further relates to electrical capacitors produced using said pastes.

Description

„ i .  "I.
Elektrisch leitfähige Pasten mit erhöhter Ladungsspeicherfähigkeit umfassend Graphenlagen und Lagen aus Schichtsilikaten oder Schichtdoopelhydroxide, sowie mit diesen Pasten hergestellte elektrische Kondensatoren Electrically conductive pastes with increased charge storage capacity comprising graphene layers and layers of phyllosilicates or layered double hydroxides, as well as electrical capacitors produced with these pastes
Die vorliegende Erfindung betrifft elektrisch leitfähige Pasten mit einer erhöhten Fähigkeit zur Speicherung elektrischer Ladung, Die Pasten umfassen hierfür ein Verbundmaterial aus Graphenlagen und Lagen aus Schichtsilikaten oder Schichtdoppelhydroxiden. Des Weiteren betrifft die vorliegende Erfindung elektrische Kondensatoren, hergestellt unter Verwendung der vorgenannten Pasten, The present invention relates to electrically conductive pastes having an increased ability to store electrical charge. The pastes for this purpose comprise a composite material of graphene layers and layers of sheet silicates or layered double hydroxides. Furthermore, the present invention relates to electrical capacitors made using the aforementioned pastes,
Graphene sind zweidimensionale Kohienstoffkristalle, die analog zu einzelnen Graphitschichten aufgebaut sind. Die Kohlenstoffatome sind in einer hexagonalen Honigwaben-Struktur angeordnet. Diese Anordnung resultiert aus der Hybridisierung („ erschmelzung") der 2s-, 2px- und 2py- Orbitaie der beteiligten Kohlenstoffatome zu sogenannten spl- Hybridorbitalen. Graphen hat metallische und nichtmetallische Eigenschaften. Metallische Eigenschaften von Graphen sind die gute elektrische und thennische Leitfähigkeit. Die nichtmetallischen Eigenschaften bewirken eine hohe thermische Beständigkeit, chemische Trägheit und Schmierfähigkeit dieser Verbindungen. Eine Möglichkeit diese Eigenschaften technischen Applikationen zugänglich zu machen ist es, Graphen in Verbundmaterialien zu integrieren. Graphenes are two-dimensional Kohienstoffkristalle, which are constructed analogous to individual graphite layers. The carbon atoms are arranged in a hexagonal honeycomb structure. This arrangement results from the hybridization ("melting") of the 2s, 2px, and 2py orbitals of the participating carbon atoms to so-called sp l hybrid orbitals Graphene has metallic and nonmetallic properties, and metallic properties of graphene are the good electrical and thennical conductivity. The non-metallic properties provide high thermal stability, chemical inertness and lubricity of these compounds, and one way to make these properties available to engineering applications is to incorporate graphene into composite materials.
Stankovich et al. [Nature, Vol. 442, July 2006] beschreiben die Hersteilung eines Graphen Verbundmaterials durch Exfoliation von Graphit und die Dispergierung von einzelnen, chemisch modifizierten Graphenlagen in Polystyrol. Stankovich et al. [Nature, Vol. 442, July 2006] describe the preparation of a graphene composite by exfoliation of graphite and the dispersion of individual, chemically modified graphene layers into polystyrene.
US2007/0158618A 1 beschreibt die Herstellung von Graphen Nanoverbundmaterialien durch Exfoliation von Graphit und Verkleinerung des daraus resultierenden Materials mit einer Kugelmühle und anschließender Vermischung dieser Graphenlagen mit Polymeren. US2007 / 0158618A 1 describes the preparation of graphene nanocomposites by exfoliation of graphite and reduction of the resulting material with a ball mill and subsequent mixing of these graphene layers with polymers.
US2007/0092716A1 beschreibt die Herstellung eines Graphen Verbundmaterials, bei dem Nanographenlagen zusammen mit polymerem Material vermischt und beispielsweise in Form von Fasern extrudiert werden. US2007 / 0092716A1 describes the preparation of a graphene composite material in which nano-sheet layers are mixed together with polymeric material and extruded in the form of fibers, for example.
Ein Nachteil der bekannten Verfahren zur Hersteilung von Graphen Verbundmaterialien ist insbesondere die Schwierigkeit die Dicke der Graphenlagen im Verbundmaterial genau einstellen zu können und Graphenlagen zu integrieren, die eine Dicke von deutlich unter 20 nm aufweisen. Graphenlagen einer solchen geringen Dicke sind aber vorteilhaft, da diese im Vergleich zum Graphit eine hohe spezifische Oberfläche aufweisen, zugleich aber wie Graphit eine zweidimensional geordnete Struktur aufweisen, die eine schnelle und räumlich gerichtete Bewegung von Ionen in dieser Struktur erlauben, was für elektrische Anwendungen von hoher Wichtigkeit ist. Graphenlagen mit einer Dicke von deutlich unter 20 nm haben im Zusammenhang mit ihrer Verwendung in einem Verbundmaterial gegenüber Grapheniagen mit einer Dicke von um die 20 nm oder darüber daher den Vorteil, dass die Perkolationsschwelle (Stoffkonzentration bei der es unmittelbar zu einer Reduktion des elektrischen Widerstands innerhalb des Verbundmaterials kommt) deutlich erniedrigt wird. Im Falle der Verwendung von einzelnen Graphenlagen (0,335 nm) liegt die Perkolationsschwelle bei weniger als 0, 1 Gew.%. Im Vergleich dazu sind bei der Verwendung von Graphenlagen mit einer Dicke von um die 20 nm Perkolationsschwellenwerte von 3-5 Gew.% beschrieben worden [Stankovich et al. Nature, Vol. 442, July 2006]. A disadvantage of the known methods for the production of graphene composite materials is in particular the difficulty of being able to precisely adjust the thickness of the graphene layers in the composite material and to integrate graphene layers having a thickness of well below 20 nm. However, graphene layers of such a small thickness are advantageous since they have a high specific surface area in comparison with graphite, but at the same time have a two-dimensionally ordered structure, such as graphite, which allow a fast and spatially directed movement of ions in this structure, which is useful for electrical applications high importance. Graphene layers with a thickness of well below 20 nm, in connection with their use in a composite material, have the advantage over graphene layers with a thickness of around 20 nm or more that the percolation threshold (substance concentration at which it directly leads to a reduction of the electrical resistance within the composite material comes) is significantly reduced. In the case of using individual graphene layers (0.335 nm), the percolation threshold is less than 0.1% by weight. By comparison, graphene layers having a thickness of about 20 nm have been described as having percolation thresholds of 3-5% by weight [Stankovich et al. Nature, Vol. 442, July 2006].
Ein weiterer Nachteil der Graphen Verbundmateriaiien gemäß den vorstehenden Dokumenten des Standes der Technik ist, dass diese in einem Verbund mit Polymermaterialien vorliegen. Polymermaterialien, wie sie in den vorstehenden Dokumenten des Standes der Technik beschrieben sind, sind nicht porös und erlauben demnach keine Bewegung von Ionen in diesen, so dass solche Verbundmateriaiien für elektrische Anwendungen und insbesondere zur Ladungsspeicherung nur wenig oder gar nicht geeignet sind. Materialien, die im Verbund mit vorgenannten Grapheniagen geeigneter erscheinen, sind die an sich bekannten Füllstoffe wie Schichtsilikate oder Schichtdoppelhydroxide, die an sich keine elektrische oder thermische Leitfähigkeit aufweisen, aber in geordneter und hoher Porosität erhältlich sind. Another disadvantage of the graphene composite materials according to the prior art documents mentioned above is that they are present in a composite with polymer materials. Polymeric materials as described in the above prior art documents are nonporous and thus do not permit movement of ions therein, so that such composite materials are little or no suitable for electrical applications and especially for charge storage. Materials which appear more suitable in combination with the aforementioned graphene layers are the fillers known per se, such as layered silicates or layered double hydroxides, which in themselves have no electrical or thermal conductivity, but are available in ordered and high porosity.
Die US 4,921 ,681 beschreibt als Zwischenprodukt zur Herstellung von Hoch-Orientiertem Pyroiytischem Graphit (HOPG) ein Verbundmaterial mit Montmorillonit (ein Schichtsilikat) und teilsweise karbonisiertem Polyacrylnitri! (Grapheniagen). US Pat. No. 4,921,681 describes a composite with montmorillonite (a layered silicate) and partially carbonated polyacrylonitrile as an intermediate for the production of highly oriented pyroiytic graphite (HOPG). (Grapheniagen).
In Beispiel 1 wird für 3 Stunden bei 700°C karbonisiert. Gemäß dem Stand der Technik (siehe Peter Morgan, Carbon fibers and their composites: Vol. 27; CRC Pres, 2005; S. 2235) hat ein solches Zwischenprodukt einen relativen Stickstoffmassenanteil von mindestens 20% bezogen auf die relative Molekülmasse von Polyacrylnitril. Der relative Stickstoffmassenanteil von Polyacrylnitril (d.h. dem Ausgangsmaterial) Siegt bei 26%. Wie im Rahmen der vorliegenden Erfindung gezeigt werden wird, eignen sich solche Verbundmaterialien aber nicht so gut für die vorgenannten erfindungsgemäßen Zwecke der Herstellung einer Paste mit erhöhter Ladungsspeicherfähigkeit, weil das hierin verwendete Verbundmaterial aus Graphenlagen und Lagen aus Schichtsilikaten oder Schichtdoppelhydroxiden einen relativen Stickstoffmassenanteil von weniger als 20% bezogen auf die relative Molekülmasse von Polyacrylnitril ausmachen sollte. Dieser Stickstoffmassenanteil determiniert unter anderem die Dicke und räumliche Struktur der erhaltenen Graphenlagen des Verbundmaterials. Jenes der US 4,921,681 hat eine HOPG Struktur mit einer gegenüber der o.g. gewünschten Dicke von 20 nm deutlich erhöhten Schichtdicke. Ein geeignetes Verbundmaterial, wie auch ein Verfahren zu dessen Herstellung offenbart aber die deutsche Patentanmeldung DE 10 2009 049 379.4. In Example 1 is carbonated for 3 hours at 700 ° C. According to the prior art (see Peter Morgan, Carbon fibers and their composites: Vol 27, CRC Pres, 2005, p 2235) such an intermediate has a relative nitrogen content of at least 20% relative to the molecular weight of polyacrylonitrile. The relative nitrogen content of polyacrylonitrile (ie the starting material) is 26%. However, as will be shown within the scope of the present invention, such composite materials are not as well suited for the aforementioned inventive purposes of producing a paste having increased charge storage capability because the composite material of graphene sheets and sheets of sheet silicates or layered double hydroxides used has a relative nitrogen content of less than 20% based on the molecular weight of polyacrylonitrile should make. Among other things, this proportion of nitrogen content determines the thickness and spatial structure of the resulting graphene layers of the composite material. That of US 4,921,681 has a HOPG structure with a significantly increased layer thickness compared to the above-mentioned desired thickness of 20 nm. However, a suitable composite material, as well as a method for its production, is disclosed in the German patent application DE 10 2009 049 379.4.
Die DE 10 2009 049 379.4 offenbart aber nicht, dass das dortige Verbundmaterial geeignet zur Ladungsspeicherung ist und offenbart auch keine mit diesen Verbundmaterialien hergestellten Pasten oder elektrischen Bauteile, wie etwa Kondensatoren. In elektrotechnischen Kondensatoren neuerer Bauart ist für eine hohe Energiedichte die Kombination aus zwei Eigenschaften wesentlich. Zum einen müssen in den Kondensatoren Lagen vorhanden sein, die eine hohe Ladungsspeicherfähigkeit aufweisen zum anderen müssen zwischen diesen Lagen weitere Lagen vorhanden sein, in denen es zu einer Ladungstrennung kommt, damit der Kondensator die gewünschte Speicherung der elektrischen Energie erlaubt. Ein aus solchen Lagen aufgebauter Kondensator sollte darüber hinaus möglichst leicht, preiswert, umweltfreundlich und klein sein, damit er sich für den massenhaften Einbau in elektrischen Schaltungen eignet. However, DE 10 2009 049 379.4 does not disclose that the composite material there is suitable for charge storage and does not disclose pastes or electrical components such as capacitors made with these composites. In more recent electrotechnical capacitors, the combination of two properties is essential for high energy density. On the one hand, layers must be present in the capacitors which have a high charge storage capacity. On the other hand, there must be further layers between these layers in which charge separation occurs so that the capacitor permits the desired storage of the electrical energy. In addition, a capacitor constructed of such layers should be as light, inexpensive, environmentally friendly and small as possible, so that it is suitable for mass installation in electrical circuits.
Einen solchen Kondensator beschreibt beispielsweise die US 3,652,902, wobei der dortige Kondensator aufgebaut ist aus wechselnden Lagen bestehend aus Aktivkohle und Lagen aus einem hochporösen nicht-leitenden Material, das mit einem leitenden, flüssigen Material gefüllt wurde. Die Aktivkohle besitzt zwar eine hohe spezifische Oberfläche, Aktivkohle hat aber amorphe Struktur und führt demnach dazu, dass die in ihren Poren gegebenenfalls gespeicherten Ladungen nur langsam aus der Aktivkohle wieder heraus permeieren können, wenn die zuvor angelegte Spannung abgeschaltet wird. Demnach ist die Kapazität eines solchen Kondensators bei sclinellen Lade-/Entladezyklen stark begrenzt, weil eben jene Prozesse nur langsam ablaufen können. Einen alternativen Kondensator beschreibt die US 5,621,607, wobei die leitenden Lagen aus einem Verbundmaterial aus Metall, speziell Aluminium, und Kohlenstoff bestehen. Die Verwendung dieses Verbundmaterials soll insbesondere eine leichte Ausführung des Kondensators erlauben. Ansonsten umfasst auch der Kondensator gemäß der US 5,621,607 wiederum einen Elektrolyten zwischen den Lagen des vorgenannten Verbundmaterials. Such a capacitor is described, for example, in US Pat. No. 3,652,902, in which the condenser there is composed of alternating layers of activated carbon and layers of a highly porous, non-conductive material which has been filled with a conductive, liquid material. Although the activated carbon has a high specific surface area, activated carbon has an amorphous structure and thus leads to the fact that the charges possibly stored in their pores can only slowly permeate out of the activated carbon when the previously applied voltage is switched off. Thus, the capacity of such a capacitor is severely limited in the case of rapid charge / discharge cycles because those processes can only proceed slowly. An alternative capacitor is described in US 5,621,607, wherein the conductive layers of a composite material made of metal, especially aluminum, and carbon. The use of this composite material is intended in particular to allow a lightweight design of the capacitor. Otherwise, the capacitor according to US 5,621,607 again comprises an electrolyte between the layers of the aforementioned composite material.
Der Nachteil eines solchen Kondensators ist, dass durch die Beimengung von Metall zum Kohlenstoff die spezifische Oberfläche verringert wird, was wiederum die absolute Ladungsspeicherfähigkeit verringert. Zugleich erlaubt diese Ausführung durch das Metall zwar einen schnelleren Ladungsabfluss, der aber wie gesagt zu Lasten der Ladungsspeicherfähigkeit geht. Ausgehend von den vorstehend skizzierten Schwächen des Standes der Technik besteht also die Aufgabe Materialien zur Verfügung zu stellen, die es erlauben Kondensatoren zu fertigen, die sowohl eine hohe ideale (d.h. bei unendlich langsamer Ladung oder Entladung) Kapazität aufweisen, als auch die Möglichkeit einer schnellen, möglichst vollständigen Ladung oder Entladung aufweisen. Außerdem sind entsprechende Kondensatoren zur Verfügung zu stellen. Ausgehend von den in der DE 10 2009 049 379.4 offenbarten Verbundmaterialien wurde nun als erster Gegenstand der vorliegenden Erfindung überraschend gefunden, dass mit diesen eine elektrisch leitfähige Paste mit erhöhter Ladungsspeicherfähigkeit, erhalten werden kann, die dadurch gekennzeichnet ist, dass sie a) zwischen 3 und 25 Gew.-% eines Verbundmaterials aus i) Schichtsilikat oder Schichtdoppelhydroxiden und ii) zumindest teilweise zu Graphenlagen zersetztem Polyacrylnitril mit einem relativen Stickstoffmassenanteil von weniger als 20% bezogen auf die relative Molekülmasse von Polyacrylnitril, b) zwischen 1 und 10 Gew.-% mindestens eines elektrisch leitfähigen Zuschlagsstoffes, sowie c) eine Elektrolytlösung umfasst. The disadvantage of such a capacitor is that the addition of metal to the carbon reduces the specific surface area, which in turn reduces the absolute charge storage capacity. At the same time, this embodiment allows a faster discharge of charge through the metal, but as previously said it is at the expense of the charge storage capability. Based on the weaknesses of the prior art outlined above, it is therefore an object to provide materials which make it possible to produce capacitors which have both a high ideal (ie at infinitely slow charge or discharge) capacity and the possibility of a fast one , as complete as possible charge or discharge. In addition, appropriate capacitors are to be provided. Starting from the composite materials disclosed in DE 10 2009 049 379.4, it has now surprisingly been found, as a first subject of the present invention, that they can be used to obtain an electrically conductive paste with increased charge storage capacity, which is characterized in that it comprises a) between 3 and 25% by weight of a composite of i) phyllosilicate or layered double hydroxides and ii) polyacrylonitrile at least partially decomposed to graphene layers with a relative nitrogen content of less than 20% relative to the relative molecular mass of polyacrylonitrile, b) between 1 and 10% by weight at least an electrically conductive additive, and c) comprises an electrolyte solution.
Ein solches Verbundmateriai weist Graphenlagen mit einer Dicke von deutlich weniger als 20 nm auf und kombiniert die Vorteile von solchen Graphenlagen (mechanische und elektrische Leitfähigkeit) mit den vorteilhaften Eigenschaften von Schichtsilikaten oder Schichtdoppelhydroxiden (Isolationsund Füllstofffunktionalität) in einem Material. Solche Verbundmaterialien bieten darüber hinaus den Vorteil, dass die Beschaffenheit des Materials ähnlich zu demjenigen von Schichtsilikaten oder Schichtdoppelhydroxiden ist, was bedeutet, dass diese Verbundmaterialien auch für bekannte Prozesse und Methoden verwendet werden können, bei denen bereits Schichtsilikate oder Schichtdoppelhydroxide als Ausgangsstoffe verwendet werden. Die in der erfindungsgemäßen Paste verwendbaren Schichtsilikate sind die aus dem Stand der Technik bekannten Silikatstrukturen mit zweidimensionalen Schichten aus SiQ4-Tetraedern (auch als Blatt- oder Phyllosilikate bezeichnet), Such a composite material has graphene layers with a thickness of significantly less than 20 nm and combines the advantages of such graphene layers (mechanical and electrical conductivity) with the advantageous properties of sheet silicates or layered double hydroxides (insulation and filler functionality) in a material. Such composites also offer the advantage that the nature of the material is similar to that of phyllosilicates or layered hydroxides, meaning that these composites can also be used for known processes and methods in which phyllosilicates or layered double hydroxides are already used as starting materials. The phyllosilicates usable in the paste according to the invention are the silicate structures known from the prior art with two-dimensional layers of SiQ 4 tetrahedra (also referred to as foliar or phyllosilicates),
Beispiele für geeignete Schichtsilikate sind Bentonit, Talk, Pyrophyllit, Glimmer, Serpentin, Kaoiinit oder Gemische davon. Die Schichtsilikate können nach bekannten Methoden modifiziert werden um den Schichtabstand zu ändern. Dafür werden beispielsweise zwischen den Schichten Ammoniumverbindungen, die mindestens eine Säuregruppe aufweisen, eingelagert (vgl. DE10351268A1). Examples of suitable phyllosilicates are bentonite, talc, pyrophyllite, mica, serpentine, kaoiinite or mixtures thereof. The layer silicates can be modified by known methods to change the layer spacing. For this purpose, for example, between the layers, ammonium compounds which have at least one acid group are intercalated (see DE10351268A1).
Die Einlagerung erfolgt durch Austausch der im Schichtgitter der Silikate enthaltenen Kationen durch die Ammoniumverbindungen mit mindestens einer Säuregruppe und führt im allgemeinen zu einer Aufweitung des Schichtabstands. Schichtsilikate, oder die nach dem oben beschriebenen Verfahren modifizierten Schichtsilikate, haben vorzugsweise einen Schichtabstand von 0,5 bis 2,5 nm und noch bevorzugter von 0,7 bis 1 ,5 nm. The storage takes place by exchanging the cations contained in the layer lattice of the silicates by the ammonium compounds with at least one acid group and generally leads to a widening of the layer spacing. Phyllosilicates, or the phyllosilicates modified by the process described above, preferably have a layer spacing of 0.5 to 2.5 nm and more preferably of 0.7 to 1.5 nm.
Unter Schichtdoppelhydroxiden werden im Rahmen der vorliegenden Erfindung Verbindungen verstanden, die unter die allgemeine Formel [M 'i.xNJ+ x (OH)2] [An~ ]x/n · y H20 fallen, Dabei ist M + ein zweiwertiges Erdalkali- oder Übergangsmetallion wie Mg +, Ni2+, Cu2 t oder Zn2+, N3+ ein dreiwertiges Hauptgruppen- oder Übergangsmetallion wie z.B. AI3 *, Cr'+, Fe3 * oder Ga3+, An~ ein Anion wie z.B. N03 ", C03 2~, Cl~ oder S04 2", x eine rationale Zahl zwischen 0 und 1 und y eine positive Zahl einschließlich 0. Under Schichtdoppelhydroxiden refers to compounds within the scope of the present invention, the [under the general formula M 'i. x N J + x (OH) 2 ] [A n ~ ] x / n x y H 2 O, where M + is a divalent alkaline earth or transition metal ion such as Mg + , Ni 2+ , Cu 2 t or Zn 2+ , N 3+ is a trivalent main group or transition metal ion such as Al 3 * , Cr ' + , Fe 3 * or Ga 3+ , A n ~ an anion such as N0 3 " , C0 3 2 ~ , Cl ~ or S0 4 2" , x is a rational number between 0 and 1, and y is a positive number, including 0.
Gemäß der vorliegenden Erfindung sind unter dem Begriff„Schichtdoppelhydroxide" auch die Oxide dieser Verbindungen miterfasst. According to the present invention, the term "layered double hydroxides" also includes the oxides of these compounds.
Bevorzugt werden als Schichtdoppelhydroxide natürliche und synthetische Hydrotalcite und Verbindungen mit einer Hydrotaicit-ähnlichen Struktur verwendet. Zur Herstellung der Hydrotalcite bzw. der Verbindungen mit einer Hydrotalcit-ähnlichen Struktur kann dabei grundsätzlich jedes dem Fachmann geläufige Verfahren eingesetzt werden (siehe beispielsweise Handbook of Clav Science, F. Bergaya, B.K.G. Theng and G. Lagaly, Developments in Clay Science, Vol. 1, Chapter 13.1 und Layered Double Hydroxides, C. Forano, T. Hibino, F. Leroux, C. Taviot-Gueho, Handbook of Clay Science, 2006). Natural and synthetic hydrotalcites and compounds having a hydrotaicit-like structure are preferably used as layered double hydroxides. For the preparation of the hydrotalcites or of the compounds having a hydrotalcite-like structure, it is possible in principle to use any process familiar to the person skilled in the art (see, for example, Handbook of Clav Science, F. Bergaya, BKG Theng and G. Lagaly, Developments in Clay Science, Vol. 1, Chapter 13.1 and Layered Double Hydroxides, C. Forano, T. Hibino, F. Leroux, C. Taviot-Gueho, Handbook of Clay Science, 2006).
In der erfindungsgemäßen Paste werden bevorzugt Hydrotalcite der allgemeinen (nominellen) Formel 2x 2+ M2 3†(OH)4X44 · A2/r,n~ · zH20, bei der M2x 2+ein divalentes Metal ausgewählt aus der Gruppe von Mg, Zn, Cu, Ni, Co, Mn, Ca und/oder Fe ist und M2' 1 ein trivalentes Metall ausgewählt aus der Gruppe von AI, Fe, Co, Mn, La, Ce und/oder Cr ist,„x" eine Zahl von 0,5 bis 10 in Intervallen von 0,5 ist, A ein interstitielles Anion ist,„n" die Ladung des interstitiellen Anions ist, welche bis 8 und normalerweise bis 4 betragen kann und„z" eine natürliche Zahl von 1 bis 6, vorzugsweise 2 bis 4 ist, verwendet. In the paste according to the invention, preference is given to hydrotalcites of the general (nominal) formula 2 × 2 + M 2 3 † (OH) 4X 44 · A 2 / r , n · · zH 2 O, where M 2x 2+ is a divalent metal selected from is the group of Mg, Zn, Cu, Ni, Co, Mn, Ca and / or Fe and M 2 ' 1 is a trivalent metal selected from the group of Al, Fe, Co, Mn, La, Ce and / or Cr , "X" is a number from 0.5 to 10 at intervals of 0.5, A is an interstitial anion, "n" is the charge of the interstitial anion, which may be up to 8 and usually up to 4, and "z" is one natural number of 1 to 6, preferably 2 to 4 is used.
Geeignete interstitielle Anionen sind üblicherweise organi sche Anionen wie Alkoholate, Alkylethersulfate, Ar lethersulfate und/oder Glycolethersulfate oder anorganische Anionen, wie beispielsweise Carbonate, Hydrogencarbonate, Nitrate, Chloride, Sulfate, B(OH)4 " und/oder Polyoxometallationen wie Mo7024b" oder V]0O2g6". Suitable interstitial anions are usually organic anions such as alkoxides, alkyl ether sulfates, aromatic ether sulfates and / or glycol ether sulfates or inorganic anions such as carbonates, bicarbonates, nitrates, chlorides, sulfates, B (OH) 4 " and / or polyoxometallates such as Mo 7 O 2 4 b " or V ] 0 O 2 g 6" .
Bevorzugte interstitielle Anionen sind C03 2" und N03 ". Preferred interstitial anions are C0 3 2 " and N0 3 " .
Das korrespondierende Metalloxid, welches durch Kalzinieren erhalten werden kann und im Verbundmaterial der erfindungsgemäßen Paste vorliegen kann, hat die allgemeine Formel M2x 2+ Μ2 3+(0)(4χ 4)/2, wobei M2x 2+,M2 3+ und„x" die gleiche Bedeutung zukommt wie oben beschrieben. The corresponding metal oxide, which can be obtained by calcining and can be present in the composite material of the paste according to the invention, has the general formula M 2x 2+ Μ 2 3+ (0) (4χ 4) / 2, where M is 2x 2+ , M 2 3 + and "x" have the same meaning as described above.
Dem Fachmann ist bekannt, dass solche Materialien insbesondere bei Kontakt mit Wasser in einer partiell hydroxylierten Form vorliegen können. It is known to the person skilled in the art that such materials may be present in a partially hydroxylated form, in particular when in contact with water.
In der erfindungsgemäßen Paste werden Verbundmaterialien mit Schichtdoppeihvdroxiden bevorzugt verwendet. Besonders bevorzugt werden Verbundmaterialien mit Hydrotalciten, die einen Schichtabstand von 0,5 bis 2,5 nm und vorzugsweise von 0,7 bis 1 ,5 nm aufweisen. In the paste of the invention, composite materials with Schichtdoppeihvdroxiden are preferably used. Especially preferred are composite materials with hydrotalcites which have a layer spacing of 0.5 to 2.5 nm and preferably of 0.7 to 1.5 nm.
Der Schichtabstand kann künstlich wie bei den Schichtsilikaten vergrößert sein, indem geeignete interkalierende Agenzien einsetzt wurden. The layer spacing can be artificially increased as in the layer silicates by using suitable intercalating agents.
Prinzipiell eignen sich dafür Anionen wie beispielsweise 3-Aminobenzolsulfonsäure, 4- Toluolsulfonsäure-Monohydrat, 4-Hydroxybenzolsulfonsäure, Dodecylsulfonsäure, Terephthalsäure. Andere Anionen sind dem Fachmann geläufig. Für die Zwecke der vor egenden Erfindung ist es nicht entscheidend, was für Anionen eingesetzt wurden. Die Anionen dienen ausschließlich der Modifizierung der Schichten der Schichtdoppelhydroxide. Sie zersetzen sich während des Herstellprozesses der Verbundmaterialien bei der thermischen Behandlung. Besonders geeignete Hydrotalcite werden von der Firma Sasol Deutschland GmbH unter dem Markennamen Pural vertrieben. In principle, anions such as, for example, 3-aminobenzenesulfonic acid, 4-toluenesulfonic acid monohydrate, 4-hydroxybenzenesulfonic acid, dodecylsulfonic acid and terephthalic acid are suitable for this purpose. Other anions are familiar to the person skilled in the art. For the purposes of the present invention, it is not critical what anions were used. The anions are used exclusively for modifying the layers of the layered double hydroxides. They decompose during the manufacturing process of the composite materials in the thermal treatment. Particularly suitable hydrotalcites are marketed by the company Sasol Deutschland GmbH under the brand name Pural.
In den Schichten des Schichtsilikats oder der Schichtdoppelhydroxide befinden sich hauptsächlich Graphenlagen, welche durch Polymerisation und Kalzinierung von Acrylnitril während dem Herstellungsprozesses des Verbundmaterials entstehen. Wie vorstehend beschrieben beschreibt die US 4,921,681 Zwischenprodukte zur Herstellung von Hoch-Orientiertem Pyrolytischem Graphit (HOPG). Dies ist ein Verbundmaterial mit Montmorillonit (ein Schichtsilikat) und teilsweise karbonisiertem Polyacrylnitnl. Dieses Zwischenprodukt weist einen relativen Stickstoffmassenanteil von mindestens 20% bezogen auf die relative Molekülmasse von Polyacrylnitril auf. Der relative Stickstoffmassenanteil von Polvacrylnitril (d.h. dem Ausgangsmaterial) liegt bei 26%. The layers of the layered silicate or the layered double hydroxides mainly contain graphene layers which are formed by polymerization and calcination of acrylonitrile during the production process of the composite material. As described above, US 4,921,681 describes intermediates for the preparation of highly oriented pyrolytic graphite (HOPG). This is a composite with montmorillonite (a layered silicate) and partially carbonated polyacrylonitrile. This intermediate has a relative nitrogen content of at least 20% relative to the molecular weight of polyacrylonitrile. The relative nitrogen content of polvacrylonitrile (i.e., the starting material) is 26%.
Das in der erfindungsgemäßen Paste eingesetzte Verbundmaterial unterscheidet sich dadurch, dass der relative Stickstoffmassenanteil weniger als 20%, vorzugsweise weniger als 1 5%, noch bevorzugter gleich oder weniger als 10%, noch bevorzugter gleich oder weniger als 5% und noch bevorzugter gleich oder weniger als 3% bezogen auf die relative Molekülmasse von Polyacrylnitril ausmacht. The composite material used in the paste of the invention differs in that the relative nitrogen content is less than 20%, preferably less than 15%, more preferably equal to or less than 10%, even more preferably equal to or less than 5%, and even more preferably equal to or less than 3% based on the molecular weight of polyacrylonitrile.
Das in der erfindungsgemäßen Paste eingesetzte Verbundmaterial hat dabei keine HOPG Struktur, sondern hat vielmehr eine Graphenlagen-Struktur mit einer Schichtdicke von 0,5 bis 2,5 nm . Die Berechnung des Stickstoffmassenanteils kann durch die bekannte und etablierte Standardmethode ICP-MS (Massenspektrometrie mit induktiv gekoppeltem Plasma) beispielsweise von einem nach DIN -ISO 17025 zertifizierten Analytiklabor durchgeführt werden. The composite material used in the paste according to the invention in this case has no HOPG structure, but rather has a graphene sheet structure with a layer thickness of 0.5 to 2.5 nm. The calculation of the nitrogen mass fraction can be carried out by the known and established standard method ICP-MS (mass spectrometry with inductively coupled plasma), for example, by a DIN ISO 17025 certified analytical laboratory.
Bei der ausschließlichen Verwendung eines Schichtdoppelhydroxides für das in der erfindungsgemäßen Paste enthaltene Verbundmaterial kann der relative Stickstoffmassenanteil bezogen auf die relative Molekülmasse von Polyacrylnitril jedoch 20%> oder auch mehr als 20% betragen. Die oben genannten, bevorzugten Werte für die relativen Stickstoffmassenanteile sind jedoch auch in diesem Fall bevorzugt. Die Reduktion des relativen Stickstoffanteils im Verbundmaterial der erfmdungsgemäßen Paste wird erreicht, indem die Kalzinierungstemperatur entsprechend erhöht wird. Um beispielsweise einen Stickstoffmassenanteil von gleich oder weniger als 10% zu erhalten, ist eine Kalzinierung bei 1000°C während mindestens 40 Minuten, vorzugsweise von mindestens 90 Minuten und noch bevorzugter von mindestens zwei Stunden in einem konventionellen Heizofen notwendig (unter Berücksichtigung der maximalen Beladungskapazität des Heizofens), In the exclusive use of a layered double hydroxide for the composite material contained in the paste according to the invention, however, the relative proportion by weight of nitrogen relative to the molecular weight of polyacrylonitrile can be 20% or even more than 20%. However, the above preferred values for the relative proportions by weight of nitrogen are also preferred in this case. The reduction of the relative nitrogen content in the composite material of the paste according to the invention is achieved by correspondingly increasing the calcining temperature. For example, to obtain a nitrogen content of equal to or less than 10%, calcination at 1000 ° C. for at least 40 minutes, preferably at least 90 minutes and more preferably at least two hours in a conventional heating furnace is necessary (taking into account the maximum loading capacity of the stove)
Der Begriff „zumindest teilweise zu Graphenlagen zersetztem Polyacrylnitril" beschreibt die Karbonisierung von Polyacrylnitril zu Graphenlagen durch den vorstehend beschriebenen Kaizinierungsschritt. Je nach Temperatur und Dauer des Kalzinierungsschrittes ist aber das Polyacrylnitril unter Umständen nicht vollständig zersetzt bzw. karbonisiert, sondern es befindet sich noch Polyacrylnitril bzw. nur teilweise zersetztes Polyacrylnitril in dem Verbundmaterial. The term "polyacrylonitrile at least partially decomposed into graphene layers" describes the carbonization of polyacrylonitrile to graphene layers by the above described calcination step partially decomposed polyacrylonitrile in the composite.
Die Temperatur hat dabei einen unmittelbaren Einfluss auf das Kohlenstoff - Stickstoff- Verhältnis. Die thermische Behandlung muss für eine bestimmte Zeit durchgeführt werden, damit möglichst alle abzuführenden Verbindungen über Diffusion nach außen (außerhalb des Verbundmaterials) geleitet werden können und sich die Verbindungen innerhalb des Verbundmaterials zu einem Gleichgewichtszustand umordnen können. The temperature has a direct influence on the carbon - nitrogen ratio. The thermal treatment must be carried out for a certain period of time, so that as far as possible all compounds to be removed can be passed via diffusion to the outside (outside the composite material) and the compounds within the composite material can rearrange to an equilibrium state.
Um dies zu gewährleisten, muss mindestens für eine Zeitdauer von 10 Minuten vorzugweise von mindestens 40 Minuten und noch bevorzugter von mindestens 90 Minuten in einem konventioneilen Heizofen oder mindestens 5 Minuten und bevorzugter mindestens 45 Minuten in einem Mikrowellen- Heizofen kalziniert werden. Der Zersetzungsprozess von Polyacrylnitril zu Graphenlagen ist bekannt. Abbauprodukte, die durch die Zersetzung von Polyacrylnitril entstehen, sind beispielsweise i k N2, M I und HCN. To ensure this, at least for a period of 10 minutes, preferably at least 40 minutes and more preferably at least 90 minutes must be calcined in a conventional heating oven or at least 5 minutes and more preferably at least 45 minutes in a microwave oven. The decomposition process of polyacrylonitrile to graphene layers is known. Degradation products which are formed by the decomposition of polyacrylonitrile are, for example, ikN 2 , MI and HCN.
Die Zersetzung von Polyacrylnitril zu Graphenlagen ist demnach im Wesentlichen abhängig von der gewählten Kalzinierungstemperatur. The decomposition of polyacrylonitrile to graphene layers is therefore essentially dependent on the chosen calcining temperature.
Eine bevorzugte Ausführungsform der Erfindung betrifft eine Paste mit einem Verbundmaterial, bei dem sich das Polyacrylnitril zu 95%, bevorzugt zu 98%, noch bevorzugter 99% und ganz besonders bevorzugt vollständig zu Graphenlagen zersetzt hat. Dafür sind Temperaturen ab 1600°C erforderlich (mindestens 95%ige Zersetzung). Vollständige Zersetzung (d.h. mindestens 99%ige Zersetzung) erreicht man mit Temperaturen um die 2000°C. Der Kalzinierungsschritt wird vorzugsweise unter inerter Atmosphäre (Argon oder Stickstoff und vorzugsweise Ar) und bei Normaldruck durchgeführt. Unter dem Begriff „Kalzinierung" wird allgemein ein thermischer Behandlungsschritt verstanden, d.h. Erhitzen eines Materials mit dem Ziel, dieses zu zersetzen. Das Material, weiches zu Graphenlagen zersetzt werden soll, ist erfindungsgemäß Polyacrylnitril. A preferred embodiment of the invention relates to a paste with a composite material in which the polyacrylonitrile has decomposed to 95%, preferably 98%, more preferably 99% and most preferably completely to graphene layers. For temperatures from 1600 ° C are required (at least 95% decomposition). Complete decomposition (ie at least 99% decomposition) is achieved with temperatures around 2000 ° C. The calcination step is preferably carried out under an inert atmosphere (argon or nitrogen and preferably Ar) and at atmospheric pressure. The term "calcination" is generally understood to mean a thermal treatment step, ie heating of a material with the aim of decomposing it The material which is to be decomposed into graphene layers is polyacrylonitrile according to the invention.
Unter dem Begriff „Graphenlage" werden zweidimensionale Kohlenstoffkristaiie verstanden, die analog zu einzelnen Graphitschichten aufgebaut sind und deren Kohlenstoffatome sich in einer hexagonalen Honigwaben- Struktur unter Bildung von sp2- Hybridorbitalen anordnen. The term "graphene layer" is understood to mean two-dimensional carbon crystals which are constructed analogously to individual graphite layers and whose carbon atoms are arranged in a hexagonal honeycomb structure with the formation of sp 2 hybrid orbitals.
Eine einzelne Graphenlage hat eine Schichtdicke von 0,335 nm. Bei einem Schichtabstand der Schichtsilikate oder Schichtdoppelhydroxide von vorzugsweise 0,5 bis 2,5 nm können sich demnach 1 bis 7 Graphenlagen innerhalb einer einzelnen Schicht befinden. A single graphene layer has a layer thickness of 0.335 nm. In the case of a layer spacing of the layered silicates or layered double hydroxides of preferably 0.5 to 2.5 nm, 1 to 7 graphene layers can therefore be located within a single layer.
In der erfindungsgemäßen Paste sind in bevorzugten Ausfuhrungsformen zwischen 5 und 25 Gew.- %, besonders bevorzugt zwischen 5 und 10 Gew.-%, ganz besonders bevorzugt zwischen 5 und 7 Gew .-"··> des Verbundmaterials enthalten. In the paste according to the invention in preferred embodiments between 5 and 25% by weight, particularly preferably between 5 and 10 wt .-%, most preferably between 5 and 7 wt .- "··> of the composite material.
Die Begrenzung des erfmdungsgemäßen Anteils an Verbundmateriai in der Paste nach unten ist deshalb vorteilhaft, weil ab dieser Menge des Verbundmaterials in der erfindungsgemäßen Paste, dessen vorteilhafte Ladungsspeicherfähigkeit in der Paste besonders merklich hervortritt. Die Begrenzung nach oben ist deshalb vorteilhaft, weil sich überraschend gezeigt hat, dass eine Steigerung bis dahin zwar immer noch gegenüber dem bisher bekannten Stand der Technik vorteilhaft ist, darüber hinaus aber die Vorteiihaftigkeit wieder abnimmt. The limitation of the inventive proportion of Verbundmateriai in the paste down is advantageous because from this amount of the composite material in the paste according to the invention, its advantageous charge storage ability in the paste emerges particularly noticeable. The limitation upwards is advantageous because it has surprisingly been found that an increase up to that point is still advantageous compared to the previously known state of the art, but beyond that the advantageousness decreases again.
Die erfindungsgemäß in der Paste befindliche Elektrolytlösung ist jeder oder jedes bei Umgebungsbedingungen (1013 hPa, 23°C) flüssige Stoff oder Stoffgemisch, das Ionen umfasst. Die Elektrolytlösung soll die elektrische Leitung in der Paste sicherstellen und/oder verbessern. The electrolytic solution present in the paste in accordance with the invention is any or all of the liquid or mixture of substances which under ambient conditions (1013 hPa, 23 ° C) comprises ions. The electrolyte solution is intended to ensure and / or improve the electrical conduction in the paste.
Beispiele für erfindungsgemäße Elektrolytlösungen sind etwa wässrige Lösungen von Salzen, Säuren oder Basen. Beispiele solcher wässriger Lösungen von Salzen, Säuren oder Basen sind etwa Lösungen von Alkali- und/oder Erdalkali-Hydroxiden, Alkali- und/oder Erdalkali-Halogeniden und Haiogenwasserstoff etc. in Wasser. In einer alternativen Ausfuhrungsform der vorliegenden Erfindung kann als Elektrolytlösung auch eine sogenannte ionische Flüssigkeit verwendet werden. Ionische Flüssigkeiten sind dem Fachmann allgemein bekannt und beispielsweise in der WO 2005/016483 AI umfassend beschrieben. Examples of electrolyte solutions according to the invention are, for example, aqueous solutions of salts, acids or bases. Examples of such aqueous solutions of salts, acids or bases are, for example, solutions of alkali metal and / or alkaline earth metal hydroxides, alkali metal and / or alkaline earth metal halides and halogenated hydrogen, etc., in water. In an alternative embodiment of the present invention, a so-called ionic liquid can also be used as electrolyte solution. Ionic liquids are generally known to the person skilled in the art and are comprehensively described, for example, in WO 2005/016483 A1.
Die erfindungsgemäße Paste umfasst neben dem Verbundmaterial und dem Elektrolyt auch noch zwischen 1 und 10 Gew.-% mindestens eines elektrisch leitfähigen Zuschlagsstoffes. Dieser Zuschlagsstoff dient neben seiner Eigenschaft als elektrischer Leiter beispielsweise auch der Veränderang der Viskosität und/oder anderer physikalischer Eigenschaften der Paste. In addition to the composite material and the electrolyte, the paste according to the invention also comprises between 1 and 10% by weight of at least one electrically conductive additive. In addition to its property as an electrical conductor, this additive also serves, for example, to change the viscosity and / or other physical properties of the paste.
Der mindestens eine Zuschlagsstoff liegt in der erfindungsgemäßen Paste bevorzugt in einem Anteil von 2 bis 8 Gew.-%, besonders bevorzugt, in einem Anteil von 5 bis 7 Gew.-% vor. Die Zuschlagsstoffe können neben den vorgenannten Eigenschaften der erfindungsgemäßen Paste auch deren Ladungsspeicherfähigkeit weiter verbessern . Für die vorliegende Erfindung ist dies aber nicht wesentlich. Die erfindungsgemäße Paste ist auch ohne die vorgenannten Zuschlagsstoffe bereits durch eine deutlich gegenüber Materialien aus dem Stand der Technik verbe sserte Ladungsspeicherfähigkeit gekennzeichnet. Allerdings führt die Anwesenheit der elektrisch leitfähigen Zuschlagsstoffe erst zur vollständigen Ausnutzung des Ladungsspeicherpotentials der in der erfindungsgemäßen Paste enthaltenen Verbundmaterialien, da durch diese die zu speichernden Ladungen entsprechend schneller an den Speicherort transportiert werden. The at least one additive is present in the paste according to the invention preferably in a proportion of 2 to 8 wt .-%, more preferably, in a proportion of 5 to 7 wt .-% before. In addition to the abovementioned properties of the paste according to the invention, the additives can also further improve their charge storage capability. However, this is not essential to the present invention. Even without the abovementioned additives, the paste according to the invention is already characterized by a charge storage capacity that is considerably greater than those of prior art materials. However, the presence of the electrically conductive additives only leads to the full utilization of the charge storage potential of the composite materials contained in the paste according to the invention, as they transport the charges to be stored correspondingly faster to the storage location.
Üblicherweise im Zusammenhang mit der erfindungsgemäßen Paste verwendbare Zuschlagsstoffe sind solche Ausgewählt aus der Liste bestehend aus Aktivkohle, Kohlenstoffnanoröhrchen (die der Fachmann auch unter dem Namen Kohlenstoffnanofasern oder anderen Namen kennt), Metallnanofasem oder Metallnanodrähte wie sie der Fachmann allgemein kennt, elektrisch leitfällige Polymere. Commonly used in connection with the paste according to the invention additives are those Selected from the list consisting of activated carbon, carbon nanotubes (the person skilled in the art also known under the name carbon nanofibers or other names), metal nanofibers or metal nanowires as the skilled person generally knows electrically conductive polymers.
Ein besonders bevorzugter Zuschlagsstoff sind Kohlenstoffnanoröhren (sowohl sogenannte„Single- Walled-Carbon-Nanotubes", als auch sogenannte„Multi-Walled-Carbon-Nanotubes"). Diese sind besonders vorteilhaft, weil diese neben einer deutlichen Erhöhung der Viskosität der Paste auch einen gewissen Beitrag zur elektrischen Leitfähigkeit derselben leisten. Darüber hinaus zeigen erfindungsgemäße Pasten mit dem Zuschlagsstoff Kohlenstoffnanoröhrchen auch noch eine noch weiter verbesserte Ladungsspeicherfähigkeit. Ohne an eine Theorie gebunden zu sein scheint es, al s würde dies auf der Tatsache beruhen, dass die Kohlenstoffnanoröhrchen, die üblicherweise in ungeordneten„Knäueln" vorliegen, in der erfindungsgemäßen Paste durch die geordneten Strukturen der Verbundmaterialien in Ebenen geordnet werden, während wiederum die Kohlenstoffnanoröhrchen die Verbundmaterialien an einem direkten Aneinanderliegen in der erfindungsgemäßen Paste hindern, was wiederum die für die Ladungsspeicherung an den Verbundmaterialien verfügbare Oberfläche erhöht. A particularly preferred aggregate are carbon nanotubes (both so-called "single-walled carbon nanotubes", as well as so-called "multi-walled carbon nanotubes"). These are particularly advantageous because they make a significant contribution to the electrical conductivity of the same in addition to a significant increase in the viscosity of the paste. In addition, pastes according to the invention with the additive carbon nanotube also show a still further improved charge storage capability. Without wishing to be bound by theory, it would appear to be based on the fact that the carbon nanotubes, which are usually in disordered "balls", are ordered in the paste according to the invention by the ordered structures of the composite materials in planes, while the Carbon nanotubes prevent the composites from directly abutting one another in the inventive paste, which in turn increases the surface available for charge storage on the composites.
Prinzipiell kann aber bei einem Anteil des Verbundmaterials im oberen Bereich der erfindungsgemäßen 5 bis 25 Gew.-% auf die Beimengung eines Zuschlagsstoffes zur Erhöhung der Viskosität verzichtet werden. Die erfindungsgemäße Paste ist besonders vorteilhaft, weil sich überraschend gezeigt hat, dass sie eine Reihe positiver Eigenschaften in sich vereint, die sie insbesondere zum Einsatz zur Herstellung von elektrischen Kondensatoren geeignet macht. In principle, however, a proportion of the composite material in the upper region of the inventive 5 to 25 wt .-% can be dispensed with the addition of an aggregate to increase the viscosity. The paste of the invention is particularly advantageous because it has surprisingly been found that it combines a number of positive properties in itself, which makes them particularly suitable for use in the production of electrical capacitors.
Durch die hohe Porosität der einzelnen Materiaien des Verbundmaterials kommt es somit zum einen dazu, dass der Elektrolyt durch die Kapillarkräfte in die Leerräume des Verbundmaterials eingesogen wird und dort ohne weitere Vorsichtsmaßnahmen verbleibt. Dies ist insbesondere dann besonders vorteilhaft, wenn beispielsweise korrosive Elektrolyte Verwendung finden sollen. Due to the high porosity of the individual materials of the composite material, on the one hand, the electrolyte is absorbed by the capillary forces into the voids of the composite material and remains there without further precautionary measures. This is especially advantageous, for example, when corrosive electrolytes are to be used.
Darüber hinaus kommt es in der erfindungsgemäßen Paste, die sodann das mit Elektrolyt vollgesogene Verbundmaterial umfasst, beim Anlegen einer Spannung zu einer (je nach Polarisation der Spannung) Konzentration von gleichnamigen Ladungen an den Oberflächen der Graphenlagen des Verbundmaterials, da diese durch die jeweils zwischen diesen befindlichen Schichtsilikate oder Schichtdoppelhydroxide gegenüber dem umliegenden Elektrolyt polarisiert werden. Hieraus resultiert auch die besonders hohe Ladungsspeicherfähigkeit der erfindungsgemäßen Paste. Moreover, in the paste according to the invention, which then comprises the composite material soaked in electrolyte, upon application of a voltage to a concentration (depending on the polarization of the voltage) of charges of the same name on the surfaces of the graphene layers of the composite material, since these interspersed between the respective layered silicates or layered double hydroxides are polarized relative to the surrounding electrolyte. This also results in the particularly high charge storage capacity of the paste according to the invention.
Noch ein Vorteil der erfindungsgemäßen Paste ist, dass sie bei Wegfall der Spannung die vorgenannten gespeicherten Ladungen wiederum sehr schnell wieder abgeben kann, was zu der prädestinierten Verwendung zur Herstellung eines Kondensators führt. Another advantage of the paste according to the invention is that it can deliver the aforementioned stored charges again very quickly when the voltage is removed, which leads to the predestined use for the production of a capacitor.
Diese vorteilhafte Eigenschaft liegt in der Kombination der Materialien des Verbundmaterials begründet. Zum einen weisen beide Materialien (Schichtsilikate oder Schichtdoppelhydroxide) und Graphenlagen eine hohe spezifische Oberfläche und Porosität auf, so dass die Ladungsmobilität sehr hoch ist, zum anderen und im wesentlichen Unterschied zu Verbundmaterialien nach dem Stand der Technik, sind die Leerräume der Materialien (Porosität) durch eine geringe Tortuosität gekennzeichnet, so dass nicht nur die theoretische spezifische Oberfläche sehr hoch ist, sondern auch die schnell verfügbare spezifische Oberfläche ähnlich hoch ist. This advantageous property is due to the combination of the materials of the composite material. On the one hand, both materials (layered silicates or layered double hydroxides) and graphene layers have a high specific surface area and porosity, so that the charge mobility is very high, and secondly and essentially different from prior art composite materials, the voids of the materials (porosity) are characterized by a low tortuosity, so that not only the theoretical specific surface is very high, but also the readily available specific surface area is similarly high.
Geringe Tortuosität bezeichnet im Zusammenhang mit der vorliegenden Erfindung insbesondere die Eigenschaft der Materialien, dass sie räumlich geordnete Poren aufweisen, die insbesondere auch zum weitgehend überwiegenden Teil von der Außenfläche der Materialien zugänglich sind (keine „Toträume"). Low tortuosity, in the context of the present invention, refers in particular to the property of the materials that they have spatially ordered pores which, in particular, are largely accessible from the outer surface of the materials (no "dead spaces").
Abschließend führt auch die geringe Dicke der Graphenlagen in dem Verbundmaterial der erfindungsgemäßen Paste dazu, dass ein schneller Transport der gespeicherten Ladungen nach außen stattfinden kann. Finally, the small thickness of the graphene layers in the composite material of the paste according to the invention means that rapid transport of the stored charges to the outside can take place.
Zusammengefasst ist die erfindungsgemäße Paste also als Material zur Herstellung von Elektroden eines Kondensators besonders geeignet, zumal sie als Paste auch noch in besonders umfangreicher Weise verwendet werden kann, da sie hinsichtlich der Formgebung der Elektroden eines Kondesators besonders variabel ist. In summary, the paste according to the invention is therefore particularly suitable as a material for the production of electrodes of a capacitor, especially as it can also be used in a particularly extensive manner as a paste, since it is particularly variable with regard to the shaping of the electrodes of a condenser.
Ein weiterer Gegenstand der vorliegenden Erfindung ist demzufolge ein Kondensator umfassend zwei Elektroden aus der erfindungsgemäßen Paste und ein zwischen diesen beiden Elektroden befindliches Dielektrikum. A further subject of the present invention is accordingly a capacitor comprising two electrodes of the paste according to the invention and a dielectric located between these two electrodes.
Das Dielektrikum kann jeder Stoff sein, dessen Dielektritätskonstante größer ist, als jene der Paste. Beispielsweise kann die Elektrolytlösung, wie sie vorstehend bereits beschrieben wurde, das Dielektrikum sein. The dielectric may be any substance whose dielectric constant is greater than that of the paste. For example, the electrolyte solution as described above may be the dielectric.
Es ist aber beispielsweise auch möglich, dass Luft das Dielektrikum ist. Bevorzugt ist das Dielektrikum zugleich ein Mittel, das den physischen Kontakt zwischen den beiden Elektroden aus der erfindungsgemäßen Paste unterbindet. Besonders bevorzugt umfasst das Dielektrikum eine poröse Membran. But it is also possible, for example, that air is the dielectric. Preferably, the dielectric is at the same time a means which prevents the physical contact between the two electrodes from the paste according to the invention. Particularly preferably, the dielectric comprises a porous membrane.
Ganz besonders bevorzugt ist das Dielektrikum eine poröse Membran, deren Porenvolumen mit einer Elektrolytlösung gefüllt ist. Alle vorstehend für die erfindungsgemäße Paste dargelegten bevorzugten Ausfuhrungsformen, sind im Rahmen des hier nun vorgestellten erfindungsgemäßen Kondensators aufgebaut unter anderem aus der erfindungsgemäßen Paste ebenso bevorzugte Ausführungsformen und somit auch hier anwendbar, ohne dass hier noch einmal im Einzelnen darauf eingegangen wird. Einzelne Aspekte der vorliegenden Erfindung werden im Folgenden anhand von Beispielen und Abbildungen näher erläutert, ohne die Erfindung allerdings hierauf zu beschränken. Most preferably, the dielectric is a porous membrane whose pore volume is filled with an electrolyte solution. All of the preferred embodiments set forth above for the paste according to the invention are, as part of the condenser according to the invention now shown, among other things made of the paste according to the invention also preferred embodiments and thus applicable here, without being discussed here in detail again. Individual aspects of the present invention are explained in more detail below with reference to examples and figures, but without limiting the invention thereto.
Die Fig. 1 zeigt den schematischen Aufbau eines erfindungsgemäßen Kondensators, wie er auch als Testsystem für das Beispiel 6 verwendet wurde. Hierbei bezeichnet (1) jeweils ein Nickel-Blech, (2) jeweils eine Teflonscheibe mit zentrischem Loch, wie in Beispiel 4 und 5 näher beschrieben, (3) eine Membran zur Trennung der beiden Kondensatorflächen (4). Fig. 1 shows the schematic structure of a capacitor according to the invention, as it was also used as a test system for Example 6. In this case, (1) each denotes a nickel sheet, (2) each a Teflon disk with a central hole, as described in more detail in Example 4 and 5, (3) a membrane for separating the two capacitor surfaces (4).
Die Fig. 2 zeigt die spezifische Kapazität (Fs) in Farad pro Gramm Kohlenstoff [F/gc] je Elektrode des Kondensators, aufgetragen über der Abtastrate (A) der zyklischen Voltametrie in Millivolt pro Sekunde [mV/s]. Hierbei entspricht eine Abtastrate von 250 mV/s einem vollständigen Lade- und Entladezyklus eines Kondensators innerhalb von vier Sekunden, eine Abtastrate von 100 mV/s einem vollständigen Lade- und Entladezyklus eines Kondensators innerhalb von zehn Sekunden und eine Abtastrate von 50 mV/s einem vollständigen Lade- und Entladezykius eines Kondensators innerhalb von zwanzig Sekunden. Dargestellt sind die jeweiligen spezifischen Kapazitäten der Kondensatoren hergestellt gemäß den Beispielen 4 (A) und 5 (B), sowie gemäß den Vergleichsbeispielen 4 (C), 5 (D) und 6 (E). Die Fig. 3 zeigt eine transmissionselektronenmikroskopische Aufnahme des in der erfindungsgemäßen Paste befindlichen Verbundmaterials. Dargestellt sind auch die Abmessungen der beiden Graphenlagen (A, C) und der dazwischen befindlichen Lage eines Schichtsilikats oder Schichtdoppelhydroxids (B). Die Abmessungen sind A ~ 3,9 nm, B ~ 4,8 nm und C ~ 2,9 ran. Figure 2 shows the specific capacitance (F s ) in farads per gram of carbon [F / gc] per electrode of the capacitor, plotted against the sampling rate (A) of the cyclic voltammetry in millivolts per second [mV / s]. Here, a sampling rate of 250 mV / s corresponds to a complete charging and discharging cycle of a capacitor within four seconds, a sampling rate of 100 mV / s to a complete charging and discharging cycle of a capacitor within ten seconds and a sampling rate of 50 mV / s complete charge and discharge cycle of a capacitor within twenty seconds. Shown are the respective specific capacitances of the capacitors produced according to Examples 4 (A) and 5 (B), and according to Comparative Examples 4 (C), 5 (D) and 6 (E). FIG. 3 shows a transmission electron micrograph of the composite material present in the paste according to the invention. Shown are also the dimensions of the two graphene layers (A, C) and the interposed layer of a layered silicate or layered double hydroxide (B). The dimensions are A ~ 3.9 nm, B ~ 4.8 nm and C ~ 2.9 ran.
Beispiele Examples
Beispiel 1 Herstellen eines Verbundmaterials Example 1 Preparation of a composite material
10 g Hydrotalcit-Material Plural MG 63 ABSA mit einem Schichtabstand von 1,7 nm der Firma Sasol Deutschland GmbH wurden in einem Ofen bei 70°C getrocknet, um überschüssige Feuchtigkeit zu reduzieren. Dieses Hydrotalcit-Material hat eine nominelle chemische Zusammensetzung aus 63 Gew.% MgO und 37 Gew.% A1203, verpackt in einer Schichtstruktur mit 0.7 nm Abstand zwischen den einzelnen Schichten. Um den Abstand zwischen den einzelnen Hydrotalcitschichten von 0.7 nm auf 1.7 nm zu erhöhen, wurde während der Herstellung des Hydrotalcits Meta-Aminobenzolsulfonsäure dazugegeben 5 ml Acrylnitrii wurden dann mit 10 mg Benzoylperoxid versetzt, wobei sich das Benzoylperoxid schnell auflöste. Diese Lösung wurde dann tropfenweise dem Hydrotalcit hinzugegeben und gerührt, bis eine homogene Mischung entstanden war. 10 g of hydrotalcite material plural MG 63 ABSA with a layer spacing of 1.7 nm from Sasol Deutschland GmbH were dried in an oven at 70 ° C. in order to reduce excess moisture. This hydrotalcite material by weight has a nominal chemical composition on 63.% MgO and 37 wt.% A1 2 0 3, packaged in a layered structure with 0.7 nm spacing between the individual layers. In order to increase the distance between the individual hydrotalcite layers from 0.7 nm to 1.7 nm, meta-aminobenzenesulfonic acid was added during the preparation of the hydrotalcite. 5 ml of acrylonitrile were then admixed with 10 mg of benzoyl peroxide, with the benzoyl peroxide rapidly dissolving. This solution was then added dropwise to the hydrotalcite and stirred until a homogeneous mixture had formed.
Bei dem vorstehenden Mischverhältnis von Flüssigkeit und Feststoff (0,5 ml Acrylnitrii pro 1 g Hydrotalcit) resultierte ein„feuchtes" Pulver, bei dem sich das Acrylnitrii in der Schichtstruktur des Hydrotalcits eingelagert hatte. At the above mixing ratio of liquid and solid (0.5 ml of acrylonitrile per 1 g of hydrotalcite) resulted in a "wet" powder in which the acrylonitrile had been incorporated in the layered structure of the hydrotalcite.
Dieses Pulver wurde anschließend in einen verschließbaren Behälter gegeben und in einem Ofen für 3 Stunden bei 70°C erhitzt. This powder was then placed in a sealable container and heated in an oven for 3 hours at 70 ° C.
Das Acrylnitrii polymerisierte zum Polyacrylnitril innerhalb der Schichten des Hydrotalcits. Der Polymerisationsinitiator baute sich hierbei während des Prozesses ab. Auf Grund der Polymerisation wechselte die Farbe des Materials von Weiß zu einem blassen Gelb. Danach wurde die Ofentemperatur auf 300°C erhöht. Während dieses Schrittes wurde das Polyacrylnitril vernetzt. The acrylonitrile polymerized to the polyacrylonitrile within the layers of hydrotalcite. The polymerization initiator degraded during the process. Due to the polymerization, the color of the material changed from white to a pale yellow. Thereafter, the furnace temperature was raised to 300 ° C. During this step, the polyacrylonitrile was crosslinked.
Das erhaltene Polyacrylnitril /Hydrotalcit Verbundmaterial war dunkelbraun. Im nachfolgenden Schritt wurde nun das Polyacrylnitril in einem Quarzofen bei 1000°C unter Argonstrom karbonisiert. Das Material wurde für zwei Stunden bei diesen Temperaturen belassen. Daraus resultierte ein Verb ndmaterial aus Graphenlagen und Hydrotalcit, welches auf Grund seines Kohlenstoffgehaltes dunkelgrau erschien. The resulting polyacrylonitrile / hydrotalcite composite was dark brown. In the subsequent step, the polyacrylonitrile was then carbonized in a quartz oven at 1000 ° C under argon flow. The material was left at these temperatures for two hours. This resulted in a verb ndmaterial of graphene layers and hydrotalcite, which appeared dark gray due to its carbon content.
Beispiel 2: Herstellen einer ersten erfindungsgemäßen Paste Die erfindungsgemäße Paste wurde hergestellt, indem das Verbundmaterial aus Beispiel 1 (Zusammensetzung ca, 13.9%C 1.9% N 84.2% MgÄ10x, mit ca. 200 m g BET Oberfläche) mit einem Elektrolyt (20% KOH-Lösung in Wasser) und Kohlenstoffnanoröhrchen (Fa. Bayer Material Science; Typ Baytubes® C150P) als Zuschlagsstoff vermischt wurde. Die Mischung setzte sich aus 1 g des Verbundmateriais gemäß Beispiel 1, 600 mg an Kohlenstoffnanoröhrchen als Zuschlagsstoff und 8.4 g einer 20%igen, wässrigen KOH-Lösung zusammen. Die Mischung wurde für eine bessere Dispergierung der Feststoffe in der KOH-Lösung einer Ultraschallbehandlung unterworfen. Man erhielt eine dunkle, hochviskose Paste. Example 2: Preparation of a first paste according to the invention The paste according to the invention was prepared by mixing the composite material from Example 1 (composition ca, 13.9% C 1.9% N 84.2% MgA10 x , with about 200 mg BET surface area) with an electrolyte (20% KOH solution in water) and carbon nanotubes ( Bayer Material Science, type Baytubes® C150P) was mixed as an aggregate. The mixture was composed of 1 g of Verbundmateriais according to Example 1, 600 mg of carbon nanotubes as an aggregate and 8.4 g of a 20% aqueous KOH solution together. The mixture was sonicated for better dispersion of the solids in the KOH solution. A dark, highly viscous paste was obtained.
Beispiel 3: Herstellen einer zweiten erfindungsgemäßen Paste Es wurde analog zu Beispiel 2 verfahren, mit dem einzigen Unterschied, dass nun nicht 1 g des Verbundmaterials und 8,4 g einer 20%igen, wässrigen KOH-Lösung eingesetzt wurden, sondern lediglich 600 mg des Verbundmaterials und 8,8 g einer 20%igen, wässrigen KOH-Lösung Verwendung fanden. Example 3 Preparation of a Second Paste According to the Invention The procedure was analogous to Example 2, with the sole difference that now not 1 g of the composite material and 8.4 g of a 20% aqueous KOH solution were used, but only 600 mg of the Composite material and 8.8 g of a 20% aqueous KOH solution were used.
Beispiele 4 und 5: Herstellen erfindungsgemäßer Kondensatoren Die Paste aus Beispiel 2 und 3 wurde auf eine flächige Nickelmetallelelektrode von 7 x 7 cm und 3 mm Dicke aufgebracht, indem auf die vorgenannte Nickelmetailelektrode eine Teflonscheibe (ebenfalls 7 x 7 cm) einer Dicke von 1 mm mit einem zentrischen Loch eines Durchmessers von 16 mm aufgelegt wurde, in die Mitte des vorgenannten Lochs die vorgenannte Paste eingebracht wurde und mit einem Rakelmesser über die Teflonscheibe gestrichen wurde, um überschüssige Paste zu entfernen. Es resultierte eine Elektrode aus der Paste eines Durchmessers von 16 mm, die über die Nickelmetallelelektrode elektrisch kontaktiert war. Das Volumen der Paste betrug somit jeweils etwa 0,2 cm3. Die Elektrode hatte einen Kohlenstoffgehalt von ca. 10 mg/cm2. Examples 4 and 5: Producing Capacitors According to the Invention The paste of Examples 2 and 3 was applied to a flat nickel metal electrode of 7 × 7 cm and 3 mm thickness by applying to the abovementioned nickel metal electrode a Teflon disc (also 7 × 7 cm) having a thickness of 1 mm was placed with a center hole of diameter 16 mm, in the middle of the aforementioned hole, the aforementioned paste was introduced and coated with a doctor blade over the Teflon disk to remove excess paste. This resulted in an electrode of 16 mm diameter paste electrically contacted via the nickel metal electrode. The volume of the paste was thus about 0.2 cm 3 each. The electrode had a carbon content of about 10 mg / cm 2 .
Der Kondensator hergestellt aus der Paste gemäß Beispiel 2, ist im Folgenden Beispiel 5, während jener hergestellt aus der Paste gemäß Beispiel 3, im Folgenden Beispiel 4 bildet. In vorstehend beschriebener Art und Weise wurde auch eine zweite Elektrode hergestellt. The capacitor prepared from the paste according to Example 2 is hereinafter Example 5, while that made from the paste according to Example 3, hereinafter Example 4 forms. In the manner described above, a second electrode was also prepared.
Die zwei in dieser Weise hergestellten Elektroden wurden auf jeweils einer Seite auf eine Glasfasermembran (#13400-42, 42mm Durchmesser, Fa. Sartorius AG, Göttingen) als poröse Trennschicht sedrückt. Die Glasfasermembran wurde zuvor mit der KOH-Lösung getränkt, die auch im Zuge der Herstellung der Paste gemäß Beispiel 2 verwendet wurde. Die Funktion der Glasfasermembran war lediglich die Elektroden zu beabstanden. Das eigentliche Dielektrikum war die vorgenannte KOH- Lösung. Diese Anordnung bildete bereits den erfindungsgemäßen Kondensator, der, nachdem dieser elektrisch kontaktiert worden war, jeweils einem Versuch gemäß Beispiel 6 unterworfen wurde. The two electrodes produced in this way were each sedimented on one side onto a glass fiber membrane (# 13400-42, 42 mm diameter, Sartorius AG, Göttingen) as a porous separating layer. The glass fiber membrane was previously impregnated with the KOH solution, which was also used in the course of the preparation of the paste according to Example 2. The function of the fiberglass membrane was merely to space the electrodes. The actual dielectric was the aforementioned KOH solution. This arrangement already formed the capacitor according to the invention, which, after it had been electrically contacted, each subjected to a test according to Example 6.
Eine schematische Ansicht des Kondensatoraufbaus zeigt Fig. 1. A schematic view of the capacitor structure is shown in FIG. 1.
Vergleichsbeispiel 1 : Herstellen einer ersten nicht erfindungsgemäßen Paste (Ruß) Comparative Example 1 Preparation of a First Noninventive Paste (Carbon Black)
Es wurde eine Paste analog zu Beispiel 2 hergestellt, mit dem einzigen Unterschied, dass von 1 g Verbundmaterial gemäß Beispiel 1 nun 1 g Ruß der Fa. Norit Typ RB4 verwendet wurde. A paste was prepared analogously to Example 2, with the only difference that of 1 g of composite material according to Example 1 now 1 g of carbon black from Norit type RB4 was used.
Vergleichsbeispiel 2: Herstellen einer zweiten nicht erfindungsgemäßen Paste (exfoliertes Graphen) Comparative Example 2 Preparation of a Second Paste Not According to the Invention (Exfoliated Graphene)
Es wurde eine Paste analog zu Beispiel 2 hergestellt, mit dem einzigen Unterschied, dass von 1 g Verb ndmaterial gemäß Beispiel 1 nun 0, 1 g exfoliertes Graphen (Fa. Angstron Materials LLC; Nano Graphene Platelets (NGPs), Typ: N008-100) verwendet wurde. A paste was prepared analogously to Example 2, with the only difference being that 1 g of compound according to Example 1 now contains 0.1 g of exfoliated graphene (from Angstron Materials LLC, Nano Graphene Platelets (NGPs), type: N008-100 ) has been used.
Vergleichsbeispiel 3: Herstellen einer dritten nicht erfin dungsgem äßen Paste (Kohlenstoffnanoröhrchen) Comparative Example 3 Preparation of a Third Noninventive Paste (Carbon Nanotube)
Es wurde eine Paste analog zu Beispiel 2 hergesteilt, mit dem einzigen Unterschied, dass von 1 g Verbundmaterial gemäß Beispiel 1 nun 1 g Kohlenstoffnanoröhrchen der Fa. Bayer Material Science Typ Baytubes® C 150P verwendet wurde. A paste was prepared analogously to Example 2, with the only difference that 1 g of carbon nanotubes from Bayer Material Science Baytubes® C 150P from 1 g of composite material was used.
Vergleichsbeispiele 4-6: Herstellen von nicht erfindungsgemäßen Kondensatoren Comparative Examples 4-6: Manufacture of noninventive capacitors
Es wurden die Pasten gemäß der Vergleichsbeispiele 1 bis 3 in gleicher Weise zu einem Kondensator zusammengesetzt, wie dies in Beispiel 3 für die erfindungsgemäße Paste beschrieben wurde, mit dem einzigen Unterschied, dass an Steile der dort verwendeten erfindungsgemäßen Paste die Pasten gemäß der Vergleichsbeispiele 1 bis 3 verwendet wurden. Vergleichsbeispiel 4 entspricht somit einem Kondensator hergestellt mit der Paste gemäß Vergleichsbeispiel 1 , Vergleichsbeispiel 5 entspricht somit einem Kondensator hergestellt mit der Paste gemäß Vergleichsbeispiel 2 und Vergleichsbeispiel 6 entspricht somit einem Kondensator hergestellt mit der Paste gemäß Vergleichsbeispiel 3. Beispiel 6: Funktionsfähigkeit der Kondensatoren The pastes according to Comparative Examples 1 to 3 were assembled in the same way to a capacitor as described in Example 3 for the paste according to the invention, with the only difference that the paste according to the Comparative Examples 1 to 3 were used. Comparative Example 4 thus corresponds to a capacitor prepared with the paste according to Comparative Example 1, Comparative Example 5 thus corresponds to a capacitor prepared with the paste according to Comparative Example 2 and Comparative Example 6 thus corresponds to a capacitor prepared with the paste according to Comparative Example 3. Example 6: Capacity of the capacitors
Der Kondensator gemäß den Beispielen 4 und 5, sowie die Kondensatoren gemäß der Vergleichsbeispiele 4-6 wurden mittels Zyklovoltametrie (von 0 bis 1 V) untersucht. Darüber hinaus wurde ihre zyklische Entladungstähigkeit im Rahmen dieser zyklovoltametnschen Untersuchungen ermittelt um ihre effektive Kapazität zu bestimmen. Die Zyklovoltametrie wurde hierfür bei Abtastraten von 250 mV/s bis 2 mV/s ausgeführt. Die Abtastrate von 250 mV/s entsprach einem vollständigen Lade-/Entladezyklus in vier (4) Sekunden und simulierte damit sehr anspruchsvolle Arbeitsbedingungen. The capacitor according to Examples 4 and 5, and the capacitors according to Comparative Examples 4-6 were examined by cyclic voltammetry (from 0 to 1 V). In addition, their cyclic discharge capacity was determined as part of these cyclic voltammetric tests to determine their effective capacity. Cyclic voltammetry was performed at sampling rates of 250 mV / s to 2 mV / s. The sampling rate of 250 mV / s was equivalent to a full charge / discharge cycle in four (4) seconds, simulating very demanding working conditions.
Die Messungen der Kapazität bei hohen und niedrigen Abtastraten erlaubten die Bestimmung des Effekts von Porosität und Stofftransportlimitierungen auf die Kapazität. Ein ideales System würde eine konstante Kapazität bei jeder Abtastrate aufweisen, während mikroporöse Systeme mit hoher Tortuosität bei hohen Abiastraten eine signifikante Abnahme der Kapazität aufweisen würden. Die absolute Kapazität des Systems bei idealen (sehr langsamen) Abtastraten wäre um so höher, je höher die spezifische Oberfläche des Elektrodensystems ist. High and low sampling rate measurements allowed the determination of the effect of porosity and mass transfer limitations on capacitance. An ideal system would have a constant capacity at each sampling rate, while high tortuosity microporous systems would have a significant decrease in capacity at high sampling rates. The absolute capacity of the system at ideal (very slow) sampling rates would be the higher the higher the specific surface area of the electrode system.
Aus der Fig. 2 geht hervor, dass der erfindungsgemäße Kondensator verglichen mit den Kondensatoren gemäß der Vergleichsbeispiele 4-6 deutlich besser ist, weil dieser auch bei hohen Lade-/Entladeraten eine im Mittel deutlich höhere Kapazität aufweist. Lediglich bei sehr langsamen Lade-/Entladeraten vermag es der Kondensator gemäß Vergleichsbeispiel 4 (Kurve C) ähnlich hohe Kapazitäten zu erreichen. Solche langsamen Lade-/Entladeraten sind aber außer für den Ersatz von Batterien nicht von Interesse. Zurückzuführen ist diese Vorteilhaftigkeit auf die deutlich dünnere Graphenlagenschicht mit geordneter m ikroporöser Struktur. Die hohe absolute Kapazität des erfindungsgem äßen Kondensators beruht auch auf der hohen Ladungsspeicherfähigkeit der als Elektrode verwendeten Paste. Es fällt ebenfalls auf, dass nicht zwangsweise ein höherer Anteil an Verbundmatenal in der erfmdungsgemäßen Paste von weiterem Vorteil sein muss . Auch wenn die prinzipielle Vorteiihaftigkeit des erfindungsgemäßen Katalysators (vgl. Kurven A und B) sowohl bei 6 Gew.-% als auch bei 10 Gew.-% des Verbundmaterials gegeben ist. From Fig. 2 it is apparent that the capacitor according to the invention compared to the capacitors according to Comparative Examples 4-6 is significantly better, because this has a significantly higher capacitance even at high charge / discharge rates. Only at very slow charge / discharge rates, the capacitor according to Comparative Example 4 (curve C) is able to achieve similarly high capacities. Such slow charge / discharge rates are not of interest except for the replacement of batteries. This advantage is attributable to the significantly thinner graphene layer with ordered microporous structure. The high absolute capacitance of the capacitor according to the invention is also based on the high charge storage capacity of the paste used as the electrode. It is also noticeable that not necessarily a higher proportion of Verbundmatenal must be in the inventive paste of further advantage. Even if the principal advantage of the catalyst according to the invention (compare curves A and B) is given both at 6% by weight and at 10% by weight of the composite material.

Claims

Elektrisch leitfähige Paste mit erhöhter Ladungsspeicherfähigkeit, dadurch gekennzeichnet, dass sie a) zwischen 3 und 25 Gew.-% eines Verbundmaterials aus i) Schichtsilikat oder Schichtdoppelhydroxiden und ii) zumindest teilweise zu Graphenlagen zersetztem Polyacrylnitril mit einem, relativen Stickstoffmassenanteil von weniger als 20% bezogen auf die relative Molekülmasse von Polyacrylnitril, b) zwischen 1 und 10 Gew. -% mindestens eines elektrisch leitfähigen Zuschlagsstoffes, sowie c) eine Elektrolytlösung umfasst. Electrically conductive paste with increased charge storage capacity, characterized in that it a) between 3 and 25 wt .-% of a composite of i) phyllosilicate or layered double hydroxides and ii) at least partially decomposed to graphene layers polyacrylonitrile with a relative nitrogen content fraction of less than 20% b) between 1 and 10% by weight of at least one electrically conductive additive, and c) an electrolyte solution.
Elektrisch leitfähige Paste gemäß Anspruch 1, dadurch gekennzeichnet, das s Verbundmaterialien mit Hydrotalciten, die einen Schichtabstand von 0,5 bis 2,5 nm und vorzugsweise von 0,7 bis 1,5 nm aufweisen, verwendet werden. Electrically conductive paste according to claim 1, characterized in that s composite materials with hydrotalcites having a layer spacing of 0.5 to 2.5 nm and preferably from 0.7 to 1.5 nm are used.
Elektrisch Ieitfahige Paste gemäß einem der Ansprüche 1 oder 2, dadurch gekennzeichnet, dass zwischen 5 und 15 Gew.-% des Verbundmaterials enthalten sind. Electrically conductive paste according to one of claims 1 or 2, characterized in that between 5 and 15% by weight of the composite material are contained.
Elektrisch leitfähige Paste gemäß Anspruch 3, dadurch gekennzeichnet, dass zwischen 5 und 10 Gew.-% des Verbundmaterials enthalten sind. An electrically conductive paste according to claim 3, characterized in that between 5 and 10 wt .-% of the composite material are included.
Elektrisch ieitfähige Paste gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass der elektrisch ieitfähige Zuschlagsstoff Kohlenstoffhanoröhrchen sind. Electrically conductive paste according to one of the preceding claims, characterized in that the electrically conductive additive are carbon nanotubes.
Elektrisch ieitfähige Paste gemäß einem der vorstehenden Ansprüche, gekennzeichnet, dass der Zuschlagsstoff in der Paste in einem Anteil von 2 bis 8 Gew.-% vorliegt. Electrically conductive paste according to one of the preceding claims, characterized in that the additive is present in the paste in a proportion of 2 to 8 wt .-%.
Elektrisch ieitfähige Paste gemäß einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die Elektrolytlösung eine wässrige Lösung von Salzen, Säuren oder Basen ist. Electrically conductive paste according to one of the preceding claims, characterized in that the electrolyte solution is an aqueous solution of salts, acids or bases.
8. Kondensator umfassend zwei Elektroden aus einer Paste gemäß einem der vorstehenden Ansprüche und ein zwischen diesen beiden Elektroden befindliches Dielektrikum. 8. A capacitor comprising two electrodes made of a paste according to one of the preceding claims and a dielectric located between these two electrodes.
9. Kondensator gemäß Anspruch 8, dadurch gekennzeichnet, dass das Dielektrikum eine poröse Membran umfasst. 10. Kondensator gemäß Anspruch 9, dadurch gekennzeichnet, dass das Porenvolumen der porösen Membran mit einer Elektrolytlösung gefüllt ist. 9. A capacitor according to claim 8, characterized in that the dielectric comprises a porous membrane. 10. A capacitor according to claim 9, characterized in that the pore volume of the porous membrane is filled with an electrolyte solution.
PCT/EP2011/062835 2010-07-28 2011-07-26 Electrically conductive pastes having increased charge storage capacity, comprising graphite layers and layers of laminar silicates or laminar double hydroxides, and electrical capacitors produced by means of said pastes WO2012013680A1 (en)

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