Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • 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
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising 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
• • 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
  • H01G11/42—Powders or particles, e.g. composition thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/64—Carriers or collectors
  • H01M4/66—Selection of materials
  • H01M4/665—Composites
  • H01M4/667—Composites in the form of layers, e.g. coatings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M2004/021—Physical characteristics, e.g. porosity, surface area
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/13—Energy storage using capacitors

Definitions

• the present invention relates to the field of active layers of current collectors used in energy storage systems such as secondary batteries, capacitors and superconductors.
• Another object of the invention is a method of manufacturing an improved collector comprising an intermediate layer having remarkable and unprecedented conduction properties.
• Electrical energy storage systems whether electrochemically or electrostatically, consist mainly of a current collector, which is the metallic conductor draining the electrons of an electrolyte, and an active film comprising the active ingredient that allows the storage of energy.
• Active films are not examples of redox systems in batteries, activated carbon in supercapacitors, or dielectric film in capacitors.
• US Pat. No. 6,191,935 describes a technique for producing an aluminum current collector in which hard granular carbon powders are pressed in to break the surface insulating alumina layer and thereby reduce the resistance. .
• the stability of the contact between the active ingredient and the collector is not ensured after a certain period of time.
• US 5,949,637 there is disclosed a technique in which sheet-shaped aluminum collector supports are drilled to reduce the contact resistance between the active material and the aluminum foil.
• U.S. Patent No. 6,094,788 discloses a current collector surrounded by a carbon fabric. This assembly requires the use of an extruded aluminum foil to reduce the resistance between active ingredient and collector. However, nothing is planned with regard to the pre-existing alumina layer which may be relatively thick and have a high contact resistance.
• JP 111 624470 discloses an aluminum foil current collector whose surface has been sprayed with alumina grains in order to increase the roughness and to impart better adhesion of the active material to the foil. aluminum. This method, if it makes it possible to reduce the contact resistance between the collector and the active material, has the disadvantage of not protecting the collector from subsequent passivation.
• US Pat. No. 4,562,511 describes a polarizable carbon electrode. It is proposed to cover the aluminum collector with a paint loaded with conductive particles. In FR 2 824 418, a paint layer including conductive particles such as graphite or charcoal, is applied between the collector and the active material, then is subjected to a heat treatment, which by removing the solvent improves the electrical characteristics of the interface.
• the paint based on epoxy resin or polyurethane, is applied by spraying. Despite the improvement provided by these paints, they have the disadvantage of containing binders that increase the interface resistance.
• the conductive material must be able to be applied in a thin layer, adhesive and covering, that is to say that the layer must be uniform, homogeneous and, essential, in contact with its support in all respects.
• Application FR 2 856 397 discloses the use of sols for the preparation of metal oxide layers on substrates, porous or non-porous.
• the method used consists of dispersing a metal oxide in a solvent added with a dispersing agent, and then adding to this mixture a polymeric solution.
• the suspension thus obtained is then deposited on the substrate by immersion-shrinkage (known under the name of "dip-coating"), dried and calcined to remove the organic matrix and leave only one oxide layer.
• this technique can not be transposed to the implementation of dispersions of fine particles of carbon. Indeed, carbon powders such as acetylene black or activated carbon, do not have the same behavior vis-à-vis solvents.
• nano-sized carbon powders can be homogeneously dispersed in a polymer matrix by the sol-gel route, provided that a number of conditions are met, some of which go against make known in this field.
• the order and duration of Preparation steps are of great importance to obtain a homogeneous dispersion of desired viscosity.
• the current collector can be covered with this sol by "dip-coating” (immersion-removal). Thanks to the surface tension properties of the soil, the composition penetrates the porosity and covers the entire surface of the support. This is then heat-treated to remove the polymeric matrix. We then obtain a support, for example a current collector, whose surface is covered with a continuous and uniform layer of conductive carbon particles.
• the present invention thus has as its first object a process for preparing a dispersion of carbonaceous particles in a polymer matrix by the sol-gel route.
• a second object of the present invention is a solution obtainable by the process in question, consisting of a dispersion of carbonaceous particles in a soil.
• Another object of the present invention is a method of depositing a homogeneous conductive layer on a metal support intended for the manufacture of a low resistance current collector.
• the subject of the invention is a process for the preparation of a dispersed solution of carbon particles of nanometric size comprising neither binder nor dispersant, essentially consisting of: a) - preparing a polymer matrix of determined viscosity, b) - introducing in said matrix a fraction of the carbonaceous particles and a fraction of a wetting agent, solvent of said matrix, c) - maintain stirring until a sol of stable viscosity is obtained, d) - repeat steps b) and c ) until the carbonaceous particles and the solvent are exhausted.
• the polymer matrix is prepared prior to suspending the particles themselves.
• the temperature must be allowed to stabilize to ensure that it has the desired viscosity before starting the soil preparation.
• Those skilled in the art have different techniques for preparing such a fixed viscosity matrix that does not vary over time. Details will be given later on this subject.
• the value of the desired viscosity for the matrix depends in particular on the desired viscosity of the final dispersed solution.
• the introduction of the particles into the matrix must be carried out in reduced fractions, in parallel with the addition of solvent. Different matrix-solvent pairs can be used. It is nevertheless necessary for the chosen solvent to act simultaneously as a wetting agent for the carbonaceous particles so that they can be inserted and dispersed in the polymer matrix. During the entire process of preparation of the dispersed solution, the soil must be maintained under vigorous stirring in order to break the agglomerates of carbonaceous material that may form and ensure their dispersion.
• the principle of this preparation is to gradually add small amounts of carbonaceous material and solvent.
• a dispersed solution of good quality that is to say homogeneous and stable over time, in particular as regards the viscosity, it is advisable to choose the proportions and the operating conditions defined below.
• 0.5 g is added to 5 g of carbonaceous particles, preferably from 1 g to 3 g, per 100 ml of polymer matrix.
• said solvent is supplied at a rate of at least 100 ml per 100 ml of polymeric matrix.
• step b) when step b) is repeated, said solvent is supplied at a rate of 20 ml to 50 ml per 100 ml of polymeric matrix.
• the ratio of carbonaceous particles to solvent is between 1 and 10% (w / v), preferably between 3% and 6% (w / v).
• This characteristic is important when it is desired to obtain a dispersed solution having a given viscosity level, suitable for the subsequent deposition of homogeneous films. Indeed, the viscosity increases with the amount of carbon material, while a solvent such as acetyl acetone for example, induces a greater fluidity.
• an excessive addition of carbonaceous particles associated with a too small amount of solvent causes the precipitation of the soil and its hardening.
• step b it has been possible to demonstrate that after three additions in accordance with step b), the carbonaceous particles already have a good dispersion and the soil is more diluted, which reduces the risk of hardening.
• the ratio of carbonaceous particles to solvent can then be higher, for example between 4% and 10% (w / v).
• steps b) and c) are carried out at least 4 times, preferably at least 6 times. In some cases, when it is desired to obtain a dispersed solution having a high concentration of carbonaceous particles, it can be necessary to repeat steps b) and c) up to 7 times or more.
• step c it is decisive for obtaining the desired result, in step c), of keeping the soil under agitation until the viscosity is stabilized. Indeed, it was found that the soil was thixotropic: its viscosity changes over time, a decrease being observed here. Stirring for two hours may sometimes be sufficient, but it is common to maintain stirring for at least 4 hours, this duration of up to 8 hours and even 12 hours for some preparations.
• a viscosity measurement for a given shear stress can be easily done using a common viscometer, such as for example a Couette viscometer. It will be considered that two viscosity values measured at one hour intervals with a deviation of less than 5% indicate a stabilization allowing continuation of the preparation process.
• the soil is subjected to ultrasound before and after each realization of step b).
• a total of 1 g is added to 4 g of carbonaceous particles per 100 ml of final dispersed solution. More preferably, 2 g are added to 3 g of carbonaceous particles per 100 ml of final dispersed solution. According to another preferred embodiment of the process according to the invention, a total of 60 ml is added to 80 ml of solvent per 100 ml of final dispersed solution. These concentrations will allow, during the deposition of the dispersed solution on a substrate, to obtain a blanket and uniform carbonaceous layer.
• said carbon particles of nanometric size are advantageously chosen from materials with a high conductive power, such as acetylene black, activated carbon, carbon nanotubes, or even graphite.
• the wetting agent which must also be a solvent of said polymeric matrix, is advantageously chosen from acetyl acetone or ethanol.
• the polymeric matrix can be obtained by one of the following methods:
• the second method is quite innovative. It follows from the observation that mechanical degradation affects current collectors made from a relatively low viscosity single matrix during heat treatment.
• This new composition of the soil has the advantage of keeping the particles in suspension and of adhering them to the substrate on which they are intended to be deposited, while providing a slower drying rate, for a satisfactory viscosity.
• ethylene glycol has not been studied as such, it is assumed that it acts on the soil drying rate, which is much slower, and reduces the mechanical stresses due to the retraction of the soil. layer which avoids the deformation of thin substrates.
• the mixed matrix according to the invention may be formed of variable proportions of polymer and ethylene glycol.
• Compositions whose polymer / ethylene glycol volume ratio is between 1: 3 and 2: 1 can be advantageously employed.
• the polymeric matrix comprises amounts of polymer and ethylene glycol in a ratio of 1: 2 by volume.
• the final viscosity is in a particular range, which is facilitated if the polymer matrix also initially has a certain viscosity. Therefore, according to a preferred embodiment of the invention, the polymeric matrix obtained in step a) has a viscosity of between 10 cP1 and 25 cP1.
• the sol has a viscosity of between 10 cIp and 40 cIl.
• This viscosity corresponds to the stresses defined by the intended use of the suspension according to the invention, which must be able to be implemented by the immersion-shrinkage technique to form a layer of a given thickness, of the order of 30 ⁇ m. at 50 microns, providing a quantity of carbonaceous material of relatively low density, namely of the order of 0.5 mg / cm 2 to 1.5 mg / cm 2 .
• a dispersed solution obtainable by the process described above, is also an object of the present invention.
• a dispersed solution of nanoscale carbon particles comprising, relative to the total volume of solution: i) 1% to 4%, preferably 2% to 4% (m / v) of carbonaceous particles in suspension, ii) 20% to 40% (v / v) of a polymeric matrix, and iii) a wetting agent, solvent of the polymeric matrix, said dispersed solution comprising neither binder nor dispersant.
• the carbonaceous particles are chosen from conductive materials such as acetylene black, activated carbon, carbon nanotubes, or graphite.
• said polymeric matrix is a condensation product of hexamethylenetetramine (HMTA) and acetyl acetone, pure (single matrix) or diluted with ethylene glycol (mixed matrix).
• the mixed matrix may contain varying proportions of polymer and ethylene glycol.
• the polymer / ethylene glycol volume ratio is between 1: 3 and 2: 1.
• the amounts of polymer and ethylene glycol are in a ratio of 1: 2 by volume.
• said wetting agent, solvent of the polymeric matrix is chosen from acetyl acetone or ethanol.
• the dispersed solution of carbonaceous particles according to the invention has a viscosity of between 10 cP and 40 cPi, which allows its implementation for the dip-coating deposition of a uniform carbonaceous layer on a substrate.
• Scattered solutions of carbonaceous particles can have various uses. For example, it is advantageous to employ a dispersion according to the invention for the preparation of conductive layers on a substrate, in particular intended for the manufacture of a current collector such as those found in energy storage systems. electric. This use is particularly interesting insofar as it makes use of both the dispersion properties and the adhesion properties of the soil.
• An object of the present invention is therefore a process for preparing a conductive carbon layer on a substrate consisting essentially of:
• the material to be deposited on the collector is therefore first suspended in a polymer matrix according to the invention. It is preferably chosen from carbonaceous materials having a high electronic conductivity, such as graphite, carbon black, activated carbon, carbon nanotubes.
• the deposition of the dispersed solution can be carried out in various ways known to those skilled in the art: immersion-shrinkage (also called “dip-coating”), spin coating (spin-coating), or slip.
• said dispersed solution of carbonaceous particles has a viscosity of between 10 cP and 40 cP1 and is deposited on said substrate by immersion-withdrawal at a rate of less than 25 cm / min.
• This technique makes it possible to deposit a layer of controlled constant thickness containing the carbonaceous material, by acting on the rate of shrinkage for a given viscosity.
• the drying step is important for the quality and performance of the final product. It can be done in the open only, and possibly supplemented by a passage in an oven.
• the drying time can be of the order of 15 minutes to one hour, but can range from 10 to 12 hours when a prepared carbonaceous dispersion is obtained. from a mixed matrix. Steaming at 80 ° C for 30 minutes can be done to finish.
• a mixed matrix of viscosity of 10 cP1 to 15 cP1 with ethanol is preferably used as the solvent for the preparation of the ground. It is thus possible to obtain a carbonaceous suspension having a viscosity of about 10 cP1 to 20 cP1, the drying time before calcination will be several hours. Such a process is particularly adapted to avoid the mechanical degradation of thin substrates during manufacture.
• the layer is calcined at a temperature of approximately 450 ° C. for 4 hours. This heat treatment is sufficient to remove the organic matrix and reveal the conductive carbon film, covering and adhering to the rough surface of the collector. It is noted that when the sol-gel route is used for the synthesis by metal oxides of controlled stoichiometry, it is necessary to apply a treatment at high temperatures, of the order of 700 ° C. to 1000 ° C., or even more which, of course, is totally unsuited to depositing a carbonaceous layer on an aluminum support, whose melting temperature is 65 ° C. This is also a reason why the sol-gel route never been used until now for the purposes of the invention.
• Total calcination of the matrix is necessary for the proper functioning of the collector. Brushing also makes it possible to remove the carbonaceous particles which have not adhered to the substrate at the end of the treatment. This step is also essential to obtain the desired performances.
• the technique according to the invention does not use any binder.
• the film obtained consists solely of the conductive carbonaceous material, which makes it possible to overcome the resistance related to the contribution of the binder.
• the technique according to the invention also does not use an adhesive polymer as is the case of coatings based on paint.
• the polymeric matrix imparts the desired adhesion properties to the solution at the time of deposition, and is then removed. No additional polymer is needed to fix the conductive particles.
• the resistance linked to an adhesive agent is overcome.
• the substrate in question is a porous support of conductive metal having previously undergone surface etching.
• This is for example a chemical etching to create a rough surface, which promotes the attachment of the layer and increases the exchange surface.
• Another object of the present invention is an electrical energy storage system comprising a metal current collector and an active film characterized in that said current collector is covered with a conductive layer obtained using a solution of carbonaceous particles according to the detailed description above.
• the current collectors obtained using the techniques described here have improved properties compared to conventional collectors. They have a reduced contact resistance between the active film and the current collector: the resistance of test cells assembled in the laboratory with aluminum current collectors decreases by 20% to 50% compared with the resistance of cells using collectors. conventional aluminum current.
• the results obtained with stainless steel strips Fe-Cr and Fe-Cr-Ni are of the same order.
• the overall resistance of the supercapacitors produced by the process according to the invention is reduced, which makes it possible to obtain a significant increase in the specific specific power.
• the simple matrix based on HMTA prepared as described in Example 1 is mixed with ethylene glycol until a homogeneous gel is obtained.
• the viscosity of this matrix is 12 cP1.
• the proportions of ingredients can easily be varied to obtain a mixed viscosity matrix of between 10 cP1 and 15 cP1.
• Such matrices are well suited to the preparation of dispersed solutions for depositing carbonaceous material on thin substrates (less than 100 ⁇ m thick).
• acetylene black it is desired to prepare 120 ml of a dispersion containing 3 g of acetylene black.
• the carbon material chosen is acetylene black, the mean particle size of which is of the order of 50 nm (Alfa Aesar, Carbon Black, ref. 2311533), which will be dispersed in a single polymeric matrix based on HMTA.
• the solvent is acetyl acetone.
• a quantity of 30 ml of polymer matrix prepared as indicated in Example 1 is stirred in a suitable container.
• the initiation of the soil is carried out by introducing 0.25 g of acetylene black wet with 40 ml of aceryl acetone.
• a sol is formed which is left stirring for 12 hours to promote the dispersion of the acetylene black and prevent the soil from hardening.
• step b) initiation and 50 ml by repeating step b) 5 times.
• the 3 g of acetylene black will be introduced at the rate of 0.25 g for the initiation phase and 2.75 g by repeating step b) 5 times, ie 2.5 g, and then preceding to a final adjustment by adding 0.25 g of acetylene black alone.
• the preparation of the dispersion is thus carried out in several days. Its final viscosity is 10.6 cPl.
• This example can be broken down by modifying the quantities of ingredients and the number of successive additions, within a certain limit and taking into account the particular effect of each of the ingredients on the characteristics of the soil.
• the carbonaceous material decreases the viscosity of the soil, whereas acetyl acetone makes it possible to increase it.
• acetyl acetone makes it possible to increase it.
• the dispersed solution prepared according to Example 3 is used to make a deposit on a substrate consisting of an aluminum foil of purity of 99.9% (Alcan), rolled and then subjected to an electrochemical treatment creating a porosity formed of deep channels of a few microns in diameter.
• the thickness of the strip after treatment varies from 150 ⁇ m to 250 ⁇ m.
• the deposition is carried out by the well known technique of withdrawal-immersion, with a withdrawal rate of between 30 cm / min and 50 cm / min.
• the strip is dried in the open air for about thirty minutes and then placed in an oven at 80 ° C for 30 minutes.
• the substrate undergoes a heat treatment by a gradual rise in temperature at a rate of at most 100 ° C / h, with a plateau of 15 minutes at 400 ° C, up to 450 ° C.
• the temperature is then maintained at this level for 4 hours in the air.
• the decomposition of the polymer matrix begins at 250-300 ° C.
• the polymer matrix is completely eliminated, which is essential to obtain good conduction performance of the carbonaceous layer, since the polymeric matrix being insulating would hinder the passage of the current between the aluminum and the active material of the collector .
• the substrate is brushed in order to remove the surplus of carbonaceous materials which have not adhered to the substrate and which can create defective gripping zones between the current collector and the active material.
• the layer deposited on the substrate is uniform, with a thickness of between 10 microns and 30 microns. It is homogeneous adhesive and covering, and essential condition, in contact with its support in all respects. It is suitable for use as a conductive carbon interface in a current collector.
• 280 ml of dispersed solution containing 10 g of acetylene black are prepared.
• the carbon material chosen is acetylene black, the mean particle size of which is of the order of 50 nm (Alfa Aesar, Carbon Black, ref. 2311533), which will be dispersed in a mixed polymeric matrix based on HMTA and ethylene glycol.
• the solvent chosen here is ethanol.
• a quantity of 120 ml of polymer matrix prepared as indicated in Example 2 is stirred in a suitable container. Initiation of the soil is carried out by introducing 3 g of acetylene black wetted with 40 ml of ethanol. A sol is formed which is left stirring for 4 hours to promote the dispersion of the acetylene black and prevent the soil from hardening. Successive additions of 2 g of acetylene black and 40 ml of ethanol are then carried out at intervals of 4 hours, that is to say when the viscosity is stabilized.
• the soil is kept under magnetic stirring at 1000 rpm. It is subjected to ultrasonic agitation (frequency 30,000 Hz, power 200 W) for 15 to 30 minutes before and after each addition of ingredients.
• n 3 times, distributed as follows: The 160 ml ethanol necessary are introduced at the rate of 40 ml in the initiation phase, then 3 replicates of 40 ml. The 10 g of acethylene black are introduced at a rate of 3 g in the initiation phase, then 3 repetitions of 2 g, plus a final adjustment of 1 g alone.
• the final composition obtained has a viscosity of 13.6 cP1. It seems that ethylene glycol promotes the rapid stabilization of the viscosity, which significantly shortens the total duration of the preparation.
• This example can be broken down by modifying the quantities of ingredients and the number of successive additions, within a certain limit and taking into account the particular effect of each of the ingredients on the characteristics of the soil.
• the example detailed above can be modulated as follows:
• the dispersed solution prepared according to Example 5 is used to deposit on a substrate consisting of an aluminum strip obtained as in Example 4, having a thickness of 50 ⁇ m to 80 ⁇ m.
• the deposit is made by the technique of withdrawal-immersion, with a withdrawal speed of between 25 cm / min and 35 cm / min.
• the strip is dried in the open air for 10 to 12 hours, then placed in an oven at 80 ° C. for 3 to 4 hours).
• the Substrate then undergoes a heat treatment at 45O 0 C for 4 hours according to the same protocol as that used in Example 4. After cooling, the substrate is brushed.
• the thin carbon layer deposited on the substrate is uniform, with a thickness of between 10 and 30 ⁇ m. It is homogeneous adhesive and covering, in contact with its support in all points. It is suitable for use as a conductive carbon interface in a current collector.

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