Method for obtaining an electrode from a recycled composite material and use in applications for electrochemical energy storage, seawater desalination and water electrolysis for hydrogen production

Abstract

The invention relates to a method for producing an electrode comprising carbon fibres, the method comprising the following consecutive steps: providing a composite material, the composite material comprising carbon fibres and a resin; pickling at least one surface of the material by scanning a laser beam over the surface to obtain a material comprising a pickled surface which has electronic conduction properties and in which the carbon fibres are at least partly stripped, the material forming a current collector of the electrode; and applying an electrochemically active material to the pickled surface. The invention also relates to an electrode obtained in particular according to this production method and to its use in an electrochemical device.

Description

[0001] METHOD FOR OBTAINING AN ELECTRODE FROM A RECYCLED COMPOSITE MATERIAL AND USE IN APPLICATIONS OF ELECTROCHEMICAL ENERGY STORAGE, SEAWATER DESALINATION AND WATER ELECTROLYSIS FOR HYDROGEN PRODUCTION

[0002] 1. Scope of the invention

[0003] The present invention relates to the fields of energy storage devices (batteries & supercapacitors), capacitive salt water desalination systems, fuel cells and electrolyzers dedicated to hydrogen production. More specifically, it concerns the use of composite materials (used, recycled or production scrap) based on carbon fibers and resin as electrodes for these different devices.

[0004] 2. Prior art

[0005] Currently, the recycling of carbon fiber / resin or fiberglass / resin composite materials is not economically viable, and used parts, manufacturing scrap, etc. are considered waste, which most often ends up in landfills. This solution is not environmentally viable in the medium term, and it is therefore necessary to find ways to reuse these materials.

[0006] It was determined that, surprisingly, these used parts and manufacturing scraps can be used for the manufacture of good quality electrodes, which can be put to various uses following laser etching treatment.

[0007] A few studies report laser stripping, or surface preparation, of carbon fiber composite materials. 1 2but not the manufacture of electrodes from the materials obtained. Moreover, in the majority of current applications, the fibers are often damaged by the pickling treatment, thus reducing the electrical conductivity and mechanical strength properties of the treated composite materials.

[0008] The main disadvantages of the prior art in the use of carbon fiber / resin composite materials are of two types:

[0009] - The applications proposed in the literature and patents use composite materials made specifically for these applications. Thus, there is no question of using existing composite materials that would be recycled in these applications. This of course leads to the use of new carbon fiber fabrics, the production cost of which and the environmental impact of which are high.

[0010] - Surface etching using laser technology on existing composite materials does not allow effective use of these materials for the manufacture of electrodes for energy storage systems, electrolysers or desalinators. Indeed, the fibres are not freed from the resin and the electronic conductivity of the treated surface is not sufficiently increased by this treatment. Also, composite materials thus etched cannot be used as current collectors in the aforementioned devices effectively.

[0011] 3. Description of the invention

[0012] These two major drawbacks are eliminated by the present invention in the sense that it makes it possible not to manufacture composite materials (carbon fibers / resin) formulated specifically for a given application but, on the contrary, it makes it possible to use existing materials, used or not, which have the required performances. Also, the present invention relates to a method for manufacturing an electrode comprising carbon fibers, said method comprising the following successive steps:

[0013] - provision of a composite material, preferably recycled, said composite material comprising carbon fibers and a resin;

[0014] - stripping at least one surface of said material by scanning a laser beam over said surface to obtain a material comprising at least one portion of stripped surface with electronic conduction properties in which the carbon fibers are at least partially stripped, said material forming a current collector of said electrode; and

[0015] - application to said stripped surface of a composition comprising an electrochemically active material.

[0016] In the present description, at least partially stripped carbon fibers are understood to mean that these carbon fibers are, at least partially, not covered with resin at the stripped surface, so that they are at least partially directly exposed to the external environment at this surface.

[0017] Thus, the laser beam stripping step of the method according to the invention is advantageously carried out so as to at least partially remove, on the surface of the material, the carbon fibers from the resin and any impurities covering them. The stripping depth required for this purpose, i.e. the height of material to be removed on the surface of the material, depends on the particular composite material used, and may in particular vary between 1 and 50 μm, preferably between 1 and 5 μm, for example between 1 and 2.5 μm. Preferably, the stripping conditions are also chosen to damage the carbon fibers as little as possible, while at least partially removing the surface layer of resin covering them.

[0018] According to a preferred aspect of the invention, the composite material is a recycled material and / or a production scrap. This material is not intended during its manufacture to be used for the manufacture of electrodes. It may, for example, come from the aeronautical industry which uses a large quantity of this type of material under the name of Carbon Fiber Reinforced Polymer or CFRP. The composite material may advantageously comprise, and / or consist essentially of carbon fibers embedded in resin, which may be a polymer. Also the surface of the starting composite material may consist, mainly or essentially, for example more than 80%, preferably more than 90%, of resin, the laser stripping step aiming to reduce this percentage and increase the surface occupied by the bare carbon fibers.The resin generally used in the manufacture of composite material is an epoxy resin; polyester, vinylester or polyamide are also used. Some types of composites incorporate, in addition to carbon fibers, other reinforcing fibers such as, for example, glass fibers.

[0019] The carbon fibers contained in the composite material used according to the invention can have any conventional dimensions in themselves, in particular a diameter of between 5 and 10 μm, and a length which can, for example, range from 100 μm to several tens of centimeters, for example from more than 1 mm to several tens of centimeters.

[0020] According to the method of the invention, one or more surfaces of the composite material are stripped, at least in part, by a laser treatment which makes it possible to obtain an electronic conductivity suitable for future use by minimally damaging the carbon fibers, thus ensuring very good electronic conductivity of the current collector thus formed. This collector can then be coated with an ink comprising an electrochemically active material suitable for the intended application. Electrodes are thus prepared and assembled together to form a device which is also an object of the invention.

[0021] According to a preferred aspect of the invention, the laser used emits a Gaussian type beam. It is advantageously a pulsed laser capable of emitting a pulsed laser beam at a wavelength between 1000 and 1080 nm. The fluence can be between 2 and 200 J / cm 2and the emitted power peak is advantageously between 1.2 and 7.5 KW. The laser used in the exemplified embodiments is a cleanLASER brand laser, 100 Watts of power, with a Gaussian type beam. It is a pulsed laser capable of emitting a pulsed laser beam at a wavelength between 1000 and 1080 nm, with a fluence between 2 and 200 J / cm 2 and a peak power between 1.2 and 7.5 kW. The CL100 Gaussian is composed of a CL100 central unit and StamplO optics. The CL100 central unit is a class 4, 1064nm fiber laser.

[0022] The laser power may be 100 Watts. It should be noted that lower powers, for example 10 Watts or higher powers, for example 200 to 1000 Watts may be deployed in order to optimize the processing time while respecting the intrinsic parameters allowing the functionality to be obtained on the surface of the structure of the composite material. Thus, preferably, but not necessarily, in particular with a 100 Watt laser, the laser treatment may comprise scanning the laser beam preferably carried out from 1 to 20 times, preferably from 2 to 10 and more preferably from 5 to 10 times.

[0023] Likewise, preferably, but not necessarily, especially with a 100 Watt laser, the laser mark speed in mm / s is advantageously chosen in the range from 3750 to 8475, preferably in the range from 3750 to 6375.

[0024] Also, preferably, but not necessarily, especially with a 100 Watt laser, the laser spacing in mm is chosen in the range of 0.0375 to 0.0850, preferably 0.0375 to 0.064.

[0025] Likewise, preferably, but not necessarily, in particular with a 100 Watt laser, the working distance in mm during said laser treatment is chosen in the range from 211 to 466, preferably from 211 to 359.

[0026] Likewise, preferably, but not necessarily, especially with a 100 Watt laser, the focal length of the lens in mm is advantageously chosen in the range from 160 to 330, preferably from 160 to 254.

[0027] Similarly, preferably, but not necessarily, especially with a 100 Watt laser, the actual spot diameter in pm is chosen in the range from 50 to 113, preferably from 50 to 85.

[0028] The method according to the invention proves to be entirely advantageous in that it makes it possible to form, from a recycled composite material, based on carbon fibers and resin, the carbon fibers preferably being distributed in a matrix of said resin, a current collector for an electrode having so-called active zones, with electronic conduction properties, formed by the stripped zones, which are of desired geometry(s) and surface(s), making it possible to adapt to all possible applications intended for the electrode. It thus makes it possible to form electrodes of all desired configurations, concerning both their geometry itself and their method of mounting within the device in which they are intended to be used.

[0029] The electrochemically active material allows good interaction with the electrolyte associated with the electrodes. It is therefore chosen according to the nature of the latter. For example, it can be chosen to allow and / or promote the insertion and deinsertion of the ions involved in the electrochemical reaction(s) involved during the operation of the device and / or comprise a catalyst for said reaction(s). Many active materials available commercially or prepared in the laboratory are thus potentially depositable on the surface of the stripped composites. Thus the electrochemically active material can, for example, comprise, or consist of: carbon, for example carbon black and preferably microporous activated carbon which is a particularly versatile material, low cost, non-polluting and suitable for many uses,

[0030] LiFePC>4 (lithium iron phosphate), Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio.sMni.sCL or Li4TisOi2 (lithium titanium oxide), in particular for lithium-ion batteries; and / or metal catalysts such as (Pd / C) and (I rCh), or platinum or another platinum group metal (ruthenium, rhodium, palladium, osmium, iridium, rhenium), particularly suitable for the production of hydrogen or oxygen.

[0031] An electronically conductive material to improve the conduction of electricity is advantageously associated with the electrochemically active material. It can be noted that a given compound can have a different function depending on the uses envisaged for the electrode. Thus, carbon black can be used for its conductive properties or its properties of interactions with the electrolyte, or even its properties as a binder. Conventional electronic conductors (carbon black, carbon fibers, etc.) can be replaced by or associated with electronically conductive polymers such as polyaniline, polypyrroles and polythiophenes, and more particularly PEDOT (poly(3,4-ethylenedioxythiophene)) often associated with PSS (polystyrenesulfonate).

[0032] The shaping of certain active materials advantageously requires the presence of a binder, generally of the polymer type, which not only facilitates the adhesion of the constituents of the ink to the current collector but also improves the cohesion of said active material, such as carbon, LiFePC>4 (lithium iron phosphate, also called LFP), Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio.sMni.sCL or even Li4TisOi2 (lithium titanium oxide), which generally requires the use of polymers which can be chosen from the group consisting of:

[0033] Water-soluble polymers such as cellulose derivatives CMC (carboxymethylcellulose) or HMC (hydroxymethylcellulose);

[0034] Copolymer latexes such as NBr (acrylonitrilebutadiene), SBr (styrene-butadiene);

[0035] Ethylene-propylene-diene terpolymer;

[0036] PVDF (polyvinylidene fluoride);

[0037] PVA (poly(vinyl alcohol); and mixtures thereof.

[0038] PTFE (polytetrafluoroethylene).

[0039] To deposit the electrochemically active material, optionally associated with a binder and / or an electronic conductor on the current collector, it can advantageously be mixed with a solvent such as water or N-methyl pyrrolidone. Thus, according to a preferred aspect of the method according to the invention, said electrochemically active material is applied in the form of a suspension of a powder in a liquid, or semi-liquid, comprising a solvent. Said electrochemically active material can comprise microporous carbon, graphite, a lithiated oxide such as LiFePCU, Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio.sMni.sCL or Li4TisOi2, and / or a carbon powder coated with palladium and / or lrC>2, or platinum or another platinum group metal. Said composition may comprise an electronically conductive additive such as carbon black, and may further comprise a binder.

[0040] Thus, the active material can advantageously be mixed with an electronic conductor (carbon black for example), a polymer binder (polyvinylydene difluoride for example), and a solvent (N-methyl pyrrolidone for example) in the appropriate proportions to obtain an ink that can be deposited on the surface of the current collectors previously prepared. Indeed, once at least partially stripped by laser treatment, the carbon fibers retain their electronic conduction properties and have an increased specific surface area compared to raw fibers coated with polymer powder (sizing), which makes them excellent current collectors for electrode materials in conversion devices (fuel cells, electrolyzers) or energy storage devices (Li-ion batteries, Na-ions, supercapacitors, hybrid systems).This latter approach is also transposable to the problems of desalination of seawater by capacitive deionization. The present invention therefore relates to the laser stripping of already formed composite materials (scrap, production offcuts, recycling), which benefits their coating with an active material preferably in the form of ink, allowing them to be given properties in energy storage (supercapacitors and batteries), hydrogen production (electrolyzers), conversion of chemical energy into electrical energy (fuel cells), and desalination of seawater (capacitive deionization).

[0041] Also another object of the invention is an electrode obtained or capable of being obtained according to the method of the invention described above. This electrode may comprise:

[0042] - a current collector based on a composite material, preferably recycled, comprising carbon fibers and a resin, said material being stripped, preferably by laser, on at least one surface portion, in which the carbon fibers are at least partially stripped - this means that they are at least partially no longer covered with resin - this stripped surface portion having electronic conduction properties;

[0043] - and a composition comprising an electrochemically active material applied to said etched surface portion, this electrochemically active material preferably comprising microporous carbon, graphite, a lithiated oxide such as LiFePCL, Li(Ni,Mn,Co)C>2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio,5Mni,s04 or Li4Ti50i2, and / or a carbon powder coated with palladium and / or lrC>2, or platinum or another platinum group metal; and wherein said composition may comprise an electronically conductive additive such as carbon black, and may further comprise a binder.

[0044] This electrode may comprise the component(s) described above with reference to the method. The current collector may in particular comprise a surface comprising both a laser-etched active portion, for example having a surface area greater than 35%, and a significant portion, for example greater than 10%, the carbon fibers of which are covered with resin.

[0045] Another object of the invention is the use of an electrode as described above, for the manufacture of an energy storage device, such as a battery or a supercapacitor, a capacitive desalination system for salt water, a fuel cell and / or an electrolyzer dedicated to the production of hydrogen.

[0046] Another subject of the invention is an energy storage device, such as a battery or a supercapacitor, a capacitive desalination system for salt water, a fuel cell and / or an electrolyzer dedicated to the production of hydrogen, comprising an electrode according to the invention. Microporous carbon is a preferred electrochemically active material for use in capacitive deionization and in a supercapacitor. Graphite, LiFePC>4, Li(Ni,Mn,Co)C>2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio.sMni.sCL, Ü4TisOi2 or other lithiated oxides are particularly suitable for lithium-ion batteries. The use of carbon powder coated with palladium and / or lrC>2, or platinum or another platinum group metal, is particularly suitable for the manufacture of an electrode for an electrolyser dedicated to the production of hydrogen.

[0047] 4. Description of figures and diagrams

[0048] Figure 1 is a view of the composite test piece P5 laser-etched according to the method of the invention of example 1 which comprises a working zone 1 and an electrical contact zone 2;

[0049] Figure 2 represents optical microscopy views of test pieces P1, P4, P5 and P6;

[0050] Figure 3 represents scanning electron microscopy views of the etched surfaces of test pieces P1, P4, P5 and P6;

[0051] Figure 4 is a view of the areas etched to be used for the manufacture of electrodes according to the invention;

[0052] Figure 5 shows cyclic voltammograms (CVs) of electrodes comprising etched material P1, P4, P5 or P6 with ink E2 cycled at 10 mV / s, 20 mV / s, 50 mV / s, 100 mV / s; Figure 6 shows a cyclic voltammogram (CV) of an electrode comprising etched material P5 with ink E2 cycled at 5 mV / s;

[0053] Figure 7 shows the constant current and voltage bias charging curve and electrochemical impedance (EIS) curves for the water to be desalinated, the desalinated water, and the salt-depleted water of Device and Method 1 of Example 3;

[0054] Figure 8 shows the constant current and voltage bias charging curve and electrochemical impedance (EIS) curves for the water to be desalinated, the desalinated water, and the salt-depleted water of Method 2 of Example 3;

[0055] Figure 9 shows the constant current and voltage bias charging curve and electrochemical impedance (EIS) curves for the water to be desalinated, the desalinated water, and the salt-depleted water of Method 3 of Example 3;

[0056] Figure 10 shows the galvanostatic cycling (charge / discharge) under constant current with potential limitation (GCPL) of a graphite electrode deposited on a composite support according to example 4;

[0057] Figure 11 shows the hydrogen evolution (HER) results in H2SO4 (pH 0) from Example 5;

[0058] Figure 12 shows the oxygen evolution (OER) results in H2SO4 (pH 0) of Example 5;

[0059] Figure 13 shows the results of a complete electrolysis cell in H2SO4 (pH 0) from Example 5;

[0060] Figure 14 shows the OER and HER clearance potentials of the cells of Example 5;

[0061] Figure 15 shows the polarization associated with the application of an increasing current in a complete cell in H2SO4 (pH 0) according to Example 5.

[0062] Example 1: Laser stripping of carbon fiber / resin composites

[0063] Composite plates of 25x50mm (specimens) were stripped using the process according to the invention. The composite material used is composed of an organic matrix of epoxy resin with carbon fiber reinforcements. This material comes from the aeronautical field. The carbon fibers and the epoxy resin were originally assembled by vacuum infusion.

[0064] The laser used is a cleanLASER brand laser, 100 Watts of power, with a Gaussian beam. It is a pulsed laser capable of emitting a pulsed laser beam at a wavelength between 1000 and 1080 nm, with a fluence between 2 and 200 J / cm 2 and a power peak between 1.2 and 7.5 kW.

[0065] The CL100 Gaussian consists of a CL100 central unit and a StamplO optic.

[0066] The CL100 central unit is a Class 4, 1064nm fiber laser with the following characteristics:

[0067] The central unit is connected to the optics via a 2.5m umbilical.

[0068] The StamplO optic, which is connected to the CleanStudio software, allows for continuous processing of parts. The characteristics of this optic are as follows:

[0069] The specific process parameters in the implementation examples are as follows:

[0070] Table 1

[0071] The application of the process on the plates was carried out on two separate areas in order to define a working area (1) and an electrical contact area (2) (see Figure 1). Comparative examples: test pieces P1, P2, P3, P4, P6.

[0072] Different parameters were used on plates of the same composite to establish the advantages of the process according to the invention. These parameters are compiled in Table 1. Microscopic observations:

[0073] Parameter sets P1 to P3 present the laser operating parameters for which only the number of passes differs. Based on visual observations, only the specimens etched with parameters P1, P4, P5 and P6 were observed by optical microscopy.

[0074] As shown in Figure 2, the surfaces stripped with the parameters, or levels, P5 and P6, respectively 0.416 cm 2 and 0.429 cm 2 , are much higher than those obtained for levels P1 and P4 (respectively 0.178 cm 2 and 0.223 cm 2 ).

[0075] However, scanning electron microscopy images (Figure 3) of the stripped surfaces show fiber damage / breakage that is more significant with level P1 and level P6 than with P5. Level P4 shows little damage.

[0076] Electrochemical tests showed better electronic conductivity for parameter P5 than for P4, which seems to indicate that to have better conductivity, it is better to have some broken fibers but with less residual resin around and between the fibers. Example 2: Production of supercapacitors

[0077] Supercapacitors are energy storage systems by adsorption of ions on the surface of carbon electrodes with a large specific surface area (e.g. activated carbons) when these electrodes are polarized. They have a moderate stored energy density compared to batteries (approximately 7 W / kg) with a much higher power density (approximately 8 kW / kg). Supercapacitor electrodes based on composite materials previously stripped as described in Example 1 were coated with an ink containing commercial activated carbon.

[0078] The active ingredient used is:

[0079] YP-50 activated carbon (supplier: Kuraray Europe GmbH 2021) i.e. mainly microporous carbon (< 2nm) with a specific pore volume of 0.7 ml / g, a specific surface area of ​​1600m / g 2 , a capacity of 28 F / g (for a two-electrode system, per total g of the two electrodes) and 19 F / cc, and

[0080] Conductive carbon (PUREREBLACK 205-110 Carbon - Superior Graphite Co. Chicago, IL, USA, referred to as SG45 in this document).

[0081] Different formulations were evaluated by electrochemical tests.

[0082] Two electrode formats are used with areas etched according to the method of Example 1 of different surfaces. These areas have a surface area of ​​0.5 cm 2 (or 9 cm 2 for example 3) and are shown in Figure 4. Once stripped, the surfaces are cleaned ultrasonically in ethanol, then dried in a vacuum oven for 2 hours at 60°C. The ink has the E2 formulation shown in Table 2:

[0083] E2 Ink

[0084] The binder of E2 ink is PVDF (polyvinylidene fluoride), brand Solef 5130, and the solvent is N-methyl-2-pyrrolidone (NM P).

[0085] This composition is deposited in liquid form and is called "ink" because of its consistency. It can be obtained using the following process: - The masses of YP50 from the company Kuraray (a microporous carbon with most of the pores smaller than 2 nm and with a cumulative pore volume close to 0.7 mL.g -1 ) and carbon black (Superior Graphite Co., >99%) are weighed on a scale accurate to 1 / 100 mg and placed in a pillbox. The mixture is then stirred using a magnetic bar whose length is almost equal to the diameter of the pillbox in order to obtain the best possible homogenization.

[0086] - The powders are mixed together to avoid the formation of clumps;

[0087] - A dilution of the PVDF binder in the NMP to obtain a solution of 7% by mass is carried out and this is poured drop by drop onto the powder mixture;

[0088] - The solvent is poured drop by drop onto the previous mixture, with stirring, until the desired mass and viscous texture are obtained; and

[0089] - Stirring is maintained until use.

[0090] The ink is deposited on the stripped composite parts as follows:

[0091] - Weighing the sample without ink;

[0092] - Depositing the ink with a pipette on the area delimited by a mask;

[0093] - Vacuum drying at 60°C;

[0094] - Weighing of the sample with ink to determine the mass of active material added;

[0095] - Conditioning of the electrode in the electrolytic medium used for the tests.

[0096] The electrochemical cell (FlatCell) used for the measurements includes:

[0097] - a reference electrode (RE): Ag / AgCI (3M NaCI in aqueous medium);

[0098] - a counter-electrode (CE): Wound Pt wire;

[0099] - a working electrode (WE), the electrode according to the invention comprising the stripped composite P1, P4 to P6 + ink (mass deposited between 2 and 4 mg on a surface of 0.5 cm 2 )

[0100] - the electrolyte is an aqueous solution of lithium nitrate (UNO3) at a concentration of 5 mol / L.

[0101] Electrochemical measurements are carried out according to the following parameters:

[0102] - Scanning speeds: 5, 10, 20, 50 and 100 mV / s;

[0103] - Number of cycles: 10;

[0104] - E+: +0.3V vs. Ag / AgCI;

[0105] - E-: -0.1V vs. Ag / AgCI.

[0106] Results :

[0107] Cycling tests at different scan rates (10, 20, 50 and 100 mV / s) show, in Figure 5, that the electronic signature of electrodes P1, P4, P5 and P6 is the classic electrochemical signature of a supercapacitor electrode.

[0108] Different quantities of ink (active material + conductive material) were deposited on a P5 electrode: either 2.19 mg or 3.88 mg at 5 mV / s. The results (see Figure 6) show that the electrode made of P5+E2 delivers on average 100 to 120F / g (of active material), which is the expected value for a YP50 carbon electrode conventionally used on a current collector made of aluminum, stainless steel or nickel for example.

[0109] For applications as supercapacitor electrodes, the best pair is P5 with E2 ink. The measured capacitance is identical to that of an electrode coated on a conventional metal current collector, thus showing that the etched composite plays the role of current collector well and that the performance is not affected by this collector compared to a standard electrode (metal current collector (stainless steel, nickel, aluminum) + ink) of a supercapacitor (Figure 6).

[0110] This is a particular application of supercapacitors where salt water is circulated between two electrodes as presented previously and by polarizing these electrodes the Na ions +and Cl' are removed from the water, which is therefore less salty at the outlet of the device. A new batch of salt water is then introduced into the device and the ions are released at the same time as electrical energy is recovered. The desalinated water undergoes several cycles of this treatment to generally end up in a reverse osmosis system which produces fresh water and the water which is saturated with salt is discharged into the sea or can be used in salt marshes. The supercapacitor electrodes prepared previously can also be used in a desalination or capacitive deionization system. This example shows a complete cell with the demonstration of the capture of NaCl during the charging of the device (desalination of seawater) and its release during the discharge with energy recovery as in a supercapacitor.

[0111] The water initially introduced undergoes several cycles of this treatment to bring it to a minimum NaCI content while the second aliquot of water introduced is supersaturated with salt and normally discharged into the sea during the process, or recovered in a salt marsh.

[0112] Preparation of the electrodes:

[0113] The electrodes used are 9cm electrodes 2 (see Figure 4) coated with ink E2 whose formulation is indicated in Table 2 of Example 2.

[0114] They are dried in a vacuum oven for 2 hours at 60°C and conditioned by immersion in the electrolyte for 5 minutes.

[0115] Electrochemical tests:

[0116] The cell used is a Plexiglas cell (20mL) designed and produced internally with:

[0117] - CE + ER: P5 stripped composite with or without E2 ink;

[0118] - WE: P5 stripped composite with or without E2 ink;

[0119] - Electrolyte: Artificial seawater or NaCI at 3g / L (0.05 M).

[0120] Different techniques were used for the evaluation of capacitive desalination performance: - Constant current charging followed by voltage polarization.

[0121] - EIS: Electrochemical impedance spectroscopy to estimate the resistance of the electrolyte and therefore the NaCI salt content.

[0122] Devices and methods 1 to 3 demonstrate the ability of electrodes to desalinate seawater.

[0123] For all tests:

[0124] => R (salt-depleted water) > R (desalinated water) > R (water to be desalinated) (Figures 7 to 9)

[0125] => The increase in resistance for the water having undergone the first treatment (compared to the initial salt water) shows that the salt content has decreased in this water (the ionic conductivity decreases, therefore the resistance increases) whereas for the second aliquot of salt water the resistance has decreased (compared to the initial water) thus showing that the Na ions + and Cl' were returned to the salt water during discharge (ionic conductivity increases, therefore resistance decreases). At the same time, the electricity initially injected into the cell to remove the Na ions + and Cl' was recovered during this same discharge.

[0126] => The best results were obtained with device and method 1. The device is effective in desalinating seawater. Example 4: lithium-ion batteries

[0127] The commercial graphite-based ink (SFG6 TIMREX Primary Synthetic Graphite from IMERYS, produced using a controlled graphitization process) was prepared with 80% by mass of active material (SFG6 graphite), 10% by mass of SOLEF binder dissolved in NM P, and 10% by mass of SG45 carbon black used in Example 2. The mixture was supplemented with NMP until the desired viscosity was obtained before being coated onto the laser-etched composite material P5.

[0128] • Preparation of inks:

[0129] - In a pillbox, place a magnetic bar of a length equal to the diameter of the pillbox (important for mixing well right up to the edges);

[0130] - Weighing of SFG6 and SG45 on a scale accurate to 1 / 100 mg;

[0131] - Mixing the powders together to avoid the formation of clumps;

[0132] - Take the binder (SOLEF) diluted in NMP at 7% and pour drop by drop until the desired mass is obtained;

[0133] - Dilution with NMP by adding drop by drop => desired viscous texture;

[0134] - Continuous stirring until use.

[0135] • Coating of ink on stripped P5 composites:

[0136] - Weighing the sample without ink;

[0137] - Deposit ink using a pipette on an area delimited by a mask;

[0138] - Vacuum drying at 60°C;

[0139] - Weighing of the active ingredient;

[0140] - Conditioning of the electrode in the electrolytic medium used.

[0141] The electrode was then cycled at constant current (C / 20 regime for the first charge then C / 10 for the following charges and discharges, the applied currents theoretically correspond to a charge in 20 hours and a discharge or charge in 10 hours thereafter, respectively) between 50mV and 1.5V with respect to a reference lithium metal electrode, in a commercial LP30 electrolyte (consisting of cyclic (ethylene: EC) and linear (dimethyl: DMC) carbonates of mass fraction 50 / 50% and LiPFe salt at 1 mol). Figure 10 shows that the first charge capacity is close to the theoretical capacity (372mAh / g) as well as the following discharge. This example shows the feasibility of a lithium-ion battery with electrodes deposited on a current collector made of laser-etched composite material.

[0142] In this last example, an electrode according to the invention is used to carry out the electrolysis of water (acidic or basic) and thus produce hydrogen and oxygen. The laser-etched composites as previously are coated, among other things, with standard catalysts for hydrogen evolution (HER) and oxygen evolution (OER) reactions. The catalysts were obtained from chemical suppliers (Alfa Aesar, Sigma Aldrich, Fischer).

[0143] Preparation of electrodes: Different formulations, with or without catalysts, were evaluated.

[0144] The catalysts used are Palladium on carbon (Pd-C) for hydrogen release (HER) and iridium oxide I rC>2 for oxygen release (OER).

[0145] The formulations of the best performing inks are given below:

[0146] ♦ E3 Ink - Pd / C:

[0147] Table 3

[0148] ♦ E4bis ink - I rO2 (80%Wt) / C:

[0149] E4 bis IrOz ink

[0150] Table 4 The electrodes used are 9cm electrodes 2 (Figure 4) coated or not with E2 (without catalyst), E3 (Pd) and E4bis (IrOz) inks.

[0151] They are dried in a vacuum oven for 2 hours at 60°C and conditioned by immersion in the electrolyte for 5 minutes.

[0152] Electrochemical tests in 1M H2SO4 (pH 0) - HER / OER: Parameters:

[0153] - The cell used is a Plexiglas cell (20mL) designed and produced internally with:

[0154] - CE: P5 stripped composite with E2 ink;

[0155] - WE: P5 stripped composite without ink and with E2 or E3 ink;

[0156] - ER: Ag / AgCI for H2SO41M (pH 0); And

[0157] - Electrolyte: H2SO4, 1M (pH 0).

[0158] The HER results in H2SO4 are given in Figure 11 and the OER results in H2SO4 are given in Figure 12.

[0159] Electrochemical tests in full cell in H2SO4 (pH 0) - CV:

[0160] Settings:

[0161] The cell used is a Plexiglas cell (20mL) designed and produced internally.

[0162] RESUME :

[0163] - CE+ER: P5 stripped composite with E2 or E3 ink;

[0164] - WE: P5 stripped composite with E2 or E4bis ink;

[0165] - Electrolyte: H2SO4 1 M (pH 0);

[0166] - 5 mv / s.

[0167] The electrolysis results are shown in Figure 13.

[0168] CV Conclusion:

[0169] The gas release (electrolysis) voltages (potential differences) are measured in Figure 14 and are compiled in Table 5 below:

[0170] Table 5

[0171] We are therefore approaching the theoretical 1.23 V for water electrolysis and we do not observe any degradation of the electrodes, which is a guarantee of durability, an important parameter for electrolysers.

[0172] Full cell electrochemical tests in H2SO4 (oH 0) - CA:

[0173] In this test, an increasing current is applied to the electrolysis cell and its polarization is measured.

[0174] ♦ Settings:

[0175] THAT :

[0176] - CE+ER: P5 stripped composite with E3 ink;

[0177] - WE: P5 etched composite with E4bis ink; - Electrolyte: H2SO4 1 M (pH 0);

[0178] - 1 imposed: variable;

[0179] ♦ Results: Figure 15

[0180] The imposed current is to be reported to the surface of the pads coated with 0.5 cm catalysts 2 The imposed current density is therefore between 100 and 400mA / cm 2which is significant for an electrolysis cell. The polarization at various current values ​​is typical for this type of catalyst, the current collector in the form of laser-etched composite material does not negatively influence this polarization. The cell also appears to have good durability, which is an important parameter for this type of device.

[0181] References

[0182] 1: Enhanced out of Plane Electrical Conductivity in Polymer Composites Induced by CO2 Laser Irradiation of Carbon Fibers, Anastasios Karakassides, Angeliki Karakassides, Michaella Konstantinidou, Alkiviadis S. Paipetis and Pagona Papakonstantinou, Appl. Sci. 2020, 10, 3561; doi:10.3390 / app10103561.

[0183] 2 : Laser Treatments for Improving Electrical Conductivity and Piezoresistive Behavior of Polymer-Carbon Nanofiller Composites, Andrea Caradonna, Claudio Badini, Elisa Padovano, Antonino Veca, Enea De Meo and Mario Pietroluongo, Micromachines 2019, 10, 63; doi:10.3390 / mi10010063.

Claims

Claims

1. A method of manufacturing an electrode comprising carbon fibers, said method comprising the following successive steps: - provision of a composite material, preferably recycled, said composite material comprising carbon fibers and a resin; - stripping at least one surface of said material by scanning a laser beam over said surface to obtain a material comprising at least one portion of stripped surface with electronic conduction properties in which the carbon fibers are at least partially stripped, said material forming a current collector of said electrode; and - application to said stripped surface of a composition comprising an electrochemically active material.

2. The method of claim 1, wherein the scanning of the laser beam is preferably carried out 1 to 20 times, preferably 2 to 10 and more preferably 5 to 10 times.

3. A method according to claim 1 or 2, wherein the speed of the mark in mm / s is chosen in the range from 3750 to 8475, preferably in the range from 3750 to 6375.

4. A method according to any one of claims 1 to 3, wherein the spacing in mm is chosen from the range of 0.0375 to 0.0850, preferably 0.0375 to 0.

064.

5. A method according to any one of claims 1 to 4, wherein the working distance in mm is chosen from the range from 211 to 466, preferably from 211 to 359.

6. A method according to any one of claims 1 to 5, wherein the focal length of the lens in mm is chosen from the range of 160 to 330, preferably 160 to 254.

7. A method according to any one of claims 1 to 6, wherein the actual dot diameter in pm is selected from the range 50 to 113, preferably 50 to 85.

8. A method according to any one of claims 1 to 7, wherein said electrochemically active material is applied as a suspension of a powder in a liquid, or semi-liquid, comprising a solvent.

9. A method according to claim 8, wherein said electrochemically active material comprises microporous carbon, graphite, a lithiated oxide such as LiFePC>4, Li(Ni,Mn,Co)O2, LiMn2O4, LiNio.sMni.sOt or Li4Ti50i2, and / or a carbon powder coated with palladium and / or lrC>2, or platinum or another platinum group metal.

10. A method according to claim 8 or 9, wherein said composition comprises an electronically conductive additive such as carbon black and / or a binder.

11. A method according to any one of claims 1 to 10, wherein said composite material consists essentially of carbon fibers embedded in said resin.

12. Electrode obtainable by a method according to any one of claims 1 to 11, comprising: - a current collector based on a composite material, preferably recycled, comprising carbon fibers and a resin, said material being stripped on at least one surface portion, in which the carbon fibers are at least partially stripped, said stripped surface portion having electronic conduction properties, and - a composition comprising an electrochemically active material applied to said stripped surface portion

13. An electrode according to claim 12, wherein said electrochemically active material comprises microporous carbon, graphite, a lithium oxide such as LiFePOt, Li(Ni,Mn,Co)C>2, LiMn2O4, LiNio.5Mn1.5O4 or Li4TisOi2, and / or a carbon powder coated with palladium and / or I rC>2, or platinum or another platinum group metal.

14. An electrode according to claim 12 or 13, wherein said composition comprises an electronically conductive additive such as carbon black, and / or a binder.

15. Use of an electrode as described in any one of claims 12 to 14, for the manufacture of an energy storage device, such as a battery or a supercapacitor, a capacitive salt water desalination system, a fuel cell and / or an electrolyzer dedicated to the production of hydrogen.

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