Process 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

Abstract

A method for manufacturing an electrode comprising carbon fibers, said method comprising the following successive steps: providing a composite material, said composite material comprising carbon fibers and a resin; stripping at least one surface of said material by scanning said surface with a laser beam to obtain a material comprising a stripped surface; and applying an electrochemically active material to said stripped surface. The invention also relates to an electrode obtained, in particular, according to this manufacturing method and its use in an electrochemical device.

Description

Title of the invention: 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 1. Scope of the invention

[0001] The present invention falls within the fields of energy storage devices (batteries & supercapacitors), capacitive desalination systems for salt water, fuel cells, and electrolyzers dedicated to hydrogen production. More specifically, it relates to the use of composite materials (used, recycled, or production offcuts) based on carbon fibers and resin as electrodes for these various devices. 2. Prior art

[0002] Currently, recycling carbon fiber / resin or fiberglass / resin composite materials is not economically viable, and used parts, manufacturing scraps, etc., are considered waste, which most often ends up in landfills. This solution is not environmentally sustainable in the medium term, and it is therefore necessary to find ways to reuse these materials.

[0003] It has been determined that, surprisingly, these used parts and manufacturing scraps can be used for the manufacture of good quality electrodes, which can be intended for various uses following a laser pickling treatment.

[0004] Some studies report on the laser stripping, or surface preparation, of carbon fiber-based composite materials1 2 but not on the fabrication of electrodes from the materials obtained. Moreover, in most current applications, the fibers are often damaged by the stripping treatment, thus reducing the electrical conductivity and mechanical strength of the treated composite materials.

[0005] The main disadvantages of the prior art regarding the use of carbon fiber / resin composite materials are of two types:

[0006] - The applications proposed in the literature and patents implement Composite materials are specifically designed for these applications. Therefore, using existing composite materials that would be recycled is out of the question. This naturally necessitates the use of new carbon fiber fabrics, which have a high production cost and environmental impact. - Surface stripping using laser technology on existing composite materials does not allow for the effective use of these materials for electrode manufacturing. energy storage systems, electrolyzers, or desalination plants are affected. Indeed, the fibers are often damaged, and the electronic conductivity of the treated surface is not sufficiently increased by this treatment. Therefore, the resulting depolished composite materials cannot be used effectively as current collectors in the aforementioned devices. 3. Description of the invention

[0007] These two major drawbacks are eliminated by the present invention in that it eliminates the need to manufacture composite materials (carbon fibers / resin) specifically formulated for a given application, but rather allows the use of existing materials, whether used or not, that exhibit the required performance. The present invention also relates to a method for manufacturing an electrode comprising carbon fibers, said method comprising the following successive steps:

[0008] - making available a composite material, said composite material comprising carbon fibers and a resin;

[0009] - stripping at least one surface of said material by scanning with a laser beam on said surface to obtain a material comprising at least a portion of stripped surface; and

[0010] - application to said stripped surface of a composition comprising a material electrochemically active.

[0011] According to a preferred aspect of the invention, the composite material is a recycled material and / or a production waste product. This material is not intended, during its manufacture, for use in the production of electrodes. It may, for example, come from the aerospace industry, which uses a large quantity of this type of material under the name Carbon Fiber Reinforced Polymer or CFRP. The composite material may advantageously comprise, and / or be essentially composed of, carbon fibers embedded in resin, which may be a polymer. The surface of the initial composite material may also be composed, predominantly or essentially, for example, of more than 80%, preferably more than 90%, of resin. The resin generally used in the manufacture of the composite material is an epoxy resin; polyester, vinyl ester, or polyamide are also used.Some types of composites incorporate, in addition to carbon fibers, other reinforcing fibers such as, for example, glass fibers.

[0012] According to the process of the invention, one or more surfaces of the composite material are etched, at least partially, by a laser treatment which makes it possible to obtain adequate electronic conductivity 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.

[0013] According to a preferred aspect of the invention, the laser used emits a Gaussian beam. Advantageously, it is 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 / cm² and the peak power emitted is advantageously between 1.2 and 7.5 kW. The laser used in the exemplified embodiments is a cleanLASER brand laser, 100 Watts, 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 / cm² and a peak power between 1.2 and 7.5 kW. The CL100 Gaussian consists of a CL100 central unit and StamplO optics. The CL100 central unit is a class 4, 1064nm fiber laser.

[0014] The laser power can be 100 Watts. It should be noted that lower powers, for example 10 Watts or higher powers, for example 200 to 1000 Watts, can 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.

[0015] Thus, preferably, but not necessarily, with a 100 Watt laser, the laser treatment can include a scanning of the laser beam carried out preferably from 1 to 20 times, preferably from 2 to 10 and more preferably from 5 to 10 times.

[0016] Similarly, preferably, but not necessarily, with a 100 Watt laser, the speed of the laser brand in mm / s is advantageously chosen in the range from 3750 to 8475, preferably in the range from 3750 to 6375.

[0017] Similarly, preferably, but not necessarily, with a 100 Watt laser, the laser spacing in mm is chosen in the range from 0.0375 to 0.0850, preferably from 0.0375 to 0.064.

[0018] Similarly, preferably, but not necessarily, with a 100 Watt laser, the working distance in mm during said laser treatment is chosen from the range of 211 to 466, preferably from 211 to 359.

[0019] Similarly, preferably, but not necessarily, 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.

[0020] Similarly, preferably, but not necessarily, with a 100-watt laser, the actual spot diameter in pm is chosen from the range of 50 to 113, preferably from 50 to 85. The electrochemically active material allows for good interaction with the electrolyte associated with the electrodes. It is therefore chosen according to of its nature. For example, it may be chosen to enable and / or promote the insertion and deinsertion of ions involved in the electrochemical reaction(s) occurring during the device's operation and / or include a catalyst for said reaction(s). Many commercially available or laboratory-prepared active materials can thus potentially be deposited on the surface of the etched composites. For example, the electrochemically active material may include, or be composed of: - carbon, for example carbon black and preferably microporous activated carbon, which is a particularly versatile, low-cost, non-polluting material suitable for many uses, - of LiFePO4 (lithium iron phosphate), of Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio>5Mnij5O4 or even of Li4Ti5O2 (lithium titanium oxide), particularly for lithium-ion batteries; and / or - metallic catalysts such as (Pd / C) and (IrO2), particularly suitable for the production of hydrogen or oxygen.

[0021] An electronically conductive material that improves electrical conductivity is advantageously combined with the electrochemically active material. It should be noted that a given compound can have a different function depending on the intended use of the electrode. Thus, carbon black can be used for its conductive properties, its interaction properties with the electrolyte, or even its properties as a binder. Conventional electronic conductors (carbon black, carbon fibers, etc.) can be replaced by, or combined with, electronically conductive polymers such as polyaniline, polypyrroles, and polythiophenes, and more specifically PEDOT (poly(3,4-ethylenedioxythiophene)), often combined with PSS (polystyrene sulfonate).

[0022] 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 ink constituents to the current collector but also improves the cohesion of said active material, such as carbon, LiFePO4 (lithiumized iron phosphate, also known as LFP), Li(Ni,Mn,Co)O2 (also known as NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNioJ5Mni>5O4 or even Li4ThO2 (lithiumized titanium oxide), which generally requires the use of polymers that can be chosen from the group consisting of: - Water-soluble polymers such as cellulosic derivatives CMC (carboxymethylcellulose) or HMC (hydroxymethylcellulose); - Copolymer latexes such as NBr (acrylonitrilebutadiene), SBr (styrene-butadiene); - The ethylene-propylene-diene terpolymer; - PVDF (polyvinylidene fluoride); - PVA (poly(vinyl alcohol); and their mixtures. - PTFE (polytetrafluoroethylene).

[0023] To deposit the electrochemically active material, possibly 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-methylpyrrolidone.

[0024] Thus, according to a preferred aspect of the process according to the invention, said electrochemically active material is applied in the form of a powder suspension in a liquid, or semi-liquid, comprising a solvent. Said electrochemically active material may comprise microporous carbon, graphite, a lithium oxide such as LiFePO4, Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio.5Mn1.5O4 or Li4Ti5O2, and / or a carbon powder coated with palladium and / or IrO2. Said composition may comprise an electronically conductive additive such as carbon black, and may, furthermore, comprise a binder.

[0025] 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-methylpyrrolidone, for example) in the appropriate proportions to obtain an ink that can be deposited on the surface of the previously prepared current collectors. Indeed, once at least partially debarked by laser treatment, the carbon fibers retain their electronic conductivity properties and exhibit a significantly higher specific surface area compared to raw fibers coated with polymer powder (ensizing), making them excellent current collectors for electrode materials in conversion devices (fuel cells, electrolyzers) or energy storage devices (Li-ion, Na-ion batteries, supercapacitors, hybrid systems).This latter approach is also applicable to the problems of seawater desalination by capacitive deionization. The present invention therefore relates to the laser stripping of already formed composite materials (scraps, production offcuts, recycling), which facilitates their coating with an active material, preferably in the form of an ink, enabling them to be given properties in energy storage (supercapacitors and batteries), hydrogen production (electrolyzers), the conversion of chemical energy into electrical energy (fuel cells), and seawater desalination (capacitive deionization).

[0026] Another object of the invention is an electrode obtained or obtainable according to the process of the invention described above. This electrode may comprise a current collector based on a material, preferably recycled, comprising carbon fibers and a resin, said material being, at least in part, etched, preferably by laser, and a composition comprising an electrochemically active material, this comprising, preferably, microporous carbon, graphite, a lithium oxide such as LiFePO4, Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNio.5Mn1.5O4 or LiTisOn, and / or a carbon powder coated with palladium and / or IrO2; and where said composition may comprise an electronically conductive additive such as carbon black, and may, in addition, comprise a binder.

[0027] This electrode may include the component(s) described above with reference to the process. It may also include a surface comprising both a laser-etched active portion, for example having a surface area greater than 35%, and a non-negligible portion, for example greater than 10%, whose carbon fibers are coated with resin.

[0028] 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 salt water desalination system, a fuel cell and / or an electrolyzer dedicated to the production of hydrogen.

[0029] Another object of the invention is an energy storage device, such as a battery or supercapacitor, a capacitive saltwater desalination system, a fuel cell, and / or an electrolyzer dedicated to hydrogen production, 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, LiFePO4, Li(Ni,Mn,Co)O2 (also called NMC, the atomic sum of the three elements being equal to 1), LiMn2O4, LiNiO5MNiO4, Li4TiO5O2, or other lithium oxides, are particularly suitable for lithium-ion batteries. The use of carbon powder coated with palladium and / or IrO2 is particularly well-suited to the manufacture of an electrode for an electrolyzer dedicated to hydrogen production. 4. Description of figures and diagrams

[0030] To be adapted according to the diagrams that will be retained in the final version. The legends are indicated below the figures in what follows.

[0031] [Fig.1] is a view of the composite specimen P5 laser-etched according to the process of the invention of Example 1 which includes a working area 1 and an electrical contact area 2;

[0032] [Fig.2] are optical microscopy views of test specimens PI, P4, P5 and P6;

[0033] [Fig.3] are scanning electron microscopy views of the stripped surfaces PI, P4, P5 and P6 test tubes;

[0034] [Fig.4] is a view of the areas stripped for use in manufacturing of electrodes according to the invention. ;

[0035] [Fig. 5] Cyclic voltammograms (CVs) of electrodes comprising the material stripped PI, P4, P5 or P6 with E2 ink cycled at 10 mV / s, 20 mV / s, 50 mV / s, 100 mV / s.

[0036] [Fig. 6] Cyclic voltammogram (CV) of an electrode comprising the material stripped P5 with E2 ink cycled at 5 mV / s;

[0037] [Fig.7] represents the constant current charging and polarization curve in voltage and electrochemical impedance curves (EIS) for water to be desalinated, desalinated water and salt-depleted water from device and method 1 of example 3.

[0038] [Fig.8] represents the constant current charging curve and voltage bias curve and the electrochemical impedance (EIS) curves for water to be desalinated, desalinated water and salt-depleted water of method 2 of example 3.

[0039] [Fig.9] represents the constant current charging and polarization curve in voltage and electrochemical impedance curves (EIS) for water to be desalinated, desalinated water and salt-depleted water from method 3 of example 3.

[0040] [Fig. 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.

[0041] [Fig. 11] shows the hydrogen evolution (HER) results in H2SO4(pH 0) from example 5

[0042] [Fig. 12] shows the oxygen release (OER) results in H2SO4(pH 0) from example 5;

[0043] [Fig. 13] shows the results of a complete electrolysis cell in H2SO4 (pH 0) from example 5;

[0044] [Fig. 14] shows the OER and HER release potentials of the cells in example 5;

[0045] [Fig. 15] shows the polarization associated with the application of an increasing current in a complete cell in H2SO4 (pH 0) according to example 5:

[0046] Example 1: Laser stripping of carbon fiber / resin composites

[0047] Composite plates measuring 25x50mm (test specimens) were pickled using the process according to the invention. The composite material used consists of an organic epoxy resin matrix with carbon fiber reinforcements. This material comes from the aeronautical field. Carbon fibers and epoxy resin were originally assembled by vacuum infusion.

[0048] The laser used is a cleanLASER brand laser, 100 Watts in 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 / cm2 and a peak power between 1.2 and 7.5 KW.

[0049] The CL100 Gaussian is composed of a CL100 central unit and a StamplO optic.

[0050] The CL100 central unit is a class 4, 1064nm fiber laser, whose characteristics are as follows: CL100 Central Unit Technical Data Dimensions - (W x D x H) [mm3] in 19” rack ~650x483x170 Dimensions - (W x D x H) [mm3] in climate-controlled bay (optional) ~850x600x1170 Weight [kg] with optics ~25 Cooling System Air Laser Source Power [W] 100 W Wavelength [nm] 1064 + / -2 Voltage [V] 230 Power [W] (full load / standby) -500W Ambient Temperature Minimum / Maximum [°C] 5-40 Humidity [%] 10 - 95, non-condensing Laser Class 4

[0051] The central unit is connected to the optics via a 2.5m umbilical cable.

[0052] The StamplO optics, which is connected to the CleanStudio software, allows parts to be processed continuously.

[0053] The characteristics of this optics are as follows: 2D Scan-Optique Stamp 10 Technical Data Dimensions (1 x w x h) [mm3] approx. 91 x 91 x 100 Weight [kg] Approx. 1.4 Focal Length (or other to be validated based on testing). 330 / 254 / 160 / 100 mm Optical Fiber Length [m] 2.5

[0054] The specific parameters of the process in the implementation examples are as follows:

[0055] Table 1

[0056] [Tables 1] Parameter Set and Test Specimens: Comparative Examples Pulse Frequency [kHz] Mark Speed ​​[ms] Power Repetition Spacing [mm] Working Distance [mm] Actual Spot Diameter [pm] Objective Focal Length [mm] P1 100 8475 100 10 0.085 466 113 330 P2 100 8475 100 2 0.085 466 113 330 P3 100 8475 100 5 0.085 466 113 330 P4 100 6375 100 10 0.064 359 85 254 P5 100 3750 100 5 0.0375 211 50 160 P6 100 3750 100 10 0.0375 211 50 160

[0057] The application of the process on the plates was carried out on two distinct areas so as to define a working area (1) and an electrical contact area (2) (cf. [Fig.1]).

[0058] Comparative examples: PI, P2, P3, P4, P6 test tubes.

[0059] 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 2.

[0060] Microscopic observations _ ;

[0061] The parameter sets PI to P3 represent the laser operating parameters for which only the number of passes differs. Based on visual observations, only the specimens cleaned with parameters PI, P4, P5 and P6 were observed by optical microscopy.

[0062] As shown in [Fig.2], the surfaces stripped with the parameters, or levels, P5 and P6, respectively 0.416 cm2 and 0.429 cm2, are much greater than those obtained for levels PI and P4 (respectively 0.178 cm2 and 0.223 cm2).

[0063] However, the images obtained by scanning electron microscopy ([Fig.3]) of the stripped surfaces show damage / breakage of the fibers which is more significant at levels PI and P6 than at P5. Level P4 shows little damage.

[0064] Electrochemical tests showed better electronic conductivity for parameter P5 than for P4, which seems to indicate that to have a better conductivity, it is better to have some broken fibers but with less residual resin around and between the fibers. Example 2#: Fabrication of supercapacitors

[0065] Supercapacitors are energy storage systems that adsorb ions onto the surface of carbon electrodes with a large specific surface area (e.g., activated carbon) when these electrodes are polarized. They exhibit a moderate 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 cleaned as described in Example 1, were coated with an ink containing commercially available activated carbon.

[0066] The active ingredient used is: YP-50 activated carbon (supplier: Kuraray Europe GmbH 2021), i.e., predominantly microporous carbon (< 2nm) with a specific pore volume of 0.7 ml / g, a specific surface area of ​​1600m² / g², a capacitance of 28 F / g (for a two-electrode system, per g total of the two electrodes) and 19 F / cc, and Conductive carbon (PUREREBLACK 205-110 Carbon - Superior Graphite Co. Chicago, IL, USA, referred to as SG45 in this document). Different formulations were evaluated by electrochemical tests, and all of these tests are presented in laboratory notebook C41776.

[0067] Two electrode formats are used with areas etched according to the process of Example 1 of different surfaces. These areas have a surface area of ​​0.5 cm² (or 9 cm² for Example 3) and are shown in [Fig. 4]. Once etched, the surfaces are cleaned ultrasonically in ethanol, then dried in a vacuum oven for 2 hours at 60°C.

[0068]

[0069] The ink has the E2 formulation indicated in Table 2: [Tables2] E2 Ink Total dry mass MA Conductor ¥PS0 SG % desired 80% to % desired mass | i oœ 800 100 ng) Actual mass (mg 882.45 100.84 j ïé actual 80.09 18.06 binder Sdef 5.1X0 tn 100 103.02 10.28 E sant t in savant 7% 1428.57 1471.70 Solvent MMP 2000 2041.12

[0070] The binder of the E2 ink is PVDF (polyvinylidene fluoride), brand name Solef 5130, and the solvent is N-methyl-2-pyrrolidone (NMP).

[0071] This composition is deposited in liquid form and is called "ink" because of its consistency. It can be obtained according to the following process: - Masses of Kuraray YP50 (a microporous carbon with most pores smaller than 2 nm and a cumulative pore volume close to 0.7 mL / g) and carbon black (Superior Graphite Co., >99%) are weighed on a balance accurate to 1 / 100 of a mg and placed in a pillbox. The mixture is then stirred using a magnetic stir bar whose length is almost equal to the diameter of the pillbox to ensure optimal homogenization.

[0072] - The powders are mixed together to avoid the formation of clumps;

[0073] - A dilution of the PVDF binder in NMP to obtain a 7% by mass solution is carried out and this is poured drop by drop onto the powder mixture; - The solvent is added drop by drop to the previous mixture, while stirring, until the desired mass and viscous texture are obtained; and

[0074] - Agitation is maintained until use.

[0075] The ink is deposited on the pickled composite parts in the following manner:

[0076] - Weighing of the sample without ink; - Deposition of ink using a pipette onto the area delimited by a mask; - Vacuum drying at 60°C; - Weighing of the sample with ink for determination of the mass of active material added; - Conditioning of the electrode in the electrolytic medium used for the tests.

[0077] The electrochemical cell (FlatCell) used for the measurements comprises

[0078] - a reference electrode (RE): Ag / AgCl (3M NaCl in aqueous medium); - a counter electrode (CE): Wound Pt wire; - a working electrode (WE), the electrode according to the invention comprising the stripped composite PI, P4 to P6 stripped composite + ink (mass deposited between 2 and 4 mg on a surface of 0.5 cm2)

[0079] - the electrolyte is an aqueous solution of lithium nitrate (LiNO3) at a concentration of 5 mol / L.

[0080] The electrochemical measurements are carried out according to the following parameters;

[0081] - Scan speeds: 5, 10, 20, 50 and 100 mV / s; - Number of cycles: 10; - E+: +0.3V vs. Ag / AgCl; -E-:-0.1Vvs. Ag / AgCl.

[0082] Results:

[0083] Cycling tests at different scan rates (10, 20, 50 and 100 mV / s) show, in [Fig.5], that the electronic signature of the PI, P4, P5 and P6 electrodes is the classic electrochemical signature of a supercapacitor electrode.

[0084] 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 [Fig. 6]) show that the electrode made of P5+E2 delivers on average 100 to 120 F / 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.

[0085] For applications as supercapacitor electrodes, the best combination is P5 with E2 ink. The measured capacitance is identical to that of a coated electrode on a conventional metallic current collector, thus showing that the de-coated composite effectively acts as a current collector and that the performance is not affected by this collector compared to a standard supercapacitor electrode (metallic current collector (stainless steel, nickel, aluminum) + ink) ([Fig. 6]). Example 3#: Capacitive desalination

[0086] This is a specific application of supercapacitors where salt water is circulated between two electrodes as described previously. By polarizing these electrodes, the Na+ and Cf ions are removed from the water, which is therefore less salty at the device outlet. A new batch of salt water is then introduced into the device, and the ions are released while electrical energy is recovered. The desalinated water undergoes several cycles of this treatment, generally ending up in a reverse osmosis system to obtain fresh water. The water that 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 evidence of the capture of NaCl during the charging of the device (desalination of seawater) and its release during discharge with energy recovery as in a supercapacitor.

[0087] The initially introduced water undergoes several cycles of this treatment to bring it to a minimum NaCl content while the second aliquot of introduced water is supersaturated with salt and normally discharged into the sea during the process, or used in a salt marsh.

[0088] Electrode preparation:

[0089] The electrodes used are 9cm2 electrodes (see [Fig.4]) coated with E2 ink, the formulation of which is indicated in Table 2 of Example 2.

[0090] They are dried in a vacuum oven for 2 hours at 60°C and conditioned by immersion in the electrolyte for 5 minutes.

[0091] Electrochemical tests:

[0092] The cell used is a Plexiglas (20mL) cell designed and manufactured in-house with: 2_ CE + ER: P5 pickled composite with or without E2 ink; WE: P5 stripped composite with or without E2 ink; 2_ Electrolyte j. Artificial seawater i.e. NaCl at 3g / L (0.05 M).

[0093] Different techniques have been used for evaluating the performance in capacitive desalination: - Constant current charging followed by voltage biasing. - EIS: Electrochemical impedance spectroscopy to estimate the resistance of the electrolyte and therefore the NaCl salt content.

[0094] Devices and methods 1 to 3 demonstrate the ability of the electrodes to desalinate seawater. 1 (Figure 7) 2 (Figure 8) 3 (Figure 9) - CE + ER: E2 ink (128 mg) - CE + ER: E2 ink (128 mg) - CE + ER: E2 ink (159 mg); - WE: E2 ink (116 mg) - WE: E2 ink (116 mg) - WE: E2 ink (196 mg) - Electrolyte: Artificial seawater diluted to a NaCl concentration of 3 g / L (0.05 M). - Electrolyte: Artificial seawater diluted to a NaCl concentration of 3 g / L (0.05 M). - Electrolyte: Artificial seawater diluted to a NaCl concentration of 3 g / L (0.05 M). - Applying a current of +20 mA up to the 1.5 V plateau - Applying a current of +20 mA up to the 1.5 V plateau - Applying a current of +20 mA up to the 1.5 V plateau - Hold for 5 min at 1.5V, then replace the "desalted" water with salt water (3 g / L) - Hold for 15 min at 1.5V, then replace the "desalted" water with salt water (3 g / L) - Hold for 50 min at 1.5V, then replace the "desalted" water with salt water (3 g / L) - Apply a current of -20 mA to 0V - Apply a current of -20 mA to 0V - Apply a current of -20 mA to the 0V plateau - Hold for 5 min at 0V. - Hold for 15 min at 0V. - Hold for 5 min at 0V.

[0095] For all tests:

[0096] => R (salt-depleted water) > R (desalinated water) > R (water to be desalinated) (Figures 7 to 9)

[0097] => The increase in resistance for water having undergone the first treatment (by Compared to the initial salt water, the resistance of the second aliquot of salt water decreased (the ionic conductivity decreased, therefore the resistance increased), while the resistance decreased (compared to the initial water), thus showing that the Na+ and Cl- ions were returned to the salt water during the discharge (the ionic conductivity increased, therefore the resistance decreased). At the same time, the electricity initially injected into the cell to remove the Na+ and Cl- ions was recovered during this same discharge.

[0098] => The best results were obtained with device and method 1. The The device does indeed desalinate seawater. Example 4#: lithium-ion batteries

[0099] The commercial graphite-based ink (SFG6 TIMREX Primary Synthetic Graphite from IMERYS, produced from a controlled graphitization process) was prepared with 80% by mass of active material (SFG6 graphite), 10% by mass of SOLEF binder dissolved in NMP, and 10% by mass of SG45 carbon black used in Example 2. The mixture was augmented with NMP until the desired viscosity was obtained before being coated onto the composite material stripped by P5 laser. • Ink preparation#:

[0100] - In a pillbox, place a magnetic rod with a length equal to the diameter of the pillbox (important for mixing well right up to the edges); - Weighing of SFG6 and SG45 on a balance accurate to 1 / 100 of mg; - Mixing the powders together to avoid the formation of clumps; - Take the binder (SOLEF) diluted in NMP at 7% and pour drop by drop until the desired mass is obtained; - Dilute with NMP by adding drop by drop => desired viscous texture; - Continuous agitation until use.

[0101] • Ink coating on P5 pickled composites:

[0102] - Weighing of the sample without ink; - Deposition of ink using a pipette on an area delimited by a mask; - Vacuum drying at 60°C; - Weighing of the active ingredient; - Conditioning of the electrode in the electrolytic medium used.

[0103] 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 relative to a reference metallic lithium electrode, in a commercial LP30 electrolyte (consisting of cyclic (ethylene: EC) and linear (dimethyl: DMC) carbonates of mass fraction 50 / 50% and 1 mol LiPF6 salt).

[0104] Figure 10 shows that the initial charge capacity is close to the theoretical capacity (372 mAh / g), as is the subsequent discharge capacity. This example demonstrates the feasibility of a lithium-ion battery with electrodes deposited on a current collector made of laser-etched composite material.

[0105] Example 5: Electrolyzers for the production of hydrogen and oxygen

[0106] In this last example, an electrode according to the invention is used to perform the electrolysis of water (acidic or basic) and thus produce hydrogen and oxygen. The composites, laser-etched as before, 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).

[0107] Electrode preparation:

[0108] Different formulations, with or without catalysts, were evaluated.

[0109] The catalysts used are Palladium on carbon (Pd-C) for hydrogen evolution (HER) and iridium oxide IrO2 for oxygen evolution (OER).

[0110] The formulations of the highest-performing inks are given below: • E3 Ink - Pd / C#: [YES] [Tables 3] E3 Ink Pd-C Name % Desired Desired Mass (mg) Actual Mass (mg) % Actual Total Dry Mass 100 102.38 MA* Pd / C 80% i 80 | 80.54 78.67% Conductor SG j 10% 10 10.33 10.09% Binder Solef5130 10% 10 11.51 11.24% Binder in Solvent 7% 142.86 164.45 Solvent NM P j 150'200 j 169.96 • E4bis ink - IrO2 (80% Wt) / C#:

[0112] [Tables4]

[0113] The electrodes used are 9cm2 electrodes ([Fig.4]) coated or not with E2 (without catalyst), E3 (Pd) and E4bis (IrO2) inks.

[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 in H2SO4_IM (pH 0) - HER / OER:

[0116] Parameters:

[0117] - The cell used is a (20mL) Plexiglas cell designed and manufactured in-house with : CE: P5 pickled composite with E2 ink; WE: P5 stripped composite without ink and with E2 or E3 ink; - _ ER: Ag / AgCl for H2SO4 IM (pH 0); And

[0118] - Electrolyte j H2SO4, IM (pH 0).

[0119] The HER results in H2SO4 are given in [Fig. 11] and the OER results in H2SO4 are given in [Fig. 12].

[0120] Electrochemical tests in a complete cell in H2SO4 (pH 0) - CV:

[0121] Parameters:

[0122] The cell used is a Plexiglas (20mL) cell designed and manufactured in-house.

[0123] CV: 2_ CE+ER: P5 pickled composite with E2 or E3 ink; WE: P5 stripped composite with E2 or E4bis ink; Electrolyte H2SO4 IM (pH 0); 5 mv / s.

[0124] The results in electrolysis are presented in [Fig. 13].

[0125] CV Conclusion:

[0126] The gas evolution (electrolysis) voltages (potential differences) are measured in [Fig. 14] and are compiled in Table 5 below:

[0127] [Tables5] System (Electrode(-) vs Electrode(+)) Electrolysis voltage of H₂SO₄ IM (V) CvsC 2.2 Pd-C vs CC vs IrO₂ 1.9 2.2 Pd-C vs IrO₂ 1.5

[0128] We are therefore approaching the theoretical 1.23 V for the electrolysis of water and we do not observe degradation of the electrodes, which is a guarantee of durability, an important parameter for electrolyzers.

[0129] Electrochemical tests in a complete cell in H2SO4 (pH 0) - CA:

[0130] In this test, an increasing current is applied to the electrolysis cell and its polarization is measured.

[0131] • Parameters:

[0132] CA: 2_ CE+ER: P5 pickled composite with E3 ink; WE: P5 stripped composite with E4bis ink; Electrolyte j H2SO4 IM (pH 0); 2_ I imposed: variable;

[0133] * Results: [Fig. 15]

[0134] The applied current is related to the surface area of ​​the catalyst-coated pads, which is 0.5 cm². The applied current density is therefore between 100 and 400 mA / cm², which is significant for an electrolysis cell. The polarization at various current values ​​is typical for this type of catalyst; the current collector, made of a laser-etched composite material, does not negatively influence this polarization. The cell also appears to exhibit good long-term stability, which is an important parameter for this type of device. References

[0135] 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 / appl0103561.

[0136] 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 / mil0010063.

Claims

Demands

1. A method for manufacturing an electrode comprising carbon fibers, said method comprising the following successive steps: - making available 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 stripped surface portion having electronic conductivity properties in which the carbon fibers are at least partially exposed, said composite material forming a current collector of said electrode; and - applying to said stripped surface a composition comprising an electrochemically active material.

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

3. A method according to claim 1 or 2, wherein the speed of the mark in mm / s is chosen from the range of 3750 to 8475, preferably from the range of 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 from 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 of 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 from 160 to 254.

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

8. A method according to any one of claims 1 to 7, wherein said electrochemically active material is applied in the form of a suspension of a powder in a liquid, or semi-liquid, comprising a solvent, wherein said electrochemically active material includes, preferably, microporous carbon, graphite, a lithiated oxide such as LiFePO4, Li(Ni,Mn,Co)O2, LiMn2O4, LiNio^Mn 15O4 or Li4Ti50i2, and / or a carbon powder coated with palladium and / or IrO2.

9. An electrode comprising: - a current collector based on a composite material, preferably recycled, comprising carbon fibers and a resin, said material being etched over at least a portion of surface, in which the carbon fibers are at least partially exposed, said etched portion of surface having electronic conductivity properties, and - a composition comprising an electrochemically active material applied over said etched portion of surface, this preferably comprising microporous carbon, graphite, a lithium oxide such as LiFePO4, Li(Ni,Mn,Co)O2, LiMn2O4, LiNio,5Mni,5O4 or Li4 Ti5Oi2, and / or a carbon powder coated with palladium and / or IrO2.

10. Use of an electrode as described in claim 9, 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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