METHOD AND SYSTEM FOR DETECTING THE CHARGE STATE OF AN OBJECT

Abstract

The present invention relates to a method for determining the voltage between the terminals of an object, comprising the following steps: (a) bringing the terminals of said object into contact, without electrical connection, with a composition comprising at least one chemical compound capable of generating an optical signal when subjected to a voltage greater than or equal to a threshold voltage, and (b) detecting any optical signal emitted by the chemical compound, such that if an optical signal is detected, the voltage between the terminals of said object is greater than or equal to the threshold voltage. The present invention also relates to an electrochemical system for determining the voltage between the terminals of an object.

Description

Title of the invention: METHOD AND SYSTEM FOR DETECTING THE CHARGE STATE OF AN OBJECT technical field

[0001] The present invention relates to the general field of evaluating the state of charge of an object and, more particularly, to evaluating the state of charge of an electrochemical generator such as a battery or cell, used or not.

[0002] The present invention relates more specifically to the phase of detecting the state of charge of an object to qualify the presence or absence of energy of the object without the use of wire, without manual operation and with a response time adapted to fields such as recycling, dismantling and more broadly the detection of objects under voltage such as batteries.

[0003] The present invention is particularly suitable for quickly determining the presence of a risk when the object has to be handled and then redirected to a dismantling or recycling operation.

[0004] To this end, the present invention proposes a method for detecting the state of charge of an object by bringing its terminals into contact with a composition that may be in the form of a liquid solution, a gel, or a foam incorporating at least one chemical compound capable of emitting an optical signal. PRIOR TECHNOLOGY

[0005] Currently, lithium batteries are used and recommended in numerous applications such as electric and hybrid vehicles, and portable applications like computers, mobile phones, camcorders, cameras, and GPS devices. The Li-ion battery market is currently experiencing strong growth due to new applications primarily related to the emergence and development of hybrid and all-electric vehicles.

[0006] Increasing environmental constraints are forcing manufacturers of Li-ion batteries to assume responsibility for recycling the batteries they sell at significant rates. Regulation (EU) No 2023 / 1542 on batteries and battery waste entered into force on August 18, 2023. It pays particular attention to the issue of resources needed for developing technologies, especially scarce and strategic resources. Li-ion batteries represent significant challenges with regard to their use (electric mobility) and recycling for the energy transition in France, Europe, and worldwide.

[0007] Lithium-ion batteries are composed of a negative electrode, a positive electrode, a separator, an electrolyte, and a casing, which may be a pouch The electrode is made of a polymer or a metallic coating. The negative electrode is typically made of graphite mixed with a carboxymethylcellulose (CMC) binder deposited on a copper foil. The positive electrode comprises a metallic lithium insert material (e.g., LiCoO2, LiMnO2, LiNiO2, LiNiO2, LiFePO4) mixed with an organic binder, such as a polymeric binder like polyvinylidene fluoride, and an electrically conductive agent, specifically a carbon-based agent, deposited on an aluminum foil. The electrolyte consists of a mixture of non-aqueous solvents and one or more lithium salts, and possibly additives to slow down side reactions.Battery electrolytes can be composed of binary or ternary mixtures based on cyclic carbonates such as ethylene carbonate, propylene carbonate or butylene carbonate, linear carbonates or branched carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or dimethoxyethane in various proportions, in which a lithium salt such as, for example, LiPF6, LiCF3SO3, LiBF4 or LiC104 is dissolved.

[0008] The operation is as follows: during charging, lithium deintercalates from the metal oxide and intercalates into the graphite, where it is thermodynamically unstable. During discharging, the process is reversed and lithium ions are intercalated into the lithium metal oxide.

[0009] As a battery is used, aging leads to a loss of capacity, and the cell is discarded and must be recycled. Many batteries to be recycled still have a significant charge. In addition, some individual cells, particularly damaged cells inside batteries, must also be recycled. These cells may have significant deposits of metallic lithium on the negative electrode, which, if exposed to air or water, would cause a significant exothermic reaction with a risk of ignition. Like end-of-life cells, damaged cells cannot be safely opened and must therefore be handled with the utmost care. Also worth mentioning are production rejects of active batteries, i.e., batteries in a state of charge that do not conform to specifications and must be recycled.

[0010] The charged state of a battery presents a risk of explosion due to the simultaneous presence of oxidizer, fuel, and energy within the battery. Therefore, removing the electrical energy from the battery to a sufficient level (close to 0% of its state of charge) is an effective way to prevent thermal runaway and avoid the risk of explosion. Removing the electrical energy is equivalent to lowering the voltage to a sufficient level (< 2.5 V) to avoid any risk of explosion. Thus, knowing this voltage threshold allows one to understand the risk associated with battery treatment.

[0011] In particular, battery recycling requires an initial safety measure to mitigate the risk of explosion. This safety measure involves removing the electrical energy to a sufficient level to guarantee the absence of an explosion during subsequent stages (physical dismantling and shredding of the object). This safety measure is essential because physically dismantling a charged battery can cause an explosion. A physical dismantling operation, including, for example, cutting and shredding, generates contact between the electrodes. In the case of a charged battery, this contact causes short circuits that release a large amount of electrical energy, potentially leading to a fire and / or explosion. Therefore, batteries must be discharged before any potentially damaging operation such as shredding.

[0012] Detecting the battery's state of charge (SOC) ensures the safety of subsequent operations. Ideally, this detection should eliminate the need for manual intervention by operators to prevent exposure to hazards (electrical, fire, explosion) and thus the associated risks and consequences for personnel. This operation must be as rapid as possible to meet processing rate and cost constraints. It must also be easy to implement and minimize the amount of reagents required.

[0013] To date, knowledge of the "charged" or "discharged" state of an object is achieved by connecting this object to electronic devices allowing voltage measurement.

[0014] Thus, international application WO 2016 / 014882 A1 [1] describes a charge status device comprising an indicator having a display threshold on an auxiliary battery. The auxiliary battery is electrically coupled to the indicator such that, when the difference between the main battery voltage and the auxiliary battery voltage is lower (or higher) than the display threshold, the indicator is inactive (or active). The charge status indicator transmits light when inactive and is colored when active. The charge status indicator is a wick coupled to thermochromic paper such that, when the indicator is active, the wick decolorizes the thermochromic paper to change from the letter "F" to the letter "E". Detecting a charge threshold involves an electrical connection and manipulation of the battery.

[0015] Similarly, patent application EP 0497616 A2 [2] proposes an electrochemical cell and a charge state tester for this cell, attached to the cell and comprising an electrochromic material that changes color according to the redox potential to which it is subjected and thus provides an indication of the cell's charge state. This electrochromic material is sandwiched between two Electrically conductive layers are connected to the two opposite terminals of the cell, with the outermost layer allowing the user to visually determine the colorimetric state of the electrochromic material. This cell therefore involves an electrical connection.

[0016] US patent application 2005 / 0118497 A1L [3] describes a method and assembly for determining the state of charge of one or more batteries without removing them from their packaging. A device is used in which they are installed, or an enclosure preventing any direct physical contact with the battery terminals. The battery terminals are electrically isolated from any connection, except for connections to conductors extending away from the terminals, to which a measuring device can be connected to determine the battery's state of charge.

[0017] Patent application EP 4020663 A1 [4] describes a wet discharge method for Li-ion batteries. The batteries are immersed in a conductive aqueous solution containing a salt, preferably sodium carbonate, at a concentration advantageously between 5% and 10% by mass. Discharge is achieved by heating the solution to a temperature between 60°C and 80°C. The end of discharge is monitored by measuring the voltage across the device.

[0018] In summary, determining the "charged" or "discharged" state of an object absolutely requires the connection of cables and operations by a person who is exposed to a potentially dangerous event (a risk inherent in the nature of the object). Furthermore, this approach requires time to connect and measure the object's state of charge. In the case of unstable or non-functional objects, the risk is increased, which is the case for many end-of-life objects, batteries that are mechanically, electrically, and / or thermally damaged, or batteries considered waste.

[0019] The inventors therefore set themselves the goal of proposing a method for detecting the state of charge of an object, and in particular the "charged" or "discharged" state of an object, without the drawbacks of prior art methods. Description of the invention

[0020] The present invention makes it possible to achieve the goal set by the inventors. Indeed, the work of the inventors has shown that it is possible to determine the voltage between the terminals of an object and in particular to detect the "charged" or "discharged" state of such an object while avoiding the drawbacks of prior art methods.

[0021] Determining whether an object under voltage, such as a cell or battery, is "charged" or "discharged" requires, in the prior art, measuring the voltage across the object's terminals. This measurement indicates the absence or presence of electrical energy. The principle of the invention is to bring a chemical compound into contact with the object and that, depending on the presence or absence of a threshold voltage (Useuii), there is a different optical response, linked to an electrochemical reaction.

[0022] Thus, when the voltage of the object, denoted "U", is greater than or equal to Useuii, an optical response is provided by the chemical molecules (active state). The response can then be detected by a suitable optical device. In the case of an electrochemical response of the molecules in the visible spectrum (400-800 nm), detection is possible by the eye and / or via the use of a camera. When the voltage U is less than Useuii, the chemical molecules remain inactive and no optical change is detected (inactive state).

[0023] The process can also take place in the reverse direction depending on the choice of the chemical system, i.e. when the voltage U is greater than or equal to Useuii, there is no optical response and when U is less than Useuii, the chemical molecules are active and it is possible to detect an optical variation.

[0024] In both cases, the principle is based on optical variation from a threshold voltage. This optical variation relies on the use of a chemical compound (which may be referred to, in the rest of the description, by the expression "chemical probe") solubilized or dispersed in a solvent, capable of generating an optical signal when subjected to a voltage greater than or equal to a threshold voltage.

[0025] Contact between a composition comprising a chemical compound in a solvent and the object causes a chemical reaction or not, depending on whether or not the threshold voltage "Useuii" is reached. The detection of a change or the absence of an optical change indicates whether the object is charged or discharged.

[0026] The present invention has many advantages over the prior art: - it allows you to determine if an object is powered by detecting a change in color without needing to electrically connect the object; - it avoids the need for an operator to connect a device, thus limiting the risks to people (dangerous objects). A change in color within the visible spectrum can be detected by an electronic optical detection system (camera, photo camera, UV spectrometer) but also with the naked eye; - It is easily implemented on a high-speed production line (minimizing costs). The response time is fast. The optical response linked to the reaction between the chemical probe and the energized object is on the order of a second or a few minutes; and - It is non-destructive and can be used on different objects (size, state of health, geometry, etc.) without risk of damaging them.

[0027] More particularly, the present invention relates to a method for determining the voltage between the terminals of an object comprising the following steps: a) bringing the terminals of said object into contact, without electrical connection, with a composition comprising at least one chemical compound capable of generating an optical signal when subjected to a voltage greater than or equal to a threshold voltage, and b) detecting any optical signal emitted by the chemical compound by means of which, if an optical signal is detected, the voltage between the terminals of said object is greater than or equal to the threshold voltage.

[0028] In other words, the method according to the invention makes it possible not only to detect the presence of a voltage across the terminals of an object but also to determine whether this voltage is less than or greater than a threshold voltage.

[0029] In the present invention, the term "object" means an electrochemical cell corresponding to a single device converting chemical energy into electrical energy, or a module corresponding to a set of electrochemical cells connected in series or in parallel, or a pack or block corresponding to a series of individual modules associated with protection systems. When the object is an electrochemical cell, it may be a cell such as, for example, a primary lithium cell of the Li-SOCl2 type, a battery such as a secondary metal-ion battery, particularly Li-ion or Na-ion, or another accumulator such as a lithium-sulfur, lithium metal, etc.

[0030] In the present invention, the expression "the terminals of an object" is equivalent to the expressions "the positive terminal and the negative terminal of an object", "the terminals of an object" and "the positive terminal and the negative terminal of an object". These expressions may be used interchangeably.

[0031] There are various cases where knowing the voltage of an object is particularly desirable, such as i) before a dismantling operation, ii) after a dismantling operation, iii) before a recycling operation, iv) after a recycling operation, and more broadly v) any other actions that require knowing the presence or absence of energy in an object such as a battery. Illustrative and non-limiting examples of such actions include before or after a transport phase, before or after a prolonged storage period, and after exposure to temperatures below or above the recommended operating temperatures.

[0032] Depending on the case considered chosen from the cases mentioned above, a person skilled in the art will be able to determine the most suitable threshold voltage value and, consequently, the chemical compound to be used.

[0033] Indeed, the method according to the invention uses a chemical compound which can also be referred to as a "chemical probe". By "chemical compound", we mean a chemical molecule exhibiting a different optical response depending on that it is in its ground state or in its charged state when an electric charge is applied to it.

[0034] A person skilled in the art will be able to determine, without inventive effort, the threshold voltage to be implemented according to the nature of the object and the requirements with regard to kinetic aspects or productivity. In a particular embodiment, the chosen threshold voltage is a voltage that allows the "charged" state of an object to be distinguished from the "discharged" state. Such a threshold voltage is notably less than 2.5 V.

[0035] Indeed, a voltage of 2.5 V corresponds to a state of charge close to 0%, regardless of the nature of the object (cell, module, or pack for a lithium-ion battery with a graphite-type active material at the negative electrode and an NMC-type active material at the positive electrode for "Nickel Manganese Cobalt Oxides," LFP (for "Lithium Iron Phosphate"), LMFP (for "Lithium Manganese Iron Phosphate"), LCO (for "Lithium Cobalt Oxide"), or NCA (for "Nickel Cobalt Aluminum Oxides"). Thus, the voltage used for this category of Li-ion batteries is 2.5 V to guarantee the absence of an explosive risk; we can therefore speak of a discharged state. It is clear that a voltage of 2.5 V is just an example, and one could choose a voltage of 2 V, 1.8 V, 1.5 V, etc. 1V, etc. for these batteries.

[0036] In the context of the present invention, the chemical compound used is chosen from the group consisting of electrochromic compounds and electroluminescent compounds.

[0037] As a reminder, electrochromic compounds have the property of reversibly changing color through an oxidation or reduction reaction when an electrical charge is applied to them, and this occurs for a short time. The color change is characterized by the modification of the wavelengths of visible light (400-800 nm) absorbed by the electrochromic compound. Light absorption refers to a physical phenomenon by which electromagnetic light is partially absorbed by a chemical molecule or chromophore. The observed color corresponds to the wavelengths of the visible spectrum that are not absorbed by the chromophore. Electrochromism benefits from a memory effect, meaning that the color obtained is maintained even when the voltage source is disconnected.The reversibility of the electrochromic reaction necessarily involves a counter-reaction of oxidation or reduction, depending on the mechanism involved in the coloring phase. In some cases, several color changes can occur successively for the same electrochromic compound; this is then referred to as polyelectrochromism or electropolychromism.

[0038] All electrochromic compounds known to a person skilled in the art are usable within the scope of the present invention, and a person skilled in the art will be able to choose the most suitable electrochromic compound according to the value of the chosen threshold voltage.

[0039] In a particular embodiment, the electrochromic compound is chosen from the group consisting of electrochromic phthalocyanines such as lutetium diphthalocyanine, spiropyrans, diarylethenes, viologens, hexacyanometalates of type M'x[M"(CN)6]y, where M' and M'' are transition metals or similar and electrochromic metal oxides.

[0040] In a more particular embodiment, especially applicable to the case where the threshold voltage is less than 2.5 V, the electrochromic compound is chosen from the group consisting of viologens, hexacyanometalates of type M'x[M"(CN)6]y, where M' and M'' are transition metals or similar, and electrochromic metal oxides.

[0041] By "viologen" is meant a derivative of 4,4'-bipyridine and in particular a substituted bipyridinium salt of formula (C5H4NR)2n+ in which R represents a possibly substituted alkyl group, a possibly substituted aryl group or a possibly substituted alkylaryl group.

[0042] By "alkyl group" is meant an alkyl group, linear, branched or cyclic, comprising from 1 to 20 carbon atoms, in particular from 1 to 15 carbon atoms and, in particular, from 1 to 10 carbon atoms, said alkyl group possibly comprising at least one heteroatom and / or at least one carbon-carbon double or triple bond.

[0043] By "heteroatom", in the context of the present invention, means an atom chosen from the group consisting of a nitrogen, an oxygen, a phosphorus, a sulfur, a silicon, a fluorine, a chlorine and a bromine.

[0044] By "substituted alkyl group", in the context of the present invention, means an alkyl group as previously defined substituted by one or more groups, identical or different, chosen from the group consisting of an alkyl, an aryl, a halogen; an amine; a diamine; a carboxyl; a carboxylate; an aldehyde; an ester; an ether; a ketone; a hydroxyl; an amide; a sulfonyl; a sulfoxide; a sulfonic acid; a sulfonate; a nitrile; a nitro; an acyl; an epoxy; a phosphonate; an isocyanate; a thiol; a glycidoxy and an acryloxy.

[0045] By way of specific examples of possibly substituted alkyl groups that can be used for R, we can mention the methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, and methoxyethoxyethane groups. Methylviologen (MV) or 1,r-dimethyl-4,4'-bipyridinium is the simplest viologen in which R represents a methyl group.

[0046] For the purposes of this invention, "aryl group" means any group comprising one or more aromatic rings, identical or different, linked or connected by a single bond or by a hydrocarbon chain, an aromatic ring having from 3 to 20 carbon atoms, in particular from 4 to 14 carbon atoms and, in particular, from 5 to 8 carbon atoms and possibly comprising a heteroatom.

[0047] By "substituted aryl group", in the context of the present invention, means an aryl group as previously defined substituted by one or more groups, identical or different, chosen from the group consisting of an alkyl, an aryl, a halogen; an amine; a diamine; a carboxyl; a carboxylate; an aldehyde; an ester; an ether; a ketone; a hydroxyl; an amide; a sulfonyl; a sulfoxide; a sulfonic acid; a sulfonate; a nitrile; a nitro; an acyl; an epoxy; a phosphonate; an isocyanate; a thiol; a glycidoxy and an acryloxy.

[0048] As a particular example of possibly substituted aryl groups usable for R, we can cite a phenyl group or a nitrophenyl group.

[0049] By "arylalkyl group", in the context of the present invention, means an alkyl group as previously defined in which a hydrogen atom is replaced by an aryl group as previously defined.

[0050] By "substituted arylalkyl group", in the context of the present invention, means an arylalkyl group as previously defined substituted by one or more groups, identical or different, chosen from the group consisting of an alkyl, an aryl, a halogen; an amine; a diamine; a carboxyl; a carboxylate; an aldehyde; an ester; an ether; a ketone; a hydroxyl; an amide; a sulfonyl; a sulfoxide; a sulfonic acid; a sulfonate; a nitrile; a nitro; an acyl; an epoxy; a phosphonate; an isocyanate; a thiol; a glycidoxy and an acryloxy.

[0051] As a particular example of possibly substituted arylalkyl groups usable for R, we can cite a phenylmethyl group of formula -CH2-C6H5.

[0052] In the case of the present invention, the counter-ion associated with a viologen is in particular chosen from among halides such as bromide, chloride, iodide and fluoride, tetrafluoroborate (BF4), hexafluorophosphate (PF6), perchlorate (C1O4) and trifluoromethylsulfonate (OTf).

[0053] In the context of the present invention, the transition metals M' and M” usable in the hexacyanometalates of type M'x[M"(CN)6]y are in particular chosen from the group consisting of iron(II), iron(III), vanadium, ruthenium, chromium, palladium, platinum and molybdenum.

[0054] In the context of the present invention, "metal similar to a transition metal" means, in particular, cadmium.

[0055] By way of particular examples of hexacyanometalates usable within the framework of the present invention, we may mention the hexacyanometallate in which M' is iron(III) and M” is iron(II), also known as “Prussian Blue”, and the hexacyanometallate in which M' is iron(III) and M” is ruthenium.

[0056] Within the framework of the present invention, the usable electrochromic metal oxides are in particular transition metal oxides such as tungsten oxides and vanadium oxides.

[0057] As a reminder, electroluminescent compounds generate photon emission in response to electrical excitation. An electroluminescent compound transitions from a stable ground state to an unstable excited state when a current is applied. The return to the ground state occurs spontaneously through radiative de-excitation with photon emission. For this type of compound, the operation is an "on / off" mode, meaning that they are capable of switching between an "off" state and an "on" state through electrical excitation extremely rapidly. By "on / off" mode of operation, we mean the transition from the "on" state to the "off" state as soon as the application of a current is stopped.

[0058] All electroluminescent compounds known to a person skilled in the art are usable within the scope of the present invention and a person skilled in the art will be able to choose the most suitable electroluminescent compound according to the value of the threshold voltage chosen.

[0059] In a particular embodiment applicable in particular to the case where the threshold voltage is less than 2.5 V, the electroluminescent compound is chosen from the group consisting of polyaromatic compounds, the luminol / hydrogen peroxide couple, organometallic complexes and zinc sulfide (ZnS) nanoparticles.

[0060] With regard to the polyaromatic compounds usable in the present invention, the electroluminescent reaction is ensured by an annihilation mechanism, that is to say, in the medium, one molecule is oxidized at the anode when another molecule is reduced at the cathode. The redox couple interacts to reform two neutral molecules in an excited state, spontaneously returning to their ground state by emission of a photon.

[0061] By way of specific examples of polyaromatic compounds usable in the present invention, mention may be made of anthracene derivatives such as diphenylanthracene and 9,10-bis(phenylethynyl)anthracene; naphthalene derivatives; tetracene derivatives; fluorene derivatives; spirofluorene derivatives; periflanthene derivatives; perylene derivatives; indoperylene derivatives; phenanthrene derivatives; pyrene derivatives; chrysene derivatives; coronene derivatives; rubrene derivatives; tetraphenylcyclopentadienone derivatives; pentaphenylcyclopentadiene derivatives; coumarin derivatives; oxazone derivatives; benzoxazole derivatives; derivatives of benzimidazole; diketopyrrolopyrrole derivatives; acridone derivatives and quinacridone derivatives.

[0062] With regard to the luminol / hydrogen peroxide couple, when an electric current passes through it, the hydrogen peroxide is oxidized to oxygen in the triplet state. The luminol (or 3-aminophthalhydrazide) reacts with the oxygen to form an unstable dianion which rapidly decomposes to release a nitrogen molecule and emit a photon.

[0063] In the present invention, the term "organometallic complex" refers to a coordination complex comprising a metal ion bonded to at least one organic ligand. Such a complex is generally associated with a counter-ion as defined above.

[0064] With regard to organometallic complexes, these can produce light when an electric current passes through them, either by an annihilation mechanism, as in the case of polyaromatic compounds, or by reaction with a co-reactant such as tripropylamine. In this second case, the organometallic complex and the tripropylamine are oxidized at the negative electrode. The two radicals formed react together to reform the neutral organometallic complex in an excited state, spontaneously returning to its ground state by emitting a photon.

[0065] By way of particular examples of organometallic complexes usable in the invention, we can mention tris(8-hydroxyquinolato)aluminium (Alq3), tris(bipyridine)ruthenium (Ru(bpy)3) and tris(bipyridine)iridium (Ir(bpy)3).

[0066] The process according to the present invention may include a step prior to step a) of preparing the composition.

[0067] In a first embodiment of the present invention, the composition implemented in step a) is in the form of a liquid solution. In this first embodiment, the object whose state of charge is to be determined is typically immersed in such a solution.

[0068] The liquid solution implemented in the process according to the invention comprises a solvent in which one or more chemical compounds as previously defined is / are solubilized.

[0069] In a second embodiment of the present invention, the composition implemented in step a) is in the form of a dispersion. In this second embodiment, the object whose state of charge is to be determined is typically immersed in such a dispersion.

[0070] The dispersion implemented in the process according to the invention comprises a solvent in which one or more chemical compounds as previously defined is / are dispersed.

[0071] The solvent of the liquid solution (first variant) or of the dispersion (second variant) used is advantageously inert with respect to the object of which we want The state of charge must be known. In other words, this solvent does not react chemically or electrochemically with the object. A relatively unreactive solvent is preferred to reduce reactivity during contact in step a) of the process according to the invention. Advantageously, the solvent has high resistivity and, even more advantageously, is not ionically conductive. This is notably the case for pure water and many organic solvents that initially lack ions. Therefore, the ohmic drop prevents solvent degradation and reactivity with the object, and promotes the reaction with the chemical probe. This aspect is particularly advantageous for avoiding / reducing degradation when processing objects with high voltages, i.e., greater than 12 V.

[0072] In addition, the solvent of the liquid solution (first variant) or of the dispersion (second variant) implemented in the process according to the invention is typically colorless to facilitate optical detection during step b) of the process according to the invention (light efficiency).

[0073] In a particular embodiment, the solvent of the liquid solution (first variant) or of the dispersion (second variant) used is chosen from the group consisting of water, organic solvents, deep eutectic solvents, and mixtures thereof. "Mixture" is understood to mean either a mixture of at least two solvents belonging to the same family of solvents or a mixture of at least two solvents belonging to two different families of solvents.

[0074] The organic solvents that can be used in the process according to the invention can be conventional organic solvents or biodegradable organic solvents such as bio-based solvents.

[0075] Examples of organic solvents that can be used in the process according to the invention include acetonitrile (ACN), dichloromethane, butanone, dimethoxyethane, linear or branched carbonates such as dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate, cyclic carbonates such as ethylene carbonate, propylene carbonate and butylene carbonate, methyl esters, A,A-dimethyldecanamide, A,A-dimethyldec-9-enamide, acetates such as hexyl acetate and butyl acetate and alcohols.

[0076] In one particular embodiment, the solvent used is water. Indeed, water is a low-viscosity solvent and is not, or only very slightly, conductive. In the context of the present invention, low ionic conductivity is preferred to avoid / limit the formation of hydrogen and oxygen during the process according to the invention.

[0077] In one particular embodiment, the solvent used is an alcohol. By "alcohol," we mean an organic compound whose carbon skeleton is bonded to at least one or more hydroxyl groups (-OH). Among the alcohols that can be used in the invention, we favours a thermally stable, low-viscosity alcohol that allows good solubility of chemical probes such as, for example, ethanol.

[0078] In another particular embodiment, the solvent used is a diol or a polyol, i.e., an alcohol having two or more hydroxyl groups (-OH). Specific examples of diols or polyols usable as solvents in the context of the invention include ethylene glycol, propylene glycol, and glycerol. Ethylene glycol (EG) is a liquid, non-ionically conductive component with a low vapor pressure, a boiling point of 197.5°C, an auto-ignition temperature of 410°C, and an average viscosity of approximately 16 x 10⁻³ Pas at 25°C. In the context of the invention, the solvent used is advantageously ethylene glycol since it provides good solubility for the chemical probes employed.

[0079] As a reminder, deep eutectic solvents (or DES, for "Deep Eutectic Solvent"), which are distinct from ionic liquids, are formed by mixing two or more compounds in an exact proportion that corresponds to the eutectic point. The melting point is lower than the melting point of each component, allowing the mixture to be liquid at 20°C, which facilitates their use.

[0080] The synthesis of DES is easy compared to that of ionic liquids, which requires several synthesis and purification steps. It is simply a matter of mixing the components of the DES in the correct proportions until a homogeneous and transparent liquid is obtained. These components are a pair of hydrogen bond donors and hydrogen bond acceptors. This type of solvent generally has an electrochemical stability window above 3 V, while still allowing the solubility of a chemical compound such as the one implemented in the invention.

[0081] In the context of the invention, a DES containing glycerol (Gly), ethylene glycol (EG), choline chloride (ChCl), and / or lithium chloride (LiCl) is advantageously chosen. Specific examples of DESs usable in the present invention include ChCl:2 Urea; ChCl:2 EG; ChCl:2 Gly; LiCl:3 EG; and LiCl:3 Gly.

[0082] When the composition used is a liquid solution, the preparation step consists of solubilizing the chemical compound(s) as previously defined in a solvent as previously defined.

[0083] When the composition implemented is a dispersion, the preparation step of the latter consists of dispersing the chemical compound(s) as previously defined in a solvent as previously defined.

[0084] In a third embodiment of the present invention, the composition implemented during step a) of the process is in the form of a foam.

[0085] This third variant of the present invention makes it possible to promote the ionic path and therefore to promote the reactivity of the chemical probes.

[0086] Furthermore, the foam used in this third variant can be easily sprayed and cover a large surface area and volume with a small amount of solution. This embodiment is therefore suitable for objects of varying nature and size.

[0087] The use of foam in this third variant facilitates its recovery and use in a closed loop. For example, the foam can be removed by a simple "blowing" operation with air.

[0088] Finally, the implementation of a foam in this third variant naturally promotes contrast since an uncoloured foam is white, which promotes detection between white and coloured during step b) of the process according to the invention.

[0089] A foam as implemented consists of a dispersion of gas bubbles in a foaming solution. This foaming solution comprises, in addition to the chemical compound(s) and solvent as previously defined, i.e. the liquid solution as implemented in the first variant of the present invention or the dispersion as implemented in the second variant of the present invention, at least one organic foaming surfactant.

[0090] By "organic surfactant" is meant an organic molecule comprising a lipophilic (nonpolar) portion and a hydrophilic (polar) portion. By "foaming organic surfactant" is meant an organic surfactant as defined above, further exhibiting a hydrophilic-lipophilic balance (HLB) of between 3 and 8.

[0091] In a particular embodiment, the organic foaming surfactant(s) used are chosen from the group consisting of non-ionic foaming surfactants, ionic foaming surfactants and mixtures thereof.

[0092] Nonionic (or neutral) surfactants are compounds whose surface-active properties, particularly hydrophilicity, are provided by uncharged functional groups such as an alcohol, an ether, an ester, or an amide, and may contain heteroatoms such as nitrogen or oxygen. Due to the low hydrophilic contribution of these functional groups, nonionic surfactant compounds are most often polyfunctional. Examples of usable nonionic foaming surfactants include polyoxyethylene(4) lauryl ether, octyl phenol ethoxylate, and t-octylphenoxypolyethoxyethanol.

[0093] Ionic foaming surfactants cover not only anionic foaming surfactants but also cationic foaming surfactants.

[0094] Anionic surfactants are surfactants whose hydrophilic portion is negatively charged. A foaming anionic surfactant usable within the scope of the present invention is typically selected from the group consisting of sulfuric acid esters, phosphoric acid esters, alkyl or aryl sulfonates, alkyl or aryl sulfates, alkyl or aryl phosphates, alkyl or aryl sulfosuccinates or alkyl or aryl sarcosinates associated with a counter ion such as an ammonium ion (NH4+), a quaternary ammonium such as tetrabutylammonium, and cations, in particular alkali cations, said cations being such as Na+, Li+, Ca2+, Mg2+, Zn2+ and K+. Examples of anionic foaming surfactants that can be used include tetraethylammonium para-toluenesulfonate, sodium dodecyl sulfate (or SDS), sodium laurylsarcosinate (or sarcosyl), sodium palmitate, sodium stearate, sodium myristate, sodium di(2-ethylhexyl)-sulfosuccinate, sodium lauryl ether sulfate, sodium dioctyl-sulfosuccinate, methylbenzene sulfonate and ethylbenzene sulfonate.

[0095] Cationic surfactants have at least one hydrocarbon chain and a polar head, the hydrophilic portion of said agent being positively charged. A foaming cationic surfactant usable within the scope of the present invention is advantageously chosen from quaternary ammonium compounds comprising at least one C4-C22 aliphatic chain associated with an anionic counter-ion chosen in particular from boron derivatives such as tetrafluoroborate or halide ions such as F, Br, I, or Cl. Examples of usable foaming cationic surfactants include tetrabutylammonium chloride, trimethyldecylammonium chloride, tetradecylammonium chloride, tetradecyltrimethylammonium bromide (TTAB), alkylpyridinium halides bearing an aliphatic chain, and alkylammonium halides.

[0096] In a particular embodiment, the organic foaming surfactant(s) used are one or more ionic foaming surfactants as previously defined.

[0097] It is evident that, in this third variant, the organic foaming surfactant(s) used must be chemically compatible with the chemical compound(s) present in the liquid solution or dispersion used.

[0098] In a particular embodiment, in the foaming solution constituting the foam implemented in the invention, the organic foaming surfactant(s) are present at a rate of 0.1 to 10% by mass and, in particular, of 0.1 to 1% by mass relative to the total mass of this solution.

[0099] In the present invention, the gas used to generate the foam can be any gas. In particular, it can be chosen from the group consisting of air, oxygen, carbon dioxide, helium, argon, and nitrogen. Advantageously, the gas used in the context of the present invention is air, carbon dioxide, or nitrogen.

[0100] In a fourth embodiment of the present invention, the composition implemented in step a) of the process is in the form of a gel.

[0101] This fourth embodiment makes it possible to detect a color change during step b) of the process according to the invention as quickly as a liquid formulation. Furthermore, the gel used in this fourth variant can be easily removed from the object by rinsing.

[0102] For the purposes of this invention, "gel" means a chemical system consisting of a three-dimensional network made up of one or more gelling agents, which may also be described as compounds with colloidal properties, forming a matrix that constitutes a continuous solid phase within which a liquid phase is trapped. According to this invention, the liquid phase comprises the solvent and the chemical compound(s) of the liquid solution as implemented in the first embodiment of the present invention or of the dispersion as implemented in the second embodiment of the present invention.

[0103] The gel implemented within the framework of the present invention can be an inorganic (or mineral) gel, an organic gel or a mixed (inorganic and organic) gel.

[0104] When the gel implemented within the framework of the present invention is inorganic, the gelling agent used is a compound with colloidal properties of the metal alkoxide type. Such an alkoxide has the formula M(0R)n, where R represents an alkyl group as previously defined and n represents the valence of the metal M. Specific examples of metal alkoxides usable in the invention include zirconium ethoxide (Zr(OC2H5)4), titanium ethoxide (Ti(OC2H5)4), tungsten ethoxide (W(OC2H5)6), and silicon ethoxide (Si(OC2H5)4). The gel forms upon dispersion of the metal alkoxides in the solvent of the liquid solution according to the first embodiment or upon dispersion according to the second embodiment.

[0105] In the present invention, all gelling agents, gel precursors generally used to prepare an organic gel can be used in the invention.

[0106] Advantageously, these precursor compounds are macromolecules which are typically relatively high molecular weight molecules having a structure essentially formed of multiple repeated units derived, de facto or by design, from low molecular weight molecules.

[0107] The organic gel used in the present invention may be a polyamide gel, a polyester gel, a polyurethane gel, an agarose gel, a sucrose gel, a sepharose gel, a chitosan gel, a xanthan gel, a carrageenan gel, a dextran gel, an agar gel, an alginate gel, a gelatin gel, a collagen gel, a fibrin gel, a polyethylene glycol gel, a hyaluronic acid gel, starch gel, silk gel, polylactic glycolic acid gel, polycaprolactone gel, polyacrylamide gel, polymethyl methacrylate gel or polyvinyl alcohol gel.

[0108] The conditions implemented in the invention to allow the formation of a gel, particularly during the preliminary stage of preparing the latter, depend on the organic gelling agents used and are known in the relevant field.

[0109] The gel can form spontaneously. For chemical compounds such as polysaccharides or certain proteins such as gelatin, it is generally necessary to heat and then cool the solution containing the gel precursors. Heating ensures the dispersion of the compounds in the solution and allows the cleavage of some of the weak bonds existing between the different compounds, which can then reorganize to form a three-dimensional network. For other chemical compounds such as collagen, gelation occurs upon cooling the solution containing the gel precursor compounds. In another example, concerning polyacrylamide gels, gel formation requires the use of a crosslinking agent and acrylamide. In yet another example, concerning photocrosslinked gels, gel formation requires the use of a photoinitiator, and the necessary condition for the formation of these gels is light..

[0110] A person skilled in the art will be able to determine, without inventive effort, the conditions to be applied to the liquid solution or dispersion comprising a solvent, one or more chemical compounds and one or more organic gelling agents as previously defined and any additives to be added to this liquid solution or dispersion to obtain a gel depending on the organic gelling agent(s) contained in this solution or dispersion.

[0111] It should be noted that the third and fourth variants of the invention have the following additional advantages: - the use of a smaller quantity of solution or dispersion compared to the first and second variants and therefore a smaller quantity of chemical compounds, which facilitates the industrial implementation of the process according to the invention and leads to economic and environmental gains; - a foam or a gel has better adhesion to an object than a liquid solution as implemented in the first variant or a dispersion as implemented in the second variant.

[0112] Regardless of the variant considered, the composition and more particularly the liquid solution of the first variant, the dispersion of the second variant, and the liquid solutions or dispersions used to prepare the foam of the third variant and the gel of the fourth variant may include one or more additional active species having an advantageous role in the process according to the invention and in particular on the light transmission efficiency, viscosity, solubility of chemical compounds, flammability of the solvent and degradation of the liquid solution or dispersion.

[0113] This or these additional active species are advantageously chosen from the group consisting of polyethylene glycol (PEG), extinguishing agents or flame retardants, contrast-enhancing agents and material-transporting agents.

[0114] Indeed, PEG can be used for the vapor pressure of the different solutions implemented in the process according to the invention.

[0115] It may be advantageous to use extinguishing or flame-retardant agents to prevent thermal runaway, particularly in the event of a breach of containment or opening of the object whose state of charge is to be determined. Typically, the extinguishing or flame-retardant agent may be an alkyl phosphate such as trimethyl phosphate or triethyl phosphate, or a fluorinated alkyl phosphate such as tris((2,2,2-trifluoroethyl) phosphate).In the composition implemented in the invention and, more particularly, the liquid solution of the first variant, the dispersion of the second variant and the liquid solutions or dispersions implemented to prepare the foam of the third variant and the gel of the fourth variant, the concentration of extinguishing or flame-retardant agents may be between 5% and 80% by mass and advantageously between 10% and 30% by mass relative to the total mass of the composition, liquid solution or dispersion.

[0116] A contrast-enhancing agent can increase the detection efficiency. It must be inert with respect to the electrochemical reaction and absorb light in a range different from that targeted by the chemical probe's reaction. Ideally, the contrast agent can be chosen from a chromatic range opposite to that of the chemical compound or chemical probe. When the chemical probe SI has a response at a voltage higher than the threshold voltage, SI can be coupled to a co-reagent Ci that is activatable at a voltage equal to the threshold voltage. Once activated, this co-reagent can induce the response of the probe Si.

[0117] Finally, a fraction of a mass transport agent or co-solvent can be added to decrease viscosity, such as 5% water. A third organic solvent can also be introduced. This co-solvent must act effectively without generating strong interference with the measurement and therefore with the detection. Specific examples of co-solvents usable in the invention include vinylene carbonate (VC), gamma-butyrolactone (γ-BL), propylene carbonate (PC), and poly(β-ethylene glycol). In the composition implemented in the invention, and more particularly in the liquid solution of the first variant, the dispersion of the second variant and the liquid solutions and dispersions used to prepare the foam of the third variant and the gel of the fourth variant, the concentration of the agent promoting the transport of matter can be between 1% and 40% by mass and advantageously between 2% and 10% by mass relative to the total mass of the composition, liquid solution or dispersion.

[0118] In the context of the present invention, the contact during step a) has a duration consistent with the deactivation times. Advantageously, this duration is less than 1 hour, in particular less than 45 minutes and, in particular, between 30 seconds and 30 minutes.

[0119] It is evident that during the contact in step a) of the process according to the invention, there must be fluidic continuity between the two terminals of the object whose state of charge we wish to determine.

[0120] In step b) of the process according to the invention, the optical signal emitted by the chemical compound when subjected to a voltage greater than or equal to a threshold voltage is a change in the absorption wavelength, luminescence, and / or color. Any means known to those skilled in the art for detecting such a change can be used in step b) of the process according to the invention. Advantageously, the optical signal or variation is in a part of the electromagnetic spectrum and, in particular, in the visible range. Specific examples of such means include the eye, an optical device such as a camera, an optical camera, or a UV spectrometer.

[0121] The process according to the present invention and in particular steps a) and b) thereof and the possible step of preparing the composition is typically carried out at room temperature (i.e. 23°C ± 5°C).

[0122] The present invention also relates to the use of a composition comprising at least one chemical compound as previously defined to determine the voltage between the terminals of an object, in the absence of any electrical connection.

[0123] The present invention finally relates to an electrochemical system for determining the voltage between the terminals of an object comprising: (i) a composition comprising at least one chemical compound capable of generating an optical signal when subjected to a voltage greater than or equal to a threshold voltage, said composition being brought into contact with the terminals of said object, without electrical connection, and ii) means for detecting any optical signal emitted by the chemical compound whereby, if an optical signal is detected, the voltage between the terminals of said object is greater than or equal to the threshold voltage.

[0124] Everything previously described for the process according to the invention also applies to the electrochemical system according to the invention (object, liquid solution, dispersion, solvent, chemical compound, foam, gel and detection means).

[0125] Other features and advantages of the present invention will become apparent to the person skilled in the art upon reading the examples below given by way of illustration and not limitation, with reference to the attached figures. Brief description of the drawings

[0126] Fig. 1 presents photographs of a chemical system in which the chemical probe (Prussian blue) is initially colored blue (left) and decolorizes under the effect of tension (right).

[0127] Fig. 2 shows photographs of a chemical system in which the chemical probe (methyl viologen chloride) is initially colorless (left) and takes on a blue tint when a voltage is applied in the presence of the chemical probe after 10 seconds of contact (middle) and more markedly after 10 min (right).

[0128] Fig. 3 shows photographs of an "on / off" system using a chemical light-emitting probe (3-aminophthalhydrazide) which emits light on contact with the object under voltage with U > 2.5 V ("on" mode, left) and stops the emission of light when the voltage is U < 2.5 V ("off" mode, right).

[0129] Figure 4 shows photographs taken at different times of an embodiment of the invention in which the composition is in the form of a foam made of the solvent water and 0.5 wt% SDS surfactant. The chemical probe is Prussian blue. The decolorization of the foam is detectable from 1 min and is very pronounced after 10 min.

[0130] Figure 5 shows photographs taken at different times of an embodiment of the invention in which the composition is in the form of a foam consisting of the solvent water and 0.5% wt. SDS surfactant. The chemical probe is Prussian blue and rhodamine B is a contrast agent. The color change of the foam is detectable from 1 min and is very pronounced after 10 min.

[0131] Figure 6 shows photographs taken at different times of an embodiment of the invention in which the composition is in the form of a gel consisting of the solvent water and 4 wt% sodium alginate. The chemical probe is Prussian blue, and rhodamine B is a contrast agent. The color change of the gel is detectable from 1 min and is very pronounced after 1.5 min.

[0132] Figure 7 shows photographs taken at different times of an embodiment of the invention in which the composition is in the form of a gel consisting of The solvent is water and 5% sodium alginate by mass. The chemical probe is Prussian blue. The color change of the gel is detectable from 5 min and is very pronounced after 10 min.

[0133] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0134] Example 1: Voltage detection by a chemical system consisting of water and Prussian blue.

[0135] A 26650 LFP battery charged to a SOC of 30% (U = 3.3 V) is placed in a container, for example, a beaker. A chemical system consisting of water (solvent L1) in which Prussian blue (Fe3[Fe(CN)6]4) is diluted to 10⁴ M (0.07 g / L) (chemical probe SI) is poured onto the battery. The solution remains in contact with the battery at room temperature, without further stirring. The decolorization of the solution is observed by the disappearance of the blue color after 10 minutes of contact between the chemical system and the battery ([Fig. 1]). This optical change indicates the charged state of the object.

[0136] Example 2: Voltage detection by a chemical system consisting of ethylene glycol and methyl viologen.

[0137] A 26650 LFP battery charged to a SOC of 30% (U = 3.3 V) is placed in a container, for example, a beaker. A chemical system consisting of ethylene glycol (solvent L2), in which methyl viologen chloride (1,1'-(dimethyl)-4,4'-bipyridinium dichloride) is diluted to 1.5 x 10³ M (3.8 g / L) (chemical probe S2), is poured onto the battery. The solution remains in contact with the battery at room temperature, without further stirring. The color change of the solution near the negative terminal of the battery is observed after 10 seconds of contact between the chemical system and the battery and is more pronounced after 10 minutes ([Fig. 2]). This optical change characterizes the charged state of the object.

[0138] Example 3: Voltage detection by a chemical system consisting of basic water with hydrogen peroxide and 3-aminophthalhydrazide.

[0139] A 26650 LFP battery charged to a 30% SOC (U = 3.3 V) is connected in parallel to another Li-ion battery cut in half. A chemical system is applied to the interface of the cut battery. The chemical system consists of an aqueous solution containing 0.1 M NaOH and 0.1 M H₂O₂ (solvent L3) in which 0.1 M (17.7 g / L) 3-aminophthalhydrazide (chemical probe S3) is diluted. The solution remains in contact with the interface at room temperature, without further stirring. Luminescence is triggered by immediate contact between the chemical solution and the live interface, with U > 2.5 V (here U = 3.3 V). When the system is at U < 2.5 V, no light is detected in the vicinity of the interface ([Fig. 3]). This result demonstrates that the present chemical system makes it possible to determine whether an object, here A battery is either powered or not. In the case of a battery, this allows the battery to detect its charged and discharged state.

[0140] Example 4: Voltage detection by a foam containing water, Prussian blue and sodium dodecyl sulfate.

[0141] An LFP 26650 battery charged to a SOC of 30% (U = 3.3 V) is connected in parallel to another Li-ion battery cut in half. Foam is applied to the surface of the cut battery. The foam contains an aqueous solution containing 0.5 wt% SDS, in which Prussian blue (Fe3[Fe(CN)6]4) is diluted to 103 M (0.7 g / L) (chemical probe S4). The solution remains in contact with the cut interface at room temperature. As shown in [Fig. 4], marked discoloration is observed after 1 min, which intensifies over time. After 10 min, the discoloration is almost complete.

[0142] Example 5: Voltage detection by a foam containing water, Prussian blue, sodium dodecyl sulfate and rhodamine B.

[0143] An LFP 26650 battery charged to a SOC of 30% (U = 3.3 V) is connected in parallel to another Li-ion battery cut in half. Foam is applied to the surface of the cut battery. The foam contains an aqueous solution of 0.5 wt% SDS, in which Prussian blue (Fe3[Fe(CN)6]4) is diluted to 103 M (0.7 g / L). A contrast agent, rhodamine B, is dissolved in the fluid to 2 x 105 M (10 mg / L). The foam remains in contact with the electrodes at room temperature. As shown in [Fig. 5], a color change is observed in certain areas after 1 min (from violet to pink). This change intensifies over time and is almost complete after 10 min.

[0144] Example 6: Voltage detection by a gel containing water, Prussian blue, sodium alginate and rhodamine B.

[0145] An LFP 26650 battery charged to a 30% SOC (U = 3.3 V) is connected in parallel to another Li-ion battery cut in half. The gel is applied to the surface of the cut battery. The gel contains an aqueous solution of 4 wt% sodium alginate, in which Prussian blue (Fe3[Fe(CN)6]4) is diluted to 103 M (0.7 g / L). A contrast agent, rhodamine B, is dissolved in the fluid to 2 x 105 M (10 mg / L). The gel remains in contact with the electrodes at room temperature. As shown in [Fig. 6], a color change is observed in certain areas after 30 seconds (from violet to pink). This change intensifies over time and is almost complete after 1.5 min, in the vicinity of the electrodes.

[0146] Example 7: Voltage detection by a gel containing water, Prussian blue, sodium alginate on a prismatic cell.

[0147] A 26650 LFP battery charged to a 30% SOC (U = 3.3 V) is connected in parallel to another Li-ion battery in deep discharge. The gel is applied to the surface of the secured battery. The gel contains an aqueous solution containing 4 wt% sodium alginate, in which Prussian blue (Fe3[Fe(CN)6]4) is diluted to 103 M (0.7 g / L). The gel remains in contact with the electrodes at room temperature. As shown in [Fig. 7], discoloration is observed near the negative terminal after 5 min. This change intensifies over time and is marked after 10 min near the negative terminal. References

[0148] [1] International Application WO 2016 / 014882 A1 on behalf of Duracell US Operations, Inc. published on January 28, 2016.

[0149] [2] Patent application EP 0497616 A2 in the name of Eveready Battery Company published on August 5, 1992.

[0150] [3] US Patent Application 2005 / 0118497 A1 in the name of Thomas B. Breen published on June 2, 2005.

[0151] [4] Patent application EP 4020663 A1 in the name of Northvolt AB published on June 29 2022.

Claims

Demands

1. A method for determining the voltage between the terminals of an object comprising the following steps: a) bringing the terminals of said object into contact, without electrical connection, with a composition comprising at least one chemical compound capable of generating an optical signal when subjected to a voltage greater than or equal to a threshold voltage, and b) detecting any optical signal emitted by the chemical compound such that if an optical signal is detected, the voltage between the terminals of said object is greater than or equal to the threshold voltage.

2. The method according to claim 1, characterized in that said object is an electrochemical cell corresponding to a single device converting chemical energy into electrical energy, or a module corresponding to a set of electrochemical cells, connected in series or in parallel, or a pack or block corresponding to a series of individual modules associated with protection systems.

3. A method according to claim 1 or 2, characterized in that said at least one chemical compound is chosen from the group consisting of electrochromic compounds and electroluminescent compounds.

4. A method according to any one of claims 1 to 3, characterized in that said at least one chemical compound is an electrochromic compound selected from the group consisting of viologens, hexacyanometalates of type M'x[M"(CN)6]y, where M' and M" are transition metals or assimilated metals and electrochromic metal oxides.

5. A method according to any one of claims 1 to 3, characterized in that said at least one chemical compound is an electroluminescent compound selected from the group consisting of polyaromatic compounds, the luminol / hydrogen peroxide pair, organometallic complexes and zinc sulfide (ZnS) nanoparticles.

6. A method according to any one of claims 1 to 5, characterized in that said method comprises a step prior to said step a), of preparing said composition.

7.

8.

9.

10.

11.

12. A process according to any one of claims 1 to 6, characterized in that said composition is in the form of a liquid solution. A process according to any one of claims 1 to 6, characterized in that said composition is in the form of a dispersion. A method according to any one of claims 1 to 6, characterized in that said composition is in the form of a foam. A method according to any one of claims 1 to 6, characterized in that said composition is in the form of a gel. A process according to any one of claims 1 to 10, characterized in that said composition comprises one or more additional active species selected from the group consisting of polyethylene glycol (PEG), extinguishing or flame-retardant agents, contrast-enhancing agents and material-transporting agents. An electrochemical system for determining the voltage across the terminals of an object comprising: (i) a composition comprising at least one chemical compound capable of generating an optical signal when subjected to a voltage greater than or equal to a threshold voltage, said composition being brought into contact with the terminals of said object, without electrical connection, and ii) means for detecting any optical signal emitted by the chemical compound such that if an optical signal is detected, the voltage between the terminals of said object is greater than or equal to the threshold voltage.

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