Method and system for detecting the state of charge of an object

Abstract

The present invention relates to a method for determining the voltage across the terminals of an object, the method comprising the following steps: (a) bringing the terminals of the 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 higher than or equal to a threshold voltage; and (b) detecting a potential optical signal emitted by the chemical compound whereby if an optical signal is detected, the voltage across the terminals of the object is higher than or equal to the threshold voltage. The present invention also relates to an electrochemical system for determining the voltage across the terminals of an object.

Description

[0001] METHOD AND SYSTEM FOR DETECTING THE CHARGE STATE OF AN OBJECT

[0002] TECHNICAL FIELD

[0003] 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.

[0004] 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 suitable for fields such as recycling, dismantling and more broadly the detection of objects under voltage such as batteries.

[0005] 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.

[0006] To achieve this, the present invention proposes a method for detecting the state of charge of an object by bringing the terminals of the latter into contact with a composition which 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.

[0007] PREVIOUS STATE OF THE ART

[0008] Currently, lithium batteries are used and recommended in numerous applications such as electric and hybrid vehicles, and portable devices like computers, mobile phones, camcorders, cameras, and GPS units. The Li-ion battery market is experiencing strong growth due to new applications primarily related to the emergence and development of hybrid and all-electric vehicles.

[0009] Increasing environmental constraints are forcing manufacturers of Li-ion batteries to take 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 focuses particularly on the issue of resources needed for developing technologies, especially scarce and strategic resources. Li-ion batteries represent significant challenges in terms of their use (electric mobility) and recycling for the energy transition in France, Europe, and worldwide.

[0010] Lithium-ion batteries consist of a negative electrode, a positive electrode, a separator, an electrolyte, and a casing, which can be a polymer pouch 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., LiCoCh, LiMnCh, LiNiC₂, LiNiO₂.9MnO₅.05OC₂.05O₂, LiFePO₄) mixed with an organic binder, such as a polymeric binder like polyvinylidene fluoride, and an electrically conductive agent, more specifically a carbon-based agent, deposited on an aluminum foil. The electrolyte comprises 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, LiPFe, LiCF₂SO₄, LiBF₄ or LiCl₄ is dissolved.

[0011] The process is as follows: during charging, lithium deintercalates from the metal oxide and intercalates within the graphite, where it is thermodynamically unstable. During discharging, the process is reversed, and lithium ions intercalate within the lithium metal oxide.

[0012] As batteries age, they lose capacity, and the cells are discarded and must be recycled. Many batteries destined for recycling still have a significant charge. Furthermore, 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 extreme care. Also worth mentioning are production waste from active batteries, i.e., batteries in a state of charge that do not meet standards and must also be recycled.

[0013] A fully charged battery presents an explosion risk 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 the risk of explosion. Removing the electrical energy means lowering the voltage to a sufficient level (< 2.5 V) to avoid any risk of explosion. Understanding this voltage threshold allows for an assessment of the risk associated with battery processing. Specifically, battery recycling requires an initial safety step to mitigate the risk of explosion. This safety step involves removing the electrical energy to a level sufficient to guarantee the absence of explosion during subsequent processing stages (physical dismantling and shredding).Safety precautions are essential, as physically dismantling a charged battery can cause an explosion. Dismantling operations such as cutting and crushing generate contact between the electrodes. In a charged battery, this contact can cause short circuits, releasing a large amount of electrical energy that can lead to a fire and / or explosion. Therefore, batteries must be discharged before any improper handling, such as crushing.

[0014] 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, preventing exposure to hazards (electrical, fire, explosion) and thus mitigating risks and consequences for personnel. This process must be as rapid as possible to meet production rate and cost constraints. It should also be easy to implement and minimize the amount of reagents required.

[0015] Currently, the knowledge of the "charged" or "discharged" state of an object is achieved by connecting this object to electronic devices that allow voltage measurement.

[0016] 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, changing from the letter "F" to the letter "E". Detecting a charge threshold involves an electrical connection and manipulation of the battery object.

[0017] 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, thus providing an indication of the cell's charge state. This electrochromic material is sandwiched between two electrically conductive layers connected to the two opposite terminals of the cell, the outermost layer allowing the user to visually determine the colorimetric state of the electrochromic material. This cell therefore involves an electrical connection.

[0018] US patent application 2005 / 0118497 A1 [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 the batteries 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. EP patent application 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.The discharge is achieved by heating the solution to a temperature between 60°C and 80°C. The end of the discharge is monitored by measuring the voltage across the object.

[0019] In summary, determining whether an object is charged or discharged absolutely requires connecting cables and performing operations by a person who is exposed to a potential hazard (a risk inherent to 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 items, batteries damaged mechanically, electrically, and / or thermally, or batteries considered waste.

[0020] 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 presenting the disadvantages of prior art methods.

[0021] DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] 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 presence or absence of electrical energy. The principle of the invention is to bring a chemical compound into contact with the object and, depending on the presence or absence of a threshold voltage (Useuii), to obtain a different optical response linked to an electrochemical reaction. Thus, when the object's voltage, denoted "U," is greater than or equal to Useuii, an optical response is provided by the chemical molecules (active state). This 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 with the naked 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 variation is detected (inactive state).

[0024] The process can also take place in the reverse direction depending on the choice of 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.

[0025] 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 can be referred to, in the rest of the presentation, as a "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.

[0026] Contact between a composition containing a chemical compound in a solvent and the object triggers a chemical reaction, or not, depending on whether or not the threshold voltage "Useuii" is reached. The detection of a change or absence of optical change indicates whether the object is charged or discharged.

[0027] The present invention has many advantages over the state of the art:

[0028] - it allows you to determine if an object is powered by detecting a change in color without needing to electrically connect the object;

[0029] - 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;

[0030] - 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

[0031] - It is non-destructive and can be used on different objects (size, state of health, geometry, etc.) without risk of damaging them.

[0032] 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.

[0033] 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 lower or higher than a threshold voltage.

[0034] 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 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 U-SOCI2 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.

[0035] 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.

[0036] There are various situations where knowing the voltage of an object is particularly desirable, such as i) before dismantling, ii) after dismantling, iii) before recycling, iv) after recycling, and more broadly v) any other action that requires knowing the presence or absence of energy in an object, such as a battery. Illustrative, but not exhaustive, examples of such actions include before or after transport, before or after prolonged storage, and after exposure to temperatures below or above the recommended operating temperatures.

[0037] 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.

[0038] 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 whether it is in its ground state or in its charged state when an electrical charge is applied to it.

[0039] 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.

[0040] Indeed, a voltage of 2.5 V corresponds to a state of charge close to 0%, regardless of the type of object (cell, module, or pack for a lithium-ion battery with a graphite-type active material on the negative electrode and an NMC-type active material on 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, 1 V, etc., for these batteries. batteries.In the context of the present invention, the chemical compound used is chosen from the group consisting of electrochromic compounds and electroluminescent compounds.

[0041] 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 change 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 waves are 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 resulting color 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 referred to as polyelectrochromism or electropolychromism.

[0042] All electrochromic compounds known to a person skilled in the art are usable within the framework 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.

[0043] In a particular embodiment, the electrochromic compound is chosen from the group consisting of electrochromic phthalocyanines such as lutetium diphthalocyanine, spiropyrans, diarylethenes, viologens, and M'-type hexacyanometalates. x [M"(CN)6] y, where M' and M" are transition metals or similar and electrochromic metal oxides.

[0044] In a more particular embodiment, especially applicable where the threshold voltage is less than 2.5 V, the electrochromic compound is chosen from the group consisting of viologens and M'-type hexacyanometalates. X [M"(CN )e] y , where M' and M" are transition metals or similar and electrochromic metal oxides.

[0045] The term "viologen" refers to a derivative of 4,4'-bipyridine, and in particular a substituted bipyridinium salt with the formula (CsH4NR)2 n+ in which R represents a possibly substituted alkyl group, a possibly substituted aryl group or a possibly substituted alkylaryl group.

[0046] 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.

[0047] For the purposes of this invention, "heteroatom" means an atom selected from the group consisting of nitrogen, oxygen, phosphorus, sulfur, silicon, fluorine, chlorine, and bromine.

[0048] For the purposes of this invention, "substituted alkyl group" means an alkyl group as previously defined substituted by one or more groups, identical or different, selected 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 sulfonylmyl; 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.

[0049] Specific examples of potentially substituted alkyl groups usable for R include methyl, ethyl, n-propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, heptyl, octyl, nonyl, and methoxyethoxyethane. Methylviologen (MV), or 1,1'-dimethyl-4,4'-bipyridinium, is the simplest viologen in which R represents a methyl group.

[0050] 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.

[0051] 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.

[0052] As a specific example of possibly substituted aryl groups that can be used for R, we can cite a phenyl group or a nitrophenyl group.

[0053] For the purposes of this invention, "arylalkyl group" means an alkyl group as previously defined in which one hydrogen atom is replaced by an aryl group as previously defined.

[0054] 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.

[0055] As a particular example of possibly substituted arylalkyl groups usable for R, we can cite a phenylmethyl group of formula -CH2-C6H5.

[0056] 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 (PFe), perchlorate (ClO4) and trifluoromethylsulfonate (OTf).

[0057] Within the framework of the present invention, the transition metals M' and M" usable in M' type hexacyanometalates x [M"(CN)6] y are notably chosen from the group consisting of iron(ll), iron(ll), vanadium, ruthenium, chromium, palladium, platinum and molybdenum.

[0058] In the context of the present invention, "metal similar to a transition metal" means, in particular, cadmium.

[0059] As 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.

[0060] Within the framework of the present invention, the usable electrochromic metal oxides are in particular oxides of transition metals such as tungsten oxides and vanadium oxides.

[0061] 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 an electric 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 they can switch between an "off" and an "on" state through electrical excitation extremely rapidly. The "on / off" mode of operation refers to the transition from the "on" state to the "off" state as soon as the application of the current is stopped.

[0062] 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.

[0063] 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.

[0064] With regard to the polyaromatic compounds used 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 emitting a photon.

[0065] As 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; benzimidazole derivatives; diketopyrrolopyrrole derivatives; acridone derivatives and quinacridone derivatives.

[0066] Regarding the luminol / hydrogen peroxide couple, when an electric current passes through it, hydrogen peroxide is oxidized to oxygen in a triplet state. Luminol (or 3-aminophthalhydrazide) reacts with oxygen to form an unstable dianion that rapidly decomposes to release a nitrogen molecule and emit a photon.

[0067] 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 previously defined.

[0068] Organometallic complexes 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-reagent such as tripropylamine. In the latter case, the organometallic complex and 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. Specific examples of organometallic complexes usable in the invention include tris(8-hydroxyquinolato)aluminum (Alq3), tris(bipyridine)ruthenium (Rufbpy), and tris(bipyridine)iridium (Ir(bpy)g).

[0069] The process according to the present invention may include a step prior to step a) of preparing the composition.

[0070] It should be noted that the composition implemented in step a) of the method according to the invention is external to the object whose terminal voltage is to be determined. In the context of the present invention, "external composition" means a composition applied to the outside of the object, without any element of this composition being integrated or incorporated into the internal structure of that object. In other words, unlike integrated devices of the prior art, the composition of the invention is applied solely to the outside of the object being tested and in no way constitutes a permanent structural or functional element thereof.

[0071] 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.

[0072] The liquid solution implemented in the process according to the invention comprises a solvent in which one or more chemical compounds as previously defined are dissolved.

[0073] 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.

[0074] 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.

[0075] The solvent in the liquid solution (first variant) or dispersion (second variant) used is advantageously inert with respect to the object whose charge state is to be determined. 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. The solvent advantageously 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 have no ions. Consequently, 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 exhibiting high voltages, i.e., greater than 12 V.

[0076] Furthermore, 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).

[0077] In one particular embodiment, the solvent for the liquid solution (first variant) or 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 solvent family or a mixture of at least two solvents belonging to two different solvent families.

[0078] 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.

[0079] 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, / V, / V-dimethyldecanamide, / V, / V-dimethyldec-9-enamide, acetates such as hexyl acetate and butyl acetate, and alcohols.

[0080] 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.

[0081] 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 usable in the invention, preference is given to a thermally stable, low-viscosity alcohol that allows good solubility of chemical probes, such as, for example, ethanol.

[0082] 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 within the scope of the invention include ethylene glycol, propylene glycol, and glycerol. Ethylene glycol (EG) is a liquid, non-ionically conductive compound 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 10⁻³⁴ 3 Not at 25°C. In the context of the invention, the solvent used is advantageously ethylene glycol since it allows good solubility of the chemical probes used.

[0083] As a reminder, deep eutectic solvents (or DES), which are distinct from ionic liquids, are formed by mixing two or more compounds in a precise proportion that corresponds to the eutectic point. The melting point is lower than the melting point of each individual component, allowing the mixture to be liquid at 20°C, thus facilitating their use.

[0084] The synthesis of DES is easy compared to that of ionic liquids, which requires several synthesis and purification steps. It involves simply 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.

[0085] 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.

[0086] 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.

[0087] When the composition used is a dispersion, the preparation step consists of dispersing the chemical compound(s) as previously defined in a solvent as previously defined.

[0088] In a third variant of the present invention, the composition implemented during step a) of the process is in the form of a foam.

[0089] 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.

[0090] 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.

[0091] 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 simply blowing air out of it.

[0092] Finally, the implementation of a foam in this third variant naturally promotes contrast since an uncolored foam is white, which promotes the detection between white and colored during step b) of the process according to the invention.

[0093] 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.

[0094] An "organic surfactant" is defined as an organic molecule comprising a lipophilic (nonpolar) portion and a hydrophilic (polar) portion. An "organic foaming surfactant" is defined as an organic surfactant as previously defined, but with a hydrophilic-lipophilic balance (HLB) between 3 and 8.

[0095] 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.

[0096] Nonionic (or neutral) surfactants are compounds whose surface-active properties, particularly hydrophilicity, are provided by uncharged functional groups such as alcohols, ethers, esters, or amides, and may contain heteroatoms such as nitrogen or oxygen. Due to the limited hydrophilic contribution of these functional groups, nonionic surfactants are most often multifunctional. Examples of usable nonionic foaming surfactants include polyoxyethylene(4) lauryl ether, octylphenol ethoxylate, and t-octylphenoxypolyethoxyethanol.

[0097] Ionic foaming surfactants cover not only anionic foaming surfactants but also cationic foaming surfactants.

[0098] 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 counterion such as an ammonium ion (NH4+). + ), a quaternary ammonium such as tetrabutylammonium, and cations, particularly alkali cations, said cations being such as Na + , Li + , That 2+ , Mg 2+ , Zn 2+ and K +Examples of anionic foaming surfactants include tetraethylammonium para-toluenesulfonate, sodium dodecyl sulfate (SDS), sodium lauryl sarcosinate, sodium palmitate, sodium stearate, sodium myristate, sodium di(2-ethylhexyl)sulfosuccinate, sodium lauryl ether sulfate, sodium dioctyl sulfosuccinate, methylbenzene sulfonate, and ethylbenzene sulfonate. Cationic surfactants have at least one hydrocarbon chain and a polar head, with the hydrophilic portion of the agent being positively charged. A cationic foaming surfactant usable within the framework of the present invention is advantageously chosen from quaternary ammoniums comprising at least one aliphatic chain in C4-C22 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 cationic foaming surfactants include tetrabutylammonium chloride, trimethyldecylammonium chloride, tetradecylammonium chloride, tetradecyltrimethylammonium bromide (TTAB), alkylpyridinium halides with an aliphatic chain and alkylammonium halides.

[0099] In a particular embodiment, the organic foaming surfactant(s) used are one or more ionic foaming surfactants as previously defined.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] In a fourth variant of the present invention, the composition implemented during step a) of the process is in the form of a gel.

[0104] This fourth embodiment allows for the detection of 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.

[0105] For the purposes of this invention, "gel" refers to 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.

[0106] The gel used in the present invention can be an inorganic (or mineral) gel, an organic gel or a mixed (inorganic and organic) gel.

[0107] When the gel used in the present invention is inorganic, the gelling agent is a compound with colloidal properties of the metal alkoxide type. Such an alkoxide has the formula M(OR)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 (ZrfC₆H₅sh), titanium ethoxide (TifC₆H₅sh), tungsten ethoxide (W(OC₂H₅)₆), and silicon ethoxide (SifC₆H₅sh). 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.

[0108] In the present invention, all gelling agents, gel precursors generally used to prepare an organic gel can be used in the invention.

[0109] Advantageously, these precursor compounds are macromolecules that are typically relatively high molecular weight molecules having a structure essentially formed of multiple repeating units derived, de facto or by design, from low molecular weight molecules.

[0110] The organic gel implemented 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, a starch gel, a silk gel, a polylactic glycolic acid gel, a polycaprolactone gel, a polyacrylamide gel, a polymethyl methacrylate gel or a polyvinyl alcohol gel.

[0111] The conditions implemented in the invention to allow the formation of a gel, particularly during the preliminary stage of its preparation, depend on the organic gelling agents used and are known in the relevant field.

[0112] Gels can form spontaneously. For chemical compounds such as polysaccharides or certain proteins like 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 between the different compounds, which can then rearrange 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, regarding photocrosslinked gels, gel formation requires the use of a photoinitiator, and the necessary condition for the formation of these gels is light.

[0113] 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.

[0114] 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;

[0115] - 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.

[0116] 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 the chemical compounds, flammability of the solvent and degradation of the liquid solution or dispersion.

[0117] This additional active species is or are advantageously chosen from the group consisting of polyethylene glycol (PEG), extinguishing or flame retardant agents, contrast-enhancing agents and material-transporting agents.

[0118] Indeed, PEG can be used for the vapor pressure of the different solutions implemented in the process according to the invention.

[0119] It can 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 charge state 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 agents or flame retardants can be between 5% and 80% by mass and advantageously between 10% and 30% by mass relative to the total mass of the composition, the liquid solution or the dispersion.

[0120] A contrast-enhancing agent can increase detection efficiency. It must be inert to the electrochemical reaction and absorb light in a different range than that targeted by the chemical probe's reaction. Ideally, the contrast agent can be chosen from a color range opposite to that of the chemical compound or probe. When the chemical probe SI exhibits a response at a voltage higher than the threshold voltage, SI can be coupled to a co-reagent Ci that is activated at a voltage equal to the threshold voltage. Once activated, this co-reagent will induce the response of the probe Si.

[0121] Finally, a fraction of a mass transport agent or co-solvent, such as 5% water, can be added to reduce viscosity. A third organic solvent can also be introduced. This co-solvent must act effectively without significantly interfering 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, the liquid solution of the first variant, the dispersion of the second variant and the liquid solutions and dispersions implemented 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, the liquid solution or the dispersion.

[0122] 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 especially between 30 seconds and 30 minutes. It is evident that during the contact in step a) of the method according to the invention, there must be fluid continuity between the two terminals of the object whose state of charge is to be determined.

[0123] As previously stated, the contact in step a) of the method according to the invention is made without an electrical connection. The expression "without an electrical connection" means that the contact of the chemical compound with the terminals of the object is not accompanied by any intentional or functional electrical connection between these terminals. In particular, no conductive element such as a wire, a conductive track, a printed conductive layer, an electrode, a metal strap, or any equivalent device is used to electrically connect the terminals or to close a circuit. Unlike integrated devices in the prior art, the applied composition therefore does not act as a conductor intended to allow the flow of current between the terminals.The optical response of the chemical compound results exclusively from the effect of the local voltage applied to the compound, without a current flowing between the terminals through a conductive device or element.

[0124] 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 change is in a portion 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.

[0125] 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).

[0126] The present invention also relates to the use of a composition comprising at least one chemical compound as previously defined for determining the voltage between the terminals of an object, in the absence of any electrical connection. The present invention further 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 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.

[0127] 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).

[0128] 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.

[0129] BRIEF DESCRIPTION OF THE DRAWINGS

[0130] Figure 1 shows 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).

[0131] Figure 2 shows photographs of a chemical system in which the chemical probe (methyl viologen chloride) is initially colorless (left) and turns blue 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).

[0132] Figure 3 shows photographs of an on / off system using a light-emitting chemical probe (3-aminophthalhydrazide) that emits light upon contact with an object under voltage when U > 2.5 V (on mode, left) and stops emitting light when the voltage is U < 2.5 V (off mode, right). 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 consisting 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.

[0133] 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.

[0134] Figure 6 shows a photograph "A" of a prismatic cell before securing (U = 3.6 V) and a photograph "B" of the same cell after securing (U = IV). The composition used is an aqueous solution containing sodium dodecyl sulfate, Prussian blue, sodium chloride, and xanthan gum.

[0135] 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 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.

[0136] Figure 8 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 5 wt% sodium alginate. The chemical probe is Prussian blue. The color change of the gel is detectable from 5 min and is very pronounced after 10 min.

[0137] Figure 9 shows photograph "A" of a prismatic module before securing and photograph "B" of the same module after securing. The composition used is an aqueous solution containing sodium dodecyl sulfate, Prussian blue, sodium chloride, and xanthan gum.

[0138] DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0139] Example 1: Voltage detection by a chemical system consisting of water and Prussian blue.

[0140] A 26650 LFP battery charged to a 30% SOC (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 (FestFefCNjeh) is diluted to 10 -4M (0.07 g / L) (SI chemical probe) is poured onto the battery. The solution remains in contact with the battery at room temperature, without further stirring. The solution decolorizes, with the blue color disappearing, after 10 minutes of contact between the chemical system and the battery (Figure 1). This optical change indicates that the object is charged.

[0141] Example 2: Voltage detection by a chemical system consisting of ethylene

[0142] An LFP 26650 battery charged to a 30% SOC (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 10 -3M (3.8 g / L) (the 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 (Figure 2). This optical change indicates the charged state of the object.

[0143] Example 3: Voltage detection by a chemical system consisting of water

[0144] 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 agitation. 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 (Figure 3). This result demonstrates that the present chemical system can determine whether an object, in this case a battery, is live or not. In the case of the battery, this allows the charged and discharged state to be detected.

[0145] Example 4: Voltage detection by a foam containing water, Prussian blue and sodium dodecvl sulfate.

[0146] A 26650 LFP battery charged to a 30% SOC (U = 3.3 V) is connected in parallel with 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)e]4) is diluted to 10 -3 M (0.7 g / L) (chemical probe S4). The solution remains in contact with the cut interface at room temperature. As shown in Figure 4, marked decolorization is observed after 1 min, which intensifies over time. After 10 min, the decolorization is almost complete.

[0147] Example 5: Voltage detection by a foam containing water, Prussian blue, sodium dodecvl sulfate and rhodamine B.

[0148] A 26650 LFP battery charged to a 30% SOC (U = 3.3 V) is connected in parallel with 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)e]4) is diluted to 10 -3 M (0.7 g / L). A contrast agent, rhodamine B, is dissolved in the fluid at 2.10 -5 M (10 mg / L). The foam remains in contact with the electrodes at room temperature. As shown in Figure 5, a color change is observed in certain areas after 1 min (from purple to pink). This change intensifies over time and is almost complete after 10 min. Example 6: Voltage detection using an aqueous liquid, Prussian blue, xanthan gum, and sodium dodecyl sulfate.

[0149] A prismatic battery with a capacity of 62.5 Ah charged to a SOC of 30% (U = 3.3 V) is sprayed with an aqueous solution containing 1% by mass of sodium dodecyl sulfate, in which Prussian blue (Fe3[Fe(CN)e]4) is diluted to 10 -3 M (0.5 g / L), sodium chloride at 0.1 M (6 g / L), and xanthan gum at 5 g / L. The liquid is applied to the surface of the battery before and after securing it. The liquid remains in contact with the electrodes at room temperature. As shown in Figure 6, discoloration is observed above the notched area of ​​the cell located in the center of the object after approximately 30 seconds. Once the object is discharged and secured at a voltage U = 1 V, the fluid is reapplied to the surface of the object. In this case, no reaction is observed.

[0150] Example 7: Voltage detection by a gel containing water, Prussian blue, sodium alginate and rhodamine B.

[0151] 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. 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)e]4) is diluted to 10 -3 M (0.7 g / L). A contrast agent, rhodamine B, is dissolved in the fluid at 2.10 -5 M (10 mg / L). The gel remains in contact with the electrodes at room temperature. As shown in Figure 7, a color change is observed in certain areas after 30 seconds (from purple to pink). This change intensifies over time and is almost complete after 1.5 minutes in the vicinity of the electrodes.

[0152] Example 8: Voltage detection by a gel containing water, Prussian blue, sodium alginate on a prismatic cell.

[0153] A 26650 LFP battery charged to a 30% SOC (U = 3.3 V) is connected in parallel with another Li-ion battery in deep discharge. The gel is applied to the surface of the secured battery. The gel contains an aqueous solution of 4 wt% sodium alginate, in which Prussian blue (Fe3[Fe(CN)e]4) is diluted to 10 -3 M (0.7 g / L). The gel remains in contact with the electrodes at room temperature. As shown in Figure 8, discoloration is observed near the negative terminal after 5 minutes. This change intensifies over time and is marked after 10 minutes near the negative terminal.

[0154] Example 9: Voltage detection by aqueous liquid, Prussian blue, xanthan gum and sodium dodecyl sulfate.

[0155] A 12-cell prismatic module of type 6s2p with a capacity of 125 Ah, charged to a SOC of 30% (U = 3.3 V), is sprayed with an aqueous solution containing 1% by mass of sodium dodecyl sulfate, in which Prussian blue (FestFefCNjeh) is diluted to 10 -3M (0.5 g / L), sodium chloride at 0.1 M (6 g / L), and xanthan gum at 5 g / L. The liquid is applied to the surface of the object before and after securing. The liquid remains in contact with the electrodes and current collectors at room temperature. As shown in Figure 9, discoloration is observed above the notched area of ​​the cell located in the center of the object, as well as at the negative current collectors, after approximately 30 seconds. The object is then partially secured, with the last two cells discharged to unit voltages U = 1 V, while the other cells retain a voltage U > 3.3 V. The fluid is reapplied to the surface of the object. In this case, no reaction is observed on the discharged cells, while discoloration of the fluid is visible on the cells still containing electrical energy.

[0156] References

[0157] [1] International application WO 2016 / 014882 Al on behalf of Duracell US Operations, Inc. published on January 28, 2016.

[0158] [2] Patent application EP 0497616 A2 in the name of Eveready Battery Company published on August 5, 1992.

[0159] [3] US patent application 2005 / 0118497 Al in the name of Thomas B. Breen published on June 2, 2005.

[0160] [4] Patent application EP 4020663 Al 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. A 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 and M-type hexacyanometalates. x [M"(CN)6] y , where M' and M" are transition metals or similar 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. A method according to any one of claims 1 to 6, characterized in that said composition is in the form of a liquid solution.

8. A method according to any one of claims 1 to 6, characterized in that said composition is in the form of a dispersion.

9. A method according to any one of claims 1 to 6, characterized in that said composition is in the form of a foam.

10. A method according to any one of claims 1 to 6, characterized in that said composition is in the form of a gel.

11. 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.

12. 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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