Method for opening and discharging an electrochemical cell of an ionic insertion-deinsertion battery and method for recycling an ionic insertion-deinsertion battery

Abstract

The invention relates to a method for opening and discharging an electrochemical cell of an ionic insertion-deinsertion battery, comprising a casing in which are housed a negative electrode, a positive electrode, a separator and an electrolyte, which comprises the following operations: opening the electrochemical cell at one or more zones of the casing, at least the opening zone(s) being brought into contact with a liquid L1, then discharging the electrochemical cell by bringing the cell into contact with a liquid L2, and which is characterized in that: - the liquid L1 comprises a solvent based on an alcohol and optionally a redox mediator, while the liquid L2 comprises a solvent based on an alcohol together with a redox mediator; and - the liquids L1 and L2 are free of chlorine.It also relates to a method for recycling an ionic insertion-deinsertion battery implementing this opening and discharging process. Applications: recycling of lithium-ion, sodium-ion, potassium-ion, calcium-ion or magnesium-ion batteries.

Description

Title of the invention: Method for opening and discharging an electrochemical cell of an ionic insertion-deinsertion battery and method for recycling an ionic insertion-deinsertion battery Technical field

[0001] The invention relates to the field of recycling used, defective, damaged or discarded batteries.

[0002] More specifically, the invention relates to a method for opening and discharging an electrochemical cell of an ionic insertion-deinsertion battery with a view to recycling the recoverable fractions of this cell.

[0003] It also relates to a method for recycling an ionic insertion-deinsertion battery implementing this opening and discharging method.

[0004] The invention, which makes it possible to safely open and neutralize electrochemical battery cells operating on the principle of insertion-deinsertion - also called intercalation-deintercalation - of metal ions within the materials constituting the electrodes of these electrochemical cells, finds application in particular in the recycling of batteries of the lithium-ion (or Li-ion), sodium-ion (or Na-ion), potassium-ion (or K-ion), calcium-ion (or Ca-ion) or even magnesium-ion (or Mg-ion) type, and in particular Li-ion batteries. State of the prior art

[0005] The market for batteries and, in particular, lithium batteries of the Li-ion type is currently expanding rapidly due, on the one hand, to the continued development of so-called "nomadic" devices (mobile phones, touch tablets, cameras, laptops, etc.) and, on the other hand, to the emergence of new applications linked to the development of hybrid or all-electric transport vehicles and the storage of intermittently produced energy (wind turbines, solar panels, etc.).

[0006] Beyond the regulatory recycling constraints imposed by the European Union, there are three reasons to recycle used, damaged or discarded batteries: - an environmental reason, namely that batteries represent waste that is harmful to the environment if they are not properly managed and the use of recycled materials instead of mining resources helps to reduce the environmental impact; - a safety reason, namely that batteries are dangerous objects which can be sources of fire in waste disposal sites; and - a strategic reason, namely that batteries contain critical and strategic metals, the recovery of which can contribute to their supply.

[0007] Battery recycling is therefore a major issue.

[0008] The electrochemical cells of Li-ion batteries are each composed of an envelope (or "casing" in English) which can be flexible, for example made of a polymer, or rigid, for example made of steel, and in which are housed a negative electrode, a positive electrode, a separator and an electrolyte.

[0009] The negative electrode is typically made of a mixture of a carbon material such as graphite powder, and an organic binder of the sodium carboxymethylcellulose or poly(styrene / butadiene) type, which is deposited on a copper foil forming a current collector.

[0010] The positive electrode is typically a mixture comprising a lithiated material (such as a lithiated metal phosphate such as LiFePO4, a lithiated metal oxide of the type LiCoO2, LiMnO2, LiNiO2, LiNixMnyCozO2 with x + y + z = 1 (also known by the abbreviation NMC) such as LiNii / 3Mni / 3Coi / 3O2 or LiNio,6Mnoj2Coo>202, or LiNixCoyAlzO2 with x + y + z = 1 (also known by the abbreviation NCA) such as LiNio.sCoojsAlo.osCL, a graphite powder and an organic binder of the PVDF type, this mixture being deposited on an aluminum foil also forming a current collector.

[0011] As for the electrolyte, it typically comprises a lithium salt (for example, LiPF6, LiCF3SO3, LiBF4, LiAsF6 or LiC104) as well as additives making it possible to slow down the secondary reactions in solution in an organic solvent or a mixture of organic solvents (for example, a mixture of carbonates).

[0012] The operation of an electrochemical cell of a Li-ion battery is as follows.

[0013] When this cell is charged by an external energy supply, the positive electrode is the site of an oxidation reaction which results in a release, by the lithiated material of this electrode, of lithium ions into the electrolyte and of electrons into the external circuit which connects the two current collectors, while the negative electrode is the site of a reduction reaction which results in an insertion of the lithium ions thus released into the carbon material of this electrode with a consumption of the electrons supplied by the external circuit.

[0014] When the cell is discharged, the reactions are reversed: it is therefore the negative electrode which is the site of an oxidation reaction with, as a result, a release of lithium ions by the carbon material of this electrode while the positive electrode is the site of a reduction reaction with, as a result, an insertion of the lithium ions thus released into the lithiated material of this electrode.

[0015] This operating principle is called: rocking-chair mechanism.

[0016] As they are used, Li-ion batteries lose capacity and must be replaced.

[0017] Nevertheless, many end-of-life batteries still have a relatively high residual charge level and their crushing is likely to produce sparks or significant ignitions, or even explosions.

[0018] Other Li-ion batteries also need to be recycled, such as defective, damaged or discarded batteries. However, defective or damaged battery cells may have significant deposits of metallic lithium on the negative electrode, which, if exposed to air or water, are highly reactive. Like end-of-life battery cells, defective or damaged battery cells cannot be safely opened and must therefore be treated with the utmost care.

[0019] Typically, upstream of a battery recycling process, such as Li-ion batteries, a pretreatment is carried out including a battery sorting phase, a battery dismantling phase to release the electrochemical cells that compose them and a phase to secure these electrochemical cells. Pyrometallurgical and / or hydrometallurgical treatments are then carried out to recover the different materials and metals contained in the electrochemical cells.

[0020] Currently, the main problem lies in the safety phase of the electrochemical cells.

[0021] Indeed, when a loss of containment occurs, leaks of the electrolyte, a toxic, flammable and corrosive product, occur, in liquid but also gaseous form. The vapors thus generated and mixed with the air can then form an explosive atmosphere (ATEX) which is likely to ignite on contact with an ignition source such as a spark or a hot surface and thus cause an explosion. In addition, the lithium salts present in the electrolytes such as LiPF6, LiBF4, LiAsF6 and LiClO4, can release particularly toxic and corrosive fumes containing phosphorus, fluorine and / or lithium. Hydrofluoric acid (HF) can also be formed. Thus, the batteries, even when completely discharged, must be opened in a well-ventilated area without the risk of sparks in order to mitigate the risks of flammability and toxicity linked to the electrolytes.

[0022] Recently, it has been proposed to use an ionic liquid or a deep eutectic solvent to carry out the safety of electrochemical cells of Li-ion or Na-ion batteries.

[0023] Thus, EP-A-3 948 994 describes a method for neutralizing an electro-cell Li-ion or Na-ion chemical which consists of discharging this cell by putting it in contact, in particular by immersion, with a solution comprising an ionic liquid as well as a redox species called oxidizing, capable of being reduced on the negative electrode of the electrochemical cell and, thus, of causing a discharge of the electrochemical cell.

[0024] Also, EP-A-3 948 993 describes a method for grinding a Li-ion or Na-ion electrochemical cell in which the cell is ground in a solution comprising an ionic liquid as well as a redox species called oxidizing, the function of which is, here too, to allow a discharge of the electrochemical cell simultaneously with the grinding. Thanks to the ionic liquid, the grinding of the electrochemical cell can be carried out in complete safety and, in particular, while avoiding the formation of an explosive atmosphere.

[0025] Finally, WO-A-2023 / 067275 describes a method for opening a Li-ion or Na-ion electrochemical cell in which this cell is immersed in a solution comprising, in addition to a so-called oxidizing redox species, an ionic liquid or a deep eutectic solvent formed from a choline chloride and a hydrogen bond donor, then opened using a cutting tool.

[0026] Although these methods are undeniably of interest, the inventor, continuing his work on the safety of electrochemical battery cells and, in particular, Li-ion batteries, has set himself the goal of providing a method which, while making it possible to neutralize an electrochemical cell in complete safety, does away with the use of ionic liquids and deep eutectic solvents based on choline chloride, these liquids and these solvents being, in fact, relatively expensive and, moreover, corrosive.

[0027] The inventor also set himself the goal of making this method simple to implement and applicable to the treatment, on an industrial scale, of worn, defective, damaged or discarded electrochemical cells. Statement of the invention

[0028] These aims are achieved by the invention which relates to a method for opening and discharging an electrochemical cell of an ionic insertion-deinsertion battery, comprising an envelope in which are housed a negative electrode, a positive electrode, a separator and an electrolyte, which method comprises the following operations: a) opening the electrochemical cell at one or more zones of the envelope, at least the opening zone(s) being brought into contact with a liquid L1; then b) discharging the electrochemical cell by bringing the cell into contact with a liquid L2; and which is characterized in that: - liquid L1 comprises a solvent based on an alcohol and optionally a redox mediator in solution in this solvent, while liquid L2 comprises a solvent based on an alcohol together with a redox mediator in solution in this solvent; and - liquids L1 and L2 are free of chlorine.

[0029] Thus, according to the invention, the following are achieved: - opening the electrochemical cell at one or more zones of its envelope to make the interior of this cell accessible and, more specifically, its two electrodes, at least the opening zone(s) being brought into contact with a liquid L1 making it possible in particular to dissipate the heat produced by the opening operation at this or these zones and thus to avoid thermal runaway of the electrochemical cell likely to lead to inflammation or even an explosion of this cell, this liquid comprising a solvent based on an alcohol and optionally a redox mediator but being free of chlorine, then - the discharge of the electrochemical cell by bringing this cell into contact with a liquid L2 capable of allowing, by oxidation-reduction reactions, a deactivation of the electrochemical cell and, thereby, a safety of this cell, this liquid comprising a solvent based on an alcohol as well as a redox mediator but also being free of chlorine.

[0030] The absence of chlorine in liquids L1 and L2 not only makes it possible to avoid the corrosion phenomena observed with the use of ionic liquids or deep eutectic solvents based on choline chloride and to reduce the costs linked to the use of these liquids and solvents but also to improve the efficiency of the process, in particular by increasing the discharge kinetics.

[0031] In the foregoing and the following, the term "redox mediator", also called "redox couple", means an oxidant / reducer couple (Ox / Red) in solution in which the oxidant can be reduced at the negative electrode of the electrochemical cell while the reducer can be oxidized at the positive electrode of this cell. Thus, when a liquid comprising a redox mediator is brought into contact with the interior of the electrochemical cell, the reduction of the oxidant coupled with the oxidation of the reducer leads to ionic deinsertion at the negative electrode and to migration via the electrolyte of the ions thus deinserted towards the positive electrode where they are immobilized. The redox mediator thus induces, in a way, a "forced" discharge of the electrochemical cell.Furthermore, the reduction of the oxidant and the oxidation of the reducer make it possible to form new oxidant / reducer species and / or to regenerate the oxidant / reducer species initially present in solution which will, in turn, be reduced / oxidized at the level of the . electrodes.

[0032] Furthermore, the expression “comprising a solvent based on an alcohol”, applied to liquids L1 and L2, means that more than 50% of the total number of moles of solvent present in these liquids are moles of an alcohol, it being understood that the molar alcohol content of the solvent can reach 100%, in which case the solvent consists solely of an alcohol.

[0033] The expression “chlorine-free”, applied to liquids L1 and L2, means that these liquids do not contain chlorine in any form whatsoever (ionic, molecular, etc.).

[0034] In addition, we hear: - by positive electrode, the electrode which acted as cathode when the electrochemical cell delivered current when it was in use, that is to say when it was in the process of discharging, and acted as an anode when the electrochemical cell was in the process of charging; and - by negative electrode, the electrode which, conversely, acted as an anode when the electrochemical cell delivered current and acted as a cathode when the electrochemical cell was in the process of charging.

[0035] According to the invention, the opening of the electrochemical cell is preferably carried out by a technique which does not cause excessive deformation of this cell, such as crushing, so as to avoid the occurrence, during this opening, of an internal short circuit likely to lead to thermal runaway and an explosion of the electrochemical cell.

[0036] Furthermore, the opening of the electrochemical cell is preferably carried out by a technique which, to ensure the opening, involves one or more non-electroconductive or weakly electroconductive elements or of which at least the part of this or these elements which is intended to be in contact with the electrochemical cell is made of a non-electroconductive or weakly electroconductive material, that is to say a material whose electrical resistance is preferably equal to or greater than 100 mohms, for example a ceramic (silicon carbide or nitride, alumina, tungsten carbide, etc.) or diamond.

[0037] The electrochemical cell can be opened by grinding but is preferably opened by cutting (or cutting, the words cutting and cutting being considered here as synonyms) or by piercing all or part of the cell envelope so as to partially or completely open this envelope.

[0038] Thus, the opening of the electrochemical cell can in particular be carried out by cutting with a knife (or blade cutting), by guillotine cutting, by wire cutting, by ultrasonic cutting, by laser cutting, by saw cutting (for example, by means of a circular or band saw), by cutting with a grinder or disc cutter (for example, by means of a circular or band saw). example, by means of a resinoid grinding wheel), by cutting by means of a jet of pressurized liquid, loaded or not with abrasive particles (such as garnet particles) or by drilling, for example by means of a drill, it being understood that, in all cases, it will be preferred - as previously indicated - that the cutting or drilling tool used or, at the very least, the part of this tool which is intended to be in contact with the electrochemical cell or the abrasive particles used (in the case where the opening is carried out by means of a jet of abrasive liquid) are made of a non-electroconductive or weakly electroconductive material.

[0039] Among these techniques, preference is given to cutting the electrochemical cell and, more specifically, to cutting with wire, saw or grinder, all preference being given to cutting with a grinder, in particular with a resinoid grinding wheel.

[0040] In any event, the opening of the electrochemical cell is carried out in the presence of the liquid L1 which is brought into contact with at least the opening zone(s), or even with the entire cell or even with the entire battery module comprising this cell.

[0041] Preferably, this contacting comprises - or is carried out by - spraying (or projecting a jet) of the liquid L1 onto the opening zone(s) of the electrochemical cell or onto the whole of this cell or of the battery module comprising this cell, this spraying possibly being such that the electrochemical cell or the battery module is partially or totally immersed in the liquid L1 during the opening.

[0042] Alternatively, the contacting can be carried out by immediately immersing the electrochemical cell or the battery module comprising this cell in the liquid L1.

[0043] According to the invention, the liquid L1 is advantageously a liquid which has at least the following characteristics: - not be or only very slightly viscous, that is to say, preferably have a dynamic viscosity of at most 40 mPa.s at room temperature (20-25 °C) so as to facilitate, on the one hand, its spraying, typically by pulverization, and, on the other hand, its filtration, once loaded with debris from the operation of opening the electrochemical cell, with a view to reusing this liquid for opening other electrochemical cells; - preferably have a flash point of at least 50°C and, better still, at least 55°C; - be as biodegradable as possible so that its use on an industrial scale has the least possible impact on the environment; and - in the case where the liquid Ll is intended to include a redox mediator, allow dissolution of this mediator.

[0044] As previously indicated, the liquid L1 may be free of redox mediator, in which case, in addition to ensuring dissipation of the heat produced by the opening of the electrochemical cell, the liquid L1 makes it possible to prevent the electrochemical cell from starting to discharge during opening and, thus, to control the reactivity of this cell. This may be particularly advantageous if the operations of opening and discharging the electrochemical cell are carried out in two separate areas of the same workshop or in two different workshops and the implementation of the method of the invention involves the transfer, in particular under air, of the electrochemical cell from one area to another or from one workshop to another.

[0045] In which case also, in addition to the above-mentioned characteristics, the liquid L1 advantageously has an electrical resistance greater than 10 ohms, preferably greater than 100 ohms, with every preference being given to a liquid which does not have ionic conductivity or which has a very low ionic conductivity, i.e. at most equal to 1,000 qS / cm at 25°C. This is particularly desirable to avoid or, at the very least, minimize the degradation of the solvent of the liquid L1 and the reactivity of the electrochemical cells, in particular in the case of the treatment of electrochemical cells having high voltages (typically greater than 12 V).

[0046] The solvent of a liquid L1 of this type may, for example, consist solely of an alcohol or comprise this alcohol in a mixture with deionized water (whose resistivity typically ranges from 1 to 10 MΩ.cm at 25°C) or ultrapure water, for example of the Milli-Q type (whose resistivity is 18.2 MΩ.cm at 25°C) and / or with one or more organic co-solvents, in an alcohol / water, alcohol / organic co-solvent(s) or alcohol / (water + organic co-solvent(s)) molar ratio greater than 1.

[0047] Alternatively, the liquid L1 may comprise a redox mediator if it is desired to initiate the discharge of the electrochemical cell during its opening, in which case this liquid does not have to satisfy the resistivity criterion previously mentioned.

[0048] As previously indicated, the discharge of the electrochemical cell is carried out by bringing the electrochemical cell into contact with the liquid L2.

[0049] According to the invention, this contacting is preferably carried out by immersion, preferably total (i.e. of the entirety), of the electrochemical cell or of the battery module comprising this cell in the liquid L2.

[0050] Furthermore, the liquid L2 which, as previously indicated, comprises a solvent based on an alcohol as well as a redox mediator, advantageously has characteristics of dynamic viscosity, volatility, biodegradability and cost similar to those stated previously for the liquid L1, as well as an ability to dissolve the redox mediator that one wishes to use.

[0051] According to the invention, the liquid L2 may comprise the same solvent as the liquid L1 or a solvent other than it.

[0052] Similarly, if liquid L1 comprises a redox mediator, then liquid L2 may comprise the same redox mediator as liquid L1 or a different redox mediator from it.

[0053] Thus, in accordance with the invention, it is possible to carry out the opening and discharge operations with, for example: - liquids L1 and L2 which differ from each other both in that they comprise different solvents (by virtue of their qualitative and / or quantitative composition) and in that liquid L1 does not comprise a redox mediator; - liquids L1 and L2 which comprise the same solvent but which differ from each other in that liquid L1 does not comprise a redox mediator; - liquids L1 and L2 which comprise the same solvent and which both comprise a redox mediator but which differ from each other in that they do not comprise the same redox mediator; - liquids L1 and L2 which comprise the same solvent and the same redox mediator but which differ from each other in that liquid L2 has a higher redox mediator content than the redox mediator content of liquid L1 (the reverse not being desirable); - liquids L1 and L2 which, although both comprising a redox mediator, or even the same redox mediator, differ from each other in that they comprise different solvents; or - liquids L1 and L2 which are identical, both in their qualitative and quantitative composition.

[0054] Within the framework of the invention, preference is given to the use of: - a liquid L1 whose solvent is identical to the solvent of liquid L2 but which is free of redox mediator, or - of a liquid L1 which is identical to liquid L2, and this, in particular for reasons of costs of implementing the process.

[0055] In the case of using liquids L1 and L2 that are different from each other, then the opening and discharging operations will necessarily be carried out in two successive steps, separated in time, whereas, in the case of using identical liquids L1 and L2, the opening and discharging operations may also be carried out in two successive steps, separated in time, but preference will be given to carrying out these operations in a single step and using a single and same liquid.

[0056] Generally speaking, preference will be given to the use of liquids L1 and L2 comprising the same solvent or solvents of very close qualitative and / or quantitative compositions so as to reduce the costs of implementing the process as much as possible.

[0057] In any case, the alcohol present in the solvent of the liquid L1 and / or in the solvent of the liquid L2 or constituting this (these) solvent(s) - in the case where this alcohol represents 100% of the total number of moles of solvent - is, advantageously, a diol, preferably a glycol and, better still: - ethylene glycol, of formula CH2OH-CH2OH, which has a dynamic viscosity of 21 mPa.s at 20 °C, a saturated vapor pressure of 7 Pa at 20 °C, a boiling point of 197.5 °C at normal atmospheric pressure (i.e. 1 atm), or - propylene glycol, of formula CH3-CHOH-CH2OH, which has a dynamic viscosity of 56 mPa.s at 20 °C, a saturated vapor pressure of 10.6 Pa at 20 °C and a boiling point of 188.2 °C at normal atmospheric pressure, or - a mixture thereof.

[0058] Preferably, the solvent of liquid L1 and / or the solvent of liquid L2 is (are) made up of ethylene glycol or propylene glycol or a mixture thereof, with all preference being given to ethylene glycol.

[0059] As for the redox mediator present in the liquid L2 and, optionally, in the liquid L1, it may be an electrochemical couple of metallic nature such as a couple Mn2+ / Mn3+, Co2+ / Co3+, Cr2+ / Cr3+, Cr3+ / Cr6+, V2+ / V3+, V4+ / V5+, Sn2+ / Sn4+, Ag+ / Ag2+, Cu+ / Cu2+, Ru4+ / Ru8+ or Fe2+ / Fe3+, which may be provided to the solvent of the liquid L2 and, where appropriate, to the solvent of the liquid L1 in the form of a metal salt other than a chloride, for example of the sulfate, nitrate, phosphate, sulfide, ascorbate, etc. type, in the form of an organometallic complex, for example metallocene (Fc / Fc+) of the ferrocene, manganocene, colbaltocene, chromocene, vanadocene type, etc., or of a salt of an organometallic complex other than a chloride.

[0060] Among these electrochemical couples, preference is given to: - on the one hand, to the Fe2+ / Fe3+ couple, which is advantageously provided to the solvent of the liquid L2 and, where appropriate, to the solvent of the liquid L1 in the form of a ferric salt, for example in the form of iron(III) sulfate, iron(III) nitrate or iron(III) phosphate (also called iron orthophosphate), the iron ions also having the advantage of being reduced to metallic iron, allowing a metallic deposition in the reactive zone or zones, which is particularly favorable to the discharge of the cell; and - on the other hand, to the Cu+ / Cu2+ couple, which is advantageously provided to the solvent of the liquid L2 and, where appropriate, to the solvent of the liquid L1 in the form of a cupric (II) salt, for example in the form of copper (II) sulfate, copper (II) nitrate or copper (II) phosphate, the copper ions also having the advantage of being reduced to metallic copper and of allowing a metallic deposition in the reactive zone(s), particularly favorable to the discharge of the cell.

[0061] Alternatively, the redox mediator may also comprise an electrochemical couple of organic nature such as a quinone / hydroquinone couple.

[0062] According to the invention, it is also possible to provide for the presence in the liquid L1 and / or the liquid L2: * of a co-solvent for, for example: - lower their viscosity and / or their flammability, in which case the co-solvent may be water or an organic co-solvent such as vinylene carbonate, γ-butyrolactone or propylene carbonate, it being understood that, in the case where the liquid L1 does not include a redox mediator, the water will preferably be deionized or ultrapure water as previously indicated; or - reduce their saturated vapor pressure, in which case the co-solvent will be, for example, a low molecular weight polyethylene glycol, i.e. less than 600 g / mol; or - provide an extinguishing agent and / or flame retardant function so as to further reduce the risk of flammability of the electrochemical cell, in which case the co-solvent will be, for example, a trialkyl phosphate such as trimethyl phosphate or triethyl phosphate, this triethyl phosphate being able to be fluorinated such as tris(2,2,2-trifluoroethyl) phosphate; it being understood that, in all cases, the alcohol / co-solvent(s) molar ratio will always be greater than 1; * of a salt (other than chloride), suitable for promoting the ionic conductivity of liquid L1 and / or liquid L2, such as an aluminum sulfate or a sodium sulfate, it being understood that this salt will only be present in liquid L2 if it is desired that liquid L1 is not ionically conductive or only very little; * a drying agent, which may be a salt (other than chloride) incapable of intervening in the reactions at the electrodes or of reacting with the solvent, for example magnesium sulfate (MgSO4), sodium sulfate (Na2SO4), calcium sulfate (CaSO4), potassium carbonate (K2CO3), sodium hydroxide (NaOH) or potassium hydroxide (KOH), it being understood that, here too, this salt will only be present in the liquid L2 if it is desired that the liquid L1 is not ionically conductive or only very little; or * of a salt(s) stabilizer of the carbonate type (K2CO3 for example) or phosphate.

[0063] Preferably: - either liquid L1 is made up of ethylene glycol while liquid L2 is made up of ethylene glycol and iron sulfate, - either liquid L1 and liquid L2 are both made up of ethylene glycol and iron sulfate.

[0064] According to the invention, the operation of opening the electrochemical cell can be carried out under an inert atmosphere, for example under argon, nitrogen, carbon dioxide or one of their mixtures, for greater safety with regard to the fire triangle. Thus, the operation of opening the electrochemical cell can be carried out in an enclosure supplied with an inert gas or a mixture of inert gases and which is associated with a control system, in particular of the oxygen content, or even of extraction of the gases produced during this opening operation.

[0065] Alternatively and preferably, the opening operation is carried out in air.

[0066] For better heat dissipation when opening the electrochemical cell, the liquid L1 can advantageously be cooled before being brought into contact with at least the opening zone(s) of the electrochemical cell, or even with the whole of this cell or the battery module comprising it.

[0067] As for the liquid L2 which is brought into contact with the electrochemical cell during the discharge operation, it is preferable that its temperature does not exceed 60°C to prevent the electrolyte of this cell from degrading as well as the occurrence of a thermal runaway process likely to lead to an explosion of the electrochemical cell.

[0068] Preferably, the liquid L2 will be at room temperature, i.e. of the order of 20-25°C.

[0069] According to the invention, the operations of opening and discharging the electrochemical cell can be carried out: - in a single step, in which case they will necessarily be carried out in the same workshop, or even in the same enclosure if the opening operation is carried out under a controlled atmosphere, or - in two successive stages, in which case they may be carried out in two separate areas of the same workshop or in two different workshops and the method will comprise an intermediate stage corresponding to the transfer of the electrochemical cell from the first area or the first workshop to the second area or the second workshop. Preferably, this transfer will be carried out in air, it being understood that the contact of the liquid L1 with at least the opening area(s) of the electrochemical cell, or even with the whole of this cell or the battery module comprising it, may or may not be maintained during this transfer.

[0070] According to the invention, the electrochemical cell may be a cell of a lithium-ion, sodium-ion, potassium-ion, calcium-ion or even magnesium-ion battery.

[0071] Preferably, the electrochemical cell is a cell of a lithium-ion or sodium-ion battery, with particular preference being given to a lithium-ion battery.

[0072] In particular, the electrochemical cell is a cell of a lithium-ion battery whose positive electrode comprises a lithiated metal oxide NMC, i.e. of formula LiNixMnyCozO2 with x + y + z = 1 such as LiNii / 3Mni / 3Coi / 3O2 or LiNio,6Mno,2 Co0j2O2, or a lithiated metal oxide NCA, i.e. of formula LiNixCoyAlzO2 with x + y + z = 1 such that LiNio.sCoo,15Alo,0502.

[0073] The invention also relates to a method for recycling an ionic insertion-deinsertion battery which comprises the implementation of an opening and discharge method as previously described.

[0074] In the above and the following, the term "battery" means both a battery module corresponding to an assembly in series or in parallel of a plurality of electrochemical cells identical to each other, and a battery block (or battery pack) corresponding to an assembly of several battery modules identical to each other.

[0075] Here too, the battery can be a lithium-ion, sodium-ion, potassium-ion, calcium-ion or even magnesium-ion battery, preference being given to a lithium-ion or sodium-ion battery and, even more so, to a lithium-ion battery.

[0076] In particular, the lithium-ion battery is a battery which comprises electrochemical cells whose positive electrode comprises a lithiated metal oxide NMC, i.e. of formula LiNixMnyCozO2 with x + y + z = 1 such as LiNii / 3Mni / 3Coi / 3O2 or LiNio,6Mnoj2Coo>202, or a lithiated metal oxide NCA, i.e. of formula LiNixCoyAlzO2 with x + y + z = 1 such as LiNio.sCoo,,15A1o,0502.

[0077] Other characteristics and advantages of the method of the invention will emerge from the additional description which follows, which relates to tests which have made it possible to validate this method and which refers to the appended figures.

[0078] It goes without saying, however, that this additional description is given only as an illustration of the method of the invention and must in no case be interpreted as a limitation thereof. Brief description of the figures

[0079] [Fig. 1] illustrates the evolution over time, noted t and expressed in minutes, of the voltage, noted U and expressed in volts, and of the temperature, noted T and expressed in °C, of ​​a Li-ion cell subjected to the opening and discharging method of the invention according to a first mode of implementation of this method; in this figure, curve 1 corresponds to the voltage while curve 2 corresponds to the temperature.

[0080] [Fig.2] is a figure similar to [Fig.l] but for a second mode of implementation of the method of the invention.

[0081] [Fig.3] is also a figure similar to [Fig.l] but for a third mode of implementation of the method of the invention.

[0082] Detailed description of particular implementation methods

[0083] Example 1: Opening and discharging a Li-ion cell in an ethylene glycol solution comprising 0.01 mol / L of iron(III) sulfate

[0084] A first 18650 Li-ion cell is submitted, of NMC chemistry and having a nominal capacity of 3 Ah, a voltage of 3.7 V and a state of charge of 30%, at a first opening and discharge test by the method of the invention.

[0085] In the present example, the cutting and discharging operations are carried out in a single step, at ambient temperature and atmosphere, using a single solution for both operations, namely an ethylene glycol solution comprising 0.01 mol / L of iron sulfate as a redox mediator.

[0086] To do this, the cell is first sprayed with the ethylene glycol solution until it is completely immersed in this solution, then, with the spraying maintained, the cell is cut using an alumina-based resinoid grinding wheel, at a speed of 1 mm / s, until a 7 mm deep notch is obtained (i.e. for less than 10 seconds).

[0087] The cell is then left immersed in the ethylene glycol solution until it has a state of charge of 0% (i.e. a voltage of 2.5 V instead of 3.7 V), without recirculation or thermalization of this solution.

[0088] As shown in [Fig. 1], which corresponds to the monitoring of the voltage U (in volts) and the temperature T (in °C) of the cell over time (in minutes), the voltage of the cell gradually decreases after stopping the cutting and spraying, shown by the arrow fl in this figure and the state of charge of 0% is reached in 5 hours and 26 minutes, or C / 16.3.

[0089] Measurement of the cell temperature during the test shows heating of this cell but this heating is sufficiently low (since the maximum temperature of the cell is 29.6°C) to allow opening and discharge without risk of explosion or ignition.

[0090] Example 2: Opening and discharging a Li-ion cell in an ethylene glycol solution comprising 0.04 mol / L of iron(III) sulfate

[0091] A second 18650 Li-ion cell having the same chemistry, voltage, nominal capacity and state of charge characteristics as the cell tested in Example 1 is subjected to a second opening and discharge test by the method of the invention.

[0092] This test differs from the test of Example 1 only in that the solution used for opening and discharging the cell is an ethylene glycol solution comprising 0.04 mol / L of iron(III) sulfate, all other operating conditions being identical to those mentioned in Example 1.

[0093] As shown in [Fig.2], which corresponds to the monitoring of the voltage U (in volts) of the cell and the temperature T (in °C) of this cell over time (in minutes), a state of charge of 0% is obtained in 29 minutes, or C / 1.5.

[0094] The heating of the cell is greater than that observed in the test of example 1 since the temperature of the cell, initially 25.5°C, reaches a maximum value of 43.6°C. This maximum temperature is nevertheless low enough for the cell to be opened and discharged without risk of explosion or ignition.

[0095] Example 3: Opening and discharging a Li-ion cell in an ethylene glycol solution comprising 0.08 mol / L of iron(III) sulfate

[0096] A third 18650 Li-ion cell having the same chemistry, voltage, nominal capacity and state of charge characteristics as the cells tested in the previous examples is subjected to a third opening and discharge test by the method of the invention.

[0097] This test differs from the previous tests only in that the solution used for opening and discharging the cell is an ethylene glycol solution comprising 0.08 mol / L of iron(III) sulfate, all other operating conditions being identical to those mentioned in Example 1.

[0098] As shown in [Fig.3], which corresponds to the monitoring of the voltage U (in volts) of the cell and the temperature T (in °C) of this cell over time (in minutes), a state of charge of 0% is obtained in 16 minutes, or C / 0.8.

[0099] The heating of the cell is substantially the same as that observed in the test of example 2, since the temperature of the cell, initially 23.3°C, reaches a maximum value of 40.9°C. Here too, this maximum temperature is nevertheless sufficiently low so that the opening and discharge of the cell can be carried out without risk of explosion or ignition. REFERENCES CITED

[0100] EP-A-3 948 994

[0101] EP-A-3 948 993

[0102] WO-A-2023 / 067275

Claims

Claims

1. A method for opening and discharging an electrochemical cell of an ionic insertion-deinsertion battery, comprising a casing in which are housed a negative electrode, a positive electrode, a separator and an electrolyte, which comprises the following operations: a) opening the electrochemical cell at one or more zones of the casing, at least the opening zone(s) being brought into contact with a liquid L1; then b) discharging the electrochemical cell by bringing the cell into contact with a liquid L2; and which is characterized in that: - the liquid L1 comprises a solvent based on an alcohol and optionally a redox mediator in solution in this solvent, while the liquid L2 comprises a solvent based on an alcohol together with a redox mediator in solution in this solvent; and - the liquids L1 and L2 are free of chlorine.

2. The method of claim 1, wherein opening the cell comprises cutting or piercing all or part of the envelope of the electrochemical cell.

3. A method according to claim 1 or claim 2, wherein, in step a), contacting at least the opening area(s) with the liquid L1 comprises spraying the liquid L1 onto at least the opening area(s).

4. A method according to any one of claims 1 to 3, wherein, in step b), contacting the electrochemical cell with the liquid L2 comprises immersing the cell in the liquid L2.

5. A method according to any one of claims 1 to 4, wherein the alcohol of the solvent of liquid L1 and / or of the solvent of liquid L2 is a diol, preferably a glycol.

6. Method according to any one of claims 1 to 5, in which the alcohol of the solvent of the liquid L1 and / or of the solvent of the liquid L2 is chosen from ethylene glycol, propylene glycol and their mixtures.

7. A method according to any one of claims 1 to 6, wherein the solvent of liquid L1 and / or the solvent of liquid L2 is (are) made up of ethylene glycol or propylene glycol or a mixture thereof.

8. A method according to any one of claims 1 to 7, wherein the

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18. Liquid solvent L1 and liquid solvent L2 are made of ethylene glycol. Method according to any one of claims 1 to 8, in which the redox mediator of the liquid L1 and / or of the liquid L2 is an electrochemical couple chosen from Mn2+ / Mn3+, Co2+ / Co3+, Cr2+ / Cr3+, Cr3+ / Cr6+, N2+IN 3+, V4+ / V5+, Sn2+ / Sn4+, Ag+ / Ag2+, Cu+ / Cu2+, Ru4+ / Ru8+ and Fe2+ / Fe3+, which is supplied to the solvent in the form of a metal salt other than a chloride, an organometallic complex or a salt of an organometallic complex other than a chloride. Method according to claim 9, in which the electrochemical couple is Fe2+ / Fe3+ which is provided in the form of a ferric salt, or Cu+ / Cu2+ which is provided in the form of a cupric salt. A method according to any one of claims 1 to 10, wherein the solvent of liquid L1 is identical to the solvent of liquid L2 but liquid L1 is free of redox mediator. The method of claim 11, wherein liquid L1 consists of ethylene glycol while liquid L2 consists of ethylene glycol and iron sulfate. Method according to any one of claims 1 to 10, in which the liquid L1 is identical to the liquid L2. The method of claim 13, wherein liquid L1 and liquid L2 consist of ethylene glycol and iron sulfate. A method according to any one of claims 1 to 14 wherein the opening and discharging operations are carried out in a single step and using the same liquid for opening and discharging. A method for recycling an ionic insertion-deinsertion battery, which comprises carrying out an opening and discharging method according to any one of claims 1 to 15. A method according to any one of claims 1 to 16, wherein the battery is a lithium-ion, sodium-ion, potassium-ion, calcium-ion or magnesium-ion battery and preferably a lithium-ion or sodium-ion battery. The method of claim 17, wherein the battery is a lithium-ion battery and preferably a battery which comprises electrochemical cells whose positive electrode comprises a lithiated metal oxide of formula LiNixMnyCozO2 with x + y + z = lof the formula LiNixCoyAlzO2 with x + y + z = 1.

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