METHOD FOR OPENING AN ELECTROCHEMICAL GENERATOR

Abstract

A method for opening an electrochemical generator (10) comprising a negative electrode (20) containing lithium or sodium and a positive electrode (30) optionally containing lithium or sodium, the method comprising the following successive steps: a) immersing the electrochemical generator (10) in a solution comprising an inert liquid and, optionally, an oxidizing redox species capable of being reduced on the negative electrode so as to discharge the electrochemical generator; b) opening the electrochemical generator in the solution with a cutting element (100) having an electrical resistance between 1 mΩ and 1 kΩ, and preferably between 5 mΩ and 100 Ω. Figure for the abstract: 3A

Description

Title of the invention: METHOD FOR OPENING AN ELECTROCHEMICAL GENERATOR Technical field

[0001] The present invention relates to a method for opening an electrochemical generator, such as an accumulator, a cell or a battery, making it possible to open the electrochemical generator safely and thus subsequently to recycle the recoverable fractions.

[0002] The invention is particularly interesting for the recycling of electrochemical systems of the accumulator or battery type treated separately or as a mixture, and in particular for the recycling of batteries and accumulators of the Li-Ion, Na-Ion, or Lithium-metal type. STATE OF THE PRIOR ART

[0003] An electrochemical generator is an electricity-producing device that converts chemical energy into electrical energy. This may be, for example, batteries or accumulators.

[0004] The market for accumulators, and in particular lithium accumulators, of the Li-ion type, is currently expanding rapidly, on the one hand, due to so-called nomadic applications (smartphone, computer, camera, etc.) and, on the other hand, due to new applications linked to mobility (electric and hybrid vehicles) and so-called stationary applications (connected to the electricity network).

[0005] Due to the growth in the number of accumulators in recent years, the question of their recycling has therefore become a major issue.

[0006] Conventionally, a lithium-ion accumulator comprises an anode, a cathode, a separator, an electrolyte and a casing.

[0007] Generally, the anode is formed from graphite mixed with a PVDF type binder deposited on a copper foil and the cathode is a lithium metal insertion material (e.g., LiCoO2, LiMnO2, LiNiO2, LiNixCoi XO2 with 0 <x<l, Li3NiMnCoO6, ou LiFePO4) mélangé à un liant et déposé sur une feuille d'aluminium.

[0008] The electrolyte is a mixture of non-aqueous solvents and lithium salts, and, optionally, additives to slow down side reactions.

[0009] The operation is as follows: during charging, the lithium deintercalates from the metal oxide and intercalates into the graphite, where it is thermodynamically unstable. During discharge, the process is reversed and the lithium ions are intercalated into the lithium metal oxide.

[0010] As it is used, aging causes a loss of capacity and the accumulator must be recycled.

[0011] Conventionally, the process of recycling accumulators comprises several steps:

[0012] - a pre-treatment step including a dismantling phase and a safety phase,

[0013] - thermal and / or hydrometallurgical treatments to recover the various valuable materials and metals contained in these batteries and accumulators.

[0014] However, several situations can complicate recycling:

[0015] - a significant number of accumulators or accumulator batteries to be recycled can still be at least partially charged and their crushing produces sparks and significant ignitions or even explosions, particularly with primary lithium batteries (Li-SOCl2),

[0016] - damaged cells can be damaged and for example have deposits of metallic lithium on the anode, which, when exposed to air or water, are very reactive.

[0017] Electrochemical systems, at the end of their life and / or damaged, to be recycled must therefore be treated with the greatest care.

[0018] To date, the main problem therefore lies in the safety and opening phase of these lithium-based electrochemical systems (primary and secondary).

[0019] Indeed, during a loss of containment, leaks of the electrolyte occur, a toxic, flammable and corrosive product, in liquid but also gaseous form. The vapors thus generated and mixed with the air can then form an explosive atmosphere (ATEX). This is likely to ignite on contact with an ignition source such as a spark or a hot surface. This then results in an explosion causing thermal effects and pressure effects. In addition, electrolyte salts such as lithium hexafluorophosphate LiPF6, lithium tetrafluoborate LiBF4, lithium perchlorate LiC104, lithium hexafluoroarsenate LiAsF6 can release particularly toxic and corrosive fumes containing phosphorus, fluorine and / or lithium. For example, hydrofluoric acid (HF) may be formed during the thermal degradation of Li-ion batteries.

[0020] To overcome these drawbacks, it is possible to grind the batteries in an enclosure with a controlled atmosphere and pressure. For example, document WO 2005 / 101564 A1 describes a method for recycling lithium anode batteries by hydrometallurgical means, at room temperature and under an inert atmosphere. During grinding, the atmosphere comprises argon and / or carbon dioxide. The two gases will drive out the oxygen and form a protective gaseous cloud above the ground charge. The presence of carbon dioxide will lead to the initiation of passivation of the metallic lithium by the formation of lithium carbonate on the surface, which slows down the reactivity of this metal. The hydrolysis of the ground charge containing lithium leads to the formation of hydrogen. To avoid the risks of ignition of the hydrogen and explosion, the ground charge containing lithium is added in a very controlled manner to the aqueous solution and very strong turbulence above the bath is created. This operation is associated with a depletion of the oxygen atmosphere. The water becomes rich in lithium hydroxide and the lithium is recovered by the addition of sodium carbonate or phosphoric acid.

[0021] In the process of US patent 5,888,463 A, the safety of the batteries and accumulators is achieved by a cryogenic process. The batteries and accumulators are frozen in liquid nitrogen at -196°C before being ground. The ground material is then immersed in water. To prevent the formation of H2S, the pH is maintained at a pH of at least 10 by the addition of LiOH. The lithium salts formed (Li2SO4, LiCl) are precipitated in the form of carbonate by the addition of sodium carbonate. Such a process is particularly expensive.

[0022] Document CA 2313 173A1 describes a method for recycling lithium ion batteries. The batteries are first cut in an inert atmosphere free of water. A first organic solvent (acetonitrile) dissolves the electrolyte and a second organic solvent (NMP) dissolves the binder. The particulate insertion material is then separated from the solution and reduced by electrolysis.

[0023] In document JP2010198865 A, a rotating insulating cutting tool is used to remove the active core from the casing of the cell. This method requires in-depth knowledge of the cells and precise positioning of each unit cell, relative to the cutting blade, which is not feasible in the context of industrial processing with high production rates.

[0024] In document WO 2011 / 113860 A1, a so-called dry method ("Dry-Technology") is described. This mechanical process is based on a two-stage crushing line followed by a magnetic and mechanical separation unit and on good ventilation management. The process does not require any pre-treatment step to discharge the Li-Ion batteries. The batteries are crushed (or chopped) by a device with teeth or blades, for example made of steel. The temperature of the crusher is maintained between 40 and 50°C and the mixture of hydrogen and oxygen, released from the batteries, is eliminated, by a cyclonic air movement, to minimize the risk of fire. The pieces of battery and dust, recovered after sieving, are cooled to room temperature. The extraction of lithium seems to be done by reaction with oxygen and humidity in the air, causing risks related to the simultaneous presence of hydrogen, oxygen and heat conducive to combustion and explosion. However, this process has several disadvantages:

[0025] - crushing these accumulators causes crushing and short circuits which could cause an explosion,

[0026] - the electrolyte is degraded, generating risks, losses and difficulties with regard to dust and gas management,

[0027] - this approach does not allow for risk-free safety of the batteries,

[0028] - maintaining the temperature of the grinder between 40 and 50°C is only possible with limited processing rates not compatible with the material flows expected in the coming years, particularly from the electric vehicle market.

[0029] Document EP 0 613 198 A1 describes a method for recovering materials from lithium batteries. The batteries are cut either under a high-pressure water jet or under an inert atmosphere to prevent a fire. Then, the lithium reacts with water, an alcohol or acid to form, respectively, lithium hydroxide, a lithium alkoxide or a lithium salt (LiCl, for example). However, the safety achieved with cutting under a high-pressure water jet requires a high consumption of water and generates H2 gas in air.

[0030] To date, the various methods for opening batteries / cells described above require high-temperature treatments, cryogenic treatments, and / or treatments under a controlled atmosphere, which are conditions that are difficult to industrialize and / or costly. Statement of the invention

[0031] An aim of the present invention is to propose a method making it possible to overcome the drawbacks of the prior art, and in particular a method making it possible to open an electrochemical generator in complete safety, the method having to be easily industrializable and therefore compatible with high production rates.

[0032] This object is achieved by a method of opening an electrochemical generator comprising a negative electrode containing lithium or sodium and a positive electrode optionally containing lithium or sodium, the method comprising the following successive steps:

[0033] a) immersion of the electrochemical generator in a solution comprising an inert liquid and, optionally, a redox species called oxidizing capable of being reduced on the negative electrode so as to discharge the electrochemical generator,

[0034] b) total or partial opening of the electrochemical generator with a cutting element having an electrical resistance of between 1 mQ and 1 kQ, and preferably between 5 mQ and 100 Q, the opening being carried out in the solution.

[0035] The invention is fundamentally distinguished from the prior art, on the one hand, by the controlled opening of the electrochemical generator (battery or accumulator) in a non-reactive liquid medium and, on the other hand, by the use of a particular cutting tool. This is designed to have a defined electrical resistance allowing a controlled discharge of the system in the inert liquid. The cutting tool makes it possible both to cut a battery and simultaneously to act on the state of charge of this battery.

[0036] According to one embodiment of the method, the cutting element is kept in contact with the electrochemical generator after opening said generator in order to promote the electrical discharge, in particular when the solution does not contain a so-called oxidizing redox species.

[0037] The inert liquid may be deionized water, an ionic liquid, or a deep eutectic solvent (DES).

[0038] Deionized water has, for example, a resistivity between 18 MΩ and 20 MΩ.

[0039] The cation of the ionic liquid is, for example, chosen from the family: imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium. Preferably, it is a cation with a wide cationic window, large enough to envisage a cathodic reaction avoiding or minimizing the degradation of the ionic liquid, such as the imidazolium cation.

[0040] The cation is associated with an anion which will be indifferently organic or inorganic, preferably having a wide anodic window. Advantageously, anions will be used which make it possible to simultaneously obtain a wide electrochemical window, a moderate viscosity, a low melting temperature (liquid at room temperature), good solubility with the other species in the solution and which do not lead to hydrolysis (degradation) of the ionic liquid.

[0041] The TFSI anion is an example that meets the previously mentioned criteria. The ionic liquid will advantageously be chosen from [BMIM][TFSI], [P66614] [TFSI], the ionic liquid l-ethyl-2,3-trimethyleneimidazolium bis(trifluoromethanesulfonyl)imide ([ETMIm][TFSI]), the ionic liquid N,N-diethyl-N-methyl-N-2-methoxyethyl ammonium bis(trifluoromethylsulfonyl)amide [DEME][TFSA], the ionic liquid N-Methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PYR14][TFSI]), the ionic liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([PP13][TFSI]).

[0042] The anion can also be of the bis(fluorosulfonyl)imide (FSA or FSI) type. The ionic liquid with such an anion is, for example, N-methyl-N-propylpyrrolidinium ionic liquid FSI ([P13][FSI]), N-methyl-N-propylpiperidinium FSI (PP13][FSI]), l-ethyl-3-methylimidazolium FSI ([EMI][FSI]), etc.

[0043] The deep eutectic solvent (DES) is, for example, formed from choline chloride and a hydrogen bond donor, such as a glycol (e.g. ethylene glycol or glycerol) or urea, in order to obtain a non-toxic and very low-cost DES.

[0044] The inert solution may comprise one or more inert liquids. The inert liquids may have one or more of the following properties: non-volatile and non-flammable, chemically stable at temperatures which may be above 200°C (e.g. between 200°C and 400°C) and / or with a wide electrochemical stability window.

[0045] The use of an inert liquid allows the introduction of the cutting element into the core of the active material of the electrochemical generator to ensure its discharge during opening, while avoiding a violent reaction with water and / or air, and also allows the evacuation of calories during the discharge process and promotes the cooling of the medium. The inert liquid secures the opening of the electrochemical generator.

[0046] The cutting element has an intrinsic electrical resistance, so as to avoid an electrical short circuit which could cause too sudden a discharge between the positive and negative elements of the electrochemical generator. It allows the control of the discharge speed so that the temperature does not exceed the runaway limit from which the cell risks exploding. The resistances chosen for the cutting element are dependent on the objects to be treated and the discharge regimes which they can withstand. The use of such a cutting element according to the invention allows the simultaneous opening and discharge of the treated objects and guarantees their safety.

[0047] The method simultaneously leads to the opening of the electrochemical generator in the inert liquid medium and to its safety by deactivating the electrical capacity of the object.

[0048] The present invention relates to a method for making batteries, all electrochemical systems of the accumulator or cell type safe, treated separately or as a mixture, whether they are still functional or faulty.

[0049] Preferably, the solution comprises a redox species capable of reacting with the lithium or sodium of the negative electrode (anode). Opening the electrochemical generator allows access to the electrodes: the redox species also performs an oxidation-reduction discharge action with the electrodes containing the lithium (or sodium). This reactive species thus participates in the discharge of the electrochemical generator during opening, which further avoids the risks of ignition and / or explosion.

[0050] According to the invention, the redox species is also capable of being reduced on the negative electrode, i.e. the redox species can react either directly on the electrode negative (anode), in the case where the accumulator case is open, or on another element electrically connected to the anode, such as the anode current collector, the anode terminal or even the ground when the anode is electrically connected to the ground.

[0051] Subsequently, when describing lithium, lithium may be replaced by sodium.

[0052] For example, in the case of a lithium-metal accumulator, the reduction reaction of the so-called oxidizing redox species leads to the oxidation of metallic lithium in ionic form.

[0053] According to another example, in the case of a lithium-ion accumulator, the reduction reaction of the so-called oxidizing redox species leads to the disinsertion of the lithium ion from the active material of the negative electrode.

[0054] The free ions extracted from the anode migrate through the ion-conducting electrolyte and are immobilized in the cathode where they form a thermodynamically stable lithium oxide. By thermodynamically stable, it is meant that the oxide does not react violently with water and / or air.

[0055] Advantageously, the solution comprises a second redox species called reducing capable of being oxidized on the positive electrode, the redox species called oxidizing and the redox species called reducing forming a pair of redox species.

[0056] By redox couple, also called redox mediator or electrochemical shuttle, we mean an oxidant / reducer couple (Ox / Red) in solution in which the oxidant can be reduced on the anode (negative electrode) and the reducer can be oxidized on the cathode (positive electrode). The oxidation of the reducer and the reduction of the oxidant make it possible to form new oxidant / reducer species and / or to regenerate the species initially present in solution. The process is economical since the redox couple in solution ensures both and simultaneously the redox reactions at the electrodes / terminals of the electrochemical generator, so that the consumption of reagent is zero; the solution can be used to open several electrochemical generators successively and / or in a mixture.

[0057] The redox species also allow the electrochemical generator to be discharged. In addition, when the electrochemical generator is opened, they will react with the internal components, so as to reduce the potential difference between the electrodes (anode and cathode). This internal discharge also contributes to making the electrochemical generator safe by reducing the chemical energy of the electrodes (and therefore the potential difference) and by reducing the internal short-circuit effect.

[0058] Advantageously, the redox species pair is a metal pair, preferably chosen from Mn27Mn3+, Co27Co3+, Cr27Cr3+, Cr37Cr6+, V27V3+, V47V5+, Sn27Sn4+, Ag7Ag2+, Cu+ / Cu2+, Ru47Ru8+ or Fe27Fe3+, a pair of organic molecules, a pair of metallocenes such as Fc / Fc+, or a pair of halogenated molecules such as C12 / C1 or C1 / C13.

[0059] According to a first advantageous variant, the opening of the electrochemical generator (step b)) is carried out in air.

[0060] According to a second advantageous variant, the opening of the electrochemical generator (step b)) is carried out under an inert atmosphere allowing the oxygen content to be controlled. Thus, the assembly is secure (with respect to the fire triangle).

[0061] The process is not a thermal process and makes it possible to manage the step of opening the electrochemical accumulator. It can advantageously be carried out at room temperature (typically between 20 and 25°C).

[0062] The ionic liquid solution may optionally be stirred and / or cooled. It is also possible to add to the solution species with advantageous heat capacities promoting cooling.

[0063] When opening the electrochemical generator, the cutting element enters the electrochemical generator.

[0064] The cutting element comprises a support covered with abrasive zones, preferably electrically insulating.

[0065] The abrasive zones may be, for example, formed of grains.

[0066] The abrasive zones may be, for example, made of silicate.

[0067] The support is, for example, made of ceramic, resin, rubber, or metal.

[0068] According to a particularly advantageous embodiment, the cutting element includes a backing covered with both abrasive areas and electrically conductive areas.

[0069] The electrically conductive zones are, for example, formed from electrically conductive grains.

[0070] The abrasive zones and / or the electrically conductive zones may be arranged randomly or regularly on the support.

[0071] The abrasive areas and / or the electrically conductive areas may be fixed to the support by a binder.

[0072] The cutting element used to open the electrochemical generator may be a blade, for example a guillotine-type blade, a circular or ribbon blade, cutting wires, knives, or a grinding wheel.

[0073] Advantageously, the opening of the electrochemical generator is carried out with a grinding wheel or a cutting wire.

[0074] Advantageously, the grinding wheel comprises a support disc covered with abrasive zones and electrically conductive zones, arranged randomly or regularly, the abrasive zones and the electrically conductive zones being associated with the support by a binder. Preferably, the abrasive zones are formed of abrasive grains and / or the electrically conductive zones are formed of electrically conductive grains.

[0075] The cutting element may be part of a tool. A tool is understood to mean a tool capable of piercing, grinding and / or cutting. Technologies that do not lead to excessive deformation (crushing) will be preferred in order to avoid short circuits. In a non-exhaustive manner, the opening may be carried out by cutting, sawing, abrasion. Preferably, the tool makes it possible to cut, partially or completely, the electrochemical generator.

[0076] Advantageously, the method comprises, prior to step a), a dismantling step and / or a sorting step.

[0077] Advantageously, the method comprises, subsequently to step b), a storage step and / or a pyrometallurgical and / or hydrometallurgical step.

[0078] The opening method according to the invention has numerous advantages:

[0079] - the method allows two operations to be carried out in a single step (safety and opening of the cells) which allows an increase in production rates and a significant saving in time and installation: the process rate is compatible with the significant material flows expected in the coming years;

[0080] - the method allows, via the opening of the electrochemical generator, direct access active materials ensuring a much faster discharge (no connection of cells, no special electrical installation, etc.);

[0081] - the control of the electrical resistance of the cutting element makes it possible to control finely regulate the discharge speed of electrochemical generators, avoiding runaway phenomena encountered when creating a short circuit;

[0082] - the process allows the treatment of all materials (modules, cells, etc.) which can arrive at the recycling input, in a discharged state or not (damaged cells for example due to mechanical degradation, degraded terminals (corrosion, etc.), with triggered internal safety devices, etc.) since it is not based on the use of the cell terminals to carry out the discharge;

[0083] - the discharge of the electrochemical generator is controlled so as to minimize the risks of temperature rise leading to thermal runaway;

[0084] - implementing the opening step in an inert liquid, thus avoiding a violent reaction with water and / or air, reduces problems related to the management of hydrogen, oxygen and heat, and therefore to the management of explosive atmospheres (safety, treatment of tributaries, additional economic cost);

[0085] - not using heat treatment helps to limit the problems linked to to the emission of gases (for example greenhouse gases or any other gas harmful and dangerous to humans and the environment) and their treatment, which reduces the financial and energy costs of the process;

[0086] - be safe and simple to implement;

[0087] - the process is carried out at low environmental and economic cost;

[0088] - the treatment is not harmful to the subsequent recycling of the components (degradation of the electrolyte, etc.);

[0089] - the process allows the cells to be secured and opened to give access to the material of interest for recycling by pyrometallurgical and / or hydrometallurgical means.

[0090] Furthermore, in the case where the solution comprises a chemical species ensuring the extraction of lithium (or sodium), the process also has the following advantages:

[0091] - improve the safety of the electrochemical generator by facilitating its discharge; such coupling allows significant time and investment savings;

[0092] - be able to use a wide choice of active species, the active species simply having to have a redox potential higher than that of lithium (lithium is the species with the most negative standard redox potential and can therefore be extracted (oxidized) with any species capable of reducing to a potential higher than -3.05V vs. ENH);

[0093] The invention also relates to a cutting element as described previously, for opening an electrochemical generator.

[0094] The cutting element has an electrical resistance of between 1 mQ and 1 kQ, and preferably of between 5 mQ and 100 Q.

[0095] Advantageously, the cutting element comprises a support covered by abrasive zones (for example abrasive grains) and electrically conductive zones (for example electrically conductive grains or wires), the abrasive zones and the electrically conductive zones being arranged randomly or regularly and being associated with the support by a binder.

[0096] Advantageously, the cutting element is a cutting wire, a grinder wheel, a circular saw blade (also called a disc) or a saw band.

[0097] The invention also relates to a cutting tool comprising such a cutting element. The cutting tool is, advantageously, a grinder or a saw, for example a circular saw or a band saw.

[0098] Other characteristics and advantages of the invention will emerge from the additional description which follows.

[0099] It goes without saying that this additional description is given only as an illustration of the subject of the invention and must in no case be interpreted as a limitation of this subject. Brief description of the drawings

[0100] The present invention will be better understood on reading the description of exemplary embodiments given purely for informational purposes and in no way limiting, with reference to the appended drawings in which:

[0101] [Fig-1] schematically represents a composition of abrasive wheel according to a particular embodiment of the invention,

[0102] [Fig.2A]

[0103] [Fig.2B]

[0104] [Fig.2C]

[0105] [Fig.2D]

[0106] [Fig.2E] represent, schematically and in section, abrasive wheels having different distributions of conductive zones and insulating zones, according to different embodiments of the method according to the invention.

[0107] [Fig.3A] is a photographic image of an 18650 cell after opening and discharging, according to a particular embodiment of the invention.

[0108] [Fig.3B] is an image obtained by scanning electron microscopy of the section of the cell of [Fig.3A].

[0109] [Fig.4] is a graph representing voltage and voltage tracking curves temperature as a function of time, when opening a Li-Ion cell, according to a particular embodiment of the invention.

[0110] The different parts represented in the figures are not necessarily on a uniform scale, in order to make the figures more readable. [YES] DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

[0112] Subsequently, even if the description refers to a Li-ion accumulator, the invention can be transposed to any electrochemical generator, for example to a battery comprising several accumulators (also called accumulator batteries), connected in series or in parallel, depending on the nominal operating voltage and / or the quantity of energy to be supplied, or even to an electric battery.

[0113] The opening process concerns all electrochemical systems of the accumulator, battery and cell type treated separately or as a mixture. For example, these may be electrochemical systems from portable devices or cells or modules from the automotive industry which have higher power and greater reactivity making their treatment more complex in terms of safety.

[0114] These different electrochemical devices can be of the metal-ion type, for example lithium-ion or sodium-ion, or of the Li-metal type,...

[0115] It can also be a primary system such as Li / MnO2, or a circulation battery (“Redox Flow Battery”).

[0116] An electrochemical generator having a potential greater than 1.5V will advantageously be chosen.

[0117] The method of opening the electrochemical generator comprises the following steps:

[0118] - immersion of the electrochemical generator in a solution comprising a liquid inert and, preferably, a redox species capable of reacting with lithium in such a way as to neutralize it, then

[0119] - opening of the electrochemical generator by a cutting element 100, the opening being made when the electrochemical generator is immersed in the solution.

[0120] The solution comprises at least one inert liquid. It may also contain a mixture of several inert liquids.

[0121] The inert liquid according to the invention is characterized by good thermal stability, in particular in the temperature range between 10°C and 150°C, and electrochemical stability making it possible to limit the effects of degradation of the medium during contact with the cells, mainly at high potentials, and during discharging.

[0122] The inert liquid may be deionized water, an ionic liquid, or a deep eutectic solvent or DES. It may also be a mixture thereof.

[0123] Deionized water (or demineralized water) has, for example, a resistance of 15MΩ to 21 MΩ, preferably of 18MΩ to 20 MΩ.

[0124] Ionic liquid is understood to mean the association of at least one cation and at least one anion which generates a liquid with a melting temperature lower than or close to 100°C. These are, for example, molten salts. The ionic liquid is thermally and electrochemically stable, minimizing a degradation effect on the medium during the discharge phenomenon.

[0125] The cation is preferably chosen from the family: imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium.

[0126] The anion is, for example, the TFSI or bis(fluorosulfonyl)imide (FSA or FSI) anion.

[0127] The ionic liquid will advantageously be chosen from l-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [BMIM][TFSI], trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)imide [P66614] [TFSI], l-ethyl-2,3-trimethyleneimidazolium bis(trifluoromethanesulfonyl)imide ([ETMIm][TFSI]), N,N-diethyl-N-methyl-N-2-methoxyethyl ammonium bis(trifluoromethylsulfonyl)amide [DEME] [TFSA], N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PYR14][TFSI]), N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide ([PP13][TFSI]), N-methyl-N-propylpyrrolidinium FSI ([P13][FSI]), N-methyl-N-propylpiperidinium FSI ([PP13][FSI]), and l-ethyl-3-methylimidazolium FSI ([EMI][FSI]).

[0128] DESs have the advantage of being non-toxic, biodegradable and low cost. For example, choline chloride will be chosen, used with a very low toxicity H-bond donor such as a glycol (glycerol or ethylene glycol for example) or urea, in order to obtain a non-toxic and very low cost DES. Such solutions have a limited electrochemical stability window, but will ensure the immersion and deactivation of an open accumulator. Proportions of components close to the eutectic points can also be advantageously selected in order to optimize the properties of the fluid such as its conductivity or viscosity. Thus, varied molar mixtures of these components can be envisaged.

[0129] For example, this could be a mixture of choline chloride and ethylene glycol in molar proportions ranging from 1:1 to 1:5.

[0130] Alternatively, choline chloride can be replaced with betaine.

[0131] The solution may further comprise other components / agents in order to confer specific properties of the solution. For example, the solution may include electrochemical shuttles or flame retardants.

[0132] The electrochemical shuttle (also called redox mediator) may be added to reduce the degradation of the medium, by ensuring the redox reactions. Redox mediator is understood to mean an ion or species in solution capable of being reduced and oxidized on the terminals of accumulators or batteries. The mediator may be a metallic electrochemical couple chosen for example from: Mn27Mn3+, Co27Co3+, Cr27Cr3+, Cr37Cr6+, V27V3+, V47V5+, Sn27Sn4+, Ag7Ag2+, Cu7Cu2+, Ru47Ru8+ or Fe27Fe3+. The solution may also contain several metallic electrochemical couples.

[0133] Alternatively, the redox mediator may be an organic species such as: 2,4,6-tri-t-butylphenoxyl, nitronyl nitroxide / 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), tetracyanoethylene, tetramethylphenylenediamine, dihydrophenazine, aromatic molecules such as methoxy, the N,N-dimethylamino group (anisole methoxybenzene, dimethoxybenzene, and N,N-dimethylaniline N,N-dimethylaminobenzene). 10-methyl-phenothiazine (MPT), 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB) and 2-(pentafluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole (PFPTFBDB) may also be mentioned.

[0134] The redox mediator can be from the family of metallocenes (Fc / Fc+, Fe(bpy)3(C104)2 and Fe(phen)3(C104)2 and its derivatives) or from the family of halogenated molecules (C12 / C1, C17C13 Br2 / Br, I2 / I,1713), or it can be tetramethylphenylenediamine.

[0135] Preferably, Fe2+ / Fe3+ and / or Cu7Cu2+ will be used. These are soluble in both their oxidation states, they are not toxic, they do not degrade the inert liquid and they have adequate redox potentials to extract the lithium in the event of opening the accumulator. Alternatively, it is advantageous to use two redox couples such as the association and V47V5+.

[0136] The solution may comprise one or more so-called "active" species, for example an extinguishing agent and / or a flame retardant intended to prevent thermal runaway, in particular when opening the accumulator. It may be an alkyl phosphate, optionally fluorinated (fluorinated alkyl phosphate), such as trimethyl phosphate, triethyl phosphate, or tris(2,2,2-trifluoroethyl) phosphate). The concentration of active species may be between 5% and 80% by mass, preferably between 30% and 10% by mass.

[0137] Optionally, the solution may comprise a drying agent, and / or an agent promoting the transport of matter, and / or a protective agent which is a stabilizer / reducer of corrosive and toxic species such as for example PF5, HF, POF3,...

[0138] The material transport promoting agent is, for example, a fraction of a cosolvent added to reduce the viscosity of the medium.

[0139] Preferably, an organic solvent will be chosen to act effectively without generating risks with regard to discharge or flammability. This may be vinylene carbonate (VC), gamma-butyrolactone (y-BL), propylene carbonate (PC), poly(ethylene glycol), dimethyl ether. The concentration of the material transport agent advantageously ranges from 1% to 40% and more advantageously from 10% to 40% by mass.

[0140] The protective agent capable of reducing and / or stabilizing corrosive and / or toxic elements is, for example, a compound of the butylamine type, a carbodiimide (N,N-dicyclohexylcarbodiimide type), N,N-diethylamino trimethyl-silane, tris(2,2,2-trifluoroethyl) phosphite (TTFP), an amine-based compound such as l-methyl-2-pyrrolidinone, a fluorinated carbamate or hexamethyl-phosphoramide. It may also be a compound of the cyclophosphazene family such as hexamethoxycyclotriphosphazene.

[0141] The cutting operation, carried out in the presence of the inert liquid, avoids a violent reaction with water and / or air. The inert liquid secures the opening of the battery / accumulator and allows, when the cutting tool is introduced into the active core of the material, to discharge the battery / accumulator during opening. Finally, the liquid inert promotes cooling of the environment and allows calories to be evacuated during the discharge process.

[0142] The inert liquid contributes to maintaining a controlled atmosphere (air, water), to the discharge in an advantageous manner and plays the role of cutting fluid (lubrication and cooling of the cutting zone).

[0143] The cutting element 100 is sufficiently electrically conductive to allow the discharging operation and sufficiently resistive to avoid a direct short circuit leading to the explosion of the cell. In other words, the cutting element 100 has a very low electrical conductivity. The electrical conductivity of the cutting element will be an average conductivity seen by the sample to be cut which will be dependent on the proportion of insulating zones and conductive zones, the rotation speed, the feed speed of the grinding wheel, etc.

[0144] The electrical resistance of the cutting element is suitable for this method of opening an electrochemical generator and is between 1 mΩ and 1 kΩ, and preferably between 5 mΩ and 100 Ω. Thus, a leakage current is generated at the cutting and makes it possible to control the discharge. The resistance is the average resistance of the cutting element. At least the part of the cutting element intended to penetrate the sample to cut it has such a resistance. The resistance can be measured with a multimeter by placing a sample between two identical conductive plates.

[0145] The technologies to be favored to achieve this opening are technologies which limit the deformation (crushing, spreading of materials on neighboring materials, etc.) which would lead to a frank and uncontrolled short circuit leading to thermal runaway and explosion of the cells.

[0146] The cutting element 100 is part of a cutting tool.

[0147] A cutting tool is understood to mean a tool that can be used to grind, and preferably to cut the material in order to partially or completely open the electrochemical generator in an inert medium. In a non-exhaustive manner, the cutting can be a guillotine type cut (blades), a sawing operation (circular, band), by drilling and, preferably, an abrasion method such as wire cutting or cutting using an abrasive wheel.

[0148] The cutting element 100 comprises a base support 101 conferring the mechanical properties to the cutting element 100.

[0149] The base support 101 may be electrically conductive or electrically insulating. The base support 101 may be metallic, resinoid or rubber-like.

[0150] The base support 101 is covered by abrasive zones 102. The abrasive zones 102 have a hardness adapted to the object and the material to be treated.

[0151] The abrasive zones 102 are, for example, made of sandstone, emery, diamond, silicon carbide and / or alumina.

[0152] Preferably, the abrasive zones are formed from abrasive grains.

[0153] Preferably, the base support 101 is covered by abrasive zones 102 and electrically conductive zones 103. The abrasive zones 102 provide the mechanical properties to the tool and electrically conductive zones 103 provide the electrical properties to the tool.

[0154] The electrically conductive zones 103 are, for example, formed by electrically conductive grains.

[0155] The electrically conductive zones 103 are, for example, made of a metal or a metal alloy. By way of illustration, it may be copper, iron, steel and / or aluminum, more broadly an electrical conductor.

[0156] The electrically conductive zones 103 may be formed from metal grains 103 or metal wires.

[0157] The abrasive grains and / or the electrically conductive grains are preferably particles having a dimension ranging, for example, from a few micrometers to a few centimeters.

[0158] The abrasive grains 102 and / or the electrically conductive grains 103 are advantageously mechanically held to the support 101 by a binder 104 ([Fig.l]). The binder may be a resin, rubber, silicate, clay, or even a ceramic.

[0159] The abrasive zones 102 and / or the electrically conductive zones 103 may be distributed regularly or randomly on the support 101.

[0160] The abrasive zones 102 and / or the electrically conductive zones 103 may be continuous or discontinuous.

[0161] According to a first embodiment, the opening of the electrochemical generator is carried out by abrasion using a wire 100. The wire 100 comprises a solid base 101, of wire form, conferring the mechanical properties. The abrasive properties are conferred by the addition of abrasive grains 102 of hardness adapted to the object and the material to be treated.

[0162] According to a second embodiment, the opening of the electrochemical generator is carried out by abrasion using a grinder. The disc of the grinder comprises a circular base support 101. The support comprises a first main face and a second main face parallel to each other as well as a lateral face (also called edge) connecting the two main faces.

[0163] The support 101 may be metallic, resinoid or rubber type. The support 101 is advantageously covered by electrically insulating abrasive zones 102 and by electrically conductive zones 103.

[0164] By way of illustration, as shown in FIGS. 2A to 2E, different configurations can be envisaged in the case of a grinding wheel comprising abrasive zones 102 (preferably abrasive grains) and electrically conductive zones 103 (preferably electrically conductive wires or grains).

[0165] The abrasive zones 102 and the electrically conductive zones 103 are, for example, distributed randomly ([Fig.2A]).

[0166] The abrasive zones 102 and the electrically conductive zones can be distributed in a controlled manner (Figures 2B to 2E).

[0167] According to an alternative embodiment, the abrasive zones 102 and the electrically conductive zones are arranged in a controlled manner in order to form an alternation of abrasive zones and non-abrasive zones.

[0168] According to another variant embodiment, the conductive zones 103 can be distributed concentrically relative to the center of the disc 100 of the grinding wheel ([Fig.2C]).

[0169] According to another variant embodiment, the conductive zones 103 can be arranged along one or more radii or along one or more diameters ([Fig.2D]), randomly or not.

[0170] According to another variant embodiment, the conductive zones 103 can be arranged only on the perimeter of the disc 100 of the grinding wheel ([Fig.2E]).

[0171] According to another variant embodiment, not shown, the electrically conductive zones 103 are arranged on the edge of the disc 101 of the grinding wheel.

[0172] The alternation of abrasive zones 102 and conductive zones 103 can be obtained by means of coatings produced by thin-film deposition techniques, for example, by physical vapor deposition (PVD), by atomic layer deposition (ALD), by chemical vapor deposition (CVD), by spin-coating or by coating techniques such as, for example, by dip-coating.

[0173] The adapted electrical resistance can also be provided by means of a conductive fabric deposited on the external faces of the cutting tool, thus making it possible to separate the mechanical properties (abrasion, controlled hardness given by the abrasive grains contained in the resin) and the electrical properties (adapted resistance, given by the external fabric).

[0174] The electrical resistances can also be modulated via the cutting fluid and the operating conditions (temperature, fluid viscosity, abrasion speed, fluid renewal, etc.).

[0175] For greater security, the opening system may optionally be associated with a gaseous atmosphere control system (inert atmosphere or system correctly sized extraction) allowing the control of the oxygen content. Thus, the assembly is secure (with respect to the fire triangle) and allows the simultaneous discharge and opening of batteries and accumulators while managing the production of gas induced by the opening of the cells.

[0176] The process can be carried out under an inert atmosphere, for example under argon, carbon dioxide, nitrogen or a mixture thereof.

[0177] The method can be carried out at temperatures ranging from 5°C to 80°C, preferably from 20°C to 60°C and even more preferably it is carried out at room temperature (20-25°C).

[0178] The solution may be cooled to remove heat during the discharge process.

[0179] The solution may be stirred to improve reagent delivery and / or improve cooling.

[0180] The opening process allows the electrochemical generator to be safely cut up for recycling (by pyrometallurgical, hydrometallurgical means or their combination) or for storage. For example, this may be temporary storage pending transfer, for example to a recycling plant to recover these different components.

[0181] Prior to opening the electrochemical generator, sorting and dismantling steps may take place. By way of illustration, a recycling process may include the following steps:

[0182] - Sorting,

[0183] - Pre-dismantling, for example moving from pack level to module level in the case of electric vehicle applications,

[0184] - opening of the electrochemical generator according to the method previously described,

[0185] - Recycling of materials by conventional means (pyrometallurgy, hydrometallurgy, etc.) and / or recycling of organic products of the solvent or electrolyte type, preferably by gentle safety measures, without increasing the temperature which degrades the organic products.

[0186] The recoverable fractions of the electrochemical generator, in particular the metals constituting the active material, can then be recovered and reused.

[0187] Illustrative and non-limiting example of an embodiment j.

[0188] In this example, a Li-Ion cell is opened with a copper resin wheel in a choline chloride / ethylene glycol medium.

[0189] The grinding wheel comprises abrasive grains made of A12O3 and a discontinuous deposit of Cu on the edge.

[0190] The solution in which the cutting is carried out is a mixture of choline chloride and ethylene glycol in a molar ratio of 1:3, further containing a shuttle electrochemical iron to limit its degradation. The viscosity of the mixture is approximately 40 cP. An 18650 Li-ion cell with NMC 811 chemistry, containing one of the most reactive cathode materials, is charged to 100% (3Ah) and placed in a tank filled with solution.

[0191] The opening action is carried out using the copper-coated resinoid grinding wheel subjected to a rotation speed of 1000 rpm for an exerted pressure of 7.5 N for 2 min. The cutting operation is carried out at room temperature (20-25°C) and under atmospheric pressure (Ibar) without recirculation or thermalization of the cutting fluid (degraded conditions). The resistance of the grinding wheel is greater than IKOhms.

[0192] The opening action by the grinding wheel creates a notch of approximately 1.5 cm2 for a thickness of 500 pm (Figures 3A and 3B). Observation of the section under a scanning electron microscope highlights the absence of crushing and deformation of the different layers of the cell.

[0193] Monitoring of voltage and temperature during cutting ([Fig.4]) shows a significant drop in voltage during the cutting phase. Discharge then takes place within the discharge fluid. This technique not only allows the cell to be opened without generating an explosion but also allows the cell to be discharged in less than 35 min by the combined action of the adapted resistance of the grinding wheel during opening and the fluid during the post-opening stage. A voltage of 0V is thus reached in less than one hour. A voltage drop during cutting and / or post-cutting can be observed.

Claims

Claims

1. Method for opening an electrochemical generator (10) comprising a negative electrode (20) containing lithium or sodium and a positive electrode (30) optionally containing lithium or sodium, the method comprising the following successive steps: a) immersing the electrochemical generator (10) in a solution comprising an inert liquid and, optionally, a so-called oxidizing redox species capable of being reduced on the negative electrode so as to discharge the electrochemical generator, b) opening the electrochemical generator, in the solution, with a cutting element (100) having an electrical resistance of between 1 mQ and 1 kQ, and preferably between 5 mQ and 100 Q.

2. Method according to claim 1, characterized in that the inert liquid is deionized water.

3. Method according to claim 1, characterized in that the inert liquid is an ionic liquid, preferably chosen from [BMIM][TFSI], [P66614][TFSI], [ETMIm][TFSI], [DEME][TFSA], [PYR14][TFSI], [PP13][TFSI], [P13][FSI] and [EMI][FSI].

4. Method according to claim 1, characterized in that the inert liquid is a deep eutectic solvent, preferably formed from a choline chloride and a hydrogen bond donor, in particular a glycol or urea.

5. Method according to any one of the preceding claims, characterized in that the solution comprises a redox species called oxidizing and a second redox species called reducing capable of being oxidized on the positive electrode, the redox species called oxidizing and the redox species called reducing forming a pair of redox species, the pair of redox species preferably being a metal pair, for example, chosen from Mn27Mn3+, Co27Co3+, Cr27Cr3+, Cr37Cr6+, V27V3+, V47V5+, Sn27Sn4+, Ag7Ag2+, Cu7Cu2+, Ru47Ru8+ or Fe27 Fe3+, a pair of organic molecules, a pair of metallocenes such as Fc / Fc+, or a pair of halogenated molecules such as for example C12 / C1 or C1 / C13_.

6. Method according to any one of the preceding claims, characterized in that the cutting element (100) comprises a support (101) covered by abrasive zones (102) and zones electrically conductive zones (103), the abrasive zones (102) and the electrically conductive zones (103) being arranged randomly or regularly and being fixed to the support (101) by a binder (104).

7. Method according to any one of claims 1 to 6, characterized in that the cutting element (100) is a grinder disc.

8. Method according to any one of claims 1 to 6, characterized in that the cutting element (100) is a cutting wire.

9. Method according to any one of the preceding claims, characterized in that step b) is carried out in air or in an inert atmosphere.

10. Method according to any one of the preceding claims, characterized in that it comprises, subsequently to step b), a storage step and / or a pyrometallurgical and / or hydrometallurgical step.

11. Cutting element (100), for opening an electrochemical generator, having an electrical resistance between ImQ and IkQ, and comprising a support (101) covered with abrasive zones (102) and electrically conductive zones (103), the abrasive zones (102) and the electrically conductive zones (103) being arranged randomly or regularly and being fixed to the support (101) by a binder (104).

12. Element (100) according to the preceding claim, characterized in that it has an electrical resistance of between 5mQ and 100Q.

13. Cutting element according to one of claims 11 and 12, characterized in that the cutting element is a circular saw blade, a saw band, a grinder wheel or a cutting wire.

14. A cutting tool comprising a cutting element according to one of claims 11 to 13, the cutting tool preferably being a grinder or a saw, for example a circular saw or a band saw.

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