Method for opening and discharging an electrochemical generator

Abstract

The invention relates to a method for opening and discharging an electrochemical generator (10) comprising a negative electrode containing lithium or sodium and a positive electrode optionally containing lithium or sodium, the method comprising the following successive steps: - opening the electrochemical generator (10) in a cutting zone, with a cutting element (20), preferably having an electrical resistance greater than 100 mΩ, the electrochemical generator being opened while spraying the cutting zone with a first solution (100), - discharging the electrochemical generator by partially or completely submerging the electrochemical generator (10) in a second solution (200).

Description

[0001] Description

[0002] Title: METHOD FOR OPENING AND DISCHARGING A GENERATOR

[0003] ELECTROCHEMICAL

[0004] TECHNICAL FIELD

[0005] The present invention relates to a method for opening and discharging an electrochemical generator, such as an accumulator, a cell or a battery, making it possible to open the electrochemical generator safely and thus subsequently recycle the recoverable fractions.

[0006] The invention is particularly interesting for the recycling of electrochemical systems, such as accumulators or batteries, treated separately or as a mixture, and in particular for the recycling of Li-lon, Na-lon, or Lithium-metal type batteries and accumulators.

[0007] STATE OF THE PRIOR ART

[0008] An electrochemical generator is an electricity-generating device that converts chemical energy into electrical energy. Examples include batteries or accumulators.

[0009] The market for accumulators, and in particular lithium accumulators, of the Li-ion type, is currently experiencing strong expansion, 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).

[0010] Due to the growth in the number of accumulators in recent years, the question of their recycling has become a major issue.

[0011] Typically, a lithium-ion battery consists of an anode, a cathode, a separator, an electrolyte and a casing.

[0012] Typically, 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- x 02 with O <x<l, LisNiMnCoOe, ou LiFePO / i) mélangé à un liant et déposé sur une feuille d'aluminium.

[0013] The electrolyte is a mixture of non-aqueous solvents and lithium salts, and possibly additives to slow down side reactions.

[0014] The way it works is as follows: during charging, lithium deintercalates from the metal oxide and intercalates into the graphite, where it is thermodynamically unstable. During discharge, the process is reversed and lithium ions are intercalated into the lithium metal oxide.

[0015] As it is used, aging causes a loss of capacity and the accumulator must be recycled.

[0016] Typically, the battery recycling process involves several steps:

[0017] - a pre-treatment stage including a dismantling phase and a safety phase,

[0018] - thermal and / or hydrometallurgical treatments to recover the various recyclable materials and metals contained in these batteries and accumulators.

[0019] However, several situations can complicate recycling:

[0020] - a significant number of accumulators or accumulator batteries to be recycled may still be at least partially charged and their crushing produces sparks and significant ignitions or even explosions, particularly with primary lithium batteries (Li-SOC),

[0021] - the 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.

[0022] Electrochemical systems, at the end of their life and / or damaged, to be recycled must therefore be treated with the greatest care.

[0023] To date, the main problem therefore lies in the safety and opening phase of these lithium-based electrochemical systems (primary and secondary).

[0024] Indeed, when containment is lost, electrolyte leaks, a toxic, flammable and corrosive product, in liquid but also gaseous form. The vapors thus generated and mixed with 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 LiPFe, lithium tetrafluoborate Li BF4, lithium perchlorate UCIO4, lithium hexafluoroarsenate LiAsFe 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.

[0025] To date, the various opening processes are based on steps including, for example, incineration, immersion in liquid nitrogen, immersion of the battery in brine (salt water) or opening under an inert atmosphere.

[0026] However, these processes have many drawbacks. Thermal processes pose major problems in terms of gas emissions, particularly greenhouse gases, and generate gases that are harmful and dangerous to humans and the environment. In addition, the thermal energy required and gas treatment have a significant impact on the economics of the processes.

[0027] Wet grinding processes pose major safety issues related to the hydrogen emitted during battery grinding and generate effluents. These have a significant impact on the economic balance of the processes.

[0028] The continued use of inert gases to open batteries poses major economic and technical challenges. Using an inert gas does not deactivate the battery, but simply controls the gaseous atmosphere during the opening of the waste. An additional step, generally involving an aqueous solution, is necessary to react the lithium and deactivate the system. This necessarily leads to the production of H2, heat, and air, which are safety issues (risk of explosion). Controlling the kinetics to reduce these risks will have a significant impact on the processing rate.

[0029] Finally, the discharge processes carried out in brines do not solve the problems of safety and costs. If the batteries are discharged in brine (salt water), their initial voltage will be higher than the electrolysis voltage of water producing gases such as hydrogen and oxygen. These gases must be ventilated to avoid an explosion (irreversible consumption reactions linked to the electrolysis of water). In addition, this creates a cost problem, on the one hand, by the consumption of a very large quantity of water, and, on the other hand, by the measures necessary to avoid having an explosive atmosphere (ventilation and large volume of water per quantity of waste).

[0030] Thus, recently, it has been proposed to open or discharge these generators in an ionic liquid medium.

[0031] Document EP 3 948 994 A1 describes a method for neutralizing an electrochemical generator. The method comprises a discharge step during which the electrochemical generator is brought into contact with an ionic liquid solution comprising a solvent ionic liquid and a so-called oxidizing redox species capable of being reduced on the negative electrode so as to discharge the electrochemical generator.

[0032] However, such a method cannot be implemented for the treatment of defective batteries / cells with corroded terminals, for example, or for cells with a current interruption device (CID). Indeed, a CID is a mechanical switch, present in the accumulator, allowing access to the battery terminals to be cut off, thus making an electrical or chemical discharge impossible.

[0033] Document EP 3 948 993 A1 describes a method for opening an electrochemical generator by grinding. The method relates to grinding an electrochemical generator in an ionic liquid solution comprising a solvent ionic liquid and a so-called oxidizing redox species capable of being reduced on the negative electrode. The grinding simultaneously allows the electrochemical generator to be discharged.

[0034] Although this process in an ionic liquid medium makes it possible to simultaneously address the safety issues of accumulators and batteries, and environmental constraints, this process requires complete immersion, which imposes constraints on process costs (CAPEX and processing rate). As soon as it is opened, the battery will be reactive, which complicates the process. In addition, pollution of the bath by the battery electrolyte is detrimental to the sustainability of the process and / or its performance.

[0035] CN 110690520 A describes a method for cutting and disassembling a lithium battery module using cutting and disassembling equipment. The lithium battery module is conveyed to a first cutting station and then to a second cutting station, both equipped with cutting devices. When cutting the lithium battery module in these stations, it is necessary to spray, in particular water, on the cutting area and thus achieve cooling and flame retardation. After cutting, the module is moved to a winding extraction station equipped with a winding ejection device. This device will push the winding into a water tank. As the winding is immersed in water for a specified period of time, the residual electricity of the winding will be eliminated and the metallic lithium precipitated on the negative electrode sheet will react with the water during multiple charging and discharging processes.

[0036] STATEMENT OF THE INVENTION

[0037] An aim of the present invention is to propose a method for overcoming the drawbacks of the prior art, and in particular a method for making an electrochemical generator safe, the method having to be easily industrializable. For this, the present invention proposes a method for opening and discharging an electrochemical generator (Li-Ion battery for example) comprising a negative electrode containing lithium or sodium and a positive electrode possibly containing lithium or sodium, the method comprising the following successive steps:

[0038] - opening the electrochemical generator with a cutting element preferably having an electrical resistance greater than 100 mΩ, the opening of the electrochemical generator being carried out by spraying the electrochemical generator, at least at the level of the area to be opened, with a first solution,

[0039] - discharge of the electrochemical generator by immersing (partially or even totally) the electrochemical generator in a second solution.

[0040] The electrochemical generator to be treated may be, in particular, a cell or a module (association of several accumulators), a battery or an accumulator. The invention is particularly interesting for the recycling of lithium-ion type batteries and accumulators. The invention is fundamentally distinguished from the prior art by a two-stage treatment:

[0041] - a first step during which the electrochemical generator is opened with a spray of liquid (or jet of liquid); the first solution prevents or moderates the discharging of the electrochemical generator in order to avoid rapid discharging leading to a risk of ignition or explosion of the object,

[0042] - a second stage, after the first stage, during which the electrochemical generator is immersed in the second solution ensuring the controlled discharge.

[0043] When opening the electrochemical generator, the first solution is applied to the electrochemical generator. At least the part of the generator to be cut is covered by the first solution. The opening can be carried out, for example, by spraying or jet of the first solution.

[0044] This first step allows heat dissipation during opening.

[0045] The electrochemical generator is discharged during the second stage by immersion in the second solution. This facilitates reactivity control. The electrochemical generator is thus deactivated or made safe.

[0046] Advantageously, the first solution is chosen from the following solutions a) to d):

[0047] - solution a) comprising, and preferably consisting of deionized water,

[0048] - solution b) comprising and, preferably, consisting of an ionic liquid,

[0049] - solution c) comprising and, preferably, consisting of a deep eutectic solvent,

[0050] - solution d) comprising and, preferably, consisting of an organic solvent.

[0051] According to a particular embodiment, the first solution is a solution having a resistance greater than 10 Ohms, preferably greater than 100 Ohms. Even more advantageously, the liquid of the first solution will not be ionically conductive. Preferably, the first solution may be, for example, deionized water or an organic solvent. Therefore, the ohmic drop prevents degradation of the solvent and reactivity with the cell. This is particularly favorable for avoiding / reducing degradation for the treatment of electrochemical generators / modules having high voltages (typically greater than 12 V). According to another particular embodiment, the solution used for opening the electrochemical generator allows a partial and controlled discharge of the electrochemical generator. The first solution may be reactive. For example, solutions b) to d) may further comprise an electrochemical shuttle.Solution a) could also include an electrochemical shuttle. Upon opening, the introduction of a reactive species will initiate the discharge of the object. A low-reactivity liquid will be preferred to reduce reactivity during the first phase. According to this particular embodiment, the first solution may be identical to the second solution.

[0052] Preferably, a first solution with low or moderate viscosity is chosen to facilitate subsequent filtration of particles / pieces from the cut. For example, the viscosity of the first solution is between 5 cP and 50 cP.

[0053] Advantageously, the second solution is chosen from the following solutions e) to g):

[0054] - solution e) comprising and, preferably, consisting of an ionic liquid and optionally an electrochemical shuttle,

[0055] - solution f) comprising and, preferably, consisting of a deep eutectic solvent and optionally an electrochemical shuttle,

[0056] - solution g) comprising and, preferably, consisting of an organic solvent and an electrochemical shuttle.

[0057] The electrochemical shuttle can either be initially present in the second solution or added, for example after the electrochemical generator has been brought into contact with the second solution.

[0058] Advantageously, we can choose the first solution and the second solution from the following pairs:

[0059] - solution a) and solution f), i.e. the first solution is deionized water and the second solution comprises a deep eutectic solvent, and possibly, in admixture with an electrochemical shuttle,

[0060] - solution d) and solution f), i.e. the first solution comprises an organic solvent, preferably a glycol solution, for example a polyethylene glycol or a propylene glycol and the second solution comprises a deep eutectic solvent, optionally mixed with an electrochemical shuttle, - solution c) and solution f), i.e. the first solution comprises a first deep eutectic solvent, optionally mixed with an electrochemical shuttle, and the second solution comprises a second deep eutectic solvent, preferably mixed with an electrochemical shuttle.

[0061] According to this last pair, the first deep eutectic solvent and the second deep eutectic solvent can be the same or different.

[0062] Advantageously, the opening and discharge steps are carried out in air.

[0063] Advantageously, the cutting element is a grinder disc or a cutting wire. The first step takes place in an opening zone (or cutting zone) and the second step takes place in a discharge zone. Preferably, the cutting zone is separate from the discharge zone.

[0064] Advantageously, between the opening step and the discharge step the generator is moved from a first opening zone (or cutting zone) to a second discharge zone, the movement preferably being carried out in air.

[0065] For example, after the first stage is implemented, the liquid jet or spray is stopped and then the electrochemical generator is moved into the discharge area.

[0066] Overall, the process has many advantages, including reducing economic and environmental costs for processing objects by implementing two separate steps to open and then discharge the electrochemical generator.

[0067] The separation of the two stages of opening and discharging is particularly advantageous since the opening solution (first solution) is distinct from the discharging solution (second solution). Indeed, pollution of the discharge bath by the battery electrolyte is detrimental. In the case of the invention, the pollution occurs essentially during opening. Thus, the process costs (treatment costs) are reduced because there is limited pollution of the discharge bath, the discharge taking place in a third-party solvent.

[0068] The first step has the following advantages:

[0069] - the implementation of an object opening technology preventing short circuits, - an opening under spraying / jet of liquid allowing the object to be cooled, which is favorable to good heat dissipation within the heating zones, when opening the electrochemical generator,

[0070] - it is very easy to set up a liquid spraying / projection system on the electrochemical generator,

[0071] - the use of a low or moderately viscous opening liquid to facilitate the filtration of pieces / particles from the opening,

[0072] - the use of a low-reactivity liquid for the treated objects, avoids or significantly reduces the discharge reactivity of the objects: this makes it possible to reduce the degradation of the opening liquid, to keep the object under air in a stable state and to move it while minimizing the risks,

[0073] - the use of a liquid that is inexpensive in its nature and formulation, compared to the discharge liquid, which reduces the process costs,

[0074] - pollution by particles and battery electrolyte occurs mainly in the first solution, which reduces the economic impact compared to losses over many treatment cycles (degradation, training).

[0075] The second step has the following advantages:

[0076] - safely discharge the electrochemical generator,

[0077] - the second solution can be used to discharge several electrochemical generators simultaneously or consecutively,

[0078] - implement a discharge step avoiding a violent reaction with water and / or air, which not only avoids problems related to the management of hydrogen, oxygen and heat, and therefore to the management of explosive atmospheres (safety, treatment of influents, additional economic cost), but also avoids using large volumes of water and therefore treating aqueous effluents; the use of an ionic liquid also avoids corrosion of the electrochemical generator,

[0079] - the discharge does not cause damage to objects and does not consume reagents.

[0080] - the discharge being controlled by the nature of the components of the ionic liquid solution, the discharge can be extremely rapid (for example less than 1 h). - not using heat treatment, which avoids problems linked to the emission of gases (for example greenhouse gases or any other gas harmful and dangerous for humans and the environment), in particular concerning their treatment, and reduces the financial and energy costs of the process,

[0081] - the safety of the electrochemical generator is simple to implement.

[0082] Other characteristics and advantages of the invention will emerge from the additional description which follows.

[0083] 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.

[0084] BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The present invention will be better understood by reading the description of exemplary embodiments given purely for informational purposes and in no way limiting, with reference to the appended drawings in which:

[0086] - Figure 1 represents, schematically and in section, the diagram of an installation for implementing the method, according to a particular embodiment of the invention,

[0087] - Figure 2 is a graph representing a monitoring curve of the voltage and temperature of a generator before implementing the method, after opening and after discharging the generator according to a particular embodiment of the invention,

[0088] - Figure 3 is a graph showing a voltage and temperature tracking curve for a process with both cutting and immersion discharge in the discharge liquid,

[0089] - Figure 4 is a graph representing a voltage and temperature monitoring curve for a process with cutting under spraying of reactive liquid (first solution) then waiting under air, and finally discharge by immersion in reactive liquid (second solution), according to a particular embodiment of the invention.

[0090] The different parts represented in the figures are not necessarily on a uniform scale, to make the figures more readable. The different possibilities (variants and embodiments) must be understood as not being mutually exclusive and can be combined with each other.

[0091] Furthermore, in the following description, terms that depend on the orientation, such as "above", "below", etc. of a structure apply with the assumption that the structure is oriented as illustrated in the figures.

[0092] DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0093] Electrochemical generator

[0094] Subsequently, the electrochemical generator is, for example, an accumulator, batteries or 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, to a battery module, or even to an electric battery. In particular, it can be a Li-lon accumulator.

[0095] The opening and discharge process concerns all electrochemical systems of the accumulator or battery type treated separately or in mixture.

[0096] These different electrochemical devices can be of the metal-ion type, for example lithium-ion or sodium-ion, or of the Li-metal type,...

[0097] It can also be a primary system such as Li / MnO2, or a circulation battery (“Redox Flow Battery”).

[0098] It is advantageous to choose an electrochemical generator with a potential greater than 1.5V.

[0099] The generator may comprise several electrochemical cells, each cell comprising a first electrode, here the anode, and a second electrode, here the cathode, a separator and an electrolyte. According to another embodiment, the first electrode and the second electrode could be reversed.

[0100] The anode (negative electrode) is preferably carbon-based, for example, graphite that can be mixed with a PVDF binder and deposited on a copper foil. It can also be a mixed lithium oxide such as lithium titanate Li / fFisO^ (LTO) for a Li-ion battery or a mixed sodium oxide such as sodium titanate for a Na-ion battery. It could also be a lithium alloy or a sodium alloy depending on the technology chosen.

[0101] The cathode (positive electrode) is a material for inserting lithium ions for a Li-ion battery. It can be a lamellar oxide of the LiMO2 type, a LiMPO4 phosphate with an olivine structure or a spinel compound LiMn2O4, with M representing a transition metal. For example, a positive electrode made of LiCoO2, LiMnO2, LiNiO2, LisNiMnCoOe, LiNi x Coi- x O2 (with 0 <x<l) ou LiFePO4.

[0102] The cathode (positive electrode) is a sodium ion insertion material for a Na-ion battery. It may be a sodium oxide type material comprising at least one transition metal element, a sodium phosphate or sulfate type material comprising at least one transition metal element, a sodium fluoride type material, or a sulfide type material comprising at least one transition metal element.

[0103] The insert material can be mixed with a polyvinylidene fluoride binder and deposited on an aluminum foil.

[0104] The electrolyte comprises lithium salts (e.g., LiPFe, LiBF4, LiClO4) or sodium salts (e.g., NsNa), depending on the battery technology chosen, dissolved in a mixture of non-aqueous solvents. The mixture of solvents is, for example, a binary or ternary mixture. The solvents are, for example, chosen from solvents based on cyclic carbonates (ethylene carbonate, propylene carbonate, butylene carbonate), linear or branched (dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dimethoxyethane) in various proportions.

[0105] Alternatively, it could also be a polymer electrolyte comprising a polymer matrix, made of organic and / or inorganic material, a liquid mixture comprising one or more metal salts, and possibly a mechanical reinforcing material. The polymer matrix may comprise one or more polymer materials, for example chosen from polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), or a poly(ionic liquid) of the poly(N-vinylimidazolium) bis(trifluoromethanesulfonylamide)), N, N-diethyl- N-(2-methoxyethyl)- N-methylammonium bis(trifluoromethylsulfonyl)imide (DEMM-TFSI) type. The cell may be wound on itself around a winding axis or have a stacked architecture.

[0106] A casing, for example a polymer pouch, or a metal packaging, for example steel, ensures the battery is watertight.

[0107] Each electrode is connected to a current collector passing through the housing and forming, outside the housing, the terminals (also called output terminals or electrical poles or terminals). The function of the collectors is twofold: to provide mechanical support for the active material and electrical conduction to the cell terminals. The terminals (also called electrical poles or terminals) form the output terminals and are intended to be connected to an "energy receiver".

[0108] Method of opening and discharging the electrochemical generator

[0109] As shown in Figure 1, the process of opening and discharging the electrochemical generator includes the following steps:

[0110] - opening the electrochemical generator 10, with a cutting element 20, the opening of the electrochemical generator being carried out by spraying the electrochemical generator with a first solution 100, at the level of the part of the electrochemical generator 10 to be opened,

[0111] - discharging the electrochemical generator by partially or even totally immersing the electrochemical generator in a second solution 200.

[0112] First stage (opening stage)

[0113] In the first step, the electrochemical generator 10 is opened, at least partially, or even completely. This operation makes the interior of the electrochemical generator accessible.

[0114] Opening means at least access to the electrodes in order to be able to discharge the electrochemical generator during the second stage. For example, this involves opening the housing to gain access to the electrodes.

[0115] The cutting operation, carried out in the presence of an 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 inert liquid promotes cooling of the environment and allows the evacuation of calories during the discharge process.

[0116] The inert liquid is sprayed onto the part to be cut, for example using a device 30 for spraying or sending a jet or spray of first solution 100 onto the electrochemical generator 100. The flow rate is, for example, between 25 L / min and 50 L / min.

[0117] This first step can be carried out above a grid or sieve 40 to filter the first solution after cutting the electrochemical generator 10 and thus separate the particles / pieces resulting from the cutting from the first solution 100 which can thus be reused.

[0118] The inert liquid helps maintain a controlled atmosphere (air, water) and acts as a cutting fluid (lubrication and cooling of the cutting area).

[0119] Advantageously, this first step avoids or significantly limits a discharge phenomenon after opening the object. Opening under spray / liquid jet controls heat dissipation during opening.

[0120] The first step 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). It is preferably carried out at atmospheric pressure (i.e. 1 bar or 101,325 Pa).

[0121] For added safety, the first step can be carried out under an inert atmosphere, for example under argon, carbon dioxide, nitrogen or a mixture thereof.

[0122] For example, the opening step can be associated with a gas atmosphere control system (inert atmosphere or correctly sized extraction system) allowing the oxygen content to be controlled. Thus, the whole thing is safe (with respect to the fire triangle) and allows the opening of batteries and accumulators while managing the gas production induced by the opening of the cells.

[0123] Preferably, the first step is carried out in air.

[0124] Advantageously, at the end of the opening step, the electrochemical generator 10 is stopped being sprayed with the first solution 100. The first step is carried out at a first zone called the cutting zone or opening zone (zone ZI in FIG. 1).

[0125] The discharge step (second step) is carried out at a second zone called the discharge zone (zone Z2 in Figure 1).

[0126] Between the opening step and the discharging step, an intermediate step is carried out during which the electrochemical generator is moved from the first zone Z1 to the second zone Z2. For example, this may involve moving the electrochemical generator from the zone Z1 containing the spraying means 30 to a tank 50. This intermediate step is preferably carried out in air.

[0127] Second stage (discharge stage)

[0128] The discharge step consists of partially or preferably completely discharging the electrochemical generator by immersion. This leads to the deactivation or safety of the object.

[0129] As mentioned previously, this second step is preferably carried out in a discharge area (zone 2 in Figure 1).

[0130] The second step is preferably carried out in air. It is also advantageously carried out at atmospheric pressure.

[0131] In this second step, the generator 10 is partially or completely immersed in the second solution. Discharge by immersion in a liquid causes chemical reactions.

[0132] The discharge is carried out in a device 50 containing the second solution 200. For example, it is carried out in a tank.

[0133] Advantageously, the thermal energy absorbed during the resistive discharge process can be recovered with a heat exchanger. Thus, it will be possible to operate a continuous process of discharge and energy recovery by continuous circulation between the discharge reactor and the heat exchanger. Advantageously, the temperature of the bath in which the accumulator is immersed does not exceed 60 °C, to avoid internal degradation reactions of the battery electrolyte. The method makes it possible to avoid a runaway process leading to degradation and / or explosion. Cutting element for implementing the opening step

[0134] The opening is made by a cutting element 20 (which can also be called a cutting tool or cutting tool) which is not electrically conductive. The cutting element 20 is sufficiently resistive to avoid a direct short circuit leading to the explosion of the cell. In other words, the cutting element 20 has very low electrical conductivity.

[0135] In particular, we will choose a tool having, for example, a resistance typically greater than 100 mQ, for example from 100 mQ to 1 kQ.

[0136] 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.

[0137] 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 resistance. Resistance can be measured with a multimeter by placing a sample between two identical conductive plates.

[0138] The technologies to be favored are those which avoid excessive deformation (crushing, spreading of materials over neighboring materials, etc.) which would lead to a frank and uncontrolled short circuit leading to thermal runaway and explosion of the cells.

[0139] A cutting tool is a tool that can grind, but preferably cut the material in order to completely or partially open the object in the presence of a liquid to cool the area subjected to mechanical heating.

[0140] The electrically non-conductive penetrating tool, which may be, but is not limited to: a guillotine-type tool (blades), a saw (circular, band), a wire, a tool for ultrasonic cutting, drilling, or abrasion with a jet of liquid (including non-conductive abrasive particles). It may also be non-conductive, cutting-off or micro-cutting knives. Advantageously, the cutting element is a cutting wire, a grinder wheel, a circular saw blade (also called a disc) or a saw band.

[0141] The operation is carried out in the presence of the first solution 100 which prevents heating and ignition of a reaction with the organic electrolyte of the accumulator and the air which could lead to flames or an explosion.

[0142] The cutting element 20 comprises a base support providing the mechanical properties to the cutting element.

[0143] The base support may be electrically conductive or electrically insulating. The base support may be metallic, resinoid, or rubber-like.

[0144] The base support is covered with abrasive areas. The abrasive areas have a hardness adapted to the object and the material to be treated.

[0145] Abrasive areas are, for example, made of sandstone, emery, diamond, silicon carbide and / or alumina.

[0146] Preferably, the abrasive zones are formed from abrasive grains.

[0147] Preferably, the base support is covered by abrasive zones and electrically conductive zones. The abrasive zones impart mechanical properties to the tool and electrically conductive zones impart electrical properties to the tool.

[0148] Electrically conductive areas are, for example, formed by electrically conductive grains.

[0149] Electrically conductive areas are, for example, made of a metal or metal alloy. For example, it can be copper, iron, steel and / or aluminum, more broadly an electrical conductor.

[0150] Electrically conductive areas can be formed from metal grains or metal wires.

[0151] The abrasive grains and / or electrically conductive grains are preferably particles having a dimension ranging, for example, from a few micrometers to a few centimeters. The abrasive grains and / or electrically conductive grains are advantageously mechanically held to the support by a binder. The binder may be a resin, rubber, silicate, clay, or even a ceramic.

[0152] The abrasive areas and / or electrically conductive areas may be distributed regularly or randomly on the support.

[0153] Abrasive areas and / or electrically conductive areas may be continuous or discontinuous.

[0154] According to a first embodiment, the electrochemical generator is opened by abrasion using a wire. The wire comprises a solid base, in the form of a wire, providing the mechanical properties. The abrasive properties are provided by the addition of abrasive grains of a hardness adapted to the object and the material to be treated.

[0155] According to a second embodiment, the opening of the electrochemical generator is carried out by abrasion using a grinder. The grinder disc comprises a circular base support. The support comprises a first main face and a second main face parallel to each other as well as a lateral face (also called a slice) connecting the two main faces.

[0156] The support may be metallic, resinoid or rubber type. The support is advantageously covered by electrically insulating abrasive zones and by electrically conductive zones.

[0157] Different configurations can be envisaged in the case of a grinding wheel comprising abrasive zones (preferably abrasive grains) and electrically conductive zones (preferably electrically conductive wires or grains).

[0158] For example, abrasive areas and electrically conductive areas are distributed randomly.

[0159] Abrasive areas and electrically conductive areas can be distributed in a controlled manner.

[0160] According to one embodiment, the abrasive zones and the electrically conductive zones are arranged in a controlled manner in order to form an alternation of abrasive zones and non-abrasive zones. According to another embodiment, the conductive zones can be distributed concentrically relative to the center of the grinding wheel disc.

[0161] According to another embodiment, the conductive zones can be arranged along one or more radii or along one or more diameters, randomly or not.

[0162] According to another embodiment, the conductive zones can be arranged only on the perimeter of the grinding wheel disc.

[0163] According to another embodiment variant, not shown, the electrically conductive zones are arranged on the edge of the grinding wheel disc.

[0164] The alternation of abrasive zones and conductive zones can be obtained using coatings produced using thin-film deposition techniques, for example, physical vapor deposition (PVD), atomic layer deposition (ALD), chemical vapor deposition (CVD), spin-coating or even coating techniques such as dip-coating.

[0165] The appropriate 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).

[0166] Electrical resistances can also be modulated via the cutting fluid and operating conditions (temperature, fluid viscosity, abrasion speed, fluid renewal, etc.).

[0167] First solution 100

[0168] The first solution 100 promotes the cooling of the electrochemical generator 10 and allows the heat to be evacuated during the opening process. To do this, the first solution 100 may optionally be cooled. The first solution may be sprayed / injected onto the opening area and / or several areas of the electrochemical generator 10. It may be sprayed / injected so as to completely cover the electrochemical generator 10.

[0169] According to a first embodiment, the first solution is a liquid that can be reactive. The introduction of a reactive species will initiate the discharge of the object during opening. In the particular case where the solution used for opening the electrochemical generator is also the solution used to discharge the electrochemical generator, a low-reactive liquid will be preferred to reduce reactivity during the first phase.

[0170] In a second embodiment, the function of the first solution is to avoid discharge to stabilize the object. The first solution advantageously has a resistance greater than 10 Ohms, preferably greater than 100 ohms and even more advantageously the first solution is not ionically conductive (this is the case for pure water and many organic solvents which do not have ions initially in solution). Therefore, the ohmic drop prevents degradation of the solvent and reactivity with the electrochemical generator 10. This is particularly favorable for avoiding / reducing degradation for the treatment of the electrochemical generator 10 with high voltages (typically greater than 12 V).

[0171] The nature of the liquid is defined to limit the discharge of the accumulators, so as to control the reactivity of the accumulators. The absence or very low reactivity ensures the control of the object which facilitates its movement under the atmosphere and the time to move it safely. The opening liquid is by nature less complex (nature of the constituents), and less expensive, so that its pollution inherent in the opening of batteries (leakage of the electrolyte of the batteries into the liquid) is less impactful for the process. Preferably, the first solution is biodegradable, cheap and / or has low volatility. Preferably, it does not generate pollution for the second solution.

[0172] Preferably, the liquid used will be low viscosity to facilitate the filtration of fines / opening particles.

[0173] Preferably, the first solution 100 is chosen from the following solutions:

[0174] - solution comprising deionized water, - solution comprising an ionic liquid,

[0175] - solution comprising a deep eutectic solvent,

[0176] - solution comprising an organic solvent.

[0177] Ionic liquid is understood to mean the association comprising at least one cation and one anion which generates a liquid with a melting temperature lower than or close to 100°C.

[0178] A deep eutectic solvent (DES) is distinguished from an ionic liquid. The term DES is used for media that differ from ionic liquid media. Deep eutectic solvents are formed by mixing two or more compounds in an exact proportion that corresponds to the eutectic point. The melting point is considerably lower than the melting point of each component and allows the mixture to be liquid at room temperature. Most of these solvents are liquid at room temperature, which makes them easy to use. The synthesis of DES is easy and clean compared to that of ionic liquids, which require several chemical synthesis and purification steps. It involves simply mixing the DES components in the correct proportions with heating until a homogeneous and transparent liquid is obtained.These components are a pair of a hydrogen bond donor and a hydrogen bond acceptor.

[0179] These eutectics have the general formula [Cat]+ .[X]- .z[Y], where [Cat]+ is the cation (usually ammonium), [X]- the halide anion (usually Cl- ), [Y] a Lewis or Brônsted acid which can be complexed by the anion X- and z the number of Y molecules. These types of eutectics are subdivided into three categories depending on the nature of Y, such as:

[0180] Eutectic type 1: Y = MCIx with for example M = Fe, Zn, Sn, Fe, Al, Ga

[0181] Eutectic type 2: Y = MCIx.yFbO with for example M = Cr, Co, Cu, Ni, Fe

[0182] Eutectic type 3: Y= RZ with R corresponding to a carbon chain and with Z a chemical function such as CONH2, COOH, OH

[0183] Regarding the solvent, we can favor the use of bio-sourced solvents (methyl esters, N,N-dimethyldecanamide, N,N-dimethyldec-9-enamide, etc.), the use of acetate (hexyl acetate, butyl acetate, etc.). These examples are not exhaustive. Water can also be used. Low ionic conduction will be favored to avoid the formation of hydrogen and oxygen.

[0184] For example, when the second solution 200 comprises a deep eutectic solvent, the first solution 100 may comprise a constituent of the DES. More generally, the liquid component of the DES which composes it and which is the hydrogen bond donor will be chosen. This must imperatively be a liquid. Preferably, it is a liquid with low viscosity and little or no conductivity.

[0185] By way of illustration, when the second solution comprises an ethaline-based DES, the first solution advantageously comprises ethylene glycol.

[0186] Ethylene glycol (EG) is a liquid, non-ionically conductive component with low vapor pressure and very low viscosity that is a constituent of Ethaline. Alternatively, propylene glycol could be used.

[0187] The first solution may consist of the liquid phase (water, solvent, ionic liquid, deep eutectic solvent). The first solution 100 may further comprise an electrochemical shuttle.

[0188] The electrochemical shuttle, also called redox mediator or redox couple, is an oxidant / reducer couple (Ox / Red) in solution in which the oxidant can be reduced on the anode (negative electrode) and the reductant can be oxidized on the cathode (positive electrode). The oxidation of the reductant 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 (or discharge if used during the second step) several electrochemical generators.

[0189] 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 the safety of the electrochemical generator by reducing the chemical energy of the electrodes (and therefore the potential difference) and by reducing the internal short-circuit effect. Advantageously, the redox species couple is a metallic couple, preferably chosen from Mn 2+ / Mn 3+ , Co 2+ / Co 3+ , Cr 2+ / Cr 3+ , Cr 3+ / Cr 6+ , V 2+ / V 3+ , V 4+ / V 5+ , Sn 2+ / Sn 4+ , Ag + / Ag 2+ , Cu + / Cu 2+ , Ru 4+ / Ru 8+ or Fe 2+ / Fe 3+ , a pair of organic molecules, a pair of metallocenes such as Fc / Fc +, or a pair of halogenated molecules such as Cl2 / C|- or CI / CI3-.

[0190] For example, we will use iron chloride.

[0191] Advantageously, the first solution consists of the liquid phase mixed with the electrochemical shuttle.

[0192] Second solution 200

[0193] The second solution 200 is a liquid allowing a chemical discharge of the electrochemical generator by immersion. In a particular case, the second solution 200 has the same composition as the first solution 100.

[0194] Discharge liquid means a bath comprising a liquid composed of ions (ionic liquid solution, DES solution, organic solution) and species which ensure the discharge of objects (batteries / accumulators) in synergy with at least one component of the bath, these species playing the role of an electrochemical shuttle. Thus there is discharge of the electrochemical generator 10 and safety / deactivation.

[0195] There will therefore be the presence of at least one liquid composed of ions which we will call ionic solvent which ensures the ionic conductivity of the ions.

[0196] The second solution is preferably chosen from one of the following solutions:

[0197] - solution comprising an ionic liquid and possibly an electrochemical shuttle,

[0198] - solution comprising a deep eutectic solvent and possibly an electrochemical shuttle,

[0199] - solution comprising an organic solvent and an electrochemical shuttle.

[0200] Ionic liquid is a solvent ionic liquid, that is to say an ionic liquid which is thermally and electrochemically stable minimizing a degradation effect of the medium during the discharge phenomenon.

[0201] A mixture of ionic liquids could be used. The additional ionic liquid promotes one or more properties with respect to the safety and discharge step. For the solvent ionic liquid Lli and for the additional ionic liquid Lh the cation is chosen from the family: imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium, preferably a cation with a large cationic window, large enough to envisage a cathodic reaction (i.e. having a large stability window) avoiding or minimizing the degradation of the ionic liquid. When the mixing and association conditions between Lli and LI2 are respected (in terms of anion nature and concentration). Advantageously Lli and LI2 will have the same cation to increase the solubility of LI2 in Lli.

[0202] Other associations are possible, with ionic liquids (Ll 1) whose cation will be associated with an anion which will be indifferently organic or inorganic, preferably having a wide anodic window.

[0203] Advantageously, anions will be used which make it possible to simultaneously obtain a moderate viscosity, a low melting temperature (liquid at room temperature) and good solubility with the ionic liquid and the other species in the solution, and this does not lead to hydrolysis (degradation) of the ionic liquid.

[0204] More advantageously, the mixture Ll 1 and LI2 will be liquid at room temperature.

[0205] The TFSI anion is an example that meets the previously mentioned criteria for many associations with e.g. Ll 1: [BMIM][TFSI], or the use of an ionic liquid of type [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(trifluoromethylsufonyl)imide ([PYR14][TFSI]), the ionic liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI). The anion can also be of the bis(fluorosulfonyl)imide (FSA or FSI) type, such as the ionic liquid N-methyl-N-propylpyrrolidinium FSI (P13-FSI), N-methyl-N-propylpiperidinium FSI (PP13-FSI), 1-ethyl-3-methylimidazolium FSI (EMI-FSI), etc.

[0206] Preferably, the second solution includes a DES which is a low-cost, non-toxic medium with low environmental impact (biodegradability). Toxicity and biodegradability are linked to those of their components. According to the general formula of DES previously presented, we will preferentially seek that "Y" also has an electrochemical shuttle role (e.g. with iron and the Fe couple 2+ / Fe 3+). A eutectic can be formed between an ionic liquid with chloride anion and FeCh and FeCls metal salts for different proportions and with different cations. This type of reaction can also be carried out with type II eutectics which integrate water molecules into the metal salts when the proportion of water is low. Type III eutectics can also be used which associate the ionic liquid and hydrogen bond donor species (Y), with a mixture of type [Lli] / [Y] where Lli can be a quaternary ammonium and Y a complexing molecule (hydrogen bond donor) such as urea, ethylene glycol, thiourea, etc.

[0207] DES can advantageously be choline chloride used with a very low toxicity H-bond donor such as glycerol or urea, which ensures a non-toxic and very low cost DES.

[0208] For example, choline chloride can be replaced by betaine. These systems have a limited electrochemical stability window, but will ensure flooding and deactivation of an open battery.

[0209] The shuttle will initially be present in the second solution 200 or added later in the second solution 200.

[0210] The electrochemical shuttle can be used to secure several electrochemical generators successively and / or in a mixture.

[0211] The redox species allow the electrochemical generator to be significantly or even completely discharged.

[0212] Advantageously, the redox species pair is one of the aforementioned pairs for the first solution 100.

[0213] For example, we will use iron chloride.

[0214] The second solution 200 can be stirred.

[0215] The first solution 100 and / or the second solution 200 may further comprise one or more active species. The active species are, for example, chosen from an extinguishing agent, a flame retardant intended to prevent thermal runaway, an agent which secures the accumulator (electrochemical shuttle or redox mediator), a salt, viscosity, solubility, hydrophobicity, conductivity stabilizer.

[0216] The extinguishing agent and / or flame retardant may be an alkyl phosphate such as: trimethyl phosphate or a triethyl phosphate, it may be fluorinated such as a fluorinated alkyl phosphate (such as tris(2,2,2-trifluoroethyl) phosphate). The concentration may be from 80% by mass to 5% with advantageously a concentration between 30% and 10% by mass. Among the choices of first solution and second solution, preferably:

[0217] - the first solution is formed from a solvent and the second solution is a DES mixed with an electrochemical shuttle, or

[0218] - the first solution is formed DES in mixture with an electrochemical shuttle and the second solution is a DES in mixture with an electrochemical shuttle; the first solution and the second solution being advantageously identical.

[0219] Even more preferentially:

[0220] - the first solution is a glycol, for example ethylene glycol or propylene glycol, and the second solution is a mixture of a DES (preferably a choline chloride / ethylene glycol or a choline chloride / betaine) and an electrochemical shuttle, or

[0221] - the first solution is a mixture of a DES (preferably a choline chloride / ethylene glycol or a choline chloride / betaine) and an electrochemical shuttle and the second solution is a mixture of a DES (preferably a choline chloride / ethylene glycol or a choline chloride / betaine) and an electrochemical shuttle; the first solution and the second solution may be identical.

[0222] The method, the subject of the present invention, allows the discharge of objects before recycling by pyrometallurgical, hydrometallurgical means or one of their combinations. Sorting and dismantling steps can take place beforehand. For example, the present invention can be implemented in a method for recycling an electrochemical generator comprising the following steps:

[0223] 1- Sorting

[0224] 2- Dismantling 3- Implementation of the present invention

[0225] 4- Recycling by conventional means (pyrometallurgy, hydrometallurgy, etc.)

[0226] Illustrative and non-limiting examples of an embodiment

[0227] Example 1: Opening a cell in an ethylene glycol medium and discharging it in a choline chloride / ethylene glycol medium

[0228] A prismatic Li-ion cell of NMC chemistry with a nominal capacity of 63 Ah is charged to 100%. The cell, under uncontrolled atmosphere (ambient air), is subjected to a grinding type cutting which is carried out using a resinoid grinding wheel containing an abrasive (AI2O3). The cutting fluid (or first solution 100) is ethylene glycol (EG). This liquid is non-conductive and has a viscosity of 18 cP. The EG fluid is sprayed onto the cutting area with a flow rate of 10 L / min. The opening action by the grinding wheel creates a notch of approximately 5 cm 2for a thickness of 500 pm. The cutting operation is carried out over a period of 4 minutes, then the cutting is stopped as well as the jet / spraying of liquid.

[0229] Figure 2 shows that the cell voltage remains perfectly constant during the cutting phase under the ethylene glycol jet, but also after the cutting phase and the stopping of the EG jet (noted post-cutting in Figure 2). The treatment time was deliberately extended to 1 hour to highlight the stability of the cell under air over a very long period.

[0230] At the same time, the measurement of the cell temperature confirms the absence of heating and reactivity of the cell.

[0231] After 1 h, the cell is immersed in a second solution 200 formed by a mixture of choline chloride and ethylene glycol in a molar ratio of 1:3 with the addition of an electrochemical shuttle of the iron chloride type. The viscosity of the mixture is approximately 40 cP. The entire process is carried out at ambient temperature and atmosphere without recirculation or thermalization of the fluid (degraded conditions). The discharge then takes place within the discharge fluid and until a state of charge of 0% is reached.

[0232] This technique not only allows the cell to be opened without generating an explosion, but also stabilizes the cell under atmospheric conditions for its movement, also in air. Then, it is possible to discharge the cell using a discharge fluid.

[0233] In comparison, a test is carried out by cutting a cell under full immersion in the discharge liquid (mixture of choline chloride and ethylene glycol in a molar ratio of 1:3 with the addition of an electrochemical shuttle of the iron chloride type). Figure 3 shows the evolution of the voltage and temperature. A decrease in voltage and an increase in the temperature of the lithium-ion battery are observed.

[0234] Example 2: Opening a module in a choline chloride and ethylene glycol environment and also discharging in a choline chloride and ethylene glycol environment

[0235] A NMC chemistry Li-ion module has a module capacity of 125 Ah, a module voltage of 16.6 V and each cell of the module is charged to 100% (initially at 3.7 V). The module is under uncontrolled atmosphere (ambient air) and is subjected to grinding type cutting carried out using a resinoid wheel containing AI2O3 abrasive. The cutting fluid (first solution 100) is a mixture of choline chloride and ethylene glycol in a molar ratio of 1:3 with the addition of an electrochemical shuttle of iron chloride type. The fluid is sprayed on the cutting area with a flow rate of 10 L / min. The opening action by the wheel creates a notch of approximately 5 cm 2 for a thickness of 500 pm. The cutting operation is carried out over a period of 5 minutes, then the cutting is stopped as well as the liquid spraying.

[0236] Figure 4 shows that the module voltage gradually decreases during the cutting phase and the stopping of the jet (denoted waiting phase in air). The stopping phase was deliberately extended to 15 minutes to highlight the evolution of the temperature in air over a significant period. The measurement of the module temperature indicates a sufficiently low heating to allow treatment without explosion or ignition, after stopping the spraying of discharge liquid, with an ambient atmosphere (in air).

[0237] After 15 minutes in air, the module is immersed in a second 200 solution formed by a mixture of choline chloride and ethylene glycol in a molar ratio of 1:3 with the addition of an electrochemical shuttle of the iron chloride type. The viscosity of the mixture is approximately 40 cP. The entire process is carried out at ambient temperature and atmosphere without recirculation or thermalization of the fluid (degraded conditions). The discharge then takes place within the discharge fluid until a state of charge of 0% is reached on each cell of the module (voltage per cell lower than IV). This technique not only allows the cell to be opened without generating an explosion but also to stabilize the cell under atmospheric conditions for its movement in air. Then, it is possible to discharge the cell by using a discharge fluid.

Claims

CLAIMS 1. Method for opening and discharging an electrochemical generator (10) comprising a negative electrode containing lithium or sodium and a positive electrode optionally containing lithium or sodium, the method comprising the following successive steps: - opening the electrochemical generator (10) with a cutting element (20), preferably having an electrical resistance greater than 100 mΩ, the opening of the electrochemical generator being carried out by spraying the electrochemical generator (10) with a first solution (100), and - discharging the electrochemical generator by immersing the electrochemical generator in a second solution (200) and, in which: - the first solution (100) is chosen from one of the following solutions a) to d): a) deionized water solution, b) solution comprising an ionic liquid, c) solution comprising a deep eutectic solvent, and d) solution comprising an organic solvent; and - the second solution (200) is chosen from one of the following solutions e) to g): e) solution comprising an ionic liquid and optionally an electrochemical shuttle, f) solution comprising a deep eutectic solvent and optionally an electrochemical shuttle, and g) solution comprising an organic solvent and an electrochemical shuttle.

2. Method according to claim 1, characterized in that the first solution (100) further comprises an electrochemical shuttle.

3. Method according to claim 1 or 2, characterized in that the second solution (200) is identical to the first solution (100).

4. Method according to claim 1 or 2, characterized in that the first solution (100) comprises water and in that the second solution (200) comprises a deep eutectic solvent and optionally an electrochemical shuttle.

5. Method according to claim 1 or 2, characterized in that the first solution (100) comprises an organic solvent, preferably a glycol solution, for example a polyethylene glycol or a propylene glycol, and in that the second solution (200) comprises a deep eutectic solvent, preferably in admixture with an electrochemical shuttle.

6. Method according to claim 1 or 2, characterized in that the first solution (100) comprises a first deep eutectic solvent, optionally mixed with an electrochemical shuttle, and in that the second solution (200) comprises a second deep eutectic solvent, preferably mixed with an electrochemical shuttle, the first eutectic solvent possibly being identical to or different from the second eutectic solvent.

7. Method according to any one of the preceding claims, characterized in that the steps of the method are carried out in air.

8. Method according to any one of the preceding claims, characterized in that the cutting element (20) is a grinder disc or a cutting wire.

9. Method according to any one of the preceding claims, characterized in that, between the opening step and the discharging step, the generator is moved from a first opening zone to a second discharging zone, the movement preferably being carried out in air.

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