Method for opening and discharging 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 optionally a positive electrode containing lithium or sodium, comprising the following consecutive steps: opening the electrochemical generator (10) in a cutting region with a cutting element (20), preferably having an electrical resistance greater than 100 m Omega, opening of the electrochemical generator is carried out while spraying the cutting region with the first solution (100),-discharging the electrochemical generator by partially or even completely immersing the electrochemical generator (10) in a second solution (200).

Description

Technical Field

[0001] The invention relates to a method for opening and discharging an electrochemical generator, such as an accumulator, a cell or a battery, which method allows safe opening of the electrochemical generator and thus subsequent recovery of recoverable fractions.

[0002] The invention is particularly suitable for the recycling of electrochemical systems of the accumulator or battery type, processed alone or as a mixture, and in particular for the recycling of batteries and accumulators of the lithium-ion, sodium-ion or lithium metal type. Background Art

[0003] An electrochemical generator is a device for generating electricity that converts chemical energy into electrical energy. For example, it can be composed of a chip or a battery.

[0004] The market for lithium-ion type batteries, in particular lithium batteries, is currently expanding rapidly, on the one hand due to so-called mobile applications (smartphones, computers, cameras, etc.) and, on the other hand, due to new applications related to mobility (electric vehicles and hybrid vehicles) and so-called stationary applications (which are connected to the power grid).

[0005] Due to the increase in the number of storage batteries in recent years, the problem of recycling them has become a major issue.

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

[0007] Typically, the anode is formed of graphite mixed with a PVDF-type binder deposited on a thin copper sheet, and the cathode is a metallic lithium insertion material (e.g., LiCoO) mixed with a binder and deposited on a thin aluminum sheet. 2 、LiMnO 2 、LiNiO 2 、LiNixCo 1- x O 2 (where 0 <x<1)、Li 3 NiMnCoO 6 or LiFePO 4 ).

[0008] The electrolyte is a mixture of a non-aqueous solvent and a lithium salt and optionally additives to slow down secondary reactions.

[0009] Here's how it works: During charging, lithium is extracted from the metal oxide and intercalated into graphite, where it is thermodynamically unstable. During discharge, the process is reversed and the lithium ions are intercalated into the lithium metal oxide.

[0010] With use, aging causes a loss of capacity and the batteries must be recycled.

[0011] Conventionally, the battery recycling method includes the following steps:

[0012] - including pre-processing steps for the disassembly phase and the safety phase,

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

[0014] However, there are several situations that complicate recycling:

[0015] - A large number of batteries or battery cells to be recycled can still be at least partially charged and grinding them can produce sparks and serious fires or even explosions, especially for primary lithium batteries (Li-SOCl 2 ),

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

[0017] Therefore, at the end of their useful life and / or when damaged, electrochemical systems must be handled very carefully to be recycled.

[0018] The main problems currently therefore exist at the stage of making these electrochemical systems containing lithium (primary and secondary) safe and at the stage of opening them.

[0019] In fact, during the loss of the seal, there is a leakage of the electrolyte, which is a toxic, flammable and corrosive product, both in liquid and gaseous form. Vapors are generated from this and, mixed with air, can then form an explosive atmosphere (ATEX). The latter can ignite on contact with a spark-type ignition source or a hot surface. This then leads to an explosion, causing thermal and pressure effects. In addition, electrolyte salts, such as lithium hexafluorophosphate LiPF 6 、Lithium tetrafluoroborate LiBF 4 、Lithium Perchlorate LiClO 4 、Lithium hexafluoroarsenate LiAsF 6 , particularly toxic and corrosive fumes containing phosphorus, fluorine and / or lithium may be released. For example, hydrofluoric acid (HF) may be formed during thermal degradation of lithium-ion batteries.

[0020] Currently, various opening methods are based on steps including, for example, incineration, immersion in liquid nitrogen, immersion of the cells in brine (salt water) or opening under an inert atmosphere.

[0021] However, these methods have a great many disadvantages. Therefore, thermal methods cause major problems of gas (especially greenhouse gas) emissions and produce gases that are harmful and dangerous to humans and the environment. In addition, the required heat energy and gas treatment greatly affect the economic balance of these methods.

[0022] Wet grinding methods pose major safety issues related to the hydrogen emitted during cell grinding and produce waste liquids. The latter greatly affects the economic balance of the process.

[0023] The continued use of inert gases to open the battery presents significant economic and technical problems. The use of inert gases does not deactivate the battery, but only controls the gaseous atmosphere during the opening of the waste. A supplementary step (usually an aqueous solution) is required to react the lithium and deactivate the system. This necessarily results in the generation of H 2 , heat and air, which are problematic for safety (explosion risk). Controlling the dynamics to reduce these risks has a very large impact on the process rate.

[0024] Finally, the method of discharge in brine does not solve the safety and cost problems. If the cells are discharged in brine (salt water), their initial voltage will be higher than the electrolysis voltage of water, so that gases such as hydrogen and oxygen are produced. These gases must be vented to prevent explosions (irreversible consumption reactions associated with the electrolysis of water). Moreover, this creates cost problems due to the consumption of very large amounts of water on the one hand and the measures required to avoid an explosive atmosphere on the other hand (ventilation and large amounts of water calculated as waste).

[0025] Therefore, recently, it has been proposed to switch on or discharge these generators in an ionic liquid medium.

[0026] 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 placed in contact with a solution having an ionic liquid containing a solvent ionic liquid and a so-called oxidizing redox species capable of being reduced at a negative electrode, in order to discharge the electrochemical generator.

[0027] However, such a method cannot be used to treat defective batteries / cells whose terminals are corroded, for example, or for cells having a current interruption device (CID). In fact, a CID is a mechanical switch present in the battery that allows to cut off access to the battery terminals, making it impossible to discharge or chemically discharge.

[0028] Document EP 3 948 994 A1 describes a method for opening an electrochemical generator by grinding. The method involves grinding the electrochemical generator in a solution with an ionic liquid, which contains a solvent ionic liquid and a so-called oxidizing redox substance that can be reduced on a negative electrode. The grinding simultaneously allows the electrochemical generator to discharge.

[0029] Although this method in an ionic liquid medium allows to solve simultaneously the problems of making accumulators and batteries safe and environmental constraints, this method requires full immersion, which imposes constraints on the cost of the method (CAPEX and processing rate). Once opened, the battery is reactive, which complicates the method. In addition, contamination of the bath by the battery electrolyte has a negative impact on the sustainability of the method and / or its efficiency.

[0030] Document CN 110690520 A describes a method for cutting and disassembling lithium battery modules using cutting and disassembling equipment. The lithium battery module is transported to a first cutting station and then to a second cutting station, both cutting stations being provided with cutting devices. During the cutting of 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 retardancy. After cutting, the module is moved to a winding extraction station provided with a winding ejection device. This device pushes the winding into a water tank. Since the winding is immersed in water for a determined duration, the residual power of the winding will be eliminated, and during multiple charging and discharging processes, the metallic lithium precipitated on the negative electrode sheet will react with water. Summary of the invention

[0031] The object of the present invention is to propose a method allowing to overcome the disadvantages of the prior art, in particular a method allowing to make electrochemical generators safe, wherein the method must be easy to industrialize.

[0032] To this end, the present invention proposes a method for opening and discharging an electrochemical generator (e.g., a lithium-ion battery), the electrochemical generator comprising a negative electrode containing lithium or sodium and optionally a positive electrode containing lithium or sodium, the method comprising the following consecutive steps:

[0033] - opening the electrochemical generator with a cutting element preferably having a resistance greater than 100 mΩ, the opening of the electrochemical generator being performed while spraying the electrochemical generator with a first solution at least at the area to be opened,

[0034] - Discharging the electrochemical generator by immersing it (partially or completely) in the second solution.

[0035] The electrochemical generator to be processed can be in particular a cell or a module (a combination of several accumulators), a battery or an accumulator. The invention is particularly suitable for the recycling of batteries and accumulators of the lithium-ion type.

[0036] The fundamental difference between the present invention and the prior art lies in the processing of two steps:

[0037] - a first step during which the opening of the electrochemical generator is carried out by injection of a liquid (or a jet of liquid); the first solution prevents or moderates the discharge of the electrochemical generator in order to avoid the risk of a rapid discharge causing a fire or explosion of an object,

[0038] - A second step, following the first step, during which the electrochemical generator is immersed in a second solution, ensuring a controlled discharge.

[0039] During the opening of the electrochemical generator, the first solution is fed to the electrochemical generator. At least the portion of the generator to be cut is covered by the first solution. For example, the opening can be carried out under a spray or jet of the first solution.

[0040] This first step allows heat dissipation during opening.

[0041] During the second step, the discharge of the electrochemical generator is carried out by immersion in the second solution. It is thus easy to control the reactivity. The electrochemical generator is thus deactivated or made safe.

[0042] Advantageously, the first solution is selected from the following solutions a) to d):

[0043] a solution a) comprising and preferably consisting of deionized water,

[0044] a solution b) which comprises and preferably consists of an ionic liquid,

[0045] a solution c) which comprises and preferably consists of a deep eutectic solvent,

[0046] - a solution d) which comprises and preferably consists of an organic solvent.

[0047] According to a specific embodiment, the first solution is a solution with a resistance greater than 10 ohms, preferably greater than 100 ohms. Even more advantageously, the liquid of the first solution is not an ionic conductor. Preferably, the first solution may be, for example, deionized water or an organic solvent. Thus, the ohmic reduction avoids degradation of the solvent and reactivity with the cell. This is particularly useful to avoid / reduce degradation in handling of electrochemical generators / modules with higher voltages (typically greater than 12V).

[0048] According to another specific embodiment, the solution used to turn on the electrochemical generator allows for 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) may also comprise an electrochemical shuttle. During the opening, the introduction of reactive species will initiate the discharge of the object. Low-reactivity liquids will be preferred to reduce reactivity during the first phase. According to this specific embodiment, the first solution may be the same as the second solution.

[0049] Preferably, a first solution with low or medium viscosity is selected to facilitate subsequent filtration of particles / fragments from the cutting. For example, the viscosity of the first solution is between 5 cP and 50 cP.

[0050] Advantageously, the second solution is selected from the following solutions e) to g):

[0051] - a solution e) comprising and preferably consisting of an ionic liquid and optionally an electrochemical shuttling agent,

[0052] a solution f) comprising and preferably consisting of a deep eutectic solvent and optionally an electrochemical shuttling agent,

[0053] - a solution g) comprising and preferably consisting of an organic solvent and an electrochemical shuttling agent.

[0054] The electrochemical shuttling agent may be initially present in the second solution or may be added, for example, after the electrochemical generator has been contacted with the second solution.

[0055] Advantageously, the first solution and the second solution may be selected from the following pair:

[0056] - solution a) and solution f), that is, the first solution is deionized water and the second solution comprises a deep eutectic solvent, optionally mixed with an electrochemical shuttling agent,

[0057] - solution d) and solution f), i.e. the first solution comprises an organic solvent, preferably a glycol solution, such as polyethylene glycol or propylene glycol, and the second solution comprises a deep eutectic solvent, optionally mixed with an electrochemical shuttling agent,

[0058] - solution c) and solution f), that is to say, the first solution comprises a first deep eutectic solvent, optionally mixed with an electrochemical shuttling agent, and the second solution comprises a second deep eutectic solvent, preferably mixed with an electrochemical shuttling agent.

[0059] According to the latter pair, the first deep eutectic solvent and the second deep eutectic solvent may be the same or different.

[0060] Advantageously, the opening step and the discharging step are performed in an air environment.

[0061] Advantageously, the cutting element is an abrasive disc or a cutting wire.

[0062] The first step takes place in the opening area (or cutting area) and the second step takes place in the discharge area. Preferably, the cutting area is different from the discharge area.

[0063] Advantageously, between the opening step and the discharging step, the generator is moved from a first opening zone (or cutting zone) to a second discharging zone, this movement preferably being carried out in an air environment.

[0064] For example, after carrying out the first step, the liquid jet or spray is stopped and the electrochemical generator is then moved into the discharge region.

[0065] In general, this method has many advantages and in particular allows reducing the economic and environmental costs of treating the object by implementing two distinct steps to turn on the electrochemical generator and then discharge it.

[0066] The separation of the two steps, the opening step and the discharge step, is particularly advantageous, since the opening solution (first solution) is different from the discharge solution (second solution). In practice, contamination of the discharge bath by the battery electrolyte is detrimental. In the case of the present invention, the contamination occurs substantially during the opening. Thus, the process costs (processing costs) are reduced, since the contamination of the discharge bath is limited and the discharge takes place in a third solvent.

[0067] The first step has the following advantages:

[0068] -Technology for opening objects to avoid short circuits is set up,

[0069] - opening under a liquid spray / jet that allows cooling of the object, which is advantageous to have good heat dissipation in the heating zone during the opening of the electrochemical generator,

[0070] - It is very easy to set up a system for spraying / jetting liquid onto the electrochemical generator,

[0071] - Use low or medium viscosity opening liquid to facilitate filtration of debris / particles from the opening,

[0072] - the use of low-reactivity liquids for the treated objects avoids or significantly reduces the discharge reactivity of the objects: this allows to reduce the degradation of the opening liquid, to keep the objects in a stable state in an air environment and to enable their movement while minimizing the risks,

[0073] - use of a liquid that is not very expensive in its nature and formulation compared to the discharge liquid, which reduces the cost of the process,

[0074] - Contamination by particles and electrolyte of the battery occurs essentially in the first solution, which reduces the economic impact of losses regarding multiple 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 successively,

[0078] - implementation of the discharge step avoiding violent reactions with water and / or air, which not only avoids the problems associated with the management of hydrogen, oxygen and heat, and therefore of explosive atmospheres (safety, handling of surpluses, additional economic costs), but also avoids the use of large quantities of water and therefore the disposal of waste water; the use of ionic liquids also avoids corrosion of the electrochemical generator,

[0079] - Discharging does not damage objects or consume reagents,

[0080] - since the discharge is controlled by the properties of the ionic liquid solution components, the discharge can be extremely fast (e.g., less than 1 hour),

[0081] - no thermal treatment is used, which avoids problems related to gaseous emissions (for example greenhouse gases or any other gas that is harmful and dangerous to humans and the environment), in particular problems related to their treatment, and reduces the financial and energy costs of the process,

[0082] - Ensure that the electrochemical generator is safe and easy to implement.

[0083] Other features and advantages of the present invention will appear from the following additional description.

[0084] It goes without saying that this additional description is given only as an illustration of the purpose of the present invention and should not be interpreted as limiting this purpose in any case. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The invention will be better understood after reading the description of the exemplary embodiments given for purely informative and non-limiting purposes, while referring to the accompanying drawings, in which:

[0086] - Figure 1 A diagram schematically shows in cross section a plant for implementing a method according to a particular embodiment of the invention,

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

[0088] - Figure 3is a graph showing voltage and temperature curves for monitoring a method of simultaneously cutting and discharging by immersion in a discharge liquid,

[0089] - Figure 4 It is a graph showing curves of voltage and temperature for monitoring a method according to a specific embodiment of the present invention, the method comprising cutting under the condition of spraying a reactive liquid (first solution), then waiting in an air environment, and finally discharging by immersing in a reactive liquid (second solution).

[0090] In order to make the drawings clearer, the various parts shown in the drawings are not necessarily to a uniform scale.

[0091] The various possibilities (alternatives and embodiments) are to be understood as not being mutually exclusive and can be combined.

[0092] Furthermore, in the following description, when considering that the structure is oriented in the manner shown in the drawings, terms depending on the orientation of the structure (such as “top”, “bottom”, etc.) apply. DETAILED DESCRIPTION

[0093] Electrochemical Generator

[0094] In the following, an electrochemical generator is, for example, a battery, a cell or a battery comprising a plurality of batteries (also referred to as battery cells) which are connected in series or in parallel depending on the rated operating voltage and / or the amount of energy to be supplied to the battery module or cell. In particular, this electrochemical generator can be a lithium-ion battery.

[0095] The opening and discharging method concerns all electrochemical systems of the battery or cell type, whether handled individually or in combination.

[0096] These various electrochemical devices may be of metal ion type (eg, lithium ion or sodium ion), or of Li metal type, or the like.

[0097] This can also be a primary system (such as Li / MnO 2 ) or flow battery (redox flow battery).

[0098] Advantageously, an electrochemical generator will be chosen with a potential greater than 1.5 V.

[0099] The generator may comprise several electrochemical cells, each of which comprises a first electrode (here an anode) and a second electrode (here a cathode), a separator and an electrolyte. According to another embodiment, the first electrode and the second electrode may be reversed.

[0100] The anode (negative electrode) is preferably carbon-based, such as graphite, which can be mixed with a binder of the PVDF type and deposited on a thin copper sheet. It can also be a mixed oxide of lithium (such as lithium titanate Li 4 Ti 5 O 12 (LTO)) or a mixed oxide of sodium (such as sodium titanate for sodium-ion batteries). Depending on the technology selected, it can also be a lithium alloy or a sodium alloy.

[0101] The cathode (positive electrode) is a lithium-ion insertion material for lithium-ion batteries. This cathode (positive electrode) can be a layered oxide of the LiMO 2 type, a phosphate with an olivine structure LiMPO 4 or a spinel compound LiMn 2 O 4 , where M represents a transition metal. For example, a positive electrode made of LiCoO 2 、LiMnO 2 、LiNiO 2 、Li 3 NiMnCoO 6 、LiNixCo 1-x (where 0 < x < 1) or LiFePO 4 is selected.

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

[0103] The insertion material can be mixed with a binder of the polyvinylidene fluoride type and deposited on a thin aluminum sheet.

[0104] Depending on the battery technology selected, the electrolyte includes a lithium salt (e.g., LiPF 6 、LiBF 4 、LiClO 4 ) or a sodium salt (e.g., N 3 Na) dissolved in a non-aqueous solvent mixture. The mixture of solvents is, for example, a binary or ternary mixture. The solvents are, for example, selected from solvents based on cyclic carbonates (ethylene carbonate, propylene carbonate, butylene carbonate), linear or branched (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethoxyethane) solvents, and are mixed in various proportions.

[0105] Alternatively, this electrolyte can also be a polymer electrolyte, which comprises a polymer matrix made of organic and / or inorganic materials, a liquid mixture comprising one or more metal salts, and optionally a mechanical reinforcement material. The polymer matrix can comprise one or more polymer materials, for example selected from polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP) or poly(N-vinylimidazolium) bis(trifluoromethanesulfonylamide), N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethylsulfonyl)imide (DEMM-TFSI) type poly(ionic liquid).

[0106] The cell can be wound on itself around a winding axis or have a stacked architecture.

[0107] A housing, for example a bag made of polymer, or a metal packaging, for example made of steel, allows the sealing of the accumulator to be ensured.

[0108] Each electrode is connected to a current collector which passes through the casing and forms a terminal (also called output terminal or electrode terminal or terminal) on the outside of the casing, respectively. The function of the current collector is twofold: to ensure mechanical support for the active material and electrical conduction up to the battery terminals. The terminals (also called electrode terminals or terminals) form the output terminals and are intended to be connected to an "energy receiver".

[0109] Method for opening and discharging an electrochemical generator

[0110] like Figure 1 As shown, the method for opening and discharging an electrochemical generator comprises the following steps:

[0111] - opening the electrochemical generator 10 with the cutting element 20, the opening of the electrochemical generator being performed while spraying the electrochemical generator with the first solution 100 at the portion of the electrochemical generator 10 to be opened,

[0112] Discharging the electrochemical generator by partially or even completely immersing it in the second solution 200 .

[0113] First step (opening step)

[0114] During a first step, the electrochemical generator 10 is at least partially or even completely opened. This operation allows access to the interior of the electrochemical generator.

[0115] Opening means at least access to the electrodes in order to be able to discharge the electrochemical generator during the second step. For example, this involves opening the housing to access the electrodes.

[0116] The cutting operation performed in the presence of an inert liquid avoids violent reactions with water and / or air. The inert liquid ensures safe opening of the cell / accumulator and allows discharging of the cell / accumulator during opening, during the introduction of the cutting tool into the active core of the material. Finally, the inert liquid facilitates the cooling of the medium and allows the removal of heat during the discharge process.

[0117] The inert liquid is sprayed onto the parts to be cut, for example by means 30 allowing a jet or spray of the first solution 100 to be sprayed or sent onto the electrochemical generator 100. The flow rate is for example between 25 L / min and 50 L / min.

[0118] This first step may be performed over a grid or screen 40 to filter the first solution after cutting the electrochemical generator 10 and thus separate particles / fragments from the cutting from the first solution 100 so that it can be reused.

[0119] The inert liquid helps maintain a controlled atmosphere (air, water) and acts as a cutting fluid (lubricating and cooling the cutting area).

[0120] Advantageously, this first step avoids or greatly limits the phenomenon of electric discharges after opening the object.Opening under a spray / jet of liquid controls the heat dissipation during opening.

[0121] The first step may be carried out at a temperature ranging from 5 to 80°C, preferably from 20 to 60°C, even more preferably at ambient temperature (20 to 25°C). It is preferably performed at atmospheric pressure (or 1 bar or 101.325 Pa).

[0122] For greater safety, the first step may be performed under an inert atmosphere, such as argon, carbon dioxide, nitrogen or a mixture thereof.

[0123] For example, the opening step can be associated with a system for controlling the gaseous atmosphere allowing the concentration of oxygen to be controlled (inert atmosphere or extraction system with the right dimensions). Thus, the assembly ensures safety (with respect to the fire triangle) and allows the opening of cells and accumulators while managing the generation of gases caused by opening the cells.

[0124] Preferably, the first step is performed in an air environment.

[0125] Advantageously, at the end of the opening step, the spraying of the electrochemical generator 10 with the first solution 100 is stopped.

[0126] The first step is to cut or open the first area ( Figure 1 Executed in area Z1).

[0127] The discharge step (second step) is carried out in the second region called the discharge region ( Figure 1 The process is performed in area Z2).

[0128] Between the opening step and the discharging step, an intermediate step is performed during which the electrochemical generator is moved from the first zone Z1 to the second zone Z2. For example, this movement may comprise moving the electrochemical generator from the zone Z1 containing the injection device 30 to the tank 50. This intermediate step is preferably performed in an air environment.

[0129] Second step (discharging step)

[0130] The discharge step consists in partially or preferably completely discharging the electrochemical generator by immersion. This results in the deactivation of the object or in making it safe.

[0131] As mentioned above, this second step is preferably carried out in the discharge region ( Figure 1 Executed in area 2).

[0132] The second step is preferably performed in an air environment. It is also advantageously performed at atmospheric pressure.

[0133] During this second step, the generator 10 is partially or completely immersed in the second solution. The electrical discharge caused by immersion in the liquid induces a chemical reaction.

[0134] The discharge is performed in the device 50 containing the second solution 200. For example, the discharge is performed in a tank.

[0135] Advantageously, the heat energy absorbed during the resistive discharge process can be recovered with a heat exchanger. Thus, by continuous circulation between the discharge reactor and the heat exchanger, a continuous discharge and energy recovery process will be possible. Advantageously, the temperature of the bath in which the battery is placed does not exceed 60° C., in order to avoid internal degradation reactions of the battery electrolyte. This method allows to avoid runaway processes leading to degradation and / or explosion.

[0136] Cutting element for carrying out the opening step

[0137] The opening is performed by a non-conductive cutting element 20 (which may also be referred to as a cutting tool). The cutting element 20 has sufficient resistance to avoid a direct short circuit that would cause the battery to explode. In other words, the cutting element 20 has a very low electrical conductivity.

[0138] In particular, we will select tools with a resistance of, for example, typically greater than 100 mΩ; (eg from 100 mΩ to 1 kΩ).

[0139] The conductivity of the cutting element is the average conductivity encountered by the sample to be cut, which will depend on the ratio of insulating and conductive areas, the rotation speed, the speed at which the grinding wheel moves forward, etc.

[0140] The resistance is the average resistance of the cutting element. At least the part of the cutting element that is intended to penetrate the sample to cut the sample has such resistance. The resistance can be measured with a multimeter by placing the sample between two identical conductive plates.

[0141] The preferred technology is one that avoids deformations too great (crushing, spreading of material onto adjacent materials, etc.) that could lead to a direct and uncontrolled short circuit, resulting in thermal runaway and explosion of the battery.

[0142] A cutting tool is a tool which can abrade, but preferably cuts material in order to completely or partially open an object in the presence of a liquid, thereby allowing cooling of the area subjected to mechanical heating.

[0143] The non-conductive penetrating tools, which can be, in a non-exhaustive manner, guillotine tools (blades), saws (circular saws, band saws), wires, tools for cutting by ultrasound, by drilling, by grinding with a liquid jet (comprising non-conductive abrasive particles). These non-conductive penetrating tools can also be non-conductive cutting or micro-cutting knives. Advantageously, the cutting element is a cutting wire, a grinding wheel, a circular saw blade (also called a disc) or a saw band.

[0144] This operation is performed in the presence of the first solution 100, which avoids heating and ignition of reactions with the organic electrolyte of the battery and air, which reactions could lead to flames or explosions.

[0145] The cutting element 20 includes a base support that imparts mechanical properties to the cutting element.

[0146] The base support may be electrically conductive or electrically insulating.The base support may be metallic, resinous or rubber type.

[0147] The base support is covered with an abrasive area. The abrasive area has a hardness adapted to the object and material to be processed.

[0148] The abrasive region is made, for example, of sandstone, corundum, diamond, silicon carbide and / or aluminum oxide.

[0149] Preferably, the abrasive region is formed by abrasive particles.

[0150] Preferably, the base support is covered with an abrasive region and a conductive region. The abrasive region imparts mechanical properties to the tool and the conductive region imparts electrical properties to the tool.

[0151] The conductive region is formed, for example, of conductive particles.

[0152] The conductive area is made of metal or metal alloy, for example. For the purpose of illustration, it can be copper, iron, steel and / or aluminum, more generally an electrical conductor.

[0153] The conductive regions may be formed of metal particles or metal wires.

[0154] The abrasive particles and / or the conductive particles are preferably particles having a size ranging, for example, from a few micrometers to a few centimeters.

[0155] The abrasive particles and / or the conductive particles are advantageously mechanically held on the support by a binder. The binder may be a resin, rubber, silicate, clay or ceramic.

[0156] The abrasive areas and / or the conductive areas may be distributed on the substrate in a regular or random manner.

[0157] The abrasive regions and / or the conductive regions may be continuous or discontinuous.

[0158] According to a first alternative embodiment, the opening of the electrochemical generator is performed by abrasion using a wire. The wire comprises a solid thread-like base, imparting mechanical properties. The abrasive properties are imparted by the addition of abrasive particles having a hardness adapted to the object and material to be treated.

[0159] According to a second alternative embodiment, the opening of the electrochemical generator is performed by abrasion using a grinder. The disc of the grinder comprises a circular base support. The support comprises a first main face and a second main face parallel to each other and a side face (also called an edge) connecting the two main faces.

[0160] The support may be of metallic, resinous or rubber type. Advantageously, the support is covered by an electrically insulating abrasive zone and an electrically conductive zone.

[0161] Where the grinding wheel includes abrasive regions (preferably abrasive particles) and conductive regions (preferably conductive wires or particles), various configurations are possible.

[0162] The abrasive areas and the conductive areas are distributed randomly, for example.

[0163] The abrasive areas and the conductive areas can be distributed in a controlled manner.

[0164] According to an alternative embodiment, the abrasive areas and the conductive areas are arranged in a controlled manner so as to form alternating abrasive areas and non-abrasive areas.

[0165] According to another alternative embodiment, the conductive areas may be distributed concentrically with respect to the center of the grinding wheel disk.

[0166] According to another alternative embodiment, the conductive areas may be arranged randomly or non-randomly along one or more radii or along one or more diameters.

[0167] According to another alternative embodiment, the conductive area may be provided only on the periphery of the grinding wheel disc.

[0168] According to another alternative embodiment that is not shown, the electrically conductive area is provided on the edge of the grinding wheel disk.

[0169] The alternation of abrasive areas and conductive areas can be obtained by a coating produced by a thin film deposition technique, for example by physical vapor deposition (or PVD), by atomic layer deposition (ALD), by chemical vapor deposition (or CVD), by spin coating or by a coating technique, such as, for example, by dip coating.

[0170] Suitable resistance can also be imparted by a conductive fabric deposited on the outer surface of the cutting tool, allowing separation of mechanical properties (abrasion, controlled hardness given by the abrasive particles contained in the resin) and electrical properties (suitable resistance given by the outer fabric).

[0171] Resistance can also be adjusted by the cutting fluid and operating conditions (temperature, fluid viscosity, wear rate, fluid renewal, etc.).

[0172] First solution 100

[0173] The first solution 100 facilitates cooling of the electrochemical generator 10 and allows heat to be discharged during the opening process. To this end, the first solution 100 can be optionally cooled. The first solution can be sprayed / injected onto the opening area and / or several areas of the electrochemical generator 10. The first solution can be sprayed / injected so as to completely cover the electrochemical generator 10.

[0174] According to a first alternative embodiment, the first solution is a liquid that may be reactive. The introduction of reactive substances will initiate the discharge of the object during the opening period. In the specific case where the solution used to open the electrochemical generator is also the solution used to discharge the electrochemical generator, a low-reactivity liquid is preferred to reduce the reactivity during the first stage.

[0175] In a second alternative 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 an ionic conductor (as is the case with pure water and many organic solvents that initially do not have ions in solution). Thus, the ohmic reduction avoids degradation of the solvent and reactivity with the electrochemical generator 10. This is particularly advantageous for avoiding / reducing degradation of the processing performance of the electrochemical generator 10 at higher voltages (typically greater than 12V).

[0176] The properties of the liquid are defined to limit the discharge of the battery so as to control the reactivity of the battery. The absence or very low reactivity ensures control of the object, which facilitates the movement of the object under the atmosphere and the time of moving the object safely. The opening liquid is inherently less complex (nature of the components) and less expensive, so that the contamination inherent to the opening battery (leakage of the battery's electrolyte into the liquid) has less impact on the method. Preferably, the first solution is biodegradable, cheap and / or has low volatility. Preferably, it does not produce contamination to the second solution.

[0177] Preferably, the liquid used is not very viscous to facilitate filtering of fines / particles.

[0178] Preferably, the first solution 100 is selected from the following solutions:

[0179] - a solution comprising deionized water,

[0180] - a solution comprising an ionic liquid,

[0181] - a solution comprising a deep eutectic solvent,

[0182] - A solution comprising an organic solvent.

[0183] An ionic liquid refers to an association comprising at least cations and anions which produces a liquid having a melting temperature below or close to 100°C.

[0184] Deep eutectic solvents (or DES) are different from ionic liquids. The term DES is used for media other than ionic liquid media. Deep eutectic solvents are formed by a mixture between two or more compounds in a precise ratio corresponding to the eutectic point. The melting point is significantly lower than the melting point of each component and allows the mixture to be liquid at ambient temperature. Most of these solvents are liquid at ambient temperature, which facilitates their use. Compared with ionic liquids that require several chemical synthesis and purification steps, the synthesis of DES is easy and clean. This is a simple mixture of the products that make up the DES in appropriate proportions under heating until a uniform and transparent liquid is obtained. These components are a pair of hydrogen bond donors and acceptors of this bond.

[0185] These eutectics have the general formula [Cat]+.[X]-.z[Y], where [Cat]+ is a cation (usually ammonium), [X]- is a halogen anion (usually Cl-), and [Y] is a Lewis acid or (Brønsted) acid, and z is the number of Y molecules.

[0186] These types of eutectics are divided into three categories based on the nature of Y, such as:

[0187] Eutectic type 1: Y=MCl x, for example, where M = Fe, Zn, Sn, Fe, Al, Ga;

[0188] Eutectic type 2: Y=MCl x.y H 2 O, where, for example, M = Cr, Co, Cu, Ni, Fe;

[0189] Eutectic type 3: Y=RZ, where R corresponds to a carbon chain and where Z is a chemical functional group such as CONH 2 , COOH, OH.

[0190] As for the solvent, it is preferred to use bio-based solvents (methyl esters, N,N-dimethyldecylamide, N,N-dimethyldec-9-enamide, etc.), use acetates (hexyl acetate, butyl acetate, etc.). These examples are not exhaustive. Water can also be used. Low ion conductivity is preferred to avoid the formation of hydrogen and oxygen.

[0191] For example, when the second solution 200 comprises a deep eutectic solvent, the first solution 100 may comprise the components of the DES. More generally, a liquid component of the DES will be selected which constitutes the DES and which is a hydrogen bond donor. The latter must be a liquid. Preferably, it is a liquid with low viscosity and little or no electrical conductivity.

[0192] For illustrative purposes, when the second solution comprises an ethanol-based DES, the first solution advantageously comprises ethylene glycol.

[0193] Ethylene glycol (EG) is a liquid component, is not ionically conductive, has a low vapor pressure and very low viscosity, and is a component of ethaline. Alternatively, propylene glycol may be used.

[0194] The first solution may consist of a liquid phase (water, solvent, ionic liquid, deep eutectic solvent). The first solution 100 may further comprise an electrochemical shuttling agent.

[0195] Electrochemical shuttles, also called redox mediators or redox pairs, are oxidant / reductant pairs (Ox / Red) in solution, the oxidant of which can be reduced at the anode (negative electrode) and the reductant of which can be oxidized at the cathode (positive electrode). The oxidation of the reductant and the reduction of the oxidant allow the formation of new oxidant / reductant species and / or the regeneration of species initially present in the solution. The method is economical because the redox pairs in the solution simultaneously ensure the redox reactions at the electrodes / terminals of the electrochemical generator, making the consumption of reagents zero; the solution can be used to turn on (or discharge if used during the second step) several electrochemical generators.

[0196] During the on-time of the electrochemical generator, they will react with the internal components, thereby reducing the potential difference between the electrodes (anode and cathode). This internal discharge also participates in ensuring 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.

[0197] Advantageously, the redox species pair is a metal pair, preferably selected from Mn 2+ / Mn 3+ 、Co 2+ / Co 3+ Cr 2+ / Cr 3+ Cr 3+ / Cr6 + 、V 2+ / V 3+ 、V 4+ / V5 + 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 (e.g., Cl 2 / Cl - or Cl - / Cl 3 - ).

[0198] For example, ferric chloride will be used.

[0199] Advantageously, the first solution consists of a liquid phase mixed with an electrochemical shuttling agent.

[0200] Second solution 200

[0201] The second solution 200 is a liquid that allows the electrochemical generator to discharge chemically by immersion. In certain cases, the second solution 200 has the same composition as the first solution 100.

[0202] The discharge liquid refers to a bath comprising a liquid composed of ions (ionic liquid solution, DES solution, organic solution) and substances that ensure the coordinated discharge of the object (battery / accumulator) with at least one component of the bath, these substances acting as electrochemical shuttles. Thus, there is discharge of the electrochemical generator 10 and ensuring safety / deactivation.

[0203] Therefore, there will be a liquid composed of at least ions, and this liquid will be called an ionic solvent that ensures ionic conductivity of the ions.

[0204] The second solution is preferably selected from one of the following solutions:

[0205] - a solution comprising an ionic liquid and optionally an electrochemical shuttling agent,

[0206] - a solution comprising a deep eutectic solvent and optionally an electrochemical shuttling agent,

[0207] - A solution comprising an organic solvent and an electrochemical shuttling agent.

[0208] Ionic liquids are solvent ionic liquids, that is to say thermally and electrochemically stable ionic liquids which minimize degradation effects of the dielectric during discharge phenomena.

[0209] Mixtures of ionic liquids may be used. The additional ionic liquids promote one or more properties with respect to ensuring safety and discharge steps.

[0210] For the solvent ionic liquid LI 1 and another ionic liquid LI 2 , the cation is selected from the group consisting of imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium, preferably a cation with a wide cation window, the window being large enough to envision a cathode reaction (i.e. having a large stability window) so as to avoid or minimize degradation of the ionic liquid. When LI is satisfied 1 With LI 2 Advantageously, LI 1 and LI 2 With the same cation to increase LI 2 In LI 1 Solubility in .

[0211] With ionic liquids (LI 1 ) are possible, the cation of the ionic liquid will associate with an anion, whether organic or inorganic, preferably with a wide anodic window.

[0212] Advantageously, anions will be used which allow to simultaneously obtain moderate viscosity, low melting temperature (liquid at ambient temperature) and good solubility with the ionic liquid and other substances of the solution, which does not lead to hydrolysis (degradation) of the ionic liquid.

[0213] More advantageously, the mixture LI 1 and LI 2 Liquid at ambient temperature.

[0214] The TFSI anion is a cation that satisfies the 1Examples of many of the above standards associated with the invention include: [BMIM][TFSI], or the use of [P66614][TFSI] type ionic liquids, ionic liquid 1-ethyl-2,3-trimethyleneimidazolium bis(trifluoromethanesulfonyl)imide ([ETMIm][TFSI]), ionic liquid N,N-diethyl-NN-2-methylethylammonium bis(trifluoromethylsulfonyl)amide [DEME][TFSA], ionic liquid N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([PYR14][TFSI]), 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.

[0215] Preferably, the second solution contains DES, which is a medium with low cost, non-toxicity and low environmental impact (biodegradability). Toxicity and biodegradability are related to its components.

[0216] According to the above general formula of DES, it is preferred to seek "Y" also to act as an electrochemical shuttling agent (e.g., with iron and Fe 2+ / Fe 3+ (right) It is possible to combine ionic liquids with chloride anions with metal salts FeCl in various ratios and with various cations. 2 and FeCl 3 When the proportion of water is low, this type of reaction can also be carried out with a Type II eutectic, which integrates water molecules into the metal salt. A Type III eutectic can also be used, which combines the ionic liquid and the hydrogen bond donor substance (Y) with [LI 1 ] / [Y] type mixture association, where LI 1 It can be a quaternary ammonium, and Y is a complexing molecule (hydrogen bond donor), such as urea, ethylene glycol, thiourea, etc.

[0217] The DES may advantageously be choline chloride used together with an H-bond donor with very low toxicity such as glycerol or urea, which ensures that a non-toxic DES is available at very low cost.

[0218] For example, choline chloride can be replaced by betaine. These systems have a limited electrochemical stability window, but allow guaranteed flooding and deactivation of the opened battery.

[0219] The shuttling agent will be initially present in the second solution 200 or will be added to the second solution 200 at a later time.

[0220] Electrochemical shuttles can be used to secure several electrochemical generators in series and / or in a mixture.

[0221] The redox species allow the electrochemical generator to be discharged significantly or even completely.

[0222] Advantageously, the redox species pair is one of the pairs described above for the first solution 100 .

[0223] For example, ferric chloride will be used.

[0224] The second solution 200 may be stirred.

[0225] The first solution 100 and / or the second solution 200 may further contain one or more active substances. The active substances are selected from, for example, fire extinguishing agents, flame retardants intended to prevent thermal runaway, agents for protecting batteries (electrochemical shuttles or redox mediators), salts, stabilizers for viscosity, solubility, hydrophobicity, and conductivity.

[0226] The fire extinguishing agent and / or flame retardant may be an alkyl phosphate, such as trimethyl phosphate or triethyl phosphate, which may be fluorinated, such as a fluorinated alkyl phosphate (such as tris(2,2,2-trifluoroethyl)phosphate). The concentration may be 80% to 5% by mass, advantageously 30% to 10% by mass.

[0227] In the selection of the first solution and the second solution, preferably:

[0228] - the first solution is formed of a solvent and the second solution is a DES mixed with an electrochemical shuttling agent, or

[0229] - the first solution is formed by DES mixed with an electrochemical shuttling agent, and the second solution is DES mixed with an electrochemical shuttling agent; the first solution and the second solution are advantageously identical.

[0230] Even more preferably:

[0231] - the first solution is a glycol, such as ethylene glycol or propylene glycol, and the second solution is a mixture of DES (preferably choline chloride / ethylene glycol or choline chloride / betaine) and an electrochemical shuttling agent, or

[0232] - the first solution is a mixture of DES (preferably choline chloride / ethylene glycol or choline chloride / betaine) and an electrochemical shuttling agent, and the second solution is a mixture of DES (preferably choline chloride / ethylene glycol or choline chloride / betaine) and an electrochemical shuttling agent; the first solution and the second solution may be identical.

[0233] The method that is the subject of the present invention allows discharging the objects before recycling through one of the pyrometallurgical, hydrometallurgical or combinations thereof.

[0234] The steps of sorting and disassembling may be performed before. For example, the present invention may be implemented in a method for recycling an electrochemical generator, the method comprising the following steps:

[0235] 1- Sorting

[0236] 2- Disassembly

[0237] 3- Setting up the present invention

[0238] 4-Recovery through conventional channels (pyrometallurgy, hydrometallurgy, etc.).

[0239] Illustrative and non-limiting example of one embodiment

[0240] Example 1: Opening a cell in ethylene glycol medium and discharging in choline chloride / ethylene glycol medium

[0241] NMC chemistry (NMC Chemical Company) prismatic lithium-ion cells with a nominal capacity of 63Ah were charged to 100%. 2 O 3 ) resin grinding wheel to perform grinding type cutting on the battery. 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 at a flow rate of 10 L / min. The action of the grinding wheel opening produces a gap of about 5 cm 2 The notch thickness was 500 μm. The cutting operation was carried out for a duration of 4 minutes, after which the cutting was stopped and the liquid jet / spray was applied.

[0242] Figure 2 It is shown that during the cutting phase under the ethylene glycol jet, and also during the cutting phase and when the EG jet is stopped (at Figure 2 The treatment time was deliberately extended to 1 hour to highlight the stability of the cell over a very long duration in air.

[0243] In parallel, measurements of the cell temperature confirm the absence of heating and the reactivity of the cell.

[0244] After 1 hour, 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 ferric chloride type. The viscosity of the mixture is about 40 cP. The entire method is performed at ambient temperature and atmosphere without recirculation or thermalization of the fluid (degradation conditions). Discharge then occurs in the discharge fluid until a 0% state of charge is reached.

[0245] This technology not only allows the battery to be opened without explosion, but also allows the cells to be stabilized under atmospheric conditions and in an air environment to enable their movement. The cells can then be discharged by using a discharge fluid.

[0246] In contrast, the tests were performed by cutting the cells while fully immersed in a discharge liquid (a mixture of choline chloride and ethylene glycol in a molar ratio of 1:3 with the addition of an electrochemical shuttling agent of the ferric chloride type). Figure 3 Represents the evolution of voltage and temperature. A voltage decrease and a temperature increase are observed for the lithium-ion battery.

[0247] Example 2: Opening the module in choline chloride and ethylene glycol medium and discharging in choline chloride and ethylene glycol medium

[0248] The NMC chemistry lithium-ion module has a module capacity of 125Ah, a module voltage of 16.6V, and each cell of the module is charged to 100% (initially 3.7V). The module is in an uncontrolled atmosphere (ambient air) and uses a battery containing Al 2 O 3 The cutting was performed by abrasive resin grinding wheels. The cutting fluid (first solution 100) was a mixture of choline chloride and ethylene glycol in a molar ratio of 1:3 with the addition of an electrochemical shuttle agent of the ferric chloride type. The fluid was sprayed onto the cutting area at a flow rate of 10 L / min. The action of the grinding wheel opening produced a gap of about 5 cm. 2 The notch thickness was 500 μm. The cutting operation was performed for a duration of 5 minutes, and then the cutting and the liquid ejection were stopped.

[0249] Figure 4 The voltage of the module is shown to be gradually reduced during the cutting phase and during the jet stop (represented as a waiting phase in air environment). The stop phase is intentionally extended to 15 minutes to highlight the temperature changes over a long period of time in air environment. The measured values ​​of the module temperature show that the heating is low enough to allow processing without explosion or fire in ambient atmosphere (in air environment) after stopping the discharge liquid jet.

[0250] After 15 minutes in air, the module 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 ferric chloride type. The viscosity of the mixture is about 40 cP. The entire method is performed at ambient temperature and atmosphere, without recirculation or thermalization of the fluid (degradation conditions). Discharge then occurs in the discharge fluid until a 0% state of charge is reached on each cell of the module (voltage of each cell less than 1 V).

[0251] This technology not only allows the battery to be opened without explosion, but also allows the cells to be stabilized in an air environment under atmospheric conditions to enable their movement. The cells can then be discharged by using a discharge fluid.

Claims

1. A method for opening and discharging an electrochemical generator (10), said electrochemical generator (10) comprising a negative electrode containing lithium or sodium and optionally a positive electrode containing lithium or sodium, said method comprising the following consecutive steps: - opening the electrochemical generator (10) with a cutting element (20) preferably having a resistance greater than 100 mΩ, the opening of the electrochemical generator being performed while spraying the electrochemical generator (10) with a first solution (100), and - discharging the electrochemical generator by immersing it in a second solution (200), And among them: - The first solution (100) is selected from one of the following solutions a) to d): a) a solution of deionized water, b) a solution comprising an ionic liquid, c) a solution comprising a deep eutectic solvent, and d) a solution comprising an organic solvent; and The second solution (200) is selected from one of the following solutions e) to g): e) a solution comprising an ionic liquid and optionally an electrochemical shuttling agent, f) a solution comprising a deep eutectic solvent and optionally an electrochemical shuttling agent, and g) A solution comprising an organic solvent and an electrochemical shuttling agent.

2. The method according to claim 1, characterized in that The first solution (100) further comprises an electrochemical shuttling agent.

3. The method according to claim 1 or 2, characterized in that: The second solution (200) is the same as the first solution (100).

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

5. The method according to claim 1 or 2, characterized in that: The first solution (100) comprises an organic solvent, preferably a solution of a glycol, such as polyethylene glycol or propylene glycol, and the second solution (200) comprises a deep eutectic solvent, preferably mixed with an electrochemical shuttling agent.

6. The 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 shuttling agent, and the second solution (200) comprises a second deep eutectic solvent preferably mixed with an electrochemical shuttling agent, wherein the first eutectic solvent can be the same as or different from the second eutectic solvent.

7. The method according to any one of the preceding claims, characterized in that The steps of the method are performed in an air environment.

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

9. The method according to any one of the preceding claims, characterized in that Between the opening step and the discharge step, the generator is moved from the first opening area to the second discharge area, said movement preferably being performed in an air environment.

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