Process for recovering cathode material from lithium-ion batteries

Abstract

Process for recovering cathode material from lithium ion batteries comprising the following stages: (a) isolating a cathode from a lithium-ion battery, said cathode comprising a cathode material comprising at least one active cathode material, at least one binder and, optionally, at least one conductive material, and a current collector, said cathode material adhered to said current collector via said at least one binder; (b) contacting the cathode with at least one glycol; (c) delaminating the cathode material from the current collector obtaining a mixture comprising a suspension of said cathode material dispersed in a liquid phase comprising said at least one glycol and a current collector immersed in said suspension; (d) recovering the cathode material and the current collector from said mixture; characterized in that said stage (c) is carried out in the presence of ultrasounds at a power comprised between 30 Watt and 500 Watt, preferably comprised between 50 Watt and 300 Watt, at a temperature comprised between 80°C and 280°C, preferably comprised between 85°C and 260°C, for a time comprised between 15 minutes and 24 hours, preferably comprised between 30 minutes and 20 hours. From the cathode material recovered through the above-mentioned process, after appropriate treatments, it is possible to obtain a restored active cathode material (for example, by a direct recycling process), or synthetic precursors that can be used in the regeneration of said active cathode material (for example, by a hydrometallurgical process), which can in turn be used in lithium-ion batteries.

Description

[0001] PROCESS FOR RECOVERING CATHODE MATERIAL FROM LITHIUM- ION BATTERIES

[0002] DESCRIPTION

[0003] The present invention concerns a process for the recovery of cathode material from lithium-ion batteries.

[0004] More specifically, the present invention concerns a process for delaminating and recovering cathode material from lithium-ion batteries which is carried out in the presence of at least one glycol and ultrasound, operating under specific power, temperature and time conditions.

[0005] From the cathode material recovered through the above-mentioned process, after appropriate treatments, it is possible to obtain a restored active cathode material (for example, by a direct recycling process), or synthetic precursors that can be used in the regeneration of said active cathode material (for example, by a hydrometallurgical process), which can in turn be used in lithium-ion batteries.

[0006] In the coming years, lithium-ion battery production will grow exponentially in both the automotive sector in relation to the increasing production of electric vehicles (“EVs”) and hybrid electric vehicles (“HEVs”) as a replacement for traditional vehicles with internal combustion engines (“ICEVs”), both in the sectors of electronic devices and stationary storage systems, for which the production of batteries with excellent electrochemical performance will be required.

[0007] Specifically, global demand for lithium-ion batteries is expected to rise from 0.5 TWh in 2022 to over 2.8 TWh in 2030 (https: / / about.bnef.com / blog / utilities-want-more- energy-storage-but-supply-remains-low / - BloombergNEF. 26 May 2022), where the main contribution will be due to the electrification of transport (1.745 TWh). As a result of this, there will be a strong increase in the demand for raw materials needed for the production of these batteries such as, for example, graphite, lithium (Li), nickel (Ni), cobalt (Co), lead (Pb), manganese (Mn), aluminium (Al), copper (Cu).

[0008] The development of innovative recycling technologies is therefore vital to cushion the incessant growth of spent lithium-ion batteries, in particular in the electric vehicles field (EVs): it is expected to reach 1 Mton / y (0.1 TWh / y) in 2030 and 10 Mton / y (1.3 TWh / y) in 2040, compared to a current recycling capacity of only 180 kton / y (source: IE A - International Energy Agency, “The role of critical minerals in clean energy transition” (2022), “World Energy Outlook”].

[0009] The situation appears to be even more worrying in view of the scarcity of certain resources defined as “critical materials”, in particular lithium (Li) and cobalt (Co), whose natural reserves will not be able to meet the ever-increasing needs required for the energy transition, as reported, for example, by Pinegar H. and others, in “Journal of sustainable Metallurgy” (2019), Vol. 5. P. 402-416 and in “Critical Minerals Market Review” (2023), IEA (International Energy Agency).

[0010] From a regulatory point of view, lithium-ion batteries used in electric vehicles (“EVS”) are regulated by the General vehicle Directives 2000 / 53 / EC and 2006 / 66 / EC. On 9thDecember 2022, the European Union, represented by the European Commission, the European Parliament and the European Council, reached an agreement on a new European Regulation for lithium-ion batteries and their recycling, which was published on 14thJune 2023 (https: / / www.consilium.europa.eu / it / press / press- releases / 2023 / 07 / 10 / council-adopts-new-regulation-on-batteries-and-waste-batteries / ). The purpose of this document is to stimulate technological progress in the field of said batteries, while minimizing the impact on the environment. The main advantage is the issuance of a sort of “battery passport” by suppliers. Indeed, any type of battery (portable, ignition, electric vehicle or industrial vehicle) must be sold together with an appropriate documentation describing its entire life cycle. This documentation will contain information on the raw material (from extraction to production), design, labelling, traceability, collection, recycling and reuse methods. These products will have to be registered electronically in order to ensure compliance with the safety and traceability requirements of the new Regulation. The “battery passport” will then be a digital document containing information about the battery manufacturer, the date of manufacture and release on the market, the type of battery and the serial number to identify it in a safe and secure manner, the source of the raw materials, the harmful substances contained in the battery, the recycled raw materials contained in the battery and any recycling and recovery processes that the battery has undergone at the end of its life (this is the case for second-life batteries). In fact, this new directive provides a great advantage to know in advance and with certainty the chemical composition of the cathode, anode and electrolyte solution, encouraging an initial sorting before said recycling and recovery processes. Among the measures introduced those of particular interest are the minimum acceptable levels of recycled materials implemented in new batteries, which shall be: 16% for cobalt (Co), 85% for lead (Pb), 6% for lithium (Li) and 6% for nickel (Ni).

[0011] Finally, once the law enters into force, sustainability requirements for performance, durability, and carbon footprint will be phased in from 2024 (https: / / ec.europa.eu / commission / presscorner / detail / en / ip_22_7588).

[0012] The recycling and recovery of spent lithium-ion batteries is therefore of increasing interest, as it can reduce the prices of raw materials and safeguard those countries, such as Europe, that are strictly dependent on the import of these minerals from an energy point of view. In addition, the environmental, social and health impacts resulting from the extraction of such critical materials would be drastically reduced.

[0013] Lithium-ion batteries are secondary generators with many advantages: long storage, high specific energy and energy density, and good cyclability. Said batteries are made up of four main components: the cathode (the positive electrode), the anode (the negative electrode), the separator and the electrolyte solution. The cathode is made up of an aluminium current collector and the cathode material comprising an active cathode material, a binder and optionally a conductive material, whereas the anode is made up of a copper current collector and anode material comprising an active anode material and a binder. The cathode and anode are separated by the separator, i.e. a polymeric membrane (for example, polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), or mixtures thereof) which serves to prevent possible contact and thus short-circuits. The cathode and anode, together with the separator, are placed inside a casing into which the electrolyte solution has been previously poured and then everything is sealed. The active cathode material is generally made up of oxides of transition metal oxides containing lithium such as, for example: LiCoCL (LCO), LiNixMnyCozCL (NMC) wherein 0 < x, y, z <1 and x+y+z=l, LiM CU (LM0), LiFePCh (LFP), and the like. Usually, small quantities of a conductive material (for example, carbon black) and the binder, generally polyvinylidene fluoride PVDF or polytetrafluoroethylene (PTFE), are added to said oxides, the purpose of which is to make the active cathode material adhere to the current collector. Instead, the active anode material is generally made up of lithiated graphite to which the binder, generally carboxymethylcellulose (CMC), is added, the purpose of which is to make the active anode material adhere to the current collector. The different components of the battery are divided in terms of percentage by weight (w / w %): plastic or steel casing (25%), active cathode material (27%), active anode material (17%), current collectors (i.e. aluminium and copper foils) (13%), electrolyte solution, generally consisting of solutions of LiPFe, LiBF4, LiCICU, LiSo2 dissolved in dimethylcarbonate, propylene carbonate, ethylene carbonate or dimethylsulfoxide (10%), separator (4%) and binder (4%) (as reported, for example, by Velasquez-Martinez O. et al. in “Batteries” (2019), 5, 68, doi: 10.3390 / batteries5040068).

[0014] The mechanism of action of lithium-ion batteries is based on the intercalation of lithium (Li): in fact, both the anode and the cathode are made up of structures that allow the crossing of the positive lithium ions (Li+) to pass through, which can diffuse within the electrolyte solution. For this reason, there will be an intercalation of positive lithium ions (Li+) from the anode to the cathode during discharge and vice versa during charging.

[0015] Several technologies have been developed in order to recycle raw materials from End-Of-Life (EOL) lithium-ion batteries.

[0016] The main recycling technologies known to date are processes aimed at extracting metals such as pyrometallurgical and hydrometallurgical processes, and “direct recycling”.

[0017] In the pyrometallurgical process, lithium-ion batteries can be directly subjected to said process, or they can be first mechanically treated to achieve the so-called “black mass” which will then be subjected to said process. The pyrometallurgical process generally consists of pyrolysis with an initial temperature ramp between 150°C and 500°C, in which electrolyte compounds and organic solvents are removed. A high- temperature process up to 1450°C is then carried out in the furnace in the presence of chemical agents (for example, graphite, coke, NaHSCU, CaCE or NH4CI) to produce metal alloys containing critical metals such as, for example, cobalt (Co), copper (Cu) and nickel (Ni), which can be subjected to separation and purification processes in order to recover said metals individually. By contrast, lithium (Li), manganese (Mn), and aluminium (Al) end up in a slag and are not therefore recovered. The pyrometallurgical process is a well-established technology, but it is energy-expensive because it is carried out at high temperatures and it is environmentally harmful because it produces toxic gases that require an adequate abatement system affecting plant and process costs, and it does not allow the recovery of lithium (Li) which can only be recovered through additional costly processes (as reported, for example, by Doose S. et al. in “Metals” (2021), 11, 291, doi.org / 10.3390 / metl 1020291).

[0018] The hydrometallurgical process is widely used to recover cathode metals and lithium by leaching. Said process must be preceded by a mechanical pre-treatment in order to achieve the so-called “black mass”. After separation of impurities such as copper, aluminium and plastic, the metal-enriched phase (mainly rich in Li, Co, Ni, Mn) is generally subjected to the following phases:

[0019] 1) leaching for the solubilisation of cathode and anode metals in presence of strong inorganic acids (for example, sulfuric acid, hydrochloric acid, nitric acid) and reducing agents (for example, hydrogen peroxide);

[0020] 2) purification of the leaching solution with removal of impurities (for example, Fe(III),

[0021] Cu(II), Al) and selective recovery of valuable metals (for example, Co, Ni, Mn, Li) by chemical precipitation or by solvent extraction.

[0022] Chemical precipitation allows metals to be recovered selectively by varying the pH by adding suitable bases or by promoting the formation of complexes by adding particular binders. Solvent extraction, depending on the solvent used, allows a metal compound to be extracted selectively, which can then be isolated by precipitation or distillation. For example, lithium can be recovered in the form of Li2COs by extraction with supercritical CO2, which constitutes the extraction solvent.

[0023] Said hydrometallurgical process is used in several large plants in China and Korea. Further details regarding the hydrometallurgical process can be found, for example, in Gaines L. et al., “Recycling (2021) 6, 31, doi.org / 10.3390 / recycling6020031; Duan X. et al., “Energies” (2022), 15, 1611, doi.org / 10.3390 / enl5051611. The hydrometallurgical process is carried out at a low temperature with less energy consumption, but with high consumption of chemical reagents and acid waste to be disposed.

[0024] It is also known that many studies have been carried out in relation to the hydrometallurgical process, with the aim of making said process more sustainable.

[0025] For example, strong mineral acids, initially used in the hydrometallurgical process, can be replaced by organic acids such as citric acid (as reported for example by Li L. et al., in “Journal of hazardous Materials’" (2010), Vol. 176, issue 1-3, page 288- 293), or with tartaric acid or malic acid, which are often used in conjunction with reducing agents such as glucose, or ascorbic acid. Said organic acids can also be produced in situ by microorganisms such as the Aspergillus niger fungus (bioleaching technology).

[0026] Recently, the direct recycling process has taken on more importance, defining a mechanism for recovering the materials that constitute the battery by separating the individual components. The aim is to recover the cathode and / or anode material by restoring its chemical and crystalline structure and allow it to be used directly in new batteries.

[0027] In general, the direct recycling process involves the disassembling of end-of-life batteries after discharge, the manual separation of the electrodes (i.e. cathode and anode) in order to prevent impurities such as, for example, iron, copper and aluminium during their crushing and sieving and, subsequently, their treatment in order to remove the electrolytes, which can also be recycled. Primarily, electrolyte removal can be accomplished by extraction with supercritical carbon dioxide (CO2) (as described, for example, in Sloop S. et al., “Sustainable Materials and Technologies’" (2020), Vol. 25, e00152). The cathode, deprived of the electrolyte, consists of a current collector, usually aluminium foil having a thickness equal to approximately 0.1 mm, coated with the cathode material comprising active cathode material, optionally conductive material (for example, acetylene carbon black, carbon black) and organic binder [for example, polyvinylidene fluoride (PVDF)]. One challenge of the above-mentioned direct recycling process is to separate said cathode material from the current collector, in particular due to the presence of the organic binder [for example, polyvinylidene fluoride (PVDF)]. For this purpose, the main technologies include thermal decomposition of the organic binder [for example, polyvinylidene fluoride (PVDF)], or its dissolution in organic solvents. The direct recycling process has a lower technological maturity than the pyrometallurgical and hydrometallurgical processes, requires presorting of batteries with the same chemistry (LCO, NMC, LMO, NCA or LFP) and a regeneration stage of the active cathode material with re-lithiation to compensate for the loss of lithium that occurs during battery use.

[0028] Generally, the recycling process of lithium-ion batteries is anticipated by a series of preparatory steps such as: battery sorting: selection of the batteries to be treated according to the different chemical compositions of the cathode and anode electrode material and their dimensions and configurations (for example, cylindrical, prismatic or pouch); battery discharge: in the recycling process, any residual charge in the spent batteries may lead to short circuits, overheating and consequent development of flames; proper discharge allows safe progress and can be achieved by immersion in aqueous saline solution (for example, aqueous solutions of sodium chloride, iron sulphate, manganese sulphate), cryogenic deactivation (for example, treatments in liquid nitrogen in a temperature range of from -175°C to -200°C, typical of the following companies Umicore, Toxco and Eco Recycling); or by thermal deactivation (for example, vacuum treatments up to 250°C resulting in evaporation of the electrolyte solution, typical of Accurec company); or by ohmic discharge using electronic loads for controlled current discharge; battery disassembly: sorting of different components including electrodes (i.e. anode and cathode), separator, casing and the battery management system (BMS); pre-treatment with the aim of making active electrode material, both cathode and anode, more accessible by separating it from the respective current collectors (copper for the anode and aluminium for the cathode) and from the separator, the so-called pre-treatment being implemented mainly by mechanical, thermal or chemical means; recovery of metals, as above-mentioned, by pyrometallurgical, hydrometallurgical, direct recycling processes.

[0029] More information regarding the above-mentioned treatments can be found, for example, in Zheng Z. et al., in “Engineering" (2018), Vol. 4, pag. 361-370; Harper G. et al., in “Nature" (2019), Vol. 575, pag. 75-86; Zheng F. et al., in “Journal of Cleaner Production" (2022), Vol. 359, 132116, doi.org / 10.1016 / j.j.clepro.2022.132116.

[0030] Specifically, the pre-treatment is one of the crucial aspects affecting, in particular, hydrometallurgical and direct recycling processes. The purpose of said pre-treatment is to remove materials such as plastics, aluminium, copper, not directly involved in the subsequent recycling process, in order to maximise the extraction efficiency of the metals of interest.

[0031] For example, in order to delaminate cathode materials from current collectors, it is necessary to inhibit the action of the binder for example, polyvinylidene fluoride (PVDF), which is a chemically very resistant fluoropolymer capable of operating at high temperatures (up to 150°C). Below some detailed examples of pre-treatments for the above purpose are reported: mechanical pre-treatments, which are the most common and established at industrial level; after disassembly, batteries undergo shredding and physical separation processes that exploit the variations of certain properties such as, for example, particle size, density, ferromagnetism, hydrophobicity; said pretreatments may include, for example, magnetic casing separation, separation of non-magnetic fractions (for example, aluminium, copper) from plastics, sieving, Eddy currents use, flotation, with a view to achieving the so-called “black mass” comprising enriched powders of active cathode and / or anode materials which are subsequently recovered through different recycling technologies; thermal pre-treatments that operate at high temperatures (400°C to 600°C) such as to inhibit the action of the binder with consequent loss of adhesion between the electrode material and the current collector; in the case of poly vinylidene fluoride (PVDF), it is decomposed and the C-F bond breaks down with the formation of hydrofluoric acid (HF); the separation between the cathode material and the current collector is subsequently performed by grinding or flotation; chemical pre-treatments using 10% by weight sodium hydroxide (NaOH) solutions for 5 hours, at room temperature (25°C), to dissolve the aluminium current collector to form Na Al Ch and NaAl(OH)+; although this method requires relatively simple preparation, it is hampered by difficult recovery of the aluminium due to its presence in ionic form within the solution; alternatively, polyvinylidene fluoride (PVDF) can be dissolved in an aprotic solvent such as, for example, 7V,7V-dimethylformamide (DMF), 7V-methyl-2-pyrrolidone (NMP) or YA -di methyl acetamide (DMAC), however, said solvents have a significant permanent dipole moment and do not easily act as proton donors, their reactivity is limited (as reported, for example, by Marshall J. E. et al., in " olymers" (2021), 13, 1354, doi.org / 10.3390 / polyml3091354); the action of these solvents can be improved by the use of ultrasound (as reported, for example, by He L. P. et al., in “Waste Management” (2015), Vol. 46, pag. 523-528);

[0032] In chemical pre-treatments, one class of potentially effective compounds are glycols.

[0033] The use of pure ethylene glycol, without any additives added, to effectively separate the cathode material from the respective aluminium (Al) current collector with a view to a direct recycling process has been described, for example by Bay Y. et al., in “ChemSusChem” (2020), Vol. 13, pag. 5664-5670. According to the authors, ethylene glycol is able to counteract the binder action by means of a competitive inhibition mechanism of the hydrogen bonds. Specifically, since poly vinylidene fluoride (PVDF) forms hydrogen bonds with the aluminium oxide (AhOn) of the current collector, ethylene glycol would “undermine” the binder, establishing hydrogen bonds with the current collector itself, by promoting the detachment of the cathode material (specifically, an active cathode material based on nickel, manganese and carbon (NMC)).

[0034] Patent application US 2021 / 0257685 concerns a method for recycling lithium-ion batteries comprising:

[0035] (a) isolating a composite electrode from a spent lithium-ion battery, said composite electrode comprising an electrode material adhered to a current collector with a polyvinylidene fluoride (PVDF) as a binder;

[0036] (b) placing the composite electrode in contact with at least one fluid polyol capable of releasing polyvinylidene fluoride (PVDF) from the current collector, thus forming a mixture; (c) delaminating the electrode material from the current collector obtaining a free electrode material and a free current collector;

[0037] (d) recovering the free electrode material and the free current collector.

[0038] The fluid polyol can be a glycol, glycerol or a mixture thereof. In case of ethylene glycol, complete delamination of the electrode material from the current collector is reported at a temperature comprised between 160°C and 198°C, in a time comprised between 2 seconds and 120 seconds. The above-mentioned method is said to be able to preserve the morphology of the electrode material which can then be reused in lithium- ion batteries.

[0039] Rose S. et al., in “ Advanced Energy & Sustainability Research" (2021), 2, 2100040, doi: 10.100 l / aesr.202100040, describe the use of ethylene glycol as an alternative to 7V-methyl-2-pyrrolidone (NMP) in the pre-treatment of a leaching process. In particular, under the same operating conditions, the authors noted an increase in the efficiency of metal recovery if pre-treatment is performed with ethylene glycol instead of 7V-methyl-2-pyrrolidone (NMP). The authors argue that ethylene glycol is a reducing agent and that even in the pre-treatment step, a partial reduction of metals is outlined, thus improving the subsequent leaching process.

[0040] Gu K. et al., in ".Journal of Cleaner production" (2022), 369, 133270, doi.org / 10.1016 / j.clepro.2022.133270, describe a hot glycerol delamination process. In particular, the authors studied the influence of the different experimental parameters (i.e. treatment time, temperature and mixing rate) on the delamination efficiency of the cathode material (specifically, an active cathode material based on nickel, manganese, cobalt (NMC)). The optimal process conditions are: target temperature of200°C, mixing speed of 350 r / min and treatment time of 15 minutes.

[0041] However, in particular from an industrial application point of view, said pretreatments may present challenges which involve, in part, the hazard of the reagents used and / or the reaction products they generate. For example: dissolution of the cathode material in sodium hydroxide (NaOH) may cause eye irritation and skin burns (hazard statement H314); in addition, said pre-treatment results in complicated management of alkaline waste water that is particularly harmful to the environment and, as one of the main reaction products is hydrogen, due care must be taken to avoid explosions; dissolution of polyvinylidene fluoride (PVDF) in aprotic solvents such as, for example, -di methyl form am ide (DMF), V-methyl-2-pyrrolidone (NMP), N,N- dimethylacetamide (DMAC), which are particularly toxic reagents, can cause environmental and operator problems; in fact, DMF, NMP and DMAC have the H360D hazard statement, which indicates possible foetal toxicity; further, in the case of DMF and DMAC, additional warnings can be identified such as, for example, hazard statements H312+H332 (toxicity in contact with skin or if inhaled) or H319 (eye irritation), NMP instead may cause respiratory irritation (hazard statement H335); thermal treatment at a high temperature, i.e. 500°C to 600°C, in order to inhibit the action of polyvinylidene fluoride (PVDF), causes evaporation and decomposition of both polyvinylidene fluoride (PVDF) and electrolyte salt (for example, LiPFe or IJBF4), leading to the formation of hydrofluoric acid (HF) in the form of a gas; for this reason, specific abatement systems of said gas are necessary, as it is fatal if ingested (hazard statement H300), in contact with skin (hazard statement H310) or if inhaled (hazard statement H330); other harmful substances that can be produced are dioxins, lithium fluoride (LiF), cobalt difluoride (C0F2) and carbon monoxide (CO); in addition, at temperatures above 600°C, the aluminium foils become brittle, making it difficult to detach the cathode material from the current collector.

[0042] Additional concerns may relate to the type of reagents used in the extraction of critical metals in hydrometallurgical processes: in fact, a typical couple of reagents used in hydrometallurgical processes is represented by sulfuric acid (H2SO4) as a leaching agent and hydrogen peroxide (H2O2) as a reducing agent.

[0043] In order to overcome these concerns, studies have been carried out in relation to the use of organic acids (for example, citric acid, malic acid, tartaric acid, oxalic acid, as an alternative to the usual inorganic acids (for example, sulfuric acid (H2SO4), hydrochloric acid (HC1), nitric acid (HNO3)), thus avoiding the formation of harmful gases (e.g., SOX, NOX, C1OX) (as reported, for example, by Meshram p. et al., in "Chemosphere" (2020), 242, 125291, doi.org / 10.1016 / J.chemosphere.2019.125291). Further studies have been carried out in relation to the use of glycols, as a green alternative, as reducing agents, as an alternative to hydrogen peroxide (H2O2) a harmful substance when ingested (H302 hazard statement) or inhaled (H332 hazard statement) and which can cause skin burns and eye damage (hazard statement H314) as reported, for example, by Zeng G. and others, in “ACS Sustainable Chemistry & Engineering" (2021), Vol. 9, pag. 16133-16142. The authors report the use of a solution of ethylene glycol and citric acid (EG-C A) in order to separate the cathode material from the current collector and to exploit the effect of the esters produced as corrosion inhibitors.

[0044] However, significant challenges still remain in relation to the initial separation of the cathode materials from the current collectors in order to recover reusable components from them in a cost-effective and environmentally friendly way.

[0045] The applicant thus set out to solve the problem of finding a new process for recovering cathode material from lithium-ion batteries.

[0046] The applicant has now found a process for recovering cathode material from lithium-ion batteries which is carried out in the presence of at least one glycol and ultrasound, operating under specific power, temperature, and time conditions. The above-mentioned process allows the cathode material to be effectively recovered from the current collector while operating at temperatures below binder decomposition temperatures with a reduced risk of producing toxic gases by binder or electrolyte salt decomposition. In addition, the above-mentioned process allows a cathode material to be obtained from which, after appropriate treatment, it is possible to obtain a restored active cathode material (for example, by direct recycling process), or synthetic precursors which can be used in the regeneration of said active cathode material (for example, by hydrometallurgical process), which can in turn be used in lithium-ion batteries.

[0047] In addition, the use of glycols, compared to other reagents used in pre-treatments, has many advantages as they are green and ecological, biodegradable, economical, easily available and recyclable.

[0048] The object of the present invention is therefore a process for recovering cathode material from lithium-ion batteries comprising the following stages:

[0049] (a) isolating a cathode from a lithium-ion battery, said cathode comprising a cathode material comprising at least one active cathode material, at least one binder and, optionally, at least one conductive material, and a current collector, said cathode material adhered to said current collector via said at least one binder;

[0050] (b) contacting the cathode with at least one glycol;

[0051] (c) delaminating the cathode material from the current collector obtaining a mixture comprising a suspension of said cathode material dispersed in a liquid phase comprising said at least one glycol and a current collector immersed in said suspension;

[0052] (d) recovering the cathode material and the current collector from said mixture; characterized in that said stage (c) is carried out in the presence of ultrasounds at a power comprised between 30 Watt and 500 Watt, preferably comprised between 50 Watt and 300 Watt, at a temperature comprised between 80°C and 280°C, preferably comprised between 85°C and 260°C, for a time comprised between 15 minutes and 24 hours, preferably comprised between 30 minutes and 20 hours.

[0053] For the purpose of the present description and the following claims, the definitions of the numeric ranges always include the extremes unless specified otherwise.

[0054] For the purpose of the present description and the following claims, the term “comprising” also includes the terms “which essentially consists of’ or “which consists of’.

[0055] The process according with the present invention is applicable to various types of lithium-ion batteries, regardless of their internal chemistry and the physical size of the batteries themselves.

[0056] According to a preferred embodiment of the present invention, said active cathode material comprises at least one lithium-containing metal oxide which can be selected, for example, from: lithium manganese oxide (LMO), lithium nickel oxide (LNO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), or mixtures thereof; mixed oxides of lithium, manganese, cobalt, nickel, aluminium, preferably selected from those having the following general formulas: LiNixMny02, Lii+zNixMnyCoi-x-yCh, LiNixCoyAlzCh, LiNixCoyMnzO2, wherein each x, y and z is typically a mole fraction comprised between 0 and 1, wherein x+y+z=l, or mixtures thereof; or mixtures thereof.

[0057] According to a preferred embodiment of the present invention, said binder can be selected, for example, from: polyvinylidene fluoride (PVDF) homopolymer, copolymers or interpolymers of polyvinylidene fluoride (PVDF) with one or more other monomers, polytetrafluoroethylene, fluorinated ethylene-propylene copolymers (for example, tetrafluoroethylene and / or hexafluoropropylene), per- or polyfluoroalkoxy polymers, or mixtures thereof; preferably polyvinylidene fluoride (PVDF) homopolymer.

[0058] Said cathode material can, for the purpose of improving its electronic conductivity, optionally comprise a conductive material.

[0059] According to a further preferred embodiment of the present invention, said conductive material can be selected, for example, from acetylene carbon black, carbon black, preferably carbon black.

[0060] For the purpose of the present invention the current collector can be in any form known in art such as, for example, sheet, foil. Said collector can be of any thickness suitable for current transport, but generally a minimum thickness will be selected in order to maximize energy density.

[0061] According to a preferred embodiment of the present invention, said current collector is an aluminium foil.

[0062] Stage (a) of isolating the cathode from a lithium-ion battery can be carried out through processes known in the art. For example, the process generally comprises discharging the lithium-ion battery before further processing, i.e. to remove any residual charge stored in the battery. Preferably, before undergoing this stage (a), the lithium-ion battery is fully discharged.

[0063] The discharge of the lithium-ion battery can be carried out using techniques known in the art, for example, by immersing the battery in an aqueous solution (for example, neutral or alkaline) containing a conducting salt (for example, NaHCCh, KHCO3, Na2CO3, K2CO3, CaCO3, MgCO3, NaOH, KOH, Ca(OH)2, Mg(OH)2, NaCl, CaCl2, and the like, or mixtures thereof). Alternatively, the discharge of the lithium-ion battery can be carried out using electronic loads for controlled current discharge.

[0064] In some embodiments, the casing of the lithium-ion battery can be drilled (for example, by perforating, cutting, etc.) before immersion in the aqueous solution for discharge. Generally, battery discharge is carried out at temperatures not exceeding 60°C.

[0065] After discharge of the lithium-ion battery, isolating the electrodes (cathode and anode) generally includes dismantling the battery and separating the electrode (cathode and anode) from the other battery components, such as separator, casing, electrolyte and battery management system (BMS).

[0066] The isolation process can be carried out in different ways with any technique known in the art. For example, isolation techniques will typically be selected considering the purpose of not damaging, destroying or otherwise rendering the electrodes less usable than they were before isolation.

[0067] In some embodiments, the spent lithium-ion battery can be shredded, cut or ground into smaller pieces (for example, by saw / blade cutting manually or computer-monitored, waterjet cutting, etc.). The obtained parts can be sized for homogeneity, greater surface area, processing capacity of the particular equipment used, etc.

[0068] In some embodiments, the electrode isolation process further comprises washing the electrodes. In said embodiments, the electrodes are typically washed with an organic solvent that is not reactive with the electrodes and is also able to remove any residual electrolyte from said electrodes.

[0069] According to a preferred embodiment of the present invention, the cathode can be washed before stage (b) with an organic solvent such as, for example, acetone, dimethylcarbonate, 2-butanone, preferably acetone, at room temperature (25°C), in an ultrasonic bath, for a time comprised between 10 minutes and 2 hours, preferably comprised between 20 minutes and 1 hour.

[0070] Preferably, said ultrasonic bath has a minimum power comprised between 50 Watts and 100 Watts.

[0071] After washing, the cathode is dried to remove any traces of solvent. Preferably, drying can be carried out at a temperature comprised between 50°C and 130°C, preferably comprised between 70°C and 120°C, for a time comprised between 1 hour and 5 hours, preferably comprised between 1.5 hours and 4 hours.

[0072] According to a preferred embodiment of the present invention, said glycol can be selected, for example, from: ethylene glycol, 1,2-butanediol, 1,3 -butanediol, 1,4- butanediol, 1,2-propanediol, 1,3 -propanediol, dipropylene glycol, glycerol, or mixtures thereof; preferably 1,3 -propanediol, 1,2-propanediol.

[0073] According to a preferred embodiment of the present invention, said stage (b) can be carried out at a cathode / glycol weight ratio comprised between 1 :5 and 1 : 150, preferably comprised between 1 : 10 and 1 : 140.

[0074] According to a preferred embodiment of the present invention, in said stage (b) the glycol, before being contacted with the cathode, can be heated to a temperature comprised between 80°C and 280°C, preferably comprised between 85°C and 260°C.

[0075] According to a preferred embodiment of the present invention, at said stage (c) the ultrasounds can be applied at different time intervals, preferably for a time comprised between 5 seconds and 60 seconds, preferably comprised between 10 seconds and 40 seconds, at time intervals comprised between 5 minutes and 60 minutes, preferably comprised between 8 minutes and 40 minutes.

[0076] The mixture obtained in stage (c) comprises a suspension of the cathode material dispersed in a liquid phase comprising glycol and a current collector (i.e. aluminium foil) immersed in said suspension. Any cathode material that has remained adhered to the current collector can be recovered as shown below in stage (d2) and optionally in stage (ds).

[0077] According to a preferred embodiment of the present invention, said stage (d) comprises the following stages:

[0078] (di) letting the mixture obtained in stage (c) to cool to room temperature (25°C) and subjecting it to sieving obtaining:

[0079] (i) a suspension of the cathode material dispersed in a liquid phase comprising glycol; and

[0080] (ii) a clean or partially clean current collector; and subjecting the suspension of the cathode material dispersed in a liquid phase comprising glycol to filtration under vacuum, washing the filtrate obtained with at least one organic solvent selected, for example, from acetone, dimethylcarbonate, 2-butanone, preferably acetone, obtaining a first cathode material, subjecting said first cathode material to drying, preferably, in an oven, at a temperature comprised between 50°C and 130°C, preferably comprised between 70°C and 120°C, for a time comprised between 1 hour and 5 hours, preferably comprised between 1.5 hours and 4 hours;

[0081] (d2) immersing the current collector obtained in stage (di) in an ultrasonic bath, in the presence of at least one organic solvent selected, for example, from acetone, dimethyl carbonate, 2-butanone, preferably acetone, obtaining a second cathode material and a clean or partially clean current collector, recovering said second cathode material through filtration under vacuum and subjecting it to drying, preferably, in an oven, at a temperature comprised between 50°C and 130°C, preferably comprised between 70°C and 120°C, for a time comprised between 1 hour and 5 hours, preferably comprised between 1.5 hours and 4 hours;

[0082] (ds) optionally, treating the current collector recovered in stage (d2) in an organic solvent selected, for example, from 7V,7V-dimethylformamide, N- methylpyrrolidone, dimethylsulfoxide, dipropylene glycol, preferably dipropylene glycol, at a temperature comprised between 100°C and 250°C, preferably comprised between 120°C and 245°C, for a time comprised between 30 minutes and 5 hours, preferably comprised between 1 hour and 4 hours, obtaining a third cathode material and a clean current collector, recovering said third cathode material through filtration under vacuum and subjecting it to drying, preferably, in an oven, at a temperature comprised between 50°C and 130°C, preferably comprised between 70°C and 120°C, for a time comprised between 1.5 and 5 hours, preferably comprised between 2 hours and 4 hours.

[0083] For the purposes of the present description and the following claims, “clean or partially clean current collector” means a current collector free of residual cathode material or a current collector in which residual cathode material is present, respectively.

[0084] Preferably, in stage (d2), said ultrasonic bath has a minimum power comprised between 50 Watt and 100 Watt.

[0085] At the end of stage (d), the first cathode material recovered in stage (di) and the second cathode material recovered in stage (d2) are joined and subjected to the following analyses. However, any third cathode material recovered at stage (ds) is only taken into account for the yield calculation. As mentioned above, from the cathode material recovered through the above process, after appropriate treatment, it is possible to obtain a restored active cathode material (for example, by direct recycling process), or synthetic precursors that can be used in the regeneration of said active cathode material (for example, by hydrometallurgical process), which can, in turn, be used in lithium-ion batteries.

[0086] For the purpose of understanding the present invention better and to put it into practice, below reported are some illustrative and non-limiting examples thereof.

[0087] The analysis and characterization methodologies reported below were used.

[0088] X-ray diffraction

[0089] For this purpose, samples of the cathode materials (approximately 1.5 g) obtained in the examples below reported were analysed using the D5000 “X-Ray Powder Diffraction (XRD) System” (Siemens) difractometer: the obtained spectra were examined using the diffract. suite EVA software and the crystalline structures were identified using the PDF-2 Release 2019 RDB database.

[0090] For comparative purposes, the starting cathode materials were also analysed for any changes in the crystalline structure of the cathode material. For that purpose, samples of the starting cathodes were prepared by removing with a spatula approximately 1.5 g of the surface cathode material, taking care not to contaminate it with the aluminium of the current collector.

[0091] Scanning Electron Microscopy (SEMI

[0092] For this purpose, samples of the cathode materials (approximately 0.5 g) obtained in the examples below reported were analysed by scanning electron microscopy (SEM) using the FESEM Inspect F50 (Thermofisher) instrument.

[0093] For comparison purposes, the starting cathodes were also analysed for any changes in the crystalline structure of the cathode material. For this purpose, samples of the starting cathodes with dimensions of 1.5 x 1.5 cm were prepared.

[0094] Attenuated Total Reflectance (ATR) Infrared Spectroscopy

[0095] In order to confirm the nature of the binder, a sample taken from the starting cathode of Example 1 was characterised by Perkin Elmer Spectrum One FT-IR spectrophotometer equipped with an ATR Diamond / ZnSe accessory with a resolution of 2 cm’1. When indicated that a compound has a peak in its infrared spectrum at a given value, it typically means that the peak is comprised between ± 2 cm’1.

[0096] The above-mentioned sample was obtained by immersing the starting cathode in 7V,7V-dimethylformamide, at 140°C, for 2.5 hours. Subsequently, the obtained solution was left to cool to room temperature (25°C) and filtered under vacuum, yielding a filtrate which was concentrated to obtain the binder which was subjected to spectroscopic analysis by means of the above spectrophotometer.

[0097] A standard sample of polyvinylidene fluoride (PVDF) (pellet - Aldrich) as such was analysed for comparison purposes.

[0098] The obtained spectra have been shown in Figure 5 where peaks not superimposable at 1663 cm’1and 2929 cm’1relate to VA-di methyl form amide used to solubilise the cathode binder.

[0099] The most identifying peaks a of the binder (PVDF) are at 763 cm’1(-CF2 bending) and 1172 cm’1(-CF2 symmetrical stretching).

[0100] EXAMPLES 1-2

[0101] A lithium-ion battery (LG BL-45F1F, Typ 2500mAh / 9.6WHr, Yantai Electronics Inc.) was discharged using the IMAX-B6AC V2 device (charger / discharger). When the cell potential was close to 0 the battery was considered discharged.

[0102] Subsequently, the battery was manually disassembled into the various components: electrodes (i.e. cathode and anode), separator, casing, electrolyte and control device (Battery Management System - BMS).

[0103] The small volume of electrolyte (a few ml) adsorbed on the surface of the cathode was removed by immersing the latter in acetone, in an ultrasonic bath, at room temperature (25°C), for about 30 minutes, the cathode was then isolated and dried in an oven, at 80°C, for 2 hours, in order to remove any traces of acetone.

[0104] The cathode obtained had the following crystalline structure: LiM CU

[0105] The cathodes of the examples were obtained by operating as described above.

[0106] 1,3-propanediol (Merck) (Example 1) or 1 ,2-propanediol (Merck) (Example 2) were placed in a 1 litre three-neck flask fitted with a bubble condenser: the free volume of the flask above the solution was inertised by maintaining a constant flow of nitrogen entering the flask exiting through the bubble condenser. A heating mantle was applied to the flask (Universal mod. 133) to reach the set-point temperature. Subsequently, a bubble condenser, cooled by the use of a Huber K20 cooling circulator, was applied over the flask to prevent evaporation of glycol. A thermocouple was used to monitor the temperature inside the flask, and when the desired temperature was reached (shown in Table 1), the cathode obtained as described above and previously weighed, was added, and ultrasound was applied using a QSONICA Q700 sonicator, with a power setting of 150 watts. Sonication was carried out by inserting the probe into the flask, from above, almost touching the bottom of the flask and returning upwards, for 30 seconds, every 30 minutes, for the time shown in Table 1.

[0107] At the end of the treatment [stage (c)], a mixture was obtained comprising a suspension of said cathode material dispersed in a liquid phase comprising said at least one glycol and a partially clean current collector (i.e. aluminium foil) immersed in said suspension.

[0108] The mixture obtained in stage (c) was left to cool to room temperature (25°C) and sieved to obtain: (i) a suspension of the cathode material dispersed in a liquid phase comprising the glycol and (ii) a partially clean current collector (i.e. aluminium foil) [stage (di)].

[0109] The suspension of the cathode material dispersed in a liquid phase comprising the glycol obtained in stage (di), was filtered under vacuum and the filtrate obtained was washed with acetone (100 ml) (Merck) and dried in an oven, at 80°C, for 3 hours, obtaining the first cathode material [stage (di)].

[0110] The current collector (i.e. aluminium foil) obtained in stage (di), was immersed in an ultrasonic bath, for about 30 minutes, in the presence of acetone (150 ml) (Merck) to facilitate the removal of the cathode material still adhered to the current collector (i.e. aluminium foil) obtaining a second cathode material and a clean current collector [stage (d2)] (Example 1). The second cathode material was recovered through filtration under vacuum, dried in an oven, at 80°C, for 3 hours, obtaining the second cathode material which was combined with the first dried cathode material obtained as described above.

[0111] In the case of Example 2, the current collector (i.e. aluminium foil) recovered in stage (d2) was treated with dipropylene glycol (Merck) (200 ml), at 243 °C, for 2 hours, obtaining a third cathode material and a clean current collector (i.e. aluminium foil) [stage (ds)]. The third cathode material was recovered through filtration under vacuum, drying in an oven at 80°C for 3 hours, obtaining the third cathode material that was taken into account in the yield calculation.

[0112] The cathode material obtained as described above (i.e. from stage (di) and stage (d2)] and the starting cathode material were analysed by X-ray diffraction and scanning electron microscopy (SEM) operating as described above. The data obtained are reported in:

[0113] Figure 1 : XRD spectrum of the starting cathode material;

[0114] Figure 2: XRD spectrum of the cathode material obtained in Example 1;

[0115] Figure 3: XRD spectrum of the cathode material obtained in Example 2;

[0116] Figure 4:

[0117] SEM images of the starting cathode material of Example 1 and Example 2 shown on the left and indicated by a) and b) respectively;

[0118] SEM images of the cathode material obtained in Example 1 and Example 2 shown on the right and indicated by letters c) and d) respectively.

[0119] Figures 1-3 show that the recovered cathode material comprises two main phases: LiM CU and MmCh supporting the fact that part of the starting material is not altered, while a certain percentage of the starting material has been converted to hausmannite (MmCU), i.e. in one of the main degradation products by distortion of the crystalline structure and loss of lithium from the structure.

[0120] Figure 4 shows that there are no morphological variations in the cathode material particles as a result of the action of the glycols. In addition, it can be observed that in the starting cathode material the binder is uniformly deposited at surface level [SEM images shown on the left and indicated by letters a) and b)], however, as a result of the heat treatment and the corresponding phase transitions, it tends to concentrate in certain areas [SEM image shown on the right and indicated by letter d)], leaving others impoverished [SEM image shown on the right and indicated by letter c)].

[0121] Table 1 shows in order: the example number (Example), the glycol used (Glycol), the time expresses in hours (h) and the temperature expressed in degrees centigrade (°C) (Experimental conditions), the amount of glycol used expressed in grams [Glycol weight (g)], the initial weight of the cathode (i.e. the weight of the starting cathode) expressed in grams (Initial foil weight TQ (g)], the cathode / glycol ratio (i.e. the starting cathode) (Ratio g / g), the weight of the current collector (i.e. the weight of the aluminium foil) obtained in [stage (d2)] in grams [Al foil weight1(g)], the weight of the current collector (i.e. the weight of the aluminium foil) obtained in [stage (ds)] expressed in grams [Al foil weight2(g)], the yield expressed in % [Yield (%)] calculated according to the following formula:

[0122] (Net weiqht of cathodic material x 100) Yield (%) = 100 - -J— - - - — - - —f

[0123] (T otal net weight of cathodic material) wherein:

[0124] Total net weight of cathode material = initial weight of current collector TQ - weight of current collector after stage (ds), - Net weight of cathode material = weight of current collector after stage (ds) - weight of current collector after stage (ds).

[0125] In Figure 6 and Figure 7 (Example = Example), the recovered current collectors (i.e. aluminium foils) are shown: as can be seen the foils are clean.

[0126]

[0127] Table 1

[0128] *: stage (ds) was not carried out as the current collector (i.e. the aluminium foil) was found to be clean and the yield was considered to be 100%.

Claims

CLAIMS1. Process for recovering cathode material from lithium ion batteries comprising the following stages:(a) isolating a cathode from a lithium-ion battery, said cathode comprising a cathode material comprising at least one active cathode material, at least one binder and, optionally, at least one conductive material, and a current collector, said cathode material adhered to said current collector via said at least one binder;(b) contacting the cathode with at least one glycol;(c) delaminating the cathode material from the current collector obtaining a mixture comprising a suspension of said cathode material dispersed in a liquid phase comprising said at least one glycol and a current collector immersed in said suspension;(d) recovering the cathode material and the current collector from said mixture; characterized in that said stage (c) is carried out in the presence of ultrasounds at a power comprised between 30 Watt and 500 Watt, preferably comprised between 50 Watt and 300 Watt, at a temperature comprised between 80°C and 280°C, preferably comprised between 85°C and 260°C, for a time comprised between 15 minutes and 24 hours, preferably comprised between 30 minutes and 20 hours.

2. Process for recovering cathode material from lithium-ion batteries according to claim 1, wherein said active cathode material comprises at least one lithium-containing metal oxide selected from: lithium manganese oxide (LMO), lithium nickel oxide (LNO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), or mixtures thereof; mixed oxides of lithium, manganese, cobalt, nickel, aluminium, preferably selected from those having the following general formulas: LiNixMny02, Lii+zNixMnyCoi-x-yCh, LiNixCoyAlzCh, LiNixCoyMnzO2, wherein each x, y and z is typically a mole fraction comprised between 0 and 1, where x+y+z=l, or mixtures thereof; or mixtures thereof.

3. Process for recovering cathode material from lithium ion batteries according to claim 1 or 2, wherein said binder is selected from: poly vinylidene fluoride (PVDF)homopolymer, copolymers or interpolymers of polyvinylidene fluoride (PVDF) with one or more other monomers, polytetrafluoroethylene, fluorinated ethylene-propylene copolymers (such as tetrafluoroethylene and / or hexafluoropropylene), per- or polyfluoroalkoxy polymers, or mixtures thereof; preferably polyvinylidene fluoride (PVDF) homopolymer.

4. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein said conductive material is selected from acetylene carbon black, carbon black, preferably carbon black.

5. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein said current collector is an aluminium foil.

6. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein the cathode, before stage (b) is washed with an organic solvent such as acetone, dimethylcarbonate, 2-butanone, preferably acetone, at room temperature (25°C), in an ultrasonic bath, for a time comprised between 10 minutes and 2 hours, preferably comprised between 20 minutes and 1 hour.

7. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein said glycol is selected from: ethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-propanediol, 1,3-propanediol, dipropylene glycol, glycerol, or mixtures thereof; preferably 1,3-propanediol, 1,2- propanediol.

8. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein said stage (b) is carried out at a cathode / glycol weight ratio comprised between 1 :5 and 1 : 150, preferably comprised between 1 : 10 and 1 : 140.

9. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein in said stage (b) the glycol, before being contacted with the cathode, is heated to a temperature comprised between 80°C and 280°C, preferably comprised between 85°C and 260°C.

10. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein in said stage (c) the ultrasounds are applied at different time intervals, preferably they are applied for a time comprised between 5seconds and 60 seconds, preferably comprised between 10 seconds and 40 seconds, at time intervals comprised between 5 minutes and 60 minutes, preferably comprised between 8 minutes and 40 minutes.

11. Process for recovering cathode material from lithium ion batteries according to any one of the preceding claims, wherein said stage (d) includes the following stages: (di) letting the mixture obtained in stage (c) to cool to room temperature (25°C) and subjecting it to sieving obtaining:(i) a suspension of the cathode material dispersed in a liquid phase comprising glycol; and(ii) a clean or partially clean current collector; and subjecting the suspension of the cathode material dispersed in a liquid phase comprising glycol to filtration under vacuum, washing the filtrate obtained with at least one organic solvent selected from acetone, dimethylcarbonate, 2-butanone, preferably acetone, obtaining a first cathode material, subjecting said first cathode material to drying, preferably, in an oven, at a temperature comprised between 50°C and 130°C, preferably comprised between 70°C and 120°C, for a time comprised between 1 hour and 5 hours, preferably comprised between 1.5 hours and 4 hours;(d2) immersing the current collector obtained in stage (di) in an ultrasonic bath, in the presence of at least one organic solvent selected from acetone, dimethyl carbonate, 2-butanone, preferably acetone, obtaining a second cathode material and a current collector clean or partially clean, recovering said second cathode material through filtration under vacuum and subjecting it to drying, preferably, in an oven, at a temperature between 50°C and 130°C, preferably between 70°C and 120°C, for a time comprised between 1 hour and 5 hours, preferably comprised between 1.5 hours and 4 hours;(ds) optionally, treating the current collector recovered in stage (d2) in an organic solvent selected from 7V,7V-dimethylformamide, A -methyl pyrrolidone, dimethylsulfoxide, dipropylene glycol, preferably dipropylene glycol, at a temperature comprised between 100°C and 250°C, preferably comprised between 120°C and 245°C, for a time comprised between 30 minutes and 5 hours,preferably comprised between 1 hour and 4 hours, obtaining a third cathode material and a clean current collector, recovering said third cathode material through filtration under vacuum and subjecting it to drying, preferably, in an oven, at a temperature comprised between 50°C and 130°C, preferably comprised between 70°C and 120°C, for a time comprised between 1.5 and 5 hours, preferably comprised between 2 hours and 4 hours.

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