New process for intercalating alkalis in materials based on transition element(s)

Abstract

A process for the solid-state alkalinization of a salt comprising at least one transition metal and being deficient in an alkali metal, the process being characterized in that it comprises the following steps: a) mixing, in solid form, said alkali-deficient (or alkali-free) salt with the corresponding alkali iodide, also in solid form, to obtain a solid mixture; b) reacting said solid mixture to obtain molecular iodine and an alkali-enriched salt of said transition metal; and, optionally, c) separating the molecular iodine from said solid mixture. No figure

Description

Title of the invention: New process for intercalating alkalis into materials based on transition element(s) Field of the invention

[0001] The invention relates to a method of intercalation or insertion of alkalis in materials based on transition element(s) allowing synthesis or recycling of materials used in batteries using alkali elements such as sodium, lithium and potassium (solid state alkalization). Prior art

[0002] The transition to electric mobility is one of the most important elements in reducing carbon emissions on a global scale today. The disposal, recovery and recycling of alkaline-based batteries and accumulators at the end of their useful life are becoming increasingly pressing problems. Indeed, the production of lithium accumulators, called lithium batteries, or lithium-ion accumulators, is only increasing, as a result of which, in the coming years, the accumulators that will reach the end of their service and will have to be disposed of will be increasingly numerous. Appropriate recycling of these is therefore essential. Such recycling notably involves methods of reintroducing alkaline elements into electrode materials, in particular the materials used in devices exchanging these alkaline ions (in particular Li, K and Na ions).

[0003] Different ways of lithiation of alkaline electrode materials are known: i) The heat treatment which is carried out after adding to the delithiated phase (FePO4) a source of lithium (Li2CO3) and a reducing agent (C) at 700 °C / 10 h under an argon atmosphere.12 This is not a direct lithiation of FePO4 but a complement of synthesis of the material at high temperature, because in this case it is the chemical reaction of Li2CO3 on the products of reduction of FePO4 by carbon. ii) Electrochemical lithiation via graphite pre-lithiation3. This method requires a controlled atmosphere and is an expensive process, difficult to apply on a large scale.

[0004] iii) chemical lithiation where lithium iodide (LiI) is dissolved in organic solvents (acetonitrile, ethanol, cyclohexane, DMSO, etc.) and then brought into contact with an end-of-life cathode material comprising FePO4 and LiFePO44'5'6. This method has slow kinetics (~20 h) and the use of large quantities of solvents that are not very compatible with the requirements of an environmentally friendly process. the environment.

[0005] It is also known to carry out the sodiation of Na3V2(PO4)2F3 to form Na4V2(PO4)2F3 by mechanical grinding using metallic Na as a reducing agent.7 The use of metallic Na requires special and expensive safety precautions (argon / dry room).

[0006] There is therefore a need for a process that is simple to implement, inexpensive, and / or environmentally friendly, allowing the synthesis and / or reintroduction of alkali ions into compounds comprising transition elements, in particular compounds intended and / or used in electrochemistry for the manufacture of electrodes. Description of the invention

[0007] An object of the invention is therefore a process for the solid-state alkalization of a compound, in particular a salt, comprising at least one transition metal, said compound being deficient in an alkali, this process being characterized in that it comprises the following steps:

[0008] a) mixing, in solid form, said salt deficient in an alkali (or not comprising it) with the corresponding alkali iodide, the latter also being in solid form, to obtain a solid mixture;

[0009] b) reacting said solid mixture to obtain molecular iodine and a salt of said transition metal enriched in said alkali; and, optionally

[0010] c) separating molecular iodine from said solid mixture,

[0011] wherein said transition metal salt enriched in said alkali is preferably chosen as having, in the solid state, and under normal conditions of pressure and temperature, an average potential relative to lithium (Lr7Li) of more than 3V.

[0012] In a particularly advantageous manner, this method makes it possible either to produce an alkali salt of a transition metal from a salt which is completely devoid of it, or to increase the quantity of said alkali in a salt of a transition metal already containing it. Thus, by "solid state alkalization", it describes both the synthesis of an alkali salt and the increase in the alkali content of a salt already containing it in part. The method of the invention can therefore be a method for synthesizing an alkali salt but can also be a method for regenerating, recycling and / or inserting alkali ions into a material comprising a transition metal.

[0013] The term "salt" is used in its modern sense to designate an ionic solid, corresponding to a reticular assembly of ions of different charges. It is not limited by properties such as solubility, appearance and flammability formerly associated with this term.

[0014] The expression "deficient" refers not only to compounds that are not saturated in a given alkali, but also to compounds that do not contain it. Similarly, the term "enriched" refers not only to compounds saturated in a given alkali but also to compounds containing a greater quantity than the starting compound.

[0015] The expression "solid state alkalization process" thus describes the synthesis of an alkali salt or the increase in the quantity of alkali in a compound already containing it. The process according to the invention allows the increase in the quantity of at least one alkali. It can also allow the introduction of different alkalis. The term "alkali" designates both the element and the corresponding ions. Among the alkalis (lithium, sodium, potassium, rubidium, cesium and francium), lithium, sodium and / or potassium are preferred and more particularly lithium. Thus the process according to the invention preferably relates to a lithiation, sodiation and / or potassiation process.

[0016] By "transition metal" is meant a chemical element whose atoms have an incomplete d electronic subshell, or which can form cations whose d electronic subshell is incomplete. As is customary, this definition also includes an element from group 12, such as zinc, cadmium and mercury. Preferably, the transition metal is selected from the group consisting of the first series titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn)), the second series (zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag) and cadmium (Cd)) and the third series (hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re), osmium (Os), iridium (Ir), platinum (Pt), gold (Au) and mercury (Hg)).

[0017] The salt comprising at least one transition metal, said salt being deficient and / or enriched in an alkali, can obviously comprise more than one transition metal and / or at least one other metal, in particular an alkaline earth metal such as for example calcium, magnesium and / or beryllium.

[0018] The average potential can be estimated based on the standard potential of the redox couple contained in the material, these standard potentials are available in the form of tables in the literature which allow the potentials to be determined. For example: https: / / www.lachimie.fr / solutions / oxidoreduction / table-potentiel-standard.php. 2. The average potentials of solid materials can be determined more precisely by measuring them using simple electrochemical techniques such as cyclic volt-amperometry (CV) or a dx / dV derivative curve of a galvanostatic curve, where x corresponds to the amount of alkali. These techniques, known to those skilled in the art, are explained in Example 20. The use of alkali iodide is advantageous because the by-product of the reaction is easily recoverable in the form of molecular iodine and iodide or triodide ion I3.

[0019] The process according to the invention therefore makes it possible to alkalize and / or realkalize many types of salts.

[0020] The salt comprising at least one transition metal, said salt being enriched in alkali, is preferably a compound used for the manufacture of electrodes in the field of batteries, accumulators and batteries. An electrochemically active salt is particularly preferred.

[0021] Thus, the salt obtained can advantageously comprise an olivine-type salt, to which the salt (LiFePO4) belongs in particular. The olivine-type salt has the general formula XYTO4, where T is one (or more) tetravalent cation (in particular Si, P, As), X at least one alkali metal cation and Y at least one non-alkali metal cation as described above. Y can advantageously be chosen from the group consisting of Fe2+, Mn2+, Co2+, Ni2+, Mg2+, Ca2+ and mixtures thereof. X can advantageously be Li+, Na+ and mixtures thereof.

[0022] The salt obtained may also advantageously comprise a salt of the LiNMC / NMC family (LiNixMnyCozO2, where x + y + z = 1) where these metals are replaced completely or partially by other metals, such as those described above. Advantageously, these metals are chosen from the group consisting of the elements Al, Fe, V, Cr, Nb, Mo and their mixtures. Li may advantageously be replaced in whole or in part by sodium. Thus, the salt may have the formula AMlxM2yM3zO2, where x + y + z = 1 where A is an alkali metal, preferably Li and / or Na and where Ml, M2 and M3 are each a non-alkali metal, preferably chosen from the group consisting of the metal ions Co3+, Ni3+, Mn3+, Al3+, Fe3+, V3+, Cr3+, Nb3+, Mo3+.

[0023] The salt alkalized according to the process according to the invention can also advantageously be doped with at least one element which can be such as a metal as described above or a rare earth, such as Ce. The doping of a compound consists of introducing, into its matrix, elements in very low concentration which can replace other atoms. The dopant(s) can replace a very small part (for example less than 5%, preferably less than 1%) of the sites occupied by other elements of the compound, in particular by the alkali and / or alkaline earth (for example Ca).

[0024] This alkalized salt can preferably be:

[0025] -a lithiated compound, and in particular a compound of formula LiCoO2 (LCO), LiFePO4 (LFP), LiMn2O4 (LMO), LiMnx Fey PO4 (LMFP) - for example LiMn0j66Fe0j34PO4, LiNi xMnyCozO2 (NMC) - for example LiNioj33Mn0j33Cooj3302 (NMC111) and LiNio,6Mn0.2Co0.2 O2 (NMC622);

[0026] - a sodium compound, in particular NaFePO4 or Na2Fe(SO4)2 4H2O; or

[0027] - a potassium compound such as K2Fe(SO4)22H2O;

[0028] where x, x', y, y' and z are independently of each other non-null real numbers less than 1. Preferably x' + y' = 1 and / or x + y + z = 1.

[0029] The transition metal, as well as the alkali, when present, is generally under cationic form in the salt. The salt comprising at least one transition metal and being deficient and / or enriched in an alkali, comprises one or more anions. This is advantageously chosen from the group consisting of oxides, sulfates, phosphates and hexacyanoferrates.

[0030] The compound comprising at least one transition metal, said compound being deficient in an alkali, may be totally or substantially free of this alkali or any alkali. For example, it may be chosen from the group consisting of FePO4, Fe2(SO4)3, Fe3O4, LieCoO2, Mn2O4, LieNixMnyCozO2. The compound may also be doped with at least one other element which may advantageously also be a transition metal, for example FePO4 doped with Mn.

[0031] The salt comprising at least one transition metal, said salt being deficient in an alkali, may comprise this alkali but not be saturated with it. Also this salt may have a saturated empirical formula, or the indices are not necessarily whole numbers and are lower, in particular for the anionic part, than the whole numbers of the corresponding empirical formula. Preferably, this salt is a partially or totally de-alkalized salt due to its use in an electrochemical device. Preferably, the salt comprising a transition metal and being deficient (or depleted) in at least one transition metal, corresponds to a salt enriched with the alkali-enriched salts described above with the exception of a lower relative quantity of alkali.

[0032] Steps a) and b) of the process according to the invention are advantageously carried out in the solid state. Alternatively, or additionally, these steps a) and b) are carried out without solvent, in a medium which is not a liquid medium, and / or where the transition metal salt is not dissolved.

[0033] According to one aspect of the invention, the solid mixture reacts by simple contact and steps a) and b) are concomitant.

[0034] According to an advantageous variant of the invention, the mixing can be carried out by grinding, which involves a reduction in the size of the particles. This grinding can be carried out by impact, by crushing, by attrition, by shearing and / or by a combination of one or more of these actions.

[0035] The process according to the invention may also advantageously comprise a heating step which may be carried out during or subsequently to step a) and / or b) and / or under normal pressure conditions, i.e. at atmospheric pressure. Preferably, this heating step is carried out at a temperature below 150°C, more preferably below 100°C. Indeed, although slight heating may sometimes be advantageous, the process according to the invention may be carried out at room temperature and in the vast majority of cases with little or no addition of thermal energy. For example, this addition may be due to the use of a grinding step. Thus, step a) and / or b) may be carried out without heating, at room temperature. ambient and / or even at low temperature.

[0036] According to a preferred aspect of the invention, steps a) and / or b) are carried out in the presence of air or under an inert atmosphere (for example under argon). In particular, the method according to the invention can be carried out simply in the presence of ambient air, and advantageously in an uncontrolled atmosphere. Preferably, the method according to the invention is carried out without heating, or a dedicated external heating source, with the possible exclusion of step c) where an external heat input can be carried out to extract the molecular iodine from the mixture.

[0037] The process according to the invention advantageously comprises a step for separating the iodine, and in particular the molecular iodine and / or the triiodide ion, from the reaction mixture. This step may comprise washing the mixture with a solvent or a mixture of solvents, preferably an organic solvent which may be an alcohol (e.g. ethanol). This solvent may also comprise the alkali metal iodide used in solution. This washing may optionally be followed by a step of drying the reacted and washed mixture.

[0038] Alternatively, a step of sublimation of molecular iodine can be used. This step can be carried out by heating the reaction mixture once the solid-state alkalization reaction has been carried out. The heating temperature can advantageously be around 100°C because the iodine evaporates well below its melting point (113°C) and passes directly to the gaseous state. This heating is preferably carried out in an inert atmosphere, for example under a flow of Ar / N2 gas. This heating can also be carried out under vacuum.

[0039] It is therefore possible, according to a variant of the process according to the invention, to implement a solid-state alkalization process without the use of solvent and / or liquid, which is particularly advantageous from an energy and environmental point of view.

[0040] The method according to the invention may be particularly suitable for the solid-state alkalization of a salt comprising a transition metal and being deficient in an alkali which has been part of an electrochemical device such as an electrode. It is therefore possible, thanks to the method according to the invention, to realkalize constituent materials of ion batteries (e.g. lithium, sodium, and potassium), in a particularly simple and economical manner.

[0041] Furthermore, according to a particularly advantageous aspect, it is possible to realkalize a salt comprising a transition metal and being deficient in an alkali while this salt is mixed with at least one other component. Advantageously, this other component is a conductive agent and / or a binder. The conductive agent may be chosen from the group consisting of graphite, carbon black, fibers and / or carbon nanotubes. The binder may be PVDF (Polyvinylidene fluoride or “Po- lyVinyliDene Fluoride" in English) and / or PTFE (Polytetrafluoroethylene). Preferably, the mixture is in the form of a powder, in particular a micrometric or nanometric powder.

[0042] Thus, another object of the invention is a method for recycling an electrochemically active material (or a mixture of materials) used in particular in an accumulator using alkaline ions for charge transfer and comprising the steps described above. The material is preferably a material constituting a cathode. The material can advantageously be recycled directly, that is to say without steps of separation and isolation of the salt to be recycled.

[0043] Another preferred aspect of the invention is the possibility of preserving the morphology and / or the crystalline structure of the alkaline salt particles comprising a transition metal. Thus it may be possible to preserve the structure of a salt such as olivine NaFePO4 which cannot be obtained by conventional direct synthesis. The transformation of the salt may therefore be of a topotactic nature and the passage from one crystalline structure to the other may be done without there being a notable upheaval and does not require considerable energy. Thus it may be possible to preserve the structure of a salt such as olivine NaFePO4 which cannot be obtained by conventional direct synthesis. Brief description of the figures

[0044] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which:

[0045] [Fig. 1] is a diffractogram obtained by X-ray Diffraction (XRD) of the powders a.) commercial LiFePO4, b.) FePO4 prepared by chemical delithiation of LiFePO4 and c.) LiFePO4 obtained by chemical lithiation of FePO4 without solvent at room temperature according to a variant of the process of the invention described in Example 1.

[0046] [Fig.2] shows a powder obtained according to example 1 and which is heated to 100°C under vacuum / under an inert Ar / N2 atmosphere to sublimate the iodine.

[0047] [Fig.3] shows the DRX diffractograms of the powders of a.) LiFePO4 cathode at the end of its life and b.) relithiated according to a process according to the invention, as well as an image obtained by scanning electron microscopy of c.) the LiFePO4 cathode powder at the end of its life and d.) the LiFePO4 cathode relithiated according to the process of example 2.

[0048] [Fig.4] shows the galvanostatic charge / discharge curves at C / 10 vs. Li+ / Li° of the LiFePO4 cathode powder a.) at the end of its life and b.) relithiated using the process according to example 2.

[0049] [Fig.5] DRX diffractograms of powders a.) FePO4 obtained by chemical delithiation of LiFePO4 and b.) LiFePO4 obtained by chemical lithiation of FePO4 under argon at 100 °C according to example 3.

[0050] [Fig.6] represents the DRX diffractograms of the powders of a.) FePO4obtained by chemical delithiation of LiFePO4 and b) LiFePO4 obtained by chemical lithiation of FePO4 under argon at 80°C according to example 4.

[0051] [Fig.7] represents the DRX diffractograms of the powders of a.) FePO4 prepared by chemical delithiation of commercial LiFePO4 and b.) LiFePO4 obtained by chemical lithiation of FePO4 by mechanical grinding according to Example 5.

[0052] [Fig.8] represents the DRX diffractograms of the powders of a.) commercial LMFP, b.) Chemically delithiated LMFP and c.) Chemically lithiated LMFP without solvent at room temperature, as well as the charge-discharge curves in galvanostatic mode vs. Li+ / Li° at C / 20 of the powder d.) Delithiated LMFP and e.) Relithiated LMFP of Example 6.

[0053] [Fig.9] represents the DRX diffractograms of the powders of a.) NMC111 com commercial, b.) chemically delithiated NMC111 and c.) chemically lithiated NMC111 without solvent at room temperature. As well as the charge-discharge curves in galvanostatic mode vs. Li+ / Li° at C / 20 of the powder d.) delithiated NMC111 and e). relithiated NMC111 of example 7.

[0054] [Fig. 10] shows the DRX diffractograms of the powders of a.) commercial NMC622, b. chemically delithiated NMC622 and c.) chemically lithiated NMC622 without solvent at room temperature; as well as the charge-discharge curves in galvanostatic mode vs. LD / Li0 at C / 20 of the powders d.) delithiated NMC622 and e.) relithiated NMC622 of Example 8.

[0055] [Fig. 11] shows the DRX diffractograms of the powders of a.) commercial LMO, b.) chemically delithiated LMO and c.) chemically lithiated LMO without solvent at room temperature; as well as the charge-discharge curves in galvanostatic mode vs. Li+ / Li° at C / 20 of the powders of d.) delithiated LMO and e.) relithiated LMO according to example 9.

[0056] [Fig. 12] shows the DRX diffractograms of the powders a.) commercial LCO, b.) chemically delithiated LCO and c.) chemically lithiated LCO without solvent at room temperature; as well as the charge-discharge curves in galvanostatic mode vs. Li + / Li 0 at C / 20 of the d.) delithiated LCO and the e.) relithiated LCO according to example 10.

[0057] [Fig. 13] shows the DRX diffractograms of the powders of a.) Fe2(SO4)3(H2O)7>25, and b.) K2Fe(SO4)2,2H2O potash as well as c.) its refinement using the FullProf optimization program https: / / www.ill.eu / sites / fullprof / php / downloads.html, according to example 11.

[0058] [Fig. 14] represents the DRX diffractograms of the powders of a.) delithiated FePO4, and b.) sodiated NaFePO4 obtained by chemical sodiation and c.) refinement of the DRX of the NaFePO4 phase according to example 12.

[0059] [Fig. 15] represents the DRX diffractograms of the powders a.) Fe2(SO4)3(H2O)7,25 and b.) Na2Fe(SO4)2,4H2O sodium according to example 13.

[0060] [Fig. 16] represents the DRX diffractogram of the FePO4.2H2O and Lil mixture prepared in air at room temperature according to comparative example 14.

[0061] [Fig. 17] represents the DRX diffractogram of the FePO4.2H2O and Nal mixture prepared in air at room temperature according to comparative example 15.

[0062] [Fig. 18] represents the DRX diffractogram of the FePO4.2H2O and Kl mixture prepared in air at room temperature according to comparative example 16.

[0063] [Fig. 19] represents the DRX diffractogram a.) of the commercial FeOOH powder and b.) the powder recovered after mixing FeOOH and Lil in air at room temperature according to comparative example 17.

[0064] [Fig.20] represents the DRX diffractogram a.) of the commercial FeOOH powder and b.) of the powder recovered after mixing FeOOH and Nal in air at 100 °C according to comparative example 18.

[0065] [Fig.21] represents the DRX diffractogram of a.) the commercial FeOOH powder and b.) the powder recovered after mixing FeOOH and Kl in air at 100 °C according to comparative example 19.

[0066] [Fig.22] shows the Cyclic Voltammetry) of LFP vs. Li+ / Li° of Example 20. Detailed description

[0067] EXAMPLE 1: Lithiation of FePO4 for the production of LiFePO4 in air at room temperature

[0068] 1 g of FePO4 powder obtained by total chemical delithiation of LiFePO4 A commercial powder using Fe3+ in solution was manually mixed in a mortar with ~880 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 for -10 minutes at room temperature / air. The powder obtained was washed with a solution of concentration 2.6 10 1 mol / L of Lil in ethanol and then dried at 60 °C. The recovered powder was characterized by XRD ([Fig.l]).

[0069] [Fig.l] shows the DRX diffractograms of the starting commercial LiFePO4 (Fig.la), the FePO4 obtained by delithiation of LiFePO4 (Fig. 1b) and the powder recovered after lithiation by LiFePO4 (Fig. 1c). The latter, [Fig.l] c.), shows the total disappearance of the diffraction peaks of the FePO4 phase and the presence of a single LiFePO4 phase with the following lattice parameters: a = 10.317(1) Â, b = 5.996(1) Â, c = 4.702(1) Â and V = 290.83(2) Â3. This result confirms the total lithiation of the FePO4 phase into LiFePO4.

[0070] DRX diffractograms were recorded using the Bruker D8 Diffractometer equipped with a Cu Ka source (❖ Kal = 1.54056 Â and ❖ Ka2 = 1.54439 Â).

[0071] Another method of separating IV LiFePO4

[0072] Alternatively, the iodine I2 formed after lithiation reaction can be removed by a other process than washing the iodide ions with alcohol, for example ethanol. It can be carried out by heating which causes the iodine to sublimate in the form of gas. This heating is preferably carried out in an inert atmosphere, for example under a flow of Ar / N2 gas, or in a vacuum, at a temperature of 100 °C. [Fig. 2] shows a powder obtained according to Example 1 and which has been heated to 100 °C in a vacuum. The iodine is released in the form of a purple vapor which allows I2 to be recovered in the form of gray crystals.

[0073] EXAMPLE 2: Regeneration of a LiFePO4 cathode at the end of its life in air at room temperature

[0074] The method according to the invention can allow regeneration by direct recycling. In this example, a LiFePO4 cathode from a used 2.3 Ah commercial battery (LiFePCVgraphite, 26650 cylindrical cell) was used for chemical lithiation. The LiFePO4 cathode powder was recovered and characterized by XRD (Fig. 3a), indicating the presence of two olivine phases, LiFePO4 triphylite (a = 10.317(1) Â, b = 5.996(1) Â, c = 4.702(1) Â) and FePO4 heterosite (a = 9.851(1) Â, b = 5.810(1) Â, c = 4.772(1) Â). The electrochemical properties of the recovered LiFePO4 cathode were evaluated versus lithium in galvanostatic mode at C / 10 (Fig. 4a). The first discharge corresponds to the reduction of the FePO4 phase. These results show that there is a lack of lithium in the cathode.

[0075] The used LiFePO4 cathode was regenerated using the process detailed above (example 1) with a molar ratio of LiI / FePO4 of 1 for the 30% of FePO4 present in the cathode. The result of the DRX analysis (Fig. 3b) confirms the total lithiation of the LiFePO4 cathode by showing the total disappearance of the characteristic peaks of the FePO4 phase as well as the presence of a single LiFePO4 phase.

[0076] The electrochemical performances of the regenerated LiFePO4 cathode were also tested under the same conditions (Fig. 4b) indicating the good electrochemical signature of LiFePO4 as well as a potential of 3.44 V. The absence of the FePO4 reduction plateau during the first discharge confirms the complete lithiation of the FePO4 phase present in the starting mixture. The material records a reversible capacity of approximately 168 mAh / g stable during tens of cycles.

[0077] This process for regenerating a used LiFePO4 cathode preserves the formulation of the electrode (LiFePO4, conductive carbon and polymer binder), the carbon coating as well as the morphology of the particles (Fig. 3c-d). This paves the way for more sustainable recycling of Li-ion batteries. In addition, the process can be carried out without the addition of solvent or additional heat treatment, which is certainly very useful for the recycling of end-of-life battery stocks in the coming years.

[0078] EXAMPLE 3: Lithiation of FePO4 for the production of LiFePO4 under argon at 100°C

[0079] 1 g of FePO4 powder obtained by total chemical delithiation of LiFePO4 commercially available solution using Fe3+ was manually mixed in a mortar with ~880 mg of lithium iodide Lil (Acros Organics, 99%) at a molar ratio of 1 for -10 minutes under argon, the mixture was heated to 100 °C for 12 hours under argon.

[0080] [Fig.5] shows the DRX diffractogram of FePO4 obtained by chemical delithiation of LiFePO4 (Fig. 5a) and that of the powder recovered after chemical lithiation (Fig. 5b), indicating the total disappearance of the peaks of the FePO4 phase in favor of the LiFePO4 phase with the appearance of by-product 12. This result confirms the total lithiation under argon of the FePO4 phase into LiFePO4.

[0081] Note: The by-product I2 formed during the reaction can be removed by washing with a solution of concentration > 2.6 10 1 mol / L of Lil in ethanol and then dried at 60 °C.

[0082] Or by sublimation under vacuum or under a flow of Ar / N2 gas or under vacuum at >100 °C.

[0083] EXAMPLE 4: Lithiation of FePO4 for the production of LiFePO4 at 80°C

[0084] 1 g of FePO4 powder obtained by total chemical delithiation of LiFePO4 commercially available solution using Fe3+ was manually mixed in a mortar with -880 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 for -10 minutes under argon, the mixture was heated at 80 °C for 72 hours under argon.

[0085] [Fig.6] shows the DRX diffractograms of FePO4 obtained by chemical delithiation of LiFePO4 (Fig. 6a) and that of the powder recovered after chemical lithiation (Fig. 6b), indicating the total disappearance of the peaks of the FePO4 phase in favor of the LiFePO4 phase. This result confirms the total lithiation of the FePO4 phase into LiFePO4.

[0086] Note: The by-product I2 formed during the reaction can be removed by washing with a solution of concentration > 2.6 101 mol / L of Lil in ethanol and then dried at 60 °C or by sublimation under vacuum or under a flow of Ar / N2 gas or under vacuum at >100 °C.

[0087] Example 5: Lithiation of FePO4 under controlled atmosphere by mechanical grinding

[0088] 1 g of FePO4 powder obtained by total chemical delithiation of LiFePO4 commercially available using Fe3+ in solution was mixed with -880 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 by mechanical grinding using a Spex™ Mixer Mill 8000M ball mill (sold by Fisher Scientific SAS, Boulevard Sébastien Brant - F67403 Illkirch) for -10 minutes under argon.

[0089] [Fig.7] shows the DRX of FePO4 obtained by chemical delithiation of LiFePO4 (Fig. 7a) and that of the powder recovered after chemical lithiation assisted by mechanical grinding (Fig. 7b), indicating the total disappearance of the peaks of the FePO4 phase in favor of the LiFePO4 phase. This result confirms the total lithiation of the FePO4 phase into LiFePO4.

[0090] Note: The by-product I2 formed during the reaction can be removed by washing with a solution of concentration > 2.6 10 1 mol / L of Lil in ethanol and then dried at 60 °C or by sublimation under vacuum or under a flow of Ar / N2 gas or under vacuum at >100 °C.

[0091] EXAMPLE 6: LiMno>66Feo34P04 (LMFP) / in air at room temperature

[0092] The powder of the commercial material LiMn0>66Feo>34P04 (Fig. 8a) was partially chemically oxidized by mixing -241 mg NO2BF4 in 40 mL of acetonitrile at room temperature (Fig. 8b), the DRX result shows a shift of the initial peaks characteristic of LiMn0>66Feo>34P04 and this indicates that the latter has indeed been delithiated (a = 10.160(1) Â, b = 5.987(1) Â, c = 4.794(1) Â and V = 291.59(2) Â3). The electrochemical properties of the delithiated LiMn0>66Feo>34P04 were evaluated versus Li+ / Li 0 in galvanostatic mode at C / 20 (Fig. 8d). The first discharge corresponds to the reduction of the delithiated phase. These results show that there is a lack of lithium in this material up to 0.63 Li which indicates that the chemically delithiated phase may correspond to Lio,37Mno,66Feo,34P04.

[0093] In order to chemically lithiate this delithiated material (LiO,37MNo,66FeO,34PO4), 0.6 g of this powder was mixed in a mortar with -500 mg of lithium iodide LiI (Acros Organics, 99%) with a molar ratio of 1 (relative to the missing 0.63 Li) for -10 minutes at room temperature / air. The powder obtained was washed with a solution of 1.5 10 1 mol / L of LiI in ethanol and then dried at 60 °C. The recovered powder was characterized by XRD (Fig. 8c), indicating the presence of a single LiMn0>66Feo>34P04 phase which is similar to the starting commercial material (a = 6.045(1) Â, b = 10.80(1) Â, c = 4.743(1) Â and V = 297.58(2) Â3).

[0094] The electrochemical performances of the regenerated LiMn0>66Feo>34P04 were also measured under the same conditions (Fig. 8e) and confirm the electrochemical signature of LiMn0>66Feo>34P04 with the total disappearance of the Mnm and Fera reduction plateaus in the first discharge. These results confirm the total relithiation of the material.

[0095] EXAMPLE 7: LiNio33Mno33Coo3302 (NMC111) / in air at room temperature

[0096] The powder of the commercial material LiNio,33Mn0,33Coo,3302 (Fig. 9a) was partially chemically oxidized by - 415 mg NO2BF4 in 40 mL of acetonitrile at room temperature (Fig. 9b), the DRX result shows a shift of the initial peaks characteristic of NMC111 and this indicates that the latter has indeed been delithiated. The properties Electrochemical properties of delithiated NMC111 were evaluated versus Li+ / Li° in galvanostatic mode at C / 20 (Fig. 9d). The first discharge corresponds to the reduction of the delithiated phase. These results show a lack of lithium in this material up to 0.37 Li which indicates that the chemically delithiated phase may correspond to Lio,63Nio,33Mno,33Coo,3302.

[0097] For the chemical relithiation of this delithiated material, 0.6 g of the powder Lio,63Nio,33Mn o,33Coo>3302Li was manually mixed in a mortar with -860 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 (relative to the missing 0.37 Li) for -10 minutes at room temperature / air. The obtained powder was washed with a solution of concentration of 2.57 101 mol / L of Lil in ethanol and then dried at 60 °C.

[0098] The recovered powder was characterized by XRD in a cell with a beryllium Be window under argon (Fig. 9c), and the presence of a single phase LiNio,33Mn0,33Co 033O2 was confirmed. The electrochemical performances of the regenerated NMC111 were also tested under the same conditions (Fig. 9e) indicating the expected electrochemical signature for NMC111 as well as a very low capacity recorded at the first discharge < 2%. These results confirm the total lithiation of the material.

[0099] EXAMPLE 8: LiNio^Mno zCoo iOz (NMC622) / in air at room temperature

[0100] The powder of the commercial material LiNio^Mno,2600,26)2 (Fig. 10a) was partially chemically oxidized by - 411 mg NO2BF4 in 40 mL of acetonitrile at room temperature (Fig. 10b), the DRX result shows a shift of the initial peaks characteristic of NMC622, indicating a change of lattice parameters in accordance with the delithiation. The electrochemical properties of the delithiated NMC111 were evaluated versus Li+ / Li° in galvanostatic mode at C / 20 (Fig. 10d). The first discharge corresponds to the reduction of the delithiated phase. These results show that there is a lack of lithium in this material of up to 0.3 Li, which indicates that the chemically delithiated phase may correspond to Lio^Nio^Mno^Coo^CL.

[0101] For the chemical relithiation of this delithiated material, 0.6 g of the powder Lio,7Nio,6Mno,2 Co0,2O2 was manually mixed in a mortar with -847 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 (relative to the missing 0.3 Li) for -10 minutes at room temperature / air. The powder obtained was washed with a solution of concentration of 2.53 101 mol / L of Lil in ethanol and then dried at 60 °C.

[0102] The recovered powder was characterized by XRD (Fig. 10c), indicating the presence of a single LiNio,6Mno,2Coo,202 phase whose lattice parameters correspond to the commercial material. The electrochemical performances of the regenerated NMC622 were also measured under the same conditions (Fig. 10e) indicating the expected electrochemical signature for NMC622 as well as a very low recorded capacity. at the first discharge < 5%. These results confirm the total lithiation of the material.

[0103] EXAMPLE 9: LiMn2O4 (LMO) / in air at room temperature

[0104] The powder of the commercial material LiMn2O4 (Fig. 1 la) was partially chemically oxidized by 220 mg NO2BF4 in 40 mL of acetonitrile at temperature (Fig. 11b), the DRX result shows a shift of the initial peaks characteristic of LMO and this indicates that the latter has indeed been delithiated. The electrochemical properties of the delithiated LMO were evaluated versus Li+ / Li° in galvanostatic mode at C / 20 (Fig. 1 Id). The first discharge corresponds to the reduction of the delithiated phase. These results show that there is a lack of lithium in this material up to 0.1 Li.

[0105] For the chemical relithiation of this delithiated material, 0.6 g of the powder Li0>9Mn2O4 was manually mixed in a mortar with -445 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 (relative to the missing 0.1 Li) for -10 minutes at room temperature / air. The powder obtained was washed with a solution of concentration of 1.33 10 1 mol / L of Lil in ethanol and then dried at 60 °C.

[0106] The recovered powder was characterized by XRD in a cell with a beryllium Be window under argon (Fig. 1 le), indicating the presence of a single LiMn2O4 phase which completely corresponds to the commercial material. The electrochemical performances of the regenerated LMO were also tested under the same conditions (Fig. 1 le) indicating the good electrochemical signature of the LMO as well as a very low capacity recorded at the first discharge < 1%. These results confirm the total lithiation of the material.

[0107] EXAMPLE 10: LiCoO2 (LCO) / in air at room temperature

[0108] The powder of the commercial material LiCoO2 (Fig. 12a) was partially chemically oxidized by 407 mg NO2BF4 in 40 mL of acetonitrile at room temperature (Fig. 12b), the DRX result shows a shift of the initial peaks characteristic of LCO and this indicates that the latter has been delithiated. The electrochemical properties of the delithiated LCO were evaluated versus Li+ / Li° in galvanostatic mode at C / 20 (Fig. 12d). The first discharge corresponds to the reduction of the delithiated phase. These results show that there is a lack of lithium in this material up to 0.25 Li.

[0109] For the chemical relithiation of this delithiated material, 0.6 g of the Li075CoO2 powder was mixed in a mortar with -835 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 (relative to the missing 0.25 Li) for -10 minutes at room temperature / air. The obtained powder was washed with a solution of concentration of 2.5.10 1 mol / L of Lil in ethanol and then dried at 60 °C.

[0110] The recovered powder was characterized by DRX (Fig. 12c), indicating the presence of a single LiMn2O4 phase which completely corresponds to the commercial material. The electrochemical performances of the regenerated LCO were also tested under the same conditions (Fig. 12e) indicating the good electrochemical signature of the LCO as well as a very low capacity recorded at the first discharge < 3%. These results confirm the total lithiation of the material.

[0111] EXAMPLE 11: Potassiation of hydrated Fe2(SO4)3 for the formation of K2 Fe(SO4)2.2H2O in air at room temperature

[0112] Commercial hydrated iron III sulfate powder was used as the starting material for chemical potassiation (Fig. 13a). 1 g of Fe2(SO4)3(H2O)7 powder 25 (JCPDS file No. 01-071-1634 Kornelite on Eva (DIFFRAC.EVA software for indexing diffractograms obtained by the X-ray diffraction method) was manually mixed in a mortar with potassium iodide Kl (Acros Organics, 99%) in excess for -10 minutes under air. The resulting powder was washed with a solution of IM concentration of Kl in ethanol and then dried at 60 °C.

[0113] The recovered powder was characterized by DRX (Fig. 13b), indicating the presence of the K2Fe(SO4)2.2H2O phase with the following lattice parameters: a = 7.307(1) Â, b = 10.810(1) Â, c = 6.533(1) Â (Fig. 13c).

[0114] EXAMPLE 12: Sodiation of FePO4 for the production of olivine NaFePO4 under argon at 300 °C

[0115] Olivine FePO4 obtained by chemical delithiation of commercial LiFePO4 by Fe3+ in water was used as the starting material for chemical sodiation (Fig. 14a). 1 g of the FePO4 powder was manually mixed in a mortar with -994 mg of sodium iodide Nal (Acros Organics, 99%) with a molar ratio of 1, and then the mixture was heated at 300 °C for 5 hours under argon. The obtained powder was washed with a solution of concentration of 2.65 101 mol / L of Nal in ethanol and then dried at 60 °C.

[0116] The recovered powder was characterized by XRD (Fig. 14b), indicating the total disappearance of the FePO4 phase peaks and the presence of a single NaFePO4 olivine phase with the following lattice parameters: a = 10.390(1) Â, b = 6.216(1) Â, c = 4.942(1) Â (Fig. 14c). This result confirms the total reduction of Fe™ to Fe11 accompanied by the insertion of sodium into the FePO4 structure.

[0117] EXAMPLE 13: Sodiation of hydrated Fe2(SO4)3 to form Na2Fe(SO4)2>4H2O in air at room temperature

[0118] Commercial hydrated iron III sulfate powder was used as the starting material for chemical sodiation (Fig. 15a). 1 g of the powder Fe2(SO4)3(H2O)7.25 (JCPDS sheet No. 01-071-1634 Kornelite) was manually mixed in a mortar with sodium iodide Nal (Acros Organics, 99%) for -10 minutes under air. The resulting powder was washed with a solution of IM concentration of Nal in ethanol then dried at 60°C.

[0119] The recovered powder was characterized by DRX (Fig. 15b), indicating the presence of a single Na2Fe(SO4)24H2O phase.

[0120] Examples of materials where the developed process cannot be applied (potential < 3 V / LiVLP)

[0121] Comparative EXAMPLE 14: Lithiation test of FePO4.2H2O in air at room temperature

[0122] 0.4 g of the commercial amorphous FePO4.2H2O powder (Sigma Aldrich) was manually mixed in a mortar with -286 mg of lithium iodide Lil (Acros Organics, 99%) with a molar ratio of 1 under air at room temperature.

[0123] [Fig. 16] shows the DRX diffractogram of the powder recovered after chemical lithiation, indicating the presence of peaks of the Lil .3H2O phase resulting from the hydration of the starting Lil and an amorphous compound which may correspond to the starting FePO4.2H2O. This result shows that the lithiation reaction did not take place (FePO4.2H2O was not chemically lithiated).

[0124] Comparative EXAMPLE 15: Sodiation test of FePO4.2H2O in air at room temperature

[0125] 0.4 g of the commercial amorphous FePO4.2H2O powder (Sigma Aldrich) was mixed in a mortar with -321 mg of sodium iodide Nal (Acros Organics, 99%) with a molar ratio of 1 to air at room temperature.

[0126] [Fig. 17] shows the DRX diffractogram of the powder recovered after chemical lithiation, indicating the presence of the peaks of the Nal and Nal .2H2O phase resulting from the hydration of the starting Nal and a diffuse (amorphous) peak which may correspond to the starting FePO 4.2H2O. This result shows that the sodiation reaction did not take place (FePO 4.2H2O was not chemically sodiated).

[0127] Comparative EXAMPLE 16: Potassiation test of FePO4.2H2O in air at room temperature

[0128] 04 g of the commercial amorphous FePO4.2H2O powder (Sigma Aldrich) was mixed manually in a mortar with -355 mg of potassium iodide Kl (Acros Organics, 99%) with a molar ratio of 1 to air at room temperature.

[0129] [Fig. 18] shows the DRX diffractogram of the powder recovered after chemical lithiation, indicating the presence of the peaks of the initial Kl phase and an amorphous one which may correspond to the initial FePO4.2H2O. This result shows that the potassiation reaction did not take place (FePO4.2H2O was not chemically potassicated).

[0130] Comparative EXAMPLE 17: FeOOH lithiation test in air at room temperature

[0131] 0.4 g of the commercial FeOOH powder was manually mixed in a mortar with -602 mg of lithium iodide Lil (Acros Organics, 99%) with a ratio molar of 1 in air at room temperature.

[0132] [Fig. 19] shows the DRX diffractogram of the commercial FeOOH powder (Fig. 19a) as well as the powder recovered after chemical lithiation (Fig. 19b), indicating the presence of the peaks of the starting compounds FeOOH and Lil .3H2O resulting from the hydration of starting Lil. This result shows that the lithiation reaction did not take place (FeOOH was not chemically lithiated).

[0133] Comparative EXAMPLE 18: FeOOH sodiation test in air at 100°C

[0134] 0.4 g of the commercial FeOOH powder was manually mixed in a mortar with -675 mg of sodium iodide Nal (Acros Organics, 99%) with a molar ratio of 1 in air at 100 °C for 12 h.

[0135] [Fig.20] shows the DRX diffractogram of the commercial FeOOH powder (Fig. 20a) as well as the powder recovered after chemical sodiation (Fig. 20b), indicating the presence of the peaks of the starting compounds namely FeOOH, Nal and Nal .2H2O resulting from the hydration of starting Nal. This result shows that the sodiation reaction did not take place (FeOOH was not chemically sodiated).

[0136] Comparative EXAMPLE 19: FeOOH potassiation test in air at 100°C

[0137] 0.4 g of the commercial FeOOH powder was manually mixed in a mortar with -747 mg of potassium iodide Kl (Acros Organics, 99%) with a molar ratio of 1 in air at 100 °C for 12 h.

[0138] [Fig.21] shows the DRX diffractogram of the commercial FeOOH powder (Fig. 21a) as well as the powder recovered after chemical sodiation (Fig. 21b), indicating the presence of the peaks of the starting compounds namely FeOOH and KL. This result shows that the potassiation reaction did not take place (FeOOH was not chemically potassicated).

[0139] EXAMPLE 20 of measurement of the average potential of (LiFePO4) vs Li7Li°

[0140] To carry out this measurement by CV on a potentiostat, an electrochemical cell, consisting of a working electrode containing the active material to be analyzed, a reference electrode as well as a counter electrode and an electrolyte, is used. The variation of the current I(mA) as a function of the potential (V) is measured by scanning the potential with scanning speeds given in (mV / s). The curve obtained during this CV generally presents, when the material is active, an oxidation peak (oxidation potential noted Eox) and a reduction peak (reduction potential noted Ered), which allow the determination of the average potential of the material E = Ered + (Eox - Ered) / 2.

[0141] In the case of the LFP cathode material (LiFePO4), the potential measurement was carried out versus lithium (which is both the anode and the reference) using two methods; after preparation of the electrochemical cells (in a glove box under argon) each containing approximately 10 mg of LFP / C active material / carbon powder as cathode. The two electrodes are separated by two glass fiber separators soaked in LP30 electrolyte, which is a molar solution of LiPF6 in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) with a mass ratio of 1 / 1.

[0142] According to a first method (CV), the measurements were carried out at 25 °C, using a VMP potentiostat, measuring the current I (mA) as a function of the potential (V) with a scanning speed of 0.1 mV / s between 2.1 V and 4.2 V. The curve obtained shows an oxidation peak around -3.64 V / Li+ / Li° and a reduction peak at -3.24 V / Li+ / Li° which indicates an average potential of the LFP of 3.44 V / Li+ / Li°. ([Fig.22]).

[0143] According to a second method, a potential / composition curve (E(V)= f(x)) in galvanostatic mode ([Fig.4]), which is the measurement of the variation of the potential as a function of the composition under a constant current with a C / 10 regime (one mole of electron exchanged in 10 hours) in the potential window 2.1 V - 4.2 V.

[0144] The derivative of x with respect to the potential (dx / dV) led to a curve similar to a CV curve (Fig. 2b). On the latter, we can observe an oxidation peak around -3.45 V / Li+ / Li° and a reduction peak at -3.40 V / Li+ / Li° which indicates an average LFP potential of 3.44 V / Li+ / Li°. References

[0145] 1 B. Chen, M. Liu, S. Cao, G. Chen, X. Guo, X. Wang, Regeneration and performance ofLiFePO4 with Li2CO3 and FePO4 as raw mate riais recovered from spent LiFePO4 batteries, Mater. Chem. Phys. 279 (2022). https: / / doi.org / ! 0.1016 / d. matchemphys.2022.125750 2 J. Zhang, J. Hu, Y. Liu, Q. Jing, C. Yang, Y. Chen, C. Wang, Sustainable and Facile Methodfor the Sélective Recovery of Lithium from Cathode Scrap of Spent LiFePO4 Batteries, ACS Sustain. Chem. Eng. 7 (2019) 5626-5631. https: / / doi.org / 10.1021 / acssuschemeng.9b00404 3 T. Wang, X. Yu, M. Fan, Q. Meng, Y. Xiao, Y.-X. Yin, H. Li, Y.-G. Guo, Direct regeneration of spent LiFePO 4 via a graphite prelithiation strategy, Chem. Common. 56 (2020) 245-248. https: / / doi.org / 10.1039 / C9CC08155K 4 MJ Ganter, BJ Lundi, CW Babbitt, A. Anctil, G. Gaustad, Cathode refunctiona-lization as a lithium ion battery recycling alternative, J. Power Sources. 256 (2014) 274-280. https: / / doi.org / !0.1016 / j.ipowsour.2014.01.078 5 B. Gangaja, S. Nair, D. Santhanagopalan, Reuse, Recycle, and Régénération of LiFePO4 Cathode from Spent Lithium-Ion Batteries for Rechargeable Lithium- And Sodium-Ion Batteries, ACS Sustain. Chem. Eng. 9 (2021) 4711-4721. https: / / doi.org / 10.1021 / acssuschemeng.0c08487 6 T. Ouaneche, Matthieu Courty, Lorenzo Stievano, Laure Monconduit, Claude Guéry, Moulay T. Sougrati, Nadir Recham, Room température efficient régénération of spent LiFeP04 by direct Chemical lithiation, Journal of Power Sources, 2023. https: / / doi.Org / 10.1016 / j.jpowsour.2023.233248 7 Biao Zhang, Romain Dugas, Gwenaelle Rousse, Patrick Rozier, Artem M. Abakumov, Jean-Marie Tarascon, Insertion, Compounds and composites made by bail millingfor advanced sodium-ion batteries. Nature communications I 7:10308 I DOI: 10.1038 / ncommsl0308 \www .nature.com / nature communications.

Claims

Claims

1. A process for the solid-state alkalization of a salt comprising at least one transition metal and being partially or totally deficient in an alkali, this process being characterized in that it comprises the following steps: a) mixing, in solid form, said salt deficient in an alkali (or not comprising it) with the corresponding alkali iodide, the latter also being in solid form, to obtain a solid mixture; b) reacting said solid mixture to obtain molecular iodine and a salt of said transition metal enriched in an alkali; and, optionally, c) separating the molecular iodine from said solid mixture, wherein said transition metal salt enriched in said alkali is chosen as having, in the solid state, and under normal conditions of pressure and temperature, an average potential with respect to lithium (Li+ / Li°) of more than 3V.

2. The method according to claim 1, wherein a heating step is carried out during or subsequent to step a) and / or b), preferably this heating step is carried out at a temperature below 150°C, more preferably below 100°C.

3. The method according to claim 1 or 2, wherein steps a) and / or b) are carried out under ambient air or under an inert atmosphere.

4. The method according to claim 1, wherein steps a) and / or b) are carried out without heating and / or at room temperature, and wherein, preferably, the method is carried out without heating to the exclusion of step c).

5. The method according to claim 1 or 4, wherein steps a) and / or b) are carried out in the presence of air.

6. The method according to any one of claims 1 to 5, wherein said salt comprising at least one alkali and one transition metal, is an electrochemically active compound such as: - an olivine-type salt having the general formula XYTO4, where T is at least one tetravalent cation (in particular Si, P, As), X is at least one alkali cation and Y at least one non-alkali metal cation; or - a compound of formula AMlxM2yM3zO2, wherex + y + z= lwhere A is an alkali, preferably Li and / or Na, and where Ml, M2 and M3 are each a non-alkali metal, preferably chosen in the group consisting of metal ions Co3+, Ni3+, Mn3+ 2, Al3+, Fe3+, V3+, Cr3+, Nb3+, Mo3+.

7. The method according to any one of claims 1 to 6, wherein said compound comprising a transition metal and being deficient in an alkali has been part of an electrode and / or is in admixture with another component such as a conductive agent, for example graphite, carbon black, fibers and / or carbon nanotubes, and / or a binder, for example polyvinylidene fluoride and / or polytetrafluoroethylene.

8. The process according to any one of claims 1 to 7, wherein the separation step c) is carried out by washing said mixture with an organic solvent such as alcohol, for example ethanol, this washing being optionally followed by a drying step.

9. The process according to any one of claims 1 to 7, wherein the separation step c) is carried out by heating said mixture under conditions allowing the sublimation of molecular iodine, preferably either under an inert atmosphere, for example under a flow of Ar / N2 gas, or under vacuum.

10. A method of recycling an electrochemically active material used in accumulators using alkali ions for charge transfer and comprising the steps described in the method according to claims 1 to 9.

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