Process of chemically inserting cations of an alkali metal into a solid compound

Abstract

A process for the chemical insertion of cations of an alkali metal into a solid compound of formula (I): A1-x1MmTO4, in which: A is chosen from lithium (Li) and sodium (Na), M is chosen from manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), magnesium (Mg) and mixtures thereof, T is chosen from phosphorus (P), arsenic (As) and mixtures thereof, 0 < x1 ≤ 1, and m = 1, the process comprising at least one step, called step (a), of bringing the solid compound of formula (I) into contact in an aqueous solution with a reducing agent and a source of cations of the alkali metal, whereby a solid compound of formula (II) is obtained: A1-x2MmTO4, in which: A, M, T and m are as defined above, 0 ≤ x2 < 1, and x2 < x1.

Description

Title of the invention: Process for the chemical insertion of cations of an alkali metal into a solid compound Technical field

[0001] The present invention relates to a method for chemically inserting cations of an alkali metal into a solid compound, a method for preparing an electroactive compound for an electric accumulator cathode, a method for preparing an electric accumulator cathode material, a method for preparing an electric accumulator cathode, and a method for directly recycling a material of a cathode at the end of the life of an electric accumulator. State of the prior art

[0002] It is known to recycle end-of-life electrode materials by hydrometallurgical or pyrometallurgical processes.

[0003] However, these processes are generally energy-intensive, complex, long, with numerous stages, so that their economic viability remains problematic.

[0004] The publication Yingnakorn, Tanongsak, et al. "Direct re-lithiation strategy for spent lithium iron phosphate battery in Li-based eutectic using organic reducing agents" RSC Sustainability 1.9 (2023): 2341-2349 describes a process for recycling an end-of-life lithium iron phosphate (LiFePO4 or LFP) cathode material.

[0005] In particular, this publication proposes a method for direct re-lithiation of said cathode material at the end of its life at room temperature, in the presence of a reducing agent.

[0006] In order to be able to carry out the direct re-lithiation process of said cathode material at the end of its life at low temperature, this publication teaches the use of a deep eutectic type organic solvent (in English Deep Eutectic Solvents, DES) because this type of organic solvent has the advantage of minimizing the use of water as a solvent.

[0007] Indeed, it is known that the use of water as a solvent could pose a problem for low-temperature lithiation because the lithium cation is highly solvated by water (i.e., its solvation sphere in water is very stable). This solvation of lithium cations by water could prevent low-temperature lithiation. This is the reason why it is known to favor the use of organic solvents rather than water as a solvent for low-temperature lithiation.

[0008] In this publication, the deep eutectic type organic solvent used consists of lithium acetate dihydrate (as a source of lithium cations) and ethylene glycol (as a hydrogen bond donor). The preparation of a such solvent requires a step of mixing lithium acetate dihydrate and ethylene glycol and a step of heating the mixture obtained to 60°C so as to obtain a homogeneous liquid. Statement of the invention

[0009] The invention aims to overcome all or part of the aforementioned drawbacks, in particular in order to respond to the problem of recycling end-of-life electrode materials.

[0010] Process for the chemical insertion of cations of an alkali metal into a solid compound of formula (I)

[0011] The invention thus relates, according to a first of its aspects, to a process for the chemical insertion of cations of an alkali metal into a solid compound of formula (I): AbxiM mTO4, in which: A is chosen from lithium (Li) and sodium (Na),

[0012] M is chosen from manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), magnesium (Mg) and mixtures thereof,

[0013] T is chosen from phosphorus (P), arsenic (As) and their mixtures,

[0014] 0 <xl<l,et

[0015] m=l, the process comprising at least one step, called step (a), of bringing the solid compound of formula (I) into contact in an aqueous solution with a reducing agent and a source of alkali metal cations, whereby a solid compound of formula (II) is obtained: Ai x2MmTO4, in which:

[0016] A, M, T and m are as defined above,

[0017] 0 <x2<l,et

[0018] x2 <xl.

[0019] Surprisingly, it is possible to carry out the chemical insertion process according to the invention in an aqueous solution, whereas one usually seeks to minimize or even eliminate the use of water as a solvent.

[0020] The use of an aqueous solution as a solvent is particularly advantageous insofar as water is a so-called "green" solvent, unlike organic solvents which are generally harmful from an environmental and health point of view.

[0021] The chemical insertion method according to the invention is also simple to implement, and inexpensive insofar as the reagents used, in particular the reducing agent, the source of alkali metal cations and the aqueous solution, are inexpensive and insofar as the method can optionally be implemented without any heating step and under ambient air.

[0022] In particular, A, M and T are identical in the solid compound of formula (I) and the solid compound of formula (II).

[0023] In an exemplary embodiment, xl = 1. This means that the solid compound of formula (I) is devoid of A.

[0024] In an exemplary embodiment, 0 < xl < 1. This means that the solid compound of formula (I) is deficient in A.

[0025] In an exemplary embodiment, 0.1 < xl < 1, preferably 0.2 < xl < 1, more preferably 0.3 < xl < 1, even more preferably 0.4 < xl < 1, and in particular 0.5 < xl < 1, 0.6 < xl < 1, 0.7 < xl < 1, 0.8 < xl < 1, 0.9 < xl < 1, or even 0.95 < xl < 1.

[0026] In an exemplary embodiment, 0 < x2 < 1. This means that the solid compound of formula (II) is deficient in A, and therefore that the chemical insertion of cations of the alkali metal into the solid compound of formula (I) is partial.

[0027] In an exemplary embodiment, x2 = 0. This means that the solid compound of formula (II) is stoichiometric, and therefore that the chemical insertion of cations of the alkali metal into the solid compound of formula (I) is total.

[0028] In an exemplary embodiment, 0.1 > x2 > 0, preferably 0.09 > x2 > 0, more preferably 0.08 > x2 > 0, even more preferably 0.07 > x2 > 0, and in particular 0.06 > x2 > 0, 0.05 > x2 > 0, 0.04 > x2 > 0, 0.03 > x2 > 0, 0.02 > x2 > 0, or even 0.01 > x2 > 0.

[0029] The alkali metal may be chosen from lithium (Li) and sodium (Na).

[0030] This means that: - when the alkali metal is lithium (Li), the method according to the invention is a method of chemical insertion of lithium cations (Li+) and the source of cations of the alkali metal is a source of lithium cations (Li+), and that - when the alkali metal is sodium (Na), the process according to the invention is a process for the chemical insertion of sodium cations (Na+) and the source of cations of the alkali metal is a source of sodium cations (Na+).

[0031] In an exemplary embodiment, the alkali metal is lithium (Li) and A represents a lithium (Li) atom.

[0032] In an exemplary embodiment, the alkali metal is sodium (Na) and A represents a sodium (Na) atom.

[0033] The solid compound of formula (I) may have an olivine-type crystallographic structure.

[0034] The solid compound of formula (I) and the solid compound of formula (II) may have the same crystallographic structure.

[0035] Thus, the process according to the invention of chemical insertion of cations of the alkali metal into the solid compound of formula (I) to obtain the solid compound of formula (II) can make it possible to preserve the crystallographic structure of the solid compound of formula (I).

[0036] For example, the solid compound of formula (I) and the solid compound of formula (II) have an olivine-type crystallographic structure.

[0037] Step (a) may comprise at least one sub-step (a1) of adding the reducing agent and the source of alkali metal cations to the aqueous solution.

[0038] In an exemplary embodiment, the reducing agent and the source of alkali metal cations are added to the aqueous solution in an amount such that the molar ratio of reducing agent to source of alkali metal cations is between 0.25 and 1.25, and preferably between 0.5 and 1.

[0039] In an exemplary embodiment, the reducing agent is added to the aqueous solution in an amount such that the concentration of the reducing agent in the aqueous solution is less than or equal to the value of the maximum solubility of the reducing agent in the aqueous solution, and in particular such that the concentration of the reducing agent in the aqueous solution is greater than or equal to 0.001 mol / L.

[0040] In an exemplary embodiment, the source of alkali metal cations is added to the aqueous solution in an amount such that the concentration of the source of alkali metal cations in the aqueous solution is less than or equal to the value of the maximum solubility of the reducing agent in the aqueous solution, and in particular such that the concentration of the source of alkali metal cations in the aqueous solution is greater than or equal to 0.001 mol / L.

[0041] In an exemplary embodiment, the reaction medium obtained in step (a) or in sub-step (a1) has a pH of between 3 and 8.

[0042] Thus, step (a) can advantageously be carried out in a wide pH range.

[0043] This may allow the use of the reducing agent in a wide range of concentrations and / or the use of a wide variety of alkali metal cation sources. Furthermore, this is advantageous in that the chemical insertion method according to the invention does not require drastic pH control.

[0044] Step (a) may comprise at least one sub-step (a2) of adding the solid compound of formula (I) to the reaction medium obtained at the end of sub-step (a1).

[0045] In an exemplary embodiment, the solid compound of formula (I) is added to the reaction medium obtained at the end of sub-step (a1) in an amount such that the molar ratio of solid compound of formula (I) to source of alkali metal cations is between 0.25 and 1.25, preferably between 0.5 and 1.

[0046] Step (a) may comprise at least one sub-step (a3) ​​of stirring, in particular mechanical and / or magnetic, of the reaction medium obtained at the end of sub-step (a2). Sub-step (a3) ​​may make it possible to improve the kinetics of the chemical insertion reaction of the alkali metal cations into the solid compound of formula (I).

[0047] In particular, sub-step (a1), sub-step (a2) and / or sub-step (a3) ​​is carried out at room temperature.

[0048] The solid compound of formula (I) is preferably stable in water, especially in aqueous solution.

[0049] By "stable in water" is meant that the solid compound of formula (I) is thermodynamically stable in water, in particular in aqueous solution, and that it does not react with water, in particular with aqueous solution. For example, no chemical or redox reaction takes place between the solid compound of formula (I) and water, in particular aqueous solution.

[0050] The solid compound of formula (I) is preferably very slightly or even insoluble in water, in particular in aqueous solution.

[0051] The solid compound of formula (I) is preferably capable of dispersing in water, and in particular in the aqueous solution, so as to form a suspension of solid particles of the solid compound of formula (I) in the water, in particular in the aqueous solution.

[0052] Preferably, the solid compound of formula (I) is added to the aqueous solution in an amount of between 20 mg / L and 700 g / L of aqueous solution.

[0053] The aqueous solution may comprise at least 50% by volume of water, preferably at least 60% by volume of water, more preferably at least 70% by volume of water, even more preferably at least 80% by volume of water, and in particular at least 90% by volume of water.

[0054] In an exemplary embodiment, the aqueous solution comprises at least 91% by volume of water, at least 92% by volume of water, at least 93% by volume of water, at least at least 94% by volume of water, at least 95% by volume of water, at least 96% by volume of water, at least 97% by volume of water, at least 98% by volume of water, or even at least 99% water by volume.

[0055] In an exemplary embodiment, the aqueous solution consists of water.

[0056] The aqueous solution may comprise at least one organic solvent.

[0057] The organic solvent is preferably soluble in water.

[0058] The organic solvent can be chosen from:

[0059] - alcohols, in particular alcohols containing from 1 to 5 carbon atoms, in particular alcohols containing 1 to 3 carbon atoms, in particular methanol, ethanol and their mixtures;

[0060] - acetonitrile;

[0061] - tetrahydrofuran (THF);

[0062] - dimethyl sulfoxide (DMSO); and

[0063] - their mixtures.

[0064] The aqueous solution may comprise at most 50% by volume of organic solvent, preferably at most 40% by volume of organic solvent, more preferably at most 30% by volume of organic solvent, even more preferably at most 20% by volume of organic solvent, and in particular at most 10% by volume of organic solvent.

[0065] In an exemplary embodiment, the aqueous solution comprises at most 9% by volume of organic solvent, at most 8% by volume of organic solvent, at most 7% by volume of organic solvent, at most 6% by volume of organic solvent, at most 5% by volume of organic solvent, at most 4% by volume of organic solvent, at most 3% by volume of organic solvent, at most 2% by volume of organic solvent, or even at most 1% by volume of organic solvent.

[0066] Step (a) can be carried out with stirring, in particular mechanical and / or magnetic stirring. This can improve the kinetics of the chemical insertion reaction of the alkali metal cations into the solid compound of formula (I).

[0067] Step (a) can be carried out at room temperature.

[0068] In an exemplary embodiment, step (a) is carried out at a temperature less than or equal to 50°C, preferably at a temperature less than or equal to 45°C, and more preferably at a temperature less than or equal to 40°C.

[0069] In an exemplary embodiment, step (a) is carried out at a temperature greater than or equal to 10°C, preferably at a temperature greater than or equal to 15°C, and more preferably at a temperature greater than or equal to 20°C.

[0070] In an exemplary embodiment, step (a) is carried out at a temperature between 10°C and 50°C, preferably at a temperature between 15°C and 45°C, and more preferably at a temperature between 20°C and 40°C.

[0071] In particular, step (a) is carried out without heating.

[0072] In an exemplary embodiment, Mm represents MlmiM2m2M3m3M4m4M5m5, with: 0 < ml < 1 ; 0 < m2 < 1 ; 0 < m3 < 1 ; 0 < m4 < 1 ; 0 < m5 < 1 ; - ml + m2 + m3 + m4 + m5 = m = 1; And - Ml, M2, M3, M4 and M5 are different and chosen from manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) and magnesium (Mg).

[0073] The solid compound of formula (I) may be chosen from Lii xiMnPO4, Lii xiFePO4, Lii xiCoPO4, Lii xiNiPO4, Lii_xiFeo,95Mgo,o5P04, Lii-xiFeo^MgojPCL, Lii-xiMno^MgojPCL, Lii xiMno^Mgo.osPC^, Li| X|Mn066Fc() î4PO4, Li1_xiMnoj6Fe0j4P04, Nai xiFePO4, Na^xiMno^eFe o,34P04, Nai_xiMn0,6Fe0,4PO4,Nai_xiMnPO4, Nai xiCoPO4, and mixtures thereof.

[0074] In an exemplary embodiment, the solid compound of formula (I) is chosen from Lib xiMnPO4,Lii xiFePO4, Lii xiCoPO4, Lii xiNiPO4, Lii-xiFeo^MgmisPC^, Lii.xiFe0,9Mgo,iP04 , Lii-xiMno,9Mgo,iP04, Lii_xiMnoj95MgojosP04, Lii-xiMno,66Feo,34P04, Lii-xiMno,6Feo,4P04, and mixtures thereof.

[0075] In an exemplary embodiment, the solid compound of formula (I) is chosen from Na1 xiFePO4, Na^xiMno^Feo^PCL, Na1.xiMn0.6Fe0.4PO4Na1.xiMnPO4, Na1 xiCoPO4, and mixtures thereof.

[0076] In an exemplary embodiment, A represents a lithium (Li) atom.

[0077] In an exemplary embodiment, T represents a phosphorus atom (P).

[0078] In an exemplary embodiment, M is chosen from manganese (Mn), iron (Fe) and their mixtures.

[0079] In an exemplary embodiment, A represents a lithium (Li) atom and T represents a phosphorus (P) atom.

[0080] In an exemplary embodiment, A represents a lithium atom (Li), T represents a phosphorus atom (P), and M is chosen from manganese (Mn), iron (Fe) and mixtures thereof.

[0081] In an exemplary embodiment, the method according to the invention is a method for the chemical insertion of lithium cations (Li+), the source of alkali metal cations is a source of lithium cations (Li+), A represents a lithium atom (Li), T represents a phosphorus atom (P), and M is chosen from manganese (Mn), iron (Fe) and mixtures thereof.

[0082] In an exemplary embodiment, step (a) is carried out with quantities of reducing agent and source of alkali metal cations such that the molar ratio of reducing agent to source of alkali metal cations is between 0.25 and 1.25, preferably between 0.5 and 1.

[0083] In an exemplary embodiment, step (a) is carried out with quantities of solid compound of formula (I) and of source of alkali metal cations such that the molar ratio of solid compound of formula (I) to source of alkali metal cations is between 0.25 and 1.25, preferably between 0.5 and 1.

[0084] In an exemplary embodiment, step (a) is carried out with an amount of reducing agent in the aqueous solution such that the concentration of the reducing agent in the aqueous solution is less than or equal to the value of the maximum solubility of the reducing agent in the aqueous solution, and in particular such that the concentration of the reducing agent in the aqueous solution is greater than or equal to 0.001 mol / L.

[0085] In an exemplary embodiment, step (a) is carried out with an amount of source of alkali metal cations in the aqueous solution such that the concentration of the source of alkali metal cations in the aqueous solution is less than or equal to the value of the maximum solubility of the source of alkali metal cations in the aqueous solution, and in particular such that the concentration of the source of alkali metal cations in the aqueous solution is greater than or equal to 0.001 mol / L.

[0086] In an exemplary embodiment, step (a) is carried out with an amount of solid compound of formula (I) in the aqueous solution of between 20 mg / L and 700 g / L of aqueous solution.

[0087] The chemical insertion of alkali metal cations, i.e. positive charges, into the solid compound of formula (I) must be compensated by the injection of electrons, i.e. negative charges, into the solid compound of formula (I).

[0088] In other words, the chemical insertion of alkali metal cations into the solid compound of formula (I) must be compensated by the reduction of M of the solid compound of formula (I).

[0089] The presence of the reducing agent can allow the reduction of M of the solid compound of formula (I).

[0090] The reducing agent is preferably soluble in water, and in particular in aqueous solution.

[0091] The reducing agent is preferably organic.

[0092] The reducing agent may be chosen from:

[0093] - ascorbic acid (C6H8O6);

[0094] - its salts, in particular monosodium ascorbate (NaC6H7O6), ascorbate disodium (Na2C6H6O6), monolithium ascorbate (LiC6H7O6), dilithium ascorbate (Li2C6H6O6), sodium lithium ascorbate (NaLiC6H6O6) and mixtures thereof; and

[0095] - their mixtures.

[0096] The reducing agent is preferably non-toxic to health and / or the environment.

[0097] Step (a) can be carried out in air, in particular in ambient air, or in inert gas, in particular in argon or in nitrogen.

[0098] The use of an inert gas, such as for example argon or nitrogen, can make it possible to limit the contact of the solid compound of formula (II) obtained with oxygen and thus limit the oxidation of M of the solid compound of formula (II). Thus, this can make it possible to reinforce the stability of the solid compound of formula (II) obtained.

[0099] The source of alkali metal cations is preferably soluble in water, and in particular in aqueous solution.

[0100] The source of cations of the alkali metal may be a salt, in particular organic or inorganic, of the alkali metal.

[0101] The source of alkali metal cations may be a source of lithium cations (Li+) or a source of sodium cations (Na+).

[0102] The source of lithium cations (Li+) may be a lithium salt, in particular organic or inorganic, preferably soluble in water, and in particular in aqueous solution.

[0103] The source of lithium cations (Li+) can be chosen from: - lithium acetate (C2H3LiO2), in particular lithium acetate dihydrate (C2H3LiO2.2H2O); - lithium carbonate (Li2CO3); - lithium ascorbate, in particular monolithium ascorbate (LiC6H7O6 ), dilithium ascorbate (Li2C6H6O6), sodium lithium ascorbate (NaLiC6H6O6) and mixtures thereof; - lithium hydroxide (LiOH), including lithium hydroxide monohydrate (LiOH.H2O); - lithium sulfate (Li2SO4); - lithium chloride (LiCl); and - their mixtures.

[0104] The source of sodium cations (Na+) may be a sodium salt, in particular organic or inorganic, preferably soluble in water, and in particular in aqueous solution.

[0105] The source of sodium cations (Na+) can be chosen from: - sodium acetate (C2H3NaO2), in particular sodium acetate trihydrate (C2H3NaO2.3H2O); - sodium ascorbate, in particular monosodium ascorbate (NaC6H7O6), disodium ascorbate (Na2C6H6O6), sodium lithium ascorbate (NaLiC6H6O6) and mixtures thereof; - sodium chloride (NaCl); and - their mixtures.

[0106] In an exemplary embodiment, the reducing agent and the source of alkali metal cations are the same compound. Thus, in this exemplary embodiment, said compound plays both the role of the reducing agent and the role of the source of alkali metal cations.

[0107] Said compound may be a lithium and / or sodium ascorbate.

[0108] Said compound may be chosen from monosodium ascorbate (NaC6H7O6), disodium ascorbate (Na2C6H6O6), monolithium ascorbate (LiC6H7O6), dilithium ascorbate (Li2C6H6O6), sodium and lithium ascorbate (NaLiC6H6O6) and mixtures thereof.

[0109] When the alkali metal is sodium (Na), the reducing agent and the source of sodium cations (Na+) can be the same compound.

[0110] Said compound is preferably a sodium ascorbate.

[0111] Said compound is preferably chosen from monosodium ascorbate (NaC6H7O6 ), disodium ascorbate (Na2C6H6O6), sodium lithium ascorbate (NaLiC6H 6O6) and mixtures thereof.

[0112] When the alkali metal is lithium (Li), the reducing agent and the source of lithium cations (Li+) can be the same compound.

[0113] Said compound is preferably a lithium ascorbate.

[0114] Said compound is preferably chosen from monolithium ascorbate (LiC6H7O6 ), dilithium ascorbate (Li2C6H6O6), sodium lithium ascorbate (NaLiC6H6O6) and mixtures thereof.

[0115] When the reducing agent and the source of alkali metal cations are the same compound, said compound is added to the aqueous solution in an amount such that the concentration of said compound in the aqueous solution is less than or equal to the value of the maximum solubility of said compound in the aqueous solution, and in particular such that the concentration of said compound in the aqueous solution is greater than or equal to 0.001 mol / L.

[0116] Step (a) may have a sufficient duration to obtain the solid compound of formula (II).

[0117] The kinetics of chemical insertion of alkali metal cations into the solid compound of formula (I) may depend on the concentrations of the reducing agent and the source of alkali metal cations in the aqueous solution, the amount of the solid compound of formula (I) dispersed in the aqueous solution and the possible presence of agitation in step (a).

[0118] In an exemplary embodiment, the duration of step (a) is sufficient to obtain the solid compound of formula (II) with 0.1 > x2 > 0, preferably with 0.09 > x2 > 0, more preferably with 0.08 > x2 > 0, even more preferably with 0.07 > x2 > 0, and in particular with 0.06 > x2 > 0, 0.05 > x2 > 0, 0.04 > x2 > 0, 0.03 > x2 > 0, 0.02 > x2 > 0, or even 0.01 > x2 > 0.

[0119] Step (a) may have a duration less than or equal to 60 minutes, preferably a duration less than or equal to 55 minutes, more preferably a duration less than or equal to 50 minutes, even more preferably a duration less than or equal to 45 minutes, and in particular a duration less than or equal to 40 minutes.

[0120] Step (a) may have a duration greater than or equal to 5 minutes, preferably a duration greater than or equal to 10 minutes, and more preferably a duration greater than or equal to 15 minutes.

[0121] Step (a) may have a duration of between 5 minutes and 60 minutes, preferably between 10 minutes and 60 minutes, and more preferably between 15 minutes and 60 minutes.

[0122] Thus, the chemical insertion method according to the invention can advantageously exhibit very rapid chemical insertion kinetics.

[0123] The process may comprise at least one step, called step (b), of separating the solid compound of formula (II) from the reaction medium obtained at the end of step (a).

[0124] Step (b) can be carried out by centrifugation of the reaction medium obtained at the end of step (a) or by filtration of the reaction medium obtained at the end of step (a).

[0125] The centrifugation can be carried out at a rotation speed of between 3000 rpm and 9000 rpm, preferably between 4000 rpm and 8000 rpm, and more preferably between 5000 rpm and 7000 rpm. For example, the centrifugation is carried out at a rotation speed of approximately 6000 rpm.

[0126] The centrifugation can be carried out for a duration of between 2 min and 8 min, preferably between 3 min and 7 min, and more preferably between 4 min and 6 min. For example, the centrifugation is carried out for a duration of approximately 5 min.

[0127] Filtration can be carried out under vacuum.

[0128] The method may comprise at least one step, called step (c), of recovering the solid compound of formula (II) thus separated at the end of step (b).

[0129] The process may comprise at least one step, called step (d), of washing the solid compound of formula (II) thus recovered at the end of step (c).

[0130] Step (d) can be carried out using an organic washing solvent.

[0131] The organic washing solvent may be an alcohol, such as for example ethanol; dimethyl carbonate; or mixtures thereof.

[0132] The use of an alcohol, such as for example ethanol, as an organic washing solvent can be advantageous to the extent that such a solvent is weakly or even non-toxic to health and / or the environment.

[0133] The use of dimethyl carbonate as an organic washing solvent can be advantageous insofar as such a solvent has a high volatility, which can help promote its evaporation at the end of step (d).

[0134] The process may comprise at least one step, called step (e), of drying the solid compound of formula (II) thus washed at the end of step (d).

[0135] Step (e) can be carried out under vacuum; under inert gas, in particular under argon or nitrogen; or under air, in particular under ambient air.

[0136] In an exemplary embodiment, step (e) is carried out at room temperature.

[0137] In an exemplary embodiment, step (e) is carried out at a temperature less than or equal to 50°C, preferably at a temperature less than or equal to 45°C, and more preferably at a temperature less than or equal to 40°C.

[0138] In an exemplary embodiment, step (e) is carried out at a temperature greater than or equal to 10°C, preferably at a temperature greater than or equal to 15°C, and more preferably at a temperature greater than or equal to 20°C.

[0139] In an exemplary embodiment, step (e) is carried out at a temperature between 10°C and 50°C, preferably at a temperature between 15°C and 45°C, and more preferably at a temperature between 20°C and 40°C.

[0140] In an exemplary embodiment, step (e) is carried out by heating to a heating temperature T of the solid compound of formula (II) thus washed at the end of step (d), for example in an oven.

[0141] The heating temperature T may be less than or equal to 50°C, preferably between 40°C and 50°C, in particular when step (e) is carried out in air, in particular in ambient air.

[0142] The heating temperature T may be greater than 50°C, preferably between 55°C and 75°C, more preferably between 60°C and 70°C, in particular when step (e) is carried out under vacuum or under inert gas, in particular under argon or under nitrogen.

[0143] Step (e) may have a duration of between 10 minutes and 60 minutes.

[0144] Process for preparing an electroactive compound for an electric accumulator cathode

[0145] The invention also relates, according to another of its aspects, to a process for preparing an electroactive compound for an electric accumulator cathode from a solid compound of formula (I) as defined above, the electroactive compound being a solid compound of formula (II) as defined above, the process comprising the step(s) of a chemical insertion process as defined above, and a step of recovering the electroactive compound thus prepared.

[0146] The electric accumulator may be an electric battery accumulator, in particular lithium-ion or sodium-ion.

[0147] Process for preparing an electric accumulator cathode material

[0148] The invention also relates, according to another of its aspects, to a method for preparing an electric accumulator cathode material, the method comprising the steps of a method for preparing an electroactive compound as defined above, and a step of mixing the electroactive compound thus prepared with at least one non-electroactive additive, whereby the cathode material is obtained.

[0149] The non-electroactive additive may be chosen from a binder, an electronically conductive agent and mixtures thereof.

[0150] Preferably, the binder comprises, or even consists of, one or more polymers.

[0151] For example, the binder comprises polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE).

[0152] Preferably, the electronically conductive agent comprises, or even consists of, carbon.

[0153] For example, the electronically conductive agent comprises carbon black, graphite, carbon fibers and / or carbon nanotubes.

[0154] In one embodiment, the non-electroactive additive comprises, or even consists of, a binder, in particular polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE), and an electronically conductive agent, in particular carbon black, graphite, carbon fibers and / or carbon nanotubes.

[0155] In one embodiment, the non-electroactive additive comprises a total quantity of binder of between 50% by weight and 75% by weight, preferably of between 55% by weight and 70% by weight.

[0156] In one embodiment, the non-electroactive additive comprises a total amount of electronically conductive agent of between 25% by weight and 50% by weight, preferably of between 30% by weight and 45% by weight.

[0157] In one embodiment, the cathode material comprises a total amount of electroactive compound of between 80% by weight and 95% by weight, preferably between 85% by weight and 95% by weight.

[0158] In one embodiment, the cathode material comprises a total amount of non-electroactive additive of between 5% by weight and 20% by weight, preferably between 5% by weight and 15% by weight.

[0159] The electric accumulator may be an electric battery accumulator, in particular lithium-ion or sodium-ion.

[0160] Process for preparing an electric accumulator cathode

[0161] The invention also relates, according to another of its aspects, to a method for preparing an electric accumulator cathode, the method comprising the steps of a method for preparing a cathode material as defined above, and a step of depositing the cathode material thus prepared on a current collector, whereby the electric accumulator cathode is obtained.

[0162] The current collector is preferably made of an electronically conductive material, in particular a metallic material.

[0163] For example, the current collector is made of aluminum or platinum.

[0164] The electric accumulator may be an electric battery accumulator, in particular lithium-ion or sodium-ion.

[0165] Process for direct recycling of a material from a cathode at the end of the life of an electric accumulator

[0166] The invention also relates, according to another of its aspects, to a method for direct recycling of a material of a cathode at the end of its life of an electric accumulator, the material of the cathode at the end of its life comprising at least one solid compound of formula (I) as defined above, the method comprising at least one step, called step (v), of treatment of the material of the cathode at the end of its life in which the solid compound of formula (I) of the material of the cathode at the end of its life is brought into contact in an aqueous solution with a reducing agent and a source of cations of the alkali metal according to a chemical insertion method as described above.

[0167] The direct recycling process can make it possible to obtain a cathode material corresponding to the end-of-life cathode material into which cations of an alkali metal have been chemically inserted according to a chemical insertion process as defined above.

[0168] In other words, the direct recycling process can allow the direct regeneration into cations of an alkali metal of a material of a cathode at the end of its life.

[0169] Thus, the direct recycling process can make it possible to obtain a cathode material regenerated into cations of an alkali metal.

[0170] The direct recycling process is particularly advantageous insofar as it can allow this regeneration while preserving the morphology of the cathode material at the end of its life, in particular the morphology of its particles.

[0171] Preferably, the end-of-life cathode material comprises at least one non-electroactive additive.

[0172] The non-electroactive additive may be chosen from a binder, an electronically conductive agent and mixtures thereof.

[0173] Preferably, the binder comprises, or even consists of, one or more polymers.

[0174] For example, the binder comprises polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE).

[0175] Preferably, the electronically conductive agent comprises, or even consists of, carbon.

[0176] For example, the electronically conductive agent comprises carbon black, graphite, carbon fibers and / or carbon nanotubes.

[0177] In one embodiment, the non-electroactive additive comprises, or even consists of, a binder, in particular polyvinylidene fluoride (PVDF) and / or polytetrafluoroethylene (PTFE), and an electronically conductive agent, in particular carbon black, graphite, carbon fibers and / or carbon nanotubes.

[0178] In one embodiment, the non-electroactive additive comprises a total quantity of binder of between 50% by weight and 75% by weight, preferably of between 55% by weight and 70% by weight.

[0179] In one embodiment, the non-electroactive additive comprises a total amount of electronically conductive agent of between 25% by weight and 50% by weight, preferably of between 30% by weight and 45% by weight.

[0180] In one embodiment, the material of the cathode at the end of its life comprises a total quantity of electroactive compound of between 80% by weight and 95% by weight, preferably of between 85% by weight and 95% by weight.

[0181] In one embodiment, the end-of-life cathode material comprises a total amount of non-electroactive additive of between 5% by weight and 20% by weight, preferably between 5% by weight and 15% by weight.

[0182] When the end-of-life cathode material comprises at least one non-electroactive additive, the direct recycling process is particularly advantageous insofar as the treatment step (v) is carried out on the entire end-of-life cathode material, i.e. on the material comprising at least one solid compound of formula (I) and at least one non-electroactive additive.

[0183] In other words, there is no need to remove the non-electroactive additive from the end-of-life cathode material before carrying out treatment step (v).

[0184] Thus, the direct recycling process can allow the regeneration into cations of an alkali metal of a material of a cathode at the end of its life while preserving the formulation of said material.

[0185] The direct recycling process may comprise at least one step, called step (i), of recovering the cathode at the end of its life from the electric accumulator.

[0186] Step (i) may include a sub-step of dismantling the electric accumulator. The direct recycling process may include at least one step, called step (ii), of washing the end-of-life cathode obtained in step (i), in particular with an organic solvent, for example with dimethyl carbonate.

[0187] Step (ii) can make it possible to eliminate any traces of electrolyte present on the end-of-life cathode obtained in step (i).

[0188] The direct recycling process may comprise at least one step, called step (iii), of drying the end-of-life cathode obtained in step (ii).

[0189] Step (iii) can be carried out under vacuum; under inert gas, in particular under argon or nitrogen; or under air, in particular under ambient air.

[0190] In an exemplary embodiment, step (iii) is carried out at room temperature.

[0191] In an exemplary embodiment, step (iii) is carried out at a temperature less than or equal to 50°C, preferably at a temperature less than or equal to 45°C, and more preferably at a temperature less than or equal to 40°C.

[0192] In an exemplary embodiment, step (iii) is carried out at a temperature greater than or equal to 10°C, preferably at a temperature greater than or equal to 15°C, and more preferably at a temperature greater than or equal to 20°C.

[0193] In an exemplary embodiment, step (iii) is carried out at a temperature between 10°C and 50°C, preferably at a temperature between 15°C and 45°C, and more preferably at a temperature between 20°C and 40°C.

[0194] In an exemplary embodiment, step (iii) is implemented by heating to a heating temperature T of the end-of-life cathode obtained in step (ii), for example in an oven.

[0195] The heating temperature T may be less than or equal to 50°C, preferably between 40°C and 50°C, in particular when step (iii) is carried out in air, in particular in ambient air.

[0196] The heating temperature T may be greater than 50°C, preferably between 55°C and 75°C, more preferably between 60°C and 70°C, in particular when step (iii) is carried out under vacuum or under inert gas, in particular under argon or under nitrogen.

[0197] Step (iii) may have a duration of between 10 minutes and 60 minutes.

[0198] The direct recycling process may comprise at least one step, called step (iv), of recovering the end-of-life cathode material obtained in step (iii).

[0199] The direct recycling process may comprise at least one step, called step (vi), of recovering the material obtained in step (v).

[0200] The direct recycling process may comprise at least one step, called step (vii), of forming a new cathode with the material obtained in step (vi).

[0201] In particular, step (vii) is carried out without adding a non-electroactive additive to the material obtained in step (vi).

[0202] Indeed, as indicated above, the direct recycling process can allow the regeneration into cations of an alkali metal of a material of a cathode at the end of its life while preserving the formulation of said material.

[0203] Thus, when the end-of-life cathode material contains at least one non-electroactive additive, the latter is still present in the material regenerated into cations. of an alkali metal so that it is not necessary to add it to the regenerated material for the formation of a new cathode from this regenerated material.

[0204] The electric accumulator may be an electric battery accumulator, in particular lithium-ion or sodium-ion. Brief description of the figures

[0205] [Fig-1] [Fig.l] represents diffractograms obtained by diffraction of X-rays (DRX) of a powder a. of FePO4 obtained by chemical delithiation and of a powder b. of LiFePO4 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 1.

[0206] [Fig.2] [Fig.2] represents diffractograms obtained by X-ray diffraction (XRD) of a powder a. of FePO4 obtained by chemical delithiation and of a powder b. of LiFePO4 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 2.

[0207] [Fig.3] [Fig.3] represents diffractograms obtained by X-ray diffraction (XRD) of a powder a. of FePO4 obtained by chemical delithiation and of a powder b. of LiFePO4 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 3.

[0208] [Fig.4] [Fig.4] represents diffractograms obtained by X-ray diffraction (XRD) of a powder a. of FePO4 obtained by chemical delithiation and of a powder b. of LiFePO4 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 4.

[0209] [Fig.5] [Fig.5] represents diffractograms obtained by X-ray diffraction (XRD) of a powder a. of FePO4 obtained by chemical delithiation and of a powder b. of LiFePO4 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 5.

[0210] [Fig.6] [Fig.6] represents charge-discharge curves in galvanostatic mode at C / 10 vs. Li7Li° of a powder a) of FePO4 obtained by chemical delithiation and of a powder b) of LiFePO4 obtained by chemical lithiation of the powder a) in an aqueous solution under air and at room temperature according to the variant of the process according to the invention described in example 5.

[0211] [Fig.7] [Fig.7] represents diffractograms obtained by diffraction of X-rays (DRX) of a powder a) of FePO4 obtained by chemical delithiation and of a powder b) of LiFePO4 obtained by chemical lithiation of the powder a) in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 6.

[0212] [Fig.8] [Fig.8] represents diffractograms obtained by X-ray diffraction (XRD) of a powder a. of Mno.66Fe0.34P04 obtained by chemical delithiation and of a powder b. of LiMn0.66Feo.34P04 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 7.

[0213] [Fig.9] [Fig.9] represents charge-discharge curves in galvanostatic mode at C / 20 vs. Li7Li° of a powder a. of Mno.66Fe0.34P04 obtained by chemical delithiation and of a powder b. of LiMno.66Feo.34P04 obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to the variant of the process according to the invention described in example 7.

[0214] [Fig. 10] [Fig. 10] represents diffractograms obtained by X-ray diffraction (XRD) of a powder a. of a material of a LiFePO4 cathode at the end of its life and of a powder b. obtained by chemical lithiation of the powder a. in an aqueous solution under air and at room temperature according to a variant of the process according to the invention described in example 8.

[0215] [Fig. 11] [Fig. 11] represents charge-discharge curves in galvanostatic mode at C / 10 vs. Li7Li° of a powder a) of a material of a LiFePO4 cathode at the end of its life and of a powder b) obtained by chemical lithiation of the powder a) in an aqueous solution under air and at room temperature according to the variant of the process according to the invention described in example 8. Examples Example 1

[0216] Solid compound of formula (I): FePO4 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiFePO4 using Fe3+ ions in solution.

[0217] Reducing agent: ascorbic acid (C6H8O6, Fisher scientific, 99%).

[0218] Source of alkali metal cations: lithium acetate dihydrate (C2H3LiO2.2H2O, Fisher scientific, 98%).

[0219] Solid compound of formula (II): LiFePO4

[0220] The solid compound of formula (I), i.e. the FePO4 powder, was characterized by DRX (Fig. 1a).

[0221] Ascorbic acid and lithium acetate dihydrate were dissolved in 50 mL of distilled water with a molar ratio of 1 / 1. Then, 1 g of FePO4 powder was added to the solution with a molar ratio of 1 to 1 Li, and then the solution was stirred for approximately 15 minutes at room temperature, in ambient air or in a controlled atmosphere (under argon for example). The solution was centrifuged (6000 rpm for 5 min) and the powder obtained was washed with ethanol and dried at 60°C.

[0222] The recovered powder was characterized by DRX (Fig. 1b.), indicating the total disappearance of the peaks of the FePO4 phase and the presence of a single LiFePO4 phase. This result confirms the total reduction of Fe111 to Fe11 and therefore the total lithiation of FePO4 to LiFePO4. Example 2

[0223] Solid compound of formula (I): FePO4 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiFePO4 using Fe3+ ions in solution.

[0224] Reducing agent: sodium ascorbate (C6H7NaO6, Fisher scientific, 99%).

[0225] Source of alkali metal cations: lithium acetate dihydrate (C2H3LiO2.2H2O, Fisher scientific, 98%).

[0226] Solid compound of formula (II): LiFePO4

[0227] The solid compound of formula (I), i.e. FePO4 powder, was characterized by DRX (Fig. 2a.).

[0228] Sodium ascorbate and lithium acetate dihydrate were dissolved in 50 mL of distilled water with a molar ratio of 1 / 1. Then, 1 g of FePO4 powder was added to the solution with a molar ratio of 1 to 1 Li, and then the solution was stirred for about 15 minutes at room temperature, under ambient air or under a controlled atmosphere (under argon for example). The solution was centrifuged (6000 rpm for 5 min) and the resulting powder was washed with ethanol and dried at 60°C.

[0229] The recovered powder was characterized by DRX (Fig. 2b.), indicating the total disappearance of the peaks of the FePO4 phase and the presence of a single LiFePO4 phase. This result confirms the total reduction of Fe111 to Fe11 and therefore the total lithiation of FePO4 to LiFePO4. Example 3

[0230] Solid compound of formula (I): FePO4 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiFePO4 using Fe3+ ions in solution.

[0231] Reducing agent: ascorbic acid (C6H8O6, Fisher scientific, 99%).

[0232] Source of alkali metal cations: lithium hydroxide monohydrate (LiOH.H2O, Fisher scientific, 98%).

[0233] Solid compound of formula (II): LiFePO4

[0234] The solid compound of formula (I), i.e. the FePO4 powder, was characterized by DRX (Fig. 3a.).

[0235] Ascorbic acid and lithium hydroxide monohydrate were dissolved in 50 mL of distilled water with a molar ratio of 0.5 / 1 respectively. Then, 1 g of FePO4 powder was added to the solution with a molar ratio of 1 to 1 Li, and then the solution was stirred for about 15 minutes at room temperature, under ambient air or under a controlled atmosphere (under argon for example). The solution was centrifuged (6000 rpm for 5 min) and the resulting powder was washed with ethanol and dried at 60°C.

[0236] The recovered powder was characterized by DRX (Fig. 3b), indicating the total disappearance of the FePO4 phase peaks and the presence of a single LiFePO4 phase. This result confirms the total reduction of Fe111 to Fe11 and therefore the total lithiation of FePO4 to LiFePO4. Example 4

[0237] Solid compound of formula (I): FePO4 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiFePO4 using Fe3+ ions in solution.

[0238] Reducing agent: ascorbic acid (C6H8O6, Fisher scientific, 99%).

[0239] Source of alkali metal cations: lithium hydroxide monohydrate (LiOH.H2O, Fisher scientific, 98%).

[0240] Solid compound of formula (II): LiFePO4

[0241] The solid compound of formula (I), i.e. FePO4 powder, was characterized by DRX (Fig. 4a.).

[0242] Ascorbic acid and lithium hydroxide monohydrate were dissolved in 50 mL of distilled water with a molar ratio of 1. Then, 1 g of FePO4 powder was added to the solution with a molar ratio of 1 to 1 Li, and then the solution was stirred for about 15 minutes at room temperature, under ambient air or under a controlled atmosphere (under argon for example). The solution was centrifuged (6000 rpm for 5 min) and the resulting powder was washed with ethanol and dried at 60°C.

[0243] The recovered powder was characterized by DRX (Fig. 4b), indicating the total disappearance of the FePO4 phase peaks and the presence of a single LiFePO4 phase. This result confirms the total reduction of Fe111 to Fe11 and therefore the total lithiation of FePO4 to LiFePO4. Example 5

[0244] Solid compound of formula (I): FePO4 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiFePO4 using Fe3+ ions in solution.

[0245] Reducing agent: ascorbic acid (C6H8O6, Fisher scientific, 99%).

[0246] Source of alkali metal cations: lithium hydroxide monohydrate (LiOH.H2O, Fisher scientific, 98%).

[0247] Solid compound of formula (II): LiFePO4

[0248] The solid compound of formula (I), i.e. FePO4 powder, was characterized by DRX (Fig. 5a.).

[0249] Ascorbic acid and lithium hydroxide monohydrate were dissolved in 50 mL of distilled water with a molar ratio of 1 / 2 respectively. Then, 1 g of FePO4 powder was added to the solution with a molar ratio of 1 to 2 Li, and then the solution was stirred for about 15 minutes at room temperature, under ambient air or under a controlled atmosphere (under argon for example). The solution was centrifuged (6000 rpm for 5 min) and the resulting powder was washed with ethanol and dried at 60°C.

[0250] The recovered powder was characterized by DRX (Fig. 5b), indicating the total disappearance of the FePO4 phase peaks and the presence of a single LiFePO4 phase. This result confirms the total reduction of Fe111 to Fe11 and therefore the total lithiation of FePO4 to LiFePO4.

[0251] Figure 6a) shows the electrochemical properties of FePO4 versus lithium in galvanostatic mode at C / 10. The first discharge corresponds to the reduction of the FePO4 phase.

[0252] Figure 6b) shows the electrochemical performance of relithiated LiFePO4 tested under the same conditions, 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 starting FePO4 phase. Example 6

[0253] Solid compound of formula (I): FePO4 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiFePO4 using Fe3+ ions in solution.

[0254] Reducing agent: ascorbic acid (C6H8O6, Fisher scientific, 99%).

[0255] Source of alkali metal cations: lithium hydroxide monohydrate (LiOH.H2O, Fisher scientific, 98%).

[0256] Solid compound of formula (II): LiFePO4

[0257] The solid compound of formula (I), i.e. FePO4 powder, was characterized by DRX (Fig. 7a)).

[0258] Ascorbic acid and lithium hydroxide monohydrate were dissolved in 1 L of distilled water with a molar ratio of 1 / 2 respectively. Then, 100 g of FePO4 powder was added to the solution with a molar ratio of 1 to 2 Li, then the solution was stirred for about 1 hour at room temperature, under ambient air. The solution was filtered and the resulting powder was washed with ethanol and dried at 60°C.

[0259] The recovered powder was characterized by DRX (Fig. 7b)), indicating the total disappearance of the peaks of the FePO4 phase and the presence of a single LiFePO4 phase. This result confirms the total reduction of Fe111 to Fe11 and therefore the total lithiation of FePO4 to LiFePO4. Example 7

[0260] Solid compound of formula (I): Mn0.66Feo.34P04 in powder form, having an olivine-type crystallographic structure, obtained by total chemical delithiation of commercial LiMnFePO4 using nitronium tetrafluoroborate NO2BF4 in acetonitrile.

[0261] Reducing agent: ascorbic acid (C6H8O6, Fisher scientific, 99%).

[0262] Source of alkali metal cations: lithium acetate dihydrate (C2H3LiO2.2H2O, Fisher scientific, 98%).

[0263] Solid compound of formula (II): LiMn0.66Fe0.34PO4

[0264] The solid compound of formula (I), i.e. the powder Mno.66Fe0.34P04, was characterized by DRX (Fig. 8a.).

[0265] Ascorbic acid and lithium acetate dihydrate were dissolved in 50 mL of distilled water with a molar ratio of 1. Then, 1 g of the powder Mn0.66Fe0.34PO4 was added to the solution with a molar ratio of 1 to 1 Li, and then the solution was stirred for about 15 minutes at room temperature, under ambient air or under a controlled atmosphere (under argon for example). The solution was centrifuged (6000 rpm for 5 min) then washed with ethanol and dried at 60°C.

[0266] The recovered powder was characterized by DRX (Fig. 8b.), indicating the total disappearance of the peaks of the Mno.66Fe0.34PO4 phase and the presence of a single LiMn066Fe o 34PO4 phase. This result confirms the total reduction of Mn111 to Mn11 and of Fe111 to Fe11 and therefore the total lithiation of Mn0.66Fe0.34PO4 to LiMn0.66Fe0.34PO4.

[0267] Figure 9a. shows the electrochemical properties of Mno.66Fe0.34PO4 versus lithium in galvanostatic mode at C / 20. The first discharge corresponds to the reduction of the Mn0.66Fe0.34PO4 phase, thus indicating two reduction plateaus at 4 V and 3.4 V corresponding to the reduction of Mn111 to Mnu and Fe111 to Fe11 respectively.

[0268] Figure 9b. shows the electrochemical performances of relithiated LiMn0.66Fe0.34PO4 tested under the same conditions, indicating the good electrochemical signature of LiMn0.66Fe0.34PO4. The absence of the reduction plateaus of Mn111 to Mn11 around 4 V and Fe111 to Fe11 at a potential of 3.4 V during the first discharge confirms the complete lithiation of the initial Mno.66Fe0.34PO4 phase. Example 8

[0269] This example illustrates a variant of the direct recycling process according to the invention.

[0270] In this example, a LiFePO4 cathode from a 1 Ah end-of-life commercial battery (LiFePO4 / graphite, 18500 cylindrical cell) was used for chemical lithiation.

[0271] The LiFePO4 cathode powder was recovered and characterized by XRD (Fig. 10a.), indicating the presence of two olivine phases, LiFePO4 triphylite and FePO 4 heterosite as the majority phase (approximately 75% of the cathode powder at the end of its life).

[0272] The electrochemical properties of the recovered LiFePO4 cathode were evaluated versus lithium in galvanostatic mode at C / 10 (Fig. 1 la)). The first discharge corresponds to the reduction of the FePO4 phase. These results confirm that there is a lack of lithium in the LiFePO4 cathode at the end of its life.

[0273] The end-of-life LiFePO4 cathode was regenerated into lithium cations (Li+) using the process detailed in Example 3 with an ascorbic acid / lithium hydroxide monohydrate / FePO4 molar ratio of 1 for the approximately 75% FePO4 present in the end-of-life cathode powder.

[0274] The result of the DRX analysis (Fig. 10b.) confirms the total lithiation of the LiFePO4 cathode at the end of its life by showing the total disappearance of the characteristic peaks of the FePO4 phase as well as the presence of a single LiFePO4 phase.

[0275] The electrochemical performances of the regenerated LiFePO4 cathode were tested under the same conditions used for the end-of-life LiFePO4 cathode (Fig. 11b) 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 mainly in the end-of-life cathode.

[0276] This process of regenerating lithium cations (Li+) from a LiFePO4 cathode at the end of its life preserves the formulation of the cathode (electroactive material, conductive carbon and polymer binder), the carbon “coating” as well as the morphology of the particles.

[0277] This direct recycling process paves the way for more sustainable recycling of Li-ion batteries.

[0278] In addition, the direct recycling process can be carried out in aqueous solution, without heat treatment, which is particularly advantageous for the recycling of end-of-life battery stocks.

Claims

Claims

1. A process for the chemical insertion of cations of an alkali metal into a solid compound of formula (I): Ai_xiMmTO4, in which: A is chosen from lithium (Li) and sodium (Na), M is chosen from manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), magnesium (Mg) and mixtures thereof, T is chosen from phosphorus (P), arsenic (As) and mixtures thereof, 0 < xl < 1, and m = 1, the process comprising at least one step, called step (a), of bringing the solid compound of formula (I) into contact in an aqueous solution with a reducing agent and a source of cations of the alkali metal, whereby a solid compound of formula (II) is obtained: Abx2 MmTO4, in which: A, M, T and m are as defined above, 0 < x2 < 1, and x2 < xl.

2. A method according to claim 1, wherein the solid compound of formula (I) has an olivine-type crystallographic structure.

3. A method according to claim 1 or 2, wherein the aqueous solution comprises at least 50% by volume of water, preferably at least 60% by volume of water, more preferably at least 70% by volume of water, even more preferably at least 80% by volume of water, and in particular at least 90% by volume of water.

4. Method according to any one of the preceding claims, in which step (a) is carried out with stirring, in particular mechanical and / or magnetic stirring.

5. Method according to any one of the preceding claims, in which step (a) is carried out at room temperature, in particular at a temperature less than or equal to 50°C.

6. Method according to any one of the preceding claims, in which step (a) is carried out in air, in particular in ambient air, or in inert gas, in particular in argon or in nitrogen.

7. A method according to any preceding claim, wherein the alkali metal is lithium (Li), and A represents a lithium (Li) atom.

8. A method according to any one of claims 1 to 6, wherein the alkali metal is sodium (Na), and A represents a sodium (Na) atom.

9. A method according to any preceding claim, wherein T represents a phosphorus atom (P).

10. A method according to any preceding claim, wherein M is selected from manganese (Mn), iron (Fe) and mixtures thereof.

11. A method according to any preceding claim, wherein the reducing agent is selected from ascorbic acid (C6H8O6), its salts and mixtures thereof.

12. The method of claim 11, wherein the reducing agent is selected from ascorbic acid, monosodium ascorbate (NaC6H7O6), disodium ascorbate (Na2C6H6O6), monolithium ascorbate (LiC6H7O6), dilithium ascorbate (Li2C6H6O6), sodium lithium ascorbate (NaLiC6H6O6) and mixtures thereof.

13. A method according to any preceding claim, wherein step (a) has a duration of less than or equal to 60 minutes.

14. Method according to any one of the preceding claims, in which 0.1 < xl < 1, preferably 0.2 < xl < 1, more preferably 0.3 < xl < 1, even more preferably 0.4 < xl < 1, and in particular 0.5 < xl < 1.

15. Method according to any one of the preceding claims, in which 0.1 > x2 > 0, preferably 0.09 > x2 > 0, more preferably 0.08 > x2 > 0, even more preferably 0.07 > x2 > 0, and in particular 0.06 > x2 > 0.

16. Process for preparing an electroactive compound for an electric accumulator cathode from a solid compound of formula (I) as defined in any one of claims 1 to 15, the electroactive compound being a solid compound of formula (II) as defined in any one of claims 1 to 15, the process comprising the step(s) of a chemical insertion process according to any one of claims 1 to 15, and a step of recovering the electroactive compound thus prepared.

17. A method of preparing an electric accumulator cathode material, the method comprising the steps of a method of preparing an electroactive compound according to claim 16, and

18.

19. a step of mixing the electroactive compound thus prepared with at least one non-electroactive additive, whereby the cathode material is obtained. A method for preparing an electric accumulator cathode, the method comprising the steps of a method for preparing a cathode material according to claim 17, and a step of depositing the cathode material thus prepared on a current collector, whereby the electric accumulator cathode is obtained. A method for directly recycling a material of an end-of-life cathode of an electric accumulator, the material comprising at least one solid compound of formula (I) as defined in any one of claims 1 to 15, the method comprising at least one step, called step (v), of treating the end-of-life cathode material in which the solid compound of formula (I) of the end-of-life cathode material is brought into contact in an aqueous solution with a reducing agent and a source of alkali metal cations according to a chemical insertion method according to any one of claims 1 to 15.

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