Methods for the alkalization or realkalization of an active electrode material

Abstract

Methods are described for the direct or indirect electrochemical alkalization of an alkali metal-deficient electrochemically active material. The methods involve an electrolysis step during the alkalization of the alkali metal-deficient electrochemically active material on an electrode current collector (direct alkalization) or during the regeneration of a reducing agent used for the alkalization of the electrochemically active material (indirect alkalization).

Description

[0001] METHODS FOR ALKALINATING OR REALKALINATING AN ACTIVE ELECTRODE MATERIAL

[0002] RELATED REQUEST

[0003] This application claims priority, under applicable law, from U.S. Provisional Patent Application No. 62 / 934,782 filed on November 13, 2019, the contents of which are incorporated herein by reference in their entirety and for all purposes.

[0004] TECHNICAL FIELD

[0005] The present technology relates generally to the field of processes for the intercalation or re-intercalation of alkali metal ions in electrochemically active materials, for example, for the production of metal oxides and phosphates comprising an alkali metal.

[0006] STATE OF THE ART

[0007] In lithium battery manufacturing, the positive electrode is typically produced by spreading a suspension of active material, conductive material, and binder onto a current collector, usually an aluminum foil, followed by drying. The active material is usually a lithium metal oxide or a lithium metal phosphate, where the metal can be a transition metal or a combination of two or more transition metals. The electrochemical cell is usually assembled with a negative electrode and a separator in the discharged state, meaning the positive electrode is fully lithium-saturated. The active material V₂O₅ is an exception, as it is spread in its non-lithiumized form onto the current collector. In such a case, the battery is assembled in the fully charged state, which poses a serious safety and fire hazard. The group of Walk et al.described a pre-lithiation process for V2O5 electrodes under electrochemical conditions using metallic lithium as the negative electrode (see U.S. Patent No. 5,496,663). Such a lithiation process is considered galvanic and requires the use of aprotic, non-aqueous electrolytes due to the presence of metallic lithium as a necessary lithium source and its incompatibility with various solvents, particularly aqueous solutions. Another drawback of this approach is that metallic lithium is not the most cost-effective lithium source, either economically or in terms of the precautions required when used in a large-scale process.

[0008] The use of metallic lithium or metallic lithium alloys for relithiation in organic solvents has also been proposed for other electrode materials by Liu et al. (see PCT publication number WO2019 / 070896 A1). However, this approach is also based on the use of metallic lithium (or one of its alloys) applied directly to the electrode material and organic electrolytic solvents in a complex, multi-step process involving steps such as the formation of a bag cell, waiting for a long period (usually over 20 hours), and then peeling off the excess metallic lithium.

[0009] To avoid the aforementioned drawbacks associated with using metallic lithium as the lithium source in the lithiation process, others have proposed using less expensive materials such as lithium chloride (instead of metallic lithium) in an organic solvent (see Grant et al., U.S. patent application number US2018 / 0040914). In this process, the electrode materials in which the lithium is intercalated are lithium-ion battery anode materials such as graphite, silicon oxides, and tin oxides. The lithium halides used in the process generate toxic and corrosive halogen gases at the counter electrode. These halogen gases can also react with any residual water in the setup and produce more corrosive acids such as HCl or HF, necessitating additional precautions during the process.

[0010] Another group presented a reconstitution of lithium-depleted battery electrode materials (see Sloop, U.S. Patent No. 9,287,552). Various approaches are described, including a high-temperature solid-state reaction, a hydrothermal process carried out in a sealed pressure vessel, and the use of reducing conditions, which could potentially be achieved in situ by introducing a reducing solution directly into a used battery. This last approach fails to consider that lithium deficiency is not the only defect in a used battery. Indeed, the electrode may also exhibit fractures in the active material and binder, lithium antisites, a passivation layer, current collector delamination, a reducing copper deposit on the cathode surface, current collector corrosion, and so on.Furthermore, Sloop proposes that the positive electrode be separated intact from the battery, which is very difficult to implement on a large scale, for example, by including the extraction of the electrode roll ("jelly-roll") from a used battery, the unwinding and sorting of the electrodes, while also handling the entire electrode strip for subsequent steps. Such a separated electrode will also exhibit the additional defects mentioned above. Sloop also refers to, but does not demonstrate, the relithiation of the used positive electrode, which is in pieces deposited in an electrically charged tray or grid. Poor electrical contact between the electrode pieces and the tray or grid will result in an uneven distribution of current and potential, promoting other electrochemical reactions (such as hydrogen evolution) and leading to low current efficiency and uneven relithiation throughout the electrode.

[0011] Therefore, there is a need for new processes for the alkalination or realkalinization of active electrode materials, including processes that can be used in the preparation of new electrode material or for its recycling.

[0012] SUMMARY

[0013] According to a first aspect, this document relates to a process for the electrochemical alkalilation of an electrochemically active material, the process comprising the steps of: a) obtaining a working electrode comprising a working electrode material on a current collector, the working electrode material comprising the electrochemically active material, optionally a binder and / or an electronically conductive material; b) introducing the working electrode into an electrochemical reactor in continuous and / or batch mode with an inert counter electrode, and a solution comprising an alkali metal salt in a solvent; c) applying a direct current between the working electrode and the counter electrode to obtain an alkali-treated electrode comprising an alkali-treated electrochemically active material; and d) removing the alkali-treated electrode obtained in step (c) from the electrochemical reactor;in which the electrochemically active material comprises a metal oxide (including complex oxides), a metal phosphate, a metal silicate, a metal sulfate, or a partially alkali metal oxide (including complex oxides), metal phosphate, metal silicate, or metal sulfate.;

[0014] In one embodiment, the electrochemically active material is alkali metal deficient. In another embodiment, the process comprises the conversion of an electrochemically active material of Formula I:

[0015] Aw-pM n+P xXyOz (I) in an electrochemically active alkaline material of Formula II:

[0016] AwM n xXyOz (II) in which,

[0017] A is an alkali metal;

[0018] M is a transition metal, a post-transition metal, or a combination of these;

[0019] X is chosen from P, Si and S;

[0020] O is an oxygen atom; w is chosen from the numbers 1 to 4 and corresponds to the number of A atoms in the electrochemically active alkali material; x is chosen from the numbers 1 to 5 and corresponds to the number of M atoms; y is chosen from the numbers 0 to 2, in which X is absent when y is zero; z is chosen from the numbers 1 to 12 and corresponds to the number of oxygen atoms in the formulas; n denotes the oxidation state of M; p in Formula I denotes both the average number of missing A atoms and the average increase in the oxidation state of M, in which p < w (preferably 0 < p < 1); and in which w, y, z, n, and p are chosen to obtain a stable, electroneutral compound.

[0021] In another embodiment, p = w, A is absent in Formula I, and the electrochemically active material of Formula I is of Formula l(a): M n+ P x X yOz. In another embodiment, X is a phosphorus, y is 1, and z is 4. In another embodiment, M is Fe, Ni, Mn, Co, or a combination of two or more of these. In an alternative embodiment, M is V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn, or a combination of two or more of these. In yet another embodiment, y is 0 and X is absent. According to some preferred embodiments, A is Li, Na, or K, or A is Li.

[0022] In another embodiment, the electrochemically active material or the alkali-active electrochemically active material is further doped by the partial substitution of M with a transition metal (e.g., V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W or Y) and / or a metal other than a transition metal (e.g., Mg, Ca, Sr, Al, Sb, or Sn).

[0023] In an additional embodiment, the solvent is chosen from an aqueous solvent, an organic solvent or one of their mixtures, for example, the solvent is water.

[0024] In other embodiments, the alkali metal salt comprises at least one alkali metal sulfate, carbonate, bicarbonate, hydroxide, nitrate, acetate, oxalate, or phosphate salt. In one embodiment, the alkali metal salt is an alkali metal sulfate. In another embodiment, the alkali metal salt is an alkali metal bicarbonate, for example, where step (b) and / or (c) is carried out in the presence of carbon dioxide gas. In another embodiment, the process further comprises a step of adjusting the pH of the solution to a pH suitable for the electrochemically active material of step (a) (for example, for FePC, the pH is adjusted to between 5 and 9, preferably between 6 and 7.5). In one embodiment, the alkali metal of the alkali metal salt is lithium.

[0025] In other embodiments, step (c) is carried out in continuous or discontinuous mode. In another embodiment, step (c) is carried out in continuous mode where the working electrode is introduced into the electrochemical reactor from one side and moves along a defined path such that the working electrode remains at a constant distance from the counter electrode while moving through an electrochemically active region of the electrochemical reactor in order to maintain a relatively uniform current and potential distribution. In another embodiment, the speed at which the working electrode moves through the electrochemical reactor is adjusted according to the residence time required for a desired level of alkalimation at an applied current density.

[0026] In yet another embodiment, step (c) is carried out in controlled current density mode between the working electrode and the counter electrode. Alternatively, step (c) is carried out in controlled voltage mode between the working electrode and the counter electrode.

[0027] In other embodiments, the electrochemically active material is FePC or a partially delithiated LiFePO4 and the current density at the working electrode is in the range of 0.001 A / g to 100 A / g of active LiFePC, preferably in the range of 1 to 15 A / g of active LiFePC.

[0028] In another embodiment, step (c) is carried out at a temperature in the range of 5°C to 90°C, preferably from 25°C to 50°C. In some embodiments, step (b) may also include a reference electrode. In other embodiments, the above process further includes a step (e) of washing the electrochemically active alkali material from the alkali electrode and / or a step of drying the electrochemically active alkali material from the alkali electrode.

[0029] In other embodiments, the working electrode material comprises a binder, the binder being selected from fluoropolymer binders and other solvent polymer binders. In one embodiment, the binder is a fluoropolymer binder such as PVDF, HFP, PVDF-Co-FIFP, or PTFE. In another embodiment, the binder is a solvent polymer binder selected from poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamides), polyurethanes, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the preceding polymers or monomers thereof, as well as a combination of two or more of these polymers, these polymers optionally being branched and / or crosslinked.

[0030] In another embodiment, the working electrode material comprises an electronically conductive material, which is selected from the group consisting of carbon black (such as Ketjen black). MC and Super P MC ), acetylene black (such as Shawinigan black and Denka black) MC ), graphite, graphene, carbon fibers or nanofibers (such as gas-formed carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and a combination of two or more of these.

[0031] In some embodiments, the working electrode material is an electrode material (for example, a positive electrode material) from a used battery, and step (a) includes at least one step of separating the electrode material from the other elements of the used battery and applying said material to the current collector. In other embodiments, step (a) includes mixing the electrochemically active material, the binder, and optionally the electronically conductive material in a solvent, applying the mixture to the current collector, and drying it.

[0032] According to a second aspect, this document concerns an electrode obtained by a process as defined above.

[0033] According to a third aspect, this document relates to a process for the electrochemical alkalinization of an electrochemically active material, the process comprising the steps of:

[0034] (i) adding the electrochemically active material to a solution containing a reducing agent and an alkali metal salt in a solvent to produce an alkali electrochemically active material;

[0035] (ii) separation of the electrochemically active alkali material and the solution; and

[0036] (iii) electrochemical treatment of the solution separated in step (ii) to regenerate the reducing agent in the solution.

[0037] In one embodiment, the electrochemically active material and the alkali-deficient electrochemically active material are as defined herein. In another embodiment, the electrochemically active material is alkali metal-deficient. In yet another embodiment, the reducing agent is the reducing member of a redox couple having a lower redox potential than that of the electrochemically active (alkali metal-deficient) material to be reduced. In one embodiment, the redox couple comprises an Fe(ll) / Fe(ll) complex, for example, selected from [Fe(CN)6] 3 7[Fe(CN)6] 4 -, the [Fe(nta)] / [Fe(nta)j-, the [Fe(tdpa)] 2 Y[Fe(tdpa)] 3 -, the [Fe(edta)]7[Fe(edta)] 2 -, [Fe(citrate)] / [Fe(citrate)]-, [Fe(TEOA)OH]7[Fe(TEOA)OH]-, and [Fe(oxalate)]7[Fe(oxalate)j.

[0038] In one embodiment, step (i) further includes a step of deoxygenating the solution. In another embodiment, steps (i) and / or (iii) are carried out in the presence of a gas that removes oxygen. In another embodiment, the alkali metal salt is selected from an alkali metal sulfate, carbonate, bicarbonate, hydroxide, nitrate, acetate, oxalate, phosphate, and combinations thereof. In one embodiment, the alkali metal salt is an alkali metal sulfate. In another embodiment, the alkali metal salt is an alkali metal bicarbonate, for example, where step (i) is carried out in the presence of carbon dioxide gas. In another embodiment, the process further includes a step of adjusting the pH of the solution to a pH suitable for the electrochemically active material of step (i) (for example, for FePC, the pH is adjusted between 5 and 9, preferably between 6 and 7.5).In one embodiment, the alkali metal in the salt is lithium. In another embodiment, the solvent is an aqueous solvent.

[0039] In one embodiment, the electrochemical treatment step (iii) is carried out in an electrolytic cell by passing a current between at least one cathode and at least one anode. In one embodiment, the electrolytic cell includes at least one ionic or non-ionic separator installed between the anode and the cathode to protect the regenerated reducing agent. In another embodiment, the electrolytic cell further includes a system for keeping the solution deoxygenated, for example, the system includes maintaining an oxygen-free gas in the electrolytic cell, such as carbon dioxide, nitrogen, or argon.

[0040] In yet another embodiment, the electrochemically active material is in suspension in the solution of step (i), and step (ii) is carried out by filtration, centrifugation or decantation, optionally followed by a washing step.

[0041] Alternatively, the electrochemically active material is contained in an electrode material on a current collector (forming an electrode) and step (ii) includes the removal of the electrode from the solution, optionally followed by a washing step.

[0042] In one embodiment of this alternative, the electrode material further comprises a binder, for example, selected from fluoropolymer binders and other solvent polymer binders. According to one embodiment, the binder is a fluoropolymer binder (such as PVDF, HFP, PVDF-Co-FIFP, or PTFE). Alternatively, the binder is a solvent polymer binder selected from poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamides), polyurethanes, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the preceding polymers or monomers thereof, as well as a combination of two or more of these polymers, optionally branched and / or crosslinked.According to another embodiment, the electrode material further comprises an electronically conductive material, for example, selected from the group consisting of carbon black (such as Ketjen black). MC and Super P MC ), acetylene black (such as Shawinigan black and Denka black) MC ), graphite, graphene, carbon fibers or nanofibers (such as gas-formed carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and a combination of two or more of these.

[0043] In another embodiment, the process further includes drying the electrochemically active alkaline material.

[0044] According to a fourth aspect, the present document relates to an electrode comprising the electrochemically active alkaline material obtained by a process as defined herein, a binder and possibly an electronically conductive material.

[0045] According to a fifth aspect, this document relates to an electrochemical cell comprising a negative electrode, a positive electrode, and an electrolyte, wherein the positive electrode is an electrode as defined herein, or to a battery comprising at least one such electrochemical cell. For example, the battery is a lithium battery or a lithium-ion battery.

[0046] In another embodiment, the electrochemical cell or battery as defined herein is for use in mobile devices, such as mobile phones, cameras, tablets, or laptops, in electric or hybrid vehicles, or in renewable energy storage. BRIEF DESCRIPTION OF FIGURES

[0047] Figure 1 presents a graph of the leaching rate during delithiation as a function of time according to Example 1(a).

[0048] Figure 2 shows the X-ray diffraction patterns of virgin LiFePO4 (top line) and its delithiated FePO4 (bottom line) according to Example 1 (a).

[0049] Figure 3 shows the linear scanning voltamperometry of a FePÛ4 electrode carried out from 0V c. OCP (open circuit potential) to -1V c. SCE (saturated calomel electrode) at a rate of 1mV / s as described in Example 1(c).

[0050] Figure 4 shows the X-ray diffraction patterns of virgin LiFePO4 (top), delithiated FePO4 (middle) and delithiated LiFePO4 (bottom) according to Example 1.

[0051] Figure 5 shows a voltammeterogram of the galvanostatic relithiation of a FePÛ4 electrode carried out at 10mA according to Example 2.

[0052] Figure 6 shows the X-ray diffraction patterns of virgin LiFePO4 (top), delithiated FePO4 (middle) and relithiated LiFePO4 (bottom) according to Example 2. Figure 7 shows the galvanic response of two FePC electrodes subjected to potentiostatic relithiation at -0.2V c. ECS at 25°C (dashed line) and 50°C (solid line) according to Example 3.

[0053] Figure 8 shows the X-ray diffraction patterns of virgin LiFePC (top), LiFePO4 relithied at 25°C (middle) and LiFePC relithied at 50°C (bottom) according to Example 3.

[0054] Figure 9 shows the linear cathodic scanning voltammetry of a FeP4 electrode carried out at a flow rate of 1 mV / s between 0 V c. PCO2 and -1.1 V c. SCE in a 0.5 M aqueous solution of L1FICO3 according to Example 4. Figure 10 shows the galvanic response of two FePC electrodes subjected to potentiostatic relithiation at -0.2 V c. SCE at 25°C in 0.25 M L12SO4 (dashed line) and 0.5 M L1FICO3 (solid line) according to Example 4.

[0055] Figure 11 shows the X-ray diffraction patterns of virgin LiFePC (top), delithiated FePÛ4 (middle) and delithiated LiFePC (bottom) according to Example 4.

[0056] Figure 12 shows the current variation over time for an electrode material applied to an aluminum current collector according to the method of Example 5.

[0057] Figure 13 shows the X-ray diffraction patterns of virgin LiFePO4 (top), delithiated FePC (middle) and delithiated LiFePC (bottom) electrode materials according to Example 5.

[0058] Figure 14 shows the discharge capacity of relithied LiFePC (circles) compared to the reference LiFePC (triangles) according to Example 5.

[0059] Figure 15 shows a voltammogram of the EDTA-Fe(ll) solution taken between 2.05 V and 4.25 V vs Li + / Li at a slew rate of 200 mV / sec according to Example 6(b).

[0060] Figure 16 shows the polarization curves in the case of an EDTA-LiOH solution (dotted line) and EDTA-Fe(lll) in LiOH (solid line) according to Example 6(b).

[0061] Figure 17 shows the variation of the redox potential of the suspension during the reduction of FePC by EDTA-Fe(ll) according to Example 7(a).

[0062] Figure 18 shows the X-ray diffraction patterns of virgin LiFePC (top), delithiated LiFePO4 (middle) and delithiated LiFePC (bottom) according to Example 7(a).

[0063] Figure 19 shows the variation of the redox potential of the suspension during the reduction of FePC by citrate-Fe(ll) according to Example 7(b).

[0064] Figure 20 shows the X-ray diffraction patterns of virgin LiFePC (top), delithiated LiFePO4 (middle), and delithiated LiFePC (bottom) according to Example 7(b). Figure 21 shows the variation of the EDTA-Fe(ll) concentration and the redox potential of the solution during the electrolysis presented in Example 8(a).

[0065] Figure 22 shows the variation of the redox potential of the suspension during the reduction of FePC by EDTA-Fe(ll) generated by electrolysis of EDTA-Fe(ll) according to Example 8(b).

[0066] Figure 23 shows the X-ray diffraction patterns of virgin LiFePC (top), delithiated LiFePO4 (middle) and delithiated LiFePC (bottom) according to Example 8(b).

[0067] DETAILED DESCRIPTION

[0068] The detailed description and examples that follow are for illustrative purposes only and should not be construed as further limiting the scope of the invention.

[0069] All technical and scientific terms and expressions used herein have the same definitions as those commonly understood by a person skilled in the art relating to this technology. However, definitions of certain terms and expressions used are provided below for clarity.

[0070] When the term "approximately" is used here, it means roughly, in the region of, and around. When the term "approximately" is used in relation to a numerical value, it can modify it, for example, above and below its nominal value by a variation of 10%. This term can also account for the probability of random errors in experimental measurements or the rounding of a value.

[0071] The terms "alkalinize" and "alkalinization" as used here refer to the reduction of an active material containing a metal, accompanied by the insertion of alkali metal ions into the active material. The terms "lithier" and "lithiation" are used when the alkali metal ions are lithium ions. Similarly, the terms "alkalinized" and "lithiated" generally refer to a material resulting from alkaliation or lithiation, respectively. Likewise, the terms "realkalinize," "realkalinization," "relithier," and "relithiation" refer to the alkalination or lithiation of an active material that has lost or is deficient in alkali metal ions or lithium ions, respectively. This document therefore concerns the alkalination of an electrochemically active material containing at least one metal in a non-zero oxidation state.The first step in this process involves obtaining a working electrode comprising an electrode material on a current collector. The electrode material includes the electrochemically active material to be alkalized and may include other components. For example, the electrochemically active material may be uniformly dispersed in a binder and possibly a conductive material.

[0072] Electrochemically active material can generally be defined as comprising metal oxides (including complex oxides), metal phosphates, metal silicates, metal sulfates, or partially alkali-stabilized versions of these oxides, phosphates, silicates, or sulfates. For example, electrochemically active material has the following formula:

[0073] Aw-pM n+ PxXyOz (I) in which,

[0074] A is an alkali metal (e.g. Li, Na and K, preferably lithium);

[0075] M is a transition metal, a post-transition metal, or a combination of these;

[0076] X is chosen from P, Si, and S; and O represents an oxygen atom; w is chosen from the numbers 1 to 4 and corresponds to the number of A atoms in the electrochemically active alkali material; x is chosen from the numbers 1 to 5 and corresponds to the number of M atoms; y is chosen from the numbers 0 to 2, in which X is absent when y is zero; z is chosen from the numbers 1 to 12 and corresponds to the number of oxygen atoms in the formula; n denotes the oxidation state of M; p denotes both the average number of missing A atoms and the average increase in the oxidation state of M, in which p < w (preferably 0 < p < 1); and in which w, y, z, n, and p are chosen to obtain a stable, electroneutral compound. The electrochemically active alkali material obtained by the process is of Formula II:

[0077] AwM nxXyOz (II) where A, M, X, O, n, w, x, y, and z are as defined here.

[0078] An example of an electrochemically active material includes the compound of Formula I, where p = w, A is absent, and the electrochemically active material of Formula I is of Formula 1(a): M n+ P x X y Oz. In some examples, X is a phosphorus, y is 1 and z is 4.

[0079] Examples of transition metals (M) include Fe, Ni, Mn, Co, or a combination thereof, preferably when X is a phosphorus, y is 1, and z is 4. In another example, the electrochemically active material is FePC or partially delithiated LiFePC. Examples of M can also include a metal chosen from V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn, or a combination of two or more of these. In some examples, y is 0 and X is absent, with Formula I representing an oxide or a complex oxide.

[0080] The electrochemically active material and / or the alkali-electrochemically active material may also be doped by partial substitution (10 mol% or less, or 5 mol% or less) of M, for example, by a transition metal (e.g., Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W or Y) and / or a metal other than a transition metal (e.g., Mg, Ca, Sr, Al, Sb, or Sn).

[0081] In the first step of the process, an alkali metal-deficient material such as that of Formula I or l(a) can be mixed with all the necessary ingredients to prepare an electrode for an energy storage device and applied to a current collector. The material to be alkalized can be commercially available and included in the working electrode material of this process to achieve alkalization before use as an electrode in an electrochemical cell. Alternatively, the electrochemically active material to be alkalized can be the result of a battery recycling process.

[0082] The electrochemically active material may be in the form of microparticles or nanoparticles and / or may further include a carbon coating.

[0083] The ingredients for the electrode material may further include at least one binder, for example a polymer binder, preferably a polar and solvent polymer binder.

[0084] Non-limiting examples of solvent polymers suitable for use as positive electrode binders include polymer binders containing fluorine atoms, such as PVDF, HFP, PVDF-Co-HFP, and PTFE. Other examples of solvent polymer binders include poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamides), polyurethanes, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the preceding polymers or monomers thereof, as well as combinations of two or more. These solvent polymers may also be branched and / or crosslinked.Other examples of binders include water-soluble binders such as SBR (styrene-butadiene rubber), NBR (acrylonitrile butadiene rubber), HNBR (hydrogenated NBR), CHR (epichlorohydrin rubber), ACM (acrylate rubber), and others like them, and cellulose-based binders (e.g., carboxyalkylcellulose, hydroxyalkylcellulose, and combinations thereof), or any combination of two or more of these. It is understood that water-soluble binders may not be used in this alkalination process when the solvent of this process is an aqueous solvent.

[0085] Examples of electronically conductive materials include, but are not limited to, carbon black (such as Ketjen black). MC and Super P MC ), acetylene black (such as Shawinigan black and Denka black) MC), graphite, graphene, carbon fibers or nanofibers (such as vehicle-generated carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and a combination of two or more of these.

[0086] A second step in the process involves introducing the working electrode into an electrochemical reactor with an inert counter electrode and a solution containing an alkali metal salt in a solvent. The electrochemical reactor may also include a reference electrode (such as a saturated calomel electrode (SCE)). In another example, the electrochemical reactor may also be equipped with a potentiostat or rectifier for electrolysis. The electrochemical reactor is configured for continuous or batch electrolysis and may include additional components such as a stirring mode to increase mass transfer to the working electrode and / or a temperature control device.

[0087] The solution included in the electrochemical reactor serves as the electrolyte and comprises at least one salt of the alkali metal to be intercalated into the active material, for example, a lithium, sodium, or potassium salt, preferably a lithium salt, preferably excluding halide salts. Examples of suitable salts include sulfate, carbonate, bicarbonate, hydroxide, nitrate, acetate, oxalate, or phosphate salts of the alkali metal, for example, A₂SO₄ or AHCO₃, where A is as defined above. The solvent of the solution is an organic solvent, an aqueous solvent, or a combination thereof, preferably an aqueous solvent. For example, the solvent is water (e.g., distilled or high-purity water). A pH adjustment step may also be included in the process. The pH of the solution must be adapted to the electrochemically active material (and its alkaline version), for example, to maintain its stability and prevent its dissolution.For example, when the electrochemically active material to be processed is alkali metal or a partially alkaline version thereof, the pH is adjusted to between 5 and 9, preferably between 6 and 7.5. For example, if the solution is too acidic, the pH can be adjusted with an alkali metal hydroxide. A supporting electrolyte may also be added to reduce the electrolyte resistance. The counter electrode is made of a material inert under the electrolysis conditions, for example, platinum, a precious metal oxide, or a lead oxide, and may optionally include a layer of a catalytic compound to reduce electrode overpotential. For example, in the case of aqueous solutions, a reaction at the counter electrode may result in the release of oxygen, and dimensionally stable anodes may be used as the counter electrode material.

[0088] A third step involves applying a direct current between the working electrode containing the alkali metal-deficient electrochemically active material and the counter electrode to obtain an alkali electrode comprising the alkali electrochemically active material (for example, as defined in Formula II). This step can be carried out at a temperature in the range of 5°C to 90°C, preferably from 25°C to 50°C.

[0089] As mentioned above, the electrochemical reactor can operate in continuous or batch mode. In continuous mode, the working electrode enters the electrochemical reactor from one side and follows a defined path such that the working electrode remains at a constant distance from the counter electrode while moving through an electrochemically active zone of the reactor to maintain a relatively uniform current and potential distribution. The speed at which the working electrode moves through the electrochemical reactor depends on the residence time required for the desired alkali level and the applied current densities. The electrochemical reactor can operate in either controlled current density mode or controlled voltage mode between the working electrode and the counter electrode.

[0090] In a specific example, the electrochemically active material is FePC or partially delithiated LiFePO4, and the current density at the working electrode is in the range of 0.001 A / g to 100 A / g of active LiFePC, preferably in the range of 1 to 15 A / g of active LiFePC. Once the target alkalinization level is reached, the working electrode is removed from the electrochemical reactor. The alkalined electrode is then preferably subjected to a washing step to remove excess electrolyte from the alkalined electrode material, followed by a drying step to remove excess wash liquid.

[0091] When present, the reference electrode can be positioned in the reactor to monitor the potential of the working electrode. Its presence will minimize parasitic reactions at the working electrode and maximize the efficiency of the alkalination current.

[0092] Alternatively, a reducing chemical process can also be used for the alkalination of the electrochemically active material as defined herein. This alternative alkalination process includes a reducing agent and, furthermore, an electrochemical regeneration step for the reducing agent. For example, the electrochemically active material can be treated with a solution of the reducing agent and an alkali metal salt in a solvent. The solution can be deoxygenated before the addition of the reducing agent and / or the electrochemically active material if these can be readily oxidized in the presence of oxygen. Similarly, this step can also be carried out in the presence of a gas that removes oxygen (such as CO2, N2, or Ar). The resulting electrochemically active material and the resulting alkali-treated electrochemically active material are as defined above.Preferably, the electrochemically active material is deficient in alkali metal.

[0093] Non-limiting examples of alkali metal salts to be used in the chemical reduction step include alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, and phosphates, or combinations thereof. The solvent used is preferably an aqueous solvent.

[0094] In this process, the material to be alkalized can be treated as a suspension in a reactor, separated from the spent reducing agent solution, rinsed and dried, and then used as the active electrode material in electrode manufacturing. The separation of the alkalized material from the spent reducing agent solution can be carried out by typical physical separation methods, for example, filtration, centrifugation, or decantation. The separated and dried alkalized material can then be mixed with the components necessary for preparing an electrode and applied to a current collector. For example, these components might include a binder and possibly an electronically conductive material as defined above.

[0095] On the other hand, the material to be alkalineized using this process can first be mixed with the electrode material components defined above, and then applied to a suitable current collector to obtain an electrode such as the working electrode described in the previous process. The prepared electrode is then treated with the reducing agent solution, for example by immersion, washed, and dried.

[0096] In both cases, the spent reducing agent is recovered and then regenerated in a subsequent step. For example, the solution containing the spent reducing agent is transferred to a high-efficiency, high-current-density electrochemical (or electrolytic) cell to reduce (and thus regenerate) the spent reducing agent, which can then be reused to treat an alkali metal-deficient material. For example, the reducing agent regeneration step is carried out by electrochemical treatment in an electrolytic cell by passing a current between at least one cathode and at least one anode. This electrolytic cell may further include at least one ionic or non-ionic separator installed between the anode and the cathode to protect the regenerated reducing agent.

[0097] When the regenerated agent is sensitive to oxidation in the presence of oxygen, the electrolytic cell may also include a system to keep the solution deoxygenated, for example, including maintaining an oxygen-free gas in the electrolytic cell, such as carbon dioxide, nitrogen, or argon.

[0098] The current density of the electrolytic cell can be increased by manipulating mass transfer within the cell using well-known methods (such as the use of turbulence promoters, temperature increase, etc.) as well as by increasing the actual surface area of ​​the cathode (for example, by using materials such as felt, grids, etc.). If the electrolytic solution solvent is water-based, the cathode material should preferably be selected from those with a high hydrogen overpotential, such as graphite, lead, etc.

[0099] Since the reducing agent can be reused almost indefinitely, it can be considered that only electrons are used as the reducing agent for the electrode material, which can be considered an indirect electrochemical reduction. This process thus offers several advantages (economic, environmental, etc.) compared to using a reducing agent without its regeneration.

[0100] Various redox couples can be used as regenerable reducing agents. The chosen redox couple will have a lower redox potential than the electrochemically active (alkali metal-deficient) material to be reduced. For example, in the case of FePC relithiation, the redox couple should have a redox potential below 3.45 V c. Li / Li+ (see A.K. Padhi, et al., J. Electrochem. Soc., 1997, 144, 1188-1194).

[0101] Another desirable characteristic for the redox couple would be relatively high solubility, particularly in its oxidized form, to avoid precipitate formation in the presence of the treated electrode material. Examples of redox couples that could be used include Fe(ll) / Fe(lll) complexes, which exhibit properties of interest for use with this indirect electrochemical approach. These complexes include, for example, [Fe(CN)6] 3 / [Fe(CN)6] 4 , the [Fe(nta)] / [Fe(nta)] _ , the [Fe(tdpa)] 2 / [Fe(tdpa)] 3 , the [Fe(edta)] / [Fe(edta)] 2 , [Fe(citrate)] / [Fe(citrate)], [Fe(TEOA)OFI] / [Fe(TEOA)OFI] · , and [Fe(oxalate)]7[Fe(oxalate)]. These redox couples are particularly interesting for the alkalilation of an electrochemically active (alkali metal-deficient) iron-containing material, such as FePC

[0102] One advantage of this indirect electrochemical approach compared to the direct electrochemical reduction of the electrode material is the ability to use much higher current densities, thus increasing the productivity of the electrochemical reactor. Electrodes prepared by the processes described above can then be used directly to prepare electrochemical cells, for example, by stacking the electrode with an active counter electrode, the two electrodes being separated by an electrolyte, such as a liquid or gel electrolyte impregnating a separator, or a solid polymer electrolyte. These electrochemical cells can also be used in the preparation of electrochemical energy storage devices.

[0103] As indicated above, the material to be alkalized by the present processes can be either a spent electrode material obtained in a battery recycling process, or a new electrode material (or its precursor) to be transformed into a discharged electrode material before its assembly in the electrochemical cell.

[0104] This description also considers a battery comprising at least one electrochemical cell as defined herein. For example, the battery is a lithium or lithium-ion battery. These batteries and electrochemical cells can be used, for example, in mobile devices such as mobile phones, cameras, tablets, or laptops, in electric or hybrid vehicles, or in renewable energy storage.

[0105] EXAMPLES

[0106] The following non-limiting examples are illustrative embodiments and should not be interpreted as further limiting the scope of the present invention. These examples will be better understood by reference to the accompanying figures.

[0107] Example 1:

[0108] (a) Preparation of FePO delithiated

[0109] An unused cathode material containing primarily LiFePC with small amounts of PVDF and graphite was used to produce a delithiated material from LiFePC samples using the process described in US patent application 2019 / 0207275 (Amouzegar et al.). Ten parts of this material were dispersed in 100 parts of an aqueous solution containing H₂O₂ (the amount of H₂O₂ was adjusted to an Fe:H₂O₂ molar ratio of 2:1.33) in a stirred reactor through which gaseous CO₂ was bubbled at a pressure of 30 psi at room temperature. Filtered samples of the suspension taken at various intervals were analyzed by ICP to measure the concentrations of Li, Fe, and P. The solid residue from the leaching was then separated by centrifugation, washed with deionized water, and dried in an oven at 120°C for 48 hours.

[0110] Seven batches were prepared in this manner and then combined. Figure 1 shows the leaching rates of Li, Fe, and P obtained for each batch. These results were then used to calculate the leaching efficiency of each element. It was observed that after 30 minutes, nearly 80% of the Li could be found in the solution, and after 75 minutes this parameter reached a value of approximately 90%. The leaching rates for Fe and P did not exceed 0.5% and 3%, respectively, demonstrating very high selectivity and efficiency for lithium extraction.

[0111] X-ray diffraction spectra of the solid composite sample and the virgin LiFePC sample were obtained using a MiniFlex 600 instrument. MCequipped with a cobalt source and are shown in Figure 2. As can be seen, the sample is composed mainly of FePC with some residual LiFePC. In fact, the X-ray diffraction results confirm a higher delithiation rate than that calculated from the ICP analysis results (90% for ICP analysis compared to 95% from the diffraction results).

[0112] (b) FePO electrode preparation

[0113] To characterize the electrochemical behavior of the delithiated material of 1 (a) during relithiation, the FePC powder was mixed with conductive carbons (Denka black). MC and VGCF MC -H, 1:1 by weight) and a binder (PVDF) in mass proportions of 87.5:7.5:5, then dispersed in N-methyl-2-pyrrolidone (NMP) to form a suspension. This suspension is finally spread onto a 4.16 cm collector 2stainless steel using a doctor's blade and dried (the final FePC charge of the electrode was approximately 4.3 mg / cm²) 2 (c) Relithiation of FePO electrode material

[0114] The electrode prepared in (b) was tested as a working electrode in a three-electrode electrochemical setup. A platinum lattice was used as the counter electrode, while a saturated calomel electrode (SCE) served as the reference. The electrolyte consisted of an aqueous solution of L12SO4 (0.25 M) to which LiOH was added to adjust the pH to 7. The temperature was set at 25°C using a double-walled glass electrochemical cell (thermostatized). Figure 3 shows the current-to-potential voltammetry curves at a potential sweep rate of 1 mV / s.

[0115] The working electrode was first swept between its open-circuit potential (in this case 165 mV cd. SCE) and -1.0 V cd. SCE using a Versastat device MC 4 (Princeton Applied Research). It can be seen that, apart from the reduction peak corresponding to the lithiation of FePO4 to LiFePO4, no other reactions occur in this potential region. This means that cell operation within this potential window would allow for good coulombic current efficiency for the relithiation process. The X-ray diffraction pattern of the relithiated sample is compared to the pattern of a virgin LiFePO4 material and to that of the delithiated composite sample, as shown in Figure 4. It is clearly demonstrated that after relithiation, the structure of the delithiated sample reverts to that of the virgin material.

[0116] Example 2:

[0117] To perform electrochemical relithiation under conditions more suitable for large-scale industrial operation, the same type of electrode prepared in Example 1(b) was relithied under galvanostatic conditions by applying a constant current of 10 mA between the cathode (FePC electrode) and the anode (inert electrode, in this case a Pt lattice). The cathode potential was measured relative to an ECS reference electrode to determine the time required to relithify almost all of the delithiated FePÛ4. Electrolysis was carried out in the same type of solution as in Example 1(c) and at the same temperature (25°C). The variation of the cathode potential as a function of electrolysis time is shown in Figure 5. The initial cathode potential was approximately 0 Vc. ECS and gradually shifted towards more cathodic potentials over time as the degree of lithiation of the cathode material increased.After approximately 1200 seconds, the electrode potential stabilizes and remains constant at -1.4 V c. ECS indicating the start of a new electrochemical reaction, which includes the release of hydrogen.

[0118] X-ray diffraction analysis of the electrode shown in Figure 6 confirmed the very high degree of FePO4 reconstitution into lithium ions, resulting in a transformation rate to the LiFePC phase close to 100%. Indeed, the FePC peaks are clearly transmuted into LiFePC peaks. Among the other phases represented in the diffractograms, we can identify the stainless steel support (2Q: 51, 54, and 90) and the conductive graphite (2Q: 30).

[0119] The coulombic efficiency of relithiation was calculated to be over 80%, thus confirming the predicted electrochemical behavior presented in Example 1, i.e. that under certain cathode current density conditions it is possible to minimize side reactions (such as hydrogen evolution) in order to obtain high current efficiency.

[0120] Example 3:

[0121] To evaluate the effect of temperature on the lithiation process, two electrodes prepared as in Example 1(b) were relithiated at temperatures of 25°C and 50°C respectively in an aqueous solution of L12SO4 (0.5 M) to which LiOH was added to adjust the pH to 7. Relithiation was carried out at a constant potential of -0.2 V c. ECS.

[0122] The variation of current between the cathode and the anode as a function of time is shown in Figure 7. The higher rate of electrochemical relithiation at a higher temperature (50°C) results in a less pronounced decrease in current at the beginning of the process as well as a shorter time to reach a practically zero current between the cathode and the anode (point of almost complete relithiation) compared to relithiation carried out at 25°C.

[0123] The X-ray diffractograms in Figure 8 confirm that both electrodes are highly relithiated with less than 8% and no detectable residual FePO4 for tests at 25°C and 50°C, respectively.

[0124] Example 4:

[0125] To demonstrate the feasibility of directly using an L1FICO3 solution produced during the processing of electrode material from spent batteries, as described in published patent application US2019 / 0207275 (Amouzegar et al.), an electrode similar to that described in Example 1(b) was relithied in an electrochemical cell using a 0.5 M aqueous L1FICO3 solution (produced by bubbling CO2 through a U2CO3 suspension in water at 30 psi and room temperature). The cell was maintained under CO2 pressure by gently bubbling gaseous CO2 through the electrolyte at pH 7 and 25°C.

[0126] Linear cathode-ray scanning voltammetry of the electrode, performed at a rate of 1 mV / s between 0 V c. PCO (open-circuit potential) and -1.1 V c. ECS, is shown in Figure 9. The same type of relithiation reduction peak observed in Example 1 using an L12SO4 solution is seen, indicating the possibility of using an L1FICO3 solution as a Li ion source during the relithiation process. In fact, relithiation in a bicarbonate-based electrolyte appears to exhibit better kinetics compared to the sulfate-based electrolyte under similar conditions, as shown in Figure 10. X-ray diffraction composition analysis also shows complete relithiation of the electrode (see Figure 11).

[0127] Example 5:

[0128] (a) Preparation of an FePO electrode

[0129] To demonstrate that the same approach is readily applicable using an industrial current collector found in commercial batteries, the same type of electrode prepared in Example 1(b) was made using a 15 µm thick aluminum current collector coated with a thin layer of carbon. Dried iron phosphate powder was mixed with conductive carbons (Denka black). MC and VGCF MC -H, 1:1 by weight) and a PVDF binder in a weight ratio of 89:6:5, dispersed in N-methyl-2-pyrrolidone (NMP). The resulting suspension was coated onto an aluminum current collector and dried in an oven. The electrode charge was determined to be approximately 7.12 mg FePCWcm 2

[0130] (b) Relithiation of FePO electrode material

[0131] To simulate an electrochemical setup operating in batch mode, a strip of the electrode prepared in (a) with a surface area of ​​37.5 cm² 2 was installed in an electrochemical cell (using an SS support to maintain a constant distance from the counter electrode) in which a 90 cm platinum lattice 2An ECS electrode was installed as a counter electrode and a reference electrode, respectively. The electrolyte consisted of 0.5 M L12SO4, and the pH was adjusted to 9 using dilute LiOH. The cathode potential was controlled at -200 mV against ECS using a Princeton Applied Research potentiostat. Electrolysis was performed with stirring at 25°C. Figure 12 shows the current variation over time. Electrolysis was stopped once the current had decreased by 95% (in this case, after 2860 seconds), and the working electrode was washed with deionized water and dried.

[0132] Comparison of X-ray diffractograms (Figure 13) obtained from virgin LiFePO4, delithiated FePC, and relithiated LiFePC confirmed that the relithiation process was successful. Indeed, the relithiated electrode was composed of 93% LiFePO4 and 7% FePC. Relithiated LiFePC exhibits an orthorhombic structure similar to that of virgin LiFePC.

[0133] (c) Use of a relithi-depleted LiFePO4 electrode in a button cell

[0134] The electrochemical properties of the relithiated electrode in (b) and of a commercial LiFePC material applied in the same way to an aluminum current collector were tested against metallic lithium in button cells. The calculated active material charges, in mg of LiFePC per unit area, were 7.32 mg LiFePCWcm². 2 and 5.88 mg of LiFePCWcm 2respectively for the relithied and virgin LiFePC samples. Both cells were cycled in duplicate between 2V and 3.8V at a discharge rate of 1C and a charge rate of C / 4. A pre-charge / discharge cycle at C / 24 was applied to each button cell before the cycling procedure. Additionally, the cycling procedure included an initial discharge at C / 12, which was repeated every 20 cycles to monitor the battery's health.

[0135] Figure 14 shows the discharge capacity curves for these electrode materials. It can be seen that both electrode materials exhibit very good capacitance stability (less than 2% loss after 100 cycles). After 100 cycles, the electrochemically relithied and reference LiFePO4 materials showed good and fairly similar discharge capacities of 138 and 143 mAh / g, respectively, at a discharge rate of 1C. The very small difference in capacity can be attributed to the slight difference in active material charge; that is, the slightly higher charge for the electrochemically relithied material may result in a slightly lower capacity.

[0136] Example 6:

[0137] (a) Preparation of Fe(ll) / Fe(lll) redox couple solutions i. Preparation of Fe(ll) and Fe(lll) citrate solutions

[0138] A citric acid solution was prepared by dissolving 3.18 parts of the acid in 200 parts of water. The solution was then alkalinized to pH 6 using a 4 M LiOH solution. The lithium concentration was adjusted to a minimum of 0.5 M before adjusting the volume to 250 parts by adding the required amount of LhSC. Next, to prepare the ferrous solution, 0.56 parts of hydrated ferrous sulfate salt (FeSO4·7H2O) were dissolved in 100 parts of the previously prepared citric acid solution. Similarly, for the ferric solution, 0.21 parts of hydrated ferric sulfate (Fe2(SO4)3·xH2O) were dissolved in 100 parts of the citric acid solution prepared above.

[0139] Each solution was filtered to 0.22 µm and then deoxygenated by argon injection before further use. If necessary, the pH of each solution was adjusted to values ​​between 4.5 and 8 using LiOH or H₂SO₄. ii. Preparation of Fe(ll) and Fe(ll) EDTA solutions

[0140] An EDTA solution was prepared by dissolving 14.6 parts of the salt in its acidic form in 100 parts of a 1 M LiOH solution. The solution was then alkalinized to a pH of 6 using a 4 M LiOH solution. The lithium concentration was adjusted to a minimum of 0.5 M before adjusting the volume to 250 parts by adding the required amount of U2SO4.

[0141] Next, to prepare the ferrous solution, 2.78 parts of hydrated ferrous sulfate salt (FeSO4-7H2O) were dissolved in 100 parts of the previously prepared EDTA solution.

[0142] Similarly, with regard to the ferric solution, 1 part of hydrated ferric sulfate (Fe2(SO4)3-xH2O) was dissolved in 100 parts of the previously prepared EDTA solution.

[0143] Each solution was filtered to 0.22 µm and then deoxygenated by argon injection before further use. If necessary, the pH of each solution was adjusted to values ​​between 4.5 and 8 using LiOH or H₂SO₄.

[0144] (b) Studies of the electrochemical characteristics of Fe(ll) / Fe(lll) redox couples

[0145] To confirm the feasibility of reducing FePO4 to LiFePO4 by each of the redox couples prepared in section (a) of this example, the electrochemical behavior of the Fe(III) solution of each iron complex was investigated in a three-electrode electrochemical setup. Each Fe(III) solution was placed in the cathode compartment of the cell (under an argon blanket) in which a glassy carbon disk (3 mm diameter) was installed as the working electrode. A Pt lattice was placed in the anodic compartment filled with electrolyte, separated by a sintered glass disk. An Ag / AgCl electrode was used as the reference electrode.

[0146] The voltammograms were obtained using a Versastat™ 4 potentiostat (Princeton Applied Research). Figure 15 shows the voltammogram of the EDTA-Fe(III) solution at pH 4.5 between 2.05 V and 4.25 V vs. Li₇Li at a sweep rate of 200 mV / sec. A large separation of values ​​(on the order of 650 mV) can be observed for the oxidation peaks of EDTA-Fe(II) and the reduction of EDTA-Fe(III), indicating relatively slow kinetics. However, the oxidation of EDTA-Fe(II) begins at potentials of approximately 3.16 V vs. Li₇Li, which is significantly lower than the minimum potential of 3.45 V vs. Li₇Li required for the reduction of FePO₄ to LiFePO₄. Table 1 shows the potential values ​​at which an oxidation current is observed for each reducing agent prepared on the basis of Fe(ll).

[0147] Table 1. Oxidation potentials

[0148] Figure 16 shows the polarization curves for a solution of EDTA-LiOH and EDTA-Fe(III) in LiOH. It can be observed that the reduction peak of EDTA-Fe(III) appears at less negative potentials than the hydrogen evolution reaction in this medium, demonstrating the possibility of performing the electrochemical regeneration of EDTA-Fe(II) from EDTA-Fe(III) at reasonable coulombic efficiencies by minimizing the current associated with hydrogen formation. Example 7:

[0149] (a) Relithiation of FeP04 by EDTA-Fe(ll)

[0150] To demonstrate the use of EDTA-Fe(II) for the relithiation of FePC, 50 mL of the solution prepared according to a protocol similar to that described in Example 6 was contacted with 0.65 g of FePC prepared in Example 1(a) under an argon atmosphere at 40°C. For this test, the EDTA concentration was increased to maintain an EDTA / Fe(II) molar ratio of 4, and the pH was adjusted to 8 with a 1 M LiOH solution to maximize the solubility of the redox couple. The FePC powder was kept in suspension using a magnetic stirrer, and the decrease in the EDTA-Fe(II) concentration and the appearance of EDTA-Fe(III) were monitored using an ORP probe placed in the suspension.

[0151] Figure 17 shows the variation of the suspension potential during relithiation. An increase in potential can be observed as EDTA-Fe(ll) is oxidized (by reducing FePO4 to LiFePO4) to EDTA-Fe(ll).

[0152] At the end of the test, the solid was separated by vacuum filtration, washed, dried, and analyzed by X-ray diffraction (Rigaku MiniFlex). MC 600). Comparison of diagrams of virgin LiFePO4, delithiated FePO4 and the solid obtained after contact with the EDTA-Fe(ll) solution and in the presence of lithium salt (Figure 18) shows that the solid treated with the EDTA-Fe(ll) solution was completely relithied to form LiFePO4.

[0153] (b) Relithiation of FeP04 by citrate-Fe(ll)

[0154] A relithiation test was performed using the citrate-Fe(ll) solution in a manner similar to the procedure described for EDTA-Fe(ll) in Section 7(a). In this example, the citrate / Fe(ll) ratio was adjusted to 2 by the addition of ferrous sulfate, and the pH was adjusted to 6 by adding 1 M LiOH. 50 mL of the solution were contacted with 0.19 g of FePO4 prepared in Example 1(a) under an argon atmosphere at 40 °C. The FePO4 powder was kept in suspension using a magnetic stirrer, and the decrease in the citrate-Fe(ll) concentration and the appearance of citrate-Fe(ll) were monitored using an ORP probe placed in the suspension (Figure 19).

[0155] At the end of the test, the solid was separated by vacuum filtration, washed, dried, and analyzed by X-ray diffraction. As in the case of the solid in Example 7(a), comparison of the diffractograms of virgin LiFePC, delithiated FePC, and the solid obtained after contact with the Fe(ll) citrate solution and in the presence of lithium salt (Figure 20) shows that the FePC was completely relithied to form LiFePC

[0156] Example 8:

[0157] (a) Electrochemical regeneration of EDTA-Fe(lll) to EDTA-Fe(ll)

[0158] An 800 mL volume of an EDTA-Fe(III) solution with initial concentrations of 0.08 M, 1 M, and 0.2 M Fe(III), 1 M U₂SO₄, and EDTA, respectively, and whose pH had been adjusted to 6.3 with LiOH, was placed in the catholyte reservoir of an ICI-FM01 filter-press electrolysis cell assembly and protected by an inert gas (Ar). The FM01 cell was assembled with a graphite cathode, a titanium anode coated with an iridium oxide layer, and a Nafion-type cationic membrane. MC 324. The geometric active area of ​​all components (cathode, anode and membrane) was 64 cm² 2 .

[0159] The flow rate of the catholyte and anolyte was 2 liters / min, with a linear velocity of approximately 16 cm / s for the catholyte. The electrolysis temperature was controlled at around 50 °C by recirculating a heat transfer fluid heated by a thermostatically controlled bath (PolyScience #PD07R-20-A11 B) through heat exchangers installed in the anolyte and catholyte tanks. Electrolysis was performed with the voltage between the anode and cathode set at 1.65 V (Instek #SPS-1230). An ORP probe was placed in the catholyte tank to monitor the evolution of the solution potential.

[0160] The concentration of EDTA-Fe(III) in each sample during electrolysis was determined by diluting 1 mL of the sample in 10 mL of a 0.2 M EDTA in LiOH solution (pH 7.70) and measuring the absorbance of the solution at 470 nm. The total iron concentration was determined by a 1000-fold dilution in water and the addition of the iron reagent FerroVer. MC from the Hach company and by measuring the absorbance at 510 nm. The difference between total iron and EDTA-Fe(ll) allowed for the evaluation of the concentration of EDTA-Fe(ll) formed during electrolysis. Figure 21 shows the variation in the concentration of EDTA-Fe(ll) and the redox potential of the solution during 240 minutes of electrolysis.

[0161] It can be observed that as the concentration of EDTA-Fe(ll) (formed by the reduction of EDTA-Fe(III) at the cathode) increases in the catholyte, the redox potential of the solution decreases. During electrolysis, the total cell current decreased from 600 mA to 300 mA.

[0162] It should be noted that the cell's current density can be increased by improving mass transfer within the cell using well-known methods (such as the use of turbulence promoters, temperature increase, etc.) as well as by increasing the actual cathode surface area (for example, by using materials such as felts, grids, etc.). Clearly, the choice of cathode material is not limited to graphite, and other cathode materials (preferably those with a high hydrogen overpotential) can be used.

[0163] (b) Relithiation of FePC>4 with electrochemically generated EDTA-Fe(ll)

[0164] The EDTA-Fe(II) solution obtained during electrolysis with the FM01 cell in (a) was then used to perform the relithiation of FePC. 50 mL of the solution were contacted with 0.32 g of FePC prepared in Example 1 (a) under an argon atmosphere at 40 °C. The FePC powder was kept in suspension using a magnetic stirrer, and the decrease in the concentration of EDTA-Fe(II) and the appearance of EDTA-Fe(III) were monitored using an ORP probe placed in the suspension. Figure 22 shows the change in the suspension potential during relithiation. The increase in potential can be observed as EDTA-Fe(II) is oxidized (reducing FePO4 to LiFePO4) to EDTA-Fe(III). At the end of the test, the solid was separated by vacuum filtration, washed, dried and analyzed by X-ray diffraction.Comparison of diagrams of virgin LiFePC, delithiated FePO4 and the solid obtained after contact with the EDTA-Fe(ll) solution generated by electrolysis and in the presence of lithium salt (Figure 23) shows that the solid has been completely relithied to form LiFePC.

[0165] Numerous modifications could be made to any of the embodiments described above without departing from the scope of the present invention as contemplated. All references, patents, or scientific literature cited in this application are incorporated herein by reference in their entirety and for all purposes.

Claims

DEMANDS 1. A process for the electrochemical alkalilation of an electrochemically active material, the process comprising the steps of: a) obtaining a working electrode comprising a working electrode material on a current collector, the working electrode material comprising the electrochemically active material, optionally a binder and / or an electronically conductive material; b) introducing the working electrode into an electrochemical reactor in continuous and / or batch mode with an inert counter electrode, and a solution comprising an alkali metal salt in a solvent; c) applying a direct current between the working electrode and the counter electrode to obtain an alkali-treated electrode comprising an alkali-treated electrochemically active material; and d) removing the alkali-treated electrode obtained in step (c) from the electrochemical reactor;in which the electrochemically active material comprises a metal oxide (including complex oxides), a metal phosphate, a metal silicate, a metal sulfate, or a partially alkali metal oxide (including complex oxides), metal phosphate, metal silicate, or metal sulfate.; 2. A method of claim 1, wherein the electrochemically active material is deficient in alkali metal.

3. The process of claim 1 or 2, comprising the conversion of the electrochemically active material of Formula I: Aw-pM n+P xXyOz (I) in an electrochemically active alkaline material of Formula II: AwlVTxXyOz (II) in which, A is an alkali metal; M is a transition metal, a post-transition metal, or a combination of these; X is chosen from P, Si, and S; O is an oxygen; w is chosen from the numbers 1 to 4 and corresponds to the number of A atoms in the electrochemically active alkali material; x is chosen from the numbers 1 to 5 and corresponds to the number of M atoms; y is chosen from the numbers 0 to 2, in which X is absent when y is zero; z is chosen from the numbers 1 to 12 and corresponds to the number of oxygen atoms in the formulas; n denotes the oxidation state of M; p in Formula I denotes both the average number of missing A atoms and the average increase in the oxidation state of M, in which p < w (preferably 0 < p < 1); and in which w, y, z, n, and p are chosen to obtain a stable, electroneutral compound.

4. A method of claim 3, wherein p = w, A is absent in Formula I, and the electrochemically active material of Formula I is of Formula l(a): M n+ P X XyOz.

5. Method of claim 3 or 4, wherein X is a phosphorus, y is 1 and z is 4.

6. A method of any one of claims 3 to 5, wherein M is Fe, Ni, Mn, Co or a combination of two or more of these.

7. A method of claim 3 or 4, wherein M is V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn or a combination of two or more of these.

8. A method of any one of claims 3, 4, and 7, wherein y is 0 and X is absent.

9. A method of any one of claims 3 to 8, wherein A is Li, Na or K, or A is Li.

10. A method of any one of claims 1 to 9, wherein the electrochemically active material or the alkali-active electrochemically active material is further doped by the partial substitution of M with a transition metal (e.g., Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W or Y) and / or a metal that is not a transition metal (e.g., Mg, Ca, Sr, Al, Sb, or Sn).

11. A method of any one of claims 1 to 10, wherein the solvent is selected from an aqueous solvent, an organic solvent, or a mixture thereof.

12. The method of claim 11, wherein the solvent is water.

13. A method of any one of claims 1 to 12, wherein the alkali metal salt comprises at least one alkali metal sulfate, carbonate, bicarbonate, hydroxide, nitrate, acetate, oxalate, or phosphate salt.

14. A method of claim 13, wherein the alkali metal salt is an alkali metal sulfate.

15. A method of claim 13, wherein the alkali metal salt is an alkali metal bicarbonate.

16. The method of claim 15, wherein step (b) and / or (c) is carried out in the presence of gaseous carbon dioxide.

17. A method of any one of claims 1 to 16, further comprising a step of adjusting the pH of the solution to a pH suitable for the material electrochemically active of step (a) (for example, for FePC, the pH is adjusted between 5 and 9, preferably between 6 and 7.5).

18. A method of any one of claims 1 to 17, wherein the alkali metal of the alkali metal salt is lithium.

19. A method of any one of claims 1 to 18, wherein step (c) is carried out in continuous or batch mode.

20. The method of claim 19, wherein step (c) is carried out in continuous mode where the working electrode is introduced into the electrochemical reactor from one side and moves along a defined path so that the working electrode remains at a constant distance from the counter electrode while moving through an electrochemically active zone of the electrochemical reactor in order to maintain a relatively uniform current and potential distribution.

21. The method of claim 20, wherein the speed at which the working electrode moves through the electrochemical reactor is adjusted according to the residence time required for a desired level of alkalination at an applied current density.

22. A method of any one of claims 1 to 21, wherein step (c) is carried out in controlled current density mode between the working electrode and the counter electrode.

23. A method of any one of claims 1 to 21, wherein step (c) is carried out in controlled voltage mode between the working electrode and the counter electrode.

24. A method of any one of claims 1 to 23, wherein the electrochemically active material is FePC or partially delithiated LiFePC and the current density at the working electrode is in the range of 0.001 A / g to 100 A / g of active LiFePC, preferably in the range of 1 to 15 A / g of active LiFePC.

25. A method of any one of claims 1 to 24, wherein step (c) is carried out at a temperature in the range of 5°C to 90°C, preferably from 25°C to 50°C.

26. A method of any one of claims 1 to 25, wherein step (b) further comprises a reference electrode.

27. A method of any one of claims 1 to 26, further comprising a step (e) of washing the electrochemically active alkaline material from the alkaline electrode.

28. A method of any one of claims 1 to 27, further comprising drying the electrochemically active alkaline material of the alkaline electrode.

29. A method of any one of claims 1 to 28, wherein the working electrode material comprises a binder, the binder being selected from fluorinated polymer binders and other solvent polymer binders.

30. The method of claim 29, wherein the binder is a fluorinated polymer binder (such as PVDF, HFP, PVDF-Co-HFP or PTFE).

31. A process of claim 29, wherein the binder is a solvent polymer binder selected from poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamides), polyurethanes, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the preceding polymers or monomers thereof, as well as a combination of two or more of them, these polymers optionally being branched and / or crosslinked.

32. A method of any one of claims 1 to 31, wherein the working electrode material comprises the electronically conductive material, which is selected from the group consisting of carbon black (such as Ketjen black). MC and Super P MC ), acetylene black (such as Shawinigan black and Denka black) MC ), graphite, graphene, carbon fibers or nanofibers (such as gas-formed carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and a combination of two or more of these.

33. A method of any one of claims 1 to 32, wherein the working electrode material is an electrode material (e.g., a positive electrode material) from a used battery and step (a) includes at least one step of separating the electrode material from the other elements of the used battery and applying said material to the current collector.

34. A method of any one of claims 1 to 32, wherein step (a) comprises mixing the electrochemically active material, the binder and optionally the electronically conductive material in a solvent, applying it to the current collector and drying it.

35. Electrode obtained by a process as defined in any one of claims 1 to 34.

36. A process for the electrochemical alkalinization of an electrochemically active material, the process comprising the steps of: (i) adding the electrochemically active material to a solution containing a reducing agent and an alkali metal salt in a solvent to produce an alkali electrochemically active material; (ii) separation of the electrochemically active alkali material and the solution; and (iii) electrochemical treatment of the solution separated in step (ii) to regenerate the reducing agent in the solution.

37. The method of claim 36, wherein the electrochemically active material and the alkali-electrochemically active material are as defined in any one of claims 1 to 10.

38. A method of claim 36 or 37, wherein the reducing agent is the reducing member of a redox couple having a lower oxidation-reduction potential than that of the electrochemically active (alkali metal deficient) material to be reduced.

39. The method of claim 38, wherein the redox couple is based on Fe(ll) / Fe(lll).

40. The method of claim 39, wherein the redox couple is chosen from the [Fe(CN)6] 3 7[Fe(CN)6] 4 -, [Fe(nta)] / [Fe(nta)]-, [Fe(tdpa)] 2 Y[Fe(tdpa)] 3 -, the [Fe(edta)]- / [Fe(edta)] 2 -, [Fe(citrate)] / [Fe(citrate)]-, [Fe(TEOA)OH]- / [Fe(TEOA)OH]-, and [Fe(oxalate)]7[Fe(oxalate)].

41. A method of any one of claims 36 to 40, wherein step (i) further comprises a step of deoxygenating the solution.

42. A method of any one of claims 36 to 41, wherein steps (i) and / or (iii) are carried out in the presence of a gas enabling the removal of the presence of oxygen.

43. A method of any one of claims 36 to 42, wherein the alkali metal salt is selected from an alkali metal sulfate, carbonate, bicarbonate, hydroxide, nitrate, acetate, oxalate, phosphate, and combinations thereof.

44. A method of claim 43, wherein the alkali metal salt is an alkali metal sulfate.

45. A method of claim 43, wherein the alkali metal salt is an alkali metal bicarbonate.

46. ​​The method of claim 45, wherein step (i) is carried out in the presence of gaseous carbon dioxide.

47. A method of any one of claims 36 to 46, wherein the alkali metal of the alkali metal salt is lithium.

48. A method of any one of claims 36 to 47, further comprising a step of adjusting the pH of the solution to a pH suitable for the electrochemically active material of step (i) (for example, for FePC, the pH is adjusted between 5 and 9, preferably between 6 and 7.5).

49. A method of any one of claims 36 to 48, wherein the solvent is an aqueous solvent.

50. A method of any one of claims 36 to 49, wherein the electrochemical treatment step (iii) is carried out in an electrolytic cell by passing a current between at least one cathode and at least one anode.

51. A method of claim 50, wherein the electrolytic cell comprises at least one ionic or non-ionic separator installed between the anode and the cathode to protect the regenerated reducing agent.

52. A method of claim 50 or 51, wherein the electrolytic cell further comprises a system for keeping the solution deoxygenated.

53. A method of claim 52, wherein the system comprises an oxygen-free gas, such as carbon dioxide, nitrogen, or argon.

54. A method of any one of claims 36 to 53, wherein the electrochemically active material is in suspension in the solution of step (i), and step (ii) is carried out by filtration, centrifugation or decantation, optionally followed by a washing step.

55. A method of any one of claims 36 to 53, wherein the electrochemically active material is contained within an electrode material on a current collector and step (ii) comprises removing the electrode from the solution, optionally followed by a washing step.

56. A method of claim 55, wherein the electrode material further comprises a binder.

57. The method of claim 56, wherein the binder is selected from fluorinated polymer binders and solvent polymer binders.

58. The method of claim 57, wherein the binder is a fluorinated polymer binder (such as PVDF, HFP, PVDF-Co-HFP or PTFE).

59. A process of claim 57, wherein the binder is a solvent polymer binder selected from poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamides), polyurethanes, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the preceding polymers or monomers thereof, as well as a combination of two or more of them, these polymers optionally being branched and / or crosslinked.

60. A method of any one of claims 55 to 59, wherein the electrode material further comprises an electronically conductive material, for example, selected from the group consisting of carbon black (such as Ketjen black). MC and Super P MC ), acetylene black (such as Shawinigan black and Denka black) MC), graphite, graphene, carbon fibers or nanofibers (such as gas-formed carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and a combination of two or more of these.

61. A method of any one of claims 36 to 60, further comprising drying the electrochemically active alkaline material.

62. Electrode comprising the electrochemically active alkaline material obtained by the process as defined in any one of claims 36 to 61, a binder and optionally an electronically conductive material.

63. Electrochemical cell comprising a negative electrode, a positive electrode and an electrolyte, wherein the positive electrode is an electrode as defined in claim 35 or 62.

64. Battery comprising at least one electrochemical cell as defined in claim 63.

65. Battery of claim 64, wherein said battery is a lithium battery or a lithium-ion battery.

66. The electrochemical cell of claim 63 or the battery of claim 64 or 65, for use in mobile devices, such as mobile phones, cameras, tablets or laptops, in electric or hybrid vehicles, or in renewable energy storage.

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