Method for alkalizing or re-alkalizing electrode active materials

Abstract

To provide a method for alkalizing or re-alkalizing an electrode active material. [Solution] A method for direct or indirect electrochemical alkalization of an alkali metal-deficient electrochemical active material is described. This method includes either an electrolytic step during the alkalization of the alkali metal-deficient electrochemical active material on an electrode current collector (direct), or during the regeneration of the reducing agent used for alkalization of the electrochemical active material (indirect). In another embodiment, the electrochemical cell or battery as defined herein is for use in portable devices such as mobile phones, cameras, tablets or laptops, electric or hybrid vehicles, or renewable energy storage.

Description

Technical Field

[0001] Related Applications This application claims priority under applicable law to U.S. Provisional Patent Application No. 62 / 934,782, filed November 13, 2019, the entire content of which is incorporated herein by reference for all purposes.

[0002] Technical Field This technology generally relates to the field of methods for electrochemically inserting or reinserting alkali metal ions into an electroactive material, for example, for the manufacture of metal oxides and metal phosphates containing an alkali metal.

Background Art

[0003] Background In the manufacture of lithium batteries, the positive electrode is generally manufactured by coating a current collector (usually aluminum foil) with a suspension of an electroactive material, a conductive material, and a binder, and then drying. The electroactive material is generally a lithiated metal oxide or a lithiated metal phosphate, where the metal may be a transition metal or a combination of two or more transition metals. Electrochemical cells are usually assembled with a negative electrode and a separator in a discharged state, i.e., the positive electrode is fully lithiated. An exception is the electroactive material V2O5 which is applied to the current collector in an unlithiated form. In such cases, the battery is assembled in a fully charged state, which represents a serious safety and fire hazard. The group of Walk et al. described the prelithiation process of a V2O5 electrode under electrochemical conditions using metallic lithium as the negative electrode (see U.S. Patent No. 5,496,663). Such a lithiation process is galvanic and requires the use of aprotic and non-aqueous electrolytes due to the presence of metallic lithium as the required lithium source and its incompatibility with various solvents (especially aqueous solutions). Another drawback of this approach relates to the fact that metallic lithium is not the most advantageous lithium source from both an economic perspective and the precautions required when used in large-scale processes.

[0004] 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 Patent Publication WO2019 / 070896A1). However, this method also relies on the use of metallic lithium (or one of its alloys) and organic electrolytic solvents directly applied to the electrode material in a complex multi-step process that requires steps such as pouch cell formation, long waiting periods (usually more than 20 hours), and then stripping off excess metallic lithium.

[0005] To avoid the drawbacks of using the aforementioned metallic lithium as a lithium source in the lithiation process, the use of other inexpensive materials, such as lithium chloride in organic solvents, has also been proposed (see Grant et al., U.S. Patent Application No. 2018 / 0040914). In this process, the electrode material into which lithium is inserted is of the lithium-ion battery, graphite anode material, silicon oxide, and tin oxide types. 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, producing more corrosive acids (such as HCl or HF), which require additional measures during the process.

[0006] Another group has presented a reproduction of electrode materials for lithium-depleted batteries (see U.S. Patent No. 9,287,552 by Sloop). The high-temperature solid-phase reaction is carried out in a sealed pressure vessel. Various methods are described here, including the use of reduced conditions, which can potentially be implemented in situ by using a hydrothermal process and introducing a reducing solution directly into the spent battery. The latter method does not take into account that lithium depletion is not the only drawback of spent batteries. In fact, electrodes may also exhibit fragmentation of the active material and binder, lithium antisite, passivation layer, delamination of the current collector, reduced copper adhesion to the cathode surface, corrosion of the current collector, etc. Furthermore, Sloop proposes that the positive electrode be separated from the battery in its entirety, which is extremely difficult to implement on a large scale, including, for example, the extraction of the rotating electrode ("jelly roll") from the spent battery, and the unfolding and sorting of the electrode while holding the entire electrode strip for subsequent steps. Such sorted electrodes also have the additional drawbacks mentioned above. Sloop also mentions the relithiation of spent positive electrodes, where the spent positive electrode is deposited in a sorted state on a charged tray or grid, but does not demonstrate this. Poor electrical contact between the electrode portion and the tray or grid leads to uneven current and potential distributions that are favorable for other electrochemical reactions (such as hydrogen generation), resulting in low current efficiency and uneven relithiation across the electrode. Accordingly, there is a need for new processes for alkalizing or re-alkalizing active electrode materials, or for reusing such materials, including processes that can be used in the preparation of novel electrode materials. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Patent No. 5,496,663 [Patent Document 2] International Publication No. 2019 / 070896 [Patent Document 3] U.S. Patent Application Publication No. 2018 / 0040914 [Patent Document 4] U.S. Patent No. 9,287,552 [Overview of the Initiative]

Means for Solving the Problem

[0008] Summary According to a first aspect, the present specification is a method for electrochemically alkalizing an electrochemically active material, comprising: a) obtaining a working electrode comprising a working electrode material on a current collector, the working electrode material comprising an electrochemically active material, optionally a binder and / or an electron conductive material; b) introducing the working electrode into an electrochemical reactor together with an inert counter electrode and a solution containing an alkali metal salt in a solvent in continuous and / or batch mode; c) applying a direct current between the working electrode and the counter electrode to obtain an alkalized electrode comprising an alkalized electrochemically active material; d) removing the alkalized electrode obtained in step (c) from the electrochemical reactor, \] wherein the electrochemically active material comprises a metal oxide (including a composite oxide), a metal phosphate, a metal silicate, a metal sulfate, or a partially alkalized metal oxide (including a composite oxide), a metal phosphate, a metal silicate, or a metal sulfate. The method is related to.

[0009] According to certain embodiments, the electrochemically active material is alkali metal deficient. In another embodiment, the method involves an electrochemically active material of formula I: A w-p M n+p x X y O z (I) being converted to an alkalized electrochemically active material of formula II: A w M n x X y O z (II) (wherein, A is an alkali metal, M is a transition metal, a post-transition metal or a combination thereof, X is selected from P, Si and S, O is an oxygen atom, w is selected from a number between 1 and 4, and corresponds to the number of A atoms in the alkalized electrochemical active material. x is selected from a number between 1 and 5 and corresponds to the number of M atoms. y is selected from a number between 0 and 2, and if y is zero, then X does not exist. z is selected from a number between 1 and 12 and corresponds to the number of oxygen atoms in the formula. n indicates the oxidation state of M. In formula I, p represents both the average number of missing A atoms and the average increase in the oxidation state of M, where p ≤ w (preferably 0 <p≦1)であり、 w, y, z, n, and p are selected to form a stable, electrically neutral compound. This includes converting to [a specific format].

[0010] In another embodiment, p=w, A does not exist in formula I, and the electrochemical active material of formula I is formula I(a):M n+p x X y O z In another embodiment, X is phosphorus, y is 1, and z is 4. In yet another embodiment, M is Fe, Ni, Mn, Co, or at least two combinations thereof. In an alternative embodiment, M is V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn, or at least two combinations thereof. 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.

[0011] In another embodiment, the electrochemical active material or alkalized electrochemical active material is further doped by partially substituting M with a transition metal (e.g., V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, or Y) and / or a non-transition metal (e.g., Mg, Ca, Sr, Al, Sb, or Sn).

[0012] In the earlier embodiment, the solvent is selected from aqueous solvents, organic solvents, or mixtures thereof, for example, the solvent is water.

[0013] In other embodiments, the alkali metal salt comprises at least one of alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, or phosphates. In one embodiment, the alkali metal salt is an alkali metal sulfate. In another embodiment, the alkali metal salt is an alkali metal bicarbonate, and for example, steps (b) and / or (c) are carried out in the presence of gaseous carbon dioxide. In another embodiment, the method further comprises the step of adjusting the pH of the solution to a pH suitable for the electrochemical active material of step (a) (for example, in the case of FePO4, the pH is adjusted to 5-9, preferably 6-7.5). In one embodiment, the alkali metal of the alkali metal salt is lithium.

[0014] In other embodiments, step (c) is carried out in continuous or batch mode. In another embodiment, step (c) is carried out in continuous mode, and the working electrode is introduced to one side of the electrochemical reactor, and the working electrode moves along a predetermined path so as to remain at a constant distance from the counter electrode while moving along the electrochemically active region of the electrochemical reactor to maintain a relatively uniform current and potential distribution. In another embodiment, the rate at which the working electrode moves through the electrochemical reactor is adjusted based on the residence time required for a predetermined level of alkalization at the applied current density.

[0015] In yet another embodiment, step (c) is performed in a mode in which the current density between the working electrode and the counter electrode is controlled. Alternatively, step (c) is performed between the working electrode and the counter electrode It is performed in a voltage-controlled mode.

[0016] In other embodiments, the electrochemical active material is FePO4 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 active LiFePO4, preferably in the range of 1 to 15 A / g active LiFePO4.

[0017] In another embodiment, step (c) is carried out at a temperature in the range of 5°C to 90°C, preferably 25°C to 50°C. In some embodiments, step (b) may further include a reference electrode.

[0018] In other embodiments, the above method further includes the step (e) of washing the alkalized electrochemically active electrode material of the alkalized electrode and / or the step of drying the alkalized electrochemically active electrode material of the alkalized electrode.

[0019] In yet another embodiment, the working electrode material includes a binder, which is selected from fluorine-containing polymer binders and other solvating polymer binders. According to one embodiment, the binder is a fluorine-containing polymer binder such as PVDF, HFP, PVDF-co-HFP, or PTFE. According to another embodiment, the binder is a solvating polymer binder selected from poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamide), polyurethane, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the above polymers or their monomers, as well as at least two combinations thereof, wherein the polymer is branched and / or crosslinked as necessary.

[0020] 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 and Super P®), acetylene black (such as Shawinigan Black and Denka® Black), graphite, graphene, carbon fibers or nanofibers (such as vapor-grown carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and at least two combinations thereof.

[0021] In some embodiments, the working electrode material is the electrode material of a spent battery (e.g., the positive electrode material), and step (a) includes at least one step of separating the electrode material from other elements of the spent battery and applying the material to a current collector.

[0022] In other embodiments, step (a) includes mixing an electrochemical active material, a binder, and optionally an electronically conductive material in a solvent; applying the mixture to a current collector; and drying.

[0023] According to a second aspect, this specification relates to electrodes obtained by the above method.

[0024] According to a third aspect, this specification provides a method for electrochemical alkalizing an electrochemical active material, (i) Adding an electrochemical active material to a solution containing a reducing agent and an alkali metal salt in a solvent to produce an alkalized electrochemical active material; (ii) A step of separating the alkalized electrochemical active material from the solution, (iii) A step of electrochemically treating the solution separated in step (ii) to regenerate the reducing agent in the solution, This includes methods.

[0025] In one embodiment, the electrochemical active material and the alkalized electrochemical active material are as defined herein. According to another embodiment, the electrochemical active material is alkali metal deficient. In another embodiment, the reducing agent is the reducing member of a redox pair having a lower redox potential than that of the electrochemical active material being reduced (alkali metal deficient). According to one embodiment, the redox pair is, for example, [Fe(CN)6] 3- / [Fe(CN)6] 4- [Fe(nta)] / [Fe(nta)] - [Fe(tdap)] 2- / [Fe(tdap)] 3- [Fe(edta)] - / [Fe(edta)] 2-[Fe (Citrate)] / [Fe (Citrate)] - [Fe(TEOA)OH] - / [Fe(TEOA)OH] - , and [Fe (oxalate)] + It contains Fe(II) / Fe(III) complexes selected from [Fe(oxalate)].

[0026] According to one embodiment, step (i) further includes a step of deoxygenating the solution. According to another embodiment, steps (i) and / or (iii) are carried out in the presence of a gas that eliminates the presence of oxygen.

[0027] In another embodiment, the alkali metal salt is selected from alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, phosphates, 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, and for example, step (i) is carried out in the presence of gaseous carbon dioxide. In another embodiment, the method further includes the step of adjusting the pH of the solution to a pH suitable for the electrochemical active material of step (i) (for example, in the case of FePO4, the pH is adjusted to 5-9, preferably 6-7.5). In one embodiment, the alkali metal of the salt is lithium. In another embodiment, the solvent is an aqueous solvent.

[0028] According to one embodiment, step (iii) of the electrochemical treatment is carried out by passing an electric current between at least one cathode and at least one anode in an electrolytic cell. In one embodiment, the electrolytic cell includes at least one ionic or nonionic separator placed between the anode and cathode to protect the regenerated reducing agent. In another embodiment, the electrolytic cell further includes a system for keeping the solution deoxygenated, for example, this system includes maintaining an oxygen-free gas (such as carbon dioxide, nitrogen, or argon) in the electrolytic cell.

[0029] In yet another embodiment, the electrochemical active material is in the form of a suspension in solution in step (i), step (ii) is carried out by filtration, centrifugation, or decantation, and then a washing step is carried out as necessary.

[0030] Alternatively, the electrochemical active material is contained in the electrode material on the current collector (forming the electrode), and step (ii) includes removing the electrode from the solution and then a washing step as necessary.

[0031] In one alternative embodiment, the electrode material further comprises a binder selected from, for example, fluorine-containing polymer binders and other solvating polymer binders. According to one embodiment, the binder is a fluorine-containing polymer binder (such as PVDF, HFP, PVDF-co-HFP, or PTFE). Alternatively, the binder is a copolymer (block, random, alternating, statistical, etc.) comprising poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamide), polyurethane, poly(vinyl alcohol), and at least one of the above polymers or their monomers, as well as these A solvated polymer binder selected from at least two combinations thereof, wherein these polymers are branched and / or crosslinked as necessary. According to another embodiment, the electrode material further includes, for example, an electronically conductive material selected from the group consisting of carbon black (such as Ketjen® Black and Super P®), acetylene black (such as Shawinigan Black and Denka® Black), graphite, graphene, carbon fibers or nanofibers (such as vapor-grown carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and at least two combinations thereof.

[0032] In another embodiment, the method further includes the step of drying the alkalized electrochemical active material.

[0033] According to a fourth aspect, this specification relates to electrodes comprising an alkalized electrochemical active material, a binder, and optionally an electronically conductive material obtained by a method defined herein.

[0034] According to a fifth aspect, this specification 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.

[0035] In another embodiment, the electrochemical cell or battery as defined herein is intended for use in portable devices such as mobile phones, cameras, tablets or laptops, electric or hybrid vehicles, or renewable energy storage. [Brief explanation of the drawing]

[0036] [Figure 1] Figure 1 shows a graph of the lithium leaching rate during delithiation as a function of time according to Example 1(a).

[0037] [Figure 2] Figure 2 shows the X-ray diffraction pattern of LiFePO4 before charging and discharging according to Example 1(a) (upper line) and its delithiated FePO4 (lower line).

[0038] [Figure 3] Figure 3 shows linear scanning voltammetry of an FePO4 electrode performed at a speed of 1 mV / s from 0 V vs. OCP (open circuit potential) to -1 V vs. SCE (saturated calomel electrode), as described in Example 1(c).

[0039] [Figure 4] Figure 4 shows the X-ray diffraction patterns of LiFePO4 (top line), delithiated FePO4 (center line), and relithiated LiFePO4 (bottom line) before charging and discharging according to Example 1.

[0040] [Figure 5] Figure 5 shows the voltammogram of constant-current relithiation of the FePO4 electrode performed at 10 mA according to Example 2.

[0041] [Figure 6] Figure 6 shows the X-ray diffraction patterns of LiFePO4 (top line), delithiated FePO4 (center line), and relithiated LiFePO4 (bottom line) before charging and discharging according to Example 2.

[0042] [Figure 7] Figure 7 shows the galvanic reaction of two FePO4 electrodes that underwent constant potential relithiation by SCE at -0.2V vs. 25℃ (dashed line) and 50℃ (solid line) according to Example 3.

[0043] [Figure 8] Figure 8 shows the X-ray diffraction patterns of LiFePO4 before charging and discharging according to Example 3 (top line), LiFePO4 relithified at 25°C (center line), and LiFePO4 relithified at 50°C (bottom line).

[0044] [Figure 9] Figure 9 shows the cathode linear scanning voltammetry of an FePO4 electrode performed at a flow rate of 1 mV / s in a 0.5 M LiHCO3 aqueous solution according to Example 4, between 0 V vs. OCP and -1.1 V vs. SCE.

[0045] [Figure 10] Figure 10 shows the galvanic reaction of two FePO4 electrodes that underwent constant potential relithiation with SCE in 0.25 M Li2SO4 (dashed line) and 0.5 M LiHCO3 (solid line) at -0.2 V vs. 25°C according to Example 4.

[0046] [Figure 11]Figure 11 shows the X-ray diffraction patterns of LiFePO4 (top line), delithiated FePO4 (center line), and relithiated LiFePO4 (bottom line) before charging and discharging according to Example 4.

[0047] [Figure 12] Figure 12 shows the change in current as a function of time for the electrode material applied to the aluminum current collector by the process of Example 5.

[0048] [Figure 13] Figure 13 shows the X-ray diffraction patterns of the LiFePO4 (top line), delithiated FePO4 (center line), and relithiated LiFePO4 (bottom line) electrode materials before charging and discharging according to Example 5.

[0049] [Figure 14] Figure 14 shows the discharge capacity of relithified LiFePO4 (circles) compared to the reference LiFePO4 (triangles) from Example 5.

[0050] [Figure 15] Figure 15 shows the voltammograms of the Fe(III)-EDTA solution performed in Example 6(b) at a scanning speed of 200 mV / sec between 2.05 V and 4.25 V vs. Li+ / Li.

[0051] [Figure 16] Figure 16 shows the polarization curves for the EDTA-LiOH solution (dashed line) and the Fe(III)-EDTA solution in LiOH (solid line) according to Example 6(b).

[0052] [Figure 17] Figure 17 shows the change in the redox potential of the suspension during the reduction of FePO4 by Fe(II)-EDTA according to Example 7(a).

[0053] [Figure 18]Figure 18 shows the X-ray diffraction patterns of LiFePO4 (top line), delithiated LiFePO4 (center line), and relithiated LiFePO4 (bottom line) before charging and discharging according to Example 7(a).

[0054] [Figure 19] Figure 19 shows the change in the redox potential of the suspension during the reduction of FePO4 by Fe(II)-citrate according to Example 7(b).

[0055] [Figure 20] Figure 20 shows the X-ray diffraction patterns of LiFePO4 (top line), delithiated LiFePO4 (center line), and relithiated LiFePO4 (bottom line) before charging and discharging according to Example 7(b).

[0056] [Figure 21] Figure 21 shows the changes in Fe(II)-EDTA concentration and the redox potential of the solution during electrolysis as presented in Example 8(a).

[0057] [Figure 22] Figure 22 shows the change in the redox potential of the suspension during the reduction of FePO4 by Fe(II)-EDTA generated by the electrolysis of Fe(II)-EDTA according to Example 8(b).

[0058] [Figure 23] Figure 23 shows the X-ray diffraction patterns of LiFePO4 (top line), delithiated LiFePO4 (center line), and relithiated LiFePO4 (bottom line) before charging and discharging according to Example 8(b). [Modes for carrying out the invention]

[0059] Detailed explanation The following detailed description and examples are illustrative and should not be construed as further limiting the scope of the invention.

[0060] All technical and scientific terms and expressions used herein have the same definitions as those commonly understood by those skilled in the art in relation to this technology. Nevertheless, for the sake of clarity, the definitions of some terms and expressions used herein are given below.

[0061] In this specification, the term "approximately" means roughly, around, and in the vicinity. When the term "approximately" is used in relation to a number, it can be adjusted, for example, by a 10% variation before or after that number. This term may also take into account the probability or rounding of the stochastic error in experimental measurements.

[0062] As used herein, the terms “alkalization” and “alkalization” refer to the reduction of a metal-containing active material, which involves the insertion of alkali metal ions into the active material. The terms “lithitization” and “lithiation” are used when the alkali metal ions are lithium ions. Similarly, the terms “alkalized” and “lithitized” generally refer to the substance resulting from alkaliization or lithiation, respectively. Similarly, the terms “re-alkalization,” “re-alkalization,” “re-lithiation,” and “re-lithiation” refer to the alkaliization or lithiation of an active material in which alkali metal ions or lithium ions, respectively, are lost or bound.

[0063] Accordingly, this specification relates to the alkalization of an electrochemical active material containing at least one metal in a non-zero-oxidation state. The first step in this method is to obtain a working electrode comprising an electrode material on a current collector. The electrode material comprises the electrochemical active material to be alkalized and may contain other components. For example, the electrochemical active material is uniformly dispersed in a binder and optionally in a conductive material.

[0064] Electrochemical active materials can generally be defined as metal oxides (including complex oxides), metal phosphates, metal silicates, metal sulfates, or partially alkalized oxides, phosphates, silicates, or sulfates thereof. For example, an electrochemical active material is given by formula I: Aw-p M n+p x X y O z (I) (In the formula, A is an alkali metal (for example, Li, Na, and K, preferably lithium), M is a transition metal, a post-transition metal, or a combination thereof. X is selected from P, Si, and S. O represents oxygen, w is selected from a number between 1 and 4, and corresponds to the number of A atoms in the alkalized electrochemical active material. x is selected from a number between 1 and 5 and corresponds to the number of M atoms. y is selected from a number between 0 and 2, and if y is zero, then X does not exist. z is selected from a number between 1 and 12 and corresponds to the number of oxygen atoms in the formula. n indicates the oxidation state of M. p represents both the average number of missing A atoms and the average increase in the oxidation state of M, where p ≤ w (preferably 0). <p≦1)であり、 w, y, z, n, and p are selected to form a stable, electrically neutral compound. That is the case.

[0065] Furthermore, the alkalized electrochemical active material obtained by this method is given by formula II: A w M n x X y O z (II) (wherein A, M, X, O, n, w, x, y, and z are as defined herein) That is the case.

[0066] Examples of electrochemically active materials include compounds of formula I, where p=w and A is absent, and the electrochemically active material of formula I is formula I(a):M n+p x X y O z In some examples, X is phosphorus, y is 1, and z is 4.

[0067] Examples of transition metals M include Fe, Ni, Mn, Co, or combinations thereof, where preferably y is 1 and z is 4 when X is phosphorus. In another example, the electrochemical active material is FePO4 or partially delithiated LiFePO4. Examples of M may also include metals selected from V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn, or at least two combinations thereof. In some examples, y is 0, X is absent, and formula I represents an oxide or composite oxide.

[0068] Electrochemical active materials and / or alkalized electrochemical active materials may also be doped by partially substituting M with transition metals (e.g., Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, or Y) and / or non-transition metals (e.g., Mg, Ca, Sr, Al, Sb, or Sn) (10 mol% or less, or 5 mol% or less).

[0069] In the first method step, an alkali metal-deficient material such as formula I or I(a) can be mixed with all the components necessary for the fabrication of electrodes for an energy storage device and applied to the current collector. The material to be alkalized may be commercially available and may be included in the working electrode material of this method to achieve alkalization before use as an electrode in an electrochemical cell. Alternatively, the electrochemical active material to be alkalized may be obtained as a result of a battery recycling process.

[0070] The electrochemical active material may be in the form of fine particles or nanoparticles, and / or may further contain a carbon coating.

[0071] The components for the electrode material may further include at least one binder, for example, a polymer binder, preferably a polar and solvating polymer binder.

[0072] Non-limiting examples of solvating polymers that may be suitable for use as cathode binders include fluorine atom-containing polymer binders such as PVDF, HFP, PVDF-co-HFP, and PTFE. Other examples of solvating polymer binders include poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamide), and poly(ethylene sulfamide). Examples of binders include copolymers (block, random, alternating, statistical, etc.) comprising uretan, poly(vinyl alcohol), and at least one of the above polymers or their monomers, as well as at least two combinations thereof. These solvated 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 cellulosic binders (e.g., carboxyalkylcellulose, hydroxyalkylcellulose, and combinations thereof), or any combination of at least two thereof. It should be understood that water-soluble binders cannot be used in this alkalization method if the solvent of the method is an aqueous solvent.

[0073] Examples of electronically conductive materials include, but are not limited to, carbon black (such as Ketjen® Black and Super P®), acetylene black (such as Shawinigan Black and Denka® Black), graphite, graphene, carbon fibers or nanofibers (vapor-grown carbon fibers (VGCF)), carbon nanotubes (e.g., single-walled or multi-walled), and at least two combinations thereof.

[0074] The second step of the method involves introducing the working electrode, along with an inert counter electrode and a solution containing an alkali metal salt in the solvent, into an electrochemical reactor. The electrochemical reactor may further include a reference electrode (such as a saturated calomel electrode (SCE)). In another example, the electrochemical reactor may also include a potentiostat or rectifier for electrolysis. The electrochemical reactor may be configured for continuous or batch mode electrolysis and may include additional elements such as a stirring mode and / or a temperature control device to increase mass transfer to the working electrode.

[0075] The solution contained in the electrochemical reactor contains at least one alkali metal salt (for example, lithium, sodium, or potassium salts, preferably lithium salts, preferably excluding halide salts) that acts as an electrolyte and is inserted into the active material. Suitable salts include alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, or phosphates, such as A2SO4 or AHCO3 (wherein A is as described 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 water or high-purity water). A pH adjustment step may also be included in the method. The pH of the solution must be suitable for the electrochemical active material (and its alkalinized form) to maintain stability and avoid dissolution. For example, when treating an electrochemical active material or a partially alkalinized form thereof, the pH is adjusted to 5-9, preferably 6-7.5. For example, if the solution is excessively acidic, the pH can be adjusted with an alkali metal hydroxide. Further supporting electrolytes may be added to reduce the electrolyte resistance.

[0076] The counter electrode is made of an inert material under electrolytic conditions, such as platinum, a precious metal oxide, or lead oxide, and can optionally contain a layer of catalyst compounds to reduce electrode overpotential. For example, in aqueous solutions, the reaction of the counter electrode results in the release of oxygen, and a dimensionally stable anode can be used as the counter electrode material.

[0077] The third step involves applying a direct current between a working electrode containing an alkali metal-deficient electrochemical active material and a counter electrode to obtain an alkalized electrode containing an alkalized electrochemical active material (for example, one specified in Formula II). This step can be carried out at a temperature in the range of 5°C to 90°C, preferably 25°C to 50°C.

[0078] As mentioned above, electrochemical reactors are operated in either continuous or batch mode. In continuous mode, the working electrode enters the electrochemical reactor from one side and follows a predetermined path, thus remaining at a constant distance from the counter electrode while moving through the electrochemically active region of the electrochemical reactor to maintain a relatively uniform current and potential distribution. The rate at which the working electrode moves through the electrochemical reactor is determined by the residence time required for a given level of alkalization and the applied current density. The electrochemical reactor can be operated in either a current density-controlled mode or a voltage-controlled mode between the working electrode and the counter electrode.

[0079] In a particular example, the electrochemical active material is FePO4 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 active LiFePO4, preferably in the range of 1 to 15 A / g active LiFePO4.

[0080] Once the target alkylation level is reached, the working electrode is removed from the electrochemical reactor. The thus alkylated electrode is then preferably subjected to a washing step to remove excess electrolyte from the alkalized electrode material, followed by a drying step to remove excess washing solution.

[0081] If present, a reference electrode can be placed in the reactor to monitor the potential of the working electrode. Its presence minimizes parasitic reactions of the working electrode and maximizes the efficiency of the alkalizing current.

[0082] Alternatively, a chemical reduction process may be used to alkalize the electrochemical active materials specified herein. This alternative alkalization method includes a reducing agent and further includes a step of electrochemically regenerating the reducing agent. For example, the electrochemical active material can be treated with a solution of a reducing agent and an alkali metal salt in a solvent. When readily oxidized in the presence of oxygen, the solution can be deoxygenated before adding the reducing agent and / or electrochemical active material. Similarly, this step can be carried out in the presence of a gas (such as CO2, N2, or Ar) to eliminate the presence of oxygen. The resulting electrochemical active material and alkalized electrochemical active material are as described above. Preferably, the electrochemical active material is alkali metal deficient.

[0083] Non-limiting examples of alkali metal salts used in the chemical reduction step include alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, and phosphates, or any combination thereof. The solvent used is preferably an aqueous solvent.

[0084] In this method, the alkalized material is treated as a suspension in the reactor, separated from the spent reducing agent solution, rinsed, dried, and then used as the active electrode in the manufacture of the electrode. Separation of the alkalized material from the spent reducing agent can be achieved by typical physical separation methods, such as filtration, centrifugation, or decantation. The separated and dried alkalized material can then be mixed with the required components to prepare an electrode, which can be applied to a current collector. For example, these components may include a binder and, optionally, the aforementioned electronically conductive material.

[0085] On the other hand, the material to be alkalized using this method can first be mixed with the components of the electrode material described above, and then applied to a suitable current collector to obtain an electrode such as the working electrode described in the previous method. Next, the prepared electrode is treated with a reducing agent solution, for example, by immersing it in the reducing agent solution, washing it, and drying it.

[0086] In both cases, the used reducing agent is recovered and then recycled in a subsequent step. Alternatively, the solution containing the spent reducing agent can be transferred to a high-efficiency, high-current-density electrochemical (or electrolytic) cell to reduce (and thereby regenerate) the spent reducing agent, which can then be reused to treat alkali metal-deficient materials. For example, the reducing agent regeneration step is carried out by electrochemical treatment in the electrolytic cell by passing an electric current between at least one cathode and at least one anode. The electrolytic cell may further include at least one ionic or nonionic separator placed between the anode and cathode to protect the regenerated reducing agent.

[0087] When the regenerated agent is prone to oxidation in the presence of oxygen, the electrolytic cell may also include a system for maintaining the solution in a deoxygenated state, for example, by maintaining an oxygen-free gas (such as carbon dioxide, nitrogen, or argon) within the electrolytic cell.

[0088] The current density of an electrolytic cell can be increased by acting on mass transfer within the electrolytic cell by known methods (such as the use of a turbulence promoter and increasing the temperature) and by increasing the effective surface area of ​​the cathode (for example, by using materials in the form of felt, grid, etc.). When the solvent of the electrolyte is aqueous, the cathode material is preferably selected from high hydrogen overpotential materials such as graphite and lead.

[0089] 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, and this can be thought of as indirect electrochemical reduction. Therefore, this method has several advantages (economic, environmental, etc.) compared to using the reducing agent without regeneration.

[0090] Various redox pairs can be used as regenerative reducing agents. The selected redox pair has a lower redox potential than the electrochemically active (alkali metal deficient) substance being reduced. For example, in the relithiation of FePO4, the redox pair is 3.45V. vs Li / Li + Having a redox potential less than (AK Padhi et al., J. (See Electrochem. Soc., 1997, 144, 1188-1194).

[0091] Another desired property of redox pairs is relatively high solubility, particularly in their oxidized state, which avoids the formation of precipitates in the presence of the treated electrode material. Examples of redox pairs that can be used include Fe(II) / Fe(III) complexes, which exhibit properties of interest for use in this indirect electrochemical method. These complexes include, for example, [Fe(CN)6] 3- / [Fe(CN)6] 4- [Fe(nta)] / [Fe(nta)] - [Fe(tdpa)] 2- / [Fe(tdpa)] 3- [Fe(edta)] - / [Fe(edta)] 2- [Fe (Citrate)] / [Fe (Citrate)] - [Fe(TEOA)OH] - / [Fe(TEOA)OH] - , and [Fe (oxalate)] + It contains [Fe (oxalate)]. These redox pairs are of particular interest for the alkalization of iron-containing electrochemically active (alkali metal deficient) substances such as FePO4.

[0092] The advantage of this indirect electrochemical method is that it can utilize much higher current densities compared to the direct electrochemical reduction of electrode materials, thus improving the productivity of the electrochemical reactor.

[0093] Subsequently, the electrodes produced by the above method can be directly used to fabricate electrochemical cells, for example, by stacking the electrodes with an active counter electrode and separating the two electrodes with an electrolyte (a liquid or gel electrolyte impregnating the separator, or a solid polymer electrolyte). These electrochemical cells can then be further used in the fabrication of electrochemical energy storage devices.

[0094] As described above, the material alkalized by this method may be either spent electrode material obtained in a battery recycling process or pre-charged electrode material (or its precursor) that is converted into discharged electrode material before assembly in an electrochemical cell.

[0095] This specification also intends to describe batteries, which include 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 in portable devices such as mobile phones, cameras, tablets or laptops, electric or hybrid vehicles, or renewable energy storage. [Examples]

[0096] The following non-limiting embodiments are illustrative and should not be construed as further limiting the scope of the invention. These embodiments will be better understood by referring to the accompanying drawings. (Example 1) (a) Preparation of delithiated FePO4

[0097] Delithiated material was produced from a LiFePO4 sample using a process described in U.S. Patent Application No. 2019 / 0207275 (Amouzegar et al.) with unused cathode material containing the main component LiFePO4 along with small amounts of PVDF and graphite. Ten parts of this material were dispersed in 100 parts of an aqueous solution containing H2O2 (the amount of H2O2 was adjusted to a Fe:H2O2 molar ratio of 2:1.33) in a stirred reactor with CO2 gas bubbles at room temperature under a pressure of 30 psi. Filtered samples of the suspension taken at various intervals were analyzed by ICP to determine the concentrations of Li, Fe, and P. The solid residue from the leachate was then separated by centrifugation, washed with deionized water, and dried in an oven at 120°C for 48 hours.

[0098] Seven batches were prepared in this manner and then combined. Figure 1 shows the leaching rates of Li, Fe, and P obtained in each batch. These results were then used to calculate the leaching efficiency of each element. After 30 minutes, approximately 80% of Li could be found in the solution, and after 75 minutes, it was observed that this parameter reached a value of approximately 90%. The leaching rates of Fe and P did not exceed 0.5% and 3%, respectively, indicating very high selectivity and efficiency of lithium extraction.

[0099] X-ray diffraction spectra of solid composite samples and LiFePO4 samples before charging and discharging were obtained using a MiniFlex 600™ instrument equipped with a cobalt source, and are shown in Figure 2. As shown in the figure, the samples consist mainly of FePO4 and some residual LiFePO4. In fact, the X-ray diffraction results confirm a higher delithiation rate than that calculated from the ICP analysis results (90% in ICP analysis compared to 95% in the diffraction results). (b) Fabrication of FePO4 electrodes

[0100] During relithiation, to characterize the electrochemical behavior of the delithiation material 1(a), FePO4 powder was mixed with conductive carbon (Denka® Black and VGCF®-H, 1:1 by weight) and a binder (PVDF) in a weight ratio of 87.5:7.5:5, and then dispersed in N-methyl-2-pyrrolidone (NMP) to form a suspension. This suspension was finally prepared by cutting it 4.16 cm using a doctor blade. 2 The stainless steel current collector is coated and dried (the final coating amount of FePO4 on the electrode is approximately 4.3 mg / cm²). 2 (That was the case.) (c) Relithiation of FePO4 electrode material

[0101] The electrode prepared in (b) was tested as the working electrode in a three-electrode electrochemical setup. A platinum mesh was used as the counter electrode, while a saturated calomel electrode (SCE) functioned as a reference. The electrolyte consisted of a 0.25 M aqueous solution of Li2SO4 adjusted to pH 7 by adding LiOH. The temperature was set to 25°C using a double-walled glass electrochemical cell (constant temperature bath). Figure 3 shows the current-to-potential voltammetry curve at a potential scanning speed of 1 mV / s.

[0102] First, the working electrode was scanned using a Versastat® 4 instrument (Princeton Applied Research) between its open-circuit potential (in this case, 165 mV vs. SCE) and -1.0 V vs. SCE. Within this potential range, no reactions occurred other than the reduction peak corresponding to the lithiation from FePO4 to LiFePO4. This suggests that operating the battery within this potential window allows for good Coulomb current efficiency for the relithiation process. The X-ray diffraction patterns of the relithiated sample were compared with those of the LiFePO4 material before charging and discharging and the delithiated composite sample, as shown in Figure 4. It is clearly demonstrated that after relithiation, the structure of the delithiated sample returns to that of the material before charging and discharging. (Example 2)

[0103] To perform electrochemical relithiation under conditions more suitable for large-scale production processes, the same type of electrode prepared in Example 1(b) was relithiated under constant current conditions by applying a constant current of 10 mA between the cathode (FePO4 electrode) and the anode (inert electrode, in this case, Pt mesh). The cathode potential was measured relative to the SCE reference electrode to determine the time required to relithiate almost all of the delithiated FePO4. The electric field was applied in the same type of solution as in Example 1(c) at the same temperature (25°C).

[0104] Figure 5 shows the change in cathode potential as a function of electrolysis time. The initial cathode potential was approximately 0V vs. SCE, and as the degree of lithiation of the cathode material increased, it gradually shifted to a higher cathode potential as a function of time. After approximately 1200 seconds, the electrode potential stabilized and remained constant at -1.4V vs. SCE, indicating the initiation of a novel electrochemical reaction, including hydrogen release.

[0105] X-ray diffraction analysis of the electrodes shown in Figure 6 confirms a very high degree of FePO4 reconstruction in lithium ions, leading to a conversion rate to the LiFePO4 phase of nearly 100%. In fact, the FePO4 peak clearly transforms into a LiFePO4 peak. Other phases represented in the diffractogram include stainless steel supports (2θ: 51, 54, and 90) and conductive graphite (2θ: 30).

[0106] The Coulomb efficiency of relithiation was calculated to be over 80%, and therefore, as presented in Example 1, it is possible to determine the electrochemical behavior estimated under specific conditions of current density at the cathode and minimize side reactions (such as hydrogen emission) to achieve high current efficiency. (Example 3)

[0107] To evaluate the effect of temperature on the lithiumization process, the two electrodes prepared in Example 1(b) were relithiated at 25°C and 50°C, respectively, in an aqueous Li2SO4 (0.5M) solution with the pH adjusted to 7 by adding LiOH. Relithiation was performed at a constant potential of -0.2V vs. SCE.

[0108] Figure 7 shows the change in current between the cathode and anode as a function of time. A higher rate of electrochemical relithiation at higher temperatures (50°C) was consequently achieved when performed at 25°C. Compared to conventional relithiation, this process exhibits less significant current reduction at the start of the process and reaches virtually zero current between the cathode and anode (when relithiation is nearly complete) in a shorter time.

[0109] The X-ray diffractogram in Figure 8 confirms that both electrodes were highly relithified in tests at 25°C and 50°C, respectively, while residual FePO4 was less than 8% and undetectable. (Example 4)

[0110] As described in the published U.S. Patent Application No. 2019 / 0207275 (Amouzegar et al.), to demonstrate the feasibility of directly using a LiHCO3 solution generated during the processing of electrode materials from spent batteries, an electrode similar to that described in Example 1(b) was relithiated in an electrochemical cell using a 0.5 M LiHCO3 aqueous solution (generated by fizzing CO2 into a Li2CO3 suspension in water at 30 psi and room temperature). The cell was maintained under CO2 by gently fizzing CO2 gas to create an electrolyte at pH 7 and 25°C.

[0111] Figure 9 shows cathode linear scanning voltammetry of the electrode performed at a rate of 1 mV / s between 0 V vs. OCP (open circuit potential) and -1.1 V vs. SCE. The same type of relithiation reduction peak observed in Example 1 using Li2SO4 solution is observed, thereby suggesting the possibility of using LiHCO3 solution as a Li ion source during the relithiation process. Indeed, relithiation in bicarbonate-based electrolytes appears to exhibit better reaction kinetics than sulfate-based electrolytes under similar conditions, as shown in Figure 10. Compositional analysis by X-ray diffraction also shows complete relithiation of the electrode (see Figure 11). (Example 5) (a) Fabrication of FePO4 electrodes

[0112] To demonstrate that the same method can be easily applied using industrial current collectors used in commercially available batteries, the same type of electrode prepared in Example 1(b) was fabricated using a 15 μm thick aluminum current collector strip coated with a carbon thin layer. Dried iron phosphate powder was mixed with conductive carbon (Denka® Black and VGCF®-H, 1:1 by weight ratio) and a PVDF binder in a weight ratio of 89:6:5 and dispersed in N-methyl-2-pyrrolidone (NMP). The resulting suspension was coated onto the aluminum current collector and dried in an oven. The electrode coating amount was approximately 7.12 mg of FePO4 / cm². 2 It was decided that this was the case. (b) Relithiation of FePO4 electrode material

[0113] To simulate the electrochemical settings operating in batch mode, a surface area of ​​37.5 cm² was used. 2 The electrode prepared in (a) is placed 90 cm (using an SS support to maintain a constant distance from the counter electrode). 2The platinum mesh and SCE electrode were placed in an electrochemical cell as the counter electrode and reference electrode, respectively. The electrodes were fabricated from Li2SO4 (0.5M) and the pH was adjusted to 9 using diluted LiOH. The cathode potential was controlled to -200mV relative to the SCE using a potentiostat from Princeton Applied Research. Electrolysis was carried out at a temperature of 25°C with stirring. Figure 12 shows the change in current as a function of time. When the current decreased by 95% (in this case, after 2860 seconds), electrolysis was stopped, the working electrode was washed with deionized water, and dried.

[0114] A comparison of X-ray diffractograms (Figure 13) obtained from LiFePO4 before charging and discharging, delithiated FePO4, and relithiated LiFePO4 shows that the relithiation process produced It was confirmed that it was used. In fact, the relithiumated electrode consisted of 93% LiFePO4 and 7% FePO4. The relithiumated LiFePO4 exhibits an orthorhombic structure similar to that of the LiFePO4 before charging and discharging. (c) Use of relithiumated LiFePO4 electrodes in coin batteries

[0115] The electrochemical properties of commercially available LiFePO4 material applied in the same manner to the relithified electrodes and aluminum current collectors in (b) were tested against metallic lithium in coin cells. The amount of active material applied, calculated as mg of LiFePO4 per unit area, was 7.32 mg of LiFePO4 / cm² for both the relithified samples and the pre-charge / discharge LiFePO4 samples. 2 and 5.88 mg of LiFePO4 / cm³ 2 Both batteries were cycled repeatedly between 2V and 3.8V with a discharge rate of 1C and a charge rate of C / 4. Prior to the cycling procedure, a pre-charge / discharge cycle at C / 24 was applied to each coin. In addition, the cycling procedure required an initial discharge at C / 12, and was repeated every 20 cycles to monitor the battery health.

[0116] Figure 14 shows the discharge capacity curves for these electrode materials. Both electrode materials appear to exhibit very good stability in terms of capacity (loss of less than 2% after 100 cycles). After 100 cycles, the electrochemically relithified LiFePO4 material and the control LiFePO4 material presented good and very similar discharge capacities at a discharge rate of 1C, at 138 and 143 mAh / g, respectively. The very small capacity difference may be related to slight differences in the amount of active material applied; i.e., the electrochemically relithified material with a slightly higher application amount may result in a slightly lower capacity. (Example 6) (a) Preparation of Fe(II) / Fe(III) redox pair solution i. Preparation of Fe(II) and Fe(III) citrate solutions

[0117] A citric acid solution was prepared by dissolving 3.18 parts of acid in 200 parts of water. The solution was then alkalized to pH 6 using a 4 M LiOH solution. After adjusting the lithium concentration to a minimum of 0.5 M, the volume was adjusted to 250 parts by adding the required amount of Li2SO4.

[0118] Next, to prepare the ferrous solution, 0.56 parts of hydrated ferrous sulfate (FeSO4·7H2O) were dissolved in 100 parts of a pre-prepared citric acid solution.

[0119] Similarly, in the case of 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.

[0120] Each solution was filtered through a 0.22 μm filter and then deoxygenated by argon injection before subsequent use. If necessary, the pH of each solution was adjusted to a value of 4.5–8 using LiOH or H2SO4. ii. Preparation of Fe(II) and Fe(III)EDTA solutions

[0121] An EDTA solution was prepared by dissolving 14.6 parts of the salt in its acidic form in 100 parts of 1 M LiOH solution. The solution was then alkalized to pH 6 using 4 M LiOH solution. After adjusting the lithium concentration to a minimum of 0.5 M, the volume was adjusted to 250 parts by adding the required amount of Li2SO4.

[0122] Next, to prepare the ferrous solution, 2.78 parts of hydrated ferrous sulfate (FeSO4·7H2O) were dissolved in 100 parts of a pre-prepared EDTA solution.

[0123] Similarly, in the case of the ferric solution, 1 part of hydrated ferric sulfate (Fe2(SO4)3·xH2O) was dissolved in 100 parts of a pre-prepared EDTA solution.

[0124] Each solution was filtered through a 0.22 μm filter and then deoxygenated by argon injection before subsequent use. If necessary, the pH of each solution was adjusted to a value of 4.5–8 using LiOH or H2SO4. (b) Testing of the electrochemical properties of Fe(II) / Fe(III) redox pairs

[0125] To determine the feasibility of reducing FePO4 to LiFePO4 using each redox pair prepared in section (a) of this example, the electrochemical behavior of Fe(III) solutions of each iron complex was tested in a three-electrode electrochemical setting.

[0126] Each Fe(III) solution was placed in the cathode chamber of a battery, where a glassy carbon disk (3 mm in diameter) was set as the working electrode (under argon coating). A Pt mesh was placed in the anode chamber, which was filled with the electrolyte separated by the sintered glass disk. An Ag / AgCl electrode was used as the reference electrode.

[0127] Voltammograms were obtained using a Versastat® 4-potentiostat (Princeton Applied Research). Figure 15 shows the results at a scanning speed of 200 mV / sec, comparing 2.05 V and 4.25 V vs. Li + / Li 0 The voltammogram of the Fe(III)-EDTA solution performed at pH 4.5 is shown below. Large separation values ​​(approximately 650 mV) can be observed in the oxidation peak of Fe(II)-EDTA and the reduction peak of Fe(III)-EDTA, indicating a relatively slow reaction kinetics. However, the oxidation of Fe(II)-EDTA is approximately 3.16 V vs. Li + Starting at a potential of / Li, this is the minimum potential of 3.45V required for the reduction from FePO4 to LiFePO4 vs. Li. + It is significantly more negative compared to / Li.

[0128] Table 1 shows the oxidation current potentials observed for each Fe(II)-based reducing agent prepared. [Table 1]

[0129] Figure 16 shows the polarization curves for EDTA-LiOH solution and Fe(III)-EDTA in LiOH. The reduction peak of Fe(III)-EDTA can be observed to appear at a lower negative potential than the hydrogen release reaction in this medium, demonstrating the possibility of electrochemical regeneration of Fe(II)-EDTA from Fe(III)-EDTA with appropriate Coulomb efficiency while minimizing the current associated with hydrogen formation. (Example 7) (a) Relithiation of FePO4 with Fe(II)-EDTA

[0130] To demonstrate the use of Fe(II)-EDTA for the relithiation of FePO4, 50 mL of a solution prepared according to the same protocol as described in Example 6 was contacted with 0.65 g of FePO4 prepared in Example 1(a) at 40°C under an argon atmosphere. In this assay, the EDTA concentration was increased to satisfy an EDTA / Fe(II) molar ratio of 4. The pH was adjusted to 8 with a 1M LiOH solution to maximize the solubility of the redox pair. The FePO4 powder was maintained in a suspension using an electromagnetic stirrer to decrease the concentration of Fe(II)-EDTA, and the appearance of Fe(III)-EDTA was monitored using an ORP sensor placed in the suspension.

[0131] Figure 17 shows the change in the potential of the suspension during relithiation. An increase in potential can be observed in response to the oxidation from Fe(II)-EDTA to Fe(III)-EDTA (by reducing FePO4 to LiFePO4).

[0132] At the end of the assay, the solid was separated by vacuum filtration, washed, dried, and analyzed by X-ray diffraction (Rigaku MiniFlex® 600). A comparison of the figures of LiFePO4 before charge / discharge, delithiated FePO4, and the solid obtained after contact with Fe(II)-EDTA solution in the presence of lithium salt (Figure 18) shows that the solid treated with Fe(II)-EDTA solution was completely relithiated to form LiFePO4. (b) Relithiation of FePO4 with Fe(II)-citrate

[0133] The relithiation assay was performed using an Fe(II)-citrate solution similar to the procedure presented for Fe(II)-EDTA in Section 7(a). In this example, the citrate / Fe(II) ratio was adjusted to 2 by adding ferrous sulfate, and the pH was adjusted to 6 by adding 1 M LiOH. 50 mL of the solution was brought into contact with 0.19 g of FePO4 prepared in Example 1(a) at 40°C under an argon atmosphere. The FePO4 powder was maintained in the suspension using an electromagnetic stirrer to decrease the concentration of Fe(II)-citrate, and the appearance of Fe(III)-citrate was monitored using an ORP sensor placed in the suspension (Figure 19).

[0134] At the end of the assay, the solid was separated by vacuum filtration, washed, dried, and analyzed by X-ray diffraction. A comparison of the diffractograms of LiFePO4 before charge / discharge, delithiated FePO4, and the solid obtained after contact with the Fe(II)-citrate solution in the presence of the lithium salt (Figure 20), as in the case of the solid in Example 7(a), shows that the FePO4 was completely relithiated to form LiFePO4. (Example 8) (a) Electrochemical regeneration of Fe(III)-EDTA in Fe(II)-EDTA

[0135] An 800 mL volume of Fe(III)-EDTA solution, with initial Fe(III), Li2SO4, and EDTA at concentrations of 0.08 M, 1 M, and 0.2 M, respectively, and adjusted to pH 6.3 with LiOH, was placed in the cathode liquid bath of an ICI-FM01 filter press electrolytic cell assembly under the protection of an inert gas (Ar). The FM01 cell was assembled with a graphite cathode, a titanium anode coated with an indium oxide layer, and a Nafion® 324 type cation membrane. The geometric active surface of all components (cathode, anode, and membrane) was 64 cm². 2 That was it.

[0136] The flow rates of the cathode and anode solutions were 2 liters / minute, and the linear velocity of the cathode solution was approximately 16 cm / s. The electrolysis temperature was controlled to approximately 50°C by recirculating a heat-conducting fluid heated by a constant-temperature bath (PolyScience #PD07R-20-A11B) through heat exchangers installed in the anode and cathode solution tanks. Electrolysis was performed by setting the voltage between the anode and cathode to 1.65V (Instek #SPS-1230). An ORP sensor was placed in the cathode solution tank to monitor the generation of the solution's potential.

[0137] The concentration of Fe(III)-EDTA in each sample during electrolysis was measured in a LiOH solution (pH 7.70). The total iron concentration was determined by diluting 1 mL of the sample in 10 mL of 0.2 M EDTA and measuring the absorbance of the solution at 470 nm. A 1000-fold dilution in water was prepared, and the total iron concentration was determined by adding FerroVer® iron reagent from Hach and measuring the absorbance at 510 nm. The difference between total iron and Fe(III)-EDTA allowed for the evaluation of the concentration of Fe(II)-EDTA formed during electrolysis. Figure 21 shows the change in Fe(II)-EDTA concentration and the redox potential of the solution for 240 minutes of electrolysis.

[0138] As the concentration of Fe(II)-EDTA (formed on the cathode by reduction of Fe(III)-EDTA) increases in the cathode solution, a decrease in the redox potential of the solution can be observed. During electrolysis, the total cell current decreased from 600 mA to 300 mA.

[0139] It should be noted that it is possible to improve mass transfer within the cell by known methods (such as the use of a turbulence promoter and temperature increase), and to increase the current density of the cell by increasing the effective surface area of ​​the cathode (for example, by using materials in the form of felt, grid, etc.). It is clear that the choice of cathode material is not limited to graphite, and other cathode materials (preferably those with a high hydrogen overpotential) can be used. (b) Relithiation of FePO4 by electrochemically generated Fe(II)-EDTA

[0140] Next, FePO4 relithiation was performed using the Fe(II)-EDTA solution obtained during electrolysis using the FM01 cell in (a). 50 mL of the solution was brought into contact with 0.32 g of FePO4 prepared in Example 1(a) at 40°C under an argon atmosphere. The FePO4 powder was maintained in the suspension using an electromagnetic stirrer to decrease the concentration of Fe(II)-EDTA, and the appearance of Fe(III)-EDTA was monitored using an ORP sensor placed in the suspension. Figure 22 shows the change in the potential of the suspension during relithiation. The increase in potential can be observed in response to the oxidation from Fe(II)-EDTA to Fe(III)-EDTA (by reducing FePO4 to LiFePO4).

[0141] At the end of the assay, the solid was separated by vacuum filtration, washed, dried, and analyzed by X-ray diffraction. A comparison of the LiFePO4 before charge / discharge, the delithiated FePO4, and the solid obtained after contact with the Fe(II)-EDTA solution generated by electrolysis in the presence of a lithium salt (Figure 23) indicates that the solid was completely relithiated to form LiFePO4.

[0142] Numerous modifications can be made to any of the embodiments described above without departing from the intended scope of the present invention. Any reference, patent or document in the scientific literature referenced herein is incorporated herein by reference in its entirety for all purposes. The present invention provides, for example, the following items: (Item 1) A method for electrochemical alkalizing an electrochemically active material, a) A step of obtaining a working electrode on a current collector, wherein the working electrode material comprises the electrochemical active material, optionally a binder and / or an electronically conductive material, b) The step of introducing the working electrode, together with an inert counter electrode and a solution containing an alkali metal salt in the solvent, into an electrochemical reactor in a continuous and / or batch mode, c) A step of applying a direct current between the working electrode and the counter electrode to obtain an alkalized electrode containing an alkalized electrochemical active material, d) The step of removing the alkalizing electrode obtained in step (c) from the electrochemical reactor, Includes, A method wherein the electrochemical active material comprises a metal oxide (including a complex oxide), a metal phosphate, a metal silicate, a metal sulfate, or a partially alkalized metal oxide (including a complex oxide), a metal phosphate, a metal silicate, or a metal sulfate. (Item 2) The method according to item 1, wherein the electrochemical active material is alkali metal deficient. (Item 3) The electrochemical active material of formula I: A w-p M n+p x X y O z (I) The alkalized electrochemical active material of formula II: A w M n x X y O z (II) (In the formula, A is an alkali metal, M is a transition metal, a post-transition metal, or a combination thereof. X is selected from P, Si, and S. O is an oxygen atom, w is selected from a number between 1 and 4, and corresponds to the number of A atoms in the alkalized electrochemical active material. x is selected from a number between 1 and 5 and corresponds to the number of M atoms. y is selected from a number between 0 and 2, and if y is zero, then X does not exist. z is selected from a number between 1 and 12 and corresponds to the number of oxygen atoms in the above formula. n indicates the oxidation state of M. In formula I, p represents both the average number of missing A atoms and the average increase in the oxidation state of M, where p ≤ w (preferably 0 <p≦1)であり、 w, y, z, n, and p are selected to form a stable, electrically neutral compound. The method described in item 1 or 2, which includes converting to [a specific format]. (Item 4) p=w, A does not exist in equation I, and the electrochemical active material in equation I is equation I(a):M n+p x X y O z The method described in item 3. (Item 5) The method according to item 3 or 4, where X is phosphorus, y is 1, and z is 4. (Item 6) The method according to any one of items 3 to 5, wherein M is Fe, Ni, Mn, Co, or at least two of these. (Item 7) The method according to item 3 or 4, wherein M is V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn, or at least two combinations thereof. (Item 8) The method described in any one of items 3, 4, and 7, wherein y is 0 and X does not exist. (Item 9) The method according to any one of items 3 to 8, wherein A is Li, Na, or K, or A is Li. (Item 10) The method according to any one of items 1 to 9, wherein the electrochemical active material or alkalized electrochemical active material is further doped by partially substituting M with a transition metal (e.g., Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, or Y) and / or a non-transition metal (e.g., Mg, Ca, Sr, Al, Sb, or Sn). (Item 11) The method according to any one of items 1 to 10, wherein the solvent is selected from aqueous solvents, organic solvents, or mixtures thereof. (Item 12) The method according to item 11, wherein the solvent is water. (Item 13) The method according to any one of items 1 to 12, wherein the alkali metal salt comprises at least one alkali metal sulfate, carbonate, bicarbonate, hydroxide, nitrate, acetate, oxalate, or phosphate. (Item 14) The method according to item 13, wherein the alkali metal salt is an alkali metal sulfate. (Item 15) The method according to item 13, wherein the alkali metal salt is an alkali metal bicarbonate. (Item 16) The method according to item 15, wherein step (b) and / or (c) are carried out in the presence of gaseous carbon dioxide. (Item 17) The method according to any one of items 1 to 16, further comprising the step of adjusting the pH of the solution to a pH suitable for the electrochemical active material of step (a) (for example, in the case of FePO4, the pH is adjusted to 5 to 9, preferably 6 to 7.5). (Item 18) The method according to any one of items 1 to 17, wherein the alkali metal of the alkali metal salt is lithium. (Item 19) The method described in any one of items 1 to 18, wherein step (c) is performed in continuous mode or batch mode. (Item 20) The method according to item 19, wherein step (c) is performed in continuous mode, the working electrode is introduced to one side of the electrochemical reactor, and the working electrode moves along a predetermined path such that it remains at a constant distance from the counter electrode while moving along the electrochemically active region of the electrochemical reactor so as to maintain a relatively uniform current and potential distribution. (Item 21) The method according to item 20, wherein the speed at which the working electrode moves through the electrochemical reactor is adjusted based on the residence time required for a predetermined level of alkalization at the applied current density. (Item 22) The method according to any one of items 1 to 21, wherein step (c) is performed in a mode in which the current density between the working electrode and the counter electrode is controlled. (Item 23) The method according to any one of items 1 to 21, wherein step (c) is performed in a mode in which the voltage between the working electrode and the counter electrode is controlled. (Item 24) The method according to any one of items 1 to 23, wherein the electrochemical active material is FePO4 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 active LiFePO4, preferably in the range of 1 to 15 A / g active LiFePO4. (Item 25) The method according to any one of items 1 to 24, wherein step (c) is carried out at a temperature in the range of 5°C to 90°C, preferably 25°C to 50°C. (Item 26) The method according to any one of items 1 to 25, wherein step (b) further includes a reference electrode. (Item 27) The method according to any one of items 1 to 26, further comprising step (e) of cleaning the alkalized electrochemically active electrode material of the alkalized electrode. (Item 28) The method according to any one of items 1 to 27, further comprising the step of drying the alkalized electrochemical active material of the alkalized electrode. (Item 29) The working electrode material includes a binder, and the binder is a fluorine-containing polymer binder. The method according to any one of items 1 to 28, selected from and other solvating polymer binders. (Item 30) The method according to item 29, wherein the binder is a fluorine-containing polymer binder (such as PVDF, HFP, PVDF-co-HFP, or PTFE). (Item 31) The method according to item 29, wherein the binder is a solvated polymer binder selected from copolymers (block, random, alternating, statistical, etc.) comprising poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamide), polyurethane, poly(vinyl alcohol), and at least one of the above polymers or their monomers, and at least two combinations thereof, wherein the polymer is branched and / or crosslinked as necessary. (Item 32) The method according to any one of items 1 to 31, wherein the working electrode material comprises the electronically conductive material, the electronically conductive material being selected from the group consisting of carbon black (such as Ketjen® Black and Super P®), acetylene black (such as Shawinigan Black and Denka® Black), graphite, graphene, carbon fibers or nanofibers (such as vapor-grown carbon fibers (VGCF)), carbon nanotubes (e.g., single-layer or multi-layer), and at least two combinations thereof. (Item 33) The method according to any one of items 1 to 32, wherein the working electrode material is an electrode material from a spent battery (e.g., a positive electrode material), and step (a) includes at least one step of separating the electrode material from other elements of the spent battery and applying the material to a current collector. (Item 34) The method according to any one of items 1 to 32, wherein step (a) comprises mixing the electrochemical active material, the binder and optionally the electronically conductive material in a solvent, applying it to the current collector, and drying it. (Item 35) An electrode obtained by the method described in any one of items 1 to 34. (Item 36) A method for electrochemical alkalizing an electrochemically active material, (i) The step of adding the electrochemical active material to a solution containing a reducing agent and an alkali metal salt in a solvent to produce an alkalized electrochemical active material, (ii) A step of separating the alkalized electrochemical active material from the solution, (iii) A step of electrochemically treating the solution separated in step (ii) to regenerate the reducing agent in the solution, Methods that include... (Item 37) The method according to item 36, wherein the electrochemical active material and the alkalized electrochemical active material are as described in any one of items 1 to 10. (Item 38) The method according to item 36 or 37, wherein the reducing agent is a reducing member of a redox pair having a lower redox potential than the electrochemical active material (alkali metal deficiency) to be reduced. (Item 39) The method according to item 38, wherein the redox pair is Fe(II) / Fe(III) based. (Item 40) The aforementioned redox pair is [Fe(CN)6] 3- / [Fe(CN)6] 4- [Fe(nta)] / [Fe(nta)] - [Fe(tdap)] 2- / [Fe(tdap)] 3- [Fe(edta)] - / [Fe(edta)] 2- [Fe (Citrate)] / [Fe (Citrate)] - [Fe(TEOA)OH] - / [Fe(TEOA)OH] - , and [Fe (oxalate)] + The method described in item 39, selected from [Fe (oxalate)]. (Item 41) The method according to any one of items 36 to 40, wherein step (i) further comprises the step of deoxygenating the solution. (Item 42) The method according to any one of items 36 to 41, wherein step (i) and / or (iii) are carried out in the presence of a gas that eliminates the presence of oxygen. (Item 43) The method according to any one of items 36 to 42, wherein the alkali metal salt is selected from alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, phosphates, and combinations thereof. (Item 44) The method according to item 43, wherein the alkali metal salt is an alkali metal sulfate. (Item 45) The method according to item 43, wherein the alkali metal salt is an alkali metal bicarbonate. (Item 46) The method according to item 45, wherein step (i) is carried out in the presence of gaseous carbon dioxide. (Item 47) The method according to any one of items 36 to 46, wherein the alkali metal of the alkali metal salt is lithium. (Item 48) The method according to any one of items 36 to 47, further comprising the step of adjusting the pH of the solution to a pH suitable for the electrochemical active material of step (i) (for example, in the case of FePO4, the pH is adjusted to 5 to 9, preferably 6 to 7.5). (Item 49) The method according to any one of items 36 to 48, wherein the solvent is an aqueous solvent. (Item 50) The method according to any one of items 36 to 49, wherein step (iii) of the electrochemical treatment is carried out by passing an electric current between at least one cathode and at least one anode in an electrolytic cell. (Item 51) The method according to item 50, wherein the electrolytic cell includes at least one ionic or nonionic separator placed between the anode and the cathode to protect the regenerated reducing agent. (Item 52) The method according to item 50 or 51, further comprising a system for the electrolytic cell to keep the solution deoxygenated. (Item 53) The method according to item 52, wherein the system includes an oxygen-free gas such as carbon dioxide, nitrogen, or argon. (Item 54) The method according to any one of items 36 to 53, wherein the electrochemical active material is in the form of a suspension in the solution of step (i), and step (ii) is carried out by filtration, centrifugation or decantation, followed by a washing step as necessary. (Item 55) The method according to any one of items 36 to 53, wherein the electrochemical active material is contained in an electrode material on a current collector, and step (ii) comprises removing the electrode from the solution and then, if necessary, a washing step. (Item 56) The method according to item 55, wherein the electrode material further comprises a binder. (Item 57) The method according to item 56, wherein the binder is selected from a fluorine-containing polymer binder and a solvating polymer binder. (Item 58) The method according to item 57, wherein the binder is a fluorine-containing polymer binder (such as PVDF, HFP, PVDF-co-HFP, or PTFE). (Item 59) The method according to item 57, wherein the binder is a solvated polymer binder selected from poly(ethylene oxide), poly(propylene oxide), poly(dimethylsiloxane), poly(alkylene carbonate), poly(alkylene sulfone), poly(alkylene sulfamide), polyurethane, poly(vinyl alcohol), and copolymers (block, random, alternating, statistical, etc.) comprising at least one of the above polymers or their monomers, and at least two combinations thereof, wherein the polymer is branched and / or crosslinked as necessary. (Item 60) The method according to any one of items 55 to 59, wherein the electrode material further comprises, for example, an electronically conductive material selected from the group consisting of carbon black (such as Ketjen® Black and Super P®), acetylene black (such as Shawinigan Black and Denka® Black), graphite, graphene, carbon fibers or nanofibers (such as vapor-grown carbon fibers (VGCF)), carbon nanotubes (e.g., single-layer or multi-layer), and at least two combinations thereof. (Item 61) The method according to any one of items 36 to 60, further comprising the step of drying the alkalized electrochemical active material. (Item 62) An electrode comprising the alkalized electrochemical active material, a binder, and optionally an electronically conductive material, obtained by the method described in any one of items 36 to 61. (Item 63) An electrochemical cell comprising a negative electrode, a positive electrode, and an electrolyte, wherein the positive electrode is the electrode described in item 35 or 62. (Item 64) A battery comprising at least one electrochemical cell as described in item 63. (Item 65) The battery described in item 64, wherein the battery is a lithium battery or a lithium-ion battery. (Item 66) An electrochemical cell as described in item 63 or a battery as described in item 64 or 65 for use in portable devices such as mobile phones, cameras, tablets or laptops, electric or hybrid vehicles, or renewable energy storage.

Claims

1. A method for electrochemical alkalizing of an electrochemical active material, wherein the method is (i) Adding the electrochemical active material to a solution containing a reducing agent and an alkali metal salt in a solvent to produce an alkalinized electrochemical active material; (ii) A step of separating the alkalized electrochemical active material from the solution, (iii) A step of electrochemically treating the solution separated in step (ii) to regenerate the reducing agent in the solution, Includes, The method further comprises, if necessary, the step of drying the alkalized electrochemical active material.

2. The method according to claim 1, wherein the electrochemical active material comprises a metal oxide, a metal phosphate, a metal silicate, a metal sulfate, or a partially alkalized metal oxide, metal phosphate, metal silicate, or metal sulfate.

3. The method according to claim 2, wherein the electrochemical active material is alkali metal deficient.

4. The electrochemical active material of formula I: A w−p M n+p x X y O z (I) The alkalized electrochemical active material of formula II: A w M n x X y O z (II) (In the formula, A is an alkali metal, M is a transition metal, a post-transition metal, or a combination thereof. X is selected from P, Si, and S. O is an oxygen atom, w is selected from a number between 1 and 4, and corresponds to the number of A atoms in the alkalized electrochemical active material. x is selected from a number between 1 and 5 and corresponds to the number of M atoms. y is selected from a number between 0 and 2, and if y is zero, X does not exist. z is selected from a number between 1 and 12 and corresponds to the number of oxygen atoms in the above formula. n indicates the oxidation state of M. In equation I, p represents both the average number of missing A atoms and the average increase in the oxidation states of M, where p ≤ w. (w, y, z, n, and p are selected to form a stable, electrically neutral compound.) The method according to claim 2, which includes converting to

5. The method according to claim 4, wherein p = w, A does not exist in formula I, and the electrochemical active material of formula I is formula I(a): M n + p x X y O z

6. The method according to claim 4, wherein X is phosphorus, y is 1, and z is 4.

7. The method according to claim 4, wherein M is Fe, Ni, Mn, Co or at least two combinations thereof, or M is V, Mn, Ni, Co, Fe, Cr, Ti, Zr, Sn or at least two combinations thereof.

8. The method according to claim 4, wherein y is 0 and X does not exist.

9. The method according to any one of claims 4 to 8, wherein A is Li, Na, or K, or A is Li.

10. The method according to any one of claims 2 to 8, wherein the electrochemical active material or alkalized electrochemical active material is further doped by partially substituting M with a transition metal and / or a non-transition metal.

11. The method according to any one of claims 1 to 8, wherein the reducing agent is a reducing member of a redox pair having a redox potential lower than that of the electrochemical active material (alkali metal deficiency) to be reduced.

12. The method according to claim 11, wherein the redox pair is an Fe(II) / Fe(III)-based redox pair.

13. The method according to any one of claims 1 to 8, wherein step (i) further comprises the step of deoxygenating the solution.

14. The method according to any one of claims 1 to 8, wherein step (i) and / or (iii) are carried out in the presence of a gas that eliminates the presence of oxygen.

15. The method according to any one of claims 1 to 8, wherein the alkali metal salt is selected from alkali metal sulfates, carbonates, bicarbonates, hydroxides, nitrates, acetates, oxalates, phosphates, and combinations thereof.

16. The method according to claim 15, wherein the alkali metal salt is an alkali metal sulfate.

17. The method according to claim 15, wherein the alkali metal salt is an alkali metal bicarbonate.

18. The method according to claim 17, wherein step (i) is carried out in the presence of gaseous carbon dioxide.

19. The method according to any one of claims 1 to 8, wherein the alkali metal of the alkali metal salt is lithium.

20. The method according to any one of claims 1 to 8, further comprising the step of adjusting the pH of the solution to a pH suitable for the electrochemical active material of step (i).

21. The method according to any one of claims 1 to 8, wherein the solvent is an aqueous solvent.

22. The method according to any one of claims 1 to 8, wherein the electrochemical treatment step (iii) is carried out by passing an electric current between at least one cathode and at least one anode in an electrolytic cell.

23. The method according to claim 22, wherein the electrolytic cell includes at least one ionic or nonionic separator placed between the anode and the cathode to protect the regenerated reducing agent, and / or the electrolytic cell further includes a system for keeping the solution deoxygenated.

24. The method according to claim 23, wherein the system includes an oxygen-free gas.

25. The method according to any one of claims 1 to 8, wherein the electrochemical active material is in the form of a suspension in the solution of step (i), and step (ii) is carried out by filtration, centrifugation or decantation, and thereafter a washing step is carried out as necessary.

26. The method according to any one of claims 1 to 8, wherein the electrochemical active material is contained in an electrode material on a current collector, and step (ii) comprises removing the electrode from the solution and then, if necessary, a washing step.

27. ​​The method according to claim 26, wherein the electrode material further comprises a binder.

28. The method according to claim 26, wherein the electrode material further comprises an electronically conductive material.

29. The method according to any one of claims 1 to 8, further comprising the step of drying the alkalized electrochemical active material.

30. An electrode comprising the alkalized electrochemical active material, a binder, and optionally an electronically conductive material obtained by the method according to any one of claims 1 to 8.

31. An electrochemical cell comprising a negative electrode, a positive electrode, and an electrolyte, wherein the positive electrode is the electrode described in claim 30.

32. A battery comprising at least one electrochemical cell as described in claim 31.

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