DESCRIPTION

TECHNICAL FIELD

The present invention relates to the field of electrodes and batteries. More specifically, the present invention relates to the field of cells comprising recyclable electrodes and ion separation devices such as redox batteries.

BACKGROUND

Different electrochemical devices for energy storage and water desalination are based on flow electrodes such as redox flow batteries, electrochemical flow capacitor (EFC) [Presser, V., et al. (2012), The Electrochemical Flow Capacitor: A New Concept for Rapid Energy Storage and Recovery. Adv. Energy Mater., 2: 895-902] or flow-electrode capacitive deionization (FCDI) cells. Generally, in those systems, the active material in the form of semi-solid electrode is pumped into an electrochemical cell for charge/discharge and pumped out to a reservoir for energy storage. Thus, the concepts proposed so far rely on a continuous flow of a slurry comprising the active material that leads to degradation of the devices (i.e. erosion by the flowing of suspended solid particles) and high energy consumption caused by pumping viscous and dense fluids.

WO2017/097228A1 discloses solid-flow electrochemical device comprising solid electrodes that allows direct replacement of the conventional electrode stack. For example, Figure 9 shows how a discharged anode belt in the anode storage region can be entirely replaced with a charged anode belt in package, and the discharged cathode belt in the cathode storage region can be entirely replaced with a charged cathode belt in package.

A primary battery is proposed by Jenson 2019 (Jenson et al. Journal of Energy Storage 23 (2019) 504-510) wherein the anode and cathode are hydrogel compositions of agar- agar comprising NaCI, acetylene black and hydrazine and lithium perchlorate. The electrodes may be extracted and filled using a syringe. However, in the battery described in Jenson et al, active materials for positive and negative electrodes are not electrically separated. Instead, the electroactive materials are held using a hydrogel in the electrodes, which limits the versatility of the proposed primary battery. For instance, the battery proposed in Jenson 2019 will not allow subsequent charge/discharge cycles (non-rechargeable) due to the electrical short-circuiting between the two compartments. Therefore, despite the above-mentioned systems, it is desirable to develop electrodes that reduce the operational cost when being part of a cell and that are able to be recycled while maintaining or improving their energy density, power density, energy efficiency, versatility and overall performance.

BRIEF DESCRIPTION OF THE INVENTION

The authors of the present invention have developed a cell comprising at least one recyclable electrode comprising compositions comprising electrode active materials, wherein the compositions are able to be extracted and replaced several times without compromising the performance of the electrode. When being recycled, the electrode of the cell of the invention allows changing the composition.

When being part of a cell, the electrode of the invention reduces the cell operational costs since the composition comprising an electrode active material, remains still during the cell work (i.e. contrary to the flow cells, in the cell of the present invention, the active material does not need to be pumped into an electrochemical cell for charge/discharge or being pumped out to a reservoir for energy storage). Then, the erosion of different parts of the cell by the flowing of suspended solid particles of the electrode and the overall cost of operation (i.e. caused by pumping viscous liquids) is significantly reduced. Moreover, the authors of the present invention have observed that the cell of the invention in addition to be a recyclable-electrode cell, has a high transport and exchange of the active species. In particular, the electrode separator of the cell in combination with the presence of a liquid electrolyte, allows the liquid electrolyte comprising active species to flow and contact the electrode active materials without dragging solid materials from the electrode composition.

An aspect of the invention is directed to a cell (1) comprising:

- a positive electrode and a negative electrode; wherein at least one electrode comprises: o an electrode compartment (6) with at least an aperture adapted to receive a refill container; and o a composition comprising an electrode active material; wherein said composition comprises between 5 and 75 wt% of solids dispersed in a liquid; and wherein the electrode compartment is suitable for confining said composition;

- a liquid electrolyte comprising active species; wherein the electrolyte comprises a first electrolyte composition and a second electrolyte composition; and

- a power/load source; wherein the electrode compartment (6) of the at least one electrode comprises a electrode separator (5); and wherein one side of the electrode separator (5) is in contact with the composition comprising an electrode active material and the opposite side is in contact with the liquid electrolyte.

Another aspect of the invention is directed to an energy storage and/or delivery system comprising at least one cell according to the invention.

Another aspect is directed to a method of storing electricity comprising the steps of: a) providing a cell (1) as defined in any of the particular embodiments of the invention; b) optionally, letting flow or pumping the electrolyte from the at least one reservoir container (8); wherein the electrolyte is first electrolyte composition and/or the second electrolyte composition; c) oxidizing the active species of the first electrolyte composition at the positive electrode to the corresponding oxidized state, while the active species of the second electrolyte composition are reduced to the corresponding reduced state at the negative electrode.

Another aspect is directed to a method of delivering electricity comprising the steps of: a) providing a cell (1) as defined in any of the particular embodiments the invention; b) optionally, letting flow or pumping the electrolyte from the at least one reservoir container (8); wherein the electrolyte is first electrolyte composition and/or the second electrolyte composition; c) reducing the active species of the first electrolyte composition at the positive electrode to their reduced state while the active species of the second electrolyte composition are oxidized to the corresponding oxidized state at the negative electrode.

Another aspect is directed to a method to modify the amount of ions in a liquid, comprising the steps of: a) providing a cell (1) as defined in any of the particular embodiments the invention; wherein the first electrolyte composition and the second electrolyte composition of the cell comprise ions; b) oxidizing the active species of the first electrolyte composition at the positive electrode to the corresponding oxidized state, while the active species of the second electrolyte composition are reduced to the corresponding reduced state at the negative electrode, and while simultaneously there is an ions exchange: between the first electrolyte composition and the positive electrode, between the second electrolyte composition and the negative electrode, and between the second electrolyte composition and the first electrolyte composition, leading to a change in the amount of ions of the first electrolyte composition and/or of the second electrolyte composition with respect to the amount of ions of the first electrolyte composition and of the second electrolyte composition of step (a).

Another aspect is directed to the use of the cell (1) as defined in any of the particular embodiments the invention, to store and/or deliver electricity.

Another aspect is directed to the use of the cell (1) of the invention, to modify the amount of ions in a liquid; preferably in an aqueous solution; more preferably for desalinization and/or recovery of ions of an aqueous solution.

Another aspect is directed to a method to recycle the cell as defined in the invention comprising the following steps: i. providing the cell of the invention; ii. extracting the composition comprising the electrode active material from the at least one electrode of the cell through the at least one aperture of the electrode compartment; and iii. filling the electrode compartment (6) with a composition comprising an electrode active material through the at least one aperture; wherein the composition of step (iii) comprises the same or different electrode active material that the composition of step (ii).

FIGURES

Figure 1. Scheme of an Ion Pumping Injectable Cell (IPIC) with injectable electrodes before and after being filled with injectable electrodes.

Figure 2. Scheme of Ion Pumping Injectable Cell (IPIC) with injectable electrodes.

Figure 3. Scheme of Ion Pumping Injectable Cell (IPIC) with injectable electrodes according to a particular embodiment of the present invention.

Figure 4. (a) Voltage and ionic conductivity profiles over time and (b) a cycling experiment with an Ion Pumping Injectable Cell (IPIC) with injectable electrodes.

Figure 5. Ciclability of an Ion Pumping Injectable Cell (IPIC) with injectable electrodes.

Figure 6. (A) Performance of the Ion Pumping Injectable Cell (IPIC) cell assembled in symmetric configuration with lithium ferrophosphate (LFP-FP) injectable electrodes cell after several injections and reinjections. Alternatively, fresh LFP electrodes (symmetric configuration; initial, R1 , R3 and R5) and carbon black (symmetric configuration R2 and R4) were injected and de-injected. (B) Comparison between hybrid (LFP- Carbon Black) and faradaic (LFP-FP) IPIC Cells and (C) comparison of the IPIC LFP-FP performance after each injection process.

Figure 7. (a) Charge and Discharge Profile of the Ion Pumping Injectable Cell (IPIC) with injectable electrodes (LFP-LMO) and asymmetric configuration and (b) Ciclability Test.

Figure 8. Performance of Membrane-free Ion Pumping Injectable Cell (IPIC) with asymmetric configuration and LFP-Prussian Blue (Nickel) electrodes, respectively. The graph describes the first charge and discharge experiment limiting the voltage discharge at 0 V (a) and (b) a second charge and discharge experiment limiting the voltage at 0.3V (B).

Figure 9. Results of viscosity measurements measured by Rheometer HAAKE RheoStress RS600 (Thermo Electron Corp); wherein the rheometer is set in a parallel plate geometry configuration ((rotorPP60 Ti) and at a Rotational speed CR-mode (shear rate 0,5-50 1/s, 20°C).

DETAILED DESCRIPTION OF THE INVENTION

As defined above, a first aspect of the invention is directed to a cell (1) comprising:

- a positive electrode and a negative electrode; wherein at least one electrode comprises: o an electrode compartment (6) with at least an aperture adapted to receive a refill container; and o a composition comprising an electrode active material; wherein said composition comprises between 5 and 75 wt% of solids dispersed in a liquid; and wherein the electrode compartment is suitable for confining said composition;

- a liquid electrolyte comprising active species; wherein the electrolyte comprises a first electrolyte composition and a second electrolyte composition; and

- a power/load source; wherein the electrode compartment (6) of the at least one electrode comprises a electrode separator (5); and wherein one side of the electrode separator (5) is in contact with the composition comprising an electrode active material and the opposite side is in contact with the liquid electrolyte.

Electrode

In a particular embodiment, the at least one electrode of the cell is recyclable. In the contexts of the present invention, the term “recyclable” regarding the electrode of the cellof the invention is directed to an electrode that can be extracted and refilled with a composition comprising an electrode active material without the electrode being damaged or without damaging the rest of the device wherein the electrode is placed. In a particular embodiment, the electrode of the cell of the invention is a refillable electrode. Particularly, the electrode of the cell of the invention may receive a composition comprising an electrode active material, and, once that composition has been used, it can be extracted and replaced by the same composition (i.e. a fresh one) or by a different one.

In a particular embodiment, the electrode compartment has a locking arrangement to securely keep the refill container in place; preferably the locking arrangement is a septum.

In a particular embodiment, the refill container is a syringe. In a more particular embodiment the refill container when locked in the locking arrangement, is in fluid communication with the compartment.

In an embodiment, the electrode compartment may be of any material compatible with the composition; in particular any material compatible with an aqueous composition such as a metallic material or polymer (e.g. steel, polyethylene, polypropylene, polyvinyl chloride).

The electrode compartment of the at least one electrode of the cell of the invention comprises an electrode separator (5); preferably the separator is a hydrophilic separator; more preferably a microporous hydrophilic separator; even more preferably a microporous separator of a thermoplastic polymer such as polypropylene.

In the content of the present invention, a “microporous separator” relates to a material comprising pores in the order of 50 nm to 10 micrometers. In a particular embodiment, the electrode separator is not selective to any species; in particular is not selective to ions; more particularly is not a membrane. In a more particular embodiment, the electrode separator “confines” the composition inside the electrode compartment. In an even more particular embodiment, the electrode separator electrically isolates the composition of the electrode.

The electrode separator separates the composition comprising an electrode active material and the liquid electrolyte since one side of the electrode separator is in contact with the composition comprising an electrode active material and the opposite side is in contact with the electrolyte.

In particular, the separator separates the composition comprising an electrode active which may be a slurry or a semisolid material from the electrolyte which is a liquid. In an embodiment, the separator forms part of the electrode compartment; preferably when the electrode compartment comprise sides; the separator is at least one side of said compartment (for example, the separator can be one or more walls defining the electrode compartment).

The authors have observed, that the use of an electrode separator improves the performance of the electrode and simplifies the electrode and thus, the cell, for example it removes the need to use any binder in the composition comprising an electrode material.

In a particular embodiment, the electrode compartment of the electrode of the cell of the invention comprises current collectors (3), preferably comprising a carbon electrically conductive material; more preferably graphite current collectors.

In a particular embodiment, the electrode compartment of the electrode of the invention comprises polymeric sheets (4); preferably gasket sheets (4). In an embodiment the gasket sheets of the electrode of the invention are between the electrode separator (5) and current collectors (3). In a particular embodiment, the electrode compartment of the electrode of the invention comprises electrode separators (5), current collectors (3) and gasket sheets (4); preferably one or more of the electrode separators (5), current collectors (3) and gasket sheets (4) act as a side or wall of the electrode compartment. In another embodiment, the electrode is suitable for confining the composition comprising an electrode active material inside the electrode compartment. In an embodiment, the compartment holds the composition. Particularly, the composition is motionless/still; particularly, the composition only enters and exits the compartment through the at least one aperture and only to be extracted or refilled. In an embodiment, once filled or extracted, the composition remains still inside the compartment. In another embodiment, the composition of the electrode does not circulate. In particular, the composition comprising an electrode active material is still inside the compartment while the electrode is working (for example as part of a cell). In the context of the present invention the term “hold” regarding the composition inside the electrode compartment , means that said composition is completely kept or confined inside the electrode compartment (i.e. does not circulate).

Composition

The composition comprising an electrode active material of the electrode of the cell of the invention comprises between 5 and 75 wt% of solids dispersed in a liquid; preferably particulate solids dispersed in a liquid (i.e. forming a slurry). In another embodiment, the composition is a slurry (i.e. is a viscous fluid). In another embodiment, the composition does not comprise a polymer; particularly a binder; more particularly a hydrogel. In another particular embodiment, the composition is not a hydrogel. In the context of the present invention, the term “hydrogel”, is understood as a three-dimensional network of polymeric chains saturated by an aqueous environment as known in the art (for example a agar-agar hydrogel). In the context of the present invention the composition of the electrode comprising an electrode active material may be referred to as just “composition”.

In an embodiment, the composition of the electrode of the cell of the invention comprises between 5 and 75 wt% of solids of the total weight of the composition; preferably comprises between 10 and 60 wt% of solids; more preferably comprises between 12 and 50 wt%; even more preferably comprises between 15 and 40 wt% of solids, wherein the solids are dispersed in a liquid; preferably in an aqueous solution. In an embodiment, the composition of the electrode of the invention consist of between 5 and 75 wt% of solids of the total weight of the composition, wherein the solids are dispersed in a liquid; preferably comprises between 10 and 60 wt% of solids; more preferably comprises between 12 and 50 wt%; even more preferably comprises between 15 and 40 wt% of solids, wherein the solids are dispersed in a liquid; preferably in an aqueous solution.

In a particular embodiment, the wt% of the solids in the total weight of the composition has been calculated at room temperature (between 15 and 35°C) and at atmospheric pressure (about 1 atm).

In an embodiment, the composition of the electrode of the cell of the invention is fluid at room temperature (between 15 and 35°C) and at atmospheric pressure (about 1 atm), particularly the composition is suitable to be pumped.

In an embodiment, the solids of the composition of the electrode of the cell of the invention comprise electrode active materials.

In another embodiment, the solids of the composition of the electrode of the cell of the invention consist of electrode active materials.

In another embodiment, the solids of the composition consist of: i) electrode active materials and ii) electrically conductive materials such as carbon black.

In a more particular embodiment, the liquid of the composition is an electrolyte solution; preferably is an aqueous solution; even more preferably is an aqueous solution comprising salts; preferably salts comprises lithium; more preferably LiCI. In an embodiment, the electrolyte comprises active species such as redox active species. In an embodiment the active species are ions. In a particular embodiment the electrolyte comprises ions; preferably ions comprising metallic cations such as lithium cations.

In a particular embodiment, the electrolyte of the electrode is an aqueous solution comprising ions; preferably selected from Li ⁺ , Na ⁺ , K ⁺ and/or Mg ²⁺ ; more preferably Li ⁺ , Na ⁺ and K ⁺ ; even more preferably Li ⁺ .

In a more particular embodiment the electrolyte comprises an element selected from Li, Fe, Ni, Mn and combinations thereof; preferably comprises lithium.

In an embodiment, the composition of the electrode of the cell of the invention has a viscosity of between 1 and 1000 cP for shear rates between 5 and 50 s ^-1 measured with a rheometer in a parallel plate geometry configuration at 20°C; preferably it has a viscosity of between 20 and 700 cP; more preferably has a viscosity of between 40 and 500 cP. In the present invention, the viscosity measurements have been performed with a Rheometer HAAKE RheoStress RS600 (Thermo Electron Corp) set in a parallel plate geometry configuration ((rotorPP60 Ti) and at a Rotational speed CR-mode (shear rate 0.5-50 1/s) at 20°C.

The composition of the electrode of the cell of the invention comprises an electrode active material. In an embodiment the electrode active material is solid; preferably is a solid in a dispersion, more preferably is a particulate solid material dispersed in a liquid (i.e. a slurry). In a more particular embodiment, the liquid is an electrolyte solution.

In an embodiment, the electrode active material of the electrode comprises an element selected from Li, Fe, Ni, Mn and combinations thereof; preferably selected from Li, Fe and combinations thereof. In an embodiment, the electrode active material of the electrode comprises Li.

In another embodiment, the electrode active material of the electrode is a lithium-ion intercalation material, preferably selected from lithium phosphate, lithium oxide, and combinations thereof; more preferably selected from lithium cobalt oxide (LiCoO 2), lithium iron phosphate (LiFePC ), lithium manganese oxide (LiM^C , Li2MnOs), lithium nickel manganese cobalt oxide (LiNiMnCoO2) and combinations thereof.

In an embodiment, the electrode active material of the composition of the electrode comprises groups selected from phosphate, oxide, cyanide and combinations thereof.

In an embodiment, the electrode active material comprises lithium phosphate, lithium oxide, prussian blue (PB) or combinations thereof; preferably comprises lithium cobalt oxide (UCOO2), lithium iron phosphate (LiFePC ), lithium manganese oxide (such as LiMn2C>4, Li2MnOs), lithium nickel manganese cobalt oxide (LiNiMnCoO2), Nickel Prussian blue (Nis(Fe(CN)6)2) and combinations thereof; more preferably lithium iron phosphate (LiFePC ), lithium manganese oxide (such as LiM^C , Li2MnOs), Nickel Prussian blue (Nis(Fe(CN)6)2) and combinations thereof; even more preferably lithium iron phosphate (LiFePC ).

In an embodiment, the electrode active material consist of lithium phosphate, lithium oxide, prussian blue (PB) or combinations thereof; preferably consist of lithium cobalt oxide (UCOO2), lithium iron phosphate (LiFePC ), lithium manganese oxide (such as LiMn2C>4, Li2MnOs), lithium nickel manganese cobalt oxide (LiNiMnCoO2), Nickel Prussian blue (Nis(Fe(CN)6)2) or combinations thereof; more preferably lithium iron phosphate (LiFePC ), lithium manganese oxide (such as LiM^C , I^Mn j), Nickel Prussian blue (Nis(Fe(CN)6)2) or combinations thereof; even more preferably lithium iron phosphate (LiFePC ).

In an embodiment, the electrode active material of the composition is in between 5 and 75 wt% of the total weight of the composition; preferably is in between 10 and 60 wt%; preferably is in between 12 and 50 wt%; even more preferably is in between 15 and 40 wt%.

In an embodiment, the electrode active material of the composition is dispersed in a liquid; preferably in a concentration of between 100 mg/ml and 1500 mg/ml; more preferably is in between 150 and 1000 mg/ml; even more preferably is in between 160 and 600 mg/ml.

In a particular embodiment, the composition of the electrode further comprises an electrically conductive additive; preferably an electrically conductive additive comprising carbon; more preferably carbon black; even more preferably carbon black in between 0.1 and 20 wt% of the total weight of the composition; even much more preferably in between 1 and 10 wt%.

In a particular embodiment, the electrically conductive additive is solid; preferably is a particulate solid dispersed in a liquid; more preferably in a concentration of between 1 mg/ml and 500 mg/ml; more preferably is in between 10 and 200 mg/ml; even more preferably is in between 20 and 100 mg/ml; even much more preferably is about 45 mg/ml.

In a particular embodiment, the composition of the electrode does not comprises a binder; in particular the composition does not comprises a polymeric binder such as agar- agar.

In a particular embodiment, the composition of the electrode consist of:

- a solid electrode active material; preferably lithium iron phosphate (LiFePC ), lithium manganese oxide (such as LiM^C , I^MnOs), Nickel Prussian blue (Nis(Fe(CN)6)2) or combinations thereof - optionally, a solid electrically conductive additive; preferably carbon black; and

- an electrolyte solution; preferably an electrolyte aqueous solution comprising ions; more preferably comprising lithium cations; preferably, wherein the solid electrode active material and optionally the solid electrically conductive material, are in between 5 and 75 wt% of the total weight of the composition; more preferably, wherein the solid electrode active material and optionally the solid electrically conductive material are dispersed in the electrolyte solution.

The main advantage the cell of the invention is that at least one electrode is recyclable because its composition is able to be extracted and replaced several times without damaging the electrode and/or the cell or device wherein the electrode is placed and without compromising the electrode performance. In addition, the authors of the present invention have observed that because of its rheological properties, the composition comprising an electrode active material of the electrode, is easier to manipulate (for example during extraction and refilling of the electrode) than other types of compositions such as those comprising binders, particularly polymeric binders. For example, compositions comprising binders, such as hydrogels need to be heated up for being pumped or manipulated, on the contrary, the composition of the electrode of the cell of the invention is fluid at room temperature.

In an embodiment, the cell of the invention comprises at least one reservoir container (8) comprising the liquid electrolyte.

In an embodiment, the two electrodes (positive and negative) of the cell are electrodes comprising: o an electrode compartment (6) with at least an aperture preferably adapted to receive a refill container; and o a composition comprising an electrode active material; wherein said composition comprises between 5 and 75 wt% of solids dispersed in a liquid; and wherein the electrode compartment is suitable for confining said composition, as defined in any of the particular embodiments described above; and wherein the electrode compartment (6) comprises a electrode separator (5); and wherein one side of the electrode separator (5) is in contact with the composition comprising an electrode active material and the opposite side is in contact with the liquid electrolyte. In another embodiment, the liquid electrolyte is between the two electrodes in the cell; particularly the liquid electrolyte is in contact with at least an electrode separator.

The cell of the invention might have a symmetric (wherein the positive and the negative electrodes of the cell have the same electrode active material) or an asymmetric (wherein the positive and the negative electrodes of the cell have different electrode active material) configuration.

In an embodiment, the liquid electrolyte of the cell comprises active species; particularly ions; more particularly cations and anions. The active species (such as ions) may be oxidized or reduced.

The liquid electrolyte of the cell comprises a first electrolyte composition and a second electrolyte composition. Preferably, the liquid in contact with the positive electrode is referred to as first electrolyte composition (that may be also named as liquid composition X) while the liquid in contact with the negative electrode is referred to as second electrolyte composition (or liquid composition Y). In a particular embodiment, the first electrolyte composition is a catholyte and the second electrolyte composition is an anolyte.

In an embodiment, the electrolyte may be any of the electrolytes defined above in any of the particular embodiments. In a particular embodiment, the electrolyte and the electrode composition comprise a chemical element in common; preferably comprise an element selected from Li, Na, K and Mg; more preferably lithium. In a more particular embodiment the electrolyte comprises lithium; preferably LiCI; more preferably LiCI in water. In a more particular embodiment the electrolyte consist of LiCI in water.

The liquid electrolyte of the cell comprises active species; in a particular embodiment the electrolyte comprises ions; preferably ions comprising metallic cations such as lithium cations. In a more particular embodiment, the liquid electrolyte comprises lithium ions; more preferably is an aqueous solution of a lithium salt; even more preferably of LiCI.

In a particular embodiment, the electrolyte is an aqueous solution comprising ions; preferably selected from Li ⁺ , Na ⁺ , K ⁺ and/or Mg ²⁺ ; more preferably Li ⁺ , Na ⁺ and K ⁺ ; even more preferably Li ⁺ . In a particular embodiment, the first electrolyte composition and/or the second electrolyte composition are aqueous solutions comprising ions; preferably selected from Li ⁺ , Na ⁺ , K ⁺ and/or Mg ²⁺ ; more preferably Li ⁺ , Na ⁺ and K ⁺ ; even more preferably Li ⁺ .

In a particular embodiment, the first electrolyte composition and the second electrolyte composition have the same or different compositions. In a more particular embodiment, the first electrolyte composition and the second electrolyte composition comprise the same active species but in different amounts; preferably in different concentration. In an embodiment, the first electrolyte composition and the second electrolyte composition of the cell of the present invention have the same composition (i.e. there is just one liquid electrolyte composition, preferably stored in one compartment). In an embodiment, the first electrolyte composition and the second electrolyte composition of the cell of the present invention comprise the same active species but in different concentration. In another embodiment, the first electrolyte composition and the second electrolyte composition of the cell of the present invention share at least one specie in common.

In an embodiment, the cell of the invention comprises a compartment suitable for holding or confining the liquid electrolyte; particularly, said compartment is separated from the electrode compartment by the at least one electrode separator (i.e. the electrode separator is suitable for separating the composition comprising an electrode active material of the electrode and the liquid electrolyte).

In an embodiment, the liquid electrolyte of the cell of the invention is in a compartment suitable for confining said liquid electrolyte; preferably at least one of the sides of said compartment is the electrode separator; more preferably two sides of said compartment are electrode separators.

In an embodiment the first electrolyte composition and the second electrolyte composition of the cell of the present invention are in the same or in different compartments of the cell of the present invention. In another embodiment, the first electrolyte composition and the second electrolyte composition are in the same compartment; wherein the compartment comprises a cell separator (7) such as a membrane, between the first electrolyte composition and the second electrolyte composition. Particularly, one side of the cell separator (7) is in contact with the first electrolyte composition and the opposite side is in contact with the second electrolyte composition.

In a particular embodiment, the cell of the invention comprises a membrane (7) between the first electrolyte composition and the second electrolyte composition; preferably wherein the membrane is an ion exchange membrane; more preferably an anion exchange membrane (AEM); much more preferably an anion exchange membrane (AEM) selective to Cl'.

In a particular embodiment the composition comprising an electrode active material of the electrode and the liquid electrolyte of the cell comprise one element in common; preferably they comprise lithium.

Electrolyte reservoir

In an embodiment, the cell of the invention of the present invention comprises at least one reservoir container (8) or tank configured to store, send and/or receive liquid electrolyte. In a particular embodiment, the reservoir container comprises at least an inlet and at least one outlet; preferably at least two inlets and at least two outlets. In an embodiment, the one reservoir container or tank is connected in fluid communication with the compartment holding the electrolyte through at least two conducts (for example, one for the first electrolyte composition and the other one for the second electrolyte composition). In another embodiment, the cell of the present invention comprises a first electrolyte composition reservoir container or tank configured to store, send and/or receive first electrolyte composition from the compartment and/or an second electrolyte composition reservoir container or tank configured to store, send and/or receive second electrolyte composition from the compartment. In an embodiment, the first electrolyte composition reservoir container and the second electrolyte composition reservoir container are connected in fluid communication with the compartment through at least one conduct.

In an embodiment, the electrolyte may circulate during operation of the cell. Therefore, in a particular embodiment, during operation of the battery, the first electrolyte composition reservoir container is able to send and to receive first electrolyte compositionto and from the compartment. In addition, during operation of the battery, the second electrolyte composition reservoir container is able to send and to receive liquid Y second electrolyte composition to and from the compartment. In a particular embodiment, the reservoir container is made of a plastic material (e.g., polypropylene, polyethylene, etc.) or a coated steel material (e.g., a plastic-coated or rubber-coated, steel tank) to substantially avoid corrosion, such as stainless steel, titanium, nickel or nickel alloys; preferably stainless steel, nickel or nickel alloys. Electrode separator

The at least one electrode of the cell of the invention comprises an electrode separator (5) between the electrode composition and the liquid electrolyte (first electrolyte composition and/or second electrolyte composition); preferably the cell separator (5) is a hydrophilic separator; more preferably a microporous hydrophilic separator; even more preferably a microporous separator of a thermoplastic polymer such as polypropylene. In a particular embodiment, the separator separates the composition of the electrode from the liquid electrolyte; particularly, the composition of the electrode is semisolid (such as a slurry) while the electrolyte is liquid (for example is a solution such as an aqueous solution comprising salts).

One side of the electrode separator is in contact with the composition of the electrode of the invention and the opposite side is in contact with the electrolyte (for example with either the first electrolyte composition or the first electrolyte composition). In an embodiment, the composition of the at least one electrode and the liquid electrolyte of the cell are electrically connected; particularly through the electrode separator. In an embodiment, the electrode separator is part of the electrode compartment and of the electrolyte compartment, being suitable for separating them.

In a particular embodiment the pores of the porous hydrophilic membrane comprise mean diameters of between 0.001 and 0.100 microns; preferably of between 0.020 and 0.080 microns; more preferably of between 0.040 and 0.070 microns. The mean diameter of the pores of the have been calculated experimentally by a significate number of measurements of a technique known in the art such as microscopy techniques.

In a particular embodiment, the cell of the invention comprises endplates; preferably polymeric endplates (2), more preferably acrylonitrile butadiene styrene (ABS) endplates (2). In an embodiment, the authors have observed that endplates provide mechanical stability to the cell. In a particular embodiment, the cell of the invention comprises polymeric sheets (4); preferably gasket sheets (4). In an embodiment the gasket sheets of the cell of the invention are between the electrode separator (5) and the cell separator (7).

Power/source load

The cell of the present invention may comprise a power/load source. The power/load source may be any external electrical device such as an electrical grid, an electric vehicle, a domestic appliance or a sensor, that draws/transfers energy from/to the battery. In general, the power/load source have controllable voltages and/or current supplies or uptakes.

The cell of the present invention may comprise an external case.

The main advantage of the cell of the invention is that is recyclable since at least one of its electrodes are able to be extracted and replaced several times without damaging the device and compromising the cell performance. In addition, the authors of the present invention have observed that since the electrode composition is not circulated through the cell (as in flow batteries), the cell does not suffer erosion and the operating cost is reduced. In addition, the cell can be used in several charging/recharging cycles until reaching the end of its working life then, the electrodes may be recycled extending the cell working life. Moreover, the authors have observed that when extracted and refilled, the electrode composition may be changed thus, changing the cell use and/or performance and allowing recycle its different parts. This allows reducing waste and materials cost of the cell.

In a particular embodiment, the cell of the invention comprises: a positive electrode and a negative electrode; wherein the at least one electrode comprises: o a electrode compartment (6) with at least an aperture adapted to receive a refill container; and o a composition comprising an electrode active material; wherein the composition comprises between 5 and 75 wt% of solids dispersed in a liquid; and wherein the electrode compartment is suitable for confining the composition

- a liquid electrolyte comprising active species; wherein the electrolyte comprises a first electrolyte composition and a second electrolyte composition;

- a cell separator (7) between the first electrolyte composition and the second electrolyte composition, preferably an anion exchange membrane; and

- a power/load source; wherein the electrode compartment of the electrode comprises a electrode separator (5); and wherein one side of the electrode separator (5) is in contact with the composition comprising an electrode active material and the opposite side is in contact with the liquid electrolyte; optionally, wherein the liquid electrolyte and the electrode active material comprise lithium.

Energy storage and/or delivery system

An aspect of the invention is directed to an energy storage and/or delivery system comprising at least one cell according to the invention. In particular, the cell may act as a redox battery; particularly as a secondary and/or rechargeable battery, i.e. the redox battery may be configured to be reversibly charged and discharged.

Methods of operation of the cell

As mentioned before, the cell of the present invention in any of its particular embodiments may be configured to act as an energy storage and delivery system, i.e. it may be configured to be reversibly charged and discharged. In the context of the present invention, the term “redox” refers to electrochemical reduction and oxidation reactions which allow energy storage in a battery during charge and deliver energy during discharge.

Method of storing electricity

Another aspect is directed to a method of storing electricity comprising the steps of: a) providing a cell (1) as defined in any of the particular embodiments of the invention; b) optionally, letting flow or pumping the liquid electrolyte from the at least one reservoir container (8); wherein the electrolyte is the first electrolyte composition and/or the second electrolyte composition; c) oxidizing the active species of the first electrolyte composition at the positive electrode to their corresponding oxidized state, while the active species of the second electrolyte composition are reduced to their corresponding reduced state at the negative electrode.

In an embodiment, during the method of storing electricity of the cell of the invention, the fluid composition of the electrode of the invention is still (does not circulate, is kept in the compartment of the electrode case). In an embodiment, only before or after any said method of the cell the fluid composition of the electrode can be extracted or inserted in the electrode case. In another embodiment, the liquid electrolyte circulates during any of the steps of the method; preferably only the liquid electrolyte is circulated during any of steps (a) to (c) of the method of the invention.

Method of delivering electricity

Another aspect is directed to a method of delivering electricity comprising the steps of: a) providing a cell (1) as defined in any of the particular embodiments of the invention; b) optionally, letting flow or pumping the liquid electrolyte from the at least one reservoir container (8); wherein the electrolyte is the first electrolyte composition and/or the second electrolyte composition; c) reducing the active species of the first electrolyte composition at the positive electrode to their reduced state while the active species of the second electrolyte composition are oxidized to their corresponding oxidized state at the negative electrode.

In an embodiment, during the method of delivering electricity of the cell of the invention, the fluid composition of the electrode of the invention is still (does not circulate, is kept in the compartment of the electrode case). In an embodiment, only before or after any said method of the cell the fluid composition of the electrode can be extracted or inserted in the electrode case. In another embodiment, the liquid electrolyte circulates during any of the steps of the method; preferably only the liquid electrolyte may be circulated during any of steps (a) to (c) of the method of the invention.

Method to modify the composition of a solution

Another aspect of the invention is directed to a method to modify the amount of ions in a liquid, comprising the steps of: a) providing a cell (1) according to the present invention in any of its particular embodiments; wherein the first electrolyte composition and of the second electrolyte composition of the cell comprise ions b) oxidizing the active species of the first electrolyte composition at the positive electrode to the corresponding oxidized state, while the redox active species of the second electrolyte composition are reduced to the corresponding reduced state at the negative electrode, and while simultaneously there is an ions exchange: between the first electrolyte composition and the positive electrode, between the second electrolyte composition and the negative electrode, and between the first electrolyte composition and the second electrolyte composition, leading to a change in the amount of ions of the first electrolyte composition and/or of in the second electrolyte composition with respect to the amount of ions of the first electrolyte composition and of the second electrolyte composition of step (a).

In an embodiment, during any of the methods of operation of the cell of the invention, the composition of the electrode of the invention is still (does not moves or circulate, is kept in the compartment of the electrode case). In an embodiment, only before or after any of the methods of operation of the cell the composition of the electrode can be extracted or inserted in the electrode case. In another embodiment, the liquid electrolyte circulates during any of the steps of the method, preferably only the liquid electrolyte may be circulated during any of steps (a) to (c) of the methods of the invention.

In an embodiment the first electrolyte composition and the second electrolyte composition of the cell the present invention are in the same of in different compartments. In another embodiment, the first electrolyte composition and the second electrolyte composition are in the same compartment; wherein the compartment comprise a cell separator (7) such as a membrane (7) between the first electrolyte composition and the second electrolyte composition. Particularly, one side of the membrane is in contact with the first electrolyte composition and the opposite side is in contact with the second electrolyte composition. In a more particular embodiment, the membrane is selective to active species of the electrolyte; preferably is selective to certain cations; more preferably is selective to anions. In an embodiment, the active species are the ions.

In a particular embodiment, the cell of the invention comprises a membrane (7) between the first electrolyte composition and the second electrolyte composition; preferably wherein the membrane is an ion exchange membrane; more preferably an anion exchange membrane (AEM).

In a particular embodiment, the amount of ions of the first electrolyte composition and/or the second electrolyte composition is reduced in between 1 and 99 % of the initial amount; preferably between 10 and 90 %. In a particular embodiment, the amount of ions of the first electrolyte composition and/or the second electrolyte composition is reduced in between 2 and 2000 ppm; preferably in between 5 and 1000 ppm. In a particular embodiment, during operation of the cell (for example while storing, delivering energy or modifying the amount of ions in a liquid) the composition comprising an electrode active material of the electrode is static, while the liquid electrolyte flows (for example it is pumped).

In a more particular embodiment, the cell is in fluid communication with one or more pumps; particularly liquid pumps.

Uses

Another aspect is directed to the use of the cell (1) of the invention, to store and/or deliver electricity. To this end, the cell of the present invention may be used individually, as modular redox battery system, or in combination with other energy storage technologies (e.g., supercapacitors, etc.) and may be integrated into or with various systems and/or devices to improve efficiency, address energy demands, etc. Furthermore, the cell of the invention in any of their embodiments, may be used in a variety of applications having different energy delivery and/or storage needs, including, but not limited to, very large scale applications (e.g., utilities, functioning as a green energy source for a smart grid, energy storage for use in combination with renewable energy resources such as wind and solar power, etc.) and smaller applications (e.g. backup power, residential power, electro-mobility sector, etc.).

Another aspect is directed to the use of the cell (1 ) of the invention to modify the amount of ions in a liquid; preferably in an aqueous solution; more preferably for desalination processes, and/or for the separation, purification and/or recovery of metals and/or for industrial water management processes; preferably for recovery of lithium.

Recycling methods

Another aspect is directed to a method to recycle or to modify the at least one electrode of the cell of the invention in any of its particular embodiments, comprising the following steps: i. providing the cell of the invention in any of its particular embodiments ; ii. extracting the composition comprising the electrode active material from the at least one electrode of the cell, through the at least one aperture of the electrode compartment; and iii. filling the electrode compartment (6) with a composition comprising an electrode active material through the at least one aperture; wherein the composition of step (iii) comprises the same or different electrode active material that the composition of step (ii).

In a particular embodiment, steps (ii) and (iii) are performed by a refill container comprising means suitable for extraction and pumping; preferably the refill container is a pump or a syringe; preferably a syringe. In another embodiment, the compartment and the refill container are in fluid communication. In a particular embodiment, step (ii) and/or (iii) are performed by using a refill container; in particular a syringe. In a more particular embodiment, the refill container and the electrode compartment are in fluid communication through the at least one aperture. In another embodiment, the compartment has a locking arrangement to securely keep the refill container in place, particularly during steps (ii) and/or (iii); preferably a septum.

In a particular embodiment, composition comprising an electrode active material of step (iii) comprises the same or different electrode active material that the composition of step (ii); preferably comprises a different material. In a more particular embodiment, the compositions of step (ii) and (iii) comprise between 5 and 75 wt% of solids dispersed in a liquid (i.a. form a slurry). The compositions of the electrode recycling method of the present invention may be any of those defined in any of the particular embodiments of the present invention.

In a particular embodiment, steps (ii) and (iii) of the method of the invention are repeated; preferably at least twice; preferably at least three times. In an embodiment, when the cell is a battery, particularly a redox-battery, the recycling method of the at least one electrode of the cell, may be performed after several charge/discharge cycles of the battery.

The present invention will be described in further detail with reference to the following examples. These examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

EXAMPLES

Different Ion Pumping Injectable Cells (IPIC) with injectable electrodes have been developed. The injectable electrodes of the invention are fluid enough to be injected into the cell or extracted out of the cell. However, during the operation of the IPIC, the injectable electrodes remain static, being the electrolyte solution the only one being pumped. EXAMPLE 1 : Ion Pumping Injectable Cell (I PIC) with injectable electrodes and symmetric configuration.

An Ion Pumping Injectable Cell (I PIC) was assembled in a symmetric configuration using LFP-LFP injectable electrodes. Semi-solid electrodes containing a mixture of the active material (1 .17 g of lithium ferrophosphate, LFP) and Ketjen Black (0.35 g of carbon black) as additive and electrolyte (6 mL) were prepared directly in a syringe by stirring with a high-shear homogenizer. The electrolyte comprises an agueous solution having a concentration of 0.2 M of LiCI.

Lithium ferrophosphate (LFP) is a lithium intercalation material selective for lithium. Lithium ions are intercalated-deintercalated in a LiFe"PO4/Fe ^lll PO4 system (namely LFP/FP) according to the following reactions:

LiFe"PO ₄ + CI’- Fe ^lll PO ₄ + LiCI

Then, viscosity measurements of the semisolid injectable electrodes were performed by Rheometer HAAKE RheoStress RS600 (Thermo Electron Corp). The rheometer was set in a parallel plate geometry configuration ((rotorPP60 Ti) and a Rotational speed CR- mode (shear rate 0.5-50 1/s, 20°C). Data (10 points) were recorded at 30 s intervals over 330 s at each preprogrammed shear rate. Results of the viscosity analysis of the LFP semisolid electrode prepared using 0.2 M LiCI are provided in Figure 9. The Ion Pumping Injectable Cell (I PIC) tested in the present experiment as a battery had four different chambers: a first chamber comprising an injectable positive electrode confined in a compartment by an expanded-graphite bipolar current collector, a gasket with a gap and a microporous separator, a compartment for the first solution to be deionized/concentrated, separated by an anion exchange membrane from the second solution compartment; and an injectable negative electrode confined in a similar way as the positive electrode by a current collector, gasket and microporous separator (see Fig. 1). Figure 2 shows a flow diagram of the deionization battery cell (1) comprising ABS endplate (2), graphite current collectors (3), Viton Gasket sheets (4), and Microporous Separator such as a porous polypropylene commercial hydrophilic membrane Celgard 3501 (thickness 25 ± 1 pm, porosity 55%, Celgard LLC 3501) (5), the semi-solid electrodes containing a mixture of the active material. Optionally, an Anion Exchange Membrane (AEM) may be used as cell separator (7), and as part of a refillable electrode compartment (6).

Performance test of the cell The first injectable electrode was injected and oxidized inside the cell in order to obtain a de-intercalated material (Fig. 2, reference A). This “activation” step might be skipped if asymmetric configuration is used, in which active materials are injected in its oxidized and reduced forms. Then, the second injectable electrode was injected in the cell (Fig. 2 reference B). With both electrodes injected, the electrolyte solution was pumped using a peristaltic pump from the solution tanks passing through the cell by an independent path and filling up the inner compartments of the cell (Fig. 2, path CF and path DE). Thus, the cell was working on a batch configuration in which the electrolyte solution is returning to the solution containers.

Charging-. In a first step, after the pre-oxidation (lithium de-intercalation process), the ion pumping process starts by applying a certain current density (mA cm ^-2 ) charging the cell up to a certain maximum voltage (Fig. 3). Simultaneously, the positive electrode (LFP) is oxidized releasing lithium ions while the preoxidized negative electrode, (FP) is reduced capturing the ion present in the electrolyte. As a response to the electrochemical unbalance, the chloride ions compensate the ion depletion by crossing the anion exchange membrane. This process leads to the production of two streams: one with a lower conductivity due to lithium sequestering and chloride migration, and another concentrated stream where the lithium chloride content was increased after the charging process.

Discharging: In a second step, the cell is discharged following the reverse processes: lithium intercalation occurs in the positive electrode and lithium de-intercalation takes place in the negative electrode leading to de lithiated and concentrated streams in the positive electrode and negative electrode, respectively. By proceeding in this way, the I PIC can be operated continuously for lithium capturing (or other ion, depending on the selective electrode chosen).

During the charging and discharging operation of the I PIC, the injectable electrodes remain static, being the electrolyte solution the only one being pumped. Figure 4 shows the (a) performance of the cell in terms of voltage and ionic conductivity profiles and (b) a cycling experiment probing the stability of the performance. In addition, results showed that the I PIC equipped with LFP electrodes demonstrates its robustness and a stable electrochemical performance (3mAh cm ^-2 , 99% Coulombic efficiency) for at least 50 cycles (Fig. 5). Thus, the performance of the I PIC cell was validated.

Performance of the cell after several injections

To study the regeneration/recycling capability of the ion pumping device, the performance of the I PIC cell after several deinjection/injections of the electrode slurries was tested.

The I PIC cell worked as usual (during several charging/discharging cycles) until reaching its end of working life and then, the electrodes were regenerated by deinjection of the slurries forming the “old” electrodes and by reinjecting new slurry electrodes.

In the present experiment, several subsequent regenerations (namely R1 , R2 R3, etc.), were performed to the I PIC cell equipped with LFP-LFP injectable electrodes described above, while its performance was tested (see Figure 6).

Figure 6 shows the results obtained after five regenerations (R1-R5) with electrodes with different composition. The particularities of each regeneration are described as follows:

R1) In regeneration R1 , both electrodes were replaced by new slurries with the same composition that the initial ones, comprising LFP and carbon black (Ketjen Black);

R2) In regeneration R2, one of the LFP electrodes was replaced by a 100 % carbon black (KetjenBlack) electrode (70 mgc/mL _e iectroiyte) conforming a hybrid system (behaving the LFP as a faradaic electrode and the carbon black as a capacitive one). This led to a capacity drop showing that the carbon does not participate in the lithium intercalation process (or store a much less amount of ions than LFP). As a consequence, the system is limited by the capacitive response of the carbon black electrode resulting in a reduction of the ion capturing capacity of an 80 %.

R3) In regeneration R3, the active materials of both electrodes were replaced, injecting fresh LFP and FP slurries. As a consequence, the ion storage capacity increased again to the values observed in cycles 1-20 (3-4 mAh cm ² ).

R4) In regeneration R4, one of the LFP electrodes was replaced by a carbon black electrode slurry, leading to a capacity drop showing that the carbon does not participate in the lithium intercalation process (or store a much less amount of ions than LFP). As a consequence, the system is affected again by the capacitive response of the carbon black resulting in a reduction of the ion storage capacity of 75 %. This result is similar to the one obtained in R2;

R5) Last regeneration injecting again fresh LFP electrodes in both sides.

The results shown in Fig. 6, indicated that despite the five regeneration/recycling processes of the device, the cell remains exhibiting excellent performance stability and providing similar values as in the first electrode injection. In particular, Figure 6 shows (a) the performance of the I PIC LFP-FP cell after several injections and reinjections with carbon black and LFP, (b) the comparison between Hybrid (LFP-Carbon Black) and Faradaic (LFP-FP) IPIC Cells and (c) a comparison of the IPIC LFP-FP performance after each injection process. The last reinjection also proves that the life of the IPIC system can be significantly extended by using the injectable electrode recycling strategy. This has a tremendous impact on the operational cost of the process since all the expensive components of the cell such as ion exchange membranes and current collectors can be reused several times being the injectable electrodes the only component that is replaced. After five consecutive regeneration/recycling of the device (injection/deinjection steps) keeping the performance, it can be considered that the easy recyclability of active materials and reuse of the cell device after end-of-life of the IPIC concept has been proven. Moreover, the injection of carbon black (capacitive electrode) instead of LFP (faradaic material) has demonstrated that the IPIC system might work using capacitive materials although having a much more limited ion removal capacity than when using faradaic materials such as LFP.

EXAMPLE 2: Ion Pumping Injectable Cell (IPIC) with injectable electrodes (LFP-LMO) and asymmetric configuration.

An Ion Pumping Injectable Cell (IPIC) cell was assembled using in asymmetric configuration with lithium ferrophosphate (LFP) and lithium manganese oxide (LMO) injectable electrodes, and subsequently tested. In this cell, the lithium ions were released from the LFP electrodes (3.4 V vs. Li/Li ⁺ ) in the charging step and intercalated in the LMO electrode (previously oxidized) that presents a higher electrode potential (3.9 V vs. Li/Li+). In the discharging process, the charge stored is being released. The cell voltage profile displayed in Fig. 7 confirms the behavior of the asymmetrical electrochemical ion pumping system and its stability while charging/discharging the cell for more than one hundred cycles. Therefore, the contribution of the asymmetric IPIC cell configuration involving two materials with distinct potentials (LFP-LMO) allow us to recover part of the energy stored in the electrodes reducing the energy consumption. This configuration might represent a low energy consumption alternative to the symmetric configuration (LFP-LFP) cell.

EXAMPLE 3: Membrane-free Ion Pumping Injectable Cell (IPIC) with asymmetric configuration and LFP-Prussian Blue (Nickel) electrodes

The membrane-free IPIC with LFP-PB electrodes and asymmetric configuration was tested using a mixture composed by 0.1 M NaCI and 0.1 M KCI in one single electrolyte solution tank. Initially, the lithium ferrophosphate (LFP) was oxidized and subsequently the Nickel Prussian Blue, Ni3(Fe(CN)e)2(PB) was injected. In the charging step, the FP intercalated sodium in its structure due to the lack of lithium in the electrolyte solution, and, in a minor proportion, some potassium as it is indicated by the presence of a second plateau shown in Fig. 8. Simultaneously, the PB released potassium (Fig. 8). In particular, Figure 8 shows the performance of an asymmetric membrane-free I PIC using PB and LFP as active materials in the positive and negative electrode, respectively, the graph describes the first charge and discharge experiment limiting the voltage discharge at 0 V (a). The second charge and discharge experiment limiting the voltage at 0.3V (b).

In the subsequent discharging step, the opposite process takes place (potassium removal and sodium release) while recovering the energy stored. Ion concentration values collected in Table 1 confirmed the sodium results.

Table 1. Ion concentration variation measured by ionic conductivity (IC) in example 3.

[Na ⁺ ] ppm [K ⁺ ] ppm

Initial 2339 3917

Charge 1 2247 3982

Discharge 1 2548 4063

Discharge 2 3124 2828

In a second experiment, the change in the potassium concentration was more clearly noted in the discharge by reducing the current density and extending the cut-off limit. As the ion concentration values revealed, the voltage cut-off modification led to the expected results aforementioned, the sodium concentration increased while potassium concentration drop due to the intercalation in the PB.

Thus, results demonstrate the versatility of the I PIC by fabricating an asymmetrical cell configuration without membrane that, along with the ability of separating specific ions and recovering energy, introduces a significant cost reduction by removing the ion exchange membrane.

Moreover, by using a different electrode material (Nickel Prussian Blue, Nis(Fe(CN)6)2) selective to potassium ions instead to lithium ions, it was introduced the possibility of using I PIC cells not only for lithium capturing but also for other applications.