Gas diffusion electrode for diaphragm electrolytic cell

Abstract

A gas diffusion electrode for a diaphragm electrolysis cell is provided. Diaphragm electrolyzers for treating salt-containing solutions are also provided. Methods for producing a base product are also provided. In particular, a gas diffusion electrode for processing lithium within a multi-chamber diaphragm electrolysis cell is provided.

Description

Cross-references to related applications

[0001] This application claims priority and benefit to U.S. Patent Application Serial No. 63 / 521,470, filed June 16, 2023, and U.S. Patent Application Serial No. 63 / 592,525, filed October 23, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure generally relates to gas diffusion electrodes (GDEs) for membrane electrolysis cells, to membrane electrolysis cells including GDEs for processing saline solutions, and to methods for producing alkaline products using such membrane electrolysis cells. In particular, this disclosure relates to GDEs within multi-chamber membrane electrolysis cells for processing saline solutions. Background Technology

[0003] The global boom in electric vehicle (EV) sales and the push for renewable energy have led to a surge in demand for high-quality battery-grade lithium (lithium hydroxide and lithium carbonate). It is projected that by 2035, the most prominent automotive segment will be all-electric vehicles.

[0004] Currently, there is a gap between the supply and demand of lithium; this means that the demand for lithium exceeds its availability. As the EV and renewable energy markets continue to grow, the gap between the demand and availability of high-quality battery-grade lithium (lithium hydroxide and lithium carbonate) will continue to widen.

[0005] Natural sources of lithium include igneous rocks, spring water, seawater, and brine from salt lakes, which are underground reservoirs containing high concentrations of dissolved salts such as lithium, potassium, and sodium. These are typically found beneath the surface of dried-up lakebeds, and are known as salt lakes.

[0006] Extracted from brine from salt lakes Traditional methods for recovering lithium from brine typically involve multiple pool evaporation and concentration steps. These steps remove high levels of sodium and potassium salts, such as NaCl and KCl, and possibly other salts, through precipitation, as these are less soluble than the desired lithium salts. Therefore, evaporation increases the lithium concentration in the brine. During this evaporation stage, some magnesium in the form of precipitated MgCl2 is also removed. The next stage involves removing boron, calcium, and magnesium from the brine as major impurities. B, Ca, and Mg ions are removed using repeated pH adjustments, solvent extraction, and precipitation steps to ensure maximum ion removal. Ion exchange removal of residual trace monovalent, divalent, and trivalent ions, in addition to lithium, further purifies the brine. Introducing soda ash (Na2CO3) to convert dissolved lithium salts into lithium carbonate (Li2CO3) is the final major step in the production of industrial-grade, high-purity lithium carbonate.

[0007] Extracted from ore mining Several minerals contain lithium in their structures. For example, at least four minerals are considered viable sources of Li. These are lepidolite (K(Li,Al,Rb)₂(Al,Si)₄O₂). 10 (F,OH)2), spodumene (LiAl(SiO3)2), petalite (LiAlSi4O) 10 Spodumene (Li,Na)AlIPO4(F,OH) is the most important ore in commercial Li production.

[0008] Traditional methods for recovering lithium from spodumene typically involve crushing the mined ore, roasting it, then cooling it, grinding it, and roasting it again with sulfuric acid in an acid leaching step. Further impurities can be removed using precipitation and / or ion exchange steps before adding soda ash to precipitate lithium carbonate as the final product.

[0009] The demand for new recycling methods and related equipment is increasing. Summary of the Invention

[0010] This disclosure provides a gas diffusion electrode for a diaphragm electrolyzer. A diaphragm electrolyzer including the gas diffusion electrode and its advantageous structural configuration are also provided. The gas diffusion electrode and diaphragm electrolyzer of this disclosure can be advantageously used to process salt solutions to produce one or more desired alkaline products.

[0011] In one embodiment, this disclosure relates to a gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer. The gas diffusion electrode is referred to herein as... GDE-1 .

[0012] In one embodiment, this disclosure relates to GDE-1 It also includes an anion exchange membrane disposed on the surface of the catalyst layer, which is configured to exchange ions from the catalyst layer to the opposite surface of the anion exchange membrane.

[0013] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an anode positioned inside the diaphragm electrolyzer and extending and positioned within the anode chamber; and including as described herein. GDE-1 The device comprises: a cathode extending inside the diaphragm electrolyzer and positioned within the cathode chamber; a cation exchange membrane between the anode chamber and the catalyst layer of the gas diffusion electrode, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane; an inlet through which a salt solution is received into the anode chamber; a gas inlet through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which the product of the salt solution is discharged from the interior of the diaphragm electrolyzer.

[0014] In one embodiment, this disclosure relates to a method for producing an alkaline product, the method comprising the steps of: receiving a saline solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and delivering the alkaline product from the diaphragm electrolyzer, wherein in carrying out the method: the saline solution is received in an anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter a cathode chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions combine with positive salt ions to produce an alkaline product; and the alkaline product is discharged from the cathode chamber.

[0015] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; a base build-up chamber between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-1The electrode comprises: a cathode; an anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the anion exchange membrane and enter the alkali generation chamber; a cation exchange membrane disposed between the anode chamber and the alkali generation chamber and configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an inlet through which a salt-containing solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0016] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in an anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the anion exchange membrane to the opposite surface of the anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0017] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber and a salt depletion chamber (salt depletion chamber, desalination chamber, salt consumption chamber) located between the cathode chamber and the anode chamber, the alkali generation chamber being located between the cathode chamber and the salt depletion chamber, and the salt depletion chamber being located between the alkali generation chamber and the anode chamber; an anode positioned extending inside the diaphragm electrolyzer and located in the anode chamber; and an anode positioned extending inside the diaphragm electrolyzer and located in the cathode chamber, comprising as described herein. GDE-1The electrode comprises: a cathode; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the first anion exchange membrane to enter the alkali generation chamber; a cation exchange membrane disposed between the salt depletion chamber and the alkali generation chamber and configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane to enter the alkali generation chamber; a second anion exchange membrane disposed between the salt depletion chamber and the anode chamber and configured to exchange ions received from the salt depletion chamber onto the opposite surface of the second anion exchange membrane to enter the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0018] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the first anion exchange membrane to the opposite surface of the first anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0019] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber, a salt-depleting chamber, and an acid-generating chamber disposed between the cathode chamber and the anode chamber, the alkali-generating chamber being disposed between the cathode chamber and the salt-depleting chamber, the salt-depleting chamber being disposed between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being disposed between the salt-depleting chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located within the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending and located within the cathode chamber, comprising as described herein. GDE-1The cathode; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the first anion exchange membrane and enter the alkali generation chamber; a first cation exchange membrane disposed between the salt depletion chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; and a second anion exchange membrane disposed between the salt depletion chamber and the acid generation chamber, the second anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; and a second anion exchange membrane disposed between the salt depletion chamber and the acid generation chamber, the second anion exchange membrane being configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the first anion exchange membrane and enter the alkali generation chamber. Ions received from the salt depletion chamber are exchanged onto the opposite surface of the second anion exchange membrane and enter the acid generation chamber; a second cation exchange membrane, located between the acid generation chamber and the anode chamber, is configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane and enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which O2-containing gas is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0020] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the first anion exchange membrane to the opposite surface of the first anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0021] In one embodiment, this disclosure relates to a gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst-coated membrane comprising a catalyst layer disposed on the membrane surface. This gas diffusion electrode is referred to herein as... GDE-2 .

[0022] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-2The cathode; a cation exchange membrane located between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane before entering the alkali generation chamber; an inlet through which a salt-containing solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0023] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in an anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate into the alkali generation chamber through the catalyst-coated membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0024] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber and a salt-depleting chamber located between the cathode chamber and the anode chamber, the alkali-generating chamber being located between the cathode chamber and the salt-depleting chamber, and the salt-depleting chamber being located between the alkali-generating chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising as described herein. GDE-2 The membrane electrolyzer includes: a cathode; a cation exchange membrane located between the salt depletion chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and the anode chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane and enter the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0025] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate into the base generation chamber through a catalyst-coated exchange membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0026] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber, a salt-depleting chamber, and an acid-generating chamber disposed between the cathode chamber and the anode chamber, the alkali-generating chamber being disposed between the cathode chamber and the salt-depleting chamber, the salt-depleting chamber being disposed between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being disposed between the salt-depleting chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located within the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending and located within the cathode chamber, comprising as described herein. GDE-2 The membrane electrolyzer comprises: a cathode; a first cation exchange membrane located between the salt depletion chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane to enter the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and the acid generation chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane to enter the acid generation chamber; a second cation exchange membrane located between the acid generation chamber and the anode chamber, the second cation exchange membrane being configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane to enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0027] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the first cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate into the alkali generation chamber through the catalyst-coated membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0028] In one embodiment, this disclosure relates to a gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer disposed on the gas diffusion layer, wherein the catalyst layer has an optimized thickness such that liquid reactants are substantially or completely consumed before diffusing through the catalyst layer to reach the gas diffusion layer. This gas diffusion electrode is referred to herein as... GDE-3 .

[0029] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber forming a single chamber together with the cathode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-3 The cathode; a cation exchange membrane located between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane before entering the alkali generation chamber; an inlet through which a salt-containing solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0030] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in an anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH -Ions migrate through the catalyst layer to the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the diaphragm electrolyzer.

[0031] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-forming chamber forming a single chamber together with the cathode chamber; a salt-depleting chamber located between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-3 The membrane electrolyzer includes: a cathode; a cation exchange membrane located between the salt depletion chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and the anode chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane and enter the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0032] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer to the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the diaphragm electrolyzer.

[0033] In one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber forming a single chamber together with the cathode chamber; a salt-depletion chamber and an acid-generating chamber located between the cathode chamber and the anode chamber, the salt-depletion chamber being located between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being located between the salt-depletion chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer extending and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer extending and located in the cathode chamber, comprising as described herein. GDE-3The membrane electrolyzer comprises: a cathode; a first cation exchange membrane located between the salt depletion chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane to enter the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and the acid generation chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane to enter the acid generation chamber; a second cation exchange membrane located between the acid generation chamber and the anode chamber, the second cation exchange membrane being configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane to enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0034] In one embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the first cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer to the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the diaphragm electrolyzer.

[0035] In one embodiment, this disclosure relates to a gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a first gas diffusion layer for diffusing oxygen-containing gas; a catalyst layer disposed on a surface of the first gas diffusion layer; a second gas diffusion layer in contact with the surface of the catalyst layer opposite to the first gas diffusion layer; and an ionomer layer disposed on a surface of an anion exchange membrane, the ionomer layer being in contact with the surface of the second gas diffusion layer opposite to the catalyst layer. This gas diffusion electrode is referred to herein as... GDE-4 In one implementation, GDE-4 It also includes a microporous layer disposed on the surface of the second gas diffusion layer, wherein the microporous layer is in contact with the surface of the catalyst layer opposite to the first gas diffusion layer.

[0036] In one embodiment, this disclosure relates to a gas diffusion layer (GDE) for a membrane electrolyzer, the GDE comprising a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer disposed on the surface of the diffusion layer. In some embodiments, the catalyst layer comprises a catalyst and an ionomer in an ionomer:catalyst ratio of 1:1 to 1:20.

[0037] In one embodiment, this disclosure relates to a gas diffusion layer (GDE) for a diaphragm electrolyzer, the GDE comprising: a diffusion layer for diffusing oxygen-containing gas, a microporous layer disposed on the surface of the gas diffusion layer, and a catalyst layer disposed on the surface of the microporous layer. In some embodiments, the catalyst layer comprises a catalyst and an ionomer in an ionomer:catalyst ratio of 1:1 to 1:20.

[0038] In one embodiment, this disclosure relates to a diaphragm electrolyzer for producing alkali, the diaphragm electrolyzer including a gas diffusion electrode (GDE) configured as an oxygen depolarization cathode to catalyze the following reaction: O2 + 2H2O + 4e - →4OH - In some embodiments, the GDE includes a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer disposed on the surface of the diffusion layer, wherein the catalyst layer comprises a catalyst and an ionomer in a 1:1 to 1:20 ratio of ionomer to catalyst.

[0039] In one embodiment, this disclosure relates to a diaphragm electrolyzer for producing alkali, the diaphragm electrolyzer including a gas diffusion electrode (GDE) configured as an oxygen depolarization cathode to catalyze the following reaction: O2 + 2H2O + 4e - →4OH - In some embodiments, the GDE includes a gas diffusion layer for diffusing oxygen-containing gas, a microporous layer disposed on the surface of the diffusion layer, and a catalyst layer disposed on the surface of the microporous layer, wherein the catalyst layer contains catalyst and ionomer in a ionomer to catalyst ratio of 1:1 to 1:20.

[0040] In one embodiment, this disclosure relates to a membrane-coated GDE for use in a diaphragm electrolyzer or any other diaphragm electrolyzer as disclosed herein, the membrane-coated GDE comprising: a GDE including a GDL for diffusing oxygen-containing gas and a catalyst layer; and an AEM coated on the GDE.

[0041] In one embodiment, this disclosure relates to a method for preparing a diaphragm-coated gas diffusion electrode, the method comprising: mixing an ionomer in a solvent to prepare a coating mixture; applying the coating mixture to a gas diffusion electrode and curing it to form a diaphragm-coated gas diffusion electrode.

[0042] Other aspects and implementations of this disclosure will be apparent from the detailed description provided herein. Attached Figure Description

[0043] Other advantages, arrangements, and combinations of this disclosure will become apparent from the above and following detailed description of various particular embodiments, taken in conjunction with the accompanying drawings, wherein each drawing is intended to be non-limiting, wherein: Figure 1 The diagram shows the structure of eight exemplary gas diffusion electrodes (GDE-1) according to this disclosure. The gas diffusion electrode includes at least a catalyst layer (CL) and a gas diffusion layer (GDL) (Plate (a)). In some exemplary embodiments of GDE-1, it also includes: a microporous layer (MPL); a mesh; an anion exchange membrane (AEM); or a combination thereof (Plate (b), (c), (d), (e), (f), (g) and (h)).

[0044] Figure 2 The diagram shows the structure of four exemplary gas diffusion electrodes (GDE-2) according to this disclosure. The gas diffusion electrode includes at least a gas diffusion layer and a catalyst-coated membrane (CCM) (Figure (a)). In some exemplary embodiments of GDE-2, it also includes: a microporous layer (MPL); a mesh; or a combination thereof (Figures (b), (c) and (d)).

[0045] Figure 3 The diagram shows the structure of two 3-D exemplary gas diffusion electrodes (GDE-3) according to the present disclosure. The gas diffusion electrode includes at least a gas diffusion layer (GDL) and a catalyst layer (CL). The thickness (τ) of the catalyst layer (CL) is configured to consume liquid reactants diffused into the GDL (Figure (a)). In another exemplary embodiment, a mesh is also included (Figure (b)).

[0046] Figure 4 The diagram shows the structure of four exemplary gas diffusion electrodes (GDE-4) according to this disclosure. The gas diffusion electrode includes at least a first gas diffusion layer (1st GDL) and a catalyst layer (CL), an ionomer layer (IL) and an anion exchange membrane (AEM) and a second gas diffusion layer (2nd GDL) therebetween (Plate (a)). In some exemplary embodiments of GDE-4, it also includes: a microporous layer (MPL); a mesh; or a combination thereof (Plate (b), (c) and (d)).

[0047] Figure 5 This is a schematic diagram of an exemplary 5-chamber diaphragm electrolyzer according to the present disclosure, showing the feed flow and product flow.

[0048] Figure 6 This is a schematic diagram of an exemplary four-chamber diaphragm electrolyzer according to the present disclosure, showing the feed flow and product flow.

[0049] Figure 7 This is a schematic diagram of an exemplary three-chamber diaphragm electrolyzer according to the present disclosure, showing the feed flow and product flow.

[0050] Figure 8 This is a schematic diagram of an exemplary two-chamber diaphragm electrolyzer according to the present disclosure, showing the feed flow and product flow.

[0051] Figure 9 This is a process flow diagram illustrating the use of a diaphragm electrolyzer in an integrated method for recovering Li from brine.

[0052] Figure 10 This is a process flow diagram illustrating the use of a diaphragm electrolyzer in an integrated method for extracting Li from mineral rocks.

[0053] Figure 11 This is a process flow diagram illustrating the implementation of in-situ generation of LiOH, Li2CO3, and HCl from LiCl brine, which is integrated into the method for recovering Li from brine in salt lakes via the LiCl→LiOH+HCl conversion.

[0054] Figure 12 This is a process flow diagram illustrating an implementation method for in-situ generation of LiOH, Li2CO3, and HCl from LiCl brine. The process is integrated into a method for recovering Li from brine in a salt lake via the LiCl→LiOH+HCl conversion.

[0055] Figure 13 This is a process flow diagram illustrating an embodiment of in-situ generation of crystalline LiOH from a mixed LiCl and NaCl brine. It is integrated into a method for recovering Li from brine in a salt lake through the conversion of LiCl → LiOH + HCl and the conversion of NaCl → NaOH + HCl in the same tank.

[0056] Figure 14 This is a process flow diagram of an implementation method for generating LiOH and H2SO4 in situ from Li2SO4, which is integrated into the lithium recovery method in hard rock mining operations through the conversion of Li2SO4→LiOH+H2SO4. Figure 15 This is a process flow diagram of an embodiment of producing LiOH from Li2CO3, wherein HCl is generated in a closed-loop method and recycled to dissolve Li2CO3.

[0057] Figure 16 This is a process flow diagram of an implementation method for LiOH production, which is integrated into a method for recovering Li from lithium brine. This method uses ion exchange resin to selectively adsorb Li, and the conversion LiCl→LiOH+HCl allows HCl to be used to regenerate the ion exchange resin.

[0058] Figure 17 This is a process flow diagram of another embodiment of LiOH production, which is integrated into a method for recovering Li from lithium brine. This method uses ion exchange resin to selectively adsorb Li, and the conversion LiCl→LiOH+HCl allows HCl to be used to regenerate the ion exchange resin.

[0059] Figure 18 This is a process flow diagram of an embodiment of alkali (e.g., LiOH) production, which is integrated into a method for recovering Li from a Li source by selectively extracting Li using solvent extraction (SX) and electrolyzing a lithium-containing salt solution. Detailed Implementation

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Although any methods and materials similar to or equivalent to those described herein may be used in the practice or testing of this disclosure, suitable methods and materials are described below.

[0061] This disclosure relates to a gas diffusion electrode (GDE) for a diaphragm electrolyzer, to a diaphragm electrolyzer including a GDE for processing salt solutions, and to a method for producing alkaline products using the diaphragm electrolyzer.

[0062] In one embodiment, the salt solution comprises LiCl, Li2SO4, Li3PO4, LiNO3, LiI, NaCl, Na2SO4, Na3PO4, NaNO3, NaI, KCl, K2SO4, K3PO4, KNO3, or KI, or combinations thereof.

[0063] In one embodiment, the alkali product comprises LiOH, NaOH, or KOH, or a combination thereof.

[0064] This disclosure provides several advantages over certain prior art. One advantage is the provision of unique GDEs and their use in multi-chamber diaphragm electrolyzers, which can use humid, undried ambient air as an oxygen source. According to some embodiments, the disclosed GDEs are used only in or within the cathode chamber of a diaphragm electrolyzer as disclosed herein.

[0065] According to other aspects, this disclosure advantageously makes it possible to improve the extraction of Li from multiple sources, including brine sources or lithium ore sources where hydrochloric acid, sodium hydroxide, and / or sulfuric acid may be required; eliminate the need for purchased acid and alkali feed materials by utilizing on-site brine derived from salt lake brine or brine solutions generated during lithium ore refining or lithium-ion battery recycling; directly convert lithium-containing salts, such as lithium chloride or lithium sulfate, into higher-value lithium hydroxide or lithium carbonate products; provide diaphragm electrolyzers for improving the treatment of brine solutions; and / or provide methods for producing lithium hydroxide or lithium carbonate using diaphragm electrolyzers.

[0066] As used herein, the terms “oxygen depolarization cathode,” “ODC,” “gas diffusion cathode,” or “GDC” are used interchangeably and / or refer to the same structure, for example, used as a cathode in a diaphragm electrolyzer. In embodiments of this disclosure, such a cathode structure may include the GDE of this disclosure.

[0067] As used herein, the terms “membrane electrode assembly” or “MEA” are used interchangeably and refer to an ion exchange membrane disposed on a gas diffusion electrode (GDE).

[0068] As used herein, the term “set upon” means any manner in which one substrate or material is permanently or continuously placed on or in contact with another substrate or material. For example, “set upon” can be used to mean one substrate or material fixed to another substrate or material, sprayed onto another substrate or material, coated onto another substrate or material, hot-pressed onto another substrate or material, Teflon-treated onto another substrate or material, laminated onto another substrate or material, placed adjacent to and in contact with another substrate or material, or any other manner in which the first substrate or material may be placed on or in contact with the second substrate or material.

[0069] As used herein, the term "porosity" refers to the percentage of void space in a material. In one embodiment, it is expressed as the ratio of the volume of voids or pores in the material to the total volume. For example, if half the volume of a material is voids or pores, then the porosity of the material is 50%.

[0070] Gas diffusion electrode (GDE) In one embodiment, this disclosure relates to a gas diffusion electrode (GDE) for a diaphragm electrolyzer.

[0071] The gas diffusion electrode comprises a porous catalyst layer disposed on a support material. The catalyst layer, which conducts electrons, catalyzes the electrochemical reaction between the liquid and the gas. Therefore, the electrochemical reaction occurs at the so-called three-phase boundary, where the gas, liquid, and solid (i.e., the catalyst) come into contact.

[0072] In one embodiment, the gas may contain oxygen and the liquid may contain water, resulting in the following cathode reaction: O2 + 2H2O + 4e - → 4OH - In this context, GDE allows diaphragm electrolyzers to operate using air as the oxygen source at the cathode. This can offer significant economic and safety advantages in terms of the ability to integrate these electrolyzers into processes for producing alkalis (e.g., alkali metal compounds such as alkali metal hydroxides).

[0073] In other embodiments, the gas may comprise a mixture of oxygen and carbon dioxide, resulting in the following cathode reaction: O2 + 2H2O + 4e - → 4OH - OH - + CO2→ HCO3 - HCO3 - + OH - → CO3 2- + H2O In this embodiment, alkali metal carbonates and alkali metal bicarbonates can be produced by electrochemical methods.

[0074] The following is based on the reference " GDE-1 " GDE-2 "and" GDE-3 Various implementations of the GDE according to this disclosure are described. Figure 1 ( GDE-1 ), Figure 2 ( GDE-2 ), Figure 3 ( GDE-3 )and Figure 4 ( GDE-4 The non-limiting constructions of these GDE implementations are shown in ().

[0075] As will be understood by those skilled in the art in consideration of this disclosure, GDEs can be prepared by any of a variety of methods known in the art for applying a catalyst layer to a substrate (e.g., a GDL or a film). The form in which the catalyst layer is prepared will influence the choice of method. For example, solid / powder (e.g., dry powder spraying, decal application), suspension (e.g., doctor blade, screen printing, inkjet printing, blade coating), aerosol (e.g., ultrasonic spraying, radiation spraying, hand-brush air spraying), vapor / plasma (e.g., magnetron sputtering, decal sputtering, helical RF sputtering, chemical vapor deposition), and electrode-assisted deposition (e.g., electrode spraying, electrodeposition, or electrophoretic deposition). In one embodiment, the catalyst layer is a suspension and can be applied by (e.g., but not limited to) a doctor blade, screen printing, inkjet printing, or blade coating.

[0076] GDE-1 In one aspect of this disclosure, a gas diffusion electrode (GDE-1) is provided, comprising a gas diffusion layer (GDL) and a catalyst layer (CL). In one embodiment, the CL is disposed on the surface of the GDL. See, for example, Figure 1 (a).

[0077] In another embodiment, the GDL of GDE-1 can be modified by treating and / or applying a microporous layer (MPL) with a hydrophobic polymer. In one embodiment, GDE further includes an MPL disposed on the surface of the GDL, wherein a CL is disposed on the surface of the microporous layer opposite the GDL. See, for example, Figure 1 (b).

[0078] In yet another embodiment, GDE-1 may include components opposite to CL (see, for example, Figure 1 (c) or the opposite of MPL (see, for example, Figure 1 (d) The mesh is in surface contact with the GDL. In one embodiment, the mesh is bonded to the GDL by Teflon annealing, hot pressing, or lamination.

[0079] In another embodiment, GDE-1 includes an anion exchange membrane (AEM), which helps prevent GDE overflow caused by liquid reactants in the electrochemical electrolyzer. In one embodiment, the AEM may be disposed on the surface of the CL, and the AEM is configured to exchange ions from the catalyst layer to the opposite surface of the AEM. See, for example, Figure 1(e)-1(h). AEM can be kept in direct contact with CL mechanically, or, for example, bonded to CL by Teflonization, hot pressing, ionomerization, or lamination. Alternatively, AEM can be coated onto the GDE. For example, anion-exchange ionomers can be mixed in a solvent to prepare a coating mixture, which can be applied to the GDE and subsequently cured (e.g., by heat) to form an AEM-coated GDE.

[0080] Therefore, in another embodiment of the invention, a membrane-coated GDE for use in this or other membrane electrolyzers is provided, the membrane-coated GDE comprising: a GDE including a GDL for diffusing oxygen-containing gas and a catalyst layer; and an ion exchange membrane coated on the GDE.

[0081] In another embodiment of the present invention, a method for preparing the membrane-coated GDE of the present invention is provided, the method comprising: mixing an ionomer in a solvent to prepare a coating mixture; applying the coating mixture to the GDE and curing it to form a membrane-coated GDE. The ionomer may be or include any suitable anion exchange ionomer, such as any one of the anion exchange ionomers disclosed herein, or any mixture thereof. In one embodiment, the ionomer includes Fumion. TM Ionomer, Ionomr TM Ionic polymers, Sustainion® ionomers, Orion ionomers, Pention TM Isopolymers or PiperION ionomers.

[0082] The ionomer can be mixed with the solvent in any suitable manner, including but not limited to stirring, blending, tumbling, spraying, etc. The solvent can be appropriately selected based on the ionomer used. In one embodiment, the solvent is a water-based or oil-based solvent. In one embodiment, the solvent is ethanol. In one embodiment, the solvent is ethanol, methanol, propanol, isopropanol, butanol, ethylene glycol, glycerol, isobutanol, or any other suitable alcohol.

[0083] The amount of ionomer mixed with the solvent can depend on the type of ionomer used and one or both of the solvents used. In one embodiment, the ionomer is mixed in the solvent at a concentration of about 0.5 wt% to about 25 wt%, more particularly about 1 wt% to about 20 wt%, and even more particularly about 2 wt% to about 15 wt%. In one embodiment, the ionomer is mixed in the solvent at a concentration of about 1 wt% to about 5 wt%. In one embodiment, the ionomer is mixed in the solvent at a concentration of about 5 wt% to about 10 wt%. In one embodiment, the ionomer is mixed in the solvent at a concentration of about 10 wt% to about 15 wt%. In one embodiment, the ionomer is mixed in the solvent at the following concentrations: about 1 wt%, about 2 wt%, about 3 wt%, about 4 wt%, about 5 wt%, about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, about 10 wt%, about 11 wt%, about 12 wt%, about 13 wt%, about 14 wt%, about 15 wt%, about 16 wt%, about 17 wt%, about 18 wt%, about 19 wt%, about 20 wt%, about 21 wt%, about 22 wt%, about 23 wt%, about 24 wt%, or about 25 wt%.

[0084] In one embodiment, the amount of coating mixture applied to the GDE is sufficient to provide a coating thickness of about 10 μm to about 250 μm, more particularly about 10 μm to about 100 μm, and even more particularly, about 20 μm to 100 μm. In one embodiment, the thickness of the coating mixture is about 10 μm to about 75 μm. In one embodiment, the thickness of the coating mixture is about 10 μm to about 50 μm. In one embodiment, the thickness of the coating mixture is about 25 μm to about 50 μm. In one embodiment, the thickness of the coating mixture is about 10 μm, about 15 μm, about 20 μm, about 25 μm, about 30 μm, about 35 μm, about 40 μm, about 45 μm, about 50 μm, about 55 μm, about 60 μm, about 65 μm, about 70 μm, about 75 μm, about 80 μm, about 85 μm, about 90 μm, about 95 μm, or about 100 μm. This can be the thickness at the time of application or the thickness after curing. As will be understood, if a specific thickness is required after curing, a slightly thicker coating mixture may need to be applied.

[0085] The curing step can be performed by any suitable means, including but not limited to heating, ultraviolet (UV) radiation, infrared radiation, etc. In one embodiment, curing is performed by heating. Not limited to, heating can be performed in an oven or some other fully or partially enclosed device, by contact between a dryer, blower, or other device and a heated surface, or by any other suitable form of heat application. In one embodiment, curing by heating is performed at temperatures ranging from about 25°C to about 200°C, more particularly from about 40°C to about 150°C, and even more particularly from about 50°C to about 140°C. In one embodiment, curing by heating is carried out at the following temperatures: about 50°C, about 550°C, about 60°C, about 65°C, about 70°C, about 75°C, about 80°C, about 85°C, about 90°C, about 95°C, about 100°C, about 105°C, about 110°C, about 115°C, about 120°C, about 125°C, about 130°C, about 135°C, about 140°C, about 145°C, or about 150°C.

[0086] GDE-2 In another aspect of this disclosure, a gas diffusion electrode (GDE-2) is provided, comprising a gas diffusion layer (GDL) and a catalyst-coated membrane (CCM). In one embodiment, a CL is disposed on the surface of the membrane to form the CCM. See, for example, see... Figure 2 (a).

[0087] In one embodiment, CCM refers to an anion exchange membrane with a surface coated with CL. CCM allows for better ion transport through the contact interface between the CL and the membrane. In one embodiment, GDL is in contact with the CL of the CCM.

[0088] In another embodiment, the GDL of GDE-2 can be modified by treating and / or applying a microporous layer (MPL) with a hydrophobic polymer. In one embodiment, the GDE further includes an MPL disposed on the surface of the GDL, wherein the MPL is in contact with the CL of the CCM. See, for example, Figure 2 (b).

[0089] In yet another embodiment, GDE-2 may include components opposite to CL (see, for example, Figure 2 (c) or the opposite of MPL (see, for example, Figure 2 (d) The mesh is in surface contact with the GDL. In one embodiment, the mesh is bonded to the GDL by Teflon annealing, hot pressing, or lamination.

[0090] GDE-3 In another aspect of this disclosure, a gas diffusion electrode (GDE-3) is provided, comprising a gas diffusion layer (GDL) and a catalyst layer (CL) disposed on the GDL, wherein the catalyst layer has an optimized thickness (τ) such that liquid reactants are substantially or completely consumed before diffusing through the CL to reach the GDL. See, for example, see Figure 3 (a).

[0091] As the liquid reactants diffuse through the CL of GDE-3, they are consumed due to electrochemical reactions. Therefore, a concentration gradient of reactants is formed along the depth of the CL. In one embodiment, the final concentration of the liquid reactants at the interface between the CL and GDL can be zero or near zero. "Near zero" means that the moisture content at the interface between the CL and GDL is insufficient to adversely affect the electrochemical reaction of GDE. In one embodiment, the moisture content on the CL surface at the interface between the CL and GDL is less than 5%, 4%, 3%, 2%, or 1% of the amount of liquid reactants. By controlling the thickness of the CL and optionally its hydrophobicity and / or porosity, the concentration gradient can be controlled to ensure more complete utilization of the reactants. Sufficient reaction of the liquid reactants in the CL eliminates the need for an ion-exchange membrane with GDE-3 in the electrochemical electrolyzer.

[0092] In one implementation, GDE-3 may include a mesh in surface contact with GDL opposite to CL (see, for example, Figure 3 (b)). In one embodiment, the web is bonded to the GDL by Teflon annealing, hot pressing, or lamination.

[0093] GDE-4 In one aspect of this disclosure, a gas diffusion electrode (GDE-4) is provided, comprising a first gas diffusion layer (1st GDL), a catalyst layer (CL), a second gas diffusion layer (2nd GDL), an ionomer layer (IL), and an anion exchange membrane (AEM). In one embodiment, CL is disposed on the surface of the 1st GDL. In another embodiment, the surface of the 2nd GDL is in contact with CL. In still other embodiments, IL is bonded to the AEM. In yet another embodiment, IL is in contact with the surface of the 2nd GDL opposite to CL. See, for example, Figure 4 (a).

[0094] In another embodiment, the second GDL of GDE-4 can be modified by treating and / or applying a microporous layer (MPL) with a hydrophobic polymer. In one embodiment, the GDE further includes an MPL disposed on the surface of the second GDL. In this embodiment, the MPL is in contact with the CL. See, for example, Figure 4 (b).

[0095] In another embodiment, GDE-4 may include a mesh in surface contact with the first GDL opposite to CL (see, for example, Figure 4 (c) or Figure 4 (d)).

[0096] As described, GDE-4 Including the first GDL and the second GDL. In one implementation, GDE-4 The first GDL and the second GDL are the same. In another implementation, GDE-4 The first GDL and the second GDL are different from each other. For example, the first GDL and the second GDL may have the same or different pore structures, the same or different porosities, the same or different thicknesses, be made of the same or different materials (e.g., any of (1a)-(5f) described herein), be treated with a hydrophobic polymer and / or have microporous layer modification applied or not be treated with a hydrophobic polymer and / or have microporous layer modification applied, or any combination thereof may be chosen independently for each of the first GDL and the second GDL.

[0097] Any surface of the GDE described herein, or any surface of the AEM disposed on the GDE described herein, may have raised and / or recessed embossed patterns to effectively increase the active surface area. Patterns may be applied by any known method, including engraving, molding, and stamping. The pattern may be any suitable pattern that increases the surface area of ​​the substrate or material.

[0098] The implementation of various features of the above-mentioned GDE, such as GDL, MPL and CL, will now be described in further detail.

[0099] Gas diffusion layer (GDL) GDLs are porous structures that can function as gas diffusers and / or current collectors. In one embodiment, a GDL may have relatively uniform pore sizes throughout its thickness. In another embodiment, a GDL may have random pore sizes throughout its thickness. In yet another embodiment, a GDL may have gradient pore sizes throughout its thickness. For example, a GDL may have a gradient from large to small pore sizes throughout its thickness in the airflow direction. Alternatively, a GDL may have a gradient from small to large pore sizes throughout its thickness in the airflow direction.

[0100] GDL can have sizes ranging from 50μm to 1000μm, 50μm to 950μm, 50μm to 900μm, 50μm to 850μm, 50μm to 800μm, 50μm to 750μm, 50μm to 700μm, 50μm to 650μm, 50μm to 600μm, 50μm to 550μm, 50μm to 500μm, 50μm to 450μm, 50μm to 400μm, 50μm to 350μm, and 50μm to 300μm. μm, 50μm to 250μm, 50μm to 200μm, 50μm to 150μm, 50μm to 100μm, 100μm to 1000μm, 150μm to 1000μm, 200μm to 1000μm, 250μm to 1000μm, 300μm to 1000μm, 350μm to 1000μm, 400μm to 1000μm, 450μm to 1000μm, 500μm to 1000μm, 550μm to 1 000μm, 600μm to 1000μm, 650μm to 1000μm, 700μm to 1000μm, 750μm to 1000μm, 800μm to 1000μm, 850μm to 1000μm, 900μm to 1000μm, 950μm to 1000μm, 100μm to 950μm, 150μm to 900μm, 200μm to 850μm, 250μm to 800μm, 300μm to 750μm Thicknesses of 350μm to 700μm, 400μm to 650μm, 450μm to 600μm, 500μm to 550μm, 200μm to 400μm, 210μm to 390μm, 220μm to 380μm, 230μm to 370μm, 240μm to 360μm, 250μm to 350μm, 260μm to 340μm, 270μm to 330μm, 280μm to 320μm, or 290μm to 310μm.

[0101] GDLs can have the following average pore sizes: 1 μm to 100 μm, 1 μm to 90 μm, 1 μm to 80 μm, 1 μm to 70 μm, 1 μm to 60 μm, 1 μm to 50 μm, 1 μm to 40 μm, 1 μm to 30 μm, 1 μm to 20 μm, or 1 μm to 10 μm.

[0102] GDL can have the following porosities: 50% to 95%, 50% to 90%, 50% to 85%, 50% to 80%, 50% to 75%, 50% to 70%, 50% to 65%, 50% to 60%, 50% to 55%, 55% to 95%, 60% to 95%, 65% to 95%, 70% to 95%, 75% to 95%, 80% to 95%, 85% to 95%, 90% to 95%, 55% to 90%, 60% to 85%, 65% to 80%, or 70% to 75%.

[0103] GDL can include carbon fiber paper, carbon cloth, carbon felt, carbon foam, metal mesh, metal foam, or any combination thereof. GDL can be modified by treating with hydrophobic polymers and / or applying a microporous layer (MPL).

[0104] Non-limiting examples of carbon fiber paper include: (1a) Toray TGP-H carbon fiber paper (e.g., TGP-H-030, TGP-H-060, TGP-H-090, TGP-H-120). (1b) AvCarb® carbon fiber paper (e.g., MGL190, MGL280, MGL370, MGL190T, MGL280T, MGL370T, EP40, EP40T, EP55, EP55T, GDS1120, GDS2120, GDS22100, GDS2230, GDS2240, GDS3215, GDS3250, GDS3260, GDS5130, MB30, P50, P50T, P75, P75T), (1c) Spectracarb™ carbon fiber paper (e.g., 2050A-0850, 2050A-1050, 2050A-1535, 2050A-1550, 2050A-1550 Treated). (1d) Freudenberg carbon fiber paper (e.g., H14, H14C7, H14C9, H14C10, H14Cx653, H15, H15C13, H15C14, H23, H23C2, H23C3, H23C5, H23C6, H23C7, H23C8, H23C9, H23Cx653, H23I2), (1e) Sigracet® carbon fiber paper (e.g., 22 BB, 25 BA, 25 BC, 28 AA, 28 BC, 29 AA, 29 BC, 36 AA, 36 BB, 39 AA, 39 BB). (1f) CeTech carbon fiber paper (e.g., GDS180S, GDS210, GDS230, GDS 250, GDS310, GDL240, GDL280, GDL340, GDS090S, GDS180HT, GDL120, GDL210SHT). (1g) JNT carbon fiber paper series (e.g., JNT15B, JNT17B, JNT18B, JNT20, JNT21, JNT30). (1h) LINQCELL carbon fiber paper (e.g., GDP180, GDP210, GDP210-MP, GDP-210MPS, GDP 240, GDP340), and (1i) Mitsubishi Chemicals PYROFIL™ GDL.

[0105] Non-limiting examples of carbon cloth include: (2a) AvCarb® carbon cloth (e.g., 1071, 1698, 1209, 1185, 1186, 7497, T1819, T1820, T1824). (2b) E-TEK carbon cloth (e.g., CC4, CC4 waterproof, CC6, CC6 waterproof, ELAT plain cloth, ELAT LT1400, ELAT LT2400W). (2c) CeTech carbon cloth (e.g., W0S1009, W0S1011, W0S1011, W1S1011). (2d) Zoltek™ Panex carbon cloth (e.g., PW03, PW06, SW08). (2e) LINQCELL carbon cloth (e.g., CF350, CF400-MP), and (2f) SAATI SCCG carbon cloth (e.g., 5N).

[0106] Non-limiting examples of carbon felt include: (3a) AvCarb® felt (e.g., C100, C200, C280, G100, G200, G300A, G475A, G600A), (3b) CeTech felts (e.g., CF120, GF20, GF100), and (3c) JNT felt (e.g., GF051BH, GF061AH).

[0107] Non-limiting examples of metal foams include: (4a) Nickel foam, (4b) Copper foam, (4c) Titanium foam, (4d) Silver foam, (4e) Stainless steel foam, (4f) Iron-nickel alloy foam, (4g) Nickel-copper alloy foam, and (4h) Cobalt foam.

[0108] Non-limiting examples of metal mesh include: (5a) Copper metal mesh, (5b) Nickel metal mesh, (5c) Titanium metal mesh, (5d) silver metal mesh, (5e) Stainless steel mesh, and (5f) Molybdenum metal mesh.

[0109] Those skilled in the art will take into account that this disclosure will provide a good understanding of other suitable materials and constructions for GDL, including those further described herein.

[0110] Hydrophobic polymer treatment of GDL In one embodiment, the GDL can be modified with a hydrophobic polymer. Treating the modified GDL with a hydrophobic polymer involves applying a hydrophobic additive to the GDL to control its wettability.

[0111] Non-limiting examples of these hydrophobic additives include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), perfluoropolyether (PFPE), and polydimethylsiloxane (PDMS). GDL can be modified with any one or any combination of these hydrophobic additives.

[0112] GDL may contain no hydrophobic additives or contain 0.01wt% to 50wt%, 0.01wt% to 45wt%, 0.01wt% to 40wt%, 0.01wt% to 35wt%, 0.01wt% to 30wt%, 0.01wt% to 25wt%, 0.01wt% to 20wt%, 0.01wt% to 15wt%, 0.01wt% to 10wt%, 0.01wt% to 5wt%, 5wt% to 50wt%, 10wt% Hydrophobic additives in the following percentages: 50 wt%, 15 wt% to 50 wt%, 20 wt% to 50 wt%, 25 wt% to 50 wt%, 30 wt% to 50 wt%, 35 wt% to 50 wt%, 40 wt% to 50 wt%, 45 wt% to 50 wt%, 5 wt% to 45 wt%, 10 wt% to 40 wt%, 15 wt% to 35 wt%, 20 wt% to 30 wt%, 25 wt% to 45 wt%, or 30 wt% to 40 wt%.

[0113] Microporous layer (MPL) Setting the MPL on the GDL can also help with conductivity and / or water treatment.

[0114] MPL comprises particulate material coated on the plane of GDL. Any suitable particulate material can be used. In one embodiment, the particulate material may be a mixture of carbon black and a hydrophobic polymer, such as polytetrafluoroethylene (PTFE).

[0115] MPL may contain 50wt% to 95wt%, 55wt% to 95wt%, 60wt% to 95wt%, 65wt% to 95wt%, 70wt% to 95wt%, 75wt% to 95wt%, 80wt% to 95wt%, 85wt% to 95wt%, 90wt% to 95wt%, 60wt% to 90wt%, 60wt% to 85wt%, 60wt% to 80wt%, 60wt% to 75wt%, 60wt% to 70wt%, 60wt% to 65wt%, 65wt% to 90wt%, 70wt% to 85wt%, or 75wt% to 80wt% of carbon black.

[0116] MPL may contain 5 wt% to 50 wt%, 5 wt% to 45 wt%, 5 wt% to 40 wt%, 5 wt% to 35 wt%, 5 wt% to 30 wt%, 5 wt% to 25 wt%, 5 wt% to 20 wt%, 5 wt% to 15 wt%, 5 wt% to 10 wt%, 10 wt% to 40 wt%, 15 wt% to 40 wt%, 20 wt% to 40 wt%, 25 wt% to 40 wt%, 30 wt% to 40 wt%, 35 wt% to 40 wt%, 10 wt% to 35 wt%, 15 wt% to 30 wt%, or 20 wt% to 25 wt% of a hydrophobic polymer.

[0117] MPL can have thicknesses of 10μm to 100μm, 10μm to 90μm, 10μm to 80μm, 10μm to 70μm, 10μm to 60μm, 10μm to 50μm, 10μm to 40μm, 10μm to 30μm, 10μm to 20μm, 20μm to 100μm, 30μm to 100μm, 40μm to 100μm, 50μm to 100μm, 60μm to 100μm, 70μm to 100μm, 80μm to 100μm, 90μm to 100μm, 20μm to 90μm, 30μm to 80μm, 40μm to 70μm, or 50μm to 60µm.

[0118] MPLs can have an average pore size of 0 μm to 10 μm, 0 μm to 9 μm, 0 μm to 8 μm, 0 μm to 7 μm, 0 μm to 6 μm, 0 μm to 5 μm, 0 μm to 4 μm, 0 μm to 3 μm, 0 μm to 2 μm, 0 μm to 1 μm, 0 μm to 0.9 μm, 0 μm to 0.8 μm, 0 μm to 0.7 μm, 0 μm to 0.6 μm, 0 μm to 0.5 μm, 0 μm to 0.4 μm, 0 μm to 0.3 μm, 0 μm to 0.2 μm, or 0 μm to 0.1 μm.

[0119] MPL can have porosities of 30% to 75%, 30% to 70%, 30% to 65%, 30% to 60%, 30% to 55%, 30% to 50%, 30% to 55%, 30% to 50%, 30% to 45%, 30% to 40%, 30% to 35%, 35% to 75%, 40% to 75%, 45% to 75%, 50% to 75%, 55% to 75%, 60% to 75%, 65% to 75%, or 70% to 75%.

[0120] Catalyst layer (CL) The catalyst layer may comprise a catalyst, and optionally an ionomer and / or a binder. In one embodiment, the catalyst layer may comprise a catalyst and an ionomer. In another embodiment, the catalyst layer may comprise a catalyst and a binder. In yet another embodiment, the catalyst layer may comprise a catalyst, an ionomer, and a binder. In still another embodiment, the GDE has only a single catalyst layer. In other embodiments, the GDE may comprise more than one catalyst layer.

[0121] For example, depending on the desired operation of the catalyst layer, the catalyst layer can be hydrophilic or hydrophobic. In one embodiment, if the GDE comprises two catalyst layers, the first catalyst layer is hydrophilic and the second catalyst layer is hydrophobic. In other embodiments, both catalyst layers can be either hydrophobic or hydrophilic.

[0122] The catalyst layer can have a thickness of 1 μm to 100 μm, 1 μm to 95 μm, 1 μm to 90 μm, 1 μm to 85 μm, 1 μm to 80 μm, 1 μm to 75 μm, 1 μm to 70 μm, 1 μm to 65 μm, 1 μm to 60 μm, 1 μm to 55 μm, 1 μm to 50 μm, 1 μm to 45 μm, 1 μm to 40 μm, 1 μm to 35 μm, 1 μm to 30 μm, 1 μm to 25 μm, 1 μm to 20 μm, 1 μm to 15 μm, 1 μm to 10 μm, 1 μm to 9 μm, 1 μm to 8 μm, 1 μm to 7 μm, 1 μm to 6 μm, 1 μm to 5 μm, 1 μm to 4 μm, 1 μm to 3 μm, or 1 μm to 2 μm.

[0123] The catalyst layer may have a porosity of 30% to 75%, 30% to 70%, 30% to 65%, 30% to 60%, 30% to 55%, 30% to 50%, 30% to 55%, 30% to 50%, 30% to 45%, 30% to 40%, 30% to 35%, 35% to 75%, 40% to 75%, 45% to 75%, 50% to 75%, 55% to 75%, 60% to 75%, 65% to 75%, or 70% to 75%.

[0124] The ratio of ionomer to catalyst can be 1:1 to 1:20, 1:1 to 1:19, 1:1 to 1:18, 1:1 to 1:17, 1:1 to 1:16, 1:1 to 1:15, 1:1 to 1:14, 1:1 to 1:13, 1:1 to 1:12, 1:1 to 1:11, 1:1 to 1:10, 1:1 to 1:9, 1:1 to 1:8, 1:1 to 1:7, 1:1 to 1:6, 1:1 to 1:5, 1:1 to 1:4, 1:1 to 1:3, 1:1 to 1:2, 1:2 to 1:20, 1:3 to 1:20, 1:4 to 1:20, 1:5 to 1:20, 1:6 to... 1:20, 1:7 to 1:20, 1:8 to 1:20, 1:9 to 1:20, 1:10 to 1:20, 1:11 to 1:20, 1:12 to 1:20, 1:13 to 1:20, 1:14 to 1:20, 1:15 to 1:20, 1:16 to 1:20, 1:17 to 1:20, 1:18 to 1:20, 1:19 to 1:20, 1:2 to 1:19, 1:3 to 1:18, 1:4 to 1:17, 1:5 to 1:16, 1:6 to 1:15, 1:7 to 1:14, 1:8 to 1:13, 1:9 to 1:12 or 1:10 to 1:11.

[0125] catalyst Catalysts may include (6) metals, (7) non-metals, or combinations thereof.

[0126] The metal can be (6a) a transition metal, (6b) a post-transition metal, (6c) a class of metals or a combination thereof or an alloy thereof.

[0127] Catalysts that include transition metals may include: (6a-a)scandium (Sr), (6a-g)cobalt (Co), (6a-m)molybdenum (Mo), (6a-b)Titanium (Ti), (6a-h)Ni, (6a-n)Ru (6a-c)vanadium (V), (6a-i)copper (Cu), (6a-o)rhodium (Rh) (6a-d)chromium (Cr), (6a-j)zinc (Zn), (6a-p)palladium (Pd) (6a-e)manganese (Mn), (6a-k)yttrium (Y), (6a-q)silver (Ag), (6a-f) Iron (Fe), (6a-l) Zirconium (Zr), (6a-r) Cadmium (Cd), Or combinations thereof or alloys thereof. In one specific embodiment, the catalyst is platinum (6a-v), silver (6a-q), nickel (6a-h), or any combination thereof. In one embodiment, the catalyst is an alloy (6a-x) of platinum and nickel (PtNi). In one embodiment, the alloy comprises a platinum to nickel weight ratio of about 5:1 to about 1:5, more particularly about 5:1 to 1:2, and more particularly about 3:1 to about 1:1. In one embodiment, the alloy comprises a platinum to nickel weight ratio of about 5:1, 4.5:1, 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, or 1:5.

[0128] Catalysts that include post-transition metals may include: (6b-a)aluminum (Al), (6b-c)indium (In), (6b-e)thallium (TI) (6b-b) gallium (Ga), (6b-d) tin (Sn), (6b-f) lead (Pb). Or combinations thereof or alloys thereof.

[0129] Catalysts that include metalloids may include (6c-a)silicon (Si), (6c-b)germanium (Ge), (6c-c)antimony (Sb), (6c-d)tellurium (Te), or combinations thereof.

[0130] Catalysts that include nonmetals may include (7a) carbon, (7b) conductive polymers, or combinations thereof.

[0131] Carbon refers to materials whose main component is carbon atoms. For example, carbon can be carbon fibers, graphite, carbon nanomaterials, or combinations thereof. Carbon nanomaterials can include carbon nanotubes, graphene, carbon nanosheets, or fullerenes. In addition, the material may optionally be doped with nonmetallic elements (e.g., B, N, P, O, or S).

[0132] The catalyst loading on GDL can range from 0.1 to 10 mg cm⁻¹ -2 0.1 to 9.0 mg cm -2 0.1 to 8.0 mg cm -2 0.1 to 7.0 mg cm -20.1 to 6.0 mg cm -2 0.1 to 5.0 mg cm -2 0.1 to 4.0 mg cm -2 0.1 to 3.9 mg cm -2 0.1 to 3.8 mg cm -2 0.1 to 3.7 mg cm -2 0.1 to 3.6 mg cm -2 0.1 to 3.5 mg cm -2 0.1 to 3.4 mg cm -2 0.1 to 3.3 mg cm -2 0.1 to 3.2 mg cm -2 0.1 to 3.1 mg cm -2 0.1 to 3.0 mg cm -2 0.1 to 2.9 mg cm -2 0.1 to 2.8 mg cm -2 0.1 to 2.7 mg cm -2 0.1 to 2.6 mg cm -2 0.1 to 2.5 mg cm -2 0.1 to 2.4 mg cm -2 0.1 to 2.3 mg cm -2 0.1 to 2.2 mg cm -2 0.1 to 2.1 mg cm -2 0.1 to 2.0 mg cm -2 0.1 to 1.9 mg cm -2 0.1 to 1.8 mg cm -2 0.1 to 1.7 mg cm -2 0.1 to 1.6 mg cm -2 0.1 to 1.5 mg cm -2 0.1 to 1.4 mg cm -2 0.1 to 1.3 mg cm -2 0.1 to 1.2 mg cm -2 0.1 to 1.1 mg cm -2 0.1 to 1.0 mg cm -2 0.1 to 0.9 mg cm -2 0.1 to 0.8 mg cm -2 0.1 to 0.7 mg cm -2 0.1 to 0.6 mg cm -2 0.1 to 0.5 mg cm -2 0.1 to 0.4 mg cm-2 0.1 to 0.3 mg cm -2 Or 0.1 to 0.2 mg cm -2 .

[0133] Isopolymer The ionomer includes polymers in which at least a portion of the repeating units of the polymer contain ionic groups (e.g., where the polymer is a copolymer containing electrically neutral units and units containing ionic groups).

[0134] In one embodiment, the ionomer comprises anion-exchange ionomers. The anion-exchange ionomers include ionomers in which the ionic groups are preferably cationic groups, and which promote anion conduction through electrostatic interactions between the anions and cationic groups.

[0135] Non-limiting examples of anion exchange ionomers (AEIs) include (8a) Fumion TM FAA-3 AEI, (8b) Ionomr TM AEIs (e.g., AF1, AF2, AF3, AP1, AP3), (8c) Sustainion® AEIs (e.g., XA-9, XB-7, XC-1, XC-2), (8d) Orion AEIs (e.g., TM1, AM, CMX), (8e) Pention TM AEI (e.g., D18, D35, D72) and (8f) PiperION AEI.

[0136] In one embodiment, the ionomer comprises a cation exchange ionomer. The cation exchange ionomer includes ionomers in which the ionic groups are preferably anionic groups, which promote cation conduction through electrostatic interactions between the anionic and cationic groups.

[0137] Non-limiting examples of cation exchange ionomers (CEIs) include Aquivion® CEIs (e.g., D72-25BS, D79-25BS, D83-24B, D98-25BS), FORBLUE™ i-SERIES CEIs (e.g., IC100, IC154), and Fumion. TM CEI (e.g., E-600, FSLA-102, FSLA-725), Ionomr TM CEI (e.g., PP1) and Nafion TM CEI (e.g., D520CS, D521CS, D2020CS, D2021CS).

[0138] CL may contain 5 wt% to 45 wt%, 5 wt% to 40 wt%, 5 wt% to 35 wt%, 5 wt% to 30 wt%, 5 wt% to 25 wt%, 5 wt% to 20 wt%, 5 wt% to 15 wt%, 5 wt% to 10 wt%, 10 wt% to 45 wt%, 15 wt% to 45 wt%, 20 wt% to 45 wt%, 25 wt% to 45 wt%, 30 wt% to 45 wt%, 35 wt% to 45 wt%, 40 wt% to 45 wt%, 10 wt% to 40 wt%, 15 wt% to 35 wt%, or 20 wt% to 30 wt% of ionomer.

[0139] adhesives In one embodiment, CL comprises an adhesive. For example, the adhesive may be a hydrophilic or hydrophobic polymer. Non-limiting examples of adhesives include (9a) PTFE.

[0140] CL may not contain adhesive, or if present, may contain 0.01wt% to 40wt%, 0.01wt% to 35wt%, 0.01wt% to 30wt%, 0.01wt% to 25wt%, 0.01wt% to 20wt%, 0.01wt% to 15wt%, 0.01wt% to 10wt%, 0.01wt% to 5wt%, 5wt% to 40wt%, 10wt% to 40wt%, 15wt% to 40wt%, 20wt% to 40wt%, 25wt% to 40wt%, 30wt% to 40wt%, 35wt% to 40wt%, 5wt% to 35wt%, 10wt% to 30wt%, or 15wt% to 25wt% of adhesive.

[0141] Several specific embodiments of the GDE disclosed herein include those described herein as follows. GDE-1 , GDE-2 , GDE-3 or GDE-4 The GDEs described have components defined as follows, where each entry is a group number as defined above:

[0142] Other specific embodiments of the GDE disclosed herein include GDE embodiments 1a-896a, each of which has the components defined in GDE embodiments 1-896, but does not include adhesives.

[0143] Those skilled in the art will understand that there are many other embodiments of the GDE disclosed herein. For example, any of embodiments 1-896 or 1a-896a for these GDEs may also include an AEM as described herein, for example, as... Figure 1 As shown in (e)-(h). Furthermore, in contrast to GDEs of types GDE-1, GDE-2, and GDE-4 as described herein, any of the embodiments 1-896 or 1a-896a of these GDEs may also include MPLs as described herein, for example, as... Figure 1 (b), (d), (f), and (h) Figure 2 (b) and (d) and Figure 4 As shown in (b) and 4(d). Furthermore, in relation to GDEs of types GDE-1, GDE-2, GDE-3, and GDE-4 as described herein, any of the embodiments 1-896 or 1a-896a of these GDEs may also include a network as described herein, for example, as... Figure 1As shown in (c)-(h), 2(c)-(d), 3(b), and 4(c) and 4(d).

[0144] As described in this article, GDE-4 This includes the 1st GDL and the 2nd GDL, each of which can be the same or different. Relative to... GDE-4 In any of embodiments 1-896 or 1a-896a, at least one of the first GDL and the second GDL is a GDL as defined for the corresponding embodiments in embodiments 1-896 or 1a-896a. In one embodiment, the first GDL and the second GDL are identical, and GDE-4 The two GDLs are defined as described in embodiments 1-896 or 1a-896a. In another embodiment, the first GDL and the second GDL are different, and only one of the GDLs is defined as described in embodiments 1-896 or 1a-896a. GDE-4 In different embodiments of the GDL, it is the first GDL as defined for the embodiments corresponding to embodiments 1-896 or 1a-896a. In which... GDE-4 In different implementations of the GDL, it is the second GDL as defined for the implementations corresponding to implementations 1-896 or 1a-896a.

[0145] Anion exchange membrane (AEM) In one embodiment, the present disclosure GDE-1 , GDE-2 or GDE-4 This may include AEM. Implementations of AEM are described elsewhere herein, and the disclosure is equally applicable to AEM as a component of GDE.

[0146] In one embodiment, the AEM of the GDE comprises a polymer having at least one positively charged cationic group bonded to at least a portion of the polymer backbone. In one embodiment, the polymer includes polyalkylene, polyfluorene, poly(arylene ether), polysulfone, poly(arylene ether sulfone), polyetherketone, polyetherimide, poly(etheroxadiazole), poly(phenylene oxide), poly(vinylbenzyl), polyphenylene, perfluoropolymer, polybenzimidazole, polystyrene, or polyphosphazene. In one embodiment, the positively charged cationic group is a primary ammonium, secondary ammonium, tertiary ammonium, or quaternary ammonium, a heterocyclic cation, a guanidine, phosphonium, sulfonium, or a metal cation.

[0147] In one implementation, the AEM of GDE is Fumasep. TM Neosepta TM Orion TM Xergy XionPention TM PiperION TM Ralex TM Sustanion TM Or Ionomr TM Anion exchange membrane.

[0148] Diaphragm electrolyzer In one embodiment, this disclosure relates to a membrane electrolyzer comprising any of the GDEs described herein. One or more ion exchange membranes are stacked in a specific order for the composition of the brine stream being treated and the desired outputs (products). The membranes are designed to allow specific charged ions to permeate through. Cation exchange membranes transfer cations, while anion exchange membranes allow only anions to be transported through the membrane structure. Ions are enabled to move by applying an external voltage using cathode and anode electrodes. Under the applied voltage, anions move toward the positively charged anode, while cations move toward the negatively charged cathode. By carefully positioning the membranes, desired chemical substances, such as acids, bases, and salts, can be produced.

[0149] In another embodiment of the invention, the method disclosed herein for producing alkali products (e.g., alkali metal compounds) includes using a diaphragm electrolyzer in conjunction with the GDE described herein.

[0150] Many different types of multi-chamber diaphragm electrolyzers can be used, such as those described in this article.

[0151] 5-chamber diaphragm electrolyzer In one embodiment, the diaphragm electrolyzer includes five chambers, such as... Figure 5 As shown. The diaphragm electrolyzer includes an alkali generation chamber, a salt depletion chamber, and an acid generation chamber located between the cathode chamber and the anode chamber. The alkali generation chamber is located between the cathode chamber and the salt depletion chamber, the salt depletion chamber is located between the alkali generation chamber and the acid generation chamber, and the acid generation chamber is located between the salt depletion chamber and the anode chamber.

[0152] The anode is housed in the anode chamber.

[0153] The cathode, including the gas diffusion electrode (GDE), is housed in a cathode chamber, wherein: • When GDE is the one described in this article GDE-1 hour, Figure 1 The CL of GDE shown in (a)-(d) and Figure 5The first AEM shown is in direct contact. Otherwise, Figure 1 The AEM of the GDE shown in (e)-(h) is Figure 5 The first AEM is shown in the diagram. The first AEM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber through the first AEM. The alkali generation chamber is defined by the first AEM and the first CEM.

[0154] • When the GDE is the GDE-2 described in this paper, Figure 2 The CCM of the GDE shown in (a)-(d) is replaced by Figure 5 The first AEM is shown in the diagram. The CCM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber via the CCM. The alkali generation chamber is defined by the CCM and the first CEM.

[0155] • When the GDE is the GDE-3 described in this paper, Figure 5 The first AEM shown is omitted, resulting in the cathode chamber and alkali generation chamber becoming a single chamber. Therefore, using GDE-3 without the first AEM effectively makes the electrolyzer a 4-chamber diaphragm electrolyzer.

[0156] • When the GDE is the GDE-4 described in this paper, Figure 4 The AEM of the GDE shown in (a)-(d) is Figure 5 The first AEM is shown in the diagram. The first AEM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber through the first AEM. The alkali generation chamber is defined by the first AEM and the first CEM.

[0157] The first CEM defines the boundary between the alkali generation chamber and the salt depletion chamber. The alkali generation chamber is in fluid communication with the salt depletion chamber through the first CEM. The salt depletion chamber is defined by the first CEM and the second AEM. The second AEM defines the boundary between the salt depletion chamber and the acid generation chamber. The salt depletion chamber is in fluid communication with the acid generation chamber through the second AEM. The acid generation chamber is defined by the second AEM and the second CEM. The second CEM defines the boundary between the acid generation chamber and the anode chamber. The acid generation chamber is in fluid communication with the anode chamber through the second CEM.

[0158] The first AEM and the second AEM are as described herein and may be the same or different. The first CEM and the second CEM are as described herein and may be the same or different.

[0159] In operation, a salt solution containing both positive and negative ions is fed into the salt depletion chamber. Oxygen-containing gas is fed into the GDE in the cathode chamber. When a voltage is applied between the anode and cathode, positive ions from the salt solution migrate through the first CEM to the negatively charged cathode chamber and remain in the alkali formation chamber because they cannot pass through the first AEM (Alternating Current Emitter). GDE-1 And GDE-4), CCM (GDE-2) or catalyst layer (GDE-3). Similarly, OH generated in GDE - Anions are generated in the alkali formation chamber because they migrate from the negatively charged cathode to the positively charged anode via the first AEM (GDE-1 and GDE-4), CCM (GDE-2), or catalyst layer (GDE-3). Similar to cations, OH- - Ions remain in the base formation chamber because they cannot pass through the first CEM. Therefore, the base is formed in the base formation chamber. Figure 5 As shown, negative ions from the salt solution migrate through the second AEM to the positively charged anolyte chamber and remain in the acid-forming chamber because they cannot pass through the second CEM. The anodic reaction results in the formation of protons, which are then transported through the second CEM into the acid-forming chamber. The protons combine with negative ions to form an acid.

[0160] If the salt solution contains LiCl, Li₂SO₄, Li₃PO₄, LiNO₃, or LiI, LiOH will be generated in the alkali formation chamber, while HCl, H₂SO₄, H₃PO₄, HNO₃, and HI will be generated simultaneously in the acid formation chambers. Similarly, if the salt solution contains NaCl, Na₂SO₄, Na₃PO₄, NaNO₃, or NaI, NaOH will be generated in the alkali formation chamber, while HCl, H₂SO₄, H₃PO₄, HNO₃, and HI will be generated simultaneously in the acid formation chambers. Furthermore, if the salt solution contains KCl, K₂SO₄, K₃PO₄, KNO₃, or KI, KOH will be generated in the alkali formation chamber, and HCl, H₂SO₄, H₃PO₄, HNO₃, and HI will be generated simultaneously in the acid formation chambers.

[0161] Therefore, in one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber, a salt-depleting chamber, and an acid-generating chamber disposed between the cathode chamber and the anode chamber, the alkali-generating chamber being disposed between the cathode chamber and the salt-depleting chamber, the salt-depleting chamber being disposed between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being disposed between the salt-depleting chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising as described herein. GDE-1The cathode; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the first anion exchange membrane to enter the alkali generation chamber; a first cation exchange membrane, located between the salt depletion chamber and the alkali generation chamber, configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane to enter the alkali generation chamber; and a second anion exchange membrane, located between the salt depletion chamber and the acid generation chamber, configured to... Ions received from the salt depletion chamber are exchanged onto the opposite surface of a second anion exchange membrane and enter the acid generation chamber; a second cation exchange membrane, located between the acid generation chamber and the anode chamber, is configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane and enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which O2-containing gas is introduced to contact a gas diffusion electrode; and at least one outlet through which the product is discharged from the interior of the membrane electrolyzer.

[0162] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and exporting the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the first anion exchange membrane to the opposite surface of the first anion exchange membrane and enter the base generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0163] In another embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber, a salt-depleting chamber, and an acid-generating chamber disposed between the cathode chamber and the anode chamber, the alkali-generating chamber being disposed between the cathode chamber and the salt-depleting chamber, the salt-depleting chamber being disposed between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being disposed between the salt-depleting chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located within the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending and located within the cathode chamber, comprising as described herein. GDE-2The membrane electrolyzer comprises: a cathode; a first cation exchange membrane located between a salt depletion chamber and an alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane to enter the alkali generation chamber; an anion exchange membrane located between a salt depletion chamber and an acid generation chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane to enter the acid generation chamber; a second cation exchange membrane located between an acid generation chamber and an anode chamber, the second cation exchange membrane being configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane to enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0164] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and exporting the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the first cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate into the alkali generation chamber through the catalyst-coated membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0165] In another embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber forming a single chamber together with the cathode chamber; a salt-depleting chamber and an acid-generating chamber located between the cathode chamber and the anode chamber, the salt-depleting chamber being located between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being located between the salt-depleting chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer extending and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer extending and located in the cathode chamber, comprising as described herein. GDE-3The membrane electrolyzer comprises: a cathode; a first cation exchange membrane located between a salt depletion chamber and an alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and an acid generation chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane and enter the acid generation chamber; a second cation exchange membrane located between the acid generation chamber and an anode chamber, the second cation exchange membrane being configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane and enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0166] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and exporting the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the first cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer into the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the diaphragm electrolyzer.

[0167] 4-chamber diaphragm electrolyzer In one embodiment, the diaphragm electrolyzer includes four chambers, such as... Figure 6 As shown in the diagram, the diaphragm electrolyzer includes an alkali generation chamber and a salt depletion chamber located between a cathode chamber and an anode chamber. The alkali generation chamber is located between the cathode chamber and the salt depletion chamber, and the salt depletion chamber is located between the alkali generation chamber and the anode chamber.

[0168] The anode is housed in the anode chamber.

[0169] The cathode, including the gas diffusion electrode (GDE), is housed in a cathode chamber, wherein: • When the GDE is the GDE-1 described in this paper, Figure 1 The CL of GDE shown in (a)-(d) and Figure 6 The first AEM shown is in direct contact. Otherwise, Figure 1 The AEM of the GDE shown in (e)-(h) is Figure 6The first AEM is shown in the diagram. The first AEM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber through the first AEM. The alkali generation chamber is defined by the first AEM and the CEM.

[0170] • When the GDE is the GDE-2 described in this paper, Figure 2 The CCM of the GDE shown in (a)-(d) is replaced by Figure 6 The first AEM is shown in the diagram. The CCM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber via the CCM. The alkali generation chamber is defined by both the CCM and the CEM.

[0171] • When the GDE is the GDE-3 described in this paper, Figure 6 The first AEM shown is omitted, resulting in the cathode chamber and alkali generation chamber becoming a single chamber. Therefore, using GDE-3 without the first AEM effectively makes the electrolyzer a 3-chamber diaphragm electrolyzer.

[0172] • When the GDE is the GDE-4 described in this paper, Figure 4 The AEM of the GDE shown in (a)-(d) is Figure 6 The first AEM is shown in the diagram. The first AEM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber through the first AEM. The alkali generation chamber is defined by the first AEM and the CEM.

[0173] The CEM defines the boundary between the alkali generation chamber and the salt depletion chamber. The alkali generation chamber is in fluid communication with the salt depletion chamber via the CEM. The salt depletion chamber is defined by the CEM and the second AEM. The second AEM defines the boundary between the salt depletion chamber and the anode chamber. The salt depletion chamber is in fluid communication with the anode chamber via the second AEM.

[0174] The first AEM and the second AEM are as described herein and may be the same or different. The CEM is as described herein.

[0175] In operation, a salt solution containing both positive and negative ions is fed into the salt depletion chamber. Oxygen-containing gas is fed into the GDE in the cathode chamber. When a voltage is applied between the anode and cathode, positive ions from the salt solution migrate through the CEM to the negatively charged cathode chamber and remain in the alkali formation chamber because they cannot pass through the first AEM (GDE-1 and GDE-4), CCM (GDE-2), or catalyst layer (GDE-3). Similarly, OH- ions generated in the GDE... - Anions are generated in the alkali formation chamber because they migrate from the negatively charged cathode to the positively charged anode via the first AEM (GDE-1 and GDE-4), CCM (GDE-2), or catalyst layer (GDE-3). Similar to cations, OH-- Ions are retained in the base formation chamber because they cannot pass through the CEM. Therefore, the base is formed in the base formation chamber. For example... Figure 6 As shown, negative ions from the salt solution migrate through the second AEM to the positively charged anode chamber.

[0176] If the salt solution contains (a) LiCl, LiBr, or LiI, (b) NaCl, NaBr, or NaI, or (c) KCl, KBr, or KI, then (a) LiOH, (b) NaOH, or (c) KOH will be generated in the alkali generation chamber, respectively. Simultaneously, HCl, HBr, or HI (depending on the input salt solution) will be generated in the anode chamber, each with the potential to produce Cl2, Br2, or I2, respectively.

[0177] If the salt solution contains Li₂SO₄, Li₃PO₄, or LiNO₃, LiOH will be generated in the alkali formation chamber, while H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber. Similarly, if the salt solution contains Na₂SO₄, Na₃PO₄, or NaNO₃, NaOH will be generated in the alkali formation chamber, while H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber. Furthermore, if the salt solution contains K₂SO₄, K₃PO₄, or KNO₃, KOH will be generated in the alkali formation chamber, and H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber.

[0178] Therefore, in one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber and a salt-depleting chamber located between the cathode chamber and the anode chamber, the alkali-generating chamber being located between the cathode chamber and the salt-depleting chamber, and the salt-depleting chamber being located between the alkali-generating chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising as described herein. GDE-1The electrode comprises: a cathode; a first anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the first anion exchange membrane to enter the alkali generation chamber; a cation exchange membrane disposed between the salt depletion chamber and the alkali generation chamber and configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane to enter the alkali generation chamber; a second anion exchange membrane disposed between the salt depletion chamber and the anode chamber and configured to exchange ions received from the salt depletion chamber onto the opposite surface of the second anion exchange membrane to enter the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0179] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the first anion exchange membrane to the opposite surface of the first anion exchange membrane and enter the base generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0180] In another embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber and a salt-depleting chamber located between the cathode chamber and the anode chamber, the alkali-generating chamber being located between the cathode chamber and the salt-depleting chamber, and the salt-depleting chamber being located between the alkali-generating chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer extending and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer extending and located in the cathode chamber, comprising as described herein. GDE-2The cathode; a cation exchange membrane located between a salt depletion chamber and an alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and into the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and an anode chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane and into the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0181] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and exporting the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate into the base generation chamber through a catalyst-coated exchange membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0182] In another embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-forming chamber forming a single chamber together with the cathode chamber; a salt-depleting chamber located between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-3 The membrane electrolyzer includes: a cathode; a cation exchange membrane located between the salt depletion chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an anion exchange membrane located between the salt depletion chamber and the anode chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane and enter the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0183] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into a salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter an alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer into the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the diaphragm electrolyzer.

[0184] 3-chamber diaphragm electrolyzer In one embodiment, the diaphragm electrolyzer includes three chambers, such as... Figure 7 As shown in the diagram, the diaphragm electrolyzer includes an alkali generation chamber located between the cathode chamber and the anode chamber.

[0185] The anode is housed in the anode chamber.

[0186] The cathode, including the gas diffusion electrode (GDE), is housed in a cathode chamber, wherein: • When the GDE is the GDE-1 described in this paper, Figure 1 The CL of GDE shown in (a)-(d) and Figure 7 The AEM shown is in direct contact. Otherwise, Figure 1 The AEM of the GDE shown in (e)-(h) is Figure 7 The AEM is shown in the diagram. The AEM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber via the AEM. The alkali generation chamber is defined by the AEM and the CEM.

[0187] • When the GDE is the GDE-2 described in this paper, Figure 2 The CCM of the GDE shown in (a)-(d) is replaced by Figure 7 The AEM is shown in the diagram. The CCM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber via the CCM. The alkali generation chamber is defined by both the CCM and the CEM.

[0188] • When the GDE is the GDE-3 described in this paper, Figure 7 The AEM shown is omitted, resulting in the cathode chamber and alkali generation chamber becoming a single chamber. Therefore, using GDE-3 without the AEM effectively transforms the electrolyzer into a 2-chamber diaphragm electrolyzer.

[0189] • When the GDE is the GDE-4 described in this paper, Figure 4 The AEM of the GDE shown in (a)-(d) is Figure 7 The AEM is shown in the diagram. The AEM defines the boundary between the cathode chamber and the alkali generation chamber. The cathode chamber is in fluid communication with the alkali generation chamber via the AEM. The alkali generation chamber is defined by the AEM and the CEM.

[0190] The CEM defines the boundary between the alkali generation chamber and the anode chamber. The alkali generation chamber is in fluid communication with the anode chamber through the CEM.

[0191] CEM and AEM are as described in this article.

[0192] In operation, a salt solution containing both positive and negative ions is fed into the anode chamber. Oxygen-containing gas is fed into the GDE in the cathode chamber. When a voltage is applied between the anode and cathode, positive ions from the salt solution migrate through the CEM to the negatively charged cathode chamber and remain in the alkali-forming chamber because they cannot pass through the AEM (GDE-1 and GDE-4), CCM (GDE-2), or catalyst layer (GDE-3). Similarly, OH- ions generated in the GDE... - Anions are generated in the alkali formation chamber because they migrate from the negatively charged cathode to the positively charged anode via the AEM (GDE-1 and GDE-4), CCM (GDE-2), or catalyst layer (GDE-3). Similar to cations, OH- - Ions are retained in the base formation chamber because they cannot pass through the CEM. Therefore, a base is formed in the base formation chamber.

[0193] If the salt solution contains (a) LiCl, LiBr, or LiI, (b) NaCl, NaBr, or NaI, or (c) KCl, KBr, or KI, then (a) LiOH, (b) NaOH, or (c) KOH will be generated in the alkali generation chamber, respectively. Simultaneously, HCl, HBr, or HI (depending on the input salt solution) will be generated in the anode chamber, each with the potential to produce Cl2, Br2, or I2, respectively.

[0194] If the salt solution contains Li₂SO₄, Li₃PO₄, or LiNO₃, LiOH will be generated in the alkali formation chamber, while H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber. Similarly, if the salt solution contains Na₂SO₄, Na₃PO₄, or NaNO₃, NaOH will be generated in the alkali formation chamber, while H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber. Furthermore, if the salt solution contains K₂SO₄, K₃PO₄, or KNO₃, KOH will be generated in the alkali formation chamber, and H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber.

[0195] Therefore, in one embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-1 The electrode comprises: a cathode; an anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the anion exchange membrane and enter the alkali generation chamber; a cation exchange membrane disposed between the anode chamber and the alkali generation chamber and configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an inlet through which a salt-containing solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0196] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a saline solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the saline solution is received in the anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate through the anion exchange membrane to the opposite surface of the anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0197] In another embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-2The cathode; a cation exchange membrane located between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane before entering the alkali generation chamber; an inlet through which a salt-containing solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0198] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a saline solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the saline solution is received in the anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions migrate into the base generation chamber through the catalyst-coated membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the alkali generation chamber.

[0199] In another embodiment, this disclosure relates to a diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber forming a single chamber together with the cathode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; and an anode positioned inside the diaphragm electrolyzer and extending into and located in the cathode chamber, comprising as described herein. GDE-3 The cathode; a cation exchange membrane located between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane before entering the alkali generation chamber; an inlet through which a salt-containing solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0200] In another embodiment, this disclosure relates to a method for producing an alkali product, the method comprising the steps of: receiving a saline solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the saline solution is received in the anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH -Ions migrate through the catalyst layer into the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and the alkali products are discharged from the diaphragm electrolyzer.

[0201] 2-chamber diaphragm electrolyzer In one embodiment, the diaphragm electrolyzer includes two chambers, such as... Figure 8 As shown in the diagram. The diaphragm electrolyzer includes a cathode chamber and an anode chamber. The cathode and anode chambers are in fluid communication via a CEM, as described herein.

[0202] The anode is housed in the anode chamber.

[0203] Including, for example Figure 1 The cathode of the GDE shown in (a)-(d) is housed in a cathode chamber. In this embodiment, the cathode chamber also functions as an alkali generation chamber in the region between the CEM and the CL of the GDE.

[0204] In operation, a salt solution containing both positive and negative ions is fed into the anode chamber. Oxygen-containing gas is fed into the GDE in the cathode chamber. When a voltage is applied between the anode and cathode, positive ions migrate through the CEM to the negatively charged cathode chamber. OH- ions are generated in the GDE. - Anions are retained in the cathode chamber because they cannot pass through the CEM. Therefore, bases are formed in the cathode chamber.

[0205] If the salt solution contains (a) LiCl, LiBr, or LiI, (b) NaCl, NaBr, or NaI, or (c) KCl, KBr, or KI, then (a) LiOH, (b) NaOH, or (c) KOH will be generated in the cathode chamber, respectively. Simultaneously, HCl, HBr, or HI (depending on the input salt solution) will be generated in the anode chamber, each with the potential to produce Cl2, Br2, or I2, respectively.

[0206] If the salt solution contains Li₂SO₄, Li₃PO₄, or LiNO₃, LiOH will be generated in the cathode chamber, while H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber. Similarly, if the salt solution contains Na₂SO₄, Na₃PO₄, or NaNO₃, NaOH will be generated in the cathode chamber, while H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber. Furthermore, if the salt solution contains K₂SO₄, K₃PO₄, or KNO₃, KOH will be generated in the cathode chamber, and H₂SO₄, H₃PO₄, or HNO₃ will be generated simultaneously in the anode chamber.

[0207] Therefore, in one embodiment, this disclosure relates to a diaphragm electrolyzer for processing salt solutions, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and positioned within the anode chamber; and comprising as described herein. GDE-1 The device comprises: a cathode extending inside the diaphragm electrolyzer and positioned within the cathode chamber; a cation exchange membrane between the anode chamber and the catalyst layer of the gas diffusion electrode, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane; an inlet through which a salt solution is received into the anode chamber; a gas inlet through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which the product of the salt solution is discharged from the interior of the diaphragm electrolyzer.

[0208] In another embodiment, this disclosure relates to a method for producing an alkaline product, the method comprising the steps of: receiving a saline solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in the preceding paragraph; and discharging the alkaline product from the diaphragm electrolyzer, wherein in carrying out the method: the saline solution is received in the anode chamber; the positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the cathode chamber; and the O2-containing gas is reduced at the cathode to form OH-. - ;OH - Ions combine with positive salt ions to produce an alkaline product; and the alkaline product is discharged from the cathode chamber.

[0209] Anion exchange membrane (AEM) Anion exchange membranes (AEMs) are membranes that are permeable to anions. An AEM comprises a polymer having multiple positively charged cationic groups bonded to at least a portion of the polymer backbone. The cationic functional groups can be attached to the backbone via extended side chains or directly.

[0210] Non-limiting examples of polymer backbones for anion exchange membranes include: polyalkylene compounds, such as polyethylene (PE); polyfluorene (PFN); poly(arylene ether) (PAE); polysulfone, poly(arylene ether sulfone) (PAES), polyether ketone (PEK), polyetherimide (PEI), poly(ether oxadiazole), polyphenylene ether (PPO); poly(vinyl benzyl) (PVB); polyphenylene (PPN); perfluoropolymer (PF); polybenzimidazole (PBI); polystyrene (PS); or polyphosphazene.

[0211] Non-limiting examples of cationic functional groups include: primary ammonium, secondary ammonium, tertiary ammonium or quaternary ammonium; heterocyclic cations such as imidazolium or pyridinium; guanidinium; phosphonium; sulfonium; and metal cations.

[0212] Non-limiting examples of anion exchange membranes include: (10a)Fumasep TM FAA AEM(free),FAA、FAA-3-20,FAA-3-25,FAA-3-30,FAA-3-50,FAA-3-PE-30,FAA-3-PK-75,FAA-3-PK-130,FAA-3-PK-150) (10b)Fumasep TM FAB AEM(only,FAB-PK-75、FAB-PK-130) (10c)Fumasep TM FAD AEM(also,FAD-55,FAD-PET-75), (10d)Fumasep TM FAM AEM(man,FAM), (10e)Fumasep TM FAAM AEM(single,FAAM-10,FAAM-15,FAAM-20,FAAM-40,FAAM-PK-75) (10f)Fumasep TM FAP AEM(free),FAP-330、FAP-450、FAP-330-PE、FAP-330-PE、FAP-420-PE、FAP-375-PP), (10g)Fumasep TM FAPQ AEM(free,FAPQ-330,FAPQ-8130-PK,FAPQ-375-PP), (10h)Fumasep TM FAS AEM(FAS-50,FAS-30,FAS-PET-75,FAS-PE-130) (10i)Neosepta TM AEM(A, ACN, ACS, AFN, AFX, AHA, AHO, AID, AMX, ASE, AXP-D) (10j)ORION TM AEM(apartment,TM1、CMX), (10k)Xergy Xion TM Pension TMAEM (for example, Pention-AEM-18-05, Pention-AEM-18-10, Pention-AEM-18-20, Pention-AEM-18-30, Pention-AEM-35-05, Pention-AEM-35- 10. Pention-AEM-35-20, Pention-AEM-35-30, Pention-AEM-72-05, Pention-AEM-72-10, Pention-AEM-72-20, Pention-AEM-72-30), (10l) PiperION TM AEM (e.g., PiperION anion exchange membrane - 15 microns, PiperION anion exchange membrane - 20 microns, PiperION anion exchange membrane - 40 microns, PiperION anion exchange membrane - 60 microns, PiperION anion exchange membrane - 80 microns). (10m) RALEX TM AEM (e.g., AMHPES, AMHPP). (10n)SELEMION TM AEM (for example, AAV, AAVN, AHO, AMT, AMV, AMVN, ASV, ASVN, DSV, DSVN), (10o) Sustainion® AEM (e.g., B22-50, E28-50, E30-50, X37-50, X37-60, X37-FA, X37-T, X37-TZ), and (10p) Ionomr AEM (e.g., Aemion).

[0213] Cation exchange membrane (CEM) A cation exchange membrane (CEM) is a membrane that is permeable to cations. In one embodiment, the CEM may be a monovalent cation-selective membrane. In another embodiment, the CEM may be a lithium-selective membrane.

[0214] CEMs can comprise polymers having multiple negatively charged anionic groups that are bonded to at least a portion of the polymer backbone. The anionic functional groups can be attached to the backbone via extended side chains or directly.

[0215] Non-limiting examples of polymer backbones for cation exchange membranes include: polyalkylene compounds, such as polyethylene (PE) or polypropylene; polyfluorene (PFN); poly(arylene ether) (PAE); polysulfone; poly(arylene ether sulfone) (PAES); polyether ketone (PEK); polyetherimide (PEI); poly(etheroxadiazole); polyphenylene ether (PPO); poly(vinyl benzyl) (PVB); polyphenylene (PPN); perfluoropolymer (PF); polybenzimidazole (PBI); polystyrene (PS); or polyphosphazene.

[0216] Non-limiting examples of anionic functional groups include: sulfonate groups, such as perfluorosulfonate groups; carboxylate groups; phosphonate groups; and phenolic anionic groups.

[0217] Non-limiting examples of cation exchange membranes include: (11a) Aquivion® CEM (e.g., E87-05S, E98-05S, E98-09S, E98-15S), (11b) Fumasep TM CEM (e.g., F-930-RFD, F-1075-PK, F-1850, F-10120, F-10120-PK, F-10150-PF, F-10270-PTFE-e, FS-720, FS-950, FS-990-PK, FS -9100-PK, FKB, FKB-PK-130, FKD-PET-75, FKD-PK-75, FKE-50, FKL-PK-130, FKM, FKS-30, FKS-50, FKS-PET-75, FKS-PET-130), (11c) Fumapem TM CEM (e.g., F-14100, F-930, F-930-RFS, FS-715-RFS, FS-930, FS-930-RFS, F-950), (11d) Nafion TM CEM (e.g., N115, N117, N324, N417, N424, N438, N551, N1110). (11e)Neosepta TM CEM (e.g., CMB, CMX, CSE, CXP-S), (11f) SELEMION TM CEM (e.g., CMD, CMF, CMTE, CMV, CMVN, CSO), and (11g)Exergy Xion TMCEM (for example, PEM-Nafion-1000-05, PEM-Nafion-1000-10, PEM-Nafion-1000-20, PEM-Nafion-1000-30, PEM-Nafion-1000- 50. PEM-Nafion-1100-05, PEM-Nafion-1100-10, PEM-Nafion-1100-20, PEM-Nafion-1100-30, PEM-Nafion-1100-50, PE M-Aquivion-720-05, PEM-Aquivion-720-10, PEM-Aquivion-720-20, PEM-Aquivion-720-30, PEM-Aquivion-720-50, P EM-Aquivion-830-05, PEM-Aquivion-830-10, PEM-Aquivion-830-20, PEM-Aquivion-830-30 and PEM-Aquivion-830-50), (11h)Ionomr TM CEM (e.g., Permion).

[0218] If the salt solution to be processed in the diaphragm electrolyzer contains lithium salt, then the CEM through which lithium ions migrate can be (11i) lithium-selective. Non-limiting examples of CEMs as lithium-selective membranes include the membranes described in WO2021026607 and WO2022173852, the contents of which are incorporated herein by reference.

[0219] Various specific embodiments of the diaphragm electrolyzer disclosed herein include diaphragm electrolyzers, each of which is defined as follows, wherein each entry is a group number as defined above: 2-chamber diaphragm electrolyzer

[0220] 3-chamber diaphragm electrolyzer

[0221] 4-chamber diaphragm electrolyzer

[0222] 5-chamber diaphragm electrolyzer

[0223] The flow rate of the salt solution in the diaphragm electrolyzer described in this article can be 0.5 to 5 L / min, 0.5 to 4.8 L / min, 0.5 to 4.6 L / min, 0.5 to 4.4 L / min, 0.5 to 4.2 L / min, 0.5 to 4.0 L / min, 0.5 to 3.8 L / min, 0.5 to 3.6 L / min, 0.5 to 3.4 L / min, 0.5 to 3.2 L / min, 0.5 to 3.0 L / min, 0.5 to 2.8 L / min, 0.5 to 2.6 L / min, 0.5 to 2.4 L / min, 0.5 to 2.2 L / min, 0.5 to 2.0 L / min, 0.5 to 1.8 L / min, 0.5 to 1.6 L / min, 0.5 to 1.4 L / min, 0.5 to 1.2 L / min, 0.5 to 1.0 L / min, 1.0 to 3.0 L / min, 1.2 to 2.8 L / min, 1.4 to 2.6 L / min, 1.6 to 2.4 L / min, or 1.8 to 2.2 L / min.

[0224] The flow rate of oxygen-containing gas in the diaphragm electrolyzer described in this article can be 5 to 25 L / min, 5 to 23 L / min, 5 to 21 L / min, 5 to 19 L / min, 5 to 17 L / min, 5 to 15 L / min, 5 to 13 L / min, 5 to 11 L / min, 5 to 9 L / min, 5 to 7 L / min, 7 to 25 L / min, 9 to 25 L / min, 11 to 25 L / min, 13 to 25 L / min, 15 to 25 L / min, 17 to 25 L / min, 19 to 25 L / min, 21 to 25 L / min, 23 to 25 L / min, 7 to 23 L / min, 9 to 21 L / min, 11 to 19 L / min, or 13 to 17 L / min.

[0225] The temperature of the salt solution in the diaphragm electrolyzer described in this article can be 40 to 70°C, 40 to 65°C, 40 to 60°C, 40 to 55°C, 40 to 50°C, 40 to 45°C, 45 to 70°C, 50 to 70°C, 55 to 70°C, 60 to 70°C, 65 to 70°C, 45 to 65°C, or 50 to 60°C.

[0226] Integrating a membrane electrolyzer, including a gas diffusion electrode, into the lithium recovery process. Figure 9 This paper illustrates a method for recovering lithium from brine in brine from salt lakes, utilizing a diaphragm electrolyzer as described herein, along with a GDE as described herein. It can be seen that sodium chloride extracted from the evaporation stage of the lithium brine recovery method is fed into the diaphragm electrolyzer as feed brine. The feed brine then undergoes a depletion process as it passes through the electrolyzer. Depletion occurs through the reaction of Na+ and OH-. - The result of ions migrating out of the salt depletion chamber and into the base formation chamber and acid formation chamber, respectively.

[0227] The ions migrating out of the salt depletion chamber depend on the types of ions in the feed brine fed into the membrane electrolyzer. Therefore, the desalinated water discharged from the salt depletion chamber can be concentrated again, and thus a readily available salt (NaCl) reserve from salt lake evaporation ponds can be used for feed brine recycling. The concentration of the feed brine plays a crucial role in providing mass transfer and supplying ions for acid and base formation. Although the membrane electrolyzer can operate at feed brine concentrations as low as 0.1 wt% salt, it is advantageous to operate at the maximum usable feed brine concentration.

[0228] The concentrations of the acid and alkali products discharged from the acid generation chamber and alkali generation chamber, respectively, can be adjusted according to the requirements of each specific method. As described herein, a diaphragm electrolyzer used with GDE can achieve caustic soda (NaOH) concentrations in the range of 5-20 wt%. Figure 9 As shown, typical uses of NaOH generated in membrane electrolyzers during lithium recovery operations from brine in salt lakes include, but are not necessarily limited to: • Neutralization and pH adjustment after solvent extraction to recycle the solvent; • Provides alkalinity for precipitation and hardness removal; • Regeneration of ion exchange resins used for hardness removal and metal removal; • Lithium carbonate is converted into lithium hydroxide through a causticization process.

[0229] All of the above methods require a sodium hydroxide (NaOH) concentration in the range of 5-20 wt% (within the range achievable in diaphragm electrolyzers).

[0230] Non-limiting examples of typical uses of hydrochloric acid produced by a diaphragm electrolyzer in lithium brine recovery processes are shown below: • Adjust the pH during the solvent extraction process to remove boron; • Regeneration of ion exchange resins used for hardness removal and metal removal; • Conversion of lithium carbonate to lithium chloride.

[0231] The concentration of hydrochloric acid used in the above applications is in the range of 4-12 wt% (achievable through a diaphragm electrolyzer).

[0232] Figure 10 The image shows a lithium ore mining process that integrates a diaphragm electrolyzer and a gas-discharge deionization (GDE) as described herein. It can be seen that sodium sulfate (Na₂SO₄) salt, the largest byproduct of lithium ore mining operations, can be used as the feed brine for the diaphragm electrolyzer. Figure 10 As shown, feeding Na2SO4 into a membrane electrolyzer will produce NaOH and H2SO4 as alkali and acid, respectively. These can be recycled and used as reagents in lithium recovery processes.

[0233] Sulfuric acid (H₂SO₄) is the primary reagent required for extracting lithium from ores in the acid roasting process. For example... Figure 10 As shown, this chemical can be regenerated from sodium sulfate byproducts readily available in lithium ore hard rock mining processes.

[0234] Similarly, the resulting sodium hydroxide can be used in a variety of ways throughout the lithium production process. Non-limiting examples of the uses of sodium hydroxide in lithium ore mining operations are shown below: • Provides alkalinity for precipitation and hardness removal; • Regeneration of ion exchange resins used for hardness removal and metal removal; • Lithium sulfate is converted into lithium hydroxide by adding NaOH to the process.

[0235] All of the above processes require a NaOH concentration in the range of 5-20 wt% (within the range achievable in diaphragm electrolyzers).

[0236] Figure 11 A first embodiment of the in-situ generation of LiOH and HCl from LiCl using a diaphragm electrolyzer with a GDE, as described herein, is shown. In one embodiment (not shown), the diaphragm electrolyzer is used to convert LiCl to LiOH in a process for recovering lithium from brine from a brine lake. Figure 11 As shown, the brine fed into the diaphragm electrolyzer is a LiCl solution, which is fed into the salt depletion chamber (not shown) of the diaphragm electrolyzer. Oxygen, preferably in the form of air, is fed to the cathode. The oxygen or air may optionally be humidified, for example by bubbling the gas through water before feeding it to the cathode. The air may optionally be purified. As shown, the outputs from the electrolyzer are LiOH and HCl, with LiOH discharged from the alkali formation chamber (not shown) and HCl discharged from the acid formation chamber (not shown). Deionized water may optionally be discharged from the electrolyzer, although this stream is not... Figure 11 As shown in the diagram, whether or not deionized water is discharged from the electrolyzer depends on the concentration of the feed brine (i.e., the LiCl aqueous solution) and the desired concentrations of the produced LiOH and HCl.

[0237] In a similar manner, water can be optionally fed into the electrolyzer instead of being discharged. Whether water is fed into the electrolyzer depends on the concentration of the feed brine (i.e., an aqueous LiCl solution) and the desired concentrations of the produced LiOH and HCl. Figure 11 As shown, in this embodiment, HCl can be used to regenerate the ion exchange resin used to remove Ca, Mg, Na, and K from the LiCl process stream entering the electrolyzer. HCl can also be used in the boron removal step to regenerate the ion exchange resin, which typically follows the evaporation / precipitation step near the start of the method. Figure 11 As shown, HCl can be used to adjust the pH of the process stream that generates CO2. CO2 can be combined with a portion of the LiOH product stream, thereby producing a stream containing both LiOH and Li2CO3. Figure 11 As shown, the LiOH / Li₂CO₃ stream can be fed to the precipitation step where Ca and Mg are discharged. Importantly, not all of the LiOH product stream is used for this precipitation step, as LiOH is the desired product. However, the ability to use LiOH in this way significantly reduces the need to purchase alkalis, such as NaOH or Na₂CO₃, to achieve the precipitation and discharge of Ca and Mg.

[0238] For reference purposes, based on tests using a 6% LiCl stream as brine feed, approximately 150-250 kWh / m³ is required when using air at the oxygen depolarization cathode (ODC). 3 The LiCl brine reduced the total salt content to 3%.

[0239] Figure 12 A second embodiment of the implementation of a membrane electrochemical electrolyzer in conjunction with the GDE described herein in the recovery of lithium from brine in a salt lake is described. In this embodiment, an aqueous LiCl solution is again used as the feed to the brine of the membrane electrolyzer. In this embodiment, as in the first embodiment, the membrane electrolyzer is used to convert LiCl to LiOH. The aqueous LiCl solution is fed into the salt depletion chamber of the membrane electrolyzer. Oxygen in the form of air is preferably fed to the cathode. The oxygen or air may optionally be humidified, for example by bubbling the gas through water before feeding it to the cathode, and the air may optionally be purified. As shown, the outputs from the electrolyzer are LiOH and HCl, with LiOH discharged from the alkali generation chamber (not shown) and HCl discharged from the acid generation chamber (not shown). As in the first embodiment, demineralized water may optionally be discharged from the electrolyzer, although... Figure 12 The stream is not displayed.

[0240] Whether demineralized water is discharged from the electrolyzer depends on the concentration of the feed brine (i.e., the LiCl aqueous solution) and the desired concentrations of the produced LiOH and HCl. Similarly, water can optionally be fed into the electrolyzer instead of being discharged. Whether water is fed into the electrolyzer depends on the concentration of the feed brine (i.e., the LiCl aqueous solution) and the desired concentrations of the produced LiOH and HCl. In this embodiment, all produced LiOH is discharged, i.e., there is no recirculation flow containing LiOH.

[0241] However, the HCl stream in the first embodiment can be recycled and used in lithium recovery processes. For example... Figure 12 As shown, HCl is used to regenerate the ion exchange resin, which is used to remove Ca and Mg from the process stream before feeding this stream as feed brine into the diaphragm electrolyzer. The HCl produced after the precipitation step can also be used to remove boron B to regenerate the ion exchange resin.

[0242] Figure 13A third embodiment is shown, illustrating the use of a diaphragm electrolyzer in conjunction with the GDE described herein in a lithium production process. In this embodiment of the method, a mixed brine solution containing both LiCl and NaCl is fed into the diaphragm electrolyzer. The electrolyzer then produces HCl and a mixed LiOH and NaOH solution. This mixed LiOH and NaOH solution is fed to a crystallization / separation step, which produces crystallized LiOH and a mixed solution of NaOH and low-concentration LiOH, the concentration of which is lower than the concentration of LiOH in the mixed LiOH and NaOH solution fed to the crystallization / separation step. Figure 13 As can be seen from this, the method is similar to Figure 9 and Figure 11 The method shown employs a diaphragm electrolyzer for existing operations to produce LiOH from brine in a salt lake. In alternative embodiments, the diaphragm electrolyzer can be applied to another waste or recycled lithium chloride stream generated in conventional lithium operations that do not contain sodium, and can convert lithium chloride into lithium hydroxide and hydrochloric acid.

[0243] Therefore, the step is: Step 1: Feed the mixed lithium chloride and sodium chloride produced by conventional brine process operation into the diaphragm electrolyzer (electrochemical electrolyzer) to produce a mixed lithium hydroxide and sodium hydroxide solution.

[0244] Step 2: The mixed lithium hydroxide and sodium hydroxide are fed to a crystallizer / separator, where they are separated due to the significant difference in solubility between the two salts—NaOH is more soluble in water than LiOH. The crystallization / separation unit can evaporate the water and optionally re-condense it, or some LiOH precipitation can be achieved simply by cooling the mixed solution of NaOH and LiOH. A more typical method is to simply evaporate the water. Lithium hydroxide crystallizes, while sodium hydroxide remains in solution. The crystallized lithium hydroxide is ready for market.

[0245] Step 3: Some lithium hydroxide remains in the solution along with sodium hydroxide and is recycled back into the process for use in the precipitation stage.

[0246] Step 4: Combine some lithium hydroxide and sodium hydroxide with carbon dioxide to produce a mixed lithium carbonate and sodium carbonate stream. This mixed lithium carbonate and sodium carbonate stream is recycled back into the overall process for further precipitation, such as... Figure 13 This can be seen from the text.

[0247] In summary, by integrating the electrochemical electrolyzer (diaphragm electrolyzer) into the entire process of recovering LiOH from brine in salt lakes, these steps result in the formation of closed or near-closed loops of sodium hydroxide, sodium carbonate, and lithium carbonate.

[0248] Then, turn to Figure 14 This illustrates a fourth embodiment of a membrane electrolyzer used in conjunction with the GDE described herein in a lithium production process. Figure 14 As shown, in the process of producing lithium from lithium-containing ore, a diaphragm electrolyzer is used to convert Li₂SO₄ to LiOH. However, those skilled in the art will understand that the brine feed stream containing an aqueous solution of Li₂SO₄ does not necessarily have to originate from a lithium ore-based process.

[0249] In some brine recovery processes, it is desirable to convert Li₂SO₄ solution into LiOH, and therefore membrane electrolyzers can also be used in this process. For example... Figure 14 As shown, the diaphragm electrolyzer uses an aqueous solution of Li₂SO₄. In other embodiments, a gaseous stream containing oxygen is also fed into the electrolyzer. This stream, preferably air, is fed to the cathode. The oxygen or air may optionally be humidified, for example by bubbling the gas through water before feeding it to the cathode, and the air may optionally be purified. As shown, the outputs from the electrolyzer are LiOH and H₂SO₄, with LiOH discharged from the alkali formation chamber (not shown) and H₂SO₄ discharged from the acid formation chamber (not shown).

[0250] As in the first and second embodiments, the demineralized water can optionally be discharged from the electrolyzer, although the flow is not in Figure 14 As shown in the diagram, whether demineralized water is discharged from the electrolyzer depends on the concentration of the feed brine (i.e., the Li₂SO₄ aqueous solution) and the desired concentrations of the produced LiOH and H₂SO₄. Similarly, water can optionally be fed into the electrolyzer instead of being discharged. Whether water is fed into the electrolyzer depends on the concentration of the feed brine (i.e., the Li₂SO₄ aqueous solution) and the desired concentrations of the produced LiOH and H₂SO₄.

[0251] In this embodiment, both LiOH and H2SO4 are recycled back into the lithium recovery process, which reduces at least some of the need to purchase additional reagents. Importantly, only a portion of the LiOH is recycled, since LiOH is, of course, the desired end product. H2SO4 is used in the acid roasting step of ore production to produce a Li2SO4 brine solution after the water leaching step. Figure 13 As shown, after the water immersion step, some of the LiOH produced can be used to precipitate Ca and Mg from the Li2SO4 salt solution.

[0252] Figure 15An exemplary embodiment of using a diaphragm electrolyzer with the GDE described herein in a closed-loop process is shown. In this closed-loop process, lithium carbonate (Li₂CO₃) produced by other methods, such as lithium carbonate produced from brine operation by precipitation of sodium carbonate or lithium carbonate produced from jadarite (LiNaSiB₃O₇OH), can be dissolved in hydrochloric acid to produce a lithium chloride solution, which is then converted to LiOH. The following describes the process... Figure 15 The method shown: Step 1: Lithium carbonate produced by other methods is converted into lithium chloride by dissolving it in hydrochloric acid.

[0253] Step 2: Treat lithium chloride in an electrochemical electrolytic cell to produce lithium hydroxide and hydrochloric acid.

[0254] Step 3: The hydrochloric acid is recycled back to further convert lithium carbonate into lithium chloride, resulting in a fully or essentially closed-loop system.

[0255] Similarly, as shown below, such as Figure 15 The method shown can be performed using sulfuric acid instead of hydrochloric acid: Step 1: Lithium carbonate produced by other methods is converted into lithium sulfate by dissolving it in sulfuric acid.

[0256] Step 2: Treat lithium sulfate in an electrochemical electrolytic cell to produce lithium hydroxide and sulfuric acid.

[0257] Step 3: The sulfuric acid is recycled back to further convert lithium carbonate into lithium sulfate, resulting in a fully or essentially closed-loop system.

[0258] As shown in the following two exemplary implementations ( Figure 16 and Figure 17 As shown, the diaphragm electrolyzer, together with the GDE described herein, can also be used in lithium recovery methods that integrate ion exchange resins. These ion exchange resins can be used directly to produce LiOH, or they can be used for recycling and / or recovering other ionic substances in lithium recovery processes. The advantages of using these embodiments (and all embodiments of the diaphragm electrolyzer disclosed herein) are multifaceted, relative to the savings in operating and capital costs.

[0259] As discussed above, lithium hydroxide is produced through a wide range of methods by treating lithium-rich brine, such as salt lake brine. This involves evaporating water from the brine over a period of 6 to 18 months to concentrate the lithium chloride in the solution to 5 wt% LiCl or higher and precipitate large amounts of sodium, calcium, and magnesium salts, as these substances are generally less soluble than LiCl.

[0260] The lithium chloride-rich brine must then undergo several purification steps. These purification steps may include, for example, removing boron by solvents or other means; removing calcium and magnesium by adding lime (calcium oxide and / or calcium hydroxide) and caustic soda, soda ash, and / or sodium bicarbonate or other substances; and further removing calcium and magnesium by adding soda ash, i.e., sodium carbonate (Na₂CO₃). These processes produce a mixed stream of lithium chloride and sodium chloride, to which the addition of additional soda ash results in the formation of lithium carbonate precipitate. The lithium carbonate can then be crystallized. Currently, this crystallized lithium carbonate is typically transported to a lithium hydroxide plant, where it is converted into lithium hydroxide by adding calcium hydroxide. The lithium hydroxide is then crystallized and sold. There are several process units associated with all these steps, and it is clear that procuring and maintaining these process units implies significant capital investment and ongoing operating costs.

[0261] Ion exchange resins with selective adsorption or binding of lithium can be used to eliminate multiple steps in these processes to selectively adsorb lithium from brine (or other sources) without time-consuming evaporation or removal of boron, calcium, magnesium, etc. For example, ion exchange resins can be used to selectively bind lithium and produce lithium chloride by desorbing lithium from the resin with HCl. A diaphragm electrolyzer, as described herein, can convert lithium chloride into lithium hydroxide and hydrochloric acid, which is then recycled back to the ion exchange resin, where the desired lithium hydroxide is collected.

[0262] In another embodiment, the ion exchange resin used for selective lithium adsorption can also be used to produce lithium sulfate by regenerating the resin with sulfuric acid. Similarly, lithium sulfate is fed into an electrolyzer to produce lithium hydroxide and sulfuric acid. The sulfuric acid is recycled back to the ion exchange resin to produce more lithium sulfate, while the desired lithium hydroxide is collected.

[0263] Ion exchange resins will eliminate the significant capital and operating expenditures and costs associated with lithium evaporation ponds and related downstream transportation.

[0264] The removal of the evaporation ponds also preserves the water lost to the atmosphere during the evaporation process. Producers will be able to pump the lithium-depleted brine back to the brine reservoir, which holds the water that would otherwise evaporate. This feature is crucial from both an environmental and legal perspective. For example, Chile, home to most of the world's lithium brine, has strict restrictions on water use and the amount of brine that lithium producers can pump. These controls aim to protect the scarce water resources in Chile's salt flat desert regions. Therefore, these restrictions effectively limit the lithium production capacity of producers. However, if the lithium-depleted brine from the ion-exchange process is pumped back to the reservoir, less net brine is pumped, and producers can increase their lithium production without exceeding government restrictions on the amount of brine they can pump or the amount of water used in operations. Using ion-exchange resins in the lithium recovery process also saves time because the evaporation step is slower. Additionally, and importantly, the reagents needed to precipitate calcium and magnesium are no longer required.

[0265] The biggest cost associated with the direct production of lithium using ion exchange resins is the need to purchase HCl, which is required to desorb or unbind lithium ions from active sites and regenerate the ion exchange resin. Electrochemical electrolyzers, as described herein, capable of converting lithium chloride to lithium hydroxide and hydrochloric acid, not only eliminate the need for the reagents required to convert lithium chloride to lithium carbonate and then to lithium hydroxide, but these electrolyzers also generate the crucial HCl needed for lithium extraction from the ion exchange resin. Therefore, the entire process from lithium chloride evaporation to lithium carbonate production and conversion, culminating in the production of lithium hydroxide for batteries, can be simplified to using only ion exchange resins and an electrochemical electrolyzer.

[0266] Furthermore, in the process of directly adsorbing lithium from brine using ion exchange resins, another exemplary application of the membrane electrolyzer is a process in which the ion exchange resin is deployed in a desert where brine from a pumped salt lake is pumped, while the membrane electrolyzer is placed in a different location. In this exemplary process, the ion exchange resin is discharged and transported to the location of the membrane electrolyzer, where it is regenerated with HCl to produce LiOH. The ion exchange resin is then transported back to its original location in the brine in the desert. Therefore, the used ion exchange resin moves in one direction, and the regenerated ion exchange resin moves in the opposite direction. Thus, in the following... Figure 15 , Figure 16 or Figure 17 In any of the exemplary processes shown, the diaphragm electrolyzer and the GDE described herein may be located in a different position from the ion exchange resin.

[0267] Non-limiting examples of suitable ion exchange resins of this kind are those that selectively bind lithium or other noble metals based on solution pH. For example, the resin may bind lithium in acid but not in alkali, and vice versa. This allows us to regenerate the resin and extract lithium from it. This enables manufacturers to regenerate the resin and extract lithium from it. The diaphragm electrolyzer then produces a solution with a suitable pH to remove the bound ions by providing HCl or NaOH. Such ion exchange resins may also include complexed metal resins, such as H... n M n O n Where H is hydrogen, M is a metallic substance, O is oxygen, and n is an integer. Non-limiting examples include LiAlO2, LiCuO2, etc.

[0268] Therefore, the following two embodiments demonstrate how a diaphragm electrolyzer can be integrated with the GDE described herein to directly produce LiOH in a lithium recovery process using ion exchange resin.

[0269] Figure 16 An exemplary embodiment of a membrane electrolyzer used in a lithium production process in which ion exchange resins are used to selectively adsorb Li from lithium brine is shown. This lithium brine does not necessarily have to be lake brine—it can be brine from other industrial processes, such as water produced from oil and gas operations, or sometimes lithium-containing geothermal brine or naturally occurring brine layers, or it can originate from lithium-ion battery recycling processes. Figure 16 As can be seen, the diaphragm electrolyzer simultaneously produces marketable LiOH and HCl for removing Li (in the form of LiCl) from the ion exchange resin, thereby regenerating the ion exchange resin. LiCl is fed into the diaphragm electrolyzer to produce the desired LiOH. In an alternative embodiment, lithium sulfate can be produced by using sulfuric acid and lithium sulfate to produce the desired lithium hydroxide in the diaphragm electrolyzer. The steps in this method are as follows: Step 1: Treat lithium-containing brine or solution with ion exchange resin or other adsorbents to adsorb lithium from the brine or solution.

[0270] Step 2: Regenerate the lithium-containing resin beads or adsorbent with hydrochloric acid to produce a lithium chloride solution. Regenerate the resin or adsorbent to protonated form with HCl. Alternatively, sulfuric acid can be used to regenerate the resin.

[0271] Step 3: Treat the lithium chloride solution in an electrochemical electrolyzer to produce lithium hydroxide and hydrochloric acid. Alternatively, the lithium sulfate solution can be treated in an electrochemical electrolyzer to produce lithium hydroxide and sulfuric acid.

[0272] Step 4: Sell the lithium hydroxide to the market or remove it from the process, while recycling the hydrochloric acid back to step 2.

[0273] Figure 17 Another exemplary use of the diaphragm electrolyzer as disclosed herein is shown, wherein a lithium-containing brine is first subjected to a boron removal process, then the brine is fed to an ion exchange resin, and then to the diaphragm electrolyzer. Figure 16 As shown, in this exemplary embodiment, the process steps after boron discharge are as follows: Step 1: Treat lithium-containing brine or solution with ion exchange resin or other adsorbents to adsorb lithium from the brine or solution.

[0274] Step 2: Regenerate the lithium-ion exchange resin beads or other suitable lithium adsorbent with hydrochloric acid to produce a lithium chloride solution. Regenerate the resin or adsorbent to protonated form with HCl. Note that the depleted lithium solution can be pumped back to the brine reservoir or pool. As mentioned above, due to appropriate water conservation restrictions generally applied to the amount of brine that can be pumped from natural reservoirs, particularly in Chile, producers can produce more lithium without exceeding legal limits on the amount of brine they can pump if the depleted solution is returned to the reservoir.

[0275] Step 3: Treat the lithium chloride solution using the membrane electrochemical electrolyzer disclosed herein to produce lithium hydroxide and hydrochloric acid. Alternatively, treat lithium sulfate using a membrane electrochemical electrolyzer to produce lithium hydroxide and sulfuric acid.

[0276] Step 4: The lithium hydroxide is sold on the market or removed from the process, while the hydrochloric acid or sulfuric acid is recycled back to Step 2.

[0277] Note that, in such Figure 17 In the process shown, air and electricity are supplied to the diaphragm electrolyzer. Therefore, the overall reactions at the anode and cathode of the electrolysis are: Anode: 2H2O O2+ 4H+ + 4e- Cathode: O2 + 2H2O + 4e- 4OH- As in the following exemplary implementation ( Figure 18 As shown in the diagram, the membrane electrolyzer can also be used in alkali (e.g., LiOH) recovery processes that integrate solvent extraction (SX) methods.

[0278] The SX method is used to separate compounds based on their solubility in two immiscible liquid phases—an organic phase and an aqueous phase. The organic phase is added to the aqueous solution to form an organic Li₂. + Complex. Li +The complex (and some residual impurity metals) transferred to the organic phase. Most of the impurity metals remained in the Li. + In the depleted aqueous solution or raffinate. Optionally wash with the extracted Li. + The organic phase of the complex is removed to remove remaining impurities. Typically, the organic phase, which has been optionally washed, is eluted with acid (strip, strip, back-extraction) to remove highly concentrated Li. + The eluent. Finally, Li + The eluted organic phase is regenerated and recycled to the extraction stage.

[0279] For Li + Extraction, the SX method can employ one or more of the following: • Chelating extractants, such as, but not limited to, crown ethers or azacrown ethers or their derivatives. Li + Examples of selective crown ethers include, but are not limited to: 12-crown-4, 13-crown-4, 14-crown-4, 15-crown-4, benzo-12-crown-4, benzo-14-crown-4 and dibenzo-14-crown-4.

[0280] • Neutral extractants, such as, but not limited to, ketones, β-diketones, phosphate esters, or phosphine oxides. Examples of neutral extractants include, but are not limited to: methyl isobutyl ketone (MIBK), 2,6-dimethyl-4-heptanone (DIBK), acetophenone (AP), 2-thiophenecarboxyltrifluoroacetone (TTA), 1-phenyldecane-1,3-dione (LIX 54), 1,3-diphenyl-1,3-propanedione (HDBM), benzoyltrifluoroacetone (BFA), 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP), benzoyl-1,1,1-trifluoroacetone (HBTA), tri-n-butyl phosphate (TBP), triphenylphosphine oxide (TPPO), tri-n-octylphosphine oxide (TOPO), and trialkylphosphine oxide (Cyanex 923).

[0281] • Ionizable extractants, such as compounds having any number of ionizable functional groups, including but not limited to carboxylic acids, phosphoric acids, or amines. Examples of ionizable extractants include, but are not limited to, organophosphates, such as di-(2-ethylhexyl)phosphoric acid (D2EHPA), 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC88A), mono-2-ethylhexylphosphonic acid (MEHPA), and bis-2,4,4-trimethylpentylphosphonic acid (Cyanex 272).

[0282] • Ionic liquids (ILs) — ILs are organic compounds composed of low-melting-point ions. They possess a variety of advantageous solvent properties, including high thermal stability, high selectivity, and high separation efficiency, but with very low volatility. Examples of ILs include, but are not limited to: 1-alkyl-3-methylimidazolium-ILs, such as 1-butyl-3-methylimidazolium hexafluorophosphate (ester) ([C4mim][PF6]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C4mim][Tf2N]), or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C2mim][Tf2N]); tetrabutylammonium bis(2-ethylhexyl)phosphonite (ester) ([N 4444 [BEHP]); Tetrabutylammonium bis(2-ethylhexyl)-phosphate (ester) ([N 4444 [DEHP]); Tetraoctylammonium bis(2-ethylhexyl)-phosphate (ester) ([N 8888 [DEHP]); Tetrabutylammonium mono-2-ethylhexyl (2-ethylhexyl) phosphate (ester) ([N 4444 [EHPMEH]); Tetrabutylammonium 2-ethylhexylhydro-2-ethylhexyl ester ([N 4444 [EHEHP]); Tetrabutylammonium diisooctyl phosphite (ester) ([N 4444 [DICP]); Tetrabutylphosphonium bis(2,4,4-trimethylpentyl)phosphonite (ester) ([P 4444 [BTMPP]); Trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide ([P 66614 [Tf2N]); N-trimethyl-N-butylammonium bis(trifluoromethanesulfonyl)imide ([N 1114 [Tf2N]); 1-Butylpyridinium bis((trifluoromethyl)sulfonyl)imide ([BPy][TF2N]); 1-Butyl-1-methylpiperidinium bis((trifluoromethyl)sulfonyl)imide ([PP 14 [TF2N]); and 1-Butyl-1-methylpyrrolidone bis((trifluoromethyl)sulfonyl)imide ([P 14 [TF2N]).

[0283] The SX method can employ a multi-component system comprising an extractant, a co-extractant, a diluent, or a combination thereof. Examples of extractants include chelating, neutral, and / or ionizable extractants as described herein. Co-extractants can be one or more extractants and / or inorganic compounds as described herein, such as, but not limited to, FeCl3. Non-limiting examples of diluents include aliphatic solvents such as kerosene; aromatic solvents such as xylene; and ionic liquids. Non-limiting examples of multi-component systems include HBTA-TOPO in kerosene, TTA-TOPO, TTA-1,10-phenanthroline in chlorobenzene, TTA-TOPO in m-xylene / MIBK / n-hexane / benzene / chloroform, N,N-bis(2-ethylhexyl)-3-oxobutyramide (NB2EHOTA)-tributyl phosphate (TBP)-FeCl3, dioctyl phthalate (DOP) / acetylated tributyl citrate (ATBC) / tributyl citrate (TBC)-TBP-FeCl3, TBP / MIBK-FeCl3-kerosene, TBP-FeCl3-kerosene, TBP-MIBK-FeCl3, and LIX 54-Cyanex 923.

[0284] Figure 18 An exemplary embodiment of a diaphragm electrolyzer used in a lithium production process is shown, wherein Li is selectively removed from a Li source containing a lithium-containing solution using solvent extraction. The solvent extraction step produces a lithium-loaded solvent, which may optionally undergo a washing step to remove additional impurities. The lithium-loaded solvent is then subjected to an eluent to produce a concentrated lithium-containing salt solution (e.g., LiCl or Li₂SO₄) and regenerate the solvent. The concentrated lithium-containing salt solution is fed into the diaphragm electrolyzer to simultaneously produce LiOH and an acid (e.g., HCl or H₂SO₄). The acid produced by the diaphragm electrolyzer can be used as an eluent to remove Li from the solvent (e.g., as LiCl or Li₂SO₄), thereby regenerating the solvent in step SX. Furthermore, a portion of the LiOH produced by the diaphragm electrolyzer may optionally be exported to a step prior to step SX for precipitation of at least one of calcium and magnesium from the lithium-containing solution. Exemplary steps in this method are shown below: Step 1: Treat the lithium-containing solution with a solvent to extract Li from the lithium-containing solution, thereby forming a lithium-loaded solvent.

[0285] Step 2: Elute the solvent containing the loaded Li using an elution solution (e.g., acid) to produce a concentrated lithium salt solution and regenerate the solvent.

[0286] Step 3: The concentrated lithium salt solution is treated by an electrochemical electrolyzer to produce lithium hydroxide and acid.

[0287] Step 4: The lithium hydroxide is either sold on the market or removed from the process, while the acid is discharged to Step 2 for use as an elution solution.

[0288] It should be understood that in all the above embodiments describing the use of membrane electrolyzers in lithium recovery processes and the GDE described herein, the role of the GDE remains essentially the same across various applications: generating OH from a humidified oxygen / air stream. - Ions. Regardless of the type of salt used as the feed brine (LiCl, Li2SO4, Li3PO4, LiNO3, LiI, NaCl, Na2SO4, Na3PO4, NaNO3, NaI, KCl, K2SO4, K3PO4, KNO3, or KI), the cathode catalyst on the GDE always plays the same role.

[0289] Example Example 1 Using Avcarb with Teflon coating TM MGL370 carbon paper, without MPL, was used as the GDL to prepare the GDE according to this disclosure. This was achieved by mixing 60% platinum / Vulcan XC-72 (60% platinum on Vulcan XC-72, a 60% Vulcan XC-72 carbon-supported platinum catalyst), Fumion... TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was then mixed with PTFE powder at a concentration of 1.5 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0290] Example 2 Using Avcarb with Teflon coating TM MGL370 carbon paper, as a GDL, does not possess MPL, and GDE is prepared according to this disclosure. This is achieved by mixing Pt Black and Fumion. TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was then mixed with 2 mg / cm³ of PTFE powder. 2 The total catalyst loading is applied to the carbon paper.

[0291] Example 3 Toray with Teflon coating TM TGP-H-120 carbon paper, as the GDL, without MPL, is used to prepare the GDE according to this disclosure. This is achieved by mixing 60% platinum / Vulcan XC-72 and Fumion... TM FAA-3 ionomer and UltraflonTM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was then prepared at a concentration of 1.5 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0292] Example 4 The GDE according to this disclosure was prepared using Teflon-modified Zoltek™ Panex PW03 carbon cloth as the GDL, without MPL. This was achieved by mixing 80% platinum / Vulcan XC-72 and Fumion. TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25PTFE powder. The catalyst ink was then prepared at a concentration of 2 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0293] Example 5 Using Avcarb with Teflon coating TM MGL370 carbon paper, as the GDL, without MPL, is used to prepare the GDE according to this disclosure. This is achieved by mixing 40% platinum / Vulcan XC-72 and Fumion... TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was prepared at a concentration of 0.4 mg / cm³. 2 The total catalyst loading is applied to carbon.

[0294] Example 6 Using Avcarb with Teflon coating TM MGL190 carbon paper, as the GDL, without MPL, is used to prepare the GDE according to this disclosure. This is achieved by mixing 40% platinum / Vulcan XC-72 and Fumion... TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was prepared at a concentration of 0.5 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0295] Example 7 Using Sigrette with Teflon coating TM 25BA carbon paper, as the GDL, without MPL, is prepared according to the GDE of this disclosure. This is achieved by mixing 40% platinum / Vulcan XC-72 and Ionomr... TM AP1 was used to prepare catalyst ink. The catalyst ink was prepared at 0.5 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0296] Example 8 Using Sigrette with Teflon coating TM 25BA carbon paper, as the GDL, without MPL, is prepared according to the GDE of this disclosure. This is achieved by mixing 20% ​​platinum / Vulcan XC-72 and Ionomr... TM AP1 was used to prepare catalyst ink. The catalyst ink was prepared at 0.5 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0297] Example 9 Using Avcarb with Teflon coating TM MGL370 carbon paper, as the GDL, without MPL, is used to prepare the GDE according to this disclosure. This is achieved by mixing 60% platinum / Vulcan XC-72 and Fumion... TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was prepared at a concentration of 2.5 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0298] Example 10 Using Avcarb TM MGL370 carbon paper, as the GDL, without MPL, is used to prepare the GDE according to this disclosure. This is achieved by mixing 40% platinum / Vulcan XC-72 and Fumion... TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25 PTFE powder. The catalyst ink was prepared at a concentration of 0.4 mg / cm³. 2 The total catalyst loading is applied to the carbon paper.

[0299] Example 11 Using Freudenberg TM H23C2 carbon paper was used as the GDL, which includes MPL, to prepare the GDE according to this disclosure. A 30wt% Pt / C catalyst coating was applied at 1 mg / cm³. 2 The total catalyst loading is applied to the GDL.

[0300] Example 12 The GDE according to this disclosure was prepared using Zoltek™ Panex PW03 carbon cloth with Teflon coating as the GDL, without MPL. This was achieved by mixing 60% platinum / Vulcan XC-72 and Fumion. TM FAA-3 ionomer and Ultraflon TM Catalyst ink was prepared using MP-25PTFE powder. The catalyst ink was prepared at a concentration of 1.5 mg / cm³.2 The total catalyst loading was applied to one side of the carbon cloth at a rate of 0.5 mg / cm³. 2 The total catalyst loading is applied to the opposite side of the carbon cloth.

[0301] Example 13 Using Sigracet TM 25BA carbon paper, as the GDL, without MPL, is prepared according to this disclosure as a GDE. This is achieved by mixing 60% platinum / Vulcan XC-72 and Fumion. TM Catalyst ink was prepared from FAA-3 ionomer. The catalyst ink was prepared at 0.4 mg / cm³. 2 The total catalyst loading was applied to the carbon paper. Then, a Teflon dispersion was applied on top of the catalyst layer at a loading of 50%.

[0302] Example 14 GDEs according to this disclosure are prepared using Teflon-modified carbon cloth as the GDL, having an MPL. This is achieved by mixing 60% silver / Vulcan XC-72 and Ionomr... TM Catalyst ink was prepared from AP3 ionomer. The catalyst ink was then used at 3 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0303] Example 15 GDEs according to this disclosure are prepared using Teflon-modified carbon cloth as the GDL, having an MPL. This is achieved by mixing 60% platinum / Vulcan XC-72 and Ionomr... TM Catalyst ink was prepared from AP3 ionomer. The catalyst ink was prepared at 1 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0304] Example 16 GDEs according to this disclosure are prepared using Teflon-modified carbon cloth as the GDL, having an MPL. This is achieved by mixing 60% platinum / Vulcan XC-72 and Ionomr... TM Catalyst ink was prepared from AP3 ionomer. The catalyst ink was prepared at 2 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0305] Example 17 GDEs according to this disclosure are prepared using Teflon-modified carbon cloth as the GDL, having an MPL. This is achieved by mixing 40% PtNi (3:1 ratio) / Vulcan XC-72 and Ionomr... TM Catalyst ink was prepared from AP3 ionomer. The catalyst ink was prepared at 1 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0306] Example 18 GDEs according to this disclosure are prepared using Teflon-modified carbon cloth as the GDL, having an MPL. This is achieved by mixing 40% Ni / Vulcan XC-72 and Ionomr... TM Catalyst ink was prepared from AP3 ionomer. The catalyst ink was prepared at 2 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0307] Example 19 GDEs according to this disclosure are prepared using Teflon-modified carbon cloth as the GDL, having an MPL. This is achieved by mixing 40% PtNi (1:1 ratio) / Vulcan XC-72 and Ionomr... TM Catalyst ink was prepared from AP3 ionomer. The catalyst ink was prepared at 1 mg / cm³. 2 The total catalyst loading is applied to the carbon cloth.

[0308] Example 20 The GDEs of Examples 1 to 19 were prepared and tested as oxygen depolarization cathodes in a multi-chamber membrane electrolyzer as described herein to produce an alkaline product (e.g., LiOH) from a salt solution (e.g., LiCl or Li2SO4). A current was obtained when a voltage was applied to the GDEs of Examples 1 to 19.

[0309] Example 21 By mixing Ionomr in a solvent TM Anion-exchange ionomers are used to prepare a coating mixture to prepare a membrane-coated GDE according to this disclosure. The coating mixture is applied to the GDE (e.g., comprising Teflon-modified carbon cloth as the GDL, having an MPL, and having a coating density of 1 mg / cm³) using a doctor blade method. 2 The total catalyst loading was applied to the Pt catalyst ink of the carbon cloth (GDE). The coating mixture was cured to form a membrane-coated GDE. In particular, three membrane-coated GDEs with membrane thicknesses of (i) 30 μm, (ii) 40 μm and (iii) 60 μm were prepared.

[0310] The three membrane-coated GDEs described above were tested as oxygen depolarization cathodes in a multi-compartment membrane electrolyzer described herein for producing alkaline products (e.g., LiOH) from salt solutions (e.g., LiCl or Li₂SO₄). Current was obtained when a voltage was applied to each of the three membrane-coated GDEs. It was observed that for a given voltage requirement at a specific current density, thinner coatings resulted in better performance. The membrane-coated GDEs also performed better than the control GDEs hot-pressed onto anion exchange membranes.

[0311] Example 22 By (i) pressing Ionomr with a pattern template under heat and pressure TM (ii) The anion exchange membrane (AEM) is subjected to a certain period of time to form a textured membrane, and the textured AEM is disposed on the GDE to form an MEA with a textured membrane, thereby preparing an MEA with a textured membrane according to the present disclosure.

[0312] The textured membrane MEA described above was used as the oxygen depolarization cathode in a multi-chamber membrane electrolyzer described herein to test the production of alkaline products (e.g., LiOH) from a salt solution (e.g., LiCl or Li₂SO₄). A current was obtained when a voltage was applied to the MEA. It was observed that, for a specific voltage requirement at a given current density, the textured membrane MEA performed better than the smooth membrane MEA.

[0313] Example 23 GDEs having an MPL according to the present disclosure were prepared by coating a GDL with an MPL formulation comprising equal parts of Teflon and carbon powder in a solvent by weight. After the MPL coating was applied to the GDL, a drying step was performed, and then a catalyst layer was applied. Several GDEs were prepared by mixing the MPL formulation using different methods (e.g., stirring, sonication, or homogenization).

[0314] Using the aforementioned GDE with MPL as an oxygen depolarization cathode, tests were conducted in a multi-chamber membrane electrolyzer described herein to produce alkali products (e.g., LiOH) from a salt solution (e.g., LiCl or Li₂SO₄). Current was obtained when a voltage was applied to the GDE with MPL. It was observed that the mixing method affected the viscosity of the MPL formulation. Furthermore, based on the mixing method, the GDE had different voltage requirements for specific current densities. However, regardless of the mixing method, the GDE with MPL generally exhibited better performance than commercially available GDEs.

[0315] Several non-limiting aspects of the present invention can be summarized as follows: Aspect 1. A gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer.

[0316] Aspect 2. The gas diffusion electrode according to aspect 1, wherein the catalyst layer is disposed on the surface of the gas diffusion layer.

[0317] Aspect 3. The gas diffusion electrode according to aspect 1 further includes a microporous layer disposed on the surface of the gas diffusion layer, wherein the catalyst layer is disposed on the surface of the microporous layer opposite to the gas diffusion layer.

[0318] Aspect 4. The gas diffusion electrode according to aspect 3, wherein the microporous layer comprises carbon black and a hydrophobic polymer.

[0319] Aspect 5. The gas diffusion electrode according to aspect 4, wherein the microporous layer comprises 50 wt% to 95 wt% carbon black and 5 wt% to 50 wt% hydrophobic polymer.

[0320] Aspect 6. A gas diffusion electrode according to any one of Aspects 1 to 5, wherein the gas diffusion layer comprises carbon fiber paper, carbon cloth, carbon felt, carbon foam, metal mesh, metal foam or any combination thereof.

[0321] Aspect 7. A gas diffusion electrode according to any one of Aspects 1 to 6, wherein the gas diffusion layer is modified with a hydrophobic polymer.

[0322] Aspect 8. The gas diffusion electrode according to aspect 7, wherein the hydrophobic polymer is polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene propylene, perfluoropolyether, polydimethylsiloxane, or any combination thereof.

[0323] Aspect 9. The gas diffusion electrode according to aspect 7 or 8, wherein the gas diffusion layer comprises 0.01 wt% to 50 wt% of a hydrophobic polymer.

[0324] Aspect 10. A gas diffusion electrode according to any one of Aspects 1 to 9, wherein the gas diffusion layer has a thickness of 50 μm to 1000 μm.

[0325] Aspect 11. A gas diffusion electrode according to any one of Aspects 1 to 10, wherein the gas diffusion layer has a porosity of 50% to 95%.

[0326] Aspect 12. A gas diffusion electrode according to any one of Aspects 1 to 11, wherein the catalyst layer comprises a catalyst and an ionomer.

[0327] Aspect 13. The gas diffusion electrode according to aspect 12, wherein the catalyst layer has an ionomer to catalyst ratio of 1:1 to 1:20.

[0328] Aspect 14. The gas diffusion electrode according to aspect 12 or 13, wherein the catalyst layer further includes a binder.

[0329] Aspect 15. The gas diffusion electrode according to aspect 14, wherein the binder is PTFE.

[0330] Aspect 16. The gas diffusion electrode according to aspect 14 or 15, wherein the catalyst layer comprises 0.01 wt% to 40 wt% binder.

[0331] Aspect 17. A gas diffusion electrode according to any one of Aspects 12 to 16, wherein the catalyst is a metal, a nonmetal, or a combination thereof.

[0332] Aspect 18. The gas diffusion electrode according to aspect 17, wherein the metal is a transition metal, a post-transition metal, a metalloid, or a combination thereof or an alloy thereof.

[0333] Aspect 19. The gas diffusion electrode according to aspect 17, wherein the nonmetal is carbon, a conductive polymer, or a combination thereof.

[0334] Aspect 20. A gas diffusion electrode according to any one of Aspects 12 to 19, wherein the ionomer is an anion-exchange ionomer.

[0335] Aspect 21. The gas diffusion electrode according to aspect 20, wherein the anion exchange ionomer is Fumion TM FAA-3, Ionomr TM Sustainion®, Orion, Pention™, or PiperION anion exchange polymers.

[0336] Aspect 22. A gas diffusion electrode according to any one of Aspects 12 to 21, wherein the catalyst layer comprises 5 wt% to 45 wt% ionomer.

[0337] Aspect 23. A gas diffusion electrode according to any one of Aspects 1 to 22, wherein the catalyst layer has a thickness of 1 μm to 100 μm.

[0338] Aspect 24. A gas diffusion electrode according to any one of Aspects 1 to 23, wherein the catalyst layer has a porosity of 30% to 75%.

[0339] Aspect 25. A gas diffusion electrode according to any one of aspects 1 to 24, wherein the gas diffusion electrode is according to GDE embodiments 1 to 896 or any one of 1a-896a as described herein.

[0340] Aspect 26. The gas diffusion electrode according to any one of aspects 1 to 25 further includes a raised and / or recessed embossed pattern on at least one surface.

[0341] Aspect 27. The gas diffusion electrode according to any one of aspects 1 to 25 further includes an anion exchange membrane disposed on the surface of the catalyst layer, the anion exchange membrane being configured to exchange ions from the catalyst layer to the opposite surface of the anion exchange membrane.

[0342] Aspect 28. The gas diffusion electrode according to aspect 27, wherein the anion exchange membrane comprises a polymer having at least one positively charged cationic group bonded to at least a portion of the polymer backbone.

[0343] Aspect 29. The gas diffusion electrode according to Aspect 28, wherein the polymer comprises polyalkylene, polyfluorene, poly(arylene ether), polysulfone, poly(arylene ether sulfone), polyether ketone, polyetherimide, poly(ether oxadiazole), polyphenylene ether, poly(vinyl benzyl), polyphenylene, perfluoropolymer, polybenzimidazole, polystyrene, or polyphosphazene.

[0344] Aspect 30. According to aspect 28 or 29, the gas diffusion electrode wherein the positively charged cation group is a primary ammonium, secondary ammonium, tertiary ammonium or quaternary ammonium, heterocyclic cation, guanidine, phosphonium, sulfonium or metal cation.

[0345] Aspect 31. A gas diffusion electrode according to any one of Aspects 27 to 30, wherein the anion exchange membrane is Fumasep TM Neosepta TM Orion TM Xergy Xion Pention TM PiperION TM Ralex TM Sustanion TM Or Ionomr TM Anion exchange membrane.

[0346] Aspect 32. The gas diffusion electrode according to any one of aspects 27 to 31 further includes a raised and / or recessed embossed pattern on at least one surface.

[0347] Aspect 33. A diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 1 to 26; a cation exchange membrane disposed between the anode chamber and a catalyst layer of the gas diffusion electrode, the cation exchange membrane being configured to exchange ions received from the anode onto the opposing surface of the cation exchange membrane; an inlet through which a salt solution is received into the anode chamber; a gas inlet through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which a product of the salt solution is discharged from the interior of the diaphragm electrolyzer.

[0348] Aspect 34. A diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 1 to 26; an anion exchange membrane disposed on a catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the anion exchange membrane and enter the alkali generation chamber; a cation exchange membrane disposed between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an inlet through which a salt solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which a product is discharged from the interior of the diaphragm electrolyzer.

[0349] Aspect 35. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber and a salt-depleting chamber located between the cathode chamber and the anode chamber, the alkali-generating chamber being located between the cathode chamber and the salt-depleting chamber, and the salt-depleting chamber being located between the alkali-generating chamber and the anode chamber; an anode positioned extending inside the diaphragm electrolyzer and positioned in the anode chamber; a cathode positioned extending inside the diaphragm electrolyzer and positioned in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 1 to 26; a first anion exchange membrane disposed on a catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode into the first anion exchange membrane. A relative surface enters the alkali generation chamber; a cation exchange membrane, located between the salt depletion chamber and the alkali generation chamber, configured to exchange ions received from the salt depletion chamber onto the relative surface of the cation exchange membrane entering the alkali generation chamber; a second anion exchange membrane, located between the salt depletion chamber and the anode chamber, configured to exchange ions received from the salt depletion chamber onto the relative surface of the second anion exchange membrane entering the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which an O2-containing gas is introduced to contact a gas diffusion electrode; and at least one outlet through which the product is discharged from the interior of the membrane electrolyzer.

[0350] Aspect 36. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber, a salt-depleting chamber, and an acid-generating chamber located between the cathode chamber and the anode chamber, the alkali-generating chamber being located between the cathode chamber and the salt-depleting chamber, the salt-depleting chamber being located between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being located between the salt-depleting chamber and the anode chamber; an anode positioned extending inside the diaphragm electrolyzer and located in the anode chamber; a cathode positioned extending inside the diaphragm electrolyzer and located in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 1 to 26; a first anion exchange membrane disposed on a catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode onto the opposite surface of the first anion exchange membrane and into the alkali-generating chamber; and a first cation exchange membrane located in the salt-depleting chamber. Between the salt depletion chamber and the acid generation chamber, the cation exchange membrane is configured to exchange ions received from the salt depletion chamber onto its opposite surface to enter the salt generation chamber; a second anion exchange membrane is located between the salt depletion chamber and the acid generation chamber, and is configured to exchange ions received from the salt depletion chamber onto its opposite surface to enter the acid generation chamber; a second cation exchange membrane is located between the acid generation chamber and the anode chamber, and is configured to exchange ions received from the anode chamber onto its opposite surface to enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which O2-containing gas is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0351] Aspect 37. A method for producing an alkaline product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 33; and discharging the alkaline product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in the anode chamber; the positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the cathode chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions combine with positive salt ions to produce an alkaline product; and the alkaline product is discharged from the cathode chamber.

[0352] Aspect 38. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 34; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in the anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate through the anion exchange membrane to the opposite surface of the anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce an alkali product; and the alkali product is discharged from the alkali generation chamber.

[0353] Aspect 39. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 35; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into the salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate through the first anion exchange membrane to the opposite surface of the first anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce an alkali product; and the alkali product is discharged from the alkali generation chamber.

[0354] Aspect 40. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 36; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into the salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate through the first anion exchange membrane to the opposite surface of the first anion exchange membrane and enter the alkali generation chamber; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce an alkali product; and the alkali product is discharged from the alkali generation chamber.

[0355] Aspect 41. A gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst-coated membrane comprising a catalyst layer disposed on the surface of the membrane.

[0356] Aspect 42. The gas diffusion electrode according to aspect 41, wherein the membrane is an anion exchange membrane.

[0357] Aspect 43. The gas diffusion electrode according to aspect 42, wherein the anion exchange membrane comprises a polymer having at least one positively charged cationic group bonded to at least a portion of the polymer backbone.

[0358] Aspect 44. The gas diffusion electrode according to aspect 43, wherein the polymer comprises polyalkylene, polyfluorene, poly(arylene ether), polysulfone, poly(arylene ether sulfone), polyether ketone, polyetherimide, poly(ether oxadiazole), polyphenylene ether, poly(vinyl benzyl), polyphenylene, perfluoropolymer, polybenzimidazole, polystyrene, or polyphosphazene.

[0359] Aspect 45. According to aspect 43 or 44, the gas diffusion electrode wherein the positively charged cation group is a primary ammonium, secondary ammonium, tertiary ammonium or quaternary ammonium, heterocyclic cation, guanidinium, phosphonium, sulfonium or metal cation.

[0360] Aspect 46. A gas diffusion electrode according to any one of Aspects 42 to 45, wherein the anion exchange membrane is Fumasep TM Neosepta TM Orion TM Xergy Xion Pention TM PiperION TM Ralex TM Sustanion TM Or Ionomr TM Anion exchange membrane.

[0361] Aspect 47. A gas diffusion electrode according to any one of aspects 41 to 46, wherein the gas diffusion layer is in contact with the catalyst layer of a catalyst-coated film.

[0362] Aspect 48. The gas diffusion electrode according to any one of aspects 41 to 46 further includes a microporous layer disposed on the surface of the gas diffusion layer, wherein the microporous layer is in contact with the catalyst layer of the catalyst-coated membrane.

[0363] Aspect 49. The gas diffusion electrode according to aspect 48, wherein the microporous layer comprises carbon black and a hydrophobic polymer.

[0364] Aspect 50. The gas diffusion electrode according to aspect 48 or 49, wherein the microporous layer comprises 50 wt% to 95 wt% carbon black and 5 wt% to 50 wt% hydrophobic polymer.

[0365] Aspect 51. A gas diffusion electrode according to any one of Aspects 41 to 50, wherein the gas diffusion layer comprises carbon fiber paper, carbon cloth, carbon felt, carbon foam, metal mesh, metal foam or any combination thereof.

[0366] Aspect 52. A gas diffusion electrode according to any one of aspects 41 to 51, wherein the gas diffusion layer is modified with a hydrophobic polymer.

[0367] Aspect 53. The gas diffusion electrode according to aspect 52, wherein the hydrophobic polymer is polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene propylene, perfluoropolyether, polydimethylsiloxane, or any combination thereof.

[0368] Aspect 54. The gas diffusion electrode according to aspect 52 or 53, wherein the gas diffusion layer comprises 0.01 wt% to 50 wt% of a hydrophobic polymer.

[0369] Aspect 55. A gas diffusion electrode according to any one of aspects 41 to 54, wherein the gas diffusion layer has a thickness of 50 μm to 1000 μm.

[0370] Aspect 56. A gas diffusion electrode according to any one of aspects 41 to 55, wherein the gas diffusion layer has a porosity of 50% to 95%.

[0371] Aspect 57. A gas diffusion electrode according to any one of aspects 41 to 56, wherein the catalyst layer comprises a catalyst and an ionomer.

[0372] Aspect 58. The gas diffusion electrode according to aspect 57, wherein the catalyst layer has an ionomer to catalyst ratio of 1:1 to 1:20.

[0373] Aspect 59. The gas diffusion electrode according to aspect 57 or 58, wherein the catalyst layer further includes a binder.

[0374] Aspect 60. Gas diffusion electrode according to aspect 59, wherein the binder is PTFE.

[0375] Aspect 61. The gas diffusion electrode according to aspect 59 or 60, wherein the catalyst layer comprises 0.01 wt% to 40 wt% binder.

[0376] Aspect 62. A gas diffusion electrode according to any one of Aspects 57 to 61, wherein the catalyst is a metal, a nonmetal, or a combination thereof.

[0377] Aspect 63. The gas diffusion electrode according to aspect 62, wherein the metal is a transition metal, a post-transition metal, a metalloid, or a combination thereof or an alloy thereof.

[0378] Aspect 64. The gas diffusion electrode according to aspect 62, wherein the nonmetal is carbon, a conductive polymer, or a combination thereof.

[0379] Aspect 65. A gas diffusion electrode according to any one of Aspects 57 to 64, wherein the ionomer is an anion-exchange ionomer.

[0380] Aspect 66. The gas diffusion electrode according to aspect 65, wherein the anion exchange ionomer is Fumion TM FAA-3, Ionomr TM , Sustainion®, Orion, Pention TM Or PiperION anion exchange polymer.

[0381] Aspect 67. A gas diffusion electrode according to any one of aspects 57 to 66, wherein the catalyst layer comprises 5 wt% to 45 wt% ionomer.

[0382] Aspect 68. A gas diffusion electrode according to any one of aspects 41 to 67, wherein the catalyst layer has a thickness of 1 μm to 100 μm.

[0383] Aspect 69. A gas diffusion electrode according to any one of Aspects 41 to 68, wherein the catalyst layer has a porosity of 30% to 75%.

[0384] Aspect 70. A gas diffusion electrode according to any one of aspects 41 to 69, wherein the gas diffusion electrode is according to GDE embodiments 1 to 896 or any one of 1a-896a as described herein.

[0385] Aspect 71. The gas diffusion electrode according to any one of aspects 41 to 70 further includes a raised and / or recessed embossed pattern on at least one surface.

[0386] Aspect 72. A diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 41 to 71; a cation exchange membrane positioned between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposing surface of the cation exchange membrane and enter the alkali generation chamber; an inlet through which a salt solution is received into the anode chamber; a gas inlet positioned in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the diaphragm electrolyzer.

[0387] Aspect 73. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber and a salt-depleting chamber located between the cathode chamber and the anode chamber, the alkali-generating chamber being located between the cathode chamber and the salt-depleting chamber, and the salt-depleting chamber being located between the alkali-generating chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and positioned in the cathode chamber, comprising a gas diffusion electrode as defined in any one of aspects 41 to 71; and a cation exchange membrane located between the salt-depleting chamber and the alkali-generating chamber. A cation exchange membrane is configured to exchange ions received from the salt depletion chamber onto the opposite surface of the cation exchange membrane and into the alkali generation chamber; an anion exchange membrane is located between the salt depletion chamber and the anode chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane and into the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0388] Aspect 74. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber, a salt-depleting chamber, and an acid-generating chamber disposed between the cathode chamber and the anode chamber, the alkali-generating chamber being disposed between the cathode chamber and the salt-depleting chamber, the salt-depleting chamber being disposed between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being disposed between the salt-depleting chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and positioned in the cathode chamber, comprising a gas diffusion electrode as defined in any one of aspects 41 to 71; a first cation exchange membrane disposed between the salt-depleting chamber and the alkali-generating chamber, the cation exchange membrane being configured to exchange ions received from the salt-depleting chamber to the anode chamber. The opposite surface of an ion exchange membrane enters the alkali generation chamber; an anion exchange membrane is located between the salt depletion chamber and the acid generation chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane to enter the acid generation chamber; a second cation exchange membrane is located between the acid generation chamber and the anode chamber, the second cation exchange membrane being configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane to enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0389] Aspect 75. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 72; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in the anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate into the alkali generation chamber through the catalyst-coated membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and alkali products are discharged from the alkali generation chamber.

[0390] Aspect 76. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 73; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into the salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate into the base generation chamber through a catalyst-coated exchange membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and alkali products are discharged from the alkali generation chamber.

[0391] Aspect 77. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 74; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into the salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the first cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate into the alkali generation chamber through the catalyst-coated membrane; OH- - Ions combine with positive salt ions in the alkali generation chamber to produce alkali products; and alkali products are discharged from the alkali generation chamber.

[0392] Aspect 78. A gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer disposed on the gas diffusion layer, wherein the catalyst layer has an optimized thickness such that liquid reactants are substantially or completely consumed before diffusing through the catalyst layer to reach the gas diffusion layer.

[0393] Aspect 79. The gas diffusion electrode according to aspect 78, wherein the gas diffusion layer comprises carbon fiber paper, carbon cloth, carbon felt, carbon foam, metal mesh, metal foam or any combination thereof.

[0394] Aspect 80. The gas diffusion electrode according to aspect 78 or 79, wherein the gas diffusion layer is modified with a hydrophobic polymer.

[0395] Aspect 81. The gas diffusion electrode according to aspect 80, wherein the hydrophobic polymer is polytetrafluoroethylene, polyvinylidene fluoride, fluorinated ethylene propylene, perfluoropolyether, polydimethylsiloxane or any combination thereof.

[0396] Aspect 82. The gas diffusion electrode according to aspect 80 or 81, wherein the gas diffusion layer comprises 0.01 wt% to 50 wt% of a hydrophobic polymer.

[0397] Aspect 83. A gas diffusion electrode according to any one of aspects 78 to 82, wherein the gas diffusion layer has a thickness of 50 μm to 1000 μm.

[0398] Aspect 84. A gas diffusion electrode according to any one of aspects 78 to 83, wherein the gas diffusion layer has a porosity of 50% to 95%.

[0399] Aspect 85. A gas diffusion electrode according to any one of aspects 78 to 84, wherein the catalyst layer comprises a catalyst and an ionomer.

[0400] Aspect 86. The gas diffusion electrode according to aspect 85, wherein the catalyst layer has an ionomer to catalyst ratio of 1:1 to 1:20.

[0401] Aspect 87. The gas diffusion electrode according to aspect 85 or 86, wherein the catalyst layer further includes a binder.

[0402] Aspect 88. The gas diffusion electrode according to aspect 87, wherein the binder is PTFE.

[0403] Aspect 89. Gas diffusion electrode according to aspect 87 or 88, wherein the catalyst layer comprises 0.01 wt% to 40 wt% binder.

[0404] Aspect 90. A gas diffusion electrode according to any one of aspects 85 to 89, wherein the catalyst is a metal, a nonmetal, or a combination thereof.

[0405] Aspect 91. The gas diffusion electrode according to aspect 90, wherein the metal is a transition metal, a post-transition metal, a metalloid, or a combination thereof or an alloy thereof.

[0406] Aspect 92. The gas diffusion electrode according to aspect 90, wherein the nonmetal is carbon, a conductive polymer, or a combination thereof.

[0407] Aspect 93. A gas diffusion electrode according to any one of aspects 85 to 92, wherein the ionomer is an anion-exchange ionomer.

[0408] Aspect 94. The gas diffusion electrode according to aspect 93, wherein the anion exchange ionomer is Fumion. TM FAA-3, Ionomr TM , Sustainion®, Orion, Pention TM Or PiperION anion exchange polymer.

[0409] Aspect 95. A gas diffusion electrode according to any one of aspects 85 to 94, wherein the catalyst layer comprises 5 wt% to 45 wt% ionomer.

[0410] Aspect 96. A gas diffusion electrode according to any one of Aspects 78 to 95, wherein the catalyst layer has a thickness of 1 μm to 100 μm.

[0411] Aspect 97. A gas diffusion electrode according to any one of aspects 78 to 96, wherein the catalyst layer has a porosity of 30% to 75%.

[0412] Aspect 98. A gas diffusion electrode according to any one of aspects 78 to 97, wherein the gas diffusion electrode is according to GDE embodiments 1 to 896 or any one of 1a to 896a as described herein.

[0413] Aspect 99. The gas diffusion electrode according to any one of aspects 78 to 98 further includes a raised and / or recessed embossed pattern on at least one surface.

[0414] Aspect 100. A diaphragm electrolyzer for processing a salt solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber forming a single chamber together with the cathode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 78 to 99; a cation exchange membrane located between the anode chamber and the alkali generation chamber, the cation exchange membrane being configured to exchange ions received from the anode onto the opposing surface of the cation exchange membrane and enter the alkali generation chamber; an inlet through which a salt solution is received into the anode chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact the gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the diaphragm electrolyzer.

[0415] Aspect 101. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber forming a single chamber together with the cathode chamber; a salt-depletion chamber located between the cathode chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending into and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and positioned in the cathode chamber, comprising a gas diffusion electrode as defined in any one of Aspects 78 to 99; and a cation exchange membrane located between the salt-depletion chamber and the alkali-generating chamber, the cation exchange membrane being configured to transfer salt from the salt-depletion chamber to the alkali-generating chamber. Ions received in the salt depletion chamber are exchanged onto the opposite surface of the cation exchange membrane and enter the alkali generation chamber; an anion exchange membrane is located between the salt depletion chamber and the anode chamber, the anion exchange membrane being configured to exchange ions received in the salt depletion chamber onto the opposite surface of the anion exchange membrane and enter the anode chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which a gas containing O2 is introduced to contact a gas diffusion electrode; and at least one outlet through which the product is discharged from the interior of the membrane electrolyzer.

[0416] Aspect 102. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali-generating chamber forming a single chamber together with the cathode chamber; a salt-depletion chamber and an acid-generating chamber located between the cathode chamber and the anode chamber, the salt-depletion chamber being located between the alkali-generating chamber and the acid-generating chamber, and the acid-generating chamber being located between the salt-depletion chamber and the anode chamber; an anode positioned inside the diaphragm electrolyzer and extending and located in the anode chamber; a cathode positioned inside the diaphragm electrolyzer and extending and located in the cathode chamber, comprising a gas diffusion electrode as defined in any one of aspects 78 to 99; a first cation exchange membrane located between the salt-depletion chamber and the alkali-generating chamber, the cation exchange membrane being configured to exchange ions received from the salt-depletion chamber into the cation exchange membrane. The membrane's opposite surface enters the alkali generation chamber; an anion exchange membrane is located between the salt depletion chamber and the acid generation chamber, the anion exchange membrane being configured to exchange ions received from the salt depletion chamber onto the opposite surface of the anion exchange membrane to enter the acid generation chamber; a second cation exchange membrane is located between the acid generation chamber and the anode chamber, the second cation exchange membrane being configured to exchange ions received from the anode chamber onto the opposite surface of the second cation exchange membrane to enter the acid generation chamber; an inlet through which a salt-containing solution is received into the salt depletion chamber; a gas inlet located in the cathode chamber through which O2-containing gas is introduced to contact a gas diffusion electrode; and at least one outlet through which products are discharged from the interior of the membrane electrolyzer.

[0417] Aspect 103. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 100; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received in the anode chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer to the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce an alkali product; and the alkali product is discharged from the diaphragm electrolyzer.

[0418] Aspect 104. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 101; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into the salt depletion chamber; positive salt ions migrate through a cation exchange membrane to the opposite surface of the cation exchange membrane and enter the alkali generation chamber; and the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer to the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce an alkali product; and the alkali product is discharged from the diaphragm electrolyzer.

[0419] Aspect 105. A method for producing an alkali product, the method comprising the steps of: receiving a salt solution containing positive and negative salt ions and a gas containing O2 in a diaphragm electrolyzer as defined in aspect 102; and discharging the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt solution is received into the salt depletion chamber; positive salt ions migrate through a first cation exchange membrane to the opposite surface of the first cation exchange membrane and enter the alkali generation chamber; the gas containing O2 is reduced at the cathode to form OH-. - ;OH - Ions migrate through the catalyst layer to the base generation chamber; OH - Ions combine with positive salt ions in the alkali generation chamber to produce an alkali product; and the alkali product is discharged from the diaphragm electrolyzer.

[0420] Aspect 106. A gas diffusion electrode for a membrane electrolyzer, the gas diffusion electrode comprising: a first gas diffusion layer for diffusing oxygen-containing gas; a catalyst layer disposed on a surface of the first gas diffusion layer; a second gas diffusion layer in contact with the surface of the catalyst layer opposite to the first gas diffusion layer; and an ionomer layer disposed on a surface of an anion exchange membrane, the ionomer layer being in contact with the surface of the second gas diffusion layer opposite to the catalyst layer.

[0421] Aspect 107. The gas diffusion electrode according to aspect 106 further includes a microporous layer disposed on the surface of the second gas diffusion layer, wherein the microporous layer is in contact with the surface of the catalyst layer opposite to the first gas diffusion layer.

[0422] Aspect 108. A method for producing LiOH from a Li source, the method comprising the steps of: (a) contacting the Li source with a solvent to remove lithium from the Li source, thereby obtaining a lithium-loaded solvent; (b) contacting the lithium-loaded solvent with a stripping agent to regenerate the solvent and produce a salt solution containing lithium ions and negative salt ions; (c) receiving the salt solution and a gas containing O2 in a diaphragm electrolyzer; and (d) exporting LiOH and / or acid from the diaphragm electrolyzer.

[0423] Aspect 109. The method according to aspect 108, wherein the salt-containing solution contains LiCl or Li2SO4.

[0424] Aspect 110. The method according to aspect 108, wherein the acid is HCl or H2SO4.

[0425] Aspect 111. The method according to any one of Aspects 108 to 110, wherein the solvent comprises one or more of a chelating extractant, a neutral extractant, an ionizable extractant, and an ionic liquid.

[0426] Aspect 112. The method according to any one of Aspects 108 to 110, wherein the solvent comprises a multi-component system comprising an extractant, a co-extractant, a diluent, or a combination thereof.

[0427] Aspect 113. The method according to any one of aspects 108 to 112 further includes the step of purifying the lithium-loaded solvent by exposing it to a washing solution before contacting the solvent with the stripping agent.

[0428] Aspect 114. The method according to any one of aspects 108 to 113 further includes feeding a portion of the acid derived in step (d) into step (b) for use as a stripping agent.

[0429] Aspect 115. The method according to any one of aspects 108 to 114 further includes precipitating at least one of calcium and magnesium from the Li source.

[0430] Aspect 116. The method according to aspect 115 further includes feeding a portion of the LiOH derived in step (d) into the step of precipitating at least one of calcium and magnesium from the Li source.

[0431] Aspect 117. A diaphragm-coated gas diffusion electrode for use in a diaphragm electrolyzer, the diaphragm-coated gas diffusion electrode comprising: a gas diffusion electrode including a gas diffusion layer for diffusing oxygen-containing gas and a catalyst layer; and an anion exchange membrane coated on the gas diffusion electrode.

[0432] Aspect 118. A method for preparing a diaphragm-coated gas diffusion electrode, the method comprising: mixing an ionomer into a solvent to prepare a coating mixture; applying the coating mixture to a gas diffusion electrode and curing it to form a diaphragm-coated gas diffusion electrode.

[0433] Aspect 119. The method according to aspect 118, wherein the ionomer comprises Fumion TM Ionomer, Ionomr TM Ionic polymers, Sustainion® ionomers, Orion ionomers, Pention TM Isopolymers or PiperION ionomers.

[0434] Aspect 120. The method according to aspect 118 or 119, wherein the solvent comprises ethanol.

[0435] Aspect 121. The method according to any one of Aspects 118 to 120, wherein the ionomer is mixed in the solvent at a concentration of 2 to 15 wt%.

[0436] Aspect 122. The method according to any one of Aspects 118 to 121, wherein the gas diffusion electrode includes a gas diffusion layer for diffusing oxygen-containing gas; and a catalyst layer.

[0437] Aspect 123. The method according to any one of aspects 118 to 122, wherein the coating mixture has a thickness of 20 μm to 100 μm.

[0438] Aspect 124. The method according to any one of Aspects 118 to 123, wherein curing is carried out at a temperature between 50°C and 140°C.

[0439] In this disclosure, all terms referred to in the singular form are intended to encompass their plural forms. Similarly, all terms referred to in the plural form are intended to encompass their singular forms. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0440] As used herein, the term “about” means a deviation of approximately + / - 10% from a given value. It should be understood that these variations are always included in any given value provided herein, whether specifically mentioned or not.

[0441] It should be understood that if a composition and method are described as “comprising,” “containing,” or “including” multiple components or steps, then the composition and method may also “consist substantially of” or “composed of” multiple components and steps. Furthermore, the indefinite articles “a” or “an” used in the claims are defined herein as indicating one or more elements introduced therein.

[0442] For the sake of brevity, this document only explicitly discloses certain ranges. However, a range from any lower limit can be combined with any upper limit to enumerate ranges not explicitly listed, and a range from any lower limit can be combined with any other lower limit to enumerate ranges not explicitly listed, just as a range from any upper limit can be combined with any other upper limit to enumerate ranges not explicitly listed. Furthermore, whenever a range of values ​​with lower and upper limits is disclosed, any value within that range and any range included therein is specifically disclosed. Specifically, each range of values ​​disclosed herein (in the form of “from about a to about b,” or equivalently, “from about a to b,” or equivalently, “from about ab”) should be understood as listing every value and range encompassed within a wider range of values, even if not explicitly listed. Thus, each point or individual value can be used as its own lower or upper limit, combined with any other point or individual value or any other lower or upper limit to enumerate ranges not explicitly listed.

[0443] Therefore, this disclosure is well adapted to achieve the stated objects and advantages, as well as those inherent therein. The specific embodiments disclosed above are merely illustrative, as this disclosure can be modified and practiced in different but equivalent ways, as will be apparent to those skilled in the art who benefit from the teachings herein. Although individual embodiments have been discussed, this disclosure covers all combinations of all such embodiments. Furthermore, no limitation is intended to be made on the details of the constructions or designs shown herein, except as described in the following claims. Moreover, the terms in the claims have their simple, general meanings unless otherwise explicitly and clearly defined by the patentee. Therefore, it is apparent that the specific illustrative embodiments disclosed above can be changed or modified, and all such variations are considered to be within the scope and spirit of this disclosure. If there is any conflict in the use of words or terms in this specification and in one or more patents or other documents that may be referenced herein, the definitions consistent with this specification shall prevail.

[0444] Based on this disclosure, those skilled in the art will conceive of numerous obvious variations of the embodiments described herein. These obvious variations are within the full scope of the appended claims.

Claims

1. A gas diffusion electrode for use in a diaphragm electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer to diffuse an oxygen-containing gas; and a catalyst layer.

2. A diaphragm electrolyzer for treating a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an anode positioned within an interior of the diaphragm electrolyzer and positioned in the anode chamber; a cathode comprising a gas diffusion electrode as defined in claim 1, the cathode positioned within the interior of the diaphragm electrolyzer and positioned in the cathode chamber; a cation exchange membrane interposed between the anode chamber and the catalyst layer of the gas diffusion electrode, the cation exchange membrane configured to exchange ions received from the anode to an opposite surface of the cation exchange membrane; an inlet through which the salt-containing solution is received into the anode chamber; a gas inlet through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which a product of a salt solution is expelled from the interior of the diaphragm electrolyzer.

3. A diaphragm electrolyzer for treating a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber interposed between the cathode chamber and the anode chamber; an anode positioned within an interior of the diaphragm electrolyzer and positioned in the anode chamber; a cathode comprising a gas diffusion electrode as defined in claim 1, the cathode positioned within the interior of the diaphragm electrolyzer and positioned in the cathode chamber; an anion exchange membrane disposed on the catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposite surface of the anion exchange membrane into the alkali generation chamber; a cation exchange membrane interposed between the anode chamber and the alkali generation chamber, the cation exchange membrane configured to exchange ions received from the anode to an opposite surface of the cation exchange membrane into the alkali generation chamber; an inlet through which the salt-containing solution is received into the anode chamber; a gas inlet positioned in the cathode chamber through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which a product is expelled from the interior of the diaphragm electrolyzer.

4. A diaphragm electrolyzer for treating a salt-containing solution, the diaphragm electrolyzer comprising: an anode chamber; a cathode chamber; an alkali generation chamber and a salt depletion chamber interposed between the cathode chamber and the anode chamber, the alkali generation chamber interposed between the cathode chamber and the salt depletion chamber and the salt depletion chamber interposed between the alkali generation chamber and the anode chamber; an anode positioned within an interior of the diaphragm electrolyzer and positioned in the anode chamber; a cathode comprising a gas diffusion electrode as defined in claim 1, the cathode positioned within the interior of the diaphragm electrolyzer and positioned in the cathode chamber; ​ ​ a first anion exchange membrane disposed on a catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposite surface of the first anion exchange membrane into the base generation compartment; a cation exchange membrane interposed between the salt depletion compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the cation exchange membrane into the base generation compartment; a second anion exchange membrane interposed between the salt depletion compartment and the anode compartment, the second anion exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the second anion exchange membrane into the anode compartment; an inlet through which the salt containing solution is received into the salt depletion compartment; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which products are expelled from an interior of the membrane electrolysis cell.

5. A membrane electrolysis cell for processing a salt containing solution, the membrane electrolysis cell comprising: an anode compartment; a cathode compartment; a base generation compartment, a salt depletion compartment, and an acid generation compartment interposed between the cathode compartment and the anode compartment, the base generation compartment interposed between the cathode compartment and the salt depletion compartment, the salt depletion compartment interposed between the base generation compartment and the acid generation compartment, and the acid generation compartment interposed between the salt depletion compartment and the anode compartment; an anode positioned extending within an interior of the membrane electrolysis cell and positioned in the anode compartment; a cathode comprising a gas diffusion electrode as defined in claim 1, the cathode positioned extending within an interior of the membrane electrolysis cell and positioned in the cathode compartment; a first anion exchange membrane disposed on a catalyst layer of the gas diffusion electrode and configured to exchange ions received from the catalyst layer of the gas diffusion electrode to an opposite surface of the first anion exchange membrane into the base generation compartment; a first cation exchange membrane interposed between the salt depletion compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the cation exchange membrane into the base generation compartment; a second anion exchange membrane interposed between the salt depletion compartment and the acid generation compartment, the second anion exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the second anion exchange membrane into the acid generation compartment; a second cation exchange membrane interposed between the acid generation compartment and the anode compartment, the second cation exchange membrane configured to exchange ions received from the anode compartment to an opposite surface of the second cation exchange membrane into the acid generation compartment; an inlet through which the salt containing solution is received into the salt depletion compartment; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which products are expelled from an interior of the membrane electrolysis cell. a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which a product is discharged from the interior of the diaphragm electrolyzer.

6. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolyzer as defined in claim 2; and directing the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt-containing solution is received into an anode compartment; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into a cathode compartment; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions combine with the positive salt ions to produce the base product; and the alkali product is discharged from the cathode compartment.

7. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolyzer as defined in claim 3; and directing the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt-containing solution is received into an anode compartment; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into an alkali generation compartment; The gas containing O2 is reduced at the cathode to form OH - ; OH - ions migrate through the anion exchange membrane to the opposite surface of the anion exchange membrane into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the alkali product is discharged from the alkali generation compartment.

8. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolyzer as defined in claim 4; and directing the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt-containing solution is received into a salt-depleted compartment; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into an alkali generation compartment; The gas containing O2 is reduced at the cathode to form OH - ; OH - ions migrate through the first anion exchange membrane to an opposite surface of the first anion exchange membrane into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the alkali product is discharged from the alkali generation compartment.

9. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolyzer as defined in claim 5; and directing the alkali product from the diaphragm electrolyzer, wherein in carrying out the method: the salt-containing solution is received into a salt-depleted compartment; the positive salt ions migrate through a first cation exchange membrane to an opposite surface of the cation exchange membrane into an alkali generation compartment; The gas containing O2 is reduced at the cathode to form OH - ; OH - ions migrate through the first anion exchange membrane to an opposite surface of the first anion exchange membrane into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the alkali product is discharged from the alkali generation compartment.

10. A gas diffusion electrode for use in a diaphragm electrolyzer, the gas diffusion electrode comprising: a gas diffusion layer to diffuse an oxygen-containing gas; and a catalyst-coated membrane comprising a layer of catalyst disposed on a surface of the membrane.

11. A diaphragm electrolyzer for treating a salt-containing solution, the diaphragm electrolyzer comprising: an anode compartment; a cathode compartment; an alkali generation compartment interposed between the cathode compartment and the anode compartment; an anode positioned extending within the interior of the diaphragm electrolyzer and positioned in the anode compartment; a cathode comprising a gas diffusion electrode as defined in claim 10, the cathode positioned extending within the interior of the diaphragm electrolyzer and positioned in the cathode compartment; ​ a cation exchange membrane interposed between the anode compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the anode to an opposite surface of the cation exchange membrane into the base generation compartment; an inlet through which the salt-containing solution is received into the anode compartment; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which products are expelled from the interior of the diaphragm electrolyzer.

12. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode compartment; a cathode compartment; a base generation compartment and a salt depletion compartment interposed between the cathode compartment and the anode compartment, the base generation compartment interposed between the cathode compartment and the salt depletion compartment, and the salt depletion compartment interposed between the base generation compartment and the anode compartment; an anode positioned extending within the interior of the diaphragm electrolyzer and positioned in the anode compartment; a cathode comprising the gas diffusion electrode defined in claim 10, the cathode positioned extending within the interior of the diaphragm electrolyzer and positioned in the cathode compartment; a cation exchange membrane interposed between the salt depletion compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the cation exchange membrane into the base generation compartment; an anion exchange membrane interposed between the salt depletion compartment and the anode compartment, the anion exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the anion exchange membrane into the anode compartment; an inlet through which the salt-containing solution is received into the salt depletion compartment; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which products are expelled from the interior of the diaphragm electrolyzer.

13. A diaphragm electrolyzer for processing a salt-containing solution, the diaphragm electrolyzer comprising: an anode compartment; a cathode compartment; a base generation compartment, a salt depletion compartment, and an acid generation compartment interposed between the cathode compartment and the anode compartment, the base generation compartment interposed between the cathode compartment and the salt depletion compartment, the salt depletion compartment interposed between the base generation compartment and the acid generation compartment, and the acid generation compartment interposed between the salt depletion compartment and the anode compartment; an anode positioned extending within the interior of the diaphragm electrolyzer and positioned in the anode compartment; a cathode comprising the gas diffusion electrode defined in claim 10, the cathode positioned extending within the interior of the diaphragm electrolyzer and positioned in the cathode compartment; a first cation exchange membrane interposed between the salt depletion compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the cation exchange membrane into the base generation compartment; an anion exchange membrane interposed between the salt-depleted chamber and the acid generation chamber, the anion exchange membrane configured to exchange ions received from the salt-depleted chamber to an opposite surface of the anion exchange membrane into the acid generation chamber; a second cation exchange membrane interposed between the acid generation chamber and the anode chamber, the second cation exchange membrane configured to exchange ions received from the anode chamber to an opposite surface of the second cation exchange membrane into the acid generation chamber; an inlet through which the salt-containing solution is received into the salt-depleted chamber; a gas inlet positioned in the cathode chamber through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which a product is expelled from an interior of the diaphragm electrolysis cell.

14. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolysis cell as defined in claim 11; and deriving the alkali product from the diaphragm electrolysis cell, wherein in carrying out the method: the salt-containing solution is received into an anode chamber; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into an alkali generation chamber; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions migrate through the catalyst-coated membrane into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the alkali product is expelled from the alkali generation chamber.

15. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolysis cell as defined in claim 12; and deriving the alkali product from the diaphragm electrolysis cell, wherein in carrying out the method: the salt-containing solution is received into a salt-depleted chamber; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into an alkali generation chamber; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions migrate through the catalyst-coated exchange membrane into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the alkali product is expelled from the alkali generation chamber.

16. A method for producing an alkali product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a diaphragm electrolysis cell as defined in claim 13; and deriving the alkali product from the diaphragm electrolysis cell, wherein in carrying out the method: the salt-containing solution is received into a salt-depleted chamber; the positive salt ions migrate through a first cation exchange membrane to an opposite surface of the first cation exchange membrane into an alkali generation chamber; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions migrate through the catalyst-coated membrane into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the alkali product is expelled from the alkali generation chamber.

17. A gas diffusion electrode for a diaphragm electrolysis cell, the gas diffusion electrode comprising: a gas diffusion layer to diffuse an oxygen-containing gas; and a catalyst layer disposed on the gas diffusion layer, wherein the catalyst layer has an optimized thickness such that a liquid reactant is substantially or completely consumed before diffusing through the catalyst layer to the gas diffusion layer.

18. A diaphragm electrolysis cell for processing a salt-containing solution, the diaphragm electrolysis cell comprising: an anode chamber; a cathode chamber; an alkali generation chamber forming a single chamber with the cathode chamber; and a gas diffusion electrode positioned in the cathode chamber, the gas diffusion electrode comprising: a gas diffusion layer to diffuse an oxygen-containing gas; and a catalyst layer disposed on the gas diffusion layer, wherein the catalyst layer has an optimized thickness such that a liquid reactant is substantially or completely consumed before diffusing through the catalyst layer to the gas diffusion layer. an anode positioned in an interior extension of the diaphragm electrolyzer and positioned in an anode compartment; a cathode comprising a gas diffusion electrode as defined in claim 17, the cathode positioned in an interior extension of the diaphragm electrolyzer and positioned in a cathode compartment; a cation exchange membrane interposed between the anode compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the anode to an opposite surface of the cation exchange membrane into the base generation compartment; an inlet through which the salt containing solution is received into the anode compartment; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which products are expelled from an interior of the diaphragm electrolyzer.

19. A diaphragm electrolyzer for processing a salt containing solution, the diaphragm electrolyzer comprising: an anode compartment; a cathode compartment; a base generation compartment forming a single compartment with the cathode compartment; a salt depletion compartment interposed between the cathode compartment and the anode compartment; an anode positioned in an interior extension of the diaphragm electrolyzer and positioned in an anode compartment; a cathode comprising a gas diffusion electrode as defined in claim 17, the cathode positioned in an interior extension of the diaphragm electrolyzer and positioned in a cathode compartment; a cation exchange membrane interposed between the salt depletion compartment and the base generation compartment, the cation exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the cation exchange membrane into the base generation compartment; an anion exchange membrane interposed between the salt depletion compartment and the anode compartment, the anion exchange membrane configured to exchange ions received from the salt depletion compartment to an opposite surface of the anion exchange membrane into the anode compartment; an inlet through which the salt containing solution is received into the salt depletion compartment; a gas inlet positioned in the cathode compartment through which a gas comprising O2 is introduced into contact with the gas diffusion electrode; and at least one outlet through which products are expelled from an interior of the diaphragm electrolyzer.

20. A diaphragm electrolyzer for processing a salt containing solution, the diaphragm electrolyzer comprising: an anode compartment; a cathode compartment; a base generation compartment forming a single compartment with the cathode compartment; a salt depletion compartment and an acid generation compartment interposed between the cathode compartment and the anode compartment, the salt depletion compartment interposed between the base generation compartment and the acid generation compartment and the acid generation compartment interposed between the salt depletion compartment and the anode compartment; an anode positioned in an interior extension of the diaphragm electrolyzer and positioned in an anode compartment; a cathode comprising a gas diffusion electrode as defined in claim 17, the cathode positioned in an interior extension of the diaphragm electrolyzer and positioned in the cathode compartment; a first cation exchange membrane, the first cation exchange membrane interposed between the salt-depletion chamber and the base-generation chamber, the cation exchange membrane configured to exchange ions received from the salt-depletion chamber to an opposite surface of the cation exchange membrane into the base-generation chamber; an anion exchange membrane, the anion exchange membrane interposed between the salt-depletion chamber and the acid-generation chamber, the anion exchange membrane configured to exchange ions received from the salt-depletion chamber to an opposite surface of the anion exchange membrane into the acid-generation chamber; a second cation exchange membrane, the second cation exchange membrane interposed between the acid-generation chamber and the anode chamber, the second cation exchange membrane configured to exchange ions received from the anode chamber to an opposite surface of the second cation exchange membrane into the acid-generation chamber; an inlet through which the salt-containing solution is received into the salt-depletion chamber; a gas inlet, the gas inlet positioned in the cathode chamber, a gas comprising O2 being introduced through the gas inlet into contact with the gas diffusion electrode; and at least one outlet through which a product is expelled from an interior of the membrane electrolysis cell.

21. A method for producing a base product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a membrane electrolysis cell as defined in claim 18; and directing the base product from the membrane electrolysis cell, wherein in carrying out the method: the salt-containing solution is received into an anode chamber; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into a base-generation chamber; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions migrate through the catalyst layer into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the base product is expelled from the membrane electrolysis cell.

22. A method for producing a base product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a membrane electrolysis cell as defined in claim 19; and directing the base product from the membrane electrolysis cell, wherein in carrying out the method: the salt-containing solution is received into a salt-depletion chamber; the positive salt ions migrate through a cation exchange membrane to an opposite surface of the cation exchange membrane into a base-generation chamber; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions migrate through the catalyst layer into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the base product is expelled from the membrane electrolysis cell.

23. A method for producing a base product, the method comprising the steps of: receiving a salt-containing solution comprising positive salt ions and negative salt ions and a gas comprising O2 in a membrane electrolysis cell as defined in claim 20; and directing the base product from the membrane electrolysis cell, wherein in carrying out the method: the salt-containing solution is received into a salt-depletion chamber; the positive salt ions migrate through a first cation exchange membrane to an opposite surface of the first cation exchange membrane into a base-generation chamber; The gas comprising O2 is reduced at the cathode to form OH - ; OH - ions migrate through the catalyst layer into the base generating chamber; OH - ions combine with the positive salt ions in the base generating chamber to produce the base product; and the base product is expelled from the membrane electrolysis cell.

24. A gas diffusion electrode for use in a membrane electrolysis cell, the gas diffusion electrode comprising: a first gas diffusion layer to diffuse an oxygen-containing gas; a catalyst layer disposed on a surface of the first gas diffusion layer; a second gas diffusion layer in contact with a surface of the catalyst layer opposite the first gas diffusion layer; and and an ionomer layer disposed on a surface of the anion exchange membrane, the ionomer layer being in contact with a surface of the second gas diffusion layer opposite the catalyst layer.

25. A method for producing LiOH from a Li source, the method comprising the steps of: (a) contacting the Li source with a solvent to expel lithium from the Li source, thereby obtaining a lithium-loaded solvent; (b) contacting the lithium-loaded solvent with a stripping agent to regenerate solvent and produce a salt-containing solution comprising lithium ions and negative salt ions; (c) receiving the salt-containing solution and a gas comprising O2 in a diaphragm cell; and (d) directing LiOH and / or an acid from the diaphragm cell.

26. A method for making a diaphragm-coated gas diffusion electrode, the method comprising: mixing an ionomer into a solvent to make a coating mixture; applying the coating mixture to a gas diffusion electrode, and curing to form the diaphragm-coated gas diffusion electrode.

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