Cells, cell systems, and methods for reversible energy and hydrogen storage and hydrogen and electricity generation

Abstract

The cell comprises a positive electrode (2) comprising a first current collector (3) coated with a catalyst (4), a negative electrode (5) comprising a second current collector (6), and an alkaline zinc-containing electrolyte (7). When the cell (1) is connected to an electrical means (8) for charging the cell and charged under electrical consumption, a zinc layer (9) is electrolytically deposited on the negative electrode (5) with simultaneous evolution of oxygen (O2) gas at the positive electrode (2). The zinc layer (9) appears as a dense solid metal with a nodular and / or layered microstructure and low porosity, and is attached to the second current collector (6). When the cell (1) is connected to an electrical means (10) for discharging the cell and discharged under electrical discharge, the zinc layer dissolves from the negative electrode (5) with simultaneous evolution of hydrogen (H2) gas at the positive electrode (2) in proportion to the evolution of electricity.

Description

Summary of the Invention

[0001] The present invention relates to cells, cell systems, and methods for the reversible storage of energy and hydrogen and the production of hydrogen and electricity.

[0002] Energy storage systems, especially electrical energy storage systems, are crucial for fossil fuel replacement and for further technological advances in general. For example, power-to-gas (often abbreviated P2G) is a technology that uses electricity to generate gaseous fuels. Most P2G systems primarily use water electrolysis to produce hydrogen. Hydrogen (power-to-gas), in particular, is expected to be used in the future to store large amounts of energy. However, the overall efficiency of electrolysis, storage, and subsequent reconversion to electricity is low, at approximately 25%–30%. Hydrogen storage itself, for example, pressure vessels and metal hydrides, has so far been characterized by high costs and often requires additional hydrogen transportation. Underground storage, such as salt caverns and liquid organic hydrogen carriers (LOHCs), is still in the development stage. Hydrogen transportation also involves losses.

[0003] For small amounts of energy, rechargeable batteries, especially lithium-ion batteries, are used. They have a high efficiency of around 90%, but are very expensive when considering costs and recycling costs. Furthermore, the availability of the necessary materials in the Earth's crust is insufficient for large-scale storage systems, and recycling methods have not yet been fully resolved. Although the price of lithium-ion batteries has fallen sharply in recent years and is expected to reach 75-100 euros / kWh at the cell level by 2025, this battery technology will remain expensive in the future for storing large amounts of energy on an economic scale, i.e., for long periods of time, such as weeks or months.

[0004] Systems that utilize electrolysis mechanisms to produce oxygen and / or hydrogen gas in molecular form (i.e., H2 and O2) are known. Hydrogen has a significant contribution to future energy technologies. In particular, so-called green hydrogen, which is produced by electrolysis using fluctuating alternative energy sources such as wind and solar, plays a key role. However, the storage and transportation of hydrogen incurs significant losses, reducing overall efficiency and requiring significant investments for storage and transportation.

[0005] Although some hydrogen-producing cells based on zinc and magnesium for microfuel cells have already been developed, these cells are not electrically rechargeable, i.e., similar to primary batteries that are discarded after use.

[0006] A major problem associated with zinc-based rechargeable systems or devices is limited cycle life, primarily due to the morphology of the zinc electrode, which is prone to change during charging or during an entire cycle. The morphology changes that cause electrode performance degradation or failure can be of several types: shape change, mossy zinc deposition, and dendrite formation. Shape change is a phenomenon associated with a change in the geometric area of ​​the zinc electrode, in which the zinc active material detaches from one location and aggregates in another. In such systems or devices, not all zinc ions are actually fixed in place, but rather flow through the electrolyte and are redeposited as metallic zinc in various locations. Dendrite formation occurs during charging and can penetrate the separator of an electrochemical cell, causing a short circuit and immediate cell failure.

[0007] Interest in developing rechargeable zinc systems or devices, such as zinc or zinc-air batteries, as high-energy power sources has prompted continued research into deposition from alkaline zincate solutions. The cycle life of such rechargeable zinc or zinc-air batteries has been found to be limited primarily due to the zinc electrode's tendency to passivate, change shape, and become soluble in concentrated alkaline solutions, which are life-limiting factors. Furthermore, morphological changes, such as the formation of dendrites and loss of porosity, can occur during charging or discharging of these systems or devices. Another concern is the potential for the formation of moss and dense spongy structures, which can lead to the detachment of zinc particles from the electrodes and cause short circuits within such systems or cells.

[0008] Therefore, there is a need for storage technologies that have significantly higher levels of efficiency than power-to-gas, while using inexpensive and readily available materials.

[0009] The present invention is based on the objective of overcoming the drawbacks of the prior art by providing a cell, cell system and method for the reversible storage of energy and hydrogen and the on-demand production of hydrogen and electricity. In particular, the present invention is based on the objective of providing a cost-effective, environmentally friendly, safe and energy-efficient solution.

[0010] This object is solved by a cell having the features of claim 1, a cell system having the features of claim 9 and a method having the features of claim 18. Preferred embodiments of the invention are defined in the respective dependent claims.

[0011] According to the present invention, there is provided a cell for the reversible storage of energy and hydrogen and the production of hydrogen and electricity, the cell comprising a positive electrode comprising a first current collector coated with a catalyst, a negative electrode comprising a second current collector, and an alkaline zinc-containing electrolyte, wherein when the cell is connected to an electrical means for charging the cell and charged under electrical consumption, a zinc layer is electrolytically deposited on the negative electrode with simultaneous evolution of oxygen gas at the positive electrode, the zinc layer appearing as a dense solid metal with a nodular and / or layered microstructure and low porosity and attached to the second current collector, and when the cell is connected to an electrical means for discharging the cell and discharged under electrical discharge, the zinc layer dissolves from the negative electrode with simultaneous evolution of hydrogen gas at the positive electrode in proportion to the release of electricity.

[0012] In terms of the present invention, a negative electrode with a second current collector, with or without zinc, may also be referred to as a zinc electrode, zinc side, negative electrode, anode, anode current collector, or anode collector. In terms of the present invention, a positive electrode with a catalyst-coated first current collector from which gaseous oxygen and hydrogen are evolved may also be referred to as a gas electrode, gas side, positive electrode, cathode, cathode collector, or cathode current collector.

[0013] In the context of the present invention, the cell may also be referred to as a rechargeable galvanic cell, galvanic cell, galvanic zinc-hydrogen cell, Zn-H2 cell, Zn-H2 generator, Zn-H2 storage cell, or H2 generator. In the context of the present invention, the electrical means for discharging the cell may be any type of electrical load, current sink, or the like; it is important that the electrical means obtain electricity from the cell. The electrical means for charging the cell may comprise any type of power source, electrical supply, or the like; it is important that electricity is supplied to the cell. It is understood that the term electrical means also includes all connections, cables, and other electronics required for charging or discharging the cell.

[0014] In the context of the present invention, when an electrode or both electrodes are referred to, the positive and negative electrodes, respectively, are intended unless otherwise specified. Furthermore, when a current collector or both current collectors are referred to, the first and second current collectors, respectively, are intended unless otherwise specified. In the context of the present invention, a current collector is a structure that is sufficiently stable in the cell environment to hold zinc or a catalyst and has good electronic conductivity.

[0015] The cell of the present invention can reversibly store hydrogen and energy in the form of Zn deposited on the negative electrode. When electrical discharge is applied between the negative and positive electrodes, the cell can simultaneously release electricity and hydrogen, allowing the resulting hydrogen and electricity to be consumed elsewhere. Zn dissolves from the negative or Zn electrode and is converted primarily to zincate and ZnO in an alkaline environment. Reversible in this context means that the cell can be charged with electricity and water, forming a zinc layer on the negative electrode, thus storing energy and potentially generating hydrogen upon discharge. By applying electrical means that consumes electricity from the cell by dissolving the zinc layer on the negative electrode, hydrogen is generated from the water. The amount of hydrogen produced is proportional to the electrical discharge applied; 6.9 cc of H2 is produced per minute at 1 A at standard temperature and pressure (STP, 100 kPa, 273.15 K).

[0016] According to a preferred embodiment, the cell further comprises a separator impermeable to ZnO, positioned between the positive and negative electrodes. The separator may be provided in the form of a membrane, ensuring a liquid phase region at the gas electrode for improved gas dynamics. The separator is only impermeable to ZnO and is not impermeable to other zinc forms, such as zincates, that may still be present in the alkaline zinc-containing electrolyte. The zinc-containing electrolyte may be enriched with a zinc source, such as ZnO, which may be present in a viscous, paste-like consistency with high viscosity. This is advantageous and desirable because a large amount of Zn can be deposited at the negative electrode, but depending on the amount of ZnO, the dynamics of hydrogen and oxygen gases generated during charge and discharge, for example, may be limited. To improve outgassing of these gases from the zinc-containing electrolyte, a separator is introduced into the cell, which can improve gas dynamics by creating a water phase region at the positive electrode by keeping ZnO away.

[0017] According to a preferred embodiment, the cell further comprises a separator that is impermeable to zincate but permeable to hydroxide ions, and is located between the positive and negative electrodes. The separator may be provided in the form of a membrane. The separator is intended to avoid a decrease in catalytic activity and to prevent short circuits caused by zinc plating during charging. For example, the catalytic activity of some catalysts can be hindered or disabled by the presence or high concentration of zincate. Such a separator or membrane allows the use of catalysts that exhibit little catalytic activity.

[0018] According to a preferred embodiment, the second current collector is not made of zinc, as the cell can only be fully discharged, i.e. discharged to 100% depth of discharge (DOD), if it were made of pure zinc, not only would the zinc layer but also the second current collector would dissolve, which would be impractical since there would be no second current collector and no negative electrode on which the zinc layer could be deposited, making further charging of the cell impossible.

[0019] According to another preferred embodiment, the zinc layer is made of non-powdered zinc. However, compared to powdered zinc anodes and their applications, the active surface of the anodes of the present invention is smaller, resulting in a larger overvoltage. In the solid, non-powdered zinc deposits of the present invention, electrical connection between the zinc and the second current collector is always present, whereas in particulate deposits, passivated particles lose electrical connection with the current collector, resulting in reduced active material utilization. It is important to understand that in the negative electrodes of the present invention, pure, solid metallic zinc is plated during charging or electrolytic deposition; no powdery deposits are formed or are no longer present. It is also understood that powdered zinc can produce mossy zinc deposits, which have the same negative properties as powdered zinc. However, such powdery deposits are undesirable in the negative electrodes of the present invention, since the zinc deposits of the present invention result in a dense, interconnected metal morphology. While the surface area may be smaller than that of zinc particles, the discharge current is not necessarily smaller because the zinc powder particles are coated with oxide layers, and the electrical conductivity of these oxides is lower than that of the solid zinc layers described herein. In the worst case, this can lead to electrical discontinuity and electrolyte blockage in zinc powder applications. The large ZnO layer impedes mass transport to and from the negative (Zn) electrode.

[0020] One advantage of the non-powder deposition of solid zinc is the high zinc utilization during discharge and hundreds of mg / cm during charge. 2 The ability to deposit thick, smooth zinc layers over such negative (Zn) electrodes is also important. Furthermore, such negative (Zn) electrodes can be subjected to a virtually unlimited number of charge / discharge cycles without permanent electrode shape change.

[0021] According to another preferred embodiment, the first and / or second current collectors are selected from the group consisting of one or more of steel, low-carbon nickel steel, nickel-plated steel, nickel-plated low-carbon steel, or nickel-phosphorus (NiP)-coated steel. Low-carbon steel has proven to be a suitable material due to its low cost, lack of corrosion in alkaline environments, and lack of spontaneous H2 evolution on its surface when plated with zinc. The electrode may also comprise at least one polymer substrate or composite material with a nickel (Ni) or NiP surface coating. Alternatively, the electrode may comprise a structure made of carbon fiber or fibers with an electrically conductive surface coating. In this case, the surface of the electrode is increased; in the case of the negative electrode, a dense, high-density, and highly conductive zinc layer is deposited on such a high-surface-area substrate.

[0022] Optional additives to reduce self-discharge may be applied to the electrolyte or deposited on the current collector.

[0023] Furthermore, according to a preferred embodiment, the first and / or second current collectors are cold formed, preferably cold rolled.

[0024] Furthermore, according to another preferred embodiment, the first and second current collectors are cold-rolled steel, particularly cold-rolled low-carbon steel. Surprisingly, cold-formed materials, particularly cold-formed or cold-rolled steel or low-carbon steel, have been found to be particularly suitable as current collector materials for producing electrodes according to the present invention. Cold-rolled low-carbon steel has been found to be a suitable material due to its very low cost, lack of corrosion in alkaline environments, and lack of surface H2 evolution during electrodeposition. These materials may have a crystalline or fine surface similar to that of pure zinc, which may facilitate the formation of a solid zinc layer. In this regard, it is surprising that the deposition of zinc on such current collectors can be achieved without the use of additives and / or binders. Naturally, additional additives or binders may be used, but it has been shown that they are not essential for the formation of electrodes according to the present invention.

[0025] According to another preferred embodiment, the zinc layer is partially or completely removed from the second current collector during the discharge cycle, and a bare second current collector is obtained when the zinc layer is completely removed by 100% depth of discharge (DOD). In other words, the discharge process can partially (DOD > 0 and < 100%) or completely (DOD = 100%) dissolve the zinc layer from the second current collector, and when the Zn layer is completely dissolved, the bare current collector is available for further electrodeposition. However, the discharge may only partially dissolve the Zn layer, after which a Zn layer can be electrodeposited again. In principle, this Zn layer formation / electrodeposition and dissolution can be repeated almost infinitely. In the context of the present invention, a bare current collector refers to a current collector in its original state as originally used, i.e., with no or almost no residue.

[0026] According to another preferred embodiment, the zinc layer is electrodeposited on a bare second current collector or on a second current collector already electrodeposited with a zinc layer, which means that the electrodeposition of the negative electrode with Zn according to the present invention can start or be carried out at a DOD of 100% or less.

[0027] According to another preferred embodiment, the zinc layer has a coating density of 3.50 to 7.14 g / cm 3 It has a density of 4.50 to 7.14 g / cm 3 The density range is preferably 5.00 to 7.00 g / cm 3 Densities in the range of 7.14 g / cm are particularly suitable. 3 These densities are approximately the same as the actual density of metallic zinc. This indicates that the zinc deposit of the present invention has a density that is approximately the same as the actual density of metallic zinc. Mossy or dendritic zinc deposits do not achieve such densities. In some experiments, zinc deposits with higher densities could be produced by the prior art, but they were very thin and partially underwent morphological changes. Furthermore, in these tests, the zinc deposits were deposited only on the reinforced zinc substrate as the current collector material, which is meaningless for commercial use. 3.5 g / cm 3A certain low porosity resulting in a density less than 0.01 can be achieved at certain deposition conditions, which may be preferable for achieving a low overvoltage due to a high surface area.

[0028] The negative electrode maintains the high capacity density of zinc. 3 The deposition density of each is 2.87Ah / cm 3 ~5.85Ah / cm 3 This corresponds to a capacity density of 100%. When used in a battery or other application, such a negative electrode according to the present invention can provide nearly infinite charge / discharge cycles for the battery or other application. The zinc deposition according to the present invention results in a dense, interconnected metal morphology. There is direct electrical connection between all portions of the zinc deposit and the second current collector. Therefore, there is no oxide barrier, as in powder / particle anode applications. A feature of the present invention is that, when used in a cell system or application, such as a battery, such a negative electrode allows the system or application to start at a discharged state of 100% depth of discharge. By using the negative electrode according to the present invention, significantly higher energy densities can be achieved in applications by using a high state of charge (SOC) (up to about 80-100% of the ZnO / zincate of the cell can be used for charging, and 100% depth of discharge (DOD) can be used for discharging). One feature of the present invention is that when the negative electrode is used in a battery, for example, a large number of cycles (virtually infinite cycles) can be achieved by introducing a 100% DOD step during the cycling process. The volume change of zinc and / or partial mossy / dendritic deposits are completely removed, and the system, specifically the negative electrode, can be restarted with a uniform and smooth zinc deposit. Therefore, the capacity and capacity density values ​​described in this invention relate to 100% DOD, i.e., full utilization of the deposited zinc for energy storage, and the resulting high capacity density.

[0029] According to another preferred embodiment, the zinc layer has a thickness of 200 mg / cm 2 , preferably 300 mg / cm 2, most preferably 400 mg / cm 2 The negative electrode according to the present invention has a mass of from several micrograms to several hundred or several thousand milligrams per square centimeter (mg / cm 2 ) of zinc deposit mass. In principle, the mass of the zinc layer according to the present invention is nearly infinite, but it is clear that there are certain limitations to the realization of such a layer. Until now, such a layer mass of solid metallic zinc could not be produced by the prior art. The negative electrode according to the present invention is therefore unique in terms of its compactness, morphology, and three-dimensionality. However, as mentioned above, in applications it is also possible to achieve higher layer masses, for example by continuously applying new zinc-containing electrolyte during electrodeposition. In such applications, it is possible to achieve layer masses of several thousand mg / cm. 2 cm 2 In terms of capacity per unit area, the present invention provides a coating composition of 200 to 400 mg / cm 2 The zinc layer has a capacity of 164~238mAh / cm 2 However, as mentioned above, this corresponds to a capacity density of several thousand mg / cm 2 Layer masses greater than 10 ...

[0030] According to another preferred embodiment, the zinc layer has a concentration of 0 to 10,000 mg / cm 2 , preferably 1 to 5000 mg / cm 2 , and more preferably 25 to 2000 mg / cm 2 has a mass of

[0031] According to another preferred embodiment, the zinc layer has a maximum of 10000 mg / cm 2 , preferably up to 5000 mg / cm 2 , more preferably up to 2000 mg / cm 2 has a mass of

[0032] According to yet another preferred embodiment, the mg / cm of the zinc layer 2 The mass of the unit is nearly unlimited.

[0033] According to yet another preferred embodiment, the zinc layer has a thickness of at least 25 mg / cm 2 has a mass of

[0034] According to another preferred embodiment, the zinc layer has a porosity of less than 50%. Because the negative electrode of the present invention is very dense, with the density of the zinc deposit ranging similar to the actual density of metallic zinc, the zinc deposit also has a low porosity of less than 50%. However, the porosity can be set even lower, up to 40%. A porosity of less than 30% is preferred, and a porosity of less than 20% is particularly preferred. Conventional zinc electrodes, let alone electrodes used in zinc-air batteries, do not achieve such low porosity values. Compared to typical electrode surfaces, the specific active surface of the anode of the present invention is hundreds to thousands of times lower than the specific active surface in zinc-air battery applications due to the low porosity. For example, the surface area of ​​zinc powder (e.g., in zinc-air batteries) according to the prior art is about 1 m 2 / g. According to the present invention, 1 cm 2 Layers of several micrograms to thousands of milligrams per layer can be achieved. For example, a layer mass of 200 mg / cm according to the present invention can be achieved. 2 In the case of zinc powder, the surface area is approximately 2000 cm 2 Thus, even if a certain degree of porosity is present in the layer according to the invention, the active surface area is several orders of magnitude smaller than in conventional electrode layers according to the most prior art.

[0035] According to a preferred embodiment, neither the second current collector nor the zinc layer includes a binder, grid, foam, fabric, or additive to bond the zinc layer to the current collector material. Unlike the prior art, the negative electrode of the present invention does not require a grid, foam, fabric, or binder, as in rechargeable Zn-air batteries or primary batteries. Thus, the negative electrode of the present invention has a significantly higher energy density than the prior art. Furthermore, the negative electrode of the present invention does not include additives, such as calcium hydroxide, that are typically present to immobilize zincates.

[0036] According to yet another preferred embodiment, the zinc layer, zinc-containing electrolyte, second current collector, and / or cathode are free of copper (Cu), copper ions, and / or copper oxides. + It has been shown that the absence of ions such as ZnO is advantageous. Such ions promote H2 evolution during charging and cause mossy zinc deposits. If the presence of copper during deposition is avoided as much as possible, zinc-plated negative electrodes will be substantially copper-free. However, it is also possible to use copper as the current collector material. However, in this case, the presence of Cu during deposition must be avoided to suppress H2 evolution during deposition. + Care must be taken to prevent dissolution of the ions. Thus, copper current collectors may be coated with Ni, NiP, or other iron (Fe) alloy coatings.

[0037] To generate electrical energy and hydrogen by plating a zinc layer on the negative electrode and then redissolving this layer, a cell may be assembled in a discharged state (DOD=100%), comprising only a negative electrode with a second current collector as the zinc side and a positive electrode with a first current collector as the gas side. The two electrodes (negative electrode, positive electrode) are connected through an electrolyte containing zinc primarily in the form of ZnO and / or zincate, rather than powdered zinc. However, within the scope of the present invention, a cell may be configured as an electrochemical cell including a second current collector, a first current collector, and a suitable electrolyte. For purposes of the present invention, an electrochemical cell is defined as a general term for various configurations used in electrochemistry or based on electrochemical processes. In this context, electrochemical cells include galvanic cells, electrolytic cells, and storage battery cells. The electrolyte may be liquid, solid, or both liquid and solid. Thus, an electrochemical cell may be defined as a configuration of two electrodes conductively connected through an electrolyte.

[0038] According to a preferred embodiment, the zinc-containing electrolyte is alkaline. Although it is contemplated that the zinc-containing electrolyte may comprise primarily zinc chloride or ammonium chloride, an alkaline environment is preferred.

[0039] According to a preferred embodiment, the zinc-containing electrolyte is non-acidic. The term acidic is defined as a pH < 7 (±0.1). Devices and systems using acidic electrolytes are known. However, these cells and systems exhibit low energy density and storage capacity, i.e., self-discharge often occurs due to the corrosion generation of hydrogen at the negative electrode where the metal is deposited. Furthermore, such cells or systems require the use of noble metal catalysts, such as iridium oxide (IrO2) or silver (Ag)-containing alloys (highly rare), in an acidic environment, which is problematic from an economic point of view. Therefore, the present invention avoids operation in such an acidic environment.

[0040] According to another preferred embodiment, the zinc-containing electrolyte comprises a zinc source selected from the group consisting of one or more of ZnO, zincates, and / or zinc complexes. When the present invention refers to a zinc-containing source or zinc-containing electrolyte, it primarily refers to one of the aforementioned substances, with ZnO and zincates being preferred. For the purposes of the present invention, a zinc complex is understood to be any type of zinc complex, but also a complex containing zinc that can be dissolved during (re)charging so that solid Zn can be further deposited on the second current collector or on a second current collector already plated with a zinc layer. The zinc source may have different viscosities and may be used as a paste or slurry, or as a solution. It is also possible to use several zinc sources in combination. However, within the scope of the present invention, it is expressly intended that the zinc-containing source or zinc-containing electrolyte does not comprise zinc in the form of powdered zinc. The use or application of powdered zinc in the form of solid zinc powder is not suitable for the present invention.

[0041] According to another preferred embodiment, the zinc source or at least one component of the zinc source becomes supersaturated after the cell is discharged. This means that during the cell discharge, the components of the zinc source are not converted exactly stoichiometrically to the components actually used at the start, but at least one component is not or cannot be further converted, so this component is present in a supersaturated concentration. For example, ZnO may be used, which is converted to zinc via zincate, and then this zinc is plated during electrodeposition. In the reverse reaction, i.e., the discharge process, zinc is converted to zincate, but not all of the zincate above the saturation point returns to ZnO, so at that point the zincate becomes supersaturated.

[0042] According to yet another preferred embodiment, the zinc-containing electrolyte comprises KOH. In this context, the electrolyte may further comprise KOH in a minimum amount of 5-25 wt. % and a maximum amount of 35-60 wt. %; a KOH amount of 26-36 wt. % is preferred, and 30 wt. % KOH is particularly preferred.

[0043] According to another preferred embodiment, the zinc-containing electrolyte comprises NaOH in a minimum range of 5-15 wt. % and a maximum range of 16-30 wt. % with 20 wt. % NaOH being preferred and 18 wt. % NaOH being particularly preferred. NaOH can be used instead of or in combination with KOH.

[0044] According to yet another preferred embodiment, the zinc-containing electrolyte, when applied to a new cell, has a minimum ZnO / KOH ratio of 190.00 g ZnO per 1 L KOH, with a minimum ZnO / KOH ratio of 100.00 g ZnO per 1 L KOH being preferred, and a minimum ZnO / KOH ratio of 8.00 g ZnO per 1 L KOH being particularly preferred; and / or the zinc-containing electrolyte has a maximum ZnO / KOH ratio of 2380.00 g ZnO per 1 L KOH, with a maximum ZnO / KOH ratio of 2670.00 g ZnO per 1 L KOH being preferred, and a maximum ZnO / KOH ratio of 2980.00 g ZnO per 1 L KOH being particularly preferred. At the end of charging, the concentration can drop significantly, so the minimum zincate or dissolved ZnO (the ZnO does not remain as ZnO because it is below the saturation point) is approximately 0.1 M in 1 L of KOH or 8 g of ZnO in 1 L of KOH. For purposes of this invention, "applied to a new cell" means that the cell is being filled for the first time or has completely fresh electrolyte. Thus, the application ratio is the ratio that exists before the start of the deposition process or charge cycle. It is understood that these parameters will change during a charge or discharge cycle.

[0045] According to yet another preferred embodiment, the zinc-containing electrolyte has a minimum ZnO concentration of 0.01 M per L of KOH in HO electrolyte, with a range of 0.1-0.8 M per L of KOH being preferred, and a maximum concentration of 0.8-1.5 M per L of KOH being preferred.

[0046] According to yet another preferred embodiment, the ZnO / KOH ratio is independent of the KOH concentration.

[0047] According to another preferred embodiment, the zinc-containing electrolyte further comprises Pb, Fe, Sn, CdMg, or other metals or alloys. The electrolyte may also contain at least one hydroxide of In, Pb, and / or Sn at a concentration of 10 to 500 ppm based on the amount of ZnO in the electrolyte. Such additions can increase the hydrogenation voltage and reduce cell self-discharge. The electrolyte may also contain at least one electrolyte additive and / or surfactant, such as polyoxyethylene octadecenyl ether phosphate, polyethylene glycol, a copolymer having acidic groups, a modified styrene-maleic acid copolymer solution, an alkylolammonium salt solution of a low-molecular-weight polycarboxylic acid polymer, a phosphate ester of alkylphenoxypolyethoxyethanol, a polyether phosphate ester, or an octylphenoxypolyethoxyethyl phosphate solution, water, phosphoric acid, and polyethylene glycol octylphenyl ether. Such additives also used in alkaline primary batteries to reduce self-discharge may be used in the present invention, such as polyoxyethylene octadecenyl ether phosphate, polyethylene glycol, copolymers having acidic groups, modified styrene-maleic acid copolymer solutions, alkylolammonium salt solutions of low molecular weight polycarboxylic acid polymers, phosphate esters of alkylphenoxypolyethoxyethanol, polyether phosphate esters, polyether phosphate esters or octylphenoxypolyethoxyethyl phosphate solutions, water, phosphoric acid, and electrolyte additives and / or surfactants such as polyethylene glycol octylphenyl ether. Such additives affect the discharge and self-discharge behavior of such devices by affecting zinc passivation.

[0048] According to yet another preferred embodiment, the first current collector is selected from the group comprising one or more of steel, low carbon steel, cold rolled steel, nickel, nickel plated steel, nickel plated low carbon steel, or nickel-phosphate (NiP) coated steel.

[0049] According to yet another preferred embodiment, the first current collector comprises a catalyst, the first current collector being partially or completely coated with the catalyst.

[0050] The positive electrode or gas electrode for alkaline electrolytes contains nickel in various forms and combinations. However, for cost reasons, nickel-plated steel sheets can be used instead of pure nickel sheets. The nickel coating prevents iron ions from dissolving during charging. To reduce overpotential, various known methods can be used to fabricate nickel surfaces with particularly large active surface areas (nano-sized nickel, Raney nickel).

[0051] In particular, catalytic systems based on Raney Ni exhibit one of the highest activities under technical conditions (h300(HER)<100mV). These catalytic systems have the advantage of an extremely high electrocatalytic active surface area. These catalysts can withstand the volume expansion (6%) caused by the formation / oxidation of Ni hydrides for hundreds to thousands of cycles. Even more advantageous than pure nickel are alloys of Ni, Mo, and Co elements. Electroplating and powder metallurgy methods can be used to manufacture catalyst-coated cathodes.

[0052] According to another preferred embodiment, the catalyst is a bifunctional catalyst for the hydrogen evolution reaction (HER) during cell discharge and for the oxygen evolution reaction (OER) during cell charge. The bifunctional catalyst can be used for both the hydrogen evolution reaction (HER) during cell discharge and the oxygen evolution reaction (OER) during cell charge. Furthermore, electrodes containing these bifunctional catalysts can be manufactured inexpensively (without the use of precious metals) on a large scale. Functionally, each cycle of cell charging and discharging can result in oxidation / reduction of the catalyst surface. Such bifunctional catalysts have also been shown to increase the lifetime of conventional cells and systems, such as electrolyzers, due to the polarity reversal of the electrodes that can occur during the replacement of old electrodes with new ones or during rapid load changes in electrolyzers. In this context, cycling tests for non-precious metal catalysts have already been developed.

[0053] According to another preferred embodiment, the catalyst or bifunctional catalyst operates at a pH in the range of about 7 to 15, with a pH of 13 to 14.8 being preferred. Bifunctional catalysts effective within the pH range of the zinc-containing electrolyte may be used in connection with the present invention. The bifunctional catalyst operates at a pH range of 9 to 15, with a pH of 14.8 being preferred when using, for example, KOH.

[0054] The potential of bifunctional HER / OER catalysts is related to the change in catalytic species upon potential reversal. Depending on the potential, the redox state of the catalytic center changes. This is most evident in Ni and Ni alloys, where Ni(OH)2 forms on the Ni surface, which is oxidized to NiOOH as the potential increases toward the OER and reduced back to Ni(OH)2 as the potential decreases toward the HER.

[0055] According to another preferred embodiment, the catalyst or bifunctional catalyst is selected from the group consisting of one or more of Ni, Ni alloys, binary Ni alloys, Raney Ni, Ni-Al, Ni-Mo, Ni-Zn, Ni-Co, Ni-W, Ni-Fe, ternary Ni alloys, NiCoMo, NiFeMo, NiCoCu, ternary Ni alloys, NiCoMoAl, NiCoMoZn, oxides of Ni, oxides of Ni alloys, oxides of binary nickel alloys, oxides of ternary nickel alloys, oxides of NiCoMn or other ternary Ni alloys, hydroxides of Ni or Ni alloys, synthetic NiFeOx nanoparticles, Ni(OH)2, NiO, Ni, Ni2P, Ni-S, NiMoNx, nitrides, sulfides, and / or carbides. Ni or Ni alloy oxides / hydroxides are particularly suitable for OER and are inactive to hydrogen production. However, synthetic NiFeOx nanoparticles also have very low HER overpotentials and can be used as bifunctional catalysts. Deposition of Ni(OH)2 or NiO on Ni or other metals can produce interfaces with particularly high catalytic activity under alkaline conditions (e.g., in KOH). Generally, phosphides, chalcogenides, oxides, nitrides, sulfides, selenides, and carbides of the transition metals mentioned above can be used as bifunctional HER-OER catalysts. Ni2P, Ni-S, or NiMoNx also have high HER reactivity, but currently, their long-term stability under alkaline conditions, such as in KOH, is still poor.

[0056] According to another preferred embodiment, the catalyst comprises two different types for HER and OER, mixed and / or patterned on at least one surface of the first current collector. Each catalyst type is optimized for a specific reaction (OER or HER) and is electrochemically stable at the potential of the other reaction (HER or OER). Furthermore, the catalyst types are generally sized to be approximately 1 μm. 2 up to 1-10mm 2 The individual areas can be patterned and coated with only alternating OER or HER type catalysts in a range of sizes.

[0057] According to another preferred embodiment, the catalyst is synthesized on a support structure. Such a support structure can be any type of nanosurface, such as carbon nanotubes (CNTs), or other support types of high surface area substrate materials. Such structures have been shown to be effective in increasing the active surface area and providing high electrical conductivity.

[0058] Furthermore, according to the present invention, there is provided a cell system for the reversible storage of energy and hydrogen and the production of hydrogen and electricity, comprising two or more cells according to one of the above-described embodiments. Although a cell system is described below, it is expressly emphasized that all the following embodiments and individual features are also applicable to a single cell.

[0059] According to a preferred embodiment, the cell system further includes a recombination catalyst used as a safety measure to remove residual H2 / O2 gas mixture, and / or temperature monitoring of the recombination catalyst is used as a fault detection mechanism for the cell system. A mixture of H2 and O2 gases can occur due to a malfunction during the charge / discharge process or a malfunction during monitoring. Furthermore, if the zincate is depleted during charging and charging continues, or if Zn from the negative electrode is depleted during discharging, electrolysis simultaneously begins to produce H2 and O2 gases. Furthermore, these gases may slightly mix if not completely removed between the charge and discharge processes. Therefore, the recombination catalyst can be placed to avoid oxyhydrogen explosions. It is also possible to place the recombination catalyst in a separate reservoir outside the cell system, in the inlet and outlet lines for the electrolyte, or in a separate manifold for the product gas. For the purposes of this invention, the recombination catalyst is also defined as a passive autocatalytic recombiner. However, an active recombination catalyst may reach temperatures that could promote oxyhydrogen explosions. Therefore, it is useful to monitor the temperature of the recombination catalyst at a critical temperature value.

[0060] According to another preferred embodiment, the recombination catalyst comprises a recombination source, the recombination source being platinum, palladium, Ni, NiCo, and / or NiCoMo, and / or the recombination source being a thin film, particle, fine powder, or nanopowder, and / or the recombination source being attached to a carrier, plate, or pallet. The recombination reaction starts spontaneously when the hydrogen concentration reaches 1 to 2 percent.

[0061] According to another preferred embodiment, the cell system further comprises a first membrane that is permeable to water, oxygen, and hydrogen, but impermeable to the alkaline zinc-containing electrolyte. This ensures that the electrolyte is maintained within the cells of the cell system during charge / discharge operations, while allowing oxygen, hydrogen, and water to pass through. This simplifies the structural requirements of such a cell system, and system designs with such a membrane have the advantage of significantly reducing maintenance work.

[0062] According to another preferred embodiment, the cell system further comprises a second membrane that is permeable to oxygen and hydrogen but impermeable to the alkaline zinc-containing electrolyte. This is to ensure that the electrolyte is maintained within the cell of the cell system during charge / discharge operations, although oxygen and hydrogen can pass through. Water consumed by the cell is supplied via another inlet or source in this case. According to the present invention, it is also possible to use both first and second membranes in a cell system.

[0063] According to another preferred embodiment, the cell system further comprises a collection volume at the bottom of each cell or cell system to allow particle aggregation without risk of short-circuiting the cell or the entire system. This collection volume is preferably intended to collect Zn particles that do not adhere to or may peel off from the negative electrode. To this end, an insulating layer or insulator is provided on the negative electrode side of this collection volume, while the positive electrode side of such a collection volume is not insulated. This allows the Zn particles to dissolve again into zincate and then into ZnO during subsequent discharge cycles, thereby allowing them to be redeposited on the negative electrode.

[0064] According to yet another preferred embodiment, the cell system further comprises a housing configured to allow gas to be collected from the cell system without losing alkaline zinc-containing electrolyte from the cell system and while minimizing ionic connections between individual cells, and / or the housing has a self-leveling ability to replenish alkaline zinc-containing electrolyte after a discharge cycle. The self-leveling ability can be designed, for example, so that the cell system is fully immersed in alkaline zinc-containing electrolyte at the beginning and / or end of a charge / discharge cycle, and then the electrolyte is drained again, leaving a predetermined volume in the individual cell chambers. Furthermore, the housing is designed to allow gas generated during charging / discharging of the cells to be released and collected, but not to release the electrolyte. The housing is also designed to prevent ionic connections between individual cells of the cell system, preventing undesired short circuits from occurring.

[0065] According to another preferred embodiment, the cells of the cell system are individually combined in the form of a stack, arrangement, array, or bipolar stack, and in the case of the bipolar stack, the cell system comprises at least one bipolar electrode, the bipolar electrode having a negative electrode on one side and a positive electrode on the other side, and the bipolar electrodes have one common current collector.

[0066] According to yet another preferred embodiment, the voltage and / or current and / or temperature of the cell or cell system and / or the temperature of the recombination catalyst are monitored during charging and discharging of the cell system for fault detection. Advantageously, the cell system monitors all relevant parameters, such as current, voltage and temperature, in particular those of any recombination catalyst present, for faults, such as excessive temperature or current and voltage drops in the recombination catalyst.

[0067] According to another preferred embodiment, the cell system generates hydrogen gas during discharge at a pressure between 0.1 and 1000 bar, preferably between 1 and 40 bar, and more preferably between 1 and 4 bar. The cell or cell system can operate at high hydrogen pressures. As the pressure increases from 0.1 bar to 1000 bar, the open circuit voltage (H2 mode) drops from approximately 0.42 V to 0.2 V. However, performance improves due to the reduced electrolyte resistance resulting from the reduced gas bubble volume. In overpressure operation, the cell or cell system can also operate at temperatures above 100°C.

[0068] According to the present invention there is further provided a method for the reversible storage of energy and hydrogen and the production of hydrogen and electricity using a cell or cell system according to one of the above-described embodiments, the method comprising the steps of: using an electrochemical cell; applying 0-30 Hz, preferably 5-20 Hz, more preferably 10 Hz, 5%-80% duty cycle pulses for zinc deposition on the current collector material until a predetermined state of charge (SOC) and / or a predetermined mass of zinc layer is reached; Pulses having a lower limit of about 0.01 Hz, preferably about 0.05 Hz, more preferably about 0.1 Hz, and an upper limit of about 500 Hz, preferably about 100 Hz, more preferably about 50 Hz, with a duty cycle of 8% to 1% or less, preferably 5% to 2% or less, more preferably 5%, and / or a current of 10 mA / cm 2 Preferably less than 8 mA / cm 2 or less, more preferably 5 mA / cm 2 until a predetermined minimum current density is reached:

[0069] According to another preferred embodiment of the method, the method applies pulses of about 0.01-500 Hz, preferably about 5-50 Hz, more preferably about 5-25 Hz, and especially preferably about 10 Hz.

[0070] According to another preferred embodiment of the method, the method comprises: applying 0-30 Hz, preferably 5-20 Hz, more preferably 10 Hz, 5%-80% duty cycle pulses for zinc deposition on the current collector material until a predetermined state of charge (SOC) and / or a predetermined mass of zinc layer is reached; Pulses of 0-30 Hz, preferably 5-20 Hz, more preferably 10 Hz, with a duty cycle of 8%-1% or less, preferably 5%-2% or less, more preferably 5%, and / or 10 mA / cm 2 Preferably less than 8 mA / cm 2 or less, more preferably 5 mA / cm 2 until a predetermined minimum current density is reached:

[0071] According to a preferred embodiment, the method comprises: 2 , preferably 5 to 170 mA / cm 2 , and more preferably 5 to 125 mA / cm 2 and applying a pulse current density in the range of

[0072] The process parameters, such as duty cycle, frequency, or current density, are optimized for charging time, charging efficiency, and structure (meaning deposition of a smooth solid zinc layer according to the present invention). However, according to the present invention, a low duty cycle (e.g., 5%) of 10 Hz and a low current density (5 mA / cm) are preferred. 2 ) produced thick zinc deposits (0.1 to several thousand mg / cm) at all ZnO / zincate concentrations. 2 ), but the charging time is very long. To shorten the charging time, a higher current density is required. For a high average current density, either (a) low duty cycle high current density, or (b) high duty cycle low current density, or both can be applied, with the average current density remaining the same in both (a) and (b). Option (a) of low duty cycle high current density has poor electrical efficiency, while option (b) of high duty cycle low current density has good electrical efficiency.

[0073] As an example, using saturated zincate in 30% KOH, (a) 40% duty cycle 80 mAh / cm 2 , or (b) 80% duty cycle 40mA / cm 2 and both (a) and (b) are 100 mg Zn / cm 2 However, plating is less than 40mA / cm 2 Option (b) indicates that the zinc deposit is approximately 100 mg / cm 2 If the thickness exceeds 100 mg / cm, it will become mossy. However, if that thickness is desired, the 100 mg / cm deposited in option (b) 2 Zinc is more electrically efficient. Supersaturated zincates require low duty cycles and low current densities until they reach a saturation point, after which they can be used at 40 mA / cm. 2 An 80% duty cycle (option (a)) of 40 mA / cm may be used. 2 Start (at saturation) at 80% duty cycle (option (b)) and then reduce to 40% duty cycle 80mAh / cm 2 Switch to option (a) and use 100 mg / cm 2 More than one combination may be used.

[0074] The parameters given here are the basic parameters by which a zinc electrode according to the present invention can be obtained. However, it is understood that the pulsing parameters are influenced by the ZnO loading, meaning, for example, the zincate concentration (or other zinc source concentration), the degree of thickness / viscosity of the applied ZnO / KOH paste. Furthermore, these initial parameters can be influenced during the deposition process, for example, by the charging progress, temperature, zinc loading / cm 2 It is also clear that the voltage varies with the application. For zinc deposition, pulses of 0-30 Hz, preferably 5-20 Hz, and more preferably 10 Hz, with a 5%-80% duty cycle are applied to the desired zinc deposition mass in order to bring zincate ions closer to the negative electrode surface, allow hydroxide to penetrate the internal structure, and avoid H2 evolution. All pulses are suitable for suppressing H2 evolution to prevent the formation of mossy or dendritic zinc deposits.

[0075] According to the present invention, there are several conditions that allow for a metallic, solid, non-powder-like, non-mossy zinc deposit during charging of the second current collector (negative electrode) in a cell or cell system, although not all of the conditions need actually be present for zinc to be deposited on the negative electrode according to the present invention; in other words, not all of the conditions are required, but are merely advantageous when present.

[0076] Optionally, e.g., Cu + It is preferable that ions such as copper oxide and copper passivation are not present during the electrodeposition of zinc, as such ions promote H2 evolution during charging and can lead to mossy zinc deposits. Furthermore, it is preferable that copper oxide or passivation is not present on the surface of the second current collector, as such oxides promote H2 evolution during charging and can lead to mossy zinc deposits.

[0077] The deposition parameters must be selected so that H2 is not generated. H2 bubbles deposit zinc around them, forming mossy zinc. In fact, high currents are the cause of H2 generation. The use of high current densities has advantages mainly at the beginning of the deposition, depending on the substrate (current collector material or already deposited Zn layer). However, H2 bubbles are mainly removed by pulses, not by high current densities. When depositing on substrates made of materials with low H2 overpotential, i.e., good H2 generation substrates or catalysts, a current of 40 mA / cm2 for a duration of a few fractions of a second is recommended to obtain an initial plating that inhibits the activity of the catalytic properties of the substrate. 2 An initial high current pulse of 1000 s is necessary. It is also advantageous to increase the number of nucleation sites on such a substrate. Otherwise, the substrate acts as a catalyst to dissolve the zinc being deposited. After the initial deposition, the current is preferably reduced; otherwise, mossy zinc will form.

[0078] The current collector material should be selected to have a high H2 overpotential to avoid H2 evolution at the start of plating on the bare current collector.

[0079] Another important condition is time. Thus, time is needed to allow the zincate ions consumed at the electrode / electrolyte interfacial layer to be replenished. This is achieved by lowering the duty cycle; for example, a very thick ZnO paste (in the context of this invention, thick means high viscosity and high ZnO concentration, as in other mentioned embodiments of the invention) between the negative electrode and the separator requires a low duty cycle, e.g., 10%, while with lower ZnO or zincate concentrations, a duty cycle of 80% is possible. However, as the zincate becomes depleted towards the end of charging, a lower duty cycle is preferably applied.

[0080] According to another embodiment of the method, the method comprises: 2 The method further includes applying pulses of 0-30 Hz, preferably 5-20 Hz, and more preferably 10 Hz, with a 5%-80% duty cycle at a current density of 0-30 Hz, preferably 5-20 Hz, and more preferably 10 Hz, or higher. This initial Zn deposition step is performed before the main zinc deposition step. For current collector materials with low H2 overpotentials, such as nickel, such a step is essential to prevent H2 evolution that may occur during zinc deposition at the parameters described in the method of the present invention. In addition, this step can increase the number of nucleation sites, which is advantageous for uniform and improved zinc deposition in the next step. This increase in the number of nucleation sites applies not only to materials with low H2 overpotentials but also to materials with high H2 overpotentials, such as cold-rolled low-carbon steel. However, for cold-rolled low-carbon steel, such a step is not required. Preferably, such a step is applied in the method of the present invention when bare current collector material is present, i.e., when zinc deposition is first applied in a cell or cell system using bare current collector material, or when a previous discharge cycle or step has completely stripped the zinc layer from the current collector material.

[0081] According to another embodiment of the method, if the electrochemical cell has previously been partially or fully discharged to form a surface passivation, the method further comprises applying a 5% to 10% duty cycle pulse at 1 to 100 kHz, preferably 30 to 70 kHz, and more preferably 50 kHz, for s seconds to m minutes. The surface passivation is preferably stripped prior to zinc deposition. Otherwise, plating onto the passivation will result in a mossy zinc deposit. However, as the zincate concentration decreases, the passivation will eventually dissolve. Stripping of the passivation is accomplished by applying a low duty cycle pulse of a fraction of a microsecond (μs) for a few seconds (e.g., 1 to 90 seconds, preferably 5 to 50 seconds, more preferably 30 seconds) to a few minutes during the initial charging or deposition process.

[0082] According to another embodiment of the method, the method further includes monitoring zinc electrodeposition for a current spike and / or voltage drop, and immediately stopping zinc electrodeposition and terminating the method if a spike and / or drop is present. Such a spike and / or drop indicates a short circuit and means that the zinc deposit is likely to be mossy or dendritic. Such unwanted deposition is remedied by full or partial discharge of the electrochemical cell, i.e., full or partial removal of the zinc layer. Thereafter, new zinc deposition can be initiated (e.g., DOD=100% in the case of full discharge).

[0083] According to another embodiment of the method, the method comprises monitoring zinc electrodeposition for a predetermined cell current limit and / or a predetermined cell or cell system voltage limit indicative of a predetermined state of charge (SOC), and when the predetermined SOC is reached, monitoring the zinc electrodeposition for a duty cycle of 8% to 1% or less, preferably 5% to 2% or less, and more preferably 5% and / or 10 mA / cm 2 Preferably less than 8 mA / cm 2 or less, more preferably 5 mA / cm 2 It further comprises applying pulses of 0-30 Hz, preferably 5-20 Hz, more preferably 10 Hz, until a predetermined minimum current density is reached:

[0084] The parameters used to monitor zinc electrodeposition may vary depending on whether a special cell or cell system design is required or whether additional temperature control is required, and the parameters for different states of charge may be fixed or may be dynamically adjusted by performing occasional electrochemical impedance spectroscopy (EIS) during charging and adjusting pulse parameters accordingly to speed charging while avoiding short circuits.

[0085] Intermittent high-speed electrochemical impedance spectroscopy (EIS) can be performed to obtain information about the device's condition and state of charge. For example, surface roughness can be indicated by EIS, with high roughness indicating undesirable mossy deposits and low roughness indicating solid Zn deposits. EIS can be performed before, immediately after, and every x hours after charging begins to indicate the presence of passivation, whether charging has started properly, and whether the Zn deposit maintains a good Zn solid structure. Surface roughness is indicated by electrochemical double-layer capacitance. A higher capacity relative to the bare current collector capacity indicates a high surface area and the formation of mossy deposits. Measurements can be performed at several frequencies, but do not necessarily require continuous frequency scans. As long as the zinc deposit maintains a relatively low roughness and a solid, non-mossy structure, the capacity will remain approximately the same as that of the bare current collector.

[0086] Furthermore, the amount of electrolyte or the amount of zincate and / or ZnO in the cell can be determined by the cell resistance (real component of the impedance), which can be achieved by low frequency measurements. Furthermore, passivation can be detected by EIS.

[0087] In a different scenario, the recombination catalyst used as a safety device can also be used as a sensor. The temperature of the recombination catalyst can be monitored for uncontrolled zinc deposition and termination of charge. In either case, as H2 evolution begins and O2 is present, the temperature of the recombination catalyst begins to rise, indicating that charging should be terminated. The same occurs during discharge: if the temperature of the recombination catalyst rises, it indicates that the polarity-reversed cell will terminate electrolysis, releasing O2 and H2 simultaneously, and therefore, discharging should be terminated.

[0088] Alternatively, the duty cycle can be adapted to the already charged capacity, the thickness of the zinc layer on the negative electrode, and the ZnO / zincate concentration during charging. Generally, the duty cycle can be increased during charging. For each type and size of cell or cell system, the required charging parameters, the duty cycle, can be determined as a function of current, state of charge, and temperature. This can be stored in a look-up table and used for discharging.

[0089] According to another embodiment of the method, the method further includes discharging the cell or cell system when an electrical means for discharging is applied between the negative and positive electrodes. This causes electrons to flow from the negative electrode (Zn side) to the positive electrode (gas side), generating a current controlled by the impedance of the path, while simultaneously decomposing water to generate H2. A stoichiometric amount of water can be added during and / or after discharge. The galvanic properties of the cell or cell system generate the current. The impedance of the electrical means varies, controlling the current generated and the rate of H2 discharge.

[0090] According to another embodiment, the method further comprises an open circuit voltage of 0.42 V at standard temperature and pressure (STP, 100 kPa, 273.15 K).

[0091] According to the present invention, full discharge means that approximately 100% of the zinc layer can be removed (depth of discharge (DOD) = 100%). In other words, the discharge process can partially (SOC > 0) or completely (SOC = 0) dissolve the zinc layer, and if the Zn layer is completely dissolved, the bare current collector is available for further electrodeposition. However, it is also possible that the discharge only partially dissolves the Zn layer, after which the Zn layer can be electrodeposited again. In principle, this formation / electrodeposition and dissolution of the Zn layer can be repeated almost indefinitely.

[0092] According to another preferred embodiment, the method further comprises discharging the cell or cell system at a discharge voltage between 0 and 500 mV, with 100 to 400 mV being preferred and 200 mV being most preferred. The rate of hydrogen generation is set by an electrical load connected to the device. A typical discharge voltage is 200 mV. However, the voltage and current (operating point) are highly dependent on temperature and pressure, as well as the catalyst used and the age of the cell or cell system.

[0093] According to another preferred embodiment, the method further comprises discharging the device at a negative voltage to completely remove the zinc layer from the current collector. A negative voltage can also be used, typically at the end of discharge, to completely dissolve any residual zinc still adhering to the current collector and reach 100% depth of discharge (DOD).

[0094] According to another preferred embodiment, the method further comprises generating hydrogen gas during discharge at a pressure of 0.1 to 1000 bar, preferably 1 to 40 bar, and more preferably 1 to 4 bar. The cell or cell system can operate at high hydrogen pressures. The open circuit voltage (H2 mode) decreases from approximately 0.42 V to 0.2 V as the pressure increases from 0.1 bar to 1000 bar. However, performance improves due to the reduced electrolyte resistance resulting from the reduced gas bubble volume. In overpressure operation, the cell or cell system can also operate at temperatures above 100°C.

[0095] According to the present invention, a cell or cell system is provided for carrying out the steps of the inventive method described above.

[0096] The determining factor in the storage aspect of the cells or cell systems described here is charging, during which oxygen is produced at the positive electrode, such as the electrolyte, but hydrogen is not produced at this positive electrode (see Table 1, Equation 5), and zincate dissolved in the zinc-containing electrolyte is reduced to metallic zinc and deposited at the negative electrode (see Table 1, Equation 3). This can occur due to the high hydrogen overpotential of zinc.

[0097] To produce hydrogen, no external energy source is required; the cell or cell system acts like a battery, with electricity and hydrogen being produced simultaneously at low potential (see Table 1, Equation 2).

[0098] [Table 1]

[0099] An additional advantage of the present invention is that its cost is significantly lower than many other energy storage systems, due to the use of readily available and easily recyclable materials. Compared to conventional battery systems for storing electrical energy, material costs are significantly lower, at less than one-tenth the cost of Li-ion batteries. This translates into a significant reduction in capital costs per kWh. Due to the inherent safety of aqueous systems and their ability to operate continuously at high temperatures, safety and cooling efforts are significantly reduced compared to Li batteries. The use of materials abundant in the Earth's crust (elements Zn, K, and Ni) allows for the construction of large storage capacities. Compared to power-to-gas electricity storage and hydrogen storage, the overall efficiency is approximately twice as high, and electricity costs are halved. With hydrogen, hydrogen is generated on-site on demand, eliminating the significant and sometimes unaccounted for additional losses associated with transporting and storing hydrogen. Because hydrogen and oxygen are constantly being produced continuously, it is significantly easier to install high-pressure systems that provide instantaneous hydrogen supply at high pressure, eliminating the need for compressors. In electrolysis, where both gases are produced simultaneously, this presents a significant challenge due to gas mixing.

[0100] The following methods, known to those skilled in the art, may be used to determine the properties and / or parameters of zinc electrodes according to the present invention and embodiments described herein.

[0101] Because the zinc layer is a solid metal with only some surface roughness and few inherent voids or closed pores, microscopic images are sufficient to determine the structure.

[0102] The structure of the zinc layer can therefore be analysed using microscopic images taken by an optical or electron microscope, for example a scanning electron microscope (SEM), the results of which can be quantified by computer image analysis.

[0103] Scanning electron microscopy (SEM) is a technique for imaging the surface morphology of materials at high magnification. This technique provides detailed three-dimensional images that can be used to identify features such as cracks, pores, and grain boundaries in metal coatings.

[0104] Additionally or alternatively, other methods may be used, such as TEM or AFM. Transmission electron microscopy (TEM) generally provides even higher magnification than SEM and can provide detailed information about the internal structure of a coating, including nanoscale features. Atomic force microscopy (AFM) is a high-resolution imaging technique that uses a sharp tip to scan the surface of a sample. It is particularly useful for studying surface roughness and can provide information about both the surface topography and the mechanical properties of a coating.

[0105] The zinc layer may be analyzed using laser confocal microscopy, which provides a direct roughness value and is used to calculate the subsurface volume.

[0106] X-ray diffraction (XRD) can be used to analyze the crystalline structure of the coating, providing information about the crystallographic phases present in the coating, the grain size, and the preferred crystal orientation.

[0107] Various porosimetry techniques, such as mercury intrusion porosimetry and gas adsorption (e.g., BET), can be used to determine the porosity of a coating. These methods help to quantify the volume and size distribution of pores within the coating.

[0108] Cross-sectional analysis involves preparing a sample with a known coating and cutting it to expose the internal structure. This allows direct observation of the coating-substrate interface and assessment of porosity and thickness. More advanced techniques use an ion beam to prepare the cross-section (focused ion beam, FIB).

[0109] Electrochemical impedance spectroscopy (EIS) can be used to evaluate the corrosion resistance of metal coatings and indirectly infer information about porosity. Changes in impedance can provide insight into the coating's ability to withstand corrosion.

[0110] Microhardness tests, such as Vickers or Knoop hardness tests, can be performed on cross sections of coated samples. Variations in hardness across the coating can indicate porosity or compositional differences. The mossy layer is very soft compared to solid or bulk zinc.

[0111] Since zinc electrodes are mostly solid, have a relatively rough surface, and are deposited on a substrate of known weight and area, it is only necessary to measure the thickness of the zinc layer to determine the Zn density.

[0112] In general, the following methods are known to those skilled in the art for determining the density of a zinc layer.

[0113] The Archimedes' principle method involves immersing a porous metal sample in a fluid (typically a liquid) and measuring the displacement of the fluid. According to Archimedes' principle, the buoyant force acting on an immersed object is equal to the weight displaced by the fluid. The density of the material can then be calculated based on the known density of the fluid.

[0114] Gas pycnometry is a technique in which gas is used to determine the pore volume in a material. By knowing the volume and mass of the sample, the density can be calculated.

[0115] X-ray computed tomography (CT) can provide a three-dimensional image of the internal structure of porous metals. By analyzing CT scans, researchers can estimate the volume of solid material and voids. Combining this information with the sample's mass allows for the calculation of density.

[0116] Ultrasonic techniques can be used to measure the speed of sound waves passing through a material. From the speed of sound and the known acoustic properties of the material, density can be inferred.

[0117] Optical and / or electron microscopes, combined with image analysis software, can be used to analyze the microstructure of porous metals. By quantifying the amount of solid metal and voids, researchers can estimate the overall density.

[0118] In the helium displacement method, helium is used to displace the air within the pores of the material, and the change in pressure or volume is then measured and the density calculated based on the ideal gas law.

[0119] Similar to Archimedes' principle, the buoyancy method involves immersing a sample in a liquid, but instead of measuring displaced fluid, the buoyancy method may directly measure the force exerted on the sample by buoyancy.

[0120] The mass of the zinc layer can be determined using a gravimetric method. This method is based on the fact that zinc is deposited on the current collector. The current collector is weighed before the start of deposition. After the zinc is deposited, it is weighed again, and the difference is the weight of the zinc coating.

[0121] The following well-known method may be used to determine the mass of the zinc layer.

[0122] A quartz crystal microbalance (QCM) is a sensitive mass measurement device that uses the change in the resonant frequency of a quartz crystal due to the addition of mass. Coatings can be deposited on the quartz crystal, changing the resonant frequency and allowing for accurate measurement of the added mass.

[0123] The coulometric method measures the amount of electricity passed during the deposition process. Knowing the electrochemical equivalent of the metal being deposited, the mass of the coating can be calculated.

[0124] In beta backscattering, beta particles are directed at the coating surface and the backscattered radiation is measured, the intensity of which is proportional to the thickness of the coating.

[0125] X-ray fluorescence (XRF) beta particles are directed at the coating surface and the backscattered radiation is measured, the intensity of which is proportional to the thickness of the coating.

[0126] Neutron activation analysis (NAA) involves irradiating a coated sample with neutrons and measuring the emitted gamma rays, the intensity of which is proportional to the amount of a particular metal in the coating.

[0127] Generally, all these methods belong to the common general knowledge of a person skilled in the art. Furthermore, a person skilled in the art may use all known methods to determine the parameters and / or properties of a zinc electrode, and is not limited to the methods described herein.

[0128] Additionally, all methodologies known in the relevant art for determining parameters and / or properties will yield the same results within a reasonable range of measurement accuracy.

[0129] Also, aspects of the present invention are described with reference to various subject matter. In particular, some aspects or embodiments are described with reference to apparatus-type claims, while other aspects are described with reference to method-type claims. However, those skilled in the art will understand from the above and following description that, unless otherwise specified, any combination of features belonging to one type of subject matter, as well as any combination of features relating to different types, is also intended to be disclosed herein. In particular, a combination of a feature relating to an apparatus-type claim with a feature relating to a method-type claim is considered to be disclosed. The present invention and its embodiments are described in more detail below in connection with the drawing(s). The figures and schematic diagrams are not to scale unless otherwise specified and are primarily used to visually illustrate example embodiments. [Brief explanation of the drawings]

[0130] [Figure 1a]1 shows a schematic diagram of the basic structure and simplified reaction schemes of a cell for charging (a) or discharging (b) according to an embodiment of the present invention. [Figure 1b] 1 shows a schematic diagram of the basic structure and simplified reaction schemes of a cell for charging (a) or discharging (b) according to an embodiment of the present invention. [Figure 2a] Schematic diagrams showing the basic structure of a cell system (b, c) with different electrode compositions (a) and different negative and positive electrode configurations when at least two or more cells are connected together as a cell system according to another embodiment of the present invention. [Figure 2b] Schematic diagrams showing the basic structure of a cell system (b, c) with different electrode compositions (a) and different negative and positive electrode configurations when at least two or more cells are connected together as a cell system according to another embodiment of the present invention. [Figure 2c] Schematic diagrams showing the basic structure of a cell system (b, c) with different electrode compositions (a) and different negative and positive electrode arrangements when at least two or more cells are connected together as a cell system according to another embodiment of the present invention. [Figure 3a] FIG. 10 shows a schematic diagram of a second current collector that may be used in a parallel-connected cell system according to another embodiment of the present invention. [Figure 3b] FIG. 10 shows a schematic diagram of a second current collector that may be used in a parallel-connected cell system according to another embodiment of the present invention. [Figure 3c] FIG. 10 shows a schematic diagram of a second current collector that may be used in a parallel-connected cell system according to another embodiment of the present invention. [Figure 3d] FIG. 10 shows a schematic diagram of a second current collector that may be used in a parallel-connected cell system according to another embodiment of the present invention. [Figure 4] 1 shows a schematic diagram of a cell system with parallel electrodes according to another embodiment of the present invention. [Figure 5] 1 shows a schematic diagram of a cell system with electrodes arranged in series according to another embodiment of the present invention. [Figure 6]10 shows a schematic diagram of a cell system design with electrodes arranged in series according to another embodiment of the present invention. FIG. [Figure 7a] 7A-7C show schematic diagrams of the design structure of FIG. 6 at various stages of uniform filling of the cells, according to another embodiment of the present invention. [Figure 7b] 7A-7C show schematic diagrams of the design structure of FIG. 6 at various stages of uniform filling of the cells, according to another embodiment of the present invention. [Figure 7c] 7A-7C show schematic diagrams of the design structure of FIG. 6 at various stages of uniform filling of the cells, according to another embodiment of the present invention. [Figure 8] 10A and 10B show schematic diagrams of alternative design configurations of cell systems according to alternative embodiments of the present invention; [Figure 9] 10 shows a schematic diagram of another type of cell / system design structure according to another embodiment of the present invention;

[0131] 1a and 1b show schematic diagrams of the basic structure and simplified reaction schemes of a cell for charging (1a) or discharging (1b) according to an embodiment of the present invention. A negative electrode 5 is shown, which includes a second current collector 6, which may be made of, for example, nickel-plated steel sheet or low-carbon steel. During charging, a zinc layer 9 is deposited on this current collector 6, so the negative electrode 5 is also referred to as the zinc electrode (see FIGS. 1a / b, Deposition of the Zinc Layer 9). On the opposite side, a positive electrode 2 is shown, which includes a first current collector 3 coated with a catalyst 4. An alkaline zinc-containing electrolyte 7 is located between the two electrodes 2 and 5. This electrolyte 7 serves as a zinc source so that zinc can be deposited on the current collector 6. Furthermore, the electrolyte 7 serves as a medium for transferring electrons between the electrodes 2 and 5. The electrodes 2 and 5 are connected to electrical means 8 and 10. During charging of the cell (see FIG. 1a), power is consumed from the electrical means 7, e.g., a power source, and oxygen (O) gas is generated at the catalyst layer 4 of the positive electrode 2. In this process, ZnO, which in this case serves as the zinc source, is reduced to zincate (not shown) and then to Zn, and a zinc layer 9 (see FIG. 1b) is deposited on the negative electrode 5. During cell discharge (see FIG. 1b), the zinc layer 9 dissolves, generating hydrogen (H2) gas at the positive electrode 2 coated with the catalyst 4. An electrical means for discharge 10, such as a current sink, consumes the power generated by the zinc dissolution in cell 1, resulting in the consumption of water by cell 1. In this scenario shown in FIG. 1, a bifunctional catalyst 4 for OER / HER is used, also called a gas electrode, to generate oxygen (O2) at the same positive electrode 2 during charging of cell 1 and hydrogen (H2) during discharging of cell 1.

[0132] Figures 2a-2c show the basic structure of different cell systems 100, where at least two or more cells 1 are connected to form the cell system 100. The cells 1 of the cell system 100 can be connected or coupled in parallel (see Figure 2b) or in series (see Figure 2c). When connected in parallel, it is advantageous to coat each positive electrode 2 and negative electrode 5 identically on both sides. The current collectors 3 and 6 for the electrodes 2 and 5 are made of suitable cold-rolled low-carbon steel or nickel-plated steel on all sides (see Figures 2a, 3, and 6). The first current collector 3 of the positive electrode 2 is coated on both sides with a layer of catalyst 4 (see Figures 2a and 4). All positive electrodes 2 are connected to each other and all negative electrodes 4 are connected to each other in the housing 13, so only one power lead-in terminal is required for each electrode. All cells are contained in an alkaline zinc-containing electrolyte 7 bath (Figure 2b), simplifying the water supply and gas (O2, H2) separation. When cells 1 are connected in series, a bipolar electrode 15 (FIG. 2a) can be used, with one side coated with a catalyst 4 and the other side uncoated or coated with a Ni compound. The latter side then receives zinc deposition during charging, forming a zinc layer 9. Thus, when using a bipolar electrode 15, the first and second current collectors 3, 6 may be the same material to form a bipolar electrode. Ionic short-circuiting between cells 1 via the electrolyte 7 in a series connection can be prevented by providing each cell 1 with its own isolated volume of zinc-containing electrolyte 4 (see FIG. 2c). Preferably, there are no favorable ionic conduction paths between cells 1 in the region of the water supply or gas manifold.

[0133] Figures 3a-3d show a second current collector 6 that can be used in the parallel-connected cell system 100. In this example, the current collector 6 is a rectangular plate, but the general principles can be easily transferred to other geometric shapes. The plate can be advantageously made of nickel-plated steel sheet or cold-rolled low-carbon steel. At the top of the plate, connections to the electrical means 8, 10 are present. Figure 3b shows that the plate is provided with an insulating material 14 or insulator along the edge or perimeter of the plate. The connections to the electrical means 8, 10 for charging and discharging the cell or cell system are not covered by the insulating material 14. It can also be seen that the insulating layer 14 or insulator at the bottom edge of the plate extends slightly deeper into the plate than at the side and top edges. This is intentional to create a collection volume 12 at the bottom of the cell system 100 where zinc particles can collect. This area prevents, for example, undesired reactions or short circuits from occurring in the collection volume 12 area of ​​the cell system 100. Figure 3c shows the plate in a side view through the cross section AA shown in Figure 3d. From Figures 3c and 3d it can be seen that at the upper and lower edges the insulator material 14 is extruded on both sides.

[0134] Figure 4 shows a cell system 100 in which electrodes 2 and 5 are arranged in parallel. In such a system, the current collector 6 described in Figures 3a-3d can be used, for example. A side view of a covered housing 13 is shown, in which a negative electrode 5 and a positive electrode 2 are arranged in parallel. As described in Figures 3a-3d, the negative electrode 5 is provided with an insulating material 14 along its edges. Connections to electrical means 8 and 10 are excluded from this. At the upper and lower edges, the insulating material 14 is slightly extruded wider. At the lower edge, the insulating material 14 extends further upward, providing a collection volume 12 within the cell system 100 to collect flaking particles and protect the system from undesired reactions and short circuits. These flaked particles are often zinc particles, which may redissolve during the discharge cycle of the cell system 100 but can be redeposited as metallic zinc on the negative electrode 5. The upper edge of the plate can also serve as a fill limit (see dashed line) for the electrolyte 7 that powers the cell system 100. In the housing 13, all the positive electrodes 2 are connected to each other and all the negative electrodes 5 are connected to each other (not shown), so that only one power input terminal is required for each pole (only one for the positive electrode 2 is shown in Figure 4).

[0135] Figure 5 shows a cell system 100 in which electrodes 2, 5, and 15 are arranged in series. The bipolar electrode 15 described in Figure 2 can be used in such a system. A side view of a covered housing 13 is shown, in which multiple bipolar electrodes 15 are arranged in series. The bipolar electrode 15 (see Figures 2a and 2b) is coated on one side with a catalyst layer 4 and on the other side with either a non-coated or Ni compound coating. Zinc subsequently deposits on the latter side during charging, forming a zinc layer 9. Therefore, when using a bipolar electrode 15, the first and second current collectors 3 and 6 are made of the same material and form a bipolar electrode current collector. However, such a system naturally requires at least one negative electrode 5 and at least one positive electrode 2, which are attached to the beginning and end of the series of bipolar electrodes, respectively (Figure 5). The individual cells 1 in this system 100 are divided into individual compartments separated from each other by insulators or insulating material 14, shown at the bottom or top edge of the housing 13. Each compartment of the cell 1 has its own electrolyte 7 reservoir and independent inlets and outlets for gas, water, and electrolyte 7. Inlets and outlets in this context include the inlet and outlet lines as well as the associated pumps and collection / supply reservoirs for gas, water, and electrolyte 7. In the lower region of each cell 1, a recess is provided in the insulator to act as a collection volume 12 or reservoir for collecting loose particles that may cause short circuits, etc. As shown in FIG. 5, a series-connected cell system 100 with bipolar electrodes 15 may be designed as a so-called flow cell system. In this case, each compartment or cell 1 of such a flow system does not have its own connection for the inlets and outlets of gas, water, and electrolyte 7, but the cells 1 share one or more inlets and outlets. It is important to note that the cells 1 do not have ionic contact through these inlets and outlets. The advantage here is that such a system 100 requires fewer inlets and outlets and associated pumps. Furthermore, monitoring such a system, for example, the amount of water / electrolyte 7 consumed or used, is easy to operate. However, special care must be taken to prevent current-carrying contact between compartments, which could lead to a short circuit in the system. Gas mixing between oxygen and hydrogen, which can occur especially early in the charging or discharging process, should also be avoided. Various design options can be used to solve the above-mentioned problems.

[0136] FIG. 6 illustrates an embodiment of such a design solution. This figure shows a cross-section of a single cell 1 of a flow cell system 100 in a front view. The electrode side of the bipolar electrode 15 is shown in dashed lines for emphasis, but this bipolar electrode 15 is located in front of or behind the illustrated cross-sectional plane. As already explained in FIG. 5, each cell 1 is separated from the other cells 1 by an insulating material 14. However, in the flow cell system, the cells have one or more shared supply / discharge lines 16. To ensure that the cells are ionically connected to each other as little as possible during charging or discharging, the electrolyte 7 in each individual cell is almost completely insulated by additional insulating material 14 in the side and upper edge regions of the cell 1 compartment. Gas is only evacuated through one or more openings in the upper edge of this additional insulating material 14, allowing for refilling with water and electrolyte, if necessary, provided the cell 1 is not being charged / discharged.

[0137] 7a-7c illustrate the design of FIG. 6. Various stages of electrolyte filling are shown, which are the same for all cells 1 or cell compartments of such a system 100. The self-leveling ability of the alkaline zinc-containing electrolyte 7 to replenish after discharge cycles ensures that the same level of electrolyte 7 is always present in each cell compartment. In FIG. 7a, the entire cell 1 is completely filled with electrolyte 7 via a shared supply / drain line 16. The excess electrolyte is then drained again (see FIG. 7b). Once the excess electrolyte 7 is completely drained or pumped out, an equal amount of electrolyte 7 remains in each cell compartment.

[0138] Figure 8 shows another version of the design shown in Figure 6. Here, the additional insulating material 14 at the top edge also serves to prevent excessive loss of electrolyte 7 if the cell 1 is tilted or during operation.

[0139] FIG. 9 shows another type of cell / system design. Here, each individual cell 1 of the system 100 is covered by a membrane 11, 17. This membrane 11, 17 may be permeable to water and gas or only to gas, but not to the electrolyte 7. Above the cell 1 with the membrane 11, 17, there is a reservoir for water and / or the evolved gases hydrogen and oxygen. Gas is discharged through the inlet and outlet 16, and water can be supplied as needed. With such a system design, the entire system 100 can be easily maintained.

[0140] It should be noted that the term "comprises" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, elements described in association with different embodiments may be combined.

[0141] It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims. [Explanation of symbols]

[0142] 1 cell 2 positive electrodes 3 First current collector 4. Catalyst 5 negative electrode 6 Second current collector 7. Zinc-containing electrolytes 8 Means for charging the cells 9 zinc layer 10. Means for discharging the cell 11 First membrane 12 Collection volume 13. Housing 14 Insulating materials 15 Bipolar electrodes 16 Shared supply / discharge lines 17 Second membrane 100 cell system H2 Hydrogen Gas O2 oxygen gas

Claims

1. A cell (1) for the reversible storage of energy and hydrogen and the production of hydrogen and electricity, comprising: a positive electrode (2) comprising a first current collector (3) coated with a catalyst (4); a negative electrode (5) having a second current collector (6); an alkaline zinc-containing electrolyte (7); Equipped with When the cell (1) is charged under electrical consumption when connected to an electrical means (8) for charging the cell, oxygen (O ) is deposited at the positive electrode (2) while a zinc layer (9) is electrodeposited at the negative electrode (5). ２ ) gas is evolved and the zinc layer (9) appears as a dense solid metal, has a nodular and / or layered microstructure, has low porosity and is adhered to the second current collector (6); When the cell (1) is discharged under the release of electricity when connected to an electrical means (10) for discharging the cell, the zinc layer dissolves from the negative electrode (5) and simultaneously hydrogen (H ２ ) Gas is generated, cell (1).

2. 2. The cell (1) of claim 1, further comprising a separator that is impermeable to ZnO, said separator being located between said positive electrode (2) and said negative electrode (5).

3. 3. The cell (1) according to claim 1 or 2, further comprising a separator that is impermeable to zincate but permeable to hydroxide ions, the separator being located between the positive electrode (2) and the negative electrode (5).

4. 4. The cell (1) according to any one of claims 1 to 3, wherein the first and / or second current collectors (3, 6) are selected from the group comprising one or more of steel, low carbon steel, nickel, nickel plated steel, nickel plated low carbon steel or NiP coated steel, and wherein the first and / or second current collectors (3, 6) are cold formed, preferably cold rolled.

5. 5. The cell (1) according to any one of claims 1 to 4, wherein the zinc layer (9) is partially or completely removed from the second current collector (6) during discharge, resulting in a bare second current collector (6) when the zinc layer (9) is completely removed by 100% depth of discharge (DOD).

6. The cell (1) according to any one of claims 1 to 5, wherein the catalyst (4) is a bifunctional catalyst for the hydrogen evolution reaction (HER) during discharge of the cell (1) and for the oxygen evolution reaction (OER) during charging of the cell (1).

7. The cell (1) according to any one of claims 1 to 6, wherein the catalyst (4) comprises two different types for HER and OER, mixed and / or applied in a pattern on at least one surface of the first current collector (3).

8. 8. The cell (1) according to any of the preceding claims, wherein the catalyst (4) is selected from the group comprising one or more of Ni, Ni alloys, binary Ni alloys, Raney Ni, Ni-Al, Ni-Mo, Ni-Zn, Ni-Co, Ni-W, Ni-Fe, ternary Ni alloys, NiCoMo, NiFeMo, NiCoCu, ternary Ni alloys, NiCoMoAl, NiCoMoZn, oxides of Ni, Ni alloy oxides, oxides of binary nickel alloys, oxides of ternary nickel alloys, oxides of NiCoMn or other ternary Ni alloys, hydroxides of Ni or Ni alloys, synthetic NiFeOx nanoparticles, Ni(OH)2, NiO, Ni, Ni2P, Ni-S NiMoNx, nitrides, sulfides and / or carbides.

9. A cell system (100) for the reversible storage of energy and hydrogen and the production of hydrogen and electricity, comprising two or more cells (1) according to one of claims 1 to 8.

10. The cell system (100) of claim 9 further comprising a recombination catalyst used as a safety measure to remove residual hydrogen (H2) / oxygen (O2) gas mixture, and / or temperature monitoring of the recombination catalyst is used as a fault detection mechanism for the cell system (100).

11. 11. The cell system (100) of claim 9 or 10, further comprising a first membrane (11) that is permeable to water, oxygen, and hydrogen, but impermeable to the alkaline zinc-containing electrolyte (7).

12. A cell system (100) according to any one of claims 9 to 11, further comprising a second membrane (17) that is permeable to oxygen and hydrogen but impermeable to said alkaline zinc-containing electrolyte (7).

13. The cell system (100) according to any one of claims 9 to 12, further comprising a collection volume (12) at the bottom of each cell (1) or the cell system (100) configuration to allow particle aggregation without risk of short-circuiting the cells (1).

14. 14. The cell system (100) of claims 9 to 13, further comprising a housing (13) configured to allow gas to be collected from the cell system (100) without losing alkaline zinc-containing electrolyte (7) from the cell system (100) and while minimizing ionic connections between individual cells (1), and / or the housing (13) having an insulating material (14) and a self-leveling ability to replenish the alkaline zinc-containing electrolyte (7) after a discharge cycle.

15. The cell system (100) of any one of claims 9 to 14, wherein the cells of the cell system (100) are individually combined in the form of a stack, an arrangement, an array, or a bipolar stack, and in the case of the bipolar stack form, the cell system (100) comprises at least one bipolar electrode (15), the bipolar electrode (15) having the negative electrode (5) on one side and the positive electrode (2) on the other side.

16. A cell system (100) as described in claims 9 to 15, wherein the voltage and / or current and / or temperature of the cell or cell system, and / or the temperature of the recombination catalyst are monitored for fault detection during charging and discharging of the cell system (100).

17. The cell system (100) according to any one of claims 9 to 16, wherein hydrogen (H2) gas is produced during discharge at a pressure of 0.1 to 1000 bar, preferably 1 to 40 bar, more preferably 1 to 4 bar.

18. A method for the reversible storage of energy and hydrogen and the production of hydrogen and electricity using a cell (1) or a cell system (100) according to one of claims 1 to 16, comprising the steps of: applying 0-30 Hz, preferably 5-20 Hz, more preferably 10 Hz, 5%-80% duty cycle pulses for zinc deposition onto said current collector material until a predetermined state of charge (SOC) and / or a predetermined mass of said zinc layer is reached; Pulses having a lower limit of about 0.01 Hz, preferably about 0.05 Hz, more preferably about 0.1 Hz, and an upper limit of about 500 Hz, preferably about 100 Hz, more preferably about 50 Hz, with a duty cycle of 8% to 1% or less, preferably 5% to 2% or less, more preferably 5%, and / or a current of 10 mA / cm ２ Preferably, 8 mA / cm or less ２ More preferably, 5 mA / cm or less ２ until a predetermined minimum current density is reached: A method comprising:

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