High power electrochemical systems and methods

Abstract

The present disclosure relates to systems and methods utilizing a metal-water battery comprising a metal anode, a water-reducing cathode, and an ion exchange layer to enable efficient energy conversion. The metal-water battery generates discharge products, including hydrogen gas, which can be converted into usable energy by a discharge product power unit, offering a high degree of operational flexibility. Systems and methods described herein can further include discharge products hygroscopic materials or desiccants of a water supply unit. In one implementation, the disclosed systems and methods can be employed in propulsion systems including aviation having demanding duty cycles. The integrated systems and associated methods described herein can deliver enhanced energy density, power density, and reliability, making it a renewable alternative to conventional propulsion systems.

Description

HIGH POWER ELECTROCHEMICAL SYSTEMS AND METHODSINVENTOR: CODY FRIESENCROSS-REFERENCE TO RELATED APPLICATION[1] This application claims priority to U.S. Provisional Application Serial No. 63 / 602,446, filed on November 24, 2023, the disclosure of which is incorporated by reference in its entirety.TECHNICAL FIELD[2] This disclosure relates to high-power electrochemical systems and methods to provide power in applications that require efficient energy delivery, including use in aviation applications for electric vertical takeoff and landing (eVTOL) aircraft and hybrid propulsion systems.BACKGROUND[3] Sustainable and alternative propulsion systems that are powered by a renewable energy source and / or avoid burning of petroleum-based fossil fuels, particularly for electric aviation and vertical takeoff and landing (eVTOL) aircraft, represent a rapidly advancing sector. Various battery technologies, including hybrid systems, are needed to achieve efficient, high- performance propulsion and flight. Current lithium-ion battery systems used for electric aircraft offer high energy density and lightweight properties. However, the specific requirements of aviation demand further advancements in both material compositions and system architectures. Propulsion systems and batteries for aviation face stringent challenges, including the need forenhanced energy density, safety, thermal stability, and longevity to meet the demanding conditions of flight.[4] One of the most significant challenges for eVTOL aircraft is their unique duty cycle, characterized by high discharge currents during takeoff and landing, coupled with a moderate power demand during the cruising phase. This cycle leaves no rest periods, placing immense stress on the battery throughout the flight. Conventional propulsion systems and batteries struggle to maintain performance under these conditions, where repeated cycles of high-power bursts are required. Therefore, there is a critical need for the development of next-generation propulsion systems that can address demands of aviation and other applications having extreme duty cycles, providing reliable and efficient power under fluctuating load conditions while ensuring long-term durability and safety.BRIEF SUMMARY[5] The present disclosure relates to systems and methods utilizing a metal-water battery including a metal anode paired with a water reducing cathode separated by an ion exchange layer. Metal -water-battery discharge products such as hydrogen, can be stored and / or further converted for a high degree of operational flexibility. The system includes a discharge product power unit that can convert the metal-water battery discharge products, generated as a byproduct of the battery's discharge process, into usable energy. The system can further include a hygroscopic material or desiccant unit to recycle water and sustain water supply to the system.[6] In one implementation, the disclosed system and methods provides a sustainable and efficient energy solution for electric aviation such as vertical takeoff and landing (eVTOL) aircraft. By addressing the demanding duty cycles of eVTOL propulsion, characterized by highdischarge during takeoff and landing and moderate cruise power, the systems and methods disclosed herein can provide enhanced energy and power density, thermal stability, and reliability under fluctuating loads. The systems and associated operational methods employing an integrated metal-water battery, discharge product power unit and water supply unit are uniquely suited to the stringent operational requirements of aviation, providing a renewable alternative to traditional propulsion systems.BRIEF DESCRIPTION OF THE DRAWINGS[7] The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers. Views in the figures are drawn to scale (unless otherwise noted), meaning the sizes of the depicted elements are accurate relative to each other for at least the embodiment in the view.[8] FIG. 1 depicts a block diagram of a high-power electrochemical system according to the present technology;[9] FIG. 2 depicts a Pourbaix diagram related to operation of a high-power electrochemical system according to the present technology;

[0010] FIG. 3 depicts a block diagram of a high-power electrochemical system according to the present technology;

[0011] FIG. 4 depicts a block diagram of a high-power electrochemical system according to the present technology;

[0012] FIG. 5 depicts a method of operating a high-power electrochemical system according to the present technology.

[0013] For simplicity and clarity of illustration, the drawing figures show the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0014] The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure.

[0015] Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and / orany other possible attachment option. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.

[0016] This disclosure includes embodiments of systems and methods, such as, for example, for water treatment and storage. The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The terms “a” and “an” are defined as one or more unless this disclosure explicitly requires otherwise. The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately,” “partially” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, 10 and 20%. Further, a device or system that is configured in a certain way is configured in at least that way, but it can also be configured in other ways than those specifically described.

[0017] The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, an apparatus that “comprises,” “has,” “includes,” or “contains” one or more elements possesses those one or more elements but is not limited to possessing only those elements Likewise, a method that “comprises,” “has,” “includes,” or “contains” one or more operations or steps possesses those one or more operations or steps, but is not limited to possessing only those one or more operations or steps.

[0018] Any embodiment of any of the apparatuses, systems, and methods can consist of or consist essentially of — rather than comprise / include / contain / have — any of the described steps,elements, and / or features. Thus, in any of the claims, the term “consisting of’ or “consisting essentially of’ can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb. The feature or features of one embodiment may be applied to other embodiments or implementations, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.

[0019] As will be described in detail below, this disclosure describes various “hybrid”, “integrated” and / or “high-power” electrochemical systems and related operational methods that can be particularly advantageous in aerospace applications. The system disclosed herein can integrate 1) a high-power metal battery (e.g., a metal-water battery), 2) a discharge product storage unit (e.g., hydrogen storage unit such as a pressurized tank, sorption bed for storage via solid materials like metal hydrides or carbon materials) and / or 3) a discharge product power unit (e.g., hydrogen power unit, fuel cell, hydrogen combustion sub-system, turbine, and / or the like) to provide high power densities with high efficiency, especially advantageous for power delivery during peak demand periods. In an example, the metal-water battery is configured for high-power capability and serves as a primary power source (e.g., for lower power demand periods, cruising or normal aircraft operation). In some implementations, the metal-water battery discharge product(s) can be stored for later use. To address peak power demands (e.g., during aircraft takeoff or climb), a power generation unit can utilize a battery discharge product (e.g., hydrogen gas evolved at the cathode and / or metal hydroxides formed from metal-water battery discharge) to generate additional electrical power, generate heat to facilitate operation of the metal -water battery (e.g., melting a liquid metal anolyte, heating a sorption material to release water for supply to a catholyte, and / or the like). Furthermore, in some implementations the discharge product powerunit can generate water which can be returned to the cathode of the metal-water battery. This dynamic synergy between the metal-water battery and the discharge product power unit can maximize power output on demand while establishing a high overall operational efficiency for the system.

[0020] FIG. 1 depicts a block diagram of an exemplary high-power electrochemical system 100 according to the present technology. System 100 comprises a metal-water battery 110 including: a metal anode 1 12 configured to oxidize a metal to form metal ions during a battery discharge operation, a cathode 114 configured to reduce water in a catholyte to evolve or generate hydrogen gas during the battery discharge operation, and an ion exchange layer 116 between the anode and the cathode to conduct metal ions (M+) therebetween. The ion exchange layer 116 can comprises a polymeric ion exchange membrane layer, a ceramic ion exchange layer, an ionic liquid, a molten salt, or a combination thereof. In various implementations ion exchange layer 116 separates an anolyte of the anode 112 and a catholyte of the cathode 114 to selectively allow ion transport while preventing the mixing of anode and cathode materials. Anolytes and catholytes of the present technology can include aqueous media, non-aqueous media, ionic liquids, molten salts and / or the like. Furthermore, the metal-water battery can include a non-aqueous anolyte and an aqueous catholyte.

[0021] In various implementations, the electrolyte 116 of the metal battery is provided as an aqueous electrolytes containing a metal hydroxide(s) M-OH (e.g., sodium hydroxide NaOH, potassium hydroxide KOH, lithium hydroxide LiOH and / or the like) and / or metal salt(s) (e.g., sodium chloride NaCl, potassium chloride KC1, lithium chloride LiCl, magnesium sulfate MgSO4 and / or the like) to provide high ionic conductivity and facilitate the transport of metal ions (M+). The electrolyte can be formulated to optimize ion mobility while minimizing parasitic reactions.Additionally, the use of other ionic species or additives such as surfactants or complexing agents can enhance the stability of the electrolyte and improve overall battery efficiency.

[0022] The metal-water battery 110 of the present technology can be provided in various configurations and include various materials to meet desired performance, energy density, power density, cost and application suitability. Various configurations can be employed including small- scale or compact single-cell configurations, mid-scale to large-scale stacked configurations with multiple cells connected in series or parallel to increase voltage and capacity, or flow battery configurations where active material(s) are stored and circulated through the electrochemical cell such as depicted in the example of FIG. 1.

[0023] As an illustrative example, the metal anode 112 can be configured to receive a liquid metal anolyte such as melted sodium metal, for example pumped or flowed into anode 112 via liquid metal sub-system or unit 118. Liquid metal sub-system or unit 118 can comprise a liquid metal reservoir for storing metal reactant and a pump to input liquid metal into the anode 112. In some implementations, heat (Q depicted in dashed lines) generated from power generation unit 124 can be used to melt the metal in liquid metal unit 118. The cathode 114 can include an aqueous catholyte, for example aqueous alkaline media such as aqueous sodium hydroxide.

[0024] System 100 further comprises a discharge product power unit 120 configured to store and / or utilize (e.g., react, combust and / or the like) discharge product(s) of the metal-water battery 110. In one example, discharge product power unit 120 is a hydrogen power unit 120 configured to store (e.g., via hydrogen storage tank 122) and / or utilize a discharge product(s) of the metal-water battery, for example hydrogen gas generated by the metal-water battery upon the battery discharge operation. In various implementations, the discharge product power unit 120, or more particularly hydrogen power unit 120, comprises a power generation unit 124 configured toconvert hydrogen gas generated from the metal -water battery 110 and oxygen (O2) from ambient air to produce electricity (e.g., via a hydrogen fuel cell) and / or heat (e.g., via auxiliary power unit, combustion reactor, turbine). As such, the hydrogen power unit 120 can comprise a hydrogen fuel cell, a hydrogen combustion subsystem, a hydrogen combustion heat exchanger, a hydrogen storage tank, or a combination thereof.

[0025] In some implementations, the system can comprise a water supply unit (e.g., 130) that can include a water storage unit (e g., 132), a water pump (e.g., 134) and / or a desiccant unit (e.g., 136) to supply water (H2O) to the cathode as catholyte of the metal-water battery 110. In one exemplary implementation, the discharge product power unit 120 generates heat to heat a hygroscopic material in the desiccant unit 136 to desorb captured water therein to sustain a water supply to the cathode of the metal-water battery. In such an example, power generation unit 124 comprising a fuel cell can react hydrogen gas generated from the metal-water battery and oxygen (e.g., from the ambient environment) to generate electricity and also form water which can then be stored via a hygroscopic material of the desiccant unit 136 during a water vapor sorption operation (i.e., so as to provide water recapture functionality). Furthermore, a controller (e.g., 140) can operate the power generation unit 124 to generate heat (Q depicted in dashed lines) to heat the hygroscopic material of the desiccant unit 136 during a desorption operation to drive desorption of recaptured water from the desiccant unit 136. The desorbed water vapor can be stored in water storage unit 132 and / or fed back to cathode 114 of battery cell 110 via water pump 134. In such instances, the power generation unit 124 can comprise a hydrogen fuel cell to generate water that is effectively recycled to the cathode of the metal-water battery such that the system operated in a closed, or at least partially closed, loop.

[0026] In some implementations, the power generation unit 124 can generate heat to melt the metal of the metal anode, for example via a heat exchanger. Various types of heat exchangers can be used to maintain the metal anode in a molten state to allow for efficient metal flow and electrochemical reactions, including shell-and-tube, plate, radiative heat exchangers.

[0027] The metal of the metal-water battery can comprise sodium, lithium, aluminum, calcium, potassium, magnesium, boron, or any combination thereof (e.g., a sodium-potassium eutectic). In various embodiments, the metal of the metal-water battery can comprise one or more alkali metals having a low melting point. As an exemplary eutectic material, a sodium-potassium eutectic (NaK) can be provided as a liquid metal alloy consisting of a mixture of sodium (Na) and potassium (K) having a lower melting point than either of the individual metals. Such a NaK eutectic mixture can be provided in a range of compositions between approximately 40% to 90% potassium (K) by weight and / or about 60-80% potassium (K) by weight, so as to provide liquid metal conductivity at relatively low temperatures.

[0028] As an illustrative example used for ease of description, a metal-water battery including a sodium metal anode will be described to enable those skilled in the art to practice the disclosure, however it should be understood that other battery systems may be employed and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure.

[0029] The cathode 114 of the metal-water battery 110 can be provided in various configurations and comprise various materials to facilitate the reduction of water and the generation and management of discharge products including hydrogen evolution, while being durable and resistant to corrosion. The cathode can include porous structures, meshes, and / or layered electrode designs to maximize surface area and facilitate gas release. For example, carbon-based materials, such as graphite, carbon cloth, and activated carbon can be used to provide high conductivity and corrosion resistance. Metal-based catalysts (e.g., platinum, nickel, cobalt and alloys thereof) can increase efficiency in promoting hydrogen evolution. Metal oxides (e.g, manganese dioxide, nickel oxide) can provide stability and catalytic activity in alkaline environments. Conductive polymers (e.g., polyaniline, polypyrrole) can also be used to enhance conductivity and provide flexible cell design options.

[0030] As an illustrative example, the metal-water battery is a sodium-water battery, wherein the metal anode is configured to oxidize a liquid sodium metal to form sodium ions upon discharge. The cathode can be configured to reduce water to generate hydrogen gas and hydroxide ions. In such an implementation, the ion exchange layer can comprise a polymer ion exchange membrane, or a ceramic ionic exchange layer or solid electrolyte such as a Sodium Super Ionic Conductor (NaSICON) solid electrolyte comprising a crystalline structure with sodium ion conductive pathways.

[0031] FIG. 2 depicts an exemplary Pourbaix diagram to illustrate the operation of systems of the present technology. Line 201 represents a metal anode reaction (e.g., sodium) for the oxidation of the metal to form metal ions upon discharge (i.e., below line 201 metal M is in a stable reduced form and above which metal is in an oxidized form having released electrons). Conventional metal-air (i.e., metal-oxygen) batteries pair a metal anode with an air cathode configured for oxygen reduction from air at the cathode which is represented by the Oxygen Reduction Reaction (ORR) line 205. While conventional metal-air batteries offer a higher cell potential (i.e., indicated as EM-OZ) relative to a metal-water battery (i.e., indicated as EM-HZO), they suffer from low power densities and lower efficiency attributed to overpotential, the difference between the thermodynamic potential and the actual potential required for operation, due to lossesor inefficiencies that are associated with the four electron ORR process O2 + 2 H2O + 4 e -> 4OH .

[0032] Metal batteries of the present technology instead preferably pair a metal anode (represented by line 201) with a cathode configured for water reduction to produce hydrogen gas H2 (represented by the Hydrogen Evolution Reaction (HER) line 203 which may be associated with a more facile two electron process (i.e., 2 H2O + 2e -> H2 + 2OH ). In comparison to conventional metal-air (i.e., metal-oxygen) batteries, the metal-water battery offers greater power densities and efficiency given the smaller overpotential for water reduction compared to oxygen reduction. Furthermore, the production of hydrogen and other discharge product(s) allows flexibility in subsequent use (e.g., storage, further conversion). While the overall cell potential for a metal-water battery is lower than that of a metal-air battery, the hybrid system architecture of the present disclosure synergistically pairs a metal-water battery generating discharge products (e.g., hydrogen, metal hydroxide) with a discharge product power unit (e.g., a hydrogen power unit) that effectively offsets or compensates for the lower cell potential of the metal-water battery. In other words, systems of the present technology enable access to the entire potential range (i.e., spanning EM-H2O and EH2-H02), but even more advantageously in that the architecture unlocks the ability to optimize, or determine via a controller, a desired operational regime (e.g., distributed between metal-water battery vs. hydrogen power unit vs. hydrogen storage) based on a particular application, environment or power demand.

[0033] A total system efficiency can be calculated by dividing the actual operating potentials of the metal-water battery (EM-H2O) and the hydrogen power unit (EH2-02) by the theoretical potential over the entire range (i.e., E° being the difference between line 201 and line 205):Total Efficiency — (EM-H2O + EH2-H02) / E°

[0034] As an illustrative non-limiting example, a sodium metal-water battery (e.g., 110) generating hydrogen can be paired with power generation unit 124 comprising a hydrogen fuel cell to effectively compensate for a lower cell potential of the sodium metal-water battery as compared to a sodium metal-air battery. In a sodium metal-water battery, sodium metal (Na) is oxidized and water (H2O) is reduced to produce hydrogen gas (H2) and sodium hydroxide (NaOH) according to the following reactions:

[0035] Anode: 2 Na — > 2 Na++ 2 e

[0036] Cathode: 2 H2O + 2 e H2+ 2 OH

[0037] Overall : 2 Na + 2 H2O 2 NaOH + H2.

[0038] While the formation energy, or standard enthalpy of formation, of sodium hydroxide is -470 kJ / mol and the formation energy of hydrogen gas from water is +242 kJ / mol, the overall reaction is exothermic as the energy released from sodium hydroxide formation is greater than the energy consumed by the formation of hydrogen. As such, the overall process in a sodium metal-water battery is energetically favorable, releasing energy that can be harvested as electricity while also forming discharge products, like hydrogen gas and sodium hydroxide, that can be stored and / or further converted in discharge product power unit 120.

[0039] The discharge product(s) from the metal-water battery (e.g., 110), for example hydrogen gas (H2) and metal hydroxide (M-OH), can be stored and / or further reacted as desired. FIG. 1 depicts system 100 wherein the hydrogen gas (H2) discharge product output from metalwater battery 110 is stored (e.g., via tank 122) and / or reacted in power generation unit 124 (e.g., a fuel cell, a combustion reactor, a turbine and / or the like).

[0040] In one example, a hydrogen fuel cell of power generation unit 124, reacts hydrogen gas (H2) with oxygen (O2) from ambient air to produce water (H2O) and generate electrical energy according to the following reaction: 2 H2 + O2 > 2 H2O. The formation energy, or standard enthalpy of formation, of water from hydrogen and oxygen is -286 kJ / mol such that the chemical potential stored in hydrogen gas can be electrochemically harvested in a fuel cell to generate electrical energy.

[0041] In related implementations, FIG. 3 and FIG. 4 depict system 100 comprising metalwater battery 110 and discharge product power unit 120. Unless otherwise specified, the numerical indicators used to refer to components in FIG. 1 are similar to those used to refer to components or features in FIG. 3 and FIG. 4.

[0042] The discharge products of metal-water battery 110, exemplified in this description as hydrogen gas and aqueous sodium hydroxide (NaOH), can be stored together or separately. Furthermore, the discharge products can be utilized in the same or different reactors. For example, storage and / or utilization can be facilitated by their different phases wherein gaseous hydrogen is captured and stored in pressurized tanks for later use or fed directly into a fuel cell for energy generation, whereas aqueous NaOH is stored in dedicated reservoirs or reacted or processed via a separate reactor unit. Alternatively, their separation can be efficiently achieved within the same reactor due to the natural phase difference, allowing hydrogen gas to rise while the sodium hydroxide solution remains at a lower portion of the unit.

[0043] As depicted in FIG. 3, a metal hydroxide discharge product (M-OH) generated upon discharge of metal -water battery 110, such as sodium hydroxide from a sodium metal -water battery, can be stored (e.g., via tank 122) and / or reacted in power generation unit 124 (e.g., a combustion reactor, a turbine and / or the like). In the example depicted in FIG. 4, a metal hydroxide(M-OH) discharge product can be stored in storage tank 152 and / or output to (e g., sprayed) or contacted with the atmosphere so as to react with atmospheric carbon dioxide in an exothermic reaction.

[0044] System 100 comprises controller 140 that can be configured to increase a total efficiency of the system, i.e., total efficiency of a discharge operation of the metal-water battery and an efficiency of discharge product (e.g., hydrogen gas) conversion by the discharge product power unit 120 (e g., fuel cell operating efficiency, hydrogen combustion efficiency). As an example, the controller 140 can increase or adjust an amount, pressure or flow rate of the liquid metal into the anode (e.g., via a pump of unit 118) based on a current or power demand threshold. Similarly, controller 140 can increase or adjust an amount, pressure or flow rate of metal-water battery discharge products such as metal hydroxide and / or hydrogen gas into power generation unit 124 based on a current or power demand threshold, a duty cycle, and / or the like.

[0045] In an aerospace application, the controller 140 can be configured to increase a power output of the system via the power generation unit based on an increase power demand of an aircraft. In one example, system 100 is employed as or as part of an auxiliary power unit (APU) for an aircraft. The discharge product power unit 120 can provide peak power via conversion of metal-water battery discharge products such as hydrogen gas generated by the metal-water battery 110. During periods of low power demand, the metal-water battery can generate hydrogen gas and / or other metal-water battery discharge products that are stored (e.g., onboard) and then consumed via the power generation unit when additional power is needed.

[0046] In advanced systems, such as hybrid-electric aircraft, controller 140 is configured to control a relative contribution of power sources (i.e., metal-water battery 110 and discharge product power unit 120) of system 100 to meet the different energy and power requirementsthroughout the duty cycle. System 100 can be configured to supply peak power (e.g., operate both metal-water battery 110 and discharge product power unit 120) in a first mode such as during takeoff and climb, and then switch to a second mode (e.g., operate metal -water battery 110 without or with minimal operation of discharge product power unit 120) during cruising and descent. For aircraft systems that generate power from chemical reactions (like metal-water batteries), the timing of when the reaction occurs and discharge products are generated can be controlled to supply the necessary energy during high-demand periods of the flight duty cycle.

[0047] In some implementations, the metal -water battery 110 can be a sodium-water battery configured to generate a sodium hydroxide (NaOH) discharge product, and the sodium hydroxide discharge product can be contacted with the ambient environment to form sodium carbonate (Na2CCh) and / or sodium bicarbonate (NaHCCh) from ambient carbon dioxide. When sodium hydroxide comes into contact with carbon dioxide, sodium bicarbonate and / or sodium carbonate can form depending on the reaction conditions including the relative amounts of sodium hydroxide and carbon dioxide, with sodium bicarbonate predominating in the presence of moderate amounts of carbon dioxide (such as in typical atmospheric air) and short term exposure to ambient air, with sodium carbonate being the more stable end product upon long term exposure or higher temperatures.

[0048] In various implementations, the discharge product(s) from the metal-water battery are reacted with ambient air (e.g., via power generation unit 124) in an exothermic reaction that can be used for power generation during flight. When a metal-water battery discharge product (M- OH) such as sodium hydroxide (NaOH) is contacted with carbon dioxide in ambient air, sodium bicarbonate can form according to NaOH + CO2 (g) — > NaHCO with an overall reaction enthalpy of approximately -129 kJ / mol, indicating an exothermic reaction that it is energetically favorable.Furthermore, the overall reaction enthalpy of sodium carbonate through the reaction of sodium hydroxide (NaOH) with carbon dioxide (CO2) according to 2 NaOH + CO2 Na2CCh + H2O is approximately -172 kJ / mol. These energetically favorable reactions converting metal -water battery discharge products can be converted into useful forms of energy for propulsion. For example, generated heat generated can be used to generate electricity via thermal energy conversion system(s) (e.g., turbine-electrical generator).

[0049] As depicted in FIG. 3, power generation unit 124 can be configured as a reactor such that a metal hydroxide (M-OH), such as sodium hydroxide (NaOH), is reacted with carbon dioxide (CO2) present in the air. Both formation of sodium carbonate and sodium bicarbonate reactions are exothermic, and the heat can be utilized to drive turbines or other power generation mechanisms of power generation unit 124. In one implementation, atmospheric air containing oxygen and carbon dioxide is introduced into a reactive chamber containing hydrogen and sodium hydroxide resulting in the formation of water, sodium carbonate and / or sodium bicarbonate as products. The generated thermal energy can be converted to electrical power, and in some implementations the solid products can be collected. This integrated approach can offer both efficient CO2 capture and sustainable power generation, particularly suited for applications such as aviation, where carbon reduction, energy efficiency and optimized power density are critical.

[0050] In the example depicted in FIG. 3, both hydrogen gas (H2) and metal hydroxide (M- OH) discharge products are input to power generation unit 124 to react with atmospheric oxygen (O2) and carbon dioxide (CO2) to form water (H2O) and metal carbonate(s). When the metal-water battery 110 is configured as a sodium metal-water battery, a sodium hydroxide (NaOH) discharge product can be fed to power generation unit 124 to react with carbon dioxide (CO2) to form sodium carbonate (Na2COa) and / or sodium bicarbonate (NaHCOs), depending on the reaction conditions.The overall exothermic reaction releases significant amounts of heat, which can be harnessed to drive a turbine or similar power-generating mechanism of the power generation unit 124, thereby producing electrical energy on demand. This approach can efficiently convert chemical energy into electrical energy which can be especially advantageous for high demand duty cycles, with the added benefit of carbon capture through the formation of stable carbonates.

[0051] The systems and methods disclosed herein provide a flexible power generation and use approach which can be particularly advantageous for high-duty flight cycles. In the example of FIG. 3, the metal hydroxide discharge product (M-OH) is fed into the power generation unit 124, where it reacts with atmospheric carbon dioxide (CO?) to form metal carbonates, releasing additional energy. This reaction not only captures atmospheric carbon dioxide, reducing emissions, but also supports increased energy and power density by utilizing the discharge products in a secondary reaction phase. This feature enables higher power output and greater flexibility, as the discharge products can be stored for subsequent use or further converted in flight depending on operational needs. This approach allows for increased system efficiency and power density, making it particularly advantageous in high-demand applications such as aviation. The system’s ability to capitalize on the exothermic nature of these reactions provides a scalable and sustainable solution for power generation, with improved efficiency, carbon capture, and energy utilization.

[0052] In an example, power generation unit 124 comprises a reactor configured to facilitate the exothermic reactions of sodium hydroxide (NaOH) discharge product from sodium metal -water battery 110 with carbon dioxide (CO2) from atmospheric air and hydrogen gas (H2) with oxygen (O2) from atmospheric air. The reactor can be configured as a gas-liquid contact unit, where gaseous hydrogen (H2) is introduced into the unit and reacted with atmospheric oxygen in a controlled chamber, generating water (H2O) and releasing energy for conversion to electricity.In some embodiments, hydrogen gas and air can be fed to a fuel cell generating water and electricity in an electrochemical reaction. Simultaneously or in a series manner, aqueous sodium hydroxide can be contacted with gaseous carbon dioxide in a same reactor module or in a separate reactor module to form sodium carbonate (Na2COs) and / or sodium bicarbonate (NaHCCh) to release heat and energy to generate electricity.

[0053] The power generation unit 124 can comprise various types of chemical conversion units, modules or reactors. For example, power generation unit 124 can comprise a packed-bed or fluidized-bed reactor, where aqueous metal hydroxide (e.g., aqueous NaOH) flows over a solid packing material to maximize gas-liquid contact with carbon dioxide to enhance mixing of gaseous and liquid phases. In yet another example, a membrane reactor can be used to selectively manage the intake of reactants and reaction rates. In some configurations, power generation unit 124 comprises a turbine system to harness thermal energy from the NaOH-CCh and / or H2-O2 reactions to drive a turbine for generation of electricity.

[0054] In one example depicted in FIG. 4, the metal-water battery discharge product (M- OH) such as a sodium hydroxide discharge product (e.g., 152) can be contacted with or output (e g., sprayed) into the atmosphere during flight to form a precipitate such as sodium carbonate and / or sodium bicarbonate upon contact with air, thereby providing carbon capture functionality while reducing weight of the aircraft during flight. Alternatively or in addition, the discharge product can be kept onboard (e.g., via storage tank 152) such that discharge product(s) are utilized subsequent to flight.

[0055] FIG. 5 depicts a method of operating a high-power electrochemical system (e.g.,100) according to the present technology.

[0056] At step 1002, the method includes discharging a metal -water battery (e.g., 110) by oxidizing a metal (M°) at an anode (e.g., 112) of the metal-water battery, generating metal ions (M+) and releasing electrons. The oxidation of the metal produces electrons that are transported through an external circuit that can be used in propulsion. In an illustrative example, sodium metal is oxidized to form a sodium hydroxide discharge product.

[0057] At step 1004, the method includes reducing water to generate discharge products that can include hydroxide ions (OH ) and hydrogen gas (Hs) during discharge of a metal-water battery. This reduction step occurs simultaneously with corresponding step 1002 of metal oxidation at the anode and forms part of the electrochemical reaction within the metal-water battery.

[0058] At optional step 1006, the method includes optionally collecting and / or storing battery discharge product(s) e.g., hydrogen gas and metal discharge products, such as metal hydroxides or metal oxides formed during the oxidation of the metal anode. These battery discharge products can be further processed for recycling or reuse in subsequent cycles, enhancing the sustainability of the system. In one example, hydrogen gas and / or sodium hydroxide is stored for power generation on demand. In another example, metal oxides can be collected and refined to extract valuable materials for reuse in battery production or other industrial processes.

[0059] At step 1008, the battery discharge products (e.g., hydrogen gas, metal hydroxide(s) and / or metal carbonate(s)) can be used to generate heat and / or electricity on demand e.g., during periods of high energy or power demand of a duty cycle (such as during flight takeoff or climb). For example, hydrogen gas produced during water reduction at the cathode can be combusted in a hydrogen fuel cell or a turbine to produce electrical energy or heat. Alternatively or additionally, exothermic reactions between metal hydroxides with atmospheric gases (e.g., carbon dioxide) canrelease heat, which may be harnessed to generate electricity via thermal energy conversion unit(s). The utilization of these discharge products provides an efficient method for converting chemical energy into heat and / or electricity, offering a secondary energy source beyond the initial output of the metal -water battery.

[0060] The methods disclosed herein enable an integrated energy generation process, where both the electrochemical reactions within the metal-water battery and the utilization of its discharge products contribute to overall system efficiency. The combination of metal -water battery oxidation and reduction processes in combination with and discharge product utilization enhances power density and energy output, making it applicable to various energy storage and generation systems.

[0061] The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the methods and systems are not intended to be limited to the particular forms disclosed. Rather, they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, elements may be omitted or combined as a unitary structure, and / or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and / or functions and addressing thesame or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0062] Furthermore, the materials selection and controls approach can be employed for any material systems used in water generators that having a lower and / or upper operational bound or limit relating to a weeping potential, swelling potential, low vapor pressure condition, swelling, a pressure drop on water uptake, mechanical instability, chemical instability, cycling stability, or combinations thereof. Accordingly, the material design and control approaches described herein can be modified such that additional embodiments may be realized with operational, logical, chemical, and / or mechanical changes without departing from the spirit and scope of the disclosure. The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) "means for" or "step for," respectively. The term “about” or “substantially,” as used herein, is intended to encompass minor deviations rather define an exact value.Provisional ApplicationHIGH POWER ELECTROCHEMICAL SYSTEMS AND METHODS INVENTOR: CODY FRIESENBRIEF DESCRIPTION OF THE DRAWINGS[1] The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers. Views in the figures are drawn to scale (unless otherwise noted), meaning the sizes of the depicted elements are accurate relative to each other for at least the embodiment in the view.[2] FIG. 1 depicts a block diagram of a high-power electrochemical system according to the present technology;[3] FIG. 2 depicts a Pourbaix diagram related to operation of a high-power electrochemical system according to the present technology;[4] FIG. 3 depicts a method of operating a high-power electrochemical system according to the present technology.[5] For simplicity and clarity of illustration, the drawing figures show the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.Provisional ApplicationDESCRIPTION OF ILLUSTRATIVE EMBODIMENTS[6] The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure.[7] Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and / or any other possible attachment option. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.[8] This disclosure includes embodiments of systems and methods, such as, for example, for water treatment and storage. The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The terms “a” and “an” are defined as one or more unless this disclosure explicitly requires otherwise. The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the termsProvisional Application“substantially,” “approximately,” “partially” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, 10 and 20%. Further, a device or system that is configured in a certain way is configured in at least that way, but it can also be configured in other ways than those specifically described.[9] The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, an apparatus that “comprises,” “has,” “includes,” or “contains” one or more elements possesses those one or more elements but is not limited to possessing only those elements Likewise, a method that “comprises,” “has,” “includes,” or “contains” one or more operations or steps possesses those one or more operations or steps, but is not limited to possessing only those one or more operations or steps.

[0010] Any embodiment of any of the apparatuses, systems, and methods can consist of or consist essentially of — rather than comprise / include / contain / have — any of the described steps, elements, and / or features. Thus, in any of the claims, the term “consisting of’ or “consisting essentially of’ can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb. The feature or features of one embodiment may be applied to other embodiments or implementations, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.

[0011] As will be described in detail below, this disclosure describes various “hybrid”, “integrated” and / or “high-power” electrochemical systems and related operational methods that can be particularly advantageous in aerospace applications. The system disclosed herein canProvisional Application integrate 1) a high-power metal battery (e.g., a metal-water battery) and 2) a hydrogen storage unit (e.g., pressurized tank, sorption onto solid materials like metal hydride or carbon materials) and / or or hydrogen power unit (e.g., fuel cell, hydrogen combustion sub-system, turbine, and / or the like) to provide high power densities with high efficiency, especially advantageous for power delivery during peak demand periods. In an example, the metal-water battery is configured for high-power capability and serves as a primary power source (e.g., for lower power demand periods, normal aircraft operation). In some implementations, the metal-water battery discharge product(s) can be stored for later use. To address peak power demands (e.g., during takeoff, climb), a hydrogen power unit can utilize a battery discharge product (e.g., hydrogen gas evolved at the cathode) to generate additional electrical power, generate heat to facilitate operation of the metal-water battery (e g., melting a liquid metal anolyte, heating a sorption material to release water for supply to a catholyte, and / or the like). Furthermore, in some implementations the hydrogen power unit can generate water which can be returned to the cathode of the metal-water battery. This dynamic synergy between the metal -water battery and the hydrogen power unit can maximize power output on demand while establishing a high overall operational efficiency for the system.

[0012] FIG. 1 depicts a block diagram of an exemplary high-power electrochemical system 100 according to the present technology. System 100 comprises a metal -water battery 110 including: a metal anode 112 configured to oxidize a metal to form metal ions during a battery discharge operation, a cathode 114 configured to reduce water in a catholyte to evolve or generate hydrogen gas during the battery discharge operation, and an ion exchange layer 116 between the anode and the cathode to conduct metal ions (M+) therebetween. The ion exchange layer 116 can comprises a polymeric ion exchange membrane layer, a ceramic ion exchange layer, an ionic liquid, a molten salt, or a combination thereof. In various implementations ion exchange layer 116Provisional Application separates an anolyte of the anode 1 12 and a catholyte of the cathode 1 14. Anolytes and catholytes of the present technology can include aqueous media, non-aqueous media, ionic liquids, molten salts and / or the like. Furthermore, the metal water battery can include a non-aqueous anolyte and an aqueous catholyte.

[0013] As an illustrative example, the metal anode 112 can be configured to receive a liquid metal anolyte such as melted sodium metal, for example pumped or flowed into anode 112 via liquid metal sub-system or unit 118. Liquid metal sub-system or unit 118 can comprise a liquid metal reservoir for storing metal reactant and a pump to input liquid metal into the anode 112. In some implementations, heat (Q depicted in dashed lines) generated from hydrogen power unit 124 can be used to melt the metal in liquid metal unit 118. The cathode 114 can include an aqueous catholyte, for example aqueous alkaline media such as aqueous sodium hydroxide.

[0014] System 100 further comprises a hydrogen power unit 120 configured to store (e.g., via hydrogen storage tank 122) and / or utilize a discharge product of the metal -water battery, for example hydrogen gas generated by the metal-water battery upon the battery discharge operation. In various implementations, the hydrogen power unit 120 comprises a power generation unit 124 configured to convert hydrogen gas generated from the metal-water battery to produce electricity (e g., via a hydrogen fuel cell) and / or heat (e.g., via auxiliary power unit, combustion reactor, turbine). As such, the hydrogen power unit 120 can comprise a hydrogen fuel cell, a hydrogen combustion subsystem, a hydrogen combustion heat exchanger, a hydrogen storage tank, or a combination thereof.

[0015] In some implementations, the system can comprise a water supply unit (e.g., 130) that can include a water storage unit (e.g., 132), a water pump (e.g., 134) and / or a desiccant unit (e.g., 136) to supply water to the cathode as catholyte of the metal-water battery 110. In oneProvisional Application exemplary implementation, the hydrogen power unit 120 generates heat to heat a hygroscopic material in the desiccant unit 136 to desorb captured water therein to sustain a water supply to the cathode of the metal-water battery. In such an example, power generation unit 124 comprising a fuel cell can react hydrogen gas generated from the metal-water battery and oxygen (e.g., from the ambient environment) to generate electricity and also form water which can then be stored via a hygroscopic material of the desiccant unit 134 during a water vapor sorption operation (i.e., so as to provide water recapture functionality). Furthermore, a controller (e.g., 140) can operate the power generation unit 124 to generate heat (Q depicted in dashed lines) to heat the hygroscopic material of the desiccant unit 134 during a desorption operation to drive desorption of recaptured water from the desiccant unit 134. The desorbed water vapor can be stored in water storage unit 132 and / or fed back to cathode 114 of battery cell 110 via water pump 134. In such instances, the hydrogen power unit 124 can comprise a hydrogen fuel cell to generate water that is effectively recycled to the cathode of the metal-water battery such that the system operated in a closed, or at least partially closed, loop.

[0016] In some implementations, the hydrogen power unit 124 can generate heat to melt the metal of the metal anode, for example via a heat exchanger.

[0017] The metal of the metal-water battery can comprise sodium, lithium, aluminum, calcium, potassium, magnesium, boron, or any combination thereof (e.g., a sodium-potassium eutectic). As an illustrative example, a metal-water battery including a sodium metal anode will be described to enable those skilled in the art to practice the disclosure, however it should be understood that other battery systems may be employed and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure.Provisional Application

[0018] As an illustrative example, the metal-water battery is a sodium-water battery, wherein the metal anode is configured to oxidize a liquid sodium metal to form sodium ions upon discharge. The cathode can be configured to reduce water to generate hydrogen gas and hydroxide ions. In such an implementation, the ion exchange layer comprises a polymer ion exchange membrane, or a ceramic ionic exchange layer or solid electrolyte such as a Sodium Super Ionic Conductor (NaSICON) solid electrolyte comprising a crystalline structure with sodium ion conductive pathways.

[0019] FIG. 2 depicts an exemplary Pourbaix diagram to illustrate the operation of systems of the present technology. Line 201 represents a metal anode reaction (e.g., sodium) for the oxidation of the metal to form metal ions upon discharge (i.e., below line 201 metal M is in a stable reduced form and above which metal is in an oxidized form having released electrons). Conventional metal-air (i.e., metal-oxygen) batteries pair a metal anode with an air cathode configured for oxygen reduction from air at the cathode which is represented by the Oxygen Reduction Reaction (ORR) line 205. While conventional metal-air batteries offer a higher cell potential (i.e., indicated as EM-O2) relative to a metal-water battery (i.e., indicated as EM-H2O), they suffer from low power densities and lower efficiency attributed to overpotential, the difference between the thermodynamic potential and the actual potential required for operation, due to losses or inefficiencies that are associated with the four electron ORR process O2 + 2 H2O + 4 e" ■> 4 OH .

[0020] Metal batteries of the present technology instead preferably pair a metal anode (represented by line 201) with a cathode configured for water reduction to produce hydrogen gas H2 (represented by the Hydrogen Evolution Reaction (HER) line 203 which may be associated with a more facile two electron process (i.e., 2 H2O + 2c -> H2 + 2OH ). In comparison toProvisional Application conventional metal-air (i.e., metal-oxygen) batteries, the metal-water battery offers greater power densities and efficiency given the smaller overpotential for water reduction compared to oxygen reduction. Furthermore, the production of hydrogen allows flexibility in subsequent use (e.g., storage, further conversion). While the overall cell potential for a metal -water battery is lower than that of a metal-air battery, the hybrid system architecture of the present disclosure synergistically pairs a metal-water battery generating hydrogen with a hydrogen power unit that effectively offsets or compensates for the lower cell potential of the metal-water battery. In other words, systems of the present technology enable access to the entire potential range (i.e., spanning EM-H2O and EH2- H02), but even more advantageously in that the architecture unlocks the ability to optimize, or determine via a controller, a desired operational regime (e.g., distributed between metal-water battery vs. hydrogen power unit vs. hydrogen storage) based on a particular application, environment or power demand.

[0021] A total system efficiency can be calculated by dividing the actual operating potentials of the metal-water battery (EM-H O) and the hydrogen power unit (EH2-02) by the theoretical potential over the entire range (i.e., E° being the difference between line 201 and line 205):Total Efficiency = (EM-H2O + EH2-H02) / E°

[0022] System 100 comprises controller 140 that can be configured to increase a total efficiency of the system, i.e., total efficiency of a discharge operation of the metal-water battery and an efficiency of hydrogen gas conversion of the hydrogen power unit (e.g., fuel cell operating efficiency, hydrogen combustion efficiency). As an example, the controller 140 can increase or adjust an amount, pressure or flow rate of the liquid metal into the anode (e.g., via a pump of unit 118) based on a current or power demand threshold. Similarly, controller 140 can increase or adjustProvisional Application an amount, pressure or flow rate of hydrogen gas into hydrogen power unit 124 based on a current or power demand threshold.

[0023] In an aerospace application, the controller 140 can be configured to increase a power output of the system via the hydrogen power unit based on an increase power demand of an aircraft. In one example, system 100 is employed as or as part of an auxiliary power unit (APU) for an aircraft. The hydrogen power unit 120 can provide peak power via conversion of hydrogen gas generated by the metal-water battery 110. During periods of low power demand, the metal water battery can generate hydrogen gas that is stored (e.g., onboard) and then consumed via the hydrogen power unit when additional power is needed.

[0024] In some implementations, the metal-water battery 110 can be a sodium -water battery configured to generate a sodium hydroxide discharge product, and the sodium hydroxide discharge product can be contacted with the ambient environment to form sodium carbonate from ambient carbon dioxide. In one example, the sodium hydroxide discharge product can be sprayed into the atmosphere during flight to precipitate sodium carbonate upon contact with air, thereby providing carbon capture functionality while reducing weight of the aircraft during flight. Alternatively, the discharge product can be kept onboard such that discharge product(s) are utilized subsequent to flight.

[0025] The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the methods and systems are not intended to be limited to the particular formsProvisional Application disclosed. Rather, they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, elements may be omitted or combined as a unitary structure, and / or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and / or functions and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0026] Furthermore, the materials selection and controls approach can be employed for any material systems used in water generators that having a lower and / or upper operational bound or limit relating to a weeping potential, swelling potential, low vapor pressure condition, swelling, a pressure drop on water uptake, mechanical instability, chemical instability, cycling stability, or combinations thereof. Accordingly, the material design and control approaches described herein can be modified such that additional embodiments may be realized with operational, logical, chemical, and / or mechanical changes without departing from the spirit and scope of the disclosure. The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) "means for" or "step for," respectively. The term “about” or “substantially,” as used herein, is intended to encompass minor deviations rather define an exact value.Provisional ApplicationHIGH POWER ELECTROCHEMICAL SYSTEMS AND METHODSINVENTOR: CODY FRIESENBRIEF DESCRIPTION OF THE DRAWINGS[1] The following drawings illustrate by way of example and not limitation. For the sake of brevity and clarity, every feature of a given structure is not always labeled in every figure in which that structure appears. Identical reference numbers do not necessarily indicate an identical structure. Rather, the same reference number may be used to indicate a similar feature or a feature with similar functionality, as may non-identical reference numbers. Views in the figures are drawn to scale (unless otherwise noted), meaning the sizes of the depicted elements are accurate relative to each other for at least the embodiment in the view.[2] FIG. 1 depicts a block diagram of a high-power electrochemical system according to the present technology;[3] FIG. 2 depicts a Pourbaix diagram related to operation of a high-power electrochemical system according to the present technology;[4] FIG. 3 depicts a method of operating a high-power electrochemical system according to the present technology.[5] For simplicity and clarity of illustration, the drawing figures show the general manner of construction, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the invention. Additionally, elements in the drawing figures are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention. The same reference numerals in different figures denote the same elements.Provisional ApplicationDESCRIPTION OF ILLUSTRATIVE EMBODIMENTS[6] The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure.[7] Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and / or any other possible attachment option. Surface shading lines may be used throughout the figures to denote different parts but not necessarily to denote the same or different materials.[8] This disclosure includes embodiments of systems and methods, such as, for example, for water treatment and storage. The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically. The terms “a” and “an” are defined as one or more unless this disclosure explicitly requires otherwise. The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the termsProvisional Application“substantially,” “approximately,” “partially” and “about” may be substituted with “within [a percentage] of’ what is specified, where the percentage includes 0.1, 1, 5, 10 and 20%. Further, a device or system that is configured in a certain way is configured in at least that way, but it can also be configured in other ways than those specifically described.[9] The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”), and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, an apparatus that “comprises,” “has,” “includes,” or “contains” one or more elements possesses those one or more elements but is not limited to possessing only those elements Likewise, a method that “comprises,” “has,” “includes,” or “contains” one or more operations or steps possesses those one or more operations or steps, but is not limited to possessing only those one or more operations or steps.

[0010] Any embodiment of any of the apparatuses, systems, and methods can consist of or consist essentially of — rather than comprise / include / contain / have — any of the described steps, elements, and / or features. Thus, in any of the claims, the term “consisting of’ or “consisting essentially of’ can be substituted for any of the open-ended linking verbs recited above, in order to change the scope of a given claim from what it would otherwise be using the open-ended linking verb. The feature or features of one embodiment may be applied to other embodiments or implementations, even though not described or illustrated, unless expressly prohibited by this disclosure or the nature of the embodiments.

[0011] As will be described in detail below, this disclosure describes various “hybrid”, “integrated” and / or “high-power” electrochemical systems and related operational methods that can be particularly advantageous in aerospace applications. The system disclosed herein canProvisional Application integrate 1) a high-power metal battery (e.g., a metal-water battery) and 2) a hydrogen storage unit (e.g., pressurized tank, sorption onto solid materials like metal hydride or carbon materials) and / or or hydrogen power unit (e.g., fuel cell, hydrogen combustion sub-system, turbine, and / or the like) to provide high power densities with high efficiency, especially advantageous for power delivery during peak demand periods. In an example, the metal-water battery is configured for high-power capability and serves as a primary power source (e.g., for lower power demand periods, normal aircraft operation). In some implementations, the metal-water battery discharge product(s) can be stored for later use. To address peak power demands (e.g., during takeoff, climb), a hydrogen power unit can utilize a battery discharge product (e.g., hydrogen gas evolved at the cathode) to generate additional electrical power, generate heat to facilitate operation of the metal -water battery (e g., melting a liquid metal anolyte, heating a sorption material to release water for supply to a catholyte, and / or the like). Furthermore, in some implementations the hydrogen power unit can generate water which can be returned to the cathode of the metal-water battery. This dynamic synergy between the metal-water battery and the hydrogen power unit can maximize power output on demand while establishing a high overall operational efficiency for the system.

[0012] FIG. 1 depicts a block diagram of an exemplary high-power electrochemical system 100 according to the present technology. System 100 comprises a metal -water battery 110 including: a metal anode 112 configured to oxidize a metal to form metal ions during a battery discharge operation, a cathode 114 configured to reduce water in a catholyte to evolve or generate hydrogen gas during the battery discharge operation, and an ion exchange layer 1 16 between the anode and the cathode to conduct metal ions (M+) therebetween. The ion exchange layer 116 can comprises a polymeric ion exchange membrane layer, a ceramic ion exchange layer, an ionic liquid, a molten salt, or a combination thereof. In various implementations ion exchange layer 116Provisional Application separates an anolyte of the anode 1 12 and a catholyte of the cathode 1 14. Anolytes and catholytes of the present technology can include aqueous media, non-aqueous media, ionic liquids, molten salts and / or the like. Furthermore, the metal water battery can include a non-aqueous anolyte and an aqueous catholyte.

[0013] As an illustrative example, the metal anode 112 can be configured to receive a liquid metal anolyte such as melted sodium metal, for example pumped or flowed into anode 112 via liquid metal sub-system or unit 118. Liquid metal sub-system or unit 118 can comprise a liquid metal reservoir for storing metal reactant and a pump to input liquid metal into the anode 112. In some implementations, heat (Q depicted in dashed lines) generated from hydrogen power unit 124 can be used to melt the metal in liquid metal unit 118. The cathode 114 can include an aqueous catholyte, for example aqueous alkaline media such as aqueous sodium hydroxide.

[0014] System 100 further comprises a hydrogen power unit 120 configured to store (e.g., via hydrogen storage tank 122) and / or utilize a discharge product of the metal -water battery, for example hydrogen gas generated by the metal-water battery upon the battery discharge operation. In various implementations, the hydrogen power unit 120 comprises a power generation unit 124 configured to convert hydrogen gas generated from the metal-water battery to produce electricity (e g., via a hydrogen fuel cell) and / or heat (e.g., via auxiliary power unit, combustion reactor, turbine). As such, the hydrogen power unit 120 can comprise a hydrogen fuel cell, a hydrogen combustion subsystem, a hydrogen combustion heat exchanger, a hydrogen storage tank, or a combination thereof.

[0015] In some implementations, the system can comprise a water supply unit (e.g., 130) that can include a water storage unit (e.g., 132), a water pump (e.g., 134) and / or a desiccant unit (e.g., 136) to supply water to the cathode as catholyte of the metal-water battery 110. In oneProvisional Application exemplary implementation, the hydrogen power unit 120 generates heat to heat a hygroscopic material in the desiccant unit 136 to desorb captured water therein to sustain a water supply to the cathode of the metal-water battery. In such an example, power generation unit 124 comprising a fuel cell can react hydrogen gas generated from the metal-water battery and oxygen (e.g., from the ambient environment) to generate electricity and also form water which can then be stored via a hygroscopic material of the desiccant unit 134 during a water vapor sorption operation (i.e., so as to provide water recapture functionality). Furthermore, a controller (e.g., 140) can operate the power generation unit 124 to generate heat (Q depicted in dashed lines) to heat the hygroscopic material of the desiccant unit 134 during a desorption operation to drive desorption of recaptured water from the desiccant unit 134. The desorbed water vapor can be stored in water storage unit 132 and / or fed back to cathode 114 of battery cell 110 via water pump 134. In such instances, the hydrogen power unit 124 can comprise a hydrogen fuel cell to generate water that is effectively recycled to the cathode of the metal-water battery such that the system operated in a closed, or at least partially closed, loop.

[0016] In some implementations, the hydrogen power unit 124 can generate heat to melt the metal of the metal anode, for example via a heat exchanger.

[0017] The metal of the metal-water battery can comprise sodium, lithium, aluminum, calcium, potassium, magnesium, boron, or any combination thereof (e.g., a sodium-potassium eutectic). As an illustrative example, a metal-water battery including a sodium metal anode will be described to enable those skilled in the art to practice the disclosure, however it should be understood that other battery systems may be employed and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure.Provisional Application

[0018] As an illustrative example, the metal-water battery is a sodium-water battery, wherein the metal anode is configured to oxidize a liquid sodium metal to form sodium ions upon discharge. The cathode can be configured to reduce water to generate hydrogen gas and hydroxide ions. In such an implementation, the ion exchange layer comprises a polymer ion exchange membrane, or a ceramic ionic exchange layer or solid electrolyte such as a Sodium Super Ionic Conductor (NaSICON) solid electrolyte comprising a crystalline structure with sodium ion conductive pathways.

[0019] FIG. 2 depicts an exemplary Pourbaix diagram to illustrate the operation of systems of the present technology. Line 201 represents a metal anode reaction (e.g., sodium) for the oxidation of the metal to form metal ions upon discharge (i.e., below line 201 metal M is in a stable reduced form and above which metal is in an oxidized form having released electrons). Conventional metal-air (i.e., metal-oxygen) batteries pair a metal anode with an air cathode configured for oxygen reduction from air at the cathode which is represented by the Oxygen Reduction Reaction (ORR) line 205. While conventional metal-air batteries offer a higher cell potential (i.e., indicated as EM-O2) relative to a metal-water battery (i.e., indicated as EM-H2O), they suffer from low power densities and lower efficiency attributed to overpotential, the difference between the thermodynamic potential and the actual potential required for operation, due to losses or inefficiencies that are associated with the four electron ORR process O2 + 2 H2O + 4 e" ■> 4 OH .

[0020] Metal batteries of the present technology instead preferably pair a metal anode (represented by line 201) with a cathode configured for water reduction to produce hydrogen gas H2 (represented by the Hydrogen Evolution Reaction (HER) line 203 which may be associated with a more facile two electron process (i.e., 2 H2O + 2c -> H2 + 2OH ). In comparison toProvisional Application conventional metal-air (i.e., metal-oxygen) batteries, the metal-water battery offers greater power densities and efficiency given the smaller overpotential for water reduction compared to oxygen reduction. Furthermore, the production of hydrogen allows flexibility in subsequent use (e.g., storage, further conversion). While the overall cell potential for a metal -water battery is lower than that of a metal-air battery, the hybrid system architecture of the present disclosure synergistically pairs a metal-water battery generating hydrogen with a hydrogen power unit that effectively offsets or compensates for the lower cell potential of the metal-water battery. In other words, systems of the present technology enable access to the entire potential range (i.e., spanning EM-H2O and EH2- H02), but even more advantageously in that the architecture unlocks the ability to optimize, or determine via a controller, a desired operational regime (e.g., distributed between metal-water battery vs. hydrogen power unit vs. hydrogen storage) based on a particular application, environment or power demand.

[0021] A total system efficiency can be calculated by dividing the actual operating potentials of the metal-water battery (EM-H O) and the hydrogen power unit (EH2-02) by the theoretical potential over the entire range (i.e., E° being the difference between line 201 and line 205):Total Efficiency = (EM-H2O + EH2-H02) / E°

[0022] System 100 comprises controller 140 that can be configured to increase a total efficiency of the system, i.e., total efficiency of a discharge operation of the metal-water battery and an efficiency of hydrogen gas conversion of the hydrogen power unit (e.g., fuel cell operating efficiency, hydrogen combustion efficiency). As an example, the controller 140 can increase or adjust an amount, pressure or flow rate of the liquid metal into the anode (e.g., via a pump of unit 118) based on a current or power demand threshold. Similarly, controller 140 can increase or adjustProvisional Application an amount, pressure or flow rate of hydrogen gas into hydrogen power unit 124 based on a current or power demand threshold.

[0023] In an aerospace application, the controller 140 can be configured to increase a power output of the system via the hydrogen power unit based on an increase power demand of an aircraft. In one example, system 100 is employed as or as part of an auxiliary power unit (APU) for an aircraft. The hydrogen power unit 120 can provide peak power via conversion of hydrogen gas generated by the metal-water battery 110. During periods of low power demand, the metal water battery can generate hydrogen gas that is stored (e.g., onboard) and then consumed via the hydrogen power unit when additional power is needed.

[0024] In some implementations, the metal-water battery 110 can be a sodium -water battery configured to generate a sodium hydroxide discharge product, and the sodium hydroxide discharge product can be contacted with the ambient environment to form sodium carbonate from ambient carbon dioxide. In one example, the sodium hydroxide discharge product can be sprayed into the atmosphere during flight to precipitate sodium carbonate upon contact with air, thereby providing carbon capture functionality while reducing weight of the aircraft during flight. Alternatively, the discharge product can be kept onboard such that discharge product(s) are utilized subsequent to flight.

[0025] The above specification and examples provide a complete description of the structure and use of illustrative embodiments. Although certain embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this invention. As such, the various illustrative embodiments of the methods and systems are not intended to be limited to the particular formsProvisional Application disclosed. Rather, they include all modifications and alternatives falling within the scope of the claims, and embodiments other than the one shown may include some or all of the features of the depicted embodiment. For example, elements may be omitted or combined as a unitary structure, and / or connections may be substituted. Further, where appropriate, aspects of any of the examples described above may be combined with aspects of any of the other examples described to form further examples having comparable or different properties and / or functions and addressing the same or different problems. Similarly, it will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

[0026] Furthermore, the materials selection and controls approach can be employed for any material systems used in water generators that having a lower and / or upper operational bound or limit relating to a weeping potential, swelling potential, low vapor pressure condition, swelling, a pressure drop on water uptake, mechanical instability, chemical instability, cycling stability, or combinations thereof. Accordingly, the material design and control approaches described herein can be modified such that additional embodiments may be realized with operational, logical, chemical, and / or mechanical changes without departing from the spirit and scope of the disclosure. The claims are not intended to include, and should not be interpreted to include, means-plus- or step-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase(s) "means for" or "step for," respectively. The term “about” or “substantially,” as used herein, is intended to encompass minor deviations rather define an exact value.

Claims

HIGH POWER ELECTROCHEMICAL SYSTEMS AND METHODSINVENTOR: CODY FRIESENCLAIMS1. A system comprising: a metal-water battery comprising: a metal anode configured to oxidize a metal to form metal ions during a discharge operation, a cathode configured to reduce water in a catholyte to generate hydrogen gas during the discharge operation, an ion exchange layer between the anode and the cathode to conduct metal ions therebetween; and, a discharge product power unit configured to utilize the hydrogen gas generated by the metal-water battery to produce electricity, heat, or a combination thereof.

2. The system of claim 1, further comprising a desiccant unit, wherein the discharge product power unit generates heat to heat a hygroscopic material in the desiccant unit to desorb captured water therein to sustain a water supply to the cathode of the metal-water battery.

3. The system of claim 1, wherein the discharge product power unit generates heat to melt the metal of the metal anode.

4. The system of claim 1, wherein the metal comprises sodium, lithium, aluminum, calcium, potassium, magnesium, boron, or a combination thereof.

5. The system of claim 1, wherein the ion exchange layer comprises a polymeric ion exchange membrane layer, a ceramic ion exchange layer, an ionic liquid, a molten salt, or a combination thereof.

6. The system of claim 1, wherein the metal anode is configured to receive a liquid metal anolyte.

7. The system of claim 1, wherein the catholyte comprises aqueous alkaline media.

8. The system of claim 1, wherein the metal comprises a sodium-potassium eutectic material.

9. The system of claim 1, wherein the battery is a sodium-water battery, wherein the metal comprises sodium, the metal anode being configured to oxidize liquid sodium metal to form sodium ions, and wherein the cathode is configured to reduce water to generate hydrogen gas and hydroxide ions.

10. The system of claim 9, wherein the ion exchange layer comprises a Sodium Super Ionic Conductor (NaSICON) solid electrolyte comprising: a crystalline structure with sodium ion- conductive pathways.

11. The system of claim 1, wherein the discharge product power unit comprises a hydrogen fuel cell, a hydrogen combustion system, a hydrogen combustion heat exchanger, a hydrogen storage tank, or a combination thereof.

12. The system of claim 1, wherein the discharge product power unit comprises a hydrogen fuel cell to generate water, wherein the water generated by the hydrogen fuel cell is input to the cathode of the metal-water battery during the discharge operation such that the system operated in a closed loop.

13. The system of claim 1, further comprising a controller configured to increase a total efficiency of the system, total efficiency based on an efficiency of a discharge operation of the metal-water battery and an efficiency of hydrogen gas conversion of the discharge product power unit.

14. The system of claim 1, further comprising a controller configured to increase a power output of the system via the discharge product power unit based on an increase power demand of an aircraft.

15. An auxiliary power unit (APU) for an aircraft comprising the system of claim 1, wherein the discharge product power unit is configured to provide peak power via conversion of hydrogen gas generated by the metal-water battery.

16. The system of claim 1, wherein the metal-water battery is a sodium metal-water battery generating a sodium hydroxide discharge product, wherein the discharge product power unit is configured to utilize the sodium hydroxide discharge product to produce electricity, heat, or a combination thereof.

17. The system of claim 16, wherein the metal-water battery is a sodium metal -water battery generating a sodium hydroxide discharge product, wherein sodium hydroxide discharge product is contacted with the ambient environment to form sodium bicarbonate, sodium carbonate, or a combination thereof.

18. A method comprising: oxidizing a metal at an anode; reducing water at a cathode to produce a discharge product including hydrogen gas; using the generated discharge product to generate electricity, heat, or a combination thereof.

19. The method of claim 18, further comprising: generating heat to heat a desiccant unit to desorb captured water therein; supplying the desorbed water to the cathode.

20. The method of claim 18, further comprising: generating heat to melt the metal in advance of input to the metal anode.Provisional ApplicationCLAIMS1. A system comprising: a metal-water battery comprising: a metal anode configured to oxidize a metal to form metal ions during a discharge operation, a cathode configured to reduce water in a catholyte to generate hydrogen gas during the discharge operation, an ion exchange layer between the anode and the cathode to conduct metal ions therebetween; and, a hydrogen power unit configured to utilize the hydrogen gas generated by the metal-water battery to produce electricity, heat, or a combination thereof.

2. The system of claim 1, further comprising a desiccant unit, wherein the hydrogen power unit generates heat to heat a hygroscopic material in the desiccant unit to desorb captured water therein to sustain a water supply to the cathode of the metal-water battery.

3. The system of claim 1, wherein the hydrogen power unit generates heat to melt the metal of the metal anode.

4. The system of claim 1, wherein the metal comprises sodium, lithium, aluminum, calcium, potassium, magnesium, boron, or a combination thereof.

5. The system of claim 1, wherein the ion exchange layer comprises a polymeric ion exchange membrane layer, a ceramic ion exchange layer, an ionic liquid, a molten salt, or a combination thereof.

6. The system of claim 1, wherein the metal anode is configured to receive a liquid metal anolyte.

7. The system of claim 1, wherein the catholyte comprises aqueous alkaline media.Provisional Application8. The system of claim 1, wherein the metal comprises a sodium-potassium eutectic material.

9. The system of claim 1, wherein the battery is a sodium -water battery, wherein the metal comprises sodium, the metal anode being configured to oxidize liquid sodium metal to form sodium ions, and wherein the cathode is configured to reduce water to generate hydrogen gas and hydroxide ions.

10. The system of claim 9, wherein the ion exchange layer comprises a Sodium Super Ionic Conductor (NaSICON) solid electrolyte comprising: a crystalline structure with sodium ion- conductive pathways.

11. The system of claim 1, wherein the hydrogen power unit comprises a hydrogen fuel cell, a hydrogen combustion system, a hydrogen combustion heat exchanger, a hydrogen storage tank, or a combination thereof.

12. The system of claim 1, wherein the hydrogen power unit comprises a hydrogen fuel cell to generate water, wherein the water generated by the hydrogen fuel cell is input to the cathode of the metal-water battery during the discharge operation such that the system operated in a closed loop.

13. The system of claim 1, further comprising a controller configured to increase a total efficiency of the system, total efficiency based on an efficiency of a discharge operation of the metal-water battery and an efficiency of hydrogen gas conversion of the hydrogen power unit.

14. The system of claim 1, further comprising a controller configured to increase a power output of the system via the hydrogen power unit based on an increase power demand of an aircraft.

15. An auxiliary power unit (APU) for an aircraft comprising the system of claim 1, wherein the hydrogen power unit is configured to provide peak power via conversion of hydrogen gas generated by the metal -water battery.Provisional Application16. The system of claim 15, wherein the metal-water battery is a sodium water battery generating a sodium hydroxide discharge product, the sodium hydroxide discharge product being configured to contact the ambient environment to form sodium carbonate.

17. A method comprising: oxidizing a metal at an anode; reducing water at a cathode to produce hydrogen gas; collecting the generated hydrogen gas; using the generated hydrogen gas to generate electricity, heat, or a combination thereof.

18. The method of claim 17, further comprising: generating heat to heat a desiccant unit to desorb captured water therein; supplying the desorbed water to the cathode.

19. The method of claim 17, further comprising: generating heat to melt the metal in advance of input to the metal anode.Provisional ApplicationCLAIMS1. A system comprising: a metal-water battery comprising: a metal anode configured to oxidize a metal to form metal ions during a discharge operation, a cathode configured to reduce water in a catholyte to generate hydrogen gas during the discharge operation, an ion exchange layer between the anode and the cathode to conduct metal ions therebetween; and, a hydrogen power unit configured to utilize the hydrogen gas generated by the metal-water battery to produce electricity, heat, or a combination thereof.

2. The system of claim 1, further comprising a desiccant unit, wherein the hydrogen power unit generates heat to heat a hygroscopic material in the desiccant unit to desorb captured water therein to sustain a water supply to the cathode of the metal-water battery.

3. The system of claim 1, wherein the hydrogen power unit generates heat to melt the metal of the metal anode.

4. The system of claim 1, wherein the metal comprises sodium, lithium, aluminum, calcium, potassium, magnesium, boron, or a combination thereof.

5. The system of claim 1, wherein the ion exchange layer comprises a polymeric ion exchange membrane layer, a ceramic ion exchange layer, an ionic liquid, a molten salt, or a combination thereof.

6. The system of claim 1, wherein the metal anode is configured to receive a liquid metal anolyte.

7. The system of claim 1, wherein the catholyte comprises aqueous alkaline media.Provisional Application8. The system of claim 1, wherein the metal comprises a sodium-potassium eutectic material.

9. The system of claim 1, wherein the battery is a sodium -water battery, wherein the metal comprises sodium, the metal anode being configured to oxidize liquid sodium metal to form sodium ions, and wherein the cathode is configured to reduce water to generate hydrogen gas and hydroxide ions.

10. The system of claim 9, wherein the ion exchange layer comprises a Sodium Super Ionic Conductor (NaSICON) solid electrolyte comprising: a crystalline structure with sodium ion- conductive pathways.

11. The system of claim 1, wherein the hydrogen power unit comprises a hydrogen fuel cell, a hydrogen combustion system, a hydrogen combustion heat exchanger, a hydrogen storage tank, or a combination thereof.

12. The system of claim 1, wherein the hydrogen power unit comprises a hydrogen fuel cell to generate water, wherein the water generated by the hydrogen fuel cell is input to the cathode of the metal-water battery during the discharge operation such that the system operated in a closed loop.

13. The system of claim 1, further comprising a controller configured to increase a total efficiency of the system, total efficiency based on an efficiency of a discharge operation of the metal-water battery and an efficiency of hydrogen gas conversion of the hydrogen power unit.

14. The system of claim 1, further comprising a controller configured to increase a power output of the system via the hydrogen power unit based on an increase power demand of an aircraft.

15. An auxiliary power unit (APU) for an aircraft comprising the system of claim 1, wherein the hydrogen power unit is configured to provide peak power via conversion of hydrogen gas generated by the metal -water battery.Provisional Application16. The system of claim 15, wherein the metal-water battery is a sodium water battery generating a sodium hydroxide discharge product, the sodium hydroxide discharge product being configured to contact the ambient environment to form sodium carbonate.

17. A method comprising: oxidizing a metal at an anode; reducing water at a cathode to produce hydrogen gas; collecting the generated hydrogen gas; using the generated hydrogen gas to generate electricity, heat, or a combination thereof.

18. The method of claim 17, further comprising: generating heat to heat a desiccant unit to desorb captured water therein; supplying the desorbed water to the cathode.

19. The method of claim 17, further comprising: generating heat to melt the metal in advance of input to the metal anode.

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