Negative electrodes for electrochemical cells

Abstract

To provide long and ultra-long duration energy storage systems.SOLUTION: There are provided a battery, a bulk energy storage system including the battery, and / or a method of operating the bulk energy storage system including the battery. The battery may include a first electrode, an electrolyte, and a second electrode, wherein one or both of the first electrode and the second electrode comprise direct reduced iron ("DRI"). The DRI may be in the form of pellets. The pellets may comprise at least about 60 wt.% iron by elemental mass, based on the total mass of the pellets. One or both of the first electrode and the second electrode comprises from about 60% to about 90% iron and from about 1% to about 40% of a component comprising one or more of materials selected from a group of SiO2, AI2O3, MgO, CaO, and TiO2.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] Related Applications This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 711,253, entitled "Negative Electrodes for Metal-Air Batteries," filed July 27, 2018, U.S. Provisional Patent Application No. 62 / 790,688, entitled "Negative Electrodes for Metal-Air Batteries," filed January 10, 2019, and U.S. Provisional Patent Application No. 62 / 868,511, entitled "Negative Electrodes for Metal-Air Batteries," filed June 28, 2019. The contents of all three applications are incorporated herein by reference in their entirety for all purposes. [Background technology]

[0002] Energy storage technologies are playing an increasingly important role in the power grid. At the most basic level, these energy storage assets provide smoothing to better match generation and demand in the grid. The services performed by energy storage devices benefit the power grid over multiple timescales, from milliseconds to years. Today, energy storage technologies exist that can support timescales from milliseconds to hours, but long-term and ultra-long-term (collectively, ≧8 hours) energy storage systems are needed.

[0003] This "Background" section is intended to introduce various aspects of the art that may be related to embodiments of the present invention. As such, the preceding discussion in this section is intended to provide a framework for better understanding the present invention and should not be construed as admissions of prior art. Summary of the Invention

[0004] Materials, designs, and methods of manufacture for metal electrodes for electrochemical cells are disclosed. In various embodiments, the negative electrode comprises metallic pellets arranged in one or more configurations comprising multiple layers.

[0005] In various embodiments, the pellets may contain one or more forms of iron ranging from highly reduced (more metallic) iron to highly oxidized (more ionic) iron. In various embodiments, the pellets may contain various iron compounds such as iron oxide, iron hydroxide, iron sulfide, or combinations thereof. In various embodiments, the pellets may contain one or more secondary phases such as silica (SiO2) or silicates, calcium oxide (CaO), magnesium oxide (MgO), etc.

[0006] In various embodiments, the pellets may be sintered iron agglomerates having a variety of different shapes. In various embodiments, the sintered iron pellets may be formed in a furnace, such as a continuous feed calcining furnace, a batch feed calcining furnace, a blast furnace, a rotary calciner, a rotary hearth, or the like. In various embodiments, the pellets may include forms of reduced and / or sintered iron-bearing precursors known to those skilled in the art as direct reduced iron (DRI) and / or by-product materials thereof. Various embodiments may include processing the pellets, including DRI pellets, using mechanical, chemical, and / or thermal processes prior to introducing the pellets into an electrochemical cell.

[0007] In various embodiments, the negative electrode may be a composite metal electrode comprised of a mixture of spherical or substantially spherical metallic pellets and powdered metal feedstock. In various embodiments, the powdered metal feedstock may be wetted by an electrolyte. In various embodiments, the negative electrode may be comprised of a mixture of iron ore (e.g., taconite, etc.) pellets and conductive DRI fines, sponge iron, and / or atomized iron. "DRI fines" is understood to mean fine particles smaller in size than DRI pellets, but produced at the same time as DRI pellets, or produced from DRI pellets by comminution, handling, or thermal or chemical means.

[0008] In various embodiments, the negative electrode may include pellets that may be grouped in an ordered array. In various embodiments, the pellets may be arranged in a bed packed such that macropores are created between two or more pellets that are in contact with each other. In various embodiments, the pellets may each include micropores. In various embodiments, the electrolyte may fill the micropores or macropores or flow through the pore space surrounding the pellets that make up the electrode.

[0009] In various embodiments, a layer of powdered iron may form an interface between the pellets and a current collector of the negative electrode, and the negative electrode further includes a layer of powdered iron configured to form an interface between the pellets and a current collector of an electrochemical cell.

[0010] Various embodiments may include systems and methods for monitoring the state of charge of a negative electrode that includes metallic pellets arranged in one or more layers.

[0011] In various embodiments, the pellets may be synthesized in a first stage of a dual use energy storage plant and used in the anode in a second stage of the dual use energy storage plant.

[0012] Various embodiments can provide a battery including a first electrode, an electrolyte, and a second electrode, where one or both of the first and second electrodes include direct reduced iron ("DRI"). Additionally, the battery can include a first electrode, an electrolyte, and a second electrode, where one or both of the first and second electrodes is a porous iron electrode including DRI. The porous iron electrode can be formed into a sheet. The porous iron electrode includes particles of DRI. The average particle size of the particles of DRI is greater than 10 nm and less than 1 mm. The particles of DRI are irregular in shape. Macropores are defined between the particles of DRI, and the particles of DRI have a microporous surface. The particles of DRI are agglomerated and physically connected. The particles of DRI are agglomerated and sintered. In various embodiments, the DRI is in the form of a pellet. In various embodiments, the pellet includes at least about 60% iron by weight, by elemental mass, based on the total mass of the pellet. In various embodiments, the pellets comprise at least about 60% metallic iron by weight based on the total weight of the pellet, the pellets have an average particle size of 4 mm to 20 mm, and the pellets comprise at least 60 percent of the total weight of at least one of the first electrode and the second electrode. In various embodiments, the pellets comprise at least about 80% metallic iron by weight based on the total weight of the pellet. In various embodiments, the pellets comprise about 90% to about 98% metallic iron by weight based on the total weight of the pellet. In various embodiments, the pellets are shaped as spheres, rods, discs, plates, briquettes, or combinations thereof. In various embodiments, the pellets are shaped as briquettes and comprise hot briquetted iron. In various embodiments, the hot briquetted iron is formed of powdered iron fines or iron pellets. In various embodiments, the pellets have an average length in the range of about 10 mm to about 500 mm, an average width in the range of about 5 mm to about 250 mm, and an average height in the range of about 5 mm to about 200 mm. In various embodiments, the DRI comprises iron ore, direct reduction grade iron ore, reduced taconite, wustite, magnetite, hematite, cementite, iron oxide, or any combination thereof. In various embodiments, the DRI comprises DRI fines or powder.In various embodiments, the pellets have an average internal porosity ranging from about 10% to about 90% by volume. In various embodiments, the pellets are about 0.19 m. 2 / g ~ approx. 18m 2The pellet has an average specific surface area in the range of 1 / g. In various embodiments, the pellet has a volume weighted average pore size in the range of 1 to 10 microns. In various embodiments, at least one of the first electrode and the second electrode has a thickness greater than 0.1 cm. In various embodiments, the pellet is spherical and has an average diameter in the range of about 0.5 mm to about 10 cm. In various embodiments, the pellet comprises greater than 0.5 wt.% silica-containing compound based on the total weight of the pellet. In various embodiments, the pellet comprises about 1 wt.% to about 5 wt.% silica-containing compound based on the total weight of the pellet. In various embodiments, the pellet comprises about 1 wt.% to about 25 wt.% silica-containing compound based on the total weight of the pellet. In various embodiments, the pellet has a loading of 30% to 74% in at least one of the first electrode and the second electrode. In various embodiments, the pellet comprises a primary phase comprising iron and a secondary phase comprising silicon or another metal. In various embodiments, the pellet comprises a primary phase comprising iron and a secondary phase comprising cementite. In various embodiments, the secondary phase comprises silica or a silicate. In various embodiments, the secondary phase comprises titanium, vanadium, manganese, magnesium, calcium, phosphorus, carbon, aluminum, zirconium, or any combination thereof. In various embodiments, at least one of the first electrode and the second electrode comprises a single layer of pellets or multiple layers of pellets. In various embodiments, the electrolyte is infiltrated between the pellets. In various embodiments, the battery may further comprise a current collector in electrical communication with the pellets. More specifically, the battery may further comprise a current collector in electrical communication with the DRI of the porous iron electrode. In various embodiments, the current collector is in contact with a bottom surface of at least one of the first electrode and the second electrode, at least one side of the first electrode and the second electrode, extends across at least one of the first electrode and the second electrode, or any combination thereof. More specifically, the DRI of the porous iron electrode is in contact with the current collector. In various embodiments, the pellets are agglomerated sintered iron pellets.In various embodiments, the agglomerated sintered iron pellets are produced using a continuous feed calciner, a batch calciner, a blast furnace, or any other type of furnace. In various embodiments, the second electrode may comprise a slurry or gel. In various embodiments, at least one of the first electrode and the second electrode is a composite metal electrode comprising a mixture of pellets and a smaller metal particle composition. In various embodiments, the smaller metal particle composition is a powdered metal feedstock. In various embodiments, the powdered metal feedstock is wetted by the electrolyte. More specifically, the DRI of the porous iron electrode is wetted by the electrolyte. In various embodiments, the smaller metal particle composition comprises DRI fines, sponge iron, atomized iron, or any combination thereof. In various embodiments, the pellets comprise DR taconite. In various embodiments, the pellets are synthesized in a first phase of operation of the dual-use energy storage plant including the battery and loaded onto at least one of the first electrode and the second electrode in a second phase of operation of the dual-use energy storage plant. In various embodiments, the pellets are packed into the bed such that macropores are created between two or more pellets that are in contact with one another, and each of the pellets includes micropores on at least their respective outer surface. In various embodiments, the pellets are fused together. In various embodiments, the pellets are pre-processed chemically, mechanically, thermally, electrically, and / or electrochemically to fuse at least a portion of the pellets and pack them into the bed. In various embodiments, the battery may further include a pump configured to flow a liquid electrolyte across the pellets in the packed bed. In various embodiments, the pellets each include micropores on their respective outer surface. In various embodiments, the pellets include pores created by immersing the pellets in an etching bath prior to placement on at least one of the first and second electrodes. In various embodiments, the etching bath is an acid bath. In various embodiments, at least one of the first and second electrodes further includes additive pellets including Bi2O3 or a metal sulfide. In various embodiments, the additive pellets include FeS, FeS2, Na2S, or combinations thereof.In various embodiments, the pellets are sintered iron pellets comprised of crushed direct reduced iron ("DRI") precursor and / or DRI fines. In various embodiments, the pellets are mechanically, chemically, electrically, electrochemically, and / or thermally pre-processed prior to placement on at least one of the first and second electrodes. In various embodiments, the pre-processing includes pre-charging the pellets. In various embodiments, the pellets are initially comprised at least in part of cementite (Fe3C) prior to operation of the battery. In various embodiments, at least one of the first and second electrodes further comprises a layer of powdered iron configured to form an interface between the pellet and a current collector of the battery. In various embodiments, the battery may further include a monitoring system configured to monitor a state of charge (SOC) and / or a state of health of at least one of the first and second electrodes. In various embodiments, the monitoring system includes one or more sensors connected to the controller. In various embodiments, the one or more sensors are selected from the group consisting of a strain gauge, a Mossbauer spectrometer, a CCD detector, an ultrasonic transducer, an ion-sensing electrode, a thermocouple, and a gas sensor. In various embodiments, at least one of the first electrode and the second electrode is a composite metal electrode comprising a mixture of pellets and conductive material dispersed among the individual pellets. In various embodiments, the conductive material comprises one or more conductive fibers, one or more wires, one or more meshes, and / or one or more sheets. In various embodiments, the first electrode is a negative electrode and comprises a DRI. Additionally, the first electrode may be a porous iron electrode that is a negative electrode and comprises a DRI. In various embodiments, the battery may further comprise an additive delivery system configured to add one or more additives to the electrolyte. In various embodiments, the additive delivery system delivers a liquid additive or a solid additive. In various embodiments, the one or more additives comprise a salt. In various embodiments, the salt is a carbonate salt or a polysulfide salt. In various embodiments, the one or more additives comprise a sulfur-based additive. In various embodiments, the one or more additives include a surfactant additive.In various embodiments, the one or more additives are configured to mitigate self-discharge and / or inhibit hydrogen evolution reaction (HER). In various embodiments, at least one of the first electrode and the second electrode is under a compressive force. The compressive force acting on the porous iron electrode is greater than 7 KPa and less than 700 KPa. In various embodiments, at least one of the first electrode and the second electrode includes an additional conductive material. In various embodiments, the additional conductive material surrounds the iron-containing pellets. In various embodiments, the additional conductive material is a foil, sheet, mesh, or wire.

[0013] Various embodiments may provide a method for operating an energy storage plant, the method including operating the energy storage plant to produce an active material; and using the active material in the energy storage plant for long-term energy storage. In various embodiments, renewable energy is used to produce the active material.

[0014] Various embodiments can provide a bulk energy storage system including one or more batteries, at least one of which includes a first electrode, an electrolyte, and a second electrode, where one or both of the first electrode and the second electrode include direct reduced iron ("DRI"). In various embodiments, at least one of the first electrode and the second electrode that includes the DRI is an anode that includes direct reduced iron ("DRI") pellets. In various embodiments, at least one of the first electrode and the second electrode further includes additive pellets. In various embodiments, the additive pellets are comprised of FeS, FeS2, Bi2O3, or metal sulfides. In various embodiments, the DRI includes sintered iron pellets comprised of crushed direct reduced iron ("DRI") precursors and / or DRI fines. In various embodiments, the DRI is comprised of direct reduced iron ("DRI") pellets that have been mechanically, chemically, and / or thermally pre-processed prior to being placed on at least one of the first electrode and the second electrode. In various embodiments, the DRI comprises at least about 60% metallic iron by weight based on a total mass of the pellets, the DRI comprises direct reduced iron pellets having an average particle size of 4 mm to 20 mm, and the direct reduced iron pellets constitute at least 60 percent of a total mass of at least one of the first electrode and the second electrode. In various embodiments, the bulk energy storage system is a long term energy storage (LODES) system.

[0015] Various embodiments may provide a long-term energy storage system configured to hold a charge for at least 24 hours, the system including a housing; a first electrode including about 60% to about 90% iron and about 1% to about 40% of a component including one or more of materials selected from the group consisting of SiO2, Al2O3, MgO, CaO, and TiO2; a second electrode; and an electrolyte. In various embodiments, the component may include about 1.5% to about 7.5% SiO2. In various embodiments, the component may include about 0.3% to about 3% Al2O3. In various embodiments, the component may include about 0.25% to about 2% MgO. In various embodiments, the component may include about 0.75% to about 2.5% CaO. In various embodiments, the component may include about 0.25% to about 1.5% TiO2. In various embodiments, the composition may include about 1% to about 10% SiO2. In various embodiments, the composition may include about 0.2% to about 5% Al2O3. In various embodiments, the composition may include about 0.1% to about 10% MgO. In various embodiments, the composition may include about 0.9% to about 10% CaO. In various embodiments, the composition may include 0.05% to 5% TiO2. In various embodiments, at least 50% of the iron is Fe 0 In various embodiments, at least 50% of the iron is metallic iron. In various embodiments, the iron is Fe 0 , Fe 2+ , and Fe 3+ In various embodiments, the storage system has a power rating of at least about 100 MW, a rated duration of at least about 100 hours, and a rated energy of at least about 2,000 MWh. In various embodiments, the storage system has a power rating of about 50 MW to about 500 MW, a rated duration of about 25 hours to about 500 hours, and a rated energy of about 3,000 MWh to about 90,000 MWh. [Brief description of the drawings]

[0016] [Figure 1]FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 2A] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 2B] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 3A] FIG. 1 is a schematic diagram of an exemplary continuous feed calciner configured to form agglomerated sintered pellets, according to various embodiments of the present disclosure. [Figure 3B] 1 is a process flow diagram of an embodiment method for forming a sintered porous metal electrode. [Figure 3C] 1 is a block diagram of an embodiment system for forming a sintered porous metal electrode. [Figure 3D] 1 is a block diagram of an embodiment system for forming a sintered porous metal electrode. [Figure 4] FIG. 1 is a schematic diagram of an electrochemical cell including a composite metal electrode having spherical pellets and a metal feedstock according to various embodiments of the present disclosure. [Diagram 5] 1 is a process flow diagram illustrating an embodiment method for on-site synthesis of active materials for bulk energy storage systems using renewable overproduction. [Figure 6] FIG. 2 is a schematic diagram of the electrochemical cell of FIG. 1, showing macropores and micropores in an enlarged view according to various embodiments of the present disclosure. [Figure 7] FIG. 2 is a schematic diagram of one pellet of the electrochemical cell of FIG. 1 according to various embodiments of the present disclosure. [Figure 8A] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 8B] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 8C] FIG. 1 is a schematic diagram of a series of fluidly connected electrochemical cells according to various embodiments of the present disclosure. [Figure 9] FIG. 2 is a schematic diagram of an electrochemical cell including a mixture of active material and additive material pellets according to various embodiments of the present disclosure. [Figure 10] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 11] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12A] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12B] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12C] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12D] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12E] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12F] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 13A] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 13B] FIG. 1 is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 14] 1 is a schematic diagram of a filtration device according to various embodiments of the present disclosure. [Figure 15] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 16] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 17] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 18] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 19]Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 20] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 21] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 22] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 23] Various exemplary systems are illustrated in which one or more aspects of various embodiments may be used as part of a bulk energy storage system. [Figure 24A] Graphs showing DRI electrode first cycle discharge specific capacity (mAh / gDRI), discharge versus cycle number, coulombic efficiency, and subsequent cycle discharge specific capacity (mAh / gDRI), respectively. [Figure 24B] Graphs showing DRI electrode first cycle discharge specific capacity (mAh / gDRI), discharge versus cycle number, coulombic efficiency, and subsequent cycle discharge specific capacity (mAh / gDRI), respectively. [Figure 24C] Graphs showing DRI electrode first cycle discharge specific capacity (mAh / gDRI), discharge versus cycle number, coulombic efficiency, and subsequent cycle discharge specific capacity (mAh / gDRI), respectively. [Figure 24D] Graphs showing DRI electrode first cycle discharge specific capacity (mAh / gDRI), discharge versus cycle number, coulombic efficiency, and subsequent cycle discharge specific capacity (mAh / gDRI), respectively. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or similar parts. References to specific examples and implementations are for illustrative purposes only and are not intended to limit the scope of the claims. The following description of embodiments of the invention is not intended to limit the invention to such embodiments, but rather to enable those skilled in the art to make and use the invention. Unless otherwise noted, the accompanying drawings are not drawn to scale.

[0018] As used herein, unless otherwise specified, room temperature is 25° C. and standard temperature and pressure are 25° C. and 1 atmosphere. Unless expressly stated otherwise, all tests, test results, physical properties, and values ​​that are temperature dependent, pressure dependent, or both, are provided at standard ambient temperature and pressure.

[0019] In general, the term "about" and the symbol "~" as used herein, unless otherwise specified, are meant to encompass a variation or range of ±10%, the experimental or instrumental error associated with obtaining the stated value, preferably whichever is greater.

[0020] As used herein, unless otherwise stated, recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise stated herein, each individual value within a range is incorporated herein as if it were individually recited herein.

[0021] As used herein, unless otherwise specified, the terms "%", "wt %", and "mass %" are used interchangeably and refer to the weight of a first component as a percentage of the weight of a total, e.g., formulation, mixture, particle, pellet, material, structure, or product. As used herein, unless otherwise specified, "volume %" and "% volume" and similar such terms refer to the volume of a first component as a percentage of the volume of a total, e.g., formulation, mixture, particle, pellet, material, structure, or product.

[0022] The following examples are provided to illustrate various embodiments of the systems and methods of the present invention. Such examples are illustrative and may be prophetic, and should not be considered limiting, and do not limit the scope of the invention in any way.

[0023] It should be noted that it is not necessary to provide or express the theory underlying the novel and innovative process, material, performance, or other beneficial features and characteristics that are the subject of or associated with the embodiments of the present invention. Nevertheless, various theories are provided herein to further advance the art. The theories presented herein are not intended to limit, restrict, or narrow in any way the scope of protection afforded to the claimed inventions unless expressly stated otherwise. Such theories may not be necessary to the utilization of the present invention or may not be practiced. Furthermore, it is understood that the present invention may be coupled with new and previously unknown theories to explain the function-characteristics of the embodiments of the methods, articles, materials, devices, and systems of the present invention. Such subsequently developed theories shall not limit the scope of protection afforded to the present invention.

[0024] Various embodiments of the systems, facilities, techniques, methods, activities, and operations shown herein can be used in various other activities and fields in addition to those shown herein. In addition, such embodiments can be used with, for example, other facilities or activities that may be developed in the future; and existing facilities or activities that may be partially modified based on the teachings herein. Furthermore, various embodiments and examples shown herein can be used with each other, in whole or in part, and in various different combinations. Thus, configurations provided in various embodiments herein can be used with each other. For example, elements of an embodiment having A, A', and B, and elements of an embodiment having A'', C, and D can be used with each other in various combinations, such as A, C, D, and A; A'', C, and D, in accordance with the teachings herein. Thus, the scope of protection given to the present invention should not be limited to the specific embodiments, configurations, or arrangements shown in the specific embodiments, examples, or in the specific illustrated embodiments.

[0025] As used herein, unless otherwise specified, the term "specific gravity", also called apparent density, should be given the broadest possible meaning and is generally intended to mean the weight per unit volume of a structure, e.g., a volumetric form of a material. This property will include the internal porosity of the particle as a fraction of its volume. It can be measured, among other techniques, with a low viscosity fluid that wets the particle surface.

[0026] As used herein, unless otherwise specified, the term "actual density," which may also be referred to as true density, should be given the broadest possible meaning and generally refers to the weight per unit volume of a material if no voids were present in that material. This measurement and characterization essentially excludes internal porosity from the material, e.g., does not include any voids in the material.

[0027] Therefore, a collection of porous foam balls (e.g., Nerf® balls) can be used to illustrate the relationship between the three density properties: The weight of the ball filling a container would be the bulk density of the ball.

[0028]

number

[0029] The weight of a single ball per spherical volume of the ball would be its apparent density.

[0030]

number

[0031] The weight of the material that makes up the skeleton of the ball, i.e., the ball with all void volume removed, per remaining volume of that material would be the actual density.

[0032]

number

[0033] Embodiments of the present invention include devices, systems, and methods for long-term and ultra-long-term low-cost energy storage. As used herein, "long-term" and "ultra-long-term" and similar such terms shall be given the broadest possible meaning unless expressly stated otherwise and shall include energy storage periods of 8 hours or longer, such as 8 hours of energy storage period, energy storage periods ranging from 8 hours to 20 hours, 20 hours of energy storage period, energy storage periods ranging from 20 hours to 24 hours, 24 hours of energy storage period, energy storage periods ranging from 24 hours to 1 week, energy storage periods ranging from 1 week to 1 year (e.g., from days to weeks to months, etc.), and shall include LODES systems. Additionally, the terms "long-term" and "ultra-long-term", "energy storage cell" including "electrochemical cell", and similar such terms shall be given the broadest possible interpretation unless expressly stated otherwise and shall include electrochemical cells that may be configured to store energy over time ranges of days, weeks, or seasons.

[0034] Generally, in one embodiment, the long-term energy storage cell may be a long-term electrochemical cell. Generally, this long-term electrochemical cell can store electricity generated by the power generation system when: (i) the power source or fuel for the generation is available, abundant, cheap, and combinations and variations thereof; (ii) the power needs or demands of the grid, customer, or other users are less than the amount of electricity generated by the power generation system, the price paid to provide such electricity to the grid, customer, or other users is below the economically efficient point for generating such electricity (e.g., the cost of generating electricity exceeds the market price of electricity), and combinations and variations thereof; and (iii) combinations and variations of (i) and (ii) and other reasons. This electricity stored in the long-term electrochemical cell can then be distributed to the grid, customer, or other users when it is economical or otherwise needed. For example, the electrochemical cell may be configured to store energy generated by solar cells during summer months when sunlight is abundant and solar power generation exceeds power grid needs, and to discharge the stored energy during winter months when sunlight may be insufficient to meet power grid needs.

[0035] Various embodiments are discussed with respect to the use of direct reduced iron (DRI) as a battery (or cell) material, as a battery (or cell) component, and combinations and variations thereof. In various embodiments, DRI may be produced from or may be material resulting from the reduction of natural or processed iron ore, such reduction being carried out without reaching the melting temperature of iron. In various embodiments, the iron ore may be taconite or magnetite or hematite or goethite, etc. In various embodiments, DRI may be in the form of pellets, which may be spherical or substantially spherical. In various embodiments, DRI may be porous and may contain open and / or closed internal porosity. In various embodiments, DRI may include material that has been further processed by hot or cold briquetting. In various embodiments, DRI is produced by reducing iron ore pellets to produce ferrous metal (Fe 0DRI can be produced by forming more metallic (more reduced, less oxidized) materials such as iron ore taconite, wustite (FeO), or composite pellets containing iron metal and residual oxide phases. In various non-limiting embodiments, DRI may be reduced iron ore taconite, direct reduced ("DR") taconite, reduced "blast furnace (BF) grade" pellets, reduced "electric arc furnace (EAF) grade" pellets, "cold direct reduced iron (CDRI)" pellets, direct reduced iron ("DRI") pellets, hot briquetted iron (HBI), or any combination thereof. In the iron and steel industry, DRI is sometimes referred to as "sponge iron" and its use is particularly common in India. Iron material embodiments, including exemplary embodiments of DRI materials for use in various embodiments described herein, including for use as an electrode material, may have one, more than one, or all of the material properties as set forth in Table 1 below. As used herein, including in Table 1, the following terms have the following meanings, unless expressly stated otherwise: "specific surface area" means the total surface area of ​​a material per unit mass, including the surface area of ​​pores in a porous structure; "carbon content" or "carbon (wt%)" means the mass of total carbon as a percentage of the total mass of the DRI; "cementite content" or "cementite (wt%)" means the mass of FeC as a percentage of the total mass of the DRI; "total Fe (wt%)" means the mass of all iron as a percentage of the total mass of the DRI; "metallic Fe (wt%)" means the mass of Fe as a percentage of the total mass of the DRI. 0 "Metallization" means the mass of iron in the Fe state as a percentage of the mass of all iron; 0 As used herein, weight and volume percentages and apparent densities are understood to exclude any electrolyte infiltrating the porosity or any transient additives within the porosity, unless otherwise stated.

[0036] [Table 1]

[0037] * The specific surface area is preferably determined by the Brunauer-Emmett-Teller adsorption method ("BET"), more preferably BET as set forth in ISO 9277, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex ion adsorption, and protein retention (PR) methods, can be used to provide results that can be correlated with the BET results.

[0038] ** Actual density is preferably determined by helium (He) pycnometer method, more preferably as set forth in ISO 12154, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results. Actual density is sometimes also referred to in the art as "true density" or "skeletal density."

[0039] *** Apparent density is determined by immersion in water, more preferably as set forth in ISO 15968, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests may be used to provide results that can be correlated with He pycnometer results. Porosity may be defined as the ratio of apparent density to actual density.

[0040]

number

[0041] **** d 孔、90%容積is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as set forth in ISO 15901-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with Hg intrusion results. 孔、90%容積 is the pore diameter above which 90% of the total pore volume resides.

[0042] ***** d 孔、50%表面積 is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as set forth in ISO 15901-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with Hg intrusion results. 孔、50%表面積 is the pore diameter above which 50% of the free surface area lies.

[0043] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as set forth in ASTM E246-10, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as tin(II) chloride reduction titration, titanium(III) chloride reduction titration, and inductively coupled plasma (ICP) spectroscopy, can be used to provide results that can be correlated to the dichromate titration.

[0044] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as set forth in ISO 16878, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as bromine-methanol titration, can be used to provide results that can be correlated to iron(III) chloride titration.

[0045] ### Metallization (%) is preferably determined by the ratio of metallic Fe to total Fe, each preferably determined by the methods described above.

[0046] ####Carbon (wt%) is preferably determined by infrared absorption after firing in an induction furnace, and more preferably as set forth in ISO 9556, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as various combustion and inert gas melting techniques, such as those set forth in ASTM E1019-18, can be used to provide results that can be correlated to infrared absorption after firing in an induction furnace.

[0047] #####Fe 2+ (wt %) is preferably determined by titration, and more preferably as set forth in ASTM D3872-05, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as Mössbauer spectroscopy, X-ray absorption spectroscopy, and the like, can be used to provide results that can be correlated to the titration method.

[0048] $Fe 3+ (wt%) is preferably total Fe (wt%), metallic Fe (wt%), Fe 2+ (wt%), and Fe 3+ It is determined by the mass balance relationship between or within the Fe (wt%). Specifically, Total Fe (wt%) = Metallic Fe (wt%) + Fe 2+ (Weight%)+Fe 3+ (wt%) must be true due to the law of conservation of mass; therefore, Fe 3+ (wt%) is Fe 3+ (wt%) = total Fe (wt%) - metallic Fe (wt%) - Fe 2+ It can be calculated as a percentage by weight.

[0049] $$SiO2 (wt%) is preferably determined gravimetrically, more preferably as set forth in ISO 2598-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), etc., can be used to provide results that can be correlated to gravimetric methods. In certain methods, SiO2 wt% is not determined directly, rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming SiO2 stoichiometry; that is, a molar ratio of Si:O is assumed to be 1:2.

[0050] $$$Ferrite (wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0051] $$$$Wüstite (FeO, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0052] $$$$$Goethite (FeOOH, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0053] + Cementite (Fe3C, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0054] Additionally, embodiments of ferrous materials, including, for example, embodiments of DRI materials, for use in various embodiments described herein, including for use as an electrode material, may have one or more of the following properties, characteristics, or features, as shown in Table 1A (note that values ​​in a row or a column may be present with values ​​in different rows or columns):

[0055] [Table 1A]

[0056] Total Fe (wt%) is preferably determined by dichromate titration, more preferably as set forth in ASTM E246-10, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as tin(II) chloride reduction titration, titanium(III) chloride reduction titration, and inductively coupled plasma (ICP) spectroscopy, can be used to provide results that can be correlated to the dichromate titration.

[0057] !!SiO2 (wt%) is preferably determined gravimetrically, more preferably as set forth in ISO2598-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), etc., can be used to provide results that can be correlated with gravimetric methods. In certain methods, SiO2 wt% is not determined directly, but rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming SiO2 stoichiometry. That is, it is assumed that the molar ratio of Si:O is 1:2.

[0058] !!!Al2O3 (wt%) is preferably determined by flame atomic absorption spectrometry, more preferably as set forth in ISO4688-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated to flame atomic absorption spectrometry. In certain methods, Al2O3 wt% is not determined directly, rather the Al concentration (including neutral and ionic species) is measured and Al2O3 wt% is calculated assuming Al2O3 stoichiometry, i.e., a molar ratio of Al:O is assumed to be 2:3.

[0059] !!!!MgO (wt%) is preferably determined by flame atomic absorption spectrometry, more preferably as set forth in ISO 10204, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated to flame atomic absorption spectrometry. In certain methods, MgO wt% is not determined directly, rather the Mg concentration (including neutral and ionic species) is measured and the MgO wt% is calculated assuming MgO stoichiometry; that is, a 1:1 molar ratio of Mg:O is assumed.

[0060] !!!!!CaO (wt%) is preferably determined by flame atomic absorption spectrometry, more preferably as set forth in ISO 10203, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated to flame atomic absorption spectrometry. In certain methods, CaO wt% is not determined directly, rather the Ca concentration (including neutral and ionic species) is measured and CaO wt% is calculated assuming CaO stoichiometry, i.e., a molar ratio of Ca:O is assumed to be 1:1.

[0061] &TiO2 (wt%) is preferably determined by diantipyrylmethane spectrophotometry, more preferably as set forth in ISO 4691, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated to diantipyrylmethane spectrophotometry. In certain methods, TiO2 wt% is not determined directly, rather the Ti concentration (including neutral and ionic species) is measured and TiO2 wt% is calculated assuming TiO2 stoichiometry; that is, a molar ratio of Ti:O is assumed to be 1:2.

[0062] && Actual density is preferably determined by helium (He) pycnometer method, more preferably as set forth in ISO 12154, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results. Actual density is sometimes also referred to in the art as "true density" or "skeletal density."

[0063] &&& Apparent density is preferably determined by immersion in water, more preferably as set forth in ISO 15968, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results.

[0064] &&&&Bulk density (kg / m 3 ) is preferably determined by measuring the mass of a test portion introduced into a container of known volume until its surface is filled to the brim, more preferably as set forth in Method 2 of ISO 3852, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with the results of gravimetric methods.

[0065] &&&&&Porosity is preferably determined by the ratio of apparent density to actual density.

[0066]

number

[0067] Also, the properties shown in Table 1 may be present in embodiments along with, in addition to, or instead of the properties in Table 1A. Also, greater and lesser values ​​of such properties may be present in various embodiments.

[0068] In an embodiment, the specific surface area of ​​the pellet is about 0.05 m 2 / g ~ approx. 35m 2 / g, approx. 0.1m 2 / g~about 5m 2 / g, approx. 0.5m 2 / g~about 10m 2 / g, approx. 0.2m 2 / g~about 5m 2 / g, approx. 1m 2 / g~about 5m 2 / g, approx. 1m 2 / g~about 20m 2 / g, and about 1m 2 / g, and is about 2m 2 / g, and is about 5m 2 / g, and may be less than about 15m 2 / g, and may be less than about 20m 2 / g, as well as combinations and variations thereof, and larger and smaller values.

[0069] Generally, iron ore pellets are produced by crushing, grinding, or milling iron ore into a fine powder-like form, which is then concentrated by removing impurity phases (so-called "gangue") liberated by the grinding operation. Generally, grinding the ore to finer (smaller) particle sizes increases the purity of the resulting concentrate. The concentrate is then formed into pellets by a pelletizing or balling process (e.g., using a drum or disk pelletizer). Generally, more energy input is required to produce higher purity ore pellets. Iron ore pellets are generally commercially or sold in two main categories: blast furnace (BF) grade pellets and direct reduction (DR grade), sometimes also called electric arc furnace (EAF) grade, with the main difference being the content of SiO2 and other impurity phases, which are higher in BF grade pellets compared to DR grade pellets. Typical critical specifications for DR grade pellets or feedstock are a total Fe content by mass in the range of 63-69 wt%, such as 67 wt%, and a SiO2 content by mass of less than 3 wt%, such as 1 wt%. Typical critical specifications for BF grade pellets or feedstock are a total Fe content by mass in the range of 60-67 wt%, such as 63 wt%, and a SiO2 content by mass in the range of 2-8 wt%, such as 4 wt%.

[0070] In certain embodiments, DRI can be produced by the reduction of "blast furnace" pellets, in which case the resulting DRI may have material properties as set forth below in Table 2. The use of reduced BF grade DRI can be advantageous because less input energy is required to produce the pellets, which translates into a lower cost finished product.

[0071] [Table 2]

[0072] *The specific surface area is preferably determined by the Brunauer-Emmett-Teller adsorption method ("BET"), more preferably BET as set forth in ISO 9277, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex ion adsorption, and protein retention (PR) methods, can be used to provide results that can be correlated with the BET results.

[0073] ** Actual density is preferably determined by helium (He) pycnometer method, more preferably as set forth in ISO 12154, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results. Actual density is sometimes also referred to in the art as "true density" or "skeletal density."

[0074] *** Apparent density is preferably determined by immersion in water, more preferably as set forth in ISO 15968, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results. Porosity can be defined as the ratio of apparent density to actual density.

[0075]

number

[0076] **** d 孔、90%容積is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as set forth in ISO 15901-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with Hg intrusion results. 孔、90%容積 is the pore diameter above which 90% of the total pore volume resides.

[0077] ***** d 孔、50%表面積 is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as set forth in ISO 15901-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with Hg intrusion results. 孔、50%表面積 is the pore diameter above which 50% of the free surface area lies.

[0078] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as set forth in ASTM E246-10, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as tin(II) chloride reduction titration, titanium(III) chloride reduction titration, and inductively coupled plasma (ICP) spectroscopy, can be used to provide results that can be correlated to the dichromate titration.

[0079] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as set forth in ISO 16878, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as bromine-methanol titration, can be used to provide results that can be correlated to iron(III) chloride titration.

[0080] ### Metallization (%) is preferably determined by the ratio of metallic Fe to total Fe, each preferably determined by the methods described above.

[0081] ####Carbon (wt%) is preferably determined by infrared absorption after firing in an induction furnace, and more preferably as set forth in ISO 9556, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as various combustion and inert gas fusion techniques, such as those set forth in ASTM E1019-18, can be used to provide results that can be correlated to infrared absorption after firing in an induction furnace.

[0082] #####Fe 2+ (wt %) is preferably determined by titration, and more preferably as set forth in ASTM D3872-05, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as Mössbauer spectroscopy, X-ray absorption spectroscopy, and the like, can be used to provide results that can be correlated to the titration method.

[0083] Fe 3+ (wt%) is preferably total Fe (wt%), metallic Fe (wt%), Fe 2+ (wt%), and Fe 3+ It is determined by the mass balance relationship between or within the Fe (wt%). Specifically, Total Fe (wt%) = Metallic Fe (wt%) + Fe 2+ (Weight%)+Fe 3+ (wt%) must be true due to the law of conservation of mass; therefore, Fe 3+ (wt%) is Fe 3+ (wt%) = total Fe (wt%) - metallic Fe (wt%) - Fe 2+ It can be calculated as a percentage by weight.

[0084] $$SiO2 (wt%) is preferably determined gravimetrically, more preferably as set forth in ISO2598-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), etc., can be used to provide results that can be correlated to gravimetric methods. In certain methods, SiO2 wt% is not determined directly, rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming SiO2 stoichiometry; that is, a molar ratio of Si:O is assumed to be 1:2.

[0085] $$$Ferrite (wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0086] $$$$Wüstite (FeO, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0087] $$$$$Goethite (FeOOH, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0088] + Cementite (Fe3C, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0089] Also, the properties shown in Table 2 may be present in embodiments along with, in addition to, or instead of the properties in Table 1 and / or Table 1A, and greater and lesser values ​​of such properties may be present in various embodiments.

[0090] In certain embodiments, the DRI can be produced by reduction of DR grade pellets, where the resulting DRI can have material properties as set forth below in Table 3. The use of reduced DR grade DRI can be advantageous due to the higher Fe content in the pellets, thereby increasing the energy density of the battery.

[0091] [Table 3]

[0092] * The specific surface area is preferably determined by the Brunauer-Emmett-Teller adsorption method ("BET"), more preferably BET as set forth in ISO 9277, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex ion adsorption, and protein retention (PR) methods, can be used to provide results that can be correlated with the BET results.

[0093] ** Actual density is preferably determined by helium (He) pycnometer method, more preferably as set forth in ISO 12154, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results. Actual density is sometimes also referred to in the art as "true density" or "skeletal density."

[0094] *** Apparent density is preferably determined by immersion in water, more preferably as set forth in ISO 15968, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests can be used to provide results that can be correlated with He pycnometer results. Porosity can be defined as the ratio of apparent density to actual density.

[0095]

number

[0096] **** d 孔、90%容積is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as set forth in ISO 15901-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with Hg intrusion results. 孔、90%容積 is the pore diameter above which 90% of the total pore volume resides.

[0097] ***** d 孔、50%表面積 is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as set forth in ISO 15901-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with Hg intrusion results. 孔、50%表面積 is the pore diameter above which 50% of the free surface area lies.

[0098] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as set forth in ASTM E246-10, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as tin(II) chloride reduction titration, titanium(III) chloride reduction titration, and inductively coupled plasma (ICP) spectroscopy, can be used to provide results that can be correlated to the dichromate titration.

[0099] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as set forth in ISO 16878, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as bromine-methanol titration, can be used to provide results that can be correlated to iron(III) chloride titration.

[0100] ### Metallization (%) is preferably determined by the ratio of metallic Fe to total Fe, each preferably determined by the methods described above.

[0101] ####Carbon (wt%) is preferably determined by infrared absorption after firing in an induction furnace, and more preferably as set forth in ISO 9556, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as various combustion and inert gas fusion techniques, such as those set forth in ASTM E1019-18, can be used to provide results that can be correlated to infrared absorption after firing in an induction furnace.

[0102] #####Fe 2+ (wt %) is preferably determined by titration, and more preferably as set forth in ASTM D3872-05, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as Mössbauer spectroscopy, X-ray absorption spectroscopy, and the like, can be used to provide results that can be correlated to the titration method.

[0103] $Fe 3+ (wt%) is preferably total Fe (wt%), metallic Fe (wt%), Fe 2+ (wt%), and Fe 3+ It is determined by the mass balance relationship between or within the Fe (wt%). Specifically, Total Fe (wt%) = Metallic Fe (wt%) + Fe 2+ (Weight%)+Fe 3+ (wt%) must be true due to the law of conservation of mass; therefore, Fe 3+ (wt%) is Fe 3+ (wt%) = total Fe (wt%) - metallic Fe (wt%) - Fe 2+ It can be calculated as a percentage by weight.

[0104] $$SiO2 (wt%) is preferably determined gravimetrically, more preferably as set forth in ISO 2598-1, the disclosure of which is incorporated herein by reference in its entirety. It is recognized that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), etc., can be used to provide results that can be correlated to gravimetric methods. In certain methods, SiO2 wt% is not determined directly, rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming SiO2 stoichiometry; that is, a molar ratio of Si:O is assumed to be 1:2.

[0105] $$$Ferrite (wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0106] $$$$Wüstite (FeO, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0107] $$$$$Goethite (FeOOH, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0108] + Cementite (Fe3C, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0109] Also, the properties shown in Table 3 may be present in an embodiment along with, in addition to, or instead of the properties in Tables 1, 1A, and / or 2. Also, greater and lesser values ​​of such properties may be present in various embodiments.

[0110] In various embodiments, the bed of conductive pellets constitutes (e.g., functions to provide an electrode, is a component of an electrode, forms an electrode, etc.) an electrode of an energy storage system. In this electrode embodiment, the pellets include iron-containing material, reduced iron material, iron in an unoxidized state, iron in a highly oxidized state, iron having a valence state of 0 to 3+, and combinations and variations thereof. In this electrode embodiment, the pellets include iron having one or more of the characteristics shown in Table 1, Table 1A, Table 2, and Table 3. In embodiments, the pellets have a porosity, e.g., an open pore structure, which may have pore sizes, e.g., ranging from a few nanometers to a few microns. For example, embodiments may have pore sizes of about 5 nm (nanometers) to about 100 μm (microns), about 50 nm to about 10 μm, about 100 nm to about 1 μm, greater than 100 nm, greater than 500 nm, less than 1 μm, less than 10 μm, less than 100 μm, and combinations and variations of such pore sizes, as well as larger and smaller pores. In some embodiments, the pellets comprise direct reduced iron (DRI) pellets.Embodiments of such electrodes in energy storage systems, particularly long-term energy storage systems, may have one or more of these above-mentioned features.

[0111] Packing of the pellets creates macropores, e.g., openings, spaces, channels, or voids, between the individual pellets. The macropores facilitate ion transport across the electrode, which in some embodiments has a minimum dimension that is still very thick compared to some other types of battery electrodes, which are multiple centimeters in dimension. The micropores within the pellets allow contact between the high surface area active material of the pellets and the electrolyte, allowing for high availability of the active material. This electrode structure is particularly useful for improving the rate capacity of very thick electrodes for stationary, long-term energy storage, where thick electrodes may be necessary to achieve very high areal capacity.

[0112] The pellets of such embodiments, particularly for use in the embodiment of electrodes for long-term energy storage systems, may be any volumetric shape, such as spheres, disks, pucks, beads, tablets, pills, rings, lenses, disks, panels, cones, truncated cones, square blocks, rectangular blocks, trusses, angles, channels, hollow enclosed chambers, hollow spheres, blocks, sheets, films, particulates, beams, rods, angles, planks, cylinders, fibers, synthetic fibers, tubes, cups, pipes, and combinations and variations thereof, as well as other more complex shapes. The pellets of an electrode may be the same or different shapes. The pellets of an electrode that is one of several electrodes in a long-term energy storage system may be the same or different from the pellets of other electrodes in the storage system.

[0113] The size of the pellet refers to the maximum cross-sectional distance of the pellet, e.g., the diameter of a sphere, unless otherwise expressly used. The pellets may be of the same size or different sizes. It is recognized that the shape, size, and both of the pellet, and typically, to a lesser extent, the shape and size of the container or housing that holds the pellet, determine the nature and size of the macropores of the electrode. The pellets may have sizes of about 0.1 mm to about 10 cm, about 5 mm to about 100 mm, 10 mm to about 50 mm, about 20 mm, about 25 mm, about 30 mm, greater than 0.1 mm, greater than 1 mm, greater than 5 mm, greater than 10 mm, and greater than 25 mm, as well as combinations and variations thereof.

[0114] In an embodiment, the pellets configured into the electrode have a mass of about 3 g / cm 3 ~Approx. 6.5g / cm 3 of about 0.1g / cm 3 ~Approx. 5.5g / cm 3 of about 2.3g / cm 3 ~Approx. 3.5g / cm 3 , 3.2g / cm 3 ~Approx. 4.9g / cm 3of about 0.5g / cm 3 Larger than approx. 1g / cm 3 Larger than approx. 2g / cm 3 Larger than approx. 3g / cm 3 Electrodes can be provided having bulk densities greater than or equal to 1000 nm, as well as combinations and various values ​​thereof, as well as greater and lesser values.

[0115] In certain embodiments, a mixture of reduced DR grade pellets and reduced BF grade pellets may be used together. In certain other embodiments, a combination of reduced material (DRI) and raw ore material (DR or BF grade) may be used.

[0116] In various embodiments, DRI may be produced by using "man-made ores" or by-product forms of iron oxide, such as waste products. As one non-limiting example, mill scale is mixed iron oxide that forms on the surface of hot rolled steel, which in various embodiments is collected and ground to form iron oxide powder, which is then agglomerated to form pellets, and then reduced to form DRI. Other waste streams may be similarly utilized to form DRI. As another non-limiting example, pickling solutions are acidic solutions that may be rich in dissolved Fe ions. In various embodiments, Fe-bearing pickling solutions may be neutralized with a base (such as caustic potash or sodium hydroxide) to precipitate iron oxide powder, which is then agglomerated to form pellets, and then reduced to form DRI.

[0117] In various embodiments, the precursor iron oxide is first reduced and then subsequently shaped into pellets or other agglomerates. In one specific non-limiting embodiment, iron oxide powder derived from natural or man-made ores is reduced to iron metal powder by heat treatment at 900° C. in a reducing gas environment, such as a linear hearth furnace having a hydrogen atmosphere ranging from 1% to 100% H2. In embodiments using hydrogen as the reducing gas, the cementite (Fe3C) content of the DRI may be as low as 0% by weight.

[0118] In various embodiments, DRI pellets or agglomerates are formed in a single process from iron oxide powder by using a rotary calciner. The rotary motion of the kiln facilitates the agglomeration of the powder into pellets or agglomerates, and the high temperature reducing gas environment provides for the simultaneous reduction of the iron oxide. In various other embodiments, a multi-stage rotary calciner may be used, where the agglomeration and reduction steps can be independently tuned and optimized.

[0119] In various embodiments, the DRI has a shape that is not spherical. In certain embodiments, the DRI may have a substantially rectilinear or brick-like shape. In certain embodiments, the DRI may have a substantially cylindrical or rod-like, or disk-like shape. In certain embodiments, the DRI may have a substantially flat or sheet-like shape. In certain embodiments, the iron oxide powder is dry-formed by die pressing into a cylinder or any other shape suitable for die pressing. In certain embodiments, the iron oxide powder is dry-formed into a sheet-like form by roll pressing with a calendar roll. In certain embodiments, the iron oxide powder is compounded with a binder, such as a clay or a polymer, and dry-processed into a rod-like shape by extrusion. In certain embodiments, the iron oxide powder is compounded with a binder, such as a clay or a polymer, and dry-processed into a sheet-like form by roll pressing with a calendar roll. The binder may be composed of a clay, such as bentonite, or a polymer, such as corn starch, polyacrylamide, or polyacrylate. Binders may include bentonite, sodium carbonate, calcium chloride, calcium hydroxide, sodium silicate, carboxymethylcellulose (CMC), Alcotac, Peridur, corn starch, Funa, wheat flour, sodium lignosulfate, molasses, or polyacrylates. Binders may be comprised of a combination of one or more clays and one or more polymers. In certain embodiments, iron oxide powder is dispersed in a liquid to form a slurry that is then used to wet mold into various shapes. In certain embodiments, the iron oxide slurry is slip cast into molds of nearly any shape. In certain embodiments, the iron oxide slurry is coated onto a sheet by doctor blading or other similar coating methods.

[0120] In various embodiments, a bed of conductive microporous pellets constitutes an electrode of an energy storage system. In some embodiments, the pellets include pellets of direct reduced iron (DRI). The packing of the pellets creates macropores between the individual pellets. The macropores facilitate ion transport across the electrode, which in some embodiments has a minimum dimension that is still very thick compared to some other types of battery electrodes, which are multiple centimeters in dimension. The macropores can form a low-torque pore space compared to the micropores in the pellets. The micropores in the pellets allow contact between the high surface area active material of the pellets and the electrolyte, allowing high availability of the active material. This electrode structure is particularly useful for improving the rate capacity of very thick electrodes for stationary, long-term energy storage, where thick electrodes may be necessary to achieve very high areal capacity.

[0121] In various embodiments, fugitive pore formers are incorporated during the production of the DRI to increase the porosity of the resulting DRI. In one embodiment, the porosity of the DRI pellets is modified by incorporating a sacrificial pore former, such as ice (solid H2O), into the pelletization process, which subsequently melts or sublimes under heat treatment. In certain other embodiments, the fugitive pore former includes naphthalene, which then sublimes, leaving behind porosity. In other embodiments, the fugitive pore former includes NH4CO3 (ammonium carbonate), which may be a fugitive pore former, which may be introduced as a solid at various times during the production of the DRI and decomposes under heat, leaving all as gaseous or liquid species (NH3+CO2+H2O). In various other embodiments, the fugitive additive may serve an additional function in the cell (e.g., may be an electrolyte component). In certain embodiments, the fugitive additive may be an alkali salt, such as KOH or NaOH or LiOH. In certain embodiments, the fugitive additive may be a soluble electrolyte additive that is solid in form under ambient dry conditions, such as lead sulfate, lead acetate, antimony sulfate, antimony acetate, sodium molybdenum oxide, potassium molybdenum oxide, thiourea, sodium stannate, ammonium thiosulfate, etc. In various other embodiments, the fugitive additive may be a binder used to agglomerate iron ore powder to form pellets or other shapes, such as sodium alginate or carboxymethyl cellulose binder.

[0122] In various embodiments, sacrificial, transformable, fugitive, or removable pore formers or techniques may be utilized. In such embodiments, the intermediate material with the pore former still present may have a total Fe weight percent ranging from 20 wt% to 90 wt%. The pore former may be partially removed prior to application as an electrode, entirely prior to or during application as an electrode, and combinations and variations thereof. In one embodiment, the intermediate may have 25 wt% to 50 wt% total Fe, and removal of the pore former provides the electrode with 60 wt% to 90 wt% total Fe.

[0123] In certain embodiments, the reducing gas used to form the DRI is hydrogen (H2). In certain embodiments, the hydrogen used as the reducing gas is a by-product of an industrial, chemical, or manufacturing process. In certain embodiments, the hydrogen is generated by electrolysis of water from a renewable power generation source, such as wind or solar energy. In certain embodiments, an electrolyzer is connected to the energy storage system. In certain embodiments, the electrolyzer is a proton exchange membrane (PEM) electrolyzer. In certain embodiments, the electrolyzer is an alkaline electrolyzer. In certain embodiments, the hydrogen is a by-product of a chloro-alkali process or plant. In embodiments using hydrogen as the reducing gas, the cementite (Fe3C) content of the DRI may be as low as 0 wt.%.

[0124] In certain embodiments, natural gas (methane, CH4) is used as a reducing agent to produce DRI. In some embodiments, the natural gas used is obtained from naturally occurring underground deposits or from agriculture. In certain embodiments, the methane used as a reducing gas is a by-product of an industrial, chemical, or manufacturing process. In certain embodiments, methane is steam reformed (by reaction with water, H2O) to produce a mixture of carbon monoxide (CO) and hydrogen (H2) by the reaction CH4+H2O->CO+3H2. In certain embodiments, this reforming reaction occurs in an auxiliary reformer separate from the reactor in which the reduction of iron occurs. In certain embodiments, reforming occurs in situ in the reduction reactor. In certain embodiments, reforming occurs in both the auxiliary reformer and the reduction reactor. In certain embodiments, coal is used as a reducing agent to produce DRI. In certain embodiments, coke is used as a reducing agent to produce DRI. In embodiments using a carbon-containing reducing gas, the cementite (Fe3C) content of the DRI may be higher, up to 80 wt.%.

[0125] In certain embodiments, a mixture of DRI produced using various reducing gases can be used to achieve beneficial combinations of compositions and properties. In one non-limiting embodiment, a 50 / 50 by mass mixture of DRI produced from BF grade pellets reduced in natural gas and DRI produced from DR grade pellets reduced in hydrogen is used as the anode of the battery. Other combinations of mass ratios, feedstock types (DR, BF, other man-made ores, etc.), and reduction media (hydrogen, natural gas, coal, etc.) can be combined in other embodiments.

[0126] In various embodiments, the DRI pellets may be crushed and the crushed pellets may comprise the bed (with or without added powder).

[0127] In various embodiments, additives beneficial to the electrochemical cycle, such as hydrogen evolution reaction (HER) inhibitors, may be added to the bed in solid form, for example as a powder or as solid pellets.

[0128] In some embodiments, the metal electrode has a low initial specific surface area (e.g., about 5 m 2 / g, preferably less than about 1 m 2 / g). Such electrodes tend to exhibit low self-discharge rates in low-rate, long-term energy storage systems. One example of a low surface area metal electrode is a bed of DRI pellets. In many typical modern electrochemical cells, such as lithium-ion or nickel-metal hydride batteries, a high surface area is desirable to facilitate high rate capacity (i.e., high power). In long-term systems, the need for rate capacity is significantly reduced, so a low surface area electrode can meet the need for a target rate capacity while minimizing the self-discharge rate.

[0129] In some embodiments, the DRI pellets are processed by mechanical, chemical, electrical, electrochemical, and / or thermal methods before the DRI pellets are used in an electrochemical cell. Such pretreatment can enable the achievement of superior chemical and physical properties, for example, increasing the capacity available during the discharge reaction. The physical and chemical properties of the DRI as purchased (sometimes referred to as "as received") may not be optimal for use as the negative electrode of an electrochemical cell. The improved chemical and physical properties can include introducing a higher content of desirable impurities, such as HER inhibitors, achieving a lower content of undesirable impurities (such as HER catalysts), achieving a higher specific surface area, achieving a higher total porosity, achieving a different pore size distribution than the starting DRI (such as a multimodal pore size distribution to reduce mass transport resistance), achieving a desired distribution of pellet sizes (such as a multimodal size distribution to allow the pellets to be packed to a desired density), modifying or selecting pellets of a desired aspect ratio (to achieve a desired bed packing density). Mechanical processing can include tumbling, milling, crushing, pulverizing, and powdering. Chemical processing can include acid etching. Chemical processing can include immersing a bed of pellets in an alkaline solution to create necking between the pellets, roughening micropores in the pellets, or dissolving impurities or secondary phases to increase the pore volume percentage or change the pore size distribution. Thermal processing can include processing the DRI at high temperatures in an inert, reducing, oxidizing, and / or carburizing atmosphere. In various embodiments, mechanical, chemical, electrical, electrochemical, and / or thermal methods for pre-processing materials that form electrodes, such as DRI pellets, can fuse materials that form electrodes to a bed, such as a bed of DRI pellets fused together.

[0130] In embodiments, as shown herein, the iron material can be processed, chemically modified, mechanically modified, or otherwise configured to change one or more of its characteristics. Such methodologies are generally described herein as being carried out with DRI materials. It is understood that such methodologies can be used with other iron-containing materials, such as reduced iron materials, iron in unoxidized states, iron in highly oxidized states, iron having valence states from 0 to 3+, and combinations and variations thereof. In this manner, iron-containing pellets for use in electrode configurations of long-term electrical storage cells are provided, having predetermined characteristics, such as those shown herein.

[0131] In certain embodiments, the DRI is subjected to mechanical operations to grind, scrape, or polish the surface and / or to remove fines. In one embodiment, the DRI pellets are spun in a trommel screen to scrape the surface and remove fines / dust from the surface. This operation can have the beneficial effect of reducing the reactivity of the pelleted DRI, making it easier and safer to ship without resorting to briquetting or other compaction operations. In another embodiment, the DRI blocks or sheets are passed under a rotating brush to remove fines from the surface. This has a similar beneficial effect.

[0132] In one embodiment, the porosity is increased by pretreating the DRI by immersion in an acid bath (e.g., concentrated HCl). The acid bath etches the iron, creating larger pores and increasing the total porosity. The etching time can be optimized to increase the total volume of the DRI pellets without losing too much active material to the acid etching solution.

[0133] In another embodiment, desirable impurities or additives are incorporated into the DRI. If such impurities are solid, they can be incorporated by ball milling the powdered additives with the DRI pellets (e.g., using a planetary ball mill or similar device). In that case, the pellets themselves act as the milling media. In this way, the powdered additives are mechanically introduced into the pores or surfaces of the DRI pellets. The DRI may also be coated with beneficial additives, for example, by rolling or immersing in a slurry containing the additives. Such desirable impurities can include alkali sulfides. Alkaline sulfide salts have been demonstrated to greatly improve the availability of active material in Fe anodes. Just as soluble alkali sulfides can be added to the electrolyte, insoluble alkali sulfides can be added to the DRI, for example, by the methods described above.

[0134] In various embodiments, the specific surface area of ​​the DRI is increased by a factor of 3 or more, preferably a factor of 5 or more, as measured by techniques such as Brunauer-Emmett-Teller gas adsorption. In some embodiments, this surface area increase is achieved by using the DRI as an electrode in an electrochemical cell and electrochemically reducing it with an applied current.

[0135] In some embodiments, the surface area of ​​a cementite or iron carbide containing material, such as a DRI pellet containing cementite or iron carbide, is increased by using the material as an anode in an electrochemical cell and discharging it. In certain embodiments, the specific current density may be 0.1-25 mA / g. This high surface area iron oxide can also be used in a variety of applications other than electrochemical cells.

[0136] In various embodiments, to increase electrical conductivity, the pellets can be mixed with more electrically conductive, but potentially more expensive, powders to produce a more conductive composite bed. This powder can increase the areal capacity of the cell by filling the voids between the pellets. This can reduce the ratio of electrolyte volume to DRI pellets in a manner that can be systematically varied and optimized. In one embodiment, this powder is used at the current collection sites to increase the contact surface area and reduce the interfacial resistivity between the current collector and the small contact area of ​​the spherical pellets, as described in more detail in the previous section. This ensures the ability to vary and control the effective current density of the pellets. Varying the particle size of the composite bed can make the cost and conductivity controllable. In another example, the use of additional powder, wire, mesh, gauze, or wool-like conductive material can increase the overall conductivity, allowing the use of low conductive pellets (sometimes referred to in the industry as "remet") in the composite bed, such as DR taconite pellets or poorly metallized direct reduced pellets. In one embodiment, the conductive component may include DRI fines or other waste materials from the DRI process.

[0137] The ratio of electrolyte to ferrous material, e.g., DRI material in a cell, is approximately 0.5 mL. 電解質 :1g 鉄材料 ~about 5mL 電解質 :1g 鉄材料 , about 0.6 mL 電解質 :1g 鉄材料 ~about 3mL 電解質 :1g 鉄材料 , about 0.6 mL 電解質 :1g 鉄材料 , about 0.7mL 電解質 :1g 鉄材料 , about 0.8 mL 電解質 :1g 鉄材料 , about 1 mL 電解質 :1g 鉄材料 , as well as combinations and variations thereof, and larger and smaller ratios.

[0138] In one embodiment, the porous sintered iron electrode may be formed of DRI, which may have been reduced in particle size or powdered, for example by crushing or grinding. DRI fines or other waste materials may also be used to form the sintered iron electrode. The sintered electrode may be molded with a binder under heat and / or pressure, and then the binder may be burned out and the green form sintered at high temperatures. DRI pellets may also be fused together directly by sintering in a non-oxidizing atmosphere without a binder, optionally with pressure, to create electrical and physical connectivity between the pellets.

[0139] In various embodiments, the porous anode may be formed by crushing, chopping, or grinding hot briquetted iron (HBI). In various embodiments, HBI may be preferred for shipping and transportation due to its lower surface area and reactivity, but the porosity of HBI may be too low for practical applications in thick electrodes due to limited ion transport. To achieve an optimal combination of transportation and performance, DRI may be shipped in briquette form to the cell assembly or manufacturing site, where it may be crushed, crushed, and / or chopped to increase the porosity of the resulting electrode.

[0140] A packed bed of DRI pellets may be a desirable configuration for an iron-based electrode because it provides an electronically conductive permeation path through the packed bed while leaving porosity available for electrolyte to occupy to facilitate ion transport. In certain embodiments, the ratio of electrolyte volume to DRI mass may range from 0.5 mL / g to 5 mL / g, such as 0.6 mL / g or 1.0 mL / g. DRI pellets are generally in contact with surrounding pellets through a small contact area compared to the pellet surface area, and in some cases the contacts may be considered "point contacts." Small cross-sectional area contacts may be constrictions for current flow, which may result in relatively low electrical conductivity across the pellet bed, which in turn may result in high electrode overpotentials and low cell voltage efficiency.

[0141] In various embodiments, the electrical conductivity of the DRI pellet bed can be increased in several ways. In some embodiments, the electrical conductivity of the DRI pellet bed can be increased by using additional conductive material that may surround individual pellets, may be embedded within individual pellets, may surround the entire pellet bed, or may penetrate the pellet bed. The conductive material may be one or more of a metal, a metal oxide, a metal carbide, a metal nitride, a semiconductor, carbon, a conductive polymer, or may be a composite that includes at least one of such electronically conductive materials. The electronically conductive material may be in the form of a powder, a wire, a mesh, or a sheet. In certain embodiments, the conductive material itself can contribute to the electrochemical reaction of the battery, including but not limited to providing storage capacity. In certain other embodiments, the electronically conductive material is not substantially electrochemically active. In one embodiment, the conductive material is a powder, and the powder fills or partially fills the spaces between the pellets or between the pellets and the current collector to improve electrical conductivity between the pellets or between the pellets and the current collector. For example, the conductive powder may consist of DRI "fines," a powder waste product of the direct reduction process that is similar in composition to DRI. In this case, the fines can serve to both increase the electrical conductivity of the bed and to increase the storage capacity of the anode. In another embodiment, the conductive material is a powder, which is applied to the surfaces of the pellets as a coating. Such a coating provides a larger area for electrical contact between the pellets.

[0142] In various embodiments, a conductive coating is applied to the low-conductivity pellets to allow them to be used in electrodes. In certain embodiments, low-conductivity pellets, such as taconite pellets or poorly metallized directly reduced pellets (sometimes referred to in the industry as "remet"), may be coated. The coating may be conductive to reduce electrical resistance from the current collector to the taconite pellets during the initial reduction step. The coating may or may not be removed during or after the reduction step. In one embodiment, the coating is a thin conformal metallic layer, such as stainless steel, that wraps circumferentially around each pellet. In another embodiment, the coating is a thin layer of lead that coats the outside of each pellet using a directional deposition technique, such as sputtering, evaporation, or other physical vapor deposition technique. In certain embodiments, the coating is applied by rotating the DRI and coating material together in a rotating vessel. In certain embodiments, the DRI in the rotating vessel is substantially spherical in shape.

[0143] In another embodiment, some or all of the individual pellets in the pellet bed are wrapped with an electrically conductive wire, foil, or sheet. In some embodiments, a clamping mechanism such as a mesh is used to apply tension to the wire, foil, or sheet. Optionally, such current collectors surrounding the individual pellets may be attached to a wire that is bound together or connected to a larger current collector. In another example, a conductive mesh, gauze, or wool is interspersed in the spaces between the DRI pellets to increase electrical connectivity. In various embodiments, the conductive material is a mesh with openings (clear size) selected to be smaller than the pellets so that the pellets do not pass through the mesh. The conductive material in this case may be stainless steel, nickel, or other metals and metal alloys. In another example, the DRI pellets are directly connected to each other by a conductive wire that penetrates or surrounds the individual pellets. For example, a wire can be threaded through the holes in the DRI pellets to provide electrical contact within the pellets as well as between them, similar to forming a string of beads. Optionally, the string of pellets can be held in contact using an electrical terminal or "stopper" where tension is optionally applied to the wire. The electrical terminal may optionally be in electrical connection with a larger current collecting fixture, such as a plate.

[0144] In another embodiment, the electrical conductivity of the pellet bed is improved by applying a compressive load to a DRI pellet bed anode to increase the inter-pellet forces and / or inter-pellet contact area or between the pellet and the current collector, thus reducing contact resistance and enhancing electrochemical performance. Typical DRI pellets are roughly spherical in shape, have internal porosity, and can elastically deform to >5% linear strain before yielding. Applying a load that compresses the DRI bed can increase the effective interfacial contact area between the pellets and between the pellet and the current collector. It is advantageous to use pellets with a yield strain that allows deformation to achieve the desired increase in electrical conductivity without fracture. In one embodiment, pellets with a compressive strength of 700-2500 psi are used for the pellet bed electrode to which the compressive load is applied. In addition, the mechanical assembly that provides the compressive load to the pellet bed can also serve as the current collector. The electrical resistance of such pellet beds, measured in the dry state before filling with any liquid electrolyte, can be reduced by a factor of 2-100 or more by applying a compressive load. In certain embodiments, the applied load may be in the range of 0.1 psi to 1000 psi, such as 50 psi or 100 psi. In certain embodiments, the applied load may be in the range of 0.1 psi to 10 psi, such as 1 psi or 5 psi. In one example, metal plates on opposing sides of the pellet bed serve to provide both current collection and a compressive load on the pellet bed. Optionally, one or more of the plates may be replaced with a macroporous current collector (e.g., metal mesh) to facilitate ion transport across the electrode. Opposing current collectors are advantageously joined, preferably so that they are at the same potential, to make the electrochemical reaction rate more uniform across the electrode. In another example, the container containing the pellet bed serves both as a current collector and as a method of applying the compressive load. In another embodiment, an array of conductive posts (or bars) is implemented that connect to a common downward current collector. Thus, multiple current collecting areas can be placed across the pellet bed.This approach can also reduce the effective transport length within the electrode from the total thickness of the pellet bed to the spacing between the posts. Additionally, these posts can be used to attach a mechanical clamping mechanism, such as a plate or perforated plate, to the top of the pellet bed to incorporate a downward force on the pellet bed while also acting as a current collecting element.

[0145] In some embodiments, the compressive load may be provided partially or entirely by magnetic forces. For example, a force may be applied using permanent magnets placed on one or more sides of the bed such that the pellets in the bed are attracted to the magnets. In the case of a DRI pellet bed, which is primarily metallic iron, the pellet bed is expected to be primarily ferromagnetic and will be attracted to the magnets. Magnets may also be embedded in other fixtures surrounding the pellet bed. The magnets and fixtures serve to hold the pellet bed in place and provide a compressive stress that results in improved electrical contact between the pellets and between the pellets and the current collector, as described above.

[0146] In some embodiments, the inter-pellet contact resistance of the pellet bed can be reduced by using a pretreatment that is applied to the pellet bed before assembly and / or operation of the battery. Some such pretreatment processes are described in the following paragraphs.

[0147] In some embodiments, the entire DRI pellets are loaded into a bed and sintered under an inert or reducing (i.e., non-oxidizing) atmosphere, optionally with mechanical pressure during sintering, for example, using materials that are stable at the sintering temperature and sintering atmosphere. The sintering temperature may range from 600 to 1100°C. The non-oxidizing atmosphere may consist partially or entirely of an inert gas, such as nitrogen or argon. The non-oxidizing atmosphere may also include a mixture of gases that tend to reduce iron, such as CO and CO2 and H2 and H2O. The exact composition of the mixture can be optimized according to the Ellingham diagram to ensure that oxidation of iron is thermodynamically unfavorable. In one embodiment, forming gas (5% H2, 95% N2) is used at sintering temperatures of about 600°C to about 1100°C, such as 600°C to about 850°C, 850°C, about 850°C to about 1100°C, etc. The combination of high temperature and a non-oxidizing atmosphere can promote atomic diffusion and grain coarsening at the pellet contacts, causing the pellets to bond together. The result is a bed of DRI pellets that are fused together and have low inter-pellet contact resistance. The pellets can also be fused to current collectors in the same process.

[0148] In another embodiment, the pellets are joined using a heat treatment in which a flux or sintering aid is used to substantially reduce the heat treatment temperature required to form sintered necks between the pellets. Examples of fluxes or sintering aids include one or more metals that have a melting point lower than iron, such as zinc, tin, copper, aluminum, bismuth, and lead, or metals that form iron alloys with a melting temperature lower than iron, such as those that exhibit low melting eutectic liquids. Other examples of sintering aids include one or more glass-forming compositions, including, but not limited to, silicates, borates, and phosphates.

[0149] In another embodiment, the pellets may be fused together electrically by a process such as welding. In some such embodiments, the welding is accomplished by passing an electric current through a bed of pellets. In some such embodiments, such an electric current is delivered by discharging a capacitor.

[0150] In various embodiments, the anode electrode is an ordered array of pellets. In certain embodiments, the pellets are arranged into a cylinder. In certain embodiments, the pellets are arranged into a plate. In certain embodiments, the pellets are arranged into a disk. In certain embodiments, the pellets are arranged into a rectangular prism. In certain embodiments, the pellets are arranged into a hexagonal prism. In certain embodiments, the pellets are arranged into a volume.

[0151] In various embodiments, an electrolyte management system can be provided in which different electrolyte additives or formulations are added to the battery when switching between operating states. The optimal electrolyte formulations for operation during charging, discharging, and idle states of the battery can be very different. The electrolyte management system of various embodiments can improve the capacity utilization of the iron electrode, improve the self-discharge of the cell, and suppress the hydrogen evolution reaction (HER). One or more such benefits can be realized simultaneously. In one embodiment of such an electrolyte management system, any number of separate electrolyte formulation reservoirs are provided, each connected to the electrochemical cell via a separate flow controller. During different stages of operation, different relative amounts of each electrolyte formulation are flowed into the cell based on the optimal concentration of the constituent species for the instantaneous operating mode (charge, discharge, idle). The electrolyte management system can be configured to adjust the electrolyte composition based on the instantaneous state of charge of the battery.

[0152] Various embodiments can provide a method and apparatus for maintaining the liquid electrolyte level of a battery. When exposed to air, a container containing water will undergo evaporation until the partial pressure of water vapor in the air is equal to the vapor pressure of water at the temperature of the system. Specifically, an electrochemical system in which an aqueous electrolyte is exposed to the environment will experience this same evaporation. Electrolyte dehydration can lead to problems due to electrolyte volume reduction, and changes in electrolyte concentration can alter electrochemical performance. To alleviate this problem, various embodiments can maintain the electrolyte level by continuously or intermittently flowing electrolyte into the cell volume. Specifically, the electrolyte liquid level can be maintained by introducing electrolyte into the container until it overflows from the overflow point. Because the liquid level cannot rise above this overflow point, this level can be maintained in a relatively controlled manner. Specifically, several volumes can be arranged in a cascade such that overflow from one chamber flows into the next chamber, establishing "liquid communication" between the cells. By connecting such cells in series, it becomes possible to simultaneously supply liquid electrolyte to multiple cells with one supply. Overflow from the last vessel can be recycled to the first vessel. In systems where a shared electrolyte is used that flows in a cascading manner between the cells, the electrolyte attributes can be monitored and processed at a central location for multiple cells. Electrolyte adjustments, such as making composition adjustments or adding components to alleviate problems with electrolyte carbonation and electrolyte dehydration, are beneficially performed at such a central source of circulating electrolyte.

[0153] Various embodiments can provide compositions and methods for adding beneficial additives to the electrolyte of an aqueous electrochemical cell. The electrolytic production of hydrogen during charging of an aqueous secondary battery can cause coulombic inefficiency, gas accumulation in the cell housing, safety concerns, and electrolyte consumption. In addition, metals can react spontaneously with the electrolyte to form metal hydroxides and produce reactive hydrogen as a product, resulting in metal electrode self-discharge. Certain solid-phase hydrogen evolution inhibitors (e.g., Bi, Sb, As) can reduce these deleterious effects, but incorporating solid-phase inhibitors into the porous metal electrodes of the battery can be costly and challenging to manufacture. Thus, various embodiments provide compositions and methods for adding beneficial additives to the electrolyte of an aqueous electrochemical cell by dissolving and ionizing the desired additive (e.g., Bi, Sb, As). 3+ , Sb 3+ , As 3+ A soluble salt of the desired hydrogen evolution inhibitor is added to the liquid electrolyte, providing a soluble salt in solution of the inhibitor's ion to the metal (e.g., Bi 3+ ->Bi 0 ) occurs at a higher half-cell potential (measured versus RHE (but at a lower cell potential) than the potential of the charging reaction of the anode active material. Thus, during charging of the battery (reduction of the metal electrode), the HER inhibitor in ionic form is electrodeposited on the surface of the metal electrode, providing an inexpensive and simple strategy to introduce HER inhibitors into the battery electrolyte chemistry. The electrodeposited inhibitor suppresses the hydrogen evolution reaction at the surface of the electrode, which may be an electrode with open porosity. During the discharge mode, the deposits can dissolve back into the electrolyte. The salt additive is preferably selected so as not to degrade the operation of the cathode during charge or discharge operations.

[0154] In another embodiment, the electrochemical cell includes electrodes that perform a hydrogen oxidation reaction (HOR) to recapture hydrogen produced in the HER side reaction and mitigate the generation of potentially dangerous hydrogen gas. Hydrogen gas bubbles that are generated during the HER may be captured and contacted with an HOR electrode, which may be the working electrode of the battery cell or an additional electrode added to the system. In one embodiment, hydrogen gas is captured by positioning the electrodes of the cell such that buoyancy transports the hydrogen gas bubbles to the HOR electrode. For example, the system may be tilted or may include a funnel designed to facilitate this flow.

[0155] In various embodiments, the liquid electrolyte flows through a pile or bed of DRI pellets. For thick (up to multiple centimeters) battery electrodes composed of active material pellets, it can be difficult to achieve sufficient transport of reactants, reactant products, and additives through a thick bed on timescales commensurate with the battery's operation (charge and discharge) timescales. Insufficient transport rate of electrolyte can have several deleterious effects, including, but not limited to, increased overpotential losses and reduced availability of active materials in pellet-based electrodes. In metal electrode batteries with alkaline electrolyte, gas bubbles can form during both charge and discharge conditions, creating pH gradients that can lead to undesirable performance degradation or corrosion of one or both electrodes. In various embodiments, the liquid electrolyte flows through a bed of DRI pellets to reduce the deleterious effects of transport limitations. The electrolyte flow provides convective transport of electrolyte to the individual pellets. Among other benefits, electrochemical reaction rates and uniformity of reaction are improved by reducing electrolyte concentration boundary layers that can occur across the entire thickness of the pellet bed or within the macropores of the pellet bed. Electrolyte flow generally reduces overpotential losses by homogenizing the electrolyte composition throughout the electrode macro- and microstructure. In some embodiments, electrolyte flow is achieved using active methods, such as mechanical pumping. The electrolyte flow rate can be low, less than 1 mL / min / cm. 2or even lower. In other embodiments, electrolyte flow is achieved by passive means, such as buoyancy-driven flow due to a thermal or compositional gradient. In a specific example, the part of the cell where the resistive dissipation of heat occurs is located at or near the bottom of the electrode bed, heating the electrolyte and causing it to rise through the bed of pellets. In another specific example, an electrode where an electrochemical reaction changes the density of the electrolyte, for example, by an exothermic or endothermic reaction or a change in the composition of the electrolyte in contact with the electrode, is located in the cell to create a buoyancy-driven flow. In this example, the electrode reaction that produces a lower density electrolyte may be located at or near the bottom of the bed of DRI pellets, and the reaction that increases the density of the electrolyte may be located at the top of the pellet bed.

[0156] In some embodiments, additives that inhibit side reactions, such as corrosion inhibitors that inhibit HER reactions or inhibit self-discharge, are combined with additives that enhance capacity utilization. Beneficially, additives to the electrolyte of batteries with metal electrodes, including iron electrodes, can perform several functions, including increasing iron capacity utilization, inhibiting undesirable side reactions, or both. Different additives have different advantages, which can be combined by combining additives at appropriate concentrations. An example of an availability-enhancing additive is sulfur or sulfide. In some embodiments, more than one corrosion inhibitor can be used with one or more sulfides. For example, sulfur assists in depassivating the iron electrode, but may be consumed during electrochemical cycling of the battery. Thus, sulfur consumption may contribute to capacity fade over many cycles. In one embodiment, a delivery system is used to replenish sulfur to maintain battery performance. One example of such a system is a pump that delivers a sulfur-bearing liquid to the battery cell. Another example is a dry hopper that delivers polysulfide salts to closed or open battery cells.

[0157] In one embodiment, iron sulfide (FeS) can be added as a sparingly soluble additive to metal-air batteries using alkaline electrolytes to improve the electrochemical stability of OER electrodes and increase electrode life. This embodiment helps reduce catalytic decay in oxygen evolution reaction (OER) electrodes under alkaline conditions, which can limit the operational life of the electrodes.

[0158] In certain embodiments, sulfur may be added to the DRI through additional process operations. In certain embodiments, the low melting temperature of sulfur may be exploited by immersing the DRI in a bath of molten sulfur. In certain other embodiments, hydrogen sulfide gas may be flowed through a hot or cold DRI to deposit a layer of sulfur and / or iron sulfide on the surface of the DRI. In certain other embodiments, sulfur may be sublimated and evaporated onto the surface of the DRI. The DRI may be hot or cold. In certain embodiments, sulfur is melt-diffused into the pores of the DRI by melting the sulfur and then wicking it into the pores of the DRI.

[0159] In some embodiments, sulfur may be added to the DRI by wet deposition with a process solvent. In certain embodiments, a colloidal mixture may be used to deposit sulfur or sulfide (e.g., FeS) species on / in the DRI. For example, a dispersion of sulfur in water may be prepared by sonication, to which the DRI is then added. The water may be evaporated to deposit the sulfur or sulfide species on the surface and in the DRI pellets. In certain other embodiments, sulfur may be dissolved in an organic solvent (e.g., ethanol or acetone). Addition of the DRI to the solution and subsequent evaporation of the solvent allows for the coating of sulfur.

[0160] In some embodiments, an additive containing molybdate ions is used in an alkaline battery containing an iron anode. Without being bound to a particular scientific interpretation, such additives can assist in suppressing the hydrogen evolution reaction (HER) at the iron electrode and improving the cycling efficiency of the battery. The concentration of the additive is selected to suppress the HER while still allowing the desired iron charge / discharge process. As an example, the molybdate ions may be added via a molybdate salt compound such as KMoO4. In one specific example, the electrolyte contains an additive concentration of 10 mM (mM is millimolar, 10 -3 In another embodiment, the electrolyte contains an additive concentration of molybdate anion in the range of 1 to 100 mM.

[0161] In some embodiments, surfactants are used to control wetting and foaming during operation of metal-air batteries. During charging, at least two gassing reactions can occur that lead to bubble formation. One is hydrogen evolution at the metal anode, which is a parasitic reaction that can contribute to poor coulombic efficiency during cycling of the battery. The other is the oxygen evolution reaction that is necessary for the functioning of metal-air batteries. Surfactant additives can mitigate the undesirable effects associated with both reactions. In the case of HER, hydrophobic surfactant additives can suppress the hydrogen evolution reaction at the metal anode by physically blocking water (an HER reactant) from the metal anode during charging. In the case of ORR, surfactant additives can reduce electrolyte surface tension and viscosity at the oxygen evolution electrode, resulting in the generation of smaller, uniformly sized, controllable gas bubbles during charging. In one non-limiting example, 1-octanethiol is added to the alkaline electrolyte at a concentration of 10 mM to mitigate both of these challenges.

[0162] In some embodiments, carbonate salts are added to the electrolyte of metal-air batteries using alkaline electrolytes to slow down the rate of carbon dioxide uptake from air. In air, electrolytes based on potassium hydroxide or sodium hydroxide lose potassium or sodium cations from solution by reaction with carbon dioxide (CO2) present in the air, resulting in the formation of potassium or sodium carbonate. This is especially problematic in batteries with air electrodes, since the lowest cost form of the desired reactant, oxygen, is provided to the oxygen reduction reaction (ORR) electrode by ambient air. Electrolyte carbonation can have several detrimental effects on battery performance in terms of undesirable side reactions and reduced electrolyte conductivity, all of which contribute to reduced operating efficiency of the battery. However, the rate of carbonate formation slows dramatically with increasing carbonate concentration in the electrolyte. In one embodiment, carbonate salts are intentionally added to the electrolyte prior to operation to slow down the rate of carbonation reaction with air during battery operation. The intentional addition of carbonate salts mitigates the detrimental effects of carbonation and maintains acceptable carbonate levels in the electrolyte over long operating life.

[0163] In one embodiment, the electrolyte health of the metal-air battery is monitored periodically or continuously. It has been found that the age and quality of the electrolyte dramatically impacts the electrochemical performance of the iron-air battery. In some cases, the degradation of performance is associated with the negative electrode, such as the iron electrode. In general, as the electrolyte ages, the discharge capacity of the negative electrode decreases. This may be due to changes in electrolyte component concentrations over time due to spontaneous reactions that form undesirable products, especially reactions upon contact with air. In some embodiments, the electrolyte health is monitored during operation of the battery to determine the appropriate time to replenish, replace, or treat the electrolyte. The feedback mechanism may be manual or automatic. In an automated system, the electrolyte quality measurement may be one input to a proportional-integral-derivative (PID) loop that continuously adjusts the electrolyte component concentrations. The electrolyte quality measurement is performed ex-situ on a small aliquot of electrolyte or in operando on the active electrolyte during operation of the cell. One non-limiting method for assessing electrolyte health is to measure the electrical conductivity of the electrolyte. One mechanism of degradation is that the electrolyte becomes carbonated over time as CO2 from the air dissolves in the electrolyte. In a specific example, an experiment is performed to show that electrolyte conductivity varies linearly with the carbonate concentration in the electrolyte. A conductivity probe is used to assess the concentration of carbonate in the electrolyte. A conductivity probe is used to monitor the health state of the electrolyte.

[0164] In some embodiments, corrosion inhibitors used in the field of iron metallurgy to inhibit aqueous corrosion are used as components of batteries with iron anodes to improve performance. In some embodiments, directed reduced iron (DRI) is used as the anode, and advantageous performance characteristics can be achieved by using one or more corrosion inhibitors in a suitable concentration range. In such embodiments, principles of corrosion science are used to prevent undesirable side reactions (e.g., hydrogen evolution) under charging conditions, mitigate the rate of spontaneous self-discharge during electrochemical hold, and maximize the availability of iron active material during discharge. In general, there are two types of corrosion inhibitors: interface inhibitors, which react with the metal surface at the metal-environment interface to prevent corrosion, and environmental scavengers, which remove corrosive elements from the environment surrounding the metal surface to inhibit corrosion. Under the broad protection of corrosion inhibitors, appropriate concentrations of inhibitors can be added to the electrochemical cell to achieve advantageous performance characteristics in terms of electrochemical cell efficiency and capacity. For the iron electrode of a metal-air battery, one applicable general type of inhibitor is liquid and interphase interface inhibitors. This category encompasses three main types of interface inhibitors: anodic inhibitors, cathodic inhibitors, and mixed inhibitors. Anodic inhibitors create a passivation layer that inhibits the anodic metal dissolution reaction. Cathodic inhibitors can either reduce the rate of the reduction reaction (HER, in the case of an iron electrode) or precipitate at the cathodic active sites to block the same reduction reaction. Mixed inhibitors can inhibit corrosion through one or both pathways and include, but are not limited to, molecules that physically or chemically adsorb to the metal surface to form a film that can block the active sites for the reduction reaction. Inhibitors can be added to the base electrolyte at any concentration.

[0165] In various embodiments, inhibitors that form a passivating layer on metal surfaces are paired with additives that depassivate the iron surface. If the concentrations are correct, an optimal balance of corrosion inhibition and active material availability can be achieved. In one specific embodiment, when direct reduced iron is used as the negative electrode, an alkaline electrolyte composed of 5.5 M potassium hydroxide or sodium hydroxide is used with 10 mM molybdate anion as the passivating agent and 10 mM sulfide anion as the depassivating agent. Specific examples of electrolyte compositions include 5.5M KOH+0.5M LiOH+10mM Na2S+10mM 1-octanethiol; 5.95M NaOH+50mM LiOH+50mM Na2S+10mM 1-octanethiol; 5.95M NaOH+50mM LiOH+50mM Na2S+10mM 1-octanethiol+10mM K2MoO4; and 5.95M NaOH+50mM LiOH+50mM Na2S+10mM 1-octanethiol+10mM K2MoO4. However, the present disclosure is not limited to any particular concentration of the above additives in the electrolyte. For example, one or more of the above additives may be included in the electrolyte at a concentration ranging from about 2mM to about 200mM, such as from about 5mM to about 50mM or from about 5mM to about 25mM.

[0166] In certain embodiments, other electrolyte additives are incorporated into the electrolyte. The electrolyte additives may be selected from the following non-limiting set: sodium thiosulfate, sodium thiocyanate, polyethylene glycol (PEG) 1000, trimethylsulfoxonium iodide, zincate (by dissolving ZnO in NaOH), hexanethiol, decanethiol, sodium chloride, sodium permanganate, lead (IV) oxide, lead (II) oxide, magnesium oxide, sodium chlorate, sodium nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, ammonium thiosulfate, lithopone. , magnesium sulfate, iron(III) acetylacetonate, hydroquinone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid, dimethyl phthalate, methyl methacrylate, methylpentynol, adipic acid, allyl urea, citric acid, thiomalic acid, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, propylene glycol, trimethoxysilylpropyldiethylene, aminopropyltrimethoxysilane, dimethylacetylene dicarboxylate (DMAD), 1,3-diethylthiourea, N,N''-Diethylthiourea, aminomethylpropanol, methylbutynol, amino modified organosilanes, succinic acid, isopropanolamine, phenoxyethanol, dipropylene glycol, benzoic acid, N-(2-aminoethyl)-3-aminopropyl, behenamide, 2-phosphonobutane tricarboxylic acid, mipa borate, 3-methacryloxypropyltrimethoxysilane, 2-ethylhexanoic acid, isobutyl alcohol, t-butylaminoethyl methacrylate, diisopropanolamine, propylene glycol n-propyl ether, sodium benzotriazolate, aminotrimethylenephosphonic acid pentasodium, sodium cocoyl sarcosine, lauryl pyridinium chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quaternium-18 chloride chloride), sodium hexametaphosphate, dicyclohexylamine nitrite, lead stearate, calcium dinonylnaphthalenesulfonate, iron(II) sulfide, sodium hydrogen sulfide, iron pyrite, sodium nitrite, complex alkyl phosphate esters (e.g., RHODAFAC® RA600 emulsifier), 4-mercaptobenzioc acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate (EDTA), 1,3-Propylenediaminetetraacetate (PDTA), nitrilotriacetate (NTA), ethylenediamine disuccinate (EDDS), diethylenetriaminepentaacetate (DTPA), and other aminopolycarboxylates (APC), diethylenetriaminepentaacetic acid, 2-methylbenzenethiol, 1-octanethiol, bismuth sulfide, bismuth oxide, antimony(III) sulfide, antimony(III) oxide, antimony(V) oxide, bismuth selenide, antimony selenide, selenium sulfide, selenium(IV) oxide, propargyl alcohol, 5-hexyn-1-ol, 1-hexyn-3-ol , N-allylthiourea, thiourea, 4-methylcatechol, trans-cinnamaldehyde, iron(III) sulfide, calcium nitrate, hydroxylamine, benzotriazole, furfurylamine, quinoline, tin(II) chloride, ascorbic acid, tetraethylammonium hydroxide, calcium carbonate, magnesium carbonate, antimony dialkyldithiophosphate, potassium stannate, sodium stannate, tannic acid, gelatin, saponin, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrogenated light oil, heavy naphthenic petroleum fractions (heavy naphthenic petroleum oil (e.g., sold as Rustlick® 631), antimony sulfate, antimony acetate, bismuth acetate, hydrotreated heavy naphtha (e.g., sold as WD-40®), tetramethylammonium hydroxide, NaSb tartrate, urea, D-glucose, C6Na2O6, potassium antimony tartrate, hydrazinsulphate, silica gel, triethylamine, potassium antimonate trihydrate, sodium hydroxide, 1,3-di-o-tolyl-2-thiourea, 1,2-diethyl-2-thiourea, 1,2-diisopropyl-2-thiourea, N-phenylthiourea, N,N'-diphenylthiourea, sodium antimony L-tartrate, rhodizonic acid disodium salt, sodium selenide, and combinations thereof.

[0167] In certain embodiments, the electrolyte is gelled. In certain embodiments, silica (SiO2) or other network-forming oxides, such as boron oxide (BO3) or alumina (Al2O3), are dissolved in an alkaline liquid to form a gel. In certain embodiments, network-forming organic molecules are dispersed in the liquid electrolyte to form a gel electrolyte. In certain embodiments, the organic molecules include a polymer. In certain embodiments, the liquid electrolyte is added to a solid polymer, such as polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylamide (PAM), or polyacrylic acid (PAA), to form a gel electrolyte. Also, bio-based polymers, such as cassava or gelatin, can be used as polymer additives. In certain embodiments, the gel electrolyte is formed in situ by dissolution of silica (or other oxides) derived from the DRI. In certain other embodiments, additional gel-forming agents are intentionally added to the liquid electrolyte for the purpose of creating a gel. In certain embodiments, the gel electrolyte is formed in situ by evaporating the solvent (e.g., water) from the electrolyte, concentrating the dissolved salts, and converting the electrolyte from a liquid to a gel or a supersaturated solution.

[0168] In certain embodiments, the electrolyte is a semi-solid or slurry electrolyte. In certain embodiments, the liquid is supersaturated with salt and the electrolyte is a two-phase mixture of solid salt and saturated solution. In certain embodiments, the electrolyte may be a saturated solution of NaOH in water with additional dispersed solid NaOH that together form a slurry electrolyte. Such an electrolyte may have similar mechanical properties as a gel electrolyte.

[0169] In certain embodiments, the electrolyte additive is delivered to the electrode as a mixture of solids. The electrolyte additive may have a range of solubilities. Some may provide the most beneficial effect when intimately mixed with the solid electrode. In one embodiment, a solid pellet is composed primarily of the additive, and such additive pellets are added or mixed with a metal electrode, which in one embodiment includes multiple DRI pellets. In another embodiment, the electrolyte additive is mixed with a metal, which may be the metal comprising the redox active electrode, and this mixture may be pelletized and is mixed with a metal electrode, which in one embodiment includes multiple DRI pellets. Non-limiting examples of additives include sodium sulfide (Na2S), potassium sulfide (K2S), lithium sulfide (Li2S), iron sulfide (FeS x , where x=1-2), bismuth sulfide (Bi2S3), lead sulfide (PbS), zinc sulfide (ZnS), antimony sulfide (Sb2S3), selenium sulfide (SeS2), tin sulfide (SnS, SnS2, Sn2S3), nickel sulfide (NiS), molybdenum sulfide (MoS2), and mercury sulfide (HgS), FeS, bismuth oxide (Bi2O3), or combinations thereof. In some embodiments, pellets with varying ratios of redox active metal to additive are prepared and pellets of different compositions are mixed to create a mixed electrode.

[0170] In some embodiments, an electrochemical formation cycle protocol is used to alter the properties of the starting DRI pellets and improve the subsequent operational electrochemical performance of the DRI as an anode. The as-manufactured DRI pellets may not be in an optimized form for the electrochemical cycle of the battery. For example, the free surface of the DRI may have native oxides that block electrochemical access to the active material, the specific surface area may be too small to reach the desired specific capacity, and / or the pore structure may restrict ion transport and limit the specific capacity. In one specific embodiment, the initial cycle, called "formation", consists of one or more repetitions of one or more of the following steps. One step may be a short charge step ("pre-charge"), during which any native oxide layers that adversely passivate the DRI as received may be chemically reduced or the specific surface area of ​​the DRI pellets may be increased, sometimes by more than 10-fold. Such changes may increase the available capacity of the DRI on subsequent discharge. Another step may be the conversion of Fe to Fe 2+ to or Fe 2+ From Fe 3+ and a discharge step to oxidize the metallic iron until one or more of the reactions to oxidize the metallic iron are fully or partially completed. The charge and discharge capacities may differ between repetitions of the formation cycle. In some embodiments, the formation may include repetitions of pre-charge and discharge cycles of systematically increasing capacity. In one specific embodiment, the formation cycle consists of pre-charging to a capacity of 250 mAh / g, then cycling through the subsequent loop n times: discharging to 25+n*25 mAh / g, then charging to (25+n*25)*1.1 mAh / g, where n is the number of cycles. The pre-charging step reduces the specific surface area of ​​the DRI to approximately 0.5 m 2 / g to 12m 2 / g or even larger area, which can enhance the available capacity for subsequent discharge. The remainder of the formation cycle is performed for n cycles at incremental capacity increments of 25 mAh / g (assuming 90% coulombic efficiency) to gradually approach the charge and discharge capacities corresponding to deep cycling.

[0171] In some embodiments, the potential at which the negative electrode is charged is controlled using a specific operating strategy. During charging of an iron-air battery, iron reduction and parasitic hydrogen evolution reactions are expected to occur simultaneously over a large potential range, but the relative rates of each reaction are potential dependent. In some potential regions, the hydrogen evolution reaction will be thermodynamically and / or kinetically favored, while in other regions, the iron reduction reaction will be favored. Strategies that involve adjusting the operating potential of the negative electrode during charging include, but are not limited to, the following strategies. For example, in one strategy, the negative electrode is charged at a higher current rate than the rate at which it is discharged. This may be achieved during constant current, constant power, or other more complex cycling conditions. By charging at a higher rate than during discharge, the electrode can be driven to a potential where iron reduction is thermodynamically and / or kinetically favored, rather than parasitic reactions such as hydrogen evolution. The result is a higher coulombic efficiency and higher electrode utilization over multiple cycles. As another example, in another strategy, the negative electrode is charged at a constant potential rather than a constant current or power. The charging potential is selected to optimize electrochemical performance. For example, the potential during charging can be optimized to maximize coulombic efficiency and higher electrode utilization. As another example, another strategy is to increase the effective resistance of other cell components (i.e., not the solid iron electrode or the negative current collector). By doing so, a greater overall cell polarization is achieved, which is the reason why the negative electrode exhibits greater polarization. If the added negative polarization is large enough, the absolute potential of the Fe electrode can be low enough to favor iron reduction over the hydrogen evolution reaction. This effect can be achieved by increasing the effective resistance of the electrolyte, the cathode, or the cathode current collector.

[0172] In some embodiments, the self-discharge of the negative electrode is limited by using a passivation chemical layer on the metal anode, which is optionally used with one or more electric pulses during charging. Metal anodes (e.g., Fe, Al, Zn) in alkaline batteries typically self-discharge by corrosion reactions, which form hydrogen gas and metal hydroxides as products of the self-discharge corrosion reaction. Passivation electrolyte additives are typically considered undesirable for delaying self-discharge, since the passivation layer also makes the metal anode unreactive to the desired discharge reaction. According to the present embodiment, an electrolyte additive (e.g., Na2MoO4) is used that forms a thin passivation film. Thus, the self-discharge of the anode is limited to only a small layer on the surface of the anode. However, to restore the reactivity of the metal anode, a short and strong charging pulse is used to reduce the surface film. Once the surface film is reduced, the discharge reaction can proceed.

[0173] In this embodiment, ex-situ measurements of the composition of the metal electrode are used to determine its state of charge and state of health. In electrochemical cells that include an iron electrode, the state of charge and state of health of the electrode correlate with the percentage of metallic iron. Thus, measurements of the percentage of metallic iron can be used to identify the state of charge or state of health of the battery. In one specific embodiment, magnetic susceptibility measurements are performed on one or more portions of the iron electrode to determine the state of charge or state of health. To perform such measurements, samples may be molded into disks or cylinders with thicknesses in the range of a few millimeters and diameters between 0.25 cm and 4 cm. The measured magnetic susceptibility is analyzed to extract the relative amounts of metallic iron, ferrous iron, and ferric iron.

[0174] In various embodiments, DRI is used as the redox active electrode material of a primary or secondary battery. In one embodiment, DRI is used as the anode active material of a primary battery. In one embodiment, DRI is used as the anode active material of a main fuel refillable (or mechanically rechargeable) primary battery where the anode is mechanically replaceable with new DRI. In one embodiment, DRI is used as the anode active material of a secondary battery. In another embodiment, DRI is used as an electrode material together with an alkaline electrolyte (pH>9). In one specific embodiment, a nickel cathode can be used in an alkaline secondary battery. In this embodiment, DRI serves as the starting material for the anode of a Ni-Fe alkaline secondary battery and may be used as received or processed prior to use according to other embodiments described herein. Other electrochemical couples (combinations of cathode and anode) of alkaline batteries in which a DRI anode is used include iron / nickel (Fe / Ni cell) or iron / silver (Fe / Ag cell). In various embodiments, DRI can serve as the anode active material of a primary or secondary battery where the pH of the electrode ranges in the acidic (pH<5.5) or neutral (5.5<pH<9) region. As an example, DRI can be used as the anode active material of a battery in which an electrolyte containing hydrochloric acid (HCl) in the concentration range of 1 to 5M is used. At the anode, DRI can participate in the following half-cell reaction during discharge: Fe + 2Cl - ->FeCl2 + 2e - can be involved.

[0175] Specifically, DRI can be used as the anode material of an all-Fe battery where Fe is the reactive species at both the anode and the cathode. In such an embodiment, DRI can serve as a solid metallic Fe anode at 100% SOC, and the anode is soluble Fe during discharge 2+The cathode active material may be a soluble inorganic Fe-based salt, such as the FeCl2 / FeCl3 redox couple. The cathode active material may also be an inorganic or organic-based coordination compound, such as K3Fe(CN)6. At the cathode, the soluble Fe species is converted to Fe 2+ / Fe 3+ One specific example of an all-Fe battery in which DRI is used as the active material would be to use DRI as the anode material, with an electrolyte containing concentrated HCl (1-5M). At the anode, DRI undergoes the following half-cell reaction upon discharge: Fe + 2Cl - ->FeCl2+2e - At the cathode, soluble FeCl3 participates in the following half-cell reaction during discharge: 2FeCl3 + 2 e- ->2FeCl2+2Cl - The complete cell reaction on discharge would be Fe + 2FeCl3 -> 3FeCl2. DRI can be used as a source of soluble FeCl2 needed in solution to enable the cathodic reaction by reacting DRI with HCl in solution, which will participate in the following spontaneous chemical reaction: Fe + 2HCl -> FeCl2 + H2.

[0176] In some embodiments, the DRI is used as the anode of a flow battery, and the DRI pellets are transported from a storage tank to an electrochemical reactor where the DRI pellets electrochemically react. The DRI pellets maintain electrical contact with each other as they flow through the electrochemical reactor, allowing for sufficient electrical percolation to provide high electrical conductivity due to the accumulation of the pellets. The electrolyte may be acidic (pH < 5), neutral (5 < pH < 9), or alkaline (pH > 9). In a specific embodiment, the discharge reaction may proceed such that the metallic Fe anode forms soluble products (e.g., FeCl2) or an insoluble (e.g., Fe(OH)2) discharge product film on the surface of the transported DRI pellets during discharge. Specific embodiments regarding methods for transporting the DRI pellets across the battery include any of the methods known in the art for transporting particulate matter or slurries or suspensions, including but not limited to pressure-driven fluid flow using a fluidized bed, mechanical conveyors such as conveyor belts, rotating drums, or transport by using a helical screw. In some embodiments, the mechanical conveyor or screw includes an electronically conductive material such as metal or carbon that also serves as a current collector for the battery.

[0177] In various embodiments, the DRI is used as a feedstock source of metallic Fe in the synthesis of FeCl2 by the following spontaneous chemical reaction: Fe + 2HCl -> FeCl2 + H2. The DRI may be used as a feedstock as pellets, or the pellets may be crushed into a powder. Further, DRI fines (pellet size or particle size < 0.5 cm), which are waste products of the DRI process, can be used as feedstock materials. Iron iodide (FeI2) and iron bromide (FeBr2) can be synthesized in a similar manner, and the alternative acids to HCl in salt synthesis would be HI and HBr.

[0178] In various embodiments, DRI is used to form a packed catalyst bed for gas-phase or liquid-phase reactions. In some embodiments, a packed catalyst bed of DRI can be used as a catalyst in the Haber-Bosch process to produce ammonia. DRI may be used in place of or in addition to the iron powder typically used in the Haber-Bosch process. In particular, the wustite coating present in commercially produced DRI may be desirable to facilitate the Haber-Bosch process reaction. In some embodiments, the iron or iron salt component of the DRI, which may be iron oxide, iron hydroxide, or iron carbide, reacts with another component, such as another metal or metal salt, to form a catalytically active surface on the DRI. DRI can be used as a feedstock for producing alkali ferrocyanide salts. First, DRI can be used to synthesize FeCl2 according to the following spontaneous chemical reaction: Fe+2HCl->FeCl2+H2. Then, FeCl2 derived from DRI can be used to synthesize Na4Fe(CN)6·10H2O according to the following reactions: calcium ferrocyanide synthesis: 6HCN + FeCl2 + 3Ca(OH)2->Ca2Fe(CN)6·11H2O + CaCl2; mixed salt conversion: Ca2Fe(CN)6·11H2O + 2NaCl->CaNa2Fe(CN)6·11H2O(s) + CaCl2(aq); and Na salt conversion: CaNa2Fe(CN)6·11H2O + Na2CO3->Na4Fe(CN)6·10H2O + CaCO3. In this conventional Na4Fe(CN)6·10H2O synthesis method, FeCl2 (~$0.2 / mol) represents about 54% of the overall raw material cost. Therefore, replacing FeCl2 with DRI (approximately $0.01 / mol) has the potential to significantly reduce the raw material cost of Na4Fe(CN)6·10H2O by half.

[0179] In various embodiments, the DRI is used as an electrode for hydrogen evolution reaction (HER) to produce hydrogen (H2) gas by electrolysis. The DRI can be used as a catalytic surface to promote HER or as a conductive substrate for one or more other catalytic materials. In substrate embodiments, the DRI can be coated with a continuous layer of catalytic material or decorated with catalytic particles. Platinum (Pt) metal is an example of a catalyst that can be used to coat or decorate the DRI substrate for HER. The DRI can be used for HER of either acidic or alkaline solutions.

[0180] In various embodiments, porous DRI pellets are used as OER electrodes. Non-limiting examples of ways in which DRIs can be used for this purpose include, as received, after electroplating the surface with a transition metal, after electroless plating the surface with a transition metal, after modifying the surface by chemical etching, after surface modification by thermal processing, or after thermally applying an OER catalyst to the DRI substrate surface.

[0181] In various embodiments, the DRI is used as an electrode for oxygen evolution reaction (OER) to produce oxygen (O2) gas by electrolysis. Non-limiting ways in which the DRI can be used include as a catalytic surface to promote OER or as a conductive substrate for one or more other catalytic materials. In embodiments in which the DRI is the substrate, the DRI may be coated with a continuous layer of catalytic material or decorated with catalytic particles. Nickel (Ni) metal is an example of a catalyst that can be used to coat or decorate the DRI substrate for OER. The DRI can be used in OER electrodes for either acidic or alkaline solutions. The DRI can be used as a catalyst or electrode substrate for alkaline electrolyzers.

[0182] In another embodiment, the DRI is used in an oxygen reduction reaction (ORR) electrode. In some embodiments, the iron or iron salt component of the DRI, which may be iron oxide, iron hydroxide, or iron carbide, reacts with another component, such as another metal or metal salt, to form an ORR catalyst. This catalyst may be formed on the surface of the DRI pellet or may infiltrate within the DRI pellet, may be part of the DRI, or may substantially convert the entirety of the DRI. DRI fines as well as DRI pellets or crushed pellets can be used as the ORR electrode. In some embodiments, the ORR catalyst formed with the DRI is a mixed metal oxide that includes iron. In other embodiments, the ORR catalyst is an oxide that includes iron and another transition metal. In various embodiments, the ORR catalyst is a spinel structure oxide that includes iron and manganese.

[0183] In various embodiments, a packed bed of DRI is used in a water filtration device. In such embodiments, the DRI is packed into a column to create a packed bed of DRI pellets. Particulate matter is trapped within the pores inside the DRI pellets and in the void spaces between the DRI pellets. The use of pelletized iron as a filtration medium can provide the ability to adjust pressure drop and filtration effectiveness.

[0184] In various embodiments, DRI is used as a metallic iron feedstock for the production of Fe-containing industrial or specialty chemicals such as ferrocyanide, iron tris-bipyridine, and ferrocene, among others.

[0185] Figure 1 is a schematic diagram of a battery (or cell) 100 according to various embodiments of the present disclosure. With reference to Figure 1, the battery 100 includes a container 101 in which an air electrode 103, a negative electrode 102, a liquid electrolyte 104, and a current collector 106 are disposed. The air electrode 103 and the negative electrode 102 may be separated by the liquid electrolyte 104.

[0186] The anode 102 may include metallic pellets 105, which may include at least 50% metal by elemental mass, such as at least 60% metal by weight. In some embodiments, the metallic pellets 105 may include at least 60% iron by elemental mass. Thus, the pellets 105 may be referred to as iron-containing pellets. The pellets 105 may be electrically connected to one another and may be arranged in one or more layers to form the anode 102. In various embodiments, the anode 102 may be a slurry. In various embodiments, the slurry may include one or more metallic pellets 105 therein. In various embodiments, the slurry may include dissolved particles, such as particles corresponding to the composition of the metallic pellets 105 as discussed herein. As a specific example, the anode 102 may be an iron-containing slurry. In various embodiments, the cathode 103 may be a slurry. In various embodiments, the anode 102 may be in the form of a gel. A flowable semi-solid anode 102 (such as, for example, a flowable semi-solid iron electrode) can be beneficial for large-scale energy storage systems due to its low manufacturing cost and ease of assembly into cell architectures. For example, iron in reduced form is highly conductive. By suspending iron particles in a polymer gel, a permeating network of iron particles can be generated, thereby creating a conductive, electrically active gel that can form the anode 102. As an example, a polymer gel can be formed by dissolving an organic polymer (e.g., carboxymethyl cellulose (CMC)) or by dissolving an inorganic oxide forming network (e.g., SiO2 dissolved in concentrated KOH). In certain embodiments, the electrolyte is gelled. In certain embodiments, silica (SiO2) or other network forming oxides such as boron oxide (BO3) or alumina (Al2O3) are dissolved in an alkaline liquid to form a gel. In certain embodiments, network forming organic molecules are dispersed in the liquid electrolyte to form a gel electrolyte. In certain embodiments, the organic molecules include a polymer.In certain embodiments, the liquid electrolyte is added to a solid polymer, such as polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylamide (PAM), or polyacrylic acid (PAA), to form a gel electrolyte. Also, bio-based polymers, such as cassava or gelatin, can be used as polymer additives. In certain embodiments, the gel electrolyte is formed in situ by dissolving silica (or other oxides) from the DRI. In certain other embodiments, additional gel formers are intentionally added to the liquid electrolyte to create a gel. In certain embodiments, the gel electrolyte is formed in situ by evaporating the solvent (e.g., water) from the electrolyte, concentrating the dissolved salts, and converting the electrolyte from a liquid to a gel or to a supersaturated solution.

[0187] In various embodiments, the pellets 105 include a primary iron-containing phase and one or more secondary phases ("gangue"). In various embodiments, the oxidation state of the primary phases may range from highly reduced (e.g., metallic iron) to highly oxidized (e.g., ionic). For example, the pellets 105 may contain substantially metallic iron, i.e., iron with a valence state of 0 (e.g., Fe 0 ). Thus, in some embodiments, the pellets may comprise at least 60% metallic iron by mass, preferably at least 80% metallic iron by mass, and in some embodiments, 90% to 98% metallic iron by mass. In various other embodiments, the pellets 105 may be comprised of iron that is fully oxidized to a 3+ valence state (e.g., Fe2O3). In various other embodiments, the iron valence state may be 0 to 3+. In various embodiments, the primary phase may be an oxide, hydroxide, sulfide, carbide, or combinations thereof. For example, the primary phase may be Fe, FeO, Fe2O3, Fe3O4, FeO x (OH) y , FeC, FeS x , FeO x S y , and / or FeO x S y H zIn some embodiments, the pellets 105 may include direct reduced iron (DRI) pellets, and the pellets 105 may comprise at least 60 percent of the total mass of the anode 102. In various embodiments, the anode 102 may be comprised of DRI pellets.

[0188] In various embodiments, the secondary phase includes silicon. For example, the secondary phase may include silica (SiO2) and / or one or more silicates, such as feldspar, mica, amphibole, pyroxene, olivine, tourmaline, and / or forsterite. In various other embodiments, the secondary phase may include titanium, vanadium, manganese, magnesium, calcium, phosphorus, carbon, aluminum, zirconium, or any combination thereof.

[0189] The pellets 105 may be spherical, as shown in FIG. 1. For example, in various embodiments, the pellets 105 may have an average diameter ranging from about 0.5 mm to about 10 cm, such as about 10 mm. As a specific example, the pellets 105 may have an average diameter ranging from 4 mm to 20 mm. As used herein, the term "spherical" is used to describe any rounded form that resembles a three-dimensional object with all of its surface points equidistant from its center, although in fact all of the surface points may not be equidistant from the center. Stated differently, "spherical" encompasses shapes that are perfect spheres, as well as shapes that may have the appearance of a general sphere, such as a ball, that may not be a perfect sphere. However, the present disclosure is not limited to any particular pellet shape. For example, the pellets may be briquette shaped, as discussed below with respect to FIG. 2A. Additionally, the pellets 105 are illustrated as whole pellets, but may also be pieces of crushed pellets. For example, the received pellets may be crushed and the fragments of such crushed pellets may form pellets 105 into the negative electrode, such as pellets 105 packed into a bed. In various embodiments, the crushed pellets may be sized between 10 nm and 100 nm, between 1 and 100 um (um=10 -6m), or 1 to 10 mm, 10 nm (nm = 10 -9 m)~10mm(mm=10 -3 m) In some embodiments, the crushed pellets may include a combination of pellets having different average particle sizes.

[0190] In various non-limiting embodiments, the pellets 105 may have an internal porosity ranging from about 2% to about 80%, such as from about 50% to about 75%. In various non-limiting embodiments, the negative electrode 102 may have a pellet packing density ranging from about 40% to about 74%. Thus, the liquid electrolyte 104 may infiltrate the spaces between the pellets 115 to impregnate the negative electrode 102. To ensure good electrical conductivity across the pellets 105, low contact resistance may be required. In various embodiments, the pellets 105 of the negative electrode 102 may be compressed to ensure contact of the pellets 105. In various embodiments, the pellets 105 may have a compressive strength of about 700 psi to about 2500 psi. In some embodiments, such compressive strength pellets 105 may be placed in a bed that constitutes the negative electrode 102, and a compressive force may be applied to the pellets to improve electrical conductivity.

[0191] The liquid electrolyte 104 may include electropositive elements such as Li, K, Na, or combinations thereof. In some embodiments, the liquid electrolyte 104 may be basic, i.e., have a pH greater than 7. In some embodiments, the pH of the electrolyte 104 is greater than 10, and in other embodiments, greater than 12. For example, the electrolyte 104 may include a 6M (moles per liter) concentration of potassium hydroxide (KOH). In one particular embodiment, the electrolyte 104 may include a combination of components such as 5.5M potassium hydroxide (KOH) and 0.5M lithium hydroxide (LiOH). For iron materials, a high pH has the benefit of promoting mechanical stability, since iron is poorly soluble in high pH liquids. In various embodiments, to ensure such low solubility of iron, the pH is greater than 10, greater than 12, or greater than 14. In contrast, at a low pH, such as a pH less than 5, a pH less than 3, or a pH less than 2, the iron will dissolve and the pellets will be soluble.

[0192] In various non-limiting embodiments, the negative electrode 102 may have a thickness ranging from about 0.5 cm to about 50 cm, such as from about 0.75 cm to about 25 cm. The pellets 105 may be disposed in the negative electrode 102 at a packing density ranging from about 30% to about 74%. In various non-limiting embodiments, the pellets 105 may be disposed relative to one another (such as by being dispersed or spread like a gravel bed) or may be mechanically attached or connected to one another by a process such as compaction or pressing. In other embodiments, the pellets 105 may be physically connected by a process such as welding or brazing. In other embodiments, the pellets 105 may be joined together by arc welding. In other embodiments, the pellets 105 may be connected by a combination of such connection processes. In other embodiments, the pellets 105 may be attached and connected to one another by conductive wires strung through holes in the pellets 105. The holes in the pellets 105 can introduce additional contact points not only throughout the thickness of the pellet 105 bed that is the anode 102, but also throughout the thickness of a single pellet 105. Once strung together, the wires can be pulled tight to enhance contact between the pellets 105 and then mechanically held in place by a conductive mechanical stopper, which in turn can be connected to a larger current collector plate such as the current collector 106. In some embodiments, the pellets 105 can be packed into a bed, optionally with the aid of mechanical pressure applied by a high temperature resistant material, and then sintered in a non-oxidizing atmosphere. The result is a bed of pellets 105 that are fused together with low inter-pellet 105 contact resistance. The sintered bed of pellets 105 can form the anode 102.

[0193] In various embodiments, the pellets 105 may be produced from iron ore pellets, such as taconite or magnetite or hematite. In various embodiments, the pellets 105 may be produced from iron ore pellets, such as taconite or magnetite or hematite, by reducing the iron ore pellets to produce ferrous metal (Fe 0The pellets 105 can be produced by forming a more metallic (more reduced, less oxidized) material, such as reduced taconite ("DR") taconite, direct reduced iron ("DRI") pellets, or any combination thereof. In various non-limiting embodiments, the pellets 105 can be reduced taconite, directly reduced ("DR") taconite, direct reduced iron ("DRI") pellets, or any combination thereof.

[0194] In various non-limiting embodiments, the pellets 105 include iron in the form of cementite (Fe3C). Although iron batteries require iron-containing starting materials, the cementite form of iron (Fe3C) may be easier to obtain or transport or less costly. In various embodiments, cementite (Fe3C) may be used as the starting electrode material for iron-containing batteries. For example, the pellets 105 may first be formed from cementite (Fe3C). The cementite (Fe3C) may first be converted to magnetite before or during initial operation of the battery 100, and the magnetite may be reversibly cycled between other iron oxidation states to store energy. The conversion to magnetite may occur in the battery 100 in either case, or may not be performed externally before assembly of the battery 100. The cementite (Fe3C) starting pellets 105 may take the form of mostly cementite (Fe3C) ore pellets and / or as shaped pellets of mostly cementite (Fe3C) powder. In various embodiments, a pellet 105 of low surface area cementite material can be treated as the anode of the battery 100 and discharged at a current density of about 25 mA / g to create a high surface area iron oxide phase. This high surface area iron oxide phase can be used as the negative electrode 102.

[0195] Commercially available DRI pellets do not always have optimal chemical and physical properties to maximize electrochemical performance. In various embodiments, ex-situ processing is performed on the DRI pellets before assembling them into the anode 102. Various embodiments include treating the DRI pellets with mechanical, chemical, and / or thermal processes (i.e., processing the DRI pellets ex-situ) before introducing them into an electrochemical cell to achieve better chemical and physical properties. The better chemical and physical properties can include a higher content of desirable impurities (e.g., hydrogen evolution reaction (HER) inhibitors), a lower content of undesirable impurities (e.g., HER catalysts), a higher specific surface area, a higher total porosity, a different pore size distribution (e.g., multimodal to reduce mass transport resistance), a different pellet size distribution (e.g., multimodal to enhance bed packing), a different aspect ratio (e.g., to enhance bed packing), and the like. Mechanical processes that can be applied ex-situ to the DRI pellets can include crushing, pulverization, and / or powdering. Thermal processes that can be applied ex-situ to the DRI pellets can include processing the DRI pellets at high temperatures in a reducing (e.g., hydrogen), oxidizing, and / or carburizing (e.g., carbon monoxide and / or carbon dioxide) atmosphere. Chemical processes that can be applied ex-situ to the DRI pellets can include acid etching, etc. In various embodiments, to increase the available capacity of the DRI pellets during the discharge reaction, the DRI pellets can be pretreated by immersing them in an acid bath (e.g., concentrated HCl) that etches the iron and enlarges the pores of the DRI pellets, increasing the total porosity of the DRI pellets compared to DRI pellets that are not etched in an acid bath. After pretreatment, the etched and now porous DRI pellets can be assembled into the anode 102. The etching time can be optimized to increase the available capacity of the DRI pellets without losing too much active material to the acid etching solution.In various embodiments, the DRI can be used as an electrode in an electrochemical cell and can be charged with an electric current, a process that can increase the surface area of ​​the DRI.

[0196] The current collector 106 may be in the form of a conductive plate that is in electrical communication with the negative electrode 102. However, the current collector 106 may have other configurations, as discussed below with respect to FIG.

[0197] The positive half-reaction that occurs during discharge at the air electrode 103 in an alkaline electrolyte is O2 + 4e - +2H2O->4OH - and the corresponding half-reaction occurring at the anode 102, starting from fully metallic iron (fully charged anode), is 2Fe -> 2Fe 2+ +4e - with a net discharge reaction of 2Fe+O2+2H2O->2Fe(OH)2. In various embodiments, oxygen may be delivered to the air electrode 103. This delivery of oxygen to the air electrode 103 may be in a form other than gaseous oxygen, including an oxygen-containing compound in a gaseous, liquid, or solid state.

[0198] A range of iron valence states (0-3+) and counter ions O 2- , O.H. - , S 2- Various configurations of starting materials are possible, such as with Fe2O3, Fe3O4, FeO, FeOOH, FeS, FeS2, etc., and combinations thereof.

[0199] In various embodiments, the pellets 105 are packed into a bed to form the anode 102, thereby creating macropores between the individual pellets 105. Additionally, in various embodiments, each individual pellet 105 may have a porous, e.g., microporous, surface. The micropores on the surface of the pellets 105 may provide a greater surface area for each individual pellet 105 than if the pellets 105 were smooth spheres. The pore sizes of the pellets may vary. In some embodiments, the pellets 105 may have a volume weighted average pore size greater than 1 micron, such as 1 micron to 10 microns. The pore size distribution within the pellets may be measured by mercury intrusion porosimetry. Mercury intrusion porosimetry is a technique that uses a pressurized chamber to force mercury into the pores of the pellets. Mercury is forced into the larger pores first, and as the chamber is gradually pressurized, the mercury is forced into the smaller and smaller pores. A physical relationship, such as the Washburn equation, may be used to relate the applied pressure to the pore size, resulting in a volume or area weighted pore size distribution. The pore size distribution may be converted to a cumulative distribution, from which the d 孔、90%容積 and d 孔、50%表面積 The value of can be estimated.

[0200] FIG. 6 is a schematic diagram of a battery 100 according to various embodiments of the present disclosure, showing a close-up of macropores 602 and micropores 604. The macropores 602 are created by gaps between individual pellets 105 when the pellets 105 are packed into a bed. The macropores 602 can facilitate ion transport across a very thick (e.g., multiple centimeters) electrode 102. The micropores 604 can be surface modifications of the pellets 105 themselves. The micropores 604 can allow high surface area active materials to contact the electrolyte 104 and enable high availability of active materials for solid-state electrochemical reactions. The micropores can include cracks in the pellets. Such cracks can be formed during pellet production or can be introduced later, such as by applying a mechanical load that causes cracks. This electrode structure with macropores 602 and micropores 604 is particularly useful for improving the rate capacity of very thick electrodes for stationary, long-term energy storage, where thick electrodes may be necessary to achieve very high areal capacity.

[0201] FIG. 7 shows a single pellet 105 of the battery 100 . The pellet 105 may include micropores 604 in a solid surface 702 of the pellet 105. The electrolyte 104 may fill the micropores 604, thereby providing the outer surface area of ​​the sphere that is the pellet 105 with both a liquid phase electrolyte region associated with the micropores 604 and a solid region surface 702. By filling the micropores 604 with electrolyte, the surface 702 reduces the solid region that exposes the electrolyte to the outer surface of the pellet, providing the pellet 105 with a low effective specific surface area (e.g., low m 2 / g), thereby reducing the electrolyte concentration boundary layer at the solid-phase surface 702. Many metal anodes (e.g., Zn, Fe, Al) in aqueous batteries are known to self-discharge by spontaneous reaction with the electrolyte to form metal oxides and hydrogen gas. For long-term energy storage systems (e.g., systems having discharge periods of 8 hours or longer, such as 8-20 hours, 20-24 hours, 24 hours, or longer), self-discharge may limit performance, as the cell may self-discharge a significant percentage of its storage capacity before a full discharge cycle is completed. In some embodiments, the specific surface area is small (e.g., low m 2 1 / g) metal electrodes are used to inhibit self-discharge in low-rate, long-term energy storage systems. In many typical modern electrochemical cells, high specific surface area is desirable to facilitate high rate capacity (i.e., high power) by introducing a large number of surface sites for reactions to occur. In long-term systems, the need for rate capacity is significantly reduced, so low specific surface area electrodes can meet the need for target rate capacity while minimizing self-discharge rates.

[0202] In various embodiments, an electrolyte 104 additive that forms a thin passivation film (e.g., Na2MoO4) is added to the battery 100. In this way, the self-discharge of the anode can be limited to only a small layer on the surface of the anode. This passivation film limits the extent of the self-discharge reaction. To restore the reactivity of the metal anode, a short, strong charging pulse can reduce the surface film. Once the surface film is reduced, the discharge reaction can proceed.

[0203] In various embodiments, a resistive element is intentionally introduced into the battery 100 to allow for slow charging. A greater overall cell polarization can be achieved by increasing the effective resistance of other cell components (i.e., those that are not the negative electrode 102 or the negative current collector 106). Doing this can cause a greater polarization of the negative electrode 102. If the added negative electrode 102 polarization is large enough, the absolute potential of the electrode 102, when the negative electrode is an Fe electrode, can be low enough to activate the Fe(OH)2->Fe reaction at lower cell level currents. This effect can be achieved by increasing the effective resistance of the electrolyte 104, the cathode (e.g., electrolyte 103), or the cathode current collector.

[0204] 2A is a schematic diagram of a battery 200 according to various embodiments of the present disclosure. Battery 200 is similar to battery 100, and therefore only the differences between them will be described in detail.

[0205] 2A, the battery 200 includes a container 101 in which an air electrode 103, a negative electrode 102, a liquid electrolyte 104, and a current collector 106 are disposed. The air electrode 103 and the negative electrode 102 may be separated by the liquid electrolyte 104. The liquid electrolyte 104 may also impregnate the negative electrode 102.

[0206] In various embodiments, the negative electrode 102 may include a briquette-shaped pellet 115. As used herein, "briquette shape" may refer to a rounded rectangular prism. For example, the pellet 115 may have a length in the range of 10-500 mm, a width in the range of 5-250 mm, and a thickness in the range of 5-200 mm. In some embodiments, the pellet 115 may have a length of about 100 mm, a width of about 50 mm, and a thickness of about 30 mm. In various non-limiting embodiments, the pellet 115 may have an internal porosity in the range of about 50% to about 1%.

[0207] In various other embodiments, the pellets 115 may be formed of hot briquetted iron ("HBI"), may be formed by combining and agglomerating pellets, or may be formed by combining and agglomerating powdered metal, such as powdered iron fines.

[0208] The current collector 106 may be formed of a conductive material that is in electrical communication with the negative electrode 102. The current collector 106 may directly contact the bottom surface and sides of the negative electrode 102. In some embodiments, the current collector 106 may optionally include protrusions 109 that extend across the negative electrode 102 to directly contact its interior regions. The protrusions 109 may also reduce the effective transport length within the electrode 102 from the total pellet bed thickness to the protrusion 109 spacing. Additionally, such protrusions 109 may be used to attach a mechanical clamping mechanism to the pellet bed to incorporate a downward force on the pellet bed while also acting as a current collecting element. For example, FIG. 2B shows an exemplary plate 250 that compresses the electrode 102 and covers the bed of pellets 115. The plate 250 can be attached to the protrusion 109 by a clamp 252 that attaches the plate 250 to the protrusion 109 and causes the plate 250 to exert a compressive force on the bed of pellets 115 that are the negative electrode 102. In this manner, the plate 250 and the clamp 252 can be a mechanical clamping mechanism. Similarly, the current collector can use a magnet to compress the material that forms the negative electrode 102. For example, the plate 250 can be a magnet that is attracted to the housing 101, the protrusion 109, and / or the bottom of the current collector 106 and can pull the plate 250 towards the pellets 115, compressing the bed of pellets 115 that are the negative electrode 102. In some embodiments, the current collector 106, the protrusion 109, and / or another element of the battery 200 can be magnetic and can pull the pellets 115 downward and / or against each other, compressing the bed of pellets 115. In some embodiments, the current collector 106 may be a two-part current collector, with a first part attached to the front surface of the negative electrode 102 and a second part attached to the rear surface of the negative electrode 102. The front surface of the electrode may be the surface generally disposed toward the electrolyte, and the rear surface of the electrode may be the surface generally disposed away from the electrolyte. In some embodiments, the first part may be attached to the front surface and may be a porous structure (e.g., a mesh), and the second part attached to the rear surface may be solid.Providing current collectors on the front and rear of the electrode can aid in the application of clamping force and can allow for more uniform reaction rates across the electrode. The front and rear of the current collectors can be shorted together to affect reaction rate distribution. In some embodiments, the current collector 106 can be clamped to the negative electrode 102.

[0209] In metal-air batteries, pelletized and briquette electrode materials have various advantages, including high surface area, large internal porosity, and high electronic conductivity. Additional advantages include significantly simplified and more efficient transportation and handling methods for pelletized and briquette materials compared to powdered materials. Additional advantages include simple manufacture of the negative electrode. In some embodiments, the electrode can be formed by dispersing or pouring the pellets into a container or vessel. The combination of high electronic conductivity of the material and the weight of the pellets may be a result of the high density of iron-rich materials, providing low contact resistance between the pellets.

[0210] The electrical conductivity of materials from which the pellets can be made is generally ranked from high to low as Fe metal > FeO > Fe3O4 > Fe2O3. However, more reduced materials with higher electrical conductivity also require greater input energy during processing and are therefore more expensive and difficult to prepare. Thus, materials such as wustite and mixed phases containing some amount of iron metal, e.g., Fe / FeO, or Fe / Fe3O4, or Fe / Fe2O3, are generally preferred. For example, wustite (FeO) can provide a desired balance of electrical conductivity with input energy and processing costs. As a specific but non-limiting example, the pellets can be produced as reduced taconite pellets, which have a composition close to FeO.

[0211] As one specific example, the pellets may be roughly spherical pellets of metallic iron with a porosity of 50% (by volume) and a typical diameter of 10 millimeters (mm). The negative electrode may be 2 centimeters (cm) thick and may be formed of a packed bed of pellets. For hard-packed spheres, it is known that the packing density of random close-packed spheres may be approximately 64%, and close-packed spheres may reach a packing density of 74%. Thus, the overall solid density of the negative electrode may be approximately 32% (50% x 64%) to 39% (50% x 74%). The negative electrode is infiltrated with a liquid electrolyte consisting of potassium hydroxide (KOH) at a concentration of 6M (mol / L).

[0212] An additional advantage of the proposed anode structure is the presence of low-tortuosity electrolyte pathways in the interstitial spaces between the pellets, which allows for rapid liquid-phase ion transport and results in thick, high-areal capacity (>0.1 Ah / cm). 2 ) metal anodes. The concepts of the present disclosure also allow for independent tuning of electrode surface area (i.e., solid-liquid interfacial area) and electrode porosity, since pellet porosity and packing density can be independently varied.

[0213] As a further advantage of the present invention, the pellets can be assembled by spreading and packing in a dry state. In other embodiments, the pellets can be first dispersed in the liquid electrolyte and then poured and spread into the battery container. In various embodiments, the container supporting the pellets can take a variety of forms. Although illustrated in Figures 1 and 2 as a pellet bed, the anode 102 can have a variety of different shapes, such as a cone, a tube, etc.

[0214] 12A-12F are cross-sectional views of exemplary batteries 1200A-1200F having alternative electrode configurations including an ordered array of pellets 105. Batteries 1200A-1200F may be similar to battery 100, and therefore only the differences therebetween will be discussed in detail.

[0215] 12A, the battery 1200A may include one or more conical containers 1202 that support the pellets 105. The conical containers 1202 may allow for self-alignment of the pellets 105. The conical containers 1202 may allow for modular design of the anode 102 by having a large "swimming pool" type reactor with multiple conical containers 1202 seated at the bottom of a swimming pool of electrolyte 104. The conical containers 1202 may be a cost-effective design for floor current collection.

[0216] 12B, battery 1200B may include a container 101 supporting an array of anode pellets 105 forming the anode 102. One or more cathode pellets 103 may be inserted into the anode 102. The pellets 105 may be electrically connected to each other and / or to a current collector 106. A separator 107 may surround and electrically insulate the cathode 103 from the anode 102.

[0217] As shown in FIG. 12C, battery 1200C may have a positive electrode 103 extending completely through an array of negative electrode pellets. In battery 1200C, pellets 105 may be arranged in an alternating stack with electrodes 103. Referring to battery 1200D in FIG. 12D, battery 1200D is similar to battery 1200C, except that the separator is omitted. In battery 1200D, pellets 105 may be arranged to be a support bed suspended in electrolyte 104 along with electrodes 103.

[0218] FIG 12E illustrates another exemplary battery 1200E according to various embodiments of the present disclosure. In battery 1200E, pellets 105 may be arranged in a hexagonal array surrounding an electrode 103 that may be circular in shape. FIG 12F illustrates another exemplary battery 1200F according to various embodiments of the present disclosure. In battery 1200F, pellets 105 may be arranged in a hexagonal array surrounding an electrode 103 that may be hexagonal in shape.

[0219] As discussed above, the pellets of the present disclosure are not limited to any particular pellet shape. In various embodiments, the pellets may be iron agglomerates having a variety of different shapes, such as the agglomerated sintered iron pellets 305 illustrated in FIG. 3A. The agglomerated sintered iron pellets may have symmetrical and / or asymmetrical shapes. As an example, the agglomerated sintered iron pellets may have symmetrical shapes, such as spherical, elliptical, cylindrical, or plate-shaped, or may have irregular shapes, such as granules. In various embodiments, the agglomerated sintered iron pellets 305 may be formed using a continuous feed calciner, a batch calciner, a blast furnace, or any other type of furnace. As a specific example, when the furnace is a continuous feed calciner, the furnace 307 may be comprised of a rotating tube. During operation, iron powder particles 302 may be fed into the furnace 307. The furnace 307 can rotate and heat the iron powder particles 302 to sinter the iron powder particles 302 together, thereby producing agglomerated sintered iron pellets, such as the agglomerated sintered iron pellets 305. The agglomerated sintered iron pellets, such as the agglomerated sintered iron pellets 305, can provide the same chemical and morphological characteristics as the sintered pellets discussed herein, such as the pellets 105, 115, and in various embodiments can be used in place of other shaped pellets. The agglomerated sintered iron pellets, such as the agglomerated sintered iron pellets 305, can include necks 309 at the sinter joints of the iron powder particles 302 that are joined together to form the agglomerated sintered iron pellets, such as the agglomerated sintered iron pellets 305.

[0220] An advantage of using pellets formed as iron agglomerates is that the production of such iron agglomerate pellets, such as the agglomerated sintered iron pellets 305, may be less expensive than the production of spherical and / or briquette shaped pellets, such as the pellets 105, 115.

[0221] In various embodiments, sintered iron electrodes, such as whole electrodes and / or individual pellets, such as pellets 105, 115, 305, can be formed from crushed precursor and / or by-product materials (e.g., fines) derived from a steelmaking process (e.g., DRI). For example, DRI precursors and DRI fines can be crushed, molded with a binder under heat and pressure, and then sintered to form porous iron electrodes in shapes such as pellets 105, 115, 305, and / or electrodes in other shapes, including, but not limited to, sheets, plates, bars, cylinders, and other shapes.

[0222] Various embodiments discussed below with reference to Figures 3B-3D provide for the fabrication of sintered porous metal electrodes for batteries such as batteries 100, 200, 400, 800, 814, 900, 1000, 1100, and 1200 described herein.

[0223] 3B illustrates one embodiment method 350 for fabricating a sintered porous metal electrode. The method 350 may include mixing a metal and one or more additives to form a green pellet at block 351, and sintering the green pellet to form a porous metal electrode at block 352.

[0224] Mixing the metal and one or more additives to form the "green" molded pellets in block 351 may include hot pressing the mixture of the metal and one or more additives to form the product pellets. In various embodiments, the metal may include iron. In various embodiments, the additives may include a combination of pore former and binder additives. As a specific example, a mixture of iron, polyethylene, and bismuth sulfide powder may be hot pressed into the product pellets. In various embodiments, polyethylene may act as both a product binder and a pore former that evaporates during the sintering step. Polyethylene may sublime at a temperature lower than the sintering temperature. In various embodiments, other pore former additives may be used that do not necessarily serve as binders, such as any inorganic or organic material that is in a solid phase at room temperature in a nitrogen (e.g., N2) or argon / hydrogen (e.g., Ar(95%) / H2(5%) or other relative argon and hydrogen concentrations) atmosphere and in a liquid or gas phase between room temperature and the sintering temperature. In various embodiments, multiple types of binders may be mixed together as additives to the metal. A mixture of multiple types of binders can be used to target specific microstructure morphologies and to stabilize the powder bed during binder burnout.

[0225] Sintering the nascent pellets to form the porous metal electrode at block 352 may include sintering the nascent pellets in a gas atmosphere with a time-temperature profile. The gas atmosphere may be a nitrogen (e.g., N2) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H2(5%) or other relative argon and hydrogen concentration) atmosphere. In various embodiments, the time-temperature profile may be a linear time-temperature profile or a non-linear time-temperature profile. For example, the linear time-temperature profile may include a linear temperature ramp period, followed by a constant soak temperature period, followed by a linear drop period. As a specific example, sintering the nascent pellets in a gas atmosphere with a time-temperature profile may include sintering the nascent pellets in a nitrogen (e.g., N2) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H2(5%) or other relative argon and hydrogen concentration) atmosphere with a linear temperature ramp to 850° C., a 15 minute soak at 850° C., and a linear drop to room temperature. As another example, the non-linear time-temperature profile may have multiple ramps and soaks to better control the evaporation rate of the pore former, such as a polyethylene pore former. For example, the non-linear time-temperature profile may have a non-linear temperature ramp period, two or more soak temperature periods with ramp and ramp periods in between, and a non-linear ramp period.

[0226] 3C illustrates an embodiment system 360 for forming a sintered porous metal electrode 362. The system 360 may include a continuous roller furnace having a series of heating elements 364 and a belt 366 configured to transport articles on the belt 366 from one end to another through the furnace while being heated by the heating elements 364. The area under the heating elements 364 may be configured to have controlled atmospheric conditions, such as an atmosphere of pure hydrogen (H2) provided by a hydrogen tank 369. The system 360 may include a powder feed 370, such as a hopper, container, drum, etc., that supports a metal powder 371, such as iron oxide powder, used to form the sintered porous metal electrode 362. If the metal powder 371 is iron oxide powder, the iron oxide powder may or may not be oxidized in air at an elevated temperature resulting in a fully oxidized (Fe2O3) powder feedstock. Metal powder 371 may be deposited on belt 366 from a powder supply and compressed before being fed into the furnace (i.e., under heating elements 364). By way of example, metal powder 371 may be compressed with a slot die, compression rollers 372, press, or other compression type device in front of the furnace. The compressed metal powder may be fed by belt 366 down the length of the furnace under heating elements 364. As metal powder 371 travels along belt 366, it is heated by heating elements 364 in a hydrogen atmosphere and HO vapor may be liberated from the metal powder. The hydrogen at high temperatures reduces iron oxide to form water and metallic iron (i.e., FeO x +H2->H2O+Fe). The resulting metal powder (e.g., iron powder) is continuously rotated through the furnace on belt 366, allowing the particles to sinter together and forming a sintered porous metal electrode 362 (e.g., a sintered porous Fe electrode) in a continuous manner. In some embodiments, once the sintered porous metal electrode 362 exits the furnace, it may be cut into pieces, such as by a knife 378, pinch cutters, cutting jet, or any other type of device configured to cut the sintered porous metal electrode 362 into pieces. In some embodiments, the sintered porous metal electrode 362 may break apart into pieces due to its weight.

[0227] FIG. 3D illustrates a system 380 for forming a sintered porous metal electrode 362. The system 380 may be similar to the system 360 described above, except that a metal sheet 382 may be laid under the metal powder 371 before the metal powder 371 is fed into the furnace. In this manner, the metal powder 371 may be directly sintered onto the metal sheet 382, ​​thereby continuously forming a sintered porous metal electrode 362 with an integrated current collector. The metal sheet 382 may be a roll of metal that is fed into the furnace with the metal powder 371 thereon and supports the metal powder 371 on the belt 366. For example, the metal sheet 382 may be fed by a reel to reel system on the belt 366 before the metal powder 371 is deposited and compressed. In various embodiments, the metal sheet 382 may be a metal foil. In various embodiments, the metal sheet 382 may be formed of any metal selected to act as a current collector, such as nickel, iron, steel, etc.

[0228] 4 is a schematic diagram of a battery 400 according to various embodiments of the present disclosure. Battery 400 is similar to battery 100, and therefore only the differences between battery 100 and battery 400 will be described in detail. Battery 400 may include spherical pellets 105 disposed in a smaller particle composition, such as a composition formed from powdered metal feedstock, metal fines, metal grains, and the like.

[0229] Long-term electrochemical energy storage can benefit from very low-cost material inputs. The spherical pellets 105 of the battery 100 can provide very low-cost materials, but electrical and ionic conductivity through the spherical pellets 105 may not be ideal due to the limited contact points that necessarily come into contact with the spherical pellets 105. One solution to provide better electrical and ionic conductivity may be to use powdered metal feedstock as an electrode, such as the anode 102. Powdered metal feedstock used as an electrode can provide tailored electrical and ionic conductivity, but powdered metal feedstock can be expensive to produce, especially compared to the spherical pellets 105.

[0230] Various embodiments can provide composite metal electrode architectures that are lower cost than electrodes of exclusively powdered metal feedstock and / or provide higher electrical conductivity than electrodes of exclusively spherical pellets. As used herein, the average width or diameter of the pellets is at least 10 times greater than the average width or diameter of the powder particles in the powdered metal feedstock. In various embodiments, the composite metal electrode architectures may include a mixture of spherical pellets and smaller metal particle compositions, such as powdered metal feedstock. For example, as shown in FIG. 4, the anode 102 may include spherical pellets 105 disposed in a smaller metal particle composition 402, such as powdered metal feedstock. The spherical pellets 105 and powdered metal feedstock as the anode 102 can provide a mixture of larger and smaller particles, similar to marbles in sand or other combinations of relative particle sizes. In some embodiments, the macropores between the larger pellets include the smaller pellets. Composite metal electrodes formed with spherical pellets 105 and powdered metal feedstock can provide electrode architectures with cost, electrical conductivity, and / or ionic conductivity that may be highly tunable. In some embodiments, the composite metal electrode may be wetted with the liquid electrolyte 104. Because the powdered metal feedstock included in the composite metal electrode may be wetted, a composite metal electrode formed with the spherical pellets 105 and the powdered metal feedstock may have a lower iron-to-electrolyte ratio than an electrode formed exclusively with the spherical pellets 105. The powdered metal feedstock 402 improves the electrical conductivity between the pellets 105 of the electrode 102 and also the overall packing density of the electrode.

[0231] In various embodiments, the composite metal electrode architecture may include a mixture of spherical pellets and smaller metal particle compositions, such as metal fines or shavings. For example, as shown in FIG. 4, the anode 102 may include spherical pellets 105 comprised of taconite and a smaller metal particle composition 402 comprised of conductive DRI fines. Combining low-cost taconite pellets used as the bulk iron feedstock for the pellets 105 with waste conductive DRI fines as the smaller metal particle composition 402 can reduce the cost of forming the conductive electrode during assembly of the battery 400. As another example, the composite metal electrode architecture may include a mixture of different sized iron ore particles, such as larger iron ore pellets (e.g., taconite, DRI, sponge iron, atomized iron, etc.) and smaller metal particle compositions, such as metal fines or shavings (e.g., fines or shavings of DRI, taconite, sponge iron, atomized iron, etc.).

[0232] In some embodiments, the electrical conductivity of the metal electrodes is increased by adding conductive fibers, wires, mesh, or sheets to the pellets such that the conductive material is dispersed between the individual pellets.

[0233] Various embodiments provide on-site synthesis of active materials for bulk energy storage systems using renewable energy excess production. In various embodiments, chemical costs can be reduced by configuring an energy storage plant including embodiment batteries, such as the dual-use metal-air electrochemical cell embodiments discussed herein. The initial use of the energy storage plant is to synthesize key active materials, such as metallic pellets, such as pellets 105, 115, 305, on-site, using much lower cost input chemicals and very cheap or free renewable energy. The next use of the energy storage plant may be as an actual energy storage plant where the synthesized chemicals are active materials, such as metallic pellets, such as pellets 105, 115, 305. For example, metal powders that will eventually be used in very large batteries can be synthesized on-site in the dual-use energy storage plant prior to battery commissioning, for example, by direct reduction using hydrogen electrochemically generated by alkaline or PEM electrolysis powered by on-site renewable resources (e.g., wind, solar, etc.). This first stage on-site production of active materials not only lowers production costs, but can potentially avoid shipping costs. In embodiments where iron ore is the source of active material, renewable energy can be used to provide thermal energy for reducing the ore in a dual-use energy storage plant. Additionally, renewable energy can optionally be used to produce hydrogen as a reducing gas for reducing the ore. The ore or reduced ore can optionally be in the form of iron-containing pellets.

[0234] In various embodiments, metallic pellets such as pellets 105, 115, 305 can be synthesized in a first stage of a dual-use energy storage plant and used for the anode in a second stage of the dual-use energy storage plant. FIG. 5 illustrates an embodiment method 500 for on-site synthesis of active materials such as metallic pellets such as pellets 105, 115, 305 for a bulk energy storage system using renewable excess production. In block 501, during a first stage of operation, the dual-use energy storage plant may be operated to produce active materials such as metallic pellets such as pellets 105, 115, 305. For example, if iron ore is the source of active materials, the ore may be reduced on-site in the dual-use energy storage plant to synthesize metallic pellets such as pellets 105, 115, 305. In block 502, during a second stage of operation, the dual-use energy storage plant may use the active materials for long-term energy storage. For example, synthesized metallic pellets such as pellets 105, 115, 305 can be loaded (or otherwise deposited, doped, formed, etc.) into a negative electrode such as electrode 102 of a battery to assist in long-term energy storage with a dual-use energy storage plant. In various embodiments, the operations of blocks 501 and / or 502 may be performed using renewable energy.

[0235] FIG. 8A is a schematic diagram of a battery 800 according to various embodiments of the present disclosure. The battery 800 is similar to the battery 100, and therefore only the differences between them shall be described in detail. The battery 800 may be configured to allow the electrolyte 104 to flow through the negative electrode 102. For example, the battery 800 may include a circulation pump 802 and piping configured to allow the electrolyte 104 to be pumped through the pellets 105 that make up the electrode 102 at a selected rate, such as a constant flow rate, a variable flow rate, etc. Transporting the electrolyte 104 through a very thick (multiple centimeters) battery electrode 102 made up of active material pellets 105 may be difficult. A low transport rate of the electrolyte 104 may increase the overvoltage loss of the electrode 102 based on the pellets 105. By flowing the electrolyte 104 through the thick electrode 102, a convective transport can be introduced that facilitates the flow of the electrolyte to the individual pellets 105. As discussed above, the pellets 105 may be microporous and reaction conditions may benefit from reducing the electrolyte 104 concentration boundary layer that may occur across the entire thickness of the pellet 105 bed of the electrode 102 and across macropores, such as macropore 602, of the pellet 105 bed. Electrolyte 104 flow generally reduces overpotential losses by homogenizing the electrolyte 104 composition throughout the macro- and microstructures of the electrode 102. The electrolyte 104 flow rate may preferably be selected such that any energy consumed by pumping is low enough so as not to consume an undesirable amount of energy. In various embodiments, the electrolyte 104 flow rate may be a constant flow rate or a variable flow rate.

[0236] In various embodiments, electrolyte 104 can be flowed at a slow but constant flow rate across a battery electrode 102 (e.g., a battery electrode 102 comprised of active material pellets 105) to introduce convective transport that facilitates the flow of electrolyte 104 to the individual pellets 105. The pellets 105 may be microporous, and reaction conditions may benefit from reducing electrolyte 104 concentration boundary layers that may occur across the entire thickness of the pellet 105 bed (e.g., across the electrode 102) and across the macropores of the pellet 105 bed (e.g., of the electrode 102). Electrolyte 104 flow can generally reduce overpotential losses by homogenizing the electrolyte 104 throughout the macro- and microstructures of the electrode 102.

[0237] In various embodiments, the electrolyte 104 formulation may be different for the charging, discharging, and idle states of the battery 800. By flowing different electrolyte 104 formulations to the battery 800 when switching states, utilization, self-discharge, and HER can be improved simultaneously. For example, in the case of a continuous flow electrolyte management system, there may be any number of separate electrolyte formulation reservoirs, each optionally connected to the electrochemical cell with a separate flow controller (e.g., three reservoir and flow controller combinations 805, 806, 807). During different runs, different relative amounts of each electrolyte formulation may be flowed based on the optimal concentration of the constituent species for the instantaneous operating mode (charge, discharge, idle). In some embodiments, the electrolyte formulation may be adjusted based on the instantaneous state of charge of the battery 800. In various embodiments, a reservoir and flow controller combination (e.g., 805, 806, 807) may be used to add additional electrolyte 104 to the battery 800, for example, to compensate for electrolyte 104 evaporation. In various embodiments, the battery 800 may include an overflow drain 820 or overflow passage that can allow the electrolyte 104 to overflow from the battery 800. For example, when the electrolyte 104 level reaches the overflow drain 820, the electrolyte 104 can exit the battery 800 to maintain the level of the electrolyte 104 at the overflow drain 820 level, thereby maintaining the level of the electrolyte 104.

[0238] 8B is a block diagram of an embodiment battery 814 that includes an additive delivery system 815. Battery 814 is similar to battery 100, and therefore only the differences therebetween will be described in detail. In one embodiment, additive delivery system 815 can be a pump that delivers an additive-bearing liquid to battery 814. In another embodiment, the additive delivery system 815 may be a dry hopper that delivers additive-bearing solids to the battery 814. As one example, the additive delivery system 815 may be a sulfur delivery system. As a specific example, when the additive delivery system 815 is a sulfur delivery system, the sulfur delivery system may be a pump that delivers a sulfur-bearing liquid to the battery 814. As another specific example, when the additive delivery system 815 is a sulfur delivery system, the sulfur delivery system may be a dry hopper that delivers a sulfur-bearing solid (e.g., polysulfide salts, iron sulfide (FeS), etc.) to the battery 814. In another example, the additive delivery system 815 may be a salt delivery system. Specifically, the additive delivery system 815 may add certain solid-phase hydrogen evolution inhibitors (e.g., Bi, Sb, As) as soluble salts. For example, the additive delivery system 815 may be a salt that dissolves and releases the ions of the desired additive (e.g., Bi 3+ , Sb 3+ , As 3+ A soluble salt of the desired hydrogen evolution inhibitor can be added to the liquid electrolyte 104 by the additive delivery system 815, which provides a soluble salt of the inhibitor in solution (e.g., Bi 3+ ->Bi 0) occurs at a higher half-cell potential (measured against RHE (but at a lower cell potential) than the potential of the charging reaction of the anode active material. Thus, during charging of the battery 800, the HER inhibitor in ionic form can be electrodeposited on the surface of the metal electrode, providing an inexpensive and simple strategy to introduce the HER inhibitor into the battery 800 electrolyte 104 chemistry. The electrodeposition inhibitor suppresses the hydrogen evolution reaction at the surface of the electrode, which may be an electrode with open porosity. During the discharge mode, the deposits can dissolve back into the electrolyte 104. The salt additive is preferably selected so as not to degrade the operation of the cathode during charge or discharge operation. As another example, the added salt may be a carbonate salt. In some embodiments, the additive delivery system 815 can deliver multiple additives to the battery 800. For example, a mixed additive composition, such as a corrosion inhibitor that suppresses the HER reaction or suppresses self-discharge, combined with an additive that improves capacity utilization, can be delivered by the additive delivery system 815. As another example, an inhibitor that forms a passivating layer on metal surfaces is paired with an additive that depassivates iron surfaces, and both can be delivered by the additive delivery system 815. In some embodiments, the additive delivery system 815 can deliver an additive that includes molybdate ions. As an example, the molybdate ions can be added via a molybdate compound, such as KMoO4. In one specific example, the electrolyte 104 can include molybdate anions at an additive concentration of 10 mM. In other embodiments, the electrolyte 104 can include molybdate anions at an additive concentration ranging from 1 to 100 mM. In some embodiments, a surfactant additive can be delivered by the additive delivery system 815. The surfactant additive can reduce the surface tension and viscosity of the electrolyte at the oxygen evolution electrode, generating smaller, uniformly sized, controllable gas bubbles during charging. In one non-limiting example, 1-octanethiol is added to the alkaline electrolyte 104 at a concentration of 10 mM. In some embodiments, the corrosion inhibitor additive may be delivered by the additive delivery system 815.In some embodiments, the additive delivery system 815 can deliver liquids and / or interphase interface inhibitors. In some embodiments, the additive delivery system 815 can deliver additives as a mixture of solids. In some embodiments, the additive delivery system 815 can deliver electrolyte additives (e.g., Na2MoO4) that form a thin passivation film. Thus, the self-discharge of the anode is limited to only a small layer on the surface of the anode. However, to restore the reactivity of the metal anode, a short, strong charging pulse can be used to reduce the surface film. Once the surface film is reduced, the discharge reaction can proceed.

[0239] FIG. 8C is a block diagram of a battery system 850 including a series of embodiment batteries 800 in fluid connection (or otherwise in liquid communication) according to various embodiments. The batteries 800 may be arranged in a cascade such that overflow electrolyte 104 from one battery 800 can flow into the next battery 800 through its overflow drain 820, establishing a "liquid communication" between the batteries 800. By connecting such batteries 800 in series, it is possible to simultaneously supply liquid electrolyte 104 to several batteries 800 with one supply. For example, a single electrolyte supply pipe 851 connected to a pump 802 can supply electrolyte 104 to a first battery 800. Overflow of electrolyte from the first battery 800 can flow to a second battery 800 and to a third battery 800. The electrolyte can overflow from the third battery 800 into a return pipe 852 and be circulated by the pump 802 back to the supply pipe 851. In this way, overflow from the last cell 800 can be recirculated to the first cell 800. In a system 850 in which a shared electrolyte 104 is used that flows in a cascading manner between the cells 800, the electrolyte attributes can be monitored and processed at a central location for multiple cells, such as a monitoring station 853. Electrolyte 104 adjustments, such as making composition adjustments or adding ingredients to mitigate issues with electrolyte carbonation and electrolyte dehydration, can be beneficially performed at the monitoring station 853. The monitoring station 853 may be collocated with a collection structure for the circulating electrolyte 104, such as a return pipe 852. As an example, the monitoring station 853 can control the supply of electrolyte 104 from a combination of different reservoirs and flow controllers (e.g., 805, 806, 807), a filtration device 860, and / or a reserve electrolyte supply tank 855. In various embodiments, the monitoring station 853 may be configured to monitor electrolyte health. The electrolyte health may be monitored during operation of the battery to determine the appropriate time to replenish, replace, or treat the electrolyte 104.The feedback mechanism used by the monitoring station 853 may be manual or automatic. If the monitoring station 853 is an automated system, the electrolyte quality measurement may be one input to a control loop, such as a proportional integral derivative (PID) loop that continuously adjusts the electrolyte component concentrations. The electrolyte quality measurement may be performed ex-situ on a small aliquot of the electrolyte 104, or in operando on the active electrolyte 104 while the battery 800 is in operation. One non-limiting method for assessing electrolyte health is to measure the electrical conductivity of the electrolyte. One mechanism of degradation is that the electrolyte becomes carbonated over time as CO2 from the air dissolves in the electrolyte. For example, a conductivity probe is used to assess the concentration of carbonate in the electrolyte. The conductivity probe is used to monitor the electrolyte health state. Although the monitoring station 853 is shown as part of the cascade system 850, it may also be part of a single battery's electrolyte delivery system, such as the electrolyte system of FIG. 8A. The monitoring station 853 can control the release of electrolyte 104 from and / or to the auxiliary electrolyte supply tank 852 to increase and / or decrease the volume of electrolyte 104 in the system 850. The monitoring station 853 can control the flow of liquid through the filtration device 860. The filtration device 860 can be configured to filter liquids flowing therethrough, such as water, electrolyte 104, and the monitoring station 853 can control the flow of liquid into and out of the filtration device 860. For example, the filtration device 860 can be a water filter, such as the water filter 1400 shown in FIG. 14. The water filter 1400 can be a packed bed 1401 of DRI, which can operate as a water filtration device. In such an embodiment, the DRI is housed in a column to create a packed bed 1401 of DRI pellets 197. Particulate matter becomes trapped within the pores within the DRI pellets 197 and in the void spaces between the DRI pellets 197 as the water flows through the bed 1401 . The use of pelletized iron as the filtration mechanism can provide the ability to adjust pressure drop and filtration effectiveness.

[0240] FIG. 9 is a schematic diagram of a battery 900 according to various embodiments of the present disclosure. Battery 900 is similar to battery 100, so only the differences between them will be described in detail. Alkaline iron electrode batteries work best with certain additives in the electrolyte / cell. They may have a range of solubilities. Some may have the most beneficial effect when intimately mixed with the solid electrode. As shown in FIG. 9, in various embodiments, pellets 902 containing additives may be mixed with pellets 105 containing primarily active material, and thus the negative electrode 102 may be a blended electrode. The additive pellets 902 may be formed partially and / or entirely with additives, e.g., iron-sulfur compounds such as FeS, FeS2, etc. In various embodiments, the liquid electrolyte 104 may include additives to suppress the hydrogen evolution reaction at the anode or cathode. These may be soluble or insoluble and may include metalloid HER inhibitors such as bismuth, antimony, tin, boron, indium, gallium, selenium, etc. The additive may plate out of solution or change phase during operation, for example starting out in solution dissolved and later precipitating as a solid.

[0241] FIG. 10 is a schematic diagram of a battery 1000 according to various embodiments of the present disclosure. The battery 1000 is similar to the battery 100, so only the differences between them will be described in detail. The interfacial resistivity between the current collector 106 and the negative electrode 102, which is composed of pellets 105, may be high due to the spherical structure of the pellets 105 that contact the current collector 106 of the battery 100. Therefore, the electrode 102 experiences an increase in effective current density at the pellet contact. In various embodiments, the interfacial resistivity can be reduced by adding a layer of powdered iron (Fe) 1002 to the interface between the electrode 102 and the current collector 106, as shown in the battery 1000 of FIG. 10. In the battery 1000, the layer of powdered iron 1002 can be added to the bottom of the bed of pellets 105 to reduce the interfacial resistivity. The layer of powdered iron 1002 may be configured to form an interface between the pellets 105 and the current collector 106 of the battery 1000. The average width or diameter of the pellets 105 is at least 10 times greater than the average width or diameter of the powder particles of the layer 1002 .

[0242] 11 is a schematic diagram of a battery 1100 according to various embodiments of the present disclosure. Because the battery 1100 is similar to the battery 100, only the differences between them shall be described in detail. The battery 1100 may include a monitoring system including one or more sensors connected (e.g., wirelessly or wired) to a controller 1110 configured to monitor the state of charge (SOC) and / or state of health (SOH) of the iron electrode 102. Monitoring the SOC and / or SOH may be beneficial for improved control and health monitoring of the battery 1100.

[0243] Various embodiments may include one or more of a variety of methods for monitoring the chemical and / or physical attributes of the anode 102, including using a Mössbauer spectrometer, using a charge-coupled device (CCD) detector (e.g., a color camera, etc.), using a strain gauge, using a temperature sensor, measuring ion concentration, measuring electrolyte level displacement, measuring pellet bed height, measuring pellet size, measuring battery 1100 cell mass, measuring magnetic susceptibility, and using gas sensing. In various embodiments, a NiOH / NiOOH electrode containing carbon conductive additives and / or binders may be used as a quasi-reference electrode for monitoring the potential. Such NiOH / NiOOH electrodes may be placed at various locations throughout the electrolyte reservoir to monitor the potential distribution throughout the system.

[0244] For example, the SOC and / or SOH may be monitored in-situ by one or more strain gauges 1102 connected to the vessel 101. The one or more strain gauges 1102 may be connected to a controller 1110 and may output measurements of strain on the vessel 101 to the controller 1110. The controller 1110 may be configured to convert the strain measurements into SOC and / or SOH measurements.

[0245] As another example, the SOC and / or SOH can be monitored in-situ by a Mössbauer spectrometer comprised of a gamma radiation source 1103 and a gamma radiation detector 1104. The gamma radiation source 1103 can output gamma radiation that passes through the battery 1100 and can be detected by the gamma radiation detector 1104. The gamma radiation source 1103 can be connected to a controller 1110, which can control the gamma radiation source 1103 to output gamma radiation. The gamma radiation detector 1104 can be connected to the controller 1110, and can output gamma radiation measurements to the controller 1110. The controller 1110 can be configured to convert the gamma radiation measurements into SOC and / or SOH measurements.

[0246] As a further example, the SOC and / or SOH can be monitored in-situ by one or more CCD detectors 1105 (e.g., color cameras, etc.) connected to the controller 1110. The CCD detectors 1105 can record and output images of the anode 102 to the controller 1110. The controller 1110 can be configured to determine SOC and / or SOH measurements using the images. For example, the controller 1110 can be configured to correlate a color of the pellets 105 in the images with the SOC and / or SOH measurements. As another example, the controller 1110 can be configured to measure a size of the pellets 105 from the image data and / or measure a pellet 105 bed height from the image data.

[0247] As a further example, the SOC and / or SOH can be monitored in-situ by one or more ultrasonic transducers 1106 connected to a controller 1110. The ultrasonic transducers 1106 can output sonic measurements to the controller 1110. The controller 1110 can be configured to use the sonic measurements to determine the SOC and / or SOH measurements. For example, based on the round trip time of a sound wave to the surface of the pellet 105 bed, a change in the height of the pellet 105 bed can be determined by the controller 1110 and correlated with the SOC and / or SOH measurements.

[0248] As a further example, SOC and / or SOH may be monitored in-situ by one or more ion sensing electrodes 1107 connected to a controller 1110. The ion sensing electrodes 1107 may output ion measurements, such as ion concentrations, to the controller 1110. The controller 1110 may be configured to use the ion measurements to determine SOC and / or SOH measurements.

[0249] As a further example, the SOC may be monitored in-situ by one or more thermocouples 1108 connected to a controller 1110. The thermocouples 1108 may output temperature measurements to the controller 1110. The controller 1110 may be configured to use the temperature measurements to determine SOC and / or SOH measurements.

[0250] As yet a further example, the SOC and / or SOH may be monitored in-situ by one or more gas sensors 1109 connected to the controller 1110. The gas sensors 1109 may output gas measurements, e.g., specific particle detection, concentrations, etc., to the detector 1110. The controller 1110 may be configured to use the gas measurements to determine the SOC and / or SOH measurements.

[0251] In various embodiments, the controller 1110 can use physical and / or chemical attributes of the battery 1100, and more specifically the anode 102, measured by the various sensors 1102-1109 to determine control actions to take with respect to the battery 1100, such as actions to ensure the health of the battery 1100, based on the monitored SOC and / or SOH of the anode 102.

[0252] FIG. 13A illustrates a battery 1300 according to various embodiments. As an example, the battery 1300 is a static type battery in which a DRI is used. In some embodiments, the battery 1300 is a non-flowing aqueous type battery. In some embodiments, the battery 1300 may be a primary battery. In some embodiments, the battery 1300 may be a secondary battery. In some embodiments, the battery 1300 may include a DRI pellet 198 in one electrode 1302 and / or a DRI pellet 199 in another electrode 1306. Although shown to include both DRI pellets 198, 199, in some configurations, only one of the electrodes 1302 or 1306 may include the DRI pellets 198, 199, respectively, and in other configurations, both electrodes 1302, 1306 may include the DRI pellets 198, 199, respectively. In various embodiments, the electrodes 1302 and 1306 may be separated by an electrolyte 1304. In various embodiments, the battery 1300 may be a sealed battery. In various embodiments, the battery 1300 may be an open battery, such as a battery open air type battery. In various embodiments, the DRI pellet 198 may be similar to the various DRI pellets (or other DRI type configurations) described herein, such as DRI pellets 105, 115, 305.

[0253] In various embodiments, electrode 1302 is the anode of battery 1300, and electrode 1306 is the cathode of battery 1300. In various embodiments, DRI is used as a redox-active electrode material when battery 1300 is a primary or secondary battery. In one embodiment, DRI (such as DRI pellet 198) is used as the anode active material when battery 1300 is a secondary battery. In another embodiment, DRI (such as DRI pellets 198, 199, etc.) is used with an alkaline electrolyte (pH > 9) as the electrode material. In one specific embodiment, when battery 1300 is an alkaline secondary battery, a nickel cathode can be used for battery 1300. In this embodiment, DRI serves as the starting material for the anode of Ni-Fe alkaline secondary battery 1300 and may be used as received or processed prior to use according to other embodiments described herein. Other electrochemical couples (combinations of cathodes and anodes) for use when battery 1300 is an alkaline battery using a DRI anode include iron / nickel (Fe / Ni cell) or iron / silver (Fe / Ag cell). In various embodiments, when battery 1300 is a primary or secondary battery where the pH of the electrodes ranges in the acidic (pH < 5.5) or neutral (5.5 < pH < 9) region, DRI can serve as the anode active material. As an example, DRI can be used as the anode active material of battery 1300 where an electrolyte containing hydrochloric acid (HCl) in the concentration range of 1 to 5 M is used. At the anode, DRI can participate in the following half-cell reaction during discharge: Fe + 2Cl - -> FeCl2 + 2e - can be involved.

[0254] Specifically, DRI can be used as the anode material when battery 1300 is an all-Fe battery where the reactive species at both the anode and the cathode is Fe. In such an embodiment, DRI can serve as a solid metallic Fe anode at 100% SOC, and the anode is soluble Fe during discharge 2+The cathode active material may be a soluble inorganic Fe-based salt, such as the FeCl2 / FeCl3 redox couple. The cathode active material may also be an inorganic or organic-based coordination compound, such as K3Fe(CN)6. At the cathode, the soluble Fe species is converted to Fe 2+ / Fe 3+ As one specific example, if the battery 1300 is an all-Fe battery using DRI as the active material, DRI can be used as the anode material with an electrolyte containing HCl (1-5M) at a concentration. At the anode, DRI reacts with the following half-cell reaction upon discharge: Fe+2Cl - ->FeCl2+2e - At the cathode, soluble FeCl3 participates in the following half-cell reaction during discharge: 2FeCl3 + 2e - ->2FeCl2+2Cl - The complete cell reaction on discharge would be Fe + 2FeCl3 -> 3FeCl2. DRI can be used as a source of soluble FeCl2 needed in solution to enable the cathodic reaction by reacting DRI with HCl in solution, which will participate in the following spontaneous chemical reaction: Fe + 2HCl -> FeCl2 + H2.

[0255] Figure 13B shows a battery 1310 according to various embodiments. The battery 1310 is similar to the battery 1300 described above, except that the battery 1310 is a flow battery that uses DRI. In various embodiments, the DRI pellets 198, 199 are transported from the corresponding storage tanks 1311, 1312 to the corresponding electrodes 1302, 1306 of the flow battery 1310 by one or more corresponding transport systems 1314, 1316. As an example, the DRI may be used as the anode of the flow battery 1310, and the DRI pellets are transported from the storage tank to an electrochemical reactor where the DRI pellets electrochemically react. The DRI pellets maintain electrical contact with each other as they flow through the electrochemical reactor, allowing for sufficient electrical penetration to provide high electrical conductivity by pellet aggregation. The electrolyte 1304 may be acidic (pH < 5), neutral (5 < pH < 9), or alkaline (pH > 9). In a specific embodiment, the discharge reaction may proceed such that the metallic Fe anode forms a soluble product (e.g., FeCl2) or an insoluble (e.g., Fe(OH)2) discharge product film on the surface of the transported DRI pellets during discharge. Specific embodiments regarding the method for transporting the DRI pellets across the battery 1310 by one or both of the transport systems 1314, 1316 include any of the methods known in the art for transporting particulate matter or slurries or suspensions. For example, one or both of the transport systems 1314, 1316 may be, but are not limited to, a pressure-driven fluid flow system, a fluidized bed system, or a mechanical conveyor system such as a conveyor belt, a rotating drum, or a helical screw. In some embodiments, the transport systems 1314, 1316 such as mechanical belts, screws, drums, etc. include an electronically conductive material such as metal or carbon that also serves as a current collector for the battery 1310.

[0256] Various embodiments provide a method for fabricating a sintered porous metal electrode, the method including mixing a metal and one or more additives to form a product pellet, and sintering the product pellet to form a sintered porous metal electrode. In various embodiments, the method includes mixing a metal and one or more additives to form a product pellet by hot pressing the mixture of the metal and one or more additives to form a product pellet. In various embodiments, the metal may include iron. In various embodiments, at least one of the one or more additives is both a pore former and a binder additive. In various embodiments, the one or more additives include a polyethylene additive and a bismuth sulfide powder additive. In various embodiments, at least one of the one or more additives is a pore former additive and at least another of the one or more additives is a binder additive. In various embodiments, the binder additive is a mixture of two or more different types of binders. In various embodiments, sintering the product pellet to form a sintered porous metal electrode includes sintering the product pellet in a gas atmosphere at a time-temperature profile. In various embodiments, the gas atmosphere is an N2 atmosphere or an Ar / H2 atmosphere. In various embodiments, the gas atmosphere is an Ar(95%) / H2(5%) atmosphere. In various embodiments, the time-temperature profile includes a linear temperature rise period, followed by a constant soaking temperature period, followed by a linear drop period. In various embodiments, the linear temperature rise period increases the temperature of the nascent pellets to 850° C., the soaking temperature is 850° C., and the linear drop period decreases the temperature of the nascent pellets to room temperature. In various embodiments, the constant soaking temperature period is 15 minutes. In various embodiments, the time-temperature profile includes a non-linear temperature rise period, two or more soaking temperature periods with drop and rise periods therebetween, and a non-linear drop period.

[0257] Various embodiments may provide a method for fabricating a sintered porous metal electrode, the method including feeding a compacted metal powder into a continuous roller furnace and passing the compacted metal powder through the furnace to sinter the metal powder together to form a sintered porous metal electrode. In various embodiments, the metal powder includes iron oxide powder. In various embodiments, the method may include compressing the metal powder before feeding the metal powder into the furnace. In various embodiments, compressing the metal powder includes passing the metal powder through a slot die or under compaction rollers. In various embodiments, the method may include underlaying a metal sheet before feeding the metal powder into the furnace. In various embodiments, the metal sheet is received from a roll of metal being fed into the furnace, the metal sheet supporting the compacted metal powder in the furnace. In various embodiments, the metal sheet is a metal foil. In various embodiments, the metal sheet includes nickel, iron, or steel. In various embodiments, the method may include cutting the sintered porous metal electrode into sections. In various embodiments, the continuous roller furnace heats the metal powder in a hydrogen atmosphere. In various other embodiments, the continuous roller furnace heats the metal powder in an inert atmosphere of nitrogen or argon. In various other embodiments, the continuous roller furnace heats the metal powder in an atmosphere that includes a mixture of hydrogen, nitrogen, and / or argon.

[0258] Various embodiments may provide devices and / or methods for use in bulk energy storage systems, such as long-term energy storage (LODES) systems, short-term energy storage (SDES) systems, etc. As an example, various embodiments may provide batteries and / or battery components for bulk energy storage systems, such as batteries for LODES systems (e.g., any of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.). Renewable energy sources are becoming increasingly popular and cost-effective. However, many renewable energy sources face intermittency issues that hinder the adoption of renewable energy sources. The impact of renewable energy sources' tendency to be intermittent can be mitigated by pairing the renewable energy sources with bulk energy storage systems, such as LODES systems, SDES systems, etc. To support the adoption of combined generation, transmission, and storage systems (e.g., power plants having renewable generation sources paired with bulk energy storage systems, and transmission facilities in either the power plant and / or the bulk energy storage system), devices and methods are needed to support the design and operation of such combined generation, transmission, and storage systems, such as the various embodiment devices and methods described herein.

[0259] A combined generation, transmission, and storage system may be a power plant that includes one or more power generation sources (e.g., one or more renewable power generation sources, one or more non-renewable power generation sources, a combination of renewable and non-renewable power generation sources, etc.), one or more transmission facilities, and one or more bulk energy storage systems. The transmission facilities in either the power plant and / or the bulk energy storage systems may be co-optimized with the power generation and storage systems or may impose constraints on the design and operation of the power generation and storage systems. The combined generation, transmission, and storage system may be configured to meet various output targets under various design and operational constraints.

[0260] Working Example

[0261] The following examples are provided to illustrate various embodiments of the systems, methods, compositions, applications, and materials of the present invention. Such examples are illustrative and may be prophetic, and should not be considered limiting, and do not limit the scope of the invention in any way.

[0262] 15-23 show various exemplary systems that use one or more aspects of various embodiments as part of a bulk energy storage system, such as a LODES system, an SDES system, etc. For example, various embodiment batteries and / or components described herein (e.g., any of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.) can be used as batteries and / or components for a bulk energy storage system, such as a LODES system, an SDES system, etc. As used herein, the term "LODES system", unless expressly used otherwise, means a bulk energy storage system configured to be capable of having a rated duration (energy / power ratio) of 24 hours (h) or longer, such as a duration of 24 hours, a duration between 24 hours and 50 hours, a duration greater than 50 hours, a duration between 24 hours and 150 hours, a duration greater than 150 hours, a duration between 24 hours and 200 hours, a duration greater than 200 hours, a duration between 24 hours and 500 hours, a duration greater than 500 hours, etc.

[0263] Example 1

[0264] The storage system has 1, 5, 10, 50, 100, 500, or more electrochemical cells having one or more electrodes containing direct reduced iron pellets. Preferably, the storage system is a long-term storage system having long-term electrochemical cells.

[0265] Example 1A

[0266] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1A below.

[0267] [Table E1A]

[0268] Example 1B

[0269] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1B below.

[0270] [Table E1B]

[0271] Example 1C

[0272] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1C below.

[0273] [Table E1C]

[0274] Example 1D

[0275] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1D below.

[0276] [Table E1D]

[0277] Example 1E

[0278] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1E below.

[0279] [Table E1E]

[0280] Example 1F

[0281] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1F below.

[0282] [Table E1F]

[0283] Example 1G

[0284] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1G below.

[0285] [Table E1G]

[0286] Example 1H

[0287] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1H below.

[0288] [Table E1H]

[0289] Example 1I

[0290] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1I below.

[0291] [Table E1I]

[0292] Example 1J

[0293] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1J below.

[0294] [Table E1J]

[0295] Example 1K

[0296] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1K below.

[0297] [Table E1K]

[0298] Example 1L

[0299] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1L below.

[0300] [Table E1L]

[0301] Example 1M

[0302] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1M below.

[0303] [Table E1M]

[0304] Example 1N

[0305] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1N below.

[0306] [Table E1N]

[0307] Example 1O

[0308] The long-term storage system of Example 1, in which the electrodes have the characteristics shown in Table E1O below.

[0309] [Table E1O]

[0310] Example 1P

[0311] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1P below.

[0312] [Table E1P]

[0313] Example 1Q

[0314] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1Q below.

[0315] [Table E1Q]

[0316] Example 1R

[0317] The long-term storage system of Example 1, wherein the electrodes have the characteristics shown in Table E1R below.

[0318] [Table E1R]

[0319] Example 2

[0320] FIG. 15 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LODES system 1504 may be electrically connected to a wind farm 1502 and one or more transmission facilities 1506. The wind farm 1502 may be electrically connected to the transmission facility 1506. The transmission facility 1506 may be electrically connected to a power grid 1508. The wind farm 1502 can generate power, and the wind farm 1502 can output the generated power to the LODES system 1504 and / or the transmission facility 1506. The LODES system 1504 can store the power received from the wind farm 1502 and / or the transmission facility 1506. The LODES system 1504 can output the stored power to the transmission facility 1506. The transmission facility 1506 can output the power received from one or both of the wind farm 1502 and the LODES system 1504 to the grid 1508 and / or can receive power from the grid 1508 and output the power to the LODES system 1504. The wind farm 1502, the LODES system 1504, and the transmission facility 1506 together can comprise a power plant 1500, which may be a combined generation, transmission, and storage system. Electricity generated by the wind farm 1502 may be fed directly into the grid 1508 via transmission equipment 1506 or may first be stored in the LODES system 1504 .In certain cases, the power provided to the grid 1508 may be entirely from the wind farm 1502, entirely from the LODES system 1504, or from a combination of the wind farm 1502 and the LODES system 1504. The distribution of power from the combined wind farm 1502 and LODES system 1504 power plant 1500 may be controlled according to a predetermined long-term (multi-day or even multi-year) schedule, or according to a day-ahead (24-hour notice) market, or according to an hour-ahead market, or in response to real-time pricing signals.

[0321] As one example of the operation of the power plant 1500, the LODES system 1504 can be used to reshape and "stabilize" the power produced by the wind farm 1502. In one such example, the wind farm 1502 may have a peak power output (capacity) of 260 megawatts (MW) and a capacity factor (CF) of 41%. The LODES system 1504 may have a power rating (capacity) of 106 MW, a rated duration (energy / power ratio) of 150 hours (h), and a rated energy of 15,900 megawatt hours (MWh). In another such example, the wind farm 1502 may have a peak power output (capacity) of 300 MW and a capacity factor (CF) of 41%. The LODES system 1504 may have a power rating (capacity) of 106 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 21,200 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 176 MW and a capacity factor (CF) of 53%. The LODES system 1504 may have a power rating (capacity) of 88 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 13,200 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 277 MW and a capacity factor (CF) of 41%. The LODES system 1504 may have a power rating (capacity) of 97 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 4,850 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 315 MW and a capacity factor (CF) of 41%. The LODES system 1504 may have a power rating (capacity) of 110 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 2,750 MWh.

[0322] Example 2A

[0323] The system of Example 2, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0324] Example 3

[0325] FIG. 16 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The system of FIG. 16 may be similar to the system of FIG. 15, except that a photovoltaic (PV) station 1602 may be used instead of the wind power station 1502. The LODES system 1504 may be electrically connected to the PV station 1602 and one or more transmission facilities 1506. The PV station 1602 may be electrically connected to the power transmission facility 1506. The power transmission facility 1506 may be electrically connected to the power grid 1508. The PV station 1602 may generate power, and the PV station 1602 may output the generated power to the LODES system 1504 and / or the power transmission facility 1506. The LODES system 1504 may store the power received from the PV station 1602 and / or the power transmission facility 1506. The LODES system 1504 may output the stored power to the power transmission facility 1506. The power transmission facility 1506 may output the power received from one or both of the PV station 1602 and the LODES system 1504 to the power grid 1508 and / or may receive power from the power grid 1508 and output the power to the LODES system 1504. The PV station 1602, the LODES system 1504, and the transmission facility 1506 may together comprise a power plant 1600, which may be a combined generation, transmission, and storage system. Electricity generated by the PV station 1602 may be fed directly to the grid 1508 via the transmission facility 1506, or may first be stored in the LODES system 1504.In certain cases, the power provided to the grid 1508 may be delivered entirely from the PV stations 1602, entirely from the LODES systems 1504, or from a combination of PV stations 1602 and LODES systems 1504. The delivery of power from the combined PV stations 1602 and LODES systems 1504 power plant 1600 may be controlled according to a predetermined long-term (multi-day or even multi-year) schedule, or according to a day-ahead (24-hour notice) market, or according to an hour-ahead market, or in response to real-time pricing signals.

[0326] As one example of the operation of the power plant 1600, the LODES system 1504 can be used to reshape and "balance" the power produced by the PV station 1602. In one such example, the PV station 1602 may have a peak power output (capacity) of 490 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 340 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 51,000 MWh. In another such example, the PV station 1602 may have a peak power output (capacity) of 680 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 410 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 82,000 MWh. In another such example, the PV station 1602 may have a peak power output (capacity) of 330 MW and a capacity factor (CF) of 31%. The LODES system 1504 may have a power rating (capacity) of 215 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 32,250 MWh. In another such example, the PV station 1602 may have a peak power output (capacity) of 510 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 380 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 19,000 MWh. In another such example, the PV station 1602 may have a peak power output (capacity) of 630 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 380 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 9,500 MWh.

[0327] Example 3A

[0328] The system of Example 3, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0329] Example 4

[0330] FIG. 17 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The system of FIG. 17 may be similar to FIG. 15 and FIG. 16, except that the wind power station 1502 and the photovoltaic (PV) station 1602 may both be power generating devices operating together in a power plant 1700. The PV stations 1602, wind farms 1502, LODES systems 1504, and transmission facilities 1506 together may comprise a power plant 1700, which may be a combined power generation, transmission, and storage system. Power generated by the PV stations 1602 and / or wind farms 1502 may be fed directly to the grid 1508 via the transmission facilities 1506, or may first be stored in the LODES systems 1504. In certain cases, the power provided to the grid 1508 may be fed entirely from the PV stations 1602, entirely from the wind farms 1502, entirely from the LODES systems 1504, or from a combination of the PV stations 1602, the wind farms 1502, and the LODES systems 1504. The distribution of power from the combined wind farm 1502, PV farm 1602, and LODES system 1504 power plant 1700 may be controlled according to a predetermined long-term (multi-day or even multi-year) schedule, or may be controlled according to a day-ahead (24-hour notice) market, or may be controlled according to an hour-ahead market, or may be controlled in response to real-time pricing signals.

[0331] As one example of the operation of the power plant 1700, the LODES system 1504 may be used to reshape and "stabilize" the power produced by the wind farm 1502 and the PV farm 1602. In one such example, the wind farm 1502 may have a peak power output (capacity) of 126 MW and a capacity factor (CF) of 41%, and the PV farm 1602 may have a peak power output (capacity) of 126 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 63 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 9,450 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 170 MW and a capacity factor (CF) of 41%, and the PV farm 1602 may have a peak power output (capacity) of 110 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 57 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 11,400 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 105 MW and a capacity factor (CF) of 51%, and the PV farm 1602 may have a peak power output (capacity) of 70 MW and a capacity factor (CF) of 31. The LODES system 1504 may have a power rating (capacity) of 61 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 9,150 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 135 MW and a capacity factor (CF) of 41%, and the PV farm 1602 may have a peak power output (capacity) of 90 MW and a capacity factor (CF) of 24%. The LODES system 1504 may have a power rating (capacity) of 68 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 3,400 MWh. In another such example, the wind farm 1502 may have a peak power output (capacity) of 144 MW and a capacity factor (CF) of 41%, and the PV farm 1602 may have a peak power output (capacity) of 96 MW and a capacity factor (CF) of 24%.The LODES system 1504 may have a power rating (capacity) of 72 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 1,800 MWh.

[0332] Example 4A

[0333] The system of Example 4, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0334] Example 5

[0335] FIG. 18 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LODES system 1504 may be electrically connected to one or more transmission facilities 1506. In this manner, the LODES system 1504 may operate in a "standalone" manner to arbitrate energy near market prices and / or avoid transmission constraints. The LODES system 1504 may be electrically connected to one or more transmission facilities 1506. The transmission facilities 1506 may be electrically connected to a power grid 1508. The LODES system 1504 may store power received from the transmission facilities 1506. The LODES system 1504 may output the stored power to the transmission facilities 1506. The transmission facilities 1506 may output power received from the LODES system 1504 to the power grid 1508 and / or may receive power from the power grid 1508 and output the power to the LODES system 1504.

[0336] The LODES system 1504 and the transmission facility 1506 together may constitute a power plant 1800. As an example, the power plant 1800 may be located downstream of the transmission constraints, close to the power consumption. In such an exemplary downstream power plant 1800, the LODES system 1504 may have a duration of 24 to 500 hours and may perform full discharges once or multiple times a year to support peak power consumption at times when the transmission capacity is not sufficient to serve customers. In addition, in such an exemplary downstream power plant 1800, the LODES system 1504 may perform several shallow discharges (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and reduce the overall cost of serving the electricity to customers. As a further example, the power plant 1800 may be located upstream of the transmission constraints, close to the power generation. In such an exemplary upstream power plant 1800, the LODES system 1504 may have a duration of 24 hours to 500 hours and may undergo one or more full charges per year to absorb excess generation at times when transmission capacity is insufficient to distribute electricity to customers. In addition, in such an exemplary upstream power plant 1800, the LODES system 1504 may undergo several shallow charge / discharges (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and maximize the value of the power generation facility's output.

[0337] Example 5A

[0338] The system of Example 5, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0339] Example 6

[0340] FIG. 19 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LDES system 1504 may be electrically connected to commercial and industrial (C&I) customers 1902, such as data centers, factories, etc. The LODES system 1504 may be electrically connected to one or more transmission facilities 1506. The transmission facilities 1506 may be electrically connected to a distribution grid 1508. The transmission facility 1506 may receive power from the grid 1508 and output the power to the LODES system 1504. The LODES system 1504 may store the power received from the transmission facility 1506. The LODES system 1504 may output the stored power to the C&I customers 1902. In this manner, the LODES system 1504 may operate to reshape the power purchased from the grid 1508 to match the consumption patterns of the C&I customers 1902.

[0341] The LODES system 1504 and the transmission facility 1506 together may comprise a power generation plant 1900. As an example, the power generation plant 1900 may be located near the electricity consumption, i.e., near the C&I customers 1902, such as between the power distribution grid 1508 and the C&I customers 1902. In such an example, the LODES system 1504 may have a duration of 24 hours to 500 hours and may purchase power from the market at a time when power is cheaper, thereby charging the LODES system 1504. The LODES system 1504 may then discharge and provide power to the C&I customers 1902 at a time when the market price is higher, thus offsetting the market purchases of the C&I customers 1902. As an alternative configuration, the power generation plant 1900 may be located not between the power distribution grid 1508 and the C&I customers 1902, but between a renewable resource, such as a PV site, a wind farm, etc., and the transmission facility 1506, which may be connected to the renewable resource. In such an alternative example, the LODES system 1504 may have a duration between 24 hours and 500 hours, and the LODES system 1504 may be charged at times when renewable output may be available. The LODES system 1504 may then discharge to cover a portion or all of the C&I customer 1902 power needs and provide the C&I customer 1902 with renewable generated electricity.

[0342] Example 6A

[0343] The system of Example 6, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0344] Example 7

[0345] FIG. 20 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LODES system 1504 may be electrically connected to a wind farm 1502 and one or more transmission facilities 1506. The wind farm 1502 may be electrically connected to the transmission facility 1506. The transmission facility 1506 may be electrically connected to a C&I customer 1902. The wind farm 1502 can generate power, and the wind farm 1502 can output the generated power to the LODES system 1504 and / or the transmission facility 1506. The LODES system 1504 can store the power received from the wind farm 1502. The LODES system 1504 can output the stored power to the transmission facility 1506. The transmission facility 1506 can output the power received from one or both of the wind farm 1502 and the LODES system 1504 to the C&I customer 1902. The wind farm 1502, the LODES system 1504, and the transmission facility 1506 can together comprise a power plant 2000, which may be a combined generation, transmission, and storage system. The power generated by the wind farm 1502 may be delivered directly to the C&I customer 1902 via the transmission facility 1506, or may first be stored in the LODES system 1504. In certain cases, the power supplied to the C&I customer 1902 may be delivered entirely from the wind farm 1502, entirely from the LODES system 1504, or from a combination of the wind farm 1502 and the LODES system 1504.The LODES system 1504 may be used to reshape electricity generated by the wind farm 1502 to match the consumption patterns of the C&I customers 1902. In one such example, the LODES system 1504 may have a duration of 24 hours to 500 hours and may charge when renewable generation by the wind farm 1502 exceeds the C&I customers 1902 loads. The LODES system 1504 may then discharge when renewable generation by the wind farm 1502 falls below the C&I customers 1902 loads to provide the C&I customers 1902 with a stable renewable profile that offsets some or all of the C&I customers 1902 electricity consumption.

[0346] Example 7A

[0347] The system of Example 7, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0348] Example 8

[0349] 21 illustrates an exemplary system in which one or more aspects of the various embodiments may be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LODES system 1504 integrates large amounts of renewable generation into a microgrid, for example, blending the output of renewable generation by the PV station 1602 and the wind farm 1502 with existing thermal generation by, for example, a thermal power plant 2102 (e.g., a gas plant, a coal plant, a diesel generator set, etc., or a combination of thermal generation methods), and may be part of a power plant 2100 where the renewable and thermal generation serve the C&I customer 1902 loads when availability is high. A microgrid, such as a microgrid comprised of the power plant 2100 and the thermal power plant 2102, may provide an availability of 90% or higher. The power generated by the PV station 1602 and / or the wind farm 1502 may be delivered directly to the C&I customer 1902 or may be stored in the LODES system 1504 first. In a particular case, the power provided to the C&I customers 1902 may be entirely from the PV sites 1602, entirely from the wind farms 1502, entirely from the LODES systems 1504, entirely from the thermal power plants 2102, or from any combination of the PV sites 1602, the wind farms 1502, the LODES systems 1504, and / or the thermal power plants 2102. As an example, the LODES systems 1502 of the power plant 2100 may have a duration of between 24 hours and 500 hours.As a specific example, the C&I customer 1902 load may be 100 MW peak, the LODES system 1504 may be rated at 14 MW power and 150 hours duration, the cost of natural gas may be $6 / MMBTU, and the renewable occupancy may be 58%. As another specific example, the C&I customer 1902 load may be 100 MW peak, the LODES system 1504 may be rated at 25 MW power and 150 hours duration, the cost of natural gas may be $8 / MMBTU, and the renewable occupancy may be 65%.

[0350] Example 8A

[0351] The system of Example 8, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0352] Example 9

[0353] 22 illustrates an exemplary system in which one or more aspects of the various embodiments may be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LODES system 1504 can be used to enhance the nuclear power plant 2202 (or other inflexible generating facilities such as thermal, biomass, and / or any other type of power plant with a ramp rate of less than 50% of rated power in an hour and a capacity factor of 80% or higher) to add flexibility to the combined output of the power plant 2200 comprised of the combined LODES system 1504 and the nuclear power plant 2202. The nuclear power plant 2202 can be operated at a high capacity factor and at its highest efficiency point, and the LODES system 1504 can be charged and discharged to effectively reshape the output of the nuclear power plant 2202 to match customer electricity consumption and / or market price of electricity. As an example, the LODES system 1502 of the power plant 2200 may have a duration of 24 hours to 500 hours. In one specific example, the nuclear power plant 2202 may have a rated power output of 1000 MW, and the nuclear power plant 2202 may be forced to operate at minimum stable power generation or even shut down for extended periods of time due to a drop in the market price of electricity. The LODES system 1502 can avoid shutting down the facility during the market price drop and charge, and then the LODES system 1502 can discharge and restore full power generation during a market price rise.

[0354] Example 9A

[0355] The system of Example 9, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0356] Example 10

[0357] FIG. 23 illustrates an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 1504. As an example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of the batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.), alone or in various combinations. The LODES system 1504 may operate in conjunction with an SDES system 2302. The LODES system 1504 and the SDES system 2302 together may constitute a power plant 2300. As an example, the LODES system 1504 and the SDES system 2302 can be co-optimized, such that the LODES system 1504 can provide various services including long-term backup and / or bridging over multi-day variations (e.g., multi-day variations in market prices, renewable generation, electricity consumption, etc.). The SDES system 2302 can provide various services including quick backup services (e.g., voltage control, frequency regulation, etc.) and / or bridging over diurnal variations (e.g., diurnal variations in market prices, renewable generation, electricity consumption, etc.). The SDES system 2302 may have a duration of less than 10 hours and a round-trip efficiency of greater than 80%. The LODES system 1504 may have a duration of 24 hours to 500 hours and a round-trip efficiency of greater than 40%. In one such example, the LODES system 1504 may have a duration of 150 hours and can support customer electricity consumption for up to one week of renewable generation shortage. The LODES system 1504 can also support customer electricity consumption during daytime generation shortage events, enhancing the capacity of the SDES system 2302. Additionally, the SDES system 2302 can supply customers during daytime generation shortage events and provide quality services such as power conditioning and voltage control and frequency regulation.

[0358] Example 10A

[0359] The system of Example 10, wherein one or more of the storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R are used in the LODES system.

[0360] Example 11

[0361] Non-limiting examples according to embodiments of the invention were constructed and tested. An electrochemical cell using direct reduced iron (DRI) pellets was assembled and tested. The DRI pellets had the properties outlined in Table 4, characterized according to the methods described above. The electrochemical cell was a beaker-type cell with three electrodes (working, counter, and reference) and filled with liquid electrolyte. The electrolyte formulation was 5.5M KOH+0.5M LiOH+10mM Na2S. The counter electrode was a NiO / NiOOH electrode salvaged from a commercial Fe / Ni (Edison-type) cell. The reference electrode was a Hg / HgO (MMO) electrode filled with 5.5M KOH+0.5M LiOH solution. Stainless steel hose clamps were used to make electrical contact with the DRI pellets. Figure 24A shows the discharge specific capacity (mAh / g) during the first electrochemical discharge cycle (oxidation of DRI) when cycled at 5mA / g specific current. DRI ) shows the voltage of the DRI electrode versus the MMO reference as a function of

[0362] [Table 4]

[0363] Example 12

[0364] Another non-limiting example according to an embodiment of the present invention was constructed and tested. A family of ten (10) electrochemical cells using direct reduced iron (DRI) pellets were assembled and tested. The DRI pellets had the properties outlined in Table 4, characterized according to the methods described above. The electrochemical cells were beaker-type cells with three electrodes (working, counter, and reference) and filled with liquid electrolyte. The electrolyte formulation was 5.5M KOH+0.5M LiOH+10mM Na2S. The counter electrode was a NiO / NiOOH electrode salvaged from a commercial Fe / Ni (Edison-type) cell. The reference electrode was a Hg / HgO (MMO) electrode filled with a 5.5M KOH+0.5M LiOH solution. A stainless steel hose clamp was used to make electrical contact with the DRI pellets. The DRI was electrochemically cycled according to the following conditions: 1) precharge for 60 min at 25 mA / g specific current; 2) discharge to 0 voltage vs. MMO at 25 mA / g specific current; 3) charge at 25 mA / g specific current and terminate under coulomb limit with total charge equal to the first discharge capacity in mAh. Figure 24B shows the specific capacity (mAh / g) of the DRI electrode for the family of cells. DRI ) versus cycle number. The average capacity of all cells is plotted with error bars representing the 95% confidence interval. Figure 24C shows the coulombic efficiency (CE) of the same DRI cell.

[0365] Example 13

[0366] In another non-limiting example, a bed of spherical DRI pellets was tested in a beaker-type cell. The DRI pellets had the properties outlined in Table 4, characterized according to the methods described above. The pellet bed had a mass of 251.86 g. The electrolyte formulation was 5.5 M KOH + 0.5 M LiOH + 60 mM Na2S, and the volume of electrolyte used was 348 mL. The counter electrode was a stainless steel mesh (100 x 100 mesh). The anode potential was measured using a Hg / HgO (MMO) reference electrode filled with a 5.5 M KOH + 0.5 M LiOH solution. A stainless steel perforated plate was used as the current collector for the DRI pellet bed, and a stainless steel slab was used as the counter electrode current collector. The cell used a 5 mA / g specific current for both charge and discharge. Figure 24D shows the discharge specific capacity (mAh / g DRI ) shows the voltage of the DRI electrode versus the MMO reference as a function of

[0367] The above method descriptions are provided as illustrative examples only and are not intended to require or imply that the steps of the various embodiments must be performed in the order presented. As one skilled in the art would understand, the order of steps in the above embodiments may be performed in any order. Words such as "then," "then," and "next" are not necessarily intended to limit the order of steps, and such words may be used to guide the reader through the method description. Furthermore, any reference to a claim element in the singular, for example, using the article "a," "an," or "the," should not be construed as limiting the element to the singular. Furthermore, any step of any embodiment described herein may be used in any other embodiment.

[0368] The foregoing description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the basic principles defined herein may be applied to other embodiments without departing from the scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A first electrode, Electrolytes, and a second electrode, The battery, wherein only one of the first electrode and the second electrode is a porous iron electrode comprising direct reduced iron ("DRI").

2. 10. The battery of claim 1, wherein the DRI comprises iron ore, direct reduction grade iron ore, reduced taconite, wustite, magnetite, hematite, cementite, iron oxide, or any combination thereof.

3. 10. The battery of claim 1, wherein the DRI comprises DRI fines or powder.

4. 10. The battery of claim 1, wherein the porous iron electrode has a thickness greater than 0.1 cm.

5. 2. The battery of claim 1, wherein the DRI of the porous iron electrode is wetted with the electrolyte.

6. 10. The battery of claim 1, further comprising a current collector in electrical communication with the DRI of the porous iron electrode.

7. 7. The battery of claim 6, wherein the current collector is in contact with a bottom surface of the porous iron electrode, in contact with a side of the porous iron electrode, extends across the porous iron electrode, or any combination thereof.

8. 7. The battery of claim 6, wherein the DRI of the porous iron electrode is in contact with the current collector.

9. 10. The battery of claim 1, wherein the second electrode further comprises a slurry or gel.

10. 2. The battery of claim 1, wherein the first electrode is negative and comprises the porous iron electrode containing the DRI.

11. 10. The battery of claim 1, wherein the porous iron electrode is under compressive force.

12. 12. The battery of claim 11, wherein the compressive force acting on the porous iron electrode is greater than 7 KPa and less than or equal to 700 KPa.

13. 2. The battery of claim 1, wherein the porous iron electrode comprises particles of the DRI.

14. 14. The battery of claim 13, wherein the particles of the DRI have an average particle size greater than 10 nm and less than or equal to 1 mm.

15. 14. The battery of claim 13, wherein the particles of the DRI are irregularly shaped.

16. 14. The battery of claim 13, wherein macropores are defined between particles of the DRI, the particles of the DRI having a microporous surface.

17. 14. The battery of claim 13, wherein the particles of the DRI are agglomerated and physically connected.

18. 20. The battery of claim 17, wherein the particles of the DRI are agglomerated and sintered.

19. 10. The battery of claim 1, wherein the porous iron electrode is formed into a sheet.

20. 6. The battery of claim 5, wherein the DRI comprises greater than or equal to 90% and less than or equal to 98% metallic iron by weight, based on the total mass of the DRI.

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