Negative electrode for electrochemical cell

Abstract

Various embodiments provide a battery, a mass energy storage system including the battery, and / or a method of operating the mass energy storage system including the battery. In various embodiments, the battery may include 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, the DRI may be in the form of pellets. In various embodiments, the pellets may include at least about 60 wt% iron, by elemental mass, based on the total mass of the pellets. In various embodiments, one or both of the first electrode and the second electrode includes from about 60% to about 90% iron and from about 1% to about 40% of a component including one or more materials selected from the group consisting of SiO2, Al2O3, MgO, CaO, and TiO2.

Description

[0001] This divisional patent application is a divisional application of the patent application for invention titled "Negative Electrode for Electrochemical Cell" with the application number CN201980063958.6 and filed on July 26, 2019.

[0002] Related Applications

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 711,253, titled "Negative Electrode for Metal-Air Batteries", filed on July 27, 2018; U.S. Provisional Patent Application No. 62 / 790,668, titled "Negative Electrode for Metal-Air Batteries", filed on January 10, 2019; and U.S. Provisional Patent Application No. 62 / 868,511, titled "Negative Electrode for Metal-Air Batteries", filed on June 28, 2019. The entire content of all three applications is incorporated herein by reference for all purposes. Background Art

[0004] Energy storage technologies play an increasingly important role in the power grid; at the most basic level, these energy storage advantages contribute to better matching power generation and demand on the power grid. The services provided by energy storage devices are beneficial to the power grid across multiple time scales, from milliseconds to years. Currently, there are energy storage technologies that can support time scales from milliseconds to hours, but there is still a need for long-duration and ultra-long-duration (total ≥ 8 hours) energy storage systems.

[0005] This background art section is intended to introduce aspects of the art that may be associated with embodiments of the present invention. Therefore, the foregoing discussion in this section provides a framework for a better understanding of the present invention and should not be construed as an admission of prior art. Summary of the Invention

[0006] Materials, designs, and fabrication methods for metal electrodes of electrochemical cells are disclosed. In various embodiments, the negative electrode includes metal agglomerates arranged in one or more configurations, including multiple layers.

[0007] In various embodiments, the agglomerates may include one or more forms of iron, ranging from highly reduced (more metallic) iron to highly oxidized (more ionic) iron. In various embodiments, the agglomerates may include various iron compounds, such as iron oxide, iron hydroxide, iron sulfide, or combinations thereof. In various embodiments, the agglomerates may include one or more second phases, such as silicon dioxide (SiO 2 ) or silicate, calcium oxide (CaO), magnesium oxide (MgO), etc.

[0008] In various embodiments, the agglomerates can be sintered iron agglomerates having a variety of different shapes. In various embodiments, the sintered iron agglomerate particles can be formed in a furnace, such as a continuous-feed calciner, a batch-feed calciner, a shaft furnace, a rotary calciner, a rotary hearth furnace, etc. In various embodiments, the agglomerates can comprise reduced and / or sintered iron precursors in forms known to those skilled in the art, such as direct reduced iron (DRI) and / or its by-product materials. Various embodiments can include using mechanical, chemical, and / or thermal methods to treat the agglomerates, including DRI agglomerates, and then introducing the agglomerates into an electrochemical cell.

[0009] In various embodiments, the negative electrode can be a composite metal electrode composed of a mixture of spherical or substantially spherical metal agglomerates and a powdered metal feedstock. In various embodiments, the powdered metal feedstock can be wetted by the electrolyte. In various embodiments, the negative electrode can be composed of a mixture of iron ore (e.g., taconite, etc.) agglomerates and conductive DRI fines, sponge iron, and / or atomized iron. "DRI fines" should be understood to mean particles that are smaller in size than the DRI agglomerates but are produced simultaneously with the DRI agglomerates, or particles produced from the DRI agglomerates by crushing, processing, or thermal or chemical means.

[0010] In various embodiments, the negative electrode can include agglomerates that can be aggregated in an ordered array. In various embodiments, the agglomerates are packed in a bed such that macropores are created between two or more agglomerates in contact with each other. In various embodiments, the agglomerates can each include micropores. In various embodiments, the electrolyte can fill the micropores or macropores, or flow through the pore space surrounding the agglomerates that comprise the electrode.

[0011] In various embodiments, an iron powder layer can form an interface between the agglomerates of the negative electrode and the current collector, wherein the negative electrode further includes an iron powder layer that is configured to form an interface between the agglomerates and the current collector of the electrochemical cell.

[0012] Various embodiments can include systems and methods for monitoring the state of charge of a negative electrode that includes metal agglomerates arranged in one or more layers.

[0013] In various embodiments, the agglomerates can be synthesized in a first stage of a dual-purpose energy storage power station and used for the negative electrode in a second stage of the dual-purpose energy storage power station.

[0014] Multiple embodiments can provide a battery that includes a first electrode, an electrolyte, and a second electrode, wherein one or both of the first electrode and the second electrode include direct reduced iron ("DRI"). In multiple embodiments, the DRI is in the form of pellets. In multiple embodiments, based on the total mass of the pellets, the pellets include at least about 60 wt% iron by elemental mass. In multiple embodiments, the pellets include at least about 60 wt% metallic iron based on the total mass of the pellets, the average particle size of the pellets is from 4 mm to 20 mm, and the pellets account for at least 60% of the total mass of at least one of the first electrode and the second electrode. In multiple embodiments, the pellets include at least about 80 wt% metallic iron based on the total mass of the pellets. In multiple embodiments, the pellets include from about 90 wt% to about 98 wt% metallic iron based on the total mass of the pellets. In multiple embodiments, the pellets are spherical, rod-shaped, disc-shaped, plate-shaped, briquetted, or a combination thereof. In multiple embodiments, the pellets are briquetted and include hot briquetted iron. In multiple embodiments, the hot briquetted iron is formed from powdered iron fines or iron pellets. In multiple embodiments, the average length of the pellets ranges from about 10 mm to about 500 mm, the average width ranges from about 5 mm to about 250 mm, and the average height ranges from about 5 mm to about 200 mm. In multiple embodiments, the DRI includes iron ore, direct reduced grade iron ore, reduced iron chert, wustite, magnetite, hematite, cementite, iron oxide, or any combination thereof. In multiple embodiments, the DRI includes DRI fines or DRI powder. In multiple embodiments, the pellets have an average internal porosity ranging from about 10 vol% to about 90 vol%. In multiple embodiments, the pellets have a range of about 0.19 m 2 / g to about 18 m 2The average specific surface area per g. In multiple embodiments, the agglomerates have a volume-weighted average pore diameter ranging from 1 micron to 10 microns. In multiple embodiments, at least one of the first electrode and the second electrode has a thickness greater than 0.1 cm. In multiple embodiments, the agglomerates are spherical and have an average diameter ranging from about 0.5 mm to about 10 cm. In multiple embodiments, based on the total weight of the agglomerates, the agglomerates include more than 0.5 wt% of a silica-containing compound. In multiple embodiments, based on the total mass of the agglomerates, the agglomerates include about 1 wt% to about 5 wt% of a silica-containing compound by elemental mass. In multiple embodiments, based on the total mass of the agglomerates, the agglomerates include about 1 wt% to about 25 wt% of a silica-containing compound by elemental mass. In multiple embodiments, the packing fraction of the agglomerates in at least one of the first electrode and the second electrode is 30% to 74%. In multiple embodiments, the agglomerates include: a primary phase containing iron; and a second phase containing silicon or another metal. In multiple embodiments, the agglomerates include: a primary phase containing iron; and a second phase containing cementite. In multiple embodiments, the second phase contains silica or silicate. In multiple embodiments, the second phase includes titanium, vanadium, manganese, magnesium, calcium, phosphorus, carbon, aluminum, zirconium, or any combination thereof. In multiple embodiments, at least one of the first electrode and the second electrode includes a single layer of the agglomerates or multiple layers of the agglomerates. In multiple embodiments, the electrolyte penetrates between the agglomerates. In multiple embodiments, the battery further includes a current collector electrically connected to the agglomerates. In multiple embodiments, the current collector contacts the lower surface of at least one of the first electrode and the second electrode, contacts the side surface of at least one of the first electrode and the second electrode, extends through at least one of the first electrode and the second electrode, or any combination of the above. In multiple embodiments, the agglomerates are sintered iron agglomerated particles. In multiple embodiments, the sintered iron agglomerated particles are made using a continuous-feed calcination furnace, a batch calcination furnace, a shaft furnace, or any other type of furnace. In multiple embodiments, the second electrode further contains a slurry or a gel. In multiple embodiments, at least one of the first electrode and the second electrode is a composite metal electrode including a mixture of the agglomerates and a smaller metal agglomerate composition. In multiple embodiments, the smaller metal particle composition is a powdered metal feedstock. In multiple embodiments, the powdered metal feedstock is wetted by the electrolyte. In multiple embodiments, the smaller metal particle composition includes DRI fines, sponge iron, atomized iron, or any combination thereof. In multiple embodiments, the agglomerates contain DRI taconite.In multiple embodiments, the pellets are synthesized during a first operating stage of the dual - use energy storage power station including the battery and loaded into at least one of the first electrode and the second electrode during a second operating stage of the dual - use energy storage power station. In multiple embodiments, the pellets are packed in a bed such that macropores are created between two or more pellets in contact with each other; and each of the pellets includes micropores on its respective outer surface. In multiple embodiments, the pellets are fused together. In multiple embodiments, the pellets are pretreated chemically, mechanically, thermally, electrically, and / or electrochemically to fuse at least a portion of the pellets packed in the bed. In multiple embodiments, the battery further includes a pump configured to cause the liquid electrolyte to flow through the pellets in the packed bed. In multiple embodiments, each of the pellets includes micropores on its respective outer surface. In multiple embodiments, the pellets include pores created by immersing the pellets in an etching bath and then installing them into at least one of the first electrode and the second electrode. In multiple embodiments, the etching bath is an acid bath. In multiple embodiments, at least one of the first electrode and the second electrode further includes an additive pellet containing Bi. 2 O 3 or an additive pellet of metal sulfide. In multiple embodiments, the additive pellets include FeS, FeS 2 , Na 2 S or combinations thereof. In multiple embodiments, the pellets are sintered iron pellets composed of crushed direct reduced iron (“DRI”) precursors and / or DRI fines. In multiple embodiments, the pellets are pretreated mechanically, chemically, electrically, electrochemically, and / or thermally and then installed into at least one of the first electrode and the second electrode. In multiple embodiments, the pretreatment includes pre - charging the pellets. In multiple embodiments, the pellets are first composed of at least a portion of cementite (Fe 3C), and then operate the battery. In multiple embodiments, at least one of the first electrode and the second electrode further includes an iron powder layer configured to form an interface between the agglomerates and the current collector of the battery. In multiple embodiments, the battery may further include a monitoring system configured to monitor the state of charge (SOC) and / or the state of health of at least one of the first electrode and the second electrode. In multiple embodiments, the monitoring system includes one or more sensors connected to a controller. In multiple embodiments, the one or more sensors are selected from strain gauges, Mössbauer spectrometers, CCD detectors, ultrasonic transducers, ion-sensing electrodes, thermocouples, and gas sensors. In multiple embodiments, at least one of the first electrode and the second electrode is a composite metal electrode including a mixture of the agglomerates and a conductive material dispersed between the respective agglomerates. In multiple embodiments, the conductive material includes one or more conductive fibers, one or more wires, one or more grids, and / or one or more flakes. In multiple embodiments, the first electrode is a negative electrode and includes the DRI. In multiple embodiments, the battery may further include an additive delivery system configured to add one or more additives to the electrolyte. In multiple embodiments, the additive delivery system delivers liquid additives or solid additives. In multiple embodiments, the one or more additives include salts. In multiple embodiments, the salt is a carbonate or a polysulfide salt. In multiple embodiments, the one or more additives include sulfur-based additives. In multiple embodiments, the one or more additives include surfactant additives. In multiple embodiments, the one or more additives are configured to mitigate self-discharge and / or inhibit the hydrogen evolution reaction (HER). In multiple embodiments, at least one of the first electrode and the second electrode is under a compressive force. In multiple embodiments, at least one of the first electrode and the second electrode includes additional conductive material. In multiple embodiments, the additional conductive material surrounds the iron-containing agglomerates. In multiple embodiments, the additional conductive material is a foil, a sheet, a screen, or a wire.

[0015] Multiple embodiments can provide a method for operating an energy storage power station, including operating the energy storage power station to produce active materials; and using the active materials in the energy storage power station for long-term energy storage. In multiple embodiments, the production of the active materials can use renewable electric energy.

[0016] Multiple embodiments can provide a large-capacity energy storage system, including one or more batteries, where at least one of the one or more batteries includes a first electrode, an electrolyte, and a second electrode, and one or both of the first electrode and the second electrode include direct reduced iron ("DRI"). In multiple embodiments, at least one of the first electrode and the second electrode includes DRI and is a negative electrode including direct reduced iron ("DRI") pellets. In multiple embodiments, at least one of the first electrode and the second electrode further includes additive pellets. In multiple embodiments, the additive pellets are composed of FeS, FeS 2 , Bi 2 O 3 or metal sulfides. In multiple embodiments, the DRI includes sintered iron pellets composed of crushed direct reduced iron ("DRI") precursors and / or DRI fines. In multiple embodiments, the DRI is composed of direct reduced iron ("DRI") pellets that are mechanically pre-treated, chemically pre-treated, and / or thermally pre-treated and then installed in at least one of the first electrode and the second electrode. In multiple embodiments, the DRI includes at least about 60 wt% metallic iron based on the total mass of the pellets, the DRI includes direct reduced iron pellets with an average size of 4 mm to 20 mm, and the direct reduced iron pellets account for at least 60% of the total mass of at least one of the first electrode and the second electrode. In multiple embodiments, the large-capacity energy storage system is a long-duration energy storage (LODES) system.

[0017] Multiple embodiments can provide a long-duration energy storage system configured to hold a charge for at least 24 hours. The system includes a housing, a first electrode, a second electrode, and an electrolyte. The first electrode includes: about 60% to about 90% iron, and about 1% to about 40% of a component, the component including one or more materials selected from SiO 2 , Al 2 O 3 , MgO, CaO, and TiO 2 . In multiple embodiments, the component can include about 1.5% to about 7.5% of SiO 2 . In multiple embodiments, the component can include about 0.3% to about 3% of Al 2 O 3 . In multiple embodiments, the component can include about 0.25% to about 2% of MgO. In multiple embodiments, the component can include about 0.75% to about 2.5% of CaO. In multiple embodiments, the component can include about 0.25% to about 1.5% of TiO 2 . In multiple embodiments, the component can include about 1% to about 10% of SiO2 In multiple embodiments, the composition may include from about 0.2% to about 5% Al 2 O 3 In multiple embodiments, the composition may include from about 0.1% to about 10% MgO. In multiple embodiments, the composition may include from about 0.9% to about 10% CaO. In multiple embodiments, the composition may include from about 0.05% to about 5% TiO 2 In multiple embodiments, at least 50% of the iron is Fe 0 In multiple embodiments, at least 50% of the iron is metallic iron. In multiple embodiments, the iron includes Fe 0 、Fe 2+ and Fe 3+ In multiple embodiments, the storage system has a rated power of at least about 100 MW, a rated duration of at least about 100 hours, and an energy rating of at least 2,000 MWh. In multiple embodiments, the storage device is a system having a rated power of from about 50 MW to about 500 MW, a rated duration of from about 25 hours to about 500 hours, and an energy rating of from about 3,000 MWh to about 90,000 MWh. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a schematic diagram of an electrochemical cell according to multiple embodiments of the present disclosure.

[0019] Figure 2A is a schematic diagram of an electrochemical cell according to multiple embodiments of the present disclosure.

[0020] Figure 2B is a schematic diagram of an electrochemical cell according to multiple embodiments of the present disclosure.

[0021] Figure 3A is a schematic diagram of an example of a continuous-feed calciner according to multiple embodiments of the present disclosure, the continuous-feed calciner being configured to form sintered agglomerated particles.

[0022] Figure 3B is a process flow diagram of a method embodiment for forming a sintered porous metal electrode.

[0023] Figure 3C is a block diagram of a system embodiment for forming a sintered porous metal electrode.

[0024] Figure 3D is a block diagram of a system embodiment for forming a sintered porous metal electrode.

[0025] Figure 4Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure, the electrochemical cell including a composite metal electrode having spherical agglomerates and a metal feedstock.

[0026] Figure 5 Is a process flow diagram showing embodiments of a process for in-situ synthesis of active materials for large-scale energy storage systems using renewable overproduction.

[0027] Figure 6 Is Figure 1 Schematic diagram of an electrochemical cell, showing enlarged views of macropores and micropores according to various embodiments of the present disclosure.

[0028] Figure 7 Is according to various embodiments of the present disclosure Figure 1 Schematic diagram of an agglomerate of an electrochemical cell.

[0029] Figure 8A Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0030] Figure 8B Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0031] Figure 8C Schematic diagram of a series of fluidly connected electrochemical cells according to various embodiments of the present disclosure.

[0032] Figure 9 Schematic diagram of an electrochemical cell including a mixture of an active material and an additive material agglomerate according to various embodiments of the present disclosure.

[0033] Figure 10 Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0034] Figure 11 Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0035] Figures 12A - 12F Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0036] Figure 13A Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0037] Figure 13B Schematic diagram of an electrochemical cell according to various embodiments of the present disclosure.

[0038] Figure 14 Schematic diagram of a filtration device according to various embodiments of the present disclosure.

[0039] Figures 15 - 23 Multiple system instances are shown, where one or more aspects of multiple embodiments can be used as part of a bulk energy storage system.

[0040] Figures 24A - 24D Are graphs respectively showing the first-cycle discharge specific capacity (mAh / g DRI) of the DRI electrode, discharge vs. number of cycles, coulombic efficiency, and subsequent-cycle discharge specific capacity (mAh / g DRI). Detailed Description

[0041] Multiple embodiments will be described in detail with reference to the accompanying drawings. The same reference numerals are used throughout the drawings to refer to the same or similar parts as much as possible. References to specific examples and implementations are for illustrative purposes and are not intended to limit the scope of the claims. The following description of the embodiments of the present invention is not intended to limit the present invention to these embodiments, but to enable those skilled in the art to make and use the present invention. Unless otherwise noted, the drawings are not drawn to scale.

[0042] As used herein, unless otherwise noted, room temperature is 25 °C. Also, standard temperature and standard pressure are 25 °C and 1 atmosphere. Unless otherwise explicitly stated, all tests, test results, physical properties, and temperature-related, pressure-related, or both-related values are provided at standard ambient temperature and pressure.

[0043] Generally, unless otherwise noted, the terms "about" and the symbol "~" as used herein are intended to include variations or ranges of ±10%, or experimental error or instrument error associated with obtaining the value, preferably the larger of the two.

[0044] Unless otherwise noted, the recitation of numerical ranges herein is only intended as a shorthand method for separately referring to each individual value falling within the range. Unless otherwise stated herein, each individual value within a range is incorporated into the specification as if it were individually recited herein.

[0045] Unless otherwise noted, the terms "%" and "wt%" and "mass%" as used herein are used interchangeably and refer to the percentage by weight of the first component in the total weight, such as a formulation, mixture, particle, agglomerate, material, structure, or product. Unless otherwise noted, the "vol%" and "% volume" and similar such terms as used herein refer to the percentage by volume of the first component in the total volume, such as a formulation, mixture, particle, agglomerate, material, structure, or product.

[0046] The following examples are provided to illustrate multiple embodiments of the systems and methods of the present invention. These examples are for illustrative purposes, may be predictive, and should not be considered limiting, and do not otherwise limit the scope of the present invention.

[0047] It should be noted that there is no need to provide or elaborate on the underlying theories of the novel and breakthrough methods, materials, properties, or other beneficial features and characteristics related to or of the subject matter of the embodiments of the present invention. However, multiple theories are provided in this specification to further advance the technology in this field. The theories presented in this specification, unless otherwise explicitly stated, in no way limit, restrict, or narrow the scope of protection provided by the claimed invention. It may not be necessary or useful to practice these theories in using the present invention. It should also be understood that the present invention may lead to new and hitherto unknown theories to explain the functional characteristics of the embodiments of the methods, articles, materials, devices, and systems of the present invention; and these later-developed theories will not limit the scope of protection provided by the present invention.

[0048] The multiple embodiments of the systems, devices, technologies, methods, applications, and operations described in this specification can be used in multiple other applications and other fields in addition to those described herein. Furthermore, for example, these embodiments can be used in: other devices or applications that may be developed in the future; and existing devices or applications that can be partially modified according to the teachings of this specification. In addition, the multiple embodiments and examples described in this specification can be used together, either in whole or in part, and in different combinations and multiple combinations with each other. Therefore, the configurations provided in the multiple embodiments of this specification can be used together with each other. For example, the components of an embodiment having A, A', and B and the components of an embodiment having A", C, and D can be used together with each other in multiple embodiments according to the teachings of this specification, such as A, C, D and A, A", C, and D, etc. Therefore, the scope of protection provided by the present invention should not be limited to the specific embodiments, examples, or the specific embodiments, configurations, or arrangements described in the embodiments in the specific drawings.

[0049] Unless otherwise specified, the term "specific gravity" (also referred to as "apparent density") as used herein shall be given its broadest possible meaning and generally refers to the weight per unit volume of a structure, such as the volume shape of a material. This property will include the internal porosity of the particles as part of its volume. Among other techniques, a low-viscosity fluid that wets the particle surface can also be used for measurement.

[0050] Unless otherwise specified, when there are no voids in a material, the term "actual density" (which can also be referred to as true density) as used herein shall be given its broadest possible meaning and the general average weight per unit volume of the material. This measurement and property essentially eliminates any internal porosity in the material, for example, it does not include any voids in the material.

[0051] Therefore, porous foam balls (e.g., Nerf @The relationship between the three density properties is illustrated for a collection of balls (spheres). The weight of the balls filling the container is the volume density of the balls:

[0052]

[0053] The apparent density of a single ball is its weight compared to its spherical volume:

[0054]

[0055] The weight of the material forming the ball skeleton, i.e., the balls with all void volume removed, compared to the remaining volume of the material will be the actual density:

[0056]

[0057] Embodiments of the present invention include apparatuses, systems, and methods for long - term and ultra - long - term, low - cost energy storage. In this document, unless otherwise explicitly stated, the terms "long - term" and "ultra - long - term" and similar terms should be given their broadest possible meaning, including energy storage times of 8 hours or longer, such as an energy storage time of 8 hours, an energy storage time of 8 to 20 hours, an energy storage time of 20 hours, an energy storage time of 20 to 24 hours, an energy storage time of 24 hours, an energy storage time of 24 hours to one week, an energy storage time of one week to one year (e.g., from days to weeks to months), etc., and may include LODES systems. Further, unless otherwise explicitly stated, for the terms "long - term" and "ultra - long - term", "energy storage cells" including "electrochemical cells", and similar terms, the broadest possible interpretation should be given; including electrochemical cells that can be configured to store energy over time spans of days, weeks, or quarters.

[0058] Typically, in one embodiment, the long-duration energy storage cell can be a long-duration electrochemical cell. Generally, such a long-duration electrochemical cell can store electrical power generated by a power generation system under the following circumstances: (i) when the power source or fuel used for power generation is available, abundant, inexpensive, and combinations and variations thereof; (ii) when the power supply requirements or electrical power demands of the power grid, consumers, or other users are less than the amount of electrical power generated by the power generation system, and the price obtained by supplying electrical power to the power grid, consumers, or other users is lower than the economically viable point of power generation (e.g., the cost of power generation exceeds the market price of electrical power), and combinations and variations thereof; and (iii), combinations and variations of (i) and (ii) and other reasons. Then, when economic or other needs arise, the electrical energy stored in the long-duration electrochemical cell can be distributed to the power grid, consumers, or other users. For example, the electrochemical cell can be configured to store the energy generated by a solar cell during summer months when there is abundant sunlight and solar power generation exceeds the grid demand, and release the stored energy during winter months when sunlight is insufficient to meet the grid demand.

[0059] Multiple embodiments related to the use of direct reduced iron (DRI) as a material for a battery (or cell), as part of a battery (or cell), and combinations and variations thereof are discussed. In multiple embodiments, the DRI can be made of a material obtained by reducing natural iron ore or processed iron ore, or can be a material obtained by reducing natural iron ore or processed iron ore, such reduction being carried out without reaching the melting temperature of iron. In multiple embodiments, the iron ore can be taconite or magnetite or hematite or goethite, etc. In multiple embodiments, the DRI can be in the form of pellets, which can be spherical or substantially spherical. In multiple embodiments, the DRI can be porous, containing open and / or closed internal porosity. In multiple embodiments, the DRI can include a material that has been further processed by hot briquetting or cold briquetting. In multiple embodiments, the DRI can be produced by reducing iron ore pellets to form a more metallic (higher degree of reduction, lower degree of oxidation) material, such as metallic iron (Fe 0) Magnetite (FeO) or composite pellets containing metallic iron and residual oxide phases. In several non-limiting embodiments, the DRI can be reduced iron ore taconite, direct reduction ("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 manufacturing industry, DRI is sometimes referred to as "sponge iron", and this usage is particularly common in India. Embodiments of the iron materials for use in the several embodiments described herein, including, for example, embodiments of DRI materials, including as electrode materials, can have one, more, or all of the material properties described in Table 1 below. Unless otherwise expressly stated, the following terms used in this specification, including Table 1, have the following meanings: "specific surface area" refers to the total surface area of a material per unit mass, including the surface area of pores in a porous structure; "carbon content" or "carbon (% by weight)" refers to the percentage of the total carbon mass in the total mass of the DRI; "cementite content" or "cementite (% by weight)" refers to the percentage of the mass of Fe 3 The percentage of the mass of C in the total mass of the DRI; "total Fe (% by weight)" is the percentage of the total iron mass in the total mass of the DRI; "metallic Fe (% by weight)" refers to the percentage of the mass of iron in the Fe 0 state in the total mass of the DRI; "metallization" refers to the percentage of the mass of iron in the Fe 0 state in the total iron mass. Unless otherwise specified, weight percentages, volume percentages, and apparent densities used herein should be understood to exclude any electrolyte infiltrating the porosity or short-term additives within the porosity.

[0060] Table 1

[0061]

[0062]

[0063] * The specific surface area is preferably determined by the Brunauer-Emmett-Teller adsorption method ("BET"), and more preferably in accordance with BET as described in ISO 9277 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex ion adsorption, and protein deposition (PR) methods, can be used to provide results that can be correlated with the BET results.

[0064] The actual density is preferably determined by helium (He) pycnometry, more preferably as described in ISO 12154 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests can be employed to provide results that can be correlated with the He pycnometry results. The actual density may also be referred to in the art as "true density" or "skeletal density".

[0065] ***The apparent density is preferably determined by immersion in water, more preferably as described in ISO 15968 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests can be employed to provide results that can be correlated with the He pycnometry results. The porosity can be defined as the ratio of the apparent density to the actual density:

[0066]

[0067] ****d 孔，90％体积 is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as described in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests (such as gas adsorption) can be employed to provide results that can be correlated with the mercury intrusion results. d 孔，90％体积 is the pore diameter at which 90% of the total pore volume is greater than.

[0068] *****d 孔,50％表面积 is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as described in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests (such as gas adsorption) can be employed to provide results that can be correlated with the mercury intrusion results. d 孔,50％表面积 is the pore diameter at which 50% of the free surface area is greater than.

[0069] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as described in ASTM E246-10 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as titration after reduction with tin(II) chloride, titration after reduction with titanium(III) chloride, inductively coupled plasma (ICP) spectrometry, can be employed to provide results that can be correlated with the dichromate titration results.

[0070] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as described in ISO 16878 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests (such as bromine-methanol titration) can be employed to provide results that are correlated with the iron(III) chloride titration results.

[0071] The metallization rate (%) is preferably determined by the ratio of metallic Fe to total Fe, each preferably determined by the aforementioned methods.

[0072] # Carbon (wt%) is preferably determined by infrared absorption method after combustion in an induction furnace, more preferably in accordance with that described in ISO 9556 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as various combustion and inert gas fusion techniques (as described in ASTM E1019-18), can be used to provide results that can be correlated with the infrared absorption method after combustion in an induction furnace.

[0073] ## Fe 2+ (wt%) is preferably determined by titration method, more preferably in accordance with that described in ASTM D3872-05 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as Mössbauer spectroscopy, X-ray absorption spectroscopy, etc., can be used to provide results that can be correlated with the titration method.

[0074] $Fe 3+ (wt%) is preferably determined by the mass balance relationship between total Fe (wt%), metallic Fe (wt%), Fe 2+ (wt%) and Fe 3+ (wt%). Specifically, according to the law of conservation of mass, the equation of total Fe (wt%) = metallic Fe (wt%) + Fe 2+ (wt%) + Fe 3+ (wt%) must hold, so Fe 3+ (wt%) can be calculated by Fe 3+ (wt%) = total iron (wt%) - metallic Fe (wt%) - Fe 2+ (wt%).

[0075] $$SiO 2 (wt%) is preferably determined by gravimetric method, more preferably in accordance with that described in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), can be used to provide results that can be correlated with the gravimetric method. In some methods, SiO 2 wt% is not directly determined, but the Si concentration (including neutral and ionic substances) is measured, and the stoichiometry of SiO 2 is assumed to calculate SiO 2 wt%; that is, the molar ratio of Si:O is assumed to be 1:2.

[0076] $$$ Ferrite (wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0077] $$$$ Wüstite (FeO, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0078] Goethite (FeOOH, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0079] + Cementite (Fe 3 C, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0080] In addition, embodiments of the iron materials for use in the various embodiments described herein, including embodiments of DRI materials, including as electrode materials, may have one or more of the following properties, characteristics, or features (note that values from one row or column may occur with values from different rows or columns) as shown in Table 1A.

[0081] Table 1A

[0082]

[0083]

[0084] ! Total Fe (wt%) is preferably determined by dichromate titration, more preferably as described in ASTM E246-10 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as titration after reduction with tin(II) chloride, titration after reduction with titanium(III) chloride, inductively coupled plasma (ICP) spectrometry, may be used to provide results that can be correlated with dichromate titration.

[0085] !! SiO 2 (wt%) is preferably determined by gravimetry, more preferably as described in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), may be used to provide results that can be correlated with gravimetry. In some methods, SiO 2 wt% is not directly determined, but the Si concentration (including neutral and ionic species) is measured and the stoichiometry of SiO 2 is assumed to calculate SiO 2 wt%; i.e., the molar ratio of Si:O is assumed to be 1:2.

[0086] !!! Al 2 O 3 (wt%) is preferably determined by flame atomic absorption spectrometry, more preferably as described in ISO 4688-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as X-ray diffraction (XRD), may be used to provide results that can be correlated with flame atomic absorption spectrometry. In some methods, Al 2 O 3is not the weight %, but rather the Al concentration (including neutral and ionic species) is measured, and the stoichiometry of Al 2 O 3 is assumed to calculate the weight % of Al 2 O 3 ; that is, the molar ratio of Al:O is assumed to be 2:3.

[0087] !!!! The MgO (weight %) is preferably determined by flame atomic absorption spectrometry, more preferably as described in ISO 10204 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as X-ray diffraction (XRD), can be employed to provide results that can be correlated with those of flame atomic absorption spectrometry. In some methods, the MgO weight % is not directly determined, but rather the Mg concentration (including neutral and ionic species) is measured, and the stoichiometry of MgO is assumed to calculate the MgO weight %; that is, the molar ratio of Mg:O is assumed to be 1:1.

[0088] !!!!!! The CaO (weight %) is preferably determined by flame atomic absorption spectrometry, more preferably as described in ISO 10203 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as X-ray diffraction (XRD), can be employed to provide results that can be correlated with those of flame atomic absorption spectrometry. In some methods, the CaO weight % is not directly determined, but rather the Ca concentration (including neutral and ionic species) is measured, and the stoichiometry of CaO is assumed to calculate the CaO weight %; that is, the molar ratio of Ca:O is assumed to be 1:1.

[0089] &TiO 2 (weight %) is preferably determined by diantipyrylmethane spectrophotometry, more preferably as described in ISO 4691 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as X-ray diffraction (XRD), can be employed to provide results that can be correlated with those of diantipyrylmethane spectrophotometry. In some methods, the TiO 2 weight % is not directly determined, but rather the Ti concentration (including neutral and ionic species) is measured, and the stoichiometry of TiO 2 is assumed to calculate the TiO 2 weight %; that is, the molar ratio of Ti:O is assumed to be 1:2.

[0090] && The actual density is preferably determined by helium (He) pycnometry, more preferably as described in ISO 12154 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests can be employed to provide results that can be correlated with those of He pycnometry. The actual density may also be referred to in the art as "true density" or "skeletal density".

[0091] &&&The apparent density is preferably determined by immersion in water, more preferably as described in ISO 15968 (the entire disclosure of which is incorporated herein by reference); other tests may be employed to provide results that can be correlated with the helium pycnometry results.

[0092] &&&&The bulk density (kg / m 3 ) is preferably determined by measuring the mass of the test portion introduced into a container of known volume up to its surface level, more preferably as described in Method 2 of ISO 3852 (the entire content of which is incorporated herein by reference); it should be understood that other tests may be employed to provide results that can be correlated with the gravimetric method.

[0093] &&&&&The porosity is preferably determined by the ratio of the apparent density to the true density:

[0094]

[0095] In addition to or in place of the properties in Table 1A, the properties listed in Table 1 may also be present in the embodiments. Greater or lesser values of these properties may also be present in multiple embodiments.

[0096] In an embodiment, the specific surface area of the agglomerates can be from about 0.05 m 2 / g to about 35 m 2 / g, from about 0.1 m 2 / g to about 5 m 2 / g, from about 0.5 m 2 / g to about 10 m 2 / g, from about 0.2 m 2 / g to about 5 m 2 / g, from about 1 m 2 / g to about 5 m 2 / g, from about 1 m 2 / g to about 20 m 2 / g, greater than about 1 m 2 / g, greater than about 2 m 2 / g, less than about 5 m 2 / g, less than about 15 m 2 / g, less than about 20 m 2 / g, and combinations and variations of these specific surface areas, as well as greater or lesser values.

[0097] Typically, iron ore pellets are produced by crushing, grinding, or milling iron ore into a fine powder, and then concentrating it by removing the impurity phase (referred to as "gangue") released by the grinding operation. Generally, as the ore is ground into a finer (smaller) particle size, the purity of the resulting concentrate is increased. The concentrate is then pelletized through a pelletizing process or a balling process (such as using a drum pelletizer or a disk pelletizer). Generally, a higher energy input is required to produce iron ore pellets of higher purity. Iron ore pellets are typically sold or marketed in two main categories: blast furnace (BF) grade pellets and direct reduction (DR grade) (sometimes also referred to as electric arc furnace (EAF) grade), with the main difference being that the content of SiO 2 and other impurity phases in BF grade pellets is higher than that in DR grade pellets. Typical key parameters for DR grade pellets or feedstock are: the total Fe content (by mass percentage) ranges from 63 wt% - 69 wt% (e.g., 67 wt%) and the SiO 2 content (by mass percentage) is less than 3 wt% (e.g., 1 wt%). Typical key parameters for BF grade pellets or feedstock are: the total Fe content (by mass percentage) ranges from 60 wt% - 67 wt% (e.g., 63 wt%) and the SiO 2 content (by mass percentage) ranges from 2 wt% - 8 wt% (e.g., 4 wt%).

[0098] In certain embodiments, DRI can be produced by reducing "blast furnace" pellets, in which case the resulting DRI can have the material properties as described in Table 2 below. Since less input energy is required to produce the pellets, this translates into a lower cost of the finished material, so it may be advantageous to use reduced BF grade DRI.

[0099] Table 2

[0100]

[0101]

[0102] *The specific surface area is preferably determined by the Brunauer - Emmett - Teller adsorption method ("BET"), more preferably in accordance with BET as described in ISO 9277 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex ion adsorption, and protein deposition (PR) methods, can be used to provide results that can be correlated with the BET results.

[0103] The actual density is preferably determined by helium (He) pycnometry, more preferably in accordance with that described in ISO 12154 (the entire disclosure of which is incorporated herein by reference); it is understood that other tests may be employed to provide results that can be correlated with the results of He pycnometry. The actual density may also be referred to in the art as "true density" or "skeletal density".

[0104] ***The apparent density is preferably determined by immersion in water and more preferably in accordance with that described in ISO 15968 (the entire disclosure of which is incorporated herein by reference); it is understood that other tests may be employed to provide results that can be correlated with the results of He pycnometry. The porosity can be defined as the ratio of the apparent density to the actual density:

[0105]

[0106] ****d 孔，90％体积 is preferably determined by mercury intrusion porosimetry, more preferably in accordance with that described in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); it is understood that other tests (such as gas adsorption) may be employed to provide results that can be correlated with the results of mercury intrusion. d 孔，90％体积 is the pore diameter at which 90% of the total pore volume is greater than.

[0107] *****d 孔，50％表面积 is preferably determined by mercury intrusion porosimetry, more preferably in accordance with that described in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); it is understood that other tests (such as gas adsorption) may be employed to provide results that can be correlated with the results of mercury intrusion. d 孔,50％表面积 is the pore diameter at which 50% of the free surface area is greater than.

[0108] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably in accordance with that described in ASTM E246-10 (the entire disclosure of which is incorporated herein by reference); it is understood that other tests, such as titration after reduction with tin(II) chloride, titration after reduction with titanium(III) chloride, inductively coupled plasma (ICP) spectrometry, may be employed to provide results that can be correlated with the results of dichromate titration.

[0109] ##Metallic Fe (wt%) is preferably determined by ferric chloride (III) titration, more preferably in accordance with that described in ISO 16878 (the entire disclosure of which is incorporated herein by reference); it is understood that other tests (such as bromine-methanol titration) may be employed to provide results that are correlated with the results of ferric chloride (III) titration.

[0110] The metallization rate (%) is preferably determined by the ratio of metallic Fe to total Fe, each preferably determined by the foregoing methods.

[0111] # Carbon (wt%) is preferably determined by infrared absorption method after combustion in an induction furnace, more preferably in accordance with that described in ISO 9556 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as various combustion and inert gas fusion techniques (as described in ASTM E1019-18), can be used to provide results that can be correlated with the infrared absorption method after combustion in an induction furnace.

[0112] ## Fe 2+ (wt%) is preferably determined by titration method, more preferably in accordance with that described in ASTM D3872-05 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as Mössbauer spectroscopy, X-ray absorption spectroscopy, etc., can be used to provide results that can be correlated with the titration method.

[0113] Fe 3+ (wt%) is preferably determined by the mass balance relationship between total Fe (wt%), metallic Fe (wt%), Fe 2+ (wt%) and Fe 3+ (wt%). Specifically, according to the law of conservation of mass, the equation of total Fe (wt%) = metallic Fe (wt%) + Fe 2+ (wt%) + Fe 3+ (wt%) must hold, so Fe 3+ (wt%) can be calculated by Fe 3+ (wt%) = total iron (wt%) - metallic Fe (wt%) - Fe 2+ (wt%).

[0114] $$SiO 2 (wt%) is preferably determined by gravimetric method, more preferably in accordance with that described in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), can be used to provide results that can be correlated with the gravimetric method. In some methods, SiO 2 wt% is not directly measured, but the Si concentration (including neutral and ionic substances) is measured, and the stoichiometry of SiO 2 is assumed to calculate SiO 2 wt%; that is, the molar ratio of Si:O is assumed to be 1:2.

[0115] $$$ Ferrite (wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0116] $$$$ Wüstite (FeO, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0117] Goethite (FeOOH, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0118] + Cementite (Fe 3 C, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0119] In addition to or instead of the properties in Table 1 and / or Table 1A, the properties listed in Table 2 may also be present in embodiments. Greater or lesser values of these properties may also be present in various embodiments.

[0120] In certain embodiments, DRI can be produced by reducing DR pellets, in which case the resulting DRI can have the material properties described in Table 3 below. Since the higher Fe content in the pellets increases the energy density of the cell, it may be advantageous to use reduced DR grade DRI.

[0121] Table 3

[0122]

[0123] * The specific surface area is preferably determined by the Brunauer-Emmett-Teller adsorption method ("BET"), more preferably in accordance with BET as described in ISO 9277 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex ion adsorption, and protein deposition (PR) methods, can be used to provide results that can be correlated with the BET results.

[0124] ** The true density is preferably determined by helium (He) pycnometry, more preferably in accordance with that described in ISO 12154 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests can be used to provide results that can be correlated with the He pycnometry results. The true density may also be referred to as "true density" or "skeletal density" in the art.

[0125] *** The apparent density is preferably determined by immersion in water, more preferably in accordance with that described in ISO 15968 (the entire disclosure of which is incorporated herein by reference); other tests can be used to provide results that can be correlated with the He pycnometry results. The porosity can be defined as the ratio of the apparent density to the true density:

[0126]

[0127] ****d 孔，90％体积Preferably determined by mercury intrusion (Hg) method, more preferably in accordance with that described in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests (such as gas adsorption) can be used to provide results that can be correlated with the mercury intrusion results. d 孔，90％体积 is the pore diameter at which 90% of the total pore volume is greater.

[0128] *****d 孔，50％表面积 Preferably determined by mercury intrusion (Hg) method, more preferably in accordance with that described in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests (such as gas adsorption) can be used to provide results that can be correlated with the mercury intrusion results. d 孔,50％表面积 is the pore diameter at which 50% of the free surface area is greater.

[0129] # Total Fe (wt%) is preferably determined by dichromate titration method, more preferably in accordance with that described in ASTM E246-10 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as titration method after reduction with tin(II) chloride, titration method after reduction with titanium(III) chloride, inductively coupled plasma (ICP) spectrometry, can be used to provide results that can be correlated with the dichromate titration method.

[0130] ## Metallic Fe (wt%) is preferably determined by ferric(III) chloride titration method, more preferably in accordance with that described in ISO 16878 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests (such as bromine-methanol titration method) can be used to provide results related to the ferric(III) chloride titration method.

[0131] Metallization rate (%) is preferably determined by the ratio of metallic Fe to total Fe, each preferably determined by the aforementioned methods.

[0132] # Carbon (wt%) is preferably determined by infrared absorption method after combustion in an induction furnace, more preferably in accordance with that described in ISO 9556 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as various combustion and inert gas fusion techniques (as described in ASTM E1019-18), can be used to provide results that can be correlated with the infrared absorption method after combustion in an induction furnace.

[0133] ## Fe 2+ (wt%) is preferably determined by titration method, more preferably in accordance with that described in ASTM D3872-05 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as Mössbauer spectroscopy, X-ray absorption spectroscopy, etc., can be used to provide results that can be correlated with the titration method.

[0134] $Fe 3+(wt%) is preferably determined by the mass balance relationship among total Fe (wt%), metallic Fe (wt%), Fe2+ (wt%) and Fe 3+ (wt%). Specifically, according to the law of conservation of mass, total Fe (wt%) = metallic Fe (wt%) + Fe 2+ (wt%) + Fe 3+ (wt%) equation must hold, so Fe 3+ (wt%) can be calculated by Fe 3+ (wt%) = total iron (wt%) - metallic Fe (wt%) - Fe 2+ (wt%).

[0135] $$SiO 2 (wt%) is preferably determined by gravimetry, more preferably as described in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference); it should be understood that other tests, such as reduced molybdosilicate spectrophotometry, X-ray diffraction (XRD), can be used to provide results that can be correlated with gravimetry. In some methods, SiO 2 wt% is not directly measured, but the Si concentration (including neutral and ionic species) is measured, and the stoichiometry of SiO 2 is assumed to calculate SiO 2 wt%; that is, the molar ratio of Si:O is assumed to be 1:2.

[0136] $$$Ferrites (wt%, XRD) are preferably determined by X-ray diffraction (XRD).

[0137] $$$$Wüstite (FeO, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0138] $$$$$Goethite (FeOOH, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0139] + Cementite (Fe 3 C, wt%, XRD) is preferably determined by X-ray diffraction (XRD).

[0140] In addition to or instead of the properties in Table 1, Table 1A and / or Table 2, the properties listed in Table 3 may also be present in the embodiments. Larger or smaller values of these properties may also be present in multiple embodiments.

[0141] In various embodiments, the conductive granule bed includes (e.g., for providing, as a component, constituting, etc.) an electrode in an energy storage system. In embodiments of the electrode, the granules include iron-containing materials, reduced iron materials, non-oxidized iron, high-oxidized iron, iron with a valence of 0 to 3+, and combinations and variations of these materials. In embodiments of the electrode, the granules include iron having one or more of the characteristics listed in Table 1, Table 1A, Table 2, and Table 3. In embodiments, the granules have porosity, such as an open pore structure, which may have, for example, a pore size ranging from a few nanometers to a few microns. For example, embodiments may have the following pore sizes: about 5 nm (nanometer) to about 100 μm (micrometer), 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 these pore sizes, as well as larger or smaller pores. In some embodiments, the granules include granules of direct reduced iron (DRI). Embodiments of these electrodes in energy storage systems, particularly long-duration energy storage systems, may have one or more of these aforementioned features.

[0142] The packing of the pellets creates macropores, such as openings, spaces, channels or voids, between the individual pellets. The macropores facilitate ion transport through the electrode, which in some embodiments has a minimum size but is still very thick compared to some other types of battery electrodes that are several centimeters in size. The micropores inside the pellets allow the high surface area active material of the pellet to contact the electrolyte to achieve high utilization of the active material. This electrode structure is particularly suitable for improving the rate performance of very thick electrodes for static long-term energy storage, where thick electrodes may be required to achieve extremely high area capacity.

[0143] The pellets of these embodiments, especially the pellets in the embodiments of electrodes for long-term energy storage systems, can be of any volume shape, such as spheres, discs, cakes, beads, small pieces, small balls, rings, crystals, discs, plates, cones, truncated cones, blocks, rectangular blocks, trusses, corners, channels, hollow sealed cavities, hollow spheres, blocks, sheets, films, granules, bundles, rods, corners, flat plates, columns, fibers, short fibers, tubes, cups, pipes and combinations and multiples of these shapes and other more complex shapes. The pellets in the electrodes can be the same shape or different shapes. In a long-term energy storage system, the pellets in an electrode that is one of the multiple electrodes can be the same or different from the pellets in other electrodes in the storage system.

[0144] Unless otherwise explicitly specified, the size of an agglomerate refers to the maximum cross-sectional distance of the agglomerate, such as the diameter of a sphere. Agglomerates can be of the same size or different sizes. It is recognized that the shape, size, and both of the agglomerates, which are typically of an order of magnitude smaller than the shape and size of the container or housing that contains the agglomerates, determine the nature and size of the macropores in the electrode. Agglomerates can have dimensions of from about 0.1 mm to about 10 cm, from 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 of these dimensions.

[0145] In an embodiment, the agglomerates disposed in the electrode can provide an electrode having the following bulk density: about 3 g / cm 3 to about 6.5 g / cm 3 、about 0.1 g / cm 3 to about 5.5 g / cm 3 、about 2.3 g / cm 3 to about 3.5 g / cm 3 、3.2 g / cm 3 to about 4.9 g / cm 3 、greater than about 0.5 g / cm 3 、greater than about 1 g / cm 3 、greater than about 2 g / cm 3 、greater than about 3 g / cm 3 ,and various combinations of these values as well as greater or smaller values.

[0146] In certain embodiments, a mixture of reduced DR grade agglomerates and reduced BF grade agglomerates can be used together. In certain other embodiments, reduced material (DRI) and virgin ore material (DR grade or BF grade) can be combined.

[0147] In various embodiments, DRI can be produced by using "artificial ore" (such as iron oxide in the form of waste or by-products). As a non-limiting example, mill scale is a mixed iron oxide formed on the surface of hot-rolled steel. In various embodiments, the mill scale is collected and ground to form iron oxide powder, and then the powder is agglomerated to form agglomerates, which are subsequently reduced to form DRI. Other waste streams can be similarly used to form DRI. As another non-limiting example, acid leach solution is an acidic solution that can be rich in dissolved Fe ions. In various embodiments, the Fe-containing acid leach solution can be neutralized with a base (such as caustic potassium or sodium hydroxide) to precipitate iron oxide powder, and then the powder is agglomerated to form agglomerates, which are subsequently reduced to form DRI.

[0148] In multiple embodiments, the precursor iron oxide is first reduced and then pelletized or otherwise agglomerated. In certain non-limiting embodiments, iron oxide powder from natural or artificial ore is reduced to metallic iron powder by heat treatment at 900 °C in a reducing gas environment, such as in a linear hearth furnace in a hydrogen atmosphere (1% H 2 to 100% H 2 ). In embodiments using hydrogen as the reducing gas, the cementite (Fe 3 C) content of the DRI can be as low as 0 wt%.

[0149] In multiple embodiments, DRI pellets or DRI agglomerates are formed from iron oxide powder in a single process using a rotary kiln. The rotary motion of the kiln promotes the coalescence of the powder into pellets or agglomerates, while the high-temperature reducing gas environment simultaneously reduces the iron oxide. In multiple other embodiments, a multi-stage rotary kiln can be used, where the agglomeration step and the reduction step can be independently adjusted and optimized.

[0150] In multiple embodiments, the DRI has a non-spherical shape. In certain embodiments, the DRI can have a substantially linear or brick-like shape. In certain embodiments, the DRI can have a substantially cylindrical or rod-like or disc-like shape. In certain embodiments, the DRI can have a substantially planar or sheet-like shape. In certain embodiments, the iron oxide powder is formed into a cylindrical shape or any other shape suitable for molding by pressing. In certain embodiments, the iron oxide powder is roll-pressed and dried by calendering rollers to form a sheet form. In certain embodiments, the iron oxide powder is mixed with a binder (such as clay or polymer) and processed into a rod shape by extrusion drying. In certain embodiments, the iron oxide powder is mixed with a binder (such as clay or polymer) and roll-pressed and dried by calendering rollers to form a sheet form. The binder can consist of clay (such as bentonite) or polymer (such as corn starch, polyacrylamide, or polyacrylate). The binder can include bentonite, sodium carbonate, calcium chloride, calcium hydroxide, sodium silicate, carboxymethyl cellulose (CMC), Alcotac, Peridur, corn starch, Funa, wheat flour, sodium lignin sulfonate, molasses, or polyacrylate, etc. The binder can consist of a combination of one or more clays and one or more polymers. In certain embodiments, the iron oxide powder is dispersed in a liquid to form a slurry, and then the slurry is used for wet forming into various shapes. In certain embodiments, the iron oxide slurry is slip-cast into a mold of nearly any shape. In certain embodiments, the iron oxide slurry is coated onto a sheet by a doctor blade coating or other similar coating process.

[0151] In multiple embodiments, the conductive microporous pellet bed includes an electrode in an energy storage system. In some embodiments, the pellets include pellets of direct reduced iron (DRI). Packing of the pellets forms macropores between individual pellets. The macropores facilitate ion transport through the electrode. In some embodiments, the electrode has a minimum size but is still very thick compared to some other types of battery electrodes that are several centimeters in size. Compared to the micropores within the pellets, the macropores can form a pore space with a low curvature. The micropores within the pellets bring the high surface area active material within the pellets into contact with the electrolyte to achieve a high utilization rate of the active material. This electrode structure is particularly suitable for improving the rate performance of extremely thick electrodes for static long-term energy storage, where thick electrodes may be required to achieve extremely high areal capacities.

[0152] In multiple embodiments, short-acting pore formers are added during the production of DRI to increase the porosity of the resulting DRI. In one embodiment, the porosity of the DRI pellets is altered by adding a sacrificial pore former such as ice (solid H 2 O) during the granulation process, and the sacrificial pore former subsequently melts or sublimes under heat treatment. In some other embodiments, the short-acting pore former comprises naphthalene, which subsequently sublimes to leave pores. In other embodiments, a short-acting pore former comprising NH 4 CO 3 (ammonium carbonate) can be a short-acting pore former and can be introduced as a solid at multiple points during DRI production and decomposes upon heating and is completely removed as a gaseous substance or a liquid substance (NH 3 +CO 2 +H 2 O). In multiple other embodiments, the short-acting additive can serve an additional role in the cell (e.g., as an electrolyte component). In some embodiments, the short-acting additive can be an alkaline salt, such as KOH, NaOH, or LiOH. In some embodiments, the short-acting additive can be a soluble electrolyte additive that is in solid form under dry conditions, such as lead sulfate, lead acetate, antimony sulfate, antimony acetate, sodium molybdate oxide, potassium molybdate oxide, thiourea, sodium stannate, ammonium thiosulfate. In multiple other embodiments, the short-acting additive can be an adhesive for coalescing iron ore powder to form pellets or other shapes, such as sodium alginate or carboxymethyl cellulose adhesives.

[0153] In multiple embodiments, sacrificial pore formers, convertible pore formers, short-lived pore formers, removable pore formers, or techniques can be used. In these embodiments, the intermediate material with the pore former remaining can have a total Fe weight percentage in the range of 20 wt% to 90 wt%. The pore former can be partially removed before being used as an electrode, completely removed before being used as an electrode, or removed during the use as an electrode, as well as combinations and variations of these methods. In one embodiment, the intermediate can have a total of 25 wt% to 50 wt% of Fe, and after removing the pore former, an electrode with a total of 60 wt% to 90 wt% of Fe is provided.

[0154] In certain embodiments, the reducing gas used to form DRI is hydrogen (H 2 ). In certain embodiments, the hydrogen used as the reducing gas is a by-product of an industrial process, a chemical process, or a manufacturing process. In certain embodiments, hydrogen is produced by electrolyzing water from a renewable power source (such as wind or solar energy). In certain embodiments, the electrolyzer is coupled to an 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, hydrogen is a by-product of a chlor-alkali process or chlor-alkali equipment. In embodiments where hydrogen is used as the reducing gas, the cementite (Fe 3 C) content of the DRI can be as low as 0 wt%.

[0155] In certain embodiments, natural gas (methane, CH 4 ) is used as the reducing agent for producing DRI. In some embodiments, the natural gas used is obtained from naturally occurring underground deposits or agriculture. In certain embodiments, the methane used as the reducing gas is a by-product of an industrial process, a chemical process, or a manufacturing process. In certain embodiments, methane is steam reformed (by reaction with water (H 2 O)) to produce a mixture of carbon monoxide (CO) and hydrogen (H 4 +) through the reaction CH 2 +H 2 O → CO + 3H 2 . In certain embodiments, the reforming reaction is carried out in an auxiliary reformer separate from the reactor where iron reduction 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 the reducing agent for producing DRI. In certain embodiments, coke is used as the reducing agent for producing DRI. In embodiments where a carbon-containing reducing gas is used, the cementite (Fe 3 C) content of the DRI can be higher, up to 80 wt%.

[0156] In certain embodiments, mixtures of DRI produced using multiple reducing gases can be used to achieve beneficial combinations of composition and properties. In one non-limiting embodiment, a mixture (mass ratio 50 / 50) 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 negative electrode of a battery. Other combinations of mass ratio, feedstock type (DR, BF, other artificial ores, etc.), and reducing medium (hydrogen, natural gas, coal, etc.) can be combined in other embodiments.

[0157] In multiple embodiments, DRI pellets can be crushed, and the crushed pellets can include a bed (with or without added powder).

[0158] In multiple embodiments, additives beneficial for electrochemical cycling, such as hydrogen evolution reaction (HER) inhibitors, can be added to the bed in solid form (e.g., as a powder or as solid pellets).

[0159] In some embodiments, the metal electrode can have a low initial specific surface area (e.g., less than about 5 m 2 / g, preferably less than about 1 m 2 / g). Such electrodes tend to have a low self-discharge rate in low-rate, long-duration energy storage systems. An example of a low specific surface area metal electrode is a bed of DRI pellets. In many typical modern electrochemical cells (e.g., lithium-ion batteries or nickel-metal hydride batteries), a high specific surface area is required to promote high-rate performance (i.e., high power). In long-duration systems, the rate performance requirements are significantly reduced, so electrodes with a low specific surface area can meet the target rate performance requirements while minimizing the self-discharge rate.

[0160] In some embodiments, the DRI pellets are treated by mechanical, chemical, electrical, electro - chemical, and / or thermal methods and then used in an electrochemical cell. Such pretreatment can achieve superior chemical and physical properties and can, for example, increase the available capacity during the discharge reaction. The physical and chemical properties of as - purchased (sometimes also referred to as "as - received") DRI may not be suitable for use as the negative electrode of an electrochemical cell. The improved chemical and physical properties can include introducing a higher content of desired impurities (such as HER inhibitors), obtaining a lower content of unwanted impurities (such as HER catalysts), obtaining a higher specific surface area, obtaining a higher total porosity, achieving a pore size distribution different from the initial DRI (e.g., a multimodal pore size distribution to reduce mass transfer resistance), achieving a desired particle size distribution (e.g., a multimodal particle size distribution that fills the pellets to a desired density), and altering or selecting pellets with a desired aspect ratio (to achieve a desired bed packing density). Mechanical treatment can include tumbling, milling, crushing, grinding, and pulverizing. Chemical treatment can include acid etching. Chemical treatment can include soaking a bed of pellets in an alkaline solution to create necking between the pellets, coarsen the micropores within the pellets, or dissolve impurities or a second phase to increase the percentage of pore volume or alter the pore size distribution. Heat treatment can include treating the DRI at an elevated temperature in an inert, reducing, oxidizing, and / or carburizing atmosphere. In various embodiments, the mechanical, chemical, electrical, electro - chemical, and / or thermal methods for pretreating the material (such as DRI pellets, etc.) that forms the electrode can fuse the material that forms the electrode into a bed (such as a bed where DRI pellets are fused together).

[0161] In the embodiments described herein, iron materials can be treated, chemically modified, mechanically modified, or otherwise configured to change one or more of their characteristics. These methods are generally described herein as being performed on DRI materials. It should be understood that these methods can be used for other iron - containing materials, such as reduced iron materials, non - oxidized iron, highly oxidized iron, iron with a valence from 0 to 3 +, and combinations and variations of these iron materials. In this way, iron - containing pellets are provided for use in the electrode configuration of a long - duration electricity - storage cell, the iron - containing pellets having predetermined characteristics, such as those described in this specification.

[0162] In certain embodiments, mechanical operations are performed on the DRI to grind, buff, or polish the surface and / or remove fines. In one embodiment, the DRI pellets are rolled in a trommel screen to buff the surface and remove fines / dust from the surface. This operation can have the beneficial effects of reducing the reactivity of the DRI pellets, making their transportation easier and safer without the need for briquetting or other compaction operations. In another embodiment, passing DRI blocks or DRI sheets under a rotating brush to remove fines from the surface has similar beneficial effects.

[0163] In one embodiment, the DRI is pretreated by immersion in an acid bath (e.g., concentrated HCl) to increase porosity. The acid bath etches iron and creates larger pores, thereby increasing the total porosity. The etching time can be optimized to increase the total capacity of the DRI pellets without losing too much of the active material of the DRI in the acid etching solution.

[0164] In another embodiment, the desired impurities or additives are incorporated into the DRI. When these impurities are solids, they can be incorporated into the powder additives together with the DRI pellets by ball milling (e.g., using a planetary ball mill or similar device), and the pellets act as their own grinding medium. The powder additives are mechanically introduced into the pores or surfaces of the DRI pellets in this way. The DRI can also be coated with beneficial additives, e.g., by rolling or dipping in a slurry containing the additives. These desired impurities can include alkali sulfides. Alkali sulfides have been shown to greatly improve the utilization rate of the active material in the Fe anode. Just as soluble alkali sulfides can be added to the electrolyte, insoluble alkali sulfides can be added to the DRI, e.g., by the above methods.

[0165] In multiple embodiments, the specific surface area of the DRI is increased by 3 times or more, preferably 5 times or more, as measured by techniques such as the Brunauer - Emmett - Teller gas adsorption method. In some embodiments, the increase in surface area is achieved by using the DRI as an electrode in an electrochemical cell and electrochemically reducing it by an applied current.

[0166] In some embodiments, the surface area of a material containing cementite or iron carbide (e.g., DRI pellets containing cementite or iron carbide) is increased by using the material as the anode of an electrochemical cell and discharging it. In certain embodiments, the specific current density can be from 0.1 mA / g to 25 mA / g. This high - surface - area iron oxide can also be used in a variety of applications other than electrochemical cells.

[0167] In multiple embodiments, to increase conductivity, pellets can be mixed with a more conductive but potentially more expensive powder to produce a composite bed with higher conductivity. The powder can increase the areal capacity of the cell by filling the voids between the pellets. This can reduce the electrolyte volume to DRI pellet ratio in a systematically varied and optimized manner. In one embodiment, the powder is used in the current collector region 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. Variations in particle size in the composite bed can result in controllable costs and conductivity. In another example, the use of additional powders, wires, meshes, yarns, or woven fabric conductive materials enables the use of low-conductivity pellets in the composite bed by increasing the total conductivity, such as insufficiently metallized (sometimes referred to as "remet" in the industry) DRI pellets or direct reduced iron pellets. In one embodiment, the conductive portion can include DRI fines or other waste from the DRI process.

[0168] The ratio of electrolyte to iron material (such as DRI material) in the cell can be about 0.5 mL 电解质 : 1 g 铁材料 to about 5 mL 电解质 : 1 g 铁材料 、about 0.6 mL 电解质 : 1 g 铁材料 to about 3 mL 电解质 : 1 g 铁材料 、about 0.6 mL 电解质 : 1 g 铁材料 、about 0.7 mL 电解质 : 1 g 铁材料 、about 0.8 mL 电解质 : 1 g 铁材料 、about 1 mL 电解质 : 1 g 铁材料 and their combinations and variations, as well as larger and smaller ratios.

[0169] In one embodiment, a porous sintered iron electrode can be formed from DRI, for example, by crushing or grinding to reduce the DRI particle size or making the DRI into a powder. DRI fines or other waste can also be used to form the sintered iron electrode. The sintered electrode can be formed with a binder under heat and / or pressure, and then the binder can be burned out and the green body sintered at a high temperature. It is also possible to directly fuse the DRI pellets together by sintering in a non-oxidizing atmosphere, optionally applying pressure, to establish electrical and physical connectivity between the pellets.

[0170] In multiple embodiments, a porous negative electrode can be formed by crushing, chopping, or grinding hot briquetted iron (HBI). In multiple embodiments, HBI is preferred for shipping and transportation due to its lower surface area and reactivity, but due to ion transport limitations, the porosity of HBI may be too low for practical applications in thick electrodes. To achieve an optimal combination of transportation and performance, DRI can be transported in briquette form to the location of cell assembly or manufacturing, where the DRI is crushed, ground, and / or chopped to increase the porosity of the resulting electrode.

[0171] A packed bed of DRI pellets may be an ideal configuration for an iron-based electrode because it provides a conductive percolation path through the packed bed while leaving porosity that can be occupied by an electrolyte that facilitates ion transport. In some embodiments, the ratio of electrolyte volume to DRI mass can range from 0.5 mL / g to 5 mL / g, such as 0.6 mL / g or 1.0 mL / g. Compared to the surface area of the pellets, DRI pellets typically contact surrounding pellets through small contact areas, and in some cases, such contact can be considered "point contact". The small cross-sectional contact may limit current flow, which may result in a relatively low conductivity across the entire pellet bed, and in turn may result in a high electrode overpotential and low voltaic efficiency of the battery.

[0172] In multiple embodiments, the conductivity of a DRI pellet bed can be increased in a variety of ways. In some embodiments, the conductivity of the DRI pellet bed can be increased by using additional conductive materials that can surround individual pellets, be embedded within individual pellets, surround the entire pellet bed, or penetrate the pellet bed. The conductive material can be one or more of a metal, metal oxide, metal carbide, metal nitride, semiconductor, carbon, conductive polymer, or a composite including at least one such conductive material. The conductive material can be in the form of a powder, wire, mesh, or sheet. In some embodiments, the conductive material itself can participate in the electrochemical reactions in the battery, including but not limited to providing storage capacity. In some other embodiments, the conductive material is substantially electrochemically inactive. In one embodiment, the conductive material is a powder, and the powder fills or partially fills the space between pellets or between the pellets and the current collector to improve the conductivity between the pellets or between the pellets and the current collector. For example, the conductive powder can consist of DRI "fines", which are powdery waste products of the direct reduction process and have a composition similar to that of DRI. In this case, the fines can be used to increase the conductivity of the bed and the storage capacity of the anode. In another embodiment, the conductive material is a powder, and the powder is applied to the surface of the pellets to form a coating. Such a coating provides a larger area for electrical contact between the pellets.

[0173] In multiple embodiments, a conductive coating is applied to low-conductivity pellets to enable their use in an electrode. In certain embodiments, low-conductivity pellets can be coated, such as taconite pellets that are not fully metallized (sometimes referred to in the industry as "remet") or direct reduced iron (DRI) pellets. The coating can be conductive to reduce the resistance from the current collector to the taconite pellets during an initial reduction step. The coating can be removed or not removed during or after the reduction step. In one embodiment, the coating is a thin conformal metal layer, such as stainless steel, that circumferentially wraps around each pellet. In another embodiment, the coating is a thin lead layer that coats the exterior of each pellet using a directed deposition technique such as sputtering, evaporation, or other physical vapor deposition techniques. In certain embodiments, the coating is applied by rolling the DRI and the coating material together in a rotating container. In certain embodiments, the DRI in the rotating container is substantially spherical.

[0174] In another embodiment, some or all of the individual pellets in a pellet bed are wrapped with conductive wires, foils, or sheets. In some embodiments, a tensioning mechanism, such as a screen, is used to apply tension to the wire, foil, or sheet. Optionally, such a current collector around an individual pellet can be attached to a bundled wire or connected to a larger current collector. In another example, a conductive mesh, yarn, or fabric is spread in the space between DRI pellets to increase electrical connection. In multiple embodiments, the conductive material is a mesh with openings (net size) that are selected to be smaller than the pellets such that the pellets do not pass through the mesh. In such cases, the conductive material can be stainless steel, nickel, or other metals and metal alloys. In another example, the DRI pellets are directly connected to each other by wires passing through or around the individual pellets. For example, a wire can be passed through holes in the DRI pellets, similar to forming a string of beads, resulting in electrical contact not only between the pellets but also within the pellets. Optionally, electrical terminals or "plugs" can be used to keep the pellet string in contact, and tension can optionally be applied to the wire at the electrical terminal or "plug". The electrical terminal can optionally be electrically connected to a larger current collecting device, such as a plate.

[0175] In another embodiment, the conductivity of the pellet bed can be increased by applying a compressive load to the DRI pellet bed anode to increase the inter-pellet forces and / or the contact area between pellets or between the pellets and the current collector, thereby reducing the contact resistance and enhancing the electrochemical performance. Typical DRI pellets are approximately spherical in shape and have internal pores and can elastically deform to >5% linear strain before yielding. Applying a load to the compressed DRI bed can increase the effective contact area at the interfaces between the pellets and between the pellets and the current collector. It is advantageous to use pellets having a yield strain that allows deformation to achieve the desired increase in conductivity without cracking. In one embodiment, pellets having a compressive strength of 700 psi to 2500 psi are used in a pellet bed electrode to which a compressive load is applied. Additionally, the mechanical assembly that provides the compressive load on the pellet bed can also serve as the current collector. The resistance of such a pellet bed (measured in the dry state before filling with liquid electrolyte) can be reduced by a factor of two to 100-fold or more by applying a compressive load. In certain embodiments, the applied load can range from 0.1 psi to 1000 psi, such as 50 psi or 100 psi. In certain embodiments, the applied load can range from 0.1 psi to 10 psi, such as 1 psi or 5 psi. In one example, metal plates on opposite sides of the pellet bed are used to provide current collection and a compressive load on the pellet bed. Optionally, one or more of the plates can be replaced with a macroporous current collector (e.g., a metal mesh) to facilitate ion transport throughout the electrode. Preferably, the opposite current collectors are connected such that they are at the same electric potential, thereby facilitating a more uniform rate of electrochemical reaction throughout the electrode. In another example, the container that holds the pellet bed serves both as the current collector and as a means for applying a compressive load. In another embodiment, an array of conductive posts (or rods) connected to a common, bottom-facing current collector is used. Thus, many current collection regions can be placed throughout the pellet bed. This method can also reduce the effective transport length within the electrode from the total pellet bed thickness to the spacing between the posts. Additionally, these posts can be used to secure a mechanical clamping mechanism, such as a plate or a perforated plate at the top of the pellet bed, to integrate the downward force onto the pellet bed while serving as current collecting elements.

[0176] In some embodiments, the compressive load can be provided in part or in whole by magnetic forces. For example, a force can be applied using permanent magnets located on one or more sides of the bed such that the pellets in the bed are attracted to the magnets. For a DRI pellet bed that is predominantly metallic iron, it is expected that the pellet bed is predominantly ferromagnetic and that the pellet bed will be attracted to the magnets. The magnets can also be embedded in other fixtures surrounding the pellet bed. The magnets and fixtures are used to hold the pellet bed in place and provide compressive stress, thereby resulting in improved electrical contact between the pellets and between the pellets and the current collector as described above.

[0177] In some embodiments, the inter-pellet contact resistance in a pellet bed can be reduced by using a pre-treatment applied to the pellet bed, followed by battery assembly and / or battery operation. Several such pre-treatment processes are described in the following paragraphs.

[0178] In some embodiments, the entire DRI pellet is filled into the bed and sintered in an inert atmosphere or a reducing (i.e., non-oxidizing) atmosphere, optionally with mechanical pressure applied during sintering, e.g., using a material that is stable at the sintering temperature and atmosphere. The sintering temperature can range from 600 °C to 1100 °C. The non-oxidizing atmosphere can consist partially or entirely of an inert gas (e.g., nitrogen or argon). The non-oxidizing atmosphere can also include a gas mixture that tends to reduce iron, such as CO and CO 2 and H 2 and H 2 O. The exact composition of the mixture can be optimized according to the Ellingham diagram to ensure that the oxidation of iron is thermodynamically unfavorable. In one embodiment, forming gas (5% H 2 , 95% N 2 ) is used at a sintering temperature of about 600 °C to about 1100 °C (e.g., 600 °C to about 850 °C, 850 °C, about 850 °C to about 1100 °C, etc.) to provide non-oxidizing conditions. The combination of high temperature and non-oxidizing atmosphere may promote atomic diffusion and pellet coarsening at the pellet contacts, resulting in the pellets binding to each other. As a result, the DRI pellet bed fuses together with a low inter-pellet contact resistance. The pellets can also be fused to the current collector by the same method.

[0179] In another embodiment, the pellets are bonded using a heat treatment, where a flux or sintering aid is used to significantly reduce the heat treatment temperature required to form a sintering neck between the pellets. Examples of fluxes or sintering aids include one or more metals with a melting point lower than that of iron, such as zinc, tin, copper, aluminum, bismuth, and lead, or metals that form an alloy with iron and have a melting point lower than that of iron (e.g., metals presenting a low melting point eutectic liquid). Other examples of sintering aids include one or more glass-forming compositions, including but not limited to silicates, borates, and phosphates.

[0180] In another embodiment, the pellets can be electrically fused together by a process such as welding. In some such embodiments, the welding is accomplished by passing an electric current through the pellet bed. In some such embodiments, such a current is delivered by discharging a capacitor.

[0181] In multiple embodiments, the anode electrode is an ordered array of agglomerates. In certain embodiments, the agglomerates are arranged as cylinders. In certain embodiments, the agglomerates are arranged as plates. In certain embodiments, the agglomerates are arranged as discs. In certain embodiments, the agglomerates are arranged as rectangular prisms. In certain embodiments, the agglomerates are arranged as hexagonal prisms. In certain embodiments, the agglomerates are arranged in any volume.

[0182] In multiple embodiments, an electrolyte management system can be provided, where different electrolyte additives or formulations are added to the battery when switching between operating states. The optimal electrolyte formulations for operation during battery charge, discharge, and idle states can be quite different. The electrolyte management systems of multiple embodiments can improve the capacity utilization of the iron electrode, the self-discharge of the cell, and inhibit the hydrogen evolution reaction (HER). One or more of such benefits can be achieved simultaneously. In one embodiment of such an electrolyte management system, any number of different electrolyte formulation reservoirs are provided, each connected to the electrochemical cell through a separate flow controller. During different operating phases, different relative amounts of each electrolyte formulation flow into the cell based on the optimal concentration of the constituent substances 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 battery charge.

[0183] Multiple embodiments can provide methods and apparatus for maintaining the liquid electrolyte level in a battery. When a container filled with water is exposed to air, evaporation will occur until the partial pressure of water vapor in the air equals the vapor pressure of water at the system temperature. Specifically, the same evaporation will occur for an aqueous electrolyte exposed to the ambient electrochemical system. Dehydration of the electrolyte can cause problems due to the reduction in electrolyte volume, and changes in electrolyte concentration can alter the electrochemical performance. To mitigate this problem, in multiple embodiments, the level of the electrolyte can be maintained by a constant or intermittent inflow of electrolyte into the cell volume. Specifically, the electrolyte level can be maintained by introducing electrolyte into the container until it flows out of the overflow point. Since the liquid level cannot rise above this overflow point, the liquid level can be maintained in a relatively controlled manner. Specifically, multiple volumes can be arranged in cascade such that the overflow from one chamber can flow into the next chamber, thereby establishing "liquid communication" between the cells. Connecting these cells in series allows a single source to supply liquid electrolyte to multiple cells simultaneously. The overflow from the final container can be recycled to the first container. In a system that utilizes shared electrolyte, where the electrolyte flows in a cascading manner between the cells, the properties of the electrolyte can be monitored and processed at a central location for many cells. To mitigate problems related to electrolyte carbonation, electrolyte dehydration, etc., electrolyte adjustments, such as compositional adjustments or addition of components, can be advantageously performed at this collection source of the recycled electrolyte.

[0184] Multiple embodiments can provide compositions and methods for adding beneficial additives to the electrolyte of an aqueous electrochemical cell. During the charging of an aqueous secondary cell, the electrolytic production of hydrogen can lead to low coulombic efficiency, gas accumulation within the cell housing, safety issues, and consumption of the electrolyte. Additionally, self-discharge of metal electrodes can occur through the spontaneous reaction of the metal with the electrolyte to form metal hydroxides, in which hydrogen is produced as a product. Certain solid-phase hydrogen evolution inhibitors (e.g., Bi, Sb, As) can reduce these detrimental effects, but integrating solid-phase inhibitors into the porous metal electrodes of the battery can be expensive and pose manufacturing difficulties. Thus, in multiple embodiments, soluble salts of the desired hydrogen evolution inhibitors are added to the liquid electrolyte and dissolved to provide the ions of the desired additives in solution (e.g., Bi 3+ 、Sb 3+ 、As 3 + ). The additives are selected such that the redox potential of the inhibitor's ion-metal electroplating reaction (e.g., Bi 3+ →Bi 0 ) occurs at a half-cell potential higher than the charging reaction potential of the anode active material (measured relative to RHE but at a lower cell potential). Thus, during battery charging (reduction of the metal electrode), the HER inhibitor in ionic form is electrodeposited onto the surface of the metal electrode, providing a cheap and simple strategy for introducing the HER inhibitor into the battery electrolyte chemistry. The electrodeposited inhibitor inhibits the hydrogen evolution reaction on the electrode surface, which can be an electrode with open pores. In the discharge mode, the deposit may dissolve back into the electrolyte. The salt additive is preferably selected such that it does not degrade the operation of the cathode during charge or discharge operation.

[0185] In another embodiment, the electrochemical cell includes an electrode on which a hydrogen oxidation reaction (HOR) occurs to capture the hydrogen produced in the HER side reaction, thereby mitigating the escape of potentially hazardous hydrogen gas. Hydrogen gas bubbles generated during the HER process may be captured and exposed to the HOR electrode, which can be the working electrode of the battery cell or an additional electrode added to the system. In one embodiment, the hydrogen is captured by arranging the electrodes of the cell such that buoyancy carries the hydrogen gas bubbles to the HOR electrode. For example, the system can be tilted, or include a funnel designed to facilitate such flow.

[0186] In multiple embodiments, a liquid electrolyte is flowed through a collection of DRI pellets or a bed of DRI pellets. For thick (up to several centimeters) battery electrodes composed of active material pellets, it can be challenging to achieve sufficient transport of reactants, reactant products, and additives through the thick bed on a time scale commensurate with the battery operation (charge and discharge) time scale. Insufficient transport rates in the electrolyte can have a variety of adverse effects, including but not limited to increased overpotential losses in pellet-based electrodes and reduced utilization of active materials. In metal electrode batteries with alkaline electrolytes, bubble formation and pH gradient formation under charge and discharge conditions can both lead to undesired performance degradation or corrosion in one or both electrodes. In multiple embodiments, a liquid electrolyte is flowed through the DRI pellet bed to reduce the adverse effects of limited transport. The flow of the electrolyte creates convective transport of individual electrolyte pellets. Among other benefits, the rate of electrochemical reactions and reaction uniformity can be improved by reducing the electrolyte concentration boundary layer, which can occur across the thickness of the entire pellet bed or within the macropores in the pellet bed. By homogenizing the electrolyte composition in the macroscopic and microscopic structures of the entire electrode, electrolyte flow generally reduces overpotential losses. In some embodiments, an active method (e.g., a mechanical pump) is used to achieve electrolyte flow. The flow rate of the electrolyte can be very low, as low as 1 mL / min / cm 2 or lower. In other embodiments, electrolyte flow is achieved passively, such as buoyancy-driven flow due to thermal gradients or component gradients. In a specific example, the portion of the battery where resistive heat dissipation occurs is located at or near the bottom of the electrode bed, causing the electrolyte to be heated and rise through the pellet bed. In another specific example, an electrochemical reaction in an electrode located within the battery changes the electrolyte density, for example, by an exothermic or endothermic reaction or a change in the composition of the electrolyte in contact with the electrode, thereby creating buoyancy-driven flow. In this example, the electrode reaction that produces the lower density electrolyte can be located at or near the bottom of the DRI pellet bed, and the reaction that increases the electrolyte density can be located at the top of the pellet bed.

[0187] In some embodiments, additives that suppress side reactions (such as corrosion inhibitors that suppress the HER reaction or self-discharge) are combined with additives that increase capacity utilization. Additives to the battery electrolyte, including metal electrodes (including iron electrodes), can advantageously perform several functions, including increasing the capacity utilization of iron, suppressing unwanted side reactions, or both. Different additives have different advantages, and these advantages can be combined by combining additives at appropriate concentrations. An example of an additive that increases utilization is sulfur or sulfide. In some embodiments, more than one corrosion inhibitor can be used in combination with one or more sulfides. For example, sulfur helps to de-passivate the iron electrode but is consumed during the electrochemical cycling of the battery. Thus, over multiple cycles, the consumption of sulfur may lead to a decrease in capacity. In one embodiment, a delivery system is used to replenish sulfur to maintain battery performance. An example of such a system is a pump that delivers a sulfur-containing liquid to the battery cell. Another example is a dry hopper that delivers polysulfide salts to a sealed or open battery cell.

[0188] In one embodiment, iron sulfide (FeS) can be added to a metal-air battery using an alkaline electrolyte as a slightly soluble additive, thereby improving the electrochemical stability of the OER electrode and extending the electrode life. This embodiment helps to mitigate the decay of the catalyst performance on the oxygen evolution reaction (OER) electrode under alkaline conditions, which may limit the operating life of the electrode.

[0189] In certain embodiments, sulfur can be added to DRI by additional process operations. In certain embodiments, the low melting temperature of sulfur can be utilized to immerse DRI in a molten sulfur bath. In certain other embodiments, hydrogen sulfide gas can flow over hot DRI or cold DRI to deposit a layer of sulfur and / or a layer of iron sulfide on the surface of DRI. In certain other embodiments, sulfur can sublime and be vapor deposited on the surface of DRI; DRI can be hot or cold. In certain embodiments, sulfur is melted and diffused into the pores of DRI by melting sulfur and then wicking it into the pores of DRI.

[0190] In some embodiments, sulfur can be added to DRI by a wet deposition process involving a process solvent. In certain embodiments, a colloidal mixture can be used to deposit sulfur or sulfide (e.g., FeS) species on or within DRI. For example, a dispersion of sulfur in water can be prepared by sonication, and then DRI can be added thereto. The water can be evaporated, thereby depositing sulfur or sulfide species on the surface and inside the DRI agglomerates. In certain other embodiments, sulfur can be dissolved in an organic solvent (e.g., ethanol or acetone). DRI is added to the solution, and then the solvent is evaporated to obtain a sulfur coating.

[0191] In some embodiments, additives comprising molybdate ions are used in alkaline batteries containing an iron anode. Without being limited by any specific scientific explanation, such additives can help suppress the hydrogen evolution reaction (HER) at the iron electrode and improve the cycle efficiency of the battery. The concentration of the additive is selected to be able to suppress the HER while still being able to carry out the desired iron charging process / iron discharging process. As an example, molybdate ions can be added through molybdate compounds (such as KMoO 4 ). In a specific example, the electrolyte contains an additive concentration of 10 mM (mM is millimole, a concentration of 10 -3 mol / L). In other embodiments, the electrolyte contains an additive concentration of molybdate anions in the range of 1 mM to 100 mM.

[0192] In some embodiments, surfactants are used to control wetting and foaming during the operation of metal-air batteries. During the charging process, at least two gas evolution reactions that lead to bubble formation may occur. One is the hydrogen evolution at the metal anode, which is a parasitic reaction that may cause a decrease in the coulombic efficiency during the battery cycle. The other is the oxygen evolution reaction that is necessary for the function of the metal-air battery. The surfactant additive can mitigate the adverse effects associated with both reactions. In the case of HER, the hydrophobic surfactant additive can suppress the hydrogen evolution reaction at the metal anode by physically blocking the entry of water (the HER reactant) into the metal anode during the charging process. In the case of ORR, the surfactant additive can reduce the surface tension and viscosity of the electrolyte at the oxygen evolution electrode, thereby generating smaller, uniformly sized, and controllable bubbles during the charging process. In a non-limiting example, 1-octanethiol at a concentration of 10 mM is added to the alkaline electrolyte to mitigate these two difficulties.

[0193] In some embodiments, carbonates are added to the electrolyte of a metal-air battery using an alkaline electrolyte to reduce the rate of carbon dioxide absorption from the air. In air, an electrolyte based on potassium hydroxide or sodium hydroxide will react with carbon dioxide (CO 2)The reaction forms potassium carbonate or sodium carbonate, resulting in the loss of potassium cations or sodium cations from the solution. This poses particular problems for batteries with air electrodes because ambient air provides the lowest-cost form of the required reactant (oxygen) to the oxygen reduction reaction (ORR) electrode. Electrolyte carbonation can lead to several adverse effects on battery performance related to unwanted side reactions and reduced electrolyte conductivity, all of which result in decreased operating efficiency of the battery. However, as the concentration of carbonate in the electrolyte increases, the rate of carbonate formation significantly slows down. In one embodiment, carbonate is intentionally added to the electrolyte prior to operation to reduce the rate of carbonation reaction of the battery with air during operation. The intentionally added carbonate can mitigate the harmful effects of carbonation and maintain an acceptable carbonate level in the electrolyte over a longer operating life.

[0194] In one embodiment, the health of the electrolyte in a metal-air battery is monitored periodically or continuously. The aging and quality of the electrolyte can significantly affect the electrochemical performance of an iron-air battery. In some cases, the performance degradation is related to the negative electrode (e.g., the iron electrode). Generally, as the electrolyte ages, the discharge capacity of the negative electrode decreases. This may be due to spontaneous reactions forming unwanted products (especially those formed due to exposure to air), resulting in a change in the concentration of electrolyte components over time. In some embodiments, the health of the electrolyte is monitored during battery operation to determine the appropriate time to replenish, replace, or treat the electrolyte. The feedback mechanism can be manual or automatic. In an automated system, the electrolyte quality measurement can be used as an input to a proportional-integral-derivative (PID) loop that continuously adjusts the concentration of electrolyte components. The electrolyte quality measurement is done ex situ on a small portion of the electrolyte or on the active electrolyte while the cell is operating. A non-limiting method for evaluating the health of the electrolyte is to measure the conductivity of the electrolyte. One mechanism of degradation is due to CO 2 dissolving from the air into the electrolyte, causing the electrolyte to carbonate over time. In a specific example, experiments were conducted to show that the electrolyte conductivity varies linearly with the carbonate concentration in the electrolyte. A conductivity probe is used to evaluate the concentration of carbonate in the electrolyte. The conductivity probe is used to monitor the health status of the electrolyte.

[0195] In some embodiments, corrosion inhibitors used to inhibit water corrosion in the field of iron and steel metallurgy are used as part of a battery with an iron negative electrode to improve performance. In some embodiments, direct reduced iron (DRI) is used as the negative electrode, and favorable performance characteristics can be obtained by using one or more corrosion inhibitors in a suitable concentration range. In these embodiments, the principles of corrosion science are used to prevent unwanted side reactions (e.g., hydrogen evolution) from occurring under charging conditions, mitigate the spontaneous self-discharge rate during electrochemical holding, and maximize the utilization of the iron active material during discharge. Generally, there are two classes of corrosion inhibitors: interfacial inhibitors that react with the metal surface at the metal-environment interface to prevent corrosion, and environmental scavengers that remove corrosive elements from the environment surrounding the metal surface to inhibit corrosion. Under the broad protection of the corrosion inhibitor, an appropriate concentration of inhibitor can be added to the electrochemical cell to obtain performance characteristics favorable with respect to the efficiency and capacity of the electrochemical cell. For the iron electrode of a metal-air battery, a class of suitable general inhibitors is liquid and interphase interface inhibitors. This class includes three main types of interface inhibitors: anodic inhibitors, cathodic inhibitors, and mixed inhibitors. Anodic inhibitors can form a passivation layer that inhibits the anodic metal dissolution reaction. Cathodic inhibitors may reduce the rate of the reduction reaction (HER in the case of an iron electrode), or precipitate on the cathodic active sites to block the same reduction reaction. Mixed inhibitors can inhibit corrosion through one or two pathways and include, but are not limited to, molecules that physically or chemically adsorb on the metal surface to form a film that can block the active sites of the reduction reaction. The inhibitor can be added to the base electrolyte at any concentration.

[0196] In multiple embodiments, an inhibitor that forms a passivation layer on the metal surface is paired with an additive that de-passivates the iron surface. At the correct concentration, an optimal balance of corrosion inhibition and active material utilization can be achieved. In one specific embodiment, when using direct reduced iron as the negative electrode, 10 mM molybdate anions are used as the passivating agent and 10 mM sulfide anions are used as the de-passivating agent in an alkaline electrolyte composed of 5.5 M potassium hydroxide or 5.5 M sodium hydroxide. Specific examples of the electrolyte composition include: 5.5 M KOH + 0.5 M LiOH + 10 mM Na 2 S + 10 mM 1-octanethiol; 5.95 M NaOH + 50 mM LiOH + 50 mM Na 2 S + 10 mM 1-octanethiol; 5.95 M NaOH + 50 mM LiOH + 50 mM Na 2 S + 10 mM 1-octanethiol + 10 mM K 2 MoO 4 ; and 5.95 M NaOH + 50 mM LiOH + 50 mMNa 2 S + 10 mM K2 MoO 4 However, the present disclosure is not limited to any specific concentration of the additives in the electrolyte described above. For example, the electrolyte may include one or more of the above additives in a concentration range of from about 2 mM to about 200 mM, such as from about 5 mM to about 50 mM or from about 5 mM to about 25 mM.

[0197] In certain embodiments, other electrolyte additives are incorporated into the electrolyte. The electrolyte additives may be selected from the following non-limiting group: 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, allylurea, citric acid, thiomalic acid, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, propylene glycol, trimethoxysilylpropyl diethyleneamine, aminopropyltrimethoxysilane, dimethyl acetylenedicarboxylate (DMAD), 1,3-diethylthiourea, N,N'-diethylthiourea, aminomethylpropanol, methylbutynol, amino-modified organosilane, succinic acid, isopropanolamine, phenoxyethanol, dipropylene glycol, benzoic acid, N-(2-aminoethyl)-3-aminopropyl, behenic acid amide, 2-phosphonobutane tricarboxylic acid, boric acid mipa salt, 3-methacryloxypropyltrimethoxysilane, 2-ethylhexanoic acid, isobutanol, tert-butylaminoethyl methacrylate, diisopropanolamine, propylene glycol n-propyl ether, sodium benzotriazole, pentasodium aminotrimethylene phosphonate, sodium cocoyl sarcosinate, laurylpyridinium chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quaternium-18 chloride, sodium hexametaphosphate, dicyclohexylammonium nitrite, lead stearate, calcium dinonylnaphthalene sulfonate, iron(II) sulfide, sodium hydrosulfide, pyrite, sodium nitrite, complex alkyl phosphate esters (such as RA 600 emulsifier), 4-mercaptobenzoic acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate (EDTA), 1,3-propanediaminetetraacetate (PDTA), nitrilotriacetate (NTA), ethylenediaminedisuccinate (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 dialkylphosphorodithioate, potassium stannate, sodium stannate, tannic acid, gelatin, saponin, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdate, potassium molybdate, hydrotreated light petroleum, heavy naphthenic petroleum (e.g., as 631 for sale), antimony sulfate, antimony acetate, bismuth acetate, hydrotreated heavy naphtha (e.g., as for sale), tetramethylammonium hydroxide, NaSb tartrate, urea, D-glucose, C 6 Na 2 O 6 , potassium antimonyl 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 antimonyl L-tartrate, disodium rhodizonate, sodium selenide and combinations thereof.

[0198] In certain embodiments, the electrolyte is gelled. In certain embodiments, silica (SiO 2 ) or other network-forming oxides (e.g., boron oxide (B 2 O 3 ) or alumina (Al 2 O 3)Dissolve in an alkaline liquid to form a gel. In certain embodiments, the organic molecules that form the network are dispersed in a liquid electrolyte to form a gel electrolyte. In certain embodiments, the organic molecules include polymers. In certain embodiments, a 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. Biologically derived polymers (such as cassava or gelatin) can also be used as polymer additives. In certain embodiments, a gel electrolyte is formed in situ by dissolving silica (or other oxides) from DRI. In certain other embodiments, additional gel formers are intentionally added to the liquid electrolyte to produce a gel. In certain embodiments, a gel electrolyte is formed in situ due to the evaporation of the solvent (e.g., water) from the electrolyte, concentrating the dissolved salts and converting the electrolyte from a liquid to a gel or supersaturated solution.

[0199] 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 can be a saturated solution of NaOH in water and additional dispersed solid phase NaOH, which together form a slurry electrolyte. Such an electrolyte can have mechanical properties similar to those of a gel.

[0200] In certain embodiments, the electrolyte additives are delivered to the electrodes as a solid mixture. The electrolyte additives can have a range of solubilities, and some electrolyte additives may have the most beneficial effects when they are closely mixed with the solid electrodes. In one embodiment, the solid agglomerates consist mainly of additives, and these additive agglomerates are added to or mixed with a metal electrode, which in one embodiment includes multiple DRI agglomerates. In another embodiment, the electrolyte additives are mixed with a metal that can be a metal containing a redox-active electrode, and the agglomerates made from this mixture are mixed with a metal electrode, which in one embodiment includes multiple DRI agglomerates. Non-limiting examples of additives include sodium sulfide (Na 2 S), potassium sulfide (K 2 S), lithium sulfide (Li 2 S), iron sulfide (FeS x , where x = 1 - 2), bismuth sulfide (Bi 2 S 3 ), lead sulfide (PbS), zinc sulfide (ZnS), antimony sulfide (Sb 2 S 3 ), selenium sulfide (SeS 2 ), tin sulfide (SnS, SnS 2 , Sn 2 S3 ) Nickel sulfide (NiS), molybdenum sulfide (MoS 2 ), mercury sulfide (HgS), FeS, bismuth oxide (Bi 2 O 3 ), their combinations, etc. In some embodiments, pellets with different ratios of redox-active metals and additives are prepared, and pellets with different compositions are mixed to produce a mixed electrode.

[0201] In some embodiments, an electrochemical formation cycle protocol is used to change the properties of the starting DRI pellets and improve the subsequent operating electrochemical performance of the DRI as an anode. The as-made DRI pellets may not be in a form optimized for electrochemical cycling in a battery. For example, there may be a natural oxide on the free surface of the DRI that hinders electrochemical contact with the active material; the specific surface area may be too low to achieve the desired specific capacity; and / or the pore structure may limit ion transport and limit the specific capacity. In one specific embodiment, the initial cycle, referred to as "formation," consists of one or more repetitions of one or more of the following steps. One step can be a short charging step ("precharging"), during which any natural oxide layer that unfavorably passivates the as-received DRI can be chemically reduced, or the specific surface area of the DRI pellets can be increased, in some cases up to 10 times. These changes may increase the available capacity of the DRI during subsequent discharges. Another step can be a discharging step of the oxidized metallic iron until one or more reactions from Fe to Fe 2+ or from Fe 2+ to Fe 3+ are completed fully or partially. Between repetitions of the formation cycle, the charge capacity and the discharge capacity may not be the same. In some embodiments, formation can include repeated precharging and discharging cycles that systematically increase the capacity. In one specific embodiment, the formation cycle includes the following steps: precharging to a capacity of 250 mAh / g, and then cycling n times through the following loop: discharging to 25 + n * 25 mAh / g, and then charging to (25 + n * 25) * 1.1 mAh / g, where n is the number of cycles. The precharging step increases the specific surface area of the DRI from about 0.5 m 2 / g to 12 m 2 / g or greater, which can enhance the available capacity of subsequent discharges. The remaining formation cycles are carried out in n cycles with an increasing capacity increment of 25 mAh / g (assuming a Coulombic efficiency of 90%), gradually approaching the charge-discharge capacity corresponding to deep cycling.

[0202] In some embodiments, specific operating strategies are used to control the potential of the negative electrode charging. During the charging process of an iron-air battery, the iron reduction reaction and the parasitic hydrogen evolution reaction are expected to occur simultaneously within a large potential range, but the relative rate of each reaction depends on the potential. In some potential cases, the hydrogen evolution reaction will be thermodynamically and / or kinetically favorable, while in other cases, the iron reduction reaction will be favorable. Strategies involving 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 current rate higher than its discharge rate. This may be affected under constant current, constant power, or other more complex cycling conditions. By charging at a greater rate than during discharge, the electrode can be driven to a potential that is thermodynamically and / or kinetically favorable for iron reduction rather than parasitic reactions (e.g., hydrogen evolution). The result is 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 constant power. The charging potential is selected to optimize the electrochemical performance. For example, the charging potential can be optimized to maximize the coulombic efficiency and achieve higher electrode utilization. As another example, in another strategy, the effective resistance of other cell components (i.e., non-solid-state Fe electrode or negative electrode current collector) is increased. By doing so, a greater overall cell polarization is achieved, which results in a greater polarization of the negative electrode. If the additional negative electrode polarization is large enough, the absolute potential of the Fe electrode can become low enough to favor iron reduction rather than the hydrogen evolution reaction. The effect can be achieved by increasing the effective resistance of the electrolyte, cathode, or cathode current collector.

[0203] In some embodiments, self-discharge of the negative electrode is restricted by using a passivating chemical layer on the metal anode, optionally in combination with one or more electrical pulses during charging. Metal anodes in alkaline batteries (e.g., Fe, Al, Zn) typically self-discharge through corrosion reactions, forming hydrogen gas and metal hydroxides as products of the self-discharge corrosion reaction. Generally, passivating electrolyte additives are considered unnecessary for slowing down self-discharge because the passivating layer also renders the metal anode non-reactive in the desired discharge reaction. According to this embodiment, an electrolyte additive (e.g., Na 2 MoO 4 ) is used to form a thin passivating film. Thus, the self-discharge of the anode is limited to a small layer on the anode surface. However, to restore the reactivity of the metal anode, short and intense charging pulses are used to reduce the surface film. Once the surface film is reduced, the discharge reaction can proceed.

[0204] 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 an electrochemical cell including an iron electrode, the state of charge and state of health of the electrode are related to the proportion of metallic iron. Thus, the state of charge or state of health of the battery can be determined by measuring the proportion of metallic iron. In a specific embodiment, magnetic susceptibility measurements are made on one or more portions of the iron electrode to determine the state of charge or state of health. To make such measurements, the sample can be shaped into a disk or cylinder with a thickness in the range of a few millimeters and a diameter from 0.25 cm to 4 cm. The measured magnetic susceptibility is analyzed to extract the relative amounts of metallic iron, ferrous iron, and ferric iron.

[0205] In multiple embodiments, DRI is used as a redox-active electrode material in primary or secondary type batteries. In one embodiment, DRI is used as the anode active material in a primary battery. In one embodiment, DRI is used as the anode active material in a primary fuelable (or mechanically rechargeable) primary battery, where the anode can be mechanically replaced with fresh DRI. In one embodiment, DRI is used as the anode active material in a secondary battery. In another embodiment, DRI is used as an electrode material with an alkaline electrolyte (pH > 9). In a specific embodiment, an alkaline secondary battery can employ a nickel cathode. In this embodiment, DRI serves as the starting material for the anode of a Ni-Fe alkaline secondary battery and can be used in its original state or processed prior to use according to other embodiments described herein. Other electrochemical couples (combinations of cathode and anode) for alkaline cells employing a DRI anode include iron / nickel (Fe / Ni cell) or iron / silver (Fe / Ag cell). In multiple embodiments, DRI can be used as the anode active material in a primary or secondary battery where the pH of the electrode spans an acidic (pH < 5.5) or neutral (5.5 < pH < 9) range. As an example, DRI can be used as the anode active material in a battery employing an electrolyte containing hydrochloric acid (HCl) in a concentration range of 1M - 5M. At the anode, DRI can participate in the following half-cell reaction during discharge: Fe + 2Cl - →FeCl 2 + 2e - .

[0206] DRI can specifically be used as the anode material in an all-Fe battery, where Fe is the reactive material for both the anode and the cathode. In such an embodiment, DRI can serve as a solid metallic Fe anode at 100% SOC, and this anode will form soluble Fe 2+ species (i.e., FeCl 2 ) during discharge. The cathode active material can be an Fe-based soluble inorganic salt, such as FeCl 2 / FeCl3 Redox couple. The cathode active material can also be an inorganic coordination compound or an organic coordination compound, such as K 3 Fe(CN) 6 . At the cathode, soluble Fe species will undergo a redox reaction related to the Fe 2+ / Fe 3+ redox couple. A specific example of an all-Fe battery using DRI as the active material is to use DRI as the anode material and an electrolyte containing HCl with a concentration of 1M - 5M. At the anode, DRI participates in the following half-cell reaction during discharge: Fe + 2Cl - →FeCl 2 + 2e - . At the cathode, soluble FeCl 3 will undergo the following half-cell reaction during discharge: 2FeCl 3 + 2e - →2FeCl 2 + 2Cl - . The overall cell reaction during discharge is Fe + 2FeCl 3 →3FeCl 2 . DRI can be used as a raw material for the required soluble FeCl 2 in the solution to carry out the cathode reaction by allowing DRI to react with HCl in the solution, thus participating in the following spontaneous chemical reaction: Fe + 2HCl → FeCl 2 + H 2 .

[0207] In some embodiments, DRI is used as the anode in a flow battery, where DRI pellets are transported from a storage tank to an electrochemical reactor where the DRI pellets undergo an electrochemical reaction. The DRI pellets remain in electrical contact with each other as they flow through the electrochemical reactor, thus enabling sufficient electroosmotic flow to provide high conductivity by collecting the pellets. The electrolyte can be acidic (pH < 5), neutral (5 < pH < 9), or basic (pH > 9). In a specific embodiment, the discharge reaction can be carried out such that the metallic Fe anode forms a soluble product (e.g., FeCl 2 ) during discharge, or a slightly soluble (e.g., Fe(OH) 2 ) discharge product film forms on the surface of the transported DRI. Specific embodiments of methods for transporting DRI pellets through the battery include any method known in the art for transporting pelletized materials or slurries or suspensions, including but not limited to pressure-driven fluid flow, using a fluidized bed, through a mechanical conveyor (such as a conveyor belt, roller, or using a screw conveyor). In some embodiments, the mechanical conveyor or screw conveyor includes a conductive material, such as metal or carbon, which also serves as the current collector of the battery.

[0208] In multiple embodiments, according to the following spontaneous chemical reaction: Fe + 2HCl → FeCl 2 + H 2 , DRI is used as a source of metallic Fe in the synthesis of FeCl 2 . DRI can be used as a raw material in the form of pellets, or the pellets can be crushed into powder. Additionally, DRI fines (pellets or particle size < 0.5 cm), which are waste products of the DRI process, can be used as raw materials. Iron iodide (FeI 2 ) and iron bromide (FeBr 2 ) can be synthesized in a similar manner, where HI and HBr are alternative acids to HCl in salt synthesis.

[0209] In multiple embodiments, DRI is used to form a packed catalyst bed for gas-phase or liquid-phase reactions. In some embodiments, the packed catalyst bed of DRI can be used as a catalyst in the Haber process for the production of ammonia. DRI can replace iron powder, or can be used together with iron powder, which is commonly used in the Haber process. Specifically, the wustite coating present in commercially produced DRI may be required to facilitate the reaction in the Haber process. In some embodiments, the iron or iron salt component of DRI (which can be iron oxide, hydroxide, or 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 raw material for the production of basic ferrocyanide. First, DRI can be used to synthesize FeCl 2 according to the following spontaneous chemical reaction: Fe + 2HCl → FeCl 2 + H 2 . Subsequently, Na 2 Fe(CN) 4 ·10H 6 O can be synthesized using FeCl 2 from DRI according to the following reactions: Synthesis of calcium ferrocyanide: 6HCN + FeCl 2 + 3Ca(OH) 2 → Ca 2 Fe(CN) 6 ·11H 2 O + CaCl 2 ; Conversion to mixed salt: Ca 2 Fe(CN) 6 ·11H 2 O + 2NaCl → CaNa 2 Fe(CN)6·11H 2 O (solid) + CaCl 2 (solution); and conversion to Na salt: CaNa 2 Fe(CN) 6 ·11H2 O + Na 2 CO 3 →Na 4 Fe(CN) 6 ·10H 2 O + CaCO 3 。In this conventional method for synthesizing Na 4 Fe(CN) 6 ·10H 2 O, FeCl 2 (about $0.2 per mole) accounts for about 54% of the total raw material cost. Therefore, replacing FeCl with DRI (about $0.01 per mole) 2 makes it possible to significantly reduce the raw material cost of Na 4 Fe(CN) 6 ·10H 2 O by half.

[0210] In various embodiments, DRI is used as an electrode for the hydrogen evolution reaction (HER) for generating hydrogen gas (H 2 ) by electrolysis. DRI can be used as a catalytic surface to facilitate HER or as a conductive substrate for one or more other catalyst materials. In embodiments where the substrate is DRI, DRI can be coated in a continuous layer of catalyst material or decorated with catalyst particles. Metallic platinum (Pt) is an example of a catalyst that can be used to coat or decorate a DRI substrate for HER. DRI can be used for HER in acidic or alkaline solutions.

[0211] In various embodiments, porous DRI agglomerates are used as OER electrodes. Non-limiting examples of ways in which DRI can be used for this purpose include: in its original state, after electroplating the surface with a transition metal, after electroless plating the surface with a transition metal, after surface modification by chemical etching, after surface modification by heat treatment, or after thermally applying an OER catalyst to the DRI substrate surface.

[0212] In various embodiments, DRI is used as an electrode for the oxygen evolution reaction (OER) for generating oxygen gas (O 2 ) by electrolysis. Non-limiting ways in which DRI can be used include as a catalytic surface to facilitate OER or as a conductive substrate for one or more other catalyst materials. In embodiments where DRI is the substrate, DRI can be coated in a continuous layer of catalyst material or decorated with catalyst particles. Metallic nickel (Ni) is an example of a catalyst that can be used to coat or decorate a DRI substrate for OER. DRI can be used for OER electrodes in acidic or alkaline solutions. DRI can be used as a catalyst or electrode substrate in alkaline electrolyzers.

[0213] In another embodiment, DRI is used in an oxygen reduction reaction (ORR) electrode. In some embodiments, the iron or iron salt component of DRI (which can be iron oxide, hydroxide, or carbide) reacts with another component (such as another metal or metal salt) to form an ORR catalyst. This catalyst can form on the surface of the DRI pellets or can penetrate into the DRI pellets and can be part of the entire DRI pellet or substantially alter the entire DRI pellet. DRI fines as well as DRI pellets or crushed pellets can be used as the ORR electrode. In some embodiments, the ORR catalyst formed from DRI is a mixed metal oxide containing iron. In other embodiments, the ORR catalyst is an oxide containing iron and another transition metal. In various embodiments, the ORR catalyst is a spinel structure oxide containing iron and manganese.

[0214] In various embodiments, a DRI packed bed is used in a water filtration device. In such an embodiment, DRI can be housed in a column to produce a packed bed of DRI pellets. The particulate matter is trapped in the pores inside the DRI pellets and in the voids between the DRI pellets. Using granular iron as a filtration medium can provide the ability to adjust the pressure drop and filtration efficiency.

[0215] In various embodiments, DRI is used as a metallic iron source for the production of iron-containing industrial or specialty chemicals such as ferrocyanates, iron tris-bipyridine, and ferrocene.

[0216] Figure 1 is a schematic diagram of a battery (or cell) 100 according to various embodiments of the present disclosure. Referring 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 provided. The liquid electrolyte 104 can separate the air electrode 103 from the negative electrode 102.

[0217] The negative electrode 102 may include metal agglomerates 105, which may contain at least 50 wt% of a metal by elemental mass, such as at least 60 wt% of a metal. In some embodiments, the metal agglomerates 105 may contain at least 60 wt% of iron by elemental mass. Thus, the agglomerates 105 may be referred to as iron-containing agglomerates. The agglomerates 105 may be electrically connected to each other and may be arranged in one or more layers to form the negative electrode 102. In various embodiments, the negative electrode 102 may be a slurry. In various embodiments, the slurry may include one or more metal agglomerates 105 therein. In various embodiments, the slurry may include dissolved particles, such as particles corresponding to the composition of the metal agglomerates 105 discussed herein. As a specific example, the negative electrode 102 may be a slurry containing iron. In various embodiments, the positive electrode 103 may be a slurry. In various embodiments, the negative electrode 102 may take the form of a gel. A flowable semi-solid negative electrode 102 (e.g., a flowable semi-solid iron electrode, etc.) may be valuable for large-scale energy storage systems due to its low manufacturing cost and ease of assembly into a cell framework. For example, reduced iron has high electrical conductivity. By suspending iron particles in a polymer gel, a percolation network of iron particles can be generated, thereby forming a conductive and electroactive gel that can form the negative electrode 102. For 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., SiO 2 ) in a concentrated KOH solution. In certain embodiments, the electrolyte is gelled. In certain embodiments, silica (SiO 2 ) or other network-forming oxides (e.g., boron oxide (B 2 O 3 ) or alumina (Al 2 O 3 ) is dissolved in an alkaline liquid to form a gel. In certain embodiments, network-forming organic molecules are dispersed in a liquid electrolyte to form a gel electrolyte. In certain embodiments, the organic molecules include polymers. In certain embodiments, a liquid electrolyte is added to a solid polymer (e.g., polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylamide (PAM), or polyacrylic acid (PAA)) to form a gel electrolyte. Biologically derived polymers (e.g., cassava or gelatin) can also be used as polymer additives. In certain embodiments, a gel electrolyte is formed in situ by dissolving silica (or other oxides) from DRI. In certain other embodiments, an additional gelling agent is intentionally added to the liquid electrolyte to produce a gel. In certain embodiments, a gel electrolyte is formed in situ due to the evaporation of a solvent (e.g., water) from the electrolyte, concentrating the dissolved salt and converting the electrolyte from a liquid to a gel or supersaturated solution.

[0218] In multiple embodiments, the agglomerate 105 comprises a primary iron-containing phase and one or more second phases ("gangue"). In multiple embodiments, the oxidation state of the primary phase can range from highly reduced (e.g., metallic iron) to highly oxidized (e.g., ionic). For example, the agglomerate 105 can be substantially metallic iron, i.e., having a valence state of 0 (e.g., Fe 0 ). Thus, in some embodiments, the agglomerate can contain at least 60 wt% metallic iron by mass, preferably at least 80 wt% metallic iron, and in some embodiments, 90 wt% to 98 wt% metallic iron. In multiple other embodiments, the agglomerate 105 can consist of iron fully oxidized to a trivalent state (e.g., Fe 2 O 3 ). In multiple other embodiments, the iron valence state can be from 0 to 3+. In multiple embodiments, the primary phase can be an oxide, hydroxide, sulfide, carbide, or a combination thereof. For example, the primary phase can have a composition of Fe, FeO, Fe 2 O 3 , Fe 3 O 4 , FeO x (OH) y , Fe 3 C, FeS x , FeO x S y and / or FeO x S y H z . In some embodiments, the agglomerate 105 can include direct reduced iron (DRI) agglomerates, and the agglomerate 105 can account for at least 60% of the total mass of the negative electrode 102. In multiple embodiments, the negative electrode 102 can consist of DRI agglomerates.

[0219] In multiple embodiments, the second phase contains silicon. For example, the second phase can contain silica (SiO 2 ) and / or one or more silicates, such as feldspar, mica, amphibole, pyroxene, olivine, tourmaline, and / or forsterite. In multiple other embodiments, the second phase can include titanium, vanadium, manganese, magnesium, calcium, phosphorus, carbon, aluminum, zirconium, or any combination thereof.

[0220] The agglomerate 105 can be spherical, as Figure 1As shown. For example, in various embodiments, the agglomerates 105 can have an average diameter ranging from about 0.5 mm to about 10 cm, such as about 10 mm. As a specific example, the agglomerates 105 can have an average diameter of 4 mm to 20 mm. As used herein, the term "spherical" is used to describe any circular form that resembles a three-dimensional object (where all surface points are equidistant from its center), but where all surface points may not actually be equidistant from the center. In other words, "spherical" encompasses shapes that are perfect spheres and shapes that may have a generally spherical appearance but may not be perfect spheres, e.g., balls. However, the present disclosure is not limited to any specific agglomerate shape. For example, the agglomerates can be briquetted, as discussed below with respect to Figure 2A In addition, although illustrated as complete agglomerates, the agglomerates 105 can be fragments of crushed agglomerates. For example, as-received agglomerates can be crushed, and those crushed agglomerate fragments can form the agglomerates 105 in the negative electrode, e.g., the agglomerates 105 filled into the bed. In various embodiments, the crushed agglomerates can have an average particle size in the range of 10 nm (nm = 10 -9 m) to 10 mm (mm = 10 - 3 m), such as in the range of 10 nm - 100 nm, 1 nm - 100 μm (μm = 10 -6 m) or 1 mm - 10 mm. In some embodiments, the crushed agglomerates can include a combination of agglomerates having different average particle sizes.

[0221] In various non-limiting embodiments, the agglomerates 105 can have an internal porosity in the range of about 2% to 80%, such as about 50% to about 75%. In various non-limiting embodiments, the negative electrode 102 can have an agglomerate packing density in the range of about 40% to about 74%. Thus, the liquid electrolyte 104 can penetrate into the spaces between the agglomerates 115 to impregnate the negative electrode 102. To ensure good electrical conductivity through the agglomerates 105, a low contact resistance may be required. In various embodiments, compression of the agglomerates 105 of the negative electrode 102 can ensure contact of the agglomerates 105. In various embodiments, the agglomerates 105 can have a compressive strength of about 700 psi to about 2500 psi. In some embodiments, such agglomerates 105 with compressive strength can be placed in the bed constituting the negative electrode 102, and a compressive force can be applied to the agglomerates to improve conductivity.

[0222] 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 alkaline, i.e., having 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 comprise potassium hydroxide (KOH) at a concentration of 6 M (mol / L). In certain embodiments, the electrolyte 104 may include a combination of components such as 5.5 M potassium hydroxide (KOH) and 0.5 M lithium hydroxide (LiOH). For iron materials, high pH is beneficial for improving mechanical stability since iron is slightly soluble in high pH liquids. In various embodiments, the pH is greater than 10, or greater than 12, or greater than 14 to ensure such low solubility of iron. In contrast, at low pH, such as pH less than 5, or pH less than 3, or pH less than 2, iron is soluble and the pellets will dissolve.

[0223] In various non-limiting embodiments, the thickness of the negative electrode 102 may range 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 arranged 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 placed adjacent to each other (e.g., by dispersion or spreading, such as in a gravel bed), or may be mechanically attached or mechanically connected to each other by methods such as compaction or pressing. In other embodiments, the pellets 105 may be physically connected by methods such as welding or brazing. In other embodiments, the pellets 105 may be joined to each other by arc welding. In other embodiments, the pellets 105 may be connected by a combination of such joining methods. In other embodiments, the pellets 105 may be attached and connected to each other by wires passing through holes in the pellets 105. The holes in the pellets may introduce additional contact points not only across the thickness of the bed of pellets 105 that forms the negative electrode 102, but also across the thickness of an individual pellet 105. Once strung, the wires may be tightened to enhance contact between the pellets 105 and may then be mechanically held in place by a conductive mechanical stopper which in turn may be connected to a larger current collector plate, such as current collector plate 106. In some embodiments, the pellets 105 may optionally be filled into the bed with the assistance of mechanical pressure applied by a high temperature resistant material and then sintered in a non-oxidizing atmosphere. The result is that the bed of pellets 105 fuses together with a low inter-pellet 105 contact resistance. The sintered bed of pellets 105 may form the negative electrode 102.

[0224] In various embodiments, the pellets 105 can be produced from iron ore pellets such as taconite or magnetite or hematite. In various embodiments, the pellets 105 can be produced by reducing the iron ore pellets to form a more metallic (higher reduced, lower oxidized) material such as metallic iron (Fe 0 ), wüstite (FeO), or a mixture thereof. In various non-limiting embodiments, the pellets 105 can be reduced taconite, direct reduced (“DR”) taconite, direct reduced iron (“DRI”) pellets, or any combination thereof.

[0225] In various non-limiting embodiments, the pellets 105 include iron in the form of cementite (Fe 3 C). Although iron batteries require an iron-containing starting material, iron in the form of cementite (Fe 3 C) may be easier or less costly to obtain or transport. In various embodiments, cementite (Fe 3 C) can be used as the starting electrode material for an iron-containing battery. For example, the pellets 105 can initially be formed from cementite (Fe 3 C). Cementite (Fe 3 C) can first be converted to magnetite before or during the early operation of the battery 100, and the magnetite can reversibly cycle between other iron oxidation states to store energy. In either case, the conversion to magnetite can occur in the battery 100 and may not be possible externally prior to assembling the battery 100. The cementite (Fe 3 C) starting pellets 105 can take the form of most cementite (Fe 3 C) ore pellets and / or pellets formed from most cementite (Fe 3 C) powder. In various embodiments, by using the pellets 105 of a low specific surface area cementite material as the anode of the battery 100 and discharging the battery 100 at a current density of about 25 mA / g, a high specific surface area iron oxide phase can be produced. This high specific surface area iron oxide phase can be used as the negative electrode 102.

[0226] Commercially available DRI pellets may not necessarily have the optimal chemical and physical properties to maximize electrochemical performance. In various embodiments, the DRI pellets are treated ex-situ before being assembled into the negative electrode 102. Various embodiments include treating the DRI pellets (i.e., treating the DRI pellets ex-situ) with mechanical, chemical, and / or thermal methods before introducing the DRI pellets into the electrochemical cell to achieve better chemical and physical properties. Better chemical and physical properties may include a higher content of desired impurities (e.g., hydrogen evolution reaction (HER) inhibitors), a lower content of unwanted impurities (e.g., HER catalysts), a higher specific surface area, a higher total porosity, different pore size distributions (e.g., multimodal pore size distributions to reduce mass transfer resistance), different pellet size distributions (e.g., multimodal pore sizes to enhance bed packing), different aspect ratios (e.g., to enhance bed packing), etc. Mechanical methods that can be applied ex-situ to the DRI pellets may include crushing, grinding, and / or powdering. Thermal methods that can be applied ex-situ to the DRI pellets may include treating the DRI pellets at an elevated temperature in a reducing (e.g., hydrogen) atmosphere, an oxidizing atmosphere, and / or a carburizing (e.g., carbon monoxide and / or carbon dioxide) atmosphere. Chemical methods that can be applied ex-situ to the DRI pellets may 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 pre-treated by soaking them in an acid bath (e.g., concentrated HCl), etching the iron and expanding the pores in the DRI pellets, which will increase the total porosity of the DRI pellets compared to DRI pellets that are not etched in the acid bath. After the pre-treatment, the etched and now porous DRI pellets can be assembled into the negative electrode 102. The etching time can be optimized to increase the available capacity of the DRI pellets without losing too much active material of the DRI in the acid etching solution. In various embodiments, the DRI can be used as an electrode in an electrochemical cell and can be charged by an electric current. This method can increase the surface area of the DRI.

[0227] The current collector 106 can be in the form of a conductive plate electrically connected to the negative electrode 102. However, the current collector 106 can have other configurations, as discussed below with respect to Figure 2A what is discussed.

[0228] The positive electrode half-reaction that occurs during discharge at the air electrode 103 in an alkaline electrolyte can be O 2 +4e - +2H 2 O → 4OH - ; the corresponding half-reaction that occurs at the negative electrode 102, starting from fully metallic iron (fully charged negative electrode), can be 2Fe → 2Fe 2+ +4e - , resulting in a net discharge reaction of 2Fe + O 2+2H 2 O → 2Fe(OH) 2 。In multiple embodiments, oxygen can be delivered to the air electrode 103. The delivery of oxygen to the air electrode 103 can be carried out in a form other than gaseous oxygen, including oxygen-containing compounds in gaseous, liquid, or solid states.

[0229] The starting materials can have various configurations, with a range of iron valence states (0 to 3+) and counterions O 2- 、OH - 、S 2- etc. For example, other possible discharge products include Fe 2 O 3 、Fe 3 O 4 、FeO, FeOOH, FeS, FeS 2 etc. and their combinations.

[0230] In various embodiments, filling the pellets 105 in the bed to form the negative electrode 102 can create macropores between the individual pellets 105. Additionally, in multiple embodiments, each of the individual pellets 105 can have a porous (e.g., microporous) surface. Compared to the pellets 105 being smooth spheres, the micropores in the surface of the pellets 105 can provide a larger surface area for each individual pellet 105. The pore size of the pellets can vary. In some embodiments, the pellets 105 can have a volume-weighted average pore size greater than 1 micron, such as 1 micron to 10 microns, etc. The pore size distribution within the pellets can be measured by mercury intrusion porosimetry. Mercury intrusion porosimetry is a technique that uses a pressure chamber to press mercury into the pores of the pellets. The mercury is first pressed into the larger pores, and as the chamber pressure increases, the mercury is pressed into increasingly smaller pores. Physical relationships (such as the Washburn equation) can be used to relate the applied pressure to the pore size, thereby obtaining a volume-weighted or area-weighted pore size distribution. The pore size distribution can be converted into a cumulative distribution, from which the values of d 孔，90％体积 and d 孔，50％表面积 given in Tables 1, 2, and 3 above can be deduced.

[0231] Figure 6is a schematic diagram of a battery 100, showing an enlarged view of macropores 602 and micropores 604 according to various embodiments of the present disclosure. When the agglomerates 105 are filled into the bed, the macropores 602 are created by the gaps between the individual agglomerates 105. The macropores 602 can facilitate ion transport through a very thick (e.g., several centimeters) electrode 102. The micropores 604 can be deformations on the surface of the agglomerates 105 themselves. The micropores 604 can allow the active material with a high surface area to contact the electrolyte 104, achieving a high utilization rate of the active material through solid-solid electrochemical reactions. The micropores can include cracks in the agglomerates. Such cracks can be formed during the production process of the agglomerates or can be introduced later, for example, by applying a mechanical load that causes cracks. This electrode structure with macropores 602 and micropores 604 is particularly suitable for improving the rate performance of extremely thick electrodes for static long-term energy storage, where thick electrodes may be required to achieve extremely high areal capacities.

[0232] Figure 7 shows a single agglomerate 105 of the battery 100. The agglomerate 105 can include micropores 604 in the solid-phase surface 702 of the agglomerate 105. The electrolyte 104 can fill the micropores 604, thus giving the outer surface area of the sphere, that is, the liquid-phase electrolyte region related to the agglomerate 105, the micropores 604, and the surface 702 of the solid-phase region. The filling of the electrolyte into the micropores 604 reduces the solid-phase region where the surface 702 contacts the electrolyte on the outer surface of the agglomerate, making the agglomerate 105 have a low effective specific surface area (e.g., low m 2 / g), which reduces the electrolyte concentration boundary layer on the solid-phase surface 702. Many metal anodes (e.g., Zn, Fe, Al) in aqueous batteries are known to self-discharge due to spontaneous reactions with the electrolyte, forming oxidized metals and hydrogen gas. For long-term energy storage systems (e.g., systems with a discharge duration of 8 hours or longer, such as 8 hours to 20 hours, 20 hours to 24 hours, 24 hours or longer, etc.), self-discharge may limit performance because the battery cell may self-discharge a large portion of its stored capacity before the end of a complete discharge cycle. In some embodiments, metal electrodes with a low specific surface area (e.g., low m 2 / g) are used to suppress self-discharge in low-rate, long-term energy storage systems. In many typical modern electrochemical battery cells, a high specific surface area is required to promote high rate performance (i.e., high power) by introducing many reactive surface sites. In long-term systems, the rate performance requirements are significantly reduced, so electrodes with a low specific surface area can meet the rate performance requirements while minimizing the self-discharge rate.

[0233] In various embodiments, an electrolyte 104 additive that forms a thin passivation film (e.g., Na 2 MoO 4) It is added to the battery 100. In this way, the self-discharge of the anode can be limited to a small layer on the anode surface only. This passivation film will limit the extent of the self-discharge reaction. To restore the reactivity of the metal anode, short and intense charging pulses can reduce the surface film. Once the surface film is reduced, the discharge reaction can proceed.

[0234] In multiple embodiments, a resistive element is intentionally introduced into the battery 100 to achieve slow charging. By increasing the effective resistance of other cell parts (i.e., not the negative electrode 102 or the negative electrode current collector 106), greater overall cell polarization can be achieved. Doing so may cause the negative electrode 102 to have greater polarization. If the polarization of the additional negative electrode 102 is large enough, when the negative electrode 102 is an Fe electrode, the absolute potential of the electrode 102 may become low enough to activate the reaction Fe(OH) 2 →Fe at a lower cell-level current. The effect can be achieved by increasing the effective resistance of the electrolyte 104, the cathode (e.g., the electrode 103), or the cathode current collector.

[0235] Figure 2A is a schematic diagram of a battery 200 according to multiple embodiments of the present disclosure. The battery 200 is similar to the battery 100, so only the differences between them will be discussed in detail here.

[0236] Referring to Figure 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 provided. The liquid electrolyte 104 can separate the air electrode 103 from the negative electrode 102. The liquid electrolyte 104 can also impregnate the negative electrode 102.

[0237] In multiple embodiments, the negative electrode 102 can include compacted pellets 115. Herein, "compacted" can refer to a round rectangular prism. For example, the pellets 115 can have a length ranging from about 10 mm to about 500 mm, a width ranging from about 5 mm to about 250 mm, and a thickness ranging from about 5 mm to about 200 mm. In some embodiments, the pellets 115 can have a length of about 100 mm, a width of about 50 mm, and a thickness of about 30 mm. In multiple non-limiting embodiments, the pellets 115 can have an internal porosity ranging from about 50% to about 1%.

[0238] In multiple other embodiments, the pellets 115 can be formed from hot briquetted iron ("HBI"), which can be formed by combining and aggregating pellets, or can be formed by combining and aggregating powdered metal (e.g., powdered iron fines).

[0239] The current collector 106 can be formed of a conductive material electrically connected to the negative electrode 102. The current collector 106 can directly contact the lower surface and the side surface of the negative electrode 102. In some embodiments, the current collector 106 can optionally include protrusions 109 that extend through the negative electrode 102 to directly contact the internal region of the negative electrode. The protrusions 109 can also reduce the effective transport length of the spacing within the electrode 102 from the total thickness of the pellet bed to the protrusions 109. Additionally, these protrusions 109 can be used to secure a mechanical clamping mechanism to apply a downward force to the pellet bed while serving as current collecting elements. For example, Figure 2B An example of a plate 250 of the compression electrode 102 above the pellet bed 115 is shown. The plate 250 is fixed to the protrusions 109 by a clamp 252. The clamp 252 attaches the plate 250 to the protrusions 109 and causes the plate 250 to apply a compressive force to the bed of pellets 115 that serve as 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 utilize a magnet to compress the material forming the negative electrode 102. For example, the plate 250 can be a magnet that is attracted to the housing 101, the protrusions 109, and / or the bottom of the current collector 106, and the magnet can pull the plate 250 onto the pellets 115 to compress the bed of pellets 115 serving as the negative electrode. In some embodiments, the current collector 106, the protrusions 109, and / or another element in the battery 200 can be magnetic and can pull the pellets 115 downward and / or together to compress the pellet bed 115. In some embodiments, the current collector 106 can be a two-part current collector, with a first part attached to the front face of the negative electrode 102 and a second part attached to the back face of the negative electrode 102. The front face of the electrode can be the surface that is typically disposed toward the electrolyte, and the back face of the electrode can be the surface that is typically disposed away from the electrolyte. In some embodiments, the first part that can be connected to the front face can be a porous structure (e.g., a grid), while the second part connected to the back face can be solid. Having current collectors on the front and back faces of the electrode can help apply a clamping force and can achieve a more uniform reaction rate across the electrode. The front and back portions of the current collector may short-circuit together, thereby affecting the reaction rate distribution. In some embodiments, the current collector 106 can be sandwiched on the negative electrode 102.

[0240] In metal-air batteries, particulate and pelletized electrode materials have several advantages, including high surface area, large internal porosity, and high electronic conductivity. Additional advantages include more efficient transport and handling methods, which are greatly simplified for particulate and pellet materials compared to powder materials. Additional advantages include simplified fabrication of the negative electrode. In some embodiments, an electrode can be formed by dispersing or pouring pellets into a container or receptacle. The combination of the high electronic conductivity of the material and the weight of the pellets (which may be a result of the high density of iron-rich materials) can provide a low contact resistance between the pellets.

[0241] The electrical conductivities of materials that can form pellets are generally arranged in descending order: metallic Fe > FeO > Fe 3 O 4 > Fe 2 O 3 . However, materials with a higher degree of reduction have higher electrical conductivity and also require greater input energy during processing, so they are more expensive and difficult to prepare. Therefore, materials such as wüstite and mixed phases containing a certain amount of metallic iron (e.g., Fe / FeO, or Fe / Fe 3 O 4 , or Fe / Fe 2 O 3 ) are generally preferred. For example, wüstite (FeO) can provide the required balance between input energy, processing cost, and electrical conductivity. As a specific but non-limiting example, pellets can be made into reduced iron ore pellets with a composition close to FeO.

[0242] As a specific example, the pellets can be mainly spherical metallic iron pellets with a porosity of 50% (by volume) and a typical diameter of 10 millimeters (mm). The negative electrode can be 2 centimeters (cm) thick and can be formed by a packed bed of pellets. For hard-packed spheres, it is known that the packing density of randomly closely packed spheres can be about 64%, while closely packed spheres can reach a packing density of 74%. Therefore, the total solid-phase density of the negative electrode can be about 32% (50% × 64%) to 39% (50% × 74%). The negative electrode is permeated by a liquid electrolyte composed of potassium hydroxide (KOH) with a concentration of 6M (moles per liter).

[0243] Other advantages of the proposed negative electrode structure include low-curvature electrolyte channels present in the gaps between the pellets, allowing for rapid liquid-phase ion transport, and thick, high-areal-capacity (>0.1 Ah / cm 2 ) metallic negative electrodes can be used. The disclosed concept also allows for independent adjustment of the electrode surface area (i.e., the solid-liquid interface area) and electrode porosity, as the pellet porosity and packing density can vary independently.

[0244] As another advantage of the present invention, the pellets can be assembled by spreading and packing in a dry state. In other embodiments, the pellets can first be dispersed in a liquid electrolyte and then poured and spread into the battery container. In multiple embodiments, the container supporting the pellets can take various forms. Although shown as a pellet bed in Figure 1 and FIG. 2, the negative electrode 102 can have a variety of different shapes, such as conical, tubular, etc.

[0245] Figures 12A through 12Fis a cross-sectional view of exemplary batteries 1200A through 1200F, which have an alternative electrode configuration including an ordered array of agglomerates 105. Batteries 1200A through 1200F may be similar to battery 100, and thus only the differences between them will be discussed in detail.

[0246] Referring Figure 12A , battery 1200A may include one or more conical containers 1202 that support the agglomerates 105. The conical containers 1202 may self-align the agglomerates 105. The conical containers 1202 may enable a modular design of the negative electrode 102 by having a large "pool" type reactor, where multiple conical containers 1202 are located at the bottom of the pool of electrolyte 104. The conical containers 1202 may be a cost-effective design for bed current collection.

[0247] Referring Figure 12B , battery 1200B may include a container 101 that supports an array of negative electrode agglomerates 105 forming the negative electrode 102. One or more positive electrodes 103 may be inserted into the negative electrode 102. The agglomerates 105 may be electrically connected to each other and / or to the current collector 106. The spacer 107 may surround the positive electrode 103 and electrically insulate the positive electrode 103 from the negative electrode 102.

[0248] As Figure 12C shown, battery 1200C may include a positive electrode 103 that extends completely through the negative electrode agglomerate array. In battery 1200C, the agglomerates 105 may be arranged in a stack alternating with the electrode 103. Referring Figure 12D , battery 1200D, battery 1200D is similar to battery 1200C, except that the spacer is omitted. In battery 1200D, the agglomerates 105 may be arranged in a support bed that floats in the electrolyte 104 together with the electrode 103.

[0249] Figure 12E Another example battery 1200E according to multiple embodiments of the present disclosure is shown. In battery 1200E, the agglomerates 105 may be arranged in a hexagonal array around the electrode 103, and the electrode 103 may be circular. Figure 12F Another example battery 1200F according to multiple embodiments of the present disclosure is shown. In battery 1200F, the agglomerates 105 may be arranged in a hexagonal array around the electrode 103, and the electrode 103 may be hexagonal.

[0250] As described above, the agglomerates of the present disclosure are not limited to any specific agglomerate shape. In multiple embodiments, the agglomerates may be iron agglomerates having a variety of different shapes, such as Figure 3AThe sintered iron agglomerate particles 305 shown in [Fig.]. The sintered iron agglomerate particles can have symmetric and / or asymmetric shapes. As an example, the sintered iron agglomerate particles can have a symmetric shape, such as spherical, oval, cylindrical, or plate-shaped, or an irregular shape (e.g., granular). In various embodiments, the sintered iron agglomerates 305 can be formed in a furnace, such as a continuous-feed calciner, a batch calciner, a shaft furnace, or any other type of furnace. As a specific example, when the furnace is a continuous-feed calciner, the furnace 307 can be configured with a rotating tube. In operation, iron powder particles 302 can be fed into the furnace 307. The furnace 307 can rotate and heat the iron powder agglomerates 302 to sinter the iron powder agglomerates 302 together, thereby fabricating sintered iron agglomerate particles, such as the sintered iron agglomerate particles 305. The sintered iron agglomerate particles, such as the sintered iron agglomerate particles 305, can provide the same chemical properties and morphology as the sintered pellets described herein (e.g., pellet 105, pellet 115, etc.) and can replace pellets of other shapes in various embodiments. The sintered iron agglomerate particles, such as the sintered iron agglomerate particles 305, can include a neck 309 at the sintered joint of the iron powder agglomerates 302 bonded together to form the sintered iron agglomerate particles, such as the sintered iron agglomerate particles 305.

[0251] The advantage of using pellets to form iron agglomerates is that fabricating such iron agglomerate pellets (e.g., sintered iron agglomerate particles 305) can be less expensive than fabricating spherical and / or briquetted pellets (e.g., pellet 105, 115, etc.).

[0252] In various embodiments, sintered iron electrodes (e.g., the entire electrode and / or individual pellets (e.g., pellet 105, 115, 305, etc.)) can be formed from crushed precursors and / or by-product materials (e.g., DRI) (e.g., fines) from a steelmaking process. For example, DRI precursors and DRI fines can be crushed, formed with a binder under heat and pressure, and then sintered to form porous iron electrodes in the shape of pellet 105, 115, 305, etc. and / or electrodes of other shapes, including but not limited to sheet, plate, strip, cylindrical, and other shapes.

[0253] Reference is made below Figures 3B - 3D The various embodiments discussed provide sintered porous metal electrodes for fabricating batteries (e.g., batteries 100, 200, 400, 800, 814, 900, 1000, 1100, and 1200 described herein).

[0254] Figure 3B An embodiment of a method 350 for fabricating a sintered porous metal electrode is shown. Method 350 can include mixing a metal and one or more additives in block 351 to form a green-shaped pellet, and sintering the green-shaped pellet in block 352 to form a porous metal electrode.

[0255] In block 351, mixing a metal and one or more additives to form a "green" shaped pellet can include hot pressing a mixture of the metal and one or more additives to form a green shaped pellet. In various embodiments, the metal can include iron. In various embodiments, the additives can include a combination of a pore former and a binder additive. As a specific example, a mixture of iron, polyethylene, and bismuth sulfide powder can be hot pressed into a green shaped pellet. In various embodiments, polyethylene can serve both as a green shaping binder and as a pore former that evaporates during the sintering step. Polyethylene can sublime at a temperature below the sintering temperature. In various embodiments, other pore former additives that do not necessarily serve as binders can be used, such as any inorganic or organic material that is solid at room temperature in a nitrogen (e.g., N 2 ) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H 2 (5%) or other corresponding argon and hydrogen concentrations) atmosphere and is liquid or gaseous in nitrogen between room temperature and the sintering temperature. In various embodiments, multiple types of binders can be mixed together as additives to the metal. The mixing of multiple types of binders can be used to target a specific microstructure morphology and to stabilize the powder bed during the binder burnout process.

[0256] In block 352, sintering the green shaped pellet to form a porous metal electrode can include sintering the green shaped pellet in a gas atmosphere according to a time-temperature profile. The gas atmosphere can be a nitrogen (e.g., N 2 ) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H 2 (5%) or other corresponding argon and hydrogen concentrations) atmosphere. In various embodiments, the time-temperature profile can be a linear time-temperature profile or a non-linear time-temperature profile. For example, a linear time-temperature profile can include a linear temperature ramp-up period, followed by a constant hold temperature period, followed by a linear decline period. As a specific example, sintering the green shaped pellet in a gas atmosphere according to a time-temperature profile can include sintering the green shaped pellet in a nitrogen (e.g., N 2 ) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H 2 (5%) or other corresponding argon and hydrogen concentrations) atmosphere, where the temperature is linearly ramped up to 850°C, held at 850°C for 15 minutes, and then linearly declined to room temperature. As another example, a non-linear time-temperature profile can have multiple heating zones and hold zones to better control the evaporation rate of the pore former (e.g., the polyethylene pore former). For example, a non-linear time-temperature profile can have a non-linear temperature ramp-up period, two or more hold temperature periods with decline and ramp-up periods therebetween, and a non-linear decline period.

[0257] Figure 3C FIG. 360 shows an embodiment of a system 360 for forming a sintered porous metal electrode 362. The system 360 can include a continuous roller furnace having a series of heating elements 364 and a belt 366, the rollers being configured to convey an article on the belt 366 from one end of the furnace to the other when heated by the heating elements 364. The area below the heating elements 364 can be configured to have controlled atmosphere conditions, such as an atmosphere of pure hydrogen (H 2 ) supplied by a hydrogen gas tank 369. The system 360 can include a powder supply source 370 (such as a hopper, container, drum, etc.) that provides a metal powder 371 (such as an iron oxide powder, etc.) for forming the sintered porous metal electrode 362. When the metal powder 371 is an iron oxide powder, the iron oxide powder may or may not be oxidized in air at high temperature, which will result in a fully oxidized (Fe 2 O 3 ) powder raw material. The metal powder 371 can be deposited from the powder supply source onto the belt 366 and compressed (i.e., below the heating elements 364) before being fed into the furnace. As an example, the metal powder 371 can be compressed by a slot die, a press roller 372, a press, or other compaction-type devices at the front of the furnace. The compressed metal powder can be fed by the belt 366 along the length of the furnace below the heating elements 364. Since the metal powder 371 is heated by the heating elements 364 in a hydrogen atmosphere while being moved by the belt 366, H 2 O vapor can be released from the metal powder 371. Hydrogen reduces iron oxide at high temperature to form water and metallic iron (i.e., FeO x +H 2 →H 2 O+Fe). The resulting metal powder (such as iron powder) rolls on the belt 366 and continuously passes through the furnace, causing the particles to sinter together to form the sintered porous metal electrode 362 (such as a sintered porous Fe electrode) in a continuous manner. In some embodiments, the sintered porous metal electrode 362 can be cut into pieces after leaving the furnace, such as by a knife 378, a guillotine cutter, a cutting jet, or any other type of device configured to cut the sintered porous metal electrode 362 into pieces. In some embodiments, the weight of the sintered porous metal electrode 362 can break it up.

[0258] Figure 3DA system 380 for forming a sintered porous metal electrode 362 is shown. System 380 may be similar to system 360 described above, except that a metal sheet 382 may be placed below the metal powder 371 before the metal powder 371 is fed into the furnace. In this way, the metal powder 371 can 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 metal coil that is fed into the furnace below the metal powder 371 and supports the metal powder 371 on the belt 366. For example, the metal sheet 382 may be fed onto the belt 366 by a reel of the reel system 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 be used as a current collector, such as nickel, iron, steel, etc.

[0259] Figure 4 is a schematic diagram of a battery according to various embodiments of the present disclosure. Battery 400 is similar to battery 100, and thus only the differences between battery 100 and battery 400 will be discussed in detail. Battery 400 may include spherical agglomerates 105 distributed in a smaller agglomerate composition (e.g., a composition formed of powdered metal raw materials, metal fine powders, metal abrasive grains, etc.).

[0260] Long-term electrochemical energy storage can benefit from very low-cost material inputs. Although the spherical agglomerates 105 of battery 100 can provide extremely low-cost materials, the electrical conductivity and ionic conductivity through the spherical agglomerates 105 may not be ideal due to the limited contact points inherent in contacting the spherical agglomerates 105. One solution to provide better electrical conductivity and ionic conductivity can be to use powdered metal raw materials as electrodes, such as negative electrode 102. Although the powdered metal raw materials used as electrodes can provide customized electrical conductivity and ionic conductivity, the production cost of the powdered metal raw materials may be very high, especially compared to the spherical agglomerates 105.

[0261] Various embodiments may provide a composite metal electrode architecture that provides a lower cost than a pure powdered metal raw material electrode and / or a higher electrical conductivity than a pure spherical agglomerate electrode. As used herein, the average width or diameter of the agglomerates is at least 10 times the average width or diameter of the powder agglomerates in the powdered metal raw material. In various embodiments, the composite metal electrode architecture may include a mixture of spherical agglomerates and a smaller metal agglomerate composition (e.g., powdered metal raw materials). For example, as Figure 4As shown, the negative electrode 102 can include spherical agglomerates 105 distributed in a smaller metal agglomerate composition 402 (such as a powdered metal feedstock). The spherical agglomerates 105 and the powdered metal feedstock can provide, as the negative electrode 102, a mixture of larger and smaller agglomerates similar to marbles in sand or other combinations of corresponding particle sizes. In some embodiments, the macropores between the larger agglomerates contain the smaller agglomerates. The composite metal electrode formed by the spherical agglomerates 105 and the powdered metal feedstock can provide an electrode framework with highly adjustable cost, conductivity, and / or ionic conductivity. In some embodiments, the composite metal electrode can be wetted with a liquid electrolyte 104. Since the powdered metal feedstock contained in the composite metal electrode can be wetted, the composite metal electrode formed by the spherical agglomerates 105 and the powdered metal feedstock can have a lower iron-to-electrolyte ratio compared to an electrode formed only by the spherical agglomerates 105. The powdered metal feedstock 402 can improve the conductivity between the agglomerates 105 in the electrode 102 and can also improve the overall packing density of the electrode.

[0262] In various embodiments, the composite metal electrode framework can include a mixture of spherical agglomerates and a smaller metal agglomerate composition (such as metal fines or metal turnings). For example, as Figure 4 shown, the negative electrode 102 can include spherical agglomerates 105 composed of taconite and a smaller metal agglomerate composition 402 composed of conductive DRI fines. By combining low-cost taconite agglomerates and scrap, which are used as the massive iron feedstock for the agglomerates 105, with conductive DRI fines used as the smaller metal agglomerate composition 402, the cost of forming a conductive electrode during the assembly of the battery 400 can be reduced. As other examples, the composite metal electrode framework can include a mixture of iron ore agglomerates of different sizes, such as larger iron ore agglomerates (such as taconite, DRI, sponge iron, atomized iron, etc.) and a smaller metal agglomerate composition, such as metal fines or metal turnings (such as fines or turnings of DRI, taconite, sponge iron, atomized iron, etc.).

[0263] In some embodiments, the conductivity of the metal electrode is increased by adding conductive fibers, wires, meshes, or sheets to the agglomerates so that the conductive material is dispersed between the individual agglomerates.

[0264] Multiple embodiments provide for in-situ synthesis of active materials for a bulk energy storage system using excess generated renewable electrical energy. In multiple embodiments, the chemical cost can be reduced by configuring an energy storage station that includes a cell embodiment (e.g., the metal-air electrochemical cell embodiments discussed herein) to be dual-purpose. The initial use of the energy storage station can be to in-situ synthesize key active materials, such as metal pellets, like pellets 105, 115, 305, etc., using a lower cost input chemical and very cheap or free renewable electrical energy. The next use of the energy storage station can be as an actual energy storage station, where the synthesized chemical is the active material, such as metal pellets, like pellets 105, 115, 305, etc. For example, the metal powder that will ultimately be used in an ultra-large battery can be in-situ synthesized at the dual-purpose energy storage station prior to the battery's commissioning, by using direct reduction of hydrogen, which is electrochemically in-situ generated by alkaline electrolysis or PEM electrolysis powered by renewable resources (e.g., wind energy, solar energy, etc.). The in-situ production of the active material in the first stage can not only reduce the production cost but also potentially avoid transportation costs. In embodiments where iron ore is the source of the active material, renewable electrical energy can be used to provide heat to reduce the ore at the dual-purpose energy storage station. Additionally, renewable electrical energy can optionally be used to produce hydrogen as a reducing gas to reduce the ore. The ore or reduced ore can optionally be in the form of iron-containing pellets.

[0265] In multiple embodiments, metal pellets (e.g., pellets 105, 115, 305, etc.) can be synthesized in the first stage of the dual-purpose energy storage station and used in the negative electrode in the second stage of the dual-purpose energy storage station. Figure 5 An embodiment of a method 500 is shown for in-situ synthesis of active materials (e.g., metal pellets, like pellets 105, 115, 305, etc.) for a bulk energy storage system using excess produced renewable electrical energy. In block 501, during the first stage of operation, the dual-purpose energy storage station can be operated to produce active materials, such as metal pellets, like pellets 105, 115, 305, etc. For example, when iron ore is the source of the active material, the ore can be in-situ reduced at the dual-purpose energy storage station to synthesize metal pellets, like pellets 105, 115, 305, etc. During the second stage of operation in block 502, the dual-purpose energy storage station can use the active materials for long-term energy storage. For example, the synthesized metal pellets (e.g., pellets 105, 115, 305, etc.) can be loaded (or otherwise deposited, added, formed, etc.) into the negative electrode (e.g., electrode 102 of a battery, etc.) to support long-term energy storage at the dual-purpose energy storage station. In multiple embodiments, renewable electrical energy can be used to perform the operations of block 501 and / or 502.

[0266] Figure 8ASchematic diagram of a battery 800 according to various embodiments of the present disclosure. The battery 800 is similar to the battery 100, and thus only the differences between them will be discussed in detail. The battery 800 can be configured to allow the electrolyte 104 to flow over the negative electrode 102. For example, the battery 800 can include a circulation pump 802 and pipes configured to pump the electrolyte 104 onto the agglomerates 105 including the electrode 102 at a selected rate (e.g., constant flow rate, variable flow rate, etc.). Transporting the electrolyte 104 through a very thick (several centimeters) battery electrode 102 (composed of active material agglomerates 105) can be challenging. The low transport rate of the electrolyte 104 may increase the overpotential loss in the electrode 102 based on the agglomerates 105. By flowing the electrolyte 104 over the thick electrode 102, convective transport can be introduced, which promotes the flow of the electrolyte to the individual agglomerates 105. As described above, the agglomerates 105 can be microporous, and the reaction conditions can benefit from reducing the electrolyte concentration boundary layer, which can occur across the thickness of the entire bed of agglomerates 105 (e.g., across the electrode 102) and at the macropores (e.g., macropore 602) in the bed of agglomerates 105. By homogenizing the electrolyte 104 composition in the macrostructure and microstructure of the entire electrode 102, electrolyte 104 flow generally reduces the overpotential loss. The flow rate of the electrolyte 104 can preferably be selected to be low enough such that any energy consumed by pumping does not consume undesirable energy. In various embodiments, the flow rate of the electrolyte 104 can be a steady flow rate or a variable flow rate.

[0267] In various embodiments, by flowing the electrolyte 104 at a low but constant flow rate over the battery electrode 102 (e.g., the battery electrode 102 composed of active material agglomerates 105), convective transport can be introduced, which promotes the flow of the electrolyte 104 to the individual agglomerates 105. The agglomerates 105 can be microporous and the reaction conditions can benefit from reducing the electrolyte concentration boundary layer, which can occur across the thickness of the entire agglomerates 105 (e.g., across the electrode 102) and at the macropores (e.g., in the electrode 102) in the bed of agglomerates 105. By homogenizing the electrolyte 104 composition in the macrostructure and microstructure of the entire electrode 102, electrolyte 104 flow can generally reduce the overpotential loss.

[0268] In multiple embodiments, the electrolyte 104 formulation can be different for the charging, discharging, and idle states of the battery 800. When switching between states, flowing different electrolyte 104 formulations into the battery 800 can simultaneously improve utilization, self-discharge, and HER. For example, in the case of an electrolyte management system with continuous flow, there can optionally be any number of different electrolyte formulation reservoirs, each connected to the electrochemical cell through a separate flow controller (e.g., a combination of three reservoirs and flow controllers 805, 806, 807). During different operations, different relative amounts of each electrolyte formulation can flow based on the optimal concentration of the constituent materials for the instantaneous operating mode (e.g., charging, discharging, idle). In some embodiments, the electrolyte formulation can be adjusted based on the instantaneous charge state of the battery 800. In multiple embodiments, the combination of reservoirs and flow controllers (e.g., 805, 806, 807) can be used to add additional electrolyte 104 to the battery 800, for example, to compensate for the evaporation of the electrolyte 104. In multiple embodiments, the battery 800 can include an overflow port 820 or an overflow channel through which the electrolyte 104 can overflow from the battery 800. For example, the level of the electrolyte 104 can be maintained because when the level of the electrolyte 104 reaches the overflow port 820, it can leave the battery 800 to maintain the level of the electrolyte 104 at the level of the overflow port 820.

[0269] Figure 8B FIG. is a block diagram of an embodiment of a battery 814 that includes an additive delivery system 815. The battery 814 is similar to the battery 100, so only the differences between them will be discussed in detail. In one embodiment, the additive delivery system 815 can be a pump that delivers an additive-containing liquid to the battery 814. In another embodiment, the additive delivery system 815 can be a dry hopper that delivers an additive-containing solid to the battery 814. As an example, the additive delivery system 815 can be a sulfur delivery system. As a specific example, when the additive delivery system 815 is a sulfur delivery system, the sulfur delivery system can be a pump that delivers a sulfur-containing liquid to the battery 814. In another specific example, when the additive delivery system 815 is a sulfur delivery system, the sulfur delivery system can be a dry hopper that delivers a sulfur-containing solid (e.g., polysulfide salts, iron sulfide (FeS), etc.) to the battery 814. In another example, the additive delivery system 815 can be a salt delivery system. Specifically, the additive delivery system 815 can add certain solid-phase hydrogen evolution inhibitors (e.g., Bi, Sb, As) as soluble salts. For example, the soluble salts of the desired hydrogen evolution inhibitor can be added to the liquid electrolyte 104 through the additive delivery system 815 and dissolved to provide the ions of the desired additive in the solution (i.e., Bi 3+ 、Sb 3+ 、As 3+) Additives can be selected such that the redox potential of the inhibitor's ion - metal electroplating reaction (e.g., Bi 3+ →Bi 0 ) can be at a half - cell potential higher than the charging reaction potential of the anode active material (measured relative to RHE but at a lower cell potential). Thus, during the charging of battery 800, the ionic form HER inhibitor is electrodeposited onto the surface of the metal electrode, providing a cheap and simple strategy for introducing the HER inhibitor into the chemistry of battery 800 electrolyte 104. The electrodeposited inhibitor suppresses the hydrogen evolution reaction on the electrode surface, which can be an electrode with open pores. In the discharge mode, the deposit may dissolve back into the electrolyte 104. Salt additives can be preferably selected such that they do not reduce the operation of the cathode during charge or discharge operation. As another example, the added salt can be a carbonate. In some embodiments, the additive delivery system 815 can deliver multiple additives to battery 800. For example, a combined additive composition can be delivered through the additive delivery system 815, such as a combination of a corrosion inhibitor that inhibits the HER reaction or self - discharge and an additive that improves capacity utilization. As another example, an inhibitor that forms a passivation layer on the metal surface is paired with an additive that depassivates the iron surface, and both can be delivered by the additive delivery system 815. In some embodiments, the additive delivery system 815 can deliver additives containing molybdate ions. As an example, molybdate ions can be added through molybdate compounds (such as KMoO 4 ). In a specific example, electrolyte 104 can contain an additive with a concentration of 10 mM molybdate anions. In other embodiments, electrolyte 104 can contain additives with a concentration range of 1 mM to 100 mM molybdate anions. In some embodiments, surfactant additives can be delivered by the additive delivery system 815. Surfactant additives can reduce the surface tension and viscosity of the electrolyte at the oxygen - evolving electrode, thereby generating smaller, uniformly sized, and controllable bubbles during charging. In a non - limiting example, 1 - octanethiol at a concentration of 10 mM is added to the alkaline electrolyte 104. In some embodiments, corrosion inhibitor additives can be delivered by the additive delivery system 815. In some embodiments, the additive delivery system 815 can deliver liquid inhibitors and / or interphase inhibitors. In some embodiments, the additive delivery system 815 can deliver additives as a solid mixture. In some embodiments, the additive delivery system 815 can deliver electrolyte additives that form a thin, passivation film (e.g., Na 2 MoO 4)。Therefore, the self-discharge of the anode is limited to a small layer on the anode surface. However, to restore the reactivity of the metal anode, short and intense charging pulses can be used to reduce the surface film. Once the surface film is reduced, the discharge reaction can proceed.

[0270] Figure 8CFIG. 850 is a block diagram of a battery system 850 according to multiple embodiments, the battery system 850 including a series of fluidly connected (or otherwise in liquid communication) battery 800 embodiments. The batteries 800 may be arranged in a cascade manner such that the overflow electrolyte 104 from one battery 800 may flow via its overflow outlet 820 into the next battery 800, thereby establishing "liquid communication" between the batteries 800. Connecting these batteries 800 in series allows a single source to supply the liquid electrolyte 104 to multiple batteries 800 simultaneously. For example, a single electrolyte supply tube 851 connected to a pump 802 may supply the electrolyte 104 to the first battery 800. The electrolyte overflowing from the first battery 800 may flow to the second battery 800 and the third battery 800. The electrolyte may overflow from the third battery 800 into a return tube 852 and be recycled by the pump 802 back to the supply tube 851. In this way, the overflow from the final battery 800 may be recycled into the first battery 800. In a system 850 that utilizes a shared electrolyte 104, the electrolyte flows in a cascade manner between the batteries 800, and the properties of the electrolyte 104 may be monitored and processed at a central location of a number of the batteries (such as a monitoring station 853). To mitigate issues related to electrolyte carbonation, electrolyte dehydration, etc., electrolyte 104 adjustment, such as composition adjustment or addition of components, may be advantageously performed at the monitoring station 853. The monitoring station 853 may be juxtaposed with a collection structure (such as the return tube 852) for recycling the electrolyte 104. As an example, the monitoring station 853 may control the supply of the electrolyte 104 from different combinations of reservoirs and flow controllers (such as 805, 806, 807), a filtration device 860, and / or a backup electrolyte supply tank 855. In multiple embodiments, the monitoring station 853 may be configured to monitor electrolyte health. The health of the electrolyte may be monitored during battery operation to determine an appropriate time to replenish, replace, or process the electrolyte 104. The feedback mechanism employed by the monitoring station 853 may be manual or automatic. When the monitoring station 853 is an automated system, the electrolyte quality measurement may be an input to a control loop (such as a proportional integral derivative (PID) loop) that continuously adjusts the concentration of the electrolyte composition. The electrolyte quality measurement may be done off-site on a small portion of the electrolyte 104, or may be done on the active electrolyte 104 while the battery 800 is operating. A non-limiting method of evaluating electrolyte health is to measure the conductivity of the electrolyte. One mechanism of degradation is due to carbon dioxide dissolving in the electrolyte from the air, causing the electrolyte to carbonate over time. For example, a conductivity probe is used to evaluate the concentration of carbonate in the electrolyte. The conductivity probe is used to monitor the health state of the electrolyte. Although shown as part of the cascade system 850, the monitoring station 853 may equally be part of an electrolyte delivery system for a single battery, such as Figure 8AThe electrolyte system. The monitoring station 853 can control the release of the electrolyte 104 from the standby electrolyte supply tank 852 and / or the release to the standby electrolyte supply tank 852 to increase and / or decrease the volume of the electrolyte 104 in the system 850. The monitoring station 853 can control the liquid flow through the filtration device 860. The filtration device 860 can be configured to filter the liquid flowing through it (such as water, electrolyte 104, etc.), and the monitoring station 853 can control the inflow and outflow of the liquid to and from the filtration device 860. For example, the filtration device 860 can be a water filter, such as Figure 14 the water filter 1400 shown. The water filter 1400 can be a packed bed 1401 of DRI, which can be used as a water filtration device. In such an embodiment, the DRI can be contained in a column to produce a packed bed 1401 of DRI pellets 197. When water flows through the bed 1401, particulate matter will be trapped in the pores inside the DRI pellets 197 and in the voids between the DRI pellets 197. The ability to adjust the pressure drop and filtration effect can be achieved using granular iron as the filtration mechanism.

[0271] Figure 9 is a schematic diagram of a battery 900 according to various embodiments of the present disclosure. The battery 900 is similar to the battery 100, so only the differences between them will be discussed in detail. The alkaline iron electrode cell operates optimally when certain additives are present in the electrolyte and / or the cell. The electrolyte additives may have a range of solubilities, and some electrolyte additives may have the most beneficial effects when closely mixed with the solid electrode. As Figure 9 shown, in various embodiments, the pellets 902 including the additive can be mixed with the pellets 105 predominated by the active material, so that the negative electrode 102 can be a mixed electrode. The additive pellets 902 can be formed partially and / or entirely of an additive, such as an iron sulfide compound, such as FeS, FeS 2 etc. In various embodiments, the liquid electrolyte 104 can include an additive to inhibit the hydrogen evolution reaction at the anode or cathode. These inhibitors can be soluble or insoluble, and can include metalloid HER inhibitors, such as bismuth, antimony, tin, boron, indium, gallium, selenium. The additive can be plated out from the solution or undergo a phase change during operation, for example, starting from a dissolved solution and then precipitating in a solid form.

[0272] Figure 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 discussed in detail. Due to the spherical structure of the pellets 105 in contact with the current collector 106 in the battery 100, the interfacial resistivity between the current collector 106 and the negative electrode 102 composed of the pellets 105 may be high. Therefore, the electrode 102 experiences an increase in the effective current density at the pellet contact. In various embodiments, asFigure 10 As shown in the battery 1000 of Figure 10 , adding an iron powder (Fe) layer 1002 to the interface between the electrode 102 and the current collector 106 can reduce the interface resistivity. In the battery 1000, the iron powder layer 1002 can be added to the bottom of the pellet 105 bed to reduce the interface resistivity. The iron powder layer 1002 can be configured to form an interface between the pellet 105 and the current collector 106 of the battery 1000. The average width or diameter of the pellet 105 is at least 10 times the average width or diameter of the powder pellets in the layer 1002.

[0273] Figure 11 is a schematic diagram of a battery 1100 according to various embodiments of the present disclosure. The battery 1100 is similar to the battery 100, and thus only the differences between them will be discussed in detail. The battery 1100 can include a monitoring system that includes one or more sensors connected (e.g., wirelessly or by wire) to a controller 1110, which is 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 can be valuable for improving the control and health monitoring of the battery 1100.

[0274] Various embodiments can include one or more of a plurality of methods for monitoring chemical and / or physical properties of the negative electrode 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 the mass of the battery 1100 cell, measuring magnetic susceptibility, and using gas sensing. In various embodiments, a NiOH / NiOOH electrode containing a carbon conductive additive and / or a binder can be used as a quasi-reference electrode to monitor the electric potential. These NiOH / NiOOH electrodes can be placed at multiple locations throughout the electrolyte container to monitor the electric potential distribution of the entire system.

[0275] For example, the SOC and / or SOH can be monitored in-situ by one or more strain gauges 1102 connected to the container 101. One or more strain gauges 1102 can be connected to the controller 1110 and can output a measurement of the strain on the container 101 to the controller 1110. The controller 1110 can be configured to convert the strain measurement into an SOC and / or SOH measurement.

[0276] As another example, the SOC and / or SOH can be monitored in-situ by a Mössbauer spectrometer including a gamma source 1103 and a gamma detector 1104. The gamma source 1103 can output gamma rays through the battery 1100, and the gamma rays can be detected by the gamma detector 1104. The gamma source 1103 can be connected to a controller 1110, and the controller 1110 can control the gamma source 1103 to output gamma rays. The gamma detector 1104 can be connected to the controller 1110 and can output the measured value of the gamma rays to the controller 1110. The controller 1110 can be configured to convert the measured value of the gamma rays into a SOC and / or SOH measured value.

[0277] As another 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 detector 1105 can capture an image of the negative electrode 102 and output it to the controller 1110. The controller 1110 can be configured to use the image to determine the SOC and / or SOH measured value. For example, the controller 1110 can be configured to correlate the color of the agglomerates 105 in the image with the SOC and / or SOH measured value. As another example, the controller 1110 can be configured to measure the size of the agglomerates 105 from the image data and / or can be configured to measure the height of the agglomerate 105 bed from the image data.

[0278] As another example, the SOC and / or SOH can be monitored in-situ by one or more ultrasonic transducers 1106 connected to the controller 1110. The ultrasonic transducer 1106 can output the acoustic wave measured value to the controller 1110. The controller 1110 can be configured to use the acoustic wave measured value to determine the SOC and / or SOH measured value. For example, based on the round-trip time of the acoustic wave to the surface of the agglomerate 105 bed, the controller 1110 can determine the height change of the agglomerate 105 bed and correlate it with the SOC and / or SOH measured value.

[0279] As another example, the SOC and / or SOH can be monitored in-situ by one or more ion sensing electrodes 1107 connected to the controller 1110. The ion sensing electrode 1107 can output the ion measured value (e.g., ion concentration) to the controller 1110. The controller 1110 can be configured to use the ion measured value to determine the SOC and / or SOH measured value.

[0280] As another example, the SOC can be monitored in-situ by one or more thermocouples 1108 connected to the controller 1110. The thermocouple 1108 can output the temperature measured value to the controller 1110. The controller 1110 can be configured to use the temperature measured value to determine the SOC and / or SOH measured value.

[0281] As another example, the SOC and / or SOH can be monitored in-situ by one or more gas sensors 1109 connected to the controller 1110. The gas sensors 1109 can output gas measurement values to the controller 1110, such as specific particle detection, concentration, etc. The controller 1110 can be configured to use the gas measurement values to determine the SOC and / or SOH measurement values.

[0282] In multiple embodiments, the physical and / or chemical properties of the battery 1100 measured by the plurality of sensors 1102 - 1109, more specifically the physical and / or chemical properties of the negative electrode 102, can be used by the controller 1100 to determine control operations to be taken regarding the battery 1100, such as ensuring healthy operation of the battery 1100 based on monitoring the SOC and / or SOH of the negative electrode 102.

[0283] Figure 13A A battery 1300 is shown according to multiple embodiments. As an example, the battery 1300 is a static battery using DRI. In some embodiments, the battery 1300 is a non-flowing aqueous battery. In some embodiments, the battery 1300 can be a primary battery. In some embodiments, the battery 1300 can be a secondary battery. In some embodiments, the battery 1300 can include DRI agglomerates 198 in one electrode 1302 and / or can include DRI agglomerates 199 in another electrode 1306. Although illustrated as both including DRI agglomerates 198, 199, in some configurations, only one of the electrodes 1302 or 1306 can include DRI agglomerates 198, 199 respectively, while in other configurations, both electrodes 1302, 1306 can include DRI agglomerates 198, 199 respectively. In multiple embodiments, the electrodes 1302 and 1306 can be separated by an electrolyte 1304. In multiple embodiments, the battery 1300 can be a sealed battery. In multiple embodiments, the battery 1300 can be an open battery, such as an air-open type battery. In multiple embodiments, the DRI agglomerates 198 can be similar to the various DRI agglomerates (or other DRI type structures) described herein, such as DRI agglomerates 105, 115, 305, etc.

[0284] In multiple embodiments, electrode 1302 is the anode of battery 1300, and electrode 1306 is the cathode of battery 1300. In multiple embodiments, when battery 1300 is of the primary or secondary type, DRI is used as the redox-active electrode material. In one embodiment, when battery 1300 is a secondary battery, DRI (e.g., DRI agglomerates 198) is used as the anode active material. In another embodiment, DRI (e.g., DRI agglomerates 198, 199) is used as the electrode material with an alkaline electrolyte (pH > 9). In a specific embodiment, when battery 1300 is an alkaline secondary battery, battery 1300 can employ a nickel cathode. In this embodiment, DRI serves as the starting material for the anode of Ni-Fe alkaline secondary battery 1300 and can be used in its original state or processed prior to use according to other embodiments described herein. When battery 1300 is an alkaline battery employing a DRI anode, other electrochemical couples (combinations of cathode and anode) can be used, including iron / nickel (Fe / Ni cell) or iron / silver (Fe / Ag cell). In multiple embodiments, when battery 1300 is a primary or secondary battery, DRI can be used as the anode active material, where the pH of the electrode spans the acidic (pH < 5.5) or neutral (5.5 < pH < 9) range. As an example, DRI can be used as the anode active material in battery 1300 with an electrolyte containing hydrochloric acid (HCl) in the concentration range of 1M - 5M. At the anode, DRI can participate in the following half-cell reaction during discharge: Fe + 2Cl - →FeCl 2 + 2e - .

[0285] When battery 1300 is an all-Fe battery, DRI can specifically be used as the anode material, where Fe is a reactive species at both the anode and the cathode. In such an embodiment, DRI can be used as the solid metal Fe anode at 100% SOC, and this anode will form soluble Fe 2+ species (e.g., FeCl 2 ) during discharge. The cathode active material can be an Fe-based soluble inorganic salt, such as the FeCl 2 / FeCl 3 redox couple. The cathode active material can also be an inorganic coordination compound or an organic coordination compound, such as K 3 Fe(CN) 6 . At the cathode, the soluble Fe species will undergo a reaction with Fe 2+ / Fe 3+Redox reactions related to redox couples. As a specific example, when the battery 1300 is a full-Fe battery using DRI as the active material, the battery 1300 can utilize DRI as the anode material and use an electrolyte containing HCl (concentration 1M - 5M). At the anode, DRI participates in the following half-cell reaction during discharge: Fe + 2Cl - →FeCl 2 + 2e - . At the cathode, soluble FeCl 3 will undergo the following half-cell reaction during discharge: 2FeCl 3 + 2e - →2FeCl 2 + 2Cl - . The full-cell reaction during discharge is Fe + 2FeCl 3 →3FeCl 2 . DRI can be used as a raw material for the required soluble FeCl 2 in the solution to participate in the cathode reaction by allowing DRI to react with HCl in the solution, thus participating in the following spontaneous chemical reaction: Fe + 2HCl → FeCl 2 + H 2 .

[0286] Figure 13B FIG. shows a battery 1310 according to multiple embodiments. The battery 1310 is similar to the above-described battery 1300, except that the battery 1310 is a flow battery using DRI. In multiple embodiments, the DRI pellets 198, 199 are transported through the respective electrodes 1302, 1306 of the flow battery 1310 by one or more corresponding transport systems 1314, 1316 from the respective storage tanks 1311, 1312. As an example, DRI can be used as the anode in the flow battery 1310, where the DRI pellets are transported from the storage tank to the electrochemical reactor where the DRI pellets undergo an electrochemical reaction. The DRI pellets remain in electrical contact with each other as they flow through the electrochemical reactor, thus enabling sufficient electroosmotic flow to provide high conductivity by collecting the pellets. The electrolyte 1304 can be acidic (pH < 5), neutral (5 < pH < 9), or basic (pH > 9). In a specific embodiment, the discharge reaction can proceed such that the metal Fe anode forms a soluble product (e.g., FeCl 2 ) during discharge, or a slightly soluble product (e.g., Fe(OH) 2)Discharge product film. Specific embodiments of a method for transporting DRI pellets through one or both of transport systems 1314, 1316 through cell 1310 include any method known in the art for transporting pelletized material or slurries or suspensions. For example, one or both of transport systems 1314, 1316 can 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, roller, or screw conveyor). In some embodiments, transport systems 1314, 1316, such as mechanical belt, screw, drum, etc., include a conductive material, such as metal or carbon, that can also serve as a current collector for cell 1310.

[0287] Multiple embodiments provide a method for preparing a sintered porous metal electrode, the method including mixing a metal and one or more additives to form a green-compacted pellet, and sintering the green-compacted pellet to form a sintered porous metal electrode. In multiple embodiments, the method includes mixing a metal and one or more additives to form a green-compacted pellet, and hot pressing a mixture of the metal and one or more additives to form a green-compacted pellet. In multiple embodiments, the metal comprises iron. In multiple embodiments, at least one of the one or more additives is both a pore-forming agent and a binder additive. In multiple embodiments, the one or more additives include a polyethylene additive and a bismuth sulfide powder additive. In multiple embodiments, at least one of the one or more additives is a pore-forming agent additive, and at least another of the one or more additives is a binder additive. In multiple embodiments, the binder additive is a mixture of two or more different types of binders. In multiple embodiments, sintering the green-compacted pellet to form a sintered porous metal electrode includes sintering the green-compacted pellet in a gas atmosphere with a time-temperature profile. In multiple embodiments, the gas atmosphere is N 2 atmosphere or Ar / H 2 atmosphere. In multiple embodiments, the gas atmosphere is Ar(95%) / H 2 (5%) atmosphere. In multiple embodiments, the time-temperature profile includes a linear temperature ramp period, followed by a constant soak temperature period, followed by a linear cool-down period. In multiple embodiments, the linear temperature ramp period raises the temperature of the green-compacted pellet to 850 °C, the soak temperature is 850 °C, and the linear cool-down period lowers the temperature of the green-compacted pellet to room temperature. In multiple embodiments, the constant soak temperature period is 15 minutes. In multiple embodiments, the time-temperature profile includes a non-linear temperature ramp period, two or more soak temperature periods with down and up periods therebetween, and a non-linear cool-down period.

[0288] Multiple embodiments can provide a method of fabricating a sintered porous metal electrode, including feeding compressed metal powder into a continuous roller furnace and passing the compressed metal powder through the furnace to sinter the metal powder together to form a sintered porous metal electrode. In multiple embodiments, the metal powder includes iron oxide powder. In multiple embodiments, the method can include compressing the metal powder before feeding the metal powder into the furnace. In multiple embodiments, compressing the metal powder includes passing the metal powder through a slot die or under compression rollers. In multiple embodiments, the method can include placing a metal sheet under the powder before feeding the metal powder into the furnace. In multiple embodiments, the metal sheet is sourced from a metal coil fed into the furnace and supports the compressed metal powder in the furnace. In multiple embodiments, the metal sheet is a metal foil. In multiple embodiments, the metal sheet includes nickel, iron, or steel. In multiple embodiments, the method can include cutting the sintered porous metal electrode into multiple parts. In multiple embodiments, the continuous roller furnace heats the metal powder in a hydrogen atmosphere. In multiple other embodiments, the continuous roller furnace heats the metal powder in an inert atmosphere of nitrogen or argon. In multiple other embodiments, the continuous roller furnace heats the metal powder in an atmosphere of a mixture including hydrogen, nitrogen, and / or argon.

[0289] Multiple embodiments can provide devices and / or methods for large-scale energy storage systems, such as long-duration energy storage (LODES) systems, short-duration energy storage (SDES) systems, etc. As an example, multiple embodiments can provide batteries and / or components for large-scale energy storage systems (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; systems 850, etc.), such as batteries for LODES systems. Renewable electrical energy is becoming increasingly common and more cost-effective. However, many renewable electrical energies face intermittency issues, which hinder the use of renewable electrical energy. By matching renewable electrical energy with large-scale energy storage systems (such as LODES systems, SDES systems, etc.), the impact of the intermittent trend of renewable electrical energy can be mitigated. To support the adoption of combined power generation, transmission, and storage systems (e.g., a power plant with a renewable power source matched with a large-scale energy storage system and transmission facilities in any power plant and / or large-scale energy storage system), devices and methods for supporting the design and operation of such combined power generation, transmission, and storage systems are needed, such as multiple device and method embodiments described herein.

[0290] A combined power generation, transmission, and storage system can be a power plant that includes one or more power sources (e.g., one or more renewable power sources, one or more non-renewable power sources, a combination of renewable and non-renewable power sources, etc.), one or more transmission facilities, and one or more bulk energy storage systems. The transmission facilities for any power plant and / or bulk energy storage system can be co-optimized with the power generation and storage system, or can impose constraints on the design and operation of the power generation and storage system. Under multiple design and operation constraints, the combined power generation, transmission, and storage system can be configured to meet multiple output objectives.

[0291] Example

[0292] The following examples are provided to illustrate various embodiments of the systems, methods, compositions, uses, and materials of the present invention. These examples are for illustrative purposes, can be predictive, and should not be considered limiting, and do not otherwise limit the scope of the present invention.

[0293] Figures 15 - 23 Multiple system examples are shown, where one or more aspects of the various embodiments are used as part of a bulk energy storage system, such as a LODES system, an SDES system, etc. For example, any of the various battery and / or component embodiments 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 the battery and / or component of a bulk energy storage system (such as a LODES system, an SDES system, etc.). As used herein, the term "LODES system" refers to a bulk energy storage system configured to have a rated duration (energy / power ratio) of 24 hours or longer, such as a 24-hour duration, a 24-hour to 50-hour duration, a duration greater than 50 hours, a 24-hour to 150-hour duration, a duration greater than 150 hours, a 24-hour to 200-hour duration, a duration greater than 200 hours, a 24-hour to 500-hour duration, a duration greater than 500 hours, etc., unless otherwise expressly specified.

[0294] Example 1

[0295] A storage system having one, five, ten, 50, 100, 500, or more electrochemical cells, the cells having one or more electrodes including direct reduced iron pellets. Preferably, the storage system is a long-duration storage system having long-duration electrochemical cells.

[0296] Example 1A

[0297] Long-term storage system of Example 1, in which the electrodes have the properties shown in Table E1A below:

[0298] Table E1A

[0299]

[0300]

[0301] Example 1B

[0302] Long-term storage system of Example 1, in which the electrodes have the properties shown in Table E1B below:

[0303] Table E1B

[0304]

[0305]

[0306] Example 1C

[0307] Long-term storage system of Example 1, in which the electrodes have the properties shown in Table E1C below:

[0308] Table E1C

[0309] Pellet Shape Sphere Total Fe in Pellets (wt%) 91 <![CDATA[The pellets contain SiO 2 (wt%)]]> 1 <![CDATA[The aggregate contains Al 2 O 3 (wt%)]]> 0.5 MgO in Pellets (wt%) 0.1 CaO in Pellets (wt%) 0.9 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.05 <![CDATA[Agglomerate contains Fe 2 C (wt%)]]> 0 Metallization (%) 94 Apparent Density of Electrodes (g / cc) 1.7 Apparent Density of Pellets (g / cc) 3.3 True Density of Pellets (g / cc) 5.9 <![CDATA[Minimum d of the aggregates 孔,90％体积 (μm)]]> 4.4 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (micrometers)]]> 11.1 <![CDATA[Specific surface area of the aggregate (m 2 / g)]]> 0.74

[0310] Example 1D

[0311] Long-term storage system of Example 1, in which the electrodes have the properties shown in Table E1D below:

[0312] Table E1D

[0313]

[0314]

[0315] Example 1E

[0316] Long-term storage system of Example 1, in which the electrodes have the properties shown in Table E1E below:

[0317] Table E1E

[0318] Pellet Shape Sphere Total Fe in Pellets (wt%) 86 <![CDATA[The aggregate contains SiO 2 (wt%)]]> 3 <![CDATA[Agglomerates contain Al 2 O 3 (wt%)]]> 3 MgO in Pellets (wt%) 0.75 CaO in Pellets (wt%) 1.5 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.75 <![CDATA[Agglomerate contains Fe 2 C (wt%)]]> 70 Metallization (%) 92 Apparent Density of Electrodes (g / cc) 1.5 Apparent Density of Pellets (g / cc) 3.3 True Density of Pellets (g / cc) 6.1 <![CDATA[Minimum d of the aggregates 孔,90％体积 (micrometers)]]> 1.77 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (μm)]]> 0.15 <![CDATA[Specific surface area of the aggregates (m 2 / g)]]> 0.12

[0319] Example 1F

[0320] Long-term storage system of Example 1, in which the electrodes have the properties shown in Table E1F below:

[0321] Table E1F

[0322] Pellet Shape Cylinder Total Fe in Pellets (wt%) 85 <![CDATA[The pellets contain SiO 2 (wt%)]]> 10 <![CDATA[The agglomerate contains Al 2 O 3 (wt%)]]> 1.5 MgO in Pellets (wt%) 0.1 CaO in Pellets (wt%) 1.5 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.05 <![CDATA[Agglomerates contain Fe 2 C (wt%)]]> 3 Metallization (%) 92 Apparent Density of Electrodes (g / cc) 2 Apparent Density of Pellets (g / cc) 3.4 True Density of Pellets (g / cc) 5.8 <![CDATA[Minimum d of the aggregates 孔,90％体积 (μm)]]> 2.55 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (μm)]]> 1.74 <![CDATA[Specific surface area of aggregates (m 2 / g)]]> 0.34

[0323] Example 1G

[0324] The long-term storage system of Example 1, where the electrode has the properties shown in Table E1G below:

[0325] Table E1G

[0326]

[0327]

[0328] Example 1H

[0329] The long-term storage system of Example 1, where the electrode has the properties shown in Table E1H below:

[0330] Table E1H

[0331] Pellet Shape Sphere Total Fe in Pellets (wt%) 84 <![CDATA[The aggregate contains SiO 2 (wt%)]]> 2 <![CDATA[The agglomerate contains Al 2 O 3 (wt%)]]> 0.2 MgO in Pellets (wt%) 10 CaO in Pellets (wt%) 0.9 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.05 <![CDATA[Agglomerates contain Fe 2 C (wt%)]]> 10 Metallization (%) 92 Apparent Density of Electrodes (g / cc) 2 Apparent Density of Pellets (g / cc) 3.4 True Density of Pellets (g / cc) 5.8 <![CDATA[Minimum d of the aggregates 孔,90％体积 (μm)]]> 1.27 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (μm)]]> 0.42 <![CDATA[Specific surface area of aggregates (m 2 / g)]]> 0.41

[0332] Example 1I

[0333] The long-term storage system of Example 1, where the electrode has the properties shown in Table E1I below:

[0334] Table E1I

[0335]

[0336]

[0337] Example 1J

[0338] The long-term storage system of Example 1, where the electrode has the properties shown in Table E1J below:

[0339] Table E1J

[0340] Pellet Shape Disk Total Fe in Pellets (wt%) 84 <![CDATA[The aggregate contains SiO 2 (wt%)]]> 4 <![CDATA[Agglomerates contain Al 2 O 3 (wt%)]]> 1 MgO in Pellets (wt%) 0.5 CaO in Pellets (wt%) 1.5 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 5 <![CDATA[The aggregate contains Fe 2 C (wt%)]]> 10 Metallization (%) 92 Apparent Density of Electrodes (g / cc) 2 Apparent Density of Pellets (g / cc) 3.4 True Density of Pellets (g / cc) 5.8 <![CDATA[Minimum d of the aggregates 孔,90％体积 (micrometers)]]> 1.52 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (μm)]]> 2.82 <![CDATA[Specific surface area of the aggregates (m 2 / g)]]> 0.51

[0341] Example 1K

[0342] The long-term storage system of Example 1, where the electrode has the properties shown in Table E1K below:

[0343] Table E1K

[0344] Pellet Shape Rod Total Fe in Pellets (wt%) 84 <![CDATA[Agglomerates contain SiO 2 (wt%)]]> 5 <![CDATA[The aggregate contains Al 2 O 3 (wt%)]]> 5 MgO in Pellets (wt%) 2 CaO in Pellets (wt%) 1 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 1.5 <![CDATA[The aggregate contains Fe 2 C (wt%)]]> 0 Metallization (%) 94 Apparent Density of Electrodes (g / cc) 1.8 Apparent Density of Pellets (g / cc) 3.5 True Density of Pellets (g / cc) 6 <![CDATA[Minimum d of the aggregates 孔,90％体积 (μm)]]> 2.72 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (μm)]]> 2.79 <![CDATA[Specific surface area of aggregates (m 2 / g)]]> 0.22

[0345] Example 1L

[0346] The long-term storage system of Example 1, where the electrode has the properties shown in Table E1L below:

[0347] Table E1L

[0348]

[0349]

[0350] Example 1M

[0351] The long-term storage system of Example 1, wherein the electrode has the properties shown in Table E1M below:

[0352] Table E1M

[0353] Pellet Shape Pressed Block Total Fe in Pellets (wt%) 91 <![CDATA[Agglomerates contain SiO 2 (wt%)]]> 3 <![CDATA[Agglomerate contains Al 2 O 3 (wt%)]]> 0.2 MgO in Pellets (wt%) 0.5 CaO in Pellets (wt%) 0.9 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.05 <![CDATA[Agglomerates contain Fe 2 C (wt%)]]> 2.5 Metallization (%) 91 Apparent Density of Electrodes (g / cc) 3.3 Apparent Density of Pellets (g / cc) 5.2 True Density of Pellets (g / cc) 6.2 <![CDATA[Minimum d of the aggregates 孔,90％体积 (μm)]]> 0.094 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (microns)]]> 0.0084 <![CDATA[Specific surface area of the aggregates (m 2 / g)]]> 0.024

[0354] Example 1N

[0355] The long-term storage system of Example 1, wherein the electrode has the properties shown in Table E1N below:

[0356] Table E1N

[0357]

[0358]

[0359] Example 1O

[0360] The long-term storage system of Example 1, wherein the electrode has the properties shown in Table E1O below:

[0361] Table E1O

[0362]

[0363]

[0364] Example 1P

[0365] The long-term storage system of Example 1, wherein the electrode has the properties shown in Table E1P below:

[0366] Table E1P

[0367] Pellet Shape Strip Total Fe in Pellets (wt%) 84 <![CDATA[Agglomerates contain SiO 2 (wt%)]]> 6 <![CDATA[The aggregate contains Al 2 O 3 (wt%)]]> 3 MgO in Pellets (wt%) 0.5 CaO in Pellets (wt%) 0.9 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.05 <![CDATA[The aggregate contains Fe 2 C (wt%)]]> 10 Metallization (%) 90 Apparent Density of Electrodes (g / cc) 1.8 Apparent Density of Pellets (g / cc) 3.9 True Density of Pellets (g / cc) 6.1 <![CDATA[Minimum d of the aggregates 孔,90％体积 (μm)]]> 1.98 <![CDATA[Minimum d of the aggregates 孔,50％表面积 (μm)]]> 0.0123 <![CDATA[Specific surface area of aggregates (m 2 / g)]]> 0.027

[0368] Example 1Q

[0369] The long-term storage system of Example 1, wherein the electrode has the properties shown in Table E1Q below:

[0370] Table E1Q

[0371]

[0372]

[0373] Example 1R

[0374] The long-term storage system of Example 1, wherein the electrode has the properties shown in Table E1R below:

[0375] Table E1R

[0376] Pellet Shape Sphere Total Fe in Pellets (wt%) 80 <![CDATA[The pellets contain SiO 2 (wt%)]]> 4.9 <![CDATA[The aggregate contains Al 2 O 3 (wt%)]]> 0.3 MgO in Pellets (wt%) 1.2 CaO in Pellets (wt%) 0.75 <![CDATA[Agglomerates contain TiO 2 (wt%)]]> 0.032 <![CDATA[Agglomerates contain Fe 2 C (wt%)]]> 5 Metallization (%) 60 Apparent Density of Electrodes (g / cc) 1.7 Apparent Density of Pellets (g / cc) 5.1 True Density of Pellets (g / cc) 5.4 <![CDATA[Minimum d 孔,90％体积 (micrometers)]]> 0.0488 <![CDATA[Minimum d 孔,50％表面积 (micrometers)]]> 0.0255 <![CDATA[Specific surface area of aggregates (m 2 / g)]]> 24

[0377] Example 2

[0378] Figure 15 An example system is shown where one or more aspects of multiple 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 multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either individually or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can be electrically connected to a wind power plant 1502 and one or more transmission facilities 1506. The wind power plant 1502 can be electrically connected to the transmission facilities 1506. The transmission facilities 1506 can be electrically connected to the power grid 1508. The wind power plant 1502 can generate electricity, and the wind power plant 1502 can output the generated electricity to the LODES system 1504 and / or the transmission facilities 1506. The LODES system 1504 can store the electricity received from the wind power plant 1502 and / or the transmission facilities 1506. The LODES system 1504 can output the stored electricity to the transmission facilities 1506. The transmission facilities 1506 can output the electricity received from one or both of the wind power plant 1502 and the LODES system 1504 to the power grid 1508, and / or can receive electricity from the power grid 1508 and output the electricity to the LODES system 1504. Together, the wind power plant 1502, the LODES system 1504, and the transmission facilities 1506 can form a power plant 1500, which can be an integrated power generation, transmission, and storage system. The electricity generated by the wind power plant 1502 can be directly fed to the power grid 1508 through the transmission facilities 1506, or can be stored in the LODES system 1504 first. In some cases, the electricity supplied to the power grid 1508 can come entirely from the wind power plant 1502, entirely from the LODES system 1504, or from a combination of the wind power plant 1502 and the LODES system 1504. The power dispatch of the power plant 1500 from the combined wind power plant 1502 and LODES system 1504 can be controlled according to a determined long-term (multi-day or even multi-year) plan, or can be controlled according to a one-day-ahead (24-hour advance notice) market, or can be controlled according to an hour-ahead market, or can respond to real-time pricing signals.

[0379] As an example of an operating power plant 1500, the LODES system 1504 can be used to reshape and "firm up" the electricity generated by the wind power plant 1502. In one such example, the wind power plant 1502 can have a peak power generation output (capacity) of 260 megawatts (MW) and a capacity factor (CF) of 41%. The LODES system 1504 can have a rated power (capacity) of 106 MW, a rated duration (energy / power ratio) of 150 hours (h), and an energy rating of 15,900 megawatt-hours (MWh). In another such example, the wind power plant 1502 can have a peak power generation output (capacity) of 300 MW and a capacity factor (CF) of 41%. The LODES system 1504 can have a rated power of 106 MW, a rated duration (energy / power ratio) of 200 hours, and an energy rating of 21,200 MWh. In another such example, the wind power plant 1502 can have a peak power generation output (capacity) of 176 MW and a capacity factor (CF) of 53%. The LODES system 1504 can have a rated power (capacity) of 88 MW, a rated duration (energy / power ratio) of 150 hours, and an energy rating of 13,200 MWh. In another such example, the wind power plant 1502 can have a peak power generation output (capacity) of 277 MW and a capacity factor (CF) of 41%. The LODES system 1504 can have a rated power (capacity) of 97 MW, a rated duration (energy / power ratio) of 50 hours, and an energy rating of 4,850 MWh. In another such example, the wind power plant 1502 can have a peak power generation output (capacity) of 315 MW and a capacity factor (CF) of 41%. The LODES system 1504 can have a rated power (capacity) of 110 MW, a rated duration (energy / power ratio) of 25 hours, and an energy rating of 2,750 MWh.

[0380] Example 2A

[0381] The system of Example 2, wherein the LODES system utilizes 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.

[0382] Example 3

[0383] Figure 16An example system is shown where one or more aspects of multiple 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 multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either individually or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). Figure 16 The system can be similar to Figure 15 the system, except that the photovoltaic (PV) power plant 1602 can replace the wind power plant 1502. The LODES system 1504 can be electrically connected to the PV power plant 1602 and one or more transmission facilities 1506. The PV power plant 1602 can be electrically connected to the transmission facilities 1506. The transmission facilities 1506 can be electrically connected to the power grid 1508. The PV power plant 1602 can generate electricity, and the PV power plant 1602 can output the generated electricity to the LODES system 1504 and / or the transmission facilities 1506. The LODES system 1504 can store the electricity received from the PV power plant 1602 and / or the transmission facilities 1506. The LODES system 1504 can output the stored electricity to the transmission facilities 1506. The transmission facilities 1506 can output the electricity received from one or both of the PV power plant 1602 and the LODES system 1504 to the power grid 1508, and / or can receive electricity from the power grid 1508 and output the electricity to the LODES system 1504. The PV power plant 1602, the LODES system 1504, and the transmission facilities 1506 together can form a power plant 1600, which can be an integrated power generation, transmission, and storage system. The electricity generated by the PV power plant 1602 can be directly fed to the power grid 1508 through the transmission facilities 1506, or can be stored in the LODES system 1504 first. In some cases, the electricity supplied to the power grid 1508 can come entirely from the PV power plant 1602, entirely from the LODES system 1504, or from a combination of the PV power plant 1602 and the LODES system 1504. The power dispatch of the power plant 1600 from the combined PV power plant 1602 and LODES system 1504 can be controlled according to a determined long-term (multi-day or even multi-year) plan, or can be controlled according to a one-day-ahead (24-hour advance notice) market, or can be controlled according to an hour-ahead market, or can respond to real-time pricing signals.

[0384] As an example of a running power plant 1600, the LODES system 1504 can be used to reshape and "firm up" the electricity generated by the PV power plant 1602. In one such example, the PV power plant 1602 can have a peak power generation output (capacity) of 490 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 340 MW, a rated duration of 150 hours (energy / power ratio), and an energy rating of 51,000 MWh. In another such example, the PV power plant 1602 can have a peak power generation output (capacity) of 680 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 410 MW, a rated duration of 200 hours (energy / power ratio), and an energy rating of 82,000 MWh. In another such example, the PV power plant 1602 can have a peak power generation output (capacity) of 330 MW and a capacity factor (CF) of 31%. The LODES system 1504 can have a rated power (capacity) of 215 MW, a rated duration of 150 hours (energy / power ratio), and an energy rating of 32,250 MWh. In another such example, the PV power plant 1602 can have a peak power generation output (capacity) of 510 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 380 MW, a rated duration of 50 hours (energy / power ratio), and an energy rating of 19,000 MWh. In another such example, the PV power plant 1602 can have a peak power generation output (capacity) of 630 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 380 MW, a rated duration of 25 hours (energy / power ratio), and an energy rating of 9,500 MWh.

[0385] Example 3A

[0386] System of Example 3, where the LODES system utilizes 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.

[0387] Example 4

[0388] Figure 17An example system is shown where one or more aspects of multiple 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 multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either individually or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). Figure 17 The system can be similar to Figure 15 and Figure 16 the system, except that the wind power plant 1502 and the photovoltaic (PV) power plant 1602 can both be generators operating together in the power plant 1700. The PV power plant 1602, the wind power plant 1502, the LODES system 1504, and the transmission facility 1506 together can form the power plant 1700, which can be an integrated power generation, transmission, and storage system. The electricity generated by the PV power plant 1602 and / or the wind power plant 1502 can be directly fed into the power grid 1508 through the transmission facility 1506, or can first be stored in the LODES system 1504. In some cases, the electricity supplied to the power grid 1508 can come entirely from the PV power plant 1602, entirely from the wind power plant 1502, entirely from the LODES system 1504, or from a combination of the PV power plant 1602, the wind power plant 1502, and the LODES system 1504. The power dispatch of the power plant 1700 from the combined wind power plant 1502, PV power plant 1602, and LODES system 1504 can be controlled according to a determined long-term (multi-day or even multi-year) plan, or can be controlled according to a one-day-ahead (24-hour advance notice) market, or can be controlled according to an hour-ahead market, or can respond to real-time pricing signals.

[0389] As an example of operating power plant 1700, the LODES system 1504 can be used to reshape and "firm up" the electricity generated by wind power plant 1502 and PV power plant 1602. In one such example, wind power plant 1502 can have a peak power generation output (capacity) of 126 MW and a capacity factor (CF) of 41%, and PV power plant 1602 can have a peak power generation output (capacity) of 126 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 63 MW, a rated duration of 150 hours (energy / power ratio), and an energy rating of 9,450 MWh. In another such example, wind power plant 1502 can have a peak power generation output (capacity) of 170 MW and a capacity factor (CF) of 41%, and PV power plant 1602 can have a peak power generation output (capacity) of 110 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 57 MW, a rated duration of 200 hours (energy / power ratio), and an energy rating of 11,400 MWh. In another such example, wind power plant 1502 can have a peak power generation output (capacity) of 105 MW and a capacity factor (CF) of 51%, and PV power plant 1602 can have a peak power generation output (capacity) of 70 MW and a capacity factor (CF) of 31%. The LODES system 1504 can have a rated power (capacity) of 61 MW, a rated duration of 150 hours (energy / power ratio), and an energy rating of 9,150 MWh. In another such example, wind power plant 1502 can have a peak power generation output (capacity) of 135 MW and a capacity factor (CF) of 41%, and PV power plant 1602 can have a peak power generation output (capacity) of 90 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 68 MW, a rated duration of 50 hours (energy / power ratio), and an energy rating of 3,400 MWh. In another such example, wind power plant 1502 can have a peak power generation output (capacity) of 144 MW and a capacity factor (CF) of 41%, and PV power plant 1602 can have a peak power generation output (capacity) of 96 MW and a capacity factor (CF) of 24%. The LODES system 1504 can have a rated power (capacity) of 72 MW, a rated duration of 25 hours (energy / power ratio), and an energy rating of 1,800 MWh.

[0390] Example 4A

[0391] The system of Example 4, where the LODES system utilizes 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.

[0392] Example 5

[0393] Figure 18 An example system is shown where one or more aspects of multiple 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 multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, individually or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can be electrically connected to one or more transmission facilities 1506. In this way, the LODES system 1504 can operate in a "stand-alone" manner to balance energy around market prices and / or avoid transmission constraints. The LODES system 1504 can be electrically connected to one or more transmission facilities 1506. The transmission facilities 1506 can be electrically connected to the power grid 1508. The LODES system 1504 can store the electricity received from the transmission facilities 1506. The LODES system 1504 can output the stored electricity to the transmission facilities 1506. The transmission facilities 1506 can receive electricity from among the LODES systems 1504 and output it to the power grid 1508, and / or can receive electricity from the power grid 1508 and output that electricity to the LODES system 1504.

[0394] The LODES system 1504 and the transfer device 1506 together can form a power plant 1800. As an example, the power plant 1800 can be located downstream of the transmission constraint, close to the power consumption end. In such a downstream power plant example 1800, the LODES system 1504 can have a duration of 24 hours to 500 hours and can experience a full discharge once or more times a year to support peak power consumption when the transmission capacity is insufficient to serve users. Additionally, in such a downstream power plant example 1800, the LODES system 1504 can experience several shallow discharges (daily or at a higher frequency) to arbitrate the difference between night and day electricity prices and reduce the total cost of power service to users. As another example, the power plant 1800 can be located upstream of the transmission constraint, close to the power generation end. In such an upstream power plant example 1800, the LODES system 1504 can have a duration of 24 hours to 500 hours and can experience a full charge once or more times a year to absorb excess generation when the transmission capacity is insufficient to distribute power to users. Additionally, in such an upstream power plant example 1800, the LODES system 1504 can experience several shallow charges and discharges (daily or at a higher frequency) to balance the difference between night and day electricity prices and maximize the output value of the power generation facility.

[0395] Example 5A

[0396] The system of Example 5, wherein the LODES system utilizes 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.

[0397] Example 6

[0398] Figure 19An example system is shown where one or more aspects of multiple embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system integrating one or more aspects of multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either alone or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can be electrically connected to commercial and industrial (C&I) users 1902, such as data centers, factories, etc. The LODES system 1504 can be electrically connected to one or more transmission facilities 1506. The transmission facility 1506 can be electrically connected to the power grid 1508. The transmission facility 1506 can receive power from the power grid 1508 and output the power to the LODES system 1504. The LODES system 1504 can store the power received from the transmission facility 1506. The LODES system 1504 can output the stored power to the C&I users 1902. In this way, the LODES system 1504 can operate to reshape the power purchased from the power grid 1508 to match the consumption pattern of the C&I users 1902.

[0399] The LODES system 1504 and the transmission device 1506 together can form a power plant 1900. As an example, the power plant 1900 can be located near the power consumption end, i.e., near the C&I users 1902, such as between the power grid 1508 and the C&I users 1902. In such an example, the LODES system 1504 can have a duration of 24 hours to 500 hours and can purchase power from the market to charge the LODES system 1504 when the power is cheaper. Then the LODES system 1504 can discharge to provide power to the C&I users 1902 when the market price is expensive, thus offsetting the market purchase of the C&I users 1902. As an alternative configuration, the power plant 1900 can be located between renewable electrical energy (e.g., PV power plants, wind power plants, etc.) and the transmission facility 1506 that can be connected to the renewable energy, rather than between the power grid 1508 and the C&I users 1902. In such an alternative example, the LODES system 1504 can have a duration of 24 hours to 500 hours, and the LODES system 1504 can be charged when the renewable output is available. Then the LODES system 1504 can discharge to provide power generated from renewable energy to the C&I users 1902, thus meeting part or all of the power demand of the C&I users 1902.

[0400] Example 6A

[0401] The system of Example 6, where the LODES system utilizes one or more storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R.

[0402] Example 7

[0403] Figure 20An example of a system is shown where one or more aspects of multiple 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 multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either alone or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can be electrically connected to a wind power plant 1502 and one or more transmission facilities 1506. The wind power plant 1502 can be electrically connected to the transmission facility 1506. The transmission facility 1506 can be electrically connected to a C&I user 1902. The wind power plant 1502 can generate electricity, and the wind power plant 1502 can output the generated electricity to the LODES system 1504 and / or the transmission facility 1506. The LODES system 1504 can store the electricity received from the wind power plant 1502. The LODES system 1504 can output the stored electricity to the transmission facility 1506. The transmission facility 1506 can output the electricity received from either or both of the wind power plant 1502 and the LODES system 1504 to the C&I user 1902. The wind power plant 1502, the LODES system 1504, and the transmission facility 1506 together can form a power plant 2000, which can be an integrated power generation, transmission, and storage system. The electricity generated by the wind power plant 1502 can be directly fed to the C&I user 1902 through the transmission facility 1506, or can be stored in the LODES system 1504 first. In some cases, the electricity supplied to the C&I user 1902 comes entirely from the LODES system 1504, or from a combination of the wind power plant 1502 and the LODES system 1504. The LODES system 1504 can be used to reshape the electricity generated by the wind power plant 1502 to match the consumption pattern of the C&I user 1902. In one such example, the LODES system 1504 can have a duration of 24 hours to 500 hours and can be charged when the renewable power generation of the wind power plant 1502 exceeds the load of the C&I user 1902. Then when the renewable power generation of the wind power plant 1502 is insufficient for the load of the C&I user 1902, the LODES system 1504 can discharge, thereby providing a reliable renewable profile to the C&I user 1902 that offsets part or all of the electricity consumption of the C&I user 1902.

[0404] Example 7A

[0405] The system of Example 7, wherein the LODES system utilizes one or more storage systems of Examples 1, 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, 1I, 1J, 1K, 1L, 1M, 1N, 1O, 1P, 1Q, and 1R.

[0406] Example 8

[0407] Figure 21An example system is shown where one or more aspects of multiple embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system integrating one or more aspects of multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either individually or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can be part of a power plant 2100 for integrating a large amount of renewable power generation into a microgrid and coordinating the output of renewable power generation such as PV power plant 1602 and wind power plant 1502 with existing thermal power generation such as thermal power plant 2102 (e.g., gas power plant, coal power plant, diesel generator set, etc., or a combination of thermal power generation methods), while the renewable power generation and thermal power generation supply the C&I user 1902 load with high availability. A microgrid, such as the microgrid composed of power plant 2100 and thermal power plant 2102, can provide an availability of 90% or higher. The power generated by the PV power plant 1602 and / or wind power plant 1502 can be directly fed to the C&I user 1902, or can be stored in the LODES system 1504 first. In some cases, the power supplied to the C&I user 1902 can come entirely from the PV power plant 1602, entirely from the wind power plant 1502, entirely from the LODES system 1504, entirely from the thermal power plant 2102, or from any combination of the PV power plant 1602, wind power plant 1502, LODES system 1504, and / or thermal power plant 2102. As an example, the LODES system 1502 of the power plant 2100 can have a duration of 24 hours to 500 hours. As a specific example, the C&I user 1902 load can have a peak of 100 MW, the LODES system 1504 can have a rated power of 14 MW and a duration of 150 hours, the cost of natural gas can be $6 per million British thermal units (MMBTU), and the renewable penetration rate can be 58%. As another specific example, the load of the C&I user 1902 can have a peak of 100 MW, the LODES system 1504 can have a rated power of 25 MW and a duration of 150 hours, the cost of natural gas can be $8 per MMBTU, and the renewable penetration rate can be 65%.

[0408] Example 8A

[0409] The system of Example 8, where the LODES system utilizes 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.

[0410] Example 9

[0411] Figure 22 An example system is shown where one or more aspects of multiple embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system integrating one or more aspects of multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, individually or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can be used to augment a nuclear power plant 2202 (or other inflexible power generation facilities, such as thermal power generation facilities, biomass power generation facilities, etc., and / or any other type of power plant with a ramp rate below 50% of the rated power and a high capacity factor of 80% or higher within one hour) to increase the flexibility of the combined output of the power plant 2200 formed by the combined LODES system 1504 and the nuclear power plant 2202. The nuclear power plant 2202 can operate at a high capacity factor and at the highest efficiency point, while the LODES system 1504 can charge and discharge to effectively reshape the output of the nuclear power plant 2202 to match the user's power consumption and / or the market price of electricity. As an example, the LODES system 1502 of the power plant 2200 can have a duration of 24 hours to 500 hours. In a specific example, the nuclear power plant 2202 can have a rated output of 1000 MW, and the nuclear power plant 2202 can be forced into long-term minimum stable power generation or even shut down due to a low market price of electricity. The LODES system 1502 can avoid shutting down the facility and charge when the market price is low; and the LODES system 1502 can then discharge and increase the total power generation output when the market price rises.

[0412] Example 9A

[0413] The system of Example 9, where the LODES system utilizes 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.

[0414] Example 10

[0415] Figure 23 An example system is shown where one or more aspects of multiple embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system integrating one or more aspects of multiple embodiments can be the LODES system 1504. As an example, the LODES system 1504 can include, either alone or in combination, any one of the multiple battery and / or component embodiments described herein (e.g., any one of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310; pellets 105, 115, 305, 198, 199; system 850, etc.). The LODES system 1504 can operate in series with the SDES system 2302. The LODES system 1504 and the SDES system 2302 together can form a power plant 2300. As an example, the LODES system 1504 and the SDES system 2302 can be co-optimized, whereby the LODES system 1504 can provide multiple services, including long-term backup and / or multi-day fluctuations (e.g., multi-day fluctuations in market pricing, renewable generation, power consumption, etc.), and the SDES system 2302 can provide multiple services, including fast ancillary services (e.g., voltage control, frequency regulation, etc.) and / or ride through daily fluctuations (e.g., daily fluctuations in market pricing, renewable generation, power consumption, etc.). The SDES system 2302 can have a duration of less than 10 hours and an energy conversion efficiency greater than 80%. The LODES system 1504 can have a duration of 24 hours to 500 hours and an energy conversion efficiency greater than 40%. In one such example, the LODES system 1504 can have a duration of 150 hours and support a user's power consumption during a week-long renewable generation deficit. The LODES system 1504 can also support a user's power consumption during a daily generation deficit event, enhancing the capabilities of the SDES system 2302. Additionally, the SDES system 2302 can supply power to users during a daily generation deficit event and provide power conditioning and quality services, such as voltage control and frequency regulation.

[0416] Example 10A

[0417] The system of Example 10, where the LODES system utilizes 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.

[0418] Example 11

[0419] Non-limiting examples according to embodiments of the present invention were established and tested. An electrochemical cell using direct reduced iron (DRI) pellets was assembled and tested. As characterized by the foregoing method, the DRI pellets have the properties listed in Table 4. The electrochemical cell is a cylindrical cell with three electrodes (working electrode, counter electrode, and reference electrode), and is filled with a liquid electrolyte. The electrolyte formulation is 5.5 M KOH + 0.5 M LiOH + 10 mM Na 2 S. The counter electrode is a NiO / NiOOH electrode obtained from a commercially available Fe / Ni (Edison type) cell. The reference electrode is a Hg / HgO (MMO) electrode filled with a 5.5 M KOH + 0.5 M LiOH solution. Electrical contact with the DRI pellets was made using a stainless steel hose clamp. Figure 24A It shows that during the first electrochemical discharge cycle (oxidizing DRI) when cycling at a specific current of 5 mA / g, the voltage of the DRI electrode relative to the MMO reference electrode is a function of the discharge specific capacity (mAh / g DRI ).

[0420] Table 4

[0421] Pellet shape Sphere Total Fe content in pellet (wt%) 88.6 <![CDATA[Agglomerates contain SiO 2 (wt%)]]> 6.1 <![CDATA[Agglomerate contains Al 2 O 3 (wt%)]]> 0.2 MgO content in pellet (wt%) 0.4 CaO content in pellet (wt%) 0.5 <![CDATA[The aggregate contains TiO 2 (wt%)]]> 0.01 <![CDATA[Agglomerates contain Fe 2 C (wt%)]]> 0.2 Metallization (%) 89.4 Apparent density of electrode (g / cc) 2.45 Apparent density of pellet (g / cc) 6.35 True density of pellet (g / cc) 6.54 <![CDATA[Minimum d 孔,90％体积 (micrometers)]]> 2.72 <![CDATA[Minimum d 孔,50％表面积 (micrometers)]]> 5 <![CDATA[Specific surface area of the aggregates (m 2 / g)]]> 0.22

[0422] Example 12

[0423] Another non-limiting example according to embodiments of the present invention was established and tested. A group of ten (10) electrochemical cells using direct reduced iron (DRI) pellets was assembled and tested. As characterized by the foregoing method, the DRI pellets have the properties listed in Table 4. The electrochemical cells are cylindrical cells with three electrodes (working electrode, counter electrode, and reference electrode), and the cells are filled with a liquid electrolyte. The electrolyte formulation is 5.5 M KOH + 0.5 M LiOH + 10 mM Na 2 S. The counter electrode is a NiO / NiOOH electrode obtained from a commercially available Fe / Ni (Edison type) cell. The reference electrode is a Hg / HgO (MMO) electrode filled with a 5.5 M KOH + 0.5 M LiOH solution. Electrical contact with the DRI pellets was made using a stainless steel hose clamp. The DRI was electrochemically cycled according to the following conditions: 1) precharged for 60 minutes at a specific current of 25 mA / g; 2) discharged to 0 voltage relative to MMO at a specific current of 25 mA / g; 3) charged at a specific current of 25 mA / g and terminated under Coulombic limitation, with the total charge equal to the first discharge capacity in mAh. Figure 24B It shows the comparison of the specific capacity (mAh / g DRI) of the DRI electrode with the number of cycles of the cell group. The average capacity of all cells and the error bars representing the 95% confidence interval were plotted. Figure 24C It shows the Coulombic efficiency (CE) of the same DRI cells.

[0424] Example 13

[0425] In another non-limiting example, a spherical DRI pellet bed was tested in a cylindrical cell. The DRI pellets had the properties listed in Table 4 as characterized by the aforementioned method. The mass of the pellet bed was 251.86 g. The electrolyte formula was 5.5 M KOH + 0.5 M LiOH + 60 mM Na 2 S, and the volume of the electrolyte used was 348 mL. The counter electrode was a stainless steel mesh (100×100 mesh). A Hg / HgO (MMO) reference electrode with 5.5M KOH + 0.5M LiOH filling solution was used to measure the anode potential. A stainless steel porous plate was used as the current collector for the DRI pellet bed, and a stainless steel plate was used as the counter electrode current collector. The cell was charged and discharged with a specific current of 5 mA / g. Figure 24D Shown is the voltage as a function of the discharge specific capacity (mAh / gDRI) of the DRI electrode relative to the MMO reference.

[0426] The above method description is provided only as an exemplary embodiment and is not intended to require or indicate that the steps of multiple embodiments must be performed in the order presented. As will be appreciated by those skilled in the art, the order of steps in the above embodiments can be performed in any order. Words such as "thereafter", "then", "next", etc. are not necessarily intended to limit the order of steps; these words can be used to guide the reader in the description of the method. In addition, any reference to a claim element in the singular form, such as the use of the article "a", "an", or "the", should not be construed as limiting the element to the singular form. In addition, any step of any embodiment described herein can be used in any other embodiment.

[0427] The foregoing description of the disclosed aspects is provided to enable any person skilled in the art to make or use the present invention. Multiple modifications to these aspects will be apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects without departing from the scope of the present invention. Therefore, the present invention is not limited to the aspects shown herein, but conforms to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A battery, comprising: a first electrode; an electrolyte; and a second electrode; wherein one or both of the first electrode and the second electrode are porous iron electrodes comprising direct reduced iron ("DRI").

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

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

4. The battery of claim 1, wherein at least one of the first electrode and the second electrode has a thickness greater than 0.1 cm.

5. The battery of claim 1, wherein the electrolyte penetrates into the DRI of the porous iron electrode.

6. The battery of claim 1, further comprising a current collector electrically connected to the DRI of the porous iron electrode.

7. The battery of claim 6, wherein the current collector contacts the lower surface of at least one of the first electrode and the second electrode, contacts the side surface of at least one of the first electrode and the second electrode, extends through at least one of the first electrode and the second electrode, or any combination thereof.

8. The battery of claim 6, wherein the DRI of the porous iron electrode contacts the current collector.

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

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

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

12. The battery of claim 11, wherein the compressive force on the porous iron electrode is greater than about 7 kPa and less than about 700 kPa.

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

14. The battery of claim 13, wherein the average particle size of the DRI particles is greater than 10 nm and less than 1 mm.

15. The battery of claim 13, wherein the DRI particles are of irregular shape.

16. The battery of claim 13, wherein macropores are formed between the DRI particles, and the DRI particles have a microporous surface.

17. The battery of claim 13, wherein the DRI particles are physically connected together in an agglomeration.

18. The battery of claim 17, wherein the DRI particles are sintered together in an agglomeration.

19. The battery of claim 1, wherein the porous iron electrode is sheet-shaped.

20. The battery of claim 1, wherein the DRI comprises at least about 90 wt% and less than about 98 wt% metallic iron based on the total mass of the DRI.

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