Negative electrode for electrochemical cell

Abstract

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

Description

[Technical Field]

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

[0002] Energy storage technologies are becoming increasingly important in power grids. At their most basic level, these energy storage assets provide smoothing to better match generation and demand in the distribution grid. The services performed by energy storage devices are beneficial to the power grid across multiple timescales, from milliseconds to years. Today, energy storage technologies exist that can support timescales from milliseconds to hours, but there is a need for long-term and ultra-long-term (collectively, ≥8 hours) energy storage systems.

[0003] This "Background Art" section is intended to introduce various aspects of the art that may be relevant to embodiments of the present invention. Therefore, the above considerations in this section are intended to provide a framework for a better understanding of the present invention and should not be considered an endorsement of prior art. [Overview of the Initiative]

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

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

[0006] In various embodiments, the pellets may be sintered iron agglomerate having various different shapes. In various embodiments, the sintered iron pellets can be formed in furnaces such as continuous feed calcining furnaces, batch feed calcining furnaces, blast furnaces, rotary calcining furnaces, and rotary hearths. In various embodiments, the pellets may include in the form of a reducing and / or sintered iron retaining precursor, and / or by-product material, known to those skilled in the art as directly reduced iron (DRI). Various embodiments may include processing the pellets containing the DRI pellets using mechanical, chemical, and / or thermal processes before introducing the pellets into an electrochemical cell.

[0007] In various embodiments, the negative electrode may be a composite metal electrode composed of a mixture of spherical or substantially spherical metallic pellets and powdered metal feed material. In various embodiments, the powdered metal feed material may be moistened with an electrolyte. In various embodiments, the negative electrode may consist of iron ore (e.g., taconite) pellets and a mixture of conductive DRI fine powder, sponge iron, and / or atomized iron. "DRI fine powder" is understood to mean fine particles smaller in size than DRI pellets but produced simultaneously with DRI pellets, or fine particles produced from DRI pellets by crushing, handling, or thermal or chemical means.

[0008] In various embodiments, the negative electrode may include pellets that are grouped in an orderly array. In various embodiments, the pellets may be arranged in a packing manner in the bed such that macropores are created between two or more pellets that are in contact with each other. In various embodiments, each pellet may contain micropores. In various embodiments, the electrolyte may fill the micropores or macropores, or flow through the pore spaces surrounding the pellets constituting the electrode.

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

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

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

[0012] Various embodiments can provide a battery comprising a first electrode, an electrolyte, and a second electrode, wherein one or both of the first and second electrodes contain directly reduced iron ("DRI"). Furthermore, a battery comprising a first electrode, an electrolyte, and a second electrode may be a battery in which one or both of the first and second electrodes are porous iron electrodes containing DRI. The porous iron electrode may be formed into a single sheet. The porous iron electrode contains particles of DRI. The average particle size of the DRI particles is greater than 10 nm and less than 1 mm. The DRI particles are irregularly shaped. Macropores are defined between the DRI particles, and the DRI particles have a microporous surface. The DRI particles are aggregated and physically connected. The DRI particles are aggregated and sintered. In various embodiments, the DRI is in the form of pellets. In various embodiments, the pellets contain at least about 60 wt% iron by elemental mass, based on the total mass of the pellets. In various embodiments, the pellets contain at least about 60 wt% metallic iron based on the total mass of the pellets, the pellets have an average particle size of 4 mm to 20 mm, and the pellets constitute at least 60 percent of the total mass of at least one of the first and second electrodes. In various embodiments, the pellets contain at least about 80 wt% metallic iron based on the total mass of the pellets. In various embodiments, the pellets contain about 90 wt% to about 98 wt% metallic iron based on the total mass of the pellets. In various embodiments, the pellets are spherical, rod-shaped, disc-shaped, plate-shaped, briquette-shaped, or a combination thereof. In various embodiments, the pellets are briquette-shaped and contain hot briquette iron. In various embodiments, the hot briquette iron is formed from powdered iron or iron pellets. In various embodiments, the pellets have an average length in the range of about 10 mm to about 500 mm, an average width in the range of about 5 mm to about 250 mm, and an average height in the range of about 5 mm to about 200 mm. In various embodiments, DRI includes iron ore, directly reduced grade iron ore, reduced taconite, wustite, magnetite, hematite, cementite, iron oxide, or any combination thereof. In various embodiments, DRI includes DRI fine powder or powder.In various embodiments, the pellets have an average internal porosity ranging from about 10% to about 90% by volume. In various embodiments, the pellets are about 0.19 m. 2 / g ~ approx. 18m 2The average specific surface area is in the range of / g. In various embodiments, the pellets have a volume-weighted average pore size in the range of 1 to 10 microns. In various embodiments, at least one of the first and second electrodes has a thickness greater than 0.1 cm. In various embodiments, the pellets are spherical and have an average diameter in the range of about 0.5 mm to about 10 cm. In various embodiments, the pellets contain more than 0.5 wt% of silica-containing compound based on the total weight of the pellets. In various embodiments, the pellets contain about 1 wt% to about 5 wt% of silica-containing compound by elemental mass based on the total mass of the pellets. In various embodiments, the pellets contain about 1 wt% to about 25 wt% of silica-containing compound by elemental mass based on the total mass of the pellets. In various embodiments, the packing density of the pellets in at least one of the first and second electrodes is 30% to 74%. In various embodiments, the pellets contain a primary phase containing iron and a secondary phase containing silicon or another metal. In various embodiments, the pellets contain a primary phase containing iron and a secondary phase containing cementite. In various embodiments, the secondary phase comprises silica or silicate. In various embodiments, the secondary phase comprises titanium, vanadium, manganese, magnesium, calcium, phosphorus, carbon, aluminum, zirconium, or any combination thereof. In various embodiments, at least one of the first and second electrodes comprises a single-layer pellet or a multi-layer pellet. In various embodiments, the electrolyte is permeated between the pellets. In various embodiments, the battery may further include a current collector electrically connected to the pellets. More specifically, it may further include a current collector electrically connected to the DRI of a porous iron electrode. In various embodiments, the current collector is in contact with at least one lower surface of the first and second electrodes, at least one side of the first and second electrodes, extends across at least one of the first and second electrodes, or any combination thereof. More specifically, the DRI of the porous iron electrode is in contact with the current collector. In various embodiments, the pellets are agglomerated sintered iron pellets.In various embodiments, agglomerated sintered iron pellets are manufactured using a continuous feed furnace, a batch furnace, a blast furnace, or any other type of furnace. In various embodiments, the second electrode may contain a slurry or a gel. In various embodiments, the first electrode and at least one of the second electrodes are composite metal electrodes comprising a mixture of pellets and a smaller metal particle composition. In various embodiments, the smaller metal particle composition is a powder metal feed material. In various embodiments, the powder metal feed material is moistened with an electrolyte. More specifically, the DRI of the porous iron electrode is moistened with an electrolyte. In various embodiments, the smaller metal particle composition includes DRI fine powder, sponge iron, atomized iron, or any combination thereof. In various embodiments, the pellets contain DR taconite. In various embodiments, the pellets are synthesized in the first stage of operation of a dual-use energy storage plant, including a battery, and loaded onto at least one of the first electrode and the second electrode in the second stage of operation of the dual-use energy storage plant. In various embodiments, the pellets are packed into the bed such that macropores are created between two or more pellets in contact with each other, and each pellet has micropores on at least its respective outer surface. In various embodiments, the pellets are fused together. In various embodiments, the pellets are pre-processed chemically, mechanically, thermally, electrically, and / or electrochemically to fuse at least a portion of the pellets and pack into the bed. In various embodiments, the battery may further include a pump configured to flow a liquid electrolyte across the pellets in the packed bed. In various embodiments, each pellet has micropores on its respective outer surface. In various embodiments, the pellets have pores created by immersing the pellets in an etching bath before being placed in at least one of the first and second electrodes. In various embodiments, the etching bath is an acid bath. In various embodiments, at least one of the first and second electrodes further includes an additive pellet containing Bi2O3 or a metal sulfide. In various embodiments, the additive pellet includes FeS, FeS2, Na2S, or a combination thereof.In various embodiments, the pellets are sintered iron pellets composed of crushed direct reduced iron ("DRI") precursor and / or DRI powder. In various embodiments, the pellets are mechanically, chemically, electrically, electrochemically, and / or thermally pre-processed before being placed on at least one of the first and second electrodes. In various embodiments, the pre-processing includes pre-charging the pellets. In various embodiments, the pellets are initially composed of at least partially cementite (Fe3C) before the battery is operational. In various embodiments, at least one of the first and second electrodes further includes a layer of powdered iron configured to form an interface between the pellet and the current collector of the battery. In various embodiments, the battery may further include a monitoring system configured to monitor the state of charge (SOC) and / or health state of at least one of the first and second electrodes. In various embodiments, the monitoring system includes one or more sensors connected to a controller. In various embodiments, one or more sensors are selected from the group consisting of strain gauges, Mossbauer spectrometers, CCD detectors, ultrasonic transducers, ion-sensing electrodes, thermocouples, and gas sensors. In various embodiments, at least one of the first and second electrodes is a composite metal electrode comprising a mixture of pellets and a conductive material dispersed between the individual pellets. In various embodiments, the conductive material comprises one or more conductive fibers, one or more wires, one or more meshes, and / or one or more sheets. In various embodiments, the first electrode is a negative electrode and contains DRI. Furthermore, the first electrode may be a negative electrode and a porous iron electrode containing DRI. In various embodiments, the battery may further include an additive delivery system configured to add one or more additives to the electrolyte. In various embodiments, the additive delivery system delivers liquid or solid additives. In various embodiments, one or more additives include salts. In various embodiments, the salts are carbonates or polysulfide salts. In various embodiments, one or more additives include sulfur-based additives. In various embodiments, one or more additives include surfactant additives.In various embodiments, one or more additives are configured to reduce self-discharge and / or suppress the hydrogen evolution reaction (HER). In various embodiments, at least one of the first and second electrodes is under compressive force. The compressive force acting on the porous iron electrode is greater than 7 kPa and less than 700 kPa. In various embodiments, at least one of the first and second electrodes includes an additional conductive material. In various embodiments, the additional conductive material surrounds the iron-containing pellet. In various embodiments, the additional conductive material is a foil, sheet, mesh, or wire.

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

[0014] Various embodiments can provide a bulk energy storage system comprising one or more batteries, at least one of which comprises a first electrode, an electrolyte, and a second electrode, wherein one or both of the first and second electrodes contain direct reduced iron ("DRI"). In various embodiments, at least one of the first and second electrodes containing DRI is a negative electrode containing direct reduced iron ("DRI") pellets. In various embodiments, at least one of the first and second electrodes further comprises additive pellets. In various embodiments, the additive pellets consist of FeS, FeS2, Bi2O3, or a metal sulfide. In various embodiments, the DRI comprises sintered iron pellets composed of crushed direct reduced iron ("DRI") precursors and / or DRI powder. In various embodiments, the DRI consists of direct reduced iron ("DRI") pellets that have been mechanically, chemically, and / or thermally pre-processed before being placed in at least one of the first and second electrodes. In various embodiments, the DRI contains at least about 60 wt% metallic iron based on the total mass of the pellets, and the DRI contains directly reduced iron pellets having an average particle size of 4 mm to 20 mm, with the directly reduced iron pellets constituting at least 60 percent of the total mass of at least one of the first and second electrodes. In various embodiments, the bulk energy storage system is a long-term energy storage (LODES) system.

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

[0016] [Figure 1]This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 2A] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 2B] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 3A] This is a schematic diagram of an exemplary continuous feed firing furnace configured to form agglomerate sintered pellets according to various embodiments of the present disclosure. [Figure 3B] This is a process flow diagram of an embodiment of a method for forming a sintered porous metal electrode. [Figure 3C] This is a block diagram of an embodiment system for forming a sintered porous metal electrode. [Figure 3D] This is a block diagram of an embodiment system for forming a sintered porous metal electrode. [Figure 4] This is a schematic diagram of an electrochemical cell including a composite metal electrode having spherical pellets and metal feed material, according to various embodiments of the present disclosure. [Figure 5] This is a process flow diagram illustrating an embodiment of a method for on-site synthesis of active materials for bulk energy storage systems using renewable excess production. [Figure 6] Figure 1 is a schematic diagram of an electrochemical cell, with macropores and micropores according to various embodiments of this disclosure shown in the enlarged view. [Figure 7] This is a schematic diagram of one pellet of the electrochemical cell shown in Figure 1 according to various embodiments of the present disclosure. [Figure 8A] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 8B] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 8C] This is a schematic diagram of a series of fluid-connected electrochemical cells according to various embodiments of the present disclosure. [Figure 9] This is a schematic diagram of an electrochemical cell containing a mixture of an active substance and an additive pellet according to various embodiments of the present disclosure. [Figure 10] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 11] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12A] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12B] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12C] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12D] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12E] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 12F] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 13A] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 13B] This is a schematic diagram of an electrochemical cell according to various embodiments of the present disclosure. [Figure 14] This is a schematic diagram of a filtration device according to various embodiments of the present disclosure. [Figure 15] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 16] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 17] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 18] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 19]This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 20] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 21] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 22] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 23] This document describes various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 24A] These graphs show the initial cycle discharge ratio capacity (mAh / gDRI) of the DRI electrode, the number of discharge cycles, the Coulomb efficiency, and the subsequent cycle discharge ratio capacity (mAh / gDRI), respectively. [Figure 24B] These graphs show the initial cycle discharge ratio capacity (mAh / gDRI) of the DRI electrode, the number of discharge cycles, the Coulomb efficiency, and the subsequent cycle discharge ratio capacity (mAh / gDRI), respectively. [Figure 24C] These graphs show the initial cycle discharge ratio capacity (mAh / gDRI) of the DRI electrode, the number of discharge cycles, the Coulomb efficiency, and the subsequent cycle discharge ratio capacity (mAh / gDRI), respectively. [Figure 24D] These graphs show the initial cycle discharge ratio capacity (mAh / gDRI) of the DRI electrode, the number of discharge cycles, the Coulomb efficiency, and the subsequent cycle discharge ratio capacity (mAh / gDRI), respectively. [Modes for carrying out the invention]

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

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

[0019] In general, the terms “approximately” and the symbol “~” as used herein, unless otherwise specified, mean to include a variation or range of ±10%, experimental error or instrument error associated with obtaining the stated values, preferably the greater of these.

[0020] Where used herein, unless otherwise specified, the enumeration of value ranges herein is intended merely as a simplified way of referring individually to each separate value that falls within the range. Unless otherwise indicated herein, each individual value within the range is incorporated herein as if it were individually enumerated herein.

[0021] As used herein, unless otherwise specified, the terms “%”, “weight%”, and “mass%” are used synonymously and refer to the weight of a first component as a percentage of the total weight of, for example, a formulation, mixture, particles, pellets, material, structure, or product. As used herein, unless otherwise specified, “volume%”, “% volume”, and similar terms refer to the volume of a first component as a percentage of the total volume of, for example, a formulation, mixture, particles, pellets, material, structure, or product.

[0022] The following examples are provided to illustrate various embodiments of the system and method of the present invention. These examples are for illustrative purposes only, may be predictive, and should not be considered limiting, nor do they limit the scope of the invention in any way.

[0023] It should be noted that it is not necessary to provide or express the theory underlying any novel, groundbreaking processes, materials, performance, or other beneficial features and properties that are the subject matter of or associated with embodiments of the present invention. Nevertheless, various theories are provided herein to further advance the art of the art. The theories presented herein do not in any way limit, restrict, or narrow the scope of protection granted to the inventions of the claims unless otherwise expressly stated. Such theories may not be necessary for the use of the present invention, nor may they be put into practice. Furthermore, it is understood that the present invention may be linked to new and previously unknown theories to describe the functional-characteristics of embodiments of the methods, articles, materials, devices, and systems of the present invention. Such subsequently developed theories do not limit the scope of protection granted to the present invention.

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

[0025] Where used herein, unless otherwise specified, the term “specific gravity,” also known as apparent density, should be given the broadest possible meaning and generally refer to the weight per unit volume of a structure, such as the volumetric shape of a material. This property will include the internal porosity of the particles as part of their volume. This can be measured, among other techniques, with a low-viscosity fluid that wets the particle surface.

[0026] Where used herein, unless otherwise specified, the term “actual density,” sometimes also called true density, should be given the broadest possible meaning, generally referring to the weight per unit volume of a material when no voids are present in the material. This measurement and property essentially eliminates internal porosity from the material and does not include, for example, any voids in the material.

[0027] Therefore, the relationship between the three density properties can be explained using an aggregate of porous foam balls (e.g., Nerf® balls). The weight of the balls filling the container would be the bulk density of the balls.

[0028]

number

[0029] The weight of a single ball per unit spherical volume is likely its apparent density.

[0030]

number

[0031] The weight of the ball's skeleton per unit volume of the remaining material, that is, the weight of the material constituting the ball after all void volume has been removed, would be its actual density.

[0032]

number

[0033] Embodiments of the present invention include apparatus, systems, and methods for long-term and ultra-long-term low-cost energy storage. In this specification, “long-term” and “ultra-long-term” and similar terms should be given the broadest possible meaning unless otherwise expressly stated, and would include energy storage periods of 8 hours or longer, such as 8-hour energy storage periods, energy storage periods ranging from 8 hours to 20 hours, 20-hour energy storage periods, energy storage periods ranging from 20 hours to 24 hours, 24-hour energy storage periods, energy storage periods ranging from 24 hours to 1 week, and energy storage periods ranging from 1 week to 1 year (e.g., from a few days to several weeks, up to several months), and would include LODES systems. Furthermore, the terms “long-term” and “ultra-long-term,” “energy storage cell” including “electrochemical cell,” and similar terms should be given the broadest possible interpretation unless otherwise expressly stated, and would include electrochemical cells that may be configured to store energy over time ranges of several days, several weeks, or seasons.

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

[0035] Various embodiments of the use of directly reduced iron (DRI) as a material for batteries (or cells), as a component of batteries (or cells), and in combinations and variations thereof are considered. In various embodiments, DRI may be produced from or be a material obtained from the reduction of natural or processed iron ore, and such reduction is carried out without reaching the melting temperature of iron. In various embodiments, the iron ore may be taconite or magnetite or hematite or goethite, etc. In various embodiments, DRI may be in the form of pellets that are spherical or substantially spherical. In various embodiments, DRI may be porous and may contain open and / or closed internal porosity. In various embodiments, DRI may include material that has been further processed by hot or cold briquetting. In various embodiments, DRI is obtained by reducing iron ore pellets to iron metal (Fe 0) can be produced by forming a more metallic (more reduced, lower degree of oxidation) material such as wustite (FeO), or a composite pellet containing iron metal and a residual oxidation phase. In various non-limiting embodiments, the DRI may 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 industry, DRI is sometimes referred to as "sponge iron", and its use is particularly common in India. Embodiments of iron materials, including exemplary embodiments of DRI materials for use in the various embodiments described herein, including use as an electrode material, may have one, more than one, or all of the material characteristics as described in Table 1 below. As used herein, including in Table 1, the following terms have the following meanings unless otherwise explicitly stated: "specific surface area" means the total surface area of the material per unit mass, including the surface area of the pores of the porous structure; "carbon content" or "carbon (% by weight)" means the mass of total carbon as a percentage of the total mass of the DRI; "cementite content" or "cementite (% by weight)" means the mass of Fe3C as a percentage of the total mass of the DRI; "total Fe (% by weight)" means the mass of all iron as a percentage of the total mass of the DRI; "metallic Fe (% by weight)" means the mass of iron in the Fe 0 state as a percentage of the total mass of the DRI; "metallization" means the mass of iron in the Fe 0 state as a percentage of the total mass of all iron. As used herein, weight percentages, volume percentages, and apparent densities are understood to exclude any electrolyte infiltrating the porosity or transient additives within the porosity, unless otherwise stated.

[0036]

Table 1

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

[0038] ** The actual density is preferably determined by the helium (He) gravity bottle method, more preferably as shown in ISO 12154 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He gravity bottle method. The actual density may also be referred to in the art as “true density” or “skeleton density.”

[0039] *** The apparent density is determined by immersion in water, more preferably as shown in ISO 15968 (the disclosure in this document is incorporated herein by reference in its entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He specific gravity bottle method. Porosity can be defined as the ratio of the apparent density to the actual density.

[0040]

number

[0041] **** d 孔、90%容積This is preferably determined by mercury (Hg) intrusion porosimetry, and more preferably as shown in ISO 15901-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with the Hg intrusion results. d 孔、90%容積 This is the pore diameter at which 90% of the total pore volume is located.

[0042] ***** d 孔、50%表面積 This is preferably determined by mercury (Hg) intrusion porosimetry, and more preferably as shown in ISO 15901-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with the Hg intrusion results. d 孔、50%表面積 This is the pore diameter at which 50% of the free surface area exists.

[0043] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as shown in ASTM E246-10 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as titration after tin(II) chloride reduction, titration after titanium(III) chloride reduction, and inductively coupled plasma (ICP) spectroscopy, can provide results that can be correlated with those obtained by dichromate titration.

[0044] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as shown in ISO 16878 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as bromine-methanol titration, can be used to provide results that can be correlated with those obtained by iron(III) chloride titration.

[0045] ### The metallization (%) is preferably determined by the ratio of metallic Fe to total Fe, each of which is preferably determined by the method described above.

[0046] #### Carbon (wt%) is preferably determined by infrared absorption after combustion in an induction furnace, and more preferably as shown in ISO 9556 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as various combustion and inert gas melting techniques, including those shown in ASTM E1019-18, can provide results that can be correlated with infrared absorption after combustion in an induction furnace.

[0047] #####Fe 2+ The (wt%) is preferably determined by titration, and more preferably as shown in ASTM D3872-05 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as Mössbauer spectroscopy and X-ray absorption spectroscopy, can be used to provide results that can be correlated with those obtained by titration.

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

[0049] $$SiO2 (wt%) is preferably determined by gravimetric methods, and more preferably as shown in ISO 2598-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as reduced molybdosilicate spectrophotometrics and X-ray diffraction (XRD), can provide results that can be correlated with gravimetric methods. In certain methods, SiO2 wt% is not determined directly, but rather the Si concentration (including neutral and ionic species) is measured and the SiO2 wt% is calculated assuming a stoichiometry of SiO2. That is, it is assumed that the molar ratio of Si:O is 1:2.

[0050] The ferrite (weight %) is preferably determined by X-ray diffraction (XRD).

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

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

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

[0054] In addition, embodiments of iron materials, including, for example, embodiments of DRI materials, for use in the various embodiments described herein, including use as electrode materials, may have one or more of the following properties, features, or characteristics, as shown in Table 1A (note that a value in one row or one column may exist together with values ​​in a different row or column).

[0055] [Table 1A]

[0056] The total Fe (wt%) is preferably determined by dichromate titration, more preferably as shown in ASTM E246-10 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as titration after tin(II) chloride reduction, titration after titanium(III) chloride reduction, and inductively coupled plasma (ICP) spectroscopy, can provide results that can be correlated with those obtained by dichromate titration.

[0057] SiO2 (wt%) is preferably determined by gravimetric methods, and more preferably as shown in ISO 2598-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as reduced molybdosilicate spectrophotometrics and X-ray diffraction (XRD), can provide results that can be correlated with gravimetric methods. In certain methods, SiO2 wt% is not determined directly, but rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming a stoichiometry of SiO2. That is, it is assumed that the molar ratio of Si:O is 1:2.

[0058] Al2O3 (wt%) is preferably determined by flame atomic absorption spectrometry, more preferably as shown in ISO 4688-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated with flame atomic absorption spectrometry. In certain methods, Al2O3 wt% is not determined directly, but rather the Al concentration (including neutral and ionic species) is measured and Al2O3 wt% is calculated based on the stoichiometry of Al2O3. That is, it is assumed that the molar ratio of Al:O is 2:3.

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

[0060] CaO (wt%) is preferably determined by flame atomic absorption spectrometry, more preferably as shown in ISO 10203 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated with flame atomic absorption spectrometry. In certain methods, CaO wt% is not determined directly, but rather the Ca concentration (including neutral and ionic species) is measured and the CaO wt% is calculated assuming a stoichiometry of CaO. That is, it is assumed that the molar ratio of Ca:O is 1:1.

[0061] TiO2 (wt%) is preferably determined by diantipyrimethane spectrophotometry, more preferably as shown in ISO 4691 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as X-ray diffraction (XRD), can be used to provide results that can be correlated with diantipyrimethane spectrophotometry. In certain methods, TiO2 wt% is not determined directly, but rather the Ti concentration (including neutral and ionic species) is measured and TiO2 wt% is calculated assuming a stoichiometry of TiO2. That is, it is assumed that the molar ratio of Ti:O is 1:2.

[0062] The actual density is preferably determined by the helium (He) gravity bottle method, more preferably as shown in ISO 12154 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He gravity bottle method. The actual density may also be referred to in the art as “true density” or “skeleton density”.

[0063] The apparent density is preferably determined by immersion in water, and more preferably as shown in ISO 15968 (the disclosure in this document is incorporated herein by reference in its entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He specific gravity bottle method.

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

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

[0066]

number

[0067] Furthermore, the characteristics shown in Table 1 may be present in the embodiment, in addition to, or instead of, the characteristics in Table 1A. Larger and smaller values ​​of these characteristics may also be present in various embodiments.

[0068] In this embodiment, the specific surface area of ​​the pellet is approximately 0.05 m². 2 / g ~ approx. 35m 2 / g, approx. 0.1m 2 / g~about 5m 2 / g, approx. 0.5m 2 / g~about 10m 2 / g, approx. 0.2m 2 / g~about 5m 2 / g, approx. 1m 2 / g~about 5m 2 / g, approx. 1m 2 / g~about 20m 2 It may also be / g, which is about 1m 2 It can be larger than / g, or about 2m 2 It can be larger than / g, or about 5m 2 It may be less than / g, approximately 15m 2 It may be less than / g, approximately 20m 2 It may be less than / g, as well as combinations and variations thereof, as well as larger and smaller values.

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

[0070] In certain embodiments, DRI can be produced by the reduction of "blast furnace" pellets, in which case the resulting DRI may have the material properties described in Table 2 below. The use of reduced BF grade DRI may be advantageous because it requires less input energy to produce the pellets, which in other words means a lower cost for the finished product.

[0071] [Table 2]

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

[0073] ** The actual density is preferably determined by the helium (He) gravity bottle method, more preferably as shown in ISO 12154 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He gravity bottle method. The actual density may also be referred to in the art as “true density” or “skeleton density.”

[0074] *** The apparent density is preferably determined by immersion in water, and more preferably as shown in ISO 15968 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He specific gravity bottle method. Porosity can be defined as the ratio of the apparent density to the actual density.

[0075]

number

[0076] **** d 孔、90%容積This is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as shown in ISO 15901-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with the Hg intrusion results. d 孔、90%容積 This is the pore diameter at which 90% of the total pore volume is located.

[0077] ***** d 孔、50%表面積 This is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as shown in ISO 15901-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with the Hg intrusion results. d 孔、50%表面積 This is the pore diameter at which 50% of the free surface area exists.

[0078] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as shown in ASTM E246-10 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as titration after tin(II) chloride reduction, titration after titanium(III) chloride reduction, and inductively coupled plasma (ICP) spectroscopy, can provide results that can be correlated with those obtained by dichromate titration.

[0079] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as shown in ISO 16878 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as bromine-methanol titration, can be used to provide results that can be correlated with those obtained by iron(III) chloride titration.

[0080] ### The metallization (%) is preferably determined by the ratio of metallic Fe to total Fe, each of which is preferably determined by the method described above.

[0081] #### Carbon (wt%) is preferably determined by infrared absorption after combustion in an induction furnace, and more preferably as shown in ISO 9556 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as various combustion and inert gas melting techniques, including those shown in ASTM E1019-18, can provide results that can be correlated with infrared absorption after combustion in an induction furnace.

[0082] #####Fe 2+ The (wt%) is preferably determined by titration, and more preferably as shown in ASTM D3872-05 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as Mössbauer spectroscopy and X-ray absorption spectroscopy, can be used to provide results that can be correlated with those obtained by titration.

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

[0084] $$SiO2 (wt%) is preferably determined by gravimetric methods, and more preferably as shown in ISO 2598-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as reduced molybdosilicate spectrophotometrics and X-ray diffraction (XRD), can provide results that can be correlated with gravimetric methods. In certain methods, SiO2 wt% is not determined directly, but rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming a stoichiometry of SiO2. That is, it is assumed that the molar ratio of Si:O is 1:2.

[0085] The ferrite (weight %) is preferably determined by X-ray diffraction (XRD).

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

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

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

[0089] Furthermore, the characteristics shown in Table 2 may be present in embodiments, in addition to, or instead of, the characteristics in Table 1 and / or Table 1A. Larger and smaller values ​​of these characteristics may also be present in various embodiments.

[0090] In certain embodiments, DRI can be produced by reducing DR-grade pellets, in which case the resulting DRI may have the material properties described in Table 3 below. The use of reduced DR-grade DRI may be advantageous because it has a higher Fe content in the pellets, thereby increasing the energy density of the battery.

[0091] [Table 3]

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

[0093] ** The actual density is preferably determined by the helium (He) gravity bottle method, more preferably as shown in ISO 12154 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He gravity bottle method. The actual density may also be referred to in the art as “true density” or “skeleton density.”

[0094] *** The apparent density is preferably determined by immersion in water, and more preferably as shown in ISO 15968 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests can be used to provide results that can be correlated with the results of the He specific gravity bottle method. Porosity can be defined as the ratio of the apparent density to the actual density.

[0095]

number

[0096] **** d 孔、90%容積This is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as shown in ISO 15901-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with the Hg intrusion results. d 孔、90%容積 This is the pore diameter at which 90% of the total pore volume is located.

[0097] ***** d 孔、50%表面積 This is preferably determined by mercury (Hg) intrusion porosimetry, more preferably as shown in ISO 15901-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as gas adsorption, can be used to provide results that can be correlated with the Hg intrusion results. d 孔、50%表面積 This is the pore diameter at which 50% of the free surface area exists.

[0098] #Total Fe (wt%) is preferably determined by dichromate titration, more preferably as shown in ASTM E246-10 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as titration after tin(II) chloride reduction, titration after titanium(III) chloride reduction, and inductively coupled plasma (ICP) spectroscopy, can provide results that can be correlated with those obtained by dichromate titration.

[0099] ##Metallic Fe (wt%) is preferably determined by iron(III) chloride titration, more preferably as shown in ISO 16878 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as bromine-methanol titration, can be used to provide results that can be correlated with those obtained by iron(III) chloride titration.

[0100] ### The metallization (%) is preferably determined by the ratio of metallic Fe to total Fe, each of which is preferably determined by the method described above.

[0101] #### Carbon (wt%) is preferably determined by infrared absorption after combustion in an induction furnace, and more preferably as shown in ISO 9556 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as various combustion and inert gas melting techniques, including those shown in ASTM E1019-18, can provide results that can be correlated with infrared absorption after combustion in an induction furnace.

[0102] #####Fe 2+ The (wt%) is preferably determined by titration, and more preferably as shown in ASTM D3872-05 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as Mössbauer spectroscopy and X-ray absorption spectroscopy, can be used to provide results that can be correlated with those obtained by titration.

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

[0104] $$SiO2 (wt%) is preferably determined by gravimetric methods, and more preferably as shown in ISO 2598-1 (the disclosures in this document are incorporated herein by reference in their entirety). It is recognized that other tests, such as reduced molybdosilicate spectrophotometrics and X-ray diffraction (XRD), can provide results that can be correlated with gravimetric methods. In certain methods, SiO2 wt% is not determined directly, but rather the Si concentration (including neutral and ionic species) is measured and SiO2 wt% is calculated assuming a stoichiometry of SiO2. That is, it is assumed that the molar ratio of Si:O is 1:2.

[0105] The ferrite (weight %) is preferably determined by X-ray diffraction (XRD).

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

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

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

[0109] Furthermore, the characteristics shown in Table 3 may be present in embodiments, in addition to, or instead of, the characteristics in Table 1, Table 1A, and / or Table 2. Larger and smaller values ​​of these characteristics may also be present in various embodiments.

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

[0111] The filling of pellets creates macropores between individual pellets, such as openings, spaces, channels, or voids. These macropores facilitate ion transport across electrodes that, in some embodiments, have dimensions of several centimeters, still having very thick minimum dimensions compared to some other types of battery electrodes. The micropores within the pellets allow for contact between the active material and the electrolyte, enabling high surface area utilization of the active material. This electrode structure is particularly useful for improving the rate capacity of very thick electrodes for stationary, long-term energy storage, where thick electrodes may be required to achieve very high area capacities.

[0112] The pellets of these embodiments, in particular for use in electrode embodiments for long-term energy storage systems, may be of any volumetric shape, such as spheres, discs, packs, beads, tablets, pills, rings, lenses, plates, panels, cones, frustocones, square blocks, rectangular blocks, trusses, angles, channels, hollow sealed chambers, hollow spheres, blocks, sheets, films, fine particles, square timbers, rods, angles, plates, cylinders, fibers, chemical fibers, tubes, cups, pipes, and various combinations thereof, as well as other more complex shapes. The electrode pellets may be the same shape or different shapes. The pellets in an electrode that is one of several electrodes in a long-term energy storage system may be the same as or different from the pellets in other electrodes in that storage system.

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

[0114] In this embodiment, the pellets that make up the electrode are approximately 3 g / cm³ 3 ~Approx. 6.5g / cm 3 Approximately 0.1 g / cm³ 3 ~Approx. 5.5g / cm 3 Approximately 2.3 g / cm³ 3 ~Approx. 3.5g / cm 3 3.2 g / cm³ 3 ~Approx. 4.9g / cm 3of 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 greater than, and electrodes having bulk densities of combinations and various values of these, as well as greater and lesser values can be provided.

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

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

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

[0118] In various embodiments, DRI pellets or agglomerates are formed from iron oxide powder in a single process using a rotary calcination furnace. The rotational motion of the furnace promotes the agglomeration of the powder into pellets or agglomerates, and the high-temperature reducing gas environment provides simultaneous reduction of iron oxide. In various other embodiments, a multi-stage rotary calcination furnace may be used, in which the agglomeration step and the reduction step can be independently controlled and optimized.

[0119] In various embodiments, the DRI has a non-spherical shape. In certain embodiments, the DRI may have a shape enclosed by substantially straight lines or a brick-like shape. In certain embodiments, the DRI may have a substantially cylindrical, rod-like, or disc-like shape. In certain embodiments, the DRI may have a substantially flat or sheet-like shape. In certain embodiments, the iron oxide powder is dry-formed by die-compression into a cylindrical shape or any other shape suitable for die pressing. In certain embodiments, the iron oxide powder is dry-formed into a sheet-like shape by roll pressing with a calender roll. In certain embodiments, the iron oxide powder is compounded with a binder such as clay or a polymer and dry-formed into a rod-like shape by extrusion. In certain embodiments, the iron oxide powder is compounded with a binder such as clay or a polymer and dry-formed into a sheet-like shape by roll pressing with a calender roll. The binder may consist of clay such as bentonite, or polymers such as corn starch, polyacrylamide, or polyacrylate. Examples of binders include bentonite, sodium carbonate, calcium chloride, calcium hydroxide, sodium silicate, carboxymethylcellulose (CMC), Alcotac, Peridur, corn starch, Funa, wheat flour, sodium lignosulfate, molasses, or polyacrylate. The binder may consist of a combination of one or more clays and one or more polymers. In certain embodiments, iron oxide powder is dispersed in a liquid to form a slurry, which is then used for wet molding into various shapes. In certain embodiments, the iron oxide slurry is slip-cast into a mold of substantially any shape. In certain embodiments, the iron oxide slurry is coated onto a sheet by a doctor blade method or other similar coating method.

[0120] In various embodiments, a bed of conductive microporous pellets constitutes the electrodes of an energy storage system. In some embodiments, the pellets include pellets of directly reduced iron (DRI). The filling of the pellets creates macropores between the individual pellets. The macropores facilitate ion transport across electrodes that, in some embodiments, have dimensions of several centimeters, still having very thick minimum dimensions compared to some other types of battery electrodes. The macropores can form less flexible pore spaces compared to micropores within the pellets. The micropores within the pellets allow for contact between the active material and the electrolyte due to the high surface area of ​​the pellets, enabling high utilization of the active material. This electrode structure is particularly useful for improving the rate capacity of very thick electrodes for stationary, long-term energy storage, where thick electrodes may be required to achieve very high area capacities.

[0121] In various embodiments, transient porosity-forming agents are incorporated during DRI production to increase the porosity of the resulting DRI. In one embodiment, the porosity of the DRI pellets is modified by incorporating a sacrificial porosity-forming agent, such as ice (solid H2O), which later melts or sublimes under heat treatment, into the pelletizing process. In certain other embodiments, the transient porosity-forming agent includes naphthalene, which then sublimes to leave behind porosity. In other embodiments, the transient porosity-forming agent includes NH4CO3 (ammonium carbonate), which can be introduced as a solid at various points in DRI production, decomposes under heating, and remains entirely as a gaseous or liquid species (NH3 + CO2 + H2O). In various other embodiments, the transient additive can perform additional functions in the cell (e.g., it may be an electrolyte component). In certain embodiments, the transient additive may be an alkali salt such as KOH, NaOH, or LiOH. In certain embodiments, the transient additive may be a soluble electrolyte additive that is solid in form under ambient dry conditions, such as lead sulfate, lead acetate, antimony sulfate, antimony acetate, sodium molybdenum oxide, potassium molybdenum oxide, thiourea, sodium stannate, or ammonium thiosulfate. In various other embodiments, the transient additive may be a binder used to aggregate the iron ore powder into pellets or other shapes, such as sodium alginate or a carboxymethylcellulose binder.

[0122] In various embodiments, sacrificial pore-forming agents, convertible pore-forming agents, transient pore-forming agents, removable pore-forming agents, or techniques can be utilized. In such embodiments, the intermediate material in which the pore-forming agent is still present may have a total Fe weight percentage in the range of 20% to 90% by weight. The pore-forming agent can be removed partially before use as an electrode, entirely before or during use as an electrode, and in combinations and variations thereof. In one embodiment, the intermediate may have a total Fe of 25% to 50% by weight, and removal of the pore-forming agent provides the electrode with a total Fe of 60% to 90% by weight.

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

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

[0125] In certain embodiments, a mixture of DRI produced using various reducing gases can be used to achieve a beneficial combination of composition and properties. In one non-limiting embodiment, a 50 / 50 mixture by mass 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.

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

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

[0128] In some embodiments, the metal electrode has a low initial specific surface area (e.g., about 5 m²). 2 Less than / g, preferably about 1m 2 They may have a specific surface area (less than / g). Such electrodes tend to exhibit a low self-discharge rate in low-rate long-term energy storage systems. One example of a low specific surface area metal electrode is a bed of DRI pellets. In many typical and modern electrochemical cells, such as lithium-ion or nickel-metal hydride batteries, a high specific surface area is desirable to facilitate high-rate capacity (i.e., high power). In long-term systems, the need for rate capacity is significantly reduced, so low specific surface area electrodes can meet the target rate capacity requirement while minimizing self-discharge.

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

[0130] In embodiments, as shown herein, iron materials can be processed, chemically modified, mechanically modified, or otherwise configured such that one or more of their characteristics are altered. These methodologies are described herein generally as being implemented with DRI materials. It is understood that these methodologies can be applied to other iron-containing materials, such as reduced iron materials, unoxidized iron, highly oxidized iron, iron with valence states of 0 to 3+, and combinations and variations thereof. Thus, iron-containing pellets having predetermined characteristics, for example, those shown herein, are provided for use in electrode configurations of long-term electrostatic storage cells.

[0131] In certain embodiments, DRI is subjected to mechanical operations for grinding, scraping, or polishing a surface and / or removing fine particles. In one embodiment, DRI pellets are rotated in a trommel sieve to scrape a surface and remove fine powder / dust from the surface. This operation can have the beneficial effect of reducing the reactivity of the DRI pellets, making shipment easier and safer without relying on briquetting or other compression operations. In another embodiment, a block or sheet of DRI is passed under a rotating brush to remove fine particles from the surface. This exhibits a similar beneficial effect.

[0132] In one embodiment, the porosity of DRI is increased by pretreatment with an acid bath (e.g., concentrated HCl). The acid bath etches the iron, creating larger pores and increasing the overall porosity. By optimizing the etching time, the total volume of the DRI pellet can be increased without excessive loss of active material into the acid etching solution.

[0133] In another embodiment, desirable impurities or additives are incorporated into the DRI. If such impurities are solid, they can be incorporated by ball milling the powder additive together with the DRI pellets (for example, using a planetary ball mill or similar apparatus). In this case, the pellets themselves act as a milling medium. In this way, the powder additive is mechanically introduced into the pores or surface of the DRI pellets. Alternatively, the DRI may be coated with beneficial additives, for example, by rotating or immersing it in a slurry containing the additives. Examples of such desirable impurities include alkali sulfides. Alkali sulfide salts have been shown to significantly improve the availability of active materials at the Fe anode. In exactly the same way that soluble alkali sulfides can be added to the electrolyte, insoluble alkali sulfides can be added to the DRI, for example, by the method described above.

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

[0135] In some embodiments, the surface area of ​​cementite or iron carbide-containing materials, such as 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 may be 0.1 to 25 mA / g. This high-surface-area iron oxide can also be used in various applications other than electrochemical cells.

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

[0137] The ratio of electrolyte to iron material, such as the DRI material of the cell, is from about 電解質 0.5 mL 鉄材料 ~ about 5 mL 電解質 :1 g 鉄材料 、 from about 電解質 0.6 mL 鉄材料 ~ about 3 mL 電解質 :1 g 鉄材料 、 from about 電解質 0.6 mL 鉄材料 、 from about 電解質 0.7 mL 鉄材料 、 from about [[ID=! 電解質 0.8 mL 鉄材料 、 from about [[ID=! 電解質 1 mL 鉄材料 、 and combinations and variations thereof, and may be larger and smaller ratios.

[0138] In one embodiment, the porous sintered iron electrode may be formed from DRI, which may have its particle size reduced by, for example, crushing or grinding, or may be in powder form. Alternatively, the sintered iron electrode may be formed using DRI powder or other waste materials. The sintered electrode may be formed with a binder under heat and / or pressure, and then the binder may be burned off, and the raw form may be sintered at a high temperature. Alternatively, the DRI pellets may be directly fused together by sintering under optional pressure in a non-oxidizing atmosphere without a binder to create electrical and physical connectivity between the pellets.

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

[0140] A DRI pellet packing bed can be a desirable configuration for iron-based electrodes because it provides an electronically conductive penetration pathway through the packing bed while leaving porosity available for the electrolyte to occupy, facilitating ion transport. In certain embodiments, the ratio of electrolyte volume to DRI mass may be in the range of 0.5 mL / g to 5 mL / g, such as 0.6 mL / g or 1.0 mL / g. DRI pellets generally come into contact with surrounding pellets via a small contact area compared to the surface area of ​​the pellets, and in some cases, the contact can be considered a "point contact." Contact with a small cross-sectional area can result in constrictions in the flow of current, which may lead to relatively low electrical conductivity across the pellet bed, and consequently, high electrode overvoltage and low battery voltage efficiency.

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

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

[0143] In another embodiment, some or all of the individual pellets in the pellet bed are wrapped in electrically conductive wire, foil, or sheet. In some embodiments, a clamping mechanism such as a mesh is used to apply tension to the wire, foil, or sheet. Optionally, such current collectors surrounding individual pellets may be bundled together or attached to wires connected to a larger current collector. In another example, conductive mesh, gauze, or wool is scattered in the spaces between DRI pellets to increase electrical connectivity. In various embodiments, the conductive material is a mesh having openings (clear size) selected to be smaller than the pellets so that the pellets do not pass through the mesh. The conductive material in this case may be stainless steel, nickel, or other metals and metal alloys. In another example, the DRI pellets are directly connected to each other by conductive wires that pass through or around the individual pellets. For example, as in forming a string of beads, wires can be passed through holes in the DRI pellets to provide electrical contact not only between pellets but also within the pellets. Optionally, the string of pellets may maintain contact using electrical terminals or “stoppers” to which tension is optionally applied. The electrical terminals may optionally be electrically connected to a larger current collector or fixing device, such as a plate.

[0144] In another embodiment, the electrical conductivity of a pellet bed is improved by applying a compressive load to the DRI pellet bed anode to increase the inter-pellet force and / or inter-pellet contact area or the contact area between the pellets and the current collector, thus reducing contact resistance and enhancing electrochemical performance. Typical DRI pellets are approximately spherical in shape, have internal porosity, and can be elastically deformed to a linear strain of >5% before yielding. Applying a compressive load to the DRI bed can increase the effective contact area between pellets and at the interface between the pellets and the current collector. It is advantageous to use pellets with a yield strain that allows deformation to achieve the desired increase in conductivity without causing fracture. In one embodiment, pellets having a compressive strength of 700 to 2500 psi are used for the pellet bed electrode to which a compressive load is applied. In addition, the mechanical assembly that provides the compressive load to the pellet bed can also serve as a current collector. The electrical resistance of such a pellet bed, measured in a dry state before any liquid electrolyte is filled, can be reduced by half to a hundredth or more by applying a compressive load. In certain embodiments, the applied load may be in the range of 0.1 psi to 1000 psi, such as 50 psi or 100 psi. In certain embodiments, the applied load may be in the range of 0.1 psi to 10 psi, such as 1 psi or 5 psi. In one example, a metal plate on the opposite surface of the pellet bed serves to provide both current collection and a compressive load to the pellet bed. Optionally, one or more of the plates may be replaced with a macroporous current collector (e.g., a metal mesh) to facilitate ion transport across the entire electrode. The opposing current collectors are preferably joined so that they are at the same potential, which is advantageous for more uniform electrochemical reaction rates across the entire electrode. In another example, the container containing the pellet bed serves both as a current collector and as a way to apply a compressive load. In another embodiment, an array of conductive posts (or rods) connected to a common downward current collector is implemented. Thus, a number of current collection areas can be arranged across the entire pellet bed.Furthermore, this method can reduce the effective transport length within the electrode from the total thickness of the pellet bed to the distance between posts. In addition, these posts can be used to attach a mechanical clamping mechanism, such as a plate or perforated plate, to the top of the pellet bed, which can act as a current collector while incorporating a downward force on the pellet bed.

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

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

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

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

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

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

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

[0152] Various embodiments can provide methods and apparatus for maintaining the liquid electrolyte level of a battery. A container containing water, when exposed to air, will experience evaporation until the partial pressure of water vapor in the air equals the vapor pressure of water at the system's temperature. Specifically, an electrochemical system in which an aqueous electrolyte is exposed to the environment will experience this same evaporation. Dehydration of the electrolyte can lead to problems resulting from a reduction in electrolyte volume, and changes in electrolyte concentration can alter electrochemical performance. To mitigate these problems, various embodiments can maintain the electrolyte level by continuously or intermittently supplying the electrolyte to the cell volume. Specifically, the electrolyte liquid level can be maintained by introducing the electrolyte into the container until it overflows from an overflow point. Since the liquid level cannot rise beyond this outflow point, this level can be maintained in a relatively controlled manner. Specifically, several volumes can be arranged in a cascade so that overflow from one chamber flows into the next chamber, establishing a "liquid communication" between cells. By connecting these cells in series, it becomes possible to supply liquid electrolyte to multiple cells simultaneously from a single source. The overflow from the last container can be recirculated to the first container. In systems using a shared electrolyte that flows in a cascade manner between cells, the properties of the electrolyte can be monitored and processed at a central location among the many cells. Electrolyte adjustments, such as compositional adjustments or addition of components to mitigate problems related to electrolyte carbonation and electrolyte dehydration, are beneficial to perform at such accumulation sources of circulating electrolytes.

[0153] Various embodiments can provide compositions and methods for adding beneficial additives to the electrolyte of an aqueous electrochemical cell. Electrolytic production of hydrogen during charging of aqueous secondary batteries can lead to Coulomb inefficiency, gas accumulation within the cell housing, safety concerns, and electrolyte consumption. Furthermore, metal electrode self-discharge can occur due to the spontaneous reaction of metals and electrolytes to form metal hydroxides, producing reactive hydrogen as a product. Certain solid-phase hydrogen generation inhibitors (e.g., Bi, Sb, As) can mitigate these harmful effects, but incorporating solid-phase inhibitors into the porous metal electrodes of batteries can be costly and pose manufacturing challenges. Therefore, various embodiments provide compositions and methods for dissolving and adding ions of the desired additive (e.g., Bi 3+ Sb 3+ As 3+ A soluble salt of the desired hydrogen evolution inhibitor is added to the liquid electrolyte, providing ) in solution. The additive is used to facilitate the plating reaction from the inhibitor ions to the metal (e.g., Bi 3+ ->Bi 0 The oxidation-reduction potential of the HER inhibitor is selected to occur at a half-cell potential (measured relative to RHE (but at lower cell potentials)) that is higher than the potential of the charging reaction of the anode active material. Thus, during battery charging (reduction of the metal electrode), the ionic form of the HER inhibitor is electrodeposited onto the surface of the metal electrode, providing an inexpensive and simple strategy for introducing the HER inhibitor into the battery electrolyte chemistry. The electrodeposition inhibitor suppresses the hydrogen evolution reaction on the electrode surface, which may be an electrode with open porosity. During the discharge mode, the deposit can dissolve back into the electrolyte. Salt additives are preferably selected so as not to degrade the operation of the cathode during charging or discharging operations.

[0154] In another embodiment, the electrochemical cell includes an electrode that carries out a hydrogen oxidation reaction (HOR) to recapture hydrogen produced in the HER side reaction and mitigate the generation of potentially hazardous hydrogen gas. Hydrogen gas bubbles generated in the HER may be captured and brought into contact with the HOR electrode, which may be the working electrode of the battery cell or an additional electrode added to the system. In one embodiment, the hydrogen gas is captured by positioning the cell's electrodes so that buoyancy carries the hydrogen gas bubbles to the HOR electrode. For example, the system may be inclined or may include a funnel designed to facilitate this flow.

[0155] In various embodiments, the liquid electrolyte flows through the pile or bed of DRI pellets. For thick (up to several centimeters) battery electrodes composed of active material pellets, achieving sufficient transport of reactants, reaction products, and additives through the thick bed over a timescale commensurate with the battery's operating (charging and discharging) timescale can be challenging. Insufficient transport rates of the electrolyte can result in several detrimental effects, including, but not limited to, increased overvoltage losses and reduced availability of the active material in the pellet-based electrodes. In metal electrode batteries with alkaline electrolytes, bubble formation and pH gradients during both charging and discharging can lead to undesirable performance degradation or corrosion of one or both electrodes. In various embodiments, the liquid electrolyte flows through the bed of DRI pellets to mitigate the detrimental effect of transport limitations. The fluidity of the electrolyte results in convective transport of the electrolyte to individual pellets. Among other advantages, electrochemical reaction rates and reaction uniformity are improved by reducing the electrolyte concentration boundary layer that can occur across the entire thickness of the pellet bed or within the macropores of the pellet bed. Electrolyte flow generally reduces overpotential loss by homogenizing the electrolyte composition throughout the macrostructure and microstructure of the electrode. In some embodiments, electrolyte flow is achieved using active methods, such as mechanical pumping. The electrolyte flow rate may be as low as 1 mL / min / cm². 2It may be as low as or even lower than that. In other embodiments, electrolyte flow is achieved by passive means, such as buoyancy-driven flow due to a thermal gradient or compositional gradient. In a specific example, a battery component where thermal resistive dissipation occurs is located at or near the bottom of the electrode bed and heats the electrolyte, causing it to rise through the pellet bed. In another specific example, an electrode that changes the density of the electrolyte by an electrochemical reaction, for example, an exothermic or endothermic reaction or a change in the composition of the electrolyte in contact with the electrode, is located in the battery to create buoyancy-driven flow. In this example, the electrode reaction that produces a lower density electrolyte may be located at or near the bottom of the DRI pellet bed, and the reaction that increases the density of the electrolyte may be located at the top of the pellet bed.

[0156] In some embodiments, additives that suppress side reactions, such as corrosion inhibitors that inhibit the HER reaction or self-discharge, are combined with additives that improve capacity utilization. Additives to the electrolyte of a battery with metal electrodes, including iron electrodes, are beneficial because they can perform several functions, including increasing the capacity utilization of iron, suppressing undesirable side reactions, or both. Different additives have different advantages, and such advantages can be combined by combining additives in appropriate concentrations. Examples of capacity-enhancing additives are sulfur or sulfides. In some embodiments, more than one corrosion inhibitor can be used together with one or more sulfides. For example, sulfur assists in the depassivation of iron electrodes but may be consumed during the electrochemical cycle of the battery. Thus, sulfur consumption may contribute to capacity attenuation over many cycles. In one embodiment, sulfur is replenished using a delivery system to maintain battery performance. One example of such a system is a pump that delivers sulfur-holding liquid to battery cells. Another example is a dry hopper that delivers polysulfide salts to closed or open battery cells.

[0157] In one embodiment, iron sulfide (FeS) can be added as a sparingly soluble additive to a metal-air battery using an alkaline electrolyte to improve the electrochemical stability of the OER electrode and increase electrode life. This embodiment helps to mitigate the decline in catalytic performance in oxygen evolution (OER) electrodes under alkaline conditions, which can limit the operating life of the electrode.

[0158] In certain embodiments, sulfur may be added to the DRI by an additional process operation. In certain embodiments, the DRI may be immersed in a molten sulfur bath, taking advantage of the low melting point of sulfur. In certain other embodiments, hydrogen sulfide gas may be flowed through a hot or cold DRI to deposit a layer of sulfur and / or iron sulfide on the surface of the DRI. In certain other embodiments, sulfur may be sublimated and deposited onto the surface of the DRI. The DRI may be hot or cold. In certain embodiments, sulfur is fused into the pores of the DRI by melting it and then wicking it into the pores of the DRI.

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

[0160] In some embodiments, additives containing molybdate ions are used in alkaline batteries containing an iron anode. While not bound by any specific scientific interpretation, such additives can help suppress the hydrogen evolution reaction (HER) at the iron electrode and improve the battery's cycle efficiency. The concentration of the additive is selected so as to suppress HER while still allowing the desired iron charge / discharge process. As an example, molybdate ions may be added via a molybdate compound such as KMoO4. In one specific example, the electrolyte is used when the additive concentration is 10 mM (mM is millimoles, 10 -3 It contains molybdate anions at a concentration of molars / L. In other embodiments, the electrolyte contains molybdate anions at an additive concentration ranging from 1 to 100 mM.

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

[0162] 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 uptake from the air. In air, electrolytes based on potassium hydroxide or sodium hydroxide will lose potassium or sodium cations from the solution through reaction with carbon dioxide (CO2) present in the air, forming potassium carbonate or sodium carbonate. This is problematic, especially in batteries with air electrodes, because oxygen, the desired reactant in its lowest-cost form, is supplied to the oxygen reduction (ORR) electrode by the ambient air. Electrolyte carbonation can result in several adverse effects on battery performance, including undesirable side reactions and a decrease in electrolyte conductivity, all of which contribute to a reduction in the battery's operating efficiency. However, the rate of carbonate formation slows dramatically as the carbonate concentration in the electrolyte increases. In one embodiment, carbonates are intentionally added to the electrolyte before operation to reduce the rate of carbonation with air during battery operation. Intentional addition of carbonates mitigates the adverse effects of carbonation and maintains an acceptable carbonate level in the electrolyte over a long operating life.

[0163] In one embodiment, the integrity of the electrolyte in a metal-air battery is monitored periodically or continuously. The lifespan and quality of the electrolyte have been found to have a dramatic impact on the electrochemical performance of iron-air batteries. In some cases, the performance degradation is associated with the negative electrode, such as the iron electrode. Generally, as the electrolyte ages, the discharge capacity of the negative electrode decreases. This may be due to changes in the concentration of electrolyte components over time, particularly due to spontaneous reactions that form undesirable products, especially those caused by contact with air. In some embodiments, the integrity of the electrolyte is monitored during battery operation to determine the appropriate time for replenishing, replacing, or treating the electrolyte. The feedback mechanism may be manual or automatic. In automated systems, electrolyte quality measurement may be a single input to a proportional-integral-derivative (PID) loop that continuously adjusts the electrolyte component concentration. Electrolyte quality measurement may be performed ex-situ on a small aliquot of the electrolyte or operandly on the active electrolyte during cell operation. One non-limiting method for assessing electrolyte integrity is to measure the electrical conductivity of the electrolyte. One mechanism of degradation is the carbonation of the electrolyte over time due to the dissolution of CO2 from the air. In a specific example, experiments are conducted to demonstrate that electrolyte conductivity changes linearly with the carbonate concentration in the electrolyte. The carbonate concentration in the electrolyte is evaluated using a conductivity probe. The integrity of the electrolyte is monitored using a conductivity probe.

[0164] In some embodiments, corrosion inhibitors used in the field of iron metallurgy to inhibit water corrosion are used as components of batteries having an iron anode for improved performance. In some embodiments, directed reduced iron (DRI) is used as the anode, and favorable performance characteristics can be achieved by using one or more corrosion inhibitors within a suitable concentration range. In such embodiments, the principles of corrosion science are used to prevent undesirable side reactions (e.g., hydrogen generation) under charging conditions, reduce the rate of spontaneous self-discharge during electrochemical retention, and maximize the availability of iron active materials during discharge. Generally, there are two types of corrosion inhibitors: interface inhibitors that react with the metal surface at the metal-environment interface to prevent corrosion, and environmental scavengers that inhibit corrosion by removing corrosive elements from the environment surrounding the metal surface. Under the broad protection of corrosion inhibitors, favorable performance characteristics in terms of the efficiency and capacity of the electrochemical cell can be achieved by adding appropriate concentrations of inhibitors to the electrochemical cell. In the case of iron electrodes in metal-air batteries, one applicable common type of inhibitor is liquid-phase interface inhibitors. This category encompasses three main types of interfacial inhibitors: anode inhibitors, cathode inhibitors, and mixed inhibitors. Anode inhibitors create a passivation layer that inhibits the anodic metal dissolution reaction. Cathode inhibitors can reduce the rate of the reduction reaction (HER in the case of iron electrodes) or precipitate at the cathode active site to block the same reduction reaction. Mixed inhibitors can inhibit corrosion via one or both pathways and include, but are not limited to, molecules that can physically or chemically adsorb onto the metal surface to form a film that can block the active site of the reduction reaction. Inhibitors can be added to the base electrolyte at any concentration.

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

[0166] In certain embodiments, other electrolyte additives are incorporated into the electrolyte. The electrolyte additives may be selected from the following non-restrictive set: sodium thiosulfate, sodium thiocyanate, polyethylene glycol (PEG) 1000, trimethylsulfoxonium iodide, zincate (by dissolving ZnO in NaOH), hexanethiol, decanethiol, sodium chloride, sodium permanganate, lead(IV) oxide, lead(II) oxide, magnesium oxide, sodium chlorate, sodium nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, ammonium thiosulfate, lithopone Magnesium sulfate, iron(III) acetylacetonate, hydroquinone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid, dimethyl phthalate, methyl methacrylate, methylpentinol, adipic acid, allylurea, citric acid, thiomalic acid, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, propylene glycol, trimethoxysilylpropyl diethylene, aminopropyltrimethoxysilane, dimethylacetylenedicarboxylate (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, behenamide, 2-phosphonobutane tricarboxylic acid, mipa borate, 3-methacryloxypropyltrimethoxysilane, 2-ethylhexoic acid, isobutyl alcohol, t-butylaminoethyl methacrylate, diisopropanolamine, propylene glycol n-propyl ether, sodium benzotriazolate, pentasodium aminotrimethylenephosphonate, sodium cocoyl sarcosinate, laurylpyridinium chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quaternium-18 chloride chloride), sodium hexametaphosphate, dicyclohexylamine nitrite, lead stearate, calcium dinonylnaphthalene sulfonate, iron(II) sulfide, sodium hydrogen sulfide, pyrite, sodium nitrite, complex alkyl phosphate ester (e.g., RHODAFAC® RA600 emulsifier), 4-mercaptobenzioc acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate (EDTA), 1,3-Propylenediamine tetraacetate (PDTA), nitrilotriacetate (NTA), ethylenediamine disuccinate (EDDS), diethylenetriamine pentaacetate (DTPA), and other aminopolycarboxylates (APCs), diethylenetriaminepentaacetic acid, 2-methylbenzenethiol, 1-octanthiol, 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 Lu, N-allylthiourea, thiourea, 4-methylcatechol, trans-cinnamaldehyde, iron(III) sulfide, calcium nitrate, hydroxylamine, benzotriazole, furfurylamine, quinoline, tin(II) chloride, ascorbic acid, tetraethylammonium hydroxide, calcium carbonate, magnesium carbonate, antimony dialkyldithiophosphate, potassium stannate, sodium stannate, tannic acid, gelatin, saponin, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrogenated light oil, heavy naphthenic petroleum fractions (heavy Naphthenic petroleum oil (e.g., marketed as Rustlick® 631), antimony sulfate, antimony acetate, bismuth acetate, hydrogenated heavy naphtha (e.g., marketed as WD-40®), tetramethylammonium hydroxide, NaSb tartrate, urea, D-glucose, C6Na2O6, potassium antimony tartrate, hydrazine sulfate, silica gel, triethylamine, potassium antimonate trihydrate, sodium hydroxide, 1,3-di-o-tolyl-2-thiourea, 1,2-diethyl-2-thiourea, 1,2-diisopropyl-2-thiourea, N-phenylthiourea, N,N'-diphenylthiourea, sodium antimony tartrate, disodium rhizonate, sodium selenide, and combinations thereof.

[0167] In certain embodiments, the electrolyte is gelled. In certain embodiments, a gel is formed by dissolving silica (SiO2), or other network-forming oxides such as boron oxide (B2O3) or alumina (Al2O3), in an alkaline liquid. In certain embodiments, a gel electrolyte is formed by dispersing network-forming organic molecules in a liquid electrolyte. In certain embodiments, the organic molecules include polymers. In certain embodiments, a gel electrolyte is formed by adding the liquid electrolyte to a solid polymer such as polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylamide (PAM), or polyacrylic acid (PAA). Bio-derived polymers such as cassava or gelatin can also be used as polymer additives. In certain embodiments, the gel electrolyte is formed in situ by the dissolution of silica (or other oxides) derived from DRI. In certain other embodiments, additional gel-forming agents are intentionally added to the liquid electrolyte for the purpose of creating a gel. In certain embodiments, the gel electrolyte is formed in situ by evaporating the solvent (e.g., water) from the electrolyte, concentrating the dissolved salt, and converting the electrolyte from a liquid to a gel or supersaturated solution.

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

[0169] In certain embodiments, the electrolyte additive is delivered to the electrode as a solid mixture. The electrolyte additive may have a range of solubility. Some may exhibit the most beneficial effects when closely mixed with the solid electrode. In one embodiment, the solid pellet consists mainly of the additive, and such additive pellet is added to or mixed with a metal electrode containing multiple DRI pellets in one embodiment. In another embodiment, the electrolyte additive is mixed with a metal which may contain a redox active electrode, and this mixture may be pelletized, and in one embodiment is mixed with a metal electrode containing multiple DRI pellets. Non-limiting examples of additives include sodium sulfide (Na2S), potassium sulfide (K2S), lithium sulfide (Li2S), and iron sulfide (FeS2S). x Examples include (where x = 1 to 2 in the formula), bismuth sulfide (Bi2S3), lead sulfide (PbS), zinc sulfide (ZnS), antimony sulfide (Sb2S3), selenium sulfide (SeS2), tin sulfide (SnS, SnS2, Sn2S3), nickel sulfide (NiS), molybdenum sulfide (MoS2), and mercury sulfide (HgS), FeS, bismuth oxide (Bi2O3), or combinations thereof. In some embodiments, pellets with varying proportions of redox-active metals to additives are prepared, and pellets with different compositions are mixed to create a mixed electrode.

[0170] In some embodiments, an electrochemical formation cycle protocol is used to alter the properties of the initial DRI pellet and improve the subsequent operating electrochemical performance of the DRI as an anode. The DRI pellet at the time of manufacture may not be in a form optimized for the electrochemical cycle of the battery. For example, the free surface of the DRI may have natural oxides that block electrochemical access to the active material, the specific surface area may be too small to reach the desired specific capacity, and / or the pore structure may restrict ion transport and limit the specific capacity. In one specific embodiment, the initial cycle, called "formation," consists of one or more repetitions of the following steps: One step may be a short charging step ("pre-charging") during which any natural oxide layers that detrimentally passivate the DRI at reception may be chemically reduced, or the specific surface area of ​​the DRI pellet may be increased, sometimes by more than 10 times. Such changes can increase the usable capacity of the DRI in subsequent discharge. Another step is Fe to Fe 2+ to or Fe 2+ From Fe 3+ The discharge step may involve oxidizing metallic iron until one or more of the reactions to are completely or partially completed. The charge and discharge capacities may differ between iterations of the formation cycle. In some embodiments, the formation may include iterations of pre-charge and discharge cycles with systematically increasing capacities. In one specific embodiment, the formation cycle consists of pre-charging to a capacity of 250 mAh / g and then cycling the subsequent loop n times: 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 pre-charge step increases the specific surface area of ​​the DRI to approximately 0.5 m². 2 / g to 12m 2Increase the capacity up to or over a larger area than mAh / g. This increases the available capacity for subsequent discharge. The remainder of the formation cycle is carried out over n cycles with a 25 mAh / g capacity increment (assuming 90% Coulomb efficiency) to gradually approach the charge and discharge capacity corresponding to deep cycling.

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

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

[0173] In this embodiment, the charge state and integrity state of a metal electrode are determined using ex-situ measurement of its composition. In an electrochemical cell containing an iron electrode, the charge state and integrity state of the electrode correlate with the proportion of metallic iron. Therefore, the charge state or integrity state of the cell can be determined using measurement of the proportion of metallic iron. In one specific embodiment, susceptibility measurements are performed on one or more portions of the iron electrode to determine the charge state or integrity state. To perform such measurements, the sample may be formed into a disc or cylinder having a thickness ranging from several millimeters and a diameter of 0.25 cm to 4 cm. The measured susceptibility is analyzed to extract the relative amounts of metallic iron, ferrous iron, and ferric iron.

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

[0175] Specifically, DRI can be used as the anode material of an all-Fe battery where Fe is a reactive species in both the anode and the cathode. In such an embodiment, DRI can serve as a solid metallic Fe anode at 100% SOC, and the anode is soluble Fe during discharge 2+This will result in the formation of a species (i.e., FeCl2). The cathode active substance may be a soluble inorganic Fe-based salt, such as an FeCl2 / FeCl3 redox pair. Alternatively, the cathode active substance may be an inorganic or organic coordination compound such as K3Fe(CN)6. In the cathode, the soluble Fe species will form Fe 2+ / Fe 3+ This will result in a redox reaction associated with the redox pair. One specific example of an all-Fe battery in which DRI is used as the active substance would be using DRI as the anode material along with an electrolyte containing HCl (1-5 M) at a concentration. At the anode, DRI undergoes the following half-cell reaction during discharge: Fe + 2Cl - ->FeCl2+2e - This will be involved. In the cathode, soluble FeCl3 undergoes the following half-cell reaction during discharge: 2FeCl3 + 2 e- -> 2FeCl2 + 2Cl - This will cause the following to occur. The complete cell reaction during discharge will be Fe + 2FeCl3 -> 3FeCl2. DRI is used as a source of soluble FeCl2 required in the solution, and by reacting DRI with HCl in the solution, a cathode reaction can be enabled, which will be involved in the following spontaneous chemical reaction: Fe + 2HCl -> FeCl2 + H2.

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

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

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

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

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

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

[0182] In another embodiment, DRI is used in an oxygen reduction reaction (ORR) electrode. In some embodiments, the iron or iron salt component of the DRI, which may be iron oxide, iron hydroxide, or iron carbide, reacts with another component, such as another metal or metal salt, to form an ORR catalyst. This catalyst may be formed on the surface of the DRI pellet, or may penetrate into the DRI pellet, may be a portion of the DRI, or may substantially convert the entire DRI. DRI powder and DRI pellets or crushed pellets can be used as ORR electrodes. In some embodiments, the ORR catalyst formed from the 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.

[0183] In various embodiments, a DRI-packed bed is used in a water filtration device. In such embodiments, DRI is placed in a column to create a DRI pellet-packed bed. Particulate matter is trapped in the pores within the DRI pellets and in the void spaces between the DRI pellets. By using pelletized iron as the filtration medium, the ability to adjust pressure loss and filtration effectiveness can be provided.

[0184] In various embodiments, DRI is used as a metallic iron feedstock for producing Fe-containing industrial or specialty chemicals, such as ferrocyanides, iron tris-bipyridines, and ferrocenes.

[0185] 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 arranged. The liquid electrolyte 104 may separate the air electrode 103 from the negative electrode 102.

[0186] The negative electrode 102 may contain metallic pellets 105, which may contain at least 50% by elemental mass of metal, such as at least 60% by weight of metal. In some embodiments, the metallic pellets 105 may contain at least 60% by elemental mass of iron. Therefore, the pellets 105 may be called iron-containing pellets. The pellets 105 may be electrically connected to one another and may be arranged in one or more layers to form the negative electrode 102. In various embodiments, the negative electrode 102 may be a slurry. In various embodiments, the slurry may contain one or more metallic pellets 105. In various embodiments, the slurry may contain dissolved particles, such as particles corresponding to the composition of the metallic pellets 105 as considered herein. As a specific example, the negative electrode 102 may be an iron-containing slurry. In various embodiments, the positive electrode 103 may be a slurry. In various embodiments, the negative electrode 102 may be in the form of a gel. A fluid semi-solid anode 102 (e.g., a fluid semi-solid iron electrode) can be beneficial in large-scale energy storage systems because it has low manufacturing costs and is easy to assemble into cell architectures. For example, reduced forms of iron are highly conductive. By suspending iron particles in a polymer gel, a permeable network of iron particles can be generated, thereby creating a conductive and electrically active gel that can form the anode 102. For example, the polymer gel can be formed by dissolving an organic polymer (e.g., carboxymethylcellulose (CMC)) or by dissolving an inorganic oxide-forming network (e.g., SiO2 dissolved in concentrated KOH). In certain embodiments, the electrolyte is gelled. In certain embodiments, a gel is formed by dissolving silica (SiO2) or other network-forming oxides such as boron oxide (B2O3) or alumina (Al2O3) in an alkaline liquid. In certain embodiments, a gel electrolyte is formed by dispersing network-forming organic molecules in a liquid 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. Alternatively, bio-derived polymers such as cassava or gelatin can be used as polymer additives. In certain embodiments, the gel electrolyte is formed in situ by the dissolution of silica (or other oxides) derived from DRI. In certain other embodiments, additional gel-forming agents are intentionally added to the liquid electrolyte for the purpose of creating a gel. In certain embodiments, the gel electrolyte is formed in situ by evaporating the solvent (e.g., water) from the electrolyte, concentrating the dissolved salt, and converting the electrolyte from a liquid to a gel or supersaturated solution.

[0187] In various embodiments, the pellet 105 comprises one primary iron-containing phase and one or more secondary phases ("gangues"). In various embodiments, the oxidation state of the primary phase may range from highly reduced (e.g., metallic iron) to highly oxidized (e.g., ionic). For example, the pellet 105 may be substantially metallic iron, i.e., with a valence state of 0 (e.g., Fe 0 ) may also be. Therefore, in some embodiments, the pellet may 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 various other embodiments, the pellet 105 may consist of iron that has been completely oxidized to a 3+ valence state (e.g., Fe2O3). In various other embodiments, the valence state of iron may be 0 to 3+. In various embodiments, the primary phase may be an oxide, hydroxide, sulfide, carbide, or a combination thereof. For example, the primary phase may be Fe, FeO, Fe2O3, Fe3O4, FeO x (OH) y Fe3C, FeS x FeO x S y , and / or FeO x S y H zThe composition may be as follows. In some embodiments, pellet 105 may contain directly reduced iron (DRI) pellets, and pellet 105 may constitute at least 60 percent of the total mass of the negative electrode 102. In various embodiments, the negative electrode 102 may be composed of DRI pellets.

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

[0189] The pellet 105 may be spherical, as shown in Figure 1. For example, in various embodiments, the pellet 105 may have an average diameter in the range of about 0.5 mm to about 10 cm, such as about 10 mm. As a specific example, the pellet 105 may have an average diameter of 4 mm to 20 mm. As used herein, the term “spherical” is used to describe any rounded shape that resembles a three-dimensional object in which all of its surface points are equidistant from its center, although in reality all of its surface points do not have to be equidistant from its center. In other words, “spherical” encompasses shapes that are perfect spheres, and shapes that are not perfect spheres but general spheres, such as those that have the appearance of a ball. However, this disclosure is not limited to any particular pellet shape. For example, the pellet may be briquette-shaped, as discussed below with respect to Figure 2A. In addition, although the pellet 105 is illustrated as a whole pellet, it may also be fragments of crushed pellets. For example, the received pellets may be crushed, and fragments of such crushed pellets can form a negative electrode on pellets 105, such as pellets 105 filled in the bed. In various embodiments, the crushed pellets are 10 nm to 100 nm, 1 to 100 μm (μm = 10 -6m), or 1-10 mm, such as 10 nm (nm = 10 -9 m) ~ 10mm (mm = 10 -3 The average particle size may be m). In some embodiments, the crushed pellets may include a combination of pellets having different average particle sizes.

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

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

[0192] In various non-limiting embodiments, the negative electrode 102 may have a thickness in the range of about 0.5 cm to about 50 cm, such as about 0.75 cm to about 25 cm. The pellets 105 may be arranged in the negative electrode 102 at a packing density in the range of about 30% to about 74%. In various non-limiting embodiments, the pellets 105 may be arranged relative to each other (such as by being dispersed or diffused like a gravel bed), or they may be mechanically attached or connected to each other by processes such as compression or pressing. In other embodiments, the pellets 105 may be physically connected by processes 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 connection processes. In other embodiments, the pellets 105 may be attached and connected to each other by conductive wires that are strung together through the holes in the pellets 105. The holes in the pellets 105 can introduce additional contact points not only across the entire thickness of the pellet bed 105 which forms the negative electrode 102, but also across the entire thickness of a single pellet 105. If strung together, the wire may be pulled tight to enhance contact between the pellets 105, and then mechanically held in place by a conductive mechanical stopper, which may in turn be connected to a larger current collector plate such as a current collector 106. In some embodiments, the pellets 105 may be filled into the bed with the help of mechanical pressure applied by an optionally high-temperature resistant material, and then sintered in a non-oxidizing atmosphere. The result is a bed of pellets 105 that are fused together, with low contact resistance between the pellets 105. The sintered bed of pellets 105 can form the negative electrode 102.

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

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

[0195] Commercially available DRI pellets do not necessarily possess the optimal chemical and physical properties for maximizing electrochemical performance. In various embodiments, the DRI pellets are subjected to ex-situ processing before being assembled to the negative electrode 102. Various embodiments include processing the DRI pellets with mechanical, chemical, and / or thermal processes (i.e., processing the DRI pellets ex-situ) before introducing them into the electrochemical cell to achieve better chemical and physical properties. Improved chemical and physical properties may include higher content of desirable impurities (e.g., hydrogen evolution reaction (HER) inhibitors), lower content of undesirable impurities (e.g., HER catalysts), higher specific surface area, higher total porosity, different pore size distributions (e.g., multimodal to reduce mass transport resistance), different pellet size distributions (e.g., multimodal to enhance bed packing), and different aspect ratios (e.g., to enhance bed packing). Mechanical processes that can be applied ex-situ to DRI pellets may include crushing, pulverization, and / or powdering. Thermal processes that can be applied ex-situ to DRI pellets include processing DRI pellets at high temperatures in a reducing atmosphere (e.g., hydrogen), an oxidizing atmosphere, and / or carburizing (e.g., carbon monoxide and / or carbon dioxide) atmosphere. Chemical processes that can be applied ex-situ to DRI pellets include acid etching. In various embodiments, to increase the usable capacity of DRI pellets during the discharge reaction, DRI pellets can be pre-treated by etching the iron and immersing them in an acid bath (e.g., concentrated HCl) which enlarges the pores of the DRI pellets, thereby increasing the total porosity of DRI pellets compared to DRI pellets that are not etched in an acid bath. After pre-treatment, the etched and now porous DRI pellets may be assembled to the negative electrode 102. The etching time can be optimized to increase the usable capacity of DRI pellets without excessive loss of active material into the acid etching solution.In various embodiments, the DRI can be used as an electrode of an electrochemical cell and can be charged with an electric current. This process can increase the surface area of the DRI.

[0196] The current collector 106 may be in the form of a conductive plate electrically connected to the negative electrode 102. However, the current collector 106 may have other configurations, as discussed below with respect to FIG. 2A.

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

[0198] A series of iron valence states (0 to 3+) and counterions O 2- 、OH - 、S 2- etc. can be used as starting materials for various configurations. For example, other possible discharge products include Fe2O3, Fe3O4, FeO, FeOOH, FeS, FeS2, etc., and combinations thereof.

[0199] In various embodiments, by filling the pellets 105 on the floor to form the negative electrode 102, macropores can be created between the individual pellets 105. Additionally, in various embodiments, each of the individual pellets 105 may have a porous, for example, microporous surface. The micropores on the surface of the pellet 105 can provide a larger surface area for each individual pellet 105 than when the pellet 105 is a smooth sphere. The pore size of the pellets can vary. In some embodiments, the pellet 105 may have a volume weighted average pore size greater than 1 micron, such as 1 micron to 10 microns. The pore size distribution within the pellet can be measured by mercury intrusion porosimetry. Mercury intrusion porosimetry is a technique that uses a pressure chamber to push mercury into the pores of the pellet. The mercury is first pushed into the larger pores, and as the chamber is gradually pressurized, the mercury is pushed into increasingly smaller pores. Using physical relationships such as the Washburn equation, the applied pressure can be related to the pore size, and a volume or area weighted pore size distribution can be obtained. The pore size distribution may be converted to a cumulative distribution, from which the values of d 孔、90%容積 and d 孔、50%表面積 can be estimated, as described in Tables 1, 2, and 3 and as discussed above.

[0200] Figure 6 is a schematic diagram of a battery 100 according to various embodiments of the present disclosure, showing enlarged views of macropores 602 and micropores 604. Macropores 602 are created by gaps between individual pellets 105 when the pellets 105 are packed into the bed. Macropores 602 can facilitate ion transport across very thick (e.g., several centimeters) electrodes 102. Micropores 604 may be deformations of the surface of the pellets 105 themselves. Micropores 604 can allow high-surface-area active materials to come into contact with the electrolyte 104, enabling high utilization of the active materials through solid-state electrochemical reactions. Examples of micropores include cracks in the pellets. Such cracks may be formed during the production of the pellets or may be introduced later, such as by applying a mechanical load that causes cracking. This electrode structure having macropores 602 and micropores 604 is particularly useful for improving the rate capacity of very thick electrodes for stationary long-term energy storage, where thick electrodes may be required to achieve very high area capacity.

[0201] Figure 7 shows a single pellet 105 of battery 100. The pellet 105 may contain micropores 604 on its solid-phase surface 702. The electrolyte 104 may fill the micropores 604, thereby providing the outer surface area of ​​the spherical pellet 105 with both a liquid-phase electrolyte region associated with the micropores 604 and a solid-phase region surface 702. The filling of the micropores 604 with electrolyte reduces the solid-phase region on the surface 702 that brings the electrolyte into contact with the outer surface of the pellet, resulting in a low effective specific surface area (e.g., low m²) for the pellet 105. 2A ( / g) is added, thereby reducing the electrolyte concentration boundary layer on the solid phase surface 702. Many metal anodes in aqueous batteries (e.g., Zn, Fe, Al) are known to undergo self-discharge through spontaneous reactions with the electrolyte, forming metal oxides and hydrogen gas. In the case of long-term energy storage systems (e.g., systems with discharge periods of 8 hours or longer, such as 8-20 hours, 20-24 hours, 24 hours, or longer), self-discharge can limit performance because the cell may self-discharge a significant percentage of its storage capacity before a complete discharge cycle is completed. In some embodiments, a small specific surface area (e.g., low m 2 / g) Use metal electrodes to suppress self-discharge in low-rate long-term energy storage systems. In many typical and modern electrochemical cells, a high specific surface area is desirable to facilitate high-rate capacity (i.e., high power) by introducing a large number of surface sites for reaction to occur. In long-term systems, the need for rate capacity is significantly reduced, so low specific surface area electrodes can meet the target rate capacity requirement while minimizing the rate of self-discharge.

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

[0203] In various embodiments, resistive elements are intentionally introduced into the battery 100 to enable slow charging. A greater overall cell polarization can be achieved by increasing the effective resistance of other cell components (i.e., those other than the negative electrode 102 or negative current collector 106). Doing so can cause a greater polarization of the negative electrode 102. If the additional polarization of the negative electrode 102 is sufficiently large, the absolute potential of electrode 102, when the negative electrode is an Fe electrode, will be sufficiently low, allowing the Fe(OH)2->Fe reaction to be activated at a lower cell-level current. This effect can be achieved by increasing the effective resistance of the electrolyte 104, the cathode (e.g., electrolyte 103), or the cathode current collector.

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

[0205] 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 arranged. The liquid electrolyte 104 may separate the air electrode 103 from the negative electrode 102. The liquid electrolyte 104 may also impregnate the negative electrode 102.

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

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

[0208] The current collector 106 may be formed of a conductive material that is electrically connected to the negative electrode 102. The current collector 106 may be in direct contact with the lower surface and sides of the negative electrode 102. In some embodiments, the current collector 106 may optionally include projections 109 that extend across the negative electrode 102 to make direct contact with its internal region. The projections 109 can also reduce the effective transport length within the electrode 102 from the total thickness of the pellet bed to the spacing of the projections 109. In addition, such projections 109 can be used to attach a mechanical clamping mechanism to the pellet bed, thereby incorporating a downward force into the pellet bed while also serving as a current collector. For example, Figure 2B shows an exemplary plate 250 that compresses the electrode 102 and covers the bed of pellets 115. The plate 250 can be attached to the projection 109 by a clamp 252 that causes the plate 250 to adhere to the projection 109, thereby causing the plate 250 to exert a compressive force on the base of the pellets 115, which are the negative electrode 102. Thus, the plate 250 and the clamp 252 may be a mechanical clamping mechanism. Similarly, the current collector may use a magnet to compress the material forming the negative electrode 102. For example, the plate 250 may be a magnet attracted to the housing 101, the projection 109, and / or the bottom of the current collector 106, which can pull the plate 250 towards the pellets 115, compressing the base of the pellets 115, which are the negative electrode 102. In some embodiments, the current collector 106, the projection 109, and / or another element of the battery 200 may be magnetic, which can pull the pellets 115 downward and / or towards each other, compressing the base of the pellets 115. In some embodiments, the current collector 106 may be a two-part current collector, with a first portion attached to the front of the negative electrode 102 and a second portion attached to the rear of the negative electrode 102. The front of the electrode may be a surface generally positioned toward the electrolyte, and the rear of the electrode may be a surface generally positioned away from the electrolyte. In some embodiments, the first portion may be attached to the front and may be a porous structure (e.g., a mesh), while the second portion attached to the rear may be solid.Providing current collectors on the front and rear surfaces of the electrodes can assist in applying clamping force and enable a more uniform reaction rate across the entire electrode. The front and rear sections of the current collector can be short-circuited together to influence the reaction rate distribution. In some embodiments, the current collector 106 can be clamped to the negative electrode 102.

[0209] In metal-air batteries, pelletized and briquetteed electrode materials offer various advantages, including high surface area, large internal porosity, and high electronic conductivity. Further advantages include significantly simpler and more efficient transportation and handling compared to powdered materials. Another advantage is the simpler manufacturing of the negative electrode. In some embodiments, electrodes can be formed by dispersing or pouring pellets into a container or vessel. The combination of the material's high electronic conductivity and the pellet's weight may result in high density in iron-rich materials, providing low contact resistance between pellets.

[0210] The electrical conductivity of materials that can make up pellets is generally ranked from highest to lowest as follows: Fe metal > FeO > Fe3O4 > Fe2O3. However, more reduced materials with higher conductivity also require greater input energy during processing, and are therefore more expensive and difficult to prepare. Therefore, materials such as mixed phases containing wustite and a certain amount of iron metal, for example, Fe / FeO, or Fe / Fe3O4, or Fe / Fe2O3, are generally preferred. For example, wustite (FeO) can provide the desired balance between input energy and processing cost and electrical conductivity. As a specific but non-limiting example, pellets can be produced as reduced taconite pellets having a composition close to FeO.

[0211] As one specific example, the pellets may be nearly spherical pellets of metallic iron with a porosity of 50% (by volume) and a typical diameter of 10 millimeters (mm). The anode may be 2 centimeters (cm) thick and may be formed from a bed of pellets. In the case of hard-packed spheres, the packing density of random close-packed spheres may be approximately 64%, and it is known that close-packed spheres can reach a packing density of 74%. Therefore, the overall solid phase density of the anode may be approximately 32% (50% × 64%) to 39% (50% × 74%). The anode is impregnated with a liquid electrolyte consisting of 6 M (mol / L) potassium hydroxide (KOH).

[0212] A further advantage of the proposed negative electrode structure is the presence of a low-flexibility electrolyte pathway in the gap space between pellets, which enables rapid liquid-phase ion transport and a thick, high-area capacity (>0.1 Ah / cm²). 2 This enables the use of a metal anode. Furthermore, the concept of this disclosure allows for independent adjustment of the electrode surface area (i.e., solid-liquid interface area) and electrode porosity, as the pellet porosity and packing density can be changed independently.

[0213] A further advantage of the present invention is that the pellets can be assembled by diffusion and filling in a dry state. In other embodiments, the pellets can first be dispersed in a liquid electrolyte, then poured into a battery container and diffused. In various embodiments, the container supporting the pellets can take various forms. Although illustrated as a pellet bed in Figures 1 and 2, the negative electrode 102 may have various different shapes such as a cone or a tube.

[0214] Figures 12A to 12F are cross-sectional views of exemplary batteries 1200A to 1200F having alternative electrode configurations including a regular array of pellets 105. Since batteries 1200A to 1200F may be similar to battery 100, only the differences between them will be considered in detail.

[0215] Referring to Figure 12A, the battery 1200A may include one or more conical containers 1202 that support the pellets 105. The conical containers 1202 can enable the pellets 105 to self-align. The conical containers 1202 can enable a modular design of the negative electrode 102 by having a large “swimming pool” type reactor in which multiple conical containers 1202 are arranged at the bottom of the swimming pool of electrolyte 104. The conical containers 1202 can be a cost-effective design for floor current collection.

[0216] Referring to Figure 12B, the battery 1200B may include a container 101 supporting an array of negative electrode pellets 105 that form the negative electrode 102. One or more positive electrodes 103 may be inserted into the negative electrode 102. The pellets 105 may be electrically connected to each other and / or to the current collector 106. A separator 107 can surround the positive electrode 103 and electrically insulate it from the negative electrode 102.

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

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

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

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

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

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

[0223] Figure 3B shows one embodiment of method 350 for fabricating a sintered porous metal electrode. Method 350 may include mixing a metal and one or more additives in block 351 to form a generated pellet, and sintering the generated pellet in block 352 to form a porous metal electrode.

[0224] In block 351, the mixing of metal and one or more additives for forming "raw" molded pellets may include hot-pressing a mixture of metal and one or more additives for forming generated pellets. In various embodiments, the metal may include iron. In various embodiments, the additives may include a combination of porosity-forming and binder additives. As a specific example, a mixture of iron, polyethylene, and bismuth sulfide powder may be hot-pressed to form generated pellets. In various embodiments, polyethylene can act as both a generated binder and a porosity-forming agent that evaporates during the sintering step. Polyethylene can sublimate at a temperature lower than the sintering temperature. In various embodiments, other porosity-forming additives that do not necessarily act as binders may be used, such as any inorganic or organic material that is solid at room temperature and liquid or gaseous between room temperature and the sintering temperature in a nitrogen (e.g., N2) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H2(5%) or other relative argon and hydrogen concentrations) atmosphere. In various embodiments, multiple types of binders may be mixed together as additives to the metal. By using a mixture of multiple types of binders, a specific microstructural morphology can be targeted, and the powder bed can be stabilized during binder incineration.

[0225] The sintering of the generated pellet for forming the porous metal electrode in block 352 may include sintering the generated pellet in a gas atmosphere with a certain time-temperature profile. The gas atmosphere may be a nitrogen (e.g., N2) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H2(5%) or other relative argon and hydrogen concentration) atmosphere. In various embodiments, the time-temperature profile may be a linear or nonlinear time-temperature profile. For example, a linear time-temperature profile may include a linear temperature rise period, followed by a constant soaking temperature period, followed by a linear temperature drop period. As a specific example, the sintering of the generated pellet in a gas atmosphere with a certain time-temperature profile may include sintering the generated pellet in a nitrogen (e.g., N2) atmosphere or an argon / hydrogen (e.g., Ar(95%) / H2(5%) or other relative argon and hydrogen concentration) atmosphere with a linear temperature rise to 850°C, soaking at 850°C for 15 minutes, and a linear temperature drop to room temperature. As another example, a nonlinear time-temperature profile may have multiple gradients and soaking periods to better control the evaporation rate of porosity-forming agents such as polyethylene porosity-forming agents. For example, a nonlinear time-temperature profile may have a nonlinear temperature rise period, two or more soaking periods with a fall and rise period in between, and a nonlinear fall period.

[0226] Figure 3C shows an embodiment system 360 for forming a sintered porous metal electrode 362. The system 360 may include a continuous roller furnace having a series of heating elements 364 and a belt 366, the rollers configured to transport articles on the belt 366 through the furnace from one end to the other while being heated by the heating elements 364. The area below the heating elements 364 may be configured to have controlled atmospheric conditions, such as an atmosphere of pure hydrogen (H2) supplied by a hydrogen tank 369. The system 360 may include a powder feeder 370, such as a hopper, container, or drum, for supporting a metal powder 371, such as iron oxide powder, used to form the sintered porous metal electrode 362. If the metal powder 371 is iron oxide powder, the iron oxide powder may or may not be oxidized in air at high temperatures, which will result in a completely oxidized (Fe2O3) powder feeder. The metal powder 371 may be deposited on the belt 366 from the powder feed and compressed before being fed into the furnace (i.e., below the heating element 364). For example, the metal powder 371 may be compressed by a slot die, compression roller 372, press, or other compression type device located in front of the furnace. The compressed metal powder may be fed by the belt 366 along the length of the furnace to below the heating element 364. As the metal powder 371 moves along the belt 366, it is heated by the heating element 364 in a hydrogen atmosphere, and H2O vapor can be released from the metal powder. Hydrogen reduces iron oxide at high temperatures to form water and metallic iron (i.e., FeO x (H2 -> H2O + Fe). The resulting metal powder (e.g., iron powder) is continuously rotated through the furnace on a belt 366, allowing the particles to be sintered and joined together, forming a sintered porous metal electrode 362 (e.g., a sintered porous Fe electrode) in a continuous manner. In some embodiments, once the sintered porous metal electrode 362 has left the furnace, it may be cut into fragments by a knife 378, a pinch cutter, a cutting jet, or any other type of device configured to cut the sintered porous metal electrode 362 into fragments. In some embodiments, the sintered porous metal electrode 362 may fall apart due to its weight, resulting in fragments.

[0227] Figure 3D shows a system 380 for forming a sintered porous metal electrode 362. System 380 may be similar to system 360 described above, except that a metal sheet 382 may be laid beneath the metal powder 371 before the metal powder 371 is fed into the furnace. In this way, the metal powder 371 can be sintered directly on the metal sheet 382, ​​thereby continuously forming a sintered porous metal electrode 362 having an integrated current collector. The metal sheet 382 may be a metal roll that is fed into the furnace with the metal powder 371 on top and supports the metal powder 371 on a belt 366. For example, the metal sheet 382 may be fed by a reel-to-reel system on the belt 366 before the metal powder 371 is deposited and compressed. In various embodiments, the metal sheet 382 may be a metal foil. In various embodiments, the metal sheet 382 may be formed from any metal selected to act as a current collector, such as nickel, iron, or steel.

[0228] Figure 4 is a schematic diagram of a battery 400 according to various embodiments of the present disclosure. Since the battery 400 is similar to the battery 100, only the differences between the battery 100 and the battery 400 will be described in detail. The battery 400 may include spherical pellets 105 arranged in a smaller particle composition, such as a composition formed from powdered metal feed material, metal fine powder, or metal particles.

[0229] Long-term electrochemical energy storage can benefit from very low-cost material inputs. While spherical pellets 105 of the battery 100 can provide very low-cost materials, the electrical and ionic conductivity through the spherical pellets 105 may not be ideal because the contact points that inevitably occur with contact with the spherical pellets 105 are limited. One solution to provide better electrical and ionic conductivity may be to use powdered metal feedstock as electrodes, such as the negative electrode 102. Powdered metal feedstock used as electrodes can provide tuned electrical and ionic conductivity, but powdered metal feedstock can be more costly to produce, especially compared to spherical pellets 105.

[0230] Various embodiments can provide composite metal electrode architectures that are exclusively lower cost than electrodes made of powdered metal feed and / or provide higher electrical conductivity than electrodes made of spherical pellets. As used herein, the average width or diameter of the pellets is at least 10 times greater than the average width or diameter of the powder particles in the powdered metal feed. In various embodiments, the composite metal electrode architecture may comprise a mixture of spherical pellets and a composition of smaller metal particles, such as the powdered metal feed. For example, as shown in Figure 4, the negative electrode 102 may comprise a spherical pellet 105 arranged in a composition of smaller metal particles 402, such as the powdered metal feed. The spherical pellet 105 as the negative electrode 102 and the powdered metal feed can provide a mixture of larger and smaller particles, similar to marbles in sand or other combinations of relative particle sizes. In some embodiments, macropores between larger pellets contain smaller pellets. The composite metal electrode formed from the spherical pellet 105 and the powdered metal feed can provide an electrode architecture having cost, electrical conductivity, and / or ionic conductivity, which may be highly tunable. In some embodiments, the composite metal electrode may be moistened with the liquid electrolyte 104. Since the powdered metal feed material contained in the composite metal electrode may be moistened, the composite metal electrode formed from the spherical pellets 105 and the powdered metal feed material may have a lower iron-to-electrolyte ratio than the electrode formed exclusively from the spherical pellets 105. The powdered metal feed material 402 improves the electrical conductivity between the pellets 105 of the electrode 102, and further improves the total packing density of the electrode.

[0231] In various embodiments, the composite metal electrode architecture may include a mixture of spherical pellets and a composition of smaller metal particles, such as metal powder or shavings. For example, as shown in Figure 4, the negative electrode 102 may include a spherical pellet 105 composed of taconite and a composition of smaller metal particles 402 consisting of conductive DRI powder. By combining low-cost taconite pellets used as the bulk iron supply material for pellet 105 with waste conductive DRI powder as the composition of smaller metal particles 402, the cost of forming the conductive electrodes during assembly of the battery 400 can be reduced. As another example, the composite metal electrode architecture may include a mixture of iron ore particles of different sizes, such as larger iron ore pellets (e.g., taconite, DRI, sponge iron, atomized iron, etc.) and a composition of smaller metal particles, such as metal powder or shavings (e.g., powder or shavings of DRI, taconite, sponge iron, atomized iron, etc.).

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

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

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

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

[0236] In various embodiments, convective transport can be introduced to facilitate the flow of electrolyte 104 to individual pellets 105 by flowing the electrolyte 104 across the battery electrode 102 (e.g., a battery electrode 102 composed of active material pellets 105) at a slow but constant flow rate. The pellets 105 may be microporous, and the reaction conditions can benefit from reducing the electrolyte 104 concentration boundary layer that may occur across the entire thickness of the pellet bed 105 (e.g., across the electrode 102) and across the macropores of the pellet bed 105 (e.g., of the electrode 102). The flow of electrolyte 104 can generally reduce overpotential loss by homogenizing the electrolyte 104 throughout the macrostructure and microstructure of the electrode 102.

[0237] In various embodiments, the electrolyte 104 composition may differ for each charging, discharging, and idle state of the battery 800. By flowing different electrolyte 104 composition into the battery 800 when switching states, availability, self-discharge, and HER can be improved simultaneously. For example, in the case of an electrolyte management system with continuous flow, there may be any number of separate electrolyte composition reservoirs, each connected to the electrochemical cell with 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 composition can be flowed in based on the optimal concentration of the component species for the operating mode at that moment (charging, discharging, idle). In some embodiments, the electrolyte composition can be adjusted based on the instantaneous charge state of the battery 800. In various embodiments, additional electrolyte 104 can be added to the battery 800 using a combination of reservoirs and flow controllers (e.g., 805, 806, 807), for example, thereby compensating for electrolyte 104 evaporation. In various embodiments, the battery 800 may include an overflow drain 820 or overflow passage that can allow the electrolyte 104 to overflow from the battery 800. For example, the electrolyte 104 can maintain its level by being able to leave the battery 800 to maintain its level at the overflow drain 820 level once its level reaches the overflow drain 820.

[0238] Figure 8B is a block diagram of an embodiment of battery 814 including an additive delivery system 815. Since battery 814 is similar to battery 100, only the differences between them will be described in detail. In one embodiment, the additive delivery system 815 may be a pump that delivers the additive-holding liquid to battery 814. In another embodiment, the additive delivery system 815 may be a dry hopper that delivers additive-containing solids to the battery 814. As one example, the additive delivery system 815 may be a sulfur delivery system. In a specific example, if the additive delivery system 815 is a sulfur delivery system, the sulfur delivery system may be a pump that delivers sulfur-containing liquids to the battery 814. In another specific example, if the additive delivery system 815 is a sulfur delivery system, the sulfur delivery system may be a dry hopper that delivers sulfur-containing solids (e.g., polysulfide salts, iron sulfide (FeS), etc.) to the battery 814. In another example, the additive delivery system 815 may be a salt delivery system. Specifically, the additive delivery system 815 can add certain solid-phase hydrogen generation inhibitors (e.g., Bi, Sb, As) as soluble salts. For example, dissolve and add ions of the desired additive (e.g., Bi 3+ Sb 3+ As 3+ A soluble salt of a desired hydrogen evolution inhibitor can be added to the liquid electrolyte 104 by the additive delivery system 815, providing ) in the solution. The additive provides the plating reaction from the inhibitor ions to the metal (e.g., Bi 3+ ->Bi 0The oxidation-reduction potential of the HER inhibitor can be selected to occur at a half-cell potential (measured relative to RHE (but at a lower cell potential)) that is higher than the potential of the charging reaction of the anode active material. Thus, during charging of the battery 800, the HER inhibitor in ionic form can be electrodeposited onto the surface of the metal electrode, providing an inexpensive and simple strategy for introducing the HER inhibitor into the battery 800 electrolyte 104 chemistry. The electrodeposited inhibitor suppresses the hydrogen evolution reaction on the electrode surface, which may be an electrode having open porosity. During the discharge mode, the deposit can dissolve back into the electrolyte 104. The salt additive is preferably selected so as not to degrade the operation of the cathode during charging or discharging. As another example, the salt added may be a carbonate. In some embodiments, the additive delivery system 815 can deliver multiple additives to the battery 800. For example, a mixed additive composition, such as a corrosion inhibitor that suppresses the HER reaction or suppresses self-discharge, combined with an additive that improves capacity utilization, can be delivered by the additive delivery system 815. As another example, inhibitors that form a passivation layer on a metal surface are paired with additives that depassivate 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. For example, molybdate ions can be added via molybdate compounds such as KMoO4. In one specific example, the electrolyte 104 may contain molybdate anions at an additive concentration of 10 mM. In other embodiments, the electrolyte 104 may contain molybdate anions at additive concentrations ranging from 1 to 100 mM. In some embodiments, surfactant additives may be delivered by the additive delivery system 815. Surfactant additives reduce the surface tension and viscosity of the electrolyte at the oxygen-evolving electrode, allowing for the generation of smaller, more uniform, and controllable bubbles during charging. In one non-limiting example, 1-octanthiol is added to the alkaline electrolyte 104 at a concentration of 10 mM. In some embodiments, corrosion inhibitor additives may be delivered by an additive delivery system 815.In some embodiments, the additive delivery system 815 can deliver liquid and / or interphase interface inhibitors. In some embodiments, the additive delivery system 815 can deliver additives as a mixture of solids. In some embodiments, the additive delivery system 815 can deliver electrolyte additives (e.g., Na2MoO4) that form a thin passivation film. Thus, the self-discharge of the anode is limited to only a small layer on the surface of the anode. However, to restore the reactivity of the metal anode, the surface film can be reduced using short, strong charging pulses. Once the surface film is reduced, the discharge reaction can proceed.

[0239] Figure 8C is a block diagram of a battery system 850 comprising a series of fluid-connected (or otherwise liquid-communicated) embodiment batteries 800 according to various embodiments. The batteries 800 may be arranged in a cascade such that overflow electrolyte 104 from one battery 800 flows into the next battery 800 through its overflow drain 820, establishing a “liquid communication” between the batteries 800. By connecting these batteries 800 in series, it becomes possible to supply liquid electrolyte 104 to several batteries 800 simultaneously from a single source. For example, a single electrolyte supply pipe 851 connected to a pump 802 can supply electrolyte 104 to a first battery 800. The overflow of electrolyte from the first battery 800 can flow to a second battery 800 and then to a third battery 800. The electrolyte overflows from the third battery 800 into a return pipe 852, which can be circulated by the pump 802 and returned to the supply pipe 851. In this way, the overflow from the last battery 800 can be recirculated to the first battery 800. In a system 850 using a shared electrolyte 104 that flows in a cascade manner between batteries 800, the properties of the electrolyte can be monitored and processed at a central location among the multiple batteries, such as a monitoring station 853. Adjustments to the electrolyte 104, such as performing compositional adjustments or adding components to mitigate problems related to electrolyte carbonation and electrolyte dehydration, may be beneficial to be carried out at the monitoring station 853. The monitoring station 853 may be located in conjunction with a collection structure for the circulating electrolyte 104, such as a return pipe 852. As an example, the monitoring station 853 can control the supply of electrolyte 104 from different reservoir and flow controller combinations (e.g., 805, 806, 807), a filtration device 860, and / or a reserve electrolyte supply tank 855. In various embodiments, the monitoring station 853 may be configured to monitor electrolyte health. The electrolyte health may be monitored during battery operation to determine the appropriate time for replenishing, replacing, or processing the electrolyte 104.The feedback mechanism used by monitoring station 853 may be manual or automatic. If monitoring station 853 is an automated system, electrolyte quality measurement may be a single input to a control loop, such as a proportional-integral-derivative (PID) loop that continuously adjusts the electrolyte component concentrations. Electrolyte quality measurement may be performed ex-situ on a small aliquot of electrolyte 104, or operandly on the active electrolyte 104 while battery 800 is operating. One non-limiting method for assessing electrolyte integrity is to measure the electrical conductivity of the electrolyte. One mechanism of degradation is the carbonation of the electrolyte over time as CO2 from the air dissolves into the electrolyte. For example, a conductivity probe may be used to assess the concentration of carbonates in the electrolyte. A conductivity probe may be used to monitor the integrity status of the electrolyte. Although monitoring station 853 is shown as part of cascade system 850, it may also be part of an electrolyte delivery system for a single battery, such as the electrolyte system in Figure 8A. The monitoring station 853 can increase and / or decrease the volume of electrolyte 104 in the system 850 by controlling the release of electrolyte 104 from and / or to the reserve electrolyte supply tank 852. The monitoring station 853 can control the flow of liquid through the filtration device 860. The filtration device 860 may be configured to filter liquid flowing through it, such as water, electrolyte 104, and the monitoring station 853 can control the flow of liquid in and out of the filtration device 860. For example, the filtration device 860 may be a water filter, such as the water filter 1400 shown in Figure 14. The water filter 1400 may be a packed bed 1401 of DRI that can operate as a water filtration device. In such embodiments, DRI is placed in a column to create a packed bed 1401 of DRI pellets 197. The particulate matter will be trapped in the pores inside the DRI pellets 197 and in the void spaces between the DRI pellets 197 as the water flows through the floor 1401. By using pelletized iron as the filtration mechanism, it is possible to provide the ability to adjust pressure loss and filtration effectiveness.

[0240] Figure 9 is a schematic diagram of a battery 900 according to various embodiments of the present disclosure. Since battery 900 is similar to battery 100, only the differences between them will be described in detail. Alkali iron electrode batteries operate best when certain additives are used in the electrolyte / cell. They may have a range of solubility. Some may have the most beneficial effect when closely mixed with the solid electrode. As shown in Figure 9, in various embodiments, a pellet 902 containing additives may be mixed with a pellet 105 mainly containing an active substance, and thus the negative electrode 102 may be a blended electrode. The additive pellet 902 may be partially and / or entirely formed of additives, such as iron-sulfur compounds such as FeS, FeS2, etc. In various embodiments, the liquid electrolyte 104 may contain additives to suppress the hydrogen evolution reaction at the anode or cathode. These may be soluble or insoluble and include metalloid-HER inhibitors such as bismuth, antimony, tin, boron, indium, gallium, and selenium. The additive may be plated from the solution during operation, for example, starting as a dissolved solution and later precipitating as a solid, or it may change phase.

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

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

[0243] Various embodiments may include one or more methods for monitoring the chemical and / or physical attributes of the negative electrode 102, including using a Mössbauer spectrometer, a charge-coupled device (CCD) detector (e.g., a color camera), a strain gauge, a temperature sensor, measuring ion concentration, measuring electrolyte level displacement, measuring pellet bed height, measuring pellet size, measuring battery 1100 cell mass, measuring magnetic susceptibility, and gas detection. In various embodiments, a NiOH / NiOOH electrode containing a carbon conductive additive and / or binder may be used as a quasi-reference electrode for monitoring potential. By placing such NiOH / NiOOH electrodes at various positions throughout the electrolyte container, the potential distribution of the entire system can also be monitored.

[0244] For example, SOC and / or SOH can be monitored in situ by one or more strain gauges 1102 connected to the vessel 101. One or more strain gauges 1102 may also be connected to a controller 1110, which can output measured strain values ​​from the vessel 101 to the controller 1110. The controller 1110 may be configured to convert the strain values ​​into SOC and / or SOH values.

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

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

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

[0248] As a further example, 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 electrodes 1107 can output ion measurements, such as ion concentrations, to the controller 1110. The controller 1110 may be configured to use the ion measurements to determine SOC and / or SOH measurements.

[0249] As a further example, the State of Cold (SOC) can be monitored in situ by one or more thermocouples 1108 connected to the controller 1110. The thermocouples 1108 can output temperature readings to the controller 1110. The controller 1110 may be configured to use the temperature readings to determine the SOC and / or SOH readings.

[0250] As a further example, 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 measurements, such as the detection of specific particles or concentrations, to the detector 1110. The controller 1110 may be configured to use the gas measurements to determine SOC and / or SOH measurements.

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

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

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

[0254] Specifically, DRI can be used as the anode material when battery 1300 is an all-Fe battery where the reactive species at both the anode and cathode is Fe.In such an embodiment, DRI can serve as a solid metallic Fe anode at 100% SOC, and the anode is soluble Fe during discharge 2+This will result in the formation of a species (e.g., FeCl2). The cathode active substance may be a soluble inorganic Fe-based salt, such as the FeCl2 / FeCl3 redox pair. Alternatively, the cathode active substance may be an inorganic or organic coordination compound such as K3Fe(CN)6. In the cathode, the soluble Fe species will form Fe 2+ / Fe 3+ This will result in a redox reaction associated with the redox pair. As a specific example, if battery 1300 is an all-Fe battery using DRI as the active material, DRI can be used as the anode material together with an electrolyte containing HCl (1-5M) at a concentration. At the anode, DRI undergoes the following half-cell reaction during discharge: Fe + 2Cl - ->FeCl2+2e - This will be involved. In the cathode, soluble FeCl3 undergoes the following half-cell reaction during discharge: 2FeCl3 + 2e - -> 2FeCl2 + 2Cl - This will cause the following reaction. The complete cell reaction during discharge will be Fe + 2FeCl3 -> 3FeCl2. DRI is used as a source of soluble FeCl2 needed in the solution, and by reacting DRI with HCl in the solution, the cathode reaction can be enabled, which will be involved in the following spontaneous chemical reaction: Fe + 2HCl -> FeCl2 + H2.

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

[0256] Various embodiments provide a method for producing a sintered porous metal electrode, comprising mixing a metal and one or more additives to form a generated pellet, and sintering the generated pellet to form a sintered porous metal electrode. In various embodiments, the method comprises mixing a metal and one or more additives to form a generated pellet by hot-pressing the mixture of the metal and one or more additives to form the generated pellet. In various embodiments, the metal may include iron. In various embodiments, at least one of the one or more additives is both a pore-forming agent and a binder additive. In various embodiments, one or more additives include a polyethylene additive and a bismuth sulfide powder additive. In various embodiments, at least one of the one or more additives is a pore-forming agent additive, and at least one of the one or more additives is a binder additive. In various embodiments, the binder additive is a mixture of two or more different types of binders. In various embodiments, sintering the generated pellet to form a sintered porous metal electrode comprises sintering the generated pellet in a gas atmosphere at a certain time-temperature profile. In various embodiments, the gas atmosphere is an N2 atmosphere or an Ar / H2 atmosphere. In various embodiments, the gas atmosphere is an Ar(95%) / H2(5%) atmosphere. In various embodiments, the time-temperature profile includes a linear temperature rise period, followed by a constant soaking temperature period, followed by a linear temperature fall period. In various embodiments, the linear temperature rise period raises the temperature of the generated pellet to 850°C, the soaking temperature is 850°C, and the linear temperature fall period lowers the temperature of the generated pellet to room temperature. In various embodiments, the constant soaking temperature period is 15 minutes. In various embodiments, the time-temperature profile includes a nonlinear temperature rise period, two or more soaking temperature periods with fall and rise periods in between, and a nonlinear temperature fall period.

[0257] Various embodiments can provide a method for producing a sintered porous metal electrode, comprising feeding compressed metal powder into a continuous roller furnace, and passing the compressed metal powder through the furnace to sinter and combine the metal powders to form a sintered porous metal electrode. In various embodiments, the metal powder includes iron oxide powder. In various embodiments, the method may include compressing the metal powder before feeding it into the furnace. In various embodiments, the compression of the metal powder includes passing the metal powder through a slot die or under a compression roller. In various embodiments, the method may include placing a metal sheet under the metal powder before feeding it into the furnace. In various embodiments, the metal sheet is received from a roll of metal being fed into the furnace, and the metal sheet supports the compressed metal powder in the furnace. In various embodiments, the metal sheet is a metal foil. In various embodiments, the metal sheet includes nickel, iron, or steel. In various embodiments, the method may include cutting the sintered porous metal electrode into sections. In various embodiments, the continuous roller furnace heats the metal powder in a hydrogen atmosphere. In various other embodiments, the continuous roller furnace heats the metal powder in an inert atmosphere of nitrogen or argon. In various other embodiments, the continuous roller furnace heats the metal powder in an atmosphere containing a mixture of hydrogen, nitrogen, and / or argon.

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

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

[0260] Examples

[0261] The following examples are provided to illustrate various embodiments of the systems, methods, compositions, applications, and materials of the present invention. These examples are for illustrative purposes only, may be predictive, and should not be considered limiting, nor do they limit the scope of the invention in any way.

[0262] Figures 15-23 illustrate various exemplary systems that use one or more aspects of the various embodiments as part of a bulk energy storage system such as a LODES system or an SDES system. For example, any of the various embodiment batteries and / or components described herein (e.g., batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.) can be used as batteries and / or components for bulk energy storage systems such as LODES systems or SDES systems. As used herein, the term “LODES system” means, unless expressly used otherwise, a bulk energy storage system configured to have a rated duration (energy / power ratio) of 24 hours (h) or longer, including but not limited to 24 hours, 24-50 hours, longer than 50 hours, 24-150 hours, longer than 150 hours, 24-200 hours, longer than 200 hours, 24-500 hours, longer than 500 hours, etc.

[0263] Example 1

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

[0265] Example 1A

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

[0267] [Table E1A]

[0268] Example 1B

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

[0270] [Table E1B]

[0271] Example 1C

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

[0273] [Table E1C]

[0274] Example 1D

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

[0276] [Table E1D]

[0277] Example 1E

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

[0279] [Table E1E]

[0280] Example 1F

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

[0282] [Table E1F]

[0283] Example 1G

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

[0285] [Table E1G]

[0286] Example 1H

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

[0288] [Table E1H]

[0289] Example 1

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

[0291] [Table E1I]

[0292] Example 1J

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

[0294] [Table E1J]

[0295] Example 1K

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

[0297] [Table E1K]

[0298] Example 1L

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

[0300] [Table E1L]

[0301] Example 1M

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

[0303] [Table E1M]

[0304] Example 1N

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

[0306] [Table E1N]

[0307] Example 10

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

[0309] [Table E1O]

[0310] Example 1P

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

[0312] [Table E1P]

[0313] Example 1Q

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

[0315] [Table E1Q]

[0316] Example 1R

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

[0318] [Table E1R]

[0319] Example 2

[0320] Figure 15 shows an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be the LODES system 1504. For example, the LODES system 1504 may include any of the batteries and / or components of the various 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.) individually or in various combinations. The LODES system 1504 may be electrically connected to a wind power station 1502 and one or more power transmission facilities 1506. The wind power station 1502 may be electrically connected to the power transmission facility 1506. The power transmission facility 1506 may be electrically connected to a power distribution network 1508. The wind power station 1502 can generate electricity, and the wind power station 1502 can output the generated electricity to the LODES system 1504 and / or the transmission equipment 1506. The LODES system 1504 can store the electricity received from the wind power station 1502 and / or the transmission equipment 1506. The LODES system 1504 can output the stored electricity to the transmission equipment 1506. The transmission equipment 1506 can output the electricity received from either or both of the wind power station 1502 and the LODES system 1504 to the distribution network 1508, and / or can receive electricity from the distribution network 1508 and output that electricity to the LODES system 1504. Together, the wind power station 1502, the LODES system 1504, and the transmission equipment 1506 can constitute a power plant 1500, which may be a combined power generation, transmission, and storage system. The electricity generated by the wind power station 1502 may be directly supplied to the distribution network 1508 via the transmission equipment 1506, or it may first be stored in the LODES system 1504.In certain cases, the electricity supplied to the distribution network 1508 may be entirely from the wind turbines 1502, entirely from the LODES system 1504, or from a combination of the wind turbines 1502 and the LODES system 1504. The distribution of electricity from the combined wind turbines 1502 and the LODES system 1504 power plant 1500 may be controlled according to a predetermined long-term (multiple days or even more years) schedule, or according to the day-ahead (24-hour prior notice) market, or according to the hour-ahead market, or according to real-time pricing signals.

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

[0322] Example 2A

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

[0324] Example 3

[0325] Figure 16 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 1504. For example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.) individually or in various combinations. The system in Figure 16 may be similar to the system in Figure 15, except that a photovoltaic (PV) base station 1602 may be used instead of a wind power base station 1502. The LODES system 1504 may be electrically connected to the PV base station 1602 and one or more power transmission facilities 1506. The PV base station 1602 may be electrically connected to the power transmission equipment 1506. The power transmission equipment 1506 may be electrically connected to the power distribution network 1508. The PV base station 1602 can generate electricity, and the PV base station 1602 can output the generated electricity to the LODES system 1504 and / or the power transmission equipment 1506. The LODES system 1504 can store the electricity received from the PV base station 1602 and / or the power transmission equipment 1506. The LODES system 1504 can output the stored electricity to the power transmission equipment 1506. The power transmission equipment 1506 can output the electricity received from either or both of the PV base station 1602 and the LODES system 1504 to the power distribution network 1508, and / or can receive electricity from the power distribution network 1508 and output that electricity to the LODES system 1504. The PV base station 1602, the LODES system 1504, and the transmission equipment 1506 together can constitute a power plant 1600, which may be a combined power generation, transmission, and storage system. The electricity generated by the PV base station 1602 may be directly transmitted to the distribution network 1508 via the transmission equipment 1506, or it may first be stored in the LODES system 1504.In certain cases, the power supplied to the distribution network 1508 may be entirely from the PV base station 1602, entirely from the LODES system 1504, or from a combination of the PV base station 1602 and the LODES system 1504. The distribution of power from the combined PV base station 1602 and the LODES system 1504 power plant 1600 may be controlled according to a predetermined long-term (multiple days or even more years) schedule, or according to the day-ahead (24-hour prior notice) market, or according to the hour-ahead market, or according to real-time pricing signals.

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

[0327] Example 3A

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

[0329] Example 4

[0330] Figure 17 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 1504. For example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.) individually or in various combinations. The system in Figure 17 may be similar to those in Figures 15 and 16, except that both the wind power base 1502 and the photovoltaic (PV) base 1602 may be power generators operating together in the power plant 1700. The PV base station 1602, the wind power station 1502, the LODES system 1504, and the transmission equipment 1506 together can constitute a power plant 1700, which may be a combined power generation, transmission, and storage system. The electricity generated by the PV base station 1602 and / or the wind power station 1502 may be directly supplied to the distribution network 1508 via the transmission equipment 1506, or it may first be stored in the LODES system 1504. In certain cases, the electricity supplied to the distribution network 1508 may be all from the PV base station 1602, all from the wind power station 1502, all from the LODES system 1504, or a combination of the PV base station 1602, the wind power station 1502, and the LODES system 1504. The distribution of electricity from the combined wind power base 1502, the PV base 1602, and the LODES system 1504 power plant 1700 may be controlled according to a predetermined long-term (multiple days or even more years) schedule, or according to the day-ahead (24-hour prior notice) market, or according to the hour-ahead market, or according to real-time pricing signals.

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

[0332] Example 4A

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

[0334] Example 5

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

[0336] The LODES system 1504 and the transmission equipment 1506 together can constitute a power plant 1800. As an example, the power plant 1800 may be located downstream of the transmission constraints, close to power consumption. In such an exemplary downstream power plant 1800, the LODES system 1504 may have a duration of 24 to 500 hours and may undergo one or more full discharges per year to support peak power consumption at times when transmission capacity is insufficient to serve customers. In addition, in such exemplary downstream power plant 1800, the LODES system 1504 may undergo several shallow discharges (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and reduce the overall cost of electricity services to customers. As a further example, the power plant 1800 may be located upstream of the transmission constraints, close to power generation. In such exemplary upstream power plants 1800, the LODES system 1504 may have a duration of 24 to 500 hours and may undergo full charges once or more times a year to absorb excess power generation when transmission capacity is insufficient to distribute electricity to customers. In addition, in such exemplary upstream power plants 1800, the LODES system 1504 may undergo several shallow charge-discharge cycles (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and maximize the value of the power generation equipment's output.

[0337] Example 5A

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

[0339] Example 6

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

[0341] The LODES system 1504 and the transmission equipment 1506 can together constitute a power plant 1900. As an example, the power plant 1900 may be located near electricity consumption, i.e., near C&I customer 1902, such as between the distribution network 1508 and C&I customer 1902. In such an example, the LODES system 1504 may have a duration of 24 to 500 hours and may purchase electricity from the market when electricity is cheaper, thereby charging the LODES system 1504. The LODES system 1504 can then discharge when market prices are high to provide electricity to C&I customer 1902, thus offsetting C&I customer 1902's market purchases. As an alternative configuration, the power plant 1900 may be located not between the distribution network 1508 and C&I customer 1902, but between renewable resources such as PV bases and wind power bases and the transmission equipment 1506 which may be connected to renewable resources. In such alternative examples, the LODES system 1504 may have a duration of 24 to 500 hours, and the LODES system 1504 may be charged at a time when renewable output may be available. The LODES system 1504 can then discharge to cover part or all of the C&I customer 1902's power demand, thereby providing the C&I customer 1902 with renewable generated electricity.

[0342] Example 6A

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

[0344] Example 7

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

[0346] Example 7A

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

[0348] Example 8

[0349] Figure 21 shows an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. As a specific example, a bulk energy storage system incorporating one or more aspects of the various embodiments may be the LODES system 1504. For example, the LODES system 1504 may include any of the various embodiment batteries and / or components described herein (e.g., any of batteries 100, 200, 400, 800, 814, 900, 1000, 1100, 1200, 1300, 1310, pellets 105, 115, 305, 198, 199, system 850, etc.) individually or in various combinations. The LODES system 1504 integrates large amounts of renewable power into a microgrid, for example, harmonizing the output of renewable power from PV base station 1602 and wind power station 1502 with existing thermal power from, for example, thermal power plant 2102 (e.g., a gas plant, coal plant, diesel generator set, etc., or a combination of thermal power generation methods), and where the availability rate is high, renewable and thermal power may be part of power plant 2100 that supplies loads to C&I customer 1902. A microgrid such as a microgrid composed of power plant 2100 and thermal power plant 2102 can provide an availability rate of 90% or higher. The electricity generated by PV base station 1602 and / or wind power station 1502 may be supplied directly to C&I customer 1902, or it may first be stored in the LODES system 1504. In certain cases, the electricity supplied to C&I customer 1902 may be entirely from PV base station 1602, entirely from wind power base station 1502, entirely from LODES system 1504, entirely from thermal power plant 2102, or from any combination of PV base station 1602, wind power base station 1502, LODES system 1504, and / or thermal power plant 2102. As an example, the LODES system 1502 of power plant 2100 may have a duration of 24 to 500 hours.As a specific example, the C&I customer 1902 load may have a peak of 100 MW, the LODES system 1504 may have a power rating of 14 MW and a duration of 150 hours, the natural gas cost may be $6 per million British MBTU, and the renewable occupancy rate may be 58%. As another specific example, the C&I customer 1902 load may have a peak of 100 MW, the LODES system 1504 may have a power rating of 25 MW and a duration of 150 hours, the natural gas cost may be $8 per million British MBTU, and the renewable occupancy rate may be 65%.

[0350] Example 8A

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

[0352] Example 9

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

[0354] Example 9A

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

[0356] Example 10

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

[0358] Example 10A

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

[0360] Example 11

[0361] Non-limiting examples according to embodiments of the present invention were constructed and tested. An electrochemical cell using directly reduced iron (DRI) pellets was assembled and tested. The DRI pellets had the properties outlined in Table 4, characterized according to the method described above. The electrochemical cell was a beaker-type cell having three electrodes (working electrode, counter electrode, and reference electrode) and filled with a liquid electrolyte. The electrolyte composition was 5.5 M KOH + 0.5 M LiOH + 10 mM Na2S. The counter electrode was a NiO / NiOOH electrode recovered from a commercially available Fe / Ni (Edison type) cell. The reference electrode was an 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 shows the discharge specific capacity (mAh / g) during the first electrochemical discharge cycle (oxidation of DRI) when cycled at a specific current of 5 mA / g. DRI The voltage between the DRI electrode and the MMO reference is shown as a function of ).

[0362] [Table 4]

[0363] Example 12

[0364] Another non-limiting example according to embodiments of the present invention was constructed and tested. A family of 10 electrochemical cells using directly reduced iron (DRI) pellets was assembled and tested. The DRI pellets had the properties outlined in Table 4, characterized according to the method described above. The electrochemical cells were beaker-type cells with three electrodes (working electrode, counter electrode, and reference electrode) and filled with a liquid electrolyte. The electrolyte composition was 5.5 M KOH + 0.5 M LiOH + 10 mM Na2S. The counter electrode was a NiO / NiOOH electrode recovered from a commercially available Fe / Ni (Edison type) cell. The reference electrode was an 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 stainless steel hose clamps. The DRI was electrochemically cycled according to the following conditions: 1) Precharge at a specific current of 25 mA / g for 60 minutes; 2) Discharge at a specific current of 25 mA / g to 0 voltage vs. MMO; 3) Charge at a specific current of 25 mA / g, terminate under Coulomb limit, with the total charge equal to the initial discharge capacity in mAh. Figure 24B shows the specific capacity (mAh / g) of the DRI electrode of the cell family. DRI Figure 24C shows the number of cycles versus the capacity of each cell. The average capacity of all cells is plotted with error bars representing the 95% confidence interval.

[0365] Example 13

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

[0367] The descriptions of the methods described above are provided merely as illustrative examples and are not intended to require or suggest that the steps of the various embodiments must be carried out in the order presented. As those skilled in the art will understand, the order of the steps in the embodiments described above can be carried out in any order. Words such as “then,” “next,” and “then” are not necessarily intended to limit the order of the steps and may be used to guide the reader throughout the description of the method. Furthermore, all references to singular claim elements using, for example, the articles “a,” “an,” or “the” should not be construed as limiting the element to the singular form. Moreover, any step of any embodiment described herein can be used in any other embodiment.

[0368] The preceding descriptions of the embodiments of this disclosure are provided to enable those skilled in the art to manufacture or use the invention. Various modifications to these embodiments will be immediately apparent to those skilled in the art, and the basic principles set forth herein can be applied to other embodiments without departing from the scope of the invention. Accordingly, the invention is not intended to be limited to the embodiments shown herein, and the broadest scope should be given that is consistent with the principles and novel features disclosed herein.

Claims

1. First electrode, Electrolytes, and A battery comprising a second electrode that is electrochemically in communication with the first electrode via the electrolyte, The second electrode is a porous iron electrode containing directly reduced iron ("DRI") pellets, The DRI pellet contains, based on its total mass, 1% to 5% by weight of a silica-containing compound by elemental mass. battery.

2. The battery according to claim 1, wherein the DRI pellet comprises at least one of iron ore, directly reduced grade iron ore, reduced taconite, wustite, magnetite, hematite, cementite, and iron oxide, or any combination thereof.

3. The battery according to claim 1, wherein the porous iron electrode has a thickness greater than 0.1 cm.

4. The battery according to claim 1, wherein the DRI pellet of the porous iron electrode is moistened with the electrolyte.

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

6. The battery according to claim 5, wherein the current collector is in contact with the lower surface of the porous iron electrode, in contact with the side surface of the porous iron electrode, extends across the porous iron electrode, or any combination thereof.

7. The battery according to claim 5, wherein the DRI pellet of the porous iron electrode is in contact with the current collector.

8. The battery according to claim 1, wherein the second electrode further comprises a slurry or gel.

9. The battery according to claim 1, wherein the first electrode is a negative electrode and includes the porous iron electrode containing the DRI pellet.

10. The porous iron electrode is under compressive force, as described in claim 1.

11. The battery according to claim 10, wherein the compressive force acting on the porous iron electrode is greater than 7 kPa and less than or equal to 700 kPa.

12. The battery according to claim 1, wherein the porous iron electrode includes particles of the DRI pellet.

13. The battery according to claim 12, wherein the average particle size of the DRI pellet particles is greater than 10 nm and less than or equal to 1 mm.

14. The battery according to claim 12, wherein the particles of the DRI pellet are irregularly shaped.

15. The battery according to claim 12, wherein macropores are defined between the particles of the DRI pellet, and the particles of the DRI pellet have a microporous surface.

16. The battery according to claim 12, wherein the particles of the DRI pellets are aggregated and physically connected.

17. The battery according to claim 1, wherein the porous iron electrode is formed into a single sheet.

18. The battery according to claim 1, wherein the DRI pellet contains metallic iron in an amount of 90% or more and 98% or less by weight, based on the total mass of the DRI pellet.

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