OA20575A - Low cost metal electrodes. - Google Patents

Abstract

Systems and methods of the various embodiments may provide metal electrodes for electrochemical cells. In various embodiments, the electrodes may comprise iron. Various methods may enable achieving high surface area with low cost for production of metal electrodes, such as iron electrodes.

Description

LOW COST METAL ELECTRODES

RELATED APPLICATIONS

[0001] This application claims the benefit of priority to U.S. Provisional Patent Application

No. 62/879,126 entitled “Low Cost Métal Electrodes” filed July 26, 2019 and U.S.

Provisional Patent Application No. 63/021,566 entitled “Low Cost Métal Electrodes” filed May 7, 2020 and the entîre contents of both applications are hereby incorporated by reference for ail purposes.

BACKGROUND

[0002] Energy storage technologies are playing an increasîngly important rôle in electric power grids; at a most basic level, these energy storage assets provide smoothing to better match génération and demand on a grid. The services perfonned by energy storage devices are bénéficiai to electric power grids across multiple time scales, from milliseconds to years.

Today, energy storage technologies exist that can support tîmescales from milliseconds to hours, but there îs a need for long and ultra-long duration (collectiveiy, >8h) energy storage Systems.

[0003] This Background section is intended to introduce varions aspects of the art, which may be associated with embodiments of the présent inventions. Thus, the foregoing discussion in this section provides a framework for better understanding the présent inventions, and is not to be viewed as an admission of prior art.

SUMMARY

[0004] Materials, designs, and methods of fabrication for métal électrodes for electrochemical cells are disclosed. in various embodiments, the electrode comprises iron. Various methods for achieving high surface area with low cost and high simple, highly scalable manufacturing methods are described.

[0005] Various embodiments may include a battery comprising: a first electrode; an electrolyte; and a second electrode, wherein at least one ofthe first electrode and the second 30 electrode comprises atomized métal powder.

[0006] Various embodiments may include a battery comprising: a first electrode; an electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises iron agglomérâtes.

[0007] Various embodiments may include a method of making an electrode, comprising:

electrochemically producing métal powder; and forming the métal powder into an electrode.

BRIEF DESCRIPTION OF THE FIGURES

[0008] The accompanying drawings, which are încorporated herein and constîtute part of this spécification, illustrate example embodiments of the claims, and together with the general

1O description given above and the detailed description given below, serve to explain the features of the claims.

[0009] FIG. 1 illustrâtes an example discharge method.

[0010] FIGS. 2 and 3 illustrate aspects of an electrode divided up into horizontal layers contained in a larger vessel.

[0011] FIG. 4 illustrâtes a métal textile with an electrode composed of direct reduced iron pellets

[0012] FIGS. 5 and 6 illustrate example porous mesh container aspects.

[0013] FIG. 7 illustrâtes an example backing plate.

[0014] FIG. 8 fastening rail may also serve as a bus bar

[0015] FIG. 9 illustrâtes a direct reduced iron (DRI) marble bed assembly.

[0016] FIG. 10 illustrâtes a module consisting of a rigid side walls.

[0017] FIGS. I IA and 1 IB show fastening techniques according to various embodiments.

[0018] FIG. 12 illustrâtes an expanding material contained within a rigid iron electrode containment assembly.

[0019] FIG. 13 illustrâtes thermal bonding.

[0020] FIG. 14 illustrâtes mechanical interactions of pellets.

[0021] FIG. 15 illustrâtes pellet beds.

[0022] FIG, 16 illustrâtes example current collectors.

[0023]

FIG.

illustrâtes a mechanically processed pellet.

[0024] FIG. 18 compares discharge product distributions.

[0025] FIG. 19 is a température plot.

[0026] FIG. 20 illustrâtes one example method of evacuating pores.

[0027] FIG. 21 illustrâtes example additive holder configurations.

[0028] FIG. 22 illustrâtes an example additive incorporation process.

[0029] FIG. 23 illustrâtes an électrode formation process.

[0030] FIGS. 24-32 illustrate various example Systems in which one or more aspects ofthe various embodiments may be used as part ofbulk energy storage Systems.

DETAILED DESCRIPTION

[0031] The various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. References made to particular examples and implémentations are for illustrative purposes and are not intended to limit the scope ofthe claims. The following description ofthe embodiments of the invention is not intended to limit the invention to these embodiments but rather to enable a person skilled in the art to make and use this invention. Unless otherwise noted, the accompanying drawings are not drawn to scale.

[0032] As used herein, unless stated otherwise, room température is 25° C. And, standard température and pressure is 25° C and 1 atmosphère. Unless expressly stated otherwise ail tests, test resuits, physical propertîes, and values that are température dépendent, pressure dépendent, or both, are provided at standard ambient température and pressure.

[0033] Generally, the term “about” and the symbol as used herein unless specified otherwise is meant to encompass a variance or range of ± 10%, the experimental or instrument error associated with obtaining the stated value, and preferably the larger of these.

[0034] As used herein unless specified otherwise, the recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value within a range is incorporated into the spécification as if it were individually recited herein.

[0035] As used herein, unless specified otherwise the terms %, weight % and mass % are used înterchangeably and refer to the weight of a first component as a percentage of the weight of the total, e.g., formulation, mixture, partie le, pellet, agglomerate, material, structure or product. As used herein, unless specified otherwise “volume %” and “% volume” and similar such tenns refer to the volume of a first component as a percentage of the volume of the total, e.g., formulation, mixture, particle, pellet, agglomerate, material, structure or product.

[0036] The following examples are provided to iilustrate various embodiments ofthe présent Systems and methods ofthe présent inventions. These examples are for illustrative purposes, io may be prophétie, and should not be viewed as Iimiting, and do not otherwise limit the scope of the présent inventions.

[0037] It is noted that there is no requirement to provide or address the theory underlying the novel and groundbreaking processes, materials, performance or other bénéficiai features and properties that are the subject of, or associated with, embodiments ofthe présent inventions.

Nevertheless, various théories are provided in this spécification to further advance the art in this area. The théories put forth in this spécification, and unless expressly stated otherwise, in no way limit, restrict or narrow the scope of protection to be afforded the claimed inventions. These théories many not be required or practiced to utilize the présent inventions. It is further understood that the présent inventions may lead to new, and heretofore un known théories to explain the function-features of embodiments of the methods, articles, materials, devices and system of the présent inventions; and such later developed théories shall not limit the scope of protection afforded the présent inventions.

[0038] The various embodiments of Systems, equipment, techniques, methods, activities and operations set forth in this spécification may be used for various other activities and in other fields in addition to those set forth herein. Additionally, these embodiments, for exampie, may be used with: other equipment or activities that may be developed in the future; and, with existing equipment or activities which may be modified, ίη-part, based on the teachings of this spécification. Further, the varions embodiments and examples set forth în this spécification may be used with each other, in whole or in part, and in different and various combinations. Thus, the configurations provided in the various embodiments of this spécification may be used with each other. For example, the components of an embodiment having A, A’ and B and the components of an embodiment having A”, C and D can be used with each other in various combination, e.g., A, C, D, and A. A” C and D, etc., in accordance with the teaching of this Spécification. Thus, the scope of protection afforded the présent inventions should not be limited to a particular embodiment. configuration or arrangement that is set forth in a particular embodiment, example, or în an embodiment in a particular figure.

[0039] As used herein, unless specified otherwise, the terms spécifie gravity, which is also called apparent density, should be given their broadest possible meanings, and generally mean weight per unit until volume of a structure, e.g., volumétrie shape of material. This property would include internai porosîty of a particle as part of its volume. It can be measured with a low viscosity fluid that wets the particle surface, among other techniques.

ίο

[0040] As used herein, unless specified otherwise, the terms actual density, which may also be called true density, should be given their broadest possible meanings, and general mean weight per unit volume of a material, when there are no voids présent in that material. This measurement and property essentîally éliminâtes any internai porosîty from the material, e.g., it does not include any voids in the material.

[0041] Thus, a collection of porous foam balls (e.g.. Nerf® balls) can be used to illustrate the relationship between the three density properties. The weight of the balls fi II ing a container would be the bulk density for the balls:

weight of balls Bulk Density = —;-------------------volume of container fillea

[0042] The weight of a single bail per the ball’s spherical volume would be its apparent density:

weight of one hall Apparent Density = —;-----—;---rvolume of that bail

[0043] The weight of the material makîng up the skeleton of the bail, i.e., the bail with ail void volume removed, per the remaining volume of that material would be the skelétal density:

weight of material

Skeletal Density = —;---------—---------volume of voia free material

[0044] As used herein, unless specified otherwise, the term agglomerate and aggregate should be given their broadest possible meanings, and in general mean assemblages of particles in a powder.

[0045] Embodiments of the présent invention include apparatus, Systems, and methods for long-duration, and ultra-long-duration, low-cost, energy storage. Herein, “long duration” and “ultra-long duration” and similar such ternis, unless expressly stated otherwise, should be given their broadest possible meanîng and include perîods of energy storage of 8 hours or longer, such as periods of energy storage of 8 hours, periods of energy storage ranging from 8 hours to 20 hours, periods of energy storage of 20 hours, periods of energy storage ranging 5 from 20 hours to 24 hours, periods of energy storage of 24 hours, periods of energy storage ranging from 24 hours to a week, periods of energy storage ranging from a week to a year (e.g., such as from several days to several weeks to several months), etc. and would include LODES Systems. Further, the terms “long duration” and “ultra-long duration”, “energy storage cells” including “electrochemical cells”, and similar such ternis, unless expressly 1O stated otherwise, should be given their broadest possible interprétation; and include electrochemical cells that may be configured to store energy over time spans of days, weeks, or seasons.

[0046] In general, in an embodiment, the long duration energy storage cell can be a long duration electrochemical cell. In general, this long duration electrochemical cell can store 15 electricity generated from an electrical génération system, when: (i) the power source or fuel for that génération is available, abundant, inexpensive, and combinations and variations of these; (ii) when the power requirements or electrical needs of the electrical grid, customer or other user, are less than the amount of electricity generated by the electrical génération system, the price paid for providing such power to the grid, customer or other user, is below 20 an economically efficient point for the génération of such power (e.g., cost of génération exceeds market price for the electricity), and combinations and variations of these; and (iii) combinations and variations of (i) and (ii) as well as other reasons. This electricity stored in the long duration electrochemical cell can then be distributed to the grid, customer or other user, at times when it is economical or otherwise needed. For example, the electrochemical 25 cells may be configured to store energy generated by solar cells during the su miner months, when sunshine is plentîful and solar power génération exceeds power grid requirements, and discharge the stored energy during the winter months, when sunshine may be insufficient to satisfy power grid requirements.

[0047] Various embodiments are discussed în relation to the use of direct reduced iron (DRI) 30 as a material a battery (or cell), as a component of a battery (or cell) and combinations and variations of these. In various embodiments, the DRI may be produced from, or may be, material which is obtained from the réduction of natural or processed iron ores, such réduction being conducted without reachingthe melting température of iron. In various embodiments the iron ore may be taconite or magnetite or hématite or goethite, etc. In varions embodiments, the DRI may be in the form of pellets, which may be spherîcal or substantially spherîcal. In varions embodiments the DRI may be porous, containing open and/or closed internai porosity. In varions embodiments the DRI may comprise materials that hâve been further processed by hot or cold briquetting. In varions embodiments, the DRI may be produced by reducing iron ore pellets to form a more metallîc (more reduced, less highly oxidized) material, such as iron métal (Fe°), wustite (FeO), or a composite pellet comprising iron métal and residual oxide phases. In varions non-limitîng embodiments, the DR] may be reduced iron ore taconite, direct reduced (“DR”) taconite, reduced “Blast Furnace (BF)

1O Grade” pellets, reduced “Electric Arc Fnrnace (EAF)-Grade” pellets, “Cold Direct Reduced Iron (CDR1)” pellets, direct reduced iron (“DRI”) pellets, Hot Briquetted Iron (HBI), or any combination thereof. In the iron and steelmaking industry, DRI is sometimes referred to as “sponge iron;” this usage is particularly common în India. Embodiments of iron materials, including for example embodiments of DRI materials, for use in various embodiments described herein, including as electrode materials, may hâve, one, more than one, or ail of the material properties as described in Table 1 below. As used in the Spécification, including Table 1, the following terms, hâve the following meaning, unless expressly stated otherwise: “Spécifie surface area” means, the total surface area of a material per unit of mass, which includes the surface area of the pores in a porous structure; “Carbon content” or “Carbon (wt%)” means the mass of total carbon as percent of total mass of DRI; “Cementite content” or “Cementite (wt%)” means the mass of FejC as percent of total mass of DRI; “Total Fe (wt%)” means the mass of total iron as percent of total mass of DRI; “Metallîc Fe (wt%)” means the mass of iron in the Fe° State as percent of total mass of DRI; and “Metaliization” means the mass of iron in the Fe° State as percent of total iron mass. Weight and volume percentages and apparent densitîes as used herein are understood to exclude any electrolyte that has in fi Itrated porosity or fugitive additives within porosity unless otherwise stated.

Table l

Material Property	Embodiment Range
Spécifie surface area*	0.01 -25 m2/g
Actual density**	4.6 - 7.1 g/cc
Apparent density***	2.3 - 6.5 g/cc
Minimum rfpore, 90% volume****	10 nm - 50 gm

•	8
	Minimum dpore, 50% surface area* * * **	1 nm - 15 pm
Total Fe (wt%)#	65 - 95 %
Metallic Fe (wt%)##	46 - 90 %
Metallization (%)w	59 - 96 %
Carbon	0 - 5 %
Fe2+	1 - 9 %
Fe3+ (wt+o)1	0.9 - 25 %
SiO2 (wt %)$î	1 - 15 %
Ferrite (wt%, XRD)m	22 - 97 %
Wustite (FeO, wt%, XR.D)$$$$	0- 13 %
Goethite (FeOOH, wt%, XRD)$mî	0 - 23 %
Cementite (Fe3C, wt%, XRD)+	« 80 %

[0048] *Specific surface area preferably determined by the Brunauer-Emmett-Teller adsorption method (“BET”), and more preferably as the BET is set forth in ISO 9277 (the 5 entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether(EGME) adsorption, electrokinetic analysis of complex-ion adsoiption· and a Protein Rétention (PR) method may be employed to provide results that can be correlated with BET results.

[0049] **Actual density preferably determined by hélium (He) pycnometry, and more preferably as îs set forth in ISO 12154 (the entire disclosure of which îs incorporated herein by reference); recognizing that other tests may be employed ta provide results that can be correlated with He pycnometry results. Actual density may also be referred to as “true density” or “skeletal density” in the art.

[0050] ***Apparent density preferably determined by immersion in water, and more 15 preferably as is set forth in ISO 15968 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests may be employed to provide results that can be correlated wîth He pycnometry results. Porosity may be defined as the ratio of apparent density to actual density:

apparent density

Porosity = ------—;------actual density

[0051] ****d_?ore,90% volume preferably determined by mercury (Hg) intrusion porosimetry, and more preferably as is set forth in ISO 15901-1 (the entire dîsclosure of which is incorporated herein by reference); recognizing that other tests, such as gas adsorption, may be empioyed to provide results that can be correlated with Hg intrusion resuits. dpore, 90% volume is the pore diameter above which 90% ofthe total pore volume exists.

[0052] *****i7p₀^, 50% surface areapreferably determined by mercury (Hg) intrusion porosimetry, and more preferably as is set forth in ISO 15901-1 (the entire dîsclosure of which is incorporated herein by reference); recognizing that other tests, such as gas adsorption, may be empioyed to provide results that can be correlated with T Ig intrusion results. d_pore, 50% surface area îs the pore diameter above which 50% of free surface area exists.

[0053] #Total Fe (wt%) preferably determined by dichromate titrimetry, and more preferably as is set forth in ASTM E246-10 (the entire dîsclosure of which is incorporated herein by reference); recognizing that other tests, such as titrimetry after tin(II) chloride réduction, titrimetry after titanium(IH) chloride réduction, inductively coupled plasma (ICP) spectrometry, may be empioyed to provide results that can be correlated with dichromate titrimetry.

[0054] ##Metallic Fe (wt%) preferably determined by iron(III) chloride titrimetry, and more preferably as is set forth in ISO 16878 (the entire dîsclosure of which is incorporated herein by reference); recognizing that other tests, such as bromine-methanol titimetry, may be empioyed to provide results that can be correlated with iron(lll) chloride titrimetry.

[0055] ###Metallization (%) preferably determined by the ratio of metallic Fe to total Fe, each as preferably determined by the methods previously described.

[0056] #### Carbon (wt%) preferably determined by infrared absorption after combustion in an induction fumace, and more preferably as is set forth in ISO 9556 (the entire dîsclosure of which is incorporated herein by reference); recognizing that other tests, such as various combustion and inert gas fusion techniques, such as are described în ASTM El019-18 may be empioyed to provide results that can be correlated with infrared absorption after combustion in an induction fumace.

[0057] ##### Fe² (wt%) preferably determined by titrimetry, and more preferably as îs set forth în ASTM D3872-05 (the entire dîsclosure of which is incorporated herein by reference); recognizing that other tests, such as Mossbauer spectroscopy, X-ray absorption spectroscopy, etc., may be empioyed to provide results that can be correlated with titrimetry.

[0058] $ Fe³⁴ (wt%) preferably determined by the mass balance relation between and among Total Fe (wt%), Metallic Fe (wt%), Fe²⁴ (wt%) and Fe³⁺ (wt%). Specifically the equality Total Fe (wt%) = Metallic Fe (wt%) + Fe²⁴ (wt%) + Fe³⁴ (wt%) must be true by conservation of mass, so Fe³⁺ (wt%) may be calculated as Fe³⁺ (wt%) = Total Fe (wt%) - Metallic Fe (wt%) - Fe²⁺ (wt%).

[0059] $$ SiO₂ (wt %) preferably determined by gravimétrie methods, and more preferably as is set forth in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference); recognizîng that other tests, such as reduced molybdosilîcate spectrophotometric methods, x-ray diffraction (XRD), may be employed to provide results that can be correlated with gravimétrie methods. In certain methods, the SiO₂ wt% is not determined directly, but rather the Si concentration (inclusive of neutral and ionic species) is measured, and the SiO₂ wt% is calculated assuming the stoîchîometry of SiO₂; that is, a 1:2 molar ratio of Si:O is assumed.

[0060] $$$ Ferrite (wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0061] $$$$ Wustîte (FeO, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0062] $$$$$ Goethite (FeOOH, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0063] + Cementite (FesC, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0064] Additionally, embodiments of iron materials, including for example embodiments of 20 DRI materials, for use in various embodiments described herein, including as electrode materials, may hâve one or more of the following properties, features or characteristics, (notîng that values from one row or one column may be présent with values in different rows or columns) as set forth in Table IA.

Table JA

Fe total (wt %)!	> 60%	> 70%	> 80%	-83-94%
SÎO2 (wt %)!!	< 12%	< 7.5%	1-10%	] .5-7.5%
A12O3 (wt%)!!!	< 10%	<5%	0.2-5%	0.3-3%
MgO (wt %)	< 10%	<5%	0.1-10%	0.25-2%
CaO (wt%)!1|!!	< 10%	<5%	0.9-10%	0.75-2.5%

TiO2 (wt %)&	< 10%	<2.5%	0.05-5%	0.25-1.5%
Size (largest cross-sectional distance, e.g. for a sphere the diameter)	< 200 mm	-50to~ 150 mm	-2 to -30 mm	-4 to -20 mm
Aetual Density (g/cm3)&&	-5	~5.8 to -6.2	-4.0 to -6.5	<7.8
Apparent Density (g/cm3)^*	<7.8	>5	>4	3.4-3.6
Bulk Density (kg/mJ)&&&&	<7	> 1.5	-2.4 to -3.4	-1.5 to -2.0
Porosity (%)&&&&&	>15%	>50%	~ 20% to -90%	-50% to -70%

[0065] ! Total Fe (wt%) preferably determined by dîchromate titrimetry, and more preferably as îs set forth in ASTM E246-10 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as titrimetry after tin(II) chloride réduction, titrimetry after titanium(III) chloride réduction, inductively coupled plasma (ICP) spectrometry, may be employed to provide results that can be correlated with dîchromate titrimetry.

[0066] !! SiO₂ (wt %) preferably determined by gravimétrie methods, and more preferably as is set forth in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference);

recognizing that other tests, such as reduced molybdosilicate spectrophotometrîc methods, xray diffraction (XRD), may be employed to provide results that can be correlated with gravimétrie methods. In certain methods, the SÎO₂ wt% is not determined directly, but rather the Si concentration (inclusive of neutral and ionic specîes) îs measured, and the SiO₂ wt% is calculated assuming the stoichîometry of SiO₂; that is, a 1:2 molar ratio of Si:O is assumed.

[0067] ü! A1₂O₃ (wt %) preferably determined by flame atomîc absorption spectrométrie method, and more preferably as is set forth in ISO 4688-1 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as x-ray diffraction (XRD), may be employed to provide results that can be correlated with flame atomîc absorption spectrométrie method. In certain methods, the AI2O3 wt% îs not determined directly, but rather the Al concentration (inclusive of neutral and ionic species) is measured, and the AI2O3 wt% is calculated assuming the stoichiometry of AI2O3; that is, a 2:3 molar ratio of A1:O îs assumed.

[0068] !!!! MgO (wt %) preferably determined by flame atomic absorption spectrométrie method, and more preferably as is set forth in ISO 10204 (the entrée disclosure of which is incorporated herein by reference); recognizing that other tests, such as x-ray diffraction (XRD), may be employed to provide resuits that can be correlated with flame atomic absorption spectrométrie method. In certain methods, the MgO wt% is not determined directly, but rather the Mg concentration (inclusive of neutral and ionic species) is measured, and the MgO wt% is calculated assuming the stoichiometry of MgO; that îs, a 1:1 molar ratio of Mg:O is assumed.

[0069] !!!!! CaO (wt %) preferably determined by flame atomic absorption spectrométrie method, and more preferably as is set forth in ISO 10203 (the entire disclosure of which is 15 incorporated herein by reference); recognizing that other tests, such as x-ray diffraction (XRD), may be employed to provide resuits that can be correlated with flame atomic absorption spectrométrie method. In certain methods, the CaO wt% is not determined directly, but rather the Ca concentration (inclusive of neutral and ionic species) is measured, and the CaO wt% is calculated assuming the stoichiometry of CaO; that is, a 1:1 molar ratio 20 of Ca:O is assumed.

[0070] & T1O2 (wt %) preferably determined by a dîantipyrylmethane spectrophotometric method, and more preferably as is set forth în ISO 4691 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as x-ray diffraction (XRD), may be employed to provîde resuits that can be correlated with the dîantipyrylmethane spectrophotometric method method. In certain methods, the T1O2 wt% is not determined directly, but rather the Ti concentration (inclusive of neutral and ionic species) is measured, and the TiO₂ wt% is calculated assuming the stoichiometry of TiO₂; that is, a 1:2 molar ratio ofTi:O is assumed.

[0071] && Actual density preferably determined by hélium (He) pyenometry, and more preferably as is set forth in ISO 12154 (the entire disclosure of which îs incorporated herein by reference); recognizing that other tests may be employed to provide resuits that can be correlated with He pycnometry results. Actual density may also be referred to as “true density” or “skeletal density” in the art.

[0072] &&& Apparent density preferably determined by immersion in water, and more preferably as is set forth in ISO 15968 (the entire disclosure of which is incorporated herein 5 by référencé); recognizing that other tests may be employed to provide results that can be correlated with He pycnometry results.

[0073] &&&& Bulk Density (kg/m³) preferably determined by measuring the mass of a test portion introduced into a container of known volume until its surface is level, and more preferably as is set forth in Method 2 of ISO 3852 (the entire disclosure of which is

1O incorporated herein by reference); recognizing that other tests may be employed to provide results that can be correlated with the massing method.

[0074] &&&&& Porosity determined preferably by the ratio of the apparent density to the actual density:

apparent density

Porosity = -----—-----actual density

[0075] The properties set forth in Table l, may also be présent in embodiments with, in addition to, or instead of the properties in Table IA. Greater and lesser values for these properties may also be présent in various embodiments.

[0076] In embodiments the spécifie surface area for the pellets can be from about 0.05 m²/g to about 35 m²/g, from about 0.1 m²/g to about 5 m²/g, from about 0.5 m²/g to about 10 m²/g, 20 from about 0.2 m²/g to about 5 m²/g, from about 1 m²/g to about 5 m²/g, from about 1 m²/g to about 20 m²/g, greater than about l m²/g, greater than about 2 m²/g, less than about 5 m²/g, less than about 15 m²/g, less than about 20 m²/g, and combinations and variations of these, as well as greater and smaller values.

[0077] In general, iron ore pellets are produced by crushing, grinding or milling of iron ore to 25 a fine powdery form, which is then concentrated by removing impurity phases (so called “gangue”) which are liberated by the grinding operation. In general, as the ore is ground to finer (smaller) particle sizes, the purity ofthe resulting concentrate is increased. The concentrate is then formed into a pellet by a pelletizing or balIing process (using, for example, a drum or disk pelletîzer). In general, greater energy input îs required to produce 30 higher purity ore pellets. Iron ore pellets are commonly marketed or sold under two principal categories: Blast Fumace (BF) grade pellets and Direct Réduction (DR Grade) (also sometimes referred to as Electric Arc Furnace (EAF) Grade) with the principal distinction being the content of S1O2 and other impurity phases being higher in the BF grade pellets relative to DR Grade pellets. Typical key spécifications for a DR Grade pellet or feedstock are a total Fe content by mass percentage in the range of 63-69 wt% such as 67 wt% and a

SiO₂ content by mass percentage of less than 3 wt% such as 1 wt%. Typical key spécifications for a BF grade pellet or feedstock are a total Fe content by mass percentage in the range of 60-67 wt% such as 63 wt% and a S1O2 content by mass percentage in the range of 2-8 wt% such as 4 wt%.

[0078] In certain embodiments the DRI may be produced by the réduction of a “Blast

Furnace” pellet, in which case the resultîng DRI may hâve material properties as described în Table 2 below. The use of reduced BF grade DRI may be advantageous due to the lesser input energy required to produce the pellet, which translates to a lower cost of the finîshed material.

Table 2

Material Property	Embodiment Range
Spécifie surface area*	0.21 -25 m2/g
Actual density**	5.5 - 6.7 g/cc
Apparent density***	3.1 - 4.8 g/cc
Minimum Jpore, 90% volume****	50 nm - 50 gm
Minimum dpOre, 50% surface area*****	1 nm - 10 gm
Total Fe (wt%)#	81.8-89.2%
Metallic Fe (wt%)ÿ#	68.7 - 83.2 %
Metallization (%)m	84 - 95 %
Carbon (wt%)##il#	0.03 - 0.35%
Fe2+	2 - 8.7 %
Fe3+ (wt%)$	0.9 - 5.2 %
S1O2 (wt %)**	3 - 7 %
Ferrite (wt%, XRD)ÏÎ3;	80 - 96 %
Wustite (FeO, wt%, XRD)ÎÎ$Î	2- 13 %
Goethite (FeOOH, wt%, xrd)ïm,îî	0 - 11 %
Cementite (FejC, wt%, XRD)+	0 - 80 %

[0079] *SpecifÎc surface area preferably determined by the Brunauer-Emmett-Teller adsorption method (“B ET”), and more preferably as the B ET is set forth în ISO 9277 (the entire disclosure of which is incorporated herein by reference); recognîzing that other tests, such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, 5 electrokinetic analysis of complex-îon adsorption' and a Protein Rétention (PR) method may be employed to provide results that can be correlated with BET results.

[0080] **Actual density preferably determined by hélium (He) pycnometry, and more preferably as is set forth in ISO 12154 (the entire disclosure of which is incorporated herein by reference); recognîzing that other tests may be employed to provide resu Its that can be 10 correlated with He pycnometry results. Actual density may also be referred to as “true densîty” or “skeletal density” in the art.

[0081] ***Apparent density preferably determined by immersion in water, and more preferably as is set forth in ISO 15968 (the entire disclosure of which is incorporated herein by reference); recognîzing that other tests may be employed to provide results that can be 15 correlated with He pycnometry results. Porosity may be defined as the ratio of apparent density to actual density:

apparent density

Porosity = ------—---_:--actual density

[0082] ****i/_Pore,90% volume preferably determined by mercury (Hg) intrusion porosimetry, and 20 more preferably as is set forth in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); recognîzing that other tests, such as gas adsorption, may be employed to provide results that can be correlated wîth Hg intrusion results. <7_ρΰΓε, 90% volume is the pore diameter above which 90% ofthe total pore volume exists.

[0083] *****d_pore, 50% surface area preferably determined by mercury (Hg) intrusion porosimetry, 25 and more preferably as is set forth in ISO 15901-1 (the entire disclosure of which is incorporated herein by reference); recognîzing that other tests, such as gas adsorption, may be employed to provide results rhat can be correlated with Hg intrusion results. d_pore, 50% surface area is the pore diameter above which 50% of free surface area exists.

[0084] #Total Fe (wt%) preferably determined by dichromate titrimetry, and more preferably 30 as is set forth in ASTM E246-I0 (the entire disclosure of which is incorporated herein by reference); recognîzing that other tests, such as titrimetry after tîn(II) chloride réduction, titrimetry after titanium(lll) chlorîde réduction, înductively coupled plasma (ICP) spectrometry, may be employed to provide results that can be correlated with dichromate titrimetry.

[0085] ##Metallic Fe (wt%) preferably determined by iron(III) chlorîde titrimetry, and more preferably as is set forth in ISO 16878 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as bromîne-methanol tîtimetry, may be employed to provide results that can be correlated with iron(III) chlorîde titrimetry.

[0086] ###Metallization (%) preferably determined by the ratio of metallic Fe to total Fe, each as preferably determined by the methods previously described.

1O [0087] #### Carbon (wt%) preferably determined by infrared absorption after combustion in an induction fumace, and more preferably as is set forth in ISO 9556 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as various combustion and inert gas fusion techniques, such as are described in ASTM E1019-18 may be employed to provide results that can be correlated with infrared absorption after combustion in an induction fumace.

[0088] ##### Fe²⁺ (wt%) preferably determined by titrimetry, and more preferably as is set forth in ASTM D3872-05 (the entire disclosure of which îs incorporated herein by reference); recognizing that other tests, such as Mossbauer spectroscopy, X-ray absorption spectroscopy, etc., may be employed to provide results that can be correlated with titrimetry.

[0089] Fe³⁺ (wt%) preferably determined by the mass balance relation between and among

Total Fe (wt%), Metallic Fe (wt%), Fe²⁺ (wt%) and Fe³⁺ (wt%). Specifically the equalîty Total Fe (wt%) = Metallic Fe (wt%) + Fe²⁺ (wt%) + Fe³⁺ (wt%) must be true by conservation of mass, so Fe³⁺ (wt%) may be calculated as Fe³⁺ (wt%) = Total Fe (wt%) - Metallic Fe (wt%) - Fe²⁺ (wt%).

[0090] $$ S1O2 (wt %) preferably determined by gravimétrie methods, and more preferably as is set forth in ISO 2598-1 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as reduced molybdosilicate spectrophotometric methods, x-ray diffraction (XRD), may be employed to provide results that can be correlated with gravimétrie methods. In certain methods, the SiOz wt% is not determined directly, but rather the Si concentration (inclusive of neutral and ionîc species) is measured, and the S1O2 wt% is calculated assuming the stoichiometry of SiO₂; that is, a 1:2 molar ratio of Si:O îs assumed.

[0091] $$$ Ferrite (wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0092] $$$$ Wustite (FeO, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0093] $$$$$ Goethite (FeOOH, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0094] + Cementite (FeaC, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[0095] The properties set forth in Table 2, may also be présent in embodiments with, in addition to, or înstead ofthe properties in Tables 1 and/or IA. Greater and lesser values for these properties may also be présent in various embodiments.

[0096] In certain embodiments the DRI may be produced by the réduction of a DR Grade pellet, in which case the resulting DRI may hâve material properties as described in Table 3 below. The use of reduced DR grade DRI may be advantageous due to the higher Fe content in the pellet which increases the energy density ofthe battery.

Table 3

Material Property	Embodiment Range
Spécifie surface area*	0.1 - 0.7 m2/g as received or 0.19 - 25 m2/g after performing a pre-charge formation step
Actual density**	4.6 - 7.1 g/cc
Apparent density***	2.3 - 5.7 g/cc
Minimum 90% volume****	50 nm - 50 pm
Minimum dpore, 50% surface area*****	1 nm - 10 pm
Total Fe (wt%)#	80 - 94 %
Metallic Fe (wt%)##	64 - 94 %
Metallization	80- 100%
Carbon (^1%)^^^	0 - 5 %
Fe2+	0 - 8 %
Fe3+ (wt%)$	0- 10%
SÎCh (wt %)ÎS	1 - 4 %
Ferrite (wt%, XRD)ÎK	22 - 80 %
Wustite (FeO, wt%, XRD)Îm	0- 13%
Goethite (FeOOH, wt%, XRD)ÏSÎÎÎ	0 - 23 %

Cementite (Fe3C, wt%, XRD)+

« 80 %

[0097] ^Spécifie surface area preferably determîned by the Brunauer-Emmett-Teller adsorption method (“BET”), and more preferably as the BET is set forth in ISO 9277 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, 5 such as methylene blue (MB) staining. ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of compiex-ion absorption and a Protein Rétention (PR) method may be employed to provide results that can be correlated with BET results.

[0098] **Actual density preferably determîned by hélium (He) pyenometry, and more preferably as is set forth in ISO 12154 (the entire disclosure of which is încorporated herein 10 by reference); recognîzing that other tests may be employed to provide results that can be correlated with He pyenometry' results. Actual density may also be referred to as “true density” or “skeletal density” in the art.

[0099] ***Apparent density preferably determîned by immersion in water, and more preferably as is set forth in ISO 15968 (the entire disclosure of which is încorporated herein 15 by reference); recognîzing that other tests may be employed to provide results that can be corrchHcd with He pyenometry results. Porosity may be defined as the ratio of apparent density to actual density:

apparent density Porosity = -------—;---_:--actual density

[00100] ****rf_Pore, 90% volume preferably determîned by mercury (Hg) intrusion porosimetry, and more preferably as is set forth in ISO 15901-1 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as gas adsorption, may be employed to provide results that can be correlated with Hg intrusion results. t/pore, 90% volume is the pore diameter above which 90% of the total pore volume exists.

[00101 ] *****^«,50% surface areapreferably detemiined by mercury (Hg) intrusion porosimetry, and more preferably as is set forth in ISO 15901-1 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as gas adsorption, may be employed to provide results that can be correlated with Hg intrusion results. 50% surface area is the pore diameter above which 50% of free surface area exists.

[00102] #Total Fe (wt%) preferably determined by dichromate titrimetry, and more preferably as is set forth in ASTM E246-10 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as titrimetry after tin(II) chloride réduction, titrimetry after titanium(IIÏ) chloride réduction, inductiveiy coupled plasma (ICP) 5 spectrometry, may be employed to provide results that can be correlated with dichromate titrimetry.

[00103] ##Metallic Fe (wt%) preferably determined by iron(III) chloride titrimetry, and more preferably as is set forth in ISO 16878 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as bromine-methanol 10 titimetry, may be employed to provide results that can be correlated with iron(III) chloride titrimetry.

[00104] ###Metaîlization (%) preferably determined by the ratio of métal lie Fe to total Fe, each as preferably determined by the methods previously described.

[00105] #### Carbon (wt%) preferably determined by infrared absorption after combustion in an induction furnace, and more preferably as is set forth in ISO 9556 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as various combustion and inert gas fusion techniques, such as are described in ASTM El019-18 may be employed to provide results that can be correlated with infrared absorption after combustion in an induction furnace.

[00106] ##### Fe²⁺ (wt%) preferably determined by titrimetry, and more preferably as îs set forth in ASTM D3872-05 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as Mossbauer spectroscopy, X-ray absorption spectroscopy, etc., may be employed to provide results that can be correlated with titrimetry.

[00107] $ Fe³⁺ (wt%) preferably determined by the mass balance relation between and among Total Fe (wt%), Metallic Fe (wt%), Fe²⁺ (wt%) and Fe³⁺ (wt%). Specîfically the equalîty Total Fe (wt%) = Metallic Fe (wt%) + Fe²⁺ (wt%) + Fe³⁺ (wt%) must be true by conservation of mass, so Fe³⁺ (wt%) may be calculated as Fe³⁺ (wt%) = Total Fe (wt%) Metallic Fe (wt%) - Fe²⁺ (wt%).

[00108] $$ S1O2 (wt %) preferably determined by gravimétrie methods, and more preferably as is set forth in ISO 2598-1 (the entire disclosure of which is încorporated herein by reference); recognîzing that other tests, such as reduced molybdosilicate spectrophotometric methods, x-ray diffraction (XRD), may be employed to provide results that can be correlated with gravimétrie methods. In certain methods, the SÎO₂ wt% is not determined directly, but rather the Si concentration (inclusive of neutral and ionic species) is measured, and the SiO₂ wt% is calculated assuming the stoichiometry of S1O2; that is, a 1:2 molar ratio of Si:O is assumed.

[00109] $$$ Ferrite (wt%, XRD) preferably determined by x-ray diffraction (XRD).

[00110] $$$$ Wustite (FeO, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[00111] $$$$$ Goethite (FeOOH, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[00112] + Cementite (Fe₂C, wt%, XRD) preferably determined by x-ray diffraction (XRD).

[00113] The properties set forth in Table 3, may also be present in embodiments with, in addition to, or instead ofthe properties in Tables 1, IA, and/or 2. Greater and lesser values for these properties may also be present in various embodiments.

[00114] An electrochemical cell, such as a battery, stores electrochemical energy by using a différence in electrochemical potentîal generating a voltage différence between the positive and négative électrodes. This voltage différence produces an eîectric current if the électrodes are connected by a conductive element. In a battery, the négative electrode and positive electrode are connected by external and internai conductive éléments in parallel.

Generally, the extemal element conducts électrons, and the internai element (electrolyte) conducts ions. Because a charge imbalance cannot be sustained between the négative electrode and positive electrode, these two flow streams must supply ions and électrons at the same rate. In operation, the electronîc current can be used to drive an external device. A rechargeable battery can be recharged by applying an opposing voltage différence that drives an electronic current and ionic current flowing in an opposite direction as that of a discharging battery in service.

[00115] In general, but particularly for long-duration storage applications, électrodes and electrode materials that are low-cost and simple to manufacture are desired.

Manufacturing and/or fabrication processes may be evaîuated and selected based on multiple 30 criteria including capital cost, material throughput, operating costs, number of unit operations, number of material transfers, number of material handling steps, required energy input, amounts of generated waste products and/or by-products, etc.

[00116] The présent invention relates to materials, électrodes and methods for electrochemical cells, including long-duration electrochemical cells for long-duration energy storage applications.

[00117] Various embodiments are discussed in relation to the use of métal agglomérâtes as a material in a battery (or cell), as a component of a battery (or cell), such as an electrode, and combinations and variations of these. In various embodiments, the iron material may be an iron powder such as a gas-atomîzed or water-atomîzed powder, or a sponge iron powder. In various embodiments, the iron agglomérâtes may be în the form of pellets, which may be spherical or substantially spherical· In various embodiments the agglomérâtes may be porous, containing open and/or closed internai porosîty. In various embodiments the agglomérâtes may comprise materials that hâve been further processed by hot or cold briquetting. Embodiments of agglomérâtes materials for use in various embodiments described herein, including as electrode materials, may hâve, one, more than one, or ail of the material properties as described in Table 4 below. As used in the

Spécification, including Table 4, the following terms, hâve the following meaning, unless expressly stated otherwîse: “Spécifie surface area” means, the total surface area of a material per unit of mass, which includes the surface area of the pores in a porous structure; “Total Fe (wt%)” means the mass of total iron as percent of total mass of agglomérâtes; “Métallie Fe (wt%)” means the mass of iron in the Fe° state as percent of total mass of agglomérâtes.

20	Table 4
	Material Property	Embodiment Range
Spécifie surface area*	0.01-25 m2/g
Skeletal density**	4.6 - 7.8 g/cc
Apparent density***	1.5 - 6.5 g/cc
Total Fe (wt%)#	65 - 100%
Metallic Fe (wt%)s#	46- 100%

[00118] *Specific surface area preferably determined by the Brunauer-Emmett-Teiler adsorption method (“BET”), and more preferably as the B ET is set forth in ISO 9277 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, 25 such as methylene blue (MB) staining, ethylene glycol monoethyl ether (EGME) adsorption, electrokinetic analysis of complex-ion adsorption- and a Protein Rétention (PR) method may be employed to provide results that can be correlated with BET results.

[00119] **Skelétal density preferably determined by hélium (He) pycnometry, and more preferably as îs set forth in ISO 12154 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests may be employed to provide resuits that can be correlated with He pycnometry resuits. Skelétal density may also be referred to as “true 5 density” or “actual density” in the art.

[00120] ***Apparent density preferably determined by immersion in water, and more preferably as is set forth in ISO 15968 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests may be employed to provide resuits that can be correlated with He pycnometry resuits. Porosity may be defined as the ratio of apparent 1O density to actual density:

apparent density

Porosity = 1--—---:--actual density

[00121] (/Total Fe (wt%) preferably determined by dichromate titrimetry, and more preferably as is set forth in ASTM E246-10 (the entire disclosure of which is incorporated herein by reference); recognizing that other tests, such as titrimetry after tîn(II) chioride 15 réduction, titrimetry after titanium(III) chioride réduction, inductively coupled plasma (ICP) spectrometry, may be employed to provide resuits that can be correlated with dichromate titrimetry.

[00122] ##Metallic Fe (wt%) preferably determined by iron(III) chioride titrimetry, and more preferably as is set forth in ISO 16878 (the entire disclosure of which is 20 incorporated herein by reference); recognizing that other tests, such as bromine-methanol titimetry, may be employed to provide resuits that can be correlated with iron(III) chioride titrimetry.

[00123] In embodiments the spécifie surface area for the agglomérâtes can be from about 0.05 m²/g to about 35 m²/g, from about 0.1 m³/g to about 5 m²/g, from about 0.5 m²/g 25 to about 10 m²/g, from about 0.2 m²/g to about 5 m²/g, from about 1 m²/g to about 5 m²/g, from about I m²/g to about 20 m²/g, greater than about l m²/g, greater than about 2 m²/g, less than about 5 m²/g, less than about 15 m²/g, less than about 20 m²/g, and combinations and variations of these, as well as greater and smaller values.

[00124] The packing of agglomérâtes créâtes macro-pores, e.g., openings, spaces, 30 channels, or voids, în between individual agglomérâtes. The macro-pores facilitate ion transport through électrodes that in some embodiments hâve a smalîest dimension that ts still very thick compared to some other types of battery électrodes, being multi-centimeter in dimension. The micro-pores within the agglomérâtes allow the high surface area active material of the agglomérâtes to be in contact with electrolyte to enabie high utilîzation of the active material. This electrode structure lends itself specifically to improving the rate capability of extremely thick électrodes for stationary long duration energy storage, where 5 thick électrodes may be required to achieve extremely high areal capacities.

[00125] In varions embodiments, a bed of conductive micro-porous agglomérâtes comprise an electrode in an energy storage System. In some embodiments, said agglomérâtes comprise agglomérâtes of direct reduced iron (DR1). The packing of agglomérâtes créâtes macro-pores in between individual agglomérâtes. The macro-pores facilitate ion transport 1O through électrodes that în some embodiments hâve a smallest dimension that is still very thick as compared to some other types of battery électrodes, being of multiple centimeters in dimension. The macropores may form a pore space of low tortuosity compared to the micropores within the agglomérâtes. The micro-pores within the agglomérâtes allow the high surface area active material of the agglomerate to be in contact with electrolyte to enabie high 15 utilîzation of the active material. This electrode structure lends itself specifically to improving the rate capability of extremely thick électrodes for stationary long duration energy storage, where thick électrodes may be required to achieve extremely high areal capacities.

[00126] The agglomérâtes for these embodiments, and in particular for use în 20 embodiments of électrodes for long duration energy storage Systems, can be any volumétrie shape, e.g., spheres, dises, pucks, beads, tablets, pills, rings, lenses, disks, panels, cônes, frustoconical shapes, square blocks, rectangular blocks, trusses, angles, channels, hollow sealed chambers, hollow spheres, blocks, sheets, films, partîculates, beams, rods, angles, slabs, cylinders, columns, fibers, staple fibers, tubes, cups, pipes, and combinations and varions of these and other more complex shapes. The agglomérâtes în an electrode can be the same or different shapes. The agglomérâtes in an electrode that is one of several électrodes în a long duration energy storage System, can be the same as, or different from, the agglomérâtes în the other électrodes in that storage System.

[00127] The size of the agglomérâtes, unless expressly used otherwise, refers to the largest cross-sectional distance of the agglomerate, e.g., the diameter of the sphere. The agglomérâtes can be the same or different sizes. It is recognized that the shape and size of both the agglomérâtes, as well as, typically to a lesser degree, the shape and size of the container or housing holding the agglomérâtes, détermines the nature and size ofthe macro pores în the electrode. The agglomérâtes can hâve sizes from about 0.1 mm to about 10 cm, about 5 mm to about 100 mm, 10 mm to about 50 mm, about 20 mm, about 25 mm, about 30 mm, greater than 0.1 mm, greater than 1 mm, greater than 5 mm, greater than 10 mm and greater than 25 mm, and combinations and variations of these.

[00128] In embodiments, the agglomérâtes as configured in an electrode can provide an electrode having a bulk density of from about 3 g/cm³ to about 6.5 g/cm³, about 0.1 g/cm³ to about 5.5 g/cm³, about 2.3 g/cm³ to about 3.5 g/cm³, 3.2 g/cm³ to about 4.9 g/cm³, greater than about 0.5 g/cm³, greater than about 1 g/cm³, greater than about 2 g/cm³, greater than about 3 g/cm³, and combinations and various of these as well as greater and lesser values.

1O [00129] In various embodiments, additives bénéficiai to electrochemical cycling, for instance, hydrogen évolution reaction (HER) suppressants may be added to the bed in solid form, for instance, as a powder, or as solid pellets.

[00130] In some embodiments, métal électrodes may hâve a low initial spécifie surface area (e.g., less than about 5 m²/g and preferably less than about 1 m²/g). Such électrodes tend 15 to hâve low self-discharge rates in low-rate, long duration energy storage Systems. One example of a low spécifie surface area métal electrode is a bed of agglomérâtes. In many typîcal, modem electrochemical cells, such as lithium ion batteries or nickel-metal-hydride batteries, a high spécifie surface area is désirable to promote high rate capability (i.e., high power). In long duration Systems, the rate capability requirement is signîficantly reduced, so 20 low spécifie surface area électrodes can meet target rate-capability requirements while mînimizing the rate of self-discharge.

[00131] In another embodiment, désirable impurities or additives are incorporated into the agglomérâtes. When these impurities are solids, they may be incorporated by ball-milling (for example, with a planetary bal! mill or similar equipment) the powder additive with métal 25 powder, the agglomérâtes serving as their own milling media. In this way the powder additive is mechanically introduced into the pores or surface ofthe agglomerate. Agglomérâtes may also be coated in bénéficiai additives, for example, by rolling or dipping in a siurry containing the additives. These désirable impurities may include alkali sulfides. Alkali sulfide salts hâve been demonstrated to vastly improve active material utilization in Fe anodes. Just as soluble alkali sulfides may be added to the electrolyte, insoluble alkali sulfides may be added to the agglomérâtes, for example, by the above method.

[00132] In varions embodiments, the spécifie surface area of the agglomérâtes is increased by a factor of 3 or more, preferably a factor of 5 or more, as measured by a technique, such as the Brunauer-Emmett-Teller gas adsorption method. In some embodiments, this surface area increase is accomplîshed by using the agglomérâtes as an 5 electrode in an electrochemical cell, and electrochemically reducing it with an applied current.

[00133] The ratio of electrolyte to iron material, for example agglomérâtes in a cell may be from about 0.5 mLelectrolyte! 1 giron-material tO about 5 mLelectrolyte: 1 giron-material, from about 0.6 mLelectrolyte! l g iron-material tO about 3 mL electrolyte: 1 giron-mate rial, about 0.6 mLelectrolyte: 1 1O giron-mate rial, about 0.7 mLelectrolyte: 1 giron-material, about 0.8 mLelectrolyte! 1 giron-materiab about 1 mLelectrolyte: 1 giron-material, and combinations and variations of these as well as larger and smaller ratios.

[00134] A packed bed of agglomérâtes may be a désirable configuration of an ironbased electrode as it provîdes for an electronically conductive percolation path through the 15 packed bed while leavîng porosity available to be occupied by an electrolyte that facilitâtes ion transport. In certain embodiments, the ratio of electrolyte volume to agglomerate mass may be in the range of 0.5 mL/g to 20 mL/g, such as 0.5 mL/g to 5mL/g, or such as 0.6 mL/g or 1.0 mL/g. The agglomérâtes are generally în contact with surrounding agglomérâtes through a small contact area compared to the surface area of the agglomerate, and in some 20 instances the contact can be considered a “point contact.” Contacts of small cross-sectional area may be constrictions for the flow of electrical current that may resuit in a relatively low electrical conductivity for the agglomerate bed as a whole, which may in turn lead to high electrode overpotentials and low voltaîc effictency of the battery.

[00135] In some embodiments, addîtives comprising a molybdate ion are used in an 25 alkaline battery comprising an iron anode. Without being bound by any particular scientific interprétation, such addîtives may aîd in suppressing the hydrogen évolution reaction (HER) at the iron electrode and improving the cycling efficiency of the battery. The concentration of the additive is selected to be able to suppress HER while still enabling the desired iron charge / discharge process. As an example, a molybdate ion may be added via a molybdate compound such as KMoC>4. In one spécifie example, the electrolyte contains an additive concentration of 10 mM (mM means millimolar, 10'³ mol/L concentration) molybdate anion. In other embodiments, the electrolyte contains additive concentrations ranging from 1-100 mM of the molybdate anion.

[00136] In some embodiments, a surfactant is used to control wetting and bubbling during operation of a métal air battery. During charging, at least two gas évolution reactions may occur that resuit in bubble formation. One is hydrogen évolution at the métal anode, which is a parasitic reaction that may contribute to poor coulombic efficiency during cycling of the battery. Another is the oxygen évolution reaction, which is necessary for the functionîng of the metal-aîr battery. A surfactant additîve can mitigate undesirable effects associated with both reactions. In the case of HER, a hydrophobie surfactant additîve may suppress the hydrogen évolution reaction at the métal anode by physically blocking water (a HER reactant) from the métal anode during charging. In the case of ORR, a surfactant additîve may reduce electrolyte surface tension and viscosity at the oxygen évolution electrode to generate smaller, uniformly sized, controllabié bubbles during charging. In one non-limîting example, 1-Octanethiol is added to the alkalîne electrolyte at a concentration of 10 mM to mitigate both of these challenges.

[00137] In some embodiments, corrosion înhibitors used in the field of ferrous metallurgy to inhibit aqueous corrosion are used as components in a battery with an iron négative electrode to împrove performance. In some embodiments, iron agglomérâtes are used as the négative electrode, and favorable performance characteristîcs may be achieved by using one or more corrosion înhibitors in a suitable range of concentrations. In these embodiments, the principles of corrosion science are used to prevent undesirable side reactions (e.g. hydrogen évolution) in the charge condition, mitigate the rate of spontaneous self-discharge during an electrochemical hold, and maximize the utilization of iron active material upon discharge. Generally, there are two classes of corrosion înhibitors: interface înhibitors which react with the métal surface at the metal-environment interface to prevent corrosion, and environmental scavengers that remove corrosive éléments from the environment surrounding the métal surface to inhibit corrosion. Under the broad umbrella of corrosion înhibitors, appropriate concentrations of înhibitors may be added to the electrochemical cell to achieve favorable performance characteristîcs with respect to the efficiency and capacity of an electrochemical cell. For the iron electrode of a métal air battery, one applicable general class of înhibitors are liquid and interphase interface înhibitors. This class encompasses three major types of interface înhibitors: anodîc, cathodic, and mixed înhibitors. Anodîc înhibitors create a passivation layer that inhibits an anodîc métal dissolution reaction. Cathodic înhibitors may decrease the rate of a réduction reaction (HER in the case of an iron electrode), or precipitate at cathodic active sites to block the same réduction reaction. Mîxed inhibitors may inhibît corrosion via one or both pathways, and include but are not limited to molécules that adsorb on the métal surface physically or chemically to form a film that may block active sites for a réduction reaction. The inhibitors can be added to a base electrolyte at any concentration.

[00138] In various embodiments, an inhibitor that forms a passivation layer on the métal surface is paired with an additive that de-passivates the iron surface. In the correct concentrations, an optimal balance of corrosion inhibition and active material utilization may be achieved. In one spécifie embodiment, when using direct reduced iron as the négative electrode, 10 mM molybdate anîon is used as the passivator, while lOmM sulfide anion is

1O used as the de-passivator in an alkaline electrolyte comprised of 5.5M potassium or sodium hydroxide. Spécifie examples of electrolyte compositions include: 5.5 M KOH + 0.5 M LiOH + 10 mMNa₂S + 10 mM 1-octanethiol; 5.95 M NaOH + 50 mM LiOH + 50mM Na₂S + 10 mM 1-octanethiol; 5.95 M NaOH + 50 mM LiOH + 50mM Na₂S + 10 mM 1octanethiol + 10 mM K₂MoO₄; and 5.95 M NaOH + 50 mM LiOH + 50mM Na₂S + 10 mM

K2MOO4. However, the présent disclosure is not limited to any particular concentration of the above additives in the electrolyte. For example, one or more of the above additives may be included in the electrolyte at concentrations ranging from about 2mM to about 200mM, such as from about 5mM to about 50mM, or about 5mM to about 25mM.

[00139] For a physically adsorbed (chemisorbed or physisorbed) inhibitor, interaction 20 with the métal surface is often strongly dépendent on température.

[00140] In one embodiment, an inhibitor is used where desorption of the inhibitor from the iron surface may be favorable at lower températures with respect to a normal operational température. During charge, the inhibitor forms a film that suppresses the évolution of hydrogen at the electrode. On discharge the température of the cell can be increased or decreased such that the inhibitor desorbs from the métal surface and exposes active material to allow for improved electrode utilization. On the subséquent charge, the température of the cell may be returned to a normal operational température to reform the film and suppress HER. This process may be repeated to achieve high charging effîciencies and high discharge utilization of the iron electrode. In one non-limîting example, octanethiol may be used as an inhibitor that can physisorb or chemisorb on a métal anode (e.g. Fe, Nî). Upon heat treatment of an electrochemical cell up to 60°C, physisorbed octanethiol is desorbed, revealing more active sites that can be oxidized during discharge. Free octanethiol in the electrolyte then physisorbs to the anode again upon cooling. At higher températures (>60°C), octanethiol may chemisorb to the electrode, forming continuons, uniform films across the surface. These chemîsorbed species may be desorbed more effectively at low températures (<100^oC).

[00141] In order to enable performance at higher température, organic film-forming inhibitors with oxygen, sulfur, Silicon, or nitrogen functional groups can be used to form 5 continuous chemîsorbed films on the iron particulate electrode to replicate the depassivating behavior of the sulfide while resisting décomposition or oxidation.

[00142] In one embodiment, 1 to lOmM octanethiol is added to the electrolyte. During charge, the system is allowed to heat to températures outside of normal operating conditions (e.g., >50°C), facilitating the formation of more complété and uniform chemîsorbed octanethiol films across the active sites of the iron particulate electrode and preventing hydrogen évolution at the surface. On discharge, the system is cooled and portions of the chemîsorbed film desorb from the surface, revealîng additional active sites for discharge. The remaining octanethiol acts to depassîvate the electrode, facilitating more complété discharge. FIG. 1 illustrâtes an example method of facilitating such complété discharge. For example,

FIG. 1 illustrâtes the electrode 102 in a discharge State at the top of the figures. A potential hydrogen évolution reaction (HER) site 104 was created during discharge where a octanethiol film desorbed from the electrode 102 surface. In the next step of the method as iliustrated in the middle of FIG. I, 1 to 10mM octanethiol is added to the electrolyte 103. During charge, the System is allowed to heat to températures outside of normal operating conditions (e.g., >50°C), facilitating the formation of more complété and uniform chemîsorbed octanethiol films across the active sites of the iron particulate electrode 102 and preventing hydrogen évolution at the surface of the electrode 102 as the octanethiol film filed in the potential HER site 104. On discharge, the system is cooled and portions of the chemisorbed film desorb from the surface, revealîng additional active sites for discharge, such as the HER site 104.

The remaining octanethiol acts to depassîvate the electrode 102, facilitating more complété discharge.

[00143] During an electrochemical rest period, it is désirable to minimize the corrosion of the métal electrode. One type of corrosive media to an iron métal electrode in an aqueous electrolyte is dissolved oxygen. During an electrochemical hold, dissolved oxygen can contact the iron electrode and corrode the active material, discharging the iron electrode.

[00144] In one embodiment, an oxygen scavenger (e.g. pyrogallol, ascorbic acid, 8hydroxyquinoline, sodium peroxîde, hydrogen peroxide) may be added to the electrolyte during an electrochemîcal hold to reduce the concentration of dissolved oxygen in the electrolyte and prevent discharge of the iron electrode.

[00145] In one embodiment, an anodîc corrosion inhibitor (e.g. K2MOO4) is added to the electrolyte at concentrations between 1 and lOmM before an electrochemîcal hold, creating a passive film that blocks the métal surface from corrosive media in the electrolyte to prevent self discharge. After the electrochemîcal hold, when the electrode must be discharged, an aggressive ion (e.g. SO4², CrOG NO3·) is added to the electrolyte to expose the active material and achieve a hîgh utilîzation of active material, thus mitigatîng self discharge.

[00146] In certain embodiments, other corrosion inhibitors are incorporated in the electrolyte as additives (i.e., as minority constituents). Electrolyte additives may be selected from the non-limiting set of 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) 15 oxide, magnésium oxide, sodium chlorate, sodium nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, ammonium thiosulfate, lithopone, magnésium sulfate, iron(III) acetylacetonate, hydroquinone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid, dimethyl phthalate, methyl méthacrylate, methyl pentynol, adipic acid, allyl urea, citric acid, thiomalic acid, N-(2-aminoethyl)-320 aminopropyl trimethoxysilane, propylene glycol, trimethoxysilyl propyl diethylene, aminopropyl trimethoxysilane, dimethyl acetylenedicarboxylate (DMAD), 1,3dîethylthiourea, Ν,Ν’-diethylthiourea, aminomethyl propanol, methyl butynol, amino modified organosîlane, succinic acid, isopropanolamine, phenoxyethanol, dipropylene glycol, benzoic acid, N-(2-aminoethyl)-3-aminopropyl, behenamide, 2-phosphonobutane tricarboxylîc, mipa borate, 3-methacryloxypropyItrimethoxysilane, 2-ethylhexoic acid, isobutyl alcohol, t-butylaminoethyl méthacrylate, diisopropanolamine, propylene glycol npropyl ether, sodium benzotriazolate, pentasodium aminotrimethylene phosphonate, sodium cocoyl sarcosinate, laurylpyridinium chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quaternium-18 chloride, sodium hexametaphosphate, dicyclohexylamine nitrite, lead stéarate, calcium dînonylnaphthalene sulfonate, iron(II) sulfide, sodium bisulfide, pyrite, sodium nitrite, complex alkyl phosphate ester (e.g. RHODAFAC® RA 600 Emulsifier), 4-mercaptobenzioc acid, ethylenediaminetetraacetic acid, ethylenediaminetetraacetate (EDTA), 1,3-propyienediaminetetraacetate (PDTA),

nitrilotrîacetate (NTA), ethylenediaminedisuccinate (EDDS), diethylenetriamînepentaacetate (DTPA), and other aminopolycarboxylates (APCs), diethylenetriaminepentaacetic acid, 2methylbenzenethiol, 1-octanethiol, manganèse dioxide, manganèse (III) oxide, manganèse (II) oxide, manganèse oxyhydroxide, manganèse (II) hydroxide, manganèse (III) hydroxide, 5 bismuth sulfide, bismuth oxide, antîmony(III) sulfide, antimony(III) oxide, antimony(V) oxide, bismuth selenide, antimony selenide, sélénium sulfide, selenium(IV) oxide, propargyl alcohol, 5-hexyn-l-ol, l-hexyn-3-ol, N-allylthiourea, thiourea, 4-methylcatechol, transcînnamaldehyde, Iron(III) sulfide, calcium nitrate, hydroxy lamines, benzotriazole, furfury lamine, quinoline, tin(II) chloride, ascorbic acid, 8-hydroxyquinoline, pyrogai loi, 10 tetraethyl ammonium hydroxide, calcium carbonate, magnésium carbonate, antimony dialkylphosphorodithioate, potassium stannate, sodium stannate, tannîc acid, gel afin, saponîn, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrotreated light petroleum oil, heavy naphthenic Petroleum oil (e.g. sold as Rustlick® 631), antimony sulfate, antimony acetate, bismuth acetate, hydrogen-treated heavy naphtha (e.g. sold as WD-40®), tétraméthylammonium hydroxide, NaSb tartrate, urea, D-glucose, C6Na2O6, antimony potassium tartrate, hydrazine sulfate, silica gel, triethylamine, potassium antimonate trihydrate, sodium hydroxide, 1,3-dio-tolyl-2-thîourea, l,2-diethyl-2-thiourea, 1,2-dîîsopropyl-2-thiourea, N-phenylthiourea, Ν,Ν'-dîphenylthiourea, sodium antimonyl L-tartrate, rhodizonîc acid disodium sait, sodium 20 selenide, potassium sulfide, and combinations thereof.

[00147] Additional additives include minerais containing SiO₂, which may hâve bénéficiai effects on electrochemical performance due to uptake of carbonate from the electrolyte or electrode. Additives which contain such functional groups may be usefully incorporated into iron electrode materials. While the spécifie mineralogy of ores and other 25 factors may détermine the exact SÎO₂-containing material added, examples of such SiO₂containing additives are silica, cristobalite, sodium silicates, calcium silicates, magnésium silicates, and other alkali métal silicates.

[00148] In certain embodiments, electrode agglomérâtes are prepared by agglomerating métal powders, such as îron containing powders, into approximately spherîcal 30 agglomérâtes. In various embodiments the agglomération is conducted at or about room température or at or about ambient outdoor température or at elevated température. In various embodiments, the agglomération is conducted in a rotary calciner, in which the powder is simultaneously agglomerated and sintered. In certain embodiments, iron powders such as atomized iron powder, sponge iron powder, îron filings, mi 11 scale, carbonyl iron powder, electrolytic iron powder, and combinations or variations thereof are used as feedstocks. In various embodiments, the heat treatment process is conducted at températures such as about 700 °C to about 1200 °C such as about 800 °C to about 1000 °C. In various embodiments the gas environment is inert (comprising N₂ or Ar) or reducing (comprising H₂, CO₂, CO, etc) or combinations thereof. In various embodiments the heat treatment process fully or partially sinters together the powder to create agglomérâtes. In various embodiments the agglomérâtes hâve size ranging from 1 um (um = 10'⁶ m) to 1 cm (cm = 10'² m) such as 10 um, 100 um, or 1 mm (mm = 10^-3 m).

1O [00149] In certain embodiments, the feedstock materials are materials known in the art as pig iron, granulated pig îron, nodule reduced iron, scrap iron, and/or scrap Steel.

[00150] In various embodiments, a fine iron powder with a substantial population of powder particles being below 44 microns (often written as -325 mesh due to the passage of such particles through a 325 mesh sieve) may be utilized as a portion of the feedstock 15 materials or entirely comprise the feedstock materials.

[00151] In certain embodiments, électrodes are fabricated by electrochemical déposition of iron from an aqueous solution. In certain embodiments the déposition solution is acidic, with a pH less than about 4, such as pH about 3, or pH about 2. In certain embodiments, the solution is near neutral, wîth a pH between about 4 and about 10, such as 20 pH about 5 or pH about 7 or pH about 9. In certain embodiments the electrolyte comprises a sait such as NaCl or LiCl or KC1. In certain embodiments the liquid electrolyte is agitated by stirring, shaking, mixing, or turbulent flow to promote an uneven déposition rate and a porous structure. In certain embodiments the liquid electrolyte is sparged or aspirated, to introduce gas bubbles into the liquid during the déposition process.

[00152] In certain embodiments, iron powders are prepared by an electrometallurgical process for making porous iron. Working from a melt, iron-comprising métal is sprayed, bubbled through, or molded onto a substrate or into a mold to produce a low-cost, high surface area iron product. In certain embodiments, these powders are subsequently agglomerated using a rotary calciner or other methods, and may be subsequently assembied into an electrode. In certain embodiments the powders are directly assembied into an electrode, with no intermediate agglomération process. In certain embodiments, a mixture or combination of agglomerated and non-agglomerated powders are used in an electrode. In certain embodiments, agglomerated and/or non-agglomerated powders produced by the electrometallurgical method are combined with other metals to fabricate an electrode.

[00153] Electrochemically produced metals offer a unique opportunity for production of hîgh surface area materials, especially if the métal is in a liquid state, in which case the 5 resulting liquid product is cooled via a variety of methods to achieve the desired properties.

For example, iron produced via high température electrometallurgical îs cooled directly în a hîgh surface area mold, spray deposîted (atomized) into particles or dispersed În a cooling media.

[00154] In certain embodiments, métal électrodes are directly prepared by

1O electrometallurgical processes such as molten oxide electrolysis. In certain embodiments, porous électrodes are made by intentionally aspirating or sparging gas into a molten oxide electrolysis cell. In certain embodiments, the gas is an inert gas such as N₂ or Ar.

[00155] In certain embodiments, molten métal from an electrometallurgical process is sprayed, bubbled through, or molded onto a substrate or into a mold to produce a low-cost, 15 hîgh surface area métal electrode. In certain embodiments the métal is substantially iron.

[00156] In one non-limiting example, iron ore comprising Fe₂O3, FeaO4, and mixtures thereof, is dissolved in an electrolyte comprising SiCh, AI2O3, MgO, and CaO in weight ratios of 60wt%, 20wt%, 10wt%, and 10wt%, respectîvely. The mixture is brought to an elevated température of about 1600 °C. Metallic iron is electrochemically reduced from the molten oxide mixture and pooled at the cathode. The molten métal îs transferred by pipes and valves to a shot tower, and is rapidly cooled in vacuum to produce a fine iron powder with average diameter of 50 uni (uni = 10'⁶ m). The iron powder is subsequently passed into a rotary calciner operating under a nitrogen (N2, 100%) atmosphère at 900 °C to iorm aggregates with average diameter of 2 mm, which are subsequently assembled by packing into a métal electrode.

[00157] In certain embodiments, the électrodes may be fabricated from the thermochemical réduction of iron oxides. In some embodiments, the réduction may proceed almost to complété réduction of the iron oxides to metallic iron. Nearly complété réduction of the iron oxide to metallic iron is the goal of many industrial thermochemical réduction processes for iron. However, there are many potential reasons why incomplète réductions of iron oxides to metallic iron would make such incompletely-reduced products particularly useful for the création of iron batteries. First, several ofthe oxide phases created during the réduction of iron are semiconducting, and thus may usefully serve as electronic conductors in an iron electrode material. For example, magnetîte is fairly conductive close to room température. Wüstite, while less conductive than magnetîte, is still highly conductive relative to most oxides. In some embodiments, one may take advantage of the semiconducting nature of wustite and magnetîte to form a battery electrode which is possîbly a composite with metallic iron. Partially reduced products may also be more electrochemically active. The inventors hâve observed that wüstite may in some circumstances be more electrochemically active than even metallic iron. Wüstite may be less expensive to thermochemically reduce due to its higher oxidation state than metallic iron Wüstite may therefore be less expensive and higher performance than iron as a component of a battery electrode. In one aspect, a positive electrode for an alkaline iron battery may be produced from indurated pellets composed of hématite traditionally fed to direct réduction or blast furnace processes. The pellets may be reduced in a vertical shaft furnace via appropriate mixtures of hydrocarbons and other reducing gases known in the art of the direct réduction of iron. The réduction process may terminale by way when a metallîzation of at most 95% is achieved (metallization îs a term used în the art of direct réduction of iron to describe the fraction of iron atoms which are fully metallic in their oxidation state). In some instances, a lower metallization may be preferred, with métallizations as low as 0% yielding large quantîties of magnetîte and wüstite as alternative input materials for a battery. The resulting partially reduced pellets, lump, fragment or other particulate may be packed into a bed of particles in order to serve as an iron electrode material. The electrode material may consist entîrely of iron oxides, and comprise prîmarily a mixture of magnetîte and wustite.

[00158] Current Collection, Compression, and other means of enhancing charge transfer

[00159] In some instances, porous iron electrode materials may suffer from high electrical résistance when assembled into a bed. As such, the performance of iron electrode materials inside a battery may be enhanced by methods for decreasing the résistance to charge transfer between and among the particulate materials, and enhanced methods for current collection from the electrode active materials. This section describes methods for enhancing the charge transfer within the packed bed through to the current collectors.

[00160] The inventors hâve discovered through experîment that the performance of porous iron électrodes may be enhanced by applying a compressive force to the anode bed during the course of battery cycling. For example, the contact résistance between porous

particulate materials may be decreased by over one order of magnitude by application of a uniaxial compressive stress of 0.01 MPa or more. Too high of compressive stresses may lead to local faiiure of the electrode material via cracking of the material (and therefore potential local decreases în electricai conduction), densification due to deformation ofthe porous iron electrode material without cracking (which may in tum lead to a réduction in the pore space available for the formation of discharge product or a decrease in the mass transport through the pore space), or other mechanical faiiure modes. The application of compressive stresses that do not lead to material faiiure but are above the stresses needed for réduction of contact résistance may lead to increases in the performance of the porous iron electrode material during electrochemical cycling. Within this régime, further increases in compressive stresses and different configurations of compressive stresses may be used to increase the conductivity of the bed, with stresses on the order of 0.1 -10 MPa yîelding enhanced performance in some Systems. As the applied stresses (and therefore forces) increase, the requirements for the mechanical enciosure which may successfully apply such stresses become more stringent, and generally the costs of the enciosure increases. Thus, in one aspect, a mechanical structure which permits simultaneous current collection and compression of a porous iron electrode material with stresses between 0.1 and 10 MPa is an especially usefui means of containing the iron electrode materials within an electrochemical cell.

[00161] In various embodiments, it may be usefui for a current collecter to serve multiple functions în the cell, inciuding serving as a structural member. In one example, the current collecter may provide structural support to the electrode by running through a middle of the packed bed of particulate material. In some embodiments, the packed bed may hâve current collectors on both sides in addition to a central current collecter. In some embodiments, the current collecter in the middle of the packed bed may be fabricated from a sheet without perforations, whereas the current collectors on the external faces may be perforated or otherwise containing holes to facilitate transport of ions to the electrode active materials. In various embodiments, air electrodes or other positive electrode materials may be piaced adjacent to the iron electrode material on both sides such that ions do not need to flow through the electrode material across a gîven depth in the electrode, this may be due to e.g. a plane of symmetry for the transport. As such, a lack of perforations in the current collecter included in the middle of the bed may usefui ly reduce costs for the center current collecting sheet while having little to no impact on the transport within the system. The iron electrode materials may be mounted to or compressed against a combined structural support and current collecter included in the middle of the packed bed. Additional functions performed by a current collecting component in an îron electrode may include: anode locating/mounting, enhanced current collection, adjacent cell séparation, and voltage stacking.

[00162] The degree to which the resistivîty of a porous electrode must be reduced to 5 reach a given level of electrochemical performance is a fonction of the current collection method, as well as the material properties. If current îs being collected from more sides, or with shorter total path lengths to the current coHector, a battery may be able to operate efficiently with a higher resistivîty path, as the ultimate voltage drop is lower. As such, the compression strategies and the current collection strategies for porous iron électrodes may be 10 usefully co-optimized to yield Systems with the lowest total cost for a given level of performance. Below, a set of techniques and designs for current collection from, and compression of, porous electrode beds which may be used in combination or separately in order to yîeld high performance porous battery électrodes with low price.

[00163] The current collecting materials may be any of those used in the art to collect 15 current in alkaline batteries at the potentials that anodes in alkaline iron-based batteries may be exposed to. The composition ofthe electrolyte, the spécifie potentials used during battery cycling, and other process variables (e.g. température) will détermine the degree to which varîous current collecting materials are stable. These materials may include nickel, nickelpiated stainless steei, copper, copper plated stainless Steel, iron of sufficient thickness, carbon 20 fiber and other carbon-based materials, and iron coated with cobalt ferrite.

[00164] In one aspect, a reactor containing a porous îron electrode may be divided up into horizontal layers contained in a larger vessel. FIGS. 2 and 3 illustrate example aspects of such an embodiment in which a larger vessel 202 is divided into horizontal layers 203-207.

With reference to FIGS. 2 and 3, these horizontal layers (e.g., 203-207) may be referred to as packets. In each of these horizontal layers (e.g., 203-207), the anode, such as particulate anode material 212, may be compressed via any ofthe methods applicable for compressing and containing particulate materials. In doing so, a current-collecting divider 210 between the packet may be inserted into the larger vessel 202 holding the packets (e.g., 203-207). Tabs 215 on the divider 210 or other compilant, conductive mechanisms may be used to hold the compressive forcer (e.g., divider 210) for the packet (e.g., 203-207) în place while also serving as a means of current collection. This is shown in FIGS. 2 and 3. The divider 210 may also include an optîonal catch lip 216 on the side.

3β

[00165] In an aspect, the current collecter may be a metallic or other conductive textile. Examples include meshes woven of nickel, copper, or graphite fibers. The current collecter may surround or be layered into the electrode materials. The current collecting textile may surround a Direct Reduced Iron (DRI) pellet bed as an electrode shown below.

The textile may be tightened, cinched, or otherwise brought into close mechanical contact with the electrode material in order to promote suffîcient electrical contact with electrode material. An illustrative example is shown in FIG. 4 for the case of a métal textile 402 with an electrode composed of direct reduced iron pellets 403. The métal textile 402 may be a mesh or screen encasing the DRI pellets 403 and providing a compressive force or load 404 10 on the DRI pellets 403 to press the DRI pellets 403 together within the métal textile 402 mesh and to establish close contact between the métal textile 402 and the DRI pellets 403. The current 405 may be collected by the métal textile 402.

[00166] In another aspect, a conductive mesh pouch or bag may be used as a means of simultaneously compressing and current-collecting from an electrode material. More specifically, a mesh pouch or bag may be filled with parti eu late iron electrode material, the bag may be cinched or otherwise reduced in volume via a belt, string, wire or other cinching mechanism in order to apply compression to the anode material. A conductive mesh tube or similar may be filled with particulate iron electrode material, and the electrode material may be compressed via application of axial tension to the conductive mesh tube. In such a case, 20 the weave ofthe mesh may be optimized such that the mesh tube undergoes substantial compression upon application of axial tension. One may understand this in analogy to the Chinese finger trap, wherein axial extension of a woven tube causes the diameter of the tube to narrow. The amount of compression applied to the particulate iron material may be adjusted by the thickness of the strands in the weave, the density of the strands in the weave, 25 and the amount of axial force/extension applied to the weave. In some instances, the porous iron electrode material may be composed of direct reduced iron pellets. In some instances, the porous iron electrode material may be composed of crushed direct reduced iron pellets. A binder may usefully be included in the particulate iron material in some cases to aid in adhesion of the pellet.

[00167] In some aspects, a porous mesh container and the particulate active materials may be disposed in a similar géométrie manner to a teabag and tea leaves, for example as illustrated in FIGS. 5 and 6. FIG. 5 illustrâtes a single cinch configuration 500 in which the porous mesh bag 501 is tied at a single cinch point 503 by the current collecter 502. FIG. 6 illustrâtes a double cinch configuration 600 in which the porous mesh bag 501 is tied at a first cinch point 503 by the current collector 502 and a second cinching point 602. This tea bag container (e.g., 501 ) may be conducting and serve as a current collector. In some aspects, the tea bag container (e.g., 501) may hâve a current collector placed inside of the tea bag container’s envelope. The tea bag container (e.g., 501) may hâve ties to aid in compression, including ties that are not at the top of the tea bag container (e.g., 501), such as a second cinch tie 602 or other placed cinch ties. The tea bag container (e.g., 501) may also hâve ties at the top of the container to maintain active material within the container. In another aspect, the tea bag container (e.g., 501) may be non-conductive and the current collective may be performed solely through a current collector placed inside of the tea bag container’s envelope.

[00168] In another aspect, a loose, flexible, conducting sheet may loosely attached at the edges to a backing plate, which may or may not be rigid, forming a pouch. Cinches, such as wires, inserted through the flexible sheet and the back, are opened to atlow filling the pouch with a pellet or powder anode material. The cinches are pulled shut to compress the anode, and may be used for current collection. The cinching wires may be conductive and serve as added current collectors distributed throughout the pouch. The pouch may also be attached in a rigid manner (by e.g. welds), or by connections which are rigid with respect to some forms of motion and flexible with respect to others (e.g. a hinged connection). In some instances, the current collection may take place from one side such that either the backing plate or the pouch are not current-collecting, whereas in other instances it may be advantageous to collect current from both sides of the pouch construction. An example of such a cinched construction 700 with a backing plate 702 is shown by way of non-limîting example in FIG. 7. In some embodiments, the backing plate 702 may be used to rigidly support pouches 705 on both sides as illustrated in FIG. 7 with cinching wires 704 running across the backing plate 702 and pouches 705. Electrode material may be poured into the pouches 705 through an opening that may be then cinched or welded dosed to form a closure 703.

[00169] In another embodiment, a particulate electrode material may be compressed within perforated sheets. The sheets may be conductive such that they serve as both a means of compressing the electrode material and a means of collecting current from the electrode material. The perforations in the sheet may be selected such that they are smalier than a characteristic size of the particulate material, and thus that the particulate material may not easily escape from the cage formed by the perforated sheet.

[00170] In various embodiments, the electrode material may be a particulate material. The desire for facile transport of ions between the positive and négative électrodes may necessitate that the materials surrounding the electrode materials are porous or otherwîse perforated. In some instances, a particulate material with a particle size finer than the porosity or perforations may be desired due to e.g. the difficulties of making very fine perforations. In characteristic sîze of the particulate material, and thus that the particulate material may not easily escape from the cage formed by the perforated sheet.

[00170] In various embodiments, the electrode material may be a particulate material. The desire for facile transport of ions between the positive and négative électrodes may necessitate that the materials surrounding the electrode materials are porous or otherwise perforated. In some instances, a particulate material with a particle size finer than the porosity or perforations may be desired due to e.g. the dîfficulties of making very fine perforations. In instances where partîcles finer than the porosity or perforations are desired, the electrode material may be agglomerated via a binder such that a secondary particle forms which is composed of many primary partîcles. The primary particle sizes thus may be finer than the perforations, but the secondary particle size may be coarser than the perforations. Such coarser partîcles will be less susceptible to egress through the porosity or perforations of the current collectors and other compressing materials, and may be more effectively compressed as a resuit. In one aspect, a polymer stable in alkaline conditions may be used to bind an agglomerate together such as poly(ethylene) or poly(tetrafluoroethylene). In another aspect, a polymer may be introduced onto the surface of the primary partîcles and subsequentiy pyrolyzed to form a conducting binder on the surface of the primary partîcles, thereby binding them together. In yet another aspect, a polymeric binder that is only partially stable in the conditions appropriate to the electrode may be introduced between the primary partîcles.

The binder may permit the electrode to be cycled a sufficient amount via e.g. several electrochemical charge and discharge cycles such that a bond forms electrochemically between the various primary partîcles prior to the disintegration or dégradation of the polymer. In another aspect, the shape of the porosity or perforations in the structure compressing the electrode materials may be engineered to retain the electrode materials within the structure, but to maximize the ionic transport through the perforations or porosity. By way of non limitîng example, long siits may be introduced into a perforated sheet such that the partîcles may not exît through the slits, but the amount of area open to mass transport is increased relative to the amount présent if the perforations were equiaxed. In one aspect, the particulate electrode material may be composed of direct reduced iron, and the perforated sheet may be composed of stainless Steel. In another aspect, the particulate electrode material may be composed of crushed direct reduced iron to a particle size several times smaller than the native pellet size, and the perforations in a current collecter may be sized such that the crushed fragments do not escape from the compressing cage.

[00171] In one aspect, a bed of particulates is vibrated, shaken, stirred, or moved so particulates settle doser together than when inîtially filled. This method may also be used period ίcal ly during the life of the system to help encourage new contact angles or arrangements between particulates as they change shape or size. In the case of a container 5 which provides pockets for particulates, its orientation may be changed, such as spinning in the case of a wheel-shaped contamment.

[00172] In another aspect, additives may be included or added to the bed of the electrode material to enhance conduction through the electrode between current collectors. The additives may be usefully concentrated at key points in the electrode structure. In one 10 aspect, a particulate anode material is stuck to a current collecter, which may take any shape, including rounded, or a hollow sphere, and may hâve particulate on both sides, using a conductive glue. The conductive glue may comprise a bînder stable in the intended environment, such as alkaline electrolyte, and a conductive particie, such as métal, such as iron, filings or powder, including Steel mil! dust. The bînder may, for example, comprise poly(ethylene) or poly(tetrafluoroethylene). The conductive glue may additionally contain additives useful to battery performance, such as sulfide sait additives, or additives intended to bond with carbonate ions in solution, such as calcium hydroxide. Creating a conductive bond between the electrode particulate materials and the current collecter may usefully enhance battery performance at low added cost when the interface résistance between the particulate 20 material and the current collecter is one of the larger résistances in the electrochemical system. The composition of the conductive glue may be between 10-80 vol.% of the conductive additive, with the remainder comprising a bînder, any additives, and a possible cosolvent or tackifier.

[00173] In another aspect, current collection may occur by creating a bond between 25 each of the particulate materials and a conductive rod. If the particulate materials are attached by a conductive bond to a current collecter, the compressive stresses need not be applied. The particulate materials may be attached to a rod along its length. The mass of anode material may extend past the end of the rod. The anode mass may be attached via sintering, welding, or other métal bonding techniques, by attachment with wire, or by déposition onto the rod 30 from solution or slurry, which may take place via magnetism or évaporation of the solvent.

The rod may be used for current collection from the anode. Anodes of this rod format may be snap-fit into a flexible ring-wîth-a-slit-like fastening mechanism for easy assembly of a compound anode. This fastening rail may also serve as a bus bar. This is schematically shown

in FIG. 8 in which rods 802 with attached iron particulate material 805 are fitted to a bus bar 803. The rod 802 may hâve any cross section, including circular or linear, and need not be straight, but may rather assume a coil or some other shape to enhance packing and limit the bus bar 803 volume needed.

[00174] In another aspect, simultaneous current collection and compression may take place via a pouch, open at the top, which may be fabricated, for instance, from crimped or welded sheet métal. The pouch may be fi lied with a particulate iron electrode material and the top may be rolled down to provide compression of the particulate materials. The compression may make use of a horizontal rod inside the rolled portion to perform the rolling. The pouch 10 may be made of conductive materials suitable to be current collectors in alkaline battery environments, and specifically at iron positive électrodes. Current may be collected from the end(s) of the rod. The pouch may be porous or perforated to permit ionic transport through the pouch, as in a métal!ic mesh made of nickel.

[00175] In another aspect, a rigid container may be formed. The rigid container may 15 hâve at least one conductive wall, and may be constructed of materials suitable for use in an alkaline electrolyte, and further may be suitable to serve in the current coHector of an iron positive electrode. The rigid container may be filled with particulate electrode material, and compressed via a piston or plunger mechanism. In one exemplary embodiment, a welded can with a bottom and wrap-around outside is filled with anode pellets (or powder) and compressed from the top using a plunger mechanism. The faces of the rigid container may be constructed of rigid, but ion permeable material such as perforated sheet métal or expanded sheet. In one aspect, an expanded sheet métal comprised the sidewalls ofthe rigid container. The platen or face used by the plunger may contain tabs or other compilant mechanisms which may mechanically engage with features in the sidewalls of the rigid container such that the plunger may only be needed to provide a compressive force for assembly. The mechanically engaging features thus enable the piston to be used for initial compression but subsequently removed. Compressive load in this and other embodiments may be applied via any ofthe means common in the art for applying compressive loads, including but not limited to bolts, hydraulics, weight, threaded rods, zip ties, and rivets. FIG. 9 shows an exemplary embodiment wherein a perforated press 902 is used to compress the iron electrode material 903 within a rigid anode container 905. Tn this case, the iron electrode material 903 may be direct reduced iron pellets, referred to as a DRI marble bed. FIG. 9 shows an exploded view on the left and an assembled view on the right.

[00176] In another aspect, iron particulate materials may be sandwiched between two sheets of conductîve, compilant material, such as a métal textile, and riveted to be fastened around the edges to provide compression. In some instances, the conductîve compilant material may be riveted, cinched, or otherwise reduced in volume intermittently throughout 5 the area of the electrode to provide more uniform compression.

[00177] In another aspect, a compilant sheet or mesh may be used in combination with a rigid side wall to provide simultaneous compression, current collection, and contaminent. More specifically, in one exempiary embodiment, such as iliustrated in FIG. 10, a module 1002 consisting of a rigid side walls 1004 may be slîghtly overfilled with iron electrode material 1005 with métal mesh top and bottom plates 1003, ail enclosed with fasteners 1006 (e.g., bolts, threaded rods, zip ties, rivets etc). The mesh 1003 applies a compressive load to the iron electrode material 1005 when the fasteners 1006 are tightened as the side walls 1004 may be slîghtly overfilled with marbles (e.g., DRI marbles as the iron electrode material 1005). The mesh 1003 may serve as a current collecter. The mesh 1003 may allow for good electrolyte circulation or diffusion to the iron electrode material 1005. The fasteners 1006, in combination with the other éléments, may keep the iron electrode material 1005 contained and may apply a clamping load. In some embodiment, the fasteners 1006 may also serve as a current collecter. The mesh 1003 may be wire mesh, perforated plate, résistive to corrosion i.e. nickel, stainless Steel etc. The side walls 1004 may be any rigid material suitably stable in 20 the electrochemical environment ofthe iron électrodes 1005, i.e. plastic, some metals, etc.

The resultîng assembly of iron electrode material 1005 and the current collecting apparatus may be a modular component or may be permanently connected to an electrochemical energy storage system entirely.

[00178] In another aspect, a compilant material, gasket-like material is used to contain 25 the iron particulate electrode material on several faces. The compilant material permits variable displacement of the force-applying éléments of the design according to the local compliance and/or packing of the bed. In one example, a compilant gasket borders a cylindrical cell and conducive, current collecting, perforated plates form the ends of the cylindrical cell. The plates are forced together at various points along the circumference of 30 the cell via, e.g. bolts penetrating through the Silicon gasket. The gasket may be made of a compilant, alkaline résistant material, such as an Ethylene propylene diene monomer (EPDM) rubber or related material. In some instances, the gasket may need to be highly compilant, in which case a fbam of a polymeric material, such as an EPDM foam, may be useful.

[00179] In another aspect, a current collecter may contain divots or other locating or contacting features on its surface. These features may serve to enhance the contact area between the current collector and the particulate iron material and/or to locate a partîculate material such that it packs efflciently as a resuit of the templating provided by the surface of the current collector. In one example, a current collector may contain a sériés of divots sized and placed such that a spherîcal set of particles, such as those from a direct réduction process, may pack in a ciose-packed manner adjacent to the surface. Other templates, such as a body- centered cubic template are possible. For particulate materials with an axis of symmetry, such as rods, the templating may hâve an axis of symmetry like a divot that is a cylindrical trough. The divots may be introduced through machining, sheet métal dimpling or other deformation processing, or may include suitably-sized perforations or through-holes in the current collector. The current collector may be shaped so as to compress the particulate materials most optîmally against each other, for example, in the case of rod-shaped particulate material, the current collector may comprise a sheet rolled into a cylinder around the cylindrical aggregates and compressed to constrain the cylinder diameter.

[00180] In order to reduce electrical résistance due to current collection, current collectors may be engineered to allow current collection to occur more homogeneously throughout the packed bed electrode by introducing current collecting components throughout the thickness of the electrode, or which penetrate a reasonable way through the thickness of the electrode.

[00181 ] In certain embodiments, a current collector may feature spikes, rods, tabs, or other high aspect ratio features that may project out into the electrode bed from a current collecting sheet or other boundary of the packed bed electrode. These high aspect ratio features may be configured in size and shape such that they contact many electrode material particles in the bed which would not be contacted by a simple, fiat sheet current collectors. In certain embodiments, a sheet métal current collector with tabs that project into the space filled with particulate material îs used as a current collector. In another aspect, an expanded sheet métal sheet is used as a current collector, and some struts within the sheet are eut and bent inward to serve as tabs projecting into the space filled with active material.

[00182] In certain embodiments, a conductive brush or sériés of wires are attached to a current collecter. The wires flexibly project into the space filied by an iron electrode material. The wires are put in contact with the material due to theîr spring constants, and the contact may be improved by use of a compressive pressure.

[00183] In many embodiments, fasteners or other compression-providing éléments are desired to retain current collectors in compressed position relative to one another. In what follows, the term fastener shall be understood to mean any element of a mechanical assembly that provides a fastening or compressive function through the use of an additional part that mechanîcally engages with other portions of the assembly. The performance of an iron positive electrode comprised of individual pellets increases when a sustaîned compressive load is applied to it before operating the cell. However, using métal fasteners such as stainless Steel bolts to sustain the load is disadvantageous because of both added part count and assembly time, and because the bolts likely need to be electrically isolated from current collectors to mitigate the hydrogen évolution reaction (an undesired parasitic side reaction that lowers coulombic efficiency) occurring on the bolts, which adds more complexity to the design and likely adds to part count. Thus, while fasteners are désirable from a mechanical perspective, métal lie fasteners are disadvantageous. Several methods of replacing metallic fasteners with other methods are considered below.

[00184] In some embodiments, non-metallîc fasteners may be used in place of metallic 20 fasteners. In one example embodiment, two sandwiching current collector plates may surround the iron electrode bed. The current collector plates could be made to apply a compressive force on the anode bed via fasteners made from an electrically insulating, nonmetallic material that is résistant to dégradation in the alkaline environment of the electrolyte. The electrically insulating and non-metallîc nature of the fasteners would resuit in a lack of 25 électron transport to the electrolyte-exposed surfaces of the fasteners, which would prevent the undesired hydrogen évolution reaction from occurring on the exposed surfaces of the fasteners. Reducing the HER rate means that more électrons participate in the desired anode réduction reaction, that is, a higher coulombic efficiency. In certain embodiments, the fasteners are bolts and nuts. In certain embodiments, the fasteners are made of one or more of acrylîc, polytetrafluoroethylene, polyethylene, low density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, polypropylene, or polyether ether ketone. In another exemplary embodiment, two sandwiching current collector plates that surround the anode bed could be made to apply a compressive force on the anode bed via

fasteners that save assembly time by the use of a “snap-in” mechanîsm rather than a screw mechanism that requires rotation of a fastener. In certain embodiments, the fasteners are duallocking snap-in supports ofthe appropriate length. Any combination ofthe above fastening techniques may be used to provide compression while avoiding the use of metallic fasteners.

Some fastening techniques are illustrated in FIGS. 1 IA and I IB. The illustration in FIG.

11A shows an electrically insulating nut 1103 sandwiching two current collecting sheets 1105 against an iron electrode material 1100 and labeled as an ‘anode active material’ in FIG. 11 A. The nut 1103 tightens on the boit 1102 to draw the sheets 1105 together, thereby compressing the anode active material 1100. A second example of snap-in compressive features, such as 10 snap in support 1110 is shown in FIG. 1 IB replacing, and operating in a similar manner to, the boit 1102 and nut 1103 of FIG. 1 IA.

[00185] In some embodiments, it may be usefui to use a compilant mechanism capable of applying a large, distributed load to a current collecter or compressive platen. In one example, the last face dimension of a rectangular prism box for containing the anode is a 15 leaf-spring mechanism that springs back after anode loading to compress and contain the pellet anode. The current collecter itself may be a compilant mechanism such that applying load on relatively few points (as occurs with a leaf spring), may resuit in a distributed load across the system.

[00186] Application of a compressive stress may be applied by alternative means from 20 compression applied via mechanical fastening of the structure. In certain cases, iron electrode material may be contained by a rigid body (for example, a prismatic cell with current collectors or other mechanical supports on ail faces), but the need for applying a compressive load during assembly may be eliminated by the use of an expanding material lining one face of the anode containment body. The expanding material may expand after assembly of the 25 cell, thus providing a compressive load on the anode bed after filling the cell with electrolyte.

In certain embodiments, the expanding material may be piaced in between the iron electrode material and one of the small faces of the iron electrode material containment body. In certain embodiments, the expanding material is an expanding hydrogel that swells when in contact with the aqueous electrolyte, thus providing a compressive load on the anode active material 30 upon filling with electrolyte. In certain embodiments, the expanding material is an inflatable plastic balloon with a port for pumping in air, thus providing a compressive load on the anode active material once pumped with air. The plastic balloon may be composed of poly(ethylene), poly(propylene) or similar polymers that are flexible and résistant to dégradation in alkaline solution. FIG. 12 illustrâtes an example of an embodiment of an expanding material 1200 contained within a rigid iron electrode containment assembly 1202. The unexpanded State is illustrated in the left hand of FIG. 12 and the expanded State of the expanding material 1200 compressing the anode active material 1202 within the anode containment assembly 1202 is illustrated on the right-hand side of FIG. 12.

[00187] In another embodiment, the container for the iron electrode material is not rigid, but still conserves its volume or has a maximal volume to within a reasonable approximation over stress ranges below -10 MPa, as with some métal textiles - this may be termed a flexible cage. In such a case, an expandable material may be placed within the

1O flexible cage, and compression provided by the expansion of expandable material within the flexible cage. The expandable materials from above may be used, as well. The flexible cage may be conducting and serve as both a current collecter and as a means of providing compression to the iron electrode material with which it is filled.

[00188] In another embodiment, the iron electrode material may exhibit a substantial magnetic moment in the presence of a magnetic field. The iron electrode material may be ferromagnetic, as is the case for iron. Thus, a magnetic field set up by one or more permanent magnets or electromagnets may be used to induce a magnetic force on the iron electrode material toward a rigid wall, thereby providing a compressive load to the anode active material.

[00189] In another embodiment, pumps existing within the system, for instance, those intended to move electrolyte, are used to provide suction on the particulate bed. The suction provided by the pump pulls the particulate bed together, and the particulates into contact with one another. Particulates are prevented from being sucked into the pump by means of a screen or mesh with openings smaller than the smallest expected particulate.

[00190] In another aspect, phosphates (including iron phosphate), phosphoric acid, or similar phosphor-containing additives may be usefully incorporated into a particulate iron electrode material in order to promote mechanical contact and bonding between particulate materials. The phosphate groups may form phosphate bridges between the métal oxide groups, thereby cementîng the particulate materials of the electrode bed together, and forming an electrode that îs better mechanîcally and electrically connected. The oxides of irons may serve as useful conductors because several of them (especially magnetite and wüstîte) are semiconducting. In the case where the bonded oxides are electrochemically reduced to metallic species, such metallic specîes may electrochemically sînter or otherwise bond. Thus, the bonding of such oxides, even transiently may lead to enhanced electrochemical performance over many cycles. The electrode materials may be pre-treated with a phosphorus-containing solution before entering the electrolyte, or a phosphorus-containing compound may be introduced into the electrolyte for the purpose of forming such phosphate bonds. Phosphate bonds may occur across a variety of metal-oxide Systems including in cadmium, magnésium, aluminum, and zinc. Phosphate additives may be particularly bénéficiai in iron électrodes as they may reduce the tendency for hydrogen évolution at the îron surface during charging as well.

[00191] In some embodiments, one may desire to create a conductive path between the particles ofthe iron electrode material via metallurgically bonding the particles of the iron electrode material prior to insertion into the electrolyte. Such a metallurgical bond may lead to sufficient conduction through the iron electrode material that compression is not needed to achieve satisfactory electrochemical performance. Below, a variety of methods for eliminating the need for compression of the iron electrode material are described.

[00192] In one embodiment, the iron electrode materials are thermally assembied via a high température process including sintering or brazing. A thermal step for bonding the iron electrode material to a current collecter may decrease the contact résistance between particulate materials by fusing similar metals to one another for a more robust electrical connection. While sintering has been considered for the manufacturing of iron electrode materials, the sintering of some particulate iron materials has not been considered to date due to their unique particulate structure. In one example, direct reduced iron is an attractive feedstock for an iron electrode material, but due to its coarse particle size, it is not an obvious candidate for thermal bonding via a sintering process. Direct reduced iron may be used in a sintering process directly, or it may be used in combination with another bonding material at the surface of the direct reduced iron such that a suitable metallurgical bond is formed. The bonding material may be paînted, sprayed or otherwise introduced onto the direct reduced iron or other particulate îron material in order to permît it to bond to other direct reduced îron particles during a thermal treatment process. The bonding material may be usefully concentrated at the contact points between the direct reduced iron or other particulate material as a means of gaining the most electrical contact wîth the smallest added cost. An example of a bonding material îs a material wîth a low sintering température which may cause a metallurgical bond during a sintering process, such as a suspension of carbonyl iron that is painted or sprayed onto the direct reduced iron or other particulate material. In a second example, a bonding material may melt, or cause a fusion weld or braze upon exposure to heat. In a second example, a nickel brazing compound may be coated onto an îron electrode material, and the material may then be heated to the appropriate température for a metallurgîcal bond to form. The thermal bonding method is illustrated in FIG. 13. FIG. 13 illustrâtes that a plurality of métal pellets 1300 are provided on an anode current collector 1302. Heat is applied to the pellets 1300 and anode current collector 1302 resulting in the pellets 1300 being fused to the current collector as illustrated in FIG. 13.

[00193] A possible manufacturîng technique for a thermally bonded particulate bed system may feature a rolled sheet of Steel which may act as the furnace belt. This belt would unroll from a eoil and straighten to become a horizontally translating surface inside of a continuous hydrogen furnace. At the inlet ofthe furnace, iron electrode material (such as direct reduced iron) would accumulate on the belt via a hopper. This iron electrode material and belt sheet would travel through the furnace rising to a maximum température bonding the iron electrode material and the belt. This iron electrode material and current collector sheet could then be eut into small sections to be used as an anode in reactors.

[00194] In various embodiments, the particulate materials for iron électrodes achieve excellent contact with each other via création of’flats’ due to the stress concentration at a contact point. In some instances, the electrode material may not need to be held at high force 20 throughout life, but rather the particulate materials may be pressed against one another during fabrication, the fiat spots created, and then held with a smaller force throughout life. To accomplish this, an electrode cage may be supported during the high-load stress application to form the flats on the particulate materials and lower the inter-particle contact résistance. The force may then be partially reîeased, the cage may be removed from the support!ng 25 structure, and then the electrode cage may be put into the reactor under this lower compressive force, but with the contact résistance that was lowered due to the application of the higher compressive force, lf, at any point during life, the cage gets jumbled or the cell gets too résistive, the cage may be removed, put into the support!ng structure, recoinpressed, and the force could be released again, the cage could be put back into the cell.

[00195] In various embodiments, the solubi 1 îty of iron intermédiares in alkaline media may be utilized to form necks between particulate material in an iron electrode material comprising a packed bed. The iron electrode may be held at appropriate pH, température, and optionally voltage ranges such that the HFeOj' soluble intermediate may form in high enough concentrations that the bonds between particles within the packed bed grow due to solutionprécipitation reactions mediated by the soluble species, as shown in the diagram below, wherein the particles are referred to as marbles. The bond between the particles may be referred to as a neck. The formation of such necks may be a preprocessing step or may happen in-situ in an electrochemîcal cell for energy storage. The coarsening may form necks between pellets to enhance inter-pellet conductivity, reducing overpotential at the anode. In one aspect of neck formation, the process involves soaking the pellet bed in an alkaline solution for >3 days, such that the soluble species coarsens the bed at the micron to millimeter scale and enhances inter-pellet contact. In another embodiment, electrochemîcal

1O cyclîng îs employed to enhance déposition of the soluble intermediate species. In a third embodiment, the pellets are coated in iron powder, such as atomized or sponge iron powder, to promote the formation of necks and reduce contact résistance between DRI pellets. As cyclîng continues, the powder particles can sinter to the host DRI pellet. Mechanîstically this can occur due to the mass transfer of the soluble intermediate Fe specîes (HFeOs) favoring déposition of discharge product at the interfaces of small and large particles, for example as illustrated in FIG. 14. Specificaiîy, FIG. 14 illustrâtes that a bed 1400 of individual DRI pièces 1402 (e.g., DR! marbles) may be provided. An electrochemîcal and/or Chemical reaction may resuit in the bed 1400 being formed into a necked together bed 1405 of DRI pièces 1402 (e.g., marbles) joined together by necks 1406 therebetween. In this manner, the bed 1405 may be a solid mass of joined DRI pièces as opposed to the original starting bed 1400 of separate pièces.

[00196] In various embodiments, the particulate materials may be bonded by techniques common for the welding of metallic materials. In one aspect, the particulate materials may be résistance welded by passage of a high current through the packed bed. The 25 current may be applîed by a compacting relier assembly such that the particles are brought into contact prior to or concurrently with a résistance welding process. In various embodiments, the particles may be mechanically deformed at high température such that a metallurgical bond forms at the contact points between the particles. In one example, a hot briquetting machine for the hot briquetting or direct reduced iron may be run at low compacting pressures such that the particulate material deforms at the contact points to form metallurgical bonds. For particulate materials with internai porosity (such as direct reduced iron) compacting may take advantage of the stress concentration at the contact points between particles such that metallurgical bonds form between particles, but the internai porosity ofthe particulate material may be largely unchanged away from the contact points. In various embodiments, the création ofthe metallurgîcal bonds may take place in inert atmosphère to prevent oxidation of the iron electrode material. In various embodiments, the bed of particulate material may be ultrasonically Consolidated or Consolidated by other vibratory means. The ultrasonic or vibratory compaction may be accompanied by an axial pressure. In various embodiments, the particulate materials may be fusion welded together via any ofthe fusion welding techniques common in the art, including but not limited to tungsten inert gas welding, métal inert gas welding, and gas métal arc welding. In another aspect, the material may be explosively welded.

[00197] In various embodiments, a conducting metallic solder may be placed at the contact points between the particulate materials such that a metallic bond may be formed between the materials. In one example, tin or a may be dip coated onto a particulate material bed. In another example, copper may be dip coated onto the particulate material. In an additional embodiment, the conducting liquid is coated onto the particulate by means of passing both through a tube or nozzle and depositîng the coated particulate. Précisé control of the nozzle allows précision placement of individual particuîates, which may aid in achievîng optimized electrode geometries. Particuîates deposited in this manner may be stacked to produce three-dimensional structures.

[00198] In various embodiments, the particulate material may be etched via any one of 20 a variety of acids and subsequently mechanîcally deformed prior to insertion into an electrochemical cell. The etching action may remove any surface oxides impeding bonding, and may permit electrical contact between the anode materials. Acids such as hydrochloric acid, nitric acid, or any other as ides used to strip iron oxides off of metallic iron surfaces may be used. In some instances, the compression may be done while the particulate material is in 25 the acid.

[00199] In various embodiments, a particulate material for an iron electrode may comprise a direct reduced iron material. The direct reduced iron material may be fabricated without the cernent coating used to decrease sticking during the réduction processing. These cements may inhibit charge transfer across the interfaces between pellets. In such a manner, 30 the direct reduced iron materials may exhibit enhanced charge transfer properties for electrochemical cycling. In one example, a fluidized bed réduction process is used în order to enable the use of direct réduction iron materials which do not require cernent coatings.

[00200] In various embodiments, particulate material to comprise an iron electrode material may be compressed around a current collecter mesh. The current collecting mesh may then be heated (e.g. by electrical résistance) such that the chîcken wîre welds to the particulate material surrounding it. The pellets are then interconnected by the mesh, and may be welded to each other. The mesh may be comparatively thick and open, like a chicken-wîre fence material.

[00201] Pellet size and shape modification before battery assembly

[00202] During operation of the battery with a pellet bed electrode, intra-pellet mass and electronic transfer may be difficult due to the size of pellets, resulting in polarization that can reduce the energy efficiency of the battery via (1) Voltage drops on charge and discharge resulting in lower voltaîc efficiency and (2) Coulombic inefficiency due to insufficient compétition with the hydrogen évolution reaction during charge. As a resuit of insufficient charging, the spécifie capacity of résultant iron électrodes is also reduced. For example, in certain cases the polarization is dominated by mass transport of hydroxide ions through pellet pores from the outside of a pellet to iron reaction sites at the center of the pellet. In other cases, the polarization îs dominated by electronic transport through the intra-pellet network of iron material from an electrical point of contact on the outside of a pellet to the center of the pellet. Eîther of these sources of polarization may resuit in local electrochemical potential within the pellet that favors the hydrogen évolution reaction during charge more than the desired réduction reaction of iron oxide species, which reduces coulombic efficiency.

[00203] In one aspect, the size of the particulates may be chosen to promote better packing. For one non-limiting example, a bed may be comprised of 50% partîcles over 5 mm in diameter, 25% partîcles between 5 mm and 1 mm in diameter, and 25% partîcles under 1 mm diameter, in order for the smaller partîcles to fil 1 space between the îarger particles.

Particles of smaller sîzes than the native DRl size may be made from DRI by the methods detailed below. These particles may be added to their containment in a spécifie order in order to ensure optimal packing, for one non-limiting example, a layer of Iarger particles may first be added, followed by an addition of smaller particles to fil 1 spaces, followed by another layer of Iarger particles and another addition of smaller particles.

[00204] Size réduction of iron pellets before battery assembly is disclosed as a method of addressing one or more of the energy efficiency and spécifie capacity losses due to the size of the pellets. Reducing the size of pellets reduces the characteristic length of intra-pellet mass and electrical transport, which reduces polarization and may enhance one or more of energy efficiency and spécifie capacity.

[00205] Reducing the size of peilets by means of a comminutîon process, such as a jaw crusher (“crushing”) before assembling into a pellet bed has been shown to resuit in higher voltaic efficiency. However, the crushing of the peilets should resuit in both less partie le-to- particle contacts on a per-partîcle basis (irregular particles achieve fewer contacts than spherical particles), and more interface résistances per particle in a bed of a given thickness. Further, ‘rattlers,’ wherein a particle is not în electrical contact with its neighbors due to the géométrie packing of the bed are more likely for polydisperse, irregular shapes than for relatively monodisperse spheres. As a resuit, it is inferred that the gains in voltaic efficiency due to enhanced intra-pellet mass and electrical transport partially mask increases in électronic resistance-based voltage drops and a lack of electrically accessed material (and therefore lower capacity) due to an increased rattler fraction.

[00206] In certain embodiments, the size of peilets is reduced to half or less of its original size through crushing, which results in a réduction of the overpotentïal of the iron electrode by more than 10 mV (mV = millivolts = 10-3 V).

[00207] Crushing of the peilets could lead to substantial performance gains if a secondary conductive additive were to be added to the pellet bed to enhance one more of inter-pellet electrical conductivity or pellet-to-current-co Hector electrical conductivity. The 20 additive would increase conductivity by increasing the conductive surface area in contact with peilets, mitigatîng the added interface résistance in a pellet bed of crushed peilets. An additive is desired which does not inhibit mass transfer and results in substantially higher electrical conductivity of the bed. The optimal additive percolates at low volume fractions and is highly conductive.

[00208] In certain embodiments, the additive is one or more of carbon black or graphite that is added to the crushed pellet bed in greater than 1 % volume fraction, such that the carbon black or graphite bridges crushed peilets together. In certain other embodiments, activated carbon or biochar or low to modest conductivity is used as a low-cost alternative to graphite.

[00209] In certain embodiments, the additives are pièces of conductive mesh such as stainless Steel wire mesh.

[00210] In certain embodiments, the additives are conductive rods such as stainless Steel rods of a diameter less than the average peliet size.

[00211] Before nominal operation of the battery, additives that improve iron electrode performance may be Chemically incorporated into the iron electrode via various processes that rely on intra-pellet mass transport of Chemical species in an electrolyte to active iron sites within the porous structure of the peliet. Homogeneous perméation of the additives into the pellets is often necessary to achieve the maximum desired performance-enhancing effect of the additive. However, ît îs often difficult to get homogeneous perméation of certain liquidsoluble and solid-state additives into pellets that are typically output from direct réduction processes, especially for those additives with low solubîlity that react with the direct reduced iron.

[00212] Size réduction of iron pellets before battery assembly is disclosed as a method of achieving more homogenous perméation of liquid-soluble and solid-state additives into the pellets during the additive incorporation process. Reducing the size of pellets reduces the 15 characteristic length of intra-pellet mass transport, which reduces gradients in concentration of the additive, thus enabling a more homogeneous perméation and incorporation of the additive into the electrode.

[00213] In certain embodiments, the additive incorporation process is one or more of soaking in an electrolyte, electrochemical platîng, and electrochemical cycling.

[00214] In certain embodiments, the additive is an initially liquid-soluble hydrogen évolution inhibitor that incorporâtes into the solid-state electrode via an electrochemical or spontaneous Chemical reaction.

[00215] In certain embodiments, the additive is an initially solid-state hydrogen évolution inhibitor that is further incorporated into the solid-state electrode via an electrochemical or Chemical dissolution-reprecipitation reaction.

[00216] In certain embodiments, additives include one or more of 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, magnésium oxide, sodium chlorate, sodium 30 nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, ammonium thiosulfate, lithopone, magnésium sulfate, îron(III) acetylacetonate, hydroquinone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid.

dimethyl phthalate, methyl méthacrylate, methyl pentynol, adipic acid, allyl urea, citric acid, thiomalîc acid, N-(2-aminoethyl)-3-aminopropyl trimethoxysilane, propylene glycol, trimethoxysîlyl propyl diethylene, amînopropyl trimethoxysilane, dimethyl acetylenedicarboxylate (DMAD), 1,3-diethylthîourea, Ν,Ν’-diethylthiourea, aminomethyl 5 propanol, methyl butynol, amino modified organosilane, succinic acid, isopropanolamine, phenoxyethanol, dipropylene glycol, benzoic acid, N-(2-aminoethyl)-3-amînopropyl, behenamïde, 2-phosphonobutane trîcarboxylîc, mipa borate, 3methacryloxypropyltrimethoxysilane, 2-ethylhexoic acid, isobutyl alcohol, t-butylaminoethyl méthacrylate, diisopropanolamine, propylene glycol n-propyl ether, sodium benzotrîazolate, 1O pentasodium aminotrimethylene phosphonate, sodium cocoyl sarcosinate, laurylpyridinium chioride, steartrimonium chioride, stearalkonium chioride, calcium montanate, quaternium-18 chioride, sodium hexametaphosphate, dicyclohexylainine nitrite, lead stéarate, calcium dinonylnaphthalene sulfonate, iron(II) sulfide, sodium bisulfide, pyrite, sodium nitrite, complex alkyl phosphate ester (e.g. RHODAFAC® RA 600 Emulsifier), 4-mercaptobenzioc 15 acid, ethylenediaminetetraacetic acid, ethylenedîaminetetraacetate (EDTA), 1,3propylenediaminetetraacetate (PDTA), nitrilotriacetate (NTA), ethylenedîaminedisuccinate (EDDS), dîethylenetriaminepentaacetate (DTPA), and other aininopoiycarboxylates (APCs), diethylenetriaminepentaacetic acid, 2-methylbenzenethiol, I-octanethiol, bismuth sulfide, bismuth oxide, antimony(III) sulfide, antîmony(III) oxide, antimony(V) oxide, bismuth selenîde, antimony selenîde, sélénium sulfide, selenium(IV) oxide, propargyl alcohol, 5hexyn-l-ol, l-hexyn-3-ol, N-allyithiourea, thîourea, 4-methyicatechol, trans-cinnamaldehyde, Iran(III) sulfide, calcium nitrate, hydroxy lamines, benzotriazole, furfury lamine, quinoline, tin(II) chioride, ascorbic acid, tetraethylammonium hydroxide, calcium carbonate, magnésium carbonate, antimony dialkylphosphorodithioate, potassium stannate, sodium stannate, tannîc acid, gelatin, saponin, agar, 8-hydroxyquinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrotreated light Petroleum oil, heavy naphthenic petroleum oil (e.g. sold as Rustlick® 631 ), antimony sulfate, antimony acetate, bismuth acetate, hydrogen-treated heavy naphtha (e.g. sold as WD-40®), tétraméthylammonium hydroxide, NaSb tartrate, urea, D-glucose, C6Na2O6, antimony potassium tartrate, hydrazine sulfate, silica gel, triethylamine, potassium antimonate trihydrate, sodium hydroxide, l,3-dî-o-tolyl-2-thiourea, l,2-diethyl-2-thiourea, 1,2diisopropyl-2-thiourea, N-phenylthiourea, Ν,Ν'-diphenylthiourea, sodium antimonyl Ltartrate, rhodîzonic acid disodium sait, sodium selenîde, potassium sulfide, and combinations thereof.

[00217] FIG. i 5 illustrâtes example pellet beds 1501 and 1502 according to varions embodiments. During operation of the battery with a pellet bed electrode, mass and électronic transfer through the pellet bed may be difficult due to the total thickness of the pellet bed, resultîng in polarization that can reduce the energy efficiency of the battery via ( 1 ) 5 voltage drops on charge and discharge resultîng in lower voltaic efficiency and (2) coulombîc inefficiency due to insuffle ient compétition with the hydrogen évolution reaction during charge. As a resuit of insufficient charging, the spécifie capacity of résultant iron électrodes is also reduced. For example, in certain cases the polarization is partially due to mass transport of hydroxide ions from outside of the pellet bed to the center of the pellet bed. In other cases, 10 the polarization is partially due to électronic transport through the network of iron pellets.

Either of these sources of polarization may resuit in local electrochemical potential within the pellet that favors the hydrogen évolution reaction during charge more than the desired réduction reaction of iron oxide species, which reduces coulombîc efficiency.

[00218] Increasing the volumétrie packing density of pellets is one way to address one 15 or more of the energy efficiency and spécifie capacity losses due to the total thickness of the pellet bed. By increasing the volumétrie packing density, the thickness ofthe pellet bed for a given electrode capacity decreases, thereby reducing through-bed polarization and enhancing one or more of energy efficiency or spécifie capacity. For example, FIG. 15 illustrâtes a pellet bed 1501 with porous pellets 1503 that are formed as spheres or marbles and pellet bed 20 1502 with porous pellet pièces 1505 that may be formed by crushing spheres, marbles, or other shapes into pièces. The intra-pellet transport length tl of the pellet bed 1501 may be greater than the intra-pellet piece length t2 ofthe pellet bed 1502.

[00219] Processing the pellets by means of a jaw crusher (“crushing”) before assembling into a pellet bed is disclosed as a method to increase volumétrie packing density 25 and reduce polarization. In this manner, the crushing may resuit in a pellet bed 1502 rather than the pellet bed 1501. Before crushing, the pellets may be roughly spherical and may hâve a narrow size range. The crushing operation may break the pellets into multiple pièces with non-spherical shapes and a broader sîze distribution that resuit in a higher volumétrie packing density. The resultîng higher volumétrie packing density reduces the thickness of the pellet 30 bed for a fixed projected area and mass of electrode material, thus reducing through-bed polarization and enhancing one or more of energy efficiency or spécifie capacity (for example when comparing peilet bed 1502 to pellet bed 1501 such that pellet bed 1502 has reduced through-bed polarization and enhanced one or more of energy efficiency or spécifie capacity in comparison to pellet bed 1502 when the material composition of the porous pellets 1503 and porous pellet pièces 1505 may be the same). FIG. 16 illustrâtes the pellet beds 1501 and 1502 with current collectors 1601 attached. The height ofthe pellet bed 1501 without crushing, h I, may be greater than the height, h2, of the pellet bed with crushing 1502 5 even though the same amount of pellet material may be présent in pellet bed 1501 and 1502.

As such, crushing may compact the size of the electrode.

[00220] In certain embodiments, the pellets after a crushing operation break into pièces with jagged edges and with a polydisperse size distribution such that smaller pièces fail within the interstices between larger pellets, thus increasing packing density.

[00221 ] Methods of regain in g performance after performance decay

[00222] Certain performance attributes of a pellet bed electrode may worsen due to time-dependent or charge-throughput dépendent mechanisms during battery operation. Performance attributes that worsen may include but are not limited to spécifie capacity (mAh/g), electrode overpotential (mV), se if-discharge rate (mAh/mo.), and coulombic 15 efficiency (%). Several methods of regaîning iron electrode performance by treatments to the battery after beginning of life are disclosed here.

[00223] In certain cases, the spécifie capacity of the electrode may decrease with battery cyclîng because of a cycle-dependent change in microstructure of the electrode that hinders mass or electronic transport, thereby reducing the accessible capacity at a given 20 polarization. More specifically, pores within the pellets may become increasingly constricted with cycling as they are filled with remnant electrochemical discharge products that hâve a larger molar volume (per mol iron) than metallic iron. The progressive pore filling results in a hindered mass transport to the iron within those pores, which may render the iron within pores less and less accessible for the electrochemical reaction to occur, which reduces spécifie capacity. In other cases, the electrical résistance to certain iron sites may increase because of a constriction of the conductive pathways provided by the metallic network within a pellet. In other cases, there may be a core of unreacted metallic iron within each pellet that is completely covered by a passivating layer.

[00224] The loss of accessible capacity due to battery use may be regained by ex-situ 30 treatments that are performed on the pellets after the electrode capacity has decayed to a minimum threshold. Varions embodiments include processing the used pellets with mechanical, Chemical, electrochemical, and/or thermal processes before re-introducing the pellets into the electrochemical cell (i.e., processing the pellets ex-situ) to return the electrode to a state with better Chemical and physical properties. Better Chemical and physical properties may include higher content of désirable impurities (e.g., hydrogen évolution reaction (HER) suppressants), lower content of undesîrable impurities (e.g., HER catalysts), 5 higher spécifie surface area, higher total porosity, different pore size distribution (e.g.

multimodal to reduce mass transport résistance), different pellet size distribution (e.g. multimodal to enhance bed packing), different aspect ratio (e.g. to enhance bed packing), etc. Mechanical processes that may be applied to the pellets ex-situ may include crushing, pulverizing, and/or powderizing that include but are not limited to size réduction. A mechanical size réduction re-exposes passivated metallîc iron at the core of pellets, which makes the previously inaccessible iron accessible, thus increasing capacity. Note that mechanical processes that expose initially passivated iron at the core of pellets may not be désirable to be donc before battery use, because more exposed metallîc iron provides more sites at which the hydrogen évolution réaction might occur, either via the Faradaic parasitic reaction during charging, or via the spontaneous self-discharge reaction. However, mechanical processes done ex-situ may be désirable as a method to regain and/or improve capacity electrical résistance that hâve decayed due to battery usage, at which point a larger fraction of iron is passivated and inaccessible as illustrated for example în FIG. 17.

Specifically, FIG. 17 shows a pellet 1702 after battery usage that is processed ex-situ, such as by crushing, pulverizing, etc., to expose the iron core 1703 in the pellet 1702. FIG. 17 shows the passivation layer 1705 which may make the core 1703 inaccessible until after processing.

[00225] Thermal processes that may be applied to the pellets ex-situ may include processing the pellets in at elevated température in reducing (e.g., hydrogen), oxidizing, and/or carburizing (e.g., carbon monoxide and/or carbon dioxide) atmosphère. In certain 25 embodiments, the reducing condition is a gas mixture is 10% nitrogen, 30% carbon monoxide, 15% carbon dioxide, and 45% hydrogen at 800°C for 90 minutes. Electrochemical processes that may be applied to the pellets ex-situ may include reverse electroplating, electrochemical dissolution, etc. Chemical processes that may be applied to the pellets ex-situ may include acid etching, etc. In various embodiments, to increase accessible capacity of the pellets during the discharge reaction, the pellets may be pretreated by soaking in an acid bath (e.g., concentrated HCI) that will etch the iron and enlarge pores in the pellets, increasing the total porosity ofthe pellets in comparison to used pellets. In various embodiments, to increase the accessible capacity ofthe pellets during the discharge reaction, the pellets may be pretreated by soaking in a neutral or slightly basic bath that removes excess discharge product from the electrode. For example, one ofthe expected discharge products, iron (H) hydroxide, is typically unstable at pH < 8. By soaking in a bath at pH < 8, the iron (II) hydroxide is preferentially removed while the metallic iron îs preserved in the electrode. In the pH range pH > 7 and pH < 8, the bath may be a diluted form of the electrolyte used during electrochemical operation ofthe battery. After pretreatment, the etched and now more porous pellets may be re-assembled into the négative electrode. The Chemical process time may be optimized to increase the usable capacity of the pellets, without losing too much active material to the acid etching solution. Any ofthe aforementioned processes may be optimized

1O to preferentially make small pores in the pellets larger. In certain embodiments, an electrochemical process utilizes one or more large current puises that resuit in a non-uniform current distribution within the pellet such that current is concentrated at sharp and small physical features within the pellet, which preferentially drives the electrochemical dissolution at small physical features and thus makes initially small pores larger. Any of the above processes may also be doue before battery operation to make the Chemical and physical properties of the pellets better relative to their unmodified, unused State.

[00226] Electrolyte additîves for controlling discharge product morphology

[00227] The shape and size of discharge product within the pores of the iron pellets can affect performance in a variety of ways. For example, a thin, unifonn layer of discharge 20 product may avoîd clogging pores, which may improve capacity rétention. On the other hand, a thin unifonn layer of discharge product that îs not porous may passivate underlying metallic iron such that mass transport of hydroxide ions through the discharge product layer during discharge becomes hindered, thus reducing accessible capacity of the electrode. In another example, an uneven, high-surface-area, porous discharge product may facilitate mass transport through the discharge layer while inereasing the active surface area for the next discharge, both of which may increase total accessible capacity. FIG. 18 compares discharge product distributions. The left side of FIG. 18 shows discharge product 1803 unevenly distributed on a surface of an anode 1802. The right side of FIG. 18 shows discharge product 1804 in an even layer on the surface of the anode 1802. The discharge product formation 30 may be mediated by the electrolyte additîves, anode additîves, and/or surface coatings of the anode 1802. Various methods of controlling discharge product morphology in iron électrodes are disclosed.

[00228] Addîtives and counterions in the electrolyte and/or in the electrode may be used to control the discharge product morphology. Addîtives and counterions may change the porosity of the discharge layer and accessibîlity electrochemically active sites by way of the following mechanism: Fe forms atwo-layer discharge product with a relatively static inner layer of Fe₃Û4 and a very porous outer layer, which is affected strongly by electrolyte composition. Bivalent cations tend to înhibit uniform discharge and help produce a more porous outer layer. Monovalent cations înhibit uniform discharge and produce a more porous outer layer when they are not well-matched in size with the Fe cations in the outer layer of discharge product. For example, lithium and césium cations tend to produce a more porous outer layer than sodium and potassium cations because lithium and césium are less matched in size with the îron cation. Addîtives and counterions to control discharge product morphology include but are not limited to sulfide (S₂-), hydrosulfide (HS-), lithium cation (Li+), sodium cation (Na+), calcium cation (Ca₂+), selenîde (Se₂-), césium cation (Cs+), and barium cation (Ba₂+). In certain embodiments, sodium sulfide, lithium hydroxide, sodium hydroxide, calcium hydroxide, sodium selenide, and/or barium hydroxide are added into the electrolyte at various concentrations to provide the soluble addîtives and counterions that act to control discharge product morphology.

[00229] In certain embodiments, the addîtives to control discharge product morphology are initially contaîned within the solid-state electrode. The solid-state addîtives 20 may be in the form of solid-state métal oxides and/or métal sulfides introduced as solids to an iron electrode. Métal sulfides and oxides of interest include: FeS, FeS₂, MnS, Bi₂S₃, Bi₂O₃, Sb₂S₃, FeAsS, PbS, SnS, HgS, AsS, Pb4FeSbôSi₄, Pb3Sn₄FeSb₂Si4, SeS₂, among others.

[00230] In certain embodiments, addîtives to control discharge product morphology include one or more of 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, magnésium oxide, sodium chlorate, sodium nitrate, sodium acetate, iron phosphate, phosphoric acid, sodium phosphate, ammonium sulfate, ammonium thiosulfate, lithopone, magnésium sulfate, iron(III) acetylacetonate, hydroquînone monomethyl ether, sodium metavanadate, sodium chromate, glutaric acid, dimethyl phthalate, methyl méthacrylate, methyl pentynol, adipic acid, allyl urea, citric acid, thiomalic acid, N-(2-aminoethyl)-3amînopropyl trîmethoxysilane, propylene glycol, trimethoxysilyl propyl diethylene, aminopropyl trîmethoxysilane, dimethyl acetylenedicarboxylate (DMAD), 1,3 diethylthiourea, Ν,Ν’-diethylthîourea, aminomethyl propanol, methyl butynol, amino modified organosîlane, succinic acid, isopropanolamine, phenoxyethanol, dipropylene glycol, benzoic acid, N-(2-aminoethyl)-3-aminopropyl, behenamide, 2-phosphonobutane tricarboxylic, mipa borate, 3-methacryloxypropyltrimethoxysilane, 2-ethylhexoic acid, isobutyl alcohol, t-butylaminoethyl méthacrylate, dî isopropanolamine, propylene glycol npropyl ether, sodium benzotriazolate, pentasodium aminotrimethylene phosphonate, sodium cocoyl sarcosinate, laurylpyridintum chloride, steartrimonium chloride, stearalkonium chloride, calcium montanate, quatemium-18 chloride, sodium hexametaphosphate, dicyclohexylamine nitrite, lead stéarate, calcium dinonylnaphthalene sulfonate, îron(II) sulfide, sodium bisulfide, pyrite, sodium nitrite, complex alkyl phosphate ester (e.g. RHODAFAC® RA 600 Emulsifier), 4-mercaptobenzîoc acid, ethylenediaminetetraacetic acid, ethylenediamînetetraacetate (EDTA), 1,3-propylenediaminetetraacetate (PDTA), nitrilotriacetate (NTA), ethylenediamînedisuccinate (EDDS), diethylenetrîaminepentaacetate (DTPA), and other aminopolycarboxylates (APCs), diethylenetriaminepentaacetic acid, 2- methylbenzenethiol, 1-octanethiol, bismuth sulfide, bismuth oxide, antimony(III) sulfide, antimony(III) oxide, antimony(V) oxide, bismuth selenide, antîmony selenide, sélénium sulfide, selenium(IV) oxide, propargyl alcohol, 5-hexyn-l-ol, l-hexyn-3-ol, N-allylthiourea, thiourea, 4-methylcatechol, trans-cinnamaldehyde, Iron(lll) sulfide, calcium nitrate, hydroxylamines, benzotriazole, furfurylamine, quinoline, tin(II) chloride, ascorbic acid, tetraethylammonium hydroxide, calcium carbonate, magnésium carbonate, antimony dialkylphosphorodithioate, potassium stannate, sodium stannate, tannîc acid, gelatîn, saponin, agar, 8-hydroxy quinoline, bismuth stannate, potassium gluconate, lithium molybdenum oxide, potassium molybdenum oxide, hydrotreated light petroleum oil, heavy naphthenic Petroleum oil (e.g. sold as Rustlick® 631), antimony sulfate, antimony acetate, bismuth acetate, hydrogen-treated heavy naphtha (e.g. sold as WD-40®), tétraméthylammonium hydroxide, NaSb tartrate, urea, D-glucose, C6Na2O6, antimony potassium tartrate, hydrazîne sulfate, silica gel, triethylamine, potassium antimonate trîhydrate, sodium hydroxide, 1,3-dio-tolyl-2-thiourea, 1,2-diethy 1-2-thiourea, l,2-diisopropyl-2-thîourea, N-phenylthiourea, N.N'-diphenylthîourea, sodium antimonyl L-tartrate, rhodizonic acid disodium sait, sodium selenide, potassium sulfide, and combinations thereof

[00231 ] A pretreatment involving electrochemical cycling may also serve to control the morphology of discharge products for an iron electrode. For example, the inventors hâve observed that the compactness of the discharge product changes with température and current

6o density. A pretreatment involving electrochemical cycling at a température and current density that is not necessarily the nominal operating condition ofthe battery may be used to form a discharge product morphology that is conducîve to high accessible capacity, and is sustained when the operating conditions are set to nominal values after the pretreatment. In various embodiments, the pretreatment consists of deep electrochemical charge and discharge cycling at 10°C at a gravimétrie current density of 25 mA/gFe for 100 cycles.

[00232] Using température as a means of improving performance

[00233] The inventors hâve found that decreasing the operating température of the iron electrode to below 30°C improves various performance attributes, such as spécifie capacity, io the rétention of spécifie capacity over many electrochemical cycles, and Coulombic efficiency of the electrode. Various mechanisms may be at play simultaneously to resuit in these effects. For example, spécifie capacity may be improved at lower températures due to an increase in electrical conductivity of the electrode material, including but not limited to iron and iron oxide discharge products. The increase in electrical conductivity of the electrode material would enhance electrical transport to electrochemical reaction sites, which would resuit in an increase in spécifie capacity at a given polarization limit of the electrode. In another example, reducing température may slow the kinetics of undesErable electrolyte dégradation or poisoning reactions that take place during the lifetime of the battery, such as carbonate formation due to carbon dioxide from the atmosphère. For example, carbonate formation consumes OH- ions, decreasing the conductivity ofthe electrolyte, which decreases the pH of the solution and leads to a decrease in spécifie capacity. Decreasing the température slows these undesirable reactions and resuit în better spécifie capacity rétention at the iron electrode over the lifetime of the battery. In another example, the decrease in température may slow the kinetics ofthe undesirable hydrogen évolution reaction more so than the desired iron réduction reaction during charging ofthe battery, thus resulting în a higher coulombic efficiency during charging. In various embodiments, the iron electrode is maintained at 20°C ± 5°C to improve electrode performance. In other embodiments, the iron electrode is maintained at IO°C ± 5°C to improve electrode performance. FIG. 19 is a température plot of spécifie capacity and Coulombic efficiency versus cycle number. .

[00234] Redox medîator to improve performance

[00235] Better electrochemical kinetics of the charging (réduction) and discharging (oxidation) reactions at the iron-based electrode would improve both voltaic efficiency and

6ι coulombic efficiency of the cell. A redox mediator can be used to improve the electrochemical kînetics of the iron-based electrode. A redox mediator is a Chemical compound that acts as an électron “shuttle” to médiate a réduction or oxidatîon reaction. Though typically used in the field of biocatalysis, redox mediators can also be used to facilitate the desired oxidatîon and réduction reactions at the iron-based electrode. Requirements of the redox mediator include (1) fast and réversible redox kînetics; (2) similar redox potential to that of the reaction it facilitâtes (including but not limited to Fe ;2Fe(OH)2 and/or Fe(OH)₂-Fe3O₄); (3) stable in the presence of the electrolyte of interest. The redox mediator can be either soluble or insoluble in the electrolyte of interest. In some to embodiments, the redox mediator contains one or more unsaturated base groups, saturated base groups, or combinations thereof. In some embodiments, the base groups contain électron-wîthdrawîng functional groups, electron-donatîng functîonal groups, or combinations thereof. In certain embodiments, the unsaturated base groups include but are not limited to cyclopenta-1,3-dîene, benzene, IH-pyrrole, pyridine, pyrazine, furan, 4H15 pyran, 1,4-dioxine, thiophene, 4H-thiopyran, 1,4-dithiine, 1-methyl-lH-pyrrole, or combinations thereof. In certain embodiments, the saturated base groups include but are not limited to cyclopentane, cyclohexane, 1,4-dioxane, tetrahydrofuran, tetrahydro-2H-pyran, i ,4-dithiane, tetrahydrothîophene, tetrahydro-2H-thiopyran, 1,4-dimethylpiperazine, 1,3,5troxane, 1,3,5-trithiane, or combinations thereof. In certain embodiments, the electron20 wîthdrawîng functional groups include but are not limited to nitro, trîchloro, cyano, carboxyl, fluoro, hydroxyl, or combinations thereof. In certain embodiments, the electron-donatîng functional groups include but are not limited to primary amîne, secondary amine, tertiary amine, amîde, methoxy, methyl, alkyl, alkenyl, alkynyl, phenyl, or combinations thereof. In one embodiment, the redox mediator for the iron-based négative electrode are vîologen-based compounds. In certain embodiments, the viologen-based compounds include but are not limited to methyl viologen, propyl viologen, hexyi viologen, octyl vîologen or combinations thereof.

[00236] Sulfide incorporation to the iron electrode via electrolyte

[00237] In an electrochemical cell wîth an iron electrode, sulfur addition to the cell unlocks utilizatîon of the iron electrode. However, sulfur is a known catalyst poison, so in electrochemical cell embodiment with a catalyst positive electrode, it may be optimal for the sulfur concentration around the iron electrode is high, while sulfur concentration at the catalyst electrode is low.

[00238] In one embodiment, sulfur may be concentrated at the iron electrode by submerging the iron electrode in a highly concentrated sulfur solution before it enters the electrochemical cell. Furthermore, if the iron electrode undergoes a single formation cycle of charge, then discharge, sulfur will be electrochemically added to the structure of the iron electrode. Then upon addition to the desired electrochemical cell it will remain concentrated near the anode.

[00239] In certain embodiments, the iron electrode is soaked in an electrolyte with a high sulfide concentration (i.e., >50 mM) prior to cycling in an electrolyte with a lower sulfîde concentration (ie 50 mM).

[00240] In certain embodiments, the porous iron electrode is soaked in an electrolyte bath with any alkali or transition métal sulfide (Na₂S, K₂S, Bi₂Ss, SbSj, etc.) to increase the presence of sulfîde.

[00241] In certain embodiments, sulfide is încorporated through a high sulfide concentration electrolyte soak prior to cycling, after which the positive electrodes are inserted into the full cell wherein the initial sulfide concentration can be in the range of 10-250 mM (1.4-33.8 mgS/gFe) or higher.

[00242] In one non-limiting example, the porous iron electrode described above comprises a bed of DRI pellets.

[00243] Unîform or controlled incorporation of sulfide or other bénéficiai additives into a porous iron electrode is difficult. One method to uniformly încorporate additives into a porous material is vacuum infiltration, where a substrate is exposed to vacuum (<1 atm) to evacuate the pores and then exposed to a liquid or molten addîtîve to infill any vacancies in the material.

[00244] In various embodiments, a substrate is exposed to vacuum sufficient to evacuate pores. FIG. 20 illustrâtes one example method of evacuating pores. The substrate 2000 is în a first step exposed to a hîgh vacuum to empty the pores 2001.

[00245] In one embodiment, the evacuated substrate is then exposed in a second step to an aqueous electrolyte formulation containing additives as specified previously at températures between 0 and 250°C resulting in pores fully or partially filled with additive 2002. After specified tîme, such as less than 48 hours, the substrate 2000 may be rinsed or centrifuged to remove excess electrolyte in a third step.

[00246] In one embodiment, the evacuated substrate is then exposed to a liquid or molten form of additive, where additives are those specified previously in section ## that someone skilled in the art could îdentify as being compatible with melt processes (e.g.

octanethiol, FeS), at températures between 25 to 250°C or 250 and 2000°C. After a specified 5 time less than 48 hours, substrate may be rinsed or centrifuged to remove excess liquid or molten material.

[00247] In one embodiment, the evacuated substrate is then exposed to a gaseous additive (e.g. H₂S, H₂Se, CS₂ above 50°C, PH3). After a specified tîme, such as less than 48 hours, substrate may be purged with an inert gas or under vacuum to remove excess of the 10 gaseous additive.

[00248] In a non-limiting example, a solution containing sodium sulfide is vacuum intîltrated into the pores of a porous iron electrode 2000 prior to cyclîng to improve the pénétration. Better pénétration of sulfide into the anode may improve overal! performance capacity.

[00249] In a non-limiting example, sodium thiosulfate îs heated until melted (>45°C) and vacuum infiltrated into the pores of a porous iron electrode prior to cycling.

[00250] Additional methods to localize the sulfide to the iron particulate material electrode include sequestering the sulfide additive in a holder of variable permeability within or adjacent to the electrode. In this way, controlled amounts of sulfide could be added to the 20 iron particulate electrode through passive or active electrochemical or Chemical dissolution.

[00251] In one embodiment, the additive may be contained in a fully or semipermeable holder, where the holder is made of a plastic stable in an alkaline solution (e.g., polypropylene, polyethylene).

[00252] In one embodiment, the additive may be contained in the holder behind an îon25 sélective membrane, which permits flow of electrolyte into the holder and the slow diffusion of additive into solution.

[00253] In one embodiment, the additive may be contained in an electricaliy conductive material (e.g., conducting polymer mesh, metallic wîre mesh).

[00254] In one embodiment, the holder may be made of a Iayer of porous oxide (e.g. 30 silica).

[00255] In one embodiment, the additive hoider may be in physical, electrical, or physîcal and electrical contact with the iron particulate material electrode.

[00256] In one embodiment, the additive hoider may be in contact with the electrolyte and only in contact with the iron particulate material electrode through ionic transport in the 5 electrolyte.

[00257] In one embodiment, the additive hoider may be submerged in a separate container of electrolyte to provide a constant source of sulfide. The electrolyte in contact with the iron particulate material electrode is then replaced with the electrolyte in contact with the additive hoider.

[00258] In one embodiment, the additive hoider may be in electrical contact with a potentiostat or system, which maintains the hoider at potentials that prevent the dissolution of the additive in the hoider. FIG. 21 illustrâtes example additive hoider configurations. In the configuration shown in the top portion of FIG. 21, the bag containing additive 2104 may be in contact with the iron particulate material 2103 disposed in the electrolyte 2100 between the current collectors 2102 along with the iron particulate material 2103. In the configuration shown in the bottom portion of FIG. 21, the bag containing additive 2104 may be suspended in the electrolyte 2100 separated from the iron particulate material 2103 and current collecter 2102, such as by an optional electrical connection 2110.

[00259] Solid sulfur containing additives

[00260] Sulfide ions in the electrolyte solution hâve been proven to increase accessible capacity and cyclability of iron électrodes in alkaline secondary batteries. Sulfide ions, however, hâve been shown to reduce in concentration in the electrolyte due to ageing with cycle number and time, which may reduce the positive impacts of the dissolved sulfide on anode performance. One method to enable improved performance throughout lifetime is to incorporate sulfur containing species directly into the iron electrode material.

[00261] In one embodiment, elemental sulfur is introduced directly into porous iron anodes by melt diffusing the sulfur into the porous métal. The sulfur will then be introduced to the anode as a solid and be in intimate contact with the active métal anode material, promoting positive interactions that improve accessible capacity and cycle life.

[00262] In another embodiment, métal sulfides are introduced as solîds to an iron anode. Métal sulfides of interest include: FeS, FeS₂, MnS, BÎ₂S3, Sb₂S₃, FeAsS, PbS, SnS, HgS, AsS, Pb4FeSbôSi4, PbjSruFeSbsSu, SeS₂, among others. The cation in the métal sulfide may contribute to the battery's capacity (i.e., Fe), be inert to the charge/discharge reaction (i.e., Mn), or retard the hydrogen évolution reaction (i.e., Pb, Sb, Hg, As, Bi).

[00263] In one non-limîting example, the métal sulfides are incorporated into a bed of direct reduced iron (DRI) pellets.

[00264] Methods for incorporation of sulfur contaîning species into iron électrodes include, but are not limited to: (1) Incorporation of bulk solid particles, powders, or agglomérâtes into voids between material in the electrode bed; (2) Incorporation via melt diffusion into the electrode pores for métal sulfides with melting points below the melting point of iron métal (i.e., BiiSs); (3) Incorporation of métal sulfide powders by mixing into oxîdized ore pellets (i.e., taconite pellets) during the pelletization process (In such an embodiment, the métal sulfide would remain in the pellet through the réduction process, producing a pellet with metallic iron, métal sulfide, and impurities.); (4) Incorporation of métal sulfides into pellets contaîning only the métal sulfide and a binder. In one non-binding example, these pellets could be directly incorporated into a pellet bed of DRI in a spécifie ratio with DRI pellets; and (5) Incorporation of meta! sulfide powder using a mixing, milling, or rolling apparatus, such as a bail mill.

[00265] In another embodiment, the above-mentioned incorporation methods are used with sulfur contaîning additives including, but not limited to, métal sulfides.

[00266] In another embodiment, sulfur contaîning additives including, but not limited 20 to, métal sulfides, are incorporated into the iron anode material via the Trommel screening process step of DRI production, such as illustrated in FIG. 22 in which DRI pellets 2200 in a mesh cylinder are infused with sulfur additives during production to resuit in DRI with sulfur additive pellets 2202.

[00267] Incorporation of sulfide or other anionic species into an Fe anode

[00268] Uniform or controiled incorporation of additives into a preformed métal electrode îs diffïcult and limits effectiveness of additives.

[00269] Various embodiments include sélective précipitation with reactive counterions. In various embodiments, a métal is incorporated into the particulate iron material electrode în the neutral or oxîdized State and subsequently reacted with a counterion 30 of choice. The concentration of the meta! additive is determined by the solubility of the source compound or final desired concentration of the reactive counterion în the electrode. In certain embodiments, this electrode is exposed to an electrolyte contaîning a source of a reactive counterion (e.g. Na₂S, K₂S, Na₂Se, Na₂Te) to form a compound (e.g. CdS, Bi₂S_3s

Bi₂Se₃) in situ where the localization and concentration may be determined by the presence, concentration, and solubi 1 ity of the additive métal, reactive counterion, or resulting compound. In certain embodiments, accessibility of these additives may be further adjusted by use of fugitive pore-formers. In certain embodiments this electrode is cycled electrochemically before or after exposure to an electrolyte containing the reactive counterion in a specified concentration to control the uptake ofthe reactive counterion.

[00270] fn a non-binding example, 0.5 to 10 wt% Bi₂O₃ îs incorporated into the electrode before being cycled electrochemically to potentials sufficiently reducing to form Bi(s). Exposure to an electrolyte containing 250mM Na₂S may form Bi₂S3 distributed throughout the electrode in the reactions shown below;

Bi₂O₃ + 3 H₂O 2 Bi (s) + 6 OH2 Bi(s) + 3 S₂--> B12S3 .

[00271] In various embodiments, an additive of interest that is a source of sulfur, sélénium, tellurium, nitrogen, or phosphorus (e.g. Na₂S, Na₂Se, Na₃PO₄) is incorporated into the electrode at a concentration determined by the solubility oi the source compound or final desired concentration of the final compound in the electrode.

[00272] In certain embodiments, this electrode is exposed to an electrolyte containing a source of a reactive métal (e.g. Fe, Bi, Hg, As, Cd, Cu, Ni, In, Tl, Zn, Mn, Ag) or metalcontaining ion (e.g., Bi(NO₃)₃, NaAsO₄, Cd(NO₃)₂, CuSO₄-xH₂O (where x = 0 to 12)) to form a compound (e.g. CdS, Bi₂S₃, Bi₂Se₃) in situ where the localization and concentration may be determined by the presence, concentration, and solubility of the additive métal, reactive counterion, or resulting compound. The solubility of the non-metallie additive may allow for the création of local concentration gradients în the electrolyte, leading to régions where précipitation is more favored. In certain embodiments, accessibility of these additives may be further adjusted by use of fugitive pore-formers. In certain embodiments this electrode îs cycled electrochemically before or after exposure to an electrolyte containing the métal or metal-containing ion in a specified concentration to control the uptake of the métal or metal-containing ion.

[00273] In a non-bînding example, Na₂S may be incorporated into the métal electrode. Exposure to an electrolyte containing Bi(NO₃)î may form Bi₂S₃ distributed throughout the electrode in the réaction shown below:

Bi(NO₃)₃ (aq) + 3 Na₂S -> 6 NaN0₃ + Bi₂S₃ (s)

[00274] In varions embodiments, an additive of interest that is a source of sulfur, sélénium, tellurium, nitrogen, or phosphorus but may be not itself be ionic (e.g. S or Se métal) is incorporated into the electrode at a concentration detennined by the solubility of the source compound or final desired concentration of the final compound in the electrode.

[00275] In varions embodiments, this electrode containing a ποη-reactive additive may be exposed to an electrolyte, which in one embodiment contains NaOH or KOH, and, in one embodiment, is electrochemîcally cycled to generate anionic species on the anode or in the electrolyte (e.g. S₂\ S₂ ²', polysulfides). The species may react to form Bi₂S₃ on the surface or sequestered in the anode as iliustrated in FIG. 23. The exposure of the anode to this electrolyte may increase the overall porosîty as the counterion reacts, which may be bénéficiai to overall accessible capacity.

[00276] Improve longevity ofsulfide in electrolyte

[00277] Water and air sensitive addîtîves can rapidly dégradé in aqueous alkalîne electrolyte. For example, compounds containing sulfide (S²‘) and bisulfide (HS‘) such as Na₂S or NaSH dégradé on exposure to oxygen by forming sulfate or other sulfur-containîng compounds (e.g. sulfite, thiosulfate, sulfur, polysulfides):

HS’ + 3 O₂ A SOa²' + 2 H⁺

2 HS + 3 O₂ + 2 OH -> SO₃ ²‘ + 2 H₂O

SO₃ ²’ + O₂ A 2 SO?’

2 SO₃ ²' + 2HS’ + O₂ À 2 S₂O₃ ²’ + 2 OH

[00278] It is favorable to maintain sulfur species in the electrode or electrolyte as sulfide or bisulfide as the réduction of sulfate or other oxidized sulfur-containîng compounds back to sulfide, bisulfide, or hydrogen sulfide is difficult.

[00279] In one embodiment, oxidized sulfur-containîng species (e.g., Na₂SO4, Na₂S₂O₃, Na₂SO₃, S métal) are added to the electrolyte in suffirent quantity to reduce or complétély suppress formation of oxidized sulfur species by shifting the equilibrium in favor of the reduced sulfur species, in accordance with Le Chatelier’s principle.

[00280] In one embodiment, oxidized sulfur-containîng species (e.g., Na₂SOi, Na₂S₂O₃, Na₂SO₃, S métal) are added to the electrode. Upon exposure to the electrolyte, these soluble additives may dissolve in the electrolyte, increasing the porosity of the electrode and reducing or suppressing the formation of oxîdized sulfur species in solution.

[00281] In one embodiment, oxîdized sulfur-containing species that also contain a metallic cation (e.g. FeSO4, FeS₂O₃, FeSO₃) is added to suppress the oxidation of reduced 5 sulfur species as well as suppress the dissolution of metallic species from the iron electrode.

[00282] High sulfide compati bility of DRI-based iron-air batteries

[00283] DRI-based iron négative électrodes exhibit compatibîlity over a wide range of initial sulfide concentrations within the electrolyte. In addition, it has been shown that the initial sulfide concentration on a gS/gFe is the driving factor, not sulfide concentration in the 10 electrolyte.

[00284] In certain embodiments, an initial sulfide concentration of 1 mM Na₂S (0.1 mgS/gFe) is sufficient for stable capacity performance.

[00285] In certain embodiments, an initial sulfide concentration of 10mM Na₂S (1.4 mgS/gFe) is sufficient for stable capacity performance.

[00286] In certain embodiments, an initial sulfide concentration of 50 mM Na₂S (6.8 mgS/gFe) is sufficient for stable capacity performance.

[00287] In certain embodiments, an initial sulfide concentration of 175 mM Na₂S (23.6 gS/gFe) is sufficient for stable capacity performance.

[00288] In certain embodiments, an initial sulfide concentration of >=250 mM Na₂S 20 (33.8 gS/gFe) is sufficient for stable capacity performance.

[00289] Further, the method of sulfide incorporation into the iron négative electrode can be achieved with a variety of techniques.

[00290] In certain embodiments, sulfide is incorporated through a high sulfide concentration electrolyte within the fuit cell.

[00291] In certain embodiments, sulfide is incorporated through a high sulfide concentration electrolyte soak prior to cycling, which can be completed in a non-sulfide containing electrolyte (may be bénéficiai for the positive électrodes).

[00292] In certain embodiments, sulfide is incorporated through a high sulfide concentration electrolyte soak prior to cycling, after which the positive électrodes are inserted into the full cell wherein the sulfide concentration can be in the range of 10-250 mM (1.433.8 mgS/gFe) or higher.

[00293] Optimal sulfide incorporation may also be achieved via maintenance methods including, but not limited to: 1) periodic addition of high sulfide concentration solution or în solid form; and 2) continuai addition of sulfide in solid or solution form, wherein the sulfide concentration can be in the range of 10-250 mM (1.4-33.8 mgS/gFe) or higher

[00294] In an embodiment, -325 mesh iron sponge powders with open porosîty internai to the particles are thermally bonded via sintering to comprise the base for an iron electrode material. Bismuth oxide and iron sulfide are incorporated throughout the sintered electrode material, and the materials are thermally bonded to a current collecting, perforated sheet, and the sintered connections to the current collectors and between the powder particles obviate the need for compression to attain conduction. An alkaline electrolyte is comprised of a mixture of 80% potassium hydroxîde, 15% sodium hydroxîde, and 5% lithium hydroxîde on a molar basis, with a total hydroxîde concentration of 6 molar (mol/L) în an aqueous solution.

[00295] In one embodiment, the iron electrode material may comprise direct reduced iron pellets, with an electrolyte comprising six molar potassium hydroxîde, 0.1 molar lithium hydroxîde, 0.05 molar sodium sulfide. The iron electrode may further comprise l wt.% bismuth sulfide distributed finely among the direct reduced iron pellets. The electrode materials may be compressed in a rigid cage comprising nickel-plated current collecting stainless Steel plates applyîng uniaxial pressure to compress the pellets within a rigid wall structure comprised ofpoly(methyl méthacrylate), the current collecting plates held in place by stainless Steel bolts which are electrically isolated from the current collectors. The bed thicknesses of such an embodiment may range from one to ten centimeters thîck.

[00296] In an embodiment, the iron electrode material may comprise a carbonyl iron powder, lead oxide, and iron sulfide. The lead oxide is added at 0.1 wt.%, and the iron sulfide is included as 1.5 wt.%, both of the total weight of solids in the electrode. The solids are lightly sintered such that they bond and agglomerate, and are subsequently compressed in a nickel mesh textile which îs compressed by inflation of a polyethylene balloon. The electrolyte is five molar sodium hydroxîde with addîtives of 0.005 molar sodium sulfide and 0.01 molar octanethiol.

[00297] In another embodiment, direct reduced iron pellets are crushed to form particle sizes in the range of 1-6 mm. The particles are mixed with natural flake graphite with a particle size of 200 microns at 1 wt.% of the solids mix and 100 micron particle size iron sulfide at 0.05 wt.%. The electrolyte is aqueous with 6.5 molar potassium hydroxide, 0.5 molar lithium hydroxide, and 0,25 molar sodium sulfide, and 0.001 molar octanethiol. The solids mix is loaded into a nickel mesh bag with a mesh size around 0.5 mm, and the bag is compressed via a cinching mechanism to compress the solids material lightly.

[00298] Various embodiments may provide devices and/or methods for use in bulk energy storage Systems, such as long duration energy storage (LODES) Systems, short duration energy storage (SDES) Systems, etc. As an example, various embodiments may provide batteries for bulk energy storage Systems, such as batteries for LODES Systems. Renewable power sources are becoming more prévalent and cost effective. However, many renewable power sources face an intermîttency problem that is hindering renewable power source adoption. The impact of the intermittent tendencies of renewable power sources may be mitigated by pairing renewable power sources with bulk energy storage Systems, such as LODES Systems, SDES Systems, etc. To support the adoption of combined power génération, transmission, and storage Systems (e.g., a power plant having a renewable power génération source paired with a bulk energy storage system and transmission facilities at any of the power plant and/or the bulk energy storage system) devices and methods to support the design and operation of such combined power génération, transmission, and storage Systems, such as the various embodiment devices and methods described herein, are needed.

[00299] A combined power génération, transmission, and storage system may be a power plant including one or more power génération sources (e.g., one or more renewable power génération sources, one or more non-renewable power générations sources, combinations of renewable and non-renewabie power génération sources, etc.), one or more transmission facilities, and one or more bulk energy storage Systems. Transmission facilities at any of the power plant and/or the bulk energy storage Systems may be co-optîmized with the power génération and storage System or may impose constraints on the power génération and storage system design and operation. The combined power génération, transmission, and storage Systems may be configured to meet various output goals, under various design and operating constraints.

[00300] FIGS. 24-102 illustrate various example Systems in which one or more aspects of the various embodiments may be used as part of bulk energy storage Systems, such as LODES Systems, SDES Systems, etc. For example, various embodiments described herein with reference to FIGS. 1A-93 may be used as batteries for bulk energy storage Systems, such as LODES Systems, SDES Systems, etc. and/or varions électrodes as described herein may be used as components for bulk energy storage Systems. As used herein, the tenu “LODES system” may mean a bulk energy storage system configured to may hâve a rated duration (energy/power ratio) of 24 hours (h) or greater, such as a duration of 24 h, a duration of 24 h 5 to 50 h, a duration of greater than 50 h, a duration of 24 h to 150 h, a duration of greater than

150 h, a duration of 24 h to 200 h, a duration greater than 200 h, a duration of 24 h to 500 h, a duration greater than 500 h, etc.

[00301] FIG. 24 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie 10 example, the bulk energy storage system incorporât!ng one or more aspects of the various embodiments may be a LODES System 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, etc. The LODES System 2404 may be electrically connected to a wînd farm 2402 and one or more transmission facilities 2406. The wind farm 2402 may be electrically connected to the transmission facilities 2406. The transmission facilities 2406 may be electrically connected to the grid 2408. The wind farm 2402 may generate power and the wind farm 2402 may output generated power to the LODES system 2404 and/or the transmission facilities 2406. The LODES system 2404 may store power received from the wind farm 2402 and/or the transmission facilities 2406. The LODES system 2404 may output stored power to the transmission facilities 2406. The transmission facilities 2406 may output power received from one or both of the wind farm 2402 and LODES system 2404 to the grid 2408 and/or may receive power from the grid 2408 and output that power to the LODES system 2404. Together the wind farm 2402, the LODES system 2404, and the transmission facilities 2406 may constitute a power plant 2400 that may be a combined power génération, transmission, and storage system. The power generated by the wînd farm 2402 may be directly fed to the grid 2408 through the transmission facilities 2406, or may be first stored in the LODES system 2404. In certain cases the power supplied to the grid 2408 may corne entirely from the wind farm 2402, entirely from the LODES System 2404, or from a combination of the wind farm 2402 and the LODES System 2404. The dispatch of power from the combined wind farm 2402 and LODES System 2404 power plant 2400 may be controlled according to a determined long-range (multi-day or even multi-year) schedule, or may be controlled according to a day-ahead (24 hour advance notice) market, or may be controlled according to an hour-ahead market, or may be controlled tn response to real time pricing signais.

[00302] As one example of operation of the power plant 2400, the LODES system 2404 may be used to reshape and “firm” the power produced by the wind farm 2402. In one such example, the wind farm 2402 may hâve a peak génération output (capacity) of 260 mégawatts (MW) and a capacity factor (CF) of 41%. The LODES system 2404 may hâve a 5 power rating (capacity) of 106 MW, a rated duration (energy/power ratio) of 150 hours (h), and an energy rating of 15,900 mégawatt hours (MWh). In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of 300 MW and a capacity factor (CF) of 41 %. The LODES system 2404 may hâve a power rating of 106 MW, a rated duration (energy/power ratio) of 200 h and an energy rating of 21,200 MWh. In another such 10 example, the wind farm 2402 may hâve a peak génération output (capacity) of 176 MW and a capacity factor (CF) of 53%. The LODES system 2404 may hâve a power rating (capacity) of 88 MW, a rated duration (energy/power ratio) of 150 h and an energy rating of 13,200 MWh. In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of 277 MW and a capacity factor (CF) of41%. The LODES system 2404 may 15 hâve a power rating (capacity) of 97 MW, a rated duration (energy/power ratio) of 50 h and an energy rating of 4,850 MWh. In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of 315 MW and a capacity factor (CF) of 41%. The LODES system 2404 may hâve a power rating (capacity) of 110 MW, a rated duration (energy/power ratio) of 25 h and an energy rating of 2,750 MWh.

[00303] FIG. 25 illustrâtes an example System in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie example, the bulk energy storage system incorporating one or more aspects ofthe various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, 25 etc. The system of FIG. 25 may be similar to the system of FIG. 24, except a photovoltaic (PV) farm 2502 may be substituted for the wind farm 2402. The LODES system 2404 may be electrically connected to the PV farm 2502 and one or more transmission facilities 2406. The PV farm 2502 may be electrically connected to the transmission facilities 2406. The transmission facilities 2406 may be electrically connected to the grid 2408. The PV farm

2502 may generate power and the PV farm 2502 may output generated power to the LODES system 2404 and/or the transmission facilities 2406. The LODES system 2404 may store power received from the PV farm 2502 and/or the transmission facilities 2406. The LODES system 2404 may output stored power to the transmission facilities 2406. The transmission facilitîes 2406 may output power received from one or both of the PV farm 2502 and LODES System 2404 to the grid 2408 and/or may receive power from the grid 2408 and output that power to the LODES system 2404, Together the PV farm 2502, the LODES System 2404, and the transmission facilitîes 2406 may constîtute a power plant 2500 that may be a combined power génération, transmission, and storage system, The power generated by the PV farm 2502 may be directly fed to the grid 2408 through the transmission facilitîes 2406, or may be first stored in the LODES system 2404. In certain cases the power supplied to the grid 2408 may corne entirely from the PV farm 2502, entirely from the LODES system 2404, or from a combination of the PV farm 2502 and the LODES System 2404. The dispatch of

1O power from the combined PV farm 2502 and LODES system 2404 power plant 2500 may be controlled according to a determined long-range (multi-day or even multi-year) schedule, or may be controlled according to a day-ahead (24 hour ad van ce notice) market, or may be controlled according to an hour-ahead market, or may be controlled in response to real time pricing signais.

[00304] As one example of operation of the power plant 2500, the LODES system

2404 may be used to reshape and “firm” the power produced by the PV farm 2502. In one such example, the PV farm 2502 may hâve a peak génération output (capacity) of 490 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power ratîng (capacity) of 340 MW, a rated duration (energy/power ratio) of 150 h and an energy ratîng of

51,000 MWh. In another such example, the PV farm 2502 may hâve a peak génération output (capacity) of 680 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power rating (capacity) of410 MW, a rated duration (energy/power ratio) of 200 h, and an energy rating of 82,000 MWh. In another such example, the PV farm 2502 may hâve a peak génération output (capacity) of 330 MW and a capacity factor (CF) of 31%. The

LODES system 2404 may hâve a power rating (capacity) of 215 MW, a rated duration (energy/power ratio) of 150 h, and an energy rating of 32,250 MWh. In another such example, the PV farm 2502 may hâve a peak génération output (capacity) of 510 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power rating (capacity) of 380 MW, a rated duration (energy/power ratio) of 50 h, and an energy rating of 19,000

MWh. In another such example, the PV farm 2502 may hâve a peak génération output (capacity) of 630 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power rating (capacity) of 380 MW, a rated duration (energy/power ratio) of 25 h, and an energy rating of 9,500 MWh.

[00305] FIG. 26 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie example, the bulk energy storage System incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES System 2404 may 5 include various embodiment batteries described herein, various électrodes described herein, etc. The system of FIG. 26 may be similar to the Systems of FIGS. 24 and 25, except the wînd farm 2402 and the photovoltaic (PV) farm 2502 may both be power generators working together in the power plant 2600. Together the PV farm 2502, wind farm 2402, the LODES system 2404, and the transmission facilîties 2406 may constitute the power plant 2600 that 10 may be a combined power génération, transmission, and storage system. The power generated by the PV farm 2502 and/or the wind farm 2402 may be dîrectly fed to the grîd 2408 through the transmission facilîties 2406, or may be first stored in the LODES system 2404. In certain cases the power supplied to the grid 2408 may corne entirely from the PV farm 2502, entirely from the wind farm 2402, entirely from the LODES System 2404, or from 15 a combination of the PV fann 2502, the wind farm 2402, and the LODES system 2404. The dispatch of power from the combined wind farm 2402, PV farm 2502, and LODES System 2404 power plant 2600 may be controlled according to a determîned long-rangé (multi-day or even multi-year) schedule, or may be controlled according to a day-ahead (24 hour advance notice) market, or may be controlled according to an hour-ahead market, or may be controlled 20 in response to real time pricing signais.

[00306] As one example of operation of the power plant 2600, the LODES system 2404 may be used to reshape and “firm” the power produced by the wind fann 2402 and the PV farm 2502. In one such example, the wind farm 2402 may hâve a peak génération output (capacity) of 126 MW and a capacity factor (CF) of 41% and the PV farm 2502 may hâve a 25 peak génération output (capacity) of 126 MW and a capacity factor (CF) of 24%. The

LODES system 2404 may hâve a power rating (capacity) of 63 MW, a rated duration (energy/power ratio) of 150 h, and an energy rating of 9,450 MWh. In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of 170 MW and a capacity factor (CF) of 41 % and the PV farm 2502 may hâve a peak génération output (capacity) of 30 110 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power rating (capacity) of 57 MW, a rated duration (energy/power ratio) of 200 h, and an energy rating of 11,400 MWh. In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of 105 MW and a capacity factor (CF) of 51% and the PV farm

2502 may hâve a peak génération output (capacîty) of 70 MW and a capacity factor (CF) of 31 The LODES system 2404 may hâve a power rating (capacity) of 61 MW, a rated duration (energy/power ratio) of 150 h, and an energy rating of 9,150 MWh. In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of i 35 MW and a capacity factor (CF) of 41% and the PV farm 2502 may hâve a peak génération output (capacity) of 90 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power rating (capacity) of 68 MW, a rated duration (energy/power ratio) of 50 h, and an energy rating of 3,400 MWh. In another such example, the wind farm 2402 may hâve a peak génération output (capacity) of 144 MW and a capacity factor (CF) of 41% and the PV farm 2502 may hâve a peak génération output (capacity) of 96 MW and a capacity factor (CF) of 24%. The LODES system 2404 may hâve a power rating (capacity) of 72 MW, a rated duration (energy/power ratio) of 25 h, and an energy rating of 1,800 MWh.

[00307] FIG. 27 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie 15 example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various electrodes described herein, etc. The LODES System 2404 may be electrically connected to one or more transmission facilities 2406. In this manner, the LODES system 2404 may operate in a “stand-alone” manner to arbiter energy around market prices and/or to avoid transmission constraints. The LODES system 2404 may be electrically connected to one or more transmission facilities 2406. The transmission facilities 2406 may be electrically connected to the grid 2408. The LODES system 2404 may store power received from the transmission facilities 2406. The LODES system 2404 may output stored power to the transmission facilities 2406. The transmission facilities 2406 may output power received from the LODES system 2404 to the grid 2408 and/or may receive power from the grid 2408 and output that power to the LODES system 2404.

[00308] Together the LODES System 2404 and the transmission facilities 2406 may constitute a power plant 900. As an example, the power plant 900 may be situated downstream of a transmission constraint, close to electricai consumption. In such an example downstream situated power plant 2700, the LODES system 2404 may hâve a duration of 24h to 500h and may undergo one or more full discharges a year to support peak electricai consumptions at times when the transmission capacity is not sufficient to serve customers.

Additionally in such an example downstream situated power plant 2700, the LODES system 2404 may undergo several shallow discharges (daily or at higher frequency) to arbiter the différence between nighttime and daytime electricity prices and reduce the overall cost of electrical service to customer. As a further example, the power plant 2700 may be situated upstream of a transmission constraint, close to electrical génération. In such an example upstream situated power plant 2700, the LODES system 2404 may hâve a duration of 24h to 500h and may undergo one or more full charges a year to absorb excess génération at times when the transmission capacity is not sufficîent to distribute the electricity to customers. Additionally in such an example upstream situated power plant 2700, the LODES system

2404 may undergo several shallow charges and discharges (daily or at higher frequency) to arbiter the différence between nighttime and daytime electricity prices and maximize the value of the output of the génération facilities.

[00309] FIG. 28 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part ofbuik energy storage system. As a spécifie example, the bulk energy storage system incorporatïng one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, etc. The LODES system 2404 may be electrically connected to a commercial and industrial (C&I) customer 2802, such as a data center, factory, etc. The LODES system 2404 may be electrically connected to one or more transmission facilities 2406. The transmission facilities 2406 may be electrically connected to the grid 2408. The transmission facilities 2406 may receive power from the grid 2408 and output that power to the LODES system 2404. The LODES System 2404 may store power received from the transmission facilities 2406. The LODES system 2404 may output stored power to the C&I customer 2802. In this manner, the LODES system 2404 may operate to reshape electricity purchased from the grid 2408 to match the consumption pattern of the C&I customer 2802.

[00310] Together, the LODES system 2404 and transmission facilities 2406 may constitute a power plant 2800. As an example, the power plant 2800 may be situated close to electrical consumption, i.e., close to the C&I customer 2802, such as between the grid 2408 30 and the C&I customer 2802. In such an example, the LODES system 2404 may hâve a duration of 24h to 500h and may buy electricity from the markets and thereby charge the LODES system 2404 at times when the electricity is cheaper. The LODES system 2404 may then discharge to provide the C&I customer 2802 with electricity at times when the market price is expensive, therefore offsetting the market purchases of the C&I customer 2802. As an alternative configuration, rather than being situated between the grid 2408 and the C&I customer 2802, the power plant 2800 may be situated between a renewable source, such as a PV farm, wind farm, etc., and the transmission facilities 2406 may connect to the renewable source. In such an alternative example, the LODES system 2404 may hâve a duration of 24h to 500h, and the LODES system 2404 may charge at times when renewable output may be available. The LODES system 2404 may then discharge to provide the C&I customer 2802 with renewable generated electricity so as to cover a portion, or the entîrety, of the C&I customer 2802 electricity needs.

1O [00311] FIG. 29 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie example, the bulk energy storage system incorporât! ng one or more aspects ofthe various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, etc. The LODES system 2404 may be electrically connected to a wind farm 2402 and one or more transmission facilities 2406. The wind iarm 2402 may be electrically connected to the transmission facilities 2406. The transmission facilities 2406 may be electrically connected to a C&l customer 2802. The wind farm 2402 may generate power and the wind farm 2402 may output generated power to the LODES system 2404 and/or the transmission facilities

2406. The LODES System 2404 may store power received from the wind farm 2402.

[00312] The LODES system 2404 may output stored power to the transmission facilities 2406. The transmission facilities 2406 may output power received from one or both ofthe wind farm 2402 and LODES system 2404 to the C&I customer 2802. Together the wind farm 2402, the LODES system 2404, and the transmission facilities 2406 may constitute a power plant 2900 that may be a combined power génération, transmission, and storage System. The power generated by the wind farm 2402 may be directly fed to the C&I customer 2802 through the transmission facilities 2406, or may be first stored in the LODES system 2404. In certain cases, the power supplied to the C&I customer 2802 may corne entire ly from the wind farm 2402, entire ly from the LODES system 2404, or from a combination of the wind farm 2402 and the LODES system 2404. The LODES system 2404 may be used to reshape the electricity generated by the wind farm 2402 to match the consumption pattern of the C&I customer 2802. In one such example, the LODES system 2404 may hâve a duration of 24h to 500h and may charge when renewable génération by the wind farm 2402 exceeds the C&I customer 2802 load. The LODES system 2404 may then discharge when renewable génération by the wind farm 2402 faits short of C&l customer 2802 load so as to provide the C&l customer 2802 with a firm renewable profile that ofFsets a fraction, or ail of, the C&I customer 2802 electrical consumptîon.

[00313] FIG. 30 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, etc. The LODES system 2404 may be part of a power plant 3000 that is used to integrate large amounts of renewable génération in mierogrids and harmonize the output of renewable génération by, for example a PV farm 2502 and wind farm 2402, with existing thermal génération by, for example a thermal power plant 3002 (e.g., a gas plant, a coal plant, a diesel generator set, etc., or a combination of thermal génération methods), white renewable génération and thermal génération supply the C&I customer 2802 load at high availability. Mierogrids, such as the microgrid constituted by the power plant 3000 and the thermal power plant 3002, may provide availability that is 90% or higher. The power generated by the PV farm 2502 and/or the wind farm 2402 may be directly fed to the C&I customer 2802, or may be first stored in the LODES system 2404.

[00314] In certain cases the power suppiied to the C&I customer 2802 may corne entirely from the PV farm 2502, entirely from the wind farm 2402, entirely from the LODES system 2404, entirely from the thermal power plant 3002, or from any combination of the PV farm 2502, the wind farm 2402, the LODES system 2404, and/or the thermal power plant 3002. As examples, the LODES system 2404 of the power plant 3000 may hâve a duration of 24h to 500h. As a spécifie example, the C&l customer 2802 load may hâve a peak of 100 MW, the LODES system 2404 may hâve a power rating of 14 MW and duration of 150 h, natural gas may cost $6/million British thermal units (MMBTU), and the renewable pénétration may be 58%. As another spécifie example, the C&I customer 2802 load may hâve a peak of 100 MW, the LODES system 2404 may hâve a power rating of 25 MW and duration of 150 h, natural gas may cost $8/MMBTU, and the renewable pénétration may be 65%.

[00315] FIG. 31 illustrâtes an example System in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifié example, the bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, etc. The LODES system 2404 may be used to augment a nuclear plant 3102 (or other inflexible génération facility, such as a thermal, a biomass, etc., and/or any other type plant having a ramp-rate lower than 50% of rated power in one hour and a high capacity factor of 80% or higher) to add flexibilîty to the combined output ofthe power plant 3100 constituted by the combined LODES system 2404 and nuclear plant 3102. The nuclear plant 3102 may operate at high capacity factor and at the highest efficiency point, while the LODES system

2404 may charge and discharge to effectively reshape the output of the nuclear plant 3102 to match a customer electrical consumptîon and/or a market price of electricity. As examples, the LODES System 2404 of the power plant 3100 may hâve a duration of 24h to 500h. In one spécifie example, the nuclear plant 3102 may hâve 1,000 MW of rated output and the nuclear plant 3102 may be forced into prolonged periods of minimum stable génération or even shutdowns because of depressed market pricing of electricity. The LODES system 2404 may avoid facility shutdowns and charge at times of depressed market pricing; and the LODES system 2404 may subsequently discharge and boost total output génération at times of inflated market pricing.

[00316] FIG. 32 illustrâtes an example system in which one or more aspects of the various embodiments may be used as part of bulk energy storage system. As a spécifie example, the bulk energy storage system incorporating one or more aspects ofthe various embodiments may be a LODES system 2404. As an example, the LODES system 2404 may include various embodiment batteries described herein, various électrodes described herein, etc. The LODES system 2404 may operate in tandem with a SDES system 3202. Together the LODES system 2404 and SDES system 3202 may constitute a power plant 3200. As an example, the LODES system 2404 and SDES system 3202 may be co-optîmized whereby the LODES system 2404 may provide various services, including long-duration back-up and/or bridging through multi-day fluctuations (e.g., multi-day fluctuations in market pricing, renewable génération, electrical consumptîon, etc.), and the SDES system 3202 may provide various services, including fast ancillary services (e.g. voltage control, frequency régulation, etc.) and/or bridging through întra-day fluctuations (e.g., intra-day fluctuations in market pricing, renewable génération, electrical consumptîon, etc.). The SDES system 3202 may hâve durations of less than 10 hours and round-trip efficiencies of greater than 80%. The

8o

LODES System 2404 may hâve durations of 24h to 500h and round-trip efficiencies of greater than 40%. In one such example, the LODES System 2404 may hâve a duration of 150 hours and support customer electrical consumption for up to a week of renewable undergeneration. The LODES system 2404 may also support customer electrical consumption during intra-day under-generation events, augmenting the capabilities of the SDES system

3202. Further, the SDES system 3202 may supply customers during intra-day undergeneration events and provide power conditioning and quality services such as voltage control and frequency régulation.

[00317] Various embodiments may include a battery comprising: a first electrode; an 10 electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises iron agglomérâtes. In some embodiments, the electrolyte comprises a soluble sulfide. In some embodiments, at least one of the first electrode and the second electrode further comprises a solid sulfide. In some embodiments, at least one of the first electrode or the second electrode is subjected to a compressive load. In some embodiments, 15 the compressive load îs applied on one side of at least one of the first electrode or second electrode by a current collecting member. In some embodiments, the iron agglomérâtes comprise at least one of magnetite, hématite, or wustite. In some embodiments, the electrolyte comprises a corrosion inhibitor. In some embodiments, the iron agglomérâtes hâve an average length ranging from about 50 um to about 50 mm. In some embodiments, 20 the iron agglomérâtes hâve an average internai porosity ranging from about 10% to about

90% by volume. In some embodiments, the iron agglomérâtes hâve an average spécifie surface area ranging from about 0.1 m²/g to about 25 m²/g. In some embodiments, the electrolyte is infiltrated between the iron agglomérâtes. In some embodiments, the electrolyte comprises 1-octanethioL In some embodiments, the electrolyte comprises a molybdate anion 25 and a sulfide anion. In some embodiments, the iron agglomérâtes are supported within a métal textile mesh providing compressive force and current collection for the iron agglomérâtes. In some embodiments, the iron agglomérâtes are bonded to one another and bonded to a current collector.

[00318] Various embodiments may include a battery comprising: a first electrode; an 30 electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises atomized métal powder. In some embodiments, the electrolyte comprises a soluble sulfide. In some embodiments, at least one of the first electrode and the second electrode further comprises a solid sulfide. In some embodiments, at least one of the first electrode or the second electrode is subjected to a compressive load. In some embodiments, the compressive load is applied on one side of at least one of the first electrode or second electrode by a current collecting member. In some embodiments, the atomized métal powder comprise at least one of magnetite, hématite, or wustite. In some embodiments, the electrolyte comprises a corrosion inhibitor. In some embodiments, the electrolyte is infiltrated between the atomized métal powder. In some embodiments, the electrolyte comprises 1-octanethiol. In some embodiments, the electrolyte comprises a molybdate anîon and a sulfide anion. In some embodiments, the atomized métal powder is supported within a métal textile mesh providing compressive force and current collection for 10 the atomized métal powder. In some embodiments, the atomized métal powder is bonded together and bonded to a current collecter.

[00319] Various embodiments include a method of making an electrode, comprising: electrochemically producing métal powder; and forming the métal powder into an electrode. In some embodiments, electrochemically producing the métal powder comprises electrochemically producing the métal powder at least in part using a molten sait electrochemistry. In some embodiments, electrochemically producing the métal powder comprises electrochemically producing the métal powder at least in part using gas atomization. In some embodiments, electrochemically producing the métal powder comprises electrochemically producing the métal powder at least in part using water atomization.

[00320] Various embodiments may include a bulk energy storage system, comprising: one or more batteries, wherein at least one of the one or more batteries comprises: a first electrode; an electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises iron agglomérâtes. In some embodiments, the bulk 25 energy storage system is a long duration energy storage (LODES) system. In some embodiments, the electrolyte comprises a soluble sulfide. In some embodiments, at least one of the first electrode and the second electrode further comprises a solid sulfide. In some embodiments, at least one of the first electrode or the second electrode is subjected to a compressive load. In some embodiments, the compressive load is applied on one side of at 30 least one of the fîrst electrode or second electrode by a current collecting member. In some embodiments, the iron agglomérâtes comprise at least one of magnetite, hématite, or wustite. In some embodiments, the electrolyte comprises a corrosion inhibitor. In some embodiments, the iron agglomérâtes hâve an average length ranging from about 50 uni to about 50mm. In some embodiments, the iron agglomérâtes hâve an average internai porosîty ranging from about 10% to about 90% by volume. In some embodiments, the iron agglomérâtes hâve an average spécifie surface area ranging from about 0.1 m²/g to about 25 m²/g. In some embodiments, the electrolyte is infdtrated between the iron agglomérâtes. In some embodiments, the electrolyte comprises 1-octanethiol. In some embodiments, the electrolyte comprises a molybdate anion and a sulfide anion. In some embodiments, the iron agglomérâtes are supported within a métal textile mesh providing compressive force and current collection for the iron agglomérâtes. In some embodiments, the iron agglomérâtes are bonded to one another and bonded to a current collecter.

[00321 ] Various embodiments may include a bulk energy storage system, comprising:

one or more batteries, wherein at least one of the one or more batteries comprises: a first electrode; an electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises atomized métal powder. In some embodiments, the bulk energy storage system is a long duration energy storage (LODES) System. In some embodiments, the electrolyte comprises a soluble sulfide. In some embodiments, at least one ofthe first electrode and the second electrode further comprises a solid sulfide. In some embodiments, at least one of the first electrode or the second electrode is subjected to a compressive load. In some embodiments, the compressive load is appiied on one side of at least one ofthe first electrode or second electrode by a current collecting member. In some embodiments, the atomized métal powder comprise at least one of magnetite, hématite, or wustîte. In some embodiments, the electrolyte comprises a corrosion inhîbitor. In some embodiments, the electrolyte is înfiltrated between the atomized métal powder. In some embodiments, the electrolyte comprises 1-octanethiol. In some embodiments, the electrolyte comprises a molybdate anion and a sulfide anion. In some embodiments, the atomized métal powder is supported within a métal textile mesh providing compressive force and current collection for the atomized métal powder. In some embodiments, the atomized métal powder is bonded together and bonded to a current collecter.

[00322] The foregoing method descriptions are provided merely as illustrative examples and are not intended to require or imply that the steps of the varions embodiments 30 must be performed in the order presented. As will be appreciated by one of skîll in the art the order of steps in the foregoing embodiments may be performed in any order. Word s such as “thereafter,” “then,” “next,” etc. are not necessarily intended ίο limit the order of the steps;

these words may be used to guide the reader through the description of the methods, Further, any reference to claim éléments in the singular, for example, using the articles “a,” “an” or “the” is not to be construed as fimiting the element to the singular. Further, any step of any embodiment described herein can be used in any other embodiment.

[00323] The preceding description of the disclosed aspects is provided to enable any person skilled in the art to make or use the présent invention. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects without departîng from the scope of the invention. Thus, the présent invention is not intended to be limited to the aspects shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed

Claims (35)

1. A battery comprising:

a first electrode;

5 an electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises at least one of:

iron agglomérâtes, and

10 atomized métal powder.

2. The battery of claim 1, wherein the electrolyte comprises a soluble sulfîde.

3. The battery of claim 1, wherein at least one of the first electrode and the second electrode

15 further comprises a solid sulfîde.

4. The battery of claim 1, wherein at least one ofthe first electrode and the second electrode is subjected to a compressive load.

20

5. The battery of claim 4, wherein the compressive load is applied on one side of at least one of the first electrode and second electrode by a current collecting member.

6. The battery of claim 1, wherein the iron agglomérâtes comprise at least one of magnetite, hématite, or wustite.

7. The battery of claim 1, wherein the electrolyte comprises a corrosion inhibitor.

8. The battery of claim 1, wherein the iron agglomérâtes hâve an average length ranging from about 50 um to about 50 mm.

9. The battery of claim I, wherein the iron agglomérâtes hâve an average internai porosity ranging from about 10% to about 90% by volume.

10. The battery of claim 1, wherein the iron agglomérâtes hâve an average spécifie surface area 5 ranging from about 0.1 m²/g to about 25 m²/g.

11. The battery of claim 1, wherein the electrolyte is infiltrated between the iron agglomérâtes.

12. The battery of claim 11, wherein the electrolyte comprises 1-octanethioL

13. The battery of claim 11, wherein the electrolyte comprises a molybdate anion and a sulfide anion.

14. The battery of claim 11, wherein the iron agglomérâtes are supported within a métal textile 15 mesh providing compressive force and current collection for the iron agglomérâtes.

15. The battery of claim 11, wherein the iron agglomérâtes are bonded to one another and bonded to a current collecter.

20

16. A method of making an electrode, comprising;

electrochemically producîng métal powder; and forming the métal powder into an electrode.

17. The method of claim 16, wherein electrochemically producîng the métal powder comprises 25 electrochemically producîng the métal powder at least in part using a molten sait electrochemîstiy.

18. The method of claim 16, wherein electrochemically producîng the métal powder comprises electrochemically producîng the métal powder at least in part using gas atomizatîon.

19. The method of claim 16, wherein electrochemically producing the métal powder comprises electrochemically producing the métal powder at least in part using water atomization.

20. A bulk energy storage system, comprising:

5 one or more batteries, wherein at least one of the one or more batteries comprises:

a first electrode;

an electrolyte; and a second electrode, wherein at least one of the first electrode and the second electrode comprises at

10 least one of:

iron agglomérâtes; and atomized métal powder.

21. The bulk energy storage system of claim 20, wherein the bulk energy storage system is a

15 long duration energy storage (LODES) system.

22. The bulk energy storage system of claim 20, wherein the electrolyte comprises a soluble sulfide.

20

23. The bulk energy storage System of claim 20, wherein at least one of the first electrode and the second electrode further comprises a solid sulfide.

24. The bulk energy storage system of claim 20, wherein at least one of the first electrode and the second electrode is subjected to a compressive load.

25. The bulk energy storage system of claim 24, wherein the compressive load is applied on one side of at least one of the first electrode and second electrode by a current collecting member.

26. The bulk energy storage system of claim 20, wherein the iron agglomérâtes comprise at least 30 one of magnetite, hématite, or wustite.

27. The bulk energy storage system of claim 20, wherein the electrolyte comprises a corrosion inhibitor.

28. The bulk energy storage system of claim 20, wherein the iron agglomérâtes hâve an average length ranging from about 50 um to about 50 mm.

29. The bulk energy storage system of claim 20, wherein the iron agglomérâtes hâve an average internai porosity ranging from about 10% to about 90% by volume.

30. The bulk energy storage system of claim 20, wherein the iron agglomérâtes hâve an average spécifie surface area ranging from about 0.1 m²/g to about 25 m²/g.

31. The bulk energy storage system of claim 30, wherein the electrolyte is infiltrated between the iron agglomérâtes.

32. The bulk energy storage system of claim 31, wherein the electrolyte comprises 1octanethiol.

33. The bulk energy storage system of claim 32, wherein the electrolyte comprises a molybdate anion and a sulfide anion.

34. The bulk energy storage system of claim 32, wherein the iron agglomérâtes are supported within a métal textile mesh providing compressive force and current collection for the iron agglomérâtes.

35. The bulk energy storage system of claim 32, wherein the iron agglomérâtes are bonded to one another and bonded to a current collector.