Porous materials for battery electrodes

Abstract

We provide long-term and ultra-long-term (for a total of at least 8 hours or more) energy storage systems. [Solution] A battery comprising a positive electrode, an electrolyte, and a negative electrode containing an iron-containing precursor material and a transient pore-forming agent, wherein the transient pore-forming agent is dispersed in the iron-containing precursor material, the iron-containing precursor material is electrochemically reducible to iron in the electrolyte, and the transient pore-forming agent is soluble in the electrolyte.

Description

Technical Field

[0001] Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 013,864, entitled "Porous Materials For Battery Electrodes," filed on April 22, 2020, the entire content of which is incorporated herein by reference for all purposes.

Background Art

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

[0003] This "Background Art" section is intended to introduce various aspects of the art that may be related to embodiments of the present invention. Accordingly, the foregoing considerations in this section provide a framework for better understanding the present invention and should not be construed as an admission of prior art.

Summary of the Invention

[0004] Systems and methods of various embodiments may provide porous materials for electrodes of an electrochemical energy storage system.

[0005] Various embodiments may include a battery comprising a positive electrode, an electrolyte, and a negative electrode, wherein the negative electrode comprises a porous metal. In various embodiments, the porous metal may be produced at least partially using at least one transient pore-forming agent. In various embodiments, the porous metal comprises iron. In various embodiments, the transient pore-forming agent is a reducing agent. In various embodiments, the reducing agent comprises carbon. In various embodiments, the transient pore-forming agent comprises iron(II) sulfate, iron(II,II) sulfate, machinawite, marcasite, pyrite, troilite, pyrrhotite, gleigate, amorphous iron(II) sulfide, or lead sulfide. In various embodiments, the transient pore-forming agent comprises coal. In various embodiments, the porous metal is produced by reduction in a hearth furnace. In various embodiments, the hearth furnace is a rotary hearth furnace or a linear hearth furnace. In various embodiments, the porous metal is produced by reduction in a rotary kiln. In various embodiments, pore formation in the porous metal occurs by electrochemical reduction in the battery. In various embodiments, the transient pore-forming agent includes silica, sodium silicate, sodium oxide, calcium oxide, or magnesium oxide. In various embodiments, the transient pore-forming agent includes a salt of the electrolyte. In various embodiments, the transient pore-forming agent includes potassium hydroxide or sodium hydroxide. In various embodiments, the transient pore-forming agent includes ammonium nitrate or potassium sulfate. In various embodiments, the porous metal is formed from a precursor material having a first size, and the particle size of the transient pore-forming agent is approximately the same as the first size. In various embodiments, the porous metal has a layer of discharge products on its surface, and the particle size of the transient pore-forming agent is more than twice the thickness of the discharge product layer. In various embodiments, at least one transient pore-forming agent comprises at least two different transient pore-forming agents. In various embodiments, the two different transient pore-forming agents are different types of pore-forming agents and / or pore-forming agents of different sizes. In various embodiments, the current collector further includes a metallurgically coupled and / or electrically conductive current collector that is aligned with at least a portion of the negative electrode.In various embodiments, the positive electrode comprises an air-breathing cathode, a nickel oxyhydroxide electrode, or a manganese dioxide electrode. In various embodiments, the iron includes steelmaking dust, mill scale, iron ore, iron mesh, iron wire, iron powder, or any combination thereof. In various embodiments, the transient pore-forming agent includes coke. In various embodiments, the porous metal may be produced using a pore-forming agent that includes, at least in part, a metal carbonate. Various embodiments include a method for forming a porous metal for the negative electrode of a battery, which involves forming pores in the porous metal using at least one transient pore-forming agent. In various embodiments, the pores of the transient pore-forming agent may be formed with or without a reduction step. [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic diagram of some electrochemical cells according to various embodiments. [Figure 2] This is a process flow diagram showing a method for forming a porous metal for negative electrodes. [Figure 3] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 4] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 5] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 6] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 7] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 8] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 9] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 10] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Figure 11] This figure shows various exemplary systems in which one or more of the various embodiments can be used as part of a bulk energy storage system. [Modes for carrying out the invention]

[0007] References to specific examples and implementations are illustrative and not intended to limit the scope of the claims. The following description of embodiments of the present invention is not intended to limit the invention to such embodiments, but rather to enable those skilled in the art to manufacture and use the invention.

[0008] The following examples are provided to illustrate various embodiments of the system and method of the present invention. These examples are illustrative, may be predictive, and should not be considered limiting, nor should they limit the scope of the invention in any way.

[0009] Various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. References to specific examples and implementations are illustrative and not intended to limit the scope of the claims. The following description of embodiments of the present invention is not intended to limit the invention to these embodiments, but rather to enable those skilled in the art to manufacture and use the invention. Unless otherwise noted, the accompanying drawings are not drawn to scale.

[0010] Where used herein, unless otherwise stated, room temperature is 25°C, and standard temperature and standard pressure are 25°C and 1 atm. Unless otherwise expressly stated, all tests, test results, physical properties, and values ​​that are temperature-dependent, pressure-dependent, or both are provided at standard ambient temperature and pressure.

[0011] Generally, the term “about” as used herein means, unless otherwise specified, to include a variation or range of ±10%, experimental error or instrument error associated with obtaining the stated value, preferably the greater of these.

[0012] Where used herein, unless otherwise specified, the enumeration of value ranges herein is intended merely as a simplified way of referring individually to each separate value that falls within the range. Unless otherwise indicated herein, each individual value within the range is incorporated herein as if it were individually enumerated herein.

[0013] The following examples are provided to illustrate various embodiments of the system and method of the present invention. These examples are illustrative, may be predictive, and should not be considered limiting, nor should they limit the scope of the invention in any way.

[0014] It should be noted that it is not necessary to provide or express the theories underlying any novel and groundbreaking processes, materials, performances, or other beneficial features and properties that are the subject matter of or associated with embodiments of the present invention. Nevertheless, various theories are provided herein to further advance the art of the art. The theories presented herein do not in any way limit, restrict, or narrow the scope of protection granted to the claimed invention unless otherwise expressly stated. Such theories may not be necessary for or in practice for the use of the present invention. Furthermore, it is understood that the present invention may be linked to new and previously unknown theories for describing the functional features of embodiments of the methods, articles, materials, devices, and systems of the present invention. Such subsequently developed theories do not limit the scope of protection granted to the present invention.

[0015] Various embodiments of the systems, equipment, techniques, methods, activities, and operations shown herein can be used in various other activities and fields in addition to those shown herein. Furthermore, such embodiments can be used, for example, with other equipment or activities that may be developed in the future; and with existing equipment or activities that may be partially modified based on the teachings herein. Moreover, the various embodiments and examples shown herein can be used together, whole or in part, and in various different combinations. Therefore, for example, the configurations provided in the various embodiments herein can be used together; and the scope of protection granted to the invention should not be limited to a particular embodiment, example, or a particular embodiment, configuration, or arrangement shown in a particular figure.

[0016] Embodiments of the present invention include devices, systems, and methods for long-term and ultra-long-term low-cost energy storage. As used herein, "long-term" and / or "ultra-long-term" can refer to an energy storage period of 8 hours, an energy storage period in the range of 8 hours to 20 hours, an energy storage period of 20 hours, an energy storage period in the range of 20 hours to 24 hours, an energy storage period of 24 hours, an energy storage period in the range of 24 hours to 1 week, an energy storage period in the range of 1 week to 1 year (e.g., from a few days to a few weeks, up to a few months), etc., that is, an energy storage period of 8 hours or more. In other words, a "long-term" and / or "ultra-long-term" energy storage cell refers to an electrochemical cell that can be configured to store energy over several days, weeks, or seasons. For example, the electrochemical cell may be configured to store energy generated by a solar cell during summer months when sunlight is abundant and solar power generation exceeds the power grid's requirements, and to discharge the stored energy during winter months when sunlight may be insufficient to meet the power grid's requirements.

[0017] FIG. 1 is a schematic diagram of an electrochemical cell, such as battery 100, according to various embodiments. Battery 100 may include a positive electrode 102, an electrolyte 106, and a negative electrode 104. In various embodiments, the negative electrode 104 may be integrated with a current collector 108. As a specific example, battery 100, positive electrode 102, electrolyte 106, negative electrode 104, and / or current collector 108 may be any battery, positive electrode, electrolyte, negative electrode, and / or current collector described in U.S. Patent Application Publication No. 2020 / 0036002, U.S. Patent Application Publication No. 2021 / 0028452, and / or U.S. Patent Application Publication No. 2021 / 0028457, and the entire contents of all three of these applications are incorporated herein by reference for all purposes. One or more batteries 100 may be connected to each other within an energy storage system, such as a long-term energy storage system or an ultra-long-term energy storage system.

[0018] In various embodiments, electrolyte 106 may be any electrolyte known in the art, for example, any electrolyte useful for an iron-alkali battery. In various embodiments, the negative electrode 104 may be formed from a porous metal such as porous iron and / or may include a porous metal such as porous iron. In various embodiments, the negative electrode 104 may be an alkali electrode such as an alkali iron electrode.

[0019] The current collector 108 may be a mesh or other porous surface integrated with a material used in a process (such as the reduction process described herein) for forming the negative electrode 104. The current collector 108 may be an iron plate. The current collector 108 may be metallurgically bonded to the electrode 104 via mechanical pressure or may be placed in an electrically conductive state with the electrode 104. Since the electrode 104 can be very conductive, it is not necessary to collect current along its entire length, and only current collection at the tab at the upper part of the electrode 104 is required. Alternatively, since the electrode 104 can be very porous, its conductivity is extremely low, and current collection is required along the entire electrode area.

[0020] The positive electrode 102 may also be referred to as a counter electrode, and the counter electrode (or positive electrode 102) for such an anode may be any counter electrode known in the art, for example, an air-breathing cathode, a nickel oxyhydroxide electrode, and a manganese dioxide electrode, but not limited thereto, and may be any counter electrode for an alkali iron battery.

[0021] Considering the large volume change between the charge products and the discharge products produced during the electrochemical cycle of an alkali iron electrode such as the negative electrode 104, the porosity can be an important indicator for determining the capacity obtained from the iron electrode. Therefore, a method for achieving a high-porosity, low-cost iron electrode is interesting for achieving a high-performance, low-cost iron battery.

[0022] Without being limited to any specific theory or model regarding the reactivity of iron electrodes such as negative electrode 104, a possible scheme for the oxidation of iron electrodes such as negative electrode 104 in an alkaline electrolyte such as electrolyte 106 can proceed according to the following two reaction steps (reactions 1 and 2 in Table 1). Additional or different reaction products may be formed (one of which is described as reaction 3 in Table 1 below), but the characteristics of the volume change after the reaction are common to all oxidation products of metallic iron.

[0023] [Table 1]

[0024] Table 2 shows some of the main physical properties of selected charge and discharge products in alkali iron electrodes such as negative electrode 104.

[0025] [Table 2]

[0026] The Pilling-Bedworth ratio is the ratio of the volume of a basic cell of a metal oxide to the volume of a basic cell of the corresponding metal (in which the oxide is formed), and is a measure of the net volume change in one step of a reaction.

[0027] Iron-based materials exhibiting high porosity can be manufactured using particulate material processing techniques. One technique for introducing porosity during particulate material processing is the introduction of a transient phase. In one embodiment, iron materials manufactured using rotary or linear hearth processes (RHF or LHF, respectively) generally utilize a coal-based reducing agent, which also acts as a transient pore-forming agent. Materials manufactured by the above processes may have advantageous properties when used as iron electrodes (e.g., negative electrode 104) in a battery (a battery may also be referred to herein as an electrochemical cell). Other methods for introducing a transient phase and forming iron-based materials by low-cost reduction techniques are also described. In some cases, the iron-based material may be electrochemically reduced inside the battery assembly (e.g., battery 100) rather than being thermochemically reduced during the processing steps prior to introduction into the battery (e.g., battery 100). In various embodiments, the iron electrode of a battery (or electrochemical cell), such as battery 100, may also be the negative electrode (e.g., negative electrode 104) of the battery (or electrochemical cell).

[0028] Various embodiments may relate to the geometric shape of the material to be introduced into the reduction process and the method for creating said geometric shape. Iron-based materials for alkaline batteries such as battery 100 can take various forms, some of which are described along with the advantages and disadvantages of each form.

[0029] Iron-based materials for use in reduction processes can be manufactured at very low cost from iron precursor pellets. Such iron precursor pellets can be formed, for example, by techniques used in the production of oxide pellets for blast furnaces and oxide pellets for direct reduction. During the pelletizing process, a transient phase can be introduced into the mixture being agglomerated, thereby providing a homogeneous mixture of the transient phase and the other components in the pellet. Such an approach is useful in that it takes advantage of the large-scale and low-cost benefits of pelletizing processes used in various industries, such as steelmaking. Pellets produced by such a process are usually nearly spherical, and their size can range from a few millimeters to tens of millimeters. The radius of the pellet may be selected to obtain a desired reaction rate in the reduction process, or to obtain desired material and electrical transfer properties when used as an electrode in an energy storage device (such as the negative electrode 104 in battery 100). An example of introducing a transient phase into a mixture used for agglomeration is the introduction of coke into pellets used in rotary hearth furnaces.

[0030] Iron-based materials may be manufactured in sheet form rather than pellet form. These sheets may be produced by extruding or doctor-blade processing an iron precursor material into a sheet. The mixture used in the sheet manufacturing process may include a transient phase. In one example, a magnetite ore concentrate mixed with coke may be doctor-blade to a thickness of approximately 5 mm and then reduced in a linear hearth furnace. In another example, the sheet may be cut into strips and then fed into a rotary hearth furnace. The thickness of the sheet may be selected to obtain a desired reaction rate in the reduction process or to obtain desired material and electrical transfer properties when used as an electrode in an energy storage device (such as the negative electrode 104 in battery 100).

[0031] For iron-based materials, other geometric shapes such as rods, discs, or plates may be possible. These geometric shapes can generally be formed by techniques for forming green bodies in particulate material processing techniques, such as roller compression of sheets, pressing and slip casting of plates, and the production of rods and discs by extrusion. Discs can be obtained by cutting the material obtained by extrusion after it exits the die when using a circular die, or by die compression, or by slip casting into a circular mold.

[0032] In some cases, the geometric shape obtained from the reduction process may then be crushed into smaller pieces. For example, a 10 mm (mm=10) piece obtained from the direct reduction process may be used. -3 Pellets having a diameter of the order of m) are ground after the reduction step and purified so that the particle size after the grinding process is substantially 1 mm to 6 mm.

[0033] Numerous processes are available to achieve the reduction of iron-containing materials to less oxidized iron or metallic iron.

[0034] In one embodiment, the iron-containing material may be reduced by the decomposition of a carbon-containing material contained in or distributed adjacent to the precursor material. This can occur by solid-state reduction using coal, coke, or other carbon-containing materials, such as in a rotary hearth furnace used for the direct production of reduced iron. In other reduction processes using carbon-containing materials, the carbon-containing material is distributed adjacent to the iron-containing material, and the reduction occurs via gas-phase transfer of reducing species from the carbon-containing material to the iron-containing material. For example, coal can be thermally decomposed in the presence of oxygen to produce various reducing species such as methane, hydrogen, and carbon monoxide. Any process used in rotary furnace reduction processes or rotary hearth reduction processes should be considered applicable to the reduction of iron-containing materials, including coal gasification, in which coal is not strictly adjacent to the iron-containing material but can still be used as a reducing agent.

[0035] Iron-containing materials can also be reduced by reactions using gaseous reducing agents. Numerous methods exist for introducing such reducing gases. These numerous methods of reduction using gaseous components may be further subdivided (into batch processes and continuous processes) depending on the machine performing the reduction process. These processes can also be considered in terms of the atmosphere used. A non-exclusive list of machines used to create a reducing atmosphere and types of reducing gases that may be used includes: 1) various machines for introducing reducing gases, e.g., batch processes (e.g., use of box furnaces, tubular furnaces, vacuum furnaces, or any other type of batch process furnace), and / or continuous processes (e.g., use of linear horizontal furnaces such as walking beam furnaces, linear hearth furnaces, belt furnaces, kiln furnaces, calcination furnaces, vertical shaft furnaces, fluidized bed reactors, grate furnaces such as moving grate furnaces into which reducing gas is introduced, or any other type of continuous process furnace); and / or 2) various types of reducing atmospheres, such as carbon monoxide, hydrogen, methane, hydrogen sulfide, nitrogen, argon, decomposed ammonia, and / or combinations thereof, and reducing atmospheres produced in various ways, including electrolysis, natural gas, reactions of natural gas with water (including the use of synthesis gas and water-gas-shifted synthesis gas).

[0036] Despite their considerable diversity, these processes all share a common requirement: temperatures generally exceeding 400°C (usually substantially higher) and continuous refreshing of the gas atmosphere to achieve a moderate reduction rate and adequate completion of the reduction reaction. The required time generally depends on many factors (starting material, desired final reduction state, particle size, powder thickness, etc.), but a typical condition range is 700°C to 1450°C and 15 minutes to 3 hours at the peak temperature.

[0037] In another embodiment, the iron-containing material may be electrochemically reduced. This can occur in an alkaline electrolyte (often having a pH greater than 12). A current collector and conductor may be provided through the pore space to facilitate the electrochemical process. Reduction may also be carried out outside the alkaline medium. The reduction may occur inside the same electrochemical cell used for electrochemical energy storage, for example, inside battery 100.

[0038] Various embodiments may include the use of a transient phase pore-forming agent for pore formation in electrodes such as the negative electrode 104. The transient phase may be used to form pore spaces within the powder compact (i.e., to act as a pore-forming agent). An essential requirement of the transient phase acting as a pore-forming agent is that, during the processing of the powder, it maintains the open volume within the powder until the powder achieves sufficient mechanical integrity (the pore-forming agent is removed, and the volume left by the pore-forming agent remains as pores). In other words, pore-forming agents can be used to increase the porosity of the material to which they are added. Since different powders achieve sufficient mechanical integrity at various points during processing, the means of introducing the pore-forming agent and the means of removing the pore-forming agent from the powder may depend on the processing applied to the powder. Several methods for introducing pore-forming agents are described below. First, the pore-forming agent itself is described based on the timing / method of its entry into and exit from the powder compact. Next, the geometric characteristics of the pore-forming agent are described within the scope of its application to the manufacture of iron-containing electrodes for energy storage.

[0039] Various embodiments may include using one or more materials as pore-forming agents. Generally, the reduction of the aforementioned iron-containing materials can occur either by thermochemical reduction at high temperatures or by electrochemical reduction at lower temperatures.

[0040] First, transient pore-forming agents for high-temperature reduction processes are described. There are at least three methods for introducing pores into materials produced by high-temperature processing via pore-forming agents: 1) removing the pore-forming agent before high-temperature processing; 2) removing the pore-forming agent during high-temperature processing; and / or 3) removing the pore-forming agent after high-temperature processing. The functional characteristics and examples of each are described below.

[0041] To remove the pore-forming agent from the powder before high-temperature processing, the pore-forming agent may be introduced into the powder first, the powder may be left to stand until it reaches some strength, and then the pore-forming agent may be removed. In this example, the pore-forming agent may be introduced into a powder containing a binder (often a water-soluble binder that hardens when dried from water). After the binder has hardened, or after the material has been strengthened in other ways, the powder may be treated so that the pore-forming agent is removed. In practice, the pore-forming agent may be any material soluble in an organic solvent (i.e., paraffin wax hexane solution), the porous body may be iron ore using cement (e.g., bentonite, sodium carbonate, calcium chloride, or sodium silicate) as a binder, and after the pellet has dried, the pore-forming agent may be dissolved by exposing the porous body to an organic solvent that dissolves the pore-forming agent but does not modify the binder. In a second example, the iron ore porous body uses cement as a binder, which may harden and become insoluble in water when dried. Therefore, pore-forming agents that dissolve in water (e.g., sodium chloride or any other water-soluble salt) can be removed from the pellets by re-exposing them to water. The pore-forming agent may also be a metallic carbonate such as sodium carbonate or calcium carbonate (e.g., limestone), which dissolves in a weakly acidic solution and leaves pores. In the last example, a solid pore-forming material that is inert during the porous body formation process but readily evaporates during subsequent processing may be added to the porous body. For example, ammonium bicarbonate may be added to a compacted magnetite ore body, the compaction being sufficient to impart sufficient mechanical integrity to the porous body, and when the ammonium bicarbonate is removed from the porous body by evaporation, some of the volume previously occupied by the ammonium bicarbonate may be retained as pores. This evaporation may occur at low temperatures (about 36-41°C) and may be achieved before high-temperature processing.

[0042] Materials removed during the high-temperature processing step may also be added. There are two steps that often occur during the processing of iron-containing precursor materials. The first step occurs before many reduction processes and after the formation of blast furnace pellets and direct reduction pellets, known as induration. During this process, the pellets or other powders are oxidized at high temperatures. Through this oxidation process, the material also acquires mechanical integrity. Coke or other materials that evaporate in the presence of high temperatures may be added to the powder to act as transient pore-forming agents. Polymers, wood fibers, and carbonaceous materials produced by torrefaction may all be added as means of inducing porosity during induration. Note that this step is not necessarily required in the processing pathway, as not all materials need to indurate before reduction.

[0043] During the high-temperature reduction process, the powder is exposed to gas (usually carbon monoxide and hydrogen), which reduces the iron-containing material. Materials that tend to change volume dramatically when exposed to such an atmosphere may be added to the iron-containing powder as a means of increasing the porosity of the resulting material. For example, iron sulfide and iron sulfate are not conventionally included in iron precursor material mixtures as inputs to the reduction process. However, in the specific case of iron-alkali electrodes, these iron-sulfur compounds can serve several useful purposes. Firstly, sulfur has been found to be a useful compound in iron electrodes for promoting improved discharge capacity. Secondly, iron sulfide and iron sulfate have a very high ratio of the molar volume of the compound to the molar volume of iron produced during decomposition. Therefore, these iron-sulfur compounds can act as pore-forming agents during sulfur and oxygen loss due to their large volume reduction. In this respect, iron(II) sulfate is a particularly inexpensive and effective pore-forming agent. The ratio of the volume of sulfate to the volume of iron during reduction is 5.9 to 1 in the anhydrous state, and an even larger volume ratio has been observed in the hydrated compound. Iron(II) sulfate is a byproduct of the pickling process in steelmaking and is typically recycled in this way to introduce pore-forming agents, which introduce residual iron and sulfur as byproducts of the pore-forming process. Other iron sulfides and sulfates can similarly be used as transient phases and deposit iron and sulfur, including but not limited to iron(II,II) sulfate, machinawite, marcasite, pyrite, troilite, pyrrhotite, gleigate, and amorphous iron(II) sulfide.

[0044] Considering that some materials can undergo useful phase transitions upon exposure to oxygen and subsequent reduction, other compounds can be usefully introduced into iron-containing materials treated by hardening and subsequent reduction. In one embodiment, lead sulfide may be pulverized into fine particles and introduced as part of the iron-containing material mixture before the hardening process. During the hardening process, the lead sulfide may be roasted to form lead oxide. It should be noted that both the melting and boiling points of lead sulfide are lower than the typical hardening temperatures of iron oxide pellets. To retain lead in the pellets, the hardening process may need to be carried out at a temperature substantially lower than the boiling point of lead sulfide (generally at least 20°C), preferably lower than the melting point of lead sulfide. At some temperatures, higher oxygen concentrations and longer times may be required to achieve the same degree of hardening as with higher-temperature hardening processes. The degree to which liquid lead affects the development of the microstructure is generally a function of the various components in the iron pellet.

[0045] The lead oxide can then be reduced to form lead metal homogeneously distributed within the pore spaces of the iron body. Lead is a known inhibitor of the hydrogen evolution reaction, which competes with the charging process of the iron electrode. Therefore, including lead sulfide in the iron-containing precursor material can simultaneously lead to pore formation and the inclusion of useful compounds in the resulting battery electrode.

[0046] The material may act as a pore-forming agent in the iron-containing material by dissolution after the reduction process. Only a limited number of materials are stable after reduction in hydrogen, often at temperatures exceeding 700°C. In one embodiment, silica, which is soluble in alkaline electrolytes, may be included. In another embodiment, sodium silicate (also known as water glass) may dissolve in aqueous solution after the reduction process. In yet another embodiment, silicates such as quartz, feldspar, mica, amphibole, pyroxene, or olivine may be incorporated as soluble, transient pore-forming agents. Basic oxides stable during the reduction process, such as sodium oxide, calcium oxide, or magnesium oxide, can be readily etched from the iron framework by acid after the reduction process (although such oxides are also soluble in alkaline solutions). In some embodiments, the basic oxide may first be added as a metal salt such as a sulfate, carbonate, or hydroxide, and the thermal decomposition of this oxide results in an initial volume reduction that improves porosity. Optionally, for further improvement of porosity, the basic oxide may then be removed by dissolution. For example, calcium carbonate in the form of limestone, or dolomite (calcium carbonate-magnesium), or calcium hydroxide or magnesium hydroxide, each decomposes thermally at temperatures ranging from 500 to 1100°C, leaving behind their respective oxides.

[0047] Finally, in the case of electrodes where reduction occurs electrochemically, the pore-forming agent may be selected to dissolve in the electrolyte. In one embodiment, the pore-forming agent may be a salt that is a component of the electrolyte. As an example, one component of an alkaline electrolyte for an iron battery may be potassium hydroxide or sodium hydroxide. A pore-forming agent made from potassium hydroxide can reduce costs by acting as both an electrolyte additive and a pore-forming agent. In another embodiment, the pore-forming agent may be a substance that is inert during the electrochemical process, such as ammonium nitrate or potassium sulfate.

[0048] In certain embodiments, the transient pore-forming agent may be a reducing agent in the conversion of iron ore (a more oxidized material) to metal iron. In certain other embodiments, the transient pore-forming agent may be reduced itself in the reduction step. In certain other embodiments, multiple pore-forming agents can be used, including combinations and variations of pore-forming agents, some acting as reducing agents, and others not participating in the reduction reaction.

[0049] The geometric relationship between the pore-forming agent and other elements of the microstructure plays a crucial role in determining the optimal size and volume fraction of the pore-forming agent. Two general regimes can be distinguished. In one regime, the performance of the battery is limited by the amount of porosity directly surrounding the iron. In this regime, the optimal pore-forming agent particle size is approximately the same as the particle size of the iron precursor particles introduced into the reduction process. In this regime, by making the size of the pore-forming agent approximately match the particle size, the porosity added by the addition of the pore-forming agent is distributed most homogeneously, and the amount of porosity not directly adjacent to the reacting iron surface is minimized. Directly adjacent can be defined as being within 1 mean pore radius from the iron surface. If the pore-forming agent particles are not approximately equiaxed, it is desirable that the short axis of the pore-forming agent approximately coincides with the diameter of the iron ore particles.

[0050] In the second system, the performance of the battery is limited by the filling of pore spaces and the transport of mass through the anode. In this system, the goal of introducing a pore-forming agent is to create sufficiently large pores that are not filled with discharge products, so that the pores can act as highly diffusive pathways through the microstructure. In this system, it is desirable that the pore-forming agent has a particle size greater than twice the thickness of the layer of discharge products observable on the reacted iron surface. Thus, the pores should remain open after the formation of discharge products and facilitate mass transport through the electrode. If the pore-forming agent is not nearly equiaxed, the guideline should be followed that the short axis of the pore-forming agent is at least twice the thickness of the layer of discharge products. When it is desired to create unobstructed diffusion pathways through the porous material, the aspect ratio of the pore-forming agent should be considered, as different aspect ratios result in different penetration thresholds for residual porosity. High aspect ratio rods penetrate randomly assembled porous materials at the lowest volume fraction, potentially resulting in the maximum increase in diffusion rate at the lowest volume fraction of pore-forming agent (and therefore lowest additional cost). In general, in the second system, the return on performance is likely to decrease when more than approximately 30–35 volume% of pore-forming agent is added (where the volume fraction of pore-forming agent is expressed as the percentage of solid added to the porous material), due to the high porosity achieved after reduction and the high likelihood of pore penetration. Nevertheless, in the relevant electrode systems, high volume fractions of pore-forming agent have been demonstrated to provide some benefit to battery performance, quantified by an increase in battery discharge capacity. The volume fraction of pore-forming agent can be up to 45 volume% in some embodiments, yet still beneficial for increasing anode capacity. While high volume fractions of pore-forming agents are generally beneficial to several aspects of battery performance, there may be a boundary at which a reasonable improvement in performance is observed, and in some cases, pore-forming agents are effective as reducing agents in the reduction process. In many situations, at least 5 volume percent of pore-forming agents is required to obtain a substantial increase in battery performance and to achieve a sufficient improvement in performance. When coke is added to magnetite ore, weight percent may be used instead to quantify the amount of pore-forming additive contained.When coke is added to magnetite ore, a weight percentage of 3–10% of coke is sufficient to achieve the desired combination of pore formation and reduction.

[0051] Pore-forming agents with pore sizes far larger than the stated limits (approximately twice the thickness of the discharge layer and approximately the average particle size) are likely to provide less performance improvement compared to finer pore-forming agents on a volume equivalent basis. In all cases, as the volume fraction of the pore-forming agent increases, mass transport becomes easier and polarization due to mass transport is reduced, but the effective conductivity of the porous material decreases, as does the volumetric energy density of the electrode. The optimal amount of pore-forming agent can be derived from impedance measurements in the system, measurements of the main impedance sources, and considerations regarding the required energy density of the system. Regarding porosity, there is a contradictory relationship: increasing porosity improves ion transport (reaction rate) but decreases energy density per unit volume; this contradictory relationship implies that there is an optimal porosity that maximizes energy density for a given rate.

[0052] Generally, the addition of pore-forming agents with much finer particle sizes than the input iron-containing material may result in other beneficial process characteristics (e.g., more effective reduction and faster reduction rates in rotary hearth reduction processes), but is unlikely to result in a substantial increase in porosity.

[0053] In some electrode configurations, a combination of the above effects can be used to achieve a desired superposition of effects. For example, fine equiaxed pore-forming agents on the order of particle size may be added to increase the accessible volume for the formation of discharge products, or high aspect ratio fibrous pore-forming agents may be added to enhance mass transport through the porous material.

[0054] Generally, pore-forming agents are usefully combined when their various roles are complementary. In one typical example, coke may be added to carry out a solid-state reduction process of an iron-containing precursor, but too much added coke can result in an undesirable high carbon content after the reduction process. In situations where a larger amount of pore-forming agent is desired than the amount that can be added without producing an undesirable high carbon content, a second pore-forming additive may be added in addition to the coke to provide pore-forming functionality without adding additional carbon, while maintaining a sufficient level of coke to achieve the desired reduction reaction.

[0055] The source of iron-containing material used in various embodiments may be any material commonly used in either iron electrodes or industrial iron reduction processes, including but not limited to: 1) steelmaking dust; 2) mill scale (e.g., mill scale may be crushed or otherwise processed to achieve appropriate size and shape); 3) iron ore, concentrated and / or beneficiated ore, including ore separated by flotation or magnetic separation (e.g., iron ore may include hematite ore, magnetite ore, iron-sulfur compounds, etc.); 4) iron mesh and iron wire embedded in electrodes to function as current collectors and / or iron sources; and 5) a combination of one or more of Examples 1-4 with iron powder, such as carbonyl iron powder, sponge iron powder, water atomized powder, etc.

[0056] In the fabrication of sintered iron electrodes, coke can also be used as a transient phase that simply forms pores without a reduction step. Coke is one of the lowest-cost pore-forming agent candidates on a per-unit volume basis, and the protective reducing environment created by the coke within the powder allows for considerably looser atmospheric control during the sintering process.

[0057] The particle size of the iron precursor material may be selected based on the particle size inherent to the upstream process used in the production of the iron ore source, the particle size required to successfully reduce the iron ore source during the appropriate reduction process applied, or the resulting iron electrode material that achieves sufficient performance during the electrochemical cycle. Generally, fine ore particles are desirable for both the reduction process and electrochemical performance, and good particle size before reduction is desirable for magnetite-based ores with a battery discharge timescale of about 10 hours. 90 <45 microns. (d N d is the particle size corresponding to the Nth percentile of the particle size distribution. For example, d 90 This refers to the 90th percentile of the particle size distribution, or in other words, 90% of the particles in a given distribution are d 90 It has a size less than . This can be measured by dynamic light scattering, imaging, or other methods known in the art. Other particle sizes are possible depending on the reduction and electrochemical processes applied, and larger particle sizes can be used if the reduction time is long and the electrochemical charge / discharge rate is low. In batteries that require much higher rate capacities, iron precursor sizes may be required, and d 50 A precursor size of approximately 8 microns is desirable. The requirement for fineness of the iron precursor material being introduced is generally balanced by considering the costs associated with performing more powerful grinding operations.

[0058] Based on the various embodiments described above, Figure 2 illustrates various embodiments of method 200 for forming an electrode such as a negative electrode 104 using one or more transient pore-forming agents.

[0059] In step 202, a material for reduction is provided to the electrode (such as the negative electrode 104). This material may be a metal-based material, such as the materials discussed above, for example, an iron-based material. The material may be a precursor material, such as an iron precursor pellet, an iron precursor sheet, an iron precursor flake, an iron precursor disc, an iron precursor rod, or an iron precursor powder. Specifically, the metal may be steelmaking dust, mill scale, iron ore, iron mesh, iron wire, iron powder, or any combination thereof.

[0060] In step 204, one or more transient pore-forming agents may be added to the material. In various embodiments, the transient pore-forming agent is a reducing agent such as carbon. In various embodiments, the transient pore-forming agent is iron(II) sulfate, iron(II,II) sulfate, machinawite, marcasite, pyrite, troilite, pyrrhotite, glygite, amorphous iron(II) sulfide, or lead sulfide. In various embodiments, the transient pore-forming agent may be coal. In various embodiments, the transient pore-forming agent may be silica, sodium silicate, sodium oxide, calcium oxide, or magnesium oxide. In various embodiments, the transient pore-forming agent may include coke. In various embodiments, the transient pore-forming agent may include a metal carbonate. In various embodiments, the transient pore-forming agent may be two or more different transient pore-forming agents.

[0061] In the high-temperature reduction process described above, the addition of one or more transient pore-forming agents in step 204 may occur before or during the reduction process.

[0062] In embodiments where electrochemical reduction of the electrode may occur, the addition of a transient pore-forming agent in step 204 may occur during electrochemical reduction, for example, during reduction within a battery (e.g., 100). For example, the transient pore-forming agent may be a salt of the electrolyte (e.g., electrolyte 106). If the addition of a transient pore-forming agent in step 204 may occur during electrochemical reduction, the transient pore-forming agent may be potassium, sodium hydroxide, ammonium nitrate, and / or potassium sulfate.

[0063] In some optional embodiments, in the optional step 205, at least a portion of the transient pore-forming agent may be removed before reduction in step 206. Thus, step 205 may be optional, as described above. The transient pore-forming agent may be dissolved or evaporated before reduction.

[0064] In step 206, reduction of the porous electrode may occur. The reduction may be by high-temperature treatment or by a lower-temperature electrochemical process, such as electrochemical reduction in a battery (e.g., 100). As described above, the reduction process, whether thermal or electrochemical, results in the removal of at least some of one or more transient pore-forming agents, thereby forming pores in the resulting electrode. Specifically, a porous metal electrode, such as an iron-containing porous metal electrode, may be formed.

[0065] In some optional embodiments, at least a portion of the transient pore-forming agent may be removed in the optional step 207 after the reduction in step 206. Thus, step 207 can be optional. As described above, the transient pore-forming agent may be dissolved in the electrolyte in the reduced cell, dissolved in an aqueous solution, etched using an acid bath after reduction, etc.

[0066] Various embodiments can provide devices and / or methods for use in bulk energy storage systems, such as long-term energy storage (LODES) systems and short-term energy storage (SDES) systems. For example, various embodiments can provide batteries for bulk energy storage systems, such as batteries for LODES systems. Renewable energy sources are becoming increasingly widespread and cost-effective. However, many renewable energy sources face intermittency issues that hinder their adoption. The impact of the intermittency tendency of renewable energy sources can be mitigated by pairing them with bulk energy storage systems, such as LODES systems and SDES systems. To support the adoption of combined power generation, transmission, and storage systems (e.g., renewable power sources paired with bulk energy storage systems, and power plants having transmission equipment in either the power plant or the bulk energy storage system), devices and methods are needed to support the design and operation of such combined power generation, transmission, and storage systems, including the various embodiments of devices and methods described herein.

[0067] A combined-use power generation, transmission, and storage system may be a power plant comprising one or more power sources (e.g., one or more renewable power sources, one or more non-renewable power sources, or a combination of renewable and non-renewable power sources), one or more transmission facilities, and one or more bulk energy storage systems. The transmission facilities in either the power plant or / or bulk energy storage system may be optimized concurrently with the power generation and storage systems, or they may impose constraints on the design and operation of the power generation and storage systems. A combined-use power generation, transmission, and storage system can be configured to meet various output targets under various design and operational constraints.

[0068] Figures 3-11 show various exemplary systems in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system such as a LODES system or an SDES system. For example, referring to Figures 1-2, the various embodiments described herein can be used as batteries for a bulk energy storage system such as a LODES system or an SDES system, and / or the various electrodes described herein can be used as components of a bulk energy storage system. As used herein, the term “LODES system” means a bulk energy storage system configured to have a rated duration (energy / power ratio) of 24 hours (h) or longer, such as a 24-hour duration, a 24-to-50-hour duration, a duration longer than 50 hours, a 24-to-150-hour duration, a duration longer than 150 hours, a 24-to-200-hour duration, a duration longer than 200 hours, a 24-to-500-hour duration, or a duration longer than 500 hours.

[0069] Figure 3 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of various embodiments described herein, various electrodes described herein, and the like. The LODES system 304 may be electrically connected to a wind power station 302 and one or more power transmission facilities 306. The wind power station 302 may be electrically connected to the power transmission facility 306. The power transmission facility 306 may be electrically connected to a power distribution network 308. The wind power station 302 can generate electricity and output the generated electricity to the LODES system 304 and / or the power transmission facility 306. The LODES system 304 can store the electricity received from the wind power station 302 and / or the power transmission facility 306. The LODES system 304 can output stored power to the transmission equipment 306. The transmission equipment 306 can output power received from either or both of the wind power station 302 and the LODES system 304 to the distribution network 308, and / or can receive power from the distribution network 308 and output that power to the LODES system 304. Together, the wind power station 302, the LODES system 304, and the transmission equipment 306 can constitute a power plant 300, which may be a combined power generation, transmission, and storage system. Power generated by the wind power station 302 may be directly supplied to the distribution network 308 via the transmission equipment 306, or it may first be stored in the LODES system 304. In certain cases, the power supplied to the distribution network 308 may be all from the wind power station 302, all from the LODES system 304, or a combination of the wind power station 302 and the LODES system 304.The distribution of electricity from the combined wind power base 302 and the LODES system 304 power plant 300 may be controlled according to a predetermined long-term (multiple days or even more years) schedule, or according to the day-ahead (24-hour prior notice) market, or according to the hour-ahead market, or according to real-time pricing signals.

[0070] As one example of the operation of power plant 300, the LODES system 304 can be used to reshape and "stabilize" the power produced by wind turbine 302. In one such example, wind turbine 302 may have a peak power output (capacity) of 260 megawatts (MW) and a capacity factor (CF) of 41%. The LODES system 304 may have a power rating (capacity) of 106 MW, a rated duration (energy / power ratio) of 150 hours (h), and a rated energy of 15,900 megawatt-hours (MWh). In another such example, wind turbine 302 may have a peak power output (capacity) of 300 MW and a capacity factor (CF) of 41%. The LODES system 304 may have a power rating of 106 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 21,200 MWh. In another such example, wind power station 302 may have a peak power output (capacity) of 176 MW and a capacity factor (CF) of 53%. The LODES system 304 may have a power rating (capacity) of 88 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 13,200 MWh. In another such example, wind power station 302 may have a peak power output (capacity) of 277 MW and a capacity factor (CF) of 41%. The LODES system 304 may have a power rating (capacity) of 97 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 4,850 MWh. In yet another such example, wind power station 302 may have a peak power output (capacity) of 315 MW and a capacity factor (CF) of 41%. The LODES system 304 may have a power rating (capacity) of 110 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 2,750 MWh.

[0071] Figure 4 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of various embodiments described herein, various electrodes described herein, and the like. The system in Figure 4 may be similar to the system in Figure 3, except that a photovoltaic (PV) base station 402 may be used instead of a wind power base station 302. The LODES system 304 may be electrically connected to the PV base station 402 and one or more power transmission facilities 306. The PV base station 402 may be electrically connected to the power transmission facility 306. The power transmission facility 306 may be electrically connected to the power distribution network 308. The PV base station 402 can generate electricity, and the PV base station 402 can output the generated electricity to the LODES system 304 and / or the power transmission facility 306. The LODES system 304 can store electricity received from the PV base station 402 and / or the transmission equipment 306. The LODES system 304 can output the stored electricity to the transmission equipment 306. The transmission equipment 306 can output electricity received from either or both of the PV base station 402 and the LODES system 304 to the distribution network 308, and / or receive electricity from the distribution network 308 and output that electricity to the LODES system 304. Together, the PV base station 402, the LODES system 304, and the transmission equipment 306 can constitute a power plant 400, which may be a combined power generation, transmission, and storage system. Electricity generated by the PV base station 402 may be directly supplied to the distribution network 308 via the transmission equipment 306, or it may first be stored in the LODES system 304. In certain cases, the power supplied to the distribution network 308 may be entirely from the PV base station 402, entirely from the LODES system 304, or from a combination of the PV base station 402 and the LODES system 304.The distribution of electricity from the combined PV base station 402 and the LODES system 304 power plant 400 may be controlled according to a predetermined long-term (multiple days or even more years) schedule, or according to the day-ahead (24-hour prior notice) market, or according to the hour-ahead market, or according to real-time pricing signals.

[0072] As one example of the operation of power plant 400, the LODES system 304 can be used to reshape and "stabilize" the power produced by PV base station 402. In one such example, PV base station 402 may have a peak power output (capacity) of 490 MW and a capacity factor (CF) of 24%. The LODES system 304 may have a power rating (capacity) of 340 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 51,000 MWh. In another such example, PV base station 402 may have a peak power output (capacity) of 680 MW and a capacity factor (CF) of 24%. The LODES system 304 may have a power rating (capacity) of 410 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 82,000 MWh. In another such example, PV base station 402 may have a peak power output (capacity) of 330 MW and a capacity factor (CF) of 31%. LODES system 304 may have a power rating (capacity) of 215 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 32,250 MWh. In another such example, PV base station 402 may have a peak power output (capacity) of 510 MW and a capacity factor (CF) of 24%. LODES system 304 may have a power rating (capacity) of 380 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 19,000 MWh. In yet another such example, PV base station 402 may have a peak power output (capacity) of 630 MW and a capacity factor (CF) of 24%. The LODES system 304 may have a power rating (capacity) of 380 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 9,500 MWh.

[0073] Figure 5 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of various embodiments described herein, various electrodes described herein, and the like. The system in Figure 5 may be similar to the systems in Figures 3 and 4, except that both the wind power station 302 and the photovoltaic (PV) station 402 may be power generators operating together in the power plant 500. Together, the PV station 402, the wind power station 302, the LODES system 304, and the transmission equipment 306 can constitute a power plant 500, which may be a combined power generation, transmission, and storage system. The power generated by the PV station 402 and / or the wind power station 302 may be directly transmitted to the distribution network 308 via the transmission equipment 306, or it may first be stored in the LODES system 304. In certain cases, the electricity supplied to the distribution network 308 may be entirely from the PV base station 402, entirely from the wind power base station 302, entirely from the LODES system 304, or from a combination of the PV base station 402, the wind power base station 302, and the LODES system 304. The distribution of electricity from the combined wind power base station 302, PV base station 402, and LODES system 304 power plant 500 may be controlled according to a predetermined long-term (multiple days or even more years) schedule, or according to the day-ahead (24-hour prior notice) market, or according to the hour-ahead market, or according to real-time pricing signals.

[0074] As one example of the operation of power plant 500, the LODES system 304 can be used to reshape and "stabilize" the power produced by wind turbines 302 and PV turbines 402. In one such example, wind turbine 302 may have a peak power output (capacity) of 126 MW and a capacity factor (CF) of 41%, and PV turbine 402 may have a peak power output (capacity) of 126 MW and a capacity factor (CF) of 24%. The LODES system 304 may have a power rating (capacity) of 63 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 9,450 MWh. In another such example, wind turbine 302 may have a peak power output (capacity) of 170 MW and a capacity factor (CF) of 41%, and PV turbine 402 may have a peak power output (capacity) of 110 MW and a capacity factor (CF) of 24%. The LODES system 304 may have a power rating (capacity) of 57 MW, a rated duration (energy / power ratio) of 200 hours, and a rated energy of 11,400 MWh. In another such example, the wind power station 302 may have a peak power output (capacity) of 105 MW and a capacity factor (CF) of 51%, and the PV station 402 may have a peak power output (capacity) of 70 MW and a capacity factor (CF) of 31%. The LODES system 304 may have a power rating (capacity) of 61 MW, a rated duration (energy / power ratio) of 150 hours, and a rated energy of 9,150 MWh. In another such example, the wind power station 302 may have a peak power output (capacity) of 135 MW and a capacity factor (CF) of 41%, and the PV station 402 may have a peak power output (capacity) of 90 MW and a capacity factor (CF) of 24%. The LODES system 304 may have a power rating (capacity) of 68 MW, a rated duration (energy / power ratio) of 50 hours, and a rated energy of 3,400 MWh. In another such example, the wind power station 302 may have a peak power output (capacity) of 144 MW and a capacity factor (CF) of 41%, and the PV station 402 may have a peak power output (capacity) of 96 MW and a capacity factor (CF) of 24%.The LODES system 304 may have a power rating (capacity) of 72 MW, a rated duration (energy / power ratio) of 25 hours, and a rated energy of 1,800 MWh.

[0075] Figure 6 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of the various embodiments described herein, various electrodes described herein, and the like. The LODES system 304 may be electrically connected to one or more power transmission facilities 306. In this way, the LODES system 304 can operate in a “standalone” manner to arbitrage energy near market prices and / or avoid power transmission constraints. The LODES system 304 may be electrically connected to one or more power transmission facilities 306. The power transmission facilities 306 may be electrically connected to a distribution network 308. The LODES system 304 can store power received from the power transmission facilities 306. The LODES system 304 can output the stored power to the power transmission facilities 306. The power transmission equipment 306 can output power received from the LODES system 304 to the distribution network 308, and / or receive power from the distribution network 308 and output that power to the LODES system 304.

[0076] The LODES system 304 and the transmission equipment 306 together can constitute a power plant 600. As an example, the power plant 600 may be located downstream of the transmission constraint, closer to power consumption. In such an exemplary downstream power plant 600, the LODES system 304 may have a duration of 24 to 500 hours and may undergo one or more full discharges per year to support peak power consumption at times when transmission capacity is insufficient to serve customers. In addition, in such an exemplary downstream power plant 600, the LODES system 304 may undergo several shallow discharges (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and reduce the overall cost of electricity services to customers. As a further example, the power plant 600 may be located upstream of the transmission constraint, closer to power generation. In such exemplary upstream power plants 600, the LODES system 304 may have a duration of 24 to 500 hours and may undergo full charges once or more times a year to absorb excess power generation when transmission capacity is insufficient to distribute electricity to customers. In addition, in such exemplary upstream power plants 600, the LODES system 304 may undergo several shallow charge-discharge cycles (daily or more frequently) to arbitrage the difference between nighttime and daytime electricity prices and maximize the value of the power generation equipment's output.

[0077] Figure 7 shows an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of the various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of the various embodiments described herein, electrodes of the various embodiments described herein, and so on. The LODES system 304 may be electrically connected to commercial and industrial (C&I) customers 702, such as data centers and factories. The LODES system 304 may be electrically connected to one or more power transmission facilities 306. The power transmission facilities 306 may be electrically connected to a power distribution network 308. The power transmission facilities 306 can receive power from the power distribution network 308 and output that power to the LODES system 304. The LODES system 304 can store the power received from the power transmission facilities 306. The LODES system 304 can output the stored power to the C&I customers 702. In this way, the LODES system 304 can reshape the electricity purchased from the distribution network 308 to match the consumption patterns of the C&I customer 702.

[0078] The LODES system 304 and the transmission equipment 306 can together constitute a power plant 700. As an example, the power plant 700 may be located near electricity consumption, i.e., near C&I customer 702, such as between the distribution network 308 and C&I customer 702. In such an example, the LODES system 304 may have a duration of 24 to 500 hours and may purchase electricity from the market when electricity is cheaper, thereby charging the LODES system 304. The LODES system 304 can then discharge when market prices are high to provide electricity to C&I customer 702, thus offsetting C&I customer 702's market purchases. As an alternative configuration, the power plant 700 may be located not between the distribution network 308 and C&I customer 702, but between renewable resources such as PV base stations and wind power base stations, and transmission equipment 306 which may be connected to renewable resources. In such alternative examples, the LODES system 304 may have a duration of 24 to 500 hours, and the LODES system 304 may be charged at a time when renewable output may be available. The LODES system 304 can then discharge to cover part or all of the power demand of the C&I customer 702, thereby providing the C&I customer 702 with renewable generated electricity.

[0079] Figure 8 shows an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of the various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of the various embodiments described herein, various electrodes described herein, and the like. The LODES system 304 may be electrically connected to a wind power station 302 and one or more power transmission facilities 306. The wind power station 302 may be electrically connected to the power transmission facility 306. The power transmission facility 306 may be electrically connected to the C&I customer 702. The wind power station 302 can generate electricity and output the generated electricity to the LODES system 304 and / or the power transmission facility 306. The LODES system 304 can store the electricity received from the wind power station 302.

[0080] The LODES system 304 can output the stored power to the transmission equipment 306. The transmission equipment 306 can output the power received from either or both of the wind turbine 302 and the LODES system 304 to the C&I customer 702. Together, the wind turbine 302, the LODES system 304, and the transmission equipment 306 can constitute a power plant 800, which may be a combined power generation, transmission, and storage system. The power generated by the wind turbine 302 may be supplied directly to the C&I customer 702 via the transmission equipment 306, or it may be first stored in the LODES system 304. In certain cases, the power supplied to the C&I customer 702 may be supplied entirely from the wind turbine 302, entirely from the LODES system 304, or from a combination of the wind turbine 302 and the LODES system 304. The LODES system 304 may be used to reshape the electricity generated by the wind turbine 302 to match the consumption patterns of the C&I customer 702. In one such example, the LODES system 304 may have a duration of 24 to 500 hours and may be charged when renewable power generation by the wind turbine 302 exceeds the load of the C&I customer 702. The LODES system 304 may then be discharged when renewable power generation by the wind turbine 302 falls below the load of the C&I customer 702, to provide the C&I customer 702 with a stable renewable profile that offsets some or all of the C&I customer 702's electricity consumption.

[0081] Figure 9 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 304. For example, the LODES system 304 may include various embodiment batteries described herein, various electrodes described herein, and the like. The LODES system 304 integrates a large amount of renewable energy into a microgrid, for example, harmonizing the output of renewable energy from PV base stations 402 and wind power base stations 302 with existing thermal power from, for example, a thermal power plant 902 (e.g., a gas plant, coal plant, diesel generator set, etc., or a combination of thermal power methods), and where the availability rate is high, the renewable and thermal power may be part of a power plant 900 supplying a C&I customer load 702. A microgrid such as the one comprising power plant 900 and thermal power plant 902 can provide an availability rate of 90% or higher. The electricity generated by PV base station 402 and / or wind power base station 302 may be supplied directly to C&I customer 702, or it may first be stored in LODES system 304.

[0082] In a particular case, the electricity supplied to C&I customer 702 may be entirely from PV terminal 402, entirely from wind power terminal 302, entirely from LODES system 304, entirely from thermal power plant 902, or from any combination of PV terminal 402, wind power terminal 302, LODES system 304, and / or thermal power plant 902. As an example, the LODES system 304 of power plant 900 may have a duration of 24 to 500 hours. In a specific example, the load on C&I customer 702 may have a peak of 100 MW, the LODES system 304 may have a power rating of 14 MW and a duration of 150 hours, the cost of natural gas may be $6 per million British pound thermal energy (MMBTU), and the renewable occupancy rate may be 58%. As another specific example, the C&I customer 702 load may have a peak of 100 MW, the LODES system 304 may have a power rating of 25 MW and a duration of 150 hours, the natural gas cost may be $8 per million British pound thermal energy (MMBTU), and the renewable occupancy rate may be 65%.

[0083] Figure 10 shows an exemplary system in which one or more aspects of the various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of the various embodiments may be a LODES system 304. For example, the LODES system 304 may include batteries of the various embodiments described herein, electrodes of the various embodiments described herein, and so on. Using the LODES system 304, a nuclear power plant 1002 (or other inflexible power generation facilities such as thermal, biomass, and / or any other type of power plant with a ramp speed of less than 50% of rated power per hour and a capacity factor of 80% or higher) can be enhanced to add flexibility to the combined output of a power plant 1000, which is comprised of a combined LODES system 304 and the nuclear power plant 1002. The nuclear power plant 1002 can operate at a high capacity factor and at its highest efficiency point, and the LODES system 304 can be charged and discharged to effectively reshape the output of the nuclear power plant 1002 to match customer electricity consumption and / or market prices for electricity. For example, the LODES system 304 of power plant 1000 may have a duration of 24 to 500 hours. In one specific example, nuclear power plant 1002 may have a rated output of 1,000 MW, and nuclear power plant 1002 may be forced to perform minimum stable power generation or even shut down for a long period due to a decline in the market price of electricity. The LODES system 304 can avoid facility shutdown when market prices fall and can be charged, and then the LODES system 304 can discharge when market prices rise and restore total power generation.

[0084] Figure 11 shows an exemplary system in which one or more aspects of various embodiments can be used as part of a bulk energy storage system. Specifically, a bulk energy storage system incorporating one or more aspects of various embodiments may be the LODES system 304. For example, the LODES system 304 may include batteries of the various embodiments described herein, various electrodes described herein, and the like. The LODES system 304 can operate in conjunction with the SDES system 1102. Together, the LODES system 304 and the SDES system 1102 may constitute a power plant 1100. For example, the LODES system 304 and the SDES system 1102 can be optimized simultaneously, thereby enabling the LODES system 304 to provide various services, including long-term backup and / or bridging, over multi-day fluctuations (e.g., market prices, renewable power generation, electricity consumption, etc.). The SDES system 1102 can provide a range of services, including rapid auxiliary services (e.g., voltage control, frequency regulation, etc.) and / or bridging, across daytime fluctuations (e.g., daytime fluctuations such as market prices, renewable power generation, and electricity consumption). The SDES system 1102 may have a duration of less than 10 hours and a round-trip efficiency greater than 80%. The LODES system 304 may have a duration of 24 to 500 hours and a round-trip efficiency greater than 40%. In one such example, the LODES system 304 may have a duration of 150 hours and can support customer electricity consumption for up to one week of renewable power shortages. The LODES system 304 can also enhance the capacity of the SDES system 1102 to support customer electricity consumption during daytime power shortage events. Furthermore, the SDES system 1102 can supply customers during daytime power shortage events and provide quality services such as power regulation, voltage control, and frequency regulation.

[0085] To illustrate various embodiments, several examples are shown below. Example 1: A battery comprising a positive electrode, an electrolyte, and a negative electrode, wherein the negative electrode comprises a porous metal. Example 2: The battery according to Example 1, wherein the porous metal is at least partially manufactured using at least one transient pore-forming agent. Example 3: The battery according to Example 1 or 2, wherein the porous metal comprises iron. Example 4: The battery according to Example 2 or 3, wherein the transient pore-forming agent is a reducing agent. Example 5: The battery according to Example 4, wherein the reducing agent comprises carbon. Example 6: The battery according to any of Examples 2 to 5, wherein the transient pore-forming agent comprises iron(II) sulfate, iron(II,II) sulfate, machinawite, marcasite, pyrite, troilite, pyrrhotite, glygite, amorphous iron(II) sulfide, or lead sulfide. Example 7: The battery according to any of Examples 2 to 5, wherein the transient pore-forming agent comprises coal. Example 8. A battery according to any of Examples 1 to 7, wherein the porous metal is produced by reduction in a hearth furnace. Example 9. A battery according to Example 8, wherein the hearth furnace is a rotary hearth furnace or a linear hearth furnace. Example 10. A battery according to any of Examples 1 to 7, wherein the porous metal is produced by reduction in a rotary kiln. Example 11. A battery according to any of Examples 1 to 7, wherein the formation of pores in the porous metal occurs by electrochemical reduction in the battery. Example 12. A battery according to Example 11, wherein the transient pore-forming agent comprises silica, sodium silicate, sodium oxide, calcium oxide, or magnesium oxide. Example 13. A battery according to Example 11, wherein the transient pore-forming agent comprises a salt of the electrolyte. Example 14. A battery according to Example 13, wherein the transient pore-forming agent comprises potassium hydroxide or sodium hydroxide. Example 15. A battery according to Example 11, wherein the transient pore-forming agent comprises ammonium nitrate or potassium sulfate. Example 16. A battery according to any of Examples 2 to 15, wherein the porous metal is formed from a precursor material having a first size, and the particle size of the transient pore-forming agent is approximately the same as the first size. Example 17. A battery according to any of Examples 2 to 15, wherein the porous metal has a layer of discharge products on its surface, and the particle size of the transient pore-forming agent is more than twice the thickness of the discharge product layer.Example 18. A battery according to any of Examples 2 to 17, wherein at least one transient pore-forming agent comprises at least two different transient pore-forming agents. Example 19. A battery according to Example 18, wherein the two different transient pore-forming agents are different types of pore-forming agents and / or pore-forming agents of different sizes. Example 20. A battery according to any of Examples 1 to 19, further comprising a current collector metallurgically bonded to the negative electrode and / or a current collector in electrical conductivity with the negative electrode, wherein the current collector is along at least a portion of the negative electrode. Example 21. A battery according to any of Examples 1 to 19, wherein the positive electrode comprises an air-breathing cathode, a nickel oxyhydroxide electrode, or a manganese dioxide electrode. Example 22. A battery according to any of Examples 3 to 21, wherein the iron comprises steelmaking dust, mill scale, iron ore, iron mesh, iron wire, iron powder, or any combination thereof. Example 23. A battery according to any of Examples 2 to 22, wherein the transient pore-forming agent comprises coke. Example 24. A battery according to any of Examples 1 to 23, wherein the porous metal is manufactured using a pore-forming agent comprising a metal carbonate at least in part. Example 25. A method for forming a porous metal for the negative electrode of a battery, comprising forming pores in the porous metal using at least one transient pore-forming agent. Example 26. The method according to Example 25, wherein the transient pore-forming agent is a transient pore-forming agent according to any of Examples 3 to 24, and the pores are formed with or without a reduction step. Example 27. A bulk energy storage system comprising one or more batteries according to any of Examples 1 to 24. Example 28. A long-term energy storage system configured to retain charge for at least 24 hours, comprising one or more batteries according to any of Examples 1 to 24.

[0086] The descriptions of the above-described methods are provided merely as illustrative examples and are not intended to require or suggest that the steps of the various embodiments must be performed in the order presented. As those skilled in the art will understand, the order of the steps in the above-described embodiments can be performed in any order. Words such as “then,” “next,” and “then” are not necessarily intended to limit the order of the steps, and such words may be used to guide the reader throughout the description of the method. Furthermore, all references to singular claim elements using, for example, the articles “a,” “an,” or “the” should not be interpreted as limiting the element to the singular form.

[0087] Furthermore, any step of any embodiment described herein can be used in any other embodiment. The preceding descriptions of the embodiments of this disclosure are provided to enable those skilled in the art to construct or use the invention. Various modifications to these embodiments will be immediately apparent to those skilled in the art, and the basic principles set forth herein can be applied to other embodiments without departing from the scope of the invention. Accordingly, the invention is not intended to be limited to the embodiments shown herein, and the broadest scope should be given that is consistent with the principles and novel features disclosed herein.

Claims

1. Positive electrode and, Electrolytes, A battery comprising a negative electrode containing an iron-containing precursor material and a transient pore-forming agent, The transient pore-forming agent is dispersed in the iron-containing precursor material. The iron-containing precursor material is electrochemically reducible to iron in the electrolyte, The transient pore-forming agent is soluble in an electrolyte. battery.

2. The transient pore-forming agent and the iron-containing precursor material have the same average particle size. The battery according to claim 1.

3. The transient pore-forming agent is equiaxed. The battery according to claim 1.

4. The transient pore-forming agent is fibrous. The battery according to claim 1.

5. The aforementioned iron-containing precursor material includes iron ore. The battery according to claim 1.

6. The average particle size of the iron-containing precursor material is between 8 microns and 45 microns. The battery according to claim 1.

7. The transient pore-forming agent is present in the negative electrode in a volume percentage greater than 5% by volume and less than 45% by volume. The battery according to claim 1.

8. The aforementioned iron-containing precursor material contains iron powder. The battery according to claim 1.

9. The aforementioned iron-containing precursor material includes iron oxide pellets. The battery according to claim 1.

10. The transient pore-forming agent is a salt, which is a component of the electrolyte. The battery according to claim 1.

11. The electrolyte is alkaline. The battery according to claim 1.

12. The pH of the electrolyte is greater than 12. The battery according to claim 11.

13. The transient pore-forming agent comprises at least one of potassium hydroxide or sodium hydroxide. The battery according to claim 11.

14. The transient pore-forming agent is inert when the iron-containing precursor material is electrochemically reduced to iron in the negative electrode. The battery according to claim 1.

15. The transient pore-forming agent comprises one or more of ammonium nitrate or potassium sulfate. The battery according to claim 14.

16. The positive electrode is an air-breathing cathode. The battery according to claim 1.

17. Furthermore, the current collector is included, and the negative electrode is metallurgically coupled to the current collector via mechanical pressure. The battery according to claim 1.

18. The current collector is arranged across the entire area of ​​the negative electrode. The battery according to claim 17.

Images