Molten metal battery system having self-priming cells

Abstract

A battery cell capable of self-priming with molten metal produced within the battery cell includes a cathode compartment configured to contain a catholyte that releases metal ions, an anode compartment at least partially containing an anode current collector that receives electrons from an external power source, an ion selective membrane disposed between the cathode compartment and the anode compartment and configured to selectively transport metal ions from the cathode compartment to the anode compartment when the battery cell is self-primed, and an electron transport structure extending within the anode compartment between the anode current collector and the ion selective membrane and configured to transport electrons from the anode current collector to the ion selective membrane when the battery cell is self-primed. Self-priming includes combining electrons with metal ions that reach an interface between the electron transport structure and the ion selective membrane to produce molten metal within the anode compartment.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 63 / 333,371, filed April 21, 2022, which is incorporated by reference herein in its entirety. [Background technology]

[0002] background The present disclosure relates generally to electrochemical batteries, and in particular to electrochemical battery systems that use molten sodium or other molten metals. Batteries are known devices used to store and release electrical energy for various purposes. To generate electrical energy, batteries typically convert chemical energy directly into electrical energy. Generally, a single battery includes one or more galvanic cells, each of which is made of two half-cells that are electrically isolated except through an external circuit. During discharge, electrochemical reduction occurs at the positive electrode of the cell and electrochemical oxidation occurs at the negative electrode of the cell. The positive and negative electrodes in the cell do not physically contact each other, and they are generally chemically connected by one or more ionically conductive and electrically insulating electrolytes, which can be either in a solid or liquid state, or a combination thereof. When an external circuit, or a load, is connected to the terminal connected to the negative electrode and the terminal connected to the positive electrode, the battery conducts electrons through the external circuit and ions move through the electrolyte.

[0003] Batteries can be classified in various ways. For example, batteries that are fully discharged only once are often referred to as primary batteries or cells. In contrast, batteries that can be discharged and recharged more than once are often referred to as secondary batteries or cells. A flow battery or redox flow battery is a type of secondary cell in which chemical energy is provided by two chemical components dissolved in liquids (i.e., anolyte and catholyte) pumped through the system on separate sides of an ion-selective membrane. While the anolyte and catholyte circulate within their own respective spaces on opposite sides of the membrane, ion transfer occurs through the membrane. The ion transfer is accompanied by the flow of electric current into or out of the electrodes (i.e., the anode and cathode) that are at least partially located within the anolyte and catholyte, respectively. The anolyte and catholyte are typically ionically conductive and electrically insulating electrolytes that facilitate ion exchange but do not conduct significant electric current. Thus, the fluid circuits through which the anolyte and catholyte flow can pass through multiple battery cells without the need to pass current between the battery cells via the anolyte or catholyte fluids.

[0004] A molten sodium battery is a special type of secondary cell that replaces both the anode and anolyte of a conventional secondary cell with molten sodium metal (elemental symbol Na). One example of a molten sodium battery is described in detail in U.S. Pat. No. 10,020,543, issued July 10, 2018, the entire disclosure of which is incorporated herein by reference. When a molten sodium battery is discharged, positively charged sodium ions or cations (Na + ) is an electron (e - ) is isolated from Na + The ions pass through the ion-selective membrane to react with the catholyte on the other side of the membrane, and the electrons are conducted through an external circuit. When a molten sodium battery is charged, the opposite reaction occurs. Na + Ions pass from the catholyte through the ion selective membrane and combine with electrons on the anode side of the membrane to form sodium metal.

[0005] Sodium metal batteries may include a molten sodium anode combined with a high energy density cathode such as a sulfur, nickel chloride, halogen, or intercalation cathode. Typically, a ceramic sodium ion conducting membrane such as sodium beta alumina or NaSICON is used to separate the molten sodium anode from the cathode. These batteries may be self-contained, where the molten sodium anode and cathode / catholyte are hermetically sealed within their respective compartments, or may be configured as a hybrid flow battery, where sodium can move between the anode chamber and an external container, and catholyte can be actively circulated between the cathode chamber and an external source.

[0006] In previous sodium metal battery systems, the battery cell must be preloaded with sodium metal and the cathode / catholyte. For example, the anode compartment of the battery cell must be pre-filled (i.e., primed) with sodium metal prior to operation. Priming is typically necessary because initially the anode compartment of the battery cell is empty, and prior to operation, the negative terminal of the battery cell (i.e., the anode current collector) is separated from the ion-selective membrane by an air gap or other non-conductive fluid. This electrical blockage prevents electrons from transferring from the negative terminal to the surface of the ion-selective membrane, where metal cations transported from the cathode compartment through the ion-selective membrane can combine with the electrons to form sodium metal in the anode compartment. Priming the anode compartment with sodium metal prior to operation provides the necessary electrical connection between the negative terminal and the ion-selective membrane because sodium metal is an electrical conductor. Typically, however, priming the anode compartment requires an initial supply of sodium metal added to the battery cell from an external source. Elaborate steps must be taken in handling the molten sodium metal and loading it into the anode compartment, increasing the complexity and cost of the battery system.

[0007] In a self-contained or sealed sodium metal battery, the anode compartment is typically preloaded with sodium metal during manufacturing (i.e., before the anode compartment is sealed). This is necessary because if the anode compartment is filled and a good sodium-membrane interface is not established, localized high current densities on the cathode and membrane can damage the battery cell during initial operation. Thus, self-contained sodium metal batteries are often conditioned using low current conditions in the manufacturing facility to establish a good sodium-membrane interface. This requires the establishment of a closed circuit before operation. In addition, preloading sodium into a self-contained sodium metal battery means that the battery cell is manufactured in a charged state. This requires that the cathode is also manufactured in a charged state. Typically, this requires dealing with more energetic chemicals such as sulfur, halogens, etc. Charged cells are also prone to self-discharge and accidental shorts. Although it is desirable to build a battery cell in a discharged state, the need to preload sodium in the anode compartment does not allow for construction in a discharged state for the reasons discussed above. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] U.S. Patent No. 10,020,543 Summary of the Invention

[0009] overview The present disclosure provides a novel solution to the problems associated with conventional molten sodium batteries and battery systems. Rather than pre-loading or priming the battery cell with molten sodium from an external source during manufacture or prior to operation, molten sodium is generated in situ in the anode compartment by drawing sodium ions from the catholyte. This eliminates the need to condition the battery cell using low current conditions to prevent hot spots and eliminates the need to close the circuit between the battery cell's negative terminal and the ion-selective membrane prior to commissioning. The present disclosure describes the construction of such a battery cell and a method of operation for generating sodium in situ, referred to herein as self-priming.

[0010] One implementation of the disclosure is a battery cell capable of self-priming with molten metal generated within the battery cell. The battery cell includes a cathode compartment configured to contain a catholyte that releases metal ions upon self-priming of the battery cell, an anode compartment at least partially housing an anode current collector that receives electrons from an external power source upon self-priming of the battery cell, an ion selective membrane disposed between the cathode compartment and the anode compartment and configured to selectively transport metal ions from the cathode compartment to the anode compartment upon self-priming of the battery cell, and an electron transport structure extending within the anode compartment between the anode current collector and the ion selective membrane and configured to transport electrons from the anode current collector to the ion selective membrane upon self-priming of the battery cell. Self-priming the battery cell includes combining electrons with metal ions that reach an interface between the electron transport structure and the ion selective membrane to generate molten metal within the anode compartment.

[0011] In some embodiments, prior to self-priming of the battery cell, no molten metal is present in the anode compartment, and upon self-priming of the battery cell, molten metal generated in the anode compartment at least partially fills the anode compartment with molten metal without the need for additional molten metal provided from an external source.

[0012] In some embodiments, the battery cell includes a conductive coating on a surface of the ion selective membrane facing the anode compartment and configured to distribute electrons received from the electron transport structure across the surface of the ion selective membrane. In some embodiments, the conductive coating includes at least one of a metal, a metal oxide, a metal sulfide, or carbon. In some embodiments, the conductive coating includes at least one of indium tin oxide, manganese oxide, titanium oxide, nickel oxide, tungsten sulfide, nickel sulfide, titanium sulfide, zirconium sulfide, vanadium sulfide, iron sulfide, molybdenum sulfide, cobalt sulfide, or copper sulfide. In some embodiments, the conductive coating includes a second metal including at least one of tin, lead, mercury, indium, and / or any metal capable of alloying with the molten metal. In some embodiments, the conductive coating forms a conductive layer between the molten metal and the ion selective membrane when the molten metal is initially generated in the anode compartment, and dissolves in the molten metal generated in the anode compartment such that the molten metal directly contacts the surface of the ion selective membrane after dissolution of the conductive coating. In some embodiments, the conductive coating has a thickness of substantially 10 nanometers to 10 micrometers. In some embodiments, the conductive coating has a conductivity of substantially 100 Siemens / cm to 10 6 (i.e., 1,000,000) Siemens / cm. In some embodiments, the conductive coating has a conductivity of substantially 10 Siemens / cm to 10 6 Siemens / cm, or a subrange thereof (e.g., 10 Siemens / cm to 10 5 Siemens / cm, 100 Siemens / cm~105 Siemens / cm, 100 Siemens / cm~10 6 It has a conductivity of 1000 siemens / cm.

[0013] In some embodiments, the electron transport structure contacts the conductive coating at a single location, and the conductive coating accepts electrons at the single location and distributes the electrons across the surface of the ion selective membrane. In some embodiments, the electron transport structure includes a conductive mesh that contacts the surface of the ion selective membrane at multiple locations and is configured to distribute electrons received from the anode current collector across the surface of the ion selective membrane. In some embodiments, the electron transport structure is substantially rigid and provides structural support to the ion selective membrane by exerting a force on the surface of the ion selective membrane. In some embodiments, the electron transport structure includes one or more wires extending between the anode current collector and the ion selective membrane.

[0014] In some embodiments, the electron transport structure provides a first electrical connection between the anode current collector and the ion selective membrane prior to self-priming of the battery cell and is configured to melt or dissolve in the molten metal generated in the anode compartment, In some embodiments, the molten metal generated in the anode compartment provides a second electrical connection between the anode current collector and the ion selective membrane after the electron transport structure melts or dissolves.

[0015] In some embodiments, the electron transport structure and the anode current collector are integrated parts of a monolithic anode scaffold structure that includes a three-dimensional lattice of conductive material. In some embodiments, the electron transport structure is located along the exterior boundary of the anode compartment such that the electron transport structure forms at least a portion of the exterior boundary of the anode compartment and contains the molten metal in the anode compartment after the molten metal is generated in the anode compartment. In some embodiments, the electron transport structure is constructed separately from the anode current collector and ion selective membrane and is constructed first before being inserted into the anode compartment.

[0016] In some embodiments, the anode current collector comprises a metal plate comprising at least one of steel, nickel, or carbon.

[0017] In some embodiments, the battery cell includes a port along a surface of the anode compartment, hi some embodiments, molten metal generated in the anode compartment passively flows between the anode compartment and an external storage vessel through the port without the need for powered components to flow the molten metal.

[0018] Another implementation of the present disclosure is a method for self-priming a battery cell with molten metal produced within the battery cell, the method including releasing metal ions from a catholyte contained within a cathode compartment of the battery cell, receiving electrons from an external power source at an anode current collector at least partially contained within an anode compartment of the battery cell, transporting the metal ions from the cathode compartment to the anode compartment through an ion selective membrane disposed between the cathode compartment and the anode compartment, transporting the electrons from the anode current collector to the ion selective membrane through an electron transport structure extending within the anode compartment between the anode current collector and the ion selective membrane, and combining the electrons and the metal ions in the anode compartment to produce molten metal in the anode compartment, thereby self-priming the battery cell.

[0019] In some embodiments, prior to self-priming the battery cell, there is no molten metal in the anode compartment, and self-priming the battery cell includes at least partially filling the anode compartment with molten metal generated within the anode compartment without requiring a supply of additional molten metal from an external source.

[0020] In some embodiments, a first portion of the metal ions released from the catholyte forms a first portion of molten metal that at least partially fills the anode compartment during self-priming of the battery cell, and in some embodiments, a second portion of the metal ions released from the catholyte forms a second portion of molten metal that flows out of the anode compartment and into an external storage vessel after self-priming of the battery cell. [Brief description of the drawings]

[0021] The present disclosure will become more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which like reference numerals refer to like elements and in which:

[0022] [Figure 1] FIG. 2 is a diagram of a self-priming battery cell ("unit cell") including an electron transport structure in the anode compartment of the unit cell, according to some embodiments.

[0023] [Diagram 2] FIG. 2 illustrates wire connections in the anode compartment of a unit cell of the example electron transport structure of FIG. 1 according to some embodiments.

[0024] [Diagram 3] 2 illustrates wire connections at least partially outside the unit cell of the example electron transport structure of FIG. 1, according to some embodiments.

[0025] [Figure 4] FIG. 2 illustrates multiple wires in the anode compartment of a unit cell of the example electron transport structure of FIG. 1 according to some embodiments.

[0026] [Diagram 5] FIG. 2 illustrates a conductive mesh in the anode compartment of a unit cell of the example electron transport structure of FIG. 1 according to some embodiments.

[0027] [Figure 6] 2 is a side view of a unit cell illustrating a contact tab extending from an anode current collector for the example electron transport structure of FIG. 1 according to some embodiments.

[0028] [Figure 7] FIG. 7 is a cross-sectional view of the unit cell of FIG. 6 taken along line AA according to some embodiments.

[0029] [Figure 8] 2 is a side view of a unit cell illustrating a node extending from an anode current collector for the example electron transport structure of FIG. 1 according to some embodiments.

[0030] [Figure 9] FIG. 9 is a cross-sectional view of the unit cell of FIG. 8 taken along line BB according to some embodiments.

[0031] [Figure 10] 2 is a perspective view of a unit cell illustrating an electron transport plate with a notch and contact tabs as an example of the electron transport structure of FIG. 1 according to some embodiments.

[0032] [Figure 11] FIG. 2 is a first perspective view of a molten sodium battery system that can use the self-priming battery cell of FIG. 1 in accordance with some embodiments.

[0033] [Figure 12] FIG. 12 is a second perspective view of the system of FIG. 11 according to some embodiments.

[0034] [Figure 13] FIG. 12 is a schematic diagram of electrical connections within the system of FIG. 11 according to some embodiments.

[0035] [Figure 14]FIG. 12 is a diagram of fluid flow in the system of FIG. 11 in a flow battery charging mode, according to some embodiments.

[0036] [Figure 15] FIG. 12 is a diagram of fluid flow in the system of FIG. 11 in a flow battery discharge mode, according to some embodiments.

[0037] [Figure 16] FIG. 12 is a diagram of fluid flow in the system of FIG. 11 in sodium production mode according to some embodiments.

[0038] [Figure 17] 12 is a diagram of fluid flow through cells of a string of the system of FIG. 11 according to some embodiments.

[0039] [Figure 18] FIG. 12 is another diagram of fluid flow through the cells of a string of the system of FIG. 11 according to some embodiments.

[0040] [Figure 19] FIG. 12 is a first perspective view of a sodium distributor of the system of FIG. 11 according to some embodiments.

[0041] [Figure 20] FIG. 20 is a second perspective view of a sodium distributor of the system of FIG. 19 according to some embodiments.

[0042] [Figure 21] 20 is a first cutaway view of the sodium distributor of FIG. 19 according to some embodiments.

[0043] [Figure 22] 20 is a second cutaway view of the sodium distributor of FIG. 19 according to some embodiments.

[0044] [Figure 23]FIG. 12 is a perspective view of a sodium concentrator of the system of FIG. 11 according to some embodiments.

[0045] [Figure 24] FIG. 24 is a first cutaway view of the sodium concentrator of FIG. 23 according to some embodiments.

[0046] [Diagram 25] FIG. 24 is a second cutaway view of the sodium concentrator of FIG. 23 according to some embodiments.

[0047] [Figure 26] 12 is a cutaway perspective view of a distributor that can be used with the system of FIG. 11 according to some embodiments.

[0048] [Figure 27] FIG. 12 is a diagram of fluid flow in the system of FIG. 11 in a first aggregate storage flow battery mode, according to some embodiments.

[0049] [Figure 28] FIG. 12 is a diagram of fluid flow in the system of FIG. 11 in a second aggregate storage flow battery mode, according to some embodiments.

[0050] [Figure 29] FIG. 1 illustrates a geographically distributed implementation of features disclosed herein, according to some embodiments.

[0051] [Diagram 30] 12 illustrates electrochemical reactions that may occur when charging a unit cell of the system of FIG. 11 and / or the self-priming battery cell of FIG. 1, in accordance with some embodiments.

[0052] [Diagram 31] 12 illustrates electrochemical reactions that may occur when discharging a unit cell of the system of FIG. 11 and / or the self-priming battery cell of FIG. 1, in accordance with some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] Detailed Description Overview Referring generally to the drawings, a molten sodium battery system having a self-priming battery cell and its components are shown according to various exemplary embodiments. Although the battery system is described and illustrated throughout this disclosure primarily as a molten sodium battery system, it is contemplated that various other molten alkali metals, other types of molten metals (i.e., non-alkali metals), molten metal alloys or eutectic mixtures, pure molten metals (i.e., not a mixture of multiple different metals), and / or other conductive fluids, substances, or materials may be used in place of molten sodium metal without departing from the teachings provided herein. The specific types of chemicals, substances, and materials provided herein are examples suitable for practicing the systems and methods of the present disclosure, but should not be considered as limiting. In the following description, for ease of description, the battery system will be primarily referred to as a molten sodium battery system or a molten metal battery system.

[0054] A molten sodium battery system may include one or more secondary cells (i.e., rechargeable battery cells), each including a molten sodium metal anode, an ion-selective membrane (as used herein, the term "membrane" refers to any suitable type of separator), and a cathode compartment through which catholyte is circulated (e.g., via an external pump). The ion-selective membrane is positioned between the molten sodium metal anode and the catholyte compartment and allows the positively charged sodium cations (Na + ) is allowed to pass through.

[0055] The molten sodium battery system can operate in multiple modes, including a flow battery mode and a sodium production mode. In the flow battery mode, the molten sodium battery system can operate to charge or discharge the battery. When charging the battery, electricity is consumed to produce sodium. + Ions pass from the catholyte through the ion-selective membrane and are released into the atmosphere (e - ) to form molten metal (Na). The charging process is illustrated in FIG. 30. In some embodiments, the catholyte (e.g., Na2S) combines with sodium cations (e.g., 2Na + ), electron (2e - ), and one or more other elements or compounds (e.g., S). In some embodiments, the reaction occurs through various polysulfides (e.g., Na2S8, Na2S7, Na2S6, Na2S5, Na2S4, Na2S3, Na2S2, Na2S). When discharging the battery, the opposite reaction occurs. Sodium metal flows from the string-specific sodium reservoir to the molten sodium anode of the unit cell and is consumed within the unit cell to produce sodium ions Na + and produces electrons. + The ions pass through the ion-selective membrane to react with the catholyte, and the electrons are discharged from the battery in the form of electricity. The discharge process is illustrated in Figure 31. In sodium production mode, the molten sodium battery system operates similarly to when charging a battery in flow battery mode. Electricity is consumed to produce Na + Ions pass from the catholyte through the ion selective membrane and are converted into electrons (e - ) to form sodium metal (Na) as shown above.

[0056] In previous molten metal battery systems that use molten metal as the anode of the battery cell, the anode compartment of the battery cell must be pre-filled (i.e., primed) with molten metal prior to operation. Priming is typically necessary because the anode compartment of the battery cell is initially empty, such that the negative terminal (i.e., the anode current collector) of the battery cell is separated from the ion-selective membrane by an air gap or other non-conductive fluid prior to operation. This electrical blockage prevents electrons from migrating from the negative terminal to the surface of the ion-selective membrane where metal cations transported from the cathode compartment through the ion-selective membrane can combine with the electrons to form sodium metal in the anode compartment. Because molten metal is an electrical conductor, priming the anode compartment with molten metal prior to operation provides the necessary electrical connection between the negative terminal and the ion-selective membrane. Typically, however, priming the anode compartment requires an initial supply of molten metal that is added to the battery cell from an external source.

[0057] Advantageously, the self-priming battery cells described herein may be capable of priming themselves with molten metal (e.g., molten sodium) without requiring an external supply of molten metal (e.g., from an external sodium source). The self-priming battery cells are capable of generating an initial amount of molten metal used to prime the anode compartment in situ (i.e., within the anode compartment), thus eliminating the need to preload the anode compartment with molten metal from an external source prior to operation. A key feature that enables self-priming is an electron transport structure, which provides an electrical connection between the negative terminal and the ion selective membrane before the anode compartment is filled with molten metal. The electron transport structure allows electrons from the negative terminal to reach the surface of the ion selective membrane, so that metal cations arriving from the cathode compartment can be reduced to molten metal as soon as they exit the ion selective membrane. In some embodiments, the surface of the ion selective membrane facing the anode compartment can be covered with a conductive coating (e.g., tin or other materials, described in more detail below), which serves to distribute electrons arriving via the electron transport structure across the surface of the ion selective membrane. This unique cell structure eliminates the need for the anode compartment to be pre-filled with molten metal to provide the necessary electrical connections prior to operation.

[0058] As the molten metal begins to form in the anode compartment, an additional electrical connection (i.e., via the molten metal) is made between the negative terminal and the ion-selective membrane. This allows the electron transport structure to be removed and / or allows for a temporary or self-dissipating electron transport structure. For example, the electron transport structure can be made of a material that dissolves, melts into, or alloys with the molten metal in the anode compartment. As the anode compartment fills with the molten metal, the conductive coating can be temporary or self-dissipating as well, as the molten metal distributes electrons across the surface of the ion-selective membrane. The electron transport structure can take any of a variety of forms, including one or more wires that contact the ion-selective membrane at one or more locations, a conductive mesh (e.g., a lattice structure, scaffold, framework, etc.) that provides structural support to the anode compartment in addition to electrical flow paths, one or more rigid panels that form the boundaries of the anode compartment, or any of a variety of other forms. These and other features of the self-priming battery cell are described in more detail below.

[0059] Self-Priming Battery Cells 1-10, a self-priming battery cell 100 according to various exemplary embodiments is shown. The self-priming battery cell 100 may be used in any type of molten metal battery system (e.g., a molten sodium battery system), or any other type of battery system using molten metal, or other types of conductive materials or combinations of conductive materials as the anode and / or cathode. An example of a molten metal battery system 1100 in which the self-priming battery cell 100 may be used is described in further detail below with reference to FIGS. 11-31. The self-priming battery cell 100 may be an embodiment of a battery cell 1700 in the system 1100 (described in further detail below) and may be capable of performing some or all of the functions of the battery cell 1700 described with reference thereto. The self-priming battery cell 100 may include some or all of the components of the battery cell 1700 and may operate in a sodium production mode, a flow battery charging mode, a flow battery discharging mode, or any other mode described in further detail with reference to FIGS. 11-31. It is contemplated that any of the components or functionality of self-priming battery cell 100 may be added to or included in battery cell 1700 and combined with any of the components or functionality described with reference thereto without departing from the teachings of the present disclosure.

[0060] Self-priming battery cell construction 1, a self-priming battery cell 100 is shown including an anode compartment 102, an ion selective membrane 104, a cathode compartment 106, an anode current collector 108, and a cathode 110. Many of the components of the self-priming battery cell 100 may be the same as or similar to the corresponding components of the battery cell 1700. For example, the cathode compartment 106 may be the same as or similar to the catholyte chamber 1704 of the battery cell 1700. The cathode compartment 106 is configured to receive metal ions (e.g., sodium cations Na ) during charging of the self-priming battery cell 100 (e.g., during operation in a sodium production mode, a flow battery charging mode, and / or self-priming). + ) can be configured to contain a catholyte that releases sodium cations (e.g., 2Na + ), electron (2e -), and one or more other elements or compounds (e.g., S). In some embodiments, the reaction occurs through various polysulfides (e.g., Na2S8, Na2S7, Na2S6, Na2S5, Na2S4, Na2S3, Na2S2, Na2S). The catholyte may include any suitable type of positive electrolyte or positive electrode solution. In some embodiments, the catholyte may be or include any type of fluid capable of exchanging metal ions (e.g., sodium ions or other metal cations) with the molten metal contained in the anode compartment 102. Examples of suitable catholytes include, but are not limited to, sodium sulfide, sodium halides, aluminum sulfide, aluminum halides, and / or any of the positive electrolytes or positive electrode solutions described in U.S. Patent No. 10,734,686, issued August 4, 2020, U.S. Patent No. 8,968,902, issued March 3, 2015, U.S. Patent Application No. 2021 / 0280898, published September 9, 2021, and / or U.S. Patent Application No. 2021 / 0277529, published September 9, 2021. The entire disclosures of each of these patents and patent application publications are incorporated by reference herein.

[0061] The catholyte may flow through a catholyte circuit 101 that connects the cathode compartment 106 with an external cathode tank 1400 located outside the self-priming battery cell 100 and a pump 1402. The pump 1402 can be controlled to cause the catholyte to flow through the catholyte circuit 101 between the cathode compartment 106 and the catholyte tank 1400, where an excess amount of catholyte is stored. The catholyte in the cathode compartment 106 may be in fluid contact with a cathode 110 (i.e., a positive electrode or terminal) located at least partially within the cathode compartment 106. The cathode 110 may be the same as or similar to the cathode 1702 of the battery cell 1700. For example, cathode 110 may be made of or may include any suitable cathode material, including, for example, nickel, nickel oxyhydroxide (NiOOH), nickel hydroxide (Ni(OH)2), sulfur compounds, sulfur halides including chlorosulfuric acid or lithium thionyl chloride, any of the positive electrode materials described in any of the patents or patent applications cited in this disclosure, and / or any other suitable positive electrode material.

[0062] The ion selective membrane 104 may be the same as or similar to the ion selective membrane 1706 of the battery cell 1700. The ion selective membrane 104 may be configured to selectively transport metal ions from the cathode compartment 106 to the anode compartment 102 upon charging of the self-priming battery cell 100. In some embodiments, the ion selective membrane 104 selectively transports sodium ions (Na +) selective and capable of selectively transporting sodium ions, may include ceramic materials, NaSICON materials, and / or beta alumina materials. However, the ion selective membrane 104 may be selective to other types of ions (i.e., other than sodium) if other anode materials are used in place of sodium metal. For example, it is contemplated that various other molten alkali metals, other types of molten metals (i.e., non-alkali metals), molten metal alloys or eutectic mixtures, pure molten metals (i.e., not a mixture of multiple different metals), and / or other conductive fluids, substances, or materials may be used in place of molten sodium metal without departing from the teachings provided herein. For ease of description, the present disclosure will refer to the anode material primarily as molten metal.

[0063] The anode compartment 102 may be the same as or similar to the anode chamber 1708 of the battery cell 1700. The anode compartment 102 may be configured to accommodate molten metal (e.g., molten sodium metal) generated in the anode compartment 102 during operation, or any other material used as an anode in the self-priming battery cell 100. Prior to operation, the anode compartment 102 may initially have no molten metal and may be filled with molten metal as molten metal is generated in the anode compartment 102 during self-priming operation. Excess molten metal generated in the anode compartment (e.g., when operating in a sodium production mode or a flow battery charging mode) may be stored in the sodium reservoir 1406, which may be fluidly connected to the anode compartment 102 via a sodium conduit. In some embodiments, the molten metal generated in the anode compartment 102 flows to the sodium 1406 as a result of the physical displacement of molten metal in the anode compartment as new molten metal is generated. Thus, a powered component, such as a pump, may not be required to flow the molten metal between the anode compartment 102 and the sodium reservoir 1406. In some embodiments, the sodium reservoir 1406 is located above (e.g., directly above or higher than) the anode compartment 102 such that when space exists in the anode compartment (e.g., when molten metal is consumed in the anode compartment 102 during a flow battery discharge mode), the molten metal in the sodium reservoir 1406 will flow back into the anode compartment 102 by gravity.

[0064] The anode current collector 108 may be a negative electrode or terminal and may be located at least partially within the anode compartment 102. The anode current collector 108 and the cathode 110 form the negative and positive terminals, respectively, of the self-priming battery cell 100. The anode current collector 108 and the cathode 110 may be electrically connected to an external power source 1408 that provides electrons to the anode current collector 108 when the self-priming battery cell 100 is charging (e.g., during self-priming or when operating in a flow battery charging mode or a sodium production mode). As illustrated in FIG. 1, electrons (e - ) can flow into the self-priming battery cell 100 through the anode current collector 108 and can be transported by the electron transport structure 112 from the anode current collector 108 to the surface of the ion selective membrane 104 facing the anode compartment 102. Electrons (e - ) is the molten metal ion (Na ) transported through the ion selective membrane 104 at the surface of the ion selective membrane 104. + ), which combines with the molten metal ions and reduces them to produce the non-ionized form of the molten metal (Na).

[0065] The electron transport structure 112 can have a variety of different forms, shapes, sizes, or other structural designs. The block diagram of the electron transport structure 112 in FIG. 1 is provided to illustrate the primary function of the electron transport structure 112 (i.e., transporting electrons from the anode current collector 108 to the ion selective membrane 104 during a self-priming operation) and is not representative of the wide variety of shapes, structures, designs, or other configurations of the electron transport structure 112 that may be used in the self-priming battery cell 100. For example, in some embodiments, the electron transport structure 112 includes one or more wires that extend between the anode current collector 108 and the ion selective membrane 104. In some embodiments, the electron transport structure 112 includes a conductive mesh that contacts the surface of the ion selective membrane 104 at multiple points and distributes electrons received from the anode current collector 108 across the surface of the ion selective membrane 104. In some embodiments, the electron transport structure 112 is substantially rigid and provides structural support to the ion selective membrane 104 by exerting a force on the surface of the ion selective membrane 104 .

[0066] In some embodiments, the electron transport structure 112 is formed (e.g., manufactured, created, constructed, etc.) separately from other components of the self-priming battery cell 100 and inserted into the anode compartment 102 after formation (e.g., after being initially manufactured or constructed). For example, the electron transport structure 112 can be a separate component that can be retrofitted to an existing battery cell to provide the battery cell with self-priming capabilities. The electron transport structure 112 can be disposed within the anode compartment 102 between the anode current collector 108 and the ion selective membrane 104 such that a side or end of the electron transport structure 112 is in physical or electrical contact with both the anode current collector 108 and the ion selective membrane 104. In some embodiments, the electron transport structure 112 is removable (e.g., not permanently attached or connected to the anode current collector 108 and the ion selective membrane 104) and can be removed from the anode compartment 102 after the self-priming operation is completed. Alternatively, the electron transport structure 112 may be welded or otherwise secured to the anode current collector 108 and / or the ion selective membrane 104 to provide a more permanent connection.

[0067] In some embodiments, the electron transport structure 112 can be integrated with one or more other components of the self-priming battery cell 100. For example, the electron transport structure 112 can be physically or structurally coupled with the anode current collector 108 and / or the ion selective membrane 104 to form a single integrated component or unitary part. In some embodiments, the electron transport structure 112 and the anode current collector 108 are part of a unitary anode scaffold structure that includes a three-dimensional lattice of conductive material that extends across the anode compartment 102. In some embodiments, the electron transport structure 112 forms a surface (e.g., a top wall, a side wall, a bottom wall, etc.) of the anode compartment 102 that contains the molten metal within the anode compartment 102 after the molten metal is generated and that collectively define the shape of the anode compartment 102 and / or the self-priming battery cell 100.

[0068] In some embodiments, the electron transport structure 112 is transient or self-dissipating. For example, the electron transport structure 112 may be made of a material that dissolves, melts, alloys, or reacts with molten metal in the anode compartment 102. Thus, the electron transport structure 112 may be initially present in the anode compartment 102 before molten metal is generated in the anode compartment 102 (i.e., when there is no molten metal in the anode compartment 102 before the self-priming operation), but may begin to dissipate (e.g., dissolve, alloy, react, etc.) as molten metal is generated in the anode compartment 102. In some embodiments, the electron transport structure 112 provides a first electrical connection between the anode current collector 108 and the ion selective membrane 104 before the start of the self-priming operation. As molten metal is generated in the anode compartment 102, the electron transport structure may begin to dissipate and be replaced by the molten metal. The molten metal generated in the anode compartment 102 may provide a second electrical connection between the anode current collector 108 and the ion selective membrane 104 after the electron transport structure has dissipated to maintain electrical conductivity between the anode current collector 108 and the ion selective membrane 104.

[0069] In some embodiments, the electron transport structure 112 can be persistent (e.g., long-lasting, permanent, etc.) such that it remains within the anode compartment 102 throughout the life of the self-priming battery cell 100. For example, the electron transport structure 112 can be made of a material that does not dissolve or react with the molten metal or melt at the temperature of the molten metal in the anode compartment 102 (e.g., a stainless steel coating or mesh that is stable to sodium metal). Thus, the electron transport structure 112 can remain within the anode compartment in substantially its original form, in some embodiments, even after the anode compartment 102 is filled with the molten metal. Some examples of different structures that can be used as the electron transport structure 112 are described in further detail with reference to FIGS. 2-10.

[0070] In some embodiments, the surface of the ion selective membrane 104 facing the anode compartment 102 is coated with a conductive coating 114. The conductive coating 114 may function to distribute the electrons received from the electron transport structure 112 across the surface of the ion selective membrane 104. Distributing the electrons across the surface of the ion selective membrane 104 may allow the electrons to combine with molten metal ions appearing anywhere along the surface of the ion selective membrane 104, facilitating efficient and rapid generation of molten metal during a self-priming operation. Distributing the electrons across the surface of the ion selective membrane 104 may also reduce electrical hot spots and avoid high current densities at selected locations along the surface of the ion selective membrane 104.

[0071] The conductive coating 114 provides greater benefits to the self-priming battery cell 100 when the electron transport structure 112 has fewer contact points with the ion selective membrane 104 (e.g., a single point contact, a small number of point contacts, etc.) or has a small contact area with the ion selective membrane 104. For example, the electron transport structure 112 may contact the conductive coating 114 at a single point (point). The conductive coating 114 may receive electrons at a single point and distribute the electrons across the surface of the ion selective membrane 104. Conversely, when the electron transport structure 112 contacts the ion selective membrane 104 at a relatively large number of points or has a relatively large contact area with the ion selective membrane 104, the conductive coating 114 may provide less benefit to the self-priming battery cell 100 because less electron distribution is required to compensate for the distribution provided by the electron transport structure 112. In some embodiments, the conductive coating 114 can be omitted and the electron transport structure 112 alone can achieve the distribution of electrons. In other embodiments, both the conductive coating 114 and the electron transport structure 112 perform the function of distributing electrons across the surface of the ion selective membrane 104 .

[0072] The conductive coating 114 may be made of or include any of a variety of conductive materials, such as metals, metal oxides, or carbon. In some embodiments, the conductive coating 114 is made of a metal oxide, such as indium tin oxide, manganese oxide, titanium oxide, or nickel oxide. In some embodiments, the conductive coating 114 may be made of a metal oxide, such as, but not limited to, tungsten sulfide (e.g., WS2 having a conductivity of about 6.7 siemens / cm), nickel sulfide (e.g., NiS2 having a conductivity of about 2-55 siemens / cm), titanium sulfide (e.g., TiS2 having a conductivity of about 30-50 siemens / cm), zirconium sulfide (e.g., ZrS2 having a conductivity of about 1.32 siemens / cm), vanadium sulfide (e.g., TiS2 having a conductivity of about 0.1 siemens / cm), or a combination of these. The conductive coating 114 may include one or more conductive sulfides such as ZnS, FeS2, FeS2 with a conductivity of about 0.6 siemens / cm, MoS2 with a conductivity of about 1,000 siemens / cm, CoS2 with a conductivity of about 6-5,000 siemens / cm, Co9S8 with a conductivity of about 290 siemens / cm, and CuS with a conductivity of about 870 siemens / cm, Cu2S with a conductivity of about 6,700 siemens / cm. In some embodiments, the conductive coating 114 is made of a metal capable of alloying with the molten metal (e.g., sodium) generated in the anode compartment 102. For example, the conductive coating 114 may be made of tin, lead, mercury, indium, or any other metal capable of alloying with the molten metal. The conductive coating 114 may have a thickness between substantially 10 nanometers and 10 microns. In some embodiments, the conductive coating 114 has a thickness between substantially 10 Siemens / cm and 10 6 Siemens / cm or a subrange thereof (e.g., 10 Siemens / cm to 10 5 Siemens / cm, 100 Siemens / cm~10 5 Siemens / cm, 100 Siemens / cm~10 6 It has a conductivity of 1000 siemens / cm.

[0073] In some embodiments, the conductive coating 114 is transitory or self-dissipating. For example, the conductive coating 114 may be made of a material that dissolves in, melts into, alloys with, or reacts with molten metal generated in the anode compartment 102. Thus, the conductive coating 114 may initially be present on the surface of the ion selective membrane 104 before molten metal is generated in the anode compartment 102 (i.e., when the anode compartment 102 has no molten metal before a self-priming operation), but may begin to dissipate from the surface of the ion selective membrane 104 as molten metal is generated in the anode compartment 102. When an initial amount of molten metal is generated in the anode compartment 102, the conductive coating 114 may form a conductive layer between the initial amount of molten metal and the ion selective membrane 104. However, the conductive coating 114 may dissipate (eg, dissolve, alloy, react, etc.) in the presence of the molten metal, and the molten metal may directly contact the surface of the ion selective membrane 104 after the conductive coating 114 dissipates.

[0074] In some embodiments, the conductive coating 114 may be persistent (e.g., long-lasting, permanent, etc.) such that the conductive coating 114 remains on the surface of the ion selective membrane 104 throughout the life of the self-priming battery cell 100. For example, the conductive coating 114 may be made of a material that does not dissolve or react with the molten metal or melt at the temperature of the molten metal in the anode compartment 102 (e.g., a stainless steel coating or mesh that is stable to sodium metal). Thus, the conductive coating 114 may remain on the surface of the ion selective membrane 104, in some embodiments, even after the anode compartment 102 is filled with the molten metal.

[0075] electron transport structure 2-10, several examples of various structures that can be used as the electron transport structure 112 in the system 1100, according to various exemplary embodiments, are shown. It should be understood that these examples are illustrative of the wide variety of structures that can be used, and that these examples are not the only structures that can be used as the electron transport structure 112, and should not be considered as limiting. In addition, it should be noted that the depiction of these structures in the figures is not necessarily to scale, and sizes / shapes of various components may be exaggerated for ease of illustration and to facilitate description of the relevant components and features.

[0076] Many of the components shown in Figures 2-10 may be the same or similar to similarly numbered components previously described. For example, various embodiments are shown to include an anode compartment 102 and a cathode compartment 106 separated by an ion selective membrane 104. A conductive coating 114 is shown on a surface of the ion selective membrane 104 that faces the anode compartment. In some embodiments, the conductive coating 114 may be formed as an etched circuit. In some embodiments, the anode compartment 102 is shown to include a port 116 that may be located at the top of the anode compartment 102. When sodium or other molten metal is generated within the anode compartment 102 and reaches the capacity of the anode compartment 102, excess molten metal may flow out of the anode compartment 102 through the port 116 and into the sodium reservoir 1406, as shown in Figure 1.

[0077] 2, a first exemplary embodiment 200 is shown in which the electron transport structure 112 includes a wire 118 that electrically connects the ion selective membrane 104 and / or the conductive coating 114 on the surface of the ion selective membrane 104 to the anode current collector 108. One end of the wire 118 may be attached to the surface of the anode current collector 108 in the anode compartment 102, while the other end of the wire 118 may be attached to the ion selective membrane 104 or the conductive coating 114. Although only a single wire 118 is shown in FIG. 2, it is contemplated that more than one wire 118 may be included.

[0078] In operation, electrons from an external power source 1408 are supplied via power line 120 to the terminals of the anode current collector 108. The electrons flow through the anode current collector 108, via wire 118, through the anode compartment 102, and arrive at the conductive coating 114. The electrons are then distributed across the surface of the ion selective membrane 104 via the conductive coating 114. When molten metal is produced in the anode compartment 102, the molten metal provides an additional electrical path, in parallel with the wire 118, for the electrons to reach the ion selective membrane 104.

[0079] 3, another exemplary embodiment 300 is shown in which the electron transport structure 112 includes a power line 122 that is at least partially outside the anode compartment 102. Unlike embodiment 200, in which the wire 118 extends between the anode current collector 108 and the ion selective membrane 104 and / or conductive coating 114 inside the anode compartment 102, the power line 122 in embodiment 300 is connected directly to the power line 120 from an external power source 1408, bypassing the anode current collector 108.

[0080] During operation, electrons from the external power source 1408 are fed in parallel to both the power line 120 and the power line 122. For example, the power lines 120 and 122 may be separate branches extending from the external power source 1408. The power line 120 connects to the anode current collector 108, while the power line 122 connects to the ion selective membrane 104 and / or the conductive coating 114. The electrons flow through the power line 122 and arrive at the conductive coating 114. The electrons are then distributed across the surface of the ion selective membrane 104 via the conductive coating 114. When molten metal is generated in the anode compartment 102, the molten metal travels in the anode compartment 102 between the anode current collector 108 and the ion selective membrane 104, thereby providing an additional electrical path for the electrons to reach the ion selective membrane 104.

[0081] 4, another exemplary embodiment 400 is shown in which the electron transport structure 112 includes a plurality of wires 118a, 118b, 118c, and 118d. Each of the wires 118a, 118b, 118c, and 118d may be an example of the wire 118 shown in FIG. 2 and may electrically connect the ion selective membrane 104 and / or the conductive coating 114 to the anode current collector 108 in the anode compartment 102. In some embodiments, the wires 118a, 118b, 118c, and 118d may be extensions of the anode current collector 108 and may be formed as an integral component therewith. Although only four wires 118a, 118b, 118c, and 118d are shown in FIG. 4, it is contemplated that any number of wires may be included.

[0082] In operation, electrons from an external power source 1408 are provided to the terminals of the anode current collector 108 via the power line 120. The electrons flow through the anode current collector 108, via the plurality of wires 118a, 118b, 118c, and 118d, through the anode compartment 102, and arrive at the conductive coating 114 and / or the ion selective membrane 104. In some embodiments, the electrons are then distributed across the surface of the ion selective membrane 104 via the conductive coating 114. Alternatively, the conductive coating 114 may be omitted, as the plurality of wires 118a, 118b, 118c, and 118d may adequately distribute the electrons across the surface of the ion selective membrane 104, without requiring the conductive coating 114 to perform this function. However, the conductive coating 114 may also be included in the embodiment 400, if desired. When molten metal is produced in the anode compartment 102 , it provides an additional electrical path for electrons to reach the ion selective membrane 104 in parallel with the wires 118 a , 118 b , 118 c , and 118 d .

[0083] 5, another exemplary embodiment 500 is shown in which the electron transport structure 112 in the anode compartment 102 includes a conductive mesh structure 124. The conductive mesh structure 124 may include a three-dimensional mesh, grid, framework, lattice, scaffolding, foam, or any other type of structure capable of conducting electrical current between the anode current collector 108 and the ion selective membrane 104 and / or conductive coating 114. In some embodiments, the conductive mesh structure 124 also provides structural support to the anode compartment 102. For example, the conductive mesh structure 124 may contact a surface of the anode current collector 108, a surface of the ion selective membrane 104, or other internal surfaces within the anode compartment 102 and convey or transmit compressive forces to structurally support the anode compartment 102 from the inside. The conductive mesh structure 124 may include pores, gaps, open spaces, hollow areas, or other unoccupied volumes within the framework or mesh structure to provide space for molten metal generated within the anode compartment 102 to be stored within the conductive mesh structure 124. In some embodiments, the conductive mesh structure 124 may be substantially gas or liquid permeable and allow the molten metal to flow through the conductive mesh structure 124 (e.g., may allow the molten metal to exit the anode compartment 102 via the port 116). The conductive mesh structure 124 may occupy some or all of the space within the anode compartment 102.

[0084] In operation, electrons from an external power source 1408 are provided to the terminals of the anode current collector 108 via the power line 120. The electrons flow through the anode current collector 108 to the conductive mesh structure 124. The conductive mesh structure 124 transports the electrons across the anode compartment 102 and is in electrical contact with the ion selective membrane 104 and / or the conductive coating 114. In some embodiments, the electrons are distributed across the surface of the ion selective membrane 104 via the conductive coating 114. Alternatively, the conductive coating 114 may be omitted, as the conductive mesh structure 124 may adequately distribute the electrons across the surface of the ion selective membrane 104 without requiring the conductive coating 114 to perform this function. However, the conductive coating 114 may also be included in the embodiment 500, if desired. When molten metal is generated in the anode compartment 102, gaps or empty spaces in the conductive mesh structure 124 are filled with the molten metal, providing an additional electrical path for the electrons to reach the ion selective membrane 104.

[0085] 6 and 7, a side view 600 and a cross-sectional view 700 of another exemplary embodiment of the electron transport structure 112 are shown. In this embodiment, the anode current collector 108 is shown as a frame with several contact tabs 126 extending from the edges of the frame. For example, the anode current collector 108 can be a substantially rectangular frame, as shown in FIG. 7, or can have any other shape (e.g., circular, oval, etc.). In some embodiments, the anode current collector 108 includes a substantially flat plate with a raised frame along the edges of the plate. The raised frame can extend in a direction substantially perpendicular to the plate (e.g., toward the ion selective membrane 104). The contact tabs 126 can extend inward from the edges of the frame, as shown in FIG. 7, and / or can extend toward the ion selective membrane 104, as shown in FIG. 6. In some embodiments, the contact tab 126 may be integral with the anode current collector 108 and formed as a single unitary component with the anode current collector 108. The contact tab 126 may extend between the anode current collector 108 and the ion selective membrane 104 and / or conductive coating 114 to provide an electrical path therebetween.

[0086] In operation, as described above, electrons from an external power source 1408 are provided to the terminals of the anode current collector 108 via the power line 120. The electrons flow through the anode current collector 108, across the anode compartment 102 via the contact tab 126, and to the conductive coating 114 and / or the ion selective membrane 104. In some embodiments, the electrons are then distributed across the surface of the ion selective membrane 104 via the conductive coating 114. Alternatively, the conductive coating 114 may be omitted and the electrons may flow directly from the contact tab 126 to the ion selective membrane 104 at the contact point. When molten metal is generated in the anode compartment 102, the molten metal provides an additional electrical path for the electrons to reach the ion selective membrane 104 in parallel with the contact tab 126.

[0087] 8 and 9, a side view 800 and a cross-sectional view 900 of another exemplary embodiment of the electron transport structure 112 are shown. In this embodiment, the anode current collector 108 is shown including several nodes 128 distributed across the surface of the anode current collector 108. The nodes 128 may have any of a variety of sizes or shapes. In some embodiments, the nodes 128 are hemispherical domes that extend from the surface of the anode current collector 108 toward the ion selective membrane 104. In some embodiments, the nodes 128 are cylinders, rectangular pillars, or any other shape that extends from the surface of the anode current collector 108 toward the ion selective membrane 104. The nodes 128 may be arranged in an array or grid, as shown in FIG. 9, and may contact the ion selective membrane 104 and / or the conductive coating 114 at multiple locations. In some embodiments, the nodes 128 may be integrated with the anode current collector 108 and formed as a single, integral component with the anode current collector 108. The node 128 may extend between the anode current collector 108 and the ion selective membrane 104 and / or the conductive coating 114 to provide an electrical path therebetween.

[0088] In operation, as described above, electrons from an external power source 1408 are provided to the terminals of the anode current collector 108 via the power line 120. The electrons flow through the anode current collector 108, across the anode compartment 102 via the contact node 128, and arrive at the conductive coating 114 and / or the ion selective membrane 104. In some embodiments, the electrons are then distributed across the surface of the ion selective membrane 104 via the conductive coating 114. Alternatively, the conductive coating 114 may be omitted and the electrons may flow directly from the node 128 to the ion selective membrane 104 at the contact point. When molten metal is generated in the anode compartment 102, the molten metal provides an additional electrical path for the electrons to reach the ion selective membrane 104, in parallel with the node 128.

[0089] 10, another exemplary embodiment 1000 is shown in which the electron transport structure 112 includes an electron transport plate 136 having several contact tabs 134 extending therefrom. The electron transport plate 136 can be substantially planar with electrical contact to the anode current collector 108 along one side of the electron transport plate 136 (i.e., the left side in FIG. 10). The electron transport plate 136 is shown including a notch 132, which can be a hole extending through the electron transport plate 136. In some embodiments, the notch 132 is formed by punching one or more areas of the electron transport plate 136 during manufacturing. The notch 132 can have any of a variety of sizes or shapes, such as a serpentine path with curved corners or rectangular corners as shown in FIG. 10. The contact tab 134 can be a portion of the electron transport plate 136 that is bent in a direction substantially perpendicular to the plane of the electron transport plate 136. In some embodiments, each of the contact tabs 134 is connected along one edge to the rest of the electron transport plate 136 and is bent along the connecting edge. The contact tabs 134 may be bent toward the ion selective membrane 104 and may electrically contact the ion selective membrane 104 (e.g., either directly or through the conductive coating 114) when the electron transport plate 136 is disposed between the anode current collector 108 and the ion selective membrane 104 in the anode compartment 102.

[0090] In operation, as described above, electrons from an external power source 1408 are provided to the terminals of the anode current collector 108 via the power line 120. The electrons flow through the anode current collector 108 to the electron transport plate 136 and arrive at the conductive coating 114 and / or ion selective membrane 104 via the contact tab 134. In some embodiments, the electrons are then distributed across the surface of the ion selective membrane 104 via the conductive coating 114. Alternatively, the conductive coating 114 may be omitted and the electrons may flow directly from the contact tab 134 to the ion selective membrane 104 at the contact point. When molten metal is generated in the anode compartment 102, the molten metal provides an additional electrical path for the electrons to reach the ion selective membrane 104 in parallel with the electron transport plate 136 and the contact tab 134. In some embodiments, the anode compartment 102 includes a sodium transport channel 130 to allow sodium or other molten metal to flow to the anode compartment 102 of the other cell. The sodium transport channel 130 can pass through the electron transport plate 136, the anode current collector 108, and / or the ion selective membrane 104, as shown in FIG.

[0091] Battery Systems 11-31 , an example of a molten sodium battery system 1100 is shown in which self-priming battery cell 100 can be used, according to an exemplary embodiment. Although different reference numbers are used to refer to battery cell 1700 of system 1100, it should be understood that self-priming battery cell 100 can be an embodiment of battery cell 1700 and / or can be used in system 1100 in place of or in addition to any of battery cells 1700. It is contemplated that any of the components or functionality of self-priming battery cell 100 can be added to or included in battery cell 1700 and combined with any of the previously described components or functionality without departing from the teachings of the present disclosure.

[0092] Overview In some battery systems, it is desirable to electrically connect multiple battery cells in series with each other such that the individual cell voltages provided by the battery cells are stacked to provide a greater overall voltage to the battery system. The principle of electrically connecting multiple battery cells in series can be readily applied to most types of batteries, including flow batteries. Flow batteries constructed in this manner typically have a single catholyte fluid circuit that circulates catholyte through the cathode side of each battery cell, which may be arranged in fluid parallel or fluid series with each other. Similarly, a flow battery may include a single anolyte fluid circuit that circulates anolyte through the anode side of each battery cell, which may be arranged in fluid parallel or fluid series with each other.

[0093] However, attempting to connect multiple molten sodium battery cells together in series is problematic because molten sodium metal has a conductivity several orders of magnitude higher (i.e., about 1×10 at 98° C.) than that of conventional battery electrolytes (i.e., about 500 mS / cm at 50° C. for conventional suitable electrolytes and about 50 mS / cm at 115° C. for conventional unsuitable or organic electrolytes). 6 This can be problematic because molten sodium battery cells have a high electrical conductivity (i.e., low solubility in sodium) of 0.1 mS / cm. This can be problematic because current can flow between molten sodium battery cells through the molten sodium metal, which equalizes the electrical potential (i.e., voltage) across the battery cells and prevents the cell voltages from stacking when electrically connected in series. The present disclosure addresses these and other challenges that arise in molten sodium battery systems.

[0094] The molten sodium battery systems described herein may include one or more secondary cells (i.e., rechargeable battery cells), each of which includes a molten sodium metal anode, an ion-selective membrane (the term "membrane" is used herein to refer to any suitable type of separator), and a cathode compartment through which catholyte is circulated (e.g., via an external pump). The ion-selective membrane is positioned between the molten sodium metal anode and the catholyte compartment and allows positively charged sodium cations (Na + ) is allowed to pass through.

[0095] In some embodiments, multiple secondary cells (referred to herein as "unit cells," "battery cells," "secondary cells," or similar terms) are arranged in series and / or parallel with each other to form a battery string (referred to herein as "string," "battery string," or similar terms). Each battery string may include one or more unit cells. In some embodiments, the unit cells in a battery string are arranged in parallel with each other. For example, a battery string may include 10 (or any number of) unit cells, each operating at 1.5 volts (V) and 20 amps (A), and may be electrically connected in parallel with each other such that the battery string has a combined voltage of 1.5 V and a current of 200 A. Sodium metal and catholyte fluid may flow through each unit cell in a battery string in parallel with each other, in series with each other, or any combination thereof. Multiple battery strings may be connected together to form a stack. For example, a stack may include 16 (or any number) battery strings electrically connected in series with each other (e.g., via electrical bus bars) such that the stack has a stack voltage of 24 V and a current of 200 A. While specific voltage and current values ​​are provided herein as examples, it should be noted that these values ​​can vary and should not be considered as limiting. Sodium metal may flow through each battery string in the stack in parallel with each other, while catholyte fluid may flow through each battery string in the stack in series with each other, in parallel with each other, or any combination thereof.

[0096] The molten sodium battery system can operate in multiple modes, including a flow battery mode and a sodium production mode. In past systems, each string receives a string-specific flow of priming sodium from a sodium distributor to initially fill or "prime" the unit cells. The sodium distributor may be configured to receive sodium from an external sodium source and distribute sodium to each of the strings in parallel with each other. Advantageously, the sodium distributor may be configured to keep the strings electrically isolated from each other by preventing current flow between the strings through the string-specific flow of priming sodium and / or through the structure of the sodium distributor (e.g., walls, surfaces, etc.). Once the unit cells are primed with an initial amount of sodium, the sodium distributor is no longer needed. These and other features of the sodium distributor are described in more detail below. As an alternative to using a sodium distributor to initially fill or prime the unit cells, the self-priming battery cell 100 may be used to provide unit cells that are self-priming and do not require a sodium distributor to provide sodium to the strings from an external sodium source.

[0097] In flow battery mode, the molten sodium battery system can be operated to either charge or discharge the battery. When charging the battery, electricity is consumed and Na + Ions pass from the catholyte through the ion-selective membrane and are released into the atmosphere on the anode side of the membrane (i.e., in the molten sodium anode). -) to form molten metal (Na) as described above. Sodium metal produced in the molten sodium anode is forced out of the unit cell via the string-specific sodium outlet (e.g., as a result of the produced sodium taking up more volume in the sodium anode) and flows into the string-specific sodium reservoir. In some embodiments, the string-specific sodium reservoir is physically located above the battery string (i.e., where the gravitational potential energy is higher) and serves as additional capacity to store sodium metal produced during battery charging. During battery discharge, the opposite reaction occurs: sodium metal flows from the string-specific sodium reservoir to the molten sodium anode of the unit cell, producing sodium ions Na + and are consumed within the unit cell to produce electrons. + The ions pass through the ion-selective membrane to react with the catholyte, and the electrons are discharged from the battery in the form of electricity. The string-specific sodium reservoirs are physically and electrically isolated from each other such that each string only contributes sodium into and receives sodium from a single sodium reservoir.

[0098] In sodium production mode, the molten sodium battery system operates similarly to when charging a battery in flow battery mode. Electricity is consumed and Na + Ions pass from the catholyte through the ion-selective membrane and are converted into electrons (e -) to form sodium metal (Na) as described above. Sodium metal produced in the molten sodium anode is forced out of the unit cell via a string-specific sodium outlet. However, in the sodium production mode, the produced sodium does not need to be stored in a string-specific sodium reservoir. Instead of providing each string-specific produced sodium stream to a separate reservoir, the string-specific produced sodium streams are delivered to a sodium concentrator. The sodium concentrator receives the string-specific sodium streams from multiple strings, aggregates (e.g., combines, collects, consolidates, etc.) the string-specific sodium streams into a single sodium pool, and delivers the aggregated sodium to an external sodium storage vessel. Advantageously, the sodium concentrator may be configured to keep the strings electrically isolated from one another by preventing electrical current from flowing between the strings via the string-specific sodium streams and / or via the structure (e.g., walls, surfaces, etc.) of the sodium concentrator. These and other features of the sodium concentrator are described in further detail below.

[0099] Battery System Components 11-12, a perspective view of a system 1100 is shown, according to some embodiments. The system 1100 can be a flow battery system, a molten alkali metal battery system, a molten sodium battery system, an alkali metal generation system, a sodium generation system, or the like. In some embodiments, the system 1100 includes some or all of the features or components of the systems described in U.S. Provisional Patent Application No. 63 / 294,658, filed Dec. 29, 2021, the entire disclosure of which is incorporated by reference herein. The system 1100 is shown including a base 1102, a first subsystem 1104 mounted on the base 1102, and a second subsystem 1106 mounted on the base 1102. The first subsystem 1104 and the second subsystem 1106 can be connected in series by a first bus bar 1108. The first subsystem 1104 and the second subsystem 1106 can be configured substantially identically.

[0100] A first subsystem 1104 is shown including a stack assembly 1110, a distributor 1112 (e.g., sodium distributor, priming distributor), and a concentrator 1114 (e.g., sodium concentrator, shunt break). The stack assembly 1110 includes a plurality of strings 1116 (shown as strings 1116a-h). In the example shown, the strings 1116 of the stack assembly 1110 are grouped into sets of four strings 1116 (e.g., strings 1116a-d and 1116e-h), with each group of strings 1116 bounded by end plates 1118a-d. The strings 1116 within each group are separated from each other by isolation plates 1120 (shown as isolation plates 1120a-f) configured to fluidly and electrically isolate adjacent strings 1116 from each other. The stack assembly 1110 also includes bus bars 1122 (shown as bus bars 1122a-g) that provide electrical connection between the strings 1116 (i.e., electrically connect the strings 1116 in series with each other), as described in further detail with reference to FIG. 13.

[0101] Each string 1116 includes a housing defined at least by an exterior wall that is visible in FIGS. 11-12. As shown in and described with reference to other figures, each string 1116 includes one or more cells (e.g., battery cells, unit cells, secondary cells, etc.) that, for example, convert sodium cations into hydrogen (i.e., Na + For example, sodium metal can be oxidized (i.e., splitting an electron off of a sodium atom) to produce the sodium cation, Na + The strings 1116 can be discharged to generate electricity by generating a current that is proportional to the number of electrodes 1116. Isolation plates 1120 provide electrical isolation between adjacent strings 1116. End plates 1118 also provide electrical isolation and structural support for the stack assembly 1110.

[0102] The distributor 1112 is configured to distribute a conductive fluid (e.g., fluid alkali metal, molten sodium) from a common source or inlet (e.g., an external sodium source) to the multiple strings 1116 while providing electrical isolation between the strings 1116. The distributor 1112 is connected to the multiple strings 1116 by tubes 1124 (e.g., one tube per string 1116a-g, eight tubes in the example shown) so that fluid can flow therebetween. As shown in Figures 11-12, the distributor 1112 is physically mounted on top of the stack assembly 1110 so that gravity on the fluid in the distributor 1112 causes the fluid to flow downward towards the strings 1116 / completely filling the strings 1116a-g. Additional details of the distributor 1112 and the electrical isolation it provides are described with reference to Figures 19-22. 11-12, it should be understood that the distributor 1112 is not required for embodiments of the system 1100 that include the self-priming battery cells 100 because there is no need to distribute sodium from an external source to the strings 1116. Thus, in some embodiments of the system 1100, the distributor 1112 may be omitted.

[0103] The condenser 1114 is configured to receive conductive fluid (e.g., alkali metal fluid, sodium fluid) from the multiple strings 1116a-g and condense the conductive fluid in a common receptacle or at a common outlet (e.g., via line 1125) while providing electrical isolation between the strings 1116. The condenser 1114 is connected to the multiple strings 1116 by tubes 1126 (e.g., one tube per string 1116, eight tubes in the illustrated example) so that fluid can flow therebetween. As shown in Figures 11-12, the condenser 1114 is physically mounted on top of the stack assembly 1110, so that when flowing from the stack assembly 1110 into the condenser 1114, the fluid must flow against the direction of gravity. This can occur as a result of conductive fluid being generated within the stack assembly 1110 and being pushed out of the stack assembly as additional mass / volume of conductive fluid is generated. Details of the aggregator 1114 and the electrical isolation it provides are provided below with reference to, for example, FIGS.

[0104] The distributor 1112 and the concentrator 1114 operate to deliver string-specific flows of conductive fluid to the strings 1116 in parallel with one another and to collect / aggregate string-specific flows of conductive fluid from the strings 1116 in parallel with one another. The distributor 1112 receives conductive fluid from an external source, divides the conductive fluid into string-specific flows, and delivers the string-specific flows to the individual strings 1116. Within the stack assembly 1110, the string-specific flows of conductive fluid are fluidically and electrically maintained from one another by isolation plates 1120 and end plates between adjacent strings 1116 to prevent electrical current from passing between adjacent strings 1116 via the conductive fluid. The concentrator receives string-specific flows of conductive fluid from the individual strings 1116 and combines or aggregates the string-specific flows into a single combined stream and provides the combined stream of conductive fluid to an external storage vessel.

[0105] In some embodiments, the flow of conductive fluid between the distributors 1112, strings 1116, aggregators 1114, and / or other components of the system 1100 occurs passively and can therefore be characterized as passive flow. Passive flow can include flow driven by gravity, naturally induced fluid flow (e.g., convection), displacement (e.g., expansion or generation of fluid within the strings 1116), or flow that occurs passively without the need for active (powered) components such as pumps, compressors, fans, etc. to drive the flow. For example, the distributors 1112, external fluid sources that feed the distributors 1112, and / or string-specific reservoirs can be positioned above the strings 1116 (e.g., directly above the strings 1116 and / or on a ridge above the strings 1116 but horizontally to the side of the strings 1116) such that the conductive fluid passively flows downwardly into the strings 1116 by gravity when space is available within the strings 1116. This may occur when priming the string 1116 and / or consuming conductive fluid within the string 1116 (e.g., during a flow battery discharge mode) to free up space within the string 1116. As another example, production of conductive fluid within the string 1116 (e.g., during a sodium production mode or a flow battery charge mode) may cause the mass of conductive fluid to increase within the string 1116. The increase in mass of conductive fluid within the string 1116 may increase fluid pressure and / or volume within the string 1116, such that excess conductive fluid that does not fit within the string 1116 may be pushed out of the string 1116 by displacement. The displaced conductive fluid may passively flow out of the string 1116 against the direction of gravity as additional mass of conductive fluid is generated within the string 1116 and flows into the condenser 1114 and / or an external reservoir located above the string 1116.

[0106] The second subsystem 1106 is configured substantially identically to the first subsystem 1106 and includes comparable or identical stack assemblies, distributors, and concentrators. As shown in FIGS. 11-12, the inlet port 1128 and the outlet port 1130 are located at one end of the second subsystem 1106. In other embodiments, the inlet port 1128 and the outlet port 1130 are located at opposite ends of the second subsystem 1106. Similar inlet and outlet ports can be provided on the end plate 1118a and / or the end plate 1118d (e.g., an inlet port on the end plate 1118a and an outlet port on the end plate 1118d). The inlet port 1128 provides an entry point for catholyte flow into the second subsystem, and the outlet port 1130 provides an exit point for catholyte flow from the second subsystem. Catholyte may flow through the cells of the system 1100 as shown in and described with reference to FIGS.

[0107] The catholyte may include any suitable type of positive electrolyte or positive electrode solution. In some embodiments, the catholyte may be or may include any type of fluid capable of exchanging ions (e.g., sodium ions or other cations) with the conductive fluid. Examples of suitable catholytes include, but are not limited to, sodium sulfide, sodium halide, aluminum sulfide, aluminum halide, and / or any of the positive electrolytes or positive electrode solutions described in U.S. Patent No. 10,734,686, granted August 4, 2020, U.S. Patent No. 8,968,902, granted March 3, 2015, U.S. Patent Application No. 2021 / 0280898, published September 9, 2021, and / or U.S. Patent Application No. 2021 / 0277529, published September 9, 2021. The entire disclosure of each of these patents and patent application publications is incorporated by reference herein. The catholyte may flow through the cathode compartment in the string 1116 and may be in fluid contact with one or more cathodes (i.e., positive electrodes) located at least partially within the cathode compartment. The cathodes may be made from or may include any suitable cathode material, including, for example, nickel, nickel oxyhydroxide (NiOOH), nickel hydroxide (Ni(OH)2), sulfur compounds, sulfur halides including chlorosulfuric acid or lithium thionyl chloride, any of the positive electrode materials described in any of the patents or patent applications cited in this disclosure, and / or other suitable positive electrode materials.

[0108] In various embodiments, the catholyte flows through some or all of the strings 1116 in series with each other, in parallel with each other, or any combination thereof. In some embodiments, the catholyte has a significantly lower conductivity than the conductive fluid and does not need to remain physically and electrically separated as it flows through the strings 1116. Only small currents through the catholyte are expected (e.g., less than a percent loss in some cases, which may vary depending on the orientation and placement of the strings 1116 and / or the flow path of the catholyte). However, it is contemplated that similar isolation measures would be taken for the catholyte if a conductive catholyte were used.

[0109] Electrical Connection Referring now to FIG. 13, a block diagram of electrical connections within a system 1100 is shown, according to some embodiments. FIG. 13 shows an example stack assembly 1110 having N strings 1116 (N is a positive integer) between a first end plate 1118a and a second end plate 1118b, illustrated as a first string (string 1) 1116a, a second string (string 2) 1116b, a third string (string 3) 1116c, a fourth string (string 4) 1116d, up to the Nth string 1116. In various embodiments, any positive integer value of N is possible. As illustrated, each string 1116 has a negative terminal (-) and a positive terminal (+). In some embodiments, each string 1116 is configured to provide a voltage difference across the string 1116, i.e., between the negative terminal (-) and the positive terminal (+). The voltage difference may be approximately 1.5V in some implementations, but may have a different magnitude (eg, X volts per string 1116) in various embodiments, uses, scenarios, etc.

[0110] The isolation plates 1120 electrically isolate adjacent strings 1116 from one another. As shown, the first isolation plate 1120a electrically isolates the first string 1116a from the second string 1116b, the second isolation plate 1120b electrically isolates the second string 1116b from the third string 1116c, the third isolation plate 1120c electrically isolates the third string 1116c from the fourth string 1116d, the fourth isolation plate 1120h electrically isolates the fourth string 1116d from the subsequent string, and the Mth isolation plate 1120m electrically isolates the Nth string 1116n from the preceding string 1116 (M=N-1). Thus, the isolation plates 1120 help prevent undesirable or unintended current flow (ie, shunt currents), voltage normalization, and / or other electrical interactions across the multiple strings 1116 .

[0111] 13 shows a bus bar 1122 connected to the positive and negative terminals of adjacent strings 1116 to connect the strings 1116 in series. As shown, a first bus bar 1122a connects the positive terminal of the first string 1116a to the negative terminal of the second string 1116b around the isolation plate 1120a, such that the only electrical connection between the first string 1116a and the second string 1116b is between the positive terminal of the first string 1116a and the negative terminal of the second string 1116b. A second bus bar 1122b connects the positive terminal of the second string 1116b to the negative terminal of the third string 1116c around the isolation plate 1120b, and similarly for bus bars 1122c,d,h...m, so that the strings 1116 are connected in series with the positive terminal of each string connected to the negative terminal of the subsequent string up to the Nth string 1116n. For N strings 1116, the embodiment of Figure 13 includes M = N-1 bus bars 1122.

[0112] When each of the N strings 1116 provides a voltage difference of X volts (X can be any value, e.g., 1.5V, 3V, 12V, 24V, etc.), the series arrangement shown in FIG. 13 causes the voltage difference across the N strings 1116 to be equal to N times X. Thus, the arrangement of the strings 1116 shown in FIG. 13 allows the stack assembly 1110 to provide or handle voltages that are significantly greater than can be provided or handled by any individual string 1116, for example. As described in more detail below, the electrical arrangement of FIG. 13 can be used to provide an alkali metal production mode (e.g., a sodium production mode) as well as discharge and charge flow battery modes in the system 1100.

[0113] Flow Battery Mode 14-15, fluid flows in a system 1100 in flow battery charging and discharging modes are shown, according to some embodiments. When operating in a flow battery charging mode (FIG. 14), the system 1100 receives external electricity and converts positively charged cations (e.g., Na + ), generating and storing neutral sodium atoms (or some other similarly reactive material, e.g., another alkali metal). When operating in a flow battery discharge mode (FIG. 15), the system 1100 splits electrons off of sodium atoms to generate sodium ions (Na + ) to the catholyte. As described in more detail below, these modes are achieved in part by providing for the flow of sodium and catholyte through different compartments and conduits of the stack assembly 1110.

[0114] System 1100 may further include components that provide circulation of catholyte through system 1100, such as a catholyte tank 1400, a pump 1402, and various tubes, conduits, etc. that provide the flow path shown in FIG. 14. Catholyte tank 1400 is configured to hold catholyte fluid and in some embodiments may provide agitation (e.g., stirring, mixing) of the catholyte fluid. The catholyte fluid may be, for example, NaCl, as described in U.S. Pat. No. 10,020,543 during the charge mode of operation of FIG. 14. + ions and Na during discharge mode operation in Figure 15. + The catholyte tank 1400 may include or consist of a molecule suitable for receiving ions, the entire disclosure of which is incorporated herein by reference. The pump 1402 operates to pump catholyte from the catholyte tank 1400 through the string 1116, across the string 1116 and back to the catholyte tank 1400. The pump 1402 may be controlled, for example, to provide a constant flow rate of catholyte through the stack assembly 1110. The catholyte tank 1400 may store or receive excess or back-up catholyte to accommodate changes in the total volume of catholyte, for example, during charge and discharge operations.

[0115] Catholyte is shown flowing through pathways within string 1116. The pathways internal to string 1116 are illustrated in further detail in Figures 17-18. The catholyte flow path continues through strings 1116 so that catholyte can flow through any of strings 1116 as it is driven by pump 1402 and circulated through system 1100. Catholyte is preferably electrically isolated so as to not provide a path for electrical current to flow between strings 1116 as it is circulated through system 1100.

[0116] The sodium reservoirs 1406 include a separate reservoir for each of the strings 1116, such that each of the sodium reservoirs 1406 receives sodium from one of the strings 1116, such as without mixing the sodium from the separate strings 1116, without contact between the sodium, etc. The sodium reservoirs 1406 may be coupled to one another, such as by sharing a wall made of one or more non-conductive, sodium-compatible materials (e.g., polymethylpentene (PMP), steel coated with an electrically insulating coating), for example, in an arrangement having a common headspace and different compartments that define the sodium reservoirs 1406. 14-15 show a first sodium reservoir 1406a connected to the first string 1116a, a second sodium reservoir 1406b connected to the second string 1116b, a third sodium reservoir 1406c connected to the third string 1116c, a fourth sodium reservoir 1406d connected to the fourth string 1116d, and an Nth sodium reservoir 1406n connected to the Nth string 1116n. This arrangement electrically isolates the sodium from each string, preventing current from flowing between the strings 1116 through the sodium, as can occur in other designs.

[0117] In a flow battery charging mode (illustrated in FIG. 14), the system 1100 is initially self-primed by the self-priming battery cells 100 generating sodium in situ in the strings 1116. A voltage is applied across the stack assembly 1110 by an external voltage source. The applied voltage creates a voltage difference across each of the strings 1116. The pump 1402 operates to circulate catholyte through the strings 1116. The voltage difference across each of the strings 1116 drives sodium through the membrane and into the anode compartment. + The cations are forced out of the catholyte, and in the anode compartment, Na +The cations combine with electrons (provided by current from an external voltage source) to produce sodium atoms. This reaction continues to produce sodium atoms in each string 1116, thereby increasing the volume of material in the sodium pathways in each string 1116, thus pushing sodium out of the strings 1116 and into the respective sodium reservoirs 1406. Thus, sodium atoms are produced and stored in the sodium reservoirs 1406, storing electricity in the form of electrochemical energy.

[0118] In a flow battery discharge mode (illustrated in FIG. 15 ), the system 1100 operates to output electricity. Sodium flows (e.g., is drawn into the strings 1116 by gravity) from the sodium reservoir 1406 (e.g., from a suction port or drip tube at the bottom) into each string 1116, and sodium atoms in the strings 1116 lose electrons, forming Na + The cations flow through the membrane into the catholyte, which continues to circulate by operation of pump 1402. The excess electrons migrate to the cathode, thereby generating electricity that can flow out of the system 1100. Thus, when operating in a flow battery discharge mode, the system 1100 is configured to generate electricity from the stored sodium atoms.

[0119] Sodium generation mode 16, fluid flow in the system 1100 in a sodium production mode is shown, according to some embodiments. As in FIGS. 14-15, the self-priming battery cell 100 can be operated to prime the sodium production mode by generating an initial amount of sodium in situ in the string 1116. In the sodium production mode, the system 1100 is arranged as shown in FIG. 16, and sodium generated by the string 1116 (via reactions as described more fully with reference to FIGS. 17-18) flows separately to the sodium concentrator 1114. The pump 1402 operates to circulate catholyte within the stack assembly 1110, including within the catholyte tank 1400. In some embodiments, the catholyte tank 1400 is a source of catholyte, which provides sufficient catholyte for continuous operation of the system to generate sodium for an indefinite period of time, e.g., by having a sufficiently large volume, by being refilled by an external source.

[0120] The sodium concentrator 1114 is configured to consolidate the sodium from the separate strings 1116 into a single output to the sodium storage vessel 1600. The sodium storage vessel 1600 provides a single, unified space that receives sodium from all of the strings 1116 (as opposed to the separate sodium reservoirs 1406 of FIGS. 14-15). The sodium in the storage vessel 1600 can then be removed as a valuable material for other uses. Advantageously (and as will be described in more detail below with reference to FIGS. 23-26), the sodium concentrator 1114 is configured to consolidate the sodium output by each string into a single mixed volume in the sodium storage vessel 1600 while maintaining electrical isolation between the sodium in each string 1116. By maintaining electrical isolation between the sodium in each string 1116, no current can flow between the strings 1116 through the sodium, and the strings 1116 can be held at different voltages. Thus, the sodium concentrator 1114 plays a key role in enabling the serial electrical connection between the strings 1116 illustrated in FIG. 13.

[0121] In the sodium production mode, the generated sodium is removed from the stack assembly 1110 via the sodium concentrator 1114 and prevented from flowing back into the strings 1116 after production. This is distinct from the flow battery mode, where the generated sodium is allowed to flow back into the stack assembly 1110 in the flow battery discharge mode of FIG. 15. In both the sodium production mode and the flow battery mode, the self-priming battery cell 100 operates to generate sodium in-situ within the stack assembly 1110 during the priming stage (and in some scenarios for maintenance purposes), but the self-priming feature is no longer necessary after the unit cells are primed (e.g., filled) with sodium during the sodium production mode of operation.

[0122] String composition Referring now to FIG. 17, a diagram of an exemplary string 1116 of a system 1100 is shown, according to some embodiments. In the example shown, each string 1116 has two cells, shown in FIG. 17 as cell A 1700a and cell B 1700b in the first string 1116a, and cell C 1700c and cell D 1700d in the second string 1116b. Each cell 1700 can be characterized as a battery cell (i.e., a secondary cell, a unit cell, etc.). In each cell 1700, a catholyte is provided on the other side of the membrane from molten sodium (or, in other embodiments, other anode materials) so that a voltage can be generated across each cell 1700 in a discharge mode, or the voltage across the cell 1700 can be used to generate sodium (or otherwise store energy) in a charge mode. The membranes of embodiments herein are sodium ion selective and can be NaSICON or beta alumina materials.

[0123] 17, cell A 1700a and cell B 1700b are arranged for parallel fluid flow therethrough such that cell A 1700a and cell B 1700b share a cathode (shared cathode 1702a). That is, the first string 1116a includes a catholyte chamber 1704a through which catholyte can flow and which fills with catholyte during operation of the system 1110. The catholyte chamber 1704a is divided by the shared cathode 1702a such that catholyte can flow in parallel along the two sides of the cathode 1702a. The catholyte chamber 1704a is bounded by a first membrane 1706a that separates the catholyte in the catholyte chamber 1704a from a first anode chamber 1708a of the string 1116a, and by a second membrane 1706b that separates the catholyte chamber 1704a from a second anode chamber 1708b. The shared cathode 1702a is positioned approximately equidistant between the first membrane 1706a and the second membrane 1706b, such that catholyte can flow through the regions of the catholyte chamber 1704a between the first membrane 1706a and the shared cathode 1702a, and between the second membrane 1706b and the shared cathode 1702a. Cell A 1700a is defined by the combination of a first anode chamber 1708a, a first membrane 1706a, a portion of the catholyte chamber 1704a, and a shared cathode 1702a, and cell B 1700b is defined by the combination of a second anode chamber 1708b, a second membrane 1706b, a portion of the catholyte chamber 1704a, and a shared cathode 1702a. Thus, the cathode 1702a is shared between adjacent unit cells 1700a and 1700b in the first string 1116a.

[0124] The first string 1116a is also shown as including a sodium conduit 1710a (e.g., a tube, a pipe, etc.) that fluidly connects the first anode chamber 1708a with the second anode chamber 1708b. The sodium conduit 1710a allows sodium (or other anode material) to flow through and between the anode chambers 1708a-b of the first string 1116a to an outlet 1712a located in the isolation plate 1120a. As illustrated in FIG. 17, both sodium and catholyte may flow in parallel through each string 1116 in the same direction, in opposite directions, or any combination thereof.

[0125] The second string 1116b is shown arranged substantially identically to the first string 1116a and includes corresponding components including a shared cathode 1702b, a catholyte chamber 1704b, a first membrane 1706c, a second membrane 1706d, a first anode chamber 1708c, a second anode chamber 1708d, a conduit 1710b, and an outlet 1712b. Figure 17 illustrates that the catholyte chamber 1704a of the first string 1116a is in fluid communication with the catholyte chamber 1704b of the second string 1116b such that catholyte can flow through the catholyte chamber 1704a of the first string 1116a into the catholyte chamber 1704b of the second string 1116b. 17 also illustrates that the anode chambers 1708a,b and conduits 1710a of the first string are isolated (including electrically isolated at least by isolation plate 1120a) from the anode chambers 1708c,d and conduits 1710b of the second string 1116b. Thus, the catholyte is shared between the first string 1116a and the second string 1116b, and the sodium (or other fluid anode) remains electrically and fluidly isolated from adjacent strings 1116.

[0126] 18, another view of the strings 1116 of the system 1100 is shown, according to some embodiments. In the example shown in FIG. 18, each string 1116 includes four cells, shown as cell A 1700a, cell B 1700b, cell C 1700c, and cell D 1700d of the first string 1116a. As in the example of FIG. 17, cell A 1700a and cell B 1700b are comprised of a first shared cathode 1702a, a portion of a catholyte chamber 1704a, a first membrane 1706a, a second membrane 1706b, a first anode chamber 1708a, and a second anode chamber 1708b arranged as described with reference to FIG.

[0127] In the example of FIG. 18, a first string 1116a is provided with additional cells (cell C 1700c and cell D 1700d) by using a second anode chamber 1708b to provide a shared anode between cell B 1700b and cell C 1700c. As shown, the second anode chamber 1708b is bounded by a second membrane 1706b and by a third membrane 1706c. The third membrane 1706c separates the second anode chamber 1708b from the portion of the catholyte chamber 1704a between the third membrane 1706c and the second shared cathode 1702b. The shared cathode 1702b is an element of cell C 1700c and cell D 1700d. Cell D 1700d also includes a third anode chamber 1708c separated from the catholyte chamber 1704a by a fourth membrane 1706d such that catholyte can flow through the catholyte chamber 1704a between the fourth membrane 1706d and the second shared cathode 1702b. As shown, the first string 1116a thus uses two cathodes and a third anode chamber to provide four cells. Strings having any number of cells (e.g., 2, 3, 4, 5, 6, 7, 8, etc.) are within the scope of this disclosure.

[0128] Sodium Distributor 19-22, various views of a distributor 1112 are shown, according to some embodiments. As mentioned above, for embodiments of the system 1110 that do not include a self-priming battery cell 100, the distributor 1112 can be used to prime the strings 1116 with an initial amount of sodium. However, the distributor 1112 is not required for this purpose for embodiments of the system 1100 that include a self-priming battery cell 100. Also, for embodiments that include an aggregate sodium storage vessel 1600 (shown in FIG. 27) rather than a string-specific sodium reservoir 1406 (shown in FIG. 14), the distributor 1112 can be used to distribute sodium stored (e.g., previously generated) in the strings 1116. The distributor 1112 can be connected in series between the sodium storage vessel 1600 and the strings 1116 of the system 1100, and is configured to distribute fluid sodium from the sodium storage vessel 1600 to the strings 1116 and prevent shunt currents from flowing between the strings 1116 via the molten sodium. 19 shows a first perspective view of the distributor 1112, FIG. 20 shows a second perspective view of the distributor 1112, FIG. 21 shows a first cut-away view of the distributor 1112, and FIG. 22 shows a second cut-away view of the distributor 1112.

[0129] As shown in Figures 19-22, the distributor 1112 includes a chamber 1900, a sodium inlet 1902 positioned on a top wall 1904 of the chamber 1900, a gas inlet 1906 positioned on the top wall 1904 of the chamber 1900, and a number of outlets 1908 extending from a bottom wall 1910 of the chamber 1900 such that the chamber 1900 is arranged between the sodium inlet 1902 and the number of outlets 1908. The chamber 1900 is airtight such that fluid can only enter or leave the interior of the chamber 1900 via the sodium inlet 1902, the gas inlet 1906, and the outlets 1908. The gas inlet 1906 is connectable to a source of an inert gas that does not react with sodium, allowing the inert gas to be provided into the chamber 1900 (e.g., at a pressure greater than atmospheric pressure) to fill any space within the chamber 1900 that is not occupied by sodium with a substance that does not react with sodium. Chamber 1900 may be made from a non-conductive material. Sodium inlet 1902 is connectable to an aggregate sodium storage vessel 1600 (shown in FIG. 27 ) and configured to introduce sodium from the aggregate sodium storage vessel 1600 into the interior of chamber 1900. Sodium inlet 1902 may regulate the rate of flow or drip of sodium into chamber 1900. Sodium inlet 1902 is shown as being substantially centered on an upper surface 1904 of chamber 1900.

[0130] Each outlet 1908 is shown as having a tubular or nozzle shape extending from a lower surface 1910 of the chamber 1900. The outlets 1908 may be made of an electrically insulating material. Each outlet 1908 may be fluidly connected to a corresponding string 1116 via a tube 1124 and configured to deliver sodium from the distributor 1112 to the corresponding string 1116. As shown in FIGS. 19-22, the outlets 1908 are arranged symmetrically in two rows of four (for a total of eight outlets 1908), although other numbers of outlets 1908 or other arrangements are possible. The number of outlets 1908 corresponds to the number of strings 1116 serviced by the distributor 1112. Each outlet 1908 may include a fitting 2100 made of an electrically insulating sodium-compatible material or other material (e.g., polytetrafluoroethylene (PTFE)) that electrically insulates the chamber 1900 from the tip 2102 of each outlet 1908. Therefore, if the tubes connecting the tips 2102 of each outlet 1908 to the stack assembly 1110 are exposed to different voltage levels, the electrical isolation provided by the equipment 2100 ensures that no significant current flows between the strings 1116 through the structure of the distributor 1112.

[0131] In some embodiments, each outlet 1908 includes a valve, flow restrictor, narrow area, nozzle, flared nozzle, droplet forming device, etc., such that fluid drips through an air gap between the chamber 1900 and the tip 2102 of each outlet 1908. The air gap may provide an electrical shunt break within the outlet 1908 (i.e., between the chamber 1900 and the tip 2102) to block electrical shunt current from flowing between the strings 1116 through the distributor 1112. In some embodiments, the pressure of the pressurized gas provided to the distributor 1112 through the gas inlet 1906 may be controlled (e.g., regulated, regulated, modulated, etc.) to promote the formation of droplets of conductive fluid at an orifice connecting the chamber 1900 to the outlet 1908. For example, the controller may measure or calculate the pressure differential across the orifice and adjust the pressure of the pressurized gas provided through the gas inlet 1906 (e.g., by operating a pump or other pressure control device) to maintain the pressure differential at a set point or target level that promotes droplet formation.

[0132] The chamber 1900 includes a number of compartments 1912, each compartment 1912 corresponding to and aligned with one of the outlets 1908. The compartments 1912 are defined by dividing walls extending from a lower wall 1910 of the chamber 1900 partway towards a top wall 1904 of the chamber 1900, leaving a space between the top wall 1904 of the chamber 1900 and the compartments 1912. The compartments 1912 are electrically isolated from one another (e.g., due to the material composition of the dividing wall), such that electrical current does not flow between fluids in the separate compartments 1912 (when the fluid level is below the height of the compartments 1912). For example, the chamber 1900, compartments 1912, etc. may be made from a non-conductive material that is compatible with or does not react with sodium (e.g., PMP). As seen in FIG. 22, the compartments 1912 are connected by overflow areas 1914 such that the height of the compartments 1912 is partially reduced at a shared corner of the compartments 1912. The overflow areas 1914 facilitate the dispersion of fluid between the compartments 1912 when the fluid level in the chamber 1110 exceeds the overflow areas 1914. By providing a common head space over the compartments 1912 and in the chamber 1900, a constant pressure can be regulated across the compartments 1912 (e.g., by introduction of pressurized gas through the gas inlet 1906), which in some embodiments may be advantageous to cause dispersion from the distributor 1112 at a constant drop rate or droplet size. In some embodiments, the overflow areas 1914 may be replaced with a distributor plate located over the compartments 1912 (e.g., in the common head space) to distribute the fluid evenly across the compartments 1912. The distributor plate may be constructed similarly to a distillation column tray (e.g., a flat surface with many small orifices distributed across it) so that fluid pools above the distributor plate and flows substantially uniformly (e.g., drips, flows, etc.) through the orifices into the compartment 1912 below.

[0133] Sodium Concentrator 23-25, multiple views of the integrator 1114 are shown, according to some embodiments. The integrator 1114 may be fluidly connected in series between the strings 1116 and the sodium storage vessel 1600 (shown in FIG. 16) and may be configured to deliver fluid sodium from the strings 1116 to the sodium storage vessel 1600 while preventing electrical shunt currents from flowing between the strings 1116 through the fluid sodium. FIG. 23 shows a first perspective view, FIG. 24 shows a first cutaway view, and FIG. 25 shows a second cutaway view.

[0134] The condenser 1114 is shown as including a chamber 2300 and a number of inlets 2302 extending upwardly from a top wall 2304 of the chamber 2300. The condenser 1114 also includes an outlet 2306 extending downwardly from a bottom wall 2308 of the chamber 2300 such that the chamber 2300 is between the inlet 2302 and the outlet 2306. The condenser 1114 also includes a gas inlet 2310 connected to the chamber 2300 to allow for the introduction of an inert gas into the chamber 2300.

[0135] The outlet 2306 is shown as being centered in a bottom wall 2308 of the chamber 2300, which is sloped toward the outlet 2306 such that gravity draws fluid within the chamber 2300 toward and flows to the outlet 2306. The bottom wall 2308 is also shown as including anti-splash members 2402 (e.g., ridges, slopes, protrusions, etc.) arranged relative to the inlet 2302 to reduce or eliminate splashing of fluid dripping from the inlet 2302 into the chamber 2300. The chamber 2300 is shown as including internal support struts 2400 extending from the bottom wall 2308 to the top wall 2304 for structural support.

[0136] Each inlet 2302 includes a horizontal tip 2500 and a vertical conduit 2502. The horizontal tip 2500 receives the fluid sodium from the string 1116, which then travels slowly to the vertical conduit 2502. The vertical conduits 2502 are configured to allow the sodium to drip down the vertical conduits 2502 and out of a terminal 2504 located at the bottom of each vertical conduit 2502. Thus, the inlets 2302 cause droplets of fluid sodium to fall through the volume of the chamber 2300 (e.g., through the inert gas provided via the gas inlet 2310) and out of the terminal 2504 into the chamber 2300, e.g., onto the anti-splash member 2402. In some embodiments, the pressure of the inert gas provided to the condenser 1114 via the gas inlet 2310 can be controlled (e.g., regulated, regulated, modulated, etc.) to promote the formation of droplets of fluid sodium at the terminal 2504. For example, the controller can measure or calculate the pressure differential across terminals 2504 and adjust the pressure of the pressurized gas provided through gas inlet 2310 (e.g., by operating a pump or other pressure control device) to maintain the pressure differential at a set point or target level that promotes droplet formation. Inlet 2302 can include an electrically insulating material, fittings to electrically isolate horizontal tip 2500 from chamber 2300.

[0137] Because the fluid enters the chamber 2300 as the droplets fall through an inert gas (e.g., a non-conductive gas) or other electrically insulating fluid, the fluid does not provide a conductive path from the interior of the chamber 2300 back to the strings 1116 or vice versa. Additionally, even when droplets are falling simultaneously from multiple inlets 2302, the droplets are electrically isolated from one another, such that no electrical connection occurs between the different inlets 2302. Thus, the condenser 1114 condenses the fluid sodium at the outlet 2306 of the condenser 1114 and prevents electrical communication between the different strings 1116 or, in various embodiments, between any of the various fluid sources that provide conductive fluid to the multiple inlets 2302.

[0138] Sodium Manifold 26, a cutaway perspective view of a manifold 2600 that can be used with the system 1100, according to some embodiments, is shown. The manifold 2600 can be used in place of the distributor 1112 as illustrated in FIGS. 11-12 and 19-22 and / or the aggregator 1114 as illustrated in FIGS. 11-12 and 23-25 ​​in any of the embodiments described herein. The manifold 2600 can be configured to distribute fluid from a common source to the multiple strings 1116 without creating electrical connections between the strings 1116 while a voltage is provided across the stack assembly 1110. The manifold 2600 can be configured to aggregate fluid received from the multiple strings 1116 and provide the aggregated fluid to a common source without creating electrical connections between the strings 1116 while a voltage is provided across the stack assembly 1110. In some embodiments, the manifold 2600 does not keep the strings 1116 electrically isolated from one another, but can also be used to prime the strings 1116 during a start-up phase of system operation and / or to purge the strings 1116 during a shutdown phase of system operation when electrical shunt breaking is not required. Instead, as described below, the manifold 2600 can be configured to keep the strings 1116 electrically isolated from one another by preventing current from flowing between the strings 1116 via a conductive fluid within the manifold 2600 and / or via the physical structure of the manifold 2600.

[0139] The manifold 2600 includes a body 2601 and a number of nozzles 2602 (e.g., eight nozzles 2602) extending from the body 2601. The nozzles 2602 are connected to the tubes 1124 such that each nozzle 2602 can be in fluid communication with one string 1116 (similar to the description of Figures 11-12), e.g., with each nozzle 2602 connected to one tube or pipe as shown in Figure 26. In some embodiments, the manifold 2600 can create an electrical shunt break (e.g., an air gap, a gap of electrically insulating fluid, etc.) that disrupts the conductive fluid stream by causing the conductive fluid within the manifold 2600 to split into individual droplets or other non-continuous fluid streams as they pass through the nozzles 2602. The nozzles 2602 can be oriented in a "V" shape as shown in Figure 26, or oriented vertically to allow droplets of conductive fluid to drip vertically through the air gap. In some embodiments, the nozzles 2602, similar to the distributors 1112 and / or concentrators 1114 as previously described, are made of an electrically insulating material to prevent electrical current from flowing between separate strings 1116 through the physical structure of the manifold 2600.

[0140] The body 2601 includes a central conduit (bore, channel, passage, opening, etc.) 2604. The central conduit 2604 is arranged to align with an interior tip 2606 of the nozzle 2602. The central conduit 2604 can be in communication with a port 2608, which can be connected, for example, via a tube (tube, pipe, etc.) to a source and / or receptacle of sodium (e.g., sodium storage vessel 1600). Thus, sodium can flow to or from the nozzle 2602 via the central conduit 2604 and the interior tip 2606.

[0141] The manifold 2600 can facilitate priming of the system 1100 by distributing sodium received at the port 2608 substantially evenly to the multiple nozzles 2602. In such a scenario, sodium flows through the port 2608 along the central conduit 2604 to the internal tip 2606 where the sodium enters the nozzles 2602. The pressure / flow of the sodium can push the sodium upward through the nozzles 2602 and into the tubes 1124. A small orifice can be included in each nozzle 2602 to provide back pressure to ensure flow to all nozzles 2602. The internal tip 2606, nozzles 2602, central conduit 2604, etc. can be sized to create a choked flow effect that ensures substantially even flow to each nozzle 2602. Alternatively, the system 1100 can be self-primed by the self-priming battery cell 100 as described above. At the end of the priming stage, sodium stops flowing to or into the central conduit 2604 via port 2608 (e.g., due to cessation of operation of a pump driving sodium from an external source). Sodium can then proceed downwardly from nozzle 2602 into the central conduit 2604 via inner tip 2606.

[0142] In some embodiments, the manifold 2600 can also promote the aggregation of sodium from the strings 1116 in the conduit 2604. For example, sodium can flow through the tubes 1124 to the nozzles 2602 at a rate such that sodium droplets form at an outer orifice of the inner tip 2606 close to the central conduit 2604, and then drip (e.g., separately and through an air gap) into the central conduit 2604. Alternatively or in addition, the nozzles 2602 can form sodium droplets near the tubes 1124 (e.g., at a reduced diameter portion of the nozzles 2602 connected to the tubes 1124), and then drip through an air gap in the nozzles 2602 between the tubes 1124 and the inner tip 2606. The sodium can then flow through the inner tip 2606 into the central conduit 2604. Nozzles 2602 may thereby be configured to provide concentration of sodium from tubes 1124 at central conduit 2604 while maintaining electrical decoupling between the sodium in different strings 1116 (and different sections of tubes 1124).

[0143] In some embodiments, the manifold 2600 can distribute sodium from the sodium storage vessel 1600 to the strings 1116 when operating in a flow battery discharge mode (i.e., consuming sodium to generate electricity). It is contemplated that the manifold 2600 can be used or modified to provide electrical isolation between the strings 1116 in a flow battery discharge mode, for example, by creating an electrical shunt break within the nozzles 2602. In some embodiments, the nozzles 2602 have an inverted "V" shape similar to the subset of nozzles 2602 in the foreground of FIG. 26, with each nozzle 2602 having a pair of legs extending downwardly from a central point in the middle of the inverted "V" shape. The end of each leg of the nozzles 2602 can include a flow restrictor (e.g., similar to the inner tip 2606), such as an orifice having a smaller diameter than the conduit passing through the nozzle 2602. Such a configuration may cause sodium to pool within the nozzle 2602 and form droplets at the flow restrictor as it exits the nozzle 2602 in either direction. The droplets may drip out of the flow restrictor through the air gap below it, resulting in a bidirectional shunt break.

[0144] In some embodiments, the system 1100 can be configured to control (e.g., adjust, regulate, modulate, etc.) the pressure of the fluid sodium in the nozzles 2602 and / or in the central conduit 2604 to promote droplet formation of the fluid sodium at a flow restrictor or other orifice in the manifold 2600. For example, the controller can measure or calculate the pressure differential across the flow restrictor and regulate the pressure of the fluid sodium in the central conduit 2604 (e.g., by providing pressurized gas to the central conduit 2604, similar to the distributor 1112 and concentrator configurations previously described). The controller can operate pumps or other pressure control devices for the sodium and / or pressurized gas to maintain the pressure differential at a set point or target level that promotes droplet formation in the manifold 2600 at one or both ends of the nozzles 2602.

[0145] Flow Battery Mode with Aggregate Storage 27, an illustration of a system 1100 arranged in a flow battery mode with aggregated storage is shown, according to some embodiments. Sodium produced during a charge mode flows out of the stack assembly 1110 to a sodium concentrator 1114, which aggregates the sodium in a sodium storage vessel 1600 as described in more detail with reference to FIG. 16. As shown in FIG. 27, the sodium storage vessel 1600 is again connected to the stack assembly 1110 via a sodium distributor 1112, allowing the produced sodium to flow back into the strings 1116 of the stack assembly 1110 during a discharge mode. The produced sodium from the sodium storage vessel 1600 can then loop back into the stack assembly 1110 to provide for the discharge of the stored energy from the sodium.

[0146] Although a sodium distributor 1112 and a sodium concentrator 1114 are shown in FIG. 27, it is contemplated that one or both of these components may be replaced with a sodium manifold 2600. In some embodiments, the distributor 1112 may be implemented as an inverted version of the concentrator 1114 shown in FIGS. 11-12 and 23-25. Additionally, it is contemplated that the sodium distributor 1112 or the concentrator 1114 may be omitted from the configuration shown in FIG. 27 to provide a version of the system 1100 that operates only in a charge mode (i.e., by omitting the distributor 1112) or only in a discharge mode (i.e., by omitting the concentrator 1114). Examples of systems specialized for charging or discharging are described in further detail with reference to FIG. 29. These and other modifications may be made to the embodiment shown in FIG. 27 as well as any of the other embodiments described herein.

[0147] In operation, the distributor 1112 is configured to break down (e.g., disperse, split, etc.) sodium stored in the sodium storage vessel 1600 into separate streams of sodium that are provided to the separate strings 1116. To effect a voltage step in each string 1116, the distributor 1112 provides electrical isolation between the separate streams of sodium that are provided to the separate strings 1116. As with other embodiments, the distributor 1112 may be a sodium dispersion drip feeder configured to emit droplets of molten sodium metal from an upper portion of the distributor 1112 such that the droplets fall through an electrically insulating fluid (e.g., an inert gas) within the distributor 1112 into multiple electrically isolated compartments located along a lower portion of the distributor 1112 and connected to separate tubes that run to the multiple strings 1116.

[0148] 27, valve 2702 is arranged along the sodium flow path and is operable to control the flow of sodium from sodium storage vessel 1600 to sodium distributor 1112. In some embodiments, valve 2702 can also have an off position in which sodium storage vessel 1600 is not fluidly connected to sodium distributor 1112. It is contemplated that valve 2702 may also be capable of electrically isolating sodium distributor 1112 and sodium storage vessel 1600 from each other to further provide an electrical shunt break (i.e., interruption of undesired electrical current) within system 1100.

[0149] 28, an illustration of another implementation of the system 1100 providing a flow battery mode is shown, according to some embodiments. In the example of FIG. 28, a sodium manifold 2600 is shown that is capable of providing both concentration of sodium produced by the strings 1116 (for provision into the sodium storage vessel 1600) and dispersion or deconcentration of sodium from the sodium storage vessel 1600. As mentioned above, the manifold 2600 can perform the functions of the distributor 1112 as shown in FIGS. 19-22 and / or the aggregator 1114 as shown in FIGS. 23-25, depending on the direction of sodium flow through the manifold 2600. Thus, the manifold 2600 is a versatile component capable of providing bidirectional shunt breaks between the strings 1116.

[0150] 28, the strings 1116 can be initially primed by generating sodium at their locations within the strings 1116 using the self-priming battery cells 100 as previously described. After self-priming the strings 1116, the system 1100 can operate in a charging mode or a sodium generation mode, where sodium is generated within the strings 1116 and flows to the manifold 2600. The manifold 2600 aggregates sodium from the separate strings 1116 for storage in the sodium storage vessel 1600 while maintaining electrical isolation between the sodium within the separate strings 1116. The generated sodium is thereby stored in the sodium storage vessel 1600.

[0151] The system 1100 can also operate in a discharge mode, where sodium from the sodium storage vessel flows (e.g., drips) back through the manifold 2600 to the multiple strings 1116. The manifold 2600 can distribute sodium substantially evenly to the strings 1116 while maintaining electrical isolation between the strings 1116 (e.g., by dripping sodium through an air gap as described elsewhere herein). The sodium thereby reaches the strings 1116 where it is consumed in an electrochemical reaction within the strings 1116 that generates electricity that is provided as an output from the stack assembly 1110. As the strings 1116 run out of sodium while operating in a discharge mode, more space may become available within the strings 1116. The sodium manifold 1116 and / or the sodium storage vessel 1600 may be physically positioned above the strings 1116 such that gravity causes the sodium to flow downward into the strings and no powered pumps are required to deliver sodium to the strings 1116. 28, each string 1116 includes one open sodium port through which sodium enters or leaves the string 1116 depending on the mode of operation. Other sodium ports used in other embodiments may be sealed or closed as they are not required in this configuration.

[0152] Geographically distributed charging and discharging Referring now to FIG. 29, a diagram illustrating a geographically distributed implementation of the system 1100, according to some embodiments, is shown. In some embodiments, components of the system 1100 can be distributed across multiple locations or physical sites to allow charging at one site and discharging at another site. As discussed above, the system 1100 can be used in a charging mode to store electricity (in the form of valence electrons of sodium atoms) and a discharging mode to generate electricity (by a reaction that allows the release of said valence electrons). The implementation of FIG. 29 illustrates transporting the generated sodium atoms from a first location (shown as a charging site 2900) to a second location (shown as a discharging site 2902) and also transporting stored electricity (i.e., electricity stored as chemical energy in the generated sodium) from the first location to the second location. At the second location, portions of the system 1100 can be used to collect the stored energy from the sodium atoms to output electricity. By doing so, electricity is transferred from the first location to the second location.

[0153] In one example scenario, the charging site 2900 can be located in a geographic area that has high availability of green, renewable, non-polluting, non-carbon emitting, and / or low-cost or free energy (e.g., an area with high geothermal activity, an area with high solar irradiance, an area with high winds, an area with existing energy production facilities), and the discharge site 2902 can be located in a geographic area that does not have such energy availability (e.g., an area that only has access to fossil fuel-based energy generation, an area that is disconnected from the energy grid, etc.). The transport of sodium from the charging site 2900 to the discharge site 2902 in such a scenario can reduce pollution (e.g., reduce carbon emissions, reduce greenhouse gases, etc.) and save costs by allowing the discharge site 2902 to benefit from the green, renewable, non-polluting, non-carbon emitting, and / or low-cost or free energy available at the charging site 2900.

[0154] In some embodiments, the charging site 2900 and the discharging site 2902 may be the same physical site. In this scenario, the produced sodium can be transported off-site (or to an on-site storage location or building) for storage and then returned to the site after a few hours or days. For example, sodium can be produced / stored, transported, and used to generate electricity seasonally (e.g., charging during dry seasons of high solar availability, discharging during rainy seasons of low solar availability, charging during seasons of low demand, discharging during seasons of high demand, etc.).

[0155] As shown in FIG. 29, a charging site 2900 receives energy from a power source 2904. The power source is connected to a first instance of a stack assembly 1110 (shown as stack assembly 1110a) and is used to provide a voltage across the stack assembly 1110a. The energy from the power source is used to drive a reaction that draws sodium ions from the catholyte and adds valence electrons to produce sodium atoms (e.g., as shown in FIG. 31), so that excess electrons from the power source 2904 are stored in the sodium atoms. The sodium then flows out of the stack assembly 1110a to the condenser 1114, as illustrated in FIG. 16, for example, with reference to the sodium production mode of the stack assembly 1110. The condenser 1114 condenses the sodium in the sodium storage vessel 1600 and prevents current flow between the strings 1116, as described in detail above. As with other embodiments, the condenser 1114 may be replaced with a manifold 2600.

[0156] In the example of FIG. 29 , the sodium storage vessel 1600 is positioned on (e.g., integrated with, loaded onto, etc.) a transport vehicle 2906. The transport vehicle 2906 may be a truck (or other vehicle that drives on a road), train, ship, plane, etc. The transport vehicle 2906 is configured to transport the sodium in the sodium storage vessel 1600 as it travels from the charging site 2900 to the discharging site 2902. In other embodiments, the transport vehicle 2906 is replaced with a pipeline connecting the charging site 2900 to the discharging site 2902 through which the sodium can flow. The transport vehicle 2906 and / or the sodium storage vessel 1600 may be designed to be robust to prevent sodium leaks, spills, etc. during transport, including in the event of a crash, collision, etc. of the transport vehicle 2906. The sodium storage vessel 1600 is preferably made of a material that ensures long-term stability of the sodium.

[0157] When the transport vehicle 2906 reaches the discharge site 2902, the sodium storage vessel 1600 is connected to a distributor 1112 that serves as a second example of a stack assembly (shown as stack assembly 1110b). The distributor 1112 distributes the sodium from the sodium storage vessel 1600 to the different strings of the stack assembly 1110b while preventing current flow through the sodium between the strings. As with the other embodiments, the distributor 1112 may be replaced with a manifold 2600. The stack assembly 1110b is configured to allow sodium atoms to release their valence electrons and dissipate the sodium. + It operates in a discharge mode such that ions flow into the catholyte. The released valence electrons flow out of the stack assembly as electricity that is provided to an electrical load 2908. The electrical load 2908, in various embodiments, can be an energy grid, the electrical system of a building, a plant, a particular unit or set of equipment (e.g., manufacturing equipment), etc.

[0158] FIG. 29 shows the catholyte (here, Na +29 further illustrates that the catholyte (enriched with ions) can be transported back onto the transport vehicle 2906 (or a different transport vehicle) to, for example, the catholyte tank 1400. The transport vehicle 2906 then transports the catholyte to the charging site 2900 where it is provided to the stack assembly 1110a of the charging site 2900. In some embodiments, the catholyte is also transported from the charging site 2900 to the discharge site 2902. This arrangement allows sodium (atoms and ions) to be looped through both the charging site 2900 and the discharge site 2902, resulting in little or no waste products (e.g., by-products, etc.). Sodium-based energy transport can thereby be provided using the geographically distributed system of FIG. 29.

[0159] Configuration of an Exemplary Embodiment When used herein in relation to numerical ranges, the terms "approximately," "about," "substantially," and similar terms generally mean + / - 10% of the disclosed value. When the terms "approximately," "about," "substantially," and similar terms are applied to structural features (e.g., to describe their shape, size, orientation, direction, etc.), these terms are intended to cover minor variations in structure that may result, for example, from manufacturing or assembly processes, and are intended to have a broad meaning consistent with common and accepted usage by those skilled in the art to which the subject matter of this disclosure pertains. Thus, these terms should be interpreted as indicating that insubstantial or insignificant modifications or variations of the subject matter described and claimed are considered to be within the scope of the disclosure set forth in the appended claims.

[0160] Although the figures and description may illustrate a particular order of method steps, unless otherwise specified above, the order of such steps may differ from that shown and described. Also, unless otherwise specified above, two or more steps may be performed simultaneously or partially simultaneously. Such variations may depend, for example, on the software and hardware systems selected, as well as designer choice. All such variations are within the scope of this disclosure. Similarly, software implementations of the described methods may be realized using standard programming techniques with rule-based logic and other logic to accomplish the various connection, processing, comparison, and decision steps.

Claims

1. A battery cell capable of self-priming using molten metal generated within the battery cell, the battery cell comprising: a cathode compartment configured to contain a catholyte that releases metal ions when the battery cell is self-primed; an anode compartment at least partially housing an anode current collector that receives electrons from an external power source when the battery cell is self-priming; an ion selective membrane disposed between the cathode compartment and the anode compartment and configured to selectively transport the metal ions from the cathode compartment to the anode compartment when the battery cell is self-primed; and an electron transport structure extending within the anode compartment between the anode current collector and the ion selective membrane and configured to transport the electrons from the anode current collector to the ion selective membrane when the battery cell is self-primed; Equipped with self-priming the battery cell includes combining the electrons with the metal ions that have reached an interface between the electron transport structure and the ion selective membrane to produce the molten metal in the anode compartment. Battery cell.

2. the anode compartment is free of the molten metal prior to self-priming the battery cell; 13. The battery cell of claim 1, wherein the molten metal generated in the anode compartment at least partially fills the anode compartment with the molten metal without requiring an additional supply of the molten metal from an external source when the battery cell is self-priming.

3. a conductive coating on a surface of the ion selective membrane facing the anode compartment and configured to distribute the electrons received from the electron transport structure across the surface of the ion selective membrane. The battery cell of claim 1 .

4. 4. The battery cell of claim 3, wherein the conductive coating comprises at least one of a metal, a metal oxide, a metal sulfide, or carbon.

5. 4. The battery cell of claim 3, wherein the conductive coating comprises at least one of indium tin oxide, manganese oxide, titanium oxide, nickel oxide, tungsten sulfide, nickel sulfide, titanium sulfide, zirconium sulfide, vanadium sulfide, iron sulfide, molybdenum sulfide, cobalt sulfide, or copper sulfide.

6. The conductive coating comprises: a second metal comprising at least one of tin, lead, mercury, indium, and / or any metal capable of alloying with the molten metal; The battery cell of claim 3 , comprising:

7. The conductive coating comprises: forming a conductive layer between the molten metal and the ion-selective membrane during initial production of the molten metal in the anode compartment; and dissolving in the molten metal produced in the anode compartment and contacting the molten metal directly with the surface of the ion selective membrane after dissolution of the conductive coating; The battery cell of claim 3 .

8. 4. The battery cell of claim 3, wherein the conductive coating has a thickness of substantially 10 nanometers to 10 micrometers.

9. The conductive coating has a resistance of substantially 100 siemens / cm to 10 ６ 4. The battery cell of claim 3 having a conductivity of 1.0 Siemens / cm.

10. the electron transport structure contacts the conductive coating at a single location; the conductive coating receives the electrons at the single location and distributes the electrons across the surface of the ion selective membrane. The battery cell of claim 3 .

11. The electron transport structure comprises: a conductive mesh contacting a surface of the ion selective membrane at a plurality of locations and configured to distribute the electrons received from the anode current collector across the surface of the ion selective membrane. The battery cell of claim 1 , comprising:

12. 10. The battery cell of claim 1, wherein the electron transport structure is substantially rigid and provides structural support to the ion selective membrane by exerting a force on a surface of the ion selective membrane.

13. 2. The battery cell of claim 1, wherein the electron transport structure comprises one or more wires extending between the anode current collector and the ion selective membrane.

14. The electron transport structure comprises: providing a first electrical connection between the anode current collector and the ion selective membrane prior to self-priming the battery cell; and Melts or dissolves in the molten metal produced in the anode compartment It is structured as follows: the molten metal produced in the anode compartment provides a second electrical connection between the anode current collector and the ion selective membrane after the electron transport structure is melted or dissolved.

10. The battery cell of claim 1 .

15. 10. The battery cell of claim 1, wherein the electron transport structure and the anode current collector are integral parts of a monolithic anode scaffold structure comprising a three-dimensional lattice of conductive material.

16. 2. The battery cell of claim 1, wherein the electron transport structure is located along an exterior boundary of the anode compartment such that the electron transport structure forms at least a portion of the exterior boundary of the anode compartment and contains the molten metal in the anode compartment after the molten metal is generated in the anode compartment.

17. 10. The battery cell of claim 1, wherein the electron transport structure is constructed separately from the anode current collector and the ion selective membrane and is constructed first and then inserted into the anode compartment.

18. The battery cell of claim 1 , wherein the anode current collector comprises a metal plate comprising at least one of steel, nickel, or carbon.

19. the battery cell comprising a port along a surface of the anode compartment; the molten metal produced in the anode compartment flows passively between the anode compartment and an external storage vessel through the port without the need for powered components to flow the molten metal; 10. The battery cell of claim 1 .

20. 1. A method for self-priming a battery cell with molten metal produced within the battery cell, comprising: releasing metal ions from a catholyte contained within a cathode compartment of the battery cell; receiving electrons from an external power source at an anode current collector at least partially contained within an anode compartment of the battery cell; transporting the metal ions from the cathode compartment to the anode compartment through an ion selective membrane disposed between the cathode compartment and the anode compartment; transporting the electrons from the anode current collector to the ion selective membrane via an electron transport structure extending between the anode current collector and the ion selective membrane in the anode compartment; self-priming the battery cell by combining the metal ions with the electrons in the anode compartment to produce the molten metal in the anode compartment; A method comprising:

21. the anode compartment is free of the molten metal prior to self-priming the battery cell; and self-priming the battery cell includes at least partially filling the anode compartment with the molten metal generated within the anode compartment without requiring an additional supply of the molten metal from an external source.

21. The method of claim 20.

22. a first portion of the metal ions released from the catholyte forms a first portion of the molten metal that at least partially fills the anode compartment when self-priming the battery cell; a second portion of the metal ions released from the catholyte forms a second portion of the molten metal that flows out of the anode compartment and into an external storage container after self-priming the battery cell.

21. The method of claim 20.

Images